JPH0914326A - Shock absorber for car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively display the function of a hard mode and a soft mode by enlarging damping force difference between the hard mode and soft mode even in case of the stroke speed of a piston being medium-high speed and allow vafious control modes to be set utilizing the damping force difference. SOLUTION: A retainer 103 constituting a piston valve 100 is composed of a first retaining member 104 protruded vertically to the fixed height from the inner end so as to support an inner end 101a of a plate spring 101 in such a way that the inner end 101a is a fixed end and that an outer end 101b is a free end, and a second retaining member 105 protruded vertically slightly less than the first retaining member 104 so as to become a secondary fulcrum when the plate spring 101 is bendingly deformed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber used in a vehicle, and in particular, it is possible to further increase the damping force difference between the soft mode and the hard mode. The present invention relates to a piston valve of a shock absorber for a vehicle, which can not only further improve the characteristics of (1) but also add another control mode between both modes.

[0002]

2. Description of the Related Art A shock absorber used for an automobile is a device for improving a feeling of getting on a vehicle by suppressing free vibration of a leaf spring which absorbs an impact received from a road surface while the automobile is running. In the shock absorber, a piston moving up and down together with an axle receives an oil flow resistance in a cylinder filled with oil to generate a damping force, thereby suppressing vibration.

Such a shock absorber increases the damping force by decreasing the damping force when the stroke speed of the piston is slow, and increases the damping feeling when the stroke speed of the piston is medium or high. However, it is required to have characteristics that improve steering stability.

Recently, a damping force control system for a shock absorber by an electronic control unit has been devised in order to selectively match the riding feeling and the steering stability of the vehicle having contradictory characteristics. This is done by installing an electrically operated valve that can finely control the flow rate of oil passing through the internal passage of the shock absorber, and changing it manually or automatically according to the road surface and running condition, It is intended to obtain a damping force.

FIG. 4 shows a conventional shock absorber provided with an electric drive valve 50 controlled by such an electronic control unit (not shown). As shown in FIG. 4, the conventional shock absorber has a cylinder 10, a piston rod 20 that is housed in the cylinder 10 and moves up and down, and a piston 30.

An upper chamber 11 and a lower chamber 12, which are respectively filled with oil, are arranged at the upper and lower parts of a piston 30 which moves up and down, respectively. A housing is installed at a constant space from the cylinder 10, whereby an oil reservoir 13 is formed between the cylinder 10 and the housing. Piston 3
The volume of the upper chamber 11 and the lower chamber 12 relatively changes in accordance with the vertical movement of 0.

In order to flow oil between the upper and lower chambers 11 and 12, piston valves 31 are installed on the upper end surface and the lower end surface of the piston 30, respectively. Inside the piston rod 20, the electric drive valve described above is installed. 50 are installed. Further, a base valve 60 is installed at the lower end of the cylinder 10 for the oil flow between the lower chamber 12 and the oil reservoir 13. As a result, the oil flows between the upper chamber 11 and the lower chamber 12, and further between the oil reservoir 13.

A pair of oil passages 14 and 15 are formed in the piston 30 in the longitudinal direction for the oil flow through the piston valve 31, and for the oil flow through the electrically driven valve 50, the piston rod 20 has A "T" shaped oil flow path 16 is formed extending upward from the lower end thereof.

The electrically operated valve 50 opens or closes the oil passage 16 and regulates the flow rate of oil through the oil passage 16 under the control of an electronic control unit (not shown). That is, the electrically driven valve 50 is opened / closed according to the road surface and the running state, and the damping force of the shock absorber is adjusted by giving priority to one of the ride feeling and the steering stability.

For example, in order to improve the riding feeling (soft mode), the electric drive valve 50 is opened and the shock absorber is used so that the oil flow rate between the chambers 11 and 12 is increased. When it is desired to reduce the damping force and, on the contrary, to improve the steering stability of the vehicle (hard mode), the electric drive valve 50 is closed to increase the damping force. Of course, electric drive valve 5
It is also possible to provide an intermediate damping force by adjusting the opening degree of 0.

