Patent Description:
Conventionally, a seal device provided in a rotating machine included in a propulsion machine of a ship or a tidal current generator, or the like seals an annular gap formed at a relative rotation portion to prevent a sealed fluid such as lubricating oil, or the like in an interior of equipment from leaking to the outside of equipment and to prevent an external fluid such as seawater from entering the interior of equipment.

For example, a seal device suitable for a propulsion machine of a ship disclosed in Patent Citation <NUM> is held by a housing with a shaft hole, through which a rotating shaft for propulsion extends, and includes three seal rings being in sliding contact with an outer peripheral surface of a liner fitted onto the rotating shaft and provided in parallel to one another in an axial direction. Air is supplied to a primary annular chamber formed between a pair of the seal rings provided on an outboard side among the seal rings, and lubricating oil is supplied to a secondary annular chamber formed between a pair of the seal rings provided on an inboard side. Specifically, the air supply is adjusted so that the primary annular chamber maintains an internal pressure of a seawater pressure plus a tightening pressure on the seal ring, and the supply of lubricating oil is adjusted so that the secondary annular chamber has an internal pressure required to blow out the air supplied to the primary annular chamber through the seal rings to the outboard side, so that the internal pressures in the primary annular chamber and the secondary annular chamber are constantly adjusted according to fluctuations in seawater pressure. Accordingly, a response to fluctuations in seawater pressure is high, and entry of seawater into the ship can be prevented.

In Patent Citation <NUM> a shaft sealing device of a propeller shaft for a vessel is described, wherein the periphery of a propelling shaft for a propeller is surrounded by four or more seal rings arranged in intervals in the axial direction and a seal ring is surrounded by a housing from the outside to form the annular chambers between the adjacent seal rings. The first and second annular chambers from the propeller shaft side are formed in the first and second air chambers, lubricating oil chambers are formed in the third and subsequent annular chambers, and lips are formed on the inner peripheral sides of the seal rings. The lips of the first and second seal rings from the propeller shaft side positioned on the propeller shaft end side is positioned to face the propeller shaft side. The shaft sealing device comprises a drain route led to the first air chamber and a drain route led to the second air chamber.

However, the seal device in Patent Citation <NUM> blows the air from the primary annular chamber to the outboard side by utilizing the internal pressure in the secondary annular chamber to which the lubricating oil is supplied, to prevent the entry of seawater into the ship, and the internal pressure in the secondary annular chamber is constantly adjusted so as to be higher than the internal pressure in the primary annular chamber. Accordingly, in case of failure of the seal rings, the high-pressure lubricating oil in the secondary annular chamber may enter the primary annular chamber through the seal rings, and the lubricating oil may be blown out from the primary annular chamber to the low-pressure outboard side together with the air to cause leakage of the lubricating oil to the outside of the ship.

The present invention has been made in view of such problems, and an object of the present invention is to provide a use of a seal device capable of reliably preventing leakage of a sealed fluid to the outside of equipment.

In order to overcome the problems described above, the present invention provides a use of a seal device at a portion where relative rotation occurs between a first member and a second member that rotates relative to the first member, wherein the seal device comprises a first seal part facing an external fluid and a second seal part arranged in parallel to the first seal part and facing a sealed fluid in an interior of equipment to prevent entry of the external fluid and leakage of the sealed fluid, wherein the seal device further comprises an intermediate seal part arranged in parallel to the first seal part and the second seal part between the first seal part and the second seal part, wherein a gas chamber is formed between the first seal part and the intermediate seal part, to which a gas having a higher pressure than the external fluid is supplied, and an intermediate chamber is formed between the intermediate seal part and the second seal part, to which a gas having a lower pressure than the gas supplied to the gas chamber and having a lower pressure than the sealed fluid is supplied. According to the aforesaid feature of the present invention, in case of failure in which the sealed fluid facing the second seal part enters the intermediate chamber through this second seal part, this sealed fluid can be stored in the intermediate chamber lower in pressure than the adjacent gas chamber on the equipment exterior side. Accordingly, leakage of the sealed fluid to the outside of equipment can be reliably prevented.

It may be preferable that the second seal part is a lip seal, and be arranged so that a lip portion thereof is pressed against the second member by the sealed fluid. According to this preferable configuration, the pressure of the sealed fluid having a higher pressure than the gas in the intermediate chamber can act as a tightening pressure on the lip seal, so that the sealed fluid is less likely to enter the intermediate chamber.

