JP2024074004A - mechanical seal - Google Patents

Abstract

To provide a mechanical seal that can evacuate an external fluid to a discharge port in various positions without fixing a blank piece by welding or the like to a seal case and a housing installed to the discharge port.SOLUTION: A seal case 12 includes a protrusion 144 disposed downstream in a rotation direction of a rotation shaft 2 in a discharge port 31.SELECTED DRAWING: Figure 5

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 equipment and a rotating shaft arranged to pass through the housing, and have the function of reducing friction on the sliding surfaces and preventing leakage of the sealed fluid by bringing the sliding surfaces of a stationary ring fixed to a fixed case attached to the housing and a rotating ring fixed to a rotating case attached to the rotating shaft into sliding contact in the circumferential direction. In such mechanical seals, an external fluid is injected into the intermediate space between the sealed fluid space and the atmospheric space to cool and clean the sliding surfaces of the stationary seal ring and the rotating seal ring.

As an example of such a mechanical seal, as shown in Patent Document 1, an intermediate space between a fixed ring and a rotating ring is filled with an external fluid, and an external flow path provided outside the mechanical seal is connected to the intermediate space. This external flow path is provided with a tank for the external fluid and a cooler for cooling the external fluid. Also, the seal case to which the fixed ring is fixed is provided with an inlet and outlet for the external fluid that communicate with the external flow path. Also, a partial impeller is fixed to the outer diameter side of the rotating ring.

As the partial impeller rotates together with the rotating ring, the external fluid is guided toward the outer diameter side of the partial impeller, which causes the external fluid to be discharged from the intermediate space to the external flow path, and at the same time, the external fluid is introduced from the external flow path into the intermediate space and circulated. This makes it possible to sequentially supply cooled external fluid to the intermediate space without using a pump or the like.

A blank piece is provided on the inner peripheral surface of the seal case. This blank piece is provided by welding or the like so that it protrudes inwardly toward the downstream side of the discharge port in the direction of rotation of the partial impeller, and the external fluid guided toward the outer diameter side of the partial impeller comes into contact with the blank piece, allowing it to be efficiently guided to the discharge port.

JP 2017-89800 A (page 7, Figure 1)

However, in mechanical seals such as that in Patent Document 1, the discharge port may be provided in the seal case or in the housing depending on the specifications of the fluid device, and furthermore, the circumferential and axial positions of the discharge port relative to the seal case or housing vary. In order to accommodate discharge ports in various positions, it is necessary to prepare a seal case and housing in which a blank piece is fixedly installed in the appropriate position for each discharge port, making it cumbersome to accommodate discharge ports in various positions. In addition, the blank piece is generally fixed to the seal case and housing by welding, which raises concerns about the durability of the welded parts in particular.

The present invention was made with an eye on these problems, and aims to provide a mechanical seal that can discharge external fluid to discharge ports in various positions without fixing a blank piece to the seal case and housing provided at the discharge port by welding or other means.

In order to solve the above problems, the mechanical seal of the present invention comprises:
A mechanical seal comprising: a seal case attached to a housing of a fluid device; a stationary seal ring fixed to the seal case; and a rotating seal ring fixed to a rotating shaft inserted through the housing and the seal case and sliding against the stationary seal ring by relative rotation, wherein an external fluid is introduced through an inlet formed in the housing or the seal case and the external fluid is discharged through a discharge port formed in the housing,
The seal case has a protrusion extending axially therefrom and disposed downstream of the discharge port in the direction of rotation of the rotary shaft.
According to this, the projection can be appropriately positioned at the outlet, so that the external fluid can be discharged to the outlet at various positions. Note that the projection can be formed without welding.

The seal case may have a divided structure having at least a holder for holding the stationary seal ring, and a stationary structure having the projection and separate from the holder.
According to this, the position of the projection can be adjusted or replaced by moving the stationary structure without disassembling the other members constituting the seal case. Also, the seal case and the stationary seal ring can be easily assembled.

The apparatus may further include a positioning mechanism for determining a relative circumferential position between the stationary structure and the seal case.
This makes it possible to prevent the circumferential position of the projection from shifting when the mechanical seal is in use.

The protrusion may have a tip end provided with a return portion extending toward the upstream side in the rotation direction of the rotary shaft.
This prevents the external fluid from escaping in the axial direction from the tip of the projection, and allows the external fluid to be efficiently guided to the discharge port.

