阅读说明：本技术 车辆的控制方法及车辆的控制装置 (Vehicle control method and vehicle control device ) 是由 越后亮 木村容康 于 2018-08-06 设计创作，主要内容包括：内燃机(7)对发电机(6)进行驱动。内燃机(7)进行待机运转。待机运转是准备辅助向驱动用电机(2)的电力供给的运转。在进行内燃机(7)的待机运转时,电池(4)的SOC处于大于或等于规定的SOC阈值的状态。待机运转时的内燃机(7)的运转点与对电池(4)进行充电时的运转点相比,处于低输出侧。待机运转时的内燃机(7)的运转点是内燃机(7)的总管压力大于或等于规定的总管压力阈值的运转点。待机运转时的内燃机(7)的运转点是稀薄燃烧区域内的运转点。(The internal combustion engine (7) drives the generator (6). The internal combustion engine (7) performs a standby operation. The standby operation is an operation for assisting the supply of electric power to the drive motor (2). When the internal combustion engine (7) is in a standby operation, the SOC of the battery (4) is greater than or equal to a predetermined SOC threshold value. The operating point of the internal combustion engine (7) during standby operation is on the low output side compared to the operating point during charging of the battery (4). The operating point of the internal combustion engine (7) during standby operation is an operating point at which the manifold pressure of the internal combustion engine (7) is greater than or equal to a predetermined manifold pressure threshold value. The operating point of the internal combustion engine (7) during standby operation is an operating point in the lean combustion region.)

1. A control method of a vehicle having:

a generator capable of supplying generated electric power to the battery;

a motor that is a drive source of the vehicle and is driven by electric power from the battery or the generator; and

an internal combustion engine that drives the generator and can change an air-fuel ratio,

in the control method of the present invention, the control unit,

when the standby operation of the internal combustion engine is to be performed in preparation for assisting the supply of electric power to the electric motor in a state where the SOC of the battery is greater than or equal to a predetermined SOC threshold value, the lean burn operation is performed at an operation point that is on a lower output side than an operation point at which the SOC of the battery is lower than the SOC threshold value and the intake pressure of the internal combustion engine is greater than or equal to a predetermined intake pressure threshold value.

2. The control method of a vehicle according to claim 1,

comprising: a vehicle speed detection unit that detects a vehicle speed of the vehicle; and

an accelerator operation amount detection portion that detects an operation amount of an accelerator pedal and an operation speed of the accelerator pedal of the vehicle,

the standby operation is performed when the vehicle speed of the vehicle is equal to or higher than a predetermined vehicle speed threshold value set in advance, and at least one of the accelerator pedal operation amount and the accelerator pedal operation speed is equal to or higher than a predetermined operation amount threshold value or a predetermined operation speed threshold value.

3. The control method of a vehicle according to claim 1 or 2,

the operating point of the internal combustion engine when the standby operation is performed is on the low load side compared to the operating point when the SOC of the battery is lower than the SOC threshold value and the battery is charged.

4. The control method of the vehicle according to any one of claims 1 to 3,

in the standby operation, the engine speed of the internal combustion engine is reduced with a predetermined speed threshold as a lower limit.

5. The control method of the vehicle according to any one of claims 1 to 4,

the output generated by the internal combustion engine during the standby operation is an output of an amount corresponding to an amount of electric power consumed by the electric motor during the standby operation.

6. The control method of the vehicle according to any one of claims 1 to 5,

supercharger with intake air supercharging

The intake pressure threshold is set at a supercharging region where supercharging is performed by the supercharger.

7. The control device of the vehicle according to claim 6,

comprising: a throttle valve located on a downstream side of the supercharger; and

an intake throttle portion located downstream of the throttle valve and capable of changing an amount of air supplied into a cylinder of the internal combustion engine,

during the standby operation, the intake throttle portion is controlled so that air is less likely to enter the cylinder of the internal combustion engine, and supercharging is performed by the supercharger.

8. The control device of the vehicle according to claim 1 or 2,

when the operation point of the internal combustion engine is within a predetermined noise/vibration deterioration region during the standby operation, the operation point of the internal combustion engine is moved outside the noise/vibration deterioration region.

9. The control apparatus of a vehicle according to claim 8,

when the noise vibration is a booming noise caused by torque variation of the internal combustion engine, the operating point is moved to a high rotational speed side.

10. The control apparatus of a vehicle according to claim 8,

the generator and the internal combustion engine are linked by a gear train,

when the noise vibration is gear noise caused by the gear train, the operating point is moved to the high load side.

11. A control device for a vehicle, comprising:

a generator capable of supplying generated electric power to the battery;

a motor that is a drive source of the vehicle and is driven by electric power from the battery or the generator;

an internal combustion engine that drives the generator and can change an air-fuel ratio; and

a control portion that controls the internal combustion engine,

wherein the content of the first and second substances,

when the standby operation of the internal combustion engine is to be performed in preparation for assisting the supply of electric power to the electric motor in a state where the SOC of the battery is greater than or equal to a predetermined SOC threshold value, the control unit performs the lean burn operation at an operation point that is on a lower output side than an operation point at which the SOC of the battery is lower than the predetermined threshold value and at which an intake pressure of the internal combustion engine is greater than or equal to a predetermined intake pressure threshold value.

Technical Field

The present invention relates to a vehicle control method and a vehicle control device.

Background

For example, in patent document 1, in a hybrid vehicle having an electric motor for driving the vehicle and an internal combustion engine for generating electric power, when the operation of the internal combustion engine for generating electric power is not required, the internal combustion engine is operated in a predetermined standby operation.

