Shaft coupling mechanism

Abstract

There is demand for a shaft coupling mechanism that reliably transfers the power of a rotating shaft to a main shaft and is also less likely to be affected by axial displacement of the main shaft.　Provided is a shaft coupling mechanism comprising: a main shaft which has a shaft hole portion; a coupling member which has an inner hole portion; a rotating shaft which can be inserted into the shaft hole portion and the inner hole portion; a first rolling element; and a second rolling element. The main shaft has a first inner groove portion, the coupling member has a second inner groove portion, and the rotating shaft has a first outer groove portion and a second outer groove portion. Disposing the first rolling element between the second outer groove portion of the rotating shaft and the second inner groove portion of the main shaft and disposing the second rolling element between the first outer groove portion of the rotating shaft and the first inner groove portion of the coupling member in a state where the main shaft and the coupling member are axially coupled together and the rotating shaft is inserted in the shaft hole portion and the inner hole portion enables axial movement of the rotating shaft and the main shaft and causes the power of the rotating shaft to be transferred to the rotating shaft via the first rolling element and the second rolling element.

Description

Shaft connection mechanism

[0001] The present disclosure relates to a shaft coupling mechanism.

[0002] Conventionally, in machine tools, mechanisms have been proposed that connect the rotating shaft of a rotating electric machine to the spindle of a spindle unit that grips a tool, and transmit the power of the rotating electric machine to the spindle (see, for example, Patent Documents 1 and 2).

[0003] Japanese Patent Laid-Open No. 5-269605 Japanese Patent Laid-Open No. 2007-168023

[0004] When the rotating electric machine and the spindle unit are arranged separately, a joint is used as a member for concentrically connecting the rotating shaft of the rotating electric machine and the spindle of the spindle unit. However, when the rotating shaft and the spindle are connected with a joint, the axial dimension of the rotating shaft and the spindle increases, and the dangerous rotation speed (the rotation speed at which vibration occurs due to resonance) decreases. As a result, the upper limit of the rotation speed of the rotating electric machine is restricted. Furthermore, if the axial dimension of the rotating shaft and the spindle increases, it is thought that the rotation characteristics may also be adversely affected.

[0005] On the other hand, by changing the structure of the joint, it is possible to shorten the axial dimension of the rotating shaft and the spindle. However, if the spindle is displaced and elongated in the axial direction due to the influence of heat during machining of a workpiece, the rotating shaft of the rotating electric machine will be pushed in the axial direction by the displaced spindle, which may lead to early damage to the rotating electric machine. It is also possible to provide a gap between the spindle and the rotating shaft in advance, taking into account the possibility of the spindle displacing in the axial direction due to the influence of heat. However, providing a gap between the spindle and the rotating shaft makes it difficult to reliably transmit the power of the rotating shaft to the spindle.

[0006] Therefore, there is a demand for a shaft coupling mechanism that can reliably transmit the power of the rotary shaft to the main shaft while being less susceptible to the influence of axial displacement of the main shaft.

[0007] A shaft coupling mechanism according to the present disclosure includes a main shaft having a hollow shaft hole portion along the axial direction, a coupling member having a hollow inner hole portion along the axial direction and coupled to the main shaft in the axial direction, a rotating shaft having an outer shape that can be inserted into the shaft hole portion of the main shaft and the inner hole portion of the coupling member when the main shaft and the coupling member are coupled in the axial direction, first rolling elements arranged between the main shaft and the rotating shaft, and second rolling elements arranged between the coupling member and the rotating shaft, wherein the main shaft has a first inner groove portion on an inner circumferential surface of the shaft hole portion that is engageable with the first rolling elements, and the coupling member has a second inner groove portion on an inner circumferential surface of the inner hole portion that is engageable with the second rolling elements, The rotating shaft has on its outer surface a first outer groove portion engageable with the first rolling element and a second outer groove portion engageable with the second rolling element, and when the main shaft and the connecting member are connected in the axial direction and the rotating shaft is inserted into the shaft hole portion of the main shaft and the inner hole portion of the connecting member, the first rolling element is arranged between the second outer groove portion of the rotating shaft and the second inner groove portion of the main shaft, and the second rolling element is arranged between the first outer groove portion of the rotating shaft and the first inner groove portion of the connecting member, so that the rotating shaft and the main shaft are freely movable in the axial direction, and the power of the rotating shaft is transmitted to the rotating shaft via the first rolling element and the second rolling element.

[0008] 2A is a configuration diagram of an electric motor 10 and a spindle unit 20 connected by a shaft connecting mechanism according to the first embodiment. FIG. 1 is a partially enlarged view. FIG. 2B is a cross-sectional view taken along line s1-s1 of FIG. 2A. FIG. 2C is an exploded perspective view of the shaft connecting mechanism according to the first embodiment. FIG. 3 is a plan view of the rotating shaft 11 as viewed from the X2 side. FIG. 4 is a plan view of the main shaft 21 as viewed from the X2 side. FIG. 5 is a plan view of the connecting member 30 as viewed from the X2 side. FIG. 6 is a plan view of the connecting member 30 as viewed from the X1 side. FIG. 7 is a perspective view of the shaft connecting mechanism according to the first embodiment. FIG. 8 is a diagram illustrating the direction in which the main shaft 21 and the connecting member 30 are pressed. FIG. 9 is a perspective view of the shaft connecting mechanism according to the second embodiment. FIG. 10 is a perspective view of the shaft connecting mechanism according to the third embodiment. FIG. 11 is a perspective view of the shaft connecting mechanism according to the fourth embodiment. FIG. 12 is a conceptual cross-sectional view showing the configuration of the shaft connecting mechanism according to the fifth embodiment. FIG. 13 is a conceptual cross-sectional view showing another configuration different from the shaft connecting mechanism according to the fifth embodiment. FIG. 14 is a conceptual cross-sectional view showing another configuration different from the shaft connecting mechanism according to the fifth embodiment.

