Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle capable of suppressing discomfort applied to a driver, when an internal combustion engine is started.SOLUTION: An electronic control device 90 is configured to (a) execute fuel cut for stopping fuel injection to an engine 12 when the engine 12 is in a stop state, (b) when starting the engine 12, engage to a clutch K0, execute cranking of the engine 12 by a motor MG and after completion of synchronization of the clutch K0, start fuel injection to the engine 12, and (c) set a start time point t sta of the fuel injection after synchronization of the clutch K0 is completed, to a time point when read ahead torque Te_pred being engine torque Te which is predicted when the fuel injection is started, becomes a predetermined target torque value Te_tgt.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle including an internal combustion engine and an electric motor as driving power sources for traveling, and a friction engagement device that disconnects and connects power transmission between the internal combustion engine and the electric motor.

Background Art

[0002] There is known a control device for a hybrid vehicle including an internal combustion engine and an electric motor as driving power sources for traveling, and a friction engagement device that disconnects and connects power transmission between the internal combustion engine and the electric motor, which executes fuel cut (stopping fuel injection to the internal combustion engine) while the internal combustion engine is stopped. For example, the one described in Patent Document 1 is such a device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a method of starting an internal combustion engine by cranking with an electric motor while engaging a friction engagement device, a method of restarting fuel injection to the internal combustion engine after synchronization of the rotational speed of the friction engagement device is completed is known in order to suppress shock generated in the vehicle.

[0005] The output torque of an internal combustion engine generated during fuel combustion varies depending on the rotational speed of the internal combustion engine, the intake air amount to the internal combustion engine, and the ignition timing (e.g., ignition retard amount). In particular, when the internal combustion engine is started, the intake air amount varies depending on the rotational amount of the internal combustion engine (e.g., the rotational amount of the crankshaft) according to the vehicle state. Therefore, variations are likely to occur in the output torque of the internal combustion engine at the start of starting, which may give the driver a sense of discomfort because the starting sound, starting shock, etc. are different each time the internal combustion engine is started due to the variation in the output torque of the internal combustion engine according to the vehicle state.

[0006] The present invention has been made against the background of the above circumstances, and an object thereof is to provide a control device for a hybrid vehicle that can suppress the discomfort given to the driver when the internal combustion engine is started.

Means for Solving the Problem

[0007] The gist of the first invention is a control device for a hybrid vehicle including an internal combustion engine and an electric motor that are driving power sources for traveling, and a friction engagement device that disconnects and connects power transmission between the internal combustion engine and the electric motor, the control device performing: (a) executing a fuel cut that stops fuel injection to the internal combustion engine when the internal combustion engine is in a stopped state; (b) when starting the internal combustion engine, performing cranking of the internal combustion engine by the electric motor while engaging the friction engagement device and starting fuel injection to the internal combustion engine after a predetermined condition that the preparation for fuel injection to the internal combustion engine is completed is satisfied; and (c) setting the start timing of the fuel injection after the predetermined condition is satisfied to a time point when a predetermined predicted torque, which is the predicted output torque of the internal combustion engine, becomes a predetermined target torque value. and (d) the predicted torque is calculated based on the amount of rotation of the internal combustion engine from the start point of the cranking to the start point of the fuel injection This is what is to be done.

Effect of the Invention

[0008] According to the control device for a hybrid vehicle of the first invention, (a) a fuel cut that stops fuel injection to the internal combustion engine is executed when the internal combustion engine is in a stopped state, (b) when the internal combustion engine is started, cranking of the internal combustion engine is executed by the electric motor while the friction engagement device is engaged, and after a predetermined condition that the preparation for fuel injection to the internal combustion engine is completed is satisfied, fuel injection to the internal combustion engine is started, and (c) the start timing of the fuel injection after the predetermined condition is satisfied is set to the timing when a predetermined predicted torque, which is the predicted output torque of the internal combustion engine, becomes a predetermined target torque value. , (d) the predicted torque is calculated based on the amount of rotation of the internal combustion engine from the start point of the cranking to the start point of the fuel injection By setting the start timing of fuel injection to the timing when the predicted torque becomes the predetermined target torque value, fluctuations in the starting sound and starting shock generated at each start of the internal combustion engine are suppressed, and the discomfort felt by the driver is suppressed. Further, by calculating the predicted torque based on the amount of rotation of the internal combustion engine from the start point of the cranking to the start point of the fuel injection, the calculation accuracy of the predicted torque is improved. By improving the calculation accuracy of the predicted torque, the setting accuracy of the start point of the fuel injection is improved, so that the starting sound and starting shock generated at each start of the internal combustion engine are accurately suppressed from fluctuating, and the discomfort felt by the driver is suppressed.

[0010] No. 2 According to the control device for a hybrid vehicle of the invention, in the first invention apparently In addition, when the accelerator opening is large, the target torque value is corrected to a larger value compared to when the accelerator opening is small. When an acceleration operation is performed by the driver, the target torque value is corrected according to the accelerator opening. When the target torque value is corrected to a larger value, the start timing of fuel injection is set to the timing when the predicted torque is higher compared to the case where it is not. Therefore, when the accelerator opening is large, the fuel injection to the internal combustion engine is started earlier compared to when the accelerator opening is small, and the output torque at the time when the output from the internal combustion engine starts is increased. As a result, while suppressing fluctuations in the starting sound and starting shock generated at each start of the internal combustion engine, vehicle responsiveness is prioritized, and the driving force for running required by the driver is realized earlier, improving drivability.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0012] 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 drawn accurately.

