阅读说明：本技术 空气涡轮用轴承单元 (Bearing unit for air turbine ) 是由 中原亨 于 2015-12-24 设计创作，主要内容包括：压缩空气不作用时,密封部件(30)与内圈(20)的外周面(21)接触。压缩空气作用时,与压缩空气不作用时相比,密封部件(30)与内圈(20)的外周面(21)的接触面积减小。由此,提供一种能够迅速停止旋转的空气涡轮轴承单元。(When the compressed air is not applied, the sealing member (30) is in contact with the outer peripheral surface (21) of the inner ring (20). When the compressed air acts, the contact area between the sealing member (30) and the outer peripheral surface (21) of the inner ring (20) is reduced as compared with when the compressed air does not act. Thus, an air turbine bearing unit capable of rapidly stopping rotation is provided.)

1. A rolling bearing for an air turbine used for a bearing unit for an air turbine, the bearing unit for an air turbine comprising:

a turbine blade that receives compressed air and rotates;

a rotating shaft to which the turbine blade is integrally fixed, and to which a tool can be attached;

a rolling bearing for rotatably supporting the rotating shaft in a housing,

the rolling bearing for an air turbine is characterized in that,

the rolling bearing includes:

an outer race fixed to the housing;

an inner ring fixed to the rotating shaft;

a plurality of rolling elements arranged between the outer ring and the inner ring so as to be rollable; and

a seal member fixed to an inner peripheral surface of the outer ring to seal a space between the outer ring and the inner ring,

the seal member has: a base extending in a radial direction; and an elastically deformable lip portion extending from a radially inner end of the base portion and inclined toward a radially inner side toward a downstream side in a supply direction of the compressed air, wherein the seal member is located in a space between the outer ring and the inner ring, the lip portion is formed in an inclined shape, and an inner peripheral surface of the lip portion of the seal member is in contact with an outer peripheral surface of the inner ring when the compressed air is not applied,

when the compressed air acts, a contact area of the sealing member with the outer peripheral surface of the inner ring is reduced as compared to when the compressed air does not act.

2. Rolling bearing for air turbines according to claim 1,

the seal member is in a non-contact state with the outer peripheral surface of the inner ring when the compressed air acts thereon.

3. A dental air turbine handpiece comprising the rolling bearing for an air turbine of claim 1 or 2.

Technical Field

The present invention relates to a bearing unit for an air turbine.

Background

As shown in fig. 26, dental air turbine handpiece 120 includes: a clamping portion 121; and a head 122 provided at a distal end portion of the clamping portion 121. The doctor holds the holding portion 121 and performs cutting processing on the tooth, for example.

As shown in fig. 27, a dental air turbine bearing unit 100 constituting a head 122 is conventionally known which includes: a rotary shaft 101 to one end of which a dental treatment tool not shown is attached; turbine blades 102 for rotationally driving the rotary shaft 101 with compressed air; and a pair of ball bearings 103 and 104 for rotatably supporting the rotary shaft 101. The rotary shaft 101, the turbine blade 102, and the pair of ball bearings 103 and 104 are disposed in a head housing 105. Outer rings 106 and 107 of the pair of ball bearings 103 and 104 are supported by rubber rings 108 mounted in annular recesses 109 and 110 of the head housing 105. The outer race 107 of the lower ball bearing 104 is biased upward by a spring washer 111, thereby applying a preload to the pair of ball bearings 103 and 104. That is, the pair of ball bearings 103 and 104 supporting the rotary shaft 101 are combined face to face, and a constant pressure preload is applied by the elastic force of the spring washer 111.

In the dental air turbine handpiece 120, compressed air is caused to impinge on the turbine blades 102, and the air pressure causes the rotary shaft 101 to rotate, thereby realizing ultra-high-speed rotation.

Incidentally, patent document 1 discloses an air turbine handpiece for dental or medical use, which includes: a head housing having an air supply port; a rotary shaft rotatably housed in the head casing and having a blade receiving the supply air from the air inlet; and a ball bearing which supports the rotating shaft rotatably in the head housing with the air supply port interposed therebetween. Here, a heat-resistant mechanical seal is provided on the side close to the air supply port of the ball bearing.

