Control unit for an electric vehicle

Abstract

Control unit for an electric vehicle (10) comprising a brake control device (50) for stabilizing vehicle behavior by controlling a friction brake (24) of a vehicle wheel (14, 15, 16, 17): an electric motor (11) which is controlled in a state in which current flows, in which the vehicle wheel (14, 15, 16, 17) is driven by a torque when current flows, and a regenerative state in which the vehicle wheels (14, 15, 16, 17) are braked by a regenerative torque, a slip determination device (50) for determining whether the brake control device (50) is to be actuated on the basis of a slip tendency of the vehicle wheel (14, 15, 16, 17) or not, and a motor control device (40) for controlling a drive state of the electric motor (11) on the basis of a determination result from the slip determination device (50), wherein the motor control means (40) prevents regenerative braking by the electric motor (11) when it has been determined that the result of the determination by the slip determination means (50) is abnormal, wherein the motor control means (40) controls the electric motor (11) to a torque during current flow which is not greater than a predetermined value when it has been determined that the result of the determination by the slip determination means (50) is abnormal, characterized by the fact that the control unit further comprises a vehicle wheel speed sensor (51, 52, 53, 54), wherein the engine control means (40) determines that the determination result of the slip determination means (50) is abnormal if an output voltage of the vehicle wheel speed sensor (51, 52, 53, 54) is outside a predetermined range and / or, wherein the control unit further comprises a brake control unit (50) which includes slip determination means (50) and an EV control unit (40) which includes the engine control means (40) and communicates with the brake control unit (50), wherein the engine control means (40) determines that the determination result of the slip determination means (50) is abnormal if an abnormality in the communication between the brake control unit (50) and the EV control unit (40) has been detected.

Description

Cross-reference to related registrations

[0001] The present application claims priority over Japanese patent application No. 2009-101876, which was filed on April 20, 2009, and which is incorporated herein in its entirety. Background of the invention; Field of the invention

[0002] The present invention relates to a control unit for an electric vehicle, which includes a brake control device for stabilizing the behavior of a vehicle or vehicle behavior by controlling a friction brake of a vehicle wheel. Description of the state of the art

[0003] In an electric vehicle that includes an electric motor to drive a wheel, the electric motor acts as a generator during braking, thus braking the vehicle using regenerative torque generated by the electric motor. However, the braking force obtained through regenerative braking using the electric motor is affected by battery characteristics, etc. Therefore, a braking force of the required strength is typically ensured with consistency by using a friction brake, such as a disc brake, in addition to regenerative braking. Furthermore, when regenerative braking and a friction brake are used in combination, it is important to coordinate the regenerative and friction brakes.

[0004] Furthermore, an electric vehicle is also equipped with a braking control device, such as an anti-lock braking system (ABS). The braking control device estimates the vehicle's behavior based on signals from a wheel speed sensor, an acceleration sensor, etc., and stabilizes the vehicle's behavior by applying the friction brakes to control the braking force applied to each wheel. Additionally, when another braking control device, such as the ABS, is active, a motor control unit simultaneously performs torque control on the electric motor. By controlling the electric motor in this way, coordinated with the braking control device, the vehicle's behavior is further stabilized.

[0005] However, if an abnormality occurs in a control system, such as in the vehicle's wheel speed sensor or in a communication network, the motor control unit may not be able to determine the operating state of the brake control device, and therefore the brake control device and the electric motor cannot be properly coordinated. For example, if coordinated control of the brake control device and the electric motor becomes difficult, regenerative torque may be generated by the electric motor even though ABS control is active. If the electric motor is controlled in this way, the vehicle's wheels may lock up, leading to instability in vehicle behavior, and as a result, the steering stability of the electric vehicle may deteriorate.

