JP2024072547A - mechanical seal - Google Patents

Abstract

[Problem] To provide a mechanical seal capable of stably preventing leakage of a sealed fluid between sliding surfaces. [Solution] A mechanical seal 1 is disposed between a housing 3 and a rotating shaft 2 which rotates relative to the housing 3, and comprises a stationary seal ring 11 attached to a stationary mounting member 10 disposed on the housing 3 side, and a rotating seal ring 21 attached to a rotating mounting member 20 disposed on the rotating shaft 2 side, and comprises a stationary side secondary seal 13 which abuts against the stationary seal ring 11 and the stationary mounting member 10, and a rotating side secondary seal 23 which abuts against the rotating seal ring 21 and the rotating mounting member 20, a stationary side spring 12 which is disposed between the stationary seal ring 11 and the stationary mounting member 10 and biases the stationary seal ring 11 towards the rotating seal ring 21, and a rotating side spring 22 which is disposed between the rotating seal ring 21 and the rotating mounting member 20 and biases the rotating seal ring 21 towards the stationary seal ring 11. [Selected Figure] Figure 1

Description

The present invention relates to a mechanical seal that seals a rotating shaft.

Mechanical seals are used by being installed between the housing of a fluid device and a rotating shaft that is arranged to pass through the housing. More specifically, mechanical seals have the function of preventing leakage of the sealed fluid by bringing the sliding surface of a stationary seal ring attached to the housing into sliding contact in the circumferential direction with the sliding surface of a rotating seal ring that is attached to the rotating shaft and rotates.

In a typical mechanical seal, as shown in Patent Document 1, for example, a stationary seal ring is arranged to be axially movable relative to a seal cover and is biased toward a rotating seal ring by a spring. The rotating seal ring is attached so that it cannot move axially relative to a sleeve fixed to a rotating shaft.

JP 2021-60079 A (pages 4 to 6, Figure 1)

In the mechanical seal of Patent Document 1, the stationary seal ring is biased toward the rotating seal ring by a spring, thereby maintaining the sliding contact between the sliding surfaces and preventing leakage of the sealed fluid. However, in Patent Document 1, when an axial force acts on the rotating shaft due to disturbance or vibration, causing axial movement, the sliding contact between the sliding surfaces may not be maintained, causing the surfaces to open up and resulting in leakage of the sealed fluid. Or, when the load between the sliding surfaces becomes large and excessive surface pressure is generated, the sliding surfaces may be damaged and the sealed fluid may leak.

The present invention was made with an eye on these problems, and aims to provide a mechanical seal that can stably prevent leakage of the sealed fluid between the sliding surfaces.

In order to solve the above problems, the mechanical seal of the present invention comprises:
A mechanical seal is disposed between a housing and a rotating shaft that rotates relative to the housing, in which a stationary seal ring is attached to a stationary-side mounting member disposed on the housing side, and a rotating seal ring is attached to a rotating-side mounting member disposed on the rotating shaft side, and the mechanical seal comprises:
a stationary secondary seal that abuts against the stationary seal ring and the stationary mounting member, and a rotating secondary seal that abuts against the rotating seal ring and the rotating mounting member,
The seal spring is provided between the stationary seal ring and the stationary side mounting member and urges the stationary seal ring toward the rotating seal ring, and a rotating side spring is provided between the rotating seal ring and the rotating side mounting member and urges the rotating seal ring toward the stationary seal ring.
According to this, the stationary seal ring and the rotating seal ring are biased in the direction approaching each other by the stationary side spring and the rotating side spring, respectively, which makes it easier to equalize the axial forces acting on the stationary seal ring and the rotating seal ring from both sides, making it possible to make it difficult for the sliding surface positions to change in the axial direction, and also makes it possible to reduce changes in load between the sliding surfaces while maintaining the sliding contact state between the sliding surfaces even if the rotating shaft moves in the axial direction due to disturbance or vibration. In this way, leakage of the sealed fluid between the sliding surfaces can be stably prevented.

The stationary seal ring and the rotating seal ring may be pressed against each other in a state in which the stationary side spring and the rotating side spring are each shorter than their natural lengths.
This allows the stationary seal ring and the rotating seal ring to move in the axial direction while suppressing changes in the load between the sliding surfaces.

An acting diameter of the stationary side spring with respect to the stationary seal ring and an acting diameter of the rotating side spring with respect to the rotating seal ring may be the same.
This makes it easier to equalize the axial forces acting on both sides of the stationary seal ring and the rotary seal ring, making it possible to make it more difficult for the sliding surface positions to change in the axial direction.

The stationary side secondary seal may be in radial contact with a peripheral surface of the stationary seal ring that is perpendicular to the sliding surface of the stationary seal ring in the extension direction, and the rotating side secondary seal may be in radial contact with a peripheral surface of the rotating seal ring that is perpendicular to the sliding surface of the rotating seal ring in the extension direction.
With this, the stationary side secondary seal and the rotating side secondary seal no longer apply axial force to the stationary seal ring and the rotating seal ring, respectively, and the load between the sliding surfaces of the stationary seal ring and the rotating seal ring can be accurately set by the biasing forces of the stationary side spring and the rotating side spring.

The stationary side mounting member may be formed with a stationary side movement regulating portion that regulates the stationary seal ring from falling over, and the rotating side mounting member may be formed with a rotating side movement regulating portion that regulates the rotating seal ring from falling over.
This makes it possible to prevent the stationary seal ring and the rotary seal ring from falling over, and to suppress an inappropriate contact state between the sliding surfaces of the stationary seal ring and the rotary seal ring.

The stationary side spring and the rotating side spring may have the same spring constant.
This makes it easier to control the axial movements of the stationary seal ring and the rotating seal ring, making it easier to reduce changes in load between the sliding surfaces.

One of the seal rings may be in axial contact with the workpiece to which the seal ring is attached.
This makes it easier to maintain the initial positions of the stationary seal ring and the rotary seal ring.

