JP2002156045A - Piston sealing structure of hydraulic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston sealing structure of the hydraulic equipment capable of improving the sealability even on a piston having a ring groove of the simple shape and the poor accuracy in shape, and reducing the sliding resistance. SOLUTION: In this hydraulic equipment formed by slidably fitting the piston 5 in a cylinder 2 through a piston ring 7 fitted to a ring groove 18 at the outer periphery of the piston 5, and mounting an annular elastic seal member 19 between the piston 5 and the piston ring 7, the elastic seal member 19 is fixed to a bottom part of the ring groove 18 formed at the outer periphery of the piston 5, a back face of the piston ring 17 is pressed to the cylinder 2 side by the elastic seal member 19 with a predetermined width W in the sliding direction of the piston 5, and an annular space S is formed between both end faces of the elastic seal member 19 and the ring groove 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piston seal structure for a hydraulic device such as a hydraulic shock absorber.

[0002]

2. Description of the Related Art In a hydraulic device such as a hydraulic shock absorber, as shown in FIG.
The piston O is slidably fitted into the cylinder 102 via a resin-made piston ring 107 fitted to the piston 105, and an annular O-ring 119 is interposed between the piston 105 and the piston ring 107. The sealing property of 105 is ensured.

[0003]

However, in order to ensure high sealing performance of the piston 105 in the above-mentioned conventional hydraulic equipment, the piston 105 and the ring groove 118 formed on its outer periphery are required to have high shape accuracy. You. or,
When the sealing property of the piston 105 is enhanced,
This causes a problem that the sliding resistance of the hydraulic device becomes large and the operation stability of the hydraulic equipment is hindered.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the sealing performance of a piston having a ring groove having a simple shape and a low shape accuracy, and to improve the sliding property. It is an object of the present invention to provide a piston seal structure of a hydraulic device that can suppress resistance.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a piston is slidably fitted in a cylinder through a piston ring fitted in a ring groove on the outer periphery of the piston. A hydraulic device comprising an annular elastic seal member interposed between the piston and the piston ring, wherein the elastic seal member is fixed to a bottom of a ring groove formed on the outer periphery of the piston. The elastic seal member presses the rear surface of the piston ring toward the cylinder with a predetermined width in the sliding direction of the piston, and an annular space is formed between both end surfaces of the elastic seal member and the ring groove. It is characterized by.

According to a second aspect of the present invention, in the first aspect, a plurality of circumferential grooves are formed on an outer surface of the elastic seal member.

According to a third aspect of the present invention, in the first or second aspect of the invention, the ring groove of the piston is constituted by two stages of an upper stage and a lower stage, the lower stage is formed by molding, and the upper stage is formed by cutting. It is characterized by having been formed.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, a molding die is pressed against the bottom of the ring groove of the piston and formed between the molding die and the bottom of the ring groove. The space is filled with a material to form the elastic seal member, and the elastic seal member is fixed to the bottom of the ring groove.

Therefore, according to the first aspect of the present invention, even if the ring groove formed in the piston has a simple shape and the accuracy of the shape is low, the piston has a back surface having a predetermined width in the sliding direction by the elastic sealing member. Thus, the piston is uniformly pressed to the cylinder side, so that the piston has a high sealing property, and the sliding resistance of the piston is suppressed low, so that the operation stability is enhanced.

According to the second aspect of the present invention, since a plurality of circumferential grooves are formed on the outer surface of the elastic seal member, the pressing force of the piston ring on the cylinder is not increased more than necessary, and the sliding resistance of the piston is reduced. , And high sealing performance can be secured. Further, the pressing force of the elastic seal member against the piston ring can be adjusted by changing the number and shape and size of the circumferential grooves.

According to the third aspect of the present invention, since the lower stage of the ring groove of the piston to which the elastic seal member is fixed is formed by molding, the lower stage has a large roughness and the elastic seal member is firmly attached to the ring groove. To be fixed. In addition, the cutting allowance for the upper stage of the ring groove can be reduced, and the number of machining steps can be reduced.

According to the fourth aspect of the present invention, the space between the molding die and the bottom of the ring groove is filled with the material by pressing the molding die against the bottom of the ring groove of the piston to provide an elastic seal. Since the member is formed, manufacture of the elastic seal member is facilitated, and high accuracy can be secured in the outer diameter of the elastic seal member after being fixed to the piston.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a pressure regulating device having a piston seal structure according to the present invention, FIG. 2 is an enlarged detailed view of a portion A of FIG. 1, and FIG. 3 is an enlarged detailed view of a portion B of FIG.

A pressure regulating device 1 shown in FIG. 1 is provided in a hydraulic shock absorber for a vehicle, and has cylinders 2 and 3 of large and small diameters concentrically connected. A rod 4 is inserted into 3 so as to be vertically movable.

A separate piston 5 is fixed to the upper end of the rod 4 by a screw 6, and this piston 5 is inserted into the cylinder 2 via a resin-made piston ring 7 fitted and held on the outer periphery thereof. Is slidably fitted up and down. A large-diameter piston portion 4a is integrally formed at the lower end of the rod 4, and this piston portion 4a is formed via a resin-made piston ring 8 and a rubber O-ring 9 fitted to the outer periphery thereof. It is fitted in the cylinder 3 so as to be slidable up and down.