Embodiment

[0013] FIG. 1 is a schematic configuration diagram of a hybrid vehicle 10 (hereinafter simply referred to as "vehicle 10") 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.

[0014] The vehicle 10 is a hybrid vehicle including an engine 12 and an electric motor MG as a driving power source PG for traveling. The power transmission path PT is between the driving power source PG (engine 12, electric motor MG) and the drive wheels 14. In the power transmission path PT in a case 18 which is a non-rotating member attached to the vehicle body of the vehicle 10, in order from the engine 12 side, there are provided an engine connecting shaft 20, a clutch K0, an electric motor connecting shaft 22, a torque converter 24, an AT input shaft 26 which is an input rotating member of an automatic transmission 28, an automatic transmission 28, and the like. Further, the vehicle 10 includes a differential gear 32 connected to an AT output shaft 30 which is an output rotating member of the automatic transmission 28 in the power transmission path PT, a pair of drive shafts 34 connected to the differential gear 32, and the like. Further, the vehicle 10 includes an inverter 52, a hydraulic control circuit 54, an electric oil pump EOP56, a battery 60, and an electronic control device 90.

[0015] The engine 12 is a well-known internal combustion engine. The engine 12 is controlled by an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, etc. provided in the vehicle 10 by an electronic control device 90 described later, and thus the engine torque Te [Nm], which is the output torque of the engine 12, is controlled. In this specification, unless otherwise distinguished, torque, driving force, power, and force (power) are synonymous.

[0016] The engine connecting shaft 20 is a member that connects the engine 12 and the clutch K0, and is, for example, a crankshaft.

[0017] The electric motor MG is a so-called motor generator having a function as an electric motor (electric motor function) that generates mechanical power from electrical energy and a function as a generator (generator function) that generates electrical energy from mechanical power. In this specification, power is synonymous with driving force, torque, and force unless otherwise distinguished. The electric motor MG is connected to a battery 60 provided in the vehicle 10 via an inverter 52 described later. The battery 60 is a power storage device that exchanges power with the electric motor MG. The electric motor MG is controlled by the inverter 52 being controlled by an electronic control device 90 described later, and thus the motor torque Tmg [Nm], which is the output torque of the electric motor MG, is controlled. Note that the electric motor MG corresponds to the "electric motor" in the present invention.

[0018] A clutch K0 is provided between an engine connecting shaft 20 connected to the engine 12 and a motor connecting shaft 22 connected to the rotor of the motor MG. The clutch K0 is a friction engagement device that disconnects and connects the power transmission between the engine 12 and the motor MG, and is, for example, a wet multi-plate hydraulic friction engagement device. The clutch K0 switches the disconnection and connection states such as a fully engaged state, a semi-engaged state (slip state), and a released state by regulating the hydraulic pressure supplied from a hydraulic control circuit 54 described later to a hydraulic actuator that controls the disconnection and connection state of the clutch K0. For example, in this embodiment, the clutch K0 is brought into the fully engaged state by increasing the hydraulic pressure supplied to the hydraulic actuator, and the clutch K0 is brought into the released state by decreasing the hydraulic pressure supplied to the hydraulic actuator. When the clutch K0 is brought into the fully engaged state, the clutch K0 enables the power transmission between the engine 12 and the motor MG. When the clutch K0 is brought into the released state, the clutch K0 cuts off the power transmission between the engine 12 and the motor MG. When the clutch K0 is brought into the semi-engaged state, the clutch K0 enables the power transmission between the engine 12 and the motor MG according to the transmission torque capacity (engagement force of the clutch K0) based on the semi-engaged state. Note that the clutch K0 corresponds to the "friction engagement device" in the present invention.

[0019] The motor MG is rotationally driven by the electric power stored in the battery 60 and outputs the driving force for traveling of the hybrid vehicle 10. Further, the motor MG generates electricity by the driving force for traveling input from the engine 12 via the clutch K0, or converts the driven force input from the drive wheel 14 side into electric power by regeneration and generates electricity. The generated electric power is charged to the battery 60 via the inverter 52.

[0020] The inverter 52 is provided between the motor MG and the battery 60, and is a power supply circuit that converts direct current to alternating current or alternating current to direct current by being controlled by an electronic control device 90. For example, the inverter 52 converts the direct current supplied from the battery 60 into alternating current and outputs it to the motor MG to drive it, or converts the alternating current generated by the motor MG into direct current and outputs it to the battery 60.

[0021] The battery 60 is a rechargeable secondary battery such as a lithium-ion battery or a nickel-metal hydride battery. The battery 60 is mainly used to supply power for driving the motor MG and to charge the power generated by the motor MG through regeneration.

[0022] The torque converter 24 is a well-known torque converter. The torque converter 24 includes a pump impeller connected to the motor connection shaft 22, a turbine impeller connected to the AT input shaft 26, and a lock-up clutch 40 that directly connects the pump impeller and the turbine impeller. The torque converter 24 is disposed in the power transmission path PT between the driving power source PG (engine 12, motor MG) for traveling and the drive wheels 14, and is a fluid transmission device that can transmit the driving power for traveling output from the driving power source PG for traveling from the motor connection shaft 22 to the AT input shaft 26 through a fluid. The vehicle 10 includes a mechanical oil pump MOP42. The MOP42 is connected to the pump impeller and is rotationally driven by the driving power source PG (engine 12, motor MG) for traveling to discharge the hydraulic oil OIL used in each part in the case 18.

