Motor unit

Abstract

To provide a motor unit capable of suitably securing a normal function even when a foreign matter such as moisture enters a housing part from the outside.SOLUTION: The motor unit 20 has a motor case 11 and a circuit board 61. The motor case 11 has a housing 21, a cover 63 for closing an opening so as to have a housing part between the housing 21 and the cover, and a bearing holder for dividing the housing part. The circuit board 61 is accommodated on the cover 63 side of the divided accommodating portion. The circuit substrate 61 has a first system area 61AA and a second system area 61BB. The first system area 61AA is included in the coating area C of the printed circuit board 61, and the second system area 61BB includes a non-coating area of the printed circuit board 61. The circuit board 61 is accommodated in the motor case 11 such that the non-coating region is located on the lower side of the circuit board 61 in the gravity direction in a state where the motor case 11 is attached to the steering mechanism.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] For example, Patent Document 1 describes a motor device in which an electric motor and a control device are housed integrally in a motor case. The motor device has a detector that detects moisture that has entered the motor case from the outside. The control device is configured to output an alarm signal when the detector detects that water has entered the motor case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-099111 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, motor units have been introduced that have two power supply systems for controlling the electric motor. In such motor units, if moisture or other foreign matter gets inside the motor case from the outside, the two power supply systems for the motor may not function properly. [Means for solving the problem]

[0005] A motor unit that can solve the above problem is a motor unit in which a motor and a circuit board are integrally housed in a motor case, and the motor case is attached to a predetermined mounting target. The motor has a stator including windings, a rotor configured to rotate when power is supplied to the windings, and an output shaft that rotates integrally with the rotor. The circuit board has a first system area in which circuits related to a first power supply system that controls the drive of the motor are mounted, and a second system area in which circuits related to a second power supply system that controls the drive of the motor are mounted. The motor case has a housing having an opening at one axial end of the output shaft and an end wall at the other axial end, a cover that closes the opening so as to form an accommodation section between the housing and the cover, and a partition that divides the accommodation section in the axial direction. The motor is housed on the end wall side of the accommodation section, and the circuit board is housed on the cover side of the accommodation section. The circuit board has the first system area and the second system area, and is divided into a coated area where the circuit board is coated and an uncoated area where the circuit board is not coated, and the first system area is included in the coated area and the second system area is included in the uncoated area. The circuit board is housed in the motor case such that, when the motor case is attached to the attachment target, the uncoated area is on the lower side of the circuit board in the direction of gravity.

[0006] With the motor unit described above, even if moisture or other foreign matter enters the housing from outside the motor unit, it is possible to prevent both the first and second power supply systems from being adversely affected by malfunctioning simultaneously, thereby ensuring the normal function of the motor unit.

[0007] In the motor unit, the circuit board has a shape that has a plurality of corners when viewed in a thickness direction of the circuit board, and the non-coated area is provided at a corner of the plurality of corners that is located on a lower side of the circuit board in a direction of gravity when the motor case is attached to the attachment target.

[0008] According to the motor unit described above, even when the circuit board is housed so that one of the corners faces downward in the direction of gravity, the motor unit can preferably function normally.

[0009] In the motor unit, the circuit board has a shape that has a plurality of sides when viewed in a thickness direction of the circuit board, and the non-coated area is provided on one of the sides that is located on a lower side of the circuit board in a direction of gravity when the motor case is attached to the attachment target.

[0010] According to the motor unit described above, even when the circuit board is housed so that one of the sides faces downward in the direction of gravity, the motor unit can be properly functioned.

[0011] In the motor unit, the second system region is configured so as not to include the coating region. With the above motor unit, while the circuits in the second system area are more susceptible to adverse effects than the circuits in the first system area, it is possible to more proactively switch to motor drive control using the first power supply system compared to when the second system area includes a coating area.

[0012] In the above motor unit, the second system region is configured to include the non-coated region and also the coated region. According to the above motor unit, although the circuits in the second system area are more susceptible to adverse effects than the circuits in the first system area, the motor drive control by the first power supply system and the second power supply system can be continued for a longer period of time than when the second system area does not include a coating area.

[0013] In the motor unit, the coating region is provided on both surfaces of the circuit board in the thickness direction. According to the above motor unit, the normal function of the motor unit can be preferably ensured.

[0014] In the motor unit described above, the material of the coating agent used for the coating includes a waterproof material. According to the motor unit described above, even if moisture enters the housing from outside the motor unit, the normal function of the motor unit can be preferably ensured.

[0015] In the motor unit, the circuit board is provided with a rotation angle sensor mounted on one of the two surfaces of the circuit board in the thickness direction, the rotation angle sensor being located on a surface facing the cover-side end of the output shaft. The circuit board includes, in addition to the first system area and the second system area, a sensor area where the rotation angle sensor is mounted, and the sensor area is included in the coating area.

[0016] According to the motor unit described above, even if moisture penetrates into the housing from outside the motor unit, the effect on the rotation angle detection of the rotation angle sensor can be reduced while improving the layout flexibility of the design of the entire circuit board. [Effects of the Invention]

[0017] According to the motor unit of the present invention, the normal function of the motor unit can be preferably ensured. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram showing a configuration of a steering device according to a first embodiment. [Figure 2] FIG. 2 is an end view of the steering device taken along line II-II in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the motor unit taken along line III-III in FIG. 2. [Figure 4] 1 is a plan view showing a state in which a cover of a motor unit according to a first embodiment is removed. [Figure 5] 2 is a diagram showing a motor unit attached to a steering mechanism in the first embodiment. FIG. [Figure 6] FIG. 10 is a diagram showing the motor unit attached to the steering mechanism in the second embodiment. [Figure 7] FIG. 11 is a diagram showing a motor unit attached to a steering mechanism in a third embodiment. [Figure 8] FIG. 10 is a plan view showing a state in which a cover of the motor unit according to the fourth embodiment is removed. [Figure 9] FIG. 11 is a plan view showing a state in which a cover of the motor unit according to the fifth embodiment is removed. DETAILED DESCRIPTION OF THE INVENTION

[0019] First Embodiment A first embodiment of the present invention will be described below. In this specification, the term "cylindrical" may refer to a cylindrical shape in which the cross section of the cylinder is circular, elliptical, or polygonal with sharp or rounded corners. In this specification, "circular" may refer not only to a perfect circle, but also to an ellipse or a substantially circular polygon with sharp or rounded corners. In this specification, a "corner" or "corner portion" may be a curved surface formed by chamfering or the like. In this specification, a "side" or "side portion" may be a curved line in which a notch or the like is formed in the middle of a straight line.

[0020] <Configuration of the steering device> As shown in Fig. 1, the steering device 1 includes a steering mechanism 200 and an actuator 4. The steering mechanism 200 steers steered wheels 300 based on the operation of a steering wheel 100 by a driver. The actuator 4 has a motor unit 20 that generates an assist force to the steering mechanism 200 to assist the steering operation.

[0021] The steering mechanism 200 includes a steering shaft 111, a rack shaft 112, and a rack housing 113. The steering shaft 111 is connected to the steering wheel 100. The rack shaft 112 moves back and forth in the axial direction in response to the rotation of the steering shaft 111. The rack housing 113 is a housing through which the rack shaft 112 is inserted so as to be able to move back and forth.

[0022] The steering shaft 111 includes a column shaft 111a, an intermediate shaft 111b, and a pinion shaft 111c. The upper end of the column shaft 111a is connected to the steering wheel 100. The lower end of the column shaft 111a is connected to the upper end of the intermediate shaft 111b. The lower end of the intermediate shaft 111b is connected to the pinion shaft 111c.

