Electric Motor

Abstract

The present invention relates to an electric motor. The boundary between the stator core and the housing can be sealed without arranging a sealing member of resin or rubber between the stator core and the housing. The feed shaft motor has a front housing fixed to the end face of the stator core. The stator core is formed of a material with iron as a main component. The front housing is formed of a material with aluminum as a main component. The stator core and the front housing are connected to each other using a welding mark generated by laser welding. The welding mark extends circumferentially in a manner covering the contact line between the stator core and the front housing. The welding mark seals the boundary between the stator core and the front housing.

Description

Technical Field

[0001] The present invention relates to an electric motor including a housing fixed to an end surface of a stator core. Background Art

[0002] It is known that electric motors are used to move or rotate parts. Devices equipped with electric motors are used in various environments. For example, electric motors are used in environments where there are many foreign objects such as dust.

[0003] For example, it is known that when cutting or grinding a workpiece, the workpiece is processed by a machine tool. Inside the processing room of the machine tool, there is dust and cutting fluid mist generated when processing the workpiece. There is a case where the motor is arranged inside the processing room. There is a case where the feed axis motor that moves the spindle head or a member supporting the workpiece is arranged inside the processing room. Since the motor is used in an environment where there is a lot of chips and cutting fluid mist, it is easy for foreign matter to enter the inside of the motor.

[0004] If foreign matter enters the interior of the motor, the performance of the motor may be degraded or the motor may fail. Therefore, it is preferable that the motor has a structure that prevents foreign matter from entering the interior.

[0005] In the prior art, there is known an electric motor in which a stator and a rotor are arranged inside a sealed container (for example, Japanese Patent Publication No. 59-101292 and Japanese Patent Publication No. 63-189685). In addition, there is known an electric motor in which a housing is fixed to an end surface of a stator core. In this electric motor, it is known that the boundary between electromagnetic steel sheets constituting the stator core and the boundary between the stator core and the housing are covered with a resin sealant (for example, Japanese Patent Publication No. 7-163083).

[0006] In the related art, there is known an electric motor in which electromagnetic steel plates of a stator core are joined together by laser welding (for example, Japanese Patent Application Laid-Open Nos. 2000-278892 and 62-171436). Summary of the invention

[0007] Problem that the invention aims to solve

[0008] For a motor in which the stator is arranged inside a sealed container, it is necessary to prepare a container surrounding the stator. On the other hand, for a motor in which the housing is fixed to the end face of the stator, it is not necessary to prepare a sealed container surrounding the stator. In this motor, in order to prevent foreign matter from entering from the boundary between the stator core and the housing, it is necessary to seal the boundary.

[0009] For example, as a sealing member, a sealing material made of a resin that solidifies over time can be arranged between the stator core and the housing. After the sealing material is applied to the contact surface of the housing, the housing and the stator core can be fixed by a fastening member. However, in the case of a liquid sealing material, if the amount of the sealing material is large, there is a possibility that the sealing material will be squeezed out from between the stator core and the housing. Even if the sealing material squeezed out to the outside is wiped off, there is a possibility that the components of the sealing material remain. There is a problem that the coating is not arranged as expected in the area where the components of the sealing material remain. On the other hand, when the amount of the sealing material is small, there is a problem that the stator core and the housing cannot be fully sealed. As described above, there is a problem that it is difficult to control the amount of the sealing material.

[0010] In addition, the liquid sealing material is arranged along the shape of the end face of the housing. The area where the liquid sealing material is arranged is an elongated area, so there is a problem that it is difficult to arrange the sealing material. For example, when the sealing material is arranged, the operator needs to be skilled. In addition, when the sealing material is arranged by a robot device, it is necessary to control the robot with high precision. As such, there is a problem that it is difficult to arrange the liquid sealing material at a desired position.

[0011] Furthermore, management is required for storing the liquid sealing material. For example, since the sealing material solidifies over time, temperature or humidity management is required when storing the sealing material. In addition, when the device for applying the sealing material is temporarily stopped, the nozzle of the device for applying the sealing material may be clogged. Thus, management for storing the sealing material is required.

[0012] In addition, a flat sealing sheet or O-ring formed of rubber or the like can be arranged between the stator core and the housing as a sealing member. When such a sealing member is used, it is necessary to form a recessed portion or the like in the housing for arranging the sealing member. In addition, the O-ring and the sealing sheet age over time and their elasticity decreases. When the stator core and the housing are fixed with bolts, the tightening force of the bolts may decrease. In this case, the sealing property may deteriorate due to the sealing member.

