bearings

Abstract

A ball bearing (5) is a bearing that supports a shaft member (7) provided with a turbine blade (8) for receiving compressed air from an air supply port (9). The ball bearing (5) includes an inner ring (10), an outer ring (20), a plurality of rolling elements (30), and a retainer (31). The ball bearing (5) further includes an annular sealing member (40) provided around an axis (x) so as to be able to block the space between the inner ring (10) and the outer ring (20). The sealing member (40) has a support ring (42) for supporting the sealing member (40) on the outer peripheral side. A seal facing groove (11) that includes a seal contact surface (13), a recess (14), and a protrusion (12) is formed on an outer peripheral surface (10b) of the inner ring (10). The seal contact surface (13) allows for contact of an inner peripheral end (41a) of the sealing member (40) thereon from the outside in the axial (x) direction. The recess (14) extends in the axial (x) direction at least in a region facing the support ring (42) in the radial direction.

Description

[Technical Field]

[0001] The present invention relates to a bearing, and more particularly to a bearing used in a dental handpiece driven by an air turbine. [Background technology]

[0002] Dental handpieces have traditionally been used in dental treatments and other procedures. A dental handpiece includes a head equipped with a rotation mechanism and a tool detachably attached to the head. In the rotation mechanism, both ends of a shaft member are supported by bearings, and turbine blades are attached to the shaft member. The bearings use ball bearings equipped with an inner ring, an outer ring, and a cage that holds multiple rolling elements (balls) interposed between the inner and outer rings. Compressed air can be supplied to the turbine blades from a supply passage, and the compressed air is blown against the turbine blades of the rotation mechanism, causing the turbine blades to rotate, the shaft member to rotate, and the tool to rotate.

[0003] Some bearings used in conventional dental handpieces have a braking function, as disclosed in Patent Document 1. Specifically, an annular seal ring is fixed to the outer ring of the bearing, and the inner end of the seal ring is capable of contacting the inner ring of the bearing. When the supply of compressed air is stopped, the inner end of the seal ring comes into contact with the inner ring of the bearing, applying a braking force to the inner ring and stopping its rotation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] German Patent Application Publication No. 102012000757 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for a configuration that enables higher speed rotation for the bearings with braking functions used in dental handpieces as described above.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a bearing that enables higher speed rotation. [Means for solving the problem]

[0007] In order to achieve the above object, a bearing according to the present invention is a bearing that supports a shaft member provided with turbine blades that rotate when subjected to compressed air, and comprises an inner ring, an outer ring installed on the outer peripheral side of the inner ring, a plurality of rolling elements interposed between the inner ring and the outer ring, a cage that holds the rolling elements at intervals in the circumferential direction, and an annular sealing member disposed between the inner ring and the outer ring and arranged around an axis x so as to be able to close the space between the inner ring and the outer ring, the sealing member having a support ring that is an annular member for supporting the sealing member on its outer peripheral side, and a seal opposing groove including a seal contact surface, a recess, and a protrusion is formed on an outer peripheral surface of the inner ring facing the outer peripheral side, the seal contact surface is capable of contacting an inner peripheral end of the sealing member from the outside in the axial direction, and the recess extends radially in the axial direction at least in a region that faces the support ring. [Effects of the Invention]

[0008] The bearing according to the present invention can enable higher speed rotation. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an external view of an example of a dental handpiece equipped with a bearing according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating an example of a head portion of the dental handpiece shown in FIG. 1. [Figure 3] 3 is a cross-sectional view showing a schematic configuration of an example of a bearing according to the present invention used in the head portion shown in FIG. 2. [Figure 4] FIG. 4 is a partially enlarged view of the bearing shown in FIG. 3. [Figure 5] FIG. 4 is a partially enlarged view of the bearing shown in FIG. 3. [Figure 6] 3 is a partially enlarged cross-sectional view showing the schematic configuration of another example of a bearing according to the present invention used in the head portion shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that in the drawings, not all of the components are labeled with reference numerals, and some of the components may be omitted.

[0011] A bearing according to one embodiment of the present invention is a high-speed ball bearing used in a dental handpiece. FIG. 1 is an external view of a dental handpiece 1 as an example of a dental handpiece equipped with a bearing according to the present invention. FIG. 2 is a cross-sectional view schematically showing a head portion 2 as an example of a head portion of the dental handpiece 1. FIG. 3 is a cross-sectional view showing the schematic configuration of a ball bearing 5 as an example of a bearing according to the present invention used in the head portion 2. FIGS. 4 and 5 are partially enlarged views of the ball bearing 5 shown in FIG. 3. FIG. 4 shows the ball bearing 5 in the dental handpiece 1 in a stopped state, and FIG. 5 shows the ball bearing 4 in the dental handpiece 1 in a driven state. The stopped state, as described below, refers to a state in which compressed air is not acting on the sealing member and the sealing member is not deformed by the action of compressed air. The driven state refers to a state in which compressed air is acting on the sealing member and the sealing member is deformed.