[0023] The rack housing 113 accommodates the rack shaft 112 and the pinion shaft 111c. The rack shaft 112 and the pinion shaft 111c are arranged within the rack housing 113 at a predetermined cross angle. The rack and pinion mechanism 118 is configured by meshing rack teeth 116 formed on the rack shaft 112 with pinion teeth 117 formed on the pinion shaft 111c. Tie rods 119 are connected to both ends of the rack shaft 112. The ends of the tie rods 119 are connected to knuckles to which the steered wheels 300 are attached. The spaces between both ends of the rack housing 113 and the tie rods 119 are covered by rack boots 119a. The rack boots 119a are bellows-shaped, waterproof members that prevent foreign matter such as moisture from entering the interior of the rack housing 113. The rotational motion of the steering shaft 111 caused by the steering operation is converted into a reciprocating linear motion in the axial direction of the rack shaft 112 via the rack and pinion mechanism 118. This reciprocating linear motion in the axial direction is transmitted to the knuckle via the tie rod 119, thereby changing the steering angle of the steered wheels 300, i.e., the traveling direction of the vehicle.

[0024] The actuator 4 includes a motor unit 20, a belt transmission mechanism 222, and a ball screw mechanism 223. A motor pulley 41 is fixed to an end of the output shaft 12 of the motor unit 20 so as to be rotatable integrally with the output shaft 12. The belt transmission mechanism 222 transmits the rotation of the motor pulley 41 to the ball screw mechanism 223. The ball screw mechanism 223 converts the rotational motion transmitted via the belt transmission mechanism 222 into reciprocating motion of the rack shaft 112. The motor pulley 41, the belt transmission mechanism 222, and the ball screw mechanism 223 form a transmission mechanism 231. The actuator 4 applies an assist force to the steering mechanism 200 by converting the rotation of the motor pulley 41 into reciprocating linear motion of the rack shaft 112 using the transmission mechanism 231. The application of the assist force to the steering mechanism 200 assists the driver's steering operation. In other words, the assist method of the steering device 1 is a rack assist method that applies an assist force to the rack shaft 112. The actuator 4 in such a rack assist system is mounted, for example, in the engine compartment of the vehicle.

[0025] <About rack housing> The rack housing 113 includes a first rack housing 114 and a second rack housing 115. The first rack housing 114 and the second rack housing 115 are connected to each other in the axial direction of the rack shaft 112 of the rack housing 113. The second rack housing 115 is a portion on the rack and pinion mechanism 118 side and houses the rack and pinion mechanism 118. The first rack housing 114 is a portion on the opposite side of the rack and pinion mechanism 118.

[0026] The first rack housing 114 has a first cylindrical portion 114a and a first tubular portion 114b. The first cylindrical portion 114a and the first tubular portion 114b have a hollow cylindrical internal shape. The inner diameter of the first cylindrical portion 114b is larger than the inner diameter of the first cylindrical portion 114a. The first cylindrical portion 114a accommodates a portion of the rack shaft 112. The first tubular portion 114b accommodates a portion of the rack shaft 112 and a portion of the transmission mechanism 231. The second rack housing 115 has a second cylindrical portion 115a and a second tubular portion 115b. The second cylindrical portion 115a and the second tubular portion 115b have a hollow cylindrical internal shape. The inner diameter of the second tubular portion 115b is larger than the inner diameter of the second cylindrical portion 115a. The second cylindrical portion 115a accommodates a portion of the rack shaft 112. The second cylindrical portion 115b accommodates a part of the rack shaft 112 and a part of the transmission mechanism 231.

[0027] Of the rack housing 113, the first cylindrical portion 114a and the second cylindrical portion 115a that accommodate the rack shaft 112 form a rack shaft accommodating portion 131. Of the rack housing 113, the first cylindrical portion 114b and the second cylindrical portion 115b that accommodate the transmission mechanism 231 form a transmission mechanism accommodating portion 132. The transmission mechanism accommodating portion 132 accommodates a part of the rack shaft 112 together with the transmission mechanism 231.

[0028] 1 and 2, the transmission mechanism accommodating portion 132 includes a first accommodating portion 132a and a second accommodating portion 132b. When the transmission mechanism accommodating portion 132 is viewed from the axial direction of the rack shaft 112, the second accommodating portion 132b includes the first accommodating portion 132a and bulges out in the radial direction of the rack shaft 112 relative to the first accommodating portion 132a. A through-hole 133 is provided in the second accommodating portion 132b at a portion that bulges out in the radial direction of the rack shaft 112 relative to the first accommodating portion 132a, the through-hole 133 being a hole that passes through the second cylindrical portion 115b that forms the second accommodating portion 132b in the axial direction of the rack shaft 112.

[0029] The first accommodating portion 132a accommodates the ball screw mechanism 223 of the transmission mechanism accommodating portion 132. The second accommodating portion 132b accommodates the belt transmission mechanism 222 of the transmission mechanism accommodating portion 132, and also accommodates the motor pulley 41.

[0030] <About the motor unit> 3, the motor unit 20 includes a motor case 11, a motor 2, a circuit board 61, and a connector 62. The motor unit 20 has the motor 2 and the circuit board 61 housed in the motor case 11 as a single unit.

[0031] The motor case 11 includes a housing 21, a cover 63, and a bearing holder 22. Hereinafter, the direction along the axis of the output shaft 12 will be referred to as the axial direction of the motor 2 or simply as the axial direction.

[0032] The housing 21 is made of, for example, metal. The housing 21 has a first peripheral wall portion 23, an end wall portion 24, a flange portion 25, and a second peripheral wall portion 26. The first peripheral wall portion 23 has a hollow cylindrical shape extending in the axial direction. The end wall portion 24 closes the other end, which is the first axial end, of the first peripheral wall portion 23. The end wall portion 24 may be formed integrally with the first peripheral wall portion 23, or may be formed separably from the first peripheral wall portion 23. The flange portion 25 extends radially outward from a second axial end of the first peripheral wall portion 23 opposite the end wall portion 24, i.e., a first opening 23a, which is one end. The flange portion 25 has a polygonal shape when viewed in the axial direction. The polygonal shape is, for example, a hexagon formed by combining a rectangle and a trapezoid, and is an integrated shape formed by sharing one short side of the rectangle with the base of the trapezoid. The second peripheral wall portion 26 extends in the axial direction from the outer peripheral edge of the flange portion 25 so as to move away from the end wall portion 24. In other words, when viewed in the axial direction, the second peripheral wall portion 26 has a polygonal shape corresponding to the flange portion 25. The axial tip of the second peripheral wall portion 26 is a second opening 26a of the housing 21.

[0033] The end wall portion 24 has a first insertion hole 27. The first insertion hole 27 penetrates a central portion of the end wall portion 24 in the axial direction. The first insertion hole 27 has a circular shape when viewed in the axial direction. A concave first retaining portion 28 is formed on the periphery of the first insertion hole 27, inside the end wall portion 24. The first retaining portion 28 retains a first bearing 29. The first bearing 29 is, for example, a sealed bearing in which a seal plate made of synthetic rubber or the like is fixed to an outer ring. The first bearing 29 rotatably supports the output shaft 12 and prevents foreign matter, such as moisture, from entering through the first insertion hole 27.

