JP7798706B2 - Vehicle control device - Google Patents

Description

The present invention relates to a control device for a vehicle equipped with a clutch that mechanically connects and disconnects the power transmission path between the engine and electric motor as power sources and the drive wheels.

Vehicle control devices equipped with a torque converter lock-up clutch that mechanically connects and disconnects the power transmission path between the engine and electric motor as power sources and the drive wheels are known. For example, the vehicle control device described in Patent Document 1 is one such device.

Patent No. 5794377

In order to suppress the occurrence of start-up shock caused by torque fluctuations being transmitted to the drive wheels when the engine is started, it is known that engine start control is initiated after the lock-up clutch is slip-engaged or released. In the vehicle described in Patent Document 1, while the vehicle is running as a BEV using only the electric motor as a power source, the torque capacity of the lock-up clutch is reduced before a request to start the engine is made, compared to when the vehicle is running using the engine as at least a power source. As a result, after a request to start the engine is made, the lock-up clutch is quickly switched from full engagement to slip-engaged or released, and engine start control is initiated, thereby achieving both suppression of start-up shock and improvement of drivability. However, further suppression of start-up shock and improvement of drivability are desired.

The present invention was made against the backdrop of the above circumstances, and its purpose is to provide a vehicle control device that suppresses starting shock and improves drivability.

The gist of the present invention is a control device for a vehicle equipped with an engine and an electric motor as a power source, a first clutch that connects and disconnects the power transmission between the engine and the electric motor, and a second clutch that mechanically connects and disconnects the power transmission path between the power source and drive wheels, the control device (a) initiating torque capacity control in which a command value for the torque capacity of the second clutch corresponds to the input torque input from the electric motor to the second clutch before a start of the engine is requested during BEV driving in which the first clutch is released and the second clutch is fully engaged and power is output only from the electric motor, and (b) after the start of the torque capacity control, When the differential rotation speed obtained by subtracting the rotation speed of the drive wheel side from the rotation speed of the electric motor side in the second clutch is equal to or greater than a predetermined judgment differential rotation value, or when the difference between the actual torque capacity of the second clutch and the input torque is within a predetermined torque range and the input torque is increasing and is estimated to continue to increase, rotation speed control is initiated to control the rotation speed of the electric motor so that the differential rotation speed in the second clutch becomes a predetermined target differential rotation value; and (c) when a start of the engine is requested, the first clutch is switched from released to fully engaged and the output torque of the electric motor is increased to start the engine.

According to the vehicle control device of the present invention, torque capacity control is initiated during BEV driving before engine start is requested, and rotational speed control is initiated in at least one of the following cases: (a) the differential rotation speed in the second clutch is equal to or greater than a predetermined reference differential rotation speed value; and (b) the torque difference between the actual torque capacity of the second clutch and the input torque is within a predetermined torque range, the input torque is increasing, and it is estimated that the input torque will continue to increase. In (a), the second clutch is in slip engagement, so the drive torque transmitted from the electric motor to the drive wheels does not increase abruptly even when rotational speed control is initiated. In (b), the input torque is currently increasing and will continue to increase, i.e., the second clutch immediately enters slip engagement due to an increase in input torque, so the drive torque transmitted from the electric motor to the drive wheels does not increase abruptly even when rotational speed control is initiated. When engine start is requested and engine start control is executed after rotational speed control is initiated, the second clutch is already in slip engagement. Therefore, engine start control is initiated more quickly than in other cases, thereby achieving both suppression of start-up shock and drivability. Furthermore, even if engine start is requested and engine start control is executed before rotation speed control begins, the command value for the torque capacity of the second clutch is set in advance according to the input torque. This allows the second clutch to be slip-engaged more quickly than otherwise and engine start control to begin, thereby achieving both suppression of start-up shock and drivability.

1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions for various controls in the vehicle. 10A and 10B are diagrams illustrating an example of the relationship between a WSC input torque and a target differential rotation value in rotation speed control. 2 is an example of a flowchart illustrating a main part of the control operation of the electronic control device shown in FIG. 1 . 4 is an example of a time chart when rotation speed control is executed in the flowchart of FIG. 3. 10 is a time chart illustrating the occurrence of engine start shock, comparing a case where torque capacity control is started before a request to start the engine with a case where torque capacity control is started after a request to start the engine.

