Patent Description:
Conventionally, in a rotating fluid machine such as a pump, in order to seal a fluid, a floating seal is used, and the floating seal shown in <FIG> is known (hereinafter, called as "Conventional Art <NUM>," for example, refer to Patent Citation <NUM>). This conventional art includes a rotation shaft <NUM> of a fluid machine, a sleeve <NUM> attached to an outer periphery of the rotation shaft <NUM> and rotated integrally with the rotation shaft, a seal ring <NUM> loosely fitted to the sleeve <NUM> while having a clearance, plate springs <NUM> provided at four points of an outer periphery of the seal ring <NUM>, and a retainer <NUM> that accommodates the seal ring <NUM>, and in a state where projections 46A of the plate springs <NUM> are engaged with grooves 42A provided in the retainer <NUM>, the seal ring <NUM> is supported by the plate springs <NUM>. By the wedge effect (effect of dynamic pressure generated in a wedge portion) generated between an inner peripheral face of the seal ring <NUM> and the sleeve <NUM> of the rotation shaft <NUM> and the Lomakin effect (aligning effect by flow losses of a fluid between surfaces of a seal ring and a shaft at the time of generation of a seal pressure difference), a gap between the inner peripheral face of the seal ring <NUM> and the rotation shaft <NUM> is held to be fixed, and the seal ring <NUM> is pressed in the axial direction from the high pressure fluid side to the retainer <NUM> side, so that the seal ring <NUM> and the retainer <NUM> are tightly sealed.

However, in Conventional Art <NUM>, the outer periphery of the seal ring <NUM> and the plate springs <NUM> are in contact with each other while being always relatively displaced. Thus, upon running for a long time, surface roughening occurs at contact portions X between the outer periphery of the seal ring <NUM> and the plate springs, and the seal ring <NUM> and the plate springs are anchored to each other. Therefore, the seal ring <NUM> may sometimes be incapable of following movement of the rotation shaft <NUM>. The projections 46A of the plate springs <NUM> may sometimes be worn away or deformed in the grooves 42A of the retainer <NUM>. As a result, the plate springs <NUM> and the seal ring <NUM> cannot follow the movement of the rotation shaft <NUM> and an automatic aligning operation is lost. Thus, there are possibilities that the rotation shaft and the seal ring are brought into contact with each other and damaged, and that a clearance is increased more than an optimal value and a proper sealing operation cannot be obtained.

Further, in Conventional Art <NUM>, assembling takes a lot of time and care. That is, in a case where the plate springs <NUM> are provided in the retainer <NUM> and then the seal ring <NUM> is inserted into the retainer <NUM>, the plate springs <NUM> have to be temporarily compressed to ensure a gap for inserting the seal ring <NUM>. Conversely, in a case where the seal ring <NUM> is arranged in the retainer <NUM> in advance and then the plate springs <NUM> are provided in the retainer <NUM>, the plate springs <NUM> have to be compressed and arranged to ensure a gap between the retainer <NUM> and the seal ring <NUM>. Thus, assembling takes a lot of time and care.

Patent Citations <NUM> and <NUM> each show a generic seal device having the features of the preamble of claim <NUM>. A further conventional seal device is shown by Patent Citation <NUM>.

The present invention is achieved focusing on such a problem, and an object thereof is to provide a seal device in which an automatic aligning operation of a seal ring is maintained even upon running for a long time, a clearance between a rotation shaft and the seal ring can be properly held, and a sealing operation by the seal ring and a vibration damping function can be exerted, the seal device to be easily assembled.

The object is achieved by a seal device having the features of claim <NUM>. A further advantageous development of the present invention is set out in the dependent claim.

According to the present invention, since the floating ring is contactlessly aligned, the floating ring is not restricted by the housing. An automatic aligning operation of the seal ring is maintained even upon running for a long time, a clearance between the rotation shaft and the seal ring is properly held, a sealing operation can be exerted, and the floating ring can be easily installed in a supporting means.

The seal device of the present invention is characterized in that the aligning means includes a first magnet arranged in the housing, the first magnet having a magnetic pole face directed in the radial direction, and a second magnet arranged in the floating ring, the second magnet having a magnetic pole face directed in the radial direction, and the magnetic pole faces of the first magnet and of the second magnet are arranged so that the same poles oppose each other.

According to the present invention, since the floating ring is pressed by magnetic repulsion force of the magnets, movement of the rotation shaft is restricted via the floating ring. Thus, vibration of the rotation shaft can be reduced.

The seal device of the present disclosure is characterized in that magnetic pole adjacent faces of the first magnet and the second magnet where the N pole and the S pole are adjacent to each other are surrounded by a non-magnetic material.