[0013] Moreover, the sealing member disposed at the boundary between the stator core and the housing is formed of resin or rubber or the like. Therefore, the heat transfer performance from the stator to the housing is deteriorated. The motor generates heat mainly in the stator. The heat generated in the stator is discharged from the stator to the atmosphere, or is cooled by air passing through a cooling passage formed inside the stator. In addition, a part of the heat generated by the stator is dissipated from the housing to the atmosphere after being transferred to the housing. However, since the sealing member is formed of resin or rubber, there is a problem that sufficient heat transfer cannot be performed. Therefore, the temperature of the motor becomes easy to rise, and there is a situation where the performance of the motor must be set lower. For example, there is a situation where the upper limit value of the current supplied to the motor is set lower in order to suppress the temperature rise of the motor.

[0014] When a sealing member is disposed between the stator core and the housing as described above, various problems arise.

[0015] Solutions for solving problems

[0016] The electric motor of the technical solution disclosed in the present invention comprises: a rotor including a shaft; a stator including a stator core and a coil wound on the stator core. The electric motor comprises a housing fixed to the end surface of the stator core. The stator core is formed of a material having iron as a main component. The housing is formed of a material having aluminum as a main component. The stator core and the housing are connected to each other using a weld mark generated by laser welding. The weld mark is formed at the boundary portion where the stator core contacts the housing. The weld mark extends circumferentially in a manner covering the contact line where the stator core contacts the housing. The weld mark seals the boundary portion between the stator core and the housing.

[0017] For the above-mentioned electric motor, the shell may have a step portion formed at the boundary portion, the stator core may have a step portion formed at the boundary portion, the step portion of the shell may contact the step portion of the stator core, and a recess may be formed at the boundary portion, the welding mark may be formed on the bottom surface of the recess, and the recess may have a depth to accommodate the welding mark inside the recess.

[0018] In the above electric motor, one of the housing and the stator core may include a step portion formed at a boundary portion, and the step portion may be formed so that a height thereof is higher than a protruding height of the welding mark.

[0019] For the above-mentioned electric motor, it can also be that the electric motor has a plurality of the shells, and the plurality of shells include a front shell arranged in the direction in which the shaft protrudes, and a rear shell arranged on the side opposite to the direction in which the shaft protrudes, and the welding mark is formed at the boundary portion between the front shell and the stator core and the boundary portion between the rear shell and the stator core.

[0020] Effects of the Invention

[0021] According to the electric motor of the technical solution disclosed in the present invention, the boundary portion between the stator core and the housing can be sealed without disposing a sealing member made of resin or rubber between the stator core and the housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a perspective view of a first electric motor according to the embodiment.

[0023] Figure 2 This is a schematic cross-sectional view of the first electric motor.

[0024] Figure 3 It is an enlarged cross-sectional view of a boundary portion between the front case and the stator core according to the embodiment.

[0025] Figure 4 It is an enlarged cross-sectional view of the boundary portion between the front case and the stator core of the comparative example.

[0026] Figure 5 It is a schematic diagram of a welding device according to an embodiment.

[0027] Figure 6 This is a perspective view for explaining the galvano mechanism.

[0028] Figure 7 This is an enlarged cross-sectional view of the boundary portion between the front housing and the stator core when laser welding is performed using a welding device.

[0029] Figure 8 It is an enlarged cross-sectional view of a boundary portion between a front case and a stator core of a second electric motor according to the embodiment.

[0030] Fig. 9 It is an enlarged cross-sectional view of a boundary portion between a front case and a stator core of a third electric motor according to the embodiment.

[0031] Fig.10 This is an enlarged plan view of the front housing and the stator core for explaining the oscillating process during laser welding. DETAILED DESCRIPTION

[0032] refer to Figures 1 to 10 The motor of the present embodiment is described below. The motor of the present embodiment has a structure that prevents foreign matter from entering between the stator core and the housing.

[0033] exist Figure 1 , a perspective view of the first motor of this embodiment is shown. Figure 2 , a schematic cross-sectional view of the first motor of this embodiment is shown. Figure 1 and Figure 2 In the figure, the motor before the surface is painted is shown for the purpose of explanation. In the present embodiment, the motor arranged in the machine tool is taken as an example for explanation.

