Motor rotor

Abstract

The objective is to provide a motor rotor that suppresses shaft displacement caused by high temperatures during motor operation. [Solution] The motor rotor 1 comprises a cylindrical magnet 2, a C shaft 3 adjacent to the magnet 2 in the axial direction, and a cylindrical armor ring 5 fitted around the outer circumference of the magnet 2 and the C shaft 3. The fitting portion 17 between the armor ring 5 and the C shaft 3 has multiple contact areas 21 where the inner circumferential surface 5a of the armor ring 5 and the outer circumferential surface 31a of the C shaft 3 are in contact, and non-contact areas 22 that divide the contact areas 21 in the axial direction, where the inner circumferential surface 5a and the outer circumferential surface 31a are not in contact.

Description

Technical Field

[0001] The present invention relates to a motor rotor.

Background Art

[0002] Conventionally, as a technology in this field, the motor rotor described in Patent Document 1 below is known. The motor built into the supercharger generates an auxiliary torque for compensating for insufficient torque. The motor rotor of this motor includes a magnet, a C-shaft and a T-shaft that sandwich the magnet on both axial sides, and a cylindrical armature ring that is shrink-fitted to the outer periphery thereof. The armature ring covers the magnet and suppresses scattering due to centrifugal force when the magnet is damaged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When this type of motor becomes hot during operation, the positional relationship between the C-shaft and the T-shaft and the armature ring may change due to differences in thermal expansion between parts, resulting in shaft displacement. Then, problems such as shaft eccentricity and vibration may occur. In view of such problems, an object of the present invention is to provide a motor rotor that rotates stably.

Means for Solving the Problems

[0005] The gist of the present invention resides in the following [1] to [5].

[0006] [1] A motor rotor comprising a cylindrical magnet, a shaft member adjacent to the magnet in the axial direction, and a cylindrical armor ring fitted around the outer circumference of the magnet and the shaft member, wherein the fitting portion between the armor ring and the shaft member has a plurality of contact areas where the inner surface of the armor ring and the outer surface of the shaft member are in contact, and non-contact areas that divide the contact areas in the axial direction, where the inner surface and the outer surface are not in contact.

[0007] [2] The motor rotor according to [1], wherein the non-contact region is formed in a shape having isotropy in the circumferential direction.

[0008] [3] In the non-contact area, grooves extending circumferentially over the entire circumference are formed on the inner surface of the armor ring or the outer surface of the shaft member. The motor rotor according to [1] or [2].

[0009] [4] The motor rotor according to any one of [1] to [3], wherein the fitting portion between the armor ring and the magnet has a plurality of second contact regions in which the inner surface of the armor ring and the outer surface of the magnet are in contact, and a second non-contact region that divides the second contact regions in the axial direction, and in which the inner surface of the armor ring and the outer surface of the magnet are not in contact.

[0010] [5] A motor rotor according to any one of [1] to [4], comprising an adhesive layer for bonding the magnet and the shaft member, wherein a heat mark exists on the portion of the adhesive layer facing the inner circumferential surface of the armor ring. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a motor rotor that suppresses shaft displacement due to high temperatures during motor operation. [Brief explanation of the drawing]

[0012] [Figure 1]This is a cross-sectional view of a turbocharger, taken from a section that includes the rotation axis H. [Figure 2] (a) is a cross-sectional view of the motor rotor, and (b) is an exploded side view of its shaft assembly. [Figure 3] This is an enlarged view of section III in Figure 2. [Figure 4] (a) to (c) are side views showing the C shaft insertion section of a modified version, respectively. [Figure 5] (a) and (b) are side views showing the C shaft insertion portion of a modified example, respectively. [Figure 6] This is an exploded cross-sectional view showing a modified motor rotor. [Figure 7] (a) is a cross-sectional view of a modified motor rotor, and (b) is an exploded side view of its shaft assembly. [Modes for carrying out the invention]

[0013] Hereinafter, an embodiment of a motor rotor according to one aspect of the present invention will be described in detail with reference to the drawings. In each figure, the same parts are denoted by the same reference numerals, and redundant explanations are omitted.