It may be preferable that the intermediate chamber may communicate with a collection chamber through a communication passage. According to this preferable configuration, the sealed fluid that has entered the intermediate chamber is collected in the collection chamber through the communication passage, so that the sealed fluid in the intermediate chamber can be easily discharged to the collection chamber that is a separate chamber. Accordingly, the leakage of the sealed fluid to the outside of equipment can be further prevented.

It may be preferable that the communication passage may be provided with a check valve that prevents backflow to a side of the intermediate chamber. According to this preferable configuration, the sealed fluid collected in the collection chamber can be prevented from flowing back into the intermediate chamber through the communication passage.

It may be preferable that the gas supplied to the intermediate chamber is a pressure-controlled compressed gas. According to this preferable configuration, the differential pressure between the pressure-controlled compressed gas and the gas supplied to the gas chamber and the differential pressure between te pressure-controlled compressed gas and the sealed fluid can be properly maintained.

It may be preferable that the compressed gas is compressed air. According to this preferable configuration, it is easy to handle, and safety can be ensured.

It may be preferable that the sealed fluid is controlled to have a lower pressure than the external fluid. According to this preferable configuration, the sealed fluid that has entered the intermediate chamber is less likely to leak to the outside of equipment.

Modes for carrying out a seal device according to the present invention will be described below based on embodiments.

A seal device according to a first embodiment of the present invention will be described with reference to <FIG> and <FIG>. In this embodiment, a seal device for a ship propulsion machine will be described as an example. Further, the left side of the drawing sheets of <FIG> and <FIG> will be described as a stern side (e.g., an outboard side) of the seal device, and the right side of the drawing sheets of <FIG> and <FIG> will be described as a bow side (e.g., an inboard side) of the seal device. In <FIG> and <FIG>, hatching a housing, and the like is omitted, and the compressed air and the lubricating oil that are supplied to and stored in each chamber are schematically shown by hatching.

As shown in <FIG>, a seal device <NUM> according to the present invention is a shaft seal device for a ship propulsion machine, and is attached from the stern side to a stern tube <NUM>, through which a propeller shaft <NUM> with a propeller <NUM> for propulsion extends. The seal device <NUM> is used to prevent lubricating oil as a sealed fluid supplied to the interior of the stern tube <NUM> constituting a hull to lubricate the propeller shaft <NUM> and a bearing (not shown) from leaking to the outside of the ship, and to prevent seawater W as an external fluid from entering the interior of the ship. The seal device <NUM> is also connected with an air control unit <NUM>, a lubricating oil circulation unit <NUM>, and a collection unit <NUM>, which are provided inboard, by respective pipelines, to constitute a stern tube seal system. Further, a seal device <NUM> provided inboard is attached to the stern tube <NUM> from the bow side, and is a shaft seal device to prevent the lubricating oil supplied to the interior of the stern tube <NUM> from entering a machine room. In this embodiment, the seal device <NUM> on the stern side will be described, and the description on the seal device <NUM> on the bow side will be omitted.

As shown in <FIG> and <FIG>, the seal device <NUM> is provided at a portion where relative rotation occurs between a housing <NUM> as a first member and a liner <NUM> that constitutes the propeller shaft <NUM> as a second member rotating relative to the housing <NUM>. The seal device <NUM> mainly includes a first lip seal <NUM> as first seal part facing the outboard seawater W, a second lip seal <NUM> as second seal part arranged in parallel on the inboard side of the first lip seal <NUM> and facing lubricating oil that fills an oil chamber <NUM> in the stern tube <NUM>, and an intermediate lip seal <NUM> as intermediate seal part arranged in parallel between the first lip seal <NUM> and the second lip seal <NUM>.

As shown in <FIG>, a first divided housing 10a, a second divided housing 10b, a third divided housing 10c, and a fourth divided housing 10d in order from the stern side are fitted to one another in an axial direction and are integrally connected with one another by bolts or the like (not shown), so that the housing <NUM> is formed into a substantially cylindrical shape. The housing <NUM> is fixed by bolts or the like (not shown) with a flange portion of the fourth divided housing 10d on the bow side being in contact with the stern tube <NUM> on the stern side.