[0034] Reference Figure 1 and Figure 2 The motor of this embodiment is a feed axis motor 1 for moving a worktable of a machine tool. The feed axis motor 1 is arranged inside a processing room of the machine tool. Inside the processing room, there are foreign matters such as dust generated when processing a workpiece and mist of cutting fluid. The feed axis motor 1 has a structure to suppress the intrusion of foreign matters.

[0035] The feed shaft motor 1 includes a rotor 11 and a stator 12. The stator 12 includes a stator core 27 having a structure formed by stacking a plurality of magnetic steel plates along the direction of the rotation axis RA. A coil 16 is wound around the stator core 27. The rotor 11 includes a shaft 13 formed in a rod shape and a rotor core 17 fixed to the outer peripheral surface of the shaft 13. A magnet 18 is arranged inside the rotor core 17. The magnet 18 of this embodiment is a permanent magnet.

[0036] The shaft 13 is connected to other components to transmit rotational force. The shaft 13 rotates around the rotation axis RA. In this embodiment, in the extension direction of the rotation axis RA, the side of the shaft 13 protruding to connect with other components is called the front side. In addition, the side opposite to the front side is called the rear side. Figure 2 In the example shown, an arrow 81 indicates the front side of the feed axis motor 1 .

[0037] The feed shaft motor 1 includes a housing as a covering member fixed to the stator core 27. In the present embodiment, a plurality of housings are provided. The feed shaft motor 1 includes a front housing 21 provided in the direction in which the shaft 13 of the rotor 11 protrudes, and a rear housing 22 provided on the opposite side to the direction in which the shaft 13 protrudes.

[0038] The front housing 21 and the rear housing 22 are formed in a cylindrical shape. The front housing 21 and the rear housing 22 support the rotor 11 rotatably via the bearings 14 and 15. The front housing 21 supports the bearing 14. The rear housing 22 supports the bearing 15 via a bearing support member 26 that supports the bearing 15. An oil seal 20 is arranged between the end of the front housing 21 and the shaft 13 to suppress the intrusion of foreign matter.

[0039] The front housing 21 and the rear housing 22 are fixed to the end faces in the axial direction of the stator core 27. The end face of the front housing 21 is in contact with the end face of the stator core 27. In addition, the end face of the rear housing 22 is in contact with the end face of the stator core 27. The front housing 21 and the rear housing 22 are fixed to the stator 12 by fastening members. In the present embodiment, the front housing 21 has a hole portion formed with an internal thread. Holes for passing bolts 30 are formed in the stator core 27 and the rear housing 22. The front housing 21 and the rear housing 22 are fixed to the stator core 27 by bolts 30 as fastening members.

[0040] In the feed shaft motor 1 of the present embodiment, the diameter of the front side housing 21 is the same as the diameter of the stator core 27 at the boundary portion between the front side housing 21 and the stator core 27. The surface of the front side housing 21 is formed so as to be continuous with the surface of the stator core 27. In addition, at the boundary portion between the rear side housing 22 and the stator core 27, the diameter of the rear side housing 22 is the same as the diameter of the stator core 27. The surface of the rear side housing 22 is formed so as to be continuous with the surface of the stator core 27. The feed shaft motor 1 of the present embodiment has a structure in which a container surrounding the outer peripheral surface of the stator core 27 is not provided.

[0041] An encoder 19 for detecting the rotational position and rotational speed of the shaft 13 is disposed at the rear end of the shaft 13. A rear cover 23 for closing the internal space of the rear housing 22 is fixed to the rear end of the rear housing 22.

[0042] exist Figure 3 , an enlarged cross-sectional view of the boundary portion between the front housing and the stator core of the first electric motor is shown. Figures 1 to 3 The stator core 27 of the present embodiment has a structure formed by stacking a plurality of electromagnetic steel sheets 28. The plurality of electromagnetic steel sheets 28 are fixed to each other. In the present embodiment, a plurality of blocks formed by stacking the electromagnetic steel sheets 28 are formed in advance. Next, the stator core 27 is formed by stacking the plurality of blocks.

[0043] Each electromagnetic steel sheet 28 is formed of a material containing iron as a main component. That is, the stator core 27 is formed of a material containing iron as a main component. On the other hand, the front side case 21 and the rear side case 22 are formed of a material containing aluminum as a main component.

[0044] In the following description, the boundary between the front case 21 and the stator core 27 will be described. In particular, the welding mark that connects the front case 21 and the stator core 27 will be described. The welding mark formed at the boundary between the rear case 22 and the stator core 27 also has the same structure, function and effect.

