Control device for hybrid vehicle

Abstract

To provide a control device of a hybrid vehicle capable of preventing or suppressing deterioration of a catalyst of an engine for driving an alternator.SOLUTION: In a control device for a hybrid vehicle provided with an alternator driven by output of an engine to generate electric power, capable of EV traveling by output torque of only a motor, and executing fuel cut for stopping supply of fuel to the engine by satisfaction of a fuel cut start condition, when there is an operation request for operating the alternator in transition to EV traveling by satisfaction of an EV traveling transition condition in a state where the engine is operated and the alternator is operated, execution of the fuel cut is prohibited to continue fuel supply to the engine (steps S3, S4).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle equipped with an engine (internal combustion engine) and a motor as power sources. [Background technology]

[0002] Patent Document 1 describes a vehicle power generation control device that aims to suppress overshoot or undershoot of engine rotation speed after fuel cut. The vehicle power generation control device described in Patent Document 1 controls a vehicle (engine vehicle) equipped with an alternator that is driven by the engine to generate electricity, and generates electricity using the alternator while a fail cut is being performed to stop or limit fuel supply to the engine. At the same time, after the fail cut is completed and fuel supply to the engine is resumed, power generation by the alternator is temporarily stopped and then the alternator's power generation voltage is gradually increased until it reaches a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-64811 Summary of the Invention [Problem to be solved by the invention]

[0004] As with the vehicle power generation control device described in Patent Document 1, by cutting fuel when the vehicle is decelerating or with the accelerator off, it is possible to reduce engine fuel consumption and improve vehicle fuel efficiency. The vehicle power generation control device described in Patent Document 1 controls the power generation state of the alternator in accordance with the timing of fuel cutoff, thereby eliminating overshoot and undershoot of engine speed after fuel cutoff ends. Meanwhile, in a hybrid vehicle that, like the vehicle described in Patent Document 1, has an alternator that is driven by the engine to generate electricity and also has a motor mounted together with the engine as a driving power source, cutting fuel off in the same way as in a conventional engine vehicle could cause deterioration of the catalyst provided in the engine's exhaust system.

[0005] For example, in a hybrid vehicle equipped with the above-mentioned alternator, the engine continues to rotate while the alternator is operating. In such a case, when the hybrid vehicle transitions to a state where it runs solely on the output torque of the motor (i.e., EV running mode), fuel supply to the engine is stopped, and the engine is essentially in a fuel-cut state. As a result, the engine enters a lean-burn state where the amount of fuel is less than the stoichiometric air-fuel ratio, and the amount of nitrogen oxides contained in the engine exhaust increases. Therefore, if the hybrid vehicle transitions to EV running mode while the alternator is operating, there is a risk of catalyst deterioration progressing.

[0006] This invention was devised with an eye on the above technical problems, and aims to provide a control device for a hybrid vehicle that can prevent or suppress deterioration of the catalyst in the engine that drives the alternator. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a control device for a hybrid vehicle that is equipped with an engine and a motor as driving power sources, and that is equipped with an alternator that is driven by the output of the engine to generate electricity, and that is capable of EV driving, essentially running on the output torque of the motor alone, with the engine stopped or running in an idling state, and that executes a fuel cut to stop or reduce fuel supply to the engine when a predetermined fuel cut start condition is met, and that includes a control unit that controls the hybrid vehicle, and when a transition to EV driving is made due to the satisfaction of a predetermined EV driving transition condition while the engine is running and the alternator is operating, the control unit determines whether there is an operation request to operate the alternator, and if there is still such an operation request, it prohibits the execution of the fuel cut and continues the supply of fuel to the engine.

[0008] In addition, the hybrid vehicle of the present invention may be configured to include a clutch provided between the engine and the motor for selectively interrupting power transmission between the engine and the motor, and an automatic transmission provided on the output side of the motor for transmitting the output torque of the engine and the motor to the drive wheels.

