Drive device

Abstract

In a drive device (101, 104) in which a motor unit (50) and an ECU (60) are configured integrally, a motor case (201) comprises a cylinder portion (22) that extends in the axial direction of the motor unit (50) and a front bottom portion (23) that holds a front bearing (56) for supporting a shaft (55) on the front side of the motor unit (50), the cylinder portion (22) and the front bottom portion (23) being formed integrally from a non-metallic molding material. A rear frame (40) is a separate component from the motor case (201), and holds a rear bearing (57) that supports the shaft (55) on the rear side of the motor unit (50). An ECU cover (70, 704) is formed from a resin material in the shape of a container that covers a substrate (65) of the ECU (60), and an end portion of a side plate (72) is joined to an end portion of the cylinder portion (22) of the motor case (201). A stator (53) is molded from a non-metallic molding material. A stator molded portion (25) from which the stator (53) is molded is molded integrally with the cylinder portion (22) of the motor case (201).

Description

Drive unit CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-002979 filed on January 12, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a drive device.

[0003] Conventionally, there are known drive devices in which an ECU (control unit) is integrally provided at one axial end of a motor. For example, in the drive device disclosed in Patent Document 1, a stator is fixed inside a cylindrical portion of a metal motor case. The cylindrical portion of the motor case and a resin ECU cover are sealed with adhesive.

[0004] Japanese Patent Application Laid-Open No. 2016-072996

[0005] In the drive device of Patent Document 1, the motor case is made of metal, so the exposed metal can corrode when exposed to moisture in the air or rainwater containing salt water, which can deteriorate the sealing ability of the adhesive between the motor case and the ECU cover. Furthermore, a metal motor case increases the weight of the motor. Furthermore, the stator fixed to the motor case is susceptible to motor vibrations.

[0006] An object of the present disclosure is to provide a drive device that is improved in corrosion resistance, lightweight, and suppresses vibration.

[0007] The drive device of the present disclosure is configured as an integral unit comprising a motor section in which a rotor arranged radially inside an annular stator rotates integrally with a shaft, and an ECU provided on one side of the axial direction of the motor section and controlling the drive of the motor section.

[0008] The side of the motor unit opposite the ECU is the front side, and the side of the motor unit facing the ECU is the rear side. A first aspect of the drive device includes a motor case, a rear frame, and an ECU cover. A second aspect of the drive device includes a motor case, a front frame, and an ECU cover.

[0009] The motor case is made of a non-metallic molding material, and preferably made of a carbon fiber composite material (CFRP) or a resin material with a glass fiber (GF) content of 35% or more.

[0010] The motor case in the first aspect is integrally formed with a cylindrical portion extending in the axial direction of the motor unit and a front bottom portion that holds a front bearing that supports the shaft on the front side of the motor unit. The motor case in the second aspect is integrally formed with a cylindrical portion extending in the axial direction of the motor unit and a rear bottom portion that holds a rear bearing that supports the shaft on the rear side of the motor unit.

[0011] In the first embodiment, the rear frame is a separate part from the motor case and holds a rear bearing that supports the shaft on the rear side of the motor unit. In the second embodiment, the front frame is a separate part from the motor case and holds a front bearing that supports the shaft on the front side of the motor unit.

[0012] In both the first and second aspects, the ECU cover is formed in a container shape using a resin material to cover the circuit board of the ECU, and an end of the side plate is joined to an end of the cylindrical portion of the motor case. Preferably, the ECU cover is formed from a resin material different from that of the motor case.

[0013] In both the first and second aspects, the stator is molded from a non-metallic molding material, and the stator molded portion that molds the stator is molded integrally with the cylindrical portion of the motor case.

[0014] In the drive unit disclosed herein, the motor case made of a non-metallic molding material and the ECU cover made of a resin material cover the interior of the motor and ECU, improving corrosion resistance. Furthermore, non-metallic molding materials are generally resin-based composite materials with a lower specific gravity than metals, enabling the motor to be made lighter. Furthermore, the stator mold, which molds the stator, is molded integrally with the cylindrical portion of the motor case using a non-metallic molding material, increasing the rigidity of the stator and suppressing vibration.

