JPH0550820A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To prevent generation of diagonal vibration at the time of a high car speed condition while contriving a feeling to ride in a vehicle at the time of a low car speed condition by controlling damping force characteristic of a shock absorber of right/left wheels at the time of the high car speed condition by front/rear two channels. CONSTITUTION:A damping force characteristic of shock absorbers 1 to 4 provided between sprung/unsprung parts of each wheel 5 to 7 is changed controlled in accordance with a mutual relation between sprung/unsprung displacement speeds. Here at the time of a low car speed condition slower than a predetermined car speed by receiving an output from a car speed sensor 15, the damping force characteristic of the shock absorbers 1 to 4 is independently changed and controlled. On the other hand, at the time of high car speed condition faster than the predetermined car speed, an output is generated to two channels of right/left front wheels 5 and rear wheels 6, 7 to control the damping force characteristic of the shock absorbers 1, 2 and 3, 4 respectively to the same phase. In this way, generation of diagonal vibration at the time of a high car speed condition can be prevented while contriving a feeling to ride in a vehicle at the time of a low car speed condition.

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 the steering 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]

However, the damping force is determined based on whether or not the relative displacement direction between the sprung and unsprung portions and the relative speed direction between the sprung portion and the unsprung portion coincide with each other. In the variable damping force type shock absorber that changes and controls the characteristics, the damping force characteristics of the shock absorber are changed and controlled independently for each wheel. When a large difference occurs in the force characteristics, there are problems that the steer characteristics change undesirably and diagonal vibration occurs.

The present invention has been made in view of the above points, and an object of the present invention is to determine the damping force characteristics of the shock absorbers of the left and right wheels at the time of high vehicle speed.
By controlling by the system, the ride comfort of the vehicle in the low vehicle speed state is achieved, while the diagonal vibration is effectively prevented from occurring in the high vehicle speed state to improve the steering stability.

Further, the damping force characteristics of the shock absorbers of the front, rear, left and right wheels are controlled more effectively at a predetermined vehicle speed,
It also aims to further improve steering stability.

[0008]

In order to achieve the above-mentioned object, a solution means provided by the invention according to claim 1 is to provide a shock absorber between the sprung and unsprung portions of each wheel, and to displace the sprung portion. It is premised on a suspension device for a vehicle that changes and controls the damping force characteristics of the shock absorber according to the relative relationship between the speed and the unsprung displacement speed. Then, the vehicle speed detecting means for detecting the vehicle speed and the output from the vehicle speed detecting means are received, and when the vehicle is in a low vehicle speed state slower than a predetermined vehicle speed, the damping force characteristic of the shock absorber of each wheel is independently changed and controlled. On the other hand, when the vehicle is in a high vehicle speed state higher than a predetermined vehicle speed, the control means outputs the two systems of the left and right front wheels and the rear wheel to control the damping force characteristics of the shock absorber between the left and right wheels in the same phase. It was done.

Further, the solution means taken by the invention according to claim 2 is premised on the suspension device for a vehicle according to claim 1, wherein the vehicle speed detecting means for detecting the vehicle speed and the output from the vehicle speed detecting means are received. , When the vehicle speed is slower than the predetermined vehicle speed, the damping force characteristics of the shock absorbers of the wheels are independently changed and controlled, while at the predetermined vehicle speed, the shock absorbers of all the front and rear wheels of the left and right wheels are controlled. And a control means for controlling the damping force characteristics to the same phase.

[0010]

With the above structure, in the invention according to claim 1,
The control means independently controls the damping force characteristics of the shock absorbers of the respective wheels when the vehicle is in a low vehicle speed state slower than a predetermined vehicle speed, depending on the relative relationship between the displacement speed on the spring and the displacement speed under the spring. As a result, the damping force characteristic of the shock absorber of each wheel is changed and controlled, and the ride comfort is improved in the low vehicle speed state. On the other hand, when the vehicle speed is higher than the predetermined vehicle speed, the damping force characteristics of the shock absorbers between the left and right wheels are controlled to be in phase by outputting to the left and right front wheels and the rear wheels. The damping force characteristics of the absorber will be changed so that the difference between them will be zero while approaching each other.
In a high vehicle speed state, diagonal vibration is effectively reduced and steering stability is improved.

Further, in the invention according to claim 2, when the vehicle speed is lower than the predetermined vehicle speed, the damping force characteristics of the shock absorbers of the respective wheels are independently controlled to be changed by the control means so that the vehicle is in the low vehicle speed state. The riding comfort in is likewise good. On the other hand, when the vehicle speed is at a predetermined speed, the damping force characteristics of all the shock absorbers of the left and right front wheels and the rear wheels are all controlled in phase so that they become hard, for example.
The steering stability in the predetermined vehicle speed state, that is, in the state immediately before the transition to the high vehicle speed state becomes better.

[0012]

As described above, according to the vehicle suspension device of the first aspect of the present invention, the control means allows the damping force characteristic of the shock absorber of each wheel to be independent when the vehicle speed is lower than the predetermined vehicle speed. The ride comfort is improved in the low vehicle speed state by controlling the change to the low speed state, and when the vehicle speed is higher than the predetermined vehicle speed, the shock absorber between the left and right wheels is output to the two systems of the left and right front wheels. By controlling the damping force characteristics of the above in the same phase, it is possible to improve the steering stability while effectively reducing the diagonal vibration in the high vehicle speed state.

According to the vehicle suspension device of the second aspect of the invention, the control means independently controls the damping force characteristics of the shock absorber of each wheel when the vehicle speed is lower than the predetermined vehicle speed. In order to improve the riding comfort at low vehicle speed, the damping force characteristics of all shock absorbers on the left and right front and rear wheels are controlled to be in phase so that they are hard at the same speed. It is possible to further improve the steering stability in the high vehicle speed state.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

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

Referring to FIG. 1, a vehicle suspension system according to a preferred embodiment of the present invention includes shock absorbers 1, 2, 3, 4 which are provided corresponding to respective wheels and which dampen vertical vibrations of the respective wheels. ing. Each of the shock absorbers 1, 2, 3 and 4 is configured to be switchable to 10 damping force characteristics having different damping coefficients by an actuator (not shown), and 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 the vertical acceleration on the spring of each wheel.
A second acceleration sensor 12, a third acceleration sensor 13, and a fourth acceleration sensor 14 are provided, and a vehicle speed sensor 15 as vehicle speed detecting means for detecting the 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 in which the damping force characteristic becomes hard is selected, and the shock absorbers 1, 2, 3, 4 are selected only within the range. Change control of damping force characteristics is performed. Further, when the soft mode is selected, only the damping coefficient in the range where the damping force characteristic becomes soft is selected, and the shock absorbers 1, 2,
Change control of damping force characteristics 3 and 4 is performed. Further, when the control mode is selected, the shock absorber 1 and the shock absorber 1 are predetermined in accordance with the map or table stored in the control unit 8 in advance.
The change control of the damping force characteristics of 2, 3 and 4 is performed.

