JPH09142126A - Vehicle suspension device - Google Patents

Abstract

(57) Abstract: In a vehicle suspension device in which a spring mechanism is provided in series with a damper device, both ride comfort and maneuverability are achieved. SOLUTION: Between the lower arm 23 and the vehicle body 21,
A spring mechanism 50 capable of changing a spring constant is provided in series with the damper device 40. Steering angle sensor 63, accelerator sensor 64,
The brake sensor 65 and the differential pressure sensor 66 detect the steering wheel angular velocity, the accelerator opening velocity, the brake pedal velocity, and the side wind that cause the posture change of the vehicle body 21. The microcomputer 67 determines a spring constant based on each detected value, and controls the spring constant of the spring mechanism 50 to the maximum value or average value of the determined spring constants. When the posture of the vehicle body 21 changes significantly, the force is efficiently transmitted between the vehicle body 21 and the road surface, and the maneuverability is improved.
When the posture of the vehicle body 21 does not change significantly, the vehicle body 21
Will be less affected by the unevenness of the road surface and the ride quality will be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension device having a spring and a damper device arranged in parallel between a wheel and a vehicle body.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
1, a spring 14 provided between the lower arm 12 connected to 1 and the vehicle body 13 to elastically support the vehicle body 13 with respect to the lower arm 12, and a bush 15 at the lower end connected to the lower arm 12 and at the upper end. A suspension device for a vehicle, which is provided in parallel with the spring 13 by being connected to the vehicle body 13 and has a damper device 16 for damping the vibration of the vehicle body 13 caused by the elastic support of the spring 14, is well known. ing.

[0003]

However, in the conventional vehicle suspension device as described above, the vehicle body 13
The damping coefficient of the damper device 16 must be maintained to a certain extent in order to damp the vibration of the. Therefore, in a situation in which the damping force of the damper device 16 acts as a vibrating force that promotes the vibration of the vehicle body depending on the running state of the vehicle, the vibration caused by the unevenness of the road surface is transmitted to the vehicle body 13, so that the riding comfort of the vehicle is improved. Becomes worse. In order to solve this, the present applicant has proposed a spring device in series with a damper device between a wheel and a vehicle body as Japanese Patent Application No. 7-107591 "Vehicle suspension device and electric control device for the same". We have proposed a vehicle suspension system with a spring mechanism that can change the force. In the proposed suspension device, when the vibration generated in the vehicle body is detected and the vibration of the vehicle body needs to be suppressed, the spring force of the spring mechanism is set to a large value to efficiently generate the damping force of the damper device. When it is not in the phase of suppressing the vibration of the vehicle body, the spring force of the spring mechanism is set to a small value to make it difficult for the damper device to generate the damping force and to prevent the damping force from acting as an exciting force on the vehicle body as described above. By doing so, the running stability and riding comfort of the vehicle are improved.

By the way, in the proposed vehicle suspension device, if the spring constant of the spring mechanism is set small in order to improve the riding comfort of the vehicle, the vehicle body will roll, yaw, dive, or squat. If the vehicle is vibrated or vibrates up and down, the transmission of force between the vehicle body and the road surface will be delayed, and it will be difficult for damping force to be generated in the damper device, and the transient ground load of the tire will not be secured, and Maneuverability may deteriorate.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to satisfy both the above-mentioned problems of riding comfort and maneuverability, and in particular, various set values are required as the spring constant of the spring mechanism due to a plurality of factors relating to changes in the attitude of the vehicle body. If this is the case, the purpose is to try to solve this reasonably.

In order to achieve the above object, the first aspect of the present invention
The structural feature of is that a spring mechanism that can change the spring constant is provided in series with the damper device between the wheel and the vehicle body, and various vehicle body attitude changes and driving operation quantities that cause various vehicle body attitude changes. And a plurality of the disturbance amounts are detected, and a plurality of spring constants for the spring mechanism corresponding to the detected plurality of detected amounts are determined to determine the spring constant of the spring mechanism. The maximum value among the determined plurality of spring constants is set.

According to this, rolling, yawing,
When various postures of the vehicle body such as dive, squat, and vertical vibration change, the maximum spring constant is selected from the spring constants for the spring mechanism required by the various posture changes, so that the vehicle body and the road surface are not changed. The transmission of forces between the two is efficient, depending on the maximum spring constant. Therefore, since the damping force is efficiently generated by the damper device, various posture changes of the vehicle body are corrected in a short time, and the transient ground load of the tire is secured, so that the vehicle stability is good. Kept in. Further, when the change in various postures of the vehicle body is small, the spring constant of the spring mechanism is set to a small value, and it becomes difficult for the spring mechanism to directly transmit the vibration due to the unevenness of the road surface to the vehicle body. It is less likely to occur and the ride comfort of the vehicle is kept good.

