JPH05614A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To prevent generation of switching sound and vibration to improve the travelling stability and ride qualities by controlling a stepping motor for switching damping force of a shock absorber in multistage so that it permits multistage switching in response to the travelling conditions by a control means. CONSTITUTION:A stepping motor for driving first - fourth atuators 41-44 to switch damping force of a shock absorber in multistages is controlled by a control unit 8. Signals of first - fourth acceleration sensors 11-14 as sprung weight vertical acceleration, along with signals of first - fourth pressure sensors 61-64 as damping force, a car speed sensor 15, an anti-braking-system 67 as road surface friction coefficient, a ground clearance diaplacement sensors 71-74, a lateral acceleration sensor 16, a steering angle sensor 65, a brake switch 66 are inputted to the unit 8. Under a travelling condition where emphasis is placed on ride comfortableness, the stepping motor is switched by one stage, and under a condition where emphasis is placed on the travelling stability, the stepping motor is switched in simultaneous multistage operation. Thus, generation of switching sound and vibration can be prevented.

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, and more particularly to a vehicle suspension device provided with a shock absorber having a variable damping force characteristic between a sprung portion and an unsprung portion. It is about.

[0002]

2. Description of the Related Art In a conventional vehicle suspension system, a vehicle body side, that is, a sprung side, and a wheel side, that is,
A shock absorber for damping vertical vibration of the wheel is generally provided between the spring and the unsprung part. As this shock absorber, it is known that the damping force characteristic can be changed. As the shock absorber of the variable damping force characteristic type, the damping force characteristic can be changed into high and low two-stage or multi-stage, or no damping force characteristic. The one that can be changed continuously is proposed.

In such a shock absorber with variable damping force, the damping force generated by the shock absorber is
The damping force of the shock absorber is changed to the low damping side, that is, the soft side when acting in the vibration direction with respect to the vertical vibration of the vehicle body, while the damping force of the shock absorber is changed when the damping force acts in the damping direction. By changing the damping force to the high damping side, that is, the hard side, the damping energy is increased with respect to the vibration energy transmitted on the spring, and the riding comfort and running stability of the vehicle are improved at the same time. Normally, it is controlled, and in JP-A-60-248419, whether or not the direction of relative displacement between the sprung and unsprung parts and the direction of relative speed between the sprung and unsprung parts are the same or not. Based on the above, when they match, it is determined that the damping force is acting in the excitation direction,
On the other hand, when they do not match, a method is disclosed in which it is determined that the damping force is acting in the damping direction and the control is performed.

[0004]

As described above, the damping force of the damping force is determined based on whether or not the direction of relative displacement between the sprung and unsprung portions and the direction of relative speed between the sprung portion and unsprung portion coincide with each other. In the damping force variable type shock absorber to be changed and controlled,
If the damping force of the shock absorber needs to be changed significantly and the damping force of the shock absorber is switched in multiple stages, a large switching noise or vibration is generated due to the pressure fluctuation of the shock absorber accompanying the switching, and these However, the phenomenon of transmission to the vehicle body occurs, and if it is attempted to prevent such switching noise and vibration, there has been a problem that traveling stability and riding comfort cannot be improved as desired.

[0005]

An object of the present invention is to provide a vehicle suspension device which includes a shock absorber between an unsprung part and an unsprung part, and which changes and controls the damping force characteristic of the shock absorber according to the vertical vibration of the vehicle body. An object of the present invention is to provide a vehicle suspension device capable of improving running stability and riding comfort while preventing generation of large switching noise and vibration due to pressure fluctuation of a shock absorber due to force switching. Is.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an actuator for changing the damping force of a shock absorber and a control means for outputting a control signal to the actuator, when the damping force characteristic of the shock absorber is switched from soft to hard. In addition, the control means is configured to allow multistage switching of the damping force of the shock absorber according to the traveling state.

In a first preferred embodiment of the present invention, the control means is configured to allow multistage switching of the damping force of the shock absorber when the vehicle speed is equal to or higher than a predetermined value. In a second preferred embodiment of the present invention, the control means is configured to allow multistage switching of the damping force of the shock absorber in the sudden braking state.

In a third preferred embodiment of the present invention, the control means is configured to allow multistage switching of the damping force of the shock absorber when the loading amount is a predetermined amount or more. In a fourth preferred embodiment of the present invention, the control means is configured to allow multistage switching of the damping force of the shock absorber when the steering angle change speed is equal to or higher than a predetermined value.

In a fifth preferred aspect of the present invention, the control means is configured to allow multistage switching of the damping force of the shock absorber when the lateral acceleration is equal to or greater than a predetermined value. In a sixth preferred embodiment of the present invention, the control means, while traveling on a good road,
It is configured to allow multistage switching of the damping force of the shock absorber.

In a seventh preferred embodiment of the present invention, the control means controls the shock absorber when the relative speed of displacement between the sprung and unsprung is zero and the speed of displacement on the spring is negative. It is configured to allow multistage switching of the damping force. In an eighth preferred embodiment of the present invention, the control means is configured to allow multistage switching of the damping force of the shock absorber when the pitch of the vehicle body is a predetermined value or more.

In a ninth preferred embodiment of the present invention, the control means is configured to permit multistage switching of the damping force of the shock absorber when the roll of the vehicle body is above a predetermined level. In a tenth preferred embodiment of the present invention, the control means is configured to allow multistage switching of the damping force of the shock absorber when the vertical movement of the vehicle body is greater than or equal to a predetermined level.

In an eleventh preferred embodiment of the present invention, the control means controls the vehicle speed to a predetermined value or less, a sudden braking state, a load amount to a predetermined value or more, a steering angle change speed to a predetermined value or more, and a lateral acceleration to a predetermined value. Above a certain value, when traveling on a good road, the relative displacement speed between the sprung and unsprung is zero and the sprung displacement speed is negative, the pitch of the vehicle body is more than a certain amount, the roll of the vehicle body is more than a certain amount, and the vehicle body moves vertically When two or more of the above conditions are satisfied, multi-stage switching of the damping force of the shock absorber is allowed.

In a twelfth preferred embodiment of the present invention, the control means is configured not to allow multistage switching of the damping force of the shock absorber when the road surface friction coefficient is less than a predetermined value. . In a thirteenth preferred embodiment of the present invention, the actuator comprises a step motor.

[0014]

According to the present invention, when the damping force characteristic of the shock absorber is switched from soft to hard, the control means allows the actuator to switch the damping force of the shock absorber in multiple stages according to the running state. Therefore, in the running state where the running stability should be emphasized rather than the occurrence of the switching noise and vibration caused by the pressure fluctuation of the shock absorber due to the switching,
The damping force of the shock absorber can be changed so as to improve the running stability, while the damping force of the shock absorber is controlled so that it can be switched step by step in a running state where importance is placed on ride comfort. It is possible to improve the riding comfort while preventing the generation of switching noise and vibration due to the pressure fluctuation of the shock absorber due to the switching.