[0009] The automatic transmission of the present invention can set at least a low speed gear stage or low speed ratio which has the largest gear ratio and is used when starting and stopping, a high speed gear stage or high speed ratio which has the smallest gear ratio and is used when traveling at high speed, and a middle speed gear stage or middle speed ratio which is intermediate between the low speed gear stage or low speed ratio and the high speed gear stage or high speed ratio, and the fuel cut start condition of the present invention includes the EV traveling condition, and the control unit of the present invention can set at least a low speed gear stage or low speed ratio which is used when starting and stopping the vehicle and the driver has not performed an acceleration request operation. When the hybrid vehicle is decelerating with the accelerator released and the automatic transmission is set to the medium speed gear stage or medium speed gear ratio or the high speed gear stage or high speed gear ratio, it may be determined that the EV driving transition condition and the fuel cut start condition are met, and the hybrid vehicle is caused to transition to the EV driving mode, and if there is an operation request when transitioning to the EV driving mode, the execution of the fuel cut may be prohibited, and the supply of fuel to the engine may continue without executing the fuel cut even if the fuel cut start condition is met.

[0010] The control unit in the present invention may be configured to release the clutch to interrupt power transmission between the engine and the motor when the EV driving is performed. [Effects of the Invention]

[0011] The hybrid vehicle controlled by this invention includes an alternator that generates electricity when driven by an engine. The hybrid vehicle controlled by this invention is capable of EV driving, essentially running on motor output torque alone, by stopping the engine or idling the engine. It is also capable of executing a fuel cut to reduce engine fuel consumption. When transitioning from a state in which the engine is operating and outputting torque to the EV driving state described above, the hybrid vehicle control device of this invention determines whether or not an alternator operation request is made. If alternator generation is required and an alternator operation request is made, execution of a fuel cut is prohibited. In this case, even if a fuel cut start condition is met, fuel cut is not executed and fuel supply to the engine continues. Therefore, even when the hybrid vehicle transitions to EV driving while the alternator is operating, fuel cut is not executed and fuel supply continues, maintaining the engine operating state. By continuing to supply fuel to the engine, it is possible to prevent the engine from unexpectedly going into a lean burn state.

[0012] Therefore, the hybrid vehicle control device of the present invention is applicable to hybrid vehicles equipped with an alternator that generates electricity when driven by the engine, and can prevent or suppress deterioration of the catalyst provided in the engine's exhaust system regardless of the behavior of the hybrid vehicle, such as a request to operate the alternator or a transition to EV driving. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram for explaining the configuration of a hybrid vehicle that is the subject of control in the present invention, and is a diagram that schematically shows its drive system and control system. [Figure 2] FIG. 2 is a flowchart illustrating an example of control executed by the control device for a hybrid vehicle of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are merely examples of specific embodiments of the present invention and are not intended to limit the scope of the present invention.

[0015] An example of a drive system and control system of a hybrid vehicle to be controlled in an embodiment of the present invention is shown in Figure 1. The hybrid vehicle (hereinafter referred to as vehicle) Ve shown in Figure 1 is equipped with an engine (ENG) 1 and a motor (MG) 2 as drive power sources. The vehicle Ve also includes a clutch 3, an automatic transmission (AT) 4, an alternator (ALT) 5, a detector 6, and a control unit (ECU) 7.

[0016] The vehicle Ve to be controlled in the embodiment of the present invention may be a "hybrid vehicle" equipped with an internal combustion engine such as engine 1 and at least one "motor" as a driving force source. As shown in FIG. 1 , the vehicle Ve may be a rear-wheel drive (FR) vehicle in which the output torque of the engine 1 and the motor 2 is transmitted to rear wheels (drive wheels) 10 via an automatic transmission 4, a propeller shaft 8, and a differential gear 9, generating driving force at the rear wheels 10. Alternatively, the vehicle Ve may be a front-wheel drive (FR) vehicle in which the output torque of the engine 1 and the motor 2 is transmitted to front wheels (not shown), generating driving force at the front wheels. Alternatively, the vehicle Ve may be a four-wheel drive (FR) vehicle in which a transfer mechanism (not shown) is provided to transmit the output torque of the motor 2 to both the front and rear wheels 10, generating driving force at both the front and rear wheels 10.