[0023] The EOP 56 is a well-known oil pump that can be driven by the rotation of the EOP drive motor 58 independently of the rotation of the engine 12 or the motor MG, which is the driving power source PG for traveling. The EOP drive motor 58 is a well-known motor, and the rotation speed of the EOP drive motor 58 is controlled by controlling an inverter (not shown) by an electronic control unit 90. The EOP 56 is rotationally driven by the EOP drive motor 58 to discharge the hydraulic oil OIL used in each part in the case 18.

[0024] The automatic transmission 28 is a well-known automatic transmission that shifts the driving force for running input from the driving force source PG (engine 12, motor MG) to the AT input shaft 26 and outputs it to the AT output shaft 30. For example, it is a stepped transmission such as a planetary gear type or a constantly meshing parallel shaft type, or a continuously variable transmission such as a belt type or a power roller type. The automatic transmission 28 is controlled by a hydraulic control circuit 54 controlled by an electronic control unit 90 so that a desired transmission ratio γat (= AT input rotational speed Ni [rpm] / AT output rotational speed No [rpm]) is formed from different transmission ratios γat. The transmission ratio γat is also called the gear ratio. In this embodiment, the automatic transmission 28 is a well-known planetary gear type automatic transmission including a plurality of sets of planetary gear devices and a plurality of transmission engaging devices CB. Each of the transmission engaging devices CB is controlled to switch between disengagement states such as a fully engaged state, a semi-engaged state, and a released state by regulating the hydraulic pressure supplied from the hydraulic control circuit 54 to a hydraulic actuator that controls the disengagement state of the transmission engaging device CB. The automatic transmission 28 forms any one of a plurality of gear stages (also called gear steps) with different transmission ratios γat by engaging any one of the engaging devices of the transmission engaging devices CB. Further, the automatic transmission 28 can also be set to a neutral state in which the driving force for running output from the driving force source PG is not transmitted to the drive wheels 14.

[0025] The differential gear 32 is a well-known differential gear that receives the driving force for running transmitted from the AT output shaft 30 of the automatic transmission 28 and transmits equal driving torques to each other while appropriately allowing a rotational speed difference for a pair of drive shafts 34.

[0026] The hydraulic control circuit 54 supplies the hydraulic oil OIL necessary for each part in the case 18 using the hydraulic pressure of the hydraulic oil OIL discharged from the MOP 42 and the EOP 56 as the source pressure. For example, the hydraulic control circuit 54 generates the hydraulic pressure for controlling the engagement and disengagement of the clutch K0, the hydraulic pressure for controlling the shift of the automatic transmission 28, and the hydraulic pressure for controlling the engagement and disengagement of the lock-up clutch 40 of the torque converter 24, respectively, and supplies them to each hydraulic actuator in the case 18.

[0027] When the clutch K0 is engaged, the driving force for running output from the engine 12 is transmitted from the engine connecting shaft 20 to the drive wheels 14 through the clutch K0, the motor connecting shaft 22, the torque converter 24, the automatic transmission 28, the differential gear 32, the drive shaft 34, etc. in sequence. The driving force for running output from the motor MG is transmitted from the motor connecting shaft 22 to the drive wheels 14 through the torque converter 24, the automatic transmission 28, the differential gear 32, the drive shaft 34, etc. in sequence regardless of the connection / disconnection state of the clutch K0.

[0028] In the vehicle 10, either a BEV running mode or an engine running mode, i.e., an HEV running mode, can be selected. The BEV running mode is a running mode in which, with the engine 12 stopped, the motor MG is power running controlled to perform BEV (Battery Electric Vehicle) running using only the motor MG as the driving force source among the driving force sources PG for running. In the BEV running mode, the clutch K0 is released and BEV running is performed. Note that the BEV running mode includes the case where the vehicle 10 is running and the case where the vehicle 10 is stopped, i.e., parked. The HEV running mode is a running mode in which, with the engine 12 running, HEV (Hybrid Electric Vehicle) running using at least the engine 12 as the driving force source among the driving force sources PG for running is performed. In the HEV running mode, the clutch K0 is fully engaged and HEV running is performed.

[0029] Whether the vehicle 10 runs in the BEV running mode or the HEV running mode is switched, for example, by a driving force source switching map. The driving force source switching map is a relationship in which the running mode is predetermined in two-dimensional coordinates with, for example, the vehicle speed V [km / h] and the required driving torque Trdem [Nm] as variables. The required driving torque Trdem is the driving torque required for the vehicle 10, and is, for example, the driving torque Tr [Nm] required for the drive wheels 14. The calculation method of the required driving torque Trdem will be described later.

[0030] In a low vehicle speed range where the vehicle speed V is relatively low and the required drive torque Trdem is relatively low (i.e., the accelerator opening θacc [%] is relatively low), and in a low load range where the engine efficiency generally decreases, it is set as the area where the BEV driving mode is selected. On the other hand, in a high vehicle speed range where the vehicle speed V is relatively high, or in a high load range where the required drive torque Trdem is relatively high (i.e., the accelerator opening θacc is relatively high), it is set as the area where the HEV driving mode is selected. Also, the BEV driving mode is applied when the state of charge value (the ratio of the actual charged amount stored in the battery 60 to the predetermined full charge capacity) SOC [%] of the battery 60 is equal to or higher than a predetermined engine start threshold value. In other words, when the state of charge value SOC of the battery 60 is less than the predetermined engine start threshold value, in the drive power source switching map, the area where the BEV driving mode is selected disappears, which is the same as the area where the HEV driving mode is selected in all cases. In the HEV driving mode, the motor rotation speed Nmg [rpm], which is the rotation speed of the motor MG, is the same value as the engine rotation speed Ne [rpm], which is the rotation speed of the engine 12. The predetermined engine start threshold value is a predetermined threshold value for determining that it is the state of charge value SOC where it is necessary to forcibly start the engine 12 to charge the battery 60.

