JP6708496B2 - mechanical seal - Google Patents

Description

The present invention relates to a mechanical seal equipped in a rotating device such as a bead mill or a stirrer.

BACKGROUND ART Conventionally, as an end-face contact type mechanical seal which is an example of a mechanical seal, for example, as disclosed in Patent Document 1, a sealed fluid region which is an internal region and an atmospheric region which is an external region are primary seals inside the aircraft. It is known to be used as a primary seal in a shaft sealing device configured to seal via a non-sealing fluid region formed between the and a secondary seal on the outside of the machine.

That is, as shown in FIG. 1 of Patent Document 1, a mechanical seal used as this primary seal (hereinafter referred to as “conventional mechanical seal”) is rotated by a stationary seal ring that is axially movable in a seal case. The sealed end face, which is the end face opposite to the rotary seal ring fixed to the shaft, makes relative rotation while contacting the sealed end face, which is the outer peripheral region of the sealed end face, and the non-sealed fluid region, which is the inner peripheral side region thereof. It is configured to shield and. A cooling liquid such as water is circulated and supplied to the non-sealed fluid region sealed by the primary seal and the secondary seal.

Thus, in the conventional mechanical seal, the rotary seal ring is integrally formed of ceramics or cemented carbide, and is opposed to a metal (stainless steel) sleeve fixed to the rotary shaft. The peripheral surfaces are fitted with each other in an O-ring sealed state, and relative rotation with respect to the sleeve is prevented by a rotation stopping mechanism.

By the way, in conventional mechanical seals, the coefficient of thermal expansion (linear expansion coefficient) of metals such as stainless steel, which is a constituent material of the sleeve, is larger than that of ceramics and cemented carbide, which are constituent materials of the rotary seal ring. If the fluid to be sealed is a high temperature fluid, if the rotary seal ring is fitted in contact with the sleeve, the thermal expansion amount of the inner diameter of the rotary seal ring due to the high temperature fluid (hereinafter referred to as "inner diameter expansion amount") In comparison, the thermal expansion amount of the outer diameter of the sleeve (hereinafter referred to as the “outer diameter expansion amount”) is large, so the internal stress of the inner diameter of the rotary seal ring is expanded by the sleeve. Will work. As a result, although ceramics and cemented carbide, which are components of the rotary seal ring, have excellent compressive strength but poor tensile strength, the rotary seal ring may be damaged due to the action of centrifugal force. is there.

Therefore, when the conventional mechanical seal is used under high temperature conditions, it is necessary to design the outer diameter of the sleeve and the inner diameter of the rotary seal ring so that the rotary seal ring fits in the sleeve in a non-contact state. Proposed. That is, the inner diameter expansion amount of the rotary seal ring and the outer diameter expansion amount of the sleeve due to contact with the high temperature fluid are predicted, and based on the prediction result, the inner diameter of the rotary seal ring at the time of operation stop (during mechanical seal assembly) is predicted. By forming an annular gap (hereinafter referred to as "design gap") between the peripheral surface and the outer peripheral surface of the sleeve, the rotary seal ring and the sleeve are thermally deformed (thermally expanded) by a high temperature fluid (sealed fluid). Even under operating conditions, the formation of the design gap prevents the rotary seal ring from being subjected to tensile stress due to the sleeve.

JP, 2009-197945, A

However, since the outer diameter expansion amount of the sleeve during operation depends on the temperature of the high temperature fluid, it can be predicted with some accuracy, but the inner diameter expansion amount of the rotary seal ring during operation depends on the temperature of the high temperature fluid. In addition, it is necessary to consider the frictional heat generated at the sealing end surface of the rotary seal ring and the cooling by the cooling liquid that contacts the inner peripheral surface of the rotary seal ring, which is extremely difficult to accurately predict.

Therefore, if the design gap is too small compared to the difference between the inner diameter expansion amount of the rotary seal ring and the outer diameter expansion amount of the sleeve during operation, tensile stress due to the sleeve acts on the rotary seal ring during operation, The above problem (damage of the rotary seal ring due to tensile stress) occurs.

