Vehicle control system

Abstract

The present invention provides a vehicle control device that can implement appropriate fail-safe procedures for the clutch, taking into account the vehicle's faulty parts. [Solution] The control device performs fail-safe control in the event of an abnormality, setting the clutch to one of the following states: a released-fixed state (disengaged and kept in the released state), an engaged-fixed state (engaged and kept in the engaged state), or a switching-prohibited state (continuing in the current state). If the abnormality is a failure that prevents the clutch from being engaged, the clutch is set to the released-fixed state; if the actuator fails, the clutch is set to the switching-prohibited state; and if the failure is both an inability to release the clutch and a failure of the power source (first motor), the clutch is set to the engaged-fixed state. As a result, in the event of a power source (first motor) failure, the clutch is set to the engaged-fixed state, allowing for appropriate retraction driving, and so on, ensuring that appropriate fail-safe control is applied to the clutch.

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle including a power source that drives a main drive wheel, an electric motor that drives an auxiliary drive wheel, and a clutch provided in a power transmission path between the auxiliary drive wheel and the electric motor.

Background Art

[0002] A control device for a vehicle including a power source that drives a main drive wheel, an electric motor that drives an auxiliary drive wheel, and a clutch provided in a power transmission path between the auxiliary drive wheel and the electric motor is well known. For example, the drive control device described in Patent Document 1 is such a device. Patent Document 1 discloses a technique for determining an abnormality of the clutch by determining using the rotational speed of the electric motor and the rotational speed of the auxiliary drive wheel when the clutch is engaged or disengaged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the aforementioned vehicle, if an abnormality, such as a malfunction, occurs in the clutch or the actuator that switches the clutch, conventional fail-safe control for the clutch has been implemented. This control has been such that if the clutch cannot be engaged, the clutch is released and remains in the released state; if the clutch cannot be released, the clutch is engaged and remains in the engaged state; or the clutch switching is prohibited and the vehicle remains in its current state. However, conventional fail-safe control does not take into account malfunctions other than those in the clutch and actuator, and there is room for improvement. For example, in the aforementioned vehicle, if the power source malfunctions while the clutch is engaged in all-wheel drive (4WD) mode, and the driver switches to two-wheel drive (2WD) mode with only the main drive wheels engaged, the clutch and actuator are functioning normally, so the clutch will be switched to the released state, which could render the vehicle inoperable. In other words, even if the malfunction is not in the clutch or actuator, depending on the location of the malfunction, if fail-safe processing for the clutch is not properly implemented, it could lead to the vehicle stopping on the road and affect the driver's safety.

[0005] The present invention was made against the above circumstances, and its objective is to provide a vehicle control device that can implement appropriate fail-safe processing on the clutch, taking into account the vehicle's fault location. [Means for solving the problem]

[0006] The gist of the first invention is a control device for a vehicle comprising: (a) a power source for driving the main drive wheels, an electric motor for driving the auxiliary drive wheels, a battery for exchanging power with the electric motor, a clutch provided in the power transmission path between the auxiliary drive wheels and the electric motor, and an actuator for switching between a disengaged state and an engaged state of the clutch, wherein (b) in the event of an abnormality, the clutch is subjected to fail-safe control to one of the following states: a disengaged fixed state in which the disengaged state is maintained, an engaged fixed state in which the engaged state is maintained, or a switching prohibited state in which the current state is maintained, and (c) if the abnormality is a failure that prevents the clutch from being engaged, the clutch is subjected to the disengaged fixed state; if the actuator fails, the clutch is subjected to the switching prohibited state; and if the clutch fails to be disengaged and the power source fails, the clutch is subjected to the engaged fixed state. [Effects of the Invention]

[0007] According to the first invention, the control device performs fail-safe control in the event of an abnormality, setting the clutch to one of the following states: a released-fixed state, an engaged-fixed state, or a switching-prohibited state, where the clutch remains in its current state. If the abnormality is a failure that prevents the clutch from being engaged, the clutch is set to the released-fixed state; if the failure is of the actuator, the clutch is set to the switching-prohibited state; and if the failure is both a failure that prevents the clutch from being released and a failure of the power source, the clutch is set to the engaged-fixed state. As a result, in the event of a power source failure, the clutch is set to the engaged-fixed state, allowing for suitable evasive driving. Thus, appropriate fail-safe control is implemented for the clutch, taking into account the fault location of the vehicle. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates the schematic configuration of a vehicle to which the present invention is applied. [Figure 2]This flowchart explains the key aspects of the control operation of an electronic control unit, and specifically illustrates an example of fail-safe control for the clutch that the electronic control unit executes when an abnormality occurs. [Figure 3] This is a flowchart illustrating the control operation of a conventional electronic control device. [Modes for carrying out the invention]