1 is a cross-sectional view showing a mechanical seal according to a first embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view showing the initial positions of the stationary seal ring and the rotating seal ring in the mechanical seal of the first embodiment. FIG. 4 is an enlarged cross-sectional view showing a state in which a rotating shaft has moved axially to the right from an initial position in the mechanical seal of the first embodiment. FIG. 4 is an enlarged cross-sectional view showing a state in which a rotating shaft has moved axially to the left from an initial position in the mechanical seal of the first embodiment. FIG. 4 is an enlarged cross-sectional view showing the initial positions of the stationary seal ring and the rotating seal ring in the first modified example of the mechanical seal of the first embodiment. FIG. 11 is an enlarged cross-sectional view showing the initial positions of the stationary seal ring and the rotating seal ring in the second modified example of the mechanical seal of the first embodiment. FIG. 11 is an enlarged cross-sectional view showing the initial positions of a stationary seal ring and a rotating seal ring in a mechanical seal according to a second embodiment of the present invention. FIG. 11 is an enlarged cross-sectional view showing a state in which a rotating shaft has been axially moved to the right from an initial position in a mechanical seal according to a third embodiment of the present invention. FIG. 11 is an enlarged cross-sectional view showing a state in which a rotating shaft has moved axially to the left from an initial position in the mechanical seal of the third embodiment.

The following describes the embodiment of the mechanical seal according to the present invention.

The mechanical seal of the first embodiment will be described with reference to Figs. 1 to 4. In the following description, the left side of Fig. 1 will be referred to as the left side, and the right side of Fig. 1 will be referred to as the right side.

As shown in FIG. 1, the mechanical seal 1 is an inside-type mechanical seal that seals against a sealed fluid F that is attempting to leak from the outer diameter side to the inner diameter side. In this description, the space on the inner diameter side between the stationary seal ring 11 and the rotating seal ring 21 is referred to as the atmosphere A side, and the space on the outer diameter side between the stationary seal ring 11 and the rotating seal ring 21 is referred to as the sealed fluid F side.

The mechanical seal 1 of this embodiment is mainly composed of a stationary seal ring 11, a rotating seal ring 21 that rotates with the rotating shaft 2, a seal cover 10 as a stationary side mounting member to which the stationary seal ring 11 is attached, a stationary side spring 12 that supports the stationary seal ring 11 against the seal cover 10 and urges it toward the rotating seal ring 21, a sleeve 20 as a rotating side mounting member to which the rotating seal ring 21 is attached, and a rotating side spring 22 that supports the rotating seal ring 21 against the sleeve 20 and urges it toward the stationary seal ring 11.

In addition, in the mechanical seal 1 of this embodiment, a stationary side O-ring 13 is disposed between the seal cover 10 and the stationary seal ring 11 as a stationary side secondary seal, and a rotating side O-ring 23 is disposed between the sleeve 20 and the rotating seal ring 21 as a rotating side secondary seal. The stationary side O-ring 13 and the rotating side O-ring 23 are formed from an elastic material such as synthetic rubber, and are secondary seals to prevent leakage of the sealed fluid F between the seal cover 10 and the stationary seal ring 11, and between the sleeve 20 and the rotating seal ring 21.

As shown in FIG. 2, the stationary seal ring 11 mainly comprises an annular base 11a, an annular protrusion 11b protruding in the axial direction from the left face, i.e., the front face, of the base 11a, and an annular protrusion 11c protruding in the axial direction from the back face and outer diameter side of the base 11a. In this embodiment, the stationary seal ring 11 is made of ceramics or carbon.

The surface of the stationary seal ring 11 facing the rotating seal ring 21 at the protruding portion 11b is the sliding surface 11d.

A ring-shaped recess 11e is formed on the inner circumference of the protrusion 11c, recessed in the axial direction from the back surface of the protrusion 11c.

The seal cover 10 is fixed to the housing 3 of the fluid device and is an annular member with a generally horizontal U-shaped cross section that opens to the left. The seal cover 10 mainly comprises an annular base 10a that abuts against the right side of the housing 3, an annular flange 10b that extends radially inward from the right end of the base 10a, and an annular protrusion 10c that protrudes to the left from the inner end of the flange 10b.

An insertion hole 10d that opens to the left is formed on the left surface of the protrusion 10c. Multiple insertion holes 10d are equally spaced around the circumference of the protrusion 10c.

A stationary side spring 12 is disposed in each of the multiple insertion holes 10d. The stationary side spring 12 is a metallic compression spring, and the left end of the stationary side spring 12 presses against the back surface 11g of the base 11a of the stationary seal ring 11, and the right end of the stationary side spring 12 presses against the bottom of the insertion hole 10d. The back surface 11g of the base 11a of the stationary seal ring 11 is parallel to the sliding surface 11d of the stationary seal ring 11. More specifically, in this embodiment, the sliding surface 11d of the stationary seal ring 11 and the back surface 11g are parallel to each other.

As shown in FIG. 1, a knock pin 14 is fixed to the left surface of the protrusion 10c at a position that is out of phase with the insertion hole 10d in the circumferential direction. The knock pin 14 is inserted into an insertion groove 11f formed on the inner circumference of the base 11a of the stationary seal ring 11. This allows the stationary seal ring 11 to move in the axial direction while restricting its rotation relative to the seal cover 10. Note that the configuration that allows the stationary seal ring 11 to move in the axial direction while restricting its rotation relative to the seal cover 10 is not limited to the knock pin 14 and the insertion groove 11f, but may be a clutch mechanism in which an extension portion extending from the seal cover 10 toward the stationary seal ring 11 can engage with a notch in the stationary seal ring 11 in the circumferential direction.