[0014] Figure 1 is a cross-sectional view of a supercharger 9 with a section including the rotation axis H. The supercharger 9 includes a motor rotor 1 according to one embodiment of the present invention. The supercharger 9 is a vehicle supercharger equipped with the motor rotor 1. In the following description, when we simply refer to "axial direction," "radial direction," and "circumferential direction," we mean the axial direction, radial direction, and circumferential direction of the T-shaft 4, which will be described later.

[0015] As shown in FIG. 1, the supercharger 9 is an electric supercharger. The supercharger 9 is applied to, for example, an internal combustion engine of a ship or a vehicle. The supercharger 9 has a turbine 91, a compressor 92, and a motor 8. The supercharger 9 is required to generate compressed air in a predetermined state. To generate compressed air, the rotating body 8R needs to have a predetermined torque. This torque is generated due to the exhaust gas of the internal combustion engine. However, the torque generated due to the exhaust gas of the internal combustion engine may not be sufficient for the torque required to generate compressed air in a predetermined state. Therefore, the motor 8 generates an auxiliary torque to supplement the insufficient torque.

[0016] The turbine 91 has a turbine housing 911 and a turbine impeller 912. The turbine housing 911 houses the turbine impeller 912. The turbine housing 911 has a scroll flow path 914. The scroll flow path 914 extends in the circumferential direction around the turbine impeller 912.

[0017] The turbine housing 911 has an inlet 913 and an outlet 915. The exhaust gas discharged from the internal combustion engine flows into the turbine housing 911 through the inlet 913. The inlet exhaust gas flows into the turbine impeller 912 through the scroll flow path 914. Then, the exhaust gas rotates the turbine impeller 912. After that, the exhaust gas flows out of the turbine housing 911 through the outlet 915.

[0018] The compressor 92 has a compressor housing 921 and a compressor impeller 922. The compressor housing 921 houses the compressor impeller 922. The compressor housing 921 has a scroll flow path 924. The scroll flow path 924 extends in the circumferential direction around the compressor impeller 922.

[0019] The compressor housing 921 has a suction port 923 and a discharge port 925. When the turbine impeller 912 rotates, the compressor impeller 922 rotates via a rotating body 8R described later. As the rotating compressor impeller 922 rotates, it sucks external air through the suction port 923. The sucked air is compressed by passing through the compressor impeller 922 and the scroll flow path 924. The air is discharged from the discharge port 925 as compressed air. The compressed air is supplied to an internal combustion engine.

[0020] The motor 8 is, for example, a brushless DC motor. The motor 8 has a motor rotor 1, a motor stator 7, and a motor housing 94.

[0021] The motor rotor 1 is housed in the motor housing 94. The motor rotor 1 is disposed between bearings 951 and 952 in the axial direction. The motor stator 7 is also housed in the motor housing 94. The motor stator 7 is disposed at substantially the same position as the motor rotor 1 in the axial direction. The motor stator 7 surrounds the motor rotor 1. The inner peripheral surface of the motor stator 7 is spaced from the outer peripheral surface of the motor rotor 1.

[0022] The motor rotor 1, together with the T - shaft 4 and the C - shaft 3, constitutes a rotating body 8R. The rotating body 8R is rotatably supported with respect to the turbine housing 911 and the compressor housing 921. A turbine impeller 912 is provided at one end of the T - shaft 4. A compressor impeller 922 is provided at one end of the C - shaft 3.

[0023] The C - shaft 3 has a thrust collar 931. The thrust collar 931 protrudes in the radial direction of the C - shaft 3. The thrust collar 931 has, for example, a disc shape. A pair of air bearings 961 and 962 are provided on both sides of the thrust collar 931. A spacer 97 that surrounds the thrust collar 931 is provided between the pair of air bearings 961 and 962.

[0024] A pair of air bearings 961, 962 and a spacer 97 are joined together by a number of fastening bolts. The air bearings 961, 962 and the spacer 97 support the C shaft 3 in the thrust direction. The thrust collar 931 is rotatable without contacting the air bearings 961, 962 and the spacer 97.

[0025] <Motor Rotor> Figure 2(a) is a cross-sectional view of the motor rotor 1 in a plane containing the central axis. Figure 2(b) is an exploded side view of the shaft assembly 11 of the motor rotor 1. The motor rotor 1 comprises the shaft assembly 11 and the armor ring 5. The shaft assembly 11 comprises the magnet 2, the C shaft 3, and the T shaft 4.