Therefore, the heat-resistant mechanical seal is elastically deformed to come into contact with the ball bearing to shield the ball bearing when the pressure of the supply air is applied to the supply port, that is, when the vane rotates. On the other hand, when the pressure of the supply air stops, that is, when the rotation of the vane stops, the vane returns to its original state so as not to contact the ball bearing. Thus, the lubricant oil filled in the ball bearing is prevented from slipping out due to the pressure of the supplied air applied to the ball bearing during use. When the rotation of the blade is stopped, the heat-resistant mechanical seal and the ball bearing are brought into a non-contact state, so that the frictional resistance between the heat-resistant mechanical seal and the blade is eliminated when the blade of the rotating shaft is started, and the smooth starting of the blade is realized.

Disclosure of Invention

Problems to be solved by the invention

The air turbine handpiece described above is rotated at an ultra high speed when used, but on the other hand, when the user stops the handpiece, it is desirable to stop the handpiece quickly for the purpose of shortening the time required for treatment or the like.

The present invention has been made in view of the above problems, and an object thereof is to provide an air turbine bearing unit capable of quickly stopping rotation.

Means for solving the problems

The above object of the present invention is achieved by the following constitution.

(1) A bearing unit for an air turbine, comprising: a turbine blade that receives compressed air and rotates; a rotating shaft to which the turbine blade is integrally fixed, and to which a tool can be attached; a rolling bearing for rotatably supporting the rotating shaft in a housing, the bearing unit for an air turbine being characterized in that,

the rolling bearing includes: an outer race fixed to the housing; an inner ring fixed to the rotating shaft; a plurality of rolling elements arranged between the outer ring and the inner ring so as to be rollable; and a seal member fixed to an inner peripheral surface of the outer ring to seal a space between the outer ring and the inner ring,

the sealing member is in contact with the outer peripheral surface of the inner ring when the compressed air is not acting, and the contact area between the sealing member and the outer peripheral surface of the inner ring is reduced when the compressed air is acting as compared with when the compressed air is not acting.

(2) The bearing unit for an air turbine according to (1),

the seal member has a lip portion capable of being brought into contact with an outer peripheral surface of the inner ring and elastically deformable,

the lip portion is shaped so as to be inclined in the direction of supply of the compressed air as it goes radially inward.

(3) The bearing unit for an air turbine according to (1),

the seal member has a lip portion capable of being brought into contact with an outer peripheral surface of the inner ring and elastically deformable,

the lip portion is inclined axially outward as it goes from the metal core or base portion of the seal member toward the radially inner side.

(4) The bearing unit for an air turbine according to any one of (1) to (3),

at least a portion of the outer peripheral surface of the inner ring, which the seal member contacts, is a flat surface.

(5) The bearing unit for an air turbine according to any one of (1) to (4),

a groove portion for fixing the seal member is formed on an inner peripheral surface of the outer ring,

a base portion of the radially outer end of the seal member, which is made of an elastic material, is fixed to the groove portion by a retaining ring.

(6) The bearing unit for an air turbine according to any one of (1) to (4),

a groove portion for fixing the seal member is formed on an inner peripheral surface of the outer ring,

the base portion of the radially outer end of the seal member, which is made of an elastic material, is fixed by caulking to the groove portion.

(7) The bearing unit for an air turbine according to any one of (1) to (4),

a groove portion for fixing the seal member is formed on an inner peripheral surface of the outer ring,

the base portion of the radially outer end of the seal member, which is made of an elastic material, is sandwiched and fixed by both axial surfaces of the groove portion.

(8) The bearing unit for an air turbine according to any one of (1) to (4),

a groove portion for fixing the seal member is formed on an inner peripheral surface of the outer ring,

the base portion of the radially outer end of the seal member, which is made of a metal material, is fixed to the groove portion by caulking.

(9) The bearing unit for an air turbine according to any one of (1) to (4),

a groove portion for fixing the seal member is formed on an inner peripheral surface of the outer ring,

the groove portion has: a tapered surface inclined radially outward toward the axially inner side; and an axial inner surface extending radially inward from an axial inner end of the tapered surface,

a base portion of the radially outer end of the seal member, which is made of a metal material, is fixed to the groove portion by being in contact with the tapered surface and the axially inner surface.

