JPH1191327A - Damping force control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both the riding comfortableness and steering stability of a vehicle by individually controlling the damping force of shock absorbers of inner wheels and outer wheels according to the load changes of the inner wheels and the outer wheels in response to the behavior state of the vehicle at the time of turning, and variably controlling the damping force in a low expansion speed range only. SOLUTION: The damping force of shock absorbers 10 (10FR, 10FL, 10RR, 10RL) is individually controlled in response to the behavior state detected when a vehicle is turned, and the turning characteristic of the vehicle is properly changed, thereby the floating of the inner rear wheel by the lateral force at the time of turning can be delayed. The damping force of the shock absorbers 10 is variably controlled in the low expansion speed range of the shock absorbers 10 only, thus the grounding property of the wheels 11 (11FR, 11FL, 11RR, 11RL)can be secured when the shock absorbers 10 are operated in a high speed range, thereby the stability and maneuverability of the vehicle are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicular damping force control device for controlling a damping force of a shock absorber used for a suspension of an automobile or the like.

[0002]

2. Description of the Related Art Generally, a shock absorber is used as one component of a suspension of an automobile or the like, and a device described in Japanese Patent Application Laid-Open No. 5-294122 is known as a device for controlling the damping force of the shock absorber. . This device is a damping coefficient control device that controls a damping coefficient of a shock absorber based on a sprung speed and a sprung and unsprung speed based on the skyhook theory. This damping coefficient control device increases the damping coefficient of the shock absorber when the low-frequency component of the vibration input from the road surface is large, so that the damping coefficient of the shock absorber is set to a low value in normal times, and the In addition to ensuring good ride comfort of a vehicle when traveling on a road, the vibration coefficient of the vehicle body is minimized by automatically increasing the damping coefficient when traveling on a undulating road.

[0003]

However, the conventional damping coefficient control apparatus has a problem that it is not possible to sufficiently achieve both ride comfort and maneuverability in a vehicle.
For example, in the above-described damping coefficient control device, the damping coefficient of the shock absorber is controlled to increase when the low frequency component in the vibration input from the road is large, and the shock is controlled when the high frequency component of the vibration input from the road is large. The damping force of the absorber is reduced. When the high frequency component of the vibration input from the road surface is large and the amplitude of the vibration is large, the vehicle body moves up and down violently, and the ride comfort of the vehicle is reduced.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to change the damping force of the shock absorber in a low speed range of the expansion and contraction speed of the shock absorber, thereby improving the riding comfort of the vehicle. It is an object of the present invention to provide a vehicular damping force control device capable of achieving both steering and steering stability.

[0005]

In order to achieve the above object, a damping force control device for a vehicle according to the present invention has a variable damping force of a shock absorber in a low speed range of the expansion and contraction speed of the shock absorber. Damping force variable means,
The vehicle includes a behavior state detection unit that detects a behavior state of the vehicle, and a damping force control unit that individually controls damping forces of the shock absorbers on the inner wheel and the outer wheel according to the behavior state of the vehicle when turning.

According to the present invention, the damping force of the shock absorbers of the inner wheel and the outer wheel is individually controlled in accordance with the change in the load applied to the inner wheel and the outer wheel according to the behavior of the vehicle at the time of turning. For this reason, stability of the vehicle at the time of turning is ensured, and riding comfort can be improved. In addition, only in the low-speed range of the expansion and contraction speed of the shock absorber, the damping force of the shock absorber is variably controlled, so that the controllability of the vehicle in the high-speed range can be secured.

In the damping force control device for a vehicle according to the present invention, the damping force control means controls the damping force of the outer wheel shock absorber to be low and the damping force of the inner wheel shock absorber to be high when the vehicle turns. According to the present invention, the stability of the vehicle at the time of turning is enhanced, and the rolling of the vehicle body is suppressed, so that the riding comfort can be improved.

Further, in the vehicle damping force control device according to the present invention, the damping force control means controls the damping force of the outer wheel shock absorber to be high and the damping force of the inner wheel shock absorber to be low when the vehicle turns. It is characterized by the following.

According to the present invention, the maneuverability of the vehicle during turning is enhanced.

[0010] The vehicle damping force control device according to the present invention is characterized in that the damping force control means controls the damping force of the shock absorber so as to change the vehicle turning characteristics based on the turning behavior of the vehicle. I do.

According to the present invention, the controllability of the vehicle turning characteristics is optimally controlled in accordance with the turning state of the vehicle, whereby the controllability and stability of the vehicle can be improved.

Further, in the damping force control device for a vehicle according to the present invention, the damping force control means reduces the damping force of the shock absorber at the rear wheel on the inner wheel side when the turning behavior is largely changed, and reduces the damping force at the other wheels. It is characterized in that control is performed to increase the damping force of the shock absorber.

According to the present invention, when a large lateral acceleration is applied during the turning of the vehicle, the lift of the rear wheel inside the turning is suppressed, and the stability of the vehicle is improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals, and the description is omitted. Also,
The dimensional ratios in the drawings do not always match those described.

(First Embodiment) FIG. 1 shows a schematic diagram of the configuration of a damping force control device according to this embodiment. 1, the damping force control device 1 includes an actuator 2 that changes the damping force of a shock absorber 10. The actuator 2 includes a shock absorber 10FR for the right front wheel 11FR and a shock absorber 10F for the left front wheel 11FL.
L, one shock absorber 10RR for the right rear wheel 11RR, and one shock absorber 10RL for the left rear wheel 11RL. The actuator 2 constitutes a part of the damping force variable means, and includes a shock absorber 10 (10FR, 10FL, 10RR, 10R).
In the case where the expansion / contraction speed of L) is in a low speed range, the ECU 8
, The damping force of the shock absorber 10 is changed.

FIG. 2 shows an example of a shock absorber to be subjected to damping force control. In FIG. 2, the shock absorber 10 (10FR, 10FL, 10RR, 10RL)
Has a function of attenuating the vibration of the coil spring 10c to improve the ride comfort of the vehicle and improving the ground contact of the wheels to improve the steering stability. Has become. The shock absorber 10 has an upper end attached to the vehicle body and a lower end attached to the wheel. For example, the upper end of the shock absorber 10 is fixed to the vehicle body 12 and the lower end is fixed to the carrier 13.

As shown in FIG. 2, the shock absorber 1
0 has a piston rod 16 and an outer cylinder 18.
A guide 10a is fixed to the outer periphery of the outer cylinder 18, and a bracket 10b is hung on the upper end of the piston rod. A coil spring 10c is provided between the guide 10a and the bracket 10b, and the vehicle body is elastically supported by the coil spring 10c.

Inside the outer cylinder 18, an inner cylinder 20 is provided.
And are arranged coaxially. 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 columnar 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 has a through hole at the center thereof. The piston rod 16 is slidably inserted through the through hole in a liquid-tight manner. A cap 24 is fixed to the upper end of the outer cylinder 18 so that the piston rod 16 passes through the center of the cap 24.

The piston rod 16 is a columnar member whose lower end has a small diameter. The piston rod 16 is arranged so that its small diameter portion is housed inside the inner cylinder 20. A rebound stopper 26 and a rebound stopper plate 28 are mounted on the piston rod 16 at a position accommodated inside the inner cylinder 20.

The rebound stopper plate 28 is an annular rigid member, and is fixed to the outer periphery of the piston rod 16. The rebound stopper 26 is an annular member having elasticity, and is mounted on an upper part of 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.

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

Sub piston 30 and main piston 32
Are provided with orifices and valve mechanisms 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. A damping force is generated according to. Details of the configuration of the sub piston 30 and the main piston 32 will be described later.

A passage 40 penetrating in the axial direction is provided inside the piston rod 16. Passage 40
A large-diameter portion 40a and a small-diameter portion 4 extending below the large-diameter portion 40a
0b. A step 40c is formed at the boundary between the large diameter portion 40a and the small diameter portion 40b of the passage 40.
An adjusting rod 42 is inserted into the large diameter portion 40 a of the passage 40.

A base valve 41 is fixed to a lower end of the outer cylinder 18. The base valve 41 is configured to allow a fluid to flow between the lower chamber 38 and the annular chamber 21. The working fluid is contained so as to fill the internal space of the inner cylinder 20 and fill the annular chamber 21 to a predetermined height.

