Vehicle control device

Abstract

To provide a vehicle controller capable of suppressing the occurrence of pull-in shock upon starting an engine.SOLUTION: When an engine is started within a prescribed period from a time point when determining that an engine start method has been switched from an early ignition start method to a push start method, a vehicle controller executes the following: (a) calculating, as available output torque, traveling driving torque out of the output torque of a rotary electric machine on the basis of the transmission torque capacity of a clutch when it is assumed that the push start method has been executed; (b) calculating, as demand torque, the amount of traveling driving torque demanded of a traveling driving force source on the basis of the transmission torque capacity of the clutch when it is assumed that the early ignition start method has been executed; and (c) executing the start control of the engine by using the early ignition start method when the available output torque is insufficient for the demand torque.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle including an engine and a rotating electric machine connected to the engine via a clutch.

Background Art

[0002] A control device for a vehicle including an engine and a rotating electric machine as a driving force source for traveling, and a clutch for disconnecting and connecting a power transmission path between the engine and the rotating electric machine is known. For example, the control device for a vehicle described in Patent Document 1 is such a device. Patent Document 1 discloses an early ignition start method in which, as a method of starting the engine, the clutch is engaged and cranked by the rotating electric machine, fuel is injected into the engine and ignited before synchronization of the clutch, and once the combustion becomes sustainable, the clutch is released and then the clutch is engaged again.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, during the running of a vehicle using a rotating electrical machine as a driving force source for running, for example, when starting the engine in the early ignition start mode when the rotational speed of the rotating electrical machine is low, the engine rotational speed is changed to the synchronous rotational speed of the clutch before the clutch is disengaged, and there is a possibility that a starting shock exceeding the allowable range may occur due to the inertia of the engine being transmitted to the rotor shaft of the rotating electrical machine via the clutch. Therefore, when such a starting shock may occur, it is desirable to start the engine in the forced start mode. The forced start mode is an engine start control method in which the clutch is engaged to increase the engine rotational speed by the rotating electrical machine, and after synchronization of the clutch, fuel is injected into the engine and ignited to start the engine. Compared with the early ignition start mode, in the forced start mode, the starting shock associated with engine start is reduced, but it is necessary to increase the assist torque for engine start. Therefore, for example, if the engine is started unconditionally in the forced start mode when the rotational speed of the rotating electrical machine is low, the output torque of the rotating electrical machine will be insufficient for the required driving torque for running and the assist torque for engine start, and a pulling-in shock may occur during engine start due to a drop in the driving torque for running.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle control device capable of suppressing the occurrence of a pulling-in shock during engine start.

Means for Solving the Problems

[0006] The gist of the present invention is a control device for a vehicle, comprising an engine and an electric rotating machine as driving power sources for running, and a clutch for disconnecting and connecting a power transmission path between the engine and the electric rotating machine, wherein the starting method of the engine is to engage the clutch and crank by the electric rotating machine, inject fuel into the engine before synchronization of the clutch, and once combustion becomes sustainable, temporarily disengage the clutch, and then re-engage the clutch. From the early ignition starting method, it is switched to the forced starting method of engaging the clutch, increasing the engine rotation speed by the electric rotating machine, injecting fuel into the engine after synchronization of the clutch, igniting, and starting the engine. Based on the fact that the rotational speed of the rotating electrical machine at the clutch synchronization timing when assuming that the early ignition start method is executed is less than the rotational speed determination value preset in order to determine that the starting shock when engine starting control is executed by the early ignition start method is within a predetermined allowable range When starting the engine within a predetermined period from the time of determination, (a) calculate the driving torque for running obtained by subtracting the transmission torque capacity of the clutch from the output torque of the electric rotating machine when assuming that the starting control of the engine is executed by the forced starting method as the outputable torque, (b) calculate the required torque by converting the required amount of driving torque for running with respect to the driving power source for running corresponding to the accelerator opening from the accelerator opening when assuming that the starting control of the engine is executed by the early ignition starting method into the torque on the rotor shaft of the electric rotating machine, and (c) when the outputable torque is insufficient with respect to the required torque, execute the starting control of the engine by the early ignition starting method.

Effect of the Invention

[0007] According to the control device for a vehicle of the present invention, the starting method of the engine is switched from the early ignition starting method to the forced starting method. Based on the fact that the rotational speed of the rotating electrical machine at the clutch synchronization timing when assuming that the early ignition start method is executed is less than the rotational speed determination value preset in order to determine that the starting shock when engine starting control is executed by the early ignition start method is within a predetermined allowable rangeWhen the engine is started within a predetermined period from the time of determination, (a) the driving torque for running obtained by subtracting the transmission torque capacity of the clutch from the output torque of the rotating electrical machine assuming that the starting control of the engine is executed by the push-start method is calculated as the outputable torque, (b) the required amount of driving torque for running with respect to the driving power source for running corresponding to the accelerator opening degree from the accelerator opening degree assuming that the starting control of the engine is executed by the early ignition start method is calculated as the required torque by converting it into the torque on the rotor shaft of the rotating electrical machine, and (c) when the outputable torque is insufficient with respect to the required torque, the starting control of the engine is executed by the early ignition start method. Thus, when the engine is started within a predetermined period from the time of determination that the starting method of the engine has been switched from the early ignition start method to the push-start method, if the driving torque component of the output torque of the rotating electrical machine is insufficient with respect to the required amount of driving torque for running with respect to the driving power source for running and a pulling shock occurs at the time of engine starting when the starting control of the engine is actually executed by the push-start method, the starting control of the engine is executed by the early ignition start method regardless of the starting method determined to have been switched. Thereby, the occurrence of a pulling shock at the time of engine starting is suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiment for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios and shapes of each part are not necessarily accurately drawn.

