Vehicle body behavior control system

Abstract

To provide a vehicle body behavior control device which can effectively suppress pitching behavior of a vehicle body.SOLUTION: A vehicle body behavior control device is provided on a vehicle 1 having a suspension device 210 which so supports wheels RWR, RWL as to be capable of stroking in a bound direction and a rebound direction with respect to a vehicle body B, and has such geometry that a center of the wheel displaces to a front side with respect to the vehicle body according to stroke in the rebound direction, and comprises: a pitching behavior detection part 141 which detects behavior of the vehicle body in a pitching direction; and braking / driving force control parts 130, 140 which perform pitching inhibitory control for periodically increasing a braking force of the wheel or periodically decreasing a driving force of the wheel for when the stroke changes to the bound side when the stroke changes to the rebound side of the suspension device in the case that the pitching behavior has been detected.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a vehicle behavior control device that suppresses pitching behavior of a vehicle.

Background Art

[0002] For example, in a vehicle having a suspension device such as an automobile, pitching behavior may occur in which the vehicle body swings around an axis along the vehicle width direction. As a technique related to suppressing pitching behavior of a vehicle body, for example, in Patent Document 1, in order to suppress fluctuations in the pitch angle of a vehicle during vehicle braking, from the start of vehicle braking, the braking forces of the front and rear wheels are adjusted based on a target front-rear braking force distribution ratio, and when the pitch angle of the vehicle deviates from the target pitch angle, compared with the case where adjustment of the braking forces of the front and rear wheels based on the target front-rear braking force distribution ratio is started, it is described that fluctuations in the pitch angle of the vehicle are suppressed. In Patent Document 2, in order to suppress fluctuations in the pitch attitude of a vehicle body when an override braking operation is performed on automatic braking control and the control of the braking force is switched, when a braking operation is started by a driver during execution of automatic braking control, the target braking force of automatic braking is distributed to the front and rear wheels at a first front-rear distribution ratio R1 to calculate the first target braking forces of the front and rear wheels, and the braking force required by the driver is distributed to the front and rear wheels at a second front-rear distribution ratio R2 preset to a value different from the first front-rear distribution ratio so that the pitch moment of the vehicle body caused by the braking force becomes 0, and it is described that control is performed so that the braking forces of the front and rear wheels become the sum of the first and second target braking forces of the front and rear wheels, respectively. In Patent Document 3, in order to dynamically adjust the distribution of the braking forces of the front and rear wheels in response to changes in the attitude of an automobile during braking and improve the riding comfort, the actual pitch angle of the automobile is detected, and the detected actual pitch angle is compared with a predetermined target pitch angle, and it is described that the distribution of the braking forces of the front and rear wheels is adjusted so that the actual pitch angle approaches the target pitch angle.

Prior Art Documents

Patent Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-177736 [Patent Document 2] Japanese Patent Publication No. 2020-124960 [Patent Document 3] Japanese Patent Publication No. 2019-77221 [Overview of the project] [Problems that the invention aims to solve]

[0004] The technologies described in Patent Documents 1 to 3 all aim to suppress pitching behavior caused by braking force during vehicle braking, but pitching behavior may occur even when not decelerating (braking). For example, when a vehicle travels on a wavy, uneven road surface, a pitching behavior may occur in which the vehicle body repeatedly oscillates periodically in the nose-up and nose-dive directions. If this behavior becomes excessive, it is a concern that it may lead to discomfort and anxiety for the occupants. In view of the above-mentioned problems, the object of the present invention is to provide a vehicle body behavior control device that can effectively suppress the pitching behavior of the vehicle body. [Means for solving the problem]

[0005] To solve the above-mentioned problems, the vehicle body behavior control device according to the first aspect of the present invention is provided on a vehicle having a suspension device that supports a wheel so as to be strokeable relative to the vehicle body in the bounding direction and the rebound direction, and has a geometry in which the center of the wheel is displaced forward relative to the vehicle body in accordance with the stroke in the rebound direction, and the pitching of the vehicle body G-election A pitching behavior detection unit detects movement, and when the pitching behavior is detected, when the stroke of the suspension device changes toward the rebound side... That was, Braking force of the wheels increase or the driving force of the wheels of decrease When the suspension device undergoes a stroke change toward the bound side, the increase in braking force or the decrease in driving force is stopped. It is characterized by comprising a braking force control unit that performs pitch suppression control. According to this, when the suspension device undergoes a stroke change on the rebound side (extension side), a pulling force is applied to the wheel by increasing the braking force or decreasing the driving force, thereby suppressing the forward movement of the wheel relative to the vehicle body. In this case, if the suspension system has a geometry in which the wheels move forward relative to the vehicle body when the stroke changes toward the rebound side, the backward pulling force of such wheels can suppress the stroke change toward the rebound side. On the other hand, in this type of geometry, the backward pulling force on the wheels promotes a change in stroke towards the bounding (compression) side. Therefore, when the stroke changes towards the bounding side, the backward pulling force on the wheels can be prevented from promoting the change in stroke towards the bounding side by stopping the increase in braking force or the decrease in driving force. As described above, according to the present invention, when pitching behavior of the vehicle body occurs, it is possible to suppress the stroke change on the rebound side of the suspension device and prevent the stroke change on the bound side from being exacerbated, thereby effectively suppressing the pitching behavior of the vehicle body with a simple configuration that relies solely on the control of braking and driving forces.

