Hybrid electric vehicle control device

Abstract

To provide a hybrid-type electric vehicle configured to start an engine while connecting the engine to a power transmission path, which can appropriately suppress variation of driving torque during initial explosion transition at the time of starting the engine depending on whether initial explosion for each cylinder occurs or not.SOLUTION: Number of times of ignition execution Nign at the time of starting an engine is counted, and torque Tetran during engine initial explosion transition is calculated in accordance with the number of times of ignition execution Nign (S4). MG torque Tmg is corrected so that variation of driving torque is suppressed on the basis of the torque Tetran during engine initial explosion transition (S5). In this situation, as the number of times of ignition execution Nign reflects whether initial explosion of the plurality of cylinders occurs or not, the torque Tetran during initial explosion transition can be appropriately determined in accordance with whether the initial explosion for each cylinder occurs or not, even if states of the engine such as a rotation speed Ne and an ignition timing of the engine differ. This can appropriately suppress variation of the driving torque due to the torque Tetran during engine initial explosion transition, by controlling the MG torque Tmg.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control device for a hybrid electric vehicle, and more particularly to a technique for suppressing fluctuations in driving torque during engine start-up by controlling the torque of a rotating machine. [Background technology]

[0002] A control device for a hybrid electric vehicle is known, which has: (a) an engine and a rotating machine as driving force sources, and an engine disconnecting device that disconnects the engine from a power transmission path; (b) an engine start control unit that starts the engine by fuel injection and ignition while the engine is connected to the power transmission path by the engine disconnecting device; and (c) an initial combustion torque compensation control unit that suppresses driving torque fluctuations caused by the torque at the initial combustion of multiple cylinders of the engine by controlling the torque of the rotating machine when the engine is started by the engine start control unit (see paragraph 0077, FIG. 11, etc. of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-35188 A Summary of the Invention [Problem to be solved by the invention]

[0004] During the engine start-up transition, there are cylinders before and after the initial explosion, and the friction torque and pumping loss are different, so that torque control of the rotating machine that reflects the presence or absence of the initial explosion for each cylinder is required to appropriately suppress the driving torque fluctuation during the initial explosion transition. In such a case, in a vehicle in which the engine is started while the engine is connected to the power transmission path by the engine disconnecting device, the engine conditions such as the engine speed, intake air amount, and ignition timing differ depending on the driving conditions such as the vehicle speed, and the torque generated during the initial explosion transition also changes, so that the problem is how to control the torque of the rotating machine that reflects the presence or absence of the initial explosion for each cylinder.

[0005] The present invention has been made against the background of the above circumstances, and its object is to enable, in a hybrid electric vehicle in which the engine is started while connected to a power transmission path by an engine disconnection device, to appropriately suppress driving torque fluctuations during the initial combustion transient at engine start, depending on the presence or absence of initial combustion for each cylinder. [Means for solving the problem]

[0006] In order to achieve this object, the present invention is a control device for a hybrid electric vehicle that (a) is applied to a hybrid electric vehicle having an engine and a rotating machine as driving force sources and an engine disconnection device that disconnects the engine from the power transmission path, and (b) an engine start control unit that starts the engine by fuel injection and ignition while the engine is connected to the power transmission path by the engine disconnection device, and (c) a first-explosion torque compensation control unit that, when the engine is started by the engine start control unit, suppresses driving torque fluctuations caused by the torque at the first explosion of multiple cylinders of the engine by controlling the torque of the rotating machine, wherein (d) the first-explosion torque compensation control unit counts the number of times ignition is performed when the engine is started by the engine start control unit, calculates engine first-explosion transient torque, which is the torque during the engine startup transient, in accordance with the number of times ignition is performed, and corrects the torque of the rotating machine based on the engine first-explosion transient torque. Effect of the Invention

