JP2004286123A - Sealing structure for hydraulic cylinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing structure for a hydraulic cylinder, reducing maintenance costs without giving influences to the operating property of the hydraulic cylinder by preventing the leakage of operating oil over a long period. <P>SOLUTION: The hydraulic cylinder comprises a cylinder tube 2, a piton 8 to be moved in the cylinder tube with the supply control of the operating oil, and a piston rod 12 fixed to one end of the piston in its moving direction for transmitting the movement of the piston as linear motion to the outside. On the inner periphery of a rod cover which is fixed to one end of the cylinder tube and inserted through the piston rod, an annular sealing member 40 is arranged which is in close contact with the outer periphery of the piston rod. Sealing hydraulic pressure Ps is generated toward the outer periphery of the piston rod for granting thrust to the sealing member 40 at all times. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a generally used hydraulic cylinder seal structure.
[0002]
[Prior art]
For example, a universal rolling mill used for rolling an H-section steel includes a pair of upper and lower horizontal rolls and a pair of left and right vertical rolls, and rolls a web of a material to be rolled down with a pair of horizontal rolls to form a material to be rolled. This device rolls and manufactures H-section steel by rolling down the flange with a pair of vertical rolls. A pair of horizontal rolls and a pair of vertical rolls of this universal rolling mill are each connected with a pressing device, and the operation of each pressing device adjusts the position of the pair of horizontal rolls and the pair of vertical rolls, thereby increasing the height. Manufactures H-beams with dimensional accuracy.
[0003]
Here, a hydraulic cylinder is generally used as the screw-down device.
As shown in FIG. 3, for example, the hydraulic cylinder includes a cylindrical cylinder tube 2, a head cover 4 and a rod cover 6 fixed to both ends of the cylinder tube 2 in the axial direction, and an axial direction in the cylinder tube 2. The piston 8 includes a sliding piston 8, oil passages 10a and 10b communicating with the cylinder chambers 2a and 2b, and a piston rod 12 fixed coaxially to one end face of the piston 8 and protruding outside from the rod cover 6. I have. When the control valve 14 is operated by the control signal of the hydraulic control unit 13, the hydraulic oil generated by the hydraulic source 16 is supplied to one of the cylinder chambers 2a, 2b via one of the hydraulic oil supply pipes 18a, 18b. The position of the pair of horizontal rolls and the pair of vertical rolls is adjusted by moving the piston rod 12 in the direction of the arrow due to the movement of the piston 8.
[0004]
Incidentally, the piston rod 12 extends through the rod insertion hole 6a provided in the rod cover 6 and extends outside. A seal member 20 is disposed between the peripheral surface of the rod insertion hole 6a and the outer periphery of the piston rod 12. It has a sealing structure. The seal member 20 is, for example, the seal member shown in FIG. The seal member 20 is a U packing (hereinafter, referred to as a U packing 20) fitted into an annular groove 6b formed on a peripheral surface of the rod insertion hole 6a. The U packing 20 is elastically deformed to be in close contact with the piston rod 12. By doing so, the operation oil is prevented from leaking to the outside (for example, Patent Document 1).
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-54608
[Problems to be solved by the invention]
By the way, the pressure (operating pressure) of the hydraulic oil of the hydraulic cylinder used as the pressure reduction device is high, and if the sealing structure of the sliding part is not securely performed, the hydraulic oil in the cylinder chamber will leak easily, and the operating characteristics of the hydraulic cylinder Will be affected. When the operating characteristics of the hydraulic cylinder change, the quality of the H-section steel is also affected.
[0007]
However, the elasticity of the U packing 20 shown in FIG. 4 tends to decrease in a relatively short time, and the U-shaped portion of the U packing 20 that slides on the piston rod 12 is also likely to deteriorate quickly. Therefore, if the U packing 20 is used as a seal member, the reliability of preventing leakage of hydraulic oil is low, and the seal member must be replaced frequently to prevent leakage of hydraulic oil. There's a problem.
[0008]
Therefore, the present invention has been made in view of the above circumstances, and by maintaining leakage prevention of hydraulic oil for a long period of time, it is possible to reduce the maintenance cost without affecting the operation characteristics of the hydraulic cylinder. An object of the present invention is to provide a seal structure for a hydraulic cylinder.
[0009]
[Means for Solving the Problems]
The seal structure for a hydraulic cylinder according to claim 1, wherein the cylinder tube, a piston that moves in the cylinder tube by controlling the supply of hydraulic oil, and one end in the moving direction of the piston are fixed to move the piston linearly. A hydraulic cylinder having a piston rod that transmits the piston rod to the outside, an inner peripheral portion of a rod cover fixed to one end of the cylinder tube and through which the piston rod is inserted, and an annular ring that is in close contact with the outer periphery of the piston rod. Hydraulic means for disposing a sealing member and applying a predetermined sealing pressure to the sealing member from the back side of the sealing member that is not in contact with the piston rod is provided.
