JP4867431B2 - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively use a mounting space of a circuit board of an ECU by reducing a space required for mounting a relay in an electric power steering device. <P>SOLUTION: Stationary contact points 712a, 712b, 722a, 722b are formed on wiring members 510, 610, 520, 620 constituting a U-phase and V-phase current supply path to a brushless motor. A U-phase movable contact point 710 capable of bridging the stationary contact points 712a and 712b for a U-phase and a V-phase movable contact point 720 capable of bridging the stationary contact points 722a and 722b for a V-phase are movably integrated with each other. A solenoid 750 as means for displacing the U-phase and V-phase movable contact points 710, 720 is embedded in a heat sink 501 in the ECU, and the U-phase and V-phase current supply path can be opened and closed by one solenoid 750. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by an electric motor, and more particularly to a relay used in the electric power steering device.

  2. Description of the Related Art Conventionally, an electric power steering apparatus that applies a steering assist force to a steering mechanism by driving an electric motor in accordance with a steering torque applied to a steering wheel (steering wheel) by a driver has been used. This electric power steering apparatus is provided with a torque sensor for detecting a steering torque applied to a steering wheel as an operation means for steering, and a current to be supplied to the electric motor based on the steering torque detected by the torque sensor. Target value (hereinafter referred to as “target current value”) is set. And the command value which should be given to the drive means of an electric motor is produced | generated by the proportional integral calculation based on the deviation of this target electric current value and the value of the electric current which actually flows into an electric motor. The drive means of the electric motor is turned on / off according to the PWM signal generation circuit that generates a pulse width modulation signal (hereinafter referred to as “PWM signal”) having a duty ratio corresponding to the command value, and the duty ratio of the PWM signal. A motor drive circuit (hereinafter also simply referred to as “drive circuit”) configured using a power transistor is provided, and a voltage corresponding to the duty ratio is applied to the electric motor. The current flowing through the electric motor by this voltage application is detected by a current detector, and the difference between the target current value and the detected current value is used as a deviation for generating the command value.

In such an electric power steering device, when a short circuit failure occurs in a FET (field effect transistor) as a switching element constituting a motor drive circuit, the handle becomes extremely heavy due to generation of an induced current due to the handle operation. There are known problems. In order to solve this problem, for example, a relay as an opening / closing means is provided between the motor and the drive circuit in order to cut off the induced current when a failure occurs. That is, in the electric power steering apparatus using the three-phase brushless motor, as shown in FIG. 8, among the three paths for supplying current to the brushless motor 6 from the drive circuit 50 including the FETs 51H to 53H and 51L to 53L. Relays (hereinafter referred to as “motor relays”) 171 and 172 for interrupting the induced current when a failure occurs are provided on the two paths. As shown in FIG. 8, an overcurrent protection relay (hereinafter referred to as “power relay”) 170 is provided between the battery 8 as a power source and the drive circuit 50.
JP 2004-106664 A JP 2001-106098 A

  As described above, in the conventional electric power steering apparatus using the brushless motor, a total of three relays including two motor relays 171 and 172 and one power supply relay 170 are provided. For these three relays, general-purpose products are usually used. The general-purpose relays are relatively large in consideration of heat dissipation and the like, and their length L, width W, and height H are, for example, L = 17 mm, W = 13 mm, and H = 15 mm (see FIG. 9). For this reason, the area occupied by the relay on the circuit board of the electronic control unit (ECU) in the electric power steering apparatus is large, and the relay as a general-purpose product greatly restricts the mounting space on the board. The general-purpose relay 770 has a fixed terminal arrangement and is connected to the drive circuit side wiring member 510 and the motor side wiring member 610 formed on the circuit board as shown in FIG. Thus, since the drive circuit side wiring member 510 and the motor side wiring member 610 need to be arranged on a straight line, the fixed terminal arrangement of the relay 770 (171) is a bus bar as the wiring members 510 and 610. Therefore, a large space is required for mounting these relays 170, 171, and 172 on the circuit board.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electric power steering device that reduces the space required for mounting a relay so that the mounting space on a circuit board of an ECU can be used effectively.

A first invention is an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by driving an electric motor in accordance with an operation for steering the vehicle,
A drive circuit for driving the electric motor;
Opening and closing means inserted in a current supply path from the drive circuit to the electric motor,
The opening / closing means includes
A fixed contact portion formed of a first contact and a second contact formed on a wiring member constituting the current supply path on a predetermined circuit board and electrically separated from each other;
A movable conductor piece capable of electrically connecting the first contact and the second contact;
Between the first position where the movable conductor piece connects the first contact and the second contact and the second position where the movable conductor piece is separated from the first and second contacts. Displacement means for displacing the movable conductor piece.