[0012] As shown in Figures 1 and 2, a dental handpiece 1 has a head portion 2 with a rotation mechanism 4 and a tool 3 detachably attached to the head portion 2. When the dental handpiece 1 is used, the tool 3 is rotated at high speed (for example, 400,000 revolutions per minute or more) to perform operations such as cutting teeth.

[0013] As shown in FIG. 2, the head unit 2 of the dental handpiece 1 includes a rotation mechanism 4 and a housing 6 that accommodates the rotation mechanism 4. As shown in FIG. 2, the rotation mechanism 4 includes a shaft member 7, a pair of ball bearings 5, turbine impellers 8, and an air supply port 9. The tool 3 is detachably attached to the shaft member 7. The shaft member 7 extends in the direction of an axis x and is rotatably supported at both ends by the housing 6 via a pair of ball bearings 5. The axis x is the axis of the ball bearings 5. Furthermore, the shaft member 7 has turbine impellers 8 attached between the pair of ball bearings 5. Supplying compressed air to the turbine impellers 8 from the air supply port 9 rotates the turbine impellers 7 at high speed. This causes the shaft member 7 and the tool 3 to rotate at high speed. The shaft member 7 rotates around the axis x as its central axis or approximately its central axis.

[0014] As described above, ball bearing 5 is a bearing that supports shaft member 7, which is provided with turbine blades 8 that rotate when compressed air is supplied from air supply port 9. Ball bearing 5 includes inner ring 10, outer ring 20 installed on the outer periphery of inner ring 10, a plurality of rolling elements 30 interposed between inner ring 10 and outer ring 20, and cage 31 that holds rolling elements 30 at intervals in the circumferential direction. Ball bearing 5 also includes an annular sealing member 40 disposed around axis x between inner ring 10 and outer ring 20 so as to close the space between inner ring 10 and outer ring 20. Sealing member 40 has support ring 42, which is an annular member that supports sealing member 40 on the outer periphery. A seal-facing groove 11 is formed on outer periphery surface 10b of inner ring 10 facing the outer periphery. The seal-facing groove 11 includes a seal contact surface 13, a recess 14, and a protrusion 12. The seal contact surface 13 is capable of contacting the inner peripheral end 41a, which is the inner peripheral end of the sealing member 40, from the outside in the direction of the axis x. The recess 14 extends radially in the direction of the axis x at least in a region facing the support ring 42. The configuration of the ball bearing 5 will now be described in detail.

[0015] The outer side is one side in the direction of the axis x, and the inner side is the other side in the direction of the axis x. In the head portion 2 of the dental handpiece 1, the inner side of the ball bearing 5 is the side close to the turbine impeller 8 in the direction of the axis x, and the outer side of the ball bearing 5 is the side away from the turbine impeller 8 in the direction of the axis x. The radial direction is the direction perpendicular to the axis x. The inner side is the inner side in the radial direction and the side approaching the axis x in the radial direction, and the outer side is the opposite end of the inner side, the outer side in the radial direction, and the side away from the axis x in the radial direction.

[0016] As shown in FIGS. 2 to 4 , the ball bearing 5 includes an inner ring 10 having a raceway groove 10c on its outer peripheral surface 10b that forms an inner ring raceway, an outer ring 20 having a raceway groove 20c on its inner peripheral surface 20a that forms an outer ring raceway, a plurality of rolling elements (balls) 30 interposed between the inner ring raceway and the outer ring raceway, and an annular cage 31 that rotatably holds the rolling elements 30 at intervals in the circumferential direction. The ball bearing 5 also includes a sealing member 40. The sealing member 40 is provided to prevent lubricant from leaking from inside the ball bearing 5 and foreign matter from entering inside the ball bearing 5. The sealing member 40 also serves as a brake mechanism for the rotation mechanism 4. As described above, the sealing member 40 is provided between the inner ring 10 and the outer ring 20 so as to be able to close the space between them.