[0006] Document JP H11-45 03 A discloses a regenerative braking device that receives target value information for the regenerative braking torque from a hydraulic braking device, and the regenerative braking torque is controlled to approximate a target value for the regenerative braking torque in the regenerative braking device. The hydraulic braking device receives information about the actual regenerative braking torque value from the regenerative braking device, and the vehicle's braking system is controlled to achieve a hydraulic braking torque target value in the hydraulic braking device, the magnitude of which is the difference between the actual regenerative braking torque and the overall braking torque target value. If the information about the actual regenerative braking torque value is not received normally, the regenerative braking torque target value is reduced and set to zero.Since the vehicle is only braked by the hydraulic deceleration torque, the braking system for the vehicle can be controlled perfectly so that the total braking torque reaches the target total deceleration torque.

[0007] Document DE 10 2007 022 849 A1 discloses a device for influencing the driving behavior of a vehicle. The vehicle's efficiency can be improved by providing a system comprising several electric machines, each assigned to one of the vehicle's wheels and capable of operating either as a motor or generator. The electric machines are preferably connected to a control unit that can individually control them to accelerate, decelerate, and / or generate a yaw moment about the vehicle's vertical axis.

[0008] Document DE 44 35 953 A1 discloses an electrically powered vehicle with a drive system comprising at least one electric motor, which is controlled and monitored by an electronic control unit to drive at least one vehicle wheel in a drive mode of the motor and to optionally contribute to the total braking torque when the motor is operated in a braking mode.It also includes a hydraulic braking system operated by the driver and acting on at least one of the vehicle's front wheels, wherein the hydraulic braking torque generated by the driver through the hydraulic braking system is adjusted in such a way that, for modulating the total braking torque acting on the vehicle's wheels, the change in the electric braking torque is arranged so that it remains within the regenerative range of the electric motor's operation, at least under predetermined vehicle operating conditions.

[0009] Document DE 196 02 359 A1 discloses a method and a circuit arrangement for monitoring a speed sensor consisting of a rotating sensor in the form of a toothed disc or the like and a stationary transducer, for which momentary changes or dips in the sensor output signal, which recur after each full revolution of the wheel, are detected and evaluated for fault detection. If this fault occurs within a predetermined number of consecutive wheel revolutions, this results in fault detection.

[0010] Document JP H10-297 462 A discloses a brake force control device fitted to an electric vehicle that prevents the generation of a driving force during braking and prevents the brakes from being effective during ABS control. The purpose is to prevent the vehicle from stalling. For this purpose, a wheel slip ratio equal to a predetermined threshold is used. When the value exceeds 0, the ABS control is initiated. During ABS operation, in a state where the slip ratio exceeds the threshold, the hydraulic braking force and the regenerative braking force are reduced simultaneously. The slip ratio is the threshold value, and the regenerative braking force is held constant while the hydraulic braking force decreases gradually. When the regenerative braking force is reduced to zero, a further reduction of the regenerative braking force is prevented. Therefore, the regenerative braking force is not a negative value. Summary of the invention

[0011] One object of the present invention is to improve the stability of an electric vehicle by appropriately controlling an electric motor, even in cases where the coordinated control of a brake control device and the electric motor is difficult.

[0012] A control unit according to the invention for an electric vehicle is a control device for an electric vehicle, which has a brake control device for stabilizing the vehicle behavior by controlling a friction brake of a vehicle wheel, and includes: an electric motor which is controlled into a state in which current flows, in which the vehicle wheel is driven by a torque when current is flowing, and a regenerative state in which the vehicle is braked by a regenerative torque, a slip orA slip determination device for determining whether or not to actuate the brake control device based on a slip / slip tendency of the vehicle wheel, and a motor control device for controlling a drive state of the electric motor based on a determination result of the slip determination device, wherein the motor control device prevents regenerative braking by the electric motor if it has been determined that the determination result of the slip determination device is abnormal.

[0013] In the control unit according to the invention for an electric vehicle, the motor control means controls the electric motor to a torque at flowing current that is not greater than a predetermined value if it has been determined that the determination result of the slip determination means is abnormal.

