JP2020041629A - Dynamic pressure bearing device and rotary electrical machine - Google Patents

Abstract

To provide a dynamic pressure bearing device that can suppress generation of seizure, and to provide a rotary electrical machine.SOLUTION: A plurality of dynamic pressure generating grooves 40 including a pair of grooves 41, 42 extending obliquely relative to a rotation direction X so as to be separated from each other as proceeding on a front side of the rotation direction X are provided in the rotation direction X at an outer peripheral surface 31a of a rotation shaft 31 of a dynamic pressure bearing device 30. In the dynamic pressure generating grooves 40, the pair of grooves 41, 42 have depths being different from each other.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a dynamic pressure bearing device and a rotating electric machine including the same.

  2. Description of the Related Art Conventionally, in a spindle device applied to a machine tool, a hard disk device, or the like, a dynamic pressure bearing device that supports a rotating shaft in a non-contact manner has been used (for example, see Patent Document 1). The dynamic pressure bearing device described in Patent Document 1 includes a rotating shaft and a bearing that supports a radial load of the rotating shaft. On the outer peripheral surface of the rotating shaft or the inner peripheral surface of the bearing, a plurality of V-shaped herringbone-shaped grooves are formed, which are formed of a pair of grooves extending at an angle to the rotating direction of the rotating shaft.

  In such a dynamic pressure bearing device, when a fluid such as air or lubricating oil flows into the herringbone-shaped groove with the rotation of the rotating shaft, the fluid is compressed and the dynamic pressure is increased. The rotating shaft is rotatably supported in a state of floating from the inner peripheral surface of the bearing by the increased dynamic pressure, that is, in a non-contact state.

JP-A-2-304214

  By the way, in the dynamic pressure bearing device having the herringbone groove as described above, the fluid is compressed and the dynamic pressure increases as the rotation speed of the rotating shaft increases. Therefore, in order to generate an appropriate dynamic pressure in the gap between the rotating shaft and the bearing, it is necessary to rotate the rotating shaft at a predetermined rotation speed or higher. However, since the temperature of the fluid increases with the compression of the fluid, the rotating shaft and the bearing thermally expand by being heated by the fluid. As a result, the clearance between the rotating shaft and the bearing is reduced, so that smooth rotation of the rotating shaft may be hindered.

  An object of the present invention is to provide a dynamic bearing device and a rotating electric machine that can rotate a rotating shaft smoothly.

  A dynamic pressure bearing device for achieving the above object includes a rotating shaft, a bearing rotatably supporting an outer peripheral surface of the rotating shaft, and any one of an outer peripheral surface of the rotating shaft and an inner peripheral surface of the bearing. On one side, a plurality of dynamic pressure generating grooves including a pair of grooves extending inclining with respect to the rotation direction are provided in the rotation direction so as to be further apart from each other as the front side in the rotation direction of the rotation shaft. At least one of the depth of the groove, the width of the groove, the inclination angle of the groove with respect to the rotation direction, and the length in the extending direction of the groove is different between one and the other of the pair of grooves. I have.

  In the above-described bearing device, when air flows into the pair of grooves with the rotation of the rotary shaft, the air is compressed to increase the dynamic pressure. The rotating shaft is rotatably supported in a state of floating from the inner peripheral surface of the bearing by the increased dynamic pressure, that is, in a non-contact state.

  According to the above configuration, at least one of the depth of the groove, the width of the groove, the inclination angle of the groove with respect to the rotation direction of the rotating shaft, and the length in the extending direction of the groove is mutually different between one and the other of the pair of grooves. Because of the difference, a difference occurs between the dynamic pressure generated in one of the pair of grooves and the dynamic pressure generated in the other when the rotation shaft rotates. Thereby, between the rotating shaft and the bearing, air moves from the higher dynamic pressure of the pair of grooves to the lower dynamic pressure. For this reason, the air which has become high temperature by being compressed by the dynamic pressure generating groove flows between the rotating shaft and the bearing along the axial direction. This flow of air makes it difficult for high-temperature air to stay between the rotating shaft and the bearing, thereby suppressing a rise in the temperature of the rotating shaft and the bearing and, consequently, a reduction in the gap between the rotating shaft and the bearing due to thermal expansion. Can be. Therefore, the rotating shaft can be smoothly rotated.

Further, a rotating electric machine for achieving the above object includes the dynamic pressure bearing device, a rotor fixed to the rotating shaft, and a stator arranged on an outer periphery of the rotor.
According to this configuration, the same operation and effect as those of the above-described hydrodynamic bearing device can be obtained, so that the rotating shaft of the rotating electric machine can be smoothly rotated.

  According to the present invention, the rotation shaft can be smoothly rotated.

