JPH0336724Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic cylinder used in a hydraulic system of general industrial machinery.

[Conventional technology]

A conventional hydraulic cylinder, a portion of which is shown in FIG. 3, will be explained.

In FIG. 3, the piston 2 is comprised of a cylinder tube 1 and a piston 2 which is slidably fitted into the cylinder tube 1 and integrally formed with a piston rod 3. The cylinder tube 1 and the piston 2 form a pressure chamber 1a on the bottom side and a pressure chamber 1b on the head side. When pressure oil is supplied to this pressure chamber 1a on the bottom side, the piston rod 3 moves rightward together with the piston 2 in FIG. 3. When pressure oil is supplied to the pressure chamber 1b on the head side,
The piston rod 3 moves to the left together with the piston 2 in FIG. The piston 2, which moves left and right within the cylinder tube 1 in this manner, is provided with a sealing member 4 at its center. This sealing member 4 includes a slipper seal 4a that comes into sliding contact with the inner surface of the cylinder tube 1, and a slipper seal 4a that comes into sliding contact with the inner surface of the cylinder tube 1.
A and an O-ring 4b that applies a pressing force to seal between the pressure chamber 1a on the bottom side and the pressure chamber 1b on the head side. Wear rings 5 are provided at both ends of this seal member 4. This wear ring 5 has a bearing function to hold the piston 2 as much as possible as shown in FIG. 3. That is, in the hydraulic cylinder, the piston rod 3 advances or retreats from the cylinder tube 1 by supplying pressure oil to the pressure chamber 1a on the bottom side or the pressure chamber 1b on the head side, as described above.
This is to relatively operate the equipment attached to the cylinder tube 1 and piston rod 3, respectively. In such an action, the piston rod 3 does not always operate in a normal state, but is deflected by buckling force due to a reaction force acting on the equipment.
For this reason, the piston 2 is also deflected, and the wear ring 5 receives the load due to this deflection. Therefore, the material selected is hard and has low sliding resistance. A dust ring 6 is provided further outside the wear ring 5.
This dust ring 6 contains foreign matter present in the pressure chamber 1a on the bottom side or the pressure chamber 1b on the head side (this foreign matter may be foreign matter that enters during the manufacture of the hydraulic cylinder or during the operation of the equipment, etc.). In particular, iron oxide has an extremely high altitude and is very fine. If such foreign matter enters between the wear ring 5 and the inner surface of the cylinder tube 1, the cylinder tube 1 will look like it has been scraped with sandpaper. Become,
The function of the seal member 4 is deteriorated. ) does not enter the wear ring 5.

[Problem that the invention attempts to solve]

The hydraulic cylinder having the above configuration has the following problems.

In this hydraulic cylinder, the dust ring 6 provided on the piston 2 is located inside the piston 2 by ΔL from the end surface of the piston 2, and forms a piston collar 2a. As mentioned above, the outer periphery of the piston collar 2a is in contact with the inner surface of the cylinder tube 1 even if the piston 2 is eccentric due to the buckling force acting on the piston rod 3 during operation of the hydraulic cylinder or the eccentric load acting on the piston rod 3. Just a gap △
S is provided. As described above, this gap ΔS is influenced by the buckling force acting on the piston rod 3 and the unbalanced load, and becomes larger or smaller than ΔS. Therefore, when dust enters the gap △S, buckling force or unbalanced load acts on the piston rod 3, and when the gap becomes smaller than the gap △S, the piston collar 2
Foreign matter will be caught between the outer periphery of a and the inner surface of the cylinder tube 1, and the inner surface of the cylinder tube 1 will be damaged as described above. In particular, the size of foreign objects is not homogeneous, and there are foreign objects of various sizes.If the gap △S is too large, the dust ring 6 will not be able to be held securely, and if it is too small, it will cause uneven loads and The piston collar 2a is formed on the inner surface of the cylinder tube 1 by bending force.
There is a problem where it hits and hurts. Therefore, it is necessary to form an appropriate gap ΔS. Therefore, there is a problem that the inner surface of the cylinder tube 1 is inevitably damaged.

[Means for solving problems]

Therefore, in order to solve the above-mentioned problems, the present invention has the following measures. That is, in a hydraulic cylinder in which a piston is slidably fitted in the axial direction of a cylinder tube and an elastic dust ring is attached to the end of the piston, the dust ring covers the outer periphery of the piston up to the end surface of the piston. At the same time, a protrusion having a gap between the piston and the cylinder tube was provided, and the thickness of the protrusion was set so that a foreign object having a size equivalent to the maximum eccentricity of the piston would fit therein.

