JPH08324220A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE: To improve comfort to ride in of a vehicle even if air pressure of a tire is high in a suspension device for a vehicle. CONSTITUTION: Between a lower arm (an unsprung member) 23 and a car body (a sprung member) 21, a spring mechanism 50 capable of changing a spring constant is arranged in series to a damper device 40. An air pressure sensor 63 detects air pressure of a tire, and when the air pressure detected by a microcomputer 66 is high, a spring constant of the spring mechanism 50 is controlled to the reducing side. Even if a spring constant of the tire becomes high since air pressure of the tire becomes high, a changing quantity of a spring constant of the tire is compensated by a change in a spring constant of the spring mechanism 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle provided with a damper device provided between an unsprung member and an unsprung member for damping a vibration of the unsprung member by generating a damping force. Regarding suspension devices.

[0002]

2. Description of the Related Art Conventionally, in a suspension device for a vehicle, a damper device interposed between an unsprung member (wheel, lower arm, etc.) and an unsprung member (vehicle body) damps the vibration of the sprung member. That is a well known thing.

It is also known, for example, in Japanese Patent Laid-Open No. 6-40232 that the damping coefficient of the damper device is variably set and the tire air pressure is detected to change and control the damping coefficient of the damper device. ing.

[0004]

Generally, when the tire pressure is high, it is preferable to set the damping coefficient of the damper device to a small value in order to improve the riding comfort of the vehicle. Even if it is made small, there is a limit, and since the damper device generates a damping force of a certain amount, a great improvement in the riding comfort of the vehicle cannot be expected. Further, if a large vibration is generated in the sprung member and the damping coefficient of the damper device is set to be large in order to suppress it, the riding comfort of the vehicle is extremely deteriorated.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a vehicle suspension device which improves the riding comfort of the vehicle even when the tire air pressure is high.

[0006]

In order to achieve the above object, the structural feature of the present invention is to provide a damping force between the unsprung member (23) and the unsprung member (21). In a vehicle suspension device including a damper device (40) for damping the vibration of an unsprung member with respect to an unsprung member, a spring that is arranged in series with the damper device between the unsprung member and the unsprung member. A spring mechanism (50) capable of changing a constant, an air pressure detecting means (63) for detecting a tire air pressure, and a control means (6) for controlling the spring constant of the spring mechanism to a smaller side when the detected air pressure is high.
6) and are provided.

[0007]

In the present invention constructed as described above, when the tire air pressure increases and the spring constant of the tire increases, the spring constant of the spring mechanism connected in series with the damper device is controlled to be small. To be done. Therefore, the change in the spring constant of the tire is compensated for by the change in the spring constant of the spring mechanism, and the spring constant of the spring element from the tire to the sprung member can always be kept substantially constant. Even if it is high, the ride comfort of the vehicle is kept good.

[0008]

【Example】

a. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows the entire suspension device according to the present invention. The mechanical part of this suspension system is
A spring 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 (not shown) at an outer end. 31 and a damper device 40. 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. Damper device 4
A spring mechanism 50 whose spring constant can be changed is arranged between 0 and the vehicle body 21 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 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.

Inside the oil passage 42b of the sleeve 42, a taper portion 46a is formed on the outer peripheral surface of the lower portion so as to face the peripheral wall of the oil passage 42b.
A cylindrical orifice member 46 which is formed so as to be movable is housed in a vertically movable manner. The vertical movement of the orifice member 46 restricts the orifice formed between the tapered portion 46a and the peripheral wall of the oil passage 42b. The amount can be changed continuously. And in this damper device 40,
As the piston 43 moves up and down, the leaf valve 45a,
A damping force is generated by the passage resistance to the hydraulic oil passing through 45b and the orifice, and the damping coefficient is changed by changing the throttle amount of the orifice. Therefore, these sleeves 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 the movable plate 51 is 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
5 also includes a clutch bar 57 for pulling the control rod 54 laterally and an electromagnetic solenoid 58 for driving the bar 57 laterally.

