Motor device

Abstract

This motor device (30) is provided with a motor (40), a substrate (52), and a heat dissipation material (65). The motor has a metal motor case (41) and a metal end wall (42) attached to an axial end of the motor case. The substrate has a heat generation portion (64) and is disposed so as to face the end wall (42) in the axial direction of the motor. The heat dissipation material has fluidity at least during application, and is interposed between the heat generation portion and the end wall. The end wall has a first surface (40B1) that contacts the heat dissipation material, and a second surface (40B2) that is adjacent to the first surface and is disposed on a specific side with respect to the first surface. The specific side is a side on which the flow of the heat dissipation material needs to be suppressed. The second surface is inclined relative to the first surface such that the second surface gradually separates from the substrate toward the specific side.

Description

Motor device

[0001] The present disclosure relates to a motor device.

[0002] Conventionally, there have been motor devices in which a motor and a circuit board are integrally provided. For example, the motor device disclosed in Patent Document 1 includes a motor, a motor housing, a heat sink, a circuit board, and a heat dissipation material. The motor housing is a cylindrical body with a circular cross section and houses the motor. The heat sink is fixed to the motor housing so as to cover the opening of the motor housing. The circuit board has a switching element for controlling the operation of the motor. The heat dissipation material, such as thermal grease, is interposed between the switching element and the heat sink. Heat from the switching element is dissipated to the heat sink via the heat dissipation material.

[0003] Japanese Patent Application Laid-Open No. 2021-61653

[0004] The motor device of Patent Document 1 has the following concerns: When assembling the motor device, the heat dissipation material may be crushed between the substrate and the heat sink, causing it to spread around the switching elements. At this time, there is a risk that some of the crushed heat dissipation material may find its way into parts of the motor device where it is not desirable for the heat dissipation material to be present.

[0005] A motor device according to one aspect of the present disclosure includes a motor, a substrate, and a heat dissipation material. The motor has a metal motor case and a metal end wall attached to an axial end of the motor case. The substrate has a heat-generating portion and is arranged opposite the end wall in the axial direction of the motor. The heat dissipation material is fluid at least when applied and is interposed between the heat-generating portion and the end wall. The end wall has a first surface that contacts the heat dissipation material and a second surface adjacent to the first surface and located on a specific side of the first surface. The specific side is a side where it is necessary to suppress the flow of the heat dissipation material. The second surface is inclined with respect to the first surface so as to move away from the substrate as it moves from the first surface toward the specific side.

[0006] FIG. 1 is an exploded perspective view of a motor device according to one embodiment. FIG. 2 is a cross-sectional view showing a main portion of the motor device of FIG. 1. FIG. 3 is a cross-sectional view showing a main portion of a motor device according to a comparative example. FIG. 4 is a cross-sectional view showing a main portion of the motor device of FIG. 1. FIGS. 5A, 5B, 5C, and 5D are diagrams illustrating the position of the power board and changes in the state of the thermal grease during assembly of the motor device of FIG. 1. FIG. 5A shows the state after the thermal grease has been applied, FIG. 5B shows the state after the thermal grease has begun to be crushed, FIG. 5C shows the state after the thermal grease has begun to protrude from the first surface to the second surface, and FIG. 5D shows the state after the thermal grease has been completely crushed. FIG. 6 is a cross-sectional view showing a main portion of a motor device according to a comparative example. FIG. 7 is a cross-sectional view showing a main portion of a motor device according to another embodiment.

[0007] A motor device 30 according to one embodiment will be described. The motor device 30 is mounted on, for example, a vehicle. <Overall Configuration> As shown in FIG. 1 , the motor device 30 has a motor 40 and a control device 50. The motor 40 is, for example, a three-phase brushless motor. The motor 40 has, for example, two winding groups. The control device 50 is attached to the axial end of the motor 40. The control device 50 independently controls the power supply to the two winding groups. The motor 40 has two control systems and two power supply systems.

[0008] The control device 50 has a control board 51, a power board 52, a connector assembly 53, and a cover 53. The control board 51 has electronic components for controlling the power supply to the motor 40. The power board 52 has electronic components for supplying power to the motor 40 through control by the control board 51. The axial end of the motor 40 has a board housing portion 40A. The control board 51 is housed inside the board housing portion 40A. The power board 52 is attached to the axial end of the motor 40 so as to cover the control board 51. The power board 52 is positioned farther from the motor 40 in the axial direction of the motor 40 than the control board 51.