The upper end of the adjusting rod 42 reaches the upper part of the piston rod 16 and is engaged with the actuator 2 mounted on the vehicle body. Actuator 2 is EC
The adjusting rod 42 is rotated in response to a signal from U8, and is constituted by, for example, a driving force transmission mechanism such as a stepping motor and a gear.

Next, referring to FIG.
The configuration of the main piston 32, the main piston 32, and its peripheral parts will be described. FIG. 3 is an enlarged view of the sub piston 30, the main piston 32, and a peripheral portion thereof. The left half of FIG. 3 shows a component that allows fluid to flow from the upper chamber 34 to the lower chamber 38, and the right half of FIG. Components that allow fluid flow to the side are shown.

As shown in FIG. 3, the adjusting rod 42 is one of the components of the damping force varying means, and has a small diameter portion 42a having an outer diameter smaller than the inner diameter of the large diameter portion 40a of the passage 40.
And a conical portion 42b formed at a lower end portion of the small diameter portion 42a.
And The adjustment rod 42 is arranged such that the tip of the conical portion 42b enters the small diameter portion 40b of the passage 40. The outer peripheral surface of the conical portion 42b and the step 40 of the passage 40
A clearance C is formed between the gap C and the gap C.

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 periphery of the small diameter portion 42 a of the adjustment rod 42 and the inner periphery of the large diameter portion 40 a 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 communicating the upper chamber 34 and the communication space 44 is provided.
Is provided. Further, the piston rod 16 is provided with a communication passage 47 extending in the radial direction and communicating the internal space of the small diameter portion 40b of the passage 40 with the external space of the small diameter portion of the piston rod 16.

The adjusting rod 42 is screwed into a large diameter portion 40a of the passage 40 at a screw portion (not shown), and the upper end thereof is engaged with the actuator 2. Therefore, the clearance C can be adjusted by rotating the adjustment rod 42 by the actuator 2 and thereby changing the vertical position of the adjustment rod 42.

On the outer periphery of the small diameter portion of the piston rod 16, a stopper plate 48, a leaf seat 49, and a leaf valve 5 are arranged in this order from the large diameter portion 16a side (the upper side in FIG. 3).
0, the sub piston 30, the leaf valve 54, and the leaf seat 56 are fitted.

The leaf valves 50 and 54 are members having a low bending rigidity and made of a thin plate. The upper and lower ends of the sub-piston 30 have annular grooves 58 respectively.
And 60 are provided. Leaf valves 50 and 54
Are arranged to close the annular grooves 58 and 60, respectively. The sub-piston 30 has an annular groove 5.
A through passage 62 that connects the internal space of No. 8 to the middle chamber 36 and a through passage 64 that connects the internal space of the annular groove 60 to the upper chamber 34 are provided.

The leaf valve 50 opens by flexing and deforming when the hydraulic pressure of the middle chamber 36 becomes higher than the hydraulic pressure of the upper chamber 34 by a predetermined valve opening pressure P1. To the upper chamber 34 from the working fluid. The leaf valve 54 opens by flexing and deforming when the hydraulic pressure of the upper chamber 34 becomes higher than the hydraulic pressure of the middle chamber 36 by a predetermined valve opening pressure P2. The flow of the working fluid toward the middle chamber 36 is allowed.

A piston ring 66 is mounted on the outer periphery of the sub piston 30. The seal between the sub-piston 30 and the inner cylinder 20 is ensured by the piston ring 66. Leaf sheet 5 around piston rod 16
6, a communication member 68, a leaf seat 70, a spacer 72, a spring seat 74,
And a spacer 76 are fitted.

The communication member 68 has a communication passage 77 penetrating in the radial direction and communicating 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 provided between the spring seat 74 and the spring seat 78.

The spacer 76 on the outer periphery of the piston rod 16
A leaf valve 82, a main piston 32, and a leaf valve 86 are fitted in order from the upper side further below. A plurality of seat surfaces 92 are provided on the upper end surface of the main piston 32. Also, the main piston 32
A plurality of sheet surfaces 94 are provided at positions not corresponding to the sheet surface 92 at the lower end surface of the. The leaf valves 82 and 86 are members formed by laminating a plurality of thin plate members, and are disposed so as to contact the top surfaces of the seat surfaces 92 and 94, respectively. A piston ring 95 is mounted on the outer periphery of the main piston 32. Piston ring 95
Thereby, the sealing property between the main piston 32 and the inner cylinder 20 is ensured.

The main piston 32 is also provided with through passages 96 and 98 penetrating in the axial direction.
The through-passage 96 is configured to open at a concave portion between the seat surfaces 92 at an upper end thereof, and to open at a top surface of the seat surface 94 at a lower end thereof. In addition, the through passage 9
Numeral 8 is configured to open at the top of the seat surface 92 at its upper end and to open into the recess between the seat surfaces 94 at its lower end.

A first orifice (see FIG. 4) for communicating the through passage 98 with the middle chamber 36 in a state where the leaf valve 82 is in contact with the seat surface 92 is formed on the thin plate material on the side of the main piston 32 that constitutes the leaf valve 82. (Not shown). A second orifice (shown in the drawing) that connects the through passage 96 and the lower chamber 38 in a state where the leaf valve 86 is in contact with the seat surface 94 is provided on the thin plate material closest to the main piston 32 that constitutes the leaf valve 86. Are formed.

A spacer 99 is fitted below the leaf valve 86 on the outer periphery of the piston rod 16.
A thread 16c is formed at the lower end of the piston rod 16, and a spring seat 100 is screwed to the thread 16c. A spring seat 102 is fitted on the outer periphery of the spacer 99 so as to be slidable in the axial direction. Spring seat 102 and spring seat 10
A spring 104 is provided between the spring 104 and the spring.

At the lower end of the small diameter portion of the piston rod 16, a screw 105 for closing the passage 40 is mounted. Therefore, communication between the passage 40 and the lower chamber 38 is interrupted, and the passage 40 communicates only with the upper chamber 34 and the middle chamber 36.

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

The leaf valves 82 and 86 are respectively
The urging force of the springs 80 and 104 presses the main piston 32 toward the top surfaces of the seat surfaces 92 and 94. When the hydraulic pressure of the lower chamber 38 becomes higher than the hydraulic pressure of the intermediate chamber 36 by a predetermined valve opening pressure P3 or more, the leaf valve 82 bends upwardly against the urging force of the spring 80 to be deformed. The valve is opened to allow the flow of the working fluid from the lower chamber 38 to the middle chamber 36. The leaf valve 86 has a predetermined valve opening pressure P that is higher than the hydraulic pressure of the middle chamber 36 compared to the hydraulic pressure of the lower chamber 38.
When the pressure becomes 4 or more, the valve opens by flexing and deforming downward against the urging force of the spring 104, allowing the flow of the working fluid from the middle chamber 36 to the lower chamber 38.

In the present embodiment, since the leaf valves 50 and 54 are formed of low rigidity thin plate members,
These valve opening pressures P1 and P2 are set to very small values. 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 relatively large values.

Next, the operation of the shock absorber 10 will be described with reference to FIG. 4 together with FIGS. FIG.
Indicates a damping force characteristic realized by the shock absorber 10. 4, the horizontal axis represents the displacement speed V of the piston rod 16, and the vertical axis represents the shock absorber 1.
0 indicates the damping force F generated. 4, the direction in which the piston rod 16 retreats from the inner cylinder 20,
That is, the damping force F when displacing in the extension direction is shown as positive.

When the piston rod 16 is displaced in the extending direction, the volume of the upper chamber 34 decreases and the volume of the lower chamber 38 increases. In order to compensate for these volume changes, the working fluid flows from the upper chamber 34 through the middle chamber 36 to the lower chamber 38. Further, when the piston rod 16 retreats from the inner cylinder 20, the volume of the inner cylinder 20 increases. In order to compensate for the increase in the volume of the inner cylinder 20, the working fluid flows from the annular chamber 21 into the lower chamber 38 via the base valve 41.

When the displacement velocity V of the piston rod 16 is sufficiently low, the differential pressure between the upper chamber 34 and the middle chamber 36 and the differential pressure between the middle chamber 36 and the lower chamber 38 are small. Both the leaf valve 54 and the leaf valve 86 are kept in a closed state. Therefore, the working fluid in the upper chamber 34 flows through the communication passage 46 of the piston rod 16, the communication space 44, the clearance C, the small diameter portion 40 b of the passage 40, the communication passage 47, and the communication passage 77 of the communication member 68. The air flows into the intermediate chamber 36 through a road (hereinafter, referred to as a bypass passage). The working fluid in the middle chamber 36 flows into the lower chamber 38 through the through passage 96 of the main piston 32 and the second orifice.

