Vehicle control device

Abstract

To suppress tip-in shock and deterioration of acceleration response when starting an engine.SOLUTION: When a power transmission state in a power transmission path is switched from a driven state to a driving state at the start of an engine, a target slip amount is changed from a driven-time target value to a driving-time target value at a predetermined gentle inclination, so that it is possible to perform backlash elimination in a manner to suppress a tip-in shock, and a second clutch is not intentionally brought into an engaged state, so that it is not necessary to delay the start of the engine. Therefore, when the engine is started, the tip-in shock can be suppressed and the deterioration of the acceleration response can be suppressed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle that has a clutch between an engine and an electric motor and between the engine and the drive wheels. [Background technology]

[0002] A well-known control device for a vehicle includes an engine, an electric motor connected to a power transmission path between the engine and drive wheels so as to transmit power, a first clutch provided in the power transmission path between the engine and the electric motor, and a second clutch provided in the power transmission path between the electric motor and the drive wheels. For example, Patent Document 1 discloses a control device for a hybrid vehicle. Patent Document 1 discloses that, when an engine start request is an increase in a driving force request and the slip polarity of the second clutch is negative, the start of engine cranking is delayed until the slip polarity becomes positive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5488712 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when the accelerator is depressed, a so-called tip-in occurs, in which the power transmission state in the power transmission path between the engine and the drive wheels is switched from a driven state to a driving state. Because the tip-in reverses the direction of backlash elimination, if backlash elimination occurs suddenly, a so-called tip-in shock, which is a backlash elimination shock caused by gear strike, may occur. To address this tip-in shock, one possible approach is to temporarily engage the second clutch to limit the rate of change of the torque of the electric motor, which provides the drive torque. However, if the second clutch is temporarily engaged to eliminate backlash and enter a slip state before starting engine start control, this may result in a delay in acceleration response, i.e., a deterioration in acceleration response.

[0005] The present invention was made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can suppress tip-in shock and suppress deterioration of acceleration response when starting the engine. [Means for solving the problem]

[0006] The gist of a first aspect of the present invention is a control device for a vehicle including: (a) an engine; an electric motor connected to a power transmission path between the engine and drive wheels so as to be able to transmit power; a first clutch provided in the power transmission path between the engine and the electric motor; and a second clutch provided in the power transmission path between the electric motor and the drive wheels, (b) a control device for a vehicle including: a control device for controlling a switching from a motor running mode in which the vehicle runs using only the electric motor as a power source when the first clutch is released to an engine running mode in which the vehicle runs using at least the engine as a power source when the first clutch is engaged; This control is executed in a state where slip control is being performed to place the second clutch in a slip state by controlling the output of the electric motor so that the slip amount, which is the rotational speed difference between the input rotational speed and the output rotational speed, becomes a predetermined target slip amount, and (c) when the power transmission state in the power transmission path switches from a driven state to a driving state when starting the engine in conjunction with the switch to engine running, the control changes the target slip amount at a predetermined gentle slope from a predetermined driven target value in the driven state to a predetermined driving target value in the driving state which is opposite in sign to the driven target value. (d) during the transient period in which the target slip amount is being changed at the gradual gradient, when backlash elimination between the meshing gears provided in the power transmission path between the second clutch and the drive wheels is completed, the target slip amount is changed to the driving target value at a gradient steeper than the gradual gradient; (e) during the transient period in which the target slip amount is being changed at the gradual gradient, the target value of the input torque to the second clutch, which is a wet friction engagement device, is set to a predetermined value close to zero that is equal to or greater than the torque that realizes the driving state and is less than the torque capacity of the second clutch when controlling the second clutch to be in a packing completion state in which pack clearance is reduced, and the second clutch is controlled so as not to produce the torque capacity when the packing completion state is achieved; (f) during the transient period in which the target slip amount is being changed at the gradual gradient, when the input rotational speed of the second clutch becomes higher than the output rotational speed of the second clutch by more than a predetermined rotational speed, it is determined that backlash elimination is completed. The reason is that [Effects of the Invention]