[0006] In the present invention, the suspension device is a rear suspension device that supports the rear wheels, and the braking and driving force control unit can be configured to increase the braking force or decrease the driving force by the pitching suppression control in synchronization with the change in attitude of the vehicle body in the nose dive direction. Generally, to suppress changes in attitude in the direction of nose dive, common measures include suppressing the vehicle's deceleration or generating acceleration in the vehicle. However, according to the present invention, the pitching behavior of the vehicle body can be effectively suppressed by using methods that differ from common technical knowledge, such as increasing braking force or decreasing driving force.

[0007] To solve the above-mentioned problems, a vehicle body behavior control device according to a second aspect of the present invention is provided on a vehicle having a suspension device that supports a wheel so as to be strokeable relative to the vehicle body in the bounding direction and the rebound direction, and has a geometry in which the center of the wheel is displaced forward relative to the vehicle body in accordance with the stroke in the bounding direction, and the pitching of the vehicle body G-election A pitching behavior detection unit detects movement, and when the pitching behavior is detected, the suspension device changes stroke toward the bound side. That was, Braking force of the wheels increase or the driving force of the wheels of decrease When the stroke of the suspension device changes toward the rebound side, the increase in braking force or the decrease in driving force is stopped. It is characterized by comprising a braking force control unit that performs pitch suppression control. According to this, when the suspension device undergoes a stroke change toward the bounding side (compression side), a pulling force is applied to the wheel by increasing the braking force or decreasing the driving force, thereby suppressing the forward movement of the wheel relative to the vehicle body. In this case, if the suspension system has a geometry in which the wheels move forward relative to the vehicle body when the stroke changes toward the bounding side, the backward pulling force of such wheels can suppress the stroke change toward the bounding side. On the other hand, in this type of geometry, the backward pulling force on the wheel promotes a stroke change towards the rebound (extension) side. Therefore, when the stroke changes towards the rebound side, it is possible to prevent the backward pulling force on the wheel from promoting the stroke change towards the rebound side by stopping the increase in braking force or the decrease in driving force. As described above, according to the present invention, when pitching behavior of the vehicle body occurs, it is possible to suppress the stroke change in the suspension device toward the bounce side and prevent the stroke change toward the rebound side from being exacerbated, thereby effectively suppressing the pitching behavior of the vehicle body with a simple configuration that relies solely on the control of braking and driving forces.

[0008] In each of the above inventions, the braking and driving force control unit may be configured to perform the pitching suppression control by using the braking force of the braking device of the wheel, and perform vehicle speed compensation control to increase the driving force of the wheel on the side where the pitching suppression control is not performed between the front wheel and the rear wheel. According to this, it is possible to suppress a decrease in vehicle speed when suppressing pitching behavior using braking force, or to maintain the vehicle speed, preventing the driver from feeling discomfort or uneasiness due to an unintended deceleration, or the need for an accelerator operation for re-acceleration.

[0009] In each of the above inventions, the vehicle is provided with an electric motor that applies at least one of driving force and braking force to the wheel, and the braking and driving force control unit may be configured to perform the pitching suppression control by periodically varying the driving torque generated by the electric motor or the regenerative power generation torque absorbed by the electric motor. According to this, with a simple configuration that controls only the electric motor, it is possible to suppress pitching behavior and suppress or maintain a decrease in vehicle speed.

Effect of the Invention

[0010] As described above, according to the present invention, it is possible to provide a vehicle body behavior control device that can effectively suppress the pitching behavior of the vehicle body.