Embodiment

[0010] FIG. 1 is a schematic configuration diagram of a vehicle 10 equipped with an electronic control device 80 according to an embodiment of the present invention, and is a functional block diagram showing the main parts of control functions for various controls in the vehicle 10.

[0011] The vehicle 10 is a hybrid vehicle including an engine 14 and a rotating electric machine MG that function as a driving power source for traveling. The power transmission device 12 includes, in a transmission case 20 as a non-rotating member, in order from the engine 14 side, a clutch K0, a torque converter 16, an automatic transmission 18, and the like. Further, the power transmission device 12 includes a propeller shaft 26 connected to a transmission output shaft 24 that is an output rotation shaft of the automatic transmission 18, a differential gear 28 connected to the propeller shaft 26, a pair of axles 30 connected to the differential gear 28, and the like. The power transmission device 12 configured in this way is preferably used for a vehicle 10 of, for example, an FR (front engine · rear drive) type. When the clutch K0 is engaged in the power transmission device 12 (hereinafter, when not particularly distinguished, it means complete engagement), the power of the engine 14 (hereinafter, when not particularly distinguished, torque and force are also synonymous) is transmitted from an engine connection shaft 32 connected to the engine 14 to a pair of drive wheels 34 sequentially via the clutch K0, the torque converter 16, the automatic transmission 18, the propeller shaft 26, the differential gear 28, and a pair of axles 30. In this way, the power transmission device 12 constitutes a power transmission path from the engine 14 to the drive wheels 34.

[0012] The engine 14 is an internal combustion engine that generates power by burning fuel. The engine 14 can be ignited and self-rotated starting from the stage where the engine rotational speed Ne [rpm] is at a low rotation, and is, for example, an in-cylinder injection type internal combustion engine that directly injects fuel into the cylinder.

[0013] The torque converter 16 is provided in the power transmission path between the rotary electric machine MG (and the engine 14) and the drive wheels 34. The torque converter 16 is a fluid transmission device that outputs the power input to the pump impeller 16a, which is an input-side rotating member, via a fluid to the turbine impeller 16b, which is an output-side rotating member. The pump impeller 16a is connected to the engine connecting shaft 32 via the clutch K0 and is directly connected to the rotary electric machine MG. The turbine impeller 16b is directly connected to the transmission input shaft 36, which is the input rotating shaft of the automatic transmission 18.

[0014] The torque converter 16 includes a known lock-up clutch 38 that directly connects between the pump impeller 16a and the turbine impeller 16b. The lock-up clutch 38 can mechanically directly connect the power transmission path between the engine 14 and the rotary electric machine MG and the drive wheels 34. An oil pump 22 is connected to the pump impeller 16a. The oil pump 22 is a mechanical oil pump that is rotationally driven by at least one of the engine 14 and the rotary electric machine MG to generate the hydraulic pressure for performing shift control of the automatic transmission 18 and disconnection / connection control (transmission torque capacity control) of the clutch K0. The lock-up clutch 38 is disconnected / connectedly controlled by the hydraulic control circuit 50 provided in the vehicle 10 using the hydraulic pressure generated by the oil pump 22 as the source pressure. For example, when the engine rotational speed Ne is at a low rotation immediately after the start control of the engine 14 starts, the lock-up clutch 38 is disconnected so that the pulsation of the engine 14 is not transmitted to the drive wheels 34.

[0015] The rotating electric machine MG is a so-called motor generator having functions as, for example, an engine that generates mechanical power from electrical energy and as a generator that generates electrical energy from mechanical energy. The rotating electric machine MG functions as a driving power source for running, as an alternative to the engine 14 or together with the engine 14. The rotating electric machine MG generates electrical energy by regeneration from the power generated by the engine 14 or the driven power input from the drive wheels 34, and performs operations such as accumulating the electrical energy in the power storage device 54 via the inverter 52. The rotating electric machine MG is connected to the power transmission path between the clutch K0 and the torque converter 16 (that is, the rotor shaft 40 of the rotating electric machine MG is connected to the clutch K0 and the pump impeller 16a), and power is transmitted mutually between the rotating electric machine MG and the pump impeller 16a. Therefore, the rotating electric machine MG is connected to the transmission input shaft 36 of the automatic transmission 18 so as to be power-transmittable without passing through the clutch K0. The MG torque Tmg, which is the output torque of the rotating electric machine MG, is controlled by an electronic control unit 80 described later.

[0016] The clutch K0 is a clutch that disconnects and connects the power transmission path between the engine 14 and the rotating electric machine MG. The clutch K0 is, for example, a wet multi-plate type hydraulic friction engagement device in which a plurality of friction plates overlapped with each other are pressed by a hydraulic actuator, and is disconnected and connected by the hydraulic control circuit 50 using the hydraulic pressure generated by the oil pump 22 as the source pressure. In the disconnection and connection control, for example, the transmission torque capacity (engagement force of the clutch K0) Tc [Nm] of the clutch K0 is changed by adjusting the pressure of a linear solenoid valve or the like in the hydraulic control circuit 50. In the engaged state of the clutch K0, the pump impeller 16a and the engine 14 are integrally rotated via the engine connection shaft 32. On the other hand, in the released state of the clutch K0, the power transmission between the engine 14 and the pump impeller 16a is blocked. That is, by releasing the clutch K0, the engine 14 and the drive wheels 34 are separated. Since the rotating electric machine MG is connected to the pump impeller 16a, the clutch K0 is provided in the power transmission path between the engine 14 and the rotating electric machine MG and also functions as a clutch that disconnects and connects the power transmission path.

