JPH06106949A - Suspension control device for vehicle - Google Patents

Abstract

PURPOSE:To always switch a suspension characteristic by the optimum timing against a delay of a control system total unit in a total running region while optimizing detecting a road surface by properly moving a road surface sensor. CONSTITUTION:Suspensions 5, 5' capable of controlling respective damping force switches are arranged in front and rear wheels 2, 3, and further a road surface sensor 10 for detecting irregularity of a road surf ace is provided in the front bottom part of a car body 1 in a manner wherein a road surface detecting position can be moved to the front of the car body. Particularly at the time of increasing a car speed, the road surface sensor 10 itself is protruded by a sensor mover unit 11, to forwardly move the road surface detecting position by steps further to output a signal of switching damping force to the front/rear wheel suspensions 5, 5' by calculating a delay time in each sensor moving condition, and at least the timing of the front wheel 2 reaching the road surface detecting position is set to always agree almost with the timing of switching the damping force of the front wheel suspension 5 by containing the delay time of a control system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension control device which is provided on each wheel of a vehicle and controls switching of suspension characteristics according to the unevenness of a road surface.
The present invention relates to a control for reliably switching the damping force with respect to the delay of the control system throughout the traveling.

[0002]

2. Description of the Related Art Generally, a suspension is provided between a vehicle body and an axle of each wheel of a vehicle having a spring and a shock absorber. The spring absorbs a shock from the road surface, and a continuous vibration of its bounce is received by the shock absorber. Is dampened by, and shocks are alleviated. For this reason, if the damping force of the shock absorber is large, the stability of the vehicle posture can be improved by suppressing the rolling of the vehicle body, etc., but it will react ruggedly to the unevenness of the road surface, resulting in a rugged riding comfort. On the contrary, if the damping force is small, the vibration input from the road surface is reduced and the ride comfort is soft. For this reason, in recent years, a damping force variable device has been added to the shock absorber to control the damping force of the suspension characteristics according to the road surface conditions on good and bad roads and the running conditions such as braking, starting, turning, etc. A semi-active suspension system has emerged that makes it possible to achieve both a comfortable ride and a comfortable ride.

Here, in the control for switching the suspension characteristics to the unevenness of the road surface, a road surface sensor such as an ultrasonic system for detecting the unevenness of the road surface is provided at the front part of the vehicle body. In this case, the road surface sensor is preferably arranged as close to the front wheels as possible to move so as to detect the road surface in order to reduce a detection error due to pitching of the vehicle.

On the other hand, if the road surface sensor is kept fixed, the time when the wheel actually reaches the road surface detection position by the road surface sensor changes depending on the vehicle speed. Also, the sensor system, the control system, and the actuator system have their own delay time. Considering the delay time of the entire control system, the road surface information detected by the road surface sensor is used for suspension characteristic switching control when the vehicle speed exceeds a certain speed. There is no time to use it, and it will not be possible to make changes at optimal timing. Therefore, it is required to control the timing at which the wheels reach the road surface detection position and the timing at which the suspension characteristics are switched in consideration of the delay time of the entire control system so as to always coincide with each other throughout the traveling of the vehicle.

Conventionally, as for the suspension characteristic switching control for the unevenness of the road surface, for example, Japanese Patent Laid-Open No. 3-182 has been proposed.
There is a prior art of Japanese Patent No. 825. Here, it is shown that a road surface unevenness sensor is provided below the front end of the vehicle body and the suspension characteristics are switched based on the sensor output.

[0006]

By the way, in the above-mentioned prior art, since the road surface unevenness sensor is fixedly provided on the vehicle body, the road surface which is always separated by a certain distance in front of the front wheels is detected. At high speeds, the suspension characteristics may not be switch-controlled at an optimum timing due to the delay time of the entire control system.

The present invention has been made in view of this point. The road surface sensor is appropriately moved to optimize the road surface detection, and the suspension characteristics are always optimized with respect to the delay of the entire control system over the entire traveling range. The purpose is to switch at timing.

