Electric vehicle

Abstract

An electric vehicle according to the present disclosure comprises a differential (5) that distributes drive force from drive sources (1, 2) to a left wheel (13) and a right wheel (14), a clutch mechanism (7) that connects and disconnects a power transmission path between a motor (2) and the differential (5), an actuator (8) that switches between the connected and disconnected states of the clutch mechanism (7), a left wheel speed sensor (11) that detects a left wheel speed, a right wheel speed sensor (12) that detects a right wheel speed, and a control device (20) that suppresses the outputs of the drive sources (1, 2) on the basis of the rotational speed difference between the left wheel speed and the right wheel speed and determines, in accordance with a travel state, whether to connect or disconnect the clutch mechanism (7). When an abnormal state associated with the wheel speeds or the actuator (8) is detected while the clutch mechanism (7) is in the connected state, the control device (20) prohibits the clutch mechanism (7) from transitioning to the disconnected state.

Description

Electric vehicle

[0007] ,

[0006] , ,

[0005] ,

[0001] This case relates to an electric vehicle equipped with a plurality of drive sources.

[0002] In an electric vehicle equipped with a motor and a differential device, a technique for preventing seizure of the differential device by limiting the motor torque based on the motor rotation speed (motor rotation speed) is known. The maximum value of the differential rotation speed on the left and right in the differential device is typically twice the rotation speed input to the differential device. Therefore, by referring to the motor rotation speed corresponding to the rotation speed input to the differential device, the maximum value of the differential rotation speed can be maintained within an appropriate range (see Patent Document 1).

[0003] Japanese Patent No. 7472976

[0004] On the other hand, in an electric vehicle equipped with a plurality of drive sources, for example, the motor may be disconnected from the power transmission path for the purpose of reducing frictional losses in the drive system. In this case, it is difficult to realize seizure prevention control of the differential device based on the motor rotation speed. In particular, when there is some defect or failure in the left and right wheel speed sensors, there is a risk that the maximum value of the differential rotation speed cannot be maintained within an appropriate range.

[0005] One of the objectives of this case was conceived in light of the above problems, and in an electric vehicle equipped with a plurality of drive sources, it is to suppress the occurrence of seizure in the differential device. In addition to this objective, the operational effects derived from each configuration shown in the "Mode for Carrying Out the Invention" described later, which are operational effects that cannot be obtained with the prior art, are also positioned as other objectives of this case.

[0006] The disclosed electric vehicle can be realized as the following disclosed modes (application examples) and solves at least some of the above problems. Each mode after Mode 2 is an additionally selectable mode as appropriate, and each mode is an omissible mode. Each mode after Mode 2 does not disclose any essential modes or configurations for this case.

[0007] Embodiment 1. The disclosed electric vehicle comprises a plurality of drive sources, including a motor as a first drive source and a second drive source. This electric vehicle includes a differential that distributes the driving force of the drive sources to the left wheel and the right wheel, a clutch mechanism that connects and disconnects the power transmission path between the motor and the differential, an actuator that switches the connected and disconnected state of the clutch mechanism, a left wheel speed sensor that detects the speed of the left wheel, and a right wheel speed sensor that detects the speed of the right wheel.

[0008] The electric vehicle includes a control device that suppresses the output of the drive source based on the difference in rotational speed between the left wheel speed and the right wheel speed, and determines whether to engage or disengage the clutch mechanism according to the driving conditions. The control device prohibits the transition of the clutch mechanism to the disengaged state if it detects an abnormal condition related to the wheel speed or the actuator while the clutch mechanism is engaged.

[0009] Embodiment 2. In an embodiment including Embodiment 1 described above, it is preferable that the control device, when it detects the abnormal state, estimates the maximum value of the differential rotation speed based on the rotation speed of the motor and suppresses the output of the drive source based on the maximum value. Embodiment 3. In an embodiment including Embodiment 1 described above, it is preferable that the electric vehicle is equipped with a detection device connected to the left wheel speed sensor and the right wheel speed sensor to acquire information on the left wheel speed and the right wheel speed. It is preferable that the abnormal state includes a poor response of the detection device.