(10) The bearing unit for an air turbine according to any one of (1) to (9),

the inner race extends to a more axially outer side than the outer race,

the inner peripheral surface of the seal member is in contact with the outer peripheral surface of the inner ring on the axially outer side of the outer ring.

(11) The bearing unit for an air turbine according to any one of (1) to (10),

the seal member is in a non-contact state with the outer peripheral surface of the inner ring when the compressed air acts thereon.

(12) The bearing unit for an air turbine according to any one of (1) to (11), characterized in that,

when the compressed air is not applied, a contact area where the inner peripheral surface of the seal member contacts the outer peripheral surface of the inner ring is 10% or more of the entire inner peripheral surface of the seal member.

(13) The bearing unit for an air turbine according to any one of (1) to (12),

when the compressed air is not applied, the contact interference of the portion of the sealing member that contacts the outer peripheral surface of the inner ring is 50 μm or more and 200 μm or less.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the air turbine bearing unit of the present invention, when the supply of compressed air is stopped for the shutdown operation, the compressed air does not act on the seal member, and therefore, the contact area between the seal member and the outer peripheral surface of the inner ring is increased as compared with the case where compressed air acts (during operation). Therefore, the seal member operates as a brake for the rotating shaft, and the rotating shaft can be quickly stopped.

Drawings

Fig. 1 is a partial cross-sectional view of a dental air turbine according to embodiment 1.

Fig. 2 is a partial sectional view of the rolling bearing according to embodiment 1 in a stopped state.

Fig. 3 is a partial cross-sectional view of the rolling bearing according to embodiment 1 in an operating state.

Fig. 4 is a cross-sectional view of the lip.

Fig. 5 is a partial cross-sectional view of a rolling bearing according to a modification of embodiment 1 in an operating state.

Fig. 6 is a partial cross-sectional view of the rolling bearing according to embodiment 2 in a stopped state.

Fig. 7 is a partial cross-sectional view of the rolling bearing according to embodiment 2 in an operating state.

Fig. 8 is a partial cross-sectional view of a rolling bearing according to a modification of embodiment 1 in an operating state.

Fig. 9 is a partial cross-sectional view of the rolling bearing according to embodiment 3 in a stopped state.

Fig. 10 is a partial sectional view of the rolling bearing according to embodiment 4 in a stopped state.

Fig. 11 is a partial cross-sectional view of the rolling bearing according to embodiment 5 in a stopped state.

Fig. 12 is a front view of a seal member according to a modification.

Fig. 13 is a front view of a seal member according to a modification.

Fig. 14 is a front view of a seal member according to a modification.

Fig. 15 is a front view of a seal member according to a modification.

Fig. 16 is a front view of a seal member according to a modification.

Fig. 17 is a front view of a seal member according to a modification.

Fig. 18 is a front view of a seal member according to a modification.

Fig. 19 is a front view of a seal member according to a modification.

Fig. 20 is a front view of a seal member according to a modification.

Fig. 21(a) is a sectional view taken along the line a-a in fig. 18 to 20, and (B) is a sectional view taken along the line B-B in fig. 18 to 20.

Fig. 22 is a partial sectional view of a rolling bearing according to another modification.

Fig. 23 is a sectional view for explaining a contact angle of the sealing member shown in fig. 1.

Fig. 24 is a partial sectional view of a conventional rolling bearing.

Fig. 25 is a diagram showing a relationship between a cross-sectional shape of a lip portion and a stop time.

Fig. 26 is a schematic side view of a dental air turbine handpiece.

Fig. 27 is a main part sectional view of the dental air turbine.

Description of reference numerals

1: rolling bearing

3: rolling ball (Rolling element)

5: holding rack

6: rim part

10: outer ring

11: inner peripheral surface

12: trough part

13. 14: axial two sides

15: conical surface

16: axial inner side surface

20: inner ring

21: peripheral surface

30: sealing member

31: base part

33: lip part

34: inner peripheral surface

35: metal core

36: 1 st extension part

37: 1 st inclined part

38: 2 nd extension part

39: 2 nd inclined part

40: check ring

41: vent hole

42: incision

100A: bearing unit for air turbine

S: bearing inner space

Detailed Description

Hereinafter, embodiments of the air turbine bearing unit according to the present invention will be described in detail with reference to the drawings. In the following description, a case where the bearing unit for an air turbine of the present invention is applied to a dental air turbine handpiece is described as an example, but the present invention may be applied to other applications such as a home electric motor.

