Rotors and Rotating Electric Machines

Abstract

To reduce shaft imbalance. [Solution] The rotor comprises a shaft having a first cylindrical surface with the axis of rotation as its central axis, a second cylindrical surface with the axis of rotation as its central axis and having a smaller diameter than the first cylindrical surface, and a third cylindrical surface with the axis of rotation as its central axis and having a smaller diameter than the second cylindrical surface, with a keyway formed at the end of the first cylindrical surface on the side of the second cylindrical surface and on the second cylindrical surface; a resolver rotor fitted into the second cylindrical surface and having a key housed in the keyway; and a ring fitted into the third cylindrical surface at a position in the direction of the axis of rotation that allows the resolver rotor to be pressed against the step between the first cylindrical surface and the second cylindrical surface.

Description

Technical Field

[0001] The present invention relates to a rotor and a rotating electrical machine.

Background Art

[0002] Rotating electrical machines such as motors and generators may include a resolver in order to detect the angle through which a rotor rotates. The resolver rotor is fixed to the shaft of the rotor of the rotating electrical machine. As a technique for fixing the resolver rotor to the shaft, for example, the technique disclosed in Patent Document 1 can be cited. This technique uses a fixing ring, a key groove formed in the rotating shaft, and a key formed in the resolver rotor to fix the resolver rotor to the rotating shaft.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described technique, only one key groove is formed in the rotating shaft. Further, the length of this key groove in the axial direction is longer than the sum of the thickness of the resolver rotor and the thickness of the fixing ring. Therefore, in the above-described technique, unbalance of the rotating shaft occurs. Unbalance of the rotating shaft may cause vibration, noise, breakage, etc. of the rotating electrical machine when the rotating shaft rotates.

[0005] Therefore, an object of the present invention is to provide a rotor and a rotating electrical machine capable of reducing the unbalance of the shaft.

Means for Solving the Problems

[0006] To solve the above-mentioned problems, the rotor of the present invention comprises a resolver rotor having a first cylindrical surface with the rotation axis as its central axis, a second cylindrical surface with the rotation axis as its central axis and having a smaller diameter than the first cylindrical surface, and a third cylindrical surface with the rotation axis as its central axis and having a smaller diameter than the second cylindrical surface, and a shaft having a key groove formed at the end of the first cylindrical surface on the side of the second cylindrical surface and on the second cylindrical surface, and a ring fitted into the second cylindrical surface and housed in the key groove, and a ring fitted into the third cylindrical surface at a position in the direction of the rotation axis that allows the resolver rotor to be pressed against the step between the first cylindrical surface and the second cylindrical surface.

[0007] In the rotor of the present invention, the ring has a protruding portion that, when fitted into the third cylindrical surface, protrudes toward the resolver rotor and is in contact with the resolver rotor.

[0008] In the rotor of the present invention, the ring is in contact with the resolver rotor over the entire circumference of the resolver rotor with the rotation axis as its central axis, at a position lower than the height of the outer surface of the resolver rotor with respect to the rotation axis.

[0009] The rotating electric machine of the present invention comprises one of the rotors described above. [Effects of the Invention]

[0010] According to the present invention, shaft imbalance can be reduced. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of a shaft related to the comparative example. [Figure 2] This is a cross-sectional view of a comparative example of a shaft, resolver rotor, and ring, taken from a plane passing through the center line of the keyway and the axis of rotation. [Figure 3] This figure shows an example of a shaft according to the embodiment. [Figure 4]This is a cross-sectional view taken from a plane passing through the center line and rotation axis of the keyway of the shaft, resolver rotor, and ring according to the embodiment. [Figure 5] This figure shows an example of a resolver rotor according to the embodiment. [Figure 6] This figure shows an example of a ring according to the embodiment. [Modes for carrying out the invention]

[0012] First, a comparative example of the present invention will be described with reference to Figures 1 and 2. In the description of the comparative example, the case in which the rotating electric machine is a motor will be used as an example. Furthermore, in the description of the comparative example, the X-axis, which is an axis parallel to the rotation axis A, the Y-axis, which is perpendicular to the X-axis, and the Z-axis, which is perpendicular to both the X-axis and the Y-axis will be used. In addition, the X-axis, Y-axis, and Z-axis form a right-handed system.

[0013] Figure 1 shows an example of a shaft according to the comparative example. Figure 2 is a cross-sectional view of the shaft, resolver rotor, and ring according to the comparative example, taken from a plane passing through the center line of the keyway and the axis of rotation. The rotor according to the comparative example comprises a shaft 100, a resolver rotor 300, and a ring 400.