The lower end of the cylinder 3 has a cap 1
0, an oil chamber S1 and a gas chamber S2 are defined in the upper and lower cylinders 2 and 3 by a piston portion 4a of a rod 4, and the oil chamber S1 is separated by a piston 5 into a first oil chamber S11. And a second oil chamber S12. The oil chamber S1 is filled with oil and the gas chamber S
2 is filled with an inert gas such as nitrogen gas. still,
The size of the piston 5 and the piston portion 4a is set so that the cross-sectional areas of the first oil chamber S11 and the second oil chamber S12 are equal.

An oil passage 11 is formed in the cylinder 2.
The second oil chamber S12 communicates with one of a pair of left and right shock absorbers (not shown) via an oil path 11 and a hydraulic pipe 12 connected thereto. The first oil chamber S11 is connected to the cylinder 2 by a plug 13. It communicates with the other shock absorber via the connected hydraulic piping 14.

Further, as shown in detail in FIG. 2, the piston 5 has a plurality of oil holes 15 and 16 penetrating therethrough. Valves for opening and closing the oil holes 15 and 16 respectively on the upper and lower surfaces of the piston 5. 17A and 17B are attached. One oil hole 15 is always open to the second oil chamber S12, and the other oil hole 16 is always open to the first oil chamber S11.

When the same amount of oil is supplied from the left and right shock absorbers to the first oil chamber S11 and the second oil chamber S12 via the hydraulic pipes 14 and 12, as described above, the piston 5 The piston part 4a is connected to the first oil chamber S11 and the second oil chamber S11.
Are set so that the cross-sectional areas of the oil chambers 12 of the first oil chamber 12 become equal, so that the first oil chamber S1 is moved even if the rod 4, the piston 5 and the piston portion 4a move down in the cylinders 2 and 3.
No oil flow occurs between the first and second oil chambers S12, and no damping force is generated due to the oil flow. The rod 4, the piston 5 and the piston portion 4 in the cylinders 2 and 3
The downward movement of “a” is permitted by the compression of the inert gas in the gas chamber S2. Conversely, the first oil chamber S11 and the second oil chamber S1
When the same amount of oil is discharged to the shock absorber via the hydraulic pipes 14 and 12 from the first oil chamber S1
No oil flow occurs between the first and second oil chambers S12. At this time, the downward movement of the rod 4, the piston 5 and the piston portion 4a in the cylinders 2 and 3 is caused by the inert gas in the gas chamber S2. Allowed by swelling.

On the other hand, when oil is supplied to the first oil chamber S11 from the hydraulic pipe 14 and oil is discharged from the second oil chamber S12 through the oil path 11 and the hydraulic pipe 12, The oil in the first oil chamber S11 pushes the valve 17B open at that pressure and flows into the second oil chamber S12 from the oil hole 16 of the piston 5, so that the oil in the first oil chamber S11 is supplied to the pressure regulating device 1 by the flow resistance of the oil at this time. The damping force is generated. Conversely, the oil flows into the second oil chamber S12 and the hydraulic pipe 12 and the oil passage 11
When the oil is discharged from the first oil chamber S11 through the hydraulic pipe 14 at the same time as the oil supplied from the first oil chamber S11, the oil in the second oil chamber S12 pushes the valve 17A at that pressure to open the piston 5A. Flows into the first oil chamber S <b> 11 from the oil hole 15, a predetermined damping force is generated in the pressure regulating device 1 by the flow resistance of the oil at this time.

Next, the details of the piston seal structure according to the present invention will be described with reference to FIGS.

A ring groove 18 is formed on the outer periphery of the piston 5. The ring groove 18 is composed of two stages, an upper stage 18a and a lower stage 18b, as shown in detail in FIG. Thus, the lower stage 18b is formed by molding.

The upper stage 18a of the ring groove 18
(A part shown in the figure) and upper and lower end faces (part b in the figure) are cut, and the upper and lower end faces of the upper step 18a are made of resin (in the present embodiment, Teflon (registered trademark)). The piston ring 7 is fitted and held, and an elastic seal member 19 made of rubber is interposed between the piston ring 7 and the piston 5.

The elastic seal member 19 is fixed to the bottom of the lower step 18b of the ring groove 18, and as shown in FIG. 3, a plurality of (six in the illustrated example) circumferential grooves 19a are formed on the outer surface thereof. Is formed. And the piston ring 7
The back surface of the elastic seal member 19 is pressed toward the cylinder 2 with a predetermined width W (see FIG. 2) in the sliding direction of the piston 5, and between the upper and lower end surfaces of the elastic seal member 19 and the ring groove 18. Annular spaces S are respectively formed.

Thus, according to the piston seal structure of the present invention, even if the ring groove 18 formed in the piston 5 has a simple shape and the shape accuracy is low, the piston 5 has the back surface formed by the elastic seal member 19. Since the piston 5 is uniformly pressed to the cylinder 2 side with a predetermined width W in the sliding direction, the piston 5 has high sealing performance, and the sliding resistance of the piston 5 is suppressed to be low, so that the operation stability is improved. Enhanced.

