Motor rotor, method for manufacturing a motor rotor, motor, and electric supercharger

Abstract

This rotor comprises: an inner sleeve that includes a holding part for holding a shaft which has a rotation axis and a first gap part including a portion which does not contact the shaft; a magnet that has a cylindrical shape provided with a magnet through hole into which the inner sleeve is inserted, the inner sleeve being disposed in magnet through hole; and a first end ring that has an end ring through hole into which the inner sleeve is press fitted. The holding part and the first gap part are each provided with respective through hole parts which insert into each other and in which the shaft is disposed. The inner diameter of the through hole part provided in the first gap part is greater than the inner diameter of the through hole part provided in the holding part. The first end ring is disposed in the first gap part.

Description

Technical Field

[0001] The present disclosure relates to a motor rotor, a method for manufacturing a motor rotor, a motor, and an electric supercharger.

Background Art

[0002] An electric supercharger rotates an impeller by a motor. The motor includes a rotor and a stator. When the rotor rotates, the impeller rotates. Patent Documents 1 and 2 disclose techniques related to the rotor included in the motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] As the performance required for the motor increases, improvement in the rotational balance of the rotor included in the motor is desired. The rotational balance of the rotor is affected by the accuracy of the shape of the components constituting the rotor and the accuracy of the assembly of the components. On the other hand, when improving the accuracy of the shape and the accuracy of the assembly, the number of steps required for processing and assembly increases.

[0005] The present disclosure describes a motor rotor and a method for manufacturing a motor rotor that can reduce the number of steps required for manufacturing the rotor. Further, the present disclosure describes a motor and an electric supercharger including the above motor rotor.

Means for Solving the Problems

[0006] A motor rotor in one embodiment of the present disclosure comprises an inner sleeve including a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not contact the outer surface of the shaft; a cylindrical magnet having a magnet through-hole into which the inner sleeve is inserted, with the inner sleeve positioned in the magnet through-hole; and an end ring including an end ring through-hole into which the inner sleeve is positioned and an end ring end face facing the end face of the magnet, with the inner sleeve press-fitted into the end ring through-hole. The holding portion and the gap portion are each provided with through-holes through which the shaft is inserted and through which the shaft is positioned. The inner diameter of the through-hole provided in the gap portion is larger than the inner diameter of the through-hole provided in the holding portion. The end ring is positioned in the gap portion. [Effects of the Invention]

[0007] This disclosure describes a motor rotor and a method for manufacturing a motor rotor that can reduce the number of steps required to manufacture the rotor. Furthermore, this disclosure describes a motor and an electric supercharger equipped with the above-mentioned motor rotor. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of an electric supercharger equipped with a rotor according to an embodiment. [Figure 2] Figure 2 is a perspective view showing the structure of the rotor in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the inner sleeve that makes up the rotor in Figure 2. [Figure 4] Figure 4 is a cross-sectional view showing a magnified view of the bump. [Figure 5] Figure 5 is a flow chart showing the manufacturing method of the rotor according to the embodiment. [Figure 6] Figure 6(a) illustrates the process of preparing the inner sleeve. Figure 6(b) illustrates the process of placing the end ring and magnet in the inner sleeve. [Figure 7]Figure 7(a) illustrates the process of grinding the outer surface of the end ring and the outer surface of the magnet. Figure 7(b) illustrates the process of press-fitting the armor ring. [Figure 8] Figure 8(a) illustrates the process of grinding the end face of the inner sleeve. Figure 8(b) illustrates the process of inserting the shaft. [Figure 9] Figure 9(a) is a diagram illustrating the process of preparing the inner sleeve in a comparative example. Figure 9(b) is a diagram illustrating the process of placing the end ring and magnet in the inner sleeve in a comparative example. [Figure 10] Figure 10(a) illustrates the process of a comparative example in which the outer surface of the end ring and the outer surface of the magnet are ground. Figure 10(b) illustrates the process of a comparative example in which the armor ring is press-fitted. [Figure 11] Figure 11(a) shows the process of a comparative example in which the outer surface of the armor ring is ground. Figure 11(b) shows the process of a comparative example in which the end face of the inner sleeve is ground and the bumps are removed. [Figure 12] Figure 12 is a diagram illustrating the process of inserting the shaft in a comparative example. [Modes for carrying out the invention]

[0009] A motor rotor in one embodiment of the present disclosure comprises an inner sleeve including a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not contact the outer surface of the shaft; a cylindrical magnet having a magnet through-hole into which the inner sleeve is inserted, with the inner sleeve positioned in the magnet through-hole; and an end ring including an end ring through-hole into which the inner sleeve is positioned and an end ring end face facing the end face of the magnet, with the inner sleeve press-fitted into the end ring through-hole. The holding portion and the gap portion are each provided with through-holes through which the shaft is inserted and through which the shaft is positioned. The inner diameter of the through-hole provided in the gap portion is larger than the inner diameter of the through-hole provided in the holding portion. The end ring is positioned in the gap portion.

[0010] The end ring is press-fitted into the inner sleeve. The press-fitted inner sleeve deforms slightly so that the inner diameter of the hole becomes smaller. The end ring is positioned in the gap of the inner sleeve. The gap includes a portion that does not contact the outer surface of the shaft. The inner diameter of the gap is larger than the inner diameter of the retaining portion that holds the shaft. As a result, when the press-fitting of the end ring deforms the through hole in which the shaft is positioned to a smaller diameter, the deformed portion is prevented from protruding further inward than the inner surface of the retaining portion. The deformed portion does not contact the outer surface of the shaft. Therefore, deformation caused by the press-fitting of the end ring can be tolerated. Furthermore, the shaft can be held by the retaining portion as intended in the design. A motor rotor in one embodiment of this disclosure does not require a process to remove the deformed portion. Therefore, the number of processes required to manufacture the rotor can be reduced.

[0011] The motor rotor described above may further include an armor ring that covers the outer surface of the magnet and the outer surface of the end ring. The armor ring protects the magnet. As a result, the permissible rotational speed can be increased.

[0012] The end face of the armor ring of the motor rotor described above may protrude further in the direction of the rotation axis than the end face of the end ring. With this configuration, a portion of the protruding part of the end face of the armor ring is machined away. As a result, the rotational balance of the motor rotor can be improved. Therefore, the allowable rotational speed can be increased.

[0013] The inner sleeve of the motor rotor described above may have a sleeve body including a magnet mounting surface where magnets are placed and an end ring mounting surface where end rings are placed, and a sleeve flange including a abutment surface facing the end face of the end ring. The end ring placed in the sleeve body abuts against the abutment surface of the sleeve flange. Therefore, the position of the end ring and the position of the magnet can be easily positioned along the rotation axis.