[0045] The front side housing 21 and the stator core 27 are connected to each other by a welding mark 35. The welding mark 35 is a portion that is melted by heat during welding and then solidified. The welding mark 35 is formed at the boundary portion between the front side housing 21 and the stator core 27. The welding mark 35 connects the outer peripheral portion of the end surface of the front side housing 21 and the outer peripheral portion of the end surface of the stator core 27. A welding line extending linearly is formed at the welding mark 35. The welding mark 35 extends in the circumferential direction in a manner covering the contact line between the front side housing 21 and the stator core 27. That is, the welding mark 35 is formed in an annular shape in a manner surrounding the front side housing 21 and the stator core 27. The welding mark 35 is formed at the entire boundary portion in the circumferential direction between the stator core 27 and the front side housing 21.

[0046] In the feed shaft motor 1 of this embodiment, the boundary between the stator core 27 and the front case 21 is sealed by the welding mark 35. Therefore, foreign matter can be prevented from entering the feed shaft motor 1 from between the stator core 27 and the front case 21.

[0047] The welding mark 35 of this embodiment is formed by laser welding. In this embodiment, different materials are welded. Fiber laser is used as the oscillation source of the laser. Laser welding can be used to connect a smaller range, so the range of melting the electromagnetic steel plate 28 and the front side housing 21 can be reduced.

[0048] In this embodiment, welding marks 35 are formed at both the boundary between the front case 21 and the stator core 27 and the boundary between the rear case 22 and the stator core 27. The welding marks 35 are not limited to this form, and may be formed at any boundary.

[0049] exist Figure 4 , an enlarged schematic cross-sectional view of the boundary portion between the front housing and the stator core of the motor of the comparative example is shown. For the motor of the comparative example, a sealing material 36 formed of resin is arranged between the front housing 21 and the stator core 27 as a sealing member. The sealing material 36 is formed by solidifying a liquid sealing material. When the liquid sealing material is arranged on the end surface of the front housing 21, there is a problem that it is difficult to arrange the sealing material in the correct position and the correct amount. In addition, the liquid sealing material needs to be managed for storage.

[0050] In addition, as a sealing member, a flat sealing sheet formed of rubber can be arranged instead of the sealing material 36. In addition, a recess can be formed in the front housing, and an O-ring formed of rubber can be arranged. In such a case, due to aging, the elasticity of the sealing sheet or the O-ring decreases, so the sealing performance decreases.

[0051] Furthermore, if a sealing member formed of resin, rubber or the like is disposed between the front case and the stator core, there is a problem that the heat transfer performance from the stator core to the front case is deteriorated.

[0052] Reference Figure 3 As described above, in the motor of this embodiment, no sealing member such as a sealing material, an O-ring, or a sealing sheet is disposed between the front housing 21 and the stator core 27. In particular, no sealing member formed of rubber or resin is disposed. The end surface of the front housing 21 and the end surface of the stator core 27 are in contact with each other.

[0053] The feed shaft motor 1 of this embodiment does not require control of the sealing material for configuring the liquid and management of the sealing material for the liquid. In addition, it is not necessary to form a recessed portion for configuring a sealing sheet or an O-ring, so that the structure can be simplified. Moreover, since a sealing member formed of resin or rubber is not inserted, a high sealing performance can be maintained even after a long time.

[0054] In addition, since the stator core 27 is in contact with the front housing 21, the heat generated by the stator 12 can be efficiently transferred from the stator core 27 to the front housing 21. The heat dissipation of the stator 12 is improved, so that the temperature rise of the motor can be suppressed. As a result, the performance of the motor can be maintained at a high level without reducing it. For example, when the upper limit value of the current is set based on the temperature rise of the motor, the rated current value can be set larger.

[0055] Furthermore, the stator core 27 and the front housing 21 are welded to each other in the entire boundary portion extending in the circumferential direction of the stator core 27 and the front housing 21, thereby improving the rigidity of the feed shaft motor 1. In particular, in the present embodiment, the entire boundary portion of the front housing 21 and the rear housing 22 in the circumferential direction is fixed to the stator core 27, thereby improving the rigidity of the feed shaft motor 1.

