Vehicle control device

Abstract

The invention provides a vehicle control device capable of suppressing power consumption of a steering actuator and preventing overheating of the steering actuator when necessary. The present invention is provided with: an electric motor (7) that generates steering force for steering rear wheels; and a trapezoidal screw (26) that converts rotational motion generated by driving of the electric motor (7) into axial linear motion for steering the rear wheels, and is configured so as to set a target steering angle of the rear wheels on the basis of steering of the steering wheel by a passenger, and to detect a current steering angle of the rear wheels. In a state in which the target steering angle of the rear wheel differs from the current steering angle of the rear wheel, control is performed such that the target steering angle of the rear wheel is adjusted on the basis of the accumulated current supplied to the electric motor (7). An energization state in which current is supplied to the electric motor (7) so that the current rear wheel rotation angle approaches the target rotation angle, and a cut-off state in which the current to the electric motor (7) is cut off are alternately switched between the energization state and the cut-off state.

Description

Technical Field

[0001] The present invention relates to a vehicle control device for a vehicle capable of controlling the turning angle of a rear wheel. Background Art

[0002] Conventionally, as a method of steering a vehicle, two-wheel steering (2Wheel Steering, hereinafter referred to as 2WS) in which only the front wheels are steered based on steering operation of a steering wheel by a passenger, and four-wheel steering (4Wheel Steering, hereinafter referred to as 4WS) in which the front wheels and the rear wheels are steered separately are known. Although 4WS has a problem of increased structural complexity compared to 2WS, there are many excellent advantages such as reducing inner circle difference, reducing turning radius, anti-slip on icy roads, and stable lane change in high-speed areas.

[0003] Here, in a vehicle that steers the rear wheels as in the above 4WS, for example, when setting the target turning angle of the rear wheel based on the steering operation of the vehicle's steering wheel and the current turning angle of the rear wheel (hereinafter, referred to as the actual turning angle) is different from the target turning angle, a steering actuator that is a drive source of the steering mechanism is driven and controlled so as to approach the target turning angle. For example, an electric motor is used as the steering actuator. However, assuming that smooth steering of a heavy vehicle and static steering during parking are also performed, the output (power consumption) of the electric motor is set to be large. There is a problem that if a large current flows through the electric motor for a long time, the durability will be reduced due to overheating. Therefore, for example, Japanese Patent Laid-Open No. 2009-298300 proposes the following technique: when the difference between the actual turning angle and the target turning angle of the rear wheel is equal to or greater than a threshold value, intermittent power supply in which switching is alternately performed is shifted without continuous power supply, thereby suppressing power consumption and preventing overheating of the electric motor.

[0004] Patent Document 1: Japanese Patent Laid-Open No. 2009-298300 (paragraphs 0111-0118, FIG. 14)

[0005] In the above Patent Document 1, although the intermittent power supply mode is shifted when the difference between the actual turning angle and the target turning angle of the rear wheel, which is expected to have a particularly large amount of power supply to the electric motor, is equal to or greater than the threshold value, for example, when a passenger slowly steers the steering wheel for a long time, that is, although the difference between the actual turning angle and the target turning angle of the rear wheel is small, there is a problem that the intermittent power supply mode is not shifted in a situation where the actual turning angle and the target turning angle of the rear wheel continue to be different for a long time. Here, the heat generation amount of the electric motor is proportional to the square of the time integral of the current flowing through the motor inverter. Therefore, even if the difference between the actual turning angle and the target turning angle of the rear wheel is small, when the steering wheel is continuously and slowly steered and the current flows for a long time, the heat generation amount becomes very large. Summary of the Invention

[0006] The present invention is completed to solve the above-mentioned existing problems, and the purpose is to provide a vehicle control device that can suppress the power consumption of a steering actuator and prevent overheating of the steering actuator in a required situation regardless of how a passenger turns and operates the steering wheel.

[0007] To achieve the above object, the vehicle control device of the present invention includes: an electric steering actuator that generates a steering force for turning the rear wheels; a trapezoidal thread that converts the rotational motion generated based on the drive of the steering actuator into a linear motion in the axial direction for turning the rear wheels; a target angle setting mechanism that sets a target angle of the rear wheels based on the turning operation of the steering wheel by the passenger; an angle detection mechanism that detects the current angle of the rear wheels; and a power supply control mechanism that controls the power supply state of the steering actuator. The power supply control mechanism controls the power supply state of supplying current to the steering actuator and the cut-off state of cutting off the current to the steering actuator to be alternately switched in a state where the turning operation is in a direction away from the neutral position and the target angle of the rear wheels is different from the current angle of the rear wheels, and the current value supplied to the steering actuator in the power supply state gradually increases over time.

[0008] In addition, "cutting off the current" does not necessarily mean only the case where the current supplied to the steering actuator is completely set to 0, and any state less than the power supply state is acceptable.

[0009] According to the vehicle control device of the present invention having the above structure, by switching between the power supply state of supplying current to the steering actuator and the cut-off state of cutting off the current to the steering actuator, regardless of how the passenger turns the steering wheel, it is possible to suppress the power consumption of the steering actuator in a required situation and prevent overheating of the steering actuator. In addition, in the cut-off state where the drive of the steering actuator is not performed, the current angle of the rear wheels can be maintained by the trapezoidal thread, so that even immediately after returning to the power supply state, the pursuit of the target angle can be started again immediately. Description of the Drawings

[0010] Figure 1 is a schematic diagram of the structure of the vehicle of this embodiment.

[0011] Figure 2 is a cross-sectional view of the rear-wheel steering device of this embodiment cut along the rotation axis of the drive shaft (rear-wheel shaft).

[0012] Figure 3 is a diagram for explaining the trapezoidal thread.

[0013] Figure 4 is a diagram for explaining the trapezoidal thread.

[0014] Figure 5It is a block diagram showing the structure of the vehicle control device of the present embodiment.

[0015] Figure 6 It is a flowchart of the vehicle control processing program of the present embodiment.

[0016] Figure 7 It is a diagram for explaining the current control of the electric motor in the past and the present embodiment.

[0017] Figure 8 It is a diagram for explaining the method of setting the time for cutting off the current.

[0018] Figure 9 It is a diagram showing an example of the transition of the target rear wheel angle, the actual angle, and the current value supplied to the electric motor 7 when the vehicle control based on the vehicle control processing program is performed.