[0031] The electronic control unit 90 is configured to include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, input / output interface, etc. 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. The electronic control unit 90 is configured to include each computer for engine control, motor control, hydraulic control, etc. as necessary. Note that the electronic control unit 90 corresponds to the "control device" in the present invention.

[0032] The electronic control unit 90 receives various signals (e.g., the engine rotational speed Ne [rpm] which is the rotational speed of the engine 12, the turbine rotational speed Nt [rpm] which is the same value as the AT input rotational speed Ni [rpm], the AT output rotational speed No [rpm] corresponding to the vehicle speed V, the rotational speed of the electric motor MG which is the electric motor rotational speed Nmg [rpm], the accelerator opening θacc [%] which is the driver's accelerator operation amount representing the magnitude of the driver's acceleration operation, the throttle valve opening θth [%] which is the opening of the electronic throttle valve, the battery temperature THbat [°C], the battery charge / discharge current Ibat [A], and the battery voltage Vbat [V] of the battery 60, the intake air amount GA [m 3 / sec], etc.) based on the detection values from various sensors (e.g., the engine rotational speed sensor 70, the turbine rotational speed sensor 72, the output rotational speed sensor 74, the electric motor rotational speed sensor 76, the accelerator opening sensor 78, the throttle valve opening sensor 80, the battery sensor 82, the air flow meter 84, etc.) provided in the vehicle 10.

[0033] The electronic control unit 90 outputs various command signals (e.g., the engine control signal Se for controlling the engine 12, the electric motor control signal Smg for controlling the electric motor MG, the shift control signal Sat for controlling the shift engagement device CB, the K0 control signal Sk0 for controlling the clutch K0, the LU control signal Slu for controlling the lock-up clutch 40, the EOP control signal Seop for controlling the EOP 56, etc.) to each device (e.g., the engine control unit 50, the inverter 52, the hydraulic control circuit 54, the EOP drive motor 58, etc.) provided in the vehicle 10.

[0034] The electronic control unit 90 functionally includes a hybrid control unit 92, a clutch control unit 94, a shift control unit 96, and a start control unit 98.

[0035] The hybrid control unit 92 functionally includes an engine control unit 92a that controls the operation of the engine 12 and an electric motor control unit 92b that controls the operation of the electric motor MG via the inverter 52, and executes hybrid drive control and the like by the engine 12 and the electric motor MG according to these control functions.

[0036] The hybrid control unit 92 calculates a required drive amount (for example, a required drive torque Trdem) for the vehicle 10 by the driver, for example, by applying the actual accelerator opening θacc and the vehicle speed V to a required drive amount map. The required drive amount map is a map in which the relationship between the accelerator opening θacc, the vehicle speed V, and the required drive amount is experimentally or design - determined and stored in advance. The required drive amount is the drive amount required for the vehicle 10, for example, the required drive torque Trdem. The required drive torque Trdem is, in other words, the required drive power Prdem [W] at the vehicle speed V at that time. As the required drive amount, the required drive force Frdem [N] at the drive wheels 14, the required output torque at the AT output shaft 30, etc. can also be used. In the calculation of the required drive amount, the AT output rotational speed No or the like may be used instead of the vehicle speed V. Thus, the required drive torque Trdem, the required drive power Prdem, the required drive force Frdem, and the required output torque at the AT output shaft 30 are synonymous in that they are the required drive amounts of the vehicle 10.

[0037] The hybrid control unit 92 outputs an engine control signal Se for controlling the engine 12 and an electric motor control signal Smg for controlling the electric motor MG so as to realize the required drive power Prdem in consideration of transmission losses, accessory loads, the gear ratio γat of the automatic transmission 28, the chargeable power Win [W] and the dischargeable power Wout [W] of the battery 60, etc. The engine control signal Se is, for example, a command value of the engine power Pe [W] which is the power of the engine 12 that outputs the engine torque Te at the engine rotational speed Ne at that time. The electric motor control signal Smg is, for example, a command value of the power consumption Wm [W] of the electric motor MG that outputs the electric motor torque Tmg at the electric motor rotational speed Nmg at that time.

[0038] The chargeable power Win of the battery 60 is the maximum input power that can be input, which defines the input power limit of the battery 60 and indicates the input limit of the battery 60. The dischargeable power Wout of the battery 60 is the maximum output power that can be output, which defines the output power limit of the battery 60 and indicates the output limit of the battery 60. The chargeable power Win and the dischargeable power Wout of the battery 60 are calculated by the electronic control unit 90 based on, for example, the battery temperature THbat and the state of charge value SOC of the battery 60.

[0039] When the hybrid control unit 92 can cover the required drive torque Trdem only with the output of the motor MG, the driving mode is set to the BEV driving mode. On the other hand, when the hybrid control unit 92 cannot cover the required drive torque Trdem without using at least the output of the engine 12, the driving mode is set to the HEV driving mode. On the other hand, even when the hybrid control unit 92 can cover the required drive torque Trdem only with the output of the motor MG, if the state of charge value SOC of the battery 60 is less than a predetermined engine start threshold value or if warm-up of the engine 12 or the like is necessary, the HEV driving mode is established. The engine start threshold value is a predetermined threshold value for determining that it is the state of charge value SOC at which it is necessary to forcibly start the engine 12 to charge the battery 60. In this way, the hybrid control unit 92 automatically stops the engine 12 during HEV driving, starts the engine 12 during BEV driving, automatically stops the engine 12 during parking, and restarts the engine 12 after the engine stop based on the required drive torque Trdem and the like, thereby switching between the BEV driving mode and the HEV driving mode.