In addition, a ring-shaped recess 10e is formed on the outer periphery of the protrusion 10c, recessed in the axial direction from the left side of the protrusion 10c. A stationary O-ring 13 is fitted on the recess 10e. More specifically, the stationary O-ring 13 is fitted on the outer periphery of the recess 10e and disposed in a space defined by the recess 10e and a recess 11e formed on the inner periphery of the protrusion 11c in the stationary seal ring 11. The axial dimension of the space defined by the recess 10e and the recess 11e is formed to be larger than the cross-sectional diameter of the stationary O-ring 13, so that the stationary seal ring 11 abuts against the seal cover 10 to prevent the stationary O-ring 13 from being crushed in the axial direction even when the rotating shaft 2 moves to the right (see FIG. 3), as described later.

The stationary O-ring 13 is held in line contact with the outer peripheral surface extending in the axial direction in the recess 10e and the inner peripheral surface extending in the axial direction in the recess 11e. In other words, the stationary O-ring 13 is in radial contact with the inner peripheral surface of the recess 11e, which is a peripheral surface that is perpendicular to the sliding surface 11d of the stationary seal ring 11 in the extension direction.

The seal cover 10 is also provided with stationary side movement restriction portions 10f, 10g on both axial sides of the stationary side O-ring 13 that can abut against the stationary seal ring 11 and restrict the stationary seal ring 11 from falling when excessive force is applied to the stationary seal ring 11.

As shown in FIG. 2, the rotary seal ring 21 mainly comprises an annular base portion 21a and an annular protrusion portion 21b that protrudes in the axial direction from the left surface, i.e., the back surface side and the outer diameter side, of the base portion 21a. In this embodiment, the rotary seal ring 21 is made of ceramics or carbon.

The surface of the rotating seal ring 21 that faces the sliding surface 11d of the stationary seal ring 11 at the base 21a forms the sliding surface 21d.

A ring-shaped recess 21e is formed on the inner circumference of the protrusion 21b, recessed in the axial direction from the back surface of the protrusion 21b.

The sleeve 20 is a cylindrical member with a generally L-shaped cross section that is fixed to the rotating shaft 2. The sleeve 20 mainly comprises a base portion 20a that covers the outer peripheral surface of the rotating shaft 2 and extends in the axial direction, and an annular flange portion 20b that extends in the outer radial direction from the left end portion of the base portion 20a.

In the right surface of the flange portion 20b, an insertion hole 20d that opens to the right side is formed. The insertion holes 20d are arranged evenly in the circumferential direction of the flange portion 20b. It is preferable that the insertion holes 20d are arranged evenly in the circumferential direction at the same intervals as the insertion holes 10d formed in the seal cover 10 in number.

A rotating side spring 22 is disposed in each of the multiple insertion holes 20d. The rotating side spring 22 is a metallic compression spring, and the right end of the rotating side spring 22 presses against the back surface 21g of the base 21a of the rotating seal ring 21, and the left end of the rotating side spring 22 presses against the bottom of the insertion hole 20d. The back surface 21g of the base 21a of the rotating seal ring 21 is parallel to the sliding surface 21d of the rotating seal ring 21. More specifically, in this embodiment, the sliding surface 21d of the rotating seal ring 21 and the back surface 21g are parallel to each other.

In this embodiment, the stationary spring 12 and the rotating spring 22 have the same specifications. Therefore, there is no risk of mis-attaching the stationary spring 12 and the rotating spring 22 during assembly.

In addition, even if they do not have the same specifications, it is preferable that the stationary side spring 12 and the rotating side spring 22 have the same spring constant, but the outer diameter, wire diameter, free height (natural length), etc. may be different.

In addition, in this embodiment, the stationary side spring 12 and the rotating side spring 22 have linear characteristics in the range of use shown in Figures 2, 3, and 4.

As shown in FIG. 1, a drive pin 24 is fixed to the right surface of the flange portion 20b at a position that is out of phase with the insertion hole 20d in the circumferential direction. The drive pin 24 is inserted into an insertion groove 21f formed on the inner circumference of the base 21a of the rotary seal ring 21. This allows the rotary seal ring 21 to move in the axial direction while restricting the rotation of the rotary seal ring 21 relative to the sleeve 20. Note that the configuration that allows the rotary seal ring 21 to move in the axial direction while restricting the rotation of the rotary seal ring 21 relative to the sleeve 20 is not limited to the drive pin 24 and the insertion groove 21f, but may be a clutch mechanism in which an extension portion extending from the sleeve 20 toward the rotary seal ring 21 can engage with a notch in the rotary seal ring 21 in the circumferential direction.

The outer periphery of the flange portion 20b is formed with an annular recess 20e that is recessed in the axial direction from the right surface of the flange portion 20b. The rotating side O-ring 23 is fitted into the recess 20e. More specifically, the rotating side O-ring 23 is fitted into the recess 20e and disposed in a space defined by the recess 20e and a recess 21e formed on the inner periphery of the protruding portion 21b of the rotating seal ring 21. The axial dimension of the space defined by the recess 20e and the recess 21e is formed to be larger than the cross-sectional diameter of the rotating side O-ring 23, so that even if the rotating shaft 2 moves to the right (see FIG. 3), the rotating seal ring 21 abuts against the sleeve 20, preventing the rotating side O-ring 23 from being crushed in the axial direction.

The rotating O-ring 23 is held in line contact with the outer peripheral surface extending in the axial direction in the recess 20e and the inner peripheral surface extending in the axial direction in the recess 21e. In other words, the rotating O-ring 23 is in radial contact with the inner peripheral surface of the recess 21e, which is a peripheral surface that is perpendicular to the sliding surface 21d of the rotating seal ring 21 in the extension direction.

The sleeve 20 is also formed with rotational side movement restriction portions 20f, 20g on both axial sides of the rotating side O-ring 23 that can abut against the rotating seal ring 21 and restrict the rotating seal ring 21 from tipping over when excessive force is applied to the rotating seal ring 21.

