JP3374393B2 - Vehicle suspension - Google Patents

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 in which the damping force of a shock absorber is controlled.

[0002]

2. Description of the Related Art A suspension system for a vehicle generally has a shock absorber provided between a wheel and a vehicle body.
The device that controls the damping force of the conventional shock absorber is
It is described in JP-A-5-294122. This device controls the damping coefficient of the shock absorber by the sprung speed and the relative speeds of the sprung and unsprung springs based on the Skyhook theory.

[0003]

However, in the vehicle suspension system equipped with the above-mentioned conventional device, the riding comfort and maneuverability of the vehicle cannot be said to be sufficient. The present invention has been made in view of the above problems, and an object thereof is to provide a vehicle suspension device that can improve the riding comfort and controllability of the vehicle.

[0004]

The vehicle suspension system according to the present invention is provided between the left and right wheels and the vehicle body and changes only the damping force characteristic in the low speed range of the expansion / contraction speed.
The left and right shock absorbers, the detection means for detecting the vertical movement of each of the left and right parts of the vehicle body, and the damping force characteristic of the shock absorber in the low speed region based on the vertical movement of the left and right parts of the vehicle body detected by the detection means.
And a control means for controlling the actuator for controlling the shock absorber damping force so that only the change occurs .

The shock absorber mounted on the suspension system for a vehicle of the present invention can change only the damping force characteristic in the low speed range of the expansion / contraction speed by the actuator. Since the expansion and contraction speeds of the left and right shock absorbers are low when the vehicle is turning, when the vertical movement of the left and right parts of the vehicle body is detected by the detection means, the control means controls the actuator based on the detection result to detect the left and right shocks. By changing the damping force of the absorber, it is possible to suppress changes in the posture of the left and right parts of the vehicle body. That is, damping force characteristics in the high speed range
Shock absorber in the low speed range without affecting
Only the damping force characteristic of the soba can be adjusted. Low speed
By changing the damping force characteristics in the range, more optimal
It is possible to obtain riding comfort and steering stability.

Further, the vehicle suspension system according to the present invention is provided between the front and rear wheels and the vehicle body, and is capable of changing only the damping force characteristic in the low speed range of the expansion and contraction speed. Only the absorber, the detection means for detecting the vertical movements of the front and rear parts of the vehicle body, and the damping force characteristics in the low speed range of the shock absorber change based on the vertical movements of the front and rear parts of the vehicle body detected by the detection means <br / > Control means for controlling an actuator for controlling a shock absorber damping force .

The shock absorber of the suspension system for the vehicle uses an actuator to reduce the damping force in the low speed range of expansion and contraction speed.
Only the characteristics can be changed . Since the expansion and contraction speed of the front and rear shock absorbers is low when the vehicle is traveling on a low-frequency swell, the control means controls the actuator based on the detection result when the up-and-down motion of the vehicle front-rear portion is detected by the detection means. By changing the damping force characteristics of the front and rear shock absorbers in the low speed range, it is possible to suppress changes in the posture of the front and rear parts of the vehicle body.

Further, according to the present invention, in the above vehicle suspension device, when the detecting means detects that both vehicle body parts move upward or downward, the control means increases the damping force of each shock absorber. Or the actuator is controlled so as to increase the damping force of one of the shock absorbers more than the other.

When the detection means detects that the left and right or front and rear shock absorbers both move upward or downward,
Since the control means increases the damping force of the left and right or front and rear shock absorbers or controls the actuator so as to increase the damping force of one of the shock absorbers more than the other, the posture change of the left and right front and rear parts of the vehicle body is suppressed. can do.

Further, the vehicle suspension system according to the present invention has four parts.
Four shock absorbers that are respectively provided between the four wheels and the vehicle body and that can change only the damping force characteristics in the low speed range of expansion and contraction speed, and detection that detects vertical movement of four vehicle body parts provided with the shock absorbers When the detection means detects that the right and left or front and rear of the vehicle body part both move upward or downward, the shock absorbers provided in the two vehicle body parts whose vertical velocity absolute value is larger than the remaining ones. Only damping force at low speed increases
And control means for controlling the Actuator <br/> eta for shock absorber damping force control to.

When the left and right or front and rear of the vehicle body part both move upward or downward, that is, when they move in the same phase, it can be estimated that the vehicle body does not make a large roll or pitch movement, respectively. . In such a case, the control means comprehensively considers the behavior of the four vehicle body parts and increases the damping force of the shock absorbers provided in the two vehicle body parts whose vertical velocity absolute values are larger than the remaining ones. As a result, the behavior of the vehicle body as a whole can be suppressed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A vehicle using a vehicle suspension system according to an embodiment will be described below. The same elements or elements having the same function will be denoted by the same reference symbols, without redundant description. Further, description of the same vehicle components as those of the conventional one will be omitted for simplicity.

FIG. 1 shows a vehicle 200 according to the embodiment. The vehicle 200 includes a vehicle body 201 and a right front wheel 11 _FR , a left front wheel 11 _FL , a right rear wheel 11 _RR , and a left rear wheel 11 _RL that are rotatably provided below the vehicle body 201. Front wheel 1
The 1 _FR and 11 _FL are steered by operating the steering handle 4a, and the front wheels 11 _FR and 11 _FL and / or the rear wheels 11 _RR and 11 _RL are rotated by transmission of the driving force of an engine (not shown). The vehicle can be driven by the engine and can change its traveling direction by operating the handle 4a.

Each wheel 11 _FR , 11 _FL , 11 _RR ,
11 _RL is the suspension system 211 _FR , 211 _FL , 211 _RR , 2
It is suspended on the vehicle body 201 by 11 _RL . Each suspension device 211 _FR , 211 _FL , 211 _RR , 211
_RL is each wheel 11 _FR , 11 _FL , 11 _RR , 11 _RL
And shock absorbers (dampers) 10 _FR , 10 _FL , 10 _RR , 10 _RL provided between the vehicle and the vehicle body 201. Suspension device 211 _FR , 211 _FL , 211 _RR , 211 _RL
Are wheels 11 _FR , 11 _FL , 11 _RR , 11 _RL inner wall and vehicle body 2
Lower arm 202 _FR , 202 _FL , 20 for connecting with 01
It has 2 _RRs and 202 _RLs .

Shock absorber 10 _FR , 10 _FL , 10
_RR and 10 _RL are lower arms 202 _FR , 202 _FL and 202
_It is arranged between the _RRs 202 _RL and the vehicle body 201 and can expand and contract in the longitudinal direction according to the load applied between both ends in the longitudinal direction. Shock absorber 10 _FR , 1
0 _FL , 10 _RR , and 10 _RL are coil springs 203 _FR ,
It penetrates through 203 _FL , 203 _RR , and 203 _RL . Coil springs 203 _FR , 203 _FL , 203 _RR , 203 _RL
The lower end of the shock absorber is 10 _FR , 10 _FL , 10
It is fixed to the outer peripheral surface of the center of the _RR and 10 _{RL in} the longitudinal direction.
The upper end is fixed to the vehicle body 201.