[0007] In such a control device for a hybrid electric vehicle, the number of times ignition is performed by the engine start control unit when the engine is started is counted, and an engine first explosion transient torque is calculated according to the number of times ignition is performed, and the torque of the rotating machine is corrected so that the driving torque fluctuation is suppressed based on the engine first explosion transient torque. In this case, since the number of times ignition is performed reflects the presence or absence of first explosion in multiple cylinders, it is possible to appropriately determine the engine first explosion transient torque according to the presence or absence of first explosion for each cylinder even when the engine rotation speed, ignition timing, and other engine conditions are different, and the driving torque fluctuation caused by the engine first explosion transient torque can be appropriately suppressed by torque control of the rotating machine. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram for explaining a drive system of a hybrid electric vehicle having a control device according to an embodiment of the present invention, and also shows control functions for various controls and main parts of the control system. [Diagram 2] 2 is a flowchart specifically illustrating the operation of a first explosion torque compensation control section that is functionally provided in the electronic control device of FIG. 1. [Diagram 3] 1 is a diagram showing a comparison between an initial engine explosion transient torque at engine start time assumed to be a steady-state engine torque Testa and an actual engine torque Tere1. [Figure 4] 1 is a diagram showing a comparison between a steady-state engine torque Testa for one cylinder, which changes according to an intake air amount Qair, and an actual engine torque Tere2 at the time of the first combustion. [Diagram 5] FIG. 1 is a cross-sectional view of an upper end portion of one cylinder, illustrating an example of a direct injection engine. [Figure 6] FIG. 3 is a diagram for explaining an example of a map for determining a correction coefficient Kco according to the number of ignitions Nign when calculating the engine initial explosion transient torque Tetran in step S4 of FIG. 2. [Figure 7]FIG. 3 is a diagram for explaining an example of a map for determining an offset torque Teoff according to the number of ignitions Nign when calculating an engine initial explosion transient torque Tetran in step S4 of FIG. 2. [Figure 8] 3 is an example of a time chart illustrating changes in rotation speeds Ne, Nmg, torques Testa, Tmg, and the number of ignitions Nign when initial explosion torque compensation control is performed according to the flowchart of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention is applied to a hybrid electric vehicle equipped with an engine and a rotating machine as a driving force source. The hybrid electric vehicle may be, for example, a FR (front engine, rear drive) type rear-wheel drive vehicle, a front-rear wheel drive vehicle with a transfer provided midway to distribute power to the front wheels, or a FF (front engine, front drive) type front-wheel drive vehicle such as a transaxle. The rotating machine may be, for example, a motor generator that functions as an electric motor and a generator, but an electric motor may also be used as the rotating machine if the driving torque fluctuation due to the engine initial explosion transient torque can be suppressed within the range of the power torque that functions as an electric motor when starting the engine during driving in the motor driving mode. The rotating machine is, for example, provided in a power transmission path between the engine and the driving wheels, and is connected to the engine via an engine disconnecting device, but may be connected to the engine at all times, or may be provided in a power transmission path separate from the engine to rotate and drive other driving wheels.

[0010] The engine disconnecting device is a device that disconnects the engine from the power transmission path, and a friction engagement device such as a friction engagement type clutch or brake is preferably used. For example, when starting the engine while the vehicle is running, the engine can be cranked by slipping the friction engagement device. A fluid transmission device such as a torque converter or a transmission is provided in the power transmission path as necessary. The transmission can be in various forms, such as a planetary gear type stepped automatic transmission consisting of a plurality of planetary gear devices and friction engagement devices, a parallel shaft type stepped transmission, a forward / reverse switching device that only switches forward / reverse, and a belt type or other continuously variable transmission and a forward / reverse switching device provided in series or in parallel.

[0011] The initial combustion torque compensation control unit is configured to calculate the engine initial combustion transient torque Tetran by correcting the steady-state engine torque Testa in the steady state determined according to the engine speed Ne, etc., according to the number of ignitions Nign. For example, as shown in the following formula (1), the engine initial combustion transient torque Tetran is obtained by multiplying the steady-state engine torque Testa by a correction coefficient Kco determined according to the number of ignitions Nign and adding an offset torque Teoff determined according to the number of ignitions Nign. Other calculation methods may be used, such as directly calculating the engine initial combustion transient torque Testan based on the engine speed Ne, the intake air amount Qair, the engine cooling water temperature THw, the ignition timing, the number of ignitions Nign, etc., without using the steady-state engine torque Testa. Tetran =Testa×Kco+Teoff (1) EXAMPLES

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings are appropriately simplified or modified for the purpose of explanation, and the dimensional ratios, angles, shapes, etc. of each part are not necessarily drawn accurately.

[0013] Fig. 1 is a schematic configuration diagram of a drive system of a hybrid electric vehicle 10 (hereinafter simply referred to as electric vehicle 10) having an electronic control device 90 as a control device according to one embodiment of the present invention, and also shows the control functions and main parts of the control system for various controls in the electric vehicle 10. In Fig. 1, the electric vehicle 10 is a parallel-type hybrid electric vehicle equipped with an engine 12 and a rotary machine MG as a driving force source for traveling. The electric vehicle 10 also includes a power transmission device 16 provided in a power transmission path between the engine 12 and drive wheels 14. The drive wheels 14 are the left and right rear wheels, and the electric vehicle 10 is a FR-type rear-wheel drive vehicle.

[0014] The engine 12 is an internal combustion engine such as a gasoline engine or a diesel engine that generates power by burning fuel, and in this embodiment is a four-stroke engine that has a plurality of cylinders, such as six, and performs intake, compression, explosion, and exhaust with two revolutions of the crankshaft. The engine 12 has an engine torque Te, which is the output torque of the engine 12, controlled by an electronic control device 90 that controls an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, etc. FIG. 5 is a cross-sectional view of the upper end of one cylinder 100 of the direct injection type engine 12, and high-pressure fine gasoline particles are directly injected into the cylinder 100 by a fuel injection device 112. In this engine 12, air flows into cylinder 100 from intake passage 102 via intake valve 104, and exhaust gas is discharged from exhaust passage 108 via exhaust valve 106. When ignition is performed by ignition device 114 at a predetermined timing, the air-fuel mixture in cylinder 100 explodes and burns, pushing piston 110 downward and rotating the crankshaft.

