Vehicle engine control device

Abstract

A hybrid control unit 20 of a vehicle 1 comprises an engine stop process control unit 52 that controls the speed of the engine 2 to be greater than or equal to a first lower-limit speed Ve1 when an operation request for an engine 2 is turned on, and that executes an engine stop process in which, if the engine speed Ve has become less than a second lower-limit speed Ve2 lower than the first lower-limit speed Ve1 when the operation request for the engine 2 is turned off, electric power is generated using a motor generator 9 to apply a load to the engine 2 and forcibly set the engine speed Ve to zero.

Description

[Technical Field]

[0001] The present invention relates to a control device for an engine for driving a vehicle. [Background technology]

[0002] Plug-in hybrid vehicles and hybrid vehicles (hereinafter collectively referred to as hybrid vehicles) equipped with an engine and an electric motor as driving sources have been known. Hybrid vehicles have various driving modes, including an EV mode in which the vehicle is driven solely by the electric motor, a series mode in which the engine drives a generator to generate electricity and the electric motor drives the vehicle, and a parallel mode in which the vehicle is driven by both the engine and the electric motor. Many hybrid vehicles automatically switch between these driving modes based on the vehicle's operating conditions.

[0003] Also, vehicles equipped with an idling stop function that automatically stops the engine when the vehicle stops traveling are known. Furthermore, for example, Patent Document 1 proposes a function that, when the engine speed falls below a predetermined speed while the vehicle is decelerating, applies a load to the engine by having the electric motor generate electricity to stop the engine, provided that the engine can be restarted by the electric motor. This allows the engine to quickly escape from a rotation speed range where operation becomes unstable, thereby reducing vibration of the vehicle body while the vehicle is traveling.

[0004] Meanwhile, Patent Document 2 proposes a control for a vehicle in which idling stop (engine stop) is performed while the vehicle is decelerating, in which if a restart of the engine is requested by operating the accelerator or the like before the engine has completely stopped after the start of engine stop control, the engine is restarted after the engine has completely stopped. This makes it possible to accurately obtain the engine crank angle at the time of restart, and to accurately perform vibration isolation control such as engine mount control based on the crank angle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-257463 [Patent Document 2] Patent No. 5667329 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in a vehicle equipped with an idling stop function that automatically stops the engine when the engine rotation speed drops, as in Patent Documents 1 and 2, if the engine is stopped while the vehicle is running and a request is made to restart the engine by operating the accelerator or the like before the engine has completely stopped, if the engine is controlled to be restarted only after the engine has completely stopped, as in Patent Document 2, there may be a delay in the application of driving torque by the engine, which may result in insufficient driving torque and reduced acceleration performance.

[0007] The present invention has been made in consideration of such problems, and its purpose is to provide an engine control device for a vehicle that can be stopped by idling while the vehicle is running, which improves acceleration performance when an acceleration operation is performed during idling stop control. [Means for solving the problem]

[0008] In order to achieve the above object, an engine control device of the present invention is an engine control device comprising: an operation request determination unit that determines an operation request for an engine for driving a vehicle; a fuel supply control unit that supplies fuel to the engine when an operation request for the engine is made; a rotation speed detection unit that detects the rotation speed of the engine; and a stop processing control unit that controls the rotation speed of the engine to be equal to or higher than a first predetermined speed when an operation request for the engine is made while the engine is in operation, and that, when an operation request for the engine is not made, executes engine stop processing that applies a load to the engine to forcibly set the rotation speed to zero if the rotation speed falls below a second predetermined speed that is lower than the first predetermined speed. The vehicle is provided with a first rotating electric machine that generates electricity using a driving torque of the engine, and when an operation request for the engine is made after the operation request for the engine is no longer made and the rotation speed of the engine has fallen below the second predetermined speed, the stop processing control unit stops the engine stop processing and starts the engine, and when the engine stop processing is stopped, the stop processing control unit stops the engine stop processing and starts the engine When the engine is in the full-speed range, the first rotating electrical machine drives the engine to increase the rotation speed of the engine, and when the rotation speed of the engine reaches or exceeds the second predetermined speed, fuel is supplied to the engine to start it, and the first predetermined speed is a value higher than a lower limit value of the rotation speed at which the engine can be stably operated, and the second predetermined speed is a value higher than a lower limit value of the rotation speed at which the engine can be stably operated. alone It is characterized by being a value higher than the lower limit engine speed at which the engine can be restarted.

