Motor

Abstract

To provide a motor, having a cover bonded to a case with an adhesive, which can improve corrosion resistance against water that enters from an adhesive coating part.SOLUTION: A case 30 is made of metal, and has a cylinder part 31 and a bottom part 37. The case has an opening on the side opposite to the bottom part 37, and the case houses a stator 50 and a rotor 60. A fixed part outer wall 22 of a rear frame 20 is fixed by interference-fitting to an intermediate part inner wall 32 of the cylinder part 31 of the case 30. At a position further on the opening side of the case 30 than the fixed part outer wall 22, a groove forming outer wall 27 forms an annular groove part 34 between itself and an opening inner wall 33 of the case 30. A cover 40 is provided so as to cover the opening of the case 30, and an edge 44 is inserted into the annular groove part 34 filled with an adhesive Ad so that the cover is bonded to the case 30. An anti-corrosion ring 70 has corrosion resistance and is fitted to the opening inner wall 33 of the case 30 by interference-fitting inside the annular groove part 34.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a motor. [Background technology]

[0002] 2. Description of the Related Art Conventionally, motors have been known that use an adhesive as a sealing means for providing a liquid-tight seal between a motor case that houses a stator and a cover that covers an opening of the motor case.

[0003] For example, Patent Document 1 discloses a drive unit that is applied to a rack-mounted electric power steering device and that is integrated with a motor unit and a control unit that controls the supply of electricity to the motor unit. In this drive unit, an annular protrusion formed on the end face of the peripheral wall of the control unit cover fits into an adhesive groove in the motor case, thereby joining the control unit cover to the motor case while ensuring waterproofing between the control unit cover and the motor case. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6160585 Summary of the Invention [Problem to be solved by the invention]

[0005] Although applying adhesive provides a certain degree of waterproofing, in an environment where water is splashed heavily, water may seep into the interior through the adhesive application area, potentially causing corrosion. Patent Document 1 does not mention preventing corrosion due to water intrusion.

[0006] The present invention was created in consideration of these points, and its purpose is to provide a motor in which the cover is joined to the case with an adhesive, which has improved corrosion resistance against water intrusion through the adhesive-applied portion. [Means for solving the problem]

[0007] The motor according to the present invention includes a case 30, a rear frame 20, a cover 40, and a corrosion-resistant ring 70. The case is made of metal and has a cylindrical portion 31 and a bottom portion 37. The side opposite the bottom is open, and houses a stator 50 and a rotor 60.

[0008] The rear frame has a fixed portion outer wall (22) and a groove-forming outer wall (27). The fixed portion outer wall is fixed to an intermediate portion inner wall (32) of the cylindrical portion of the case by interference fit. The groove-forming outer wall forms an annular groove (34) between itself and an opening inner wall (33) of the case on the opening side of the case relative to the fixed portion outer wall. The cover is It has a top wall (41) and a peripheral wall (42), It is provided to cover the opening of the case. The peripheral wall has an eave portion (43) that protrudes radially outward at its end on the case side, and an annular edge portion (44) that extends from the end face of the eave portion on the case side toward the case side. The edge (44) is inserted into an annular groove filled with adhesive (Ad) and bonded to the case.

[0009] The corrosion-resistant ring has corrosion resistance and is attached to the inner wall of the opening of the case in the annular groove by an interference fit. Note that "interference fit" includes press fitting, shrink fitting, and cold fitting. A person skilled in the art can determine that the corrosion-resistant ring is fixed to the case by an interference fit by observing or analyzing the completed motor. Therefore, the description "attached by an interference fit" specifies the structure by showing the completed state of the motor, and does not specify the product by the manufacturing method.

[0010] The cover-side end face of the corrosion-resistant ring and the cover-side end face of the cylindrical portion of the case face each other at the same position in the axial direction and are opposed to the case-side surface of the eave portion.

[0011] In one embodiment, the corrosion-resistant ring is made of an aluminum alloy. For example, the corrosion-resistant ring is an aluminum die-cast product that has been anodized, laser-treated, or coated with a corrosion inhibitor. Alternatively, the corrosion-resistant ring is an aluminum cold-forged or pressed product. Another implementation In one example, the corrosion-resistant ring is made of an iron alloy. For example, the corrosion-resistant ring is a cold-forged or pressed product made of stainless steel. Alternatively, the corrosion-resistant ring is a cold-forged or pressed product that is plated. In another embodiment, the corrosion-resistant ring is made of a resin.

