JPH06211021A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To provide a vehicle suspension device allowing the riding comfort and maneuvering stability of a vehicle to be secured in all conditions. CONSTITUTION:A vehicle suspension device is provided with a control means (e) having a damping coefficient control part (d) for outputting a changeover signal to each damping coefficient changing means (a) so that the stroke side of each shock absorber (b) in the same direction as each sprung speed is controlled to an optimum damping coefficient by a specified control constant on the basis of the sprung speed in each wheel part detected by each sprung speed detecting means (c). The control means (e) is provided with a computing part (f) for computing the distance from the center-of-gravity of a body to the instantaneous rotation center axis of the body on the basis of the value and direction of each sprung speed, and a control constant adjusting part (g) for changing the control constant of the damping coefficient control part (d) in the enlarged direction with the decrease of the distance computed by the computing part (f).

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 part and an unsprung part of a vehicle, and more particularly to suppressing rotation of the vehicle such as rolls, dives and scuts. Related to control.

[0002]

2. Description of the Related Art Conventionally, as such a vehicle suspension device, for example, one disclosed in Japanese Utility Model Laid-Open No. 61-127007 has been known.

This vehicle suspension system measures the sprung displacement and the sprung-unsprung relative speed at each wheel portion, and when the sign of the sprung displacement matches the sign of the sprung-unsprung relative speed. The shock absorber is provided with a damping coefficient control means for controlling the damping coefficient to a high damping coefficient and controlling the damping coefficient to a low damping coefficient when they do not match.

[0004]

However, in such a conventional vehicle suspension system, in response to an input from the road surface, each wheel portion can independently obtain an effective damping coefficient control effect. However, under conditions where inertial force acts on the spring, such as during steering, braking, and sudden acceleration, the control force is insufficient and rotation of the vehicle body such as rolls, dives, and scuts may occur. There is a problem in that the steering stability of the vehicle cannot be secured because it cannot be sufficiently suppressed.

The present invention has been made in view of such a problem, and an object thereof is to provide a vehicle suspension system capable of ensuring the riding comfort and steering stability of a vehicle under all conditions. To do.

[0006]

In the present invention, as shown in the claim correspondence diagram of FIG. 1, there is provided a damping coefficient changing means a provided between each wheel of the vehicle and the vehicle body for changing the damping coefficient. The shock absorber b, sprung speed detecting means c for detecting the sprung speed of each wheel portion, and c A control means e having a damping coefficient control section d for outputting a switching signal to each damping coefficient changing means a in order to control the stroke side of each shock absorber b having the same direction as the optimum damping coefficient by a predetermined control constant; An arithmetic unit f provided in the control means e for calculating the distance from the center of gravity of the vehicle body to the instantaneous rotation center axis of the vehicle body based on the value of each sprung velocity and its direction, and the arithmetic unit f Distance decreases Brought in to a means and a control constant adjusting unit g for changing the control constant to greatly horizontal damping coefficient control unit d.

[0007]

The function of the present invention will be described. The reference numerals in the description correspond to those in FIG. When the vehicle travels, the shock absorber b is accompanied by inputs from both the unsprung part and the unsprung part, and the stroke of the shock absorber b is performed.

At this time, in the computing unit f, the distance from the center of gravity of the vehicle body to the instantaneous center axis of rotation of the vehicle body is determined based on the value of the sprung velocity of each wheel detected by each sprung velocity detecting means c and its direction. Is calculated, and the control constant adjustment unit g makes an adjustment to increase the control constant of the damping coefficient control unit d as the distance decreases.

Then, the damping coefficient control section d determines the stroke side of each shock absorber b in the same direction as the sprung speed based on the sprung speed at each wheel portion detected by each sprung speed detecting means c. A switching signal is output to each damping coefficient changing means a in order to control the damping coefficient to the optimum value based on the control constant set by the control constant adjusting unit g.

That is, when the vehicle is running straight at a constant speed on a flat road surface where the inertial force acting on the spring is small, the distance from the center of gravity of the vehicle body to the instantaneous rotation center axis becomes long, so the control constant is set small. Thus, it is possible to secure the vibration damping property of the vehicle with respect to the road surface input.

Contrary to the above, on the other hand, the inertial force acting on the spring is large during steering, braking, sudden acceleration, etc., so that the vehicle body rotates greatly in the left-right direction or the front-rear direction (roll, dive, scut). Under such a circumstance, the distance from the center of gravity of the vehicle body to the instantaneous center axis of rotation becomes short, so the control constant is set to a large value, which suppresses the vehicle body rotation sufficiently to improve the steering stability of the vehicle. Can be secured.

