JPH0381024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shock absorber such as that used in a vehicle suspension system. More specifically, the buffer of the present invention includes:
This invention relates to a double-cylinder hydraulic shock absorber, which is composed of a double cylinder whose upper and lower sides are connected to each other, and in which compressed gas is sealed in the upper part of a reservoir defined between the inner and outer cylinders, and the lower part is filled with liquid.

[Conventional technology]

In this type of shock absorber, due to air ration that occurs during vehicle operation or operation, it is necessary to return the air that entered the working cylinder provided by the inner cylinder to the space between the inner and outer cylinders, and in the compression stroke, Since the pressure in the reservoir chamber provided by the cylinder increases somewhat, it is necessary to prevent air from entering the inner cylinder at this time.

As a known hydraulic shock absorber that provides such a function, for example, there is a one-way valve in which the proximal end is fixed to a rod guide and the distal end is in contact with the outer periphery of the piston rod so that it can move toward and away from the piston rod. 47−16873
No., Italian Patent No. 549781, British Patent No.
No. 1077587). However, in such a device, the tip side is always in contact with the outer periphery of the piston rod. For this reason, the tip side is extremely easily thermally deformed due to the heat of sliding, resulting in deterioration and deformation of the material and shape in a short period of time. Moreover, constant contact between the tip end and the piston rod causes the tip end to wear out very easily. Furthermore, since the tip side is always driven by even the slightest movement of the piston rod, fatigue accumulates on the tip side. As a result, the valve itself has a very short service life.

Another known example is a one-way valve by providing an O-ring inside a rod guide and expanding and contracting it in the radial direction (Japanese Patent Publication No. 46-36526).
In this device, an O-ring made of rubber or other flexible material is mounted in an elastically stretched state in an annular recess in a rod guide, and permanently seals the entrances of a number of radially extending passages. It is elastically compressed and retained on the inlet portion as shown in FIG. However, since the O-ring is compressed and held in an annular recess, it is very difficult to control the operating pressure of the O-ring, and in addition, since the O-ring has a circular cross section, it is ensured that the O-ring will pass through the passage. Before returning to the closed position, fluid movement from between each wall surface and the O-ring surface occurs frequently, making it difficult to expect desired pressure control. Furthermore, since there is no fixed part of the O-ring when the diameter is expanded, the entire O-ring deforms freely, making it easy for unexpected backflow of high-pressure air to occur, making it difficult to function as a check valve. A defect exists.

Furthermore, a one-way valve is known in which an annular lip is integrally provided on the sealing member, and the tip of the lip is brought into contact with the upper surface of the rod guide so as to be able to move toward and away from the rod guide (Utility Model Publication No. 48-25495). However, in such a device, a flexible annular lip (one-way valve) is integrally formed at the lower end portion of the inner portion of the oil seal serving as the sealing member that slides into contact with the piston rod. This lip abuts the upper surface of the flat rod guide in the axial direction, thereby achieving a seal between the vents. That is,
Since the oil seal is in sliding contact with the surface of the reciprocating piston rod and scraping oil from the surface of the piston rod, the oil seal is constantly subjected to vertical movement due to the reciprocating movement of the piston rod. The lip formed integrally with the receiving oil seal is similarly subjected to vertical movement in the axial direction, and its axial position changes. Therefore, the lip always has variations in its opening load, and normal sealing function cannot be expected. In addition, extremely precise and careful work is required when assembling this annular lip. That is, if there is variation in the axial dimension of the annular lip, a similar variation will occur in the valve opening load of the lip. If a valve opening load is generated due to such poor assembly, it will act synergistically with the above-mentioned variation in the valve opening load due to the sliding of the piston rod, resulting in a disadvantage that a normal sealing action cannot be expected at all. Furthermore, since the one-way valve and the sealing member are integrally molded, it is not possible to construct the sealing member with a material that has a rich sealing action, and the one-way valve with a material that has a rich valve action. It is not possible to form each member using a material that can exhibit the following properties.

[Problem to be solved by the invention]

In order to overcome the drawbacks of such known devices, the present invention is capable of functioning reliably as a one-way valve and increases its durability, thereby ensuring stable operation of the device itself and extending its service life. It provides an increased buffer.

Further, the present invention provides a shock absorber in which the sealing member and the one-way valve can be constructed of materials that can exhibit their respective optimal functions, so that the sealing member and the one-way valve can exhibit optimal workability.

