Vehicle control system

Abstract

The present application relates to a vehicle control system. A control device is configured to execute, when a steering request is received in a parking state or a creep state in which a vehicle speed does not exceed a predetermined vehicle speed from the parking state, a caster change control of controlling a driving force application device or a driving force application device and a braking force application device in such a manner that a caster of the steering wheel is reduced, the control device applying, in the caster change control, a driving force in a direction toward the other wheel to one of front and rear wheels and applying a braking force or a driving force in a direction toward the one wheel to the other wheel so as to become the parking state or the creep state in response to a request related to acceleration or deceleration.

Description

Technical Field

[0001] This invention relates to vehicle control systems. Background Technology

[0002] For example, Japanese Patent Application Publication No. 2009-035081 describes a positioning adjustment device for adjusting wheel alignment. This device adjusts wheel alignment, for example, by reducing vehicle rolling resistance. It also allows for camber adjustment.

[0003] When performing so-called static steering—changing the steering wheel angle while the vehicle is stationary—a significant force is required due to the friction between the tires and the contact patch. For example, in a steering system with steer-by-wire, the actuator must output a large force during static steering, resulting in a heavy load on the actuator. Furthermore, steering operations at very low speeds (extremely low speeds), such as when the vehicle is parked, also bear a similarly heavy load as static steering. Moreover, even in power steering systems, the force required to operate the steering wheel or the auxiliary force generated by the electric motor increases during steering operations while stationary or at very low speeds. Thus, in conventional systems, there is room for improvement in reducing the load on the system when changing the steering wheel angle while stationary or at very low speeds. Summary of the Invention

[0004] The purpose of this invention is to provide a vehicle control system that can reduce the force required to change the steering angle of the steering wheels when the vehicle is parked or traveling at low speed.

[0005] The vehicle control system of the present invention includes: a drive force applying device that applies a drive force to at least one of the front wheels and the rear wheels; a braking force applying device that applies a braking force to the front wheels and the rear wheels; and a control device that controls the drive force applied by the drive force applying device and the braking force applied by the braking force applying device. The control device is configured to: when a steering request is received in a parking state where the vehicle is parked, or in a low-speed driving state where the vehicle is traveling at a speed not exceeding a predetermined speed from the parking state in a predetermined direction in either the forward or reverse direction, execute a control to reduce the caster angle of the steering wheels, or a caster angle change control of the drive force applying device and the braking force applying device. In the caster angle change control, the control device applies a drive force in the direction of the other wheel to one of the front wheels and the rear wheels, and applies a braking force or a drive force in the direction of the other wheel to the other wheel, so as to respond to the parking state or the low-speed driving state in response to a request related to acceleration or deceleration.

[0006] Caster angle is the angle between the kingpin axis and the vertical line (plumb line) of the road surface when viewed laterally (from the left-right direction of the vehicle). The kingpin axis is tilted forward with its lower part leaning more forward than its upper part. Generally, the smaller the caster angle, the smaller the restoring torque relative to the steering of the wheels when driving. In addition, if the caster angle is smaller when the vehicle is stationary, the caster trail is smaller, and the resistance to steering of the wheels is smaller.

[0007] According to the present invention, if a steering request is received while the vehicle is stationary or traveling at a low speed, the control device performs caster angle change control. In caster angle change control, a driving force is applied to one wheel in the direction of the other wheel, and a force opposing it is applied to the other wheel, thus applying a force (torque) to the vehicle body similar to the inertial force applied during deceleration while moving forward. In other words, it can be said that a pitching moment in the forward turning direction is applied to the vehicle body by caster angle change control. By applying such a force to the vehicle body, a forward force is applied to the upper part of the passage point that is structurally located above the kingpin axis, and the elastic component (e.g., bushing) disposed on the upper part elastically deforms. Through this elastic deformation, the upper part and the passage point above the kingpin axis move forward relative to the passage point below the kingpin axis.

[0008] Thus, according to the present invention, by intentionally elastically deforming the elastic component of the upper part so that the kingpin axis is upright when viewed from the side, the upper part moves forward relative to the lower part, thereby reducing the caster angle. By reducing the caster angle, the force required to steer the steering wheel is reduced. According to the present invention, in a stopped state or at low speed, the force required to change the steering angle of the steering wheel can be reduced.

[0009] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements. Attached Figure Description

[0010] Figure 1 This is a schematic diagram showing the overall structure of a vehicle equipped with the vehicle control system of this embodiment.

[0011] Figure 2 This is a schematic diagram showing the structure around the front wheels of this embodiment as viewed from the front of the vehicle.

[0012] Figure 3 This is a schematic diagram used to illustrate the backslope angle in the structure of this embodiment.

[0013] Figure 4 This is a schematic diagram used to illustrate the outward tilt angle in the structure of this embodiment.

[0014] Figure 5 This is a schematic diagram showing the upper arm of this embodiment as viewed from above the vehicle.

[0015] Figure 6 This is a schematic diagram showing the adjustment cam of this embodiment as viewed from the front of the vehicle.

[0016] Figure 7 This is a schematic diagram used to explain the first backslope angle change control in this embodiment.

[0017] Figure 8 This is a schematic diagram used to explain the second backslope angle change control in this embodiment.

[0018] Figure 9 This is a schematic diagram used to explain the third backslope angle change control in this embodiment.