[0014] The outer peripheral surface of the sleeve flange of the motor rotor described above may be a cylindrical surface. The outer diameter of the sleeve flange may be smaller than the outer diameter of the magnet. According to this configuration, leakage of the magnetic path generated by the magnet can be reduced.

[0015] The outer peripheral surface of the holding portion of the motor rotor described above may include the magnet placement surface. Even with this configuration, deformation caused by press-fitting of the end ring can be well tolerated.

[0016] The outer peripheral surface of the motor rotor gap portion described above may include the magnet placement surface, the end ring placement surface, and the outer peripheral surface of the sleeve flange. Even with this configuration, deformation caused by press-fitting of the end ring can be well tolerated.

[0017] In the motor rotor described above, the thickness from the inner peripheral surface of the through-hole portion provided in the holding portion to the magnet placement surface may be larger than the thickness from the inner peripheral surface of the through-hole portion provided in the gap portion to the magnet placement surface. Even with this configuration, deformation caused by press-fitting of the end ring can be well tolerated.

[0018] In the motor rotor described above, the thickness from the inner peripheral surface of the through-hole portion provided in the sleeve flange and communicating with the through-hole portion of the gap portion to the outer peripheral surface of the sleeve flange may be larger than the thickness from the inner peripheral surface of the through-hole portion provided in the holding portion to the magnet placement surface. The outer peripheral surface of the sleeve flange may be constituted by a part of the outer peripheral surface of the gap portion. Even with this configuration, deformation caused by press-fitting of the end ring can be well tolerated.

[0019] The material of the inner sleeve of the motor rotor described above may be a non-magnetic material.

[0020] Another embodiment of the present disclosure is a method for manufacturing a rotor, comprising the steps of: preparing an inner sleeve including a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not contact the outer surface of the shaft; arranging a cylindrical magnet, which has a magnet through-hole into which the inner sleeve is inserted, into the inner sleeve; and press-fitting an end ring into the inner sleeve, which includes an end ring through-hole into which the inner sleeve is placed and an end ring end face facing the end face of the magnet. In the step of arranging the magnet into the inner sleeve, the magnet is placed in the holding portion. In the step of press-fitting the end ring into the inner sleeve, the end ring is placed in the gap portion.

[0021] According to this motor rotor manufacturing method, there is no need to remove the deformed portion caused by the press-fitting of the end ring. Therefore, the number of steps required for rotor manufacturing can be reduced.

[0022] The above manufacturing method may further include, after the steps of arranging the magnet in the inner sleeve and press-fitting the end ring into the inner sleeve, a step of arranging an armor ring to cover the outer circumferential surface of the magnet and the outer circumferential surface of the end ring. This step makes it possible to manufacture a motor rotor that can increase the allowable rotational speed.

[0023] The above manufacturing method may further include a step of grinding the end face of the inner sleeve after the steps of arranging the magnet in the inner sleeve and press-fitting the end ring into the inner sleeve. This step eliminates deformation of the end face of the inner sleeve caused by press-fitting the end ring. Therefore, a decrease in the accuracy of the shape of the components constituting the rotor can be suppressed.

[0024] A motor in yet another form of this disclosure comprises the motor rotor described above and a stator including coils arranged to surround the motor rotor. Because the motor has the motor rotor described above, the number of manufacturing steps can be reduced. As a result, the manufacturing cost of the motor can be reduced.

[0025] An electric supercharger in yet another form of the present disclosure comprises a motor having a motor rotor and a stator including coils arranged to surround the motor rotor, and an impeller driven by the motor. Because this electric supercharger has the motor rotor described above, the number of manufacturing steps can be reduced. As a result, the manufacturing cost of the electric supercharger can be reduced.

[0026] The motor rotor, the method for manufacturing the motor rotor, the motor, and the electric supercharger of this disclosure will be described in detail below with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0027] Figure 1 shows an electric supercharger 1 with a motor rotor according to an embodiment. In the following description, the motor rotor will be simply referred to as "rotor 4". The electric supercharger 1 is applied, for example, to an internal combustion engine in a vehicle or a ship. The electric supercharger 1 has a compressor 2. The electric supercharger 1 has an embedded permanent magnet type motor 3. The motor 3 has a rotor 4 and a stator 5. The motor 3 generates torque through the interaction of the rotor 4 and the stator 5. The torque is transmitted to the compressor 2 via a shaft 6 to which the rotor 4 is attached. When the compressor 2 is driven by the torque, a fluid such as air is compressed. As a result, the compressor 2 discharges compressed air.

[0028] The electric supercharger 1 comprises a shaft 6 and an impeller 7. The shaft 6 is rotatably mounted relative to the housing 9. The shaft 6 is mounted in the housing 9. The shaft 6 is supported at both ends by two bearings 11. The bearings 11 are press-fitted onto the shaft 6. The bearings 11 rotatably support the shaft 6 relative to the housing 9. The bearings 11 are located near the tip and near the base of the shaft 6, respectively. The bearings 11 support the shaft 6 from both sides. The bearings 11 are, for example, grease-lubricated radial ball bearings. The bearings 11 may be deep groove ball bearings. The bearings 11 may be angular contact ball bearings. The shaft 6 rotates around a linear axis of rotation A. The impeller 7 is mounted on the tip of the shaft 6.

[0029] The housing 9 comprises a compressor housing 91, a motor housing 92, and a base housing 93. The compressor housing 91 houses the impeller 7. The compressor housing 91 includes an intake port 91a, a scroll passage 91b, and a discharge port 91c. The motor housing 92 houses the rotor 4 and the stator 5. The base housing 93 closes the opening on the other end (right side in the figure) of the motor housing 92.

[0030] The rotor 4 is fixed to the axial center of the shaft 6. The rotor 4 includes one or more magnets 41. The stator 5 includes a coil 51 to which alternating current is supplied. The coil 51 is arranged to surround the rotor 4.

[0031] When alternating current is supplied to the stator 5, interaction occurs between the rotor 4 and the stator 5. This interaction causes the shaft 6 and the impeller 7 to rotate together. As the impeller 7 rotates, it draws in outside air through the intake port 91a. The drawn-in air is compressed and then discharged from the outlet port 91c. The compressed air discharged from the outlet port 91c is supplied, for example, to an internal combustion engine.

[0032] The rotor 4 of this embodiment will now be described in detail. The rotor 4 works in cooperation with the stator 5 to form a rotating field type synchronous motor (Surface Permanent magnet motor: SPM motor).

[0033] Figure 2 is a perspective view of the rotor 4. The rotor 4 has as its main components a magnet 41, an inner sleeve 42, a first end ring 43, a second end ring 44, and an armor ring 45.