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

FIG. 6 is a schematic perspective view of the step motor 27. The step motor 27 includes a tubular body 50 and a tubular body 50.
Rotor 51, stator 52 and lid 53 housed inside
It consists of FIG. 7 is a schematic plan view of the rotor 51 and the stator 52. As with a normal step motor, a plurality of rectangular teeth are formed on the outer peripheral portion of the rotor 51, and the inner peripheral portion of the stator 52 is Corresponding to this, a plurality of rectangular teeth are formed, the stator 52,
The solenoid 54 is wound. 2 for rotor 51
Book stopper pins 55 and 56 are formed, and as shown in FIG.
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 soot Dk becomes larger and the damping force characteristic becomes harder. On the other hand, when the rotor 51 rotates counterclockwise, the damping coefficient Dk becomes smaller and the damping force characteristic becomes smaller. Is becoming softer, and
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 the vehicle suspension system according to the embodiment of the present invention.

In FIG. 9, the control unit 8 constituting the control system of the vehicle suspension system according to the embodiment of the present invention is provided with a calculation determining means 80 and a permissible value setting means 81. , A first pressure sensor 61, a second pressure sensor 62, and a third pressure sensor 6 provided on the shock absorbers 1, 2, 3, 4 respectively.
The damping force Fsi of each shock absorber 1, 2, 3, 4 detected by the third and fourth pressure sensors 64 (where i is each wheel, i = 1, 2, 3, 4). The detection signal, the detection signal of the vertical acceleration ai on the spring detected by the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14, and the vehicle speed sensor 1.
The detection signals of the vehicle speed V detected by No. 5 are input respectively. Further, the allowable value setting means 81 has a detection signal of the vehicle speed V detected by the vehicle speed sensor 15, a detection signal of the steering angle θ detected by the steering angle sensor 65, and a road surface from the anti-braking system (ABS) 66. Estimated signals of the estimated value μ of the friction coefficient are input.

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

FIG. 10 is a flow chart showing a routine of the damping coefficient selection control according to the traveling state, which is carried out by the control unit 8 when the control mode is selected by the mode selection switch 16. In the coefficient selection control routine, the damping coefficient Dki is changed too 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, the vehicle speed V detected by the vehicle speed sensor 15 is input, and the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14 are input. The vertical acceleration ai on the spring detected by 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 on the sprung ai exceeds the predetermined value ai0. Determine if it is medium or not.

As a result, the vertical acceleration ai on the spring
If it is determined that the vehicle is traveling on a rough road in which the absolute value of exceeds 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 at step SA5 is YES, that is, when the vehicle speed V is equal to or higher than the third predetermined vehicle speed V3, at step SA6, the damping force characteristic is comparatively emphasized with an emphasis on improving the 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 it is possible to achieve both running stability and improvement of riding comfort. 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, when the determination in step SA4 is NO, that is, when 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 check for 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, when the determination in step SA8 is NO, that is, when the vehicle speed V exceeds the second predetermined vehicle speed V2, the vehicle speed V is further increased in step SA10.
Is a fourth predetermined vehicle speed V4, for example, 60 km / h or less.

As a result, when it is determined that the vehicle speed V is in the relatively medium speed running state of the fourth predetermined vehicle speed V4 or less, the routine proceeds to step SA11, where two requests are made to improve running stability and riding comfort. Since it is possible to achieve both, it is possible to set the damping coefficient Dki in the range of D2i to D6i in order to change and control the damping force 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 the riding comfort.
The damping coefficient Dki is set in the range of D4i to D6i in order to slightly change the damping force characteristics of the shock absorbers 1, 2, 3, 4 while satisfying both requirements. Therefore, in the basic routine of the damping force characteristic changing control of FIG. 10, the damping coefficient Dki becomes the lower limit value of D4i,
The damping coefficient Dki is held at D4i even if the condition to be further changed to soft is satisfied, while D6i becomes the upper limit value, and even if the condition to be further changed to hard is satisfied, the damping coefficient Dki is It will be held at D6i.

On the other hand, the vehicle speed V is the fifth predetermined vehicle speed V5.
When it is determined to be NO in 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 to 14 show the damping force characteristic changing 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 vehicle speed V is input by the vehicle speed sensor 15, and it is determined in step SB2 whether the vehicle speed V exceeds the fifth predetermined vehicle speed V5 (80 km / h). As a result, when it is determined that the vehicle speed V is in the medium speed running state lower than the fifth predetermined vehicle speed V5, NO, the flag F is set to F = 0 in step SB3. In this embodiment, when the vehicle speed V exceeds the predetermined vehicle speed V5 and the integrated control of the left and right wheels is started forward and backward, the flag F is set to F =
It is set to 1.

Next, in step SB4, the vertical acceleration ai on the spring detected by the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14 and the first pressure sensor 61, Second pressure sensor 62, third pressure sensor 63, fourth pressure sensor 64
The damping force Fsi detected by is input. Then, in step SB5, the vertical acceleration ai input in step SB4 is integrated to obtain the displacement speed Xsi (= Σ on the spring).
ai) is calculated.

Thereafter, in step SB6, the displacement speed Xsi on the spring calculated in step SB5 is multiplied by a predetermined constant K (K <0) to calculate the skyhook damping force Fai which is an ideal damping force. .. Then, in step SB7, hα is calculated according to the following expression hα = Fsi (Fai−αFsi) ..., And it is determined in step SB8 whether or not hα is positive. To do.

As a result, if hα is positive and YES, the routine proceeds to step SB9, where the first actuator 41, the second actuator 42, and the third actuator of the shock absorbers 1, 2, 3, 4 whose hα is positive. 43, 4th
A control signal is output to the actuator 44, the step motor 27 is rotated clockwise by one step in FIG. 8, and the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (K + 1) i.
While changing to be harder, h
If α is not positive, proceed to step SB10
Further, hβ is calculated according to the equation hβ = Fsi (Fai−βFsi) ... And it is determined in step SB11 whether hβ is negative.

As a result, if hβ is negative and YES, in step SB12, 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 to rotate the stepper motor 27 one step counterclockwise in FIG.
The damping coefficient Dki is one smaller than the previous damping coefficient Dki D (k
-1) Change to i, that is, to be softer. On the other hand, when hβ is NO and is not negative, in step SB13, the stepping 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.

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

That is, when Fsi and Fai have the same sign,
Since (Fai−αFsi) in the 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 match the actual damping force Fsi with the ideal Skyhook damping force Fai, and the damping coefficient Di is zero. It is desirable to make Fsi closer to Fai by changing the value closer to Fai, that is, by changing it to be softer. 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 changes the damping coefficient Dki 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 such a request. ..