An end face of the protrusion on an upstream side in a rotation direction of the rotating shaft may extend from a tip end of the protrusion toward the seal case and incline toward a downstream side in the rotation direction of the rotating shaft.
This prevents the external fluid from escaping in the axial direction from the tip of the projection, and allows the external fluid to be efficiently guided to the discharge port.

An end face of the protrusion on an upstream side in a rotation direction of the rotating shaft may be inclined from an inner diameter side to an outer diameter side toward the downstream side in the rotation direction of the rotating shaft.
This allows the external fluid to be efficiently guided toward the outlet on the outer diameter side.

In order to solve the above problems, the mechanical seal of the present invention comprises:
A mechanical seal comprising: a seal case attached to a housing of a fluid device; a stationary seal ring fixed to the seal case; and a rotating seal ring fixed to a rotating shaft inserted through the housing and the seal case and sliding relative to the stationary seal ring through relative rotation, wherein an external fluid is introduced through an inlet formed in the housing or the seal case and the external fluid is discharged through a discharge port formed in the seal case,
the seal case has a divided structure including at least an outlet forming body in which the outlet is provided and the stationary structure separate from the outlet forming body,
The stationary structure includes a protrusion disposed downstream of the discharge port in the direction of rotation of the rotating shaft.
According to this, the protrusion of the stationary structure can be appropriately positioned at the discharge port, so that the external fluid can be discharged to discharge ports at various positions. The position of the protrusion can be adjusted or replaced by moving the stationary structure without moving the seal case. The seal case and the stationary seal ring can be easily assembled. Furthermore, the protrusion can be constructed without welding.

1 is a schematic cross-sectional view showing a mechanical seal according to a first embodiment of the present invention. 1A is a top view showing the stationary structure, and FIG. 1B is a cross-sectional view taken along the line A-A. 1A is a schematic cross-sectional view showing a means for restricting relative rotation between the case and the stationary structure, FIG. 1B is a schematic cross-sectional view showing a means for restricting relative axial movement between the case and the stationary structure, and FIG. 1B is a schematic cross-sectional view showing a fixing means for fixing the case and the stationary structure. FIG. 2 is a schematic diagram of a partial impeller and a stationary structure as viewed from the outer diameter side. This is a cross-sectional view taken along line B-B of FIG. 5A to 5C are schematic diagrams showing the shape of a protrusion in Example 2 of the present invention. 13A and 13B are schematic diagrams showing the shape of a protrusion in Example 3 of the present invention. 13A and 13B are schematic diagrams showing the shape of a protrusion in Example 4 of the present invention. FIG. 11 is a schematic cross-sectional view showing a mechanical seal according to a fifth embodiment of the present invention.

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 5. 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, mechanical seal 1 is used to seal the annular space between a rotating shaft 2 and a housing 3 of a fluid device. In addition, another mechanical seal (not shown) is provided on the axial left side of this mechanical seal 1, and a space S filled with an external fluid is formed between mechanical seal 1 and the other mechanical seal. Furthermore, the left side of space S is the sealed fluid side space, and the right side of space S is the atmospheric space.

This mechanical seal 1 mainly comprises a rotating seal ring 11, a case 12 as a retainer, a stationary seal ring 13, a stationary structure 14, and a partial impeller 15.

The rotating seal ring 11 is annular and is attached using a sleeve 4 as a rotating shaft side member that is fixed to the outer circumferential surface of the rotating shaft 2, and is rotatable together with the rotating shaft 2. The rotating seal ring 11 may also be attached directly to the rotating shaft 2.

The case 12 is a cylindrical member through which the rotating shaft 2 is inserted. The case 12 is fixed to the right axial side of the housing 3 by a bolt extending in the axial direction (not shown). The case 12 may also be attached to the housing 3 by using a housing side member such as a spacer member.

The case 12 has an inlet 121 and an annular groove 122.

The inlet 121 is connected to an end of a fluid circuit 20 provided externally. This fluid circuit 20 includes a cooling section that cools the external fluid and a tank that stores the cooled external fluid (not shown).

The groove 122 is a stepped groove that opens to the left in the axial direction on the inner diameter side of the case 12. Specifically, the groove 122 is composed of a first annular recess 122A and a second annular recess 122B.

The first recess 122A is composed of an inner wall portion 123 of the case 12, a side wall portion 124 that rises from the right end of the inner wall portion 123 toward the outer diameter side, and an outer wall portion 125 that extends to the left from the outer diameter end of the side wall portion 124.

The second recess 122B is provided at the left end of the outer wall 125 so as to expand the opening of the first recess 122A toward the outer diameter side. A step is formed between the first recess 122A and the second recess 122B.