[0014] The shaft 100 is inserted into the rotor and supports the rotor in a manner that allows it to rotate around the rotation axis A. As shown in Figures 1 and 2, the shaft 100 includes a cylindrical surface 101, a cylindrical surface 102, and a conical surface 105. The cylindrical surfaces 101, 102, and 105 all have the rotation axis A as their central axis. The cylindrical surface 102 has a smaller diameter than the cylindrical surface 101. The diameter of the conical surface 105 decreases towards the +X direction, and is smaller than the cylindrical surface 102 throughout the entire direction of the rotation axis A.

[0015] Furthermore, as shown in Figures 1 and 2, the shaft 100 has a keyway 200 formed on its cylindrical surface 102. The keyway 200 is symmetrical with respect to a plane that passes through the axis of rotation A and is parallel to the XY plane. Therefore, the keyway 200 is located on this plane and has a central axis that is a straight line parallel to the axis of rotation A. The end of the keyway 200 on the -X side is formed to accommodate the key 350 of the resolver rotor 300. The rest of the keyway 200 is formed to allow the key 350 of the resolver rotor 300 to pass through when the resolver rotor 300 is attached to the shaft 100.

[0016] The resolver rotor 300 is the rotor of the resolver for detecting the angle of rotation of the rotor supported by the shaft 100. By rotating together with the shaft 100 around axis A, the resolver rotor 300 changes the reactance of a coil attached to a resolver stator (not shown). This change in reactance is converted into an electrical signal for detecting the angle of rotation of the rotor attached to the shaft 100.

[0017] The resolver rotor 300 comprises an annular portion 310 and a key 350. The annular portion 310 is an annular member in which the height of the outer circumferential surface relative to the rotation axis A changes periodically in the direction of the rotation axis A. The annular portion 310 has an inner diameter approximately equal to the inner diameter of the cylindrical surface 102 and is fitted into the cylindrical surface 102. For example, the annular portion 310 is designed so that its inner diameter is within the fit tolerance range for the cylindrical surface 102 and is press-fitted into the cylindrical surface 102. The key 350 is integrally formed with the annular portion 310. The key 350 is housed at the -X direction end of the keyway 200, thereby fixing the position of the resolver rotor 300 relative to the shaft 100 around the rotation axis A. The resolver rotor 300 is manufactured by stacking and crimping plate-shaped members made of electromagnetic steel in the direction of the rotation axis A.

[0018] The ring 400 has an inner diameter approximately equal to the diameter of the cylindrical surface 102 and is fitted into the cylindrical surface 102. For example, the ring 400 is designed such that its inner diameter is within the range of the fitting tolerance with respect to the cylindrical surface 102 and is press-fitted into the cylindrical surface 102. However, the ring 400 does not adhere closely to the cylindrical surface 102 at the portion where the key groove 200 is formed. The ring 400 fixes the position of the resolver rotor 300 in the direction of the rotation axis A by pressing the resolver rotor 300 against the step between the cylindrical surface 101 and the cylindrical surface 102.

[0019] Since the key groove 200 is formed in the shaft 100 according to the comparative example, unbalance has occurred. Also, the length of the key groove 200 in the direction of the rotation axis A is longer than the sum of the dimension of the resolver rotor 300 in the direction of the rotation axis A and the dimension of the ring 400 in the direction of the rotation axis A. For this reason, the shaft 100 generates an unbalance that is larger than necessary. Therefore, when the rotation axis rotates, the shaft 100 may cause vibrations, noises, damages, etc. of the rotating electrical machine due to the unbalance.

[0020] The fixing force of the ring 400 according to the comparative example with respect to the cylindrical surface 102 becomes weaker by the amount that the ring 400 does not contact the cylindrical surface 102 at the portion where the key groove 200 is formed. To compensate for this, it is necessary to design the maximum value of the fitting tolerance of the inner diameter of the ring 400 to be small, and it is necessary to design the dimension in the direction of the rotation axis A to be a predetermined dimension or more. Therefore, the degree of freedom in designing the fitting tolerance of the inner diameter and the degree of freedom in designing the dimension in the direction of the rotation axis A of the ring 400 have become low.