Further, in the housing <NUM>, an outer diameter portion of the first lip seal <NUM> is held in a substantially sealed manner between the first divided housing 10a and the second divided housing 10b, an outer diameter portion of the intermediate lip seal <NUM> is held in a substantially sealed manner between the second divided housing 10b and the third divided housing 10c, and an outer diameter portion of the second lip seal <NUM> is held in a substantially sealed manner between the third divided housing 10c and the fourth divided housing 10d.

Further, a through hole is formed in the second divided housing 10b, the third divided housing 10c, and the fourth divided housing 10d to constitute a part of a first air supply passage <NUM> communicating with the air control unit <NUM> and a first annular chamber <NUM> as a gas chamber. A supply port 11a in communication with the first air supply passage <NUM> is formed on an upper side of an inner peripheral surface of the second divided housing 10b.

Further, a through hole is formed in the third divided housing 10c and the fourth divided housing 10d to constitute a part of a second air supply passage <NUM> communicating with the air control unit <NUM> and a second annular chamber <NUM> as an intermediate chamber. A supply port 12a in communication with the second air supply passage <NUM> is formed on an upper side of an inner peripheral surface of the third divided housing 10c. In addition, a through hole is formed in the third divided housing 10c and the fourth divided housing 10d to constitute a part of a communication passage <NUM> communicating with the second annular chamber <NUM> and the collection unit <NUM>. A discharge port 14a in communication with the communication passage <NUM> is formed on a lower side of an inner peripheral surface of the third divided housing 10c.

As shown in <FIG>, the lip seals <NUM>, <NUM>, and <NUM> are made of an elastic material such as fluoro-rubber or nitrile rubber that has excellent water resistance and oil resistance. Each of the lip seals <NUM>, <NUM>, and <NUM> according to this embodiment has a well-known configuration, and detailed description thereof will be omitted.

Further, the lip seals <NUM>, <NUM>, and <NUM> are arranged in parallel in the axial direction with their outer diameter portions held in a substantially sealed manner in the housing <NUM>. Respective inner peripheral surfaces of lip portions 21a, 22a, and 23a extending on the inner diameter side and extending in the axial direction toward the high pressure side are in sliding contact with an outer peripheral surface of the liner <NUM> fitted onto the propeller shaft <NUM>, so that the first annular chamber <NUM> is formed between the first lip seal <NUM> and the intermediate lip seal <NUM>, and the second annular chamber <NUM> is formed between the intermediate lip seal <NUM> and the second lip seal <NUM>. Further, the annular oil chamber <NUM> is formed between the second lip seal <NUM> and a lip seal <NUM> on the stern side of the seal device <NUM> on the bow side.

The first annular chamber <NUM> is supplied with compressed air as a compressed gas adjusted so as to have a higher pressure than the seawater W from the air control unit <NUM> through the first air supply passage <NUM>. Further, the second annular chamber <NUM> is supplied with compressed air as a compressed gas adjusted so as to have a lower pressure than the compressed air supplied from the air control unit <NUM> to the first annular chamber <NUM> through the second air supply passage <NUM>, and so as to have a lower pressure than the lubricating oil supplied from the lubricating oil circulation unit <NUM> to the oil chamber <NUM> in the stern tube <NUM>.

Further, the first lip seal <NUM> provided on the stern side of the first annular chamber <NUM> is arranged so that the lip portion 21a thereof faces the outboard side, and the seawater pressure PW acts as a part of a tightening pressure on the lip portion 21a. Further, the intermediate lip seal <NUM> provided on the bow side of the first annular chamber <NUM> and on the stern side of the second annular chamber <NUM> is arranged so that the lip portion 22a thereof faces the outboard side, that is, the side of the first annular chamber <NUM>, and an air pressure P<NUM> in the first annular chamber <NUM> acts as a part of a tightening pressure on the lip portion 22a. Further, the second lip seal <NUM> provided on the bow side of the second annular chamber <NUM> is arranged so that the lip portion 23a thereof faces the inboard side, that is, the side of the stern tube <NUM>, and a hydraulic pressure PO in the oil chamber <NUM> in the stern tube <NUM> acts as a part of a tightening pressure on the lip portion 23a.

Next, the air control unit <NUM>, the lubricating oil circulation unit <NUM>, and the collection unit <NUM> that constitute the stern tube seal system together with the seal device <NUM> will be described.

