Angular contact ball bearing, bearing unit for dental air turbine, and dental air turbine handpiece

Abstract

To provide an angular contact ball bearing which makes wear of balls less likely to occur to inhibit reduction of a rotation speed of a dental air turbine over a long time, and to provide a bearing unit for a dental air turbine and a dental air turbine hand piece.SOLUTION: An angular contact ball bearing includes: an outer ring in which an outer ring raceway surface is formed on an inner peripheral surface; an inner ring in which an inner ring raceway surface is formed on an outer peripheral surface; and multiple balls disposed between the outer ring raceway surface and the inner ring raceway surface. The multiple balls include multiple large diameter balls each of which has a contact angle with the outer ring raceway surface and the inner ring raceway surface; and multiple small diameter balls each of which does not have a contact angle with the outer ring raceway surface and the inner ring raceway surface and has a diameter smaller than that of the large diameter ball. The multiple large diameter balls and the multiple small diameter balls are alternately arranged in a circumferential direction and made of the same kind of material and have different colors.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an angular ball bearing, a bearing unit for a dental air turbine, and a dental air turbine handpiece. Regarding. [Background technology]

[0002] Fig. 15 is a schematic side view showing a typical dental air turbine handpiece 120. Fig. 16 is a cross-sectional view of a main part of a conventional dental air turbine bearing unit 100. A dental air turbine handpiece 120 as shown in Fig. 15 has been known. The dental air turbine handpiece 120 includes a grip portion 121 and a head portion 122 provided at the tip of the grip portion 121, and an operator holds the grip portion 121 to perform, for example, cutting processing of a tooth.

[0003] As shown in FIG. 16, the dental air turbine bearing unit 100 constituting the head portion 122 comprises a rotating shaft 101 to which a dental treatment tool (not shown) is attached, a turbine blade 102 provided on the rotating shaft 101 for rotating the rotating shaft 101 with compressed air, a pair of ball bearings 103, 104 which rotatably support the rotating shaft 101, and a head housing 105 which has these disposed therein and supports the rotating shaft 101 via the pair of ball bearings 103, 104.

[0004] Outer rings 106, 107 of the pair of ball bearings 103, 104 are supported via rubber rings 108 mounted in annular recesses 109, 110 of a head housing 105. The outer ring 107 of the lower ball bearing 104 is urged upward by a spring washer 111, so that a preload is applied to the pair of ball bearings 103, 104. That is, the pair of ball bearings 103, 104 that support the rotating shaft 101 are assembled face-to-face, and a constant preload is applied by the elastic force of the spring washer 111 (see, for example, Patent Document 1).

[0005] In high-speed medical rotary cutting instruments such as dental air turbine handpieces, cutting tools driven by air turbines rotate at high speeds of several hundred thousand to 500,000 revolutions per minute (rpm). Full ball bearings are known as one type of rolling bearing for such high-speed rotation. Full ball bearings are used in, for example, the dental handpiece of Patent Document 2 and the spindle motor of Patent Document 3, and support a shaft that rotates at high speed.

[0006] The full ball bearings in Patent Documents 2 and 3 both have single-row raceway surfaces on the inner and outer rings, and the balls have a single diameter. In the full ball bearing in Patent Document 2, the balls are made of ceramic material to improve wear resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 11-37162 [Patent Document 2] Japanese Patent Application Publication No. 1-223951 [Patent Document 3] JP 2003-172359 A Summary of the Invention [Problem to be solved by the invention]

[0008] FIG. 17 is a cross-sectional view of a conventional full-sized ball bearing 200. This full-sized ball bearing 200 includes an outer ring 210, an inner ring 220, and a plurality of balls 230 arranged between the outer ring 210 and the inner ring 220. When such a full-sized ball bearing 200 is used in a dental air turbine, it is used at a high rotation speed of several hundred thousand to about 500,000 revolutions per minute, so that even a slight decrease in ball accuracy causes a large difference in the revolution speed of each ball 230. When the difference in revolution speed becomes large, the surfaces of adjacent balls 230 may collide while rotating in opposite directions (see FIG. 17). In that case, even if ceramic balls with improved wear resistance are used as the balls 230, wear occurs in the ceramic balls, and the uniform distribution of the balls 230 is lost. In this case, problems such as the rotation speed of the dental air turbine being easily reduced and the current value of the motor increasing may occur.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide an angular contact ball bearing, a bearing unit for a dental air turbine, and a dental air turbine handpiece which reduce ball wear and can prevent a decrease in the rotational speed of the dental air turbine over the long term. [Means for solving the problem]