On the other hand, FIG. 12 shows that when the determination in step SB2 is YES, that is, when the vehicle speed V exceeds the fifth predetermined vehicle speed V5 and the vehicle is traveling at high speed, the left and right front and rear shock absorbers 1, 2, Threshold value hα of damping force characteristics of 3 and 4
6 is a flowchart for calculating F, hαR and hβF, hβR respectively.

In step SB14 of FIG. 12, it is determined whether the flag F is set to F = 1. as a result,
When it is determined that the flag F should not be set to F = 1, in step SB15, the running stability is prioritized and the damping force characteristics of the shock absorbers 1, 2, 3 and 4 are changed and controlled in the hardest manner. Then, the damping coefficients Dki of the shock absorbers 1, 2, 3, 4 of the front, rear, left and right wheels are all integrated and set to D10i, and the flag F is set to F in step SB16.
Set to = 1. On the other hand, if it is determined in step SB14 that the flag F should be set to F = 1, the process proceeds to step SB17 and subsequent cycles. That is, in step SB17, the average threshold value hαF on the hard side of the left and right front wheels is calculated in accordance with the following formula hαF = (hαFL-hαFR) / 2 ... In step SB18, the average threshold value hαR on the hard side of the left and right front wheels is calculated in accordance with the following formula hαR = (hαRL-hαFR) / 2 ... Then, step S
The average threshold hβ on the soft side of the left and right front wheels at B19
F is calculated according to the following equation hβF = (hβFL-hβFR) / 2 ..., and in step SB20, the average threshold value hαR on the soft side of the left and right front wheels is calculated. HβR is calculated according to the following formula hβR = (hβRL-hβFR) / 2 ....

Next, FIG. 13 is a flow chart showing a routine of damping force characteristic change control when the damping coefficients DkFi of the shock absorbers 1 and 2 for the left and right front wheels are integrated. In step SB21 of FIG. 13, it is determined whether or not hαF calculated in step SB17 is positive. As a result, if hαF is positive and YES, the routine proceeds to step SB22, where a control signal is output to the first actuator 41 and the second actuator 42 of the shock absorbers 1, 2 whose hαF is positive and the step motor 2
7 is rotated clockwise by one step in FIG. 8 to obtain the damping coefficient DkF
i is D (K + 1) i, which is one larger than the previous damping coefficient DkFi
While changing to be harder, h
When αF is not positive, the process proceeds to step SB23, and it is determined whether or not hβF calculated in step SB19 is positive. As a result, if hβF is negative and YES, in step SB24, a control signal is output to the first actuator 41 and the second actuator 42 of the shock absorbers 1 and 2 having negative hβF, and the step motor 27 is operated. It is rotated counterclockwise by 8 by one step, and the damping coefficient DkFi is changed to D (k-1) i, which is one smaller than the previous damping coefficient Dki, that is, softer. On the other hand, when hβF is non-negative, in step SB25 the step motor 2
7 is not rotated, that is, the damping coefficient DkFi is maintained without changing the previous damping coefficient Dki, and the process proceeds to the next cycle.

FIG. 14 is a flow chart showing a routine of damping force characteristic changing control when the damping coefficients DkRi of the shock absorbers 3 and 4 for the left and right rear wheels are integrated.

In step SB26 of FIG. 14, it is determined whether or not hαR calculated in step SB18 is positive. As a result, if hαR is positive and YES, the routine proceeds to step SB27, where a control signal is output to the third actuator 43 and the fourth actuator 44 of the shock absorbers 3, 4 where hαR is positive and the step motor 27 Is rotated clockwise one step in FIG. 8, and the damping coefficient D
kRi is D (K + 1) i, which is one greater than the previous damping coefficient DkFi
While changing to be harder, h
If αR is not positive, the process proceeds to step SB28, and it is determined whether hβR calculated in step SB20 is positive. As a result, if hβR is negative and YES, in step SB29 a control signal is output to the third actuator 43 and the fourth actuator 44 of the shock absorbers 3, 4 whose hβR is negative, and the step motor 27 is operated. The counterclockwise rotation of 8 is performed by one step, and the damping coefficient DkRi is changed to D (k-1) i, which is one smaller than the previous damping coefficient Dki, that is, softer. On the other hand, when hβR is not negative, in step SB30, the step motor 2
7 is not rotated, that is, the damping coefficient Dki is maintained without changing the previous damping coefficient Dki, and the process proceeds to the next cycle.

Note that the range of the damping coefficient Dki (DkFi, DkRi) changed in the flowcharts of FIGS. 11 to 14 is limited by the damping coefficient selection control routine according to the running state of FIG. Figure 8
Even if the damping coefficient Dki should be changed to D (k + 1) i, which is one larger than the previous damping coefficient Dki, by rotating one step clockwise, the previous damping coefficient Dki is maintained and the stepping motor 27 is used. Even if the damping coefficient Dki should be changed by one step counterclockwise in FIG. 8 so that the damping coefficient Dki becomes D (k-1) i which is one or two smaller than the previous damping coefficient Dki. Is equal to the lower limit of the damping coefficient Dki selected in the damping coefficient selection control routine, the damping coefficient Dki is maintained as the previous damping coefficient Dki.

FIGS. 15 to 17 show the case where the control mode is selected by the mode selection switch 16.
Changing the damping force characteristics of the left and right front wheel shock absorbers 1, 2 and the left and right rear wheel shock absorbers 3, 4 executed by the allowable value setting means 81 and the calculation determination means 80 of the control unit 8 to prevent diagonal vibration. It is a flow chart which shows a control routine.

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

On the other hand, the vehicle speed V is the fourth predetermined vehicle speed V
When NO is 4 or more, it is determined that the vehicle is running at a medium speed or higher, the process proceeds to step SC3, and if the difference between the damping coefficients Dki of the shock absorbers of the left and right wheels 1, 2 or 3, 4 is large, the steering is stopped. Since the 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 routine proceeds to step SC4, where it is determined whether the estimated value μ of the road surface friction coefficient is equal to or less than a predetermined value μ0.

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

As a result, if the absolute value | θ | of the steering angle θ is equal to or larger than the first predetermined steering angle θ1, YES, step SC6
, The absolute value | θ | of the steering angle θ is the second predetermined steering angle θ2
It is determined whether or not the above. As a result, the absolute value of the steering angle θ | θ
When | is YES which is equal to or greater than the second predetermined steering angle θ2, it is recognized that the vehicle is traveling on a road surface having a small road surface friction coefficient and the steering wheel is largely operated, so that a load movement is very likely to occur. In step SC7, the tolerance value setting means 81 sets the tolerance value t to t1, for example 1, and outputs the tolerance value signal to the calculation determining means 80 (step SC8 in FIG. 17). On the other hand, the determination in step SC6 is
When the absolute value | θ | of the steering angle θ is less than the second predetermined steering angle θ2, it means that the vehicle is traveling on a road surface having a small road surface friction coefficient, but the steering wheel is not operated so much. Since it is recognized, the allowable value t is t
2, for example, set to 2, and the allowable value signal is calculated by the determination means 8
Output to 0.

