Retainer, rolling bearing, bearing unit, and rotating machine

Abstract

To suppress loads received from rolling bodies even if a difference occurs in revolution speeds of the rolling bodies.SOLUTION: A cage 28 comprises an annular main body part 30 arranged between an inner ring and an outer ring which are arranged on a common axial line O, and also arranged coaxially with the axial line, and a plurality of holding holes 31 which is formed so as to penetrate the main body part in a radial direction, and holds a plurality of rolling bodies arranged between the inner ring and the outer ring so as to be rollable in a state in which the rolling bodies 27 are aligned with intervals in a peripheral direction. The holding holes have first peripheral wall faces 35 and second peripheral wall faces 36 which are arranged so as to oppose each other with the rolling bodies sandwiched therebetween, and axial wall faces 37 oriented in an axial direction of the main body part, and connecting the first peripheral wall faces and the second peripheral wall faces. The axial wall faces are formed so as to flatly extend in the peripheral direction so that a maximum interval between the first peripheral wall faces and the second peripheral wall faces in the peripheral direction becomes an interval which is larger than diameters of the rolling bodies.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a cage, a rolling bearing, a bearing unit, and a rotating device.

Background Art

[0002] Generally, a rolling bearing includes an outer ring and an inner ring arranged coaxially, a plurality of rolling elements disposed between the inner ring and the outer ring, and a cage that rotatably holds each rolling element in a state where the plurality of rolling elements are evenly arranged in the circumferential direction. This type of rolling bearing comes in a wide variety of types depending on the type of load to be supported (radial load, axial load, etc.) and the application, and is incorporated into various rotating devices for use. In particular, a ball bearing that uses balls as rolling elements is suitably used for a rotating device having a rotating shaft portion that rotates at high speed.

[0003] As rotating devices, conventionally, for example, spindles of high-speed machines, dental handpieces (see Patent Document 1 below), etc. are known. In recent years, however, vacuum cleaners, dryers, Fan motors for servers, etc. are also known, and further high-speed operation is progressing in order to achieve higher performance. Therefore, a rotating device adopts a configuration in which at least two rolling bearings are used to stably support a rotating shaft portion that rotates at high speed, in order to cope with high-speed operation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Bearings incorporated in rotating machines are fixed in various ways. For example, there are methods of fixing the inner ring to the rotating shaft portion by interference fit and fixing the outer ring to the housing by clearance fit, or fixing the inner ring to the rotating shaft portion by clearance fit and also fixing the outer ring to the housing by clearance fit, etc., which are generally known. As yet another method, for example, in a dental handpiece, there is known a method of fixing the rotating shaft portion to the inner ring by interference fit and fixing it to a support such as a housing after attaching an O-ring to the outer ring. In this case, one axial end face of the outer ring is restrained and the other axial end face is pressed by a biasing member such as a spring.

[0006] In any of the methods described above, the plurality of rolling elements disposed between the inner ring and the outer ring are held in a rotatable state by a cage and are capable of revolving around the rotation axis together with the cage while rotating. Thereby, the plurality of rolling elements and the cage are capable of revolving smoothly with less resistance along with the relative movement between the inner ring and the outer ring. However, for example, when some load acts on the rotating shaft portion during the use of a rotating machine or the like, there may occur inconveniences such as a deviation due to inclination or a radial deviation between the central axis of the inner ring and the central axis of the outer ring. In particular, the higher the rotational speed of the rotating machine, the more likely such inconveniences occur. Moreover, the higher the rotational speed of the rotating shaft portion, the more centrifugal force acts, making it easier to promote the occurrence of the above inconveniences.

[0007] When the above inconveniences occur, the contact positions of each of the plurality of rolling elements within the inner ring rolling surface and the outer ring rolling surface will be different, so that variations will occur in the individual revolution speeds of the rolling elements. On the other hand, since the cage always tries to revolve at a constant speed, rolling elements will occur whose revolution speeds differ from the revolution speed of the cage. Such rolling elements will, for example, lag behind the revolution speed of the cage, and thus act as a brake against the rotation of the cage.

[0008] Therefore, there has been a risk that the holding portion of the cage that rotatably holds the rolling elements is likely to receive strong stress from the rolling elements and cause problems such as wear, or problems such as deformation of the cage. In particular, when the cage itself is deformed, there is a possibility that the inner ring or the outer ring may come into contact with the cage, leading to further wear and the like.

[0009] Furthermore, the wear and the like described above also affect the rotation of the rotating shaft portion, leading to a decrease in the rotation performance of the rotating device. In particular, in a rotating device such as a dental handpiece that performs significant high-speed rotation, since there are at least two rolling bearings, a difference in the revolution speed of the rolling elements is likely to occur between the two rolling bearings. Therefore, not only is the rotation performance of the rotating device likely to decrease, but there is also a possibility that the rolling elements acting as brakes will cause severe wear between the rolling elements and the cage.

[0010] The present invention has been made in consideration of such circumstances, and its object is to provide a cage, a rolling bearing, a bearing unit, and a rotating device that can suppress the load received from the rolling elements even when there is a difference in the revolution speed of the rolling elements.