[0034] The shape of the magnet 41 is cylindrical. For example, the magnet 41 may be a neodymium magnet or a samarium-cobalt magnet. The magnet 41 has a magnet through-hole 41H. An inner sleeve 42 is placed in the magnet through-hole 41H. The magnet 41 has an inner circumferential surface 41a, an outer circumferential surface 41b, a first magnet end face 41c, and a second magnet end face 41d.

[0035] The inner circumferential surface 41a of the magnet defines the magnet through-hole 41H. The inner circumferential surface 41a of the magnet is fixed to the outer circumferential surface of the inner sleeve 42. For example, the inner circumferential surface 41a of the magnet is bonded to the outer circumferential surface of the inner sleeve 42. The outer circumferential surface 41b of the magnet is fixed to the armor ring 45. For example, the outer circumferential surface 41b of the magnet is bonded to the armor ring 45. The first magnet end face 41c faces the first end ring 43. The first magnet end face 41c may be fixed to the first end ring 43. The first magnet end face 41c may simply be in contact with the first end ring 43. The second magnet end face 41d faces the second end ring 44. Similar to the first magnet end face 41c, the second magnet end face 41d may be fixed to the second end ring 44. The second magnet end face 41d may simply be in contact with the second end ring 44.

[0036] The shape of the first end ring 43 is a disc. The first end ring 43 is made of a non-magnetic material. For example, the first end ring 43 may be made of a titanium alloy. The outer diameter of the first end ring 43 is approximately the same as the outer diameter of the magnet 41. The inner diameter of the first end ring 43 is approximately the same as the inner diameter of the magnet 41. The inner diameter of the first end ring 43 does not exactly match the inner diameter of the magnet 41. The length of the first end ring 43 along the axis of rotation A is shorter than the length of the magnet 41 along the axis of rotation A.

[0037] The first end ring 43 has an end ring through hole 43H. An inner sleeve 42 is positioned in the end ring through hole 43H. The relationship between the inner diameter of the end ring through hole 43H and the outer diameter of the sleeve body 421 of the inner sleeve 42 is a so-called interference fit. The first end ring 43 has an inner circumferential surface 43a, an outer circumferential surface 43b, an outer end ring end face 43c, and an inner end ring end face 43d.

[0038] The inner circumferential surface 43a of the end ring defines the end ring through hole 43H. The inner circumferential surface 43a of the end ring is fixed to the outer circumferential surface of the inner sleeve 42. Unlike the magnet 41, the inner circumferential surface 43a of the end ring is pressed against the outer circumferential surface of the inner sleeve 42.

[0039] The outer circumferential surface 43b of the end ring is fixed to the armor ring 45. For example, the outer circumferential surface 43b of the end ring is pressed against the armor ring 45. The inner end ring end face 43d faces the first magnet end face 41c. The outer end ring end face 43c includes a facing region 43c1 and an exposed region 43c2. The facing region 43c1 faces the sleeve flange 422 of the inner sleeve 42. The exposed region 43c2 is exposed from the sleeve flange 422 without facing the sleeve flange 422. The area of ​​the facing region 43c1 is smaller than the area of ​​the exposed region 43c2. With this configuration, it is possible to suppress the bias of the magnetic path caused by the magnet 41 due to the sleeve flange 422. The state of the magnetic path can be set to the intended state.

[0040] The shapes of the opposing region 43c1 and the exposed region 43c2 are both annular. The opposing region 43c1 is located inside the exposed region 43c2. The outer edge of the opposing region 43c1 is the inner edge of the exposed region 43c2. The inner edge of the opposing region 43c1 is the outer edge of the end ring through hole 43H. The outer edge of the exposed region 43c2 is the outer edge of the first end ring 43.

[0041] The shape of the second end ring 44 is the same as the shape of the first end ring 43. The second end ring 44 has an end ring through hole 44H. The second end ring 44 has an inner circumferential surface 44a, an outer circumferential surface 44b, an outer end ring face 44c, and an inner end ring face 44d. The second end ring 44 does not abut against the sleeve flange 422. Therefore, unlike the outer end ring face 43c of the first end ring 43, the outer end ring face 44c of the second end ring 44 is entirely exposed. The second end ring 44 faces the second magnet end face 41d of the magnet 41. The magnet 41 is sandwiched between the first end ring 43 and the second end ring 44 along the direction of the rotation axis A. Regarding the second end ring 44, the explanation of the parts common to the first end ring 43 is omitted.

[0042] The shape of the armor ring 45 is a thin-walled cylinder. The armor ring 45 protects the magnet 41. As a result, the permissible rotational speed of the rotor 4 can be increased. The armor ring 45 also contributes to the transmission of torque generated by the magnet 41 and the coil 51. The armor ring 45 is formed from a non-magnetic material. For example, the armor ring 45 may be formed from a titanium alloy.

[0043] The armor ring 45 has an armor ring through hole 45H. The inner sleeve 42, the magnet 41, the first end ring 43, and the second end ring 44 are arranged in the armor ring through hole 45H. The armor ring 45 has an inner circumferential surface 45a, an outer circumferential surface 45b, a first end face 45c, and a second end face 45d.

[0044] The inner circumferential surface 45a of the armor ring defines the armor ring through hole 45H. The inner circumferential surface 45a of the armor ring faces the outer circumferential surface 41b of the magnet, the outer circumferential surface 43b of the end ring 43, and the outer circumferential surface 44b of the end ring 44. The inner circumferential surface 45a of the armor ring is fixed to the outer circumferential surface 41b of the magnet by adhesive or the like. The inner circumferential surface 45a of the armor ring is pressed against the outer circumferential surfaces 43b and 44b of the end rings. The outer circumferential surface 45b of the armor ring forms the outer circumferential surface of the rotor 4. The end face 45c of the first armor ring protrudes in the direction of the rotation axis A more than the outer end face 43c of the first end ring 43. The armor ring 45 includes a portion 45a1 that does not surround the first end ring 43. The portion 45a1 that does not surround the first end ring 43 faces the outer circumferential surface of the sleeve flange 422. With this configuration, the rotational balance of the rotor 4 can be improved by machining a portion of the protruding part of the end face of the armor ring 45. In other words, the rotational balance of the motor rotor can be improved by machining a portion of the portion 45a1 of the end face of the armor ring 45 that does not surround the first end ring 43. As a result, the allowable rotational speed can be increased.

