JPH0848124A - Damping force controller of vehicle - Google Patents

Abstract

PURPOSE:To provide a car damping force controller which is made up so as to reconcile the riding comfortableness and steerability of a car in time of traveling on a rough road. CONSTITUTION:A vertical acceleration G detected by a vertical acceleration sensor built in a car body is subjeted to a band pass filter process, thereby extracting a rough road vibro-component Gb (step 106). On the basis of this rough road vibro-component Gb, a degree of unevenness on a traveling road surface is judged (steps 112 and 114). According to the judged result, the damping force of each shock absorber of both front-wheel and rear-wheel sides is separately controlled, and in proportion as a degree of unevenness growing larger, each damping force at both the front-wheel and the rear-wheel sides is lessened, and the damping force at the front-wheel side is made larger than that at the rear-wheel side (steps 116 to 120). Each damping force at both the front-wheel and the rear-wheel sides is lessened too, whereby the extent of riding comfortablenss of a car is secured and simultaneously the damping force at the front-wheel side is made larger, through which groundability in the front wheels is made so better and thereby steerability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle damping force control device for controlling a damping force with respect to a vertical movement of a vehicle body, and particularly to improve ride comfort and steerability of the vehicle when traveling on a bad road. The present invention relates to a damping force control device for a vehicle.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-60-1511.
As disclosed in Japanese Patent Publication No. 11, the vertical vibration of the vehicle body is detected, the detected vibration is separated into low-frequency and high-frequency components, and based on the level of each separated frequency component, Determine whether the cause of the vibration is related to the road surface with a large period of swell or the bad road with fine irregularities, and use the damping force when driving on the rough road There is known a damping force control device that is set to be smaller than the damping force when the vehicle is running to avoid deterioration of riding comfort when traveling on a rough road.

[0003]

However, in the above-mentioned conventional device, if the damping force during traveling on a bad road is set too small, the ground contactability of each wheel will be deteriorated and the vehicle stability will be improved. Is not good. Also, to avoid this,
If the damping force during traveling on a rough road is set to a large value, the riding comfort of the vehicle deteriorates. The present invention has been made to address the conflicting problems as described above, and an object thereof is to provide a damping force control device for a vehicle that achieves both ride comfort and steerability of the vehicle when traveling on a rough road. To do.

[0004]

In order to achieve the above object, the structural feature of the present invention is to detect the degree of unevenness of a traveling road surface, and to detect front and rear wheels according to the detected degree of unevenness. Side damping force changing mechanism is controlled independently, the damping force on the front wheel side and the rear wheel side are both reduced as the degree of unevenness increases, and the damping force on the front wheel side is compared to the damping force on the rear wheel side. I tried to make it bigger.

[0005]

In the present invention constructed as described above, when the vehicle is traveling on a bad road and the degree of unevenness on the road surface increases, the damping force on both the front wheels and the rear wheels decreases. The unevenness of the road surface does not directly affect the vehicle body, and the ride comfort of the vehicle is kept good. Also, since the damping force on the front wheel side is set to a large value, the front wheel's grounding property is good and the vehicle's maneuverability is maintained well.Because it is closer to the passenger's seat than the front wheel, it affects the ride comfort of the vehicle. Since the damping force on the rear wheel side that gives the torque is set to be small, a good riding comfort of the vehicle is also secured.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 conceptually shows shock absorbers 10A to 10D as a vehicle damping force changing mechanism according to the present invention, and the same absorber 10A. 10D is a block diagram showing an electric control device 20 for controlling 10D.

The shock absorbers 10A to 10D are respectively arranged between the left and right front wheels and the left and right rear wheels, more specifically, between a lower arm (unsprung member) connected to each wheel and a vehicle body (sprung member). Each shock absorber 10A ~
Reference numeral 10D includes hydraulic cylinders 12a to 12d that are partitioned into upper and lower chambers by pistons 11a to 11d, and the cylinders 12a to 12d are supported by lower arms, respectively. The piston rod 1 is attached to the pistons 11a to 11d.
3a to 13d are respectively connected at the lower ends, and the same rod 1
3a to 13d respectively support the vehicle body at the upper end.
The upper and lower chambers of the hydraulic cylinders 12a to 12d are electromagnetic valves 1
4a to 14d are in communication with each other, and the valves 14a to
The shock absorbers 10A to 10A depending on the opening degree of 14d.
The damping force of D can be switched in multiple stages. Each of the lower chambers of the hydraulic cylinders 12a to 12d has a gas spring unit 15a to 1a for absorbing a volume change of the upper and lower chambers due to the vertical movement of the piston rods 13a to 13d.
5d are respectively connected.