Shock absorber 10 _FR , 10 _FL , 10
The damping forces of _RR and 10 _RL are variable in the low speed range of expansion and contraction speed. Shock absorber 10 _FR , 1
The damping forces of 0 _FL , 10 _RR , and 10 _RL are made variable by driving the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL provided on the vehicle body 201. Actuator 2 _FR , 2
_FL, 2 _RR, 2 _RL of drive is controlled by a control signal inputted from the absorber control computer (ECU) 8 disposed in the vehicle body 201 to the actuator _{2 FR, 2 FL, 2 RR} , 2 RL. Therefore, the ECU 8 controls the damping force of the shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 _RL .

The vehicle 200 has wheels 11 _FR , 11 _FL , 1
Wheel speed sensors 6 _FR , 6 _FL provided for every 1 _RR , 11 _RL ,
It is equipped with 6 _RR and 6 _RL and various sensors that measure the posture change and acceleration of the vehicle body. The ECU 8 determines the shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 based on these information.
The damping force of _RL is controlled, and the control of this damping force will be described later. Next, the suspension device will be described in more detail.

FIG. 2 is a sectional view of the vehicle 200 shown in FIG. 1 taken along a line perpendicular to the longitudinal direction. In the figure, suspensions 211 _FR and 211 _FL for the front wheels are shown. . The structure of the suspensions 211 _RR and 211 _RL for the rear wheels is the same as that of the suspensions 211 _FR and 211 _FL for the front wheels, and the description thereof will be omitted. Inside the front wheels 11 _FR and 11 _FL ,
Steering knuckles 206 _FR and 206 _FL that rotatably support wheels 11 _FR and 11 _FL , to which one ends of lower arms 202 _FR and 202 _FL are connected, are provided. Upper _ends of steering knuckles 206 _FR and 206 _FL have upper portions. One _ends of the arms 207 _FR and 207 _FL are connected. Lower arm 202 _FR , 202 _FL and upper arm 20
The other _ends of 7 _FR and 207 _FL are swingably connected to the vehicle body 201.

When the vehicle 200 starts to turn left, for example, the vehicle body 201 tries to rotate right about the axis of the roll center RC parallel to the traveling direction, and the center of gravity G of the vehicle is caused by the turning centrifugal force and the moment around the roll center RC. Is added, the vehicle body 201 leans to the outside of turning, that is, to the right. Therefore, the left shock absorber 10 _FL and the coil spring 203 _FL try to expand according to the spring force of the coil spring 203 _{FL as} the load applied thereto decreases, and the right shock absorber 10 _FR and the coil spring 203 _FR As the load applied thereto increases, the coil spring 203 _FR tries to contract against the spring force of the _FR .

The expansion and contraction speeds of the left and right shock absorbers 10 _FL and 10 _FR during such turning are 0.05 m / s.
The following low speeds are lower than the speed of expansion and contraction when overcoming a small obstacle while the vehicle is straight ahead. The shock absorbers 10 _FL and 10 _FR can change the damping force in the low speed range of the expansion / contraction speed. Although various types of shock absorbers 10 _FL and 10 _FR capable of varying the damping force in the low speed range can be considered, a suitable shock absorber according to the present embodiment will be described below.

FIG. 3 is a cross-sectional view (II-II arrow cross-sectional view) of the main part of the suspension device including the front right shock absorber 10 _FR shown in FIG. 2 taken along the longitudinal direction of the shock absorber 10 _FR . In addition, the remaining shock absorber 1
The structure of 0 _FL , 10 _RR , and 10 _RL is shock absorber 1
The description is omitted because it is the same as 0 _FR . The shock absorber 10 _FR serves to reduce the vibration of the coil spring 203 _FR during traveling to improve the riding comfort of the vehicle and to improve the ground contact of the wheels to improve the steering stability. The structure is such that it can be expanded and contracted according to the state of the vehicle. The shock absorber 10 _FR has its upper end attached to the vehicle body 201, and its lower end attached to the shaft body 13 fixed to the lower arm 202 _FR shown in FIG. The shock absorber 10 _FR includes a piston rod 16 and an outer cylinder 18. An annular tray type guide 10a is fixed to the outer periphery of the central portion of the outer cylinder 18 in the longitudinal direction so as to surround the outer periphery. A bracket 10b is hooked on the upper end portion of the piston rod 16, and a rubber member 10c is interposed between the bracket 10b and the vehicle body 201. Further, between the guide 10a and the bracket 10b and the coil spring 203 _FR is disposed in body 201 is supported elastically by the coil spring 203 _FR.

Inside the outer cylinder 18, an inner cylinder 20 is provided.
Is arranged coaxially with. An annular chamber 21 is formed between the outer cylinder 18 and the inner cylinder 20. A rod guide 22 is fitted into the upper end of the outer cylinder 18. The rod guide 22 is a cylindrical rigid member having a large diameter portion 22a and a small diameter portion 22b. The outer peripheral surface of the small diameter portion 22b is engaged with the inner peripheral surface of the inner cylinder 20, and the outer peripheral surface of the large diameter portion 22a is engaged with the inner peripheral surface of the outer cylinder 18. The rod guide 22 is provided with a through hole at the center thereof. The piston rod 16 is inserted into the through hole so as to be liquid-tight and slidable. A cap 24 is fixed to the upper end of the outer cylinder 18 so that the piston rod 16 penetrates through the center of the cap 24.

The piston rod 16 is a cylindrical hollow member whose lower end has a small diameter. Piston rod 16
Is arranged such that its small diameter portion is housed inside the inner cylinder 20. A rebound stopper 26 and a rebound stopper plate 28 are attached to the piston rod 16 at a position to be housed inside the inner cylinder 20.

The rebound stopper plate 28 is an annular rigid member and is fixed to the outer circumference of the piston rod 16. Further, the rebound stopper 26 is an annular member having elasticity, and is mounted on the rebound stopper plate 28. When the piston rod 16 is displaced upward by a predetermined distance, the rebound stopper 26 comes into contact with the rod guide 22 and further displacement of the piston rod 16 is restricted.

The sub-piston 30 and the main piston 32 are fixed to the lower end of the piston rod 16 in this order from the upper side. The inner space of the inner cylinder 20 includes an upper chamber 34 above the sub-piston 30, a middle chamber 36 between the sub-piston 30 and the main piston 32, and a main piston 32 due to the sub-piston 30 and the main piston 32.
It is partitioned into a lower chamber 38 below.