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

[0010] Figure 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied. In Figure 1, the vehicle 10 is equipped with left and right front wheels 12, a front drive unit 20 that drives the front wheels 12, left and right rear wheels 14, and a rear drive unit 30 that drives the rear wheels 14, all spaced apart from each other. The vehicle 10 is also equipped with a battery 40, which is a rechargeable DC power source, and an on-board charger 42 that charges the battery 40 with power from an external power source. Note that "left and right" above refers to left and right with respect to the forward direction of the vehicle 10.

[0011] Vehicle 10 is an all-wheel drive vehicle in which the drive torque distribution between the front wheels 12 and the rear wheels 14 can be adjusted. All-wheel drive (AWD) and four-wheel drive (4WD) are synonymous. In addition to driving in 4WD mode, vehicle 10 can also drive in two-wheel drive (2WD) mode in which drive torque is distributed only to the rear wheels 14. The rear wheels 14 correspond to the "main drive wheels" of this invention, and the front wheels 12 correspond to the "secondary drive wheels" of this invention.

[0012] The front drive unit 20 comprises a second electric motor MG2 and a front PCU (Power Control Unit) 24. The second electric motor MG2 is a known rotating electric machine, a so-called motor generator, and is connected to the battery 40 via the front PCU 24. The second electric motor MG2 is an electric motor that drives the front wheels 12, which are auxiliary drive wheels. The front PCU 24 is a motor control device that controls the power exchanged between the battery 40 and the second electric motor MG2 and controls the operation of the second electric motor MG2, and controls the power of the second electric motor MG2 by being controlled by the electronic control device 80 described later.

[0013] The front drive unit 20 includes a counter gear mechanism 50, a counter shaft 52, a final gear 54, a front differential gear (hereinafter referred to as front differential) 56, etc. The front drive unit 20 also includes left and right front drive shafts 58 connected to the front differential 56, etc. The counter gear mechanism 50 is a gear pair having a drive gear 50a and a driven gear 50b that meshes with the drive gear 50a. The drive gear 50a is connected to the second electric motor MG2, and the driven gear 50b is connected to the final gear 54 via the counter shaft 52. The final gear 54 meshes with the differential ring gear 56r of the front differential 56. The front drive shafts 58 connect the front differential 56 to the front wheels 12. The front drive unit 20 transmits power from the second electric motor MG2 to the front wheels 12.

[0014] The front drive unit 20 is equipped with a clutch mechanism 60. The clutch mechanism 60 is equipped with a dog clutch 62 and an actuator 64. The dog clutch 62 is a known meshing clutch provided in the power transmission path between the front wheel 12 and the second electric motor MG2. The actuator 64 is, for example, an electrically driven or hydraulically driven actuator, and switches between the engaged and disengaged states of the dog clutch 62 under control from the electronic control unit 80 described later. The dog clutch 62 corresponds to the "clutch" of the present invention.

[0015] The dog clutch 62 is provided, for example, in the power transmission path between the front differential 56 and the left front wheel 12. The dog clutch 62 has a first dog tooth 62a and a second dog tooth 62b as opposing meshing teeth. The first dog tooth 62a is connected to the front differential 56 and is the meshing tooth on the second electric motor MG2 side of the opposing meshing teeth. The second dog tooth 62b is connected to the left front drive shaft 58 and is the meshing tooth on the front wheel 12 side of the opposing meshing teeth. The dog clutch 62 is engaged when the first dog tooth 62a and the second dog tooth 62b mesh, and is released when their meshing is disengaged.

[0016] The rear drive unit 30 comprises a first electric motor MG1 and a rear PCU 34. The first electric motor MG1 is a known rotating electric machine, a so-called motor generator, and is connected to the battery 40 via the rear PCU 34. The first electric motor MG1 is the power source that drives the rear wheels 14, which are the main drive wheels. The rear PCU 34 has the same function as the front PCU 24 and controls the power of the first electric motor MG1 by being controlled by the electronic control unit 80 described later.

