Hybrid vehicles

Abstract

To reduce occurrences of muffled sound from an internal combustion engine during motoring effectively.SOLUTION: A vehicle 1 can switch its mode between a regenerative braking mode in which electric power is generated by a front motor 4 for travel drive to charge a drive battery 11 when the vehicle 1 travels while slowing down and a motoring mode in which motoring for forcibly driving an engine 2 by driving a motor generator 9 is performed when a charging rate SOC of the drive battery 11 is higher than or equal to a predetermined value during the regenerative braking mode. In the motoring mode, a rotation speed of the motoring is controlled according to the charging rate SOC of the drive battery 11 and a power generation amount of the front motor 4. Further, a target value of an opening of a throttle valve 30 of the engine 2 is controlled according to the rotation speed of the motoring. An upper limit of the opening of the throttle valve 30 is set. The upper limit is set so as to become smaller as the rotation speed of the motoring increases.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control technique for an internal combustion engine during regenerative power generation in a hybrid vehicle. [Background technology]

[0002] Among hybrid vehicles that have been developed in recent years, there is known a vehicle equipped with an internal combustion engine, a generator that is driven by the internal combustion engine to generate electricity, a drive battery (storage battery) that can be charged by receiving power from the generator, and a drive motor that is supplied with power from the drive battery or the generator to drive the driving wheels. In hybrid vehicles such as those described above, when the vehicle decelerates, regenerative power is generated by the drive motor, and the generated power is supplied to the drive battery for charging. When the drive battery is nearly fully charged, some vehicles perform so-called motoring, in which fuel supply to the internal combustion engine is restricted and the internal combustion engine is forcibly driven by a generator (motor generator) to consume power, thereby enabling regenerative braking.

[0003] Patent Document 1 also discloses a vehicle that combines a generator and a drive motor, and controls the throttle valve of the internal combustion engine to be open when decelerating, thereby reducing pump loss in the internal combustion engine and increasing the power generation torque of the generator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-183794 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the internal combustion engine is forcibly driven by motoring during regenerative power generation, if the throttle valve is open, there is a problem that a muffled noise occurs in the internal combustion engine and its intake and exhaust system.On the other hand, if the throttle valve opening is small during motoring during regenerative power generation, oil rise occurs, in which lubricating oil in the internal combustion engine is sucked up into the cylinders. In particular, when motoring, it is possible to change and set the engine's forced drive rotation speed to maintain an appropriate battery charge rate, but it is desirable to always appropriately reduce muffled noise and oil leaks when motoring.

[0006] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a hybrid vehicle that makes it possible to effectively reduce the muffled noise generated by the internal combustion engine when motoring. [Means for solving the problem]

[0007] In order to achieve the above object, a hybrid vehicle of the present invention is a hybrid vehicle having an internal combustion engine mounted on the vehicle, a first electric motor capable of driving the internal combustion engine, a second electric motor that drives the vehicle and is capable of generating regenerative electricity when the vehicle is decelerating, a storage battery that supplies power to the second electric motor, and a control unit that controls the first electric motor, the second electric motor, and a throttle valve provided in an intake passage of the internal combustion engine, and further comprising a charge amount detection unit that acquires the charge amount of the storage battery, and the control unit is configured to: The system is capable of switching between a motoring mode in which, when the charge level of the storage battery is equal to or greater than a predetermined value, the first electric motor is driven to forcibly drive the internal combustion engine, thereby consuming the power regenerated by the second electric motor, and a motoring mode in which, when the charge level of the storage battery is equal to or greater than a predetermined value, the first electric motor is driven to forcibly drive the internal combustion engine, thereby consuming the power regenerated by the second electric motor.In the motoring mode, the motoring rotation speed is controlled according to the charge level of the storage battery and the amount of power regenerated by the second electric motor, and the target value of the throttle valve opening is controlled according to the motoring rotation speed, and an upper limit is set for the throttle valve opening, and the upper limit is set to decrease as the motoring rotation speed increases.