Brief Description of the Drawings

[0011] [Figure 1] It is a diagram schematically showing the configuration of a vehicle having a first embodiment of a vehicle body behavior control device to which the present invention is applied. [Figure 2] It is a diagram schematically showing the configuration of a rear suspension device of a vehicle having a vehicle body behavior control device of the first embodiment. [Figure 3] It is a diagram showing an example of the pitch angle transition in a vehicle having a vehicle body behavior control device of the first embodiment and a vehicle of a comparative example of the present invention. [Figure 4]It is a diagram showing an example of the transition of the front-wheel single-wheel drive torque, the rear-wheel single-wheel braking torque, and the vehicle speed when pitching behavior occurs in a vehicle having a vehicle body behavior control device according to the first embodiment. [Figure 5] It is a diagram showing another example of the transition of the front-wheel single-wheel drive torque, the rear-wheel single-wheel braking torque, and the vehicle speed when pitching behavior occurs in a vehicle having a vehicle body behavior control device according to the first embodiment. [Figure 6] It is a diagram showing an example of the transition of the front-wheel single-wheel drive torque, the rear-wheel single-wheel braking torque, and the vehicle speed when pitching behavior occurs in a vehicle having a second embodiment of a vehicle body behavior control device to which the present invention is applied. [Figure 7] It is a diagram showing another example of the transition of the front-wheel single-wheel drive torque, the rear-wheel single-wheel braking torque, and the vehicle speed when pitching behavior occurs in a vehicle having a vehicle body behavior control device according to the second embodiment. [Figure 8] It is a diagram showing an example of the pitching angle transition in a vehicle having a vehicle body behavior control device according to the second embodiment and a vehicle of a comparative example of the present invention. [Figure 9] It is a diagram schematically showing the configuration of a rear suspension device of a vehicle having a third embodiment of a vehicle body behavior device to which the present invention is applied. [Figure 10] It is a diagram schematically showing the configuration of a rear suspension device of a vehicle having a fourth embodiment of a vehicle body behavior device to which the present invention is applied. [Figure 11] It is a diagram schematically showing the configuration of a vehicle having a fifth embodiment of a vehicle body behavior control device to which the present invention is applied.

Embodiments for Carrying Out the Invention

[0012] <First Embodiment> Hereinafter, the first embodiment of the vehicle body behavior control device to which the present invention is applied will be described. The vehicle body behavior control device according to the first embodiment is provided, for example, in an automobile such as a four-wheel passenger car having wheels on the front, rear, left, and right, and has a function of suppressing the pitching behavior of the vehicle body (here, it means the part above the spring of the suspension device). Figure 1 is a schematic diagram showing the configuration of a vehicle having a vehicle body behavior control device according to the first embodiment.

[0013] As shown in Figure 1, Vehicle 1 is a four-wheeled automobile such as a passenger car, having a right front wheel (FWR), left front wheel (FWL), right rear wheel (RWR), and left rear wheel (RWL). Vehicle 1 includes an engine 10, a transmission 20, a right front brake 31R, a left front brake 31L, a right rear brake 32R, a left rear brake 32L, a hydraulic control unit 40, and the like.

[0014] The engine 10 is a power source for the vehicle 1, and is, for example, a reciprocating internal combustion engine that uses gasoline or the like as fuel. The transmission 20 is a power transmission device that transmits the output of the engine 10 to the right front wheel FWR and the left front wheel FWL via the drive shaft 21. The transmission 20 is configured by housing, for example, a starting device such as a torque converter, a forward / reverse switching mechanism, a gear shifting mechanism (for example, a variator for a chain-type CVT), a final reduction gear, a front differential, etc., within a transmission case fastened to the rear side of the engine 10. In the first embodiment, the vehicle 1 is a front-wheel drive (FWD) vehicle that transmits the output of the engine 10 only to the right front wheel FWR and the left front wheel FWL.

[0015] The right front brake 31R, left front brake 31L, right rear brake 32R, and left rear brake 32L are hydraulic service brakes (braking devices) that generate braking force and are installed on the right front wheel FWR, left front wheel FWL, right rear wheel RWR, and left rear wheel RWL, respectively. The right front brake 31R, left front brake 31L, right rear brake 32R, and left rear brake 32L each consist of a disc-shaped brake disc (rotor) fixed to the wheel and rotating with the wheel, and a caliper that clamps the brake disc with brake pads having a friction material. The caliper has a wheel cylinder that houses a piston that presses against the brake pads using the hydraulic pressure of the brake fluid. Each brake generates braking force (braking torque) corresponding to the brake fluid pressure transmitted to the wheel cylinder.

[0016] The hydraulic control unit 40 is a hydraulic pressure generator that can individually control the brake fluid pressure transmitted to the wheel cylinders of the right front brake 31R, left front brake 31L, right rear brake 32R, and left rear brake 32L in response to commands from the brake control unit 130. The hydraulic control unit 40 is configured to include, for example, an electric pump for pressurizing brake fluid, a supply valve for controlling the hydraulic pressure of each wheel cylinder, a holding valve, a pressure reducing valve, and the like. The hydraulic control unit 40 overrides the brake fluid pressure generated by a master cylinder (not shown) in response to the driver's brake pedal operation, and can individually adjust the brake fluid pressure of each wheel cylinder.

[0017] Vehicle 1 is further equipped with an engine control unit 110, a transmission control unit 120, a brake control unit 130, a vehicle body behavior control unit 140, and the like. Each of these units can be configured as a microcontroller having an information processing unit such as a CPU, a storage unit such as RAM or ROM, an input / output interface, and a bus to connect them. Furthermore, each unit is connected in a way that allows communication, either via an in-vehicle LAN such as a CAN communication system, or directly.

[0018] The engine control unit 110 comprehensively controls the engine 10 and its auxiliary equipment. The engine control unit 110 has the function of setting the required torque based on, for example, the amount of operation of an acceleration control unit (typically the accelerator pedal) not shown, and controlling the engine 10 so that the actual output (actual torque) of the engine 10 matches the required torque.

