JP3374394B2 - 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]

SUMMARY OF THE INVENTION A vehicle suspension system according to the present invention is provided between a plurality of wheels and a vehicle body and changes only a damping force characteristic in a low speed range of expansion / contraction speed.
Wherein as the plurality of shock absorbers, the damping force of all of the shock absorber as the state change of the vehicle body during turning is greater in the low speed range is increased, which can bets
And a control means for controlling an actuator for controlling a shock absorber damping force .

The shock absorber of the suspension system for a vehicle uses an actuator to reduce a damping force in a low speed range of expansion and contraction speed.
Only the characteristics can be changed . Since the expansion and contraction speed of the shock absorber is low when the vehicle is turning, the control means can control the actuator to increase the damping force of all the shock absorbers and reduce the roll of the vehicle body. That is, it affects the damping force characteristics in the high speed range.
Shock absorber in the low speed range without giving
It is possible to adjust only the damping force characteristic of. In the low speed range
By changing the damping force characteristics
The ground and steering stability can be obtained.

[0006] The vehicle suspension system according to the present invention, the damping force Japanese in the low speed range of the stretch rate is provided between the wheel and the vehicle body
The shock absorber capable of changing only the characteristics, and the shock absorber so that the damping force of the shock absorber in the low speed range changes according to the state change of the vehicle body during transient turning or the running state during steady turning.
Control means for controlling the actuator for controlling the damping force .

According to the suspension system for a vehicle, the control means is
During transient turning, the damping force of the shock absorber changes only in the low speed range according to the vehicle running state such as vehicle speed, steering angle, yaw rate, lateral acceleration, etc. Since the actuator is controlled as described above, the controllability and stability of the vehicle can be improved.

It is preferable that the state change is a roll rate of the vehicle body, a differential value of the yaw rate or a differential value of the lateral acceleration. Particularly, since the roll of the vehicle body occurs after the change of the yaw rate, it depends on the yaw rate differential value. If the damping force of the shock absorber is controlled, the damping force can be controlled so as to suppress the roll before the vehicle body roll actually occurs.

Further, it is preferable that the control means controls the actuator so that the damping force of the shock absorber on the outside of the turning becomes larger than the damping force of the shock absorber on the inside of the turning. At the time of turning, a load is applied to the turning outer wheel side, and the vehicle body tries to roll to the outside of the turning. In this control, the actuator is controlled so that the damping force of the shock absorber on the outer side of the turning becomes larger than the damping force of the shock absorber on the inner side of the turning, so that the roll of the vehicle body can be suppressed.

[0010]

DETAILED DESCRIPTION OF THE INVENTION A vehicle equipped with a vehicle suspension system according to an embodiment will be described below. The same symbols shall be used for the same elements or elements having the same function,
A duplicate description will be omitted. 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 supported by 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
Is a lower arm 202 _FR , 202 _FL , 202 _RR , 20 that connects a vehicle body 201 with a knuckle as a supporting member that rotatably supports the wheels 11 _FR , 11 _FL , 11 _RR , 11 _RL.
It has 2 _RL .

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 cross-sectional view of the vehicle 200 shown in FIG. 1 taken vertically in 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 system including the right front wheel 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 portion 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 respectively between the upper chamber 34 and the middle chamber 36 and the middle chamber 36.
An orifice and a valve mechanism that allow the fluid to flow between the lower chamber 38 and the lower chamber 38 are provided, and a damping force is generated according to the forward and backward movement of the piston rod 16.

A base valve 41 is fixed to the lower end of the outer cylinder 18. The base valve 41 is configured to allow 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.
Also referred to as the valve opening speed, and the damping forces F1 and f2 when the leaf valves 50 and 82 open are also
These are called the first valve opening damping force and the second valve opening damping force.

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 sensors 7 _FR , 7 _FL , which are provided in the vehicle and output individual vertical acceleration signals according to the vertical acceleration of the vehicle body for each wheel position.
7 _RR and 7 _RL . The steering angle signal, wheel speed signal, yaw rate signal, vertical acceleration signal, lateral acceleration signal, roll rate signal, and individual vertical acceleration signal are processed by the ECU.
8 and the ECU 8 controls the damping force of the shock absorber and various controls based on the input signal.

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 by using the outputs of various sensors.

