Electric Fluid Pump

Abstract

To provide an electric fluid pump which effectively radiates heat of a substrate without adding a new heat radiation member.SOLUTION: An electric fluid pump includes: a pump part 2 which transports a fluid; a motor part 3 which drives the pump part 2; a substrate 4 formed with a control circuit which controls the motor part 3; and a housing 5 including a pump housing part 53 which houses the pump part 2, a motor housing part 54 which houses the motor part 3, and a substrate housing part 55 which houses the substrate 4. The pump housing part 53, the motor housing part 54, and the substrate housing part 55 are a metallic integrated member.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric fluid pump. [Background technology]

[0002] 2. Description of the Related Art As an electric fluid pump mounted on a vehicle, for example, an electric oil pump that maintains hydraulic pressure in a transmission when the vehicle is stopped in a vehicle equipped with an idling stop mechanism (a mechanism that automatically stops the engine when the vehicle is stopped) is known.

[0003] This type of electric fluid pump is equipped with a board (control board) on which various electronic components such as a capacitor are mounted to control the fluid pressure. When a current flows through the electronic components on the board, the electronic components generate heat, and the heat can affect the efficiency of circuit operation and can even damage the electronic components.

[0004] For this reason, the following Patent Documents 1 and 2 disclose a configuration including a heat sink as a heat dissipation member for dissipating heat from electronic components and a board. By dissipating heat from electronic components on a board via the heat sink, it is possible to avoid a decrease in function or damage to electronic components due to a rise in temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-184542 A [Patent Document 2] JP 2020-195196 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned measure of adding a separate heat dissipation member such as a heat sink has problems in that it increases the number of parts and requires design changes such as changes to the part layout.

[0007] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an electric fluid pump that can effectively dissipate heat from a board without adding a new heat dissipation member. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides an electric fluid pump having a pump section that transports fluid, a motor section that drives the pump section, a board on which a control circuit that controls the motor section is formed, and a housing that includes a pump accommodating section that accommodates the pump section, a motor accommodating section that accommodates the motor section, and a board accommodating section that accommodates the board, wherein the pump accommodating section, the motor accommodating section, and the board accommodating section are integral members made of metal.

[0009] In this way, in the present invention, the pump housing, the motor housing, and the circuit board housing are an integrated metal member, so that the heat transfer in the housing is improved and the heat of the circuit board can be effectively dissipated through the housing. In addition, since there is no need to add a new heat dissipation member, major design changes can be avoided.

[0010] The substrate is preferably in contact with the housing via a metal foil on the substrate, which improves thermal conductivity from the substrate to the housing and therefore improves heat dissipation from the substrate.

[0011] The substrate is preferably fixed to the housing by a metal fastener, which also improves the thermal conductivity from the substrate to the housing, thereby improving the heat dissipation of the substrate.

[0012] It is also preferable that the substrate and the housing are in contact with each other on the surface of the substrate facing the pump housing section, which shortens the heat transfer path from the substrate to the pump housing section, making it easier to transfer heat from the substrate to the fluid in the pump housing section and further improving the heat dissipation performance of the substrate.

[0013] In addition, when the housing has a plurality of board mounting parts for mounting the boards, it is preferable that some of the board mounting parts are disposed closer to the pump housing than the other board mounting parts. In this case, the heat transfer path via the board mounting parts on the pump housing side is particularly short, so that the heat of the board is easily transferred to the pump housing.

[0014] In addition, the substrate is preferably disposed along the tangent direction of a circle passing through the axis of the motor unit. In this case, the electric fluid pump can be made smaller (thinner) in the direction perpendicular to the substrate, and the heat transfer path from the substrate to the pump housing is shortened, making it easier to transfer heat from the substrate to the pump housing. Effect of the Invention

[0015] According to the present invention, heat from the board can be effectively dissipated without adding a new heat dissipation member. [Brief description of the drawings]

