Patent Description:
Heretofore, a sealing structure <NUM> illustrated in <FIG> is known as a sealing structure for use in a piston type accumulator <NUM> which is a kind of the hydraulic and pneumatic device. The sealing structure <NUM> is structured so that seal portions <NUM> sealing a seal fluid, such as seal gas or a fluid, backup ring portions <NUM> backing up the seal portions <NUM>, and a bearing portion <NUM> coaxially holding a piston <NUM> to a shell <NUM> are attached to an outer periphery portion of the piston <NUM> to be inserted into the shell <NUM> as illustrated in <FIG> in an enlarged manner. Patent Document <NUM> discloses a sealing structure according to the preamble of claim <NUM>. Patent Documents <NUM> and <NUM> disclose further prior art.

However, according to the conventional technique, the seal portions <NUM> and the bearing portion <NUM> are separate components and the backup ring portions <NUM> and the bearing portion <NUM> are also separate components, and therefore there is room for a further improvement in the following respects.

In view of the above-described respects, it is an object of the present invention to provide a seal structure which enables a reduction in the number of components and an improvement of the stability in sliding of a seal portion or a backup ring portion in comparison with conventional techniques.

The above object is solved by a sealing structure according to claim <NUM> or a sealing structure according to claim <NUM>.

By forming the seal portion or the backup ring portion and the bearing portion into the integral structure, the number of components can be reduced and, moreover, since the seal portion or the backup ring portion is held by the bearing portion, the stability in sliding thereof can be improved. The integral structure desirably includes the following aspects.

The sealing structure of the present invention is preferably used as a piston seal or a rod seal in a piston type accumulator in which a piston is inserted into a shell, a hydraulic cylinder in which a piston is inserted into a cylinder tube, or the like.

As described above, the present invention can reduce the number of components and can improve the stability in sliding of a seal portion or a backup ring portion in comparison with conventional techniques.

Next, embodiments of the present invention are described with reference to the drawings.

<FIG> illustrates a piston type accumulator <NUM> having a sealing structure <NUM> according to a first embodiment, in which the internal space of a shell <NUM> is divided into a gas chamber <NUM> sealing gas (gas, such as nitrogen gas) and a fluid chamber (liquid chamber) <NUM> introducing a fluid (liquid, such as pressure oil) by the slidable insertion of a piston <NUM> into the shell <NUM> as an accumulator housing. In a bottom surface portion of the shell <NUM> having a bottomed cylindrical shape, a gas injection hole <NUM> is provided and is hermetically sealed by a plug <NUM>, an oil port <NUM> is fixed to an opening portion of the shell <NUM>, and a connection portion <NUM> to pressure piping is provided thereto.

Between the shell <NUM> and the piston <NUM>, the sealing structure <NUM> according to this embodiment is provided.

As illustrated in <FIG> in an enlarged manner, the sealing structure <NUM> has seal portions <NUM> sealing a seal fluid, such as seal gas or a fluid, backup ring portions <NUM> disposed on the rear surface sides (low-pressure side) of the seal portions <NUM> to back up the seal portions <NUM>, and a bearing portion <NUM> coaxially holding the piston <NUM> to the shell <NUM> and is formed by combining them. Among the above, the backup ring portions <NUM> and the bearing portion <NUM> are formed into an integral structure and the backup ring portions <NUM> are integrally provided to end portions in the axial direction of the bearing portion <NUM>.

The seal portions <NUM> contain a lip-shaped packing molded by a predetermined rubber-like elastic body and are mounted in mounting grooves <NUM> provided in the outer peripheral surface of the piston <NUM>. The backup ring portions <NUM> and the bearing portion <NUM> contain resin having low friction characteristics, such as PTFE, and are fitted into a fitting portion <NUM> provided in the outer peripheral surface of the piston <NUM>. Therefore, the sealing structure <NUM> has a form as a piston seal.

Moreover, the sealing structure <NUM> has a first seal portion 61A sealing seal gas, a first backup ring portion 71A disposed on the rear surface side of the first seal portion 61A to back up the first seal portion 61A, a second seal portion 61B sealing a fluid, a second backup ring portion 71B disposed on the rear surface side of the second seal portion 61B to back up the second seal portion 61B, and the bearing portion <NUM> coaxially holding the piston <NUM> to the shell <NUM> and is formed by combining them. Among the above, the first and second backup ring portions 71A and 71B and the bearing portion <NUM> are formed into an integral structure and the backup ring portions 71A and 71B are individually integrally provided to both the end portions in the axial direction of the bearing portion <NUM>.