[0010]
According to a second aspect of the present invention, in the seal structure for a hydraulic cylinder according to the first aspect, an O-ring is disposed on a back surface side of the seal member that is not in contact with the piston rod, and an elastic restoring force of the O-ring is provided. By pressing the seal member in a direction toward the outer periphery of the piston rod, the O-ring serves as auxiliary means for assisting the hydraulic means.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a seal structure for a hydraulic cylinder according to the present invention will be described with reference to FIGS. The same components as those shown in FIGS. 3 and 4 are denoted by the same reference numerals, and description thereof will be omitted.
In the hydraulic cylinder of the present embodiment, as shown in FIG. 1, a rod cover 26 is formed by two cover members 22 and 24 that are overlapped and joined in the axial direction, and are provided at one end of the cylinder tube 2 in the axial direction. Fixed. The piston rod 12 is inserted into a rod insertion hole 26a formed in the rod cover 26.
[0012]
In addition, a first annular groove 28 is formed on the peripheral surface of the rod insertion hole 26a on the side of the cylinder chamber 2a, and a second annular groove 30 is formed on the outside air side. A third annular groove 32 is formed between the second annular groove 30 and the second annular groove 30.
An annular second seal member 34 is fitted in the second annular groove 30 and is in contact with the piston rod 12 while being elastically deformed.
[0013]
The third annular groove 32 has an annular third seal member 36 that is in close contact with the piston rod 12 and a third seal member 36 that presses the third seal member 36 toward the piston rod 12 by generating an elastic restoring force. An O-ring 38 is fitted.
The first annular groove 28 has an annular first seal member 40 in contact with the piston rod 12 and an elastically deformed state between the first seal member 40 and the inner wall of the first annular groove 28. And a first O-ring 42 that presses the first seal member 40 toward the piston rod 12 when an elastic restoring force is generated is fitted.
[0014]
In the rod cover 26, a seal pressure supply path 44 which is open in the first annular groove 28 is formed. A part of the hydraulic oil generated by the hydraulic pressure source 16 is reduced to a predetermined pressure by the pressure reducing valve 46, and is supplied to the first annular groove 28 through the seal pressure supply path 44 as the seal pressure Ps. When the seal oil pressure Ps is supplied to the first annular groove 28, a back pressure (pressure on the side not facing the piston rod 12) acts on the first seal member 40 by the seal oil pressure Ps, and It is continuously pressed by the rod 12 side.
[0015]
Here, the seal pressure Ps is set to 8 to 12 MPa when the operating pressure of the hydraulic cylinder is 21 MPa. In other words, when the pressure is less than 8 MPa, the leakage cannot be completely prevented due to insufficient pressure. When the pressure exceeds 12 MPa, the contact pressure with the piston rod 12 is too strong, and the piston rod 12 is damaged. Preferably, 5 to 6 MPa is optimal for suppressing wear.
[0016]
One end of the rod cover 26 is opened on the peripheral surface between the first annular groove 28 and the third annular groove 32, and a leak detecting means (not shown) is connected to the opening at the other end. The leak detection oil passage 33 is formed. When the leak detecting means detects that the hydraulic oil is leaking to the peripheral surface between the first annular groove 28 and the third annular groove 32, the first seal member 40 disposed in the first annular groove 28 Is determined to be impaired, and a new first seal member 40 is replaced.
[0017]
In the hydraulic cylinder having the above-described configuration, the first seal member 40, the first O-ring 42, and the seal oil pressure Ps fitted in the first annular groove 28 prevent the hydraulic oil in the cylinder chamber 2a from leaking to the outside. This is the leak seal part. In addition, the third seal member 36 and the third O-ring 38 fitted into the third annular groove 32 serve as a sub leak seal portion. Then, the second seal member 34 fitted into the second annular groove 30 serves as a dust seal portion for preventing intrusion of dust or dust from the outside.
[0018]
Here, the first seal member 40 constituting the main leak seal portion is formed of a synthetic resin such as polytetrafluoroethylene, and comes into contact with the piston rod 12 which reciprocates in the axial direction. The part gradually wears.
Then, even if the first seal member 40 is slightly worn by sliding with the piston rod 12, the elastic restoring force of the first O-ring 42 acts on the first seal member 40, so that the piston rod 12 Side, and the seal pressure Ps is supplied to the first annular groove 28 to continue to be pressed toward the piston rod 12, so that the piston rod 12 and the first seal member 40 come into close contact with each other to operate the cylinder chamber 2a. Ensure that oil does not leak outside.
[0019]
Further, as shown in FIG. 2, the first seal member 40 is significantly worn due to long-time sliding with the piston rod 12 (the radial dimension of the first seal member 40 is reduced), and Even when the first O-ring 42 does not elastically deform and does not press the first seal member 40, the seal oil pressure Ps supplied to the first annular groove 28 still causes the first seal member 40 to Since the piston rod 12 and the first seal member 40 are kept in close contact with each other, the hydraulic oil in the cylinder chamber 2a is reliably prevented from leaking to the outside.