The electric control unit 20 includes a vehicle speed sensor 21 and a vertical acceleration sensor 22. The vehicle speed sensor 21 detects the vehicle speed V and outputs a detection signal indicating the vehicle speed V. The vertical acceleration sensor 22 is attached to a part of the vehicle body, for example, the vehicle body at the right front wheel position, detects the vertical acceleration G due to the vibration of the vehicle body, and outputs a detection signal indicating the same acceleration G. These sensors 21 and 22 are connected to the microcomputer 23. The microcomputer 23 repeatedly executes a program corresponding to the flowchart shown in FIG. 2 at a predetermined short time under the control of a built-in timer circuit to switch and control the damping forces of the shock absorbers 10A to 10D. Further, in the microcomputer 23, regarding the shock absorbers 10A to 10D, the vehicle speed V
A base step number table that stores the front wheel base step number BSF (solid line in FIG. 3) and the rear wheel base step number BSR (dashed line in FIG. 3) that changes in accordance with The target stage number table that stores the target stage number TSF for front wheels (solid line in FIGS. 5A and 5B) and the target stage number TSR for rear wheels (broken line in FIGS. 5A and 5B) that change according to the degree of It is provided. Note that FIG. 5A shows the target speeds TSF and TSR at low vehicle speeds, and FIG. 5B shows the target speeds TSF and TSR at high vehicle speeds. The microcomputer 23 includes shock absorbers 10A to 10A.
Drive circuits 24a to 24d corresponding to D are respectively connected, and each drive circuit 24a to 24d responds to a control signal from the microcomputer 23 to the electromagnetic valve 14a.
The opening degree of 14d is controlled by switching.

Next, the operation of the embodiment configured as described above will be described. When the ignition switch is turned on, the microcomputer 23 starts its operation and repeatedly executes the program including steps 100 to 128 in FIG. 2 every predetermined time. In this program, in step 102, the vehicle speed V and the vertical acceleration G are input from the vehicle speed sensor 21 and the vertical acceleration sensor 22, respectively, and in step 104, the base stage number table for the front wheels BSF corresponding to the vehicle speed V is referred by referring to the base stage number table. (Solid line in FIG. 3) and the rear wheel base stage number BSR (broken line in FIG. 3) are determined. Next, in step 106, about 1 to 2H is applied to the input vertical acceleration G.
A tilt vibration component Ga and a rough road vibration component Gb are calculated by performing band-pass filter processing with z and about 3 to 8 Hz as each pass band. Shaking vibration component Ga
Represents slow vertical vibration of the vehicle body related to the swell of the road surface having a long cycle and the resonance frequency of the vehicle body, and the bad road vibration component Gb represents vertical vibration of the vehicle body related to the bad road having fine unevenness on the road surface. It represents.

After the processing of step 106, step 1
At 08, it is determined whether or not the swing vibration component Ga is less than a predetermined small value Ga0, and at step 110, it is determined whether the swing vibration component Ga is a predetermined large value Ga1 (> Ga0) or more. To do. If the swing vibration of the vehicle body is small and the swing vibration component Ga is less than the predetermined value Ga0, it is determined to be "YES" in step 108 and the program proceeds to step 126. It should be noted that when the vehicle travels on a bad road, some swinging vibration is also generated in the vehicle body, and in this case, the bad road vibration component Gb is also extremely small. Step 1
In 26, the control signal representing the front wheel base stage number BSF determined by the process of step 104 is output to the drive circuits 24a and 24b, and the control signal representing the rear wheel base stage number BSR is output to the drive circuits 24c and 24d. To do. The drive circuits 24a to 24d store these supplied control signals, respectively, and set the opening degrees of the electromagnetic valves 14a to 14d based on the stored control signals. Therefore, the shock absorbers 10A and 10B for the front wheels are the front wheels. Is set to the base stage number BSF for rear wheels, and the shock absorbers 10C and 10D for rear wheels are set to the base stage number BSR for rear wheels.