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 is engaged with the inner peripheral surface of each of the through holes 33b and 56a of the clutch bar 57, the fixed plate 33, and the frame 56, and the rod 54 is equivalent to that 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, and an air pressure sensor 63.

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 64 is connected to the acceleration sensor 61, and the integrator 64 integrates the detection signal representing the acceleration to obtain the vertical speed of the vehicle body 22 with respect to the absolute space (hereinafter, referred to as absolute speed Zd). Output the signal that represents.

The vehicle height sensor 62 is a vehicle body 21 (a sprung member).
And a lower arm 23 (unsprung member), the displacement amount sensor is mounted between the lower arm 23 and the lower arm 23 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 displacement amount. However, this relative displacement amount is an increase amount from the reference value due to the positive value (extension side of the damper device 40).
Represents the decrease amount from the reference value (damper device 40
The contraction side of). This vehicle height sensor 62 has a differentiator 65
Is connected, and the differentiator 65 differentiates the detection signal indicating the displacement amount and outputs a signal indicating the vertical speed of the vehicle body 21 with respect to the lower arm 23 (hereinafter, referred to as relative speed Yd).

The air pressure sensor 63 is attached to the wheel 22, and a part of the air pressure sensor 63 is inserted into the tire to detect the air pressure in the tire, and outputs a detection signal representing the detected tire air pressure TP.

The air pressure sensor 63, the integrator 64 and the differentiator 65 are connected to a microcomputer 66. The microcomputer 66 repeatedly executes the program corresponding to the flowchart of FIG. 3 every predetermined short time under the control of the built-in timer. By executing this program, the microcomputer 66 causes the drive circuits 67 and 68 to output control signals for electrically controlling the damping coefficient of the damper device 40 and the spring constant of the spring mechanism 50.
Output to. The drive circuits 67 and 68 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 constructed as described above will be described with reference to a flow chart. The microcomputer 66 executes the program in step 100 of FIG. 3 in response to turning on of an ignition switch (not shown). Then, in step 102, the tire pressure TP, the absolute velocity Zd and the relative velocity Yd are input from the air pressure sensor 63, the integrator 64 and the differentiator 65, respectively.

Next, in step 104, the built-in TP-K
The target spring constant K corresponding to the tire air pressure TP is determined with reference to the map (FIG. 4). Then, step 106
At, a control signal representing the target spring constant K is output to the drive circuit 68. The drive circuit 68 energizes the electromagnetic solenoids 58 corresponding to the target spring constant K in response to the control signal, 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.

After the processing of step 106, the microcomputer 66 performs the processing of steps 108-116.
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. If the positive and negative signs of the absolute speed Zd and the relative speed Yd are different, the target damping coefficient C is set to the minimum damping coefficient Cmin in step 110 based on the determination of "NO" in step 108. Further, if the positive and negative signs of the absolute speed Zd and the relative speed Yd match, “YES” in step 108.
In step 112, the absolute speed Zd is divided by the relative speed Yd to calculate the speed ratio Zd / Yd, and in step 114, the built-in Zd / Yd-C map (see FIG. 5) is referred to. Then, the target damping coefficient C corresponding to the speed ratio Zd / Yd is determined.

Then, in step 116, a control signal representing the determined target damping coefficient C is output to the drive circuit 67. The drive circuit 67 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 108 to 114 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. It should be noted that this target damping coefficient C is calculated in step 108 through step 108.
When the target damping coefficient C determined by the process of 114 increases, it is immediately changed, but when it decreases, it is not changed until a predetermined time elapses.

As described above, according to the first embodiment, the spring mechanism 50 whose spring constant can be changed is provided in series with the damper device 40, the tire air pressure TP is increased, and the spring constant of the tire is increased. When it becomes larger, the spring constant of the spring mechanism 50 is controlled to be smaller. Therefore, the change in the spring constant of the tire can be compensated by the change in the spring constant of the spring mechanism 50, and the spring constants of the spring elements from the tire to the vehicle body 21 can always be kept substantially constant. The ride comfort of the vehicle is maintained even when the vehicle is high.

