JP7767962B2 - Drive unit - Google Patents

Description

The present invention relates to a drive device.

Conventionally, drive devices in which the motor and control unit are integrated are known in which the control unit's power module and circuit board are arranged along the rotation axis direction. This type of "vertical arrangement" of the circuit board allows for radial miniaturization.

For example, in the electric power steering device disclosed in Patent Document 1, the heat sink has a rectangular parallelepiped pillar portion extending in the axial direction of the rotation shaft. Two sets of control boards and power modules that make up two motor drive circuits are respectively arranged in a pair of arrangement portions corresponding to two opposing sides of the pillar portion and in arrangement portions corresponding to the other two opposing sides.

International Publication No. 2019/073594

In this specification, the choke coil and capacitor, which are cylindrical electronic components that make up the control unit, are defined as large components. In the device of Patent Document 1, the cylindrical axis of the capacitor, which is a large component, is positioned so that it is perpendicular to the axial direction of the rotation shaft. As a result, when using a larger-sized capacitor, there is an issue in that it cannot be accommodated in the gap space of the unit case (housing in Patent Document 1).

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a drive unit in which the circuit board is arranged vertically and which can suppress an increase in radial size even when larger components are used.

The drive device according to the present invention comprises a motor (80), a control unit (101, 102), a heat sink (601, 602), and a unit case (20). The motor includes a stator (84) and a rotor (86) that rotates around a shaft (87) provided on a rotation axis (O). The control unit is provided integrally with the motor on one axial side of the rotation axis and drives and controls the motor.

The heat sink has pillars (610, 620) that support the control unit. The pillars have a pair of first arrangement sections (631, 632) arranged on either side of the rotation axis, and one or a pair of second arrangement sections (641, 642) that connect the pair of first arrangement sections and face radially outward. A cylindrical unit case covers the control unit supported by the pillars.

The control unit has one or more circuit boards (301, 302, 400, 401, 402) fixed to the first or second placement section of the column.

The choke coil (33) and capacitor (34), which are cylindrical electronic components that make up the control unit, are defined as large components. Multiple large components are arranged inside the unit case with their cylindrical axes aligned with the axial direction of the rotation shaft. For example, at least some of the multiple large components are arranged in series along the axial direction of the rotation shaft. Furthermore, for example, one choke coil and one or more capacitors are arranged in series along the axial direction of the rotation shaft.

While there is a limit to the radial distance between the circuit board fixed to the pillar and the inner wall of the unit case, there is a space at least equal to the longitudinal dimension of the board in the axial direction of the rotation shaft. In this invention, the cylindrical axes of multiple large components are arranged along the axial direction of the rotation shaft, so even larger components can be efficiently accommodated in the gap space within the unit case.

1 is a schematic diagram illustrating the configuration of an electric power steering device to which a drive device is applied. Circuit diagram of a dual-motor drive system. FIG. 2 is an axial cross-sectional view of the drive device according to the first embodiment. 4 is a view of the column portion of FIG. 3 taken in the direction of arrow IV. FIG. 4 is a view taken in the direction of the arrow V in FIG. 3 . FIG. 6 is a radial cross-sectional view taken along line VI-VI in FIG. 3 . FIG. 2 is a side view of the heat sink according to the first embodiment. FIG. 8 is a view taken in the direction of arrow VIII in FIG. 7 . 9 is a view taken in the direction of an arrow IX in FIG. 7, with a rotation angle sensor board added thereto. FIG. 10 is a diagram showing a modified example of the first embodiment relating to the arrangement of capacitors. FIG. 6 is an axial cross-sectional view of a drive device according to a second embodiment. 12 is a radial cross-sectional view taken along line XII-XII in FIG. 11 . FIG. 10 is an exploded side view of a heat sink according to a second embodiment. FIG. 14 is a view taken in the direction of an arrow XIV in FIG. 14 is a view taken in the direction of the arrow XV in FIG. 13, with a rotation angle sensor board added thereto. FIG. 4 is a radial cross-sectional view of a drive device according to a comparative example.

Several embodiments of the drive device according to the present invention will be described with reference to the drawings. Substantially identical components in the various embodiments will be assigned the same reference numerals and will not be described again. The first and second embodiments will be collectively referred to as "the present embodiment." The drive device of this embodiment is used, for example, as a steering assist motor for an electric power steering device. This drive device is a so-called "electromechanical integrated" drive device in which a motor and a control unit that controls the drive of the motor are integrated into one unit. Furthermore, in the drive device of this embodiment, the circuit board for the control unit is arranged along the direction of the motor's rotational axis. This arrangement of the circuit boards is referred to as a "vertical arrangement."