According to the first to twelfth preferred embodiments of the present invention, the damping force of the shock absorber is switched step by step in a traveling state in which the ride comfort should be prioritized.
In the driving state where it is necessary to prevent the generation of switching noise and vibration due to the pressure fluctuation of the shock absorber due to the switching, and to emphasize the improvement of running stability rather than the riding comfort,
Since the multistage switching of the damping force of the shock absorber by the actuator is allowed to improve the running stability, it is possible to improve the running stability and the riding comfort at the same time.

According to the thirteenth preferred embodiment of the present invention, since the step motor is used as the actuator and the damping force of the shock absorber is controlled by the open control, it is further compact and inexpensive. The computer allows the damping force characteristic of the shock absorber to be modified and controlled as desired, thus improving the running stability and the riding comfort.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of a vehicle including a vehicle suspension device according to a preferred embodiment of the present invention.

Referring to FIG. 1, a vehicle suspension device according to a preferred embodiment of the present invention includes shock absorbers 1, 2, 3, 4 which are provided corresponding to respective wheels and which dampen vertical vibrations of the respective wheels. ing. Each of the shock absorbers 1, 2, 3 and 4 is configured to be switchable to 10 damping force characteristics having different damping coefficients by an actuator (not shown), and includes a pressure sensor (not shown). In FIG. 1, 5 is a left front wheel, 6 is a left rear wheel, and the right front wheel and the right rear wheel are not shown. Further, 7 is each shock absorber 1, 2, 3, 4
Is a coil spring arranged on the outer periphery of the upper part of the
Is a control unit that outputs a control signal to the actuators of the shock absorbers 1, 2, 3, and 4 to change and control the damping force characteristics of the shock absorbers 1, 2, 3, and 4.

On the spring of the vehicle 9, the first acceleration sensor 1 for detecting the vertical acceleration on the spring of each wheel.
1, a second acceleration sensor 12, a third acceleration sensor 13, a fourth acceleration sensor 14, a vehicle speed sensor 15 for detecting a vehicle speed in the meter of the instrument panel, and a lateral acceleration sensor in the center of gravity of the vehicle 9. 16 are provided respectively. In FIG. 1, reference numeral 17 indicates that the driver controls the damping force characteristics of the shock absorbers 1, 2, 3, and 4.
Shows the mode selection switch to switch to either hard mode, soft mode or control mode.When the hard mode is selected, only the damping coefficient in the range where the damping force characteristic becomes hard is selected. Only when the change control of the damping force characteristics of the shock absorbers 1, 2, 3 and 4 is performed and the soft mode is selected, only the damping coefficient in the range where the damping force characteristics become soft is selected. The change control of the damping force characteristics of the shock absorbers 1, 2, 3, 4 is performed only within the
When the control mode is selected,
According to a map or table stored in the control unit 8, change control of the damping force characteristics of the shock absorbers 1, 2, 3, 4 is performed in a predetermined manner.

FIG. 2 is a schematic sectional view of the main part of the shock absorber 1 provided for the left front wheel. However, the pressure sensor is omitted for convenience. In FIG. 2, the shock absorber 1 includes a cylinder 21 and a cylinder 2
A piston unit 22, in which a piston and a piston rod are integrally connected, is slidably fitted in the inside of 1. The cylinder 21 and the piston unit 22 are coupled to the unsprung and sprung, respectively.

The piston unit 22 has two orifices 23 and 24 formed therein. One orifice 2
3 is always open, and the passage area of the other orifice 24 is changed by the first actuator 41.
It is formed so that it can be changed in 10 steps. FIG. 3 is an exploded schematic perspective view of the first actuator 41 provided in the shock absorber 1. As shown in FIGS. 2 and 3, the first actuator 41 includes the piston unit 22.
A shaft 26 rotatably provided in a sleeve 25 fixed to the shaft 26, a step motor 27 for rotating the shaft 26, and a lower end portion of the shaft 26, which are integrally attached to each other. First with hole 28
The orifice plate 29 and the sleeve 25 are integrally provided at the lower end of the sleeve 25, and arcuate elongated holes 30 are provided along the circumference thereof.
The second orifice plate 31 is formed. Here, the nine circular holes 28 formed in the first orifice plate 29 and the elongated hole 30 formed in the second orifice plate 31 allow the rotation of the shaft 26 and the first orifice plate 29 by the rotation of the step motor 27. Therefore, the nine circular holes 28 are formed so as to be able to communicate with the long holes 30 in the range of 0 to 9.

Upper chamber 32 and lower chamber 33 in the cylinder 21
The inside is filled with a fluid having a predetermined viscosity, and is movable between the upper chamber 32 and the lower chamber 33 through the orifices 23 and 24. 2 and 3,
Although only the structure of the shock absorber 1 is shown, the shock absorbers 2, 3 and 4 provided for the other wheels also have the same structure as the shock absorber 1 shown in FIG. , A second actuator 42, a third actuator 43, and a fourth actuator similar to those shown in FIG.
The actuator 44 is provided.

FIG. 4 shows the shock absorbers 1, 2, 3,
4 is a graph showing the damping force characteristics of No. 4, and D1 to D10
Indicate the damping coefficients of the shock absorbers 1, 2, 3, and 4, respectively. In FIG. 4, the vertical axis represents the damping force generated by the shock absorbers 1, 2, 3, and 4, and the horizontal axis represents the difference between the displacement speed Xs on the spring and the displacement speed Xu under the spring, that is, on the spring. Unsprung relative displacement velocity (Xs-
Xu). As shown in FIG. 4, the damping force characteristics of the shock absorbers 1, 2, 3, 4 have a damping coefficient D
By selecting either 1 to D10, 10
It is configured so that it can be changed in stages. In FIG. 4, D1 indicates a damping coefficient that generates the softest damping force, and D10 indicates a damping coefficient that generates the hardest damping force. Here, the damping coefficient Dk (k is a positive integer, 1 to 10) is equal to that of the nine circular holes 28 formed in the first orifice plate 29.
The (10-i) circular holes 28 are selected when they communicate with the elongated holes 30 formed in the second orifice plate 31. Therefore, the damping coefficient D1
Is selected when all nine circular holes 28 formed in the first orifice plate 29 are in communication with the long holes 30 formed in the second orifice plate 31, and the damping coefficient D10 is the first orifice. All of the nine circular holes 28 formed in the plate 29 are in communication with the elongated holes 30 formed in the second orifice plate 31, and none of the nine circular holes 28 formed in the first orifice plate 29. , The long hole 3 formed in the second orifice plate 31
It will be selected when it does not communicate with 0.

FIG. 5 is a vibration model diagram of a suspension system for a vehicle according to an embodiment of the present invention. Ms is an unsprung mass, mu is an unsprung mass, xs is an unsprung displacement, and xu is an unsprung displacement. , Is set to take a positive value when displaced upward, ks is the spring constant of the coil spring 7,
kt is the tire spring constant, and D _k is the damping coefficient of the shock absorbers 1, 2, 3, 4.

