JPH0681881A - Damping force variable shock absorber - Google Patents

Abstract

PURPOSE:To prevent a load of driving an actuator from being increased and damping force from being inaccurately controlled due to fluid force influenced relating to a valve unit of a damping force control valve by operating fluid of passing through a bypass passage. CONSTITUTION:A valve hole 58 and the first/second bypass passages 128, 54 for respectively connecting the valve hole and the first/second cylinder chambers 20, 22 are provided in a piston 18, and a valve unit 56 for controlling a degree of communication of these bypass passages is reciprocatably fitted to the valve hole. The valve unit has a protruded part 114 protruded in a diametric direction, and the protruded part partitions respectively the first/second pressure chambers 118, 120 in a side of the first/second cylinder chambers relating to the protruded part in cooperation with the valve hole, to connect the first/second pressure chambers respectively to the first/second cylinder chambers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber, and more particularly to a shock absorber having a variable damping force.

[0002]

2. Description of the Related Art As one of shock absorbers of a variable damping force type for vehicles such as automobiles, for example, an actual Kaihei 2-6674 is used.
As described in Japanese Unexamined Patent Publication No. 2 (1994), a cylinder, a piston that reciprocally fits in the cylinder and cooperates with the cylinder to define the cylinder upper chamber and the cylinder lower chamber, and the relative movement of the piston relative to the cylinder. A damping force generator that applies a flow resistance to the flowing working liquid to generate a damping force, a bypass passage provided in the piston for connecting the cylinder upper chamber and the cylinder lower chamber to each other, and a valve provided in the middle of the bypass passage. A shock absorber having a hole, a spool valve that reciprocally fits in the valve hole and selectively controls the degree of communication of a bypass passage, and an actuator that drives and positions the spool valve has been conventionally known.

In such a shock absorber, the position of the spool valve is controlled by the actuator and the degree of communication of the bypass passage is controlled, so that the shock absorber operates between the upper chamber and the lower chamber of the cylinder through the bypass passage. Since the flow rate of the liquid is controlled, the flow rate of the working liquid passing through the damping force generating device is changed, whereby the damping force generated by the damping force generating device is variably controlled.

[0004]

In the conventional shock absorber as described above, the operation is performed when the spool valve is opened and the working liquid passes through the bypass passage between the spool valve and the wall surface of the valve hole. A fluid force that urges the spool valve in the reciprocating direction acts in response to a change in the momentum of the liquid in the reciprocating direction of the spool valve. The direction and magnitude of the fluid force vary depending on the flow direction of the working liquid and the opening amount of the spool valve, which causes a problem that the driving load of the actuator becomes high and the control of the damping force becomes inaccurate.

In view of the above-mentioned problems in the conventional damping force type shock absorber, the present invention is improved so that the driving load of the actuator can be reduced and the damping force can be accurately controlled as compared with the prior art. The purpose of the present invention is to provide a shock absorber with variable damping force.

[0006]

SUMMARY OF THE INVENTION According to the present invention, the above object is to provide a cylinder and a first cylinder chamber and a second cylinder chamber that are reciprocally fitted in the cylinder and cooperate with the cylinder. A piston to be defined, a means for generating a damping force by giving a flow resistance to the working liquid flowing with the relative movement of the piston with respect to the cylinder, and a valve hole provided in the piston and extending along an axis line, A first bypass passage communicating at one end with the valve hole in a direction substantially transverse to the axis and at the other end communicating with the first cylinder chamber, and at one end the valve hole substantially with the axis. A second bypass passage communicating with the second cylinder chamber at the other end, and the first and second bypass passages fitted in the valve hole so as to reciprocate along the axis. A valve body for selectively controlling the degree of communication of An actuator for reciprocating and positioning a body, the valve body has a convex portion projecting in a direction transverse to the axis, and the convex portion cooperates with the valve hole to form the first portion with respect to the convex portion. First and second pressure chambers are defined on the sides of the first and second cylinder chambers, respectively, and the first and second pressure chambers are connected to and communicate with the first and second cylinder chambers, respectively. And a variable damping force type shock absorber.