[0017] The rear drive unit 30 includes a counter gear mechanism 70, a counter shaft 72, a final gear 74, a rear differential gear 76, and left and right rear drive shafts 78. The rear drive unit 30 has the same functions as the front drive unit 20 and transmits power from the first electric motor MG1 to the rear wheels 14.

[0018] In vehicle 10, the rear wheels 14 are driven when in 2WD and 4WD states, and the front wheels 12 are driven only when in 4WD state. In 4WD state, the dog clutch 62 is engaged and both the front wheels 12 and rear wheels 14 are driven, and the power transmission path between the front wheels 12 and the second electric motor MG2 is connected. In 2WD state, the dog clutch 62 is disengaged and only the rear wheels 14 are driven, and the power transmission path between the front wheels 12 and the second electric motor MG2 is disconnected. In 2WD state, the disconnected state prevents the rotation of the rotating members of the front drive unit 20 on the second electric motor MG2 side from the dog clutch 62 and the rotation of the second electric motor MG2 from occurring. This prevents or suppresses power loss due to the rotation of the counter gear mechanism 50, final gear 54, front differential 56, etc. The dog clutch 62 is a disconnect mechanism that can disconnect the power transmission path between the front wheel 12 and the second electric motor MG2.

[0019] Vehicle 10 is further equipped with an electronic control unit 80 as a control device for vehicle 10. The electronic control unit 80 comprises an integrated ECU (Electronic Control Unit) 82 and a clutch ECU 84. The integrated ECU 82 controls the systems related to the driving of vehicle 10, including the front PCU 24 (second motor MG2), rear PCU 34 (first motor MG1), and battery 40. The clutch control ECU 84 controls the actuator 64 to switch between the engaged and disengaged states of the dog clutch 62 based on command signals from the integrated ECU 82. The integrated ECU 82 and the clutch ECU 84 are controllers that include a so-called microcomputer.

[0020] Various signals based on the detection values of various devices and various sensors provided in the vehicle 10 are respectively supplied to the integrated ECU 82. The various devices and various sensors are, for example, the front PCU 24, the rear PCU 34, the in-vehicle charger 42, the clutch ECU 84, the accelerator opening sensor 90, the brake sensor 92, the driving state setting switch 94, the battery charge remaining amount sensor 96, the acceleration sensor 98, the yaw acceleration sensor 100, the wheel speed sensor 102, the in-vehicle camera 104, etc. The various signals include, for example, the MG2 operation information Img2 including the rotational speed Nmg2, the drive current Amg2, the internal temperature Tmg2, etc. of the second motor MG2, the MG1 operation information Img1 including the rotational speed Nmg1, the drive current Amg1, the internal temperature Tmg1, etc. of the first motor MG1, the charger operation information Ibc indicating the operation state of the in-vehicle charger 42, the clutch operation information Ic including the stroke position Ldg of the dog clutch 62 and the drive current Adg (or drive hydraulic pressure Pdg) of the actuator 64, the accelerator opening θacc, the brake operation amount Bra, the driving state setting signal Dmd, the battery charge remaining amount SOC of the battery 40, the lateral acceleration Gy of the vehicle 10, the yaw acceleration Ryaw which is the rotational angular velocity around the vertical axis of the vehicle 10, the left front wheel rotational speed Nwfl, the right front wheel rotational speed Nwfr, the left rear wheel rotational speed Nwrl, the right rear wheel rotational speed Nwrr, the in-vehicle camera imaging information Iard, etc. The driving state setting switch 94 is a switch for the driver to select the driving state of driving in the 2WD state or the 4WD state, and a driving state setting signal Dmd corresponding to the selected driving state is supplied. The lateral acceleration Gy and the yaw acceleration Ryaw indicate the left and right acceleration and the turning acceleration generated in the vehicle 10, respectively.