In this case, when the working fluid flows through the bypass passage and the second orifice, a damping force is generated due to the flow resistance. The damping force F generated by the shock absorber 10 includes a 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 a damping force F generated from the middle chamber 36 to the lower chamber 38. This is the sum with the damping force Fb generated according to the flow resistance R2 when flowing. For this reason. As shown by reference numeral A1 in FIG.
It rises with a large gradient as the number increases.

When the flow resistance R1 when the working fluid flows from the upper chamber 34 to the middle chamber 36 increases, the upper chamber 34 and the middle chamber 36
And the pressure difference between them rises. Further, when the flow resistance R2 when the working fluid flows from the middle chamber 36 to the lower chamber 38 increases,
The pressure difference between the middle chamber 36 and the lower chamber 38 increases. And
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 is referred to as a first valve opening speed V1 and a first valve opening damping force F1, respectively. As described above, in the present embodiment, the valve opening pressure P2 of the leaf valve 54 is set sufficiently small so that the first valve opening damping force F1 becomes a very small value, for example, 3 to 5 kgf. When the valve opening pressure P2 of the leaf valve 54 is set as described above, the first valve opening speed V1 becomes 0.05 m.
/ S which is very low.

When the leaf valve 54 opens, the upper chamber 34
The movement of the fluid from the inner chamber 36 to the inner 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 flows from the upper chamber 34 to the middle chamber 36 decreases. When the flow resistance R1 decreases, the damping force F increases in a region where the displacement speed V exceeds the first valve opening speed V1, as indicated by reference numeral A2 in FIG.
Increase slope decreases.

When the displacement speed V further increases and the pressure difference between the middle chamber 36 and the lower chamber 38 reaches the valve opening pressure P4 of the leaf valve 86, the leaf valve 86 opens. Hereinafter, the displacement speed V and the damping force F when the leaf valve 86 opens are referred to as a second valve opening speed V2 and a second valve opening damping force F2, respectively.
Called. In the present embodiment, the second valve opening damping force F2
Is set to, for example, about 50 kgf.
6, a valve opening pressure P4 is set. In this case, the second valve opening speed V2 has a value of about 0.2 m / s.

When the leaf valve 86 is opened, the middle chamber 36
By increasing the flow passage area of the flow passage from the lower chamber 38 to the lower chamber 38,
The flow resistance R2 when the working fluid flows from the middle chamber 36 to the lower chamber 38 is reduced. For this reason, FIG.
As shown by, 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 contraction direction,
As the volume of the upper chamber 34 increases, the volume of the lower chamber 38 decreases. In order to compensate for these volume changes, the working fluid flows from the lower chamber 38 via the middle chamber 36 into the upper chamber 34. In addition, as the piston rod 16 enters the inner cylinder 20, the volume of the inner cylinder 20 decreases. In order to compensate for the decrease in the volume of the inner cylinder 20, the working fluid flows out from the lower chamber 38 to the annular chamber 21 via the base valve 41.

In this embodiment, the valve opening pressure P1 of the leaf valve 54 is provided so as to substantially coincide with the valve opening pressure P2 of the leaf valve 54. Therefore, when the displacement speed V reaches v1 substantially equal to the first valve opening speed V1, and the damping force F becomes f1 substantially equal to the first valve opening damping force F1,
The leaf valve 50 opens. Also, the leaf valve 82
The valve opening pressure P3 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) smaller than the second valve opening speed V2, and the damping force F becomes f2 (for example, about 3.0 kgf) smaller than the second valve opening damping force F2. At this point, the leaf valve 82 opens. Hereinafter, v1 and v2, which are displacement speeds V of the piston rod 16 when the leaf valves 50 and 82 open, are also referred to as a first valve opening speed and a second valve opening speed, respectively. F1 is a damping force F when the valve 82 is opened.
And f2 are referred to as a first valve opening damping force and a second valve opening damping force, respectively.

Accordingly, even when the piston rod 16 is displaced in the contracting direction, similarly to the case where the piston rod 16 is displaced in the extending direction, the displacement speed V of the piston rod 16 reaches the first valve opening speed v1. 4, the damping force F rises with a relatively large gradient, as indicated by reference numeral B1 in FIG. When the displacement speed V reaches the first valve opening speed v1, the leaf valve 50 is opened, and the increasing gradient of the damping force F decreases as indicated by reference numeral B2 in FIG. Further, when the displacement speed V reaches the second valve opening speed v2, the leaf valve 82 is opened, and the symbol B in FIG.
As shown by 3, the increasing gradient of the damping force F further decreases.

As described above, according to the shock absorber 10, the displacement speed V of the piston rod 16 is in the low speed range (first range).
Damping such that the increasing gradient of the damping force F gradually decreases in accordance with the transition from the valve opening speed V1, v1 or lower region to the high speed region (region exceeding the first valve opening speed V1, v1). Force characteristics are realized.

The degree of opening of the bypass passage changes according to the size of the clearance C. As the opening degree of the bypass passage increases, the flow resistance of the working fluid flowing through the bypass passage decreases. When the flow resistance when flowing through the bypass passage decreases, the differential pressure between the upper chamber 34 and the middle chamber 36 generated for a constant displacement speed V decreases, and the damping force F decreases. That is, the gradient of the damping force characteristic is small as shown by the broken lines with the reference numerals a1 and b1 in FIG.

Therefore, by adjusting the clearance C, the displacement speed V of the piston rod 16 becomes equal to the first valve opening speed V.
1, while the damping force characteristic in a region larger than v1, that is, a high-speed region is maintained substantially constant, the 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 speed V1, v1 is 0.05
It is set to a low value of m / s or less. Therefore, according to the shock absorber 10 according to the present embodiment, by changing the clearance C, the damping of the shock absorber 10 in the low-speed region of 0.05 m / s or less without affecting the damping force characteristics in the high-speed region. Only the force characteristics can be adjusted. Further, by controlling the driving of the actuator 2 to change the clearance C stepwise, it is possible to change the gradient of the damping force characteristic of the shock absorber 10 stepwise in the low speed range of the piston rod 16.

According to an experiment conducted by the present inventor using the shock absorber 10 according to the present embodiment, the ride comfort and the steering stability of the vehicle greatly change depending on the damping force characteristics in a low speed range. I know. For example, if the clearance C is reduced to increase the gradient of the damping force characteristic in the low speed range, the steering holding force at the time of cornering increases, and the feeling of steering response increases. In addition, the responsiveness of the vehicle's rolling speed during turning and the responsiveness of the vehicle's yawing change during steering are sensitive to changes in the damping force characteristics in the low speed range. Therefore, according to the shock absorber 10 according to the present embodiment, by adjusting the clearance C and changing the damping force characteristic in the low speed range, more optimal riding comfort and steering stability can be obtained. In the present invention, the shock absorber to be controlled for the damping force is:
The present invention is not limited to the shock absorber 10 described above, and may have another structure as long as the damping force can be varied in a low speed range of the expansion and contraction speed.

On the other hand, as shown in FIG. 1, the damping force control device 1 is provided with a vehicle speed sensor 3. Vehicle speed sensor 3
Is a detector for detecting the traveling speed of the vehicle. The damping force control device 1 is provided with a steering angle sensor 4. The steering angle sensor 4 is a detector that detects the steering angle of the steering wheel. The damping force control device 1 is provided with a yaw rate sensor 5. Yaw rate sensor 5
Is a detector that detects the rotational speed around a vertical axis passing through the center of gravity of the vehicle. The damping force control device 1 is provided with a vehicle height sensor 6. The vehicle height sensor 6 is provided for each wheel 11
, And is provided for each wheel 11 one by one. Further, the damping force control device 1 is provided with a vertical acceleration sensor 7. The vertical acceleration sensor 7 is a detector that detects the sprung acceleration of each wheel 11, and is provided for each wheel 11.

In FIG. 1, the damping force control device 1 has E
A CU 8 is provided. The ECU 8 controls the entire damping force control device 1, and is connected to each of the sensors 3 to 7, and receives output signals of the sensors 3 to 7, respectively. The ECU 8 is connected to the actuator 2 of each wheel 11 so that a drive signal can be output to each actuator 2. Further, the ECU 8 functions as a behavior state detection unit that detects the behavior state of the vehicle. For example, the ECU 8 uses the vehicle speed V based on the output signal of the vehicle speed sensor 3, the steering angle θ based on the output signal of the steering angle sensor 4, and the yaw rate γ based on the output signal of the yaw rate sensor 5 using the following equation (1). The vehicle body slip angle β is calculated, and the vehicle body slip angular velocity β ′ is calculated from the vehicle body slip angle β.