As shown in <FIG>, the air control unit <NUM> is a unit that supplies the compressed air supplied from a compressor (not shown) provided inboard, whose pressure is adjusted by a pressure reducing valve, a flow rate control valve, or the like (not shown), to the first annular chamber <NUM>, the second annular chamber <NUM>, and a lubricating oil tank <NUM> of the lubricating oil circulation unit <NUM> described later, through the first air supply passage <NUM>, the second air supply passage <NUM>, and the third air supply passage <NUM>.

Specifically, the air control unit <NUM> adjusts the air pressure P<NUM> in the first annular chamber <NUM> so that the air pressure P<NUM> always exceeds the seawater pressure PW in accordance with the seawater pressure PW that presses the lip portion 21a of the first lip seal <NUM> arranged on the stern side of the first annular chamber <NUM>.

The seawater pressure PW fluctuates according to the draft of the ship, and the air control unit <NUM> adjusts the air pressure in accordance with such fluctuations in seawater pressure PW. Further, the signal corresponding to the seawater pressure PW, that is, the signal corresponding to the air pressures in the first air supply passage <NUM> and the first annular chamber <NUM> is output to a pressure reducing valve <NUM> that is as a part of the air control unit <NUM> and is provided at the branch portion between the first air supply passage <NUM> and the second air supply passage <NUM>. A part of the compressed air is supplied to the second annular chamber <NUM> through the second air supply passage <NUM> as compressed air having the air pressure P<NUM> that has been reduced based on the output signal during the passage through the pressure reducing valve <NUM> so as to be lower than the air pressure P<NUM> of the compressed air supplied to the first annular chamber <NUM> and so as to be a lower than the hydraulic pressure PO of the lubricating oil supplied to the oil chamber <NUM> in the stern tube <NUM> by a preset differential pressure.

The lubricating oil circulation unit <NUM> is a unit that supplies lubricating oil from the lubricating oil tank <NUM> provided inboard to the interior of the stern tube <NUM> through a first lubricating oil circulation passage <NUM> with a pump <NUM>, and again returns the lubricating oil from the interior of the stern tube <NUM> to the lubricating oil tank <NUM> through a second lubricating oil circulation passage <NUM> to circulate the lubricating oil. The signal corresponding to the seawater pressure PW is output to a pressure reducing valve <NUM> that is a part of the air control unit <NUM> and is provided at the branch portion between the first air supply passage <NUM> and the third air supply passage <NUM>. A part of the compressed air is adjusted based on the output signal during passing through the pressure reducing valve <NUM> so as to have a higher pressure than the air pressure P<NUM> of the compressed air supplied to the second annular chamber <NUM>, and so as to have a lower pressure than the seawater pressure PW by a preset differential pressure or so as to have the same pressure as the seawater pressure PW, and is then supplied to the lubricating oil tank <NUM> through the third air supply passage <NUM>. Accordingly, the lubricating oil in the lubricating oil tank <NUM> is brought into contact with the such pressure-reduced compressed air with the oil surface as a boundary surface, so that the hydraulic pressure PO of the lubricating oil in the lubricating oil tank <NUM> is adjusted so as to be higher than the air pressure P<NUM> of the second annular chamber <NUM> and so as to be lower than or be the same as the seawater pressure PW.

That is, the seawater pressure PW, the air pressure P<NUM> in the first annular chamber <NUM>, the air pressure P<NUM> in the second annular chamber <NUM>, and the hydraulic pressure PO in the oil chamber <NUM> are adjusted so that the air pressure P<NUM> > the seawater pressure PW ≧ the hydraulic pressure PO > the air pressure P<NUM> is always satisfied.

The collection unit <NUM> is a unit that in case of failure in which lubricating oil enters the second annular chamber <NUM> from the oil chamber <NUM> in the stern tube <NUM>, collects this lubricating oil in a collection chamber <NUM> provided inboard through the communication passage <NUM>. Further, the communication passage <NUM> is provided with a check valve <NUM> to prevent the lubricating oil collected in the collection chamber <NUM> from flowing back into the second annular chamber <NUM>.

As described above, in the seal device <NUM> according to this embodiment, the compressed air, whose pressure has been reduced to the air pressure P<NUM> by the air control unit <NUM> so as to be lower than the air pressure P<NUM> of the compressed air supplied to the first annular chamber <NUM> through the first air supply passage <NUM>, is supplied to the second annular chamber <NUM> through the second air supply passage <NUM>. Accordingly, even in case of failure in which the lubricating oil in the oil chamber <NUM> facing the second lip seal <NUM> enters the second annular chamber <NUM> through the second lip seal <NUM>, the lubricating oil that has the air pressure P<NUM> lower than that in the adjacent first annular chamber <NUM> on the outboard side and has entered the second annular chamber <NUM>, can be retained, and the leakage of the lubricating oil to the outside of the ship can be reliably prevented.

