JPH0550821A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To surely prevent a while contriving temperature decrease of an actuator by detecting responsiveness of the actuator to change a damping force characteristic of a shock absorber based on a predetermined condition relating to the actuator. CONSTITUTION:Damping force, sprung vertical acceleration and sprung/unsprung relative displacement are detected respectively by the first to fourth pressure sensors 61 to 64 of each shock absorber, first to fourth acceleration sensors 11 to 14 and the first to fourth car height sensors 71 to 74. Signals of these sensors are input with a signal of a car speed sensor 15 to a control unit 8, and a permissible value setting means 81 of receiving a road surface friction signal of an ABS66 and a signal of a steering angle sensor 65 are inputted to a threshold value setting means 82 to output an arithmetic result to an arithmetic decision means 80. From the arithmetic result here, damping force is adjusted by the first to fourth actuators 41 to 44 to decrease a changing frequency of a damping force characteristic when an action response speed of the actuator is a predetermined value or less. Accordingly, temperature decrease of the actuator and trouble are prevented to enable running stability to improve.

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 system for a vehicle is equipped with a shock absorber for damping vertical vibration of a wheel between a sprung body side and an unsprung side wheel side. In this shock absorber, as a variable damping force characteristic type, damping force characteristics (characteristics having different damping coefficients) can be changed in two steps, high and low, and damping force characteristics 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 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 force to the low damping side (ie soft side) and changing the damping force of the shock absorber to the high damping side (ie hard side) when the damping force acts in the damping direction. On the other hand, the damping energy is increased to improve both the riding comfort and 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 or the damping direction of the sprung vertical vibration.
For example, in Japanese Unexamined Patent Publication No. 60-248419, it is investigated whether or not the sign of the relative displacement between the sprung and unsprung parts and the sign of the relative speed 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]

[Problems to be Solved by the Invention] However, in this way,
A shock absorber with a variable damping force characteristic that controls the damping force characteristic based on whether the direction of relative displacement between the sprung and unsprung parts matches the direction of relative velocity between the sprung member and the unsprung member. When the damping force of the shock absorber is controlled by feedback control, the direction of relative displacement between the sprung and unsprung parts and the direction of relative speed between the sprung part and unsprung part often coincide with each other. Because the discrepancy repeats,
Inevitably, there has been a problem that the control computer becomes large and expensive.

Therefore, when solving the above problem and controlling the damping force of the shock absorber by the open control, it is conceivable to use a step motor as an actuator. The direction of relative displacement with the unsprung part and the direction of relative velocity with the sprung part and the unsprung part frequently match and mismatch, so the damping force is changed from the soft side to the hard side, and further from the hard side. It is necessary to drive the step motor so that it is changed between the soft side and the hard side at an extremely high speed, such as on the soft side. In such a case,
There is a problem that the stepping motor heats up or goes out of step, so that the damping force of the shock absorber cannot be controlled as desired according to the vertical vibration state of the vehicle body, which in turn impairs running stability. ..

The present invention has been made in view of the above points, and an object of the present invention is to meet the following requirements:
By effectively changing the damping force characteristic of the shock absorber without deteriorating the running stability, the temperature of the actuator (step motor) is lowered, and the step-out of the actuator is surely prevented.

[0008]

In order to achieve the above object, a solution means devised 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 vehicle suspension device in which the damping force characteristic of the shock absorber is changed and controlled according to the relative relationship between the speed and the unsprung displacement speed.
An actuator that changes the damping force characteristic of the shock absorber, a control unit that outputs a control signal to the actuator to operate the actuator, a responsiveness detection unit that detects an operation response speed of the actuator, and the responsiveness detection unit. And a correction means for correcting the control signal of the control means to the actuator so as to reduce the change frequency of the damping force characteristic of the shock absorber when the signal is slower than a predetermined operation response speed. It is configured.

The solution means taken by the invention according to claim 2 is dependent on the invention according to claim 1, wherein the correction means is an input frequency for detecting the frequency of the input applied to the vehicle body. The output signal from the detection means is input, the output signal from the input frequency detection means is received, and the actuator is supplied with the output signal only when the signal is in a low frequency vibration region lower than a predetermined vibration frequency. The control signal of the control means is corrected.

Further, the solution means taken by the invention according to claim 3 is dependent on the invention according to claim 1, wherein the correction means uses a signal from the response detection means as a predetermined operation response speed. The control signal of the control means to the actuator is corrected so as to regulate the range of change of the damping force characteristic of the shock absorber by the actuator at a later time.

Further, the solution means taken by the invention according to claim 4 is dependent on the invention according to claim 1, wherein the correction means uses a signal from the response detection means as a predetermined operation response speed. The control signal of the control means to the actuator is corrected so that the damping force characteristic of the shock absorber is changed by one step at a slower speed.

[0012]

With the above structure, in the invention according to claim 1,
The actuator that changes the damping force characteristic of the shock absorber changes the damping force characteristic of the shock absorber when a decrease in responsiveness is detected when the operation response speed detected by the response detecting means is slower than a predetermined operation response speed. Since it operates by the control signal of the control means corrected by the correction means so as to reduce the frequency, the operation of the actuator which changes between the soft side and the hard side at an extremely high speed and tends to overheat, that is, the change frequency of the correction means. By the correction, the temperature of the actuator can be lowered, and the step-out of the actuator can be prevented.

In the invention according to claim 2, the correction means is in a low frequency vibration region in which the output signal from the input frequency detection means for detecting the frequency of the input applied to the vehicle body is lower than a predetermined vibration frequency. Since the control signal of the control means to the actuator is corrected only when, the control signal of the control means to the actuator is output when the output signal from the input frequency detection means is in the high frequency vibration region higher than the predetermined vibration frequency. Is not corrected by the correction means, and is maintained as, for example, the previous damping force characteristic, and the frequency of changing the damping force characteristic of the shock absorber is reduced, so that uncomfortable low-frequency vibration input to the vehicle body It is possible to reduce the temperature of the actuator while suppressing the above, and it is possible to prevent the out-of-step of the actuator.

In the invention according to claim 3, the correction means corrects the control signal of the control means to the actuator when the actuation response speed of the actuator is slower than a predetermined actuation response speed, and the damping force of the shock absorber. Since the changing range of the characteristic is restricted, the damping force characteristic of the shock absorber is restricted to the range on the hard side that secures the steering stability, for example, and the changing frequency of the actuator is reduced by the correction of the correction means, and It is possible to reduce the temperature of the actuator and prevent the actuator from being out of step while ensuring stability and the like.

Further, in the invention according to claim 4, the correction means corrects the control signal of the control means to the actuator when the actuation response speed of the actuator is slower than the predetermined actuation response speed, and the damping force of the shock absorber. Since the characteristics are changed by one step, the damping force characteristics of the shock absorber are rapidly switched, and the damping force characteristic change control is performed quickly. It is possible to lower the temperature of the actuator and prevent out-of-step of the actuator.

[0016]

As described above, according to the vehicle suspension device of the first aspect of the present invention, the damping force characteristic of the shock absorber is corrected by the correcting means when the actuation response speed of the actuator is slower than the predetermined actuation response speed. Since the control signal of the control means is corrected so as to reduce the change frequency, it is possible to reliably prevent the out-of-step of the actuator while reducing the temperature of the overheated actuator, and improve the running stability.

According to the vehicle suspension device of the second aspect of the invention, the correction means corrects the control signal of the control means to the actuator only when the input frequency applied to the vehicle body is in the low frequency vibration region. In the high frequency vibration region, the control signal of the control means to the actuator is held in the previous damping force characteristic, and the frequency of changing the damping force characteristic of the shock absorber is reduced to suppress unpleasant low frequency vibration, It is possible to reliably prevent the out-of-step of the actuator while lowering the temperature of the actuator.

According to the vehicle suspension device of the third aspect of the present invention, the correction means regulates the range of change of the damping force characteristic of the shock absorber when the actuation response speed of the actuator is slower than the predetermined actuation response speed. Since the control signal of the control means to the actuator was corrected so that the damping frequency characteristic of the shock absorber is restricted to the range on the hardware side that secures the steering stability, the actuator change frequency is reduced and the steering stability is reduced. It is possible to reliably prevent out-of-step of the actuator while ensuring the above, and reducing the temperature of the actuator.

Further, according to the vehicle suspension device of the fourth aspect of the present invention, the correction means changes the damping force characteristic of the shock absorber by one step when the actuation response speed of the actuator is slower than a predetermined actuation response speed. Since the control signal of the control means to the actuator is corrected as described above, it is possible to improve the control speed for changing the damping force characteristic of the shock absorber, reduce the temperature of the actuator, and prevent out-of-step of the actuator.

[0020]

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 device according to a preferred embodiment of the present invention includes shock absorbers 1, 2, 3, 4 which are provided corresponding to respective wheels and which dampen vertical vibrations of the respective wheels. ing. Each of the shock absorbers 1, 2, 3 and 4 is configured to be switchable to 10 damping force characteristics having different damping coefficients by an actuator (not shown), and also has 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, 4 to change and control the damping force characteristics of the shock absorbers 1, 2, 3, 4. is there.