Sub piston 30 and main piston 32
Are provided with an orifice and a valve mechanism that allow fluid to flow between the upper chamber 34 and the middle chamber 36 and between the middle chamber 36 and the lower chamber 38, respectively, and respond to the forward and backward movement of the piston rod 16. Generates damping force. A base valve 41 is fixed to the lower end of the outer cylinder 18. The base valve 41 is
It is configured to allow the fluid to flow between the lower chamber 38 and the annular chamber 21. A working fluid F _OIL such as oil is contained inside the outer cylinder 18 so as to fill the inner space of the inner cylinder 20 and the annular chamber 21 to a predetermined height.

FIG. 4 is an enlarged view of the region III of the shock absorber shown in FIG. In the left half of FIG. 4, the upper chamber 3
The components that allow the fluid to flow from the 4th side to the lower chamber 38 side are shown, and the components that allow the fluid to flow from the lower chamber 38 side to the upper chamber 34 side are shown in the right half of FIG. It is shown. The working fluid F _OIL is not shown for simplicity. A passage 40 is provided inside the piston rod 16 so as to penetrate therethrough in the axial direction. The passage 40 has a large diameter portion 40a.
And a small diameter portion 40b extending below the large diameter portion 40a. A step 40c is formed at the boundary between the large diameter portion 40a and the small diameter portion 40b of the passage 40. This passage 4
An adjusting rod 42, which is movable along the longitudinal direction of the piston rod 16 by driving the above-mentioned actuator, is inserted in the large diameter portion 40a of 0.

The upper end of the adjusting rod 42 reaches the upper part of the piston rod 16 and engages with the actuator 2 _FR mounted on the vehicle body 201. Actuator 2
_FR is for moving the adjusting rod 42 along the longitudinal direction of the piston rod 16 in response to a signal from the ECU 8, and is composed of, for example, a driving force transmission mechanism such as a stepping motor and a gear.

The adjusting rod 42 is one of the constituent members of the damping force varying means, and is formed in the small diameter portion 42a having an outer diameter smaller than the inner diameter of the large diameter portion 40a of the passage 40 and the lower end portion of the small diameter portion 42a. And a conical portion 42b that is formed. The adjusting rod 42 is arranged such that the tip of the conical portion 42b enters the small diameter portion 40b of the passage 40. Cone 42
A clearance C is formed between the outer peripheral surface of b and the step 40c of the passage 40.

An O-ring 43 is mounted on the outer periphery of the adjusting rod 42 above the small diameter portion 42a. The O-ring 43 defines an annular communication space 44 between the outer circumference of the small diameter portion 42a of the adjusting rod 42 and the inner circumference of the large diameter portion 40a of the passage 40. The communication space 44 communicates with the internal space of the small diameter portion 40b of the passage 40 via the clearance C.

A communication passage 46 extending in the radial direction of the piston rod 16 and connecting the upper chamber 34 and the communication space 44.
Is provided. Further, the piston rod 16 is provided with a communication passage 47 that extends in the radial direction and communicates the internal space of the small diameter portion 40 b of the passage 40 with the middle chamber 36.

The adjusting rod 42 is threadedly engaged with the large diameter portion 4Oa of the passage 40 at a threaded portion (not shown), and the upper end portion thereof is engaged with the actuator 2 _FR . For this reason,
The clearance C can be adjusted by rotating the adjusting rod 42 by the actuator 2 _FR and changing the vertical position of the adjusting rod 42 by this.

A stopper plate 48, a leaf seat 49, a leaf valve 50, a sub piston 30, a leaf valve 54, and a leaf seat 56 are fitted on the outer periphery of the small diameter portion of the piston rod 16 in this order from the upper side.

The leaf valves 50 and 54 are members made of thin plate material and having low bending rigidity. An annular groove 58 is formed on the upper end surface and the lower end surface of the sub-piston 30, respectively.
And 60 are provided. Leaf valves 50 and 54
Are arranged so as to close the annular grooves 58 and 60, respectively. In addition, the sub-piston 30 has an annular groove 5
A through passage 62 that communicates the internal space of 8 with the middle chamber 36, and a through passage 64 that communicates the internal space of the annular groove 60 with the upper chamber 34 are provided.

The leaf valve 50 opens by being flexibly deformed when the hydraulic pressure in the middle chamber 36 becomes higher than the hydraulic pressure in the upper chamber 34 by a predetermined valve opening pressure P1. To allow the flow of the working fluid F _OIL from the upper chamber 34 to the upper chamber 34. Also,
The leaf valve 54 opens by being flexibly deformed when the hydraulic pressure in the upper chamber 34 becomes higher than the hydraulic pressure in the middle chamber 36 by a predetermined valve opening pressure P2, and opens from the upper chamber 34 to the middle chamber. Allow the flow of working fluid towards 36.

A piston ring 66 is attached to the outer circumference of the sub piston 30. The piston ring 66 ensures the sealing performance between the sub piston 30 and the inner cylinder 20. Leaf sheet 5 on the outer circumference of the piston rod 16
Below 6 is a hollow communication member 6 in order from the upper side.
8, leaf sheets 70, spacers 72, spring sheets 74, and spacers 76 are fitted.

The communication member 68 is provided with a communication passage 77 which penetrates in the radial direction and communicates with the communication passage 47 of the piston rod 16. A spring seat 78 is fitted on the outer periphery of the spacer 76 so as to be slidable in the axial direction. A spring 80 is arranged between the spring seat 74 and the spring seat 78.

Spacer 76 on the outer circumference of the piston rod 16
The leaf valve 82, the main piston 32, and the leaf valve 86 are fitted in order from the upper side to the lower side of the. A plurality of seat surfaces 92 are provided on the upper end surface of the main piston 32. A plurality of seat surfaces 94 are provided on the lower end surface of the main piston 32 at positions that do not correspond to the seat surface 92. The leaf valves 82 and 86 are members formed by stacking a plurality of thin plate materials, and are arranged so as to contact the top surfaces of the seat surfaces 92 and 94, respectively. A piston ring 95 is attached to the outer circumference of the main piston 32. The piston ring 95 ensures the sealing property between the main piston 32 and the inner cylinder 20.

The main piston 32 is also provided with through passages 96 and 98 penetrating its axial direction.
The through passage 96 is configured such that the upper end thereof opens into the recess between the seat surfaces 92, and the lower end thereof opens into the top surface of the seat surface 94. Also, the through passage 9
8 is configured to open at the upper end thereof to the top surface of the seat surface 92 and to open at the lower end thereof into a recess between the seat surfaces 94.

In the thin plate material closest to the main piston 32 constituting the leaf valve 82, the first orifice (FIG. 2) for communicating the through passage 98 and the inner chamber 36 with the leaf valve 82 in contact with the seat surface 92. (Not shown) is formed.