On the other hand, if the design clearance is too large compared to the difference between the inner diameter expansion amount of the rotary seal ring and the outer diameter expansion amount of the sleeve, during operation, a large gap is created between the opposing peripheral surfaces of the rotary seal ring and the sleeve. Therefore, there is a possibility that the rotary seal ring may be largely eccentric with respect to the sleeve due to the action of torque due to relative rotational sliding contact with the mating seal ring (stationary seal ring), vibration of the rotary shaft, and the like. Then, if the rotary seal ring is largely eccentric, the concentricity between the seal end face of the rotary seal ring and the seal end face of the mating seal ring is impaired, the two seal end faces are not properly contacted, and the sealing function is well exhibited. It may disappear.

By the way, in the conventional mechanical seal, the detent mechanism comprises a metal key fixed to the sleeve and a key groove formed on the inner peripheral surface of the rotary seal ring, and the key is engaged with the key groove. Is configured to prevent relative rotation of the rotary seal ring with respect to the sleeve. Therefore, in the mechanical seal that employs such a rotation preventing mechanism, the design clearance is excessive compared to the difference between the inner diameter expansion amount of the rotary seal ring and the outer diameter expansion amount of the sleeve during operation. As described above, since the rotary seal ring is largely eccentric with respect to the sleeve, the rotary seal ring may be damaged as in the case where the design clearance is too small compared to the difference between the inner and outer expansion amounts. ..

That is, the key fixed to the sleeve and the key groove formed on the inner peripheral surface of the rotary seal ring merely prevent the rotary seal ring from rotating relative to the sleeve (rotary shaft). The key and the key groove are not tightly engaged with each other for the reason of being easy to fix the rotary seal ring to the sleeve, etc. Engaged. Further, since the rotary seal ring is made of a ceramic material such as a sintered material or a cemented carbide, it has a high strength against torque in a circular cross-sectional shape portion without unevenness, but has a high fracture toughness. It is a brittle material that is easily affected by the local defect structure of No. 3, and in a non-circular cross-sectional shape part with unevenness such as a key groove, it may be destroyed from the uneven part due to stress concentration due to torque ..

Therefore, if the rotary seal ring is not eccentric with respect to the sleeve, or if the amount of eccentricity is small even if eccentric, the key comes into surface contact with the key groove, and stress concentrates at the key groove in the contact portion with the key. However, if the rotary seal ring is largely eccentric with respect to the sleeve, the key will come into line contact with the keyway without making surface contact, and as a result, the rotary seal ring will come into contact with the key contact portion. Large torque may be concentrated due to the torque due to relative rotation in the contact state with the seal ring, and the rotary seal ring may be damaged.

The present invention has been made to solve such a problem, and provides a mechanical seal capable of exhibiting a good sealing function for a long period of time by preventing damage to the rotary sealing ring during operation as much as possible. The purpose is to do.

The present invention comprises a stationary seal ring held in a seal case so as to be movable in the axial direction, and a rotary seal ring fixed to a rotary shaft penetrating the seal case. A mechanical device that shields a sealed fluid region, which is an outer peripheral side region of the sealed end face, and a non-sealed fluid region, which is an inner peripheral side region thereof, by relatively rotating while a sealing end face that is an end face facing the sealing ring is in contact with the sealing ring. A seal, wherein the fluid in the non-sealing fluid region (hereinafter referred to as “non-sealing fluid”) has a lower temperature than the fluid in the sealed fluid region (hereinafter referred to as “sealing fluid”), and the rotary sealing ring is made of ceramic or super The sleeve is made of hard alloy and is fixed to the rotating shaft. The sleeve is fitted in a non-contact state in which the space between the opposing peripheral surfaces is sealed by a seal member, and the sleeve and the rotary seal ring are opposed to each other. The present invention proposes a mechanical seal in which rotation is blocked by a rotation stop mechanism and a diamond film is formed on the inner peripheral surface of a rotary seal ring.

In a preferred embodiment of the mechanical seal of the present invention, the sealed fluid is a fluid having a temperature at which the rotary seal ring and the sleeve are thermally expanded, and the rotation preventing mechanism is fixed to an outer peripheral portion of the sleeve. A metal key is engaged with a key groove formed in the inner peripheral portion of the rotary seal ring.

Further, in the mechanical seal of the present invention, it is preferable to form a diamond film continuous with the diamond film on the surface portion of the rotary sealing ring with which the non-sealing fluid comes into contact. Further, it is preferable that a diamond film is formed on the sealing end surface of the rotary sealing ring in a form separated from the diamond film. Further, the diamond film preferably has a thickness of 1 μm or more.