[0015] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an overall configuration diagram of an electric power steering device to which a drive unit is applied, Fig. 2 is a schematic cross-sectional view of a drive unit of a first embodiment, Fig. 3 is a view taken in the direction of arrow III in Fig. 2, Fig. 4 is a schematic cross-sectional view of a drive unit of a second embodiment, Fig. 5 is a schematic cross-sectional view of a drive unit of a third embodiment, and Fig. 6 is a schematic cross-sectional view of a drive unit of a fourth embodiment.

[0016] Several embodiments of a drive device according to the present disclosure will be described with reference to the drawings. Substantially identical components in the several embodiments are designated by the same reference numerals, and description thereof will be omitted. The first to fourth embodiments will be collectively referred to as "the present embodiment." The drive device of the present embodiment is applied, for example, as a steering assist motor for an electric power steering device, and is configured such that a motor unit and an ECU that controls the drive of the motor unit are integrated.

[0017] The schematic configuration of an electric power steering device 99 will be described with reference to Figure 1. Although a rack-assist electric power steering device is shown as an example, the drive unit 10 of this embodiment is also applicable to a column-assist electric power steering device. A steering system 90 including the electric power steering device 99 includes a steering wheel 91, a steering shaft 92, a pinion gear 96, a rack shaft 97, wheels 98, and the electric power steering device 99.

[0018] A torque sensor 93 that detects steering torque is provided on a steering shaft 92 to which a steering wheel 91 is connected. A pinion gear 96 that meshes with a rack shaft 97 is provided at the tip of the steering shaft 92. When the driver turns the steering wheel 91, the rotational motion of the steering shaft 92 is converted into linear motion of the rack shaft 97 by the pinion gear 96. A pair of wheels 98 connected to both ends of the rack shaft 97 are steered to an angle that corresponds to the amount of displacement of the rack shaft 97.

[0019] The electric power steering device 99 includes a drive unit 10, a gearbox 80, etc. The drive unit 10 has a so-called "mechatronically integrated" configuration in which the motor unit 50 and the ECU 60 that controls the driving of the motor unit 50 are integrally configured. The motor unit 50 is fixed to the end face of the gearbox 80 with bolts using mounting holes 285 (see FIG. 3 ) provided in the motor flange 28. The gearbox 80 houses a reduction gear that reduces the rotation of the motor unit 50 and transmits it to the rack shaft 97.

[0020] In the drive system 10 of this embodiment, the motor unit 50 is a two-system three-phase brushless motor having two sets of three-phase windings. The ECU 60 supplies power to the two sets of three-phase windings via two systems of inverter circuits. A connector 74 of the ECU 60 receives DC power from a battery and also receives and transmits communication signals to and from a vehicle communication network (CAN). A sensor signal is also input from a torque sensor 93. The motor unit 50 outputs steering assist torque when supplied with three-phase AC power converted from DC power by the inverter circuit of the ECU 60.

[0021] However, in rack-assist electric power steering devices, moisture such as rainwater and condensation easily penetrates the drive unit, making waterproofing particularly important. Therefore, the motor case and ECU cover are sealed with an adhesive. However, if the metal motor case is exposed, there is a risk of metal corrosion due to contact with moisture (including saltwater), deteriorating the sealing performance. Furthermore, a metal motor case increases the weight of the motor. Furthermore, there is a problem in that the stator fixed to the motor case is easily affected by motor vibrations.

[0022] Therefore, in the drive unit 10 of this embodiment, all exposed parts covering the interior of the motor unit 50 and ECU 60 are formed from non-metallic materials to improve corrosion resistance and reduce weight. Furthermore, to suppress vibration, the stator is molded from a non-metallic molding material, and the stator molded part that molds the stator is molded integrally with the motor case. The configuration of the drive unit 10 of each embodiment will now be described in order. The reference numerals for the drive units of the first to fourth embodiments have the embodiment number added as the third digit following "10."

