JP2000002207A - Hydraulic cylinder - Google Patents

Abstract

(57) [Problem] To provide a hydraulic cylinder in which a pipe does not come off without machining a hole diameter of an oil passage and a pipe outer diameter with high precision. SOLUTION: A piston rod is movably inserted into a cylinder via a piston, the piston partitions a rod-side oil chamber and a piston-side oil chamber in the cylinder, and the piston-side oil chamber is selectively connected to a pump or a tank. The rod-side oil chamber communicates with a reservoir in the piston rod via an oil hole formed below the piston rod, and a fitting portion for connecting the piston rod is raised at the upper end of the piston, and is fitted with the piston. A central hole communicating with the reservoir and the piston-side oil chamber is formed in the joint, and a relief valve is provided in the middle of the central hole so as to be openable and closable. In the hydraulic cylinder into which the outer periphery is inserted, a thin-walled cylindrical portion is erected on the rim of the center hole of the fitting portion, and the base outer periphery of the pipe is inserted through the cylindrical portion into the center hole of the fitting portion. Press it into the top You.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder mounted on, for example, a forklift for lifting and lowering cargo.

[0002]

2. Description of the Related Art As this type of hydraulic cylinder, for example,
The hydraulic cylinder shown in FIG. 3 has been developed. The hydraulic cylinder has a bottom 15 and a bearing 1 at both ends of the cylinder 14.
6 is provided, and a piston rod 18 is movably inserted into the cylinder 14 via the piston 17 and the bearing 16. The piston 17 partitions a rod-side oil chamber 19 and a piston-side oil chamber 20 within the cylinder 14. The rod-side oil chamber 19 communicates with a reservoir 22 in the piston rod 18 through an oil hole 21 formed below the piston rod 18,
In the central passage 23 of the piston 17, the reservoir 22
Relief valve 24 for opening and closing the oil chamber 20 and the piston side oil chamber 20
The piston side oil chamber 20 is selectively connected to a pump or a tank via an external switching valve through an oil passage 26 formed in the bottom 15.

Further, the piston 17 comprises a piston body 33, and a fitting portion 34 for connecting the piston rod 18 is integrally erected at the center of the upper end of the piston body 33. A hollow portion along the axial direction is formed as an oil passage 23.

At the upper end of the inner periphery of the fitting portion 34, a pipe 41 stands upright. The amount of oil in the rod-side oil chamber 19 required for the cushion at the height of the pipe 41, in other words, is higher than the upper end of the oil hole 21. It regulates the height of the oil level.

The lower portion of the pipe 41 is press-fitted into the inner periphery of the hollow portion of the fitting portion 34, and a step formed on the outer periphery of the pipe 41 is locked to the upper end of the fitting portion 34. The center of the pipe 41 connects the reservoir 22 and the oil passage 23.

The above-mentioned hydraulic cylinder is mounted on, for example, a forklift for raising and lowering luggage. In this case, when high-pressure oil is supplied from the pump to the piston-side oil chamber 20, the piston 17 and the piston rod 18 rise, The load supported by the outer end of the piston rod 18 rises.

When lowering the load or lowering the piston rod 18 independently from the extension operation, the piston-side oil chamber 20 may be connected to the tank via a switching valve.
This causes the piston rod 18 to descend to the most compressed position due to its own weight and the weight of the piston rod 18.

[0008]

The above-mentioned conventional hydraulic cylinder is not particularly defective in function, but the following improvement is desired.

That is, the pipe 41 composed of a raw pipe is connected to the oil passage 23.
Although it is press-fitted into the barrel hole, the hole diameter is set smaller than the outer diameter of the pipe 41 to prevent the pipe from coming off in this case.

For this reason, when the pipe 41 is pressed into the hole, the rigidity of the pipe 41 is smaller than that of the thick fitting portion 34 because the pipe 41 is formed to be thin. Pressing and holding is performed only at the mouth of the small hole, and there is a possibility that the hole will be pulled out with a small force.

Therefore, it has been found that if the dimensions of the pipe outer diameter and the hole diameter are set with high precision so that the pipe 41 does not plastically deform and maintain a predetermined stress, the holding force is increased. Processing the diameter and hole diameter with high precision is economically disadvantageous.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic cylinder in which a pipe is prevented from coming off without machining a hole diameter for an oil passage and a pipe outer diameter with high precision.

[0013]