[0014] In the control unit according to the invention for an electric vehicle, the torque is changed based on a driving condition when current is flowing through the electric motor.

[0015] In the control unit according to the invention for an electric vehicle, the motor control means controls a torque acting on the vehicle wheel towards zero by controlling the electric motor to the torque when current is flowing, which is not greater than the predetermined value.

[0016] In the control unit according to the invention for an electric vehicle, the brake control device is an anti-lock braking system to prevent the vehicle wheel from locking up during braking.

[0017] According to the invention, regenerative braking by the electric motor is prevented if it has been determined that the result of the slip determination is abnormal, and therefore the vehicle behavior can be stabilized, leading to an improvement in the stability of the electric vehicle. Brief description of the drawing Fig. Figure 1 is a schematic representation showing the configuration of an electric vehicle. Fig. 2 is a block diagram showing the connection states of various elements in relation to a brake control unit, Fig. 3 is a flowchart that shows an example of the process of engine torque control during vehicle braking. Fig. 4A is a timing diagram showing an engine torque control state when an ABS control system is normal, and Fig. 4B is a timing diagram showing the engine torque control state when an ABS control system is abnormal, and Fig. Figure 5 is an illustrative view showing a torque map of a motor-generator. Description of preferred embodiments

[0018] One embodiment of the present invention is described in detail below with reference to the drawing. Fig. Figure 1 is a schematic representation showing the configuration of an electric vehicle 10. The control unit for an electric vehicle according to an embodiment of the present invention is used in the electric vehicle 10. As shown in Fig. As shown in Figure 1, the electric vehicle 10 is equipped with a motor-generator (electric motor) 11 to drive a vehicle wheel. A drive shaft 13 is coupled to the motor-generator 11 via a gear transmission 12, and the vehicle wheels 14 and 15 are coupled to the drive shaft 13. When the motor-generator 11 is controlled in a current-flowing state, it can function as a motor that delivers torque when current is flowing, and as a result, the vehicle wheels 14 and 15 can be driven. Conversely, when the motor-generator 11 is controlled in a regenerative state, it can function as a power generator that delivers regenerative torque, and as a result, the vehicle wheels 14 and 15 can be braked. The electric vehicle 10 is also equipped with a high-voltage battery unit 18, which serves as a power supply for the motor-generator 11.For example, a 400 V lithium-ion battery is used as a high-voltage battery unit 18.

[0019] An inverter 20 is connected to the motor-generator 11, and the high-voltage battery unit 18 is connected to the inverter 20 via current-carrying cables 21 and 22. When the motor-generator 11 is operated as a motor, a direct current from the high-voltage battery unit 18 is converted into an alternating current by the inverter 20, and this alternating current supplies the motor-generator 11. Conversely, when the motor-generator 11 is operated as a power generator, an alternating current from the motor-generator 11 is converted into a direct current by the inverter 20, and this is supplied to the high-voltage battery unit 18.

[0020] Furthermore, by controlling the current value and frequency of the alternating current using the inverter 20, the torque and rotational speed of the motor-generator 11 can be controlled. It should be noted that the current-carrying cables 21 and 22, which are connected to the high-voltage battery unit 18, are equipped with a main relay 23.

[0021] Furthermore, the electric vehicle 10 is provided with a friction brake 24 to brake the respective vehicle wheels 14 to 17. The friction brake 24 comprises a master cylinder 26, which, upon depression of a brake pedal 25 by a driver, generates an oil pressure, and brake calipers 27, which brake the respective vehicle wheels 14 to 17 using the oil pressure from the master cylinder 26. A hydraulic unit 28 is also provided between the master cylinder 26 and the brake calipers 27 for controlling (increasing, maintaining, and decreasing) the oil pressure supplied to the respective brake calipers 27. The hydraulic unit 28 includes a plunger pump, a solenoid valve, a reservoir, etc., which are not shown in the drawing. A vacuum brake booster 29 is also attached to the master cylinder 26, and an electric vacuum pump 30 is connected to the vacuum brake booster 29.

