JP4962103B2 - Rolling bearings for dental handpieces - Google Patents

Description

  The present invention relates to a rolling bearing used for a dental handpiece such as a straight handpiece or an angle handpiece.

  Conventionally, dental handpieces such as straight handpieces and angle handpieces are known (see, for example, Patent Documents 1 and 2).

  An example of such a dental angle handpiece is shown in FIG. 1A is an external view of a dental handpiece, FIG. 1B is an enlarged cross-sectional view of a head portion of the dental handpiece, and FIG. 1C is a partial cross-sectional view of a rolling bearing used in the head portion.

  The dental handpiece 1 has a mechanism in which various tools 5 such as a drill and a grindstone are detachably attached to the head portion 3 and the tool 5 is rotated at a high speed. The configuration of the head unit 3 will be described in detail. The tool 5 is mounted on a rotary shaft 7 in the head unit 3, and the rotary shaft 7 is rotatable to the housing 11 via a pair of upper and lower rolling bearings 9, 9. It is supported by. Further, a turbine blade 13 is attached to a portion between the pair of rolling bearings 9 and 9 on the rotating shaft 7, and the rotating shaft 7 and the tool 5 are also rotated at high speed by rotating the turbine blade 13 by air pressure. Can be rotated.

  A plurality of water injection holes 15 for injecting water toward the tool 5 and a plurality of air injection holes 17 for injecting air toward the tool are disposed on the outer periphery of the rotating shaft 7. Each water injection hole 15 is connected to a water introduction path 21 via a circumferential groove 19 provided around the rotation shaft 7, and each air injection hole 17 has a circumferential groove 23 provided around the rotation shaft 7. To the air introduction path 25. The water injection holes 15 and the air injection holes 17 are paired with each other, and are arranged on the outer periphery of the rotating shaft 7 at a predetermined interval. The water and the air injection holes 17 are injected from the water injection holes 15. The air is designed to intersect with the air on the way to the tool 5. Each air injection hole 17 is disposed inside each water injection hole 15. With such a configuration, the water jetted from the water jet holes 15 is diffused by the air jetted from the air jet holes 17, and water can be efficiently jetted to the entire tool 5 during dental treatment.

The rolling bearings 9 and 9 include an inner ring 27 and an outer ring 29 configured to be relatively rotatable, balls 31 arranged between the inner and outer rings, and a holder 33 that holds the balls 31 in a freely rollable manner. The inner ring 27 is fitted on the rotary shaft 7, and the outer ring 29 is fitted on the housing 11. The outer ring 29 has a flange 35 on one end side, and a sealing member 37 is provided on the other end side. An annular ring 39 made of brass, for example, is externally fitted on the body of the outer ring 29 and is in contact with the flange 35, and an O-ring 41 made of rubber, for example, is externally fitted on the annular ring 39. When the rolling bearings 9 and 9 are incorporated into the head portion 3 for positioning, the housing 11 and the O-ring 41 are brought into contact with each other, so that a preload is applied to the rolling bearings 9 and 9.
JP 2001-321391 A Japanese Patent Laid-Open No. 7-23980

  By the way, rolling bearings for dental handpieces are required to have very high performance such as being able to withstand high-speed rotation of 300,000 revolutions per minute and high-temperature sterilization treatment exceeding 100 ° C. In order to realize a higher-performance bearing, it was necessary to increase the dimensional accuracy and rotational accuracy of the bearing and to devise materials for the cage.

  In addition, when a resin-based material is used as a material for a conventional rolling bearing for handpieces, there is one formed of polyamideimide (Toron 4275) of about 30% graphite powder and about 3% PTFE. There is a problem that the cost is increased because the injection molding cannot be performed and it must be manufactured by a shaving process.

  Therefore, an object of the present invention is to provide a rolling bearing for a dental handpiece that is low in cost and has improved bearing rotation performance under high-speed rotation.