[0015] The rotating machine MG is a so-called motor generator having a function as an electric motor that generates mechanical power from electric power and a function as a generator that generates electric power from mechanical power, and is, for example, a permanent magnet type three-phase AC synchronous motor, and is connected to a battery 54 via an inverter 52. The rotating machine MG controls the inverter 52 by an electronic control device 90, thereby controlling the MG torque Tmg of the rotating machine MG. The rotating machine MG generates power for traveling by electric power supplied from the battery 54 via the inverter 52 instead of or in addition to the engine 12. The rotating machine MG also generates electric power by being regeneratively controlled when it is driven to rotate by the power of the engine 12 or the driven force input from the driving wheels 14 side. The electric power generated by the electric power generation of the rotating machine MG is stored in the battery 54 via the inverter 52. The battery 54 is an electric power storage device that supplies and receives electric power to the rotating machine MG.

[0016] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, and an automatic transmission 24 in series from the engine 12 side in a case 18 that is a non-rotating member attached to the vehicle body, and a rotary machine MG is connected to the power transmission path between the K0 clutch 20 and the torque converter 22. The K0 clutch 20 is a clutch provided between the engine 12 and the rotary machine MG in the power transmission path between the engine 12 and the drive wheels 14, and is an engine disconnecting device that connects and disconnects between the engine 12 and the power transmission device 16, specifically, between the engine 12 and the rotary machine MG. The torque converter 22 is a fluid-type power transmission device provided between the rotary machine MG and the automatic transmission 24, and is connected to the engine 12 via the K0 clutch 20. The automatic transmission 24 is connected to the torque converter 22 and is interposed in the power transmission path between the torque converter 22 and the drive wheels 14. The power transmission device 16 includes a propeller shaft 28 connected to a transmission output shaft 26 which is an output rotating member of the automatic transmission 24, a differential gear 30 connected to the propeller shaft 28, a pair of drive shafts 32 connected to the differential gear 30, etc. The power transmission device 16 also includes an engine connecting shaft 34 which connects the engine 12 and the K0 clutch 20, an MG connecting shaft 36 which connects the K0 clutch 20 and the torque converter 22, etc., and a rotor of the rotating machine MG is connected to the MG connecting shaft 36.

[0017] The K0 clutch 20 is a wet or dry friction engagement device constituted by, for example, a multi-plate or single-plate clutch pressed by an actuator. The K0 clutch 20 switches between control states such as an engaged state and an released state by changing the K0 torque Tk0, which is the torque capacity of the K0 clutch 20, by the adjusted K0 oil pressure PRk0 supplied from the oil pressure control circuit 56. An input side member of the K0 clutch 20 is connected to the engine connecting shaft 34 and rotated integrally with the engine connecting shaft 34. An output side member of the K0 clutch 20 is connected to the MG connecting shaft 36 and rotated integrally with the MG connecting shaft 36. In the engaged state of the K0 clutch 20, the rotor of the rotating machine MG and the pump impeller 22a of the torque converter 22 and the engine 12 are rotated integrally via the engine connecting shaft 34. On the other hand, in the released state of the K0 clutch 20, power transmission between the rotor of the rotating machine MG and the pump impeller 22a and the engine 12 is interrupted.

[0018] The rotating machine MG is connected to the MG connecting shaft 36 in the case 18 so as to be capable of transmitting power. The rotating machine MG is connected to a power transmission path between the engine 12 and the drive wheels 14, in particular to a power transmission path between the K0 clutch 20 and the torque converter 22. In other words, the rotating machine MG is connected to the torque converter 22 and the automatic transmission 24 so as to be capable of transmitting power without passing through the K0 clutch 20. The torque converter 22 and the automatic transmission 24 transmit driving force from the driving force sources of the engine 12 and the rotating machine MG to the drive wheels 14, respectively.

[0019] The torque converter 22 includes a pump wheel 22a connected to an MG connecting shaft 36, and a turbine wheel 22b connected to a transmission input shaft 38 that is an input rotating member of the automatic transmission 24. The pump wheel 22a is connected to the engine 12 via the K0 clutch 20, and is also directly connected to the rotary machine MG. The pump wheel 22a is an input member of the torque converter 22, and the turbine wheel 22b is an output member of the torque converter 22. The MG connecting shaft 36 is also an input rotating member of the torque converter 22. The transmission input shaft 38 is also an output rotating member of the torque converter 22 that is formed integrally with a turbine shaft that is driven to rotate by the turbine wheel 22b. The torque converter 22 includes an LU clutch 40 that connects the pump wheel 22a and the turbine wheel 22b. The LU clutch 40 is a direct clutch that connects the input and output rotating members of the torque converter 22, that is, a known lock-up clutch.