[0007]

In the shock absorber constructed as described above, the pressure in the first cylinder chamber is higher than the pressure in the second cylinder chamber, and the working liquid in the first cylinder chamber is in the first bypass passage, When flowing into the second cylinder chamber through the valve hole and the second bypass passage, when the working liquid passes through the narrowest part (hereinafter referred to as the variable orifice) between the valve body and the wall surface of the valve hole, Due to the increase in the momentum of the spool valve in the reciprocating direction, a fluid force is applied to the spool valve to urge it toward the first cylinder chamber.
On the contrary, the pressure in the second cylinder chamber is higher than the pressure in the first cylinder chamber, and the working liquid in the second cylinder chamber passes through the second bypass passage, the valve hole, and the first bypass passage to the first cylinder. When it flows into the chamber, it causes the spool valve to urge it toward the second cylinder chamber due to a decrease in the momentum of the spool valve in the reciprocating direction as it passes through the variable orifice. The fluid force that acts acts.

According to the above-mentioned structure, the first and second pressure chambers are connected to the first and second cylinder chambers, respectively, so that the pressure in the first cylinder chamber is equal to the pressure in the second cylinder chamber. When higher than the pressure of, the pressure in the first pressure chamber becomes higher than the pressure in the second pressure chamber, and the differential pressure urges the valve element toward the second cylinder chamber,
Conversely, when the pressure in the second cylinder chamber is higher than the pressure in the first cylinder chamber, the pressure in the second pressure chamber becomes higher than the pressure in the first pressure chamber, and the differential pressure causes the valve body to Is biased toward the cylinder chamber of the valve body, so that at least a part of the fluid force acting on the valve body when the hydraulic fluid flows around the valve body is a differential pressure between the pressures in the first and second pressure chambers. By being offset by the urging force due to, the overall force acting on the valve element is reduced, which reliably avoids high drive load on the actuator and inaccurate positioning of the valve element.

[0009]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing a main part of an embodiment of a shock absorber according to the present invention configured as a twin-tube type shock absorber, and FIG. 2 is a view of a piston of the embodiment shown in FIG. FIG. 3 is an enlarged partial vertical sectional view showing a portion of the spool valve in a fully closed position, and FIG. 3 is an enlarged partial vertical sectional view showing the spool valve of the embodiment shown in FIGS. 1 and 2 in a fully opened position. .

In FIG. 1, reference numerals 10 and 12 denote an inner cylinder and an outer cylinder extending concentrically along an axis 14, and both ends of these cylinders are closed by end caps not shown in the drawing. Has been. The cylinders 10, 12 and the end cap cooperate with each other to define an annular chamber 16. A piston 18 is arranged in the inner cylinder 10 so as to be capable of reciprocating along an axis 14. The piston 18 extends along the axis 14 through a piston body 24 that divides the inside of the inner cylinder 10 into a cylinder upper chamber 20 and a cylinder lower chamber 22, and a piston body 24 integrally connected to the body and penetrating an end cap at the upper end. And a piston rod 26. The piston body 24 is the nut 2
8 is fixed to the tip end portion of the piston rod 26, and the piston body 24 has a well-known structure for a damping force generating device for the extension stroke (the check valve 30 and the damping force generating valve 3).
2, see FIG. 2).

Although not shown in FIG. 1, a base valve assembly having a structure known per se is provided in the lower portion of the inner cylinder 10, and the base valve assembly is used for extension stroke. A damping force generator for contraction stroke similar to the damping force generator of FIG. Further, the cylinder upper chamber 20, the cylinder lower chamber 22, and a part of the annular chamber 16 are filled with oil 34 as a working liquid, and the upper portion of the annular chamber 16 is filled with high-pressure gas. Although not shown in FIG. 1, the upper end of the piston rod 26 is connected to the vehicle body as a sprung body, and the outer cylinder 12 or the end cap at the lower end is connected to a suspension member as a unsprung body not shown. It is supposed to be done.

As shown in FIG. 2, the piston rod 26 includes a rod member 42 having a hollow bore 40 extending along the axis 14. A valve housing 44 is fixed to the lower end of the rod member 42 by screwing, and an actuator 46 is accommodated in the hollow hole 40.
In the illustrated embodiment, the actuator 46 includes a step motor 48 and a ball screw device 50, and the ball screw device functions as a motion conversion device for converting the rotational motion of the step motor into the reciprocating motion of the shaft 52. ing.

The valve housing 44 has a rod portion 44a, which projects downward from the lower end of the rod member 42 along the axis 14. The nut 28 is the rod portion 44
It is fixed to the lower end of a by screwing. Rod part 4
4a has a hollow hole 54 extending along the axis 14, and the upper portion of the hollow hole defines a valve hole 58 for reciprocally receiving the spool valve 56 along the axis 14. A stopper 6 is provided between the piston body 24 and the valve housing 44.
0, the spacer 62, and the bypass device 64 are the rod portion 44a.
It is fixed in a state of being fitted to.

