JP2004286080A - Sealing structure of lubricating oil for motor bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing structure of lubricating oil for a motor bearing capable of preventing deterioration of the lubricating oil, and sealing the leakage of the lubricating oil in an axial direction without using a sealing structure by mechanically contacting and sliding. <P>SOLUTION: A flow passage 9 of the lubricating oil 2 leaking from an oil seal 5 to an end surface of a housing 3 is formed between a shaft 4 and the housing 3. The housing 3 is provided with an oil supplying hole 6 and a oil draining hole 7 for draining the lubricating oil 2 supplied from the oil supplying hole 6. A discharging hole 11 penetrating the housing 3 to discharge the leaked lubricating oil 2 from the flow passage 9 side to the outside is provided between the end surface of the housing 3 and the oil seal 5. An intercepting member 12 intercepting the flow passage 9, having a surface opposite to the housing 3, forming a clearance with the opposite surface, and forming a sealing clearance 10 sealing the lubricating oil 2 by surface tension of the lubricating oil 2 in the clearance, is attached to the shaft 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bearing lubricating oil sealing structure for sealing lubricating oil used for a bearing of an electric motor such as a motor.
[0002]
[Prior art]
The main shaft of a motor such as a motor rotates at a high speed during use. Therefore, such a main shaft needs to be rotatably supported in a housing by a bearing such as a rolling bearing and to supply a sufficient lubricating oil to the inside of the bearing.
[0003]
As a lubricating device that supplies lubricating oil to the inside of the bearing, providing a lubricating space for storing lubricating oil such as grease in the housing and a nozzle hole communicating from the lubricating space to the inside of the bearing, and applying pressure to the lubricating space In some cases, an appropriate amount of lubricating oil is intermittently or continuously supplied to the inside of the bearing (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-2002-161922 (pages 3 to 5, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, during use for a long time, the supplied low-viscosity base oil of the lubricating oil (grease) is released and leaks from the gap in the sliding portion between the housing side and the spindle side, and is provided at the spindle end. There is a problem that the pulley and other parts are adversely affected.
[0006]
Further, when a seal member such as an O-ring is used for the sliding portion, it needs to be replaced periodically due to wear or deterioration, and there is a problem that maintenance work becomes complicated.
[0007]
Further, there is a problem in that the lubricating oil deteriorated due to long-term use accumulates inside, and it is necessary to disassemble and assemble the bearing in order to remove the deteriorated lubricating oil.
[0008]
The present invention solves the above-described problems, and can prevent deterioration of the lubricating oil, and can prevent leakage of the lubricating oil in the axial direction without using a sealing structure by mechanical contact and sliding. It is an object of the present invention to provide a lubricating oil sealing structure for a motor bearing that can seal the lubricating oil.
[0009]
[Means for Solving the Problems]
The sealing structure for lubricating oil for a bearing of a motor according to the present invention includes a housing, a shaft supported by the housing via a bearing, and rotating in the housing, and an oil supply hole for supplying lubricating oil to the bearing. An oil seal that seals the leakage of the lubricating oil in the axial direction;
A flow path through which the lubricating oil flows is formed between the shaft and the housing from the oil seal toward the axial end surface of the housing,
The housing is provided with an oil supply hole and an oil drainage hole for extracting lubricating oil supplied from the oil supply hole,
A discharge hole is provided in the housing between the axial end surface of the housing and the oil seal to discharge the lubricating oil flowing through the flow path from the flow path side to the outside of the housing,
The shaft has an axial end surface and an opposing surface of the housing, forms a gap between the opposing surfaces, and forms a sealing gap that seals the lubricating oil by the surface tension of the lubricating oil in the gap. And a blocking member for blocking the lubricating oil flowing through the flow path.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a sectional view showing a lubricating oil sealing structure according to Embodiment 1 of the present invention.
[0011]
As shown in the figure, an oil seal 5 is provided at an axial end of the bearing 1. The oil seal 5 is fixed to the housing 3, and is provided so that the distal end slides on the rotating shaft 4, and suppresses leakage of lubricating oil from the bearing 1 in the central axis direction of the shaft 4.
[0012]
As the oil seal 5, a lip seal or a mechanical seal can be used, or a sealed ball bearing 1 in which a seal is included may be used.