[0009] As a result, when there is a request to operate the engine, the engine is operated at a first predetermined speed or higher, but if the request to operate the engine disappears while the engine is running and the engine rotation speed falls below a second predetermined speed, the engine rotation speed is forcibly set to 0 by engine stop processing, thereby making it possible to quickly escape from the low rotation range where combustion in the engine may become unstable.

[0010] In addition, since the second predetermined speed at which the engine stop process is initiated is a value lower than the first predetermined speed, for example, when the engine is running and the request for operation disappears, fuel injection stops, and the engine rotation speed gradually decreases, the timing at which the engine stop process is initiated can be delayed. As a result, even if the engine rotation speed drops below the first predetermined speed, if a request to operate the engine is made when the engine rotation speed is equal to or higher than the second predetermined speed, fuel can be supplied to the engine without executing engine stop processing, thereby quickly increasing the engine output torque and rotation speed. Furthermore, if a request to operate the engine is received when the request to operate the engine disappears while the engine is running and the engine rotation speed falls below a second predetermined speed, the engine stop process is stopped and the engine is started, so that the engine can be started quickly and the output torque from the engine can be increased quickly. Furthermore, when the engine stop process is canceled, the engine is driven by the first rotating electric machine, which quickly increases the engine speed above the first predetermined speed, allowing the engine to more quickly escape from the low rotation range where combustion in the engine may become unstable.In addition, by supplying engine fuel and starting the engine after it has escaped the low rotation range, unstable operation at engine start can be avoided.

[0011] The engine startable lower limit rotation speed is preferably near idling speed, or in the range of 500 rpm to 1000 rpm. Also, Preferably, when there is no request to operate the engine during the engine stop process, the stop process control unit drives the first rotating electric machine using inertia torque of the engine to generate electricity. As a result, when there is no request to operate the engine during the engine stop process, the first rotating electric machine is driven by the inertia torque of the engine to generate electricity, which easily places a load on the engine and rapidly reduces the engine rotation speed. [Effects of the Invention]

[0015] According to the vehicle engine control device of the present invention, even if the engine rotation speed drops below a first predetermined speed when an operation request is removed while the engine is running, if an engine operation request is made when the engine rotation speed is equal to or greater than a second predetermined speed, fuel can be supplied to the engine without executing engine stop processing, thereby quickly increasing the engine output torque and rotation speed. This makes it possible to quickly increase the vehicle's drive torque when an engine operation request is made, thereby improving the vehicle's acceleration performance.

[0016] Furthermore, since fuel is not supplied to the engine when there is no request for engine operation, even if the engine speed drops below the first predetermined speed, vibrations due to unstable combustion in the engine do not occur, and the comfort of the vehicle occupants is not impaired. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a plug-in hybrid vehicle equipped with a drive control device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a configuration diagram of an engine control unit in the hybrid control unit according to the present embodiment. [Figure 3] 4 is a time chart showing an example of changes in engine rotation speed, generator torque, and drive torque when engine stop control is being executed; [Figure 4] 10 is a time chart showing another example of changes in engine rotation speed, generator torque, and drive torque during execution of engine stop control. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a plug-in hybrid vehicle (hereinafter referred to as vehicle 1) equipped with a drive control device according to one embodiment of the present invention.

[0019] A vehicle 1 of this embodiment is capable of traveling by driving front wheels 3 with the output of an engine 2 mounted on the vehicle 1, and is provided with an electric front motor 4 that drives the front wheels 3 (traveling drive wheels).

[0020] The engine 2 is, for example, a gasoline engine, and is capable of driving the drive shaft 8 of the front wheels 3 via a reduction gear 7, and is also capable of driving a motor generator 9 (first rotating electric machine) via the reduction gear 7 to generate electricity.