Embodiments of the present invention will now be described in detail with reference to the drawings. Please note that the drawings in the following embodiments have been simplified or modified as appropriate, and the dimensional proportions and shapes of each part are not necessarily drawn accurately.

Figure 1 is a diagram illustrating the general configuration of a vehicle 10 to which the present invention is applied, as well as a diagram illustrating the main control functions for various controls in the vehicle 10. The vehicle 10 is a hybrid vehicle equipped with an engine 12 and an electric motor MG, which function as a power source. In the power transmission path PT between the power source and the drive wheels 14, the vehicle 10 is connected, in order from the power source side, with an electric motor connecting shaft 32, a starting clutch WSC, a transmission input shaft 38, an automatic transmission 20, a reduction gear mechanism 22, a differential gear 24, and a pair of drive shafts 28, all of which are well-known components. The vehicle 10 also includes an inverter 52, a battery 54, a hydraulic control circuit 56, and an electronic control unit 90.

The engine 12 is a well-known internal combustion engine such as a gasoline engine or diesel engine. The engine 12 is controlled by an engine control device 50, which includes a throttle actuator, a fuel injection device, an ignition device, etc., to control the engine torque Te [Nm], which is the output torque of the engine 12. The electric motor MG is a rotating electric machine that functions as both a motor and a generator, and is a so-called motor generator. The electric motor MG outputs the MG torque Tmg [Nm], which is the output torque of the electric motor MG, as power by controlling the inverter 52 using power supplied from the battery 54. The electric motor MG also generates power using the power of the engine 12 and the driven force input from the drive wheels 14, and the generated power charges the battery 54. When no particular distinction is made, the above-mentioned power can also be referred to as driving force, torque, and force.

The on-off clutch K0 is a clutch that connects and disconnects the power transmission between the engine 12 and the electric motor MG. The starting clutch WSC is a clutch that mechanically connects and disconnects the power transmission path PT, particularly between the electric motor MG and the automatic transmission 20. The on-off clutch K0 and the starting clutch WSC correspond to the "first clutch" and "second clutch," respectively, in this invention. The engine connecting shaft 30 is disposed between the engine 12 and the on-off clutch K0, and the electric motor MG is connected to the electric motor connecting shaft 32 disposed between the on-off clutch K0 and the starting clutch WSC so that power can be transmitted. The on-off clutch K0 and the starting clutch WSC are each hydraulic friction engagement devices, constituted, for example, by a multi-plate or single-plate clutch pressed by an actuator. The on-off clutch K0 and the starting clutch WSC each have their torque capacity changed by the regulated hydraulic pressure supplied from the hydraulic control circuit 56, thereby switching between control states such as full engagement, slip engagement, and release. Hereinafter, when there is no need to distinguish between full engagement and slip engagement, we will simply refer to it as "engagement." Torque capacity is the amount of torque that a clutch can transmit, and is equivalent to the clutch engagement force.

The automatic transmission 20 is a well-known planetary gear automatic transmission equipped with, for example, one or more planetary gear devices (not shown) and engagement devices CB. The engagement devices CB include, for example, multiple well-known hydraulic friction engagement devices. The automatic transmission 20 is a stepped transmission in which one of multiple gear stages (also referred to as gear ratios) with different speed ratios (also referred to as gear stages) γat (= AT input rotation speed Ni [rpm] / AT output rotation speed No [rpm]) is formed by engaging one of the engagement devices CB. The AT input rotation speed Ni is the rotational speed of the transmission input shaft 38, which is the input member of the automatic transmission 20, and the AT output rotation speed No is the rotational speed of the transmission output gear 26, which is the output member of the automatic transmission 20. The automatic transmission 20 can also be placed in neutral by, for example, disengaging all of the engagement devices CB.

The hydraulic control circuit 56 uses hydraulic oil discharged from at least one of a mechanical oil pump or an electric oil pump (not shown) provided on the vehicle 10 as the source pressure, and supplies adjusted hydraulic pressure to the actuators that control the control states of the on-off clutch K0, the starting clutch WSC, and the engagement device CB.

When the on-off clutch K0 and the starting clutch WSC are both engaged, the power output from the engine 12 is transmitted to the drive wheels 14 via the power transmission path PT. Regardless of the control state of the on-off clutch K0, when the starting clutch WSC is engaged, the power output from the electric motor MG is transmitted to the drive wheels 14 via the power transmission path PT.

