Electric machine and method for manufacturing an electric machine

Abstract

A motor in which a shaft is welded or fused to a metal member. The motor shaft is formed of metal and has an outer peripheral portion formed of a manganese-containing martensitic stainless steel; and a base having a zinc-containing covering layer, the metal member being covered by the covering layer, the shaft being fixed to the base, a stator being fixed to the base, a rotor being rotatable relative to the shaft, the shaft having two end portions, the outer peripheral portion between the two end portions of the shaft having a cylindrical surface, a concave surface extending in the circumferential direction, the covering layer having an opening, the metal member having an exposed portion exposed from the opening, the concave surface of the shaft and the exposed portion being fused or welded, the concave surface being located on the base side in the length direction of the shaft relative to the cylindrical surface, the shaft having a welded portion of the concave surface and the exposed portion on the inner side of the exposed portion, the welded portion being located on the concave surface side in the length direction of the shaft relative to the surface of the base on the side of the cylindrical surface, the surface of the base being a reference surface, and the cylindrical surface being a surface for positioning.

Description

[0001] This application is a divisional application of patent application No. 201980034603.4, filed on May 13, 2019, entitled "Electric Motor and Method of Manufacturing an Electric Motor". Technical Field

[0002] This invention relates to an electric motor and a method for manufacturing an electric motor, and particularly to an electric motor having a shaft welded or fused to a metal component and a method for manufacturing an electric motor. Background Technology

[0003] Previously, there was a known type of motor that had a structure in which the shaft was welded or fused to a metal component.

[0004] Patent document 1 discloses the following: when joining a shaft and a plate of a rotating body such as a motor, laser welding is performed by irradiating the joint of the shaft and the plate with a laser while rotating the plate.

[0005] (Existing technical documents) (Patent Documents) Patent Document 1: JP2004-090030A Publication Summary of the Invention

[0006] (The problem that the invention aims to solve) The purpose of this invention is to provide an electric motor with a shaft welded or fused to a metal component and a method for manufacturing the motor.

[0007] (Methods used to solve problems) To achieve the above objectives, according to one embodiment of the present invention, the motor comprises: a shaft formed of metal; and a base having a metal member covered by a cover layer having an opening, the metal member having an exposed portion exposed from the opening, the outer periphery of the shaft and the exposed portion being fused or welded.

[0008] The outer periphery of the preferred shaft has a concave surface extending circumferentially, and the concave surface and the exposed portion are fused or welded together.

[0009] Preferably, the outer periphery of the shaft has a cylindrical surface, and the concave surface and the cylindrical surface are arranged in the length direction of the shaft, with the entire concave surface located inside the cylindrical surface in the radial direction.

[0010] The preferred substrate has a resin component with wires formed thereon.

[0011] The preferred coating layer has zinc.

[0012] The preferred shaft is made of lead-free martensitic stainless steel.

[0013] The preferred motor has: a rotor capable of rotating relative to the shaft; and a polygon mirror mounted on the rotor.

[0014] The preferred motor has bearings, and the multifaceted mirror is set in the bearings.

[0015] According to another embodiment of the present invention, a method for manufacturing an electric motor includes the following steps: a first step in which a portion of the covering layer of a metal component covered by a covering layer is removed; and a second step in which the outer periphery of a shaft formed of metal is fused or welded to the exposed portion of the metal component exposed in the first step.

[0016] Preferably, in the first step, a hole is formed in the metal component by a cutting tool and the covering layer around the hole is cut to remove the covering layer. In the second step, the outer periphery and exposed part of the shaft inserted into the hole are fused or welded.