First, the control using the roll rate signal R _R output from the roll rate sensor 226 will be described. In this example, the control of step S2 is not performed,
Further, the roll rate signal R _R has a larger output value as the posture change rate of the vehicle body 201 in the roll direction is larger.

In step S1, the ECU 8 detects a roll rate signal R _R indicating a vehicle body roll movement as one form of the vehicle state. Next, the ECU 8 sends the roll rate signal R _R
It is determined whether the absolute value | R _R | of the output value is larger than the threshold value C _R (S3). If it is determined that the output value is greater than the threshold value C _R, it is determined that the vehicle body 201 has changed its posture in the roll direction. All shock absorbers 1 for 4 wheels
The damping forces of 0 _FR , 10 _FL , 10 _RR , and 10 _RL increase as the absolute value | R _R | of the output value of the roll rate signal R _R increases until the absolute value | R _R | reaches a predetermined value R _SAT. Such control signals are output to the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL , respectively (see the frame graph in step S4).

More specifically, when the absolute value | R _R | of the output value of the roll rate signal is not less than the threshold value C _{R and not} more than the predetermined value R _SAT , it is estimated that the roll of the vehicle body 201 is caused by turning. can do. Further, the expansion and contraction speeds of the shock absorbers 10 _FR , 10 _FL , 10 _RR , and 10 _RL during turning are low. This shock absorber 10 _FR , 10 _FL ,
10 _RR and 10 _RL can change the damping force in the low speed range of the expansion / contraction speed. When it is determined that this turning is being performed, the ECU 8 determines that the actuators 2 _FR , 2 _FL , 2 _RR , 2 _RL.
To output a control signal to the shock absorber 1
The damping force of 0 _FR , 10 _FL , 10 _RR , and 10 _RL can be varied. When the absolute value of output value | R _R | exceeds a predetermined value R _{S AT} , shock absorbers 10 _FR , 10 _FL , 10 _RR , 10
_Since the expansion and contraction speed of _RL is high, shock absorber 1
The damping force becomes substantially constant due to the characteristics of 0 _FR , 10 _FL , 10 _RR , and 10 _RL itself.

If it is determined in step S3 that the absolute value | R _R | of the output value of the roll rate signal R _R is less than or equal to the threshold value C _R , the ECU 8 causes the vehicle 200 to make a substantially straight or steady turn. If it is determined that the normal sprung mass damping control is performed (S5). That is,
When determining that the vehicle 200 is traveling straight ahead, the ECU 8 sends a control signal for controlling the damping force of the shock absorbers 10 _FR , 10 _FL , 10 _RR , and 10 _RL to the actuator 2 _FR , based on the skyhook control theory. 2 _FL , 2 _RR , 2
Output to _RL . In the control when the vehicle goes straight ahead,
Based on the vertical acceleration signal output from the vertical G sensor 217, the ECU 8 calculates the relative speed of the sprung and unsprung,
Calculates the damping force that provides the optimum damping effect according to the road surface condition. After that, the ECU 8 turns the shock absorber 1
Actuator 2 _FR , 2 outputs a control signal such that the damping force of 0 _FR , 10 _FL , 10 _RR , 10 _RL becomes the calculated damping force.
Output to _FL , 2 _RR , 2 _RL .

The ECU 8 uses the wheels 11 _FR , 11 _FL , 11 _RR , 11 instead of the output signals of the vertical G sensor 217.
Wheels 11 _FR , 1 to detect vertical acceleration for each _RL
1 _FL , 11 _RR , 11 _RL Damping of each shock absorber 10 _FR , 10 _FL , 10 _RR , 10 _RL by using the output signal of G sensor 7 _FR , 7 _FL , 7 _RR , 7 _RL provided for each position Force control may be performed, or wheels 11 _FR , 11 _FL , 1
The sprung and unsprung relative velocities may be calculated using the output from a stroke sensor (not shown) that detects the relative positions of 1 _RR and 11 _RL with respect to the vehicle body 201.

Since the steering wheel 4a is not largely operated while the vehicle 200 is traveling straight, it is determined that the steering angle of the steering wheel 4a is within a predetermined value from the steering angle signal output from the steering angle sensor 4b. Vehicle 2 by judging
The straight traveling state of 00 may be determined.