[0020] The LU clutch 40 switches between operating states, i.e., control states, by changing the LU clutch torque Tlu, which is the torque capacity of the LU clutch 40, with the regulated LU oil pressure PRlu supplied from the hydraulic control circuit 56. The control states of the LU clutch 40 include a fully released state in which the LU clutch 40 is released, a slip state in which the LU clutch 40 is engaged with slipping, and a fully engaged state in which the LU clutch 40 is engaged. By placing the LU clutch 40 in the fully released state, the torque converter 22 is placed in a torque converter state in which a torque amplification effect is obtained. Also, by placing the LU clutch 40 in the fully engaged state, the torque converter 22 is placed in a lock-up state in which the pump wheel 22a and the turbine wheel 22b are rotated together.

[0021] The automatic transmission 24 is a known planetary gear type automatic transmission including, for example, one or more planetary gear devices and a plurality of engagement devices CB. The engagement devices CB are hydraulic friction engagement devices including, for example, a multi-plate or single-plate clutch or brake pressed by a hydraulic actuator, or a band brake tightened by a hydraulic actuator. The engagement devices CB have their respective torque capacities, or CB torques Tcb, changed by the regulated CB hydraulic pressure PRcb supplied from the hydraulic control circuit 56, thereby switching between control states such as an engaged state and a disengaged state.

[0022] The automatic transmission 24 is a stepped transmission in which one of a plurality of gear stages with different gear ratios γat (=AT input rotation speed Ni / AT output rotation speed No ) is formed by engaging one of the engagement devices CB. The automatic transmission 24 selectively forms a plurality of gear stages, in other words, a plurality of gear stages, which are formed according to the driving state such as the accelerator operation of the driver (=operator) and the vehicle speed V, by the electronic control device 90. In addition, when all of the engagement devices CB are released, the automatic transmission 24 is in neutral, which cuts off the power transmission. The AT input rotation speed Ni is the rotation speed of the transmission input shaft 38, and is the input rotation speed of the automatic transmission 24. The AT input rotation speed Ni is also the rotation speed of the output rotating member of the torque converter 22, and is equal to the turbine rotation speed Nt, which is the output rotation speed of the torque converter 22. The AT output rotation speed No is the rotation speed of the transmission output shaft 26, and is the output rotation speed of the automatic transmission 24.

[0023] In the power transmission device 16, when the K0 clutch 20 is engaged, the power output from the engine 12 is transmitted from the engine connecting shaft 34 to the driving wheels 14 via the K0 clutch 20, MG connecting shaft 36, torque converter 22, automatic transmission 24, propeller shaft 28, differential gear 30, drive shaft 32, etc. in this order. Moreover, the power output from the rotating machine MG is transmitted from the MG connecting shaft 36 to the driving wheels 14 via the torque converter 22, automatic transmission 24, propeller shaft 28, differential gear 30, drive shaft 32, etc. in this order, regardless of the control state of the K0 clutch 20.

[0024] The electric vehicle 10 includes the MOP 58, which is a mechanical oil pump, the EOP 60, which is an electric oil pump, and a pump motor 62. The MOP 58 is connected to the pump impeller 22a, and is rotated and driven by a driving force source (the engine 12, the rotary machine MG) to discharge hydraulic oil OIL used in the power transmission device 16. The pump motor 62 is a motor dedicated to the EOP 60 for rotating and driving the EOP 60. The EOP 60 is rotated and driven by the pump motor 62 to discharge hydraulic oil OIL. The hydraulic oil OIL discharged by the MOP 58 and the EOP 60 is supplied to the hydraulic control circuit 56. The hydraulic control circuit 56 supplies the CB hydraulic pressure PRcb, the K0 hydraulic pressure PRk0, the LU hydraulic pressure PRlu, and the like, which are adjusted based on the hydraulic oil OIL discharged by the MOP 58 and / or the EOP 60. The hydraulic oil OIL is also used for lubrication and cooling of various parts including the automatic transmission 24, and is also a lubricating oil. The hydraulic oil OIL is stored in an oil reservoir such as an oil pan provided in the lower part of the case 18, and is pumped up by the MOP 58 and / or EOP 60 and supplied to the hydraulic control circuit 56.

[0025] The electric vehicle 10 includes an electronic control device 90 as a control device that executes various controls. The electronic control device 90 includes a so-called microcomputer that includes, for example, a CPU, a RAM, a ROM, an input / output interface, and the like, and the CPU executes various controls of the electric vehicle 10 by performing signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM. The electronic control device 90 can be configured using a single computer, but in this embodiment, it includes an HEV-ECU 92, an MG-ECU 94, an engine-ECU 96, an ECT-ECU 98, and the like. "HEV" is the abbreviation for Hybrid Electric Vehicle, "MG" is the abbreviation for Motor Generator, "ECT" is the abbreviation for Electronic Controlled Transmission, and "ECU" is the abbreviation for Electronic Control Unit. The HEV-ECU 92, the MG-ECU 94, the engine-ECU 96, and the ECT-ECU 98 are connected to each other via a communication bus such as a CAN (Controller Area Network) communication line, and are capable of transmitting and receiving various information required for control.