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

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

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

On the other hand, when the determination in step SC3 is NO, that is, when the vehicle speed V exceeds the fifth predetermined vehicle speed V5 and the vehicle is in the restricted traveling state, the steer characteristic changes more than in the medium speed traveling state. Since it is easy to produce and diagonal vibration is more likely to occur, the same determination as in the medium speed running state is made in steps SC16 to SC18, step SC22 and step SC24 of FIG. 16, and steps SC19 to SC21.
, Step SC23, step SC25 and step SC
26, the allowable value t is smaller than that in the medium speed running state,
For example, the value is set to a smaller value by one and the allowable value signal is output to the calculation determination means 80.

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

Here, the range of the damping coefficient Dki changed in the flowcharts of FIGS. 15 to 17 is shown in FIG.
Is limited by the routine of the damping coefficient selection control according to the change range of the step motor 27, the step motor 27 is rotated clockwise by one step in FIG. 8, and the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (k + 1). Even when it should be changed to i, if the previous damping coefficient Dki is equal to the upper limit value of the damping coefficient Dki selected by the damping coefficient selection control routine, the damping coefficient Dki
The value of ki is kept as the previous damping coefficient Dki.

Therefore, in the above embodiment, when the vehicle speed V detected by the vehicle speed sensor 15 does not exceed the fifth predetermined vehicle speed V5 in the low vehicle speed state and the medium vehicle speed state,
The damping coefficient Dki of the shock absorbers 1, 2, 3, 4 of each wheel is independently changed and controlled by the control unit 8. That is, the damping coefficients Dki of the shock absorbers 1, 2, 3, 4 of the respective wheels are within the range of the threshold values hα and hβ selected by the damping coefficient selection control, and the shock absorbers 1, 1 of the left and right front wheels and the rear wheels. The allowable value of the difference between the damping coefficients Dki of 2 and 3 and 4 is set to be relatively soft while being changed according to the steering angle θ and the estimated value μ of the road surface friction coefficient, and is set at the low vehicle speed state and the medium vehicle speed state. It is possible to improve the riding comfort.

On the other hand, when the vehicle speed is higher than the fifth predetermined vehicle speed V5, the damping coefficient of the shock absorbers 1, 2 and 3 and 4 between the left and right wheels is output by outputting to the two systems of the left and right front and rear wheels. The damping coefficient Dki of the shock absorbers 1, 2 and 3 and 4 on the left and right wheels is controlled so that they are in phase with each other, and within the range of Dki = D7i to D10i, the threshold value hαF is set so that the difference becomes 0 while approaching each other. , HαR and hβF, hβR are changed, so that the diagonal vibration at the time of high vehicle speed can be effectively reduced and the steering stability can be improved. Moreover, when the vehicle speed is higher than the fifth predetermined vehicle speed V5, and the flag F is not set to F = 1 (F = 0) before the integrated control of the left and right wheels is started in the front and rear, the front, rear, left, and right The damping coefficient Dki of all shock absorbers 1, 2 and 3, 4 of the wheel is the hardest D
The fifth predetermined vehicle speed V5 is controlled by controlling the same phase so as to be 10i.
It is possible to further improve the steering stability while ensuring the safety in the time, that is, the state immediately before shifting to the high vehicle speed state.

The present invention is not limited to the above embodiment, but includes various other modifications.
For example, in the above embodiment, the damping coefficient Dki of all the shock absorbers 1, 2, 3 and 4 of the front, rear, left and right wheels is set to the hardest D10i in order to ensure the safety in the state immediately before shifting to the high vehicle speed state. However, the damping coefficients of all the shock absorbers of the front, rear, left and right wheels are set to D in order to ensure safety in the state immediately before shifting to the high vehicle speed state.
You may make it control in-phase by any one damping coefficient within the range of 7i-D9i. Further, immediately before the vehicle speed is shifted to the high vehicle speed state, the vehicle speed is controlled without controlling the damping coefficients Dki of all the shock absorbers 1, 2 and 3, 4 of the front and rear wheels to the hardest D10i in the same phase. The fifth wheel may be controlled so that the left and right wheels are in phase with the front and rear systems immediately when the low vehicle speed is exceeded.

Further, in the above embodiment, the road surface friction coefficient μ
Is estimated based on the detection signal of ABS66,
The road surface friction coefficient μ may be estimated based on the 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 step 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 and 56 are formed in the rotor 51 of the step motor 27, and the grooves 57 and 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 flow chart showing a basic routine of damping force characteristic change control of the shock absorber for each wheel executed by the control unit.

FIG. 12 is a flow chart showing a first half part of damping force characteristic change control of front and rear shock absorbers executed by a control unit.

FIG. 13 is a flowchart showing a second half of the damping force characteristic change control of the left and right front wheel shock absorbers executed by the control unit.

FIG. 14 is a flowchart showing the latter half of the damping force characteristic changing control of the left and right rear shock absorbers executed by the control unit.

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

FIG. 16 is a flowchart showing the latter half of the damping force characteristic change control of the left and right wheel shock absorbers executed by the allowable value setting means.

FIG. 17 is a flowchart showing a routine of damping force characteristic change control for the shock absorbers for the left and right wheels, which is executed by a calculation determining means.

[Explanation of symbols]

 1, 2, 3, 4 Shock absorber 6, 7 Wheels 8 Control unit (control means) 15 Vehicle speed sensor (vehicle speed detection means) V5 5th predetermined vehicle speed (predetermined vehicle speed)

[Procedure amendment]

[Submission date] October 24, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

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

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, a suspension 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 the steering 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]

However, the damping force is determined based on whether or not the relative displacement direction between the sprung and unsprung portions and the relative speed direction between the sprung portion and the unsprung portion coincide with each other. In the variable damping force type shock absorber that changes and controls the characteristics, the damping force characteristics of the shock absorber are changed and controlled independently for each wheel. When a large difference occurs in the force characteristics, there are problems that the steer characteristics change undesirably and diagonal vibration occurs.

The present invention has been made in view of the above points, and an object of the present invention is to determine the damping force characteristics of the shock absorbers of the left and right wheels at the time of high vehicle speed.
By controlling by the system, the ride comfort of the vehicle in the low vehicle speed state is achieved, while the diagonal vibration is effectively prevented from occurring in the high vehicle speed state to improve the steering stability.