[0007] According to the first aspect of the present invention, when the power transmission state in the power transmission path switches from the driven state to the driving state during engine start, the target slip amount is changed at a predetermined gentle slope from the driven state target value to the driving state target value, so that backlash can be eliminated to suppress tip-in shock, and because the second clutch is not intentionally brought into engagement, there is no need to delay the start of the engine. Therefore, when starting the engine, tip-in shock can be suppressed and deterioration of acceleration response can be suppressed. In addition, when backlash elimination is completed during a transition in which the target slip amount is being changed at a predetermined gentle gradient, the target slip amount is changed to the driving target value at a steep gradient, so that the target slip amount is quickly made to become the driving target value. Furthermore, during the transient period in which the target slip amount is changed at a predetermined gentle slope, the target value of the input torque to the second clutch is set to a predetermined value close to zero, and the second clutch is controlled so as not to produce the torque capacity required for completing packing, so that backlash is eliminated by dragging the second clutch rather than intentionally engaging the second clutch. Also, if the input rotational speed of the second clutch becomes higher than the output rotational speed of the second clutch by more than a predetermined rotational speed during the transient period in which the target slip amount is changed at a predetermined gentle slope, it is determined that backlash elimination is complete, so that completion of backlash elimination is appropriately determined. [Brief explanation of the drawings]

[0008] [Figure 1] 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 and control systems for various controls in the vehicle. [Figure 2] FIG. 4 is a diagram showing an example of a PT characteristic of a starting clutch. [Figure 3] 10A and 10B are diagrams illustrating an example of eliminating backlash between meshing gears. [Figure 4] 1 is a flowchart illustrating a main part of the control operation of the electronic control device, and is a flowchart illustrating the control operation for suppressing tip-in shock and suppressing deterioration of acceleration response when starting the engine. [Figure 5] 5 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 4 is executed. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0010] Fig. 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied, as well as a diagram illustrating the main parts of the control functions and control systems for various controls in the vehicle 10. In Fig. 1, the vehicle 10 is a hybrid vehicle equipped with an engine 12 and an electric motor MG, which function as power sources. The vehicle 10 also has drive wheels 14 and a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14.

[0011] The engine 12 is a known internal combustion engine. An engine control device 50 provided in the vehicle 10 is controlled by an electronic control device 90 (described later), whereby the engine torque Te of the engine 12 is controlled.

[0012] The electric motor MG is a known rotating electric machine, a so-called motor generator, that functions as a motor that generates mechanical power from electric power and as a generator that generates electric power from mechanical power. The electric motor MG is connected to a battery 54 provided in the vehicle 10 via an inverter 52 provided in the vehicle 10. The inverter 52 is controlled by an electronic control device 90 (described later), thereby controlling the MG torque Tm of the electric motor MG. When no particular distinction is made, the term "power" also refers to driving force, torque, and force.

[0013] The power transmission device 16 is provided with a case 18, which is a non-rotating member attached to the vehicle body, and includes a make-and-break clutch K0, a starting clutch WSC, an automatic transmission 20, a reduction gear mechanism 22, a differential gear 24 connected to the reduction gear mechanism 22, etc. The make-and-break clutch K0 is a first clutch provided between the engine 12 and the electric motor MG in the power transmission path between the engine 12 and the drive wheels 14. The starting clutch WSC is a second clutch provided between the electric motor MG and the drive wheels 14 in the power transmission path between the engine 12 and the drive wheels 14. The reduction gear mechanism 22 is connected to a transmission output gear 26, which is an output rotating member of the automatic transmission 20.

[0014] The power transmission device 16 also includes a pair of drive shafts 28 connected to the differential gear 24. Inside the case 18, the power transmission device 16 also includes an engine connecting shaft 30 that connects the engine 12 to the on-off clutch K0, an electric motor connecting shaft 32 that connects the on-off clutch K0 to the starting clutch WSC, a mechanical oil pump 34, a transmission member 36 that connects the electric motor connecting shaft 32 to the mechanical oil pump 34, and the like.

[0015] The electric motor MG is connected to an electric motor connecting shaft 32 in the case 18, that is, to a power transmission path between the engine 12 and the drive wheels 14 so as to be capable of transmitting power.

[0016] The on-off clutch K0 is, for example, a known friction engagement device. The on-off clutch K0 switches between operating states, i.e., control states, such as an engaged state, a slip state, and a released state by changing a torque capacity Tk0 of the on-off clutch K0 using a regulated K0 oil pressure PRk0 supplied from a hydraulic control circuit 56 provided in the vehicle 10.

[0017] The starting clutch WSC is a wet friction engagement device constituted by, for example, a multi-plate clutch pressed by a hydraulic actuator. The control state of the starting clutch WSC is switched by changing the WSC torque capacity Twsc of the starting clutch WSC using the regulated WSC oil pressure PRwsc supplied from the hydraulic control circuit 56.