Means for Solving the Problems

[0011] (1) The cage according to the present invention is disposed between an inner ring and an outer ring disposed on a common axis, and has an annular main body portion disposed coaxially with the axis, and is formed so as to penetrate the main body portion in the radial direction. A plurality of holding holes for separately and rotatably holding the plurality of rolling elements disposed between the inner ring and the outer ring at intervals in the circumferential direction, the holding holes being arranged so as to face each other in the circumferential direction with the rolling elements interposed therebetween, and an axial wall surface facing the axial direction of the main body portion and connecting the first circumferential wall surface and the second circumferential wall surface in the circumferential direction, the axial wall surface being formed so as to extend flatly along the circumferential direction so that the maximum interval along the circumferential direction between the first circumferential wall surface and the second circumferential wall surface is larger than the diameter of the rolling element. , a first contact portion where the rolling elements can come into contact earlier than the remaining portions of the first circumferential wall surface is provided at a portion of the first circumferential wall surface located at the center in the axial direction, and a second contact portion where the rolling elements can come into contact earlier than the remaining portions of the second circumferential wall surface is provided at a portion of the second circumferential wall surface located at the center in the axial direction. The axial wall surface is formed to extend flatly along the circumferential direction such that the interval along the circumferential direction between the first contact portion and the second contact portion is larger than the diameter of the rolling elements. An allowable space for allowing the movement of the rolling elements along the circumferential direction is secured in the holding hole between the first contact portion and the second contact portion. The first contact portion and the second contact portion are formed in a protrusion shape with a hemispherical cross section protruding toward the rolling elements. It is characterized by this.

[0012] According to the cage of the present invention, rolling elements can be rotatably held in a holding hole defined by a first circumferential wall surface, a second circumferential wall surface, and an axial wall surface, and revolve at a constant speed about an axis due to relative movement between the inner ring and the outer ring. At this time, each of the plurality of rolling elements revolves in the same direction as the cage about the axis while rotating within the holding hole. Therefore, each rolling element revolves about the axis while being supported on, for example, the axial wall surface constituting the holding hole and while contacting or approaching the first circumferential wall surface (or the second circumferential wall surface).

[0013] In particular, the axial wall surface constituting the holding hole is formed to extend flatly along the circumferential direction, whereby the maximum distance along the circumferential direction between the first circumferential wall surface and the second circumferential wall surface is made larger than the diameter of the rolling element. Thereby, an allowable space (play space) for allowing movement of the rolling element along the circumferential direction can be secured within the holding hole. Therefore, even when, for example, a displacement due to inclination or a displacement in the radial direction occurs between the inner ring and the outer ring, and the contact positions of each of the plurality of rolling elements within the inner ring rolling surface and the outer ring rolling surface are different, resulting in differences such as variations in the individual revolution speeds of the rolling elements, a rolling element that, for example, lags behind the revolution speed of the cage can be moved in the circumferential direction within the holding hole. Therefore, a rolling element with a lag can be moved on the axial wall surface, for example, from the first circumferential wall surface toward the second circumferential wall surface (or from the second circumferential wall toward the first circumferential wall).

[0014] Thereby, it is possible to suppress a situation where a rolling element with a lag applies a load that acts as a brake against the rotation (revolution) of the cage, and to suppress the time during which the load is applied. Therefore, it is possible to make it difficult for problems such as wear of the holding hole and deformation of the cage to occur, to maintain good rotational characteristics, and to obtain a high-quality cage with improved durability. Furthermore, when each of the plurality of rolling elements revolves in the same direction as the cage around the axis while rotating within the holding hole, it is possible to bring the rolling element into contact with the first contact portion or the second contact portion. Thereby, it is easy to position the rolling element at a fixed position by using the first contact portion or the second contact portion. Therefore, even when the rolling elements rotate at high speed, it is easy to suppress fluctuations in frictional force, vibrations can be suppressed, and a cage having stable rotational characteristics can be obtained.

[0015] (2) The first circumferential wall surface and the second circumferential wall surface may be formed in a curved surface shape corresponding to the radius of curvature of the outer surface of the rolling element.

[0016] In this case, since the first circumferential wall surface and the second circumferential wall surface are formed in a curved shape, for example, it can be suitably used as a cage of a ball bearing that uses balls as rolling elements.

[0019] ( 3 ) The holding hole includes opposing wall surfaces arranged to face each other in the axial direction with respect to the axial wall surface across the rolling element, and the opposing wall surfaces may be formed to connect the first circumferential wall surface and the second circumferential wall surface in the circumferential direction and extend flatly along the circumferential direction corresponding to the axial wall surface.

[0020] In this case, the first circumferential wall surface and the second circumferential wall surface facing each other in the circumferential direction, and the axial wall surface and the opposing wall surface facing each other in the axial direction can hold the rolling element in the holding hole while surrounding the periphery of the rolling element. Thereby, it can be suitably used as a so-called cage type cage.

[0021] ( 4 ) The holding hole is formed to open through an opening portion in one direction opposite to the axial wall surface in the axial direction, and the interval along the circumferential direction between the first circumferential wall surface and the second circumferential wall surface at the opening portion may be an interval equal to or less than the diameter of the rolling element.

[0022] In this case, the rolling element can be fitted into the holding hole through the opening portion, and it can be suitably used as a so-called crown type cage.

