motor

Abstract

One aspect of the invention is a motor comprising: a rotor having a shaft extending along a central axis about which it rotates; a stator having a stator core and coils mounted on the stator core, the stator being radially opposed to the rotor; a bearing supporting the shaft for rotation; a bearing cage holding the bearing; and a housing made of resin material in which the stator and bearing cage are embedded. The housing comprises: a first molded portion in which the stator is embedded; and a second molded portion in which the first molded portion and bearing cage are embedded.

Description

Technical Field

[0001] This invention relates to motors.

[0002] This application claims priority based on Japanese Patent Application No. 2020-061931, filed on March 31, 2020, the contents of which are incorporated herein by reference. Background Technology

[0003] In recent years, motors made by molding the stator with resin have been developed for purposes such as simplifying assembly processes. Patent Document 1 discloses a motor having a resin housing obtained by molding the stator.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-22191 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] When the stator is molded to form the housing, the wall thickness of different parts of the housing is uneven. In the parts of the housing with larger wall thickness, the shrinkage during resin curing (so-called shrinkage marks) is also greater, thus making dimensional management more difficult.

[0009] In view of the above, one of the objects of the present invention is to provide a motor capable of suppressing the formation of shrinkage marks in a housing obtained by molding the stator.

[0010] Methods for solving problems

[0011] One aspect of the invention is a motor comprising: a rotor having a shaft extending along a central axis about which the rotor rotates; a stator having a stator core and coils mounted on the stator core, the stator being radially opposed to the rotor; a bearing supporting the shaft and enabling the shaft to rotate; a bearing cage holding the bearing; and a housing made of resin material into which the stator and the bearing cage are embedded. The housing comprises: a first molded portion into which the stator is embedded; and a second molded portion into which the first molded portion and the bearing cage are embedded.

[0012] Invention Effects

[0013] According to one aspect of the invention, a motor is provided that can suppress the formation of shrinkage marks in a housing obtained by molding the stator. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of a motor along its central axis in one embodiment.

[0015] Figure 2 This is a cross-sectional view of a motor in one embodiment, perpendicular to its central axis.

[0016] Figure 3 This is a perspective view of a busbar unit according to one implementation method.

[0017] Figure 4 This is a perspective view of a bearing cage according to one embodiment.

[0018] Figure 5 This is a perspective view of an intermediate molded product according to one implementation method. Detailed Implementation

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0020] In the following description, the central axis J (refer to...) will be used. Figure 1 The parallel direction is simply referred to as "axial" or "vertical direction," the radial direction centered on the central axis J is simply referred to as "radial," and the circumferential direction centered on the central axis J, i.e., the direction around the central axis J, is simply referred to as "circumferential." Furthermore, in this specification, the axial side along the central axis J is simply referred to as "upper side," and the other axial side is simply referred to as "lower side." Additionally, the vertical direction in this specification is only for illustrative purposes and does not limit the posture of the motor during use or circulation.

[0021] Additionally, the Y-axis is shown in the attached diagram. The Y-axis direction is parallel to the central axis J of motor 1. Furthermore, the +Y side is the upper side, and the -Y side is the lower side.

[0022] Figure 1 This is a cross-sectional view of motor 1 along its central axis J, according to one embodiment. Additionally, Figure 2 This is a cross-sectional view of motor 1 in one embodiment, perpendicular to the central axis J.

[0023] like Figure 1 As shown by the imaginary line (double-dotted line), the motor 1 is mounted on the external device 9 located on the upper side of the motor 1 using fixing bolts 9e. The motor 1 transmits power to the external device 9.

[0024] The motor 1 has a rotor 10, a stator 20 surrounding the rotor 10, a bearing 15 holding the rotor 10 so that it can rotate, a bearing cage 80 holding the bearing 15, a busbar unit 70, and a housing 30. The bearing cage 80 is embedded in the housing 30.

[0025] Furthermore, in this specification, the term "embedded" is defined as follows: it includes not only the case of covering the entire outer surface of an object, but also the case of covering at least a portion of the outer surface while leaving a portion of the outer surface exposed.

[0026] The rotor 10 rotates about a central axis J extending in the vertical direction. The rotor 10 has a shaft 11 extending along the central axis J, a rotor core 12, and a rotor magnet 13.

[0027] The shaft 11 is connected at its upper end (the end on the axial side) to the power transmission mechanism 9d of the external device 9. The shaft 11 is supported by a bearing 15 so that it can rotate about the central axis J. A rotor core 12 is fixed to the outer circumferential surface of the shaft 11. In addition, a rotor magnet 13 is fixed to the outer circumferential surface of the rotor core 12. Alternatively, multiple rotor magnets 13 may be embedded inside the rotor core 12.

[0028] The stator 20 surrounds the rotor 10 radially outward. The stator 20 is radially opposed to the rotor 10. The stator 20 has a stator core 21, an insulator 22, and coils 29.