[0017] Furthermore, the vehicle Ve to be controlled in the embodiment of the present invention may be, for example, a well-known "parallel hybrid vehicle" in addition to the so-called "FR-single motor hybrid vehicle" as shown in FIG. 1 . Alternatively, it may be a "series-parallel (or split) hybrid vehicle." For example, it may be a "split hybrid vehicle" equipped with an "engine," two "motors," and a "power split mechanism (planetary gear set)."

[0018] In the vehicle Ve shown in FIG. 1 , engine 1 is an internal combustion engine, such as a gasoline engine or a diesel engine, that obtains power by burning fuel. Engine 1 is configured so that its operating states, such as output adjustment, start and stop, etc., are electrically controlled. In the case of a gasoline engine, the throttle valve opening, fuel supply or injection amount, fuel injection timing, ignition on / off, and ignition timing are electrically controlled. An alternator 5 (described later) is connected to engine 1 so as to transmit power, and is driven by the output torque of engine 1. An ordinary catalytic converter (not shown) is also provided in the exhaust system (not shown) of engine 1. As will be described later, a hybrid vehicle control device according to an embodiment of the present invention determines whether or not an operation request is made to alternator 5 in order to protect the catalyst. Based on the determination result, various controls are executed to determine whether or not to cut fuel to engine 1.

[0019] The motor 2 is configured, for example, by a permanent magnet synchronous motor or an induction motor. The motor 2 at least functions as a prime mover that is driven by a supply of electric power and outputs torque. The motor 2 may also function as a generator that generates electric power when driven by external torque. That is, the motor 2 may be a so-called motor-generator that combines the functions of a prime mover and a generator. A battery (not shown) is connected to the motor 2 via an inverter (not shown). Therefore, electric power stored in the battery can be supplied to the motor 2, causing the motor 2 to function as a prime mover and output driving torque. The motor 2 can also function as a generator using torque transmitted from the drive wheels 10, and the regenerative power generated during this operation can be stored in the battery. The output speed and output torque of the motor 2 are electrically controlled by a control unit 7 (described later). For example, a required driving force is calculated from the amount of operation of an accelerator pedal (not shown) by the driver and the vehicle speed, and the output torque of the motor 2 is controlled based on the required driving torque (i.e., the control target value of the motor 2) set corresponding to the required driving force.

[0020] The clutch 3 is provided between the engine 1 and the motor 2. Specifically, an output shaft 1a of the engine 1 and an input shaft (the input side of the rotating shaft) 2a of the motor 2 are connected via the clutch 3. Therefore, by controlling the engaged and disengaged states of the clutch 3, power transmission between the engine 1 and the motor 2 is selectively interrupted. For example, as will be described later, when performing so-called EV driving, in which the vehicle Ve is driven by the output torque of the motor 2 alone, the clutch 3 is released to interrupt the power transmission between the engine 1 and the motor 2, thereby reducing drag loss caused by the engine 1 and improving energy efficiency during EV driving.

[0021] The automatic transmission 4 is a power transmission device that transmits the output torque of the engine 1 and the motor 2 to the drive wheels 10, and is a transmission that changes the rotational speed of the engine 1 or the motor 2 to transmit the output torque. The automatic transmission 4 is a power transmission device that can appropriately change the ratio of the rotational speed of the output shaft 4b to the rotational speed of the input shaft 4a, i.e., the gear ratio, and automatically controls the control to change the gear ratio (gear stage), i.e., the gear control. The automatic transmission 4 may be, for example, a "stepped (step-type) automatic transmission" that sets multiple gear stages with different gear ratios. Alternatively, it may be a "belt-type continuously variable transmission" that can continuously (steplessly) change the gear ratio. Therefore, the automatic transmission 4 can be set to at least a low-speed gear stage or low-speed gear ratio (e.g., first gear) having the largest gear ratio and used when starting and stopping, a high-speed gear stage or high-speed gear ratio (e.g., fifth gear or sixth gear) having the smallest gear ratio and used when driving at high speeds, and a medium-speed gear stage or medium-speed gear ratio (e.g., second gear, third gear, fourth gear) intermediate between the low-speed gear stage or low-speed gear ratio and the high-speed gear stage or high-speed gear ratio.