Note that FIG. 2 shows the initial positions of the stationary seal ring 11 and the rotating seal ring 21 when the fluid equipment to which the mechanical seal 1 of this embodiment is applied is stopped or in normal operation. In the mechanical seal 1 of this embodiment, the opposing stationary side spring 12 and rotating side spring 22 press the stationary seal ring 11 and the rotating seal ring 21 together in a compressed state that is shorter than their natural lengths, and the stationary seal ring 11 and the rotating seal ring 21 can move from their initial positions to both sides in the axial direction. Note that in this embodiment, the stationary side spring 12 and the rotating side spring 22 are arranged on approximately the same line and face each other, but this is not limited to the above, and the two may be arranged in different phases and face each other.

In addition, when the stationary seal ring 11 and the rotating seal ring 21 are in their initial positions, the loads applied to the stationary seal ring 11 and the rotating seal ring 21 from the stationary side spring 12 and the rotating side spring 22, respectively, are balanced. Hereinafter, the load applied between the sliding surfaces 11d, 21d, i.e., the seal portion, when the stationary seal ring 11 and the rotating seal ring 21 are in their initial positions is referred to as the reference seal load.

In addition, in this embodiment, the stationary side spring 12 and the rotating side spring 22 are located on the inner diameter side of the seal portion. Also, the acting diameters on which the biasing forces of the stationary side spring 12 and the rotating side spring 22 act on the stationary seal ring 11 and the rotating seal ring 21 are the same.

In addition, the entire back surfaces of the stationary seal ring 11 and the rotating seal ring 21 are subjected to pressure from the sealed fluid F, which contributes to the surface pressure bias between the sliding surfaces 11d, 21d.

Furthermore, in the mechanical seal 1 of this embodiment, the pressure acting diameters of the stationary seal ring 11 and the rotating seal ring 21, which are determined by the stationary side O-ring 13 and the rotating side O-ring 23, are the same. In addition, the mechanical seal 1 of this embodiment is a balanced type mechanical seal in which the seal portion is formed to a position on the inner diameter side of the pressure acting diameters of the stationary seal ring 11 and the rotating seal ring 21. As a result, in the mechanical seal 1 of this embodiment, the influence of the pressure of the sealed fluid F acting in the axial direction on the stationary seal ring 11 and the rotating seal ring 21 is reduced. In addition, the stationary side O-ring 13 abuts radially against the inner peripheral surface of the recess 11e of the stationary seal ring 11, and the rotating side O-ring 23 abuts radially against the inner peripheral surface of the recess 21e of the rotating seal ring 21. Furthermore, the axial dimension of the space defined by the recesses 10e and 11e in which the stationary O-ring 13 is housed is formed to be larger than the cross-sectional diameter of the stationary O-ring 13, and the axial dimension of the space defined by the recesses 20e and 21e in which the rotating O-ring 23 is housed is formed to be larger than the cross-sectional diameter of the rotating O-ring 23. As a result, in the mechanical seal 1 of this embodiment, the stationary O-ring 13 and the rotating O-ring 23 always abut against the back surfaces of the stationary seal ring 11 and the rotating seal ring 21 and are not crushed between the seal cover 10 and the sleeve 20, and the stationary O-ring 13 and the rotating O-ring 23 do not apply axial forces to the stationary seal ring 11 and the rotating seal ring 21 due to their own restoring forces. Therefore, the load between the sliding surfaces 11d and 21d can be set with high precision by the biasing forces of the stationary spring 12 and the rotating spring 22.

Next, the operation of the stationary side spring 12 and the rotating side spring 22 when axial movement of the rotating shaft 2 occurs in the mechanical seal 1 of this embodiment will be explained using Figures 3 and 4. Note that in the initial positions of the stationary seal ring 11 and the rotating seal ring 21 shown in Figure 2, the stationary side spring 12 and the rotating side spring 22 are assumed to have the same length.

As shown in FIG. 3, when the rotating shaft 2 moves to the right, both the stationary side spring 12 and the rotating side spring 22, which face each other, operate to further compress from their compressed states.

In this way, in the mechanical seal 1 of this embodiment, when the rotating shaft 2 moves to the right, the stationary side spring 12 and the rotating side spring 22 operate to compress by the same amount. At this time, the amount of compression of the stationary side spring 12 and the rotating side spring 22, i.e., the amount of movement of the stationary seal ring 11 (L11) and the amount of movement of the rotating seal ring 21 (L21), is half the amount of movement of the rotating shaft 2 (L2). Note that the directions of the arrows L11 and L21 in Figure 3 indicate the direction of movement relative to the seal cover 10, which is the stationary side mounting member, and the sleeve 20, which is the rotating side mounting member, and this is the same in the following embodiments.

The amount of movement of the stationary seal ring 11 (L11) and the amount of movement of the rotating seal ring 21 (L21) therefore reduces the amount of load change of the stationary side spring 12 and the rotating side spring 22 to half that of a conventional mechanical seal with a spring on only one side. As a result, the amount of change in the seal load between the sliding surfaces 11d, 21d is half that of a conventional mechanical seal with a spring on only one side, stabilizing the sealing performance. In this way, the biasing forces of the stationary side spring 12 and the rotating side spring 22 increase by approximately the same amount from the initial position, making it easier to maintain balance between the biasing forces of the stationary side spring 12 and the rotating side spring 22.

In addition, in the mechanical seal 1 of this embodiment, all of the axial forces acting on the stationary seal ring 11 and the rotating seal ring 21 are absorbed by the compression of the opposing stationary side spring 12 and rotating side spring 22, so only the increased load caused by the compression of the stationary side spring 12 and rotating side spring 22 acts between the sliding surfaces 11d, 21d, and as a result, the increase in load can be made gentler.

