JPH09142128A - 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. The sensors 63 to 66 detect physical quantities related to changes in the attitude of the vehicle body, and the microcomputer 68 determines spring constants that increase as the physical quantities increase. In determining the spring constant, when the vehicle speed detected by the vehicle speed sensor 67 increases, each spring constant is set to a large value. Then, the microcomputer 68 controls the 50 spring constants of the spring mechanism to the maximum value or the average value of the spring constants. As a result, the spring constant of the spring mechanism 50 is appropriately set according to the posture change of the vehicle body 21, and the ride comfort of the vehicle and the maneuverability are both achieved.

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, the unevenness of the road surface is easily transmitted directly to the vehicle body 13, and particularly when the unevenness is suddenly transmitted to the vehicle body 13, the riding comfort of the vehicle is deteriorated. In order to solve this, the present applicant has filed Japanese Patent Application No. 7-1.
As No. 07591 "Vehicle suspension device and electric control device for the same", a spring mechanism is provided in series with a damper device between a wheel and a vehicle body, and a spring constant of the spring mechanism is usually set to a small value. Then, we proposed a suspension system for a vehicle in which the spring constant is set to a large value when the amount of various posture changes of the vehicle body and the amount of driving operation that causes various changes in the posture of the vehicle body become large. This allows
During normal traveling of the vehicle, the damping efficiency of the damper device is less likely to occur due to a decrease in the efficiency of transmission of force between the wheels and the vehicle body, and the ride comfort of the vehicle is kept good. When the amount of driving operation is large, the damping force is efficiently generated in the damper device by efficiently transmitting the force between the wheel and the vehicle body, and the transient ground load of the tire is secured, Changes in vehicle behavior are corrected quickly, and vehicle stability is also maintained.

However, the influence of the posture change amount and the driving operation amount of the vehicle body on the behavior change of the vehicle depends on the traveling speed of the vehicle. That is, since the influence increases as the traveling speed of the vehicle increases, it is desirable to make the control of the spring constant of the spring mechanism dependent on the traveling speed of the vehicle.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to satisfy the above-mentioned requirements, and its structural feature is that various posture change amounts of a vehicle body, driving operation amounts and disturbance amounts that cause various posture changes of the vehicle body are detected. Attitude change detecting means for detecting at least one of them and vehicle speed detecting means for detecting a vehicle speed are provided, and increase with an increase in the detection amount detected by the attitude change detecting means, and the same detection amount is obtained. A value that becomes larger when the vehicle speed detected by the vehicle speed detection means is higher than the value when the vehicle speed is low is determined as the target spring constant, and the target spring constant is arranged between the wheel and the vehicle body in series with the damper device. The spring constant of the spring mechanism is set to the target spring constant.

According to this, the spring constant of the spring mechanism is set to a target spring constant that increases as the amount of various posture changes of the vehicle body, the driving operation amount and the amount of disturbance causing the various posture changes of the vehicle body increase. At the same time, since the target spring constant is set to a large value as the vehicle speed increases, the efficiency of force transmission between the wheels and the vehicle body tends to increase as the vehicle speed increases, and damping force is generated by the damper device. Higher efficiency. Therefore, even if the traveling speed of the vehicle becomes high, the change in the vehicle attitude caused by the attitude change of the vehicle body, the driving operation amount and the disturbance amount causing the attitude change of the vehicle body can be corrected quickly. As a result, the maneuverability of the vehicle becomes even better than in the case of using the proposed device.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows the entire vehicle suspension device according to the present invention. The mechanical portion of this suspension device includes a vehicle body (sprung member) 21 and wheels (unsprung member) 2 connected to the vehicle body 21 at the inner end and at the outer end.
A spring 31 and a damper device 40 arranged in parallel with a lower arm (unsprung member) 23 that supports 2 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
A damping force is generated at the time of vertical vibration of 1 to damp the same vibration. A spring mechanism 50 whose spring constant can be changed is arranged in series with the damper device 40 between the damper device 40 and the vehicle body 21.

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 variable mechanism for variably controlling the damping coefficient of the mechanism, and is connected to the lower arm 23 at the lower end of the cylinder 40a so as to be tiltable. 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 for liquid-tightly partitioning the inside of the cylinder 40a into upper and lower oil chambers R1 and R2 is fixed on the outer periphery of the lower portion of the sleeve 42, and hydraulic oil (liquid) is stored in the upper and lower oil chambers R1 and R2. 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.

This 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 device 60 includes various sensors 61 to 67.

