JPH0532109A - Suspension device of vehicle - Google Patents

Abstract

PURPOSE:To prevent any undesirable change of steering characteristic and prevent the generation of diagonal vibration by controlling shock absorbers of left and right wheels by means of the frequency of input acting on a car body in suck a way that a large difference can not be generated in damping force characteristics. CONSTITUTION:Signals of the pressure sensors 61-64 of the shock absorbers of respective wheels as damping force, signals of acceleration sensors 11-14, and signals of height sensors 71-74 and a speed sensor 15 are input to the operation determining means 80 of a control unit 8. And, signals of the speed sensor 15, etc., are input to an allowable value setting means 81, the input frequency acting on a vehicle body is detected by an input frequency detecting means 83, the operation determining means 80 computes the damping force characteristic values of respective shock absorbers by adding up the signal of an allowable value changing means 82, and controls the difference of damping force characteristic below an allowable value through actuators 41-44. Therefore, riding comfort and attitude stability can be enhanced, and diagonal vibration can be reduced effectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system, and more particularly to an improvement of a suspension system provided with a shock absorber having a variable damping force characteristic between a sprung portion and an unsprung portion.

[0002]

2. Description of the Related Art Generally, a suspension device for a vehicle is equipped with a shock absorber for damping vertical vibration of a wheel between a sprung portion on the vehicle body side and an unsprung portion on the wheel side. In this shock absorber, as the damping force characteristic variable type, the damping force characteristic (characteristic with different damping coefficient) can be changed in two steps of high and low, and the damping force characteristic can be changed in multiple steps or continuously. There are various things such as things.

Basically, such a damping force control type shock absorber control method basically damps the shock absorber when the damping force generated by the shock absorber acts in the vibration direction with respect to the vertical vibration of the vehicle body. Excitation energy transmitted to the spring by changing the damping force of the shock absorber to the high damping side (ie hard side) when the damping force is on the low damping side (ie soft side) and the damping force acts in the damping direction. On the other hand, the damping energy is increased to improve both the riding comfort and the running stability of the vehicle.

Various methods have been proposed for determining whether the damping force of the shock absorber acts in the vibration direction of the sprung vertical vibration or in the vibration damping direction.
For example, in Japanese Patent Laid-Open No. 60-248419, it is examined whether the sign of the relative displacement between the sprung and unsprung parts and the sign of the relative velocity between the sprung and unsprung parts, which is the differential value, match. There is disclosed a method of determining the vibration direction when they match, and determining the vibration direction when they do not match.

[0005]

However, 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 variable-damping-type shock absorber whose characteristics are changed and controlled, the damping force characteristics of the shock absorber are changed and controlled independently for each wheel. May occur, and as a result, there is a problem that an unfavorable change occurs in the steer characteristic or diagonal vibration occurs.

The present invention has been made in view of the above points, and an object thereof is to cause a large difference in the damping force characteristics of the shock absorbers of the left and right wheels based on the frequency of the input applied to the vehicle body. Control not to
It is intended to prevent undesired changes in the steer characteristics and effectively prevent the occurrence of diagonal vibration.

[0007]

In order to achieve the above-mentioned object, a solution means provided by the invention according to claim 1 is to provide a shock absorber between the sprung and unsprung portions of each wheel, and to displace the sprung portion. It is premised on a suspension device for a vehicle that changes and controls the damping force characteristic of the shock absorber according to the relative relationship between the speed and the unsprung displacement speed. Then, the control means for changing and controlling the damping force characteristics of the shock absorber of each wheel, the input frequency detecting means for detecting the frequency of the input applied to the vehicle body, and the signals from the input frequency detecting means, The configuration is provided with a permissible value changing means for changing the control of the control means so as to change the permissible value of the difference in the damping force characteristics of the shock absorbers between the wheels.

Further, a solution means taken by the invention according to claim 2 is dependent on the invention according to claim 1, wherein the allowable value changing means is a damping force characteristic of the shock absorber between the left and right wheels. The allowable value of the difference is greatly changed when the frequency of the input applied to the vehicle body is in the high frequency vibration area, while it is changed to be small when the frequency of the input applied to the vehicle body is in the low frequency vibration area.

Further, the solution means taken by the invention according to claim 3 is dependent on the invention according to claim 1, wherein the allowable value changing means is a damping force characteristic of the shock absorber between the left and right wheels. Is independently controlled by increasing the allowable value when the input frequency applied to the vehicle body is in the high-frequency vibration region, while setting the allowable value to 0 when the input frequency applied to the vehicle body is in the low-frequency vibration region. It is controlled in the same phase.

[0010]

With the above construction, in the invention according to claims 1 and 2, the allowable value changing means allows the difference in damping force characteristics of the shock absorbers between the left and right wheels according to the signal from the input frequency detecting means. The control of the control means is changed to change the value. For example, when the frequency of the input applied to the vehicle body is in the high-frequency vibration region, the allowable value that allows the difference in the damping force characteristics of the shock absorbers between the left and right wheels is changed to be large, and the shock absorbers of the left and right wheels are The damping force characteristics are regulated within a range of large allowable values, such as changing the damping force characteristics of a harder shock absorber to a slightly soft side, and changing the damping force characteristics of a softer shock absorber to a slightly hard side. The ride comfort and posture stability in the vibration region are both good. On the other hand, when the frequency of the input applied to the vehicle body is in the low-frequency vibration region, the allowable value that allows the difference in the damping force characteristics of the shock absorbers between the left and right wheels is changed to be smaller, and the shock absorbers for the left and right wheels are changed. The damping force characteristic of is regulated within a small allowable value range by changing the damping force characteristic of a harder shock absorber to the soft side and the damping force characteristic of a softer shock absorber to the hard side.
The steering stability becomes good in the low frequency vibration region, and the diagonal vibration is effectively reduced.

Further, in the invention according to claim 3, the damping force characteristics of the shock absorbers on the left and right wheels are independently controlled, for example, when the input frequency applied to the vehicle body is in a very high frequency vibration region. Therefore, the damping force characteristics of the shock absorbers on the left and right wheels do not change the damping force characteristics of the softer shock absorber while maintaining the damping force characteristics of the harder shock absorber. Are regulated (controlled) by, and both the riding comfort and the posture stability in the super high frequency vibration region are improved. On the other hand, when the input frequency applied to the vehicle body is in a very low frequency vibration region, the damping force characteristics of the shock absorbers on the left and right wheels are controlled in phase, and the damping force characteristics of the shock absorbers on the left and right wheels are The difference is changed so as to be closer to each other so that the difference becomes 0, the steering stability becomes good in the extremely low frequency vibration region, and the diagonal vibration is effectively reduced.

[0012]

As described above, according to the vehicle suspension device of the first aspect of the present invention, the difference between the damping force characteristics of the shock absorbers between the left and right wheels according to the input frequency applied to the vehicle body is changed by the allowable value changing means. Since the control of the control means is changed to increase or decrease the allowable value of, it is possible to achieve both ride comfort and posture stability in the high frequency vibration region, while manipulating stability and diagonal vibration in the low frequency vibration region. Can be effectively reduced.

According to the vehicle suspension device of the second aspect of the invention, the allowable value changing means allows the damping force characteristic of the shock absorber between the left and right wheels to fall within a large allowable value range in the high frequency vibration region. Control the control means to improve both riding comfort and posture stability in the high frequency vibration region, while allowing a small damping force characteristic of the shock absorber between the left and right wheels in the low frequency vibration region. It is possible to effectively control the diagonal vibration while restricting the control of the control means within the range of values to improve the steering stability in the low frequency vibration region.

Further, according to the vehicle suspension device of the third aspect of the invention, the damping force characteristics of the shock absorbers on the left and right wheels are independently controlled within a very large allowable range in the ultra-high frequency vibration region. In this way, both the riding comfort and the posture stability in the super high frequency vibration region can be improved, while the difference in the damping force characteristics of the shock absorbers on the left and right wheels becomes zero in the super low frequency vibration region. It is possible to effectively reduce the diagonal vibration while improving the steering stability in the extremely low frequency vibration region by performing the in-phase control.

[0015]

Embodiments of the present invention will be described below with reference to the 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 system 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 as 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. is there.

Further, on the spring of the vehicle body 9, a first acceleration sensor 11 for detecting the vertical acceleration on the spring of each wheel,
A second acceleration sensor 12, a third acceleration sensor 13, a fourth acceleration sensor 14, and a vehicle speed sensor 15 for detecting the vehicle speed are provided in the meter of the instrument panel. Reference numeral 16 denotes a mode selection switch that allows the driver to switch the control of the damping force characteristics of the shock absorbers 1, 2, 3, 4 to either the hard mode, the soft mode or the control mode. Then, when the hard mode is selected by the mode selection switch 16, only the damping coefficient in the range in which the damping force characteristic becomes hard is selected, and the shock absorbers 1, 2, 3, 3 are only within the range.
The change control of the damping force characteristic of No. 4 is performed. Further, when the soft mode is selected, only the damping coefficient in the range where the damping force characteristic becomes soft is selected, and the damping force characteristic change control of the shock absorbers 1, 2, 3, 4 is controlled only within that range. Is done. Further, when the control mode is selected, the change control of the damping force characteristics of the shock absorbers 1, 2, 3, 4 is performed in a predetermined manner according to the map or table stored in the control unit 8 in advance. Has become.

FIG. 2 is a schematic sectional view of a 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 is
A cylinder 21 is provided, and in the cylinder 21, a piston unit 22 in which a piston and a piston rod are integrally connected is slidably fitted. The cylinder 21 and the piston unit 22 are connected to the unsprung part and the sprung part, respectively.

The piston unit 22 has two orifices 23 and 24 formed therein. One orifice 2
3 is always open, and the other orifice 24 has a passage area of 10 by the first actuator 41.
It is formed so that it can be changed in stages.

FIG. 3 is an exploded schematic perspective view of the first actuator 41 provided in the shock absorber 1, and FIG.
And as shown in FIG. 3, the first actuator 41
Includes a shaft 26 rotatably provided in a sleeve 25 fixed to the piston unit 22, and a shaft 2
6, a step motor 27 that rotates 6 and a first orifice plate 29 that is integrally attached to the lower end of the shaft 26 and has nine circular holes 28 along the circumference of the step motor 27 and the lower end of the sleeve 25. The second orifice plate 31 is provided and has an arc-shaped long hole 30 formed along the circumference thereof. 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 are the rotation of the shaft 26 and the first orifice plate 29 by the rotation of the step motor 27. According to 9 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, only the structure of the shock absorber 1 is shown, but the shock absorbers 2, 3 and 4 provided for other wheels are also the shock absorber 1 shown in FIG. 3 shows the same structure as the above, and includes a second actuator 42, a third actuator 43, and a fourth actuator 44 similar to those shown in FIG. 3, respectively.

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 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, 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, the relative displacement speed (dXs / d
t-dXu / dt) is shown. As shown in FIG. 4, the damping force characteristics of the shock absorbers 1, 2, 3, 4 are configured so that they can be changed in 10 steps by selecting one of the damping coefficients D1 to D10. ing. 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 the nine circular holes 2 formed in the first orifice plate 29.
Among the eight, (10-i) circular holes 28 are selected when they communicate with the long holes 30 formed in the second orifice plate 31. Therefore, the damping coefficient D1 is such that all nine circular holes 28 of the first orifice plate 29 have the long holes 3 of the second orifice plate 31.
The damping coefficient D10 is selected when none of the nine circular holes 28 of the first orifice plate 29 are in communication with the slot 30 of the second orifice plate 31. Become.

FIG. 5 is a vibration model diagram of a vehicle suspension system according to an embodiment of the present invention. Ms is an unsprung mass, mu is an unsprung mass, xs is an unsprung displacement, xu is an unsprung displacement, ks. Is the spring constant of the coil spring 7, kt is the spring constant of the tire, Dk is the shock absorbers 1, 2,
The attenuation coefficients are 3 and 4.