FIG. 5 is an enlarged view of a part of FIG. 4 in order to show the piston valve 31 in more detail.
As shown in FIG. 5, the conventional piston valve 31
Is an oil passage 1 formed in the piston 30 by hydraulic pressure.
A leaf spring 32 for opening and closing 4 or 15; and a valve washer 33 for supporting the outer end of the leaf spring 32 which is a free end when the leaf spring 32 is pressed by hydraulic pressure and for restricting further displacement. A retainer 34, which is disposed between the leaf spring 32 and the valve washer 33, acts as a fulcrum for supporting the inner end of the leaf spring 32, and provides a space in which the outer end of the leaf spring 32 moves up and down, and further includes a closure. In the state, the leaf spring 3
2 and the sheet 35 with which the outer end of the sheet 2 abuts.

The operation of the conventional shock absorber constructed as described above will be described below. First,
When the shock absorber is operated in the soft mode in which the electric drive valve 50 is opened, when the piston 30 is moved upward at a low speed, the pressure difference between the upper chamber 11 and the lower chamber 12 causes the leaf spring 32 to move. Of the piston valve 31 cannot be overcome and the piston valve 31 cannot be opened. Therefore, when the stroke speed of the piston 30 is in a low speed range, for example, 0.3 m / s or less, the oil in the upper chamber 11 remains in the oil passage as indicated by an arrow U1 while the piston valve 31 is closed. Flow downwards along 16 and into the lower chamber 12 through the electrically actuated valve 50.

At this time, a damping force primarily acts on the piston 30 due to the flow resistance of the oil passing through the electrically driven valve 50. When the stroke speed of the piston 30 increases and becomes equal to or higher than a predetermined speed, the difference between the hydraulic pressure in the upper chamber 11 and the hydraulic pressure in the lower chamber 12 overcomes the elastic force of the leaf spring 32, and The oil flows downward along the oil passage 14 and flows into the lower chamber 12 as shown by an arrow U2.
At this time, the damping force is further increased by the hydraulic pressure that pushes the leaf spring 32 having a constant elastic coefficient.

On the other hand, when the piston 30 moves downward, the oil flows in the low speed section as indicated by the arrow V1 and in the middle / high speed section as well as the piston valve 31 as indicated by the arrow V2. Like At this time, the damping force is increased in the same manner as when the piston 30 moves upward.

On the other hand, although not specifically shown, the oil flows between the lower chamber 12 and the reservoir 13 through the base valve 60 installed at the lower end of the cylinder 10 as the piston 30 moves up and down. Be distributed.

Contrary to the above, when the shock absorber is operated in the hard mode in which the electric drive valve 50 is closed, the oil flow to the arrows U1 and V1 is cut off. Further, until the pressure difference between the chambers 11 and 12 exceeds the elastic force of the piston valve 31, the piston valve 31 is substantially closed and oil cannot flow from there.

When the stroke speed of the piston 30 increases above a predetermined speed, that is, when the pressure difference between the chambers 11 and 12 exceeds the elastic force of the piston valve 31, the piston valve 31 is opened. , The oil is distributed. After that, as the displacement of the plate spring 32 of the piston valve 31 increases, the elastic force increases, and accordingly, the damping force of the shock absorber also increases linearly.

As described above, in the hard mode, until the stroke speed of the piston 30 reaches a certain speed or higher,
Virtually no oil flow is made. FIG. 6 schematically shows the change of the damping force with respect to the stroke speed of the piston 30 in the conventional shock absorber that operates as described above. The solid line shows the change of the damping force in the hard mode, and the dotted line shows the change of the damping force in the soft mode. Shows.

To explain this graph roughly, firstly,
As indicated by the dotted line, in the soft mode, due to the pressure difference between the chambers 11 and 12, the piston valve 3
Until 1 is opened (point a in the graph), the damping force increases quadratically due to the flow resistance of the oil passing through the electrically driven valve 50.

After the point a at which the piston valve 31 is opened, the damping force linearly increases due to the increase of the elastic force accompanying the deformation of the leaf spring 32 of the piston valve 31.

On the other hand, as shown by the solid line, in the hard mode, the hydraulic pressure difference between the two chambers 11 and 12 is kept until the piston valve 31 starts to open (point b).
As a result of the structural orifice action of the piston valve 31, the piston valve 31 increases in a quadratic function, offset to the vertical axis, as compared with the soft mode.

When point b is exceeded, the damping force increases linearly with the same slope as in the soft mode.