[0022] The alternator 5 is an "alternating current generator" that generates electricity when driven by the output of the engine 1. The alternator 5 is connected to the output shaft 1a of the engine 1 via a fan belt (not shown) or the like, and is driven by the output torque of the engine 1. The electricity generated by the alternator 5 is stored in an auxiliary battery (a secondary battery such as a lead-acid battery; not shown) or the like. Then, for example, when the remaining charge of the auxiliary battery falls below a predetermined value, an operation request is output to the alternator 5, and the alternator 5 is operated. Specifically, the rotation of the engine 1 is maintained to drive the alternator 5, and the alternator 5 operates.

[0023] The detection unit 6 is a device or apparatus for acquiring various data and information required to control the vehicle Ve, and includes, for example, a power supply unit, a microcomputer, sensors, an input / output interface, etc. In this embodiment of the present invention, the detection unit 6 detects the running state and control state of the vehicle Ve, and in particular detects various data for determining whether or not an operation request is made to the alternator 5, various data for performing a fuel cut of the engine 1, various data for performing EV running, etc.

[0024] Specifically, the detection unit 6 includes, for example, a vehicle speed sensor 6a that detects the vehicle speed, an engine rotation speed sensor 6b that detects the rotation speed of the engine 1, a motor rotation speed sensor (or resolver) 6c that detects the rotation speed of the motor 2, a motor current sensor 6d that detects the current value of the motor 2, an accelerator opening sensor 6e that detects the depression amount or depression angle of the accelerator pedal (not shown), a SOC sensor 6f that detects the remaining charge (SOC) of the auxiliary battery, a shift position sensor 6g that detects the current gear (gear ratio) of the automatic transmission 4, and a timer 6h that detects the detection time or timing of each sensor or the control time of each part. The detection unit 6 is electrically connected to a control unit 7 (described later) and outputs electrical signals corresponding to the detected values ​​or calculated values ​​of the various sensors, devices, and apparatuses described above to the control unit 7 as detection data.

[0025] The control unit 7 is an electronic control device mainly composed of, for example, a microcomputer. The control unit 7 in this embodiment of the present invention controls the motor 2 for driving the vehicle, thereby controlling the driving force of the vehicle Ve. Various data detected or calculated by the detection unit 6 are input to the control unit 7. The control unit 7 performs calculations using the input various data, pre-stored data, calculation formulas, etc. The control unit 7 outputs the calculation results as control command signals and is configured to control the running state of the vehicle Ve and the operating state of the driving force sources (engine 1 and motor 2), as described above. In particular, the control device for a hybrid vehicle in this embodiment of the present invention executes various controls for determining whether or not there is a request to operate the alternator 5, various controls for cutting fuel from the engine 1, and various controls for EV running, as will be described later.

[0026] Although FIG. 1 above shows an example in which one control unit 7 is provided, the control unit 7 in the embodiment of the present invention may be provided in multiple units, one for each device or equipment to be controlled, or one for each control content.

[0027] As described above, the hybrid vehicle control device according to the embodiment of the present invention is configured to control a hybrid vehicle Ve equipped with an alternator 5 driven by an engine 1, and to prevent or suppress deterioration of a catalyst provided in the exhaust system of the engine 1. An example of control executed by the control unit 7 for this purpose is shown in the flowchart of FIG.

[0028] The control shown in the flowchart of FIG. 2 is executed when the engine 1 is running, i.e., when the alternator 5 is operating by receiving the output torque of the engine 1, and when the vehicle transitions from this state to EV running. EV running is a running mode in which the vehicle Ve runs solely on the output torque of the motor 2, and the torque required for running is output by the motor 2. At the same time, the engine 1 is stopped, or the engine 1 is operated in an idling state. In other words, in EV running, fuel supply to the engine 1 is stopped or limited. Therefore, the engine 1 is stopped or operated at a low speed, approximately equivalent to idling. As mentioned above, during EV running, the clutch 3 may be disengaged to reduce drag loss caused by the engine 1.