FIG. 6 is a schematic perspective view of the step motor 27. The step motor 27 includes a tubular body 50 and a tubular 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 Corresponding to this, a plurality of rectangular teeth are formed, the stator 52,
The solenoid 54 is wound. 2 for rotor 51
Book stopper pins 55 and 56 are formed, and as shown in FIG. 8, the lid 53 has stopper pins 55 and 56.
Two grooves 57 and 58 are formed in the circumferential direction at positions corresponding to. The groove 57 is for engaging with the stopper pin 55 formed on the rotor 51 to control the movable range of the step motor 27, while the groove 58 is for the stopper pin 56.
By engaging the stopper pins 55 and 56 with the grooves 57 and 58, it is possible to align the center of gravity of the rotor 51 with the center of rotation when the lid 53 is covered. To do. Therefore, the lid 53
The circumferential angle of the groove 57, 58 seen from the center of the groove is
8 is larger than the groove 57, and the grooves 57 and 58 are formed so that the movable range of the step motor 28 is determined exclusively by the groove 57. In FIG. 8, when the rotor 51 rotates clockwise, the damping soot 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 and the damping force characteristic becomes smaller. Is becoming softer,
When the rectangular teeth of the rotor 51 are moved to a position facing the adjacent rectangular teeth of the stator 52, that is, when the step motor 27 rotates one step, the damping coefficient Dk changes by one. ing. 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, and the shock absorber 1 generates the hardest damping force, while
When 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 becomes D1, and the shock absorber 1 produces 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.

In FIG. 9, the control unit 8 constituting the control system of the vehicle suspension system according to the embodiment of the present invention includes a calculation determining means 80 and an allowable value setting means 81.
And the allowable value changing means 82, and the calculation determining means 80 includes a first pressure sensor 61 and a second pressure sensor 6 provided on the shock absorbers 1, 2, 3 and 4, respectively.
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
(Here, i indicates each wheel, i = 1, 2, 3, 4) detection signal, first acceleration sensor 11, second acceleration sensor 12, third acceleration sensor 13, fourth acceleration The detection signal of the vertical acceleration ai on the spring detected by the sensor 14, the first vehicle height sensor 71, the second vehicle height sensor 72, and the third vehicle height sensor 72.
The detection signals of the sprung unsprung relative displacement (Xs-Xu) detected by the vehicle height sensor 73 and the fourth vehicle height sensor 74 and the detection signal of the vehicle speed V detected by the vehicle speed sensor 15 are input. Further, the allowable value setting means 81 has a detection signal of the vehicle speed V detected by the vehicle speed sensor 15, a detection signal of the steering angle θ detected by the steering angle sensor 65, and a road surface from the anti-braking system (ABS) 66. The estimated signals of the estimated value μ of the friction coefficient are input. Further, the calculation determining means 80 includes the first to fourth vehicle height sensors 71 to 74.
The relative sprung-spring-unsprung relative displacement (Xs-Xu) signal detected by is differentiated by a numerical differentiation method or the like to calculate the sprung-spring unsprung relative velocity (dXs / dt-dXu / dt).
A vertical acceleration ai on the spring detected by the first to fourth acceleration sensors 11 to 14 is integrated by a numerical integration method or the like to calculate a displacement speed Xsi (Σai) on the spring, which will be described later with reference to FIG.
The frequency of the input applied to the vehicle body is detected based on the map showing the change characteristics of the gain of the sprung mass relative speed with respect to the vibration frequency of The input frequency detecting means 83 is provided, and the determination signal determined by the input frequency detecting means 83 is used as the allowable value changing means 8.
It is entered in 2. In this case, the displacement speed on the spring Xsi
Is an absolute sprung speed at the positions of the first to fourth acceleration sensors 11 to 14, and is used as a sprung absolute speed at the positions of the shock absorbers 1 to 4.

The calculation determining means 80, based on the detection signal of the vertical acceleration ai and the detection signal of the vehicle speed V,
According to a map or table stored in advance, a damping coefficient Dki that determines the damping force characteristics of the shock absorbers 1, 2, 3, 4 of each wheel is calculated, a control symbol is generated, and the first actuator 41, 2 actuator 42, 3rd actuator 43, 4th actuator 4
4 to control the damping force characteristics of the shock absorbers 1, 2, 3 and 4, and when the allowable value signals are input from the allowable value setting means 81 and the allowable value changing means 82, the shocks of the left and right front wheels are received. Absolute value of the difference between the damping coefficients Dki of the absorbers 1 and 2 and the left and right rear wheel shock absorbers 3 and 4 | Dkl-Dkr | (where l = 1, 3, r =
2 and 4) is greater than or equal to the allowable value t, the damping coefficient D
The damping coefficient Dki of the shock absorbers 1, 2, 3, 4 for wheels with small ki is one larger than the previous damping coefficient Dki by D (k
+1) i, a control symbol is generated and output to the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44 to attenuate the shock absorbers 1, 2, 3, and 4. Control force characteristics. Further, the allowable value setting means 81 is based on the detection signal of the vehicle speed V detected by the vehicle speed sensor 15, the detection signal of the steering angle θ detected by the steering angle sensor 65, and the estimation signal of the estimated value μ of the road surface friction coefficient from the ABS 66. , An allowable value of the difference between the damping coefficients Dki of the shock absorbers 1, 2, 3, 4 of the left and right wheels and the front and rear wheels is calculated according to a map or a table stored in advance, and the allowable value signal is output to the calculation determining means 80. . Further, the permissible value changing means 82 changes the permissible value of the difference between the damping coefficients Dki of the shock absorbers 1, 2, 3, 4 of the left and right wheels and the front and rear wheels according to the judgment signal judged by the input frequency detecting means 83. The allowable value change signal is output to the calculation determining means 80.

Here, the damping force Fsi takes a continuous value, and when it acts upward on the sprung, that is, when it is contracted between the sprung and unsprung, it has a positive value and when it acts downward, that is, the spring. It is set so as to have a negative value when the upper part and the unsprung part are extended, and the vertical acceleration ai on the spring is set.
Is set to a positive value when facing upward and a negative value when facing downward.

FIG. 10 is a flowchart showing a routine of the damping coefficient selection control according to the traveling state, which is carried out by the control unit 8 when the control mode is selected by the mode selection switch 16. In the coefficient selection control routine, the damping coefficient Dki is changed too frequently, and as a result, the change control is performed according to the running state in order to prevent a large noise or vibration from occurring or a response delay. This limits the range of the damping coefficient Dki to be obtained.

In FIG. 10, first, in step SA1, the vehicle speed V detected by the vehicle speed sensor 15 is input, and the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14 are input. Input the vertical acceleration ai on the spring detected by.

Then, in step SA2, the vehicle speed V
Is the first predetermined vehicle speed V1 which is a low speed value, for example, 3 km / h
It is determined whether or not the following.

As a result, the vehicle speed V becomes the first predetermined vehicle speed V1.
In case of NO below, the routine proceeds to step SA3, where the vehicle speed V is extremely low. Therefore, in order to prevent the Scott and the braking dive, the damping coefficient of the shock absorbers 1, 2, 3 and 4 is made hard so that the damping force characteristic becomes hard. Fix Dki to D8i.
Therefore, since the damping coefficient Dki is fixed to D8i, the damping force characteristic changing control according to the basic routine of the damping force characteristic changing control shown in FIG. 10 is not performed.

On the other hand, when the vehicle speed V exceeds the first predetermined vehicle speed V1, YES, the routine proceeds to step SA4, where the absolute value of the vertical acceleration on the sprung ai exceeds the predetermined value ai0. Determine if it is medium or not.

As a result, the vertical acceleration ai on the spring
If it is determined that the vehicle is traveling on a rough road in which the absolute value of exceeds a predetermined value ai0, the process proceeds to step SA5, where the vehicle speed V is the third value.
The predetermined vehicle speed V3, for example, 50 km / h or more is determined.

When the determination at step SA5 is YES, that is, when the vehicle speed V is equal to or higher than the third predetermined vehicle speed V3, at step SA6, the damping force characteristics are comparatively emphasized with an emphasis on improving running stability. The damping coefficient Dki is set in the range of D5i to D7i in order to control the change within the hard range. As a result, in the basic routine of the damping force characteristic changing control shown in FIG. 10, the damping coefficient Dki becomes the lower limit value of D5i, and even if the condition to be further changed to soft is satisfied, the damping coefficient Dki becomes The damping coefficient Dki is held at D7i even if the value is held at D5i, on the other hand, D7i becomes the upper limit value, and the condition to be changed to a harder condition is satisfied.

On the other hand, when the determination in step SA5 is NO, that is, when the vehicle speed V is less than the predetermined vehicle speed V3, the process proceeds to step SA7, in which both traveling stability and ride comfort can be improved. Since it is possible, the damping coefficient Dki is set in the range of D3i to D7i in order to change and control the damping force characteristic within a range from a relatively soft state to a hard state. Therefore, in the basic routine of the damping force characteristic change control shown in FIG. 10, the damping coefficient Dki becomes the lower limit value, and even if the condition to be further changed softly is satisfied, the damping coefficient Dki becomes D3i. On the other hand, D7i becomes the upper limit value, and even if the condition to be changed to a harder condition is satisfied, the damping coefficient Dki remains D7i.
Will be held in.

On the other hand, if the determination in step SA4 is NO, that is, the absolute value of the vertical acceleration ai on the sprung is less than or equal to the predetermined value ai0, the process proceeds to step SA8, where a normal road is not a bad road Since it is considered that the vehicle is traveling, the vehicle speed V is further set to the second predetermined vehicle speed V in step SA8.
2. For example, it is determined whether the speed is 30 km / h or less.

As a result, when it is determined that the vehicle speed V is in the low speed traveling state of the second predetermined vehicle speed V2 or less, YES is emphasized in step SA9 to improve the riding comfort, so that the damping force characteristic is relatively soft. The damping coefficient Dki is set in the range of D1i to D3i so that the change control is performed within the range.
Therefore, in the basic routine of the damping force characteristic change control shown in FIG. 10, when the damping coefficient Dki is D1i,
The damping coefficient Dki is held at D1i even if the condition to be further changed to soft is satisfied, while D3i becomes the upper limit value, and the damping coefficient Dki is set to D3i even if the condition to be changed to harder is satisfied. Will be retained.

On the other hand, when the determination in step SA8 is NO, that is, when the vehicle speed V exceeds the second predetermined vehicle speed V2, the vehicle speed V is further increased in step SA10.
Is a fourth predetermined vehicle speed V4, for example, 60 km / h or less.

As a result, when it is determined that the vehicle speed V is in the relatively medium speed running state which is equal to or lower than the fourth predetermined vehicle speed V4, the process proceeds to step SA11 to make two requests to improve running stability and riding comfort. Since it is possible to achieve both, it is possible to set the damping coefficient Dki in the range of D2i to D6i in order to change and control the damping force characteristics within a range from a relatively soft state to a hard state. To do. Therefore, in the basic routine of the damping force characteristic changing control shown in FIG. 10, the damping coefficient Dki becomes the lower limit value of D2i, and the damping coefficient Dki is held at D2i even if the condition to be changed softer is satisfied. On the other hand, D6i becomes the upper limit value, and the damping coefficient Dki is held at D6i even if the condition to be further changed to hardware is satisfied.

On the other hand, when the determination in step SA10 is NO, that is, when the vehicle speed V exceeds the fourth predetermined vehicle speed V4, the routine proceeds to step SA12, where the vehicle speed V is the fifth predetermined vehicle speed V5, for example. It is determined whether it is 80 km / h or less.

As a result, when it is determined that the vehicle speed V is in the medium speed running state which is equal to or lower than the fifth predetermined vehicle speed V5, the process proceeds to step SA13 to improve the running stability and the riding comfort.
The damping coefficient Dki is set in the range of D4i to D6i in order to slightly change the damping force characteristics of the shock absorbers 1, 2, 3, 4 while satisfying both requirements. Therefore, in the basic routine of the damping force characteristic changing control of FIG. 10, the damping coefficient Dki becomes the lower limit value of D4i,
The damping coefficient Dki is held at D4i even if the condition to be further changed to soft is satisfied, while D6i becomes the upper limit value, and even if the condition to be further changed to hard is satisfied, the damping coefficient Dki is It will be held at D6i.