[0023] ( 5 ) The holding hole has first holding claws and second holding claws that protrude from the main body portion in the one direction in the axial direction and are formed to face each other with an interval in the circumferential direction, and the inner circumferential surface of the first holding claw is a part of the first circumferential wall surface, the inner circumferential surface of the second holding claw is a part of the second circumferential wall surface, and the portion located between the tip of the first holding claw and the tip of the second holding claw may be the opening portion.

[0024] In this case, the rolling elements can be held more stably in a rollable manner by using the first holding claw and the second holding claw. Further, since the first holding claw and the second holding claw are provided, the axial height of the main body portion itself can be suppressed, and it is easy to achieve weight reduction and the like. Further, in the circumferentially adjacent holding holes, it is possible to hold, for example, grease by using the portion located between the first holding claw of one holding hole and the second holding claw of the other holding hole, so that it is easy to use and the convenience can be improved.

[0025] ( 6 ) The rolling bearing according to the present invention includes the cage, an inner ring disposed coaxially with the axis and inside the cage in the radial direction, an outer ring disposed coaxially with the axis and outside the cage in the radial direction, and a plurality of rolling elements arranged at intervals in the circumferential direction between the inner ring and the outer ring and rotatably held by the holding holes.

[0026] According to the rolling bearing of the present invention, since the above-described cage, that is, a high-quality cage capable of maintaining good rotational characteristics and having improved durability is provided, a high-quality rolling bearing with stable rotational performance can be obtained. In particular, since the cage is difficult to deform or the like, the possibility that the inner ring or the outer ring comes into contact with the cage and causes wear or the like is low, and good rotational characteristics can be maintained.

[0027] ( 7 ) The bearing unit according to the present invention includes the rolling bearing and a rotating shaft portion disposed coaxially with the axis and inside the inner ring in the radial direction. A plurality of the rolling bearings are arranged at intervals in the axial direction, and the inner rings of the plurality of rolling bearings are fixed to the rotating shaft portion.

[0028] According to the bearing unit of the present invention, since a plurality of rolling bearings are used to rotatably support the rotating shaft portion, it is possible to stably rotatably support a rotating shaft portion that rotates at high speed. In particular, since each rolling bearing is provided with the cage described above, even between a plurality of rolling bearings, it is difficult for a difference to occur in the revolution speed of the cage due to a delay of rolling elements or the like. Therefore, also in this respect, it is possible to stably support a rotating shaft portion that rotates at high speed.

[0029] (8) The rotating device according to the present invention is characterized by including the bearing unit.

[0030] According to the rotating device of the present invention, since it includes the above-described bearing unit, it can be suitably used for a rotating device that rotates significantly at high speed, such as a dental handpiece. In particular, since the rotational resistance of the rotating shaft portion can be suppressed to obtain good rotational performance, it is easy to achieve high quality and power saving.

Effects of the Invention

[0031] According to the present invention, even if a difference occurs in the revolution speed of the rolling elements, it is possible to provide a cage, a rolling bearing, and a rotating device that can suppress the load received from the rolling elements.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Mode for Carrying Out the Invention

[0033] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a dental handpiece will be described as an example of a rotating device.

[0034] As shown in FIGS. 1 and 2, the dental handpiece (rotating device according to the present invention) 1 of this embodiment includes a handpiece shaft portion 2 that can be gripped by a user, a head portion 3 provided at the tip of the handpiece shaft portion 2, and a dental treatment tool 4 detachably attached to the head portion 3.

[0035] Inside the handpiece shaft portion 2, an air supply passage 5 that supplies compressed air F supplied through an air tube (not shown) or the like into the head portion 3, and an exhaust passage (not shown) that discharges the compressed air F from the head portion 3 are formed. The head portion 3 is integrally combined with the tip of the handpiece shaft portion 2. The head portion 3 is composed of a housing fixed to the tip of the handpiece shaft portion 2 and a head cap removably attached to the housing. In FIG. 2, the illustration of the head portion 3 is simplified.

[0036] (Bearing unit) As shown in FIG. 2, a bearing unit 10 having a rotating shaft portion 11 that rotates about the axis O and a rolling bearing 12 that pivotally supports the rotating shaft portion 11 is provided inside the head portion 3. In the present embodiment, the direction intersecting the axis O in a plan view seen from the axis O is referred to as the radial direction, the direction orbiting around the axis O is referred to as the circumferential direction, and the direction along the axis O is referred to as the axial direction. Further, among the axial directions, the direction from the bearing unit 10 toward the tip of the dental treatment tool 4 is referred to as the downward direction, and the opposite direction is referred to as the upward direction.

[0037] The rotating shaft portion 11 is formed, for example, in a cylindrical shape extending along the axis O. However, the shape of the rotating shaft portion 11 is not limited to this case, and it may be formed, for example, in a columnar shape. At the lower end of the rotating shaft portion 11, the dental treatment tool 4 is arranged simultaneously with the axis O and is removably attached via a chuck mechanism (not shown). Thereby, the dental treatment tool 4 can rotate (forward and reverse rotation) around the axis O as the rotating shaft portion 11 rotates. The dental treatment tool 4 is a treatment tool used, for example, when polishing teeth or metal restorations.

