motor

Abstract

We provide high-quality motors that improve work efficiency during assembly. [Solution] The stator 2 consists of a stator core 21 and a frame portion 24 that fixes the stator core 21, a rotor 3 rotatably supported inside the stator 2, a circuit board 5 on which mounted components 51 are mounted, and a bracket 4 fixed to the non-load side of the stator 2. The bracket 4 and the stator 2 are fitted together at a cylindrical mating surface 242, the circuit board 5 contacts the substrate contact surface 41 of the bracket 4 via a heat dissipation sheet 7, and the bracket 4 has a projection 42 extending in the direction toward the stator, the projection 42 fits into the cylindrical mating surface 242 of the stator 2 before the substrate contact surface 41 contacts the heat dissipation sheet 7 when the bracket 4 is assembled to the stator 2.

Description

Technical Field

[0001] This disclosure relates to a motor.

Background Art

[0002] In the case of a motor incorporating a drive circuit board, how to dissipate the heat generated by the circuit board has been an issue. A structure in which a member having a heat sink function is brought into contact with the circuit board via a heat dissipation sheet at the heat generating part of the circuit board is generally adopted. For the purpose of improving this heat dissipation problem, an electric motor having a structure in which a bracket having the role of a heat sink is pressed against a circuit board for heat dissipation of the circuit board built in the motor has been disclosed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1, a heat dissipation sheet made of a soft material is adopted to absorb the accumulation of dimensional variations of assembled parts, and it is used after being crushed in the thickness direction when assembled to the motor. Therefore, the reaction force of the crushing load is applied to the heat dissipation parts and the circuit board, and strains occur between them. Since the heat dissipation parts are made of a metal with high thermal conductivity such as aluminum, strain does not become a problem. However, the circuit board is a composite part that is likely to fail when strained, such as resin, thin metal foil, integrated circuits, capacitors, etc. Also, the heat dissipation sheet is insulating, and if there are scratches and misalignment, the quality of the motor may deteriorate. In addition, when assembling the bracket to the stator, since the mating parts cannot be visually inspected, the parts get caught on each other, and there is a problem with the assembly workability.

[0005] This disclosure provides technology to solve the above-mentioned problems, and aims to provide a motor that is of high quality and can improve assembly workability. [Means for solving the problem]

[0006] The motor of this disclosure comprises a stator consisting of a stator core around which coils are wound and a frame portion that fixes the stator core, a rotor fixed to a shaft rotatably supported inside the stator, a circuit board on which mounted components are mounted, and a bracket fixed to the non-load side of the stator opposite to the load side where a load is connected to the shaft, and sealing the rotor and the circuit board, wherein the bracket and the stator are fitted together at a cylindrical mating surface, the circuit board abuts against the substrate contact surface of the bracket via a heat dissipation sheet, the bracket has a projection extending in the axial direction toward the stator at the cylindrical mating surface, and the projection fits into the cylindrical mating surface of the stator before the substrate contact surface contacts the heat dissipation sheet when the bracket is assembled to the stator. [Effects of the Invention]

[0007] According to the motor of this disclosure, a high-quality motor can be obtained that can improve assembly workability. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of the motor according to Embodiment 1. [Figure 2] This is a cross-sectional view of the motor bracket according to Embodiment 1. [Figure 3] This is a perspective view of the motor bracket according to Embodiment 1. [Figure 4] This is a perspective view of the stator frame portion of the motor according to Embodiment 1. [Figure 5] This is a cross-sectional view of the frame portion of the stator of the motor according to Embodiment 1. [Figure 6]Figure 6A is an explanatory diagram of the structure of a motor as a comparative example according to Embodiment 1. Figure 6B is an explanatory diagram of the structure of a motor as a comparative example according to Embodiment 1. Figure 6C is an explanatory diagram of the structure of a motor as a comparative example according to Embodiment 1. [Figure 7] Figure 7A is an explanatory diagram of the structural features of the motor according to Embodiment 1. Figure 7B is an explanatory diagram of the structural features of the motor according to Embodiment 1. Figure 7C is an explanatory diagram of the structural features of the motor according to Embodiment 1. [Figure 8] This is an internal configuration diagram of the non-load side of the motor according to Embodiment 1. [Figure 9] Figure 9A is a cross-sectional view of the motor bracket according to Embodiment 2. Figure 9B is a partially enlarged view of Figure 9A. [Modes for carrying out the invention]