On the other hand, the vehicle speed V is the fifth predetermined vehicle speed V5.
When it is determined to be NO in a high-speed running state that exceeds the limit, the process proceeds to step SA14, and the damping coefficient Dki is set so that the damping force characteristics are changed and controlled within a hard range, with an emphasis on improving running stability. Set in the range of D7i to D10i. Therefore, in the basic routine of the damping force characteristic change control of FIG. 10, the damping coefficient Dki becomes the lower limit value of D7i, and even if the condition to be further changed softly is satisfied, the damping coefficient Dki is satisfied.
Is held in D7i, and on the other hand, the damping coefficient Dki is held in D10i even if a condition to be further changed to hard is satisfied.

FIG. 11 shows a basic routine of the damping force characteristic changing control of the shock absorbers 1, 2, 3, 4 of each wheel which is executed by the control unit 8 when the control mode is selected by the mode selection switch 16. It is a flowchart shown.

In FIG. 11, first, in step SB1, the first acceleration sensor 11, the second acceleration sensor 12,
Vertical acceleration ai on the spring detected by the third acceleration sensor 13 and the fourth acceleration sensor 14, and the first pressure sensor 61, the second pressure sensor 62, the third pressure sensor 63, and the fourth
The damping force Fsi detected by the pressure sensor 64 is input. Next, in step SB2, the vertical acceleration ai input in step SB1 is integrated to calculate the sprung displacement speed Xsi (= Σai).

Then, in step SB3, the displacement speed Xsi on the spring calculated in step SB2 is multiplied by a predetermined constant K (K <0) to calculate the skyhook damping force Fai, which is the ideal damping force. . Then, in step SB4, hα is calculated according to the following expression hα = Fsi (Fai−αFsi) ..., And it is determined in step SB5 whether or not hα is positive. To do.

As a result, if hα is positive and YES, the routine proceeds to step SB6, where the first actuator 41, the second actuator 42, and the third actuator of the shock absorbers 1, 2, 3, 4 whose hα is positive. 43, 4th
A control signal is output to the actuator 44, the step motor 27 is rotated clockwise by one step in FIG. 8, and the damping coefficient Dki is D (K + 1) i, which is one larger than the previous damping coefficient Dki.
, That is, while changing to be harder, h
If α is not positive, the process proceeds to step SB7, and hβ = Fsi (Fai−βFsi) ..... hβ is calculated according to the equation, and hβ is calculated at step SB8. Is determined to be negative.

As a result, when hβ is negative and YES, in step SB9, the first actuator 41, the second actuator 42, the third actuator 43, of the shock absorbers 1, 2, 3, 4 whose hβ is negative are Fourth
A control signal is output to the actuator 44 to rotate the step motor 27 one step counterclockwise in FIG. 8, and the damping coefficient Dki is one smaller than the previous damping coefficient Dki D (k-1) i.
To be, that is, to be softer. On the other hand, when hβ is not negative, in step SB10, the stepping motor 27 is not rotated, that is, the damping coefficient Dki is set to the previous damping coefficient Dki.
Keep ki as it is and change it to the next cycle.

Here, α and β are threshold values for preventing a large sound or vibration and a response delay from being generated when the damping coefficient Dki is changed too frequently. There is usually α> 1, 0 <β <1
Is set to.

That is, when Fsi and Fai have the same sign,
Since (Fai−αFsi) in the expression is α> 1, it is more likely to have a different sign from Fsi than when Fsi is not multiplied by α, and as a result, hα is likely to be negative, so attenuation It is difficult to change the coefficient Dki, and further, in the formula (F
ai−βFsi) is 0 <β <1, so that it tends to have the same sign as Fsi as compared to the case where Fsi is not multiplied by β, and as a result, hβ tends to be positive. D
It becomes difficult to change ki.

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 Di close to zero, that is, to change it so that it becomes softer, in order to bring Fsi closer to Fai. Therefore, in the present embodiment, when Fsi and Fai have different signs, both hα and hβ are negative values, and as a result, the control unit 8
As a result, the damping coefficient Dki is changed to D (k-1) i, which is one smaller than the previous damping coefficient Dki, that is, becomes softer, so that it is possible to satisfy this requirement.

Note that the range of the damping coefficient Dki changed in the flowchart of FIG. 11 is limited by the damping coefficient selection control routine according to the running state of FIG. 10, and the step motor 27 is rotated one step clockwise in FIG. Then, the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (k + 1) i.
Even if it should be changed to, the previous damping coefficient Dki is maintained as it is, and the stepping motor 27 is rotated counterclockwise in FIG.
Even if it should be changed to two or two smaller D (k-1) i, if the previous damping coefficient Dki is equal to the lower limit value of the damping coefficient Dki selected in the routine for damping coefficient selection control, damping is performed. The coefficient Dki is retained as it was the previous damping coefficient Dki.

12 to 14 show that when the control mode is selected by the mode selection switch 16,
Changing the damping force characteristics of the left and right front wheel shock absorbers 1, 2 and the left and right rear wheel shock absorbers 3, 4 executed to prevent diagonal vibration by the allowable value setting means 81 and the calculation determining means 80 of the control unit 8. It is a flow chart which shows a control routine.

First, in step SC1 of FIG. 12, the vehicle speed V detection signal detected by the vehicle speed sensor 15, the steering angle θ detection signal detected by the steering angle sensor 65, and the road surface friction coefficient estimated value μ from the ABS 66 are estimated. Input each signal. Next, at step SC2, it is determined whether or not the vehicle speed V is equal to or lower than a fourth predetermined vehicle speed V4. When the determination is YES that the vehicle speed V is equal to or lower than the fourth predetermined vehicle speed V4, it is determined that the vehicle is in a low speed traveling state. Therefore, even if the difference between the damping coefficients Dki of the shock absorbers of the left and right wheels 1, 2 or 3, 4 is large,
Since the steer characteristic does not change so much and diagonal vibration does not matter, the allowable value signal is not output. Therefore, the damping coefficient D of the shock absorber 1, 2, 3, 4 of each wheel is
ki is retained as the previous damping coefficient Dki, and the allowable value signal is not output.

On the other hand, the vehicle speed V is the fourth predetermined vehicle speed V.
When NO is 4 or more, it is determined that the vehicle is running at a medium speed or higher, the process proceeds to step SC3, and if the difference between the damping coefficients Dki of the shock absorbers of the left and right wheels 1, 2 or 3, 4 is large, the steering is stopped. Since the characteristics change and diagonal vibration occurs, it is further determined whether or not the vehicle speed V is equal to or lower than a fifth predetermined vehicle speed V5 in order to determine what value the allowable value should be set to. As a result, the vehicle speed V is the fourth predetermined vehicle speed V4.
Yes, but is below the fifth predetermined vehicle speed V5 YES
If so, the process proceeds to step SC4, and it is determined whether the estimated value μ of the road surface friction coefficient is equal to or less than a predetermined value μ0.

As a result, when the vehicle is traveling on a road surface having a small road surface friction coefficient such that the estimated value μ of the road surface friction coefficient is less than or equal to a predetermined value μ0, the shock absorbers 1 for the left and right wheels are
Even if the difference between the damping coefficients Dki of 2 or 3 or 4 is not so large, load movement is likely to occur and running stability may be impaired. Therefore, in order to determine how much load movement is likely to occur, step SC5 At, it is determined whether the absolute value | θ | of the steering angle θ is greater than or equal to the first predetermined steering angle θ1.

As a result, if the absolute value | θ | of the steering angle θ is greater than or equal to the first predetermined steering angle θ1, YES, step SC6
, The absolute value | θ | of the steering angle θ is the second predetermined steering angle θ2
It is determined whether or not the above. As a result, the absolute value of the steering angle θ | θ
When | is YES which is equal to or larger than the second predetermined steering angle θ2, it is recognized that the vehicle is traveling on a road surface having a small road surface friction coefficient and the steering wheel is largely operated, and the vehicle is in a traveling state in which load movement is very likely to occur. In step SC7, the tolerance value setting means 81 sets the tolerance value t to t1, for example 1, and outputs the tolerance value signal to the operation determination means 80 (step SC8 in FIG. 15). On the other hand, the determination in step SC6 is
When the absolute value | θ | of the steering angle θ is less than the second predetermined steering angle θ2, it means that the vehicle is traveling on a road surface having a small road surface friction coefficient, but the steering wheel is not operated so much. Since it is recognized, the allowable value t is set to t in step SC9.
2, for example, set to 2, and the allowable value signal is calculated by the determination means 8
Output to 0.

On the other hand, when the absolute value | θ | of the steering angle θ in step SC5 is less than the first predetermined steering angle θ1, NO, the vehicle is running on a road surface having a small road surface friction coefficient, Since it is recognized that the vehicle is in a traveling state in which it is not largely operated, the allowable value t is set to t3 in
For example, the value is set to 3 and the allowable value signal is output to the calculation determining means 80.

On the other hand, if the determination in step SC4 is NO, that is, the estimated value μ of the road surface friction coefficient exceeds the predetermined value μ0, in step SC11 the absolute value | θ | of the steering angle θ is set to the second predetermined value. It is determined whether the steering angle is less than θ2, and the steering angle θ
If the absolute value | θ | of is less than the second predetermined steering angle θ2, the allowable value t is set to t3 in step SC12 and the allowable value signal is output to the calculation determining means 80, while the steering angle θ Absolute value | θ | exceeds the second predetermined steering angle θ2 YES
If so, it is determined in step SC13 whether the absolute value | θ | of the steering angle θ is greater than or equal to the third predetermined steering angle θ3.

As a result, when the absolute value | θ | of the steering angle θ is equal to or larger than the third predetermined steering angle θ3, it is recognized that the steering wheel is largely operated and the load is very likely to move. Therefore, the allowable value t is set to t in step SC14.
It is set to 1 and the allowable value signal is output to the calculation determining means 80. On the other hand, when the determination in step SC13 is NO, that is, when the absolute value | θ | of the steering angle θ is less than the third predetermined steering angle θ3, the allowable value t is set to t2 in step SC15 and the allowable value signal is set. Is output to the calculation determining means 80.

On the other hand, when the determination in step SC3 is NO, that is, when the vehicle speed V exceeds the fifth predetermined vehicle speed V5 and the vehicle is in the restricted traveling state, the steer characteristic changes more than in the medium speed traveling state. Since it is easy to perform and diagonal vibration is more likely to occur, steps SC16 to SC18, step SC22
In step SC24, the same judgment as in the medium speed running state is performed, and the allowable value t is smaller than that in the medium speed running state in steps SC19 to SC21, step SC23, step SC25 and step SC26, for example, one by one. The allowable value signal is set to a small value, and the allowable value signal is calculated and determined by the calculation determining means 8
Output to 0.

When the allowable value signal from each of the above steps is input to step SC8 of the calculation determining means 80, the difference between the damping coefficients Dki of the left and right shock absorbers 1, 2 and 3, 4 is calculated in step SC8. Absolute value of | Dkl
-Dkr | determines whether or not the allowable value t is exceeded, and the above absolute value | Dkl-Dkr | exceeds the allowable value t YES
In step SC27, in step SC27, a control signal is output to select one of the shock absorbers 1, 2 and 3 and 4 for the left and right wheels, whichever has a smaller damping coefficient Dki and is softer than the step motor. 27 is rotated clockwise by one step to change the damping coefficient Dki to D (k + 1) i which is one larger than the previous damping coefficient Dki, while the above absolute value | Dkl-Dkr | When the value is less than t,
No control signal is output.

Here, the range of the damping coefficient Dki changed in the flowcharts of FIGS. 12 to 14 is shown in FIG.
Is limited by the routine of the damping coefficient selection control according to the change range of the step motor 27, and the step motor 27 is rotated clockwise by one step in FIG. 8 to increase the damping coefficient Dki by one larger than the previous damping coefficient Dki by D (k + 1). Even if it should be changed to i, if the previous damping coefficient Dki is equal to the upper limit value of the damping coefficient Dki selected by the damping coefficient selection control routine, the damping coefficient Dki
Ki is retained as the previous damping coefficient Dki.