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 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 and outputs a signal representing the vertical velocity of the vehicle body 22 with respect to the absolute space (hereinafter referred to as absolute velocity Zd). 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. The bandpass filter 61c limits the band of the detection signal representing the acceleration to within 9 to 13 Hz and outputs the band, thereby setting the unsprung resonance frequency (the resonant frequency of the unsprung member) as one of the attitude change amounts of the vehicle body. It outputs the vibration component G2 of the corresponding car body.

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 65, together with the differentiator 65a, detects the brake pedal speed Bv as one of the driving operation amounts that cause a dive of the vehicle body. The brake sensor 65 detects the depression amount B of the brake pedal, and the differentiator 65a differentiates the depression amount B to output a signal representing the brake pedal speed Bv.

The differential pressure sensor 66 is for detecting the speed of the side wind received by the vehicle, which is one of the disturbance amounts causing rolling and yawing of the vehicle body 21.
The cross winds are input to both sides of 1 to detect the difference in wind pressure due to both cross winds, and a signal representing the same wind pressure difference P is output. The vehicle speed sensor 67 detects the vehicle speed V and outputs a detection signal indicating the detected vehicle speed V.

These integrator 61a, low-pass filter 61b, band-pass filter 61c, and differentiators 62a, 6
The 3a, 64a and 65a, the differential pressure sensor 66 and the vehicle speed sensor 67 are connected to a microcomputer 68. The microcomputer 68 repeatedly executes a program corresponding to the flowchart of FIG. 3 (including the subroutines of FIGS. 5, 8, 10, 12, and 14) every predetermined short time under the control of the built-in timer. By executing this program, the microcomputer 68 outputs a control signal for electrically controlling the damping coefficient of the damper device 40 and the spring constant of the spring mechanism 50 to the drive circuits 71 and 72. The drive circuits 71 and 72 respond to the control signal by
The step motor 49 in the damper device 40 and the electromagnetic solenoid 58 in the spring mechanism 50 are driven.

Next, the operation of the suspension device configured as described above will be described with reference to a flow chart. The microcomputer 68 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 in step 102, the vertical vibration components G1 and G2 of the vehicle body, the steering angular velocity θv, the accelerator opening velocity Av,
The brake pedal speed Bv, the wind pressure difference P, and the vehicle speed V are input, and various spring constants KF, KR, KS, KD, KY for the spring constant of the spring mechanism 50 are input in steps 104 to 112.
To determine.

The details of the KF determination routine of step 104 are shown in FIG. 5, and the execution of the routine is started at step 200. After this execution is started, the microcomputer 68 determines in step 202 that the vehicle speed V is the predetermined vehicle speed Vo.
It is determined whether or not this is the case. If the vehicle speed V is equal to or higher than the predetermined vehicle speed Vo, based on the determination of "YES" in step 202, the G1-K1 map A (solid line in FIG. 6) and the G2-K2 map A (FIG. 7) are processed in steps 204 and 206. (Solid line), the absolute values of both vibration components G1 and G2 | G1 |, |
The spring constants K1 and K2 are determined according to G2 |. As a result, the spring constants K1 and K2 are determined by the absolute values | G1 | and | G2.
When | is less than or equal to each predetermined value G1a, G2a, it is set to the minimum value Kmin. When each absolute value | G1 |, | G2 | is greater than each predetermined value G1a, G2a, the same absolute value | G1 |, |
It is set to a value that increases as G2 | increases. If the vehicle speed V is less than the predetermined vehicle speed Vo, step 20
Based on the judgment of “NO” in Step 2,
By the processing of 210, referring to the G1-K1 map B (broken line in FIG. 6) and the G2-K2 map B (broken line in FIG. 7), depending on the absolute values | G1 | and | G2 | of both vibration components G1 and G2. Determine the spring constants K1 and K2. As a result, the spring constants K1 and K2
Are the absolute values | G1 | and | G2 |
A value which is set to the minimum value Kmin when it is 2b or less, and which increases as the absolute values | G1 | and | G2 | increase above the respective predetermined values G1b and G2b. Is set to. The predetermined values G1a and G2a are smaller than the predetermined values G1b and G2b, respectively, and the rate of increase of the spring constants K1 and K2 in the map A (solid line) is shown in the map B (broken line).
7 and the maximum value Kmax1 in FIG. 6 is larger than those in FIG.
Is larger than the maximum value Kmax2 of. Steps 206 and 2
After the processing of 10, the microcomputer 68 executes step 2
The larger value of the spring constants K1 and K2 is set as the target spring constant K by the processing of 12 to 216, and the execution of the KF determination routine is ended in step 218.