Vehicle 10 is equipped with an electronic control unit 90, which serves as a controller including the control devices of vehicle 10. The electronic control unit 90 is configured to include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input/output interface, etc., and the CPU executes various controls of vehicle 10 by performing signal processing according to programs stored in advance in ROM while utilizing the temporary storage function of the RAM.

The electronic control unit 90 receives various signals based on detection values from various sensors (e.g., engine rotation speed sensor 70, MG rotation speed sensor 72, input rotation speed sensor 74, output rotation speed sensor 76, accelerator position sensor 78, etc.) provided on the vehicle 10 (e.g., engine rotation speed Ne [rpm], which is the rotation speed of the engine 12; MG rotation speed Nmg [rpm], which is the rotation speed of the electric motor MG and also the rotation speed of the input side member of the starting clutch WSC; AT input rotation speed Ni; AT output rotation speed No, which corresponds to vehicle speed V [km/h]; accelerator position θacc [%], which is the driver's accelerator operation amount indicating the magnitude of the driver's acceleration operation). The electronic control unit 90 corresponds to the "controller" in this invention.

The electronic control unit 90 outputs various signals (e.g., an engine control signal Se for controlling the engine 12, an MG control signal Smg for controlling the drive of the electric motor MG, a CB hydraulic control signal Scb for controlling the engagement and disengagement of the engagement device CB, a K0 hydraulic control signal Sk0 for controlling the engagement and disengagement of the on-off clutch K0, a WSC hydraulic control signal Swsc for controlling the engagement and disengagement of the starting clutch WSC, etc.) to various devices provided in the vehicle 10 (e.g., the engine control unit 50, the inverter 52, the hydraulic control circuit 56, etc.).

The electronic control unit 90 functionally comprises a power source control unit 92, a clutch control unit 94, a transmission control unit 96, and a rotational speed control unit 98 to realize various controls in the vehicle 10.

The power source control unit 92 includes a function for controlling the operation of the engine 12 and a function for controlling the operation of the electric motor MG, and these control functions are used to perform hybrid drive control using the engine 12 and the electric motor MG.

The power source control unit 92 selectively switches between a BEV drive mode, which realizes BEV (Battery Electric Vehicle) driving using only the electric motor MG as a power source, and an HEV drive mode, which realizes HEV (Hybrid Electric Vehicle) driving using at least the engine 12 as a power source. During BEV driving, the on-off clutch K0 is disengaged and the starting clutch WSC is engaged. During HEV driving, the on-off clutch K0 and the starting clutch WSC are both engaged. During BEV driving, starting of the engine 12 is requested in cases where the driver's drive demand for the vehicle 10 cannot be met without using the output of the engine 12, where charging of the battery 54 is required, or where warming up of the engine 12, etc. is required. When starting of the engine 12 is requested, engine start control is executed to start the engine 12, and the HEV drive mode is selected.

The power source control unit 92 calculates the driver's drive demand for the vehicle 10, for example, by applying the accelerator opening θacc and vehicle speed V to a drive demand map. The drive demand map is a relationship for calculating the drive demand, which is determined experimentally or by design and stored in advance. The drive demand is the drive demand required for the vehicle 10. Examples of the drive demand may include the required drive torque Trdem [Nm] at the drive wheels 14, the required amount of AT output torque To [Nm] output from the transmission output gear 26 of the automatic transmission 20, the required drive force Frdem [N] at the drive wheels 14, and the required drive power Prdem [W] at the current vehicle speed V. The power source control unit 92 outputs an engine control signal Se for controlling the engine 12 and an MG control signal Smg for controlling the electric motor MG to achieve the required drive power Prdem, for example, taking into account transmission loss, accessory load, and the gear ratio γat of the automatic transmission 20.

The on-off clutch control unit 94 controls the on-off state of the on-off clutch K0 during engine start control. For example, when a request is made to start the engine 12, the on-off clutch control unit 94 controls the on-off clutch K0 from disengagement to slip engagement and then fully engaged in order to transmit to the engine 12 the cranking torque Tcr [Nm] required to crank the engine 12, which is the torque that increases the engine rotation speed Ne.