A second structural feature of the present invention is that instead of setting the spring constant of the spring mechanism to the maximum value of the determined plurality of spring constants, the determined plurality of springs is set. This is because the average value of constants is set.

Also by this, if the posture of the vehicle body changes variously such as rolling, yawing, dive, squat, and vertical vibration, the spring constant of the spring mechanism is set to a value in consideration of the magnitude of various posture changes. , The vehicle has good maneuverability.

[0010]

[Embodiment]

a. First Embodiment First, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an entire vehicle suspension device according to the present invention. The mechanical portion of this suspension device is arranged in parallel between a vehicle body (sprung member) 21 and a lower arm (unsprung member) 23 connected to the vehicle body 21 at an inner end and supporting a wheel 22 at an outer end. The spring 31 and the damper device 40 are provided. The spring 31 elastically supports the vehicle body 21 with respect to the lower arm 23. The damper device 40 is configured so that the damping coefficient can be changed, and when the vehicle body 21 vibrates vertically, a damping force is generated to damp the vibration. Between the damper device 40 and the vehicle body 21, a spring mechanism 5 whose spring constant can be changed.
0 is arranged in series with the damper device 40.

FIG. 2 shows an example of a mechanical portion of such a suspension device. The spring 31 is held at its lower end by a retainer 32 fixed on the outer peripheral surface of the cylinder 40a of the damper device 40, and at its upper end, the outer end of a fixed plate 33 fixed to the lower surface of the circular opening of the vehicle body 21. It is held on the lower surface via a bush 34.

The damper device 40 has a built-in damping force generating mechanism and a damping coefficient varying mechanism for variably controlling the damping coefficient of the damping mechanism, and is tiltably connected to the lower arm 23 at the lower end of the cylinder 40a. A piston rod 41 projects from the upper surface of the cylinder 40a, and a cylindrical sleeve 42 having a step is provided at the lower end of the rod 41.

A piston 43, which liquid-tightly divides the interior of the cylinder 40a into upper and lower oil chambers R1 and R2, is fixed on the outer circumference of the lower portion of the sleeve 42. It is enclosed. The upper and lower oil chambers R1 and R2 communicate with each other via oil passages 43a and 43b provided in the piston 43, and oil passages 42a to 4a provided in the sleeve 42.
It is designed to communicate via 2d. The oil passages 42a to 42d, 43a, 43b form orifices. A free piston 4 is provided below the lower oil chamber R2.
4 defines a gas chamber R3, and the gas chamber R3 is divided into upper and lower oil chambers R1 by the amount of invasion of the piston rod 41 into the upper oil chamber R1 by the vertical movement of the free piston 44.
Absorbs volume changes of 1 and R2.

A leaf valve 45a that opens only downward is attached to the lower open end of the oil passage 43a. The valve 45a extends from the upper oil chamber R1 to the lower oil chamber R2 only when the piston 43 moves upward. Allow movement of hydraulic oil. A leaf valve 4 that opens only upward at the upper open end of the oil passage 43b.
5b is assembled, and the valve 45b is provided from the lower oil chamber R2 to the upper oil chamber R only when the piston 43 moves downward.
Allow hydraulic oil to move to 1.

In the oil passage 42b of the sleeve 42, a cylindrical orifice member 46 having a taper portion 46a formed on the lower outer peripheral surface is housed so as to be vertically movable so as to face the peripheral wall of the oil passage 42b. The orifice member 46 is capable of continuously changing the throttle amount of the orifice formed between the tapered portion 46a and the peripheral wall of the oil passage 42b by the vertical movement thereof. In the damper device 40, the leaf valves 45a, 4a
A damping force is generated by the passage resistance to the hydraulic oil passing through 5b and the orifice, and
The damping coefficient is changed by changing the throttle amount of the orifice. Therefore, the sleeve 42, the piston 43, the leaf valves 45a and 45b, and the orifice member 46 form a damping force generating mechanism of the damper device 40.

The orifice member 46 is a drive rod 47.
Is fixed to the lower portion of the rod 47, and the upper end portion of the rod 47 is screwed to the nut 48 via a large number of balls. Nut 4
8 is a step motor 49 which constitutes an electric actuator.
Is driven to rotate, and the rotation causes the drive rod 47 and the orifice member 46 to move up and down. Therefore, the nut 48 and the step motor 49 constitute a damping coefficient variable mechanism.