Further, on the spring of the vehicle body 9, there is provided a first acceleration sensor 11 for detecting vertical acceleration on the spring of each wheel.
A second acceleration sensor 12, a third acceleration sensor 13, a fourth acceleration sensor 14 are provided, and a vehicle speed sensor 15 for detecting a vehicle speed is 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. 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.
Change control of the damping force characteristic of No. 4 is performed. Further, when the soft mode is selected, only the damping coefficient within 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. Is becoming

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. Inside 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 coupled to the unsprung and sprung, respectively.

The piston unit 22 is formed with two orifices 23 and 24. 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 for rotating 6 and a first orifice plate 29 integrally attached to the lower end of the shaft 26 and having nine circular holes 28 along the circumference thereof, and integrally with the lower end of the sleeve 25. The second orifice plate 31 is provided and has an arc-shaped elongated 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, 4 provided for other wheels are also the shock absorber 1 shown in FIG. The second actuator 42, the third actuator 43, and the fourth actuator 44 are the same as those shown in FIG. 3, respectively.

FIG. 4 shows the shock absorbers 1, 2, 3,
4 is a graph showing damping force characteristics of No. 4, D1 to D10
Indicates the damping coefficients of the shock absorbers 1, 2, 3, and 4, respectively. In FIG. 4, the vertical axis represents the damping force generated by the shock absorbers 1, 2, 3, 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 represents a damping coefficient that produces the softest damping force, and D10 represents a damping coefficient that produces 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 oblong hole 30 of the second orifice plate 31. Become.

FIG. 5 is a vibration model diagram of a vehicle suspension device 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 cylindrical body 50 and a cylindrical body 50.
Rotor 51, stator 52 and lid 53 housed inside
It consists of FIG. 7 is a schematic plan view of the rotor 51 and the stator 52. As with a normal step motor, a plurality of rectangular teeth are formed on the outer peripheral portion of the rotor 51, and the inner peripheral portion of the stator 52 is 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.
Two grooves 57 and 58 are formed in the circumferential direction at positions corresponding to. The groove 57 engages with the stopper pin 55 formed on the rotor 51 to control the movable range of the step motor 27, while the groove 58 has 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 circumference 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 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 portion 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 a control system of a vehicle suspension device according to an embodiment of the present invention.

Referring to 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 a threshold setting 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, 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 A detection signal of vertical acceleration ai on the spring detected by the sensor 14, a sprung spring detected by the first vehicle height sensor 71, the second vehicle height sensor 72, the third vehicle height sensor 73, and the fourth vehicle height sensor 74. The detection signal of the lower relative displacement (Xs-Xu) and the detection signal of the vehicle speed V detected by the vehicle speed sensor 15 are input. Further, the detection signal of the vehicle speed V detected by the vehicle speed sensor 15 and the estimation signal of the estimated value μ of the road surface friction coefficient from the anti-braking system (ABS) 66 are input to the allowable value setting means 81. .. Further, the threshold value setting means 82 receives the steering angle θ detection signal from the steering angle sensor 65 and the allowance value signal from the allowance value setting means 81, and the threshold value setting means 82 calculates the threshold value signal. It is adapted to be output to the means 80. Then, the calculation determining means 80 integrates the vertical acceleration ai on the spring detected by the first to fourth acceleration sensors 11 to 14 by a numerical integration method or the like to calculate the displacement speed Xsi (Σa) on the spring.
i), that is, the output signal from the input frequency detecting means 83 for detecting the frequency of the input applied to the vehicle body is calculated while being converted and used as the sprung mass absolute velocity at the position of each shock absorber 1-4. The vibration frequency region that has been input is compared with the later-described vibration frequency gain of FIG. 15 to determine the vibration frequency region.

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 the wheels 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, 4. The allowable value setting means 81 also detects the vehicle speed V detected by the vehicle speed sensor 15 and the steering angle sensor 6.
5, the shock absorbers 1, 2, 3 for the left and right wheels and the front and rear wheels are stored in accordance with a map or table stored in advance based on the detection signal of the steering angle θ detected by the vehicle 5 and the estimation signal of the estimated value μ of the road surface friction coefficient from the ABS 66. , 4 to calculate the permissible value of the difference between the damping coefficients Dki, and output the permissible value signal to the threshold value setting means 82. Further, the threshold setting means 8
2 is the shock absorbers 1, 2 and 3 and 4 for the left and right wheels according to a map or table stored in advance based on the detection signal of the steering angle θ detected by the steering angle sensor 65.
A threshold value for changing the sensitivity of changing the damping coefficient Dki is set, and the threshold value 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 spring, 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 that it will take a negative value when the upper part and the unsprung part are stretched.
Is set to a positive value when it is pointing up and a negative value when it is pointing down.

Further, the calculation determining means 80 is provided with a responsiveness detecting means 92 and a correcting means 91, and the responsiveness detecting means 92 is controlled by the control signal of the calculation determining means 80. When the operation of the third actuator 43 and the fourth actuator 44 is slower than a predetermined operation response speed, an output signal is output to the correction means 91. Further, the correction means 91 is responsive to the output signal from the responsiveness detection means 92 to determine the shock absorber 1,
To reduce the frequency of changing the damping force characteristics of 2, 3 and 4,
The control signals from the calculation determining means 80 to the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44 are respectively corrected.

FIG. 10 is a flow chart showing a routine of the damping coefficient selection control according to the running 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 often, and as a result, a large amount of noise or vibration is generated during the change, or a response delay is controlled in order to prevent a response delay. This limits the range of the damping coefficient Dki to be obtained.

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

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 the case of NO at the following, 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 force characteristics of the shock absorbers 1, 2, 3, 4 are made hard so that the damping coefficient 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, if 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 ai on the sprung 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 the predetermined value ai0, the process proceeds to step SA5 and the vehicle speed V is the third
The predetermined vehicle speed V3, for example, 50 km / h or more is determined.

When the determination in step SA5 is YES, that is, when the vehicle speed V is equal to or higher than the third predetermined vehicle speed V3, in step SA6, the damping force characteristic is 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 in D7i even if it is held in D5i, while 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 improvement in riding comfort can be achieved. 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 changing control shown in FIG. 10, the damping coefficient Dki becomes the lower limit value, and even if the condition to be further changed to soft 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, if 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 to drive on a normal road instead of a rough 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 running state of the second predetermined vehicle speed V2 or less, YES is given to the improvement of the riding comfort in step SA9, 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 changing 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, if the determination in step SA8 is NO, that is, 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 the running stability and the 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 characteristic 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 the speed is 80 km / h or less.

As a result, if the vehicle speed V is YES in the middle speed running state of the fifth predetermined vehicle speed V5 or less, the process proceeds to step SA13 to improve the running stability and 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 the 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 the 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 that should be further changed to soft is satisfied, the damping coefficient Dki.
Is held in D7i, while on the other hand, the damping coefficient Dki is held in D10i even if the condition to be further changed to hard is satisfied.

11 and 12 show the damping force characteristic change control of the shock absorbers 1, 2, 3, 4 of the respective wheels which is executed by the control unit 8 when the control mode is selected by the mode selection switch 16. It is a flowchart which shows a basic routine.

First, in step SB1 of FIG. 11, 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 value μ of the road surface friction coefficient from the ABS 66 are estimated. Input each signal. Next, at step SB2, 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 SB3, and when 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 characteristic changes 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 SB4, 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, the estimated value μ of the road surface friction coefficient is less than the predetermined value μ 0, and when the vehicle is traveling on a road surface having a small road surface friction coefficient, if YES, the allowable value τ is set to the predetermined value τ 0 in step SB5. , The estimated value μ of the road surface friction coefficient exceeds the predetermined value μ0. When the vehicle is traveling on a road surface having a large road surface friction coefficient, if NO, the allowable value τ is set to a predetermined value τ1 larger than τ0 in step SB6. , And outputs the allowable value signal to step SB7 as the threshold value setting means 82.

On the other hand, if the determination in step SB3 is NO, which exceeds the fifth predetermined vehicle speed V5, step SB8
Then, it is determined whether the estimated value μ of the road surface friction coefficient is less than or equal to a predetermined value μ 0. As a result, the estimated value μ of the road surface friction coefficient is less than the predetermined value μ0, and when the vehicle is traveling on a road surface having a small road surface friction coefficient, if YES, the allowable value τ is set to the predetermined value τ1 in step SB9, while the road surface friction is set. The estimated value μ of the coefficient exceeds the predetermined value μ 0. When the vehicle is traveling on a road surface having a large road friction coefficient, if NO, the allowable value τ is set to τ in step SB10.
The predetermined value .tau.2 larger than 1 is set, and the allowable value signals are output to step SB7 (threshold value setting means 82). In this case, the allowable value setting means 8 is set by the above steps SB1 to SB6 and steps SB8 to SB10.
1 is configured.

In step SB7, when the allowable value signal is input from the allowable value setting means 81, the first value
Based on the vertical acceleration ai on the spring input from the acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14, the vertical movement component G is calculated according to the formula, and the vertical movement component G is calculated according to the formula. , And the roll component R, respectively.