Accordingly, leakage flux of permanent magnets can be reduced. Thus, magnetic force can be efficiently utilized.

Modes for carrying out a seal device according to the present invention will be described in detail with reference to the drawings. However, the present invention is not interpreted while being limited to this. As long as not departing from the scope of the present invention, various modifications, corrections, and improvements can be added based on the knowledge of those skilled in the art.

A seal device <NUM> according to a first embodiment of the present invention will be described with reference to <FIG> and <FIG>. A rotation shaft <NUM> of a fluid machine is arranged so as to pass through a casing <NUM>, and the left side is the high pressure side and the right side is the low pressure side. The seal device <NUM> is mainly formed by a floating ring <NUM>, and a housing <NUM> that accommodates the floating ring <NUM>.

The housing <NUM> is mainly formed by a holder 11a and a flange 11b. The holder 11a is fixed to the casing <NUM> by a fastening means <NUM>. Each of the holder 11a and the flange 11b has a predetermined gap from the rotation shaft <NUM>, and has a hole through which the rotation shaft <NUM> passes. The floating ring <NUM> is accommodated in a space S surrounded by the holder 11a, the flange 11b, and the rotation shaft <NUM> passing through the housing <NUM>. Plural (four in the present embodiment) permanent magnets <NUM> (first magnet of the present invention) are provided in an inner peripheral portion of the flange 11b while being separated from each other in the circumferential direction. Spacers <NUM> made of a non-magnetic material are arranged between the plural permanent magnets <NUM>. The permanent magnets <NUM> and the spacers <NUM> hold circumferential positions of each other. Inner peripheral faces of the permanent magnets <NUM> and the spacers <NUM> are formed in cylindrical faces having the same inner diameter size, and the inner peripheral faces of the permanent magnets <NUM> and the spacers <NUM> form an inner peripheral face of the flange 11b. The floating ring <NUM> is biased by a bias means <NUM> such as a spring, and an end face 13c of a seal ring <NUM> and an end face 11c of the holder 11a are tightly attached to each other, so that the seal ring <NUM> and the holder 11a are tightly sealed. Hereinafter, a tightly sealing means by tight attachment between the end face 13c of the seal ring <NUM> and the end face 11c of the holder 11a will be called as a secondary seal.

The floating ring <NUM> is mainly formed by the seal ring <NUM>, a retainer <NUM> fitted to an outer periphery of the seal ring <NUM>, and permanent magnets <NUM> (second magnet of the present invention) arranged in an outer periphery of the retainer <NUM>.

The seal ring <NUM> is a ring-shaped member having a substantially-rectangular section, made of a material having a favorable sliding property such as carbon. An inner peripheral face 13a of the seal ring <NUM> is formed in a cylindrical face having a minute radial gap h (inside gap) with respect to an outer peripheral face 20a of the rotation shaft <NUM>.

The retainer <NUM> is an annular member made of a non-magnetic material such as austenite stainless and plastic. The retainer <NUM> adds compression force to the seal ring <NUM> by being tightly fitted to the outer periphery of the seal ring <NUM> made of carbon, etc. Thereby, even when the seal ring <NUM> is made of a brittle material such as carbon, breakage of the seal ring <NUM> due to contact with the rotation shaft <NUM>, etc. can be prevented. Plural groove portions 12a are provided in the outer periphery of the retainer <NUM> while being separated from each other in the circumferential direction. The plural groove portions 12a are provided at positions opposing the permanent magnets <NUM>, and the permanent magnets <NUM> (second magnet of the present invention) are fixed to the groove portions 12a. An outer peripheral face of the retainer <NUM> and outer peripheral faces of the permanent magnets <NUM> are formed in cylindrical faces having the same size, and the outer peripheral face of the retainer <NUM> and the outer peripheral faces of the permanent magnets <NUM> form an outer peripheral face of the floating ring <NUM>. The permanent magnets <NUM> may be attached to the permanent magnets <NUM> while providing spacers in the outer periphery of the retainer <NUM>. Similarly, the permanent magnets <NUM> may be attached to grooves provided in an inner periphery of the flange 11b like the permanent magnets <NUM>.