Furthermore, in the mechanical seal 1 of this embodiment, the opposing stationary side spring 12 and rotating side spring 22 are compression springs with the same spring constant, which makes it easier to hold the stationary seal ring 11 and the rotating seal ring 21 in a central position between the seal cover 10 and the sleeve 20. This makes it easier to suppress the occurrence of excessive surface pressure between the sliding surfaces 11d, 21d.

As shown in Figure 4, when the rotating shaft 2 moves to the left, both the stationary side spring 12 and the rotating side spring 22, which face each other, expand from their compressed state. Note that Figure 4 shows the state in which the axial movement of the rotating shaft 2 to the left is at its maximum.

In this way, in the mechanical seal 1 of this embodiment, when the rotating shaft 2 moves to the left, the stationary side spring 12 and the rotating side spring 22 operate to expand by the same amount. At this time, the expansion amount of the stationary side spring 12 and the rotating side spring 22, that is, the movement amount of the stationary seal ring 11 (L11') and the movement amount of the rotating seal ring 21 (L21'), is half the movement amount of the rotating shaft 2 (L2'). Therefore, since the biasing forces of the stationary side spring 12 and the rotating side spring 22 are reduced by approximately the same amount from the initial position, the load between the sliding surfaces 11d, 21d decreases from the reference seal load, but the stationary side spring 12 and the rotating side spring 22 maintain the state in which the sliding surfaces 11d, 21d are pressed against each other in a compressed state, so that the surface opening between the sliding surfaces 11d, 21d can be reliably prevented. That is, in this embodiment, the initial set amount of the stationary side spring 12 and the rotating side spring 22 is set to an amount sufficiently larger than half the axial movement amount to the left.

As described above, the mechanical seal 1 comprises a stationary side O-ring 13 that radially abuts against the inner circumferential surface of the recess 11e, which is a peripheral surface that is perpendicular to the sliding surface 11d of the stationary seal ring 11 in the extension direction, a rotating side O-ring 23 that radially abuts against the inner circumferential surface of the recess 21e, which is a peripheral surface that is perpendicular to the sliding surface 21d of the rotating seal ring 21 in the extension direction, a stationary side spring 12 that urges the stationary seal ring 11 toward the rotating seal ring 21, and a rotating side spring 22 that urges the rotating seal ring 21 toward the stationary seal ring 11. As a result, the stationary seal ring 11 and the rotating seal ring 21 are biased toward each other by the stationary side spring 12 and the rotating side spring 22, respectively, i.e., in the axial direction, which makes it easier to equalize the axial forces acting on the stationary seal ring 11 and the rotating seal ring 21 from both sides, making it difficult to change the position of the sliding surfaces 11d, 21d in the axial direction, and even if the rotating shaft 2 moves in the axial direction due to disturbance or vibration, the sliding contact state between the sliding surfaces 11d, 21d can be maintained while reducing the load change between the sliding surfaces 11d, 21d. In this way, leakage of the sealed fluid F between the sliding surfaces 11d, 21d can be stably prevented.

The stationary side spring 12 contacts the back surface 11g parallel to the sliding surface 11d of the stationary seal ring 11 from the seal cover 10, and the rotating side spring 22 contacts the back surface 21g parallel to the sliding surface 21d of the rotating seal ring 21 from the sleeve 20, and the structure applies a load only to the back surfaces 11g, 21g parallel to the sliding surfaces 11d, 21d. Therefore, the positions of the stationary seal ring 11 and the rotating seal ring 21, for example, the initial positions, can be determined only by the load design of the stationary side spring 12 and the rotating side spring 22. Therefore, for example, even if the shapes of the stationary seal ring and the rotating seal ring are different, more specifically, even if the shapes of the sliding surface of the stationary seal ring and the sliding surface of the rotating seal ring are different, the stationary seal ring and the rotating seal ring can be set to the desired positions.

In addition, the mechanical seal 1 has a stationary side spring 12 provided between the stationary seal ring 11 and the seal cover 10, and a rotating side spring 22 provided between the rotating seal ring 21 and the sleeve 20. This allows the load between the sliding surfaces 11d, 21d to be stabilized with a simple structure. In addition, the stationary side spring 12 and the rotating side spring 22 are less likely to change shape or spring constant due to the effects of heat compared to other biasing members such as rubber bellows, so the load between the sliding surfaces 11d, 21d can be stabilized regardless of the operating temperature.

In addition, compared to other biasing members such as rubber bellows, the stationary side spring 12 and the rotating side spring 22 do not change the load or acting diameter on the stationary seal ring 11 and the rotating seal ring 21 even when pressure is applied, so the load between the sliding surfaces 11d and 21d can be stabilized.

The stationary side spring 12 and the rotating side spring 22 are arranged in an insertion hole 10d formed in the seal cover 10 and an insertion hole 20d formed in the sleeve 20, respectively. As a result, the inner circumferences of the insertion holes 10d, 20d formed in the stationary side mounting member and the rotating side mounting member guide the expansion and contraction of the stationary side spring 12 and the rotating side spring 22, respectively, and prevent the stationary side spring 12 and the rotating side spring 22 from buckling or tilting, thereby stabilizing the axial movement of the stationary seal ring 11 and the rotating seal ring 21 and stabilizing the load between the sliding surfaces 11d, 21d.

Furthermore, the stationary seal ring 11 is guided in its axial movement by the outer peripheral surfaces of the convex portion 10c and concave portion 10e of the seal cover 10, while the rotating seal ring 21 is guided in its axial movement by the outer peripheral surfaces of the flange portion 20b and concave portion 20e of the sleeve 20. This makes it possible to further stabilize the axial movement of the stationary seal ring 11 and the rotating seal ring 21.

In addition, the mechanical seal 1 can apply an axial load to the stationary seal ring 11 and the rotating seal ring 21 by the stationary side spring 12 and the rotating side spring 22, so the load between the sliding surfaces 11d, 21d at the initial position of the stationary seal ring 11 and the rotating seal ring 21 can be set with high precision by designing the load of the opposing stationary side spring 12 and rotating side spring 22.