[0016] [Figure 1] 1 is an axial cross-sectional view of an electric oil pump according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a cross-sectional view showing a cross section along line II-II in FIG. [Diagram 3] FIG. 2 is a cross-sectional view showing the cross section III-III in FIG. [Figure 4] FIG. 2 is a plan view of the substrate as viewed from the mounting surface side. [Diagram 5] 1 is a perspective view of an electric oil pump according to an embodiment of the present invention; [Figure 6] FIG. 4 is a cross-sectional view showing a mounting structure of a substrate. [Figure 7] FIG. 2 is an enlarged cross-sectional view showing a part of FIG. [Figure 8] 4 is a side view of the circuit board as viewed from the axial direction of the motor unit. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

[0018] The electric oil pump of this embodiment supplies hydraulic pressure to the transmission while the engine is stopped. It draws oil from an oil reservoir at the bottom of the transmission case, and then discharges the oil under pressure into the transmission, thereby ensuring the necessary hydraulic pressure within the transmission.

[0019] 1 to 3, electric oil pump 1 of this embodiment has a pump section 2 that generates hydraulic pressure, a motor section 3 that drives pump section 2, a substrate 4, and a housing 5 that accommodates pump section 2, motor section 3, and substrate 4. Each of the members or elements will be described in detail below.

[0020] In the following description, the direction parallel to the axis O of the motor unit 3 is referred to as the "axial direction," and the radial direction of a circle centered on the axis O is referred to as the "radial direction" (the "inner diameter direction" and the "outer diameter direction" also refer to the inner diameter direction and the outer diameter direction of the circle). Also, the circumferential direction of the circle centered on the axis O is referred to as the "circumferential direction."

[0021] As shown in Figures 1 and 2, the pump section 2 of this embodiment is a trochoroid pump having an inner rotor 21 with a plurality of external teeth, an outer rotor 22 with a plurality of internal teeth, and a pump case 23 as a stationary member that houses the inner rotor 21 and the outer rotor 22. The inner rotor 21 is disposed on the inner diameter side of the outer rotor 22. The outer rotor 22 is located eccentrically relative to the inner rotor 21. Some of the teeth of the outer rotor 22 mesh with some of the teeth of the inner rotor 21. If the number of teeth of the inner rotor 21 is n, the number of teeth of the outer rotor 22 is (n+1).

[0022] The outer circumferential surface of the outer rotor 22 and the inner circumferential surface of the pump case 23 are both cylindrical surfaces that can be fitted into each other. The outer rotor 22 is rotatably disposed on the inner circumferential surface of the pump case 23 so as to be rotated in accordance with the rotation of the inner rotor 21.

[0023] As shown in Fig. 1, the motor unit 3 is arranged alongside the pump unit 2 in the axial direction. For example, a three-phase brushless DC motor is used as the motor unit 3. As shown in Figs. 1 and 3, the motor unit 3 has a stator 30 having a plurality of coils 30a, a rotor 31 arranged inside the stator 30 with a gap therebetween, and an output shaft 32 coupled to the rotor 31. The stator 30 has coils 30a formed thereon corresponding to the three phases, U-phase, V-phase, and W-phase.

[0024] The output shaft 32 protrudes on both axial sides of the stator 30. The portions of the output shaft 32 protruding from the stator 30 on both axial sides are rotatably supported with respect to the housing 5 via bearings 33 and 34 (for example, rolling bearings such as deep groove ball bearings).

[0025] The inner rotor 21 of the pump section 2 is attached to the end of the output shaft 32 on the pump section 2 side. No reducer is arranged between the output shaft 32 and the pump section 2, and the inner rotor 21 is directly connected to the output shaft 32 of the motor section 3. A seal 35 having a seal lip that slides on the outer circumferential surface of the output shaft 32 is arranged between the bearing 33 located on the axial side of the pump section 2 and the inner rotor 21. This seal 35 prevents oil from leaking from the pump section 2 to the motor section 3. An elastic member 36 compressed in the axial direction is arranged between the bearing 33 on the axial side of the pump section 2 and the seal 35.

[0026] In order to detect the rotation angle of the rotor 31 in the motor unit 3, a rotation angle detection unit 37 is provided between the rotating side and the stationary side of the motor unit 3. As shown in Fig. 1, the rotation angle detection unit 37 in this embodiment can be composed of a sensor magnet 37a (e.g., a neodymium bonded magnet) attached via a bracket 38 to the axial end of the output shaft 32 on the side opposite the pump unit, and a magnetic sensor 37b such as an MR element provided in the housing 5 on the stationary side. The magnetic sensor 37b is disposed opposite the axial end of the output shaft 32 on the side opposite the pump, and is attached to a sub-board 39 disposed in a direction perpendicular to the output shaft 32. A detection value of the magnetic sensor 37b is input to a control circuit of a board 4 (main board) described later.

