JP5043785B2 - Vehicle attitude control device - Google Patents

Description

  The present invention relates to a vehicle attitude control device provided with a damping force variable damper and an EBD, and more particularly to a technique for preventing a vehicle attitude disorder and an unnatural deceleration feeling when nose dives are suppressed.

  In recent years, various types of cylindrical dampers used in automobile suspensions have been developed that can control the damping force stepwise or steplessly in order to improve ride comfort and steering stability ( Patent Document 1). In a vehicle equipped with a variable damping force damper (hereinafter simply referred to as a damper), it is possible to improve ride comfort and driving stability by variably controlling the damping force of the damper according to the running state of the vehicle. . For example, when the vehicle is turning, the vehicle body rolls in the left-right direction due to inertial force (lateral acceleration) that accompanies lateral movement, but the vehicle body becomes excessively large by increasing the target damping force of the damper according to the differential value of the lateral acceleration. Rolls can be suppressed. Further, during braking, the nose dive of the vehicle body can be suppressed by increasing the target damping force of the damper according to the longitudinal acceleration (deceleration) and the vehicle speed.

On the other hand, since the load distribution on the front and rear changes greatly depending on the number of passengers and the number of luggage in automobiles, the rear wheel braking force is secured during heavy loading, etc., and the rear wheels are prevented from idling (locking) during light loading. Therefore, those equipped with an EBD (Electronic Brake force Distribution system) that variably controls the front / rear braking force distribution according to the rear wheel load are increasing (see Patent Document 2). In EBD, for example, when the deceleration during braking exceeds a predetermined value, the ratio between the wheel speed on the rear wheel side and the wheel speed on the front wheel side becomes a predetermined value (the wheel speed on the rear wheel side is By driving and controlling the braking force distribution device (ABS modulator unit, etc.) so that it is slightly higher than the wheel speed on the front wheel side, it is possible to decelerate and stop in a short time while preventing the rear wheel from idling. .
JP 2007-290461 A JP-A-9-136627

  However, in a vehicle in which a damping force variable damper and an EBD are provided, when the nose dive suppression control is performed by the damping force variable damper, the front / rear braking force distribution may not be appropriately performed. Normally, the forward pitch moment acts on the vehicle body due to the inertial force acting on the center of gravity during braking, so if the target damping force of the variable damping force damper is increased by nose dive suppression control, A pulling force (that is, a force that reduces the ground contact load of the rear wheel) acts. For this reason, if normal front / rear braking force distribution by EBD is performed when nose dives are suppressed, excessive braking force acts on the rear wheel side even though the ground contact load is reduced. There is a possibility that the vehicle posture may be disturbed or the driver may feel an unnatural deceleration.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a vehicle attitude control device that prevents the vehicle attitude from being disturbed and an unnatural feeling of deceleration during nose dive suppression.

According to a first aspect of the present invention, there is provided a variable damping force damper interposed between a vehicle body and each wheel, and braking during deceleration that reduces a braking force distribution to the rear wheel side by a predetermined amount at least when the longitudinal acceleration exceeds a predetermined value. A vehicle attitude control device comprising a braking force distribution means for controlling, a nose dive prediction means for predicting a nose dive of a vehicle body, and a damping force variable damper based on a prediction result of the nose dive prediction means In contrast, when it is determined that nose dive suppression means for performing nose dive suppression control and the nose dive suppression control has been executed, the braking force distribution means is more controlled to the rear wheel side than during the deceleration braking control. Brake force distribution control means for further reducing power distribution is provided.

  According to a second aspect of the present invention, in the vehicle attitude control device according to the first aspect of the invention, the braking force distribution control means includes the nose dive based on deceleration of the vehicle body and stroke information of the damping force variable damper. The execution of the suppression control is determined.

  According to a third aspect of the present invention, in the vehicle attitude control device according to the first aspect of the invention, the braking force distribution control unit determines execution of the nose dive suppression control based on control information of the nose dive suppression unit. It is characterized by that.

  According to the first invention, even when the target damping force of the damping force variable damper is increased during braking and the ground contact load on the rear wheel is reduced, the braking force distribution on the rear wheel side is reduced, so that The vehicle posture will not be disturbed, and the driver will not feel unnatural deceleration. According to the second aspect of the invention, since the braking force distribution control unit determines the execution of the nose dive suppression control independently of the nose dive suppression unit, it is not necessary to exchange signals between both units. Further, according to the third invention, since the braking force distribution control means determines the execution of the nose dive suppression control based on the control information from the nose dive suppression means, it is not necessary to process the output signal from the sensor, etc. The program can be simplified and the control response can be improved.

  Hereinafter, embodiments in which the present invention is applied to a four-wheeled vehicle will be described in detail with reference to the drawings. FIG. 1 is a plan view schematically illustrating a device configuration of an automobile according to the embodiment, and FIG. 2 is a block diagram illustrating a main configuration of a control device according to the embodiment.