The transmission control unit 96 determines whether to shift the automatic transmission 20 using, for example, a shift map, and outputs a CB hydraulic control signal Scb to the hydraulic control circuit 56 to execute shift control as necessary. The shift map is a predetermined relationship on a two-dimensional coordinate system with, for example, vehicle speed V and required drive torque Trdem as variables, and has shift lines for determining whether to shift the automatic transmission 20. The shift map may use, for example, the AT output rotation speed No instead of vehicle speed V, or the required amount of AT output torque To [Nm], accelerator opening θacc, or throttle valve opening θth [%], which is the opening of the electronic throttle valve, instead of required drive torque Trdem.

The rotational speed control unit 98 functionally comprises a torque determination unit 98a, a starting clutch control unit 98b, a start determination unit 98c, and a differential rotation control unit 98d.

The torque determination unit 98a determines whether the WSC input torque Twsc [Nm], which is the torque input from the electric motor MG to the starting clutch WSC during BEV driving, is less than the torque value Twsc_jdgx (>0). The torque value Twsc_jdgx is a determination value that is determined in advance experimentally or by design in order to suppress a decrease in the power generation efficiency of the electric motor MG due to regenerative braking. Note that the WSC input torque Twsc corresponds to the "input torque" in this invention. The torque value Twsc_jdgx corresponds to the "predetermined second torque value" in this invention.

The torque determination unit 98a determines whether the WSC input torque Twsc exceeds the torque value Twsc_jdgy. The torque value Twsc_jdgy is a determination value set to be equal to or greater than the torque value Twsc_jdgx, which is predetermined experimentally or by design. Preferably, the torque value Twsc_jdgy is set higher than the torque value Twsc_jdgx so that the start and end of the rotation speed control described below is not frequently repeated. The torque value Twsc_jdgy corresponds to the "predetermined first torque value" in this invention.

When the torque determination unit 98a determines that the WSC input torque Twsc exceeds the torque value Twsc_jdgy during BEV driving, the starting clutch control unit 98b initiates torque capacity control to equalize the torque capacity command value Tc_tgt [Nm], which is the command value for the torque capacity Tc [Nm] of the starting clutch WSC, with the WSC input torque Twsc. The torque capacity command value Tc_tgt corresponds to the "command value" in this invention. The "WSC input torque Twsc" for which the torque capacity command value Tc_tgt is equalized corresponds to "corresponding to the input torque" in this invention. "Coresponding to the input torque" refers to the torque capacity command value Tc_tgt that can transmit the input WSC input torque Twsc to the drive wheels 14 at approximately the same magnitude, i.e., a value close to the torque capacity command value Tc_tgt at which the starting clutch WSC switches from full engagement to slip engagement.

After the starting clutch control unit 98b starts torque capacity control, the start determination unit 98c determines whether the start conditions for rotational speed control are met. The conditions for starting the rotational speed control are that either of the following is true: (a) the differential rotation ΔN (=Nmg-Ni) obtained by subtracting the AT input rotational speed Ni, which is the rotational speed of the drive wheel 14 side of the starting clutch WSC, from the MG rotational speed Nmg, is equal to or greater than a predetermined judgment differential rotation value ΔN_jdg (>0); or (b) the torque difference ΔT (=Tc_real-Twsc) between the torque capacity actual value Tc_real, which is the actual value of the torque capacity Tc of the starting clutch WSC, is within a predetermined torque range ΔT_jdg, the change (rate of change) α [Nm/sec] of the command value To_tgt (dynamic) of the AT output torque To [Nm] is a positive value, and it is estimated that the command value To_tgt (dynamic) will continue to increase in the future. The predetermined determination rotational difference value ΔN_jdg is a value determined experimentally or by design, for example, a positive value near zero, to determine whether the starting clutch WSC is actually in slip engagement. The actual torque capacity value Tc_real can be estimated, for example, by detecting the oil pressure supplied to an actuator that controls the engagement and disengagement of the starting clutch WSC using a sensor (not shown). The predetermined torque range ΔT_jdg is a determination value determined experimentally or by design, within which shock caused by an increase in drive torque transmitted from the electric motor MG to the drive wheels 14 remains within an acceptable range even when rotational speed control is initiated. The command value To_tgt (dynamic) will be described later.