G = (a1 + a2 + a3 + a4) / 4 ... R = (a1 + a3) / 2- (a2 + a4) / 2 ... Next, in step SB11, the steering angle sensor It is determined whether or not the absolute value | θ | of the steering angle θ input from 65 is in a substantially straight traveling state smaller than the predetermined steering angle θ0, and the absolute value | θ | of the steering angle θ is smaller than the predetermined steering angle θ0. If YES in the small straight traveling state, it is determined in step SB12 whether or not | R / G | is larger than the allowable value τ.

On the other hand, when the determination at step SB11 is NO in the turning state in which the absolute value | θ | of the steering angle θ is larger than the predetermined steering angle θ0 (| θ | ≧ θ0), | R / G | Is larger than the allowable value τ, it cannot be determined that the damping forces of the left and right shock absorbers 1, 2 and 3 and 4 change the steer characteristics to cause diagonal vibration. Therefore, in step SB13 , Threshold α, β
Are set to αsi and βsi, respectively, and output to step SB14 as the operation determining means 80. In this case, when | R / G | is NO smaller than the allowable value τ in the determination of step SB12, the shock absorbers 1, 2 and 3, for the left and right wheels are
Since it is not recognized that the damping force of 4 is different to the extent that the steer characteristic is changed to generate diagonal vibration, the threshold setting means 82 sets the thresholds α and β to αsi and βsi, respectively. And outputs the result to step SB14 (calculation determining means 80) in FIG.

On the other hand, the determination in the above step SB12 is │R
If / G | is larger than the allowable value τ, YES, it is determined in step SB15 whether R> 0. If YES, in step SB16, the damping of the shock absorbers 2, 4 for the right front wheel and the right rear wheel is performed. The thresholds α2, β2 and α4, β4 for changing the sensitivity of changing force characteristics are αh2, βh2, respectively.
And .alpha.h4, .beta.h4, and output to step SB14. On the other hand, the determination in step SB15 is R ≦ 0 NO
In step SB17, the thresholds α1, β1 and α3, β3 for changing the sensitivity of changing the damping force characteristics of the left front wheel and the left rear wheel shock absorbers 1, 3 are set to αh1, βh1 and αh3, βh3, respectively. Set and output to step SB14.

FIGS. 13 (a) and 13 (b) are graphs showing the relationship between the damping force, the relative displacement speed (dXsi / dt-dXui / dt) between the sprung and unsprung parts, and the threshold values αi and βi. This graph is stored in the threshold value setting means 82 in the form of a map.

In FIGS. 13 (a) and 13 (b), Rh is a characteristic region in which the damping force characteristic is changed to the hard side, that is, the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (k
+1) i is the characteristic region where Rs is the characteristic region where the damping force characteristic is changed to the soft side, that is, the damping coefficient Dki.
Respectively indicate the characteristic regions that are changed to D (k + 1) i, which is one smaller than the previous damping coefficient Dki, and the threshold values αh1,
The region between βh1 and the regions between the thresholds αsi and βsi represent regions where the damping force characteristics are not changed, that is, dead zones.

As is clear from FIGS. 13 (a) and 13 (b), the threshold values αhi and βhi shown in FIG. 13 (b) are as shown in FIG. 13 (a).
Is set so that the inclination becomes smaller than the threshold values αsi and βsi shown in FIG. 3, and as a result, the characteristic region Rs in which the damping force characteristic is changed to the soft side is the threshold value αi.
, Βi are smaller than the case where αsi, βsi are selected as the thresholds αi, βi, and the damping force characteristic is changed to the hard side in the characteristic region Rh. Is αhi, βhi as the thresholds αi, βi
If is selected, αs is set as the thresholds αi and βi.
When i and βsi are selected, the damping force characteristics are not easily changed to the soft side and are changed to the hard side when αhi and βhi are selected as the thresholds αi and βi. Threshold value αhi,
βhi, αsi, and βsi are set. It should be noted that the threshold value setting means 82 normally outputs the threshold value signals α = αsi and β = βsi to the operation determining means 80.

Then, the calculation determining means 80, based on the threshold value signal inputted from the threshold value setting means 82,
In the same manner as 1, shock absorbers 1 for the left and right front wheels,
The damping coefficient Dki of the shock absorbers 2 and 4 of the right or left front wheel 3 is controlled.

In step SB14 of FIG. 12, when the threshold value signal is input from the threshold value setting means 82, the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor Vertical acceleration ai on the spring detected by the sensor 14 and the first pressure sensor 6
The damping force Fsi detected by the first, second pressure sensor 62, third pressure sensor 63, and fourth pressure sensor 64 is input. Next, in step SB18, the vertical acceleration ai input in step SB14 is integrated to calculate the sprung displacement speed Xsi (= Σai).

Thereafter, in step SB19, the displacement speed Xsi on the spring calculated in step SB18 is multiplied by a predetermined constant K (K <0) to calculate the skyhook damping force Fai which is the ideal damping force. .. And step SB2
At 0, hα is calculated according to the following expression hα = Fsi (Fai−αFsi) ..., And it is determined at step SB21 whether or not hα is positive.

As a result, if hα is positive and YES, the process proceeds to step SB22, where the first actuators 41, 41 of the shock absorbers 1, 2, 3, 4 whose hα is positive are
A control signal is output to the second actuator 42, the third actuator 43, and the fourth actuator 44, and the step motor 27 is rotated clockwise by one step in FIG. 8, and the damping coefficient Dki is set to one from the previous damping coefficient Dki. Large D (K +
1) i, that is, to change to harder, when hα is not positive NO, the process proceeds to step SB23, and according to the equation, hβ = Fsi (Fai−βFsi). ..................... hβ is calculated, and it is determined in step SB24 whether hβ is negative.

As a result, if YES, that is, hβ is negative, then in step SB25, the first actuators 41, 41 of the shock absorbers 1, 2, 3, 4 whose hβ is negative.
A control signal is output to the second actuator 42, the third actuator 43, and the fourth actuator 44, and the step motor 27 is rotated counterclockwise by one step in FIG. 8 so that the damping coefficient Dki is one more than the previous damping coefficient Dki. Small D (k-
1) Change to i, that is, to become softer. On the other hand, when hβ is NO and is not negative, in step SB26, the step motor 27 is not rotated, that is, the damping coefficient Dki is maintained without changing the previous damping coefficient Dki and the next cycle is started. Transition. In this case, the calculation determining means 80 is determined by the above steps SB14 and SB18 to SB26.
Is configured.

Here, α and β are threshold values for preventing generation of a large noise or vibration or a delay in response as a result of changing the damping coefficient Dki 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 equation 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 make the actual damping force Fsi equal to the skyhook damping force Fai which is an ideal damping force.
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.

The range of the damping coefficient Dki changed in the flow chart of FIG. 12 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 damping coefficient Dki of the previous time is kept as it is, and the stepping motor 27 is rotated counterclockwise in FIG.
Even if it should be changed so as to be 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 damping coefficient selection control routine, damping is performed. The coefficient Dki is retained as it was the previous damping coefficient Dki.

FIG. 14 is executed to reduce the frequency of changing the damping force characteristics of the shock absorber by the response detecting means 92 and the correcting means 91 of the control unit 8 when the control mode is selected by the mode selection switch 16. Shock absorber for each wheel 1,
It is a flowchart which shows the routine of damping force characteristic change control of 2, 3 and 4.

First, after the timer t is started (ON) in step SC1 of FIG. 14, in step SC2, the control symbol generated by the calculation determining means 80, that is, the damping coefficient of the shock absorbers 1, 2, 3, 4 is set. Dki to D (k +
x) i to change the signal to the first actuator 41, the second
It is determined whether or not the signals are output to the actuator 42, the third actuator 43, and the fourth actuator 44. In this case, the range in which the damping coefficient Dki is changed to D (k + x) i is as shown in FIG.
It is limited by the routine of the damping coefficient selection control according to the running state of 0, and the determination is executed only when the damping coefficient D (k + x) i is included in this range.

As a result, if YES when the signal for changing the damping coefficient Dki to D (k + x) i is output, the process proceeds to step SC3 while the signal for changing the damping coefficient Dki to D (k + x) i. When NO is not output, the first actuator 41,
It is determined that the second actuator 42, the third actuator 43, and the fourth actuator 44 are operating normally, and the next control signal is determined. Then, in step SC3, the first actuator 41, the second actuator 4
2, third actuator 43, fourth actuator 44
Input the operation signal of the shock absorber 1,
It is determined whether or not the damping coefficient Dki of 2, 3, 4 has been changed to D (k + x) i, and the damping coefficient Dki has not been changed to D (k + x) i N
When it is O, it is determined in step SC4 whether the timer has passed the first predetermined time t0. As a result, when the timer is NO when the first predetermined time t0 has not elapsed, it waits until the damping coefficient Dki changes to D (k + x) i until the first predetermined time t0 elapses. On the other hand, the timer indicates the first predetermined time t0.
If YES is obtained, it is determined again in step SC5 whether or not the damping coefficient Dki of the shock absorbers 1, 2, 3, 4 of the respective wheels has been changed to D (k + x) i, and the damping coefficient is determined. When Dki is NO, which is not changed to D (k + x) i, it is determined in step SC6 whether or not the timer has passed the second predetermined time t1 longer than the first predetermined time t0.