[0008] This allows the muffled noise of the internal combustion engine to be suppressed during motoring by setting an upper limit for the throttle valve opening during motoring. Also, by setting the upper limit for the throttle valve opening to decrease as the motoring rotation speed increases, the muffled noise of the internal combustion engine can be suppressed over a wide range of motoring rotation speeds.

[0009] Preferably, the motoring mode involves supplying fuel to the internal combustion engine and burning it while motoring with the first electric motor, and when the target value exceeds the upper limit value, the control unit sets the target value to the upper limit value and sets the combustion state of the internal combustion engine to an output torque suppression state. This suppresses the decrease in exhaust temperature due to motoring, which involves combustion, improves the exhaust purification performance of an exhaust purification device provided in the exhaust passage of the internal combustion engine, and suppresses the occurrence of oil leaking during motoring. Also, by keeping the target value of the throttle valve opening at or below the upper limit, the rotational speed of the internal combustion engine is suppressed and the power consumption of the first electric motor during motoring is reduced, but by suppressing the output torque of the internal combustion engine, the power consumption of the first electric motor can be increased and regenerative braking force can be secured.

[0010] Preferably, the control unit corrects the target value in accordance with at least one of an intake air temperature of the internal combustion engine, a temperature of the internal combustion engine, and atmospheric pressure. This makes it possible to appropriately set the target opening of the throttle valve in accordance with the intake air temperature of the internal combustion engine, the temperature of the internal combustion engine, and the atmospheric pressure. Preferably, the control unit changes the upper limit value in accordance with the traveling speed of the vehicle.

[0011] This makes it possible to increase the power consumption due to motoring while suppressing the booming noise of the internal combustion engine during motoring to an inconspicuous level in response to the running noise of the vehicle. Preferably, the upper limit value has a first upper limit value and a second upper limit value greater than the first upper limit value, and the control unit sets the upper limit value to the first upper limit value when the vehicle's traveling speed is equal to or less than a predetermined speed, sets the upper limit value to the second upper limit value when the traveling speed exceeds the predetermined speed, and if knocking occurs while the vehicle is traveling, sets the upper limit value to the first upper limit value even when the traveling speed exceeds the predetermined speed.

[0012] This makes it possible to suppress knocking during motoring accompanied by combustion. [Effects of the Invention]

[0013] According to the hybrid vehicle of the present invention, in motoring mode, the upper limit value of the throttle valve opening is set to decrease as the motoring rotation speed increases, thereby effectively suppressing the muffled noise of the internal combustion engine over a wide range of motoring rotation speeds. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a hybrid vehicle according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram of an intake and exhaust system of an engine according to an embodiment of the present invention; [Figure 3] 4 is an example of a map for setting a throttle valve opening degree during motoring. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of a hybrid vehicle of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a driving system of a hybrid vehicle (hereinafter referred to as vehicle 1) according to one embodiment of the present invention. In one embodiment of the present invention, the vehicle 1 is a vehicle such as a plug-in hybrid vehicle or hybrid vehicle that generates electricity by driving a motor generator 9 (first electric motor) using the output of an engine 2 (internal combustion engine) and is equipped with an electric front motor 4 (second electric motor) that drives the front wheels 3.

[0016] The engine 2 is capable of driving a drive shaft 8 of the front wheels 3 via a front transaxle 7, and is also capable of driving a motor generator 9 via the front transaxle 7 to generate electricity. The engine 2 and the front wheels 3 are connected via a clutch 16 disposed within the front transaxle 7. The front motor 4 is powered by a drive battery 11 (storage battery) and a motor generator 9 mounted on the vehicle 1 via a control unit 20, and drives the drive shaft 8 of the front wheels 3 via a front transaxle 7.

[0017] The electric power generated by the motor generator 9 can charge the drive battery 11 and can also supply power to the front motor 4. The drive battery 11 is composed of a secondary battery such as a lithium ion battery. The drive battery 11 also includes a charge rate detector 11a (charge amount detector) that detects the state of charge (SOC) of the drive battery 11.

