JP7779031B2 - Drive unit - Google Patents

Description

The present invention relates to a drive device.

A known example of a conventional drive device is that described in Patent Document 1. In Patent Document 1, an electric actuator having a motor and a drive control device acting as a control unit for controlling the motor are integrally provided.

Japanese Patent Application Laid-Open No. 2015-180155

In Patent Document 1, the wiring pattern to which the motor drive switching elements are connected is formed up to the fastening holes for fixing the circuit board, and the circuit board is tightly attached to the ECU housing by fastening screws, allowing heat transferred from the switching elements to the wiring pattern to escape to the ECU housing. However, there is a possibility that heat may be transferred to other circuits mounted on or near the path of the wiring pattern.

The present invention was made in consideration of the above points, and its purpose is to provide a drive device that can reduce the heat given off by the motor drive element to other circuits.

The drive device of the present invention integrally comprises a motor (20) and a control unit (40) that controls the motor. The control unit has a heat sink (33) arranged outside the rotation axis (O) of the motor, a substrate (41) arranged on the rotation axis (O) of the motor, a fixing member (51) that fixes the substrate, a motor drive element (55) that energizes the motor, a power wiring pattern (56) that is connected to the motor drive element to supply power, and a control circuit (61) that sends a control signal to the motor drive element.

The portion of the substrate within a predetermined distance from the rotation axis and closer to the rotation axis than the outer edge (44) of the substrate is defined as the substrate center (45). The portion of the substrate other than the substrate center is defined as the substrate outer periphery (46).

The control circuit is located in the center of the board. The power wiring pattern includes a power supply pattern connected to the high-potential side of the motor drive element to supply power, and a ground pattern connected to the low-potential side of the motor drive element, and is located at the outer periphery of the board so that a portion of the pattern overlaps the projection area of the ground pattern . The fixing member is made of a material with a higher thermal conductivity than the board, and is located at the outer periphery of the board and fixes the board to a heat sink. The motor drive element is located between the fixing member and the control circuit, closer to the fixing member. Regarding the board, the surface on which the motor drive element is mounted is referred to as the first mounting surface, and the opposite side to the first mounting surface is referred to as the second mounting surface. At the outer periphery of the board, the power supply pattern is located on the first mounting surface, and the ground pattern is located on the backside of the power supply pattern on the second mounting surface side. The power supply pattern has a relief recess that opens toward the inside of the board where the fixing member is located so as not to overlap with the area of the fixing member, while the ground pattern does not have a relief recess.

This structure allows the heat from the motor drive element to be absorbed and dissipated by the heat sink via the fixing member, preventing the temperature of the motor drive element from rising. Because the motor drive element is positioned closer to the fixing member than the control circuit, the heat from the motor drive element is less likely to be transferred to the control circuit. This reduces the impact of heat from the motor drive element on other circuits.

In conventional designs, wiring patterns are formed all the way to fastening holes for heat dissipation rather than for the transmission and reception of power and signals, which increases manufacturing costs. In contrast, with this invention, heat from the motor drive elements is dissipated to the heat sink via the fixing member, eliminating the need to make the wiring patterns larger than necessary for heat dissipation, thereby reducing manufacturing costs.

FIG. 2 is a longitudinal sectional view of the drive device according to the embodiment. 2 is a view of the substrate, electronic components, and screws of FIG. 1 as viewed from the direction of arrow II. FIG. 3 is an enlarged view of part III of FIG.

An embodiment of the drive unit is described below with reference to the drawings.

[One embodiment]
1, the drive device 10 integrally comprises a motor 20 and a control unit 40 that controls the motor 20. The control unit 40 controls the motor 20 to generate a desired torque based on information input from the outside and information such as the motor current detected within the control unit 40. The torque of the motor 20 is output to the outside from the output end of the rotating shaft 26.

The motor 20 is a three-phase brushless motor and includes a stator 21, a rotor 25, and a housing 31 that houses them. The stator 21 has a stator core 22 fixed to the housing 31 and a three-phase winding set 23 assembled to the stator core 22. The three-phase winding set 23 is connected to the control unit 40 via lead wires (not shown).

The rotor 25 has a rotating shaft 26 supported by a rear bearing 35 and a front bearing 36, and a rotor core 27 into which the rotating shaft 26 is fitted. The rotor 25 is provided inside the stator 21 and can rotate relative to the stator 21. A permanent magnet 37 is provided on one end of the rotating shaft 26.