The standby operation of the internal combustion engine in patent document 1 is performed in an operation region where the load and the engine speed are small or an operation region where lean combustion is performed.

However, patent document 1 does not disclose the operation point (load and engine speed) of the internal combustion engine in the case where the operation region in which lean combustion is performed is used during the standby operation.

When the SOC of the battery is high and the battery is operated in a standby mode while avoiding overcharging, if the output (load or engine speed) of the internal combustion engine is simply reduced as in the stoichiometric combustion, the combustion may become unstable due to the deterioration of the in-cylinder gas flow, resulting in deterioration of the exhaust performance.

Patent document 1: japanese laid-open patent publication No. 5-328526

Disclosure of Invention

The vehicle of the present invention includes: a generator capable of supplying generated electric power to the battery; a motor that is a drive source of the vehicle and is driven by electric power from the battery or the generator; and an internal combustion engine that drives the generator and can change an air-fuel ratio.

When the standby operation of the internal combustion engine is to be performed in preparation for assisting the supply of electric power to the electric motor in a state where the SOC of the battery is greater than or equal to a predetermined SOC threshold value, the lean burn operation is performed at an operation point that is on the output side lower than an operation point at which the SOC of the battery is lower than the SOC threshold value and the intake pressure of the internal combustion engine is greater than or equal to a predetermined intake pressure threshold value.

Therefore, in the standby operation for improving the acceleration responsiveness when there is an acceleration request, it is possible to suppress overcharge in the standby operation and to ensure combustion stability of the internal combustion engine in the standby operation.

Drawings

Fig. 1 is an explanatory diagram schematically showing a system configuration of a hybrid vehicle to which the present invention is applied.

Fig. 2 is an explanatory diagram schematically showing a system configuration of the internal combustion engine.

Fig. 3 is an explanatory diagram schematically showing the setting of the combustion region of the internal combustion engine.

Fig. 4 is an explanatory diagram schematically showing a correlation between the manifold pressure, the load of the internal combustion engine, and the intake air throttle.

Fig. 5 is an explanatory diagram schematically showing a supercharging region of the internal combustion engine.

Fig. 6 is a flowchart showing a control flow of the vehicle.

Detailed Description

An embodiment of the present invention is described in detail below with reference to the drawings.

Fig. 1 is an explanatory diagram schematically showing a system configuration of a hybrid vehicle to which the present invention is applied.

The hybrid vehicle includes a drive wheel 1 of the vehicle, a drive motor 2 for rotationally driving the drive wheel 1, an inverter 3 for supplying ac power to the drive motor 2, a battery 4 for supplying power to the inverter 3, and a power generation unit 5.

The drive wheels 1 of the vehicle are rotationally driven using a drive motor 2 as a drive source.

The driving motor 2 corresponds to an electric motor, and is constituted by, for example, a synchronous motor using a permanent magnet for a rotor.

The driving motor 2 is a driving source of the vehicle and is driven by ac power from the inverter 3. The driving motor 2 functions as a generator when the vehicle decelerates. That is, the driving motor 2 can charge the battery 4 via the inverter 3 with the regenerative energy generated when the vehicle decelerates as electric power.

The inverter 3 is a power conversion circuit that converts power generated by the power generation unit 5 and the driving motor 2 into dc power and supplies the dc power to the battery 4. The inverter 3 is also a power conversion circuit that converts dc power output from the battery 4 into ac power and supplies the ac power to the driving motor 2.

The battery 4 is a secondary battery capable of charging the electric power generated by the power generation unit 5 and the driving motor 2 as dc power. The battery 4 supplies the charged electric power to the driving motor 2 via the inverter 3.

The power generation unit 5 is generally composed of a generator 6, an internal combustion engine 7 for generating power for driving the generator 6, and a reduction gear 8 disposed between and connecting the generator 6 and the internal combustion engine 7.

That is, the hybrid vehicle to which the present invention is applied operates the internal combustion engine 7 to drive the generator.

The power generation unit 5 can operate (operate and stop) independently of the driving motor 2.

The generator 6 is constituted by, for example, a synchronous motor using a permanent magnet for a rotor.

The generator 6 converts rotational energy generated in the internal combustion engine 7 into electric energy, and supplies the electric energy to the battery 4 and the driving motor 2 via the inverter 3. The generator 6 also functions as a starter motor when the internal combustion engine 7 is started.

The speed reducer 8 corresponds to a gear train, has a plurality of gears (not shown), and transmits the rotation of the internal combustion engine 7 to the generator 6 at a predetermined reduction ratio (rotation speed ratio). When the generator 6 is used as a starter motor for the internal combustion engine 7, the reducer 8 transmits the rotation of the generator to the internal combustion engine 7.

Fig. 2 is an explanatory diagram schematically showing a system configuration of the internal combustion engine 7.

The internal combustion engine 7 is a so-called reciprocating internal combustion engine that converts a reciprocating linear motion of a piston 11 into a rotational motion of a crankshaft (not shown) and outputs the converted rotational motion as power. The internal combustion engine 7 is configured to be capable of changing an air-fuel ratio. The internal combustion engine 7 may be started by a dedicated starter motor different from the generator 6.

The internal combustion engine 7 has an intake passage 12 and an exhaust passage 13. The intake passage 12 is connected to a combustion chamber 15 via an intake valve 14. The exhaust passage 13 is connected to a combustion chamber 15 via an exhaust valve 16.