[0010] Embodiment 4. With respect to an embodiment including Embodiment 1 described above, it is preferable that the electric vehicle is equipped with an instruction device that outputs a drive signal to the actuator based on the judgment of the control device. It is preferable that the abnormal condition includes a poor response of the instruction device. Embodiment 5. With respect to an embodiment including Embodiment 4 described above, it is preferable that the abnormal condition is a poor response of the instruction device occurring for a predetermined number of consecutive times or more.

[0011] Embodiment 6. With respect to embodiments including Embodiment 1 described above, it is preferable that the clutch mechanism has a first gear located on the motor side and a second gear located on the differential side. When the control device detects the abnormal state while the clutch mechanism is disengaged, it is preferable that the control device increases or decreases the first rotational speed of the first gear and determines to engage the clutch mechanism after the difference between the first rotational speed and the second rotational speed of the second gear becomes less than or equal to a predetermined value.

[0012] Embodiment 7. In an embodiment including Embodiment 6 above, it is preferable that the control device estimates the second rotational speed based on the left wheel speed detected by the left wheel speed sensor or the right wheel speed detected by the right wheel speed sensor. Embodiment 8. In an embodiment including Embodiment 6 above, it is preferable that the control device estimates the second rotational speed based on the rotational speed of the second drive source. Embodiment 9. In an embodiment including any of Embodiments 6 to 8 above, it is preferable that the control device informs the occupant of the possibility of a shock occurring when the clutch mechanism is engaged.

[0013] According to the disclosed electric vehicle, by prohibiting the disengagement of the clutch mechanism when an abnormal condition is detected, the output of the drive source can be suppressed based on the motor's rotational speed, thereby preventing differential burnout. Furthermore, since the disengagement of the clutch mechanism is permitted when no abnormal condition is detected, the drive loss on the motor side when driven solely by the second drive source can be reduced, improving energy efficiency.

[0014] This is a block diagram of an electric vehicle to which the vehicle drive system of the embodiment is applied. (A) is an example of a map stored in the control device of Figure 1, showing the relationship between the difference in rotational speed between the left wheel speed and the right wheel speed and the axle required torque. (B) is an example of a map stored in the control device of Figure 1, showing the relationship between the motor rotational speed and the axle required torque. This is a flowchart of the control procedure to suppress differential gear seizure. This is a flowchart of the control procedure to suppress differential gear seizure.

[0015] The disclosed vehicle drive system is applicable to electric vehicles such as electric vehicles (EVs) and hybrid electric vehicles (HEVs). This electric vehicle comprises at least a plurality of drive sources. These drive sources include a motor as a first drive source and a second drive source. The second drive source is, for example, an engine, a second motor, a generator, etc. This electric vehicle is equipped with a traction battery (not shown) that stores electricity for driving the motor.

[0016] The disclosed vehicle drive system is preferably applicable to a hybrid electric vehicle comprising a motor as a first drive source and an engine as a second drive source. Hybrid electric vehicles include plug-in hybrid electric vehicles (PHEVs). A plug-in hybrid electric vehicle means a hybrid vehicle that can be externally charged to a traction battery and / or externally powered from a traction battery. A plug-in hybrid electric vehicle is provided with a charging port (inlet, charging socket) for inserting a charging cable into which power is supplied from an external charging facility, and an outlet (power supply socket) for external power supply.

[0017] [1. Configuration] Figure 1 is a block diagram of an electric vehicle to which the vehicle drive system 10 as an embodiment is applied. This electric vehicle is equipped with multiple drive sources. One of the multiple drive sources is called the first drive source, and another is called the second drive source. The first drive source is a motor 2 that converts electricity into rotational driving force. On the other hand, the type of the second drive source is not particularly limited, and may be, for example, an engine 1 that converts the pressure generated by the combustion of fuel into rotational driving force, or a second motor (not shown) or a generator 3 that converts electricity into rotational driving force. The vehicle drive system 10 shown in Figure 1 is equipped with an engine 1, a motor 2, a generator 3, a transaxle 4, a differential 5, an engine clutch 6, a motor clutch 7 (clutch mechanism), and an actuator 8.