Further, the damping force characteristics of the shock absorbers of the front, rear, left and right wheels are controlled more effectively at a predetermined vehicle speed,
It also aims to further improve steering stability.

[0008]

In order to achieve the above-mentioned object, a solution means provided by the invention according to claim 1 is to provide a shock absorber between the sprung and unsprung portions of each wheel, and to displace the sprung portion. It is premised on a suspension device for a vehicle that changes and controls the damping force characteristics of the shock absorber according to the relative relationship between the speed and the unsprung displacement speed. Then, the vehicle speed detecting means for detecting the vehicle speed and the output from the vehicle speed detecting means are received, and when the vehicle is in a low vehicle speed state slower than a predetermined vehicle speed, the damping force characteristic of the shock absorber of each wheel is independently changed and controlled. On the other hand, when the vehicle is in a high vehicle speed state higher than a predetermined vehicle speed, the control means outputs the two systems of the left and right front wheels and the rear wheel to control the damping force characteristics of the shock absorber between the left and right wheels in the same phase. It was done.

Further, the solution means taken by the invention according to claim 2 is premised on the suspension device for a vehicle according to claim 1, wherein the vehicle speed detecting means for detecting the vehicle speed and the output from the vehicle speed detecting means are received. , When the vehicle speed is slower than the predetermined vehicle speed, the damping force characteristics of the shock absorbers of the wheels are independently changed and controlled, while at the predetermined vehicle speed, the shock absorbers of all the front and rear wheels of the left and right wheels are controlled. And a control means for controlling the damping force characteristics to the same phase.

[0010]

With the above structure, in the invention according to claim 1,
The control means independently controls the damping force characteristics of the shock absorbers of the respective wheels when the vehicle is in a low vehicle speed state slower than a predetermined vehicle speed, depending on the relative relationship between the displacement speed on the spring and the displacement speed under the spring. As a result, the damping force characteristic of the shock absorber of each wheel is changed and controlled, and the ride comfort is improved in the low vehicle speed state. On the other hand, when the vehicle speed is higher than the predetermined vehicle speed, the damping force characteristics of the shock absorbers between the left and right wheels are controlled to be in phase by outputting to the left and right front wheels and the rear wheels. The damping force characteristics of the absorber will be changed so that the difference between them will be zero while approaching each other.
In a high vehicle speed state, diagonal vibration is effectively reduced and steering stability is improved.

Further, in the invention according to claim 2, when the vehicle speed is lower than the predetermined vehicle speed, the damping force characteristics of the shock absorbers of the respective wheels are independently controlled to be changed by the control means so that the vehicle is in the low vehicle speed state. The riding comfort in is likewise good. On the other hand, when the vehicle speed is at a predetermined speed, the damping force characteristics of all the shock absorbers of the left and right front wheels and the rear wheels are all controlled in phase so that they become hard, for example.
The steering stability in the predetermined vehicle speed state, that is, in the state immediately before the transition to the high vehicle speed state becomes better.

[0012]

As described above, according to the vehicle suspension device of the first aspect of the present invention, the control means allows the damping force characteristic of the shock absorber of each wheel to be independent when the vehicle speed is lower than the predetermined vehicle speed. The ride comfort is improved in the low vehicle speed state by controlling the change to the low speed state, and when the vehicle speed is higher than the predetermined vehicle speed, the shock absorber between the left and right wheels is output to the two systems of the left and right front wheels. By controlling the damping force characteristics of the above in the same phase, it is possible to improve the steering stability while effectively reducing the diagonal vibration in the high vehicle speed state.

According to the vehicle suspension device of the second aspect of the invention, the control means independently controls the damping force characteristics of the shock absorber of each wheel when the vehicle speed is lower than the predetermined vehicle speed. In order to improve the riding comfort at low vehicle speed, the damping force characteristics of all shock absorbers on the left and right front and rear wheels are controlled to be in phase so that they are hard at the same speed. It is possible to further improve the steering stability in the high vehicle speed state.

[0014]

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.

[0016] In FIG. 1, a suspension apparatus for a vehicle according to a preferred embodiment of the present invention is provided corresponding to the wheels, shock absorbers 1, 2, 3 order to attenuate the vertical vibration of the wheels Is equipped with. 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 the 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
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 the vertical acceleration on the spring of each wheel.
A second acceleration sensor 12, a third acceleration sensor 13, and a fourth acceleration sensor 14 are provided, and a vehicle speed sensor 15 as vehicle speed detecting means for detecting the 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 in which the damping force characteristic becomes hard is selected, and the shock absorbers 1, 2, 3, 4 are selected only within the range. Change control of damping force characteristics is performed. Further, when the soft mode is selected, only the damping coefficient in the range where the damping force characteristic becomes soft is selected, and the shock absorbers 1, 2,
Change control of damping force characteristics 3 and 4 is performed. Further, when the control mode is selected, the shock absorber 1 and the shock absorber 1 are predetermined in accordance with the map or table stored in the control unit 8 in advance.
The change control of the damping force characteristics of 2, 3 and 4 is performed.

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

FIG. 6 is a schematic perspective view of the step motor 27. The step motor 27 includes a tubular body 50 and a tubular body 50.
Rotor 51, stator 52 and lid 53 housed inside
It consists of FIG. 7 is a schematic plan view of the rotor 51 and the stator 52. As with a normal step motor, a plurality of rectangular teeth are formed on the outer peripheral portion of the rotor 51, and the inner peripheral portion of the stator 52 is Corresponding to this, a plurality of rectangular teeth are formed, the stator 52,
The solenoid 54 is wound. 2 for rotor 51
Book stopper pins 55 and 56 are formed, and as shown in FIG.
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 getting softer, and again
When the rectangular teeth of the rotor 51 are moved to a position facing the adjacent rectangular teeth of the stator 52, that is, when the step motor 27 rotates one step, the damping coefficient Dk changes by one. ing. Therefore, when the stopper pin 55 is located at the first reference position which is the right end of the groove 57, the damping coefficient Dk becomes D10, and the shock absorber 1 generates the hardest damping force, while
When the stopper pin 55 is located at the second reference position which is the left end portion of the groove 57, the damping coefficient Dk becomes D1, and the shock absorber 1 produces the softest damping force.