[0009] Embodiment 1. Embodiment 1 comprises a stator consisting of a stator core around which a coil is wound and a frame portion that fixes the stator core, a rotor rotatably supported inside the stator, a circuit board on which mounted components are mounted, and a bracket fixed to the non-load side of the stator and sealing the rotor and the circuit board. The bracket and the stator are fitted together at a cylindrical mating surface, the circuit board contacts the substrate contact surface of the bracket via a heat dissipation sheet, and the bracket has a projection that extends in the axial direction toward the stator at the cylindrical mating surface, the projection fitting into the cylindrical mating surface of the stator before the substrate contact surface contacts the heat dissipation sheet when the bracket is assembled to the stator.

[0010] The motor according to Embodiment 1 will be described below based on Figure 1, a cross-sectional view of the motor; Figure 2, a cross-sectional view of the motor bracket; Figure 3, a perspective view of the motor bracket; Figure 4, a perspective view of the stator frame of the motor; Figure 5, a cross-sectional view of the stator frame; Figures 6A, 6B, and 6C, which are explanatory diagrams of the structure of a motor as a comparative example; Figures 7A, 7B, and 7C, which are explanatory diagrams of the structural features of the motor; and Figure 8, which is an internal configuration diagram of the non-load side of the motor. In each figure, the same or corresponding parts are denoted by the same reference numerals.

[0011] First, the overall configuration of the motor 1 will be described based on FIG. 1. FIG. 1 shows a cross-section along the central axis of the motor 1, that is, the central axis of the rotor 3. Note that FIG. 1 is a cross-sectional view seen from the arrow B-B in FIG. 8, which will be described later. In the following description, the direction of the rotation axis (the left-right direction in FIG. 1) will be defined as the axial direction (X), the direction of the center of the rotation axis (the up-down direction in FIG. 1) will be defined as the radial direction (R), and the direction along the rotation direction centered on the rotation axis will be defined as the circumferential direction (P) for explanation. Also, regarding the axial direction (X), the side where a load (not shown) is connected to the shaft 31 of the rotor 3 will be described as the + side, and the opposite side (the anti-load side) will be described as the - side.

[0012] The motor 1 of the first embodiment includes, as main components, a stator 2, a rotor 3, a bracket 4, a circuit board 5, an anti-load side housing 6, and a heat dissipation sheet 7.

[0013] The stator 2 has a coil 22 wound around a stator core 21 via an insulator 23 which is an insulator, and is held by a frame portion 24 formed of a mold resin. Note that the frame portion 24 of the stator 2 has mating surfaces with the bracket 4 and the anti-load side housing 6. These mating surfaces will be described in FIGS. 2 and 4. Also, at the axial direction (X) + side end of the frame portion 24 of the stator 2, a flange 9 which is a waterproof and dustproof component is installed.

[0014] The rotor 3 is fixed to a shaft that is rotatably supported inside the stator 2. The load side bearing 32 supports the load side of the shaft 31, and the anti-load side bearing 33 supports the anti-load side of the shaft 31. The frame portion 24 of the stator 2 supports the load side bearing 32, and the anti-load side housing 6 supports the anti-load side bearing 33.

[0015] The bracket 4 has the function of a lid with respect to the stator 2 and also has the function of a cooler. The circuit board 5 controls the motor 1 by controlling the current flowing through the coil 22 of the stator 2. In addition, the heat dissipation sheet 7 is provided to improve the heat transfer efficiency between the bracket 4 having the function of a cooler and the circuit board 5 which is a heat generating body. Furthermore, the terminal of the coil 22 of the stator 2 is connected to the stator coil end portion 93, and the stator coil end portion 93 is soldered to the circuit board 5. The connector 91 of the circuit board 5 is connected to an external power source and a device that emits a drive command signal by a lead wire 92. The mounted components 51 on the circuit board 5 convert the current supplied from the outside into a motor drive current in accordance with the drive command signal and supply it to the coil 22 of the stator 2.

