JPS63270932A - Cylinder device - Google Patents

Abstract

PURPOSE:To prevent a viscous fluid from being leaked through the slide surfaces of a piston and a cylinder by forming the piston out of a ferrous material which is superior in workability and also forming a cylinder out of a steel material. CONSTITUTION:A piston 30 put in a cylinder 1 is provided with orifices 32, 33 and valve plates 34, 35, and these valve plates 34, 35 are opened and closed by the up and down movements of the piston 30 and display damping force by moving a viscous fluid in the cylinder 1. Also, a sealing member 40 is fixed at the outer perimeter of the piston 30, and prevents leakage at slide surfaces. As a result, the change of a putting-in precision due to a temperature change can be kept to a minimum and leakage through the slide surfaces can be made minimum by making the cylinder 1 out of a steel material and making the piston 30 out of a worked item of plasticity of a ferrous material.

Description

[Detailed description of the invention] "Technical field" The present invention relates to improvements in cylinder devices.

"Prior art and its problems" Cylinder devices that utilize hydraulic pressure are widely used in various fields of hydraulic equipment, but conventionally, the pistons have been formed by sintering, especially when the shape is complex. It was common. FIG. 3 shows an example of a shock absorber for a vehicle as a cylinder device having this type of piston. This shock absorber has one cylinder inside.
The lower end of the outer shell 2 housing the outer shell 2 is connected to a wheel (not shown), and the upper end of the piston rod 4 of the piston 3 slidably fitted into the cylinder 1 is connected to the vehicle body. The cylinder 1 is filled with a viscous fluid, and the chamber between the cylinder 1 and the outer shell 2 constitutes a viscous fluid reservoir 5. A guide bush 9 is fixed to the upper ends of the cylinder 1 and the outer shell 2, and the piston rod 4 passes through the guide bush 9 and the oil seal 6 and extends upward. 7 is an outer cylinder of the guide bush 9 and the oil seal 6.

As conceptually shown in the figure, the piston 3 has an orifice 10 passing through it in the axial direction, and a pulp 11 that opens and closes the orifice 10 as the piston 3 moves. Further, a seal member 12 is provided on the outer periphery of the piston 3 and is in sliding contact with the inner wall of the cylinder 1.

In the shock absorber described above, when an elastic force (vibration) is applied between the upper and lower ends of the shock absorber, that is, the upper end of the piston rod 4 and the lower end of the cylinder 1, the piston 3 slides relative to each other within the cylinder, and the pulp 11 opens and closes. The viscous fluid in the cylinder 1 then passes through the orifice 10. A damping force is exerted by the resistance of the viscous fluid at this time.

This damping force is determined in principle by the diameter and length of the orifice 10 and the opening/closing characteristics of the pulp 11. In particular, the recent seal member 12 has a high sealing performance, and almost no leakage occurs on the sliding surface between the pulp 11 and the piston 3, so it is natural to think that the damping characteristics are determined by the orifice 10 and the pulp [1]. Even if a small amount of leakage occurs from the sealing member 12, if the orifice 10 and pulp 11 are determined taking this leakage into consideration, the damping force can be easily set, and damping characteristics different from the set value, There should be no variation in damping characteristics. This damping characteristic is
In such a piston, this is considered as a leakage characteristic value.

However, when the present applicant calculated the orifice 10 and pulp 11 based on the required leak characteristic values and conducted an actual test, only the set leak characteristic values were not achieved. Unacceptable variations in leak characteristic values occur. Conventionally, the cause of this problem was found to be variations in the sealing performance of the seal member 12, and rough improvements to the seal member 12 were sought.

However, the good sealing performance of the sealing member 12 itself has been proven by, for example, basic evaluation tests on the sealing performance of individual sealing members, and even if the sealing performance of the sealing member 12 were to be improved from the current level, It is unlikely that this will have a significant effect on the performance (damping characteristics) of the shock absorber.

Due to these circumstances, it is virtually difficult to precisely set the characteristics of the shock absorber. At present, the cause of this is unknown.

``Object of the Invention'' Therefore, the present invention directly aims to provide a cylinder device in which the leak characteristics can be precisely set in the above shock absorber.

"Summary of the Invention" The present invention was developed after examining various reasons why it is not possible to set the leak characteristics in a shock absorber closely.
This was achieved by unexpectedly discovering that viscous fluid leaks from the piston itself. Leaking from the piston itself is a technological blind spot.