[0010] The above object of the present invention can be achieved by the following configuration. (1) an outer ring having an outer ring raceway formed on its inner peripheral surface; an inner ring having an inner ring raceway surface formed on an outer peripheral surface; a plurality of balls disposed between the outer ring raceway surface and the inner ring raceway surface; An angular contact ball bearing having The plurality of balls are a plurality of large diameter balls having a contact angle with the outer ring raceway surface and the inner ring raceway surface; a plurality of small diameter balls having no contact angle with the outer ring raceway surface and the inner ring raceway surface and having a smaller diameter than the large diameter balls; Including, The plurality of large diameter balls and the plurality of small diameter balls are arranged alternately in the circumferential direction, are made of the same material, and are different in color. Angular contact ball bearing characterized by: (2) A preload is applied to the angular contact ball bearing, The difference between the diameter of the large diameter ball and the diameter of the small diameter ball is greater than the sum of the amounts of elastic deformation in the contact angle direction of the outer ring, the inner ring, and the large diameter ball caused by the preload. Angular contact ball bearing according to (1). (3) The difference between the diameter of the large ball and the diameter of the small ball is less than 2% of the diameter of the small ball. Angular contact ball bearing according to (2). (4) When the plurality of large diameter balls and the plurality of small diameter balls are arranged at equal intervals in the circumferential direction, the distance between adjacent large diameter balls and adjacent small diameter balls is 2% to 4% of the diameter of the small diameter balls. The angular contact ball bearing according to any one of (1) to (3). (5) A bearing internal space is disposed between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, The outer ring and the inner ring are integrally formed with annular sealing portions that cover the openings at both axial ends of the bearing internal space. The angular contact ball bearing according to any one of (1) to (4). (6) a rotation axis; a turbine blade provided on the rotary shaft and configured to rotate the rotary shaft by compressed air; An angular ball bearing according to any one of (1) to (5) that rotatably supports the rotating shaft; a housing that supports the rotating shaft via the angular ball bearing; A bearing unit for a dental air turbine comprising: (7) A dental air turbine handpiece equipped with the bearing unit for a dental air turbine described in (6). Effect of the Invention

[0011] According to the present invention, it is possible to provide an angular ball bearing, a bearing unit for a dental air turbine, and a dental air turbine handpiece that make it difficult for ball wear to occur and can suppress a decrease in the rotational speed of the dental air turbine over the long term. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a front view of an angular ball bearing according to a first embodiment. [Diagram 2] FIG. 2 is a partially cutaway perspective view of the angular contact ball bearing. [Diagram 3] FIG. 3 is a side view of an angular contact ball bearing. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is an enlarged view of a main portion of FIG. [Figure 6] FIG. 6 is a cross-sectional view of the outer ring. [Figure 7] FIG. 7 is a side view with a portion of the inner ring cut away. [Figure 8] FIG. 8 is a diagram for explaining the rotating state of the large diameter ball and the small diameter ball. [Figure 9] FIG. 9 is a front view of the angular ball bearing according to the second embodiment. [Figure 10] FIG. 10 is a partially cutaway perspective view of an angular contact ball bearing. [Figure 11] FIG. 11 is a cross-sectional view of the outer ring. [Figure 12] FIG. 12 is a side view with a portion of the inner ring cut away. [Figure 13] FIG. 13 is a cross-sectional view of an angular contact ball bearing according to the third embodiment. [Figure 14] FIG. 14 is a sectional view of an angular ball bearing according to the fourth embodiment. [Figure 15] FIG. 15 is a schematic side view showing a typical dental air turbine handpiece. [Figure 16] FIG. 16 is a cross-sectional view of a main portion of a conventional dental air turbine. [Figure 17] FIG. 17 is a cross-sectional view of a conventional full ball bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0014] (First embodiment) Fig. 1 is a front view of an angular ball bearing 1 of a first embodiment. Fig. 2 is a perspective view with a portion of the angular ball bearing 1 cut away. Fig. 3 is a side view of the angular ball bearing 1. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. Fig. 5 is an enlarged view of a main portion of Fig. 4. Fig. 6 is a cross-sectional view of an outer ring 10. Fig. 7 is a side view with a portion of the inner ring 20 cut away.