The stationary seal ring 13 is annular and is provided in the first recess 122A of the case 12 in a non-rotating state and movable in the axial direction. An elastic member 7 is disposed between the stationary seal ring 13 and the side wall portion 124 of the case 12 (see FIG. 3(b)). The elastic member 7 biases the stationary seal ring 13 to the left in the axial direction.

The rotating seal ring 11 and the stationary seal ring 13 are typically formed of SiC (hard material) or a combination of SiC (hard material) and carbon (soft material), but any sliding material used as a sliding material for mechanical seals can be used. Examples of SiC include sintered bodies using boron, aluminum, carbon, etc. as sintering aids, as well as materials consisting of two or more phases with different components and compositions, such as SiC with dispersed graphite particles, reaction sintered SiC consisting of SiC and Si, SiC-TiC, and SiC-TiN, and examples of carbon include carbonaceous and graphitic mixtures, resin-molded carbon, and sintered carbon. In addition to the above sliding materials, metal materials, resin materials, surface-modified materials (coating materials), composite materials, etc. can also be used.

The partial impeller 15 is annular and is attached to the sleeve 4 at a position to the left of the rotating seal ring 11. The partial impeller 15 has a bottomed cylindrical portion consisting of a first portion 151 and a second portion 152. The first portion 151 extends from the sleeve 4 toward the outer diameter side. The second portion 152 extends from the outer diameter edge of the first portion 151 to the right in the axial direction.

The second portion 152 of the partial impeller 15 is located on the inner diameter side of the housing 3. The housing 3 is also provided with an outlet 31, which is connected to an end of the external fluid circuit 20.

The second portion 152 has multiple through holes 152a formed in the circumferential direction, penetrating in the radial direction. These through holes 152a are inclined to the right in the axial direction as they move from the inner diameter side to the outer diameter side. Note that it is sufficient to have at least one through hole 152a, and the number and shape can be freely changed.

When the partial impeller 15 rotates together with the rotating shaft 2, the external fluid in the space S is guided to the outer diameter side. This causes the external fluid to be discharged from the space S to the fluid circuit 20. The flow of the external fluid when the rotating shaft 2 rotates will be explained in detail later.

The stationary structure 14 is disposed on the inner diameter side of the housing 3 and the case 12. The stationary structure 14 and the case 12 constitute a seal case. The housing 3 refers to a component on the fluid device side, and the seal case refers to a component on the mechanical seal 1 side that is attached to the housing 3. The seal case is composed of one component or a divided structure of multiple components.

More specifically, as shown in Figures 2(a) and 2(b), the stationary structure 14 includes a first cylindrical portion 141, a second cylindrical portion 142, an attachment step portion 143, and a protrusion 144.

The first cylindrical portion 141 is located to the left of the second cylindrical portion 142 and has a slightly smaller diameter than the second cylindrical portion 142.

The right end of the second cylindrical portion 142 has multiple cutouts 142a that are recessed to the left and are arranged at equal intervals in the circumferential direction. The cutouts 142a are formed by cutting the second cylindrical portion 142.

The mounting step 143 is formed by protruding in an annular shape toward the outer diameter side at the boundary between the first cylindrical portion 141 and the second cylindrical portion 142. The outer edge of the mounting step 143 on the right axial direction is a chamfered inclined surface 143a.

The protrusion 144 is a protruding piece that is approximately rectangular in a radial view and is provided at one circumferential location on the left end of the first cylindrical portion 141, protruding axially to the left. The protrusion 144 is formed by cutting the first cylindrical portion 141. In other words, the protrusion 144 has the same thickness as the first cylindrical portion 141, and is smoothly connected in the axial direction. In this way, the protrusion 144 can be formed without using welding.

Returning to FIG. 1, the stationary structure 14 is arranged such that the first cylindrical portion 141 is inserted into the inner diameter side of the housing 3, the second cylindrical portion 142 is inserted into the first recess 122A of the case 12, and the mounting step portion 143 is fitted into the second recess 122B of the case 12.

The first cylindrical portion 141 is arranged on the inner diameter side of the housing 3 so as to be capable of relative rotation. There is a small gap between the first cylindrical portion 141 and the housing 3. This allows the distance between the stationary structure 14 and the housing 3 to be maintained.

In addition, the protrusion 144 is cantilevered on the first cylindrical portion 141, and there is a gap in the outer diameter direction, so it is less likely to be damaged by bending even when subjected to external forces from the partial impeller 15, etc.