[0009] The connector assembly 53 is made of synthetic resin. The connector assembly 53 has a first power connector 53A and a second power connector 53B. The first power connector 53A extends in the opposite direction from the motor 40 and opens in the opposite direction from the motor 40. The first power connector 53A has a power terminal and a ground terminal. A mating power plug is mated with the first power connector 53A. The power plug is provided at a first end of a power line. A second end of the power line is connected to a DC power source such as an on-board battery. Power from the DC power source is supplied to the control board 51 and the power board 52 via the power terminal and the ground terminal. The second power connector 53B has a configuration similar to that of the first power connector 53A. The DC power source corresponds to an external power source.

[0010] The connector assembly 53 has a first signal connector 53C and a second signal connector 53D. The first signal connector 53C extends in the opposite direction from the motor 40. The first signal connector 53C has a signal terminal. A mating signal plug is mated with the first signal connector 53C. The signal plug is provided at a first end of a signal line. A second end of the signal line is connected to, for example, a vehicle control device. Signals are exchanged between the control board 51 and the vehicle control device via the signal terminal. The second signal connector 53D has a configuration similar to that of the first signal connector 53C.

[0011] The cover 54 is made of synthetic resin. The cover 54 is a box-shaped body that opens toward the motor 40. An end wall of the cover 54 has a fitting hole 54A. The fitting hole 54A is fitted with the outer periphery of the connector assembly 53. The connectors (53A, 53B, 53C, 54C) of the connector assembly 53 pass through the fitting hole 54A and protrude from the end wall of the cover 54 to the outside of the cover 53. The cover 54 is attached to the axial end of the motor 40. The cover 54, together with the connector assembly 53, covers the end of the motor 40.

[0012] <Assembly State of Motor Device 30> Next, the assembly state of the motor device 30 will be described. As shown in FIG. 2, the motor 40 has a motor case 41 and a lid 42. An end of the motor case 41 is open in the axial direction. This end is the end of the motor case 41 on which the control device 50 is mounted. The lid 42 is fitted into the opening of the motor case 41 to close the opening. The lid 42 functions as an axial end wall of the motor case 41. The motor case 41 and the lid 42 are each made of metal. The metal is, for example, iron or an aluminum alloy. The lid 42 also functions as a heat sink.

[0013] The lid 42 has a through-hole 42A. The through-hole 42A penetrates the lid 42 in the axial direction. A portion of the through-hole 42A opens toward the substrate accommodating portion 40A at the boundary between the substrate accommodating portion 40A and the heat dissipation portion 40B. The lid 42 also has a bearing holding portion 42B. The bearing holding portion 42B is a portion of the lid 42 where the diameter of the through-hole 42A is increased. A bearing 42C is attached to the bearing holding portion 42B.

[0014] The motor 40 has an output shaft 43. The output shaft 43 is rotatably supported by the motor case 41 and the lid 42. A first end of the output shaft 43 is inserted into a through-hole 42A of the lid 42 in a non-contact state. The first end is the end of the output shaft 43 that is closer to the control device 50. The first end is rotatably supported by a bearing 42C relative to the lid 42. A second end of the output shaft 43 is rotatably supported by a bearing different from the bearing 42C relative to the motor case 41. The second end is the end of the output shaft 43 opposite the first end.

[0015] The first end of the output shaft 43 has a holder 43A, a magnet 43B, and a spacer 43C. The magnet 43B is fixed to the first end of the output shaft 43 by the holder 43A. A spacer 43C is interposed between the first end of the output shaft 43 and the magnet 43B. The holder 43A and the spacer 43C are each made of a non-magnetic material such as synthetic resin.

[0016] The control board 51 is fixed to the connector assembly 53. The connector assembly 53 has a plurality of first support posts 53H. Only one first support post 53H is shown in FIG. 2 . The first support post 53H is provided at the end of the connector assembly 53 opposite the power connectors (53A, 53B). The first support post 53H extends from the connector assembly 53 toward the lid 42. The control board 51 is fixed to the tip of the first support post 53H with a screw 53I. The tip is the end of the first support post 53H closest to the lid 42.

[0017] With the connector assembly 53 attached to the end of the motor case 41, the control board 51 is housed inside the board housing portion 40A. The control board 51 faces the end wall surface of the board housing portion 40A in the axial direction. The control board 51 contacts the end wall surface of the board housing portion 40A via the ground connection member 61.

[0018] The power board 52 is fixed to the connector assembly 53. The connector assembly 53 has a plurality of second support columns 53J. The second support columns 53J are provided at the end of the connector assembly 53 opposite the power connectors (53A, 53B). The second support columns 53J extend from the connector assembly 53 toward the lid 42. The protruding length of the second support columns 53J from the connector assembly 53 is shorter than the protruding length of the first support columns 53H from the connector assembly 53. The power board 52 is fixed to the tip of the second support columns 53J with screws 53K. The tip is the end of the second support columns 53J closest to the lid 42.