Considering the structure of the sintered piston, the sintered material is made by bonding microscopic powders under high temperature and pressure.
Microscopically, it is porous, and each pore can be considered to be continuous.In terms of foam, it is an open cell.

The present invention was made based on this discovery, and the idea was to construct the piston, which was conventionally constructed from a sintered material, from a non-sintered material (solid material), which has no possibility of leakage from itself. Based on this, the combination of materials and processing methods for the piston and cylinder was perfected after careful consideration.

That is, the cylinder device of the present invention is characterized in that the piston is made of a plastically worked product made of iron-based material with excellent workability and productivity, and the cylinder into which the piston is fitted is made of steel. Plastic working is at least
Forging and deep drawing (can be done in this way).

The combination of the plastically worked product of iron-based materials and the steel material has roughly similar coefficients of thermal expansion.
The effect is that the fitting accuracy between the piston and the cylinder can be maintained at a high level over a wide temperature range.

Therefore, leakage from the sliding surfaces of the piston and cylinder due to temperature changes can be minimized.

This means that it is not necessary to use a highly accurate sealing means between the piston and the cylinder that can compensate for deterioration in fitting accuracy due to temperature changes. In other words, this sealing means needs to be rougher than when there is a difference in thermal expansion coefficient between the cylinder and the piston that is larger than the difference in thermal expansion coefficient between the steel material and the iron-based material. Therefore, it is possible to obtain an inexpensive silicidation device as a whole.

However, this sealing means itself must be able to maintain substantially zero leakage from the sliding surfaces of the cylinder and the piston. If leakage at sliding surfaces cannot be reduced to virtually zero, the advantage of constructing the piston itself from a leak-free plastic product is offset, and such sealing means cannot be achieved with current sealing technology. , it is possible to measure it sufficiently.

The cylinder is made of drawn steel pipe, such as seamless steel pipe ST.
If it is formed from M, it can be manufactured at low cost.

Also, the piston is made of iron-based material, such as 515C1SIOC.
It is possible to forge low carbon w4 such as, and form it into a predetermined shape. Forging has better workability and productivity than machining such as cutting, and can be mass-produced if the shape is similar to the piston of a shock absorber.

Rough pistons can also be made by deep drawing of iron-based materials.
/ Can be formed with high processability and productivity.

For deep drawing, for example, hot rolled steel plates such as 5PHE, 5PC
A cold rolled steel plate such as E or the like can be used.

Although the cylinder device of the present invention was directly developed based on the discovery of the above-mentioned problems with the sintered piston of a shock absorber, it is a cylinder device that uses a single sintered piston. Generally applicable.

"Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. FIG. 1 shows an embodiment in which the present invention is applied to a cylinder device of a shock absorber, but as mentioned above, the present invention does not relate to the structure of the cylinder device, but to the material thereof. Therefore, the structure shown in FIG. Orifices 32 and 33 are formed, and valve plates 34 are provided on opposite end surfaces of the orifices 32 and 33, respectively.
．． 35 is in elastic contact via compression springs 36, 37, and normally closes the orifice 32, 33. pulp plate 3
4 opens when the piston 30 moves relatively downward in the cylinder 1 in the figure, and 35 opens when the piston 30 rises in the cylinder 1 to direct the viscous fluid in the cylinder 1 through orifices 32 and 33 to the top and bottom of the piston 30. move it to The viscous resistance at this time exerts a damping force.

A seal member 40 is fixed to the outer periphery of the piston 30,
This seal member 4o comes into sliding contact with the cylinder 1. This seal member 4o substantially eliminates leakage between the sliding surfaces of the cylinder 1 and the piston 30 (seal member 40).

Further, the present invention provides, for example, a cylinder device for a shock absorber configured as described above, in which the cylinder 118
: Constructed from steel material, and characterized in that the piston 30 is constructed from a plastically worked product of iron-based material.

According to this combination, since the coefficients of thermal expansion of the cylinder 1 and the piston 30 are similar, the fitting precision between the cylinder 1 and the piston 30 can be maintained at a high level even if there is a temperature change. Therefore, leakage from the sliding surfaces of the cylinder 1 and piston 3o due to temperature changes can be minimized.

Therefore, there is no need to use a highly accurate sealing member 40 that can compensate for deterioration in fitting accuracy due to temperature changes, and an inexpensive sealing member of 4° may be sufficient, resulting in overall cost reduction.