[0038] At an intermediate portion of the rotating shaft portion 11, a turbine blade 15 having a plurality of blade portions 15a arranged at intervals in the circumferential direction is fixed. The position of the turbine blade 15 is adjusted with respect to the air supply passage 5 so that the compressed air F supplied through the air supply passage 5 is blown against the blade portions 15a. Thereby, by supplying the compressed air F into the head portion 3 through the air supply passage 5, it is possible to rotate the turbine blade 15 and the rotating shaft portion 11 around the axis O. Therefore, it is possible to rotate the dental treatment tool 4 attached to the rotating shaft portion 11 around the axis O. Specifically, it is possible to rotate the dental treatment instrument 4 at a rotational speed of around 300,000 to 400,000 revolutions per minute. The compressed air F blown against the blade portion 15a is exhausted from inside the head portion 3 through the exhaust passage.

[0039] The above-described rotating shaft portion 11 is pivotally supported by two rolling bearings 12. The two rolling bearings 12 are arranged axially apart with the turbine blade 15 interposed therebetween. Of the two rolling bearings 12, the first rolling bearing 20 located above the turbine blade 15 rotationally supports the upper end portion side of the rotating shaft portion 11, and the second rolling bearing 21 located below the turbine blade 15 rotationally supports the lower end portion side of the rotating shaft portion 11. Thereby, by using the first rolling bearing 20 and the second rolling bearing 21, the rotating shaft portion 11 can be rotationally supported at two locations above and below, and it is possible to stably support the rotating shaft portion 11 that rotates at high speed.

[0040] Hereinafter, the first rolling bearing 20 will be described in detail. Since the second rolling bearing 21 has the same configuration as the first rolling bearing 20, a detailed description thereof will be omitted.

[0041] (Rolling bearing) As shown in FIGS. 2 and 3, the first rolling bearing 20 is arranged coaxially with the axis O and is arranged between the rotating shaft portion 11 and the head portion 3. The first rolling bearing 20 includes an inner ring 25 and an outer ring 26 that are raceways, a plurality of rolling elements 27, and a cage 28.

[0042] The inner ring 25 is arranged radially inward of the cage 28, is externally inserted into the rotating shaft portion 11, and is fixed to the rotating shaft portion 11 by, for example, an interference fit or the like. Thereby, the inner ring 25 functions as a rotating ring that rotates together with the rotating shaft portion 11. The inner ring 25 is formed in an annular shape from a metal material such as stainless steel or bearing steel. However, the inner ring 25 is not limited to being made of metal and may be formed of other materials.

[0043] On the outer peripheral surface of the inner ring 25, an inner-ring rolling surface 25a that is recessed toward the inner side in the radial direction is formed. The inner-ring rolling surface 25a is formed in a hemispherical shape in a cross-sectional view so as to follow the outer surface of the rolling element 27, and is formed in an annular shape that extends in the circumferential direction over the entire circumference of the outer peripheral surface of the inner ring 25. Note that the radius of curvature of the inner-ring rolling surface 25a is formed to be the same as or slightly larger than the radius of curvature of the outer surface of the rolling element 27. In the illustrated example, the inner-ring rolling surface 25a is formed in a portion located at the center in the axial direction of the outer peripheral surface of the inner ring 25. Note that the portion of the outer peripheral surface of the inner ring 25 excluding the inner-ring rolling surface 25a extends in the axial direction with a constant outer diameter.

[0044] The outer ring 26 is disposed on the outer side in the radial direction than the cage 28, and is fixed to the inside of the head portion 3 by, for example, clearance fitting or the like. However, it is not limited to this case, and for example, the outer ring 26 may be fixed in a state where a preload is applied via an O-ring or the like (not shown) to the inside of the head portion 3. Thereby, the outer ring 26 functions as a fixed ring fixed to the head portion 3. The outer ring 26 surrounds the inner ring 25 and the cage 28 from the outer side in the radial direction in a state where an annular space is provided between the outer ring 26 and the inner ring 25. The outer ring 26 is formed in an annular shape from a metal material such as stainless steel or bearing steel, for example. However, the outer ring 26 is not limited to being made of metal, and may be formed of other materials.

[0045] On the inner peripheral surface of the outer ring 26, an outer-ring rolling surface 26a that is recessed toward the outer side in the radial direction is formed. The outer-ring rolling surface 26a is formed in a hemispherical shape in a cross-sectional view so as to follow the outer surface of the rolling element 27, and is formed in an annular shape that extends in the circumferential direction over the entire circumference of the inner peripheral surface of the outer ring 26. Note that the radius of curvature of the outer-ring rolling surface 26a is formed to be the same as or slightly larger than the radius of curvature of the outer surface of the rolling element 27. In the illustrated example, the outer-ring rolling surface 26a is formed in a portion located at the center in the axial direction of the inner peripheral surface of the outer ring 26, and is disposed so as to face the inner-ring rolling surface 25a in the radial direction. Note that the portion of the inner peripheral surface of the outer ring 26 excluding the outer-ring rolling surface 26a extends in the axial direction with a constant outer diameter.

[0046] The plurality of rolling elements 27 are disposed between the inner ring 25 and the outer ring 26. Specifically, the plurality of rolling elements 27 are rotatably held by a cage 28 and are evenly arranged at intervals in the circumferential direction. And the plurality of rolling elements 27 are disposed between the inner ring rolling surface 25a and the outer ring rolling surface 26a, and are capable of revolving around the axis O while rotating along the inner ring rolling surface 25a and the outer ring rolling surface 26a. In this embodiment, the rolling element 27 is formed in a spherical shape by a metal material such as stainless steel or bearing steel, or a ceramic material such as zirconia.