Further, since a plurality of circumferential grooves 19a are formed on the outer surface of the elastic seal member 19, the pressing force of the piston ring 7 to the cylinder 2 is not increased more than necessary, and the sliding resistance of the piston 5 is suppressed low. At the same time, a high sealing property can be ensured by improving the contact surface pressure. Also, dynamic leakage of oil is prevented by the labyrinth effect of the plurality of circumferential grooves 19a formed on the outer surface of the elastic seal member 19. The pressing force of the elastic seal member 19 on the piston ring 7 can be adjusted by changing the number and shape and size of the circumferential grooves 19a.

Further, since the lower stage 18b to which the elastic seal member 19 of the ring groove 18 of the piston 5 is fixed is formed by molding, the lower stage 1 to which the elastic seal member 19 is adhered is formed.
The elastic seal member 19 is firmly fixed to the ring groove 18 by increasing the roughness of the bottom surface of 8b. Also, since the upper portion 18a of the ring groove 18 is cut only at the bottom portion (a portion in the drawing) and the upper and lower end surfaces (b portion in the drawing), the cutting allowance is reduced and the number of processing steps is reduced.

Next, a method of forming the elastic seal member 19 will be described with reference to FIG. FIG. 4 is a cross-sectional view illustrating a method of forming the elastic seal member. When forming the elastic seal member 19, as shown in FIG.
In a state set between the lower die 51 and the lower die 51, the middle die 52 divided in the circumferential direction is pressed against the bottom of the ring groove 18 of the piston 5. Here, the middle mold 52 is heated to a predetermined temperature, and a space formed between the middle mold 52 and the bottom of the ring groove 18 is filled with a rubber material as a material, and the elastic seal member 19 is formed by a so-called heat press method. Is vulcanized into a predetermined shape, and the elastic seal member 19 is
8 fixed to the bottom. When the divided middle dies 52 are joined from the left and right, a gap is formed between the two middle dies 52, and the rubber material leaking from this gap is removed by a deburring process using a knife.

When the elastic seal member 19 is formed by the above method, the manufacture of the elastic seal member 19 is facilitated, and the outer diameter of the elastic seal member 19 after being fixed to the ring groove 18 of the piston 5. High accuracy in dimensions can be ensured.

Although the present invention has been described with reference to a form in which the present invention is particularly applied to a piston seal structure of a pressure regulating device, the present invention is similarly applicable to a piston seal structure of any other hydraulic equipment. Of course.

[0032]

As apparent from the above description, according to the present invention, the piston is slidably fitted in the cylinder via the piston ring fitted in the ring groove on the outer periphery of the piston. In a hydraulic device having an annular elastic seal member interposed between the piston and the piston ring, the elastic seal member is fixed to a bottom of a ring groove formed on an outer periphery of the piston. By pressing the rear surface of the piston ring toward the cylinder with a predetermined width in the sliding direction of the piston, and forming an annular space between both end surfaces of the elastic seal member and the ring groove, a simple shape is provided. Even in the case of a piston having a ring groove having a low shape accuracy, the sealing effect can be improved and the sliding resistance can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a hydraulic shock absorber provided with a piston seal structure according to the present invention.

FIG. 2 is an enlarged detail view of a portion A in FIG. 1;

FIG. 3 is an enlarged detail view of a portion B in FIG. 2;

FIG. 4 is a cross-sectional view illustrating a method of forming an elastic seal member.

FIG. 5 is a sectional view of a main part of a hydraulic shock absorber showing a conventional piston seal structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure regulator (hydraulic equipment) 2, 3 Cylinder 5 Piston 7 Piston ring 18 Ring groove 18a Upper stage 18b Lower stage 19 Elastic seal member 19a Circumferential groove 50 Upper die (molding die) 51 Lower die (molding die) 52 Middle die (molding) Type) S Annular space

Claims (4)

[Claims] A piston is slidably fitted in a cylinder via a piston ring fitted in a ring groove on an outer periphery of the piston, and an annular elastic seal member is provided between the piston and the piston ring. The elastic seal member is fixed to the bottom of a ring groove formed on the outer periphery of the piston, and the elastic seal member moves the back surface of the piston ring to a predetermined width in the sliding direction of the piston. A piston seal structure for a hydraulic device, wherein an annular space is formed between both end faces of the elastic seal member and the ring groove while being pressed toward the cylinder. 2. The piston seal structure for a hydraulic device according to claim 1, wherein a plurality of circumferential grooves are formed on an outer surface of said elastic seal member. 3. The hydraulic device according to claim 1, wherein the ring groove of the piston is constituted by two stages of an upper stage and a lower stage, the lower stage is formed by molding, and the upper stage is formed by cutting. Piston seal structure. 4. A molding die is pressed against the bottom of the ring groove of the piston to fill a space formed between the molding die and the bottom of the ring groove to form the elastic seal member. 4. The piston seal structure for a hydraulic device according to claim 1, wherein the elastic seal member is fixed to a bottom of the ring groove.