[0029] like Figure 2 As shown, the stator core 21 has an annular core back 21a centered on the central axis J and a plurality of teeth 21b extending radially inward from the core back 21a. The teeth 21b are arranged at equal intervals around the central axis J. A coil 29 is mounted on the teeth 21b. Grooves 21g extending axially are provided on the outer peripheral surface of the core back 21a and radially outward of each tooth 21b.

[0030] like Figure 1 As shown, the stator core 21 of this embodiment is composed of multiple electromagnetic steel plates 21t stacked along the axial direction. The stacked electromagnetic steel plates 21t have the same shape as each other. Each electromagnetic steel plate 21t is formed by stamping.

[0031] The coil 29 is mounted on the stator core 21 through the insulator 22. More specifically, the coil 29 is formed by winding coil wire through the insulator 22 onto the tooth portion 21b. The end of the coil 29 is led out to the underside of the stator 20 as a lead wire 29a. The lead wire 29a is the end at the beginning or end of the winding of the coil 29. The lead wire 29a extends from the lower surface of the housing 30 in which the coil 29 is embedded and connects to the busbar 71 of the busbar unit 70.

[0032] Busbar unit 70 is located on the lower side of stator 20 (on the other side of the axial direction). Busbar unit 70 has a terminal 71a connected to control device 8 and a connection portion 71c connected to lead wire 29a, and provides alternating current supplied from control device 8 to each coil 29.

[0033] The busbar unit 70 has a busbar retainer 75 made of resin and a plurality of busbars 71 embedded in the busbar retainer 75. The plurality of busbars 71 are embedded in the busbar retainer 75 by insert molding. The busbar retainer 75 is made of an insulating resin material.

[0034] Figure 3 This is a three-dimensional view of busbar unit 70.

[0035] Busbar 71 is made of a highly conductive metal material (such as a copper alloy). Busbar 71 is plate-shaped. Busbar 71 is formed by stamping the plate. Busbar 71 has a main body 71b, a terminal 71a, and multiple connecting parts 71c.

[0036] The busbar body 71b extends in an arc shape circumferentially around the central axis J. The busbar body 71b connects the connecting portion 71c to the terminal 71a. The busbar body 71b connects multiple connecting portions 71c to each other. The terminal 71a extends downward from the busbar body 71b. The connecting portion 71c extends radially outward from the busbar body 71b. The busbar body 71b is embedded in the busbar retainer 75. On the other hand, the terminal 71a and the connecting portion 71c are exposed from the busbar retainer 75.

[0037] The busbar retainer 75 has a retainer body 76, a terminal support 78, and multiple legs (first legs) 77. That is, the busbar unit 70 has a retainer body 76, a terminal support 78, and multiple legs 77. The retainer body 76 is annular about a central axis J. A busbar body 71b is embedded inside the retainer body 76.

[0038] The terminal support portion 78 is block-shaped. It is located on the lower side of the main body portion 76 and circumferentially. The base ends of a plurality of terminals 71a are embedded in the terminal support portion 78. As described later, the terminals 71a are inserted into the socket portion 8a of the control device 8 (see reference). Figure 1 During insertion, an upward force from the control device 8 is applied to the terminal 71a. The terminal support 78 bears the upward force received by the terminal 71a from the control device 8.

[0039] The busbar retainer 75 has a plurality of legs 77 (three in this embodiment). The plurality of legs 77 are arranged at equal intervals around a central axis. The busbar retainer 75 is supported by the housing 30 at the legs 77.

[0040] The leg 77 has a radial extension 77a that extends radially outward from the outer edge of the cage body 76 and an axial extension 77b that extends upward (to the axial side) from the radially outward front end of the radial extension 77a.

[0041] like Figure 1 As shown, bearing 15 is located on the upper side of stator 20. Bearing 15 supports the upper end of shaft 11. In this embodiment, bearing 15 is a ball bearing. However, bearing 15 can also be other types of bearings such as needle roller bearings. Bearing 15 is held in bearing cage 80.

[0042] The bearing cage 80 is located on the upper side (axial side) of the stator 20. The bearing cage 80 is made of aluminum alloy. Furthermore, the bearing cage 80 is manufactured by die casting. The bearing cage 80 is embedded in the housing 30.

[0043] Figure 4 This is a three-dimensional view of the bearing cage 80.

[0044] The bearing cage 80 has a cage portion 81, multiple nut portions 85, multiple arm portions 88, an outer ring portion 87, and a base plate portion 89.

[0045] like Figure 1 As shown, the bearing cage 80 holds the bearing 15 at the cage portion 81. When viewed from the axial direction, the cage portion 81 is located at the center of the bearing cage 80.