[0045] The end face 45d of the second armor ring protrudes in the direction of the rotation axis A more than the outer end ring end face 44c of the second end ring 44. The armor ring 45 includes a portion 45a2 that does not surround the second end ring 44. The portion 45a2 that does not surround the second end ring 44 faces the outer circumferential surface of the sleeve body 421 of the inner sleeve 42. This configuration also allows for improving the rotational balance of the rotor 4 by machining a portion of the protruding part of the end face of the armor ring 45. In other words, the rotational balance of the motor rotor can be improved by machining a portion of the portion 45a2 of the end face of the armor ring 45 that does not surround the second end ring 44. As a result, the allowable rotational speed can be increased.

[0046] The inner sleeve 42 includes a cylindrical portion having a first outer diameter and a cylindrical portion having a second outer diameter larger than the first outer diameter. The cylindrical portion having the first outer diameter is the sleeve body 421. The cylindrical portion having the second outer diameter is the sleeve flange 422. The magnet 41, the first end ring 43, and the second end ring 44 are arranged in the sleeve body 421. The first end ring 43 abuts against the sleeve flange 422. The inner sleeve 42 has a sleeve through hole 42H. The sleeve through hole 42H penetrates the sleeve body 421 and the sleeve flange 422. The shaft 6 is arranged in the sleeve through hole 42H.

[0047] The inner sleeve 42 will be described in more detail with reference to Figure 3. The inner sleeve 42 may be made of iron-based structural alloy steel. For example, the inner sleeve 42 may be made of chromium-molybdenum steel (SCM435). The inner sleeve 42 may be made of a relatively lightweight material. The inner sleeve 42 may be made of a non-magnetic material. Examples of such materials include titanium alloys and ceramic materials.

[0048] The inner sleeve 42 has a first sleeve end face 42c and a second sleeve end face 42d. The first sleeve end face 42c is the end face of the sleeve flange 422. The second sleeve end face 42d is the end face of the sleeve body 421.

[0049] The inner sleeve 42 has a main body outer surface 421s, a flange outer surface 422s, and a flange abutment surface 42s.

[0050] The outer circumferential surface 421s of the main body is arranged on the magnet 41, the first end ring 43, and the second end ring 44. More specifically, the outer circumferential surface 421s of the main body includes a magnet arrangement surface 421a on which the magnet 41 is arranged, a first end ring arrangement surface 421b on which the first end ring 43 is arranged, and a second end ring arrangement surface 421c on which the second end ring 44 is arranged. The length of the sleeve body 421 along the axis of rotation A is longer than the combined length of the magnet 41, the first end ring 43, and the second end ring 44 along the axis of rotation A. Therefore, the outer circumferential surface 421s of the main body further includes exposed portions on which the magnet 41, the first end ring 43, and the second end ring 44 are not arranged. The exposed portion further includes a portion 421d facing the armor ring 45 and a portion 421e that protrudes from the second armor ring end face 45d of the armor ring 45 and does not face the armor ring 45.

[0051] The magnet 41, the first end ring 43, and the second end ring 44 are not positioned on the outer circumferential surface 422s of the flange. The outer circumferential surface 422s of the flange includes a surface 422d facing the armor ring 45 and a surface 422e not facing the armor ring 45. The surface 422e that does not face the armor ring 45 protrudes from the first armor ring end face 45c of the armor ring 45.

[0052] The flange abutment surface 42s is the end face of the sleeve flange 422. The flange abutment surface 42s is created by the difference between the outer diameter of the sleeve body 421 and the outer diameter of the sleeve flange 422. The flange abutment surface 42s faces the direction of the rotation axis A. In other words, the flange abutment surface 42s extends in a direction perpendicular to the rotation axis A. As a result, the flange abutment surface 42s faces the first end ring 43. The flange abutment surface 42s may simply be in contact with the first end ring 43. The flange abutment surface 42s may also be actively fixed to the first end ring 43 by adhesive or the like. In short, the first end ring 43, positioned on the sleeve body 421, abuts against the flange abutment surface 42s of the sleeve flange 422. Therefore, the position of the first end ring 43 and the position of the magnet 41 along the rotation axis A can be easily positioned.

[0053] The inner sleeve 42 has two parts that are distinct from their function with respect to the shaft 6. The inner sleeve 42 has a retaining portion 423, a first gap portion 425, and a second gap portion 426. The retaining portion 423 holds the shaft 6. In other words, the retaining portion 423 is fixed to the shaft 6. The retaining portion 423 contributes to the transmission of torque from the inner sleeve 42 to the shaft 6. The first gap portion 425 and the second gap portion 426 do not hold the shaft 6. In other words, the first gap portion 425 and the second gap portion 426 are not fixed to the shaft 6. The first gap portion 425 and the second gap portion 426 do not contribute to the transmission of torque from the inner sleeve 42 to the shaft 6.

[0054] The retaining portion 423 is located approximately in the center of the inner sleeve 42 along the direction of the rotation axis A. The first gap 425 and the second gap 426 are located along the direction of the rotation axis A, sandwiching the retaining portion 423. The first gap 425 is located on the side of the sleeve flange 422. The second gap 426 is located on the side of the second sleeve end face 42d.

[0055] We will focus on the relationship between the holding portion 423, the first gap portion 425, and the second gap portion 426, and the outer circumferential surface 421s of the main body and the outer circumferential surface 422s of the flange.

[0056] The magnet placement surface 421a includes the entire outer circumferential surface 423a of the holding portion 423. The magnet placement surface 421a includes a portion 425a of the outer circumferential surface of the first gap portion 425 and a portion 426a of the outer circumferential surface of the second gap portion 426. As a result, the magnet 41 is arranged across the first gap portion 425, the holding portion 423, and the second gap portion 426.

[0057] The first end ring placement surface 421b is formed by a portion 425b of the outer circumferential surface of the first gap 425. The first end ring 43 is placed in the first gap 425. The second end ring placement surface 421c is formed by a portion 426b of the outer circumferential surface of the second gap 426. The second end ring 44 is placed in the second gap 426.

[0058] On the outer circumferential surface 421s of the main body, the portion 421d facing the armor ring 45 and the portion 421e not facing the armor ring 45 are formed by a part 426c of the outer circumferential surface of the second gap 426. On the outer circumferential surface 422s of the flange, the surface 422d facing the inner circumferential surface 45a of the armor ring and the surface 422e not facing the inner circumferential surface 45a of the armor ring are formed by a part 425c of the first gap 425.