As described above, according to the present invention, the riding comfort and steering stability of the vehicle can be secured under all conditions.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, the configuration of the embodiment will be described. FIG. 2 is a system block diagram of an embodiment of the present invention, in which 1 is a shock absorber of variable damping force, 2 is a pulse motor, 3 is a sprung acceleration sensor, and 5 is 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 coefficient position of the shock absorber 1, and the damping coefficient position of each shock absorber 1 is changed in multiple stages by step driving.

The sprung acceleration sensor 3 is mounted on a sprung vehicle body, and detects the vertical acceleration on the spring,
An electric signal corresponding to the detected sprung acceleration is output. Then, the sprung speed V of each wheel is calculated based on the detected value of the sprung acceleration. The sprung acceleration sensor 3 is also provided for each shock absorber 1.

The control unit 5 constitutes a control means and includes an interface circuit 5a and a CPU 5
b, a drive circuit 5c, and the interface circuit 5a
An output signal from each vertical acceleration sensor 3 is input to.

Then, the calculation unit of the control unit 5 calculates the distance from the center of gravity of the vehicle body to the instantaneous center axis of rotation of the vehicle body based on the value of each sprung velocity and its direction and the vehicle width of the vehicle. That is, FIG. 13 is an operation explanatory view showing the bouncing state of the vehicle body. As shown in FIG. 13, when bouncing during straight running at a constant speed on a relatively flat road surface, the left and right or front and rear wheel parts are Since the directions of the sprung speeds V are the same, the distance L ₁ from the center of gravity G of the vehicle body to the instantaneous rotation center axis P ₁ of the vehicle body becomes long. On the other hand, FIG. 14 is an operation explanatory view showing a rotation state of the vehicle body. As shown in FIG. 14, pitching due to traveling on a sway, roll due to cornering, scut due to sudden acceleration, dive due to braking, etc. When the vehicle is in a rotating state, the direction of the sprung speed V is opposite to the left, right, front and rear of the wheel portion, so the distance L ₂ from the center of gravity G of the vehicle body to the instantaneous rotation center axis P ₂ of the vehicle body is short. Become.

As described above, the magnitude of rotation of the vehicle body is inversely proportional to the distances L ₁ and L ₂ from the center of gravity G of the vehicle body to the instantaneous rotation center axes P ₁ and P ₂ of the vehicle body. As shown in the control constant characteristic diagram of FIG. 15, the control constant adjusting unit of No. 2 makes an adjustment to increase the control constant α of the damping coefficient control unit as the distance L calculated by the arithmetic unit decreases. And in the figure,
α ₁ is the minimum value of the control constant, and is the value of the optimum control constant when the damping coefficient control is performed for the road surface input when the vehicle is traveling straight at a constant speed, and α ₂ is the maximum value of the control constant. The values of the optimum control constants for performing damping coefficient control for suppressing the rotation of the vehicle body when the maximum lateral acceleration acts on the vehicle are shown.

In the damping coefficient control section of the control unit 5, each sprung speed V calculated based on the input from each sprung acceleration sensor 3 provided on each wheel and the control constant adjusting section set. A control signal is output to the step motor 2 in order to control the shock absorber 1 to an optimum damping coefficient based on the control constant α thus determined.

Next, FIG. 3 is a sectional view showing the structure of the shock absorber 1. The shock absorber 1 is
A cylinder 30, a piston 31 defining the cylinder 30 into 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 movement 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 bumper bar 37.

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

The vertical groove 23 and the first and second lateral holes 2 are also provided.
The adjuster 6 in which 4, 25 are formed can switch the position of the damping coefficient in multiple stages among the three positions shown in FIGS. 5 to 7 based on the step rotation by the driving of the pulse motor 2. .

That is, the second position shown in FIG.
Position), the expansion side first flow path D and the compression side first flow path D
The flow passage H and the pressure-side second flow passage J are allowed to flow,
As a result, as shown in FIG. 9, the extension side has a high damping coefficient (+ Xmax position in FIG. 12), and the compression side of the reverse stroke has a predetermined low damping coefficient (-Xsoft position in FIG. 12).

Next, in the first position (position in FIG. 8) shown in FIG. 6, the four flow paths D,
E, F, G and all of the three flow paths H, J, G of the pressure stroke are allowed to flow, and as a result, as shown in FIG. 10, both the expansion side and the compression side have a predetermined low damping coefficient. (± Xsoft position in FIG. 12).