Α · β + I · γ ′ + (σ · γ) / V = ξ · θ (1) where I is the moment of inertia of the vehicle body, and α, σ, and ξ are constants.

Here, the vehicle body slip angle β refers to the angle between the forward direction X ₀ of the vehicle body and the traveling direction X of the vehicle body as shown in FIG. 1, and for convenience of explanation, when the vehicle turns left, The vehicle body slip angle generated around the vehicle is assumed to be positive.

The ECU 8 stores a map (β-β ′ map) defined by the vehicle body slip angle β and the vehicle body slip angular velocity β ′ as shown in FIG. Slip angular velocity β '
Is calculated based on the calculated value of the vehicle, and the behavior state of the vehicle is detected. That is, in FIG.
As a result of the map calculation, the ECU 8 determines that the vehicle is stable or shifts to a stable direction when the vehicle is in the region II.
It is determined that the behavior state of the vehicle is stable. On the other hand, when the vehicle is in the region I and the region III, the vehicle is in an unstable state or shifts to an unstable state, so that it is determined that the behavior state of the vehicle is unstable. The “vehicle behavior state” here is not limited to the vehicle slip state based on the vehicle body slip angle and the vehicle body slip angular velocity. The behavior state may be based on the following.

The ECU 8 functions as damping force control means for individually controlling the damping force of the shock absorber 10 on the inner wheel and the outer wheel according to the behavior state of the vehicle when turning. For example, the ECU 8 issues a drive signal to the actuator 2 of each wheel 11 according to the result of the map calculation based on the vehicle body slip angle β and the vehicle body slip angular velocity β ′, and individually controls the damping force of each shock absorber 10.

Next, the operation of the damping force control device 1 will be described.

FIG. 6 is a flowchart showing the operation of the damping force control device 1 when the vehicle turns. When the vehicle turns by operating the steering wheel of the driver during running of the vehicle, the damping force of each shock absorber 10 is individually controlled by the damping force control device 1 for each wheel 11 according to the behavior state of the vehicle as shown in FIG. Is controlled. Whether the vehicle is in a turning state is determined based on an output signal of the steering angle sensor 4 and the like. Also, the "turning state of the vehicle" referred to here
The term “state” means a state other than the state where the vehicle is traveling straight when the vehicle is traveling, and is not limited to the case where the vehicle turns a curve, and also includes a course change when the vehicle changes lanes.

In step S10 of FIG.
Accordingly, the vehicle speed V is read based on the output signal of the vehicle speed sensor 3, the steering angle θ is read based on the output signal of the steering angle sensor 4, and the yaw rate γ is read based on the output signal of the yaw rate sensor 5.

In step S12, the ECU 8 calculates the vehicle body slip angle β and the vehicle body slip angular velocity β ′ based on the vehicle speed V, the steering angle θ, and the yaw rate γ.
The calculation of the vehicle body slip angle β and the vehicle body slip angular velocity β ′ is performed by the calculation using the above equation (1). Next, the process proceeds to step S14, and a map calculation is performed based on the calculated vehicle body slip angle β and vehicle body slip angular velocity β ′. That is, as shown in FIG. 5, based on the calculated values of the vehicle body slip angle β and the vehicle body slip angular velocity β ′, it is determined from the map stored in the ECU 8 in advance what the behavior state of the vehicle is. .

Then, the flow shifts to step S16, where it is determined whether or not the behavior state of the vehicle belongs to the area II in the map of FIG. In step S16, when it is determined that the behavior state of the vehicle belongs to the region II, it is determined that the behavior state of the vehicle at the time of turning is stable.
From 8, no drive signal is output to the actuator 2 of each wheel 11, and the damping force characteristic of the shock absorber 10 does not change. In this case, the damping force of the shock absorber 10 is determined according to the characteristics (A1, B1, etc.) shown by the solid line in FIG. Then, returning to step S10, the ECU 8 again reads the vehicle speed V based on the output signal of the vehicle speed sensor 3, reads the steering angle θ based on the output signal of the steering angle sensor 4, and calculates the yaw rate γ based on the output signal of the yaw rate sensor 5. The reading is performed, and the processes of steps S12 and S14 are sequentially performed.

On the other hand, when it is determined in step S16 that the behavior state of the vehicle does not belong to region II, the process proceeds to step S18, and it is determined whether the behavior state of the vehicle belongs to region I.

When it is determined in step S18 that the behavior state of the vehicle belongs to the region I, the process proceeds to steps S20 and S22, where the right wheels 11FR and 11RR are set.
The damping force of the shock absorbers 10FR and 10RR is increased, and the damping force of the shock absorbers 10FL and 10RL of the left wheels 11FL and 11RL is reduced. To increase or decrease the damping force of the shock absorbers 10FR, 10RR, 10FL, and 10RL, a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the actuator 2 operates based on the drive signal, and the adjusting rod 42 of the shock absorber 10 is moved. This is performed by appropriately moving up and down. The damping force of the shock absorber 10 is increased or decreased based on, for example, a map of damping force characteristics with respect to the expansion and contraction speed of the piston rod 16 stored in the ROM of the ECU 8 or the like.

Here, the case where the behavior state of the vehicle belongs to the region I corresponds to, for example, a case where the vehicle body slips clockwise greatly due to turning the steering wheel to the left during running. In this case, the right wheel 1 which is a turning outer wheel
1FR, 11RR shock absorber 10FR, 10
The RR damping force is increased, and the left wheel 1 is a turning inner wheel.
1FL, 11RL shock absorber 10FL, 10
By reducing the damping force of the RL, the rolling of the vehicle body is suppressed, the riding comfort is improved, and the running stability of the vehicle is maintained. Further, the control steps from step S10 to step S22 are the same as those of the shock absorber 1
0 expansion and contraction speed is in a low range (for example, expansion and contraction speed is 0.1 m /
s or less). For this reason,
When the shock absorber 10 expands and contracts in a high-speed range, the damping force of the shock absorber 10 is not reduced and the grounding of the wheels 11 is ensured, so that the maneuverability of the vehicle is improved.

Then, in step S22, the left wheel 11
When the damping force of the shock absorber 10 has been reduced,
It returns to step S10.

On the other hand, when it is determined in step S18 that the behavior state of the vehicle does not belong to the region I,
The process proceeds to steps S24 and S26, and the right wheel 11FR,
The damping force of the shock absorbers 10FR and 10RR of 11RR is reduced, and the damping force of the shock absorbers 10FL and 10RL of the left wheels 11FL and 11RL is increased. This shock absorber 10FR, 10RR, 10
The increase and decrease of the damping force of FL and 10RL are determined by the EC
The actuator 2 of each wheel 11 operates based on the drive signal from U8, and the adjusting rod 42 of each shock absorber 10
Is appropriately moved up and down.

Here, the case where the behavior state of the vehicle does not belong to the region I means that the behavior state of the vehicle is the region III in FIG.
For example, when the steering wheel is turned to the right while the vehicle is running, the vehicle body slips largely counterclockwise. In this case, the shock absorber 1 of the right wheels 11FR and 11RR which are the turning inner wheels is used.
The damping force of 0FR and 10RR is reduced, and the shock absorber 1 of the left wheels 11FL and 11RL as the turning outer wheels is provided.
By increasing the damping force of 0FL and 10RL, the riding comfort is kept good and the rolling of the vehicle body is effectively reduced.

Then, in steps S24 and S26, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10.

The damping force control shown in FIG. 6 is performed when the vehicle is turning. When the vehicle is traveling straight, the damping force control of the shock absorber 10 as shown in FIG. 6 is not performed. , For example, a vehicle height sensor 6
The damping force control based on the skyhook theory is performed using the detection signal of the vertical acceleration sensor 7 and the like.