The housing 31 has a cylindrical case 32, a front end frame 33 attached to one end of the case 32, and a rear end frame 34 attached to the other end of the case 32. The front end frame 33 and the rear end frame 34 are fastened to each other with bolts (not shown). The front end frame 33 also functions as a heat sink for the control unit 40. Hereinafter, when describing the function of the front end frame 33 as a heat sink, it will be referred to as the "heat sink 33" as appropriate.

As shown in Figures 1 and 2, the control unit 40 includes a heat sink 33 and a substrate 41 arranged on the rotation axis O of the motor 20, a screw 51 as a fixing member for fixing the substrate 41, a motor drive element 55 that supplies current to the motor 20, a power wiring pattern 56 connected to the motor drive element 55 to supply power, a control circuit 61 that sends a control signal to the motor drive element 55, and a rotation angle sensor 62 that detects the rotation angle of the rotating shaft 26.

The substrate 41 is disposed on the opposite side of the heat sink 33 from the stator 21. In one embodiment, there is one substrate 41, but in other embodiments, there may be two or more substrates. The screw 51 passes through a through-hole 42 in the substrate 41. The motor drive element 55 is composed of a switching element such as a MOSFET, and performs switching operation in response to a control signal from the control circuit 61, switching the current flow state of the three-phase winding set 23. The control circuit 61 performs calculations based on information from the outside and from the rotation angle sensor 62, etc., and generates signals to command the motor drive element 55, etc.

The control unit 40 further includes a cover 64 arranged to cover the board 41 and the electronic components mounted thereon, and a connector 66 for connecting the control unit 40 to the outside.

The cover 64 protects the control unit 40 from external impacts and prevents dust, water, and other contaminants from entering the control unit 40. Electronic components other than the motor drive element 55 and control circuit 61 are not shown in Figures 1 and 2. The connector 66 is fixed to the connector connection portion 43 of the circuit board 41 with a screw 63 and extends outside the cover 64 through an opening 65.

The portion of the substrate 41 that is within a predetermined distance from the rotation axis O and is closer to the rotation axis O than the outer edge 44 of the substrate 41 is defined as the substrate center 45. Furthermore, the portion of the substrate 41 other than the substrate center 45 is defined as the substrate outer periphery 46.

The control circuit 61 is disposed in the central portion 45 of the substrate. In one particular embodiment, the control circuit 61 is disposed on the rotation axis O and approximately in the center of the central portion 45 of the substrate.

The screws 51 are arranged on the outer periphery 46 of the board to ensure sufficient mounting area, and secure the board 41 to the heat sink 33. In one embodiment, three screws 51 are provided spaced apart circumferentially around the rotation axis O.

The power wiring pattern 56 and motor drive element 55 are arranged on the outer periphery 46 of the board. The power wiring pattern 56 is arranged radially outward (i.e., closer to the outer edge 44) than the motor drive element 55, and is formed so as to surround the motor drive element 55 and control circuit 61 by more than half the circumference and extend along the outer edge 44.

The mounting surface of the substrate 41 opposite the heat sink 33 is defined as the first mounting surface 47. The mounting surface of the substrate 41 facing the heat sink 33 is defined as the second mounting surface 48.

The motor drive element 55 is arranged on the first mounting surface 47. In other words, the motor drive element 55 is arranged on the opposite side of the substrate 41 from the heat sink 33.

The power wiring pattern 56 includes a power supply pattern 57 arranged on the first mounting surface 47 and connected to the high-potential side of the motor drive element 55 to supply power, and a ground pattern 58 arranged on the second mounting surface 48 and connected to the low-potential side of the motor drive element 55.

The screw 51 is made of a metal material with a higher thermal conductivity than the resin substrate 41, and has a heat receiving portion 52, a threaded portion 53, and a connecting portion 54. The heat receiving portion 52 is formed from the head of the screw 51 and is positioned near the motor drive element 55 on the first mounting surface 47. The threaded portion 53 is threaded into the heat sink 33. The connecting portion 54 connects the heat receiving portion 52 and the threaded portion 53.

The motor drive element 55 is positioned between the screw 51 and the control circuit 61, closer to the screw 51. In other words, the gap between the motor drive element 55 and the heat receiving portion 52 is narrower than the gap between the motor drive element 55 and the control circuit 61.

(effect)
As described above, in one embodiment, the control circuit 61 is disposed in the substrate central portion 45. The power wiring pattern 56 is disposed in the substrate peripheral portion 46. The screw 51 is made of a material having a higher thermal conductivity than the substrate 41, is disposed in the substrate peripheral portion 46, and fixes the substrate 41 to the heat sink 33. The motor drive element 55 is disposed between the screw 51 and the control circuit 61, closer to the screw 51.

