JP2603385Y2 - Vehicle suspension system - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension for controlling a damping force of a shock absorber provided between a sprung portion and a unsprung portion of a vehicle.

[0002]

2. Description of the Related Art Conventionally, as such a vehicle suspension device, for example, one described in Japanese Patent Application Laid-Open No. 64-60411 is known. This vehicle suspension device detects a damping force generated in a shock absorber, estimates a relative displacement from the signal strength thereof, and calculates a relative displacement of a good road or a bad road from a cycle when the relative displacement exceeds a predetermined threshold value. Judgment is performed, when it is determined that the road is good, control is performed to the low damping force side, and when bad road is determined, the damping force is controlled to the high damping force only for a predetermined interval time. By controlling the high damping force only while the threshold value is exceeded, it is possible to ensure the running performance on a rough road.

[0003]

However, in such a conventional vehicle suspension, an interval time for judging a road surface condition is required, so that the damping force control is delayed and a rough road is generated. Since the switching from the low damping force to the high damping force is performed abruptly after a predetermined interval time has elapsed after entering the running state, there is a problem that the riding comfort and the steering stability of the vehicle are deteriorated.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a vehicle suspension device which can ensure both ride comfort and steering stability of a vehicle. .

[0005]

According to the present invention, as shown in the claim correspondence diagram of FIG. 1, a shock provided between a vehicle wheel and a vehicle body and having a damping force changing means a for changing a damping force is provided. Absorber b, sprung acceleration detecting means c for detecting the sprung acceleration of the vehicle, sprung speed detecting means d for detecting the sprung speed of the vehicle, and sprung acceleration detected by the sprung acceleration detecting means c When the value is less than the predetermined threshold value, the signal for controlling the stroke side of the shock absorber b, which is the same as the direction of the sprung speed detected by the sprung speed detecting means d, to a damping force value proportional to the sprung speed is damped. Output to the force changing means a, and when the sprung acceleration becomes equal to or more than a predetermined threshold, from that time until a predetermined time elapses after the sprung acceleration falls below the predetermined threshold. Control at that time And a means for the 衰力 value and a predetermined damping force control means a signal for controlling the correction damping force value obtained by subtracting the damping force value and outputs the damping force change means a e.

[0006]

The operation of the present invention will be described. Note that reference numerals in the description correspond to FIG. When the vehicle travels on a good road, the sprung acceleration does not exceed a predetermined threshold value. Therefore, the damping force control means e sets the sprung speed on the stroke side of the shock absorber b in the same direction as the sprung speed at that time. The control of switching the damping force (high damping proportional control) is performed so that the damping force value becomes proportional to the damping force. Therefore, when traveling on a good road, the vibration side of the vehicle body is suppressed by controlling the stroke side of the shock absorber b in the same direction as the sprung speed at that time to a damping force value proportional to the sprung speed. , Steering stability can be ensured.

Further, when the vehicle is traveling on a rough road, the sprung acceleration exceeds a predetermined threshold, and the damping force control means e thereafter reduces the sprung acceleration to below the predetermined threshold. Until a predetermined time elapses after lowering,
Switching of the damping force such that the stroke side of the shock absorber b in the same direction as the sprung speed at that time becomes a corrected damping force value obtained by subtracting a predetermined damping force value from the control damping force value proportional to the sprung speed. Control (medium damping proportional control) is performed. That is, when the vehicle passes on a rough road during the vibration damping control with a high damping force value proportional to the sprung speed, the road surface input is damped by reducing the damping force by a predetermined damping force value. The transmission to the vehicle body is suppressed by absorbing with a lower damping force than at the time of the control, whereby the riding comfort of the vehicle when passing through a rough road can be secured.

As described above, in the present invention, damping force control is performed at any time according to the input of the sprung speed and the sprung acceleration.
Since a rough road is not determined, a high control response can be obtained, and both the riding comfort and the steering stability of the vehicle can be secured.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. First, the configuration of the embodiment will be described. FIG. 2 is a system block diagram of the embodiment of the present invention. In the figure, reference numeral 1 denotes a variable damping force type shock absorber, 2 denotes a pulse motor, 3 denotes a sprung acceleration sensor, and 5 denotes a control unit.

A total of four shock absorbers 1 are provided between each of the four wheels and the vehicle body.
The pulse motor 2 switches the damping force position of the shock absorber 1, and is driven by a step drive.
The damping force position of each shock absorber 1 is changed in multiple stages.

The sprung acceleration sensor 3 comprises sprung acceleration detecting means and sprung speed detecting means.
Attached to a vehicle body on a sprung body, it detects a vertical sprung acceleration and outputs an electric signal corresponding to the detected value. The sprung speed is calculated from the sprung acceleration. The sprung acceleration sensor 3 is also provided one for each shock absorber 1.