[0018] The input side member of the starting clutch WSC is integrally connected to the electric motor connecting shaft 32. The output side member of the starting clutch WSC is integrally connected to the transmission input shaft 38, which is the input rotational member of the automatic transmission 20. The hydraulic actuator provided in the starting clutch WSC is composed of a piston, a return spring, an oil chamber, etc. When the WSC oil pressure PRwsc is supplied to the oil chamber, the piston moves toward the multiple friction plates of the starting clutch WSC against the biasing force of the return spring, and the WSC torque capacity Twsc is changed by the WSC oil pressure PRwsc, thereby switching the control state. When the oil chamber of the starting clutch WSC is filled with hydraulic oil OIL and the pressing force of the piston reduces the clearance between the multiple friction plates, i.e., the pack clearance of the starting clutch WSC is reduced, the starting clutch WSC is in a so-called fully packed state. The WSC oil pressure PRwsc for achieving the packing completion state is the WSC oil pressure PRwsc for causing the piston to reach the stroke end without generating the WSC torque capacity Twsc, i.e., the pack stroke end (=PSE) pressure PRpse. In this embodiment, the WSC torque capacity Twsc at the PSE pressure PRpse is referred to as the PSE torque Tpse. The PSE torque Tpse is the WSC torque capacity Twsc when the starting clutch WSC is controlled to achieve the packing completion state.

[0019] Figure 2 is a diagram showing an example of the PT characteristic, which is the relationship between the WSC oil pressure PRwsc and the WSC torque capacity Twsc in the starting clutch WSC. In Figure 2, when the WSC oil pressure PRwsc is equal to or greater than the PSE pressure PRpse, the WSC torque capacity Twsc increases in proportion to the WSC oil pressure PRwsc. Furthermore, because the starting clutch WSC is a wet friction engagement device, in the stroke-back region where the WSC oil pressure PRwsc is equal to or less than the PSE pressure PRpse, a WSC torque capacity Twsc corresponding to the drag loss, or drag torque, is generated between the multiple friction plates.

[0020] 1 , the automatic transmission 20 is a known planetary gear type automatic transmission that includes, for example, a planetary gear device and an engagement device CB. The engagement device CB includes, for example, a plurality of known friction engagement devices. The control state of each of the engagement devices CB is switched by changing the CB torque capacity Tcb, which is the torque capacity of each of the engagement devices CB, using the regulated CB oil pressure PRcb supplied from the oil pressure control circuit 56.

[0021] The hydraulic oil OIL discharged by at least one of the mechanical oil pump 34 driven by the power source (engine 12, electric motor MG) and the electric oil pump 58 driven by the pump motor 60 provided in the vehicle 10 is supplied to the hydraulic control circuit 56.

[0022] The vehicle 10 is equipped with an electronic control device 90 that includes a control device for the vehicle 10. The electronic control device 90 is configured to include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc., and executes various controls of the vehicle 10.

[0023] The electronic control device 90 is supplied with various detection signals from various sensors 70, 72, 74, 76, 78, 80, 82, 84, 86, etc. provided on the vehicle 10 (for example, engine rotation speed Ne, which is the rotation speed of the engine 12; MG rotation speed Nm, 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; input rotation speed Ni, which is the rotation speed of the transmission input shaft 38 and also the rotation speed of the output side member of the starting clutch WSC; output rotation speed No, which is the rotation speed of the transmission output gear 26 corresponding to the vehicle speed V; accelerator opening θacc; throttle valve opening θth; brake signal Bon; battery temperature THbat; battery charge / discharge current Ibat; battery voltage Vbat; hydraulic oil temperature THoil, which is the temperature of the hydraulic oil OIL, etc.).

[0024] The electronic control device 90 outputs various command signals (e.g., engine control command signal Se, MG control command signal Sm, CB hydraulic control command signal Sbc, K0 hydraulic control command signal Sk0, WSC hydraulic control command signal Swsc, electric oil pump control command signal Seop, etc.) to each of the devices 50, 52, 56, 60, etc. provided in the vehicle 10.

[0025] The electronic control unit 90 includes a power source control means, i.e., a power source control section 92, and a clutch control means, i.e., a clutch control section 94, in order to realize various controls in the vehicle 10.

[0026] 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 executes hybrid drive control by the engine 12 and the electric motor MG using these control functions.

[0027] The power source control unit 92 calculates the amount of driving demanded by the driver for the vehicle 10, for example, by applying the accelerator opening θacc and the vehicle speed V to a driving demand map. The driving demand map is a relationship for calculating the driving demand that is determined experimentally or by design and stored in advance, i.e., a predetermined relationship. The driving demand is, for example, a required driving torque Trdem [Nm] or a required driving force Frdem [N] at the drive wheels 14. The required driving torque Trdem can be viewed as a required driving power Prdem [W] at the current vehicle speed V. The power source control unit 92 outputs an engine control command signal Se for controlling the engine 12 and an MG control command signal Sm for controlling the electric motor MG so as to realize the required driving power Prdem, taking into account transmission loss, auxiliary load, the gear ratio of the automatic transmission 20, and the like.