An aligning means <NUM> of the present invention is formed by the retainer <NUM> in which the permanent magnets <NUM> are arranged and the housing <NUM> in which the permanent magnets <NUM> are arranged. The permanent magnets <NUM> and the permanent magnets <NUM> are made of ferrite magnets, neodymium magnets, samarium-cobalt magnets, alnico magnets, praseodymium magnets, etc., and the magnets are selected according to a temperature condition for use and required magnetic force. The permanent magnets <NUM> and the permanent magnets <NUM> are respectively magnetized so that magnetic flux flows in the radial direction. The permanent magnets <NUM> are attached to the inner peripheral portion of the flange 11b, and the permanent magnets <NUM> are respectively attached to an outer peripheral portion of the retainer <NUM>. The plural permanent magnets are attached so that the same magnetic pole faces oppose each other in the radial direction. For example, as shown in <FIG>, the permanent magnets are attached so that S magnetic pole faces <NUM> of the permanent magnets <NUM> are directed to the radially inside, and S magnetic pole faces <NUM> of the permanent magnets <NUM> are directed to the radially outside, and arranged so that the S magnetic pole faces <NUM> and the S magnetic pole faces <NUM> oppose each other. Alternatively, the permanent magnets may be attached so that N magnetic pole faces 14N of the permanent magnets <NUM> are directed to the radially inside and N magnetic pole faces 17N of the permanent magnets <NUM> are directed to the radially outside, and arranged so that the N magnetic pole surfaces 14N and the N magnetic pole surfaces 17N oppose each other.

The floating ring <NUM> loosely fitted to an outer periphery of the rotation shaft <NUM> passing through the housing <NUM> is arranged in the space S of the housing <NUM>. Thereby, the permanent magnets <NUM> of the floating ring <NUM> and the permanent magnets <NUM> of the inner peripheral portion of the flange 11b are attached in a state where a predetermined gap g (outside gap) is held by magnetic repulsion force, and the floating ring is attached and accommodated in the space S of the housing <NUM> in a state where the inner peripheral face 13a of the floating ring <NUM> has the gap h (inside gap) from the outer peripheral face 20a of the rotation shaft <NUM>. Thereby, the aligning means <NUM> can hold the gap g over the entire circumference between the outer peripheral face of the floating ring <NUM> and the inner peripheral face of the flange 11b of the housing <NUM> by the magnetic repulsion force of the permanent magnets <NUM> and the permanent magnets <NUM>, and hold the gap h over the entire circumference between the inner peripheral face 13a of the floating ring <NUM> and the outer peripheral face 20a of the rotation shaft <NUM>, and the floating ring <NUM> autonomously aligns a radial position without contact with the housing <NUM> in the radial direction. The gap h and the gap g are formed within a range of <NUM> ≤ g/h ≤ <NUM>. Thereby, in addition to an aligning operation by the magnetic repulsion force of the aligning means <NUM>, by an aligning effect and a damping effect by a fluid coming in and out of the gaps h and g, vibration of the rotation shaft <NUM> can be furthermore reduced. A circumferentially-positioning means (not shown) is provided in the floating ring <NUM>.

In the permanent magnets <NUM> and the permanent magnets <NUM>, magnetic pole adjacent faces 14a, 14b, 17a, 17b where different magnetic poles are adjacent to each other are covered by a non-magnetic material such as austenite stainless, plastic, and the air. In the magnetic pole adjacent faces 14a, 14b, 17a, 17b of the permanent magnets <NUM> and the permanent magnets <NUM>, the N pole and the S pole are close to each other. Thus, leakage flux in which magnetic flux is short-circuited and flows from the N pole to the S pole is large. Therefore, by covering the magnetic pole adjacent faces 14a, 14b, 17a, 17b of the permanent magnets <NUM> and the permanent magnets <NUM> by a non-magnetic material having high magnetic resistance, the leakage flux can be reduced, and the magnetic repulsion force between the permanent magnets <NUM> and the permanent magnets <NUM> can be enhanced. Plastic and the air have a larger effect of reducing the leakage flux than austenite stainless.

Next, operations of the seal device <NUM> having the above configuration will be described. During stoppage of the rotating fluid machine, the aligning means <NUM> automatically aligns in the radial direction so that the floating ring <NUM> and the flange 11b of the housing <NUM> hold the gap g by the magnetic repulsion force of the permanent magnets <NUM> of the flange 11b of the housing <NUM> and the permanent magnets <NUM> of the floating ring <NUM>, and aligns in the radial direction so that the inner peripheral face 13a of the seal ring <NUM> of the floating ring <NUM> and the outer peripheral face 20a of the rotation shaft <NUM> hold the gap h. In such a way, even during the stoppage where no wedge effect is generated between the floating ring <NUM> and the rotation shaft <NUM>, the minute gap h is held between the inner peripheral face 13a of the floating ring <NUM> and the outer peripheral face 20a of the rotation shaft <NUM>. Thus, wear of the seal ring <NUM> at the time of start-up of the rotating fluid machine can be prevented. The secondary seal by the tight attachment between the end face 13c of the seal ring <NUM> and the end face 11c of the holder 11a soundly functions even during the stoppage.