The second cylindrical portion 142 is arranged on the inner diameter side of the outer wall portion 125 of the case 12 so as to be capable of relative rotation. The outer peripheral surface of the second cylindrical portion 142 abuts against the inner peripheral surface of the outer wall portion 125 of the case 12. This positions the first cylindrical portion 141 and the case 12 in the radial direction.

The mounting step 143 is axially sandwiched between the housing 3 and the case 12. An O-ring 5 is disposed between the mounting step 143 and the outer wall 125 of the case 12. An O-ring 6 is disposed between the mounting step 143 and the housing 3.

As shown in FIG. 3(a), a pin 8 extending leftward from the side wall 124 of the case 12 fits into any of the cutouts 142a. This defines the relative circumferential positions of the case 12 and the stationary structure 14. In other words, the cutouts 142a and the pin 8 function as a circumferential positioning mechanism for the case 12 and the stationary structure 14.

In this embodiment, the pin 8 is provided at one location around the circumference of the case 12, but it may be provided at multiple locations around the circumference.

As shown in FIG. 3(b), a plurality of screw holes 126 are provided in the circumferential direction on the left end face of the case 12. When the flat head screw 9 is screwed into the screw hole 126, the head of the flat head screw 9 abuts against the inclined surface 143a of the mounting step 143 of the stationary structure 14, and the relative axial positions of the case 12 and the stationary structure 14 are determined. In other words, the flat head screw 9 functions as an axial positioning mechanism for the case 12 and the stationary structure 14.

Note that Figures 3(a) and (b) show parts that are different in phase in the circumferential direction from Figure 1.

As shown in FIG. 4, when the mechanical seal 1 is in use, the protrusion 144 is located near the downstream side of the exhaust port 31 of the housing 3 in the direction of rotation of the rotating shaft 2.

Next, the flow of the external fluid when the rotating shaft 2 rotates will be explained with reference to Figure 5.

As shown in FIG. 5, when the rotating shaft 2 rotates, the partial impeller 15 also rotates (see the white arrow in FIG. 5). At this time, centrifugal force acts on the external fluid in each through hole 152a, and the external fluid is guided to the outer diameter side of each through hole 152a.

The external fluid guided to the outer diameter side of each through hole 152a moves circumferentially between the housing 3 and the partial impeller 15 in response to the rotation of the partial impeller 15. The external fluid then comes into contact with the protrusion 144 of the stationary structure 14, and is thereby guided in the outer diameter direction and discharged to the discharge port 31.

Furthermore, the through hole 152a of the partial impeller 15 is more susceptible to pressure differences than conventional grooves, so the fluid pressure of the external fluid can be increased, allowing the external fluid to be discharged more efficiently.

In addition, the protrusions 144 extend in the axial direction and do not protrude in the inner diameter direction as in conventional blank pieces, ensuring the diameter of the partial impeller 15 and preventing a decrease in the centrifugal effect.

As described above, the case 12 is provided with a stationary structure 14 having a protrusion 144 that is positioned downstream of the outlet 31 in the direction of rotation of the rotating shaft 2. By appropriately positioning the protrusion 144 relative to the outlet 31, it becomes possible to discharge external fluid to the outlet 31 at various positions.

In addition, since the stationary structure 14 is separate from the case 12, the position of the protrusion 144 can be adjusted or replaced by moving the stationary structure 14. In other words, the relative position of the protrusion 144 and the discharge port 31 can be changed or replaced with another stationary structure 14 without moving the case 12. Furthermore, interference between the protrusion 144 and the stationary seal ring 13 can be avoided, making it easy to assemble the case 12 and the stationary seal ring 13.

In addition, the case 12 and the stationary structure 14 are circumferentially positioned by the engagement between the notch 142a of the stationary structure 14 and the pin 8 of the case 12, so the circumferential position of the protrusion 144 can be prevented from changing when the mechanical seal 1 is in use.

The stationary structure 14 also extends axially from the case 12 toward the housing 3, and can be attached so that the protrusion 144 extends into the interior of the housing 3, allowing the protrusion 144 to be positioned appropriately relative to the exhaust port 31 provided in the housing 3.

In addition, the protrusions 144 are formed by cutting the first cylindrical portion 141 and are integrally formed with the first cylindrical portion 141. This means that there are no radially raised portions as with welding, etc., and the protrusions continue smoothly in the axial direction, allowing the radial dimensions to be reduced.

Next, the mechanical seal according to the second embodiment will be described with reference to FIG. 6. Note that the description of the same configuration as the first embodiment will be omitted.

