Control device for compression ignition engine
阅读说明:本技术 压缩着火式发动机的控制装置 (Control device for compression ignition engine ) 是由 松岛佑斗 东尾理克 砂流雄刚 高山真二 氏原健幸 增田雄太 于 2019-07-19 设计创作,主要内容包括:本发明提供一种压缩着火式发动机的控制装置,为了在混合气的空燃比及涡流的强度互不相同的第一模式与第二模式之间切换模式的发动机中在模式切换时确保燃料消耗性能,切换部(10e)接收从第一模式至第二模式的切换要求,以使涡流比切换要求之前增强的形式向涡流产生部(涡流控制阀(56))输出信号,且在判定涡流到达了规定强度时允许第二模式部(10c)开始第二模式。(In order to ensure fuel consumption performance at the time of mode switching in an engine that switches between a first mode and a second mode in which the air-fuel ratio of an air-fuel mixture and the strength of a swirl are different from each other, a switching unit (10 e) receives a request for switching from the first mode to the second mode, outputs a signal to a swirl generation unit (swirl control valve (56)) in such a manner as to increase the swirl ratio before the request for switching, and allows the second mode unit (10 c) to start the second mode when it is determined that the swirl has reached a predetermined strength.)
1. A control device for a compression ignition engine,
the disclosed device is provided with:
a combustion chamber of an engine formed by a cylinder, a piston reciprocating in the cylinder, and a cylinder head closing one end of the cylinder;
an air conditioning unit for adjusting an amount of air to be filled into the combustion chamber;
a fuel injection unit attached to the cylinder head and injecting fuel supplied into the combustion chamber;
an ignition portion that is disposed facing the combustion chamber and ignites an air-fuel mixture in the combustion chamber;
a vortex generating unit for generating a vortex in the combustion chamber;
a measurement unit that measures a parameter related to operation of the engine; and
a control unit connected to the air conditioning unit, the fuel injection unit, the ignition unit, the vortex generation unit, and the measurement unit, respectively, and configured to receive a measurement signal from the measurement unit, perform calculation, and output signals to the air conditioning unit, the fuel injection unit, the ignition unit, and the vortex generation unit;
the control unit includes: a first mode portion that operates the engine in a first mode; a second mode portion to operate the engine in a second mode; and a switching unit that receives a switching request from the first mode to the second mode and performs mode switching;
the first mode section outputs a signal to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a first air-fuel ratio, and outputs an ignition signal to the ignition section so that the remaining unburned air-fuel mixture is combusted by self-ignition after combustion accompanied by flame propagation is started by forced ignition of the ignition section for a part of the air-fuel mixture;
the second mode portion outputs a signal to the fuel injection portion and the air conditioning portion so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a second air-fuel ratio larger than the first air-fuel ratio, and outputs an ignition signal to the ignition portion so that a part of the air-fuel mixture starts combustion accompanied by flame propagation by forced ignition of the ignition portion and thereafter the remaining unburned air-fuel mixture is combusted by self-ignition;
the switching unit, upon receiving the switching request, outputs a signal to the air-conditioning unit and the fuel injection unit so that the air-fuel ratio of the mixture becomes a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, and outputs a signal to the swirl generation unit so that the swirl ratio is increased before the switching request;
the switching unit may allow the second mode unit to start the second mode when it is determined that the eddy current has reached a predetermined intensity.
2. The control device of a compression ignition engine according to claim 1,
the swirl generating portion has a swirl control valve attached to an intake passage of the engine;
the control portion adjusts the opening degree of the swirl control valve, thereby adjusting the strength of the swirl in the combustion chamber in such a manner that the swirl is increased when the opening degree is on the closed side than when the opening degree is on the open side.
3. The control device of a compression ignition engine according to claim 1 or 2,
the vortex flow generating part generates a vortex flow having a vortex flow ratio of 4 or more.
4. The control device of a compression ignition engine according to claim 1 or 2,
the switching unit outputs a signal to the air conditioning unit so as to increase the air amount before the switching request, and outputs a signal to the fuel injection unit so as to increase the fuel amount in accordance with an increase in the air amount so that the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, thereby performing torque adjustment for suppressing an increase in the torque of the engine with respect to the increase in the fuel amount;
the switching unit may terminate the increase in the fuel amount and the torque adjustment and allow the second mode unit to start the second mode when it is determined that the swirl flow has reached a predetermined intensity and the air amount has reached a predetermined amount.
5. The control device of a compression ignition engine according to claim 4,
the switching unit switches from the first mode to the second mode while maintaining the torque of the engine constant or substantially constant.
6. The control device of a compression ignition engine according to claim 4,
the switching unit outputs a signal for retarding an ignition timing to the ignition unit, thereby suppressing an increase in torque of the engine.
7. The control device of a compression ignition engine according to claim 4,
the switching unit starts the increase of the air amount, the increase of the fuel amount, and the torque adjustment when it is determined that the swirl flow has reached a predetermined intensity,
and when it is determined that the air amount has reached a predetermined amount, the increase in the fuel amount and the torque adjustment are ended, and the second mode section is allowed to start the second mode.
8. The control device of a compression ignition engine according to any one of claims 1, 2, 5 to 7,
the first air-fuel ratio is a theoretical air-fuel ratio or substantially the theoretical air-fuel ratio;
the second air-fuel ratio is 25 or more.
9. A control device for a compression ignition engine,
the disclosed device is provided with:
a combustion chamber of an engine formed by a cylinder, a piston reciprocating in the cylinder, and a cylinder head closing one end of the cylinder;
an air conditioning unit for adjusting an amount of air to be filled into the combustion chamber;
a fuel injection unit attached to the cylinder head and injecting fuel supplied into the combustion chamber;
an ignition portion that is disposed facing the combustion chamber and ignites an air-fuel mixture in the combustion chamber;
a vortex generating unit for generating a vortex in the combustion chamber;
a measurement unit that measures a parameter related to operation of the engine; and
a control unit connected to the air conditioning unit, the fuel injection unit, the ignition unit, the vortex generation unit, and the measurement unit, respectively, and configured to receive a measurement signal from the measurement unit, perform calculation, and output signals to the air conditioning unit, the fuel injection unit, the ignition unit, and the vortex generation unit;
the control unit includes: a first mode portion that operates the engine in a first mode; a second mode portion to operate the engine in a second mode; and a switching unit that receives a switching request from the second mode to the first mode and performs mode switching;
the first mode section outputs a signal to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a first air-fuel ratio, and outputs an ignition signal to the ignition section so that the remaining unburned air-fuel mixture is combusted by self-ignition after combustion accompanied by flame propagation is started by forced ignition of the ignition section for a part of the air-fuel mixture;
the second mode portion outputs a signal to the fuel injection portion and the air conditioning portion so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a second air-fuel ratio larger than the first air-fuel ratio, and outputs an ignition signal to the ignition portion so that a part of the air-fuel mixture starts combustion accompanied by flame propagation by forced ignition of the ignition portion and thereafter the remaining unburned air-fuel mixture is combusted by self-ignition;
the switching unit outputs a signal to the air-conditioning unit and the fuel injection unit so that an air-fuel ratio of the mixture becomes a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio when the switching request is received, and outputs a signal to the swirl generation unit so that the swirl ratio is decreased before the switching request is received;
the switching unit further allows the first mode unit to start the first mode when it is determined that the eddy current has reached a predetermined intensity.
10. The control device of a compression ignition engine according to claim 9,
the control unit has a target torque setting unit that receives the measurement signal from the measurement unit and sets a target torque of the engine;
the first mode section outputs signals to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the target torque and the air-fuel ratio of the air-fuel mixture becomes the first air-fuel ratio;
the second mode portion outputs a signal to the fuel injection portion and the air conditioning portion so that the fuel amount corresponds to the target torque and the air-fuel ratio of the air-fuel mixture becomes the second air-fuel ratio.