As described above, according to the damping force control device 1 according to the present embodiment, when the vehicle is turning, the inner ring and the outer ring are changed in accordance with the load on the inner and outer wheels according to the behavior of the vehicle at the time of turning. The damping force F of the outer ring shock absorber 10 is individually controlled. For this reason, stability of the vehicle at the time of turning is ensured, and riding comfort can be improved. Also, only in the low-speed range of the expansion and contraction speed of the shock absorber 10,
By variably controlling the damping force of the shock absorber 10, the grounding of the wheels 11 when the shock absorber 10 operates in a high-speed range is ensured, and the maneuverability of the vehicle is improved.

(Second Embodiment) Next, a damping force control device according to a second embodiment will be described.

The damping force control device according to the present embodiment separately controls the damping force of the shock absorbers of the inner turning wheel and the outer turning wheel according to the behavior of the vehicle when the vehicle is turning stably. Is controlled. The damping force control device includes an actuator 2, a vehicle speed sensor 3, a steering angle sensor 4, a yaw rate sensor 5, a vehicle height sensor 6, a vertical acceleration sensor 7, and an ECU 8, similarly to the damping force control device 1 according to the first embodiment. The shock absorber 10 is a damping force control target.

The operation of the damping force control device will be described with reference to FIG. FIG. 7 is a flowchart showing the operation of the damping force control device when the vehicle turns. When the vehicle turns due to a driver's steering wheel operation or the like during running of the vehicle, the damping force of each shock absorber 10 is individually controlled by the damping force control device for each wheel 11 according to the behavior state of the vehicle as shown in FIG. Controlled. Whether the vehicle is in a turning state is determined based on an output signal of the steering angle sensor 4 and the like.

Steps S10 to S14 in FIG. 7 are the same as those in the first embodiment, and a description thereof will be omitted. In FIG. 7, the process proceeds from step S14 to step S30, and it is determined whether the behavior state of the vehicle belongs to the area II in the map of FIG. In step S30,
When it is determined that the behavior state of the vehicle does not belong to the region II, no drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the damping force characteristic of the shock absorber 10 is not changed. That is, it is determined that the behavior state of the vehicle at the time of turning is unstable.
The damping force characteristic of 0 cannot be changed. And in this case,
In step S10, reading of the vehicle speed V based on the output signal of the vehicle speed sensor 3, reading of the steering angle θ based on the output signal of the steering angle sensor 4, and reading of the yaw rate γ based on the output signal of the yaw rate sensor 5 are performed again. .

On the other hand, when it is determined in step S30 that the behavior state of the vehicle belongs to the region II, the process proceeds to step S32, and it is determined whether the yaw rate γ of the vehicle is positive, zero, or negative. . here,
For example, when the vehicle is viewed from above, the counterclockwise yaw rate is positive, and the clockwise yaw rate is negative.

In step S32, the yaw rate γ of the vehicle is zero (the vehicle is not rotating in either direction).
If it is determined that the vehicle speed V has been determined, the process returns to step S10 and the vehicle speed V and the like are read again.

In step S32, the yaw rate γ of the vehicle is positive (the vehicle is rotating counterclockwise).
When it is determined that the shock absorbers 10FR, 11RR of the right wheels 11FR, 11RR are reduced, the shock absorbers 10FL, 10RR of the left wheels 11FL, 11RL are reduced.
The 0 RL damping force is increased. To increase or decrease the damping force of the shock absorbers 10FR, 10RR, 10FL, and 10RL, a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the actuator 2 is operated based on the drive signal to operate the adjustment rod 4 of the shock absorber 10.
2 is appropriately moved up and down. Further, the increase and decrease of the damping force of the shock absorber 10 may be determined, for example, by ECU
8 based on a map of the damping force characteristic with respect to the expansion / contraction speed of the piston rod 16 stored in the ROM or the like.

In steps S34 and S36, the damping force of the shock absorbers 10FR and 10RR of the right wheels 11FR and 11RR as the turning outer wheels is reduced, and the shock absorbers 10FL and 10RL of the left wheels 11FL and 11RL as the turning inner wheels are reduced. By increasing the damping force,
Since the position of the vehicle body, that is, the position of the center of gravity of the vehicle body, is lowered, the maneuverability of the vehicle is improved. In this case, since the behavior state of the vehicle is stable, the shock absorber 10
Even if the damping force of the vehicle is controlled, there is no fear that running stability of the vehicle is impaired.

Then, in steps S34 and S36, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10.

On the other hand, in step S32, the yaw rate γ of the vehicle is negative (the vehicle is rotating clockwise).
When it is determined that the shock absorbers 10FR and 11RR of the right wheels 11FR and 11RR are increased, the damping force of the shock absorbers 10FR and 10RR of the right wheels 11FR and 11RR is increased, and the shock absorbers 10FL and 1FL of the left wheels 11FL and 11RL are increased.
The 0 RL damping force is reduced. To increase or decrease the damping force of the shock absorbers 10FR, 10RR, 10FL, and 10RL, a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the actuator 2 is operated based on the drive signal to operate the adjustment rod 4 of the shock absorber 10.
2 is appropriately moved up and down. Further, the increase and decrease of the damping force of the shock absorber 10 may be determined, for example, by ECU
8 based on a map of the damping force characteristic with respect to the expansion / contraction speed of the piston rod 16 stored in the ROM or the like.

In steps S38 and S40, the damping force of the shock absorbers 10FR and 10RR of the right wheels 11FR and 11RR that are the turning inner wheels is increased, and the shock absorbers 10FL and 10RL of the left wheels 11FL and 11RL that are the turning outer wheels are increased. By reducing the damping force,
Since the position of the vehicle body, that is, the position of the center of gravity of the vehicle body, is lowered, the maneuverability of the vehicle is improved. In this case, since the behavior state of the vehicle is stable, the shock absorber 10
Even if the damping force of the vehicle is controlled, there is no fear that running stability of the vehicle is impaired.

Then, in steps S38 and S40, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10. In the control processes of steps S10 to S14 and steps S30 to S40, the expansion and contraction speed of the shock absorber 10 is in a low range (for example, when the expansion and contraction speed is set to 0. 1).
Speed range of 1 m / s or less). For this reason, when the shock absorber 10 expands and contracts in a high-speed range, the damping force characteristic of the shock absorber 10 can be kept substantially constant, and the grounding of the wheels 11 can be ensured.

Incidentally, the above-described damping force control shown in FIG. 7 is performed when the vehicle is turning, and when the vehicle is traveling straight, the damping force control of the shock absorber 10 as shown in FIG. 7 is not performed. , For example, a vehicle height sensor 6
The damping force control based on the skyhook theory is performed using the detection signal of the vertical acceleration sensor 7 and the like.

As described above, according to the damping force control device according to the present embodiment, when the vehicle is turning, the inner ring and the outer ring are changed in accordance with the behavior of the vehicle at the time of turning and the load applied to the inner and outer wheels. Damping force F of the shock absorber 10
Are individually controlled. For this reason, stability of the vehicle at the time of turning is ensured, and riding comfort can be improved. Also, only by controlling the damping force of the shock absorber 10 variably only in the low-speed range of the expansion and contraction speed of the shock absorber 10, the grounding of the wheels 11 when the shock absorber 10 operates in the high-speed range is ensured, and the maneuverability of the vehicle is improved. Is good.

(Third Embodiment) Next, a damping force control device according to a third embodiment will be described.

The damping force control device according to the present embodiment, like the damping force control device 1 according to the first embodiment, has an actuator 2, a vehicle speed sensor 3, a steering angle sensor 4, a yaw rate sensor 5, a vehicle height sensor 6, Vertical acceleration sensor 7, ECU 8
And the shock absorber 10 is a target of damping force control.

The operation of the damping force control device will be described with reference to FIG. FIG. 8 is a flowchart showing the operation of the damping force control device when the vehicle turns. During vehicle running, when the vehicle turns by a driver's steering wheel operation or the like, the damping force of each shock absorber 10 is individually controlled by the damping force control device for each wheel 11 according to the behavior state of the vehicle as shown in FIG. Controlled. Whether the vehicle is in a turning state is determined based on an output signal of the steering angle sensor 4 and the like.

In FIG. 8, steps S10 to S14 are the same as in the first embodiment, and a description thereof will be omitted. When the process proceeds from step S14 to step S50, it is determined whether the yaw rate γ of the vehicle is positive, zero, or negative. Here, for example, when the vehicle is viewed from above, the left-handed yaw rate is positive, and the right-handed yaw rate is negative.

In step S50, the yaw rate γ of the vehicle is zero (the vehicle is not rotating in either direction).
If it is determined that the vehicle speed V has been determined, the process returns to step S10 and the vehicle speed V and the like are read again.