[0022] It should be noted that the friction brake shown in the drawing is a disc brake, but the present invention is not limited to this and a drum brake can instead be provided as the friction brake 24.

[0023] The electric vehicle 10 is further equipped with an electric vehicle control unit (EVCU) 40, which performs the overall control of the electric vehicle 10. A sensor 42 of an accelerator pedal or drive foot lever, for detecting the degree of actuation of an accelerator pedal or drive foot lever 41, a brake pedal sensor 43, for detecting the degree of actuation of the brake pedal 25, a vehicle speed sensor 44, for detecting the speed of the vehicle, a range switch 46, for detecting an operating position of a selector lever 45, etc., are connected to the EVCU 40. Based on various signals, the degree of actuation of the accelerator pedal 41, the degree of actuation of the brake pedal 25, the speed of the vehicle, the area position, etc., the EVCU 40 sets a target torque and a target rotational speed of the motor-generator 11, and based on these target values, the EVCU 40 outputs a control signal to the inverter 20.In other words, the EVCU 40 serves as an engine control unit.

[0024] For example, the EVCU 40 determines the torque of the motor-generator 11 during current flow with reference to a torque map during current flow, based on the vehicle speed and the degree of deactivation of the accelerator pedal 41. Furthermore, the EVCU 40 determines the regenerative torque of the motor-generator 11 with reference to a regenerative torque map, based on the vehicle speed and the degree of deactivation of the brake pedal 25. The EVCU 40 determines the target torque by adding the torque during current flow and the regenerative torque and outputs a control signal to the inverters 20 based on the target torque.It should be noted that when the accelerator pedal 41 and the brake pedal 25 are both pressed, the torque at current flowing through the motor-generator 11 can be limited by setting a limiting factor, which can be determined according to the degree of actuation of the brake pedal 25, and by multiplying the limiting factor by the torque at current flowing.

[0025] The electric vehicle 10 is further equipped with a brake control unit (ABSCU) 50 to control the operating state of the friction brake 24. Fig. Figure 2 is a block diagram showing the connection states of various elements in relation to the ABSCU 50. As shown in Fig. 1 and Fig. As shown in Figure 2, vehicle wheel speed sensors 51 to 54, for detecting the rotational speed of the respective vehicle wheels 14 to 17 (vehicle wheel speeds), an acceleration sensor for forward-reverse accelerations 55, for detecting acceleration in the forward-reverse direction of the vehicle, an acceleration sensor for lateral accelerations 56, for detecting acceleration in the lateral direction of the vehicle, a steering wheel angle sensor 57, for detecting steering angle and steering direction of a steering device, oil pressure sensors 58 to 61, for detecting oil pressure of a brake line, etc., are connected to the brake control unit 50. Based on the detection signals from the various sensors 51 to 61, the brake control unit 50 estimates the vehicle's behavior and calculates a braking force to be applied to the respective vehicle wheels 14 to 17 in order to stabilize the vehicle's behavior.The brake control unit 50 then sets the oil pressure with which the respective brake calipers 27 are supplied (hereinafter referred to as brake oil pressure) by controlling the hydraulic unit 28 so that the braking force calculated with respect to each vehicle wheel 14 to 17 is achieved.