[0019] Explanation of reference numerals

[0020] 1... Vehicle control device, 2... Vehicle, 3... Vehicle body, 4... Steering wheel, 5... Power steering device, 6... Rear wheel steering ECU, 7... Electric motor (steering actuator), 8... Rear wheel steering device, 9A to 9D... Wheels, 13... Torque sensor, 23, 24... Drive shafts, 26... Trapezoidal thread, 27... Resolver, 28... Stroke sensor, 41... CPU. Detailed description of the specific embodiment

[0021] Hereinafter, an embodiment in which the vehicle control device of the present invention is embodied will be described in detail with reference to the drawings. First, the vehicle 2 equipped with the vehicle control device 1 of the present embodiment will be described below. Figure 1 It is a schematic diagram of the structure of the vehicle 2 of the present embodiment.

[0022] Here, the vehicle 2 can be, for example, an automobile (internal combustion engine vehicle) having an internal combustion engine (engine, etc.) as a drive source, an automobile (electric vehicle, fuel cell vehicle, etc.) having an electric motor (motor, etc.) as a drive source, or an automobile (hybrid vehicle) having both of them as drive sources. In addition, regardless of the vehicle type, it can be a passenger car, a commercial large truck, a bus, etc. In addition, as long as it has front wheels and rear wheels, it can also be a forklift, a construction machine, etc.

[0023] In addition, the vehicle 2 of the present embodiment is a vehicle that adopts four-wheel steering (4WS), which controls the turning angles of the front wheels and the rear wheels separately based on the driver's steering operation of the steering wheel, particularly as a steering control method. Although the structure of 4WS includes a mechanical type in which the steering operation of the front wheels is mechanically transmitted to the rear wheels via an input gearbox on the front wheel side and a steering gearbox on the rear wheel side, and an electronically controlled type in which the rear wheels are steered electronically by controlling actuators, various valves, etc. based on the steering amount, in the present embodiment, an example of the electronically controlled type is used for explanation. That is, it is assumed that the steering wheel and the rear wheels are not mechanically connected but are connected by a wire (electrical communication).

[0024] As Figure 1 shown, the vehicle 2 includes: a vehicle body 3; a steering wheel 4 that is an operation object operated by a passenger; a power steering device 5 that assists the steering operation of the steering wheel 4; a rear-wheel steering control ECU (electronic control unit) 6; a rear-wheel steering device 8 that includes an electric motor (steering actuator) 7 as a drive source and steers the rear wheels based on converting the rotational motion of the electric motor 7 into a linear motion in the axial direction for turning the rear wheels; and wheels 9A to 9D. In the following description, the left front wheel is designated as 9A, the right front wheel is designated as 9B, the left rear wheel is designated as 9C, and the right rear wheel is designated as 9D. In addition, a vehicle control device 1 is provided that includes a control section related to the control of the power steering device 5, the rear-wheel steering control ECU 6, the electric motor 7, the rear-wheel steering device 8, and the other wheels 9A to 9D.

[0025] In addition, when an "actuator" generally refers to a mechanism that also includes a drive source such as a motor and is used to transmit or convert the driving force from the drive source, it also includes a case where it is distinguished from the mechanism for transmitting or converting the driving force and only refers to the drive source part. In the following description, the latter is used. That is, in the present embodiment, it is assumed that only the electric motor 7 in the rear-wheel steering device 8 is used as the steering actuator for explanation.

[0026] Hereinafter, each structural member included in the vehicle 2 will be described. First, the steering wheel (also referred to as the steering wheel) 4 is provided at the driver's seat and is a rudder that changes the traveling direction of the vehicle 2 by being held by a passenger and performing a turning operation. Basically, when changing the traveling direction to the right direction, the steering wheel 4 is rotated to the right direction (clockwise), and when changing the traveling direction to the left direction, the steering wheel 4 is rotated to the left direction (counterclockwise). In addition, a power steering device 5 is connected to the steering shaft 11 connected to the steering wheel 4. Based on the assistance of the power steering device 5, the turning angles of the front wheels 9A and 9B are displaced in a direction corresponding to the rotation direction of the steering wheel 4 by driving a rack gear and a pinion 12 located at the front end of the steering shaft 11 according to the rotation of the steering wheel 4.

[0027] In addition, a torque sensor 13 is provided on the steering shaft 11 to detect the steering torque of the passenger's operation of the steering wheel 4 and send it to the power steering device 5 and the rear-wheel steering ECU 6. In addition to the steering torque, the torque sensor 13 can also detect the steering angle and the angular velocity of the angle, and send the information of these as well. The power steering device 5 controls the torque applied to the steering shaft 11 (the auxiliary force for steering operation) based on the steering torque, steering angle, and angular velocity of the angle detected by the torque sensor 13, and the rear-wheel steering ECU 6 controls the angles of the rear wheels 9C and 9D based on the steering torque, steering angle, and angular velocity of the angle detected by the torque sensor 13.

[0028] In addition, the angle control of 4WS, for example, has in-phase control that controls the angles of the front wheels and the rear wheels in the same direction, and anti-phase control that controls the angles of the front wheels and the rear wheels in the opposite direction. Any one of the controls is appropriately selected and executed through the operation of the passenger or the vehicle-side judgment corresponding to the vehicle condition. As an example, in the case of changing lanes at high speed or driving on an icy road surface, in-phase control is performed for stability, and in the case of making a low-speed turn, anti-phase control is performed to reduce the turning radius.

[0029] On the other hand, the power steering device 5 is a device that assists the steering operation of the steering wheel 4. Generally divided, it has a hydraulic type, an electro-hydraulic type, and an electric type. In this embodiment, the electric type is particularly adopted. In addition, the electric type is also divided into a column assist type, a pinion assist type, and a rack assist type according to the position of the motor 16 for steering operation. Although any method can be adopted, in the following description, the column assist type will be taken as an example for description.

[0030] In the power steering device 5, on the basis of adjusting the current amount according to the steering torque, steering angle, and angular velocity of the angle detected by the torque sensor 13, the motor 16 is driven. The motor 16 is connected to the steering shaft 11 via a worm gear and a wheel gear, and a torque is applied to the steering shaft 11 by driving the motor 16 to assist the steering operation of the passenger's steering wheel.

[0031] The rear-wheel steering ECU 6 is a control device that controls the angles of the rear wheels 9C and 9D according to the steering torque, steering angle, and angular velocity of the angle detected by the torque sensor 13. Especially in this embodiment, as will be described later, current control for the electric motor 7 is also performed. The rear-wheel steering ECU 6 is connected to various sensors and the torque sensor 13 located in the power steering device 5, the electric motor 7, and the rear-wheel steering device 8 via an in-vehicle network such as CAN. In addition, it is also connected to a vehicle speed sensor, an acceleration sensor, etc. mounted on the vehicle 2. In addition, the details of the rear-wheel steering ECU 6 will be described later.