In order to solve the above problems, the present invention provides an inner ring having an inner ring raceway on an outer peripheral surface, an outer ring having an outer ring raceway on an inner peripheral surface, and an inner ring raceway disposed between the inner and outer rings in proximity to the inner ring, Built in the head part of a dental handpiece with an annular cage that holds a plurality of rolling elements interposed between the outer ring raceway and a plurality of rolling elements in pockets provided in a plurality of circumferential directions. The inner ring is externally fitted to a rotating shaft to which a tool is attached , and the outer ring is fitted to a housing, thereby being a rolling bearing for a dental handpiece that rotatably supports the rotating shaft, the holding The vessel is composed of a heat-resistant resin composition, and the base resin of the resin composition is polyphenylene sulfide containing glass fiber and / or carbon fiber, or glass fiber and / or glass. A polyether ether ketone blended with carbon fibers, and the roundness of the inner periphery and the outer periphery of the said cage in a cross section when cut by a plane perpendicular to the rotation axis of the retainer 5 to 10 [mu] m, the The outer peripheral surface of the inner ring fitted on the rotation shaft becomes the guide surface of the cage, the roughness of the guide surface is 0.7 s or less, and the clearance between the guide surface and the opposing surface of the cage is 0. 0.02 to 0.06 mm.

  In a preferred aspect of the present invention, the plurality of rolling elements are balls, the curvature of the groove of the inner ring raceway is 55% to 60% with respect to the curvature of the ball, and the curvature of the groove of the outer ring raceway is the ball. 60% to 65% with respect to the curvature.

  According to the present invention, it is possible to reduce costs and improve bearing rotation performance under high-speed rotation.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 is a cross-sectional view of a rolling bearing for a dental handpiece according to an embodiment of the present invention.

  The rolling bearing 43 has an inner ring 49 having an inner ring raceway 47 on an outer peripheral surface 45 and an outer ring 55 having an outer ring raceway 53 on an inner peripheral surface 51. The inner ring 49 and the outer ring 55 have the same center, and this is indicated by the symbol O. A plurality of rolling elements 57 are interposed between the inner ring raceway 47 and the outer ring raceway 53. In this embodiment, the rolling element 57 is a ball, and the plurality of balls have the same material and shape, and are denoted by the same reference numeral 57. Between the inner and outer rings, an annular retainer 59 that holds the balls 57 in respective pockets provided at a plurality of locations in the circumferential direction is provided. The shape of the retainer 59 is not particularly limited, and may be any of a crown retainer, a press retainer, a machined retainer, and the like. The inner circumferential surface 61 of the cage 59 faces the outer circumferential surface 45 of the inner ring 49, and the outer circumferential surface 63 of the cage 59 faces the inner circumferential surface 51 of the outer ring 55.

  Further, the outer ring 55 is provided with a sealing member 65 such as a seal or a shield in order to prevent the lubricant from leaking from the inside of the bearing or foreign matters from entering the inside of the bearing. The rolling bearing 43 is configured as described above, and the inner and outer rings are relatively rotatable about the rotation center axis XX.

  Although the form of the dental handpiece incorporating the rolling bearing 43 is not particularly limited, for example, the same one as the above-described example (see FIG. 1) can be considered. Here, as shown in FIG. 2, in this embodiment, the outer ring 55 is not formed with a flange, but the configuration in the head portion of the handpiece can be made almost the same. Further, the outer ring 55 may be a flanged outer ring. The outer ring 55 is fitted in the housing, and the inner ring 49 is fitted on the rotating shaft to which the tool is attached. The inner ring 49 rotates with respect to the outer ring 55 at high speed.

  In the present embodiment, the inner and outer rings 49 and 55 are made of highly corrosion-resistant stainless steel, and the balls 57 are also made of stainless steel or ceramic. The cage 59 is closer to the inner ring 49 than the outer ring 55, and the cage 59 is guided to the inner ring 49 during high-speed rotation. An outer peripheral surface 45 portion of the inner ring 49 excluding the inner ring raceway 47 serves as a guide surface for guiding the cage 59. As another form, the retainer 59 may be an outer ring guide type that is closer to the outer ring 55 than the inner ring 49. In this case, the inner peripheral surface 51 portion of the outer ring 55 excluding the outer ring raceway 53 becomes the guide surface of the cage 59.