[0013]
The housing 3 holding the bearing 1 is provided with an oil supply hole 6 for supplying lubricating oil to the bearing 1 and an oil draining hole 7 for discharging periodically deteriorated lubricating oil. A lid 8 is provided in each of the oil drain holes 7 so that the lubricating oil can be replaced without disassembling the assembly of the bearing 1.
[0014]
To replace the lubricating oil, the lid 8 of the oil drain hole 7 is removed, the old lubricating oil is discharged from the oil drain hole 7, and then the new lubricating oil is supplied from the oil supply hole 6. When replacing high-viscosity grease, the lid 8 is removed, grease is pushed in from the oil supply hole 6, and old grease is pushed out from the oil drain hole 7 and grease is discharged until new grease is discharged from the oil drain hole 7. Push in from oil supply hole 6. Further, it is possible to easily replace the lubricating oil by sucking out the old lubricating oil through the oil drain hole 7 and supplying new lubricating oil through the oil supply hole 6.
[0015]
When the performance of the oil seal 5 is deteriorated due to long-term use, the lubricating oil 2 leaking from the oil seal 5 flows along the flow path 9 toward the shaft end of the shaft 4.
[0016]
According to the present invention, the shielding member 12 is attached to the shaft 4, the flow passage 9 of the lubricating oil 2 is blocked by the shielding member 12, and the end surface of the shielding member 12 and the end surface of the housing 3 have an angle α from the center axis direction of the shaft 4. An angled sealing gap 10 is formed, and the housing 3 has a discharge hole 11 penetrating outside the housing 3 between the oil seal 5 and the sealing gap 10.
[0017]
Most of the lubricating oil 2 leaking from the oil seal 5 passes through the discharge hole 11 and is discharged from a tube (not shown) connected to the outside of the discharge hole 11 to a predetermined storage portion. In addition, a part of the lubricating oil 2 is not discharged from the discharge hole 11, and the lubricating oil 2 remaining in the flow path 9 accumulates at the inner end of the flow path 9 without passing through the sealing gap 10 due to its surface tension.
[0018]
FIG. 2 is a cross-sectional view for explaining the effect of the surface tension of the lubricating oil. As shown in the drawing, the dimension of the radial gap between the shaft 4 and the housing 3 in the flow path 9 is H (the height of the lubricating oil that can be held in the flow path 9), Assuming that the size of the gap is h, the surface tension of the lubricating oil 2 is γ, the density of the lubricating oil 2 is ρ, and the contact angle between the lubricating oil 2 and the shielding member 12 is θ, the lubricating oil 2 The height H is represented by the following equation (1). In the following equation (1), g is the gravitational acceleration.
[0019]
(2γ · cos θ) / (ρ · gh · h) (1)
[0020]
Therefore, if the size of the radial gap between the shaft 4 of the flow passage 9 and the housing 3 is smaller than the value obtained by the above equation (1), even if the flow passage 9 is filled with the lubricating oil, The lubricating oil 2 is discharged from the discharge hole 11 to the outside without leaking from the sealing gap 10.
[0021]
Although FIG. 1 shows the case where one discharge hole 11 is provided, a plurality of discharge holes 11 may be provided in the circumferential direction. Although the sealing gap 10 is formed by the end surface of the housing 3, the sealing gap 10 may be formed by attaching another member to the end surface of the housing 3.
[0022]
As described above, in the present invention, the housing 3 is provided with the oil supply hole 6 for supplying the lubricating oil to the bearing 1 and the oil drain hole 7 for discharging the lubricating oil. By discharging and supplying new lubricating oil to the bearing 1 from the oil supply hole 6, the lubricating oil can be replaced without disassembling the assembly of the bearing 1, and the maintenance cost can be reduced.
[0023]
Further, a shielding member 12 is attached to the shaft 4, the shielding member 12 blocks the flow path 9 of the lubricating oil 2 leaked from the oil seal 5, and the end surface of the shielding member 12 and the end surface of the housing 3 Since the sealing gap 10 for sealing the lubricating oil is formed by the surface tension, and the housing 3 has the discharge hole 11 penetrating outside the housing 3 between the oil seal 5 and the sealing gap 10. The sealing between the rotating side (shielding member 12) and the fixed side (housing 3) can be performed in a non-contact manner, so that high reliability without mechanical wear can be achieved and leakage from the oil seal 5 can be achieved. The discharged lubricating oil 2 can be discharged from the discharge hole 11 to a predetermined place.