A sleeve-shaped spacer 198 is fitted on the outer circumference of the piston rod 16 and below the leaf valve 86. A screw portion 16c is formed at the lower end of the piston rod 16, and the spring seat 100 is screwed to the screw portion 16c. Spacer 1
A spring seat 102 is mounted on the outer periphery of 98 so as to be slidable in the axial direction. A spring 104 is arranged between the spring seat 102 and the spring seat 100.

A screw 105 for closing the passage 40 is attached to the lower end of the small diameter portion of the piston rod 16. Therefore, the communication between the passage 40 and the lower chamber 38 is blocked, and the passage 40 communicates only with the upper chamber 34 and the middle chamber 36 when the leaf valves 82 and 86 are closed.

The member arranged on the outer periphery of the lower diameter portion of the lower part of the piston rod 16 is pressed by the lower spring seat 100 toward the step surface at the boundary between the large diameter portion 16a and the small diameter portion, so that the piston It is integrally fixed to the rod 16.

The leaf valves 82 and 86 are respectively
The urging force of the springs 80 and 104 pushes the main piston 32 toward the top surfaces of the seat surfaces 92 and 94. When the fluid pressure in the lower chamber 38 becomes higher than the fluid pressure in the middle chamber 36 by a predetermined valve opening pressure P3 or more, the leaf valve 82 is bent and deformed upward against the biasing force of the spring 80. The valve is opened to allow the flow of the working fluid from the lower chamber 38 to the middle chamber 36. Further, in the leaf valve 86, the fluid pressure in the middle chamber 36 is higher than the fluid pressure in the lower chamber 38 by a predetermined valve opening pressure P.
At a high pressure of 4 or more, the valve is opened by bending and deforming downward against the urging force of the spring 104, and allows the flow of the working fluid from the middle chamber 36 to the lower chamber 38.

In the present embodiment, the leaf valve 50
The valve opening pressures P1 and P2 are set to very small values because the valves 54 and 54 are made of a low-rigidity thin plate member. On the other hand, since the leaf valves 82 and 86 are pressed by the springs 80 and 104, respectively,
The valve opening pressures P3 and P4 are set to values higher than the valve opening pressures P1 and P2.

FIG. 5 shows damping force characteristics realized by the shock absorber 10 _FR . Horizontal axis is piston rod 1
6 shows the longitudinal displacement velocity V, and the vertical axis shows the damping force F generated by the shock absorber 10 _FR . In the following description, the damping force F when the piston rod 16 is displaced in the direction of withdrawing from the inner cylinder 20, that is, the extension direction is positive.

Piston rod 16 extends in the positive direction
Is displaced to the lower chamber 3 and the volume of the upper chamber 34 decreases.
The volume of 8 increases. In order to compensate for these volume changes, the working fluid F _OIL shown in FIG.
6 and flows into the lower chamber 38. Furthermore, piston rod 1
The volume of the inner cylinder 20 increases as 6 moves out of the inner cylinder 20. In order to compensate for the increase in the volume of the inner cylinder 20, the working fluid F _OIL flows from the annular chamber 21 into the lower chamber 38 via the base valve 41.

When the displacement speed V of the piston rod 16 is sufficiently low, the pressure difference between the upper chamber 34 and the middle chamber 36 and the pressure difference between the middle chamber 36 and the lower chamber 38 are small. Both the leaf valve 54 and the leaf valve 86 are held in the closed state. Therefore, the working fluid F _OIL in the upper chamber 34
Is a communication passage 46 of the piston rod 16, a communication space 44,
Clearance C, small diameter portion 40b of passage 40, communication passage 4
7 and the communication passage 68 of the communication member 68 (hereinafter referred to as a bypass passage) to flow into the middle chamber 36. The working fluid in the inner chamber 36 is the main piston 3
The second through-passage 96 and the second orifice or the first orifice formed in the leaf valve 86 flow into the lower chamber 38. When the working fluid F _OIL flows through the bypass passage and these orifices, a damping force due to the flow resistance is generated.

The damping force F exerted by the shock absorber 10 is the damping force Fa generated according to the flow resistance R1 when the working fluid flows from the upper chamber 34 to the middle chamber 36, and the damping fluid F from the middle chamber 36 to the working fluid. It is the sum of the damping force Fb generated according to the flow resistance R2 when flowing into the chamber 38. For this reason. As indicated by reference numeral A1 in FIG. 5, the damping force F rises with a large gradient as the displacement speed V increases.

When the flow resistance R1 when the working fluid F _OIL flows from the upper chamber 34 to the middle chamber 36 increases, the differential pressure between the upper chamber 34 and the middle chamber 36 increases. Also, the working fluid F _OIL
When the flow resistance R2 when the air flows from the middle chamber 36 to the lower chamber 38 increases, the differential pressure between the middle chamber 36 and the lower chamber 38 increases. Then, when the displacement speed V increases until the pressure difference between the upper chamber 34 and the middle chamber 36 reaches the valve opening pressure P2 of the leaf valve 54, the leaf valve 54 opens. Hereinafter, the displacement speed V of the piston rod 16 when the leaf valve 54 opens and the damping force F generated by the shock absorber 10 _FR.
Are respectively referred to as a first valve opening speed V1 and a first valve opening damping force F1.

As described above, in the present embodiment, the first valve opening damping force F1 has a very small value, for example, 3 to 5k.
The valve opening pressure P2 of the leaf valve 54 is set to be sufficiently small so as to be gf. In this way, the leaf valve 54
When the valve opening pressure P2 of 1 is set, the first valve opening speed V1 becomes a very low speed of 0.05 m / s or less.

When the leaf valve 54 opens, the upper chamber 34
The movement of the fluid from the inside to the middle chamber 36 is performed through the through passage 64 together with the bypass passage. For this reason,
The flow resistance R1 when the working fluid F _OIL flows from the upper chamber 34 toward the middle chamber 36 is reduced. And distribution resistance R1
Is reduced, as shown by the reference numeral A2 in FIG.
In the region where the displacement speed V exceeds the first valve opening speed V1, the increasing gradient of the damping force F decreases.

When the displacement speed V further increases and the differential pressure between the middle chamber 36 and the lower chamber 38 reaches the valve opening pressure P4 of the leave valve 86, the leaf valve 86 opens. Hereinafter, the displacement speed V and the damping force F when the leaf valve 86 opens will be calculated as the second valve opening speed V2 and the second valve opening damping force F2, respectively.
Called. In the present embodiment, the second valve opening damping force F
The valve opening pressure P4 of the leaf valve 86 is set so that 2 becomes about 50 kgf, for example. In this case, the second valve opening speed V2 has a value of about 0.2 m / s.

When the leaf valve 86 opens, the inner chamber 36
By increasing the flow passage area of the flow passage from the lower chamber to the lower chamber 38,
The flow resistance R2 when the working fluid F _OIL flows from the middle chamber 36 to the lower chamber 38 becomes small. Therefore, as indicated by reference numeral A3 in FIG. 5, in the region where the displacement speed V exceeds the second valve opening speed V2, the increasing gradient of the damping force F further decreases.