The spring mechanism 50 incorporates a spring element and a spring constant varying mechanism for varying the spring constant of the spring element, and a movable plate 51 fixed to the upper end of the piston rod 41 in parallel with the fixed plate 33. Is equipped with.
Guide rods 52 are provided upright on the upper surface of the movable plate 51 at appropriate positions.
Slides on the inner peripheral surface of the through hole 33a provided in the fixed plate 33 to move the movable plate 51 up and down while keeping the movable plate 51 parallel to the fixed plate 33. In addition, the movable plate 51
On the upper surface of n (for example,
Several to ten or so coil springs 53 are erected and fixed at their lower ends. Each coil spring 5
The upper end of 3 is fixed to a stopper plate 54a provided at the lower end of the control rod 54, and the rod 54 slidably penetrates the inner peripheral surface of a through hole 33b provided in the fixed plate 33.

Each control rod 54 also penetrates a casing 55 fixed to the upper surface of the fixed plate 33 so as to be vertically movable. The casing 55 is the fixed plate 33.
An L-shaped frame 56 fixed to the upper surface of the is housed. A through hole 56a is formed in the horizontal portion of the frame 56, and the upper end portion of the control rod 54 is slidably passed through the hole 56a. Also, the casing 5
The clutch bar 57 for pulling the control rod 54 to the side and the electromagnetic solenoid 58 for driving the bar 57 to the side are also incorporated in the apparatus 5.

The clutch bar 57 is supported by a support frame 59 fixed to the upper surface of the fixed plate 33 so as to be displaceable in the axial direction, and the tip end thereof is bent in a hook shape so as to engage with the intermediate portion of the control rod 54. Has become.
The clutch bar 57 is constantly urged to the right in the figure by springs 57a having both ends connected to the casing 55 and the clutch bar 57, respectively. Electromagnetic solenoid 5
8 is also fixed to the casing 55 and sucks the clutch bar 57 to the left in the figure in the energized state.

In the spring mechanism 50 thus constructed, when the electromagnetic solenoid 58 is de-energized, the clutch bar 57 is displaced to the right in FIG. 2 by the urging force of the spring 57a. In this state, the engagement between the tip end of the clutch bar 57 and the control rod 54 is released, and the rod 54 is fixed to the fixed plate 33 and the frame 5 until the stopper plate 54a abuts the fixed plate 33.
It can move up and down freely without being restricted by 6. Therefore, until the stopper plate 54a contacts the fixed plate 33, the coil spring 53 corresponding to the electromagnetic solenoid 58 that is not energized does not exert a spring action (the spring constant of the coil spring 53 is kept at "0"). .

On the other hand, when the electromagnetic solenoid 58 is energized,
The clutch bar 57 is displaced leftward in FIG.
The tip of the pulls the control rod 54 in the same direction. In this state, the control rod 54 engages with the clutch bar 57, the fixed plate 33, and the inner peripheral surfaces of the through holes 33b and 56a of the frame 56, and is equivalent to the rod 54 fixed to the fixed plate 33. Become. Therefore, the coil spring 53 corresponding to the energized electromagnetic solenoid 58 exhibits a spring action, and its spring constant becomes a predetermined value k of the spring 53.

As described above, n coil springs 53 are provided, and each coil spring 53 can be selectively operated by energizing or de-energizing the electromagnetic solenoid 58 corresponding to each coil spring 53. m
When (m <n) electromagnetic solenoids 58 are energized, m
The individual coil springs 53 function, which is equivalent to inserting a spring element having a spring constant mk between the movable plate 51 (damper device 40) and the vehicle body 21. Therefore, in the spring mechanism 50, the spring constants of the spring elements composed of the n coil springs 53 provided between the damper device 40 and the vehicle body 21 are electrically controlled to 0, k, 2k, ... , Nk can be selected and set. Therefore, the spring constant changing mechanism that changes the spring constant of the spring element including the plurality of springs 53 includes the clutch bar 57 and the electromagnetic solenoid 58.

Next, the electric control device 60 for electrically controlling the mechanical portion of the suspension device will be described. The electric control device 60 includes an acceleration sensor 61, a vehicle height sensor 62, a steering angle sensor 63, an accelerator sensor 64, a brake sensor 65, and a differential pressure sensor 66.