In addition, the lip portion 22a of the intermediate lip seal <NUM> provided on the stern side of the second annular chamber <NUM> is arranged so as to face the side of the first annular chamber <NUM>, so that the lip portion 22a of the intermediate lip seal <NUM> is pressed radially inward toward the outer peripheral surface of the liner <NUM> due to the differential pressure between the air pressure P<NUM> in the first annular chamber <NUM> and the air pressure P<NUM> in the second annular chamber <NUM> to the seal the lubricating oil. Accordingly, the lubricating oil that has entered the second annular chamber <NUM> is prevented from entering the first annular chamber <NUM>, and the leakage of the lubricating oil to the outside of the ship can be further prevented.

Further, in case of failure in which the lubricating oil in the oil chamber <NUM> in the stern tube <NUM> enters the second annular chamber <NUM> through the second lip seal <NUM>, the lubricating oil that has entered the second annular chamber <NUM> is collected in the inboard collection chamber <NUM> through the communication passage <NUM>. Accordingly, the lubricating oil can be easily discharged from the interior of the second annular chamber <NUM>, so that the leakage of the lubricating oil to the outside of the ship can be further prevented.

Further, the pressure of the lubricating oil supplied from the lubricating oil circulation unit <NUM> to the oil chamber <NUM> in the stern tube <NUM> is reduced so as to be lower than the seawater pressure PW by a preset differential pressure, so that the hydraulic pressure PO in the oil chamber <NUM> is controlled to be lower than the seawater pressure PW. Accordingly, even if the lubricating oil enters the second annular chamber <NUM>, it is less likely to leak to the outside of the ship.

Further, the pressure of the compressed air supplied from the air control unit <NUM> to the second annular chamber <NUM> is reduced so as to be lower than that of the lubricating oil supplied to the oil chamber <NUM> in the stern tube <NUM> by a preset differential pressure, so that the lip portion 23a of the second lip seal <NUM> is pressed radially inward toward the outer peripheral surface of the liner <NUM> due to the differential pressure between the pressure in the second annular chamber <NUM> and the pressure in the oil chamber <NUM> to seal the lubricating oil. Accordingly, the lubricating oil supplied to the oil chamber <NUM> can be prevented from entering the second annular chamber <NUM>. In addition, the compressed air supplied to the second annular chamber <NUM> can be also prevented from entering the oil chamber <NUM>.

Further, the second annular chamber <NUM> is supplied with the pressure-adjusted compressed air through the air control unit <NUM>, and the differential pressure from the compressed air supplied to the first annular chamber <NUM> or from the lubricating oil supplied into the oil chamber <NUM> can be properly maintained. The load particularly on the intermediate lip seal <NUM> and the second lip seal <NUM> that constitute the second annular chamber <NUM> can be maintained substantially constant, and their long life can be extended.

Further, since the first annular chamber <NUM> and the second annular chamber <NUM> are supplied with the compressed air through the air control unit <NUM>, it is easy to handle and safety can be ensured.

Further, the compressed air whose pressure is adjusted so as to be air pressure P<NUM> equal to or higher than the seawater pressure PW in the air control unit <NUM> is supplied to the first annular chamber <NUM> through the first air supply passage <NUM>, so that the seawater W is prevented from entering the annular chamber <NUM> from a gap between the lip portion 21a of the first lip seal <NUM> and the liner <NUM>. In addition, the air having the air pressure P<NUM> supplied to the first annular chamber <NUM> is blown from the gap between the lip portion 21a of the first lip seal <NUM> and the liner <NUM> to the outside of the ship against the seawater pressure PW, so that the fluctuations in seawater pressure PW can be detected in the air control unit <NUM>. Accordingly, other additional detection tanks or pipes are not required.

Further, the air pressure P<NUM> in the second annular chamber <NUM> is set to be lower than the seawater pressure PW, so that the hydraulic pressure PO in the oil chamber <NUM> can be less than the seawater pressure PW. Accordingly, pump equipment for increasing the pressure of lubricating oil or the lubricating oil tank <NUM> is not required to be installed at a high place, and the entire stern tube seal system can be simplified.