[0026] <Magnet> The shape of magnet 2 is cylindrical. That is, magnet 2 is solid and does not have a through hole. For the material of magnet 2, for example, neodymium (Nd-Fe-B) or samarium cobalt may be used.

[0027] <Cシャフト> The C-shaft 3 is connected to the compressor impeller 922. The C-shaft 3 has a C-shaft insertion portion 31 and a C-shaft projection portion 32. The C-shaft insertion portion 31 is cylindrical in shape, and the C-shaft projection portion 32 is cylindrical in shape. The C-shaft insertion portion 31 is covered by an armor ring 5, while the C-shaft projection portion 32 is not covered by the armor ring 5.

[0028] <Tシャフト> The T-shaft 4 is connected to the turbine blade 912. The T-shaft 4 has approximately the same configuration as the C-shaft 3. That is, the T-shaft 4 has a T-shaft insertion portion 41 and a T-shaft projection portion 42. The shape of the T-shaft insertion portion 41 is cylindrical, and the shape of the T-shaft projection portion 42 is cylindrical. The T-shaft insertion portion 41 is covered by an armor ring 5, while the T-shaft projection portion 42 is not covered by the armor ring 5.

[0029] <Shaft Assembly> In the shaft assembly 11, the magnet 2 is sandwiched axially between the C shaft 3 and the T shaft 4. One end face of the magnet 2 is bonded to the end face of the C shaft insertion portion 31, and an adhesive layer 13 is formed between them. Similarly, the other end face of the magnet 2 is bonded to the end face of the T shaft insertion portion 41, and an adhesive layer 13 is formed between them.

[0030] <Armor Ring> The armor ring 5 suppresses the scattering of fragments of the magnet 2 due to centrifugal force in the event of damage to the magnet 2. The armor ring 5 is cylindrical in shape. The armor ring 5 houses the magnet 2. Furthermore, the armor ring 5 covers the C-shaft insertion portion 31, which is part of the C-shaft 3, and the T-shaft insertion portion 41, which is part of the T-shaft 4.

[0031] <Motor rotor construction> The motor rotor 1 of this embodiment is manufactured by shrink-fitting an armor ring 5 onto the outer circumference of a shaft assembly 11. Specifically, the shaft assembly 11 is assembled by first bonding and integrating the C shaft 3, magnet 2, and T shaft 4. The C shaft insertion portion 31, magnet 2, and T shaft insertion portion 41 are formed to have the same diameter with high precision. Subsequently, the shaft assembly 11 at room temperature is inserted into the armor ring 5, which has been heated to approximately 500°C, and then slowly cooled, so that the heat-shrunk armor ring 5 is firmly fixed around the shaft assembly 11.

[0032] Through this shrink-fitting process, the armor ring 5 is fixed so as to cover the C-shaft insertion portion 31, the magnet 2, and the T-shaft insertion portion 41. In the completed motor rotor 1, the C-shaft insertion portion 31, the magnet 2, and the T-shaft insertion portion 41 are all attached to the armor ring 5 in an interference fit relationship. In addition, in the completed motor rotor 1, there is a heat-deformed portion 13a (heat mark) in the adhesive layer 13 that faces the inner circumferential surface 5a of the armor ring 5, which is a heat-deformed portion caused by the high temperature of the armor ring 5.

[0033] Since the motor rotor 1 is manufactured by shrink-fitting, residual stress exists in the finished motor rotor 1 in a radial direction, where the inner surface of the armor ring 5 and the outer surface of the shaft assembly 11 press against each other. The frictional force between the two due to this residual stress firmly assembles the armor ring 5 and the shaft assembly 11. In addition to the radial residual stress mentioned above, axial residual stress also exists. That is, residual stress exists in the axial tensile direction in the armor ring 5, and residual stress exists in the axial compressive direction in the shaft assembly 11.

[0034] During operation of the supercharger 9, the shaft assembly 11 may become hot due to self-heating of the magnet 2 and heat generation of the thrust collar 931 by the air bearing. As a result of axial thermal expansion of the shaft assembly 11, the axial residual stress is released, and the shaft assembly 11 is displaced relative to the armor ring 5. If this release of residual stress occurs unevenly in the circumferential direction, the displacement of the shaft assembly 11 relative to the armor ring 5 will also occur unevenly in the circumferential direction, which may result in eccentricity of the shaft assembly 11 and malfunctions such as vibration. In view of this problem, the motor rotor 1 has the configuration described below.