According to a second invention, in the first invention,
The electric motor is a brushless motor;
The opening / closing means includes
First and second fixed contact portions corresponding to the fixed contact portion;
Including first and second movable conductor pieces corresponding to the movable conductor pieces,
The first fixed contact portion is formed on a wiring member constituting a first current supply path from the drive circuit to the brushless motor, and includes first and second contacts that are electrically separated from each other,
The second fixed contact portion is formed on a wiring member constituting a second current supply path from the drive circuit to the brushless motor, and includes first and second contacts that are electrically separated from each other,
In the displacing means, the first movable conductor piece connects the first contact and the second contact in the first fixed contact portion, and the second movable conductor piece is the second fixed contact portion. A first position for connecting the first contact and the second contact in the first movable contact piece, the first movable conductor piece being separated from the first and second contacts in the first fixed contact portion, and the second The first and second movable conductor pieces are integrally displaced between the second movable conductor piece and the second position spaced apart from the first and second contacts in the second fixed contact portion. Features.

According to a third invention, in the first invention,
The wiring member is formed in a thermally conductively the circuit board to a predetermined sink,
The displacement means is embedded in the case of the circuit board or the heat sink.

According to a fourth invention, in the first invention,
The displacement means is
Closed drive means for displacing the movable conductor piece from the second position to the first position by electromagnetic force;
Opening drive means for displacing the movable conductor piece from the first position to the second position by a biasing force of a spring is included.

According to the first aspect of the invention, the fixed contact portion of the switching means inserted into the current supply path from the drive circuit to the motor is formed on the wiring member constituting the current supply path on the predetermined circuit board . Therefore, the space required for mounting the opening / closing means can be reduced. This enables downsizing of the electronic control unit (ECU) or its circuit board in the electric power steering apparatus, and contributes to cost reduction. In addition, it is not necessary to route the wiring on the circuit board as in the case where a relay as a general-purpose product is used, so that the shortening of the wiring length of the current supply path contributes to suppression of overheating.

  According to the second aspect of the invention, the opening and closing of the first and second current supply paths from the drive circuit to the brushless motor integrally displaces the first and second movable conductor pieces by one displacement means. Therefore, the space required for mounting the opening / closing means can be further reduced.

  According to the third aspect, the wiring member constituting the current supply path from the drive circuit to the brushless motor is formed on the predetermined circuit board so as to be able to conduct heat to the predetermined heat sink. Embedded in the circuit board case or heat sink. For this reason, the space required for mounting the opening / closing means is reduced, and the heat dissipation characteristics of the opening / closing means are improved. This improvement in heat dissipation characteristics enables the size of the opening / closing means to be reduced.

  According to the fourth aspect of the invention, since the displacement means is constituted by the closed drive means based on the electromagnetic force and the open drive means based on the biasing force of the spring, the current for generating the electromagnetic force in the closed drive means When supply becomes impossible due to a failure or the like, the opening / closing means is opened by the biasing force of the spring. Such a configuration is effective in terms of failsafe.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
<1. Overall configuration>
FIG. 1 is a schematic diagram showing a configuration of an electric power steering apparatus according to an embodiment of the present invention, together with a vehicle configuration related thereto. This electric power steering apparatus includes a steering shaft 102 having one end fixed to a handle (steering wheel) 100 as an operation means for steering, a rack and pinion mechanism 104 connected to the other end of the steering shaft 102, a handle A torque sensor 3 for detecting a steering torque applied to the steering shaft 102 by an operation of 100, a brushless motor 6 for generating a steering assist force for reducing a driver's load in a steering operation (steering operation), and its steering assist The torque sensor receives a power supply from a ball screw drive unit 11 that transmits force to the rack shaft, a position sensor 12 such as a resolver that detects the rotational position of the rotor of the motor 6, and an on-board battery 8 via an ignition switch 18. 3, vehicle speed sensor 4, position sensor 1 Based on the sensor signals from and an electronic control unit (ECU) 5 for controlling the driving of the motor 6.

  When the driver operates the handle 100 in a vehicle equipped with such an electric power steering device, the torque sensor 3 detects the steering torque by the operation and outputs a steering torque signal Ts indicating the steering torque. On the other hand, the vehicle speed sensor 4 detects the vehicle speed, which is the traveling speed of the vehicle, and outputs a vehicle speed signal Vs indicating the vehicle speed. The ECU 5 as the control device drives the motor 6 based on the steering torque signal Ts and the vehicle speed signal Vs and the rotational position of the rotor detected by the position sensor 12. As a result, the motor 6 generates a steering assist force, and this steering assist force is applied to the rack shaft via the ball screw drive unit 11, thereby reducing the driver's load in the steering operation. That is, the rack shaft reciprocates by the sum of the steering force generated by the steering torque applied by the steering wheel operation and the steering assist force generated by the motor 6. Both ends of the rack shaft are connected to a wheel 108 via a connecting member 106 composed of a tie rod and a knuckle arm, and the direction of the wheel 108 changes according to the reciprocating motion of the rack shaft.