[0023] (First embodiment) A drive device 101 of the first embodiment will be described with reference to Figures 2 and 3. In Figure 2, the direction parallel to the rotation axis O of the motor unit 50 is referred to as the "axial direction," and the direction perpendicular to the axial direction is referred to as the "radial direction." The stator 53, rotor 54, and shaft 55 are arranged coaxially with the rotation axis O. In the motor unit 50, the rotor 54, which is arranged radially inside the annular stator 53, rotates integrally with the shaft 55. The ECU 60 is provided on one side of the motor unit 50 in the axial direction. The side of the motor unit 50 opposite the ECU 60 is referred to as the "front side," and the side of the motor unit 50 facing the ECU 60 is referred to as the "rear side."

[0024] The stator 53 has motor windings 51 wound around an annular stator core. Lead wires 52 of the motor windings 51 are connected to a circuit board 65 of the ECU 60. The ECU 60 controls the supply of current to the motor windings 51, thereby forming a rotating magnetic field in the stator 53. The rotor 54 has a plurality of permanent magnets 545 provided along the outer periphery of the rotor core. The rotor 54 rotates around the shaft 55 due to the rotating magnetic field formed in the stator 53.

[0025] The shaft 55 is fixed to the center of the rotor 54. The front bearing 56 rotatably supports the shaft 55 on the front side of the motor unit 50. The rear bearing 57 rotatably supports the shaft 55 on the rear side of the motor unit 50. A wave washer 58 is fitted to the seat surface of the rear bearing 57.

[0026] The drive unit 101 of the first embodiment includes a motor case 201, a rear frame 40, and an ECU cover 70. The motor case 201 is formed from a non-metallic molding material, and a tubular portion 22, a front bottom portion 23, and a motor flange portion 28 are integrally formed. The tubular portion 22 extends in the axial direction of the motor unit 50 radially outside the stator 53. The front bottom portion 23 forms the front bottom portion of the motor unit 50 and holds the front bearing 56. More specifically, a metal retaining collar 236, into which the front bearing 56 is press-fitted, is insert-molded into the center of the front bottom portion 23.

[0027] 3, the motor flange portion 28 is provided so as to protrude radially outward at two circumferential locations on opposite sides of the rotation axis O. A metal fastening collar 286 having a mounting hole 285 is insert-molded into the motor flange portion 28. The drive unit 101 is fixed to the gearbox 80 by fastening a bolt through the mounting hole 285 into a threaded hole in the gearbox 80.

[0028] The motor case 201 of the first embodiment is cylindrical and has a bottom that opens to the rear side. Therefore, for example, the parting line of the molding die is set near the rear opening, and a core protruding from the parting line forms a space up to the front bottom 23.

[0029] Preferably, a carbon fiber composite material (CFRP) or a resin material containing 35% or more of glass fiber (GF) is used as the "non-metallic molding material" that is the material of the motor case 201. Therefore, the strength of the motor case 201 that forms the outer shell of the motor section 50 is reinforced.

[0030] The stator 53 is molded from a non-metallic molding material (i.e., a resin-based material). The non-metallic material portion that molds the stator 53 is referred to as the stator mold portion 25. The stator mold portion 25 is molded integrally with the cylindrical portion 22 of the motor case 201. In FIG. 2, the motor case 201 and the stator mold portion 25 are hatched with a common resin pattern, and a dashed line is drawn at the boundary. This dashed line indicates that the boundary between the motor case 201 and the stator mold portion 25 is fused together in the appearance of the finished product, making it indistinguishable, but suggests that they may have been manufactured in separate processes. Specifically, the following two manufacturing methods are possible.

[0031] [1] The motor case 201 and the stator molded portion 25 are molded simultaneously in one process using a mold into which the stator 53 is inserted. In this case, the stator molded portion 25 is made of the same material as the motor case 201 and is molded integrally with the cylindrical portion 22 of the motor case 201. In other words, this can be simply expressed as "the stator 53 is molded integrally with the cylindrical portion 22 of the motor case 201." This configuration allows for a relatively simple mold structure, and molding can be performed using a general injection molding machine.