FIG. 2 is a cross-sectional view schematically illustrating the configuration of the rotating electric machine according to the embodiment. FIG. 2 is an enlarged cross-sectional view schematically showing part A of FIG. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. 4 is a graph showing a relationship between a depth of a pair of grooves in a dynamic pressure generating groove and a generated dynamic pressure. FIG. 7 is an enlarged cross-sectional view corresponding to FIG. 2, focusing on a dynamic pressure generating groove of the dynamic pressure bearing device in a first modified example. It is a figure corresponding to Drawing 2, and an enlarged sectional view centering on a dynamic pressure generating groove of a dynamic pressure bearing device in the 2nd modification. It is a figure corresponding to Drawing 2, and is an expanded sectional view centering on a dynamic pressure generating groove of a dynamic pressure bearing device in the 3rd modification.

Hereinafter, an embodiment of a rotating electric machine including a hydrodynamic bearing device will be described with reference to FIGS. 1 to 4.
As shown in FIG. 1, the rotating electric machine 10 includes a cylindrical housing 20, and a dynamic pressure having a bearing 32 provided inside the housing 20 and rotatably supporting a rotating shaft 31 and an outer peripheral surface 31 a of the rotating shaft 31. The rotor includes a bearing device 30, a rotor 50 fixed to the rotating shaft 31, and a stator 60 arranged on the outer periphery of the rotor 50.

The housing 20 includes a cylindrical main body 21 having a bottom 23 on one side, and a lid 24 for closing an opening 22 of the main body 21.
Through holes 25 and 26 are provided at the bottom 23 of the main body 21 and at the center of the lid 24 facing the bottom 23, respectively. A bearing 32 is fitted in each of the through holes 25 and 26. The bearing 32 of the present embodiment is a radial bearing that supports the radial load of the rotating shaft 31.

  The outer diameter of the rotating shaft 31 is slightly smaller than the inner diameter of the bearing 32. That is, when the rotating shaft 31 and the bearing 32 are on the same axis, a gap (clearance) is provided over the entire circumference between the outer peripheral surface 31a of the rotating shaft 31 and the inner peripheral surface 32a of the bearing 32. I have.

A plurality of permanent magnets (not shown) are embedded in the rotor 50.
The stator 60 is attached to the inner surface of the housing 20 and has a coil 61 wound therearound.

  As shown in FIGS. 1 and 2, a herringbone-shaped dynamic pressure generating groove 40 is provided on a portion of the outer peripheral surface 31 a of the rotating shaft 31 facing the inner peripheral surface 32 a of the bearing 32, in the rotation direction X of the rotating shaft 31. Are provided. The rotation direction X of the rotation shaft 31 is a counterclockwise direction when the rotation shaft 31 is viewed from the right in FIG. Hereinafter, the rotation direction X of the rotation shaft 31 is simply referred to as the rotation direction X. The axial direction Y of the rotating shaft 31 is simply referred to as the axial direction Y.

  The dynamic pressure generating groove 40 is configured by a pair of grooves (first groove 41 and second groove 42) that extend obliquely with respect to the rotation direction X so that they are further apart from each other toward the front side in the rotation direction X. At the rear side in the rotation direction X of the dynamic pressure generating groove 40, a junction 40a where the first groove 41 and the second groove 42 merge is formed. The first groove 41 is located on the side separated from the rotor 50 and the stator 60 in the axial direction Y with respect to the junction 40a. The second groove 42 is located closer to the rotor 50 and the stator 60 in the axial direction Y than the junction 40a.

  As shown in FIGS. 2 and 3, in the present embodiment, the first groove 41 and the second groove 42 have different groove depths. More specifically, as shown in FIG. 3, the depth D1 of the first groove 41 is larger than the depth D2 of the second groove 42 (D1> D2).

  As shown in FIG. 2, the first groove 41 and the second groove 42 have shapes symmetric about a virtual plane passing through the junction 40 a and orthogonal to the axial direction Y at points other than the groove depth. ing. That is, the width of the grooves 41 and 42, the inclination angle of the grooves 41 and 42 with respect to the rotation direction X, and the length of the grooves 41 and 42 in the extending direction are the same in the first groove 41 and the second groove 42. .

  Here, as shown in FIG. 4, the relationship between the pair of grooves having the same groove depth and the dynamic pressure generated in the groove is such that the smaller the groove depth, the smaller the dynamic pressure generated in the groove. There is a range of the groove depth that decreases and a range of the groove depth where the dynamic pressure generated in the groove increases as the groove depth decreases.