[0023]

However, in the conventional shock absorber, the damping force difference between the soft mode and the hard mode is shown in FIG. 6 until the stroke speed of the piston 30 reaches a point a which is a low speed section. As described above, a slightly large value (maximum W1) is maintained, but after the point a, it has a fairly small constant value (W2).

Therefore, in the low speed section, a relatively large damping force difference can be utilized to take advantage of the characteristics of the hard mode for steering stability and the soft mode for riding comfort. In the medium / high speed section where the value is small, it is not possible to provide a significant difference in damping force between the hard mode and the soft mode.

This is a great limitation for effectively utilizing the vibration absorbing action of the shock absorber so as to match the characteristics of each mode. In particular, when it is desired to select one of riding comfort and driving stability, the damping force difference between the soft mode and the hard mode must be increased mainly in the middle / high speed section.

However, since the conventional shock absorber cannot satisfy such requirements, it is not possible to set various changes in the damping force of the shock absorber according to the stroke speed of the piston.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to provide the functions of the hard mode and the soft mode even when the stroke speed of the piston becomes medium or high. It is an object of the present invention to provide a vehicle shock absorber that can set various control modes by utilizing changes in the damping force as well as effectively exhibiting the effect.

[0028]

The present invention for achieving the above object is characterized by a piston valve which is housed in a cylinder filled with oil and installed in a vertically moving piston.

That is, when the piston valve is actuated, the leaf spring is bent by hydraulic pressure to open the flow passage, the seat against which the leaf spring abuts so as to block the flow passage when the piston valve is not actuated, Sandwich the leaf spring,
The retainer is arranged to face the seat.

The retainer is vertically protruded from the inner end to a certain height, and supports the inner end so that the inner end of the leaf spring serves as a fixed end and the outer end thereof serves as a free end. A retaining portion, and a second retaining portion that is vertically protruded at a position apart from the first retaining portion by a certain distance and is slightly lower than a protrusion height of the first retaining portion, and serves as a secondary fulcrum when the leaf spring is bent and deformed. Composed of.

[0031]

If the hydraulic pressure difference between the upper chamber and the lower chamber formed according to the stroke speed of the piston overcomes the primary elastic force of the leaf spring due to the action of the first retaining portion, the first retaining portion will be removed. As a fulcrum, the free end of the leaf spring is bent and the piston valve is gradually opened.

Accordingly, a damping force that linearly increases in proportion to the displacement of the leaf spring acts on the piston. When the deformation of the plate spring further increases as the stroke speed of the piston increases, the substantially middle portion of the plate spring contacts the second retaining portion. From this point, the length between the free end of the leaf spring and the fulcrum becomes relatively short, and the elastic coefficient becomes even larger than when the leaf spring acts with the first retaining portion as the fulcrum. The rate of increase of the damping force with the stroke speed of the piston is further increased.

Further, in the hard mode, the damping force has already reached the elastic force region due to the secondary fulcrum and a larger damping force is acting at a speed such that the stroke speed of the piston leaves the low speed section. In soft mode, when the stroke speed of the piston is high enough to move out of the low speed section, the damping force reaches the elastic force corresponding to the primary fulcrum, and in that section, a relatively small damping force acts on the piston. doing. Then, after passing through the high-speed section, the damping force reaches the elastic force corresponding to the secondary fulcrum.

Therefore, in the hard mode, the shock absorber receives a damping force that linearly increases with a large inclination due to the secondary fulcrum in a part of the medium speed section and the high speed section. In the soft mode, the shock absorber receives the damping force that linearly increases with a smaller inclination due to the primary fulcrum. This makes it possible to greatly adjust the damping force deviation between the hard mode and the soft mode in the medium / high speed section.

As a result, the characteristics of each mode are more effectively exhibited in the medium and high speed sections. Further, various control modes can be set by using another damping force between both modes, whereby the damping force by the shock absorber can be further widely used.

[0036]

DETAILED DESCRIPTION OF THE INVENTION Referring to the accompanying drawings,
A preferred embodiment of the present invention will be described in detail.

For the same components as the conventional one,
The description is given with the same reference numerals. FIG. 1 shows a shock absorber according to an embodiment of the present invention. As shown in the drawings, the shock absorber of this embodiment is housed in an oil-filled cylinder 10 and moves up and down, a piston rod 20 and a piston 30, and an upper chamber 11 and a lower chamber 12 formed by the piston 30. , Installed on the upper and lower ends of the piston 30,
The piston valves 100 are opened and closed by a hydraulic pressure difference between the chambers 11 and 12, and are installed inside a piston rod 20 penetrating the piston 30, and are automatically opened and closed so that a damping force can be changed. And an electrically operated valve 50.