[0024]
Embodiment 2 FIG.
FIG. 3 is a cross-sectional view showing a lubricating oil sealing structure according to a second embodiment of the present invention. In the figure, the same reference numerals as those in the first embodiment denote the same or corresponding parts.
[0025]
As shown in FIG. 3, in this embodiment, a groove 13 is formed in the discharge hole 11 on the side of the flow path 9 into which the lubricating oil 2 flows.
[0026]
The lubricating oil 2 leaking from the oil seal 5 is temporarily held in the groove 13, and the accumulated lubricating oil 2 is discharged to the outside from the discharge hole 11 by its own weight. Therefore, the amount of the lubricating oil 2 reaching the sealing gap 10 provided at the end of the flow path 9 can be reduced, and the reliability of the lubricating oil sealing can be increased.
[0027]
Embodiment 3 FIG.
4 and 5 are cross-sectional views showing a sealing structure for lubricating oil according to Embodiment 3 of the present invention. In the drawings, the same reference numerals as those in Embodiment 1 indicate the same or corresponding parts. .
[0028]
In the first and second embodiments, the lubricating oil sealing structure in the horizontal motor is described. However, the same lubricating oil sealing structure can be applied to the vertical motor.
[0029]
As shown in FIG. 4, in the case of a vertical motor, a sealing gap 10 similar to that of the first embodiment is provided, and the discharge hole 11 is inclined with respect to the central axis direction of the shaft 4 to achieve sealing. The gap 10 prevents the lubricating oil 2 from leaking and allows the lubricating oil 2 to be discharged from the discharge hole 11 to the outside of the housing 3.
[0030]
The distance H from the discharge hole 11 of the flow path 9 to the sealing gap 10 shown in FIG. 4 is obtained by the above equation (1). By setting the distance H smaller than the value obtained by the above equation (1), the lubricating oil can be sealed by the sealing gap 10.
[0031]
Further, as shown in FIG. 5, by providing the groove 13 on the inner circumference of the discharge hole 11 and the flow path 9 side, the lubricating oil 2 leaked from the oil seal 5 is temporarily held in the groove 13, The amount of the lubricating oil 2 that reaches the sealing gap 10 provided at the end of the flow path 9 can be reduced, and a highly reliable sealing structure for sealing the lubricating oil can be obtained.
[0032]
Embodiment 4 FIG.
FIG. 6 is a cross-sectional view showing a sealing structure for lubricating oil according to Embodiment 4 of the present invention, and FIG. 7 is a cross-sectional view for explaining the effect of surface tension of lubricating oil. The same reference numerals indicate the same or corresponding parts.
[0033]
When it is necessary to use a lubricating oil having a low viscosity, the surface tension of the lubricating oil is reduced. Therefore, the radial gap H between the housing 3 and the shaft 4 determined by the above equation (1) is reduced. The necessity arises and the assemblability of the electric motor may be deteriorated.
[0034]
In such a case, as shown in FIG. 6, the gap H can be increased by providing the shielding member 12 with a stepped portion 12a having a plane perpendicular to the vertical plane.
[0035]
As shown in FIG. 7, the contact angle θ of the lubricating oil 2 in the case where the stepped portion 12a is provided on the shielding member 12 (b) is smaller than that in the case where the stepped portion is not provided (a). Since the angle H is increased by the angle of 12a (90 ° in FIG. 7), the gap H can be increased as compared with the case where the stepped portion 12a is not provided, and the workability of assembly can be improved.
[0036]
Embodiment 5 FIG.
FIG. 8 is a cross-sectional view showing a lubricating oil sealing structure according to Embodiment 5 of the present invention. In the figure, the same reference numerals as those in Embodiment 1 above denote the same or corresponding parts.