Further, according to the first embodiment, the damping coefficient of the damper device 40 and the spring constant of the spring mechanism 50 are controlled independently, so that the vibration of the vehicle body 21 can be suppressed well.

B. Second Embodiment Next, a second embodiment of the present invention will be described. This second
In the embodiment, vibrations G1 and G2 of the vehicle body 20 and tire pressure T
The spring constant of the spring mechanism 50 is changed and controlled according to P.

As shown by the broken line in FIG. 1, the vehicle suspension system according to the second embodiment has a low-pass filter 71 and a band-pass filter 72 connected to the acceleration sensor 61 in addition to the first embodiment. I have it. The low-pass filter 71 outputs the vibration component G1 of the vehicle body corresponding to the sprung resonance frequency (resonance frequency of the sprung member) by limiting and outputting the band of the detection signal indicating the acceleration to 2 Hz or less. The bandpass filter 72 is
By limiting and outputting the band of the detection signal indicating the acceleration within 9 to 13 Hz, the vibration component G2 of the vehicle body corresponding to the unsprung resonance frequency (resonance frequency of the unsprung member) is output.

The low pass filter 71 and the band pass filter 72 are also connected to the microcomputer 66. The microcomputer 66 executes the program in which the processing of steps 102 and 104 of FIG. 3 of the first embodiment is changed to the processing of steps 102a and 120 to 144 of FIG. Other parts are the same as those in the first embodiment.

Next, the operation of the second embodiment constructed as above will be described. The microcomputer 66 is the first
Similar to the embodiment, the execution of the program is started in step 100, and in addition to the tire pressure TP, the absolute speed Zd and the relative speed Yd, the low-pass filter 7 is started in step 102a.
1 and the vibration components G1 and G2 are input from the bandpass filter 72, respectively.

Next, at step 120, the tire air pressure TP is compared with a predetermined predetermined value TP0 which is approximately equal to the upper limit of the normal tire air pressure. Tire pressure T
If P is larger than the predetermined value TP0, it is determined to be "YES" at step 120 and the map flag MP is set to "1" at step 122. If the tire pressure TP is less than or equal to the predetermined value TP0, it is determined to be "NO" in step 120, and the map flag MP is set to "0" in step 124.
Set to.

After the processing in steps 120 to 124, the target spring constant K is set in accordance with the magnitudes of the input vibration components G1 and G2 by the processing in steps 126 to 144. Absolute values of both vibration components G1 and G2 | G1 |, | G2 |
Is greater than or equal to the predetermined threshold values G10 and G20, the microcomputer 66 proceeds to steps 126 to.
By the processing of 132, referring to the built-in G1-K1 map (FIG. 7) and G2-K2 map (FIG. 8), both vibration components G
1st and 2nd spring constants K1 respectively corresponding to 1 and G2,
Determine K2. In determining the spring constants K1 and K2, if the map flag MP is "0", the characteristic maps shown by the solid lines in FIGS. 7 and 8 are referred to. Also,
If the map flag MP is “1”, the characteristic maps shown by the broken lines in FIGS. 7 and 8 are referred to. Therefore, when the tire air pressure TP is high, both spring constants K1 and K2 are set to small values. Note that Kmax in FIGS.
1 and Kmax2 have a relationship of Kmax1> Kmax2. afterwards,
By the processing of steps 134, 136 and 142, the larger value of the first and second spring constants K1 and K2 is set as the target spring constant K. Absolute value of vibration component G1 | G1 |
Is the threshold value G10 or more and the absolute value of vibration component G2 | G2 |
Is less than the threshold value G20, steps 126 to 13
The first spring constant K1 determined by referring to the G1-K1 map is set as the target spring constant K by the processing of 0,136. Absolute value | G1 | of vibration component G1 is less than threshold value G10,
If the absolute value | G2 | of the vibration component G2 is greater than or equal to the threshold value G20, the second spring constant K determined by referring to the G2-K2 map by the processing of steps 126 and 138-142.
Set 2 as the target spring constant K. These G1-K1
When referring to the map and the G2-K2 map, the map flag MP selectively refers to one of the characteristics indicated by the solid line and the broken line in FIGS. Furthermore, both vibration components G1,
The absolute values | G1 | and | G2 | of G2 are the threshold values G, respectively.
If less than 10, G20, steps 126, 138, 14
By the processing of 4, the minimum spring constant Kmin is set as the target spring constant K.