[0028] When the required driving power Prdem can be met solely with the output of the electric motor MG, the power source control unit 92 sets the driving mode for driving the vehicle 10 to BEV driving mode. The BEV driving mode is a motor driving mode that enables motor driving (=BEV driving) using only the electric motor MG as a driving source when the on-off clutch K0 is disengaged. On the other hand, when the required driving power Prdem cannot be met without using at least the output of the engine 12, the power source control unit 92 sets the driving mode to engine driving mode, i.e., HEV driving mode. The HEV driving mode is a hybrid driving mode that enables engine driving (=HEV driving) using at least the engine 12 as a driving source when the on-off clutch K0 is engaged. On the other hand, even when the required driving power Prdem can be met solely with the output of the electric motor MG, the power source control unit 92 establishes the HEV driving mode when, for example, the battery 54 needs to be charged or the engine 12 needs to be warmed up.

[0029] The power source control unit 92 determines whether there is an engine start request to switch the control state of the engine 12 from a stopped state to an operating state. For example, the power source control unit 92 determines whether there is an engine start request based on whether, in the BEV drive mode, the required drive power Prdem has increased beyond a range that can be covered by the output of the electric motor MG alone, whether the engine 12 and the like need to be warmed up, or whether the battery 54 needs to be charged. Alternatively, in the BEV drive mode, the power source control unit 92 determines whether there is an engine start request based on whether, in the BEV drive mode, the known shift position has been switched from the automatic transmission position "D" to a manual transmission position "M" or the like, or whether the known driving mode has been switched from an eco mode or a normal mode to a sport mode or the like.

[0030] When the power source control unit 92 determines that there is an engine start request, the clutch control unit 94 controls the make-and-break clutch K0 to execute start control of the engine 12. For example, the clutch control unit 94 outputs a K0 hydraulic control command signal Sk0 to control the make-and-break clutch K0 from a released state toward an engaged state so as to obtain a K0 torque capacity Tk0 for transmitting the cranking torque Tcr to the engine 12. The cranking torque Tcr is a predetermined torque required for cranking the engine 12 to increase the engine rotation speed Ne.

[0031] When it is determined that there is an engine start request, the power source control unit 92 controls the engine 12 and the electric motor MG to execute start control of the engine 12. For example, the power source control unit 92 outputs an MG control command signal Sm for causing the electric motor MG to output cranking torque Tcr in conjunction with the switching of the on-off clutch K0 to the engaged state by the clutch control unit 94. Furthermore, the power source control unit 92 outputs an engine control command signal Se for starting fuel supply, engine ignition, and the like in conjunction with the cranking of the engine 12.

[0032] Here, the power source control unit 92 switches from BEV driving to HEV driving, i.e., executes start control of the engine 12, while slip control CNslp of the starting clutch WSC is being performed. The slip control CNslp is a control that puts the starting clutch WSC into a slip state. This makes it possible to suppress start shock caused by torque fluctuations that accompany the start control of the engine 12. The start shock is caused by, for example, a control error in the engine torque Te when the connecting / disconnecting clutch K0 is partially engaged, during synchronization, and after synchronization.

[0033] Slip control CNslp is a rotational speed feedback control that controls MG power Pm, which is the output of the electric motor MG, so that the WSC differential rotational speed ΔNw becomes a target differential rotational speed ΔNwt. The WSC differential rotational speed ΔNw is the differential rotational speed of the starting clutch WSC, and is the amount of slip, which is the rotational speed difference between the input rotational speed and the output rotational speed of the starting clutch WSC. The input rotational speed of the starting clutch WSC is equal to the MG rotational speed Nm. The output rotational speed of the starting clutch WSC is equal to the input rotational speed Ni. In other words, the WSC differential rotational speed ΔNw is the rotational speed difference between the MG rotational speed Nm and the input rotational speed Ni. In this embodiment, the value obtained by subtracting the input rotational speed Ni from the MG rotational speed Nm is set to the WSC differential rotational speed ΔNw (=Nm-Ni). The target differential rotational speed ΔNwt is the target value of the WSC differential rotational speed ΔNw, i.e., the target amount of slip. When starting control of the engine 12 is performed, a target differential rotation speed ΔNwt, that is, a predetermined target slip amount, is determined in advance to suppress the start shock.

[0034] During execution of slip control CNslp, the clutch control unit 94 controls the starting clutch WSC so as to obtain a WSC torque capacity Twsc equivalent to the target WSC input torque Tiwt that realizes the required drive torque Trdem. The WSC input torque Tiw is the input torque to the starting clutch WSC. The target WSC input torque Tiwt is a target value of the WSC input torque Tiw obtained by converting the required drive torque Trdem onto the electric motor connecting shaft 32, for example.