As a result, when the timer is NO in which the first predetermined time t1 has not elapsed, the damping coefficient Dki is passed between the first predetermined time t0 and the second predetermined time t1.
Waits for a change to D (k + x) i, while the timer
If YES after elapse of the predetermined time t1, step SC7
In, the control unit 8 determines that a failure such as a wire break has occurred between the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44, and Fail is determined, and the process ends.

On the other hand, when the determination at step SC5 is YES when the damping coefficient Dki of the shock absorbers 1, 2, 3, 4 for each wheel is changed to D (k + x) i, that is, the first
When the damping coefficient Dki is changed to D (k + x) i in the period from the passage of the predetermined time t0 to the passage of the second predetermined time t1,
At step SC8, it is determined whether or not the sprung mass absolute velocity gain Gav is larger than the predetermined value Gav0 according to the characteristic diagram showing the change characteristic of the sprung mass absolute velocity gain with respect to the vibration frequency stored in the correction means as a map. To determine. If the determination is NO, that is, the gain Gav of the sprung absolute velocity is smaller than the predetermined value Gav0, the gain Gav of the sprung absolute velocity exceeds the sprung resonance point ω1 and the unsprung resonance point ω2 and becomes smaller. It is determined that the region is moving to a certain high frequency vibration region, and step SC9
To D (k +) of the damping coefficient Dki in the high frequency vibration region.
x) Prohibit changes to i. On the other hand, if the determination in step SC8 is YES, that is, if the gain Gav of the sprung mass absolute speed is larger than the predetermined value Gav0, then the gain Gav of the sprung mass absolute speed is obtained.
Is determined to be in the low-frequency vibration region near the sprung resonance point ω1 and the unsprung resonance point ω2, the process proceeds to step SC10, and the change range of the damping coefficient Dki of the shock absorbers 1, 2, 3, 4 for each wheel is changed. Correct to regulate to D5i to D10i. In this case, the regulation of the damping coefficient Dki within the D5i to D10i range is performed according to the range of the damping coefficient Dki limited by the routine of the damping coefficient selection control according to the running state of FIG. If the range of the damping coefficient Dki limited accordingly is, for example, the range of D1i to D3i, the range of D5i to
Regulation within the D10i range is not performed, and within the D3i to D7i range, regulation within the D5i to D10i range is D5i to D7i.
Is regulated within the range of.

Then, step SC11 and step S
At C12, shock absorbers 1, 2, 3 for each wheel
The threshold α is set to α × 2 and the threshold β is set to β × 2 so that the damping coefficient Dki of 4 is changed by one step.

When the determination in step SC3 is YES, that is, when the damping coefficient Dki is changed to D (k + x) i, that is, the first
The damping coefficient Dki is D (k +
x) i, when the first actuator 41, the second actuator 42, the third actuator 43, the fourth actuator
When it is determined that the actuator 44 is operating normally or returning to normal, it is reset in step SC13 to prepare for the determination of the next control signal.

Therefore, the response detecting means 90 for detecting the operation response speed of the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44 is constituted by the steps SC3 to SC6 of the above flow. There is. Also, by step SC8,
The input frequency detecting means 83 for detecting the frequency of the input applied to the vehicle body is configured.

Therefore, in the above embodiment, the first damping coefficient Dki of the shock absorbers 1, 2, 3, 4 is changed.
The actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44 output an operation signal from the control unit 8, that is, a signal for changing the damping coefficient Dki to D (k + x) i, and the first predetermined time t0
When the damping coefficient Dki is changed to D (k + x) i during the period of time that elapses and the second predetermined time t1 elapses, a decrease in responsiveness is detected, and the shock absorbers 1, 2, 3, 4 are detected. The actuator 1 is operated by the operation signal of the control unit 8 corrected by the correction means 91 so as to reduce the frequency of changing the damping coefficient Dki of the actuator 1. Therefore, the actuator 1 is changed between the soft side and the hard side at an extremely high speed and becomes slightly overheated. , 2,
The operation of 3, 4 or the change frequency is reduced by the correction of the correction means 90.

In this case, the actuators 1, 2, 3, 4 only when the output signal from the input frequency detecting means for detecting the frequency of the input applied to the vehicle body is in the low frequency vibration region lower than the predetermined vibration frequency. When the output signal from the input frequency detecting means 83 is higher than a predetermined vibration frequency, that is, when the gain Gav of the sprung mass absolute speed is in a high frequency vibration region smaller than a predetermined value Gav0 by correcting the operation signal to The actuation signals to the actuators 1, 2, 3 and 4 are maintained at the previous damping coefficient Dki, and the damping coefficient D of the shock absorbers 1, 2, 3 and 4 is maintained.
The frequency of changing ki is reduced to suppress unpleasant low-frequency vibrations input to the vehicle body. In addition, when the gain Gav of the sprung mass absolute velocity is in the low frequency vibration region larger than the predetermined value Gav0, the range of change of the damping coefficient Dki of the shock absorbers 1, 2, 3 and 4 is corrected to be restricted to D5i to D10i. Shock absorbers 1, 2, 3, 4
The damping coefficient Dki is further restricted to a range on the hardware side that secures the steering stability within the range selected according to the speed V, and the frequency of changing the actuator is reduced to secure the steering stability. Further, when the sprung mass absolute velocity gain Gav is in a low-frequency vibration region larger than a predetermined value Gav0, and is restricted to a range on the hardware side that secures steering stability within a range selected according to the speed V. In order to change the damping coefficient Dki of the shock absorbers 1, 2, 3, 4 by one step, the threshold α is set to α × 2 and the threshold β is set to β × 2. The damping coefficients Dki of 1, 2, 3 and 4 are swiftly switched, and the damping coefficient change control is performed quickly to improve the damping force characteristic change control speed. As a result,
While lowering the temperature of the actuators 1, 2, 3, 4
It is possible to reliably prevent the step out of the actuators 1, 2, 3, 4.

The present invention is not limited to the above embodiment, but includes various other modifications.
For example, in the above embodiment, the gain Gav of the absolute sprung velocity is
Is a low-frequency vibration region larger than a predetermined value Gav0,
In addition, when the range is selected in accordance with the speed V within the range on the hardware side that ensures steering stability, the damping coefficient Dki of the shock absorbers 1, 2, 3, 4 is changed by one step, The threshold value α is set to α × 2 and the threshold value β is set to β × 2, but when the gain on the sprung mass absolute velocity is in a high frequency vibration region smaller than a predetermined value, the operation signal to the actuator is The damping coefficient of the shock absorber is changed in the low frequency vibration range where the gain of the sprung mass absolute speed is larger than the predetermined value while keeping the previous damping coefficient as it is and reducing the frequency of changing the damping coefficient of the shock absorber. The control may be performed normally. Further, when the gain of the sprung mass absolute velocity is in a low frequency vibration region in which the gain is larger than a predetermined value, the change range of the damping coefficient of the shock absorber may be corrected so as to be restricted to D5i to D10i.

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 signal of the wiper, and whether or not the road is a bad road is determined based on the amount of change in the vertical acceleration ai within a predetermined time. The bad road may be determined by another method.

Further, in the above embodiment, the stepping motor 2 is operated in the traveling state in which it is determined that the ride comfort should be emphasized.
Rotate 7 in two stages and set the damping coefficient Dki to the previous damping coefficient D
Although it is changed to D (k-2) i which is two smaller than ki, 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 may be formed, and further, the stopper pins 55, 5 may be formed.
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.
Grooves 57 and 58 formed on one side of the stopper pins 55 and 56 are engaged with the lid 53 of the step motor 27 and the other stopper pins 55 and 56 formed on the lid 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 first half of a basic routine of damping force characteristic change control of each shock absorber executed by the control unit.

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

FIG. 13 is a characteristic diagram showing the relationship between damping force, relative speed between sprung mass and unsprung mass, and threshold values α and β.

FIG. 14 is a flowchart showing a routine of damping force characteristic change control of each shock absorber, which is executed by the correction means.

FIG. 15 is a characteristic diagram showing a change characteristic of a gain of the sprung mass absolute speed with respect to a vibration frequency.