[Means to solve the problem]

In order to solve the above problems, the present invention has an operating cylinder filled with oil, an outer cylinder loosely fitted radially outwardly of the operating cylinder, and an upper cylinder between the operating cylinder and the outer cylinder. a piston rod having a piston at its lower end that slides in the axial direction within the working cylinder; a rod guide that closes the upper part of the working cylinder and fits and guides the piston rod; and a piston rod that is fixed above the rod guide. A sealing member is placed at an interval of An annular one-way valve whose side is pressed and positioned by a spring member, whose tip side extends in the axial direction and whose diameter can be expanded and contracted in the radial direction, and which is configured separately from the sealing member, and a valve that is radially outward from the outer periphery of the piston rod. an annular valve seat surface located on one side and extending in the axial direction along the outer periphery of the piston rod, and on which the distal end side of the annular one-way valve expands and contracts in diameter in the radial direction to separate and seat;
A gap is defined between the rod guide and the sealing member by the piston rod, a one-way valve, and a valve seat surface, and communicates with the inside of the working cylinder through a gap between the piston rod and the rod guide, and the gap communicates with the gas chamber. The one-way valve allows the flow from the gap to the gas chamber by expanding the diameter of the distal end side in the radial direction and separating from the valve seat surface, but allows the flow in the opposite direction. The present invention provides a hydraulic shock absorber characterized in that the distal end side is seated on a valve seat surface to prevent damage.

〔Example〕

FIG. 1 is a sectional view of a shock absorber according to the present invention, and numbers 1 and 2 are eye fittings for mounting on the sprung and unsprung parts of a vehicle, respectively. A piston rod 3 is fixed to the eye fitting 1, and the other end of the rod 3 is provided with a piston 11 having a known disc valve 10 for generating both expansion and contraction damping force on the shock absorber. The piston 11 slides in an oil-filled working cylinder 4. The upper end of the cylinder 4 is sealed by a rod guide 9 that guides the piston rod 3, and the lower end of the cylinder is fitted into and held by a sealing cap 12 fixed to the eye fitting 2. There is a notch at the lower end of the cylinder 4, which forms a passage 5. The passage 5 communicates with the inside of the cylinder 4 and with the inside of the outer cylinder 13 whose lower end is sealed and held by the outer wall surface of the sealing cap 12, that is, with the reservoir chamber 6.
The upper end of the outer cylinder 13 is hermetically supported by the hanging part of the packing cap 7 which holds the rod guide 9. The seal cap 7 is composed of an inner seal member 19 that seals the inside and outside of the cylinder between the cap 7 and the rod guide 9, and a holding member 20 that holds the outer seal member 19 that constitutes a one-way valve. Sealing means 2
It has 8. The sealing member 19 is a tight fit on the rod 3. On the other hand, the holding member 20 is urged toward the packing cap 7 from the rod guide 9 by a spring 15 interposed between the rod guide 9 and an annular spring receiver 14 supporting the lower part of the holding member 20. There is. The holding member 20 also has an annular protrusion 21 extending downward in the radial direction.

The rod guide 9 has an annular recess for receiving one end of the spring 15 so as to maintain a predetermined gap from the sealing member 19 and the holding member 20. The valve has a protrusion 9a forming a valve seat surface, and the protrusion 21 of the holding member 20 is in contact with this portion from the radial direction. In addition, there is a piston rod 3 in the center part.
A hole having a diameter slightly larger than the diameter of the piston rod 3 is provided, through which the piston rod 3 is inserted. A gap passage 16 is formed between the hole and the piston rod 3. The passage 16 is connected to the working cylinder 4
The inside of the piston 10 is communicated with a gap 17 formed by the sealing member 19, the holding member 20, the piston rod 3, and the rod guide 9. Further, the rod guide 9 has one or more grooves on its outer circumferential portion, and the grooves form a passage 9b between the rod guide 9 and the hanging portion of the packing cap 7. The passage 9b includes a reservoir chamber 6, a space 18 formed by the holding member 20, the rod guide 9, and the packing cap 7,
are communicating. The void 17 and the space 18 are the outer wall surface of the annular protrusion 9a of the rod guide 9, and as will be described later, there is a surface that acts as a valve seat and a surface that contacts that surface from the radially outward direction. It is separated by a protrusion 21 of the holding member 20 which functions as a one-way valve. Note that the holding member 20 and the protrusion 21 constitute a one-way valve, and the holding member 2
0 is the proximal end of the one-way valve, and the protrusion 21 is the distal end thereof.

As is known to those skilled in the art, oil is filled in the upper and lower chambers of the actuating cylinder 4 and lower in the reservoir chamber 6.
Further, compressed gas is sealed above the reservoir chamber 6 to form a gas chamber therein.

In this device, when the piston rod 3 is pushed into the working cylinder 4, the oil located below in the working cylinder 4 is pressurized by the piston 11 fixed to the piston rod 3. The pressurized oil flows through the disc valve 1 provided on the piston 11.
The outer peripheral edge of the piston 11 is bent upward to form a flow path, which flows into the chamber above the piston 11, generating a damping force at this time. Further, the oil increased when the piston rod 3 enters the working cylinder 4 flows into the reservoir chamber 6 through the passage 5. Even if the pressure of the compressed gas in the gas chamber above the reservoir chamber 6 increases by the volume of oil entering and moves into the space 18, the annular protrusion 21 forms the space 18 toward the valve seat formed by the protrusion 9a. Since the one-way valve is seated and blocks the flow of compressed gas from the space 18 to the cavity 17, the passage 16, and the working cylinder 4, the compressed gas that has moved to the space 18 will not flow into the working cylinder 4. will not enter.

