JP3066441B2 - 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 system for controlling a damping coefficient of a shock absorber provided between a sprung portion and a unsprung portion of a vehicle, and more particularly to a device for controlling roll suppression during steering.

[0002]

2. Description of the Related Art Conventionally, as such a vehicle suspension device, for example, one described in Japanese Utility Model Laid-Open Publication No. 62-70008 is known.

In this vehicle suspension system, a roll angle of a vehicle is calculated from a vehicle speed detected by a vehicle speed detecting means and a steering angle detected by a steering angle detecting means, and the roll angle exceeds a predetermined threshold value. At the time, based on the steering direction at that time, the damping coefficient of the shock absorber is controlled by controlling the extension side to a high damping coefficient on the steering direction side and the compression side to the high damping coefficient on the side opposite to the steering direction, respectively. The roll of the vehicle was suppressed.

[0004]

However, in such a conventional vehicle suspension system, the apparent roll state is determined based on the steering angle and the steering direction detected by the steering angle detecting means. Therefore, there is no problem when the steering is single-shot, but when continuous steering such as slalom is performed, there is a phase difference between the roll angle calculated by the steering angle and the actual roll angle of the vehicle. This causes the damping coefficient to be controlled in the direction opposite to the actual roll control direction, thereby increasing the length of the roll, deteriorating the steering stability, and setting the damping coefficient irrespective of the direction of the sprung speed. Therefore, there is a problem that the input from the road surface is easily transmitted to the sprung portion and the ride quality is deteriorated.

The present invention has been made in view of such a problem. For continuous steering such as slalom, the roll of the vehicle is suppressed to ensure the steering stability, and at the same time, the roll control during the roll control is performed. It is an object of the present invention to provide a vehicle suspension device that can ensure the riding comfort of a vehicle.

[0006]

According to the present invention, as shown in the claim correspondence diagram of FIG. 1, one stroke side of the extension side and the compression side is provided between each wheel of the vehicle and the vehicle body, and high attenuation is provided. When controlling to the coefficient side, a shock absorber b having a damping coefficient changing means a having a structure in which the reverse stroke side has a low damping coefficient, a sprung speed detecting means c for detecting a sprung speed in each wheel portion, and a vehicle A steering angle detecting means d for detecting the steering angle of the vehicle, and when the steering angle detected by the steering angle detecting means d is smaller than a predetermined threshold value, each wheel portion detected by the sprung speed detecting means c Damping for outputting a switching signal to the damping coefficient changing means a in order to control the stroke side of each shock absorber b in the same direction as the sprung speed based on the sprung speed at the optimum damping coefficient by a predetermined control gain. Coefficient control unit When the steering angle detected by the steering angle detection means d is equal to or greater than a predetermined threshold, the control means f is provided with the control means f, and after the steering angle has decreased to a value less than the predetermined threshold, a predetermined A roll control unit g for setting the control gain of the damping coefficient control unit a higher until the time passes.

[0007]

The operation of the present invention will be described. Note that reference numerals in the description correspond to FIG. When a steering operation is performed while the vehicle is running, the vehicle body rolls. At this time, when the steering angle detected by the steering angle detecting means d is equal to or larger than a predetermined threshold, a large roll is generated on the vehicle body by large steering. The stroke side of each shock absorber b, which is the same as the sprung speed direction of each wheel, from the time when the predetermined threshold value or more is reached to the time when the predetermined time elapses after the value falls below the predetermined threshold value. The control gain of the damping coefficient control unit a is set to a high value so as to control each of the shock absorbers to a high damping coefficient. As a result, the transient roll of the vehicle body is suppressed, and the road surface input on the reverse stroke side is absorbed with a low damping coefficient, so that the riding comfort during roll control is ensured.

As described above, since the switching control of the damping coefficient of each shock absorber b is performed in accordance with the actual roll direction of the vehicle, the control timing does not deviate even for continuous steering such as slalom. In addition, it is possible to reliably suppress the roll of the vehicle and secure the steering stability and the riding comfort.