A pair of piston valves 100, which is a characteristic part of the present invention, has a piston 30 similar to the conventional example.
Are installed on the upper end surface and the lower end surface, respectively. As shown in detail in FIG. 2, the piston valve 100 includes a plate spring 101 formed by stacking a plurality of disc-shaped elastic plates.
A seat 102 against which the leaf spring 101 abuts when not in operation, and further, the leaf spring 10 when in operation.
1 and a retainer 103 having a function of a fulcrum while providing a space to be opened.

The retainer 103 supporting one end of the leaf spring 101 is provided with a first retaining portion 104 and a second retaining portion 104 so that the leaf spring 101 can be bent by hydraulic pressure.
The retaining portion 105 is provided to form two fulcrums. The first retaining portion 104 is located at an inner end of the retainer 103, and is formed to vertically project to a certain height. The second retaining portion 105 is arranged at an intermediate portion of the retainer 103, and is formed so as to project slightly lower than the first retaining portion 104. Therefore, the first retaining portion 104 is the inner end 101 of the leaf spring 101.
When the leaf spring 101 is displaced to a predetermined position, the second retaining portion 105 acts as a secondary fulcrum when the leaf spring 101 is always in contact with a and acts as a primary fulcrum of the leaf spring 101 at the initial stage of operation. To do.

As shown in FIG. 2B, since the length by which the leaf spring 101 can be displaced by the first retaining portion 104 is long, the elastic modulus of the spring is relatively low, and as shown in FIG. Depending on the retaining portion 105, the displaceable length of the leaf spring 101 becomes shorter and the spring elastic modulus becomes relatively higher.

Therefore, when the stroke speed of the piston 30 is in the low speed section, the damping force of the piston valve 100 increases to a lower level due to the action of the first retaining portion 104, but as the stroke speed of the piston 30 increases, Two
If the retaining portion 105 acts, the piston valve 1
The damping force due to 00 increases further. That is, if the piston 30 moves at a medium or high speed, the damping force rapidly increases.

Since the configuration other than the above is the same as the conventional one, further structural description will be omitted. The operation of this embodiment will be described below.

First, if the shock absorber is operated in a soft mode for a feeling of riding, the electrically driven valve 50 is kept open. If the piston 30 moves upward in this state, as shown in FIG. 2A, the hydraulic pressure difference between the upper chamber 11 and the lower chamber 12 causes the elastic force of the leaf spring 101 supported by the first retaining portion 104. The piston 30 receives only the damping force associated with the oil flow passing only through the electrically driven valve 50 until the pressure exceeds the above value.

If the hydraulic pressure difference between the chambers 11 and 12 increases as the stroke speed of the piston 30 increases,
As shown in FIG. 2B, the leaf spring 101 is supported and deformed by the first retaining portion 104. As a result, the oil also flows through the piston valve 100, and the damping force due to the displacement of the leaf spring 101 increases linearly. When the stroke speed of the piston 30 further increases, as shown in FIG. 2C, the leaf spring 101 causes the second retaining portion 10 to move.
5 is supported and displaced, and the damping force is accordingly
Further, it increases linearly with a large slope.

In the case of the soft mode described above, the change of the damping force with the stroke speed of the piston 30 is shown by the line II in FIG.
Indicated by On the other hand, if the shock absorber is operated in the hard mode for steering stability, the electric drive valve 50 is closed and the damping force is applied only by the piston valve 100. That is, as shown by the line I in FIG. 3, in the hard mode, the oil movement through the electrically driven valve 50 is blocked, so that both chambers 11 and 12 are blocked.
When the piston 30 is in a relatively low speed section as compared with the soft mode, the pressure difference of becomes large in a short time,
The damping force exceeds the elastic force of the leaf spring 101 by the first retaining portion 104.

Therefore, thereafter, the leaf spring 101 is used.
The damping force increases linearly with displacement. Piston 30
The stroke speed of the two chambers 11 and 12 is further increased.
If the pressure difference between them exceeds the elastic force of the leaf spring 101 by the second retaining portion 105, the leaf spring 101
Further, the damping force due to increases linearly with a large slope.