The first and second seal portions 61A and 61B individually contain a lip-shaped packing molded by a predetermined rubber-like elastic body and are mounted in a first or second mounting groove 10A or 10B provided in the outer peripheral surface of the piston <NUM>. The first and second backup ring portions 71A and 71B and the bearing portion <NUM> contain resin having low friction characteristics, such as PTFE, and are fitted into the fitting portion <NUM> provided between the first and the second mounting grooves 10A and 10B in the outer peripheral surface of the piston <NUM>.

The first and second backup ring portions 71A and 71B are individually formed into a flange shape projected radially inward from both the end portions in the axial direction of the bearing portion <NUM>. In both the end portions in the axial direction of the fitting portion <NUM>, step-shaped recessed portions 12A and 12B for disposing the flange-shaped backup ring portions 71A and 71B, respectively, are provided.

The sealing structure <NUM> of the above-described configuration has the seal portions <NUM>, the backup ring portions <NUM>, and the bearing portion <NUM>, and therefore exhibits a seal function, a backup function, and a bearing function. Moreover, the backup ring portions <NUM> and the bearing portion <NUM> are formed into an integral structure, and therefore the number of components can be reduced and, since the backup ring portions <NUM> are held by the bearing portion <NUM>, the stability in sliding of the backup ring portions <NUM> can be improved in comparison with conventional techniques.

In the embodiment described above, the outer diameter dimension of the bearing portion <NUM> and the outer diameter dimension of the backup ring portions <NUM> are set to be equal, so that a flush cylindrical outer peripheral surface is formed. However, by setting an outer diameter dimension d<NUM> of the bearing portion <NUM> to be larger than an outer diameter dimension d<NUM> of the backup ring portions <NUM> as illustrated in <FIG>, a gap in the radial direction may be formed between the backup ring portions <NUM> and the shell <NUM> when the bearing portion <NUM> contacts the inner peripheral surface of the shell <NUM>. In this case, the backup ring portions <NUM> are not in contact with the inner peripheral surface of the shell <NUM>. Therefore, the backup ring portions <NUM> can be prevented from contacting the inner peripheral surface of the shell <NUM> and being deformed in sliding.

<FIG> illustrates a piston type accumulator <NUM> having a sealing structure <NUM> according to a second embodiment of the present invention, in which the internal space of a shell <NUM> is divided into a gas chamber <NUM> sealing gas and a fluid chamber <NUM> introducing a fluid by the slidable insertion of a piston <NUM> into the shell <NUM> as an accumulator housing. In a bottom surface portion of the shell <NUM> having a bottomed cylindrical shape, a gas injection hole <NUM> is provided and is hermetically sealed by a plug <NUM>, an oil port <NUM> is fixed to an opening portion of the shell <NUM>, and a connection portion <NUM> to pressure piping is provided thereto.

As illustrated in <FIG> in an enlarged manner, the sealing structure <NUM> has seal portions <NUM> sealing a seal fluid, such as seal gas or a fluid, backup ring portions <NUM> disposed on the rear surface sides of the seal portions <NUM> to back up the seal portions <NUM>, and a bearing portion <NUM> coaxially holding the piston <NUM> to the shell <NUM> and is formed by combining the same. Among the above, the backup ring portions <NUM> and the bearing portion <NUM> are formed into an integral structure and the backup ring portions <NUM> are integrally provided to end portions in the axial direction of the bearing portion <NUM>.

The first and second seal portions 61A and 61B individually contain a lip-shaped packing molded by a predetermined rubber-like elastic body and are mounted in a first or second mounting groove 10A or 10B provided in the outer peripheral surface of the piston <NUM>. The first and second backup ring portions 71A and 71B and the bearing portion <NUM> contain resin having low friction characteristics, such as PTFE, and are fitted into the fitting portion <NUM> provided between the first and second mounting grooves 10A and 10B in the outer peripheral surface of the piston <NUM>.

The first and second backup ring portions 71A and 71B are individually formed into an annular protrusion shape projected in one direction or the other direction in the axial direction from both the end portions in the axial direction of the bearing portion <NUM>. When an inner diameter dimension d<NUM> (<FIG>) of each of the first and second backup ring portions 71A and 71B is compared with an inner diameter dimension d<NUM> (<FIG>) of the bearing portion <NUM>, the inner diameter dimension d<NUM> of the bearing portion <NUM> is smaller, and therefore a groove-shaped recessed portion <NUM> for disposing the bearing portion <NUM> is provided in the fitting portion <NUM>.