The internal combustion engine 7 includes a 1 st fuel injection valve 17 for directly injecting fuel (gasoline) into the combustion chamber 15, and a 2 nd fuel injection valve 18 for injecting fuel (gasoline) into the intake passage 12 on the upstream side of the intake valve 14. The fuel injected from the 1 st fuel injection valve 17 and the 2 nd fuel injection valve 18 is ignited by an ignition plug 19 in the combustion chamber 15.

The intake passage 12 is provided with an air cleaner 20 for collecting foreign matters in the intake air, an air flow meter 21 for detecting the amount of intake air, and an electrically operated throttle 23 whose opening degree is controlled in accordance with a control signal from a control unit 22.

The airflow meter 21 is disposed upstream of the throttle valve 23. The air flow meter 21 incorporates a temperature sensor and is capable of detecting the intake air temperature at the intake air inlet. The air cleaner 20 is disposed upstream of the air flow meter 21.

An upstream side exhaust catalyst device 24 such as a three-way catalyst and a downstream side exhaust catalyst device 25 such as a NOx trap catalyst are provided in the exhaust passage 13. The downstream-side exhaust catalyst device 25 is disposed downstream of the upstream-side exhaust catalyst device 24.

The internal combustion engine 7 includes a supercharger (turbocharger) 28, and the supercharger 28 includes a compressor 26 provided in the intake passage 12 and an exhaust turbine 27 provided in the exhaust passage 13 coaxially therewith. The compressor 26 is disposed upstream of the throttle valve 23 and downstream of the airflow meter 21. The exhaust turbine 27 is disposed upstream of the upstream exhaust catalyst device 24.

A return passage 29 is connected to the intake passage 12. One end of the return passage 29 is connected to the intake passage 12 on the upstream side of the compressor 26, and the other end is connected to the intake passage 12 on the downstream side of the compressor 26.

An electrically operated return valve 30 is disposed in the return passage 29, and the return valve 30 can release the boost pressure from the downstream side of the compressor 26 to the upstream side of the compressor 26. As the return valve 30, a so-called check valve that opens only when the pressure on the downstream side of the compressor 26 is equal to or higher than a predetermined pressure may be used.

Further, an intercooler 31 is provided in the intake passage 12 on the downstream side of the compressor 26, and the intercooler 31 cools the intake air compressed (pressurized) by the compressor 26, thereby improving the charging efficiency. The intercooler 31 is located downstream of the downstream end of the return passage 29 and upstream of the throttle 23.

An exhaust bypass passage 32 that bypasses the exhaust turbine 27 and connects the upstream side and the downstream side of the exhaust turbine 27 is connected to the exhaust passage 13. The downstream end of the exhaust bypass passage 32 is connected to the exhaust passage 13 at a position upstream of the upstream exhaust catalyst device 24. An electrically operated wastegate 33 that controls the flow rate of exhaust gas in the exhaust bypass passage 32 is disposed in the exhaust bypass passage 32. The wastegate valve 33 can bypass a part of the exhaust gas guided to the exhaust turbine 27 to the downstream side of the exhaust turbine 27, and can control the boost pressure of the internal combustion engine 7.

Further, 34 in fig. 1 is a manifold portion of the intake passage 12. If the internal combustion engine 7 is a multi-cylinder internal combustion engine, a portion of the intake passage 12 on the downstream side of the main pipe portion 34 branches into cylinders as an intake manifold.

The supercharger 28 is not limited to the above-described turbocharger, and may be, for example, a mechanical supercharger (supercharger) that drives a compressor disposed in the intake passage 12 by the internal combustion engine 7, or an electric supercharger that drives a compressor disposed in the intake passage 12 by an electric motor.

The internal combustion engine 7 has, as the valve mechanism of the intake valve 14, an intake variable valve mechanism 41 capable of changing the valve timing (opening/closing timing) of the intake valve 14.

The intake variable valve mechanism 41 is a variable phase mechanism that continuously advances or retards the phase of the central angle of lift of the intake valve 14 (relative to the phase of a crankshaft (not shown)). The phase variable mechanism is a known mechanism for delaying or advancing the phase of the intake camshaft 42 that drives the intake valve 14 to open and close with respect to a crankshaft (not shown), for example, in japanese patent application laid-open No. 2002-89303.

The valve mechanism of the exhaust valve 16 is a normal direct-acting valve mechanism. That is, the phases of the lift operating angle and the lift center angle of the exhaust valve 16 are always constant.

The intake variable valve mechanism 41 is, for example, a hydraulically driven mechanism, and is controlled by a control signal from the control unit 22. That is, the control means 22 corresponds to a control unit that controls the intake variable valve mechanism 41. The control unit 22 is capable of variably controlling the valve timing of the intake valve 14. The intake variable valve mechanism 41 can change the amount of air in the cylinder by changing the closing timing of the intake valve 14. For example, when the intake valve closing timing is delayed from the bottom dead center, the intake throttle making it difficult for air to enter the cylinder can be executed by delaying the intake valve closing timing to be away from the bottom dead center. Further, for example, when the intake valve closing timing is advanced from the bottom dead center, the intake throttle making it difficult for air to enter the cylinder can be executed by advancing the intake valve closing timing away from the bottom dead center. That is, the intake variable valve mechanism 41 corresponds to an intake throttle portion capable of changing the amount of air supplied into the cylinder. That is, the intake throttle portion is a component located on the downstream side of the throttle valve 23, and can change the amount of air supplied into the cylinder, and can throttle the intake air that makes it difficult for the air to enter the cylinder. In other words, the intake air throttle portion is a component different from the throttle valve 23, and is a component located on the downstream side of the main pipe portion 34, for example, and capable of controlling the amount of air in the cylinder.