On the other hand, when the piston rod 16 is displaced in the direction of entering the inner cylinder 20, that is, in the contracting direction,
As the volume of the upper chamber 34 increases, the volume of the lower chamber 38 decreases. To compensate for these volume changes, the working fluid F _OIL flows from the lower chamber 38, through the middle chamber 36 and into the upper chamber 34. Further, as the piston rod 16 enters the inner cylinder 20, the volume of the inner cylinder 20 decreases. Such inner cylinder 2
To compensate for the zero volume reduction, the working fluid flows from the lower chamber 38 through the base valve 41 into the annular chamber 21.

In the present embodiment, the leaf valve 50
The valve opening pressure P1 is set to substantially match the valve opening pressure P2 of the leaf valve 54. Therefore, the displacement speed V
Reaches v1 which is almost equal to the first valve opening speed V1, and the damping force F
The leaf valve 50 opens at a time point when f1 becomes substantially equal to the first valve opening damping force F1.

Further, the valve opening pressure P3 of the leaf valve 82 is
It is set to be slightly smaller than the valve opening pressure P4 of the leaf valve 86. Therefore, the displacement speed V reaches v2 (for example, about 0.15 m / s) that is smaller than the second valve opening speed V2, and the damping force F becomes f2 (for example, about 30 kgf) that is smaller than the second valve opening damping force F2. At that point, the leaf valve 82 opens. The leaf valve 50 will be described below.
V1 and v2, which are the displacement speeds of the piston rod 16 when the valves 82 and 82 open, are also the first valve opening speed and the second valve speed, respectively.
The valve opening speed is also referred to, and the damping forces F1 and f2 when the leaf valves 50 and 82 are opened are also referred to as the first valve opening damping force and the second valve opening damping force, respectively.

Even when the piston rod 16 is displaced in the contracting direction, as in the case where the piston rod 16 is displaced in the extending direction, until the displacement velocity V of the piston rod 16 reaches the first valve opening velocity v1, 5, the damping force F rises with a relatively large gradient. Then, when the displacement speed V reaches the first valve opening speed v1, the leaf valve 50 is opened, so that the symbol B in FIG.
As indicated by the reference numeral 2, the increasing gradient of the damping force F decreases.
Further, when the displacement speed V reaches the second valve opening speed v2, the leaf valve 82 opens, so that the increasing gradient of the damping force F further decreases, as indicated by reference numeral B3 in FIG.

Thus, this shock absorber 10 _FR
According to the above, the displacement speed V of the piston rod 16 transits from a low speed range (first valve opening speed V1, v1 or less) to a high speed range (area exceeding the first valve opening speed V1, v1). Accordingly, the damping force characteristic in which the increasing gradient of the damping force F decreases gradually is realized.

The opening of the bypass passage changes according to the size of the clearance C. The larger the opening of the bypass passage, the smaller the flow resistance when the working fluid F _OIL flows through the bypass passage. When the flow resistance when flowing through the bypass passage is reduced, the pressure difference between the upper chamber 34 and the middle chamber 36 that is generated for a constant displacement speed V is reduced,
The damping force F becomes smaller. That is, reference numerals a1 and b in FIG.
As indicated by the dashed line with a 1, the gradient of the damping force characteristic becomes small.

Therefore, by adjusting the clearance C, the damping force characteristic in the region where the displacement velocity V of the piston rod 16 is higher than the first valve opening velocity V1, v1, that is, in the high speed region, is maintained substantially constant, First valve opening speed V
It is possible to change the damping force characteristic at 1, v1 or less. As described above, the first valve opening speeds V1 and v1 are 0.05
It is set to a low value of m / s or less. Therefore, according to the shock absorber 10 _FR according to the present embodiment,
By changing the clearance C, 0.05 m /
Only the damping force characteristic of the shock absorber 10 _FR in the low speed range of s or less can be adjusted. Further, by controlling the drive of the actuator 2 _FR to change the clearance C stepwise, it is also possible to change the gradient of the damping force characteristic of the shock absorber 10 _FR stepwise in the low speed range of the piston rod 16. .

Shock absorber 1 according to the present embodiment
A running experiment was conducted using 0 _FR , 10 _FL , 10 _RR , and 10 _RL . As a result, depending on the damping force characteristics in the low speed range,
The riding comfort and steering stability of the vehicle have changed significantly. For example, when the clearance C is decreased to increase the gradient of the damping force characteristic in the low speed range, the steering holding force of the steering wheel during turning is increased, and the feeling of steering response is increased. In addition, the responsiveness of the rolling speed of the vehicle during turning and the yawing change of the vehicle during steering change sensitively to changes in the damping force characteristics in the low speed range. Therefore, according to the shock absorber 10 _FR according to the present embodiment, by adjusting the clearance C and changing the damping force characteristics in the low speed range, it is possible to obtain more optimal riding comfort and steering stability.

The shock absorber whose damping force is to be controlled is not limited to the shock absorber 10 _FR described above, and any other structure can be used as long as the damping force can be varied in the low speed range of expansion / contraction speed. It may be one.

Next, the above-mentioned shock absorber 10 _FR , 1
The system configuration of the vehicle 200 equipped with 0 _FL , 10 _RR , and 10 _RL will be described.

FIG. 6 shows a system configuration of vehicle 200 according to the present embodiment. The vehicle 200 includes a steering angle sensor 4b that outputs a steering angle signal corresponding to the steering angle of the steering wheel 4a, and wheels 11 _FR , 11 _FL , 11 _RR ,
Wheel speed sensors 6 _FR , 6 _FL , 6 _RR , 6 _RL that output wheel speed signals corresponding to the rotation speed of 11 _RL are provided. Also,
The vehicle 200 includes a yaw rate sensor 5 that outputs a yaw rate signal according to the angular velocity of the vehicle body 201 in the yaw direction, a vertical G sensor 217 that outputs a vertical acceleration signal according to the vertical acceleration of the vehicle body 201, and the left and right sides of the vehicle body 201. Lateral G sensor 21 that outputs a lateral acceleration signal according to the directional acceleration
9, a roll rate sensor 226 that outputs a roll rate signal according to the angular velocity of the vehicle body 201 in the roll direction, and the vehicle body 201 for each position of the wheels 11 _FR , 11 _FL , 11 _RR , 11 _RL.
G sensor 7 _FR , which is provided at a portion of which outputs an individual vertical acceleration signal according to the vertical acceleration of the vehicle body for each wheel position,
7 _FL , 7 _RR , 7 _RL . These steering angle signal, wheel speed signal, yaw rate signal, vertical acceleration signal, lateral acceleration signal, roll rate signal and individual vertical acceleration signal are input to the ECU 8, and the ECU 8 controls the damping force of the shock absorber based on the input signals. And various controls.