The second annular chamber <NUM> is preferably provided with a pressure control valve such as a pressure reducing valve or a relief valve so that when the high-pressure compressed air enters from the first annular chamber <NUM>, an excess pressure can be discharged. This can prevent air from entering the oil chamber <NUM>.

Next, a seal device according to a second embodiment of the present invention will be described with reference to <FIG> and <FIG>. The same components as those shown in the embodiment described above are designated by the same reference numerals, and overlapping description will be omitted.

A seal device <NUM> according to the second embodiment of the present invention will be described. As shown in <FIG>, the seal device <NUM> is provided at a portion where relative rotation occurs between a housing <NUM> as a first member and the liner <NUM> that constitutes the propeller shaft <NUM> as a second member rotating relative to the housing <NUM>. The seal device <NUM> mainly includes the first lip seal <NUM>, the intermediate lip seal <NUM>, the second lip seal <NUM>, and an auxiliary lip seal <NUM> arranged in parallel on the bow side of the second lip seal <NUM>.

As shown in <FIG>, the first divided housing 10a, the second divided housing 10b, the third divided housing 10c, the fourth divided housing 210d, and a fifth divided housing 210e in order from the stern side are fitted to one another in an axial direction and are integrally connected with one another by bolts or the like (not shown), so that the housing <NUM> is formed into a substantially cylindrical shape.

Further, an outer diameter portion of the auxiliary lip seal <NUM> is held in a substantially sealed manner between the fourth divided housing 210d and the fifth divided housing 210e in the housing <NUM>. In addition, an annular second oil chamber <NUM> is formed between the second lip seal <NUM> and the auxiliary lip seal <NUM>.

Further, a through hole is formed in the fourth divided housing 210d and the fifth divided housing 210e to constitute a part of a branch communication passage <NUM> that branches from the first lubricating oil circulation passage <NUM> extending from the lubricating oil circulation unit <NUM> and communicates with the second oil chamber <NUM>. A supply port 234a in communication with the branch communication passage <NUM> is formed on the lower side of an inner peripheral surface of the fourth divided housing 210d. The branch communication passage <NUM> is provided with an on/off valve <NUM>. Further, the lubricating oil tank <NUM> constituting the lubricating oil circulation unit <NUM> is configured as a pressurized tank capable of adjusting the pressure of the lubricating oil according to the pressure of the compressed air supplied from the air control unit <NUM> through the third air supply passage <NUM>.

Further, the second lip seal <NUM> provided on the stern side of the second oil chamber <NUM> is arranged so that the lip portion 23a thereof faces the inboard side, that is, the side of the second oil chamber <NUM>, and the hydraulic pressure PO2 in the second oil chamber <NUM> acts as a part of a tightening pressure on the lip portion 23a. In addition, the auxiliary lip seal <NUM> provided on the bow side of the second oil chamber <NUM> is arranged so that the lip portion 24a thereof faces the inboard side, that is, the side of the stern tube <NUM>, and the hydraulic pressure PO1 in the oil chamber <NUM> in the stern tube <NUM> acts as a part of a tightening pressure on the lip portion 24a.

As described above, in the seal device <NUM> according to this embodiment, the lip portion 23a of the second lip seal <NUM> is arranged so as to face the side of the second oil chamber <NUM>, so that the lip portion 23a of the second lip seal <NUM> is pressed radially inward toward the outer peripheral surface of the liner <NUM> due to the differential pressure between the second annular chamber <NUM> and the second oil chamber <NUM> to seal the lubricating oil. Accordingly, the lubricating oil supplied to the second oil chamber <NUM> can be prevented from entering the second annular chamber <NUM>. In addition, the lubricating oil supplied from the lubricating oil circulation unit <NUM> to the second oil chamber <NUM> through the branch communication passage <NUM> is sealed by the second lip seal <NUM>, so that the hydraulic pressure PO2 in the second oil chamber <NUM> is equal to or higher than the hydraulic pressure PO1 in the oil chamber <NUM> (i.e., the hydraulic pressure PO2 ≧ the hydraulic pressure PO1). Accordingly, the lubricating oil can flow into the oil chamber <NUM> from a gap between the lip portion 24a of the auxiliary lip seal <NUM> and the liner <NUM>, and the lubricating oil supplied to the second oil chamber <NUM> is less likely to enter the second annular chamber <NUM>. The lubricating oil that has flowed out from the second oil chamber <NUM> into the oil chamber <NUM> returns to the lubricating oil tank <NUM> through the second lubricating oil circulation passage <NUM>.

