JP2596465Y2 - Oil seal structure for hydraulic cylinder - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an improvement in an oil seal structure in a hydraulic cylinder.

[0002]

2. Description of the Related Art Various oil seal structures for hydraulic cylinders have been proposed.
The single-acting ram type hydraulic cylinder C shown in FIG. 5 has the following oil seal structure.

[0003] First, when the single-acting ram type hydraulic cylinder C is supplied with pressure oil from an external hydraulic supply / discharge source P into the cylinder body C1, the rod body C2 is moved from the cylinder body C1. The base end side on the left side in the figure is configured to protrude outside and extend.

[0004] When the base end side of the rod body C2 protrudes to the outside through the cylinder head portion C3, the oil in the form of a coating film adhered to the outer periphery of the base end side of the rod body C2 is removed. The oil seal portion disposed in the head portion C3 is configured to be scraped off to the so-called inner side, which is the annular gap S side.

Next, looking at the structure of the cylinder head portion C3 in detail, as shown in FIG. 6, the head member 1 disposed so as to close the open end of the cylinder body C1 is opened. An oil seal structure is provided such that the fixing is performed by a holder member 2 screwed to the outer periphery of the end, and the head member 1 and the holder member 2 constitute a so-called housing.

That is, a step seal 3, which is a so-called oil seal, whose inner periphery is in sliding contact with the outer periphery of the rod body C2, is provided at an end portion which is located on the inner periphery of the head member 1 and is adjacent to the holder member 2. An O-ring 4 is disposed adjacent to the outer periphery of the step seal 3 and functions as a backup ring. The step seal 3 and the O-ring 4 are integrated to form an oil seal structure. And

Although not shown, the step seal 3 may be a slipper seal having a rectangular cross section.

Incidentally, the step seal 3 is formed in a form having a lip portion 3a which is in sliding contact with the outer periphery of the rod body C2 on the inner periphery thereof, and the lip portion 3a scrapes off the oil.

A bearing 5 whose inner periphery is in sliding contact with the outer periphery of the rod body C2 is interposed on the inner periphery of the head member 1, and the inner periphery of the head member 1 is arranged on the outer periphery of the rod body C2. A dust seal 6 that slides is interposed.

The inner circumference of the holder member 2 is not slidably contacted with the outer circumference of the rod body C2, and has an appropriate gap (not shown) between the inner circumference and the outer circumference of the rod body C2. Is set.

An O-ring 7 as a seal member is interposed between the outer periphery of the head member 1 and the inner periphery of the open end of the cylinder C1 facing the head member 1.

Therefore, in the conventional oil seal structure configured as described above, when the base end side of the rod body C2 protrudes from the cylinder body C1, it adheres to the outer periphery of the base end side. The oil in the form of a coating is applied to the cylinder head C3.
Is scraped off to the bearing 5 side, that is, the so-called inner side, that is, the annular gap S side, by the oil seal structure provided in the step seal 3, that is, the lip portion 3a on the inner peripheral side of the step seal 3.

As a result, even if the rod body C2 repeatedly appears and retracts with respect to the cylinder body C1, the cylinder head C3
This prevents a situation in which oil is scraped off from the protruding end of the rod body C2 in the above, and prevents a situation in which the protruding end is contaminated with oil.

When the rod body C2 is immersed in the cylinder body C1, dust that may adhere to the outer periphery of the rod body C2 on the tip side is scraped off by the dust seal 6 to the so-called outside. You will not be able to get inside.

[0015]

However, the following problems have been pointed out in the above-mentioned conventional oil seal structure.

That is, in this type of hydraulic cylinder,
Normally, the pressure in the annular gap S is set to be substantially equal to the atmospheric pressure when the rod body C2 is largely immersed in the cylinder body C1 and is in a so-called maximum compression state.

Accordingly, the step seal 3 and the O-ring 4 constituting the oil seal structure receive pressure from the annular gap S when the rod C2 is extended from the cylinder C1. Also, during the pressure side operation in which the rod body C2 is immersed in the cylinder body C1, the pressure is received from the annular gap S side.