[0035] The power source control unit 92 performs slip control CNslp by increasing the MG power Pm that realizes the required drive power Prdem by a predetermined amount. The increase in the MG power Pm is consumed by putting the start clutch WSC into a slip state, but the MG power Pm that realizes the required drive power Prdem is transmitted to the drive wheels 14.

[0036] When executing slip control CNslp, the power source control unit 92 sets, for example, a target MG rotation speed Nmt and controls MG power Pm by feedback control so that the MG rotation speed Nm becomes the target MG rotation speed Nmt. The control of MG power Pm is, for example, control of MG torque Tm at the target MG rotation speed Nmt. The target MG rotation speed Nmt is a target value of the MG rotation speed Nm, and is a value obtained by adding the input rotation speed Ni to the target differential rotation speed ΔNwt (=ΔNwt+Ni).

[0037] Incidentally, tip-in may occur due to an increase in the required drive torque Trdem caused by, for example, accelerator depression. That is, the drive torque Tr may be switched from a negative torque, which puts the vehicle 10 in a driven state, to a positive torque, which puts the vehicle 10 in a driving state. The driving state is a state in which the drive wheels 14 are rotated by the torque output from the power source (engine 12, electric motor MG). The driven state is a state in which the torque input from the drive wheels 14 rotates rotating members and the like of a power transmission device provided in a power transmission path between the engine 12 and the drive wheels 14. The power transmission device includes the automatic transmission 20, the reduction gear mechanism 22, the differential gear 24, the drive shaft 28, and the like.

[0038] FIG. 3 is a diagram illustrating an example of backlash elimination, in which backlash between meshing gears provided between the starting clutch WSC and the drive wheels 14 in the power transmission path between the engine 12 and the drive wheels 14 is eliminated. In FIG. 3, the power source side gear GRa and the drive wheel side gear GRb are meshing gears provided between the starting clutch WSC and the drive wheels 14, such as gears constituting the differential gear 24. The power source side gear GRa is a gear that is closer to the power source (engine 12, electric motor MG) than the drive wheel side gear GRb in the power transmission path between the engine 12 and the drive wheels 14. The dashed line in the power source side gear GRa indicates a state in which backlash elimination has been performed when the vehicle 10 is in a driven state. On the other hand, the solid line in the power source side gear GRa indicates a state in which backlash elimination has been performed when the vehicle 10 is in a driven state. When the power transmission state is switched from a driven state to a driving state, the direction of backlash elimination is reversed. Therefore, if a sudden reduction in backlash occurs, there is a risk of tip-in shock. To prevent such tip-in shock, it is effective to limit the rate of change when the drive torque Tr switches from negative torque to positive torque.

[0039] When the engine 12 is switched from a driven state to a driving state during start-up control, the target differential rotation speed ΔNwt is switched from the driven-state target differential rotation speed ΔNwtn to the driving-state target differential rotation speed ΔNwtp. The driven-state target differential rotation speed ΔNwtn is a negative value, and the driving-state target differential rotation speed ΔNwtp is a positive value whose sign is opposite to that of the driven-state target differential rotation speed ΔNwtn. The driven-state target differential rotation speed ΔNwtn is a predetermined driven-state target value in the driven state that is predetermined as the target differential rotation speed ΔNwt used for start-up control in the driven state. The driving-state target differential rotation speed ΔNwtp is a predetermined driving-state target value in the driving state that is predetermined as the target differential rotation speed ΔNwt used for start-up control in the driving state.

[0040] When the power transmission state is switched from a driven state to a driving state during start control of the engine 12, it is possible to temporarily engage the starting clutch WSC to limit the rate of change of the MG torque Tm, which becomes the driving torque Tr. If cranking occurs by the on-off clutch K0 while the starting clutch WSC is temporarily engaged, a start shock may be transmitted to the drive wheels 14. On the other hand, when the starting clutch WSC is temporarily engaged, the starting clutch WSC is changed from an engaged state to a slip state, and the engagement shock or release shock of the starting clutch WSC may be transmitted to the vehicle 10 as fluctuations in acceleration. In response to this, suppressing changes in the WSC oil pressure PRwsc or temporarily engaging the starting clutch WSC to eliminate backlash and then starting control of the engine 12 after the clutch is slipped may result in a deterioration in acceleration response.