[0017] As shown in FIG. 3 , the inner peripheral surface of the cage 31 faces the outer peripheral surface 10b of the inner ring 10, and the outer peripheral surface of the cage 31 faces the inner peripheral surface 20a of the outer ring 20. The cage 31 has a plurality of pockets (not shown) formed at regular or approximately regular intervals in the circumferential direction to hold the rolling elements 30 so that they can roll. As shown in FIG. 2 , the outer peripheral surface 20b of the outer ring 20 is fitted into the housing 6, and a shaft member 7 is fitted into the inner peripheral surface 10a of the inner ring 10. Specifically, in the head portion 2, a pair of ball bearings 5 ​​supports the shaft member 7 with a turbine impeller 8 sandwiched therebetween. In the ball bearings 5, the inner ring 10 and the outer ring 20 are rotatable relative to each other about the axis x. That is, when the dental handpiece 1 is driven, that is, when compressed air is supplied to the turbine impeller 8, the inner ring 10 rotates at high speed relative to the outer ring 20.

[0018] As shown in Figures 2 to 4, the sealing member 40 is provided in the open portion between the inner ring 10 and the outer ring 20 on the side where compressed air that has passed through the ball bearing 5 is discharged. That is, in each of a pair of ball bearings 5 ​​that face each other across the turbine blade 8, the sealing member 40 is provided in the outer open portion between the inner ring 10 and the outer ring 20. As shown in Figures 3 and 4, the sealing member 40 includes a seal body 41, a support ring 42, and a snap ring 43. The sealing member 40 is fixed to the end portion 21 of the outer ring 20. The end portion 21 is the outer end portion in the direction of the axis x.

[0019] As shown in FIGS. 4 and 5 , the seal body 41 is an elastic, elastically deformable member, and is a plate-like member having an annular shape about the axis x. The support ring 42 is, for example, a plate-like member having a predetermined rigidity and having an annular shape about the axis x. The inner diameter D2 of the support ring 42 is larger than the inner diameter D1 of the seal body 41. The snap ring 43 is, for example, an elastic member having an annular or substantially annular shape about the axis x. The snap ring 43 is a member for fixing the sealing member 40 to the outer ring 20 via the support ring 42. The snap ring 43 is, for example, a C-ring. As shown in FIGS. 3 and 4 , the seal body 41, the support ring 42, and the snap ring 43 are stacked in this order from the outside in the direction of the axis x, and are fixed to the end portion 21 of the outer ring 20. Specifically, the seal body 41 and the support ring 42 are sandwiched between the end 21 of the outer ring 20 and the snap ring 43 by the snap ring 43 and fixed to the end 21 of the outer ring 20 .

[0020] As shown in Figures 3 and 4, when the dental handpiece 1 is stopped, the seal body 41 is configured so that its inner end (inner end 41a) comes into contact with the inner ring 10. As shown in Figure 2, when compressed air is supplied to the turbine impeller 8 from the air supply port 9, some of the discharged air flows from inside the rotation mechanism 4 through the gap between the inner ring 10 and the outer ring 20 of the ball bearing 5 toward the seal body 41. That is, some of the discharged air flows from the inside to the outside through the gap between the inner ring 10 and the outer ring 20 of each ball bearing 5 and hits the seal body 41 from the inside. Due to the pressure of this discharged air, the seal body 41 deforms, as shown in Figure 5, and the inner end 41a of the seal body 41 separates from the inner ring 10, and the air is discharged to the outside of the ball bearing 5.

[0021] Even if the supply of compressed air is stopped to stop the rotating tool 3, the turbine impeller 8 and shaft member 7 continue to rotate for a while due to inertia. During this time, the inside of the ball bearing 5 experiences a negative pressure, lower than the air pressure outside the ball bearing 5. This can cause foreign matter-laden air to be sucked into the ball bearing 5 or the housing 6 from around the dental handpiece 1. This air suction into the housing 6 when the dental handpiece 1 is stopped is called the suck-back phenomenon. The air flow during the suck-back phenomenon presses the sealing member 40 against the inner ring 10, suppressing the suction of air from the outside and preventing the inflow of foreign matter. The sealing member 40 also acts as a brake for the rotation mechanism 4, applying a braking force to the inner ring 10 as it rotates due to inertia. Therefore, the sealing member 40 can shorten the time it takes for the dental handpiece 1 to stop.

[0022] As described above, the support ring 42 contacts the outer peripheral portion of the seal body 41 over the entire circumference around the axis x. This prevents or inhibits the seal body 41 from coming off the outer ring 20 when subjected to pressure from compressed air. The support ring 42 also reinforces the contact between the inner peripheral end 41a of the seal body 41 and the seal contact surface 13 of the inner ring 10. This allows the support ring 42 to further strengthen the braking force of the braking function of the seal body 41.