As shown in FIG. 7, this pressure action acts on the step seal 3 and the O-ring 4 on the right side of the annular gap, which is the right end in the drawing, as a pressure p1. The pressures p2 and p3 are also accumulated between the outer end of the O-ring 4 at the left end in the drawing and the inner end surface of the holder member 2 adjacent thereto at the right end in the drawing.

As a result, in the step seal 3,
The inner peripheral side lip portion 3a is brought into contact with the step seal 3 with a contact force greater than the preset force, and additionally with the O-ring 4 with a backup force greater than the preset force.
The rod body C2 is pressed against the outer periphery.

Therefore, at this time, the step seal 3
, The sliding resistance with respect to the rod body C2 becomes greater than or equal to the set value, and the so-called slidability of the rod body C2 is reduced.

From the above situation, when the so-called pressure accumulation phenomenon is further enhanced, as shown in FIG.
Since the pressure p2 is increased, the lip portion 3a of the step seal 3 is pushed by the rod C
The rod body C2 is pressed against the outer periphery of the rod body 2, and at this time, a disadvantage that the so-called slidability of the rod body C2 is significantly reduced is caused.

If the step seal 3 is a slipper seal, the rod body C in the slipper seal may be used.
Since the contact area with the step seal 2 is much larger than the contact area with the step seal 3, the above-described decrease in the slidability is remarkable.

As a result, when the rod C2 is moved in and out of the cylinder C2, particularly when the rod C2 protrudes from the cylinder C1 at a low speed, the lip of the step seal 3 is extended. There is a problem that a vibration phenomenon called chatter is generated in the rod body C2 due to the vibration of the rod 3a or a sound generation phenomenon is generated in the entire hydraulic cylinder.

This invention has been made in view of the above-mentioned circumstances, and its purpose is to enable a predetermined oil seal while ensuring a predetermined sliding performance.
Moreover, it is an object of the present invention to provide an oil seal structure in a hydraulic cylinder which is free from fear of chattering and abnormal noise.

[0025]

In order to achieve the above object, the present invention provides a head member for penetrating a rod body through a shaft core and closing an open end of a cylinder body, and an open end of a cylinder body. An oil seal that forms a housing with a holder member that is screwed to the outer periphery to fix the head member, and is slidably contacted with the outer periphery of the rod body in the housing;
And a backup ring adjacent to the outer periphery of the oil seal, wherein one or both of the oil seal and a housing accommodating the oil seal are provided on the outer end side of the backup ring. It is characterized in that a pressure releasing means formed of a notched groove or a small-diameter hole that opens is provided, and the pressure accumulated on the outer end side of the backup ring is released outside the housing via the pressure releasing means.

It is assumed that the oil seal comprises a step seal or a slipper seal, and the backup ring comprises an O-ring.

The notch grooves constituting the pressure release means are:
Specifically, the outer end of the oil seal is formed on the inner wall surface of the adjacent housing, or the outer end of the oil seal is formed on the inner wall surface of the adjacent housing. Or formed into.

Further, the small-diameter hole constituting the depressurizing means may be formed in the housing, and in this case, a notch groove may be formed at the outer end of the oil seal.

[0029]

Therefore, when pressure from the annular gap side acts on the inner side end of the oil seal and the backup ring, that is, the annular gap side end, the pressure becomes adjacent to the outer side end of the oil seal and the backup ring. Even if the pressure builds up between the inner end surface of the housing and the internal pressure, the accumulated pressure is released to the outside by the pressure release means.

When the rod body projects from the cylinder body, the oil in the form of a coating film adhered to the outer periphery of the rod body is scraped off by the oil seal to the inner side as the annular gap side.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on the illustrated embodiment.
Basically, it has the same configuration as the above-mentioned conventional hydraulic cylinder.

Therefore, portions having the same configuration are denoted by the same reference numerals in the drawings, except where necessary, and detailed description thereof will be omitted. Different portions in this embodiment will be described below. I will explain mainly.