[0018] Engine 1 is an internal combustion engine, such as a gasoline engine or a diesel engine. A generator 3 is connected to the output shaft of engine 1, for example, via several transmission gears. A portion of the driving force generated by engine 1 is transmitted to the generator 3, and the other portion of the driving force is transmitted to the differential gear 5. The driving force transmitted to the differential gear 5 is distributed to the left wheel 13 and the right wheel 14, which are the drive wheels.

[0019] The generator 3 is an electric motor and generator that combines the functions of cranking and starting the engine 1 and generating electricity using the driving force of the engine 1. The electricity generated by the generator 3 is used to drive the motor 2 and to charge the traction battery (not shown). The generator 3 may also have the function of driving the drive wheels by transmitting a portion of the driving force to the differential 5.

[0020] Motor 2 is an electric motor and generator that combines the function of generating driving force using power from the traction battery and the power generated by the generator 3, and the function of charging the traction battery with power generated by regenerative power generation. The driving force generated by motor 2 is transmitted to the differential 5. The driving force transmitted to the differential 5 is distributed according to the rotational speed (rotational velocity) of each of the left and right drive wheels (left wheel 13 and right wheel 14). Motor 2 has a built-in resolver 15 that detects the motor rotational speed (the number of rotations per unit time of motor 2, rotational velocity). The motor rotational speed information detected by the resolver 15 is transmitted to the control device 20, which will be described later.

[0021] An engine clutch 6 is interposed in the power transmission path between the engine 1 and the differential 5. The engine clutch 6 has the function of disconnecting (releasing) or connecting (engaging) the power transmission path between the engine 1 and the differential 5. When the engine clutch 6 is disengaged, the engine 1 and the generator 3 become disconnected from the drive wheels. Therefore, for example, by operating only the motor 2 in this state, the EV mode is realized. In addition to this, by operating the engine 1 and generating electricity with the generator 3, the series mode is realized.

[0022] Furthermore, multiple reduction mechanisms with different reduction ratios may be interposed in the power transmission path between the engine 1 and the differential 5. These multiple reduction mechanisms may include, for example, a low-speed gear with a relatively large reduction ratio and a high-speed gear with a relatively small reduction ratio. One of these gears may be selected, for example, depending on the operator's input or driving conditions.

[0023] A motor clutch 7 is interposed in the power transmission path between the motor 2 and the differential gear 5. The motor clutch 7 has the function of disconnecting (releasing) or connecting (engaging) the power transmission path between the motor 2 and the differential gear 5. When the motor clutch 7 is engaged, the motor 2 becomes connected to the drive wheels. Therefore, for example, by driving the engine 1 and motor 2 in this state, the first parallel mode (parallel mode with motor clutch 7 engaged) is realized. When the motor clutch 7 is disengaged, the motor 2 becomes disconnected from the drive wheels. Therefore, for example, by operating only the engine 1 in this state, the second parallel mode (engine mode, parallel mode with motor clutch 7 disengaged) is realized.

[0024] The motor clutch 7 includes a first gear 16 located on the motor 2 side, a second gear 17 located on the differential gear 5 side, a sleeve 18 for controlling the engagement and disengagement states of these gears, and an actuator 8 for driving the sleeve 18. The first gear 16 is connected to the motor 2, for example, via a predetermined first reduction gear. Similarly, the second gear 17 is connected to the differential gear 5 via a predetermined second reduction gear.

[0025] The sleeve 18 has splines on its cylindrical inner surface and is slidably mounted in a direction along the rotation axes of the first gear 16 and the second gear 17. The actuator 8 drives the sleeve 18, engaging the sleeve 18 with the first gear 16 and the second gear 17, thereby engaging the motor clutch 7. Conversely, disengaging this engagement disengages the motor clutch 7. The operating state of the actuator 8 is controlled by an indicator device 22, which will be described later.

[0026] A left wheel speed sensor 11 is provided near the left wheel 13, and a right wheel speed sensor 12 is provided near the right wheel 14. The left wheel speed sensor 11 detects the left wheel speed, which is the wheel speed of the left wheel 13, and the right wheel speed sensor 12 detects the right wheel speed, which is the wheel speed of the right wheel 14. The information on the left wheel speed and the right wheel speed is transmitted to a detection device 21, which will be described later.