The acceleration sensor 61 is fixed to the vehicle body 21 or the fixed plate 33, detects the vertical acceleration of the vehicle body 21 (sprung member) with respect to an absolute space, and outputs a detection signal representing the same acceleration. . However, the detected acceleration represents an upward acceleration by a positive value and a downward acceleration by a negative value. An integrator 61a, a low pass filter 61b, and a band pass filter 61c are connected to the acceleration sensor 61. The integrator 61a integrates the detection signal representing the acceleration to obtain the vehicle body 2 in the absolute space.
A signal representing the vertical velocity of 2 (hereinafter referred to as absolute velocity Zd) is output. The low-pass filter 61b limits the band of the detection signal indicating the acceleration to 2 Hz or less and outputs it, so that the vehicle body corresponding to the sprung resonance frequency (resonance frequency of the sprung member) as one of the attitude change amounts of the vehicle body. The vibration component G1 of is output. Bandpass filter 61c
Limits the band of the detection signal indicating the acceleration to within 9 to 13 Hz and outputs it, so that the unsprung resonance frequency (resonance frequency of the unsprung member) as one of the attitude change amounts of the vehicle body.
The vibration component G2 of the vehicle body corresponding to is output.

The vehicle height sensor 62 is a vehicle body 21 (a sprung member).
Is mounted between the lower arm 23 and the lower arm 23 (unsprung member) to detect a relative displacement amount of the vehicle body 21 with respect to the lower arm 23 and output a detection signal indicating the same displacement amount. However, the relative displacement amount is positive when the amount of increase from the reference value (expansion side of the damper device 40) is represented, and is negative when the amount of decrease from the reference value (side of the damper device 40 is contracted). A differentiator 62a is connected to the vehicle height sensor 62, and the differentiator 62a differentiates the detection signal representing the displacement amount,
A signal indicating the vertical speed of the vehicle body 21 with respect to the lower arm 23 (hereinafter referred to as the relative speed Yd) is output.

The steering angle sensor 63, together with the differentiator 63a,
The steering angular velocity θv is detected as one of the driving operation amounts that cause rolling and yawing of the vehicle body. The steering angle sensor 63 detects the steering angle θ, and the differentiator 63a differentiates the steering angle θ and outputs a signal representing the steering angular velocity θv. The accelerator sensor 64 is a differentiator 6
Along with 4a, the accelerator opening speed Av, which is one of the driving operation amounts causing the squat of the vehicle body, is detected. The accelerator sensor 64 detects the accelerator opening A based on the accelerator pedal depression amount or the throttle opening, and the differentiator 64
a differentiates the accelerator opening A, and the accelerator opening speed Av
Is output. The brake sensor 64, together with the differentiator 64a, detects the brake pedal speed Bv as one of the driving operation amounts that cause a dive of the vehicle body. The brake sensor 64 detects the depression amount B of the brake pedal, and the differentiator 64a differentiates the depression amount B to output a signal representing the brake pedal speed Bv. The differential pressure sensor 66 is for detecting the velocity of the cross wind received by the vehicle, which is one of the disturbance amounts causing the rolling and yawing of the vehicle body 21, and inputs the cross wind on both sides of the vehicle body 21. The difference in wind pressure due to both crosswinds is detected, and a signal representing the same wind pressure difference P is output.

These integrator 61a, low-pass filter 61b, band-pass filter 61c, and differentiators 62a, 6
3a, 64a, 65a and the differential pressure sensor 66 are connected to a microcomputer 67. The microcomputer 67 repeatedly executes a program corresponding to the flowchart of FIG. 3 (including the subprograms of FIGS. 5, 7, and 10) under a control of a built-in timer every predetermined short time. By executing this program, the microcomputer 67 causes the damping coefficient of the damper device 40 and the spring mechanism 50.
A control signal for electrically controlling the spring constant of is output to the drive circuits 68 and 69. The drive circuits 68 and 69 drive the step motor 49 in the damper device 40 and the electromagnetic solenoid 58 in the spring mechanism 50, respectively, in response to the control signal.

Next, the operation of the suspension device configured as described above will be described with reference to a flow chart. The microcomputer 67 starts repeatedly executing the program of FIG. 3 in response to turning on of an ignition switch (not shown). This program is executed in step 10
0, and at step 102, based on the steering angular velocity θv, accelerator opening velocity Av, brake pedal velocity Bv, vertical vibration components G1, G2 of the vehicle body, and wind pressure difference P, the respective amounts θv, Av, Bv. , G1, G2, P, spring constants KR, KS, KD, K for suppressing the change in the posture of the vehicle body
Determine F and KY.

The subprogram executed in the process of step 102 for determining the spring constant KR corresponding to the steering angular velocity θv is shown in detail in FIG. The execution of this subprogram is started in step 200, and in step 202, the steering wheel angular velocity θv is changed from the differentiator 63a.
Is input and the absolute value | θv | of the same steering angular velocity θv is the predetermined value θ
If vo or less, the spring constant KR is set to the minimum spring constant Kmin by the processing of steps 204 and 208. In addition, the absolute value of steering wheel angular velocity θv | θv |
If it is larger, the spring constant KR is set to a value that increases as the absolute value | θv | increases based on the θv-KR map of FIG. 6 by the processing of steps 204 and 206.