In the mechanical seal of the present invention, the inner surface of the rotary seal ring, which is in contact with a liquid (unsealed fluid) whose temperature is lower than that of the sealed fluid, is higher than that of the constituent material of the seal ring, such as ceramics or cemented carbide. Since a diamond film with a very low coefficient of thermal expansion is formed, heat transfer (cooling) to the diamond film by contact with a non-sealing fluid causes transfer of frictional heat generated at the sealed end surface to the inner peripheral surface. The heat transfer due to the contact with the sealed fluid having a temperature higher than that of the heat and the non-sealed fluid can be effectively blocked, the temperature rise of the inner peripheral portion can be prevented as much as possible during operation, and the rotation including the inner peripheral surface can be prevented. The temperature of the inner peripheral portion of the sealing ring is substantially controlled by the temperature of the non-sealing fluid. Therefore, the thermal expansion amount (inner diameter expansion amount) of the inner diameter of the rotary seal ring during operation can be predicted to some extent accurately based on the temperature of the non-sealing fluid, and the rotary seal ring during operation stop (mechanical seal assembly) can be predicted. The annular clearance (designed clearance) formed between the opposing peripheral surfaces of the sleeve and the sleeve is an annular clearance (hereinafter referred to as “operating clearance”) between the opposing peripheral surfaces during operation, and the operational clearance is possible. It can be designed to be small. As a result, during operation, tensile stress due to thermal expansion of the sleeve does not act on the rotary seal ring, and the rotary seal ring does not become largely eccentric with respect to the sleeve. It can exert its function.

It is sectional drawing which shows an example of the mechanical seal which concerns on this invention. It is a detailed view which expands and shows the principal part of FIG. FIG. 3 is a sectional view of a main part taken along the line III-III in FIG. 2. It is sectional drawing of the principal part equivalent to FIG. 2 which shows the modification of the mechanical seal which concerns on this invention. It is sectional drawing of the principal part equivalent to FIG. 2 which shows the other modification of the mechanical seal which concerns on this invention.

Hereinafter, a mode for carrying out the present invention will be specifically described with reference to the drawings.

FIG. 1 is a sectional view showing an example of a shaft sealing device equipped with a mechanical seal according to the present invention as a primary seal, FIG. 2 is a detailed view showing an enlarged main part of FIG. 1, and FIG. FIG. 3 is a sectional view of a main part taken along line III-III of FIG. In the following description, front and rear mean left and right in FIGS. 1 and 2.

In the shaft sealing device shown in FIG. 1, a primary seal 3 and a secondary seal 4 are arranged in a row in an axial direction (front-rear direction) between a housing 1 of a rotating device and a rotating shaft 2 penetrating the housing 1 to provide an in-machine region. The sealed area A, which is a non-sealed area, and the atmospheric area B, which is an outboard area, are sealed via a non-sealed fluid area C formed between the seals 3 and 4. The fluid A (sealed fluid) is a high-temperature fluid at a temperature (for example, 75 degrees or more) that thermally expands the rotary seal ring 6 and the sleeve 8 described later, and the fluid in the unsealed fluid region B (unsealed fluid) is covered. It is used under the condition that the cooling liquid S has a temperature lower than that of the sealed fluid.

In the description below, the axis means the center line of the rotary shaft 2, and the axis direction means the same direction as the axis.

As shown in FIG. 1, the primary seal 3 is the end face contact type mechanical seal of the present invention, and includes a seal case 5 attached to the housing 1, a rotary seal ring 6 fixed to the rotary shaft 2, and a seal case 5. The stationary seal ring 7 held so as to be movable in the axial direction (front-back direction) and the spring member 8 for urging the stationary seal ring 7 to contact the rotary seal ring 6 in a pressed state. The sealed end surfaces 6a, 7a, which are the opposite end surfaces of 6, and 7 relatively rotate while being in contact with each other, so that the sealed fluid area A that is the outer peripheral side area of the sealed end surfaces 6a, 7a and the non-sealed fluid area that is the inner peripheral side area thereof. It is configured to shield and seal C and C.