Further, since the branch communication passage <NUM> is provided with the on/off valve <NUM>, switching can be made so that, for example, when the second lip seal <NUM> is damaged, the on/off valve <NUM> is closed to stop the supply of the lubricating oil to the second oil chamber <NUM>, and the auxiliary lip seal <NUM> mainly seals the lubricating oil.

Further, the lubricating oil tank constituting the lubricating oil circulation unit is not limited to the one configured as a pressurized tank capable of adjusting the pressure of the lubricating oil according to the pressure of the compressed air supplied from the air control unit <NUM>. For example, as a modification of the stern tube seal system with the seal device <NUM> according to the second embodiment, as shown in <FIG>, a lubricating oil tank <NUM> constituting a lubricating oil circulation unit <NUM> may be configured as a gravity tank that supplies the lubricating oil at a constant pressure by gravity. The lubricating oil circulation unit <NUM> shown in <FIG> may be applied to the stern tube seal system with the seal device <NUM> according to the first embodiment.

Next, a seal device according to a third embodiment of the present invention will be described with reference to <FIG>. The same components as those shown in the embodiments described above are designated by the same reference numerals, and overlapping description will be omitted. In this embodiment, a seal device for a center-open type tidal current generator will be described as an example. Further, the left side of the drawing sheet of <FIG> will be described as an inner diameter side of the seal device, and the right side of the drawing sheet of <FIG> will be described as an outer diameter side of the seal device.

A seal device <NUM> according to the third embodiment of the present invention will be described. As shown in <FIG>, the seal device <NUM> for a center-open type tidal current generator prevents the lubricating oil from flowing to the outside of equipment, which is supplied to the interior of equipment in order to lubricate a pair of bearings <NUM>, <NUM> provided between an annular rotor <NUM> including a plurality of blades <NUM> on the inner peripheral surface and an annular power generation unit <NUM> arranged on the outer diameter side of the rotor <NUM> and including a coil <NUM>, and prevents the seawater W from entering the interior of equipment. The rotor <NUM> is provided with a magnet <NUM> extending in the circumferential direction of the outer peripheral surface, and the rotor <NUM> that has received the tidal current from the blades <NUM> rotates relative to the power generation unit <NUM> to generate power.

The seal device <NUM> is provided at a portion where relative rotation occurs between a pair of annular housings <NUM>, <NUM> as first members attached from the inner diameter side to a pair of annular casings <NUM>, <NUM> arranged in front of and in back of the rotor <NUM> and the power generation unit <NUM>, and the rotor <NUM> as a second member rotating relative to the housings <NUM>, <NUM>. The seal device <NUM> mainly includes a pair of annular first lip seals <NUM>, <NUM> as a first seal part facing the seawater W, a pair of second lip seals <NUM>, <NUM> as a second seal part arranged in parallel to the first lip seals <NUM>, <NUM>, respectively, and facing the lubricating oil in the interior of equipment, and intermediate lip seals <NUM>, <NUM> as an intermediate seal part arranged in parallel between the first lip seals <NUM>, <NUM> and the second lip seals <NUM>, <NUM>, respectively.

As shown in <FIG>, a first divided housing 310a, a second divided housing 310b, a third divided housing 310c, and a fourth divided housing 310d in order from the inner diameter side are fitted to one another and are integrally connected with one another by bolts or the like (not shown), so that the housings <NUM>, <NUM> are each formed into a substantially cylindrical shape. The housings <NUM>, <NUM> are fixed by bolts or the like (not shown) with respective flange portions of the first divided housings 310a, 310a on inner diameter side being fitted to the inner peripheral surfaces of the casings <NUM>, <NUM>.

Further, in each of the housings <NUM>, <NUM>, one end portion of the first lip seal <NUM> is held in a substantially sealed manner between the first divided housing 310a and the second divided housing 310b, one end portion of the intermediate lip seal <NUM> is held in a substantially sealed manner between the second divided housing 310b and the third divided housing 310c, and one end portion of the second lip seal <NUM> is held in a substantially sealed manner between the third divided housing 310c and the fourth divided housing 310d. Further, a first annular chamber <NUM> is formed between the first lip seal <NUM> and the intermediate lip seal <NUM>, and a second annular chamber <NUM> is formed between the intermediate lip seal <NUM> and the second lip seal <NUM>. Further, an annular oil chamber <NUM> is formed between the second lip seal <NUM> and the bearing <NUM>.