[0027] [2. Electronic Control Units] The vehicle drive system 10 is equipped with multiple electronic control units. An electronic control unit is a computer (ECU, Electronic Control Unit) that incorporates a processor (arithmetic processing unit), main memory (storage device), and storage (external storage device). The content of the control performed by each electronic control unit (control program) is stored, for example, in the storage. The content of the control is appropriately read into the main memory and executed by the processor. The vehicle drive system 10 is equipped with a control device 20, a detection device 21, and an instruction device 22.

[0028] The control device 20 is, for example, a HEV (Hybrid Electric Vehicle) ECU that has higher control authority than the detection device 21 and the instruction device 22. The control device 20 suppresses the output of the drive source based on the difference in rotational speed between the left wheel speed and the right wheel speed, and also determines whether to engage or disengage the motor clutch 7 (clutch mechanism) depending on the driving conditions.

[0029] Figure 2(A) is a graph illustrating the relationship between the difference in rotational speed between the left and right axles in the differential gear 5 and the required axle torque. The solid line in the graph represents the torque limit, and the dashed line represents the torque at which seizure may occur in the differential gear 5. The dashed line graph shows that the required axle torque on the vertical axis is approximately inversely proportional to the difference in rotational speed on the horizontal axis. The control device 20 uses this relationship to suppress the output of the drive source.

[0030] If no abnormal condition related to wheel speed or actuator 8 is detected, the control device 20 determines whether to engage or disengage the motor clutch 7 according to the driving conditions. For example, when the electric vehicle is cruising at high speed, the motor clutch 7 is disengaged, and the vehicle enters second parallel mode. This reduces drive losses in the power transmission path on the motor 2 side of the motor clutch 7, improving energy efficiency.

[0031] On the other hand, the control device 20 prohibits the transition of the motor clutch 7 to the disengaged state if it detects an abnormal condition related to the wheel speed or actuator 8 while the motor clutch 7 is engaged. The control device 20 determines whether or not there is an abnormal condition related to the wheel speed or actuator 8 by referring to the operating status of the detection device 21 and the instruction device 22. If no abnormal condition related to the wheel speed or actuator 8 is detected while the motor clutch 7 is engaged, the decision to engage or disengage the motor clutch 7 is made according to the driving conditions as described above.

[0032] Figure 2(B) is a graph illustrating the relationship between motor speed and axle torque. The solid line in the graph represents the torque limit, and the dashed line represents the torque at which seizure may occur in the differential gear 5. The dashed graph shows that the axle torque on the vertical axis is approximately inversely proportional to the motor speed on the horizontal axis. The value obtained by multiplying the motor speed by a predetermined coefficient corresponds to the maximum value of the difference in rotational speed between the left and right sides of the differential gear 5. Therefore, the control device 20 uses this relationship to suppress the output of the drive source and prevent seizure.

[0033] If the control device 20 detects an abnormal condition related to the wheel speed or actuator 8 while the motor clutch 7 is disengaged, it performs control to nearly synchronize the rotational speeds of the first gear 16 and the second gear 17 in the motor clutch 7. That is, the control device 20 increases or decreases the first rotational speed of the first gear 16 (i.e., the motor rotational speed), and determines to engage the motor clutch 7 when the difference between the first rotational speed and the second rotational speed of the second gear 17 falls below a predetermined value.

[0034] The predetermined value referred to here is set in advance as a value that provides "a difference in rotational speed that does not cause excessive shock when the sleeve 18, which rotates at the same speed as the second gear 17, is engaged with the first gear 16." The predetermined value is preferably a relatively small value close to 0. The predetermined value may be a fixed value that does not depend on the rotational speeds of the first gear 16 and the second gear 17, or it may be a variable value that changes according to the rotational speeds of the first gear 16 and the second gear 17.

[0035] When engaging the motor clutch 7, the control device 20 may inform the occupants that a shock may occur. For example, it may activate displays or speakers located around the driver's seat to inform the occupants of the warning. This makes it possible to more reliably communicate to the occupants that the control to engage the motor clutch 7 is an emergency control that responds to failures.