[0027] It should be noted that a Hall element can also be used as the magnetic sensor 37b. In addition to the magnetic sensor, an optical encoder, a resolver, or the like can also be used as the rotation angle detection unit 37. It should be noted that the motor unit 3 can also be driven without a sensor.

[0028] As shown in Fig. 4, the substrate 4 is formed into a rectangular shape in a plan view. As shown in Fig. 1 and Fig. 3, the substrate 4 is disposed parallel to the output shaft 32 of the motor unit 3, and the mounting surface 40 of the substrate 4 extends in a tangent direction of a circle centered on the axis O of the motor unit 3 (see Fig. 8). Both ends of the substrate 4 in the tangential direction are located at positions protruding beyond the outer circumferential contour M of the motor unit 3 (the outer circumferential contour of the stator) in the tangential direction.

[0029] A plurality of electronic components 41 are mounted on one surface of the substrate 4. As shown in Fig. 4, the electronic components include a capacitor (an electrolytic capacitor such as an aluminum electrolytic capacitor) 41a, a CPU 41b, and a semiconductor element (inverter) 41c such as a MOS-FET, as well as integrated circuits such as a driver IC, resistors, etc. As shown in Figs. 2 and 3, the substrate 4 is disposed such that a surface (mounting surface) 40 on which the electronic components 41 are mounted faces the pump section 2 and the motor section 3.

[0030] Power is supplied to the board 4 from an external power source via a connector 42. A control circuit in the board 4 controls the polarity of the drive current. The controlled current is supplied to each coil 30a provided in the stator 30 of the motor unit 3 via a bus bar 43 connected to the board 4, as shown in FIG. 1. A heat dissipation sheet 44 is attached to a surface 45 of the board 4 opposite to the mounting surface 40 as a heat dissipation member. The heat dissipation sheet 44 is made of a material that has high thermal conductivity and is compressible. The heat dissipation sheet 44 is arranged so as to come into contact with a high heat generating component (e.g., a semiconductor element 41c) among the electronic components.

[0031] The housing 5 has a cylindrical housing body 50 that is open at both ends, a first lid portion 51 that closes the opening on the axial side of the housing body 50 on the pump side, and a second lid portion 52 that closes the opening on the axial side of the housing body 50 on the anti-pump side. The first lid portion 51 and the second lid portion 52 are fixed to the housing body 50 using a plurality of fastening bolts B1, B2, respectively.

[0032] The second cover 52 has a cylindrical bearing case 52a that supports the bearing 34 on the side opposite the pump section, and a cover 52b that closes the opening of the bearing case 52a on the side opposite the pump section. The sub-substrate 39 is disposed on the inner diameter side of the bearing case 52a. The cover 52b is attached to the bearing case 52a using a fastening member (not shown).

[0033] The housing body 50 has, integrally as a single component, a pump accommodating section 53 that accommodates the pump section 2, a motor accommodating section 54 that accommodates the motor section 3, and a board accommodating section 55 that accommodates the board 4. The housing body 50, the first lid section 51, and the second lid section 52 are formed of a metallic material that is a conductor and has good thermal conductivity, such as an aluminum alloy.

[0034] The pump accommodating portion 53 of the housing 5 has a generally cylindrical shape including the pump case 23 of the pump section 2. A partition wall 56 is provided on the inner circumferential surface of the pump accommodating portion 53 to divide the interior of the housing into a pump section 2 side and a motor section 3 side. The inner circumferential surface of the partition wall 56 extends to a position close to the outer circumferential surface of the output shaft 32. The inner circumferential surface of the partition wall 56 and the outer circumferential surface of the output shaft 32 are not in contact with each other, thereby allowing the output shaft 32 to rotate.