[0017] According to the above invention, it is possible to provide an electric motor with shaft welded or fused to a metal component and a method for manufacturing the electric motor. Attached Figure Description

[0018] Figure 1 This is a perspective view showing an example of an electric motor according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of the motor; Figure 3 This is a cross-sectional view showing the portion where the metal substrate and the shaft meet; Figure 4 This is the first diagram illustrating the manufacturing process of an electric motor; Figure 5 This is the second diagram illustrating the manufacturing process of the electric motor; Figure 6 This is the third diagram illustrating the manufacturing process of the electric motor; Figure 7 This is the fourth diagram illustrating the manufacturing process of the electric motor; Figure 8 This is a cross-sectional view of the motor involved in a variation of this embodiment. Detailed Implementation

[0019] Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

[0020] In this embodiment, a motor (multifaceted mirror scanner motor) used for laser scanning and rotating a multifaceted mirror in a laser beam printer or the like will be described.

[0021] [Implementation Method] Figure 1 This is a perspective view showing an example of a motor 1 according to an embodiment of the present invention. Figure 2This is a cross-sectional view of motor 1.

[0022] In the following description, the direction along axis 5 will be away from the faceted mirror 70 and closer to the substrate 80. Figure 2 The direction below (in the image) is called the downward direction, and along axis 5, the direction moves away from the substrate 80 and towards the polygon mirror 70. Figure 1 The direction above (in the equation) is called the upward direction.

[0023] Reference Figure 1 and Figure 2 In this embodiment, the motor 1 is a motor that drives the multifaceted mirror 70 mounted on the rotor 10. The motor 1 mainly includes a shaft 5, a rotor 10, a stator 20, a multifaceted mirror 70, and a base plate 80.

[0024] Shaft 5 is fixed to base plate 80. Stator 20 is disposed on base plate 80. Rotor 10 is mounted to be rotatable relative to shaft 5.

[0025] The rotor 10 has a frame 11, a magnet 12, and a sleeve (an example of a bearing) 40.

[0026] Frame 11 is a component that prevents magnetic fields from leaking from its interior, and is made of, for example, a magnet. Frame 11 has the following characteristics along a direction perpendicular to axis 5 (outer circumferential direction). Figure 2 The portion extending laterally (in the middle); and along the direction parallel to axis 5 (in the middle) Figure 2 The portion extending vertically (in the middle) to form the sidewall. The frame 11 has a cylindrical shape that is closed at the top and open downwards.

[0027] The magnet 12 is ring-shaped, or more specifically, cylindrical. The magnet 12 is mounted on the inner wall surface of the outer periphery of the frame 11.

[0028] The sleeve 40 extends vertically through the center of the frame 11. The sleeve 40 is fixed to a hole formed in the center of the upper surface of the frame 11. The polygonal mirror 70 is fixed to the upper part of the sleeve 40. The center of the sleeve 40 is a cylindrical portion 41, into which the shaft 5 is inserted. The gap between the sleeve 40 and the shaft 5 is filled with, for example, lubricant to form a radial hydrodynamic bearing. Thus, the rotor 10 can rotate relative to the shaft 5. It should be noted that, on the inner side of the cylindrical portion 41 of the sleeve 40, herringbone grooves are formed axially at two locations (not shown), but this is not a limitation.

[0029] The thrust plate 45 and the thrust shield 46 are installed on the upper part of the cylindrical portion 41 of the sleeve 40. The thrust shield 46 covers the upper end of the cylindrical portion 41. The thrust plate 45 is disposed between the thrust shield 46 and the upper end face of the shaft 5.

[0030] The stator 20 includes: a stator core 21 having a plurality of teeth extending radially outward from the center; and a stator coil 22 wound around the teeth. The stator 20 is positioned further inward than the magnet 12, spaced apart from it. The stator coil 22 generates a magnetic field when energized. A driving force (a force that rotates the rotor 10) is generated through the interaction of the magnetic field of the stator coil 22 and the magnetic field of the magnet 12.

[0031] The polygon mirror 70 is fixed to the upper part of the sleeve 40 and located above the frame 11. The polygon mirror 70 is clamped and fixed by a spring 51 located above and a part of the sleeve 40. A clamping ring 52 is arranged on the upper part of the spring 51, and the spring 51 is positioned vertically by the clamping ring 52.

[0032] The substrate (an example of a base) 80 has a metal substrate (an example of a metal component) 81 and a circuit board (an example of a resin component) 89. The circuit board 89 is superimposed on the upper surface of the metal substrate 81 to form a substrate 80.