[0019] The transmission control unit 120 comprehensively controls the transmission 20 and its auxiliary equipment. The transmission control unit 120 controls the gear ratio in the transmission mechanism and the engagement force of the lock-up clutch provided in the torque converter.

[0020] The brake control unit 130 has the function of giving commands to the hydraulic control unit 40 to individually control the wheel cylinders of the right front brake 31R, left front brake 31L, right rear brake 32R, and left rear brake 32L. The brake control unit 130 has functions such as anti-lock brake control, vehicle stabilization control, and torque vectoring control.

[0021] Anti-lock brake control intermittently reduces the braking force on a wheel that locks up during braking, thereby restoring the wheel's rotation. Vehicle stabilization control generates a yaw moment in the direction that suppresses understeer or oversteer behavior by creating a difference in braking force between the left and right wheels. Torque vectoring control applies braking force to the inner wheel during a turn, generating a yaw moment that promotes yaw motion. Furthermore, the brake control unit 130 has the function of generating braking force on the right rear brake 32R and the left rear brake 32L in response to commands from the vehicle body behavior control unit 140. This point will be explained in more detail later. The brake control unit 130, in conjunction with the vehicle body behavior control unit 140 and the like, functions as the braking and driving force control unit of the present invention.

[0022] The brake control unit 130 is connected to a vehicle speed sensor 131, an acceleration sensor 132, a yaw rate sensor 133, and the like. The vehicle speed sensor 131 is installed in the hub portion that supports each wheel and generates a vehicle speed signal corresponding to the rotational speed of each wheel. The brake control unit 130 can calculate the rotational speed of each wheel individually based on the output of the vehicle speed sensor 131. The acceleration sensor 132 detects acceleration acting on the vehicle body in the longitudinal direction and the vehicle width direction, respectively. The yaw rate sensor 133 is a gyro sensor that detects the yaw rate (rotational speed around the vertical axis) of the vehicle.

[0023] The vehicle body behavior control unit 140 performs vehicle body behavior control (pitching suppression control) that suppresses the pitching behavior of the vehicle body (above the sprung mass) by periodically generating braking force on the right rear brake 32R and the left rear brake 32L. The specific details of the pitching suppression control will be explained in more detail later. A suspension stroke sensor 141 is connected to the vehicle body behavior control unit 140. The suspension stroke sensor 141 is a pitching behavior detection unit that detects the stroke amount of the front suspension supporting the right front wheel FWR and left front wheel FWL, and the rear suspension supporting the right rear wheel RWR and left rear wheel RWL.

[0024] Figure 2 is a schematic diagram showing the configuration of the rear suspension system of a vehicle having a vehicle body behavior control device according to the first embodiment. Figure 2 shows the rear suspension system supporting the right rear wheel (RWR) as viewed from the outside in the vehicle width direction. In Figure 2, for ease of understanding, only the elements of the rear suspension system that dominate the behavior of the wheel center C during stroke, as viewed from the vehicle width direction, are illustrated. (The same applies to Figures 9 to 10 described later.)

[0025] In the first embodiment, the rear suspension device 210 is, for example, of the trailing link arm type. A hub bearing housing (not shown) to which the right rear wheel RWR is mounted is attached to the vehicle body B via a trailing arm 211. The trailing arm 211 protrudes forward and diagonally upward from the wheel center C of the rear wheel RW. The front end 212 of the trailing arm 211 is connected to the vehicle body B so as to be able to swing around a central axis along the vehicle width direction, on the front and above side with respect to the wheel center C.

[0026] In such a trailing arm type rear suspension device 210, the trajectory of the wheel center C during stroke is an arc centered on the front end 212 of the trailing arm 211, as shown by the dashed line in Figure 2. In this case, when the rear suspension device 210 strokes in the bounding direction (compression direction), the wheel center C moves backward while rising relative to the vehicle body B. Furthermore, when the rear suspension device 210 strokes in the rebound direction (extension direction), the wheel center C moves forward while descending relative to the vehicle body B.

[0027] In the first embodiment, when pitching behavior (pitching vibration) of the vehicle body B occurs due to, for example, unevenness of the road surface, the vehicle body behavior control device performs pitching suppression control to suppress the stroke change in the rebound direction of the rear suspension device 210 in order to suppress the pitching behavior. Figure 3 shows an example of the pitch angle transition in a vehicle having the vehicle body behavior control device of the first embodiment and in a comparative example of the present invention. Figure 3 shows the conditions when a vehicle passes over a road surface with wavy irregularities (for example, approximately 1.7 Hz when traveling at a vehicle speed of 60 km / h). In Figure 3, the horizontal axis represents time, the upper vertical axis represents the pitch angle of the vehicle (positive (upward) is the nose dive direction, negative (downward) is the nose up direction), and the lower vertical axis represents the driving torque of the front and rear wheels. (The same applies to Figure 8, which will be described later.) In this case, although the output torque of engine 10 is constant, the drive torque of the front wheels fluctuates periodically due to the twisting of the drivetrain's shaft members, etc., as the right front wheel FWR and left front wheel FWL, which are the drive wheels, pass over the wavy uneven surface.