[Explanation of symbols]

 1, 2, 3, 4 Shock absorber 6, 7 Wheel 8 Control unit (control means) 9 Vehicle body 41, 42, 43, 44 Actuator 83 Input frequency detecting means 91 Correcting means 92 Responsiveness 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 corrected] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Suspension device for vehicle

[Claims]

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 system for a vehicle is equipped with a shock absorber for damping vertical vibration of a wheel between a sprung body side and an unsprung side wheel side. In this shock absorber, as a variable damping force characteristic type, damping force characteristics (characteristics having different damping coefficients) can be changed in two steps, high and low, and damping force characteristics 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 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 force to the low damping side (ie soft side) and changing the damping force of the shock absorber to the high damping side (ie hard side) when the damping force acts in the damping direction. On the other hand, the damping energy is increased to improve both the riding comfort and 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 or the damping direction of the sprung vertical vibration.
For example, in Japanese Unexamined Patent Publication No. 60-248419, it is investigated whether or not the sign of the relative displacement between the sprung and unsprung parts and the sign of the relative speed 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]

[Problems to be Solved by the Invention] However, in this way,
A shock absorber with a variable damping force characteristic that controls the damping force characteristic based on whether the direction of relative displacement between the sprung and unsprung parts matches the direction of relative velocity between the sprung member and the unsprung member. When the damping force of the shock absorber is controlled by feedback control, the direction of relative displacement between the sprung and unsprung parts and the direction of relative speed between the sprung part and unsprung part often coincide with each other. Because the discrepancy repeats,
Inevitably, there has been a problem that the control computer becomes large and expensive.

Therefore, when solving the above problem and controlling the damping force of the shock absorber by the open control, it is conceivable to use a step motor as an actuator. The direction of relative displacement with the unsprung part and the direction of relative velocity with the sprung part and the unsprung part frequently match and mismatch, so the damping force is changed from the soft side to the hard side, and further from the hard side. It is necessary to drive the step motor so that it is changed between the soft side and the hard side at an extremely high speed, such as on the soft side. In such a case,
There is a problem that the stepping motor heats up or goes out of step, so that the damping force of the shock absorber cannot be controlled as desired according to the vertical vibration state of the vehicle body, which in turn impairs running stability. ..

The present invention has been made in view of the above points, and an object of the present invention is to meet the following requirements:
By effectively changing the damping force characteristic of the shock absorber without deteriorating the running stability, the temperature of the actuator (step motor) is lowered, and the step-out of the actuator is surely prevented.

[0008]

In order to achieve the above object, a solution means devised 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 vehicle suspension device in which the damping force characteristic of the shock absorber is changed and controlled according to the relative relationship between the speed and the unsprung displacement speed.
An actuator that changes the damping force characteristic of the shock absorber, a control unit that outputs a control signal to the actuator to operate the actuator, a responsiveness detection unit that detects an operation response speed of the actuator, and the responsiveness detection unit. And a correction means for correcting the control signal of the control means to the actuator so as to reduce the frequency of changing the damping force characteristic of the shock absorber when the signal is slower than a predetermined operation response speed. It is configured.

The solution means taken by the invention according to claim 2 is dependent on the invention according to claim 1, wherein the correction means is an input frequency for detecting the frequency of the input applied to the vehicle body. The output signal from the detection means is input, the output signal from the input frequency detection means is received, and the actuator is supplied with the output signal only when the signal is in a low frequency vibration region lower than a predetermined vibration frequency. The control signal of the control means is corrected.

Further, the solution means taken by the invention according to claim 3 is dependent on the invention according to claim 1, wherein the correction means uses a signal from the response detection means as a predetermined operation response speed. The control signal of the control means to the actuator is corrected so as to regulate the range of change of the damping force characteristic of the shock absorber by the actuator at a later time.

Further, the solution means taken by the invention according to claim 4 is dependent on the invention according to claim 1, wherein the correction means uses a signal from the response detection means as a predetermined operation response speed. The control signal of the control means to the actuator is corrected so that the damping force characteristic of the shock absorber is kept longer when the speed is slower.

[0012]

With the above structure, in the invention according to claim 1,
The actuator that changes the damping force characteristic of the shock absorber changes the damping force characteristic of the shock absorber when a decrease in responsiveness is detected when the operation response speed detected by the response detecting means is slower than a predetermined operation response speed. Since it operates by the control signal of the control means corrected by the correction means so as to reduce the frequency, the operation of the actuator which changes between the soft side and the hard side at an extremely high speed and tends to overheat, that is, the change frequency of the correction means. By the correction, the temperature of the actuator can be lowered, and the step-out of the actuator can be prevented.

In the invention according to claim 2, the correction means is in a low frequency vibration region in which the output signal from the input frequency detection means for detecting the frequency of the input applied to the vehicle body is lower than a predetermined vibration frequency. Since the control signal of the control means to the actuator is corrected only when, the control signal of the control means to the actuator is output when the output signal from the input frequency detection means is in the high frequency vibration region higher than the predetermined vibration frequency. Is not corrected by the correction means, and is maintained as, for example, the previous damping force characteristic, and the frequency of changing the damping force characteristic of the shock absorber is reduced, so that uncomfortable low-frequency vibration input to the vehicle body It is possible to reduce the temperature of the actuator while suppressing the above, and it is possible to prevent the out-of-step of the actuator.

In the invention according to claim 3, the correction means corrects the control signal of the control means to the actuator when the actuation response speed of the actuator is slower than a predetermined actuation response speed, and the damping force of the shock absorber. Since the changing range of the characteristic is restricted, the damping force characteristic of the shock absorber is restricted to the range on the hard side that secures the steering stability, for example, and the changing frequency of the actuator is reduced by the correction of the correction means, and It is possible to reduce the temperature of the actuator and prevent the actuator from being out of step while ensuring stability and the like.

Further, in the invention according to claim 4, the correction means corrects the control signal of the control means to the actuator when the actuation response speed of the actuator is slower than the predetermined actuation response speed, and the damping force of the shock absorber. Since the characteristics are maintained for a long time , the frequency of actuator changes
Uncomfortable low frequency input to the car body
While suppressing the vibration, the temperature of the actuator can be lowered and the step-out of the actuator can be prevented.

[0016]

As described above, according to the vehicle suspension device of the first aspect of the present invention, the damping force characteristic of the shock absorber is corrected by the correcting means when the actuation response speed of the actuator is slower than the predetermined actuation response speed. Since the control signal of the control means is corrected so as to reduce the change frequency, it is possible to reliably prevent the out-of-step of the actuator while reducing the temperature of the overheated actuator, and improve the running stability.

According to the vehicle suspension device of the second aspect of the invention, the correction means corrects the control signal of the control means to the actuator only when the input frequency applied to the vehicle body is in the low frequency vibration region. In the high frequency vibration region, the control signal of the control means to the actuator is held in the previous damping force characteristic, and the frequency of changing the damping force characteristic of the shock absorber is reduced to suppress unpleasant low frequency vibration, It is possible to reliably prevent the out-of-step of the actuator while lowering the temperature of the actuator.

According to the vehicle suspension device of the third aspect of the present invention, the correction means regulates the range of change of the damping force characteristic of the shock absorber when the actuation response speed of the actuator is slower than the predetermined actuation response speed. Since the control signal of the control means to the actuator was corrected so that the damping frequency characteristic of the shock absorber is restricted to the range on the hardware side that secures the steering stability, the actuator change frequency is reduced and the steering stability is reduced. It is possible to reliably prevent out-of-step of the actuator while ensuring the above, and reducing the temperature of the actuator.

Further, according to the vehicle suspension device of the fourth aspect of the invention, the damping force characteristic of the shock absorber is long when the actuation response speed of the actuator is slower than the predetermined actuation response speed by the correction means.
Since the control signal of the control means to the actuator is corrected so as to be held, it is possible to reduce the frequency of changing the actuator, reduce the temperature of the actuator, and prevent out-of-step of the actuator.

[0020]

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 device according to a preferred embodiment of the present invention includes shock absorbers 1, 2, 3, 4 which are provided corresponding to respective wheels and which dampen vertical vibrations of the respective wheels. ing. Each of the shock absorbers 1, 2, 3 and 4 is configured to be switchable to 10 damping force characteristics having different damping coefficients by an actuator (not shown), and also has 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, 4 to change and control the damping force characteristics of the shock absorbers 1, 2, 3, 4. is there.

Further, on the spring of the vehicle body 9, there is provided a first acceleration sensor 11 for detecting vertical acceleration on the spring of each wheel.
A second acceleration sensor 12, a third acceleration sensor 13, a fourth acceleration sensor 14 are provided, and a vehicle speed sensor 15 for detecting a vehicle speed is 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 where the damping force characteristic becomes hard is selected, and the shock absorbers 1, 2, 3, 3 are only within the range.
Change control of the damping force characteristic of No. 4 is performed. Further, when the soft mode is selected, only the damping coefficient within 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 and 4 is performed in a predetermined manner according to the map or table stored in the control unit 8 in advance. Is becoming

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. Inside 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 coupled to the unsprung and sprung, respectively.

The piston unit 22 is formed with two orifices 23 and 24. 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 for rotating 6 and a first orifice plate 29 integrally attached to the lower end of the shaft 26 and having nine circular holes 28 along the circumference thereof, and integrally with the lower end of the sleeve 25. The second orifice plate 31 is provided and has an arc-shaped elongated 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, 4 provided for other wheels are also the shock absorber 1 shown in FIG. The second actuator 42, the third actuator 43, and the fourth actuator 44 are the same as those shown in FIG. 3, respectively.