[0041] Therefore, when the start control of the engine 12 and tip-in overlap, the power source control unit 92 applies smoothing to the switch from the driven-state target differential rotational speed ΔNwtn to the driving-state target differential rotational speed ΔNwtp. In other words, when starting the engine 12 in conjunction with switching to HEV driving, if the power transmission state in the power transmission path between the engine 12 and the drive wheels 14 switches from a driven state to a driving state, the power source control unit 92 changes the target differential rotational speed ΔNwt from the driven-state target differential rotational speed ΔNwtn to the driving-state target differential rotational speed ΔNwtp at a predetermined gentle slope. The predetermined gentle slope is, for example, a rate of change of the target differential rotational speed ΔNwt that is set in advance to suppress tip-in shock.

[0042] It is desirable that the WSC input torque Tiw be quickly reversed from negative to positive when the required drive torque Trdem switches from negative to positive during execution of slip control CNslp accompanying start control of the engine 12. In other words, it is desirable that the backlash be quickly eliminated when switching from the driven-state target differential rotation speed ΔNwtn to the driving-state target differential rotation speed ΔNwtp.

[0043] Therefore, when the power transmission state switches from the driven state to the driving state while the slip control CNslp is being performed in the driven state, the power source control unit 92 changes the target differential rotation speed ΔNwt at a predetermined gentle slope before changing the target differential rotation speed ΔNwt at the driven state at a slope that is steeper than the gentle slope. The steep slope may be a step-like change or a predetermined steep slope.

[0044] When backlash elimination is completed during a transition in which the target differential rotation speed ΔNwt has a predetermined gentle slope, it is desirable to quickly set the target differential rotation speed ΔNwt to the driving-time target differential rotation speed ΔNwtp.

[0045] Therefore, when the elimination of backlash in the power transmission path between the engine 12 and the drive wheels 14 is completed during a transition in which the target differential rotation speed ΔNwt is being changed at a predetermined gentle gradient, the power source control unit 92 changes the target differential rotation speed ΔNwt to the driving-time target differential rotation speed ΔNwtp at a gradient steeper than the predetermined gentle gradient. The steep gradient may be a step-like change or a predetermined steep gradient.

[0046] In this embodiment, this series of controls, in which the target differential rotation speed ΔNwt is changed to a zero value at a steep gradient, then changed at a predetermined gentle gradient, and then changed at a steep gradient to the driving-time target differential rotation speed ΔNwtp after the backlash elimination is completed, is referred to as backlash elimination control during slip control CNslp. The driving-time target differential rotation speed ΔNwtp is the target differential rotation speed ΔNwt before smoothing, and is a static target differential rotation speed ΔNwt. The target differential rotation speed ΔNwt that is changed to a zero value at a predetermined gentle gradient, and then changed at a steep gradient to the driving-time target differential rotation speed ΔNwtp is the smoothed target differential rotation speed ΔNwt, and is a dynamic target differential rotation speed ΔNwt.

[0047] During the transition when the target differential rotational speed ΔNwt is being changed at a predetermined gentle slope, the starting clutch WSC is not intentionally engaged, but rather the drag of the starting clutch WSC eliminates backlash. For example, if the input rotational speed Ni is in a free-spin state due to backlash between the meshing gears provided between the starting clutch WSC and the drive wheels 14, the power transmission path between the starting clutch WSC and the drive wheels 14 is essentially in a power transmission disabled state, i.e., neutral state. Referring to FIG. 3, the free-spin state of the input rotational speed Ni occurs during the backlash elimination transition when the power source side gear GRa transitions from the dashed line state to the solid line state. When the power transmission path is in the neutral state, the starting clutch WSC synchronizes the input and output rotational speeds by its own drag. The rotational synchronization of the starting clutch WSC is equivalent to the synchronization of the MG rotational speed Nm and the input rotational speed Ni. When the starting clutch WSC is in rotational synchronization due to drag torque, the backlash elimination transition is in progress. When a difference occurs between the MG rotation speed Nm and the input rotation speed Ni during the backlash elimination transition, that is, when a positive WSC differential rotation speed ΔNw occurs, the backlash elimination is completed.

[0048] Therefore, during the transient period in which the target differential rotation speed ΔNwt is changed at a predetermined gentle slope, the power source control unit 92 sets the target WSC input torque Tiwt to a predetermined near-zero value that is equal to or greater than the torque required to achieve the driving state and less than the PSE torque Tpse. At this time, the clutch control unit 94 controls the starting clutch WSC so as not to generate the PSE torque Tpse. The predetermined near-zero value is a predetermined transient target value for eliminating backlash, taking into account, for example, variations, that can achieve the driving state and synchronize the rotation of the starting clutch WSC by dragging it.

[0049] Then, during the transient period in which the target differential rotation speed ΔNwt is being changed at a predetermined gentle slope, if the MG rotation speed Nm becomes higher than the input rotation speed Ni by a predetermined rotation speed Nf, the power source control unit 92 determines that backlash elimination is complete. The predetermined rotation speed Nf is, for example, a predetermined threshold value for determining that the WSC differential rotation speed ΔNw has definitely become a positive value.