[0046] The retainer portion 81 has a retainer cylinder portion 82 and an upper plate portion 83 extending radially inward from the inner side of the retainer cylinder portion 82. The retainer cylinder portion 82 is cylindrical about the central axis J. A bearing 15 is disposed radially inward of the retainer cylinder portion 82 and below the upper plate portion 83. The upper plate portion 83 covers the upper side of the outer ring of the bearing 15. A central hole 83a extending axially is provided in the upper plate portion 83. The shaft 11 passes through the central hole 83a. On the outer peripheral surface of the retainer portion 81, near the upper end, a stepped surface 81a facing upward is provided. The stepped surface 81a is a plane perpendicular to the central axis J.

[0047] Multiple nut portions 85 are arranged circumferentially. Each nut portion 85 is cylindrical, extending along an axis J2 parallel to the central axis J. The upper end face 85a of each nut portion 85 protrudes from the housing 30. The upper end face 85a of each nut portion 85 protrudes outward from the housing 30. Each nut portion 85 has a threaded hole 86 that opens at the upper end face 85a and extends downward along the axis J2. The inner circumferential surface of the threaded hole 86 protrudes from the housing 30. A shaft portion into which a fixing bolt 9e is inserted is inserted.

[0048] The external device 9 has a retaining cylinder portion 9a and a plate-shaped fixing plate portion 9f extending radially outward from the lower end of the retaining cylinder portion 9a. The retaining cylinder portion 9a is cylindrical about a central axis J. The retaining cylinder portion 9a surrounds the retainer portion 81 on the upper side of the stepped surface 81a. A groove 9b extending in a circumferential annular shape is provided on the lower end face of the retaining cylinder portion 9a. The groove 9b is open on the lower side. A sealing member 9c is housed in the groove 9b. The sealing member 9c is, for example, a gasket. The groove 9b is covered by the stepped surface 81a of the retainer portion 81. The gasket 9c is compressed between the bottom surface of the groove 9b and the stepped surface 81a. As a result, the gasket 9c prevents moisture or oil from seeping into the radially inner side of the retainer portion 81.

[0049] The mounting plate 9f of the external device 9 has a plurality of mounting holes 9g extending axially. A mounting bolt 9e is inserted into the mounting holes 9g from above. The mounting bolt 9e is tightened into the threaded hole 86 of the nut portion 85, thereby fixing the motor 1 to the external device 9. According to this embodiment, the nut portion 85 is made of metal, therefore, compared to the case where the external device 9 is directly fixed to the resin housing 30, damage to the fastening portion due to stress during tightening can be suppressed.

[0050] like Figure 4 As shown, the outer ring portion 87 is cylindrical with the central axis J as its center. The outer ring portion 87 connects to a plurality of nut portions 85 arranged circumferentially.

[0051] Multiple arms 88 extend radially outward from the retainer portion 81. The multiple arms 88 are arranged at equal intervals along the circumference. The arms 88 connect the retainer portion 81 and the nut portion 85. Additionally, the base plate portion 89 is plate-shaped and perpendicular to the central axis J. The base plate portion 89 extends radially outward from the retainer portion 81 and connects to the outer ring portion 87. Furthermore, the base plate portion 89 is connected to the lower end of the arms 88.

[0052] According to this embodiment, the retainer portion 81 and the nut portion 85 are constituted as a single component connected via the arm portion 88. Therefore, the rigidity of the nut portion 85 can be increased, thereby enabling the motor 1 to be securely fixed to the external device 9. In addition, the inherent frequency of the vibration of the motor 1 relative to the vibration frequency emitted by the motor 1 during operation can be sufficiently increased. As a result, resonance of the motor 1 can be suppressed, thereby effectively reducing the vibration of the motor 1 during operation.

[0053] like Figure 1 As shown, a cylindrical leg (second leg) 87a that contacts the housing 30 is provided in the lower region of the outer ring portion 87. That is, the bearing cage 80 has a cylindrical leg 87a. The lower end face of the cylindrical leg 87a contacts the housing 30 in which the stator 20 is embedded.

[0054] The housing 30 has a first molding portion 31 and a second molding portion 32. The first molding portion 31 and the second molding portion 32 are each made of resin material. The stator 20 is embedded in the first molding portion 31. Furthermore, the first molding portion 31 and the bearing cage 80 are embedded in the second molding portion 32. That is, the housing 30 is made of resin material, and the stator 20 and the bearing cage 80 are embedded therein.

[0055] Furthermore, in this specification, the term "resin material" can also refer to a composite material reinforced with fiber materials such as glass fiber or carbon fiber. That is, the housing 30 can also be a fiber-reinforced resin material.

[0056] like Figure 1 As shown, the first molding part 31 has a first covering part 31a covering the coil 29 and a second covering part 31b covering the surface of the back of the iron core 21a.

[0057] The first covering portion 31a surrounds the tooth portion 21b and the coil 29 from both circumferential sides and winds between the circumferentially adjacent teeth 21b and coil 29. That is, the first molding portion 31 holds the teeth 21b and coil 29 at the first covering portion 31a. In addition, the first covering portion 31a does not cover the radially inward-facing inner surface 21ba of the teeth 21b. The inner surface 21ba contacts the mold that forms the first molding portion 31 and is used for radial positioning of the stator 20 within the mold.

