JPH0942354A - Piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of damping characteristic caused by reduction of sealing property between the opening part of an orifice and a check valve, and prevent breakage of the check valve. SOLUTION: A piston bearing 2 which is formed integratedly with a piston main body 1, which has elasticity, and which is made of synthetic resin, is provided with a valve seat 24 which is fixed on the axial direction both end surfaces 1a, 1b of the piston main body 1. In the one end surface 1a of the piston main body 1, a reciprocating orifice 14 is opened to a valve seat with which a check valve 4 is tightly brought in contact. In the other end surface 1b side of the piston main body 1, the reciprocating orifice 13 is opened to the valve seat 24, and the reciprocating orifice 14 is opened to the end surface 1b of the piston main body 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston arranged in a cylinder such as a shock absorber of an automobile.

[0002]

2. Description of the Related Art As a piston arranged in the cylinder of a shock absorber, there is one in which a piston bearing made of a synthetic resin material such as PTFE, which is a low friction material, is integrally provided on the outer peripheral surface. A typical conventional example of this type of piston is, for example, a piston main body made of a sintered metal or a synthetic resin, a bearing main body attached to the outer peripheral surface of the piston main body, and a skirt projecting from one axial end thereof. And a seal lip that is in close contact with the inner peripheral surface of the cylinder. In the piston body, orifices whose one end opening is opened and closed by a check valve and orifices whose other end opening is opened and closed by a check valve are alternately formed in the circumferential direction. Therefore, when the piston moves axially in the cylinder due to shock input, the check valve at one end or the other end in the axial direction selectively opens and closes the orifice according to the moving direction of the piston to check the enclosed fluid in the cylinder. Flows in the orifice opened by the valve to the side opposite to the moving direction,
Damping is obtained by the flow resistance at this time.

[0003]

In the above-mentioned conventional example, the piston bearing is formed by pressing a sheet-shaped PTFE on the outer peripheral surface of the piston body into a cylindrical shape and is crimped. Therefore, a plurality of annular grooves are formed on the outer peripheral surface of the piston body to secure the fixing force with the piston bearing.However, if the piston body is made of sintered metal, these annular grooves are machined. Since it has to be formed by the above method, an increase in processing cost cannot be avoided. If the piston body is made of synthetic resin, there is no such problem, but the flatness of the valve surface formed at the end of the orifice is low, so there is a gap between the piston and the check valve. , The damping characteristics may be deteriorated because the orifice is not completely blocked, and the check valve may violently contact the end surface of the piston body when the valve is closed, increasing the impact load and damaging the check valve. . Further, the fixing force of the piston bearing with respect to the piston body depends only on the fitting force due to the biting of the inner peripheral surface of the piston bearing with respect to the annular groove, and therefore it is required to further improve its reliability.

The present invention has been made under the circumstances as described above, and its technical problem is that the damping characteristic is deteriorated due to the deterioration of the sealing property between the orifice opening of the piston and the check valve, The purpose is to prevent damage to the check valve and improve performance.

[0005]

The above-mentioned technical problems are as follows.
This can be effectively solved by the present invention. That is, the piston according to the present invention comprises a piston body made of synthetic resin having a forward-moving orifice and a backward-moving orifice penetrating in the axial direction, and a piston bearing integrally provided on the piston main body and made of fluororesin. The piston bearing has a bearing main body fixed to the outer peripheral surface of the piston main body, a seal lip formed to project from the outer peripheral surface of the bearing main body, and fixed to one end surface of the piston main body while the forward movement is performed. The valve seat has one end of the orifice opened, and the valve seat fixed to the other end surface of the piston body and the other end of the return orifice opened.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The piston of the present invention is typically arranged in a sealed cylinder in a shock absorber so as to be movable in the axial direction, and the end portion of a rod inserted into the cylinder. Is connected to the valve seat so that the axial motion is input from the outside through this rod, and the valve seat with the forward and backward orifices opened has a flow of fluid from within the orifice. A check valve is arranged to allow only that.

In this embodiment, the piston bearing is
The bearing body has a bearing function to hold the piston concentrically on the inner circumference of the cylinder, and the seal lip is in close contact with the cylinder to restrict the flow of the enclosed fluid on the outer circumference of the bearing body, and the valve seat seals the seal when the check valve is closed. Improve. In addition, since the fluororesin that constitutes the piston bearing is flexible and has appropriate elasticity, the valve seat cushions the shock when the check valve is closed,
This has the effect of increasing the fixing force of the piston bearing body.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a preferred embodiment of a piston according to the present invention, in which (a) and (b) are half cross-sectional views cut in mutually different directions by planes passing through the axis. In this figure, reference numeral 1 is a piston body, which is molded from a synthetic resin material such as phenol resin or PPS (polyphenylene sulfide), and reference numeral 2 is a piston bearing integrally provided on the piston body 1. The injection molding fluororesin (PFA) has an appropriate elasticity and excellent slidability.