[Configuration of electric power steering device]
The schematic configuration of an electric power steering device 99 will be described with reference to Figure 1. Although a rack-assist type electric power steering device is shown in Figure 1, the drive unit 800 of this embodiment is also applicable to a column-assist type electric power steering device. A steering system 90 including the electric power steering device 99 includes a steering wheel 91, a steering shaft 92, a pinion gear 96, a rack shaft 97, wheels 98, and the electric power steering device 99.

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

The electric power steering device 99 includes a "mechanically and electrically integrated" drive unit 800 in which the motor 80 and control unit 10 are integrated, and a reduction gear 89 that reduces the rotation of the motor 80 and transmits it to the rack shaft 97. The motor 80 is a dual-system three-phase brushless motor with two sets of three-phase windings, and its output shaft rotates around the rotation axis O.

The control unit 10 is integral with the motor 80 on one axial side of the rotation axis O and drives and controls the motor 80. Two inverter systems within the control unit 10 supply three-phase AC power to two sets of three-phase windings, causing the motor 80 to output steering assist torque. DC power is supplied from the vehicle's batteries BT1 and BT2 to the power supply system connector 23 of the control unit 10. A sensor signal detected by an external torque sensor 93 is input to the signal system connector 24 via a harness 94.

Figure 2 shows the circuit configuration of a dual-system motor drive system. The stator of the motor 80 has two winding sets 810, 820. The power circuit 310 of the first system converts the power of the first battery BT1 and supplies it to the first winding set 810 in accordance with commands from the control circuit 410. The power circuit 320 of the second system converts the power of the second battery BT2 and supplies it to the second winding set 820 in accordance with commands from the control circuit 420. Because the configurations of the power circuits 310, 320 and the control circuits 410, 420 of the first and second systems are the same, the components of each system will be assigned the same reference numerals without distinction.

The dual-system system shown in Figure 2 is a "fully dual-system" configuration in which the power circuits 310, 320 of each system are connected to individual batteries BT1, BT2. Alternatively, a "dual-drive system" configuration may be used in which the power circuits 310, 320 of each system are connected to a common battery. The power circuits 310, 320 include a choke coil 33, a power supply relay 35, a reverse connection protection relay 36, a capacitor 34, an inverter 370, motor relays 381, 382, 383, etc. In the following description, the reference numerals for the batteries BT1, BT2 will be omitted where appropriate.

The choke coil 33, power relay 35, and reverse polarity protection relay 36 are provided on the power line connecting the positive terminal of the battery and the high-potential side of the inverter 370. The capacitor 34 is, for example, an aluminum electrolytic capacitor, and is connected in parallel with the inverter 370 on the input side of the inverter 370. While FIG. 2 shows the capacitor 34 for each system with a single symbol, multiple capacitors 34 may be connected in parallel to ensure sufficient capacity. The choke coil 33 and capacitor 34 form an LC filter and function as noise suppression elements that reduce noise. In this specification, the choke coil 33 and capacitor 34, which are cylindrical components that make up the control unit 10, are defined as "large components."

The power supply relay 35 and reverse connection protection relay 36 are composed of, for example, MOSFETs. The parasitic diode of the power supply relay 35 conducts current from the inverter 370 side to the battery side. When the battery is connected in forward direction, the power supply relay 35 cuts off current from the battery side to the inverter 370 side when it is turned off. The parasitic diode of the reverse connection protection relay 36 conducts current from the battery side to the inverter 370 side. When the battery is connected in reverse, the reverse connection protection relay 36 cuts off current from the inverter 370 side to the battery side when it is turned off.

Inverter 370 includes multiple three-phase upper and lower arm switching elements 371-376, each composed of, for example, MOSFETs. More specifically, upper arm switching elements 371, 372, and 373 for the U, V, and W phases and lower arm switching elements 374, 375, and 376 are bridge-connected. The switching elements 371-376 of inverter 370 (hereinafter also referred to as "inverter elements 371-376") are "heat-generating elements" that generate heat when current is applied to motor 80.

In the configuration example shown in Figure 2, shunt resistors are provided as current sensors to detect phase currents on the ground side of the lower arm switching elements 374, 375, and 376 of each phase. The phase currents detected by the current sensors are input to the microcomputer 43 and used for current feedback control, etc. The arrangement and configuration of the current sensors are not limited to the example shown in Figure 2, and any well-known technology may be used.