The control unit 5 constitutes a damping force control means, and controls the step motor 2 based on an input signal from the sprung acceleration sensor 3 so that the shock absorber 1 has an optimum damping force. Output a signal. That is, the control unit 5 includes an interface circuit 5a, a CPU 5b, and a drive circuit 5c. An output signal from the sprung acceleration sensor 3 is input to the interface circuit 5a.

Next, FIG. 3 is a cross-sectional view showing the structure of the shock absorber 1.
A cylinder 30, a piston 31 defining the cylinder 30 in an upper chamber and a lower chamber B, an outer cylinder 33 having a reservoir chamber C formed on the outer periphery of the cylinder 30, a lower chamber B and a reservoir chamber C;
And a guide member 35 for guiding the sliding of the piston rod 7 connected to the piston 31
, A suspension spring 36 interposed between the outer cylinder 33 and the vehicle body, and a bump rubber 37.

More specifically, as shown in FIG. 4, the shock absorber 1 is provided with a flow passage through which the fluid in the upper chamber A compressed in the expansion stroke can flow to the lower chamber B side. A first flow path D extending from the position 11 to the lower chamber B by opening the inner and outer peripheral portions of the expansion damping valve 12;
An extension-side second flow path E that opens the outer peripheral portion of the extension-side damping valve 12 from the position of the extension-side outer groove 15 through the port 13, the vertical groove 23, and the fourth port 14 to the lower chamber B; 2 port 1
3, the extension side check valve 17 is opened via the vertical groove 23 and the fifth port 16 and the extension side third flow path F reaching the lower chamber B
And a bypass flow path G extending to the lower chamber B via the third port 18, the second horizontal hole 25 and the hollow portion 19, and the lower chamber B compressed in the pressure stroke. Of the pressure side damping valve 20
The first pressure passage H on the pressure side leading to the upper chamber A by opening the valve
9, the pressure-side second flow path J that opens the pressure-side check valve 22 via the first horizontal hole 24 and the first port 21 to reach the upper chamber A, the hollow portion 19, the second horizontal hole 25, and the third Port 18
There are three flow paths with the bypass flow path G which reaches the upper chamber A through the above.

The vertical groove 23 and the first and second horizontal holes 2
The adjuster 6 on which the pulse motors 4 and 25 are formed can switch the position of the damping force between the three positions shown in FIGS. .

First, at the second position shown in FIG. 5 (the position shown in FIG. 8), the expansion-side first flow path D, the compression-side first flow path H, and the compression-side second flow path J can flow. As a result, as shown in FIG. 9, the extension side has a high damping force (FIG. 12).
(+ Xmax position), the pressure side of the reverse stroke becomes a predetermined low damping force (-Xsoft position in FIG. 12).

Next, in the first position (the position shown in FIG. 8) shown in FIG. 6, the four flow paths D,
E, F, and G, and all three flow paths H, J, and G of the pressure stroke can be circulated. As shown in FIG. 10, both the extension side and the compression side have a predetermined low damping force. (± in FIG. 12)
Xsoft position).

Next, in a third position shown in FIG. 7 (a position shown in FIG. 8), the extension side first to third flow paths D, E, F
And the pressure side first flow path H can be circulated, whereby, as shown in FIG. 11, the pressure side has a high damping force (− in FIG. 12).
At the Xmax position), the extension side of the reverse stroke becomes a predetermined low damping force (+ Xsoft position in FIG. 12). The first and third positions can be switched in multiple steps according to the step rotation angle of the adjuster 6, and only the damping force on the high damping force side is proportionally proportional to the step rotation angle. It is possible to change it.

That is, in the shock absorber 1, by rotating the adjuster 6, the damping force based on the rotation is changed from the low damping force to the characteristic shown in FIG. It is configured so that it can be changed in multiple steps within the range of high damping force. Also, as shown in FIG. 8, when the adjuster 6 is rotated counterclockwise from the position where both the extension side and the compression side are set to the low damping force, only the extension side changes to the high damping force side, and conversely, When the adjuster 6 is rotated clockwise, only the pressure side changes to the high damping force side.

Next, the operation flow of the control unit 5 will be described with reference to the flowchart shown in FIG. First, in step 101, loads the sprung acceleration G _0, is calculated by calculating the following step 102 sprung acceleration G ₀ to the spring on the velocity V ₀ at. Next step 1
03 is a step for determining whether or not the absolute value | G ₀ | of the sprung acceleration ± G ₀ has exceeded the absolute value | a | of the predetermined threshold value ± a.
If S, proceed to step 106.