11. A control device for a compression ignition engine,
the disclosed device is provided with:
a combustion chamber of an engine formed by a cylinder, a piston reciprocating in the cylinder, and a cylinder head closing one end of the cylinder;
an air conditioning unit for adjusting an amount of air to be filled into the combustion chamber;
a fuel injection unit attached to the cylinder head and injecting fuel supplied into the combustion chamber;
an ignition portion that is disposed facing the combustion chamber and ignites an air-fuel mixture in the combustion chamber;
a vortex generating unit for generating a vortex in the combustion chamber;
a measurement unit that measures a parameter related to operation of the engine; and
a control unit connected to the air conditioning unit, the fuel injection unit, the ignition unit, the vortex generation unit, and the measurement unit, respectively, and configured to receive a measurement signal from the measurement unit, perform calculation, and output signals to the air conditioning unit, the fuel injection unit, the ignition unit, and the vortex generation unit;
the control unit includes:
a first mode portion that operates the engine in a first mode based on a measurement signal of the measurement portion;
a second mode portion that operates the engine in a second mode based on a measurement signal of the measurement portion;
a determination unit that outputs a request for switching from the first mode to the second mode when it is determined that a switching condition is satisfied, based on a measurement signal of the measurement unit; and
a switching unit for receiving the switching request and switching the modes;
the first mode section outputs a signal to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a first air-fuel ratio, and outputs an ignition signal to the ignition section so that the remaining unburned air-fuel mixture is combusted by self-ignition after combustion accompanied by flame propagation is started by forced ignition of the ignition section for a part of the air-fuel mixture;
the second mode portion outputs a signal to the fuel injection portion and the air conditioning portion so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a second air-fuel ratio larger than the first air-fuel ratio, and outputs an ignition signal to the ignition portion so that a part of the air-fuel mixture starts combustion accompanied by flame propagation by forced ignition of the ignition portion and thereafter the remaining unburned air-fuel mixture is combusted by self-ignition;
the switching unit, upon receiving the switching request, outputs a signal to the air-conditioning unit and the fuel injection unit so that the air-fuel ratio of the mixture becomes a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, and outputs a signal to the swirl generation unit so that the swirl ratio is increased before the switching request;
the switching unit may allow the second mode unit to start the second mode when it is determined that the eddy current has reached a predetermined intensity.
12. A control device for a compression ignition engine,
the disclosed device is provided with: a combustion chamber of an engine formed by a cylinder, a piston reciprocating in the cylinder, and a cylinder head closing one end of the cylinder;
an air conditioning unit for adjusting an amount of air to be filled into the combustion chamber;
a fuel injection unit attached to the cylinder head and injecting fuel supplied into the combustion chamber;
an ignition portion that is disposed facing the combustion chamber and ignites an air-fuel mixture in the combustion chamber;
a vortex generating unit for generating a vortex in the combustion chamber;
a measurement unit that measures a parameter related to operation of the engine; and
a control unit connected to the air conditioning unit, the fuel injection unit, the ignition unit, the vortex generation unit, and the measurement unit, respectively, and configured to receive a measurement signal from the measurement unit, perform calculation, and output signals to the air conditioning unit, the fuel injection unit, the ignition unit, and the vortex generation unit;
the control unit includes:
a first mode portion that operates the engine in a first mode based on a measurement signal of the measurement portion;
a second mode portion that operates the engine in a second mode based on a measurement signal of the measurement portion;
a determination unit that outputs a request for switching from the second mode to the first mode when it is determined that a switching condition is satisfied, based on a measurement signal of the measurement unit; and
a switching unit for receiving the switching request and switching the modes;
the first mode section outputs a signal to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a first air-fuel ratio, and outputs an ignition signal to the ignition section so that the remaining unburned air-fuel mixture is combusted by self-ignition after combustion accompanied by flame propagation is started by forced ignition of the ignition section for a part of the air-fuel mixture;
the second mode portion outputs a signal to the fuel injection portion and the air conditioning portion so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a second air-fuel ratio larger than the first air-fuel ratio, and outputs an ignition signal to the ignition portion so that a part of the air-fuel mixture starts combustion accompanied by flame propagation by forced ignition of the ignition portion and thereafter the remaining unburned air-fuel mixture is combusted by self-ignition;
the switching unit outputs a signal to the air-conditioning unit and the fuel injection unit so that an air-fuel ratio of the mixture becomes a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio when the switching request is received, and outputs a signal to the swirl generation unit so that the swirl ratio is decreased before the switching request is received;
the switching unit further allows the first mode unit to start the first mode when it is determined that the eddy current has reached a predetermined intensity.
13. The control device of a compression ignition engine according to claim 12,
the control unit has a target torque setting unit that receives the measurement signal from the measurement unit and sets a target torque of the engine;
the first mode portion receives the target torque, and outputs signals to the fuel injection portion and the air conditioning portion so that the target torque is equal to a fuel amount corresponding to the target torque and an air-fuel ratio of a mixture is equal to the first air-fuel ratio;
the second mode unit receives the target torque, and outputs a signal to the fuel injection unit and the air conditioning unit so that the target torque is equal to a fuel amount corresponding to the target torque and the air-fuel ratio of the air-fuel mixture is equal to the second air-fuel ratio.
Technical Field
The technology disclosed herein relates to a control device for a compression ignition engine.
Background
It is known that combustion by compression self-ignition, which causes mixture to burn at once without flame propagation, can maximize fuel consumption efficiency because of a minimum combustion period. However, combustion by compression self-ignition is required to solve various problems in an automobile engine. For example, in the case of automobiles, since the operating conditions and environmental conditions vary greatly, it is a big problem to stably compress the self-ignition therein. In an automobile engine, combustion by compression self-ignition has not been put to practical use.
In order to solve this problem, for example,
CI combustion in SPCCI combustion occurs when the in-cylinder temperature reaches an ignition temperature determined by the composition of the air-fuel mixture. If the in-cylinder temperature reaches the ignition temperature near compression top dead center to cause CI combustion, the fuel consumption efficiency can be maximized. The in-cylinder temperature rises in accordance with the rise of the in-cylinder pressure. The in-cylinder pressure in the SPCCI combustion is a result of two pressure rises, a pressure rise due to compression work of the piston in the compression stroke and a pressure rise due to heat release of the SI combustion.
Disclosure of Invention
The problems to be solved by the invention are as follows:
since SPCCI combustion is one form of compression ignition combustion, stable combustion can be achieved even when the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio as described in
However, in SPCCI combustion, the pressure rise caused by SI combustion depends on the combustion speed, i.e., the flame propagation speed. If the flame propagation of the SI combustion is unstable, the pressure rise due to the heat release of the SI combustion cannot be sufficiently ensured, and it is difficult to raise the in-cylinder temperature to the ignition temperature. As a result, the amount of the air-fuel mixture that undergoes CI combustion decreases, and a large amount of the air-fuel mixture undergoes SI combustion or CI combustion occurs in the latter half of the expansion stroke. So that the thermal efficiency of the engine is not maximized.
For example, when the engine is in a specific operating condition, such as when the engine water temperature is low or when the intake air temperature is low, it is difficult to stably SI-combust an air-fuel mixture whose fuel is lean. Even if the SPCCI combustion is performed, the thermal efficiency of the engine is not maximized. Therefore, when the engine water temperature is low, when the intake air temperature is low, or the like, it is conceivable to perform SPCCI combustion such that the air-fuel ratio of the air-fuel mixture in the engine becomes the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio. If the air-fuel ratio of the air-fuel mixture is the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, flame propagation of SI combustion in SPCCI combustion is stable even when the engine water temperature is low, the intake air temperature is low, or the like. Therefore, CI combustion can be started near compression top dead center, thereby improving the thermal efficiency of the engine. Further, when the air-fuel ratio of the mixture is made the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, NOx in the exhaust gas can also be purified by the three-way catalyst attached to the exhaust passage.
The present inventors have devised, in an engine that performs SPCCI combustion, to achieve both improvement in exhaust emission performance and improvement in thermal efficiency, switching between the following modes depending on the state of the engine: a mode (i.e., a first mode) in which the mixture having the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio is subjected to SPCCI combustion, and a mode (i.e., a second mode) in which the mixture having an air-fuel ratio leaner than the stoichiometric air-fuel ratio is subjected to SPCCI combustion.
However, since the second mode combusts the mixture that is leaner in fuel than the first mode, there is room for improvement in the stability of flame propagation in SI combustion as compared to the first mode. Therefore, the present inventors have conceived of generating a swirl in the combustion chamber and controlling the formation of the distribution of the air-fuel mixture by the swirl, thereby ensuring ignitability of ignition and improving stability of SI combustion.
In the case of such a configuration, the stability of the SI combustion is higher as the swirl becomes stronger, but if the swirl is excessively strengthened, the cooling loss via the inner wall surface of the combustion chamber increases, and therefore it is considered that the strength of the swirl (specifically, the strength of the flow of the swirl) is appropriately changed in accordance with the mode of the engine. For example, in the first mode, the strength of the eddy current is weakened as compared with the second mode, whereby a decrease in thermal efficiency associated with cooling loss can be suppressed.
