Integrated electric power steering device

Abstract

An integrated electric power steering device according to the present disclosure comprises a motor (30), and a control unit (10) that is provided integrally with the motor and controls the motor. The control unit is provided with: a wiring board (1) that has an electrically insulating base material (11), and electrically conductive wiring formed on the base material; a connector (4) that has a connector terminal connected to the wiring board; and a circuit component that is surface-mounted on the wiring board. A through-hole penetrating from one surface to the other surface is formed in the wiring board. At least a portion of the wiring is formed between the through-hole and the circuit component along a direction tangent to a circle that is concentric with the through-hole.

Description

Integrated electric power steering device

[0001] The present disclosure relates to an integrated electric power steering device.

[0002] Conventionally, there is an electric power steering device that includes a wiring board having electronic components that constitute an inverter circuit and a control circuit that controls the inverter circuit, and a motor. The motor winding ends and power terminals are connected to the wiring board, for example, by solder joints. Flux is sometimes used at solder joints to improve solderability. When electronic components are mounted near solder joints on the wiring board, flux can adhere to the electronic components. When flux adheres to electronic components, ion migration occurs, which can affect the insulation between the electrodes of the electronic components. Removing the flux is an effective solution to this problem, but this requires a lengthy cleaning process.

[0003] In contrast, there are soldering techniques that do not require flux cleaning. For example, Patent Document 1 discloses a technique in which oxides on the electrodes and solder of electronic components are removed using a nitrogen-hydrogen mixed gas containing hydrogen, which is a reducing gas, before soldering.

[0004] JP 2014-157858 A

[0005] With the technology disclosed in Patent Document 1, it was not easy to solve the problem of reduced insulation caused by flux.

[0006] In view of the above circumstances, the present disclosure has an object to provide an integrated electric power steering device that can suppress the influence of flux on electrical characteristics.

[0007] One aspect of an integrated electric power steering device according to the present disclosure comprises a motor and a control unit that is integral with the motor and controls the motor, the control unit comprising a wiring board having an electrically insulating base material and conductive wiring formed on the base material, a connector having connector terminals connected to the wiring board, and circuit components surface-mounted on the wiring board, wherein a through hole is formed in the wiring board, penetrating from one side to the other, and at least a portion of the wiring is formed between the through hole and the circuit component along a tangent to a circle concentric with the through hole.

[0008] According to the present disclosure, it is possible to provide an integrated electric power steering device that can suppress the influence of flux on electrical characteristics.

[0009] 1 is a cross-sectional view of an integrated electric power steering device according to Embodiment 1. FIG. 2 is a circuit diagram of the integrated electric power steering device according to Embodiment 1. FIG. 3 is a plan view of a wiring board of the integrated electric power steering device according to Embodiment 1. FIG. 4 is a plan view of a part of the wiring board of the integrated electric power steering device according to Embodiment 1. FIG. 5 is a cross-sectional view of a part of the wiring board of the integrated electric power steering device according to Embodiment 1. FIG. 6 is a cross-sectional view of a part of the wiring board of the integrated electric power steering device according to Embodiment 1. FIG. 7 is a cross-sectional view of a part of the wiring board of the integrated electric power steering device according to Embodiment 1. FIG. 8 is a cross-sectional view of a part of the wiring board of the integrated electric power steering device according to Embodiment 2. FIG. 9 is a cross-sectional view of a part of the wiring board of the integrated electric power steering device according to Embodiment 2. FIG. 10 is a cross-sectional view of a part of the wiring board of the integrated electric power steering device according to Embodiment 2.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the scope of the present disclosure is not limited to the following embodiments and can be modified as desired within the scope of the technical concept of the present disclosure.

[0011] Embodiment 1 Fig. 1 is a cross-sectional view of an integrated electric power steering device 100 according to Embodiment 1. Fig. 2 is a circuit diagram of the integrated electric power steering device 100. Hereinafter, the integrated electric power steering device will be simply referred to as the "electric power steering device."

[0012] As shown in FIG. 1 , the electric power steering device 100 includes a motor 30 and a control unit 10 that controls the motor 30 .

[0013] The motor 30 includes a motor housing 31, a rotating shaft 32, and a motor body 33. The motor 30 is, for example, a three-phase brushless motor.

[0014] The motor housing 31 includes a cylindrical portion 31a and a bottom portion 31b. The motor housing 31 is made of, for example, metal (e.g., aluminum). A through-hole 31c is formed in the center of the bottom portion 31b, through which the rotary shaft 32 passes. A first bearing 41 is attached to the bottom portion 31b.