[0032] In addition, the electric motor 7 is assembled as part of the rear-wheel steering device 8 and is a drive source that generates a steering force for steering the rear wheels. Moreover, the rear-wheel steering device 8 is a drive mechanism that converts the rotational motion of the electric motor 7 into a linear motion in the axial direction for steering the rear wheels. Hereinafter, the electric motor 7 and the rear-wheel steering device 8 will be described in more detail. Figure 2 More specifically, the electric motor 7 and the rear-wheel steering device 8 will be described. Figure 2 FIG. is a cross-sectional view of the rear-wheel steering device 8 taken along the rotation axis of the drive shaft (rear axle).

[0033] As Figure 2 shown, the rear-wheel steering device 8 includes: an ECU folder 22 for housing and fixedly arranging the substrate 21 on which the above-described rear-wheel steering operation ECU 6 is disposed; an electric motor 7; a drive shaft 23 that is supported inside the rear-wheel steering device 8 so as to be rotatable and is rotationally driven by the electric motor 7; a planetary gear 25 that uses the drive shaft 23 as an input shaft, reduces the rotational speed, and increases the torque, and outputs the drive shaft 24 having the same rotation axis as the drive shaft 23 as an output shaft; a trapezoidal thread 26 that converts the rotational motion of the drive shaft 24 with reduced rotational speed and increased torque into a linear motion in the axial direction and integrally moves the drive shafts 23 and 24 in the axial direction; a resolver 27 that detects the rotation angle of the rotor of the electric motor 7; a stroke sensor 28 that detects the left-right position deviation with respect to the forward position of the drive shafts 23 and 24 (the positions of the drive shafts 23 and 24 when the rear wheels face the forward direction); and a cylindrical housing (frame) 29 that houses the above-described components. In addition, in Figure 2 the example shown, although the rear-wheel steering operation ECU 6 is assembled as part of the rear-wheel steering device 8, the rear-wheel steering operation ECU 6 may also be arranged independently of the rear-wheel steering device 8.

[0034] Here, the electric motor 7 is, for example, a brushless motor, and includes a rotor 30 having a cylindrical permanent magnet disposed on the outer peripheral surface and a stator 31 having a plurality of coils disposed around the rotor 30. The rotor 30 is coaxial with and integral with the drive shaft 23. By flowing an electric current through the coils of the stator 31, the rotor 30 rotates, and accordingly, the drive shaft 23 also rotates.

[0035] In addition, the electric motor 7 is also provided with a motor drive circuit 32, which is, for example, an inverter circuit or an H-bridge circuit composed of switching elements not shown in the figure. The on / off state of the switching elements is controlled by a control signal from the rear-wheel steering ECU 6, and electric power corresponding to the control signal is supplied to the electric motor 7. In particular, the rotation direction and torque of the rotor 30 can be controlled. In addition, the motor drive circuit 32 is provided with a motor current sensor 46. The motor current sensor 46 detects the value of the current flowing from the motor drive circuit 32 to the electric motor 7 and outputs a signal representing the current value to the rear-wheel steering ECU 6.

[0036] In addition, the planetary gear 25 is composed of a combination of a sun gear, a planetary gear, a carrier for picking up the revolution motion of the planetary gear, an internal gear, and other gears, and the gear ratio can be set by the number of teeth of each gear. In particular, in the present embodiment, the drive shaft 23 rotationally driven by the electric motor 7 is used as the input shaft. The rotation speed is reduced and the torque is increased, and the rotation drive of the drive shaft 24 (output shaft) having the same rotation axis as the drive shaft 23 is converted. The drive shafts 23 and 24 are supported by bearings 33 and 34 formed at the left and right ends of the housing 29 so as to be rotatable and integrally movable in the axial direction, and both ends are connected to the rear wheels 9C and 9D via tie rods, knuckle arms, etc. not shown in the figure. The drive shafts 23 and 24 also serve as rear-wheel axles.

[0037] In addition, the trapezoidal thread 26 is a screw mechanism that converts the rotational drive of the drive shaft 24, which has been decelerated and has increased torque by the planetary gear 25, into a linear motion in the axial direction for rear-wheel steering. Specifically, as Figure 3 shown, it has a convex portion (thread tooth) 35 formed in a trapezoidal shape in cross section on the outer periphery of the drive shaft 24 in a spiral shape, and a nut 37 having a concave portion 36 corresponding to the convex portion 35 formed in the same spiral shape on the inner side. The nut 37 is fixed to the housing 29, that is, the vehicle body 3. On the other hand, the drive shafts 23 and 24 are supported by bearings 33 and 34 formed at the left and right ends of the housing 29 so as to be rotatable and movable in the axial direction. Therefore, when the drive shaft 24 rotates, the drive shaft 24 moves axially relative to the nut 37, that is, the vehicle body 3, due to the engagement of the convex portion 35 and the concave portion 36. As described above, both ends of the drive shafts 23 and 24 are connected to the rear wheels 9C and 9D via tie rods, knuckle arms, etc., and the rear wheels 9C and 9D are steered by the axial displacement of the drive shafts 23 and 24. That is, the rear wheels 9C and 9D can be steered by the rotational drive of the drive shafts 23 and 24 by the electric motor 7. In addition, the left and right movement directions of the drive shafts 23 and 24, that is, the steering directions of the rear wheels 9C and 9D, are determined by the rotation direction of the rotor 30 of the electric motor 7, and the left and right movement amounts of the drive shafts 23 and 24, that is, the steering angles of the rear wheels 9C and 9D, are determined by the rotation angle of the rotor 30.

[0038] In addition, as Figure 4 shown, the trapezoidal thread 26 is designed such that when the rotation of the drive shaft 24 stops, assuming that even if an external force is applied axially to the drive shaft 24, the frictional force generated between the convex portion 35 and the concave portion 36 due to the external force, that is, the frictional force acting in the direction that the drive shaft 24 does not rotate, is greater than the external force component acting in the direction that the drive shaft 24 rotates. That is, even if a strong external force is applied axially to the drive shaft 24, the drive shaft 24 does not rotate and does not move axially. That is, in the state where the electric motor 7 stops, even if the vehicle travels in this state, the turning angle of the rear wheels does not return to the forward direction and maintains the current turning angle.