FIG. 7 shows the shock absorbers 10 _FR and 10 _FR .
It is a flow chart for explaining damping force control of _FL , 10 _RR , and 10 _RL . The damping force control of the shock absorber can be performed using the outputs of the G sensors 7 _FR , 7 _FL , 7 _RR , 7 _RL .

First, in step S1, the ECU 8
Vertical velocity V _FR of the vehicle body front right portion provided with the front right shock absorber 10 _FR, front left shock absorber 10 _FL
Vertical velocity V _FL, vertical velocity V _RR, the vehicle body rear left portion provided with the rear left shock absorber 10 _RL of the vehicle body rear right portion provided with the rear right shock absorbers 10 _RR of provided the vehicle body front left part of The up-and-down velocity V _RL is detected. Next, in step S2, the ECU 8 controls the shock absorbers 10 _FR , 10 _FL , 1 so as to suppress the vehicle body behavior according to the detected vertical velocities V _FR , V _FL , V _RR , V _RL.
Actuator 2 _FR , 2 _FL , 2 with damping force of 0 _RR , 10 _RL
It is controlled by controlling _RR and 2 _RL . The details will be described below.

First, the detection of the vertical velocities V _FR , V _FL , V _RR and V _RL in step S1 will be described. The vertical velocities V _FR , V _FL , V _RR , and V _RL are obtained by integrating the vertical accelerations of the corresponding vehicle body parts detected by the G sensors 7 _FR , 7 _FL , 7 _RR , and 7 _RL , respectively.
8 can obtain vertical velocities V _FR , V _FL , V _RR , and V _RL by temporally integrating the vertical acceleration of the corresponding vehicle body part. When the vehicle has a stroke sensor that detects the displacement amount of the lower arm, the wheels 11 _FR ,
The relative velocities of 11 _FL , 11 _RR , and 11 _RL can be obtained. If the road surface is assumed to be substantially horizontal, the relative speed can be regarded as the vertical speeds V _FR , V _FL , V _RR , and V _RL . Also, the four vertical velocities V _FR ,
When three of V _FL , V _RR , and V _RL are known, the remaining one can be estimated and detected from the three known. For example, vertical velocities V _FR , V _FL , V
_{If RR} is known, then V _RL = V _FL −V _FR + V _RR .

Next, the actuator damping force control based on the detected vertical velocities V _FR , V _FL , V _RR , and V _RL in step S2 will be described.

First, the first roll-direction vehicle body behavior suppressing damping force control will be described. Among the vertical velocities V _FR , V _FL , V _RR , V _RL detected as described above, the signs of the vertical velocities V _FR , V _FL (or V _RR , V _RL ) for the left and right wheels are the same. When the ECU 8 determines that,
When it is determined that the left and right vehicle body parts are both moving upward or downward (in phase), it is determined that the vehicle body is not rolling, and the ECU 8 is provided on the left and right wheels as shown in FIG. Shock absorber 10 _FR , 10 _FL , (or 1
0 _RR , 10 _RL ) The damping force F in the expansion / contraction speed low speed range is the absolute value of the vertical speed difference | V _FR −V _FL | (or | V
Actuator 2 _FR , 2 _FL , (or 2 _RR , 2 _RL ) so that both increase up to a predetermined value as _RR −V _RL |) increases
To control.

Of the vertical velocities V _FR , V _FL , V _RR , V _RL detected as described above, the vertical velocities V _FR , V _FL (or V _RR , V _RL ) of the left and right wheels are detected. When the ECU 8 determines that the signs are not the same, that is, when the left and right vehicle body parts are moving in different directions (opposite phase), it is determined that the vehicle body is rolling, and the ECU
As shown in FIG. 9, the damping force F _{(VA) of} the shock absorber 10 _FR (or 10 _RR ) provided on the right wheel in the low expansion / contraction velocity range is the vehicle body part vertical velocity difference V _FL −V _FR.
The actuator 2 _FR (or 2 _RR ) is controlled so as to increase to a predetermined value as (or V _RL −V _RR ) increases in the positive direction. Further, at this time, the ECU 8 determines that the damping force F _{(VB) of} the shock absorber 10 _FL (or 10 _RL ) provided on the left wheel in the low expansion / contraction speed range is the vehicle body part vertical speed difference V _FL −V _FR (or V _RL). The actuator 2 _FL (or 2 _RL ) is controlled so as to decrease to a predetermined value with an increase in −V _RR ) in the positive direction.

Further, in the case of this reverse phase, as shown in FIG. 9, the ECU 8 controls the damping force F _{(VA) of} the shock absorber 10 _FR (or 10 _RR ) provided on the right wheel in the low expansion / contraction speed range. However, the actuator 2 _FR (or 2 _RR ) is controlled so as to decrease to a predetermined value as the vehicle body part vertical direction speed difference V _FL −V _FR (or V _RL −V _RR ) increases in the negative direction. At this time, the ECU 8 determines that the damping force F _{(VB) of} the shock absorber 10 _FL (or 10 _RL ) provided on the left wheel in the low expansion / contraction speed region is the vehicle body portion vertical speed difference V _FL −V.
Actuator 2 _FL (or 2 _RL ) so as to increase to a predetermined value as _FR (or V _RL −V _RR ) increases in the negative direction
To control.

In other words, when the left and right vehicle body parts are moving in phase, the ECU 8 increases the shock absorber damping forces of the left and right wheels together in accordance with the absolute value of the vertical speed difference so that the left and right vehicle body parts are When the vehicle is moving in the opposite phase, it is estimated that the vehicle is turning, and the shock absorber damping force of the turning outer wheel is increased and at the same time the shock absorber damping force of the turning inner wheel is decreased.

Next, the second roll direction vehicle body behavior suppressing damping force control will be described. In this control, the vertical velocities V _FR , V _FL , V _RR , V detected as described above are used.
_{When the} ECU 8 determines that the vertical velocities V _FR and V _FL (or V _RR and V _RL ) of the left and right wheels of the _RL are the same (in phase), the ECU 8 determines the vertical velocities V _FR and V _FL ,
The damping force of two shock absorbers provided at corresponding vehicle body parts that provide two of V _RR and V _RL in descending order of absolute value is increased to suppress rolling of the vehicle body.