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

In FIG. 9, the control unit 8 constituting the control system of the vehicle suspension system according to the embodiment of the present invention is provided with a calculation determining means 80 and a permissible value setting means 81. , A first pressure sensor 61, a second pressure sensor 62, and a third pressure sensor 6 provided on the shock absorbers 1, 2, 3, 4 respectively.
The damping force Fsi of each shock absorber 1, 2, 3, 4 detected by the third and fourth pressure sensors 64 (where i is each wheel, i = 1, 2, 3, 4). The detection signal, the detection signal of the vertical acceleration ai on the spring detected by the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14, and the vehicle speed sensor 1.
The detection signals of the vehicle speed V detected by No. 5 are input respectively. Further, the allowable value setting means 81 has a detection signal of the vehicle speed V detected by the vehicle speed sensor 15, a detection signal of the steering angle θ detected by the steering angle sensor 65, and a road surface from the anti-braking system (ABS) 66. Estimated signals of the estimated value μ of the friction coefficient are input.

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

FIG. 10 is a flow chart showing a routine of the damping coefficient selection control according to the traveling state, which is carried out by the control unit 8 when the control mode is selected by the mode selection switch 16. In the coefficient selection control routine, the damping coefficient Dki is changed too 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, the vehicle speed V detected by the vehicle speed sensor 15 is input, and the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14 are input. The vertical acceleration ai on the spring detected by 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 on the sprung ai exceeds the predetermined value ai0. Determine if it is medium or not.

As a result, the vertical acceleration ai on the spring
If it is determined that the vehicle is traveling on a rough road in which the absolute value of exceeds 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 at step SA5 is YES, that is, when the vehicle speed V is equal to or higher than the third predetermined vehicle speed V3, at step SA6, the damping force characteristic is comparatively emphasized with an emphasis on improving the 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 it is possible to achieve both running stability and improvement of riding comfort. 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, when the determination in step SA4 is NO, that is, when 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 check for 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, when the determination in step SA8 is NO, that is, when the vehicle speed V exceeds the second predetermined vehicle speed V2, the vehicle speed V is further increased in step SA10.
Is a fourth predetermined vehicle speed V4, for example, 60 km / h or less.

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

On the other hand, when the determination in step SA10 is NO, that is, when the vehicle speed V exceeds the fourth predetermined vehicle speed V4, the routine proceeds to step SA12, where the vehicle speed V is the fifth predetermined vehicle speed V5, for example. It is determined whether 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 the riding comfort.
The damping coefficient Dki is set in the range of D4i to D6i in order to slightly change the damping force characteristics of the shock absorbers 1, 2, 3, 4 while satisfying both requirements. Accordingly, the routine of the damping coefficient selection control in FIG. 10, the damping coefficient Dki is D4i becomes the lower limit, even if conditions for further changes to the software is satisfied damping coefficient D
ki is held in D4i, while D6i becomes the upper limit value, and the damping coefficient Dki is held in D6i even if the condition to be further changed to hardware is satisfied.

On the other hand, the vehicle speed V is the fifth predetermined vehicle speed V5.
When it is determined to be NO in 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 to 14 show the damping force characteristic changing 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 vehicle speed V is input by the vehicle speed sensor 15, and it is determined in step SB2 whether the vehicle speed V exceeds the fifth predetermined vehicle speed V5 (80 km / h). As a result, when it is determined that the vehicle speed V is in the medium speed running state lower than the fifth predetermined vehicle speed V5, NO, the flag F is set to F = 0 in step SB3. In this embodiment, when the vehicle speed V exceeds the predetermined vehicle speed V5 and the integrated control of the left and right wheels is started forward and backward, the flag F is set to F =
It is set to 1.

Next, in step SB4, the vertical acceleration ai on the spring detected by the first acceleration sensor 11, the second acceleration sensor 12, the third acceleration sensor 13, and the fourth acceleration sensor 14 and the first pressure sensor 61, Second pressure sensor 62, third pressure sensor 63, fourth pressure sensor 64
The damping force Fsi detected by is input. Then, in step SB5, the vertical acceleration ai input in step SB4 is integrated to obtain the displacement speed Xsi (= Σ on the spring).
ai) is calculated.

Thereafter, in step SB6, the displacement speed Xsi on the spring calculated in step SB5 is multiplied by a predetermined constant K (K <0) to calculate the skyhook damping force Fai which is an ideal damping force. .. Then, in step SB7, hα is calculated according to the following expression hα = Fsi (Fai−αFsi) ..., And it is determined in step SB8 whether or not hα is positive. To do.

As a result, if hα is positive and YES, the routine proceeds to step SB9, where the first actuator 41, the second actuator 42, and the third actuator of the shock absorbers 1, 2, 3, 4 whose hα is positive. 43, 4th
A control signal is output to the actuator 44, the step motor 27 is rotated clockwise by one step in FIG. 8, and the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (K + 1) i.
While changing to be harder, h
If α is not positive, proceed to step SB10
Further, hβ is calculated according to the equation hβ = Fsi (Fai−βFsi) ... And it is determined in step SB11 whether hβ is negative.

As a result, if hβ is negative and YES, in step SB12, the first actuators 41, 41 of the shock absorbers 1, 2, 3, 4 whose hβ is negative.
The second actuator 42, third actuator 43, and outputs a control signal to the fourth actuator 44, Step
Motor 27 is rotated by one step in the counterclockwise direction in FIG. 8, a small damping coefficient Dki is one than the previous damping coefficient Dki 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 SB13, the stepping 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.

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

That is, when Fsi and Fai have the same sign,
Since (Fai−αFsi) in the 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 match the actual damping force Fsi with the ideal Skyhook damping force Fai, and the damping coefficient Di is zero. It is desirable to make Fsi closer to Fai by changing the value closer to Fai, that is, by changing it to be softer. 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 changes the damping coefficient Dki 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 such a request. ..

On the other hand, FIG. 12 shows that when the determination in step SB2 is YES, that is, when the vehicle speed V exceeds the fifth predetermined vehicle speed V5 and the vehicle is traveling at high speed, the left and right front and rear shock absorbers 1, 2, Threshold value hα of damping force characteristics of 3 and 4
6 is a flowchart for calculating F, hαR and hβF, hβR respectively.

In step SB14 of FIG. 12, it is determined whether the flag F is set to F = 1. as a result,
When it is determined that the flag F should not be set to F = 1, in step SB15, the running stability is prioritized and the damping force characteristics of the shock absorbers 1, 2, 3 and 4 are changed and controlled in the hardest manner. Then, the damping coefficients Dki of the shock absorbers 1, 2, 3, 4 of the front, rear, left and right wheels are all integrated and set to D10i, and the flag F is set to F in step SB16.
Set to = 1. On the other hand, if it is determined in step SB14 that the flag F should be set to F = 1, the process proceeds to step SB17 and subsequent cycles. That is, in step SB17, the average threshold value hαF on the hard side of the left and right front wheels is calculated according to the following formula hαF = (hαFL + hαFR) / 2 ... according to the following equation hαR = (hαRL + hα RR) / 2 ··········· average threshold Etchiarufaaru in the hard side of the left and right front wheels in step SB18, calculates the Etchiarufaaru. Then, step S
The average threshold hβ on the soft side of the left and right front wheels at B19
Fβ is calculated according to the following formula hβF = (hβFL + hβFR) / 2 ..., and in step SB20 the average threshold value hαR on the soft side of the left and right front wheels is calculated. according to the following equation hβR = (hβRL + hβ RR) / 2 ···········, it calculates the Etchibetaaru.