[0039] On the other hand, the resolver 27 is a sensor that is disposed near the rotor 30 of the electric motor 7 and detects the rotation angle of the rotor 30 of the electric motor 7. For example, it is composed of a combination of an induction coil and a detection coil that face each other, and the induction coil is disposed with respect to the rotor 30. Moreover, when the electric motor 7 is driven and the rotor 30 rotates, the induction coil also rotates integrally. When the induction coil rotates, the change in the magnetic field detected by the detection coil can detect the change in the rotation angle of the induction coil, that is, the change in the rotation angle of the rotor 30, by the amount of change in this magnetic field. As described above, since the steering angle of the rear wheels 9C, 9D is determined by the rotation angle of the rotor 30, the rear-wheel steering ECU 6 can also detect the steering angle of the rear wheels by detecting the rotation angle of the rotor 30 of the electric motor 7 by the resolver 27. However, in the resolver 27, only the change in the rotation angle (relative rotation angle) can be detected. Therefore, in order to detect the current rotation angle (actual rotation angle) of the rear wheels 9C, 9D, the detection result of the stroke sensor 28 described later is also required.

[0040] On the other hand, the stroke sensor 28 is composed of a combination of a Hall element and a permanent magnet, for example. Permanent magnets are disposed on the drive shafts 23, 24, and the Hall element is fixed to the housing 29 side. When the drive shafts 23, 24 are in the forward position (the position of the drive shafts 23, 24 where the rear wheels face the forward direction), it is designed such that the Hall element and the permanent magnet are in opposed positions.

[0041] Moreover, if the electric motor 7 is driven and the trapezoidal thread 26 converts it into an axial linear motion to drive the drive shafts 23 and 24 to shift from the forward position to the left and right directions, the amount of Hall current generated by the Hall element changes due to the magnetic field change. By detecting the amount of Hall current based on the fact that the amount of Hall current changes according to the offset amount, the offset amount from the forward position of the drive shafts 23 and 24 can be detected. Moreover, the rear-wheel steering ECU 6 can determine the initial angle value based on the detection signal of the stroke sensor 28 at the ignition device on-time, and can calculate the actual angles of the rear wheels 9C and 9D through the angle change amount (relative angle) compared with the initial angle value obtained based on the output signal from the resolver 27 after that.

[0042] In addition, in addition to Figure 1 the structural members shown, the vehicle 2 also has, as basic structural members of the vehicle 2, but only the steering control of the wheels 9A to 9D and the structure related to its control, and the control related to this structure.

[0043] Next, use Figure 5 to describe the structure of the vehicle control device 1 in more detail. Figure 5 It is a block diagram showing the structure of the vehicle control device 1 of the present embodiment.

[0044] The vehicle control device 1 of the present embodiment includes the above-mentioned power steering device 5 / rear-wheel steering ECU 6 / electric motor 7 and a control part related to the control of the other wheels 9A to 9D. In particular, the rear-wheel steering ECU 6 is an electronic control unit (ECU: electronic control unit) that performs various controls related to the running of the vehicle, such as the angle control of the rear wheels 9C and 9D, and the control parts included in the power steering device 5 and the other vehicle control devices 1 all have various mechanisms as processing algorithms. For example, the target angle setting mechanism sets the target angle of the rear wheels based on the driver's steering operation of the steering wheel. The angle detection mechanism detects the current angle of the rear wheels. The energization control mechanism controls the energization state of the electric motor 7.

[0045] Specifically, as Figure 5 shown, in addition to the CPU 41 as an arithmetic device and a control device, and the RAM 42 used as a working memory when the CPU 41 performs various arithmetic processes, and the control program, it also has a vehicle control processing program described later recorded (refer to Figure 6Internal storage devices such as the ROM 43 and the flash memory 44 that stores the program read from the ROM 43. In addition, it also has a timer 45 as a mechanism for measuring time. On the other hand, the rear-wheel steering control ECU 6 is also connected to the power steering device 5, the electric motor 7, the resolver 27, the stroke sensor 28, the torque sensor 13 provided on the vehicle 2, the motor current sensor 46, the vehicle speed sensor 47, the acceleration sensor 48, etc. via an in-vehicle network such as CAN.

[0046] In addition, the vehicle speed sensor 47 is a sensor for detecting the moving distance and vehicle speed of the vehicle 2, generates pulses based on the rotation of the drive wheels of the vehicle 2, and outputs the pulse signal to the rear-wheel steering control ECU 6. In addition, the acceleration sensor 48 detects the acceleration generated in the front-rear direction (the direction parallel to the traveling direction of the vehicle) and the left-right direction (the direction crossing the traveling direction of the vehicle) with respect to the vehicle body of the vehicle 2, and outputs it to the rear-wheel steering control ECU 6. Moreover, the rear-wheel steering control ECU 6 can calculate the vehicle speed and moving distance of the vehicle by counting the pulses output from the vehicle speed sensor 47, and set the target angles of the rear wheels 9C and 9D based on the steering angle and the angular velocity of the steering angle detected by the torque sensor 13, the vehicle speed detected by the vehicle speed sensor 47, and the acceleration detected by the acceleration sensor 48. In addition, as described above, the rear-wheel steering control ECU 6 can calculate the actual angles of the rear wheels 9C and 9D based on the detection results of the resolver 27 and the stroke sensor 28, and perform angle control of the rear wheels 9C and 9D so that the actual angles are close to the rear wheels 9C and 9D.

[0047] Next, in the vehicle control device 1 having the above structure, based on Figure 6 A vehicle control processing program specifically executed by the rear-wheel steering control ECU 6 will be described. Figure 6 is a flowchart of the vehicle control processing program of this embodiment. Here, the vehicle control processing program is executed after the ACC power supply (accessory power supply) of the vehicle is turned on, and is a program for performing various controls related to the running of the vehicle, such as angle control of the rear wheels 9C and 9D. In addition, in the following Figure 6 The program represented by the flowchart is stored in the RAM 42, ROM 43, etc. provided in the rear-wheel steering control ECU 6 and is executed by the CPU 41.

[0048] First, in step (hereinafter simply referred to as S) 1, the CPU 41 acquires via CAN the steering angle and the angular velocity of the steering angle detected by the torque sensor 13, that is, the steering operation content of the driver on the steering wheel. Moreover, similarly, information related to the current vehicle behavior such as the vehicle speed detected by the vehicle speed sensor 47 and the acceleration detected by the acceleration sensor 48 is acquired.