[0019] The power board 52 is also fixed to the lid 42. The lid 42 has a plurality of support portions 42D. Only one support portion 42D is shown in FIG. 2 . The support portion 42D is provided on the axially outer end surface of the lid 42. The power board 52 is fixed to the tip of the support portion 42D with a screw 42E. The tip is the end of the support portion 42D that is farther from the axially outer end surface of the lid 42.

[0020] The power board 52 has a rotation angle sensor 62. The rotation angle sensor 62 is provided on a surface of the power board 52 that faces the lid 42 in the axial direction. The rotation angle sensor 62 faces the magnet 43B in the axial direction via the holder 43A.

[0021] With connector assembly 53 attached to the end of motor case 41, power board 52 is supported by a portion of lid 42 so as to cover control board 51. Power board 52 is also connected to control board 51 via an inter-board connector 63. Inter-board connector 63 includes a first connector portion provided on power board 52 and a second connector portion provided on control board 51.

[0022] The power connectors (53A, 53B) have a power terminal 53E and a ground terminal 53F. The power terminal 53E and the ground terminal 53F each have a first end and a second end. The first end is located inside the peripheral wall of the power connectors (53A, 53B). The second end penetrates the power board 52 in a direction perpendicular to the power board 52. The second end is connected to the power board 52 by soldering.

[0023] The signal connectors (53c, 53D) have a plurality of signal terminals 53G. The signal terminals 53G have a first end and a second end. The first end is located inside the peripheral wall of the second signal connector 53D. The second end penetrates the power board 52 in a direction perpendicular to the power board 52. The second end is connected to the power board 52 by soldering.

[0024] The power board 52 is connected to the positive terminal of the DC power supply via a power supply terminal 53E. The power board 52 is connected to the negative terminal of the DC power supply via a ground terminal 53F. DC power from the DC power supply is supplied to the power board 52 via the power supply terminal 53E and the ground terminal 53F. DC power is supplied to the control board 51 via an inter-board connector 63.

[0025] The power board 52 is connected to, for example, a vehicle control device via a signal terminal 53G. The power board 52 can exchange signals with the vehicle control device via the signal terminal 53G. The control board 51 can exchange signals with the vehicle control device via an inter-board connector 63.

[0026] <Heat Dissipation Structure of Motor Device 30> Next, the heat dissipation structure of the motor device 30 will be described. As shown in FIG. 2, the lid 42 has a board accommodating portion 40A and a heat dissipation portion 40B. The board accommodating portion 40A and the heat dissipation portion 40B are provided at the outer axial end of the lid 42. The board accommodating portion 40A and the heat dissipation portion 40B are adjacent to each other in a direction perpendicular to the axial direction. A step is provided between the board accommodating portion 40A and the heat dissipation portion 40B. That is, the axial positions of the end wall surfaces of the board accommodating portion 40A and the heat dissipation portion 40B are different from each other. The end wall surface of the board accommodating portion 40A is axially farther from the end wall of the cover 54 than the end wall surface of the heat dissipation portion 40B. In other words, the end wall surface of the board accommodating portion 40A is located axially inward of the motor 40 than the end wall surface of the heat dissipation portion 40B. The heat dissipation portion 40B is a portion of the lid 42 that exchanges heat with the power board 52 .

[0027] The power board 52 has a plurality of heat-generating elements 64. The heat-generating elements 64 are electronic components that generate heat when energized and are heat-generating portions of the power board 52. The heat-generating elements 64 include, for example, switching elements of an inverter circuit. The switching elements are, for example, field effect transistors (FETs), which are one of the electronic components that generate a particularly large amount of heat. The inverter circuit converts DC power from a DC power source into three-phase AC power. The AC power generated by the inverter circuit is supplied to the windings of the motor 40 via a power supply path such as a bus bar.

[0028] The heating element 64 is provided, for example, on a portion of the power board 52 that faces the end wall surface of the heat dissipation unit 40B. The surface of the heating element 64 opposite the power board 52 is in contact with the heat dissipation unit 40B via a heat dissipation material 65. The heat dissipation material 65 is, for example, thermal grease. Thermal grease has high thermal conductivity. By applying the thermal grease between the heating element 64 and the heat dissipation unit 40B, gaps caused by minute irregularities between the heating element 64 and the heat dissipation unit 40B are filled. This promotes thermal conduction between the heating element 64 and the heat dissipation unit 40B.