In order to achieve the above-mentioned object, a means of the present invention is that a piston rod is movably inserted into a cylinder via a piston, and the piston is provided in the cylinder with a rod-side oil chamber and a piston. The piston-side oil chamber selectively communicates with a pump or a tank, the rod-side oil chamber communicates with a reservoir in the piston rod through an oil hole formed below the piston rod, and a piston-side oil chamber is formed. At the upper end of the piston, a fitting part for connecting the piston rod is erected, and the piston and the fitting part are formed with a central hole communicating the reservoir and the piston side oil chamber, and a relief valve is provided in the middle of the central hole. In a hydraulic cylinder, which is provided to be openable and closable, and further inserts a base end outer periphery of a pipe into an upper portion in a center hole of the fitting portion, a thin-walled cylindrical portion is erected on an edge of the center hole of the fitting portion, Through this tube The base end outer periphery of the pipe is characterized in that is pressed into a central bore in the upper of the fitting portion.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a hydraulic cylinder according to an embodiment of the present invention. As in a conventional hydraulic cylinder, a bottom 15 and a bearing 16 are provided at both ends of a cylinder 14, and a piston 17 and a piston rod 18 are movably inserted into the cylinder 14 via the bearing 16 described above. Defines a rod-side oil chamber 19 and a piston-side oil chamber 20 in the cylinder 14, and the rod-side oil chamber 19 communicates with a reservoir 22 in the piston rod 18 via an oil hole 21 formed below the piston rod 18. A relief valve 24 for opening and closing the reservoir 22 and the piston-side oil chamber 20 is provided in a hole serving as a central passage 23 of the piston 17 through a freely openable and closable valve. Ton side oil chamber 20 is obtained so as to be selectively communicating via an external switching valve to the pump or tank through an oil passage 25 formed in the bottom 15.

A cap is connected to the upper end of the cylinder 14 via a screw and a seal. The bearing 16, an oil seal and a dust seal are provided on the inner periphery of the cap to guide the piston rod 18.

A bearing 31 and a seal 32 are provided on the outer periphery of the piston 17, and the piston 17 slides on the inner periphery of the cylinder 14 via the bearing 31 and the seal 32.

The piston 17 comprises a piston body 33, and a piston rod 18 is provided at the center of the upper end of the piston body 33.
Are formed integrally with each other, and a hole extending in the axial direction is formed as the oil passage 23 in the center between the piston body 33 and the fitting portion 34.

A hollow valve housing 35 is fixed below the hollow portion of the piston 17, that is, on the inner periphery of the piston body 33 via a seal and a stopper.
A step is formed above the inner periphery of the valve housing 3 and the valve housing 3
The relief valve 24 composed of a valve body 36 and a spring that presses the valve body 36 toward the step portion is inserted into 5.

When the piston rod 18 is extended in a state in which the oil amount in the rod-side oil chamber 19 is increased due to oil leakage from the seal 32 or the like, the pressure in the lot-side oil chamber 19 rises due to the contraction thereof. And rod side oil chamber 1
In some cases, the internal pressure in the reservoir 9 and the reservoir 22 may rise abnormally. At this time, the valve body 36 opens against the spring by this internal pressure, and the pressure in the reservoir 22 is released to the piston side oil chamber 20.

The lower part of the piston rod 18 is formed in a cylindrical shape so as to partition the reservoir 22 composed of an oil chamber and a gas chamber below. Is fitted around the outer periphery.

Opposite grooves are formed between the outer periphery of the fitting portion 34 and the base recess 18a of the piston rod 18 forming the reservoir 22, and the snap ring 3 fitted in this groove is formed.
7 or another stopper is fitted to fix the base end of the piston rod 18 to the fitting portion 34.

A conical taper 38 is formed on the outer periphery of the upper end of the fitting portion 34. In order to fit the snap ring 37 into the above-mentioned groove, the snap ring 37 is fitted into the groove of the piston rod 18 in advance and then forcibly. When the base end of the piston rod 18 is fitted downward into the fitting portion 34, the snap ring 37 is guided by the taper 38 and can be mounted while smoothly expanding the diameter.

Further, a throttle hole 39 is also formed at the lowermost end of the piston rod 18, and the throttle hole 39
The oil hole 40 communicates with the throttle hole 39 and the oil passage 4.
The lower part of the rod-side oil chamber 19 communicates with the reservoir 22 via the “0”.

The lower oil hole 21 formed in the piston rod 18 communicates with the rod-side oil chamber 19 and the reservoir 22, and when the piston rod extends and the oil hole 21 is closed by the bearing 16, the rod-side oil chamber is closed. The flow from 19 to the reservoir 22 has a throttle effect. Also, the throttle hole 39
Is to allow the oil in the rod-side oil chamber 19 to flow out to the reservoir 22 while squeezing the oil, even if the oil hole 21 is closed by the bearing 16, so that the piston 17 can move to the extended state in which the piston 17 hits the cap.

At the upper end of the inner periphery of the fitting portion 34, a pipe 41 is erected. The amount of oil in the rod-side oil chamber 19 required for the cushion at the height of the pipe 41, in other words, is higher than the upper end of the oil hole 21. It regulates the height of the oil level.

The center of the pipe 41 is connected to the reservoir 22 and the oil passage 2.
3 is connected. By the way, in the present invention, a thin-walled cylindrical portion 46 is erected on the upper edge of the oil passage 23 which is the center hole of the fitting portion 34, and the outer periphery of the base end of the pipe 41 is moved through the cylindrical portion 46 as described above. The oil passage 23 is press-fitted into the upper part in the center hole.

In this case, the outer diameter of the pipe 41 is
When the pipe 41 is press-fitted and the pipe 41 is press-fitted, the cylindrical portion 46 is thin and has low rigidity, so that the generated stress of both becomes an approximate value. Thereby, the pipe can be press-fitted without being plastically deformed, and a holding force can be obtained.