The spring constants KS and KD corresponding to the accelerator opening speed Av and the brake pedal speed Bv, respectively.
Also, based on the respective subprograms similar to FIG. 5 and the Av-KS map and Bv-KD map similar to FIG. 6, if the respective speeds Av and Bv are equal to or less than the predetermined values Avo and Bvo, the minimum spring constant Kmin. The speeds Av and Bv are set to a predetermined value Av.
If it is larger than o and Bvo, it is set to a value that increases as the speed Av and Bv increase.

The subprogram executed in the processing of step 102 to determine the spring constant KF corresponding to the vibration components G1 and G2 is shown in detail in FIG. The microcomputer 67 starts the execution of the subprogram in step 300, and inputs the vibration components G1 and G2 from the lowpass filter 61b and the bandpass filter 61c in step 302, respectively. Then, the spring constant KF is determined according to the input vibration components G1 and G2 by the processing of steps 304 to 322, and step 3
At 24, the execution of the program ends.

Absolute values of both vibration components G1 and G2 | G1 |,
| G2 | are predetermined threshold values G10 and G20, respectively.
If it is above, the microcomputer 67 first refers to the built-in G1-K1 map (FIG. 8) and G2-K2 map (FIG. 9) by the processes of steps 304 to 310, and determines both vibration components G1 and G2. The corresponding first and second spring constants K1 and K2 are determined. Then, steps 312 and 3
By the processing of 14,320, the first and second spring constants K
The larger one of 1 and K2 is set as the spring constant KF.

The absolute value | G1 | of the vibration component G1 is the threshold value G.
10 or more and the absolute value | G2 | of the vibration component G2 is the threshold value G
If it is less than 20, the first spring constant K1 determined by referring to the G1-K1 map is set as the spring constant KF by the processing of steps 304 to 308 and 314. If the absolute value | G1 | of the vibration component G1 is less than the threshold value G10 and the absolute value | G2 | of the vibration component G2 is not less than the threshold value G20, the G2-K2 map is obtained by the processing of steps 304 and 316 to 320. The second spring constant K2 determined with reference to is set as the spring constant KF. Further, if the absolute values | G1 | and | G2 | of both vibration components G1 and G2 are less than the threshold values G10 and G20, respectively, the minimum spring constant Kmin is set to the spring constant Kmin by the processing of steps 304, 316 and 322. Set as KF. By the processing of these steps 302 to 322, the spring constant KF becomes the absolute value | G1 |, of the vibration components G1 and G2.
It is set to a value that increases as | G2 | increases.

Further, the sub-program executed in the process of step 102 for determining the spring constant KY corresponding to the wind pressure difference P is shown in detail in FIG. The execution of this sub-program is started in step 400, the wind pressure difference P is input from the differential pressure sensor 66 in step 402, and if the wind pressure difference P is less than or equal to a predetermined value Po, the springs are processed in steps 404 and 408. The constant KR is set to the minimum spring constant Kmin. Also, the wind pressure difference P is a predetermined value Po.
If it is larger, the spring constant KY is set to a value that increases as the same wind pressure difference P increases based on the P-KY map of FIG. 11 by the processing of steps 404 and 406.

The spring constants KR, KS, KD, KD, KY in the subprograms of the step 102 are each.
In determining, the spring constants KR, KS, KD, K
When F and KY increase, they are changed immediately, but when they decrease, they are not changed until a predetermined time has elapsed.

Spring constants KR and K of step 102
After determining S, KD, KF, and KY, the microcomputer 67 sets the target spring constant K to the determined spring constant KR in step 104. Then, step 106-
By the processing of 120, each spring constant KS, KD, KF, K
If Y is larger than the currently set target spring constant K, the target spring constant K is set to the respective spring constants KS, KD, KD, KY.
To each spring constant KS, KD, KF, KY
If is equal to or less than the currently set target spring constant K, the value of the target spring constant K is held. As a result, the maximum value of the spring constants KR, KS, KD, KF and KY is set as the target spring constant K.

Next, at step 122, the target spring constant K
And the spring constant KN currently set in the spring mechanism 50 are compared, and if both spring constants K and KN match, the program proceeds to step 128 based on the determination of "YES" in step 122. If the spring constants K and KN do not match, the program proceeds to steps 124 and 126 based on the determination of "NO" in step 122. In step 124, a control signal representing the target spring constant K is output to the drive circuit 68, and in step 126, the current spring constant KN is changed to the target spring constant K.