[0023] The inner ring 10 and the outer ring 20 are made of, for example, stainless steel, and the rolling elements 30 are made of, for example, stainless steel or ceramics.

[0024] The sealing member 40 and the structure formed by the sealing member 40, the inner ring 10 and the outer ring 20 will now be described in more detail.

[0025] As shown in Figures 3 and 4, the sealing member 40 is fixed to the seal groove 22 of the outer ring 20. The seal groove 22 is a groove recessed toward the outer peripheral surface 20b of the outer ring 20 and extends annularly around the axis x. As shown in Figure 4, the seal groove 22 includes an inclined surface 23, an annular surface 24, and a bottom surface 25. The inclined surface 23 is a cylindrical surface about the axis x and is located on the outer side of the seal groove 22 in the direction of the axis x. The inclined surface 23 increases in diameter from the outer side to the inner side in the direction of the axis x and, in cross section, is inclined radially outward as it moves from the outer side to the inner side in the direction of the axis x. The annular surface 24 is an annular surface extending along a plane perpendicular to the axis x and faces outward in the direction of the axis x. The bottom surface 25 is an annular surface facing radially inward and extends between the inclined surface 23 and the annular surface 24.

[0026] As shown in FIG. 4 , the seal groove 22 has a cylindrical surface 26 and a torus surface 27 that form a step adjacent to the torus surface 24. The cylindrical surface 26 is a cylindrical surface about the axis x that extends inward in the direction of the axis x from the inner peripheral end of the torus surface 24. The cylindrical surface 26 is, for example, a cylindrical surface. The torus surface 27 is an annular surface that extends along a plane perpendicular to the axis x and faces outward in the direction of the axis x. The torus surface 27 extends from the inner end of the cylindrical surface 26.

[0027] 4, the outer peripheral end portion (outer peripheral end portion 41b) of seal body 41 is housed in a step formed by cylindrical surface 26 and annular surface 27, and is supported in contact with cylindrical surface 26 and annular surface 27. Snap ring 43 is in contact with inclined surface 23, and sandwiches seal body 41 between outer ring 20 and snap ring 43 via support ring 42, fixing seal body 41 and support ring 42 to seal groove 22.

[0028] The seal body 41 is a circular sheet-shaped member. The seal body 41 contains, as a base resin, at least one resin selected from fluororesin, fluororubber, nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, ethylene propylene diene rubber, etc. The base resin may be a resin in which a porous resin (e.g., a three-dimensional network structure) is impregnated with an elastomer. Examples of the fluororesin include polytetrafluoroethylene and perfluoroelastomer. The fluororesin may be a composite of polytetrafluoroethylene and perfluoroelastomer to provide sliding properties and elasticity. The composite of polytetrafluoroethylene and perfluoroelastomer may be, for example, a composite obtained by curing a liquid perfluoroelastomer impregnated into porous polytetrafluoroethylene (e.g., a three-dimensional network structure). Examples of the fluororubber include vinylidene fluoride, tetrafluoroethylene-propylene, and tetrafluoroethylene-perfluorovinyl ether.

[0029] The hardness of the seal body 41 is, for example, Shore A60 to 90 (based on JIS K6253:2012) or Shore A70 to 90 (based on JIS K6253:2012). The thickness T1 of the seal body 41 is, for example, 0.5 mm or less, 0.2 mm or less, or 0.1 mm or less. The radial length W0 of the contact area between the seal body 41 and the support ring 42 is, for example, 1 / 2 to 3 / 4, or 2 / 3 to 3 / 4 of the radial width W1 of the seal body 41. With these hardnesses and dimensions, the seal body 41 is likely to deform appropriately when the air turbine that supplies compressed air is operating (when compressed air passes through the ball bearing 5).

[0030] The tear strength of the seal body 41 in accordance with JIS K6252:2007 is not particularly limited, but is, for example, 50 N / mm or more, 65 N / mm or more, or 80 N / mm or more. The tensile strength of the seal body 41 in accordance with JIS K6251:2010 is, for example, 30 MPa or more. By having such tear strength and tensile strength, the durability of the seal body 41 is further improved when the air turbine is repeatedly operated and stopped.

[0031] The support ring 42 is an annular member made of metal or resin. The support ring 42 has a higher hardness than the seal body 41. The snap ring 43 is a member made of metal or resin. The snap ring 43 has a structure that generates a radially outward biasing force. This biasing force acts on the inclined surface 23 of the seal groove 22, biasing the snap ring 43 inward in the direction of the axis x. As a result, as described above, the snap ring 43 presses the seal body 41 and the support ring 42 against the annular surface 27 of the outer ring 20. In this example, the inner diameter D2 of the support ring 42 is larger than the inner diameter D1 of the seal body 41, and the inner diameter D3 of the snap ring 43 is larger than the inner diameter D2 of the support ring 42.