[0029] Heat generated by the heat generating element 64 is dissipated via the heat dissipation path A1, which is a heat transfer path between the heat generating element 64 of the power board 52 and the lid 42. The heat dissipation path A1 includes the power board 52, a contact portion between the power board 52 and the lid 42, and a non-contact portion between the power board 52 and the lid 42.

[0030] A portion of the heat generated by the heating element 64 is transferred to the lid 42 by thermal conduction through the power board 52 and the contact portion between the power board 52 and the lid 42. The heat is efficiently transferred to the lid 42 via the heat dissipation material 65. A portion of the heat is transferred directly to the lid 42 by radiation. The heat transferred to the lid 42 is radiated to the outside via the motor case 41. A portion of the heat is also transferred to the atmosphere by convection.

[0031] <About Thermal Grease Extrusion> The following concerns exist regarding the motor device 30. As shown in Figure 3, when assembling the motor device 30, the connector assembly 53 is attached to the end of the motor case 41 with a heat dissipation material 65 applied to the surface of the heat dissipation unit 40B that faces the power board 52 in the axial direction. At this time, the fluid heat dissipation material 65 is crushed by the power board 52 and the heat-generating element 64. As a result, the heat dissipation material 65 spreads around the heat-generating element 64 along the gap between the power board 52 and the heat dissipation unit 40B.

[0032] Depending on the amount of heat dissipation material 65 applied or the distance between the heating element 64 and the through-hole 42A in the radial direction of the motor 40, there is a risk that part of the heat dissipation material 65 that has spread around the heating element 64 may find its way into the through-hole 42A. The closer the heating element 64 is to the through-hole 42A, the more likely the heat dissipation material 65 will find its way into the through-hole 42A. If the heat dissipation material 65 finds its way into the through-hole 42A, there is a concern that the heat dissipation material 65 that has found its way into the through-hole 42A may fall out due to vibration or the like.

[0033] Therefore, in this embodiment, the following configuration is adopted to prevent the heat dissipation material 65 from entering the through-holes 65. <Structure for Suppressing Flow of Heat Dissipation Material 65> As shown in FIG. 4 , the heat dissipation section 40B has a first surface 40B1 and a second surface 40B2. The first surface 40B1 is the surface of the heat dissipation section 40B that faces the heat-generating element 64 via the heat dissipation material 65. The second surface 40B2 is the surface of the heat dissipation section 40B adjacent to the first surface 40B1 and is located between the first surface 40B1 and the through-holes 42A. The second surface 40B2 is located on a specific side of the first surface 40B1. The specific side is the side where the flow of the heat dissipation material 65 needs to be suppressed, specifically, the side where the through-holes 42A are located relative to the first surface 40B1. The through-holes 42A are portions of the motor device 30 where it is undesirable for the heat dissipation material 65 to enter.

[0034] The second surface 40B2 is provided at the open end of the through-hole 42A of the cover 42. The second surface 40B2 is provided so as to surround the periphery of the through-hole 42A. The second surface 40B2 is an inclined surface inclined with respect to the first surface 40B1. The second surface 40B2 is inclined so as to move away from the power board 52 in the axial direction of the motor 40 as it moves from the first surface 40B1 toward the through-hole 42A in the radial direction of the motor 40. The inclination angle θ1 of the second surface 40B2 with respect to the first surface 40B1 is, for example, approximately 30°.

[0035] The heat generated by the heating element 64 diffuses from the heating element 64 at a predetermined diffusion angle θ2. The diffusion angle θ2 is the angle at which heat from the heating element 64 diffuses. Specifically, the diffusion angle θ2 is the heat transfer angle with respect to an imaginary plane appropriately set on the side where the heat diffuses. The imaginary plane is parallel to the power board 52. The diffusion angle θ2 that can efficiently dissipate the heat generated by the heating element 64 as the heat dissipation path DP is, for example, about 45°. The second surface 40B2 is arranged so as not to interfere with the heat dissipation path DP.

[0036] The relationship between the axial position of the power board 52 and the state change of the heat dissipation material 65 during assembly of the motor device 30 is as follows. As shown in Figure 5A, when assembling the motor device 30, first, heat dissipation material 65 is applied to the surface of the heat dissipation section 40B that faces the power board 52 in the axial direction of the motor 40. The position of the connector assembly 53 is adjusted so that the heat-generating element 64 faces the heat dissipation material 65 in the axial direction. In this state, the connector assembly 53 is brought close to the end of the motor 40. The power board 52 approaches the heat dissipation section 40B.