FIG. 15 shows the mode selection switch 16
When the control mode is selected by, the shock absorbers 1 and 2 of the left and right front wheels and the shock absorbers 1 and 2 of the left and right rear wheels which are executed to prevent diagonal vibration by the allowable value changing means 82 and the calculation determining means 80 of the control unit 8 It is a flow chart which shows the routine of damping force characteristic change control of shock absorbers 3 and 4. Further, FIG. 16 is a map showing a change characteristic of the gain of the sprung unsprung relative speed with respect to the vibration frequency, and FIG. 17 is a map showing a change characteristic of the gain of the sprung absolute speed with respect to the vibration frequency.

In FIG. 15, first, in step SD1,
It is determined whether or not the gain Grev of the sprung sprung unsprung relative speed shown in FIG. 16 is smaller than a predetermined value Grev0. When the gain Grev of the sprung unsprung relative speed is smaller than the predetermined value Grev0 is YES, It is determined that the gain Srev of the sprung relative velocity is in the vibration frequency region other than the sprung mass resonance point ω1 and the unsprung mass resonance point ω2, and the process proceeds to step SD2, as shown in FIG.
It is determined whether or not the sprung mass absolute velocity gain Gav shown in 7 is larger than a predetermined value Gav0. Then, if the determination is YES that the gain Gav of the sprung mass absolute velocity is larger than the predetermined value Gav0, the gain Gre of the sprung mass unsprung relative velocity Gre
It is determined that v is in the ultra-low frequency vibration region where the sprung mass resonance point ω1 has not been reached, the process proceeds to step SD3, the allowable value t is changed to t3, and the allowable value signal is output to the calculation determining means 80. . On the other hand, when the determination in step SD2 is NO that the gain Gav of the sprung absolute velocity is smaller than the predetermined value Gav0, the gain Grev of the sprung unsprung relative velocity becomes smaller than the unsprung resonance point ω2. It is determined that the high-frequency vibration region is moving to the ultra-high-frequency vibration region, the process proceeds to step SD4, and the allowable value t is set to the damping coefficient Dki of the left and right wheel shock absorbers 1, 2 and 3, 4.
The setting value is changed to t ∞ where the difference is not regulated, and the allowable value signal is output to the calculation determining means 80.

On the other hand, if the determination at step SD1 is NO, that is, the gain Srev between unsprung and unsprung relative speeds is greater than a predetermined value Grev0, the gain G of unsprung unsprung relative velocity is G.
It is determined that rev is in the vibration frequency range including the sprung resonance point ω1 and the unsprung resonance point ω2, the process proceeds to step SD5, where the allowable value t is set to the damping coefficient Dki of the shock absorbers 1, 2 and 3 and 4 for the left and right wheels. Is in-phase, that is, the setting is changed to t0 which regulates so that the difference becomes 0, and the allowable value signal is output to the calculation determining means 80.

Then, the allowable value signal from each of the above steps is the step SC8 of the flow of the operation judging means 80 of FIG.
In step SC8, it is determined whether or not the absolute value | Dkl-Dkr | of the difference between the damping coefficients Dki of the left and right shock absorbers 1, 2 and 3, 4 exceeds the allowable value t, and YES If so, a control signal is output in step SC27 to output shock absorbers 1, 2 and 3 for the left and right wheels.
8 shows the step motor 27 of the shock absorber 1, 2, 3 or 4 which has a smaller damping coefficient Dki and is softer.
While rotating one step clockwise to change the damping coefficient Dki to D (k + 1) i, which is one larger than the previous damping coefficient Dki.
When NO, the control signal is not output.

Here, the range of the damping coefficient Dki changed in the flowcharts of FIGS. 14 and 15 is shown in FIG.
Similarly, the damping coefficient selection control routine according to the change range of the
Even when the value should be changed to D (k + 1) i, which is larger by one, if the previous damping coefficient Dki is equal to the upper limit value of the damping coefficient Dki selected by the routine of the damping coefficient selection control, the damping coefficient Dki is changed. The previous damping coefficient Dki is retained.

Therefore, step S of the above flow chart.
By D1 and step SD2, the input frequency detecting means 83 for detecting the frequency range of the input applied to the vehicle body is configured according to the change characteristics of both gains of the sprung mass relative speed and the sprung mass absolute speed with respect to the vibration frequency. ing. Further, in steps SD3, SD4 and SD5, the shock absorber 1 between the left and right wheels is based on the determination signal from the input frequency detecting means 83.
Absolute value of the difference in damping coefficient of 2 or 3, 4 | Dkl-Dkr |
That is, the allowable value changing means 82 for changing the allowable value t is configured.

Therefore, in the above embodiment, the absolute value | Dkl-Dkr | of the difference between the damping coefficients Dki of the left and right wheel shock absorbers 1, 2 and 3 exceeds the allowable value t, and the steer characteristic changes. When there is a possibility that diagonal vibration will occur, the allowable value changing means 92 determines the damping coefficient of the shock absorbers 1, 2 and 3 and 4 between the left and right wheels in accordance with the determination signal from the input frequency detecting means 91. The control of the damping coefficient Dki of the shock absorbers 1, 2 and 3, 4 for the left and right wheels by the control unit 8 is changed so as to change the absolute value | Dkl−Dkr | (allowable value) of the difference.

That is, when the gain Grev of the sprung unsprung relative speed is smaller than the predetermined value Grev0 and the gain Gav of the sprung absolute speed is larger than the predetermined value Gav0,
Since it is determined that the gain Grev of the unsprung relative speed between unsprung parts is in the very low frequency vibration region where the sprung resonance point ω1 has not been reached and the allowable value t is set to t3, the shock absorber 1 for the left and right wheels is changed. , 2 and 3, 4 the absolute value of the difference between the damping coefficients Dki | Dkl−Dkr | becomes large, and the damping coefficients of the shock absorbers 1, 2 and 3, 4 on the left and right wheels are the damping force of the harder shock absorber. The characteristics are regulated slightly to the soft side, and the damping force characteristics of the softer shock absorber are regulated to the hard side. It is possible to effectively reduce the diagonal vibration. Moreover, when the gain Grev of the sprung unsprung relative speed is larger than the predetermined value Grev0, the gain Srev of the unsprung unsprung relative speed is in the low frequency vibration region including the sprung resonance point ω1 and the unsprung resonance point ω2. Since the allowable value t is determined so that the difference between the damping coefficients Dki of the left and right wheel shock absorbers 1, 2 or 3, 4 is 0, the left and right wheel shock absorbers 1, 2 and 3 are regulated. , 4 have the same phase, and it is possible to improve the steering stability and effectively reduce the diagonal vibration in the low frequency vibration region including the sprung resonance point ω1 and the unsprung resonance point ω2.

On the other hand, the gain G of the relative speed between the sprung part and the unsprung part is
When rev is smaller than the predetermined value Grev0 and the gain Gav of the sprung absolute velocity is smaller than the predetermined value Gav0, the gain Grev of the sprung unsprung relative velocity is becoming smaller than the unsprung resonance point ω2. Since the allowable value t is set and changed to t∞ because it is determined to be in the region moving from the high frequency vibration region to the ultra high frequency vibration region, the damping coefficients of the left and right wheel shock absorbers 1, 2 and 3, 4 are set. The absolute value of the Dki difference | Dkl-Dkr | becomes so large that it is not regulated, and the shock absorbers 1, 2 and 3, on the left and right wheels are
The damping coefficient of No. 4 is maintained as the previous damping coefficient Dki, and it is possible to improve both the riding comfort and the posture stability in the high frequency region and the ultra high frequency region.

The present invention is not limited to the above embodiment, but includes various other modifications.
For example, in the above embodiment, when the gain Grev of the sprung sprung unsprung relative speed is larger than the predetermined value Grev0, the allowable value t
Although the damping coefficient Dki of the shock absorbers 1, 2 or 3, 4 for the left and right wheels is controlled in phase by setting t0 to t0, the gain Grev of the sprung sprung unsprung relative speed is smaller than the predetermined value Grev0 and the sprung absolute value. Speed gain Gav is a predetermined value G
When the value is larger than av0, the allowable value smaller than the changed allowable value t3, that is, the allowable value t may be changed to t1 or t2. In this case as well, the sprung resonance point ω1 and the unsprung resonance are set. It is possible to improve the steering stability in the low frequency region including the point ω 2 and effectively reduce the diagonal vibration.

Further, in the above embodiment, the allowable value t is set to t3 when the gain Srev between the sprung unsprung relative speeds is smaller than the predetermined value Grev0 and the gain Savant absolute speed Gav is larger than the predetermined value Gav0. Although the setting was changed, in this region, the gain Grev of the sprung unsprung relative speed is set to the predetermined value Gre.
Since it is smaller than v0, the allowable value t may be changed to t1. In this case, when the gain Grev of the sprung sprung unsprung relative speed is larger than the predetermined value Grev0, that is, the sprung portion In the low-frequency vibration region including the resonance point ω1 and the unsprung resonance point ω2, it is necessary to hold the allowable value t at t0 and control the damping coefficients Dki of the shock absorbers 1, 2 and 3, 4 for the left and right wheels in phase.

Further, in the above embodiment, the road surface friction coefficient μ
Is estimated based on the detection signal of ABS66,
The road surface friction coefficient μ may be estimated based on the wiper signal, and whether or not the road is a bad road is determined based on the variation amount of the vertical acceleration ai within a predetermined time. The bad road may be determined by another method.

Further, in the above embodiment, the step motor 2 is used in the traveling state in which it is determined that the ride comfort should be emphasized.
Rotate 7 in two steps and set the damping coefficient Dki to the previous damping coefficient D
The step motor 27 is changed to D (k-2) i, which is two smaller than ki, but the step motor 27 may be rotated in three or more stages.

Further, in the above embodiment, the two stopper pins 55, 56 are formed in the rotor 51 of the step motor 27, and the grooves 57, 58 engaging with the two are formed in the lid 53 of the step motor 27. There are stopper pins 55, 5
6 is formed on the lid 53 of the step motor 27, and grooves 57 and 58 engaging with the lid 53 are formed on the rotor 5 of the step motor 27.
1, and the stopper pins 55, 5
6 is formed on the rotor 51 of the step motor 27, and the other is formed on the lid 53 of the step motor 27.
The grooves 57 and 58 formed on the cover 53 of the step motor 27 are engaged with the other stopper pins 55 and 56 formed on the cover 53 of the step motor 27. The grooves 57 and 58 may be formed in the rotor 51 of the step motor 27.

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

[Brief description of drawings]

FIG. 1 is a perspective view showing a component layout of a suspension device.

FIG. 2 is a vertical sectional front view showing a main part of a shock absorber.

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

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

FIG. 5 is a schematic diagram showing a vibration model of a suspension device.

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

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

FIG. 8 is a bottom view of the lid.

FIG. 9 is a block diagram of a control unit of the suspension device.

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

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

FIG. 12 is a flowchart showing a first half part of a routine of a damping force characteristic change control of the left and right wheel shock absorbers executed by the allowable value setting means.

FIG. 13 is a flowchart showing a second half of a basic routine of the damping force characteristic change control of the left and right wheel shock absorbers executed by the allowable value setting means.

FIG. 14 is a flowchart showing a routine for damping force characteristic change control of the left and right wheel shock absorbers, which is executed by a calculation determining means.

FIG. 15 is a flowchart showing a routine of damping force characteristic change control of the left and right wheel shock absorbers executed by the allowable value changing means.

FIG. 16 is a characteristic diagram showing a change characteristic of a gain of relative sprung mass velocity with respect to a vibration frequency.

FIG. 17 is a characteristic diagram showing a change characteristic of a gain of an absolute sprung speed with respect to a vibration frequency.

[Explanation of symbols]

1,2,3,4 shock absorber 6,7 wheels 8 control unit (control means) 9 car body 82 Allowable value changing means 83 Input frequency detecting means

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[Procedure amendment]

[Submission date] October 24, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system, and more particularly to an improvement of a suspension system provided with a shock absorber having a variable damping force characteristic between a sprung portion and an unsprung portion.