In view of the above, it is conceivable to change not only the air-fuel ratio of the air-fuel mixture but also the strength of the swirl generated in the combustion chamber when the first mode and the second mode are switched. When the mode of the engine is switched from the first mode to the second mode, the swirl flow generated in the combustion chamber is intensified, but if the operation in the second mode is started during the period in which the strength of the swirl flow is intensified, the strength of the swirl flow is temporarily too small. At this time, the flame propagation speed in the SI combustion is reduced, so that the CI combustion occurs in the latter half of the expansion stroke, and there is a fear that the thermal efficiency of the engine is not maximized. This is disadvantageous in improving the fuel consumption performance of the engine.
The same problem occurs when the mode of the engine is switched from the second mode to the first mode. At this time, if the operation in the first mode is started during the period in which the intensity of the vortex is weakened, there is a possibility that the intensity of the vortex may be temporarily excessive. In this case, the cooling loss temporarily increases, which is disadvantageous from the viewpoint of fuel consumption performance.
The technology disclosed herein has been made in view of the above circumstances, and an object thereof is to ensure fuel consumption performance at the time of mode switching in an engine in which the modes are switched between a first mode and a second mode in which the air-fuel ratio of the mixture and the strength of swirl are different from each other.
Means for solving the problems:
the inventors of the present application allowed mode switching after adjusting the intensity of the eddy current.
Specifically, the technology disclosed herein relates to a control device of a compression ignition engine. The control device for the engine is provided with: a combustion chamber of an engine formed by a cylinder, a piston reciprocating in the cylinder, and a cylinder head closing one end of the cylinder; an air conditioning unit for adjusting an amount of air to be filled into the combustion chamber; a fuel injection unit attached to the cylinder head and injecting fuel supplied into the combustion chamber; an ignition portion that is disposed facing the combustion chamber and ignites an air-fuel mixture in the combustion chamber; a vortex generating unit for generating a vortex in the combustion chamber; a measurement unit that measures a parameter related to operation of the engine; and a control unit connected to the air conditioning unit, the fuel injection unit, the ignition unit, the vortex generation unit, and the measurement unit, respectively, for receiving a measurement signal from the measurement unit, performing calculation, and outputting a signal to the air conditioning unit, the fuel injection unit, the ignition unit, and the vortex generation unit; the control unit includes: a first mode portion that operates the engine in a first mode; a second mode portion to operate the engine in a second mode; and a switching unit that receives a switching request from the first mode to the second mode and switches the modes.
The first mode section outputs a signal to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a first air-fuel ratio, and outputs an ignition signal to the ignition section so that the remaining unburned air-fuel mixture is combusted by self-ignition after combustion accompanied by flame propagation is started by forced ignition of the ignition section for a part of the air-fuel mixture; the second mode unit outputs a signal to the fuel injection unit and the air conditioning unit so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a second air-fuel ratio larger than the first air-fuel ratio, and outputs an ignition signal to the ignition unit so that a part of the air-fuel mixture starts combustion accompanied by flame propagation by forced ignition of the ignition unit and thereafter the remaining unburned air-fuel mixture is combusted by self-ignition.
When the switching unit receives the switching request, the switching unit outputs a signal to the air-conditioning unit and the fuel injection unit so that the air-fuel ratio of the mixture becomes a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, and outputs a signal to the swirl generation unit so that the swirl ratio is increased before the switching request; the switching portion further allows the second mode portion to start the second mode when it is determined that the eddy current is increased to a predetermined intensity.
According to this configuration, the first mode portion burns the air-fuel mixture SPCCI at the first air-fuel ratio, thereby operating the engine. The second mode part burns a mixture SPCCI of a second air-fuel ratio larger than the first air-fuel ratio, thereby operating the engine.
Here, the first air-fuel ratio may be, for example, a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio. Thus, the exhaust gas can be purified by the three-way catalyst attached to the exhaust passage of the engine. The "stoichiometric air-fuel ratio or substantially stoichiometric air-fuel ratio" may also be referred to as an air-fuel ratio that falls within the purification zone of the three-way catalyst. The second air-fuel ratio may be set to an appropriate air-fuel ratio of 25 or more, for example. This can suppress generation of RawNOx during combustion of the air-fuel mixture.
The switching unit increases the swirl by the swirl generator before switching the engine mode from the first mode to the second mode, for example, to improve stability of SI combustion in the second mode. The switching unit allows the second mode unit to start the second mode when the eddy current reaches a predetermined intensity. The second mode unit thereby starts the second mode and completes switching from the first mode to the second mode.
In this way, by increasing the strength of the vortex in advance, the second mode can be started without excessively decreasing the strength of the vortex. Thus, the thermal efficiency of the engine can be maximized, and the fuel consumption performance of the engine can be improved.
The swirl generator may include a swirl control valve attached to an intake passage of the engine; the control portion adjusts the opening degree of the swirl control valve, thereby adjusting the strength of the swirl in the combustion chamber in such a manner that the swirl is increased when the opening degree is on the closed side than when the opening degree is on the open side.
According to this configuration, the strength of the vortex can be adjusted by adjusting the opening degree of the vortex control valve.
The vortex flow generating unit may generate a vortex flow having a vortex flow ratio of 4 or more.
Here, the swirl ratio is a value obtained by dividing a value obtained by measuring the intake flow lateral angular velocity for each valve lift and integrating the measured intake flow lateral angular velocity by the engine angular velocity. The intake air flow lateral angular velocity can be measured by bench (rig) testing.
When the swirl ratio is 4 or more, the injected fuel can be moved over a wide range in the combustion chamber by the swirl, and therefore a more homogeneous air-fuel mixture can be formed. Therefore, the mixture distribution in the combustion chamber can be controlled with higher accuracy.
The switching unit may output a signal to the air conditioning unit so as to increase the air quantity before the switching request, and output a signal to the fuel injection unit so as to increase the fuel quantity in accordance with an increase in the air quantity so as to make the air-fuel ratio of the air-fuel mixture equal to the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, and may perform torque adjustment for suppressing an increase in the torque of the engine with respect to the increase in the fuel quantity; the switching unit may terminate the increase in the fuel amount and the torque adjustment and allow the second mode unit to start the second mode when it is determined that the swirl flow has reached a predetermined intensity and the air amount has reached a predetermined amount.
In the case where the first mode and the second mode are used separately as described above, the air-fuel ratio of the air-fuel mixture changes as the modes are switched, and therefore the amount of air to be filled into the combustion chamber needs to be changed. When the mode of the engine is switched from the first mode to the second mode, the amount of air to be filled into the combustion chamber must be increased, but during the delay period until the amount of air increases to a predetermined amount, the air-fuel ratio of the mixture becomes greater than the stoichiometric air-fuel ratio (for example, 14.7) and 25 or less capable of suppressing the generation of RawNOx. If the air-fuel ratio of the mixture is 25 or more and less than the stoichiometric air-fuel ratio, not only the RawNOx is generated during combustion of the mixture, but also the air-fuel ratio deviates from the purification zone of the three-way catalyst, and therefore it is difficult to purify the NOx in the exhaust gas.
Therefore, the present inventors increased the fuel amount so that the air-fuel ratio of the mixture becomes the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio during the period when the air amount changes during the switching mode.
However, increasing the amount of fuel increases the torque of the engine by the amount corresponding to the increase. Therefore, the inventors of the present application increased the amount of fuel and performed torque adjustment that suppressed the increase in torque of the engine.
That is, when the mode of the engine is switched from the first mode to the second mode, the second air-fuel ratio is larger than the first air-fuel ratio, and therefore, the amount of air to be filled into the combustion chamber must be increased. The switching unit outputs a signal to the air conditioning unit so that the air amount is increased more than before the switching request. The air conditioning unit may change the opening degree of the throttle valve from small to large, for example.
The air-fuel ratio of the mixture deviates from the first air-fuel ratio by the increase of the air amount. The air-fuel ratio of the mixture also deviates from the second air-fuel ratio due to the delay in the increase of the air amount. Since the exhaust emission performance may be degraded, the switching portion outputs a signal for increasing the amount of fuel to the fuel injection portion for an increasing amount of air. The air-fuel ratio of the mixture becomes the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, so the exhaust gas can be purified by the three-way catalyst.
The switching unit also performs torque adjustment for suppressing an increase in torque of the engine with respect to an increase in the amount of fuel. This can suppress the increase in the torque of the engine by the fuel increase amount. Occurrence of unnecessary torque shock can be suppressed.