[0021] The front motor 4 is driven by high-voltage power supplied from a drive battery 11 (storage battery) and a motor generator 9 mounted on the vehicle 1 via a front inverter 10, and drives a drive shaft 8 of the front wheels 3 via a reduction gear 7. In the reduction gear 7, the power transmission path between the engine 2 and the drive shaft 8 and the power transmission path between the front motor 4 and the drive shaft 8 are separate paths. The reduction gear 7 has a built-in engine clutch 7a that can switch between connecting and disconnecting the transmission of power between the output shaft of the engine 2 and the drive shaft 8 of the front wheels 3. The reduction gear 7 also has a built-in motor clutch 7b that can switch between connecting and disconnecting the transmission of power between the front motor 4 and the drive shaft 8.

[0022] The electric power generated by the motor generator 9 can be used to charge the drive battery 11 via the front inverter 10, and can also be used to supply electric power to the front motor 4. The drive battery 11 is composed of a secondary battery such as a lithium ion battery, has a battery module (not shown) composed of multiple battery cells, and further has a battery monitoring unit 11a that monitors the charging rate (State Of Charge, hereinafter referred to as SOC) of the battery module.

[0023] The front inverter 10 has a function of controlling the output of the front motor 4 based on a control signal from the hybrid control unit 20, and also of controlling the amount of power generated by the motor generator 9. The vehicle 1 is also provided with a charger 21 that charges the drive battery 11 from an external power source.

[0024] The hybrid control unit 20 is a control device for performing overall control of the vehicle 1, and is configured to include an input / output device, a storage device (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), and the like.

[0025] The input side of the hybrid control unit 20 is connected to a battery monitoring unit 11a of the drive battery 11, a front inverter 10, an engine control unit 22 (fuel supply control unit), an accelerator opening sensor 40 that detects the accelerator operation amount, an engine rotation speed sensor 41 (rotation speed detection unit) that detects the rotation speed of the engine 2, etc., and detection and operation information from these devices is input.

[0026] On the other hand, the output side of the hybrid control unit 20 is connected to the front inverter 10, the reduction gear 7 (clutches 7a, 7b), and the engine control unit 22.

[0027] The hybrid control unit 20 then calculates the vehicle required output and drive torque required to drive the vehicle 1 based on the above-mentioned various detected quantities and various operational information from the accelerator opening sensor 40, engine rotation speed sensor 41, etc., and sends control signals to the engine control unit 22, front inverter 10, and reducer 7 to switch the driving mode (EV mode: electric vehicle mode, series mode, parallel mode), and control the output of the engine 2 and front motor 4, and the output (generated power) of the motor generator 9.

[0028] In the EV mode, the engine clutch 7a of the reduction gear 7 is disengaged and the engine 2 is stopped, and the front motor 4 is driven by power supplied from the drive battery 11 to propel the vehicle 1.

[0029] In series mode, the engine clutch 7a of the reduction gear 7 is disengaged and the motor generator 9 is operated by the engine 2. The front motor 4 is then driven by the electric power generated by the motor generator 9 and the electric power supplied from the drive battery 11 to drive the vehicle. Also, in series mode, the rotational speed of the engine 2 is set to a predetermined rotational speed and surplus electric power is supplied to the drive battery 11 to charge it.

[0030] In parallel mode, the engine clutch 7a of the reducer 7 is connected, and power is mechanically transmitted from the engine 2 via the reducer 7 to drive the front wheels 3. The front motor 4 is driven by electric power generated by operating the motor generator 9 using the engine 2 and electric power supplied from the drive battery 11, causing the vehicle to travel.

[0031] Although the motor clutch 7b is basically in a connected state, by disconnecting it when decelerating in parallel mode, for example, it is possible to suppress the co-rotation of the inactive front motor 4, reduce the driving load, and suppress fuel consumption.

[0032] The hybrid control unit 20 sets the driving mode to the parallel mode in areas where the engine 2 is efficient, such as high speed areas. In areas other than the parallel mode, i.e., in the medium to low speed area, the hybrid control unit 20 switches between the EV mode and the series mode based on the required driving torque of the vehicle 1 and the state of charge (SOC) of the driving battery 11.

[0033] The hybrid control unit 20 includes an engine operation request determination unit 51 and an engine stop processing control unit 52.