In response to the control signal, the drive circuit 68 energizes as many electromagnetic solenoids 58 as the target spring constant K, and deenergizes the other electromagnetic solenoids 58. As a result, as described above, only the coil spring 53 corresponding to the energized electromagnetic solenoid 58 exerts the spring action, and the spring constant of the spring mechanism 50 is set to the target spring constant K. As a result, the spring constant of the spring mechanism 50 is set to the maximum value of the spring constants KR, KS, KD, KF, KY.

Next, in step 128, the microcomputer 67 inputs the detection signals representing the absolute velocity Zd and the relative velocity Yd from the integrator 61a and the differentiator 62a. Then, by the processing of steps 130 to 138, the damping coefficient of the damping force generating mechanism incorporated in the damper device 40 is controlled according to the absolute speed Zd and the relative speed Yd. Absolute speed Z
If the positive and negative signs of d and the relative speed Yd are different, step 1
Based on the determination of "NO" in 30, the target damping coefficient C is set to the minimum damping coefficient Cmin in step 136. If the positive and negative signs of the absolute speed Zd and the relative speed Yd match, the absolute speed Zd is set to the relative speed Yd in step 132 based on the determination of "YES" in step 130.
The speed ratio Zd / Yd is calculated by dividing by, and the target damping coefficient C corresponding to the speed ratio Zd / Yd is determined in step 134 by referring to the built-in Zd / Yd-C map (FIG. 4).

Then, in step 138, a control signal representing the determined target damping coefficient C is output to the drive circuit 69, and in step 140, the execution of this program is completed. The drive circuit 69 controls the rotational position of the step motor 49 of the damper device 40 to a position corresponding to the target damping coefficient C in response to the control signal. As a result, as described above, the damping coefficient of the damper device 40 is set to the target damping coefficient C. The processing of steps 128 to 136 is to determine the target damping coefficient C based on the skyhook theory, and as a result, the vibration of the vehicle body 21 is suppressed based on the skyhook theory. Regarding the setting of this target damping coefficient C, in the processing of step 138,
When the target damping coefficient C determined by the processing of steps 128 to 136 increases, it is changed immediately, but when it decreases, it does not change until a predetermined time elapses.

As described above, according to the first embodiment, the spring constant KR, which corresponds to the steering angular velocity θv and the wind pressure difference P that causes the rolling, yawing, etc. of the vehicle body 21, is calculated by the process of step 102. KY is determined, the spring constant KS is determined according to the accelerator opening speed Av that causes the squat of the vehicle body 21, and the spring constant KD is determined according to the brake pedal speed Bv that causes the dive of the vehicle body 21, Vibration component G representing vertical vibration of the vehicle body 21
1, the spring constant KF is determined according to G2, and step 104
By the processing of ~ 120, each of these spring constants KR, KS,
The maximum value of KD, KF, and KY is selected as the target spring constant K, and the spring mechanism 5 is processed by the processing of steps 122 to 126.
The spring constant of 0 is set as the target spring constant K. Therefore, when various posture changes of the vehicle body become large or become large, the force is efficiently transmitted between the vehicle body 21 and the road surface according to the maximum target spring constant K. As a result, the damping force is efficiently generated in the damper device 40 according to the maximum target spring constant K, so that the vehicle body 21
The various posture changes of the vehicle are corrected in a short time, and the transient ground load of the tire is secured, so that the steering stability of the vehicle is kept good. Further, when changes in various postures of the vehicle body 21 are small, the spring constant of the spring mechanism 50 is set to be small, and it becomes difficult for the spring mechanism 50 to transmit vibrations due to unevenness of the road surface to the vehicle body. Is less likely to occur and the ride comfort of the vehicle is kept good.

In the above embodiment, the rolling operation, yawing, squat, and dive of the vehicle body 21 are detected as the driving operation amount and the disturbance amount of the vehicle which cause them, and the spring is detected according to these detected amounts. Constant KR, K
Although S, KD, and KY are determined, a rotation amount sensor, a rotation speed sensor, a displacement amount sensor, a displacement speed sensor of the vehicle body 21 are provided, and the rolling, yawing, squat and dive of the vehicle body 21 Detects the physical quantity that represents the posture change, and according to the detected quantity, the spring constant K
R, KS, KD, KY may be determined.

B. Second Embodiment Next, a second embodiment of the present invention will be described. In addition to the configuration of the first embodiment, the second embodiment is similar to FIG.
A vehicle speed sensor 71 is provided as indicated by a broken line. The vehicle speed sensor 71 detects the vehicle speed V and outputs a detection signal indicating the detected vehicle speed V to the microcomputer 67. The microcomputer 67 repeatedly executes the program of FIG. 12 obtained by modifying a part of the program of FIG. 3 every predetermined short time. Other configurations are the same as those in the first embodiment.