  The cage 59 is made of a heat-resistant resin composition, and the base resin of the resin composition is polyphenylene sulfide (PPS) in which glass fibers and / or carbon fibers are mixed, or glass fibers and / or carbon fibers. Polyether ether ketone (PEEK). The cage 59 using such a material can be injection-molded, and the cost for producing the cage can be greatly reduced. Further, the handpiece is subjected to high-temperature sterilization, but the cage 59 using the above material has a very small dimensional change due to temperature. In addition, the dimensional change of the cage 59 is very small because of the material having a very low water absorption rate even with respect to the steam applied during the sterilization process. Therefore, according to the cage 59 using the above material, it is possible to reduce the cost and prevent deterioration of the rotational accuracy of the rolling bearing 43.

  Further, the roundness of the inner and outer circumferences of the cage 59, that is, the roundness of the inner and outer circumferences of the cage 59 in a cross section when the cage 59 is cut along a plane perpendicular to the rotation center axis XX. The degree is set to 10 μm or less. Further, the roughness of the guide surface of the retainer 59 (as described above, the outer peripheral surface 45 of the inner ring 49 in the present embodiment) is 0.7 s or less. Further, the clearance between the guide surface and the inner peripheral surface 61 of the cage 59 facing the guide surface is set to 0.02 to 0.06 mm. By precisely controlling each value in this way, the bearing rotation accuracy under high-speed rotation is ensured, and noise and vibration are suppressed.

  Further, the curvature of the groove of the inner ring raceway 47 is set to 55% to 60% with respect to the curvature of the ball 57, and the curvature of the groove of the outer ring raceway 53 is set to 60% to 65% with respect to the curvature of the ball 57. Here, the curvature of the grooves of the inner and outer ring raceways 47 and 53 means the curvature of the raceways 47 and 53 in a cross section when the bearing 43 is cut along a plane including the rotation center axis XX as shown in FIG. To do. Since a dental handpiece driven by air of a constant pressure is affected by the torque of the bearing, it is desirable to reduce the torque of the bearing as much as possible. By controlling the curvature of the raceway groove as described above, the contact ellipse formed at the contact portion between the rolling surface of the ball 57 and the inner ring raceway 47 and the outer ring raceway 53 is reduced. Therefore, the rolling resistance and spin generated at the contact ellipse during rotation are reduced, the torque of the bearing 43 is reduced, and the number of revolutions can be further increased with a constant air pressure.

  3 to 6, using the rolling bearing having the same shape and material as the rolling bearing for the dental handpiece of the present embodiment, the above-described cage roundness (μm), guide surface roughness (s), and guidance are provided. The relationship between the clearance (mm), each value of the curvature of the groove of the inner and outer ring raceways, and the rotational speed is shown. The number of rotations is shown as a rotation number ratio with 1 being 400,000 rotations per minute. In addition, FIG. 3 also shows the test results for the vibration ratio and FIG. 6 for the torque ratio. The bearing used for the test was SR144, and the preload was 0.3 kgf.

  FIG. 3 is a graph showing the relationship between the roundness of the cage, the vibration and the rotational speed. It can be seen that the vibration increases when the roundness of the cage exceeds 10 μm, and the rotational speed gradually decreases. According to the present embodiment, since the roundness of the cage is 10 μm or less, vibration can be suppressed and a large rotation speed can be ensured.

  FIG. 4 is a graph showing the relationship between the guide surface roughness and the rotational speed. It can be seen that the rotational speed ratio decreases and becomes smaller than 1 when the guide surface roughness exceeds 1 s. According to this embodiment, since the guide surface roughness is 0.7 s or less, a large rotational speed can be ensured.

  FIG. 5 is a graph showing the relationship between the guide gap and the rotation speed. It can be seen that the rotation speed ratio does not reach 1 when the guide gap is too small or too large. According to this embodiment, since the guide gap is adjusted within the range of 0.02 to 0.06 mm, a large rotational speed can be ensured.