  In the present embodiment, the depths of the grooves 41 and 42 are different from each other within a range of the groove depth where the dynamic pressure generated in the groove decreases as the groove depth decreases. That is, the depth D1 of the first groove 41 and the depth D2 of the second groove 42 are set so that the dynamic pressure generated in the second groove 42 is lower than the dynamic pressure generated in the first groove 41 within the above range. Is set.

The operation of the present embodiment will be described.
First, the basic operation of the hydrodynamic bearing device 30 of the present embodiment will be described.
With the rotation of the rotating shaft 31, the surrounding air flows into the grooves 41 and 42 of the dynamic pressure generating groove 40 provided on the outer peripheral surface 31a of the rotating shaft 31 from the front side in the rotating direction X. The air that has flowed into the grooves 41 and 42 flows toward the rear side in the rotation direction X along the extending direction of the grooves 41 and 42, and is joined and compressed at the joining portion 40 a to increase the dynamic pressure. . As a result, a higher dynamic pressure is generated at the junction 40a than at the surroundings. Such a dynamic pressure is generated over the entire circumference of the rotating shaft 31 and the bearing 32. When the dynamic pressure becomes larger than the predetermined dynamic pressure, the rotating shaft 31 floats on the bearing 32. Thus, the rotating shaft 31 is rotatably supported on the bearing 32 in a non-contact state.

  The dynamic pressure bearing device 30 of the present embodiment is configured such that the depth D1 of the first groove 41 is smaller than the second groove 42 so that the dynamic pressure generated in the second groove 42 is smaller than the dynamic pressure generated in the first groove 41. Is set to be larger than the depth D2. Therefore, when the dynamic pressure is generated by the dynamic pressure generation groove 40, the flow of air from the first groove 41 to the second groove 42 having a lower dynamic pressure than the dynamic pressure in the first groove 41, that is, the axial direction Y , A flow of air toward the inside of the housing 20 is generated. Since the outer peripheral surface 31a of the rotating shaft 31 is provided with the dynamic pressure generating grooves 40 on both sides in the axial direction Y, the flow of the air toward the inside of the housing 20 is generated as a whole of the dynamic pressure bearing device 30. Become. Due to the flow of air, the rotor 50 and the stator 60 that have generated heat by driving the rotating electric machine 10 are cooled.

The effect of the present embodiment will be described.
(1) The outer peripheral surface 31a of the rotating shaft 31 of the dynamic pressure bearing device 30 includes a pair of grooves 41 and 42 that extend obliquely with respect to the rotation direction X so as to be further away from each other toward the front side in the rotation direction X. A plurality of dynamic pressure generating grooves 40 are provided in the rotation direction X. In the dynamic pressure generating groove 40, the depths of the pair of grooves 41 and 42 are different from each other.

  According to such a configuration, since the depths of the pair of grooves 41 and 42 are different from each other, a difference occurs between the dynamic pressure generated in the first groove 41 and the dynamic pressure generated in the second groove 42 when the rotating shaft 31 rotates. . Thereby, between the rotating shaft 31 and the bearing 32, air moves from the higher dynamic pressure to the lower dynamic pressure of the pair of grooves 42, 42. For this reason, the air that has been heated by the compression by the dynamic pressure generating groove 40 flows between the rotating shaft 31 and the bearing 32 along the axial direction. Such an air flow makes it difficult for high-temperature air to stay between the rotating shaft 31 and the bearing 32, and increases the temperature of the rotating shaft 31 and the bearing 32, and further reduces the gap between the rotating shaft 31 and the bearing 32 due to thermal expansion. Can be suppressed. Therefore, the rotating shaft 31 can be smoothly rotated.

  (2) The rotating electric machine 10 includes the dynamic pressure bearing device 30, the rotor 50 fixed to the rotating shaft 31, and the stator 60 arranged on the outer periphery of the rotor 50. The dynamic pressure generating groove 40 of the dynamic pressure bearing device 30 is configured such that the dynamic pressure generated in the second groove 42 of the pair of grooves 41 and 42 that is closer to the rotor 50 and the stator 60 is formed by the rotor 50 and the stator 60. The depths are different from each other so as to be lower than the dynamic pressure generated in the first groove 41 on the side away from the first groove 41.

  According to such a configuration, since the above operation is achieved, the heat generation of the rotor 50 and the stator 60 can be suppressed, so that the same effect as the effect (1) of the dynamic pressure bearing device 30 can be obtained. Therefore, the rotating shaft 31 of the rotating electric machine 10 can be smoothly rotated.

This embodiment can be implemented with the following modifications. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
In the above-described embodiment, the depth of the grooves 41 and 42 is made different from each other within the range of the groove depth where the dynamic pressure generated in the groove becomes lower as the groove depth becomes smaller, so that the groove moves from the outside to the inside in the axial direction. An oncoming airflow was created. Similarly, as shown in FIG. 4, if the depths D3 and D4 of the grooves 41 and 42 are different from each other within the range of the groove depth where the dynamic pressure generated in the groove increases as the groove depth decreases. By doing so, a flow of air from the outside in the axial direction to the inside may be generated.