[Effect]

In the present invention having the above-mentioned technical means, the protrusion of the dust ring covers the piston end face up to the piston end face and has a gap between it and the cylinder tube, so it actively traps foreign matter in this gap. let them get involved. The thickness of the protrusion is such that a foreign object having a size equivalent to the maximum eccentricity can be immersed therein, so that the foreign object will not enter the protrusion of the dust ring and damage the inner surface of the cylinder tube.

〔Example〕

Hereinafter, one embodiment of the present invention will be described below.
A case in which the present invention is applied to the hydraulic cylinder shown in Fig.) will be explained. 1 differs from the hydraulic cylinder shown in FIG. 3 in the structure of the dust ring attached to the end of the piston. The dust ring 8 used in this embodiment has a protrusion 8a on the outside that covers the piston outer circumference (separation ΔL) up to the piston end, leaving a gap ΔS between it and the cylinder tube 1. There is. Furthermore, the thickness ΔH of the protrusion 8a is determined under the following conditions.

Since the piston 2 slides while receiving an eccentric load or a biased load from the piston rod 3, a gap is created between the cylinder tube 1 and the dust ring 8, and the maximum value of this gap is approximately equal to the maximum amount of eccentricity of the piston 2. . In other words, foreign matter such as dust and iron powder is actively trapped in the gap ΔS up to a maximum eccentricity amount that may damage the inner surface of the cylinder tube, and is then trapped in the protrusion 8a to be collected. . To this end, the thickness ΔH of the protrusion 8a is set to be greater than the maximum eccentricity. In addition, in order to be able to insert a new foreign object into the protrusion 8a while a foreign object with a size equivalent to the maximum eccentricity remains immersed in the protrusion 8a, it is necessary to
Naturally, a thickness ΔH considerably exceeding the maximum eccentricity is required. In short, the thickness ΔH of the protrusion 8a is set to such a value that a foreign object corresponding to the maximum eccentricity of the piston can be immersed therein and the immersion state can be maintained. Since the dust ring 8 is made of a relatively hard elastic material such as synthetic resin, the first Sufficient thickness △H as shown
The protrusion 8a has the following.

Next, the operation of the hydraulic cylinder having the above-mentioned configuration will be explained with reference to FIG. FIG. 2a shows a case in which a gap ε approximately equal to the maximum eccentricity is created due to eccentricity of the piston, and FIG. 2b shows a case in which there is no eccentricity in the piston. In Fig. 2a, piston 2
When the piston slides while being subjected to an eccentric load or a biased load, and a gap ε approximately equal to the maximum eccentricity of the piston is created, a foreign object 9 whose size is equivalent to the maximum eccentricity tries to get caught in this gap ε. However, before that, in the state shown in FIG. 2b, the foreign matter 9 gets caught in the gap ΔS, enters the protrusion 8a, and is collected. By the way, the thickness ΔH of the protrusion 8a is such that a foreign object 9 having a size equivalent to the maximum eccentricity can be immersed therein.
The particles sink into the protrusion 8a and are collected. Therefore, these foreign substances 9 will not damage the inner surface of the cylinder tube 1.

[Effect of idea]

As is clear from the above description, according to the hydraulic cylinder of the present invention, the dust ring covers the outer circumference of the piston up to the end face of the piston, and is provided with a protrusion having a gap between the dust ring and the cylinder tube. The thickness of the part is set to a thickness that allows a foreign object equivalent to the maximum eccentricity of the piston to enter therein, so that the foreign object is actively caught in the gap between the protrusions. The thickness of the protrusion is such that a foreign object having a size equivalent to the maximum eccentricity can be inserted into the protrusion, and the foreign object will not be absorbed into the protrusion and damage the inner surface of the cylinder tube. Therefore, it is possible to prevent damage to the inner surface of the cylinder tube due to foreign substances such as dust and iron powder mixed in the oil, as well as a reduction in the sealing function due to this damage.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view showing an embodiment of the hydraulic cylinder of the present invention, Fig. 2 is a partial sectional view showing the operation of the same hydraulic cylinder, and Fig. 3 is a partial sectional view showing a conventional hydraulic cylinder. be. 1...Cylinder tube, 2...Piston, 3
...Piston rod, 8...Dust ring, 8a
...Protrusion, 9...Foreign object.

Claims (1)

[Claims for Utility Model Registration] A hydraulic cylinder in which a piston is slidably fitted in the axial direction of a cylinder tube, and an elastic dust ring is attached to the end of the piston, the dust ring extending up to the end face of the piston. A protrusion covering the outer circumference of the piston and having a gap between the piston and the cylinder tube is provided, and the protrusion has a thickness such that a foreign object having a size equivalent to the maximum eccentricity of the piston can enter therein. hydraulic cylinder.