The switching unit may switch from the first mode to the second mode while maintaining the torque of the engine constant or substantially constant.
Since the torque of the engine is made constant or substantially constant during the switching from the first mode to the second mode, the amount of fuel corresponding to the target torque is substantially constant.
In the above configuration, the switching portion increases the amount of fuel in accordance with an increase in the air amount, and therefore the torque of the engine increases. However, the switching unit adjusts the torque to suppress the increase in torque, thereby making the torque of the engine constant or substantially constant.
The switching unit may output a signal for retarding the ignition timing to the ignition unit, thereby suppressing an increase in the torque of the engine.
By retarding the ignition timing, the timing of SI combustion is retarded, and the timing of CI combustion start in SPCCI combustion is also retarded. The torque of the engine is effectively reduced.
The switching unit may start the increase in the amount of the air, the increase in the amount of the fuel, and the torque adjustment when it is determined that the swirl flow has reached a predetermined intensity, end the increase in the amount of the fuel and the torque adjustment when it is determined that the amount of the air has reached a predetermined amount, and allow the second mode unit to start the second mode.
According to this configuration, the switching unit starts the increase of the air volume when the swirl reaches the predetermined intensity, and allows the second mode unit to start the second mode when the air volume reaches the predetermined amount. Thereby, the second mode can be started in a state where the intensity adjustment of the eddy current is completed. Thus, the thermal efficiency of the engine can be maximized, which is advantageous for improving the fuel consumption performance of the engine.
Further, since the combustion stability of the SPCCI combustion is improved by enhancing the swirl in the combustion chamber, for example, in the case of a configuration in which the ignition timing is retarded as a torque adjustment, the ignition timing is retarded after enhancing the swirl, whereby misfire and the like can be suppressed even if the retardation amount is increased. Enhancing the eddy currents facilitates shifting the hysteresis limit in the hysteresis direction.
The control device for a compression ignition engine disclosed herein includes: a combustion chamber of an engine formed by a cylinder, a piston reciprocating in the cylinder, and a cylinder head closing one end of the cylinder; an air conditioning unit for adjusting an amount of air to be filled into the combustion chamber; a fuel injection unit attached to the cylinder head and injecting fuel supplied into the combustion chamber; an ignition portion that is disposed facing the combustion chamber and ignites an air-fuel mixture in the combustion chamber; a vortex generating unit for generating a vortex in the combustion chamber; a measurement unit that measures a parameter related to operation of the engine; and a control unit connected to the air conditioning unit, the fuel injection unit, the ignition unit, the vortex generation unit, and the measurement unit, respectively, for receiving a measurement signal from the measurement unit, performing calculation, and outputting a signal to the air conditioning unit, the fuel injection unit, the ignition unit, and the vortex generation unit; the control unit includes: a first mode portion that operates the engine in a first mode; a second mode portion to operate the engine in a second mode; and a switching unit that receives a switching request from the second mode to the first mode and performs mode switching.
The first mode section outputs a signal to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a first air-fuel ratio, and outputs an ignition signal to the ignition section so that the remaining unburned air-fuel mixture is combusted by self-ignition after combustion accompanied by flame propagation is started by forced ignition of the ignition section for a part of the air-fuel mixture; the second mode portion outputs a signal to the fuel injection portion and the air conditioning portion so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a second air-fuel ratio larger than the first air-fuel ratio, and outputs an ignition signal to the ignition portion so that a part of the air-fuel mixture starts combustion accompanied by flame propagation by forced ignition of the ignition portion and thereafter the remaining unburned air-fuel mixture is combusted by self-ignition;
when the switching unit receives the switching request, the switching unit outputs a signal to the air-conditioning unit and the fuel injection unit so that the air-fuel ratio of the mixture becomes a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, and outputs a signal to the swirl generation unit so that the swirl ratio is decreased before the switching request; the switching unit further allows the first mode unit to start the first mode when it is determined that the eddy current has reached a predetermined intensity.
The switching unit attenuates the swirl by the swirl generator before switching the engine mode from the second mode to the first mode. The switching unit allows the first mode unit to start the first mode when the eddy current weakens to a predetermined strength. Thus, the first mode unit starts the first mode and completes switching from the second mode to the first mode.
In this way, by reducing the intensity of the eddy current in advance, the first mode can be started without excessively increasing the intensity of the eddy current. In this way, the cooling loss due to the swirl can be suppressed while ensuring the stability of the SI combustion, and the fuel consumption performance of the engine can be improved.
The control unit may include a target torque setting unit that receives the measurement signal from the measurement unit and sets a target torque of the engine; the first mode section outputs signals to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the target torque and the air-fuel ratio of the air-fuel mixture becomes the first air-fuel ratio; the second mode portion outputs a signal to the fuel injection portion and the air conditioning portion so that the fuel amount corresponds to the target torque and the air-fuel ratio of the air-fuel mixture becomes the second air-fuel ratio.
The control device for a compression ignition engine disclosed herein includes: a combustion chamber of an engine formed by a cylinder, a piston reciprocating in the cylinder, and a cylinder head closing one end of the cylinder; an air conditioning unit for adjusting an amount of air to be filled into the combustion chamber; a fuel injection unit attached to the cylinder head and injecting fuel supplied into the combustion chamber; an ignition portion that is disposed facing the combustion chamber and ignites an air-fuel mixture in the combustion chamber; a vortex generating unit for generating a vortex in the combustion chamber; a measurement unit that measures a parameter related to operation of the engine; and a control unit connected to the air conditioning unit, the fuel injection unit, the ignition unit, the vortex generation unit, and the measurement unit, respectively, for receiving a measurement signal from the measurement unit, performing calculation, and outputting a signal to the air conditioning unit, the fuel injection unit, the ignition unit, and the vortex generation unit; the control unit includes: a first mode portion that operates the engine in a first mode based on a measurement signal of the measurement portion; a second mode portion that operates the engine in a second mode based on a measurement signal of the measurement portion; a determination unit that outputs a request for switching from the first mode to the second mode when it is determined that a switching condition is satisfied, based on a measurement signal of the measurement unit; and a switching unit that receives the switching request and performs mode switching.
The first mode section outputs a signal to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a first air-fuel ratio, and outputs an ignition signal to the ignition section so that the remaining unburned air-fuel mixture is combusted by self-ignition after combustion accompanied by flame propagation is started by forced ignition of the ignition section for a part of the air-fuel mixture; the second mode unit outputs a signal to the fuel injection unit and the air conditioning unit so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a second air-fuel ratio larger than the first air-fuel ratio, and outputs an ignition signal to the ignition unit so that a part of the air-fuel mixture starts combustion accompanied by flame propagation by forced ignition of the ignition unit and thereafter the remaining unburned air-fuel mixture is combusted by self-ignition.
When the switching unit receives the switching request, the switching unit outputs a signal to the air-conditioning unit and the fuel injection unit so that the air-fuel ratio of the mixture becomes a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, and outputs a signal to the swirl generation unit so that the swirl ratio is increased before the switching request; the switching unit may allow the second mode unit to start the second mode when it is determined that the eddy current has reached a predetermined intensity.
The control device for a compression ignition engine disclosed herein includes: a combustion chamber of an engine formed by a cylinder, a piston reciprocating in the cylinder, and a cylinder head closing one end of the cylinder; an air conditioning unit for adjusting an amount of air to be filled into the combustion chamber; a fuel injection unit attached to the cylinder head and injecting fuel supplied into the combustion chamber; an ignition portion that is disposed facing the combustion chamber and ignites an air-fuel mixture in the combustion chamber; a vortex generating unit for generating a vortex in the combustion chamber; a measurement unit that measures a parameter related to operation of the engine; and a control unit connected to the air conditioning unit, the fuel injection unit, the ignition unit, the vortex generation unit, and the measurement unit, respectively, for receiving a measurement signal from the measurement unit, performing calculation, and outputting a signal to the air conditioning unit, the fuel injection unit, the ignition unit, and the vortex generation unit; the control unit includes: a first mode portion that operates the engine in a first mode based on a measurement signal of the measurement portion; a second mode portion that operates the engine in a second mode based on a measurement signal of the measurement portion; a determination unit that outputs a request for switching from the second mode to the first mode when it is determined that a switching condition is satisfied, based on a measurement signal of the measurement unit; and a switching unit that receives the switching request and performs mode switching.