Next, the yaw rate signal R _Y output from the yaw rate sensor 5 in place of the roll rate sensor 226.
The control using will be described. Note that the yaw rate signal R _Y increases as the angular velocity of the vehicle body 201 in the yaw direction increases.
It is assumed that the output value is large.

In step S1, the ECU 8 detects the yaw rate signal R _Y indicating the yaw direction rotational movement as one form of the vehicle state. Next, the ECU 8 calculates the differential value of the yaw rate signal R _Y that indirectly indicates the roll rate (S
2), it is determined whether or not the output value absolute value | ΔR _Y | of the differential value of the yaw rate signal R _Y , which is the calculation result, is larger than the threshold value _CΔRY (S3). It is determined that the vehicle body 201 is about to change its posture in the roll direction, and the damping forces of all the shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 _RL provided on the four wheels are differentiated from the yaw rate signal R _Y. output value absolute value | △ R _Y | absolute value with increasing | △ R _Y | a predetermined value R a control signal for increasing until _SAT actuator 2 _FR, 2 _FL,
It outputs to 2 _RR and 2 _RL respectively (S4).

If it is determined in step S3 that the absolute output value | ΔR _Y | of the differential value of the yaw rate signal R _Y is less than or equal to the threshold value C Δ _RY , the ECU 8 determines that the vehicle 20
It is determined that 0 is traveling substantially straight or is making a steady turn, and ordinary sprung mass damping control such as skyhook control is performed in the same manner as above (S5).

Next, control using the lateral acceleration signal A _L output from the lateral G sensor 219 instead of the roll rate sensor 226 will be described. The lateral acceleration signal A
_It is assumed that _L has a larger output value as the acceleration in the width direction of the vehicle body 201 increases.

In step S1, the ECU 8 detects a lateral acceleration signal A _L indicating a lateral movement as a form of the vehicle state. Next, the ECU 8 calculates the differential value of the lateral acceleration signal A _L that indirectly indicates the roll rate (S2), and outputs the absolute value of the differential value of the lateral acceleration signal A _L that is the calculation result | ΔA _L
| Is, it is determined that the vehicle 201 is about to change in posture in a roll direction when it is determined that the threshold C △ determining whether greater than _AL (S3), a large, 4
All shock absorbers 10 _FR , 10 mounted on the wheel
The damping force of _FL , 10 _RR , and 10 _{RL is} the absolute value | with the increase of the output value absolute value | ΔA _L | of the differential value of the lateral acceleration signal A _L |
Control signals are output to the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL so that ΔA _L | increases until _{reaching a} predetermined value R _SAT (S4).

In step S3, the absolute value of the differential value of the lateral acceleration signal A _L | ΔA _L |
When it is determined that _ΔAL or less, the ECU 8 determines that the vehicle 200
Is determined to be substantially straight or is making a steady turn, and normal sprung mass damping control such as skyhook control is performed in the same manner as above (S5).

FIG. 8 shows the shock absorbers 10 _FR and 10 _FR .
It is a flowchart for _{demonstrating} another damping force control of _FL , _10RR , _10RL . In the present control, a wheel speed signal and a steering angle signal are further used in addition to any one of the output signals of the roll rate sensor 226, the yaw rate sensor 5 and the lateral G sensor 219. The details will be described below.

First, the control using the roll rate signal R _R output from the roll rate sensor 226 will be described. Note that the control of step S12 is not performed in this example. Further, the roll rate signal R _R has a larger output value as the posture change rate of the vehicle body 201 in the roll direction is larger.

In step S11, the ECU 8 detects a roll rate signal R _R indicating a vehicle body roll movement which is one form of the vehicle state. Next, the ECU 8 sends the roll rate signal R _R
Of the absolute value | R _R | of the output value is larger than the threshold value C _R (S13). In step S13,
When it is determined that the absolute output value | R _R | is larger than the threshold value C _R , it is determined that the vehicle body 201 is changing its posture in the roll direction, and the left outer wheel (right wheel) during left turn is determined. ) Side shock absorbers 10 _FR , 10 _RR damping force increases as the output value R _R of the roll rate signal increases in the positive direction, and the shock absorber 10 _FL on the turning inner wheel (left wheel) side,
The control signals are output to the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL so that the damping force of 10 _RL decreases as the output value R _R of the roll rate signal increases in the positive direction.