[0056] Next, a welding device and a welding method for forming a welding mark according to the present embodiment will be described. Figure 5 , a schematic diagram of a welding device of the present embodiment is shown. The welding device 3 of the present embodiment is a laser welding device that uses laser to partially melt the workpieces for joining. The welding device 3 includes a base 51 as a base, and a column 52 erected from the base 51. An X-axis guide rail 56 extending in the X-axis direction is arranged on the upper surface of the base 51. A saddle 53 is arranged on the X-axis guide rail 56. The saddle 53 is formed in a manner that moves along the X-axis guide rail 56 as shown by arrow 85. A Y-axis guide rail 57 extending in the Y-axis direction is arranged on the upper surface of the saddle 53. A workbench 54 is arranged on the Y-axis guide rail 57. The workbench 54 is formed in a manner that moves along the Y-axis guide rail 57.

[0057] A support member 61 for supporting the rotating mechanism 62 is fixed to the workbench 54. The cross-sectional shape of the support member 61 is formed into an L-shape. The rotating mechanism 62 is fixed to the support member 61. The rotating mechanism 62 includes a workpiece fixing portion 63 for fixing the workpiece 71. The rotating mechanism 62 includes a motor for rotating the workpiece fixing portion 63. The workpiece fixing portion 63 is rotated in the A-axis direction by driving the motor. In the present embodiment, the axis of the A-axis extends in the horizontal direction.

[0058] A Z-axis guide rail 58 extending in the Z-axis direction is disposed on the column 52. A moving member 59 is engaged with the Z-axis guide rail 58. A laser welding head 41 emitting laser light is fixed to the moving member 59. As shown by arrow 86, the moving member 59 is formed to move along the Z-axis guide rail 58.

[0059] The welding device 3 of the present embodiment is a numerical control type. The welding device 3 includes a moving device that moves at least one of the laser welding head 41 and the workpiece 71 along the feed axis. The welding device 3 includes a control device 64 that controls the moving device. The control device 64 is composed of a calculation processing device (computer) having a CPU (Central Processing Unit) as a processor. The moving device includes a motor configured corresponding to each feed axis. For the welding device 3 of the present embodiment, the motor is used to move the moving member 59, the saddle 53 and the workbench 54. The control device 64 drives the motor corresponding to the feed axis based on the action program. In addition, the control device 64 drives the motor configured in the rotating mechanism 62 based on the action program.

[0060] The welding device 3 of this embodiment can change the relative position of the laser welding head 41 with respect to the workpiece 71 while irradiating the workpiece 71 with laser light. In this way, welding can be performed in various shapes by moving the laser welding head 41 relative to the workpiece 71. The workpiece 71 of this embodiment is an assembly in which the front housing 21 and the rear housing 22 are fixed to the stator core 27 by bolts 30.

[0061] The welding device 3 includes a laser oscillator 42 for oscillating laser. The laser oscillator 42 oscillates the laser light and passes through the optical fiber 43 to be supplied to the laser welding head 41. The laser oscillator 42 includes a light source for oscillating the laser light. The light source of the present embodiment is an optical fiber laser. The laser oscillator can include any light source that can perform welding of the workpiece. For example, the laser oscillator can include any type of light source that can perform laser welding such as a carbon dioxide laser. The control device 64 controls the laser oscillator 42 and the laser welding head 41 based on the operation program.

[0062] exist Figure 6 , a schematic diagram showing the internal mechanism of the laser welding head of the present embodiment. The laser welding head 41 emits laser light from an emission port. The laser welding head 41 of the present embodiment has a driving mechanism for driving a lens for adjusting a focal length. Furthermore, the laser welding head 41 includes an emission direction adjustment mechanism 44 for adjusting the direction in which the laser light is emitted from the laser welding head 41. The emission direction adjustment mechanism 44 of the present embodiment is an electrical detection mechanism.

[0063] The emission direction adjustment mechanism 44 includes a plurality of reflection plates and a reflection mirror driving motor. Figure 6In the example shown, as a reflector, there are an X-axis reflector 45a for adjusting the direction of emission in the X-axis direction, and a Y-axis reflector 45b for adjusting the direction of emission in the Y-axis direction. The laser emitted from the optical fiber 43 is reflected by the X-axis reflector 45a and the Y-axis reflector 45b. As a result, as shown by arrow 89, the laser is emitted toward the workpiece 71.

[0064] If the X-axis motor 47a changes the orientation of the X-axis mirror 45a as indicated by arrow 87, the orientation of the laser light emitted in the X-axis direction changes. If the Y-axis motor 47b changes the orientation of the Y-axis mirror 45b as indicated by arrow 88, the orientation of the laser light emitted in the Y-axis direction changes. The orientation of the emitted laser light is adjusted by adjusting the orientation of the X-axis mirror 45a and the orientation of the Y-axis mirror 45b.