[0016] Next, the structure of the bracket 4 will be described based on FIG. 2 which is a cross-sectional view of the bracket 4 and FIG. 3 which is a perspective view. The bracket 4 of the first embodiment has a disc shape and has an outer mating surface 45 that fits with the frame portion 24 of the stator 2 near the outer periphery of the disc shape. The cylindrical mating surface 43 is provided on the inner diameter side of this outer mating surface 45. The cylindrical mating surface 43 of this cylinder has a protrusion 42 whose shape extends the cylindrical surface further in the axial direction (X)+ side. This protrusion 42 protrudes on the axial direction (X)+ side from the substrate contact surface 41. The bracket 4 is provided with a planar substrate contact surface 41 that is brought into contact via the heat dissipation sheet 7 for heat dissipation of the circuit board 5. The material of the bracket 4 is preferably a metal such as an aluminum alloy or steel with high thermal conductivity.

[0017] The bracket has a screw hole 49 for fixing the bracket at a position that does not overlap with the protrusion 42. The corner of the cylindrical mating surface 43 of the protrusion 42 has a taper guide portion 44, which improves the guiding property when fitting the cylindrical mating surface 43 of the bracket 4 and the cylindrical mating surface 242 of the stator 2. In Figure 2, the tapered guide portion 44 is shown as a conical surface, but the same effect can be achieved by using a fillet radius shape or a combination of a tapered conical surface and a fillet radius shape. Furthermore, although Figure 3 shows three projections 42 at equal intervals in the circumferential direction (P), there may be four or more projections.

[0018] Next, the structure of the frame portion 24 of the stator 2 will be explained based on the perspective view Figure 4 and the cross-sectional view Figure 5 of the frame portion 24 of the stator 2.

[0019] The frame portion 24 of the stator 2 has an outer mating surface 241 with the same diameter as the outer mating surface 45 of the bracket 4 at the non-load side end, and a cylindrical mating surface 242 with the same diameter as the cylindrical mating surface 43 of the bracket 4, which are fitted together when the bracket 4 is assembled to the stator 2. The frame portion 24 further has a housing fitting surface 243 on the axial (X)+ side that engages with the non-load side housing 6.

[0020] The frame portion 24 of the stator 2 is provided with a screw base 246 for fixing the motor 1 to its installation location. A groove-shaped lead wire outlet 247 is provided on a part of the outer mating surface 241 for drawing out lead wires 92 via the connector 91 on the circuit board 5. On the inside of the cylindrical mating surface 242, screw holes 244 for fixing the bracket are provided at positions corresponding to the screw holes 49 of the bracket 4. Furthermore, screw holes 245 for fixing the housing are provided on the inside of the cylindrical mating surface 242 to secure the non-load side housing 6.

[0021] Due to manufacturing variations, the outer mating surfaces 45, 241 and cylindrical mating surfaces 43, 242 provided on the frame portion 24 of the bracket 4 and stator 2 exhibit variations in geometric accuracy such as coaxiality and roundness, as well as dimensional accuracy such as inner and outer diameters. As a result, if both mating surfaces are made into an interference fit, stress will be created, making it difficult to assemble the bracket 4. Therefore, the clearance dimensions are set such that one or both of the outer mating surfaces 45, 241 and the cylindrical mating surfaces 43, 242 leave a gap.

[0022] Next, the effects of the projection 42 of the bracket 4 in this embodiment 1 protruding axially from the substrate contact surface 41 will be explained based on Figures 6A to 6C and 7A to 7C. Figures 6A to 6C are comparative examples to clarify the effects of the projection 42 in this embodiment 1, and Figures 7A to 7C are explanatory diagrams for the structure of this embodiment 1. Furthermore, since Figures 6A-6C and 7A-7C are conceptual diagrams, detailed reference numerals and other symbols have been omitted. In addition, to indicate that it is a comparative example, the letter R has been added to the reference numeral in Figure 6.