[0009] Hereinafter, an embodiment of a shaft coupling mechanism according to the present disclosure will be described. The drawings attached to this specification are all schematic diagrams, and the shape, scale, aspect ratio, and the like of each part have been modified or exaggerated from the actual product in consideration of ease of understanding, etc.

[0010] 1 and other figures show a coordinate system of X, Y, and Z that are orthogonal to each other. In this coordinate system, the direction parallel to the rotation shaft 11 of the electric motor 10 and the central axis OA of the spindle 21 of the spindle unit 20 is defined as the X direction (hereinafter also referred to as the "axial direction X"). In the axial direction X, the direction in which the spindle unit 20 is disposed is defined as X1, and the direction in which the electric motor 10 is disposed is defined as X2.

[0011] Furthermore, one of the directions perpendicular to the axial direction X is the Y direction, and the other direction is the Z direction. The Y direction and the Z direction are perpendicular to each other when viewed from the axial direction X. In the Y direction, one direction is Y1, and the other direction is Y2. In the Z direction, one direction is Z1, and the other direction is Z2. Furthermore, the circumferential direction centered on the central axis OA of the rotating shaft 11, the main shaft 21, and the connecting member 30 is the R direction (hereinafter also referred to as the "circumferential direction" or the "circumferential direction R"). In this specification, "direction" may also be referred to as "side" as appropriate.

[0012] First Embodiment FIG. 1 is a configuration diagram of an electric motor 10 and a spindle unit 20 connected by a shaft connection mechanism according to a first embodiment. In FIG. 1, the shape of the connection member 30 and other components is simplified. FIG. 2A is a partially enlarged view of FIG. 1. FIG. 2B is a cross-sectional view taken along line s1-s1 of FIG. 2A. In FIG. 2B, the first rolling element 41 and the second rolling element 42 are omitted from illustration. FIG. 3 is an exploded perspective view of the shaft connection mechanism according to the first embodiment. In FIG. 3, only the portions of the rotating shaft 11 and the spindle 21 that are exposed from the electric motor 10 and the spindle unit 20 are shown (the same applies to other related drawings). FIG. 4 is a plan view of the rotating shaft 11 as viewed from the X2 side. FIG. 5 is a plan view of the spindle 21 as viewed from the X2 side. FIG. 6A is a plan view of the connecting member 30 as viewed from the X2 side. FIG. 6B is a plan view of the connecting member 30 as viewed from the X1 side.

[0013] 1 and 2A, the shaft coupling mechanism according to the first embodiment is a mechanism that couples the rotating shaft 11 of the electric motor 10 and the main shaft 21 of the main shaft unit 20 with a coupling member 30, a first rolling element 41, and a second rolling element 42, thereby transmitting the power of the electric motor 10 from the rotating shaft 11 to the main shaft 21. The electric motor 10 of the first embodiment (and other embodiments) is a rotating electric machine used as a power source for a machine tool, for example, but its use is not limited to machine tools.

[0014] In the electric motor 10 shown in FIG. 1 , the rotating shaft 11 is a shaft member that supports a rotor (not shown) disposed therein. The rotor rotates due to magnetic interaction with a rotating magnetic field generated by a stator (not shown) disposed in a housing 12. Rotation of the rotor generates power (rotational force) in the rotating shaft 11. The rotating shaft 11 is inserted so as to penetrate the axial center of the rotor and is fixed coaxially with the rotor. A pair of bearings (not shown) are provided on both sides of the rotating shaft 11 in the axial direction X. The bearings are members that rotatably support the rotating shaft 11 and are fixed inside the housing 12. The housing 12 is a casing that holds the rotating shaft 11 via the bearings. The rotating shaft 11 is held rotatably about the axial direction X by the housing 12, the bearings, etc.

[0015] 3 , the rotating shaft 11 is inserted into a shaft hole 22 (described later) of the main shaft 21 and an inner hole 31 (described later) of the connecting member 30. The portion of the rotating shaft 11 exposed from the electric motor 10 only needs to have an "outer shape" that allows it to be inserted into the shaft hole 22 of the main shaft 21 and the inner hole 31 of the connecting member 30. Hereinafter, the description of the outer shape of the rotating shaft 11 will be limited to the portion of the rotating shaft 11 exposed from the electric motor 10.

[0016] 4, the rotating shaft 11 has a substantially circular shape when viewed from the axial direction X, and is provided on its outer circumferential surface with a first outer groove portion 13 and a second outer groove portion 14. In the following description, when there is no need to distinguish between the first outer groove portion 13 and the second outer groove portion 14, they are also referred to as "outer groove portions."

[0017] The first outer grooves 13 are grooves that can engage with the first rolling elements 41 (described later) and are provided to extend along the axial direction X (see FIG. 3 ). The cross-sectional shape of the first outer grooves 13 is configured to be approximately half the cross-sectional shape of the first rolling elements 41 (approximately semicircular arc shape). The cross-sectional shape of the first outer grooves 13 is not limited to the approximately semicircular arc shape of this embodiment, and may be a combination of various curved surfaces and straight lines as long as a surface capable of transmitting power to the rotating shaft 11 or the main shaft 21 when the first rolling elements 41 move in the circumferential direction R is ensured. As shown in FIG. 4 , the first outer grooves 13 are provided in the Z1 direction and the Z2 direction, sandwiching the central axis OA therebetween. The number of first outer grooves 13 is not limited to four. It is desirable for the first outer grooves 13 to be equally spaced about the central axis OA, but they may also be point-symmetric with respect to the central axis OA or line-symmetric with respect to a line intersecting the central axis OA.