<2. Configuration of control device>
FIG. 2 is a block diagram showing a configuration of the ECU 5 which is a control device of the electric power steering device. The ECU 5 includes a motor control unit 20, a motor drive unit 30, a relay drive circuit 7, two current detectors 81 and 82, and a voltage stabilizing capacitor 9. The motor control unit 20 is a control calculation means constituted by a microcomputer and operates by executing a predetermined program stored in its internal memory. The motor drive unit 30 includes a PWM signal generation circuit 40 and a drive circuit 50.

  The drive circuit 50 is disposed on the power supply line side, and is disposed on the ground line side with FETs (field effect transistors) 51H, 52H, and 53H that are power switching elements corresponding to the U phase, V phase, and W phase of the motor 6, respectively. FETs 51L, 52L, and 53L, which are power switching elements corresponding to the U phase, V phase, and W phase of the motor 6, respectively, and include power line side FETs (hereinafter referred to as “Hi side FETs”) corresponding to the same phase. 5jH and a ground line side FET (hereinafter abbreviated as “Lo side FET”) 5jL are connected in series so as to be paired with each other (j = 1, 2, 3).

  Connection points Nu, Nv, Nw between the Hi-side FET 5jH and the Lo-side FET 5jL of each phase are connected to terminals 61 to 63 of each phase of the motor by power lead wires (specifically, constituted by bus bars). ing. Thereby, a current supply path for supplying a drive current from the drive circuit 50 to the motor 6 is formed for each phase. A first opening / closing portion 701 is connected to a current supply path (hereinafter referred to as “U-phase current supply path”) formed by a lead wire connecting the connection point Nu corresponding to the U phase and the motor terminal 61, with V A second opening / closing portion 702 is inserted into a current supply path (hereinafter referred to as “V-phase current supply path”) formed by a lead wire connecting the connection point Nv corresponding to the phase and the motor terminal 62. Yes. As will be described later, the first and second opening / closing sections are realized by one relay 71 (hereinafter referred to as “motor relay”). In addition, a power supply relay 70 as an opening / closing means is inserted between a connection point (power supply side branch point) where the source terminals of the Hi side FETs 51 </ b> H to 53 </ b> H are connected to each other in the drive circuit 50. An opening / closing means such as a relay is inserted in a current supply path (hereinafter referred to as “W-phase current supply path”) formed by a lead wire connecting the connection point Nw corresponding to the W phase and the motor terminal 63. Absent.

  The capacitor 9 is composed of one or a plurality of electrolytic capacitors connected in parallel with the drive circuit 50, and stabilizes the voltage of the power supply line. Hereinafter, the capacitor 9 is referred to as a “voltage stabilizing capacitor”.

  One of the two current detectors 81 and 82 detects the U-phase current flowing in the lead wire (U-phase current supply path) that connects the connection point Nu of the drive circuit 50 and the motor terminal 61. The other current detector 82 detects the V-phase current flowing in the lead wire (V-phase current supply path) connecting the connection point Nv of the drive circuit 50 and the motor terminal 62. The current values detected by these current detectors 81 and 82 are input to the motor control unit 20 as a U-phase current detection value Iu and a V-phase current detection value Iv, respectively.

The motor control unit 20 uses the steering torque detected by the torque sensor 3, the vehicle speed detected by the vehicle speed sensor 4, and the U-phase and V-phase current detection values Iu and Iv detected by the current detectors 81 and 82. receive. Further, the motor control unit 20 determines a target current value to be supplied to the motor 6 based on the steering torque and the vehicle speed with reference to a table called an assist map that associates the steering torque with the target current value. Then, the command values V ^* u, V ^{* of the} respective phase voltages to be applied to the motor 6 by the proportional-integral calculation based on the deviation between the target current value and the motor current value calculated from the motor current detection values Iu, Iv ^. v and V ^* w are calculated.

Further, the motor control unit 20 calculates the command values V ^* u, V ^* v, and V ^* w for each phase voltage as described above, and also results of a predetermined failure detection process (for example, a short circuit of the FET in the drive circuit 50). A relay control signal for controlling the relay drive circuit 7 is also output based on the detection of the failure. That is, the motor control unit 20 constitutes a relay control means together with the relay drive circuit 7.

In the motor drive unit 30, the PWM signal generation circuit 40 receives the command values V ^* u, V ^* v, V ^* w of each phase voltage from the motor control unit 20, and those command values V ^* u, V ^* v, A PWM signal whose duty ratio changes according to V ^* w is generated. The drive circuit 50 is a PWM voltage source inverter configured using the Hi-side FETs 51H to 53H and the Lo-side FETs 51L to 53L as described above, and the FET signals 51H to 53H and 51L to 53L are turned on by the PWM signal. By turning off / off, the phase voltages Vu, Vv, Vw to be applied to the motor 6 are generated. These phase voltages Vu, Vv, Vw are output from the ECU 5 and applied to the motor 6. In response to this voltage application, current flows through coils (not shown) of the phases u, v, and w of the motor 6, and the motor 6 generates torque for assisting steering (motor torque) in accordance with the current.