In step S13, absolute value of output value |
If it is determined that R _R | is larger than the threshold C _R ,
When the vehicle is turning to the right, the damping force of the shock absorbers 10 _FL and 10 _RL on the turning outer wheel (left wheel) side during turning to the right causes an increase in the output value R _R of the roll rate signal in the negative direction. The actuator controls the control signal such that the damping force of the shock absorbers 10 _FR and 10 _RR on the turning inner wheel (right wheel) side decreases with the increase of the output value R _R of the roll rate signal in the negative direction. Output to 2 _FR , 2 _FL , 2 _RR , and 2 _RL , respectively (see step S16 and S17 in-frame graph).

If it is determined in step S13 that the absolute value | R _R | of the output value of the roll rate signal R _R is less than or equal to the threshold value C _R , the ECU 8 causes the vehicle 200 to make a substantially straight or steady turn. Since it can be determined that the vehicle behavior is one, it is determined in step S14 whether the vehicle behavior is one of these.

For this determination, the steering angle signal M _A shown in FIG. 9 is used.
A graph showing the relationship between the vehicle speed v and the vehicle speed v is used. That is, when the vehicle speed v is equal to or higher than the predetermined value and the steering angle M _A is equal to or higher than the predetermined value, it can be considered that the vehicle 200 is making a steady turn. Therefore, the vehicle speed v and the steering angle signal M Figure _A is _A
Satisfy the relationship within the regions I and II of. Further, when the vehicle speed v is smaller than a predetermined value or when the steering angle M _A is smaller than a predetermined value, it cannot be considered that the vehicle 200 is making a steady turn. Corner signal M
_A satisfies the relationship outside regions I and II of FIG. Therefore, the vehicle speed v and the steering angle signal M obtained from the wheel speed signal
_{When A} satisfies the relationship within the regions I and II in FIG. 9, it can be determined that the vehicle 200 is making a steady turn, and when A does not satisfy the relationship, the vehicle 200 is substantially straight or the vehicle behavior is extremely high. It can be determined that the person is doing a little exercise.

When it is determined in step S14 that the vehicle 200 is making a steady turn, the ECU 8 controls the damping force according to the product v × M _A of the vehicle speed v and the steering angle signal M _A.

That is, when it is determined in step S14 that the vehicle 200 is making a steady turn,
Shock absorber 1 on the turning outer wheel (right wheel) side when turning left
0 _FR, 10 _RR damping force is increased with increasing in the positive direction of the product v × M _A, turning inner (left wheel) side damping force of the shock absorber 10 _FL, 10 _RL of the product v × M control signals of the actuator 2 _FR so as to decrease with an increase in the positive direction of _{a, 2 FL, 2 RR,} 2 outputs, respectively _RL.

In step S14, if it is determined that the vehicle 200 is making a steady turn, and if the vehicle is making a right turn, the shock absorber 10 _FL on the turning outer wheel (left wheel) side during right turn, The damping force of 10 _RL is the product v × M _A
The damping force of the shock absorbers 10 _FR , 10 _RR on the turning inner wheel (right wheel) side increases as the product v
× M control signals, such as decreases with increasing in the negative direction of the _A actuator _{2 F R, 2 FL, 2} RR, 2 outputs, respectively _RL (see the chart steps S18 and S19 frame).

When it is determined in step S14 that the vehicle 200 is moving substantially straight or in which the vehicle body behavior is extremely small, normal sprung mass damping control such as skyhook control is performed in the same manner as in step S5 described above. (S15).

Next, control using the yaw rate signal R _Y output from the yaw rate sensor 5 will be described. The output value of the yaw rate signal R _Y increases as the yaw angular velocity in the yaw direction of the vehicle body 201 increases.

In step S11, the ECU 8 detects a yaw rate signal R _Y indicating a motion having a yaw direction angular velocity which is one form of the vehicle state. Then, ECU 8 calculates a time differential value △ R _Y of the output value of the yaw rate signal R _Y (S1
2) determines whether the differential value △ R _Y is greater than the threshold value C △ _RY (S13). Yaw rate derivative ΔR _Y
Indicates the roll rate indirectly because it can be associated with the roll rate.