[0017] The automatic transmission 18 forms part of the power transmission path between the engine 14, the rotary electric machine MG, and the drive wheels 34, and is a transmission that transmits power from the driving power sources (the engine 14 and the rotary electric machine MG) to the drive wheels 34. The automatic transmission 18 is, for example, a known planetary gear type multi-stage transmission in which a plurality of shift stages (gear stages) with different gear ratios γ (= input rotational speed Nin of the transmission / output rotational speed Nout of the transmission) can be selectively established, or a known continuously variable transmission in which the gear ratio γ can be continuously changed steplessly. In the automatic transmission 18, for example, a hydraulic actuator is controlled by a hydraulic control circuit 50 so that a predetermined gear ratio γ is set according to the driver's accelerator operation, vehicle speed V, etc.

[0018] The vehicle 10 includes an electronic control unit 80 which is a control device of the vehicle 10. The electronic control unit 80 is configured to include a so-called microcomputer including, for example, a CPU, a RAM, a ROM, an input / output interface, etc., and the CPU performs signal processing according to a program stored in the ROM in advance while using the temporary storage function of the RAM to execute various controls of the vehicle 10. For example, the electronic control unit 80 executes output control including starting control of the engine 14, drive control of the rotary electric machine MG including regeneration control of the rotary electric machine MG, shift control of the automatic transmission 18, connection / disconnection control of the clutch K0, connection / disconnection control of the lock-up clutch 38, etc., and is configured to be divided into engine control, rotary electric machine control, hydraulic control, etc. as necessary. Note that the electronic control unit 80 corresponds to the "control device" in the present invention.

[0019] The electronic control unit 80 receives various signals (for example, the engine rotational speed Ne [rpm] which is the rotational speed of the engine 14, the turbine rotational speed Nt [rpm], that is, the input rotational speed Nin [rpm] of the transmission input shaft 36, the output rotational speed Nout [rpm] of the transmission output shaft 24 corresponding to the vehicle speed V, the MG rotational speed Nmg [rpm] which is the rotational speed of the rotating electrical machine MG, the accelerator opening θacc corresponding to the driver's driving demand amount for the vehicle 10, the throttle valve opening θth of the electronic throttle valve, the state of charge value (the ratio of the actually stored charge amount to the charge capacity) SOC [%] of the power storage device 54, etc.) based on the detection values from various sensors (for example, the engine rotational speed sensor 56, the turbine rotational speed sensor 58, the output shaft rotational speed sensor 60, the MG rotational speed sensor 62, the accelerator opening sensor 64, the throttle sensor 66, the battery sensor 68, etc.).

[0020] From the electronic control unit 80, for example, the engine control signal Se for controlling the output of the engine 14, the MG control signal Smg for controlling the operation of the rotating electrical machine MG, the hydraulic control signal Sp for operating solenoid valves (solenoid valves) etc. included in the hydraulic control circuit 50 to control the hydraulic actuators of the clutch K0, the lock-up clutch 38, and the automatic transmission 18, etc. are output to the engine control device such as the throttle actuator and the fuel injection device, the inverter 52, the hydraulic control circuit 50, etc. respectively.

[0021] FIG. 2 is a diagram showing an example of an EV / EHV region map used for switching between the motor driving mode and the hybrid driving mode.

[0022] Vehicle 10 switches the driving mode based on the vehicle state indicated by the actual vehicle speed V and the drive demand amount (such as the accelerator opening θacc) from a predetermined relationship (EV / EHV region map) having, for example, a motor driving region (EV region) and a hybrid driving region (EHV region). When the vehicle state is in the EV region, the driving mode is set to the motor driving mode, and motor driving is performed with only the rotating electrical machine MG as the driving power source for driving. When the vehicle state is in the EHV region, the driving mode is set to the hybrid driving mode, and hybrid driving is performed with at least the engine 14 as the driving power source for driving.

[0023] For example, when the driver depresses the accelerator pedal further and the accelerator opening θacc increases, and the vehicle state moves from the EV region to the EHV region, the engine 14 is started and the driving mode is set to the hybrid driving mode. The engine starting method of the vehicle 10 includes an early ignition starting method and a forced starting method.

[0024] The early ignition start method engages the clutch K0 and cranks with the rotating electric machine MG. Before synchronization of the clutch K0, fuel is injected into the engine 14 and ignited. Once the combustion can be sustained, the clutch K0 is released, and then the clutch K0 is engaged again. In the early ignition start method, fuel is injected and ignited near the compression TDC (Top Dead Center) at a low engine rotation speed Ne, and the engine 14 is started. The push start method engages the clutch K0 and raises the engine rotation speed Ne with the rotating electric machine MG. After synchronization of the clutch K0, fuel is injected into the engine 14 and ignited to start it. Compared with the push start method, in the early ignition start method, since the combustion torque (engine torque Te) of the engine 14 is used for starting the engine 14, the assist torque for the rotating electric machine MG to crank can be reduced, and the starting responsiveness is good. The assist torque is the torque transmitted to the engine 14 when the rotating electric machine MG cranks, and is the same magnitude as the transmission torque capacity (engagement force of the clutch K0) Tc of the clutch K0 during the starting control of the engine 14. Note that the "starting" of the engine 14 here refers not only to the period until the engine 14 explodes completely (starts operating) and becomes capable of self-sustained operation, but also to a series of control operations related to the engine starting until the clutch K0 is fully engaged.

[0025] Figure 3 is a diagram for explaining the relationship between the starting shock generated during the starting of the engine 14 by the early ignition start method and the MG rotation speed Nmg. Figure 3 is an example of a time chart assuming that the starting control of the engine 14 is executed by the early ignition start method by the electronic control unit 80 shown in Figure 1, and shows three cases with different MG rotation speeds Nmg at the start time of the starting control of the engine 14. Note that the K0 hydraulic pressure shown in Figure 3 is the hydraulic pressure for controlling the connection / disconnection state of the clutch K0, and is the hydraulic pressure supplied to the hydraulic actuator of the clutch K0.