Next, at the third position shown in FIG. 7 (the position shown in FIG. 8), the extension side first to third flow paths D, E and F are provided.
And the pressure-side first flow path H are allowed to flow, and as a result, as shown in FIG. 11, the compression side has a high damping coefficient (-Xmax position in FIG. 12) and the extension side of the reverse stroke has a predetermined low damping 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 according to the step rotation angle. Can be changed.

That is, in the shock absorber 1, when the adjuster 6 is rotated, the damping coefficient is based on the rotation, and the damping coefficient has characteristics as shown in FIG. It is configured so that it can be changed in multiple steps within the range of high damping coefficient. In addition, as shown in FIG.
When the adjuster 6 is rotated counterclockwise from the position where both the compression side is set to the low damping coefficient (± Xsoft position in FIG. 12), only the extension side is changed to the high damping coefficient side, and conversely,
When the adjuster 6 is rotated clockwise, only the compression side changes to the high damping coefficient side.

Next, the control operation of the control unit 5 in the embodiment will be described.

(B) During constant-speed straight-ahead traveling During constant-speed straight-ahead traveling on a relatively flat road surface, the inertial force acting on the vehicle body is small and the vehicle body rotation is also small. As shown in, the center of gravity G of the vehicle body
Since the distance L ₁ from the vehicle to the instantaneous rotation center axis P ₁ of the vehicle body becomes long, the control constant is adjusted to the minimum value α
_{At the same time,} the damping coefficient control section of the control unit 5 sets the shock absorber in the same direction as the direction of the sprung speed V based on the low control constant α ₁ and the sprung speed V detected at each wheel portion. Switching control of the damping coefficient is performed so that the stroke side of 1 has an optimum damping coefficient (C = α ₁ · V) proportional to the sprung mass velocity V. That is, a) When the direction of the sprung speed V is upward (+), the extension side, which is in the same direction as the direction of the sprung speed V at that time, is proportional to the sprung speed + V based on the low control constant α ₁ . At the high damping coefficient position, the opposite pressure side is switched to the second position (position in FIGS. 8 and 9) where a predetermined low damping coefficient (-Xsoft position) is achieved.

B) When the direction of the sprung speed V is downward (-), the pressure side, which is in the same direction as the direction of the sprung speed V at that time, becomes the sprung speed -V based on the low control constant α _1. At the proportionally high damping coefficient position, the opposite expansion side is switched to the third position (position in FIG. 8 and FIG. 11) side where a predetermined low damping coefficient (+ Xsoft position) is achieved.

[0031] Thus, when the small inertia constant speed straight running acting on the vehicle body, a lower control constants α sprung speed ± same shock absorber and direction V 1 of the time based on its ₁
The stroke direction side is set to a high damping coefficient proportional to the sprung speed ± V to appropriately suppress the vibration of the sprung body (vehicle body), thereby improving the steering stability and the sprung portion at that time. A predetermined low damping coefficient is set on the stroke side of the shock absorber 1 in the direction opposite to the direction of the speed ± V to absorb the road surface input in the direction opposite to the stroke direction during the vibration damping control to ensure the ride comfort of the vehicle. It has the feature that it can.

(B) Roll, dive, scut occurrence Under conditions where the inertial force acting on the vehicle body becomes large, such as during steering, braking, and sudden acceleration, the action explanatory diagram of FIG. As shown, the rotation of the car body increases and rolls,
A dive, a scut, or the like occurs, which shortens the distance L ₂ from the center of gravity G of the vehicle body to the instantaneous rotation center axis P ₂ of the vehicle body, so that the control constant adjusting unit has a high control constant α.
_While being set to _X , the damping coefficient control section of the control unit 5 uses the high control constant α _X and the sprung mass velocity V detected at each wheel portion to determine the shock absorber in the same direction as the sprung mass velocity V. Switching control of the damping coefficient is performed so that the stroke side of 1 has a higher damping coefficient (C = α _X · V) proportional to the sprung mass velocity V.

By thus setting the switching to the high control constant α _X , the expansion and contraction speed of each shock absorber 1 and the suppression force of the stroke are increased.
It has the characteristic that the rotation of the vehicle body such as rolls, dives, and scuts can be suppressed with a damping coefficient that is stronger than usual.