[0065] In this way, the laser welding head 41 can two-dimensionally control the irradiation position of the laser light on the workpiece 71 by controlling the reflection angle of the laser light by the X-axis mirror 45a and the Y-axis mirror 45b. Such a laser welding head 41 is called a galvano scanner.

[0066] In addition, the laser welding head may not have an emission direction adjustment mechanism. In addition, as the emission direction adjustment mechanism, any mechanism that can adjust the direction of the laser emission can be used. For example, it is not a problem to use a laser welding head that includes a mechanism for adjusting the emission direction of the laser using a lens, such as a trepanning head.

[0067] Reference Figure 2 In the method for manufacturing the electric motor of the present embodiment, a plurality of electromagnetic steel sheets 28 punched into a predetermined shape are prepared in advance. Then, a block of electromagnetic steel sheets is generated by caulking the plurality of electromagnetic steel sheets. Furthermore, the stator core 27 can be formed by stacking the plurality of electromagnetic steel sheet blocks.

[0068] Next, the coil 16 is arranged around the teeth of the stator core 27. Next, the front case 21 and the rear case 22 are fixed to the stator core 27 by bolts 30. An assembly including the front case 21, the stator core 27, and the rear case 22 is formed.

[0069] In this embodiment, bolts 30 are used as fastening members to fix the front case 21 and the rear case 22 to the stator core 27, but the present invention is not limited to this. The front case, the stator core, and the rear case may be fastened to each other by any fastening member.

[0070] Next, laser welding is performed using the welding device 3. Figure 5The assembly is mounted as the workpiece 71 on the workpiece fixing portion 63 of the welding device 3. At this time, the assembly is fixed to the workpiece fixing portion 63 so that the rotation axis RA of the feed shaft motor 1 and the rotation axis of the workpiece fixing portion 63 coincide with each other.

[0071] Based on the operation program, the control device 64 moves the workpiece 71 in the X-axis direction and the Y-axis direction so that the position of the workpiece 71 irradiated with the laser becomes a predetermined position. In addition, the control device 64 moves the movable member 59 in the Z-axis direction so that the laser welding head 41 is separated from the workpiece 71 by a predetermined distance.

[0072] Next, the control device 64 drives the laser oscillator 42 to irradiate the boundary portion between the front housing 21 and the stator core 27 with laser. The control device 64 controls the table 54 to move in the Y-axis direction while irradiating the laser and controls the workpiece 71 to rotate in the A-axis direction. In addition, the control of moving the laser welding head 41 in the Z-axis direction is implemented as needed. With this control, the welding mark 35 can be formed along the circumferential direction of the workpiece 71.

[0073] The laser welding head 41 of this embodiment includes the emission direction adjustment mechanism 44. Therefore, when adjusting the irradiation position of the laser beam on the workpiece 71 in the X-axis direction or the Y-axis direction, the laser beam may be moved using the emission direction adjustment mechanism 44.

[0074] exist Figure 7 , an enlarged cross-sectional view of the boundary portion of the front housing and the stator core when irradiated with laser is shown. In the laser welding of this embodiment, a member mainly composed of aluminum and a member mainly composed of iron are welded to each other. Since the melting point of aluminum is lower than that of iron, the welding device 3 irradiates the laser 75 to a position slightly offset from the position where the electromagnetic steel sheet 28 contacts the front housing 21 toward one side of the electromagnetic steel sheet 28.

[0075] As a processing condition of the present embodiment, for example, the output of the fiber laser can be set to 600W±20%. In the present embodiment, the laser is oscillated continuously. In addition, the processing speed (moving speed of the irradiation position) can be set within the range of 10000mm / min±20%. The irradiation position of the laser can be set within the range of 0.1mm±20% from the position where the electromagnetic steel plate 28 contacts the front shell 21. The laser 75 can be irradiated from a direction of 90°±20% relative to the surface of the electromagnetic steel plate 28. In addition, the focal position of the laser is 0mm. That is, the position of the laser welding head 41 in the Z direction is adjusted so that the focus is arranged on the surface of the electromagnetic steel plate 28.

[0076] The laser irradiation conditions are not limited to the above-described conditions, and any conditions can be adopted that allow the front housing 21 and the stator core 27 to be welded. For example, welding may be performed under conditions that reduce the laser output and slow the processing speed.