[0026] While the vehicle 10 is traveling with only the rotary electric machine MG as the driving force source for traveling, for example, the accelerator opening θacc may be increased by the driver stepping harder on the accelerator pedal. For example, it is a case where the accelerator pedal is changed from a state where it is not depressed (accelerator opening θacc = 0) to a state where it is depressed (accelerator opening θacc > 0).

[0027] At time x0, due to the increase in the accelerator opening θacc, the start control of the engine 14 by the early ignition start method is started. The increased accelerator opening θacc is maintained constant until the start control of the engine 14 is completed even after the start control of the engine 14 is started. The time point when the start control is completed is when the clutch K0 that has been once released in the early ignition start method is engaged again later. With the start of the start control of the engine 14, the commanded pressure of the K0 hydraulic pressure is once set to a high hydraulic pressure for quickly packing the pack clearance after time x0, and then is set to the hydraulic pressure that engages the clutch K0. The actual pressure of the K0 hydraulic pressure rises according to the commanded pressure of the K0 hydraulic pressure.

[0028] Due to the engagement of the clutch K0, from time x1, the engine 14 is cranked by the rotary electric machine MG, fuel is injected into the engine 14 and ignited, and the engine rotational speed Ne rises. At time x2 when the combustion of the engine 14 becomes sustainable, the commanded pressure of the K0 hydraulic pressure for releasing the clutch K0 is output. The commanded pressure of the K0 hydraulic pressure is once set to zero after time x2, and then is set to the hydraulic pressure (>0) for packing the pack and keeping it in the released state. The actual pressure of the K0 hydraulic pressure drops according to the commanded pressure of the K0 hydraulic pressure.

[0029] At time x4, the commanded pressure of the K0 hydraulic pressure is gently increased to engage the clutch K0 again, and the actual pressure of the K0 hydraulic pressure rises according to the commanded pressure. Due to the rise in the actual pressure of the K0 hydraulic pressure, for example, the clutch K0 is brought into a fully engaged state through a semi-engaged state (slip engaged state), so that the engine 14 and the rotary electric machine MG are connected and the start control of the engine 14 is completed. As a result, the vehicle 10 travels in hybrid mode with the engine 14 and the rotary electric machine MG as the driving force sources for traveling.

[0030] Incidentally, when the actual pressure of the K0 hydraulic pressure has not sufficiently decreased (that is, the clutch K0 is not in the released state) at the synchronization timing of the clutch K0 where the engine rotation speed Ne and the MG rotation speed Nmg are the same, the inertia of the engine 14 is transmitted to the rotor shaft 40 of the rotating electrical machine MG via the clutch K0, and a starting shock exceeding a predetermined allowable range may occur in the vehicle 10. Note that "the clutch K0 is synchronized" means that the engine rotation speed Ne, which is the same value as the rotation speed of the engine connection shaft 32 on one side of the power transmission path that the clutch K0 controls for disconnection and connection, and the MG rotation speed Nmg on the other side are the same. The synchronization timing is the time when the clutch K0 is synchronized.

[0031] The transmission torque capacity Tc of the clutch K0 changes as shown in FIG. 3 according to the actual pressure of the K0 hydraulic pressure.

[0032] In the case of case 1 where the MG rotation speed Nmg at the start of the start control of the engine 14 is the lowest, the clutch K0 is synchronized at time x3a. At the synchronization timing, the MG rotation speed Nmg is the rotation speed value Nmg1 [rpm].

[0033] In the case of case 3 where the MG rotation speed Nmg at the start of the start control of the engine 14 is the highest, the clutch K0 is synchronized at time x3c. At the synchronization timing, the MG rotation speed Nmg is the rotation speed value Nmg3 [rpm].

[0034] In the case of case 2 where the MG rotation speed Nmg at the start of the start control of the engine 14 is between case 1 and case 3, the clutch K0 is synchronized at time x3b (x3a < x3b < x3c). At the synchronization timing, the MG rotation speed Nmg is the rotation speed value Nmg2 [rpm].

[0035] The higher the MG rotational speed Nmg at the synchronization timing, the longer the period required for the engine rotational speed Ne to increase to the same rotational speed as the MG rotational speed Nmg, that is, the longer the period from the start of the start control of the engine 14 until the clutch K0 synchronizes. Therefore, the higher the MG rotational speed Nmg at the synchronization timing, the lower the actual pressure of the K0 hydraulic pressure that once releases the clutch K0 at the synchronization timing tends to be, and the lower the transmission torque capacity Tc at the synchronization timing tends to be. On the other hand, the lower the MG rotational speed Nmg at the synchronization timing, the less likely the actual pressure of the K0 hydraulic pressure that once releases the clutch K0 at the synchronization timing is to decrease, and the higher the transmission torque capacity Tc at the synchronization timing tends to be.

[0036] When the clutch K0 synchronizes, the clutch K0 transmits the engine torque Te as a disturbance to the rotor shaft 40 of the rotating electrical machine MG. If the transmission torque capacity Tc at the synchronization timing is large, the engine torque Te transmitted by the clutch K0 tends to increase and the starting shock is likely to exceed the predetermined allowable range. If the transmission torque capacity Tc at the synchronization timing is small, the engine torque Te transmitted by the clutch K0 tends to decrease and the starting shock is likely to be within the predetermined allowable range.

[0037] Here, when the MG rotational speed Nmg at the synchronization timing is the rotational speed value Nmg2 as in Case 2, it is assumed that the transmission torque capacity Tc of the clutch K0 at the synchronization timing is the upper limit value that can tolerate the starting shock. In the case of Case 1, the starting shock associated with the starting of the engine 14 by the early ignition starting method is outside the predetermined allowable range. Therefore, in the case of Case 1, the execution of the starting control of the engine 14 is suitable for the push-start control. In the case of Case 3, the starting shock associated with the starting of the engine 14 by the early ignition starting method is within the predetermined allowable range. Therefore, in the case of Case 3, the starting control of the engine 14 is suitable for the early ignition starting method. That is, when the MG rotational speed Nmg at the synchronization timing is equal to or higher than the rotational speed value Nmg2, the starting shock associated with the starting of the engine 14 by the early ignition starting method is within the predetermined allowable range, and when the MG rotational speed Nmg at the synchronization timing is less than the rotational speed value Nmg2, the starting shock associated with the starting of the engine 14 by the early ignition starting method is outside the predetermined allowable range.