  The relay drive circuit 7 controls opening and closing of the power supply relay 70 and the motor relay 71 based on a relay control signal output from the motor control unit 20. That is, the relay drive circuit 7 keeps the relays 70 and 71 closed until the signal indicating that a failure has been detected from the motor control unit 20 during the operation of the electric power steering apparatus, and the motor drive unit 30. The power supply to the motor 6 is continued. When a failure is detected in the failure detection process in the motor control unit 20, the relay drive circuit 7 receives a signal indicating that a failure has been detected from the motor control unit 20. As a result, the relay drive circuit 7 opens the relays 70 and 71 and cuts off the power supply to the motor drive unit 30 and the motor 6. Note that the first and second opening / closing sections 701 and 702 in the motor relay 71 operate in conjunction with each other as will be described later, and the open state (off state) of the motor relay 71 is the first and second opening / closing sections 701. , 702 are both open, and the closed state (on state) of the motor relay 71 means that both the first and second opening / closing parts 701, 702 are closed.

<3. Configuration and operation of motor relay>
Next, the configuration and operation of the motor relay 71 in this embodiment will be described with reference to FIGS. 3 and 4.

  3A and 3B are a cross-sectional view and a plan view showing the motor relay 71 in the open state in the present embodiment, and FIGS. 4A and 4B are cross-sectional views showing the motor relay 71 in the closed state. It is a figure and a top view. As shown in FIG. 2, the motor relay 71 includes the first opening / closing portion 701 for opening / closing the U-phase current supply path and the second opening / closing section for opening / closing the V-phase current supply path. And a single solenoid 750 as a displacement means for displacing the movable conductor piece for opening and closing the first and second opening and closing portions 701 and 702.

  On the circuit board in the ECU 5, a heat sink 501 is composed of Al (aluminum), and a wiring member made of Al (aluminum), Cu (copper), or the like is formed thereon via insulating layers 522 and 622 made of synthetic resin. Has been. In the present embodiment, as shown in FIG. 3B, the wiring member constituting the U-phase current path and the wiring member constituting the V-phase current path are mounted with the motor relay 71 on the circuit board in the ECU 5. In position, the drive circuit side and the motor side are electrically separated from each other. The first opening / closing portion 701 in the motor relay 71 is a fixed contact (hereinafter referred to as “a”) formed by plating the drive circuit side wiring member 510 constituting the U-phase current supply path with Cu (copper) and Ag (silver). 712a) and a fixed contact formed by plating the motor-side wiring member 610 constituting the U-phase current supply path with Cu and Ag (hereinafter referred to as "U-phase second contact"). 712b and a U-phase movable contact portion 710 which is a movable conductor piece that can electrically bridge the U-phase first contact 712a and the U-phase second contact 712b, that is, a movable conductor piece that can be bridged. . The second opening / closing part 702 constitutes a V-phase current supply path with a fixed contact (hereinafter referred to as “V-phase first contact”) 722a formed on the drive circuit side wiring member 520 constituting the V-phase current supply path. V, which is a movable conductor piece capable of bridging the fixed contact (hereinafter referred to as “V-phase second contact”) 722b formed on the motor-side wiring member 620, the V-phase first contact 722a, and the V-phase second contact 722b. And a phase movable contact portion 720. In the U-phase movable contact portion 710, a first contact element 711a is formed at a position facing the U-phase first contact 712a, and a second contact element 711b is formed at a position facing the U-phase second contact 712b. In the V-phase movable contact portion 720, a second contact element 721a is formed at a position facing the V-phase first contact 722a, and a second contact element 721b is formed at a position facing the V-phase second contact 722b. These U-phase movable contact portion 710 and V-phase movable contact portion 720 are coupled to be movable (displaceable) integrally by a coupling member 730 made of an insulating material. The U-phase first and second contacts 712a and 712b constitute a U-phase fixed contact portion, and the V-phase first and second contacts 722a and 722b constitute a V-phase fixed contact portion.