In step S50, the yaw rate γ of the vehicle is positive (the vehicle is rotating counterclockwise).
When the determination is made, the process proceeds to step S51. In step S51, it is determined whether the behavior state of the vehicle belongs to the area II in the map of FIG.

If it is determined in step S51 that the behavior state of the vehicle belongs to region II, the flow proceeds to step S51.
The process sequentially proceeds to 52, 53, 54, and 55, and a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11,
By driving the actuator 2, the damping force of the shock absorber 10 is appropriately increased or decreased. That is, step S
At 52, the damping force of the shock absorber 10FR of the right front wheel 11FR, which is the front wheel on the outside of turning, is increased. In step S53, the front left wheel 11F that is the front wheel inside the turn
The damping force of the L shock absorber 10FL is reduced. In step S54, the damping force of the shock absorber 10RR of the right rear wheel 11RR that is the rear wheel on the outside of the turn is reduced. In step S55, the damping force of the shock absorber 10RL of the rear left wheel 11RL, which is the rear inner wheel, is increased. The damping force of each shock absorber 10 is increased or decreased based on, for example, a map of the damping force characteristic with respect to the expansion and contraction speed of the piston rod 16 stored in the ROM of the ECU 8 or the like. It is desirable to fine-tune the damping force.

In steps S52 to S55, the damping force of the shock absorber 10 at the front wheel on the outside of the turn and the rear wheel on the inside of the turn is increased, and the damping force of the shock absorber 10 on the front wheel on the inside of the turn and the rear wheel on the outside of the turn is reduced. As a result, the US-OS characteristic (steer characteristic: oversteer / understeer characteristic) of the vehicle is corrected to be slightly oversteer, and the maneuverability of the vehicle during turning of the vehicle is improved. In the control process of steps S52 to S55, since the behavior state of the vehicle is stable,
There is no worry that vehicle stability will be compromised.

Then, in steps S52 to S55, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
Returning to step S10, the ECU 8 again reads the vehicle speed V based on the output signal of the vehicle speed sensor 3, reads the steering angle θ based on the output signal of the steering angle sensor 4, and reads the yaw rate γ based on the output signal of the yaw rate sensor 5. Steps S12 and S14 are sequentially performed.

On the other hand, when it is determined in step S51 that the behavior state of the vehicle does not belong to the area II, the flow sequentially proceeds to steps S56, 57, 58, and 59 to determine whether the EC
A drive signal is output from U8 to the actuator 2 of each wheel 11, and the driving of the actuator 2 causes the damping force of the shock absorber 10 to increase or decrease as appropriate. That is, in step S56, the right front wheel 11 which is the front wheel on the outside of the turn.
The damping force of the FR shock absorber 10FR is reduced. In step S57, the damping force of the shock absorber 10FL of the front left wheel 11FL, which is the front wheel inside the turn, is increased. In step S58, the damping force of the shock absorber 10RR of the right rear wheel 11RR, which is the rear wheel on the outside of the turn, is increased. In step S59, the shock absorber 10RL of the rear left wheel 11RL, which is the inner rear wheel, is turned.
Is reduced. Each shock absorber 10
The damping force is increased or decreased based on, for example, a map of the damping force characteristic with respect to the expansion and contraction speed of the piston rod 16 stored in the ROM of the ECU 8 or the like. It is desirable to adjust.

In steps S56 to S59, the damping force of the shock absorber 10 at the front wheel inside the turn and the rear wheel outside the turn is increased, and the damping force of the shock absorber 10 at the front wheel outside the turn and the rear wheel inside the turn is reduced. Thereby, the US-OS characteristic of the vehicle is corrected to be understeer. In the control processes of steps S56 to S59, the behavior state of the vehicle is unstable, so that the vehicle is in an understeer state, thereby improving the stability of the vehicle during turning.

Then, in steps S56 to S59, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10.

When it is determined in step S50 that the yaw rate γ of the vehicle is negative (the vehicle is rotating clockwise), the process proceeds to step S60. In step S60, it is determined whether or not the behavior state of the vehicle belongs to region II in the map of FIG.

If it is determined in step S60 that the behavior state of the vehicle belongs to region II, the process proceeds to step S60.
The sequence sequentially proceeds to 61, 62, 63, and 64, and a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11,
By driving the actuator 2, the damping force of the shock absorber 10 is appropriately increased or decreased. That is, step S
At 61, the damping force of the shock absorber 10FR of the front right wheel 11FR, which is the front wheel inside the turn, is reduced. In step S62, the front left wheel 11F which is the front wheel on the outside of the turn
The damping force of the L shock absorber 10FL is increased. In step S63, the damping force of the shock absorber 10RR of the right rear wheel 11RR, which is the inner rear wheel, is increased. In step S64, the damping force of the shock absorber 10RL of the rear left wheel 11RL, which is the rear wheel on the outside of the turn, is reduced. The damping force of each shock absorber 10 is increased or decreased based on, for example, a map of the damping force characteristic with respect to the expansion and contraction speed of the piston rod 16 stored in the ROM of the ECU 8 or the like. It is desirable to fine-tune the damping force.

In steps S61 to S64, the damping force of the shock absorber 10 at the front wheel on the outside of the turn and the rear wheel on the inside of the turn is increased, and the damping force of the shock absorber 10 on the front wheel at the inside of the turn and the rear wheel on the outside of the turn are reduced. Thereby, the US-OS characteristic of the vehicle is corrected to be oversteer, and the maneuverability of the vehicle during turning of the vehicle is improved. Further, in the control process of steps S61 to S64, since the behavior state of the vehicle is stable, there is no concern that the stability of the vehicle is impaired even if the controllability of the vehicle is improved.

Then, in steps S61 to S64, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10.

If it is determined in step S60 that the behavior state of the vehicle does not belong to the region II, the flow sequentially proceeds to steps S65, 66, 67, and 68 to determine whether the EC
A drive signal is output from U8 to the actuator 2 of each wheel 11, and the driving of the actuator 2 causes the damping force of the shock absorber 10 to increase or decrease as appropriate. That is, in step S65, the front right wheel 11 which is the front wheel inside the turn
The damping force of the FR shock absorber 10FR is increased. In step S66, the damping force of the shock absorber 10FL of the front left wheel 11FL, which is the front wheel on the outside of the turn, is reduced. In step S67, the damping force of the shock absorber 10RR of the right rear wheel 11RR, which is the inner rear wheel, is reduced. In step S68, the shock absorber 10RL of the left rear wheel 11RL, which is the outer rear wheel, is turned.
Is increased. Each shock absorber 10
The damping force is increased or decreased based on, for example, a map of the damping force characteristic with respect to the expansion and contraction speed of the piston rod 16 stored in the ROM of the ECU 8 or the like. It is desirable to adjust.

In steps S65 to S68, the damping force of the shock absorber 10 at the front wheel inside the turning and the rear wheel outside the turning is increased, and the damping force of the shock absorber 10 at the front wheel outside the turning and the rear wheel inside the turning is decreased. Thereby, the US-OS characteristic of the vehicle is corrected to be understeer. In the control process of steps S65 to S68, the behavior state of the vehicle is unstable, and thus the vehicle is improved in stability during turning of the vehicle by being in an understeer state.

Then, in steps S65 to S68, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10.

Steps S10 to S14 and step S5
The control steps from 0 to 68 are performed only in the low-speed range where the expansion and contraction speed of the shock absorber 10 is low (for example, the speed range where the expansion and contraction speed is 0.1 m / s or less). For this reason, when the shock absorber 10 expands and contracts in a high-speed range, the damping force characteristics of the shock absorber 10 can be kept substantially constant, and the grounding of the wheels 11 can be ensured.

The above-described damping force control shown in FIG. 8 is performed when the vehicle is turning, and when the vehicle is traveling straight, the damping force control of the shock absorber 10 as shown in FIG. 8 is not performed. For example, damping force control based on the skyhook theory is performed.

As described above, according to the damping force control device according to the present embodiment, when the vehicle turns, the damping force F of the shock absorber 10 of the inner wheel and the outer wheel varies depending on the behavior of the vehicle at the time of turning. , And the turning characteristics of the vehicle are appropriately changed. Therefore, the maneuverability of the vehicle at the time of turning can be improved, and the stability of the vehicle can be ensured. Also, only by controlling the damping force of the shock absorber 10 variably only in the low-speed range of the expansion and contraction speed of the shock absorber 10, the grounding of the wheels 11 when the shock absorber 10 operates in the high-speed range is ensured, and the maneuverability of the vehicle is improved. Is good.