<FIG> illustrates a hydraulic cylinder <NUM> having a sealing structure <NUM> according to a third embodiment of the present invention, in which the internal space of a cylinder tube <NUM> is divided into a first pressure chamber <NUM> continuous to a first port <NUM> and a second pressure chamber <NUM> continuous to a second port <NUM> by the slidable insertion of a piston <NUM> into the cylinder tube <NUM>. In a bottom surface portion of the cylinder tube <NUM> having a bottomed cylindrical shape, a shaft hole <NUM> is provided and a cylinder rod <NUM> is slidably inserted into and passed through the shaft hole <NUM>. A cylinder cover <NUM> is fixed to an opening portion of the cylinder tube <NUM> and the second port <NUM> is provided thereto.

The sealing structure <NUM> according to this embodiment is provided between the cylinder tube <NUM> and the piston <NUM> (C portion of <FIG>).

As illustrated in <FIG> in an enlarged manner, the sealing structure <NUM> has seal portions <NUM> sealing a seal fluid, such as pressure oil, back ring portions <NUM> disposed on anti-sliding surface sides (inner peripheral side) of the seal portions <NUM> to elastically support the seal portions <NUM>, a bearing portion <NUM> coaxially holding the piston <NUM> to the cylinder tube <NUM> and is formed by combining them. Among the above, the seal portions <NUM> and the bearing portion <NUM> are formed into an integral structure and the seal portions <NUM> are integrally provided to end portions in the axial direction of the bearing portion <NUM>.

The seal portions <NUM> contain a cap-shaped packing molded with resin having low friction characteristics, such as PTFE, and are disposed in opening portions of mounting grooves <NUM> provided in the outer peripheral surface of the piston <NUM>. The bearing portion <NUM> similarly contains resin having low friction characteristics, such as PTFE, and is fitted into a fitting portion <NUM> provided in the outer peripheral surface of the piston <NUM>. The seal portions <NUM> and the bearing portion <NUM> are integrally provided through thin annular connection portions <NUM> having an inner diameter dimension larger than that of both the seal portions <NUM> and the bearing portion <NUM> and more specifically the seal portions <NUM>, the connection portions <NUM>, and the bearing portion <NUM> are integrally provided. A groove-shaped recessed portion <NUM> for disposing the bearing portion <NUM> is provided in the fitting portion <NUM>. The back ring portions <NUM> contain a ring body, such as an O ring, molded by a predetermined rubber-like elastic body and are disposed at groove bottom portions of the mounting grooves <NUM>. Therefore, the sealing structure <NUM> has a form as a piston seal.

Moreover, the sealing structure <NUM> has a first seal portion 61A sealing a seal fluid, such as pressure oil, on the first pressure chamber <NUM> side, a first back ring portion 91A disposed on the anti-sliding surface side (inner peripheral side) of the first seal portion 61A to elastically support the first seal portion 61A, a second seal portion 61B sealing a seal fluid, such as pressure oil, on the second pressure chamber <NUM> side, a second back ring portion 91B disposed on the anti-sliding surface side (inner peripheral side) of the second seal portion 61B to elastically support the second seal portion 61B and the bearing portion <NUM> coaxially holding the piston <NUM> to the cylinder tube <NUM> and is formed by combining them. Among the above, the first and second seal portions 61A and 61B and the bearing portion <NUM> are formed into an integral structure and the seal portions 61A and 61B are individually integrally provided to both the end portions in the axial direction of the bearing portion <NUM>.

The first and second seal portions 61A and 61B individually contain a cap-shaped packing molded by resin having low friction characteristics, such as PTFE, and are disposed in opening portions of the first and second mounting grooves 31A and 31B provided in the outer peripheral surface of the piston <NUM>. The bearing portion <NUM> similarly contains resin having low friction characteristics, such as PTFE, and is fitted into a fitting portion <NUM> provided in the outer peripheral surface of the piston <NUM>. The first seal portion 61A and the bearing portion <NUM>, and the second seal portion 61B and the bearing portion <NUM> are individually integrally provided through a first or second connection portion 92A or 92B having an annular shape and an inner diameter dimension larger than that of either of the first seal portion 61A, the second seal portion 61B, and the bearing portion <NUM> and more specifically the first seal portion 61A, the first connection portion 92A, the bearing portion <NUM>, the second connection portion 92B, and the second seal portion 61B are integrally provided. A groove-shaped recessed portion <NUM> for disposing the bearing portion <NUM> is provided in the fitting portion <NUM>. The first and second back ring portions 91A and 91B individually contain a ring body, such as an O ring, molded by a predetermined rubber-like elastic body and are disposed at a groove bottom portion of the first or second mounting groove 31A or 31B, respectively.