When the steering angle is smaller than the predetermined threshold value, the roll control unit g does not operate and the damping coefficient control unit e detects the sprung speed because the vehicle is in a steady roll state during steady turning. Damping coefficient changing means for controlling the stroke side of each shock absorber b in the same direction of each sprung speed based on the sprung speed at each wheel portion detected by the means c to an optimum damping coefficient by a predetermined control gain. A switching signal is output to each of the switches a, so that the steering stability and the riding comfort of the vehicle during steady turning can be ensured.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. First, the configuration of the embodiment will be described. FIG. 2 is a system block diagram of the embodiment of the present invention, in which SA is a variable damping force type shock absorber, 1 is a vehicle speed sensor, 2 is a pulse motor, 3 is a sprung acceleration sensor,
Denotes a steering sensor, and 5 denotes a control unit.

A total of four shock absorbers SA are provided between each of the four wheels and the vehicle body.

The vehicle speed sensor 1 detects the vehicle speed of the vehicle and outputs an electric signal corresponding to the detected vehicle speed.

The pulse motor 2 switches the damping coefficient position of the shock absorber SA, and changes the damping coefficient position of each shock absorber SA in multiple steps by step driving.

The sprung acceleration sensor 3 is attached to a sprung vehicle body, and detects a sprung vertical acceleration.
An electric signal corresponding to the detected sprung acceleration is output. The sprung acceleration sensor 3 is also provided one for each shock absorber SA.

The steering sensor 4 constitutes a steering angle detecting means. The steering sensor 4 is provided on the steering wheel and outputs an electric signal according to the steering angle.

The control unit 5 constitutes a control means, and its damping coefficient control unit controls the shock absorber SA based on an input signal from the sprung acceleration sensor 3 so that the shock absorber SA has an optimum damping coefficient. In addition to outputting a control signal to the motor 2, the roll control unit performs control to set the damping coefficient of each shock absorber SA higher on the stroke side in order to suppress roll. That is, the control unit 5 includes an interface circuit 5a, a CPU 5b, and a drive circuit 5c. Output signals from the vertical acceleration sensor 3 and the steering sensor 4 are input to the interface circuit 5a.

FIG. 3 is a sectional view showing the structure of the shock absorber SA.
Is a cylinder 30 and an upper chamber and a lower chamber B
And a base 34 defining a lower chamber B and a reservoir chamber C, and a piston rod 7 connected to the piston 31. Guide member 3 for guiding sliding
5, 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 SA is provided with an expansion-side inner groove as a flow path through which the fluid in the upper chamber A compressed in the expansion stroke can flow to the lower chamber B side. From the position 11, the inner and outer peripheral portions of the expansion-side damping valve 12 are opened and the expansion-side first flow path D that leads to the lower chamber B, and the second port 13, the vertical groove 23, and the fourth port 14 The outer peripheral portion of the expansion-side damping valve 12 is opened from the position of the expansion-side outer groove 15 to reach the lower chamber B through the expansion-side second flow path E, the second port 13, the vertical groove 23, and the fifth port 16. The third flow path F extending to the lower chamber B by opening the extension check valve 17 and the bypass flow reaching the lower chamber B via the third port 18, the second horizontal hole 25, and the hollow portion 19. There are four flow paths to the path G, and the fluid in the lower chamber B compressed in the pressure stroke flows to the upper chamber A side. As capacity flow path, the compression side damping valve 2
0, and opens the pressure side check valve 22 via the hollow portion 19, the first lateral hole 24, and the first port 21 to the pressure side first flow path H leading to the upper chamber A. Compression side second
Channel J, hollow portion 19, second lateral hole 25, and third port 1
8 with the bypass flow path G that leads to the upper chamber A via
There are two channels.