<< Configuration of Embodiment >>
<Automobile device configuration>
First, a schematic configuration of an automobile according to an embodiment will be described with reference to FIG. In the description, for the four wheels and members arranged for them, that is, tires, suspensions, and the like, subscripts indicating front, rear, left and right are attached to the reference numerals, for example, left front wheel 3fl, right front wheel 3fr, left For example, the rear wheel 3rl and the right rear wheel 3rr are collectively referred to as the wheel 3.

  In the automobile 1 shown in FIG. 1, four wheels 3 are respectively installed on the front, rear, left and right of the vehicle body 2, and each wheel 3 includes a suspension arm, a spring, a damping force variable damper (hereinafter simply referred to as a damper) 4, and the like. The vehicle body 2 is supported via a suspension 5. Each wheel 3 is provided with a tire 6 on its outer periphery and a brake (disc brake caliper) 7 on its inner periphery. The automobile 1 has an engine 8 mounted on the front thereof. In addition, the automobile 1 includes a steering angle sensor 11 that detects the steering angle, a yaw rate sensor 12 that detects the yaw rate of the vehicle body 2, a longitudinal G sensor 13 that detects the longitudinal acceleration of the vehicle body 2, and a lateral G that detects the lateral acceleration of the vehicle body 2. In addition to providing the sensor 14 and the like in the vehicle interior, a wheel speed sensor 15 for detecting the wheel speed and a stroke sensor 16 for detecting the stroke of the damper 4 are provided for each wheel 3.

  The automobile 1 has a vehicle ECU (Vehicle Stability Assist system) -ECU (Electronic Control Unit) 21 in addition to a damper ECU 22 that controls the drive of the damper 4 and an engine 8 in the vehicle interior. An engine ECU 23 to be controlled and a hydraulic unit 24 for supplying pressure oil to each brake 7 are installed. Each of the ECUs 21 to 23 includes a microcomputer, a ROM, a RAM, a peripheral circuit, an input / output interface, various drivers, and the like, and is connected to each other via a communication line (CAN (Controller Area Network) in this embodiment). It is connected. The hydraulic unit 24 includes four systems such as an electromagnetic valve and a hydraulic circuit that are PWM-controlled. In addition to supplying pressure oil to the brake 7 of each wheel 3 in accordance with a driver's brake operation, the hydraulic unit 24 has a VSA-ECU 21. Is supplied to the brake 7 of each wheel 3 on the basis of the operation command.

<Main part configuration of control device>
As shown in FIG. 2, the damper ECU 22 includes a nose dive prediction unit 31 in addition to a known damping force control unit (not shown) that sets a target damping force of each damper 4 according to the motion state of the automobile 1. A nose dive suppressing portion 32 is internally provided. The nose dive prediction unit 31 predicts the nose dive (nose dive amount) of the automobile 1 based on the longitudinal acceleration Gx and the vehicle speed V. Further, the nose dive suppression unit 32 determines whether nose dive suppression control is necessary based on the prediction result of the nose dive prediction unit 31. At the same time as outputting the target current, a nose dive suppression signal Snd is output to the VSA-ECU 21.

  The VSA-ECU 21 includes a nose dive suppression determination unit 42, an EBD operation ratio setting unit 43, a braking control unit 41 that sets a target braking amount, and an engine control unit (not shown) that sets a target engine output. Is decorated. The nose dive suppression determination unit 42 determines whether or not nose dive suppression control is executed based on the nose dive suppression signal Snd input from the nose dive suppression unit 32 of the damper ECU 22. The EBD operation ratio setting unit 43 sets the EBD operation ratio based on the determination result of the nose dive suppression determination unit 42 and outputs it to the braking control unit 41. The brake control unit 41 controls the brake control signal for each brake 7 based on the EBD operation ratio input from the EBD operation ratio setting unit 43 in addition to the operation amount of the brake pedal (not shown), the steering angle, the yaw rate, the lateral acceleration, and the like. Is output to the hydraulic unit 24.

<< Operation of Embodiment >>
When the automobile 1 is in operation, the VSA-ECU 21 repeatedly executes vehicle behavior control at a predetermined control interval (for example, 10 ms) based on the detection signals from the sensors 11 to 15 described above. When the vehicle behavior control is started, the VSA-ECU 21 calculates the reference yaw rate based on the vehicle speed and the steering angle after estimating the vehicle speed based on the wheel speed. Next, the VSA-ECU 21 sets a braking control amount and an output control amount based on the difference between the input signal from the yaw rate sensor 12 and the standard yaw rate, and then controls the hydraulic unit 24 and the engine ECU 23 to control signals. Is output. As a result, undesired behavior of the vehicle body 2 is suppressed even when turning or running in the rain, and the steering stability of the automobile 1 is improved. Further, the VSA-ECU 21 sets the left and right rear wheels 3rl, 3rr side by a predetermined ratio (for example, 3%) when the deceleration G exceeds a predetermined value (for example, about 0.4G) during braking. The hydraulic unit 24 (braking force distribution means) is driven and controlled so that the wheel speed wr is higher than the wheel speed wf on the left and right front wheels 3fl, 3fr side. Thereby, regardless of the change in the front and rear load distribution, securing of the braking force on the left and right rear wheels 3rl, 3rr and prevention of idling are realized, and smooth deceleration or stop is realized.