The intake variable valve mechanism 41 may be configured to be able to independently change the opening timing and the closing timing of the intake valve 14. The intake variable valve mechanism 41 is not limited to a hydraulically driven mechanism, and may be an electrically driven mechanism such as an electric motor.

The intake variable valve mechanism 41 corresponding to the intake throttle portion may be a lift/operating angle variable mechanism capable of changing the lift and operating angle of the intake valve 14. The lift operating angle variable mechanism is a known mechanism, for example, from japanese patent laid-open publication No. 2002-89303, and simultaneously and continuously increases or decreases the lift amount and the operating angle of the intake valve 14.

When the intake variable valve mechanism 41 is a variable lift/operating angle mechanism, air can be made less likely to enter the cylinder by increasing the lift of the intake valve 14 to a small extent, by increasing the operating angle to a small extent, or the like.

The intake variable valve mechanism 41 corresponding to the intake throttle portion may be constituted by a phase variable mechanism that continuously advances or retards the phase of the center angle of the lift of the intake valve 14, and a lift/operating angle variable mechanism that can change the lift and operating angle of the intake valve 14.

The control unit 22 is a well-known digital computer having a CPU, ROM, RAM, and input/output interfaces.

In addition to the detection signals from the air flow meter 21, detection signals from various sensors such as an intake-side camshaft position sensor 43 that detects the valve timing of the intake valve 14, a vehicle speed sensor 44, a crank angle sensor 45 that detects the crank angle of the crankshaft, an accelerator opening sensor 46 that detects the amount of depression of the accelerator pedal, and an intake pressure sensor 47 that detects the manifold pressure, which is the intake pressure at the manifold portion 34, are also input to the control unit 22.

The intake-side camshaft position sensor 43 detects the phase of the intake camshaft 42 relative to the crankshaft.

The vehicle speed sensor 44 corresponds to a vehicle speed detecting unit.

The crank angle sensor 45 is capable of detecting the engine speed of the internal combustion engine 7.

The accelerator opening degree sensor 46 can detect an accelerator opening degree as an operation amount of an accelerator pedal, and can also detect an accelerator change speed as an operation speed of the accelerator pedal. That is, the accelerator opening sensor 46 corresponds to an accelerator operation amount detection unit.

The crank angle sensor 45 is capable of detecting the engine speed of the internal combustion engine 7.

The control unit 22 optimally controls the injection amount and injection timing of the fuel injected from the 1 st fuel injection valve 17 and the 2 nd fuel injection valve 18, the ignition timing of the internal combustion engine 7 (spark plug 19), the intake air amount, and the like, and controls the air-fuel ratio of the internal combustion engine 7, based on detection signals of various sensors and the like.

The control unit 22 calculates a requested load of the internal combustion engine (load of the internal combustion engine) using the detection value of the accelerator opening degree sensor 46.

In addition, the control unit 22 can detect SOC (State of Charge), which is a ratio of the remaining Charge amount to the Charge capacity of the battery 4.

The hybrid vehicle of the above embodiment is a so-called series hybrid vehicle, and travels by driving the driving motor 2 with electric power from the generator 6 driven by the internal combustion engine 7 and electric power from the battery 4. With the series hybrid vehicle, if the SOC of the battery 4 becomes low, the internal combustion engine 7 is driven in order to charge the battery 4.

In the series hybrid vehicle, the amount of electric power that can be supplied to the driving motor 2 is substantially determined by the battery capacity of the battery 4 that supplies electric power to the driving motor 2. In the case of a series hybrid vehicle, the battery capacity of the battery 4 that supplies electric power to the drive motor 2 is often small, and the amount of electric power from the battery 4 may be limited. Therefore, in the series hybrid vehicle in which the amount of electric power from the battery 4 is limited, there is a limit in power performance when the driving motor 2 is operated.

In the series hybrid vehicle, when a large output is required for the driving motor 2, the internal combustion engine 7 needs to be operated to assist the electric power generated by the generator 6 in addition to the electric power from the battery 4.

However, even if a large output is required for the driving motor 2 in a state where the internal combustion engine 7 is stopped, the internal combustion engine 7 cannot instantaneously generate a desired output. That is, when the internal combustion engine 7 is started after the acceleration request is received, there is a possibility that the power performance of the vehicle is adversely affected until the internal combustion engine 7 generates a desired output.

Therefore, in the internal combustion engine 7, in consideration of the fact that the output request of the driving motor 2 increases due to the acceleration request, it is necessary to perform a standby operation for preparing to assist the power supply to the driving motor 2 for operation.

In the standby operation, basically, the driving motor 2 is supplied with electric power obtained by combining electric power supplied from the battery 4 and electric power generated by the generator 6 by operating the internal combustion engine 7.

In this standby operation, since the electric power supply to the driving motor 2 is prepared for assistance, smooth acceleration of the vehicle can be realized when an acceleration request is made.

In the series hybrid vehicle, the battery 4 that supplies electric power to the drive motor 2 often has a small battery capacity. Therefore, in the series hybrid vehicle, if the operating point of the internal combustion engine 7 is operated at the highest heat efficiency point during the standby operation, the battery 4 is fully charged in a short time.

In order not to fully charge the battery 4 during the standby operation, it is effective to set the operating point of the internal combustion engine 7 during the standby operation to an operating point at which the thermal efficiency is not the best, but an operating point at which the output is low.