[0050] FIG. 4 is a flowchart illustrating the main control operations of the electronic control unit 90, which are for suppressing tip-in shock and suppressing deterioration of acceleration response when starting the engine 12, and which are executed repeatedly, for example, when controlling the start of the engine 12.

[0051] In FIG. 4, each step in the flowchart corresponds to the function of the power source control unit 92 or the clutch control unit 94. In step (hereinafter, "step" is omitted) S10, it is determined whether or not the slip control CNslp is being performed. If the determination in S10 is affirmative, it is determined in S20 whether or not backlash elimination control (see "phases 1 to 3") is being performed during the slip control CNslp. If the determination in S20 is negative, it is determined in S30 whether or not the required drive torque Trdem has switched from negative to positive. If the determination in S10 is negative, or if the determination in S30 is negative, the backlash elimination control is not executed in S40. If the determination in S30 is affirmative, "phase 1" of the backlash elimination control is activated in S50. "phase 1" is a control that changes the dynamic target differential rotational speed ΔNwt from the driven-state target differential rotational speed ΔNwtn to zero at a steep gradient. If the determination in S20 above is positive, then in S60 it is determined whether "phase 3" of the backlash elimination control is in operation. "Phase 3" is control that changes the dynamic target differential rotation speed ΔNwt to the static target differential rotation speed ΔNwt at a steep gradient after backlash elimination is complete. If the determination in S60 above is negative, then in S70 it is determined whether "phase 2" of the backlash elimination control is in operation. "Phase 2" is control that changes the dynamic target differential rotation speed ΔNwt at a predetermined gentle gradient. If the determination in S70 above is negative, then in S80 it is determined whether the dynamic target differential rotation speed ΔNwt has become equal to or greater than zero. If the determination in S80 above is negative, then in S90 the dynamic target differential rotation speed ΔNwt is changed at a steep gradient to zero. If the determination in S70 above is affirmative, then in S100 it is determined whether the MG rotation speed Nm has become higher than the input rotation speed Ni by exceeding a predetermined rotation speed Nf. If the determination in S80 above is affirmative, or if the determination in S100 above is negative, then in S110 "phase 2" is executed. If the determination in S60 above is affirmative, then in S120 it is determined whether the dynamic target differential rotation speed ΔNwt has reached the static target differential rotation speed ΔNwt.If the determination in S100 above is positive, or if the determination in S120 above is negative, "phase 3" is executed in S130. If the determination in S120 above is positive, the backlash elimination control is terminated in S140.

[0052] FIG. 5 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 4 is executed. FIG. 5 illustrates a case where the accelerator pedal is depressed while slip control CNslp is being performed for start control of the engine 12 in the driven state, for example. In FIG. 5, during start control in the driven state, when the WSC input torque Tiw is reduced to the target WSC input torque Tiwt, the slip control CNslp is initiated (see before time t1). When the required drive torque Trdem is switched from negative to positive, "phase 1" of the backlash-eliminating control during the slip control CNslp is initiated (see time t1). The static target WSC input torque Tiwt is a value corresponding to the required drive torque Trdem. The dynamic target WSC input torque Tiwt is a transient target value during the slip control CNslp, and the MG torque Tm is controlled using this target value. The static target MG rotation speed Nmt is a value corresponding to the static target differential rotation speed ΔNwt, and the dynamic target MG rotation speed Nmt is a value corresponding to the dynamic target differential rotation speed ΔNwt. In "phase 1," the dynamic target MG rotation speed Nmt is increased at a steep gradient toward the input rotation speed Ni (see time t1-t2). When the dynamic target MG rotation speed Nmt coincides with the input rotation speed Ni (see time t2), "phase 2" of the backlash elimination control is started, and the dynamic target MG rotation speed Nmt is increased at a gentle gradient (see time t2-t3). When the MG rotation speed Nm becomes higher than the input rotation speed Ni by exceeding a predetermined rotation speed Nf during the backlash elimination transition in "phase 2," it is determined that the backlash elimination is completed (see time t3). When it is determined that the backlash elimination is completed, "phase 3" of the backlash elimination control is started, and the dynamic target MG rotation speed Nmt is increased at a steep gradient toward the static target MG rotation speed Nmt (see time t3-t4). When the dynamic target MG rotation speed Nmt reaches the static target MG rotation speed Nmt, the backlash elimination control is ended (see time t4).