FIG. 6 is a schematic perspective view of the step motor 27. The step motor 27 includes a cylindrical body 50 and a cylindrical body 50.
Rotor 51, stator 52 and lid 53 housed inside
It consists of FIG. 7 is a schematic plan view of the rotor 51 and the stator 52. As with a normal step motor, a plurality of rectangular teeth are formed on the outer peripheral portion of the rotor 51 and the inner peripheral portion of the stator 52 is formed. Corresponding to this,
A plurality of rectangular teeth are formed, and a solenoid 54 is wound around the stator 52. Two stopper pins 55 and 56 are formed on the rotor 51,
As shown in FIG. 8, the stopper pin 5 is provided on the lid 53.
5, two grooves 57 in the circumferential direction at positions corresponding to 5, 56,
58 is formed. The groove 57 engages with the stopper pin 55 formed on the rotor 51, and the step motor 27
The groove 58 engages the stopper pin 56, and the stopper pin 55, 56 is engaged with the groove 57, 58 to cover the lid 53. The position of the rotor 51 can be aligned so that the center of gravity of the rotor 51 coincides with the center of rotation. Therefore, the circumferential angle of the grooves 58, 58 viewed from the center of the lid 53 is larger in the groove 58 than in the groove 57.
Grooves 57 and 58 are formed so that the movable range of 8 is determined. In FIG. 8, when the rotor 51 rotates clockwise, the damping coefficient Dk becomes larger and the damping force characteristic becomes harder. On the other hand, when the rotor 51 rotates counterclockwise, the damping coefficient Dk becomes smaller. Then, the damping force characteristic becomes softer, and when the rectangular teeth of the rotor 51 are moved to the positions facing the adjacent rectangular teeth of the stator 52, that is, When the step motor 27 is rotated one stage, the damping coefficient Dk changes by one. Therefore,
When the stopper pin 55 is located at the first reference position which is the right end of the groove 57, the damping coefficient Dk becomes D10,
When the shock absorber 1 generates the hardest damping force, while the stopper pin 55 is located at the second reference position which is the left end portion of the groove 57, the damping coefficient Dk is D
It becomes 1, and the shock absorber 1 is designed to generate the softest damping force.

FIG. 9 is a block diagram of the control system of the vehicle suspension system according to the embodiment of the present invention. Referring to FIG. 9, a control unit 8 constituting a control system of a vehicle suspension device according to an embodiment of the present invention includes a first pressure sensor 61 and a second pressure sensor provided on shock absorbers 1, 2, 3, and 4, respectively. Pressure sensor 6
2, damping force Fsi of each shock absorber 1, 2, 3, 4 detected by the third pressure sensor 63 and the fourth pressure sensor 64
(Where i is each wheel, i = 1, 2, 3, 4) and the detection signal of the load Wi on the spring, the first acceleration sensor 11, the second acceleration sensor 12, A vertical acceleration acceleration ai detection signal detected by the third acceleration sensor 13 and the fourth acceleration sensor 14, a vehicle speed V detection signal detected by the vehicle speed sensor 15, and a lateral acceleration sensor 16.
The lateral acceleration GL detected by the steering angle sensor 65, the steering angle θ detected by the steering angle sensor 65, the brake signal BR detected by the brake switch 66, the anti-braking system (AB
S) 67 estimation signal of road surface friction coefficient μ, first vehicle height displacement sensor 71 of each wheel, second vehicle height displacement sensor 72, third
The detection signal of the vehicle height displacement xsi detected by the vehicle height displacement sensor 73 and the fourth vehicle height displacement sensor 74 and the mode signal from the mode selection switch 17 are input, respectively. The control unit 8 generates a control signal based on these input signals by using a map or a table stored in advance, and the first actuator 4
1, second actuator 42, third actuator 4
It outputs to the third and fourth actuators 44 to control the damping force characteristics of the shock absorbers 1, 2, 3, and 4.

Here, the damping force Fsi takes a continuous value and acts downward on a positive value when acting on the sprung, that is, when the space between the sprung and the unsprung is contracted. Is set to a negative value when the sprung and unsprung portions are extended, the vertical acceleration ai on the sprung is positive when upward, and downward when downward. It is set to be a negative value.

FIG. 10 is a flow chart showing a routine of the damping coefficient selection control according to the traveling state when the control mode is selected by the mode selection switch 17, and the damping coefficient selection control routine of FIG. The damping coefficient Dki is changed too often, resulting in a loud noise or vibration when changing.
In order to prevent the occurrence of a response delay, the range of the damping coefficient Dki that can be changed and controlled is limited according to the traveling state.

In FIG. 10, first, the control unit 8 includes a vehicle speed V detected by a vehicle speed sensor 15, a first acceleration sensor 11, a second acceleration sensor 12, and a third acceleration sensor.
Vertical acceleration ai on the spring detected by the acceleration sensor 13 and the fourth acceleration sensor 14 is input. Then, the control unit 8 determines whether or not the vehicle speed V is a first predetermined vehicle speed V1 which is a low speed value, for example, 3 km / h or less.

As a result, the vehicle speed V becomes the first predetermined vehicle speed V1.
In the following cases, since the speed is extremely low, the shock absorbers 1, 2,
The control unit 8 fixes the damping coefficient Dki to D8i so that the damping force characteristics of 3 and 4 become hard. On the other hand, when the vehicle speed V exceeds the first predetermined vehicle speed V1, is the control unit 8 further traveling on a rough road based on the variation amount of the vertical acceleration ai on the spring within the predetermined time? Determine whether or not.

As a result, when it is determined that the vehicle is traveling on a rough road, the control unit 8 further determines the vehicle speed V.
However, it is determined whether or not the third predetermined vehicle speed V3 is, for example, 50 km / h or more. When the determination result is YES, that is, when it is determined that the vehicle speed V is equal to or higher than the third predetermined vehicle speed V3, the control unit 8 emphasizes the improvement of the running stability, and controls the damping force characteristics to be relatively high. The damping coefficient Dki is set in the range of D5i to D7i in order to control the change within the hard range.

On the other hand, when the determination result is NO, that is, when it is determined that the vehicle speed V is lower than the predetermined vehicle speed V3, it is possible to achieve both improvement in running stability and riding comfort. Therefore, the control unit 8 can change and control the damping force characteristic within a range from a relatively soft state to a hard state, so that the damping coefficient Dki is controlled.
Is set in the range of D3i to D7i.

On the other hand, when it is determined that the vehicle is traveling on a normal road instead of a rough road, the control unit 8
Further, the vehicle speed V is the second predetermined vehicle speed V2, for example, 30
Determine if it is less than km / h. As a result, when YES,
That is, when it is determined that the vehicle speed V is in the low speed traveling state equal to or lower than the second predetermined vehicle speed V2, the control unit 8 determines that the damping force characteristic is
The damping coefficient Dki is set in the range of D1i to D3i so that the change control is performed within a relatively soft range.