[0058] The second covering portion 31b is located radially outward of the first covering portion 31a. The second covering portion 31b covers the upper and lower surfaces and the radially outward-facing surface of the core back 21a with a substantially uniform wall thickness. The second covering portion 31b has an upper surface 31ba located on the upper side of the core back 21a, a lower surface 31bb located on the lower side of the core back 21a, and an outer surface 31bc located radially outward of the core back 21a. The upper surface 31ba is a plane facing upward (on one axial side), the lower surface 31bb is a plane facing downward (on the other axial side), and the outer surface 31bc is a curved surface facing radially outward.

[0059] like Figure 2 As shown, a groove 31bd extending axially is provided on the outer surface 31bc. The groove 31bd opens radially outward. The groove 31bd is provided by the first molding portion 31 covering the surface of the groove 21g of the back surface 21a of the stator core with a constant wall thickness. Therefore, the wall thickness of the second covering portion 31b at the groove 31bd does not become very thin. In addition, according to this embodiment, a portion of the second molding portion 32 penetrates into the groove 21g of the stator core 21, thereby suppressing the positional displacement of the first molding portion 31 relative to the stator core 21 in the circumferential direction.

[0060] The second covering portion 31b is provided with an upper opening (opening) 31p located at the corner of the upper surface 31ba and the outer side surface 31bc, and a lower opening (opening) 31q located at the corner of the lower surface 31bb and the outer side surface 31bc. That is, the first molding portion 31 has an upper opening 31p and a lower opening 31q.

[0061] The upper opening 31p and the lower opening 31q extend axially to the axially facing surface of the stator 20 (the upper or lower surface of the core back 21a). Thus, the upper opening 31p exposes a portion of the upper surface of the core back 21a from the first molding portion 31. Similarly, the lower opening 31q exposes a portion of the lower surface of the core back 21a from the first molding portion 31.

[0062] Figure 5 This is a perspective view of the stator 20 embedded in the first molding section 31. The state in which the stator 20 is embedded in the first molding section 31 is called the intermediate molded product 20A.

[0063] like Figure 5 As shown, multiple upper openings 31p and lower openings 31q are provided on the first molding part 31. The multiple upper openings 31p and multiple lower openings 31q are arranged at equal intervals along the circumferential direction. In this embodiment, when viewed from the axial direction, the upper openings 31p and lower openings 31q overlap each other.

[0064] The mold forming the first molding part 31 has a support pin that contacts the upper and lower surfaces of the back of the iron core 21a and holds the stator 20. The upper opening 31p is the trace of the support pin that contacts the upper surface of the back of the iron core 21a, and the lower opening 31q is the trace of the support pin that contacts the lower surface of the back of the iron core 21a.

[0065] like Figure 1 As shown, the second molding section 32 embeds the intermediate molded part 20A and the bearing cage 80. That is, the housing 30 fixes the stator 20 and the bearing cage 80 to each other. As a result, the process of fixing the bearing cage 80 to the stator 20 can be omitted, thereby simplifying the manufacturing process.

[0066] In general, in resin molded products, if the wall thickness is large, the shrinkage during resin curing (so-called shrinkage marks) becomes greater, resulting in surface irregularities and making dimensional control more difficult. To address this, in this embodiment, the housing 30 is manufactured through a two-stage molding process involving a first molding section 31 and a second molding section 32. Therefore, by stacking two layers (the first molding section 31 and the second molding section 32) to form the thicker sections of the housing 30, shrinkage marks in these thicker sections can be suppressed. This improves the overall dimensional accuracy of the housing 30. Furthermore, the thinner sections of the housing 30 are formed only by the first molding section 31 or the second molding section 32, allowing for different wall thicknesses within the housing 30.

[0067] Furthermore, this effect can be achieved regardless of whether the first molding part 31 and the second molding part 32 are made of the same resin material or different resin materials.

[0068] The second molding section 32 has an embedded retaining section 32a in which an intermediate molded part 20A and a bearing retainer 80 are embedded, and a lower cylinder section 32t located below the embedded retaining section 32a.

[0069] The lower cylindrical portion 32t extends downward from the embedded retaining portion 32a. The lower cylindrical portion 32t is cylindrical with the central axis J as its center. The outer peripheral surface of the lower cylindrical portion 32t extends in connection with the outer peripheral surface of the embedded retaining portion 32a. The inner peripheral surface 32ta of the lower cylindrical portion 32t is located radially inward than the outer surface 31bc of the second covering portion 31b of the first molding portion 31. The lower cylindrical portion 32t surrounds the busbar unit 70 radially outward.