[0053] As described above, according to this embodiment, when the power transmission state switches from the driven state to the driving state when starting the engine 12, the target differential rotation speed ΔNwt is changed at a predetermined gentle slope from the driven-state target differential rotation speed ΔNwtn to the driving-state target differential rotation speed ΔNwtp, so that backlash can be eliminated to suppress tip-in shock, and further, because the start clutch WSC is not intentionally brought into an engaged state, there is no need to delay the start of the engine 12. Therefore, when starting the engine 12, tip-in shock can be suppressed and deterioration of acceleration response can be suppressed.

[0054] Furthermore, according to this embodiment, when slip control CNslp is being performed in a driven state and the state is switched from the driven state to the driving state, the target differential rotational speed ΔNwt is changed to a zero value at a steep slope before being changed at a predetermined gentle slope, so that the WSC input torque Tiw is quickly reversed from negative to positive.

[0055] Furthermore, according to this embodiment, when backlash elimination is completed during a transient period in which the target differential rotational speed ΔNwt is being changed at a predetermined gentle slope, the target differential rotational speed ΔNwt is changed at a steep slope to the target differential rotational speed during driving ΔNwtp, so that the target differential rotational speed ΔNwt is quickly made to become the target differential rotational speed during driving ΔNwtp.

[0056] Furthermore, according to this embodiment, during the transient period in which the target differential rotational speed ΔNwt is changed at a predetermined gentle slope, the target WSC input torque Tiwt is set to a predetermined value close to zero, and the starting clutch WSC is controlled so as not to generate the PSE torque Tpse, so that the starting clutch WSC is not intentionally brought into an engaged state but rather backlash elimination is performed by dragging the starting clutch WSC. Furthermore, during the transient period in which the target differential rotational speed ΔNwt is changed at a predetermined gentle slope, if the MG rotational speed Nm becomes higher than the input rotational speed Ni by more than the predetermined rotational speed Nf, it is determined that backlash elimination is complete, and therefore the completion of backlash elimination is determined appropriately.

[0057] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0058] For example, in the above-described embodiment, the second clutch may be an engagement device CB that can place the automatic transmission 20 in a neutral state, instead of the starting clutch WSC. Alternatively, if the vehicle 10 is equipped with a hydrodynamic power transmission instead of the starting clutch WSC, the second clutch may be a lock-up clutch included in the hydrodynamic power transmission. Note that if the starting clutch WSC is used as the second clutch, the automatic transmission 20 does not need to be provided.

[0059] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0060] 10: Vehicle 12: Engine 14: Drive wheel 90: Electronic control device (control device) K0: Disengagement clutch (first clutch) WSC: Starting clutch (second clutch) MG: Electric motor

Claims

1. A control device for a vehicle including an engine, an electric motor connected to a power transmission path between the engine and drive wheels so as to be able to transmit power, a first clutch provided in the power transmission path between the engine and the electric motor, and a second clutch provided in the power transmission path between the electric motor and the drive wheels, A switch from motor running, in which the vehicle runs using only the electric motor as a power source when the first clutch is in a released state, to engine running, in which the vehicle runs using at least the engine as a power source when the first clutch is in an engaged state, is performed in a state where slip control is being performed to put the second clutch into a slip state by controlling the output of the electric motor so that a slip amount, which is a rotational speed difference between an input rotational speed and an output rotational speed of the second clutch, becomes a predetermined target slip amount, when starting the engine in conjunction with the switch to engine running, if the power transmission state in the power transmission path switches from a driven state to a driving state, the target slip amount is changed at a predetermined gentle slope from a predetermined driven target value in the driven state to a predetermined driving target value in the driving state that is opposite in sign to the driven target value, During the transition in which the target slip amount is being changed at the gentle slope, when a clearance between the meshing gears provided in the power transmission path between the second clutch and the drive wheels is eliminated, the target slip amount is changed to the driving target value at a slope that is steeper than the gentle slope, During the transient period in which the target slip amount is being changed at the gentle slope, a target value of input torque to the second clutch, which is a wet friction engagement device, is set to a predetermined value close to zero that is equal to or greater than the torque that realizes the drive state and is less than the torque capacity of the second clutch when the second clutch is controlled to be in a packing completion state in which the pack clearance is reduced, and the second clutch is controlled so as not to produce the torque capacity when the packing completion state is achieved, A vehicle control device characterized in that, during the transient period in which the target slip amount is changed at the gradual slope, if the input rotational speed of the second clutch becomes higher than the output rotational speed of the second clutch by more than a predetermined rotational speed, it is determined that the elimination of backlash has been completed.

2. 2. The vehicle control device according to claim 1, wherein when the power transmission state switches from the driven state to the driving state while the slip control is being performed in the driven state, the target slip amount is changed from the driven target value to zero at a slope that is steeper than the gentle slope before being changed at the gentle slope.

Images