[0037]
In the fourth embodiment, the stepped portion 12a has a surface perpendicular to the vertical surface of the shielding member 12. However, as shown in FIG. With such a configuration, the contact angle θ of the lubricating oil 2 can be further increased. In this case, if the contact angle of the lubricating oil 2 on the surface of the flow path 9 of the housing 3 in the sealing hole 10 is small, the smaller contact angle affects the sealing of the lubricating oil 2, It is necessary to form the groove 3a so that the angle formed by the flow path 9 surface of the housing 3 with the end surface (vertical surface) is substantially the same.
[0038]
Embodiment 6 FIG.
FIG. 9 is a cross-sectional view showing a lubricating oil sealing structure according to the sixth embodiment of the present invention. In the figure, the same reference numerals as those in the first embodiment denote the same or corresponding parts.
[0039]
In the first embodiment, the lubricating oil sealing structure in the electric motor whose shaft rotates is described. However, the same lubricating oil sealing structure can be applied even when the shaft is fixed and the housing rotates. .
[0040]
In this embodiment, as shown in FIG. 9, the same sealing gap 10 as that of the first embodiment is provided, and the shielding member 12 is provided with a discharge hole 11 so that the lubricating oil 2 And the lubricating oil 2 can be discharged from the discharge hole 11 to a predetermined storage part.
[0041]
Further, an oil supply hole 6 for supplying lubricating oil to the bearing 1 and an oil draining hole 7 for discharging lubricating oil are provided on the end surface of the housing 3, and periodically degraded lubricating oil is discharged from the oil draining hole 7. By supplying new lubricating oil to the bearing 1 from 6, the lubricating oil can be replaced without disassembling the assembly of the bearing 1, and maintenance costs can be reduced.
[0042]
The size of the radial gap between the shaft 4 and the housing 3 in the flow passage 9 is made smaller than the value obtained by the above equation (1), so that the lubricating oil 2 is sealed with the sealing gap 10. be able to.
[0043]
Embodiment 7 FIG.
FIG. 10 is a cross-sectional view showing a lubricating oil sealing structure according to a seventh embodiment of the present invention, and FIG. 11 is a cross-sectional view for explaining an effect of the present embodiment. The same reference numerals indicate the same or corresponding parts.
[0044]
In the first embodiment, when the viscosity of the lubricating oil used is small, the temperature becomes high depending on the operation state and the use environment of the electric motor, and the viscosity and the surface tension of the lubricating oil decrease, the above equation (1) is used. It is necessary to reduce the required gap H.
[0045]
In such a case, as shown in FIG. 10, the gap H is increased by providing the oil-repellent treatment section 14 on the opposing surface of the sealing gap 10 formed by the shielding member 12 and the housing 3. And the assemblability of the bearing 1 and the like is improved.
[0046]
As the oil repellent treatment, a fluorine-based resin is applied or baked. The fluorine-based resin, PTFE (polytetrafluoroethylene), PFE (perfluoro propyl vinyl ether, FEP (6- hexafluoropropylene copolymer), a CF ₃ based polymers and the like.
[0047]
By this oil repellent treatment, the contact angle θ of the lubricating oil 2 in the oil repellent treatment unit 14 can be increased by four times or more as compared with the case where ordinary iron is used.
[0048]
According to this embodiment, by providing the oil-repellent treatment section 14 on the surface facing the sealing gap, the radial gap H between the shaft 4 and the housing 3 can be increased, and the workability of assembling the bearing 1 and the like can be improved. Can be improved.
[0049]
Also, as shown in FIG. 11, when dust 15 enters the sealing gap 10, the lubricating oil 2 may leak through the dust 15 due to the capillary phenomenon as shown in FIG. The provision of 14 prevents the lubricating oil 2 from leaking because the surface tension is larger than the force of spreading the lubricating oil 2 through the dust 15.
[0050]
Embodiment 8 FIG.
FIG. 12 is a cross-sectional view showing a lubricating oil sealing structure according to Embodiment 7 of the present invention, and FIG. 13 is a cross-sectional view for explaining the effect of surface tension of lubricating oil. The same reference numerals as in Embodiment 1 indicate the same or corresponding parts.