The target spring constant K is determined by the step 1
In the processing of 36, 142 and 144, when the spring constant K increases, it is immediately changed, but when it decreases, it is not changed until a predetermined time elapses.

After setting the target spring constant K, the microcomputer 66 sets the spring constant of the spring mechanism 50 to the target spring constant K in step 106, as in the case of the first embodiment. Then, the damping coefficient of the damper device 40 is controlled by the processing after step 108 similar to that of the first embodiment.

As described above, according to the second embodiment, the processing in steps 126 to 144 results in a specific frequency range (sprung resonance frequency and unsprung resonance frequency).
When the vibration components G ₁ and G _{2 of} the vehicle body 21 corresponding to are large, the target spring constant K is set to a large value.
_{When 1} and G ₂ are small, the target spring constant K is set to a small value. When setting the target spring constant K, the target spring constant K is set to a small value when the tire air pressure TP is high, and set to a small value when the tire air pressure TP is low by the map reference processing in steps 128, 132 and 140. The target spring constant K is set to a large value.

Therefore, when the vibration components of the sprung resonance frequency and the unsprung resonance frequency (specific frequency range) of the vehicle body 21 are large, the spring constant of the spring mechanism 50 is set to a large value, so that the spring mechanism 50 is difficult to bend. Become. Therefore, the damper device 40 generates a required amount of damping force with good responsiveness, so that the vibration of the vehicle body 21 is effectively suppressed. On the other hand, in other cases, the spring mechanism 50
Since the spring constant of is set to be small, the spring mechanism 50 is easily bent, and even if there is a road surface input, the damper device 4
The damping force generated by 0 is suppressed to be small, and the generation of the damping force is delayed. As a result, the damping force of the damper device 40 caused by the road surface input is less likely to act on the vehicle body 21 as an exciting force, and the action is mitigated, so that the vehicle body 21 is not always directly affected by the road surface. , The ride comfort of the vehicle is kept good. Also in this second embodiment, the change in the spring constant of the tire is compensated by the change in the spring constant of the spring mechanism 50, and the spring constants of the spring elements from the tire to the vehicle body 21 are always kept substantially constant. Therefore, even if the tire air pressure TP is high, the ride comfort of the vehicle can be kept good.

Next, a first modification of the second embodiment will be described. In this first modification, as shown in FIG. 9, the processing of steps 120 to 124 in FIG. 6 is deleted and the processing of steps 150 to 154 is inserted between steps 136, 142, 144 and step 106. Is. In the first modification, the microcomputer 66 is
In step 150, the built-in TP-Kup map (Fig. 1
0), the upper limit value Kup of the target spring constant K corresponding to the tire air pressure TP is determined. Then, step 152
By the processing of ~ 154, the target spring constant K determined by the processing of steps 126-144 is limited to the upper limit value Kup or less. Then, in step 106, the spring mechanism 50
Is set to the target spring constant K of which the upper limit is limited.

As described above, in this first modified example, the upper limit of the target damping force K is controlled to be smaller as the tire air pressure TP increases, so that the target damping force K increases as the tire air pressure increases. Controlled to be set to a small value. Therefore, also in the first modification, the same effect as that of the second embodiment can be expected.