[0032] 4, the inner ring 10 has, on its outer periphery, an outer peripheral surface 10b formed with raceway grooves 10c along which the rolling elements 30 move, and a seal-opposing groove 11 that faces the sealing member 40. The seal-opposing groove 11 is a groove recessed toward the inner peripheral surface 10a of the inner ring 10, and extends annularly around the axis x.

[0033] As shown in FIG. 4, the seal facing groove 11 includes a seal contact surface 13, a recess 14, and a protrusion 12. The seal contact surface 13 is an annular surface around the axis x and faces outward in the direction of the axis x. The seal contact surface 13 is connected to the outer surface 10b at its inner circumferential end. As shown in FIG. 4, the inner circumferential end 41a of the seal body 41 contacts the seal contact surface 13 when the air turbine is stopped (when no pressure from compressed air is applied), that is, when the dental handpiece 1 is at rest. Thus, when the dental handpiece 1 is at rest, the seal body 41, which has not been deformed by the action of compressed air, contacts the seal contact surface 13 of the inner ring 10 from the outside at its inner circumferential end 41a. When the dental handpiece 1 is stopped, the inner peripheral end 41a of the seal body 41 may or may not be biased toward the seal contact surface 13 of the inner ring 10. In other words, when the dental handpiece 1 is stopped, the seal body 41 may be deformed and the inner peripheral end 41a may be pressed against the seal contact surface 13, or the seal body 41 may not be deformed and the inner peripheral end 41a may be in contact with the seal contact surface 13 without generating a reaction force.

[0034] As shown in Fig. 4, the recess 14 extends outward from the seal contact surface 13 in the direction of the axis x, and forms an annular groove recessed radially inward between the seal contact surface 13 and the protrusion 12. When viewed in the radial direction, the recess 14 extends in the direction of the axis x in a region facing at least the inner peripheral end (inner peripheral end 42a) of the support ring 42, and when viewed in the radial direction, the recess 14 faces at least the inner peripheral end 42a of the support ring 42. It is preferable that at least a portion of the recess 14 has a cylindrical surface 14a extending in the direction of the axis x. The cylindrical surface 14a is a cylindrical surface or an approximately cylindrical surface with the axis x as its central axis or approximately central axis. In one aspect of the present invention, as shown in FIG. 4 , the recess 14 has a cylindrical surface 14a between the end (inner end 14b) connected to the seal contact surface 13 and the protrusion 12. The cylindrical surface 14a faces the inner peripheral end 42a of the support ring 42 and the inner peripheral end (inner peripheral end 43a) of the snap ring 43 in the radial direction. As an example, as shown in FIG. 4 , the cylindrical surface 14a extends outward from the snap ring 43 in the direction of the axis x. Since the recess 14 extends in the direction of the axis x in the region radially facing the sealing member 40, the flow of the exhausted compressed air is less likely to be obstructed. This improves the exhaust efficiency of the supplied compressed air, increases the flow velocity of the compressed air supplied to the turbine blades 8, and allows the ball bearing 5 to rotate at a higher speed. This allows the tool 3 to rotate at a higher speed.

[0035] As shown in FIG. 4, the protrusion 12 is a flange-shaped portion connected to the outer end of the recess 14 in the axial x direction. The protrusion 12 is located further outward in the axial x direction than the snap ring 43. The outer diameter D4 of the protrusion 12 is smaller than the inner diameter D1 of the seal body 41. The inner edge (edge ​​12a) of the protrusion 12 in the axial x direction is curved. For example, in the cross section shown in FIG. 4, the edge 12a of the protrusion 12 forms a convex curve on the outer periphery and inward. This makes it less likely that the flow of discharged compressed air will be obstructed. On the other hand, when a suck-back phenomenon occurs, the air flow stagnates around the protrusion 12, and some of the air moves toward the seal body 41. This prevents air from flowing into the ball bearing 5 when a suck-back phenomenon occurs. This suppresses the suck-back phenomenon and reduces the amount of foreign matter that enters the ball bearing 5 due to the suck-back phenomenon. Furthermore, the time from when the supply of compressed air is stopped until the seal body 41 contacts the seal contact surface 13 can be shortened, thereby shortening the time until the tool 3 stops. In this way, the braking performance can be improved.