[0034] The flange portion 25 has a window portion 31. The window portion 31 is a through-hole that passes through the center portion of the flange portion 25 in the axial direction. The window portion 31 has, for example, a rectangular shape. The cover 63 has a main body 91 and a cover peripheral wall 92. The cover 63 is made of, for example, resin. When viewed in the axial direction, the main body 91 has a polygonal shape corresponding to the flange 25. The cover peripheral wall 92 extends from the outer periphery of the main body 91 along the axial direction toward the housing 21. The cover 63 is configured to prevent liquid from passing through the cover 63 from the outside. The cover 63 is fitted to the second peripheral wall 26 via the tip of the cover peripheral wall 92 so as to close the second opening 26a of the housing 21. As a result, the space surrounded by the housing 21 and the cover 63 forms the storage section R. The cover peripheral wall 92 and the second peripheral wall 26 are fitted together with a seal via an outer peripheral seal 93. The outer peripheral seal 93 is provided around the entire periphery of the cover peripheral wall 92 and the second peripheral wall 26. As a result, the space between the housing 21 and the cover 63 is sealed.

[0035] The bearing holder 22 has a cylindrical shape. The bearing holder 22 is made of, for example, the same metal as the housing 21. The bearing holder 22 is press-fitted and fixed into the first opening 23a of the first peripheral wall portion 23. In other words, the bearing holder 22 closes the first opening 23a. The bearing holder 22 divides the accommodation portion R into an accommodation portion R1 on the housing 21 side, particularly on the end wall portion 24 side, and an accommodation portion R2 on the cover 63 side. The bearing holder 22 has a second insertion hole 34a and a third insertion hole 34b. The second insertion hole 34a penetrates the center of the bearing holder 22 in the axial direction. The second insertion hole 34a has a circular shape when viewed in the axial direction. The third insertion hole 34b penetrates the outer peripheral edge side of the bearing holder 22 in the axial direction. The third insertion hole 34b has a rectangular shape when viewed in the axial direction. Two third insertion holes 34b are provided on the outer peripheral edge side of the bearing holder 22, at equal distances from the second insertion hole 34a. A concave second retaining portion 35 is formed on the periphery of the second insertion hole 34a on the housing portion R1 side of the bearing holder 22. The second retaining portion 35 retains a second bearing 36. The second bearing 36 is, for example, a sealed bearing with a seal plate made of synthetic rubber or the like fixed to its outer ring. The second bearing 36 rotatably supports the output shaft 12 and prevents foreign matter such as moisture from entering through the second insertion hole 34a. In this embodiment, the bearing holder 22 is an example of a dividing portion.

[0036] The motor 2 includes an output shaft 12, a stator 13, a rotor 14, and a bus bar module 15. The motor 2 is housed in the housing portion R1. The output shaft 12 has a first end 12a and a second end 12b opposite to the first end 12a. The output shaft 12 is rotatably supported relative to the housing 21. The first end 12a of the output shaft 12 is supported by a first bearing 29. The second end 12b of the output shaft 12 is supported by a second bearing 36. The first end 12a protrudes to the outside of the housing 21 through a first insertion hole 27. A motor pulley 41 is fixed to the first end 12a so as to be rotatable integrally with the output shaft 12. A sensor magnet 42 is fixed to the second end 12b so as to be rotatable integrally with the output shaft 12. The sensor magnet 42 is housed in the second insertion hole 34a.

[0037] The stator 13 includes a stator core 51, an insulator 52, and a plurality of windings 53. The stator core 51 is fixed to the inner circumferential surface of the first circumferential wall portion 23. Each winding 53 is wound around a tooth 51a of the stator core 51 via the insulator 52. The plurality of windings 53 include a first winding group 53A and a second winding group 53B. Each of the first winding group 53A and the second winding group 53B includes three-phase windings (coils) of U, V, and W. Power is supplied to the first winding group 53A and the second winding group 53B via a circuit board 61 and a connector 62. Hereinafter, the power supply system for supplying power to the first winding group 53A will be referred to as the first power supply system, and the power supply system for supplying power to the second winding group 53B will be referred to as the second power supply system.

[0038] The rotor 14 has a rotor core 54 and a motor magnet 55. The rotor 14 is made of, for example, metal. The output shaft 12 is fixed to the center of the rotor core 54 so as to rotate integrally with the rotor core 54. The motor magnet 55 is fixed to the outer circumferential surface of the rotor core 54. Note that the motor magnet 55 may be embedded inside the rotor core 54.

[0039] The busbar module 15 is disposed between the bearing holder 22 and the stator 13. The busbar module 15 includes a busbar holder 56 and a plurality of busbars 57. The busbar holder 56 has a cylindrical shape. The busbar holder 56 is made of, for example, resin. The plurality of busbars 57 are held by the busbar holder 56. The plurality of busbars 57 include a first busbar 57A constituting a first power supply system and a second busbar 57B constituting a second power supply system. The first busbar 57A is connected to the windings 53 corresponding to the first winding group 53A. Each second busbar 57B is connected to the windings 53 corresponding to the second winding group 53B. The plurality of busbars 57 are inserted into the third insertion holes 34b of the bearing holder 22 and extend to the circuit board 61. The gaps between the bus bars 57 and the third insertion holes 34b are closed by bus bar caps 57a. The bus bar caps 57a have a rectangular shape corresponding to the third insertion holes 34b. The bus bar caps 57a are made of, for example, resin.

[0040] Three-phase AC power is supplied to the first winding group 53A via the first bus bar 57A. Three-phase AC power is supplied to the second winding group 53B via the second bus bar 57B. This generates a rotating magnetic field in the stator 13, causing the rotor 14 to rotate integrally with the output shaft 12. The first winding group 53A and the first bus bar 57A constitute a first power supply system. The second winding group 53B and the second bus bar 57B constitute a second power supply system. The rotor 14 rotates when power is supplied to at least one of the first winding group 53A and the second winding group 53B.

[0041] As shown in FIGS. 3 and 4, the circuit board 61 has a polygonal shape corresponding to the second peripheral wall portion 26 and the main body portion 91 of the cover 63 when viewed in the axial direction. The circuit board 61 is made of, for example, resin. As shown in FIG. 4, the circuit board 61 is formed to be slightly smaller than the outer periphery of the flange portion 25 when viewed in the axial direction. The polygonal shape of the circuit board 61 is, for example, a hexagon formed by six corners 500 and six sides 600 connecting adjacent corners 500. The circuit board 61 is accommodated in the accommodation portion R2 so that the thickness direction of the circuit board 61 coincides with the axial direction of the motor 2. The circuit board 61 is fixed to the motor case 11 with a plurality of screws 65.

[0042] The first surface 66 and the second surface 67, which are both surfaces of the circuit board 61, are flat surfaces perpendicular to the axial direction. The first surface 66 is the surface on the cover 63 side and faces the inner surface of the cover 63 in the axial direction. The second surface 67 is the surface on the housing 21 side and faces the flange portion 25, the bearing holder 22, and the connector 62 in the axial direction.

[0043] A plurality of electronic components are mounted on each of a first surface 66 and a second surface 67 of the circuit board 61. The circuit board 61 has electronic components mounted on the first surface 66 side, electronic components mounted on the second surface 67 side, and a plurality of conductor wirings, through holes, and vias for electrically connecting these components to each other. In this way, an electronic circuit is formed on the circuit board 61.

[0044] The connector 62 has a connector body 81 and connection terminals 82. The connector body 81 is fixed to the flange portion 25 via the window portion 31. When viewed in the axial direction, the connector body 81 has a rectangular shape that is larger than the window portion 31 of the housing 21. The connector body 81 is made of, for example, resin. The connector body 81 has a connection port 83. The connection port 83 houses the connection terminal 82. The connection port 83 extends from the window portion 31 in the axial direction, away from the cover 63. The gap between the inner peripheral edge of the window portion 31 and the connector body 81 is sealed by a connector sealant 84. The connector sealant 84 is provided around the entire periphery of the window portion 31. This seals the gap between the window portion 31 and the connector body 81.