[0034] The engine operation request determination unit 51 receives information such as the determined driving mode and accelerator operation amount as described above and determines the operation request for the engine 2. For example, the engine operation request is ON in the series mode or parallel mode, but is OFF when the required drive torque decreases during deceleration in the series mode and the vehicle switches to the EV mode, or when the vehicle idles during low-speed driving. The engine operation request determination result is output to the engine control unit 22, which controls the operation of the engine 2. When the engine operation request is ON, the engine control unit 22 supplies fuel to the engine 2 and ignites the engine 2 to operate it. Note that when the engine operation request is ON while the engine is stopped, the motor generator 9 drives the engine 2 as a starter motor, along with supplying fuel to the engine 2 and igniting the engine 2. On the other hand, when the engine operation request is OFF, the supply of fuel to the engine 2 is stopped and the operation of the engine 2 is stopped.

[0035] The engine stop processing control unit 52 sets a lower limit rotation speed Velow of the engine 2. When the operation request is turned OFF while the engine is running and fuel supply to the engine 2 is stopped, the rotation speed Ve of the engine 2 drops below the lower limit rotation speed Velow.

[0036] Furthermore, when the operation request is turned OFF and the engine rotation speed Ve falls below the lower limit rotation speed Velow, the engine stop process control unit 52 executes engine stop process to forcibly stop the engine 2. For example, when the engine operation request is turned OFF, such as during the above-described idle stop during low-speed driving or when the required drive torque decreases during deceleration driving in the series mode and the vehicle switches to the EV mode, the supply of fuel to the engine 2 is stopped, and the rotation speed of the engine 2 gradually decreases. When the engine rotation speed Ve falls below the lower limit rotation speed Velow, the engine stop process control unit 52 performs engine stop process by causing the motor generator 9 to consume the rotation torque (inertia torque) of the engine 2 to generate electricity. This engine stop process applies a load to the engine 2 and can rapidly reduce the engine rotation speed Ve. The engine stop process is continued until the engine rotation speed Ve becomes 0, i.e., until the engine 2 completely stops. This is executed to reset the detected crank angle of the engine 2 by completely stopping the engine 2, thereby improving the accuracy of crank angle detection during subsequent engine operation and improving the accuracy of the timing of fuel injection, etc., based on the crank angle.

[0037] When the engine operation request is ON, the engine stop processing control unit 52 sets the lower limit rotation speed Velow to a first lower limit rotation speed Ve1 (first predetermined speed). The first lower limit rotation speed Ve1 may be set to a value slightly higher than the lower limit at which the engine 2 can operate stably, for example. In this way, by setting the lower limit rotation speed of the engine 2, unstable operation of the engine 2 can be stopped and vibration of the vehicle 1 can be suppressed.

[0038] Furthermore, when the engine operation request is OFF, the engine stop process control unit 52 sets the lower limit rotation speed Velow to a second lower limit rotation speed Ve2 (second predetermined speed) that is lower than the first lower limit rotation speed Ve1. The second lower limit rotation speed Ve2 may be set to a value that is slightly higher than the engine startable lower limit rotation speed Ve3, for example, at which the engine can be restarted. As a result, when the engine operation request is OFF and the engine rotation speed Ve falls below the first lower limit rotation speed Ve1, but is still equal to or higher than the second lower limit rotation speed Ve2, the engine stop process is not executed.

[0039] 3 and 4 are time charts showing an example of changes in the engine rotation speed Ve, generator torque Tg (regenerative (power generation) torque, powering torque of the motor generator 9), and drive torque Te of the vehicle 1 when engine stop control is being executed. Also shown in FIGS. 3 and 4 is a comparative example of the related art, in which the lower limit rotation speed Velow is always set to the first lower limit rotation speed Ve1, with the dashed line representing the comparative example and the solid line representing this embodiment.

[0040] FIG. 3 shows an example of the changes in the engine rotation speed Ve, generator torque Tg, and drive torque Te of the vehicle 1 when the accelerator is turned ON while the vehicle is traveling with the accelerator turned ON, and the engine rotation speed Ve has decreased to between the first lower limit rotation speed Ve1 and the second lower limit rotation speed Ve2.