[0018] The control unit 20 (controller) has the function of controlling the driving mode, the output of the front motor 4, the power generation amount and output of the motor generator 9, the fuel injection amount and fuel injection timing of the engine 2, and the engagement and disengagement of the clutch 16 in the front transaxle 7. The driving modes include an EV driving mode, an engine driving mode, a parallel driving mode, and a series driving mode. The control unit 20 is a control device for performing overall control of the vehicle 1. The control unit 20 includes an input / output device, a memory device (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer, etc.

[0019] In the EV mode, the engine 2 is stopped and the motor 46 is driven to run the vehicle. In series mode, the clutch 16 of the front transaxle 7 is disengaged, and the engine 2 drives the motor generator 9 to generate electricity, while driving the front motor 4 to drive the vehicle. In series mode, the rotational speed of the engine 2 is set to an efficient value.

[0020] In the parallel mode, the clutch 16 of the front transaxle 7 is connected, and the power of the engine 2 and the front motor 4 is transmitted to drive the front wheels 3. The control unit 20 sets the driving mode to parallel mode in a range where the engine 2 is efficient, such as a high-speed range. In a range other than parallel mode, i.e., a medium-to-low speed range, the control unit 20 switches between EV mode and series mode based on the state of charge (SOC) of the drive battery 11.

[0021] 2 is a schematic diagram of the intake and exhaust system of the engine 2. The engine 2 is, for example, a multi-cylinder internal combustion engine. For simplicity, only one cylinder is shown in FIG. The engine 2 is configured so that fuel can be injected into the intake port 31 of each cylinder from a fuel injection valve 32 provided in the intake port 31 of each cylinder at any injection timing and injection amount, and can be ignited by an ignition plug 34.

[0022] An intake passage 33 of the engine 2 is provided with a throttle valve 30 for adjusting the flow rate of fresh air. An exhaust passage 40 of the engine 2 is provided with an exhaust purification device 41 such as a three-way catalyst. A linear air-fuel ratio sensor (LAFS) 44 is provided in the exhaust passage 40 upstream of the exhaust purification device 41 and adjacent to the exhaust purification device 41. The LAFS 44 is used for feedback control of the fuel injection amount so that the detected value becomes a value indicating a target air-fuel ratio, for example, a stoichiometric air-fuel ratio.

[0023] The control unit 20 calculates the target opening of a throttle valve 30 provided in an intake passage based on the two target output torques of the engine, and controls the throttle valve 30. In addition, the control unit 20 is capable of a regenerative braking mode in which, when the vehicle is decelerating, the front motor 4 is forcibly driven using the rotational force of the front wheels 3 to generate electricity (regenerative power generation), and regenerative braking is performed to apply braking force to the front wheels 3.

[0024] The regenerative braking force in the regenerative braking mode can be changed by selecting the gearshift lever. Furthermore, in the regenerative braking mode when the vehicle is decelerating, for example, when the charge rate of the drive battery 11 reaches or exceeds a threshold value (predetermined value) near full charge, the control unit 20 is capable of a motoring mode in which electric power is supplied to the motor generator 9 to operate it and perform motoring by rotating the engine 2. In this embodiment, in the motoring mode, the fuel injection amount is set to about idling to suppress output while continuing combustion, and motoring is performed at a torque or rotational speed (motoring speed) that exceeds the torque or rotational speed of the engine 2 due to combustion.

[0025] In the motoring mode, power is consumed by driving the engine 2 with the motor generator 9. This ensures a regenerative braking force even when the charge rate of the drive battery 11 is close to full charge. In motoring mode, the control unit 20 controls the engine rotation speed (motoring speed) due to motoring by controlling the motor generator 9 in accordance with the charge amount (charging rate) of the drive battery 11 and the amount of regenerative power generated by the front motor 4. For example, the amount of regenerative power generated by the front motor 4 may be input from the control unit 20. Furthermore, the control unit 20 sets an upper limit value for the opening degree of the throttle valve 30 in motoring mode.