The bypass device 64 includes a housing 66, a ring member 68 and an end cap 70 which cooperate with one another to define an interior space 72 which extends annularly about the axis 14. The housing 66 is provided with a plurality of grooves 74 communicating with the internal space 72 and extending in the radial direction, and a plurality of passages 76 extending in the vertical direction in the drawing are provided in the end wall thereof. There is. End cap 7
0 is provided with a plurality of passages 78 extending vertically in the drawing. Ring member 68 defines an annular port 80 that cooperates with housing 66 to communicate with groove 74.
The rod portion 44a of the valve housing is provided with a plurality of radial passages 82 communicating with the annular port 80 and an annular port 84 communicating with the passages and opening to the valve hole 58.

Check valves 86 and 88 are provided on the end wall of the housing 66 and the end cap 70, respectively, in contact with their upper surfaces. The check valve 86 allows only oil to flow from the internal space 72 and the groove 74 toward the cylinder upper chamber 20, and the check valve 88 allows the oil to flow.
Only the flow of oil from 0 toward the internal space 72 and the groove 74 is allowed.

As shown in detail in FIG. 3, the spool valve 56 has a hollow bore 90 extending in its longitudinal direction, the diameter of the hollow bore being set slightly larger than the diameter of the shaft 52. As a result, the spool valve 56 is loosely fitted to the shaft 52. An annular groove 92 is provided near the lower end of the shaft 52, and a stopper ring 94 is mounted in the annular groove. Stopper ring 9
A washer 96 is interposed between the No. 4 and the lower end of the spool valve 56. An annular groove 98 is provided on the shaft 52 at a position above the upper end of the spool valve 56, and a stopper ring 100 is attached to the annular groove 98.

A compression coil spring 106 is fitted between the spring seat 102 disposed in contact with the stopper ring 100 and the end surface of the counter bore 104 provided at the upper end of the spool valve 56 in a state of being fitted to the shaft 52. It is equipped with ammunition. The spring force of the compression coil spring 106 is set to a minimum value sufficient to hold the spool valve in a position in contact with the washer 96 as shown in the figure against the fluid force and frictional force acting on the spool valve 56. , This allows spool valve 5
6 reciprocates according to the shaft when it is reciprocated along the axis 14 by the shaft 52.
It can be relatively displaced relative to the shaft in a direction crossing the axis.

The spool valve 56 cooperates with a valve hole 58 to define an upper chamber 108 and a lower chamber 110 above and below the valve hole 58. These chambers are the counter bore 104, the hollow hole 90 and the shaft 5.
2 and the spool valve, the washer 96, the shaft 52, and the clearance passage between the stopper ring 94. The lower end of the spool valve 56 is tapered so that when the spool valve is in the fully closed position shown in FIG.
4 is disconnected from the lower chamber 110, but when the spool valve is driven upward from the fully closed position in the figure as shown in FIG. 3, the annular port 84 and the lower chamber 110 are connected to each other. The variable orifice 112 is defined.

Further, the spool valve 56 has an annular convex portion 11 projecting radially outward at the longitudinal central portion of its cylindrical outer peripheral surface.
4, the convex portion fits reciprocally into the large diameter portion of the valve hole 58 so as to reciprocate substantially, and the upper end portion of the spool valve reciprocates to the sleeve 116 press-fitted and fixed to the valve housing 44. Movable and substantially tightly fitted. The convex portion 114 cooperates with the valve housing 44 and the sleeve 116, and the upper pressure chamber 11
8 and the lower pressure chamber 120 are defined. Upper pressure chamber 1
Reference numeral 18 denotes a communication hole 122 provided in the valve housing 44 and a plurality of radial grooves 1 provided in a shoulder portion of the valve housing.
24, the lower pressure chamber 120 is communicatively connected to the cylinder upper chamber 20, and the lower pressure chamber 120 is communicatively connected to the space between the spool valve and the shaft 52 by a plurality of communication holes 126 provided in the spool valve 56. As a result, the lower cylinder chamber 2
2 is connected in communication.

Thus, the passages 76 and 78, the internal space 7
2, groove 74, annular port 80, passage 82, annular port 8
Reference numeral 4 denotes a first bypass passage 1 that connects the cylinder upper chamber 20 and the valve hole 58 to each other and connects the valve hole and the valve hole 58 in a direction perpendicular to the axis 14.
28, and the hollow hole 54 defines a second bypass passage that connects the cylinder lower chamber 22 and the valve hole 58 to each other and communicates with the valve hole along the axis 14. The degree of communication between the passages is variably controlled by controlling the effective passage sectional area of the orifice 112 by the spool valve 56.