Vertical velocities V _FR , V relating to the left and right wheels
_{When the} ECU 8 determines that the signs of _FL (or V _RR , V _RL ) are different (opposite phase), the ECU 8 performs the control when it is determined that they are in phase in the first roll direction vehicle body behavior suppression damping force control. The shock absorber damping force on the left and right in the low speed range. Absolute value of vertical speed difference | V _FR −V _FL |
(Or | V _RR -V _RL |) to increase to a predetermined value together to suppress the roll of the vehicle body. In this control, when the ECU 8 determines that the vertical velocities V _FR and V _FL (or V _RR and V _RL ) of the left and right wheels have different signs (reverse phase), the shock absorbers of all four wheels in the low speed range are used. The damping force may be increased to a predetermined value as the absolute value of vertical speed difference | V _FR −V _FL | (or | V _RR −V _RL |) increases to suppress the roll of the vehicle body.

Next, the first pitch direction vehicle body behavior suppressing damping force control will be described. Among the vertical velocities V _FR , V _FL , V _RR , V _RL detected as described above, if the vertical velocities V _FR , V _RR (or V _FL , V _RL ) of the front and rear wheels have different signs, the ECU 8 When it is determined that the vehicle body parts in the front and rear are moving in different directions (opposite phase), it is determined that the posture of the vehicle body is changing in the pitch direction. The shock absorbers 10 _FR and 10 _RR (or 1
0 _FL , 10 _RL ) The damping force F in the low speed range of expansion / contraction speed is the absolute value of the vertical speed difference | V _FR −V _RR | (or | V
Actuator 2 _FR , 2 _RR , (or 2 _FL , 2 _RL ) so that both increase up to a predetermined value as _FL- V _RL |) increases
To control.

In the present control, when the ECU 8 determines that the vertical velocities V _FR and V _RR (or V _FL and V _RL ) of the front and rear wheels are different (reverse phase), all the four wheels in the low speed range are controlled. Actuator 2 _FR , 2 _RR , (or the actuator shock absorber 2 _FR , 2 _RR , (or the shock absorber damping force of the vertical direction speed difference absolute value | V _FR −V _RR | (or | V _FL −V _RL |) 2 _FL , 2 _RL ) may be controlled to suppress the pitching of the vehicle body.

Of the vertical velocities V _FR , V _FL , V _RR , V _RL detected as described above, the vertical velocities V _FR , V _RR (or V _FL , V _RL ) relating to the front and rear wheels are used. When the ECU 8 determines that the signs are the same, that is, when the front and rear vehicle body parts are moving in the same direction (in phase), it is determined that the vehicle body is not pitched, and the EC
In U8, as shown in FIG. 9, the damping force F _(VA) in the expansion / contraction speed low speed range of the shock absorbers 10 _FR and 10 _FL provided on the front wheels is a vehicle body part vertical direction speed difference V _FR −V _RR (or V _FL). The actuators 2 _FR and 2 _FL are controlled so that they both increase to a predetermined value with an increase in −V _RL ) in the positive direction,
The damping force F _{(VB) of} the shock absorbers 10 _RR and 10 _RL provided on the rear wheels in the expansion / contraction speed low speed range is directed toward the positive direction of the vehicle body part vertical speed difference V _FR −V _RR (or V _FL −V _RL ). The actuators 2 _RR and 2 _RL are controlled so that they both decrease to a predetermined value with an increase.

Further, in the case of this in-phase, as shown in FIG. 9, the shock absorbers 10 _FR , 1 provided on the front wheels are arranged.
The damping force F _(VA) in the low expansion / contraction velocity range of 0 _FL both decreases to a predetermined value as the vehicle body part vertical velocity difference V _FR −V _RR (or V _FL −V _RL ) increases in the negative direction. The actuators 2 _FR and 2 _FL are controlled as described above, and the damping force F _{(VB) of} the shock absorbers 10 _RR and 10 _RL provided on the rear wheels in the low speed range of the expansion / contraction speed is V _FR −V.
_The actuators 2 _RR and 2 _RL are controlled so that they both increase up to a predetermined value as _RR (or V _FL −V _RL ) increases in the negative direction.

In other words, the ECU 8 increases the shock absorber damping force of the front and rear wheels together in accordance with the absolute value of the speed difference in the vertical direction when the front and rear vehicle body parts move in opposite phases, and If the vehicle is moving in the same phase, it is estimated that the vehicle body is bounding, and the shock absorber damping force of the one with a higher upward movement speed is increased, and at the same time the shock absorber damping force of the one with a smaller upward movement speed is increased. Reduce and keep the front and rear parts of the vehicle horizontal.

Next, the second pitch direction vehicle body behavior suppressing damping force control will be described. In this control, the vertical velocities V _FR , V _FL , V _RR , V detected as described above are used.
_{When the} ECU 8 determines that the vertical speeds V _FR , V _RR (or V _FL , V _RL ) of the front and rear wheels are the same among the _RL (in phase), the ECU 8 determines the vertical speeds V _FR , V _FL ,
The damping force of two shock absorbers provided in corresponding vehicle body parts that provide two of V _RR and V _RL in descending order of absolute value is increased, and vehicle body pitching is suppressed.

Vertical velocities V _FR , V for front and rear wheels
_{When the} ECU 8 determines that the signs of _RR (or V _FL , V _RL ) are different (reverse phase), the ECU 8 performs control when it is determined to be the reverse phase in the first pitch direction vehicle body behavior suppression damping force control. And the shock absorber damping force of the front and rear shock absorbers in the low speed range is adjusted to the absolute value of the vertical speed difference | V _FR −V _RR |
(Or | V _FL −V _RL |) to increase to a predetermined value together to suppress pitching of the vehicle body. In this control, the vertical velocities V _FR and V _RR (or V
If the ECU 8 determines that the signs of _FL , V _RL ) are different (opposite phase), the shock absorber damping forces of all four wheels in the low speed range are calculated by using the absolute value of the vertical speed difference | V _FR −V _RR | (or | V _FL -V _RL |) may be increased to a predetermined value to suppress pitching of the vehicle body.

The damping force of each shock absorber may be controlled by combining the second roll direction vehicle body behavior suppressing damping force control and the second pitch direction vehicle body behavior suppressing damping force control. In the roll or pitching judgment of the vehicle body, the absolute value of the speed difference in the vertical direction of the roll direction | V _FR
-V _FL | (or | V _RR -V _RL |) or absolute value of velocity difference in the pitch direction up and down | V _FR -V _RR | (or | V _FL
It is also possible to determine whether each −V _RL |) exceeds the reference value, and if it does not exceed the reference value, control is not performed, and if it exceeds, the subsequent damping force control may be performed.

Furthermore, the roll determination is performed by determining the output of the roll rate sensor 226, the time derivative of the output of the yaw rate sensor 5, or the time derivative of the output of the lateral G sensor 219.
Alternatively, the output of the wheel speed sensors 6 _FR , 6 _RR , 6 _FL , 6 _RL and the steering angle sensor 4b may be used, and the determination of the pitching may be performed by using an output of a pitch rate sensor (not shown) Alternatively, the time differential value or the time differential value of the output of the vehicle front-rear G sensor may be used.