[0032] [2] First, the stator 53 is molded with a primary molding material in a primary molding die. Next, the semi-finished product after primary molding, consisting of the stator 53 and the stator mold portion 25, is inserted into a secondary molding die and molded integrally with the cylindrical portion 22 of the motor case 201 with a secondary molding material. In this case, the primary molding material and the secondary molding material may be the same or different materials. However, if the same material is used, method [1] should be adopted, and there is no advantage to adopting the time-consuming method [2]. Therefore, when method [2] is adopted, it can be said that "the stator mold portion 25 is molded integrally with the cylindrical portion 22 of the motor case 201 using a material different from that of the motor case 201."

[0033] This configuration requires the use of two molds, a primary mold and a secondary mold, and a special molding machine such as a multi-color molding machine. However, it is possible to use different materials depending on their respective characteristics, such as using a high-strength material for the motor case 201 and a material that is advantageous for heat suppression, magnetic transmission, cost reduction, etc. for the stator mold portion 25.

[0034] In addition, to check whether the material of the stator mold portion 25 and the material of the motor case 201 of a finished drive unit are the same or different, for example, the product can be cut to scrape out samples of each part, and chemical analysis can be performed to determine this.

[0035] The rear frame 40 is a separate part from the motor case 201 and is made of metal such as an aluminum alloy. The rear frame 40 is fixed to the motor case 201 by fitting an outer fitting wall 42 into an inner fitting wall 222 of the cylindrical portion 22 of the motor case 201. The rear frame 40 holds a rear bearing 57 and also supports a circuit board 65 of the ECU 60. Heat generated by electronic elements 66 (mainly switching elements of the inverter circuit) mounted on the circuit board 65 is dissipated to the rear frame 40. In other words, the rear frame 40 functions as a heat sink.

[0036] The ECU cover 70 is made of a resin material such as PBT that is different from the material of the motor case 201. The ECU cover 70 is formed in the shape of a container having a top plate 71 and side plates 72, and covers the circuit board 65 of the ECU 60. Because the ECU cover 70 does not require the same strength as the motor case 201, using a resin material that does not contain carbon fiber or glass fiber can suppress mold wear and extend the mold life.

[0037] A connector 74 is integrally formed on the top plate 71, with its opening facing away from the motor unit 50. The connector 74 is connected to the circuit board 65 via connector terminals 67. In the example shown in FIG. 3, a vehicle system connector 74p having a power supply terminal and a CAN communication terminal, and a signal system connector 74s having a sensor signal terminal are provided. However, the number and arrangement of the openings of the connectors 74 are not limited to this example. For example, in a drive device in which power supplies and signals are input redundantly, two sets of vehicle system connectors and two sets of signal system connectors may be provided. A configuration in which the connectors face in different directions will be described later as a fourth embodiment.

[0038] An end 721 of the side plate 72 of the ECU cover 70 is joined to an end 221 of the tubular portion 22 of the motor case 201 with adhesive S. Although the detailed shape of the portion into which adhesive S is filled is not shown in the drawings, an adhesive groove may be formed. This seals the gap between the ECU cover 70 and the motor case 201, preventing the intrusion of rainwater and the like.

[0039] As described above, in the drive unit 101 of the first embodiment, the motor case 201 made of a non-metallic molding material and the ECU cover 70 made of a resin material cover the interior of the motor unit 50 and the ECU 60, improving corrosion resistance. Furthermore, non-metallic molding materials are generally resin-based composite materials, which have a lower specific gravity than metals, thereby realizing a reduction in the weight of the motor unit 50.

[0040] Furthermore, the stator mold portion 25 that molds the stator 53 is made of a non-metallic molding material and is molded integrally with the cylindrical portion 22 of the motor case 201, which increases the rigidity of the stator 53 and suppresses vibration. Also, because the stator 53 and the motor case 201 are one component, the number of parts required in the assembly process is reduced.