[0018] The second outer grooves 14 are grooves that can engage with second rolling elements 42 (described later) and are provided to extend along the axial direction X (see FIG. 3 ). The cross-sectional shape of the second outer grooves 14 is configured to be approximately half the cross-sectional shape of the second rolling elements 42 (substantially semicircular arc shape). Like the cross-sectional shape of the first outer grooves 13, the cross-sectional shape of the second outer grooves 14 is not limited to a substantially semicircular arc shape. As shown in FIG. 4 , the second outer grooves 14 are provided in the Y1 direction and the Y2 direction, sandwiching the central axis OA therebetween. When the rotating shaft 11 is viewed from the axial direction X, the first outer grooves 13 and the second outer grooves 14 are arranged at equal intervals (90° intervals in this example) around the central axis OA.

[0019] The outer shape of the rotating shaft 11 may be, for example, an outer shape having a key groove, a flat portion, a tapered portion, or the like in part. Also, for example, the rotating shaft 11 may be configured such that an outer groove portion is formed in a cylindrical member, and a columnar member is separably fitted inside the cylindrical member. In this way, the rotating shaft 11 is not limited to the example of the embodiment as long as it can be inserted into the shaft hole portion 22 of the main shaft 21 and the inner hole portion 31 of the connecting member 30 and has an outer groove portion.

[0020] (Spindle) The spindle unit 20 (see FIG. 1) is a device that rotatably holds the spindle 21. The spindle 21 is a part that rotates or fixedly holds a tool holder (not shown) that grips a tool on the side opposite to the electric motor 10 (X1 side). As shown in FIG. 3, the spindle 21 has a hollow shaft hole portion 22 that extends along the axial direction X. The shaft hole portion 22 is a through hole into which the rotating shaft 11 is inserted. In this embodiment, the shaft hole portion 22 is a through hole that penetrates the entire length of the spindle 21, but is not limited to this. The shaft hole portion 22 may be a blind hole that is closed on the X1 side of the spindle 21, or may have a stepped interior.

[0021] The shaft hole portion 22 has an inner diameter that allows the rotary shaft 11 to be inserted therein. The inner diameter of the shaft hole portion 22 is set to a degree that leaves an appropriate gap between the rotary shaft 11 and the shaft hole portion 22 when the rotary shaft 11 is inserted therein.

[0022] 5, the main shaft 21 has a first inner groove portion 23 and a second inner groove portion 24 on the inner peripheral surface of the shaft hole portion 22. In the following description, when there is no need to particularly distinguish between the first inner groove portion 23 and the second inner groove portion 24, they are also referred to as "inner groove portions."

[0023] The first inner groove 23 is a groove that engages with the first rolling element 41 and is provided to extend along the axial direction X (see FIG. 3 ). The cross-sectional shape of the first inner groove 23 is configured to be approximately half the cross-sectional shape of the first rolling element 41 (substantially semicircular arc shape). Like the cross-sectional shape of the first outer groove 13, the cross-sectional shape of the first inner groove 23 is not limited to a substantially semicircular arc shape. As shown in FIG. 5 , the first inner groove 23 is provided on both the Z1 side and the Z2 side of the central axis OA.

[0024] The second inner groove portion 24 is provided to extend along the axial direction X (see FIG. 3 ). The cross-sectional shape of the second inner groove portion 24 is configured to be approximately half the cross-sectional shape of the second rolling element 42 (substantially semicircular arc shape). Like the cross-sectional shape of the first inner groove portion 23, the cross-sectional shape of the second inner groove portion 24 is not limited to a semicircular arc shape. As shown in FIG. 5 , the second inner groove portion 24 is provided on each of the Y1 side and the Y2 side, sandwiching the central axis OA therebetween. The arrangement of the second inner groove portion 24 with respect to the central axis OA may be the same as the arrangement of the second outer groove portion 14 provided on the rotating shaft 11 in phase around the central axis OA.

[0025] The first inner groove portion 23 and the second inner groove portion 24 are disposed at equal intervals (90° intervals in this example) around the central axis OA when the main shaft 21 is viewed from the axial direction X. As with the outer groove portions provided on the rotating shaft 11, the arrangement of the first inner groove portion 23 and the second inner groove portion 24 when viewed from the axial direction X is not limited to the above arrangement.

[0026] As shown in Fig. 3, the spindle 21 includes a spindle recess 25 and a spindle protrusion 26. The spindle recess 25 is a recess that fits with a connecting protrusion 35 (described later) of the connecting member 30 in the axial direction X. As shown in Fig. 5, the spindle recess 25 is provided on the Y1 side and the Y2 side, with the central axis OA sandwiched therebetween. The spindle protrusion 26 is a protrusion that fits with a connecting recess 36 (described later) of the connecting member 30 in the axial direction X. As shown in Fig. 5, the spindle protrusion 26 is provided on the Z1 side and the Z2 side, with the central axis OA sandwiched therebetween.

[0027] As shown in Fig. 5, the main shaft protrusion 26 is provided with a threaded hole 27. A female thread is formed on the inner peripheral surface of the threaded hole 27, which is capable of threadably engaging with a first set bolt (first pressing member / phase adjustment portion) 28. As shown in Fig. 5, the threaded holes 27 are provided on the Z1 side and the Z2 side when the main shaft 21 is viewed from the axial direction X. The threaded holes 27 open in directions parallel to each other, with the central axis OA sandwiched therebetween.

[0028] The first set bolt 28 is a member for applying a preload to the first rolling element 41 disposed between the main shaft 21 and the rotary shaft 11. A male thread is formed on the outer circumferential surface of the first set bolt 28, and is capable of engaging with the female thread of the screw hole 27. With the main shaft 21 and the connecting member 30 fitted together, when the first set bolt 28 is screwed into the female thread of the screw hole 27 and turned in the fastening direction (for example, clockwise), the tip of the bolt protrudes from the main shaft protrusion 26 and is pressed against a connecting protrusion 35 (described later) of the connecting member 30.