Motor relays 381, 382, and 383 are configured, for example, with MOSFETs, and are provided in the current paths connecting the inter-arm connection points of each phase of inverter 370 with winding sets 810 and 820. When motor relays 381, 382, and 383 are turned OFF, the reverse input from motor 80 to inverter 370 is cut off.

The control circuits 410, 420 include a microcomputer 43 and a driver IC 45, and control the operation of the inverter 370 based on input signals. The microcomputer 43 receives signals such as the rotation angle of the motor 80 detected by the rotation angle sensor 53 and the driver's steering torque detected by an external torque sensor 93. The microcomputer 43 performs control calculations based on the input signals and outputs command signals to the driver IC 45. The driver IC 45 outputs drive signals to the switching elements 371-376 of the inverter 370, the power supply relay 35, the reverse connection protection relay 36, and the motor relays 381, 382, and 383. The microcomputers 43 of the two control circuits 410, 420 may communicate control information, abnormality information, etc. between the systems via inter-microcomputer communication to perform coordinated control.

[Configuration of driving device]
Next, a specific configuration of the drive device 800 will be described. In this embodiment, the circuit board is "vertically arranged" along the axial direction of the rotation axis O. A conventional drive device in which the circuit board is vertically arranged is disclosed in Patent Document 1 (International Publication No. 2019/073594). FIG. 16 shows a configuration of the conventional technology based on FIGS. 2 and 3 of Patent Document 1 as a comparative example. The reference numerals in Patent Document 1 are quoted as they are, but because the letters "a" to "f" are added to the end, they are not confused with the reference numerals of this embodiment.

In the drive device of the comparative example, control boards 4a and 4b are arranged in a pair of arrangement sections 41d and 41e of the column section 41b, and power modules 50a and 50b are arranged in the other pair of arrangement sections 41f and 41g. Power modules 50a and 50b are configured by resin-sealing multiple switching elements that make up the inverter circuit while mounted on wiring. Smoothing capacitors 30a and 30b are fixed to support members 45a and 45b and are stacked vertically radially outward from the control boards 4a and 4b. This comparative example drive device has the following issues [A]-[C].

[A] In the device of the comparative example, the heat sink comprises a disk-shaped base and a rectangular parallelepiped pillar 41b standing upright in the center of the base. The base is located inside the inner circumferential wall of the cylindrical portion of the motor. Control boards 4a, 4b and power modules 50a, 50b are arranged on a pair of arrangement sections 41d, 41e and another pair of arrangement sections 41f, 41g located on the four sides of pillar 41b, and pillar 41b is entirely covered by a unit case (housing in Patent Document 1). In other words, the heat sink has no exposed parts. As a result, the heat dissipation effect from heat-generating elements that generate heat when current is applied to the motor, such as switching elements that make up the inverter, is insufficient.

[B] In the comparative example, the power modules 50a and 50b are attached in close contact with the heat sink via the signal lines 50c and 50d and the output terminals 51a and 51b. If the close contact with the heat sink is broken due to vibration caused by an external force, there is a risk that the heat dissipation effect from the power modules 50a and 50b will decrease.

[C] In the device of the comparative example, the cylindrical axes of the large components, capacitors 30a and 30b, are positioned so that they are perpendicular to the axial direction of the rotation shaft. Therefore, when using larger capacitors, there was an issue that they could not be accommodated in the gap space of the unit case (housing in Patent Document 1).

This embodiment therefore provides a drive device that solves these problems with a configuration in which the circuit boards are arranged vertically. That is, it provides a drive device that addresses problem A by providing a high heat dissipation effect from the heat-generating elements, addresses problem B by providing a high heat dissipation effect from the switching elements that make up the inverter, and addresses problem C by preventing radial size increases even when using larger components. In the following explanation of the effects of the configuration of this embodiment, the corresponding symbols for problems A to C are written in parentheses.

(First embodiment)
The configuration of the drive device of the first embodiment will be described with reference to Figures 3 to 9. Figures 3 to 6 show the drive device in an assembled state. Figures 7 to 9 show the heat sink 601 alone, and Figure 9 also shows the rotation angle sensor board 501. Here, the heat sink of the first embodiment is designated by the reference numeral "601", and the control unit is designated by the reference numeral "101". The drive device 800 mainly comprises a motor 80, a heat sink 601, a control unit 101, and a unit case 20.