[0028] In the first embodiment, the vehicle body behavior control unit 140 calculates the pitch angle of the vehicle body B based on the output of the suspension stroke sensor 141. When the vehicle body behavior control unit 140 detects the occurrence of pitching behavior (pitching vibration) in which the vehicle body B oscillates along the vehicle width direction, it performs control to generate a braking force BF (see Figure 2) so that a braking torque of, for example, 100 Nm is periodically generated in the right rear brake 32R and the left rear brake 32L in accordance with the pitching behavior. This braking force BF is generated in sync with the timing of the vehicle body B transitioning from a nose-up direction to a nose-dive direction. At this time, the front suspension device changes stroke toward the bound side (compression side), and the rear suspension device 210 changes stroke toward the rebound side (extension side).

[0029] Here, as shown in Figure 2, in the first embodiment, when the rear suspension device 210 changes stroke toward the rebound side, the wheel center C of the right rear wheel RWR moves forward relative to the vehicle body B. At this time, when the right rear brake 32R generates a braking force BF and applies a backward pulling force BF to the right rear wheel RWR, a moment M and an anti-dive force Fa are generated that rotate the trailing arm 211 in the bound direction (clockwise direction in Figure 2), thereby suppressing the stroke change of the rear suspension device 210 toward the rebound side. (The same applies to the left rear wheel RWL.) The anti-dive force Fa is a downward force acting on the front end 212 of the trailing arm 211. The anti-dive force Fa works in conjunction with the aforementioned moment M to reduce pitching behavior by suppressing the upward movement of the rear of the vehicle body. The anti-dive force Fa is given by Fa = BF × tanθ, where θ is the inclination of the straight line connecting the front end 212 of the trailing arm 211 and the wheel center C in the side view shown in Figure 2.

[0030] In the comparative examples and the embodiments described later, the same reference numerals are used for parts common to the previous embodiments, and their descriptions are omitted. The differences will be explained in detail. In the comparative example vehicle of the present invention, periodic generation of braking force in response to the pitching behavior described above (pitching suppression control) is not performed. As shown in the upper part of Figure 3, according to the first embodiment, by periodically generating a braking force in response to pitching vibrations, the pitching behavior of the vehicle body can be suppressed compared to the comparative example.

[0031] According to the first embodiment described above, when the stroke of the rear suspension device 210 changes toward the rebound side, the increase in braking force BF applies a backward pulling force to the right rear wheel RWR and the left rear wheel RWL, thereby suppressing the forward movement of the right rear wheel RWR and the left rear wheel RWL relative to the vehicle body B. Here, the rear suspension device 210 has a geometry in which the rear wheel moves forward relative to the vehicle body B when the stroke changes toward the rebound side. Therefore, this backward pulling force on the rear wheel can suppress the stroke change toward the rebound side. On the other hand, in this type of geometry, the backward pulling force on the right rear wheel (RWR) and left rear wheel (RWL) promotes a change in stroke towards the bounding side. Therefore, by stopping the increase in braking force when the stroke changes towards the bounding side, it is possible to prevent the backward pulling force on the right rear wheel (RWR) and left rear wheel (RWL) from promoting a change in stroke towards the bounding side. Therefore, according to the first embodiment, when pitching behavior of the vehicle body B occurs, it is possible to suppress the stroke change in the rear suspension device 210 toward the rebound side and prevent the stroke change toward the bound side from being exacerbated, thereby effectively suppressing the pitching behavior of the vehicle body B with a simple configuration that relies solely on braking force control. Generally, to suppress changes in attitude in the direction of nose dive, common measures include suppressing the vehicle's deceleration or generating acceleration in the vehicle. However, according to the first embodiment, the pitching behavior of the vehicle body B can be effectively suppressed by using a method that differs from common technical knowledge, namely by increasing the braking force BF.

[0032] <Second Embodiment> Next, a second embodiment of a vehicle body behavior control device to which the present invention is applied will be described. The vehicle body behavior control device of the second embodiment performs vehicle speed compensation control, as described below, in addition to pitching suppression control similar to that of the first embodiment. Figure 4 shows an example of the changes in the front wheel single-wheel drive torque, rear wheel single-wheel braking torque, and vehicle speed when pitching behavior occurs in a vehicle equipped with the vehicle body behavior control device of the first embodiment. Figure 5 shows another example of the changes in the front wheel single-wheel drive torque, rear wheel single-wheel braking torque, and vehicle speed when pitching behavior occurs in a vehicle equipped with the vehicle body behavior control device of the first embodiment. In Figures 4 and 5, the horizontal axis represents time, and the vertical axis represents vehicle speed, front wheel single-wheel driving torque, and rear wheel single-wheel braking torque. (The same applies to Figures 6 and 7, which will be discussed later.) Figure 4 shows the case where the braking torque generated periodically on the right rear brake 32R and the left rear brake 32L in response to the pitching behavior is 100 Nm, and Figure 5 shows the case where it is 600 Nm.