The first mode section outputs a signal to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a first air-fuel ratio, and outputs an ignition signal to the ignition section so that the remaining unburned air-fuel mixture is combusted by self-ignition after combustion accompanied by flame propagation is started by forced ignition of the ignition section for a part of the air-fuel mixture; the second mode unit outputs a signal to the fuel injection unit and the air conditioning unit so that the fuel amount corresponds to the load of the engine and the air-fuel ratio of the air-fuel mixture becomes a second air-fuel ratio larger than the first air-fuel ratio, and outputs an ignition signal to the ignition unit so that a part of the air-fuel mixture starts combustion accompanied by flame propagation by forced ignition of the ignition unit and thereafter the remaining unburned air-fuel mixture is combusted by self-ignition.
When the switching unit receives the switching request, the switching unit outputs a signal to the air-conditioning unit and the fuel injection unit so that the air-fuel ratio of the mixture becomes a stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, and outputs a signal to the swirl generation unit so that the swirl ratio is decreased before the switching request; the switching unit further allows the first mode unit to start the first mode when it is determined that the eddy current has reached a predetermined intensity.
The control unit may include a target torque setting unit that receives the measurement signal from the measurement unit and sets a target torque of the engine; the first mode section outputs signals to the fuel injection section and the air conditioning section so that the fuel amount corresponds to the target torque and the air-fuel ratio of the air-fuel mixture becomes the first air-fuel ratio; the second mode portion outputs a signal to the fuel injection portion and the air conditioning portion so that the fuel amount corresponds to the target torque and the air-fuel ratio of the air-fuel mixture becomes the second air-fuel ratio.
The invention has the following effects:
as described above, according to the control device for a compression ignition engine described above, fuel consumption performance can be ensured at the time of mode switching.
Drawings
Fig. 1 is a diagram illustrating a structure of an engine;
FIG. 2 is a view illustrating a structure of a combustor, an upper view corresponding to a plan view of the combustor, and a lower view being a sectional view taken along line II-II;
FIG. 3 is a plan view illustrating the structure of a combustion chamber and an intake system;
fig. 4 is a block diagram illustrating the structure of a control device of the engine;
FIG. 5 is a diagram illustrating waveforms of SPCCI combustion;
fig. 6 is a diagram illustrating a map (map) of the engine, the upper diagram being a map in a warm state, the middle diagram being a map in a semi-warm state, and the lower diagram being a map in a cold state;
fig. 7 is a diagram illustrating details of the map in a warm state;
fig. 8 is a diagram illustrating a Layer (Layer) structure of a map of the engine;
FIG. 9 is a flow chart illustrating the control flow involved in layer selection for a map;
FIG. 10 is a flowchart illustrating a control flow involved in layer selection for a map different from that of FIG. 9;
fig. 11 is a diagram illustrating a relationship between the atmospheric pressure and the engine water temperature threshold value in the upper diagram, and fig. 11 is a diagram illustrating a relationship between the atmospheric pressure and the intake air temperature threshold value in the lower diagram;
fig. 12 is a flowchart illustrating basic control of the engine;
fig. 13 is a diagram illustrating a configuration example of functional blocks of the ECU relating to switching between layer 2 and layer 3;
FIG. 14 is a flow chart illustrating control involved in a layer 2 to layer 3 handover;
fig. 15 is a diagram illustrating a calculation procedure of the delay (Retard) limit torque;
fig. 16 is a diagram illustrating a calculation procedure of the rich limit torque;
fig. 17 is a flowchart illustrating control involved in the handover of layer 3 to layer 2;
fig. 18 is a timing chart illustrating changes in parameters when layer 2 switches to layer 3;
fig. 19 is a timing chart illustrating changes in parameters when layer 2 switches to layer 3;
fig. 20 is a timing chart illustrating changes in parameters when layer 3 switches to layer 2;
fig. 21 is an explanatory diagram illustrating a magnitude relationship between the SCV opening degree and the EGR valve opening degree between the layers 2 and 3;
fig. 22 is a flowchart illustrating an estimation step of the EGR rate;
description of the symbols:
1, an engine;
10 an ECU (control unit);
10a target torque setting unit;
10b a first mode part;
10c a second mode part;
10d a determination unit;
10e a switching unit;
11 cylinders;
13 a cylinder head;
17 a combustion chamber;
25 spark plugs (ignition portions);
3, a piston;
43 throttle valves (air conditioning portions);
56 a vortex flow control valve;
6 injectors (fuel injection portions);
an SW1 air flow sensor (measuring section);
an SW2 first intake air temperature sensor (measuring section);
an SW3 first pressure sensor (measuring section);
an SW4 second intake air temperature sensor (measuring section);
an SW5 second pressure sensor (measuring section);
an SW6 pressure indicating sensor (measuring section);
an SW7 exhaust gas temperature sensor (measuring section);
SW8 Linear O 2A sensor (measuring section);
SW9 λO 2a sensor (measuring section);
an SW10 water temperature sensor (measuring section);
SW11 crank angle sensor (measuring section);
an SW12 accelerator opening degree sensor (measuring section);
an SW13 intake cam angle sensor (measuring section);
an SW14 exhaust cam angle sensor (measuring section);
an SW15 EGR differential pressure sensor (measuring section);
an SW16 fuel pressure sensor (measuring section);
the SW17 third intake air temperature sensor (measuring section).
Detailed Description
Hereinafter, an embodiment of a control device for a compression ignition engine will be described in detail with reference to the drawings. The following description is an example of an engine and an engine control device.
Fig. 1 is a diagram illustrating a structure of a compression ignition type engine. Fig. 2 is a diagram illustrating a structure of a combustion chamber of the engine. Fig. 3 is a diagram illustrating the structure of the combustion chamber and the intake system. In fig. 1, the intake side is the left side of the drawing, and the exhaust side is the right side of the drawing. The intake side in fig. 2 and 3 is the right side of the drawing, and the exhaust side is the left side of the drawing. Fig. 4 is a block diagram illustrating the configuration of the control device of the engine.
The
(Structure of Engine)
The
A piston 3 is slidably inserted into each cylinder 11. The piston 3 is connected to a
The lower surface of the
The upper surface of the piston 3 is raised toward the top surface of the
The geometric compression ratio of the
An
An
An
An
The intake electric motor S-VT23 and the exhaust electric motor S-VT24 adjust the length of the overlap period in which both the
An
The
The
An ignition plug 25 is attached to the
An
A
A
An electromagnetic clutch 45 is interposed between the
An
A
The ECU10 opens the
When the
In the present configuration example, the supercharging
The
An
An exhaust gas purification system having a plurality of catalytic converters is disposed in the
An
A water-cooled
In the present configuration example, the
In fig. 1 and 4,
The control device for the compression ignition Engine includes an ECU (Engine control unit) 10 for operating the
As shown in fig. 1 and 4, various sensors SW1 to SW17 are connected to the
Air flow sensor SW 1: a flow rate measuring unit disposed downstream of the
first intake air temperature sensor SW 2: a temperature measuring unit disposed downstream of the
first pressure sensor SW 3: a pressure measuring unit that is disposed upstream of the
second intake air temperature sensor SW 4: a temperature measuring unit that is disposed downstream of
second pressure sensor SW 5: a
pressure indication sensor SW 6: a
exhaust gas temperature sensor SW 7: a temperature measuring unit disposed in the
linear O2 sensor SW 8: disposed upstream of the catalytic converter on the
λ O2 sensor SW 9: disposed downstream of the three-
water temperature sensor SW 10: is mounted to the
crank angle sensor SW 11: a measurement unit that is attached to the
accelerator opening degree sensor SW 12: an accelerator opening degree measuring unit that is attached to the accelerator pedal mechanism and measures an accelerator opening degree corresponding to an operation amount of an accelerator pedal;
intake cam angle sensor SW 13: mounted to the
exhaust cam angle sensor SW 14: mounted to the
EGR differential pressure sensor SW 15: a differential pressure measurement device disposed in the
fuel pressure sensor SW 16: a
third intake temperature sensor SW 17: the temperature of the gas in the
The ECU10 determines the operating state of the
The ECU10 outputs electric signals of the calculated control amounts to the
For example, the ECU10 sets a target torque of the
The ECU10 sets the target EGR rate based on the operating state of the
Further, when the EGR rate is large, a relatively large amount of external EGR gas is introduced into the
As described above, the EGR rate, which is the EGR amount, can be adjusted by adjusting the opening degree of the
Further, the ECU10 executes air-fuel ratio feedback control when a predetermined control condition is satisfied. Specifically, the ECU10 is based on linear O
2Sensor SW8 and λ O
2Oxygen concentration in exhaust gas measured by sensor SW9The fuel injection amount of the
The details of the other control of the
(concept of SPCCI Combustion)
The
SPCCI combustion is a morphology as follows: the
By adjusting the heat release amount of the SI combustion, the temperature unevenness in the
In SPCCI combustion, the heat release during SI combustion is gentler than the heat release during CI combustion. The slope of the rise in the waveform of the heat release rate in the SPCCI combustion as illustrated in fig. 5 is smaller than the slope of the rise in the waveform of the CI combustion. Also, the pressure fluctuation (dp/d θ) in the
When the unburned air-fuel mixture self-ignites after the SI combustion starts, the slope of the waveform of the heat release rate may change from small to large at the self-ignition timing. The waveform of the heat release rate sometimes has an inflection point X at the timing θ CI at which CI combustion starts.