[0077] In welding using a fiber laser, the spot diameter can be made smaller than the spot diameter of welding using other lasers. With fiber laser, laser welding in a fine range can be performed with high precision. For example, the electromagnetic steel plate 28 can be formed with a thickness of about 0.5 mm. In addition, by performing welding using a fiber laser, the width of the weld mark can be suppressed to about 0.1 mm. In this way, in welding using a fiber laser, high-quality processing with a smaller width of the weld mark can be performed. In addition, laser welding is not limited to welding using a fiber laser. It is also acceptable to form the weld mark using any welding device such as a welding device using a carbon dioxide laser.

[0078] Next, a welding mark 35 is formed at the boundary between the rear housing 22 and the stator core 27 by the same method as described above. Next, an impregnation agent is arranged on the surface of the assembly and the coil. By arranging the impregnation agent, the coil can be fixed or insulated. In addition, by arranging the impregnation agent, the gap between the electromagnetic steel sheets can be sealed. After that, the surface of the assembly can be painted.

[0079] In addition, in this embodiment, a welding device is used to move the workpiece in the X-axis direction and the Y-axis direction and to move the laser welding head in the Z-axis direction, but the present invention is not limited to this method. Any device that can form a welding mark at the boundary between the front housing and the stator core can be used. For example, the laser welding head can be installed on a multi-joint robot as a working tool. In addition, it is not a problem even if the robot changes its position and posture to perform laser welding along the outer peripheral surface of the assembly.

[0080] exist Figure 8 , an enlarged cross-sectional view of the boundary portion between the front side housing and the stator core of the second motor of the present embodiment is shown. The front side housing 21 of the second motor has a step portion 21a formed at the end portion joined to the stator core 27. In addition, for the stator core 27, a step portion 28a is formed at the end portion of the electromagnetic steel sheet 28 joined to the front side housing 21. The steps 21a, 28a are formed at the boundary portion between the front side housing 21 and the stator core 27. The step portion 21a of the front side housing 21 contacts the step portion 28a of the stator core 27, so that a recess 29 is formed at the boundary portion. The recess 29 is formed in a manner recessed from the outer peripheral surface of the stator core 27 and the outer peripheral surface of the front side housing 21. The recess 29 is formed throughout the entire circumference.

[0081] The welding mark 35 is formed inside the recessed portion 29. The welding mark 35 is formed on the bottom surface of the recessed portion 29. The recessed portion 29 has a depth that can accommodate the welding mark 35 inside the recessed portion 29. There is a case where the welding mark 35 has a portion protruding from the welded surface. In addition, there is a case where the surface of the welding mark 35 becomes rough and unevenness is formed on the surface.

[0082] In the second electric motor, when the weld mark 35 has a portion protruding outward, the weld mark 35 is formed so as not to protrude from the outer peripheral surface of the stator core 27 and the outer peripheral surface of the front case 21 .

[0083] exist Fig. 9 , an enlarged cross-sectional view of the boundary portion between the front housing and the stator core of the third motor of the present embodiment is shown. For the third motor, the stator core 27 is formed in a manner that the outer diameter is smaller than the outer diameter of the front housing 21. In addition, a step portion 21a is formed in a manner that is recessed from the outer peripheral surface of the front housing 21 at the boundary portion between the front housing 21 and the stator core 27. The diameter of the bottom surface 21b of the step portion 21a is the same as the diameter of the outer peripheral surface of the stator core 27. The step portion 21a is formed in a manner that its height is higher than the height of the welding mark 35 protruding from the surface of the stator core 27 and the bottom surface 21b of the step portion 21a. The step portion 21a is formed throughout the entire circumference. For the third motor, the welding mark 35 is formed in a manner that does not protrude from the outer peripheral surface of the front housing 21.

[0084] For the second motor and the third motor, the outer diameter of the motor can be suppressed from increasing by the welding mark 35. In addition, when the motor is mounted on other devices, it is possible to avoid the situation where the motor cannot be mounted in a desired state due to the welding mark 35. For example, when the feed shaft motor 1 is fixed to the mounting surface, it is possible to avoid the welding mark contacting the mounting surface. In addition, when the motor is transported by a robot device, it is possible to avoid the situation where the hand cannot hold the motor due to the welding mark 35.

[0085] The second motor and the third motor have the same structure, function, effect and manufacturing method as the first motor except for the above, and thus will not be described again here.