As shown in FIG. 1, the seal case 5 has a cylindrical structure, and includes a main body portion 5a, a flange portion 5b attached to a front end portion (rear end portion) of the main body portion 5a, and a spring holding portion 5c integrally formed on an inner peripheral portion thereof. And a seal ring holding portion 5d integrally formed at the front end portion (rear end portion) of the main body portion 5a and the flange portion 5b, and the spring holding portion 5c and the seal ring holding portion 5d are located inside the housing 1. It is attached to the housing 1.

As shown in FIG. 1, the main body portion 5a of the seal case 5 is provided with a supply passage 5e and a discharge passage 5f for the cooling liquid S which communicate with the non-sealing fluid region C, and are lower in temperature and higher in pressure than the sealed fluid. The cooling liquid S is circulated and supplied to the non-sealed fluid region C as a sealed liquid (non-sealed fluid). The cooling liquid S is a liquid at room temperature or a liquid cooled to a temperature below room temperature by a cooling means arranged in a cooling liquid circulation path connecting the supply/drainage liquid passages 5e and 5f. Fresh water, a solvent, etc., which does not hinder the leakage to the region B, are used, and the temperature thereof is kept substantially constant.

The rotary shaft 2 is made of metal such as stainless steel, and penetrates the seal case 5 concentrically. As shown in FIG. 1, a cylindrical sleeve 9 made of metal such as stainless steel is fixed to the rotary shaft 2. The sleeve 9 has a tip (front end) protruding from the main body 5a of the seal case 5 to the atmosphere region B side, and a base end (rear end) from the seal ring holding portion 5d of the seal case 5 into the housing 1. In the projected state, it is fixed to the rotary shaft 2 by the fixing ring 10 and the set screws 11a and 11b fitted to the tip portion.

As shown in FIGS. 1 and 2, the rotary seal ring 6 is integrally formed of ceramics such as silicon carbide or cemented carbide, and has a tip end surface (front end surface) of an annular smooth surface orthogonal to the axis. It is an annular body having a constant outer diameter, which includes a tip portion 6b formed on a certain sealed end surface 6a and a base end portion 6c having an inner peripheral surface 6e larger in diameter than the inner peripheral surface 6d of the tip portion 6b. The rotary seal ring 6 is disposed in the housing 1 on the sealed fluid region A side (rear side) of the seal ring holding portion 5d of the seal case 5, and the rotary shaft 2 has a sleeve 9 and an example of a seal material. It is fixed via an O-ring 12 and a key 13.

That is, as shown in FIGS. 1 to 3, the rotary seal ring 6 is fitted in a sleeve 9 in a non-contact state in which a peripheral surface between the sleeve 9 and the sleeve 9 is sealed by an O-ring 12 made of a rubber material such as perfluoro rubber. At the same time, the relative rotation with respect to the sleeve 9 is prevented by the rotation stopping mechanism. In this example, the anti-rotation mechanism engages the metal key 13 fixed to the outer peripheral portion of the sleeve 9 with the key groove 6f formed on the inner peripheral surface 6d of the tip portion 6b of the rotary seal ring 6.
As the rotation preventing mechanism, a combination of a drive pin and an engagement hole or the like can be adopted in addition to the combination of the key 13 and the key groove 6f described in the present embodiment. Further, the seal material is not limited to the O-ring 12, and any kind of seal material such as a V-ring seal can be used as long as it can exhibit the sealing function between the rotary seal ring 6 and the sleeve 9.

As shown in FIG. 2, the O-ring 12 is loaded in a compressed state between the inner peripheral surface 6e of the base end portion 6c of the rotary seal ring 6 and the outer peripheral surface 9a of the sleeve 9 facing the inner peripheral surface 6e. 6e and 9a are sealed, and the rotary seal ring 6 is fixed to the sleeve 9 by frictional engagement force. The O-ring loading space between the inner and outer peripheral surfaces 6e and 9a is an inner peripheral side portion 6g of the tip portion 6b protruding inward from the inner peripheral surface 6e of the base end portion 6c of the rotary seal ring 9 in the axial direction. And an annular projection 9b formed at the base end of the sleeve 9 are closed.

As shown in FIG. 2 and FIG. 3, the key 13 is a parallel key made of metal such as stainless steel having a rectangular sectional shape parallel to the axis and a sectional shape orthogonal to the axis, and the base end portion 13 a is attached to the sleeve 9. By fitting into the formed key groove 9c extending in the axial direction, the tip portion 13b is fixed to the sleeve 9 in a state of protruding from the outer peripheral surface 9a of the sleeve 9.