Since both of the base stages BSF and BSR correspond to the relatively low stage numbers of the shock absorbers 10A to 10D, that is, the low damping force side, the absorber 1 is the same.
The damping force of 0A to 10D is set low, and the ride comfort of the vehicle is kept good. Also, the number of base stages BSF, BS
Since R increases gradually as the vehicle speed V increases (see FIG. 3), each damping force by the shock absorbers 10A to 10D increases as the vehicle speed V increases,
As the vehicle speed V increases, safety is emphasized. Further, the front wheel base stage number BSF is the rear wheel base stage number BSR.
Since it is set to a larger value (see FIG. 3), the damping force on the front wheel side is set to be larger than the damping force on the rear wheel side, and the grounding property on the front wheel side is good, so that the vehicle maneuverability is improved. The damping force on the rear wheel side, which is closer to the occupant's seat than the front wheels and affects the riding comfort of the vehicle, is set smaller than that of the front wheels, so that the riding comfort of the vehicle is maintained extremely excellent.

If the swinging vibration of the vehicle body is large and the swinging vibration component Ga is equal to or larger than the predetermined value Ga1, it is judged "YES" in step 110 and the program proceeds to step 116. In step 116, the target number of stages TSF and TSR for the front wheels and the rear wheels are set to the number of stages CMF in consideration of the vehicle speed V as well.
1, set to CMR1. In this case, both the target speed table for low vehicle speed (FIG. 5 (A)) and the target speed table for high vehicle speed (FIG. 5 (B)) are referred to, and the speeds read from both tables are set according to the vehicle speed V. And interpolate the number of stages CMF1, CM
Determine R1. After the processing in step 116, in step 122, the control signal representing the set front wheel target stage number TSF is output to the drive circuits 24a and 24b, and the control signal representing the rear wheel target stage number TSR is provided in the drive circuit 2.
Output to 4c and 24d. Therefore, the shock absorbers 10A to 10D have the target number of stages TSF in the same manner as described above.
(= CMF1) and TSR (= CMR1).
Since the step numbers CMF1 and CMR1 are extremely large values as shown in FIG. 5, the shock absorbers 10A to 10A-10
The damping force of D becomes extremely large.

After the processing of step 122, step 1
The program proceeds to step 126 after waiting a predetermined holding time by the processing of 24. In step 126,
As described above, the shock absorbers 10A to 10D are set to have small damping forces corresponding to the front wheel and rear wheel base stage numbers BSF and BSR. Step 11 like this
By the processing of 6 to 124, the shock absorber 10A to
Since the damping force of 10D is switched to the larger side for a predetermined holding time, the swing vibration of the vehicle body is quickly damped.

If the swinging vibration of the vehicle body is large to some extent and the vibration component Ga is equal to or more than the predetermined value Ga0 and less than the predetermined value Ga1, both are determined to be "NO" in steps 108 and 110, and the program is executed. Through steps 112 and 11
Go to 4. In steps 112 and 114, the degree of unevenness on the road surface (bad road) is detected. In step 112, it is determined whether the rough road vibration component Gb is less than a predetermined small value Gb1, and in step 114 it is determined whether the vibration component Gb is less than a predetermined large value Gb2.

If the rough road vibration component Gb is less than the predetermined value Gb1, it is judged "YES" at step 112 and the program is advanced to step 116. At step 116, the vehicle speed V is also taken into consideration as described above. Then, the target step numbers TSF and TSR for the front wheels and the rear wheels are set to the step numbers CMF1 and CMR1. The rough road vibration component Gb is greater than or equal to the predetermined value Gb1 and the predetermined value Gb2
If it is less than the above, "NO" is determined in step 112 and "YES" is determined in step 114, and the program is advanced to step 118.
Similar to the process of 16, the target speeds TSF and TSR for the front wheels and rear wheels are set to the speeds CMF2 and CMR2 in consideration of the vehicle speed V. If the rough road vibration component Gb is greater than or equal to the predetermined value Gb2, it is determined to be "NO" in step 114 and the program is advanced to step 120. In step 120, the vehicle speed V is also considered as in the processing of step 116. Then, the target number of stages TSF and TSR for the front wheels and the rear wheels are set to the number of stages CMF3.
Set to CMR3 (see FIG. 5).