Next, the piston rod 3 extends and the piston 11
When the piston 11 in the working cylinder 4 rises, the piston 11 in the working cylinder 4
The oil above is pressurized. A portion of the oil above the piston 11 enters the cavity 17 via the passage 16. When the piston rod 3 further extends and the oil fills the gap 17, the fluid in the gap 17 opens the protrusion 21 and flows through the space 18 and the passage 9b to the reservoir chamber 6.
be returned to. At the same time, the remaining oil above the piston 11 bends the inner peripheral edge of the disc valve 10 downward, forms a flow path, and flows downward. At this time, a damping effect is obtained.

FIG. 2 is a partially enlarged view of the apparatus of the present invention. The sealing member 19 is tightly fitted into the rod 3 and performs the original function of a seal. On the other hand, a holding member 20 is provided between the seal member 19 and the packing cap 7 so as to be engaged with the outer surface of the seal member 19 and to be able to deflect outwardly but to be restricted from deflecting inwardly.
The annular protrusion 21 simply engages with the valve seat portion 9a of the rod guide 9 to perform a one-way valve action without contacting the rod 3 at all. For this reason, the holding member 20 can be shaped like a plate similar to the spring receiver 14, and furthermore, the holding member 20 can be arranged upward between the lower end of the spring 15 and the rod guide 9. Configuring the sealing member 19 and the holding member 20 separately is advantageous because the temperature of the sealing part that contacts the rod 3 becomes very high due to the heat of sliding, so only that part is made of a heat-resistant material (for example, fluorocarbon rubber). ) is the best structure when you want to use it.

〔Effect of the invention〕

The present invention has a structure in which the one-way valve and the valve seat surface can overlap in the axial direction. Therefore, in addition to good sealing performance, even if some dimensional variation or assembly error occurs in the axial length of the cylinder, outer cylinder, rod guide, sealing means, etc.
These variations or errors are completely absorbed, and no inconvenience occurs in the operation of the valve member. Further, due to such an overlap structure, even if the pressure in the reservoir increases, the valve body is easily supported by the valve seat surface, and therefore, the valve body does not buckle.
This also allows the wall thickness of the valve body to be made thinner.
Therefore, the valve opening pressure can be made extremely low, and the gas accumulated in the inner cylinder can be immediately returned to the reservoir, making it possible to maintain the damping force characteristics set by the hydraulic shock absorber.

Further, in the present invention, the sealing member and the one-way valve member are constructed as separate and independent members. Therefore, in the present invention, it is possible to select the most suitable material for each member, and it is possible to always perform a normal check valve function as a one-way valve.

Furthermore, the present invention has a structure in which the one-way valve does not touch the piston rod. Therefore, the one-way valve is not affected by wear caused by sliding of the piston rod, and its durability can be improved.

Further, as a result of the above-mentioned effects, the present invention can provide a shock absorber that ensures stable operation of the device itself and increases its useful life.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the shock absorber of the present invention, and FIG. 2 is an enlarged view of the seal portion of FIG. 1. Explanation of symbols, 1, 2... Eye fitting, 3... Piston rod, 4... Operating cylinder, 5... Passage,
6... Reservoir chamber, 7... Packing cap, 9
... Rod guide, 9b ... Passage, 10 ... Disc valve, 11 ... Piston, 12 ... Sealing cap, 13 ... Outer cylinder, 14 ... Spring receiver, 15
...Spring, 16...Passway, 17...Gap, 18...
... Space, 19 ... Seal member, 20 ... Holding member, 21 ... Annular protrusion.

Claims (1)

[Claims] 1. An operating cylinder filled with oil, an outer cylinder loosely fitted radially outward of the operating cylinder, and an outer cylinder formed above between the operating cylinder and the outer cylinder. a gas chamber; a piston rod having a piston at its lower end that slides in the axial direction within the working cylinder; a rod guide that closes the upper part of the working cylinder and guides the piston rod in a fitted manner; A sealing member is placed between the rod guide and the sealing member, which seals the inside and outside of the hydraulic shock absorber, and is tightly fitted to the piston rod in a liquid-tight manner. An annular one-way valve that is pressed and positioned, has a distal end that extends in the axial direction and can expand and contract in the radial direction, and is configured separately from the sealing member; extending axially along the outer circumference of the piston rod,
A piston rod, a one-way valve, and a valve seat surface are defined between the rod guide and the seal member, and the piston rod and the rod guide a gap that communicates with the inside of the actuating cylinder through a gap between the valve and the gas chamber, and a passage means that communicates the gap and the gas chamber, and the one-way valve has a distal end that directs the flow from the gap to the gas chamber. What is claimed is: 1. A hydraulic shock absorber characterized in that the diameter is expanded in the radial direction and the buffer is allowed to flow out of the valve seat surface, but the flow in the opposite direction is blocked by the distal end being seated on the valve seat surface.