[0008]

In order to achieve the above object, the present invention provides a vehicle in which a wheel is provided with a spring, a shock absorber having a damping force varying device, and a suspension provided with an actuator for switching control of the damping force. , A road surface sensor for detecting the unevenness of the road surface in the lower front part of the vehicle body is provided with a moving device so that the road surface detection position can be moved to the front of the vehicle body, and the control unit processes the signal of the road surface sensor and the running state, It outputs a stepwise movement signal to the moving device so as not to cause a delay in the control system, and at least in the sensor fixed state and each sensor moving state, at least the time for the front wheels to reach the road surface detection position according to the vehicle speed and the entire control system. The delay time is adjusted according to the delay time to output the damping force switching signal to the actuator.

[0009]

According to the above structure, the road surface is accurately detected by the road surface sensor, and the damping force of the suspension is switched based on the road surface information from the road surface sensor. At low speeds, the road surface sensor is fixed at the shortest position.In this state, the delay time of the entire control system is subtracted from the time it takes for the front wheels to reach the road surface detection position according to the vehicle speed, and the delay time is calculated. Output a force switching signal to the actuator. Also, when the vehicle speed rises and the front wheels reach the road surface detection position quickly, the road surface sensor itself is projected by the moving device, and the road surface detection position moves in a stepwise manner toward the front of the vehicle body to move away from it. The delay time of the entire control system is secured for each. In each moving state as well, by similarly calculating the delay time and outputting the damping force switching signal, at least the timing at which the front wheels reach the road surface detection position and the delay time of the control system are added to reduce the damping force of the front wheel suspension. The timing of switching is always substantially the same, and thus the vehicle attitude can be reliably stabilized over the entire traveling range.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. An outline of a vehicle suspension control system will be described with reference to FIG. Reference numeral 1 denotes a vehicle body, and a suspension 5, between the axle 4 of the front wheels 2 and the rear wheels 3 and the vehicle body 1.
5'is installed respectively. Front wheel suspension 5
Is configured such that a spring 6 and a variable damping force type shock absorber 20 are provided in parallel between the vehicle body 1 and the axle 4, and an electric motor 7 is provided above the shock absorber 20 as an actuator for switching control of the damping force. To be done. The rear wheel suspension 5'has the same configuration, and the same parts are denoted by the same reference numerals with a dash and the description thereof is omitted.

In front of the front wheel 2 of the vehicle body 1, a road surface sensor 10 for detecting the unevenness of the road surface is mounted on a moving device 11, and the motor 12 of the actuator linearly moves the road surface sensor 10 forward. It is possible to change the road surface detection position. Further, it has a vehicle speed sensor 13 for detecting a traveling state. The signals of the road surface sensor 10 and the vehicle speed sensor 13 are input to the control unit 14, and the front and rear wheel suspensions 5, 5 are output by the control unit 14.
The motors 7 and 7'of 5'and the motor 12 of the moving device 11 are configured to operate.

The control unit 14 selects the damping force switching signal according to the road surface information, and controls the output timing of the damping force switching signal and the road surface detection position with respect to the delay of the control system. The control law will be described below. Let V be the vehicle speed, Δt be the delay time of the entire control system, Lo be the shortest front-rear distance between the sensor and the tire center, ΔL be the sensor movement amount, and ΔT be the delay time adjusted when the road surface unevenness information is used for control. , The following equation holds. (Lo + ΔL) / V = Δt + ΔT Therefore, the delay time ΔT is calculated by the following equation. ΔT = (Lo + ΔL) / V−Δt Therefore, in relation to the vehicle speed V, the sensor movement amount ΔL is always (L
When the road surface detection position is moved toward the front of the vehicle body by increasing and changing so that o + ΔL) / V−Δt ≧ 0, the delay time ΔT can always be calculated. By controlling so that the damping force switching signal is output after the delay time ΔT has passed, the delay time Δt of the entire control system is always secured, and at least the front wheels 2 reach the road surface detection position over the entire traveling range. The damping force of the front wheel suspension 5 can be switched at the matched optimum timing.