The features of the present invention will be described below with reference to FIG. Comparing the changes in the damping force between the hard mode indicated by the line I and the soft mode indicated by the line II in FIG. 3, when the stroke speed of the piston 30 exceeds the medium speed in the soft mode, The damping force of the piston 30 is increased with a relatively gentle inclination by the elastic force of the leaf spring 101 supported by the first retaining member 104, but in the hard mode,
At this time, the elastic force of the second retaining portion 105 has already increased with a relatively steep inclination. Therefore, the difference in the damping force between the hard mode and the soft mode is further increased at a medium speed or higher.

This is the line indicated by the dotted line in FIG.
Further comparison will be made by comparing line III with line IV. Line III
The lines IV and IV respectively show changes in damping force in the hard mode and the soft mode when the leaf spring is displaced only by the primary fulcrum, as in the conventional case. When the stroke speed of the piston 30 becomes a medium speed or higher, the difference in the damping force between the soft mode and the hard mode due to the leaf spring having only the primary fulcrum becomes W3, but the secondary fulcrum as in the present invention. The value due to the leaf spring having is increased by W4 from that value.

[0049]

As described above, the shock absorber according to the present invention can basically increase the difference in damping force between the hard mode and the soft mode in the medium / high speed section, so that the shock and It is possible to realize various control modes by using a larger difference in damping force by using an electronic control device that controls vibration.

In particular, if the position of the primary fulcrum by the first retaining portion is adjusted so that the initial elastic force of the leaf spring becomes smaller than in the conventional case, in the hard mode, the leaf spring moves further at a lower speed. By coming into contact with the second retaining portion, it is possible to obtain a sharp damping force characteristic due to the secondary fulcrum. Further, in the soft mode, the leaf spring acts with a low damping force even at a relatively high speed of the piston. This allows the characteristics of each mode to be used more effectively.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a vehicle shock absorber according to an embodiment of the present invention.

2 is an enlarged view showing the structure of the piston valve indicated by "A" in FIG. 1, FIG. 2A being a non-actuated position, and FIG. 2B being a fulcrum of the leaf spring at the first retaining portion. 2C shows a state in which the leaf spring is displaced with the second retaining portion as a fulcrum.

FIG. 3 is a graph illustrating changes in damping force by the vehicle shock absorber of the present invention.

FIG. 4 is a cross-sectional view of a conventional vehicle shock absorber.

5 is an enlarged sectional view showing the structure of the piston valve of FIG.

FIG. 6 is a graph showing a change in damping force by a conventional vehicle shock absorber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Cylinder 11 ... Upper chamber 12 ... Lower chamber 20 ... Piston rod 30 ... Piston 50 ... Electric drive valve 100 ... Piston valve 101 ... Leaf spring 102 ... Seat 103 ... Retainer 104 ... First retaining section 105 ... Second retaining section

Claims (1)

[Claims] 1. A piston rod 20 which is housed in a cylinder 10 filled with oil and which moves up and down, and a piston 3.
0, the upper chamber 11 and the lower chamber 12 formed by the piston 30, and the piston 30
Piston valves 100 installed at the upper and lower ends of the chamber and opened and closed by the hydraulic pressure difference between the chambers 11 and 12,
A shock absorber for a vehicle, comprising an electric drive valve 50 installed inside a piston rod 20 penetrating the piston 30 and automatically opened and closed so as to change a damping force. Is a leaf spring 101 that is bent and opened by hydraulic pressure during operation, a seat 102 against which the leaf spring 101 abuts so as to block a flow path when not operating, and a seat that sandwiches the leaf spring 101. Retainer 10 arranged to face 102
3, the retainer 103 is vertically protruded from the inner end thereof to a certain height, and the retainer 103 has an inner end 10 of the leaf spring 101.
1a is a fixed end, and its outer end 101b is a free end, and a first retaining portion 104 supporting the inner end 101a and a first retaining portion 104 at a position separated from the first retaining portion 104 by a predetermined distance. A shock absorber for a vehicle, comprising a second retaining portion 105 which vertically protrudes slightly lower than a protruding height of the retaining portion 104 and serves as a secondary fulcrum when the leaf spring 101 is bent and deformed.