[0037] As shown in Fig. 5B, the heat-generating element 64 eventually comes into contact with the heat-dissipating material 65. As the power board 52 approaches the heat-dissipating section 40B, the heat-dissipating material 65 begins to be crushed. As shown in Fig. 5C, as the heat-dissipating material 65 is crushed by the power board 52 and the heat-generating element 64, the heat-dissipating material 65 spreads around the heat-generating element 64 along the gap between the power board 52 and the heat-dissipating section 40B. Eventually, the heat-dissipating material 65 extends beyond the boundary between the first surface 40B1 and the second surface 40B2 and protrudes onto the second surface 40B2.

[0038] As shown in Figure 5D, once the connector assembly 53 is attached to the end of the motor 40, the power board 52 is supported by a portion of the lid 42. This prevents the power board 52 from moving toward the heat dissipation section 40B. The heat dissipation material 65 is completely crushed. The heat dissipation material 65 that protrudes beyond the second surface 40B2 is held between the second surface 40B2 and the power board 52 without entering the through-hole 42A.

[0039] When the following formula (1) is satisfied, the heat dissipation material 65 does not enter the through-hole 42A, but is maintained sandwiched between the second plane 40B2 and the power board 52. D1>D2 (1) "D1" is the first distance. "D2" is the second distance.

[0040] The first distance D1 is the difference between the third distance and the fourth distance. The third distance is the distance between the power board 52 and the first surface 40B1 when the heat dissipation material 65 begins to protrude onto the second surface 40B2. The fourth distance is the distance between the power board 52 and the first surface 40B1 when the heat dissipation material 65 is completely crushed.

[0041] The second distance D2 is the difference between the filling depth of the heat dissipation material 65 that protrudes onto the second surface 40B2 and the thickness of the heat dissipation material 65 sandwiched between the power board 52 and the first surface 40B1. The filling depth of the heat dissipation material 65 is the axial distance between the first surface 40B1 and the portion of the heat dissipation material 65 that protrudes onto the second surface 40B2 that is farthest from the first surface 40B1 in the axial direction of the motor 40.

[0042] Equation (1) is valid when the inclination angle θ1 of the second surface 40B2 relative to the first surface 40B1 is, for example, about 30°. Therefore, by providing the second surface 40B2 around the through-hole 42A of the lid 42 and setting the inclination angle θ1 of the second surface 40B2 to about 30°, it is possible to prevent the heat dissipation material 65 from entering the inside of the through-hole 42A.

[0043] However, the inclination angle θ1 can be set within a range from a few degrees to approximately 45° depending on the axial position of the power board 51 when the connector assembly 53 is attached to the end of the motor 40. When the connector assembly 53 is attached to the end of the motor 40, the longer the distance between the power board 52 and the first surface 40B1, the less the heat dissipation material 65 protrudes onto the second surface 40B2. Therefore, depending on the axial position of the power board 51 when the connector assembly 53 is attached to the end of the motor 40, the heat dissipation material 65 may not protrude onto the second surface 40B2.

[0044] <Operation of the Present Embodiment> Next, the operation of the present embodiment will be described. As shown in FIG. 6, it is also possible to provide a groove 40B3 in the heat dissipation portion 40B instead of the second surface 40B2. The groove 40B3 is open to the through-hole 42A side. The groove 40B3 has an inner circumferential surface extending in the axial direction of the motor 40 and an end wall surface extending in the radial direction of the motor 40. The inner circumferential surface of the groove 40B3 is perpendicular to the end wall surface of the groove 40B3 and the first surface 40B1.

[0045] In this case, it is difficult to ensure a sufficient contact area between the heat dissipation material 65 and the inner circumferential surface of the groove 40B3, and between the heat dissipation material 65 and the power board 52. Therefore, depending on the size of the groove 40B3 in the radial direction of the motor 40, the heat dissipation material 65 protruding into the groove 40B3 may not be supported, and part of the heat dissipation material 65 may fall into the through-hole 42A.

[0046] In order to support the heat dissipation material 65 that protrudes into the groove 40B3, it is conceivable to increase the size of the groove 40B3 in the radial direction of the motor 40. However, in this case, there is a concern that a part of the groove 40B3 may block a part of the heat dissipation path DP, thereby reducing the heat dissipation performance of the heat generated by the heating element 64.

[0047] In order to avoid interference between the groove 40B3 and the heat dissipation path DP, it is conceivable to reduce the size of the groove 40B3 in the radial direction of the motor 40 to, for example, about half the size of the groove 40B3 shown in Fig. 6. However, in this case, the space in which the heat dissipation material 65 accumulates becomes narrower, and as mentioned above, there is a risk that the heat dissipation material 65 protruding into the groove 40B3 may not be supported.