In the series hybrid vehicle, if the charge/discharge efficiency of the battery 4 for supplying electric power to the driving motor 2 is taken into consideration, it is preferable that the energy obtained by the power generation is directly supplied to the driving motor 2 and used without being stored in the battery 4 as much as possible.

In the series hybrid vehicle, if the generator 6 generates electric power in an amount of energy required for running during the standby operation, the series hybrid vehicle can be operated with energy loss associated with charge/discharge efficiency suppressed.

However, the rapid transition of the operating point may cause deterioration of fuel economy due to the accuracy of the intake air amount control at the time of transition and the fuel injection amount control at the time of transition of the internal combustion engine 7. That is, during the standby operation, the operating point of the internal combustion engine 7 may be desired to be set to a lower output operating point.

As a method of reducing the output of the internal combustion engine 7, reduction of the engine speed, reduction of the load, reduction of the engine speed and the load, and the like are conceivable.

Here, it is known that the gas flow in the cylinder is easily deteriorated and ideal combustion is difficult to achieve in the low-load low-speed operation. In particular, in the case of lean combustion which becomes highly lean combustion, securing of combustion stability by the gas flow in the cylinder has a great influence on establishment of the lean combustion. That is, in the internal combustion engine 7 during lean combustion, if the combustion stability deteriorates, the exhaust performance deteriorates, and therefore, it is necessary to have restrictions on the load and the engine speed.

The restrictions on the load and the engine speed of the internal combustion engine 7 during lean combustion vary depending on the specifications of the internal combustion engine 7. Therefore, the respective threshold values of the load of the internal combustion engine 7 and the engine speed during the lean combustion are set by individually confirming them as appropriate. The internal combustion engine 7 is preferably operated at a load and an engine speed that can ensure combustion stability by constantly monitoring the combustion stability.

It is known that the internal combustion engine 7 can suppress fluctuations in the distribution of the amount of air in the cylinder due to fluctuations in the components of the intake system by pushing air into the cylinder by the supercharging performed by the compressor 26.

In the internal combustion engine 7 with the supercharger 28, since the combustion stability is easily ensured by suppressing the distribution fluctuation of the in-cylinder air amount, it is preferable to perform the lean combustion in the supercharging region.

Further, when lean combustion cannot be performed because combustion stability cannot be ensured, the internal combustion engine 7 needs to be switched to stoichiometric combustion in which the air-fuel ratio is set to the stoichiometric air-fuel ratio. However, when stoichiometric combustion is performed, if the amount of stored O2 in a three-way catalyst (upstream exhaust catalyst device 24) provided in the exhaust system of the internal combustion engine 7 becomes too large, so-called rich spike, in which the fuel injection amount is temporarily increased, needs to be performed, which causes deterioration in fuel economy.

When the engine speed is reduced to reduce the output of the internal combustion engine 7, a booming sound may be generated in the vehicle interior depending on the vehicle and the system.

When the load of the internal combustion engine 7 is reduced to reduce the output of the internal combustion engine 7, gear noise due to torque variation may be generated depending on the vehicle and the system. Gear noise is generated in the reduction gear 8 disposed between the internal combustion engine 7 and the generator 6.

Therefore, when the engine speed and the load of the internal combustion engine 7 are reduced to reduce the output of the internal combustion engine 7, it is necessary to suppress the occurrence of booming noise and gear noise and suppress the deterioration of the sound vibration performance by controlling the manner of reduction of the engine speed and the load in accordance with the vehicle.

Since the occurrence region of the booming noise or the gear noise differs depending on the vehicle or system, it is necessary to individually determine whether or not the indicated operating point of the internal combustion engine corresponds to the occurrence region of the booming noise or the gear noise for each vehicle or system.

Therefore, in the series hybrid vehicle of the above embodiment, the standby operation of the internal combustion engine 7 is performed in preparation for assisting the supply of electric power to the driving motor 2 at the operating point on the lower output side than the operating point at the time of charging the battery 4 and at which the manifold pressure of the internal combustion engine 7 is equal to or higher than the predetermined manifold pressure threshold (intake pressure threshold).

Here, the operating point is determined by the load of the internal combustion engine 7 and the engine speed of the internal combustion engine.

In addition, during the standby operation of the internal combustion engine 7 in preparation for assisting the electric power supply to the driving motor 2, a lean burn operation is performed in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio. That is, the internal combustion engine 7 is operated at an operating point within a predetermined lean combustion range in which a lean combustion operation is performed, as shown in fig. 3, in preparation for a standby operation for assisting the supply of electric power to the drive motor 2.

The manifold pressure threshold corresponds to an intake pressure threshold. The manifold pressure threshold is an index of combustion stability of the internal combustion engine 7, and is determined in advance through experiments or the like. The manifold pressure threshold value is a value in a supercharging operation region of the internal combustion engine 7. With the internal combustion engine 7, if the manifold pressure is less than the manifold pressure threshold, combustion may become unstable.

This makes it possible to prepare for a standby operation of the internal combustion engine 7 that assists the supply of electric power to the drive motor 2, and to improve the acceleration response when an acceleration request is made. In addition, this standby operation can ensure combustion stability of the internal combustion engine 7 during the standby operation while suppressing overcharge during the standby operation.

The combustion state (combustion stability) of the internal combustion engine 7 may be determined using, for example, a detection signal of an in-cylinder pressure sensor capable of detecting the in-cylinder pressure of the internal combustion engine 7 or a detection signal of a sensor capable of detecting a rotational fluctuation of the crankshaft (for example, the crank angle sensor 45).