The details of the KR determination routine of step 106 are shown in FIG. 8, and the execution of the routine is started at step 300. After this execution is started, the microcomputer 68 determines in step 302 whether the vehicle speed V is equal to or higher than a predetermined vehicle speed Vo. If the vehicle speed V is equal to or higher than the predetermined vehicle speed Vo, based on the determination of “YES” in step 302, the processing of step 304 refers to the θv-KR map A (solid line in FIG. 9) to determine the steering wheel angular velocity θv. Determines the spring constant KR. As a result, the spring constant K
R is set to a minimum value Kmin when the steering angle velocity θv is less than or equal to a predetermined value θva, and is set to a value that increases as the steering angle velocity θv increases when the steering angle velocity θv is greater than a predetermined value θva. If the vehicle speed V is less than the predetermined vehicle speed Vo, the θv-KR map B is determined by the process of step 306 based on the determination of "NO" in step 302.
With reference to (dotted line in FIG. 9), the spring constant KR is determined according to the steering wheel angular velocity θv. As a result, the spring constant KR
Is set to a minimum value Kmin when the steering angle velocity θv is less than or equal to a predetermined value θvb, and is set to a value that increases as the steering angle velocity θv increases when the steering angle velocity θv is greater than a predetermined value θvb. The predetermined value θva is smaller than the predetermined value θvb, and the increase rate of the spring constant KR in the map A (solid line) is larger than that in the map B (broken line).

Further, KS and K in steps 108 to 112
Details of the D and KY determination routines are shown in FIGS. 10, 12, and 14, respectively, and KS, KD, and KY shown in the respective drawings.
By the processing of the determination routine, the spring constants KS, KD, KY
The accelerator opening speed A is also the same as in the case of the spring constant KR.
It is determined according to v, the brake pedal speed Bv, and the differential pressure difference P. In these cases as well, the θv-KR maps A and B are
Av-KS maps A and B (Fig.
1), Bv-KD maps A and B (FIG. 13) and P-KY
The maps A and B (FIG. 15) are selectively referred to by the vehicle speed V. The spring constants KF, KR, KS in the subroutines of steps 104 to 112 are
In determining KD and KY, each spring constant KF and K
When R, KS, KD, and KY increase, they are changed immediately, but when they decrease, they do not change until a predetermined time elapses.

After the processing in steps 104 to 112, in step 114, the respective KF, KR, KS determined as described above are
The maximum value is selected from KD and KY, and the maximum value is set as the target spring constant K. Next, in step 116, the target spring constant K is compared with the spring constant KN currently set in the spring mechanism 50, and if both spring constants K and KN match, it is determined as “YES” in step 116. Based on the above, the program proceeds to step 122. Both spring constants K,
If the KNs do not match, “NO” in step 116.
Based on this determination, the program proceeds to steps 118 and 120. In step 118, a control signal representing the target spring constant K is output to the drive circuit 71, and in step 120, the current spring constant KN is changed to the target spring constant K.

In response to the control signal, the drive circuit 71 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.

Next, the microcomputer 68 inputs the detection signals representing the absolute velocity Zd and the relative velocity Yd from the integrator 61a and the differentiator 62a in step 122. Then, by the processing of steps 124 to 130, 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 24, the target damping coefficient C is set to the minimum damping coefficient Cmin in step 130. 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 126 based on the determination of "YES" in step 124.
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 128 by referring to the built-in Zd / Yd-C map (FIG. 4).

Then, in step 132, a control signal representing the determined target damping coefficient C is output to the drive circuit 72, and in step 134, the execution of this program is completed. The drive circuit 72 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 in steps 122 to 130 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 the target damping coefficient C, in the process of step 132, when the target damping coefficient C determined by the processes of steps 122 to 130 increases, it is changed immediately, but when it decreases, Does not change until a predetermined time elapses.