On the other hand, when NO, that is, when it is determined that the vehicle speed V exceeds the second predetermined vehicle speed V2, the control unit 8 further determines that the vehicle speed V is
It is determined whether or not the fourth predetermined vehicle speed V4 is, for example, 60 km / h or less. As a result, when it is determined that the vehicle speed V is in a relatively medium speed running state that is equal to or lower than the fourth predetermined vehicle speed V4, it is possible to achieve both of the two requirements of improving running stability and riding comfort. Because there is, control unit 8
Sets the damping coefficient Dki in the range of D2i to D6i in order to change and control the damping force characteristic within a range from a relatively soft state to a hard state.

On the other hand, when it is determined that the vehicle speed V exceeds the fourth predetermined vehicle speed V4, the control unit 8
Further, it determines whether the vehicle speed V is a fifth predetermined vehicle speed V5, for example, 80 km / h or less. As a result, YES
In other words, when it is determined that the vehicle speed V is in the middle speed running state which is equal to or lower than the fifth predetermined vehicle speed V5, the shock absorber 1 achieves both the requirements of running stability and improvement of riding comfort. In order to control the damping force characteristics of 2, 3, 4 to be slightly hard, the control unit 8
Sets the damping coefficient Dki in the range of D4i to D8i.

On the other hand, when the result is NO, that is, when it is determined that the vehicle speed V is in the high-speed traveling state in which the vehicle speed V exceeds the fifth predetermined vehicle speed V5, the control unit is emphasized to improve the traveling stability. 8 sets the damping coefficient Dki in the range of D7i to D10i so that the damping force characteristic is changed and controlled within a hard range. 11 and 12 show the shock absorbers 1, 2, which are executed when the control mode is selected by the mode selection switch 17.
11 is a flowchart showing a basic routine of damping force characteristic change control of 3 and 4, and the damping coefficient Dki can be changed and controlled only within the range of the damping coefficient Dki selected by the routine of the damping coefficient selection control of FIG. 10. It is like this.

In FIGS. 11 and 12, first, the control unit 8 includes a first acceleration sensor 11 and a second acceleration sensor.
Vertical acceleration ai on the spring detected by the acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14,
The detection signal of the damping force Fsi detected by the first pressure sensor 61, the second pressure sensor 62, the third pressure sensor 63, and the fourth pressure sensor 64 and the detection signal of the load Wi on the spring, and the vehicle speed V detected by the vehicle speed sensor 15. Detection signal, lateral acceleration sensor 1
6, the lateral acceleration GL detected by the steering angle sensor 65, the steering angle θ detected by the steering angle sensor 65, the brake signal BR detected by the brake switch 66, the anti-braking system (A
BS) 67 estimated signal μ of road friction coefficient,
The detection signals of the vehicle height displacement xsi detected by the first vehicle height displacement sensor 71, the second vehicle height displacement sensor 72, the third vehicle height displacement sensor 73, and the fourth vehicle height displacement sensor 74 of each wheel are input.
Then, the control unit 8 integrates the input vertical acceleration ai to calculate the displacement speed Xsi on the spring.

The control unit 8 further adds a predetermined constant K (K <0) to the calculated displacement velocity Xsi on the spring.
Multiply by the ideal damping force, Skyhook damping force Fai
Is calculated and hα is calculated according to the formula to determine whether or not hα is positive. hα = Fsi (Fai−αFsi) .................. As a result, when it is determined that hα is not positive, the control unit 8 further follows the equation:
hβ is calculated to determine whether hβ is negative.

Hβ = Fsi (Fai−βFsi) ... As a result, when hβ is negative, the control unit 8 determines that the control signal is a shock determined to be negative. The stepper motor 27 is output to the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44 of the absorbers 1, 2, 3, and 4, so that the step motor 27 is generated as shown in FIG.
In the above, the counterclockwise rotation is performed by one step, and the damping coefficient Dki is changed to D (k-1) i, which is one smaller than the previous damping coefficient Dki, that is, to be softer. , Hβ is not negative, the control unit 8 does not output a control signal, that is, holds the damping coefficient Dki as the previous damping coefficient Dki,
Move to the next cycle.

On the other hand, when hα is positive, the control unit 8 further
hγ is calculated to determine whether hγ is negative. hγ = Fsi (Fai−γFsi) ... As a result, when hγ is not positive, the control unit 8 sends the control signal to the shock absorber 1, which is determined to be not positive, 2, 3, 4 first actuator 41, second actuator 42, third actuator 43, fourth
Output to the actuator 44 to output the step motor 27
In FIG. 8, the damping coefficient Dki is rotated by one step in the clockwise direction, and the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (k
Change to +1) i, that is, harder.

On the other hand, when hγ is positive, the difference between the skyhook damping force Fai and the actual damping force Fsi is large, and the stepping motor 27 is rotated by two or more steps to set the damping coefficient Dki to Two or more larger than the previous damping coefficient Dki,
That is, it is recognized that the vehicle is in a running state in which two or more hardware changes are required, but when the step motor 27 is rotated by two or more steps, switching noise or vibration is generated due to the pressure fluctuation of the shock absorber due to the switching. Therefore, in the present embodiment, the stepping motor 27 is rotated by two steps only in the running state where the running stability should be emphasized, and the damping coefficient Dki is increased by two larger than the previous damping coefficient Dki. It is controlled to change to (k + 2) i in order to improve both riding comfort and running stability.

Here, regarding the threshold values α, β, γ, the damping coefficient Dki is changed too often, and as a result,
It is a threshold value for preventing a large switching noise or vibration or a response delay when changing the damping coefficient Dki, and normally α> 1, 0 <β <1, γ> α. Is set. That is, when Fsi and Fai have the same sign, since (Fai-αFsi) in the equation is α> 1, it is easy to have a different sign from Fsi, as compared with the case where Fsi is not multiplied by α. As a result, hα tends to be negative, so it is difficult to change the damping coefficient Dki, and further, in the formula (Fai
Since −βFsi) is 0 <β <1, it is easy to have the same sign as Fsi as compared with the case where Fsi is not multiplied by β, and as a result, hβ tends to be positive.
Since it is difficult to change ki and γ is set to a value larger than α, (Fai-γFsi) in the equation
Is more likely to have a different sign from Fsi than the expression (Fai−αFsi), and as a result, hγ is more likely to be negative than hα. Therefore, even when hα is positive, the damping coefficient Dki is Only one larger than the previous damping coefficient Dki
It is easy to change to (k + 1) i and difficult to change to D (k + 2) i.

On the other hand, when Fsi and Fai have different signs, it is impossible to match the actual damping force Fsi with the ideal skyhook damping force Fai.
It is desirable to make the damping coefficient Dki close to zero, that is, to change it so as to be softer, in order to bring Fsi closer to Fai. In the present embodiment, when Fsi and Fai have opposite signs, both hα and hβ are negative values, and as a result, the control unit 8 causes the damping coefficient Dki to be one smaller than the previous damping coefficient Dki. Since it is changed to (k-1) i, that is, to be softer, it is possible to satisfy such a request.