[0036] The detection device 21 is connected to the left wheel speed sensor 11 and the right wheel speed sensor 12 to acquire information on the left and right wheel speeds. The detection device 21 is, for example, an ETACS (Electronic Time and Alarm Control System) ECU that manages the status of electrical components installed in an electric vehicle. The detection device 21 can acquire not only information on the left and right wheel speeds, but also information on the operating status of the main power switch, keyless operation switch, wipers, door mirrors, headlights, etc. The left and right wheel speed information acquired by the detection device 21 is transmitted to the control device 20.

[0037] The control device 20 determines that an abnormal condition related to wheel speed has been detected if the signal transmitted from the detection device 21 to the control device 20 is as follows: Abnormal condition 1. A fault flag has been received from the wheel speed sensors 11 and 12. Abnormal condition 2. No wheel speed information is available. Abnormal condition 3. The wheel speed value is outside the normal range.

[0038] The instruction device 22 is connected to the actuator 8 and outputs a drive signal to the actuator 8 based on the judgment of the control device 20. When the motor clutch 7 is engaged, if the control device 20 prohibits the transition of the motor clutch 7 to the disengaged state, the engaged state of the motor clutch 7 is maintained even when the electric vehicle is cruising at high speed. Also, when the motor clutch 7 is disengaged, if the control device 20 prohibits the transition of the motor clutch 7 to the disengaged state, control is performed to engage the motor clutch after nearly synchronizing the rotational speed of the motor clutch 7.

[0039] The control device 20 determines that an abnormal condition related to the actuator 8 has been detected if the signal transmitted from the instruction device 22 to the control device 20 is as follows: Abnormal condition 4. The actuator 8 fault flag has been received. Abnormal condition 5. There is a poor response from the actuator 8 to the instruction device 22. Abnormal condition 6. There is a poor response from the instruction device 22 to the control device 20. Abnormal condition 7. There has been a predetermined number of consecutive poor responses from the instruction device 22 to the control device 20.

[0040] [3. Flowchart] Figures 3 and 4 are flowcharts showing the control flow to suppress seizure of the differential gear 5. The processes described in this flowchart are repeatedly performed by the control device 20 at a predetermined cycle. In step A1 of Figure 3, it is determined whether or not the motor clutch 7 is engaged. If this condition is met, the process proceeds to step A2; otherwise, the process proceeds to step A7 of Figure 4.

[0041] In step A2, it is determined whether an abnormal condition related to the wheel speed or actuator 8 has been detected based on the signals transmitted from the detection device 21 and the instruction device 22. If this condition is met, the process proceeds to step A3, and the transition to the disengaged state of the motor clutch 7 is prohibited. For example, the transition from series mode, EV mode, or first parallel mode to second parallel mode is prohibited. In the following step A4, the maximum differential rotation speed of the differential 5 is estimated based on the motor rotation speed detected by the resolver 15.

[0042] In the subsequent step A6, the axle required torque is calculated based on the maximum differential rotation speed and the map shown in FIG. 2(A). Thereafter, the output of the drive sources (engine 1 and motor 2) is controlled such that the total torque input to the differential device 5 does not exceed the axle required torque, thereby suppressing the occurrence of seizure of the differential device 5. For example, even if the left wheel speed sensor 11 or the right wheel speed sensor 12 malfunctions, the occurrence of seizure of the differential device 5 can be suppressed.

[0043] If the condition of step A2 is not satisfied, the process proceeds to step A5. In step A5, the differential rotation speeds are calculated based on the left wheel speed detected by the left wheel speed sensor 11 and the right wheel speed detected by the right wheel speed sensor 12. In the subsequent step A6, the axle required torque is calculated based on the differential rotation speed and the map shown in FIG. 2(A). Thereafter, the output of the drive sources (engine 1 and motor 2) is controlled such that the total torque input to the differential device 5 does not exceed the axle required torque, thereby suppressing the occurrence of seizure of the differential device 5. For example, even when the left wheel speed sensor 十一 and the right wheel speed sensor 十二 are not malfunctioning, the occurrence of seizure of the differential device 5 can be suppressed.