Even during running, the aligning means <NUM> aligns to hold the gap g by the magnetic repulsion force of the permanent magnets <NUM> of the flange 11b of the housing <NUM> and the permanent magnets <NUM> of the floating ring <NUM>, and further, the floating ring <NUM> and the rotation shaft <NUM> are aligned to hold the gap h by dynamic pressure due to the wedge effect. In such a way, in the floating ring <NUM> held on the outer peripheral side and the inner peripheral side, the gap h from the outer peripheral face 20a of the rotation shaft <NUM> can be substantially uniform over the entire circumference, so that a favorable sealing state can be obtained.

During the running, in the floating ring <NUM>, in addition to pressing force of the bias means <NUM>, by pressure from the high pressure fluid side to the low pressure fluid side, the end face 13c of the seal ring <NUM> and the end face 11c of the holder 11a are further tightly attached to each other. Thus, a sealing effect of the secondary seal is further enhanced.

When the rotation shaft <NUM> largely runs out by the vibration during the running, core displacement occurs between the floating ring <NUM> and the rotation shaft <NUM>, so that the gap g on the outer peripheral side of the floating ring <NUM> and the gap h on the inner peripheral side become non-uniform. However, even when the gap h is decreased by eccentricity, force to solve the core displacement between the seal ring <NUM> and the rotation shaft <NUM> acts between the inner peripheral face 13a of the floating ring <NUM> and the outer peripheral face 20a of the rotation shaft <NUM> by the dynamic pressure due to the wedge effect, and the radial position of the floating ring <NUM> is aligned. Further, on the outer peripheral side of the floating ring <NUM>, the magnetic repulsion force of the aligning means <NUM> also acts. Thus, the radial position of the floating ring <NUM> is automatically aligned. In such a way, even when the rotation shaft <NUM> largely runs out and the floating ring <NUM> is vibrated, the dynamic pressure due to the wedge effect acts on the inner peripheral side of the floating ring <NUM>, the magnetic repulsion force acts on the outer peripheral side of the floating ring <NUM>, and vibration of the floating ring <NUM> is reduced, so that the vibration of the rotation shaft <NUM> is also reduced via the floating ring <NUM>.

The present invention exerts the following excellent effects.

The floating ring <NUM> is aligned in the radial direction from the outer peripheral side so that the clearance g is contactlessly held by the magnetic repulsion force of the aligning means <NUM>, and further held from the inner peripheral side so that the minute clearance h is held by the dynamic pressure due to the wedge effect. Thus, during the stoppage and during the running, a favorable sealing state can be obtained, so that wear of the seal ring <NUM> can be prevented.

The floating ring <NUM> arranged on the inner diameter side of the housing <NUM> has the gap with respect to the housing <NUM> and in no contact with the housing. Thus, a tool, etc. for attachment is not required, and only by inserting into the housing <NUM>, the floating ring can be simply arranged inside the housing.

The floating ring <NUM> is held by the magnetic repulsion force of the aligning means <NUM> on the outer peripheral side, and held by the dynamic pressure due to the wedge effect on the inner peripheral side. That is, by the floating ring <NUM> whose movement is held from the outer peripheral side and the inner peripheral side, the vibration of the rotation shaft <NUM> is regulated, so that the vibration can be reduced.

By the magnetic repulsion force of the aligning means <NUM>, the floating ring <NUM> is automatically aligned in no contact with the housing <NUM>. Thus, without being anchored to the floating ring <NUM> and the housing <NUM>, the aligning means <NUM> can exert the function for a long time.

The magnetic pole adjacent faces 14a, 14b of the permanent magnets <NUM> where different magnetic poles are adjacent to each other and the axial magnetic pole adjacent faces 17a, 17b of the permanent magnets <NUM> are covered by a non-magnetic material. Thus, the leakage flux is reduced, so that the repulsion force between the permanent magnets <NUM> and the permanent magnets <NUM> can be efficiently enhanced.

The seal ring <NUM> is made of a material excellent in a self-lubricating property and a sliding property such as carbon. Thus, even when the seal ring is always relatively displaced with respect to the end face 11c of the holder 11a during the running, wear, surface roughening, etc. can be prevented, so that the function of the secondary seal can be maintained over a long time.

Next, a seal device according to a second embodiment will be described with reference to <FIG>. The same and overlapping configurations as the above embodiment will not be described. A seal device <NUM> according to the second embodiment is chiefly different from the seal device <NUM> of the first embodiment in a point that permanent magnets <NUM>, <NUM> of an aligning means are formed in an annular shape but the other basic configurations are the same as the first embodiment. Thus, the same members will be given the same reference signs and overlapping descriptions will be omitted.