  On the other hand, when the automobile 1 is in operation, the damper ECU 22 attenuates at a predetermined control interval (for example, 10 ms) based on detection signals from the sensors 11 to 15 and the stroke sensor 16 input via the VSA-ECU 21. Repeat force control. When the damping force control is started, the damper ECU 22 determines the vehicle 1 based on the acceleration of the vehicle body 2 obtained from the longitudinal G sensor 13, the lateral G sensor 14, and the vertical G sensor (not shown), the vehicle speed, the steering angle, and the like. The motion state is determined, and the roll control target value, pitch control target value, and skyhook control target value of each damper 4 are calculated according to the determination result. Thereafter, the damper ECU 22 selects (high-selects) a target damping force having the largest absolute value in the same direction as the stroke direction of the damper 4 among these control target values, and sets each damper 4 to the target damping. Output control current to generate force. As a result, excessive roll movement, pitch movement, vertical movement and the like of the vehicle body 2 are suppressed, and improvement in steering stability and ride comfort is realized. Further, during sudden braking or the like, the nose dive is predicted based on the longitudinal acceleration (deceleration) and the vehicle speed, and the nose dive of the vehicle body 2 is suppressed by temporarily increasing the target damping force of each damper 4.

<Nose dive suppression process>
In parallel with the normal vehicle behavior control, the VSA-ECU 21 repeatedly executes a nose dive suppression process whose procedure is shown in the flowchart of FIG. 3 at a predetermined control interval (for example, 10 ms). When the nose dive suppression process is started, the VSA-ECU 21 informs whether or not the nose dive suppression control is being performed by the damper ECU 22 in step S1 of FIG. 3 (from the damper ECU 22 performing the nose dive suppression control). A signal (whether or not nose dive suppression signal Snd) is input is determined. If this determination is No, the process returns to the start without performing any processing. Whether or not nose dive suppression control is being performed is determined by comparing the longitudinal acceleration (deceleration of the vehicle body 2) associated with braking with the stroke signal of the damper 4 input from the stroke sensor 16. Also good.

  When the nose dive suppression signal Snd is input from the damper ECU 22 and the determination in step S1 is Yes, the VSA-ECU 21 reduces the braking force distribution on the left and right rear wheels 3rl, 3rr side in step S2. Specifically, the wheel speed wr on the left and right rear wheels 3rl, 3rr side becomes higher than the wheel speed wf on the left and right front wheels 3fl, 3fr side by a ratio when the nose dive is suppressed (for example, 6%) that is larger than the EBD operation ratio. Thus, the hydraulic unit 24 is driven and controlled. As a result, even if the target damping force of the damping force variable damper is increased by the nose dive suppression control and the ground load on the rear wheels is reduced, excessive braking force does not act on the left and right rear wheels 3rl, 3rr, and the vehicle is turning. The vehicle posture is not disturbed during braking, and the driver does not feel an unnatural deceleration.

  Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the damper ECU performs prediction and suppression of the nose dive, but the VSA-ECU may perform from the prediction of the nose dive to the EBD operation ratio. In addition, the specific configuration of the vehicle, the specific procedure of the control, and the like can be appropriately changed without departing from the gist of the present invention.

It is a top view which shows the apparatus structure of the vehicle which concerns on embodiment. It is a block diagram which shows the principal part structure of the control apparatus which concerns on embodiment. It is a flowchart which shows the procedure of the process at the time of nose dive suppression which concerns on embodiment.

Explanation of symbols

1 Car 2 Car Body 3 Wheel 4 Damper (Damping Force Variable Damper)
7 Brake (disc brake caliper)
11 Steering angle sensor 16 Stroke sensor 21 VSA-ECU (braking force distribution control means)
22 Damper ECU
24 Hydraulic unit (braking force distribution means)
31 Nose dive prediction unit (nose dive prediction means)
32 Nose dive suppression part (nose dive suppression means)
41 Braking control unit 42 Nose dive suppression determination unit 43 EBD operation ratio setting unit (braking force distribution control means)

Claims (3)

A damping force variable damper interposed between the vehicle body and each wheel, and braking force distribution for performing braking control during deceleration that reduces the braking force distribution to the rear wheel side by a predetermined amount at least during deceleration when the longitudinal acceleration exceeds a predetermined value A vehicle attitude control device comprising means,
Nose dive prediction means for predicting the nose dive of the vehicle body,
Nose dive suppression means for performing nose dive suppression control on the damping force variable damper based on the prediction result of the nose dive prediction means;
If it is determined that the nose dive suppression control is executed, and a braking force distribution control means to further reduce the braking force distributed to the rear wheel side than when said deceleration during braking control on the braking force distribution means An attitude control apparatus for a vehicle characterized by the above.   2. The vehicle according to claim 1, wherein the braking force distribution control unit determines execution of the nose dive suppression control based on a deceleration of a vehicle body and stroke information of the damping force variable damper. Attitude control device.   2. The vehicle attitude control device according to claim 1, wherein the braking force distribution control unit determines execution of the nose dive suppression control based on control information of the nose dive suppression unit. 3.

Images