[0019] Figure 10 This is a flowchart illustrating a control example of this embodiment. Detailed Implementation

[0020] Hereinafter, the methods for carrying out the present invention will be described with reference to the accompanying drawings. Figure 1 and Figure 2 As shown, the vehicle control system 1 of this embodiment includes a drive force imparting device 2 that imparts driving force to at least one of the front wheels 11 and the rear wheels 12, a braking force imparting device 3 that imparts braking force to the front wheels 11 and the rear wheels 12, a control device 4 that controls the driving force imparted by the drive force imparting device 2 and the braking force imparted by the braking force imparting device 3, a steering system 5, and a suspension device 6. The front wheels 11 consist of a right front wheel and a left front wheel, and the rear wheels 12 consist of a right rear wheel and a left rear wheel. Hereinafter, the front wheels 11 and the rear wheels 12 will also be collectively referred to as wheels 11 and 12. In-vehicle communication is performed via CAN (vehicle area network or controllable area network). Furthermore, in Figure 1 In the image, some of the communication lines are omitted from the display.

[0021] The drive force applying device 2 is a device capable of independently applying drive force to the front wheel 11 and the rear wheel 12. The drive force applying device 2 includes in-wheel motors 21FL, 21FR, 21RL, and 21RR (hereinafter collectively referred to as "in-wheel motors 21") installed as drive units for each wheel 11, 12, and a drive ECU 22 that controls each in-wheel motor 21. Each wheel 11, 12 is driven to rotate by the in-wheel motors 21 disposed inside the wheel. The specific structure of the in-wheel motors 21 can use known structures and is therefore omitted.

[0022] The drive ECU 22 is an electronic control unit equipped with a CPU, memory, etc., and is communicatively connected to the in-wheel motors 21 via CAN. The drive ECU 22 controls the in-wheel motors 21, for example, based on accelerator operation or acceleration / deceleration requests (e.g., acceleration requests) from other ECUs. The drive ECU 22 calculates the current vehicle speed, for example, based on wheel speed information received from the wheel speed sensors 91. Additionally, an acceleration sensor 92 installed in the vehicle detects the vehicle's acceleration in the longitudinal direction and sends it to the drive ECU 22, etc.

[0023] The braking force applying device 3 is a brake-by-wire braking system. The braking force applying device 3 is a device capable of independently applying braking force to the front wheels 11 and the rear wheels 12. The braking force applying device 3 includes a brake pedal 30 as a brake operating component, a master cylinder 31, a hydraulic adjustment device 32, brake devices 33FL, 33FR, 33RL, and 33RR (hereinafter collectively referred to as "brake devices 33"), and a brake ECU 34. The master cylinder 31 outputs brake fluid according to the amount of brake pedal 30 operation.

[0024] The hydraulic adjustment device 32 is a device that supplies brake fluid to each brake device 33 according to the instructions of the brake ECU 34. The hydraulic adjustment device 32 is a so-called brake actuator, such as an ESC actuator, equipped with an electric motor, a pump, and a solenoid valve (not shown). The hydraulic adjustment device 32 can independently adjust the braking force applied by each brake device 33 by increasing or decreasing the hydraulic pressure of the brake calipers of each brake device 33. The hydraulic adjustment device 32 can adjust the braking force according to the instructions of the brake ECU 34 regardless of whether the brake pedal 30 is operated. The brake device 33 is, for example, a disc brake or a drum brake.

[0025] The brake ECU 34 is an electronic control unit equipped with a CPU, memory, etc., and is communicatively connected to the hydraulic adjustment device 32. The brake ECU 34 controls the hydraulic adjustment device 32, for example, based on braking requests based on the operation of the brake pedal 30 or braking requests from other ECUs. Furthermore, the brake ECU 34 controls the hydraulic adjustment device 32 based on detection results from various sensors, such as wheel speed sensors 91 installed on each wheel 11, 12, for example, performing anti-skid control (ABS control), sideslip prevention control (ESC control), etc.

[0026] The steering system 5 is a steer-by-wire system, comprising a steering operating device 51, a wheel steering device 52 for steering a pair of front wheels 11, and a steering ECU 53. The steering operating device 51 is essentially a device that detects the driver's steering intention through driver input. Specifically, the steering operating device 51 includes a steering wheel 511 as a steering operating component, a steering column 512, a reaction force motor 513, and an operating angle sensor 514.

[0027] The steering column 512 holds the steering wheel 511 in a rotatable position and is held to the vehicle body (BD). The reaction force motor 513 is a device that applies an operating reaction force to the steering wheel 511. The operation angle sensor 514 detects the angle (operation angle) of the steering wheel 511 from the neutral position to the left or right. The neutral position refers to the state where the steering wheel 511 is in the forward position.

[0028] The wheel steering system 52 is a device that changes the steering angle of the front wheel 11, which serves as the steering wheel, based on the detection results of the operating angle sensor 514 (according to the instruction of the steering ECU 53). Specifically, the wheel steering system 52 includes a pair of steering knuckles 521 and a steering actuator 522. The steering knuckles 521 are suspension arms (not shown) that are rotatably held on the left and right sides respectively, and hold the corresponding front wheel 11 in a rotatable position. In addition, the steering knuckles 521 also serve as the housing of the in-wheel motor unit, including the in-wheel motor 21, the reduction gear, etc. That is, the in-wheel motor 21 is disposed inside the steering knuckles 521, which serve as the housing.

