阅读说明：本技术 内燃机的控制系统 (Control system for internal combustion engine ) 是由 永崎岳人 田中大二郎 高须康嗣 于 2019-06-24 设计创作，主要内容包括：一种内燃机的控制系统,在燃烧室内生成正滚流的中央喷射发动机中抑制高负荷区域中的发动机输出的降低。中央喷射发动机是指在燃烧室的顶部的大致中央具备直喷喷射器和点火装置的发动机。正滚流以在燃烧室的顶部侧从进气口侧朝向排气口侧,在活塞的顶部侧从排气口侧朝向进气口侧的方式流动。ECU基于发动机负荷算出喷射时期。在第1喷射控制中,发动机负荷越高则使喷射时期的结束曲轴角越迟。(A control system for an internal combustion engine suppresses a decrease in engine output in a high load region in a center-injection engine that generates a positive tumble flow in a combustion chamber. The central injection engine is an engine provided with a direct injector and an ignition device at substantially the center of the top of a combustion chamber. The positive tumble flows from the intake port side toward the exhaust port side on the top side of the combustion chamber and from the exhaust port side toward the intake port side on the top side of the piston. The ECU calculates an injection timing based on the engine load. In the injection control 1, the higher the engine load, the later the end crank angle of the injection timing.)

1. A control system for an internal combustion engine, comprising:

a combustion chamber of an internal combustion engine that generates a positive tumble flow;

an ignition device provided substantially at the center of the top of the combustion chamber;

a direct injection injector disposed adjacent to the ignition device; and

a control unit that controls an injection timing of the direct injector based on a load of the internal combustion engine,

the control unit is used for controlling the operation of the electronic device,

in a low load region of the internal combustion engine, the injection timing is controlled to a crank angle section corresponding to an intake stroke,

in a high load region of the internal combustion engine, at least an end crank angle of the injection timing is controlled to be at a retard side with respect to the end crank angle in the low load region,

the end crank angle in the high load region includes a crank angle interval corresponding to a first half of a compression stroke.

2. The control system of an internal combustion engine according to claim 1,

further comprises a fuel pipe for supplying the pressurized fuel to the direct injector,

the control unit further controls the pressure of the fuel in the fuel piping based on the load of the internal combustion engine in the high load region,

as the load of the internal combustion engine becomes higher, the pressure becomes lower.

3. The control system of an internal combustion engine according to claim 1,

further, in the high load region, the control means controls the start crank angle of the injection timing to be at a delay side from the start crank angle in the low load region,

the start crank angle in the high load region is included in a crank angle interval corresponding to an intake stroke.

Technical Field

The present invention relates to a control system for an internal combustion engine.

Background

Japanese patent application laid-open publication No. 2011-012555 discloses a system for controlling an engine including an injector (hereinafter, also referred to as a "direct injector") for directly injecting fuel into a combustion chamber. This conventional system changes the injection timing of the direct injector according to the operating state of the engine. Specifically, in the conventional system, when the operating state is in the high load region, the injection timing is advanced.

Fuel injection from the direct injector is performed in the intake stroke. Therefore, when the injection timing approaches the bottom dead center, the injected fuel directly collides with the cylinder wall surface and adheres to the cylinder wall surface, thereby diluting the engine oil (lubricating oil). In the high load region, the fuel injection amount increases, so that the amount of fuel adhering to the cylinder wall surface also increases as the injection timing approaches the bottom dead center. In this regard, if the injection timing is advanced in the high load region, the amount of fuel deposited can be reduced to suppress dilution of the engine oil.

Disclosure of Invention

Problems to be solved by the invention

Consider a central injection engine that generates tumble flow within the combustion chamber. The central injection engine is an engine provided with a direct injector and an ignition device at substantially the center of the top of a combustion chamber. The tumble flow is assumed to flow from the intake port side toward the exhaust port side on the top side of the combustion chamber (that is, the bottom side of the cylinder head) and from the exhaust port side toward the intake port side on the top side of the piston. Hereinafter, the tumble flow flowing in such a direction is defined as "positive tumble flow".

The engine constituting the above-described conventional system includes a direct injector in a side portion of the combustion chamber, and a cylinder wall surface is located forward in an injection direction. In contrast, in the center-injection engine, the piston crown is positioned forward in the injection direction. Therefore, if the injection control similar to that of the above-described conventional system is performed when the operating state of the center-injection engine is in the high load region, the following problems occur. That is, if the injection timing is advanced in the high load region, the injected fuel is likely to adhere to the piston crown.