As shown in <FIG>, an aligning means <NUM> is formed by the ring-shaped permanent magnet <NUM> attached to an outer peripheral portion of a retainer <NUM>, and the ring-shaped permanent magnet <NUM> arranged in an inner peripheral portion of a flange 11b of a housing <NUM>. The permanent magnet <NUM> and the permanent magnet <NUM> are made by forming a ferrite magnet or a rare-earth magnet into an annular shape, or made of a plastic magnet formed by mixing powder of a ferrite magnet or a rare-earth magnet with rubber or plastic. Since resin is mixed in, the plastic magnet can be formed into a complicated shape and a thin shape, so that high size precision can be obtained without finish processing. The permanent magnet <NUM> and the permanent magnet <NUM> formed in a ring shape are respectively magnetized so that magnetic flux flows in the radial direction. The permanent magnet <NUM> arranged in the inner peripheral portion of the flange 11b and the permanent magnet <NUM> arranged in the outer peripheral portion of the retainer <NUM> are attached so that the same poles oppose each other across a gap g. Thereby, the permanent magnet <NUM> and the permanent magnet <NUM> can obtain uniform magnetic repulsion force over the entire circumference. Thus, an outer peripheral face of the ring-shaped permanent magnet <NUM> attached to the outer peripheral portion of the retainer <NUM> and an inner peripheral face of the ring-shaped permanent magnet <NUM> attached to the inner peripheral portion of the flange 11b of the housing <NUM> have the gap g over the entire circumference, and the permanent magnets are attached in a state of having a gap h over the entire circumference between an inner peripheral face 13a of a seal ring <NUM> and a rotation shaft <NUM>. The permanent magnet <NUM> and the permanent magnet <NUM> may be integrally formed in a ring shape, or members formed by dividing in the circumferential direction may be attached to the inner peripheral portion of the flange 11b of the housing <NUM> and the outer peripheral portion of the retainer <NUM> so as to be formed in a ring shape.

The embodiments of the present invention are described above with the drawings. However, specific configurations are not limited to these embodiments but the present invention includes modifications and additions within a range not departing from the scope of the appended claims.

For example, in the above embodiments, the floating ring <NUM> is an annular integrated body. However, the present invention is not limited to this but members formed by dividing in the circumferential direction may be assembled into an annular integrated body.

In the above embodiments, the floating ring <NUM> is biased by the bias means <NUM>. However, without using the bias means <NUM>, the end face 13c of the seal ring <NUM> and the end face 11c of the holder 11a may be further tightly attached to each other by the pressure from the high pressure fluid side to the low pressure fluid side, so as to form the secondary seal.

In the above embodiment, the aligning means <NUM> is formed by the permanent magnets <NUM> attached to the outer peripheral portion of the retainer <NUM> and the permanent magnets <NUM> attached to the inner peripheral portion of the flange 11b of the housing <NUM>. However, the present invention is not limited to this. For example, permanent magnets may be attached to the outer peripheral portion of the retainer <NUM> and electromagnets may be attached to the inner peripheral portion of the flange 11b of the housing <NUM>.

In a case where a working fluid of a pump is a super-low-temperature fluid such as liquid helium, superconducting magnets may be used in place of the permanent magnets. The superconducting magnets have the flux pinning effect. Thus, an effect that a detent for the floating ring is not required can also be obtained.

Claim 1:
A seal device (<NUM>) that seals between a housing (<NUM>) and a rotation shaft (<NUM>) passing through the housing (<NUM>), the seal device (<NUM>) comprising:
a floating ring (<NUM>) arranged with an inside gap (h) with respect to the rotation shaft (<NUM>), and with an outside gap (g) with respect to the housing (<NUM>), and
an aligning means (<NUM>) that contactlessly aligns a position of the floating ring (<NUM>), characterized in that
the aligning means (<NUM>) includes a first magnet (<NUM>) arranged in the housing (<NUM>), the first magnet (<NUM>) having a magnetic pole face (14N, <NUM>) directed in the radial direction, and a second magnet (<NUM>) arranged in the floating ring (<NUM>), the second magnet (<NUM>) having a magnetic pole face (17N, <NUM>) directed in the radial direction,
wherein
the magnetic pole faces (14N, <NUM>, 17N, <NUM>) of the first magnet (<NUM>) and of the second magnet (<NUM>) are arranged so that the same poles oppose each other, and
the inside gap (h) and the outside gap (g) are formed within a range of <NUM> ≤ g/h ≤ <NUM>.