[0036] As shown in FIG. 5 , the outer end (outer end 14c) of the recess 14 in the direction of the axis x is preferably located further outward in the direction of the axis x than the inner end 41a of the deformed seal body 41 when the dental handpiece 1 is in operation (when compressed air pressure is applied). Furthermore, the minimum distance L1 between the deformed seal body 41 and the recess 14 or the protrusion 12 is preferably equal to or greater than the thickness T1 of the seal body 41. Although the minimum distance L1 is the radial distance between the deformed seal body 41 and the recess 14 in the embodiment of the present invention shown in FIG. 5 , the minimum distance L1 is not limited thereto. For example, the minimum distance L1 may be the distance in the direction of the axis x. It is more preferable that the minimum distance L1 be equal to or greater than 1.2 times the thickness of the seal body 41. It is more preferable that the size of the gap between the deformed seal body 41 and the seal contact surface 13, the recess 14, and the protrusion 12 gradually increase toward the minimum distance L1. In this way, the recess 14 has a sufficiently long extension length in the direction of the axis x, and the gap between the seal body 41 and the recess 14 or the protrusion 12 is sufficiently large, so that the flow of the discharged compressed air is less likely to be obstructed.

[0037] As described above, the seal body 41 is made of a material that makes the seal body 41 more easily deformable. The hardness and dimensions of the seal body 41 also make the seal body 41 more easily deformable. Therefore, the seal body 41 is more easily deformable than conventional seal bodies. As a result, when compressed air acts on the seal body 41 in the dental handpiece 1 in the driven state, the seal body 41 deforms more significantly, making it less likely to impede the flow of compressed air that passes through the ball bearing 5 and is discharged to the outside of the head portion 2.

[0038] In this way, the ball bearing 5 makes it less likely that the flow of compressed air passing through the ball bearing 5 and being discharged to the outside of the head portion 2 will be obstructed, and the rotation speed of the rotation mechanism 4 of the dental handpiece 1 in the driven state can be increased.

[0039] Furthermore, as described above, the seal body 41 is more easily deformed than conventional seal bodies. Therefore, when the dental handpiece 1 is stopped and the turbine impeller 8 and the shaft member 7 continue to rotate by inertia, when a negative pressure is generated inside the ball bearing 5, this negative pressure can press the seal body 41 more strongly against the seal contact surface 13. Therefore, even if the seal body 41 wears over time, deterioration of the braking performance of the seal body 41 can be suppressed. In this way, the ball bearing 5 can improve the durability of the brake mechanism, thereby extending the period during which the desired braking performance is exhibited. Furthermore, the braking performance of the seal body 41 can be improved.

[0040] Furthermore, for example, by adjusting the inner diameter D2 of the support ring 42, the operating range of the inner peripheral end 41a of the seal body 41 when compressed air is applied can be varied. This allows the flow rate of compressed air discharged to the outside of the head portion 2 through the ball bearing 5 to be adjusted. For example, by increasing the inner diameter D2 of the support ring 42, the inner peripheral end 41a of the seal body 41 can be deformed more greatly, thereby increasing the flow rate of compressed air discharged to the outside of the head portion 2 through the ball bearing 5. This allows the rotation mechanism 4 of the dental handpiece 1 to rotate at a higher speed when driven. On the other hand, by decreasing the inner diameter D2 of the support ring 42, the rotation speed of the rotation mechanism 4 of the dental handpiece 1 can be reduced and the braking performance of the seal body 41 can be improved.

[0041] In this way, with the ball bearing 5, when adjusting the rotation speed and braking performance of the rotating mechanism 4 of the dental handpiece 1, it is possible to simply change the inner diameter D2 of the support ring 42, without having to change the various components of the dental handpiece, such as changing the internal structure of the bearing or the lubricant, changing the design of the dental handpiece, or adjusting the flow rate of compressed air, as was previously required. This makes it easy to adjust the rotation speed and braking performance of the rotating mechanism 4 of the dental handpiece 1.

[0042] As described above, the ball bearing 5 according to the embodiment of the present invention can enable higher speed rotation.

[0043] Next, we will explain ball bearing 5A as another example of a bearing according to the present invention. Compared to the above-described ball bearing 5, ball bearing 5A has a seal-opposing groove 11A that is different from seal-opposing groove 11. In the following, with regard to the configuration of ball bearing 5A, components that are the same as or have similar functions to those of the above-described ball bearing 5 will be assigned the same reference numerals and their explanation will be omitted, and only components that are different from the above-described ball bearing 5 will be explained.