[0002]

2. Description of the Related Art Generally, a suspension device for a vehicle is equipped with a shock absorber for damping vertical vibration of a wheel between a sprung portion on the vehicle body side and an unsprung portion on the wheel side. In this shock absorber, as the damping force characteristic variable type, the damping force characteristic (characteristic with different damping coefficient) can be changed in two steps of high and low, and the damping force characteristic can be changed in multiple steps or continuously. There are various things such as things.

Basically, such a damping force variable type shock absorber control method basically damps the shock absorber when the damping force generated by the shock absorber acts in the vibration direction with respect to the vertical vibration of the vehicle body. Excitation energy transmitted to the spring by changing the damping force of the shock absorber to the high damping side (ie hard side) when the damping force is on the low damping side (ie soft side) and the damping force acts in the damping direction. On the other hand, the damping energy is increased to improve both the riding comfort and the running stability of the vehicle.

Various methods have been proposed for determining whether the damping force of the shock absorber acts in the vibration direction of the sprung vertical vibration or in the vibration damping direction.
For example, in Japanese Patent Laid-Open No. 60-248419, it is examined whether the sign of the relative displacement between the sprung and unsprung parts and the sign of the relative velocity between the sprung and unsprung parts, which is the differential value, match. There is disclosed a method of determining the vibration direction when they match, and determining the vibration direction when they do not match.

[0005]

However, 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 variable-damping-type shock absorber whose characteristics are changed and controlled, the damping force characteristics of the shock absorber are changed and controlled independently for each wheel, so that there is a large difference in the damping force characteristics of the left and right wheels. May occur, and as a result, there is a problem that an unfavorable change occurs in the steer characteristic or diagonal vibration occurs.

The present invention has been made in view of the above points, and an object thereof is to cause a large difference in the damping force characteristics of the shock absorbers of the left and right wheels based on the frequency of the input applied to the vehicle body. Control not to
It is intended to prevent undesired changes in the steer characteristics and effectively prevent the occurrence of diagonal vibration.

[0007]

In order to achieve the above-mentioned object, a solution means provided by the invention according to claim 1 is to provide a shock absorber between the sprung and unsprung portions of each wheel, and to displace the sprung portion. It is premised on a suspension device for a vehicle that changes and controls the damping force characteristic of the shock absorber according to the relative relationship between the speed and the unsprung displacement speed. Then, the control means for changing and controlling the damping force characteristics of the shock absorber of each wheel, the input frequency detecting means for detecting the frequency of the input applied to the vehicle body, and the signals from the input frequency detecting means, The configuration is provided with a permissible value changing means for changing the control of the control means so as to change the permissible value of the difference in the damping force characteristics of the shock absorbers between the wheels.

Further, a solution means taken by the invention according to claim 2 is dependent on the invention according to claim 1, wherein the allowable value changing means is a damping force characteristic of the shock absorber between the left and right wheels. The allowable value of the difference is greatly changed when the frequency of the input applied to the vehicle body is in the high frequency vibration area, while it is changed to be small when the frequency of the input applied to the vehicle body is in the low frequency vibration area.

Further, the solution means taken by the invention according to claim 3 is dependent on the invention according to claim 1, wherein the allowable value changing means is a damping force characteristic of the shock absorber between the left and right wheels. Is independently controlled by increasing the allowable value when the input frequency applied to the vehicle body is in the high-frequency vibration region, while setting the allowable value to 0 when the input frequency applied to the vehicle body is in the low-frequency vibration region. It is controlled in the same phase.

[0010]

With the above construction, in the invention according to claims 1 and 2, the allowable value changing means allows the difference in damping force characteristics of the shock absorbers between the left and right wheels according to the signal from the input frequency detecting means. The control of the control means is changed to change the value. For example, when the frequency of the input applied to the vehicle body is in the high-frequency vibration region, the allowable value that allows the difference in the damping force characteristics of the shock absorbers between the left and right wheels is changed to be large, and the shock absorbers of the left and right wheels are The damping force characteristics are regulated within a range of large allowable values, such as changing the damping force characteristics of a harder shock absorber to a slightly soft side, and changing the damping force characteristics of a softer shock absorber to a slightly hard side. The ride comfort and posture stability in the vibration region are both good. On the other hand, when the frequency of the input applied to the vehicle body is in the low-frequency vibration region, the allowable value that allows the difference in the damping force characteristics of the shock absorbers between the left and right wheels is changed to be smaller, and the shock absorbers for the left and right wheels are changed. The damping force characteristic of is regulated within a small allowable value range by changing the damping force characteristic of a harder shock absorber to the soft side and the damping force characteristic of a softer shock absorber to the hard side.
The steering stability becomes good in the low frequency vibration region, and the diagonal vibration is effectively reduced.

Further, in the invention according to claim 3, the damping force characteristics of the shock absorbers on the left and right wheels are independently controlled, for example, when the input frequency applied to the vehicle body is in a very high frequency vibration region. Therefore, the damping force characteristics of the shock absorbers on the left and right wheels do not change the damping force characteristics of the softer shock absorber while maintaining the damping force characteristics of the harder shock absorber. Are regulated (controlled) by, and both the riding comfort and the posture stability in the super high frequency vibration region are improved. On the other hand, when the input frequency applied to the vehicle body is in a very low frequency vibration region, the damping force characteristics of the shock absorbers on the left and right wheels are controlled in phase, and the damping force characteristics of the shock absorbers on the left and right wheels are The difference is changed so as to be closer to each other so that the difference becomes 0, the steering stability becomes good in the extremely low frequency vibration region, and the diagonal vibration is effectively reduced.

[0012]

As described above, according to the vehicle suspension device of the first aspect of the present invention, the difference between the damping force characteristics of the shock absorbers between the left and right wheels according to the input frequency applied to the vehicle body is changed by the allowable value changing means. Since the control of the control means is changed to increase or decrease the allowable value of, it is possible to achieve both ride comfort and posture stability in the high frequency vibration region, while manipulating stability and diagonal vibration in the low frequency vibration region. Can be effectively reduced.

According to the vehicle suspension device of the second aspect of the invention, the allowable value changing means allows the damping force characteristic of the shock absorber between the left and right wheels to fall within a large allowable value range in the high frequency vibration region. Control the control means to improve both riding comfort and posture stability in the high frequency vibration region, while allowing a small damping force characteristic of the shock absorber between the left and right wheels in the low frequency vibration region. It is possible to effectively control the diagonal vibration while restricting the control of the control means within the range of values to improve the steering stability in the low frequency vibration region.

Further, according to the vehicle suspension device of the third aspect of the invention, the damping force characteristics of the shock absorbers on the left and right wheels are independently controlled within a very large allowable range in the ultra-high frequency vibration region. In this way, both the riding comfort and the posture stability in the super high frequency vibration region can be improved, while the difference in the damping force characteristics of the shock absorbers on the left and right wheels becomes zero in the super low frequency vibration region. It is possible to effectively reduce the diagonal vibration while improving the steering stability in the extremely low frequency vibration region by performing the in-phase control.

[0015]

Embodiments of the present invention will be described below with reference to the 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 system 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 as 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. is there.

Further, on the spring of the vehicle body 9, a first acceleration sensor 11 for detecting the vertical acceleration on the spring of each wheel,
A second acceleration sensor 12, a third acceleration sensor 13, a fourth acceleration sensor 14, and a vehicle speed sensor 15 for detecting the vehicle speed are provided in the meter of the instrument panel. Reference numeral 16 denotes a mode selection switch that allows the driver to switch the control of the damping force characteristics of the shock absorbers 1, 2, 3, 4 to either the hard mode, the soft mode or the control mode. Then, when the hard mode is selected by the mode selection switch 16, only the damping coefficient in the range in which the damping force characteristic becomes hard is selected, and the shock absorbers 1, 2, 3, 3 are only within the range.
The change control of the damping force characteristic of No. 4 is performed. Further, when the soft mode is selected, only the damping coefficient in the range where the damping force characteristic becomes soft is selected, and the damping force characteristic change control of the shock absorbers 1, 2, 3, 4 is controlled only within that range. Is done. Further, when the control mode is selected, the change control of the damping force characteristics of the shock absorbers 1, 2, 3, 4 is performed in a predetermined manner according to the map or table stored in the control unit 8 in advance. Has become.

FIG. 2 is a schematic sectional view of a 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 is
A cylinder 21 is provided, and in the cylinder 21, a piston unit 22 in which a piston and a piston rod are integrally connected is slidably fitted. The cylinder 21 and the piston unit 22 are connected to the unsprung part and the sprung part, respectively.

The piston unit 22 has two orifices 23 and 24 formed therein. One orifice 2
3 is always open, and the other orifice 24 has a passage area of 10 by the first actuator 41.
It is formed so that it can be changed in stages.

FIG. 3 is an exploded schematic perspective view of the first actuator 41 provided in the shock absorber 1, and FIG.
And as shown in FIG. 3, the first actuator 41
Includes a shaft 26 rotatably provided in a sleeve 25 fixed to the piston unit 22, and a shaft 2
6, a step motor 27 that rotates 6 and a first orifice plate 29 that is integrally attached to the lower end of the shaft 26 and has nine circular holes 28 along the circumference of the step motor 27 and the lower end of the sleeve 25. The second orifice plate 31 is provided and has an arc-shaped long hole 30 formed along the circumference thereof. 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 are the rotation of the shaft 26 and the first orifice plate 29 by the rotation of the step motor 27. According to 9 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, only the structure of the shock absorber 1 is shown, but the shock absorbers 2, 3 and 4 provided for other wheels are also the shock absorber 1 shown in FIG. 3 shows the same structure as the above, and includes a second actuator 42, a third actuator 43, and a fourth actuator 44 similar to those shown in FIG. 3, respectively.

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 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, 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, the relative displacement speed ( Xs-Xu
) Is shown. As shown in FIG. 4, the damping force characteristics of the shock absorbers 1, 2, 3, 4 have a damping coefficient D1.
By selecting any one of D10 to D10, it is possible to change in 10 steps. Figure 4
In the above, D1 represents the damping coefficient that produces the softest damping force, and D10 represents the damping coefficient that produces the hardest damping force. Where the damping coefficient Dk
(K is a positive integer, 1 to 10) is (10 to 10) out of the nine circular holes 28 formed in the first orifice plate 29.
-I) The number of circular holes 28 is equal to that of the second orifice plate 31.
It is selected when it communicates with the long hole 30 formed in. Therefore, the damping coefficient D1 is
It is selected when all nine circular holes 28 of the orifice plate 29 are in communication with the elongated holes 30 of the second orifice plate 31, and the damping coefficient D10 is equal to that of the nine circular holes 28 of the first orifice plate 29. Is not selected to communicate with the long hole 30 of the second orifice plate 31.

FIG. 5 is a vibration model diagram of a vehicle suspension system according to an embodiment of the present invention. Ms is an unsprung mass, mu is an unsprung mass, xs is an unsprung displacement, xu is an unsprung displacement, ks. Is the spring constant of the coil spring 7, kt is the spring constant of the tire, Dk is the shock absorbers 1, 2,
The attenuation coefficients are 3 and 4.

FIG. 6 is a schematic perspective view of the step motor 27. The step motor 27 includes a tubular body 50 and a tubular 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 Corresponding to this, a plurality of rectangular teeth are formed, the stator 52,
The solenoid 54 is wound. 2 for rotor 51
Book stopper pins 55 and 56 are formed, and as shown in FIG. 8, the lid 53 has stopper pins 55 and 56.
Two grooves 57 and 58 are formed in the circumferential direction at positions corresponding to. The groove 57 is for engaging with the stopper pin 55 formed on the rotor 51 to control the movable range of the step motor 27, while the groove 58 is for the stopper pin 56.
By engaging the stopper pins 55 and 56 with the grooves 57 and 58, it is possible to align the center of gravity of the rotor 51 with the center of rotation when the lid 53 is covered. To do. Therefore, the lid 53
The circumferential angle of the groove 57, 58 seen from the center of the groove is
8 is larger than the groove 57, and the grooves 57 and 58 are formed so that the movable range of the step motor 28 is determined exclusively by the groove 57. 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 and the damping force characteristic becomes smaller. It ’s getting softer,
When the rectangular teeth of the rotor 51 are moved to a position facing the adjacent rectangular teeth of the stator 52, that is, when the step motor 27 rotates one step, the damping coefficient Dk changes by one. ing. 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, and the shock absorber 1 generates the hardest damping force, while
When 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 becomes D1, and the shock absorber 1 produces 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.