The lower side of Figure 3 corresponds to the front side where the output shaft of the motor 80 is provided, and the upper side of Figure 3 corresponds to the rear side where the connector is provided. In the following description, the terms "upper" and "lower" may be used as appropriate for convenience, based on the viewing direction of Figure 3. The motor 80 includes a stator 84 and a rotor 86 housed in a motor case 83. The motor case 83 is formed in a generally bottomed cylindrical shape consisting of a bottom portion 831 and a cylindrical portion 832, with the control unit 101 provided on the opening side. The outer wall of the opening side of the cylindrical portion 832 is provided with a fastening receiving portion 837 used to fasten to the partition wall portion 70 of the heat sink 601.

The stator 84 has two three-phase winding groups 810, 820 wound around an iron stator core 845 fixed inside the cylindrical portion 832 of the motor case 83. The stator core 845 is made of laminated steel plates or the like. When electricity is applied from the control unit 101 to the winding groups 810, 820 via the motor wires 85, a rotating magnetic field is formed in the stator 84.

The rotor 86 has multiple permanent magnets 866 attached to the outer periphery of an iron rotor core 865. The rotor core 865 is made of laminated steel plates or the like. The rotor 86 rotates around a shaft 87 mounted on the rotation axis O due to the rotating magnetic field generated by the stator 84. The shaft 87 fixed to the rotor 86 is rotatably supported by a front bearing 873 held in the bottom 831 of the motor case 83 and a rear bearing 874 held in the partition wall 70 of the heat sink 601. In the first embodiment, a sensor magnet 881 for detecting the rotation angle is attached to the rear end face of the shaft 87.

The heat sink 601 is made of an aluminum alloy or the like. As shown in Figures 7 to 9, the heat sink 601 has a substantially rectangular parallelepiped pillar portion 610 with the rotation axis O as its axis of symmetry, and a plate-shaped partition wall portion 70. The pillar portion 610 of the heat sink 601 in the first embodiment has a hollow shape with a recess 649 formed on one surface.

A heat sink 601 with a hollow pillar portion 610 is suitable for manufacturing the pillar portion 610 and partition wall portion 70 as a single unit by casting or die-casting. By forming the single unit, heat transfer is less likely to be blocked, enabling efficient heat dissipation (Challenge A). However, the pillar portion 610 and partition wall portion 70 may also be manufactured as two separate components and then joined by welding or brazing.

A pair of first arrangement portions 631, 632 and one second arrangement portion 641 that support the control unit 101 are provided on three side surfaces of the pillar portion 610, facing radially outward. The pair of first arrangement portions 631, 632 are arranged parallel to each other with the rotation axis O in between. The one second arrangement portion 641 is perpendicular to the pair of first arrangement portions 631, 632 and connects the pair of first arrangement portions 631, 632. The connector side end face 65, which is the end face of the pillar portion 610 opposite the motor 80, faces the inner wall of the top panel portion 21 of the unit case 20.

Support portions 67 to which the power circuit boards 301, 302 are fixed are protruding from the first arrangement portions 631, 632 at multiple locations, i.e., four locations near both ends in the axial and circumferential directions of the rotation axis O. Support portions 67 to which the control circuit board 400 is fixed are protruding from the second arrangement portion 641 at two locations on the circumferential centerline, one at each end in the axial direction. The top surface of each support portion 67 forms a flat seat surface 68.

The surface of the second arrangement portion 641 facing the rotation axis O functions as an exposed heat dissipation surface 643. As described below, the surface of the second arrangement portion 64 facing the rotation axis O corresponds to the surface opposite to the surface to which the control circuit board 400 is fixed. In the first embodiment, the heat dissipation surface 643 is secured by forming a recess 649 in the column portion 610, thereby improving the heat dissipation effect (issue A).

The partition wall 70 is plate-shaped and perpendicular to the rotation axis O, separating the motor 80 and the control unit 101 in the axial direction of the rotation axis O. By isolating the motor 80 and the control unit 101 with the partition wall 70, heat from both can be efficiently dissipated (issue A). The upper surface 72 of the main body 71 of the partition wall 70 is connected to the column 610 side. The lower surface 73 of the main body 71 faces the stator 84 and rotor 86 of the motor 80.