FIG. 4 shows the shock absorbers 1, 2, 3,
4 is a graph showing damping force characteristics of No. 4, D1 to D10
Indicates the damping coefficients of the shock absorbers 1, 2, 3, and 4, respectively. In FIG. 4, the vertical axis represents the damping force generated by the shock absorbers 1, 2, 3, 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 D1 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 out of 9 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 elongated hole 30 of the second orifice plate 31.

FIG. 5 is a vibration model diagram of a vehicle suspension device 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 cylindrical body 50 and a cylindrical body 50.
Rotor 51, stator 52 and lid 53 housed inside
It consists of FIG. 7 is a schematic plan view of the rotor 51 and the stator 52. As with a normal step motor, a plurality of rectangular teeth are formed on the outer peripheral portion of the rotor 51, and the inner peripheral portion of the stator 52 is 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.
Two grooves 57 and 58 are formed in the circumferential direction at positions corresponding to. The groove 57 engages with the stopper pin 55 formed on the rotor 51 to control the movable range of the step motor 27, while the groove 58 has 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 circumference 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 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 portion 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.

Referring to 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 a threshold setting 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, 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 A detection signal of vertical acceleration ai on the spring detected by the sensor 14, a sprung spring detected by the first vehicle height sensor 71, the second vehicle height sensor 72, the third vehicle height sensor 73, and the fourth vehicle height sensor 74. The detection signal of the lower relative displacement ( xs-xu ) and the detection signal of the vehicle speed V detected by the vehicle speed sensor 15 are input. Further, the detection signal of the vehicle speed V detected by the vehicle speed sensor 15 and the estimation signal of the estimated value μ of the road surface friction coefficient from the anti-braking system (ABS) 66 are input to the allowable value setting means 81. .. Further, the threshold value setting means 82 receives the steering angle θ detection signal from the steering angle sensor 65 and the allowance value signal from the allowance value setting means 81, and the threshold value setting means 82 calculates the threshold value signal. It is adapted to be output to the means 80. Then, the calculation determining means 80 integrates the vertical acceleration ai on the spring detected by the first to fourth acceleration sensors 11 to 14 by a numerical integration method or the like to calculate the displacement speed Xsi (Σa) on the spring.
i), that is, the output signal from the input frequency detecting means 83 for detecting the frequency of the input applied to the vehicle body is calculated while being converted and used as the sprung mass absolute velocity at the position of each shock absorber 1-4. The vibration frequency region that has been input is compared with the later-described vibration frequency gain of FIG. 15 to determine the vibration frequency region.

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 the wheels 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, 4. The allowable value setting means 81 also detects the vehicle speed V detected by the vehicle speed sensor 15 and the steering angle sensor 6.
5, the shock absorbers 1, 2, 3 for the left and right wheels and the front and rear wheels are stored in accordance with a map or table stored in advance based on the detection signal of the steering angle θ detected by the vehicle 5 and the estimation signal of the estimated value μ of the road surface friction coefficient from the ABS 66. , 4 to calculate the permissible value of the difference between the damping coefficients Dki, and output the permissible value signal to the threshold value setting means 82. Further, the threshold setting means 8
2 is the shock absorbers 1, 2 and 3 and 4 for the left and right wheels according to a map or table stored in advance based on the detection signal of the steering angle θ detected by the steering angle sensor 65.
A threshold value for changing the sensitivity of changing the damping coefficient Dki is set, and the threshold value 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 spring, 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 that it will take a negative value when the upper part and the unsprung part are stretched.
Is set to a positive value when it is pointing up and a negative value when it is pointing down.

Further, the calculation determining means 80 is provided with a responsiveness detecting means 92 and a correcting means 91, and the responsiveness detecting means 92 is controlled by the control signal of the calculation determining means 80. When the operation of the third actuator 43 and the fourth actuator 44 is slower than a predetermined operation response speed, an output signal is output to the correction means 91. Further, the correction means 91 is responsive to the output signal from the responsiveness detection means 92 to determine the shock absorber 1,
To reduce the frequency of changing the damping force characteristics of 2, 3 and 4,
The control signals from the calculation determining means 80 to the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44 are respectively corrected.

FIG. 10 is a flow chart showing a routine of the damping coefficient selection control according to the running 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 often, and as a result, a large amount of noise or vibration is generated during the change, or a response delay is controlled in order to prevent a response delay. This limits the range of the damping coefficient Dki to be obtained.

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

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 the case of NO at the following, 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 force characteristics of the shock absorbers 1, 2, 3, 4 are made hard so that the damping coefficient 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, if 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 ai on the sprung 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 the predetermined value ai0, the process proceeds to step SA5 and the vehicle speed V is the third
The predetermined vehicle speed V3, for example, 50 km / h or more is determined.

When the determination in step SA5 is YES, that is, when the vehicle speed V is equal to or higher than the third predetermined vehicle speed V3, in step SA6, the damping force characteristic is 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 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 improvement in riding comfort can be achieved. 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
As 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, if 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 to drive on a normal road instead of a rough 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 running state of the second predetermined vehicle speed V2 or less, YES is given to the improvement of the riding comfort in step SA9, 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, if the determination in step SA8 is NO, that is, 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 the running stability and the 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 the speed is 80 km / h or less.

As a result, if the vehicle speed V is YES in the middle speed running state of the fifth predetermined vehicle speed V5 or less, the process proceeds to step SA13 to improve the running stability and 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 the 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 the 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, while on the other hand, the damping coefficient Dki is held at D10i even if the condition for further hard change is satisfied.

11 and 12 show the damping force characteristic change control of the shock absorbers 1, 2, 3, 4 of the respective wheels which is executed by the control unit 8 when the control mode is selected by the mode selection switch 16. It is a flowchart which shows a basic routine.

First, in step SB1 of FIG. 11, 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 value μ of the road surface friction coefficient from the ABS 66 are estimated. Input each signal. Next, at step SB2, 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 SB3, and when 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 characteristic changes 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 SB4, 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, the estimated value μ of the road surface friction coefficient is less than the predetermined value μ 0, and when the vehicle is traveling on a road surface having a small road surface friction coefficient, if YES, then the allowable value τ is set to the predetermined value τ 0 in step SB5. , The estimated value μ of the road surface friction coefficient exceeds the predetermined value μ0. When the vehicle is traveling on a road surface having a large road surface friction coefficient, if NO, the allowable value τ is set to a predetermined value τ1 larger than τ0 in step SB6. , And outputs the allowable value signal to step SB7 as the threshold value setting means 82.

On the other hand, if the determination in step SB3 is NO, which exceeds the fifth predetermined vehicle speed V5, step SB8
Then, it is determined whether the estimated value μ of the road surface friction coefficient is less than or equal to a predetermined value μ 0. As a result, the estimated value μ of the road surface friction coefficient is less than the predetermined value μ0, and when the vehicle is traveling on a road surface having a small road surface friction coefficient, if YES, the allowable value τ is set to the predetermined value τ1 in step SB9, while the road surface friction is set. The estimated value μ of the coefficient exceeds the predetermined value μ 0. When the vehicle is traveling on a road surface having a large road friction coefficient, if NO, the allowable value τ is set to τ in step SB10.
The predetermined value .tau.2 larger than 1 is set, and the allowable value signals are output to step SB7 (threshold value setting means 82). In this case, the allowable value setting means 8 is set by the above steps SB1 to SB6 and steps SB8 to SB10.
1 is configured.

In step SB7, when the allowable value signal is input from the allowable value setting means 81, the first value
Based on the vertical acceleration ai on the spring input from the acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14, the vertical movement component G is calculated according to the formula, and the vertical movement component G is calculated according to the formula. , And the roll component R, respectively.

G = (a1 + a2 + a3 + a4) / 4 ... R = (a1 + a3) / 2- (a2 + a4) / 2 ... Next, in step SB11, the steering angle sensor It is determined whether or not the absolute value | θ | of the steering angle θ input from 65 is in a substantially straight traveling state smaller than the predetermined steering angle θ0, and the absolute value | θ | of the steering angle θ is smaller than the predetermined steering angle θ0. If YES in the small straight traveling state, it is determined in step SB12 whether or not | R / G | is larger than the allowable value τ.

On the other hand, when the determination in step SB11 is NO in the turning state where the absolute value | θ | of the steering angle θ is larger than the predetermined steering angle θ0 (| θ | ≧ θ0), | R / G | Is larger than the allowable value τ, it cannot be determined that the damping forces of the left and right shock absorbers 1, 2 and 3 and 4 change the steer characteristics to cause diagonal vibration. Therefore, in step SB13 , Threshold α, β
Are set to αsi and βsi, respectively, and output to step SB14 as the operation determining means 80. In this case, when | R / G | is smaller than the allowable value τ in the determination of step SB12, the shock absorbers 1, 2 and 3 for the left and right wheels are
Since it is not recognized that the damping force of 4 is different to the extent that the steer characteristic is changed to generate diagonal vibration, the threshold setting means 82 sets the thresholds α and β to αsi and βsi, respectively. And outputs the result to step SB14 (calculation determining means 80) in FIG.