[0023] As mentioned above, bracket 4 is preferably made of a metal such as aluminum or steel, which has high thermal conductivity, and in order to manufacture them with high productivity, aluminum die casting or sheet metal drawing is often employed. Therefore, the outer surface of bracket 4 cannot be made as flat as it would be with machining. When bracket 4 is assembled to stator 2, bracket 4 will have an outer surface. When assembled by an assembly device, the parts that are not very flat will be held in place, which may cause variations in the orientation of bracket 4. As a countermeasure, machining the outside of bracket 4 can improve its flatness, but this increases the machining cost. Also, if the worker assembles bracket 4 by hand, the mating surface is hidden and cannot be seen during insertion, making it difficult to ensure proper alignment and parallelism.

[0024] Under the above premise, if the projection 42R does not protrude axially from the substrate contact surface 41R as shown in Figure 6A, there is a possibility that the corner of the substrate contact surface 41 may come into contact with the heat dissipation sheet 7 before the mating surfaces are fitted together, due to variations in the orientation of the bracket 4R caused by the worker or assembly equipment. Therefore, scratches or indentations indicated by the symbol F may occur on the heat dissipation sheet 7, as shown in Figure 6B. Furthermore, problems such as a decrease in heat dissipation performance and insulation performance due to misalignment, as shown in Figure 6C, and the resulting load on the circuit board 5, may occur, potentially leading to failure.

[0025] On the other hand, as shown in Figures 7A to 7C, if the projection 42 protrudes beyond the substrate contact surface 41, even if the bracket 4 is tilted, the substrate contact surface 41 does not come into contact with the heat dissipation sheet 7 first, and guidance of the fitting surfaces of the bracket 4 and the stator 2 begins. After this, the upper surface of the heat dissipation sheet 7 and the substrate contact surface 41 begin to come into stable contact so that they are parallel. By uniformly compressing the heat dissipation sheet 7, assembly can be performed without causing misalignment of the heat dissipation sheet 7 or localized strain on the circuit board 5.

[0026] Specifically, as shown in Figure 7A, if the bracket 4 is tilted at the start of insertion, the cylindrical mating surface 242 of the frame portion 24 of the stator 2 and the projection 42 of the bracket 4 come into contact, guiding the position and orientation of the bracket 4 and correcting it to the orientation shown in Figure 7B. Subsequently, while continuing to guide the position and orientation of the bracket 4, the substrate contact surface 41 is brought into contact with the heat dissipation sheet 7. Then, pressure is applied until a predetermined amount of compression is achieved, and the bracket 4 is fixed to the stator 2 (Figure 7C).

[0027] In this embodiment 1, the bracket 4 and the stator 2 are fixed by screw fastening, but the effects of this embodiment can also be obtained with other mechanical fastening means such as adhesive bonding, welding, or welding.

[0028] As shown in Figures 7A to 7C, the components 51 on the circuit board 5 are mounted on the back surface of the side that comes into contact with the heat dissipation sheet 7. As a result, variations in the assembly of mounted components 51 can be avoided from affecting the amount of compression of the heat dissipation sheet 7, and variations in the strain generated in the circuit board 5 can be suppressed. Furthermore, variations in the assembly of mounted components 51 can be expected in cases where mounted components 51 are placed between the heat dissipation sheet 7 and the circuit board 5, and even in cases where there are no mounted components 51, variations in the height of the solder in the through-holes can have an effect. Furthermore, mounting components 51 that generate little heat and can be kept away from the contact area with the heat dissipation sheet 7 may be mounted on the side that contacts the heat dissipation sheet 7.

[0029] Next, the internal structure of the non-load side of motor 1 will be explained based on Figure 8, which shows the motor with bracket 4 removed, viewed from the non-load side, i.e., the axial (X) negative side. To make the positional relationships easier to understand, the circuit board 5 (double dashed line) and heat dissipation sheet 7 (single dashed line) are shown transparently, and the mounted components 51 are omitted.

[0030] The non-load side housing 6 is made of resin and consists of a housing disc portion 61 and a housing fixing portion 62. The non-load side housing 6 has its outer circumference of the housing disc portion 61 fitted with the housing fitting surface 243 of the frame portion 24 of the stator 2, and is fixed to the frame portion 24 with screws at the housing fixing portion 62.