In the operation of the illustrated embodiment, the pressure in the cylinder lower chamber 22 becomes lower than the pressure in the cylinder upper chamber 20 and the annular chamber 16 in the extension stroke of the piston, so that the cylinder upper chamber And a part of the oil in the annular chamber circulates to the cylinder lower chamber, and at that time, a damping force generator for extension stroke and 30 and 32 provided in the piston give a flow resistance to the oil, which causes the damping force. Is generated.

Similarly, in the compression stroke of the piston, the pressure in the lower cylinder chamber 22 is changed to the upper cylinder chamber 20 and the annular chamber 16.
When the internal pressure becomes higher than the internal pressure, a part of the oil in the cylinder lower chamber flows into the cylinder upper chamber and the annular chamber, and at that time, it is converted into oil by the damping force generator for the compression stroke provided in the base valve assembly. A flow resistance is given to the flow resistance, which generates a damping force.

Further, in both the extension stroke and the contraction stroke of the piston, when the spool valve 56 is in the fully closed position shown in FIG. 2, the bypass passages 128 and 54 are in the state of being blocked from each other. The oil does not flow between the cylinder upper chamber 20 and the cylinder lower chamber 22 through the bypass passage, and always passes through the damping force generator provided in the piston and the damping force generator provided in the base valve assembly. However, a high damping force is generated by these damping force generators, whereby the shock absorber operates in a so-called hard mode.

On the other hand, when the coil of the step motor 48 is energized and the spool valve 56 is switched to the fully open position shown in FIG. 3 or an intermediate position between the fully closed position and the fully open position, the annular port 84 and the lower chamber. 110 is the orifice 112
Since the bypass passages are in communication with each other, a part of the oil in the cylinder upper chamber 20 and the cylinder lower chamber 22 circulates through the bypass passages, and The damping force generated is reduced, whereby the shock absorber operates in a so-called soft mode or an intermediate mode between the soft mode and the hard mode depending on the opening position of the spool valve.

In this case, in the extension stroke of the piston, the oil in the cylinder upper chamber 20 passes through the check valve 88 when flowing into the cylinder lower chamber 22 through the bypass passage, while in the compression stroke of the piston. In this case, the oil in the cylinder lower chamber 22 passes through the check valve 86, but since the check valve 86 is not biased by the spring, the damping force generated in the compression stroke of the piston is the extension of the piston. Lower than in the journey.

Further, in the extension stroke and the contraction stroke of the piston when the spool valve 56 is opened, the oil passes through the bypass passages 128 and 54 and the variable orifice 112, so that the spool valve 56 has the axis 14 A fluid force acts along. In the illustrated embodiment, the fluid force is such that the downward direction in the figure is positive, and the broken line A in FIG.
Occurs as shown in. As can be seen from FIG. 4, in the extension stroke of the piston, the downstream side of the orifice 112,
That is, the fluid force acting on the spool valve has a negative value except for a small displacement range of the spool valve in which a relatively strong negative pressure region is generated on the bypass passage 54 side with respect to the orifice.

According to the illustrated embodiment, during the extension stroke of the piston, the pressure in the cylinder upper chamber 20 changes to the cylinder lower chamber 22.
4 and the pressure in the upper pressure chamber 118 becomes higher than that in the lower pressure chamber 120, the differential pressure between these two pressure chambers causes the spool valve 56 to have a dashed line in FIG. A downward force B acts along the axis 14 as indicated by the arrow, so that the overall force acting on the spool valve 56 is reduced as indicated by the solid line C in FIG.

On the contrary, in the compression stroke of the piston, the pressure in the lower cylinder chamber becomes higher than that in the upper cylinder chamber, and the pressure in the lower pressure chamber becomes higher than that in the upper pressure chamber. 4 causes an upward force B to act on the spool valve 56 along the axis 14 as indicated by the alternate long and short dash line in FIG. 4, so that the overall force acting on the spool valve 56 is shown in FIG. Is reduced as indicated by the solid line C.

The positive fluid force acts in the direction of reducing the effective passage cross-sectional area of the orifice 112 by urging the spool valve 56 downward in the drawing, while the negative fluid force causes the spool valve 56 to be illustrated. And acts to expand the effective passage cross-sectional area of the orifice 112, the sign of the fluid force changes in the extension stroke of the piston as indicated by the broken line A in FIG. In the region where the ball screw device 50 and its bearings have axial backlash, the spool valve vibrates due to positive and negative fluctuations in the fluid force.
For this reason, abnormal noise is likely to occur and the damping force tends to fluctuate unstablely.