If the start determination unit 98c determines that the start conditions for rotational speed control are met, the differential rotation control unit 98d initiates rotational speed control by feedback-controlling the MG rotational speed Nmg so that the differential rotation ΔN becomes equal to a predetermined target differential rotation value ΔN_tgt. The target differential rotation value ΔN_tgt is a target value for the differential rotation ΔN and is a predetermined value determined experimentally or by design. Figure 2 illustrates an example of the relationship between the WSC input torque Twsc and the target differential rotation value ΔN_tgt in rotational speed control. In rotational speed control, for example, as shown in Figure 2, when the WSC input torque Twsc exceeds the torque value Twsc_jdgx, the target differential rotation value ΔN_tgt is increased as the WSC input torque Twsc increases and gradually saturated at a constant value. Furthermore, when the WSC input torque Twsc is equal to or less than the torque value Twsc_jdgx, the target differential rotation value ΔN_tgt is set to zero. Therefore, the target MG rotation speed Nmg_tgt [rpm], which is the target value of the MG rotation speed Nmg during rotation speed control, is the sum of the AT input rotation speed Ni and the target differential rotation value ΔN_tgt.

Returning to Figure 1, if the torque determination unit 98a determines that the WSC input torque Twsc is less than the torque value Twsc_jdgx during BEV driving, the differential rotation control unit 98d terminates rotational speed control, and then the starting clutch control unit 98b controls the torque capacity command value Tc_tgt to be higher than the WSC input torque Twsc so that the starting clutch WSC is fully engaged.

Once rotation speed control is initiated by the differential rotation control unit 98d, execution of rotation speed control continues until the torque determination unit 98a determines that the WSC input torque Twsc is less than the torque value Twsc_jdgx during BEV driving.

When a request to start the engine 12 is made during BEV driving, the power source control unit 92 and the on-off clutch control unit 94 crank the engine 12 using the electric motor MG and the on-off clutch K0. During this cranking, in accordance with the on-off clutch control unit 94 switching the control state of the on-off clutch K0 from disengagement to full engagement, the power source control unit 92 controls the electric motor MG to output cranking torque Tcr until cranking is completed. In other words, the electric motor MG outputs MG torque Tmg, which is the WSC input torque Twsc that generates the required drive torque Trdem plus the cranking torque Tcr.

Figure 3 is an example of a flowchart illustrating the main control operations of the electronic control unit 90 shown in Figure 1. The flowchart in Figure 3 is executed repeatedly while the BEV is running.

First, in step S10 (hereinafter, "step" will be omitted), which corresponds to the function of the torque determination unit 98a, it is determined whether the WSC input torque Twsc is less than the torque value Twsc_jdgx. If the determination in S10 is positive, the rotational speed control is terminated in S20, which corresponds to the function of the differential rotation control unit 98d, and the torque capacity control is terminated in S30, which corresponds to the function of the starting clutch control unit 98b, and the process then returns.

If the determination in S10 is negative, S40, which corresponds to the function of the torque determination unit 98a, determines whether the WSC input torque Twsc exceeds the torque value Twsc_jdgy. If the determination in S40 is positive, S50, which corresponds to the function of the starting clutch control unit 98b, begins torque capacity control. S60, which corresponds to the function of the start determination unit 98c, determines whether the differential rotation speed ΔN is equal to or greater than a predetermined determination differential rotation speed value ΔN_jdg. If the determination in S60 is negative, S70, which corresponds to the function of the start determination unit 98c, determines whether the torque difference ΔT is within a predetermined torque range ΔT_jdg, the change amount α in the command value To_tgt (dynamic) is positive, and the command value To_tgt (dynamic) is estimated to continue to increase. If the determination in either S60 or S70 is positive, rotational speed control is initiated in S80, which corresponds to the function of the differential rotation speed control unit 98d, and the process returns. If the determination in either S40 or S70 is negative, the process returns.

Figure 4 is an example of a time chart when rotation speed control is performed in the flowchart of Figure 3. Figure 4 shows an example in which S80 is performed when the determination in S60 or S70 in Figure 3 is positive. For convenience, Figure 4 shows a case in which the determinations in both S60 and S70 are positive.