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 coefficient 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 attenuation coefficient (FIG. 12).
(+ Xmax position), the pressure side of the reverse stroke becomes a predetermined low damping coefficient (-Xsoft position in FIG. 12).

Next, at 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 in the pressure stroke can be circulated, whereby both the extension side and the compression side have a predetermined low damping coefficient as shown in FIG. (± Xsoft position in FIG. 12).

Next, in the third position shown in FIG. 7 (the position shown in FIG. 8), the extension side first to third flow paths D, E, F
In addition, the pressure side first flow path H can be circulated, and as a result, as shown in FIG.
(-Xmax position), the extension side of the reverse stroke becomes a predetermined low attenuation coefficient (+ Xsoft position in FIG. 12). The first and third positions can be switched in multiple stages according to the step rotation angle of the adjuster 6, and only the damping coefficient on the high damping coefficient side is proportional to the step rotation angle. It is possible to change it.

That is, in the shock absorber SA, by rotating the adjuster 6, the damping coefficient based on the rotation is changed from the low damping coefficient to the characteristic shown in FIG. It is configured so that it can be changed in multiple steps within the range of the high attenuation coefficient. As shown in FIG. 8, when the adjuster 6 is rotated counterclockwise from the position where both the extension side and the compression side have a low attenuation coefficient (± Xsoft position in FIG. 12), only the extension side has a high attenuation coefficient. Change to the side, and conversely,
When the adjuster 6 is rotated clockwise, only the pressure side changes to the high damping coefficient side.

Next, an operation flow of the damping coefficient position control in the control unit 5 will be described with reference to a flowchart shown in FIG.

First, in step 101, initialization is performed, and in subsequent steps 102 and 103, the sprung speed V and the steering angle θn are detected.

The following step 104 is a step for determining whether or not the steering angle θn has exceeded a predetermined threshold value θc. If the steering angle θn is equal to or greater than the predetermined threshold value θc (YES), the routine proceeds to step 105, where the roll control condition is set. Is turned on, the routine proceeds to step 108, where it is less than the predetermined threshold value θc (N
If the answer is O), the routine proceeds to step 106. FIG. 16 shows a change characteristic of the roll control threshold value θc with respect to the vehicle speed. As shown in FIG.
Decreases in inverse proportion to the increase in vehicle speed. This is because even if the steering angle is small, a large roll is generated if the vehicle speed at that time is high.

Step 106 is after the roll control condition is switched to ON, and thereafter, the steering angle θ
In the step of determining whether or not n exceeds the predetermined threshold value θc for a predetermined time T, if the roll control condition is ON and the continuation is longer than a predetermined time T (YES), Proceeds to step 107 to set the roll control condition to OF
After the F state, the process proceeds to step 108, and if the roll control condition is OFF (NO), or if the continuation is less than the predetermined time T (NO) even after the roll control condition is ON, the process directly proceeds to step 108. Proceed to 108.

In step 108, the roll control condition is ON.
If the roll control condition is ON (YES) in the step of determining whether the roll control condition is ON, the process proceeds to step 109 to set the roll control gain, and then proceeds to step 111 where the roll control condition is OFF (NO). In the case of, the routine proceeds to step 110, where the normal control gain is set, and then the routine proceeds to step 111. FIG. 15 shows a change characteristic of the control gain with respect to the vehicle speed. As shown in FIG. 15, the roll control gain indicated by the dotted line and the normal control gain indicated by the solid line respectively increase in proportion to the increase of the vehicle speed. It is supposed to. This is because the roll of the vehicle generated by the steering increases in proportion to the increase in the vehicle speed.

At step 111, the target damping coefficient is calculated from the sprung speed V and the respective control gains, and then the routine proceeds to step 112.

In step 112, the control point of the pulse motor 2 is calculated based on the respective target damping coefficients. In the following step 113, a signal is output to drive the pulse motor 2 toward the control point of the pulse motor 2.

As described above, the control unit 5 repeats the above control flow, and such control is performed independently for each shock absorber SA.