A shaft hole 75 is formed in the center of the partition wall 70, into which the rear end of the shaft 87 is inserted. A rotation angle sensor board 501, on which a rotation angle sensor 53 is mounted, is installed directly above the shaft hole 75 at the bottom of the recess 649 of the pillar 610. The rotation angle sensor 53 detects the rotation angle of the rotor 86 based on changes in magnetic flux of a sensor magnet 881 attached to the rear end face of the shaft 87. The rotation angle signal detected by the rotation angle sensor 53 is transmitted to the microcomputer 43 via the rotation angle signal wiring 54. A motor wire hole 76, into which three-phase, dual-system motor wires 85 are inserted, is formed on the outside of the pillar 610.

Fastening portions 77 for fastening to the motor case 83 are provided at multiple locations (e.g., three locations) on the outer periphery of the main body 71. Screws 17 inserted through threaded holes 78 of the fastening portions 77 thread into fastening receptacles 837 of the motor case 83, thereby fixing the heat sink 601 and motor 80 together.

The outer peripheral side surface 74 of the partition wall 70 is exposed to the outside. In other words, whereas in the comparative example the entire heat sink is covered by other components, in this embodiment, the heat sink 601 is fixed to the motor 80 with a portion of it exposed to the outside. This allows heat from heat-generating elements such as the inverter elements 371-376 to be efficiently released to the outside via the heat sink 601, resulting in a high heat dissipation effect (Challenge A).

Next, the control unit 101 will be described. Comprehensively describing all embodiments, the control unit 10 has "one or more circuit boards fixed to the first arrangement portion or the second arrangement portion of the column portion of the heat sink." In the first embodiment, the control unit 101 has three circuit boards 301, 302, and 400, while in the second embodiment, the control unit 102 has four circuit boards 301, 302, 401, and 402. Note that the "circuit boards" do not include the rotation angle sensor board 501. The three circuit boards in the first embodiment are two power circuit boards 301 and 302 and one control circuit board 400. Heat-generating elements are mounted on at least the power circuit boards 301 and 302 as "at least one circuit board."

Figure 4 shows the mounting layout of the power circuit board 301 of the first system. Since the mounting layout of the power circuit board 302 of the second system is similar, the power circuit board 301 of the first system will be used as an example and explained with reference to Figure 2. The power circuit board 301 of the first system is mounted with multiple switching elements 371-376 that constitute the inverter 370 in the power circuit 310 that supplies power to the motor 80. The upper arm elements 371-373 of each phase are connected to the power terminal 25p of the power system connector 23 via the power line 27p. The lower arm elements 374-376 of each phase are connected to the ground terminal 25g of the power system connector 23 via the ground line 27g.

In addition, a power supply relay 35 and a reverse connection protection relay 36 are mounted on the power supply line 27p, and motor relays 381, 382, and 383 are mounted on the motor 80 side of the inverter 370. As shown by dashed lines (i.e., hidden lines) in Figure 4, the inverter elements 371-376, which are heat-generating elements, and the relays 35, 36, 381, 382, and 383 are mounted on the surface of the power circuit board 301 facing the heat sink 601. A heat dissipation gel 18 is filled between the power circuit board 301 and the heat sink 601. This allows for efficient heat dissipation (Challenge A).

The large components, the choke coil 33 and capacitor 34, are arranged on the opposite side of the power circuit board 301 from the heat sink 601. The arrangement of the large components will be described later after discussing the unit case 20. In this way, the two power circuit boards 301, 302 are provided with two systems of power circuits 310, 320, each of which supplies power to the corresponding winding sets 810, 820 of the motor 80. The configuration is simplified by using circuit boards with the same specifications in common.

As shown in Figures 3 to 6, two power circuit boards 301, 302 are fixed to a pair of first placement sections 631, 632. In this embodiment, instead of using a power module as in the comparative example, the power circuit boards 301, 302, on which the inverter elements 371-376 are directly mounted individually, are fixed to the first placement sections 631, 632 of the heat sink 601. This makes it possible to maintain a high heat dissipation effect from the inverter elements 371-376, regardless of vibrations caused by external forces (Challenge B). Furthermore, because a power module is not used, the wiring patterns can be made thicker, reducing loss.

More specifically, the power circuit boards 301, 302 are fastened by board screws 16 while abutting against bearing surfaces 68 of support portions 67 that protrude from the first arrangement portions 631, 632 at multiple locations in the axial direction of the rotation axis O. A locking adhesive may be applied to the outer periphery of the board screws 16 or to the screw holes. For example, the support portions 67 are provided at positions corresponding to one end and the other end of the power circuit boards 301, 302 in the axial direction of the rotation axis O, i.e., at two locations in the axial direction. This allows the power circuit boards 301, 302 to be stably fixed to the heat sink 601. Therefore, heat generated by the inverter elements 371-376 mounted on the power circuit boards 301, 302 is efficiently dissipated (Challenge B).