[0045] <Motor unit installation> As shown in FIGS. 1 and 2, the motor unit 20 is attached to the steering mechanism 200 so that the output shaft 12 and the rack shaft 112 are parallel to each other. More specifically, the motor unit 20 is attached to the rack housing 113 with the motor pulley 41 housed in the second housing portion 132b via the through-hole 133. The motor unit 20 is fixed to the second housing portion 132b of the rack housing 113, i.e., the second cylindrical portion 115b, via the housing 21 of the motor case 11. For example, the motor unit 20 is fastened to the rack housing 113 with fastening members such as bolts. For example, the protruding direction of the second housing portion 132b is downward in the direction of gravity. In this case, the through-hole 133 of the second housing portion 132b is disposed downward in the direction of gravity relative to the first housing portion 132a. The output shaft 12 is disposed downward in the direction of gravity relative to the rack shaft 112. Therefore, the motor unit 20 is disposed lower in the direction of gravity than the ball screw mechanism 223 and the rack shaft 112. In this embodiment, the steering mechanism 200 including the rack housing 113, i.e., the steering device 1, is an example of an object to be attached. A vehicle on which the steering device 1 is mounted is also an example of an object to be attached.

[0046] As shown in FIG. 2, when the motor unit 20 is attached to the rack housing 113, the motor unit 20 has an outer contour that is hexagonal and one of the corners is positioned at the lowest position in the direction of gravity. The outer contour of the motor unit 20 when viewed from the axial direction is the shape of the cover 63 and the second peripheral wall portion 26 of the housing 21. In this case, the circuit board 61 accommodated in the accommodation portion R2 inside the cover 63 has one corner 500a of the hexagonal shape positioned at the lowest position in the direction of gravity. This can be rephrased as follows: When the center of gravity of the circuit board 61 is defined as center of gravity G, the corner 500a of the circuit board 61 is positioned below the center of gravity G in the direction of gravity. Furthermore, when the circuit board 61 is divided into an upper circuit board portion and a lower circuit board portion in a virtual horizontal plane passing through the center of gravity G, the corner 500a of the circuit board 61 is positioned at the lower side of the circuit board. In this embodiment, the mounting state of the motor unit 20 is referred to as a lower corner mounting, and the corner 500a that is positioned at the lowest side in the direction of gravity in the lower corner mounting is referred to as a lower corner.

[0047] <Circuit board layout> As shown in FIG. 4, a first surface 66 of the circuit board 61 is divided into a first region 61A (upper side in FIG. 4), a second region 61B (lower side in FIG. 4), and a sensor region 61C. The first region 61A and the second region 61B are defined by a first imaginary line V1 that divides the first surface 66 by a straight line. The sensor region 61C is defined by a second imaginary line V2 that divides the first surface 66 by a curved line. The second surface 67 of the circuit board 61 is defined into the first region 61A, the second region 61B, and the sensor region 61C in correspondence with the first surface 66. That is, on the first surface 66 and the second surface 67, the first region 61A, the second region 61B, and the sensor region 61C overlap each other in the plate thickness direction.

[0048] More specifically, when viewed in the axial direction, the first imaginary line V1 extends along the long side of the circuit board 61 and also extends so as to equally divide the short side of the circuit board 61. When viewed in the axial direction, the second imaginary line V2 is a line that defines a circular range that straddles the first imaginary line V1. The first imaginary line V1 and the second imaginary line V2 intersect such that the first imaginary line V1 forms one of the diameters of the circle defined by the second imaginary line V2.

[0049] The first region 61A includes a first power circuit region 701A and a first control circuit region 702A. The first power circuit region 701A is equipped with a first power circuit 71A for supplying power to the first winding group 53A. The first control circuit region 702A is equipped with a first control circuit 72A for outputting a control signal for controlling the first power circuit 71A. The second region 61B includes a second power circuit region 701B and a second control circuit region 702B. The second power circuit region 701B is equipped with a second power circuit 71B for supplying power to the second winding group 53B. The second control circuit region 702B is equipped with a second control circuit 72B for outputting a control signal for controlling the second power circuit 71B. The region of the first region 61A where the first power circuit 71A and the first control circuit 72A are equipped constitutes a first system region 61AA. Within the second area 61B, the area where the second power circuit 71B and the second control circuit 72B are mounted constitutes a second system area 61BB. The first power circuit 71A and the first control circuit 72A constitute a first power supply system. The second power circuit 71B and the second control circuit 72B constitute a second power supply system.

[0050] The first power circuit 71A is a circuit including a first inverter, a first smoothing capacitor 77A, and conductive wiring connecting these. The first inverter converts DC power supplied from a DC power source into three-phase AC power. The first inverter includes multiple switching elements 73A and shunt resistors for current detection. For example, the switching elements 73A and the shunt resistors are mounted on the second surface 67. The first connection end 58A is formed of three through holes. A first bus bar 57A connected to the first winding group 53A is inserted through the first connection end 58A. The first smoothing capacitor 77A smoothes the power supplied to the first power circuit 71A. The first smoothing capacitor 77A protrudes more from the circuit board 61 than other electronic components, i.e., is taller. For example, the first smoothing capacitor 77A is mounted on the first surface 66.

[0051] The first control circuit 72A is a circuit including, for example, a first microcomputer 74A, a first ASIC 78A, and conductive wiring connecting them. The first microcomputer 74A outputs control signals for executing control over the first power circuit 71A, i.e., the first power supply system, according to a program stored in memory. For example, the first microcomputer 74A is mounted on the first surface 66. The first ASIC 78A is an integrated IC configured by packaging a logic circuit that combines electronic circuits, flip-flops, etc. The first ASIC 78A includes a power supply circuit that adjusts the voltage supplied to the first microcomputer 74A. For example, the first ASIC 78A is mounted on the first surface 66.

[0052] The second power circuit 71B is a circuit including a second inverter, a second smoothing capacitor 77B, and conductor wiring connecting these. The second inverter converts DC power supplied from a DC power source into three-phase AC power. The second inverter includes multiple switching elements 73B and shunt resistors for current detection. For example, the switching elements 73B and the shunt resistors are mounted on the second surface 67. The second connection end 58B is formed of three through holes. A second bus bar 57B connected to the second winding group 53B passes through the second connection end 58B. The second smoothing capacitor 77B smoothes the power supplied to the second power circuit 71B. The second smoothing capacitor 77B protrudes more from the circuit board 61 than other electronic components, i.e., is a tall electronic component. For example, the second smoothing capacitor 77B is mounted on the first surface 66.

[0053] The second control circuit 72B is a circuit including, for example, a second microcomputer 74B, a second ASIC 78B, and conductive wiring connecting them. The second microcomputer 74B outputs control signals for executing control of the second power circuit 71B, i.e., the second power supply system, according to a program stored in memory. For example, the second microcomputer 74B is mounted on the first surface 66. The second ASIC 78B is an integrated IC configured by packaging a logic circuit that combines electronic circuits, flip-flops, etc. The second ASIC 78B includes a power supply circuit that adjusts the voltage supplied to the second microcomputer 74B. For example, the second ASIC 78B is mounted on the first surface 66.

[0054] For example, the first microcomputer 74A and the second microcomputer 74B are configured to be able to send and receive information by inter-microcomputer communication (inter-microcomputer communication) via serial communication, etc. Through inter-microcomputer communication, the first microcomputer 74A and the second microcomputer 74B can grasp each other's status, including the status of the power supply system.