[0049] Next, in S2, the CPU 41 sets the target angles of the rear wheels 9C and 9D (hereinafter referred to as the rear-wheel target angles) using the steering angle, the angular velocity of the steering angle, the vehicle speed, the angular velocity, etc. obtained in the above S1. Further, based on a determination of which of in-phase control for controlling the front and rear wheels to turn in the same direction and anti-phase control for controlling the front and rear wheels to turn in opposite directions is to be performed, the rear-wheel target angles are set. For example, in-phase control is performed to improve stability when the vehicle changes lanes at high speed or travels on an icy road surface, and anti-phase control is performed to reduce the turning radius when making a low-speed turn. Further, information related to the vehicle behavior obtained in the above S1 is used in the above determination. Further, regarding which of in-phase control and anti-phase control is to be executed, it may not be automatically determined on the vehicle side, but may be determined by the operation of a passenger to execute either in-phase control or anti-phase control.

[0050] Then, in in-phase control, for example, the rear-wheel target angles are set so as to be the same as the angle of the front wheels, and in anti-phase control, for example, the rear-wheel target angles are set so that the angle of the rear wheels becomes about 1 / 10 to 1 / 20 in the opposite direction with respect to the angle of the front wheels. Here, the above example is just an example, and the optimal rear-wheel target angles are set according to the current vehicle conditions.

[0051] Further, the processes after S1 are repeatedly executed during vehicle travel (for example, in units of 10 msec), and the rear-wheel target angles are set based on the steering angle at each such moment. Here, when a passenger operates the steering wheel when changing the traveling direction of the vehicle, the operation is performed in such a way that the steering angle gradually increases, or conversely in such a way that the steering angle gradually decreases. Therefore, as Figure 7 shown, when changing the traveling direction such as when the vehicle turns or changes lanes, the rear-wheel target angles are not substantially fixed, but gradually change according to the operation of the vehicle's steering wheel (the rear-wheel target angles change with the passage of time).

[0052] Then, in S3, the CPU 41 obtains the angle of the rear wheels at the current moment (the actual angle). Here, as described above, the actual angle of the rear wheels is obtained using the detection results of the resolver 27 and the stroke sensor 28. Specifically, the initial angle value is determined based on the detection signal of the stroke sensor 28 at the moment when the ignition device is turned on, and the actual angles of the rear wheels 9C and 9D are calculated by the angle change amount (relative angle) obtained by comparing with the initial angle value obtained based on the output signal from the subsequent resolver 27.

[0053] Next, in S4, the CPU 41 determines whether the target rear-wheel steering angle set in S2 above is different from the actual rear-wheel steering angle obtained in S3 above, that is, whether rear-wheel steering (a change in the steering angle) is required.

[0054] Then, when it is determined that the target rear-wheel steering angle set in S2 above is different from the actual rear-wheel steering angle obtained in S3 above, that is, when rear-wheel steering is required (S4: YES), the process proceeds to S5 where the rear wheels should be steered. In contrast, when it is determined that the target rear-wheel steering angle set in S2 above is the same as the actual rear-wheel steering angle obtained in S3 above, that is, when rear-wheel steering is not required (S4: NO), the rear wheels are not steered (the current steering angle is maintained) and the process proceeds to S14. In this case, no current is supplied to the electric motor 7, and the drive shafts 23 and 24 do not rotate and there is no new axial movement. Also, as Figure 4 shown, in the present embodiment, the rear-wheel steering device 8 has a trapezoidal thread 26, and it is assumed that even if a large force is applied from the outside, the current rear-wheel steering angle (i.e., the actual steering angle that coincides with the target rear-wheel steering angle) is maintained in a state where the electric motor 7 is not driven.

[0055] In S5, the CPU 41 reads out from the RAM 42 a parameter, i.e., State, indicating the control state of the current vehicle control device 1, and determines whether State is "in feedback control". Also, in the processes after S6 described later, State is set by switching between the two states of "in feedback control" and "in current-off" according to the cumulative current and the passage of time. In addition, in the initial state value at the moment when the ACC power supply is turned on, it is set to "in feedback control".

[0056] Here, in the vehicle control device 1 of the present embodiment, in a state where the target rear-wheel steering angle is different from the current actual rear-wheel steering angle, although control is performed to make the actual steering angle approach the target steering angle after S5, in particular, the following control is performed, that is, based on the cumulative current supplied to the electric motor 7, the "energized state in which the current is supplied to the electric motor 7 in such a way that the current rear-wheel steering angle approaches the target steering angle" and the "cut-off state in which the current to the electric motor 7 is cut off" are alternately switched.

[0057] As a result, as Figure 7As shown, in a state where the target rear-wheel angle is different from the actual rear-wheel angle of the current rear wheel, for example, when a steering-wheel operation is performed and the target angle changes with the passage of time, current is continuously supplied to the electric motor 7. Therefore, there is a problem that the service life of the electric motor 7 is reduced due to overheating. Here, the heat generation amount of the electric motor is proportional to the square of the time integral of the current flowing in the motor inverter. Therefore, even if the difference between the actual rear-wheel angle and the rear-wheel target angle is small, when the steering wheel is continuously and slowly turned and the current flows for a long time, the heat generation amount becomes very large.

[0058] In the present embodiment, in a state where the target rear-wheel angle is different from the actual rear-wheel angle of the current rear wheel, for example, when a steering-wheel operation is performed and the target angle changes with the passage of time, the following control is performed, that is, current is not continuously supplied to the electric motor 7, and based on the cumulative current supplied to the electric motor 7, the above-mentioned energized state and the cut-off state are alternately switched. Thereby, even when the steering wheel is continuously and slowly turned, the heat generation amount can be suppressed. Among them, as Figure 7 shown, before the cumulative current supplied to the electric motor 7 reaches a preset control start value (before time t0) after the start of the rear-wheel angle control, that is, in the stage where the heat generation amount is low immediately after the start of the drive of the electric motor 7, it is not necessary to suppress the heat generation amount. Therefore, the same as in the past, the control of continuously supplying current to the electric motor 7 is performed. Moreover, when State is "in feedback control" in the above S5, it indicates that the above-mentioned energized state is in the current moment, and when State is "current off", it indicates that the above-mentioned cut-off state is in.

[0059] Moreover, when State is "in feedback control" (S5: yes), it moves to S6. In contrast, when State is "current off" (S5: no), it moves to S9.