[0029] Furthermore, the vehicle transitions to the EV driving state when a predetermined EV driving transition condition is met. The EV driving transition condition is at least that the engine 1 is operating, the vehicle Ve is decelerating with the accelerator off and no acceleration request operation by the driver, and the automatic transmission 4 is set to a medium speed gear or a medium speed gear ratio or a high speed gear or a high speed gear ratio. When all of these conditions are met, the EV driving transition condition is determined to be met. The EV driving transition condition is included in the fuel cut start condition. In other words, the EV driving transition condition overlaps with part of the fuel cut start condition. Therefore, when the EV driving transition condition is met, the fuel cut start condition is also met.

[0030] However, when the above-described EV running transition condition is met (i.e., the fuel cut start condition is also met) and the vehicle Ve transitions to EV running, if there is a request to operate the alternator 5 and fuel cut is implemented while the engine 1 continues to operate, the engine 1 will enter a lean burn state. As a result, the amount of nitrogen oxides contained in the exhaust gas from the engine 1 will increase, and deterioration of the catalyst in the exhaust system of the engine 1 will progress. Therefore, when the EV running transition condition is met, the control device for a hybrid vehicle in an embodiment of the present invention determines whether there is a request to operate the alternator 5, and if there is a request to operate the alternator 5, prohibits execution of fuel cut for the engine 1.

[0031] Specifically, as shown in the flowchart of FIG. 2, first, in step S1, it is determined whether or not there is a request to prohibit fuel cut (F / C) due to a request to operate the alternator 5. As described above, for example, when the remaining charge of the auxiliary battery falls below a predetermined value, a request to operate the alternator 5 is output, and power is generated by the alternator 5. Therefore, when there is a request to operate the alternator 5, the rotation of the engine 1 is maintained to drive the alternator 5. If the vehicle Ve transitions to EV running while the engine 1 is rotating in this manner, and fuel supply to the engine 1 is stopped, that is, a fuel cut is executed, there is a risk that deterioration of the catalyst in the exhaust system of the engine 1 will progress, as described above.

[0032] Therefore, in the control device for a hybrid vehicle according to the embodiment of the present invention, when the vehicle Ve transitions to EV running while there is a request to operate the alternator 5 as described above, execution of fuel cut to the engine 1 is prohibited. That is, a request to prohibit fuel cut due to a request to operate the alternator 5 is output. By outputting the request to prohibit fuel cut, execution of fuel cut is prohibited and fuel supply to the engine 1 is continued. Furthermore, when the vehicle Ve transitions to EV running, if there is no request to operate the alternator 5 as described above, fuel supply to the engine 1 is stopped. That is, fuel cut is executed.

[0033] Therefore, if there is no request to operate the alternator 5 and therefore no request to prohibit fuel cut due to the request to operate the alternator 5, and therefore the determination in step S1 is "No," the process proceeds to step S2, where fuel supply to the engine 1 is stopped. That is, fuel cut is executed. Then, the routine shown in the flowchart of FIG. 2 is temporarily ended.

[0034] On the other hand, if there is a request to operate the alternator 5 and therefore a request to prohibit fuel cut due to the request to operate the alternator 5, and therefore the answer is "Yes" in step S1, proceed to steps S3 and S4.

[0035] In step S3, a request to prohibit fuel cut for the engine 1 is output. That is, execution of fuel cut for the engine 1 is prohibited.

[0036] Then, in step S4, since the execution of fuel cut is prohibited in step S3, fuel supply (fuel injection) to the engine 1 is continued. Then, after that, the routine shown in the flowchart of Fig. 2 is temporarily ended.