[0070] A control device 8 for controlling the motor 1 is mounted on the inner circumferential surface 32ta of the lower cylinder 32t. A socket portion 8a is provided on the upper surface of the control device 8. The socket portion 8a is a hole extending downward from the upper surface. The busbar 71 is electrically connected to the control device 8 by being inserted into the socket portion 8a through a terminal 71a. In addition, the control device 8 has a mounting surface 8b facing radially outward. The mounting surface 8b is a cylindrical surface centered on the central axis J and facing radially outward. The mounting surface 8b is embedded in the inner circumferential surface 32ta of the lower cylinder 32t. A groove 8g for receiving a washer 8c is provided on the mounting surface 8b. The washer 8c is compressed between the bottom surface of the groove 8g and the inner circumferential surface 32ta of the lower cylinder 32t. The washer 8c prevents moisture or oil from seeping into the radially inner side of the lower cylinder 32t.

[0071] The embedded retaining portion 32a has an outer covering portion 32b that covers the outer surface 31bc of the first molding portion 31, and an upper step portion (step portion) 32c and a lower step portion (step portion) 32d located above and below the outer covering portion 32b. That is, the second molding portion 32 has an outer covering portion 32b, an upper step portion 32c, and a lower step portion 32d. The upper step portion 32c contacts the upper surface 31ba of the second covering portion 31b of the first molding portion 31. In addition, the lower step portion 32d contacts the lower surface 31bb of the second covering portion 31b of the first molding portion 31.

[0072] The first molding portion 31 is embedded in the second molding portion 32. However, the first molding portion 31 and the second molding portion 32 are not bonded to each other. Therefore, in the event of an impact or other event to the housing 30, the interface between the first molding portion 31 and the second molding portion 32 may peel off, causing them to shift relative to each other. According to this embodiment, the second molding portion 32 contacts the upper surface 31ba of the first molding portion 31 at the upper step portion 32c. This suppresses the downward movement of the second molding portion 32 relative to the first molding portion 31. Similarly, the second molding portion 32 contacts the lower surface 31bb of the first molding portion 31 at the lower step portion 32d. This suppresses the upward movement of the second molding portion 32 relative to the first molding portion 31. Furthermore, the second molding portion 32 has a structure in which the upper step portion 32c and the lower step portion 32d are connected by the outer covering portion 32b. Therefore, the relative movement of the second molding portion 32 relative to the first molding portion 31 in the up-down direction is suppressed.

[0073] like Figure 2 As shown, a portion of the outer covering portion 32b penetrates into the groove 31bd provided on the outer surface 31bc of the first molding portion 31. Therefore, the first molding portion 31 and the second molding portion 32 are in contact with each other on the surfaces facing the circumferential sides, thereby suppressing the relative rotation of the second molding portion 32 with respect to the first molding portion 31.

[0074] like Figure 1 As shown, the embedded holding portion 32a of the second molding portion 32 has an upper filling portion (filling portion) 32p and a lower filling portion (filling portion) 32q that are respectively filled in the upper opening portion 31p and the lower opening portion 31q of the first molding portion 31.

[0075] The upper opening 31p and the lower opening 31q are traces of the retaining pins that hold the stator core 21 in the mold forming the first molding part 31, and expose the surface of the stator core 21. Therefore, the upper filling part 32p and the lower filling part 32q respectively close the upper opening 31p and the lower opening 31q, thereby preventing the stator core 21 from being exposed to external environments such as moisture or oil. As a result, the deterioration of the stator core 21's properties, such as rusting, can be suppressed.

[0076] The embedded retaining portion 32a has a retainer surrounding portion 32e that surrounds the bearing retainer 80 radially outward and an upper covering portion 32f located on the upper side of the bearing retainer 80. The retainer surrounding portion 32e is located radially outward of the nut portion 85 and the outer ring portion 87 of the bearing retainer 80 and positions the bearing retainer 80 radially. The upper covering portion 32f is connected to the upper end of the retainer surrounding portion 32e and extends radially inward from the retainer surrounding portion 32e. Furthermore, the upper end face 85a of the nut portion 85 protrudes from the upper covering portion 32f. The upper end face 85a contacts the downward-facing inner surface of the mold forming the second molding portion 32. This inner surface inhibits upward movement of the bearing retainer 80 and the intermediate molded part 20A and positions the bearing retainer 80 and the intermediate molded part 20A axially within the mold.

[0077] As described above, the bearing cage 80 is located on the upper side of the stator 20. The bearing cage 80 has a facing surface 80a located on the upper side of the coil 29 and facing downward. The facing surface 80a is a flat surface perpendicular to the central axis J. The facing surface 80a faces the upper surface of the first covering portion 31a of the first molding portion 31 across a gap G. That is, the bearing cage 80 and the first covering portion 31a are axially separated by a gap G. The shape of the coil 29 after winding is difficult to form in the same shape between products, so each product is slightly different. The first covering portion 31a covers the coil 29, so it is assumed that the wall thickness varies according to the shape of the coil 29, so the amount of shrinkage of each product is different according to the wall thickness. Therefore, when the bearing cage 80 is in contact with the first covering portion 31a, the positional accuracy of the bearing cage 80 may be reduced. According to this embodiment, the bearing cage 80 and the first covering portion 31a are arranged with a gap G and do not directly contact each other. Therefore, it is possible to suppress the decrease in axial positional accuracy of the bearing cage 80 caused by the shrinkage amount of the first covering portion 31a.