[0055] The sensor region 61C is equipped with a first sensor 75A and a second sensor 75B, which are rotation angle sensors for detecting the rotation angle of the motor 2. The first sensor 75A and the second sensor 75B form a single IC package 76. The IC package 76 is disposed so as to face a sensor magnet 42 fixed to the output shaft 12 in the axial direction. For example, the IC package 76 is mounted at a corresponding position on a second surface 67, which is an opposing surface facing the sensor magnet 42 in the axial direction. The first sensor 75A and the second sensor 75B are magnetic sensors such as MR sensors. Each of the first sensor 75A and the second sensor 75B generates an electric signal corresponding to the direction of the magnetic field applied by the sensor magnet 42, i.e., the rotation angle of the output shaft 12. The first sensor 75A outputs the generated electric signal to the first control circuit 72A. The second sensor 75B outputs the generated electric signal to the second control circuit 72B. The first control circuit 72A and the second control circuit 72B generate control signals that indicate the rotation angle of the output shaft 12 based on these electrical signals.

[0056] <Coating for circuit boards> As shown in FIGS. 3 and 4 , the first surface 66 and the second surface 67 of the circuit board 61 include a coating area C that has been coated with a coating agent. For example, the coating agent is primarily composed of a waterproof material such as silicone. The areas of the first surface 66 and the second surface 67 other than the coating area C are uncoated areas that have not been coated. For example, the coating can be achieved by potting or applying the coating agent from the first surface 66 and the second surface 67 of the circuit board 61 toward the coating area C. Alternatively, the coating can be achieved by forming a peripheral wall on the circuit board 61 so as to surround the portion that will form the coating area C with a rubber member, and then injecting the coating agent into the peripheral wall.

[0057] More specifically, the first system area 61AA and the sensor area 61C are included in the coating area C. That is, the electronic components mounted in the first system area 61AA and the sensor area 61C are coated with a coating agent. On the other hand, the second system area 61BB includes a non-coating area that has not been subjected to a coating process. That is, the electronic components mounted in the second system area 61BB are not coated with a coating agent, i.e., are exposed.

[0058] <Motor drive control by the first and second power supply systems> For example, the motor unit 20 employs a redundant control system for controlling the drive of the motor 2, switching between dual-system drive using both the first and second power supply systems, and single-system drive using either the first or second power supply system. When employing such a system, the first microcomputer 74A and the second microcomputer 74B monitor each other's status, i.e., the status of the first and second power supply systems, via inter-microcomputer communication. The statuses of the first and second power supply systems include normal and abnormal. Normality is defined in terms of whether power can be supplied to the motor 2 normally. In other words, abnormality is defined in terms of whether power cannot be supplied to the motor 2 normally. For example, inability to supply power to the motor 2 normally includes abnormalities in electronic components or conductor wiring, and abnormalities in inter-microcomputer communication. The first microcomputer 74A and the second microcomputer 74B may determine that there is an abnormality in the corresponding power supply system, or the first microcomputer 74A and the second microcomputer 74B may determine that there is an abnormality in another power supply system.

[0059] The first microcomputer 74A and the second microcomputer 74B switch between dual-system drive and single-system drive depending on the status of the first and second power supply systems. Single-system drive includes first single-system drive, which uses one of the first power supply system, and second single-system drive, which uses one of the second power supply system. The first microcomputer 74A and the second microcomputer 74B switch to dual-system drive when both the first and second power supply systems are normal. When either the first or second power supply system becomes abnormal, the first microcomputer 74A and the second microcomputer 74B switch to single-system drive using the normal power supply system. In other words, the first microcomputer 74A and the second microcomputer 74B can continue to control the drive of the motor 2 as long as neither the first nor the second power supply system is abnormal. On the other hand, if both the first power supply system and the second power supply system are abnormal, the first microcomputer 74A and the second microcomputer 74B are forced to stop the drive control of the motor 2 (stop both systems).

[0060] <Actions and Effects of the First Embodiment> For example, in the motor unit 20, moisture may enter the housing portion R2 from outside the motor unit 20. This may be caused by a combination of factors, such as damage to the rack boot 119a, deterioration in the sealing performance of the sealed bearings included in the first bearing 29 and the second bearing 36, or deterioration in the sealing performance of the bus bar cap 57a. Damage to the cover 63 may also be a cause.

[0061] For example, the dashed arrow L1 in FIG. 1 indicates a manner in which moisture infiltrates the housing portion R2 from outside the motor unit 20 in the case where damage to the rack boot 119a and deterioration of the sealing performance of the sealed bearings included in the first bearing 29 and the second bearing 36 occur in combination. More specifically, the rack boot 119a may be damaged as a result of the rack housing 113 receiving an external impact or the like. If the vehicle drives through a puddle or the like with the rack boot 119a damaged, the rack housing 113 may be submerged, i.e., the rack boot 119a may be submerged. In this case, moisture may infiltrate the rack housing 113 through the damaged portion of the rack boot 119a. When moisture infiltrates the rack housing 113, the infiltrating moisture is transferred by gravity downward in the direction of gravity to the rack shaft housing portion 131, the first housing portion 132a, and the second housing portion 132b, and eventually reaches the through-hole 133 through which the motor pulley 41 is inserted. Moisture that reaches the through-hole 133 accumulates near the through-hole 133, on the lower side in the direction of gravity, due to the influence of gravity. Moisture that accumulates near the through-hole 133 can infiltrate into the housing R1 from outside the motor unit 20 if the sealing performance of the sealed bearing included in the first bearing 29 deteriorates. Once moisture has infiltrated into the housing R1, the infiltrating moisture reaches the bus bar cap 57a or the second bearing 36. Moisture that has reached the bus bar cap 57a or the second bearing 36 can infiltrate into the housing R2 if the sealing performance of the sealed bearing included in the second bearing 36 or the sealing performance of the bus bar cap 57a deteriorates. The dashed arrow L2 in FIG. 1 indicates the manner in which moisture infiltrates into the housing R2 from outside the motor unit 20 when damage to the cover 63 is the cause.

[0062] When moisture enters the housing R2, it flows downward in the direction of gravity due to the effect of gravity. If the moisture flowing downward in the direction of gravity comes into contact with the circuit board 61, it may have adverse effects that lead to abnormalities in the power supply system, such as failure of electronic components or short circuit failure of conductor wiring.

[0063] In this embodiment, when the motor unit 20 is attached to the rack housing 113, the circuit board 61 is housed in the motor case 11 so that the non-coated area of ​​the circuit board 61 is on the lower side in the direction of gravity. More specifically, as shown in FIG. 5 , the first system area 61AA included in the coating area C is on the upper side in the direction of gravity, and the second system area 61BB including the non-coated area is housed in the motor case 11 so that the second system area 61BB including the non-coated area is on the lower side in the direction of gravity. This can be said in other words that, when the position of the center of gravity of the circuit board 61 is defined as center of gravity G, the second system area 61BB including the non-coated area is disposed on the circuit board 61 so that it is at least located below the center of gravity G. Furthermore, when the circuit board 61 is divided into an upper side and a lower side in a virtual horizontal plane passing through the center of gravity G, the second system area 61BB including the non-coated area is disposed on the circuit board 61 so that it is at least located on the lower side of the circuit board.

[0064] As a result, moisture that enters the housing R2 from outside the motor unit 20 flows out toward the second system area 61BB due to the influence of gravity. In particular, moisture that enters through the third insertion hole 34b corresponding to the first connection end 58A flows out toward the second system area 61BB via the first system area 61AA included in the coating area C. In FIG. 5, the path of such moisture is indicated by the dashed arrow L2, and the flowed-out moisture is illustrated as W. Here, below the housing R2 in the direction of gravity, there is a non-coated area included in the second system area 61BB. If the migrated moisture comes into contact with the non-coated area, the circuitry of the second system area 61BB is adversely affected. On the other hand, even if the circuitry of the first system area 61AA included in the coating area C comes into contact with moisture that moves downward toward the housing in the direction of gravity due to gravity, the moisture will come through the coating area C. Therefore, even if moisture enters the housing R2 from outside the motor unit 20, the circuit in the first system area 61AA is unlikely to be adversely affected, even if the circuit in the second system area 61BB is adversely affected. Therefore, even if moisture enters the housing R2 from outside the motor unit 20, it is possible to prevent both the first power supply system and the second power supply system from being adversely affected. Therefore, normal function of the motor unit 20 can be preferably ensured.