[0026] For example, during vehicle braking with the brake pedal 25 depressed, the brake control unit 50 estimates the vehicle body speed based on signals from various sensors and calculates a slip / slip ratio of the vehicle wheels 14 to 17 based on the vehicle body speed and the speeds of the vehicle wheels. If the slip ratio of the vehicle wheels 14 to 17 exceeds a predetermined limit, or in other words, if the vehicle wheels 14 to 17 show a tendency to lock up, the brake control unit 50 activates the hydraulic unit 28 to control the brake fluid pressure, thereby controlling the braking forces of the respective vehicle wheels 14 to 17 to stabilize the vehicle's behavior.Consequently, the friction brake 24 and the brake control unit 50 together form an anti-lock braking device (brake control unit) to prevent the vehicle wheels 14 to 17 from locking up during braking, or in other words, an anti-lock braking system (hereinafter referred to as ABS). Furthermore, when the brake fluid pressure is reduced to restore the vehicle wheels 14 to a rotating state, a control signal is output from the EVCU 40 to the inverter 20, according to the operating state of the ABS, thereby controlling the motor-generator 11 into a state in which current flows and in which a predetermined torque is delivered with current flow.

[0027] Furthermore, the brake control unit 50 calculates a desired target behavior of the driver based on detection signals from the steering angle sensor 57, the accelerator pedal sensor 42, the brake pedal sensor 43, etc., and calculates actual vehicle behavior based on signals from the forward / reverse acceleration sensor 55, the lateral acceleration sensor 56, the vehicle wheel speed sensors 51 to 54, etc. The brake control unit 50 then determines a degree of understeer or oversteer based on the target behavior and the actual behavior, and if the brake control unit 50 determines that the vehicle wheels are slipping due to unstable vehicle behavior, orIf the vehicle begins to slip, the brake control unit 50 activates the hydraulic unit 28 to control the brake oil pressure and thereby adjust the braking force applied to the vehicle wheels 14 to 17 to stabilize the vehicle's behavior. By configuring the brake control device with the friction brake 24 and the brake control unit 50 in this way, the brake control device performs a so-called vehicle dynamics control (hereinafter referred to as VDC).

[0028] It should be noted that when the braking force of the vehicle wheels 14 to 17 is adjusted by the VDC control, the motor torque exerted by the motor-generator 11 is also controlled simultaneously to stabilize the vehicle behavior.

[0029] As in Fig. As shown in Figure 2, the brake control unit 50 is further equipped with a self-diagnostic unit 50a to determine the presence of an abnormality in the ABS control system. For example, if the output voltages of the vehicle wheel speed sensors 51 to 54 deviate from a prescribed range, this indicates that the vehicle wheel speed sensors 51 to 54 are not operating normally, and therefore the self-diagnostic unit 50a determines that an abnormality has occurred in the ABS control system. Furthermore, during ABS control, the friction brake 24 and the motor-generator 11 are controlled in a coordinated manner; therefore, the self-diagnostic unit 50a also determines that an abnormality has occurred in the ABS control system if an abnormality is found in the communication between the EVCU 40 and the brake control unit 50.It should be noted that the diagnostic object of the self-diagnostic unit is not limited to an abnormality in the communication between the vehicle wheel speed sensors 51 to 54 and the units 40 and 50, and in a case where, for example, the forward-reverse acceleration sensor 55, the lateral acceleration sensor 56, the steering angle sensor 57, etc. are used for ABS control, the self-diagnostic unit 50a can determine the presence of an abnormality affecting the ABS control system according to output signals from these sensors 55 to 57.

[0030] As in Fig. As shown in Figure 1, the electric vehicle 10 is equipped with a battery control unit (BCU) 70 to control the charging and discharging of the high-voltage battery unit 18. A low-voltage battery unit 72 is connected to the high-voltage battery unit 18 via a DC-DC converter 71. A 12 V lead-acid battery, for example, is used as the low-voltage battery unit 72. The low-voltage battery unit 72 serves as a power supply for the inverter 20, the converter 71, and the respective control units 40, 50, and 70, and also as a power supply for an air conditioner, headlights, etc., which are not shown in the drawing. Furthermore, a communication network 73 is installed in the electric vehicle 10, and the EVCU 40, the brake control device 50, the inverter 20, the battery control unit 70, the converter 71, etc., are interconnected via the communication network 73.