[0035] The motor accommodating portion 54 is formed in a cylindrical shape. The stator 30 of the motor section 3 is press-fitted or adhesively fixed to the cylindrical inner peripheral surface of the motor accommodating portion 54 (see FIG. 3). The bearing 33 and seal 35 on the pump section 2 side described above are attached to the inner peripheral surface of the motor accommodating portion 54, which is closer to the pump section 2 in the axial direction than the motor section 3. The bearing 33 and seal 35 are located on the opposite side of the pump section in the axial direction than the partition wall 56.

[0036] FIG. 5 is a perspective view of the electric oil pump 1 shown in FIG. 1 when viewed upside down from the pump unit 2 side and the board accommodating unit 55 side. As shown in FIG. 5, the board accommodating unit 55 of the housing 5 has a rectangular frame shape when viewed from the radial direction, and has a peripheral wall 55a with an opening on the outer diameter side in the radial direction. The board 4 arranged in the board accommodating unit 55 is surrounded by the peripheral wall 55a. After the board 4 is arranged in the board accommodating unit 55, the opening of the board accommodating unit 55 is closed by a cover 57 as a closing unit. The cover 57 is attached to the housing body 50 by using a fastening member B3. The fastening member refers to a bolt in general, including a tapping screw. In this state, the cover 57 is in contact with the heat dissipation sheet 44 shown in FIG. 1. This allows the heat from the electronic components 41 of the board 4, which become hot, to be efficiently released to the cover 57 and further to the housing body 50 via the heat dissipation sheet 44. At this time, since the heat path includes the cover 57 exposed to the outside air, a cooling effect by the outside air can also be expected.

[0037] 1, bottom surface 55b of substrate accommodating portion 55 is formed by the outer circumferential surface of pump accommodating portion 53 and the outer circumferential surface of motor accommodating portion 54. At bottom surface 55b, there is a radial step between the outer circumferential surface of pump accommodating portion 53 and the outer circumferential surface of motor accommodating portion 54, and the outer circumferential surface of pump accommodating portion 53 is located closer to axis O of motor section 3 in the radial direction than the outer circumferential surface of motor accommodating portion 54.

[0038] 1 and 5, flange-shaped mounting portions 58, 59 for mounting the electric oil pump 1 to an object to be mounted (a transmission case in this embodiment) are formed integrally on both axial sides of the housing body 50. Two fastening holes 58a are formed in the mounting portion 58 on the pump portion 2 side, and two fastening holes 59a are formed in the mounting portion 59 on the opposite side to the pump portion. Fastening members (not shown) are inserted into these fastening holes 58a, 59a and then screwed into the object to be mounted, thereby mounting the electric oil pump 1 to the object to be mounted.

[0039] Flat mounting surfaces 58b, 59b (see FIG. 5) that come into contact with the mounting object are formed around the fastening holes 58a, 59a of the mounting portions 58, 59. The mounting surfaces 58b, 59b are disposed on a common plane that extends in a direction perpendicular to the substrate 4 accommodated in the substrate accommodating portion 55.

[0040] 1, an oil flow passage 6 connected to the pump section 2 is provided in the housing body 50. The oil flow passage 6 includes an intake oil flow passage 60 and a discharge oil flow passage 61 that are separated from each other.

[0041] 2, the suction side oil flow path 60 has a suction side space 60a that opens to the meshing portion between the inner rotor 21 and the outer rotor 22, a suction hole 60b that opens to the surface of the housing body 50, and a suction side communication passage 60c that communicates between the suction side space 60a and the suction hole 60b. Similarly, the discharge side oil flow path 61 has a discharge side space 61a that opens to the meshing portion between the inner rotor 21 and the outer rotor 22, a discharge hole 61b that opens to the surface of the housing body 50, and a discharge side communication passage 61c that communicates between the discharge side space 61a and the discharge hole 61b.

[0042] The suction side space 60a and the discharge side space 61a are both provided in the pump housing 53 in a region on the axial side of the pump section 2 opposite the pump section. The suction side space 60a and the discharge side space 61a are both formed in an arc shape extending in the circumferential direction of the output shaft 32, and are provided at positions that are 180° opposed to each other in the circumferential direction. In this embodiment, the suction side space 60a is disposed closer to the board 4 than the discharge side space 61a. Also, the suction hole 60b and the discharge hole 61b are opened in the surface of the housing 5 that faces the mounting object, as shown in FIG. 5. The suction hole 60b and the discharge hole 61b are located on a plane including the mounting surfaces 58b, 59b of the mounting sections 58, 59. This eliminates the need to route oil piping around the electric oil pump 1, and the peripheral structure of the electric oil pump 1 can be simplified.