[0031] The non-load side housing 6 is equipped with multiple board support pins 63 to support the circuit board 5, suppressing distortion of the circuit board 5 caused by the reaction force pressing against the heat dissipation sheet 7. By reducing the area of ​​the board support pins 63 and distributing them in a dispersed manner, the area to be supported is minimized, improving heat dissipation performance while ensuring layout margin for mounted components 51. Specifically, by configuring the polygon, with its vertices at the contact points between the circuit board 5 and the board support pins 63, to overlap only a portion of the heat dissipation sheet 7 when viewed from the axial direction (X), it is possible to apply pressure to the heat dissipation sheet 7 while suppressing distortion of the circuit board 5. Figure 8 also shows the connector 91, the stator coil end 93, and the screw base 246 on the circuit board 5.

[0032] As described above, when assembling the bracket 4 to the stator 2, the projection 42 of the bracket 4 fits into the cylindrical mating surface 242 on the stator 2 side before the substrate contact surface 41 contacts the heat dissipation sheet 7. As a result, indentations and misalignment of the heat dissipation sheet 7 and localized strain on the circuit board 5 are prevented, providing a high-quality motor 1. In Embodiment 1, the frame portion 24 of the stator 2 is made of resin, and the stator is shown as an example of a molded structure. However, even in a structure in which an annular frame is shrink-fitted or press-fitted into the stator core 21, the effects of Embodiment 1 can be achieved if a mating surface is formed on the frame.

[0033] In the above Embodiment 1, a radial gap motor with an inner rotor configuration was described as an example. However, in the case of an axial gap motor, the same effects as in Embodiment 1 can be obtained by providing a mating surface between the stator and the bracket and configuring a projection on the bracket.

[0034] As described above, the motor of Embodiment 1 provides a high-quality motor that can improve assembly workability.

[0035] Embodiment 2. The motor in Embodiment 2 has a structure that reduces the insertion force of the bracket compared to Embodiment 1, thereby improving assembly workability.

[0036] The motor of Embodiment 2 will be explained, focusing on the differences from Embodiment 1, based on Figure 9A, a cross-sectional view of the motor bracket, and Figure 9B, an enlarged view of part A in Figure 9A. In the drawings of Embodiment 2, parts that are the same as or corresponding to those in Embodiment 1 are denoted by the same reference numerals. To distinguish it from Embodiment 1, this embodiment is described as having a bracket 104, a projection 142, a cylindrical mating surface 143, a tapered guide portion 144, and an outer mating surface 145.

[0037] In this second embodiment, the outer surface of the projection 142 is not made flush with the cylindrical mating surface 143 of the bracket 104, but is instead made into a stepped cylindrical surface 146 with a smaller diameter than the cylindrical mating surface 143, without losing the effect described in Figure 7. This reduces the insertion force of the bracket 104 compared to the first embodiment, improving assembly workability.

[0038] Furthermore, when machining is performed to ensure the accuracy of the cylindrical mating surface 143, intermittent machining can be avoided by leaving the stepped cylindrical surface 146 with a normal tolerance and not machining it. As a result, the machining accuracy of the cylindrical mating surface 143 can be stabilized.

[0039] As described above, the motor of Embodiment 2 provides a high-quality motor with improved assembly workability. Furthermore, it can reduce the insertion force of the bracket and improve assembly workability.

[0040] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are conceivable within the scope of the art disclosed in this specification. These include, for example, modifying, adding or omitting at least one component, or even extracting at least one component and combining it with components of other embodiments.

[0041] The various aspects of this disclosure are summarized below as an appendix.