For example, the mechanical seal of this embodiment will be explained in comparison with a conventional floating seal. In a floating seal that combines a sealing function with a rotation prevention function, such as an O-ring, a strong radial force is generated on the stationary seal ring and the rotating seal ring, and the deformation of the stationary seal ring and the rotating seal ring that are subjected to this radial force may cause distortion of the sliding surfaces, which may lead to leakage between the sliding surfaces.

In contrast, in the mechanical seal 1 of this embodiment, the stationary side spring 12 and the rotating side spring 22 generate force only in the axial direction against the stationary seal ring 11 and the rotating seal ring 21, and the stationary side O-ring 13 and the rotating side O-ring 23 provided as secondary seals are held in radial line contact with the stationary seal ring 11 and the rotating seal ring 21, so they do not generate axial force but generate radial force.

The radial force generated by the stationary O-ring 13 and the rotating O-ring 23 is very small compared to the radial force generated by the O-ring in the floating seal described above, so it does not cause deformation of the stationary seal ring 11 and the rotating seal ring 21 that would lead to leakage between the sliding surfaces 11d, 21d as in this embodiment.

The anti-rotation function of the stationary seal ring 11 and the rotating seal ring 21 in the mechanical seal 1 of this embodiment is provided by the knock pin 14 and the drive pin 24. That is, in the mechanical seal 1, the stationary side O-ring 13 and the rotating side O-ring 23 only have a sealing function as a secondary seal, and the structure in which the opposing stationary side spring 12 and rotating side spring 22 apply a load between the sliding surfaces 11d, 21d can stably prevent leakage of the sealed fluid F between the sliding surfaces 11d, 21d.

Furthermore, even if the stationary side O-ring 13 and the rotating side O-ring 23 deteriorate over time, the biasing force of the stationary side spring 12 and the rotating side spring 22 remains unchanged, preventing leakage of the sealed fluid F between the sliding surfaces 11d, 21d. In addition, since the stationary side spring 12 and the rotating side spring 22 are metallic compression springs, they are less susceptible to deterioration over time compared to O-rings made of synthetic rubber, etc., and it is possible to prevent the surface gap between the sliding surfaces 11d, 21d from forming over a long period of time.

Furthermore, in conventional floating seals, even if the rotating shaft moves axially, the O-ring acts as a biasing member to hold the stationary seal ring and the rotating seal ring in place, generating a radial force. This means that the O-ring does not roll, but deforms while remaining fixed between the rotating housing and the stationary housing and the stationary seal ring and the rotating seal ring. This means that the stationary seal ring and the rotating seal ring tend to swing radially, and there is a risk that the abutment state between the sliding surfaces of the stationary seal ring and the rotating seal ring may become inappropriate.

In contrast, in the mechanical seal 1 of this embodiment, the only biasing means for biasing the stationary seal ring 11 and the rotating seal ring 21 are the stationary side spring 12 and the rotating side spring 22, and there are stationary side movement regulating portions 10f, 10g and rotating side movement regulating portions 20f, 20g that regulate the collapse of the seal rings, as well as the stationary side O-ring 13 and rotating side O-ring 23 that serve as secondary seals. Therefore, even if axial movement occurs in the stationary seal ring 11 and the rotating seal ring 21, the stationary seal ring 11 and the rotating seal ring 21 can be moved axially while suppressing radial vibration. In detail, the radial movement of the stationary seal ring 11 and the rotating seal ring 21 is restricted by the stationary side movement restricting parts 10f, 10g and the rotating side movement restricting parts 20f, 20g, so that the stationary side O-ring 13 and the rotating side O-ring 23 are not substantially deformed, and the stationary seal ring 11 and the rotating seal ring 21 can be moved in the axial direction by rotating and rolling, thereby preventing the contact state between the sliding surfaces 11d, 21d from becoming inappropriate.

In addition, the stationary side O-ring 13 and the rotating side O-ring 23 are not always in contact with the back surface of the stationary seal ring 11 and the rotating seal ring 21, and are not crushed between the seal cover 10 and the sleeve 20. The stationary side O-ring 13 and the rotating side O-ring 23 are not required to generate axial force due to their own restoring force. For example, as shown in modified example 1 of FIG. 5, the stationary side O-ring 13 is arranged in an annular groove 110e recessed in the inward direction from the outer peripheral surface of the convex portion 110c of the seal cover 110, and is in radial contact with the inner peripheral surface of the concave portion 111e of the stationary seal ring 111, and the rotating side O-ring 23 is arranged in an annular groove 120e recessed in the inward direction from the outer peripheral surface of the flange portion 120b of the sleeve 120, and is in radial contact with the inner peripheral surface of the concave portion 121e of the rotating seal ring 121. In addition, the seal cover 110 and sleeve 120 of variant 1 also have stationary side movement restriction parts 110f, 110g and rotating side movement restriction parts 120f, 120g.

Also, as shown in modified example 2 of FIG. 6, the stationary side O-ring 13 may be arranged in an annular groove 111h recessed in the outer diameter direction from the inner peripheral surface of the recess 111e in the stationary seal ring 111, and may be configured to abut radially against the outer peripheral surface of the protrusion 110c in the seal cover 110, and the rotating side O-ring 23 may be arranged in an annular groove 121h recessed in the outer diameter direction from the inner peripheral surface of the recess 121e in the rotating seal ring 121, and may be configured to abut radially against the outer peripheral surface of the flange portion 120b in the sleeve 120. Note that the seal cover 110 and sleeve 120 of modified example 2 are also formed with stationary side movement restricting portions 110f, 110g and rotating side movement restricting portions 120f, 120g.

The stationary side spring 12 and the rotating side spring 22 press the stationary seal ring 11 and the rotating seal ring 21 together in a compressed state that is shorter than their natural length. This allows the stationary seal ring 11 and the rotating seal ring 21 to move axially while suppressing changes in the load between the sliding surfaces 11d and 21d.