[0065] According to the present embodiment described above, the following effects can be further obtained. (1-1) In the motor unit 20 employing the redundant control system, foreign matter such as moisture can adversely affect both the circuits in the first system area 61AA and the second system area 61BB. This can cause an abnormality in both the first and second power supply systems, potentially resulting in a shutdown of both systems.

[0066] From the perspective of ensuring the normal function of the motor unit 20, it can be said that drive control of the motor 2 by single-system drive ensures the normal function of the motor unit 20 in that it allows the drive control of the motor 2 to continue continuously. Therefore, to ensure the normal function of the motor unit 20, single-system drive of the motor 2 is acceptable, but stopping of both systems of the motor 2 is not acceptable. Therefore, in a motor unit 20 that employs a redundant control system, it is required to proactively switch to single-system drive before an unintended stoppage of both systems occurs.

[0067] In contrast, the motor unit 20 of this embodiment can prevent both the first and second power supply systems from stopping, i.e., prevent both systems of the motor 2 from stopping. As a result, drive control of the motor 2 can be continued using the first power supply system, which is the normal system, i.e., drive control of the motor 2 can be continued using the first single-system drive. Therefore, in that drive control of the motor 2 can be continued continuously, normal function of the motor unit 20 can be suitably ensured.

[0068] (1-2) In the motor unit 20 of this embodiment, if moisture enters the housing portion R2 from outside the motor unit 20, the moisture flows out toward the corner 500a in the second system area 61BB due to the influence of gravity. Therefore, even if the motor unit 20 is attached to the lower side of the corner, the normal function of the motor unit 20 can be preferably ensured.

[0069] (1-3) Even after transitioning from dual-system drive to first single-system drive, in which the motor 2 is driven and controlled by the first power supply system, the first system area 61AA is included in the coating area C, so that the normal function of the first power supply system can be ensured. Therefore, the drive and control of the motor 2 can be continued for a long period of time by the first single-system drive, and therefore the normal function of the motor unit 20 can be ensured for an even longer period of time.

[0070] (1-4) When the second system area 61BB does not include the coating area C, the situation in which the circuit of the second system area 61BB is adversely affected by contact with moisture can be increased compared to when the second system area 61BB includes the coating area C. Therefore, while the circuit of the second system area 61BB is more susceptible to adverse effects than the circuit of the first system area 61AA, the second system area 61BB can be switched to the first single-system drive more aggressively compared to when the second system area 61BB includes the coating area C.

[0071] Furthermore, compared to when the second system area 61BB includes a coating area, the coating area of ​​the entire circuit board 61 is smaller, so the cost of coating can be reduced.

[0072] (1-5) In the motor unit 20, the mounting position on the circuit board 61 of the rotation angle sensor that detects the magnetic field is determined by the relationship between the IC package 76, which is the rotation angle sensor, and the output shaft 12. According to this embodiment, the sensor area 61C corresponding to the IC package 76 is the coated area C. Therefore, the sensor area 61C can be mounted on the circuit board 61 as the coated area C regardless of whether the circuits in the first system area 61AA and the second system area 61BB are coated or not. This makes it possible to improve the layout flexibility of the design of the entire circuit board 61 while suppressing the effect of moisture when detecting the rotation angle of the rotation angle sensor.

[0073] <Second embodiment> The second embodiment will be described below with reference to the drawings. This embodiment differs from the first embodiment in the state in which the motor unit 20 is attached to the steering mechanism 200. Therefore, the same components as those in the first embodiment are designated by the same reference numerals and their description will be omitted.

[0074] As shown in FIG. 6 , when the motor unit 20 is attached to the rack housing 113, the motor unit 20 has an outer contour viewed from the axial direction such that one long side of the multiple sides forming a hexagon is positioned at the lowest in the direction of gravity. The outer contour of the motor unit 20 viewed from the axial direction is the shape of the cover 63 and the second peripheral wall portion 26 of the housing 21. In this case, the circuit board 61 accommodated in the accommodation portion R2 inside the cover 63 has one long side 600a of the multiple sides 600 forming the hexagon positioned at the lowest in the direction of gravity. This can be rephrased as follows: when the position of the center of gravity of the circuit board 61 is defined as center of gravity G, the long side 600a of the circuit board 61 is positioned below the center of gravity G in the direction of gravity. Furthermore, when the circuit board 61 is divided into an upper side and a lower side in a virtual horizontal plane passing through the center of gravity G, the long side 600a of the circuit board 61 is positioned at the lower side of the circuit board. In this embodiment, the mounting state of the motor unit 20 is referred to as "long-side-down mounting," and the long side located at the bottom in the direction of gravity in this long-side-down mounting is referred to as the "lower long side." When the motor case 11 of the motor unit 20 is mounted to the steering mechanism 200, the circuit board 61 is housed in the motor case 11 so that the non-coated area of ​​the circuit board 61 faces downward in the direction of gravity. More specifically, as shown in FIG. 6 , the long side 600a on the second system area 61BB side is housed in the motor case 11 so that it faces downward in the direction of gravity. The long side 600a is one of multiple sides of the hexagonal circuit board 61. This can be rephrased as follows: When the center of gravity of the circuit board 61 is defined as center of gravity G, the second system area 61BB, including the non-coated area, is disposed on the circuit board 61 below center of gravity G in the direction of gravity. Furthermore, when the circuit board 61 is divided into an upper circuit board and a lower circuit board in a virtual horizontal plane passing through the center of gravity G, it can be said that the second system area 61BB including the non-coated area is positioned on the lower side of the circuit board.

[0075] <Effects of the second embodiment> According to the second embodiment described above, the effects of the first embodiment and the effects (1-1), (1-3) to (1-5) can be obtained, and further the effects described below can be obtained.

[0076] (2-1) In the motor unit 20 of this embodiment, if moisture enters the housing portion R2 from outside the motor unit 20, the moisture flows out toward the long side portion 600a in the second system region 61BB due to the influence of gravity. Therefore, even if the motor unit 20 is installed on the lower side of the long side portion, the normal function of the motor unit 20 can be preferably ensured.

[0077] <Third embodiment> The third embodiment will be described below with reference to the drawings. This embodiment differs from the first embodiment in the state in which the motor unit 20 is attached to the steering mechanism 200. Therefore, the same components as those in the first embodiment are designated by the same reference numerals and their description will be omitted.