(embodiment 1)

Fig. 1 shows a bearing unit for an air turbine according to the present embodiment, and fig. 2 shows a rolling bearing 1 constituting the bearing unit for an air turbine according to the present embodiment. As shown in fig. 1, the bearing unit 100A for an air turbine includes: a turbine blade 102 that receives compressed air and rotates; a rotating shaft 101 to which a turbine blade 102 is integrally fixed and which can be attached to a tool (e.g., a dental treatment tool) at one end; a rolling bearing 1 for rotatably supporting the rotary shaft 101 to the housing 105. Therefore, in the rolling bearing 1 shown in fig. 2, compressed air is supplied from the right to the left when the hand piece is driven. The air turbine bearing unit of the present embodiment is different from the conventional structure shown in fig. 26 in the structure of the rolling bearing 1. Therefore, the turbine blades 102, the rotary shaft 101, the head housing 105, and the like are denoted by the same reference numerals as in the related art or equivalent structures. The air turbine bearing unit is not limited to the configuration of fig. 1.

The rolling bearing 1 includes: an outer ring 10 fixed to the housing 105; an inner ring 20 fixed to the rotary shaft 101; a plurality of balls (rolling elements) 3 rollably disposed between the outer ring 10 and the inner ring 20; and a cage 5 for holding the plurality of balls 3. The cage 5 is a so-called crown type cage, and a substantially annular rim portion 6 is positioned on the upstream side (rightward in the drawing) of the supply direction of the compressed air with respect to the balls 3.

A groove 12 for fixing the seal member 30 is formed on the inner circumferential surface 11 of the outer ring 10 on the downstream side (left side in the drawing) of the balls 3 in the compressed air supply direction. The sealing member 30 is not limited to the configuration in which it is disposed on the downstream side of the balls 3 in the supply direction of the compressed air as in the present embodiment, as long as it can exhibit a braking function described later, and may be disposed on the upstream side (rightward in the drawing) of the balls 3 in the supply direction of the compressed air, or may be disposed in 1 pair on both the downstream side and the upstream side of the balls 3 in the supply direction of the compressed air.

The seal member 30 includes: a base 31 made of an elastic material extending in the radial direction; and a lip 33 formed of an elastic material integrally formed with the base 31. The base 31 covers the metal core 35 at its radially inner side portion, maintaining shape and strength. The base 31 abuts against the retainer ring 40, and is inserted into and fixed to the groove 12. In the present embodiment, the C-ring retainer is used as the retainer 40 in consideration of ease of mounting, but an annular retainer or the like may be used. When the compressed air strikes the seal member 30, the seal member 30 is firmly fixed to the outer ring 10 by the frictional force between the metal retainer ring 40 and the base 31.

The lip 33 is substantially annular and inclined in the compressed air supply direction (in fig. 2, the direction from the right to the left) toward the radially inner side, and can abut against the outer peripheral surface 21 of the inner ring 20. That is, the lip 33 is inclined axially outward from the metal core 35 toward the radially inner side. Referring to the sectional view of fig. 4, the inner peripheral surface 34 of the lip 33 has a substantially circular ring shape (a substantially circular cross section), that is, the seal inner diameter has a substantially circular ring shape. Further, since at least the portion of the outer peripheral surface 21 of the inner ring 20 that the lip portion 33 contacts is flat (substantially circular), the inner peripheral surface 34 of the lip portion 33, which is the seal inner diameter, can be in contact with the outer peripheral surface 21 of the inner ring 20 over substantially 100% of the entire area, that is, in a substantially complete contact state. Thus, the seal member 30 seals the bearing inner space S between the inner circumferential surface 11 of the outer ring 10 and the outer circumferential surface 21 of the inner ring 20.