[0015] The angular contact ball bearing 1 of this embodiment includes an outer ring 10 having an outer ring raceway surface 11 formed on its inner peripheral surface, an inner ring 20 having an inner ring raceway surface 21 formed on its outer peripheral surface, and a plurality of balls 30 arranged between the outer ring raceway surface 11 and the inner ring raceway surface 21. The angular ball bearing 1 is a so-called full ball bearing that does not include a cage.

[0016] 7, the inner ring 20 has a shoulder 23 on the rear side (the side where the contact angle occurs) of the inner ring raceway surface 21, and a counterbore 25 on the front side (the opposite side to the side where the contact angle occurs) of the inner ring raceway surface 21. As a result, in the angular contact ball bearing 1, large diameter balls 30A (described later) are arranged between the outer ring raceway surface 11 and the inner ring raceway surface 21 with a contact angle, forming an inner ring counter angular contact bearing.

[0017] The multiple balls 30 include multiple large diameter balls 30A that have a contact angle with the outer ring raceway surface 11 and the inner ring raceway surface 21, and multiple small diameter balls 30B that do not have a contact angle with the outer ring raceway surface 11 and the inner ring raceway surface 21 and have a smaller diameter than the large diameter balls 30A. The multiple large diameter balls 30A and the multiple small diameter balls 30B are arranged alternately in the circumferential direction, and the small diameter balls 30B have the role of evenly distributing the large diameter balls 30A in the circumferential direction.

[0018] When multiple large diameter balls 30A and multiple small diameter balls 30B are arranged at equal intervals in the circumferential direction, the distance between adjacent large diameter balls 30A and small diameter balls 30B is 2% to 4% of the diameter d2 of the small diameter balls 30B (see FIG. 5). This has the effect of suppressing the generation of abnormal noise when the handpiece rotates, for example, when the angular ball bearing 1 is applied to a dental air turbine handpiece. On the other hand, it has been confirmed that when the distance between adjacent large diameter balls 30A and small diameter balls 30B is smaller than 2% and larger than 4% of the diameter d2 of the small diameter balls 30B, abnormal bearing noise occurs when the handpiece rotates.

[0019] The large balls 30A and the small balls 30B are made of the same material, for example, the same type of ceramic. In this type of angular ball bearing 1, the large balls 30A and the small balls 30B are made of ceramic, so they are more wear-resistant and less prone to wear than steel balls. As a result, almost no wear powder is generated. In addition, irregularities are less likely to form on the surfaces of the large balls 30A and the small balls 30B, so rotation problems are less likely to occur over long periods of time.

[0020] Although the large balls 30A and the small balls 30B have different diameters, when the angular ball bearing 1 is used in a dental air turbine handpiece, the difference between the diameter d1 of the large balls 30A and the diameter d2 of the small balls 30B is 2% or less of the diameter d2 of the small balls 30B. Therefore, it is difficult to distinguish between the two with the naked eye, which can cause inconveniences during assembly and in the inspection process after completion. Therefore, if the large balls 30A and the small balls 30B are made of different materials and have a difference in appearance (for example, a difference in color), the above-mentioned inconveniences can be eliminated.

[0021] Therefore, in this embodiment, the large diameter ball 30A and the small diameter ball 30B are configured to have different colors. With this configuration, the large diameter ball 30A and the small diameter ball 30B can be distinguished without measuring the diameter, so there is no risk of problems occurring during assembly or in the inspection process after completion.

[0022] For example, an operator can visually check adjacent spheres of the assembled angular contact ball bearing 1 with the naked eye to determine whether the large diameter balls 30A and the small diameter balls 30B are regularly and alternately arranged.