  The solenoid 750 includes a fixed iron core 751 having a magnet attracting surface, a coil 752 wound around the magnet core 750, a movable iron piece 753, and an X-shaped spring 755. As shown in FIG. It is embedded in a recess provided in the heat sink 501). The solenoid 750 is arranged such that the longitudinal direction of the fixed iron core 751 is perpendicular to the main surface of the circuit board (the surface on which the wiring members 510, 610, 520, and 620 are formed, hereinafter referred to as “substrate surface”). Arranged and fixed to the circuit board by screws 761, 762. Excitation current to the coil 752 is supplied by the relay drive circuit 7 based on a relay control signal from the motor control unit 20. The movable iron piece 753 includes a portion that penetrates the solenoid main body (the storage portion of the coil 752) along the longitudinal direction of the fixed iron core 751, a portion that faces the magnet attracting surface of the fixed iron core 751 (hereinafter referred to as “head”), It consists of a part (hereinafter referred to as “rear part”) facing the bottom surface (surface opposite to the magnet attracting surface) of the solenoid body, and is movable (displaceable) in the longitudinal direction of the fixed iron core 751, that is, in the direction perpendicular to the substrate surface. It is configured. The head of the movable iron piece 753 is fixed to a coupling member 730 that couples the U-phase movable contact portion 710 and the V-phase movable contact portion 720, and is attached to the rear outer surface (surface opposite to the solenoid body). The X-shaped spring 755 is fixed.

  In the motor relay 71 having such a configuration, in a state where no current is supplied to the coil 752 of the solenoid 750, as shown in FIGS. 3A and 3B, the U-phase movable contact portion 710 has the U-phase first contact 712 a and The V-phase movable contact portion 720 is located at a position separated from the U-phase second contact 712b, and the V-phase movable contact portion 720 is located at a position separated from the V-phase first contact 722a and the V-phase second contact 722b. The position of the part 710 and the V-phase movable contact part 720 or the position of the movable iron piece 753 is referred to as “open position”). At this time, the U-phase current supply path and the V-phase current supply path are both cut off.

  On the other hand, when a current is supplied to the coil 752 of the solenoid 750 by the relay drive circuit 7, the fixed iron core 751 is magnetized, and the head of the movable iron piece 753 is attracted against the magnet attracting surface against the biasing force of the spring 755. Is done. Since this movable iron piece 753 is fixed to a coupling member 730 that couples the U-phase movable contact portion 710 and the V-phase movable contact portion 720, the attraction by the magnetization (electromagnetic force) causes the movable iron piece 753 to be shown in FIGS. As shown in FIG. 4, the U-phase movable contact portion 710 moves to a position where it contacts the U-phase first and second contacts 712a and 712b, and the V-phase movable contact portion 720 moves to the V-phase first and second contacts 722a and 722b. The position moves to a contact position (hereinafter, the position of the U-phase movable contact portion 710 and the V-phase movable contact portion 720 or the position of the movable iron piece 753 at this time is referred to as a “closed position”). Therefore, the fixed iron core 751 and the coil 752 constitute a closed drive means for causing the motor relay 71 to transition from the open state to the closed state.

  In the closed position, the U-phase first contact 712a and the U-phase second contact 712b are bridge-connected by the U-phase movable contact portion 710, and the V-phase first contact 722a and the V-phase second contact 722b are movable in the V-phase. The contact part 720 is cross-linked. In this closed position, when the current supply to the coil 752 by the relay drive circuit 7 is interrupted, the movable iron piece 753 returns to the open position shown in FIG. As a result, the U-phase first contact 712a and the U-phase second contact 712b are electrically disconnected and the U-phase current supply path is cut off, and the V-phase first contact 722a and the V-phase second contact are disconnected. 722b is electrically disconnected and the V-phase current supply path is cut off. Therefore, the spring 755 functions as an opening drive unit that causes the motor relay 71 to transition from the closed state to the open state.

  In the present embodiment, the relay drive circuit 7 performs the closing operation of the motor relay 71 based on the relay control signal from the motor control unit 20 when the power supply relay 70 is in the open state (off state). The current supply to the coil 752 of the solenoid 750 is controlled. That is, when the relay drive circuit 7 moves the U-phase and V-phase movable contact portions 710 and 720 from the open position to the closed position (when the motor relay 71 is changed from the open state to the closed state), the power relay 70 is left open. In this way, it is possible to prevent arc generation in the motor relay 71 during normal operation.

  Next, another configuration example of the motor relay 71 in the present embodiment will be described with reference to FIG. In the configuration examples described below, the same or corresponding parts as those in the above configuration are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 5A is a cross-sectional view showing this configuration example, and FIG. 5B is a plan view showing this configuration example. Also in this configuration example, as in the above configuration, the heat sink 501 is formed of Al (aluminum) on the circuit board in the ECU 5, and Al (aluminum) or the insulating layer 522 622 made of synthetic resin is formed thereon. Wiring members 510, 610, 520, and 620 made of Cu (copper) or the like are formed. However, the solenoid 750 is embedded in a recess provided in the lid member 504 (case) of the ECU 5 instead of being embedded in the circuit board (the heat sink 501 in the circuit board). The solenoid 750 is arranged so that the longitudinal direction of the fixed iron core 751 is perpendicular to the main surface (substrate surface) of the circuit board when the lid member 504 of the ECU 5 is closed, and is covered by screws 761 and 762. It is fixed to the member 504. Similarly to the above configuration, the movable iron piece 753 includes a portion that penetrates the solenoid body (the storage portion of the coil 752) along the longitudinal direction of the fixed iron core 751, and a head that is a portion facing the magnet attracting surface of the fixed iron core 751. The rear portion is a portion facing the bottom surface of the solenoid body. However, unlike the above configuration, the X-shaped spring 755 is interposed between the bottom surface of the solenoid body and the rear portion of the movable iron piece 753 and is fixed to both.