[0038] Returning to FIG. 1, the electronic control device 80 functionally includes a starting method setting unit 80a, a starting determination unit 80b, an assist torque determination unit 80c, an outputable torque calculation unit 80d, a required torque calculation unit 80e, a starting method determination unit 80f, and a starting control unit 80g.

[0039] The starting method setting unit 80a sets the starting method of the engine 14. Note that the starting method set by the starting method setting unit 80a is not necessarily executed.

[0040] For example, assuming that the early ignition start method is executed as the starting control of the engine 14 based on the current MG rotation speed Nmg, the system shaft torque Tsys, and the turbine rotation speed Nt, the starting method setting unit 80a calculates (i.e., predicts) the MG rotation speed Nmg at the synchronization timing of the clutch K0 as the synchronization vehicle state value at that time. Here, "current" refers to the time when the starting method of the engine 14 is set. The system shaft torque Tsys is the required amount on the rotor shaft 40 of the driving torque for the driving power source (engine 14 and rotating electric machine MG) of the vehicle 10, and corresponds to, for example, the target value of the input torque input to the torque converter 16, and is the target value of the driving torque for driving the drive wheels 34 (torque converter 16) by the engine 14 and the rotating electric machine MG shown in FIG. 1. Note that the system shaft torque Tsys corresponds to the "required torque" in the present invention. For example, the system shaft torque Tsys calculates the target value of the output torque at the drive wheels 34 based on the accelerator opening θacc and the vehicle speed V, and converts the calculated target value into the torque on the rotor shaft 40 in consideration of transmission losses, auxiliary load, the gear ratio γ of the automatic transmission 18, the state of charge value SOC of the power storage device 54 (in other words, the charge and discharge required amount of the power storage device 54), and the like.

[0041] For example, the relationship between the current, i.e., the actual MG rotation speed Nmg, the system shaft torque Tsys, and the turbine rotation speed Nt at the time when the starting method of the engine 14 is set, and the MG rotation speed (predicted value) Nmg at the synchronization timing of the clutch K0 is applied to a map determined in advance experimentally or by design for the current MG rotation speed Nmg, the system shaft torque Tsys, and the turbine rotation speed Nt, thereby calculating the MG rotation speed Nmg at the synchronization timing of the clutch K0. Since the control of the K0 hydraulic pressure from the start of the starting control of the engine 14 to the synchronization timing of the clutch K0 is determined in advance, the control of the operating state of the clutch K0 (including the state of the transmission torque capacity Tc) is determined in advance, and the MG rotation speed Nmg at the synchronization timing of the clutch K0 can be calculated based on the current MG rotation speed Nmg, the system shaft torque Tsys, and the turbine rotation speed Nt.

[0042] For example, the starting method setting unit 80a determines whether or not the MG rotational speed Nmg at the predicted synchronization timing is equal to or higher than a predetermined MG rotational speed determination value Nmg_jdg [rpm]. The predetermined MG rotational speed determination value Nmg_jdg is a determination value that is experimentally or designedly determined in advance to determine that the starting shock when the starting control of the engine 14 is executed by the early ignition starting method is within a predetermined allowable range. For example, it is the rotational speed value Nmg2 in FIG. 3 described above. When it is determined that the MG rotational speed Nmg at the predicted synchronization timing is equal to or higher than the predetermined MG rotational speed determination value Nmg_jdg, the starting method setting unit 80a sets the early ignition starting method as the starting method of the engine 14. When it is determined that the MG rotational speed Nmg at the predicted synchronization timing is less than the predetermined MG rotational speed determination value Nmg_jdg, the starting method setting unit 80a sets the forced starting method as the starting method of the engine 14.

[0043] In this way, the starting method setting unit 80a sets the starting method of the engine 14 as needed, for example, every predetermined cycle, based on whether or not the starting shock that occurs when it is assumed that the early ignition starting method is executed as the starting control of the engine 14 is within a predetermined allowable range.

[0044] Further, the starting method setting unit 80a determines whether or not the starting method of the engine 14 has switched from the early ignition starting method to the forced starting method. Hereinafter, the time point when it is determined by the starting method setting unit 80a that the starting method of the engine 14 has switched from the early ignition starting method to the forced starting method is referred to as the "switching time point".

[0045] When the starting method set by the starting method setting unit 80a is the early ignition starting method, in case the starting control of the engine 14 is executed by the early ignition starting method, an assist torque for early ignition starting is secured as an early ignition starting guaranteed torque from the MG torque Tmg, and the remainder is distributed as an MG traveling distributed torque Tr (see Fig. 5). The MG traveling distributed torque Tr is the torque on the rotor shaft 40 that can be distributed as the driving torque for traveling among the MG torques Tmg, and is the driving torque for traveling that can be output to the drive wheels 34 (torque converter 16) by the rotating electrical machine MG. Note that the MG traveling distributed torque Tr corresponds to the "outputable torque" in the present invention. When the starting method set by the starting method setting unit 80a is the push-starting method, in case the starting control of the engine 14 is executed by the push-starting method, an assist torque for push-starting is secured as a push-starting guaranteed torque from the MG torque Tmg, and the remainder is distributed as an MG traveling distributed torque Tr (see Fig. 5). Note that by controlling the MG traveling distributed torque Tr to be larger than the system shaft torque Tsys, the driving force required by the driver for the vehicle 10 can be satisfied. On the other hand, the energy usage efficiency (electricity cost) of the rotating electrical machine MG deteriorates as the MG traveling distributed torque Tr becomes larger than the system shaft torque Tsys.