[0078] In this embodiment, the lower surface of the cylindrical leg 87a of the bearing cage 80 contacts the upper surface 31ba of the first molding portion 31. Furthermore, the bearing cage 80 is covered from above by the second molding portion 32. Therefore, the bearing cage 80 is held vertically by the housing 30. Thus, the bearing cage 80 is securely held vertically by the housing 30.

[0079] The second molding portion 32 partially exposes the lower surface 31bb of the first molding portion 31. Therefore, the lower surface 31bb functions as an axially exposed surface 31f. That is, the first molding portion 31 has an exposed surface 31f that protrudes from the second molding portion 32. The exposed surface 31f contacts the upper-facing inner surface of the mold from which the second molding portion 32 is formed. According to this embodiment, since the first molding portion 31 has an axially exposed surface 31f, by mating the mold with the exposed surface 31f during the molding of the second molding portion 32, the axial positional accuracy of the intermediate molded article 20A can be improved within the mold. As a result, the positional accuracy of the second molding portion 32 relative to the intermediate molded article 20A (i.e., the stator 20 and the first molding portion 31) can be improved.

[0080] In this embodiment, the exposed surface 31f is a plane perpendicular to the axial direction. Therefore, the inner surface of the mold can stabilize the support of the exposed surface 31f, thereby suppressing the positional displacement of the intermediate molded article 20A within the mold.

[0081] In this embodiment, the intermediate molded article 20A is housed in the mold with the bearing retainer 80 overlapping on its upper side. The intermediate molded article 20A and the bearing retainer 80 are held together in the mold in a vertical direction at the exposed surface 31f of the intermediate molded article 20A and the upper end surface 85a of the bearing retainer 80. Therefore, the holding strength of the intermediate molded article 20A and the bearing retainer 80 in the mold is improved, thereby suppressing the positional displacement of the stator 20 caused by the injection pressure of the resin during molding.

[0082] The lower surface 31bb (i.e., exposed surface 31f) of the first molding portion 31 contacts the leg 77 of the busbar unit 70. That is, the busbar unit 70 contacts the axially oriented lower surface 31bb of the housing 30. Therefore, the busbar unit 70 is positioned axially with reference to the lower surface 31bb of the first molding portion 31.

[0083] In this embodiment, the stator core 21 is composed of multiple electromagnetic steel plates 21t stacked axially. The electromagnetic steel plates 21t are formed by stamping. Therefore, the dimensional error of the base material of the electromagnetic steel plates 21t in the stator core 21 accumulates axially, resulting in an increase in dimensional tolerance. Consequently, if the busbar unit 70 is to be directly contacted with the electromagnetic steel plates 21t for axial positioning, the axial position of the busbar unit 70 will deviate.

[0084] In this embodiment, the axial positioning of the busbar unit 70 is based on the lower surface 31bb of the first molding portion 31. The lower surface 31bb of the first molding portion 31 originates from the surface of the mold that forms the first molding portion 31, thus making it less susceptible to dimensional errors in the electromagnetic steel plate 21t. Therefore, the axial positioning accuracy of the busbar unit 70 can be improved, thereby ensuring a stable connection between the terminal 71a and the control device 8.

[0085] According to this embodiment, the busbar unit 70 is in contact with the first molding portion 31 within the housing 30. A portion of the first molding portion 31 is embedded within the housing 30 in the second molding portion 32. Therefore, the dimensional tolerance of the second molding portion 32 is sometimes obtained by adding the dimensional deviation of the second molding portion 32 itself to the dimensional deviation of the first molding portion 31. According to this embodiment, the busbar unit 70 is positioned with reference to the lower surface 31bb of the first molding portion 31, thus suppressing the influence of dimensional deviations of the second molding portion 32.

[0086] According to this embodiment, the busbar unit 70 contacts the housing 30 at the leg 77 extending axially toward the stator 20. Therefore, the busbar 71 can be arranged overlappingly on the underside of the coil, thereby enabling the overall miniaturization of the motor 1. In addition, the connecting portion 71c can be arranged in the space between the legs 77 in the circumferential direction, thereby enabling the miniaturization of the busbar unit 70 by effectively utilizing space.

[0087] According to this embodiment, the bearing cage 80 contacts the axially facing surface (upper surface 31ba) of the housing 30. Therefore, the axial positioning of the bearing cage 80 is performed with reference to the upper surface 31ba of the first molding portion 31. The upper surface 31ba and lower surface 31bb of the first molding portion 31 are similarly less susceptible to dimensional errors of the electromagnetic steel plate 21t. Therefore, the axial positional accuracy of the bearing cage 80 can be improved.