[0021] The closer the outer diameter of the ring 400 is to the outer peripheral surface of the resolver rotor 300, the more it affects the reactance of the coil attached to the resolver stator, reducing the accuracy of detection by the resolver. Therefore, the ring 400 needs to be designed to have a thickness below a predetermined thickness so that its outer diameter is as far as possible from the outer peripheral surface of the resolver rotor 300. On the other hand, since the ring 400 is press-fitted into the cylindrical surface 102, it receives a force in the direction away from the rotation axis A in the direction perpendicular to the rotation axis A from the cylindrical surface 102. Also, the ring 400 receives a centrifugal force due to the rotation of the shaft 100. In order to withstand these forces, the ring 400 needs to be made of a material having a strength of a predetermined strength or more and needs to be designed to have a thickness of a predetermined thickness or more. Therefore, the ring 400 is restricted in the design of the mechanical properties of the material and the thickness. That is, the degree of freedom in the design of the strength of the ring 400 has become low.

[0022] Next, embodiments of the present invention will be described with reference to FIGS. 3 to 6. In the description of the embodiments, the case where the rotating electrical machine is a motor will be described as an example. Also, in the description of the embodiments, an X-axis that is an axis parallel to the rotation axis A, a Y-axis that is orthogonal to the X-axis, and a Z-axis that is orthogonal to the X-axis and the Y-axis are used. Also, the X-axis, Y-axis, and Z-axis form a right-handed system.

[0023] FIG. 3 is a diagram showing an example of a shaft according to an embodiment. FIG. 4 is a cross-sectional view taken along a plane passing through the center line of the key groove and the rotation axis of the shaft, resolver rotor, and ring according to the embodiment. FIG. 5 is a diagram showing an example of a ring according to the embodiment. FIG. 6 is a diagram showing an example of a resolver rotor according to the embodiment. The rotor according to the embodiment includes a shaft 10, a resolver rotor 30, and a ring 40.

[0024] The shaft 10 is inserted into the rotor and supports the rotor in a manner that allows it to rotate around the rotation axis A. As shown in Figures 3 and 4, the shaft 10 comprises a first cylindrical surface 11, a second cylindrical surface 12, a third cylindrical surface 13, and a conical surface 15. The first cylindrical surface 11, the second cylindrical surface 12, the third cylindrical surface 13, and the conical surface 15 all have the rotation axis A as their central axis. The second cylindrical surface 12 has a smaller diameter than the first cylindrical surface 11. The third cylindrical surface 13 has a smaller diameter than the second cylindrical surface 12. The diameter of the conical surface 15 decreases towards the +X direction, and across the entire direction of the rotation axis A, its diameter is smaller than that of the third cylindrical surface 13.

[0025] Furthermore, as shown in Figures 3 and 4, the shaft 10 has a keyway 20 formed on the end of the first cylindrical surface 11 that faces the second cylindrical surface 12, and on the second cylindrical surface 12. The keyway 20 is a groove that passes through the axis of rotation A and is symmetrical with respect to a plane parallel to the XY plane. Therefore, the keyway 20 is located on this plane and has a central axis that is a straight line parallel to the axis of rotation A. The keyway 20 is formed to house the key 35 of the resolver rotor 30.

[0026] The resolver rotor 30 is the rotor of a resolver used to detect the angle of rotation of a rotor supported by the shaft 10. By rotating together with the shaft 10 around the rotation axis A, the resolver rotor 30 changes the reactance of a coil attached to a resolver stator (not shown). This change in reactance is converted into an electrical signal for detecting the angle of rotation of the rotor attached to the shaft 10. The resolver rotor 30 is manufactured by stacking and crimping plate-shaped members made of electromagnetic steel in the direction of the rotation axis A. For example, eight circular recesses shown in Figure 5 are crimped.

[0027] The resolver rotor 30 comprises an annular portion 31 and a key 35. The annular portion 31 is an annular member in which the height of its outer circumferential surface, with respect to the rotation axis A, changes periodically in the direction of the rotation axis A. The annular portion 31 has an inner diameter approximately equal to the inner diameter of the second cylindrical surface 12 and is fitted into the second cylindrical surface 12. For example, the annular portion 31 is designed so that its inner diameter is within the fit tolerance range for the second cylindrical surface 12 and is press-fitted into the second cylindrical surface 12. Furthermore, the dimensions of the annular portion 31 in the direction of the rotation axis A are smaller than the dimensions of the second cylindrical surface 12 in the direction of the rotation axis A. The key 35 is integrally formed with the annular portion 31. The key 35 is housed in the keyway 20, thereby fixing the position of the resolver rotor 30 around the rotation axis A relative to the shaft 10.