[0044] When the motor clutch 7 is in the disengaged state, the process proceeds to step A7 in FIG. 4. For example, in the second parallel mode, the process proceeds to step A7. In step A7, it is determined whether an abnormal state related to the wheel speed or the actuator 8 is detected based on the signals transmitted from the detection device 21 and the instruction device 22. If this condition is satisfied, the process proceeds to step A8. If this condition is not satisfied, the process proceeds to step A13.

[0045] In step A8, the second rotation speed, which is the rotation speed of the second gear 17, is estimated. The second rotation speed is estimated based on, for example, the detection value of the non-faulty one of the left wheel speed sensor 11 and the right wheel speed sensor 12. Alternatively, the second rotation speed is estimated based on the rotation speed of the engine 1. In the subsequent step A9, it is determined whether the difference between the first rotation speed of the first gear 16 and the second rotation speed of the second gear 17 is less than or equal to a predetermined value.

[0046] If the condition of step A9 is not satisfied, the process proceeds to step A10. In step A10, control is performed to increase or decrease the rotation of motor 2. For example, if the first rotational speed is lower than the second rotational speed, the rotation of motor 2 is accelerated. As a result, the first rotational speed increases and the difference between the first rotational speed and the second rotational speed decreases. Also, if the first rotational speed is higher than the second rotational speed, the rotation of motor 2 is decelerated. As a result, the first rotational speed decreases and the difference between the first rotational speed and the second rotational speed decreases.

[0047] Thereafter, the process proceeds to steps A8 and A9 again, and the process of step A10 is repeated until the condition of step A9 is satisfied. When the condition of step A9 is satisfied, the process proceeds to step A11, and the control device 20 instructs the indicating device 22 to connect the motor clutch 7. As a result, the indicating device 22 drives the actuator 8, and the motor clutch 7 is connected by the sleeve 18 fitting into the first gear 16 and the second gear 17. When connecting the motor clutch 7, the control device 20 may operate a display or a speaker to issue an alarm and notify the occupant that there may be a shock.

[0048] In the subsequent step A12, the maximum differential rotational speed of the differential device 5 is estimated based on the motor rotational speed detected by the resolver 15. Also, in the subsequent step A14, the axle required torque is calculated based on the maximum differential rotational speed and the map shown in FIG. 2(A). Thereafter, the output of the drive source (engine 1 and motor 2) is suppressed so that the total torque input to the differential device 5 does not exceed the axle required torque. As a result, for example, even when the left wheel speed sensor 11 or the right wheel speed sensor 12 fails, the occurrence of seizure of the differential device 5 is suppressed.

[0049] If the conditions in step A7 are not met, the process proceeds to step A13. In step A13, the difference in rotational speed is calculated based on the left wheel speed detected by the left wheel speed sensor 11 and the right wheel speed detected by the right wheel speed sensor 12. In the following step A14, the axle required torque is calculated based on the difference in rotational speed and the map shown in Figure 2(A). Subsequently, the output torque of the drive source (engine 1 and motor 2) is suppressed so that the sum of the torques input to the differential 5 does not exceed the axle required torque. This prevents the differential 5 from seizing up, even when, for example, the left wheel speed sensor 11 and the right wheel speed sensor 12 are not malfunctioning.

[0050] [4. Effects] (1) The above-mentioned electric vehicle is equipped with a motor 2 as a first drive source and a second drive source (engine 1, generator 3), and a plurality of drive sources. This electric vehicle is equipped with a differential 5 that distributes the driving force of the drive sources to the left wheel 13 and the right wheel 14, a motor clutch 7 (clutch mechanism) that connects and disconnects the power transmission path between the motor 2 and the differential 5, an actuator 8 that switches the connected and disconnected state of the motor clutch 7, a left wheel speed sensor 11 that detects the left wheel speed, which is the wheel speed of the left wheel 13, and a right wheel speed sensor 12 that detects the right wheel speed, which is the wheel speed of the right wheel 14.

[0051] Furthermore, this electric vehicle is equipped with a control device 20 that suppresses the output of the drive source based on the difference in rotational speed between the left wheel speed and the right wheel speed, and determines whether to engage or disengage the motor clutch 7 according to the driving conditions. The control device 20 prohibits the transition of the motor clutch 7 to the disengaged state if it detects an abnormal condition related to the wheel speed or actuator 8 while the motor clutch 7 is engaged.