[0015] The motor body 33 is housed in the cylindrical portion 31a. The motor body 33 includes a rotor 36 and a stator 37. The rotor 36 is provided around the rotating shaft 32. A plurality of permanent magnets are provided on the outer peripheral surface of the rotor 36. The stator 37 is provided on the outer peripheral side of the rotor 36. The stator 37 includes the windings 30a.

[0016] A motor frame 40 is provided on top of the cylindrical portion 31a of the motor housing 31. The motor frame 40 is made of metal (e.g., aluminum). A through-hole 40a is formed in the center of the motor frame 40, through which the rotating shaft 32 passes. A second bearing 42 is attached to the motor frame 40. The first bearing 41 and the second bearing 42 rotatably support the rotating shaft 32.

[0017] A sensor magnet 35 is attached to the upper end of the rotating shaft 32. The sensor magnet 35 rotates together with the rotating shaft 32. The sensor magnet 35 has one or more north poles and one or more south poles. The sensor magnet 35 rotates together with the rotating shaft 32.

[0018] The control unit 10 includes a wiring board 1, a connector assembly 4 (connector), and circuit components 29 (see FIG. 4). The wiring board 1 includes a substrate 11, a control circuit 2, and wiring 6 (see FIG. 4). The substrate 11 is electrically insulating. The substrate 11 is formed in a flat plate shape. The wiring board 1 is, for example, a multilayer printed circuit board in which multiple insulating layers and multiple conductor layers are stacked.

[0019] The wiring board 1 is fixed to the motor housing 31 with, for example, screws. The wiring board 1 is covered with a cover 3. The cover 3 is fixed to the motor housing 31. The cover 3 has a function of protecting the wiring board 1 from electromagnetic noise and a function of suppressing leakage of electromagnetic noise from the wiring board 1. The cover 3 is made of metal (for example, aluminum).

[0020] 2, the control circuit 2 includes a CPU 21, inverter circuits 25 and 26 (see FIG. 3), an input circuit 23, a power supply circuit 24, and an FET driver circuit 22. The CPU 21 performs, for example, calculations to control the rotation of the motor 30. The CPU 21 may be mounted on either side of the substrate 11. In this embodiment, the control circuit 2 includes one CPU 21.

[0021] The inverter circuits 25, 26 (first inverter circuit 25 and second inverter circuit 26) supply AC power to the motor 30 (see FIG. 1). The inverter circuits 25, 26 include, for example, field-effect transistors, smoothing capacitors, and choke coils. The field-effect transistors perform current switching. The smoothing capacitors suppress voltage fluctuations associated with switching. The choke coils suppress noise leakage from the control unit 10 to the outside and noise inflow from the outside to the control unit 10.

[0022] The inverter circuits 25 and 26 each include a bridge circuit that connects the windings 30a of each phase of the motor 30 to the battery 5 (power source). Each bridge circuit supplies current to each of the three-phase (U, V, W) windings 30a of the motor 30.

[0023] The input circuit 23 receives various input signals. Specific examples of the input signals include information from the sensors 27, the voltages of various parts in the inverter circuit, the magnitude of the drive current of the motor 30 detected by the inverter circuit, and the rotation angle detected by the MR sensor 20. Specific examples of the information from the sensors 27 include the vehicle speed detected by a vehicle speed sensor and the steering torque of the steering wheel detected by a torque sensor.

[0024] The power supply circuit 24 determines the power supply voltage required for the operation of electronic circuits such as the CPU 21. At least one power supply circuit 24 is provided. The FET driver circuit 22 (FET: Field Effect Transistor) drives the field effect transistors of the inverter circuits 25 and 26. The control circuit 2 may also include a torque sensor interface circuit, a vehicle communication interface circuit, etc.

[0025] The UVW terminals of the motor 30 are electrically connected to the wiring board 1. By electrically connecting the UVW terminals to the wiring board 1, a current is supplied from the inverter circuit to the motor 30, causing the rotating shaft 32 to rotate. The UVW terminals are joined to the wiring board 1 by, for example, partial jet soldering.