[0060] In S6, the CPU 41 determines whether the cumulative current supplied to the electric motor 7 after the start of the energized state of the electric motor 7 reaches the threshold value. In addition, as Figure 7As shown, before the cumulative current supplied to the electric motor 7 reaches the preset control start value (before t0) after the start of the rear wheel steering angle control, the control of continuously supplying current to the electric motor 7 is performed. Therefore, after the start of the rear wheel steering angle control and before it is initially determined to be "yes" in S6, the threshold value of S6 is set to a control start value larger than the normal value. On the other hand, during the control of alternately switching the energized state and the cut-off state (after t0), it is determined whether the cumulative current supplied to the electric motor 7 reaches the threshold value (< control start value) after the most recent recovery from the cut-off state to the energized state. Regarding the current value flowing through the electric motor 7, it can be detected by the motor current sensor 46. In addition, the control start value and the threshold value that are the determination criteria of S6 can be set appropriately. For example, the values can also be changed according to the vehicle type, the standard of the electric motor 7, the driving environment of the vehicle, etc.

[0061] Moreover, when it is determined that the cumulative current supplied to the electric motor 7 reaches the threshold value after the start of the energized state of the electric motor 7 (S6: yes), the process proceeds to S7. In contrast, when it is determined that the cumulative current supplied to the electric motor 7 does not reach the threshold value after the start of the energized state of the electric motor 7 (S6: no), the process proceeds to S8.

[0062] In S7, the CPU 41 substitutes 0 as the value of "command current (thermal protection)". Although the "command current (thermal protection)" becomes the value representing the current value to be supplied to the electric motor 7 at the current time, the "command current (thermal protection)" is not necessarily indicated to the motor drive circuit 32 as a control signal, but is corrected in S12 described later in such a manner that there is no sharp current change, and then is output to the motor drive circuit 32 as a control signal (S13).

[0063] In addition, in S7, the CPU 41 reads out the parameter State representing the control state of the current vehicle control device 1 from the RAM 42 and sets "current off" indicating the transition to the cut-off state. Then, the process proceeds to S12.

[0064] On the other hand, in S8, the CPU 41 substitutes, as the value of "command current (thermal protection)", the current value that needs to be supplied to the electric motor 7 in order to make the actual turning angle of the current rear wheel close to the rear wheel target turning angle. Here, the current value substituted in the above S8 is determined based on the actual turning angle at the current time and the difference between the actual turning angle at the current time and the rear wheel target turning angle. That is, the larger the turning angle, the larger the torque required to further change the turning angle according to this turning angle. Therefore, if the actual turning angle becomes larger, the current value that needs to be supplied to the electric motor 7 for steering also becomes larger. In addition, the larger the difference between the actual turning angle and the rear wheel target turning angle, the larger the torque needs to be increased in order to quickly approach the rear wheel target turning angle. Therefore, if the difference between the actual turning angle and the rear wheel target turning angle becomes larger, the current value that needs to be supplied to the electric motor 7 to approach the rear wheel target turning angle also becomes larger. In particular, in the present embodiment, by using the resolver 27 and the stroke sensor 28 to detect the actual turning angle in real time for feedback control, in order to make the actual turning angle of the current rear wheel close to the rear wheel target turning angle, the current value that needs to be supplied to the electric motor 7 is set based on the feedback control. Among them, it is not necessarily the same as S7. The "command current (thermal protection)" is indicated to the motor drive circuit 32 as a control signal, and is corrected in S12 described later in such a way that there is no sharp current change, and then is output to the motor drive circuit 32 as a control signal (S13). Then, it moves to S12.

[0065] On the other hand, in S9, after the CPU 41 moves to the cut-off state (State = "current off"), the elapsed time is measured by the timer 45, and it is determined whether the timer value is equal to or greater than a specified time. In addition, the specified time that becomes the determination criterion for the above S9 can be set appropriately, but in order to prevent the passenger from noticing that the current has been cut off, it is preferably set as short as possible within the range where the heat generation of the electric motor 7 can be suppressed. For example, it is set to 100 msec.

[0066] In addition, in the present embodiment, when the rear wheel target turning angle changes with the passage of time, as Figure 8 shown, it is preferable that the faster the change speed, the shorter the above specified time for cutting off the current. The reason for setting it like that is that in the state where the current is cut off, the actual turning angle does not change. Therefore, basically, the longer the current cut-off time, the larger the difference between the rear wheel target turning angle and the actual turning angle. When returning from the cut-off state to the energized state, the change in the actual turning angle is also larger. However, if the change amount of the actual turning angle becomes larger (the step difference of the dotted line representing the actual turning angle shown in Figure 8 becomes larger), there is a concern that the passenger will notice that the current has been cut off. Therefore, it is preferable to suppress the change amount. As Figure 8As shown in the left figure, if the change speed of the rear wheel target angle is slow, even if the current cut-off period is long, the change amount of the actual angle at the time of current recovery can be suppressed, so the current cut-off time can also be set relatively long. On the other hand, as shown in the right figure of Figure 8 , if the change speed of the rear wheel target angle is fast, when the current cut-off period is extended, the change amount of the actual angle at the time of current recovery becomes large, so it is necessary to set the current cut-off time as short as possible.

[0067] Moreover, when it is determined that the elapsed time is equal to or longer than the specified time after moving to the cut-off state (S9: Yes), it moves to S11. In contrast, when it is determined that the elapsed time is less than the specified time after moving to the cut-off state (S9: No), it moves to S10.

[0068] In S10, the CPU 41 continues the cut-off state of cutting off the current to the electric motor 7, so 0 is substituted as the value of "command current (thermal protection)". In addition, although "command current (thermal protection)" is a value indicating the current value to be supplied to the electric motor 7 at the current moment, "command current (thermal protection)" is not necessarily indicated as a control signal to the motor drive circuit 32, and after being corrected in S12 described later in a manner that there is no sharp current change, it is output as a control signal to the motor drive circuit 32 (S13).

[0069] On the other hand, in S11, the CPU 41 substitutes the current value of the current to be supplied to the electric motor 7 in order to recover from the cut-off state of cutting off the current to the electric motor 7 and to make the current actual turning angle of the rear wheels close to the rear wheel target turning angle as the value of "command current (thermal protection)". Here, the current value substituted in the above S11 is determined based on the actual turning angle at the current time and the difference between the actual turning angle at the current time and the rear wheel target turning angle. That is, the larger the turning angle, the larger the torque required to further change the turning angle from this turning angle. Therefore, if the actual turning angle becomes larger, the current value to be supplied to the electric motor 7 for steering also becomes larger. In addition, the larger the difference between the actual turning angle and the rear wheel target turning angle, the larger the torque needs to be increased in order to quickly approach the rear wheel target turning angle. Therefore, if the difference between the actual turning angle and the rear wheel target turning angle becomes larger, the current value to be supplied to the electric motor 7 to approach the rear wheel target turning angle also becomes larger. In particular, in the present embodiment, the actual turning angle is detected in real time by using the resolver 27 and the stroke sensor 28 to perform feedback control. In order to make the current actual turning angle of the rear wheels close to the rear wheel target turning angle, the current value to be supplied to the electric motor 7 is set based on the feedback control. Among them, it is not necessarily the same as S7. The "command current (thermal protection)" is indicated to the motor drive circuit 32 as a control signal, and after being corrected in S12 described later in a manner without a sharp current change, it is output to the motor drive circuit 32 as a control signal (S13). Then, it moves to S12.