[0078] As shown in FIG. 7 , when the motor unit 20 is attached to the rack housing 113, the motor unit 20 has an outer contour when viewed from the axial direction, with one short side of the multiple sides forming a hexagon being positioned at the lowest in the direction of gravity. The outer contour when viewed from the axial direction of the motor unit 20 is the shape of the cover 63 and the second peripheral wall portion 26 of the housing 21. In this case, the circuit board 61 accommodated in the accommodation portion R2 inside the cover 63 has one short side 600b of the sides 600 forming the hexagon being positioned at the lowest in the direction of gravity. This can be rephrased as follows: when the position of the center of gravity of the circuit board 61 is defined as center of gravity G, the short side 600b of the circuit board 61 is positioned below center of gravity G in the direction of gravity. Furthermore, when the circuit board 61 is divided into an upper side and a lower side in a virtual horizontal plane passing through center of gravity G, the short side 600b of the circuit board 61 is positioned at the lower side of the circuit board. In this embodiment, the mounting state of the motor unit 20 is referred to as short-side-down mounting, and the short side located at the bottom in the direction of gravity in the short-side-down mounting is referred to as the lower short side. When the motor case 11 of the motor unit 20 is mounted to the steering mechanism 200, the circuit board 61 is housed in the motor case 11 so that the uncoated area of ​​the circuit board 61 faces downward in the direction of gravity. More specifically, as shown in FIG. 7 , the circuit board 61 is housed in the motor case 11 so that the short side 600b, which straddles the first system area 61AA and the second system area 61BB, is the lower short side, which is the side that faces downward in the direction of gravity. The short side 600b is one of multiple sides of a rectangle that forms the hexagon of the circuit board 61. In this case, not only the second system area 61BB side but also the first system area 61AA side faces downward in the direction of gravity. This can be rephrased as follows: when the center of gravity of the circuit board 61 is defined as the center of gravity G, the second system area 61BB including the non-coated area is positioned on the circuit board 61 so that it is at least below the center of gravity G in the direction of gravity.In other words, when the circuit board 61 is divided into an upper circuit board and a lower circuit board in a virtual horizontal plane passing through the center of gravity G, the second system area 61BB including the non-coated area is positioned so that it is at least present on the lower side of the circuit board.

[0079] <Advantages of the third embodiment> According to the third embodiment described above, the effects of the first embodiment and the effects (1-1), (1-3) to (1-5) can be obtained, and further the effects described below can be obtained.

[0080] (3-1) In the motor unit 20 of this embodiment, if moisture enters the housing portion R2 from outside the motor unit 20, the moisture flows out toward the short side portion 600b in the second system region 61BB due to the influence of gravity. Therefore, even if the motor unit 20 is attached to the lower side of the short side portion, the normal function of the motor unit 20 can be preferably ensured.

[0081] <Fourth embodiment> The fourth embodiment will be described below with reference to the drawings. This embodiment differs from the first embodiment in the coating area C on the first surface 66 and the second surface 67 of the circuit board 61. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0082] 8, of the first surface 66 and the second surface 67 of the circuit board 61 of this embodiment, the second system area 61BB includes a coated area C. That is, a coating process is applied to a portion of the second system area 61BB. More specifically, the second power circuit area 701B of the second system area 61BB is included in the coated area C. This is an example of an aspect in which the second system area 61BB of the first surface 66 and the second surface 67 of the circuit board 61 includes a non-coated area and also includes the coated area C.

[0083] <Effects of the Fourth Embodiment> According to the fourth embodiment described above, the effects of the first embodiment and the effects (1-1) to (1-3) and (1-5) can be obtained, and further the effects described below can be obtained.

[0084] (4-1) When the second system area 61BB includes the coating area C, the situation in which the circuit of the second system area 61BB is adversely affected by contact with moisture can be reduced compared to when the second system area 61BB does not include a coating area. Therefore, while the circuit of the second system area 61BB is more susceptible to adverse effects than the circuit of the first system area 61AA, drive control of the motor 2 by dual-system drive can be continued for a longer period of time compared to when the second system area 61BB does not include a coating area.

[0085] (4-2) Because the second power circuit area 701B of the second system area 61BB is included in the coating area C, it is possible to increase the number of situations in which the second microcomputer 74B is adversely affected if moisture enters the housing R2 from outside the motor unit 20. This allows the first microcomputer 74A to quickly determine, via inter-microcomputer communication, that the second power supply system is not in a normal state.

[0086] <Fifth embodiment> The fifth embodiment will be described below with reference to the drawings. This embodiment differs from the first embodiment in the coating region C on the first surface 66 and the second surface 67 of the circuit board 61. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0087] As shown in FIG. 9 , the second system area 61BB of the first surface 66 and the second surface 67 of the circuit board 61 of this embodiment includes a coated area C. That is, a portion of the second system area 61BB is coated. More specifically, the second power circuit area 701B and the second control circuit area 702B of the second system area 61BB include the coated area C. In the second power circuit area 701B and the second control circuit area 702B, the area between the first virtual line V1 and the third virtual line V3 is included in the coated area C. The third virtual line V3 is obtained by translating the first virtual line V1 toward the second area 61B until it circumscribes the circle defined by the second virtual line V2. This is an example of an aspect in which the second system area 61BB of the first surface 66 and the second surface 67 of the circuit board 61 includes both a non-coated area and a coated area C.

[0088] <Effects of the Fifth Embodiment> According to the fifth embodiment described above, the effects of the first embodiment and the effects (1-1) to (1-3) and (1-5) can be obtained.

[0089] <Other embodiments> The above-described embodiments may be modified as follows: In addition, the following other embodiments may be combined with each other within the scope of technical compatibility.

[0090] In the first embodiment, the system is not limited to the rack assist system, but may be a pinion assist system in which an assist force is applied to the pinion shaft 111c or an additional pinion shaft. The other embodiments described herein can be similarly applied to the second to fifth embodiments.

[0091] In the first embodiment, the actuator 4 is not limited to a system that applies an assist force to the rack shaft 112 via the belt transmission mechanism 222. For example, the actuator 4 may apply an assist force to the rack shaft 112 via a worm and wheel mechanism. The other embodiments described herein can be similarly applied to the second to fifth embodiments.

[0092] The first embodiment may employ a power supply control system in which the first and second power supply systems are in a master-slave relationship. For example, the first power supply system (the system on the coated side) is the main system, and the second power supply system (the system on the uncoated side) is the sub-system. During normal use, the motor 2 is primarily driven by the main system. If the main system malfunctions, the sub-system backs up the drive of the motor 2. This ensures that the motor unit 20 continues to function normally for a longer period of time, especially when the motor 2 is driven by a single-system drive, i.e., the main power supply system. A specific example of a power supply control system in which a master-slave relationship is established is a master-slave system. In the master-slave system, during normal use when both the master system and the slave system are normal, the control variables required to drive the motor 2 are calculated by both the master system and the slave system. During normal use, the control variables calculated by the master system are used to drive the motor 2, and the control variables calculated by the slave system are discarded. When the master system becomes abnormal, the motor 2 is driven by one-system drive using the control amount calculated in the slave system. The other embodiments described here can be similarly applied to the second to fifth embodiments.

[0093] The first embodiment may employ a control method for switching between first single-system drive and second single-system drive. In this case, when both the first and second power supply systems are normal, the motor 2 is driven by single-system drive using either the first or second power supply system. When an abnormality occurs in one of the systems, the motor 2 is driven by single-system drive using the system that is not abnormal. Even in this case, the first and second power supply systems may have a master-slave relationship as described above. The other embodiments described herein can be similarly applied to the second to fifth embodiments.

[0094] In the first embodiment, the first system area 61AA, which is composed of the first power circuit 71A and the first control circuit 72A, is included in the coating area C. However, this is not limited to this. For example, areas of the first area 61A other than the first system area 61AA, such as the portion where the screw 65 is fastened, the portion where the first connecting end 58A is inserted, or the surrounding areas thereof, may be included in the coating area C. Also, for example, the entire area of ​​the first area 61A may be included in the coating area C. The other embodiments described herein can be similarly applied to the second to fifth embodiments.

[0095] In the first embodiment, the sensor area 61C is included in the coating area C, but it is not essential that the sensor area 61C be included in the coating area C. Also, a portion of the sensor area 61C, for example, the area of ​​the sensor area 61C that includes the first sensor 75A, may be selectively included in the coating area C. The other embodiments described here can be similarly applied to the second to fifth embodiments.