  FIG. 6 is a graph showing the relationship between the curvature of the grooves of the inner and outer ring raceways, the torque and the rotational speed. In the figure, ri represents the curvature of the groove of the inner ring raceway when the curvature of the ball is 1, and re represents the curvature of the groove of the outer raceway when the curvature of the ball is 1. In this embodiment, ri = 0.55 to 0.60 and re = 0.60 to 0.65. The three bar graphs compare the torque of the bearings for two examples of the conventional product and this embodiment. Specifically, in order from the left, the torque ratio of the conventional product (this is assumed to be 1), the torque ratio of the bearing in which ri and re are minimized in this embodiment, and the bearing in which ri and re are maximized in this embodiment Torque ratio. The rotational speed ratio is also shown for two examples of the conventional product and the present embodiment. As can be seen from the figure, the present embodiment has a low torque and can increase the rotational speed as compared with the conventional product.

  As described above, according to the bearing for a dental handpiece of the present embodiment, it is possible to prevent a reduction in rotational accuracy as well as a significant cost reduction. Moreover, the bearing rotation accuracy under high-speed rotation is ensured, and noise and vibration are suppressed. Further, the torque can be reduced and the rotational speed can be increased.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible.

(A) is an external view of a dental handpiece, (b) is an enlarged cross-sectional view of a head portion of the dental handpiece, and (c) is a partial cross-sectional view of a rolling bearing used in the head portion. It is a cross-sectional view of a rolling bearing for a dental handpiece according to an embodiment of the present invention. It is a graph which shows the relationship between a cage | basket roundness, a vibration, and rotation speed. It is a graph which shows the relationship between guide surface roughness and rotation speed. It is a graph which shows the relationship between a guidance clearance gap and rotation speed. It is a graph which shows the relationship between the curvature of the groove | channel of an inner and outer ring track, torque, and rotation speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Dental handpiece 3 ... Head part 5 ... Tool 7 ... Rotating shaft 43 ... Rolling bearing 45 ... Inner ring outer peripheral surface 47 ... Inner ring Track 49 ... Inner ring 51 ... Outer ring inner peripheral surface 53 ... Outer ring raceway 55 ... Outer ring 57 ... Rolling element 59 ... Retainer 61 ... Retainer Inner peripheral surface 63 ··· Outer peripheral surface of cage

Claims (2)

An inner ring having an inner ring raceway on the outer peripheral surface;
An outer ring having an outer ring raceway on the inner peripheral surface;
A circle that is disposed between the inner and outer rings in the vicinity of the inner ring, and holds a plurality of rolling elements interposed between the inner ring raceway and the outer ring raceway in respective pockets provided at a plurality of locations in the circumferential direction. An annular cage,
For a dental handpiece that is built in a head portion of a dental handpiece, the inner ring is externally fitted on a rotary shaft to which a tool is attached , and the outer ring is fitted in a housing so that the rotary shaft is rotatably supported. Rolling bearing of
The cage is made of a heat-resistant resin composition, and the base resin of the resin composition is polyphenylene sulfide containing glass fiber and / or carbon fiber, or polyether containing glass fiber and / or carbon fiber. Ether ketone,
The roundness of the inner periphery and the outer periphery of the said cage in a cross section when cut by a plane perpendicular to the rotation axis of the cage to 5 to 10 [mu] m,
The outer peripheral surface of the inner ring fitted around the rotating shaft becomes the guide surface of the cage, and the roughness of the guide surface is 0.7 s or less, and a gap between the guide surface and the opposing surface of the cage is provided. A rolling bearing for a dental handpiece, characterized by being 0.02 to 0.06 mm. The plurality of rolling elements are balls,
The groove curvature of the inner ring raceway is 55% to 60% with respect to the curvature of the ball, and the curvature of the groove of the outer ring raceway is 60% to 65% with respect to the curvature of the ball. Rolling bearings for dental handpieces as described in 1.

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