[0026] The electronic control device 90 receives various signals based on detection values ​​by various sensors provided in the electric vehicle 10 (for example, an engine rotation speed sensor 70, a turbine rotation speed sensor 72, an output rotation speed sensor 74, a MG rotation speed sensor 76, an accelerator opening sensor 78, a throttle valve opening sensor 80, an air flow meter 82, an intake air temperature sensor 83, an engine cooling water temperature sensor 84, an oil temperature sensor 86, a battery sensor 88, etc.) (for example, an engine rotation speed Ne which is the rotation speed of the engine 12, a turbine rotation speed Nt which is the same value as the AT input rotation speed Ni, an AT output rotation speed No corresponding to the vehicle speed V, an MG rotation speed Nmg which is the rotation speed of the rotating machine MG, an accelerator opening θacc which is an accelerator operation amount (for example, an accelerator pedal depression operation amount) which represents an acceleration request amount by the driver, a throttle valve opening θth which is an opening amount of the electronic throttle valve, an intake air amount Qair of the engine 12, an intake air temperature THair, an engine cooling water temperature THw, a hydraulic oil OIL used in the hydraulic control circuit 56, and the like). The engine speed sensor 70 is a crank position sensor or the like that can detect the engine speed Ne as well as a crank angle Φ that is the rotation angle from TDC (top dead center) of the multiple cylinders 100 of the engine 12.

[0027] The electronic control device 90 outputs various command signals (e.g., an engine control command signal Se for controlling the engine 12, an MG control command signal Smg for controlling the rotating machine MG, a CB hydraulic control command signal Sbc for controlling the engagement device CB, a K0 hydraulic control command signal Sk0 for controlling the K0 clutch 20, an LU hydraulic control command signal Slu for controlling the LU clutch 40, an EOP control command signal Seop for controlling the EOP 60, etc.) to each device (e.g., an engine control device 50, an inverter 52, a hydraulic control circuit 56, a pump motor 62, etc.) provided in the electric vehicle 10. The engine control command signal Se is a signal for controlling, for example, a fuel injection amount, an injection timing, an ignition timing, a throttle valve opening θth, etc. The hydraulic control circuit 56 is provided with a plurality of solenoid valves for switching oil paths and controlling hydraulic pressure according to the CB hydraulic control command signal Sbc, the K0 hydraulic control command signal Sk0, and the LU hydraulic control command signal Slu.

[0028] The HEV-ECU 92 of the electronic control device 90 functions as a hybrid control unit that controls the operation of the rotary machine MG and the engine 12 in a coordinated manner. That is, the HEV-ECU 92 executes hybrid drive control by the engine 12 and the rotary machine MG using the MG-ECU 94 that controls the operation of the rotary machine MG via the inverter 52 and the engine-ECU 96 that controls the operation of the engine 12. The HEV-ECU 92 calculates a drive demand amount for the electric vehicle 10 by the driver, for example, by applying the accelerator opening θacc and the vehicle speed V to a drive demand amount map. The drive demand amount is, for example, a required drive torque Trdem at the drive wheels 14, etc. The HEV-ECU 92 calculates a required input torque Tindem, which is an input torque of the torque converter 22 required to realize the required drive torque Trdem, for example, taking into consideration a transmission loss, an auxiliary load, a speed ratio γat of the automatic transmission 24, a torque ratio of the torque converter 22, a chargeable power Win and a dischargeable power Wout of the battery 54, and outputs an MG control command signal Smg for controlling the rotary machine MG via the MG-ECU 94 and an engine control command signal Se for controlling the engine 12 via the engine-ECU 96 so that the required input torque Tindem is obtained. The required input torque Tindem includes negative torques such as an engine brake torque during coasting when the accelerator opening θacc is 0 and a regenerative braking torque due to regenerative control of the rotary machine MG.

[0029] The chargeable power Win of the battery 54 is the maximum power that can be input, which specifies the limit on the input power of the battery 54, and indicates the input limit of the battery 54. The dischargeable power Wout of the battery 54 is the maximum power that can be output, which specifies the limit on the output power of the battery 54, and indicates the output limit of the battery 54. The chargeable power Win and dischargeable power Wout of the battery 54 are calculated by the electronic control device 90 based on, for example, the battery temperature THbat and the state of charge value SOC [%] of the battery 54. The state of charge value SOC of the battery 54 is a value that indicates the state of charge of the battery 54, i.e., the remaining amount of electricity, and can be calculated based on, for example, the battery charge / discharge current Ibat and the battery voltage Vbat.