[0029] The steering actuator 522 is configured to hold the steering lever 523 and move the steering lever 523 left and right according to the instructions of the steering ECU 53. Each end of the steering lever 523 is connected to a steering arm (not shown) extending from the steering knuckle 521 via a link 524.

[0030] Specifically, the steering actuator 522 includes a housing 522a that holds the steering rod 523 and a steering motor 522b. The steering rod 523, within the housing 522a, has a threaded groove. Within the housing 522a, a nut (not shown) that holds bearing balls (not shown) and engages with the threaded groove of the steering rod 523 is rotatably held. That is, the steering actuator 522 has a ball screw mechanism consisting of the steering rod 523 and the nut. The steering motor 522b is arranged parallel to the housing 522a and rotates the nut via a drive belt 522c.

[0031] The steering actuator 522 causes the front wheel 11 to turn at an angle corresponding to the rotation of the nut, i.e., the rotation of the steering motor 522b. The steering angle of the front wheel 11 is proportional to the left and right movement of the steering rod 523. The steering actuator 522 is equipped with a steering amount sensor 522d that detects the amount of movement of the steering rod 523, which corresponds to the steering angle of the front wheel 11, via a rack and pinion mechanism.

[0032] The steering ECU 53 is an electronic control unit equipped with a CPU, memory, etc., and is communicatively connected to the steering operation device 51 and the wheel steering device 52. The steering ECU 53 controls the steering system 5, for example, by executing a predetermined program. If normal control without automatic driving is taken as the basic control, the steering ECU 53 sets a target steering amount based on the detection result (operation angle) of the operation angle sensor 514, and controls the rotation amount of the steering motor 522b in such a way that the detection result (steering amount) of the steering amount sensor 522d becomes the target steering amount. Furthermore, the steering ECU 53 controls the reaction force motor 513 to apply an operating reaction force to the steering wheel 511 of a magnitude corresponding to the detected operation angle, restoring the steering to the aforementioned neutral state.

[0033] like Figure 2 As shown, suspension device 6 is a double wishbone suspension device. In the description, the front wheel 11 (in...) Figure 2 The axis of rotation of the left front wheel (in the middle) is defined as the wheel axle WL, and the line passing through the center of the contact surface SC (which is the center of the contact surface of the front wheel 11) and perpendicular to that contact surface is defined as the vertical line VL. Additionally, in Figure 2 and Figure 3 In this configuration, the wheel axle WL is parallel to the road surface. Additionally, it is sometimes used as... Figure 2 and Figure 3 The direction in which the wheel axle WL extends is called the Y-direction, the vertical direction is called the Z-direction, and the direction perpendicular to the wheel axle and horizontal is called the X-direction. When the front wheel 11 is not turning, the X-direction is consistent with the longitudinal direction of the vehicle. The front wheel 11 has a wheel 13 and a tire 14.

[0034] The suspension system 6 includes a base plate 61, a steering knuckle 521, a lower arm 62, an upper arm 63, and a spring damper assembly 66. The base plate 61 is a support that is detachably mounted to the vehicle body BD. The steering knuckle 521 is a bracket that holds the front wheel 11 in a rotatable position. In this embodiment, the steering knuckle 521 also serves as the housing of the in-wheel motor unit.

[0035] The lower arm 62 is an arm component that is rotatably supported on the base plate 61 at one end (base end) and on the lower part of the steering knuckle 521 at the other end (front end). The lower arm 62 is shaped such that one end is divided into two shapes, or in other words, the two arms are joined together at the other end (e.g., V-shaped). One end of the lower arm 62 is connected to two brackets 61a arranged side by side at the lower end of the base plate 61.

[0036] The upper arm 63 is an arm component that is rotatably supported on the base plate 61 at one end (base end) and on the upper part of the steering knuckle 521 at the other end (front end). Similar to the lower arm 62, the upper arm 63 is shaped such that one end is divided into two, or in other words, the two arms are joined together at the other end (e.g., V-shaped). One end of the upper arm 63 is connected to two brackets 61b arranged side by side at the upper end of the base plate 61.

[0037] The other end of the lower arm 62 is connected to the steering knuckle 521 via a ball joint 64 (or a three-ball-pin constant velocity universal joint). The other end of the upper arm 63 is connected to the steering knuckle 521 via a ball joint 65. The steering knuckle 521 is rotatable about the kingpin axis KL defined by the ball joints 64 and 65. The kingpin axis KL is, for example, a straight line passing through the center 64a of the connection between the ball joint 64 and the steering knuckle 521, and the center 65a of the connection between the ball joint 65 and the steering knuckle 521. The spring damper assembly 66 is rotatably supported on the base plate 61 at its upper end and connected to the lower arm 62 at its lower end.

[0038] like Figure 3 As shown, when the kingpin axis KL and the vertical line VL are projected onto a plane perpendicular to the wheel axis WL (hereinafter referred to as the "XZ plane"), the angle formed by these kingpin axes KL and the vertical line VL on this XZ plane is the caster angle θ1. The kingpin axis KL is tilted in a manner that the lower part is more forward than the upper part.