After the CI combustion is started, the SI combustion is performed simultaneously with the CI combustion. The heat release from CI combustion is greater than SI combustion and therefore the heat release rate is relatively increased. However, CI combustion is performed after compression top dead center, and therefore the slope of the waveform of the heat release rate is prevented from becoming excessively large. The pressure fluctuation (dp/d theta) during CI combustion is also relatively gradual.
The pressure fluctuation (dp/d θ) can be used as an index indicating the combustion noise. As described above, the SPCCI combustion can reduce the pressure fluctuation (dp/d θ), and thus can avoid excessive combustion noise. The combustion noise of the
SPCCI combustion ends by the end of CI combustion. CI combustion has a shorter combustion period than SI combustion. The combustion end period of SPCCI combustion is earlier than SI combustion.
First heat release rate part Q formed by SI combustion of heat release rate waveform of SPCCI combustion SIAnd a second heat release rate part Q formed by CI combustion CIFormed in such a way as to be connected in this order.
Here, the SI rate is defined as a parameter showing the characteristics of the SPCCI combustion. The SI rate is defined as an index related to the ratio of the amount of heat generated by SI combustion relative to the total amount of heat generated by SPCCI combustion. The SI rate is a ratio of heat generated by two kinds of combustion having different combustion forms. The higher the SI rate, the higher the SI combustion ratio, and the lower the SI rate, the higher the CI combustion ratio. It is also possible that the SI rate is defined as the ratio of the amount of heat generated by SI combustion relative to the amount of heat generated by CI combustion. That is, in the SPCCI combustion, the crank angle at which CI combustion starts may be set as the CI combustion start timing θ CI, and in the
The
When a strong vortex is generated in the
Further, the strength of the swirl flow can be adjusted by adjusting the opening degree of the
(operating region of Engine)
Fig. 6 and 7 illustrate maps for controlling the
The
Each of the
The
The
Here, the low rotation region, the middle rotation region, and the high rotation region may be the low rotation region, the middle rotation region, and the high rotation region when the entire operation region of the
The low load region may be a region including a light load operating state, the high load region may be a region including a fully open load operating state, and the intermediate load may be a region between the low load region and the high load region. The low load region, the intermediate load region, and the high load region may be the low load region, the intermediate load region, and the high load region when the full operation region of the
(operation of Engine in Each zone)
Hereinafter, the operation of the
(Low load region)
When the
In order to improve the fuel consumption performance of the
The vortex generating portion forms a strong vortex in the
The
The fuel concentration of the air-fuel mixture in the central portion of the
The air-fuel ratio (a/F) of the mixture is leaner than the stoichiometric air-fuel ratio (i.e., the air excess ratio λ > 1) in the
After the fuel injection is completed, the
As described above, the fuel concentration of the air-fuel mixture in the central portion is relatively high, and therefore, the ignitability is improved and the SI combustion propagating through the flame is stabilized. By stabilizing the SI combustion, the CI combustion is started at an appropriate timing. In SPCCI combustion, the controllability of CI combustion is improved. The generation of combustion noise is suppressed. The fuel consumption performance of the
(middle and high load region)
The
The
In the middle and high load range a2 and the high load middle rotation range A3, the
The air-fuel ratio (A/F) of the air-fuel mixture in the
Since the EGR gas is introduced into the
When the load of the
When the load of the
After the fuel injection, the
The exhaust gas discharged from the
(operation of supercharger)
Here, as shown in the
In each of the high-load medium rotation region A3, the high-load low rotation region a4, and the high rotation region a5, the
(high rotation region)
When the rotation speed of the
Therefore, when the
The
The
The air-fuel ratio (A/F) of the mixture gas is substantially equal to the theoretical air-fuel ratio (A/F ≈ 14.7) throughout the
The
After the fuel injection ends, the
(layer structure of map)
Layer 2 is a
Layer 3 is a layer overlying layer 2. Layer 3 corresponds to the low load region a1 of the
The
When the atmospheric pressure is equal to or higher than a predetermined atmospheric pressure threshold value (for example, 95 kPa), the wall temperature of the
When the wall temperature of the
When the wall temperature of the
The wall temperature of the
SPCCI combustion proceeds as described above by generating a strong swirl in the
The CI combustion in the SPCCI combustion is performed from the outer peripheral portion to the central portion of the
When the wall temperature of the
When the wall temperature of the
When the wall temperature of the
However, if the atmospheric pressure is low, the amount of air filling the
Further, the stability of the SI combustion is higher as the swirl becomes stronger, but since the cooling loss via the inner wall surface of the
For example, the layer 2 in which the air-fuel mixture of substantially the stoichiometric air-fuel ratio is burned is more stable in SI combustion than the layer 3 in which the leaner air-fuel mixture is burned. Therefore, in the layer 2, the strength of the vortex is weakened as compared with the layer 3 within a range in which the stability of the SI combustion is ensured, whereby a decrease in thermal efficiency due to the cooling loss can be suppressed (see fig. 8).
Next, a control example related to the layer selection of the map executed by the ECU10 will be described with reference to the flowchart of fig. 9. First, in step S91 after the start, the ECU10 reads signals of the sensors SW1 to
In step S93, ECU10 determines whether or not the wall temperature of
The ECU10 selects the
In step S94, ECU10 determines whether the atmospheric pressure is equal to or greater than an atmospheric pressure threshold. If the determination at step S94 is yes, the flow proceeds to step S97, and if not, the flow proceeds to step S96. As described above, the ECU10 selects the
The ECU10 selects
Fig. 10 shows a flow chart relating to layer selection different from fig. 9. First, in step S101 after the start, the ECU10 reads signals of the sensors SW1 to
In step S103, the ECU10 determines whether the engine water temperature is equal to or higher than a predetermined engine water temperature threshold and the intake air temperature is equal to or higher than a predetermined intake air temperature threshold.
Here, the engine water temperature threshold value is set based on the
Fig. 11 is a lower view illustrating a
Returning to the flowchart of fig. 10, if the determination at step S103 is yes, the flow proceeds to step S104, and if not, the flow proceeds to step S106.
The ECU10 selects
The ECU10 selects
(basic control of Engine)
Fig. 12 shows a flow of basic control of the
The ECU10 also controls the SPCCI combustion using two parameters, SI rate and θ ci, when performing the SPCCI combustion. Specifically, the ECU10 determines a target SI rate and a target θ ci corresponding to the operating state of the
In step S121 of the flow of fig. 12, the ECU10 reads signals of the sensors SW1 to SW17, and in the next step S122, the ECU10 sets a target acceleration based on the accelerator opening. In step S123, the ECU10 sets a required target torque to achieve the set target acceleration.
In step S124, the ECU10 determines the operating state of the
Steps S125 to S128 correspond to steps of setting control target values of the respective devices when the
Steps S129 to S1212 correspond to steps of setting control target values of the respective devices when the
In step S1213, the ECU10 adjusts the throttle opening of the
In step S1214, the ECU10 causes the
(switching between layer 2 and layer 3)
As described above, the
Here, the air-fuel ratio of the mixture is made the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio in the layer 2, and the air-fuel ratio of the mixture is made the air-fuel ratio leaner than the stoichiometric air-fuel ratio in the layer 3 (that is, the value of the air-fuel ratio is made larger). Therefore, when the operation of the
As the amount of air charged into the
Similarly, when switching from layer 3 to layer 2, as the amount of air charged into the
In order to suppress the deterioration of the exhaust emission performance, it is conceivable to maintain the air-fuel ratio of the mixture at the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio at the time of transition of the switching of the operation of the
Therefore, in the
Also, the present inventors have found a new problem relating to fuel consumption performance after further research, and newly created means for solving the problem.