[0030] The HEV-ECU 92 functionally includes a travel mode switching control unit 92a. When the required input torque Tindem can be satisfied only by the output of the rotating machine MG, the travel mode switching control unit 92a selects a BEV (Battery Electric Vehicle) travel mode, which is a motor travel mode in which the rotating machine MG is driven only by the power from the battery 54 to travel. In the BEV travel mode, the K0 clutch 20 is opened to stop the engine 12, and BEV travel is performed in which only the rotating machine MG is used as a driving force source. In this BEV travel mode, the MG torque Tmg is controlled to realize the required input torque Tindem. On the other hand, when the required input torque Tindem cannot be satisfied without using at least the output of the engine 12, the travel mode switching control unit 92a selects an HEV (Hybrid Electric Vehicle) travel mode, which is an engine travel mode. In the HEV travel mode, the K0 clutch 20 is engaged to perform engine travel, i.e., HEV travel, in which at least the engine 12 is used as a driving force source to travel. In the HEV driving mode, the engine torque Te is controlled so as to realize all or a part of the required input torque Tindem, and the MG torque Tmg is controlled so as to compensate for the torque that is insufficient in the engine torque Te with respect to the required input torque Tindem. On the other hand, the driving mode switching control unit 92a establishes the HEV driving mode when the engine 12 or the like needs to be warmed up, even if the required input torque Tindem can be satisfied only by the output of the rotary machine MG. In this way, the driving mode switching control unit 92a switches between the BEV driving mode and the HEV driving mode by automatically stopping the engine 12 during HEV driving, restarting the engine 12 after the engine is stopped, starting the engine 12 during BEV driving, automatically stopping the engine 12 while the vehicle is stopped, and starting the engine 12, based on the required input torque Tindem, etc. Automatic stopping and restarting of the engine 12 are also expressed as intermittent operation of the engine 12.

[0031] The ECT-ECU 98 is involved in the control of the automatic transmission 24, and has the function of a shift control unit that executes shift control to automatically switch the gear of the automatic transmission 24 based on the driving conditions of the electric vehicle 10, such as the vehicle speed V and the accelerator opening θacc. That is, the ECT-ECU 98 performs shift determination of the automatic transmission 24 using a shift map, which is a predetermined shift condition, and outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 as necessary to execute the shift control of the automatic transmission 24. The shift map is a predetermined relationship having a shift line for determining a shift of the automatic transmission 24 on a two-dimensional coordinate system having, for example, the vehicle speed V and the required drive torque Trdem as variables.

[0032] The engine-ECU 96 functionally includes an engine start control unit 96a that starts the engine 12 according to an engine start instruction from the traveling mode switching control unit 92a. When the engine start control unit 96a starts the engine 12 according to an instruction from the traveling mode switching control unit 92a during vehicle traveling in the BEV traveling mode in which the K0 clutch 20 is released and the engine 12 is stopped, the engine start control unit 96a first slip-engages the K0 clutch 20 to crank the engine 12 by the inertia of the electric vehicle 10 and raises the engine rotation speed Ne. Then, when the engine rotation speed Ne reaches the MG rotation speed Nmg corresponding to the vehicle speed V, the K0 clutch 20 is fully engaged to connect the engine 12 to the MG connecting shaft 36, and in this state, starting control such as fuel injection and ignition is performed to start the engine 12. The engagement control of the K0 clutch 20 for cranking the engine 12 is executed by hydraulic control of the K0 hydraulic pressure PRk0 by the K0 engagement / release control unit 98a that the ECT-ECU 98 functionally includes. Furthermore, when the engine rotation speed Ne is increased by slipping the K0 clutch 20, a driving torque fluctuation occurs due to the inertia of the engine 12, etc., so in order to suppress this driving torque fluctuation by torque control of the rotating machine MG, the MG-ECU 94 is provided with a cranking torque compensation control unit 94a. The cranking torque compensation control unit 94a increases the MG torque Tmg so that the required input torque Tindem is maintained regardless of the increase in the engine rotation speed Ne. When the rotating machine MG is regeneratively controlled due to coasting or the like and the MG torque Tmg is a negative regenerative torque, the regenerative torque is reduced and, if necessary, is changed to the positive power running side.

[0033] The MG-ECU 94 also includes an initial combustion torque compensation control unit 94b for suppressing driving torque fluctuations caused by torque at the initial combustion of the multiple cylinders 100 of the engine 12 when the engine 12 is started by fuel injection and ignition. The initial combustion torque compensation control unit 94b counts the number of ignitions Nign performed when the engine 12 is started by the engine start control unit 96a, calculates an engine initial combustion transient torque Tetran, which is a torque at the start transient of the engine 12, according to the number of ignitions Nign, and corrects the MG torque Tmg based on the engine initial combustion transient torque Tetran, and executes initial combustion torque compensation control according to steps S1 to S6 of the flowchart in FIG. 2.