[0039] In addition, such as Figure 2 As shown, when the kingpin axis KL and the vertical line VL are projected onto a plane parallel to the wheel axis WL and perpendicular to the road surface (hereinafter, there exists a case referred to as the "YZ plane"), the angle formed by these kingpin axes KL and the vertical line VL on this YZ plane is the kingpin inclination angle θk. Furthermore, as... Figure 4 As shown, the angle formed by the centerline CL of tire 14 and the vertical line VL on the YZ plane is the camber angle θ2. The centerline CL of tire 14 is a straight line orthogonal to the wheel axis WL and passing through the center of the width direction of tire 14. Additionally, as... Figure 2 As shown, in the XZ plane, the distance between the ground contact center SC and the intersection of the ground contact and the kingpin axis KL is the backslope trailing distance CT.

[0040] like Figure 5 As shown, at each end of the upper arm 63, an adjusting cam 67 is inserted through a cylindrical bushing 71 as a connecting member to the bracket 61b. A through hole extending in the front-rear direction is formed at each end of the upper arm 63. The bushing 71 is disposed in the through hole of the upper arm 63, and the adjusting cam 67 is disposed inside the bushing 71.

[0041] For example, if the vehicle body BD moves forward while the front wheels 11 are stationary, the base plate 61 (bracket 61b) also experiences a forward force from the vehicle body BD, pressing forward on one end of each upper arm 63. Due to the pressing force from the upper arm 63, the bushing 71 elastically deforms (crushes), reducing its front-to-back width. Consequently, the center 65a of the upper arm 63 and the ball joint 65 moves slightly forward relative to the stationary front wheels 11. If a forward force is applied to the vehicle body BD while a counterforce (e.g., braking force, rearward driving force) is acting on the front wheels 11, the upper arm 63 is more susceptible to force than the lower arm 62, which is closer to the road surface, due to torque. Therefore, under these conditions, the bushing 71 of the upper arm 63 is prone to elastic deformation.

[0042] like Figure 5 and Figure 6 As shown, as an example, the adjusting cam 67 includes a graduated cam plate 671, a cam bolt 672, and a nut 673. The head of the cam bolt 672 is disposed on the surface side of the cam plate 671. An eccentric cam portion 672a, which is thicker than other portions, is formed on the shank portion of the cam bolt 672. By rotating the cam bolt 672, the eccentric cam portion 672a rotates, and the position of the upper arm 63 is changed by being pressed by the eccentrically protruding portion. The mechanism of the adjusting cam 67 is known, so a detailed description is omitted.

[0043] The output shaft of an electric motor 68 is connected to the head of the cam bolt 672, for example, via a reduction gear. Although not shown, the electric motor 68 is fixed to the vehicle body BD in a way that prevents rotation relative to the vehicle body BD and allows for movement in the longitudinal direction. Rotation of the cam 67 is adjusted by rotating the output shaft of the electric motor 68, thereby changing the left-right position of the upper arm 63.

[0044] Control device 4 is an electronic control unit equipped with a CPU, memory, etc., and can be communicatively connected to various devices via CAN. For example, control device 4 can be communicatively connected to drive ECU 22, brake ECU 34, steering ECU 53, electric motor 68, and various sensors. Control device 4 is configured to control the driving force applied by drive force application device 2 by instructing drive ECU 22, and to control the braking force applied by braking force application device 3 by instructing brake ECU 34.

[0045] Control device 4 obtains information about vehicle speed from, for example, drive ECU 22, steering information from, for example, steering information from, and braking information from, for example, brake ECU 34. Information about vehicle speed includes, for example, wheel speed, vehicle speed, and acceleration / deceleration requests (requested acceleration, target acceleration, etc.). Information about steering includes, for example, the steering wheel 511 operating angle and steering requests (target steering angle, etc.). Information about braking includes, for example, braking requests (requested deceleration, target deceleration, or target braking force, etc.). For example, in autonomous driving and various specific controls, acceleration / deceleration requests, braking requests, and steering requests are output to the CAN bus even without driver intervention. In other words, the control unit of vehicle control system 1 is configured to include control device 4, drive ECU 22, and brake ECU 34.

[0046] (Lean Angle Change Control)

[0047] The control device 4 is configured to, when receiving a steering request in a parking state where the vehicle is parked, or in a low-speed driving state where the vehicle is traveling at a speed not exceeding a specified speed from the parking state in a pre-set direction in the forward or reverse direction, perform a control to change the caster angle of the drive force application device 2, or the drive force application device 2 and the braking force application device 3, by reducing the caster angle of the front wheel 11 which is the steering wheel.

[0048] In caster angle change control, control device 4 applies a driving force in the direction of the other wheel to one of the front wheels 11 and rear wheels 12, and applies braking force or a driving force in the direction of the other wheel to the other wheel, so as to achieve a stopped state or a low-speed driving state in response to requests related to acceleration and deceleration. Control device 4 determines whether the vehicle is stopped or in a low-speed driving state, for example, based on the acquired vehicle speed information.

[0049] The timing of caster angle change control is assumed to be set when the vehicle is parked in a parking lot or similar location. The specified speed is, for example, set to below 10 km / h. In determining whether the vehicle speed exceeds the specified speed, this determination is reset when the vehicle is parked (speed is 0). That is, if the vehicle speed exceeds the specified speed, even if it subsequently decelerates to below the specified speed, it is not considered a low-speed driving state. A low-speed driving state can also be described as the state in which the vehicle starts from a parked position in a pre-set forward or reverse direction and maintains a speed below the specified speed.