In FIG. 9, the control unit 8 constituting the control system of the vehicle suspension system according to the embodiment of the present invention includes a calculation determining means 80 and an allowable value setting means 81.
And the allowable value changing means 82, and the calculation determining means 80 includes a first pressure sensor 61 and a second pressure sensor 6 provided on the shock absorbers 1, 2, 3 and 4, respectively.
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
(Here, i indicates each wheel, i = 1, 2, 3, 4) detection signal, first acceleration sensor 11, second acceleration sensor 12, third acceleration sensor 13, fourth acceleration The detection signal of the vertical acceleration ai on the spring detected by the sensor 14, the first vehicle height sensor 71, the second vehicle height sensor 72, and the third vehicle height sensor 72.
The detection signal of the relative displacement between the sprung portions ( xs-xu ) detected by the vehicle height sensor 73 and the fourth vehicle height sensor 74 and the detection signal of the vehicle speed V detected by the vehicle speed sensor 15 are input. Further, the allowable value setting means 81 has a detection signal of the vehicle speed V detected by the vehicle speed sensor 15, a detection signal of the steering angle θ detected by the steering angle sensor 65, and a road surface from the anti-braking system (ABS) 66. The estimated signals of the estimated value μ of the friction coefficient are input. Further, the calculation determining means 80 includes the first to fourth vehicle height sensors 71 to 74.
The sprung unsprung relative displacement ( xs-xu ) signal detected by is differentiated by a numerical differentiation method or the like to calculate the sprung unsprung relative velocity ( Xs-Xu ), and at the same time, the first to fourth acceleration sensors 11 Up to vertical acceleration ai on the spring detected by ˜14 is integrated by a numerical integration method or the like to calculate displacement speed Xsi on the spring.
(Σai) is calculated, and a map showing the change characteristic of the gain of the sprung unsprung relative speed with respect to the vibration frequency of FIG. 16 and the map showing the change characteristic of the gain of the sprung absolute speed with respect to the vibration frequency of FIG. Input frequency detecting means 83 for detecting the frequency of the input applied to the vehicle body based on
Is provided, and the determination signal determined by the input frequency detecting means 83 is input to the allowable value changing means 82. In this case, since the displacement speed Xsi on the spring is the absolute spring speed at the positions of the first to fourth acceleration sensors 11 to 14, it is converted and used as the absolute spring speed at the positions of the shock absorbers 1 to 4.

The calculation determining means 80, based on the detection signal of the vertical acceleration ai and the detection signal of the vehicle speed V,
According to a map or table stored in advance, a damping coefficient Dki that determines the damping force characteristics of the shock absorbers 1, 2, 3, 4 of each wheel is calculated, a control symbol is generated, and the first actuator 41, 2 actuator 42, 3rd actuator 43, 4th actuator 4
4 to control the damping force characteristics of the shock absorbers 1, 2, 3 and 4, and when the allowable value signals are input from the allowable value setting means 81 and the allowable value changing means 82, the shocks of the left and right front wheels are received. Absolute value of the difference between the damping coefficients Dki of the absorbers 1 and 2 and the left and right rear wheel shock absorbers 3 and 4 | Dkl-Dkr | (where l = 1, 3, r =
2 and 4) is greater than or equal to the allowable value t, the damping coefficient D
The damping coefficient Dki of the shock absorbers 1, 2, 3, 4 for wheels with small ki is one larger than the previous damping coefficient Dki by D (k
+1) i, a control symbol is generated and output to the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44 to attenuate the shock absorbers 1, 2, 3, and 4. Control force characteristics. Further, the allowable value setting means 81 is based on the detection signal of the vehicle speed V detected by the vehicle speed sensor 15, the detection signal of the steering angle θ detected by the steering angle sensor 65, and the estimation signal of the estimated value μ of the road surface friction coefficient from the ABS 66. , An allowable value of the difference between the damping coefficients Dki of the shock absorbers 1, 2, 3, 4 of the left and right wheels and the front and rear wheels is calculated according to a map or a table stored in advance, and the allowable value signal is output to the calculation determining means 80. . Further, the permissible value changing means 82 changes the permissible value of the difference between the damping coefficients Dki of the shock absorbers 1, 2, 3, 4 of the left and right wheels and the front and rear wheels according to the judgment signal judged by the input frequency detecting means 83. The allowable value change signal is output to the calculation determining means 80.

Here, the damping force Fsi takes a continuous value, and when it acts upward on the sprung, that is, when it is contracted between the sprung and unsprung, it has a positive value and when it acts downward, that is, the spring. It is set so as to have a negative value when the upper part and the unsprung part are extended, and the vertical acceleration ai on the spring is set.
Is set to a positive value when facing upward and a negative value when facing downward.

FIG. 10 is a flowchart showing a routine of the damping coefficient selection control according to the traveling state, which is carried out by the control unit 8 when the control mode is selected by the mode selection switch 16. In the coefficient selection control routine, the damping coefficient Dki is changed too frequently, and as a result, the change control is performed according to the running state in order to prevent a large noise or vibration from occurring or a response delay. This limits the range of the damping coefficient Dki to be obtained.

In FIG. 10, first, in step SA1, the vehicle speed V detected by the vehicle speed sensor 15 is input, and the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14 are input. Input the vertical acceleration ai on the spring detected by.

Then, in step SA2, the vehicle speed V
Is the first predetermined vehicle speed V1 which is a low speed value, for example, 3 km / h
Determines whether or not the on the following.

As a result, the vehicle speed V becomes the first predetermined vehicle speed V1.
In case of NO below, the routine proceeds to step SA3, where the vehicle speed V is extremely low. Therefore, in order to prevent the Scott and the braking dive, the damping coefficient of the shock absorbers 1, 2, 3 and 4 is made hard so that the damping force characteristic becomes hard. Fix Dki to D8i.
Therefore, the damping coefficient Dki is because is fixed to D8i, change control of the damping force characteristic by attenuation coefficient selection control routine shown in FIG. 10 is not performed.

On the other hand, when the vehicle speed V exceeds the first predetermined vehicle speed V1, YES, the routine proceeds to step SA4, where the absolute value of the vertical acceleration on the sprung ai exceeds the predetermined value ai0. Determine if it is medium or not.

As a result, the vertical acceleration ai on the spring
If it is determined that the vehicle is traveling on a rough road in which the absolute value of exceeds a predetermined value ai0, the process proceeds to step SA5, where the vehicle speed V is the third value.
The predetermined vehicle speed V3, for example, 50 km / h or more is determined.

When the determination at step SA5 is YES, that is, when the vehicle speed V is equal to or higher than the third predetermined vehicle speed V3, at step SA6, the damping force characteristics are comparatively emphasized with an emphasis on improving running stability. The damping coefficient Dki is set in the range of D5i to D7i in order to control the change within the hard range. As a result, in the Le <br/> routine of attenuation coefficient selection control shown in FIG. 10, the damping coefficient Dki is, D5i becomes the lower limit, even if satisfied even further conditions to be changed to the soft, damping coefficient Dki is held in D5i, while D7i becomes the upper limit value, and the damping coefficient Dki is held in D7i even if a condition to be changed to a harder condition is satisfied.

On the other hand, when the determination in step SA5 is NO, that is, when the vehicle speed V is less than the predetermined vehicle speed V3, the process proceeds to step SA7, in which both traveling stability and ride comfort can be improved. Since it is necessary , the damping coefficient Dki is set in the range of D3i to D7i so that the damping force characteristic can be changed and controlled within a range from a relatively soft state to a hard state. Accordingly, the damping coefficient selection control routine shown in FIG. 10, the damping coefficient D
For ki, even if D3i becomes the lower limit value and the condition to be changed to a softer condition is satisfied, the damping coefficient Dki is held at D3i, while D7i becomes the upper limit value, and even if it is harder to change. Even if is satisfied, the damping coefficient Dki is held at D7i.

On the other hand, if the determination in step SA4 is NO, that is, the absolute value of the vertical acceleration ai on the sprung is less than or equal to the predetermined value ai0, the process proceeds to step SA8, where a normal road is not a bad road Since it is considered that the vehicle is traveling, the vehicle speed V is further set to the second predetermined vehicle speed V in step SA8.
2. For example, it is determined whether the speed is 30 km / h or less.

As a result, when it is determined that the vehicle speed V is in the low speed traveling state of the second predetermined vehicle speed V2 or less, YES is emphasized in step SA9 to improve the riding comfort, so that the damping force characteristic is relatively soft. The damping coefficient Dki is set in the range of D1i to D3i so that the change control is performed within the range.
Accordingly, in Le chromatography <br/> Chin damping coefficient selection control shown in FIG. 10, the damping coefficient Dki is, when the D1i, the damping coefficient Dki even if they further conditions to be changed software is established D1i On the other hand, D3i becomes the upper limit value, and the damping coefficient Dki is held at D3i even if the condition to be changed to a harder condition is satisfied.

On the other hand, when the determination in step SA8 is NO, that is, when the vehicle speed V exceeds the second predetermined vehicle speed V2, the vehicle speed V is further increased in step SA10.
Is a fourth predetermined vehicle speed V4, for example, 60 km / h or less.

As a result, when it is determined that the vehicle speed V is in the relatively medium speed running state which is equal to or lower than the fourth predetermined vehicle speed V4, the process proceeds to step SA11 to make two requests to improve running stability and riding comfort. Since it is necessary to achieve both of the above, it is necessary to set the damping coefficient Dki within the range of D2i to D6i in order to change and control the damping force characteristics within a range from a relatively soft state to a hard state. To do. Accordingly, the damping coefficient selection control routine shown in FIG. 10, the damping coefficient Dki is D2i becomes the lower limit value, the damping coefficient Dki be conditions to be changed are satisfied soft than if retained in D2i, On the other hand, D6i becomes the upper limit value, and even if the condition to be further changed to hardware is satisfied, the damping coefficient Dki
Will be held at D6i.

On the other hand, when the determination in step SA10 is NO, that is, when the vehicle speed V exceeds the fourth predetermined vehicle speed V4, the routine proceeds to step SA12, where the vehicle speed V is the fifth predetermined vehicle speed V5, for example. It is determined whether it is 80 km / h or less.

As a result, when it is determined that the vehicle speed V is in the medium speed running state which is equal to or lower than the fifth predetermined vehicle speed V5, the process proceeds to step SA13 to improve the running stability and the riding comfort.
The damping coefficient Dki is set in the range of D4i to D6i in order to slightly change the damping force characteristics of the shock absorbers 1, 2, 3, 4 while satisfying both requirements. Accordingly, the routine of the damping coefficient selection control in FIG. 10, the damping coefficient Dki is D4i becomes the lower limit, even if conditions for further changes to the software is satisfied damping coefficient D
ki is held in D4i, while D6i becomes the upper limit value, and the damping coefficient Dki is held in D6i even if the condition to be further changed to hardware is satisfied.

On the other hand, the vehicle speed V is the fifth predetermined vehicle speed V5.
When it is determined to be NO in a high-speed running state that exceeds the limit, the process proceeds to step SA14, and the damping coefficient Dki is set so that the damping force characteristics are changed and controlled within a hard range, with an emphasis on improving running stability. Set in the range of D7i to D10i. Accordingly, the routine of the damping coefficient selection control in FIG. 10, the damping coefficient Dki is D7i becomes the lower limit value, even further damping coefficient Dki be conditions to be changed are satisfied soft D
7i, and on the other hand, the damping coefficient Dki is held at D10i even if the condition to be further changed to hard is satisfied.