When the in-cylinder pressure sensor is used, it is possible to determine whether or not the combustion state of the internal combustion engine is stable by using combustion analysis of the in-cylinder pressure detected in real time.

In the case of using a sensor capable of detecting rotational fluctuations of the crankshaft, it is possible to determine whether or not the combustion state of the internal combustion engine is stable from changes in the angular velocity of the crankshaft. For example, when the amount of change in the angular velocity of the crankshaft is less than or equal to a prescribed angular velocity change threshold value, it may be determined that the combustion state of the internal combustion engine 7 is stable.

That is, the operation point at which the standby operation of the internal combustion engine 7 is prepared to assist the supply of electric power to the driving motor 2 may be an operation point on the lower output side than the operation point at the time of charging the battery 4 and at which the combustion stability of the internal combustion engine 7 is ensured.

More specifically, when the vehicle speed of the vehicle is equal to or higher than a predetermined vehicle speed threshold value set in advance and at least one of the accelerator pedal operation amount and the accelerator pedal operation speed is equal to or higher than a predetermined operation amount threshold value or a predetermined operation speed threshold value, the standby operation of the internal combustion engine 7 is performed in preparation for assisting the electric power supply to the driving motor 2.

The vehicle speed threshold may be determined in consideration of the weight of the vehicle. For example, the vehicle speed threshold value is set to a smaller value as the vehicle weight of the vehicle is heavier. The weight of the vehicle may be detected by the vehicle weight detecting unit during traveling. The vehicle weight detection unit detects a suspension stroke or the like by a sensor, for example, and detects the vehicle weight based on the degree of sinking of the vehicle when the vehicle is stopped.

The operating point of the internal combustion engine 7 at the time of standby operation of the internal combustion engine 7 for preparing for assisting the supply of electric power to the driving motor 2 is on the low load side compared to the operating point at the time of charging the battery 4 with the SOC of the battery 4 being lower than the predetermined SOC threshold value.

This enables the internal combustion engine 7 to reduce the output.

In the standby operation of the internal combustion engine 7 for assisting the power supply to the driving motor 2, the engine speed of the internal combustion engine may be decreased with a predetermined speed threshold as a lower limit.

This also enables the internal combustion engine to reduce the output.

In the standby operation of the internal combustion engine 7 for assisting the supply of electric power to the driving motor 2, the output generated by the internal combustion engine 7 may be an output of an amount corresponding to the amount of electric power consumed by the driving motor 2 in the standby operation.

In this case, the standby operation can be performed without increasing the SOC of the battery 4.

The manifold pressure threshold may also be set at a boost region boosted by the supercharger 28.

In this case, since the boost pressure acts during the standby operation in preparation for assisting the supply of electric power to the drive motor 2, the internal combustion engine 7 can reduce fluctuations in various air distributions on the downstream side of the supercharger 28, and can realize more stable lean combustion.

Further, when the standby operation of the internal combustion engine 7 is performed in preparation for assisting the supply of electric power to the driving motor 2, the intake variable valve mechanism 41 may be controlled so that air is less likely to enter the cylinder of the internal combustion engine 7, and supercharging by the supercharger 28 may be performed.

Fig. 4 is an explanatory diagram schematically showing a correlation among the manifold pressure, the load of the internal combustion engine 7, and the intake throttle valve. If the manifold pressure is less than the prescribed combustion stability threshold value P1, the combustion stability of the internal combustion engine 7 deteriorates. In addition, if the intake-side variable valve mechanism 41 is controlled in such a manner that air hardly enters the cylinder and the load of the internal combustion engine 7 is maintained, the manifold pressure rises.

If the intake-side variable valve mechanism 41 is controlled so that air is less likely to enter the cylinder and supercharging is performed by the supercharger 28, the manifold pressure can be increased without changing the amount of air in the cylinder. That is, if the intake-side variable valve mechanism 41 is controlled so that air is less likely to enter the cylinder and supercharging is performed by the supercharger 28, the amount of air in the cylinder can be reduced without changing the manifold pressure.

By controlling the intake side variable valve mechanism 41 so that air hardly enters the cylinder and performing supercharging, the lower limit value of the load of the internal combustion engine 7 that becomes the combustion stability threshold P1 is lowered from R1 to R2 as shown in fig. 4 and 5.

In other words, by controlling the intake-side variable valve mechanism 41 in such a manner that air hardly enters the cylinder and performing supercharging, the supercharging region of the internal combustion engine 7 can be expanded to the low load side as shown by the broken line in fig. 5. In the plenum, the manifold pressure is greater than or equal to atmospheric pressure.

When the operation point of the internal combustion engine 7 is within the predetermined noise/vibration deterioration region during the standby operation of the internal combustion engine 7 for preparing for assisting the supply of electric power to the driving motor 2, the operation point of the internal combustion engine 7 may be moved outside the noise/vibration deterioration region.

This can suppress noise vibration.

For example, when the noise vibration is a booming sound due to torque variation of the internal combustion engine 7, the operating point is shifted to the high rotation speed side.

The operating region of the internal combustion engine 7 in which the booming sound is generated may be predetermined according to the engine speed and the load.

Thereby, the operating point of the internal combustion engine 7 moves to the outside of the operating region where the booming noise occurs. Therefore, the vehicle can suppress noise vibration caused by the booming sound.