Next, a second modification of the second embodiment will be described. This second modified example corresponds to the first modified example shown in FIG.
Steps 150-154 of FIG.
It is a modified one like 166. In this second modification, the microcomputer 66 executes the step 16
At 0, the decrease amount ΔK corresponding to the tire air pressure TP is determined with reference to the built-in TP-ΔK map (FIG. 12). Next, in step 162, the steps 126 to
The determined decrease amount ΔK is subtracted from the target spring constant K determined by the processing of 144. After this subtraction, step 1
The target damping force K resulting from the subtraction is limited to the minimum value Kmin (FIGS. 7 and 8) or more by the processing of 64 and 166. Then, in step 106, the spring constant of the spring mechanism 50 is set to the target spring constant K limited to the upper limit value.

As described above, in the second modified example, the decrease amount ΔK, which increases as the tire air pressure TP increases, is subtracted from the target damping force K so that the target damping force increases when the tire air pressure increases. It is controlled so that K is set to a small value. Therefore, also in the second modification, the same effect as that of the second embodiment can be expected.

In the above embodiments and modifications,
Although the tire air pressure TP is directly detected, the vibration component of the vehicle body 21 (acceleration sensor of the above-described embodiment is disclosed, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-4023 described in the section of the prior art. 61), the vibration component of the unsprung member (lower arm 23), the vibration component of the vehicle body 21 with respect to the unsprung member (corresponding to the relative speed Yd in the above embodiment).
Of the above, the vibration component specific to the tire may be extracted, and the tire air pressure may be estimated and detected from the change in the frequency of the extracted vibration component.

Further, in the above embodiment, the spring mechanism 50 in which the spring constant can be changed by selectively actuating the plurality of coil springs 53 has been described, but the spring mechanism 50 changes the spring constant. 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. Also, cylinder 4
The gas pressure in the gas chamber R3 in 0a can be changed from the outside.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing an embodiment of a vehicle suspension device according to 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 flow chart showing a program executed by the microcomputer of FIG. 1 according to the first embodiment of the present invention.

FIG. 4 is a TP-K provided in the same microcomputer.
It is a graph which shows the change characteristic of the target spring constant K with respect to the tire air pressure TP in a map.

FIG. 5: 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 -K map.

FIG. 6 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. 7: 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. 8: 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.

FIG. 9 is a flowchart showing a part of a program executed by the microcomputer of FIG. 1 according to a first modification of the second embodiment of the present invention.

FIG. 10 is a TP- provided in the same microcomputer.
It is a graph which shows the change characteristic of the upper limit Kup of the target spring constant K with respect to the tire air pressure TP in a Kup map.

FIG. 11 relates to a second modification of the second embodiment of the present invention,
3 is a flowchart showing a part of a program executed by the microcomputer of FIG. 1.

FIG. 12 is a TP- provided in the same microcomputer.
7 is a graph showing a change characteristic of a decrease amount ΔK of a target spring constant K with respect to a tire air pressure TP in a ΔK map.

[Explanation of symbols]

21 ... Vehicle body (sprung member), 22 ... Wheels, 23 ... Lower arm (unsprung member), 31 ... Spring, 40 ... Damper device, 40a ... Cylinder, 41 ... Piston rod, 42
... Sleeves 42a to 42d ... Oil passages (orifices), 4
3 ... Piston, 43a, 43b ... Oil passage (orifice),
45a, 45b ... Leaf valve, 46 ... Orifice member, 48 ... Nut, 49 ... Step motor, 50 ... Spring mechanism, 53 ... Coil spring, 54 ... Control rod, 57 ... Clutch bar, 58 ... Electromagnetic solenoid, 6
0 ... Electric control device, 61 ... Acceleration sensor, 62 ... Vehicle height sensor, 63 ... Air pressure sensor, 64 ... Integrator, 65 ... Differentiator, 66 ... Microcomputer, 71 ... Low pass filter, 42 ... Band pass filter.

Claims (1)

[Claims] 1. A vehicle suspension device comprising a damper device provided between an unsprung member and an unsprung member for damping a vibration of the unsprung member by generating a damping force. A spring mechanism that is arranged in series with the damper device between the member and the sprung member and that can change the spring constant; an air pressure detecting means that detects the air pressure of the tire; and A vehicle suspension device comprising: a control unit that controls a spring mechanism to reduce a spring constant.