[0051]
In the first embodiment, when the lubricating oil 2 adheres to the wall surface of the flow path 9 for a long period of time and the motor is operated or left in an extremely high temperature environment, the lubricating oil 2 is vaporized and flows. It is assumed that the lubricating oil 2 floating in the path 9 and vaporized passes through the sealing gap 10.
[0052]
In such a case, as shown in FIG. 12, by providing the lipophilic processing section 16 on the wall surface of the flow path 9, it becomes easier to flow in the lipophilic processing section 16, and the lubricating oil 2 is supplied for a long time to the flow path 9. The lubricating oil 2 is not vaporized and passes through the sealing gap 10 because the lubricating oil 2 is guided to the discharge hole 11 without staying on the wall surface.
[0053]
The lipophilic processing section 22 can be obtained by forming a TiO ₂ film and exciting the film with ultraviolet rays.
[0054]
Further, as shown in FIG. 13A, assuming that the contact angle of the lubricating oil 2 in the lipophilic processing unit 16 is θ ₁ and the contact angle of the oleophobic processing unit 14 is θ ₂ , When the oil-repellent processing unit 14 is provided (FIG. 13B), the contact angle becomes θ ₂ −θ ₁ . Assuming that the contact angle of the lubricating oil 2 in the portion where the lipophilic processing section 16 is not provided is θ ₁ ′, θ ₁ <θ ₁ ′, so that the contact angle θ ₂ −θ ₁ > θ ₂ −θ ₁ ′, It can be seen that the provision of the processing unit 16 can increase the contact angle of the lubricating oil 2 in the oil repellent processing unit 14.
[0055]
【The invention's effect】
According to the bearing lubricating oil sealing structure of the present invention, the housing, the shaft supported by the housing via the bearing, and rotating in the housing, and the oil supply hole for supplying the bearing with lubricating oil are provided. An oil seal that seals the leakage of the lubricating oil in the axial direction;
A flow path through which the lubricating oil flows is formed between the shaft and the housing from the oil seal toward the axial end surface of the housing,
The housing is provided with an oil supply hole and an oil drainage hole for extracting lubricating oil supplied from the oil supply hole,
A discharge hole is provided in the housing between the axial end surface of the housing and the oil seal to discharge the lubricating oil flowing through the flow path from the flow path side to the outside of the housing,
The shaft has an axial end surface and an opposing surface of the housing, forms a gap between the opposing surfaces, and forms a sealing gap that seals the lubricating oil by the surface tension of the lubricating oil in the gap. Therefore, since a blocking member for blocking the lubricating oil flowing through the flow path is attached, the lubricating oil can be replaced without disassembling the bearing assembly, and the maintenance cost can be reduced. Seals the member and housing in a non-contact manner, eliminates the need for a seal member, eliminates mechanical wear, increases reliability, and discharges lubricant oil leaking from the oil seal. Can be discharged to a predetermined place.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a lubricating oil sealing structure according to Embodiment 1 of the present invention.
FIG. 2 is a cross-sectional view for explaining the action of the surface tension of the lubricating oil according to Embodiment 1 of the present invention.
FIG. 3 is a cross-sectional view showing a lubricating oil sealing structure according to a second embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a lubricating oil sealing structure according to a third embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a lubricating oil sealing structure according to Embodiment 3 of the present invention.
FIG. 6 is a cross-sectional view showing a lubricating oil sealing structure according to a fourth embodiment of the present invention.
FIG. 7 is a cross-sectional view for describing an action of surface tension of lubricating oil according to Embodiment 4 of the present invention.
FIG. 8 is a cross-sectional view showing a lubricating oil sealing structure according to a fifth embodiment of the present invention.
FIG. 9 is a cross-sectional view showing a lubricating oil sealing structure according to a sixth embodiment of the present invention.
FIG. 10 is a cross-sectional view showing a lubricating oil sealing structure according to a seventh embodiment of the present invention.
FIG. 11 is a cross-sectional view for explaining an operation of an oil-repellent processing section according to Embodiment 7 of the present invention.
FIG. 12 is a cross-sectional view showing a lubricating oil sealing structure according to an eighth embodiment of the present invention.
FIG. 13 is a cross-sectional view for explaining the action of surface tension of lubricating oil according to Embodiment 8 of the present invention.