[0048] In contrast, the second surface 40B2 of the present embodiment is an inclined surface. This makes it easy to ensure a space for the heat dissipation material 65 to accumulate. The space is the space between the second surface 40B2 and the power board 52. Furthermore, it is easy to ensure a contact area between the heat dissipation material 65 and the second surface 40B2 and a contact area between the heat dissipation material 65 and the power board 52. This ensures a sufficient flow resistance between the heat dissipation material 65 and the second surface 40B2 and between the heat dissipation material 65 and the power board 52. This prevents the heat dissipation material 65 between the second surface 40B2 and the power board 52 from flowing toward the through-hole 42A and thereby from entering the through-hole 42A.

[0049] Furthermore, the inclination angle θ1 of the second surface 40B2 relative to the first surface 40B1 is smaller than the diffusion angle θ2 of the heat diffusing from the heat-generating element 64. Therefore, it is easy to provide the second surface 40B2 without interfering with the heat dissipation path DP. Because the second surface 40B2 does not interfere with the heat dissipation path DP, the heat dissipation performance of the heat generated by the heat-generating element 64 can be ensured.

[0050] The heat dissipation material 65 may be, for example, hardening type heat dissipation grease or high viscosity heat dissipation grease. Hardening type heat dissipation grease is semi-solid and fluid when applied, but hardens after a certain period of time. High viscosity heat dissipation grease has particularly high viscosity and low fluidity among various types of heat dissipation grease.

[0051] When hardening type thermal grease is used as the heat dissipation material 65, the heat dissipation material 65 that protrudes onto the second surface 40B2 hardens and does not flow, thereby appropriately preventing the heat dissipation material 65 from flowing along the second surface 40B2, which is an inclined surface, toward the through-hole 42A.

[0052] Furthermore, when high-viscosity thermal grease is used as the heat dissipation material 65, the heat dissipation material 65 that overflows onto the second surface 40B2 is less likely to flow toward the through-hole 42A, which appropriately prevents the heat dissipation material 65 from entering the inside of the through-hole 42A along the second surface 40B2, which is an inclined surface.

[0053] Effects of the Embodiment The present embodiment provides the following effects. (1) The motor device 30 includes a motor 40, a power board 52, and a heat dissipation material 65. The motor 40 has a metal motor case 41 and a metal end wall attached to an axial end of the motor case 41. The end wall is a lid 42 that functions as a heat sink. The power board 52 has a heat-generating portion and is disposed opposite the end wall in the axial direction of the motor 40. The heat-generating portion includes a heat-generating element 64. The heat dissipation material 65 has fluidity and is interposed between the heat-generating portion and the end wall.

[0054] The motor device 30 has the following concerns. When assembling the motor device 30, the heat dissipation material 65 may be crushed between the power board 52 and the end wall, causing it to spread around the heat-generating portion. At this time, there is a risk that part of the crushed heat dissipation material 65 may get into a part of the motor device 30 where it is undesirable for the heat dissipation material 65 to get in. An example of a part of the motor device 30 where it is undesirable for the heat dissipation material 65 to get in is the through-hole 42A.

[0055] Therefore, in this embodiment, the end wall has the following configuration. That is, the end wall has a first surface 40B1 that contacts the heat dissipation material 65 and a second surface 40B2 that is adjacent to the first surface 40B2 and is located on a specific side of the first surface 40B1. The specific side is the side where it is necessary to suppress the flow of the heat dissipation material 65, i.e., the side where a portion of the motor device 30 where it is undesirable for the heat dissipation material 65 to enter is located. The second surface 40B2 is inclined with respect to the first surface 40B1 so as to move away from the power board 52 as it moves from the first surface 40B1 toward the specific side.

[0056] According to this configuration, a space in which the heat dissipation material 65 accumulates is formed between the second surface 40B2 and the power board 52. Therefore, even if a portion of the heat dissipation material 65 flows from the first surface 40B1 toward a particular side, the heat dissipation material 65 is retained in the space between the second surface 40B2 and the power board 52. This makes it possible to prevent the heat dissipation material 65 from entering portions of the motor device 30 where it is undesirable for the heat dissipation material 65 to enter, i.e., the through-holes 42A.

[0057] (2) Because the heat dissipation material 65 is prevented from entering the through-hole 42A, the heat generating element 64 can be disposed near the through-hole 42A without reducing the amount of heat dissipation material 65 applied. In other words, even if the heat generating element 64 is disposed near the through-hole 42A, it is possible to ensure the heat dissipation performance of the motor device 30 while preventing the heat dissipation material 65 from entering the through-hole 42A during assembly of the motor device 30. The heat generated by the heat generating element 64 is appropriately transferred to the lid 42 via the heat dissipation material 65.