On the other hand, the determination in the above step SB12 is │R
If / G | is larger than the allowable value τ, YES, it is determined in step SB15 whether R> 0. If YES, in step SB16, the damping of the shock absorbers 2, 4 for the right front wheel and the right rear wheel is performed. The thresholds α2, β2 and α4, β4 for changing the sensitivity of changing force characteristics are αh2, βh2, respectively.
And .alpha.h4, .beta.h4, and output to step SB14. On the other hand, the determination in step SB15 is R ≦ 0 NO
In step SB17, the thresholds α1, β1 and α3, β3 for changing the sensitivity of changing the damping force characteristics of the left front wheel and the left rear wheel shock absorbers 1, 3 are set to αh1, βh1 and αh3, βh3, respectively. Set and output to step SB14.

FIGS. 13 (a) and 13 (b) show damping force, relative displacement velocity ( Xs-Xu ) between sprung and unsprung, and thresholds αi and β.
It is a graph showing the relationship of i, and this graph is stored in the threshold setting means 82 in the form of a map.

In FIGS. 13 (a) and 13 (b), Rh is a characteristic region in which the damping force characteristic is changed to the hard side, that is, the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (k
+1) i is the characteristic region where Rs is the characteristic region where the damping force characteristic is changed to the soft side, that is, the damping coefficient Dki.
Indicate the characteristic regions that are changed to D (k −1 ) i, which is one smaller than the previous damping coefficient Dki, and the threshold values αh1,
The region between βh1 and the regions between the thresholds αsi and βsi represent regions where the damping force characteristics are not changed, that is, dead zones.

As is clear from FIGS. 13 (a) and 13 (b), the threshold values αhi and βhi shown in FIG. 13 (b) are as shown in FIG. 13 (a).
Is set so that the inclination becomes smaller than the threshold values αsi and βsi shown in FIG. 3, and as a result, the characteristic region Rs in which the damping force characteristic is changed to the soft side is the threshold value αi.
, Βi are smaller than the case where αsi, βsi are selected as the thresholds αi, βi, and the damping force characteristic is changed to the hard side in the characteristic region Rh. Is αhi, βhi as the thresholds αi, βi
If is selected, αs is set as the thresholds αi and βi.
When i and βsi are selected, the damping force characteristics are not easily changed to the soft side and are changed to the hard side when αhi and βhi are selected as the thresholds αi and βi. Threshold value αhi,
βhi, αsi, and βsi are set. It should be noted that the threshold value setting means 82 normally outputs the threshold value signals α = αsi and β = βsi to the operation determining means 80.

Then, the calculation determining means 80, based on the threshold value signal inputted from the threshold value setting means 82,
In the same manner as 1, shock absorbers 1 for the left and right front wheels,
The damping coefficient Dki of the shock absorbers 2 and 4 of the right or left front wheel 3 is controlled.

In step SB14 of FIG. 12, when the threshold value signal is input from the threshold value setting means 82, the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor Vertical acceleration ai on the spring detected by the sensor 14 and the first pressure sensor 6
The damping force Fsi detected by the first, second pressure sensor 62, third pressure sensor 63, and fourth pressure sensor 64 is input. Next, in step SB18, the vertical acceleration ai input in step SB14 is integrated to calculate the sprung displacement speed Xsi (= Σai).

Thereafter, in step SB19, the displacement speed Xsi on the spring calculated in step SB18 is multiplied by a predetermined constant K (K <0) to calculate the skyhook damping force Fai which is the ideal damping force. .. And step SB2
At 0, hα is calculated according to the following expression hα = Fsi (Fai−αFsi) ..., And it is determined at step SB21 whether or not hα is positive.

As a result, if hα is positive and YES, the process proceeds to step SB22, where the first actuators 41, 41 of the shock absorbers 1, 2, 3, 4 whose hα is positive are
A control signal is output to the second actuator 42, the third actuator 43, and the fourth actuator 44, and the step motor 27 is rotated clockwise by one step in FIG. 8, and the damping coefficient Dki is set to one from the previous damping coefficient Dki. Large D (K +
1) i, that is, to change to harder, when hα is not positive NO, the process proceeds to step SB23, and according to the equation, hβ = Fsi (Fai−βFsi). ..................... hβ is calculated, and it is determined in step SB24 whether hβ is negative.

As a result, if YES, that is, hβ is negative, then in step SB25, the first actuators 41, 41 of the shock absorbers 1, 2, 3, 4 whose hβ is negative.
A control signal is output to the second actuator 42, the third actuator 43, and the fourth actuator 44, and the step motor 27 is rotated counterclockwise by one step in FIG. 8 so that the damping coefficient Dki is one more than the previous damping coefficient Dki. Small D (k-
1) Change to i, that is, to become softer. On the other hand, when hβ is NO and is not negative, in step SB26, the step motor 27 is not rotated, that is, the damping coefficient Dki is maintained without changing the previous damping coefficient Dki and the next cycle is started. Transition. In this case, the calculation determining means 80 is determined by the above steps SB14 and SB18 to SB26.
Is configured.

Here, α and β are threshold values for preventing generation of a large noise or vibration or a delay in response as a result of changing the damping coefficient Dki 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 equation 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 make the actual damping force Fsi equal to the skyhook damping force Fai which is an ideal damping force.
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.

The range of the damping coefficient Dki changed in the flow chart of FIG. 12 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 damping coefficient Dki of the previous time is kept as it is, and the stepping motor 27 is rotated counterclockwise in FIG.
Even if it should be changed so as to be 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 damping coefficient selection control routine, damping is performed. The coefficient Dki is retained as it was the previous damping coefficient Dki.

FIG. 14 is executed to reduce the frequency of changing the damping force characteristics of the shock absorber by the response detecting means 92 and the correcting means 91 of the control unit 8 when the control mode is selected by the mode selection switch 16. Shock absorber for each wheel 1,
It is a flowchart which shows the routine of damping force characteristic change control of 2, 3 and 4.

First, after the timer t is started (ON) in step SC1 of FIG. 14, in step SC2, the control symbol generated by the calculation determining means 80, that is, the damping coefficient of the shock absorbers 1, 2, 3, 4 is set. Dki to D (k +
x) i to change the signal to the first actuator 41, the second
It is determined whether or not the signals are output to the actuator 42, the third actuator 43, and the fourth actuator 44. In this case, the range in which the damping coefficient Dki is changed to D (k + x) i is as shown in FIG.
It is limited by the routine of the damping coefficient selection control according to the running state of 0, and the determination is executed only when the damping coefficient D (k + x) i is included in this range.

As a result, if YES when the signal for changing the damping coefficient Dki to D (k + x) i is output, the process proceeds to step SC3 while the signal for changing the damping coefficient Dki to D (k + x) i. When NO is not output, the first actuator 41,
It is determined that the second actuator 42, the third actuator 43, and the fourth actuator 44 are operating normally, and the next control signal is determined. Then, in step SC3, the first actuator 41, the second actuator 4
2, third actuator 43, fourth actuator 44
Input the operation signal of the shock absorber 1,
It is determined whether or not the damping coefficient Dki of 2, 3, 4 has been changed to D (k + x) i, and the damping coefficient Dki has not been changed to D (k + x) i N
When it is O, it is determined in step SC4 whether the timer has passed the first predetermined time t0. As a result, when the timer is NO when the first predetermined time t0 has not elapsed, it waits until the damping coefficient Dki changes to D (k + x) i until the first predetermined time t0 elapses. On the other hand, the timer indicates the first predetermined time t0.
If YES is obtained, it is determined again in step SC5 whether or not the damping coefficient Dki of the shock absorbers 1, 2, 3, 4 of the respective wheels has been changed to D (k + x) i, and the damping coefficient is determined. When Dki is NO, which is not changed to D (k + x) i, it is determined in step SC6 whether or not the timer has passed the second predetermined time t1 longer than the first predetermined time t0.

As a result, when the timer is NO in which the first predetermined time t1 has not elapsed, the damping coefficient Dki is passed between the first predetermined time t0 and the second predetermined time t1.
Waits for a change to D (k + x) i, while the timer
If YES after elapse of the predetermined time t1, step SC7
In, the control unit 8 determines that a failure such as a wire break has occurred between the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44, and Fail is determined, and the process ends.