As shown in FIG. 6, the mechanical seal of this embodiment 2 has a different shape of the protrusion 244 of the stationary structure 24 from the protrusion 144 of the first embodiment.

Specifically, the protrusion 244 is composed of a base portion 244a and a return portion 244b. The base portion 244a has a generally rectangular shape when viewed in the radial direction.

The return portion 244b extends from the tip of the projection 244, i.e., the left axial end of the base portion 244a, toward the upstream side in the rotation direction of the rotating shaft 2. The right surface of the return portion 244b is curved so as to be concave toward the downstream side in the rotation direction when viewed in the radial direction.

As a result, the external fluid that moves circumferentially between the housing 3 and the partial impeller 15 in response to the rotation of the partial impeller 15 is prevented from escaping to the left in the axial direction by the return portion 244b, and the external fluid is efficiently guided to the discharge port 31.

In this second embodiment, the return portion 244b is provided only at the tip of the protrusion 244, but for example, two return portions may extend from the base portion so as to be positioned on both axial sides of the discharge port.

Next, the mechanical seal of Example 3 will be described with reference to FIG. 7. Note that the description of the same configuration as Example 1 will be omitted.

As shown in FIG. 7, the mechanical seal of this embodiment 3 has a different shape of the protrusion 344 of the stationary structure 34 from the protrusion 144 of the first embodiment.

Specifically, the end face 344a of the protrusion 344 on the upstream side in the rotation direction of the rotating shaft 2 extends from the left side to the right side so as to be inclined toward the downstream side in the rotation direction of the rotating shaft 2.

As a result, the external fluid that moves circumferentially between the housing 3 and the partial impeller 15 in response to the rotation of the partial impeller 15 is prevented from escaping to the axial left by the end face 344a, and the external fluid is efficiently guided to the discharge port 31.

In addition, since the end surface 344a is inclined as a whole, it is expected that the pressure loss when the external fluid comes into contact with the protrusion 344 will be reduced.

In this third embodiment, the end face 344a extends linearly when viewed in the radial direction, but may be curved so as to be concave toward the downstream side in the direction of rotation when viewed in the radial direction.

Next, the mechanical seal of Example 4 will be described with reference to FIG. 8. Note that the description of the configuration that is the same as that of Example 1 will be omitted.

As shown in FIG. 8, the mechanical seal of this embodiment 4 has a different shape of the protrusion 444 of the stationary structure 44 from the protrusion 144 of the first embodiment.

The end face 444a of the protrusion 444 on the upstream side in the rotation direction of the rotating shaft 2 is inclined from the inner diameter side toward the outer diameter side toward the downstream side in the rotation direction. In more detail, the end face 444a is curved so as to be concave toward the downstream side in the rotation direction when viewed in cross section.

As a result, the end face 444a is inclined radially, i.e., toward the discharge port 31, and the external fluid that moves circumferentially between the housing 3 and the partial impeller 15 in response to the rotation of the partial impeller 15 is guided toward the outer diameter side by the end face 444a, so that more external fluid can be guided to the discharge port 31 while reducing pressure loss, and the external fluid is efficiently guided to the discharge port 31.

In this fourth embodiment, the end face 444a is curved so as to be concave toward the downstream side in the direction of rotation in cross section, but may be formed, for example, in a straight line in cross section.

Next, the mechanical seal of Example 5 will be described with reference to FIG. 9. Note that the description of the same configuration as Example 1 will be omitted.

As shown in FIG. 9, the mechanical seal of this embodiment 5 has an exhaust port 531 provided in the case 512. The case 512 is the exhaust port forming body of the present invention. The case 512 is fixed to the housing 53 via a stationary structure 54.

The stationary seal ring 513 is held against the case 512 via the elastic member 7 at a position to the right of the discharge port 531 in the case 512. The rotating seal ring 511 is fixed to a sleeve 4 that is fixed to the outer circumferential surface of the rotating shaft 2, and is positioned to the right of the stationary seal ring 513.

The partial impeller 515 is annular and is attached to the sleeve 4 at a position to the left of the stationary seal ring 513. The partial impeller 515 has multiple through holes 515a formed in the circumferential direction that penetrate radially. These through holes 515a are inclined axially to the right as they move from the inner diameter side to the outer diameter side.

The stationary structure 54 has a protrusion 544 extending to the right and is positioned downstream of the discharge port 531 in the direction of rotation of the rotating shaft 2.