Therefore, first, when ΔL = 0, the set vehicle speed Lo / Δt capable of calculating the delay time at a low speed is obtained. After this set vehicle speed, the sensor movement amount ΔL is set to the vehicle speed V
.DELTA.L = L1, L2, L3, ... (L1
<L2 <L3 ...), and the movement signal is output to the mobile device 11. Further, in each sensor moving state, the delay time ΔT is calculated by the above equation, and after the delay time ΔT has elapsed, the damping force switching signal is output to the front and rear wheel suspensions 5, 5 ′.

Referring to FIG. 2, a specific structure of the damping force type shock absorber 20 will be described. In the shock absorber 20, a rod 22 on the vehicle body 1 side has a piston 23 and is movably inserted into a cylinder 21 on the axle 4 side. The piston 23 divides the rod 22 into an upper chamber 24 and a lower chamber 25 and fills with oil O. To be done. The piston 23 is provided with an extension side main passage 26 and a main valve 26a, and a contraction side main passage 27 and a main valve 27a. When the rod is extended and the main valve 26a is opened, the oil O flows from the upper chamber 24 to the lower chamber 25 through the main passage 26. Conversely, when the rod is compressed and the main valve 27a is contracted, the other main valve 27a is opened. Open lower chamber 25
From the oil O flows into the upper chamber 24 via the main passage 27. Here, the orifice diameters of the main passages 26 and 27 are set to be small, so that the same hard damping force is generated on the extension side and the contraction side.

A damping force varying device 30 is provided inside the rod 22. This damping force varying device 30
A communication hole 31 is provided at the center of the rod 22 so that the lower end thereof communicates with the lower chamber 25, and the communication hole 31 extends toward the extension side sub passage 3.
2 and the sub-valve 32a, the contraction-side sub-passage 33 and the sub-valve 33a, and the sub-passage 34 that serves both functions, and communicates with the upper chamber 24. Further, a shutter 35 from the motor 7 is rotatably inserted into the communication hole 31 via a connecting rod 36, and three types of holes 38, 3 are formed on the circumference of the shutter 35.
9, 40 are provided by being displaced by a predetermined rotation angle.

Therefore, when the shutter 35 is rotated by a predetermined angle by the motor 7 and only the hole 38 communicates with the sub passage 32, when the rod is contracted by the sub valve 32a.
Closes. When the rod rises and extends, the sub-valve 32a also opens, and the oil O in the upper chamber 24 also flows into the sub-passage 32 to increase the orifice diameter. This causes the extension side to be soft and the contraction side to be hard in the first mode in FIG. It becomes the damping force characteristic of. Next, when the other hole 39 is communicated with the sub passage 33 by the motor 7, in this case, the sub valve 33a is also opened to increase the orifice diameter only when the rod is contracted by the downward movement of the rod contrary to the above description. The damping force characteristic of the second mode in FIG. 3 is hard and soft on the contraction side. Further, the motor 7 causes the other hole 40 to move to the sub passage 3
In this case, since the oil O always flows through the sub passage 34 to increase the orifice diameter in this case, both the extension side and the contraction side have slightly soft third mode damping characteristics in FIG.
In this way, the motor 7 can obtain damping characteristics of three types of modes.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. First, when the vehicle is traveling, the vehicle speed V is read in step S1, the sensor position is fixed to the shortest distance by setting ΔL = 0 in step S2, and the vehicle speed V in this case and the set vehicle speed Vs0 in which the delay time can be calculated in step S3.
The running state is checked by comparing (Lo / Δt). Here, as a practical numerical value, for example, Lo = 0.5 m, Δt
= 0.03 seconds, Lo / Δt = 60 Km / h.

Therefore, when the vehicle speed is lower than the set vehicle speed Vs0,
In step S4, the delay time ΔT is calculated. Therefore, the delay time ΔT is calculated by subtracting the delay time Δt of the entire control system from the time Lo / V at which the front wheels 2 reach the road surface detection position (Lo) according to the vehicle speed V.
As in the curve a0 of the control delay time characteristic of (a), it is adjusted in a decreasing function. Therefore, when the vehicle speed V is low and the front wheels 2 reach the road surface detection position of the road surface sensor 10 relatively late, the delay time ΔT is correspondingly long.