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 steering angle θn, and FIG.
FIG. 3C shows the control gain, FIG. 3D shows the sprung speed V, and FIG. 3E shows the pulse motor control point.

(A) When the steering angle is small As shown in FIG. 14A, the absolute value of the steering angle ± θn | θn |
When does not exceed the absolute value | θc | of the predetermined threshold value ± θc, the roll generated by the steering is small. At this time, the control is switched to the normal damping coefficient control based on the normal control gain. The switching control of the damping coefficient position is performed such that the stroke side of the shock absorber SA in the same direction as the sprung speed ± V has a high damping coefficient proportional to the sprung speed ± V. A) The absolute value | θn | of the steering angle ± θn is a predetermined threshold value ± θc
Is less than the absolute value of | θc | and the direction of the sprung speed V is upward (+), the extension side in the same direction as the direction of the sprung speed V at that time is proportional to the sprung speed + V. At the high damping coefficient position, the pressure side is switched to the second position (the position in FIGS. 8 and 9) where the opposite pressure side has a predetermined low damping coefficient (-Xsoft position).

B) When the absolute value | θn | of the steering angle ± θn is less than the absolute value | θc | of the predetermined threshold value ± θc and the direction of the sprung speed V is downward (-) The pressure side which is the same direction as the direction of the sprung speed V at that time is the sprung speed-
At the high damping coefficient position in proportion to V, the expansion side is switched to the third position (the position in FIG. 8 and FIG. 11) in which the predetermined low damping coefficient (+ Xsoft position) is reached.

Therefore, the state of roll occurrence is predicted by detecting the steering angle, and when there is no possibility that the roll becomes severe, that is, during steady turning with a small steering angle, the same direction as the direction of the sprung speed ± V at that time is used. By controlling the stroke direction side of the shock absorber SA to a moderately high damping coefficient proportional to the sprung speed ± V based on a predetermined control gain, sprung (vehicle) vibration is moderately suppressed and steering stability is improved. And the ride comfort can be improved, and the sprung speed at that time ± V
The stroke side of the shock absorber SA in the direction opposite to the direction of the above is set as a predetermined low damping coefficient, absorbing the road surface input in the direction opposite to the stroke direction during vibration suppression control, preventing transmission to the vehicle body, and improving ride comfort. It can be further improved.

(B) When the steering angle is large As shown in FIG. 14B, the absolute value of the steering angle ± θn | θn |
Once exceeds the absolute value | θc | of the predetermined threshold value ± θc, the roll generated by large steering becomes excessive, so that the roll control condition is switched to the ON state, and the sprung speed ± V at that time Shock absorber S in the same direction as
By controlling the stroke side of A to a high damping coefficient proportional to the sprung speed ± V based on the roll control gain which is higher than the normal control gain, transient damping of the vehicle body is caused by a higher damping force than during normal control. Roll is suppressed. Then, the absolute value of the steering angle ± θn | θ
Even if n | falls below the absolute value | θc | of the predetermined threshold value ± θc, since the roll state is continued, the ON state of the roll control condition is maintained for a predetermined time T set in advance. Then, the roll control condition is switched to the OFF state only after the time T has elapsed, thereby returning to the normal damping coefficient control state shown in (a).

Thus, the absolute value of the steering angle ± θn | θn |
At the time when the absolute value | θc | of the predetermined threshold value ± θc is exceeded, the control delay is eliminated, and the sprung speed ± V at each wheel portion is eliminated.
The switching control of the damping coefficient corresponding to the actual roll direction of the vehicle is performed by switching the damping coefficient of each wheel based on the direction of the vehicle, thereby controlling the continuous steering such as slalom. There is a feature that the rolls of the vehicle can be reliably suppressed without causing a timing shift and steering stability can be ensured.