In this embodiment 5, the case 512, which is the retaining body, is disposed on the outer side of the stationary structure 54, i.e., on the opposite side of the housing 53, but the retaining body may be disposed on the inner side of the stationary structure, i.e., on the housing side. In this case, it is sufficient that the protrusion of the stationary structure extends toward the inner side of the machine.

In addition, the outlet formation is not limited to the case 512, but may be provided on another member connected to the case 512.

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-mentioned Examples 1 to 5, the stationary structure is separate from the case, but this is not limited thereto. For example, the case and the stationary structure may be integrally formed, and the position of the protrusion may be adjusted relative to the exhaust port formed in the housing.

In addition, in the above-mentioned Examples 1 to 5, the inlet is provided in the case, but this is not limited thereto, and the inlet may be provided in the housing.

In addition, in the above-mentioned Examples 1 to 4, the notch 142a and the mating portion of the pin 8 are described as the circumferential positioning mechanism between the stationary structure and the case. However, for example, the mating portion between the protrusion from the stationary structure and the recess in the case may be the circumferential positioning mechanism.

In addition, in the above embodiments 1 to 5, the axial positioning mechanism between the stationary structure and the case was described as a flat head screw 9, but this is not limited to this and may be freely changed.

In addition, in the above-mentioned Examples 1 to 5, a configuration in which one protrusion is provided in the circumferential direction of the stationary structure is exemplified, but multiple protrusions may be provided in the circumferential direction of the stationary structure.

In addition, in the above-mentioned Examples 1 to 5, a mechanical seal was described in which the external fluid is discharged to the discharge port by the partial impeller 15. However, it is also possible to circulate the external fluid by an external pump provided in the external flow path without providing a partial impeller, or to use a combination of a partial impeller and an external pump.

In addition, in the above embodiments 1 to 5, the partial impeller has a through hole, but it may have a square groove or an R groove on the outer diameter side to guide the external fluid.

1 Mechanical seal 2 Rotating shaft 3 Housing 8 Pin (positioning mechanism)
11 Rotary seal ring 12 Case (retainer)
13: Stationary seal ring 14: Stationary structure 15: Partial impeller 20: Fluid circuit 24: Stationary structure 31: Discharge port 34: Stationary structure 44: Stationary structure 121: Inlet port 142a: Notch portion (positioning mechanism)
144 Protrusion 244 Protrusion 244b Return portion 344 Protrusion 344a End surface 444 Protrusion 444a End surface S Space

Claims (7)

A mechanical seal comprising: a seal case attached to a housing of a fluid device; a stationary seal ring fixed to the seal case; and a rotating seal ring fixed to a rotating shaft inserted through the housing and the seal case and sliding relative to the stationary seal ring through relative rotation, wherein an external fluid is introduced through an inlet formed in the housing or the seal case and the external fluid is discharged through a discharge port formed in the housing,
The seal case is a mechanical seal having a protrusion extending axially from the seal case and positioned downstream of the discharge port in the direction of rotation of the rotating shaft. The mechanical seal according to claim 1, wherein the seal case is a split structure having at least a retainer that holds the stationary seal ring and a stationary structure having the protrusion that is separate from the retainer. The mechanical seal according to claim 2, further comprising a positioning mechanism for determining the relative circumferential position of the stationary structure and the seal case. The mechanical seal according to claim 1, wherein the tip of the protrusion is provided with a return portion that extends toward the upstream side in the direction of rotation of the rotating shaft. The mechanical seal according to claim 1, wherein the end face of the protrusion on the upstream side in the rotation direction of the rotating shaft extends from the tip of the protrusion toward the seal case at an incline toward the downstream side in the rotation direction of the rotating shaft. The mechanical seal according to claim 1, wherein the end face of the protrusion on the upstream side in the rotation direction of the rotating shaft is inclined from the inner diameter side to the outer diameter side toward the downstream side in the rotation direction of the rotating shaft. A mechanical seal comprising: a seal case attached to a housing of a fluid device; a stationary seal ring fixed to the seal case; and a rotating seal ring fixed to a rotating shaft inserted through the housing and the seal case and sliding relative to the stationary seal ring through relative rotation, wherein an external fluid is introduced through an inlet formed in the housing or the seal case and the external fluid is discharged through a discharge port formed in the seal case,
the seal case has a divided structure including at least an outlet forming body in which the outlet is provided and the stationary structure separate from the outlet forming body,
The stationary structure is a mechanical seal having a protrusion disposed downstream of the discharge port in the direction of rotation of the rotating shaft.

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