[0088] According to this embodiment, the bearing cage 80 is in contact with the first molding portion 31 in particular within the housing 30. Therefore, the bearing cage 80 is positioned axially without being affected by dimensional deviations of the second molding portion 32.

[0089] According to this embodiment, the bearing cage 80 contacts the housing 30 at the cylindrical leg 87a extending axially toward the stator 20. Therefore, space can be effectively utilized by arranging a portion of the coil 29 on the radially inner side of the cylindrical leg 87a, thereby enabling the overall miniaturization of the motor 1.

[0090] In this embodiment, the first molding portion 31 and the second molding portion 32 are made of different resin materials. Different components are embedded in the first molding portion 31 and the second molding portion 32. Therefore, the required performance of the first molding portion 31 and the second molding portion 32 may sometimes differ. According to this embodiment, the housing 30 has a first molding portion 31 and a second molding portion 32. Therefore, a resin material suitable for the first molding portion 31 and the second molding portion 32 can be selected according to the required performance.

[0091] In this embodiment, the resin material of the first molding portion 31 preferably has higher insulation properties than the resin material of the second molding portion 32. The first molding portion 31 covers the coil 29 through which current flows. Therefore, it is preferable that the insulation properties of the first molding portion 31 are sufficiently high. On the other hand, the second molding portion 32 does not directly cover the portion through which current flows, so insulation is not necessarily required. Therefore, it is preferable that the resin material of the first molding portion 31 has higher insulation properties than the resin material of the second molding portion 32.

[0092] Considering insulation properties, polybutylene terephthalate (PBT) resin is selected as the resin material for the first molding section 31, and phenolic resin (PF) resin is selected as the resin material for the second molding section 32.

[0093] In this embodiment, the resin material of the second molding portion 32 is preferably more resistant to the external environment than the resin material of the first molding portion 31. In this embodiment, the second molding portion 32 is cylindrical, surrounding the stator 20 from the radially outer side, and the first molding portion 31 is disposed on the radially inner side of the cylindrical second molding portion 32. An external device 9 is connected to the motor 1 from the top, and a control device 8 is connected to the motor 1 from the bottom. Furthermore, the external device 9 has gaskets 9c and 8c to prevent moisture or oil from seeping into the radially inner side of the second molding portion 32. That is, the first molding portion 31, disposed on the radially inner side of the second molding portion 32, is less likely to be exposed to moisture or oil from the external environment. On the other hand, the second molding portion 32 forms the outer surface of the motor 1, and therefore may be exposed to the external environment. Therefore, as the resin material of the second molding portion 32, it is preferable to select a resin material with higher resistance to the external environment than the resin material of the first molding portion 31.

[0094] Furthermore, here, external environment refers to, for example, resistance to moisture and resistance to pharmaceuticals. In motor 1 used in an environment exposed to moisture, the resin material of the second molding section 32 preferably has higher resistance to hydrolysis than the resin material of the first molding section 31.

[0095] Considering hydrolysis resistance, polybutylene terephthalate (PBT) resin is selected as the resin material for the first molding section 31, and polyphenylene sulfide (PPS) resin is selected as the resin material for the second molding section 32.

[0096] Furthermore, in motor 1 used in environments exposed to oil or chemicals, the resin material of the second molding part 32 preferably has higher resistance to the oil or chemicals than the resin material of the first molding part 31.

[0097] Considering chemical resistance, polybutylene terephthalate resin (PBT) is selected as the resin material for the first molding section 31, and polyphenylene sulfide resin (PPS) is selected as the resin material for the second molding section 32.

[0098] In this embodiment, the resin material of the first molding section 31 preferably has a higher fluidity than the resin material of the second molding section 32. The first molding section 31 covers the coil 29, thus firmly holding the coil 29 by inserting it between the coil wires. Therefore, by selecting a resin material with higher fluidity for the first molding section 31, the holding strength of the coil 29 can be improved. On the other hand, when the resin material has high fluidity, the molten resin easily penetrates the boundaries between the molds, potentially generating a large number of burrs. The second molding section 32 is an exposed part, so if a large number of burrs are generated, it is necessary to remove them. Therefore, as the second molding section 32, a resin material with less fluidity is preferably used. Therefore, as the resin material of the first molding section 31, a resin material with higher fluidity than the resin material of the second molding section 32 is preferably selected. Furthermore, here, the fluidity of the resin material refers to the viscosity of the resin material in its molten state.

[0099] Considering fluidity, polybutylene terephthalate (PBT) resin is selected as the resin material for the first molding section 31, and polyether ether ketone (PEEK) resin is selected as the resin material for the second molding section 32.