The piston body 1 is formed with a plurality of annular grooves 11 continuously extending in the circumferential direction on the outer peripheral surface thereof, a rod mounting hole 12 is formed through the shaft center portion, and the periphery thereof is axially formed. Each of the four forward-moving orifices 13 and the backward-moving orifices 14 penetrating therethrough are alternately formed in the circumferential direction. In this case, the annular groove 11, the rod mounting hole 12, the forward movement orifice 1
Since the 3 and the return orifice 14 can be formed at the same time when the piston body 1 is molded with resin, there is no need for machining or the like. The piston bearing 2 includes a bearing main body 21 fixed to the outer peripheral surface of the piston main body 1, a seal lip 22 extending in a skirt shape near one axial end of the bearing main body 21, and the bearing main body 21. It is composed of valve seats 23 and 24 which are extended and fixed on both axial end surfaces 1a and 1b of the piston body 1, and are integrated with the piston body 1 at the time of molding.

As shown in FIGS. 2 and 4, the valve seat 23 on the one end face 1a side of the piston main body 1 is radially separated from the outer peripheral side corresponding to the opening position of each return orifice 14. And a ring-shaped portion 23b on the inner peripheral side formed so as to surround the one end opening 12a of the rod mounting hole 12. Then, on the side of the one end face 1a, the return orifice 14 is opened to each strip portion 23a of the valve seat 23, and the forward orifice 13 is located on the end face 1a of the piston body 1 exposed between the strip portions 23a. It is open.

Similarly, the other end surface 1b of the piston body 1
As shown in FIG. 3, the valve seat 24 on the side of the valve seat 24 has radial strip portions 24 a on the outer peripheral side which are separated in the circumferential direction corresponding to the opening positions of the respective forward movement orifices 13, and the other end opening of the rod mounting hole 12. The inner peripheral side annular portion 24b is formed so as to surround the periphery of the portion 12b. On the side of the other end face 1b, the forward movement orifice 13 is opened in each strip-shaped portion 24a of the valve seat 24, and the return orifice 14 is formed in the end face 1b of the piston body 1 exposed between the strip-shaped portions 24a. It is open.

The piston of this embodiment is arranged in a cylinder (not shown) of the shock absorber so as to be movable in the axial direction, and a viscous fluid such as oil is sealed in the cylinder. The rod 3 which is axially inserted into the cylinder is inserted into the rod mounting hole 12 of the piston body 1 from the outside, the nut 3b is screwed into the shaft end 3a, and the rod 3 is formed by tightening the nut 3b. Step 3c
The piston body 1 is fixed between and. Check valves 4 and 5 each made of a disc-shaped valve body having flexibility are arranged on both axial sides of the piston body 1, and one of the check valves 4 has an inner peripheral portion having the nut 3b. And the annular portion 23b of one of the valve seats 23 is tightly fixed. The other check valve 5 includes the step portion 3c and the annular portion 24b of the other valve seat 24.
It is tightly fixed between and.

That is, the one check valve 4 is provided so as to close the return orifice 14 opened in the belt-shaped portion 23a by closely contacting the respective belt-shaped portions 23a of the valve seat 23. The valve is opened by the pressure from ₁₎ and is always in the open position with respect to the forward-moving orifice 13 via a gap G ₁ corresponding to the thickness of the band-shaped portion 23a. Similarly, the check valve 5 on the opposite side is provided so as to close the forward-moving orifice 13 opened in the belt-shaped portion 24 a by closely contacting the respective belt-shaped portions 24 a of the valve seat 24. The valve is opened by the pressure from, and is always in the open position with respect to the return orifice 14 via the gap G ₂ corresponding to the thickness of the band-shaped portion 24a.

In the above structure, when an axial load is input from the outside of the cylinder via the rod 3, the piston body 1 is made concentric with the inner peripheral surface of the cylinder by the bearing function of the bearing body 21 of the piston bearing 2. While being maintained, the seal lip 22 moves axially in the cylinder while the outer periphery is sealed. In the piston bearing 2, not only is the inner peripheral surface of the bearing main body 21 fixed to the outer peripheral surface of the piston main body 1 in a state of biting into the annular groove 11, but also a valve extending from both axial sides of the bearing main body 21. The seats 23, 24 are both end faces 1a of the piston body 1,
Since it is fixed to 1b, the piston body 1 has a large disengagement resistance and therefore has excellent pressure resistance.