Next, FIG. 13 is a flow chart showing a routine of damping force characteristic change control when the damping coefficients DkFi of the shock absorbers 1 and 2 for the left and right front wheels are integrated. In step SB21 of FIG. 13, it is determined whether or not hαF calculated in step SB17 is positive. As a result, if hαF is positive and YES, the routine proceeds to step SB22, where a control signal is output to the first actuator 41 and the second actuator 42 of the shock absorbers 1, 2 whose hαF is positive and the step motor 2
7 is rotated clockwise by one step in FIG. 8 to obtain the damping coefficient DkF
i is D (K + 1) i, which is one larger than the previous damping coefficient DkFi
While changing to be harder, h
When αF is not positive, the process proceeds to step SB23, and it is determined whether or not hβF calculated in step SB19 is positive. As a result, if hβF is negative and YES, in step SB24, a control signal is output to the first actuator 41 and the second actuator 42 of the shock absorbers 1 and 2 having negative hβF, and the step motor 27 is operated. It is rotated counterclockwise by 8 by one step, and the damping coefficient DkFi is changed to D (k-1) i, which is one smaller than the previous damping coefficient Dki, that is, softer. On the other hand, when hβF is non-negative, in step SB25 the step motor 2
7 is not rotated, that is, the damping coefficient DkFi is maintained without changing the previous damping coefficient Dki, and the process proceeds to the next cycle.

FIG. 14 is a flow chart showing a routine of damping force characteristic changing control when the damping coefficients DkRi of the shock absorbers 3 and 4 for the left and right rear wheels are integrated.

In step SB26 of FIG. 14, it is determined whether or not hαR calculated in step SB18 is positive. As a result, if hαR is positive and YES, the routine proceeds to step SB27, where a control signal is output to the third actuator 43 and the fourth actuator 44 of the shock absorbers 3, 4 where hαR is positive and the step motor 27 Is rotated clockwise one step in FIG. 8, and the damping coefficient D
kRi is D (K + 1) i, which is one greater than the previous damping coefficient DkFi
While changing to be harder, h
If αR is not positive, the process proceeds to step SB28, and it is determined whether hβR calculated in step SB20 is positive. As a result, if hβR is negative and YES, in step SB29 a control signal is output to the third actuator 43 and the fourth actuator 44 of the shock absorbers 3, 4 whose hβR is negative, and the step motor 27 is operated. The counterclockwise rotation of 8 is performed by one step, and the damping coefficient DkRi is changed to D (k-1) i, which is one smaller than the previous damping coefficient Dki, that is, softer. On the other hand, when hβR is not negative, in step SB30, the step motor 2
7 is not rotated, that is, the damping coefficient Dki is maintained without changing the previous damping coefficient Dki, and the process proceeds to the next cycle.

Note that the range of the damping coefficient Dki (DkFi, DkRi) changed in the flowcharts of FIGS. 11 to 14 is limited by the damping coefficient selection control routine according to the running state of FIG. Figure 8
Even if the damping coefficient Dki should be changed to D (k + 1) i, which is one larger than the previous damping coefficient Dki, by rotating one step clockwise, the previous damping coefficient Dki is maintained and the stepping motor 27 is used. even if to be changed to be in a counterclockwise direction by one step rotation damping coefficient Dki one than the previous damping coefficient Dki small again D (k-1) i in FIG. 8, the last attenuation coefficient Dki attenuate Damping coefficient Dki selected in the coefficient selection control routine
If it is equal to the lower limit value of, the damping coefficient Dki is retained as it was the previous damping coefficient Dki.

FIGS. 15 to 17 show the case where the control mode is selected by the mode selection switch 16.
Changing the damping force characteristics of the left and right front wheel shock absorbers 1, 2 and the left and right rear wheel shock absorbers 3, 4 executed by the allowable value setting means 81 and the calculation determination means 80 of the control unit 8 to prevent diagonal vibration. It is a flow chart which shows a control routine.

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

On the other hand, the vehicle speed V is the fourth predetermined vehicle speed V
When NO is 4 or more, it is determined that the vehicle is running at a medium speed or higher, the process proceeds to step SC3, and if the difference between the damping coefficients Dki of the shock absorbers of the left and right wheels 1, 2 or 3, 4 is large, the steering is stopped. Since the 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 routine proceeds to step SC4, where it is determined whether the estimated value μ of the road surface friction coefficient is equal to or less than a predetermined value μ0.

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

As a result, if the absolute value | θ | of the steering angle θ is equal to or larger than the first predetermined steering angle θ1, YES, step SC6
, The absolute value | θ | of the steering angle θ is the second predetermined steering angle θ2
It is determined whether or not the above. As a result, the absolute value of the steering angle θ | θ
When | is YES which is equal to or greater than the second predetermined steering angle θ2, it is recognized that the vehicle is traveling on a road surface having a small road surface friction coefficient and the steering wheel is largely operated, so that a load movement is very likely to occur. In step SC7, the tolerance value setting means 81 sets the tolerance value t to t1, for example 1, and outputs the tolerance value signal to the calculation determining means 80 (step SC8 in FIG. 17). On the other hand, the determination in step SC6 is
When the absolute value | θ | of the steering angle θ is less than the second predetermined steering angle θ2, it means that the vehicle is traveling on a road surface having a small road surface friction coefficient, but the steering wheel is not operated so much. Since it is recognized, the allowable value t is t
2, for example, set to 2, and the allowable value signal is calculated by the determination means 8
Output to 0.

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

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

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

On the other hand, when the determination in step SC3 is NO, that is, when the vehicle speed V exceeds the fifth predetermined vehicle speed V5 and the vehicle is in a high speed traveling state, the steer characteristic changes more than in the medium speed traveling state. Since it is easy to produce and diagonal vibration is more likely to occur, the same determination as in the medium speed running state is made in steps SC16 to SC18, step SC22 and step SC24 in FIG.
, Step SC23, step SC25 and step SC
26, the allowable value t is smaller than that in the medium speed running state,
For example, the value is set to a smaller value by one and the allowable value signal is output to the calculation determination means 80.

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

Here, the range of the damping coefficient Dki changed in the flowcharts of FIGS. 15 to 17 is shown in FIG.
Is limited by the routine of the damping coefficient selection control according to the change range of the step motor 27, the step motor 27 is rotated clockwise by one step in FIG. 8, and the damping coefficient Dki is one larger than the previous damping coefficient Dki by D (k + 1). Even when it should be changed to i, if the previous damping coefficient Dki is equal to the upper limit value of the damping coefficient Dki selected by the damping coefficient selection control routine, the damping coefficient Dki
The value of ki is kept as the previous damping coefficient Dki.