As described above, in order to improve both the riding comfort and the running stability, the control unit 8
Further determines whether the vehicle speed V is lower than a predetermined second vehicle speed V2, for example, 30 km / h. as a result,
When the answer is YES, it is not a running state where importance is placed on running stability, but rather due to the pressure fluctuations of the shock absorbers 1, 2, 3, 4 due to the switching of the step motor 27,
Since it is recognized that the vehicle is in a traveling state in which sound and vibration should be prevented from occurring, the stepping motor 27 is rotated only one step, and the damping coefficient Dki is set to 1 from the previous damping coefficient Dki.
Only change to one larger D (k + 1) i.

On the other hand, when the vehicle speed V is equal to or higher than the second vehicle speed V2, it may be necessary to execute control with emphasis on traveling stability. Therefore, the control unit 8 further applies the brake input from the brake switch 66. It is determined whether the signal BR is on. As a result, when the brake signal BR is on, that is, when the brake is operated, the control unit 8 differentiates the vehicle speed V input from the vehicle speed sensor 15 to calculate the acceleration dV, and its absolute value. ｜ dV
It is determined whether or not | is equal to or greater than the predetermined value dVO, and if YES,
Since the control unit 8 is in a sudden braking state and a braking dive may occur, the control unit 8 operates the step motor 27.
Is rotated twice, and the damping coefficient Dki is changed to D (k + 2) i which is two larger than the previous damping coefficient Dki. On the other hand, NO
When, the brake is operated, but there is no danger of a braking dive because it is not in a sudden braking state. Therefore, the control unit 8 further performs anti-braking
It is determined whether the estimated value μ of the road surface friction coefficient input from the system (ABS) 67 is smaller than a predetermined value μo.
Even when the brake signal BR input from the brake switch 66 is not on, the control unit 8 determines whether the estimated value μ of the road surface friction coefficient is smaller than the predetermined value μo.

As a result, if YES, the vehicle 9 is traveling on a road surface having a small road friction coefficient μ, and if the damping coefficient Dki is suddenly and greatly changed, the load movement becomes large and spin is likely to occur. Therefore, it is desirable to roll the vehicle 9 to reduce the load movement and thus to increase the grip force of the tire. Therefore, the control unit 8 rotates the step motor 27 only one step and reduces the damping coefficient Dki. , Only D (k + 1) i, which is one larger than the previous damping coefficient Dki.

On the other hand, when NO, the control unit 8 further causes the first pressure sensor 61, the second pressure sensor 62, the third pressure sensor 63, and the fourth pressure sensor 6 to operate.
It is determined whether or not the load Wi on the spring inputted from 4 is larger than a predetermined value Wo. As a result, if YES,
Since the vehicle load is large and it is necessary to obtain a sufficient vibration damping effect, the control unit 8 uses the step motor 27.
Is rotated in two stages to change the damping coefficient Dki to D (k + 2) i, which is two larger than the previous damping coefficient Dki. On the other hand, when NO, the steering angle sensor 65 further inputs Rudder angle θ
Is calculated, and it is determined whether or not the absolute value is greater than or equal to a predetermined value dθo.

As a result, when the answer is YES, the steering wheel is being rapidly operated, and the running stability should be emphasized. Therefore, the control unit 8 operates the step motor 27.
Is rotated in two steps to change the damping coefficient Dki to D (k + 2) i, which is two larger than the previous damping coefficient Dki. On the other hand, when NO, the lateral acceleration sensor 16 inputs the lateral acceleration. It is determined whether or not the absolute value of the directional acceleration GL is greater than or equal to a predetermined value GLo.

As a result, if YES, it is determined that the vehicle is in a sharp turn, and the running stability should be emphasized.
The control unit 8 rotates the step motor 27 in two stages to set the damping coefficient Dki to the previous damping coefficient Dki.
If it is changed to D (k + 2) i, which is larger by two, on the other hand, when NO, the control unit 8 controls the vertical acceleration ai.
It is determined whether or not the vehicle is traveling on a good road based on the variation amount within the predetermined time.

As a result, when it is determined that the vehicle is traveling on a good road, the damping coefficient Dki can be made harder to improve the traveling stability. , Rotate it two steps,
The damping coefficient Dki is 2 larger than the previous damping coefficient Dki by D
If (k + 2) i is changed to NO, on the other hand, if NO, the vehicle is traveling on a rough road, and if the step motor 27 is rotated by two steps, switching shock may occur. Is based on the vehicle height displacement xsi detected by the first vehicle height displacement sensor 71, the second vehicle height displacement sensor 72, the third vehicle height displacement sensor 73, and the fourth vehicle height displacement sensor 74. The relative displacement velocity Xsi-Xui with respect to the bottom is calculated, and it is determined whether or not this is zero.

As a result, in the case of NO, the sprung mass and the unsprung mass are relatively displaced, and immediately the damping coefficient Dki is reached.
Is changed to D (k + 2) i, which is two larger than the previous damping coefficient Dki, to make it hard, due to the pressure fluctuations of the shock absorbers 1, 2, 3, 4 accompanying the switching of the step motor 27. , Sound and vibration are generated, the control unit 8 rotates the step motor 27 only one step, and changes the damping coefficient Dki to D (k + 1) i, which is one larger than the previous damping coefficient Dki. Stay.

On the other hand, if YES, the control unit 8 further determines whether or not the displacement speed Xsi on the spring is positive. Here, the displacement speed Xsi on the spring is
In FIG. 5, when the sprung displacement xs is displaced upward, it is set to a positive value, and as described above, the vertical acceleration ai on the spring is set to a positive value when it is directed upward. Therefore, it is set to have a positive value when the sprung is displaced upward. As a result, when NO, it is recognized that the tire is in a state immediately after the hole falls,
Since it is required to make the damping coefficient Dki harder, the control unit 8 changes the damping coefficient Dki to D (k + 2) i, which is two larger than the previous damping coefficient Dki, and when YES is determined. In order to prevent the generation of noise and vibration due to the pressure fluctuation of the shock absorbers 1, 2, 3, 4 accompanying the switching of the step motor 27, the control unit 8 sets the damping coefficient Dki to the previous damping coefficient Dki.
Only change to D (k + 1) i, which is one larger than ki.

Note that the range of the damping coefficient Dki changed in the flowcharts of FIGS. 11 and 12 is limited by the damping coefficient selection control routine according to the running state of FIG. Rotate clockwise one or two steps to obtain damping coefficient Dki
Is one or two greater than the previous damping coefficient Dki
Even when it should be changed to (k + 1) i or D (k + 2) i, if the previous damping coefficient Dki is equal to the upper limit value of the damping coefficient Dki selected in the damping coefficient selection control routine, The control unit 8 changes the damping coefficient Dki to the previous damping coefficient Dki.
The value of ki is maintained, and the step motor 27 is rotated counterclockwise by one step so that the damping coefficient Dki becomes D (k-1) i, which is one smaller than the previous damping coefficient Dki. Even if it should be done, if the previous damping coefficient Dki is equal to the lower limit of the damping coefficient Dki selected in the damping coefficient selection control routine, the control unit 8 determines
Ki is held as it is as the previous damping coefficient Dki.