[0026] The detailed control of the motoring speed and the opening of the throttle valve 30 in the motoring mode will now be described. FIG. 3 is an example of a map for setting the throttle valve opening during motoring. The control unit 20 calculates the target opening value WOT of the throttle valve 30 based on the motoring speed, i.e., the engine rotation speed Ne during motoring. Specifically, the motoring speed is determined so that the portion of the regenerative power generated by the front motor 4 that cannot be charged to the drive battery 11 can be consumed, and the opening of the throttle valve 30 corresponding to the motoring speed determined based on the thick line in Figure 3 is set as the target opening value WOT.

[0027] As shown in FIG. 3, the target opening value WOT of the throttle valve 30 during motoring is set to an upper limit value WOTmax that is equal to or less than 100%. Furthermore, the upper limit WOTmax of the target opening value of the throttle valve 30 during motoring is set to decrease as the motoring rotation speed increases. If the target opening value WOT exceeds the upper limit value WOTmax, the target opening value WOT is updated to the upper limit value WOTmax, and motoring is performed at a motoring speed corresponding to the updated target opening value WOT (upper limit value WOTmax).

[0028] The muffled noise during motoring occurs when the throttle valve 30 is opened too far, and the higher the motoring speed, i.e., the greater the intake air volume, the more the muffled noise occurs even at a small throttle valve 30 opening. Therefore, by setting the upper limit value WOTmax of the target opening value of the throttle valve 30 so that it decreases as the motoring rotation speed increases, as described above, it is possible to suppress muffled noise over a wide range of motoring rotation speeds.

[0029] Furthermore, in this embodiment, in motoring mode as described above, fuel supply to the engine 2 is not completely stopped, but a small amount of fuel is supplied to maintain combustion. By maintaining combustion by reducing the amount of fuel supplied in this way, it is possible to suppress a temperature drop in the internal combustion engine and a temperature drop in an exhaust purification device such as a three-way catalyst provided in the exhaust passage of the engine 2. As a result, when transitioning from motoring mode to, for example, acceleration driving, it is possible to suppress a decrease in exhaust performance immediately after acceleration driving. Furthermore, by switching to motoring mode which involves combustion, it is possible to suppress the occurrence of oil leaking during motoring.

[0030] In this way, in a motoring mode involving combustion, if the target opening of the throttle valve 30 exceeds the upper limit value WOTmax, the target opening is suppressed to the upper limit value, and the ignition timing is retarded, for example, to enter a combustion state (output torque suppression state) in which the output torque of the engine 2 is further suppressed. As a result, the target opening is limited to an upper limit value, which reduces the rotational speed (motoring speed) of engine 2 and reduces the power consumption due to motoring below the required amount. However, by retarding the ignition timing and reducing the output torque of engine 2, the friction due to motoring is increased, which increases the power consumption by motor generator 9 and ensures regenerative braking force.

[0031] Furthermore, the target opening of the throttle valve 30 in the motoring mode may be corrected in accordance with at least one of the intake air temperature, the temperature of the internal combustion engine (water temperature, oil temperature, etc.), and the atmospheric pressure. For example, when the intake temperature is low, when the engine temperature (water temperature or oil temperature) is low, or when the atmospheric pressure is high, the target opening of the throttle valve 30 is corrected to be smaller, and when the intake temperature is high, when the engine temperature (water temperature or oil temperature) is high, or when the atmospheric pressure is low, the target opening is corrected to be larger. In this embodiment, the target opening is corrected by changing the slope of the thick line in Figure 3.

[0032] When the intake temperature is low, when the engine temperature (water temperature or oil temperature) is low, or when the atmospheric pressure is high, the intake amount must be increased to maintain combustion in engine 2, so the target opening is increased. The control unit 20 may also change the upper limit value WOTmax based on the vehicle speed (traveling speed of the vehicle 1). As shown in Fig. 2, when the vehicle speed is equal to or lower than a predetermined speed (e.g., 80 km / h), the upper limit value WOTmaxLv1 (first upper limit value) is set, and when the vehicle speed exceeds the predetermined speed, the upper limit value WOTmaxLv2 (second upper limit value) higher than the upper limit value WOTmaxLv1 is set. Note that both the upper limit values ​​WOTmaxLv1 and WOTmaxLv2 are set to decrease as the motoring speed increases.