Therefore, in the above embodiment, when the vehicle speed V detected by the vehicle speed sensor 15 does not exceed the fifth predetermined vehicle speed V5 in the low vehicle speed state and the medium vehicle speed state,
The damping coefficient Dki of the shock absorbers 1, 2, 3, 4 of each wheel is independently changed and controlled by the control unit 8. That is, the damping coefficients Dki of the shock absorbers 1, 2, 3, 4 of the respective wheels are within the range of the threshold values hα and hβ selected by the damping coefficient selection control, and the shock absorbers 1, 1 of the left and right front wheels and the rear wheels. The allowable value of the difference between the damping coefficients Dki of 2 and 3 and 4 is set to be relatively soft while being changed according to the steering angle θ and the estimated value μ of the road surface friction coefficient, and is set at the low vehicle speed state and the medium vehicle speed state. It is possible to improve the riding comfort.

On the other hand, when the vehicle speed is higher than the fifth predetermined vehicle speed V5, the damping coefficient of the shock absorbers 1, 2 and 3 and 4 between the left and right wheels is output by outputting to the two systems of the left and right front and rear wheels. The damping coefficient Dki of the shock absorbers 1, 2 and 3 and 4 on the left and right wheels is controlled so that they are in phase with each other, and within the range of Dki = D7i to D10i, the threshold value hαF is set so that the difference becomes 0 while approaching each other. , HαR and hβF, hβR are changed, so that the diagonal vibration at the time of high vehicle speed can be effectively reduced and the steering stability can be improved. Moreover, when the vehicle speed is higher than the fifth predetermined vehicle speed V5, and the flag F is not set to F = 1 (F = 0) before the integrated control of the left and right wheels is started in the front and rear, the front, rear, left, and right The damping coefficient Dki of all shock absorbers 1, 2 and 3, 4 of the wheel is the hardest D
The fifth predetermined vehicle speed V5 is controlled by controlling the same phase so as to be 10i.
It is possible to further improve the steering stability while ensuring the safety in the time, that is, the state immediately before shifting to the high vehicle speed state.

The present invention is not limited to the above embodiment, but includes various other modifications.
For example, in the above embodiment, the damping coefficient Dki of all the shock absorbers 1, 2, 3 and 4 of the front, rear, left and right wheels is set to the hardest D10i in order to ensure the safety in the state immediately before shifting to the high vehicle speed state. However, the damping coefficients of all the shock absorbers of the front, rear, left and right wheels are set to D in order to ensure safety in the state immediately before shifting to the high vehicle speed state.
You may make it control in-phase by any one damping coefficient within the range of 7i-D9i. Further, immediately before the vehicle speed is shifted to the high vehicle speed state, the vehicle speed is controlled without controlling the damping coefficients Dki of all the shock absorbers 1, 2 and 3, 4 of the front and rear wheels to the hardest D10i in the same phase. 5th place
The right and left wheels may be immediately controlled to be in phase with the front and rear two systems when the constant vehicle speed is exceeded.

Further, in the above embodiment, the road surface friction coefficient μ
Is estimated based on the detection signal of ABS66,
The road surface friction coefficient μ may be estimated based on the 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 .

[0075] Further, in the above embodiment, two stopper pins are used.
55,56TheFormed on rotor 51 of step motor 27
And the grooves 57 and 58 engaging with thisTheStep motor 27
It is formed on the lid 53 ofTwoStopper pinIsTe
PmooOn the lidFormationWasEngage with thisThe groove isTe
PumoOfLowToFormationTo beMaybe
HasTwoStopper pinOfon the other handIsTep MoOfB
-To, On the other handIsTep MoOn each lidFormationIt
Re,LowToFormed stopper pinOfEngage one
The groove isTep MoOn the lid, Step mOn the lidFormation
The other stopper pinWithEngageThe groove isTep Mo
OfLowTo eachFormationBe doneYou may do it.

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

[Procedure Amendment 2]

[Document name to be amended] Statement

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

[Correction method] Change

[Correction content]

[Brief description of drawings]

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

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

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

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

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

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

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

FIG. 8 is a bottom view of the lid.

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

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

FIG. 11 is a flow chart showing a basic routine of damping force characteristic change control of the shock absorber for each wheel executed by the control unit.

FIG. 12 is a flow chart showing a first half part of damping force characteristic change control of front and rear shock absorbers executed by a control unit.

FIG. 13 is a flowchart showing a second half of the damping force characteristic change control of the left and right front wheel shock absorbers executed by the control unit.

FIG. 14 is a flowchart showing the latter half of the damping force characteristic changing control of the left and right rear shock absorbers executed by the control unit.

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

FIG. 16 is a flowchart showing the latter half of the damping force characteristic change control of the left and right wheel shock absorbers executed by the allowable value setting means.

FIG. 17 is a flowchart showing a routine of damping force characteristic change control for the shock absorbers for the left and right wheels, which is executed by a calculation determining means.

[Explanation of reference signs] 1, 2, 3, 4 Shock absorber 6, 7 Wheels 8 Control unit (control means) 15 Vehicle speed sensor (vehicle speed detection means) V5 Fifth predetermined vehicle speed (predetermined vehicle speed)

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

Claims (2)

[Claims] 1. A shock absorber is provided between an unsprung portion and an unsprung portion of each wheel, and a damping force characteristic of the shock absorber is changed according to a relative relationship between a displacement speed on the spring and an unsprung displacement speed. In a vehicle suspension device to be controlled, a vehicle speed detecting means for detecting a vehicle speed and an output from the vehicle speed detecting means are used to independently determine a damping force characteristic of a shock absorber of each wheel when the vehicle speed is lower than a predetermined vehicle speed. While changing to control, the output is output to the two systems of the left and right front wheels and rear wheels when the vehicle speed is higher than the predetermined vehicle speed, and the damping force characteristics of the shock absorbers between the left and right wheels are controlled in phase. And a vehicle suspension device. 2. A shock absorber is provided between the sprung and unsprung portions of each wheel, and the damping force characteristic of the shock absorber is changed according to the relative relationship between the displacement speed on the spring and the unsprung displacement speed. In a vehicle suspension device to be controlled, a vehicle speed detecting means for detecting a vehicle speed and an output from the vehicle speed detecting means are used to independently determine a damping force characteristic of a shock absorber of each wheel when the vehicle speed is lower than a predetermined vehicle speed. And a control means for controlling the damping force characteristics of all the left and right front and rear shock absorbers in the same phase when the vehicle speed is a predetermined vehicle speed.