Thereafter, in step S5, the output Ln of the road surface sensor 10 is read, and in step S6, the road surface height ΔH is calculated by the sensor mounting height Ho and the sensor output Ln, and ΔH = Ln-H.
It is calculated by o. In step S7, the road surface height ΔH
The time history data Δh is created, and the road surface height information Δh (ΔT) required to change the damping force this time is calculated based on the time history data Δh, the microcomputer calculation cycle, etc. in step S8. Then, in step S9, the road surface height information Δh (Δ
The damping force characteristic suitable for T) is determined, and this damping force switching signal is simultaneously output to the motors 7, 7'of the shock absorbers 20,20 'of the front and rear wheel suspensions 5,5' after the lapse of the delay time .DELTA.T. . Therefore, when the vehicle speed V is low, the damping force switching signal is output late due to the long delay time ΔT, so that the damping force of the front wheel suspension 5 is generated at an optimum timing at least approximately when the front wheels 2 reach the road surface detection position. The variable device 30 switches to an appropriate damping force.

Therefore, as shown in FIG. 6, when the road surface sensor 10 detects the convex portion A, the damping force switching signal of the second mode in FIG. 3 is output to the motors 7 and 7 ', and the damping force of the front wheel suspension 5 is varied. The device 30 switches to that characteristic. Therefore, when the front wheel 2 actually travels on the convex portion A and moves upward, the damping force varying device 30 has a soft damping action on the contracting side and a hard damping action on the extending side. Next, when the rear wheel 3 travels on the convex portion A, the rear wheel suspension 5'has already been switched to the same characteristic, so that the rear wheel suspension 5'is similarly damped and the upward movement of the vehicle body 1 is suppressed.

On the other hand, when the road surface sensor 10 detects the recess B, the damping force switching signal of the first mode in FIG. 3 is output to the motors 7 and 7 ', and the front wheel 2 and the rear wheel 3 actually detect the recess B. When running and moving downward, the front and rear wheel suspensions 5,
In the damping force varying device 30 of 5 ′, the extension side is softly damped on the extension side and the compression side is hard on the damping side, and the downward movement of the vehicle body 1 is suppressed. In this way, the vehicle body 1 of the vehicle is reliably controlled so as to maintain a posture in which there is little vertical movement with respect to the uneven portions A and B of the road surface.

Next, when the vehicle speed is set to Vs0 or higher, the process proceeds from step S3 to step S10 in the flowchart of FIG.
Set like the curve b1 of the sensor movement characteristic of (b),
This movement signal is output. Therefore, the road surface sensor 10 itself projects by the moving device 11 toward the front of the vehicle body, and the road surface detection position moves forward by the sensor movement amount L1. Therefore, in response to the front wheels 2 reaching the road surface detection position quickly due to the increase of the vehicle speed V, the road surface detection position can be moved away from the front of the vehicle body with a margin, and thus again the delay time of the entire control system as described above. Δt is secured, and the delay time ΔT can be calculated.

In this case, the set vehicle speed Vs1 is (Lo + L
1) / Δt, and the vehicle speed V and the set vehicle speed Vs1 are compared in step S11. When the vehicle speed is lower than the set vehicle speed Vs1, the process proceeds to step S12, in which the delay time Δt of the entire control system is subtracted from the time (Lo + L1) / V at which the front wheels 2 reach the road surface detection position according to the vehicle speed V and the delay time. ΔT is calculated, and this delay time ΔT is shown in FIG.
The curve a1 in (a) is obtained and the adjustment is performed in the same manner as described above. Then, after step S5 again, the road surface information based on the sensor signal is obtained to determine the damping force characteristic, and this damping force switching signal is output after the delay time ΔT has elapsed. Therefore, even when the vehicle speed increases, the damping force varying device 30 of the front wheel suspension 5 switches to an appropriate damping force at least at the optimum timing substantially coincident with the front wheel 2 reaching the road surface detection position, and the front wheel 2 and the rear wheel 3 are also changed. When the vehicle reaches the uneven portions A and B on the road surface, the front and rear wheel suspensions 5 and 5'have a damping action, so that the vehicle posture is reliably and stably controlled.