[0021] Various command signals are respectively output from the integrated ECU 82 to each device provided in the vehicle 10. The various devices are, for example, the front PCU 24, the rear PCU 3, the in-vehicle charger 42, the clutch ECU 84, etc. The various command signals are, for example, the MG2 control signal Smg2 for controlling the second motor MG2, the MG1 control signal Smg1 for controlling the first motor MG1, the charger control signal Sbc for controlling the in-vehicle charger, and the clutch control signal Sc for controlling the switching between the engaged state and the released state of the dog clutch 62.

[0022] The integrated ECU 82 calculates a required acceleration or deceleration for the vehicle 10 based on the accelerator opening θacc and / or the brake operation amount Bra, etc., and switches the driving state based on the required acceleration or deceleration, wheel slip, the driving state setting by the driver, etc. For example, when the 4WD state is selected by the driver's operation on the driving state setting switch 94 during the 2WD state, the integrated ECU 82 makes the first dog rotation speed Ndg1 of the first dog tooth 62a calculated from the rotation speed Nmg2 of the second motor MG2 and the second dog rotation speed Ndg2 of the second dog tooth 62b corresponding to the left front wheel rotation speed Nwfl synchronize, and outputs a clutch control signal Sc to the clutch ECU 84 so as to make the dog clutch 62 in an engaged state. Then, the clutch ECU 84 controls the actuator 64 to switch the dog clutch 62 to the engaged state, thereby switching to the 4WD state.

[0023] FIG. 3 is a flowchart for explaining a conventional example of fail-safe control for the dog clutch 62 executed by the integrated ECU 82 in the electronic control device 80 when an abnormality occurs, and is executed repeatedly, for example.

[0024] First, in step (hereinafter, steps are omitted) S101, it is determined whether or not multiple failures have occurred in the vehicle 10. If the determination in S101 is affirmative, in S102, the vehicle 10 is shut down to a non-drivable state and this routine is terminated.

[0025] If the determination in S101 is negative, then in S103, it is determined whether a failure has occurred that prevents the dog clutch 62 from being engaged. This determination is made, for example, when the dog clutch 62 is in the engaged state. If the rotations of the first dog tooth 62a and the second dog tooth 62b are not synchronized, that is, if the absolute value of the dog rotation speed difference ΔNdg, which is the rotation speed difference between the first dog rotation speed Ndg1 and the second dog rotation speed Ndg2, is greater than a preset predetermined value N1 (ΔNdg = |Ndg1 - Ndg2| > N1), it is determined that a failure has occurred. If the determination in S103 is affirmative, that is, if a failure has occurred that prevents the dog clutch 62 from being engaged, the power transmission by the dog clutch 62 is not guaranteed. In S104, a clutch control signal Sc is output to the clutch ECU 84 to disengage the dog clutch 62, and it is set to a release fixed state in which the release state is continued, and this routine is terminated.

[0026] If the determination in S103 is negative, then in S105, it is determined whether a failure has occurred that prevents the dog clutch 62 from being disengaged. This determination is made, for example, when the dog clutch 62 is in the disengaged state. If the synchronization between the first dog tooth 62a and the second dog tooth 62b is not eliminated, that is, if the dog rotation speed difference ΔNdg is less than a preset predetermined value N2 (ΔNdg = |Ndg1 - Ndg2| < N2), it is determined that a failure has occurred. If the determination in S105 is affirmative, that is, if a failure has occurred that prevents the dog clutch 62 from being disengaged, the disengagement of the dog clutch 62 is not guaranteed. In S106, a clutch control signal Sc is output to the clutch ECU 84 to engage the dog clutch 62, and it is set to an engagement fixed state in which the engaged state is continued, and this routine is terminated.

[0027] If the judgment in S105 is denied, then in S107, it is determined whether or not a malfunction has occurred in the actuator 64. This determination is made, for example, by checking whether or not there is an abnormality in the stroke position Ldg or drive current Adg (or drive hydraulic pressure Pdg) in the clutch operation information Ic, and if there is an abnormality, it is determined that a malfunction has occurred. If the judgment in S107 is affirmed, that is, if a malfunction has occurred in the actuator 64, then the switching operation between the engaged state and the disengaged state of the dog clutch 62 is not guaranteed, and in S108, the dog clutch 62 is set to a switching-prohibited state in which it remains in its current state, and this routine is terminated.