[0047] (Cage) As shown in FIGS. 3 and 4, the cage 28 is coaxially disposed with the axis O between the inner ring 25 and the outer ring 26 and is formed in an annular shape as a whole. The cage 28 is formed of a metal material such as carbon steel, high-strength brass, or aluminum alloy, or a synthetic resin material. Examples of the synthetic resin material include polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyether sulfone (PES), polyimide (PI), polyamideimide (PAI), polyamide (PA), etc. Further, the strength may be enhanced by containing, for example, glass fiber or carbon fiber in these synthetic resin materials.

[0048] The cage 28 includes an annular main body portion 30 disposed coaxially with the axis O and a plurality of holding holes 31 formed to penetrate the main body portion 30 in the radial direction.

[0049] The main body portion 30 is formed such that, for example, the thickness in the radial direction is about 1 / 2 to 1 / 3 of the diameter D of the rolling element 27, and the length along the axial direction is about 1 / 3 of the axial lengths of the inner ring 25 and the outer ring 26. However, the outer dimension of the main body portion 30 is not limited to this case.

[0050] The plurality of holding holes 31 are provided corresponding to the number of rolling elements 27, and serve to hold the plurality of rolling elements 27 in a state of being evenly arranged at intervals in the circumferential direction so as to be rotatable. In this embodiment, a case where seven holding holes 31 are formed in the main body portion 30 will be described as an example. However, the number of holding holes 31 is not limited to seven and may be changed as appropriate.

[0051] In addition to being formed so as to penetrate the main body portion 30 in the radial direction, the holding hole 31 is formed so as to open through an opening 32 toward the upper side (one direction in the axial direction). Thereby, the cage 28 of the present embodiment functions as a crown-type cage capable of incorporating the rolling element 27 into the holding hole 31 from above. As shown in FIGS. 4 and 5, the holding hole 31 includes a first circumferential wall surface 35 and a second circumferential wall surface 36 arranged to face each other in the circumferential direction with the rolling element 27 interposed therebetween, and an axial wall surface 37 that faces upward of the main body portion 30 and connects the first circumferential wall surface 35 and the second circumferential wall surface 36 in the circumferential direction.

[0052] The first circumferential wall surface 35 and the second circumferential wall surface 36 are formed in a curved surface shape corresponding to the radius of curvature of the outer surface of the rolling element 27. Specifically, the first circumferential wall surface 35 and the second circumferential wall surface 36 are formed in a hemispherical shape in a cross-sectional view having a radius of curvature that is the same as or slightly larger than the radius of curvature of the outer surface of the rolling element 27. The axial wall surface 37 is formed to extend flatly along the circumferential direction such that the maximum interval H1 along the circumferential direction between the first circumferential wall surface 35 and the second circumferential wall surface 36 is larger than the diameter D of the rolling element 27. Thereby, an allowable space (play space) R for allowing the movement of the rolling element 27 along the circumferential direction is secured between the first circumferential wall surface 35 and the second circumferential wall surface 36 in the holding hole 31.

[0053] The holding hole 31 configured as described above opens through an opening 32 located above the axial wall surface 37. At this time, the circumferential interval H2 between the first circumferential wall surface 35 and the second circumferential wall surface 36 in the opening 32 is set to an interval equal to or less than the diameter D of the rolling element 27. This prevents the rolling element 27 incorporated in the holding hole 31 from passing through the opening 32 and coming out of the holding hole 31.

[0054] In the first rolling bearing 20 configured as described above, for example, a pair of shield members formed in an annular plate shape centered on the axis O may be attached to the inner ring 25 or the outer ring 26 so as to face each other in the axial direction with a plurality of rolling elements 27 interposed therebetween. Thereby, the sealing performance between the inner ring 25 and the outer ring 26 can be improved, and the entry of foreign substances and the like from the outside can be suppressed.

[0055] The second rolling bearing 21 is configured in the same manner as the first rolling bearing 20 as shown in FIG. 2, and rotatably supports the lower end portion side of the rotary shaft portion 11. Thereby, by using the first rolling bearing 20 and the second rolling bearing 21, the rotary shaft portion 11 can be rotatably supported at two locations, upper and lower, and the dental treatment tool 4 can be stably rotatably supported about the axis O.

[0056] (Operation of Dental Handpiece) The operation of the dental handpiece 1 configured as described above will be described. As shown in FIG. 2, when performing a treatment using the dental treatment tool 4, by blowing the compressed air F supplied into the air supply passage 5 against the blade portion 15a of the turbine blade 15, the rotary shaft portion 11 and the dental treatment tool 4 can be rotated at an ultra-high speed, for example, at a rotational speed of around 300,000 to 400,000 rpm. Thereby, a treatment such as a dental treatment can be performed using the dental treatment tool 4.

[0057] Incidentally, during the rotation of the dental treatment instrument 4, as the inner ring 25 rotates about the axis O along with the rotation of the rotary shaft portion 11, accordingly, the cage 28 revolves about the axis O at a constant speed, and each of the plurality of rolling elements 27 revolves about the axis O in the same direction as the cage 28 while rotating within the holding holes 31. Therefore, each rolling element 27 revolves about the axis O while being supported on the shaft wall surface 37 and contacting or approaching the first circumferential wall surface 35 as shown by the solid line in FIG. 5, for example.