As shown in FIGS. 2 and 3, the tip portion 13b of the key 13 has a slight allowance in the circumferential direction and the radial direction of the rotary seal ring 6 in the key groove 6f formed in the tip portion 6b of the rotary seal ring 6. Are engaged with each other to prevent relative rotation of the rotary seal ring 6 with respect to the sleeve 9. In this example, the front end surface of the key 13 and the bottom surface of the key groove 6f facing the front end surface are arcuate surfaces in a sectional shape orthogonal to the axis, as shown in FIG. Further, as shown in FIGS. 1 and 2, a snap ring 14 is attached to the sleeve 9 while being in contact with the key 13.

Thus, the inner diameter of the rotary seal ring 6 is set larger than the outer diameter of the sleeve 9 by a predetermined amount, and the rotary seal ring 6 is fitted in the sleeve 9 in a non-contact state. That is, when the operation is stopped (when the mechanical seal is assembled), as shown in FIG. 2, between the inner peripheral surface 6d of the tip portion 6b of the rotary seal ring 6 and the outer peripheral surface 9a of the sleeve 9 and the base of the rotary seal ring 6. Between the inner peripheral surface 6e of the end portion 6c and the outer peripheral surface 9d of the annular protrusion 9b of the sleeve 9, an annular clearance (hereinafter referred to as "design clearance") having a predetermined interval is formed. As will be described later, this design clearance takes into consideration the thermal expansion coefficient (linear expansion coefficient) of the components of the rotary seal ring 6 and the sleeve 9 and the temperatures of the sealed fluid and the cooling liquid S, and the rotary seal ring 5 during operation. Of the inner peripheral surface 6d, 6e of the rotary seal ring 5 and the outer periphery of the sleeve 9 during operation by predicting the thermal expansion amount of the inner diameter (inner diameter expansion amount) and the outer diameter of the sleeve 9 (outer diameter expansion amount). The surfaces 9a and 9d are set so as not to come into contact with each other and to be as close to each other as possible.

As shown in FIGS. 1 and 2, the stationary sealing ring 7 is an annular body made of ceramics such as silicon carbide or cemented carbide, and has a circular annular smooth surface orthogonal to the axis at the front end surface (rear end surface). The sealing end surface 7a is formed and is fitted to the inner peripheral portion of the sealing ring holding portion 5b of the seal case 5 via the O-ring 15 so as to be movable in the axial direction. The stationary seal ring 7 is allowed to move in the axial direction within a predetermined range by engaging the drive pin 16 protruding from the spring holding portion 5c with the recess 7b formed in the inner peripheral portion of the stationary seal ring 7 relative to the seal case 5. Relative rotation is blocked.

As shown in FIG. 1, the spring member 8 is composed of a plurality of coil springs loaded between the stationary seal ring 7 and the spring holding portion 5 c of the seal case 5, and the stationary seal ring 7 is connected to the rotary seal ring 6. It is urged to press. The outer diameter of the sealing end surface 7a of the stationary sealing ring 7 is the same as the outer diameter of the sealing end surface 6a of the rotary sealing ring 6, and the inner diameter is larger than the inner diameter of the sealing end surface 6a. Is brought into contact with the outer peripheral side portion of the sealed end surface 6a while being pressed.

As shown in FIGS. 1 to 3, in the primary seal 3 as the mechanical seal described above, the inner peripheral surfaces 6d and 6e of the rotary seal ring 6 include the inner peripheral surface of the key groove 6f. A diamond film 17 is formed in series over the entire surface. The diamond film 17 is formed by, for example, a hot filament chemical vapor deposition method, a microwave plasma chemical vapor deposition method, a high frequency plasma method, a direct current discharge plasma method, an arc discharge plasma jet method, a combustion flame method, or the like.

In the following description, when it is necessary to distinguish between the rotary seal ring 6 and the diamond film 17 formed on the rotary seal ring 6, the former is referred to as a “sealing ring base material”.

The thickness of the diamond film 17 is preferably 1 μm or more, and more preferably 1 μm to 25 μm. If the thickness of the diamond film 17 is less than 1 μm, it is difficult to effectively exert the heat transfer and cooling effects described later, and if it exceeds 25 μm, it is difficult to sufficiently secure the layer strength of diamond.