The sealing structure <NUM> of the above-described configuration has the seal portions <NUM>, the back ring portions <NUM>, and the bearing portion <NUM>, and therefore exhibits a seal function and a bearing function. Moreover, the seal portions <NUM> and the bearing portion <NUM> are formed into an integral structure, and therefore the number of components can be reduced and, since the seal portions <NUM> is held by the bearing portion <NUM>, the stability in sliding of the seal portions <NUM> can be improved in comparison with conventional techniques.

In the embodiment described above, although the seal portions <NUM> and the bearing portion <NUM> are integrally provided through the connection portions <NUM> thinner than the seal portions <NUM> and the bearing portion <NUM>, the connection portions <NUM> may be omitted and, more specifically, the seal portions <NUM> and the bearing portion <NUM> may be directly integrally provided as illustrated in <FIG>.

In this embodiment, the sealing structure <NUM> is separately provided also between the cylinder tube <NUM> and the rod <NUM> (D portion of <FIG>).

More specifically, as illustrated in <FIG> in an enlarged manner, the sealing structure <NUM> has a seal portion <NUM> sealing a seal fluid, such as pressure oil, a back ring portion <NUM> disposed on an anti-sliding surface side (outer peripheral side) of the seal portion <NUM> to elastically support the seal portion <NUM>, a bearing portion <NUM> coaxially holding the rod <NUM> to the cylinder tube <NUM> and is formed by combining them. Among the above, the seal portion <NUM> and the bearing portion <NUM> are formed into an integral structure and the seal portion <NUM> is integrally provided to an end portion in the axial direction of the bearing portion <NUM>.

The seal portion <NUM> contains a cap-shaped packing molded with resin having low friction characteristics, such as PTFE, and is disposed in an opening portion of a mounting groove <NUM> provided in the inner peripheral surface of the shaft hole <NUM> of the cylinder tube <NUM>. The bearing portion <NUM> similarly contains resin having low friction characteristics, such as PTFE, and is fitted into a fitting portion <NUM> provided in the inner peripheral surface of the shaft hole <NUM> of the cylinder tube <NUM>. The seal portion <NUM> and the bearing portion <NUM> are integrally provided through a thin annular connection portion <NUM> having an outer diameter dimension smaller than that of both the seal portion <NUM> and the bearing portion <NUM> and, more specifically, the seal portion <NUM>, the connection portion <NUM>, and the bearing portion <NUM> are integrally provided. The back ring portion <NUM> contains a ring body, such as an O ring, molded by a predetermined rubber-like elastic body and is disposed at a groove bottom portion of the mounting groove <NUM>. Therefore, the sealing structure <NUM> has a form as a rod seal.

The sealing structure <NUM> of the above-described configuration has the seal portion <NUM>, the back ring portion <NUM>, and the bearing portion <NUM>, and therefore exhibits a seal function and a bearing function. Moreover, the seal portion <NUM> and the bearing portion <NUM> are formed into an integral structure, and therefore the number of components can be reduced and, since the seal portion <NUM> is held by the bearing portion <NUM>, the stability in sliding of the seal portion <NUM> can be improved in comparison with conventional techniques.

Claim 1:
A sealing structure (<NUM>) suitable to seal two members (<NUM>, <NUM>) which move relatively to each other, the sealing structure (<NUM>) comprising:
a bearing portion (<NUM>) suitable to be placed between the two members (<NUM>, <NUM>) and contacting both members so as to coaxially hold the two members to each other;
first and second seal portions (<NUM>, 61A, 61B) individually containing a lip-shaped packing; and
a first backup ring portion (<NUM>, 71A) disposed on a rear surface side of the first seal portion (<NUM>, 61A) to back up the first seal portion (<NUM>, 61A), and a second backup ring portion (<NUM>, 71B) disposed on a rear surface side of the second seal portion (<NUM>, 61B) to back up the second seal portion (<NUM>, 61B), wherein
the two backup ring portions (<NUM>, 71A, 71B) are integrally provided to both end portions in the axial direction of the bearing portion (<NUM>) and suitable to be placed between the two members (<NUM>, <NUM>),
the two backup ring portions (<NUM>, 71A, 71B) and the bearing portion (<NUM>) are formed into an integral structure, and
the bearing portion (<NUM>) has a cylindrical shape, characterized in that
the first and second backup ring portions (<NUM>, 71A, 71B) are individually formed into an annular protrusion shape projected in one direction or the other direction in the axial direction from both the end portions in the axial direction of the bearing portion (<NUM>), and
an inner diameter dimension (d4) of the bearing portion (<NUM>) is smaller than an inner diameter dimension (d3) of each of the first and second backup ring portions (<NUM>, 71A, 71B).