[0029] When the bolt tip is pressed against the connecting protrusion 35 of the connecting member 30, the connecting member 30 is pressed in a direction away from the main shaft 21 in the circumferential direction R, changing the positional relationship between the connecting member 30 and the main shaft 21. As a result, a preload is applied to the first rolling element 41, which is disposed between the main shaft 21 and the rotating shaft 11, in the counterclockwise direction (second direction) as viewed from the X2 side. The amount of preload applied to the first rolling element 41 can be adjusted by the amount by which the bolt tip of the first set bolt 28 protrudes from the main shaft protrusion 26. In other words, the amount of preload applied to the first rolling element 41 can be adjusted by using the first set bolt 28 to adjust the circumferential positional relationship (phase) between the connecting member 30 and the main shaft 21.

[0030] (Coupling Member) Coupling member 30 is a component that is coupled to main shaft 21 in axial direction X. The "coupling" between coupling member 30 and main shaft 21 means that coupling protrusion 35 (described later) of coupling member 30 and main shaft recess 25 of main shaft 21 are fitted together in axial direction X, and coupling recess 36 (described later) of coupling member 30 and main shaft protrusion 26 of main shaft 21 are fitted together in axial direction X.

[0031] As shown in Fig. 3, the connecting member 30 has a hollow inner hole 31 along the axial direction X. The inner hole 31 is a through hole into which the rotating shaft 11 is inserted. The inner hole 31 has an inner diameter that allows the rotating shaft 11 to be inserted. The inner diameter of the inner hole 31 is set to an extent that an appropriate gap is formed between the rotating shaft 11 and the inner hole 31 when the rotating shaft 11 is inserted.

[0032] As shown in Fig. 6A, the connecting member 30 has a first inner groove 33 and a second inner groove 34 on the inner circumferential surface of the inner hole 31. The first inner groove 33 is provided to extend along the axial direction X (see Fig. 3). The cross-sectional shape of the first inner groove 33 is configured to be approximately half the cross-sectional shape of the first rolling element 41 (a substantially semicircular arc shape). As shown in Fig. 6A, the first inner groove 33 is provided on the Z1 side and the Z2 side, sandwiching the central axis OA therebetween.

[0033] The second inner groove 34 is a groove that engages with the second rolling element 42 and is provided to extend along the axial direction X (see FIG. 3). The cross-sectional shape of the second inner groove 34 is configured to be approximately half the cross-sectional shape of the second rolling element 42 (a substantially semicircular arc shape). As shown in FIG. 6A, the second inner groove 34 is provided on both the Y1 side and the Y2 side of the central axis OA.

[0034] The first inner groove portions 33 and the second inner groove portions 34 are provided at equal intervals (90° intervals in this example) around the central axis OA when the connecting member 30 is viewed from the axial direction X. As with the first inner groove portions 23 and the second inner groove portions 24 of the main shaft 21, the arrangement of the first inner groove portions 33 and the second inner groove portions 34 when viewed from the axial direction X is not limited to the arrangement described above.

[0035] When the rotating shaft 11 is inserted into the inner hole 31 of the connecting member 30 and the shaft hole 22 of the main shaft 21 while the connecting member 30 and the main shaft 21 are connected, two through holes 51 and two through holes 52 are formed along the outer periphery of the rotating shaft 11, as shown in FIG. 2B . The through holes 51 are cylindrical openings into which the first rolling elements 41 are inserted. The through holes 51 are formed by the first inner groove 23 of the main shaft 21, the first inner groove 33 of the connecting member 30, and the first outer groove 13 of the rotating shaft 11. The above-mentioned components are configured so that the through holes 51 have an inner diameter large enough to insert the first rolling elements 41.

[0036] The through hole 52 is a cylindrical opening into which the second rolling element 42 is inserted. The through hole 52 is formed by the second inner groove portion 24 of the main shaft 21, the second inner groove portion 34 of the connecting member 30, and the second outer groove portion 14 of the rotating shaft 11. These portions are configured so that the through hole 52 has an inner diameter that allows the second rolling element 42 to be inserted therein.

[0037] As shown in Fig. 3, coupling member 30 includes coupling protrusions 35 and coupling recesses 36. Coupling protrusions 35 are protrusions that fit into spindle recesses 25 of spindle 21 in the axial direction X. As shown in Fig. 6B, coupling protrusions 35 are provided on the Y1 and Y2 sides, with central axis OA sandwiched therebetween. Coupling recesses 36 are recesses that fit into spindle protrusions 26 of spindle 21 in the axial direction X. As shown in Fig. 6B, coupling recesses 36 are provided on the Z1 and Z2 sides, with central axis OA sandwiched therebetween.

[0038] 6B , the connecting protrusion 35 includes a threaded hole 37. The threaded hole 37 has a female thread that can be threadably engaged with a second set bolt (second pressing member / phase adjustment portion) 38. When the connecting member 30 is viewed from the axial direction X, the threaded holes 37 are provided on the Y1 side and the Y2 side, respectively. The threaded holes 37 open in directions parallel to each other with the central axis OA sandwiched therebetween.

[0039] The second set bolt 38 is a member for applying a preload to the second rolling element 42 disposed between the connecting member 30 and the rotating shaft 11. A male thread is formed on the outer circumferential surface of the second set bolt 38, which can be threaded into the female thread of the screw hole 37. With the main shaft 21 and the connecting member 30 fitted together, when the second set bolt 38 is threaded into the female thread of the screw hole 37 and turned in the fastening direction, the tip of the bolt protrudes from the connecting protrusion 35 and is pressed against the main shaft protrusion 26 of the main shaft 21.

[0040] When the bolt tip is pressed against the main shaft protrusion 26 of the main shaft 21, the main shaft 21 is pressed in the circumferential direction R in a direction away from the connecting member 30, changing the positional relationship between the main shaft 21 and the connecting member 30. As a result, a preload is applied to the second rolling elements 42 arranged between the connecting member 30 and the rotating shaft 11 in a clockwise direction (first direction) when viewed from the X2 side. The amount of preload applied to the second rolling elements 42 can be adjusted by the amount by which the bolt tip of the second set bolt 38 protrudes from the connecting protrusion 35. In other words, the amount of preload applied to the second rolling elements 42 can be adjusted by adjusting the positional relationship (phase) between the main shaft 21 and the connecting member 30 using the second set bolt 38.