  In addition, the coupling member 732 made of an insulating material that couples the U-phase movable contact portion 710 and the V-phase movable contact portion 720 so as to be integrally movable with respect to the U-phase movable contact portion 710 and the V-phase movable contact portion 720. It is attached to the opposite side (lid member side) from the circuit board. Unlike the above configuration, the coupling member 732 is fixed to the rear part of the movable iron piece 753 of the solenoid 750.

  In such a motor relay 71 of this configuration example, when no current is supplied to the coil 752 of the solenoid 750, as shown in FIGS. 5A and 5B, the U-phase movable contact portion 710 has the U-phase first contact. 712a and the U-phase second contact 712b, and the V-phase movable contact portion 720 is spaced from the V-phase first contact 722a and the V-phase second contact 722b, and the U-phase current supply path and V Both phase current supply paths are cut off.

  On the other hand, when a current is supplied to the coil 752 of the solenoid 750 by the relay drive circuit 7, the fixed iron core 751 is magnetized, and the head of the movable iron piece 753 is attracted against the magnet attracting surface against the biasing force of the spring 755. Is done. Since the movable iron piece 753 is fixed to the coupling member 732 that couples the U-phase movable contact portion 710 and the V-phase movable contact portion 720, the U-phase movable contact portion 710 is attracted by the magnetization so that the U-phase movable contact portion 710 While moving to a position in contact with the second contacts 712a and 712b, the V-phase movable contact portion 720 moves to a position in contact with the V-phase first and second contacts 722a and 722b.

  In this closed position, the U-phase first contact 712a and the U-phase second contact 712b are bridge-connected by the U-phase movable contact portion 710, and the V-phase first contact 722a and the V-phase second contact 722b are movable in the V-phase. The contact part 720 is cross-linked. In this closed position, when the current supply to the coil 752 by the relay drive circuit 7 is interrupted, the movable iron piece 753 is returned to the open position shown in FIG. As a result, the U-phase first contact 712a and the U-phase second contact 712b are electrically disconnected and the U-phase current supply path is cut off, and the V-phase first contact 722a and the V-phase second contact are disconnected. 722b is electrically disconnected and the V-phase current supply path is cut off.

<4. Mounting method of voltage stabilization capacitor>
FIG. 6 is a plan view for explaining a mounting method of the voltage stabilizing capacitor 9 used for stabilizing the voltage of the power supply line in the conventional electric power steering apparatus. In this conventional example, two electrolytic capacitors 91 and 92 are used as the voltage stabilizing capacitor 9, and the positive lead wires 191p and 192p of these electrolytic capacitors 91 and 92 are resistance to the positive bus bar Bp forming the power supply line. While being connected by welding, the negative electrode lead wires 191n and 192n are connected by resistance welding to the negative bus bar Bn forming the ground line. Therefore, in order to form four connection points (welding points) 291p, 292p, 291n, 292n corresponding to these four lead wires 191p, 192p, 191n, 192n, resistance welding electrodes are used as connection points. It is necessary to execute the process of pressing four times. Further, since the connection points are arranged in a plane and a space for the electrodes for resistance welding (dotted circle shown in FIG. 6) is also required, a relatively large space is required for mounting the voltage stabilizing capacitor 9. Cost.