[0026] As shown in Fig. 1, a magnetoresistive sensor (hereinafter referred to as "MR sensor") 20 is mounted on a wiring board 1. The MR sensor 20 is mounted, for example, on a non-switching element surface 2b (the lower surface in Fig. 1) of the wiring board 1. The MR sensor 20 detects the rotation angle of the rotating shaft 32 by detecting a magnetic field generated by a sensor magnet 35. By improving the rotation angle detection accuracy, the motor 30 can be rotated with good controllability.

[0027] The MR sensor 20 is disposed, for example, in an area overlapping with the sensor magnet 35 when viewed from the axial direction of the motor 30. By disposing the MR sensor 20 in an area overlapping with the sensor magnet 35, the accuracy of detecting the rotation angle can be improved. The MR sensor 20 may also be disposed on the switching element mounting surface 2a of the wiring board 1. The MR sensor 20 may also be disposed outside the area overlapping with the sensor magnet 35.

[0028] 3 is a plan view of the switching element mounting surface 2a side of the wiring board 1. As shown in FIG. 3, in this embodiment, the first inverter circuit 25 supplies AC power to the motor 30 (see FIG. 1). The second inverter circuit 26 supplies AC power to the motor 30 (see FIG. 1) via a path different from that of the first inverter circuit 25.

[0029] The first inverter circuit 25 has upper arm switching elements 25uU, 25uV, 25uW, lower arm switching elements 25dU, 25dV, 25dW, motor relay switching elements 25mU, 25mV, 25mW, a power supply relay, and shunt resistors 25rV, 25rW, 25rU.

[0030] The second inverter circuit 26 includes upper-arm switching elements 26uU, 26uV, and 26uW, lower-arm switching elements 26dU, 26dV, and 26dW, motor relay switching elements 26mU, 26mV, and 26mW, a power supply relay, and shunt resistors 26rV, 26rW, and 26rU. The reference numerals of the elements of the inverter circuits 25 and 26 include reference numerals (u, v, and w) corresponding to the phases (U, V, and W) of the motor 30.

[0031] The upper arm switching elements 25uU, 25uV, 25uW, 26uU, 26uV, and 26uW are connected to, for example, the positive electrode of the battery 5 (see FIG. 2). The lower arm switching elements 25dU, 25dV, 25dW, 26dU, 26dV, and 26dW are connected to, for example, the negative electrode of the battery 5 (see FIG. 2).

[0032] Motor relay switching elements 25mU, 25mV, 25mW, 26mU, 26mV, and 26mW are provided as a motor relay between the inverter circuit and the motor 30. The power supply relay can switch between conducting and blocking current flowing from the power supply to the motor via the inverter circuit. The reverse polarity protection relay protects the inverter circuit from reverse current flow when the power supply is reverse-connected. The power supply relay and reverse polarity protection relay are provided in the power supply line connecting the power supply and the inverter circuit. The power supply relay and reverse polarity protection relay are connected in series. The reverse polarity protection relay is connected so that its parasitic diode is oriented in the opposite direction to the power supply relay.

[0033] The inverter circuits 25 and 26 may or may not include a motor relay, a power supply relay, and a reverse connection protection relay.

[0034] 1, the connector ASSY 4 connects to the control unit 10 a battery voltage line, a ground line, and the like required for the control unit 10 to control and drive the motor 30. The connector ASSY 4 has, for example, a plurality of connectors.

[0035] The connector ASSY 4 can combine, for example, a battery voltage line, a ground line, a torque sensor signal, a vehicle communication signal, etc. The connector ASSY 4 may also include a connector for the torque sensor signal and the vehicle communication signal, separate from the connectors for the battery voltage line and the ground line, depending on the vehicle design situation, for example.

[0036] The connector ASSY 4 has, for example, metal bus bars, terminals, etc. extending from the terminals of each connector. The connector ASSY 4 is electrically connected to the wiring board 1. The connector ASSY 4 is, for example, a component that integrally combines connectors, bus bars, terminals, etc. The connector terminals (connector terminals) and the wiring board 1 are joined by, for example, partial jet soldering.

[0037] The wiring board 1 is fixed to the motor housing 31. The connector assembly 4 is provided on the cover 3. The circuit components 29 are provided on the wiring board 1. Therefore, the control unit 10 is provided integrally with the motor 30.

[0038] Fig. 4 is a plan view of a portion of the wiring board 1. Fig. 5 is a cross-sectional view of a portion of the wiring board 1. Fig. 5 is a cross-sectional view taken along line II shown in Fig. 4. As shown in Figs. 4 and 5, the wiring board 1 has through holes 50 formed therein for soldering UVW terminals, connector terminals, etc. The through holes 50 are formed so as to penetrate the wiring board 1 from one surface (switching element mounting surface 2a) of the wiring board 1 (specifically, the base material 11) to the other surface (switching element non-mounting surface 2b).