FIG. 11 shows a basic routine of the damping force characteristic changing control of the shock absorbers 1, 2, 3, 4 of each wheel which is executed by the control unit 8 when the control mode is selected by the mode selection switch 16. It is a flowchart shown.

In FIG. 11, first, in step SB1, the first acceleration sensor 11, the second acceleration sensor 12,
Vertical acceleration ai on the spring detected by the third acceleration sensor 13 and the fourth acceleration sensor 14, and the first pressure sensor 61, the second pressure sensor 62, the third pressure sensor 63, and the fourth
The damping force Fsi detected by the pressure sensor 64 is input. Next, in step SB2, the vertical acceleration ai input in step SB1 is integrated to calculate the sprung displacement speed Xsi (= Σai).

Then, in step SB3, the displacement speed Xsi on the spring calculated in step SB2 is multiplied by a predetermined constant K (K <0) to calculate the skyhook damping force Fai, which is the ideal damping force. . Then, in step SB4, hα is calculated according to the following expression hα = Fsi (Fai−αFsi) ..., And it is determined in step SB5 whether or not hα is positive. To do.

As a result, if hα is positive and YES, the routine proceeds to step SB6, where the first actuator 41, the second actuator 42, and the third actuator of the shock absorbers 1, 2, 3, 4 whose hα is positive. 43, 4th
A control signal is output to the actuator 44, the step motor 27 is rotated clockwise by one step in FIG. 8, and the damping coefficient Dki is D (K + 1) i, which is one larger than the previous damping coefficient Dki.
, That is, while changing to be harder, h
If α is not positive, the process proceeds to step SB7, and hβ = Fsi (Fai−βFsi) ..... hβ is calculated according to the equation, and hβ is calculated at step SB8. Is determined to be negative.

As a result, when hβ is negative and YES, in step SB9, the first actuator 41, the second actuator 42, the third actuator 43, of the shock absorbers 1, 2, 3, 4 whose hβ is negative are Fourth
A control signal is output to the actuator 44 to rotate the step motor 27 one step counterclockwise in FIG. 8, and the damping coefficient Dki is one smaller than the previous damping coefficient Dki D (k-1) i.
To be, that is, to be softer. On the other hand, when hβ is not negative, in step SB10, the stepping motor 27 is not rotated, that is, the damping coefficient Dki is set to the previous damping coefficient Dki.
Keep ki as it is and change it to the next cycle.

Here, α and β are threshold values for preventing a large sound or vibration and a response delay from being generated when the damping coefficient Dki is changed too frequently. There is usually α> 1, 0 <β <1
Is set to.

That is, when Fsi and Fai have the same sign,
Since (Fai−αFsi) in the expression is α> 1, it is more likely to have a different sign from Fsi than when Fsi is not multiplied by α, and as a result, hα is likely to be negative, so attenuation It is difficult to change the coefficient Dki, and further, in the formula (F
ai−βFsi) is 0 <β <1, so that it tends to have the same sign as Fsi as compared to the case where Fsi is not multiplied by β, and as a result, hβ tends to be positive. D
It becomes difficult to change ki.

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 Di close to zero, that is, to change it so that it becomes softer, in order to bring Fsi closer to Fai. Therefore, in the present embodiment, when Fsi and Fai have different signs, both hα and hβ are negative values, and as a result, the control unit 8
As a result, the damping coefficient Dki is changed to D (k-1) i, which is one smaller than the previous damping coefficient Dki, that is, becomes softer, so that it is possible to satisfy this requirement.

Note that the range of the damping coefficient Dki changed in the flowchart of FIG. 11 is limited by the damping coefficient selection control routine according to the running state of FIG. 10, and the step motor 27 is rotated one step clockwise in FIG. Then, the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (k + 1) i.
Even if it should be changed to, the previous damping coefficient Dki is maintained as it is, and the stepping motor 27 is rotated counterclockwise in FIG.
One small again D even if (k-1) should be changed to be i, the attenuation coefficient in the case the previous damping coefficient Dki is equal to the lower limit value of the damping coefficient Dki chosen routine damping coefficient selection control Dki Is retained as the previous damping coefficient Dki.

12 to 14 show that when the control mode is selected by the mode selection switch 16,
Changing the damping force characteristics of the left and right front wheel shock absorbers 1, 2 and the left and right rear wheel shock absorbers 3, 4 executed to prevent diagonal vibration by the allowable value setting means 81 and the calculation determining means 80 of the control unit 8. It is a flow chart which shows a control routine.

First, in step SC1 of FIG. 12, the vehicle speed V detection signal detected by the vehicle speed sensor 15, the steering angle θ detection signal detected by the steering angle sensor 65, and the road surface friction coefficient estimated value μ from the ABS 66 are estimated. Input each signal. Next, at step SC2, it is determined whether or not the vehicle speed V is equal to or lower than a fourth predetermined vehicle speed V4. When the determination is YES that the vehicle speed V is equal to or lower than the fourth predetermined vehicle speed V4, it is determined that the vehicle is in a low speed traveling state. Therefore, even if the difference between the damping coefficients Dki of the shock absorbers of the left and right wheels 1, 2 or 3, 4 is large,
Since the steer characteristic does not change so much and diagonal vibration does not matter, the allowable value signal is not output. Therefore, the damping coefficient D of the shock absorber 1, 2, 3, 4 of each wheel is
ki is retained as the previous damping coefficient Dki, and the allowable value signal is not output.

On the other hand, the vehicle speed V is the fourth predetermined vehicle speed V.
When NO is 4 or more, it is determined that the vehicle is running at a medium speed or higher, the process proceeds to step SC3, and if the difference between the damping coefficients Dki of the shock absorbers of the left and right wheels 1, 2 or 3, 4 is large, the steering is stopped. Since the characteristics change and diagonal vibration occurs, it is further determined whether or not the vehicle speed V is equal to or lower than a fifth predetermined vehicle speed V5 in order to determine what value the allowable value should be set to. As a result, the vehicle speed V is the fourth predetermined vehicle speed V4.
Yes, but is below the fifth predetermined vehicle speed V5 YES
If so, the process proceeds to step SC4, and it is determined whether the estimated value μ of the road surface friction coefficient is equal to or less than a predetermined value μ0.

As a result, when the vehicle is traveling on a road surface having a small road surface friction coefficient such that the estimated value μ of the road surface friction coefficient is less than or equal to a predetermined value μ0, the shock absorbers 1 for the left and right wheels are
Also the difference between the damping coefficient Dki of 2 or 3 and 4 is not so large, because there may impair run line stability, how run
In order to determine whether the line stability is likely to be impaired , step S
At C5, the absolute value | θ | of the steering angle θ is the first predetermined steering angle θ
Determine if it is 1 or more.

As a result, if the absolute value | θ | of the steering angle θ is greater than or equal to the first predetermined steering angle θ1, YES, step SC6
, The absolute value | θ | of the steering angle θ is the second predetermined steering angle θ2
It is determined whether or not the above. As a result, the absolute value of the steering angle θ | θ
When | is YES which is equal to or larger than the second predetermined steering angle θ2, it is recognized that the vehicle is traveling on a road surface having a small road surface friction coefficient and the steering wheel is largely operated, and the vehicle is in a traveling state in which load movement is very likely to occur. In step SC7, the tolerance value setting means 81 sets the tolerance value t to t1, for example 1, and outputs the tolerance value signal to the operation determination means 80 (step SC8 in FIG. 15). On the other hand, the determination in step SC6 is
When the absolute value | θ | of the steering angle θ is less than the second predetermined steering angle θ2, it means that the vehicle is traveling on a road surface having a small road surface friction coefficient, but the steering wheel is not operated so much. Since it is recognized, the allowable value t is set to t in step SC9.
2, for example, set to 2, and the allowable value signal is calculated by the determination means 8
Output to 0.

On the other hand, when the absolute value | θ | of the steering angle θ in step SC5 is less than the first predetermined steering angle θ1, NO, the vehicle is running on a road surface having a small road surface friction coefficient, Since it is recognized that the vehicle is in a traveling state in which it is not largely operated, the allowable value t is set to t3 in
For example, the value is set to 3 and the allowable value signal is output to the calculation determining means 80.

On the other hand, if the determination in step SC4 is NO, that is, the estimated value μ of the road surface friction coefficient exceeds the predetermined value μ0, in step SC11 the absolute value | θ | of the steering angle θ is set to the second predetermined value. it is determined whether the steering angle θ2 on than, the steering angle θ
If the absolute value | θ | of is less than the second predetermined steering angle θ2, the allowable value t is set to t3 in step SC12 and the allowable value signal is output to the calculation determining means 80, while the steering angle θ Absolute value | θ | exceeds the second predetermined steering angle θ2 YES
If so, it is determined in step SC13 whether the absolute value | θ | of the steering angle θ is greater than or equal to the third predetermined steering angle θ3.

As a result, when the absolute value | θ | of the steering angle θ is equal to or larger than the third predetermined steering angle θ3, it is recognized that the steering wheel is largely operated and the load is very likely to move. Therefore, the allowable value t is set to t in step SC14.
It is set to 1 and the allowable value signal is output to the calculation determining means 80. On the other hand, when the determination in step SC13 is NO, that is, when the absolute value | θ | of the steering angle θ is less than the third predetermined steering angle θ3, the allowable value t is set to t2 in step SC15 and the allowable value signal is set. Is output to the calculation determining means 80.

On the other hand, when the determination in step SC3 is NO, that is, when the vehicle speed V exceeds the fifth predetermined vehicle speed V5 and is in a high speed traveling state, the steer characteristic changes more than in the medium speed traveling state. Since it is easy to perform and diagonal vibration is more likely to occur, steps SC16 to SC18, step SC22
In step SC24, the same judgment as in the medium speed running state is performed, and the allowable value t is smaller than that in the medium speed running state in steps SC19 to SC21, step SC23, step SC25 and step SC26, for example, one by one. The allowable value signal is set to a small value, and the allowable value signal is calculated and determined by the calculation determining means 8
Output to 0.

When the allowable value signal from each of the above steps is input to step SC8 of the calculation determining means 80, the difference between the damping coefficients Dki of the left and right shock absorbers 1, 2 and 3, 4 is calculated in step SC8. Absolute value of | Dkl
-Dkr | determines whether or not the allowable value t is exceeded, and the above absolute value | Dkl-Dkr | exceeds the allowable value t YES
In step SC27, in step SC27, a control signal is output to select one of the shock absorbers 1, 2 and 3 and 4 for the left and right wheels, whichever has a smaller damping coefficient Dki and is softer than the step motor. 27 is rotated clockwise by one step to change the damping coefficient Dki to D (k + 1) i which is one larger than the previous damping coefficient Dki, while the above absolute value | Dkl-Dkr | When the value is less than t,
No control signal is output.

Here, the range of the damping coefficient Dki changed in the flowcharts of FIGS. 12 to 14 is shown in FIG.
Is limited by the routine of the damping coefficient selection control according to the change range of the step motor 27, and the step motor 27 is rotated clockwise by one step in FIG. 8 to increase the damping coefficient Dki by one larger than the previous damping coefficient Dki by D (k + 1). Even if it should be changed to i, if the previous damping coefficient Dki is equal to the upper limit value of the damping coefficient Dki selected by the damping coefficient selection control routine, the damping coefficient Dki
Ki is retained as the previous damping coefficient Dki.

FIG. 15 shows the mode selection switch 16
When the control mode is selected by, the shock absorbers 1 and 2 of the left and right front wheels and the shock absorbers 1 and 2 of the left and right rear wheels which are executed to prevent diagonal vibration by the allowable value changing means 82 and the calculation determining means 80 of the control unit 8 It is a flow chart which shows the routine of damping force characteristic change control of shock absorbers 3 and 4. Further, FIG. 16 is a map showing a change characteristic of the gain of the sprung unsprung relative speed with respect to the vibration frequency, and FIG. 17 is a map showing a change characteristic of the gain of the sprung absolute speed with respect to the vibration frequency.

