JPS6255209A - Suspension control device - Google Patents

Abstract

PURPOSE:To enhance the drive comfortability of a vehicle on a wavy surface road, by providing such an arrangement that the road surface is judged as a wavy road surface when the relative displacement between the spring load member and the nonspring load member exceeds a predetermined value and the relative speed therebetween is below a predetermined value, and then the suspension characteristic is made rigid. CONSTITUTION:A vehicle level sensor 30 detects the relative displacement X between the spring load member and the nonspring load member and the relative speed V therebetween,and delivers detection signals to a control circuit 32. CPU 36 judges the condition of the road surface in accordance with the relative displacement X and the relative speed V under the control of a program stored in a memory. That is, when the relative displacement X exceeds a predetermined value but the relative speed V is below a predetermined value, the road surface is judged as a wavy road surface, and a drive circuit 46 is energized to drive an actuator 28 to make the suspension characteristic harder. With this arrangement it is possible to enhance the drive comfortability of the vehicle even on a wavy road surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a suspension control device that controls the characteristics of a suspension that connects a vehicle body and an axle.

[Conventional technology]

A rough road is determined by detecting the speed of the lower jaw of the spring and the relative displacement between the sprung mass and the unsprung mass, and in the case of a rough road, the damping force is made larger than that on a good road, and the spring constant is set to the same as that on a good road. A suspension control device that similarly sets the suspension to a small value has been devised (Japanese Patent Application Laid-Open No. 59-23712).

[Problem that the invention seeks to solve]

However, since control is carried out specifically for rough roads, there is a drawback that even if the road is rough, when the road surface is undulating, the low-frequency amplitude of the vertical movement of the vehicle increases, which actually worsens the ride comfort. .

In view of these drawbacks, it is an object of the present invention to provide a suspension control device that can improve ride comfort even on a undulating road surface.

[Means for solving problems]

In the present invention, in a suspension control device that detects relative displacement and relative speed between a sprung mass and a sprung mass to control suspension characteristics, the relative displacement is greater than or equal to a predetermined value and the relative velocity is less than or equal to a predetermined value. Sometimes, the system determines that the road is undulating and makes the suspension characteristics stiffer than on a good road.

[Effect]

Even if the road is rough, in the case of a undulating road, the relative displacement between the sprung mass and the unsprung mass becomes more than a predetermined value, and the relative speed between the sprung mass and the unsprung mass becomes less than the predetermined value. Therefore, this relative displacement and relative speed are detected to determine whether the road is undulating, and if it is determined that the road is undulating, the suspension characteristics are made stiffer than when the road is smooth. This reduces the vibration of the vehicle body on undulating roads, improving ride comfort.

〔Example〕

Embodiments of the suspension control device of the present invention will be described with reference to the drawings.

As shown in FIG. 1, an arm 12 supporting an axle 10 and a vehicle body 14 are connected by an air spring 16 with a shock absorber. This air spring with shock absorber 16 is composed of a lower shock absorber 18 and an upper air spring 20. The shock absorber 18 has a variable orifice diameter, and the damping force can be changed to three levels: soft (small), medium (medium), and hard (large). The air spring 20 also has a main air chamber 22. It has 24.26 secondary air chambers, and the effective volume of the air chambers and the diameter of the communication path between the air chambers can be varied to adjust the spring constant to three levels: soft (small), medium (medium), and hard (large). It is possible to switch to.

In addition, the bushing is, for example, a fluid-filled type, and the sealed fluid is divided into two chambers, and by blocking communication between each chamber with an actuator 28, the dynamic stiffness of the bushing can be adjusted to two levels (soft, hard). It is possible to switch to Actuator 2 switches the damping force and spring constant.
Performed by B. Further, the vehicle height sensor 30 detects the distance between the arm 12 and the vehicle body 14, that is, the relative displacement X between the sprung portion and the unsprung portion.

The damping force and spring constant are controlled by a control circuit 32. That is, the output signal of the vehicle height sensor 30 is sent to the A/D converter 34.
After being converted into a digital signal by , it is supplied to CPtJ36. Further, the output signal of the vehicle height sensor 30 is differentiated by a differentiating circuit 38, and then converted into a digital value by an A/D converter 34 and supplied to the CPU 36. Therefore, the cPtJ36 can read the relative displacement X between the sprung mass and the sprung mass and the relative velocity V thereof. The CPU 36 calculates the relative displacement X according to the program loaded into the memory 44.
, the road surface is determined based on the value of the relative velocity V, the spring constant and the target values of the damping force are determined, and a drive signal is supplied to the actuator 28 via the drive circuit 46.