[0070] In addition, in the above S11, the CPU 41 reads out the parameter State indicating the control state of the current vehicle control device 1 from the RAM 42 and sets "in feedback control" indicating the transition to the energized state. Then, it moves to S12.

[0071] In S12, the CPU 41 calculates the "command current (output value)" indicated to the motor drive circuit 32 as the current value to be supplied to the electric motor 7. Specifically, based on the "command current (thermal protection)" set in the above S7, S8, S10, and S11, it is calculated by the following equations (1) and (2).

[0072] Perform upper limit processing on the command current change amount = (command current (thermal protection) - the previous value of the command current (output value)), that is, when it exceeds the upper limit value, set the upper limit value as the command current change amount ··· (1)

[0073] Command current (output value) = the previous value of the command current (output value) + command current change amount ··· (2)

[0074] According to the above formulas (1) and (2), the change amount of the current per unit time is as close as possible to the "command current (thermal protection)" within a range not exceeding the upper limit, and the value becomes the "command current (output value)". In addition, regarding the upper limit of the change amount of the current, it is preferably set as large as possible within a range where no sound or vibration is generated. Here, if the torque of the electric motor 7 changes sharply, there is a problem of sound and vibration generated due to the contact of internal components. In the above S12, by setting an upper limit on the change amount of the current, the generation of such sound and vibration is prevented. Moreover, as Figure 9 shown, regarding the upper limit α of the change amount during the process of reducing the current amount when transferring from the energized state to the cut-off state, and the upper limit β of the change amount during the process of increasing the current amount when transferring from the cut-off state to the energized state, they can also be different values. For example, the upper limit α of the change amount in the case of reducing the current amount is set as a fixed value as large as possible within a range where no sound or vibration is generated. On the other hand, the upper limit β of the change amount in the case of increasing the current amount is set within a range where no sound or vibration is generated and considering the difference between the actual rotation angle and the rear wheel target rotation angle when recovering from the cut-off state. That is, the upper limit β of the change amount in the case of increasing the current amount is not a fixed value, and for example, it changes according to the change speed of the rear wheel target rotation angle and the cut-off current time (the specified time in S9).

[0075] Then, in S13, the CPU 41 sends a control signal instructing the supply of current to the electric motor 7 to the motor drive circuit 32 provided in the electric motor 7. In addition, the "command current (output value)" is included as the target value of the supplied current amount in the control signal. In addition, in the motor drive circuit 32 that receives the above control signal, the target current value of the electric motor 7 is set to the "command current (output value)", and the current value detected by the motor current sensor 46 is fed back, and the duty ratio of the switching element of the motor drive circuit 32 is controlled so that the current value becomes the target current value.

[0076] As a result, especially when in the energized state (wherein, even in the cut-off state, there is a case where the electric motor 7 is driven immediately after switching from the energized state), as described above, a current flows in the stator 31 to drive the electric motor 7, and the rotational motion of the electric motor 7 is converted into a linear motion in the axial direction for steering the rear wheels, and the rear wheels 9C and 9D are steered, especially in such a way that the actual rotation angle becomes the rear wheel target rotation angle. On the other hand, in the cut-off state, the drive of the electric motor 7 is stopped. Among them, as Figure 4 shown, in the present embodiment, the rear wheel steering device 8 has a trapezoidal thread 26, and in a state where the electric motor 7 is not driven, it is assumed that even if a large force is applied from the outside, the current rotation angle of the rear wheel is maintained.

[0077] Then, in S14, it is determined whether the vehicle has finished traveling. If the vehicle has not finished traveling (S14: No), the process returns to S1 to continue the vehicle travel control. In addition, the processes after S1 are repeatedly executed at intervals of, for example, 10 msec during vehicle travel. On the contrary, if the vehicle has finished traveling (S14: Yes), the vehicle control processing program is terminated.

[0078] Next, a specific example will be given to illustrate the vehicle control performed by the above vehicle control processing program. Figure 9 An example showing the transitions of the rear wheel target angle, the actual angle, and the current value supplied to the electric motor 7 when performing the vehicle control executed by the above vehicle control processing program is shown. In addition, the horizontal axis represents the elapsed time. Figure 9 The example shown particularly shows a case where a passenger slowly turns the steering wheel for a long time, that is, a case where the rear wheel target angle slowly rises in proportion to the elapsed time.

[0079] As Figure 9 shown, if a passenger turns the steering wheel and sets a new rear wheel target angle, since the actual angle is different from the rear wheel target angle, it is determined that rear wheel steering is required (S4: Yes), and the power supply to the electric motor 7 is started. The torque required for steering is proportional to the actual angle at that moment. Therefore, as Figure 9 shown, the amount of electric power required to be supplied to the electric motor 7 gradually increases substantially according to the passage of time (as the angle becomes larger). However, in the present embodiment, as described above, if the cumulative current supplied to the electric motor 7 reaches the threshold value (the control start value for the first time) after the power-on state of the electric motor 7 is started (S6: Yes), the supply of current to the electric motor 7 is cut off for a specified time and shifted to the cut-off state.

[0080] Thereby, heat generation of the electric motor 7 caused by the continuous flow of current for a long time can be suppressed. In addition, as Figure 4 shown, in the present embodiment, the rear wheel steering device 8 has a trapezoidal thread 26, and the current rear wheel angle can be maintained in the cut-off state where the electric motor 7 is not driven. Therefore, even immediately after the power-on state is restored, the pursuit of the rear wheel target angle can be started again. Moreover, the angle of the rear wheel is fixed in the cut-off state and is not synchronized with the operation of the passenger's steering wheel. However, since the steering wheel and the rear wheel are not mechanically connected but are connected by a line (electric communication), even if it is not completely synchronized with the steering wheel operation, if it is not noticeable externally, the passenger will not notice. Particularly in the present embodiment, the duration of the cut-off state is short (for example, 100 msec), and the change amount of the actual angle at the time of current recovery does not become large, so the passenger does not feel discomfort.