[Explanation of symbols]
1 bearing, 2 lubricating oil, 3 housing, 3a, 13 groove, 4 shaft,
5 oil seal, 6 oil supply hole, 7 oil drain hole, 8 lid, 9 flow path,
10 sealing gap, 11 discharge hole, 12 shielding member, 12a stepped portion,
14 oil repellent processing section, 15 dust, 16 lipophilic processing section.

Claims (10)

A housing, a shaft supported by the housing via a bearing, and rotating within the housing, an oil supply hole for supplying lubricating oil to the bearing, and an oil seal for sealing leakage of the lubricating oil in the axial direction In the sealing structure of the bearing lubricating oil in the motor having
A flow path through which the lubricating oil flows is formed between the shaft and the housing from the oil seal toward the axial end surface of the housing,
The housing is provided with an oil supply hole and an oil drainage hole for extracting lubricating oil supplied from the oil supply hole,
A discharge hole is provided in the housing between the axial end surface of the housing and the oil seal to discharge the lubricating oil flowing through the flow path from the flow path side to the outside of the housing,
The shaft has an end surface in the axial direction of the housing and an opposing surface, forms a gap in the opposing surface, and forms a sealing gap that seals the lubricating oil by the surface tension of the lubricating oil in the gap. A sealing member for shutting off the lubricating oil flowing through the flow path. A shaft, a housing supported on the shaft via a bearing, and rotating about the shaft as a center axis, an oil supply hole for supplying lubricating oil to the bearing, and sealing the leakage of the lubricating oil in the axial direction. In a sealing structure of lubricating oil for bearings in an electric motor having an oil seal,
A flow path through which the lubricating oil flows from the oil seal toward the end surface of the housing is formed between the shaft and the housing,
The housing is provided with the oil supply hole and an oil drain hole for extracting lubricating oil supplied from the oil supply hole,
The shaft has an end surface and an opposing surface of the housing, forms a gap between the opposing surfaces, and forms a sealing gap that seals the lubricating oil by the surface tension of the lubricating oil in the gap. Attach a blocking member that blocks the lubricating oil flowing through the flow path,
A sealing structure for lubricating oil for bearings of an electric motor, wherein a discharge hole for discharging the lubricating oil flowing through the flow path from the flow path side to the outside is provided in the blocking member. The motor is a horizontal type, the surface tension of the lubricating oil is γ, the contact angle of the lubricating oil in the sealing gap is θ, the density of the lubricating oil is ρ, and the distance between the opposing surfaces of the sealing gap is h. The distance H between the axis and the housing in the flow path is smaller than (2γ · cos θ) / (ρ · gh ·), where g is the gravitational acceleration. 3. A sealing structure for lubricating oil for a bearing of an electric motor according to 1 or 2. The electric motor is a vertical type, the surface tension of the lubricating oil is γ, the contact angle of the lubricating oil in the sealing gap is θ, the density of the lubricating oil is ρ, and the distance between opposing surfaces of the sealing gap is h. The distance H from the sealing gap to the discharge hole is set to be smaller than (2γ · cos θ) / (ρ · g · h), where gravitational acceleration is g. Sealing structure for lubricating oil for motor bearings. The lubricating oil sealing structure for an electric motor according to claim 1 or 2, wherein a groove is provided on the flow path side of the discharge hole. The lubricating oil sealing structure for an electric motor according to claim 1 or 2, wherein an oil-repellent portion is formed on a surface of the sealing gap facing the housing and the blocking member. 7. The sealing structure for lubricating oil for a motor according to claim 6, wherein a lipophilic processing portion connected to the oil repellent processing portion is formed in the housing and the blocking member of the flow path. 3. The sealing structure for lubricating oil for a motor according to claim 1, wherein the sealing gap is inclined from a center axis direction of the shaft. The said blocking member has the surface of the said radial direction of the said shaft, and the surface from the said radial surface to the edge part of the said sealing clearance | gap toward a center axis direction, The Claim 1 or 2 characterized by the above-mentioned. Sealing structure for lubricating oil for motor bearings. The sealing of lubricating oil for bearings of an electric motor according to claim 9, wherein an angle between the radial surface and a surface extending to the end of the sealing gap in the direction of the central axis is an acute angle. Construction.

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