[0028] If the judgment in S107 is denied, that is, if there is no malfunction in the actuator 64, then in S109, it is determined whether or not there is a request to switch the driving state by the driver's operation. If the judgment in S109 is denied, this routine is terminated. If the judgment in S109 is affirmed, then in S110, a clutch control signal Sc is output to the clutch ECU 84 in response to the request to switch the driving state, that is, to switch the dog clutch 62 to the disengaged state in the case of a request to switch to the 2WD state, and to switch the dog clutch 62 to the engaged state in the case of a request to switch to the 4WD state, and this routine is terminated.

[0029] In conventional designs, if a failure occurred in the clutch mechanism 60 (dog clutch 62, actuator 64), fail-safe control for the dog clutch 62 was implemented, as described above, by setting it to a disengaged state, an engaged state, or a switching-prohibited state. However, the conventional fail-safe control did not consider failures occurring in locations other than the clutch mechanism 60. For example, in vehicle 10, if the first electric motor MG1 failed in the 4WD state with the dog clutch 62 engaged, and the driver operated the driving state setting switch 94 to set it to 2WD, the dog clutch 62 would switch to the disengaged state because the clutch mechanism 60 was functioning normally, potentially rendering the vehicle inoperable. In other words, even if the failure was in a location other than the clutch mechanism 60, if fail-safe processing for the dog clutch 62 was not properly implemented, it could lead to the vehicle stopping on the road and affect driver safety.

[0030] Figure 2 is a flowchart illustrating an example of fail-safe control operation for the dog clutch 62 performed by the integrated ECU 82 in the electronic control unit 80 of this embodiment when an abnormality occurs, and is, for example, executed repeatedly.

[0031] The control operations from S1 to S8 and from S12 to S13 are the same as the control operations from S101 to S108 and from S109 to S110 in Figure 3 (conventional example), and the flowchart in Figure 2 (this embodiment) adds the control operations from S9 to S11 between S7 and S12. Therefore, the explanation of the common steps is omitted, and only the added steps are explained.

[0032] If the judgment in S7 (whether or not a malfunction has occurred in actuator 64) is denied, then in S9 and S10, it is sequentially determined whether or not a malfunction has occurred in either the second electric motor MG2 or the onboard charger 42. The judgment in S9 is performed, for example, by checking whether there are any abnormalities in the rotational speed Nmg2, drive current Amg2, etc., in the MG2 operation information Img2 for the output of the MG2 control signal Smg2, and if there are abnormalities, it is determined that a malfunction has occurred. Similarly, the judgment in S10 is performed, for example, by checking whether there are any abnormalities in the charger operation information Ibc for the output of the charger control signal Sbc, and if there are abnormalities, it is determined that a malfunction has occurred. If the judgment in either S9 or S10 is affirmative, the process transitions to S8, and the dog clutch 62 is set to a switching-prohibited state, which allows it to remain in its current state, and the routine is terminated. If a malfunction occurs in either the second electric motor MG2 or the onboard charger 42, the switching operation of the dog clutch 62 between the engaged and disengaged states cannot be guaranteed, the dog clutch 62 is put into a switching-prohibited state, and the switching operation is prohibited.

[0033] If the judgments in S9 and S10 are all negative, then in S11, it is determined whether or not a malfunction has occurred in the first motor MG1. This determination is made, for example, by checking whether there are any abnormalities in the rotational speed Nmg1, drive current Amg1, etc., in the MG1 operation information Img1 in relation to the output of the MG1 control signal Smg1, and if there are abnormalities, it is determined that a malfunction has occurred. If the judgment in S11 is affirmative, that is, if a malfunction has occurred in the first motor MG1, then in S6, a clutch control signal Sc is output to the clutch ECU 84 to engage the dog clutch 62 so that power transmission between the second motor MG2 and the front wheel 12 is maintained, and the routine is terminated with the dog clutch 62 in an engaged state.

[0034] If the judgment in S11 is rejected, the process proceeds to S12, and thereafter the same control operations as when the process proceeds to S109 in Figure 3 (conventional example) are executed.

[0035] In addition to the example of operation shown in Figure 2, preferably, if an event occurs in which the switching operation of the dog clutch 62 between the open state and the engaged state is restricted, such as when the battery charge level (SOC) of the battery 40 falls below a predetermined level or when the internal temperature (Tmg2) of the second motor MG2 rises above a predetermined temperature, the dog clutch 62 is set to a switching-prohibited state. This restricts the switching operation of the dog clutch 62, thereby enabling appropriate fail-safe control for the dog clutch 62.