(Fourth Embodiment) Next, a damping force control device according to a fourth embodiment will be described.

The damping force control device according to the present embodiment, like the damping force control device 1 according to the first embodiment, has an actuator 2, a vehicle speed sensor 3, a steering angle sensor 4, a yaw rate sensor 5, a vehicle height sensor 6, Vertical acceleration sensor 7, ECU 8
And the shock absorber 10 is a target of damping force control.

The operation of the damping force control device will be described with reference to FIG. FIG. 9 is a flowchart showing the operation of the damping force control device when the vehicle turns. When the vehicle turns due to a driver's steering operation or the like during running of the vehicle, the damping force of each shock absorber 10 is individually controlled by the damping force control device for each wheel 11 according to the behavior state of the vehicle as shown in FIG. Controlled. Whether the vehicle is in a turning state is determined based on an output signal of the steering angle sensor 4 and the like.

Steps S10 to S14 in FIG. 9 are the same as those in the first embodiment, and a description thereof will be omitted. In FIG. 9, the process proceeds from step S14 to step S70, and it is determined whether or not the behavior state of the vehicle belongs to the area II in the map of FIG. When it is determined in step S70 that the behavior state of the vehicle belongs to the region II, it is determined that the behavior state of the vehicle at the time of turning is stable.
No drive signal is output from U8 to the actuator 2 of each wheel 11, and the damping force characteristic of the shock absorber 10 does not change. In this case, the characteristics indicated by the solid line in FIG. 4 (A1, B1, etc.) according to the expansion and contraction speed of the piston rod 16
Thus, the damping force of the shock absorber 10 is determined.
Then, in step S70, when it is determined that the behavior state of the vehicle belongs to region II, step S10
The ECU 8 again reads the vehicle speed V based on the output signal of the vehicle speed sensor 3, reads the steering angle θ based on the output signal of the steering angle sensor 4, and reads the yaw rate γ based on the output signal of the yaw rate sensor 5. , Steps S12 and S14 are sequentially performed.

On the other hand, when it is determined in step S70 that the behavior state of the vehicle does not belong to region II, the process proceeds to step S71 to determine whether the behavior state of the vehicle belongs to region I.

If it is determined in step S71 that the behavior state of the vehicle belongs to the region I, the flow shifts to step S72 to determine whether the product of the vehicle body slip angle β and the vehicle body slip angular velocity β ′ is positive. It is determined whether or not.

If it is determined in step S72 that the product of the vehicle body slip angle β and the vehicle body slip angular velocity β 'is not positive, the process returns to step S10. That is, in this case, even if the vehicle body slip angle β occurs, the vehicle body slip state velocity shifts to a direction in which the vehicle behavior state at the time of turning becomes stable because the vehicle body slip angular velocity β ′ occurs in the direction in which the vehicle body slip angle β decreases. No drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the damping force characteristics of the shock absorber 10 do not change.

On the other hand, when it is determined in step S72 that the product of the vehicle body slip angle β and the vehicle body slip angular velocity β 'is positive, steps S73, 74, and 7 are executed.
The process sequentially proceeds to steps 5 and 76, and a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the damping force of the shock absorber 10 is appropriately increased or decreased by driving the actuator 2. That is, in this case, the vehicle is turning left with a lateral acceleration (lateral G), and the damping force of the shock absorber 10FR of the right front wheel 11FR, which is the front wheel on the outside of the turn, is increased in step S73. In step S74, the front left wheel 11, which is the front wheel inside the turn
The damping force of the shock absorber 10FL of the FL is increased. In step S75, the damping force of the shock absorber 10RR of the right rear wheel 11RR that is the rear wheel on the outside of the turn is increased. In step S76, the damping force of the shock absorber 10RL of the rear left wheel 11RL, which is the rear wheel inside the turn, is reduced. The damping force of each shock absorber 10 is increased or decreased based on, for example, a map of the damping force characteristic with respect to the expansion and contraction speed of the piston rod 16 stored in the ROM of the ECU 8 or the like. It is desirable to fine-tune the damping force.

In steps S73 to S76, the damping force of the shock absorber 10 on the rear wheel inside the turning is reduced, and the shock absorbers 10 on the other wheels are reduced.
, The lifting of the rear wheel on the inside of the turn is delayed, and the stability of the vehicle at the time of turning of the vehicle is secured.

Then, in steps S73 to S76, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
Returning to step S10, the ECU 8 again reads the vehicle speed V based on the output signal of the vehicle speed sensor 3, reads the steering angle θ based on the output signal of the steering angle sensor 4, and reads the yaw rate γ based on the output signal of the yaw rate sensor 5. Steps S12 and S14 are sequentially performed.

In step S71, when it is determined that the behavior state of the vehicle does not belong to the region I, it means that the behavior state of the vehicle belongs to the region III.
In this case, the flow shifts to step S77 to determine whether or not the value of the product of the vehicle body slip angle β and the vehicle body slip angular velocity β ′ is positive.

If it is determined in step S77 that the product of the vehicle body slip angle β and the vehicle body slip angular velocity β 'is not positive, the process returns to step S10. That is, in this case, even if the vehicle body slip angle β occurs, the vehicle body slip state velocity shifts to a direction in which the vehicle behavior state at the time of turning becomes stable because the vehicle body slip angular velocity β ′ occurs in the direction in which the vehicle body slip angle β decreases. No drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the damping force characteristics of the shock absorber 10 do not change.

On the other hand, when it is determined in step S77 that the product of the vehicle body slip angle β and the vehicle body slip angular velocity β 'is positive, steps S78, 79, and 8 are executed.
The process sequentially proceeds to 0 and 81, and a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the damping force of the shock absorber 10 is appropriately increased or decreased by driving the actuator 2. That is, in this case, the vehicle is turning right with lateral acceleration (lateral G), and the damping force of the shock absorber 10FR of the front right wheel 11FR, which is the front wheel inside the turn, is increased in step S78. In step S79, the front left wheel 11, which is the front wheel on the outside of the turn
The damping force of the shock absorber 10FL of the FL is increased. In step S80, the damping force of the shock absorber 10RR of the right rear wheel 11RR, which is the inner rear wheel, is reduced. In step S81, the damping force of the shock absorber 10RL of the rear left wheel 11RL, which is the rear wheel on the outside of turning, is increased. The damping force of each shock absorber 10 is increased or decreased based on, for example, a map of the damping force characteristic with respect to the expansion and contraction speed of the piston rod 16 stored in the ROM of the ECU 8 or the like. It is desirable to fine-tune the damping force.

In steps S78 to S81, the damping force of the shock absorber 10 on the rear wheel inside the turning is reduced, and the shock absorbers 10 on the other wheels are reduced.
, The lifting of the rear wheel on the inside of the turn is delayed, and the stability of the vehicle at the time of turning of the vehicle is secured.

Then, in steps S78 to S81, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10. In the control processes of steps S10 to S14 and steps S70 to S81, the expansion and contraction speed of the shock absorber 10 is in a low range (for example, the expansion and contraction speed is set to 0. 1).
Speed range of 1 m / s or less). For this reason, when the shock absorber 10 expands and contracts in a high-speed range, the damping force characteristics of the shock absorber 10 can be kept substantially constant, and the grounding of the wheels 11 can be ensured.

The above-described damping force control shown in FIG. 9 is performed when the vehicle is turning, and when the vehicle is traveling straight, the damping force control of the shock absorber 10 as shown in FIG. 9 is not performed. For example, damping force control based on the skyhook theory is performed.

As described above, according to the damping force control device according to the present embodiment, when the vehicle turns, the damping force F of the shock absorbers 10 of the inner wheel and the outer wheel depends on the behavior of the vehicle at the time of turning. , And the turning characteristics of the vehicle are appropriately changed. For this reason, the lifting of the inner rear wheel due to the lateral force during turning can be delayed, and the stability of the vehicle can be secured. This is particularly effective when the vehicle is a front engine front drive (FF) vehicle. Also, only in the low speed range of the expansion and contraction speed of the shock absorber 10, the shock absorber 1
By variably controlling the damping force of 0, the grounding of the wheels 11 when the shock absorber 10 operates in a high-speed range is ensured, and the maneuverability of the vehicle is improved.