On the other hand, according to the illustrated embodiment, since the overall force acting on the spool valve 56 does not become negative, even if there is play in the ball screw device 50 or its bearing, the spool It is possible to reliably prevent the generation of abnormal noise and the unstable fluctuation of the damping force due to the vibration of the valve,
It is not necessary to assemble the actuator 46 with high accuracy, and the durability of the actuator can be improved.

Further, according to the illustrated embodiment, as described above, the spool valve 56 is loosely fitted to the shaft 52, and is held by the compression coil spring 106 at the position where it is brought into contact with the washer 96. It is urged against the stopper ring 94 along the shaft 52 with a minimum spring force. Therefore, the spool valve 56 can be relatively freely displaced relative to the shaft in the direction transverse to the axis line 14,
Further, since the compression coil spring 106 is not substantially pressed against the wall surface of the valve hole 58, the shaft 52
Alternatively, even if these members are assembled in a state where the axis of the spool valve 56 and the axis of the valve hole 58 are displaced from each other, sliding resistance when the spool valve reciprocates does not increase. The spool valve can smoothly reciprocate along the valve hole.

Further, according to the illustrated embodiment, the actuator 46 comprises a step motor 48 capable of accurate driving and positioning and a ball screw device 50 as a motion converting device for converting rotational motion of the step motor into reciprocating motion. Therefore, the spool valve 56 can be accurately driven and positioned as compared with the case where a reciprocating actuator is used.

Although the above embodiment is constructed as a twin-tube type shock absorber, the shock absorber according to the present invention may be constructed as a so-called mono-tube type shock absorber.

The actuator in the shock absorber of the present invention is not limited to the actuator having the structure shown in the illustrated embodiment, but may have any structure as long as the valve body can be reciprocated and positioned. You may

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and other various embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art that it is possible.

[0037]

As is apparent from the above description, according to the present invention, at least a part of the fluid force acting on the valve body when the working liquid flows around the valve body is the first and second pressures. Since the total pressure acting on the valve element is reduced by being offset by the pressure difference between the pressures in the room, it is possible to reduce the drive load of the actuator, thereby reducing the actuator size and energy consumption. By smoothly driving and accurately positioning the valve element, the damping force of the shock absorber can be accurately controlled and the responsiveness of damping force control can be improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a main part of one embodiment of a shock absorber according to the present invention configured as a twin-tube type shock absorber.

FIG. 2 is an enlarged partial vertical cross-sectional view showing a main part of the piston of the embodiment shown in FIG. 1 in a state where the spool valve is in a fully closed position.

FIG. 3 is an enlarged partial vertical sectional view showing the spool valve of the embodiment shown in FIGS. 1 and 2 in a fully opened position.

FIG. 4 is a graph showing the relationship between the amount of displacement of the spool valve and the axial force acting on the spool valve.

[Explanation of symbols]

 10 ... Inner cylinder 12 ... Outer cylinder 18 ... Piston 20 ... Cylinder upper chamber 22 ... Cylinder lower chamber 24 ... Piston body 30, 32 ... Damping force generator 34 ... Oil 46 ... Actuator 48 ... Step motor 50 ... Ball screw device 54 ... Second bypass passage 56 ... Spool valve 58 ... Valve hole 112 ... Variable orifice 114 ... Convex portion 118 ... Upper pressure chamber 120 ... Lower pressure chamber 128 ... First bypass passage

Claims (1)

[Claims] 1. A cylinder, a piston that reciprocally fits in the cylinder and cooperates with the cylinder to demarcate the first and second cylinder chambers, and with the relative movement of the piston with respect to the cylinder. Means for applying a flow resistance to the working fluid flowing to generate a damping force, a valve hole provided in the piston and extending along an axis, and at one end in a direction substantially crossing the axis with the valve hole. A first bypass passage that communicates with the first cylinder chamber at the other end, and communicates with the valve hole at one end substantially along the axis and with the second cylinder chamber at the other end. A second bypass passage communicating with the valve body; a valve body fitted in the valve hole so as to reciprocate along the axis; and a valve body for selectively controlling the degree of communication between the first and second bypass passages; An actuator for reciprocating and positioning The valve body has a convex portion projecting in a direction transverse to the axis, and the convex portion cooperates with the valve hole to form a first portion on the first and second cylinder chamber sides with respect to the convex portion. And a second pressure chamber, and the first and second pressure chambers are connected to and communicate with the first and second cylinder chambers, respectively, and a variable damping force type shock absorber is provided. .