[0036] Preferably, when the vehicle 10 is in a driving state where the lateral acceleration Gy or yaw acceleration Ryaw is greater than a predetermined acceleration, or when it is driving on a low-friction road, or when the driving state or driving environment of the vehicle 10 is worse than normal, the dog clutch 62 is engaged and locked. As a result, when the driving state or driving environment of the vehicle 10 is more severe than normal, the vehicle switches to 4WD mode, thereby improving driving stability. The determination of whether it is driving on a low-friction road is made, for example, by calculating the road surface friction value RE according to a predetermined calculation method based on the fluctuation trends of the left front wheel rotation speed Nwfl, the right front wheel rotation speed Nwfr, the left rear wheel rotation speed Nwrl, and the right rear wheel rotation speed Nwrr, as well as information from the road surface image acquired from the onboard camera imaging information Iard from the onboard camera 104, and determining whether the road surface friction value RE is lower than a predetermined value Rn. The predetermined value Rn is a set value that has been determined in advance, either by design or experiment, in order to determine whether it is a low-friction road.

[0037] Preferably, if the second electric motor MG2 is determined to be faulty in S9 of Figure 2, and the dog clutch 62 is set to a disengagement state in S8, and then the vehicle 10 stops moving, the dog clutch 62 is set to a disengaged state. The vehicle 10 stops moving, for example, when the rotation speed of the left front wheel Nwfl, the rotation speed of the right front wheel Nwfr, the rotation speed of the left rear wheel Nwrl, and the rotation speed of the right rear wheel Nwrr are all below a predetermined value. This prevents the vehicle 10 from being hindered from moving due to a failure of the second electric motor MG2 when the vehicle 10 starts moving again after stopping.

[0038] Preferably, if the abnormality is a failure of the integrated ECU 82, the clutch ECU 84 puts the dog clutch 62 into a switching-disabled state. When a failure occurs in the integrated ECU 82, the switching operation between the engaged and disengaged states of the dog clutch 62 is not guaranteed, and the clutch ECU 84 puts the dog clutch 62 into a switching-disabled state, thus prohibiting the switching operation. A failure of the integrated ECU 82 is detected, for example, by a failure notification from the integrated ECU 82 or by a prolonged period of no response.

[0039] As described above, according to the electronic control device 80 of this embodiment, when an abnormality occurs, fail-safe control is performed to set the dog clutch 62 to one of the following states: a released fixed state in which it is released and the released state is maintained; an engaged fixed state in which it is engaged and the engaged state is maintained; or a switching prohibited state in which it remains in its current state. If the abnormality is a failure that prevents the dog clutch 62 from being engaged, the dog clutch 62 is set to the released fixed state; if the actuator 64 fails, the dog clutch 62 is set to the switching prohibited state; and if the failure prevents the dog clutch 62 from being released and the first electric motor MG1 fails, the dog clutch 62 is set to the engaged fixed state. As a result, in the case of a failure of the first electric motor MG1, the dog clutch 62 is set to the engaged fixed state, allowing for suitable retraction driving. Thus, appropriate fail-safe control is performed on the clutch mechanism 60, taking into account the fault location of the vehicle 10.

[0040] Furthermore, according to the electronic control device 80 of this embodiment, if the abnormality is a failure of either the second electric motor MG2 or the onboard charger 42, the dog clutch 62 is put into a switching-disabled state. In the event of a failure of either the second electric motor MG2 or the onboard charger 42, the switching operation of the dog clutch 62 between the engaged and disengaged states cannot be guaranteed, and by putting the dog clutch 62 into a switching-disabled state, appropriate fail-safe control is implemented for the dog clutch 62.

[0041] Furthermore, according to the electronic control device 80 of this embodiment, if an abnormality occurs, such as a decrease in the battery charge level (SOC) of the battery 40 or a rise in the internal temperature (Tmg2) of the second motor MG2, and no actual malfunction has occurred but the switching operation of the dog clutch 62 between the open and engaged states is restricted, the dog clutch 62 is set to a switching-prohibited state. As a result, appropriate fail-safe control is implemented for the dog clutch 62 by restricting its switching operation.