[0033] The circuit board 89, for example, is a printed wiring board, a resin component with wiring formed thereon. The resin component is, for example, formed of epoxy resin. Electronic components 95 are mounted on the upper surface of the circuit board 89. Figure 1 (The upper surface of the circuit board 89). The electronic component 95 includes, for example, a drive / control integrated circuit for driving and controlling the motor. The electronic component 95 is bonded to the upper surface of the circuit board 89 by means of solder. In addition, the circuit board 89 may also be provided with various circuit elements such as Hall elements that detect the rotation angle and number of revolutions of the magnet 12 based on the change of the magnetic field received from the magnet 12, chip-type circuit elements (resistors, capacitors), and drive ICs for applying / cutting off current to each stator coil 22.

[0034] The metal substrate 81 is, for example, made of a substrate formed of iron. A hole 85 is formed in the metal substrate 81. The shaft 5 is inserted into the hole 85. As described later, the shaft 5 and the metal substrate 81 are securely fixed together by laser welding the joint between the shaft 5 and the hole 85 on the lower surface side of the metal substrate 81. After fixing the shaft 5 to the metal substrate 81, a circuit board 89 is mounted on the metal substrate 81, and a stator 20 and a rotor 10 are installed, thereby manufacturing the motor 1.

[0035] Furthermore, the shaft 5 has a protrusion 5c that protrudes downward from the substrate 80. By providing the protrusion 5c, when the motor 1 is mounted on a device or the like that utilizing the motor 1, the protrusion 5c is inserted into a hole provided on the device side, thereby enabling the positioning of the motor 1. The shaft of the protrusion 5c is aligned with the rotation axis of the polygon mirror 70 of the motor 1, therefore, the positioning of the polygon mirror in a device utilizing the motor 1 can be easily and accurately achieved.

[0036] Figure 3 This is a cross-sectional view showing the portion where the metal substrate 81 and the shaft 5 meet.

[0037] exist Figure 3 The metal substrate 81 and shaft 5 are shown, but other components are not shown. Furthermore, regarding the metal substrate 81, a cross-section through the central axis of shaft 5 is shown.

[0038] In this embodiment, the metal substrate 81 is a galvanized steel sheet with JIS designations such as "SECC", "SECD", "SECE", "SECF", and "SECG" as determined according to JIS specifications. That is, the surface of the metal substrate 81 is covered by a cover layer 83. The metal substrate 81 has galvanized layers, namely the cover layer 83, for covering both the upper and lower surfaces respectively. The cover layer 83 is a layer provided for corrosion protection. It should be noted that... Figure 3 The following figures schematically show the cover layer 83. Since the metal substrate 81 is formed using widely available and readily available galvanized steel sheet, the manufacturing cost of the motor 1 can be kept low.

[0039] Shaft 5 is formed of a metal component. In this embodiment, shaft 5 is formed of lead-free martensitic stainless steel. For example, shaft 5 is a stainless steel with JIS designations such as "SUS420F", "SUS420J2", "SUS420J1", "SUS403", "SUS410", "SUS416", "SUS431", "SUS440C", etc., as determined according to JIS specifications. These stainless steels have excellent wear resistance and improved machinability, and contain no added lead (virtually lead-free). Therefore, lead-free martensitic stainless steel refers to stainless steel without added lead (virtually lead-free). Shaft 5 is a stainless steel containing manganese. It should be noted that the material of shaft 5 is not limited to this.

[0040] exist Figure 3In this embodiment, on the lower surface of the metal substrate 81, the metal substrate 81 has a recess (an example of an exposed portion) 84. The recess 84 is, for example, a region that is recessed upwards from the surface of the metal substrate 81 with a diameter D2 and a dimension t1, and is formed approximately concentrically with the hole 85. The depth (dimension t1) of the recess 84 is slightly greater than the thickness of the cover layer 83. As described later, the recess 84 is formed by cutting the surface of the metal substrate 81. That is, the lower cover layer 83 has an opening 83b by providing the recess 84. In other words, it can be said that the metal substrate 81 has an exposed portion (recess 84) where the portion of iron not covered by the cover layer 83 is exposed downwards through the opening 83b provided in the cover layer 83.