[0040] The engine control unit 92a controls the engine torque Te so as to realize the drive demand amount for the vehicle 10. The motor control unit 92b controls the motor torque Tmg so as to realize the drive demand amount for the vehicle 10. Specifically, in the BEV driving mode, the motor control unit 92b controls the motor torque Tmg so as to realize the required drive torque Trdem. In the HEV driving mode, the engine control unit 92a controls the engine torque Te so as to realize all or part of the required drive torque Trdem, and the motor control unit 92b controls the motor torque Tmg so as to compensate for the torque shortage that cannot be provided by the engine torque Te with respect to the required drive torque Trdem. When the engine 12 is in a stopped state where its operation has stopped, for example, in the BEV driving mode, the engine control unit 92a executes a fuel cut that stops the fuel injection to the engine 12 in the fuel injection device of the engine control device 50.

[0041] The clutch control unit 94 controls the engagement and disengagement state of the clutch K0 in the engine start control for starting the engine 12. For example, when it is determined by the start determination unit 98a described later that there is a start request for the engine 12, the clutch control unit 94 controls the clutch K0 to change from the released state to the fully engaged state through the semi-engaged state in order to transmit the cranking torque Tcr [Nm] required for cranking the engine 12, which is the torque for increasing the engine rotation speed Ne, to the engine 12 side. For example, in the engine start control, the transmission torque capacity of the clutch K0 is controlled to gradually increase according to a time chart for K0 determined in advance experimentally or by design so that the engagement speed of the clutch K0 (= the acceleration rate of the transmission torque capacity of the clutch K0) and the engagement shock are within the allowable range.

[0042] The shift control unit 96 performs shift determination for the automatic transmission 28 using, for example, a shift map, and outputs a shift control signal Sat for executing shift control to the hydraulic control circuit 54 as necessary. The shift map has a predetermined relationship having shift lines for determining shifts of the automatic transmission 28 on a two-dimensional coordinate with, for example, the vehicle speed V and the required drive torque Trdem as variables. In the shift map, the AT output rotational speed No or the like may be used instead of the vehicle speed V, or the required driving force Frdem, the accelerator opening θacc, the throttle valve opening θth, or the like may be used instead of the required drive torque Trdem.

[0043] The start control unit 98 controls the electric motor MG and the engine 12 so as to execute engine start control. The start control unit 98 functionally includes a start determination unit 98a, a cranking control unit 98b, a synchronization determination unit 98c, and an injection start control unit 98d.

[0044] The start determination unit 98a determines whether or not starting of the engine 12 is requested in the BEV driving mode. That is, the start determination unit 98a determines whether or not there is a request to start the engine 12. For example, when the driving mode is the BEV driving mode, the start determination unit 98a determines that there is a request to start the engine 12 when (a) the required drive torque Trdem increases beyond the range that can be covered by only the output of the electric motor MG, (b) warming up of the engine 12 or the like is necessary, or (c) the state of charge value SOC of the battery 60 is less than the engine start threshold value.

[0045] When it is determined by the starting determination unit 98a that starting of the engine 12 is requested, the cranking control unit 98b and the clutch control unit 94 crank the engine 12 using the electric motor MG and the clutch K0. In this cranking, the cranking control unit 98b controls the electric motor MG to output a cranking torque Tcr until cranking ends in accordance with the switching of the clutch K0 from the released state to the fully engaged state by the clutch control unit 94. In the engine starting control in the BEV running mode, the cranking control unit 98b causes the electric motor MG to output an electric motor torque Tmg obtained by adding the cranking torque Tcr to the electric motor torque Tmg for generating the electric motor torque Tmg for BEV running, that is, the driving torque Tr. Further, the clutch control unit 94 controls the clutch K0 to be in the fully engaged state via the semi-engaged state from the released state in order to transmit the cranking torque Tcr to the engine 12 side as described above. That is, when starting the engine 12, cranking of the engine 12 is executed by the electric motor MG while the clutch K0 is engaged. Further, the cranking control unit 98b determines whether or not cranking has started.

[0046] When the cranking of the engine 12 is started by the cranking control unit 98b and the clutch control unit 94, the synchronization determination unit 98c determines whether the synchronization of the clutch K0 is completed. That the synchronization of the clutch K0 is completed means that the engine rotation speed Ne and the motor rotation speed Nmg are the same, that is, it is synonymous with the clutch K0 not slipping and being in a fully engaged state. For example, when a state where the rotation speed difference ΔN (= Nmg - Ne), which is the difference between the motor rotation speed Nmg and the engine rotation speed Ne, is within the synchronization determination width ΔN_jdg [rpm] including a predetermined zero value continues for a predetermined first elapsed period P1 [ms] or more, it is determined that the synchronization is completed. The synchronization determination width ΔN_jdg and the predetermined first elapsed period P1 are determination widths and periods predetermined experimentally or by design, respectively, for determining that the synchronization of the clutch K0 is completed. The condition that the synchronization of the clutch K0 is completed is a condition for determining that the preparation for fuel injection into the engine 12 is completed, and corresponds to the "predetermined condition" in the present invention.

[0047] The injection start control unit 98d predicts the predicted torque Te_pred. The predicted torque Te_pred is a predicted value of the engine torque Te at the time when fuel injection into the engine 12 is started and the engine 12 starts to output after the synchronization of the clutch K0 is completed. Hereinafter, although the description is omitted in this specification, ignition of the engine 12 is also started simultaneously with the start of fuel injection into the engine 12. Note that the predicted torque Te_pred corresponds to the "predetermined predicted torque" in the present invention.