[0041] The first rolling element 41 is a spherical member and is disposed between the first inner groove portion 23 of the main shaft 21 and the first outer groove portion 13 of the rotating shaft 11. The second rolling element 42 is a spherical member and is disposed between the second inner groove portion 34 of the connecting member 30 and the second outer groove portion 14 of the rotating shaft 11. In this embodiment, two first rolling elements 41 and two second rolling elements 42 are disposed. The first rolling elements 41 and the second rolling elements 42 are made of, for example, ceramic. In the following description, when there is no particular distinction between the first rolling elements 41 and the second rolling elements 42, they are also referred to as "rolling elements."

[0042] Next, a mechanism for connecting the rotating shaft 11 and the main shaft 21 by the shaft connecting mechanism according to the first embodiment will be described. Fig. 7 is a perspective view of the shaft connecting mechanism according to the first embodiment. Fig. 8 is a diagram illustrating the direction in which the main shaft 21 and the connecting member 30 are pressed against each other.

[0043] 7 , connecting member 30 can be connected to main shaft 21 by fitting connecting protrusion 35 of connecting member 30 into main shaft recess 25 of main shaft 21 in axial direction X and fitting connecting recess 36 of connecting member 30 into main shaft protrusion 26 of main shaft 21 in axial direction X. Rotating shaft 11 is inserted into inner hole 31 (see FIG. 6A ) and shaft hole 22 (see FIG. 5 ) that pass through main shaft 21 and connecting member 30 in the axial direction X.

[0044] The first rolling element 41 is inserted through the through hole 51 (see FIG. 2B ) and disposed at a position where the main shaft 21, the connecting member 30, and the rotating shaft 11 overlap in the axial direction X. The second rolling element 42 is inserted through the through hole 52 (see FIG. 2B ) and disposed at a position where the connecting member 30 and the rotating shaft 11 overlap in the axial direction X, just like the first rolling element 41. Each rolling element can be disposed at an appropriate position by, for example, inserting a long, thin rod-shaped tool (not shown) into one or both of the respective through holes. Note that the outer groove and the inner groove in which the rolling elements are disposed are not limited to shapes that penetrate along the axial direction X, and may have groove ends, as in a fifth embodiment described later.

[0045] As shown in Figure 7, with the rotating shaft 11 and the main shaft 21 connected by the connecting member 30, the first rolling body 41, and the second rolling body 42, preload can be applied to the first rolling body 41 and the second rolling body 42 by rotating the first set bolt 28 and the second set bolt 38 in the fastening direction.

[0046] 8, when the first set bolt 28 of the main shaft 21 is turned in the fastening direction, a preload is applied in the counterclockwise direction (second direction / arrow A) as viewed from the X2 side to the two first rolling elements 41 that engage with the first internal groove portion 23 of the main shaft 21. Furthermore, when the second set bolt 38 of the connecting member 30 is turned in the fastening direction, a preload is applied in the clockwise direction (first direction / arrow B) as viewed from the X2 side to the two second rolling elements 42 that engage with the second internal groove portion 34 of the connecting member 30.

[0047] In this way, when each set bolt is turned in the fastening direction, preload is applied to the two first rolling elements 41 in the counterclockwise direction in the axial direction X, and preload is applied to the two second rolling elements 42 in the clockwise direction. As a result, the same number of rolling elements are preloaded in opposite directions in the axial direction X, and the preload forces are balanced in the circumferential direction, thereby suppressing rattle between the main shaft 21 and the rotating shaft 11 in the rotational direction. Furthermore, when preload is applied to the first rolling elements 41 and the second rolling elements 42, the main shaft 21 and the rotating shaft 11 are movably connected. Therefore, even if the main shaft 21 is displaced so as to extend in the axial direction X due to the influence of heat, the relative positions of the main shaft 21 and the rotating shaft 11 change, thereby absorbing the elongation of the main shaft 21. Note that a similar effect can be obtained even if the rotating shaft 11 is displaced so as to extend in the axial direction X due to the influence of heat.

[0048] Furthermore, because the first rolling element 41 and the second rolling element 42 are movable in the axial direction X within the through holes 51 and 52, respectively, even if the main shaft 21 is displaced so as to extend in the axial direction X, they can move in the axial direction X by the amount of that extension. This prevents the rotating shaft 11 from being pressed in the axial direction X by the displaced main shaft 21. Even if the first rolling element 41 and the second rolling element 42 move in the axial direction X, the preload force applied to each rolling element does not change, so rattle in the rotational direction between the main shaft 21 and the rotating shaft 11 can be continuously prevented. Therefore, the shaft coupling mechanism according to the first embodiment can reliably transmit the power of the rotating shaft 11 to the main shaft 21 while being less susceptible to the displacement of the main shaft 21 in the axial direction X.

[0049] The shaft coupling mechanism according to the first embodiment includes the first set bolt 28 and the second set bolt 38 as phase adjusters that adjust the circumferential phase between the main shaft 21 and the coupling member 30. Therefore, in the shaft coupling mechanism according to the first embodiment, the amount of preload applied to the first rolling element 41 and the second rolling element 42 can be easily adjusted.

[0050] Second Embodiment A shaft coupling mechanism according to the second embodiment differs from the first embodiment in the configuration of the first rolling element 41 and the second rolling element 42. The other configurations of the shaft coupling mechanism according to the second embodiment are the same as those of the first embodiment. Therefore, in Fig. 9, only the shaft coupling mechanism is shown, and the electric motor 10 and the spindle unit 20 are not shown. Furthermore, in the explanation and drawings of the second embodiment, the same reference numerals as in the first embodiment are used for components and the like that are equivalent to those in the first embodiment, and redundant explanations will be omitted.