[0028] The ring 40 comprises an annular portion 41 and a protruding portion 45. The annular portion 41 is an annular member. The annular portion 41 has an inner diameter approximately equal to the diameter of the third cylindrical surface 13 and is fitted into the third cylindrical surface 13. For example, the annular portion 41 is designed so that its inner diameter is within the fit tolerance range for the third cylindrical surface 13 and is press-fitted into the third cylindrical surface 13. The annular portion 41 is fitted in a position in the direction of the rotation axis on the third cylindrical surface 13 where the protruding portion 45 can press the resolver rotor 30 against the step between the first cylindrical surface 11 and the second cylindrical surface 12. Furthermore, since no keyway 20 is formed on the third cylindrical surface 13, the annular portion 41 is in contact with the third cylindrical surface 13 over its entire circumference with the rotation axis A as its central axis.

[0029] The projection 45 is an annular member that protrudes in the -X direction from the -X direction side surface of the annular portion 41. When the projection 45 is fitted into the third cylindrical surface 13, it protrudes toward the resolver rotor 30. Also, as shown in Figure 4, gaps D1 and D2 are provided between the shaft 10 and the ring 40. Therefore, regardless of dimensional errors of each part, the ring 40 can avoid interference with the shaft 10 and make the -X direction end of the projection 45 contact the resolver rotor 30. Furthermore, the projection 45 contacts the resolver rotor 30 at a position lower than the height of the outer circumferential surface of the resolver rotor 30 with respect to the rotation axis A, over the entire circumference of the resolver rotor 30 with the rotation axis A as its central axis. As a result, the projection 45 presses the resolver rotor 30 against the step between the first cylindrical surface 11 and the second cylindrical surface 12.

[0030] The rotor according to the embodiment has been described above. The rotor according to the embodiment comprises a shaft 10, a resolver rotor 30, and a ring 40. The shaft 10 comprises a first cylindrical surface 11, a second cylindrical surface 12, and a third cylindrical surface 13. The first cylindrical surface 11, the second cylindrical surface 12, and the third cylindrical surface 13 all have the rotation axis A as their central axis. The second cylindrical surface 12 has a smaller diameter than the first cylindrical surface 11. The third cylindrical surface 13 has a smaller diameter than the second cylindrical surface 12. In addition, the shaft 10 has a keyway 20 formed on the end of the first cylindrical surface 11 that faces the second cylindrical surface 12 and on the second cylindrical surface 12.

[0031] The resolver rotor 30 is fitted onto the second cylindrical surface 12 and has a key 35 housed in a keyway 20. In other words, the rotor according to this embodiment eliminates the portion of the keyway 200 in the comparative example that allows the key 350 to pass through, and forms only the keyway 20 in which the key 35 of this embodiment is housed on the shaft 10. The ring 40 is fitted onto the third cylindrical surface 13 at a position in the direction of the rotation axis A that allows the resolver rotor 30 to be pressed against the step between the first cylindrical surface 11 and the second cylindrical surface 12.

[0032] As a result, the rotor according to the embodiment can reduce the imbalance of the shaft 10 by eliminating the portion of the keyway 200 that allows the key 350 to pass through, as in the comparative example. Therefore, the rotor according to the embodiment can reduce motor vibration, noise, damage, etc., caused by imbalance when the shaft 10 rotates around the rotation axis A.

[0033] Furthermore, since the ring 40 does not have a keyway 20 formed on the third cylindrical surface 13, it is in contact with the third cylindrical surface 13 over its entire circumference with the rotation axis A as its central axis. As a result, it is easier to secure a fixing force for the ring 40 to the third cylindrical surface 13 than for the ring 400 in the comparative example. Therefore, the rotor according to the embodiment makes it possible to design the maximum fit tolerance of the inner diameter of the ring 40 to be larger than that of the ring 400 in the comparative example, and makes it possible to design the dimensions in the direction of the rotation axis A to be smaller than those of the ring 400 in the comparative example. In other words, the rotor according to the embodiment increases the degree of freedom in designing the fit tolerance of the inner diameter and the degree of freedom in designing the dimensions in the direction of the rotation axis A.

[0034] Furthermore, the ring 40 contacts the resolver rotor 30 at a position lower than the height of the outer surface of the resolver rotor 30 relative to the rotation axis A, over the entire circumference of the resolver rotor 30 with the rotation axis A as its central axis. As a result, the rotor according to this embodiment can reduce the possibility that the ring 40 will affect the reactance of the coil attached to the resolver stator, thereby reducing the accuracy of detection by the resolver.