[0023] Also, by measuring the overall color difference of the surface color, it is possible to determine whether the large diameter balls 30A and the small diameter balls 30B are arranged alternately in a regular pattern. If the overall color difference of the surface color is less than 0.2, it may be difficult to reliably distinguish the large diameter balls 30A and the small diameter balls 30B due to the measurement accuracy and reproducibility of the overall color difference. Even if both balls are made of the same type of material, if the overall color difference of the surface color is 0.2 or more, the large diameter balls 30A and the small diameter balls 30B can be distinguished without measuring the diameter.

[0024] Here, we will explain the overall color difference. Color can be quantified by a numerical value called color value. This color value can be measured with a spectrophotometer or a color difference meter. The difference in the color values ​​of two colors is the color difference. There are three color difference values: ΔL* (color difference in brightness), Δa* (color difference in redness), and Δb* (color difference in yellowness), and the overall color difference is calculated from these three numerical values.

[0025] A preload is applied to such an angular ball bearing 1 by applying an axial load. In Fig. 5, the diameter d1 of the large diameter ball 30A, the diameter d2 of the small diameter ball 30B, the elastic deformation ΔOR of the outer ring 10 and the large diameter ball 30A on the outer ring 10 side caused by the preload in the contact angle direction, and the elastic deformation ΔIR of the inner ring 20 and the large diameter ball 30A on the inner ring 20 side caused by the preload in the contact angle direction are shown. Here, the difference (d1-d2) between the diameter d1 of the large diameter ball 30A and the diameter d2 of the small diameter ball 30B is greater than the sum (ΔOR+ΔIR) of the elastic deformations of the outer ring 10, the inner ring 20, and the large diameter ball 30A caused by the preload in the contact angle direction (d1-d2>ΔOR+ΔIR). With this configuration, the small diameter ball 30B is not preloaded, so the small diameter ball 30B is in a freely supported state without a contact angle.

[0026] In addition, the difference (d1-d2) between the diameter d1 of the large ball 30A and the diameter d2 of the small ball 30B is preferably smaller than 2% of the diameter d2 of the small ball 30B. If the difference (d1-d2) is 2% or more, the small ball 30B may fall off to the outside of the angular ball bearing 1. Therefore, in order to prevent the small ball 30B from falling off, it is desirable to set the engagement allowance at the intersection of the inner ring raceway surface 21 and the counterbore 25 in FIG. 7 within the range of 0.5 to 2% of the diameter d2 of the small ball 30B. If it exceeds 2%, there is a risk of causing defects such as indentations inside the bearing when the large ball 30A passes through the engagement allowance during assembly of the bearing. In addition, if it is 0.5% or less, the bearing radial clearance set based on the large ball 30A increases the degree of freedom of the small ball 30B, making it easier for the small ball 30B to overcome the engagement allowance and fall off to the outside.

[0027] FIG. 8 is a diagram for explaining the rotating state of the large diameter ball 30A and the small diameter ball 30B. As shown in FIG. 8, when the inner ring 20 rotates, the large diameter ball 30A having a contact angle rotates with the rotation of the inner ring 20, but the small diameter ball 30B having no contact angle is only affected by the rotation of the inner ring 20 and does not rotate much. Therefore, when the large diameter ball 30A and the small diameter ball 30B come into contact with each other, the small diameter ball 30B rotates with the rotation of the large diameter ball 30A, so that the rotation directions of the adjacent large diameter ball 30A and the small diameter ball 30B coincide at the contact portion between them. Therefore, the surfaces of the adjacent large diameter ball 30A and the small diameter ball 30B are prevented from colliding while rotating in the opposite directions, and the occurrence of wear is suppressed. Therefore, the function of the small diameter ball 30B to maintain the equal distribution of the large diameter balls 30A is also appropriately maintained.

[0028] Moreover, the angular ball bearing 1 can be incorporated into a dental air turbine bearing unit 100 as shown in Fig. 16 in place of a pair of conventional ball bearings 103, 104. In this case, a decrease in the rotational speed of the dental air turbine bearing unit 100 can be suppressed over a long period of time.

[0029] Second embodiment Next, an angular contact ball bearing 1 according to a second embodiment will be described. In the following description, the same or equivalent parts as those in the first embodiment will be given the same reference numerals, and the description thereof will be omitted or simplified.