[0033] As shown in Figures 4 and 5, the vehicle speed decreases by periodically generating braking force on the right rear brake 32R and the left rear brake 32L in response to the pitching behavior. This decrease in vehicle speed is particularly noticeable when the braking force is increased, as shown in Figure 5. Therefore, in the second embodiment, when pitching suppression control is performed, the vehicle body behavior control unit 140 gives commands to the engine control unit 110 and the transmission control unit 120 to increase the driving force transmitted to the right front wheel FWR and the left front wheel FWL, thereby performing vehicle speed compensation control to suppress the decrease in vehicle speed. Specifically, the engine control unit 110 performs control to increase the torque generated by the engine 10. In this case, if maintaining vehicle speed is difficult with only an increase in engine torque 10, the transmission control unit 120 shifts the transmission 20 to increase the gear ratio (reduction ratio), thereby increasing the torque at the right front wheel FWR and the left front wheel FWL.

[0034] Figure 6 shows an example of the changes in the front wheel single-wheel drive torque, rear wheel single-wheel braking torque, and vehicle speed when pitching behavior occurs in a vehicle equipped with the vehicle body behavior control device of the second embodiment. Figure 7 shows another example of the changes in the front wheel single-wheel drive torque, rear wheel single-wheel braking torque, and vehicle speed when pitching behavior occurs in a vehicle equipped with the vehicle body behavior control device of the second embodiment. Figure 6 shows the case where the braking torque generated periodically on the right rear brake 32R and the left rear brake 32L in response to the pitching behavior is 100 Nm, and Figure 7 shows the case where it is 600 Nm.

[0035] In the second embodiment, as shown in Figures 6 and 7, by increasing the driving force of the front wheels through vehicle speed compensation control, it is possible to suppress the decrease in vehicle speed or maintain the vehicle speed even when pitching suppression control using braking force is performed. Figure 8 shows an example of the pitch angle transition in a vehicle having the vehicle body behavior control device of the second embodiment and in a comparative example of the present invention. Figure 8 shows a case where a braking torque of 600 Nm is generated per rear wheel in pitching suppression control. As shown in Figure 8, in the second embodiment, by performing vehicle speed compensation control during pitching suppression control, the decrease in vehicle speed can be suppressed. Therefore, even if the braking torque generated during pitching suppression control is increased, it is possible to prevent the occupants from feeling uncomfortable or anxious due to unintended deceleration, and to prevent the driving operation from becoming complicated due to the need to operate the accelerator to re-accelerate. Furthermore, since the braking torque generated in the pitching suppression control can be set to a larger value, the effect of suppressing pitching behavior can be improved.

[0036] According to the second embodiment described above, in addition to the effects similar to those of the first embodiment described above, it is possible to suppress the decrease in vehicle speed when suppressing pitching behavior using braking force BF, or to maintain vehicle speed, thereby preventing unintended deceleration from causing discomfort or anxiety to the occupants, and preventing the need for accelerator operation to re-accelerate.

[0037] <Third Embodiment> Next, a third embodiment of a vehicle body behavior control device to which the present invention is applied will be described. The vehicle body behavior control device of the third embodiment is installed in a vehicle having a strut-type suspension system 220, which will be described below, instead of the trailing arm type suspension system of the first and second embodiments. Figure 9 is a schematic diagram showing the configuration of the rear suspension system of a vehicle having a vehicle body behavior control device according to the third embodiment.

[0038] The rear suspension system 220 has a strut 221. The strut 221 has a hydraulic shock absorber (damper) that generates damping force according to the suspension stroke speed. The strut 221 is positioned with its extension and contraction direction (the direction of the shock absorber rod axis) tilted backward relative to the vertical, such that the upper end is on the rearward side of the vehicle relative to the lower end.

[0039] The upper end of the strut 211 is attached to the vehicle body B via an elastic mount, such as rubber. The lower end of the strut 211 is connected to the hub bearing housing that supports the right rear wheel (RWR) and the left rear wheel (RWL). In this rear suspension device 220 as well, similar to the rear suspension device 210 of the first embodiment, when stroked in the bounding direction (compression direction), the wheel center C rises and moves backward relative to the vehicle body B. Furthermore, when the rear suspension device 220 strokes in the rebound direction (extension direction), the wheel center C moves forward while descending relative to the vehicle body B.

[0040] The third embodiment described above can also achieve the same effects as the first and second embodiments by performing pitching suppression control similar to that of the first and second embodiments described above.

[0041] <Fourth Embodiment> Next, a fourth embodiment of a vehicle body behavior control device to which the present invention is applied will be described. The vehicle body behavior control device of the fourth embodiment is installed in a vehicle having a double wishbone type rear suspension device 230, which will be described below, instead of the trailing arm type suspension device of the first and second embodiments. Figure 10 is a schematic diagram showing the configuration of the rear suspension system of a vehicle having a vehicle body behavior control device according to the fourth embodiment.