Further, another problem arises when injection control is performed in reverse to the above-described injection control in order to reduce the amount of fuel deposited on the piston crown portion. That is, if the injection timing is retarded in the high load region, the positive tumble flow in the combustion chamber is disturbed from the middle of the intake stroke. As a result, although the engine output is reduced in the high load region where high output is expected.

The present invention has been made in view of at least one of the above problems, and an object thereof is to suppress a decrease in engine output in a high load region in a central injection engine in which a positive tumble flow is generated in a combustion chamber.

Means for solving the problems

The invention of claim 1 is a control system for an internal combustion engine for solving the above problems, and has the following features.

The control system includes a combustion chamber of an internal combustion engine, an ignition device, a direct injector, and a control unit.

Generating a positive tumble flow in the combustion chamber.

The ignition device is disposed substantially in the center of the top of the combustion chamber.

The direct injection injector is disposed adjacent to the ignition device.

The control unit is configured to control an injection timing of the direct injector based on a load of the internal combustion engine.

The control unit is configured to control the operation of the motor,

in a low load region of the internal combustion engine, the injection timing is controlled to a crank angle section corresponding to an intake stroke,

in a high load region of the internal combustion engine, at least an end crank angle of the injection timing is controlled to be at a retard side of the end crank angle in the low load region.

The end crank angle in the high load region includes a crank angle interval corresponding to a first half of a compression stroke.

The invention of claim 2 is also characterized in that in the invention of claim 1.

The control system is further provided with a fuel pipe.

The fuel pipe is configured to supply fuel in a pressurized state to the direct injector.

The control unit is further configured to control the pressure of the fuel in the fuel line in the high load region based on a load of the internal combustion engine.

As the load of the internal combustion engine becomes higher, the pressure becomes lower.

The invention of claim 3 is also characterized in that in the invention of claim 1.

The control means is further configured to control a start crank angle of the injection timing to be at a delay side from the start crank angle in the low load region in the high load region.

The start crank angle in the high load region includes a crank angle interval corresponding to a crank angle of an intake stroke.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the invention 1, the end crank angle of the injection period in the high load region is retarded to the first half of the compression stroke. If the end crank angle is delayed to the first half of the compression stroke, the positive tumble flow may start to be disturbed from the middle of the intake stroke. However, the present inventors obtained the following findings: in the center injection engine, if the end crank angle is delayed to the first half of the compression stroke, an advantage over this disadvantage can be obtained. That is, if the end crank angle is retarded to the first half of the compression stroke, the highly turbulent state of the air-fuel mixture is maintained immediately before ignition. Therefore, according to the invention 1, the output reduction of the engine in the high load region can be suppressed by the advantage over the above-described disadvantage.

According to the invention of claim 2, in the high load region, the pressure of the fuel in the fuel pipe is controlled to a low value as the load of the internal combustion engine becomes higher. Therefore, the end crank angle can be delayed to the first half of the compression stroke.

According to the 3 rd aspect of the present invention, the start crank angle of the injection timing in the high load region is retarded within the range of the crank angle section corresponding to the intake stroke. Therefore, the end crank angle can be delayed to the first half of the compression stroke without changing the pressure of the fuel in the fuel line.

Drawings

Fig. 1 is a diagram illustrating a system configuration of an internal combustion engine according to an embodiment of the present invention.

Fig. 2 is a diagram illustrating a relationship between a lift amount of an intake valve and a tumble ratio.

Fig. 3 is a diagram for explaining a problem in the case where the injection period is delayed toward the BDC side with an extension of the injection period.

Fig. 4 is a diagram for explaining a problem in the case where the injection timing is advanced to the TDC side with an extension of the injection period.

Fig. 5 is a diagram illustrating an outline of the fuel injection control according to the present embodiment.

Fig. 6 is a diagram illustrating an outline of another fuel injection control according to the present embodiment.

Fig. 7 is a diagram illustrating a state of disturbance of the air-fuel mixture in the compression stroke.

Fig. 8 is a diagram for explaining a specific example of the fuel injection control (the 1 st injection control) according to the present embodiment.

Fig. 9 is a diagram for explaining a specific example of another fuel injection control (injection control No. 2) according to the present embodiment.