[0051] Fig. 9 is a perspective view of the shaft coupling mechanism according to the second embodiment. As shown in Fig. 9, in the shaft coupling mechanism according to the second embodiment, two each of the first rolling elements 41 and the second rolling elements 42 are arranged along the axial direction X. By arranging a plurality of the first rolling elements 41 and the second rolling elements 42 along the axial direction X in this manner, the power of the rotating shaft 11 can be more reliably transmitted to the main shaft 21. Note that the number of the first rolling elements 41 and the second rolling elements 42 arranged along the axial direction X is not limited to two, and may be three or more.

[0052] (Third Embodiment) The shaft coupling mechanism according to the third embodiment differs from the first embodiment in the shapes of the first rolling element 41 and the second rolling element 42. The other configurations of the shaft coupling mechanism according to the third embodiment are the same as those of the first embodiment. Therefore, in Fig. 10, only the shaft coupling mechanism is shown, and the electric motor 10 and the spindle unit 20 are not shown. Furthermore, in the explanation and drawings of the third embodiment, the same reference numerals as in the first embodiment are used for components and the like that are equivalent to those in the first embodiment, and redundant explanations will be omitted.

[0053] Fig. 10 is a perspective view of a shaft coupling mechanism according to the third embodiment. As shown in Fig. 10, in the shaft coupling mechanism according to the third embodiment, the first rolling element 41 and the second rolling element 42 are formed of cylindrical members. The outer groove portion of the rotating shaft 11 and the inner groove portions of the main shaft 21 and the coupling member 30 are configured to have a shape (substantially rectangular) that is approximately half the cross-sectional shape of the respective rolling elements taken along a plane parallel to the rotation axis CA.

[0054] 10, even when the first rolling element 41 and the second rolling element 42 are cylindrical, the same effect as that of the shaft coupling mechanism of the first embodiment can be obtained. In the configuration of the third embodiment, the first rolling element 41 and the second rolling element 42 need to be arranged so that the plane F perpendicular to their respective rotation axes CA is parallel to the central axis OA.

[0055] (Fourth embodiment) The shaft coupling mechanism according to the fourth embodiment differs from the first embodiment in the shapes of the first rolling element 41 and the second rolling element 42. The other configurations of the shaft coupling mechanism according to the fourth embodiment are the same as those of the first embodiment. Therefore, in Fig. 11, only the shaft coupling mechanism is shown, and the electric motor 10 and the spindle unit 20 are not shown. Furthermore, in the explanation and drawings of the fourth embodiment, the same reference numerals as in the first embodiment are used for the same components and the like, and redundant explanations will be omitted.

[0056] FIG. 11 is a perspective view of a shaft coupling mechanism according to a fourth embodiment. As shown in FIG. 11 , in the shaft coupling mechanism according to the fourth embodiment, the first rolling element 41 and the second rolling element 42 are barrel-shaped members. The outer groove of the rotating shaft 11 and the inner grooves of the main shaft 21 and the coupling member 30 are each configured to have a shape that is approximately half the cross-sectional shape parallel to the rotation axis CA of the rolling element. The term "barrel-shaped" refers to, for example, a shape in which two opposing long sides of a rectangle or one of two opposing sides of a square bulges outward in an arc-like shape. In this embodiment, the "barrel-shaped" shape is an example of a shape in which two opposing long sides of a rectangle bulge outward in an arc-like shape.

[0057] 11 , the shaft coupling mechanism of the fourth embodiment, in which the first rolling element 41 and the second rolling element 42 are barrel-shaped, can also achieve the same effects as the shaft coupling mechanism of the first embodiment. In the configuration of the fourth embodiment, the first rolling element 41 and the second rolling element 42 need to be arranged so that the plane F perpendicular to their respective rotation axes CA is parallel to the central axis OA.

[0058] Fifth Embodiment A shaft coupling mechanism according to the fifth embodiment differs from the first embodiment in the configuration of the outer groove portion provided on the rotating shaft 11 and the inner groove portion provided on the main shaft 21. The other configurations of the shaft coupling mechanism according to the fifth embodiment are the same as those of the first embodiment. Therefore, in the drawings described below, only the main parts of the shaft coupling mechanism are shown, and the electric motor 10 and the main shaft unit 20 are not shown. Furthermore, in the explanations and drawings of the fifth embodiment, members equivalent to those of the first embodiment are given the same reference numerals as those of the first embodiment, and redundant explanations will be omitted.

[0059] 12A and 12B are conceptual cross-sectional views showing the configuration of a shaft coupling mechanism according to the fifth embodiment. In Fig. 12A and Fig. 12B, the axial direction X of the rotation shaft 11 and the main shaft 21 is parallel to the direction of gravity (the same applies to Fig. 13A and Fig. 13B described later).

[0060] 12A and 12B, the coupling member 30 coupled to the main shaft 21 is omitted (the same applies to FIGS. 13A and 13B described later). Therefore, in the following description, "a state in which the rotating shaft 11 and the main shaft 21 are coupled" means "a state in which the rotating shaft 11, the main shaft 21, and the coupling member 30 (not shown) are coupled." Furthermore, in FIGS. 12A and 12B, of the outer groove portions and inner groove portions provided on the rotating shaft 11 and the main shaft 21, the first outer groove portion 13 and the first inner groove portion 23 provided on one radial side will be described as representatives (the same applies to FIGS. 13A and 13B described later).

[0061] 12A , in the configuration of the fifth embodiment, the first outer groove portion 13 of the rotating shaft 11 has groove end portions 131 at both ends in the axial direction X. The groove end portions 131 are portions that restrict movement of the first rolling element 41 to the X1 side and the X2 side in the axial direction X of the first outer groove portion 13.

[0062] In the configuration of the fifth embodiment, the first inner groove portion 23 of the main shaft 21 has a groove end portion 231 at the end on the X1 side in the axial direction. The groove end portion 231 is a portion that restricts movement of the first rolling element 41 toward the X1 side in the axial direction of the first inner groove portion 23.