[0042] The rear suspension system 230 includes a front upper link 231, a rear upper link 232, a front lower link 233, and a rear lower link 234. Each link has its inner end in the vehicle width direction pivotably connected to the vehicle body B, and its outer end in the vehicle width direction pivotably connected to the hub bearing housing H that supports the right rear wheel RWR and the left rear wheel RWL.

[0043] The front upper link 231 and rear upper link 232 are positioned above the wheel centers C of the right rear wheel RWR and left rear wheel RWL, and are arranged sequentially from the front of the vehicle. The front lower link 233 and rear lower link 234 are positioned below the wheel center C of the right rear wheel RWR and left rear wheel RWL, and are arranged sequentially from the front of the vehicle.

[0044] The end of the front upper link 231 on the vehicle body B side is positioned higher than the end of the rear upper link 232 on the vehicle body B side. The housing H-side end of the front upper link 231 is positioned higher than the housing H-side end of the rear upper link 232. The end of the front lower link 233 on the vehicle body B side is positioned higher than the end of the rear lower link 234 on the vehicle body B side. The H-side end of the front lower link 233 is positioned higher than the H-side end of the rear lower link 234.

[0045] With this arrangement, the rear suspension device 230, like the rear suspension device 210 of the first embodiment, has a geometry in which, when stroked in the bounding direction (compression direction), the wheel center C rises and moves backward relative to the vehicle body B. Furthermore, when the rear suspension device 230 strokes in the rebound direction (extension direction), the wheel center C moves forward while descending relative to the vehicle body B.

[0046] The fourth embodiment described above can also achieve the same effects as the first and second embodiments by performing pitching suppression control similar to that of the first and second embodiments described above.

[0047] <Fifth Embodiment> Next, a fifth embodiment of a vehicle body behavior control device to which the present invention is applied will be described. In the fifth embodiment, the vehicle 1A is an electric vehicle such as a battery electric vehicle (BEV), an engine-electric series hybrid vehicle (HEV), or a fuel cell vehicle (FCV), which has independent motor generators on the front wheel side and the rear wheel side, respectively. Figure 11 is a schematic diagram showing the configuration of a vehicle having a vehicle body behavior control device according to the fifth embodiment. Vehicle 1A of the fifth embodiment is equipped with a front motor generator 50F, a rear motor generator 50R, a motor generator control unit 150, etc., which are described below, in place of the engine 10, transmission 20, engine control unit 110, and transmission control unit 120 of Vehicle 1 of the first embodiment.

[0048] The front motor generator 50F has a rotating electric machine, such as a permanent magnet synchronous motor, that generates driving force for the right front wheel FWR and the left front wheel FWL. The front motor generator 50F has the function of absorbing torque from the right front wheel FWR and the left front wheel FWL, and performing regenerative power generation. The rear motor generator 50R has a rotating electric machine such as a permanent magnet synchronous motor that generates driving force for the right rear wheel RWR and the left rear wheel RWL. The rear motor generator 50R has the function of absorbing torque from the right rear wheel (RWR) and the left rear wheel (RWL) and performing regenerative power generation. The front motor generator 50F and the rear motor generator 50R are connected to the left and right wheels via the drive shaft 51. The front motor generator 50F and the rear motor generator 50R have a differential (not shown) that absorbs the difference in rotational speed between the left and right wheels during turns, etc.

[0049] The motor-generator control unit 150 has the function of individually controlling the target torque when the front motor-generator 50F and the rear motor-generator 50R are driven, and the amount of regenerative power generated (braking force (braking torque) of the regenerative braking system) when regenerative power generation is performed. In the fifth embodiment, the driving force control of the right front wheel FWR and left front wheel FWL, and the periodic braking force application control (pitching suppression control) of the right rear wheel RWR and left rear wheel RWL, similar to the first and second embodiments, are performed by controlling the driving torque of the front motor generator 50F and the regenerative power generation amount of the rear motor generator 50R. In the fifth embodiment described above, the same pitching behavior suppression effect as in the first and second embodiments described above can be obtained.