As described above, in the layer 2, the strength of the eddy current is weakened as compared with the layer 3, and thereby the reduction of the thermal efficiency due to the cooling loss can be suppressed.
Therefore, when the operation of the
In this way, when switching between the layers 2 and 3, it is necessary to change not only the air-fuel ratio of the mixture but also the strength of the swirl generated in the
The same problem occurs when the operation of the
Therefore, in the
Fig. 13 shows the structure of the functional blocks of the
The target
The
The second mode portion 10c outputs signals to at least the
The
The
Fig. 14 shows a flow of layer 2 to layer 3 handover. First, in step S141, the ECU10 reads signals of the sensors SW1 to SW17, and in the next step S142, the ECU10 determines whether or not switching from the layer 2 to the layer 3 is necessary.
Specifically, the
As described above, when switching from the layer 2 to the layer 3 is performed, as shown in fig. 8 and 21, the air-fuel ratio of the mixture changes from the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio to a leaner air-fuel ratio, the EGR rate changes from the high EGR rate to the low EGR rate, and the swirl changes from the weak swirl to the strong swirl.
In step S143, the ECU10 adjusts the opening degree of the
In the next step S144, the ECU10 determines whether or not the eddy current has reached a predetermined intensity. Specifically, in this step S144, the ECU10 determines whether the SCV opening degree substantially matches the SCV threshold value. If the subsequent step is proceeded to in the case where the determination is no, the strength of the swirl flow may be temporarily excessively small, possibly making it impossible to maximize the thermal efficiency of the
Therefore, if the determination at step S144 is no, the flow returns to step S144 (that is, the determination at step S144 is repeated until the determination is yes). On the other hand, if yes, the flow proceeds to step S145 and step S148.
The SCV threshold is preset and stored in the memory 102 of the
The SCV threshold may or may not coincide with the target SCV opening degree. In the latter case, the SCV threshold value may be set to a value larger than the target SCV opening degree. If the SCV threshold value ≠ target SCV opening degree, the SCV opening degree continues to decrease until reaching the target SCV opening degree after it becomes yes in step S144.
Before switching from the layer 2 to the layer 3, the strength of the swirl is increased by the
As will be described later, the opening degree of the
By changing the opening degree of the
In addition, the ECU10 may estimate the EGR rate in the intake manifold and predict the estimation result as the EGR rate achieved in the
Fig. 22 is a flowchart illustrating an EGR rate estimation procedure.
In step S221 of fig. 22, the ECU10 reads signals of the respective sensors. Specifically, in step S221, ECU10 reads at least the detection signal of airflow sensor SW1 and linear O
2A detection signal of the sensor SW8 and a detection signal of the EGR differential
In the next step S222, the ECU10 calculates the flow rate of the EGR gas passing through the
In the next step S223, the ECU10 bases on the linear O 2The EGR gas concentration in the exhaust gas (the EGR rate of the exhaust gas) is calculated from the oxygen concentration in the exhaust gas, which is the detection result of the sensor SW 8.
Then, in step S224, the ECU10 calculates the EGR rate in the intake manifold based on the fresh air amount obtained from the detection result of the air flow sensor SW1, the flow rate of the EGR gas calculated in step S222, and the EGR gas concentration calculated in step S223. The ECU10 regards the EGR rate thus calculated as the EGR rate achieved in the
Returning to the flow of fig. 14, the flow of steps S145 to S147 is performed in parallel with the flow of steps S148 to S1418. These flows are executed by the
In step S145, the ECU10 sets the target air amount in layer 3, and in the next step S146, the ECU10 sets the target throttle opening based on the set target air amount. Also, in step S147, the ECU10 adjusts the opening degree of the
In step S148, the ECU10 reads the amount of air actually filled in the
The retard limit torque means the torque of the
The rich limit torque means the torque of the
Fig. 15 is a block diagram showing a procedure of calculating the delay limit torque. The ECU10 calculates the delay bound torque based on the thermal efficiency of the
The ECU10 calculates the mfb50 position of the retard limit from the engine speed, the charging efficiency, and the
Although
The ECU10 sets the efficiency relative to MBT based on the mfb50 position of the delay bound and the preset map 152. Map 152 specifies the mfb50 position of the delay bound versus efficiency relative to MBT. The efficiency with respect to MBT is "1" when the mfb50 position of the retard limit is a predetermined crank angle on the advance side, and approaches zero as the mfb50 position of the retard limit is retarded.
The map 152 defines a reference curve (see a solid line) that is corrected in accordance with the operating state of the
The reference curve of the map 152 shown by the solid line decreases downward as shown by the broken line as the efficiency gradient determined based on the map 153 increases, and increases upward as the efficiency gradient decreases. The ECU10 determines the efficiency with respect to MBT at the delay bound (see the arrow of the chain line) based on the map 152 corrected by the efficiency slope.
The ECU10 determines the thermal efficiency at the delay bound based on the efficiency with respect to the MBT and the map 154 set in advance. The map 154 specifies the relationship between the rotation speed of the
When the ECU10 calculates the thermal efficiency at the delay limit, it calculates a torque (i.e., delay limit torque) corresponding to the thermal efficiency based on the thermal efficiency at the delay limit, the volume of each cylinder, and the heat release amount of the injection amount for making the air-fuel ratio of the mixture stoichiometric or substantially stoichiometric.
Fig. 16 is a block diagram showing a procedure of calculating the rich limit torque. The ECU10 calculates the rich limit torque based on the thermal efficiency of the
The ECU10 calculates the mfb50 position of the rich limit from the engine speed, the rich limit injection amount, and the map 161 set in advance. Map 161 defines the relationship between the engine speed, the rich limit injection amount, and the position of
The maps 162, 163, and 164 of fig. 16 are the same as the maps 152, 153, and 154 of fig. 15, respectively.
The ECU10 sets the efficiency with respect to MBT based on the mfb50 position of the rich limit and the map 162 set in advance (see the arrow of the chain line).
The reference curve (solid line) of the map 162 is corrected by an efficiency slope determined from the map 163 and the operating state of the
The ECU10 determines the thermal efficiency at the rich limit based on the efficiency with respect to MBT and a map 164 set in advance. The map 164 specifies the relationship between the rotation speed of the
When the thermal efficiency at the rich limit is calculated, the ECU10 calculates a torque corresponding to the thermal efficiency (i.e., rich limit torque) based on the thermal efficiency at the rich limit, the volume of each cylinder, and the heat release amount of the rich limit injection amount.
Returning to the flowchart of fig. 14, in step S1410, the ECU10 determines whether the calculated rich limit torque does not match the target torque. If yes, that is, if the calculated rich limit torque does not match the target torque, the flow proceeds to step S1411. If it is determined as no, that is, if the calculated rich limit torque and the target torque are equal or substantially equal, the flow proceeds to step S1417.
If the determination at step S1410 is yes, the amount of air filled in the
In the next step S1412, a target ignition timing is set based on the target fuel injection amount and the target torque set in step S1411. The target ignition timing set here is retarded in a manner to reduce the amount of torque that rises due to an increase in the amount of fuel. In SPCCI combustion, the timing for starting CI combustion is retarded as well as the timing for starting SI combustion by retarding the ignition timing. The torque of the
In step S1413, the ECU10 determines whether the delay limit torque calculated in step S149 is equal to or less than the target torque. If the retard limit torque is equal to or less than the target torque, the torque of the
On the other hand, if the determination in step S1413 is no, that is, if the retard limit torque exceeds the target torque, the torque of the
Therefore, if the determination at step S1413 is no, the flow proceeds to step S1416, and the ECU10 increases the load on the alternator at step S1416. Thereby, the torque of the
The flow repeats steps S1411 to S1416 until the determination of step S1410 is no. When the amount of air charged into the
In step S1417, the ECU10 makes a transition to layer 3. Specifically, the ECU10 reduces the increased injection amount in such a manner that the air-fuel ratio of the mixture becomes leaner than the stoichiometric air-fuel ratio. The injection amount becomes an injection amount corresponding to the target torque. The ECU10 advances the retarded ignition timing.
In the next step S1418, the ECU10 sets the layer 3 switching flag to 0 to complete the switching from layer 2 to layer 3.