[0041] As shown in Figure 3, when the accelerator is turned off while the engine 2 is running due to the accelerator operation ON and the vehicle 1 is traveling, the engine operation request changes from ON to OFF accordingly, and fuel injection of the engine 2 is stopped (a in Figure 3). As a result, the engine rotation speed Ve gradually decreases due to the friction of the engine 2 and the regeneration (electricity generation) of the motor generator 9.

[0042] In a reference example in which the lower limit rotation speed Velow is always set to the first lower limit rotation speed Ve1, engine stop processing is executed when the engine rotation speed Ve becomes less than the first lower limit rotation speed Ve1 (b in FIG. 3). The engine stop processing continues by applying a load to the engine 2 as described above until the engine rotation speed Ve becomes 0 (Pesb in FIG. 3). Therefore, even if an engine operation request is made by operating the accelerator after the engine rotation speed Ve becomes less than the first lower limit rotation speed Ve1 (c in FIG. 3), the engine 2 is restarted after the engine rotation speed Ve becomes 0 (d in FIG. 3). Note that while the engine is operating, the motor generator 9 generates electricity, and even during the engine stop processing period Pesb, the motor generator 9 continues to generate electricity until the engine rotation speed becomes 0.

[0043] Immediately after the engine starts, until the engine rotation speed reaches a predetermined value or more (for example, Ve2 or more) and engine torque is secured, power is supplied to the motor generator 9 as needed to drive it and increase the drive torque (Peug in FIG. 3).

[0044] In contrast, in this embodiment, the lower limit rotation speed Velow is set to a second lower limit rotation speed Ve2 that is lower than the first lower limit rotation speed Ve1, and therefore the engine stop process is not executed until the engine rotation speed Ve becomes less than the second lower limit rotation speed Ve2. Therefore, if the accelerator is operated to turn on the engine operation request before the engine rotation speed Ve becomes less than the first lower limit rotation speed Ve1 and falls below the second lower limit rotation speed Ve2 (c in FIG. 3), fuel injection of the engine 2 is immediately resumed, and the engine rotation speed Ve increases.

[0045] As a result, when the engine operation request is turned OFF and the engine rotation speed Ve decreases, and when the engine operation request is turned ON while the engine rotation speed Ve is between the first lower limit rotation speed Ve1 and the second lower limit rotation speed Ve2, in the reference example, the engine 2 is not restarted until the engine rotation speed Ve becomes 0, and the driving torque Te is the driving torque of the motor generator 9 and the front motor 4 supplied with power from the driving battery 11, and will be insufficient for the required torque until the output torque of the engine 2 increases sufficiently after the restart (e in Figure 3).

[0046] On the other hand, in this embodiment, fuel injection of the engine 2 is resumed immediately after the engine operation request is turned ON, and the driving torque Te is quickly increased, thereby making it possible to obtain a driving torque close to the requested torque.

[0047] FIG. 4 shows an example of the changes in engine speed Ve, generator torque Tg, and drive torque Te when the accelerator is turned OFF while the vehicle is running with the accelerator operated ON, and the engine speed Ve has decreased to less than the second lower limit rotation speed Ve2, and then the accelerator is turned ON.

[0048] As shown in Figure 4, in a reference example in which the lower limit rotation speed Velow is always set to the first lower limit rotation speed Ve1, the engine stop process is executed (Pesb in Figure 4) when the engine rotation speed Ve becomes less than the first lower limit rotation speed Ve1 (b in Figure 4). Therefore, even if the accelerator is operated and the engine operation request is turned ON after the engine rotation speed Ve becomes less than the second lower limit rotation speed Ve2, the engine 2 is restarted after the engine rotation speed Ve becomes 0 (d in Figure 4).

[0049] In contrast, in this embodiment, the engine stop process is executed after the engine rotation speed falls below the second lower limit rotation speed Ve2 (Pesa in FIG. 4). However, if an engine operation request is turned ON before the engine rotation speed reaches 0, the engine stop process is stopped at that point and the engine 2 is started. More specifically, if an engine operation request is turned ON by accelerator operation after the engine rotation speed Ve has fallen below the second lower limit rotation speed Ve2, the motor generator 9 drives the engine 2 to increase the engine rotation speed Ve (Peug in FIG. 4). Then, once the engine rotation speed Ve reaches or exceeds the second lower limit rotation speed Ve2, for example, fuel injection is initiated and the engine 2 is started.