[0039] Circuit components 29 are surface-mounted on the switching element mounting surface 2a of the wiring board 1. Examples of the circuit components 29 include upper arm switching elements 25uU and 26uV, and motor relay switching elements 25mU, 25mW, 26mV, and 26mW. The through holes 50 are formed in positions close to the circuit components 29. The circuit components 29 may be electronic components (capacitors, resistors, diodes, etc.) that constitute noise suppression components, surge protection components, etc. The circuit components 29 may be, for example, at least one of the switching elements (upper arm switching elements, motor relay switching elements, etc.) and the electronic components.

[0040] 4, conductive wiring 6 is provided on the switching element mounting surface 2a between the through hole 50 and the circuit component 29. The wiring 6 has a certain thickness and is therefore formed to protrude from the switching element mounting surface 2a.

[0041] When viewed from a direction perpendicular to the switching element mounting surface 2a, at least a portion of the wiring 6 is formed along a tangent direction of a circle C that is concentric with the through hole 50. The circle C has a common center with the through hole 50. At least a portion of the wiring 6 is located between the through hole 50 and the circuit component 29. The circuit component 29 shown in FIG. 4 is the circuit component closest to the target through hole 50 (the central through hole 50 of the three through holes 50 shown in FIG. 4).

[0042] The wiring 6 can be made of a metal such as copper. The wiring 6 can be formed by, for example, an additive method or a subtractive method. The direction in which the wiring 6 extends is perpendicular to a line L1 connecting the centers of the through-hole 50 and the circuit component 29 (see FIG. 4). The wiring 6 is perpendicular to the line L1 at least at the intersection with the line L1.

[0043] The wiring 6 prevents the flux applied near the through-hole 50 from wetting and spreading over the surface of the wiring board 1 toward the circuit components 29 when soldering the terminals (UVW terminals, connector terminals, etc.) to the wiring board 1. The wiring 6 prevents the flux from reaching the circuit components 29.

[0044] 6 and 7 are cross-sectional views of a portion of the wiring board 1. In the example shown in FIG. 6, a UVW terminal 101 (motor terminal) of the motor 30 is inserted into the through hole 50. The UVW terminal 101 is joined to the wiring board 1 by a solder joint 102 formed in the through hole 50. The solder joint 102 is formed, for example, from solder containing flux. Note that the flux does not have to be contained in the solder. In this case, flux is applied to the wiring board 1 separately from the solder.

[0045] 7, a connector terminal 103 of the connector ASSY 4 (see FIG. 1) is inserted into the through hole 50. The connector terminal 103 is joined to the wiring board 1 by a solder joint 102.

[0046] The operation of the control circuit 2 will now be described. The CPU 21 calculates the magnitude of the drive current to be supplied to each winding 30a of the motor 30 based on an input signal acquired via the input circuit 23. Based on the calculation result, the CPU 21 issues control instructions to the inverter circuits 25, 26. Control by the inverter circuits 25, 26 is performed for each phase (U, V, W) of the motor 30. The inverter circuits 25, 26 cause a predetermined current to flow through the winding 30a of each phase (U, V, W).

[0047] The lower end of the rotating shaft 32 of the motor 30 is used as an output end. A driven object (e.g., a steering system of a vehicle) is connected to the lower end of the rotating shaft 32. A reducer or the like may be interposed between the rotating shaft 32 and the driven object. The output of the motor 30 is transmitted to the driven object via the rotating shaft 32.

[0048] In the electric power steering device 100 according to this embodiment, at least a portion of the wiring 6 is formed between the through hole 50 and the circuit component 29 along the tangential direction of the circle C concentric with the through hole 50, which can suppress adhesion of flux to the circuit component 29. This can reduce the risk of the circuit component 29 failing due to ion migration.

[0049] Embodiment 2 Fig. 8 is a plan view of a portion of a wiring board 201 of an electric power steering device 200 according to Embodiment 2. Fig. 9 is a cross-sectional view of a portion of the wiring board 201. Fig. 9 is a cross-sectional view taken along line II-II shown in Fig. 8. Components common to the electric power steering device 100 according to Embodiment 1 are given the same reference numerals, and description thereof will be omitted.