As shown in FIG. 1, the secondary seal 4 is an end face contact type mechanical seal similar to the primary seal 3, and is arranged on the atmosphere region side (front side) of the primary seal 3 and has a main body portion 5 a of the seal case 5. The case side sealing ring 18 fixed in a state of being fitted to the shaft side, the shaft side sealing ring 20 held by the sleeve 9 movably in the axial direction via the O ring 19, and the shaft side sealing ring 20 on the case side. A spring member 21 is provided for urging the seal ring 18 while pressing it. The secondary seal 4 has a non-sealing fluid region C, which is an outer peripheral region of the sealed end faces 18a and 20a, when the sealed end faces 18a and 20a, which are opposed end faces of the two sealed rings 18 and 20, are relatively rotated while contacting each other. It is configured so as to shield and seal the atmosphere area (outside the machine area) B that is the inner peripheral side area. The shaft-side seal ring 20 is prevented from rotating relative to the rotary shaft 2 in a state where the drive pin 23 engaged with the spring holding ring 22 fixed to the sleeve 9 is allowed to move in the axial direction within a predetermined range. Has been done. Further, the spring member 21 is loaded between the shaft-side seal ring 20 and the spring holding ring 22, and urges the shaft-side seal ring 20 into pressure contact with the case-side seal ring 18. Further, in the spring retaining ring 22, the cooling liquid S in the non-sealing fluid region portion on the sealed fluid region side of the sleeve retaining ring 22 is forced to flow to the non-sealing fluid region portion on the atmosphere region side of the sleeve retaining ring 22. A pumping hole 22a is formed to allow it.

In the primary seal 3 as a mechanical seal configured as described above, it is generated in the sealing end surface 6a of the rotary sealing ring 6 by relative rotation while being in contact with the mating sealing end surface (sealing end surface 7a of the stationary sealing ring 7). The frictional heat that is generated heats the rotary seal ring 6 to a high temperature. That is, the rotary seal ring 6 is heated to a high temperature by the frictional heat generated by the friction between the sealed end faces 6a and 7a in addition to the heating due to the contact with the sealed fluid which is a higher temperature fluid than the unsealed fluid or the cooling liquid S.

However, since the diamond film 17 is formed on the inner peripheral surfaces 6d and 6e of the rotary seal ring 6 and the diamond film 17 is in contact with the cooling liquid S whose temperature is lower than that of the fluid to be sealed, the rotary seal ring 6 is formed. The temperature rise of the inner peripheral surfaces 6d and 6e of 6 is prevented as much as possible.

That is, diamond, which is a constituent material of the diamond film 17, has extremely high thermal conductivity as compared with ceramics such as silicon carbide and cemented carbide which are constituent materials of the rotary seal ring (sealing ring base material) 6. (For example, the thermal conductivity of silicon carbide is 70 to 120 W/mK, whereas the thermal conductivity of diamond is 1000 to 2000 W/mK). Therefore, the diamond film 17 is in contact with the cooling liquid S. The temperature of the cooling liquid S is instantaneously transferred from the existing portion (the portion on the non-sealing fluid region C side of the contact point of the O-ring 12 in the diamond film 17). This heat transfer (hereinafter referred to as "cooling liquid heat transfer") reaches the inner peripheral surfaces 6d and 6e of the rotary seal ring 6 from the seal end surface 6a of the rotary seal ring 6 where frictional heat is generated, along the seal ring base material. The heat transfer (hereinafter referred to as "friction heat transfer") and the outer peripheral surface of the rotary seal ring 6 heated by contact with a high-temperature fluid (sealed fluid) travels through the seal ring base material to reach the inner peripheral surfaces 6d, 6e. It is performed prior to heat transfer (hereinafter referred to as "high temperature fluid heat transfer"). Therefore, the frictional heat transfer and the high temperature fluid heat transfer to the inner peripheral surfaces 6d and 6e of the rotary seal ring 6 are blocked as effectively and effectively as possible by the diamond film 17 cooled by the cooling liquid heat transfer. Become.

As a result, temperature rise due to frictional heat transfer and high temperature fluid heat transfer in the inner peripheral portion of the rotary seal ring 6 is prevented as much as possible, and the temperature of the inner peripheral portion, that is, the diamond film 17 is formed. The temperatures of the inner peripheral surfaces 6d and 6e and their surroundings are substantially controlled by the temperature of the cooling liquid S.