[0041] Shaft 5 is inserted into hole 85 through metal substrate 81. The diameter D1 of shaft 5 is slightly smaller than the inner diameter of hole 85.

[0042] In this embodiment, for example, dimension t1 is a size ranging from 0.01 mm to 0.1 mm, diameter D1 is 2.368 mm ± 0.0005 mm, and diameter D2 is a size ranging from 3.3 mm to 4.8 mm. The inner diameter of the hole 85 is a size ranging from 2.0 mm to 5.0 mm.

[0043] The outer peripheral portion of the shaft 5 protruding downward from the hole 85 and the recess 84 are welded by laser welding. Welding is performed on the entire circumference of the shaft 5. By welding, a radially recessed concave surface 87 is formed at the upper end of the portion protruding downward from the recess 84 in the shaft 5. The concave surface 87 extends circumferentially along the shaft 5. Weld marks are formed on the surface of the concave surface 87. On the surface of the recess 84 and near the shaft 5, the alloy formed during welding manifests as weld marks. That is, the concave surface 87 and the recess 84 are welded together.

[0044] The outer periphery of shaft 5 has a cylindrical surface. Furthermore, the protrusion 5c and the concave surface 87 are arranged side by side in the longitudinal direction of shaft 5. The concave surface 87 is located further inward in the radial direction than the cylindrical surface of the protrusion 5c. That is, in the portion where the concave surface 87 is formed, there is no portion of the concave surface 87 that is further outward than the outer periphery of shaft 5, which is set to diameter D1.

[0045] As described above, a concave surface 87 is formed on the shaft 5. Therefore, in the protrusion dimension Z2 from the lower surface of the metal substrate 81 toward the lower part of the shaft 5, the cylindrical surface of the shaft 5 is ensured to be formed with high precision over the entire area of ​​dimension Z1 after removing a portion of the vertical dimension of the concave surface 87. Since the vertical dimension Z1 of the cylindrical surface of the shaft 5 can be ensured to a large extent, the motor 1 can be positioned with high precision using the protrusion 5c. Since the downward protrusion dimension Z2 of the shaft 5 can be made smaller, the device for mounting the motor 1 can be miniaturized.

[0046] Furthermore, in the manufacturing process of the motor 1, the shaft 5 is fixed relative to the metal substrate 81 through the following steps. Moreover, after the shaft 5 is fixed to the metal substrate 81 in the following manner, a circuit board 89 on which electronic components 95 are mounted is mounted on the metal substrate 81, and the stator 20 and the rotor 10 are mounted on the substrate 80, thereby manufacturing the motor 1.

[0047] Figure 4 This is the first diagram illustrating the manufacturing process of motor 1.

[0048] First, such as Figure 4 As shown, a hole 85 is formed in a metal substrate 81 using a cutting tool 901 such as a drill, end mill, or reamer. At this time, the cover layer 83 around the hole 85 is removed by cutting it after the hole 85 is formed. This forms a recess 84 together with the hole 85. Alternatively, for example, a second cutting tool 903, such as an end mill or file, coaxially arranged with the cutting tool 901, can be used to process the metal substrate 81 from below, thereby removing the cover layer 83 through the same process as forming the hole 85. This shortens the manufacturing process. Furthermore, the formation of the hole 85 and the removal of the cover layer 83 (formation of the recess 84) can be performed through different processes. Additionally, the tools / processes used for forming the hole 85 and removing the cover layer 83 are not limited to the methods described above. For example, the hole 85 can also be formed by stamping.

[0049] Figure 5 This is the second diagram illustrating the manufacturing process of motor 1.

[0050] Next, as Figure 5 As shown, insert the shaft 5 into the hole 85. At this time, simply insert the shaft 5 from above the metal substrate 81.

[0051] Figure 6 This is the third diagram illustrating the manufacturing process of motor 1.