[0096] In the first embodiment, both the first surface 66 and the second surface 67 of the circuit board 61 include the coating area C, but this is not limited to this. For example, depending on the mounting manner of electronic components on the circuit board 61 or the mounting manner of the circuit board 61, only one of the first surface 66 and the second surface 67 may include the coating area C. The other embodiments described here can be similarly applied to the second to fifth embodiments.

[0097] In the first embodiment, the coating process is applied to all of the electronic components and wiring constituting the first power circuit 71A and the first control circuit 72A. However, this is not limited to this. For example, focusing on the degree of influence of the electronic components and wiring on the drive control of the motor 2, the coating process may be selectively applied to the first microcomputer 74A, the switching element 73A, or the wiring connected thereto. Focusing on the fact that circuit failures manifest as current changes, for example, the coating process may be selectively applied to current detection shunt resistors or the wiring connected thereto. Focusing on the size of the electronic components, for example, the coating process may be selectively applied to electronic components and wiring excluding the tall first smoothing capacitor 77A. As a result, the normal function of the motor unit 20 can be ensured while reducing the cost of the coating process. The other embodiments described herein can be similarly applied to the second to fifth embodiments.

[0098] In the first embodiment, if the circuits in the second system area 61BB are adversely affected, the first system area 61AA may include a partially uncoated area as long as the circuits in the first system area 61AA are not adversely affected first. That is, it is sufficient that the first system area 61AA is generally included in the coated area over the entire area of ​​the circuit board 61. The other embodiments described here can be similarly applied to the second to fifth embodiments.

[0099] In the first embodiment, the IC package 76 is mounted on the second surface 67, but the IC package 76 may be mounted on the first surface 66. The other embodiments described here can be similarly applied to the second to fifth embodiments.

[0100] In the first embodiment, among the multiple corners 500 forming the hexagonal shape of the circuit board 61, the corners 500 corresponding to the rectangular portions are arranged so as to face downward in the direction of gravity, but this is not limited thereto. For example, among the multiple corners 500 forming the hexagonal shape, the corners 500 corresponding to the trapezoidal portions may be arranged so as to face downward in the direction of gravity.

[0101] In the third embodiment, the short side portions 600b corresponding to the rectangular portions of the multiple sides 600 forming the hexagonal shape of the circuit board 61 are arranged so as to face downward in the direction of gravity, but this is not limiting. For example, the short side portions 600b corresponding to the trapezoidal portions of the multiple sides 600 may be arranged so as to face downward in the direction of gravity.

[0102] In the fourth embodiment, it is sufficient that the second power circuit area 701B is included in the coated area C, and a part of the second control circuit area 702B may be included in the coated area C. In other words, it is sufficient that at least the second microcomputer 74B or the wiring conducting to the second microcomputer 74B is in a non-coated area.

[0103] In the fourth embodiment, the second power circuit area 701B is included in the coated area C. However, the second control circuit area 702B may be included in the coated area C. This is also an example of an aspect in which the second system area 61BB of the first surface 66 and the second surface 67 of the circuit board 61 includes both a non-coated area and the coated area C. This increases the number of situations in which the shunt resistor for current detection is adversely affected if moisture enters the housing R2 from outside the motor unit 20. This enables the first microcomputer 74A or the second microcomputer 74B to quickly grasp changes in current due to a circuit failure. Also, in this case, as in the previous paragraph, a portion of the second power circuit area 701B may be included in the coated area C.

[0104] In the fifth embodiment, the third virtual line V3 is set to be obtained by translating the first virtual line V1 toward the second region 61B to a position where the first virtual line V1 circumscribes the circle defined by the second virtual line V2. However, this is not limited to this. For example, assuming that the second region 61B includes a non-coated region, the third virtual line V3 may be set to be obtained by further translating the third virtual line V3 toward the second region 61B or the first region 61A from the circle defined by the second virtual line V2. In other words, it is sufficient that the second system region 61BB side also includes the coated region C. For example, the portion where the screw 65 is fastened, the portion where the second connection end 58B is inserted, the second control circuit region 702B, or their surrounding areas may be coated.

[0105] In the first embodiment, the coating agent may be a coating agent whose main component is a material other than a waterproof material, as long as it contributes to preventing direct contact with moisture. The other embodiments described here can be similarly applied to the second to fifth embodiments.

[0106] In each embodiment, the non-coated area may be coated with a general coating other than the coating agent of the present embodiment. General coatings include, for example, solder resist on the surface of a circuit board or thermal grease applied to heat dissipation components. [Explanation of symbols]

[0107] 2...Motor 11...Motor case 12...Output shaft 13...Stator 14...Rotor 20...Motor unit 21. Housing 53...winding 61...Circuit board 61AA…1st system area 61BB…Second system area 63...Cover 71A...First power circuit (circuit related to the first power supply system) 72A...First control circuit (circuit related to the first power supply system) 71B...Second power circuit (circuit related to the second power supply system) 72B...Second control circuit (circuit related to the second power supply system) 200...Steering mechanism (installation target) C...Coating area R (R1, R2)... Housing

Claims

1. A motor unit in which a motor and a circuit board are integrally housed in a motor case, and the motor case is attached to a predetermined attachment target, the motor includes a stator including a winding, a rotor configured to rotate when power is supplied to the winding, and an output shaft that rotates integrally with the rotor; the circuit board has a first system area in which circuits related to a first power supply system that is a system for controlling the drive of the motor are mounted, and a second system area in which circuits related to a second power supply system that is a system for controlling the drive of the motor are mounted, the motor case includes a housing having an opening at one end in the axial direction of the output shaft and an end wall at the other end in the axial direction, a cover that closes the opening so as to define a storage section between the housing and the cover, and a partition that divides the storage section in the axial direction; The motor is accommodated in the end wall portion side of the compartment, The circuit board is accommodated in the cover side of the compartment, On the premise that the circuit board has the first system area and the second system area, and can be divided into a coated area where the circuit board is coated and a non-coated area where the circuit board is not coated, the first system region is included in the coating region, the second system region includes the non-coated region, A motor unit in which the circuit board is housed in the motor case so that, when the motor case is attached to the attachment object, the non-coated area is on the lower side of the circuit board in the direction of gravity.

2. The circuit board has a shape having a plurality of corners when viewed in a thickness direction of the circuit board, 2. The motor unit according to claim 1, wherein the non-coated area is provided at one of the plurality of corners that is positioned lower in the direction of gravity on the circuit board when the motor case is attached to the attachment target.

3. The shape of the circuit board has a plurality of sides when viewed in a thickness direction of the circuit board, 2. The motor unit according to claim 1, wherein the non-coated area is provided on one of the plurality of side portions that is positioned on a lower side of the circuit board in the direction of gravity when the motor case is attached to the attachment object.

4. The motor unit according to claim 1 , wherein the second system region does not include the coating region.

5. The motor unit according to claim 1 , wherein the second system region includes the non-coated region and also includes the coated region.

6. The motor unit according to claim 1 , wherein the coating region is provided on both surfaces of the circuit board in the thickness direction.

7. The motor unit according to claim 1 , wherein a material of the coating agent used for the coating includes a waterproof material.

8. a rotation angle sensor for detecting a rotation angle of the output shaft is mounted on the circuit board at a position corresponding to an opposing surface of the circuit board that faces the end of the output shaft on the cover side, among both surfaces of the circuit board in a plate thickness direction; the circuit board includes a sensor area in which the rotation angle sensor is mounted, in addition to the first system area and the second system area, The motor unit according to claim 1 or 4, wherein the sensor region is included in the coating region.

Images