As described above, the temperature of the inner peripheral portion including the inner peripheral surfaces 6d and 6e of the rotary seal ring 6 is substantially governed by the temperature of the cooling liquid S, so that the inner peripheral surfaces 6d and 6e of the rotary seal ring 6 during operation are controlled. The amount of thermal expansion (the amount of expansion of the inner diameter of the rotary seal ring 6) is not taken into consideration without considering the heat of friction generated at the seal end surface 6a and the temperature of the sealed fluid which is a high temperature fluid, and the coefficient of thermal expansion (linear expansion of the seal ring base material). It can be predicted to some extent from the coefficient) and the temperature of the cooling liquid S. On the other hand, the thermal expansion amount of the outer peripheral surfaces 9a and 9d of the sleeve 9 (the outer diameter expansion amount of the sleeve 9) is accurately predicted from the thermal expansion coefficient (linear expansion coefficient) of the constituent material of the sleeve 9 and the temperature of the sealed fluid. You can do it.

Therefore, an annular clearance (design clearance) between the inner peripheral surfaces 6d and 6e of the rotary seal ring 6 and the outer peripheral surfaces 9a and 9d of the sleeve 9 when the operation is stopped (mechanical seal assembly) is set to the rotary seal ring 6 during operation. When the sleeve 9 is thermally expanded and the inner diameter of the rotary seal ring 6 and the outer diameter of the sleeve 9 are expanded and deformed, an annular gap (during operation gap) is formed between the opposing peripheral surfaces of the rotary seal ring 6 and the sleeve 9. It can be set so that it will occur and the gap during operation will be as small as possible.

Thus, in the mechanical seal used in the primary seal 3 of the present invention, the design clearance can be set so that such a clearance is created during operation, so that the sleeve thermally expanded during operation. The inner diameter of the rotary seal ring 6 is not expanded by 9 and the tensile force that damages the rotary seal ring 6 does not act on the rotary seal ring 6.

Further, the design clearance can be set so that the clearance during operation is as small as possible, and the rotary seal ring 6 will not be eccentric with respect to the sleeve 9 during operation, or will be temporarily eccentric. Since the amount of eccentricity is small, the concentricity between the sealing end surface 6a of the rotary sealing ring 6 and the sealing end surface 7a of the mating sealing ring 7 is not impaired, and the contact between the both sealing end surfaces 6a, 7a is proper. It can be performed to exert a good sealing function.

Further, in the case where the relative rotation of the rotary seal ring 6 with respect to the sleeve 9 is prevented by the rotation stopping mechanism formed by engaging the key 13 fixed to the sleeve 9 with the key groove 6f formed in the rotary seal ring 6, As described above, since the rotary seal ring 6 is not eccentric with respect to the sleeve 9 or even if it is eccentric, the eccentric amount is small, so that the key 13 of the sleeve 9 is linearly aligned with the key groove 6f of the rotary seal ring 6. Since there is no such contact and surface contact is made, stress concentration does not occur at the contact portion with the key 13 in the key groove 6f, and damage to the rotary seal ring 6 due to stress concentration is reliably prevented.

Therefore, according to the mechanical seal adopted in the primary seal 3 of the present invention, the rotary seal ring 6 is not damaged even under high temperature conditions such that the rotary seal ring 6 and the sleeve 9 are thermally expanded, and the mechanical seal can be used for a long period of time. A good sealing function can be exerted throughout.

The configuration of the present invention is not limited to the above-described embodiments, and can be appropriately improved and changed without departing from the basic principle of the present invention.

That is, the diamond film as described above can be formed in series including the inner peripheral surfaces 6d and 6e at the surface portion of the rotary seal ring 6 that is in contact with the cooling liquid S. For example, in the rotary seal ring 6 having the above-described shape, as shown in FIG. 4, the diamond is provided at a portion that is on the inner peripheral side of the seal end face 6a and does not contact the mating seal end face (sealing end face of the stationary seal ring 7) 7a. A diamond film 17a connected to the film 17 can be formed in series. In this way, if the diamond film 17a is formed on the cooling liquid contact surface other than the inner peripheral surfaces 6d and 6e as well, the contact area with the cooling liquid S increases, so that the inner peripheral portion of the rotary seal ring 6 is cooled more. Done effectively.