  The configuration for making the dynamic pressure generated in the first groove 41 different from the dynamic pressure generated in the second groove 42 is not limited to the groove depth. At least one of the depth of the grooves 41 and 42, the width of the grooves 41 and 42, the inclination angle of the grooves 41 and 42 with respect to the rotation direction X, and the length of the grooves 41 and 42 in the extending direction is defined as the first groove 41. By making them different from each other in the second groove 42, the dynamic pressure generated in the first groove 41 and the dynamic pressure generated in the second groove 42 can be made different. Hereinafter, the modified example will be described with reference to FIGS. In the following first to third modified examples shown in FIGS. 5 to 7, respectively, the same components as those in the above embodiment are denoted by the same reference numerals, and the corresponding components are “100” and “100”, respectively. A duplicate description is omitted by assigning a code obtained by adding “200” and “300”.

  As shown in FIG. 5, instead of the dynamic pressure bearing device 30 of the present embodiment, the first dynamic pressure generated in the first groove 141 and the dynamic pressure generated in the second The dynamic pressure bearing device 130 in which the inclination angle α1 of the groove 141 with respect to the rotation direction X and the inclination angle α2 of the second groove 142 with respect to the rotation direction X are different from each other may be employed. In the first modification, the inclination angle α1 is larger than the inclination angle α2 (α1> α2). According to such a configuration, the same operation and effect as the above embodiment can be obtained.

  As shown in FIG. 6, instead of the dynamic pressure bearing device 30 of the present embodiment, the first dynamic pressure generated in the first groove 241 and the first dynamic pressure generated in the second groove 242 are set to be different from each other. The dynamic pressure bearing device 230 in which the width W1 of the groove 241 and the width W2 of the second groove 242 are different from each other can be adopted. In the second modification, the width W1 is larger than the width W2 (W1> W2). According to such a configuration, the same operation and effect as the above embodiment can be obtained.

  As shown in FIG. 7, instead of the dynamic pressure bearing device 30 of the present embodiment, the first dynamic pressure generated in the first groove 341 and the first dynamic pressure generated in the second groove 342 are set to be different from each other. The dynamic pressure bearing device 330 in which the length L1 in the extending direction of the groove 341 and the length L2 in the extending direction of the second groove 342 are different from each other may be employed. In the third modification, the length L1 is longer than the length L2 (L1> L2). According to such a configuration, the same operation and effect as the above embodiment can be obtained.

  -Instead of the outer peripheral surface 31a of the rotating shaft 31, a dynamic pressure generating groove 40 can be provided on the inner peripheral surface 32a of the bearing 32.

  DESCRIPTION OF SYMBOLS 10 ... Rotating electric machine, 20 ... Housing, 21 ... Body part, 22 ... Opening, 23 ... Bottom part, 24 ... Lid part, 25, 26 ... Through-hole, 30, 130, 230, 330 ... Dynamic pressure bearing device, 31, 131 , 231, 331... Rotating shaft, 31 a, 131 a, 231 a, 331 a, outer peripheral surface, 32, bearing, 32 a, inner peripheral surface, 40, 140, 240, 340. Converging portions, 41, 141, 241, 341: first groove, 42, 142, 242, 342: second groove, 50: rotor, 60: stator, 61: coil.

Claims (3)

A rotation axis,
Bearing that rotatably supports the outer peripheral surface of the rotating shaft,
One of the outer peripheral surface of the rotating shaft and the inner peripheral surface of the bearing has a pair of grooves extending obliquely with respect to the rotation direction so as to be more separated from each other as the front side in the rotation direction of the rotation shaft. A plurality of dynamic pressure generating grooves, including:
At least one of the depth of the groove, the width of the groove, the inclination angle of the groove with respect to the rotation direction, and the length in the extending direction of the groove is different between one of the pair of grooves and the other. ,
Dynamic pressure bearing device. A hydrodynamic bearing device according to claim 1,
A rotor fixed to the rotating shaft,
And a stator disposed on the outer periphery of the rotor.
Rotating electric machine. Of the pair of grooves, the dynamic pressure generated in the groove on the side close to the rotor and the stator is lower than the dynamic pressure generated in the groove on the side separated from the rotor and the stator, At least one of a depth of the pair of grooves, a width of the pair of grooves, an inclination angle of the pair of grooves with respect to the rotation direction, and a length in an extending direction of the pair of grooves is different from each other.
The rotating electric machine according to claim 2.

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