[0012] In the motor of the present invention, a corrosion-resistant ring is attached to the inner wall of the opening of the case by an interference fit, thereby improving corrosion resistance against water intrusion through the adhesive-coated area, even in environments where water is heavily splashed. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating the overall configuration of an electric power steering device to which a motor according to an embodiment is applied; [Figure 2] FIG. 1 is a schematic cross-sectional view of a motor according to an embodiment. [Figure 3] FIG. 3 is an enlarged cross-sectional view of part III in FIG. 2. [Figure 4] (a) Plan view and (b) side view of the corrosion-resistant ring. DETAILED DESCRIPTION OF THE INVENTION

[0014] (One embodiment) An embodiment of a motor will be described below with reference to the drawings. The motor of this embodiment is applied to an electric power steering device of a vehicle and generates steering assist torque. The motor of this embodiment is an "electromechanically integrated" motor in which an ECU (i.e., a control device) is integrated on one side of the motor in the axial direction.

[0015] First, referring to Figure 1, an example of the configuration of an electric power steering device 90 is shown. Steering torque from a driver is transmitted from a steering wheel 91 via a steering shaft 92 to an intermediate shaft 93, and the rotational motion is converted into linear motion of a rack shaft 95 by a rack and pinion mechanism 94. A pair of wheels 99 is then steered to an angle corresponding to the linear motion displacement of the rack shaft 95.

[0016] The motor 80 is attached to a power transmission unit 96 attached to a rack shaft 95. The exterior of the motor 80 consists of a metal (e.g., iron) case 30 attached to the power transmission unit 96 and a resin cover 40 located on the opposite side of the power transmission unit 96. The rotation of the output shaft of the motor 80 is transmitted to the rack shaft 95 while being decelerated via gears and pulleys within the power transmission unit 96.

[0017] As described in Patent Document 1 (Japanese Patent No. 6160585), in a rack-mounted electric power steering device 90, rainwater splashing off the road surface, rainwater running down the rack shaft 95, condensation, leaked radiator fluid, washer fluid, etc., are likely to splash on the motor 80. Therefore, to prevent water from seeping into the interior through the joint between the case 30 and the cover 40, an adhesive is applied to the joint between the case 30 and the cover 40. While this provides a certain degree of waterproofing, in an environment where water is heavily splashed, water may seep into the interior through the adhesive-applied area, potentially causing corrosion. This embodiment focuses on this issue and aims to provide a motor with improved corrosion resistance against water seepage through the adhesive-applied area.

[0018] Next, the configuration of an axial cross section of the motor 80 will be described with reference to Figures 2 and 3. The output shaft side of the motor 80 shown in the lower part of Figure 2 is referred to as the "front side," and the cover 40 side shown in the upper part of Figure 2 is referred to as the "rear side." The ECU 10 is disposed on the rear side of the motor 80, coaxial with the rotation axis Z.

[0019] The electromechanical integrated motor 80 mainly comprises a case 30, a stator 50, a rotor 60, and a rear frame 20 that constitute a motor section, and an ECU 10 and a cover 40 that constitute a control section. The motor section is a three-phase brushless motor, and the ECU 10 controls the driving of the motor section.

[0020] The case 30 is made of a metal such as iron and has a tubular portion 31 and a bottom portion 37, with the inside of an end portion 36 opening on the rear side opposite the bottom portion 37. The stator 50 and rotor 60 are housed on the bottom portion 37 side of the case 30, and the rear frame 20 is fitted to the opening side. At the portion where the rear frame 20 is fitted, the tubular portion 31 of the case 30 is formed in a stepped shape with a receiving step portion 35 interposed between a middle portion inner wall 32 with a relatively small inner diameter and an opening portion inner wall 33 with a relatively large inner diameter.

[0021] The stator 50 is configured by stacking multiple thin iron stator cores in the axial direction. The outer wall of the stator 50 is fixed to the inner wall of the cylindrical portion 31 of the case 30 by an "interference fit." Hereinafter, the term "interference fit," including the fixation of the rear frame 20 and the corrosion-resistant ring 70, includes press fitting, shrink fitting, and cooling fitting.

[0022] A three-phase winding 52 is wound around the stator 50. The three-phase winding 52 is connected to the circuit board 15 of the ECU 10 via a motor terminal 53. The ECU 10 controls the supply of current to the three-phase winding 52, thereby forming a rotating magnetic field in the stator 50.

[0023] The rotor 60 is configured by stacking multiple iron thin plate-shaped rotor cores in the axial direction. The rotor 60 is provided inside the stator 50, and a shaft 63 is fixed to the center of the rotor 60. The shaft 63 is rotatably supported by a front bearing 61 held by the bottom 37 of the case 30 and a rear bearing 62 held by the rear frame 20.

[0024] A plurality of permanent magnets 65 are provided on the outer periphery of the rotor 60. The rotor 60 may be of either an SPM type, in which the permanent magnets 65 are provided on the surface of the rotor core, or an IPM type, in which the permanent magnets 65 are embedded inside the rotor core. The rotor 60 rotates around the shaft 63 as an axis due to a rotating magnetic field formed in the stator 50 when current is applied to the three-phase windings 52. A joint 67 that transmits the rotation is provided at the front end of the shaft 63. A sensor magnet 68 for detecting the rotation angle is provided at the rear end of the shaft 63.