[0050] As a result, when the engine operation request is turned OFF, the engine rotation speed Ve decreases, the engine rotation speed Ve becomes less than the second lower limit rotation speed Ve2, and the engine operation request is turned ON. In the reference example, the engine 2 is not started until the engine rotation speed reaches 0, and the driving torque Te is the driving torque of the motor generator 9 and the front motor 4 supplied with power from the driving battery 11, and is insufficient for the required torque until the output torque of the engine 2 increases sufficiently after restart (e in FIG. 4). On the other hand, in this embodiment, the motor generator 9 increases the engine rotation speed Ve immediately after the engine operation request is turned ON, and fuel supply to the engine 2 is resumed to start the engine. As a result, even if the engine rotation speed Ve decreases below the second lower limit rotation speed Ve2, the driving torque Te can be quickly increased to obtain an output torque close to the required torque.

[0051] Furthermore, instead of restarting fuel injection immediately after the engine operation request is turned ON, the engine rotation speed is increased to above the second lower limit rotation speed Ve2 by the motor generator 9 before fuel supply to the engine 2 is restarted, thereby improving the operating stability of the engine 2 immediately after fuel supply is restarted.

[0052] Although the description of the embodiment has been completed above, the aspects of the present invention are not limited to the above embodiment. For example, although the vehicle 1 of this embodiment is a front-wheel drive vehicle, the present invention can also be applied to a four-wheel drive vehicle equipped with rear motors that drive the left and right rear wheels 5, for example. Furthermore, the vehicle 1 of this embodiment is a plug-in hybrid vehicle (PHEV) that can be externally charged or externally fed, but the present invention can also be applied to hybrid vehicles that do not have a charging function. [Explanation of symbols]

[0053] 1 vehicle (hybrid vehicle) 2 engines 9 Motor generator (first rotating electric machine) 20 Hybrid control unit 22 Engine control unit (fuel supply control unit) 41 Engine rotation speed sensor (rotation speed detection section) 51 Engine operation request determination unit (operation request determination unit) 52 Engine stop processing control unit (stop processing control unit)

Claims

1. a driving requirement determination unit that determines a driving requirement of an engine for driving the vehicle; a fuel supply control unit that supplies fuel to the engine when an operation request for the engine is made; a rotation speed detection unit that detects the rotation speed of the engine; a stop processing control unit that controls the rotation speed of the engine to be equal to or higher than a first predetermined speed when there is a request to operate the engine while the engine is in operation, and that applies a load to the engine to forcibly set the rotation speed to zero when the rotation speed falls below a second predetermined speed that is lower than the first predetermined speed when there is no request to operate the engine, the vehicle includes a first rotating electric machine that generates electricity using the driving torque of the engine; The stop processing control unit When a request to operate the engine is received in a state where an operation request is no longer made during operation of the engine and the rotation speed of the engine is less than the second predetermined speed, the engine stop process is stopped and the engine is started; when the engine stop process is stopped, if the rotation speed of the engine is at least less than the second predetermined speed, the engine is driven by the first rotating electric machine to increase the rotation speed of the engine, and when the rotation speed of the engine becomes equal to or greater than the second predetermined speed, fuel is supplied to the engine to start it; the first predetermined speed is a value higher than a lower limit of a rotation speed at which the engine can be stably operated, The second predetermined speed is a value higher than the engine startable lower limit rotation speed at which the engine can be restarted by itself. An engine control device characterized by:

2. The engine startable lower limit rotation speed is near the idling rotation speed.

2. The engine control device according to claim 1.

3. The engine startable lower limit rotation speed is in the range of 500 rpm to 1000 rpm.

2. The engine control device according to claim 1.

4. The stop processing control unit drives the first rotating electric machine by an inertia torque of the engine to generate electricity when there is no request to operate the engine during the engine stop processing.

2. The engine control device according to claim 1.

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