[0033] In this way, as vehicle speed increases, the amount of power generated by regenerative power generation increases, so by setting the upper limit WOTmax higher, it is possible to increase the amount of power consumed by motoring. At this time, since the vehicle speed is high, the running noise is loud and the muffled noise is not noticeable. Also, when the vehicle speed decreases, the upper limit WOTmax is set lower to suppress the muffled noise. Furthermore, when the upper limit values ​​WOTmaxLv1 and WOTmaxLv2 are set according to the vehicle speed, if knocking occurs in the engine 2 while the vehicle is running, specifically while the engine 2 is running with combustion, it is preferable to limit the upper limit value WOTmaxLv1 even if the vehicle speed exceeds a predetermined speed. Note that the occurrence of knocking can be detected by a knock sensor provided in the engine 2. This makes it possible to suppress the occurrence of knocking during motoring accompanied by combustion.

[0034] The present invention is not limited to the above-described embodiment. For example, the details of the various controls described above may be modified as appropriate. In addition, in the above-described embodiment, motoring is performed with combustion when the motoring mode is executed. However, motoring may be performed with fuel injection stopped (without combustion), as in the regenerative power generation mode. Furthermore, motoring with combustion and motoring without combustion may be switched as appropriate. Furthermore, the output torque suppression state is not limited to retarding the ignition timing, and may further suppress the fuel injection amount, for example.

[0035] The present invention can be widely applied to hybrid vehicles capable of regenerative power generation and motoring. [Explanation of symbols]

[0036] 1 vehicle 2. Engine (internal combustion engine) 4 Front motor (second electric motor) 9 Motor generator (first electric motor) 11 Drive battery (storage battery) 11a Charging rate detection unit (charging amount detection unit) 30 Throttle valve 20 Control unit (control section)

Claims

1. A hybrid vehicle having an internal combustion engine mounted on a vehicle, a first electric motor capable of driving the internal combustion engine, a second electric motor that drives the vehicle and is capable of regenerative power generation during deceleration, a storage battery that supplies electric power to the second electric motor, and a control unit that controls the first electric motor, the second electric motor, and a throttle valve provided in an intake passage of the internal combustion engine, a charge amount detection unit for acquiring a charge amount of the storage battery; The control unit a regenerative braking mode in which the vehicle is decelerated by regeneratively generating electricity using the second electric motor and charging the storage battery, and a motoring mode in which, when the charge amount of the storage battery is equal to or greater than a predetermined value during the regenerative braking mode, motoring is performed to forcibly drive the internal combustion engine by driving the first electric motor, thereby consuming the electric power regenerated by the second electric motor; during the motoring mode, a rotation speed of the motoring is controlled in accordance with a charge amount of the storage battery and an amount of regenerative power generated by the second electric motor, and a target value of an opening degree of the throttle valve is controlled in accordance with the rotation speed of the motoring; An upper limit is set for the opening of the throttle valve, and the upper limit is set to decrease as the rotation speed of the motoring increases. A hybrid vehicle characterized by:

2. the motoring mode is a mode in which fuel is supplied to the internal combustion engine and burned while the first electric motor performs the motoring; When the target value exceeds the upper limit value, the control unit sets the target value to the upper limit value and sets the combustion state of the internal combustion engine to an output torque suppression state.

2. The hybrid vehicle according to claim 1.

3. The control unit corrects the target value in accordance with at least one of an intake air temperature of the internal combustion engine, a temperature of the internal combustion engine, and an atmospheric pressure.

2. The hybrid vehicle according to claim 1.

4. The control unit changes the upper limit value in accordance with the traveling speed of the vehicle.

2. The hybrid vehicle according to claim 1.

5. the upper limit value includes a first upper limit value and a second upper limit value that is greater than the first upper limit value, the control unit sets the upper limit value to the first upper limit value when the traveling speed of the vehicle is equal to or less than a predetermined speed, and sets the upper limit value to the second upper limit value when the traveling speed exceeds the predetermined speed, When knocking occurs while the vehicle is traveling, the first upper limit value is set even if the traveling speed exceeds the predetermined speed.

5. The hybrid vehicle according to claim 4.

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