[0042] Furthermore, according to the electronic control device 80 of this embodiment, when the vehicle 10 is in a driving state where the lateral acceleration Gy or yaw acceleration Ryaw is large, or when driving on a low-friction road, or when the driving state or driving environment of the vehicle 10 is worse than normal, the dog clutch 62 is locked into an engaged state. As a result, when the driving state or driving environment of the vehicle 10 is more severe than normal, the system switches to 4WD mode, thereby improving driving stability.

[0043] Furthermore, according to the electronic control device 80 of this embodiment, if the dog clutch 62 is put into a disengagement state due to a failure of the second electric motor MG2 and the vehicle 10 stops moving, the dog clutch 62 is put into a disengaged state. This prevents the vehicle 10 from being hindered from moving due to a failure of the second electric motor MG2 when the vehicle 10 starts moving again after stopping.

[0044] Furthermore, according to the electronic control device 80 of this embodiment, if an abnormality occurs due to a failure of the integrated ECU 82, the clutch ECU 84 puts the dog clutch 62 into a switching-disabled state. When a failure occurs in the integrated ECU 82, the switching operation between the engaged and disengaged states of the dog clutch 62 is not guaranteed, and the clutch ECU 84 puts the dog clutch 62 into a switching-disabled state, thereby implementing appropriate fail-safe control for the dog clutch 62.

[0045] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0046] For example, in the embodiment described above, the power source for the rear drive unit 30 may be an engine in addition to, or instead of, the first electric motor MG1. Alternatively, the main drive wheels may be the front wheels 12 and the secondary drive wheels may be the rear wheels 14. In this case, the system includes a power source for driving the front wheels 12, an electric motor for driving the rear wheels 14, and a clutch provided in the power transmission path between the rear wheels 14 and the electric motor.

[0047] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0048] 10: Vehicle 12: Front wheels (auxiliary drive wheels) 14: Rear wheels (primary drive wheels) 40: Battery 42: Onboard charger 62: Dog clutch (clutch) 64: Actuator 80: Electronic control unit (control unit) 82: Integrated ECU 84: Clutch ECU Gy: Lateral acceleration MG1: First motor (power source) MG2: Second motor (motor) Ryaw: Yaw acceleration SOC: Battery charge level Tmg2: Internal temperature

Claims

1. A control device for a vehicle comprising: a power source for driving the main drive wheels; an electric motor for driving the auxiliary drive wheels; a battery for exchanging power with the electric motor; a clutch provided in the power transmission path between the auxiliary drive wheels and the electric motor; and an actuator for switching between a disengaged state and an engaged state of the clutch, In the event of an abnormality, fail-safe control is performed to set the clutch to one of the following states: a released-fixed state in which the clutch remains in the released state; an engaged-fixed state in which the clutch remains in the engaged state; or a switching-prohibited state in which the clutch remains in its current state. If the malfunction prevents the clutch from being engaged, the clutch is set to the disengaged and fixed state; if the actuator malfunctions, the clutch is set to the disengaged and disabled state; and if the malfunction prevents the clutch from being disengaged and the power source malfunctions, the clutch is set to the engaged and fixed state. A vehicle control device characterized by the following features.

2. The vehicle further includes an onboard charger that charges the battery from an external power source, If the aforementioned abnormality is due to a failure of either the electric motor or the onboard charger, the clutch is set to the disabled state. The vehicle control device according to feature 1.

3. If the aforementioned abnormality is an event in which no malfunction has occurred but the switching operation between the disengaged and engaged states of the clutch is restricted, the clutch will be set to the disengaged state. The vehicle control device according to feature 1.

4. If the vehicle's driving conditions or driving environment are worse than normal, the clutch will be set to the engaged and locked state. The vehicle control device according to feature 1.

5. If the vehicle stops moving after the clutch has been set to the disabled state due to a malfunction of the electric motor, the clutch will be set to the released and fixed state. The vehicle control device according to feature 2.

6. The control device comprises a clutch ECU that controls the actuator and an integrated ECU that controls the system related to vehicle operation, including the power source, the electric motor, and the battery. If the abnormality is due to a failure of the integrated ECU, the clutch ECU will put the clutch into the disabled state. The vehicle control device according to feature 1.

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