[0044] Fig. 6 is a partially enlarged cross-sectional view showing the schematic configuration of a ball bearing 5A as another example of a bearing according to the present invention used in the head portion 2. Fig. 6 shows the ball bearing 5A in the dental handpiece 1 when it is at rest. In other words, no compressed air acts on the seal body 41 of the ball bearing 5A shown in Fig. 6, and the seal body 41 is not deformed. As shown in Fig. 6, the inner ring 10 of the ball bearing 5A has a seal-opposing groove 11A that is different from the seal-opposing groove 11 of the ball bearing 5 described above.

[0045] 6, when compressed air is not acting on the seal body 41, that is, when the seal body 41 is not deformed, the seal contact surface 13 of the seal opposing groove 11A is not in contact with the inner circumferential end 41a of the seal body 41. In other words, as shown in Fig. 6, when compressed air is not acting on the seal body 41, an annular gap G is formed between the inner circumferential end 41a of the seal body 41 and the seal contact surface 13 of the seal opposing groove 11A, and the inner circumferential end 41a of the seal body 41 faces the seal contact surface 13 of the seal opposing groove 11A from the outside in the direction of the axis x, via the gap G.

[0046] The width W of the gap G is set so that when the dental handpiece 1 is stopped and the turbine impeller 8 and the shaft member 7 are rotating by inertia, a negative pressure is generated inside the ball bearing 5, causing the seal body 41 to be sucked by the negative pressure, and the inner peripheral end 41a of the seal body 41 is pressed against the seal contact surface 13. The width W of the gap G is the width of the gap G in the direction of the axis x. For example, the width W of the gap G is equal to or smaller than the thickness T1 of the seal body 41.

[0047] According to ball bearing 5A, seal body 41 contacts seal contact surface 13 only when the dental handpiece 1 is stopped and the turbine impeller 8 and shaft member 7 are rotating by inertia, creating a negative pressure inside ball bearing 5. This shortens the time that seal body 41 contacts seal contact surface 13 of rotating inner ring 10, thereby reducing wear of seal body 41 between seal contact surface 13. This reduces wear between seal body 41 and seal contact surface 13, even if the inner diameter D2 of support ring 42 is reduced to make inner peripheral end 41a of seal body 41 less likely to deform. This improves the durability of seal body 41 while improving the braking ability of seal body 41.

[0048] Furthermore, the ball bearing 5A can achieve the same functions as the ball bearing 5 described above, and can achieve the same effects as the ball bearing 5 described above.

[0049] In the above-described ball bearing 5, even when the inner peripheral end 41a of the seal body 41 is not biased toward the seal contact surface 13 of the inner ring 10 while the dental handpiece 1 is stopped, it is possible to reduce wear between the seal body 41 and the inner ring 10, as with the above-described ball bearing 5A, and improve the braking ability and durability of the seal body 41. This is because the time during which the seal body 41 is in contact with the seal contact surface 13 can be shortened while the dental handpiece 1 is running or stopped.

[0050] Although the present invention has been described above through the above embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0051] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. Furthermore, the above-described embodiments do not limit the scope of the present invention, and the present invention may include any and all applications. The components of the above-described embodiments, as well as their arrangement, materials, conditions, shape, size, etc., are not limited to those illustrated and may be modified as appropriate. For example, the present invention includes differences that arise during implementation due to manufacturing tolerances, etc. Furthermore, components illustrated in different embodiments may be partially substituted or combined within the scope of technical inconsistency. Furthermore, the various configurations may be selectively combined as appropriate to achieve at least some of the above-described problems and effects. [Explanation of symbols]

[0052] 1 dental handpiece, 2 head portion, 3 tool, 4 rotating mechanism, 5, 5A ball bearing, 6 housing, 7 shaft member, 8 turbine blade, 9 air supply port, 10 inner ring, 10a inner peripheral surface, 10b outer peripheral surface, 10c raceway groove, 11, 11A seal counter groove, 12 protrusion, 12a edge, 13 seal contact surface, 14 recess, 14a cylindrical surface, 14b inner end, 14c outer end, 20 outer ring, 20a inner peripheral surface, 20b outer peripheral surface, 20c raceway groove, 21 end, 22 seal groove, 23 inclined surface, 24 annular surface, 25 bottom surface, 26 cylindrical surface, 27 annular surface, 30 rolling element, 31 cage, 40 sealing member, 41 seal body, 41a inner peripheral end, 41b Outer peripheral end, 42 support ring, 42a inner peripheral end, 43 snap ring, 43a inner peripheral end, D1, D2, D3, D4 inner diameter, G clearance, L1 minimum distance, T1 thickness, W width, x axis