Further, as described above, the switching of the damping coefficient in each shock absorber SA is performed with reference to the direction of the sprung speed ± V of each wheel portion. The road surface input in the opposite direction is surely absorbed with a low damping coefficient, so that the ride comfort when the vehicle body rolls can be ensured.

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.

[0040]

As described above, in the vehicle suspension system according to the present invention, when the steering angle is smaller than the predetermined threshold value, the same direction as the direction of each sprung speed is determined based on the sprung speed. Control means having a damping coefficient control unit for outputting a switching signal to the damping coefficient changing means to control the stroke side of the shock absorber to an optimum damping coefficient by a predetermined control gain; At one time, a roll control unit for setting the control gain of the damping coefficient control unit to a higher value until the predetermined time elapses after the voltage has dropped below the predetermined threshold value, so that the actual roll of the vehicle is provided. Switching control of the damping coefficient according to the direction becomes possible, which ensures stable control of the roll of the vehicle without causing a shift in control timing even for continuous steering such as slalom. It is possible to ensure,
The road surface input in the direction opposite to the stroke of each shock absorber can be reliably absorbed with a predetermined low damping coefficient, so that the effect of ensuring the riding comfort of the vehicle during roll control can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a system block diagram showing a vehicle suspension system according to an 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. 4, FIG. 5B is a cross-sectional view taken along line LL of FIG.
FIG. 5 is a sectional view taken along line NN of FIG. 4.

6 is a sectional view showing a state of a first position, (a) is a sectional view taken along line KK of FIG. 4, (b) is a sectional view taken along line LL of FIG. 4, (c)
FIG. 5 is a sectional view taken along line NN of FIG. 4.

FIGS. 7A and 7B are sectional views showing a state of a third position, wherein FIG. 7A is a sectional view taken along line KK of FIG. 4, FIG. 7B is a sectional view taken along line LL of FIG.
FIG. 5 is a sectional view taken along line NN of FIG. 4.

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

FIG. 9 is a characteristic diagram of a damping coefficient with respect to a piston speed in a second position.

FIG. 10 is a characteristic diagram of a damping coefficient with respect to a piston speed in a first position.

FIG. 11 is a characteristic diagram of a damping coefficient with respect to a piston speed at a third position.

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

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.

FIG. 15 is a graph showing a change characteristic of a control gain with respect to a vehicle speed.

FIG. 16 is a graph showing a change characteristic of a roll control threshold value with respect to a vehicle speed.

[Explanation of symbols]

 a damping coefficient changing means b shock absorber c sprung speed detecting means d steering angle detecting means e damping coefficient control part f control means g roll control part

Continuation of the front page (56) References JP-A-59-120508 (JP, A) JP-A-59-206214 (JP, A) JP-A-3-42320 (JP, A) JP-A-2-74411 (JP) JP-A-3-42319 (JP, A) JP-A-64-103528 (JP, A) JP-A-61-249810 (JP, A) JP-A-61-163711 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60G 17/015

Claims (1)

(57) [Claims] 1. A damping mechanism which is provided between each wheel of a vehicle and a vehicle body and has a low damping coefficient on the reverse stroke side when one of the extension side and the compression side is controlled to a high damping coefficient side. Shock absorber having coefficient changing means, sprung speed detecting means for detecting sprung speed in each wheel portion, steering angle detecting means for detecting a steering angle of the vehicle, and steering detected by the steering angle detecting means When the angle is less than the predetermined threshold, the stroke side of each shock absorber in the same direction as the sprung speed is determined based on the sprung speed at each wheel detected by the sprung speed detecting means. Control means having a damping coefficient control unit for outputting a switching signal to the damping coefficient changing means for controlling the damping coefficient to an optimum damping coefficient by the control gain; and a steering angle detected by the steering angle detecting means provided in the control means. A roll control unit that sets the control gain of the damping coefficient control unit to a higher value until a predetermined time has elapsed after the voltage has dropped below the predetermined threshold when the value is equal to or more than the predetermined threshold. A vehicle suspension device.