As described above, according to the above embodiment, the spring constant KF that increases with the increase of the vibration components G1 and G2 representing the vertical vibration of the vehicle body 21 is determined by the processing of steps 104 to 112. Rolling of the body 21,
Rudder angular velocity θv and wind pressure difference P that cause yawing
The spring constants KR and KY, which increase with the increase of, are respectively determined, and the spring constant K increases with the increase of the accelerator opening speed Av that causes the squat of the vehicle body 21.
S is determined, and the spring constant KD increases as the brake pedal speed Bv that causes the dive of the vehicle body 21 increases.
Is determined, the maximum value of these spring constants KF, KR, KS, KD, KY is selected as the target spring constant K by the processing of step 114, and the spring constant of the spring mechanism 50 is determined by the processing of steps 116-120. The target spring constant K is set. 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, damping force is efficiently generated by the damper device 40, various posture changes of the vehicle body 21 are corrected in a short time, and a transient ground load of the tire is secured, so that the vehicle is safe to operate. The goodness is maintained. In addition, when various posture changes of the vehicle body 21 are small,
The spring constant of the spring mechanism 50 is set small, and as a result,
Damping force is less likely to be generated in the damper device 40, and the influence of the unevenness of the road surface is less likely to be transmitted to the vehicle body, and the ride comfort of the vehicle is kept good.

Further, in the above embodiment, the vehicle speed V is taken into consideration when determining the spring constants KF, KR, KS, KD, KY, and the spring constants KF, KR, KS, KD, K are taken into consideration.
Since Y is set to a large value as the vehicle speed increases, when the traveling speed of the vehicle increases, the wheels 22 and the vehicle body 21
The efficiency of transmission of force between the two tends to increase, and the efficiency of generating damping force in the damper device increases. Therefore, even if the traveling speed of the vehicle becomes high, the attitude change of the vehicle body, the behavior change of the vehicle due to the driving operation amount and the disturbance amount that cause the attitude change of the vehicle body are promptly corrected, and the vehicle stability is improved. Will be better.

In the above embodiment, the vehicle body 21
The rolling operation, yawing, squat, and dive of the vehicle are detected as the driving operation amount and the disturbance amount of the vehicle, which cause these, and the spring constants KR, K are determined according to the detected amounts.
Although S, KD, and KY are determined, the vehicle body 21 is provided with a rotation amount sensor, a rotation speed sensor, a displacement amount sensor, a displacement speed sensor, and the like, and the vehicle body 21 such as rolling, yawing, squat, and dive. It is also possible to detect a physical quantity that represents the change in posture and determine the spring constants KR, KS, KD and KY according to the detected quantity.

Further, in the above embodiment, the maximum value of each spring constant KF, KR, KS, KD, KY is set as the target spring constant K in step 114.
Even if the average value of these spring constants KF, KR, KS, KD, and KY is set as the target spring constant K, substantially the same effect as in the above embodiment can be expected. Further, in the above-described embodiment, a plurality of types of vehicle body posture change amounts, a plurality of types of driving operation amounts and disturbance amounts causing the same body posture changes, and a plurality of types of spring constants KF, KR, KS, K based on the disturbance amount.
Although D and KY are determined, the present invention can be applied to the case where only one spring constant is determined.
In this case, the process of step 114 is unnecessary and the one spring constant may be used as the target spring constant K.

Further, in the above-described embodiment, the example in which the spring mechanism 50 is used in which the spring constant can be changed by selectively acting the plurality of coil springs 53 has been described. A spring mechanism having various structures can be used as long as it 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 an overall schematic diagram of a vehicle suspension device according to an embodiment 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.

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 flowchart showing details of a KF determination routine of FIG.

FIG. 6 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. 7: 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.

8 is a flowchart showing details of a KR determination routine of FIG.

FIG. 9: θv-K provided in the same microcomputer
7 is a graph showing a change characteristic of a spring constant KR with respect to a steering wheel angular velocity θv in an R map.

10 is a flowchart showing details of a KS determination routine of FIG.

FIG. 11: Av- installed in the same microcomputer
It is a graph which shows the change characteristic of the spring constant KS with respect to the accelerator opening speed Av in a KS map.

FIG. 12 is a flowchart showing details of the KD determination routine of FIG.

FIG. 13: Bv- provided in the same microcomputer
It is a graph which shows the change characteristic of the spring constant KD with respect to the brake pedal speed Bv in a KD map.

14 is a flowchart showing details of a KY determination routine of FIG.

FIG. 15 shows a 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. 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 ...
Vehicle speed sensor, 68 ... Microcomputer.

Claims (1)

[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. Attitude change detecting means for detecting at least one of a driving operation amount and a disturbance amount, a vehicle speed detecting means for detecting a vehicle speed, an increase in the detected amount detected by the attitude change detecting means, and A value that is larger when the vehicle speed detected by the vehicle speed detecting means is higher than when the vehicle speed is low with respect to the same value of the detected amount is determined as a target spring constant for the spring mechanism. A vehicle suspension device, comprising: spring constant determining means; and spring constant control means for setting the spring constant of the spring mechanism to the determined target spring constant.