[0058] In such a situation, for example, when some external force acts on the dental treatment instrument 4 and a deviation due to inclination or a radial deviation occurs between the inner ring 25 and the outer ring 26, the contact positions within the inner ring rolling surface 25a and the outer ring rolling surface 26a are different for each of the plurality of rolling elements 27, and there may be differences such as variations in the individual revolution speeds of the rolling elements 27.

[0059] Even in such a case, according to the cage 28 of the present embodiment, the shaft wall surface 37 constituting the holding hole 31 is formed to extend flatly along the circumferential direction, whereby the maximum interval along the circumferential direction between the first circumferential wall surface 35 and the second circumferential wall surface 36 is set to be larger than the diameter D of the rolling element 27. Thereby, an allowable space R for allowing the movement of the rolling element 27 along the circumferential direction is secured within the holding hole 31. Therefore, even if a rolling element 27 that lags behind the revolution speed of the cage 28 occurs, for example, as shown by the dotted line in FIG. 5, the rolling element 27 can be moved in the circumferential direction within the holding hole 31. That is, the rolling element 27 with a lag can be moved on the shaft wall surface 37 from the first circumferential wall surface 35 toward the second circumferential wall surface 36 by utilizing the allowable space R.

[0060] Thereby, it is possible to suppress the situation where the rolling element 27 with a lag applies a load that acts as a brake to the rotation (revolution) of the cage 28, and to suppress the time for applying the load. Therefore, it is possible to make it difficult to cause problems such as wear of the holding hole 31 and deformation of the cage 28, to maintain good rotational characteristics, and to obtain a high-quality cage 28 with improved durability.

[0061] Furthermore, according to the rolling bearing 12 (the first rolling bearing 20 and the second rolling bearing 21) including such a cage 28, the rotation performance is stabilized, and since the cage 28 is difficult to be deformed or the like, the possibility that the inner ring 25 or the outer ring 26 contacts the cage 28 and causes wear or the like is low, and good rotation characteristics can be maintained.

[0062] Therefore, according to the bearing unit 10 of the present embodiment, since the rotary shaft portion 11 can be rotationally supported by using the two rolling bearings 12 (the first rolling bearing 20 and the second rolling bearing 21), the rotary shaft portion 11 that rotates at high speed can be stably rotationally supported. In particular, even between the two rolling bearings 12, since it is difficult for a difference to occur in the revolution speed of the cage 28 due to the delay of the rolling elements 27 or the like, the rotary shaft portion 11 that rotates at high speed can also be stably supported in this regard. Therefore, according to the dental handpiece 1 of the present embodiment, the rotary shaft portion 11 and the dental treatment tool 4 that rotate at ultra-high speed can be rotated with good rotation performance while suppressing the rotational resistance, and it is easy to achieve high quality and power saving.

[0063] As described above, the embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. The embodiments and their modifications include, for example, those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the equivalent range.

[0064] For example, in the above embodiment, the dental handpiece 1 has been described as an example of the rotating device, but it is not limited to this case. For example, as the rotating device, it may be applied to a fan motor, or may be applied to at least one of the spindle motor and the swing arm of a hard disk drive. Furthermore, in the above-described embodiment, the bearing unit 10 including two rolling bearings 12 has been described as an example. However, for example, a bearing unit including three or more rolling bearings 12 may also be used.

[0065] Furthermore, in the above-described embodiment, the cage 28 may be formed by, for example, injection molding or machining, but is not limited to this case. For example, the cage 28 may be configured by integrally combining divided bodies that are divided into a plurality of parts (for example, two parts) in the axial direction or the circumferential direction by various joining methods such as thermal caulking and ultrasonic welding.

[0066] Furthermore, in the above-described embodiment, the spherical rolling elements 27 have been described as an example. However, the present invention is not limited to this case, and for example, cylindrical rollers may be adopted as the rolling elements 27.

[0067] Furthermore, in the above-described embodiment, for example, as shown in FIGS. 6 and 7, a cage (crown-shaped cage) 40 having a pair of holding claws may also be used. In this case, the cage 40 has first holding claws 41 and second holding claws 42 formed such that each holding hole 31 protrudes upward from the main body portion 30 and faces each other at intervals in the circumferential direction. The first holding claws 41 and the second holding claws 42 are formed to rise in an arc shape such that the distance between them approaches as they go upward. The inner peripheral surface of the first holding claw 41 is part of the first peripheral wall surface 35, and the inner peripheral surface of the second holding claw 42 is part of the second peripheral wall surface 36. Thereby, the rolling elements 27 can be held rotatably by using the first holding claws 41 and the second holding claws 42.

[0068] Note that a portion located between the tip of the first holding claw 41 and the tip of the second holding claw 42 is an opening 32. Therefore, the interval H2 along the circumferential direction between the tip of the first holding claw 41 and the tip of the second holding claw 42 is set to be equal to or less than the diameter D of the rolling element 27.