[0035] Figure 3 is an enlarged view of part III of Figure 2(a). As shown in Figures 2 and 3, multiple grooves 15 extending circumferentially are formed on the outer circumferential surface 31a of the C shaft insertion portion 31. Due to the presence of these grooves 15, contact areas 21 and non-contact areas 22 are alternately formed in the axial direction in the fitting portion 17 between the armor ring 5 and the C shaft 3. The contact areas 21 are the areas where the inner circumferential surface 5a of the armor ring 5 and the outer circumferential surface 31a of the C shaft insertion portion 31 are in contact. The non-contact areas 22 are the areas where the inner circumferential surface 5a and the outer circumferential surface 31a are not in contact, and divide the contact areas 21 in the axial direction. In the example of Figure 2, three grooves 15 are formed on the C shaft insertion portion 31, but it is sufficient for at least one groove 15 to be formed on the C shaft insertion portion 31. Furthermore, although the groove 15 in the example shown in the figure has a rectangular cross-section, the cross-sectional shape of the groove 15 may also be an arc (U-shaped) or a V-shaped.

[0036] The T-shaft 4 has approximately the same configuration as the C-shaft 3. That is, the same groove 15 as described above is formed on the outer circumferential surface 41a of the T-shaft insertion portion 41. Furthermore, the fitting portion 17 between the armor ring 5 and the T-shaft 4 also has a contact area 21 and a non-contact area 22.

[0037] The effects and advantages of the motor rotor 1 described above will now be explained. In the motor rotor 1, the contact region 21, where the armor ring 5 and the C shaft insertion portion 31 are joined, is divided into short sections in the axial direction, separated by the non-contact region 22. During the manufacturing of the motor rotor 1, the axial strain of the armor ring 5 and the C shaft insertion portion 31 generated by shrink fitting is released in the non-contact region 22, so residual stress does not easily accumulate. Therefore, the residual stress released during the operation of the supercharger 9 is small, and as a result, the displacement of the C shaft insertion portion 31 relative to the armor ring 5 is also small. By the same principle as above, the displacement of the T shaft insertion portion 41 relative to the armor ring 5 is also small. In other words, the displacement of the shaft assembly 11 is suppressed, and problems such as vibration due to eccentricity of the shaft assembly 11 are suppressed. As a result, the motor rotor 1 rotates stably.

[0038] Furthermore, since the groove 15 extends circumferentially around the entire circumference of the C-shaft insertion portion 31 and the T-shaft insertion portion 41, the non-contact area 22 has a shape that is isotropic in the circumferential direction. Therefore, the release of residual stress during the operation of the supercharger 9 also tends to be isotropic in the circumferential direction. In other words, the release of residual stress tends to be uniform in the circumferential direction, and as a result, the possibility of eccentricity of the shaft assembly 11 is further suppressed. Note that the groove for obtaining this effect is not limited to the groove 15 that extends circumferentially around the entire circumference, but any groove with a shape that is isotropic in the circumferential direction is acceptable. "Isotropic in the circumferential direction" means that the mass of the C-shaft insertion portion 31 and the T-shaft insertion portion 41 in which the groove is formed does not vary (or has little variation in the circumferential direction) in the circumferential direction. Other examples of C-shaft insertion portions 31 provided with such grooves are shown in Figures 4(a) to 4(c) and Figures 5(a) to 5(b). Figures 4(a) to 4(c) and 5(a) to 5(b) show examples of the C shaft insertion section 31, but the example of the T shaft insertion section 41 is similar, so redundant explanations are omitted.

[0039] In the C-shaft insertion portion 31A illustrated in Figure 4(a), a screw-shaped (spiral) groove 15A is formed on the outer circumferential surface 31a. In the C-shaft insertion portion 31B illustrated in Figure 4(b), a knurled groove 15B is formed on the outer circumferential surface 31a. In the C-shaft insertion portion 31C illustrated in Figure 4(c), short grooves 15C extending in the circumferential direction are arranged in a staggered pattern on the outer circumferential surface 31a. In the C-shaft insertion portion 31D illustrated in Figure 5(a), short grooves 15D extending in the circumferential direction are arranged in a grid pattern on the outer circumferential surface 31a. In the C-shaft insertion portion 31E illustrated in Figure 5(b), short grooves 15E extending in the circumferential direction are arranged on the outer circumferential surface 31a with a phase shift in the axial direction.