Further, through holes are formed in the second divided housings 310b, 310b to constitute a part of the first air supply passages <NUM>, <NUM> communicating with the air control unit <NUM> provided in the interior of equipment and the first annular chambers <NUM>, <NUM> as gas chambers.

Further, through holes are formed in the third divided housings 310c, 310c to constitute a part of the second air supply passages <NUM>, <NUM> communicating with the air control unit <NUM> and the second annular chambers <NUM>, <NUM> as intermediate chambers.

As described above, in the seal device <NUM> according to this embodiment, the compressed air, whose pressure has been reduced to the air pressure P<NUM> by the air control unit <NUM> so as to be lower than the air pressure P<NUM> of the compressed air supplied to the first annular chambers <NUM>, <NUM> through the first air supply passages <NUM>, <NUM>, is supplied to the second annular chambers <NUM>, <NUM> through the second air supply passages <NUM>, <NUM>. Accordingly, in case of failure in which the lubricating oil in the oil chamber <NUM> in the interior of equipment, which faces the second lip seals <NUM>, <NUM>, enters the second annular chambers <NUM>, <NUM> through the second lip seals <NUM>, <NUM>, the lubricating oil that has entered the second annular chambers <NUM>, <NUM> and has the air pressure P<NUM> lower than that in the adjacent first annular chambers <NUM>, <NUM> on the equipment exterior side can be stored, and the lubricating oil can be reliably prevented from leaking to the outside of the ship.

Although the embodiments according to the present invention have been described above with reference to the drawings, the specific configurations are not limited to these embodiments, and any changes or additions within the scope of the present invention as defined by the claims are included in the present invention.

For example, it goes without saying that in the seal device according to the embodiments described above, not only the lubricating oil but also the seawater W that has entered from the outside of equipment can be collected in the second annular chamber as the intermediate chamber. Further, the external fluid is not limited to seawater, and may be, for example, freshwater. Further, the sealed fluid is not limited to lubricating oil.

Further, in the embodiments described above, the air control unit <NUM> has been described as being configured to reduce the pressure of the compressed air with the pressure reducing valves <NUM>, <NUM>, but the present invention is not limited to this, and various pressure control valves such as a relief valve may be used to reduce the pressure of the compressed air. Further, the compressed gas is not limited to compressed air.

Further, in the first and second embodiments, the mode in which the lip seals are in sliding contact with the outer peripheral surface of the liner <NUM> fitted onto the propeller shaft <NUM> has been described, but the present invention is not limited to this, and the lip seals are directly in sliding contact with the outer peripheral surface of the propeller shaft <NUM>. Further, in the embodiments described above, each sealing part is not limited to one composed of a lip seal.

Claim 1:
Use of a seal device (<NUM>, <NUM>, <NUM>) at a portion where relative rotation occurs between a first member (<NUM>, <NUM>, <NUM>) and a second member (<NUM>, <NUM>) that rotates relative to the first member (<NUM>, <NUM>, <NUM>), wherein the seal device comprises
a first seal part (<NUM>, <NUM>) facing an external fluid and a second seal part (<NUM>, <NUM>) arranged in parallel to the first seal part (<NUM>, <NUM>) and facing a sealed fluid in an interior of equipment to prevent entry of the external fluid and leakage of the sealed fluid, wherein
the seal device (<NUM>, <NUM>, <NUM>) further comprises an intermediate seal part (<NUM>, <NUM>) arranged in parallel to the first seal part (<NUM>, <NUM>) and the second seal part (<NUM>, <NUM>) between the first seal part (<NUM>, <NUM>) and the second seal part (<NUM>, <NUM>),
wherein a gas chamber (<NUM>, <NUM>) is formed between the first seal part (<NUM>, <NUM>) and the intermediate seal part (<NUM>, <NUM>), to which a gas having a higher pressure than the external fluid is supplied, wherein
an intermediate chamber (<NUM>, <NUM>) is formed between the intermediate seal part (<NUM>, <NUM>) and the second seal part (<NUM><NUM>), and a gas having a lower pressure than the gas supplied to the gas chamber (<NUM>, <NUM>) and having a lower pressure than the sealed fluid is supplied to the intermediate chamber (<NUM>, <NUM>).