[0025] The rear frame 20 is made of an aluminum alloy or the like, and is disposed at the opening of the case 30 so as to face the rear end faces of the stator 50 and the rotor 60. A shaft hole 28 through which a shaft 63 is inserted is formed in the center of the main body 21. A screw seat portion used for screwing the circuit board 15 is disposed on the rear side of the main body 21, and a rear bearing 62 is held on the front side of the main body 21. The rear frame 20 supports the circuit board 15 and the rear bearing 62, and also functions as a heat sink that receives heat dissipated from elements mounted on the ECU 10 circuit board.

[0026] A flange 23 that protrudes radially outward is provided on the outer periphery of the main body 21. A front end face 25 of the flange 23 abuts against a receiving step 35 of the case 30. The fixing portion outer wall 22 on the front side of the flange 23 is fixed to the middle portion inner wall 32 of the case 30 by an interference fit. The outer wall 24 of the flange 23 is inserted into the opening inner wall 33 of the case 30 by a clearance fit. As a result, the rear frame 20 is fixed in a state where it is positioned axially relative to the case 30.

[0027] A groove-forming outer wall 27 is provided on the opening side of the case 30 relative to the flange 23 of the rear frame 20. The groove-forming outer wall 27 faces the opening inner wall 33 of the case 30 in the radial direction, and forms an annular groove 34 between the groove-forming outer wall 27 and the opening inner wall 33 of the case 30, with the rear end face 26 of the flange 23 serving as the groove bottom. The annular groove 34 is filled with, for example, a silicone-based adhesive Ad.

[0028] The ECU 10 includes a board 15 fixed to the rear frame 20 and various electronic components mounted on the board 15. The board 15 is fixed to the rear frame 20 with screws. A plurality of switching elements and a rotation angle sensor 18 disposed to face a sensor magnet 68 provided at the tip of a shaft 63 are mounted on the surface of the board 15 facing the rear frame 20. A microcomputer, a capacitor, etc. are mounted on the surface of the board 15 opposite the rear frame 20. In addition, a motor terminal 53 is connected to the board 15 by penetrating the rear frame 20. Note that although the example in FIG. 2 shows one board 15, two or more boards may be provided in other embodiments.

[0029] The cover 40 is made of, for example, resin, has a top wall 41 and a peripheral wall 42, and is provided to cover the opening of the case. The end of the peripheral wall 42 on the case 30 side is formed with an eave portion 43 that protrudes radially outward, and an annular edge portion 44 that is inserted into the annular groove portion 34. The inner diameter of the edge portion 44 is set slightly larger than the outer diameter of the groove-forming outer wall 27 of the rear frame 20.

[0030] When the edge 44 is inserted into the annular groove 34 filled with adhesive Ad, the edge 44 pushes in the adhesive Ad, sealing the gap and joining the cover 40 to the case 30. FIG. 3 shows an enlarged view of the joining portion. The cover 40 protects the electronic components mounted on the board 15 from external impacts and prevents dust, water, and the like from entering the ECU 10. Note that a connector (not shown) to which an external power supply cable or signal cable is connected may be provided in part of the cover 40.

[0031] 3, water may seep in from the adhesive surface between the adhesive Ad and the case 30, reaching the internal circuit board 15 and motor terminals 53, causing corrosion. To solve this problem, a corrosion-resistant ring 70 is attached to the inner wall 33 of the opening of the case 30 in the annular groove 34 with a tight fit.

[0032] As shown in Fig. 4, the corrosion-resistant ring 70 literally has a ring shape. The corrosion-resistant ring 70 is formed from a material with excellent corrosion resistance and adhesive properties, or is subjected to a surface treatment. Table 1 shows several examples of specific materials and manufacturing methods for the corrosion-resistant ring 70.

[0033] [Table 1]

[0034] [1A] Material: ADC12 and other die-cast aluminum alloys, Manufacturing method: Die-casting and cutting The aluminum die-cast product is machined to a ring shape with concentricity and surface roughness within tolerances. After machining, the product is anodized, laser-irradiated, or coated with an antiseptic. Compared to applying these surface treatments to the case (e.g., steel) 30, applying surface treatments only to the corrosion-resistant ring 70 is easier, requires less processing, and is more cost-effective.

[0035] [1B] Material: Aluminum alloy, Construction method: Cold forging or pressing The ring shape is made by cold forging or pressing aluminum alloy, which has excellent corrosion resistance and workability. Since cutting and post-processing are not required, processing costs are reduced.