When the noise vibration is caused by the gear noise of the reduction gear 8, the operating point is shifted to the high load side.

The operating region of the internal combustion engine 7 in which gear noise is generated can be determined in advance in accordance with the engine speed and the load.

Thereby, the operating point of the internal combustion engine 7 moves to the outside of the operating region where the gear noise is generated. Therefore, the vehicle can suppress noise vibration caused by gear noise.

Fig. 6 is a flowchart showing a control flow of the vehicle in the above embodiment. This processing flow is repeatedly executed by the control unit 22 at predetermined time intervals (for example, at every 10 ms).

In step S1, it is determined whether the SOC of the battery 4 is greater than or equal to the SOC threshold value. If the SOC of the battery 4 is greater than or equal to the SOC threshold value in step S1, the flow proceeds to step S2. If the SOC of the battery 4 is less than the SOC threshold value in step S1, the flow proceeds to step S15. In step S15, the internal combustion engine 7 is operated at the operation point for charging.

The operating point for charging is an operating point with good fuel efficiency. In addition, when the output request of the internal combustion engine 7 is high, the operating point of the stoichiometric combustion region at which stoichiometric combustion is performed may be selected as the operating point for charging.

That is, the operating point for charging set in step S15 is basically the operating point in the lean combustion region, but becomes the operating point in the stoichiometric combustion region when the output request of the internal combustion engine 7 is high.

Further, when the process proceeds to step S15 with the internal combustion engine 7 stopped, the internal combustion engine 7 starts operating at the operating point for charging in step S15.

In step S2, it is determined whether the vehicle speed is greater than or equal to a vehicle speed threshold. If the vehicle speed is greater than or equal to the vehicle speed threshold in step S2, the routine proceeds to step S3. If the vehicle speed is less than the vehicle speed threshold in step S1, the routine proceeds to step S16. In step S16, the internal combustion engine 7 is stopped.

Further, when the process proceeds to step S16 while the internal combustion engine 7 is stopped, the internal combustion engine 7 maintains the stopped state in step S16.

When the vehicle speed is less than the vehicle speed threshold value, the electric power required for driving the motor 2 may be small. That is, when the vehicle speed is less than the vehicle speed threshold value, the electric power required for the driving motor 2 can be stably supplied only by the electric power charged in the battery 4. Therefore, when the vehicle speed is less than the vehicle speed threshold value, it is not necessary to perform the standby operation of the internal combustion engine 7 for assisting the power supply to the driving motor 2.

In step S3, it is determined whether or not the accelerator opening degree or the accelerator opening speed, which is the accelerator change speed, is greater than or equal to a predetermined threshold value. That is, it is determined whether the accelerator opening is greater than or equal to a predetermined opening threshold or the accelerator opening speed is greater than or equal to a predetermined opening speed threshold. The accelerator opening speed is an accelerator change speed when the accelerator pedal is operated to the depression side.

If the accelerator opening degree or accelerator opening speed is greater than or equal to the prescribed threshold value in step S3, the routine proceeds to step S4. If the accelerator opening or accelerator opening speed is less than the predetermined threshold value in step S3, it is determined that the driver' S request for acceleration is small and the standby operation is not required, and the process proceeds to S16.

In step S4, it is determined whether the load on the internal combustion engine 7 is greater than or equal to a preset gear noise lower limit value. The gear noise lower limit value is an upper limit value of a load in an operation region where gear noise is generated (a region where gear noise is generated). That is, in an operation region where the load of the internal combustion engine 7 is smaller than the gear noise lower limit value, the reduction gear 8 may generate gear noise.

The initial setting of the operating point of the internal combustion engine 7 during the standby operation is the same as the operating point for charging in the lean combustion region.

In the case where the load of the internal combustion engine 7 is greater than or equal to the gear noise lower limit value in step S4, the routine proceeds to step S5. That is, if the load on the internal combustion engine 7 can be reduced in a range where the reduction gear 8 does not generate gear noise, the process proceeds from step S4 to step S5. In the case where the load of the internal combustion engine 7 is less than the gear noise lower limit value in step S4, the routine proceeds to step S17.

In step S17, the load on the internal combustion engine 7 is set to the gear noise lower limit value. When the load of the internal combustion engine 7 is smaller than the gear noise lower limit value, the gear noise can be suppressed by setting the load of the internal combustion engine 7 to the gear noise lower limit value.

In step S5, the target load at the operating point during the standby operation of the internal combustion engine 7 is lowered by a predetermined amount in order to ensure the combustion stability of the internal combustion engine 7. Specifically, the load of the internal combustion engine 7 is reduced so that the manifold pressure does not fall below the manifold pressure threshold.

In step S5, for example, the load on the internal combustion engine 7 may be reduced so that power generation corresponding to the amount of power consumed by the driving motor 2 is possible. The amount of load reduction in step S5 may be set based on the power consumption of the driving motor 2, the lowest output load and rotation allowable in the current driving situation, and the like.

It is determined in step S6 whether or not it is necessary to further reduce the output of the internal combustion engine 7. Specifically, it is determined whether or not the output of the internal combustion engine 7 needs to be further reduced based on at least two values of the SOC of the battery 4, the amount of electric power used by the driving motor 2, and the amount of electric power generated by the generator 6. Specifically, when the SOC of the battery 4 increases, when the amount of power generation is larger than the amount of power consumed by the driving motor 2, or the like, it is determined that the output of the internal combustion engine 7 needs to be further reduced to avoid charging the battery 4.