[0041] Next, with reference to Figures 4 to 6, second to fourth embodiments, each of which has a configuration partially different from that of the first embodiment, will be described in order. In each embodiment, the motor cases 201 and 202 are formed from a non-metallic molding material, specifically, a carbon fiber composite material or a resin material with a glass fiber content of 35% or more. The ECU covers 70 and 704 are formed from a resin material different from that of the motor cases 201 and 202.

[0042] The stator 53 is molded from a "non-metallic molding material" that may be the same as or different from the motor cases 201 and 202. A stator mold portion 25 that molds the stator 53 is molded integrally with the cylindrical portions 22 of the motor cases 201 and 202.

[0043] The basic effects of this configuration are the same as those of the first embodiment. That is, the drive device of each embodiment has improved corrosion resistance and the motor unit 50 is lighter. Also, vibration of the stator 53 is suppressed. Below, the differences in other configurations and effects will be mainly described.

[0044] Second Embodiment A drive unit 102 according to a second embodiment will be described with reference to Figure 4. In the second embodiment, the configuration of the motor case and frame that constitute the housing of the motor unit 50 differs from that of the drive unit 101 according to the first embodiment. The motor case 202 of the drive unit 102 has a cylindrical portion 22, a rear bottom portion 24, and a motor flange portion 28 integrally formed therein. The ECU cover 70 is the same as that of the first embodiment.

[0045] The rear bottom portion 24 holds the rear bearing 57 in place of the rear frame 40 of the first embodiment, and also supports the base plate 65. A metal retaining collar 246 into which the rear bearing 57 is press-fitted is insert-molded in the center of the rear bottom portion 24.

[0046] The motor case 202 of the second embodiment is cylindrical and has a bottom that is open on the front side. Therefore, for example, the parting line of the molding die is set near the front opening, and a core protruding from the parting line forms a space up to the rear bottom 24.

[0047] The drive unit 102 also includes a front frame 30. The front frame 30 is a separate part from the motor case 202 and holds the front bearing 56. The front frame 30 is formed of a non-metallic material, just like the motor case 202, and its outer peripheral wall fits inside the motor flange portion 28 of the motor case 202. A metal retaining collar 36, into which the front bearing 56 is press-fitted, is insert-molded in the center of the front frame 30.

[0048] Because the front frame 30 as well as the motor case 202 are made of a non-metallic material, the effect of improving the corrosion resistance of the motor unit 50 is maintained. Furthermore, in the second embodiment, the motor case 202 and the rear bottom portion 24 have an integrated structure, so strength in the rear direction can be ensured even in an environment where stress in the rear direction is high.

[0049] (Third Embodiment) A drive unit 103 of a third embodiment will be described with reference to FIG. 5 . In addition to the configuration of the drive unit 102 of the second embodiment, the drive unit 103 includes a metal plate 64 between a circuit board 65 of the ECU 60 and the rear bottom 24. The metal plate 64 is made of an aluminum alloy or the like. Heat generated by electronic elements 66 (mainly switching elements of the inverter circuit) mounted on the circuit board 65 is dissipated to the metal plate 64. In other words, the metal plate 64 functions as a heat sink, similar to the rear frame 40 of the first embodiment. The metal plate 64 also supports the circuit board 65.

[0050] Heat from the electronic elements 66 is dissipated to the metal plate 64 provided between the circuit board 65 and the non-metallic rear bottom 24, thereby preventing performance degradation or failure due to temperature rise in the ECU 60 when the motor is driven.

[0051] (Fourth embodiment) A drive device 104 of a fourth embodiment will be described with reference to Figure 6. The drive device 104 has the same configuration of the motor unit 50 as the drive device 101 of the first embodiment, but differs in the shape of the ECU cover in relation to the arrangement of the connector 74. The ECU cover 704 of the drive device 104 is formed to protrude to one side in the radial direction of the motor unit 50. The connector 74 is provided at the protruding portion of the ECU cover 704, opening to the front side (downward in the figure).

[0052] The ECU cover 704 is formed by separately forming an upper cover including the top plate 71 and side plates 72 and a lower cover 77 at the protruding portion, and joining them with an adhesive. As shown by the dashed line in Figure 6 , the lower cover 77 and the motor case 201 may be formed separately or integrally. Forming them integrally reduces the number of parts. Note that the ECU cover 704 protruding radially to one side of the motor unit 50 may also be applied to the drive units 102, 103 of the second and third embodiments.