Further, as shown in FIG. 5, a diamond film 17b can be formed on the sealing end surface 6a of the rotary sealing ring 6 as well. By doing so, it is extremely hard, and the coefficient of friction is extremely low compared to all sealing ring constituent materials such as ceramics and cemented carbide (generally, the coefficient of friction (μ) of diamond is 0.03). Since it has a coefficient of friction much lower than that of polytetrafluoroethylene (PTFE), which is much lower than that of any sealing ring constituent material, the sealing end surface 6a covered with the diamond film 17b is the same as the mating sealing end surface 7a. The heat generation and wear caused by the relative rotary sliding contact are extremely reduced, and the influence of the frictional heat generated on the sealing end surface 6a on the inner peripheral portion of the rotary sealing ring 6 is further reduced. The diamond film 17b formed on the sealed end surface 6a is the same as the diamond film 17 formed on the inner peripheral surfaces 6d and 6e (including the diamond film formed on the cooling liquid contact surface other than the inner peripheral surfaces 6d and 6e connected thereto). It is preferable to form them separately. When the diamond film 17b is continuous with the diamond film 17 that is in contact with the cooling liquid S, the friction heat generated at the sealing end surface 6a is transferred to the inner peripheral surfaces 6d, 6e of the rotary seal ring 6 by the diamond film 17b formed on the sealing end surface 6a. This is because the cooling effect by heating and forming the diamond film 17 on the inner peripheral surfaces 6d and 6e is reduced.

Further, in the above-described embodiment, the present invention is applied to the primary seal 3 of the shaft sealing device (double seal) that uses the non-sealing fluid as the cooling liquid (sealing liquid) S that has a higher pressure and lower temperature than the sealed fluid. The present invention is, for example, a primary seal for a shaft sealing device used under conditions where a cooling liquid S having a lower pressure than a sealed fluid is used as an unsealed fluid, and a primary seal for a shaft sealing device that does not use a mechanical seal as a secondary seal. Can also be applied to. That is, the present invention is a mechanical system that is used under the condition that the inner peripheral side regions (non-sealing fluid regions) B of the sealing end faces 6a, 7a of both sealing rings 6, 7 are liquid regions having a lower temperature than the sealed fluid region A. If it is a seal, it can be suitably applied as in the above-mentioned embodiment regardless of the structure, type, and use conditions.

1 Housing 2 Rotating shaft 3 Primary seal (Mechanical seal)
5 Seal Case 6 Rotating Seal Ring 6a Sealing End Face 6f Key Groove 7 Stationary Seal Ring 7a Sealing End Face 9 Sleeve 12 O Ring (Seal Member)
13 key 17 diamond film 17a diamond film 17b diamond film A sealed fluid region C non-sealed fluid region S cooling liquid (non-sealed fluid)

Claims (3)

A stationary seal ring held in the seal case in a state capable of moving in the axial direction; and a rotary seal ring fixed to a rotary shaft penetrating the seal case,
By the relative rotation of the sealing end faces, which are the facing end faces of the stationary sealing ring and the rotating sealing ring, in contact with each other, the sealed fluid region which is the outer peripheral side region of the sealing end face and the non-sealing fluid which is the inner peripheral side region thereof. A mechanical seal that shields the area from the
The fluid in the unsealed fluid region is colder than the fluid in the sealed fluid region,
The rotary seal ring is formed of ceramics or cemented carbide, and is fitted in a non-contact state in which a metal sleeve fixed to the rotary shaft is sealed with a sealing material between the peripheral surfaces facing the rotary sleeve. Relative rotation between the sleeve and the rotary seal ring is prevented by a detent mechanism formed by engaging a metal key provided on the outer peripheral part of the sleeve with a key groove formed on the inner peripheral part of the rotary seal ring. ,
A mechanical seal in which a series of diamond films are formed on a surface portion of a rotary sealing ring which is in contact with a fluid in a non-sealing fluid region and which includes the key groove except a sealing end surface of the rotary sealing ring . The mechanical seal according to claim 1, wherein the fluid in the sealed fluid region is a fluid having a temperature at which the rotary sealing ring and the sleeve are thermally expanded and having a temperature of 75 degrees or higher . Mechanical seal according to claim 1 or 2 thick Ru der than 1μm of the diamond film.

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