When the AT output torque To is changed, a sudden change in the driving force of the vehicle 10 may cause torsional vibrations in the power transmission path PT, so a change-slowing process (also called a smoothing process) is performed. The command value To_tgt (static) for the AT output torque To shown in Figure 4 is the target value for the AT output torque To calculated based on the current vehicle speed V and accelerator opening θacc, and the command value To_tgt (dynamic) for the AT output torque To is the command value To_tgt (static) that has been subjected to change-slowing process.

MG torque Tmg, which is equivalent to WSC input torque Twsc during BEV driving, is controlled based on command value To_tgt (dynamic). From the perspective of the drive demand of vehicle 10 during BEV driving, command value To_tgt (dynamic) is the same as required WSC input torque Twscrq, which is the required value (target value) of WSC input torque Twsc. Because command value To_tgt (dynamic) changes with a delay from command value To_tgt (static), it is possible to estimate not only the current change amount α in command value To_tgt (dynamic), but also the future change amount α in command value To_tgt (dynamic). Therefore, it is possible to estimate that MG torque Tmg during BEV driving, i.e., WSC input torque Twsc, is currently increasing and will continue to increase. Furthermore, because the control of the electrically controlled electric motor MG has good responsiveness, there is little difference between WSC input torque Twsc and required WSC input torque Twscrq.

At time t1, the determination in S40 is affirmative, and execution of S50 begins. That is, because the required WSC input torque Twscrq exceeds the torque value Twsc_jdgy, the torque capacity command value Tc_tgt is reduced from the capacity value Tc1 that fully engages the starting clutch WSC to a capacity value Tc2 equal to the WSC input torque Twsc. Note that the capacity value Tc2 corresponds to "corresponding to the input torque" in this invention. Figure 4 shows a case where the torque capacity command value Tc_tgt is on the higher side of the range of control variation in the torque capacity Tc of the starting clutch WSC. This control variation in the torque capacity Tc of the starting clutch WSC arises due to variation in components such as the friction plates in the starting clutch WSC and variation in the controllability of the actuator that controls the engagement and disengagement of the starting clutch WSC. Because the starting clutch WSC is hydraulically controlled to engage and disengage, the actual torque capacity value Tc_real changes with a delay following changes in the torque capacity command value Tc_tgt. Meanwhile, the required WSC input torque Twscrq is controlled by the MG torque Tmg of the electric motor MG, resulting in higher responsiveness than hydraulic control. That is, while a difference between the actual torque capacity value Tc_real and the torque capacity command value Tc_tgt is likely to occur due to the relatively low responsiveness, a difference between the actual value and the command value of the MG torque Tmg is unlikely to occur due to the relatively high responsiveness. Note that, even if torque capacity control is initiated after time t1 and until time t2 (described below), due to the aforementioned control variability, it is unclear whether the starting clutch WSC will slip. For example, as shown in FIG. 4, if the torque capacity command value Tc_tgt is on the high side of the range of control variability, the starting clutch WSC may not slip.

At time t2 (> t1), (a) for example, if the differential rotation speed ΔN is equal to or greater than a predetermined reference differential rotation speed value ΔN_jdg, rotational speed control is initiated. Alternatively, at time t2, (b) for example, if the torque difference ΔT is within a predetermined torque range ΔT_jdg, the change amount α is positive, and it is estimated that the command value To_tgt (dynamic) will continue to increase, rotational speed control is initiated. Note that (b) is the case when it is estimated that the increase in the WSC input torque Twsc corresponding to the future increase in the command value To_tgt (dynamic) due to the change amount α at time t2 will exceed the range of control variation of the starting clutch WSC, resulting in slip engagement of the starting clutch WSC. For example, if the required WSC input torque Twscrq increases due to an increase in the accelerator opening θacc, the required WSC input torque Twscrq increases faster than the actual torque capacity value Tc_real due to the difference in responsiveness described above. This causes the starting clutch WSC to be slip engaged.

If the torque capacity command value Tc_tgt is on the higher side of the range of control variation and the starting clutch WSC is not in slip engagement, when rotational speed control is executed, the starting clutch WSC is put into slip engagement, which increases the MG torque Tmg and causes a sudden increase in driving force by the amount of the control variation. This may cause a shock that the driver may feel uncomfortable. Furthermore, depending on the feedback gain of the rotational speed control, a sudden increase in the MG torque Tmg may cause a shock that the driver may feel uncomfortable.