[0069] Even with the cage 40 configured as described above, the same operational effects as those of the above-described embodiment can be achieved. In particular, the rolling elements 27 can be held more stably so as to be able to roll by using the first holding claws 41 and the second holding claws 42. Furthermore, since the first holding claws 41 and the second holding claws 42 are provided, the axial height of the main body portion 30 itself can be suppressed, and it is easy to achieve weight reduction and the like. Furthermore, in the circumferentially adjacent holding holes 31, a portion located between the first holding claw 41 of one holding hole 31 and the second holding claw 42 of the other holding hole 31 can be used as a grease pocket G or the like for holding grease. Therefore, since the grease can be stably held by using the grease pocket G, the cage 40 can be made easy to use and improved in convenience.

[0070] Furthermore, the cage 28 is not limited to a crowned cage, and for example, it may be a so-called basket-type cage in which holding holes 31 surrounding the rolling elements 27 are formed. For example, in the cage 50 shown in FIGS. 8 and 9, the holding holes 31 are formed so as to penetrate the main body portion 30 in the radial direction and are non-open upward. Thereby, the holding holes 31 include opposing wall surfaces 51 arranged so as to face each other in the axial direction with respect to the axial wall surface 37 with the rolling elements 27 interposed therebetween. That is, the holding holes 31 are defined by the first circumferential wall surface 35, the second circumferential wall surface 36, the axial wall surface 37, and the opposing wall surface 51. The opposing wall surface 51 is formed so as to connect the first circumferential wall surface 35 and the second circumferential wall surface 36 in the circumferential direction and to extend flatly along the circumferential direction corresponding to the axial wall surface 37.

[0071] Even with the cage 50 configured as described above, the same operational effects as those of the above-described embodiment can be achieved. In particular, according to this cage 50, the rolling elements 27 can be held in the holding holes 31 while surrounding the rolling elements 27 by the first circumferential wall surface 35 and the second circumferential wall surface 36 facing each other in the circumferential direction and the axial wall surface 37 and the opposing wall surface 51 facing each other in the axial direction. Thereby, it can be suitably used as a cage for an angular contact ball bearing or the like, for example.

[0072] Furthermore, in the above-described embodiment, the case where the first circumferential wall surface 35 and the second circumferential wall surface 36 are formed in a curved surface shape corresponding to the radius of curvature of the outer surface of the rolling element 27 has been described as an example, but the present invention is not limited to this case. For example, as shown in FIG. 10, a first contact portion 35a where the rolling element 27 can come into contact earlier than the remaining portion of the first circumferential wall surface 35 is provided at a portion located at the center in the axial direction of the first circumferential wall surface 35, and a second contact portion 36a where the rolling element 27 can come into contact earlier than the remaining portion of the second circumferential wall surface 36 is provided at a portion located at the center in the axial direction of the second circumferential wall surface 36. Such a configuration may be adopted.

[0073] The portion of the first circumferential wall surface 35 excluding the first contact portion 35a (the above remaining portion) is formed in a curved surface shape having a radius of curvature slightly larger than the radius of curvature of the outer surface of the rolling element 27. The first contact portion 35a is formed in a curved surface shape having a radius of curvature even larger than the above radius of curvature. Thereby, it becomes possible to bring the rolling element 27 into contact with the first contact portion 35a earlier than the portion of the first circumferential wall surface 35 excluding the first contact portion 35a. Similarly, the portion of the second circumferential wall surface 36 excluding the second contact portion 36a (the above remaining portion) is formed in a curved surface shape having a radius of curvature slightly larger than the radius of curvature of the outer surface of the rolling element 27. The second contact portion 36a is formed in a curved surface shape having a radius of curvature even larger than the above radius of curvature. Thereby, it becomes possible to bring the rolling element 27 into contact with the second contact portion 36a earlier than the portion of the second circumferential wall surface 36 excluding the second contact portion 36a.

[0074] Furthermore, in the cage 28 configured as described above, the axial wall surface 37 is formed to extend flatly along the circumferential direction such that the interval H3 along the circumferential direction between the first contact portion 35a and the second contact portion 36a is larger than the diameter D of the rolling element 27. Thereby, an allowable space (play space) R for allowing the movement of the rolling element 27 along the circumferential direction is secured between the first contact portion 35a and the second contact portion 36a in the retaining hole 31.

[0075] Even with the cage 28 configured as described above, the same operational effects as those of the above-described embodiment can be achieved. In addition, according to the cage 28 in this case, when each of the rolling elements 27 revolves in the same direction as the cage 28 around the axis while rotating within the holding holes 31, it is possible to bring the rolling elements 27 into contact with the first contact portion 35a or the second contact portion 36a. Thereby, it is easy to position the rolling elements 27 at a fixed position by using the first contact portion 35a or the second contact portion 36a. Therefore, even when the rolling elements 27 rotate at high speed, it is easy to suppress fluctuations in frictional force, suppress the generation of vibration, and a cage 28 having stable rotational characteristics can be obtained.

[0076] As shown in FIG. 11, the first contact portion 35a and the second contact portion 36a may be employed in a cage 50 of a so-called cage-type cage in which holding holes 31 surrounding the periphery of the rolling elements 27 are formed. Even in this case, the same operational effects as those of the cage 28 shown in FIG. 10 can be achieved.

[0077] Furthermore, as shown in FIG. 12, the cage 28 may be formed such that the first contact portion 35a and the second contact portion 36a are not formed in a curved surface shape but in a flat surface shape extending along the axial direction. Even in this case, it is possible to bring the rolling elements 27 into contact with the first contact portion 35a and the second contact portion 36a formed in a flat surface shape. Therefore, even in this case, the same operational effects can be achieved.