[0046] In the push-starting method, since the engine torque Te is not used for starting the engine 14, the push-starting guaranteed torque is larger than the early ignition starting guaranteed torque. Therefore, immediately after the starting method set by the starting method setting unit 80a is switched from the early ignition starting method to the push-starting method, the assist torque is switched from the early ignition starting guaranteed torque to the push-starting guaranteed torque, so the MG traveling distributed torque Tr among the MG torques Tmg rapidly decreases. If the starting control of the engine 14 is executed by the push-starting method at the timing when this MG traveling distributed torque Tr rapidly decreases, the MG traveling distributed torque Tr may become insufficient with respect to the system shaft torque Tsys, and there is a risk of generating a pulling shock at the time of engine starting.

[0047] The start determination unit 80b determines whether to execute the start control of the engine 14. For example, based on the fact that the vehicle state has moved from the EV region to the EHV region in the EV / EHV region map shown in FIG. 2 described above, it is determined to execute the start control of the engine 14. Further, when the start determination unit 80b determines to execute the start control of the engine 14, it determines whether the determination time is within a predetermined period T from the switching time. The predetermined period T is a period necessary to ensure that the distributed torque Tr for MG running in the MG torque Tmg can be secured by an amount necessary so that the pulling shock at engine start is within the allowable range even if the forced start is executed, and is determined experimentally or designed in advance. For example, it is a period necessary to increase the MG torque Tmg or change the gear ratio γ of the automatic transmission 18.

[0048] When it is determined by the start determination unit 80b to execute the start control of the engine 14 and it is determined that the determination time is within the predetermined period T from the switching time, the assist torque determination unit 80c determines whether the assist torque of the clutch K0 has increased due to the switching of the start method set by the start method setting unit 80a. That is, it is determined whether the forced start guarantee torque has increased with respect to the early ignition start guarantee torque due to the switching of the start method. When the assist torque has not increased, the distributed torque Tr for MG running in the MG torque Tmg has not decreased.

[0049] When it is determined by the start determination unit 80b to execute the start control of the engine 14 and it is determined that the determination time is within the predetermined period T from the switching time, the outputable torque calculation unit 80d calculates the distributed torque Tr for MG running in the MG torque Tmg as the outputable torque based on the transmission torque capacity Tc of the clutch K0 when the forced start method is assumed to be executed as the start control of the engine 14.

[0050] When it is determined by the start determination unit 80b that the start control of the engine 14 is to be executed and it is determined that the determination timing is within a predetermined period T from the switching timing, the required torque calculation unit 80e calculates the By converting the required amount of driving torque for running corresponding to the accelerator opening θacc from the accelerator opening θacc into the torque on the rotor shaft 40 of the rotating electrical machine MG system shaft torque Tsys as the required torque.

[0051] The start method determination unit 80f basically determines either the early ignition start method or the forced start method set by the start method setting unit 80a as the method for executing the start control of the engine 14. However, in the following two cases, the start method determination unit 80f determines the method for executing the start control of the engine 14 as the early ignition start method regardless of the start method set by the start method setting unit 80a. The first case is when it is determined by the assist torque determination unit 80c that the assist torque of the clutch K0 has not increased. The second case is when the MG running distribution torque Tr calculated by the outputable torque calculation unit 80d is smaller than the system shaft torque Tsys calculated by the required torque calculation unit 80e, that is, when the MG running distribution torque Tr is insufficient with respect to the system shaft torque Tsys. Thus, the determination of the method for executing the start control of the engine 14 by the start method determination unit 80f emphasizes the suppression of the occurrence of the pull-in shock when the engine start control is executed by the forced start method compared to the suppression of the occurrence of the start shock when the engine start control is executed by the early ignition start method. Note that even if it falls under the above two cases, for example, when the start control of the engine 14 by the early ignition start method is disabled due to requirements on the engine 14 side, the start method determination unit 80f determines the forced start method as the method for executing the start control of the engine 14.

[0052] When the early ignition start method is determined as the method for executing the start control of the engine 14 by the start method determination unit 80f, the start control unit 80g executes the start control of the engine 14 by the early ignition start method. Note that the transmission torque capacity Tc of the clutch K0 in the case where the start control of the engine 14 is executed by the early ignition start method regardless of the start method set by the start method setting unit 80a is that in the early ignition start method. When the push start method is determined as the method for executing the start control of the engine 14 by the start method determination unit 80f, the start control unit 80g executes the start control of the engine 14 by the push start method.

[0053] FIG. 4 is an example of a flowchart for explaining a main part of the control operation of the electronic control device 80 shown in FIG. 1. For example, when it is determined to execute the start control of the engine 14 while the vehicle 10 is traveling with the motor, the flowchart of FIG. 4 is executed.

[0054] In step S10 corresponding to the function of the start determination unit 80b, it is determined whether or not it is determined to execute the start control of the engine 14 within a predetermined period T from the time when it is determined that the start method of the engine 14 has switched from the early ignition start method to the push start method. If the determination in step S10 is affirmative, step S20 is executed. If the determination in step S10 is negative, step S70 is executed.

[0055] In step S20 corresponding to the function of the assist torque determination unit 80c, it is determined whether or not the assist torque of the clutch K0 has increased due to the change of the start method. If the determination in step S20 is affirmative, step S30 is executed. If the determination in step S20 is negative, step S100 is executed.

[0056] In step S30 corresponding to the function of the available torque calculation unit 80d, based on the transmission torque capacity Tc of the clutch K0 when it is assumed that the push start method is executed as the starting control of the engine 14, the distribution torque Tr for MG traveling among the MG torques Tmg is calculated as the available torque. Then, step S40 is executed.