[0059] The holding portion 423, the first gap portion 425, and the second gap portion 426 are provided with through holes 423H, 425H, and 426H, respectively. The through holes 423H, 425H, and 426H are coaxial. The through holes 423H, 425H, and 426H constitute a single sleeve through hole 42H extending from the first sleeve end face 42c to the second sleeve end face 42d. The inner diameter D423 of the through hole 423H in the holding portion 423 is approximately the same as or slightly smaller than the outer diameter of the shaft 6. The inner diameter D425 of the through hole 425H in the first gap portion 425 is clearly larger than the outer diameter of the shaft 6. The inner diameter D426 of the through hole 426H in the second gap portion 426 is also clearly larger than the outer diameter of the shaft 6. The inner diameter D425 of the through-hole 425H of the first gap 425 is larger than the inner diameter D423 of the through-hole 423H of the holding portion 423. The inner diameter D426 of the through-hole 426H of the second gap 426 is also larger than the inner diameter D423 of the through-hole 423H of the holding portion 423. The inner diameter D425 of the through-hole 425H of the first gap 425 is the same as the inner diameter D426 of the through-hole 426H of the second gap 426. However, the inner diameter D425 of the through-hole 425H of the first gap 425 may be different from the inner diameter D426 of the through-hole 426H of the second gap 426.

[0060] Let's focus on the wall thickness of the inner sleeve 42. The sleeve body 421 has an outer diameter of D421. The sleeve flange 422 has an outer diameter of D422. The through hole 423H of the retaining portion 423 has an inner diameter of D423. The through hole 425H of the first gap portion 425 has an inner diameter of D425. The through hole 426H of the second gap portion 426 has an inner diameter of D426. The wall thickness of the inner sleeve 42 is determined by the combination of outer diameters D421, D422, D423, D425, and D426. Specifically, the inner sleeve 42 has a first wall thickness t1, a second wall thickness t2, and a third wall thickness t3. The first wall thickness t1 is determined by the outer diameter D421 and the inner diameter D423. The second wall thickness t2 is determined by the outer diameter D421 and the inner diameter D425. The third wall thickness t3 is determined by the outer diameter D422 and the inner diameter D425. Assume that the inner diameters D426 and D425 are the same. Therefore, the wall thickness determined by the outer diameter D421 and the inner diameter D426 is also the second wall thickness t2.

[0061] The thickness of the retaining portion 423 is the first thickness t1. The thickness of the first gap portion 425 is the second thickness t2 and the third thickness t3. The portion of the first gap portion 425 with the second thickness t2 corresponds to a part of the sleeve body 421 that constitutes the first gap portion 425. The portion of the first gap portion 425 with the third thickness t3 corresponds to the sleeve flange 422 that constitutes the first gap portion 425. The thickness of the second gap portion 426 is the second thickness t2.

[0062] Viewed from the magnet placement surface 421a, the first end ring placement surface 421b, and the second end ring placement surface 421c, the following is observed: The thickness of the magnet placement surface 421a includes a portion with a first thickness t1 and a portion with a second thickness t2. The thickness of the first end ring placement surface 421b and the second end ring placement surface 421c is the second thickness t2.

[0063] The inner sleeve 42 having the above configuration provides the following effects. Let's explain this by focusing on the first end ring 43. The inner sleeve 42 provides similar effects when focusing on the second end ring 44.

[0064] The first end ring 43 is press-fitted onto the sleeve body 421. As a result, the first end ring mounting surface 421b receives a force F along the radial direction. In other words, the first end ring mounting surface 421b receives a force F from the first end ring 43 that reduces its outer diameter. This force F causes a slight deformation in the sleeve body 421. This deformation of the sleeve body 421 is manifested on the inner circumferential surface 425s of the through-hole 425H of the first gap 425. A portion of the inner circumferential surface 425s on the side opposite to the outer circumferential surface, the first end ring mounting surface 421b, bulges slightly radially toward the axis of rotation A. For the sake of explanation, this bulging portion will be referred to as "bump B".

[0065] Where bump B occurs, the inner diameter becomes smaller by the height of bump B. If the inner diameter before bump B occurred was equal to the outer diameter of shaft 6, then bump B may obstruct the insertion of shaft 6. If the height of bump B is large, it becomes impossible to insert shaft 6 into inner sleeve 42 at all. If the height of bump B is small, it is possible to press-fit shaft 6 into inner sleeve 42. However, unintended distortion may occur due to the relative positional relationship between inner sleeve 42 and shaft 6.

[0066] Refer to Figure 4, which shows an enlarged view of region P in Figure 2. The inner sleeve 42 has an inner diameter D425 at the location where bump B occurs that is larger than the outer diameter D6 of the shaft 6. A gap HS exists between the outer circumferential surface 6a of the shaft 6 and the inner circumferential surface 425s of the first gap 425. As a result, even if bump B occurs on the inner circumferential surface 425s of the first gap 425, bump B will not come into contact with the outer circumferential surface 6a of the shaft 6, as long as the height HB of bump B does not exceed the length of the gap HS. Therefore, bump B caused by the press-fitting of the first end ring 43 does not affect the insertion of the shaft 6 into the inner sleeve 42. As a result, it is possible to assemble the inner sleeve 42 and the shaft 6 so that their relative positional relationship is as intended.

[0067] In short, the first end ring 43 and the second end ring 44 are press-fitted into the inner sleeve 42. The press-fitted inner sleeve 42 is slightly deformed so that the inner diameter of the sleeve through hole 42H becomes smaller. The first end ring 43 is positioned in the first gap 425 of the inner sleeve 42. The second end ring 44 is positioned in the second gap 426 of the inner sleeve 42.

[0068] The first gap 425 and the second gap 426 include portions that do not contact the outer circumferential surface 6a of the shaft 6. The inner diameters of the first gap 425 and the second gap 426 are larger than the inner diameter of the retaining portion 423 that holds the shaft 6. As a result, we assume that the press-fitting of the first end ring 43 and the second end ring 44 deforms the inner diameters of the through-holes 425H and 426H in which the shaft 6 is positioned, causing them to become smaller. Even in this case, the deformed portion, the bump B, is prevented from protruding further inward than the inner circumferential surface 423s of the retaining portion 423. The bump B does not contact the outer circumferential surface 6a of the shaft 6. Therefore, the deformation caused by the press-fitting of the first end ring 43 and the second end ring 44 can be tolerated. Furthermore, the shaft 6 can be held by the retaining portion 423 as intended during the design phase.

[0069] As shown in Figure 4, the first gap 425 is formed not only at the position where the first end ring 43 is placed, but also in a part of the position where the magnet 41 is placed. The bump B is basically formed in the region of the inner circumferential surface 425s that is located on the back side of the first end ring placement surface 421b. However, the bump B may extend beyond the region located on the back side. Therefore, the first gap 425 extends to the back side of the magnet placement surface 421a. The boundary between the first gap 425 and the holding portion 423 can be defined by the stepped surface 427. The stepped surface 427 defining the tip of the first gap 425 is formed further back (towards the magnet 41) than the first magnet end face 41c. Similarly, in the second gap 426, the stepped surface 428 (see Figure 3) defining the tip of the second gap 426 is formed further back (towards the magnet 41) than the second magnet end face 41d.