Next, the operation of the second embodiment configured as described above will be described. The microcomputer 67 is shown in FIG.
In step 500, the execution of the program is started, and in step 502, each spring constant K is set as in the first embodiment.
In addition to determining R, KS, KD, KF, and KY, the spring constant KV corresponding to the vehicle speed V is determined. This spring constant K
The subprogram that determines V is shown in detail in FIG.

Step 60 is the execution of this subprogram.
0, the vehicle speed V is input from the vehicle speed sensor 71 in step 602, and if the vehicle speed V is less than or equal to a predetermined value Vo, the spring constant KV is processed in steps 604 and 608.
Is set to the minimum spring constant Kmin. If the vehicle speed V is higher than the predetermined value Vo, the spring constant KV is set to a value that increases as the vehicle speed V increases based on the V-KV map of FIG. 14 by the processing of steps 604 and 606. Then, in step 610, the execution of this subprogram is ended. The maximum value KVmax of the spring constant KV in FIG. 14 is the spring constant KR,
Maximum values KRmax, Kmax of KS, KD, K1, K2, KY,
It is set to a value smaller than KDmax, Kmax1, Kmax2 and KYmax. Also in this case, each spring constant KR, K
In determining S, KD, KF, KY, and KV, when the spring constants KR, KS, KD, KF, KY, and KV increase, they are changed immediately, but when they decrease, a predetermined time elapses. It won't change until you do.

After the processing of step 502, step 5
At 04, variables KT and N for calculating the average value of the spring constants KR, KS, KD, KF and KY are initialized to "0". Next, steps 506-510, 512-51
6,518-522, 524-528, 530-534
The respective spring constants KR, KS, and
Only when KD, KF, KY is larger than the determined spring constant KV, each spring constant KR, KS, KD, KF, K
Y is added to the variable KT and "1" is added to the variable N. Then, steps 536 to 540
If the variable is kept at "0" by the processing of step 1, the target spring constant K is set to the spring constant KV. On the other hand, the variable is "0"
If larger, a value obtained by dividing the variable KT by the variable N is set as the target spring constant K. As a result, all spring constants K
If R, KS, KD, KF, and KY are equal to or less than the spring constant KV, the target spring constant K is set to the spring constant KV. If even one of the spring constants KR, KS, KD, KF, and KY is larger than the spring constant KV, the target spring constant K is larger than the spring constant KV.
It is set to the average value of D, KF and KY.

After the processing of steps 536 to 540, the microcomputer 67 executes the processing of step 122 and subsequent steps similar to those of the first embodiment to set the spring constant of the spring mechanism 50 to the target spring constant K, and The current spring constant KN is changed to the target spring constant K, and the damping coefficient of the damper device 40 is set to the target damping coefficient C based on the skyhook theory.

As can be understood from the above description of the operation, according to the second embodiment, all spring constants KR, KS, K.
If D, KF, and KY are small, the spring constant of the spring mechanism 50 is set to the spring constant KV that increases as the vehicle speed V increases. Therefore, in this case, the force is efficiently transmitted between the vehicle body 21 and the road surface as the vehicle speed V increases, and the transitional ground load of the tire is secured. Good maneuverability is maintained. Further, when the spring constants KR, KS, KD, KF, KY are large and the posture of the vehicle body changes variously such as rolling, yawing, dive, squat, and vertical vibration, the spring constants of the spring mechanism 50 are various postures. Since the value is set in consideration of the magnitude of the change, the maneuverability of the vehicle is improved.

Also in the second embodiment, instead of the method of determining the spring constants KR, KS, KD and KY, physical quantities representing changes in vehicle body attitude such as rolling, yawing, squat and dive of the vehicle body 21. Of each spring constant KR, KS, KD, K
Y may be determined.

Further, a modified example in which a part of the second embodiment is modified will be described. In this modification, a part of the program of FIG. 12 executed by the microcomputer 67 is changed to a process in which “a” is added to each step code in FIG. In this case, the values a to e in the processing of each step with "a" added are the spring coefficients K
R, KS, KD, KF, KY weighting coefficients,
It is preset to a value of "1" or more. According to the program of FIG. 15, the target spring constant K is set to the respective spring coefficients KR, KS, KD, K by the processing of steps 504 to 538.
It is set to the average value of F and KY with predetermined weighting, so rolling, yawing, dive, squat,
The spring constant of the spring mechanism 50 is set more accurately with respect to various changes in the posture of the vehicle body such as vertical vibration, and the steering stability of the vehicle becomes better.