FIG. 16 is a perspective view showing the sprung mass velocity values and their directions in each of the four wheel portions when a scut is generated, and FIG. 17 is a plan view of each, showing these figures. As described above, due to the sudden acceleration of the vehicle, the sprung speed V at the front wheel side shock absorber mounting portions 1a and 1b is
a, the direction of Vb is upward, the rear wheel side shock absorbers mounting portion 1c, sprung velocity -Vc in 1d, the direction of -Vd is facing down, in the longitudinal direction around the rotation axis P ₃ instant vehicle It has been rotated. Therefore, also in this case, the distance L ₃ from the center of gravity G of the vehicle body to the instantaneous rotation center axis P ₃ of the vehicle body is shortened, so that the setting for switching to the higher control constant α ₂ side is made. The extension stroke side damping coefficient and the rear wheel side damping stroke side damping coefficient are respectively set to be high, whereby scat of the vehicle can be suppressed.

As described above, this embodiment is characterized in that the riding comfort and steering stability of the vehicle can be secured under all conditions.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific structure is not limited to this embodiment, and there may be design changes and the like within the scope not departing from the gist of the present invention. Included in the present invention.

For example, in the embodiment, the case where the control constant is changed in proportion to the distance has been shown, but it may be changed stepwise as shown in FIG.

Further, in the embodiment, when controlling one stroke side of the extension side and the compression side to the high damping coefficient side, a shock absorber having a structure in which the reverse stroke side has a low damping coefficient is used.
It is possible to use a structure in which both the extension side and the compression side are switched to a low damping coefficient or a high damping direction.

Further, in the embodiment, the case where the damping coefficient is proportionally controlled according to the value of the sprung speed has been shown. However, a predetermined threshold value is set for the sprung speed, and the damping is performed at this threshold value. The coefficients may be switched stepwise.

[0040]

As described above, in the vehicle suspension system of the present invention, the arithmetic unit for calculating the distance from the center of gravity of the vehicle body to the instantaneous rotation center axis of the vehicle body based on the value of each sprung velocity and its direction. And a control constant adjusting unit that changes the control constant of the damping coefficient control unit in the direction of increasing as the distance calculated by the calculating unit decreases, so that a predetermined value for input from the road surface can be obtained. The control constant can ensure the vibration damping property of the vehicle body, and the rotation of the vehicle body can be sufficiently suppressed by the large control constant for roll, dive, scut, etc. due to the inertial force acting on the spring.
Therefore, it is possible to obtain the effect that the riding comfort and the steering stability of the vehicle can be secured under all conditions.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a vehicle suspension device of the present invention.

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

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

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

5 is a sectional view showing a state of a second position, (a) is a sectional view taken along the line KK of FIG. 4, (b) is a sectional view taken along the line LL of FIG. 4, (c).
FIG. 6 is a sectional view taken along line N-N of FIG. 4.

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

7 is a sectional view showing a state of a third position, (a) is a sectional view taken along the line KK of FIG. 4, (b) is a sectional view taken along the line LL of FIG. 4, (c).
FIG. 6 is a sectional view taken along line N-N 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 damping coefficient with respect to piston speed in the second position.

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

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

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

FIG. 13 is an operation explanatory view showing a bouncing state of the vehicle body.

FIG. 14 is an operation explanatory view showing a rotating state of the vehicle body.

FIG. 15 is a control constant changing characteristic diagram in the apparatus of the embodiment.

FIG. 16 is a perspective view illustrating an operation when a scut is generated.

FIG. 17 is a plan view of FIG. 16 for explaining the action when a scut occurs.

FIG. 18 is a control constant changing characteristic diagram in another embodiment.

[Explanation of symbols]

 a damping coefficient changing means b shock absorber c sprung speed detecting means d damping coefficient control section e control means f computing section g control constant adjusting section

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 20, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (1)

[Claims] 1. A vehicle body is provided between each wheel of a vehicle and a vehicle body,
A shock absorber having damping coefficient changing means for changing the damping coefficient, a sprung speed detecting means for detecting sprung speed of each wheel portion, and a sprung portion for each wheel portion detected by each sprung speed detecting means. A damping coefficient control unit that outputs a switching signal to each damping coefficient changing means in order to control the stroke side of each shock absorber, which is the same as the direction of each sprung speed based on the speed, to the optimum damping coefficient by a predetermined control constant. A control unit having the same, a calculation unit provided in the control unit for calculating a distance from the center of gravity of the vehicle body to the instantaneous rotation center axis of the vehicle body based on the value of each sprung velocity and its direction, and the calculation unit And a control constant adjusting unit for changing the control constant of the damping coefficient control unit in a direction of increasing as the distance is decreased.