[0070] The shape of the inner sleeve 42 also has the effect of allowing some of the manufacturing process of the rotor 4 to be omitted. Next, the manufacturing method of the rotor 4 will be described with reference to Figures 5, 6, 7, and 8.

[0071] Prepare the inner sleeve 42 (S1: see Figure 6(a)). The sleeve body 421 and sleeve flange 422 are formed by machining the outer surface of the cylindrical material. A through hole with an inner diameter D423 is made in the material. Part of the through hole becomes the retaining portion 423. In this process, the portion that becomes the retaining portion 423 is finished to meet the desired dimensional accuracy. Further, a hole with an inner diameter D425 is made from one end of the material. This hole, which will become the first gap 425, is made from the first sleeve end face 42c to the desired depth. Similarly, a hole with an inner diameter D426 is made from the other end of the material. This hole, which will become the second gap 426, is made from the second sleeve end face 42d to the desired depth.

[0072] The first end ring 43, the magnet 41, and the second end ring 44 are arranged in this order in the inner sleeve 42 (S3: see Figure 6(b)). First, the first end ring 43 is press-fitted into the sleeve body 421 from the second sleeve end face 42d side. Next, the first end ring 43 is abutted against the flange abutment surface 42s of the sleeve flange 422. The arrangement of the first end ring 43 creates the first bump B. Next, the magnet 41 is inserted into the sleeve body 421 from the second sleeve end face 42d side. Since the magnet 41 is bonded to the sleeve body 421, adhesive may be applied in advance to the inner circumferential surface 41a of the magnet or the magnet placement surface 421a of the sleeve body 421. Next, the second end ring 44 is press-fitted into the sleeve body 421 from the second sleeve end face 42d side. Then, the second end ring 44 is brought into contact with the second magnet end face 41d. The arrangement of the second end ring 44 creates a second bump B.

[0073] The outer surface 43b of the first end ring, the outer surface 41b of the magnet, and the outer surface 43b of the second end ring are ground G (S5: see Figure 7(a)). In Figure 7(a), the dashed line indicates the position where grinding is performed. First, a so-called centering operation is performed. Specifically, in grinding using a lathe, when the jig is inserted from both sides of the sleeve through hole 42H and rotated, the first opening edge 42ce and the second opening edge 42de of the sleeve through hole 42H are ground so that the axis of rotation coincides with the design axis of rotation A of the inner sleeve 42. After that, the outer surface 43b of the first end ring, the outer surface 41b of the magnet, and the outer surface 44b of the second end ring are ground G. By grinding G, the outer surface 43b of the first end ring, the outer surface 41b of the magnet, and the outer surface 44b of the second end ring coincide. Conformity means that there is no significant step difference between the outer surface 43b of the first end ring and the outer surface 41b of the magnet. Furthermore, conformity means that there is no significant step difference between the outer surface 41b of the magnet and the outer surface 44b of the second end ring.

[0074] The armor ring 45 is positioned (S7: see Figure 7(b)). The armor ring 45 is press-fitted onto the first end ring 43 and the second end ring 44. Press-fitting the armor ring 45 may cause the first bump B and the second bump B to become even larger.

[0075] The first sleeve end face 42c and the second sleeve end face 42d are finished (S9: Figure 8(a)). "Finishing" means, for example, grinding the first sleeve end face 42c so that it is perpendicular to the rotation axis A. It has already been mentioned that the inner sleeve 42 is slightly deformed by the press-fitting of the first end ring 43 and the second end ring 44. This deformation was explained as the first bump B and the second bump B. The deformation of the inner sleeve 42 caused by press-fitting is not limited to the first bump B and the second bump B. The first sleeve end face 42c and the second sleeve end face 42d may also be slightly deformed into an arc by press-fitting. Therefore, in step S9, the distorted first sleeve end face 42c and the second sleeve end face 42d are ground G. As a result, each end face is perpendicular to the direction of the rotation axis A.

[0076] The shaft 6 is inserted into the sleeve through hole 42H of the inner sleeve 42 (S11: see Figure 8(b)). The inner sleeve 42 has a first bump B and a second bump B. However, the height HB of the first bump B (see Figure 4) does not exceed the gap HS (see Figure 4). As a result, the first bump B does not contact the shaft 6. The same applies to the second bump B. Therefore, the shaft 6 is held as intended by the retaining part 423.

[0077] Next, we will explain the effects and advantages of the manufacturing method for rotor 4.

[0078] The rotor 4 allows for the presence of bumps B caused by the press-fitting of the first end ring 43 and the second end ring 44. Furthermore, the rotor 4 can suppress a decrease in the precision of the shapes of the components that make up the rotor 4. On the other hand, it is also conceivable to place the shaft in the inner sleeve after removing the bumps B. Therefore, a manufacturing method of a comparative example rotor, including the step of removing the bumps B, will be described with reference to Figures 9, 10, 11, and 12.

[0079] Prepare the inner sleeve 142 (S1A: see Figure 9(a)). In this step S1A, the sleeve through hole 142H of the inner sleeve 142 is formed. The inner diameter of the sleeve through hole 142H is the same as that of the retaining portion 423.

[0080] The first end ring 143, the magnet 141, and the second end ring 144 are arranged in this order on the inner sleeve 142 (S3A: see Figure 9(b)). The press-fitting of the first end ring 143 creates the first bump B. The press-fitting of the second end ring 144 creates the second bump B.

[0081] The outer surfaces of the first end ring 143, the magnet 141, and the second end ring 144 are ground (S5A: see Figure 10(a)). Similar to the embodiment, after the centering work is performed, the outer surfaces of the first end ring 143, the magnet 141, and the second end ring 143 are ground (S5A: see Figure 10(a)).

[0082] Position the armor ring 145 (S7A: see Figure 10(b)).

[0083] In the manufacturing method of the rotor 4 of the embodiment, a step is performed that was not performed in the manufacturing method of the rotor of the comparative example. In the manufacturing method of the rotor of the comparative example, a step of removing bump B is performed. The step of removing bump B is roughly the same as the step of providing the sleeve through hole 142H. That is, the outer surface of the workpiece is held by a chuck. The workpiece is rotated by rotating the chuck. Even when rotating the workpiece using a chuck, it is required that the central axis of the workpiece and the rotation axis of the chuck coincide. The chuck grips the outer surface of the workpiece. Therefore, as preparation for the step of removing bump B, the work of machining the outer surface of the armor ring 145 (S8A: see Figure 11(a)) is performed.