[0040] The present invention can be implemented in various forms, including the embodiments described above, by making various changes and improvements based on the knowledge of those skilled in the art. Furthermore, it is possible to construct modified versions by utilizing the technical matters described in the embodiments described above. The configurations of each embodiment may be used in appropriate combinations.

[0041] For example, in order to form the contact area 21 and non-contact area 22 as described above, instead of forming grooves 15 in the C shaft insertion portion 31 and the T shaft insertion portion 41, grooves 15 may be formed on the inner circumferential surface 5a of the armor ring 5 as shown in Figure 6.

[0042] Furthermore, as shown in Figures 7(a) and 7(b), in addition to the grooves 15 in the C shaft insertion portion 31 and the T shaft insertion portion 41, grooves 15 may also be formed on the outer circumferential surface 2a of the magnet 2. As a result, the fitting portion 18 between the armor ring 5 and the magnet 2 also has multiple contact areas 23 (second contact areas) where the inner circumferential surface 5a of the armor ring 5 and the outer circumferential surface 2a of the magnet 2 are in contact, and non-contact areas 24 (second non-contact areas) that divide the contact areas 23 axially and where the inner circumferential surface 5a and the outer circumferential surface 2a are not in contact.

[0043] Alternatively, the shaft assembly 11 and the armor ring 5 may be joined by shrink-fitting and then further joined by welding. In this case, the presence of the non-contact area 22 reduces the stress acting on the weld by releasing axial residual stress that may occur during the operation of the supercharger 9, thereby suppressing fatigue failure of the weld caused by this stress.

[0044] Furthermore, although the embodiments described an example of a motor rotor 1 in which the shaft assembly 11 and the armor ring 5 are joined by shrink fitting, the present invention can also be applied to a motor rotor in which the shaft assembly 11 and the armor ring 5 are joined with stress in a radially compressive direction. For example, the present invention can also be applied to a motor rotor in which the shaft assembly 11 is press-fitted into the armor ring 5 and joined thereto. [Explanation of Symbols]

[0045] 1 Motor Rotor 2 Magnets 2a Outer surface 3 C shaft (shaft member) 4 T-shaft (shaft member) 5 アーマーリング 5a Inner circumferential surface 13 Next layer 13a Thermal damage part (ヒートマーク) 15, 15A~15E Ditch 17,18 embedded parts 21. Areas of Contact 22. Non-contact fields 23. Contact Area (Second Contact Area) 24. Non-contact area (Second non-contact area) 31a, 41a outer peripheral surface

Claims

1. A cylindrical magnet, The device comprises a shaft member adjacent to the magnet in the axial direction, and a cylindrical armor ring fitted around the outer circumference of the magnet and the shaft member, The fitting portion between the armor ring and the shaft member is as follows: Multiple contact areas where the inner circumferential surface of the armor ring and the outer circumferential surface of the shaft member are in contact, A motor rotor having a non-contact region where the inner circumferential surface and the outer circumferential surface are not in contact, separated axially from the aforementioned contact regions.

2. The motor rotor according to claim 1, wherein the non-contact region is formed in a shape having isotropy in the circumferential direction.

3. In the non-contact area, a groove extending circumferentially over the entire circumference is formed on the inner circumferential surface of the armor ring or the outer circumferential surface of the shaft member. The motor rotor according to claim 1.

4. The fitting portion between the armor ring and the magnet is as follows: A plurality of second contact regions where the inner circumferential surface of the armor ring and the outer circumferential surface of the magnet are in contact, The motor rotor according to claim 1, wherein the second contact regions are separated in the axial direction, and a second non-contact region exists in which the inner circumferential surface of the armor ring and the outer circumferential surface of the magnet are not in contact.

5. The magnet and the shaft member are bonded together by an adhesive layer, The motor rotor according to claim 1, wherein a heat mark exists in the portion of the adhesive layer that faces the inner circumferential surface of the armor ring.

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