[0052] Then, as Figure 6As shown, with a portion of the shaft 5 inserted into the hole 85, laser welding is performed on the outer periphery of the shaft 5 and the exposed recess 84. At this time, two locations near the joint where the recess 84 near the hole 85 and the shaft 5 meet are designated as irradiation points for two laser beams L1 and L2, respectively, and the metal substrate 81 and the shaft 5 are rotated relative to the laser beams L1 and L2. For example, the irradiation points of the two laser beams L1 and L2 are offset by 180 degrees around the shaft 5, and the positions of the laser beams L1 and L2 are not changed while the metal substrate 81 and the shaft 5 are rotated 180 degrees around the shaft 5. This allows welding of the outer periphery of the shaft 5 and the recess 84 along the entire circumference, thereby fixing the shaft 5 to the metal substrate 81. It should be noted that laser welding can be performed simply by reversing the shaft 5 and the metal substrate 81 (with the protrusion 5c of the shaft 5 positioned upwards).

[0053] Figure 7 This is the fourth diagram illustrating the manufacturing process of motor 1.

[0054] exist Figure 7 The diagram schematically illustrates the state after laser welding. Through laser welding, a portion of the outer periphery of the shaft 5 and a portion of the recess 84 melt, forming a welded portion 86 that creates a weld mark. The portion of the shaft 5 melts and flows to form the welded portion 86, thereby forming a recess 87 on the outer periphery of the shaft 5. Furthermore, the welded portion 86 extends radially from the recess 84 near the hole 85. The welded portion 86 remains inside the recess 84. In other words, the size of the recess 84 is set in such a way that the welded portion 86 does not extend radially further than the recess 84. This prevents the welded portion 86 from protruding from the surface of the metal substrate 81, and enables more precise positioning of the motor 1 with the surface of the metal substrate 81 as a reference plane.

[0055] As explained above, in this embodiment, the motor 1 is formed by a manufacturing method comprising the following steps: removing a portion of the cover layer 83 of the metal substrate 81 covered by the cover layer 83; and welding the outer periphery of the metal shaft 5 to the recess 84 of the metal substrate 81 exposed by the above steps. That is, the motor 1 has a structure in which the recess 84 of the metal substrate 81 and the outer periphery of the shaft 5 are welded together. Since the shaft 5 is directly fixed to the metal substrate 81 by welding, components that protrude significantly to the lower surface of the metal substrate 81 can be discarded, and the shaft 5 can be securely fixed. Therefore, the reliability of the motor 1 can be improved. Furthermore, the motor 1 can be made thinner. Additionally, the manufacturing cost of the motor 1 can be reduced.

[0056] Here, when the shaft 5 is welded to the metal substrate 81 covered by the cover layer 83, if the cover layer 83 melts or evaporates, it may sometimes cause unevenness on the outer periphery of the shaft 5 due to adhesion to the outer periphery of the protrusion 5c. For example, if the cover layer 83 is a zinc-plated layer, it may sometimes melt and produce tin, which may then adhere to the outer periphery of the shaft 5. This may sometimes result in poor positioning of the motor 1 using the protrusion 5c. When stainless steel with a high manganese content is used as the material for the shaft 5, manganese, with its low melting point, is prone to evaporation. This may cause foreign matter to adhere to the outer periphery of the shaft 5 due to melting or evaporation, making the aforementioned problems more pronounced.

[0057] In this embodiment, the recess 84 on the metal substrate 81, where the cover layer 83 has been removed, and the shaft 5 are directly welded together. Therefore, the cover layer 83 and the like will not melt or evaporate, and the aforementioned problems can be prevented.

[0058] Furthermore, by appropriately adjusting the irradiation position, angle, and intensity of the lasers L1 and L2 used for laser welding, the amount of molten material on the shaft 5 and the metal substrate 81 can be reduced. For example, by positioning the irradiation position of the lasers L1 and L2 close to the vicinity of the hole 85 on the shaft 5, the output of the lasers L1 and L2 can be weakened, thereby reliably fixing the shaft 5 to the metal substrate 81.