As described above, according to the present embodiment, in the traveling state in which the ride comfort is more important than the traveling stability, the step motor 27 is rotated only one step, and the damping coefficient Dki is set to be one less than the previous damping coefficient Dki. Since it is only changed to a large D (k + 1) i, a large switching noise or vibration is generated due to the pressure fluctuation of the shock absorbers 1, 2, 3, 4 accompanying the switching of the step motor 27. On the other hand, in a traveling state in which importance is placed on traveling stability rather than riding comfort, the step motor 27 is rotated in two steps, and the damping coefficient Dki is increased by two from the previous damping coefficient Dki. Since the vehicle is made harder, it is possible to sufficiently improve the running stability in a running state where the running stability should be ensured, and it is possible to achieve both running stability and riding comfort.

13 and 14 show another example of the basic routine of the damping force characteristic change control of each shock absorber 1, 2, 3, 4 which is executed when the control mode is selected by the mode selection switch 17. 11 is a flow chart showing the above, so that the damping coefficient Dki can be changed and controlled only within the range of the damping coefficient Dki selected by the damping coefficient selection control routine of FIG. 10, as in the cases of FIGS. 11 and 12. It has become.

The flowcharts of FIGS. 13 and 14 are as follows.
What is input to the control unit 8 is only the vertical acceleration ai and the damping force Fsi, and hγ
The control in the case where is determined to be positive is different from that in the above-described embodiment, and is otherwise the same. When it is determined that hγ is positive, the control unit 8
The average value of the vertical acceleration a1 detected by the acceleration sensor 11 and the vertical acceleration a2 detected by the second acceleration sensor 12, the vertical acceleration a3 detected by the third acceleration sensor 13, and the fourth acceleration sensor 14 The difference P between the detected vertical acceleration a4 and the average value is calculated, and it is determined whether or not the absolute value of P is larger than a predetermined value Po.

As a result, when the answer is YES, the pitch of the vehicle body is larger than the predetermined pitch, and the running stability should be emphasized. Therefore, the control unit 8 rotates the step motor 27 in two stages, Damping coefficient Dki
Is changed to D (k + 2) i which is two larger than the previous damping coefficient Dki. On the other hand, when NO, the control unit 8 further calculates the difference R between the vertical acceleration a1 detected by the first acceleration sensor 11 and the vertical acceleration a2 detected by the second acceleration sensor 12. Then, it is determined whether or not the absolute value of R is larger than the predetermined value Ro.

As a result, if YES, the roll of the vehicle body is larger than the predetermined roll, and therefore running stability should be emphasized. Therefore, the control unit 8 rotates the step motor 27 in two stages, Damping coefficient Dki
Is changed to D (k + 2) i which is two larger than the previous damping coefficient Dki. On the other hand, when NO, the control unit 8
Is a vertical acceleration a1 detected by the first acceleration sensor 11, a vertical acceleration a2 detected by the second acceleration sensor 12, a vertical acceleration a3 detected by the third acceleration sensor 13, and a fourth acceleration sensor. An average value G of the vertical acceleration a4 detected by 14 is calculated, and it is determined whether or not the absolute value of G is larger than a predetermined value Go.

As a result, if YES, the vertical movement of the vehicle body is large, and it is recognized that the vehicle is in a traveling state where importance is attached to traveling stability. Therefore, the control unit 8 rotates the step motor 27 in two stages. , The damping coefficient Dki is changed to D (k + 2) i which is two larger than the previous damping coefficient Dki. On the other hand, when NO, the control unit 8
Is a damping coefficient Dki in order to prevent sound and vibration from occurring due to the pressure fluctuations of the shock absorbers 1, 2, 3, 4 accompanying the switching of the step motor 27.
Is changed to D (k + 1) i, which is one larger than the previous damping coefficient Dki.

The range of the damping coefficient Dki changed in the flowcharts of FIGS. 13 and 14 is limited by the routine of the damping coefficient selection control according to the running state of FIG. Rotate clockwise one or two steps to obtain damping coefficient Dki
Is one or two greater than the previous damping coefficient Dki
Even when it should be changed to (k + 1) i or D (k + 2) i, if the previous damping coefficient Dki is equal to the upper limit value of the damping coefficient Dki selected in the damping coefficient selection control routine, The control unit 8 changes the damping coefficient Dki to the previous damping coefficient Dki.
The value of ki is maintained, and the step motor 27 is rotated counterclockwise by one step so that the damping coefficient Dki becomes D (k-1) i, which is one smaller than the previous damping coefficient Dki. Even if it should be done, if the previous damping coefficient Dki is equal to the lower limit of the damping coefficient Dki selected in the damping coefficient selection control routine, the control unit 8 determines
Ki is held as it is as the previous damping coefficient Dki.

As described above, according to this embodiment, the pitch of the vehicle body,
In a traveling state in which roll and vertical movement are not great and riding comfort is more important than traveling stability, the step motor 27
Is rotated by two or more steps and the damping coefficient Dki is increased by two or more from the previous damping coefficient Dki to make it hard, even if the step motor 27 is rotated only one step, the damping coefficient Dki is set to the previous value. D (k + 1) i, which is one greater than the damping coefficient Dki
However, it is possible to prevent a large switching noise or vibration from being generated due to the pressure fluctuation of the shock absorbers 1, 2, 3, 4 accompanying the switching of the step motor 27. , Body pitch, roll,
In a traveling state in which the vertical movement is large and traveling stability is more important than riding comfort, the step motor 27 is rotated in two steps, and the damping coefficient Dki is increased by two from the previous damping coefficient Dki to make the operation more difficult. Therefore, in a traveling state where traveling stability should be ensured, traveling stability can be sufficiently improved, and both traveling stability and riding comfort can be achieved.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that this is what is done. For example,
In each of the above embodiments, the thresholds α, β and γ are set to α> 1, 0 <β <1, γ> α, but if α> β, γ> α Well, α> 1, 0 <β <1
It is not always necessary to set to. However, from the viewpoint of emphasizing traveling stability, α> 1, α>β> 0
Moreover, it is desirable to set the threshold values α, β and γ so that γ> α.