Therefore, if it is determined in step S13 that the differential value ΔR _Y is larger than the threshold value CΔ _RY , it is determined that the vehicle body 201 is about to change its posture in the roll direction, and the vehicle turns left. The damping force of the shock absorbers 10 _FR and 10 _RR on the outer turning wheel (right wheel) side during turning increases as the output value R _R of the yaw rate signal increases in the positive direction, and the shock absorber on the inner turning wheel (left wheel) side turns. 10 _FL ,
The control signals are output to the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL so that the damping force of 10 _RL decreases as the differential value ΔR _Y of the yaw rate signal increases in the positive direction.

If it is determined in step S13 that the differential value ΔR _Y is larger than the threshold value CΔ _RY and the vehicle is making a right turn, the turning outer wheel (left wheel) when making a right turn. The damping force of the shock absorbers 10 _FL , 10 _RL on the side increases as the differential value ΔR _Y of the yaw rate signal increases in the negative direction, and the damping force of the shock absorbers 10 _FR , 10 _RR on the inner wheel (right wheel) side of the turning is increased. The control signals are output to the actuators 2 _FR , 2 _FL , 2 _RR , 2 _RL so that the damping force decreases as the differential value ΔR _Y of the yaw rate signal increases in the negative direction (steps S16 and S17). See the graph inside).

If it is determined in step S13 that the differential value ΔR _Y of the yaw rate signal R _R is less than or equal to the threshold value C Δ _RY , the ECU 8 determines that the vehicle 200 is substantially straight or makes a steady turn. Therefore, it is determined whether the vehicle behavior is any of these in step S14.

For this determination, a graph showing the relationship between the yaw rate signal R _Y and the vehicle speed v shown in FIG. 9 is used. That is, when the vehicle speed v is equal to or higher than the predetermined value and the yaw rate signal R _Y
Is greater than or equal to a predetermined value, it can be considered that the vehicle 200 is making a steady turn, and therefore the vehicle speed v and the yaw rate signal R _Y satisfy the relationships within the regions I and II in FIG. 9. When the vehicle speed v is smaller than a predetermined value or when the yaw rate signal R _Y is smaller than a predetermined value, the vehicle 2
Since it is not possible to consider that 00 is making a steady turn, the vehicle speed v and the yaw rate signal R _Y are
And the relationship outside II. Therefore, when the vehicle speed v and the yaw rate signal R _Y obtained from the wheel speed signal satisfy the relationship within the regions I and II in FIG. 9, it can be determined that the vehicle 200 is making a steady turn, and the condition is satisfied. If there is not, it can be determined that the vehicle 200 is moving in a substantially straight line or having very little body behavior.

When it is determined in step S14 that the vehicle 200 is making a steady turn, the ECU 8 controls the damping force according to the product v × R _Y of the vehicle speed v and the yaw rate signal R _Y.

That is, when it is determined in step S14 that the vehicle 200 is making a steady turn,
Shock absorber 1 on the turning outer wheel (right wheel) side when turning left
The damping force of 0 _FR , 10 _RR increases as the product v × R _Y increases in the positive direction, and the damping force of the shock absorbers 10 _FL , 10 _RL on the turning inner wheel (left wheel) side increases by the product v × R. Control signals that decrease as _Y increases in the positive direction are output to the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL , respectively.

[0097] In step S14, if the vehicle 200 is determined as being normal turning, when the vehicle is turning right, the turning outer wheel (left wheel) at right turning side of the shock absorber 10 _FL, The damping force of 10 _RL is the product v × R _Y
The damping force of the shock absorbers 10 _FR , 10 _RR on the turning inner wheel (right wheel) side increases as the product v
The control signals that decrease with the increase of × R _{Y in} the negative direction are output to the actuators 2 _{F R} , 2 _FL , 2 _RR , and 2 _RL , respectively (see the frame graphs in steps S18 and S19).

If it is determined in step S14 that the vehicle 200 is moving in a substantially straight line or having very little body behavior, normal sprung mass damping control such as skyhook control is performed in the same manner as in step S5. (S15).

Next, control using the lateral acceleration signal A _L output from the lateral G sensor 219 will be described. In addition,
The lateral acceleration signal A _L has a larger output value as the lateral acceleration in the width direction of the vehicle body 201 increases.

In step S11, the ECU 8 detects a lateral acceleration signal A _L indicating a motion having a lateral acceleration which is one form of the vehicle state. Then, ECU 8 calculates a time differential value △ A _L of the output value of the lateral acceleration signal A _L (S12), it determines whether the differential value △ A _L is larger than the threshold value C △ _AL (S13) . The differential value ΔA _L of the lateral acceleration can be associated with the roll rate, and thus indirectly indicates the roll rate.