Furthermore, the stationary side spring 12 and the rotating side spring 22 press the stationary seal ring 11 and the rotating seal ring 21 together in a compressed state within the axial movement range of the stationary seal ring 11 and the rotating seal ring 21. In other words, the extension length of one spring is greater than or equal to the contraction length of the other spring. This allows one spring to always follow the expansion and contraction of the other spring, thereby suppressing load changes between the sliding surfaces 11d and 21d and reliably preventing surface opening between the sliding surfaces 11d and 21d and tilting of the sliding surfaces 11d and 21d.

In addition, because the diameter on which the spring force of the stationary side spring 12 acts on the stationary seal ring 11 is the same as the diameter on which the spring force of the rotating side spring 22 acts on the rotating seal ring 21, it becomes easier to make the axial forces acting on the stationary seal ring 11 and the rotating seal ring 21 from both sides more uniform, making it difficult to change the positions of the sliding surfaces 11d, 21d in the axial direction.

In addition, because the stationary side spring 12 and the rotating side spring 22 are springs with the same spring constant, it becomes easier to control the axial movement of the stationary seal ring 11 and the rotating seal ring 21. In other words, the stationary seal ring 11 and the rotating seal ring 21 are more likely to be held in a central position between the seal cover 10 and the sleeve 20, making it easier to reduce the load change between the sliding surfaces 11d, 21d.

Next, the mechanical seal according to the second embodiment will be described with reference to FIG. 7. Note that the description of the same configuration as the previous embodiment will be omitted.

As shown in FIG. 7, the mechanical seal 201 of this embodiment 2 differs from the embodiment 1 in that the flange portion 220b of the sleeve 220 is longer in the axial direction than the flange portion 20b of the embodiment 1, and the insertion hole 220d formed on the right surface of the flange portion 220b is deeper than the insertion hole 20d of the embodiment 1. Therefore, the rotating seal ring 21 abuts against the sleeve 220 at the initial positions of the stationary seal ring 11 and the rotating seal ring 21.

In more detail, the opposing stationary side spring 12 and rotating side spring 22 press the stationary seal ring 11 and rotating seal ring 21 together in a compressed state, and the stationary seal ring 11 can move in both axial directions from the initial position, but the rotating seal ring 21 can only move to the right in the axial direction from the initial position. In addition, at the initial positions of the stationary seal ring 11 and rotating seal ring 21, the loads applied to the stationary seal ring 11 and rotating seal ring 21 by the stationary side spring 12 and rotating side spring 22 are balanced.

This suppresses vibration of the stationary seal ring 11 and the rotating seal ring 21, which are pressed against each other by the opposing stationary side spring 12 and rotating side spring 22, making it easier to maintain the initial positions of the stationary seal ring 11 and the rotating seal ring 21.

In addition, the rotating seal ring 21 can only move from the initial position to the right in the axial direction, i.e., toward the stationary seal ring 11, so that it is possible to reliably prevent surface separation between the sliding surfaces 11d and 21d.

For ease of explanation, the illustration is omitted, but the mechanical seal may be configured so that the stationary seal ring 11 abuts against the seal cover when the stationary seal ring 11 and the rotating seal ring 21 are in their initial positions. In particular, the stationary seal ring 11 may be movable only axially to the left from its initial position, and the rotating seal ring 21 may be movable axially to both sides from its initial position.

Next, the mechanical seal according to the third embodiment will be described with reference to Figures 8 and 9. Note that the description of the same configuration as the previous embodiment will be omitted.

As shown in Figures 8 and 9, the mechanical seal 301 of this embodiment 3 differs from that of the above-mentioned embodiment 1 in that the stationary side spring 312 and the rotating side spring 322 are compression springs with different spring constants. More specifically, the spring constant of the rotating side spring 322 is greater than the spring constant of the stationary side spring 312. Note that in the initial positions of the stationary seal ring 11 and the rotating seal ring 21, the stationary side spring 312 and the rotating side spring 322 are described as having the same length.

As shown in FIG. 8, when the rotating shaft 2 moves to the right, both the stationary side spring 312 and the rotating side spring 322, which face each other, move further from their compressed states. Note that the amount of movement (L2) of the rotating shaft 2 in this embodiment is smaller than the amount of movement of the rotating shaft 2 in the first embodiment.

In this way, in the mechanical seal 301 of this embodiment, when the rotating shaft 2 moves to the right, the stationary side spring 312 operates to compress more than the rotating side spring 322. In other words, the amount of movement (L11) of the stationary seal ring 311 is greater than the amount of movement (L21) of the rotating seal ring 321.

As shown in FIG. 9, when the rotating shaft 2 moves to the left, both the stationary side spring 312 and the rotating side spring 322 that face each other expand from their compressed states. Note that the amount of movement (L2') of the rotating shaft 2 in this embodiment is smaller than the amount of movement of the rotating shaft 2 in the first embodiment.

In this way, in the mechanical seal 301 of this embodiment, when the rotating shaft 2 moves toward the left, the stationary side spring 312 operates to stretch more than the rotating side spring 322. In other words, the amount of movement of the stationary seal ring 311 (L11') is greater than the amount of movement of the rotating seal ring 321 (L21').

In this embodiment, the spring constant of the rotating side spring 322 is greater than the spring constant of the stationary side spring 312, but this is not limiting. The spring constant of the rotating side spring may be smaller than the spring constant of the stationary side spring.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

For example, in the above embodiments 1 to 3, the lengths of the opposing stationary side spring and rotating side spring are the same in the initial positions of the stationary seal ring and rotating seal ring, but this is not limited thereto, and the opposing springs may have different lengths in the initial positions.