Here, in order to drive the dental air turbine handpiece, when the compressed air is supplied to the turbine blade, the compressed air flows from the right to the left in the bearing inner space S as shown by an arrow a in fig. 3. This compressed air acts on the seal member 30 to elastically deform the lip 33 in the left direction. Therefore, when the compressed air acts, the contact area between the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 is reduced as compared with when the compressed air does not act. In the example of fig. 3, the inner peripheral surface 34 of the lip 33 is in a non-contact state with the outer peripheral surface 21 of the inner ring 20, and the contact area is zero. That is, the lip 33 is in an open state. As shown in the example of fig. 5, the inner peripheral surface 34 of the lip 33 may be configured to maintain a contact state with the outer peripheral surface 21 of the inner ring 20 when the compressed air is applied, and the contact area between the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be reduced as compared with when the compressed air is not applied.

On the other hand, when the supply of the compressed air is stopped in order to stop the dental air turbine handpiece, the compressed air does not act on the lip portion 33, and therefore, the lip portion 33 returns to the state shown in fig. 2, the inner peripheral surface 34 of the lip portion 33 is in a contact state with the outer peripheral surface 21 of the inner ring 20, and the contact area with the outer peripheral surface 21 of the inner ring 20 increases. Namely, the lip 33 is in a closed state. Therefore, the lip 33 operates as a brake for the inner ring 20 and the rotary shaft 101 to which the inner ring 20 is fixed, and the rotary shaft 101 can be stopped quickly.

Further, as described above, since the shape of the lip 33 is an inclined shape that is easily elastically deformed by the action of the compressed air, the opening and closing operation of the lip 33 can be performed with good sensitivity by the compressed air.

Further, since at least the portion of the outer peripheral surface 21 of the inner ring 20 that is in contact with the inner peripheral surface 34 of the lip portion 33 is flat (substantially annular), the contact area between the outer peripheral surface 21 of the inner ring 20 and the inner peripheral surface 34 of the lip portion 33 can be increased, and the braking function by the lip portion 33 can be improved. In particular, in the present embodiment, the inner peripheral surface 34 of the lip 33 has a substantially circular ring shape similar to the outer peripheral surface 21 of the inner ring 20. Therefore, the inner peripheral surface 34 of the lip 33 is in contact with the outer peripheral surface 21 of the inner ring 20 over an area of approximately 100% of the entire area, and therefore, the braking function by the lip 33 can be further improved.

Further, a groove 12 for fixing the seal member 30 is formed in the inner peripheral surface 11 of the outer ring 10, and a base 31 made of an elastic material at the outer end in the radial direction of the seal member 30 is fixed to the groove 12 by a retainer ring 40. Therefore, since the seal member 30 is firmly fixed to the outer ring 10, the seal member 30 can be prevented from coming off when compressed air is received.

(embodiment 2)

In the present embodiment, a method of fixing the outer ring 10 to the seal member 30 is different from that of the above-described embodiment. As shown in fig. 6 and 7, the base 31 of the seal member 30 covers the metal core 35 by its entirety, maintaining the shape and strength. The lip 33 is inclined axially outward as it goes from the metal core 35 to the radially inner side. The radially outer end of the base 31 is fixed by caulking to the groove 12 of the outer ring 10. Even with such a fixing method, since the seal member 30 is firmly fixed to the outer ring 10, the seal member 30 can be prevented from coming off even when compressed air is received. Other configurations and effects are the same as those of the above embodiment.

In the present embodiment, the contact area between the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 is reduced when compressed air acts as compared with when compressed air does not act. That is, the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be in a non-contact state (the contact area is zero), and as shown in the example of fig. 8, the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be configured to maintain a contact state, and the contact area may be reduced as compared with the case where the compressed air is not applied.

(third embodiment)

In the present embodiment, the method of fixing the outer ring 10 to the seal member 30 is different from the above-described embodiment, as shown in fig. 9, the base portion 31 of the seal member 30 covers the outside of the cylindrical portion of the metal core 35 having the L-shaped cross section, and maintains the shape and strength, the lip portion 33 is inclined to the outside in the axial direction as it goes from the metal core 35 to the inside in the radial direction, and the outer end portion in the radial direction of the base portion 31 is sandwiched and fixed in the axial direction by the both surfaces 13, 14 in the axial direction of the groove portion 12 of the outer ring 10, and even in such a fixing method, since the seal member 30 is firmly fixed to the outer ring 10, the seal member 30 can be prevented from dropping when receiving compressed air, and other configurations and effects are the same as those of.