In the sealing means shown in FIG. 1, a cylindrical sealing member 40 covering the outer periphery of the piston 3° is made of a low-friction synthetic resin, such as a resin containing polytetrafluoroethylene (PTFE) or PTFE. The seal member 40 is formed from a seal member, and both ends of the seal member 40 in the axial direction are formed into engaging portions 44 that deeply engage inside the piston 30. It has an hourglass shape in which the contact pressure with the inner circumferential surface of the cylinder 1 is high at the middle part of the cylinder.

FIG. 2 shows another example of the sealing means, in which an annular groove 38 is formed on the outer periphery of the piston 30 and is made of a low-friction synthetic resin, such as polytetrafluoroethylene (PTFE).
Alternatively, an annular projection 41 that engages with the annular groove 38 is provided on the inner surface of the seal member 40 made of resin containing PTFE. The tip of each protrusion 41 has a semicircular cross section with a diameter equal to the width of the annular groove 38. Further, an engaging portion 42 that deeply engages inside the flange 39 at the end of the piston 30 is provided at the end of the seal member 40 on the side where the piston rod 4 is not located in the axial direction. The end portion of the piston 30 is an extended cylindrical portion 43 that extends from the piston 30 in a cylindrical shape. This extended cylindrical portion 43 (or seal member 4o
The entire body is fixed on the engaging portion 42 side, has elasticity that tends to open outward in the radial direction, and generates effective sealing pressure between it and the cylinder 1.

According to these structures, the seal member 40 and the piston 30
are firmly connected to each other, and leakage from the sliding surface can be reduced to substantially zero.

Next, the present invention will be explained in detail based on experimental results.

"Sample 1" When a fluid pressure of 24 kg/cm was applied to one end surface,
A sintered piston that leaked 4 to 7 cc/cm.

"Sample 2" Forged iron piston (material 815G).

"Sample 3" Deep drawn iron product (material 5PCE).

For Samples 2 and 3 above, leakage was measured under the same conditions as Sample 1, that is, when a fluid pressure of 24 kc+/cm was applied to one end surface, and no leakage occurred in either case.

"Effects of the Invention" As described above, according to the cylinder device of the present invention, a piston made of a plastically processed iron-based material is used instead of a stone made of a sintered material, and the cylinder is made of steel. There is no chance of fluid leaking through it. Since the coefficients of thermal expansion of the piston and cylinder are similar, it is possible to maintain the fitting accuracy of the piston and cylinder over a wide temperature range, making it easier to prevent leakage from sliding surfaces. In addition, leakage from the sliding surfaces of the piston and cylinder can be reduced to substantially zero by using a simpler sealing means. Since the rough piston is formed by plastic working such as forging and deep drawing, workability and productivity comparable to those of sintering can be obtained. In addition, the cylinder can be formed by drawing steel pipes, so it has good workability as a whole, especially when a specific damping characteristic is required, such as a shock absorber.
By eliminating fluid leakage from the piston, the damping characteristics (leak characteristics) can be determined almost uniquely by the characteristics of the orifice and the on-off valve. Therefore, design becomes easier and more highly controlled damping characteristics (leakage characteristics ff) can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the cylinder device according to the present invention, FIG. 2 is a sectional view showing another example of the sealing means, and FIG. 3 is a sectional view showing an example of a conventional shock absorber as a cylinder device. It is a diagram. 1... Cylinder, 30-... Piston, 31... Fixing nut, 32.33... Orifice, 34.35-
...Pulp plate, 36.37-...Compression spring, 40
... Seal member.

Claims (7)

[Claims] (1) In a cylinder device in which a piston that receives hydraulic pressure is fitted into a cylinder, and a sealing means is interposed between the cylinder and the piston, the cylinder is formed from a steel material, and the piston is a plastically worked product of iron-based material. A cylinder device characterized in that it is formed from. (2) The cylinder device according to claim 1, wherein the cylinder is made of a drawn steel pipe. (3) The cylinder device according to claim 1 or 2, wherein the cylinder and the piston are those of a shock absorber. (4) The cylinder device according to any one of claims 1 to 3, wherein the sealing means substantially eliminates leakage from a sliding surface between the cylinder and the piston. (5) In claim 4, the sealing means:
The cylinder device is a low-friction synthetic resin layer fixed to the outer circumference of the piston. (6) In claim 5, the synthetic resin layer is
A shock absorber that is shaped like a drum, with both ends engaging inside the piston and the middle part contacting the inner surface of the cylinder with the highest contact pressure. (7) In claim 5, the synthetic resin layer is
A shock absorber having elasticity in a direction in which one end in the axial direction engages inside the piston, and at least the other end expands in diameter to strongly engage the cylinder.