[0057] In step S40 corresponding to the function of the required torque calculation unit 80e, when it is assumed that the early ignition start method is executed as the starting control of the engine 14 By converting the required amount of driving torque for running corresponding to the accelerator opening θacc from the accelerator opening θacc into the torque on the rotor shaft 40 of the rotating electrical machine MG , the system axis torque Tsys is calculated as the required torque. Then, step S50 is executed.

[0058] In step S50 corresponding to the function of the starting method determination unit 80f, it is determined whether the distribution torque Tr for MG traveling calculated in step S30 is smaller than the system axis torque Tsys calculated in step S40. If the determination in step S50 is affirmed, step S60 is executed. If the determination in step S50 is negated, step S100 is executed.

[0059] In step S60 corresponding to the function of the starting method determination unit 80f, it is determined whether the starting control of the engine 14 by the early ignition start method is possible. If the determination in step S60 is affirmed, step S80 is executed. If the determination in step S60 is negated, step S100 is executed.

[0060] In step S70 corresponding to the function of the starting determination unit 80b, it is determined whether it has been decided to execute the starting control of the engine 14 within the period when the starting method of the engine 14 is the early ignition start method. If the determination in step S70 is affirmed, step S60 is executed. If the determination in step S70 is negated, step S100 is executed.

[0061] In step S80 corresponding to the function of the start method determination unit 80f, the start method of the engine 14 to be actually executed is determined to be the early ignition start method. Then step S90 is executed.

[0062] In step S90 corresponding to the function of the start control unit 80g, start control of the engine 14 is executed by the early ignition start method. Then a return is made.

[0063] In step S100 corresponding to the function of the start method determination unit 80f, the start method of the engine 14 to be actually executed is determined to be the forced start method. Then step S110 is executed.

[0064] In step S110 corresponding to the function of the start control unit 80g, start control of the engine 14 is executed by the forced start method. Then a return is made.

[0065] FIG. 5 is an example of a time chart for explaining the control operation of the electronic control device 80 shown in FIG. 1. The horizontal axis in FIG. 5 is time t [sec].

[0066] Before time t0, the vehicle 10 is traveling by the motor, and the traveling road is an uphill road. For example, as the driver depresses the accelerator pedal more, the accelerator opening θacc gradually increases, and the driving requirement amount for the vehicle 10 gradually increases. On the other hand, due to traveling on this uphill road, the MG rotational speed Nmg of the rotary electric machine MG, which is the driving power source for traveling, gradually decreases.

[0067] The starting method of the engine 14 is set to either the early ignition starting method or the forced starting method at each time. For example, the starting method of the engine 14 is determined based on whether the starting shock that occurs when it is assumed that the early ignition starting method is executed as the starting control of the engine 14 is within a predetermined allowable range. At time t0, the starting method of the engine 14 is switched from the early ignition starting method to the forced starting method. At time t1 (> t0), it is determined to execute the starting control of the engine 14. This time t1 is between time t0 and time t3 when a predetermined period T has elapsed from that time t0. At time t1, the starting control of the engine 14 is started (cranking by the rotating electric machine MG is started), and at time t4, the starting control of the engine 14 is completed, and the vehicle 10 is switched to hybrid running. Regarding whether the starting control of the engine 14 is executed by either the early ignition starting method or the forced starting method, it will be described later. Note that the initial stages of both the early ignition starting method and the forced starting method are common in that the clutch K0 is engaged and cranked by the rotating electric machine MG. Also, since it takes time for the actual pressure of the K0 hydraulic pressure that engages the clutch K0 for this cranking to rise, it takes time from the start of the starting control of the engine 14 until the engine rotation speed Ne starts to rise. The period between time t1 and time t4 is the execution period of the starting control of the engine 14.

[0068] In Fig. 5, the distribution torque Tr for MG running calculated at each time is shown by a broken line. The distribution torque Tr for MG running is the remaining part obtained by subtracting the assist torque for engine starting from the MG torque Tmg. Before time t0, the distribution torque Tr for MG running is calculated while ensuring the assist torque for engine starting (guaranteed torque for early ignition starting) in the case where the early ignition starting method is executed as the engine starting control of the engine 14. That is, the distribution torque Tr for MG running is calculated based on the transmission torque capacity Tc of the clutch K0 in the case where the engine starting control is executed by the early ignition starting method. After time t0, the distribution torque Tr for MG running is calculated while ensuring the assist torque for engine starting (guaranteed torque for forced starting) in the case where the forced starting method is executed as the engine starting control of the engine 14. That is, the distribution torque Tr for MG running is calculated based on the transmission torque capacity Tc of the clutch K0 in the case where the engine starting control is executed by the forced starting method.

[0069] In Fig. 5, two cases regarding the system axis torque Tsys at each time are shown by the arrows of the one-dot chain line and the two-dot chain line, respectively. The system axis torque Tsys after time t1 is a predicted value calculated based on the transmission torque capacity Tc of the clutch K0 in the case where the execution of the early ignition starting method is started as the engine starting control of the engine 14 at time t1.

[0070] When the system shaft torque Tsys changes as indicated by the dashed-dotted arrow, during the execution period of the engine start control, the MG driving distribution torque Tr is predicted to be smaller than the system shaft torque Tsys. Therefore, if the start control of the engine 14 is executed by the forced start method, there is a possibility of generating a shock at engine start. Therefore, in such a case, the engine 14 is to be started and controlled by the early ignition start method instead of the forced start method. Note that the executed engine start control is switched from the forced start method to the early ignition start method at the time t2, which is delayed by the time required for the calculation time, etc. in the electronic control unit 80 from the time t1. This time t2 is earlier than the time when the shock occurs when the forced start method is executed. Thereby, an increase in the starting torque (assist torque) is suppressed, the MG driving distribution torque Tr is ensured, and the generation of a shock at engine start is suppressed.