In FIG. 15, first, in step SD1,
It is determined whether or not the gain Grev of the sprung sprung unsprung relative speed shown in FIG. 16 is smaller than a predetermined value Grev0. When the gain Grev of the sprung unsprung relative speed is smaller than the predetermined value Grev0 is YES, It is determined that the gain Srev of the sprung relative velocity is in the vibration frequency region other than the sprung mass resonance point ω1 and the unsprung mass resonance point ω2, and the process proceeds to step SD2, as shown in FIG.
It is determined whether or not the sprung mass absolute velocity gain Gav shown in 7 is larger than a predetermined value Gav0. Then, if the determination is YES that the gain Gav of the sprung mass absolute velocity is larger than the predetermined value Gav0, the gain Gre of the sprung mass unsprung relative velocity Gre
It is determined that v is in the ultra-low frequency vibration region where the sprung mass resonance point ω1 has not been reached, the process proceeds to step SD3, the allowable value t is changed to t3, and the allowable value signal is output to the calculation determining means 80. . On the other hand, when the determination in step SD2 is NO that the gain Gav of the sprung absolute velocity is smaller than the predetermined value Gav0, the gain Grev of the sprung unsprung relative velocity becomes smaller than the unsprung resonance point ω2. It is determined that the high-frequency vibration region is moving to the ultra-high-frequency vibration region, the process proceeds to step SD4, and the allowable value t is set to the damping coefficient Dki of the left and right wheel shock absorbers 1, 2 and 3, 4.
The setting value is changed to t ∞ where the difference is not regulated, and the allowable value signal is output to the calculation determining means 80.

On the other hand, if the determination at step SD1 is NO, that is, the gain Srev between unsprung and unsprung relative speeds is greater than a predetermined value Grev0, the gain G of unsprung unsprung relative velocity is G.
It is determined that rev is in the vibration frequency range including the sprung resonance point ω1 and the unsprung resonance point ω2, the process proceeds to step SD5, where the allowable value t is set to the damping coefficient Dki of the shock absorbers 1, 2 and 3 and 4 for the left and right wheels. Is in-phase, that is, the setting is changed to t0 which regulates so that the difference becomes 0, and the allowable value signal is output to the calculation determining means 80.

Then, the allowable value signal from each of the above steps is the step SC8 of the flow of the operation judging means 80 of FIG.
In step SC8, it is determined whether or not the absolute value | Dkl-Dkr | of the difference between the damping coefficients Dki of the left and right shock absorbers 1, 2 and 3, 4 exceeds the allowable value t, and YES If so, a control signal is output in step SC27 to output shock absorbers 1, 2 and 3 for the left and right wheels.
8 shows the step motor 27 of the shock absorber 1, 2, 3 or 4 which has a smaller damping coefficient Dki and is softer.
While rotating one step clockwise to change the damping coefficient Dki to D (k + 1) i, which is one larger than the previous damping coefficient Dki.
When NO, the control signal is not output.

Here, the range of the damping coefficient Dki changed in the flowcharts of FIGS. 14 and 15 is shown in FIG.
Similarly, the damping coefficient selection control routine according to the change range of the
Even when the value should be changed to D (k + 1) i, which is larger by one, if the previous damping coefficient Dki is equal to the upper limit value of the damping coefficient Dki selected by the routine of the damping coefficient selection control, the damping coefficient Dki is changed. The previous damping coefficient Dki is retained.

Therefore, step S of the above flow chart.
By D1 and step SD2, the input frequency detecting means 83 for detecting the frequency range of the input applied to the vehicle body is configured according to the change characteristics of both gains of the sprung mass relative speed and the sprung mass absolute speed with respect to the vibration frequency. ing. Further, in steps SD3, SD4 and SD5, the shock absorber 1 between the left and right wheels is based on the determination signal from the input frequency detecting means 83.
Absolute value of the difference in damping coefficient of 2 or 3, 4 | Dkl-Dkr |
That is, the allowable value changing means 82 for changing the allowable value t is configured.

Therefore, in the above embodiment, the absolute value | Dkl-Dkr | of the difference between the damping coefficients Dki of the left and right shock absorbers 1, 2 and 3, 4 exceeds the allowable value t, and the steer characteristic changes. If there is a possibility that diagonal vibration will occur, the damping coefficient of the shock absorbers 1, 2 and 3, 4 between the left and right wheels is determined by the allowable value changing means 92 according to the determination signal from the input frequency detecting means 91. The control of the damping coefficient Dki of the shock absorbers 1, 2 and 3, 4 for the left and right wheels by the control unit 8 is changed so as to change the absolute value | Dkl−Dkr | (allowable value) of the difference.

That is, when the gain Grev of the sprung unsprung relative speed is smaller than the predetermined value Grev0 and the gain Gav of the sprung absolute speed is larger than the predetermined value Gav0,
Since it is determined that the gain Grev of the unsprung relative speed between unsprung parts is in the very low frequency vibration region where the sprung resonance point ω1 has not been reached and the allowable value t is set to t3, the shock absorber 1 for the left and right wheels is changed. , 2 and 3, 4 the absolute value of the difference between the damping coefficients Dki | Dkl−Dkr | becomes large, and the damping coefficients of the shock absorbers 1, 2 and 3, 4 on the left and right wheels are the damping force of the harder shock absorber. The characteristics are regulated slightly to the soft side, and the damping force characteristics of the softer shock absorber are regulated to the hard side. It is possible to effectively reduce the diagonal vibration. Moreover, when the gain Grev of the sprung unsprung relative speed is larger than the predetermined value Grev0, the gain Srev of the unsprung unsprung relative speed is in the low frequency vibration region including the sprung resonance point ω1 and the unsprung resonance point ω2. Since the allowable value t is determined so that the difference between the damping coefficients Dki of the left and right wheel shock absorbers 1, 2 or 3, 4 is 0, the left and right wheel shock absorbers 1, 2 and 3 are regulated. , 4 have the same phase, and it is possible to improve the steering stability and effectively reduce the diagonal vibration in the low frequency vibration region including the sprung resonance point ω1 and the unsprung resonance point ω2.

On the other hand, the gain G of the relative speed between the sprung part and the unsprung part is
When rev is smaller than the predetermined value Grev0 and the gain Gav of the sprung absolute velocity is smaller than the predetermined value Gav0, the gain Grev of the sprung unsprung relative velocity is becoming smaller than the unsprung resonance point ω2. Since the allowable value t is set and changed to t∞ because it is determined to be in the region moving from the high frequency vibration region to the ultra high frequency vibration region, the damping coefficients of the left and right wheel shock absorbers 1, 2 and 3, 4 are set. The absolute value of the Dki difference | Dkl-Dkr | becomes so large that it is not regulated, and the shock absorbers 1, 2 and 3, on the left and right wheels are
The damping coefficient of No. 4 is maintained as the previous damping coefficient Dki, and it is possible to improve both the riding comfort and the posture stability in the high frequency region and the ultra high frequency region.

The present invention is not limited to the above embodiment, but includes various other modifications.
For example, in the above embodiment, when the gain Grev of the sprung sprung unsprung relative speed is larger than the predetermined value Grev0, the allowable value t
Although the damping coefficient Dki of the shock absorbers 1, 2 or 3, 4 for the left and right wheels is controlled in phase by setting t0 to t0, the gain Grev of the sprung sprung unsprung relative speed is smaller than the predetermined value Grev0 and the sprung absolute value. Speed gain Gav is a predetermined value G
When the value is larger than av0, the allowable value smaller than the changed allowable value t3, that is, the allowable value t may be changed to t1 or t2. In this case as well, the sprung resonance point ω1 and the unsprung resonance are set. It is possible to improve the steering stability in the low frequency region including the point ω 2 and effectively reduce the diagonal vibration.

Further, in the above embodiment, the allowable value t is set to t3 when the gain Srev between the sprung unsprung relative speeds is smaller than the predetermined value Grev0 and the gain Savant absolute speed Gav is larger than the predetermined value Gav0. Although the setting was changed, in this region, the gain Grev of the sprung unsprung relative speed is set to the predetermined value Gre.
Since it is smaller than v0, the allowable value t may be changed to t1. In this case, when the gain Grev of the sprung sprung unsprung relative speed is larger than the predetermined value Grev0, that is, the sprung portion In the low-frequency vibration region including the resonance point ω1 and the unsprung resonance point ω2, it is necessary to hold the allowable value t at t0 and control the damping coefficients Dki of the shock absorbers 1, 2 and 3, 4 for the left and right wheels in phase.

Further, in the above embodiment, the road surface friction coefficient μ
Is estimated based on the detection signal of ABS66,
The road surface friction coefficient μ may be estimated based on the wiper signal, and whether or not the road is a bad road is determined based on the variation amount of the vertical acceleration ai within a predetermined time. The bad road may be determined by another method .

[0079] Further, in the above embodiment, two stopper pins are used.
55,56TheFormed on rotor 51 of step motor 27
And the grooves 57 and 58 engaging with thisTheStep motor 27
It is formed on the lid 53 ofTwoStopper pinIsTe
PmooOn the lidFormationDone, Engage with thisThe groove isTe
PumoTo each rotorFormationTo beEven if
Even more,TwoStopper pinOfon the other handIsTepmo
-OfLowTo, On the other handIsTep MoOn each lid
FormationDone,LowToFormed stopper pinOfOne side
CombineThe groove isTep MoOn the lid, Step mLid
ToThe other stopper pin formedWithEngageThe groove isTe
PumoOfLowTo eachFormationBe doneDo it
Yes.

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

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a perspective view showing a component layout of a suspension device.

FIG. 2 is a vertical sectional front view showing a main part of a shock absorber.

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

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

FIG. 5 is a schematic diagram showing a vibration model of a suspension device.

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

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

FIG. 8 is a bottom view of the lid.

FIG. 9 is a block configuration diagram of a control unit of the suspension device.

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

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

FIG. 12 is a flowchart showing a first half part of a routine of a damping force characteristic change control of the left and right wheel shock absorbers executed by the allowable value setting means.

FIG. 13 is a flowchart showing a second half of a basic routine of the damping force characteristic change control of the left and right wheel shock absorbers executed by the allowable value setting means.

FIG. 14 is a flowchart showing a routine for damping force characteristic change control of the left and right wheel shock absorbers, which is executed by a calculation determining means.

FIG. 15 is a flowchart showing a routine of damping force characteristic change control of the left and right wheel shock absorbers executed by the allowable value changing means.

FIG. 16 is a characteristic diagram showing a change characteristic of a gain of relative sprung mass velocity with respect to a vibration frequency.

FIG. 17 is a characteristic diagram showing a change characteristic of a gain of an absolute sprung speed with respect to a vibration frequency.

[Explanation of symbols] 1,2,3,4 shock absorber 6,7 wheels 8 control unit (control means) 9 car body 82 Allowable value changing means 83 Input frequency detecting means

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Change

[Correction content]

[Figure 10]

Claims (3)

[Claims] 1. A shock absorber is provided between an unsprung portion and an unsprung portion of each wheel, and a damping force characteristic of the shock absorber is changed according to a relative relationship between a displacement speed on the spring and an unsprung displacement speed. In a vehicle suspension device to be controlled, control means for changing and controlling the damping force characteristics of the shock absorber of each wheel, input frequency detecting means for detecting the frequency of an input applied to the vehicle body, and input frequency detecting means A suspension system for a vehicle, comprising: a tolerance change means for changing the control of the control means so as to change the tolerance of the difference between the damping force characteristics of the shock absorbers between the left and right wheels in response to the signal. . 2. The allowable value changing means largely changes the allowable value of the difference between the damping force characteristics of the shock absorbers between the left and right wheels when the input frequency applied to the vehicle body is in the high frequency vibration region, while The vehicle suspension device according to claim 1, wherein the input frequency is changed to a small value when the input frequency is in a low-frequency vibration region. 3. The allowable value changing means independently controls the damping force characteristic of the shock absorber between the left and right wheels by increasing the allowable value when the frequency of the input applied to the vehicle body is in the high frequency vibration region. 2. The vehicle suspension device according to claim 1, wherein when the input frequency applied to the vehicle body is in a low-frequency vibration region, the allowable value is set to 0 and control is performed in the same phase.