[0030] Fig. 9 is a front view of the angular ball bearing 1 of the second embodiment. Fig. 10 is a partially cutaway perspective view of the angular ball bearing 1. Fig. 11 is a sectional view of the outer ring 10. Fig. 12 is a partially cutaway side view of the inner ring 20.

[0031] In the first embodiment, an example of an angular contact bearing of an inner race counter is shown, but the angular contact ball bearing 1 of the second embodiment is an angular contact ball bearing of an outer race counter.

[0032] As shown in Fig. 11, the outer ring 10 has a shoulder 13 on the rear side (the side where the contact angle occurs) of the outer ring raceway surface 11, and a counterbore 15 on the front side (the opposite side to the side where the contact angle occurs) of the outer ring raceway surface 11. On the other hand, as shown in Fig. 12, the inner ring 20 has no shoulder or counterbore on either side of the inner ring raceway surface 21. As a result, in the angular contact ball bearing 1, the large diameter balls 30A are arranged between the outer ring raceway surface 11 and the inner ring raceway surface 21 with a contact angle, forming an outer ring counter angular contact bearing.

[0033] The other configurations and effects are similar to those of the first embodiment.

[0034] Third embodiment FIG. 13 is a cross-sectional view of an angular ball bearing 1 according to the third embodiment.

[0035] In this embodiment, the outer ring 10 has a shoulder 13 on the back side (the side where the contact angle occurs) of the outer ring raceway surface 11, and a counterbore 15 on the front side (the side opposite to the side where the contact angle occurs) of the outer ring raceway surface 11. On the other hand, the inner ring 20 has no shoulder or counterbore on either side of the inner ring raceway surface 21. As a result, in the angular contact ball bearing 1, the large diameter balls 30A are arranged between the outer ring raceway surface 11 and the inner ring raceway surface 21 with a contact angle, forming an outer ring counter angular contact bearing.

[0036] A bearing internal space S is disposed between the inner peripheral surface of the outer ring 10 and the outer peripheral surface of the inner ring 20. The outer ring 10 has an annular sealing portion 17 formed integrally with the outer ring 10 at the back end of the inner peripheral surface and extending radially inward. The sealing portion 17 faces the outer peripheral surface of the inner ring 20 with a gap in the radial direction. If the inner diameter of the sealing portion 17 is Rc and the outer diameter of the back end of the outer peripheral surface of the inner ring 20 is Rd, then Rc-Rd>0. The inner ring 20 has an annular sealing portion 27 formed integrally with the inner ring 20 at the front end of the outer peripheral surface and extending radially outward. The sealing portion 27 faces the counterbore 15 of the outer ring 10 with a gap in the radial direction. If the outer diameter of the front end of the counterbore 15 of the outer ring 10 is Ra and the outer diameter of the sealing portion 27 is Rb, then Ra-Rb>0.

[0037] According to the angular ball bearing 1 configured as described above, the outer ring 10 and the inner ring 20 have integrally formed sealing portions 17, 27, which cover the openings at both axial ends of the bearing internal space S and prevent foreign matter from entering the bearing internal space S without the need for a separate sealing member. This requires a small number of parts and does not require an attachment structure for attaching a separate sealing member, so the shapes of the outer ring 10 and the inner ring 20 can be simplified. The other configurations and effects are the same as those of the first embodiment.

[0038] (Fourth embodiment) FIG. 14 is a cross-sectional view of an angular ball bearing 1 according to the fourth embodiment.

[0039] In this embodiment, the inner ring 20 has a shoulder 23 on the back side (the side where the contact angle occurs) of the inner ring raceway surface 21, and a counterbore 25 on the front side (the side opposite to the side where the contact angle occurs) of the inner ring raceway surface 21. On the other hand, the outer ring 10 has no shoulder or counterbore on either side of the outer ring raceway surface 11. As a result, in the angular contact ball bearing 1, the large diameter balls 30A are arranged between the outer ring raceway surface 11 and the inner ring raceway surface 21 with a contact angle, forming an angular contact bearing of the inner ring counter.