[0034] In step S1 of FIG. 2, it is determined whether or not the engine start control by the engine start control unit 96a is in progress, and if not, the process ends as is, but if engine start control is in progress, step S2 is executed. Whether or not engine start control is in progress can be determined, for example, by a signal from the engine start control unit 96a, but it may also be determined based on the engine rotation speed Ne, MG rotation speed Nmg, K0 oil pressure PRk0, etc. In step S2, it is determined whether or not fuel injection control of the engine 12 has started, for example, by whether an engine control command signal Se for fuel injection has been output, and if fuel injection control has started, step S3 is executed. In step S3, it is determined whether or not the crank angle Φ of the engine 12 has become the MG torque correction command crank angle Φcomg, and if Φ=Φcomg, the MG torque correction control in steps S4 and thereafter is executed.

[0035] The MG torque correction command crank angle Φcomg is calculated based on the engine rotation speed Ne at a crank angle Φ that is a response delay time MGdelay of the MG torque Tmg before the crank angle Φt at which the initial combustion torque occurs, according to the following formula (2) based on the engine rotation speed Ne, so that the MG torque Tmg is corrected in accordance with the generation timing of the initial combustion torque of each of the multiple cylinders 100 of the engine 12. The initial combustion torque generation crank angle Φt is obtained based on the ignition crank angle Φign at which ignition is performed, and the engine rotation speed Ne is converted to a crank angular speed. The response delay time MGdelay includes a calculation time of the engine initial combustion transient torque Tetran required to correct the MG torque Tmg, a delay time until the MG torque Tmg changes according to the MG control command signal Smg, and a transmission time during which information on the crank angle Φ is sent from the engine-ECU 96. In this embodiment, the MG torque correction command crank angle Φcomg is later than the fuel injection crank angle Φj at which fuel injection is performed and earlier than the ignition crank angle Φign. Instead of determining the MG torque correction command crank angle Φcomg, the MG torque correction command timing may be determined based on the crank angle or elapsed time from the fuel injection crank angle Φj, or the crank angle or elapsed time from a predetermined reference crank angle, etc. After step S4 of calculating the engine initial explosion transient torque Tetran, the MG torque correction command timing may be determined based on the crank angle Φ, the elapsed time, etc. Φcomg=Φt -Ne ×MGdelay ···(2)

[0036] In step S4, the engine first explosion transient torque Tetran is calculated by correcting the steady-state engine torque Testa according to the number of ignitions Nign based on the steady-state engine torque Testa when the engine 12 is in a steady state. The number of ignitions Nign can be counted by reading the engine control command signal Se for ignition output from the engine-ECU 96. The steady-state engine torque Testa has been used conventionally in various types of control, such as engine control, and is determined in advance by a map or the like using the engine speed Ne, the intake air amount Qair, the ignition timing, the engine cooling water temperature THw, and other conditions of the engine 12 as variables. However, during the start-up transient of the engine 12, there are cylinders 100 before and after the first explosion, and the friction torque and pumping loss are different, so that a deviation occurs between the steady-state engine torque Testa and the actual engine torque Tere1, as shown in FIG. 3, for example. Time ta in Fig. 3 is the time when fuel injection etc. of engine start control is started, and time tb is the time when the initial explosion of all cylinders 100 is completed. When the initial explosion of all cylinders 100 is completed, the actual engine torque Tere1 becomes substantially equal to the steady-state engine torque Testa. Note that the actual engine torque Tere1 in Fig. 3 is the median value between the maximum and minimum values ​​of the torque fluctuation due to the explosion of each cylinder 100. Also, in Fig. 3, the negative side of the engine torque is omitted.

[0037] On the other hand, when comparing the steady-state engine torque Testa for one cylinder 100, which changes according to the intake air amount Qair, with the actual engine torque Tere2 at the time of the first explosion, the actual engine torque Tere2 is larger as shown in Fig. 4. That is, as shown in Fig. 5, when the piston 110 reaches the top dead center during the exhaust stroke, there is a gap 116 above the piston 110, and in the steady state while the engine 12 is operating, combustion gas (exhaust gas) remains in the gap 116, but air (new air) enters the gap 116 before the first explosion, so that the engine torque Tere2 at the time of the first explosion is larger by that amount.

[0038] As is clear from Fig. 3 and Fig. 4, there is a difference between the steady-state engine torque Testa and the actual engine torques Tere1 and Tere2 during the engine start transient. Therefore, as shown in the above formula (1), the steady-state engine torque Testa is multiplied by the correction coefficient Kco determined according to the number of ignitions Nign, and an offset torque Teoff determined according to the number of ignitions Nign is added to calculate the engine first explosion transient torque Tetran close to the actual engine torque Tere1 even during the start transient. The correction coefficient Kco and the offset torque Teoff are determined in advance by experiments, for example, as shown in the maps of Fig. 6 and Fig. 7, with the number of ignitions Nign as a variable. In Fig. 6 and Fig. 7, α of the number of ignitions Nign is the number of cylinders of the engine 12, and is 6 for a 6-cylinder engine, for example. The correction coefficient Kco and the offset torque Teoff may be determined using only the number of ignitions Nign as a variable, or may be determined using other variables that represent the state of the engine 12, such as the engine speed Ne, the ignition timing, and the engine coolant temperature THw, in addition to the number of ignitions Nign.