Description of the reference symbols

10: an internal combustion engine;

12: a combustion chamber;

14: a spark plug;

16: an ignition coil;

18: a direct injection injector;

20: a fuel pump;

22: an air inlet;

24: an exhaust port;

26: a throat;

30：ECU；

32: a crankshaft angle sensor;

34: a fuel pressure sensor;

TF: positive tumble flow.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in the embodiments described below, when numerical values such as the number, the quantity, the amount, the range, and the like of each element are mentioned, the present invention is not limited to the mentioned numerical values except for the case where the numerical values are specifically indicated and the case where the numerical values are clearly specified in principle. The structures, steps, and the like described in the embodiments shown below are not necessarily essential to the present invention, except for the case where they are specifically shown or the case where they are clearly specified in principle.

1. Description of the constitution of the System

Fig. 1 is a diagram illustrating a system configuration of an internal combustion engine according to an embodiment of the present invention. The system shown in fig. 1 includes an internal combustion engine (hereinafter, also referred to as "engine") 10 mounted on a vehicle. The engine 10 is a four-stroke cycle engine. The engine 10 is also a central injection engine. The engine 10 is also a supercharged engine equipped with a supercharging system. The supercharging system is, for example, a system that compresses intake air using energy of exhaust gas of the engine 10. However, such a supercharging system is not essential to the present invention, and therefore, illustration thereof is omitted.

The engine 10 has a plurality of cylinders. However, only one of the cylinders is depicted in FIG. 1. A combustion chamber 12 is formed in each cylinder. The combustion chamber 12 is generally defined as a space surrounded by the bottom surface of the cylinder head, the wall surface of the cylinder block, and the top surface of the piston.

A spark plug 14 is mounted on the top of the combustion chamber 12. The mounting position of the spark plug 14 is substantially the center of the top portion. The ignition plug 14 is connected to an ignition coil 16 that applies a high voltage to the ignition plug 14. The ignition plug 14 and the ignition coil 16 constitute an ignition device. When the ignition coil 16 is driven by the ECU30, a discharge spark is generated at the ignition plug 14.

A direct injector 18 is also mounted on the top of the combustion chamber 12. The direct injector 18 is mounted closer to the intake port 22 than the ignition plug 14. The direct injector 18 is connected to a fuel supply system including at least a fuel pump 20. The fuel pump 20 pressurizes fuel drawn from a fuel tank and discharges the fuel to a fuel pipe. When the direct injector 18 is driven by the ECU30, the pressurized fuel is injected from the direct injector 18. A plurality of injection holes are radially formed in the tip end portion of the direct injector 18. Therefore, the pressurized fuel is radially injected.

An intake port 22 and an exhaust port 24 communicate with the combustion chamber 12. The intake port 22 extends substantially straight from upstream toward downstream. The cross-sectional area of the flow path of the intake port 22 is reduced at a throat portion 26 which is a connecting portion with the combustion chamber 12. The shape of the throat portion 26 is such that intake air drawn into the combustion chamber 12 from the intake port 22 generates a positive tumble flow TF. The positive tumble flow TF flows from the intake port 22 side toward the exhaust port 24 side on the top side of the combustion chamber 12, and from the exhaust port 24 side toward the intake port 22 side on the top surface side of the piston.

The system shown in fig. 1 further includes an ECU (Electronic Control Unit) 30 as a Control device. The ECU30 includes a RAM (Random Access Memory), a ROM (Read only Memory), a CPU (Central Processing Unit), and the like. ECU30 performs acquisition processing of signals from various sensors mounted on the vehicle.

The various sensors include at least a crank angle sensor 32 that detects the rotation angle of the crankshaft, and a fuel pressure sensor 34 that detects the pressure of fuel in the fuel line (hereinafter also referred to as "fuel pressure"). The ECU30 processes the signals of the respective sensors taken in and operates the various actuators according to a predetermined control program. The actuators operated by the ECU30 include at least the ignition coil 16, the direct injection injector 18, and the fuel pump 20.

2. Features of Engine control according to embodiments

The engine control by the ECU30 includes fuel injection control of the direct injector 18. In the fuel injection control, the ECU30 calculates the fuel injection amount based on the operating state of the engine 10. The operating state is determined by the speed and load of the engine 10. Basically, the fuel injection amount is set to a larger value as the engine speed is higher, and the fuel injection amount is set to a larger value as the engine load is higher. Further, the ECU30 calculates the injection timing based on the engine load. The injection timing is basically set in a crank angle section corresponding to the intake stroke, and is set to the retard side as the engine load becomes higher.