[0037] As described above, in the hybrid vehicle control device according to the embodiment of the present invention, when transitioning from a state in which the engine 1 is operating and outputting torque to a state in which the vehicle travels using the output torque of the motor 2, the presence or absence of an operation request for the alternator 5 is determined. If power generation by the alternator 5 is necessary and an operation request for the alternator 5 is made, execution of fuel cut is prohibited. In that case, even if the fuel cut start condition is met, fuel cut is not executed and fuel supply to the engine 1 is continued. Therefore, even if the vehicle Ve transitions to EV traveling while the alternator 5 is operating, if an operation request for the alternator 5 is made, fuel cut is not executed and the operating state of the engine 1 is maintained. By continuing the supply of fuel to the engine 1, it is possible to prevent the engine 1 from unexpectedly entering a lean burn state.

[0038] Therefore, according to the hybrid vehicle control device of this embodiment of the present invention, for a hybrid vehicle Ve equipped with an alternator 5 driven by an engine 1 to generate electricity, it is possible to prevent or suppress deterioration of the catalyst provided in the exhaust system of the engine 1 regardless of the behavior of the hybrid vehicle Ve, such as a request to operate the alternator 5 or a transition to EV driving. [Explanation of symbols]

[0039] 1 Engine (ENG) 1a (engine) output shaft 2 motors (MG) 2a (Motor) input shaft 3. Clutch 4 Automatic transmission (AT) 4a (automatic transmission) input shaft 4b (automatic transmission) output shaft 5 Alternator (ALT) 6. Detection unit 6a (detection part) vehicle speed sensor 6b (Detection section) Engine speed sensor 6c (detection part) motor rotation speed sensor 6d (detection part) motor current sensor 6e (detection part) accelerator opening sensor 6f SOC sensor (detection part) 6g Shift position sensor (detection part) 6h (detector) timer 7 Control Unit (ECU) 8 propeller shaft 9 Differential gear 10 Rear wheels (drive wheels) Vehicle (hybrid vehicle)

Claims

1. A control device for a hybrid vehicle that is equipped with an engine and a motor as driving power sources, has an alternator that is driven by the output of the engine to generate electricity, is capable of EV driving by running on the output torque of the motor alone, and executes a fuel cut to stop or reduce fuel supply to the engine when a predetermined fuel cut start condition is met, a control unit for controlling the hybrid vehicle; The control unit When a predetermined EV travel transition condition is satisfied and the vehicle transitions to the EV travel mode while the engine is running and the alternator is operating, the vehicle transitions to the EV travel mode and the alternator is activated. If there is a request for operation, the execution of the fuel cut is prohibited and fuel supply to the engine is continued. A control device for a hybrid vehicle.

2. 2. The control device for a hybrid vehicle according to claim 1, The hybrid vehicle is a clutch provided between the engine and the motor, the clutch selectively interrupting power transmission between the engine and the motor; an automatic transmission provided on the output side of the motor and transmitting the output torque of the engine and the motor to drive wheels; A control device for a hybrid vehicle.

3. 3. The control device for a hybrid vehicle according to claim 2, The automatic transmission is At least a low speed gear stage or low speed gear ratio having the largest gear ratio and used when starting and stopping, a high speed gear stage or high speed gear ratio having the smallest gear ratio and used when traveling at high speed, and a middle speed gear stage or middle speed ratio intermediate between the low speed gear stage or low speed gear ratio and the high speed gear stage or high speed gear ratio can be set, The fuel cut start condition includes the EV driving transition condition, The control unit At least when the engine is operating, the hybrid vehicle is decelerating in a state where the accelerator is off and there is no acceleration request operation by the driver, and the medium speed gear stage or medium speed gear ratio or the high speed gear stage or high speed gear ratio is set in the automatic transmission, it is determined that the EV driving transition condition and the fuel cut start condition are satisfied, and the hybrid vehicle is transitioned to the EV driving, and When the vehicle is shifted to the EV driving mode, if there is an operation request, the fuel cut is not executed even if the fuel cut start condition is met. A control device for a hybrid vehicle.

4. 4. The control device for a hybrid vehicle according to claim 3, The control unit When the EV driving is performed, the clutch is released to cut off the power transmission between the engine and the motor. A control device for a hybrid vehicle.

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