If it is determined in step S6 that the output of the internal combustion engine 7 needs to be further reduced, the routine proceeds to step S7. If it is determined in step S6 that it is not necessary to further reduce the output of the internal combustion engine 7, the routine proceeds to step S14.

In step S7, it is determined whether the internal combustion engine 7 has a supercharger 28. If the internal combustion engine 7 has the supercharger 28, the routine proceeds to step S8. If the internal combustion engine 7 does not have the supercharger 28, the process proceeds to step S11.

In step S8, it is determined whether or not the internal combustion engine 7 has an intake throttle portion. When the internal combustion engine 7 has an intake air throttle portion (for example, the intake side variable valve mechanism 41), the process proceeds to step S9. If the internal combustion engine 7 does not have an intake air throttle portion (for example, the intake side variable valve mechanism 41), the routine proceeds to step S11.

In step S9, the intake air is throttled by the intake air throttle portion (e.g., the intake side variable valve mechanism 41) to expand the supercharging region of the supercharger 28 toward the low load side. For example, when the intake valve closing timing is retarded from the bottom dead center, the intake air is throttled (the intake air is throttled) by retarding the intake valve closing timing by a predetermined amount set in advance. Further, for example, when the intake valve closing timing is advanced from the bottom dead center, the intake air is throttled (the intake air is throttled) by advancing the intake valve closing timing by a predetermined amount set in advance.

In step S10, it is determined whether the supercharging region has reached the expansion limit. That is, if the intake air by the intake side variable valve mechanism 41 can be further throttled so that the manifold pressure is not less than or equal to the manifold pressure threshold value, the routine proceeds to step S9. If the intake air by the intake-side variable valve mechanism 41 cannot be further throttled in such a manner that the manifold pressure is not less than or equal to the manifold pressure threshold value, the routine proceeds to step S11.

In step S11, it is determined whether the engine speed of the internal combustion engine 7 is greater than or equal to a preset booming noise rotation threshold value.

The booming noise rotation threshold value is an upper limit value of the engine speed in an operation region where the booming noise is generated (a booming noise generation region). That is, in an operation region where the engine speed of the internal combustion engine 7 is lower than the booming noise rotation threshold value, booming noise may occur.

In the case where the engine speed of the internal combustion engine 7 is greater than or equal to the booming sound rotation threshold in step S11, the routine proceeds to step S12. That is, if the engine speed of the internal combustion engine 7 can be reduced in a range where no booming noise is generated, step S12 is performed from step S11. When the engine speed of the internal combustion engine 7 is lower than the booming sound rotation threshold in step S11, step S18 is performed.

In step S18, the standby operation of the internal combustion engine 7 is performed with the engine speed of the internal combustion engine 7 set to the booming rotation threshold value and the load on the internal combustion engine 7 set to the value set in the present processing flow. When the engine speed of the internal combustion engine 7 is lower than the booming noise rotation threshold value, the generation of booming noise can be suppressed by setting the engine speed of the internal combustion engine 7 to the booming noise rotation threshold value.

In step S18, the standby operation of the internal combustion engine 7 is performed at the operation point set in the present process flow. The operating point of the standby operation performed in step S18 is the operating point in the lean combustion region.

Further, when the process proceeds to step S18 while the internal combustion engine 7 is stopped, the internal combustion engine 7 starts a standby operation in step S18.

In step S12, the rotation speed of the generator 6 is reduced to reduce the output of the internal combustion engine 7. That is, in step S12, the output of the internal combustion engine 7 is reduced by reducing the target engine speed at the operating point during the standby operation of the internal combustion engine 7 by a predetermined amount. Specifically, the engine speed of the internal combustion engine 7 is reduced so that the manifold pressure does not fall below the manifold pressure threshold.

In step S12, for example, the engine speed of the internal combustion engine 7 may be reduced so that power generation corresponding to the amount of power consumed by the driving motor 2 is enabled. The reduction amount of the engine speed in step S12 may be set based on the power consumption of the driving motor 2, the load and the rotation of the lowest output allowable in the current running condition, and the like.

In step S13, it is determined whether or not it is necessary to further reduce the output of the internal combustion engine 7. Specifically, it is determined whether or not the output of the internal combustion engine 7 needs to be further reduced based on at least two values of the SOC of the battery 4, the amount of electric power used by the driving motor 2, and the amount of electric power generated by the generator 6. Specifically, when the SOC of the battery 4 increases, the amount of power generation is larger than the amount of power consumed by the driving motor 2, or the like, it is determined that the output of the internal combustion engine 7 needs to be further reduced to avoid charging the battery 4.

When it is determined in step S13 that the output of the internal combustion engine 7 needs to be further reduced, the routine proceeds to step S11. When it is determined in step S13 that it is not necessary to further reduce the output of the internal combustion engine 7, the routine proceeds to step S14.

In step S14, the standby operation of the internal combustion engine 7 is performed at the operation point set in the present process flow. The operating point of the standby operation performed in step S14 is the operating point in the lean combustion region. Further, when the process proceeds to step S14 while the internal combustion engine 7 is stopped, the internal combustion engine 7 starts a standby operation in step S14.

When the output of the internal combustion engine 7 is reduced while the standby operation of the internal combustion engine 7 is being performed in preparation for assisting the supply of electric power to the driving motor 2, the load may be reduced before the engine speed is reduced. The reduction in load enables the output of the internal combustion engine 7 to be reduced with good responsiveness as compared with the reduction in engine speed.

The above-described embodiments relate to a control method of a vehicle and a control apparatus of a vehicle.