Claims

1. A bearing for supporting a shaft member provided with turbine blades that rotate by receiving compressed air, With inner circle, an outer ring disposed on the outer peripheral side of the inner ring; a plurality of rolling elements interposed between the inner ring and the outer ring; a cage that holds the rolling elements at intervals in the circumferential direction; a sealing member that is annular about the axis and is provided between the inner ring and the outer ring so as to be able to close a space between the inner ring and the outer ring, the sealing member has a support ring which is an annular member for supporting the sealing member on an outer circumferential side, a seal-facing groove, which is a groove recessed toward the inner circumference, is formed in an outer peripheral surface of the inner ring that faces the outer peripheral side and includes a seal contact surface and a recess extending outward from the seal contact surface in the axial direction, the seal contact surface is an annular surface facing outward in the axial direction, and an inner peripheral end of the sealing member can contact the seal contact surface from the outside in the axial direction; The recess extends in the axial direction at least in a region facing the support ring in the radial direction, When the compressed air is not being received, the seal contact surface does not contact the inner peripheral end of the sealing member. Bearing.

2. The engine further includes a snap ring, which is an annular member, for fixing the sealing member to the outer ring via the support ring, The recessed portion extends in the axial direction in a region facing the snap ring and the support ring in a radial direction.

2. The bearing according to claim 1.

3. The seal-facing groove includes a protruding portion that protrudes outward from the recessed portion, the protruding portion is adjacent to the seal contact surface from the outside in the axial direction with the recessed portion interposed therebetween, and the protruding portion is located outward in the axial direction from the snap ring, The outer diameter of the protrusion is smaller than the inner diameter of the sealing member.

3. The bearing according to claim 2.

4. A curved surface is formed at an inner end of the protrusion in the axial direction.

4. The bearing according to claim 3.

5. an outer end of the recess in the axial direction is located outer than an inner peripheral end of the sealing member deformed by the compressed air, in the axial direction; 3. The bearing according to claim 2.

6. a minimum distance between the inner peripheral end of the sealing member deformed by the compressed air and the recess or the protrusion is equal to or greater than a thickness of the sealing member; 4. The bearing according to claim 3.

7. The minimum distance is equal to or greater than 1.2 times the thickness of the sealing member.

7. A bearing according to claim 6.

8. the sealing member includes a seal body that is an annular elastic member around the axis, The base material of the seal body is a porous resin impregnated with an elastomer.

2. The bearing according to claim 1.

9. The base material of the seal body is a composite of porous polytetrafluoroethylene and perfluoroelastomer.

9. A bearing according to claim 8.

10. The hardness of the seal body in accordance with JIS K 6253:2012 is Shore A 60 to 90.

9. A bearing according to claim 8.

11. The hardness of the seal body in accordance with JIS K 6253:2012 is Shore A70 to 90.

11. A bearing according to claim 10.

12. the sealing member includes a seal body that is an annular elastic member around the axis, The thickness of the seal body is 0.5 mm or less.

2. The bearing according to claim 1.

13. The thickness of the seal body is 0.2 mm or less.

13. A bearing according to claim 12.

14. The thickness of the seal body is 0.1 mm or less.

14. A bearing according to claim 13.

15. the sealing member includes a seal body that is an annular elastic member around the axis, The radial length of the contact area between the seal body and the support ring is equal to or greater than 1 / 2 and equal to or less than 3 / 4 of the radial width of the seal body.

2. The bearing according to claim 1.

16. The radial length of the contact area between the seal body and the support ring is 2 / 3 or more and 3 / 4 or less of the radial width of the seal body.

16. A bearing according to claim 15.

17. the sealing member includes a seal body that is an annular elastic member around the axis, The tear strength of the material of the seal body in accordance with JIS K6252:2007 is 50 N / mm or more.

2. The bearing according to claim 1.

18. The tear strength of the material of the seal body in accordance with JIS K6252:2007 is 65 N / mm or more.

18. A bearing according to claim 17.

19. The tear strength of the material of the seal body in accordance with JIS K6252:2007 is 80 N / mm or more.

19. A bearing according to claim 18.

20. the sealing member includes a seal body that is an annular elastic member around the axis, The tensile strength of the material of the seal body in accordance with JIS K6251:2010 is 30 MPa or more.

2. The bearing according to claim 1.

21. The shaft member is included in a rotation mechanism of a dental handpiece.

2. The bearing according to claim 1.

22. a pair of bearings that support the shaft member with the turbine blades interposed therebetween, The inner side in the axial direction is the side of the turbine blade.

22. A bearing according to claim 21.

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