[0050] 8 and 9, a first through hole 50 is formed in the wiring board 201. The wiring board 201 does not have the wiring 6 (see FIG. 4), but instead has a plurality of second through holes 51 formed between the first through hole 50 and the circuit component 29. In this respect, the wiring board 201 differs from the wiring board 1 shown in FIG.

[0051] The second through holes 51 are formed penetrating the wiring board 1 from one surface (switching element mounting surface 2a) of the wiring board 1 to the other surface (switching element non-mounting surface 2b). At least some of the second through holes 51 are arranged along a tangent direction of a circle C concentric with the first through hole 50. At least some of the second through holes 51 are located between the first through hole 50 and the circuit component 29. The arrangement direction of the second through holes 51 is perpendicular to a line L2 connecting the centers of the through holes 50 and the circuit component 29 (see FIG. 8). A line L3 extending along the arrangement direction of the second through holes 51 is perpendicular to the line L2 at least at the intersection with the line L2.

[0052] The second through holes 51 restrict the flux applied near the first through holes 50 from wetting and spreading across the surface of the substrate 11 toward the circuit components 29 when soldering terminals (UVW terminals, connector terminals, etc.) to the wiring board 201. A portion of the flux flows into the second through holes 51, for example.

[0053] 10 and 11 are cross-sectional views of a portion of the wiring board 201. In the example shown in Fig. 10, a UVW terminal 101 (motor terminal) of the motor 30 is inserted into the first through hole 50. The UVW terminal 101 is joined to the wiring board 201 by a solder joint 102. In the example shown in Fig. 11, a connector terminal 103 of the connector ASSY 4 is inserted into the first through hole 50. The connector terminal 103 is joined to the wiring board 201 by the solder joint 102.

[0054] In the electric power steering device 200 according to this embodiment, at least some of the second through holes 51 are formed between the first through holes 50 and the circuit components 29 along the tangential direction of the circle C concentric with the first through holes 50, which makes it possible to suppress the adhesion of flux to the circuit components 29. This makes it possible to reduce the risk of the circuit components 29 failing due to ion migration.

[0055] 8 has a plurality of second through holes 51 arranged in a row, but elongated (slit-shaped) second through holes may be used instead of the plurality of second through holes 51. At least a portion of the second through holes is formed between the first through holes 50 and the circuit component 29 along the tangent direction of a circle C concentric with the first through holes 50.

[0056] The technical scope of the present disclosure is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present disclosure. In Fig. 2, the motor line connected to the winding 30a of the motor 30 is one system, but the motor line may be two or more systems. In Fig. 2, the battery line connected to the battery 5 and the ground line are each one system, but these may be two or more systems. The number of CPUs 21 included in the control circuit 2 is not limited to one, and may be multiple.

[0057] DESCRIPTION OF SYMBOLS 1, 201... Wiring board 10... Control unit 11... Base material 6... Wiring 29... Circuit component 30... Motor 50... Through hole 50... First through hole 51... Second through hole 100, 200... Integrated electric power steering device 101... UVW terminal (motor terminal) 103... Connector terminal C... Circle

Claims

1. An integrated electric power steering device comprising: a motor; and a control unit provided integrally with the motor and controlling the motor, wherein the control unit comprises: a wiring board having an electrically insulating base material and conductive wiring formed on the base material; a connector having connector terminals connected to the wiring board; and circuit components surface-mounted on the wiring board, wherein a through hole is formed in the wiring board, penetrating from one side to the other, and at least a portion of the wiring is formed between the through hole and the circuit component along a tangent to a circle concentric with the through hole.

2. The integrated electric power steering device according to claim 1, wherein a terminal of the motor is inserted into the through hole.

3. The integrated electric power steering device according to claim 1, wherein the connector terminal is inserted into the through hole.

4. An integrated electric power steering device comprising: a motor; and a control unit provided integrally with the motor and controlling the motor, wherein the control unit comprises: a wiring board having an electrically insulating base material; a connector having connector terminals connected to the wiring board; and circuit components surface-mounted on the wiring board, wherein a first through hole and a plurality of second through holes penetrating from one side to the other side are formed in the wiring board, and at least some of the plurality of second through holes are formed between the first through hole and the circuit components and arranged along the tangent direction of a circle concentric with the first through hole.

5. An integrated electric power steering device according to claim 4, wherein a terminal of the motor is inserted into the first through hole.

6. The integrated electric power steering device according to claim 4, wherein the connector terminal is inserted into the first through hole.

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