  Therefore, in this embodiment, a mounting method as shown in FIG. 7 is adopted for the voltage stabilizing capacitor 9 in order to improve these points. That is, in the positive side bus bar Bp forming the power supply line, portions Bp1 and Bp2 perpendicular to the substrate surface on which the positive electrode bus bar Bp is disposed are formed so that the two vertical portions Bp1 and Bp2 collide with each other. Arrange it. Similarly, in the negative side bus bar Bn forming the ground line, portions Bn1 and Bn2 perpendicular to the substrate surface on which the negative electrode bus bar Bn is disposed are formed so that the two vertical portions Bn1 and Bn2 collide with each other. Place it in. In addition, two electrolytic capacitors 91 and 92 to be used as the voltage stabilizing capacitor 9 are arranged such that the vertical portions Bp1, Bp2, Bn1 and Bn2 are located between them, and around the central axis as compared with FIG. It arrange | positions so that it may be in the state rotated 90 degree | times. Further, as shown in FIG. 7 (a), the positive lead wires 191p and 192p of the electrolytic capacitors 91 and 92 are shaped so as to sandwich the contact portions of the vertical portions Bp1 and Bp2 in the positive bus bar Bp from both sides. The negative lead wires 191p and 192p are formed, and the negative lead wires 191n and 192n of the electrolytic capacitors 91 and 92 are shaped so as to sandwich the abutting portions of the vertical portions Bn1 and Bn2 in the negative electrode bus bar Bn from both sides. 191n and 192n are formed in advance. Then, the two electrodes are sandwiched between two electrodes (positive electrode and negative electrode) for resistance welding at the abutting portion of the vertical portions Bp1 and Bp2 of the positive electrode bus bar Bp sandwiched between the positive electrode lead wires 191p and 192p. The positive lead wires 191p and 192p are connected to the positive bus bar Bp by pressing and passing a large current for a short time between the two electrodes. Similarly, the two electrodes are sandwiched between two electrodes (positive electrode and negative electrode) for resistance welding at the abutting portion of the vertical portions Bn1 and Bn2 of the negative electrode bus bar Bn sandwiched between the negative electrode lead wires 191n and 192n. And a negative current lead 191n, 192n is connected to the negative bus bar Bn by flowing a large current between the two electrodes for a short time.

  According to such a mounting method, four connection points (welding points) can be obtained only by executing the process of pressing the electrode for resistance welding to the portion to be the connection point of the electrolytic capacitors 91 and 92 twice. Since it is formed, the number of steps for mounting the voltage stabilizing capacitor 9 can be reduced. Further, since the electrodes for resistance welding are pressed from both sides to the abutting portions of the vertical portions of the bus bars Bp and Bn, the work space for mounting can be reduced as compared with the conventional case. Furthermore, in the conventional example, four connection points are arranged in a plane. However, according to the mounting method described above, the connection points are arranged on both sides of the abutting portion of the vertical portion of the bus bars Bp and Bn. The mounting space itself of the stabilization capacitor 9 is also reduced.

<5. Effect>
According to the present embodiment as described above, the fixed contacts 712a, 712b, 722a, 722b of the motor relay 71 are connected to the wiring members 510, 610, 520, 620 on the circuit board of the ECU 5, as shown in FIGS. And the solenoid 750 is embedded in the circuit board or the lid member 504 of the ECU 5 (that is, the heat sink 501 or a part of the ECU 5 casing serves as the case of the solenoid 750). It is possible to reduce the necessary space. This enables the ECU 5 or its circuit board to be miniaturized and contributes to cost reduction.

  In addition, the opening / closing part means for cutting off the two current supply paths corresponding to the two phases of the brushless motor 6 is realized by one motor relay 71, and the U phase constituting the two current supply paths Wiring members 510 and 610 for wiring and V phase wiring members 520 and 620 are arranged in parallel, and solenoid 750 as a displacement means of the movable contact portion is shared. Thereby, the mounting space of the motor relay 71 can be further reduced.

  Furthermore, since the wiring members 510, 610, 520, and 620 in which the fixed contacts 712a, 712b, 722a, and 722b in the motor relay 17 are formed are connected to the heat sink 501 through a low thermal resistance so as to be able to conduct heat, In comparison, the heat dissipation characteristics of the motor relay 71 are also improved. In particular, when the solenoid 750 is embedded in the heat sink 501 (FIGS. 3 and 4), the heat dissipation characteristics are further improved. This contributes to miniaturization of the motor relay 71 and miniaturization of the ECU 5. In addition, wiring on the circuit board (see FIG. 9) as in the case of using a relay as a general-purpose product becomes unnecessary, and the wiring length of the current supply path is shortened. This contributes to suppression of overheating in the ECU 5.

<6. Modification>
In the above embodiment, the closing operation (transition from the open state to the closed state) in the motor relay 71 is realized by the electromagnetic force generated by the exciting current of the coil 752 in the solenoid 750, and the opening operation (from the closed state to the open state). Transition) is realized by the biasing force of the spring 755. This configuration is effective from the viewpoint of fail-safe because the motor relay 71 is opened when current supply to the coil 752 becomes impossible. However, a configuration in which the closing operation is realized by the biasing force of the spring 755 and the opening operation is realized by an electromagnetic force is also possible.

  In the above embodiment, the first and second opening / closing portions 701 and 702 corresponding to the two phases of the motor 6 are realized by one motor relay 71, but one motor relay is provided for each phase. It may be a configuration. In this case, one solenoid is provided as a displacement means for one movable contact portion (movable conductor piece) for bridge-connecting a pair of fixed contacts.

  In the above embodiment, the brushless motor 6 is used, but the present invention can be applied even when a brushed motor is used. In this case, a motor relay is inserted into one of the two current supply paths from the drive circuit to the brushed motor.