[0050] (Effect of caster angle control)

[0051] According to caster angle change control, a driving force is applied to one wheel in the direction of the other wheel, and a force opposing it (braking force or driving force towards one wheel) is applied to the other wheel. Therefore, a force (torque) similar to the inertial force generated during deceleration while moving forward is applied to the vehicle body BD. In other words, it can be said that a pitching moment in the forward turning direction is applied to the vehicle body BD by caster angle change control. By applying such a force to the vehicle body BD, a forward force is applied to the upper part (in this example, the upper arm 63 and the ball joint 65) that constitutes the upper side of the kingpin axis KL, and the elastic component (in this example, the bushing 71) disposed on the upper part elastically deforms. Through this elastic deformation, the upper arm 63 and the upper side of the kingpin axis KL's passing point 65a move forward relative to the lower side of the kingpin axis KL's passing point 64a.

[0052] Thus, according to this embodiment, by intentionally elastically deforming the elastic component mounted on the vehicle such that it is erected on the kingpin axis KL in the XZ plane, the upper part (upper arm 63) moves forward relative to the steering wheel (front wheel 11), thereby reducing the caster angle θ1. The bushing 71 elastically deforms due to the forces acting on the vehicle body BD and the upper arm 63, and correspondingly, the upper arm 63 moves forward relative to the front wheel 11. Due to the elastic deformation of the bushing 71, the relative position of the center 65a on the upper arm 63 side relative to the center 64a on the lower arm 62 side moves forward, thereby reducing the caster angle θ1.

[0053] The smaller the caster angle θ1, the smaller the restoring torque relative to the front wheels 11 during driving. Furthermore, when stationary, if the caster angle θ1 decreases, the caster trail CT decreases, and the resistance to steering relative to the front wheels 11 decreases. In other words, by controlling the caster angle to decrease θ1, the force required to steer the front wheels 11 when stationary or traveling at low speeds is reduced. According to this embodiment, changing the steering angle of the steering wheels when stationary or traveling at low speeds can reduce the force required for steering.

[0054] Furthermore, according to this embodiment, the load (required torque) on the steering motor 522b can be reduced when it is in a parking state or a low-speed driving state, where it is prone to becoming a high-load condition. Therefore, it is also possible to miniaturize the steering motor 522b. In the steering system 5 with steer-by-wire, no operating force is given to the steering wheels by the driver, and the steering motor 522b bears almost all of the required torque, so the reduction in required torque brought about by the caster angle change control is particularly effective.

[0055] It can also be set so that, for example, when the vehicle speed exceeds the specified speed, or when the steering request disappears (e.g., when the actual steering angle reaches the target steering angle), the control device 4 terminates the caster angle change control in progress. Hereinafter, to explain the caster angle change control in more detail, the control device 4 can selectively execute the first caster angle change control, the second caster angle change control, and the third caster angle change control.

[0056] (First caster angle change control)

[0057] The first caster angle change control is a control that can be performed in a vehicle, i.e., a rear-wheel drive vehicle or a four-wheel drive vehicle, configured with a drive force imparting device 2 capable of imparting drive force to the rear wheels 12. In the first caster angle change control, the micro-speed driving state is the state in which the vehicle moves forward without exceeding a specified speed from the stationary state (hereinafter also referred to as "micro-speed forward state").

[0058] When a steering request is received while the vehicle is stopped or moving at a low speed, as a first caster angle change control, the control device 4 applies braking force to the front wheels 11 and driving force in the forward direction to the rear wheels 12. Figure 7 As shown, according to the first caster angle change control, the vehicle body BD wants to move forward due to the driving force of the rear wheels 12, while the front wheels 11 want to stop. Therefore, when the vehicle body BD is given a torque in the forward turning direction, the bushing 71 on the upper arm 63 side undergoes elastic deformation. As a result, the kingpin axis KL stands up and the caster angle θ1 decreases.

[0059] For example, in the case of maintaining a stationary state without acceleration request, the control device 4 applies braking force to the front wheels 11 in the first caster angle change control, which is sufficient to maintain a stationary state even when subjected to the driving force of the rear wheels 12. The driving force of the rear wheels 12 is, for example, set to the force required to crush the bushing 71 (the force required to crush the bushing 71).

[0060] Additionally, for example, if the vehicle continues to move at a low speed without an acceleration request, the control device 4 sets the driving force of the rear wheel 12 and the braking force of the front wheel 11 in the first caster angle change control so that the driving force of the rear wheel 12 overcomes the braking force of the front wheel 11, allowing the vehicle to move at a low speed and the bushing 71 to crush. When an acceleration or deceleration request is received during the execution of the first caster angle change control, the control device 4 changes the driving force according to the request, and continues to execute the first caster angle change control as long as the execution conditions (0 ≤ vehicle speed ≤ specified speed) are met.

[0061] (Second caster angle change control)

[0062] The second caster angle change control is a control that can be performed in a vehicle, i.e., a front-wheel drive vehicle or a four-wheel drive vehicle, configured with a drive force imparting device 2 capable of imparting drive force to the front wheels 11. In the second caster angle change control, the micro-speed driving state is the state in which the vehicle reverses when the speed does not exceed the specified speed from the stationary state (hereinafter also referred to as the "micro-speed reverse state").