[0053] (Other Embodiments) (a) In the above embodiment, the motor flange portion 28 for attaching the drive unit 10 to the end face of the gear box 80 is formed integrally with the motor cases 201, 202. However, the object to which the drive unit 10 is attached is not limited to the gear box 80, and the attachment method is not limited to the flange method. In a configuration that does not use a flange, the motor flange portion does not need to be formed on the motor case.

[0054] (b) The configurations of the board 65 and the connector 74 of the ECU 60 are not limited to those exemplified in the above embodiment. For example, a plurality of boards may be stacked.

[0055] (c) The drive unit 10 of the present disclosure is not limited to being used as a steering assist motor for an electric power steering device, but may also be used as a reaction motor or steering motor for a steer-by-wire system, or as a drive unit for any other motor.

[0056] As described above, the present disclosure is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present disclosure.

[0057] The present disclosure has been described based on the embodiments. However, the present disclosure is not limited to the embodiments and structures. The present disclosure also encompasses various modifications and variations within the scope of equivalents. Furthermore, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A motor unit (50) in which a rotor (54) disposed radially inside an annular stator (53) rotates integrally with a shaft (55), and an ECU (60) provided on one axial side of the motor unit and controlling the drive of the motor unit are integrally formed. When the side opposite to the ECU with respect to the motor unit is defined as the front side and the ECU side with respect to the motor unit is defined as the rear side, a motor case (201) integrally formed with a cylindrical portion (22) formed of a non-metallic molding material and extending in the axial direction of the motor unit, and a front bottom portion (23) holding a front bearing (56) supporting the shaft on the front side of the motor unit; a rear frame (40) which is a separate component from the motor case and holds a rear bearing (57) supporting the shaft on the rear side of the motor unit; and an ECU cover (70, 704) formed in a container shape covering a substrate (65) of the ECU with a resin material and having an end portion of a side plate (72) joined to an end portion of the cylindrical portion of the motor case. The stator is molded with a non-metallic molding material, and a stator molding portion (25) molding the stator is integrally formed with the cylindrical portion of the motor case as a driving device.

2. A motor unit (50) in which a rotor (54) disposed radially inside an annular stator (53) rotates integrally with a shaft (55), and an ECU (60) provided on one axial side of the motor unit to control the drive of the motor unit are integrally configured. When the side opposite to the ECU with respect to the motor unit is defined as the front side and the ECU side with respect to the motor unit is defined as the rear side, a motor case (202) formed of a non-metallic molding material and integrally formed with a cylindrical portion (22) extending in the axial direction of the motor unit and a rear bottom portion (24) holding a rear bearing (57) that supports the shaft on the rear side of the motor unit; a front frame (30) that is a separate component from the motor case and holds a front bearing (56) that supports the shaft on the front side of the motor unit; and an ECU cover (70, 704) formed in a container shape to cover the substrate (65) of the ECU with a resin material and having an end portion of a side plate (72) joined to an end portion of the cylindrical portion of the motor case. The stator is molded with a non-metallic molding material, and a stator mold portion (25) that molds the stator is integrally formed with the cylindrical portion of the motor case.

3. The drive device according to claim 2, further comprising a metal plate (64) provided between the substrate of the ECU and the rear bottom portion of the motor case to dissipate heat generated by an electronic element (66) mounted on the substrate.

4. The drive device according to any one of claims 1 to 3, wherein the motor case is formed of a carbon fiber composite material or a resin material having a glass fiber blending ratio of 35% or more, and the ECU cover is formed of a resin material different from the material of the motor case.

5. The drive device according to claim 4, wherein the stator mold portion is formed of the same material as the motor case and is integrally formed with the cylindrical portion of the motor case.

6. The drive device according to claim 4, wherein the stator mold portion is formed of a material different from the motor case and is integrally formed with the cylindrical portion of the motor case.

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