[0048] Generally, the engine torque Te changes according to the engine rotation speed Ne, the intake air amount GA [m3 / sec], and the ignition timing (for example, the ignition retard angle amount θdly [deg]).

[0049] At the start time of starting the engine 12 in engine start control (the start time tsta of fuel injection into the engine 12), the engine speed Ne is the synchronous rotation speed Nmg_syn which is, for example, the motor rotation speed Nmg when the synchronization of the clutch K0 is completed. This synchronous rotation speed Nmg_syn can be calculated (i.e., predicted) based on the vehicle speed V and the gear ratio γat of the automatic transmission 28.

[0050] The ignition retard amount θdly at the start time tsta of fuel injection into the engine 12 in engine start control is determined according to the state of the vehicle 10. For example, the ignition retard amount θdly is set to MBT (Minimum advance for the Best Torque) which is the time when the engine torque Te is maximum, but this MBT changes according to the operating state of the engine 12 such as the engine speed Ne. For example, the ignition retard amount θdly can be calculated (i.e., predicted) using an ignition retard map which is a map in which the relationship between the engine speed Ne and the ignition retard amount θdly that becomes MBT is experimentally or designedly determined in advance.

[0051] During the execution of engine start control, every time the air in a surge tank (not shown) is sucked into the engine 12 by cranking, the pressure in the surge tank is reduced from the atmospheric pressure. The surge tank is a tank provided between the intake manifold and the throttle valve so that intake pulsation does not occur in the intake system in the fuel injection type engine 12. The intake air amount GA of the engine 12 in engine start control decreases as the pressure in the surge tank is reduced from the atmospheric pressure.

[0052] Here, the intake air amount GA of the engine 12 at the start time tcrn of cranking is set to a predetermined first intake air amount GA1. When the fuel injection to the engine 12 is stopped, the intake air amount GA of the engine 12 during the execution of the engine start control gradually decreases from the predetermined first intake air amount GA1 according to the rotation amount of the engine 12 ( = the number of rotations of the engine 12) starting from the start time tcrn of cranking, and then becomes stable at a predetermined second intake air amount GA2 (<GA1). For example, an intake air amount map, which is a map experimentally or designedly predetermined and stored in advance of the relationship between the rotation amount of the engine 12 starting from the start time tcrn of cranking and the intake air amount GA of the engine 12, is used, so that the intake air amount GA of the engine 12 can be calculated (i.e., predicted). Note that the rotation amount of the engine 12 can be calculated by integrating the engine rotation speed Ne after the start time tcrn of cranking.

[0053] Therefore, the predicted torque Te_pred is calculated based on a predicted torque map, which is a map in which the relationship between the engine rotation speed Ne, the intake air amount GA, and the ignition retard angle θdly predicted at the start time tsta of fuel injection to the engine 12, for example, after the synchronization of the clutch K0 is completed, and the predicted torque Te_pred is predetermined. In this way, the predicted torque Te_pred is calculated based on the rotation amount of the engine 12 from the start time tcrn of cranking to the start time tsta of fuel injection. The calculated predicted torque Te_pred gradually decreases as the rotation amount of the engine 12 increases. In this way, the predicted torque Te_pred gradually decreases as the start time tsta of fuel injection is set later.

[0054] The injection start control unit 98d sets the time point at which the predicted torque Te_pred after the synchronization of the clutch K0 is completed becomes the target torque value Te_tgt as the start time tsta of fuel injection. The target torque value Te_tgt is a torque value determined in advance experimentally or by design in order to suppress fluctuations in the starting sound and starting shock generated each time the engine 12 is started. Here, when the start time tsta of fuel injection is set, the period from the start time tcrn of cranking to the time point tsyn when the synchronization of the clutch K0 is completed (hereinafter referred to as "synchronization completion time point tsyn") is referred to as the "engagement period Pcon [ms]", and the period from the synchronization completion time point tsyn to the start time tsta of fuel injection is referred to as the "waiting period Pwait [ms]", and the period from the start time tsta of fuel injection to the time point when the engine torque Te actually starts to be output is referred to as the "delay period Pdly [ms]". In other words, when fuel injection into the engine 12 is started at the time point after the waiting period Pwait has elapsed from the synchronization completion time point tsyn, the engine torque Te (i.e., the predicted torque Te_pred) that starts to be output from the engine 12 at the time point after the delay period Pdly has elapsed from the start time tsta of fuel injection becomes the target torque value Te_tgt. In terms of specifying the time point at which to start fuel injection into the engine 12, setting the start time tsta of fuel injection and setting the waiting period Pwait are synonymous. Note that the delay period Pdly is, for example, a fixed value determined in advance experimentally or by design.

[0055] For example, when the engagement period Pcon, which is the period from the start time tcrn of cranking to the completion time tsyn of synchronization, is short (for example, when the synchronous rotation speed Nmg_syn is low or the engagement speed of the clutch K0 is high), the predicted torque Te_pred at the completion time tsyn of synchronization when the start time tsta of fuel injection is set becomes larger compared to the case where the engagement period Pcon is long. Therefore, when the engagement period Pcon is short, by increasing the period from the completion time tsyn of synchronization to the start time tsta of fuel injection compared to the case where the engagement period Pcon is long, the predicted torque Te_pred is made to be the target torque value Te_tgt. Specifically, when the synchronous rotation speed Nmg_syn is low or the hydraulic pressure supplied to the hydraulic actuator that controls the engaged / disengaged state of the clutch K0 is high, the start time tsta of fuel injection is set to be later compared to the case where this is not so, and the period from the completion time tsyn of synchronization to the start time tsta of fuel injection is increased. On the other hand, when the synchronous rotation speed Nmg_syn is high or the hydraulic pressure supplied to the hydraulic actuator that controls the engaged / disengaged state of the clutch K0 is low, the start time tsta of fuel injection is set to be earlier compared to the case where this is not so, and the period from the completion time tsyn of synchronization to the start time tsta of fuel injection is decreased.