In addition, in the above-mentioned Examples 1 to 3, the opposing stationary side spring and rotating side spring are exemplified as being located on the inner diameter side of the seal portion, but this is not limited thereto, and the opposing springs may be positioned freely relative to the seal portion as long as they can appropriately bias the stationary seal ring and rotating seal ring in the axial direction.

In addition, in the above-mentioned Examples 1 to 3, the working diameters on which the biasing forces of the stationary side spring and the rotating side spring act on the stationary seal ring and the rotating seal ring are the same are exemplified, but this is not limited thereto, and the working diameters on which the biasing forces of the opposing springs act may be different.

In addition, in the above-mentioned Examples 1 to 3, the stationary side spring and the rotating side spring are both multi-springs in which multiple springs are evenly arranged in the circumferential direction, but this is not limiting, and the stationary side spring and the rotating side spring may be composed of other types of springs, such as single springs or wave springs. Furthermore, the stationary side spring and the rotating side spring may be composed of the same type of spring, or may be composed of a combination of different types of springs.

In addition, in the above-mentioned Examples 1 to 3, the stationary side spring arranged between the seal cover and the stationary seal ring directly presses against the stationary seal ring, thereby biasing the stationary seal ring toward the rotating seal ring. However, this is not limited to the above, and for example, the stationary side spring arranged between the housing and the seal cover may press against the seal cover, thereby biasing the stationary seal ring toward the rotating seal ring via the seal cover. In this case, it is preferable that the stationary side spring abuts against the back surface of the seal cover that is parallel to the sliding surface of the stationary seal ring. It goes without saying that the rotating seal ring may also be biased toward the stationary seal ring by the rotating side spring via another member.

In addition, in the above-mentioned Examples 1 to 3, the stationary mounting member to which the stationary seal ring is attached is a seal cover, but this is not limited thereto, and the stationary seal ring may be directly attached to the housing as the stationary mounting member.

In addition, in the above-mentioned Examples 1 to 3, the rotating side mounting member to which the rotating seal ring is attached is a sleeve, but this is not limited thereto, and the rotating seal ring may be directly mounted to the rotating shaft as the rotating side mounting member.

In addition, in the above-mentioned Examples 1 to 3, the stationary seal ring and the rotating seal ring are asymmetrical, but the stationary seal ring and the rotating seal ring may be symmetrical. By making the stationary seal ring and the rotating seal ring symmetrical and using the same material, the load applied to the stationary seal ring and the rotating seal ring from the stationary side spring and the rotating side spring is made the same, making it easier to position the stationary seal ring and the rotating seal ring in their initial positions. In addition, the weight of the stationary seal ring and the rotating seal ring are the same, which makes it possible to prevent misalignment of the stationary seal ring and the rotating seal ring.

In addition, in the above embodiments 1 to 3, an inside-type mechanical seal is used as an example, but this is not limited thereto, and an outside-type mechanical seal may also be used.

In addition, in the above embodiments 1 to 3, a balanced mechanical seal is used as an example, but this is not limited thereto, and an unbalanced mechanical seal may also be used.

In addition, in the above embodiments 1 to 3, the pressure acting diameters of the stationary seal ring and the rotating seal ring are the same, but the pressure acting diameters of the stationary seal ring and the rotating seal ring may be different.

The sealed fluid F may be any of gas, liquid, or a mixture of gas and liquid. The fluid on the leaking side is not limited to the atmosphere A, but may be any of gas, liquid, or a mixture of gas and liquid.

1, 201, 301 Mechanical seal 2 Rotating shaft 3 Housing 10 Seal cover (stationary side mounting member)
10f, 10g Stationary side movement restricting portion 11 Stationary seal ring 11d Sliding surface 11g Back surface 12, 312 Stationary side spring 13 Stationary side O-ring (stationary side secondary seal)
14 Knock pin 20 Sleeve (rotating side mounting member)
20f, 20g Rotation side movement restricting portion 21 Rotation seal ring 21d Sliding surface 21g Back surface 22, 322 Rotation side spring 23 Rotation side O-ring (rotation side secondary seal)
24 Drive pin

Claims (7)

A mechanical seal is disposed between a housing and a rotating shaft that rotates relative to the housing, in which a stationary seal ring is attached to a stationary-side mounting member disposed on the housing side, and a rotating seal ring is attached to a rotating-side mounting member disposed on the rotating shaft side, and the mechanical seal comprises:
a stationary secondary seal that abuts against the stationary seal ring and the stationary mounting member, and a rotating secondary seal that abuts against the rotating seal ring and the rotating mounting member,
a stationary side spring that is provided between the stationary seal ring and the stationary side mounting member and urges the stationary seal ring toward the rotating seal ring, and a rotating side spring that is provided between the rotating seal ring and the rotating side mounting member and urges the rotating seal ring toward the stationary seal ring. The mechanical seal according to claim 1, in which the stationary seal ring and the rotating seal ring are pressed together while the stationary side spring and the rotating side spring are each shorter than their natural lengths. The mechanical seal according to claim 1, wherein the working diameter of the stationary side spring relative to the stationary seal ring is the same as the working diameter of the rotating side spring relative to the rotating seal ring. The mechanical seal according to claim 1, wherein the stationary secondary seal radially abuts against a peripheral surface of the stationary seal ring that is perpendicular to the sliding surface of the stationary seal ring in the extension direction, and the rotating secondary seal radially abuts against a peripheral surface of the rotating seal ring that is perpendicular to the sliding surface of the rotating seal ring in the extension direction. The mechanical seal according to claim 1, wherein the stationary mounting member is formed with a stationary movement restriction portion that restricts the inclination of the stationary seal ring, and the rotating mounting member is formed with a rotating movement restriction portion that restricts the inclination of the rotating seal ring. The mechanical seal according to any one of claims 1 to 5, wherein the stationary side spring and the rotating side spring have the same spring constant. The mechanical seal according to claim 1 or 2, in which one of the seal rings abuts in the axial direction against the member to which the seal ring is attached.

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