[0035] Furthermore, the ring 40 is fitted onto a third cylindrical surface 13, which has a smaller diameter than the second cylindrical surface 12 fitted onto the resolver rotor 30. Therefore, the ring 40 can be designed to be thicker than the ring 400 fitted onto the cylindrical surface 102 together with the resolver rotor 300 in the comparative example. Consequently, the rotor according to the embodiment can increase the maximum design thickness of the ring 40 and reduce the required strength of the material of the ring 40. In other words, the rotor according to the embodiment increases the design freedom of both the thickness and strength of the ring 40.

[0036] Furthermore, the ring 40 is fitted onto a third cylindrical surface 13, which has a smaller diameter than the second cylindrical surface 12 fitted onto the resolver rotor 30. Therefore, even if the thickness of the ring 40 increases, it is easier to make its outer diameter smaller than the height of the outer circumference of the resolver stator relative to the rotation axis A. Consequently, the rotor according to this embodiment can reduce the possibility that the ring 40 will affect the reactance of the coil attached to the resolver stator, thereby reducing the accuracy of detection by the resolver.

[0037] Furthermore, the ring 40 has a projection 45 that protrudes toward the resolver rotor 30 and contacts the resolver rotor 30 when fitted into the third cylindrical surface 13. As a result, the rotor according to the embodiment can reliably press the resolver rotor 30 against the step between the first cylindrical surface 11 and the second cylindrical surface 12, and stabilize the position of the resolver rotor 30 in the direction of the rotation axis A. In addition, as a result, the rotor according to the embodiment can reliably press the resolver rotor 30 against the step between the first cylindrical surface 11 and the second cylindrical surface 12 even when the dimension of the resolver rotor 30 in the direction of the rotation axis A is smaller than the dimension of the second cylindrical surface 12 in the direction of the rotation axis A.

[0038] In the embodiments described above, the example given was that the rotating electric machine is a motor, but the invention is not limited to this. The shaft 10, resolver rotor 30, and ring 40 in the embodiment may be elements that constitute a generator instead of a motor, for example.

[0039] Furthermore, although the above-described embodiment was explained using the example of a case where the ring 40 has a projection 45 which is an annular member, the embodiment is not limited to this. The ring according to the embodiment may be, for example, a projection that protrudes from the -X direction side surface of the annular portion and is formed in multiple locations on the circumference of the annular portion.

[0040] Furthermore, although the above-described embodiment was explained using the case where the ring 40 has a protrusion 45 as an example, it is not limited to this. The ring according to the embodiment does not have a protrusion. In this case, the ring according to the embodiment has the -X direction side surface of the annular portion in contact with the resolver rotor 30, pressing the resolver rotor 30 against the step between the first cylindrical surface 11 and the second cylindrical surface 12.

[0041] Preferred embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments described above. That is, the present invention includes embodiments that have been modified, substituted, or redesigned in accordance with the spirit of the present invention, and these embodiments are not excluded. [Explanation of Symbols]

[0042] 10...Shaft, 11...First cylindrical surface, 12...Second cylindrical surface, 13...Third cylindrical surface, 15...Conical surface, 20...Keyway, 30...Resolver rotor, 31...Annular section, 35...Key, 40...Ring, 41...Annular section, 45...Protrusion, A...Rotation axis

Claims

1. A shaft having a first cylindrical surface with the axis of rotation as its central axis, a second cylindrical surface with the axis of rotation as its central axis and having a smaller diameter than the first cylindrical surface, and a third cylindrical surface with the axis of rotation as its central axis and having a smaller diameter than the second cylindrical surface, wherein a keyway is formed on the end of the first cylindrical surface on the side of the second cylindrical surface and on the second cylindrical surface, A resolver rotor having a key fitted into the second cylindrical surface and housed in the keyway, A ring fitted into the third cylindrical surface at a position in the direction of the rotation axis that allows the resolver rotor to be pressed against the step between the first cylindrical surface and the second cylindrical surface, A rotor equipped with a rotor.

2. The ring, when fitted onto the third cylindrical surface, has a protruding portion that extends toward the resolver rotor and contacts the resolver rotor. The rotor according to claim 1.

3. The ring is in contact with the resolver rotor at a position lower than the height of the outer surface of the resolver rotor relative to the rotation axis, over the entire circumference of the resolver rotor with the rotation axis as its central axis. The rotor according to claim 1.

4. A rotating electric machine comprising a rotor according to any one of claims 1 to 3.

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