Therefore, if it is determined in step S13 that the differential value ΔA _L is larger than the threshold value C Δ _AL , it is determined that the vehicle body 201 is about to change its posture in the roll direction, and the vehicle turns left. The damping force of the shock absorbers 10 _FR , 10 _RR on the turning outer wheel (right wheel) side at the time of turning increases as the output value R _R of the lateral acceleration signal increases in the positive direction, and the shock on the turning inner wheel (left wheel) side increases. Absorber 10 _FL ,
The control signals are output to the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL so that the damping force of 10 _RL decreases as the differential value ΔA _L of the lateral acceleration signal increases in the positive direction.

[0102] In step S13, if the differential value △ A _L is determined to be greater than the threshold value C △ _AL, when the vehicle is turning right, the at right turning turning outer wheel (left wheel) The damping force of the side shock absorbers 10 _FL , 10 _RL increases as the differential value ΔA _L of the lateral acceleration signal increases in the negative direction, and the shock absorbers 10 _FR , 10 _RR on the turning inner wheel (right wheel) side Damping force is the differential value of the lateral acceleration signal ΔA
Control signals that decrease with an increase in _{L in} the negative direction are output to the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL , respectively (see step S16 and S17 framed graph).

[0103] Further, in step S13, if the differential value of the lateral acceleration signal A _L △ A _L is equal to or less than the threshold value C △ _AL, ECU 8 is to that vehicle 200 is substantially straight or steady turning Since it can be determined, in step S14 it is determined whether the vehicle behavior is one of these.

For this determination, the lateral acceleration signal A shown in FIG. 9 is used.
A graph showing the relationship between _L and the vehicle speed v is used. That is,
When the vehicle speed v is equal to or higher than the predetermined value and the lateral acceleration signal A _L is equal to or higher than the predetermined value, it can be considered that the vehicle 200 is making a steady turn. Therefore, the vehicle speed v and the lateral acceleration signal A
_L satisfies the relationship in regions I and II of FIG. Also,
When the vehicle speed v is smaller than a predetermined value, or the lateral acceleration signal A
_{When L} is smaller than a predetermined value, it cannot be considered that the vehicle 200 is making a steady turn, and therefore the vehicle speed v
And the lateral acceleration signal A _L satisfy the relationship outside the regions I and II in FIG. Therefore, when the vehicle speed v and the lateral acceleration signal A _L obtained from the wheel speed signal satisfy the relationship in the regions I and II of FIG. 9, it can be determined that the vehicle 200 is making a steady turn, Vehicle 2 if not satisfied
It can be determined that 00 is moving in a substantially straight line or having very little vehicle behavior.

When it is determined in step S14 that the vehicle 200 is making a steady turn, the ECU 8 controls the damping force according to the product v × A _L of the vehicle speed v and the lateral acceleration signal A _L.

That is, when it is determined in step S14 that the vehicle 200 is making a steady turn,
Shock absorber 1 on the turning outer wheel (right wheel) side when turning left
The damping force of 0 _FR , 10 _RR increases as the product v × A _L increases in the positive direction, and the damping force of the shock absorbers 10 _FL , 10 _RL on the turning inner wheel (left wheel) side increases by the product v × A. Control signals are output to the actuators 2 _FR , 2 _FL , 2 _RR , and 2 _RL that decrease as _L increases in the positive direction.

If it is determined in step S14 that the vehicle 200 is making a steady turn, and if the vehicle is making a right turn, the shock absorber 10 _FL on the turning outer wheel (left wheel) side during right turn, The damping force of 10 _RL is the product v × A _L
The damping force of the shock absorbers 10 _FR , 10 _RR on the turning inner wheel (right wheel) side increases as the product v
× A control signal such as decreases with increasing in the negative direction of the _L actuators _{2 F R, 2 FL, 2} RR, 2 outputs, respectively _RL (see the chart steps S18 and S19 frame).

If it is determined in step S14 that the vehicle 200 is moving in a substantially straight line or having very little body behavior, normal sprung mass damping control such as skyhook control is performed in the same manner as in step S5. (S15).