[0063] 12A , when the rotating shaft 11 and the main shaft 21 are coupled, the end (groove end 231) of the first inner groove portion 23 on the X1 side in the axial direction is configured to be located further toward the X1 side than the end on the X1 side in the axial direction of the rotating shaft 11. On the X2 side in the axial direction of the first inner groove portion 23, the groove shape is provided all the way to the end.

[0064] In the above configuration, when the first rolling element 41 inserted between the first outer groove portion 13 and the first inner groove portion 23 is moved to the end on the X1 side in the axial direction using, for example, a long, thin rod-shaped tool or by its own weight, the first rolling element 41 hits the groove end portion 131 on the X1 side of the first outer groove portion 13 (rotating shaft 11) as shown in Fig. 12A, and movement toward the X1 side from that position is restricted. Therefore, with the rotating shaft 11 and the main shaft 21 coupled, the position of the first rolling element 41 can be determined to be the end on the X1 side.

[0065] When the first rolling element 41 is positioned at the end on the X1 side, if the rotating shaft 11 and the main shaft 21 are displaced and elongated in the axial direction X due to the influence of heat, the rotating shaft 11 will be displaced in the direction of arrow a1 (the axial direction X1), and the main shaft 21 will be displaced in the direction of arrow a2 (the axial direction X2), as shown in Figure 12B.

[0066] When the rotating shaft 11 and the main shaft 21 are displaced in the axial direction X so as to extend in opposite directions, a force acts on the first rolling element 41, moving it toward the X1 side in the axial direction relative to the main shaft 21. As a result, the first rolling element 41 rotates in the direction of arrow a3 (clockwise direction) as shown in Figure 12B. At this time, the outer circumferential surface of the first rolling element 41 does not abut against the edge of the groove end portion 131 in the rotational direction, and therefore, rotation is not restricted.

[0067] As a result, even if the rotating shaft 11 and the main shaft 21 are displaced and elongated in the axial direction X due to the influence of heat, the elongation can be absorbed by the rotation of the first rolling elements 41, and therefore, the problem of the rotating shaft 11 being pushed in the axial direction X by the rotating shaft 11 and the main shaft 21 displaced due to the influence of heat can be suppressed. The same effect can be obtained even if only the main shaft 21 is displaced and elongated in the axial direction X1 due to the influence of heat.

[0068] 13A and 13B are conceptual cross-sectional views showing another configuration different from the shaft coupling mechanism according to the fifth embodiment. As shown in FIG. 13A , in this configuration, the first outer groove portion 13 of the rotating shaft 11 has a groove end portion 131 at its end on the X2 side in the axial direction. The groove shape of the first outer groove portion 13 extends to the end on the X1 side in the axial direction. Furthermore, the first inner groove portion 23 of the main shaft 21 has a groove end portion 231 at its end on the X1 side in the axial direction.

[0069] 13A, the groove end 231 on the X1 side of the first inner groove portion 23 is configured to be located further toward the X2 side than the end on the X1 side in the axial direction of the rotating shaft 11 when the rotating shaft 11 and the main shaft 21 are coupled. On the X2 side in the axial direction of the first inner groove portion 23, the groove shape is provided all the way to the end.

[0070] In the above configuration, when the rotating shaft 11 and the main shaft 21 are displaced and elongated in the axial direction X due to the influence of heat, the rotating shaft 11 is displaced in the direction of arrow a1 (axial direction X1) as shown in Figure 13B, and the main shaft 21 is displaced in the direction of arrow a2 (axial direction X2).

[0071] When the rotating shaft 11 and the main shaft 21 are displaced in the axial direction X so as to extend in opposite directions, a force acts on the first rolling element 41, moving it toward the X1 side in the axial direction relative to the main shaft 21. As a result, the first rolling element 41 attempts to rotate in the direction of arrow a3 (clockwise direction), as shown in Figure 13A. However, in other configurations, the outer circumferential surface of the first rolling element 41 abuts against the edge of the groove end 231 in the rotational direction, thereby restricting rotation.

[0072] As a result, when the rotating shaft 11 and the main shaft 21 are displaced and elongated in the axial direction X due to the influence of heat, the elongation cannot be absorbed by the rotation of the first rolling elements 41. Therefore, it becomes difficult to prevent the problem that the rotating shaft 11 is pushed in the axial direction X by the rotating shaft 11 and the main shaft 21 displaced due to the influence of heat. The same applies when only the main shaft 21 is displaced and elongated in the axial direction X1 due to the influence of heat.

[0073] 12A, the shaft coupling mechanism of the fifth embodiment shown in FIG. 12A can reliably transmit the power of the rotating shaft 11 to the main shaft 21, while suppressing the problem of the rotating shaft 11 being pushed in the axial direction X by the rotating shaft 11 and main shaft 21 displaced due to the influence of heat. Furthermore, the shaft coupling mechanism of the fifth embodiment can determine the first rolling element 41 at a predetermined position in the axial direction X when the rotating shaft 11 and main shaft 21 are coupled together.

[0074] (Modifications) Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. In the following description, unless a distinction is made between the first to fourth embodiments, they will also be referred to as "embodiments."

[0075] In the embodiment, as shown in Fig. 2B, a configuration has been described in which two through holes 51 and two through holes 52 are provided along the outer periphery of the rotating shaft 11, but the present invention is not limited to this. Three or more through holes 51 and three or more through holes 52 may be provided along the outer periphery of the rotating shaft 11. Even in this case, it is desirable to have the same number of through holes 51 and 52 so that the preload forces are balanced in the circumferential direction.