[0059] Figure 8 This is a cross-sectional view of the motor 101 involved in a variation of this embodiment.

[0060] like Figure 8 As shown, the method of fixing the polygon mirror 70 differs between motor 101 and motor 1 in the above embodiment. Specifically, in motor 101, the spring 51 is positioned vertically using a protrusion 140b formed radially on the upper part of the sleeve 140. This configuration eliminates the need for clamps or similar components for positioning the spring 51, thereby reducing the number of parts in motor 101.

[0061] [other] The shaft and the recessed portion of the metal substrate can be joined together by fusion welding. Alternatively, welding can be performed using methods other than laser welding.

[0062] The structure of each part of the motor is not limited to the structure shown in the above embodiments. Various structures configured in a manner consistent with the purpose of this invention can be applied.

[0063] The substrate is not limited to a structure that combines a metal substrate and a circuit board. The substrate can be a substrate on which wiring is implemented through an insulating layer, and it is not limited to a layered structure as described in the above embodiments; it can have more layers.

[0064] The motor is not limited to the motor used to rotate the multifaceted mirror as described above. The structure of mounting the shaft to the substrate in the above embodiment can be used in motors with substrates for various applications.

[0065] It should be understood that the above embodiments are merely illustrative in all respects and do not limit the scope of the invention. The scope of the invention is not defined by the foregoing description, but by the claims, which include the scope equivalent to the claims and all modifications within that scope.

[0066] Explanation of reference numerals in the attached figures 1, 101: Motor; 5: Shaft; 10: Rotor; 40, 140: Sleeve (an example of a bearing); 70: Multifaceted mirror; 80: Substrate (an example of a substrate); 81: Metal substrate (an example of a metal component); 83: Covering layer; 83b: Opening; 84: Recess (an example of an exposed portion); 85: Hole; 86: Welded portion; 87: Concave surface; 89: Circuit board (an example of a resin component).

Claims

1. An electric motor, comprising: A shaft, formed of metal, having an outer periphery formed of manganese-containing martensitic stainless steel; and A substrate having a zinc-containing coating layer and a metal component covered by the coating layer. The shaft is fixed to the base. The stator is fixed to the substrate. The rotor is capable of rotating relative to the shaft. The shaft has two ends. The outer periphery located between the two ends of the shaft has a cylindrical surface and a concave surface extending circumferentially. The covering layer has an opening. The metal component has an exposed portion protruding from the opening. The concave surface of the shaft and the exposed portion are fused or welded together. The concave surface is located on the base side relative to the cylindrical surface along the length of the axis. The exposed portion has a concave surface of the shaft and a welded portion therein. The welded portion, relative to the cylindrical surface of the substrate, is located on the concave side along the length of the axis. The surface of the substrate is called the reference plane. The cylindrical surface is used for positioning.

2. The motor according to claim 1, wherein, The metal component is a flat plate.

3. The motor according to claim 2, wherein, The concave surface is radially inward relative to the cylindrical surface.

4. The motor according to any one of claims 1 to 3, wherein, The substrate has a resin component with wiring formed on it.

5. The motor according to any one of claims 1 to 3, wherein, The shaft is formed of lead-free martensitic stainless steel.

6. The motor according to any one of claims 1 to 3, comprising: The multifaceted mirror is mounted on the rotor.

7. The motor according to claim 6, wherein it comprises bearings, The multifaceted mirror is disposed on the bearing.

8. An electric motor, comprising: A shaft, which is formed of metal; and A base having a covering layer and a metal component covered by the covering layer. The outer periphery of the shaft has a cylindrical surface and a concave surface extending circumferentially. The covering layer has an opening. The metal component has an exposed portion protruding from the opening. The concave surface of the shaft and the exposed portion are fused or welded together. The concave surface is located on the base side relative to the cylindrical surface along the length of the axis. The exposed portion has a concave surface of the shaft and a welded portion therein. The welded portion, relative to the substrate, is located on the concave side of the cylindrical surface along the length of the axis. The surface of the substrate becomes the reference plane.

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