As described above, the vehicle according to the above-described embodiment is provided between the plurality of wheels 11 _FR , 11 _FL , 11 _RR , and 11 _RL and the vehicle body 201, and the damping force in the low speed range of the expansion / contraction speed. Of a plurality of shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 _RL, and a plurality of actuators 2 _FR , 2 _FL , 2 for varying the damping force of the shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 _{RL RR} , 2 _RL and the state change of the vehicle body 201 during turning, that is, the roll rate of the vehicle body
The larger the differential value of the torque and the yaw rate or the differential value of the lateral acceleration, the more shock absorbers 10 _FR , 10 _FL , 1
The control means 8 controls the actuators 2 _FR , 2 _FL , 2 _RR , 2 _RL so that the damping force of 0 _RR , 10 _RL increases (S4).
With.

Further, the control means 8 of the present vehicle shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 according to the state change of the vehicle body 201 during transient turning or the running state during steady turning.
Actuator 2 _FR , so that the damping force of _RL is variable,
Controls 2 _FL , 2 _RR , and 2 _RL .

According to the present vehicle, the control means 8 makes a steady turn (S18 to S1) in which the vehicle body state does not change according to the state change of the vehicle body 201 during the transient turn (S16 to S17).
9), the actuators 2 _FR , 2 _FL , 2 _RR , so that the damping force of the shock absorber varies according to the vehicle running state such as vehicle speed, steering angle, yaw rate or lateral acceleration.
Since 2 _RL is controlled, it is possible to improve the maneuverability and stability of the vehicle. In this case, the control means 8 controls the shock absorbers 10 _FR , 10 _FL , 1 on the outer side of turning.
Actuators 2 _FR , 2 _FL , 2 _RR , 2 _RL so that the damping force of 0 _RR , 10 _RL is greater than the damping force of the shock absorbers 10 _FR , 10 _FL , 10 _RR , 10 _{RL on} the inner side of the turn.
To control. That is, when turning, a load is applied to the turning outer wheel side, and the vehicle body 201 tries to roll outward of the turning,
The control means 8 controls the actuators 2 _FR , 2 _FL , 2 _RR , 2 so that the damping force of the shock absorber on the outside of the turn becomes larger than the damping force of the shock absorber on the inside of the turn.
_{Since the RL} is controlled, the roll of the vehicle body 201 can be suppressed.

[0112]

As described above, according to the vehicle of the present invention, the control means controls the actuator to increase the damping force of all the shock absorbers, the vehicle body state changes during the transient turning, or the steady turning. Since the damping force of the shock absorber is changed according to the running state at the time, it is 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 flowchart for explaining damping force control in the ECU.

FIG. 9 is a graph showing the relationship between steering angle, yaw rate or lateral G, and vehicle speed.

[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.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Sasaki 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Shigeki Ikeda 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Yoshiyuki Hashimoto 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (56) Reference JP-A-6-219129 (JP, A) JP-A-5-193322 (JP, A) JP HEI 6-239124 (JP, A) JP-A 8-104121 (JP, A) Actual development Sho 61-67009 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60G 17 / 015

Claims (6)

(57) [Claims] 1. A damping force characteristic in a low speed range of expansion and contraction speed that is provided between each of a plurality of wheels and a vehicle body.
A plurality of shock absorbers capable of controlling the shock absorber damping force control so that the damping force of all the shock absorbers in the low speed range increases as the state change of the vehicle body during turning increases . A suspension system for a vehicle, comprising: a control unit that controls an actuator. 2. A damping force characteristic, which is provided between a wheel and a vehicle body and can change only in a low speed range of expansion / contraction speed,
The shock absorber and the vehicle speed during the transient turn or the running state during the steady turn in the low speed range.
As the damping force of kicking the shock absorber is changed
A suspension system for a vehicle, comprising: a control unit that controls an actuator for controlling the shock absorber damping force . 3. The vehicle suspension system according to claim 1, wherein the state change is a roll rate of the vehicle body. 4. The vehicle suspension system according to claim 1, wherein the state change is a differential value of a yaw rate of the vehicle body. 5. The vehicle suspension system according to claim 1, wherein the state change is a differential value of a lateral acceleration of the vehicle body. 6. The control means controls the actuator so that the damping force of the shock absorber on the outside of the turning is greater than the damping force of the shock absorber on the inside of the turning. Item 3. The vehicle suspension device according to item 2.