[0081] In addition, since the timing of the transition to the cut-off state is determined by the cumulative current, the larger the current amount, the shorter the interval for the transition from the energized state to the cut-off state. On the other hand, as also shown in Figure 8 the specified time for which the cut-off state continues is determined by the change speed of the rear-wheel target angle. If the change speed is fast, when the period for cutting off the current is made longer, the change amount of the actual angle at the time of current recovery becomes larger. Therefore, the cut-off time of the current is set as short as possible.

[0082] In addition, upper limits are set for the change amounts of the current ( Figure 9 angles α, β) when transitioning from the energized state to the cut-off state and when transitioning from the cut-off state to the energized state. Therefore, it is possible to prevent the generation of noise and vibration caused by a sharp change in the torque of the electric motor 7.

[0083] Moreover, particularly when transitioning from the cut-off state to the energized state, as shown in Figure 9 a current slightly larger than the originally required current amount is supplied immediately after returning to the energized state. As a result, even when there is a large difference between the actual angle and the rear-wheel target angle immediately after the return to the energized state, it is possible to quickly bring the actual angle close to the rear-wheel target angle and resume following the rear-wheel target angle again.

[0084] As described in detail above, in the vehicle control device 1 of the present embodiment and the computer program executed in the vehicle control device 1, there is an electric motor 7 that generates a steering force for steering the rear wheels, and a trapezoidal thread 26 that converts the rotational motion generated by the drive of the electric motor 7 into a linear motion in the axial direction for steering the rear wheels. The target angle of the rear wheels is set based on the steering operation of the driver on the steering wheel (S2), and the current angle of the rear wheels is detected (S3). In a state where the target angle of the rear wheels is different from the current angle of the rear wheels, the following control is performed: alternately switching the cumulative current supplied to the electric motor 7 to supply current to the electric motor 7 in an energized state in such a way that the current angle of the rear wheels approaches the target angle; and a cut-off state in which the current to the electric motor 7 is cut off (S5 to S13). Therefore, regardless of the steering operation of the driver's steering wheel, the power consumption of the electric motor 7 can be suppressed in a required situation, and overheating of the electric motor 7 can be prevented. In addition, since the current angle of the rear wheels can be maintained in the cut-off state where the electric motor 7 is not driven by the trapezoidal thread, it is possible to immediately resume following the target angle even immediately after returning to the energized state.

[0085] In addition, by repeatedly executing the first control of switching from the energized state to the cut-off state at the moment when the cumulative current supplied to the electric motor 7 after the start of the energized state reaches the threshold value, and the second control of restoring from the cut-off state to the energized state after a predetermined time has elapsed since the cut-off state was set, the energized state and the cut-off state are switched (S5 to S13). Therefore, the energized state is managed by the amount of current flowing through the electric motor 7, thereby preventing overheating of the electric motor 7.

[0086] In addition, when the target rotation angle changes with the passage of time, the faster the change speed, the shorter the predetermined time is set. Therefore, it is possible to prevent a large deviation between the target rotation angle and the actual rotation angle when restoring from the cut-off state to the energized state, that is, a situation where the actual rotation angle changes greatly when restoring from the cut-off state to the energized state.

[0087] In addition, when switching from the energized state to the cut-off state and when switching from the cut-off state to the energized state, control is performed such that the change amount of the current supplied to the electric motor 7 per unit time is less than the upper limit value. Therefore, it is possible to prevent the generation of noise and vibration caused by a sharp change in the torque of the electric motor 7.

[0088] In addition, the present invention is not limited to the above-described embodiments, and various improvements and modifications can of course be made without departing from the gist of the present invention.

[0089] For example, in the present embodiment, although the cut-off state is a state in which the supply of current to the electric motor 7 is set to 0, as long as the heat generation of the electric motor 7 can be suppressed, even a state in which a little current flows is not a problem. That is, the cut-off state can also be set to a state in which the amount of current supplied to the electric motor 7 is reduced compared to the energized state.

[0090] In addition, in the present embodiment, although a vehicle with 4WS that separately controls the rotation angles of the front wheels and the rear wheels based on the steering operation of the steering wheel by the passenger is taken as an example, if it is a vehicle that can steer the rear wheels, it does not necessarily need to be a vehicle with 4WS.

[0091] In addition, in the present embodiment, Figure 4 Although the execution subject of the vehicle control processing program shown is a dedicated electronic control unit for performing the steering operation of the rear wheels, that is, the rear wheel steering operation ECU6, the unified control ECU that controls the entire vehicle can also perform part or all of the processing. Or other in-vehicle devices such as a navigation device can also be the execution subject. In addition, an external server device can also perform part of the processing.

Claims

1. A vehicle control device, comprising: an electric steering actuator that generates a steering force for steering the rear wheels; A trapezoidal thread that converts a rotational motion generated by driving the steering actuator into an axial linear motion for steering the rear wheels; a target turning angle setting mechanism that sets a target turning angle of the rear wheels based on a passenger's steering manipulation of the steering wheel; A turning angle detection mechanism, which detects the current turning angle of the rear wheels; as well as an energization control mechanism, which controls the energization state of the steering actuator, The vehicle control device is characterized in that The power control mechanism controls the steering actuator to be powered on and powered off by switching between the power supply state and the power supply state when the steering actuator is turned away from the neutral direction and the target steering angle of the rear wheels is different from the current steering angle of the rear wheels. The current value supplied to the steering actuator in the energized state gradually increases with the passage of time.

2. The vehicle control device according to claim 1, characterized in that: The energization control means performs switching control between the energized state and the disconnected state based on an accumulated current supplied to the steering actuator.

3. The vehicle control device according to claim 2, characterized in that: The power supply control mechanism switches the power supply state and the disconnection state alternately by repeatedly executing the first control and the second control. The first control is a control for switching from the energized state to the disconnected state at a time when the accumulated current supplied to the steering actuator reaches a threshold value after the energized state is started. The second control is a control for returning from the cutoff state to the energized state after a predetermined time has elapsed since the cutoff state was set.

4. The vehicle control device according to claim 3, characterized in that: When the target rotation angle changes with the passage of time, the energization control means sets the predetermined time to be shorter as the speed of change is faster.

5. The vehicle control device according to any one of claims 1 to 4, characterized in that: The energization control means controls the steering actuator so that a change in current per unit time supplied to the steering actuator is smaller than an upper limit value when switching from the energized state to the disconnected state and when switching from the disconnected state to the energized state.

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