  In the above embodiment, the circuit board on which the wiring members 510, 610, 520, and 620 are formed includes the heat sink 501 (FIGS. 3 to 5), but the heat sink 501 is separate from the circuit board. It may be configured that the wiring members 510, 610, 520, and 620 are connected to the heat sink through the low thermal resistance member so as to conduct heat. Moreover, in the said embodiment, although the fixed contacts 712a, 712b, 722a, 722b in the motor relay 71 are formed as convex parts in the wiring members 510, 610, 520, 620 (FIGS. 3 to 5), It may be a flat surface that is plated only with Cu and Ag without forming a convex portion. Furthermore, in the said embodiment, although the X-shaped spring 755 is used in the motor relay 71, the kind of spring which can be used is not limited to this.

It is the schematic which shows the structure of the electric power steering apparatus which concerns on one Embodiment of this invention with the vehicle structure relevant to it. It is a block diagram which shows the structure of ECU which is a control apparatus in the electric power steering apparatus which concerns on the said embodiment. It is sectional drawing (a) and top view (b) which show the motor relay of the open state in the said embodiment. It is sectional drawing (a) and the top view (b) which show the motor relay of the closed state in the said embodiment. It is sectional drawing (a) and the top view (b) which show the other structural example of the motor relay in the said embodiment. It is a top view for demonstrating the mounting method of the voltage stabilization capacitor | condenser in the conventional electric power steering apparatus. It is the top view (a) and side view (b) for demonstrating the mounting method of the voltage stabilization capacitor | condenser in the said embodiment. It is a circuit diagram for demonstrating the power supply relay and motor relay in the conventional electric power steering apparatus. It is a perspective view for demonstrating mounting of the motor relay in the conventional electric power steering apparatus.

Explanation of symbols

5 electronic control unit (ECU), 6 brushless motor, 7 relay drive circuit, 20 motor control unit, 30 motor drive unit, 40 PWM signal generation circuit, 50 drive circuit, 51H to 53H Hi side FET (Hi side switching element), 51L-53L Lo side FET (Lo side switching element), 61-63 Motor terminal, 70 Power relay, 71, 72 Relay (opening / closing means), 501 Heat sink, 510, 520 Driving circuit side wiring member, 610, 620 Motor side wiring Member, 710, 720 Movable contact part (movable conductor piece), 712a U-phase first contact (U-phase fixed contact part), 712b U-phase second contact (U-phase fixed contact part), 722a V-phase first contact (V-phase fixed contact portion), 722b V-phase second contact (V-phase fixed contact portion), 730 coupling member, 750 solenoid (displacement hand) Stage), 751 fixed iron core, 752 coil, 753 movable iron piece, 755 spring.

Claims (4)

An electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by driving an electric motor according to an operation for steering the vehicle,
A drive circuit for driving the electric motor;
Opening and closing means inserted in a current supply path from the drive circuit to the electric motor,
The opening / closing means includes
A fixed contact portion formed of a first contact and a second contact formed on a wiring member constituting the current supply path on a predetermined circuit board and electrically separated from each other;
A movable conductor piece capable of electrically connecting the first contact and the second contact;
Between a first position where the movable conductor piece connects the first contact and the second contact and a second position where the movable conductor piece is separated from the first and second contacts, An electric power steering apparatus comprising: displacement means for displacing the movable conductor piece. The electric motor is a brushless motor;
The opening / closing means includes
First and second fixed contact portions corresponding to the fixed contact portion;
Including first and second movable conductor pieces corresponding to the movable conductor pieces,
The first fixed contact portion is formed on a wiring member constituting a first current supply path from the drive circuit to the brushless motor, and includes first and second contacts that are electrically separated from each other,
The second fixed contact portion is formed on a wiring member constituting a second current supply path from the drive circuit to the brushless motor, and includes first and second contacts that are electrically separated from each other,
In the displacing means, the first movable conductor piece connects the first contact and the second contact in the first fixed contact portion, and the second movable conductor piece is the second fixed contact portion. A first position for connecting the first contact and the second contact in the first movable contact piece, the first movable conductor piece being separated from the first and second contacts in the first fixed contact portion, and the second The first and second movable conductor pieces are integrally displaced between the second movable conductor piece and the second position spaced apart from the first and second contacts in the second fixed contact portion. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is characterized. The wiring member is formed in a thermally conductively the circuit board to a predetermined sink,
The electric power steering apparatus according to claim 1, wherein the displacement unit is embedded in a case of the circuit board or the heat sink. The displacement means is
Closed drive means for displacing the movable conductor piece from the second position to the first position by electromagnetic force;
2. The electric power steering apparatus according to claim 1, further comprising opening drive means for displacing the movable conductor piece from the first position to the second position by a biasing force of a spring.

Images