Therefore, a sufficient holding force can be obtained even if the pipe 41 is press-fitted in the state of a raw tube.

It is preferable to provide a slight taper at the opening of the cylindrical portion 46 so that the pipe 41 can be easily viewed.

Similarly, the entire pipe 41 is formed by cutting a base tube to a predetermined length, but may be tapered or chamfered at a lower end portion so as to easily look into a central hole serving as the oil passage 23. The operation of press-fitting the pipe 41 is extremely easy if a predetermined press-fit amount is performed by a press while guiding the pipe 41 with a predetermined jig.

When the base end of the pipe 41 passes through the cylindrical portion 46 and further enters the oil passage 23, the pipe 41 is gradually pressed down by a taper, so that the pipe 41 is pressed down while maintaining a slight tension. .

The above-mentioned hydraulic cylinder is mounted on, for example, a forklift to lift and lower a load. In this case, when high-pressure oil is supplied from the pump to the piston side oil chamber 20, the piston 17 and the piston rod 18 rise, and the load supported by the outer end of the piston rod 18 rises.

In the vicinity of the maximum extension, the upper oil hole 21 is gradually narrowed by the bearing 16, and the oil in the rod-side oil chamber 19 flows out to the reservoir 22 through the narrowed oil passage, so that the cushion is gradually effective.

At the time of the maximum extension, the upper oil hole 21 is closed, but the lower throttle hole 39 is open.
7 can be extended until it abuts the upper cap.

When the load is lowered or the piston rod 18 is lowered independently from the extension operation, the piston side oil chamber 20 is connected to the tank via the switching valve. In this case, the load and the piston rod 18 move down to the most compressed position by their own weight.

In the above-described hydraulic cylinder, the fitting portion is raised above the piston, and the base end of the piston rod is fitted to the fitting portion. Therefore, no dead space is formed between the fitting portion and the piston rod. Therefore, unnecessary oil does not remain, and the oil can be used effectively.

Further, since the pipe is press-fitted into the fitting portion 34, welding work is unnecessary, and since the pipe 41 is assembled while being pressed into the fitting portion 34, the pipe mounting work is improved. . Further, since welding is unnecessary, spatters and the like do not enter the oil.

[0038]

According to the present invention, the following effects can be obtained.

A thin-walled tubular portion is erected at the upper end of the fitting portion, and the base end of the pipe is pressed into the central hole of the fitting portion via this tubular portion. The stress generated with the pipe is an approximate value, and even if the press-fitting allowance is set large by the spring effect, the elasticity of the cylindrical part can obtain the holding force even with the press-fit without plastic deformation of the pipe. Even if there is, it does not come off, and it can be prevented that the cushion oil comes off. Therefore, a sufficient holding force can be obtained even if the pipe is press-fitted with the material size.

A fitting portion is erected at the center of the upper end of the piston,
Since the base end of the piston rod is fitted to this fitting portion, no annular space is formed between the outer periphery of the fitting portion and the inner periphery of the base end of the piston rod, and thus unnecessary oil remains. Nothing. Therefore, the entire amount of oil can be used effectively.

Similarly, since the pipe is press-fitted into the upper portion of the inner periphery of the fitting portion and raised, the work of mounting the pipe is improved, and welding is not required. Therefore, the problem that contamination generated during welding remains is eliminated. Is done.

[Brief description of the drawings]

FIG. 1 is a partially enlarged front view of a hydraulic cylinder according to an embodiment of the present invention.

FIG. 2 is a partially cutaway front view of the hydraulic cylinder.

FIG. 3 is a vertical sectional front view of a conventional hydraulic cylinder.

[Explanation of symbols]

 14 Cylinder 15 Bottom 16 Bearing 17 Piston 18 Piston rod 19 Rod side oil chamber 20 Piston side oil chamber 21 Oil hole 22 Reservoir 24 Relief valve 33 Piston main body 34 Fitting part 37 Snap ring 38 Taper 40 Oil passage 41 Pipe 46 Tube part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Fujii 2-4-1 Hamamatsucho, Minato-ku, Tokyo World Trade Center Building Kayaba Industry Co., Ltd. F-term (reference) 3F333 AA02 AB13 BD02 BE02 DB03 DB08 FH02 3H081 AA03 BB02 CC20 DD02 HH03

Claims (1)

[Claims] 1. A piston rod is movably inserted into a cylinder via a piston, the piston partitions a rod-side oil chamber and a piston-side oil chamber in the cylinder, and the piston-side oil chamber is selected from a pump or a tank. The rod-side oil chamber communicates with the reservoir in the piston rod through an oil hole formed below the piston rod, and a fitting portion for connecting the piston rod is raised at the upper end of the piston, and A central hole communicating with the reservoir and the piston side oil chamber is formed in the fitting portion, and a relief valve is provided in the middle of the central hole so as to be openable and closable. In the hydraulic cylinder where the base outer circumference is inserted,
A hydraulic cylinder characterized in that a thin cylindrical portion is erected on the edge of the center hole of the fitting portion, and the outer periphery of the base end of the pipe is press-fitted into the upper portion of the fitting portion through the cylindrical portion. .