Figure 5 is a time chart illustrating the occurrence of engine 12 starting shock, comparing (a) the case where torque capacity control begins after a start request for the engine 12 ("without torque capacity control" in Figure 5) with (b) the case where torque capacity control begins before a start request for the engine 12 ("with torque capacity control" in Figure 5). In Figure 5, the case (a) above is a comparative example, and the case (b) above is this embodiment. Note that the MG torque Tmg shown in Figure 5 represents the WSC input torque Twsc that generates the required drive torque Trdem and the torque required for rotational speed control, and the cranking torque Tcr component is not shown.

At time t11, a request is made to start the engine 12 while the BEV is running.

In the comparative example, at time t11, the starting clutch WSC is fully engaged. Therefore, in order to suppress starting shock, after a request to start the engine 12 is made, the torque capacity command value Tc_tgt is reduced to the WSC input torque Twsc, and from the time when it is estimated that the actual torque capacity value Tc_real has reduced to the WSC input torque Twsc (see time t12), the MG torque Tmg is increased and rotational speed control is initiated. Then, after the starting clutch WSC is engaged in slipping, engine start control is initiated.

In this embodiment, at time t11, either (b1) the starting clutch WSC is in slip engagement and rotational speed control is being performed, or (b2) the starting clutch WSC is fully engaged but the actual torque capacity value Tc_real is low enough that it is prone to slip engagement.

In the case of (b1) of this embodiment, although not shown in Figure 5, even if engine start control is initiated immediately from time t11, the starting clutch WSC is already in slip engagement, which allows for both suppression of start-up shock and drivability compared to cases where this is not the case.

In the case of (b2) of this embodiment, as shown in FIG. 5, the MG torque Tmg is increased immediately at time t11 to start rotational speed control. Then, after the starting clutch WSC is slipped, engine start control is started. In the case of (b2) of this embodiment, torque capacity control is already performed at time t11. Therefore, if the period from when the start of the engine 12 is requested to be started to the completion of engine start control is the same, the period during which the starting clutch WSC is slipped can be set longer by rotational speed control than in the comparative example. Therefore, compared to the comparative example, the MG rotational speed Nmg can be increased more gradually in rotational speed control, and the torque increase amount by feedback control in rotational speed control, for example, the P term of PID control, can also be increased more gradually. Therefore, the change in vehicle acceleration Acc [m/sec ² ], which is the acceleration in the forward/rearward direction of the vehicle 10, can also be made more gradual, thereby suppressing start-up shock.

According to this embodiment, torque capacity control is initiated during BEV driving before engine 12 start-up is requested, and rotational speed control is initiated in at least one of the following cases: (a) the differential rotation speed ΔN is equal to or greater than a predetermined reference differential rotation speed value ΔN_jdg; and (b) the torque difference ΔT is within a predetermined torque range ΔT_jdg, the change amount α in the command value To_tgt (dynamic) is positive, and it is estimated that the WSC input torque Twsc will continue to increase. In (a), the starting clutch WSC is in slip engagement, so even if rotational speed control is initiated, the drive torque transmitted from the electric motor MG to the drive wheels 14 will not increase abruptly. In (b), the starting clutch WSC is currently and will continue to increase, i.e., the starting clutch WSC will immediately enter slip engagement due to an increase in the WSC input torque Twsc. Therefore, even if rotational speed control is initiated, the drive torque transmitted from the electric motor MG to the drive wheels 14 will not increase abruptly. When engine 12 start-up is requested and engine start-up control is executed after rotational speed control has begun, the starting clutch WSC is already in slip engagement. This allows engine start-up control to begin more quickly than otherwise, thereby achieving both suppression of start-up shock and drivability. Furthermore, even when engine 12 start-up is requested and engine start-up control is executed before rotational speed control begins, the torque capacity command value Tc_tgt is already set according to the WSC input torque Twsc. This allows the starting clutch WSC to be slip-engaged more quickly than otherwise to begin engine start-up control, thereby achieving both suppression of start-up shock and drivability.