After the steps 116 to 120, the shock absorbers 10A and 10B are set to the front wheel target step number TSF and the shock absorbers 10C and 10D are set to the rear wheel target step number TSR at step 122. After the shock absorbers 10A to 10D are held in the set state for a predetermined holding time by the processing of steps 124 and 126, the shock absorbers 10A to 10D are held.
D is the number of base stages BSF, B for the front and rear wheels described above.
Return to SR.

By the processing of these steps 112 to 124, as is clear from FIG. 5, the shock absorbers 10A to 10A as the rough road vibration component Gb increases.
The setting step number of D is set to be low, that is, the damping force of the absorbers 10A to 10D is set to be small. Therefore, as the unevenness of the traveling road surface becomes more severe while the vehicle is traveling on a bad road, the vehicle body does not respond to the unevenness of the traveling road surface, the vertical movement of the vehicle body is reduced, and the riding comfort of the vehicle is kept good. Further, since the set number of steps of the front wheel shock absorbers 10A, 10B is larger than the set number of steps of the rear wheel shock absorbers 10C, 10D, the damping force of the front wheel side shock absorbers 10A, 10B is set high and the rear wheel side is set. Shock absorber 10
The damping force of C and 10D is set low. Therefore, even when the vehicle is traveling on a rough road, the front wheels are well grounded and the steering stability of the vehicle is kept good. Since the damping force on the rear wheel side that affects the comfort is set to be small, a good riding comfort of the vehicle is also ensured. Furthermore, FIG. 5 (A)
By comparing (B), shock absorbers 10A-10D
Since each damping force of 1 becomes larger as the vehicle speed V increases, the maneuverability becomes more important as the vehicle speed V increases.

Although the vertical acceleration sensor 22 is used as the vibration sensor for detecting the vertical vibration of the vehicle body in the above embodiment, the vertical acceleration sensor 2 is used.
Instead of 2, a vehicle height sensor mounted on the vehicle body to detect the height from the road surface, and a relative displacement between the vehicle body (sprung member) and the wheel side member (unsprung member) provided in the suspension device. A stroke sensor that detects the A damping force sensor for detecting may be used as the vibration sensor.

Further, in the above embodiment, the bad road is determined based on the output of the vertical acceleration sensor, but instead of this, the bad road may be determined based on the fluctuation of the wheel speed. In this case, the wheel speed sensor 25 for detecting the wheel speed is connected to the microcomputer 23 as shown by the broken line in FIG. 1, and the microcomputer 23 differentiates the detected wheel speed to calculate the fluctuation of the wheel speed, A bandpass filter process with a pass band of 3 to 8 Hz is applied to the signal representing the speed variation, and the degree of unevenness of the road surface is determined according to the magnitude of the processed signal value.

[Brief description of drawings]

FIG. 1 is a block diagram of a shock absorber and an electric control device for the shock absorber according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a program executed by the microcomputer of FIG.

FIG. 3 is a graph showing a change characteristic of the number of base stages for front wheels and rear wheels with respect to a vehicle speed.

FIG. 4 is a frequency characteristic graph of a filtering process for separating the tilting vibration component and the rough road vibration component of the vehicle body.

FIG. 5A is a graph showing the change characteristics of the target number of steps for the front wheels and the rear wheels with respect to the rough road vibration level at low vehicle speed, and FIG. 5B is the front and rear wheels with respect to the rough road vibration level at high vehicle speed. It is a graph which shows the change characteristic of the number of target steps for wheels.

[Explanation of symbols]

10A to 10D ... Shock absorbers, 12a to 12d
... hydraulic cylinders, 14a to 14d ... electromagnetic valves, 20 ...
Electric control device, 21 ... Vehicle speed sensor, 22 ... Vertical acceleration sensor, 23 ... Microcomputer, 25 ... Wheel speed sensor.

Claims (1)

[Claims] 1. A damping force control device for a vehicle for controlling a damping force changing mechanism, which is provided between each of front wheels and rear wheels and a vehicle body and is capable of changing a damping force with respect to vertical movement of the vehicle body, The detection means for detecting the degree of unevenness of the road surface on which the vehicle is running, and the damping force changing mechanism on the front wheel side and the rear wheel side are independently controlled according to the detected degree of unevenness, and the degree of unevenness is A vehicle provided with damping force control means for decreasing both the damping force on the front wheel side and the damping force on the rear wheel side as the damping force increases and increasing the damping force on the front wheel side compared to the damping force on the rear wheel side. Damping force control device.