JP3016526B2 - 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 vehicle suspension device such as a roll, dive, and scut. To perform control.

[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. 61-127007 is known.

This vehicle suspension system measures the sprung displacement and the sprung-unsprung relative speed of each wheel portion, and when the sign of the sprung displacement and the sign of the sprung-unsprung relative speed coincide with each other. The shock absorber was provided with a damping coefficient control means for controlling the damping coefficient to a high damping coefficient, and controlling the shock absorber to a low damping coefficient in the case of a mismatch.

[0004]

However, in such a conventional vehicle suspension system, effective control of the damping coefficient can be obtained independently for each wheel unit with respect to the input from the road surface. 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. Therefore, there was a problem that the steering stability of the vehicle could not be secured.

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 the riding comfort and the steering stability of a vehicle under all conditions. Is what you do.

[0006]

According to the present invention, as shown in the claim correspondence diagram of FIG. 1, there is provided damping coefficient changing means a provided between each wheel of the vehicle and the vehicle body to change the damping coefficient. A shock absorber b, a sprung speed detecting means for detecting a sprung speed of each wheel portion, and c; a sprung speed of each wheel portion detected based on the sprung speed detected by the sprung speed detecting device c; 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 in the same direction as a predetermined damping coefficient by a predetermined control constant; A calculating unit f provided in the control unit e 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 each sprung speed value and direction thereof; 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 operation of the present invention will be described. Note that reference numerals in the description correspond to FIG. When the vehicle travels, the shock absorber b is subjected to input from both the unsprung portion and the sprung portion, and the stroke of the shock absorber b is performed.

At this time, the calculation unit f calculates 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 and direction of the sprung speed of each wheel detected by each sprung speed detecting means c. Is calculated, and the control constant adjusting unit g performs adjustment to change the control constant of the damping coefficient control unit d in a direction to increase as the distance decreases.

Then, the damping coefficient control unit 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 detected by the sprung speed detecting means c. A switching signal is output to each of the attenuation coefficient changing means a in order to control to an optimal attenuation coefficient based on the control constant set by the control constant adjusting section g.

That is, when the vehicle travels straight at a constant speed on a flat road surface having a small inertia force acting on a sprung portion, the distance from the center of gravity of the vehicle body to the instantaneous rotation center axis becomes long, so that the control constant is set small. Thus, it is possible to secure the vibration damping property of the vehicle against road surface input.

Contrary to the above, the inertia force acting on the sprung is large at the time of steering, braking, rapid acceleration, etc., so that the vehicle body is largely rotated in the left-right or front-rear direction (roll, dive, scut). In such situations, the distance from the center of gravity of the vehicle body to the instantaneous rotation center axis is short, so the control constant is set large, thereby sufficiently suppressing the rotation of the vehicle body and improving the steering stability of the vehicle. Can be secured.

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

[0013]

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 FIG. 2, 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 coefficient position of the shock absorber 1. The stepping drive changes the damping coefficient position of each shock absorber 1 in multiple steps.

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. Then, based on the detected value of the sprung acceleration, the sprung speed V of each wheel portion is calculated. The sprung acceleration sensor 3 is also provided one for each shock absorber 1.

The control unit 5 constitutes control means, and includes an interface circuit 5a, a CPU 5
b, a drive circuit 5c, and the interface circuit 5a
Is input with an output signal from each of the vertical acceleration sensors 3.

The arithmetic unit of the control unit 5 calculates 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 and direction of each sprung speed and the width of the vehicle. That is, FIG. 13 is an operation explanatory view showing the bouncing state of the vehicle body. As shown in this figure, when bouncing while traveling straight ahead at a constant speed on a relatively flat road surface, the left and right or front and rear wheel portions since the direction of the sprung mass velocity V is in the same direction, the distance L ₁ from the vehicle body center of gravity G to the instantaneous rotation center axis P ₁ of the vehicle body is increased. On the other hand, FIG. 14 is an operation explanatory view showing the rotating state of the vehicle body. As shown in FIG. 14, the pitching due to running on a undulating road, the roll due to cornering, the scut due to rapid acceleration, the 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 and right or front and rear of the wheel portion, so that the distance L ₂ from the center of gravity G of the vehicle to the instantaneous rotation center axis P ₂ of the vehicle 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 adjustment unit adjusts the control coefficient α of the damping coefficient control unit so as to increase as the distance L calculated by the calculation unit decreases. And in the figure,
alpha ₁ is a minimum value of the control constant, indicates the value of the optimum control constants for performing the damping coefficient control with respect to the road surface input at constant-speed straight running of the vehicle, also, alpha ₂ is a maximum value of the control constant This shows the value of the optimal control constant when performing the damping coefficient control for suppressing the rotation of the vehicle body when the maximum lateral acceleration acts on the vehicle.

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

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 path 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 coefficient between the three positions shown in FIGS. .

That is, the second position shown in FIG.
), The extension side first flow path D and the compression side first flow path D
The flow path H and the pressure side second flow path J can be circulated,
Thus, as shown in FIG. 9, the extension side has a high damping coefficient (+ Xmax position in FIG. 12), and the compression side in the reverse stroke has a predetermined low damping coefficient (-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 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
As shown in FIG. 11, the compression side has a high damping coefficient (-Xmax position in FIG. 12) and the expansion side in 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 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 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. Also, as shown in FIG.
When the adjuster 6 is rotated counterclockwise from the position where the compression side has a low damping coefficient (± Xsoft position in FIG. 12), only the extension side changes to the high damping coefficient side, and conversely,
When the adjuster 6 is rotated clockwise, only the pressure side changes to the high damping coefficient side.