[0036] [2] Material: Iron alloy, Construction method: Cold forging or pressing The ring shape is made from cold-forged or pressed iron alloys. In the case of stainless steel alloys, no post-processing is required. In the case of general steel other than stainless steel alloys, corrosion-resistant plating is applied.

[0037] [3] Material: Resin, Construction method: Injection molding Resin is non-corrosive, eliminating the need for cutting or post-processing after molding.

[0038] As described above, in this embodiment, the corrosion-resistant ring 70 is attached to the inner wall 33 of the opening of the case 30 by an interference fit, which improves the corrosion resistance of the seal portion inside the case against water intrusion from the adhesive application portion. Furthermore, improving corrosion resistance shortens the creepage distance (see FIG. 3) of the adhesive portion, which allows the motor 80 to be made smaller.

[0039] Furthermore, the amount of adhesive Ad filled in the annular groove 34 is reduced, which shortens the takt time of the adhesive application process. Additionally, even if a material with good adhesive properties cannot be selected for the case 30, corrosion resistance and adhesive properties can be ensured by using the corrosion-resistant ring 70 as a common part.

[0040] Regarding the ease of assembly of the corrosion-resistant ring 70, the end face of the corrosion-resistant ring 70 can be abutted against the rear end face 26 of the flange 23 of the rear frame 20 to determine its axial position. The interference fit may be a press fit or a shrink fit. In the case of a shrink fit, the fit is not dependent on the strength properties of the material of the corrosion-resistant ring 70.

[0041] (Other embodiments) (a) The present invention is not limited to an electromechanical integrated motor in which the ECU 10 is integrated with the motor 80 (i.e., the "drive device" in Patent Document 1), but may also be applied to an electromechanically separated motor in which the ECU 10 is connected to a separate control device via a harness. In this case, the rear frame 20 may simply be a member that holds the rear bearing 62 at the opening of the case 30, without functioning as a heat sink that dissipates heat generated by elements on the board.

[0042] (b) The fitting portion between the rear frame 20 and the case 30 is not limited to the configuration of the flange portion 23, receiving step portion 35, etc. shown in Figures 2 and 3, and the step portion and fixing portion may be arranged in any manner. The minimum requirements are that the outer wall of the rear frame 20 is fixed to the inner wall of the tubular portion 31 of the case 30 by an interference fit, and that an annular groove portion 34 is formed between the rear frame 20 and the case 30.

[0043] (c) The cover 40 is not limited to being made of resin. Furthermore, the cover 40 is not limited to being formed as a single part. For example, the cover body and the connector to which the cable is connected may be formed separately and joined with an adhesive or the like. In this case, the edge 44 may be formed at the end of the "connector constituting part of the cover" on the case 30 side.

[0044] (c) The case 30 is not limited to a configuration in which the bottom portion 37 is formed integrally with the tubular portion 31, and a front frame formed separately from the tubular portion 31 may be fixed to the tubular portion 31.

[0045] (d) The motor of the present invention is not limited to a permanent magnet type polyphase AC motor, but may be a DC motor, an induction motor, etc. Also, it may function as a generator.

[0046] (e) The motor of the present invention is not limited to being applied to rack-mounted electric power steering devices, but may also be applied to column-mounted electric power steering devices. Furthermore, the motor may also be applied to in-vehicle devices other than electric power steering devices, and various devices other than devices mounted on vehicles.

[0047] The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0048] 20···Rear frame, 22... Fixed part outer wall, 27... Groove forming outer wall, 30 cases, 32: Inner wall of intermediate portion; 33: Inner wall of opening portion; 34: Annular groove portion; 40... Cover; 44... Edge; 50···Stator, 60··· rotor, 70···Corrosion-resistant ring, 80···Motor.

Claims

[Claim 1] a metal case (30) having a cylindrical portion (31) and a bottom portion (37), the opposite side of the bottom being open, and containing a stator (50) and a rotor (60); a rear frame (20) having a fixed portion outer wall (22) fixed by interference fit to an intermediate portion inner wall (32) of the cylindrical portion of the case, and a groove forming outer wall (27) forming an annular groove portion (34) between the fixed portion outer wall and an opening inner wall (33) of the case on the opening side of the case; a cover (40) having a top wall (41) and a peripheral wall (42), provided to cover the opening of the case, the peripheral wall having an eave portion (43) protruding radially outward at the end of the case side, and an annular edge portion (44) extending from the end face of the eave portion on the case side toward the case, the edge portion being inserted into the annular groove filled with adhesive (Ad) and joined to the case; a corrosion-resistant ring (70) that is corrosion-resistant and is attached to the inner wall of the opening of the case in the annular groove by interference fit; Equipped with A motor in which the cover-side end face of the corrosion-resistant ring and the cover-side end face of the cylindrical portion of the case face the case-side surface of the eave portion at the same axial position.

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