[0084] The first sleeve end face 142c is finished, and the second sleeve end face 142d is also finished. Furthermore, bump B is machined away (S9A: Figure 11(b)).

[0085] In contrast, the manufacturing method of the rotor 4 in the embodiment does not involve the process of removing the bump B in the first place. Therefore, the preparatory work of machining the outer surface 45b of the armor ring 45, which is necessary for the process of removing the bump B, is also not required. In other words, in the manufacturing method of the rotor in the embodiment, the part that holds the shaft 6 only requires one machining step.

[0086] Insert the shaft 106 into the sleeve through hole 142H of the inner sleeve 142 (S11A: see Figure 12).

[0087] In the manufacturing method of rotor 4, if bump B is to be machined off, the machined bump B and the preparatory work for that machined bump B (S8A) are required. In contrast, in the manufacturing method of rotor 4 of this embodiment, the machined bump B is not machined off. Furthermore, the preparatory work for machined bump B (S8A) is also not required. Therefore, the manufacturing method of rotor 4 of this embodiment can reduce the number of work steps required to manufacture rotor 4. As a result, the manufacturing cost of rotor 4 can also be reduced.

[0088] In short, the motor rotor manufacturing method of this embodiment does not require the step of removing the deformed portion caused by the press-fitting of the end ring. Therefore, the number of steps required for rotor manufacturing can be reduced.

[0089] This disclosure is not limited to the embodiments described above.

[0090] For example, the electric supercharger 1 using rotor 4 is not limited to vehicles. The electric supercharger 1 may be used in a ship's engine. The electric supercharger 1 may be used in other engines. The electric supercharger 1 is not limited to internal combustion engines. The electric supercharger 1 may be used in a fuel cell system. The rotor 4 is not limited to application to a motor 3 used in an electric supercharger 1. The rotor 4 may be used in a device that simply functions as a motor 3. The rotor 4 may be used as the rotor of a generator.

[0091] [Note] This disclosure includes the following components:

[0092] The motor rotor of the present disclosure is [1] "a motor rotor comprising: an inner sleeve including a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not contact the outer circumferential surface of the shaft; a cylindrical magnet having a magnet through-hole into which the inner sleeve is inserted, with the inner sleeve positioned in the magnet through-hole; and an end ring including an end ring through-hole into which the inner sleeve is positioned and an end ring end face facing the end face of the magnet, with the inner sleeve press-fitted into the end ring through-hole; the holding portion and the gap portion each having through-hole portions that are inserted through each other and into which the shaft is positioned, the inner diameter of the through-hole portion provided in the gap portion being larger than the inner diameter of the through-hole portion provided in the holding portion, and the end ring being positioned in the gap portion."

[0093] The motor rotor of the present disclosure is [2] "the motor rotor according to [1] above, further comprising an armor ring covering the outer circumferential surface of the magnet and the outer circumferential surface of the end ring."

[0094] The motor rotor of the present disclosure is [3] "the motor rotor according to [2] above, wherein the end face of the armor ring protrudes more in the direction of the rotation axis than the end face of the end ring."

[0095] The motor rotor of the present disclosure is [4] "the motor rotor according to any one of the above [1] to [3], wherein the inner sleeve comprises a sleeve body including a magnet arrangement surface on which the magnets are arranged and an end ring arrangement surface on which the end rings are arranged, and a sleeve flange including a stopper surface facing the end face of the end rings."

[0096] The motor rotor of the present disclosure is [5] "the motor rotor according to [4] above, wherein the outer circumferential surface of the sleeve flange is a cylindrical surface, and the outer diameter of the sleeve flange is smaller than the outer diameter of the magnet."

[0097] The motor rotor of the present disclosure is [6] "the motor rotor according to [4] or [5] above, wherein the outer circumferential surface of the holding portion includes the magnet arrangement surface."

[0098] The motor rotor of the present disclosure is [7] "the motor rotor according to any one of the above [4] to [6], wherein the outer circumferential surface of the gap portion includes the magnet arrangement surface, the end ring arrangement surface, and the outer circumferential surface of the sleeve flange."

[0099] The motor rotor of the present disclosure is [8] "a motor rotor according to any one of the above [4] to [7], wherein the thickness from the inner circumferential surface of the through hole provided in the holding portion to the magnet arrangement surface is greater than the thickness from the inner circumferential surface of the through hole provided in the gap portion to the magnet arrangement surface."

[0100] The motor rotor of the present disclosure is [9] "a motor rotor according to any one of the above [4] to [8], wherein the thickness from the inner circumferential surface of the through hole provided in the sleeve flange and communicating with the through hole in the gap portion to the outer circumferential surface of the sleeve flange is greater than the thickness from the inner circumferential surface of the through hole provided in the holding portion to the magnet arrangement surface, and the outer circumferential surface of the sleeve flange is composed of a part of the outer circumferential surface included in the gap portion."

[0101] The motor rotor of the present disclosure is

[10] "the motor rotor according to any one of the above [1] to [9], wherein the material of the inner sleeve is a non-magnetic material."

[0102] The method for manufacturing a motor rotor according to the present disclosure is

[11] "a method for manufacturing a motor rotor comprising the steps of: preparing an inner sleeve including a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not contact the outer surface of the shaft; arranging a cylindrical magnet, which has a magnet through hole into which the inner sleeve is inserted, in the inner sleeve; and press-fitting an end ring, which includes an end ring through hole into which the inner sleeve is arranged and an end ring end face facing the end face of the magnet, into the inner sleeve, wherein in the step of arranging the magnet in the inner sleeve, the magnet is arranged in the holding portion, and in the step of press-fitting the end ring into the inner sleeve, the end ring is arranged in the gap portion."

[0103] The method for manufacturing a motor rotor according to the present disclosure is

[12] "the method for manufacturing a motor rotor according to

[11] , further comprising the steps of arranging the magnet in the inner sleeve and press-fitting the end ring into the inner sleeve, and then arranging an armor ring that covers the outer circumferential surface of the magnet and the outer circumferential surface of the end ring."

[0104] The method for manufacturing a motor rotor according to the present disclosure is

[13] "the method for manufacturing a motor rotor according to

[11] or

[12] , further comprising the steps of arranging the magnet in the inner sleeve and press-fitting the end ring into the inner sleeve, followed by grinding the end face of the inner sleeve."

[0105] The motor of the present disclosure is

[14] "a motor comprising the motor rotor described in any one of the above [1] to

[10] and a stator including coils arranged to surround the motor rotor."