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

(A) When the vehicle is traveling straight ahead at a constant speed When traveling straight ahead at a constant speed on a relatively flat road surface, the inertia force acting on the vehicle body is small and the rotation of the vehicle body is small. As shown in FIG.
The distance L ₁ of the instantaneous to the rotational center axis P ₁ of the vehicle body is increased from a control constant adjusted minimum value control constant is in part α
_{In addition,} the damping coefficient control unit of the control unit 5 sets the shock absorber in the same direction as the sprung speed V based on the low control constant α ₁ and the sprung speed V detected at each wheel. The switching control of the damping coefficient is performed so that the stroke side of 1 becomes the optimum damping coefficient (C = α ₁ · V) proportional to the sprung speed V. That is, the direction of a) the sprung speed V when an upward (+), based on the lower control constant alpha _1, the extension side is the same direction as the direction of the sprung speed V at that time is proportional to the sprung speed + V In the high damping coefficient position, the opposite pressure side is switched to the second position (the position in FIGS. 8 and 9) where the predetermined low damping coefficient (-Xsoft position) is reached.

[0030] b) the direction of the sprung speed V down (- when) a is lower based on the control constants alpha _1, the direction and the compression side speed on spring -V is the same direction of the sprung speed V at that time At the proportionally high damping coefficient position, the opposite extension side is switched to the third position (the position in FIGS. 8 and 11) where the predetermined low damping coefficient (+ Xsoft position) is reached.

[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
As a high damping coefficient in proportion to the sprung speed ± V on the stroke direction side, the vibration of the sprung body (vehicle) is appropriately suppressed, whereby the steering stability can be improved, and the sprung at that time can be improved. By setting the stroke side of the shock absorber 1 in the direction opposite to the direction of the speed ± V as a predetermined low damping coefficient, a road surface input in the direction opposite to the stroke direction can be absorbed at the time of vibration suppression control to secure the riding comfort of the vehicle. It has the feature of being able to.

(B) Roll, dive, and scut occurrences Under conditions where the inertia force acting on the vehicle body becomes large, such as during steering, braking, and sudden acceleration, the operation of FIG. As shown, the rotation of the car body increased,
Dive, or the like occurs squat, thereby, the distance L ₂ from the vehicle body center of gravity G to the instantaneous rotation center axis P ₂ of the vehicle body is shortened, high control constants in the control constant adjusting section α
_X , and based on the high control constant α _X and the sprung speed V detected at each wheel, the damping coefficient control unit of the control unit 5 uses the same shock absorber as the direction of the sprung speed V. 1 stroke side switching control of the damping coefficient such that the damping coefficient higher in proportion to the sprung velocity _{V (C = α X · V} ) is performed.

As described above, by setting the switching to the high control constant α _X , the expansion / contraction speed of each shock absorber 1 and the suppressing force of the stroke are increased.
It has the feature that the rotation of the vehicle body such as roll, dive, scut, etc. can be suppressed with a higher damping coefficient than usual.

FIG. 16 is a perspective view showing values and directions of sprung velocities at four wheel portions when a scut occurs. FIG. 17 is a plan view of the same, and FIG. As described above, the sprung speed V at the front wheel side shock absorber mounting portions 1a, 1b is generated by the rapid acceleration of the vehicle.
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 is in a state where rotation has occurred. Therefore, also in this case, since the distance L ₃ from the vehicle body center of gravity G to the instantaneous rotation center axis P ₃ of the vehicle body is shortened, made the switching setting to high control constants alpha ₂ side, Therefore, in the front wheel side The damping coefficient on the extension stroke side and the damping coefficient on the compression stroke side on the rear wheel side are set to be higher, respectively, whereby the scut of the vehicle can be suppressed.

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

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

Further, in the embodiment, when one of the stroke side on the extension side and the compression side is controlled to the high damping coefficient side, the shock absorber having the structure in which the reverse stroke side has the low damping coefficient is used.
A structure in which both the extension side and the compression side switch to a low damping coefficient or a high damping direction can be used.

Further, in the embodiment, the case where the damping coefficient is proportionally controlled in accordance with the value of the sprung speed is shown. The coefficient may be switched stepwise.

[0040]

As described above, in the vehicle suspension system according to the present invention, the calculation 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 each sprung speed value and its direction. And a control constant adjustment unit that changes the control constant of the damping coefficient control unit in a direction to increase as the distance calculated by the calculation unit decreases, so that a predetermined The control constant can ensure the vibration damping of the vehicle body, and the roll, dive, scut, etc. due to the inertia force acting on the sprung can sufficiently suppress the rotation of the vehicle body by the large control constant.
Therefore, an effect is obtained that the riding comfort and the driving stability of the vehicle can be ensured under all conditions.

[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 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 change characteristic diagram in the apparatus of the embodiment.

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

FIG. 17 is a plan view of FIG. 16 for explaining an operation when a scut occurs.

FIG. 18 is a control constant change 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 part e control means f calculating part g control constant adjusting part

Claims (1)

(57) [Claims] Claims: 1. An apparatus is provided between each wheel of a vehicle and a vehicle body,
A shock absorber having damping coefficient changing means for changing a damping coefficient, a sprung speed detecting means for detecting a sprung speed of each wheel portion, and a sprung mass at each wheel portion detected by the 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 in the same direction as the sprung speed based on the speed to an optimum damping coefficient by a predetermined control constant. A control 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 each sprung speed value and its direction; And a control constant adjusting unit that changes the control constant of the damping coefficient control unit in a direction to increase as the distance that has been reduced decreases.