[0058] It should be noted that by reducing the amount of heat dissipation material 65 applied, it is possible to reduce the degree to which the heat dissipation material 65 is crushed and spread between the power board 52 and the end wall. However, in this case, there is a risk that the heat dissipation performance will be reduced by the amount of heat dissipation material 65 applied.

[0059] (3) The heat generating elements 64 can be disposed near the through holes 42A. Therefore, by concentrating the heat generating elements 64 near the through holes 42A, the power board 52 and, ultimately, the motor device 30 can be made smaller.

[0060] By positioning the heat generating element 64 away from the through hole 42A, it is possible to prevent the heat dissipation material 65 from entering the inside of the through hole 42A without reducing the amount of heat dissipation material 65 applied. However, in this case, the size of the power board 52, and therefore the motor device 30, may increase by the amount that the heat dissipation material 65 is positioned away from the through hole 42A.

[0061] (4) When assembling the motor device 30, the heat dissipation material 65 is prevented from entering the through-hole 42A. This prevents the heat dissipation material 65 that has entered the through-hole 42A from falling off due to vibration or the like. The fallen heat dissipation material 65 will not enter the bearing 42C. This prevents the generation of abnormal noise caused by the heat dissipation material 65 entering the bearing 42C. This also ensures the product life of the bearing 42C. This improves the reliability of the motor device 40.

[0062] (5) The second surface 40B2 is disposed outside the heat dissipation path DP of the heat generated by the heat-generating portion. Because the second surface 40B2 does not interfere with the heat dissipation path DP, the heat dissipation performance of the motor device 30 can be ensured.

[0063] (6) The inclination angle θ1 of the second surface 40B2 relative to the first surface 40B1 is smaller than the diffusion angle θ2 of the heat diffusing from the heat-generating element 64. Therefore, it is easy to provide the second surface 40B2 on the end wall of the motor 40 without interfering with the heat dissipation path DP. The end wall is the lid 42.

[0064] (7) The inclination angle θ1 is set so that the first distance D1 is greater than the second distance D2. The first distance D1 is the difference between the third distance and the fourth distance. The third distance is the distance between the power board 52 and the first surface 40B1 when the heat dissipation material 65 applied to the first surface 40B1 is crushed by the power board 52 and begins to protrude from the first surface 40B1 onto the second surface 40B2 during attachment of the power board 52 to the motor 40. The fourth distance is the distance between the power board 52 and the first surface 40B1 when attachment of the power board 52 to the motor 40 is complete. The second distance D2 is the difference between the filling depth of the heat dissipation material 65 protruding from the first surface 40B1 onto the second surface 40B2 and the thickness of the heat dissipation material 65 sandwiched between the power board 52 and the first surface 40B1.

[0065] With this configuration, the heat dissipation material 65 that protrudes from the first surface 40B1 onto the second surface 40B2 does not enter a portion of the motor device 30 where it is undesirable for the heat dissipation material 65 to enter, and is held between the second surface 40B2 and the power board 52. An example of a portion of the motor device 30 where it is undesirable for the heat dissipation material 65 to enter is the through-hole 42A.

[0066] (8) The second surface 40B2 is provided at the open end of the through hole 42A in the end wall and extends in the circumferential direction of the through hole 42A. Therefore, even if a portion of the heat dissipation material 65 flows from the first surface 40B1 toward the through hole 42A, the heat dissipation material 65 can be appropriately prevented from entering the inside of the through hole 42A.

[0067] (9) The heat dissipation material 65 is a hardening type heat dissipation grease or a high-viscosity heat dissipation grease. This configuration prevents the heat dissipation material 65 from flowing along the second surface 40B2, which is an inclined surface. This appropriately prevents the heat dissipation material 65 from entering portions of the motor device 30 where it is not desirable, such as the inside of the through-hole 42A.

[0068] Other Embodiments This embodiment may be modified as follows. As shown in FIG. 7 , the heat generating element 64 may be provided on the surface of the power board 52 opposite the heat dissipation portion 40B. Heat generated by the heat generating element 64 is transferred to the lid 42, which serves as a heat sink, via the power board 52 and the heat dissipation material 65. The heat dissipation material 65 is crushed by the power board 52 and protrudes from the first surface 40B1 to the second surface 40B2. The heat dissipation material 65 protruding onto the second surface 40B2 does not enter the through-hole 42A and is held between the second surface 40B2 and the power board 52. The heat generating portion of the power board 52 includes a portion of the power board 52 corresponding to the heat generating element 64.