2.1 relationship between valve Lift and tumble ratio

In the present embodiment, the state of the air-fuel mixture immediately before ignition is improved by the positive tumble flow TF generated in the combustion chamber 12. Fig. 2 is a diagram illustrating a relationship between a lift amount of an intake valve and a tumble ratio (the engine speed is also set constant). The tumble ratio is defined as a value obtained by dividing the angular velocity of the positive tumble flow TF by the rotation speed of the engine. As shown in fig. 2, when the lift amount increases with the opening of the intake valve, the tumble ratio increases. The tumble ratio is highest near the crank angle at which the lift amount becomes maximum. The tumble ratio decreases with the closing of the intake valve. The tumble ratio temporarily rises in the compression stroke. This is a result of the piston rising.

The crank angle CA1 shown in FIG. 2 is the start crank angle of the injection period, and the crank angle CA2 is the end crank angle of the injection period. The crank angle CA1 is included in the crank angle section until the tumble ratio rises to reach the maximum value. The crank angle CA2 is a crank angle in the vicinity of the start of the tumble ratio. If such injection period determined by the crank angles CA1 and CA2 is set, it is possible to promote the mixture of the injected fuel and air by the strong positive tumble flow TF. That is, the homogenization of the air-fuel mixture in the combustion chamber 12 can be promoted. Therefore, fuel economy can be improved.

2.2 problem points in the high Engine load region

When the fuel pressure is constant, if the fuel injection amount is increased, the injection period needs to be extended. That is, in the middle to high engine load region, the injection timing needs to be advanced or retarded as compared to the low engine load region in the case where the fuel pressure is constant.

However, if the injection timing is delayed with the extension of the injection period, the following problems arise. Fig. 3 is a diagram for explaining a problem in the case where the injection timing is delayed. In fig. 3, the start crank angle (crank angle CA1) of the injection period is not changed, but the end crank angle (crank angle CA3) is made to approach BDC. The crank angle CA3 is included in the crank angle section closer to BDC than the crank angle at which the tumble ratio is the highest. Therefore, as shown by the solid line in fig. 3, the fuel injected in the crank angle section on the BDC side promotes the decrease in the tumble ratio. As a result, the positive tumble flow TF is disturbed from the middle of the intake stroke, the speed of homogenization of the mixture decreases, and the fuel economy improvement effect by the positive tumble flow TF is impaired.

On the other hand, when the injection timing is advanced with the extension of the injection period, the following problems occur. Fig. 4 is a diagram for explaining a problem in the case where the injection timing is advanced. In fig. 4, the ending crank angle (crank angle CA2) of the injection period is not changed, but the starting crank angle (crank angle CA4) is moved away from BDC. When the injection is started from the crank angle CA4, the injected fuel easily collides directly against the top surface of the piston to generate smoke. This is because: at the crank angle CA4, the distance between the tip end portion of the direct injector 18 and the top face of the piston becomes shorter.

2.3 overview of Engine control of the embodiment

In view of such a problem, in the fuel injection control of the present embodiment, the injection timing is greatly delayed in the high engine load region. Fig. 5 is a diagram illustrating an outline of the fuel injection control according to the present embodiment. In FIG. 5, the start crankshaft angle (crankshaft angle CA5) and the end crankshaft angle (crankshaft angle CA6) are retarded in such a way that the injection period crosses BDC. As described in the description of fig. 3, the decrease in tumble ratio is promoted if the crank angle approaches BDC at the end of the injection period. This drawback also arises in fuel injection control in which the injection period crosses BDC.

However, in the fuel injection control of the present embodiment, the crank angle CA6 is delayed until the crank angle section corresponding to the first half of the compression stroke (i.e., the crank angle section from BDC to 90 BTDC; hereinafter, also referred to simply as "the first half of the compression stroke"). Therefore, as shown by the solid line in fig. 5, the degree of increase in the tumble ratio that temporarily increases during the compression stroke can be increased. That is, it is possible to suppress a decrease in the angular velocity of the forward rolling flow TF and delay collapse of the forward rolling flow TF.

Ignition of the mixture is performed near TDC. In addition, in a crank angle section corresponding to the latter half of the compression stroke (i.e., a crank angle section from 90BTDC to TDC), the positive tumble flow TF collapses as the piston rises. In this regard, if collapse of the positive tumble flow TF is delayed, homogenization of the mixture proceeds to just before ignition.