In the flowcharts of FIGS. 11 and 12, when hγ is positive, the vehicle speed V is the predetermined vehicle speed V2.
With the above, the brake signal BR is on and the acceleration dV
Is greater than or equal to the predetermined value dVO, the vehicle speed V is greater than or equal to the predetermined vehicle speed V2, the brake signal BR is off, the estimated road friction coefficient μ is greater than or equal to the predetermined value μo, and the spring is When the upper load Wi is larger than the predetermined value Wo, the vehicle speed V
Is above the predetermined vehicle speed V2, the brake signal BR is off,
When the estimated value μ of the road surface friction coefficient is a predetermined value μo or more, the load Wi on the spring is a predetermined value Wo or less, and the absolute value of the change rate dθ of the steering angle θ is a predetermined value dθo or more, the vehicle speed V Is a predetermined vehicle speed V2 or more, the brake signal BR is off, the estimated value μ of the road surface friction coefficient is a predetermined value μo or more, the spring load Wi is a predetermined value Wo or less, and the change rate dθ of the steering angle θ is
The absolute value of is less than the specified value dθo and the lateral acceleration GL
Is equal to or greater than the predetermined value GLo, the vehicle speed V is equal to or higher than the predetermined vehicle speed V2, the brake signal BR is off, the estimated value μ of the road surface friction coefficient is equal to or greater than the predetermined value μo, and the load Wi on the spring is equal to the predetermined value W
When the absolute value of the rate of change dθ of the steering angle θ is less than a predetermined value dθo, the lateral acceleration GL is less than the predetermined value GLo, and the vehicle is traveling on a good road, the vehicle speed V is less than o. At a predetermined vehicle speed V2 or more, the brake signal BR is off, the estimated value μ of the road surface friction coefficient is a predetermined value μo or more, the load Wi on the spring is a predetermined value Wo or less, and the change rate dθ of the steering angle θ If the absolute value is less than the predetermined value dθo, the lateral acceleration GL is
If the relative displacement speed Xsi-Xui between the sprung and unsprung is zero and the displacement speed Xsi on the spring is not positive, the vehicle speed V is equal to or higher than the predetermined vehicle speed V2. , The brake signal BR is on, the absolute value | dV | of the acceleration dV is less than the predetermined value dVO, the estimated value μ of the road surface friction coefficient is not less than the predetermined value μo, and the load Wi on the spring is
When it is larger than the predetermined value Wo, the vehicle speed V is equal to or higher than the predetermined vehicle speed V2, the brake signal BR is on, and the absolute value of the acceleration dV |
dV | is less than the predetermined value dVO, the estimated value μ of the road surface friction coefficient is not less than the predetermined value μo, and the load Wi on the spring is the predetermined value W.
When the absolute value of the change rate dθ of the steering angle θ is equal to or more than a predetermined value dθo, the vehicle speed V is equal to or more than the predetermined vehicle speed V2,
Brake signal BR is on and absolute value of acceleration dV ｜ dV ｜
Is less than a predetermined value dVO, the estimated value μ of the road surface friction coefficient is a predetermined value μo or more, the sprung load Wi is a predetermined value Wo or less, and the absolute value of the change rate dθ of the steering angle θ is a predetermined value. dθo
When the lateral acceleration GL is equal to or greater than the predetermined value GLo, the vehicle speed V is equal to or greater than the predetermined vehicle speed V2, the brake signal BR is on, and the absolute value | dV | of the acceleration dV is less than the predetermined value dVO, The estimated value μ of the road surface friction coefficient is greater than or equal to a predetermined value μo, the load Wi on the spring is less than or equal to a predetermined value Wo, the absolute value of the change rate dθ of the steering angle θ is less than the predetermined value dθo, and the lateral acceleration is When GL is less than the predetermined value GLo and is traveling on a good road, and when the vehicle speed V is the predetermined vehicle speed V2 or more, the brake signal BR is ON, and the absolute value | dV | of the acceleration dV is the predetermined value. Estimated road friction coefficient μ is less than the specified value μo
The load Wi on the spring is equal to or less than the predetermined value Wo, the absolute value of the change rate dθ of the steering angle θ is less than the predetermined value dθo, the lateral acceleration GL is less than the predetermined value GLo, and the road is good. Relative displacement speed Xsi− between unsprung and unsprung
When Xui is zero and the displacement speed Xsi on the spring is not positive, the control unit 8 rotates the step motor 27 by two steps to set the damping coefficient Dki to two more than the previous damping coefficient Dki. It is controlled to change to a large D (k + 2) i, but when one of these conditions is satisfied, when some of these conditions are satisfied, or
When the combination of these conditions is changed and all or some of them are satisfied, the control unit 8
The stepping motor 27 is rotated in two stages to set the damping coefficient D
ki may be changed to D (k + 2) i, which is two larger than the previous damping coefficient Dki.
In this embodiment, when the absolute value of the difference P between the average value of the vertical accelerations a1 and a2 and the average value of the vertical accelerations a3 and a4 is larger than the predetermined value Po, the vertical acceleration is When the absolute value of the difference R between a1 and a2 is larger than the predetermined value Ro, and when the absolute value of the average value G of the vertical accelerations a1, a2, a3 and a4 is larger than the predetermined value Go, respectively, the control unit 8 Controls the stepping motor 27 to rotate in two stages to change the damping coefficient Dki to D (k + 2) i, which is two larger than the previous damping coefficient Dki. When two or more are satisfied, the control unit 8 rotates the step motor 27 by two steps to change the damping coefficient Dki to D (k + 2) i which is two larger than the previous damping coefficient Dki. You may do it. Furthermore, the conditions in the embodiment of FIGS. 11 and 12 are combined with the conditions in the embodiments of FIGS. 13 and 14, and when some or all of these are satisfied, the control unit 8 causes the step motor 27 may be rotated in two stages to change the damping coefficient Dki to D (k + 2) i that is two larger than the previous damping coefficient Dki.

Further, in the above-described embodiment, the difference R between the vertical acceleration a1 detected by the first acceleration sensor 11 and the vertical acceleration a2 detected by the second acceleration sensor 12 indicates the roll state of the vehicle body. I use it as a value,
Vertical acceleration a1 detected by the first acceleration sensor 11
And the vertical acceleration a detected by the second acceleration sensor 12
Even if the difference from 2 is used as a value indicating the roll state of the vehicle body, the average of the vertical acceleration a1 detected by the first acceleration sensor 11 and the vertical acceleration a3 detected by the third acceleration sensor 13 is also averaged. Even if the difference between the value and the average value of the vertical acceleration a2 detected by the second acceleration sensor 12 and the vertical acceleration a4 detected by the fourth acceleration sensor 14 is used as the value indicating the roll state of the vehicle body. Of course, instead of the vertical accelerations a1, a2, a3, and a4, differential values of these may be used.

Further, in the above-mentioned embodiment, the estimated value μ of the road surface friction coefficient is set to the anti-braking system (A
Although it is calculated based on the detection signal of BS) 67, the estimated value μ of the road surface friction coefficient may be calculated based on the signal of the wiper. Furthermore, in the above-described embodiment, in the traveling state in which it is determined that the traveling stability should be emphasized,
The control unit 8 rotates the step motor 27 in two stages to set the damping coefficient Dki to the previous damping coefficient Dki.
I try to change it to D (k + 2) i, which is two larger.
It is also possible to rotate the step motor 27 in three or more stages.