[0031] Next, a torque control of a motor, which is carried out during vehicle braking, in which the brake pedal 25 is pressed, is described. Fig. Figure 3 is a flowchart showing an example of a torque control procedure for a motor, executed during vehicle braking. As shown in Fig. As shown in Figure 3, step S10 determines whether the brake pedal is pressed or not. If the brake pedal is pressed, the process proceeds to step S11, which determines whether an abnormality has occurred in the ABS control system, or more precisely, whether an abnormality has occurred in the vehicle wheel speed sensors 51 to 54, the communication network 73, etc. If step S11 determines that the ABS control system is normal, the process proceeds to step S12, which determines whether a braking condition requiring ABS control has been detected. In step S12, the brake control unit (the slip determination device) 50 estimates the vehicle body speed based on the signals from the various sensors and calculates the slip or braking force.The slip ratio (tendency to slip) of the vehicle wheels 14 to 17 is determined based on the vehicle body speed and the speeds of the vehicle wheels. If the slip ratio of the vehicle wheels 14 to 17 exceeds a predetermined threshold, in other words, if the vehicle wheels 14 to 17 exhibit a tendency to lock up, the brake control unit 50 decides to execute ABS control to stabilize the vehicle behavior by controlling the braking force applied to the vehicle wheels 14 to 17. After the brake control unit 50 has decided to execute ABS control, it outputs an ABS control signal (determination result) to the EVCU 40, indicating that the ABS is operational. It should be noted that the slip ratio is used as an index to determine the slip or...to specify the slip tendency of the vehicle wheels 14 to 17, however the invention is not limited to this, and instead, for example, the determination of whether an ABS control should be implemented can be carried out by determining the slip tendency of the vehicle wheels 14 to 17, based on a rotation difference between the respective vehicle wheels 14 to 17.

[0032] As described above, if in step S12 it was determined that the slip ratio of the vehicle wheels 14 to 17 exceeds the predetermined threshold, and therefore an ABS control action was initiated, the process proceeds to step S13, in which the regenerative torque of the motor-generator 11 is set to zero. The process then proceeds to step S14, in which the torque during current flow of the motor-generator 11 is determined based on the operating state of the ABS. In step S15, the target torque is determined by adding the regenerative torque and the torque during current flow, and in the subsequent step S16, the torque control of the motor at the motor-generator 11 is executed based on the target torque.Consequently, when the ABS system is functioning normally and ABS control is executed during vehicle braking, the torque is delivered by the motor-generator 11 according to the ABS operating state. As a result, the brake fluid pressure is reduced by the ABS control, and the vehicle wheels 14 to 17 can be reliably returned to a rotating state, thereby stabilizing the vehicle's behavior.

[0033] If in step S12 it was determined that the slip ratio of the vehicle wheels 14 to 17 is smaller than the predetermined threshold, and therefore it was decided not to execute ABS control, the process continues to step S17, in which the regenerative torque of the motor-generator 11 is determined on the basis of the vehicle braking condition.

[0034] The process continues to step S18, in which the torque of the motor-generator 11 is set to zero when current is flowing. Next, as described above, the target torque is determined by adding the regenerative torque to the torque when current is flowing in step S15, and in the following step S16, the motor control of the motor-generator 11 is executed based on the target torque. Therefore, if the ABS control system is functioning normally and ABS control is not executed during vehicle braking, a regenerative torque is exerted by the motor-generator 11 according to the braking condition. This results in regenerative braking by the motor-generator 11, so that kinetic energy from the electric vehicle 10 is converted into electrical energy and stored.

[0035] Meanwhile, in step S11, it was determined that an abnormality had occurred in the ABS control system. In other words, if it was determined that an ABS operating signal to the EVCU 40 was abnormal, the process proceeds to step S19, in which regenerative braking by the motor-generator 11 is prohibited. The process then proceeds to step S18, in which the torque at current flow to the motor-generator 11 is set to a predetermined value T1. It should be noted that the torque at current flow T1, set in step D20, is a minimum torque required to return the vehicle wheels 14 and 15 to a state of rotation.Then, as described above, the target torque is determined by adding together the regenerative torque and the torque during current flow in step D15, and in the following step S16, we execute the motor control of the motor-generator 11 based on the target torque.