[0056] Preferably, prior to setting the start time tsta of fuel injection, the injection start control unit 98d corrects the target torque value Te_tgt according to the accelerator opening θacc. Specifically, when the driver performs an acceleration operation and the accelerator opening θacc is large, the target torque value Te_tgt is corrected to a larger value compared to when the accelerator opening θacc is small. When the target torque value Te_tgt is corrected to a larger value, the start time tsta of fuel injection is set to an earlier time. When the accelerator opening θacc is large, by correcting the target torque value Te_tgt to a larger value compared to when the accelerator opening θacc is small, the start time tsta of fuel injection is set at a time when the predicted torque Te_pred is high. Note that although the throttle valve opening θth is changed according to the magnitude of the accelerator opening θacc when the driver performs an acceleration operation, by delaying the instruction to change the throttle valve opening θth for a predetermined period, the intake air amount GA can be accurately predicted, and thus the predicted torque Te_pred can be accurately predicted. The predetermined period is a period determined in advance experimentally or by design in order to accurately predict the intake air amount GA.

[0057] When the set start time tsta of fuel injection is reached, the injection start control unit 98d controls to start fuel injection and ignition to the engine 12.

[0058] FIG. 2 is an example of a flowchart for explaining the control operation of the electronic control unit 90 shown in FIG. 1. The flowchart of FIG. 2 is repeatedly executed in the BEV driving mode.

[0059] First, in step S10 corresponding to the function of the cranking control unit 98b (hereinafter, steps are omitted), it is determined whether cranking in engine start control has started.

[0060] If the determination in S10 is affirmative, in S20 corresponding to the function of the synchronization determination unit 98c, it is determined whether the synchronization of the clutch K0 is completed. If the determination in S10 is negative, the process ends.

[0061] When the determination in S20 is negative, S20 is executed again. When the determination in S20 is positive, in S30 corresponding to the function of the injection start control unit 98d, a waiting period Pwait is calculated, which is the period from the synchronization completion time tsyn to the time point (i.e., the fuel injection start time tsta) when the release of the fuel cut is instructed according to the accelerator opening θacc.

[0062] After the execution of S30, in S40 corresponding to the function of the injection start control unit 98d, it is determined whether or not the waiting period Pwait has elapsed from the synchronization completion time tsyn. If the determination in S40 is negative, S40 is executed again. If the determination in S40 is positive, in S50 corresponding to the function of the injection start control unit 98d, the fuel injection to the engine 12 is started and then ends.

[0063] FIG. 3 is an example of a time chart when the flowchart of FIG. 2 is executed. FIG. 3 is an example when the engine start control is executed in the BEV driving mode, and the accelerator opening θacc in the engine start control is a zero value. The horizontal axis of FIG. 3 is time t [ms].

[0064] In FIG. 3, the intake air amount GA shows the transition when there is no start of fuel injection to the engine 12. In FIG. 3, the predicted torque Te_pred shows the transition when fuel injection to the engine 12 is started at each time, and the actual engine torque Te_real shows the transition of the actual engine torque Te when fuel injection to the engine 12 is started at time t4.

[0065] At time t1, the engine 12 starts rotating by cranking. During the period from time t1 to time t3 (>t1), the engine rotation speed Ne gradually increases, and the synchronization of the clutch K0 is completed at time t3. The period from time t1 to time t3 is the engagement period Pcon.

[0066] After time t3 (after the synchronization completion time tsyn), the motor rotation speed Nmg, that is, the synchronous rotation speed Nmg_syn, is determined based on the vehicle speed V and the gear ratio γat of the automatic transmission 28. This synchronous rotation speed Nmg_syn is the target value of the engine rotation speed Ne during cranking. The rising speed of the engine rotation speed Ne (= the increase amount per unit time in the engine rotation speed Ne) is determined based on the hydraulic control according to the aforementioned time chart for K0 that causes the clutch K0 to transition from the released state through the semi-engaged state to the fully engaged state. Therefore, the engagement period Pcon, which is the period from the start time tcrn of cranking to the synchronization completion time tsyn, varies depending on the synchronous rotation speed Nmg_syn and the rising speed of the engine rotation speed Ne. The transition of the engine rotation speed Ne after time t1 can be predicted based on the transmission torque capacity by the hydraulic control of the clutch K0 and the synchronous rotation speed Nmg_syn.

[0067] Based on the predicted value of the engine rotation speed Ne after time t1, the rotation amount of the engine 12 at each time is calculated, and further, the intake air amount GA is predicted based on the calculated rotation amount of the engine 12. The predicted intake air amount GA significantly decreases at time t2 (t1 < t2 < t3) and gradually decreases toward a predetermined second intake air amount GA2 after time t2, as shown in, for example, FIG. 3.

[0068] The predicted torque Te_pred gradually decreases in response to the decrease in the predicted intake air amount GA after time t2. The time t4 (> t3) is predicted as the time when the predicted torque Te_pred becomes the target torque value Te_tgt. This predicted time t4 is set as the start time tsta of fuel injection. The period from time t3 to time t4 is the waiting period Pwait.