In the above embodiment, the two stopper pins 55 and 56 are connected to the rotor 5 of the step motor 27.
1 and the grooves 57 and 58 to be engaged therewith are formed in the lid 53 of the step motor 27.
5, 56 may be formed on the lid 53 of the step motor 27, and grooves 57, 58 engaging with the lid 53 may be formed on the rotor 51 of the step motor 27.
One of 5, 56 is connected to the rotor 51 of the step motor 27.
The other side is formed in the lid 53 of the step motor 27, and the grooves 57 and 58 engaging with one of the stopper pins 55 and 56 formed in the rotor 51 are formed in the lid 53 of the step motor 27.
Further, grooves 57 and 58 that engage with the other stopper pins 55 and 56 formed on the lid 53 of the step motor 27 may be formed in the rotor 51 of the step motor 27.

Further, in the above embodiment, the step motor 27 is used as the actuator for changing the damping force of the shock absorbers 1, 2, 3, 4 and the shock absorbers 1, 2, 3, 4 are opened by the open control.
The damping force of the shock absorbers 1, 2, 3, 4 may be controlled by feedback control using a DC motor instead of the step motor 27.

[0068]

According to the present invention, in a suspension device for a vehicle, a shock absorber is provided between the sprung portion and the unsprung portion, and the damping force characteristic of the shock absorber is changed and controlled according to the vertical vibration of the vehicle body. It is possible to provide a vehicle suspension device capable of improving running stability and riding comfort while preventing generation of large switching noise and vibration due to pressure fluctuation of the shock absorber due to switching of damping force. Become.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a vehicle including a vehicle suspension device according to a preferred embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a main part of each shock absorber.

FIG. 3 is an exploded schematic perspective view of an actuator.

FIG. 4 is a graph showing a damping coefficient of a shock absorber.

FIG. 5 is a vibration model diagram of a vehicle suspension device according to an embodiment of the present invention.

FIG. 6 is a schematic perspective view of a step motor.

FIG. 7 is a schematic plan view of a rotor and a stator.

FIG. 8 is a schematic bottom view of the lid.

FIG. 9 is a block diagram of a control system of a vehicle suspension device according to an embodiment of the present invention.

FIG. 10 is a flowchart showing a routine of damping coefficient selection control according to a traveling state.

FIG. 11 is a flowchart showing a first half of a basic routine of damping force characteristic change control of each shock absorber executed by the control unit.

FIG. 12 is a flowchart showing a second half of a basic routine of damping force characteristic change control of each shock absorber executed by the control unit.

FIG. 13 is a flowchart showing the first half of another example of the basic routine of the damping force characteristic change control of each shock absorber executed by the control unit.

FIG. 14 is a flowchart showing the latter half of another example of the basic routine of the damping force characteristic change control of each shock absorber executed by the control unit.

[Explanation of symbols]

1, 2, 3, 4 shock absorber 5 left front wheel 6 left rear wheel 7 coil spring 8 control unit 9 vehicles 11 First acceleration sensor 12 Second acceleration sensor 13 Second acceleration sensor 14 Fourth acceleration sensor 15 vehicle speed sensor 16 Lateral acceleration sensor 17 Mode selection switch 21 cylinders 22 Piston unit 23, 24 Orifice 25 sleeves 26 shaft 27 step motor 28 circular holes 29 First Orifice Plate 30 long holes 31 Second Orifice Plate 32 upper chamber 33 lower chamber 41 First Actuator 42 Second actuator 43 Third Actuator 44th actuator 50 tubular 51 rotor 52 Stator 53 lid 54 solenoid 55, 56 Stopper pin 57, 58 groove 61 First Pressure Sensor 62 Second pressure sensor 63 Third pressure sensor 64 Third pressure sensor 65 rudder angle sensor 66 Brake switch 67 Anti-braking system 71 1st vehicle height displacement sensor 72 Second vehicle height displacement sensor 73 Third vehicle height displacement sensor 74 Fourth vehicle height displacement sensor

Claims (14)

[Claims] 1. A suspension device for a vehicle, comprising a shock absorber between an unsprung part and an unsprung part, and changing and controlling a damping force characteristic of the shock absorber in accordance with vertical vibration of a vehicle body. An actuator that changes the force and a control unit that outputs a control signal to the actuator are provided, and when the damping force characteristic of the shock absorber is switched from soft to hard, the control unit controls the actuator according to a running state. A suspension device for a vehicle, which is configured to allow multistage switching of the damping force of the shock absorber. 2. The vehicle suspension according to claim 1, wherein the control means is configured to allow multistage switching of the damping force of the shock absorber when the vehicle speed is equal to or higher than a predetermined value. apparatus. 3. The control means, when in a sudden braking state,
The vehicle suspension device according to claim 1, wherein the suspension device is configured to allow multistage switching of the damping force of the shock absorber. 4. The control means is configured to allow multistage switching of the damping force of the shock absorber when the load capacity is a predetermined value or more.
The vehicle suspension device described in. 5. The control unit according to claim 1, wherein the control unit is configured to allow multistage switching of the damping force of the shock absorber when the steering angle change speed is equal to or higher than a predetermined value. Vehicle suspension system. 6. The vehicle according to claim 1, wherein the control means is configured to allow multistage switching of the damping force of the shock absorber when the lateral acceleration is equal to or greater than a predetermined value. Suspension device. 7. The suspension device for a vehicle according to claim 1, wherein the control means is configured to allow multistage switching of the damping force of the shock absorber during traveling on a good road. 8. The control means permits multistage switching of the damping force of the shock absorber when the relative displacement speed between the sprung and unsprung portions is zero and the displacement speed on the spring is negative. The suspension device for a vehicle according to claim 1, wherein the suspension device is configured. 9. The vehicle according to claim 1, wherein the control means is configured to allow multistage switching of the damping force of the shock absorber when the pitch of the vehicle body is equal to or larger than a predetermined value. Suspension device. 10. The vehicle according to claim 1, wherein the control means is configured to allow multistage switching of the damping force of the shock absorber when the roll of the vehicle body is equal to or larger than a predetermined value. Suspension device. 11. The vehicle according to claim 1, wherein the control means is configured to allow multistage switching of the damping force of the shock absorber when the vertical movement of the vehicle body is more than a predetermined value. Suspension device. 12. The control means controls the vehicle speed to be a predetermined value or more,
Sudden braking, load capacity above a certain value, rudder angle change speed above a certain value, lateral acceleration above a certain value, running on a good road, relative displacement speed between sprung and unsprung is zero, and displacement speed on the spring Is negative, the pitch of the vehicle body is a predetermined value or more, the roll of the vehicle body is a predetermined value or more, and the vertical movement of the vehicle body is a predetermined value or more, two or more conditions are satisfied. The vehicle suspension device according to claim 1, wherein the suspension device is configured to allow switching. 13. The control means is configured so as not to allow multistage switching of the damping force of the shock absorber when the road surface friction coefficient is less than a predetermined value. 2. A vehicle suspension device according to item 1. 14. The vehicle suspension device according to claim 1, wherein the actuator is a step motor.