Control circuit board 400 is mounted with components for control circuits 410, 420 that control the operation of inverter 370 based on input signals. In the first embodiment, one control circuit board 400 is provided with two control circuits 410, 420 that control the operation of two inverters 370. This reduces the number of components required.

In Figure 3, the microcomputer 43, driver IC 45, etc. of the first system control circuit 410 are mounted to the right of the center line of the control circuit board 400, and the microcomputer 43, driver IC 45, etc. of the second system control circuit 420 are mounted to the left of the center line. The components of the control circuits 410, 420 of each system are arranged symmetrically. This ensures that the conductor distances are equal for each system, resulting in good balance. As with the power circuit boards 301, 302, the components of the control circuits 410, 420 are mounted on the surface of the control circuit board 400 facing the heat sink 601. In addition, heat dissipation gel 18 is filled between the control circuit board 400 and the heat sink 601.

An external signal is input to the microcomputer 43 from the control terminal 26 of the control system connector 24 via the external signal wiring 28. A rotation angle signal is also input from the rotation angle sensor 53 mounted on the rotation angle sensor board 501 via the rotation angle signal wiring 54. The microcomputer 43 and driver IC 45 are connected by a communication line 44. The driver IC 45 outputs drive signals via drive signal wiring 46 to the inverter elements 371-376 of the power circuit boards 301 and 302 and to each of the relays 35, 36, 381, 382, and 383.

As shown in Figures 3 to 6, in the first embodiment, one control circuit board 400 is fixed to one second arrangement portion 641. As with the power circuit boards 301 and 302, the control circuit board 400 is fastened by board screws 16 while abutting against the bearing surfaces 68 of support portions 67 that protrude from the second arrangement portion 641 at multiple locations in the axial direction of the rotation axis O.

The unit case 20 is made of a resin material and has a cylindrical shape with a bottom and a top plate 21 and an outer cylinder 22. The unit case 20 covers the control unit 101 supported by the column 610. For example, the lower end of the outer cylinder 22 is inserted into and adhered to an annular groove formed on the upper surface 72 of the main body 71 of the partition 70. A power supply connector 23 and a signal system connector 24 are provided on the top plate 21. As shown in FIG. 5, in a complete dual-system configuration, a power supply connector 23 and a signal system connector 24 are provided redundantly for each system. In contrast, in a dual-drive system configuration in which a common battery or external signal is used for both systems, a single set of connectors 23, 24 may be provided.

As shown in Figures 3 and 6, the choke coil 33 and capacitor 34, which are cylindrical electronic components defined as large components, are arranged in the gap between the cylindrical unit case 20 and the power circuit boards 301 and 302. The choke coil 33 and capacitor 34 are arranged inside the unit case 20 with their cylindrical axes aligned with the axial direction of the rotation axis O.

Furthermore, the choke coils 33 and capacitors 34 of the same system are arranged in series along the axial direction of the rotation axis O. Furthermore, in the modified example shown in Figure 10, in a configuration in which each system includes multiple capacitors 34, one or more choke coils 33 and multiple capacitors 34 are arranged in series along the axial direction of the rotation axis O. In other words, at least some of the multiple large components are arranged in series along the axial direction of the rotation axis O.

Here, "arranged in series" means that other large components are included within the projected range of the large component with the largest diameter. The large components do not need to be arranged strictly on the same axis, and may be eccentric within the projected range. This allows the large components to be arranged more efficiently in the gaps within the unit case 20 compared to the comparative example in which the cylindrical axis of the capacitor is arranged perpendicular to the axial direction of the rotation shaft (Challenge C). Therefore, even if a larger-sized large component is used, it can be efficiently accommodated in the gaps within the unit case 20.

Furthermore, as shown in Figure 6, the large components 33 and 34 of the first and second systems are positioned point-symmetrically with respect to the rotation axis O. This allows the large components 33 and 34 to be efficiently positioned in the gap space where the radial distance from the rotation axis O is maximized (Challenge C).