[0100] In this embodiment, the resin material of the first molding portion 31 preferably has higher elasticity than the resin material of the second molding portion 32. The first molding portion 31 covers the stator core 21. The electromagnet plate 21t constituting the stator core 21 is made of an iron alloy. The thermal expansion coefficient of the stator core 21 is higher than that of the first molding portion 31. When the stator core 21 and the coil 29 heat up due to the drive of the motor 1, the expansion amount of the stator core 21 is greater than that of the first molding portion 31, thereby applying a load to the first molding portion 31. By using a resin material with higher elasticity as the first molding portion 31, damage to the first molding portion 31 due to the load caused by the difference in thermal expansion coefficients can be suppressed. On the other hand, the second molding portion 32 does not come into direct contact with the heated metal material, so it is not easy to generate a large load caused by the difference in thermal expansion coefficients, and therefore elasticity is not necessarily required. Therefore, as the resin material of the first molding portion 31, a resin material with higher elasticity than the resin material of the second molding portion 32 is preferably selected. As for elasticity, it can be measured by Shore hardness (according to JIS Z 2246:2000).

[0101] Considering elasticity, polyamide resin (PA) is selected as the resin material for the first molding section 31, and polybutylene terephthalate resin (PBT) is selected as the resin material for the second molding section 32.

[0102] In this embodiment, the resin material of the second molding portion 32 has higher toughness and impact resistance than the resin material of the first molding portion 31. The second molding portion 32 is an exposed part and is therefore sometimes subjected to external impacts. By using a resin material with higher toughness and impact resistance for the second molding portion 32, damage to the motor 1 from external impacts can be suppressed. In contrast, the first molding portion 31 is not easily subjected to impacts and therefore does not necessarily require high toughness and impact resistance. Therefore, it is preferable to select a resin material with higher toughness and impact resistance than the resin material of the first molding portion 31 as the resin material for the second molding portion 32. The Charpy impact characteristic (JIS K 7111-1:2012) can be used as an indicator for toughness and impact resistance.

[0103] Considering toughness and impact resistance, polyamide resin (PA) is selected as the resin material for the first molding part 31, and polybutylene terephthalate resin (PBT) is selected as the resin material for the second molding part 32.

[0104] The above description illustrates one embodiment of the present invention. However, the structures and combinations thereof in the embodiment are merely examples, and additions, omissions, substitutions, and other modifications to the structures are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments described herein.

[0105] The application of the motor 1 in the above embodiments is not particularly limited. The motor 1 in the above embodiments and their modifications is, for example, mounted on an electric pump and an electric power steering system.

[0106] Label Explanation

[0107] 1: Motor; 8: Control device; 10: Rotor; 11: Shaft; 15: Bearing; 20: Stator; 21: Stator core; 21a: Back of core; 21b: Tooth; 21t: Electromagnetic steel plate; 29: Coil; 30: Housing; 31: First molding part; 31a: First covering part; 31b: Second covering part; 31f: Exposed surface; 31p: Upper opening (opening); 31q: Lower opening (opening); 3 2: Second molding part; 32b: Outer covering part; 32c: Upper step part (step part); 32d: Lower step part (step part); 32p: Upper filling part (fill part); 32q: Lower filling part (fill part); 70: Busbar unit; 71: Busbar; 71a: Terminal; 77: Leg (first leg); 80: Bearing cage; 87a: Cylindrical leg (second leg); G: Clearance; J: Central axis.

Claims

1. A motor having: A rotor having a shaft extending along a central axis about which it rotates; A stator having a stator core and coils mounted on the stator core, the stator being radially opposed to the rotor; A bearing that supports the shaft and enables the shaft to rotate; A bearing cage that holds the bearing; The housing, which is made of resin material, has the stator and the bearing cage embedded therein; as well as A busbar unit, having terminals for connection to a control device, is located on the side of the stator opposite to the side where the bearing cage is located, and is in contact with the axially facing surface of the housing. The housing has: A first molding section, in which the stator is embedded; and The second molding part has the first molding part and the bearing cage embedded within it. The busbar unit is in contact with the first molding part.

2. The motor according to claim 1, wherein, The first molding portion has a first covering portion that covers the coil. The bearing cage is located on one axial side of the stator. The bearing cage and the first cover are axially opposed by a gap.

3. The motor according to claim 1 or 2, wherein, The stator core has a back side and a plurality of teeth extending radially from the back side, wherein the coil is mounted on the plurality of teeth. The first molding portion has a second covering portion that covers the surface of the back of the iron core. The bearing cage has legs located on the axial side of the stator and in contact with the axially facing surface of the second cover.

4. The motor according to claim 1 or 2, wherein, The stator core has a back side and a plurality of teeth extending radially from the back side, wherein the coil is mounted on the plurality of teeth. The first molding portion has a second covering portion that covers the surface of the back of the iron core. The second molding part has: An outer covering portion that covers the radially oriented surface of the second covering portion; and The stepped portion contacts the surface of the second covering portion facing one axial side or the other axial side.

5. The motor according to claim 1 or 2, wherein, The first molding part and the second molding part are made of different resin materials.

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