[0069] At time t4, fuel injection into the engine 12 is started. At time t5, which is a point in time delayed by a delay period Pdly from time t4, the actual engine torque Te_real, which is the actual engine torque Te, starts to be output from the engine 12. The actual engine torque Te_real at the time when it starts to be output from the engine 12 at time t5 is the target torque value Te_tgt.

[0070] According to this embodiment, (a) a fuel cut that stops fuel injection into the engine 12 when the engine 12 is in a stopped state is executed, (b) when the engine 12 is started, cranking of the engine 12 is executed by the electric motor MG while the clutch K0 is engaged, and fuel injection into the engine 12 is started after the synchronization of the clutch K0 is completed, and (c) the start time point tsta of fuel injection after the synchronization of the clutch K0 is completed is set to the time point when the predicted torque Te_pred becomes the target torque value Te_tgt. By setting the start time point tsta of fuel injection to the time point when the predicted torque Te_pred becomes the target torque value Te_tgt, fluctuations in the starting sound and starting shock generated at each start of the engine 12 are suppressed, and the discomfort felt by the driver is suppressed.

[0071] According to this embodiment, the predicted torque Te_pred is calculated based on the rotation amount of the engine 12 from the start time point tcrn of cranking to the start time point tsta of fuel injection. By calculating the predicted torque Te_pred based on the rotation amount of the engine 12 from the start time point tcrn of cranking to the start time point tsta of fuel injection, the calculation accuracy of the predicted torque Te_pred is improved. By improving the calculation accuracy of the predicted torque Te_pred, the setting accuracy of the start time point tsta of fuel injection is improved, so that fluctuations in the starting sound and starting shock generated at each start of the engine 12 are accurately suppressed, and the discomfort felt by the driver is suppressed.

[0072] According to this embodiment, when the accelerator opening θacc is large, the target torque value Te_tgt is corrected to a larger value compared to when the accelerator opening θacc is small. When an acceleration operation is performed by the driver, the target torque value Te_tgt is corrected according to the accelerator opening θacc. When the target torque value Te_tgt is corrected to a larger value, the start time tsta of fuel injection is set at a point in time when the predicted torque Te_pred is higher compared to when it is not. Therefore, when the accelerator opening θacc is large, the engine torque Te at the time when fuel injection into the engine 12 starts and the engine starts to output is increased compared to when the accelerator opening θacc is small. As a result, while suppressing fluctuations in the starting sound and starting shock that occur every time the engine 12 starts, vehicle responsiveness is prioritized, and the driving force for running required by the driver is realized early, improving drivability.

[0073] 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 in other aspects.

[0074] In the above-described embodiment, the torque converter 24, which is a fluid transmission device, is provided in the power transmission path PT between the driving power source PG for running and the automatic transmission 28, but the present invention is not limited to this embodiment. For example, instead of the torque converter 24, other fluid transmission devices such as a fluid coupling without a torque amplification function may be used. Further, the fluid transmission device does not necessarily have to be provided and may be replaced with, for example, a clutch for starting.

[0075] In the above-described embodiment, the clutch K0 is a wet friction engagement device, but it is not limited thereto and may be a dry friction engagement device.

[0076] In the foregoing embodiments, the "predetermined conditions" were only the condition that the synchronization of the clutch K0 was completed, but it is not limited to this mode. For example, the "predetermined conditions" may be, in addition to the condition that the synchronization of the clutch K0 is completed, that the clutch K0 can transmit the torque fluctuation of the engine torque Te at the start time tsta of fuel injection into the engine 12, and a predetermined second elapsed period P2 [ms] that has elapsed after it is determined that the synchronization of the foregoing clutch K0 is completed may be added. Immediately after the synchronization of the clutch K0 is completed, the transmission torque capacity of the clutch K0 is not sufficient, and the clutch K0 cannot transmit the torque fluctuation of the engine torque Te (the engine torque Te at the time when it starts to be output) caused by the start of fuel injection into the engine 12, and the clutch K0 may slip. The predetermined second elapsed period P2 is a period predetermined experimentally or by design so that the clutch K0 does not slip due to the torque fluctuation of the engine torque Te caused by the start of fuel injection into the engine 12.

[0077] Note that what has been described 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 Reference Numerals

[0078] 10: Hybrid vehicle 12: Engine (internal combustion engine) 90: Electronic control unit (control unit) K0: Clutch (friction engagement device) MG: Electric motor PG: Driving power source for traveling Te_tgt: Target torque value Te_pred: Predicted torque tsta: Start time of fuel injection

Claims

【Claim 1】 A control device for a hybrid vehicle, comprising: an internal combustion engine and an electric motor as driving power sources for traveling; and a friction engagement device that disconnects and connects power transmission between the internal combustion engine and the electric motor, When the internal combustion engine is in a stopped state, execute a fuel cut to stop fuel injection into the internal combustion engine, When starting the internal combustion engine, while engaging the friction engagement device, crank the internal combustion engine with the electric motor and start fuel injection into the internal combustion engine after a predetermined condition that the preparation for fuel injection into the internal combustion engine is completed is satisfied, Set the start timing of the fuel injection after the predetermined condition is satisfied to the timing when a predetermined predicted torque, which is the predicted output torque of the internal combustion engine, becomes a predetermined target torque value, The predicted torque is calculated based on the rotation amount of the internal combustion engine from the start timing of the cranking to the start timing of the fuel injection, A control device for a hybrid vehicle, characterized by the above.

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