In addition, the power circuit boards 301, 302 on which the large components 33, 34 are mounted are fixed to support parts 67 provided at multiple locations on the first placement parts 631, 632. The large components 33, 34 of each system are arranged on a plane X whose cylindrical axis passes through the middle of the multiple support parts 67 in the circumferential direction of the rotation axis O. This allows the large components 33, 34 to be arranged in a balanced manner on the stably fixed power circuit boards 301, 302 (Challenge C).

Second Embodiment
With reference to Figures 11 to 15, the configuration of the drive unit of the second embodiment will be described, particularly the differences from the first embodiment. Figures 11 to 12 show the drive unit in an assembled state. Figures 13 to 15 show the heat sink 602 alone, and Figure 9 also shows the rotation angle sensor board 502. Here, the heat sink of the second embodiment is designated by the reference numeral "602," and the control unit is designated by the reference numeral "102."

The drive unit 800 mainly comprises a motor 80, a heat sink 602, a control unit 102, and a unit case 20. The motor 80 is the same as in the first embodiment except for the placement of the sensor magnet 882. The unit case 20 is the same as in the first embodiment. The right side view of the power circuit board 301 in Figure 11 corresponds to Figure 4 of the first embodiment.

As shown in Figures 13 to 15, the heat sink 602 of the second embodiment has a solid pillar portion 620 without any recesses, and a plate-shaped partition portion 70. For example, the heat sink 602 is formed by joining two parts, the pillar portion 620 and the partition portion 70, by welding or brazing. In other words, the motor-side end surface 66 of the pillar portion 620 is joined to the upper surface 72 of the partition portion 70. In particular, the outer periphery of the motor-side end surface 66 is firmly fixed to the upper surface 72 of the partition portion 70. This simplifies manufacturing. However, the pillar portion 620 and the partition portion 70 may also be manufactured as a single molded component.

A pair of first arrangement portions 631, 632 and a pair of second arrangement portions 641, 642 that support the control unit 102 are provided on the four side surfaces of the pillar portion 620 facing radially outward. The pair of first arrangement portions 631, 632 are the same as in the first embodiment. The pair of second arrangement portions 641, 642 are perpendicular to the pair of first arrangement portions 631, 632 and connect the pair of first arrangement portions 631, 632. Similar to the first arrangement portions 631, 632, the second arrangement portions 641, 642 have protruding support portions 67 at four locations near both axial and circumferential ends of the rotation axis O, to which the control circuit boards 401, 402 are fixed.

In the second embodiment, a sensor magnet 882 for detecting the rotation angle is attached to the outer periphery of the shaft 87. The sensor magnet 882 and the rotation angle sensor board 502 on which two rotation angle sensors 53 are mounted are disposed on the motor 80 side of the partition 70. This allows for configurations where there is no recess in the column 620 and the rotation angle sensor board cannot be installed on the control unit 102 side of the partition 70. As shown in FIG. 15 , the two rotation angle sensors 53 detect the rotation angle of the rotor 86 based on changes in magnetic flux from the sensor magnet 882. The rotation angle signals detected by each rotation angle sensor 53 are transmitted to the microcomputer 43 of each system via the rotation angle signal wiring 54.

As described above, in the second embodiment, the control unit 102 has four circuit boards 301, 302, 401, and 402. As shown in FIG. 12 , the two power circuit boards 301 and 302 are fixed to a pair of first arrangement portions 631 and 632, as in the first embodiment. The two control circuit boards 401 and 402 are fixed to a pair of second arrangement portions 641 and 642. The control circuit boards 401 and 402 are fastened by board screws 16 while abutting against the bearing surfaces 68 of support portions 67 that protrude from each of the second arrangement portions 641 and 642 at multiple locations in the axial direction of the rotation axis O.

Two control circuit boards 401, 402 are provided with two control circuits 410, 420 for each system, which control the operation of the two inverters 370. As shown in FIG. 11, the control circuit board 401 is equipped with a microcomputer 43, driver IC 45, etc. for the first system control circuit 410. A rotation angle signal is input to the microcomputer 43 from a rotation angle sensor 53 mounted on the rotation angle sensor board 502 via a rotation angle signal wiring 54. A second system control circuit 420 is similarly provided on the control circuit board 402. The configuration is simplified by using circuit boards with the same specifications in common.

The other configurations of the heat sink 602 and control unit 102 in the second embodiment are the same as those in the first embodiment. The effects of the common configurations are as described above.