[0063] When a steering request is received while the vehicle is stopped or in a slow reverse position, as a second caster angle change control, the control device 4 applies a reverse driving force to the front wheels 11 and a braking force to the rear wheels 12. Figure 8 As shown, according to the second caster angle change control, the vehicle body BD wants to move backward due to the driving force of the front wheels 11, while the rear wheels 12 want to stop. This generates a torque in the forward turning direction in the vehicle body BD, causing the bushing 71 of the upper arm 63 to elastically deform, the kingpin axis KL to stand upright, and the caster angle θ1 to decrease. The same consideration method as the first caster angle change control is applied to the setting of the driving force and braking force in the second caster angle change control.

[0064] (Third caster angle change control)

[0065] The third caster angle change control is a control that can be performed in a vehicle, i.e., a four-wheel drive vehicle, configured such that the drive force application device 2 can apply drive force to the front wheels 11 and the rear wheels 12. When a steering request is received while the vehicle is parked or traveling at a low speed, as the third caster angle change control, the control device 4 applies a reverse drive force to the front wheels 11 and a forward drive force to the rear wheels 12.

[0066] When maintaining a stationary state and performing the third caster angle change control, the control device 4 sets the braking force of the front wheel 11 and the rear wheel 12 to be the same, or sets the driving force of either the front or rear wheel 11 to be greater than the other, so that the vehicle does not move and the bushing 71 elastically deforms. When maintaining a slow forward state and performing the third caster angle change control, the control device 4 sets the driving force of the rear wheel 12 to be greater than the driving force of the front wheel 11, so that the vehicle moves at a slow forward speed and the bushing 71 elastically deforms. When maintaining a slow reverse state and performing the third caster angle change control, the control device 4 sets the driving force of the front wheel 11 to be greater than the driving force of the rear wheel 12, so that the vehicle reverses at a slow forward speed and the bushing 71 elastically deforms.

[0067] In the third caster angle change control, driving force is applied to the front wheel 11 and the rear wheel 12 in the direction that the distance between the front wheel 11 and the rear wheel 12 decreases. Therefore, it can be said that, for example, in a parked state, compared with the first and second caster angle change controls, the third caster angle change control makes it easier to apply the force that causes the bushing 71 to elastically deform to the vehicle body BD, and makes it easier to make the kingpin axis KL stand up (easier to reduce the caster angle).

[0068] Thus, the low-speed driving state in the third caster angle change control includes a low-speed forward state and a low-speed reverse state. Therefore, in vehicles capable of performing the first to third caster angle change controls as in this embodiment, for example, it can be preset which caster angle change control to perform in each of the states of parking, low-speed forward, and low-speed reverse. Furthermore, the control device 4 can also be configured to select from the first to third caster angle change controls according to the situation.

[0069] (Camber angle change control)

[0070] The control device 4 is configured to also perform camber angle change control. As described above, the vehicle control system 1 includes an adjustment cam 67, which is positioned relative to the front wheel 11 (steering wheel) and whose camber angle θ2 can be changed by rotation, and an electric motor 68 that rotates the adjustment cam 67. The adjustment cam 67 is an example of a camber angle adjustment mechanism, and the electric motor 68 is an example of a drive source. The control device 4 controls the electric motor 68 according to the vehicle speed to perform camber angle change control by adjusting the camber angle θ2. The rotation of the adjustment cam 67 by the rotation of the electric motor 68 changes the left-right position of the upper arm 63. Hereinafter, the camber angle θ2 will be explained using the absolute value of the camber angle θ2.

[0071] For example in Figure 4 In the state of negative camber, the center 65a of the upper arm 63 is connected to the center side of the vehicle body BD by adjustment via the adjusting cam 67. Figure 4 When the left side moves, the kingpin axis KL tilts to the left, and the centerline CL of tire 14 also tilts to the left. As a result, the camber angle θ2 increases. On the other hand, in Figure 4 In this state, from the center 65a outwards ( Figure 4 When the kingpin axis (KL) moves to the right, the centerline CL also tilts to the right. As a result, the outward tilt angle θ2 decreases until the centerline CL exceeds the vertical line VL.

[0072] The larger the camber angle θ2, the more inclined the centerline CL of tire 14 becomes, and the smaller the contact area between tire 14 and the ground (e.g., road surface). Therefore, the friction between tire 14 and the ground surface decreases when changing the steering angle of the front wheel 11, and the steering force required decreases. The control device 4 can also be set to increase the camber angle θ2 when the vehicle speed is below a specified speed, and decrease the camber angle θ2 when the vehicle speed exceeds the specified speed. Thus, increasing the camber angle θ2 at low speeds reduces the steering force required, and returning the camber angle θ2 to the initial set angle at normal driving speeds allows the specified performance to be achieved.

[0073] In this embodiment, the control device 4 performs camber angle change control based on the execution of caster angle change control, and increases the camber angle θ2. That is, the control device 4 increases the camber angle θ2 while performing caster angle change control. As a result, the steering force required is further reduced when the vehicle is stationary or traveling at low speed. The control device 4 performs camber angle change control, for example, after performing caster angle change control. Furthermore, the timing of camber angle change control can be before, after, or simultaneously with the execution of caster angle change control. Camber angle change control can be performed in both vehicles with negative camber and vehicles with positive camber. Caster angle change control and camber angle change control can also be considered as suspension geometry adjustment control.