[0039] Returning to FIG. 2, in the next step S5, a correction command is output to reduce the MG torque Tmg by the engine initial explosion transient torque Tetran calculated in step S4 so that the driving torque fluctuation caused by the engine initial explosion transient torque Tetran is suppressed. If the engine initial explosion transient torque Tetran is greater than the MG torque Tmg, regenerative control is performed to make the MG torque Tmg negative. In step S6, it is determined whether or not a termination condition for terminating the initial explosion torque compensation control is satisfied, specifically, whether or not the number of ignitions Nign has reached the number of cylinders α, and steps S3 and thereafter are repeatedly executed until the number of ignitions Nign reaches the number of cylinders α. As a result, the required input torque Tindem can be maintained regardless of the engine initial explosion transient torque Tetran, and the driving torque fluctuation caused by the engine initial explosion transient torque Tetran is suppressed.

[0040] FIG. 8 is an example of a time chart for explaining the changes in the rotation speed Ne, Nmg, torque Testa, Tmg, and the number of ignitions Nign when the initial combustion torque compensation control is performed according to the flowchart of FIG. 2. FIG. 8 shows a case where the engine start control is performed by the engine start control unit 96a during coasting with the accelerator opening θacc being 0 in the BEV driving mode, the engine 12 is cranked by the engagement of the K0 clutch 20, and the MG torque Tmg is controlled by the cranking torque compensation control unit 94a so that the driving torque fluctuation is suppressed regardless of the cranking. Time t1 is the time when the first fuel injection is performed and the determination in step S2 becomes YES (affirmative). Time t2 is the time when the first ignition is performed, and time t3 is the time when the number of ignitions Nign reaches the number of cylinders α and the initial combustion torque compensation control is ended. That is, between time t1 and time t3, the initial combustion torque compensation control of steps S3 to S6 is performed, and the driving torque fluctuation caused by the torque at the time of the initial combustion is suppressed by the control of the MG torque Tmg. The temporary deviation between the engine rotation speed Ne and the MG rotation speed Nmg regardless of the engagement of the K0 clutch 20 is due to torsional deformation of the engine connecting shaft 34 and the MG connecting shaft 36, and the increase in the engine rotation speed Ne due to the initial combustion torque of the engine 12 can be suppressed by controlling the MG torque Tmg.

[0041] In this way, according to the first explosion torque compensation control unit 94b of the electric vehicle 10 of this embodiment, the number of ignitions Nign performed at the start of the engine 12 by the engine start control unit 96a is counted, and the engine first explosion transient torque Tetran is calculated according to the number of ignitions Nign, and the MG torque Tmg is corrected so that the driving torque fluctuation is suppressed based on the engine first explosion transient torque Tetran. In this case, since the number of ignitions Nign reflects the presence or absence of first explosions in multiple cylinders 100, even if the state of the engine 12, such as the engine rotation speed Ne and ignition timing, is different, the engine first explosion transient torque Tetran can be appropriately obtained according to the presence or absence of first explosion for each cylinder 100, and the driving torque fluctuation caused by the engine first explosion transient torque Tetran can be appropriately suppressed by controlling the MG torque Tmg. In particular, in this embodiment, the engine initial explosion transient torque Tetran is calculated by correcting the steady-state engine torque Testa according to the formula (1) using the correction coefficient Kco and offset torque Teoff calculated according to the number of ignitions Nign, so that the engine initial explosion transient torque Tetran can be calculated with high accuracy, and the driving torque fluctuation caused by the engine initial explosion transient torque Tetran can be more appropriately suppressed.

[0042] Although the embodiment of the present invention has been described in detail above with reference to the drawings, this is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0043] 10: Hybrid electric vehicle 12: Engine 16: Power transmission device (power transmission path) 20: K0 clutch (engine disconnect device) 90: Electronic control device (control device) 94b: First combustion torque compensation control unit 96a: Engine start control unit 100: Cylinder MG: Rotating machine Tmg: MG torque (torque of rotating machine) Tetran: Engine first combustion transient torque Nign: Number of ignitions

Claims

[Claim 1] The present invention is applied to a hybrid electric vehicle that includes an engine and a rotary machine as a driving force source, and is provided with an engine disconnection device that disconnects the engine from a power transmission path, an engine start control unit that starts the engine by fuel injection and ignition in a state in which the engine is connected to the power transmission path by the engine disconnection device; an initial combustion torque compensation control unit that suppresses a driving torque fluctuation caused by a torque at the initial combustion of a plurality of cylinders of the engine by controlling a torque of the rotary machine when the engine is started by the engine start control unit; A control device for a hybrid electric vehicle having The initial combustion torque compensation control unit counts the number of times ignition is performed by the engine start control unit when starting the engine, calculates an engine initial combustion transient torque, which is a torque during a startup transition of the engine, in accordance with the number of times ignition is performed, and corrects the torque of the rotating machine based on the engine initial combustion transient torque. A control device for a hybrid electric vehicle.

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