In the damping force control device according to the present embodiment, the behavior of the vehicle may be determined based on the yaw rate γ, and the damping force of the shock absorber 10 of each wheel 11 may be controlled.

FIG. 10 shows an example of the operation of such a damping force control device.

Steps S10 to S71 in FIG.
Since the content is the same as that of the fourth embodiment, the description is omitted. When it is determined in step S71 in FIG. 10 that the behavior state of the vehicle belongs to the region I, the process proceeds to step S72a, and it is determined whether the yaw rate γ of the vehicle is positive.

In step S72a, the yaw rate γ
Is not positive, the process returns to step S10. That is, in this case, no drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the damping force characteristic of the shock absorber 10 does not change.

On the other hand, if it is determined in step S72a that the yaw rate γ is positive, the process proceeds to step S7.
3, 74, 75, and 76, a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the shock absorber 1 is driven by the driving of the actuator 2.
The damping force of 0 is appropriately increased or decreased. That is, in this case, the vehicle is turning left with a lateral acceleration (lateral G), and the damping force of the shock absorber 10FR of the right front wheel 11FR, which is the front wheel on the outside of the turn, is increased in step S73. In step S74, the damping force of the shock absorber 10FL of the front left wheel 11FL, which is the front wheel inside the turn, is increased. In step S75, the shock absorber 10RR of the right rear wheel 11RR, which is the rear wheel on the outside of the turn.
Is increased. In step S76, the shock absorber 1 of the rear left wheel 11RL, which is the inner rear wheel, is turned.
The 0 RL damping force is reduced. The damping force of each shock absorber 10 is increased or decreased based on, for example, a map of damping force characteristics with respect to the expansion and contraction speed of the piston rod 16 stored in a ROM or the like of the ECU 8.
It is desirable that the damping force be finely adjusted by raising and lowering step by step.

In steps S73 to S76, the damping force of the shock absorber 10 on the rear wheel inside the turning is reduced, and the shock absorber 10 on the other wheels is reduced.
, The lifting of the rear wheel on the inside of the turn is delayed, and the stability of the vehicle at the time of turning of the vehicle is secured.

Then, in steps S73 to S76, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10.

In step S71, when it is determined that the behavior state of the vehicle does not belong to the region I, it is when the behavior state of the vehicle belongs to the region III.
In this case, the process proceeds to step S77a, and it is determined whether or not the yaw rate γ of the vehicle is negative.

In step S77a, the yaw rate γ
If it is determined that is not negative, the process returns to step S10. That is, in this case, no drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the damping force characteristic of the shock absorber 10 does not change.

On the other hand, if it is determined in step S77a that the yaw rate γ is negative, the process proceeds to step S7.
8, 79, 80, and 81 sequentially, a drive signal is output from the ECU 8 to the actuator 2 of each wheel 11, and the drive of the actuator 2 causes the shock absorber 1
The damping force of 0 is appropriately increased or decreased. That is, in this case, the vehicle is turning right with lateral acceleration (lateral G), and the damping force of the shock absorber 10FR of the front right wheel 11FR, which is the front wheel inside the turn, is increased in step S78. In step S79, the damping force of the shock absorber 10FL of the front left wheel 11FL, which is the front wheel on the outside of the turn, is increased. In step S80, the shock absorber 10RR of the right rear wheel 11RR, which is the inner rear wheel of the turn.
Is reduced. In step S81, the shock absorber 1 of the rear left wheel 11RL, which is the rear wheel on the outside of the turn.
The 0 RL damping force is increased. The damping force of each shock absorber 10 is increased or decreased based on, for example, a map of damping force characteristics with respect to the expansion and contraction speed of the piston rod 16 stored in a ROM or the like of the ECU 8.
It is desirable that the damping force be finely adjusted by raising and lowering step by step.

In steps S78 to S81, the damping force of the shock absorber 10 on the rear wheel inside the turning is reduced, and the shock absorbers 10 on the other wheels are reduced.
, The lifting of the rear wheel on the inside of the turn is delayed, and the stability of the vehicle at the time of turning of the vehicle is secured.

Then, in steps S78 to S81, the wheels 11
When the damping force of the shock absorber 10 has been increased or decreased,
It returns to step S10.

Steps S10 to S14 and step S7
The control steps from 0 to 81 are performed only in a low-speed range where the expansion and contraction speed of the shock absorber 10 is low (for example, a speed region where the expansion and contraction speed is 0.1 m / s or less). For this reason, when the shock absorber 10 expands and contracts in a high-speed range, the damping force characteristics of the shock absorber 10 can be kept substantially constant, and the grounding of the wheels 11 can be ensured.

The damping force control shown in FIG. 10 is performed when the vehicle is turning. When the vehicle is traveling straight, the damping force control of the shock absorber 10 as shown in FIG. 10 is not performed. For example, damping force control based on the skyhook theory is performed.

As described above, in the damping force control device, the behavior state of the vehicle is determined based on the yaw rate γ, and each wheel 1
Even when the damping force of the first shock absorber 10 is controlled, the same operation and effect can be obtained as when judging the behavior state of the vehicle based on the vehicle body slip angle β and the vehicle body slip angular velocity β ′.

[0147]

As described above, according to the present invention, the following effects can be obtained.

By controlling the damping force of the shock absorbers of the inner wheel and the outer wheel individually in accordance with the change in the load applied to the inner wheel and the outer wheel according to the behavior state of the vehicle at the time of turning, the stability of the vehicle at the time of turning is ensured. Thus, the controllability and ride comfort of the vehicle can be improved. In addition, by manipulating the damping force of the shock absorber variably only in the low speed range of the expansion and contraction speed of the shock absorber, the controllability of the vehicle in the high speed range of the shock absorber can be ensured.

Further, by controlling the damping force of the shock absorber so as to change the turning characteristics of the vehicle based on the turning behavior, the steerability or stability of the vehicle can be improved.

By controlling the damping force of the shock absorber on the inner rear wheel to decrease while turning the vehicle and increasing the damping force of the shock absorber on the other wheels, when a large lateral acceleration is applied when turning the vehicle, The lift of the rear wheel inside the turning is delayed, and the stability of the vehicle can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a damping force control device.

FIG. 2 is an explanatory diagram of a shock absorber.

FIG. 3 is an enlarged explanatory view of a piston portion of the shock absorber.

FIG. 4 is a diagram showing a damping force characteristic of a shock absorber.

FIG. 5 shows a vehicle body slip angle β and a vehicle body slip angular velocity β ′
FIG. 4 is a diagram showing a behavior area of a vehicle based on the vehicle.

FIG. 6 is a flowchart illustrating an operation of the damping force control device according to the first embodiment.

FIG. 7 is a flowchart illustrating an operation of the damping force control device according to the second embodiment.

FIG. 8 is a flowchart illustrating an operation of the damping force control device according to the third embodiment.

FIG. 9 is a flowchart illustrating an operation of the damping force control device according to the fourth embodiment.

FIG. 10 is a flowchart illustrating an operation of the damping force control device according to the fourth embodiment.

[Explanation of symbols]

1: damping force control device, 2: actuator, 8: EC
U, 10: shock absorber, 11: wheels.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Suzuki 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Shigeki Ikeda 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Yoshiyuki Hashimoto 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (5)

[Claims] 1. A damping force varying means capable of varying a damping force of the shock absorber in a low speed range of an expansion and contraction speed of the shock absorber; a behavior state detecting means for detecting a behavior state of a vehicle; A damping force control device for a vehicle, comprising: damping force control means for individually controlling damping forces of a shock absorber on an inner wheel and an outer wheel according to a behavior state. 2. The damping force for a vehicle according to claim 1, wherein the damping force control means controls the damping force of the shock absorber of the outer wheel to be low and the damping force of the shock absorber of the inner wheel to be high. Control device. 3. The damping force for a vehicle according to claim 1, wherein the damping force control means controls the damping force of the shock absorber of the outer wheel to be high and the damping force of the shock absorber of the inner wheel to be low. Control device. 4. The vehicle according to claim 1, wherein the damping force control means controls a damping force of the shock absorber so as to change a vehicle turning characteristic based on a turning behavior of the vehicle. Damping force control device. 5. The damping force control means decreases a damping force of a shock absorber on a rear wheel on the inner wheel side and increases a damping force of a shock absorber on another wheel when the change of the turning behavior is large. 2. The vehicle damping force control device according to claim 1, wherein the control is performed in such a manner.