As described above, by increasing the intensity of the eddy current in advance before switching from the layer 2 to the layer 3, the operation under the layer 3 can be started without excessively decreasing the intensity of the eddy current. This maximizes the thermal efficiency of the
Further, by starting the increase of the air amount when the EGR gas amount is decreased to the predetermined amount, the operation in the layer 3 can be started in a state where the adjustment of the intensity of the swirl flow is completed. In this way, the thermal efficiency of the
Further, since the combustion stability of the SPCCI combustion is improved by intensifying the swirl generated in the
Fig. 17 shows a flow of layer 3 to layer 2 handover. First, in step S171, the ECU10 reads signals of the sensors SW1 to SW17, and in the next step S172, the ECU10 determines whether or not switching from the layer 3 to the layer 2 is necessary.
Specifically, the
When the layer 3 is switched to the layer 2, as shown in fig. 8 and 21, the air-fuel ratio of the mixture changes from an air-fuel ratio leaner than the stoichiometric air-fuel ratio to the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, the EGR rate changes from the low EGR rate to the high EGR rate, and the swirl changes from the strong swirl to the weak swirl.
Steps S173 and S174 are related to the opening degree adjustment of the
In step S173, the ECU10 adjusts the opening degree of the
Since the layer 2 combusts the mixture SPCCI at the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, combustion stability is more easily ensured than that of the layer 3. Therefore, unlike when the layer 2 is switched to the layer 3, the opening adjustment of the
Alternatively, the opening degree of the
Alternatively, the opening degree of the
In the present configuration example, the opening degree of the
In the next step S174, the ECU10 determines whether or not the eddy current is reduced to a predetermined intensity. Specifically, in step S174, the ECU10 determines whether the SCV opening degree substantially matches the SCV threshold value. If the operation under the layer 2 is started in the case where the determination is no, the strength of the eddy current may be temporarily excessive, and the cooling loss may be temporarily increased. This is disadvantageous from the viewpoint of fuel consumption performance.
Therefore, if the determination at step S174 is no, the flow returns to the determination at step S174, and if the determination is yes, the flow returns. That is, the ECU10 repeats step S174 until the determination is yes.
The SCV threshold is preset and stored in the memory 102 of the
The SCV threshold may or may not coincide with the target SCV opening degree. In the latter case, the SCV threshold value may be set to a value smaller than the target SCV opening degree. If the SCV threshold value ≠ target SCV opening degree, the SCV opening degree continues to increase until reaching the target SCV opening degree after it becomes yes in step S174.
Before switching from layer 3 to layer 2, the strength of the vortex is reduced by the
In step S175, the ECU10 sets the target air amount in level 2, and in the next step S176, the ECU10 sets the target throttle opening based on the set target air amount. In step S177, the ECU10 adjusts the opening degree of the
In step S178, the ECU10 reads the amount of air actually filled in the
In step S1710, the ECU10 determines whether the calculated rich limit torque matches the target torque. If it is determined as no, that is, if the calculated rich limit torque does not match the target torque, the flow proceeds to step S1711.
In step S1711, the ECU10 continues to layer 3. The injection amount is maintained for a reduction in the amount of air actually filled in the
If the determination at step S1710 is yes, that is, if the calculated rich limit torque matches or substantially matches the target torque, if the amount of air filled in the
In step S1712, the ECU10 sets a target fuel injection amount at which the air-fuel ratio of the mixture becomes the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio, based on the actual air amount. The target fuel injection amount set here is increased as compared to the injection amount required for the engine to output the target torque.
In the next step S1713, a target ignition timing is set based on the target fuel injection amount and the target torque set in step S1712. The target ignition timing set here is retarded in a manner to reduce the degree corresponding to the amount of torque that is raised by the increase in the amount of fuel. As described above, in the present configuration example, the ECU10 performs the retardation of the ignition timing together with the opening degree adjustment of the
In step S1714, the ECU10 determines whether the delay bound torque calculated in step S179 is equal to or less than the target torque. When the retard limit torque is equal to or less than the target torque, the torque of the
In step S1718 following step S1716, the ECU10 determines whether or not the amount of air filled in the
In step S1719, the ECU10 transitions to layer 2. The
In step S1719, the ECU10 ends the increase in the injection amount, and retards the ignition timing until the SCV opening reaches the target SCV opening. In the next step S1720, the ECU10 sets the floor 2 switching flag to 0 to complete the switching from floor 3 to floor 2.
In this way, by reducing the intensity of the eddy current in advance before switching from the layer 3 to the layer 2, the operation under the layer 2 can be started without excessively increasing the intensity of the eddy current. In this way, the cooling loss due to the swirl can be suppressed while ensuring the stability of the SI combustion, and the fuel consumption performance of the
Next, switching between layer 2 and layer 3 is described with reference to timing charts shown in fig. 18 to 20. The time in these timing diagrams moves from left to right in the page. In the switching between the layers 2 and 3, it is assumed that the target torque of the
Fig. 18 illustrates changes in parameters when switching from layer 2 to layer 3 is performed. When the layer 3 switching flag is switched to 1 at time t11 (see fig. 18 a), the opening degrees of the
When the SCV opening degree reaches the predetermined SCV threshold value at time t12, the opening degree of
When the opening degree of the
Since the injection amount of fuel is increased, the ignition timing is retarded so that the torque of the
In the example shown in fig. 18, the retard limit torque is lower than the target torque, and the torque of the
When the rich limit torque is the target torque at time t13, the increase in fuel and the retardation of the ignition timing are ended. Although the
Instead of comparing the rich limit torque with the target torque, the ECU10 may end the increase in fuel and the delay in ignition timing based on the virtual air-fuel ratio. That is, the ECU10 may end the increase of fuel and the retardation of the ignition timing when determining that the virtual air-fuel ratio has reached the predetermined threshold (rich limit threshold).
By allowing the air-fuel ratio of the air-fuel mixture to be rich with fuel to the extent that RawNOx is not generated, the increase in fuel and the retardation of the ignition timing can be ended early. Contributing to improvement of the fuel consumption performance of the
Thereafter, at time t14, the air amount reaches the target air amount, and the switching to layer 3 is completed. Further, the increase of the fuel and the delay of the ignition timing may be held until the air amount reaches the target air amount, and the increase of the fuel and the delay of the ignition timing may be ended by the air amount reaching the target air amount.
Fig. 19 also illustrates changes in the parameters when the layer 2 is switched to the layer 3. When the layer 3 switching flag is switched to 1 at time t21 (see fig. 19 a), the opening degrees of the
When the SCV opening degree reaches the predetermined SCV threshold value at time t22, the opening degree of
When the opening degree of the
At time t23, the delay bound torque may exceed the target torque. That is, the retard amount of the ignition timing reaches the retard limit (see the dashed-dotted line of 19 h). Since the ignition timing cannot be further retarded, the ECU10 maintains the retard amount of the ignition timing. That is, the delay of the ignition timing is suppressed. Thereby, the
At time t24, when the rich limit torque becomes the target torque (or when the virtual air-fuel ratio becomes a predetermined threshold), the increase in fuel and the retardation of the ignition timing are ended. Thereafter, at time t25, the air amount reaches the target air amount, and the switching to layer 3 is completed.
When the tier 2 is switched to the tier 3, the delay between the increase in the fuel amount and the ignition timing may be continued until the air amount reaches the target air amount (until time t14 or t 25), and the delay between the increase in the fuel amount and the ignition timing may be terminated when the air amount reaches the target air amount.
Further, the increase of fuel and the retardation of the ignition timing may be finished at the timing when the retard limit torque reaches the target torque, and the transition may be made to the layer 3.
Fig. 20 illustrates changes in parameters when performing a handover of layer 3 to layer 2. When the floor 2 switching flag is switched to 1 at time t31 (see fig. 20 a), the opening degree of the
When the opening degree of the
At time t32, when the rich limit torque reaches the target torque, the fuel injection amount is increased so that the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio (see 20g and 20 i). The exhaust gas can be purified by the three-way catalyst.
As the amount of fuel increases, the ignition timing lags behind (refer to 20 h). As a result, the torque of the
At time t32, the opening degrees of the
When the air amount reaches the target air amount at time t33, the increase in fuel and the delay in the ignition timing are finished, and the switching to the layer 2 is completed.
In addition, when the tier 3 is switched to the tier 2, the increase in the fuel amount and the delay in the ignition timing may be started (from time t 31) simultaneously with the start of the opening adjustment of the
(other embodiment)
In addition, the technology disclosed herein is not limited to being applied to the