On the other hand, when the determination at step SC5 is YES when the damping coefficient Dki of the shock absorbers 1, 2, 3, 4 for each wheel is changed to D (k + x) i, that is, the first
When the damping coefficient Dki is changed to D (k + x) i in the period from the passage of the predetermined time t0 to the passage of the second predetermined time t1,
At step SC8, it is determined whether or not the sprung mass absolute velocity gain Gav is larger than the predetermined value Gav0 according to the characteristic diagram showing the change characteristic of the sprung mass absolute velocity gain with respect to the vibration frequency stored in the correction means as a map. To determine. When the determination is NO, that is, the gain Gav of the sprung absolute velocity is smaller than the predetermined value Gav0, the gain Gav of the sprung absolute velocity exceeds the sprung resonance point ω1 and the unsprung resonance point ω2 and becomes smaller. It is determined that the region is moving to a certain high frequency vibration region, and step SC9
To D (k +) of the damping coefficient Dki in the high frequency vibration region.
x) Prohibit changes to i. On the other hand, if the determination in step SC8 is YES, that is, if the gain Gav of the sprung mass absolute speed is larger than the predetermined value Gav0, then the gain Gav of the sprung mass absolute speed is obtained.
Is determined to be in the low-frequency vibration region near the sprung resonance point ω1 and the unsprung resonance point ω2, the process proceeds to step SC10, and the change range of the damping coefficient Dki of the shock absorbers 1, 2, 3, 4 for each wheel is changed. Correct to regulate to D5i to D10i. In this case, the regulation of the damping coefficient Dki within the D5i to D10i range is performed according to the range of the damping coefficient Dki limited by the routine of the damping coefficient selection control according to the running state of FIG. If the range of the damping coefficient Dki limited accordingly is, for example, the range of D1i to D3i, the range of D5i to
Regulation within the D10i range is not performed, and within the D3i to D7i range, regulation within the D5i to D10i range is D5i to D7i.
Is regulated within the range of.

Then, step SC11 and step S
At C12, shock absorbers 1, 2, 3 for each wheel
The threshold value α is set to α × 2 and the threshold value β is set to β / 2 so that the damping coefficient Dki of 4 is held long .

When the determination in step SC3 is YES, that is, when the damping coefficient Dki is changed to D (k + x) i, that is, the first
The damping coefficient Dki is D (k +
x) i, when the first actuator 41, the second actuator 42, the third actuator 43, the fourth actuator
When it is determined that the actuator 44 is operating normally or returning to normal, it is reset in step SC13 to prepare for the determination of the next control signal.

Therefore, the response detecting means 90 for detecting the operation response speed of the first actuator 41, the second actuator 42, the third actuator 43, and the fourth actuator 44 is constituted by the steps SC3 to SC6 of the above flow. There is. Also, by step SC8,
The input frequency detecting means 83 for detecting the frequency of the input applied to the vehicle body is configured.

Therefore, in the above embodiment, the shock absorber
The first to change the damping coefficient Dki of the busers 1, 2, 3, 4
Actuator 41, second actuator 42, third actuator
The actuator 43 and the fourth actuator 44 are
The operation signal from the roll unit 8, that is, the damping coefficient Dki
The signal for changing to D (k + x) i is output and the first predetermined time t0
Within a period of time and before the second predetermined time t1
Decreased responsiveness was detected when the extinction coefficient Dki was changed to D (k + x) i.
The shock absorbers 1, 2
By the correction means 91 so as to reduce the change frequency of the number Dki
Created by the corrected operation signal of the control unit 8.
Move between the soft side and the hard side at extremely high speed.
Actuator that is changed by and becomes overheatedFour1,Four
TwoFourThreeFourThe operation of 4, that is, the change frequency of the correction means 90
I am trying to reduce it by correction.

In that case, the frequency of the input applied to the vehicle body is detected.
The output signal from the input frequency detecting means for outputting is predetermined
When the low frequency vibration region is lower than the vibration frequency of
Only actuatorFour1,FourTwoFourThreeFourOperation signal to 4
From the input frequency detecting means 83 by correcting the signal
Output signal is higher than a given vibration frequency, i.e. spring
The gain Gav of the absolute speed is higher than the predetermined value Gav0.
Actuator when in frequency vibration rangeFour1,Four
TwoFourThreeFourThe operating signal to 4 is the same as the previous damping coefficient Dki.
So that the shock absorbers 1, 2,
Decrease the frequency of changing the damping coefficient Dki of 3 and 4
It suppresses unpleasant low-frequency vibrations that are input. Also,
The sprung absolute velocity gain Gav is larger than a predetermined value Gav0.
Shock absorber when the low frequency vibration range
The change range of the attenuation coefficient Dki of 1, 2, 3, 4 is set to D5i to D10.
By compensating to regulate i,
The damping coefficient Dki of the sovers 1, 2, 3, 4 depends on the speed V.
To ensure steering stability within the selected range.
Actuator is further restricted to the range on the41,4
2,43,44To reduce maneuvering stability
Have secured. In addition, the gain Gav of absolute sprung velocity is
It is a low frequency vibration region larger than the predetermined value Gav0.
Stability within the range selected according to the vehicle speed V
To ensure a shock when regulated to the hard side range
The damping coefficient Dki of the absorber 1, 2, 3, 4 isHeld long
Be, The threshold α is α × 2 and the threshold β is β÷Two
By setting each toActuator 41,
Input to the vehicle body after reducing the change frequency of 42, 43, 44
Suppresses unpleasant low frequency vibrations. As a result,
ActuatorFour1,FourTwoFourThreeFourFigure 4 temperature drop
ActuatorFour1,FourTwoFourThreeFourStep out of 4
Can be reliably prevented.

The present invention is not limited to the above embodiment, but includes various other modifications.
For example, in the above embodiment, the gain Gav of the absolute sprung velocity is
Is a low-frequency vibration region larger than a predetermined value Gav0,
In addition, the damping coefficient Dki of the shock absorbers 1, 2, 3 and 4 is held long when it is restricted to the range on the hard side that secures the steering stability within the range selected according to the speed V. , The threshold α is set to α × 2 and the threshold β is set to β ÷
Each of them is set to 2, but when the gain of the sprung mass absolute velocity is in a high-frequency vibration region where the gain is smaller than a predetermined value, the actuation signal to the actuator is kept at the previous damping coefficient and the damping coefficient of the shock absorber is changed. While decreasing the frequency, the control of changing the damping coefficient of the shock absorber may be performed normally when the gain of the sprung mass absolute velocity is in the low frequency vibration region in which the gain is larger than a predetermined value.
Further, when the gain of the sprung mass absolute velocity is in a low frequency vibration region in which the gain is larger than a predetermined value, the change range of the damping coefficient of the shock absorber may be corrected so as to be restricted to D5i to D10i.

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 signal of the wiper, and whether or not the road is a bad road is determined based on the amount of change in the vertical acceleration ai within a predetermined time. The bad road may be determined by another method.

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

[0087] In the above embodiment, to form the two stopper pins 55, 56 to the rotor 51 of the scan Teppumota 27, scan the grooves 57, 58 for engagement therewith Teppumota 27
Although the forms on the lid 53, is formed in two Sutoppapi Ngasu Te <br/> Ppumo data of the lid, it is formed on Mizogasu Te'<br/> Pumo data row data to be engaged therewith may be in so that, furthermore, the two Sutoppapi emissions of one gas Teppumo other Russia <br/> over data, respectively is formed on the other gas Teppumo data of the lid
Is, for one engages in Sutoppapi emissions formed in the rotor
The lid of Mizogasu Teppumo data, Mizogasu Teppumo to other Sutoppapi emissions engage formed in the lid of the step motor
It may be respectively formed data row data.

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. Although it has to, using a DC motor instead of the step motor 27 may be controlled <br/> damping force of the shock absorber by a 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 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 first half of a basic routine of damping force characteristic change control of each shock absorber executed by the control unit.

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

FIG. 13 is a characteristic diagram showing the relationship between the damping force, the sprung unsprung relative speed, and the threshold values α and β.

FIG. 14 is a flowchart showing a routine of damping force characteristic change control of each shock absorber, which is executed by the correction means.

FIG. 15 is a characteristic diagram showing a change characteristic of a gain of the sprung mass absolute speed with respect to a vibration frequency.

[Explanation of reference numerals] 1, 2, 3, 4 Shock absorber 6, 7 Wheels 8 Control unit (control means) 9 Vehicle body 41, 42, 43, 44 Actuator 83 Input frequency detecting means 91 Correcting means 92 Responsiveness detecting means

[Procedure Amendment 2]

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[Figure 4]

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[Figure 9]

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[Document name to be corrected] Drawing

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[Figure 10]

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FIG. 14

Claims (4)

[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 that is controlled, an actuator that changes a damping force characteristic of the shock absorber, a control unit that outputs a control signal to the actuator to operate the actuator, and a response that detects an operation response speed of the actuator. Control means for controlling the actuator so as to reduce the change frequency of the damping force characteristic of the shock absorber when the detection means and the signal from the responsiveness detection means are received and the signal is slower than a predetermined operation response speed. A suspension device for a vehicle, comprising: a correcting unit that corrects a signal. 2. The correcting means is adapted to receive an output signal from the input frequency detecting means for detecting the frequency of the input applied to the vehicle body, and to receive the output signal from the input frequency detecting means, The vehicle suspension device according to claim 1, wherein the control signal of the control means to the actuator is corrected only when the signal is in a low frequency vibration region lower than a predetermined vibration frequency. 3. The control means for controlling the actuator to control the range of change of the damping force characteristic of the shock absorber by the actuator when the signal from the response detecting means is slower than a predetermined operation response speed. The vehicle suspension system according to claim 1, wherein the signal is corrected. 4. The correction means sends a control signal of the control means to the actuator so as to change the damping force characteristic of the shock absorber by one step when the signal from the response detection means is slower than a predetermined operation response speed. The vehicle suspension system according to claim 1, wherein the suspension is corrected.