[0042] (Note 1) A motor having a structure comprising a stator consisting of a stator core around which a coil is wound and a frame portion that fixes the stator core, a rotor fixed to a shaft that is rotatably supported inside the stator, a circuit board on which mounted components are attached, and a bracket fixed to the non-load side of the stator opposite to the load side where the load is connected to the shaft, and which seals the rotor and the circuit board, The bracket and the stator are fitted together at a cylindrical mating surface. The circuit board is in contact with the substrate contact surface of the bracket via a heat dissipation sheet. The bracket is provided with a projection extending in the axial direction toward the stator on the cylindrical mating surface, The aforementioned projection is a motor that, when assembling the bracket to the stator, fits into the cylindrical fitting surface of the stator before the substrate contact surface comes into contact with the heat dissipation sheet. (Note 2) The motor as described in Appendix 1, wherein the aforementioned projection protrudes axially towards the stator side from the substrate contact surface. (Note 3) The motor as described in Appendix 1 or Appendix 2, wherein the aforementioned protrusions are arranged in multiple locations in the circumferential direction of the bracket. (Note 4) The motor according to Appendix 1 or Appendix 2, wherein the non-load side housing supporting the circuit board is positioned between the circuit board and the stator. (Note 5) The motor according to Appendix 3, wherein the non-load side housing supporting the circuit board is positioned between the circuit board and the stator. (Note 6) The motor described in Appendix 4 or Appendix 5, wherein the non-load side housing is made of resin. (Note 7) The motor described in any one of the appendices 1 to 6, wherein the mounted component on the circuit board is located on the side opposite to the surface in contact with the heat dissipation sheet. (Note 8) The motor according to any one of the appendices 1 to 7, wherein the outer circumferential surface of the projection has a smaller diameter than the cylindrical mating surface of the bracket. (Note 9) The motor according to any one of the appendices 1 to 8, wherein a taper is provided on the outer circumferential surface side of the axial tip of the projection. [Explanation of Symbols]

[0043] 1. Motor, 2. Stator, 3. Rotor, 4. Bracket, 5. Circuit board. 6 Non-load side housing, 7 Heat dissipation sheet, 9 Flinger, 21 Stator core, 22 Coil, 23 Insulator, 24 Frame, 31 Shaft, 32 Load-side bearing, 33 Non-load-side bearing, 41 Substrate contact surface, 42 Protrusion, 43 Cylindrical mating surface, 44 Tapered guide section, 45 Outer mating surface, 49 Screw hole, 51 Mounted components, 61 Housing disc section, 62 Housing fixing section, 91 Connector, 92 Lead wire, 93 Stator coil end, 104 Bracket, 142 Protrusion, 143 Cylindrical mating surface, 144 Tapered guide section, 145 Outer mating surface, 146 Stepped cylindrical surface, 241 Outer mating surface, 242 Cylindrical mating surface, 243 Housing mating surface, 244 Screw hole, 245 Screw hole, 246 Screw base, 247 Lead wire outlet.

Claims

1. A motor having a structure comprising a stator consisting of a stator core around which a coil is wound and a frame portion that fixes the stator core, a rotor fixed to a shaft that is rotatably supported inside the stator, a circuit board on which mounted components are attached, and a bracket fixed to the non-load side of the stator opposite to the load side where the load is connected to the shaft, and which seals the rotor and the circuit board, The bracket and the stator are fitted together at a cylindrical mating surface. The circuit board is in contact with the substrate contact surface of the bracket via a heat dissipation sheet. The bracket is provided with a projection extending in the axial direction toward the stator on the cylindrical mating surface, The aforementioned projection is a motor that, when assembling the bracket to the stator, fits into the cylindrical fitting surface of the stator before the substrate contact surface comes into contact with the heat dissipation sheet.

2. The motor according to claim 1, wherein the projection protrudes axially toward the stator side from the substrate contact surface.

3. The motor according to claim 1 or claim 2, wherein the projections are arranged in multiple locations in the circumferential direction of the bracket.

4. The motor according to claim 1 or claim 2, wherein the non-load side housing supporting the circuit board is disposed between the circuit board and the stator.

5. The motor according to claim 3, wherein the non-load side housing supporting the circuit board is disposed between the circuit board and the stator.

6. The motor according to claim 4, wherein the non-load side housing is made of resin.

7. The motor according to claim 1 or claim 2, wherein the mounted component on the circuit board is arranged on the side opposite to the surface that contacts the heat dissipation sheet.

8. The motor according to claim 1 or claim 2, wherein the outer circumferential surface of the projection has a smaller diameter than the cylindrical mating surface of the bracket.

9. The motor according to claim 1 or claim 2, wherein a taper is provided on the outer circumferential surface side of the axial tip of the projection.

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