[0076] The first rolling elements 41 and the second rolling elements 42 shown in the first, third, and fourth embodiments can also be used in appropriate combination. For example, in Fig. 2B, the cross-sectional shape of the through hole 52 may be rectangular, and a cylindrical second rolling element 42 (third embodiment) may be inserted into the through hole 52. In this configuration in which rolling elements of different shapes are combined, a configuration in which a plurality of each rolling element is arranged in the axial direction X, as in the second embodiment, may also be applied.

[0077] The following supplementary note is further disclosed regarding the above embodiment. (Supplementary note 1) A rotating shaft (11) includes a main shaft (21) having a hollow shaft hole (22) along the axial direction, a connecting member (30) having a hollow inner hole (31) along the axial direction and connected to the main shaft in the axial direction, a rotating shaft (11) having an outer shape that can be inserted into the shaft hole of the main shaft and the inner hole of the connecting member when the main shaft and the connecting member are connected in the axial direction, first rolling elements (41) arranged between the main shaft and the rotating shaft, and second rolling elements (42) arranged between the connecting member and the rotating shaft, wherein the main shaft has a first inner groove (23) on the inner peripheral surface of the shaft hole that can be engaged with the first rolling elements, and the connecting member has a second inner groove (34) on the inner peripheral surface of the inner hole that can be engaged with the second rolling elements. ), the rotating shaft has, on its outer peripheral surface, a first outer groove portion (13) engageable with the first rolling element and a second outer groove portion (14) engageable with the second rolling element, the main shaft and the connecting member are connected in the axial direction, and in a state where the rotating shaft is inserted into the shaft hole portion of the main shaft and the inner hole portion of the connecting member, the first rolling element is disposed between the second outer groove portion of the rotating shaft and the second inner groove portion of the main shaft, and the second rolling element is disposed between the first outer groove portion of the rotating shaft and the first inner groove portion of the connecting member, thereby making the rotating shaft and the main shaft movable in the axial direction, and power of the rotating shaft is transmitted to the rotating shaft via the first rolling element and the second rolling element. (Supplementary Note 2) The main shaft and the connecting member are connected in the axial direction, and a phase adjustment unit is provided that can adjust the circumferential phase between the main shaft and the connecting member when the rotating shaft is inserted into the shaft hole of the main shaft and the inner hole of the connecting member. (Supplementary Note 3) The main shaft has a recess (25) that opens toward the connecting member in the axial direction, and the connecting member has a protrusion (35) that protrudes toward the main shaft in the axial direction, and the phase adjustment unit includes a first pressing member (28) that presses the first rolling element in a first direction and a second pressing member (38) that presses the second rolling element in a second direction opposite to the first direction when the recess of the main shaft and the protrusion of the connecting member are fitted in the axial direction. (Supplementary Note 4) A plurality of the first rolling elements and the second rolling elements are arranged along the axial direction.(Supplementary Note 5) The first rolling element and the second rolling element may be spherical, cylindrical, or barrel-shaped.

[0078] 10: electric motor (rotating electric machine), 11: rotating shaft, 13: first outer groove portion, 14: second outer groove portion, 20: spindle unit, 21: spindle, 22: shaft hole portion, 23: first inner groove portion, 24: second inner groove portion, 25: spindle recess portion, 26: spindle protrusion portion, 28: first set bolt (first pressing member / phase adjustment portion), 30: connecting member, 31: inner hole portion, 33: first inner groove portion, 34: second inner groove portion, 35: connecting protrusion portion, 36: connecting recess portion, 38: second set bolt (second pressing member / phase adjustment portion)

Claims

1. A shaft comprising: a main shaft having a hollow shaft hole portion along the axial direction; a connecting member having a hollow inner hole portion along the axial direction and connected to the main shaft in the axial direction; a rotating shaft having an outer shape capable of being inserted into the shaft hole portion of the main shaft and the inner hole portion of the connecting member when the main shaft and the connecting member are connected in the axial direction; a first rolling element disposed between the main shaft and the rotating shaft; and a second rolling element disposed between the connecting member and the rotating shaft, wherein the main shaft has a first inner groove portion on the inner circumferential surface of the shaft hole portion that is engageable with the first rolling element, the connecting member has a second inner groove portion on the inner circumferential surface of the inner hole portion that is engageable with the second rolling element, and the rotating shaft has a first outer groove portion on the outer circumferential surface that is engageable with the first rolling element and a second outer groove portion on the outer circumferential surface that is engageable with the second rolling element, A shaft coupling mechanism in which the main shaft and the connecting member are axially connected, and the rotating shaft is inserted into the shaft hole portion of the main shaft and the inner hole portion of the connecting member, the first rolling element is disposed between the second outer groove portion of the rotating shaft and the second inner groove portion of the main shaft, and the second rolling element is disposed between the first outer groove portion of the rotating shaft and the first inner groove portion of the connecting member, thereby allowing the rotating shaft and the main shaft to move freely in the axial direction, and the power of the rotating shaft is transmitted to the rotating shaft via the first rolling element and the second rolling element.

2. A shaft coupling mechanism as set forth in claim 1, further comprising a phase adjustment section that is capable of adjusting the circumferential phase between said main shaft and said coupling member when said main shaft and said coupling member are axially coupled and said rotating shaft is inserted into said shaft hole section of said main shaft and said inner hole section of said coupling member.

3. A shaft connecting mechanism as set forth in claim 2, wherein the main shaft has a recess that opens toward the connecting member in the axial direction, the connecting member has a convex portion that protrudes toward the main shaft in the axial direction, and the phase adjustment portion has a first pressing member that presses the first rolling element in a first direction, and a second pressing member that presses the second rolling element in a second direction opposite to the first direction, when the recess of the main shaft and the convex portion of the connecting member are fitted in the axial direction.

4. A shaft coupling mechanism as claimed in any one of claims 1 to 3, wherein the first rolling body and the second rolling body are arranged in a plurality of parts along the axial direction.

5. A shaft coupling mechanism as set forth in any one of claims 1 to 4, wherein the first rolling element and the second rolling element are either spherical, cylindrical or barrel-shaped.