[0078] As shown in FIG. 13, the first contact portion 35a and the second contact portion 36a formed in a flat surface shape may be employed in a cage 50 of a so-called cage-type cage in which holding holes 31 surrounding the periphery of the rolling elements 27 are formed. Even in this case, the same operational effects can be achieved.

[0079] Furthermore, as shown in FIG. 14, the cage 28 may be formed such that the first contact portion 35a and the second contact portion 36a are formed in a protruding hemispherical cross-sectional protrusion shape directed toward the rolling elements 27. Even in this case, it is possible to bring the rolling element 27 into contact with the first contact portion 35a and the second contact portion 36a formed in a protruding shape. Therefore, even in this case, the same operational effects can be achieved.

[0080] In addition, as shown in FIG. 15, the first contact portion 35a and the second contact portion 36a formed in a protruding shape may be employed for a cage-type retainer 50 in which a retaining hole 31 surrounding the periphery of the rolling element 27 is formed. Even in this case, the same operational effects can be achieved.

Explanation of Reference Numerals

[0081] O... Axis 1... Dental handpiece (rotating device) 10... Bearing unit 11... Rotating shaft portion 12... Rolling bearing 25... Inner ring 26... Outer ring 27... Rolling element 28, 40, 50... Retainers 30... Main body portion 31... Retaining hole 32... Opening 35... First peripheral wall surface 35a... First contact portion 36... Second peripheral wall surface 36a... First contact portion 37... Axial wall surface 41... First retaining claw 42... Second retaining claw 51... Opposing wall surface

Claims

1. It is disposed between an inner ring and an outer ring disposed on a common axis, and has an annular main body portion disposed coaxially with the axis, A plurality of rolling elements formed so as to penetrate the main body portion in the radial direction and arranged at intervals in the circumferential direction between the inner ring and the outer ring, and a plurality of holding holes for separately and rotatably holding the rolling elements, The holding hole is A first circumferential wall surface and a second circumferential wall surface disposed so as to face each other in the circumferential direction with the rolling element interposed therebetween, An axial wall surface that faces the axial direction of the main body portion and connects the first circumferential wall surface and the second circumferential wall surface in the circumferential direction, The axial wall surface is formed so as to extend flatly along the circumferential direction so that the maximum interval along the circumferential direction between the first circumferential wall surface and the second circumferential wall surface is larger than the diameter of the rolling element, A first contact portion where the rolling element can come into contact earlier than the remaining portion of the first circumferential wall surface is provided at a portion located at the center in the axial direction of the first circumferential wall surface, A second contact portion where the rolling element can come into contact earlier than the remaining portion of the second circumferential wall surface is provided at a portion located at the center in the axial direction of the second circumferential wall surface, The axial wall surface is formed so as to extend flatly along the circumferential direction so that the interval along the circumferential direction between the first contact portion and the second contact portion is larger than the diameter of the rolling element, An allowable space for allowing the movement of the rolling element along the circumferential direction is secured between the first contact portion and the second contact portion in the holding hole, The first contact portion and the second contact portion are formed in a protruding, hemispherical cross-sectional shape protruding toward the rolling element, and the cage is characterized by this.

2. In the cage according to Claim 1, The first circumferential wall surface and the second circumferential wall surface are formed in a curved surface shape corresponding to the radius of curvature of the outer surface of the rolling element, and the cage is characterized by this.

3. In the cage according to Claim 1 or 2, The holding hole includes opposing wall surfaces disposed so as to face the axial wall surface in the axial direction with the rolling element interposed therebetween, The opposing wall surface connects the first circumferential wall surface and the second circumferential wall surface in the circumferential direction and is formed so as to extend flatly along the circumferential direction corresponding to the axial wall surface, and the cage is characterized by this.

4. In the cage according to Claim 1 or 2, The holding hole is formed so as to open through an opening portion in one direction opposite to the axial wall surface in the axial direction, The cage is such that the circumferential interval between the first circumferential wall surface and the second circumferential wall surface in the opening is an interval equal to or less than the diameter of the rolling element.

5. In the cage according to claim 4, the holding holes have first holding claws and second holding claws that project from the main body portion toward the one axial direction and are formed to face each other with a circumferential interval therebetween, the inner circumferential surface of the first holding claw is a part of the first circumferential wall surface, the inner circumferential surface of the second holding claw is a part of the second circumferential wall surface, and the part located between the tip of the first holding claw and the tip of the second holding claw is the opening. The cage.

6. A cage according to any one of claims 1 to 5, an inner ring arranged coaxially with the axis and arranged radially inside the cage, an outer ring arranged coaxially with the axis and arranged radially outside the cage, and a plurality of rolling elements arranged with a circumferential interval between the inner ring and the outer ring and rotatably held by the holding holes. A rolling bearing characterized by comprising.

7. A rolling bearing according to claim 6, and a rotating shaft portion arranged coaxially with the axis and arranged radially inside the inner ring, wherein a plurality of the rolling bearings are arranged with an axial interval therebetween, and the inner rings of the plurality of rolling bearings are fixed to the rotating shaft portion. A bearing unit characterized by this.

8. A rotating device characterized by comprising the bearing unit according to claim 7.

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