[0071] When the system shaft torque Tsys changes as indicated by the two-dot chain line arrow, during the execution period of the engine start control, the MG driving distribution torque Tr is predicted not to be smaller than the system shaft torque Tsys. Therefore, even if the start control of the engine 14 is executed by the forced start method, there is no possibility of generating a shock at engine start. Therefore, in such a case, the engine 14 is to be started and controlled by the forced start method. That is, the engine start control executed from the time t1 is executed by the forced start method after the time t2.

[0072] When starting the engine 14 at time t3 after a predetermined period T has elapsed since time t0 immediately after the starting method has switched from the early ignition starting method to the push-starting method, if it is predicted that the distribution torque Tr for MG running becomes smaller than the system shaft torque Tsys during the execution period of the engine starting control, the starting control to be executed is set to the early ignition starting method before time t3 and the push-starting method after time t3, as indicated by the dashed-dotted line. Also, when starting the engine 14 at time t0 immediately after the starting method has switched from the early ignition starting method to the push-starting method, if it is predicted that the distribution torque Tr for MG running does not become smaller than the system shaft torque Tsys during the execution period of the engine starting control, the starting control to be executed is set to the early ignition starting method before time t0 and the push-starting method after time t0, as indicated by the double-dashed-dotted line.

[0073] According to the present embodiment, when the engine 14 is started within a predetermined period T from the time when it is determined that the starting method of the engine 14 has switched from the early ignition starting method to the push-starting method, (a) the transmission torque capacity Tc of the clutch K0 when it is assumed that the starting control of the engine 14 is executed by the push-starting method by MG torque Tmg obtained by subtracting from The distribution torque Tr for MG running, which is the driving torque for running, is calculated as the outputtable torque, and (b) when it is assumed that the starting control of the engine 14 is executed by the early ignition starting method By converting the required amount of driving torque for running corresponding to the accelerator opening θacc from the accelerator opening θacc into the torque on the rotor shaft 40 of the rotating electrical machine MGWhen the system shaft torque Tsys is calculated as the required torque and (c) the available output torque is insufficient with respect to the required torque, the starting control of the engine 14 is executed in the early ignition starting mode. Thus, when the engine 14 is started within a predetermined period T from the time when it is determined that the starting mode of the engine 14 has switched from the early ignition starting mode to the push-starting mode, if the MG driving distribution torque Tr becomes insufficient with respect to the system shaft torque Tsys and a pulling shock occurs at the time of engine starting when the starting control of the engine 14 is actually executed in the push-starting mode, the starting control of the engine 14 is executed in the early ignition starting mode regardless of the starting mode determined to have been switched. Thereby, the occurrence of a pulling shock at the time of engine starting is suppressed.

[0074] As described above, the embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is also applicable to other aspects.

[0075] In the above-described embodiment, the electronic control unit 80 functionally includes the assist torque determination unit 80c, but it is not necessarily required to include it. In the control operation of the electronic control unit 80 that does not include the assist torque determination unit 80c, for example, step S20 in the flowchart of FIG. 4 is omitted.

[0076] In the above-described embodiment, the system shaft torque Tsys (required torque) and the MG driving distribution torque (available output torque) are calculated as the torque on the rotor shaft 40, but the present invention is not limited thereto, and they may be calculated as the torque on the transmission output shaft 24 or the transmission input shaft 36. In such an aspect, when the available output torque is insufficient with respect to the required torque, that is, when the available output torque converted on the same shaft is smaller than the required torque, the starting control of the engine 14 is executed in the early ignition starting mode regardless of the starting mode determined to have been switched.

[0077] In the foregoing embodiment, the setting of the starting method of the engine 14 by the starting method setting unit 80a is performed based on whether or not the starting shock in the case where the early ignition starting method is executed as the starting control of the engine 14 is within a predetermined allowable range, but it is not limited to this mode. For example, when the state of charge value SOC of the power storage device 54 is equal to or greater than a predetermined value, the starting method setting unit 80a may set the pressing start method with a relatively large assist torque as the starting method of the engine 14, and when it is less than the predetermined value, the early ignition starting method with a relatively small assist torque may be set as the starting method of the engine 14.

[0078] Note that the above is merely an embodiment of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art without departing from the spirit thereof.

Explanation of Signs

[0079] 10: Vehicle 14: Engine (driving power source for traveling) 80: Electronic control unit (control unit) K0: Clutch MG: Rotating electric machine (driving power source for traveling) T: Predetermined period Tc: Transmission torque capacity Tmg: MG torque (output torque of rotating electric machine) Tr: MG traveling distribution torque (driving torque for traveling among the output torques of the rotating electric machine, outputtable torque) Tsys: System shaft torque (required amount of driving torque for traveling with respect to the driving power source for traveling, required torque)

Claims

【Claim 1】 A control device for a vehicle, comprising: an engine and a rotating electric machine as driving power sources for traveling; and a clutch that disconnects and connects a power transmission path between the engine and the rotating electric machine, wherein when it is determined, based on the rotational speed of the rotating electric machine at the clutch synchronization timing when it is assumed that the early ignition starting method is executed being less than a preset rotational speed determination value for determining that the starting shock when the engine starting control is executed by the early ignition starting method is within a predetermined allowable range, to start the engine within a predetermined period from the time of determination, when starting control of the engine is assumed to be executed by the forced starting method, the driving torque for traveling obtained by subtracting the transmission torque capacity of the clutch from the output torque of the rotating electric machine is calculated as the outputable torque, and the required torque is calculated as the required torque by converting the required amount of driving torque for the driving power source for traveling corresponding to the accelerator opening from the accelerator opening when starting control of the engine is assumed to be executed by the early ignition starting method into torque on the rotor shaft of the rotating electric machine. When the outputable torque is insufficient with respect to the required torque, the starting control of the engine is executed by the early ignition starting method. A control device for a vehicle, characterized by the above.

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