[0036] Consequently, if an abnormality occurs in the ABS control system, if the operating state of the ABS cannot be detected by the EV control unit 40, or if it is suspected that the ABS is not operating normally, regenerative braking by the motor-generator 11 is prohibited, regardless of the operating conditions of the ABS. By prohibiting regenerative braking by the motor-generator 11 in advance in this way, it is possible to prevent the vehicle wheels from locking up, thereby stabilizing vehicle behavior even if the ABS is suddenly activated before the EVCU 40 has received the ABS operating signal, and consequently improving the stability of the electric vehicle 10.Furthermore, the motor-generator 11 is driven by electricity and applies the torque when current flows T1, and therefore the vehicle wheels can be actively returned from a blocked state to a rotational state, which enables a further improvement in the stability of the electric vehicle 10.

[0037] Fig. 4A is a timing diagram showing an engine torque control state when the ABS control system is normal, and Fig. Figure 4B is a timing diagram showing the engine torque control status when the ABS control system is abnormal. Furthermore, Fig. Figure 5 is an illustrative view showing a torque characteristic (torque during current flow, regenerative torque) of the motor-generator 11. It should be noted that the following applies: Fig. The torque map shown in section 5 is referenced when the selector lever 45 has been moved to a driving range.

[0038] As in Fig. As shown in Figure 4A, if a diagnostic result of the ABS control system is normal, the determination of whether or not to execute ABS control is based on the slip ratio of the vehicle wheels, and the engine torque control is executed based on the operating state of the ABS. More precisely, if the slip ratio is less than the predetermined threshold, so that ABS control is not executed, the motor-generator 11 is controlled into a regenerative state in which regenerative torque is output. Conversely, if the slip ratio exceeds the predetermined threshold, so that ABS control is executed, the motor-generator 11 is controlled into a current-flow state in which torque is output.

[0039] As in Fig. Figure 4B shows, on the other hand, that if the diagnostic result of the ABS control system indicates an abnormality, regenerative braking by the motor-generator 11 is immediately prohibited, and the motor-generator 11 is subjected to an electric current drive, so that the torque is output when current T1 flows. More precisely, as shown in Fig. Figure 5 shows that when an abnormality occurs in the ABS control system, setting regenerative torque values ​​Ta and Tb in the motor-generator 11 is prohibited, and the torque during current flow in the motor-generator 11 is set as T1. Consequently, when an abnormality is found in the ABS control system, the motor-generator 11 is controlled to prevent the vehicle wheels 14 and 15 from locking up, and therefore the vehicle behavior of the electric vehicle 10 can be stabilized, leading to improved stability. It should be noted that the in Fig. 5 shown regenerative torque Tb, a torque that is set to prevent the vehicle from moving backwards on a steep incline.

[0040] As described above, if an abnormality occurs in the ABS control system, the torque is delivered by the motor-generator 11 when current T1 flows. However, this torque is not limited to a fixed value and can be increased or decreased according to the vehicle speed and the resistance of the road surface, which serve as driving conditions. As described in Fig.As shown in Figure 5, if an abnormality occurs in the ABS control system, an upper limit of the torque during current flow can be reduced from Tm1 to Tm2 (predetermined values), after which the torque during current flow is increased and decreased within a range from zero to Tm2 according to the driving conditions. Furthermore, if an abnormality occurs in the ABS control system, the reduced upper limit Tm2 of the torque during current flow can be controlled according to driving conditions such as vehicle speed and road surface resistance. Therefore, the torque during current flow of the motor-generator 11 can be appropriately controlled according to the driving conditions, and as a result, the vehicle behavior can be more appropriately controlled.