[0021] In step 104 side calculates the damping position in proportion to the sprung mass velocity V ₀ which then, in the subsequent step 105, the drive signal to the stepping motor 2 to switch to the calculated attenuation position is outputted,
This completes one flow.

On the other hand, on the step 106 side, a damping position proportional to the sprung speed V ₀ at that time is calculated.
In the following step 107, an attenuation position obtained by subtracting a predetermined position from the calculated attenuation position is calculated. In the following step 108, a drive signal is output to the step motor 2 to switch to the reduced low attenuation position. Go to 109. This step 109 is a step for determining whether or not the absolute value | G ₀ | of the sprung acceleration ± G ₀ has decreased below the absolute value | a | of the predetermined threshold value ± a.
Returning to step 6, if YES, proceed to step 110.

Step 110 is a step for judging whether or not the timer time has elapsed. If NO, the process proceeds to step 111 to start the timer, and then to step 1
Proceed to step 12, and if YES, proceed directly to step 112. This step 112 is a step for determining whether or not the measured time of the timer has exceeded a predetermined interval time. If NO, the process returns to the step 106, and YES
If so, this ends one flow. The control unit 5 repeats the above flow.

Next, the operation of the embodiment will be described with reference to FIG.

That is, FIG. 14 is a time chart for explaining the operation when the vehicle is running. FIG. 14A shows the sprung speed V ₀ ,
FIG. 3B shows the sprung acceleration G ₀ , and FIG. 3C shows the damping position.

(A) Running on a good road When the vehicle is running on a good road with little unevenness, the absolute value | G ₀ | of the sprung acceleration ± G _{0 is} the absolute value of the predetermined threshold ± a.
a |, the stroke side of the shock absorber 1 which is the same as the direction of the sprung speed V ₀ at that time is the sprung speed V _0.
The switching control of the damping force (high damping proportional control) is performed such that the damping force becomes proportional to the damping force. A) The absolute value of the sprung acceleration ± G ₀ | G ₀ | is the absolute value of the predetermined threshold value ± a
| a | is less than, and, when the direction of the sprung speed V ₀ is upward, the high attenuation extension side is the same direction as the direction of the sprung velocity V ₀ which at that time was proportional to the sprung speed V ₀ a force position (+ X _X), the pressure side of the reverse is switched to become the second position (position of FIG and FIG. 9) side (-Xsoft position of FIG. 12) a predetermined low damping force.

B) The absolute value | G ₀ | of the sprung acceleration ± G ₀ is less than the absolute value | a | of the predetermined threshold value ± a, and
When the direction of the sprung mass speed V ₀ is lowered direction, at that time a high damping force position direction and the compression side in the same direction of the sprung speed V ₀ is proportional to the sprung velocity V ₀ which (-X _X), The opposite extension side is switched to the third position (the positions in FIGS. 8 and 11) where the predetermined low damping force (+ Xsoft position in FIG. 12) is obtained.

[0028] Therefore, in the time of a good road, the vehicle body by controlling the high damping force proportional stroke side of the shock absorber 1 in a direction the same sprung velocity V ₀ which at that time sprung speed V ₀ Vibration is suppressed, whereby steering stability can be ensured, and the sprung speed V ₀ at that time can be suppressed.
The shock absorber 1 has a predetermined low damping force on the stroke side in the opposite direction to the direction of the shock absorber 1, and absorbs a road surface input in a direction opposite to the stroke direction during vibration suppression control to prevent transmission to the vehicle body. The ride comfort of the vehicle can be ensured. Further, by performing the control in proportion to the sprung speed, the change in the damping force at the time when the stroke of the shock absorber is switched can be smoothed.

(B) Running on a Bad Road When the vehicle is running on a bad road, the absolute value | G ₀ | of the sprung acceleration ± G ₀ exceeds the absolute value | a | of the predetermined threshold value ± a. in this case, stroke side of the shock absorber 1 in a direction the same sprung velocity V ₀ which at that time, sprung velocity V ₀
In the middle damping force position (± X _Xn ) obtained by subtracting the predetermined damping position (± X _n ) from the high damping force position (± X _X ) in proportion to the predetermined low damping force (± X _X ). Switching control (medium damping proportional control) of the damping force is performed so as to be in the range of ± Xsoft position in FIG.

That is, when the vehicle passes on a rough road during the vibration damping control by the high damping force, the damping force is reduced by a predetermined position to absorb the road surface input with a lower damping force. Transmission to the vehicle body is suppressed, and thereby, the riding comfort of the vehicle when passing through a rough road can be ensured.