[0069] The heating element 64 may include, for example, a power supply circuit and a pre-driver. The power supply circuit converts, for example, a voltage supplied from an external power supply into a voltage suitable for the operation of the electric circuit provided on the control board 51. The pre-driver drives, for example, an inverter circuit based on a command from the control board 51.

[0070] The second surface 40B2, which is an inclined surface, may be provided in a portion of the lid 42 other than the periphery of the through-hole 42A. For example, if the heat-generating element 64 is disposed near the motor terminal, the second surface 40B2 is formed in a groove shape around the motor terminal. The second surface 40B2 is disposed on a specific side of the heat-generating element 64. The specific side is the side where the flow of the heat dissipation material 65 needs to be suppressed, more specifically, the side where the motor terminal is located relative to the heat-generating element 64. The motor terminal protrudes from the surface of the heat dissipation portion 40B facing the power board 52 and is connected to the power board 52 by soldering.

[0071] The control board 51 and the power board 52 may be provided as a single board. In this case, the lid 42 may be configured without the board accommodating portion 40A. That is, the end wall surface of the board accommodating portion 40A may be flush with the end wall surface of the heat dissipation portion 40B. The end wall surface of the heat dissipation portion 40B that includes the area corresponding to the board accommodating portion 40A is the first surface 40B1. The second surface 40B2 may be provided around the entire periphery of the through-hole 42A.

[0072] The motor 40 may have one winding group. The control system and power supply system of the motor 40 may each be one system. In this case, the connector assembly 53 may be configured without the first power connector 53A and the first signal connector 53C, or without the second power connector 53B and the second signal connector 53D.

[0073] The motor device 30 may be a drive source for an electric power steering device. In this case, the motor 40 functions as an assist motor. The assist motor generates an assist force applied to the steering wheel.

[0074] Motor device 30 may be a drive source for a steer-by-wire steering device. In this case, motor 40 functions as a reaction motor or a steering motor. The reaction motor generates a steering reaction force applied to the steering wheel. The steering motor generates a steering force for steering the steered wheels of the vehicle.

[0075] The motor device 30 can be used as a drive source for various mechanical devices, in addition to a steering device for a vehicle. The mechanical device may be, for example, a machine tool driven by the motor 40.

Claims

1. A motor device comprising a motor, a substrate, and a heat dissipation material, wherein the motor has a metal motor case and a metal end wall attached to an axial end of the motor case, the substrate has a heat generating portion and is arranged opposite the end wall in the axial direction of the motor, the heat dissipation material is fluid at least when applied and is interposed between the heat generating portion and the end wall, the end wall has: a first surface in contact with the heat dissipation material; and a second surface adjacent to the first surface and arranged on a specific side of the first surface, the specific side being a side on which the flow of the heat dissipation material needs to be suppressed, and the second surface is inclined with respect to the first surface so as to move away from the substrate as it moves from the first surface to the specific side.

2. The motor device according to claim 1, wherein the substrate has a heat generating element that generates heat when energized, and the heat generating portion is the heat generating element or a portion of the substrate corresponding to the heat generating element.

3. A motor device according to claim 1 or claim 2, wherein the second surface is disposed outside a heat dissipation path for heat generated by the heat generating portion.

4. A motor device according to claim 1 or 2, wherein the inclination angle of said second surface relative to said first surface is smaller than the diffusion angle of heat diffusing from said heat generating portion.

5. The motor device described in claim 4, wherein the inclination angle is set so that the first distance is greater than the second distance, the first distance is the difference between the third distance and the fourth distance, the third distance is the distance between the substrate and the first surface when the heat dissipation material applied to the first surface is crushed by the substrate and begins to protrude from the first surface onto the second surface when the substrate is attached to the motor, the fourth distance is the distance between the substrate and the first surface when attachment of the substrate to the motor is complete, and the second distance is the difference between the filling depth of the heat dissipation material protruding from the first surface onto the second surface and the thickness of the heat dissipation material sandwiched between the substrate and the first surface.

6. A motor device as described in claim 1 or claim 2, wherein the motor has an output shaft and a bearing that rotatably supports the output shaft, the end wall has a through hole through which the output shaft passes without contact and a bearing holding portion that holds the bearing, and the specific side is the side on which the through hole is located relative to the first surface.

7. The motor device according to claim 6, wherein the second surface is provided on the end wall at the open end of the through hole and extends in the circumferential direction of the through hole.

8. A motor device according to claim 1 or 2, wherein the heat dissipation material is a hardening type heat dissipation grease or a high viscosity heat dissipation grease.

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