[0043] In the electric oil pump having the above configuration, the inner rotor 21 rotates when the motor unit 3 is driven. When the inner rotor 21 rotates, the outer rotor 22 meshed with it rotates, and the space formed between the teeth of both rotors expands and contracts with the rotation. Therefore, oil stored in an oil reservoir in the transmission case is sucked into the pump unit 2 via the suction side oil flow path 60, and this oil is discharged into the transmission via the discharge side oil flow path 61.

[0044] The electric oil pump according to this embodiment having the above configuration has the following features.

[0045] As described above, in the electric oil pump according to this embodiment, the housing 5 (housing main body 50) including the pump accommodating portion 53, the motor accommodating portion 54, and the board accommodating portion 55 is integrally formed from an aluminum alloy with good thermal conductivity, improving heat transfer in the housing 5. As a result, heat from the board 4 and the electronic components 41 is easily transferred to the housing 5 and the oil circulating within the housing 5. In FIG. 1, arrow H indicates part of the path of heat transferred from the board 4.

[0046] As described above, in this embodiment, since the heat transfer from the board 4 to the housing 5 is improved, the heat of the board 4 and the electronic component 41 can be effectively dissipated via the housing 5. This effectively prevents the performance of the electronic component 41 from being deteriorated or damaged due to an increase in temperature, improving the reliability and durability of the electric oil pump. In addition, in this embodiment, the heat of the board can be effectively dissipated without adding a new heat dissipation member, so that a major design change can be avoided.

[0047] 6, in this embodiment, the board 4 is in contact with the convex board attachment portion 50a provided on the housing main body 50 via the metal foil (copper foil) 62 forming a circuit pattern, and is fixed by metal fasteners (screws) 63, so that heat is efficiently transferred from the board 4 to the housing 5 via these metal members (the metal foil 62 and the fasteners 63). This improves the heat dissipation of the board 4 and the electronic components 41.

[0048] In addition, in this embodiment, as shown in FIG. 6, the board 4 and the board mounting portion 50a of the housing main body 50 are in contact with each other on the surface of the board 4 facing the pump housing portion 53, so that the heat transfer path from the board 4 to the pump housing portion 53 is shortened, and the heat of the board 4 and the electronic components 41 is easily transferred to the oil in the pump housing portion 53. Furthermore, in this embodiment, of the four board mounting portions 50a shown in FIG. 4, two board mounting portions 50a1 are closer to the pump housing portion 53 in the direction of the axis O of the motor portion 3 than the other two board mounting portions 50a2 (see FIG. 6), so that the heat transfer path via the board mounting portion 50a1 on the pump housing portion 53 side is particularly short. In this way, in this embodiment, a configuration is adopted that shortens the heat transfer path from the board 4 to the pump housing portion 53 as much as possible, so that the heat of the board 4 can be efficiently transferred to the pump housing portion 53 and the oil therein, and the heat of the board 4 and the electronic components 41 can be effectively dissipated. That is, the relationship in magnitude between the temperatures of the oil, the pump housing portion 53, the board 4, and the electronic component 41 is oil temperature<temperature of the pump housing portion 53<temperature of the board 4<temperature of the electronic component 41.

[0049] In addition, since this embodiment has the following structural features, it has an advantageous effect in terms of heat dissipation.

[0050] As described above, in this embodiment, since the bottom surface 55b of the substrate accommodating portion 55 has a radial step, as shown in Fig. 7, the region radially facing the pump accommodating portion 53 can be utilized as a space for arranging tall components (e.g., electrolytic capacitor 41a) among the electronic components 41 of the substrate 4. On the other hand, low-profile components (e.g., semiconductor element 41c, integrated circuit, or resistor) are concentrated and arranged in the region of the substrate 4 radially facing the motor accommodating portion 54.