When the vehicle speed V rises above the set vehicle speed Vs1, steps S11 to S13 in the flow chart of FIG.
Then, the sensor movement amount ΔL is increased to L2, and the same control is performed thereafter. Here, the specific numerical value described above, Lo =
If 0.5 m, Δt = 0.03 seconds, and the maximum sensor movement amount ΔL is ΔL = 0.5 m, the maximum controllable vehicle speed is 120 Km / h, which is sufficiently practical.

When the road surface sensor 10 detects a flat road surface, the damping force varying device 30 is controlled so that the extension side and the contraction side are slightly soft according to the characteristics of the third mode of FIG.
This improves ride comfort.

Although the semi-active suspension system has been described as the embodiment of the present invention, it can be applied to the active suspension system and the vehicle behavior characteristic changing means.

[0027]

As described above, according to the present invention, the road surface sensor is provided on the vehicle body, and the road surface sensor always detects the road surface close to the wheels in the control for switching the characteristics of the suspension according to the unevenness of the road surface. Since it is configured on the premise that the road surface can be accurately detected in a state in which the influence of vehicle pitching or the like is small, the control accuracy is also improved.
In response to the delay of the control system, the road surface sensor itself projects to move the road surface detection position forward stepwise to always secure the delay time of the control system, and in this state, calculate the delay time and output the damping force switching signal. Since the control is performed in this manner, the suspension characteristics can be switched at the optimum timing with respect to the delay of the control system, and the vehicle attitude can be reliably stabilized over the entire traveling range. In addition, the road surface sensor needs only a small amount of protrusion, and the delay time facilitates control.

The road surface sensor has a simple structure and high practicability because it is configured to move back and forth by a moving device. Since the road surface sensor gradually projects toward the front of the vehicle body as the vehicle speed increases, it does not become an obstacle or damage during a very low speed small turn. In addition, the road surface sensor has no influence on the vehicle design.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a vehicle suspension control device according to the present invention.

FIG. 2 is a cross-sectional view showing a variable damping force type shock absorber.

FIG. 3 is a diagram showing a damping force characteristic of a suspension.

FIG. 4 is a flowchart showing suspension characteristic switching control according to the unevenness of the road surface.

FIG. 5 is a diagram showing an adjustment state of a delay time and a sensor movement amount.

FIG. 6 is a schematic view showing a concavo-convex state of a road surface.

[Explanation of symbols]

 1 vehicle body 2 front wheel 3 rear wheel 5,5 'suspension 6,6' spring 7,7 'motor 10 road surface sensor 11 moving device 13 vehicle speed sensor 14 control unit 20, 20' shock absorber 30 damping force varying device

Claims (2)

[Claims] 1. A vehicle in which a wheel is provided with a spring, a shock absorber having a damping force varying device, and a suspension equipped with an actuator for switching control of the damping force, and a road surface sensor for detecting unevenness of the road surface at a lower front portion of a vehicle body, A moving device is provided so that the road surface detection position can be moved to the front of the vehicle body. The road surface sensor and the signal of the running state are processed by the control unit, and the moving device is stepped so as not to delay the control system. It outputs a movement signal and adjusts the delay time according to the time required for at least the front wheels to reach the road surface detection position according to the vehicle speed and the delay time of the entire control system in the shortest fixed sensor state and each sensor movement state, and the damping force switching signal is adjusted. A suspension control device for a vehicle, which is configured to output to an actuator. 2. The suspension control device for a vehicle according to claim 1, wherein the control unit adjusts the delay time in a decreasing function with respect to the vehicle speed in each sensor moving state.