[0086] In addition, Fig. 9 In the example shown, the step portion 21a is formed at the end of the outer circumference of the front case 21, but the present invention is not limited to this. Even if the step portion is not formed at the end of the outer circumference of the front case 21, a step portion may be formed at the end of the outer circumference of the stator core 27.

[0087] In the laser welding of the present embodiment, laser welding is performed without using welding wire as a welding material, but the present invention is not limited to this method. It is also possible to use welding wire for laser welding. By using welding wire, the surface of the welding mark can be made smooth. In the case of using welding wire for welding, the portion of the welding mark protruding from the outer peripheral surface of the front housing and the outer peripheral surface of the stator core becomes higher. Therefore, it is preferable to form a recess or a step portion at the boundary portion between the front housing and the stator core.

[0088] exist Fig.10 , an explanatory diagram showing another welding method according to the present embodiment. Fig.10 It is an enlarged plan view of the boundary portion between the front housing 21 and the stator core 27. In the welding method of the above-described embodiment, the welding device 3 is driven so that the irradiation position of the laser beam is linearly moved relative to the assembly.

[0089] In contrast, in another irradiation method, the welding device 3 is driven so that the irradiation position irradiated with the laser moves in a spiral shape relative to the assembly. As shown by arrow 90, the laser is irradiated so that the laser spot 76 moves in a spiral shape. Such an irradiation method can be implemented by controlling the emission direction adjustment mechanism 44 so that the laser spot 76 moves along a circular orbit and moving the workpiece 71 in the Y-axis direction. The processing method in which the laser spot 76 moves in a spiral shape is called oscillating processing.

[0090] By using the oscillating process to weld the boundary portion between the front housing 21 and the stator core 27, the width of the weld mark 35 can be increased. Since the spot diameter of the laser is small, high-precision control is required to move the laser along the contact line between the front housing 21 and the stator core 27. Therefore, there is a case where the laser spot is offset from the desired position. However, by performing the oscillating process, the weld mark 35 can be formed in a manner that reliably covers the contact line. And the boundary portion between the front housing 21 and the stator core 27 can be more reliably sealed.

[0091] In this embodiment, the feed axis motor of a machine tool is used as an example for explanation as a motor, but the present invention is not limited to this method. The motor of this embodiment can be configured in any device. In particular, the structure of this embodiment is suitable for a motor used in an environment where there are many foreign objects.

[0092] According to the electric motor of the technical solution disclosed in the present invention, the boundary portion between the stator core and the housing can be sealed without disposing a sealing member made of resin or rubber between the stator core and the housing.

[0093] The above-mentioned embodiments can be combined appropriately. In the above-mentioned drawings, the same or equivalent parts are marked with the same reference numerals. In addition, the above-mentioned embodiments are examples and do not limit the invention. In addition, in the embodiments, changes to the embodiments shown in the claims are included.

Claims

1. An electric motor, characterized in that: The motor has: a rotor comprising a shaft; a stator including a stator core and a coil wound around the stator core; and a housing fixed to an end surface of the stator core, The stator core is formed of a material containing iron as a main component. The housing is formed of a material containing aluminum as a main component. The stator core and the housing are connected to each other by a welding mark generated by laser welding. The welding mark is formed at the boundary portion where the stator core contacts the housing, and extends circumferentially in a manner covering the contact line between the stator core and the housing, thereby sealing the boundary portion between the stator core and the housing. At least one of the housing and the stator core has a step portion formed at a boundary portion, and the step portion is formed so that a height thereof is higher than a protruding height of the welding mark.

2. The electric motor according to claim 1, characterized in that The housing has a step portion formed at the interface portion, The stator core has a step portion formed at a boundary portion, The step portion of the housing contacts the step portion of the stator core, and a recess is formed at the boundary portion. The welding mark is formed on the bottom surface of the recessed portion, The recess has a depth that allows the welding mark to be accommodated inside the recess.

3. The electric motor according to claim 1, characterized in that One of the housing and the stator core has a step portion formed at a boundary portion, and the welding mark is formed in an annular shape so as to surround the housing and the stator core.

4. The electric motor according to any one of claims 1 to 3, characterized in that: The electric motor includes a plurality of the housings. The plurality of housings include a front housing arranged in a direction in which the shaft protrudes, and a rear housing arranged on a side opposite to the direction in which the shaft protrudes. The welding marks are formed at the boundary portions between the front case and the stator core and at the boundary portions between the rear case and the stator core.

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