[0074] If we take the first caster angle change control as an example to explain the control example of vehicle control system 1, then as follows: Figure 10 As shown, based on information from various sensors, it is determined whether the vehicle is in a stopped state or a state of slight forward movement (S1). If the vehicle is in a stopped state or a state of slight forward movement (S1: Yes), it is determined whether there is a steering request (S2). If there is a steering request (S2: Yes), braking force is applied to the front wheels 11 (S3). Next, driving force in the forward direction is applied to the rear wheels 12 (S4). Through steps S3 and S4, the first caster angle change control is performed, and the caster angle θ1 decreases. Next, camber angle change control is performed (S5), and the camber angle θ2 increases. Thus, according to this embodiment, in the stopped state or the state of slight forward movement, the caster angle θ1 decreases and the camber angle θ2 increases, and the force required for steering becomes smaller.

[0075] If the vehicle speed exceeds the specified speed, the caster angle adjustment control ends, and the normal driving force corresponding to the acceleration / deceleration request is applied. Furthermore, if the vehicle speed exceeds the specified speed after the caster angle θ2 has increased through caster angle adjustment control, the control device 4 reduces the caster angle θ2 (for example, returning it to its initial value) through caster angle adjustment control.

[0076] When the second caster angle change control is executed instead of the first caster angle change control, in step S1 it is determined whether the vehicle is in a stopped state or a slightly reversed state. In step S3, braking force is applied to the rear wheels 12, and in step S4, a reverse driving force is applied to the front wheels 11. When the third caster angle change control is executed instead of the first caster angle change control, in step S1 it is determined whether the vehicle is in a stopped state or a slightly moving state. The braking force in step S3 is not applied. In step S4, a reverse driving force is applied to the front wheels 11 and a forward driving force is applied to the rear wheels 12 simultaneously.

[0077] (Steering assist control)

[0078] As a control to reduce the force required for steering (the load on the steering motor 522b), the control device 4, in addition to caster angle change control and camber angle change control, can also perform steering assist control by applying different driving forces to the left and right wheels. For the control device 4, when moving the vehicle forward and turning, as a steering assist control, for example, it can apply a forward driving force to the outer turning wheel and a reverse driving force to the inner turning wheel. This generates a yaw moment in the direction of the desired turn, reducing the force required for steering. In the aforementioned steering assist control, the control device 4 can apply a forward driving force (including 0) to the inner turning wheel that is smaller than the driving force to the outer turning wheel, or it can apply a braking force. This also generates a yaw moment in the direction of the desired turn. Based on the same principle as forward movement, steering assist control can also be performed when reversing.

[0079] (other)

[0080] This invention is not limited to the embodiments described above. For example, the drive source of the drive force imparting device 2 is not limited to the in-wheel motor 21; it could also be an engine or a motor configured in the vehicle body BD. This invention can also be applied to any of gasoline vehicles, hybrid vehicles, electric vehicles, and fuel cell vehicles. Furthermore, if the vehicle is a rear-wheel drive vehicle, a first caster angle change control can be applied; if the vehicle is a front-wheel drive vehicle, a second caster angle change control can be applied. Additionally, this invention can also be applied to autonomous vehicles.

[0081] Furthermore, the braking force application device 3 can be, for example, an electric parking brake. Also, the steering system 5 is not limited to steer-by-wire; it can also be a power steering system. Even in vehicles equipped with a power steering system, by controlling the caster angle, the force required to change the steering angle is reduced, thus reducing the force required for steering assistance or the driver's operating force. Furthermore, the elastically deformable component is not limited to bushing 71; it can be other elastic components, such as bushings installed on various rods.

[0082] Alternatively, control device 4 can be configured to perform caster angle change control only when the vehicle is stationary. In this case, when the vehicle starts moving from a stationary position, caster angle change control ends, the force and inertial force applied to the vehicle body BD disappear, but the crushing of bushing 71 slowly recovers, so it takes a certain amount of time for the caster angle θ1 to return to its initial state. Therefore, the effect of caster angle change control is temporarily maintained even after starting. It is not limited to the end of caster angle change control; by starting the vehicle while caster angle change control is in effect, the force state can change, but in this case, the caster angle θ1 also slowly recovers, and the effect of caster angle change control is maintained to a certain extent. Furthermore, control device 4 can also be configured to perform caster angle change control only when the vehicle is traveling at a low speed. Additionally, control device 4 can also be configured to perform caster angle change control without performing camber angle change control.

[0083] Furthermore, the suspension device 6 is not limited to a double wishbone type; for example, it can also be a strut type. In this case, for example, the center of the upper end of the shock absorber supported on the upper support member of the vehicle body is the point through which the upper side of the kingpin axis KL passes, corresponding to the connection center 65a of the upper arm 63 in this embodiment. Such a structure also uses elastic components in each part, so the kingpin axis KL can be raised by adjusting the caster angle. In addition, even with a strut type, camber angle adjustment control can be performed, for example, by adjusting the position of the lower arm.

[0084] Furthermore, even with a strut-type design, for example, an adjusting cam can be used as a strut bolt to perform camber angle adjustment control with an electric motor, similar to the embodiment described above. Additionally, the camber angle adjustment mechanism can, for example, consist of a nut fixed to one end of the upper arm 63 and a bolt tightened to the nut. By rotating the bolt with the driving force of an electric motor as in the embodiment, the left-right positions of the nut and the upper arm 63 can be adjusted. Furthermore, the connection structure between the upper arm 63 and the base plate 61 is not limited to the adjusting cam 67; it can also be a structure using a bolt and nut. Even with such a structure, a resilient component (e.g., a bushing) is provided at the connection point. Thus, in addition to the embodiments described above, the present invention can be implemented in various modified and improved ways based on the knowledge of those skilled in the art.