C. Other Modifications Further, in the above-described first and second embodiments, the example in which the spring mechanism 50 that can change the spring constant by selectively operating the plurality of coil springs 53 is used is described. As the mechanism 50, a spring mechanism having various structures can be used as long as the spring constant can be changed. For example, an elastic member such as rubber in which a liquid is sealed is interposed between the movable plate 51 and the fixed plate 33, and the elastic coefficient (spring constant) of the elastic member is changed by changing the amount of the sealed liquid. Stuff available. In addition, cylinder 4
The gas pressure in the gas chamber R3 in 0a can be changed from the outside.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing an entire vehicle suspension device according to first and second embodiments of the present invention.

FIG. 2 is a partial cross-sectional view showing an example of a mechanical portion of the suspension device.

FIG. 3 is a flowchart showing a program executed by the microcomputer of FIG. 1 according to the first embodiment of the present invention.

FIG. 4 Zd / Yd provided in the same microcomputer
It is a graph which shows the change characteristic of target damping coefficient C to relative velocity Zd / Yd in a-C map.

5 is a subprogram for determining a spring constant KR executed in step 102 of FIG.

FIG. 6 θv-K provided in the same microcomputer
Steering wheel angular velocity θv (and accelerator opening velocity Av, in the R map (and Av-KS map, Bv-KD map))
It is a graph which shows the change characteristic of spring constant KR (and spring constants KS and KD) to brake pedal speed Bv.

FIG. 7 is a sub-program for determining a spring constant KF executed in step 102 of FIG.

FIG. 8: G1-K1 provided in the same microcomputer
It is a graph which shows the change characteristic of the spring constant K1 with respect to the vibration component G1 in a map.

FIG. 9: G2-K2 provided in the same microcomputer
It is a graph which shows the change characteristic of the spring constant K2 with respect to the vibration component G2 in a map.

10 is a sub-program for determining a spring constant KY executed in step 102 of FIG.

FIG. 11: PK provided in the same microcomputer
7 is a graph showing a change characteristic of a spring constant KY with respect to a wind pressure difference P in a Y map.

FIG. 12 is a flowchart showing a part of a program executed by the microcomputer of FIG. 1 according to the second embodiment of the present invention.

FIG. 13 is a subprogram for determining a spring constant KV executed in step 102 of FIG.

FIG. 14 is a diagram showing a VK provided in the same microcomputer.
7 is a graph showing a change characteristic of a spring constant KV with respect to a vehicle speed V in a V map.

FIG. 15 is a flowchart showing a part of a program executed by the microcomputer of FIG. 1 according to the modified example of the second embodiment.

FIG. 16 is a schematic view of a conventional vehicle suspension device.

[Explanation of symbols]

21 ... Car body, 22 ... Wheels, 23 ... Lower arm, 31 ... Spring, 40 ... Damper device, 50 ... Spring mechanism, 60 ...
Electric control device, 61 ... Acceleration sensor, 61a ... Integrator,
61b ... Low pass filter, 61c ... Band pass filter, 62 ... Vehicle height sensor, 63 ... Steering angle sensor, 64 ... Accelerator sensor, 65 ... Brake sensor, 66 ... Differential pressure sensor, 62a, 63a, 64a, 65a ... Differentiator, 67 ...
Microcomputer.

Claims (2)

[Claims] 1. A spring, which elastically supports the vehicle body with respect to the wheel, and a damper device, which generates a damping force to damp vibration of the vehicle body with respect to the wheel, are provided in parallel between the wheel and the vehicle body. In a vehicle suspension device, a spring mechanism that is arranged in series with the damper device between a wheel and a vehicle body and that can change a spring constant, and causes various posture change amounts of the vehicle body and various posture changes of the vehicle body. Detecting means for detecting any one of a plurality of driving operation amounts and disturbance amounts, and determining means for determining a plurality of spring constants for the spring mechanism respectively corresponding to the detected plurality of detected amounts. And a selection means for selecting a maximum value of the determined plurality of spring constants, and a spring constant control means for setting the spring constant of the spring mechanism to the selected maximum value. You The vehicle suspension system. 2. A spring for elastically supporting the vehicle body with respect to the wheel and a damper device for damping a vibration of the vehicle body with respect to the wheel are provided in parallel between the wheel and the vehicle body. In a vehicle suspension device, a spring mechanism that is arranged in series with the damper device between a wheel and a vehicle body and that can change a spring constant, and causes various posture change amounts of the vehicle body and various posture changes of the vehicle body. Detecting means for detecting any one of a plurality of driving operation amounts and disturbance amounts, and determining means for determining a plurality of spring constants for the spring mechanism respectively corresponding to the detected plurality of detected amounts. And a calculation unit that calculates an average value of the determined plurality of spring constants, and a spring constant control unit that sets the spring constant of the spring mechanism to the calculated average value. Suspension system.