[0041] Furthermore, the magnitude of the torque during current flow, which is determined when an abnormality occurs in the ABS control system, is preferably set such that the torque acting on the vehicle wheels 14 and 15 is zero. In other words, the control is designed to prevent the vehicle wheels 14 and 15 from accelerating or decelerating depending on the torque during current flow supplied by the motor-generator 11. This prevents the vehicle's behavior from being destabilized by the motor-generator 11, and as a result, an improvement in steering stability can be achieved.Furthermore, by reducing the torque during current flow when an abnormality occurs in the ABS control system, the current throughput of the electric vehicle 10 can be reduced, and therefore driving conditions requiring ABS operation can be avoided in advance, and the driver can be informed about the abnormality in the ABS control system.

[0042] Furthermore, in the foregoing description, regenerative braking by the motor-generator 11 is prohibited if an abnormality occurs in the ABS control system, such that the motor-generator 11 is subjected to a current drive; however, the present invention is not limited thereto, and regenerative braking in the motor-generator 11 can also be prohibited in such a way that the motor-generator 11 is likewise controlled in a current-flowing state if an abnormality is found in the VDC control system, or in other words, in the vehicle wheel speed sensors 51 to 54, the forward-reverse acceleration sensor 55, the lateral acceleration sensor 56, the steering angle sensor 57, the communication network 73, etc.By controlling the motor-generator 11 to prevent the vehicle wheels 14 to 15 from slipping when an abnormality is found in the VDC control system, the vehicle behavior of the electric vehicle 10 can also be stabilized, which allows for an improvement in stability.

Claims

[1] Control unit for an electric vehicle (10) comprising a brake control device (50) for stabilizing vehicle behavior by controlling a friction brake (24) of a vehicle wheel (14, 15, 16, 17), comprising: an electric motor (11) which is controlled in a state in which current flows, in which the vehicle wheel (14, 15, 16, 17) is driven by a torque when current flows, and a regenerative state in which the vehicle wheels (14, 15, 16, 17) are braked by a regenerative torque, a slip determination device (50) for determining whether the brake control device (50) is to be actuated on the basis of a slip tendency of the vehicle wheel (14, 15, 16, 17) or not, and a motor control device (40) for controlling a drive state of the electric motor (11) on the basis of a determination result from the slip determination device (50), wherein the motor control means (40) prevents regenerative braking by the electric motor (11) when it has been determined that the result of the determination by the slip determination means (50) is abnormal, wherein the motor control means (40) controls the electric motor (11) to a torque during current flow which is not greater than a predetermined value when it has been determined that the result of the determination by the slip determination means (50) is abnormal, characterized by , that the control unit further comprises a vehicle wheel speed sensor (51, 52, 53, 54), wherein the engine control means (40) determines that the determination result of the slip determination means (50) is abnormal if an output voltage of the vehicle wheel speed sensor (51, 52, 53, 54) is outside a predetermined range and / or, wherein the control unit further comprises a brake control unit (50) which includes slip determination means (50) and an EV control unit (40) which includes the engine control means (40) and communicates with the brake control unit (50), wherein the engine control means (40) determines that the determination result of the slip determination means (50) is abnormal if an abnormality in the communication between the brake control unit (50) and the EV control unit (40) has been detected. [2] Control unit for an electric vehicle (10) according to claim 2, wherein the torque is controlled on the basis of a driving condition when current flows through the electric motor (11). [3] Control unit for an electric vehicle (10) according to claim 2 or 3, wherein the motor control means (40) controls a torque acting on the vehicle wheel (14, 15, 16, 17) towards zero by controlling the electric motor (11) to the torque during current flow which is not greater than the predetermined value. [4] Control unit for an electric vehicle (10) according to one of claims 1 to 3, wherein the brake control device (50) is an anti-lock brake control device (50) to prevent the vehicle wheel (14, 15, 16, 17) from locking up during vehicle braking.

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