[0020]
Therefore, according to the seal structure of the hydraulic cylinder of the present embodiment, even if the first seal member 40 is slightly deteriorated (wear), the first O-ring 42 causes the first seal member 40 to be moved by the piston rod by the elastic restoring force. 12, the first seal member 40 continues to be pressed toward the piston rod 12 by supplying the seal oil pressure Ps to the first annular groove 28, so that the piston rod 12 and the first seal member 40 Are always in close contact with each other, and leakage of hydraulic oil in the cylinder chamber 2a can be reliably prevented.
[0021]
In addition, even if the first seal member 40 is greatly worn due to sliding with the piston rod 12 and the pressing force is not applied from the first O-ring 42, the seal supplied to the first annular groove 28 is not required. Since the hydraulic pressure Ps keeps pressing the first seal member 40 toward the piston rod 12, the piston rod 12 and the first seal member 40 are always kept in close contact with each other, so that the leakage of hydraulic oil in the cylinder chamber 2a is reliably prevented. Can be. Therefore, the present embodiment has a highly reliable seal structure.
[0022]
Further, since the allowable wear amount of the first seal member 40 can be increased when preventing the leakage of hydraulic oil, the life of the first seal member 40 can be extended, that is, the first seal member 40 can be extended. Need not be replaced frequently, so that maintenance costs can be reduced.
Furthermore, since it is possible to maintain the prevention of hydraulic oil leakage for a long period of time, a hydraulic cylinder with stable operating characteristics is used.If this hydraulic cylinder is used as a rolling device of a rolling mill, high quality rolled material can be obtained. Obtainable.
[0023]
【Example】
FIG. 5 shows a comparison between the seal characteristics of the above-described embodiment (the present invention) and the seal characteristics of a conventional seal structure (a seal structure in which a U packing (seal member) is closely attached to a piston rod). Show. The horizontal axis in FIG. 5 indicates the sliding state of the seal member and the piston rod by the total sliding distance, and the vertical axis in FIG. 5 indicates the amount of hydraulic oil leaked to the outside (leakage amount). In addition, the seal characteristics of the seal structure of the present embodiment are indicated by solid lines, and the seal characteristics of the conventional seal structure are indicated by broken lines.
[0024]
As is clear from FIG. 5, the seal structure according to the present embodiment in which the seal oil pressure Ps keeps pressing the first seal member 40 toward the piston rod 12 can be used even when the hydraulic cylinder is used for a long time. It can be understood that there is almost no leakage and the seal structure has high reliability.
In the present embodiment, a hydraulic cylinder used as a rolling device of a rolling mill has been described. However, the gist of the present invention is not limited to this, and a hydraulic cylinder used as an actuator in another field may be used. The same operation and effect can be obtained.
[0025]
【The invention's effect】
As described above, according to the hydraulic cylinder seal structure of the present invention, the annular seal member that is in close contact with the outer periphery of the piston rod is disposed on the inner peripheral portion of the rod cover, and the seal member is moved toward the outer periphery of the piston rod. Since the pressing force applying means for constantly applying the pressing force is provided, a highly reliable seal structure that reliably prevents the leakage of the hydraulic oil can be provided. Further, since the allowable wear amount of the seal member can be increased, the seal member does not need to be replaced frequently, so that the maintenance cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view of a principal part in an axial direction showing a seal structure of a hydraulic cylinder of the present invention.
FIG. 2 is a view showing a state in which a seal member constituting the present invention is worn.
FIG. 3 is a diagram showing an overall configuration of a hydraulic cylinder.
FIG. 4 is a view showing a seal member conventionally used in a hydraulic cylinder.
FIG. 5 is a graph comparing the seal characteristics of the seal structure of the present invention and the conventional seal structure.
[Explanation of symbols]
2 Cylinder tubes 2a, 2b Cylinder chamber 12 Piston rod 13 Hydraulic controller 16 Hydraulic source 26 Rod cover 26a Rod insertion hole 28 Annular groove 40 Seal member 42 O-ring 44 Seal pressure supply path 46 Pressure reducing valve Ps Seal pressure

Claims (2)

A hydraulic system comprising a cylinder tube, a piston that moves in the cylinder tube by supply control of hydraulic oil, and a piston rod that is fixed to one end of the piston in the movement direction and that transmits the movement of the piston to the outside as linear motion. In the cylinder,
An annular seal member that is in close contact with the outer periphery of the piston rod is disposed on the inner peripheral portion of the rod cover that is fixed to one end of the cylinder tube and that penetrates the piston rod, and that is not in contact with the piston rod. A seal structure for a hydraulic cylinder, wherein a hydraulic means for applying a predetermined sealing pressure to the seal member from the back side of the seal member is provided. An O-ring is arranged on the back surface side of the seal member that is not in contact with the piston rod, and the seal member is pressed in a direction toward the outer periphery of the piston rod by an elastic restoring force of the O-ring. 2. A seal structure for a hydraulic cylinder according to claim 1, wherein said auxiliary means is an auxiliary means for assisting said hydraulic means.

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