According to this embodiment, if the WSC input torque Twsc exceeds the torque value Twsc_jdgy before a request to start the engine 12 occurs during BEV driving, torque capacity control is initiated. If the WSC input torque Twsc is less than the torque value Twsc_jdgx, torque capacity control is terminated and the torque capacity command value Tc_tgt is controlled so that the starting clutch WSC is fully engaged. This prevents a decrease in the power generation efficiency of the electric motor MG due to regenerative braking and suppresses the occurrence of startup shock when the engine 12 is started. Furthermore, the difference between the torque values Twsc_jdgy and Twsc_jdgx prevents the start and end of rotational speed control from being frequently repeated.

The above describes in detail an embodiment of the present invention based on the drawings, but the present invention can also be applied in other aspects.

In the above-described embodiment, torque capacity control is initiated when the WSC input torque Twsc exceeds the torque value Twsc_jdgy, and terminated when the WSC input torque Twsc is less than the torque value Twsc_jdgx. However, for example, the torque values Twsc_jdgy and Twsc_jdgx may be the same value. Even in this embodiment, there is a risk that the start and end of rotation speed control may be frequently repeated, but otherwise the same effects as the above-described embodiment are achieved. Furthermore, for example, torque capacity control may be initiated regardless of the value of the WSC input torque Twsc. Even in this embodiment, there is a risk that the decrease in power generation efficiency of the electric motor MG due to regenerative braking may not be suppressed, but otherwise the same effects as the above-described embodiment are achieved.

In the above-described embodiment, the starting clutch WSC was the "second clutch," but, for example, the starting clutch WSC may be replaced by an engagement device CB that mechanically connects and disconnects the power transmission path PT within the automatic transmission 20. Also, the starting clutch WSC may be replaced by a fluid-type transmission device such as a torque converter or fluid coupling, and an engagement device (for example, a lock-up clutch) that mechanically connects and disconnects the power transmission path PT within that fluid-type transmission device may be provided.

The above is merely an example of the present invention, 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, without departing from the spirit of the invention.

10: Vehicle, 12: Engine, 14: Drive Wheels, 90: Electronic Control Unit (Control Unit), K0: Disconnection Clutch (First Clutch), MG: Electric Motor, Ni: AT Input Rotational Speed (Drive Wheel Rotational Speed), Nmg: MG Rotational Speed (Motor Rotational Speed), PT: Power Transmission Path, Tc: Torque Capacity (Second Clutch Torque Capacity), Tc_tgt: Torque Capacity Command Value (Command Value), Tc_real: Torque Capacity Actual Value (Actual Value), Tmg: MG Torque (Motor Output Torque), Twsc: WSC Input Torque (Input Torque), Twsc_jdgx: Torque Value (Predetermined Second Torque Value), Twsc_jdgy: Torque Value (Predetermined First Torque Value), WSC: Starting Clutch (Second Clutch), ΔN: Differential Rotation, ΔN_jdg: Determining Differential Rotation Value, ΔN_tgt: Target Differential Rotation Value, ΔT: Torque Difference, ΔT_jdg: Predetermined Torque Range

Claims (2)

A control device for a vehicle including an engine and an electric motor as a power source, a first clutch that connects and disconnects power transmission between the engine and the electric motor, and a second clutch that mechanically connects and disconnects a power transmission path between the power source and a drive wheel,
a torque capacity control is started to set a command value of the torque capacity of the second clutch according to the input torque input from the electric motor before a start of the engine is requested during the BEV traveling in which the first clutch is released and the second clutch is fully engaged and power is output only from the electric motor;
After the torque capacity control is started, in at least one of the cases where a differential rotation speed obtained by subtracting the rotation speed of the drive wheel side from the rotation speed of the electric motor side in the second clutch is equal to or greater than a predetermined judgment differential rotation value, and where a torque difference between the actual value of the torque capacity of the second clutch and the input torque is within a predetermined torque range and the input torque has increased and is estimated to continue to increase, a rotation speed control is started to control the rotation speed of the electric motor so that the differential rotation speed in the second clutch becomes a predetermined target differential rotation value,
a control device for a vehicle, wherein, when a start of the engine is requested, the first clutch is switched from released to fully engaged and an output torque of the electric motor is increased to start the engine. 2. The vehicle control device according to claim 1, wherein, when the input torque exceeds a predetermined first torque value before a request to start the engine is made during BEV traveling, the torque capacity control is started, and when the input torque is less than a predetermined second torque value that is lower than the first torque value, the torque capacity control is ended and a command value of the torque capacity of the second clutch is controlled so that the second clutch is fully engaged.