[0050] (modified version) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, all of which fall within the technical scope of the present invention. (1) The configuration of the vehicle body behavior control device, suspension system, vehicle, etc. is not limited to the embodiments described above and can be modified as appropriate. (2) In each embodiment, pitching behavior is detected by detecting the stroke of the suspension device, but the method for detecting pitching behavior is not limited to this and can be changed as appropriate. For example, pitching behavior may be detected based on the wheel speed of each wheel, the longitudinal acceleration of the vehicle body, and the vertical acceleration. Alternatively, sensors such as gyro sensors may be provided to detect the angular velocity in the pitch direction of the vehicle body, various accelerations, etc. (3) In each embodiment, pitching behavior is suppressed by applying braking force to the rear wheels. However, if the wheel to which pitching suppression control is applied is a drive wheel, a configuration that periodically reduces the driving force or a configuration that periodically switches from a driving state to a braking state may be used. (4) In each embodiment, pitching behavior is suppressed by controlling the braking and driving force of the rear wheels, but a configuration in which braking and driving force control is performed on the front wheels is also possible. In this case as well, pitching behavior can be suppressed by periodically controlling the braking and driving force in accordance with the forward and backward movement of the wheels relative to the vehicle body during the stroke of the front suspension device. In this case, pitching suppression control may be performed independently or in coordination for the front wheels and the rear wheels. (5) In the first to fourth embodiments, the vehicle was a front-wheel drive vehicle as an example, but the present invention is not limited to this and can also be applied to rear-wheel drive vehicles and four-wheel drive vehicles (AWD vehicles). In addition, in AWD vehicles, if there is a restraining mechanism that restrains the rotational speed difference between the front-wheel drive mechanism and the rear-wheel drive mechanism (for example, a coupling such as a wet multi-plate clutch provided in the AWD transfer case), the restraining force in the restraining mechanism can be reduced compared to normal conditions, preferably to a released state, in order to suppress the influence of the internal circulating torque transmitted between the front-wheel drive mechanism and the rear-wheel drive mechanism. (6) In the fifth embodiment, a motor generator that drives both the left and right wheels is used, but the present invention is not limited to this, and for example, a configuration in which independent motor generators are provided for the left and right wheels (typically an in-wheel motor) may also be used. Alternatively, a motor-generator may be provided on only one of the front or rear wheels, while the other is driven by another power source, such as an internal combustion engine, or the other wheel may not have a power source for driving. [Explanation of symbols]

[0051] 1 Vehicle (First Embodiment) 1A Vehicle (Sixth Embodiment) B Body FWR Right front wheel FWL Left front wheel RWR Right rear wheel RWL Left rear wheel C Wheel center BF Braking force 10 Engine 20 Transmission 21 Drive shaft 31R Right front brake 31L Left front brake 32R Right rear brake 32L Left rear brake 40 Hydraulic Control Unit 50F Front Motor Generator 50R Rear Motor Generator 51 Drive shaft 110 Engine control unit 120 Transmission control unit 130 Brake control unit 131 Vehicle speed sensor 132 Accelerometer 133 Yaw rate sensor 140 Vehicle body behavior control unit 141 Suspension stroke sensor 150 Motor Generator Control Unit 210 Rear suspension system (first embodiment) 211 Trailing arm 212 Front end 220 Rear suspension system (third embodiment) 221 Strut 230 Rear suspension system (fourth embodiment) 231 Front upper link 232 Rear upper link 233 Front lower link 234 Rear lower link

Claims

1. A suspension system is provided in a vehicle having a suspension device that supports the wheel so as to be able to stroke relative to the vehicle body in the bounding direction and the rebound direction, and has a geometry in which the center of the wheel is displaced forward relative to the vehicle body in accordance with the stroke in the rebound direction. A pitching behavior detection unit for detecting the pitching behavior of the vehicle body, When the aforementioned pitching behavior is detected, a braking and driving force control unit performs pitching suppression control by increasing the braking force of the wheel or decreasing the driving force of the wheel when the stroke of the suspension device changes toward the rebound side, and stopping the increase in braking force or the decrease in driving force when the stroke of the suspension device changes toward the bound side. A vehicle body behavior control device characterized by being equipped with

2. The suspension device is a rear suspension device that supports the rear wheels. The braking and driving force control unit increases the braking force or decreases the driving force by the pitching suppression control in synchronization with the change in the vehicle body's attitude in the nose dive direction. A vehicle body behavior control device according to claim 1, characterized by the above.

3. A suspension system is provided for a vehicle having a suspension device that supports a wheel so as to be able to stroke relative to the vehicle body in the bounding direction and the rebound direction, and has a geometry in which the center of the wheel is displaced forward relative to the vehicle body in accordance with the stroke in the bounding direction. A pitching behavior detection unit for detecting the pitching behavior of the vehicle body, When the aforementioned pitching behavior is detected, a braking and driving force control unit performs pitching suppression control by increasing the braking force of the wheel or decreasing the driving force of the wheel when the stroke of the suspension device changes toward the bounce side, and stopping the increase in braking force or the decrease in driving force when the stroke of the suspension device changes toward the rebound side. A vehicle body behavior control device characterized by being equipped with

4. The braking force control unit performs pitch suppression control using the braking force of the wheel's braking device, and also performs vehicle speed compensation control to increase the driving force of the wheel on the side of the front and rear wheels that is not being subjected to pitch suppression control. A vehicle body behavior control device according to any one of claims 1 to 3, characterized by the above.

5. The vehicle is provided with an electric motor that provides at least one of a driving force and a braking force to the wheels. The braking force control unit performs the pitching suppression control by periodically varying the drive torque generated by the electric motor or the regenerative power generation torque absorbed by the electric motor. A vehicle body behavior control device according to any one of claims 1 to 3, characterized by the above.

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