This structure allows the heat from the motor drive element 55 to be absorbed and dissipated by the heat sink 33 via the screw 51, preventing the temperature of the motor drive element 55 from rising. Because the motor drive element 55 is positioned closer to the screw 51 than the control circuit 61, the heat from the motor drive element 55 is less likely to be transferred to the control circuit 61. This reduces the impact of heat from the motor drive element 55 on other circuits.

In conventional configurations, wiring patterns are formed all the way to the fastening holes in the circuit board for heat dissipation rather than for the transmission and reception of power and signals, which increases manufacturing costs. In contrast, in one embodiment, heat from the motor drive element 55 is dissipated to the heat sink 33 via the screws 51, eliminating the need to make the power wiring pattern 56 larger than necessary for heat dissipation, thereby reducing manufacturing costs.

In one embodiment, the power wiring pattern 56 is positioned radially outward compared to the motor drive element 55 and is formed to extend along the outer edge 44. By positioning the power wiring pattern 56, which carries a larger current than the signal wiring pattern, as far outward as possible in this manner, heat from the power wiring pattern 56 is more easily released to the outside rather than being trapped inside the drive device.

In one embodiment, the motor drive element 55 is positioned on the opposite side of the substrate 41 from the heat sink 33. The screw 51 has a heat receiving portion 52 positioned near the motor drive element 55 on the first mounting surface 47 of the substrate 41, a threaded portion 53 that screws into the heat sink 33, and a connecting portion 54 that connects the heat receiving portion 52 and the threaded portion 53. This allows the heat received by the motor drive element 55 at the heat receiving portion 52 near the motor drive element 55 to be effectively dissipated to the heat sink 33 via the connecting portion 54 and the threaded portion 53.

Other Embodiments
In other embodiments, the number of screws is not limited to three, but may be two or less, or four or more. Furthermore, instead of screws, other types of fixing members, such as clips or pins, may be used. Furthermore, the motor drive element may be disposed across the outer periphery and the center of the substrate.

The present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the spirit of the invention.

10 Drive device, 20 Motor, 33 Heat sink, 40 Control unit, 41 Board, 44 Outer edge, 45 Board center, 46 Board outer periphery, 51 Screw (fixing member), 55 Motor drive element, 56 Power wiring pattern, 61 Control circuit, O Rotation axis.

Claims (3)

A drive device integrally comprising a motor (20) and a control unit (40) that controls the motor,
The control unit includes a heat sink (33) arranged outside the rotation axis (O) of the motor, a substrate (41) arranged on the rotation axis (O) of the motor, a fixing member (51) for fixing the substrate, a motor drive element (55) for supplying current to the motor, a power wiring pattern (56) connected to the motor drive element for supplying power, and a control circuit (61) for sending a control signal to the motor drive element,
A portion of the substrate within a predetermined distance from the rotation axis and closer to the rotation axis than the outer edge (44) of the substrate is defined as a substrate central portion (45), and a portion of the substrate other than the substrate central portion is defined as a substrate outer peripheral portion (46).
the control circuit is disposed in the center of the substrate;
the power wiring pattern includes a power supply pattern connected to a high potential side of the motor drive element to supply power, and a ground pattern connected to a low potential side of the motor drive element, and is arranged on the outer periphery of the substrate;
the fixing member is made of a material having a higher thermal conductivity than the substrate, and is disposed at an outer periphery of the substrate so as to overlap a portion of the projection area of the ground pattern , and fixes the substrate to the heat sink;
the motor drive element is disposed between the fixed member and the control circuit and closer to the fixed member,
a surface of the substrate on which the motor drive element is mounted is defined as a first mounting surface, and a surface opposite to the first mounting surface is defined as a second mounting surface; the power supply pattern is provided on the first mounting surface at the outer periphery of the substrate, and the ground pattern is provided on the second mounting surface side and on a back side of the power supply pattern ;
a power supply pattern having an escape recess formed in a location where the fixing member is provided, the escape recess opening toward the inside of the substrate so as not to overlap with the area of the fixing member, and the ground pattern having no escape recess formed therein . The drive device described in claim 1, wherein the power wiring pattern is positioned radially outward relative to the motor drive element and is formed to extend along the outer edge. the motor drive element is disposed on the opposite side of the substrate from the heat sink,
3. The drive device of claim 1, wherein the fixing member has a heat receiving portion (52) arranged near the motor drive element on the mounting surface (47) of the board, a threaded portion (53) that screws into the heat sink, and a connecting portion (54) that connects the heat receiving portion and the threaded portion.