As described above, in this embodiment, the damping force control is performed as needed in accordance with the input of the sprung speed V ₀ and the sprung acceleration G _0. Since the road is not determined, high control responsiveness can be obtained, and both riding comfort and driving stability of the vehicle can be secured.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. Included in the present invention. For example, in the embodiment, when one of the stroke side of the extension side and the compression side is controlled to the high damping force side, the shock absorber having a structure in which the reverse stroke side has a low damping force is used, but both the extension side and the compression side are used. A structure that switches in the direction of low damping force or high damping force can also be used.
The threshold a may be changed to that value by the direction of the sprung acceleration G _0.

[0033]

As described above, in the vehicle suspension system of the present invention, when the sprung acceleration detected by the sprung acceleration detecting means is less than a predetermined threshold, the sprung speed detecting means detects the sprung acceleration. A signal for controlling the stroke side of the shock absorber in the same direction as the direction of the sprung speed to a damping force value proportional to the sprung speed is outputted to the damping force changing means, and the sprung acceleration becomes equal to or more than a predetermined threshold value. When a predetermined damping force value is subtracted from the control damping force value at that time until a predetermined time has elapsed after the sprung acceleration has dropped below the predetermined threshold value from that point, a corrected damping force value The damping force control means that outputs a control signal to the damping force changing means, so that when traveling on a good road, the shock absorber performs the stroke in the same direction as the sprung speed direction at the sprung speed. Proportional decrease While controlling the vibration on the sprung by controlling the force value, the road surface input can be absorbed by the low damping force of the shock absorber to prevent the transmission to the sprung on rough roads. In addition, when performing this damping force control, the damping force control is performed as needed according to the input of the sprung speed and the sprung acceleration, so that high control responsiveness is obtained, and both the riding comfort and the steering stability of the vehicle are secured. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a view corresponding to a claim showing the vehicle suspension device of the present invention.

FIG. 2 is a system block diagram showing the vehicle suspension device according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a shock absorber applied to the embodiment device.

FIG. 4 is an enlarged sectional view showing a main part of the shock absorber.

5A and 5B are cross-sectional views showing a state of a second position, wherein FIG. 5A is a cross-sectional view taken along line KK of FIG. 3, FIG. 5B is a cross-sectional view taken along line LL of FIG.
FIG. 4 is a sectional view taken along line NN of FIG. 3.

FIGS. 6A and 6B are sectional views showing a state of a first position, wherein FIG. 6A is a sectional view taken along line KK of FIG. 3, FIG. 6B is a sectional view taken along line LL of FIG.
FIG. 4 is a sectional view taken along line NN of FIG. 3.

FIGS. 7A and 7B are cross-sectional views showing a state of a third position, wherein FIG. 7A is a cross-sectional view taken along line KK of FIG. 3, FIG.
FIG. 4 is a sectional view taken along line NN of FIG. 3.

FIG. 8 is a diagram showing a damping force switching characteristic of the shock absorber.

FIG. 9 is a graph showing a damping force characteristic with respect to a piston speed in a second position.

FIG. 10 is a graph showing a damping force characteristic with respect to a piston speed in a first position.

FIG. 11 is a graph showing a damping force characteristic with respect to a piston speed at a third position.

FIG. 12 is a variable characteristic diagram of a damping force with respect to a piston speed of the embodiment device.

FIG. 13 is a flowchart showing an operation flow of a control unit of the embodiment device.

FIG. 14 is a time chart for explaining the operation of the embodiment device when the vehicle is running.

[Explanation of symbols]

 a damping force changing means b shock absorber c sprung acceleration detecting means d sprung speed detecting means e damping force controlling means

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-208212 (JP, A) JP-A-5-85124 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60G 17/015

Claims (1)

(57) [Scope of request for utility model registration] 1. A shock absorber provided between a vehicle wheel and a vehicle body and having damping force changing means for changing damping force; sprung acceleration detecting means for detecting sprung acceleration of the vehicle; A sprung speed detecting means for detecting a sprung speed, and a direction of the sprung speed detected by the sprung speed detecting means when the sprung acceleration detected by the sprung acceleration detecting means is less than a predetermined threshold value. A signal for controlling the stroke side of the same shock absorber to a damping force value proportional to the sprung speed is output to damping force changing means, and when the sprung acceleration exceeds a predetermined threshold value, After that, the signal for controlling to the corrected damping force value obtained by subtracting the predetermined damping force value from the control damping force value at that time until the predetermined time elapses after the sprung acceleration falls below the predetermined threshold value is attenuated. Power change hand And a damping force control means for outputting to a step.