[0052] In this way, by prohibiting the disengagement of the motor clutch 7 when an abnormal condition is detected, the output of the drive source can be suppressed based on the rotational speed of the motor 2, thereby preventing the differential 5 from seizing up. Furthermore, since the disengagement of the motor clutch 7 is permitted when no abnormal condition is detected, the drive loss on the motor 2 side can be reduced, for example, when driven only by the second drive source (engine 1, generator 3), thereby improving energy efficiency.

[0053] (2) When the above-mentioned electric vehicle detects an abnormal condition, it estimates the maximum value of the differential rotation speed based on the rotation speed of the motor 2 and suppresses the output of the drive source based on that maximum value. This makes it possible to more reliably avoid seizure of the differential gear 5, even in the event of a failure of, for example, the left wheel speed sensor 11 or the right wheel speed sensor 12. Furthermore, by using the information from the relatively high-precision resolver 15, seizure of the differential gear 5 can be avoided even more reliably.

[0054] (3) The above-mentioned electric vehicle is equipped with a detection device 21 connected to the left wheel speed sensor 11 and the right wheel speed sensor 12 to acquire information on the left wheel speed and the right wheel speed. Furthermore, the above-mentioned abnormal conditions include a failure of the detection device 21 to respond. This makes it possible to suppress burnout of the differential gear 5 due to a failure of the device on the side that inputs information to the control device 20 (sensor failure, disconnection, no signal, sensor signal value outside a predetermined range).

[0055] (4) The above-mentioned electric vehicle is equipped with an instruction device 22 that outputs a drive signal to the actuator 8 based on the judgment of the control device 20. Furthermore, the above-mentioned abnormal conditions include a poor response of the instruction device 22. This makes it possible to avoid malfunctions caused by failures on the instruction device 22 side (failure of the actuator 8, disconnection of wire, no response, abnormal drive signal). In addition, by prohibiting the disengagement of the motor clutch 7, the motor 2 can be kept in a usable state.

[0056] (5) Preferably, the abnormal condition described above is that the indicator device 22 fails to respond for a predetermined number of consecutive times or more. This allows the actuator 8 to be driven when the sleep state is subsequently released, for example, if the indicator device 22 was in a sleep state. Therefore, seizure of the differential 5 can be avoided more reliably.

[0057] (6) The motor clutch 7 has a first gear 16 located on the motor 2 side and a second gear 17 located on the differential gear 5 side. As shown in Figures 3 and 4, when the control device 20 detects an abnormal condition when the motor clutch 7 is disengaged, it increases or decreases the first rotational speed of the first gear 16 and determines to engage the motor clutch 7 after the difference between the first rotational speed and the second rotational speed of the second gear 17 falls below a predetermined value. This suppresses the shock when the motor clutch 7 is engaged, suppresses the output of the drive source based on the rotational speed of the motor 2, and prevents the differential gear 5 from seizing up.

[0058] (7) The control device 20 can estimate the second rotational speed based on the left wheel speed detected by the left wheel speed sensor 11 or the right wheel speed detected by the right wheel speed sensor 12. The information detected by the wheel speed sensor 11, 12 that is not malfunctioning will be a value corresponding to the second rotational speed. Therefore, by using this information, the second rotational speed can be determined with high accuracy, and the shock when the motor clutch 7 is engaged can be suppressed.

[0059] (8) The control device 20 can estimate the second rotational speed based on the rotational speed of the second drive source (engine 1, generator 3). For example, when the engine clutch 6 is engaged, the rotational speed of the second drive source will be a value corresponding to the second rotational speed. Therefore, by using the rotational speed information of the second drive source, the second rotational speed can be easily determined, and shock when the motor clutch 7 is engaged can be suppressed with a simple configuration.

[0060] (9) The control device 20 may notify the occupants of the possibility of a shock occurring when the motor clutch 7 is engaged. The notification to the occupants may be given as an alarm, for example, by the control device 20 activating a display or speaker. This allows the occupants to be informed that engaging the motor clutch 7 is an emergency measure in response to a fail (i.e., in response to the detection of an abnormal condition related to wheel speed or actuator 8).