[0040] A bearing internal space S is disposed between the inner peripheral surface of the outer ring 10 and the outer peripheral surface of the inner ring 20. The outer ring 10 has an annular sealing portion 17 formed integrally with the outer ring 10 at the front end of the inner peripheral surface and extending radially inward. The sealing portion 17 faces a counterbore 25 of the inner ring 20 with a gap in the radial direction. If the inner diameter of the sealing portion 17 is Rg and the outer diameter of the front end of the counterbore 25 of the inner ring 20 is Rh, then Rg-Rh>0. The inner ring 20 has an annular sealing portion 27 formed integrally with the inner ring 20 at the back end of the outer peripheral surface and extending radially outward. The sealing portion 27 faces the inner peripheral surface of the outer ring 10 with a gap in the radial direction. If the inner diameter of the back end of the inner peripheral surface of the outer ring 10 is Re and the outer diameter of the sealing portion 27 is Rf, then Re-Rf>0.

[0041] According to the ball bearing 1 configured as described above, the outer ring 10 and the inner ring 20 have integrally formed sealing portions 17, 27, which cover the openings at both axial ends of the bearing internal space S and prevent foreign matter from entering the bearing internal space S without using a separate sealing member. This requires a small number of parts and does not require an attachment structure for attaching a separate sealing member, so the shapes of the outer ring 10 and the inner ring 20 can be simplified. The other configurations and effects are the same as those of the first embodiment.

[0042] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates mutual combinations of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the descriptions in the specification and well-known technologies, and these are included in the scope of protection sought.

[0043] For example, the angular ball bearing 1 is not limited to a specific application, and can be suitably used for other high-speed rotation applications (cleaners, motors, cooling fans, etc.) in addition to the dental air turbine described above. [Explanation of symbols]

[0044] 1 Angular contact ball bearing 10 Outer ring 11 Outer ring raceway 13 Shoulder 15 Counterbore 17 Sealed part 20. Inner Circle 21 Inner ring raceway surface 23 Shoulder 25 Counterbore 27 Sealed part 30 balls 30A Large diameter ball 30B small diameter ball S Bearing internal space

Claims

1. an outer ring having an outer ring raceway surface formed on an inner peripheral surface; an inner ring having an inner ring raceway surface formed on an outer peripheral surface; a plurality of balls disposed between the outer ring raceway surface and the inner ring raceway surface; An angular contact ball bearing having The plurality of balls are a plurality of large diameter balls having a contact angle with the outer ring raceway surface and the inner ring raceway surface; a plurality of small diameter balls having no contact angle with the outer ring raceway surface and the inner ring raceway surface and having a smaller diameter than the large diameter balls; Including, The plurality of large diameter balls and the plurality of small diameter balls are arranged alternately in the circumferential direction, are made of the same material, and are different in color. The plurality of large diameter balls and the plurality of small diameter balls are made of the same type of ceramics. Angular contact ball bearing characterized by:

2. A preload is applied to the angular ball bearing, The difference between the diameter of the large diameter ball and the diameter of the small diameter ball is greater than the sum of the amounts of elastic deformation in the contact angle direction of the outer ring, the inner ring, and the large diameter ball caused by the preload.

2. The angular contact ball bearing according to claim 1.

3. The difference between the diameter of the large ball and the diameter of the small ball is less than 2% of the diameter of the small ball.

3. The angular contact ball bearing according to claim 2.

4. When the plurality of large diameter balls and the plurality of small diameter balls are arranged at equal intervals in the circumferential direction, the distance between adjacent large diameter balls and small diameter balls is 2 to 4% of the diameter of the small diameter ball. The angular contact ball bearing according to any one of claims 1 to 3.

5. A bearing internal space is disposed between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, The outer ring and the inner ring are integrally formed with annular sealing portions that cover the openings at both axial ends of the bearing internal space. The angular contact ball bearing according to any one of claims 1 to 4.

6. A rotation axis; a turbine blade provided on the rotary shaft and configured to rotate the rotary shaft by compressed air; an angular contact ball bearing according to any one of claims 1 to 5 that rotatably supports the rotating shaft; a housing that supports the rotating shaft via the angular ball bearing; A bearing unit for a dental air turbine comprising:

7. A dental air turbine handpiece comprising the bearing unit for a dental air turbine according to claim 6.

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