Here, the piston body 1 is A in FIG.
In the case of axially moving toward the side (forward movement), the check valve 4 facing the front side in the moving direction is pressed against the band-shaped portion 23a of the valve seat 23 by the pressure of the enclosed fluid on the A side, and is pressed against the band-shaped portion 23a. Although the backward moving orifice 14 that has been opened is closed, the forward moving orifice 13 has the opening facing the A side which is always open through the gap G _1. Therefore, the check valve 5 located on the rear side in the moving direction, that is, the B side. Is bent by the pressure of the A-side enclosed fluid acting through the forward-moving orifice 13 and is separated from the belt-shaped portion 24a of the valve seat portion 24. Therefore, the forward movement orifice 13 is opened, and the enclosed fluid flows from the A side to the B side through the forward movement orifice 13. At this time, the check valve 4 is brought into close contact with the band-like portion 23a of the valve seat 23 made of a flexible fluororesin, and the flow of the enclosed fluid is surely restricted only to the forward orifice 13. Therefore, the damping force can be effectively reduced. Can be prevented.

On the contrary, when the piston body 1 moves (returns) in the axial direction toward the B side in FIG. 1, the check valve 5 facing the front side in the moving direction is controlled by the pressure of the B side enclosed fluid. The forward-moving orifice 13 that is pressed against the belt-shaped portion 24a of the seat 24 and opens in the belt-shaped portion 24a.
However, since the opening of the return orifice 14 facing the B side is always open through the gap G ₂ , the check valve 4 located on the rear side in the moving direction, that is, the A side,
It is bent by the pressure of the B-side sealed fluid acting through the return orifice 14 and is separated from the belt-shaped portion 23a of the valve seat 23. Therefore, the return orifice 14 is opened, and the enclosed fluid flows from the B side to the A side through the forward orifice 13. At this time, the check valve 5 is satisfactorily brought into close contact with the belt-shaped portion 24a of the valve seat 24 made of a flexible fluororesin, and the flow of the enclosed fluid is surely restricted only to the return orifice 14, so that the damping force is effectively reduced. Can be prevented.

The forward passage orifice 13 and the backward passage orifice 14 are formed to have different flow passage cross-sections. Therefore, when the piston moves forward to the A side,
A different damping force is produced when returning to the B side.

According to this embodiment, as described above, the damping force with respect to the input kinetic energy is improved, and the check valves 4 and 5 are integral with the bearing body 21 and are made of flexible fluororesin valve seats 23 and 24. Since the check valves 4 and 5 are brought into and out of contact with each other, the impact load at the time of the valve closing operation of the check valves 4 and 5 is alleviated, and the damage thereof is effectively prevented.

[0019]

According to the piston according to the present invention, the following effects are realized. (1) The closeness of the check valve is improved, so that the flow of the enclosed fluid during piston movement can be surely restricted to the forward or backward orifice, and the damping performance is improved. (2) Since the impact load at the time of closing the check valve is relieved, the damage can be prevented. (3) Since the fixing force of the piston bearing with respect to the piston body is increased, the piston bearing is less likely to come off and the pressure resistance is improved. (4) Since it is not necessary to machine the piston body, it can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 shows a preferred embodiment of a piston according to the present invention mounted on a rod together with a check valve, in which (a) is a half sectional view taken along a plane passing through a forward orifice and an axial center. b) is a half cross-sectional view taken along a plane passing through the return orifice and the axis.

FIG. 2 is a diagram of the above embodiment as viewed from the A side in FIG.

FIG. 3 is a diagram of the above embodiment as viewed from the side B in FIG.

FIG. 4 is a partially separated perspective view showing the above embodiment together with a check valve, a shaft end of a rod, and a nut.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston main body 1a, 1b End surface 11 Annular groove 12 Rod mounting hole 13 Forward orifice 14 Backward orifice 2 Piston bearing 21 Bearing body 22 Seal lip 23, 24 Valve seat 23a, 24a Band-like part 23b, 24b Annular part 3 Rod 3a Shaft End 3b Step 3c Nut 4,5 Check valve

Claims (1)

[Claims] 1. A forward-moving orifice (1) penetrating in the axial direction.
3) and a piston body (1) made of synthetic resin having a return orifice (14), and a piston bearing (2) made of fluororesin integrally provided on the piston body (1). The bearing (2) has a bearing body (21) fixed to the outer peripheral surface of the piston body (1), a seal lip (22) formed so as to project from the outer periphery of the bearing body (21), and the piston body ( (1) is fixed to one end surface (1a) of the forward valve (13) and one end of the forward orifice (13) is opened, and the other end surface (1b) of the piston body (1) is fixed. A piston comprising a valve seat (24) having the other end of the return orifice (14) opened.