As described above, the second embodiment differs from the first embodiment mainly in the following points.
(1) The control unit 102 has a total of four circuit boards, including two control circuit boards 401 and 402.
(2) The solid pillar portion 620 has a pair of second arrangement portions 641 and 642 .
(3) The sensor magnet 882 and the rotation angle sensor board 502 are disposed on the motor 80 side of the partition wall 70 .

However, these features are not necessarily realized as a set, and items (2) and (3) may be combined independently with the three-board configuration of the first embodiment. For example, in the first embodiment, a solid pillar portion 620 may be used, and the control circuit board 400 may be fixed to only one side of the pair of second placement portions 641, 642. Also, in the first embodiment, the configuration of the sensor magnet and rotation angle sensor board may be replaced with that of the second embodiment.

(Other embodiments)
(a) The cross section of the column portion of the heat sink perpendicular to the rotation axis is not limited to a rectangle, but may be a parallelogram or a trapezoid. The shape of the partition wall and the fastening structure to the motor case are not limited to those of the above embodiment, and any shape or structure may be used as long as it provides the same effects as those of the above embodiment.

(b) The drive device of the present invention is not limited to a two-system configuration and may also be applied to a single-system motor drive system. In this case, one power circuit board may be fixed to only one of the pair of first arrangement sections. Alternatively, the electronic components constituting one power circuit may be mounted separately on two power circuit boards and fixed to the pair of first arrangement sections. Furthermore, in the case of a two-system configuration, rather than dividing the two power circuits into two power circuit boards for each system, the electronic components for the two systems may be mounted separately on two power circuit boards depending on the type of electronic component, etc.

(c) In a configuration in which two control circuits are mounted on a single control circuit board, if an asymmetric arrangement is more advantageous for wiring or layout reasons, the components of each system do not have to be arranged symmetrically.

(d) The method of fastening the power circuit board and control circuit board to the column is not limited to fastening with screws, and may also be crimping or pressure welding. Furthermore, as mentioned above, screw fastening and the application of a thread locking adhesive may be used in combination.

(e) The arrangement of large components is not limited to the above embodiment, and some or all of the large components may be arranged so that the axis of the cylinder is different from the axial direction of the rotation shaft. Furthermore, multiple large components do not have to be arranged in series.

(f) The drive unit 800 of the present invention is not limited to being used as a steering assist motor in an electric power steering device, but may also be used as a reaction motor or steering motor in a steer-by-wire system, or as a drive unit for any other motor.

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

101, 102 (10) ...control unit,
20...unit case,
301, 302...power circuit board (circuit board),
33...Choke coil (large part),
34... Capacitor (large part),
370: Inverter; 371-376: Switching elements (heat generating elements);
400, 401, 402...Control circuit board (circuit board),
601, 602...heat sink,
610, 620... Column part,
631, 632...first arrangement part,
641, 642... second arrangement part,
80...Motor,
84: stator, 86: rotor, 87: shaft.

Claims (5)

a motor (80) including a stator (84) and a rotor (86) that rotates around a shaft (87) provided on a rotation axis (O);
a control unit (101, 102) that is provided integrally with the motor on one side of the rotation shaft in the axial direction and that drives and controls the motor;
a heat sink (601, 602) including a pair of first arrangement portions (631, 632) arranged on either side of the rotation axis, and one or a pair of second arrangement portions (641, 642) connecting the pair of first arrangement portions, which are provided facing radially outward, and having pillar portions (610, 620) that support the control unit;
a cylindrical unit case (20) that covers the control unit supported on the pillar portion;
A drive device comprising:
the control unit has one or more circuit boards (301, 302, 400, 401, 402) fixed to the first arrangement portion or the second arrangement portion of the column;
If the choke coil (33) and the capacitor (34), which are cylindrical electronic components that constitute the control unit, are defined as large components,
A drive device in which the multiple large parts are arranged within the unit case with their cylindrical axes aligned with the axial direction of the rotation shaft. The drive unit described in claim 1, wherein at least some of the multiple large components are arranged in series along the axial direction of the rotation shaft. The drive unit described in claim 2, wherein one or more of the choke coils and one or more of the capacitors are arranged in series along the axial direction of the rotating shaft. The drive unit described in any one of claims 1 to 3, wherein the multiple large components are arranged in point-symmetric positions with respect to the rotation axis. The circuit board on which the large component is mounted is fixed to support portions (67) provided at a plurality of locations in the first arrangement portion,
5. The drive device according to claim 1, wherein the large component has a cylindrical axis arranged on a plane that passes through midpoints of the plurality of support portions in the circumferential direction of the rotation shaft.