In the case where the end crank angle of the injection period is delayed to the first half of the compression stroke, there is a disadvantage that the temperature decrease of the air-fuel mixture based on the latent heat of vaporization of the injected fuel is suppressed in addition to the disadvantage described in the explanation of fig. 3. However, according to the investigation of the present inventors, the following situation has been confirmed: in the center injection engine, if the end crank angle is delayed to the first half of the compression stroke in the high engine load region, the advantages associated with the homogenization of the air-fuel mixture are more than the above-described disadvantages.

2.4 outline of other Engine control of embodiment

Fig. 6 is a diagram illustrating an outline of another fuel injection control according to the present embodiment. In fig. 6, the start crank angle (crank angle CA1) of the injection period is not changed, but the end crank angle (crank angle CA7) is retarded in such a way that the injection period crosses BDC. Further, the start crank angle may not necessarily be the crank angle CA 1. That is, the start crank angle may be a retard crank angle or an advance crank angle with respect to the crank angle CA 1.

In the fuel injection control illustrated in fig. 5, it is assumed that the fuel pressure is constant in the high engine load region. In contrast, the fuel injection control described in fig. 6 is performed simultaneously with the fuel pressure control for reducing the fuel pressure in the high engine load region. If such fuel pressure control is performed simultaneously with the fuel injection control, the end crank angle can be delayed to the first half of the compression stroke.

If the end crank angle is delayed to the first half of the compression stroke, the degree of increase in the tumble ratio that temporarily increases during the compression stroke can be increased. Also, according to the investigation of the present inventors, the following has been confirmed: according to the combination of the fuel pressure control and the fuel injection control, the same advantages as those of the fuel injection control illustrated in fig. 5 can be obtained.

Hereinafter, for convenience of explanation, the fuel injection control explained in fig. 5 is also referred to as "injection control 1", and the fuel injection control explained in fig. 6 is also referred to as "injection control 2".

2.5 other effects based on the 1 st injection control and the 2 nd injection control

Other effects based on the 1 st injection control and the 2 nd injection control will be described with reference to fig. 7.

Fig. 7 is a diagram illustrating a state of disturbance of the air-fuel mixture in the compression stroke. The broken line shown in fig. 7 indicates the transition of the disturbance before the end crank angle is delayed, and the solid line indicates the transition of the disturbance after the end crank angle is delayed. Comparing the two results, it is found that if the end crank angle is delayed to the first half of the compression stroke, the highly disturbed state is maintained near TDC. That is, the highly turbulent state is maintained until immediately before ignition.

The maintenance of a highly turbulent state immediately before ignition means that it is in an environment where flames generated by ignition of the mixture easily propagate to the surroundings. Therefore, according to the 1 st injection control or the 2 nd injection control, the propagation speed of the flame can be increased to increase the output of the engine.

3. Specific example of Fuel injection control of the embodiment

Next, specific examples of the 1 st injection control and the 2 nd injection control will be described with reference to fig. 8 to 9.

3.1 specific example of the 1 st injection control

Fig. 8 is a diagram for explaining a specific example of the 1 st injection control. The horizontal axis of fig. 8 represents the engine load, and the vertical axis represents the end crank angle of the injection timing. As shown in fig. 8, in the injection control 1, the higher the engine load, the later the end crank angle is. However, unlike the "conventional example" shown by the broken line in fig. 8, the 1 st injection control shown by the solid line greatly delays the end crank angle in the high engine load region. The engine load LH for greatly retarding the end crank angle is set, for example, in accordance with the engine load range in which the throttle valve is fully opened.

The relationship shown in fig. 8 is stored in the memory of the ECU30 in the form of a control map, and if the injection period is controlled based on this control map, the fuel economy improving effect and the output improving effect based on the 1 st injection control can be obtained.

3.2 specific example of the 2 nd injection control

Fig. 9 is a diagram for explaining a specific example of the 2 nd injection control. In fig. 9, the horizontal axis represents the engine load and the vertical axis represents the fuel pressure. As shown in fig. 9, in the 2 nd injection control, the fuel pressure is adjusted to a higher value as the engine load is higher in the low engine load region, and the fuel pressure is adjusted to a highest value in the medium engine load region. In the high engine load region, the fuel pressure is adjusted to a lower value as the engine load is higher. Further, the adjustment of the fuel pressure can be performed by the control of the fuel pump 20. As for the control method of the fuel pump 20, a known method may be applied.

The relationship shown in fig. 9 is stored in the memory of the ECU30 in the form of a control map, and if the injection period is controlled such that the end crank angle is in the first half of the compression stroke while the fuel pressure is controlled based on this control map, the fuel economy improving effect and the output improving effect based on the 2 nd injection control can be obtained.