In the present embodiment, the contact area between the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 is reduced when compressed air acts as compared with when compressed air does not act. That is, the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be in a non-contact state (contact area thereof is zero), or the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be in a contact state, and the contact area may be reduced as compared with the case where the compressed air is not applied.

(embodiment 4)

In the present embodiment, a method of fixing the outer ring 10 to the seal member 30 is different from that of the above-described embodiment. As shown in fig. 10, the seal member 30 includes: a lip 33; and a base portion 31 made of a metal material covered with the lip portion 33 at a radially inner end portion and extending radially outward from the lip portion 33. The lip portion 33 is inclined axially outward as it goes from the base portion 31 radially inward. As described above, in the present embodiment, the base portion 31 is not covered with the elastic material, and the metal material (peeled) is exposed. The radially outer end of the base 31 is fixed by caulking to the groove 12 of the outer ring 10. Even with such a fixing method, since the seal member 30 is firmly fixed to the outer ring 10, the seal member 30 can be prevented from coming off even when compressed air is received. Other configurations and effects are the same as those of the above embodiment.

In the present embodiment, the contact area between the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 is reduced when compressed air acts as compared with when compressed air does not act. That is, the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be in a non-contact state (contact area thereof is zero), or the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be in a contact state, and the contact area may be reduced as compared with the case where the compressed air is not applied.

(embodiment 5)

In the present embodiment, a method of fixing the outer ring 10 to the seal member 30 is different from that of the above-described embodiment. As shown in fig. 11, the groove portion 12 of the outer ring 10 includes: a tapered surface 15 that is inclined radially outward toward the axially inner side (the ball 3 side); and an axial inner surface 16 extending radially inward from an axial inner end of the tapered surface 15.

Further, the seal member 30 includes: a lip 33; and a base portion 31 made of a metal material covered with the lip portion 33 at a radially inner end portion and extending radially outward from the lip portion 33. The lip portion 33 is inclined axially outward as it goes from the base portion 31 radially inward. As described above, in the present embodiment, the base portion 31 is not covered with the elastic material, and the metal material is peeled (exposed). Further, the base 31 has: a 1 st extending portion 36 extending radially inward from the lip portion 33; a 1 st inclined portion 37 obliquely extending from the 1 st extending portion 36 to the radially inner side and the axially inner side; a 2 nd extending portion 38 extending radially inward from the 1 st inclined portion 37; and a 2 nd inclined portion 39 obliquely extending from the 2 nd extending portion 38 toward the radial inner side and the axial outer side.

Then, the axial inner surface of the 2 nd extending portion 38 is brought into contact with the axial inner surface 16 of the groove portion 12, and the outer peripheral surface of the 2 nd inclined portion 39 is brought into contact with the tapered surface 15 of the groove portion 12, whereby the base portion 31 is fixed to the groove portion 12. Even with such a fixing method, since the seal member 30 is firmly fixed to the outer ring 10, the seal member 30 can be prevented from coming off even when compressed air is received. Other configurations and effects are the same as those of the above embodiment.

In the present embodiment, the contact area between the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 is reduced when compressed air acts as compared with when compressed air does not act. That is, the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be in a non-contact state (contact area thereof is zero), or the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 may be in a contact state, and the contact area may be reduced as compared with the case where the compressed air is not applied.

The present invention is not limited to the above embodiments, and modifications, improvements, and the like can be appropriately made.

For example, a modification in which the inner diameter of the seal member 30, that is, the shape of the inner peripheral surface 34 of the lip 33 is, for example, substantially elliptical in cross section (see fig. 12) or substantially triangular in cross section (see fig. 13) without changing the outer diameter shape of the seal member 30 is also within the scope of the present invention. Further, as shown in fig. 14, at least 1 vent hole 41 may be provided in the inner peripheral surface 34 of the lip 33, and as shown in fig. 15 to 17, at least 1 notch 42 may be provided. Fig. 14 shows an example in which 1 circular vent hole 41 is provided, but the number of vent holes 41 may be 2 or more, and the shape of the vent hole 41 is not limited to a circular shape. In addition, although fig. 15 to 17 show examples in which 2, 4, and 8 cuts 42 are provided at equal intervals in the circumferential direction, the number and the interval in the circumferential direction of the cuts 42 are not limited to these examples.