That is, the hydraulic cylinder C shown in FIGS.
The oil seal structure shown in FIG. 5 includes a housing composed of a head member 1 and a holder member 2 in which an oil seal composed of a step seal 3 and a backup ring composed of an O-ring 4 are housed.

The housing is a member called a cylinder head member in which the head member 1 and the holder member 2 are integrated instead of the head member 1 and the holder member 2. It may be formed by.

Alternatively, the step seal 3 may be a slipper seal having a rectangular cross section.

The step seal 3 has a lip portion 3a on the outer peripheral side, the inner periphery of which is in sliding contact with the outer periphery of the rod body C2.

By the way, with respect to the depressurizing means which is a main part in the present invention, in the embodiment shown in FIG. 1, the step seal 3 is cut out from the cutout groove 3b formed on the outer end which is the left end in the drawing. It is going to be.

The cutout groove 3b is formed at the outer end of the step seal 3 so as to cut out the outer end in the radial direction.

Since the outer end of the step seal 3 is adjacent to the inner end face of the holder member 2 constituting the housing, which is the right end face in the drawing, the notch groove 3b
Will form a pressure relief passage adjacent to the inner end face.

The pressure relief passage, that is, the notch groove 3b communicates with a gap between the inner circumference of the holder member 2 and the outer circumference of the rod body C2, and the inner circumference of the dust seal 6 and the rod body 2
To the outside through the outer periphery of the

Therefore, in the oil seal structure of this embodiment formed as described above, the notch groove 3b is formed at the outer end of the step seal 3, so that the outer side of the step seal 3 is formed. Even if the pressure p3 (see FIG. 7) is accumulated between the end and the inner end face of the holder member 2 adjacent to the end, the accumulated pressure is eliminated beforehand.

In the embodiment shown in FIG. 2, the depressurizing means is formed by a notch formed in the inner end face of the holder member 2 constituting the housing, that is, the outer end face of the step seal 3 and the outer end of the O-ring 4. It is assumed that the groove 2a is formed.

The cutout groove 2a is formed in the inner end face of the holder member 2 so as to cut out the end face in a radial direction from the inner peripheral end.

However, the length is the same as that of the step seal 3 and O
The length is set to substantially match the length dimension of the ring 4 superimposed.

The notched groove 2a communicates with the inner peripheral side of the holder member 2 which faces the rod C2.

Therefore, in the oil seal structure of this embodiment, the notch groove 2a is formed in the inner end surface of the holder member 2 where the outer ends of the step seal 3 and the O-ring 4 are adjacent. The pressure p2 (see FIG. 7) and the pressure p3 are accumulated between the notch groove 2a, that is, between the inner end surface of the holder member 2 and the outer end of the step seal 3 and the O-ring 4 adjacent thereto. It will be prevented beforehand.

In the embodiment shown in FIG. 3, the depressurizing means is a notch groove 3b formed at the outer end of the step seal 3 as in the case of FIG. , That is, a notch groove 1a formed in the outer end face adjacent to the end face of the holder member 2.

The cutout groove 1a is formed on the outer end face of the head member 1 so as to cut out the end face in the radial direction from the outer peripheral end.

The notch groove 1a is formed by a gap (not shown) formed between the outer periphery of the head member 1 and the inner periphery of the holder member 2 facing the head member 1 and the gap between the holder member 2 and the cylinder body C1. It communicates with the outside via a threaded portion (not shown).

Therefore, in the oil seal structure of this embodiment, the notch groove 3b is formed at the outer end of the step seal 3, and the notch groove 1a is formed at the outer end surface of the head member 1. Therefore, the pressures p2 and p3 are prevented from being accumulated between the inner end surface of the holder member 2 and the outer end of the O-ring 4 with the step seal 3 adjacent thereto.

In the embodiment shown in FIG. 4, the depressurizing means is formed in the notch groove 3b formed on the outer end of the step seal 3 as in the case of FIG. And a small-diameter hole 2b.