Next, a method of determining the road surface from the data of the relative displacement X and relative velocity V will be explained with reference to FIG. Data of relative displacement X and relative velocity (2) are sampled n pieces at regular time intervals. Then, the maximum value X max of the relative displacement X and the average value V avr of the relative velocity ■ are determined. FIG. 3 is obtained experimentally, and the horizontal axis is Xmax and the vertical axis is V avr. To summarize this diagram, Xm
If the set of 'ax and V avr values is close to the origin, it is determined to be a good road, if it is located at a medium distance from the origin, it is determined to be a moderately bad road, and if it is far from the origin, it is determined to be a very bad road. do. However, even if the road is far from the origin, if the VavrO value is below a certain value, it is determined that the road is undulating.

FIG. 4 shows a control table for controlling the characteristics of the suspension according to the determination of the road surface to achieve a high balance between ride comfort and handling. When the road is good, the spring constant, bushing characteristics, and damping force are set to soft (small). In addition, the damping force is set to medium in the case of a moderately rough road, and set to soft in other cases. In the case of a very rough road, the spring constant and damping force are set to medium, and the bushing characteristics are set to soft. Furthermore, in the case of a undulating road, the spring constant, damping force, and bushing characteristics are all set to hard (large) values.

Next, the operation of this embodiment configured as described above will be explained with reference to the flowchart shown in FIG.

In step 100, the RAM and output are initialized. Next, the process proceeds to step 102, where the vehicle height sensor 3
The relative displacement X between the arm 12 and the vehicle body 14 and the relative speed ■ of the relative displacement are read from 0. Then step 104
, move the value of relative displacement X to array element X (i),
Move the value of relative velocity ■ to array element V (i). Also, i
Increment the value of . Here the value of i is step 1
It is initialized to 1 in 00. Then step 1
The process advances to step 06, and if the value of i is less than or equal to n, the process returns to step 102 and the above process is repeated. In this way, n sets of values of relative displacement X and relative velocity V are read at regular intervals,
Proceed to step 108. Then, the maximum value of the n values of relative displacements X is determined and set as Xmax. Also, find the average value of n absolute values of the values of each relative velocity V, and calculate this as V
Let it be avr.

Next, the process proceeds to step 110, where the table in the memory 44 in which the map shown in FIG. 3 is stored is referred to, and the X ma
The road surface is determined from the set of x and Vavr values. Next, the process proceeds to step 112, in which the target values of the spring constant, bushing characteristics, and damping force are determined with reference to the control table shown in FIG. 4 stored in the memory 44. Next, the process proceeds to step 114, where the actuator 28 is driven to reach the target value. Next, the process advances to step 100 and the above processing is repeated.

In this way, in the case of a undulating road, the low-frequency amplitude of the vertical movement of the vehicle body becomes smaller, and the suspension characteristics are controlled by distinguishing between a very rough road and a undulating road, which were not previously distinguished, and improving ride comfort and handling. Able to maintain altitude balance.

〔Effect of the invention〕

The suspension control device according to the present invention detects the relative displacement and relative speed between the sprung mass and the sprung mass, and determines that the road is a undulating road when the relative displacement is greater than or equal to a predetermined value and the relative velocity is less than or equal to a predetermined value. Since the suspension characteristics are made stiffer than when driving on a good road, the low-frequency amplitude of the vertical movement of the vehicle body becomes smaller when driving on a undulating road, making it possible to distinguish undulating roads from rough roads, which previously could not be distinguished. It has the excellent effect of being able to achieve a high balance between ride comfort and handling.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of a suspension control device according to the present invention, FIG. 2 is a control flowchart, FIG. 3 is a road surface determination map, and FIG. 4 is a control table. 18...Shock absorber, 20...Air spring, 30...Vehicle height sensor, X...Relative displacement between sprung mass and unsprung mass.

Claims (1)

[Claims] In a suspension control device that detects relative displacement and relative speed between a sprung mass and a sprung mass to control suspension characteristics, when the relative displacement is greater than a predetermined value and the relative velocity is less than a predetermined value, a undulating road is detected. A suspension control device characterized in that the suspension characteristics are determined to be stiffer than those on a good road.