[0051] This allows the board 4 to be disposed close to the bottom surface 55b of the board housing portion 55. Therefore, the electric oil pump 1 can be made smaller (thinner) in the direction perpendicular to the board 4, and the heat transfer path from the board 4 to the pump housing portion 53 is shortened, so that the heat of the board 4 and the electronic components 41 can be transferred well to the oil in the pump housing portion 53. In order to obtain this effect, it is preferable that the outer diameter d of the pump portion 2 is smaller than the outer diameter D of the motor portion 3 (d <D)。

[0052] In this embodiment, as shown in Fig. 8, the substrate 4 is disposed along the tangential direction of a circle passing through the axis O of the motor unit 3, so that the electric oil pump 1 can be made smaller (thinner) in the direction perpendicular to the substrate 4. In addition, in this tangential direction, both ends (the right end and the left end in the figure) of the substrate 4 extend to both areas sandwiching the axis O of the motor unit. Therefore, the end of the substrate 4 in this tangential direction is farther away from the cylindrical outer circumferential surface of the motor housing portion 54 than the center. Therefore, both ends of the substrate 4 in the tangential direction can be used as a space for arranging a tall component (electrolytic capacitor 41a).

[0053] In particular, in the present embodiment, as shown in FIG. 8, the center P of the substrate 4 in the tangential direction is displaced in the tangential direction with respect to the axis O of the motor unit 3 (displacement width α). For this reason, at one end of the substrate in the tangential direction, the distance to the outer peripheral surface of the motor housing portion 54 can be further increased. Thereby, in one end of the substrate 4 in the tangential direction, it is possible to surely secure an installation space for the electrolytic capacitor 41a which is a high-profile component, and it becomes easier to further reduce the size of the electric oil pump 1 in the direction orthogonal to the substrate 4. Thus, in the present embodiment, since the size of the electric oil pump 1 in the direction orthogonal to the substrate 4 can be reduced, the heat transfer property from the substrate 4 to the pump housing portion 53 is improved, and the heat radiation of the substrate 4 and the electronic component 41 can be performed more effectively.

[0054] Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention.

[0055] In the above-described embodiment, the case where the present invention is applied to an electric oil pump has been described as an example. However, the present invention is not limited to the case where it is applied to an electric pump using oil. The present invention is also applicable to an electric fluid pump that pumps a fluid other than oil, such as a water pump that pumps cooling water.

Explanation of Reference Numerals

[0056] 1 Electric oil pump (electric fluid pump) 2 Pump unit 3 Motor unit 4 Substrate 5 Housing 53 Pump housing portion 54 Motor housing portion 55 Substrate housing portion 62 Metal foil (metal member) 63 Fixture (metal member)

Claims

1. A pump unit that transports a fluid; A motor unit that drives the pump unit; A substrate on which a control circuit for controlling the motor unit is formed; a housing including a pump accommodating portion for accommodating the pump portion, a motor accommodating portion for accommodating the motor portion, and a board accommodating portion for accommodating the board; An electric fluid pump having the pump accommodating portion, the motor accommodating portion, and the board accommodating portion are integral members made of metal, a bottom surface of the substrate accommodating portion disposed on the pump accommodating portion side and the motor accommodating portion side has a step that is closer to the pump accommodating portion on the pump accommodating portion side than on the motor accommodating portion side, An electric fluid pump, characterized in that a taller electronic component is mounted on the surface of the board facing the bottom surface of the board accommodating section, on the side of the pump accommodating section closer to the motor accommodating section than to the side of the motor accommodating section, with the step as the boundary.

2. 2. The electric fluid pump according to claim 1, wherein the substrate contacts the housing via a metal foil on the substrate.

3. 3. The electric fluid pump according to claim 1, wherein the substrate is fixed to the housing by a metal fastener.

4. The electric fluid pump according to claim 1 , wherein the substrate and the housing are in contact with each other on a surface of the substrate facing the pump accommodating portion.

5. the housing has a plurality of board mounting portions for mounting the board; The electric fluid pump according to claim 1 , wherein some of the plurality of board mounting portions are disposed closer to the pump housing portion than other board mounting portions.

6. The electric fluid pump according to claim 1 , wherein the substrate is disposed along a tangent direction of a circle having an axis center of the motor unit as a center.

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