Claims

1. A vehicle control system, comprising: The drive force imparting device imparts drive force to at least one of the front wheel and the rear wheel; Braking force applying device, which applies braking force to the front wheel and the rear wheel; and The control device controls the driving force imparted by the driving force imparting device and the braking force imparted by the braking force imparting device. in, The control device is configured to: when a steering request is received while the vehicle is in a parked state, or while the vehicle is traveling at a low speed in a pre-set direction in either the forward or reverse direction at a speed not exceeding a predetermined speed from the parked state, execute a control to reduce the caster angle of the steering wheels, or to change the caster angle of both the driving force application device and the braking force application device. In the caster angle change control, the control device applies a driving force to one of the front and rear wheels in the direction of the other wheel, and applies a braking force or a driving force in the direction of the other wheel, in order to respond to a request related to acceleration or deceleration, to a stopped state or a low-speed driving state. The drive force application device is configured to apply drive force to the rear wheels. The low-speed driving state refers to the state in which the vehicle moves forward while its speed does not exceed the prescribed speed, starting from the stopped state. When the steering request is received in the parking state or the low-speed driving state, as the caster angle change control, the control device applies braking force to the front wheels and applies driving force in the forward direction to the rear wheels.

2. The vehicle control system according to claim 1, wherein, It has a steering system with steer-by-wire capability.

3. The vehicle control system according to claim 1 or 2, wherein, It also has: A camber adjustment mechanism is provided relative to the steering wheel and adjusts the camber angle; and The drive source enables the camber adjustment mechanism to operate. The control device controls the drive source and adjusts the camber angle according to the vehicle speed.

4. The vehicle control system according to claim 3, wherein, The control device controls the drive source to increase the camber angle in response to the execution of the camber angle change control.

5. A vehicle control system, comprising: The drive force imparting device imparts drive force to at least one of the front wheel and the rear wheel; Braking force applying device, applying braking force to the front wheel and the rear wheel; and The control device controls the driving force imparted by the driving force imparting device and the braking force imparted by the braking force imparting device. in, The control device is configured to: when a steering request is received while the vehicle is in a parked state, or while the vehicle is traveling at a low speed in a pre-set direction in either the forward or reverse direction at a speed not exceeding a predetermined speed from the parked state, execute a control to reduce the caster angle of the steering wheels, or to change the caster angle of both the driving force application device and the braking force application device. In the caster angle change control, the control device applies a driving force to one of the front and rear wheels in the direction of the other wheel, and applies a braking force or a driving force in the direction of the other wheel, in order to respond to a request related to acceleration or deceleration, to a stopped state or a low-speed driving state. The drive force application device is configured to apply drive force to the front wheels. The low-speed driving state refers to the state in which the vehicle is reversing when its speed does not exceed the prescribed speed, starting from the stopped state. When the steering request is received in the parking state or the low-speed driving state, as the caster angle change control, the control device applies a driving force in the reverse direction to the front wheels and a braking force to the rear wheels.

6. The vehicle control system according to claim 5, wherein, It has a steering system with steer-by-wire capability.

7. The vehicle control system according to claim 5 or 6, wherein, It also has: A camber adjustment mechanism is provided relative to the steering wheel and adjusts the camber angle; and The drive source enables the camber adjustment mechanism to operate. The control device controls the drive source and adjusts the camber angle according to the vehicle speed.

8. The vehicle control system according to claim 7, wherein, The control device controls the drive source to increase the camber angle in response to the execution of the camber angle change control.

9. A vehicle control system, comprising: The drive force imparting device imparts drive force to at least one of the front wheel and the rear wheel; Braking force applying device, applying braking force to the front wheel and the rear wheel; and The control device controls the driving force imparted by the driving force imparting device and the braking force imparted by the braking force imparting device. in, The control device is configured to: when a steering request is received while the vehicle is in a parked state, or while the vehicle is traveling at a low speed in a pre-set direction in either the forward or reverse direction at a speed not exceeding a predetermined speed from the parked state, execute a control to reduce the caster angle of the steering wheels, or to change the caster angle of both the driving force application device and the braking force application device. In the caster angle change control, the control device applies a driving force to one of the front and rear wheels in the direction of the other wheel, and applies a braking force or a driving force in the direction of the other wheel, in order to respond to a request related to acceleration or deceleration, to a stopped state or a low-speed driving state. The drive force application device is configured to apply drive force to the front wheels and the rear wheels. When the steering request is received in the parking state or the low-speed driving state, as the caster angle change control, the control device applies a driving force in the reverse direction to the front wheels and a driving force in the forward direction to the rear wheels.

10. The vehicle control system according to claim 9, wherein, It has a steering system with steer-by-wire capability.

11. The vehicle control system according to claim 9 or 10, wherein, It also has: A camber adjustment mechanism is provided relative to the steering wheel and adjusts the camber angle; and The drive source enables the camber adjustment mechanism to operate. The control device controls the drive source and adjusts the camber angle according to the vehicle speed.

12. The vehicle control system according to claim 11, wherein, The control device controls the drive source to increase the camber angle in response to the execution of the camber angle change control.

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