[0106] The electric supercharger of the present disclosure is

[15] "an electric supercharger comprising a motor having the motor rotor described in any one of the above paragraphs [1] to

[10] and a stator including coils arranged to surround the motor rotor, and an impeller driven by the motor." [Explanation of symbols]

[0107] 1. Electric supercharger 3 motors 4. Rotor (Motor Rotor) 5 status 6 shafts 6a Outer surface 41 Magnets 41H Magnetic through-hole 42 Inner Sleeve 43, 44 End rings 43H, 44H End ring through hole 45 Armoring 51 coils 421a Magnet placement surface 421b First end ring arrangement surface 421c Second end ring placement surface 422 Sleeve flange 423 Holding part 423H,425H,426H Through hole part 425 First gap 426 Second gap 425s Inner surface A axis of rotation

Claims

1. An inner sleeve including a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not contact the outer surface of the shaft, The magnet has a cylindrical shape with a magnet through-hole into which the inner sleeve is inserted, and the inner sleeve is placed in the magnet through-hole. The end ring includes an end ring through hole in which the inner sleeve is disposed and an end ring end face facing the end face of the magnet, and the inner sleeve is press-fitted into the end ring through hole, The holding portion and the gap portion are each provided with through holes through which the shaft is inserted, The inner diameter of the through-hole provided in the gap is larger than the inner diameter of the through-hole provided in the holding portion. The end ring is positioned in the gap, The motor rotor includes a magnet arrangement surface on the outer circumferential surface of the holding portion where the magnets are arranged.

2. The motor rotor according to claim 1, further comprising an armor ring covering the outer circumferential surface of the magnet and the outer circumferential surface of the end ring.

3. The motor rotor according to claim 2, wherein the end face of the armor ring protrudes more than the end face of the end ring in the direction of the rotation axis.

4. The aforementioned inner sleeve is A sleeve body including the magnet placement surface and the end ring placement surface on which the end ring is placed, The motor rotor according to claim 1, further comprising a sleeve flange including a butt surface facing the end face of the end ring.

5. The outer circumferential surface of the sleeve flange is a cylindrical surface, The motor rotor according to claim 4, wherein the outer diameter of the sleeve flange is smaller than the outer diameter of the magnet.

6. The gap comprises a first gap including a portion that does not come into contact with the outer surface of the shaft, and a second gap including a portion that does not come into contact with the outer surface of the shaft. The holding portion is positioned between the first gap and the second gap. The motor rotor according to claim 1, wherein the end ring comprises a first end ring disposed in the first gap and a second end ring disposed in the second gap.

7. The motor rotor according to claim 4 or 5, wherein the outer circumferential surface of the gap includes the magnet arrangement surface on which a part of the magnet is arranged, the end ring arrangement surface, and the outer circumferential surface of the sleeve flange.

8. An inner sleeve including a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not contact the outer surface of the shaft, The magnet has a cylindrical shape with a magnet through-hole into which the inner sleeve is inserted, and the inner sleeve is placed in the magnet through-hole. The end ring includes an end ring through hole in which the inner sleeve is disposed and an end ring end face facing the end face of the magnet, and the inner sleeve is press-fitted into the end ring through hole, The holding portion and the gap portion are each provided with through holes through which the shaft is inserted, The inner diameter of the through-hole provided in the gap is larger than the inner diameter of the through-hole provided in the holding portion. The end ring is positioned in the gap, The aforementioned inner sleeve is A sleeve body including a magnet arrangement surface on which the magnet is arranged and an end ring arrangement surface on which the end ring is arranged, The sleeve flange includes a stopper surface facing the end face of the end ring, A motor rotor in which the thickness from the inner circumferential surface of the through-hole provided in the holding portion to the magnet arrangement surface is greater than the thickness from the inner circumferential surface of the through-hole provided in the gap portion to the magnet arrangement surface.

9. An inner sleeve including a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not contact the outer surface of the shaft, The magnet has a cylindrical shape with a magnet through-hole into which the inner sleeve is inserted, and the inner sleeve is placed in the magnet through-hole. The end ring includes an end ring through hole in which the inner sleeve is disposed and an end ring end face facing the end face of the magnet, and the inner sleeve is press-fitted into the end ring through hole, The holding portion and the gap portion are each provided with through holes through which the shaft is inserted, The inner diameter of the through-hole provided in the gap is larger than the inner diameter of the through-hole provided in the holding portion. The end ring is positioned in the gap, The aforementioned inner sleeve is A sleeve body including a magnet arrangement surface on which the magnet is arranged and an end ring arrangement surface on which the end ring is arranged, The sleeve flange includes a stopper surface facing the end face of the end ring, The sleeve flange is provided with a through-hole that communicates with the through-hole in the gap, and the thickness from the inner circumferential surface of the sleeve flange to the outer circumferential surface of the sleeve flange is greater than the thickness from the inner circumferential surface of the through-hole in the holding portion to the magnet placement surface. The outer circumferential surface of the sleeve flange is formed by a portion of the outer circumferential surface that includes the gap, in the motor rotor.

10. The motor rotor according to claim 1, wherein the material of the inner sleeve is a non-magnetic material.

11. A step of preparing an inner sleeve which includes a holding portion for holding a shaft having a rotation axis and a gap portion including a portion that does not come into contact with the outer surface of the shaft, A step of placing a cylindrical magnet, which has a magnet through-hole into which the inner sleeve is inserted, into the inner sleeve, The process includes pressing an end ring, which includes an end ring through hole in which the inner sleeve is placed and an end ring end face facing the end face of the magnet, into the inner sleeve, The outer circumferential surface of the holding portion includes the magnet arrangement surface on which the magnet is placed. In the step of arranging the magnet in the inner sleeve, the magnet is placed on the magnet arrangement surface, A method for manufacturing a motor rotor, wherein in the step of press-fitting the end ring into the inner sleeve, the end ring is positioned in the gap.

12. A method for manufacturing a motor rotor according to claim 11, further comprising the steps of arranging the magnet in the inner sleeve and press-fitting the end ring into the inner sleeve, followed by arranging an armor ring that covers the outer circumferential surface of the magnet and the outer circumferential surface of the end ring.

13. A method for manufacturing a motor rotor according to claim 11, further comprising the steps of arranging the magnet in the inner sleeve and press-fitting the end ring into the inner sleeve, followed by grinding the end face of the inner sleeve.

14. The motor rotor according to claim 1, A motor comprising a stator including coils arranged to surround the motor rotor.

15. A motor comprising the motor rotor described in claim 1, and a stator including coils arranged to surround the motor rotor, An electric supercharger comprising an impeller driven by the aforementioned motor.

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