As shown in fig. 18 to 20, the tip end portion of the lip 33 may be continuously notched in the circumferential direction, and the inner circumferential surface 34 of the lip 33 may partially contact the outer circumferential surface 21 of the inner ring 20. In fig. 18 to 20, the inner peripheral surface 34 of each lip 33 is: the contact area (arc length) with the outer peripheral surface 21 of the inner ring 20 is 50%, 25%, 10% of the entire inner peripheral surface 34.

Fig. 21(a) is a cross-sectional view taken along the line a-a in fig. 18 to 20, and fig. 21(B) is a cross-sectional view taken along the line B-B in fig. 18 to 20.

When the compressed air acts, it is preferable that the inner peripheral surface 34 of the lip 33 does not completely contact the outer peripheral surface 21 of the inner ring 20, but when the sealing member 30 changes from the contact state to the non-contact state, a frictional force is generated with the outer peripheral surface 21 of the inner ring 20, and therefore, the state may not be smoothly changed. Therefore, by providing the air holes 41 or the notches 42 in the inner peripheral surface 34 of the lip 33 or by locally bringing the inner peripheral surface 34 of the lip 33 into contact with the outer peripheral surface 21 of the inner ring 20, the compressed air can easily pass through the seal member 30, and the change from the contact state to the non-contact state can be promoted. By changing the shape of the inner peripheral surface 34 of the lip 33 in this way, the contact area between the inner peripheral surface 34 and the outer peripheral surface 21 of the inner ring 20 can be appropriately changed, and the desired braking performance and sealing performance of the lip 33 can be satisfied.

In order to realize the braking function, it is preferable that a contact area (arc length in fig. 18 to 20) of the inner peripheral surface 34 of the lip portion 33 shown in fig. 12 to 20 is in contact with the outer peripheral surface 21 of the inner ring 20 over at least 10% of the entire inner peripheral surface thereof when the compressed air is not applied. This is to facilitate the change of the sealing member 30 from the contact state to the non-contact state when the compressed air strikes the sealing member 30. When the contact area is 10% or less of the entire inner peripheral surface, the contact between the inner peripheral surface 34 of the lip 33 and the outer peripheral surface 21 of the inner ring 20 is small when the compressed air is not applied, and therefore, the braking function may not be sufficiently exhibited.

In the case where the axial width of the inner peripheral surface 34 of the lip 33 in contact with the inner ring 20 is uniform in the circumferential direction, the contact area of the inner peripheral surface 34 of the lip 33 may be at least 10% or more of the entire area of the inner peripheral surface thereof when the compressed air is not applied.

As long as the sealing performance can be obtained, as shown in fig. 22, the inner ring 20 may be extended axially outward of the outer ring 10, and the seal member 30 may be extended axially outward of the outer ring 10. In this case, the inner peripheral surface 34 of the lip 33 of the seal member 30 abuts against the outer peripheral surface 21 of the inner ring 20 at the axially outer side than the outer ring 10. According to this configuration, since the inclination of the lip 33 can be increased, the opening and closing operation of the lip 33 can be performed more easily by the compressed air.

As shown in fig. 23, it is preferable that the inclination angle α of the lip 33 of the seal member 30 is set to 35 to 55 °, and the lip 33 is brought into contact with the outer peripheral surface 21 of the inner ring 20, whereby air efficiently acts on the lip 33 when compressed air acts, and the seal member 30 can be smoothly opened, and as a result, can be rotated at high speed with small air pressure.

When the compressed air is not applied, the lip 33 of the seal member 30 is brought into contact with the outer peripheral surface 21 of the inner ring 20, but when the contact interference between the contact portion of the seal member 30 and the outer peripheral surface 21 of the inner ring 20 is less than 50 μm, the braking action is weakened, and the stop time of the turbine is prolonged. On the other hand, if the contact interference exceeds 200 μm, elastic deformation is less likely to occur during the action of compressed air, and it is difficult to reduce the contact area. Therefore, the contact interference is preferably 50 μm or more and 200 μm or less.