In the illustrated example, the small-diameter hole 2b is formed by drilling the holder member 2 in the axial direction which is the left-right direction in the drawing, and the inner end face side of the holder member 2, that is, The outer end of the O-ring 4 is set so as to directly communicate the adjacent end face to the outside.

Therefore, in the oil seal structure of this embodiment, the notch groove 3b is formed at the outer end of the step seal 3, and the small-diameter hole 2b is formed in the holder member 2. This prevents the pressures p2 and p3 from being accumulated between the inner end face of the member 2 and the step seal 3 and the outer end of the O-ring 4 adjacent thereto.

[0054]

As described above, according to the present invention, the pressure from the annular gap side acts on the inner side end of the oil seal and the backup ring, that is, the annular gap side end, and the pressure is reduced by the oil seal. Even if the pressure is accumulated between the outer end of the backup ring and the inner end surface of the adjacent housing, the accumulated pressure is released to the outside by the depressurizing means.

As a result, the oil seal is not slid on the outer periphery of the rod body with a contact force exceeding the set value, so that the so-called slidability of the rod body is not reduced. At the time of movement, the oil seal does not vibrate or the like, so that a vibration phenomenon called chattering occurs in the rod body, and a sound generation phenomenon does not occur in the entire hydraulic cylinder.

Further, according to this invention, it is sufficient to form a cutout groove or a small-diameter hole in one or both of the oil seal and the housing accommodating the oil seal as the pressure release means. Compared to the case where the desired effect is obtained by using a kind, it is easy to carry out, and since only a slight modification to the constituent members is enough, it is possible to avoid an unnecessary increase in product cost, and There is an advantage that improvement of the property can be expected.

[Brief description of the drawings]

FIG. 1 is a partially enlarged longitudinal sectional view showing an oil seal structure in a hydraulic cylinder according to an embodiment of the present invention.

FIG. 2 is a partially enlarged longitudinal sectional view showing an oil seal structure according to another embodiment, similarly to FIG.

FIG. 3 is a partially enlarged longitudinal sectional view showing an oil seal structure according to still another embodiment, similarly to FIG.

FIG. 4 is a partially enlarged longitudinal sectional view showing an oil seal structure according to still another embodiment, similarly to FIG.

FIG. 5 is a front view showing a hydraulic cylinder as a conventional example, partially cut away.

6 is a partially enlarged longitudinal sectional view showing an oil seal structure in the hydraulic cylinder of FIG. 5, similarly to FIG.

FIG. 7 is a partially enlarged cross section showing a pressure accumulation state in an oil seal portion.

FIG. 8 is a partially enlarged cross section showing another state of accumulating pressure in the oil seal portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head member which comprises a housing 1a Notch groove 2 Holder member which comprises a housing 2a Notch groove 2b Small diameter hole 3 Step seal which comprises an oil seal 3b Notch groove 4 O-ring which comprises a backup ring C1 Cylinder body C2 Rod body

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Iwao Niitsu, 1048 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Works, Ltd. (56) References JP-A 4-88564 (JP, U) JP-A 4- 44565 (JP, U) Shokai 56-158508 (JP, U) Shokai 55-135806 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F16J 15/18 F15B 15 / 14 355 F16F 9/36

Claims (1)

(57) [Scope of request for utility model registration] 1. A housing comprising: a head member that penetrates a rod body through a shaft core portion and closes an open end of a cylinder body; and a holder member that is screwed to the outer periphery of the open end of the cylinder body to fix the head member. An oil seal in the housing having an oil seal slidably in contact with the outer periphery of the rod body, and a backup ring adjacent to the outer periphery of the oil seal. A pressure relief means consisting of a cutout groove or a small-diameter hole opened on the external end side of the backup ring is provided in one or both of the housings for housing the backup ring, and the external end side of the backup ring via the pressure relief means. An oil seal structure in a hydraulic cylinder, wherein the pressure accumulated in the hydraulic cylinder is released outside the housing.