[0061] [5. Others] The application of the present invention is not limited to plug-in hybrid electric vehicles. For example, the above-described vehicle drive system 10 is applicable to electric vehicles that do not have an engine 1. The above-described vehicle drive system 10 is also applicable to hybrid electric vehicles that do not have an external charging function and an external power supply function. The above-described vehicle drive system 10 is applicable to electric vehicles equipped with a plurality of drive sources, including at least a motor 2 as a first drive source and a second drive source (engine 1, generator 3, second motor not shown, etc.).

[0062] The above-described vehicle drive system 10 includes a control device 20, a detection device 21, and an indicator device 22, but these may be integrated into a single electronic control device. For example, the functions of the detection device 21 and the indicator device 22 may be built into the control device 20. The physical configuration of the control device 20, the detection device 21, and the indicator device 22 can be changed as appropriate, as long as their respective functions are achieved.

[0063] This technology is applicable to the manufacturing industry of electric vehicles (electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, etc.). It is also applicable to the manufacturing industry of vehicle drive systems used in electric vehicles.

[0064] 1. Engine 2. Motor 3. Generator 4. Transaxle 5. Differential 6. Engine clutch 7. Motor clutch (clutch mechanism) 8. Actuator 10. Vehicle drive system 11. Left wheel speed sensor 12. Right wheel speed sensor 13. Left wheel 14. Right wheel 15. Resolver 16. First gear 17. Second gear 18. Sleeve 20. Control device 21. Detection device 22. Indicator device

Claims

1. An electric vehicle comprising a motor as a first drive source and a plurality of drive sources including a second drive source, the electric vehicle comprising: a differential device that distributes the driving force of the drive sources to the left wheel and the right wheel; a clutch mechanism that connects and disconnects the power transmission path between the motor and the differential device; an actuator that switches the connected and disconnected state of the clutch mechanism; a left wheel speed sensor that detects the speed of the left wheel; a right wheel speed sensor that detects the speed of the right wheel; and a control device that suppresses the output of the drive sources based on the difference in rotational speed between the left wheel speed and the right wheel speed, and determines whether to connect or disconnect the clutch mechanism according to the driving state, wherein the control device prohibits the transition of the clutch mechanism to the disconnected state when it detects an abnormal state related to the wheel speed or the actuator while the clutch mechanism is connected.

2. The electric vehicle according to claim 1, characterized in that when the control device detects the abnormal condition, it estimates the maximum value of the differential rotation speed based on the rotation speed of the motor, and suppresses the output of the drive source based on the maximum value.

3. The electric vehicle according to claim 1, further comprising a detection device connected to the left wheel speed sensor and the right wheel speed sensor for acquiring information on the left wheel speed and the right wheel speed, wherein the abnormal condition includes a poor response of the detection device.

4. The electric vehicle according to claim 1, further comprising an instruction device that outputs a drive signal to the actuator based on the judgment of the control device, wherein the abnormal condition includes a poor response of the instruction device.

5. The electric vehicle according to claim 4, characterized in that the abnormal condition is that the instruction device fails to respond for a predetermined number of consecutive times or more.

6. The electric vehicle according to claim 1, wherein the clutch mechanism has a first gear located on the motor side and a second gear located on the differential side, and the control device, when it detects the abnormal state while the clutch mechanism is disengaged, increases or decreases the first rotational speed of the first gear, and determines to engage the clutch mechanism after the difference between the first rotational speed and the second rotational speed of the second gear falls below a predetermined value.

7. The electric vehicle according to claim 6, characterized in that the control device estimates the second rotational speed based on the left wheel speed detected by the left wheel speed sensor or the right wheel speed detected by the right wheel speed sensor.

8. The electric vehicle according to claim 6, characterized in that the control device estimates the second rotational speed based on the rotational speed of the second drive source.

9. The electric vehicle according to any one of claims 6 to 8, characterized in that the control device informs the occupant of the possibility of a shock occurring when the clutch mechanism is engaged.

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