As described above, the vehicle suspension system mounted on the vehicle 200 according to the above-described embodiment includes the left and right or front and rear wheels 11 _FR , 11 _FL , 11 _RR , 11 _RL and the vehicle body 2.
01 and left and right or front and rear shock absorbers 10 _FR , 10 _FL , 10 _RR , and 10 _RL that can vary the damping force in the low speed range of expansion and contraction speed, and shock absorbers 10 _FR , 10 _FL , and 10 _RR , Left and right or front and rear actuators 2 _FR , 2 _FL , which respectively vary the damping force of 10 _RL ,
2 _RR , 2 _RL and detecting means 7 _FR , 7 _FL , 7 _RR for detecting vertical movements of the left and right parts or the front and rear parts of the vehicle body 201.
7 _RL and the damping force of the shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 _RL based on the vertical movement of the vehicle body left and right parts or the front and rear parts detected by the detection means 7 _FR , 7 _FL , 7 _RR , 7 _RL . Actuator 2 _FR , 2 _FL , 2
_And a control means 8 for controlling _RR and 2 _RL .

Further, in the vehicle suspension system mounted on the vehicle 200 according to the above-described embodiment, the detection means 7 _FR , 7 indicates that the respective vehicle body parts move upward or downward.
_{When FL} , 7 _RR , 7 _RL is detected, the control means 8 causes the corresponding shock absorber 10 _FR , 10 _FL , 1 to be detected.
Increase the damping force of 0 _RR , 10 _RL together, or corresponding shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 _RL
The corresponding actuators 2 _FR , 2 _FL , 2 _RR , 2 _RL are controlled so that the damping force of one of them is increased more than the other.

In addition, the vehicle suspension system mounted on the vehicle 200 according to the above-described embodiment has four wheels 11 _FR and 11 _FR .
Four shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 _RL provided between the _FLs , 11 _RRs , 11 _RL and the vehicle body 201 and capable of varying damping force in the low speed range of expansion and contraction speed
And shock absorbers 10 _FR , 10 _FL , 10 _RR , 10
Four actuators 2 that change the damping force of _RL respectively
_FR , 2 _FL , 2 _RR , 2 _RL and shock absorber 10 _FR ,
Detecting means 7 _FR , 7 _FL , 7 _RR , 7 for detecting vertical movement of four vehicle body parts provided with 10 _FL , 10 _RR , 10 _{RL
When the} detection means detects that both _RL and the left and right or front and rear of the vehicle body parts move upward or downward, the shock absorbers 10 provided in the two vehicle body parts whose vertical velocity absolute values are larger than the remaining ones. _FR , 10 _FL , 10 _RR , 10 _RL
Actuator 2 _FR , so as to increase the damping force of
2 _FL , 2 _RR , 2 _RL . Therefore, if the above control is used, the behavior of the vehicle body can be suppressed and the maneuverability and stability of the vehicle can be improved.

[0088]

As described above, according to the vehicle of the present invention, the control means controls the actuator to change the damping force of the shock absorber based on the vertical movement of the left and right or front and rear parts of the vehicle body. It is also possible to improve the maneuverability and stability of the vehicle.

[Brief description of drawings]

FIG. 1 is a perspective view of a vehicle.

FIG. 2 is a sectional view of the vehicle shown in FIG.

3 is a sectional view of the main part of the suspension device shown in FIG. 2, taken along the line II-II.

4 is a partially enlarged view of the shock absorber shown in FIG.

FIG. 5 is a graph showing the relationship between the damping force of the shock absorber and the expansion / contraction speed.

FIG. 6 is a system configuration diagram showing a vehicle system.

FIG. 7 is a flowchart for explaining damping force control in the ECU.

FIG. 8 is a graph showing a relationship between a left-right (front-rear) vehicle body part vertical direction speed difference absolute value and a damping force in a low speed range.

FIG. 9 is a graph showing the relationship between the speed difference between the left and right (front and rear) vehicle body parts in the vertical direction and the damping force in the low speed range.

[Explanation of symbols]

11 _FR , 11 _FL , 11 _RR , 11 _RL ... Wheels, 201 ... Car body, 10 _FR , 10 _FL , 10 _RR , 10 _RL ... Shock absorber, 2 _FR , 2 _FL , 2 _RR , 2 _RL ... Actuator, 8 ...
Control means.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuya Sasaki               Toyota City, Toyota-cho, Toyota City, Aichi Prefecture               Motor Co., Ltd. (72) Inventor Shigeru Ikeda               Toyota City, Toyota-cho, Toyota City, Aichi Prefecture               Motor Co., Ltd. (72) Inventor Yoshiyuki Hashimoto               Toyota City, Toyota-cho, Toyota City, Aichi Prefecture               Motor Co., Ltd.                (56) Reference JP-A-6-219129 (JP, A)                 JP-A-8-104121 (JP, A)                 Actual Development Sho 61-67009 (JP, U)                 Actually open 62-11010 (JP, U)

Claims (4)

(57) [Claims] 1. A damping force characteristic in a low speed range of expansion / contraction speed, which is provided between the left and right wheels and the vehicle body, is changed.
A left and right shock absorber, a detection means for detecting the vertical movement of each of the left and right parts of the vehicle body, and the low level of the shock absorber based on the vertical movement of the left and right parts of the vehicle body detected by the detection means.
The sucrose so that only the damping force characteristics in the speed range is changed
And a control means for controlling an actuator for controlling the damping force of the shock absorber . 2. A damping force characteristic in a low speed range of expansion / contraction speed that is respectively provided between the front and rear wheels and the vehicle body is changed.
And front and rear shock absorbers can be, detection means for detecting a vertical motion of the front and rear portions each of the vehicle body, lower the of the shock absorber on the basis of the vertical motion of the vehicle body longitudinal portion detected by said detecting means
The sucrose so that only the damping force characteristics in the speed range is changed
And a control means for controlling an actuator for controlling the damping force of the shock absorber . 3. The control means increases the damping force of each of the shock absorbers when the detection means detects that both of the vehicle body parts move upward or downward together, or the control means increases the damping force of each of the shock absorbers. The vehicle suspension system according to claim 1 or 2, wherein the actuator is controlled so as to increase the damping force of one of the absorbers more than the other. 4. A damping force characteristic in a low speed range of expansion / contraction speed that is provided between each of the four wheels and the vehicle body is changed.
Four shock absorbers that can be activated, a detection unit that detects vertical movements of the four vehicle body parts provided with the shock absorbers, and that the left and right or front and rear of the vehicle body parts both move upward or downward. If the detection means detects a vertical direction velocity absolute value is remaining by <br/> urchin the only damping force increases in the low speed range of the shock absorber which is provided on two of the vehicle body portion larger than A suspension system for a vehicle, comprising: a control unit that controls an actuator for controlling a shock absorber damping force .