JP2008174097A - Electric power steering device - Google Patents

Abstract

To electrically connect a metal substrate and a control substrate, a base substrate in which a conductive plate is integrated with a resin base material by insert molding is required, but the number of parts and the number of electrical connection points increase. . When the motor current is increased with the increase in the size of the vehicle, the Joule heat due to the electrical resistance of the wiring pattern and the temperature rise of the high current component are increased, and the durability of the wiring pattern and the joining reliability of the components are reduced.
An electric motor that outputs an auxiliary torque and a control device that controls driving of the electric motor are provided. The control device controls a main substrate on which a semiconductor switching element that switches a current of the electric motor is mounted, and the semiconductor switching element. A control board that generates a drive signal to be transmitted, a conductive member that configures a wiring pattern of the semiconductor switching element and electrically connects the main board and the control board, and a connector that connects the control board to an external power source. The conductive member and the connector are integrally insert-molded with a mold resin.
[Selection] Figure 1

Description

  The present invention relates to a configuration of an electric power steering apparatus including an electric motor that outputs an auxiliary torque to a steering wheel of a vehicle, and a control device that controls driving of the electric motor, and a manufacturing method thereof.

2. Description of the Related Art Conventionally, there is known an electric power steering apparatus that includes an electric motor that outputs auxiliary torque to a steering wheel of a vehicle and a control device that drives and controls the electric motor, and the control device is attached to the electric motor. . (For example, see Patent Document 1 and Patent Document 2)
In this electric power steering apparatus, a metal board on which a bridge circuit for causing a motor current to flow in an electric motor according to steering torque is mounted, a control board on which a control circuit for controlling the bridge circuit is mounted, a metal board, A base board that is a support member for stacking and fixing control boards and at the same time a plurality of conductive plates and a resin base material are integrated by insert molding and mounted with large current components such as electrolytic capacitors and relays. Have. A metal substrate, a control substrate, and a base substrate are stacked on the heat sink.

Japanese Patent No. 3638269 Japanese Patent No. 36005630

In a conventional electric power steering apparatus, a plurality of metal parts having a power circuit constituted by a bridge circuit and a control board having a control circuit for controlling the bridge circuit are electrically connected to each other by insert molding. Since a base substrate in which the conductive plate is integrated with a resin base material is required, the number of parts increases and the number of electrical connection points increases. As a result, there are problems that the cost is increased, the size is increased, and the reliability of electrical connection is lowered.
In recent years, with the increase in the size of vehicles equipped with devices, it has been required to increase the motor current. However, since the thickness of the copper foil forming the wiring pattern on the metal substrate is limited, the motor is simply When the current is increased, the Joule heat due to the electrical resistance of the wiring pattern increases, and the durability of the wiring pattern decreases, the temperature rise of the large current component increases, and the bonding reliability of the component decreases. . On the other hand, when trying to reduce the Joule heat by increasing the width of the wiring pattern, there is a problem that the apparatus becomes large and the in-vehicle property is deteriorated.

  An electric power steering apparatus according to the present invention includes an electric motor that outputs an auxiliary torque to a steering wheel of a vehicle, and an electric power steering apparatus that includes a control device that controls driving of the electric motor. A main board on which a plurality of semiconductor switching elements for switching current are mounted; a control board for generating a drive signal for controlling the plurality of semiconductor switching elements; and a wiring pattern for the plurality of semiconductor switching elements and the main board A conductive member that electrically connects the control board and a connector that electrically connects the control board to an external power source, and the control device includes the main board, the conductive member, and the connector. It is insert-molded integrally with mold resin.

According to the electric power steering apparatus of the present invention, the main board that is a large current board, the conductive member that electrically connects the main board and the control board that is an insulating multilayer board, and the control apparatus and the external power source are electrically connected. Since the connectors for connecting them are integrally formed by insert molding with mold resin, the reliability can be improved by downsizing, lowering the cost by reducing the number of parts, and reducing the number of electrical connections. .
Furthermore, since the size of the conductive member can be freely selected, it is possible to provide an electric power steering device that can cope with an increase in motor current.

Embodiments of the present invention will be described below with reference to the drawings.
In the drawings, the same reference numerals indicate the same or corresponding parts.

Embodiment 1 FIG.
1 is a cross-sectional view showing an electric power steering apparatus according to Embodiment 1 of the present invention.
The electric power steering apparatus includes an electric motor 1 that generates an auxiliary torque in accordance with a steering torque detected by a torque sensor (not shown) with respect to a steering system of a vehicle handle, and a control device that drives and controls the electric motor 1. 2 and a connector 3 for electrical connection with an external power source and sensors.
The electric motor 1 is a three-phase brushless motor, and a rotor 6 in which a permanent magnet 5 having eight magnetic poles is fixed to the output shaft 4 and the output shaft 4, and a stator provided around the rotor 6. 7 and
A rotational position sensor (not shown) is provided on the output side of the output shaft 4 and detects the rotational position of the rotor 6.
The stator 7 includes twelve salient poles 8 opposed to the outer periphery of the permanent magnet 5, an insulator 9 attached to the salient poles 8, a winding around the insulator 9, and three phases U, V, and W. And the armature winding 10 connected to the.
A reduction gear 11 is fixed to the electric motor 1. The reduction gear 11 includes a gear case 13 connected to the motor housing 12 of the electric motor 1, a worm gear 14 provided in the gear case 13 for reducing the rotation of the output shaft 4, and a worm wheel meshed with the worm gear 14. 15. A spline is formed at the end of the worm gear 14. A coupling 16 having a spline formed inside is press-fitted into an end of the output shaft 4. The coupling 16 and the end of the worm gear 14 are spline-fitted so that torque is transmitted from the electric motor 1 to the reduction gear 11.

  FIG. 2 is an exploded perspective view showing the electric power steering apparatus of FIG. 1, and FIG. 3 is an exploded perspective view showing the control apparatus 2 of FIG. 4 is a front view showing the insulating multilayer substrate 18 which is the control substrate of FIG. 3, and FIG. 5 is a front view showing the large current substrate 19 which is the main substrate of FIG.

The control device 2 is composed of a power circuit that supplies a motor current to the electric motor 1 and a control circuit that generates a drive signal for controlling a bridge circuit, which will be described later, in terms of an electric circuit (a circuit diagram is not shown). (See Patent Document 1 and Patent Document 2).
The power circuit includes a large-capacity electrolytic capacitor 20 that removes a ripple component of the motor current flowing in the electric motor 1, a shunt resistor 21 for detecting the motor current, a coil 22 that removes electromagnetic noise, and a motor current. The bridge circuit is composed of a semiconductor switching element 23 for switching according to the rotational position of the rotor 6 and the magnitude and direction of the auxiliary torque.

  The control circuit calculates auxiliary torque based on a circuit element constituting a current detection circuit for detecting a motor current value flowing through the electric motor 1 via the shunt resistor 21 and a steering torque signal from the torque sensor. A microcomputer that calculates the motor current corresponding to the auxiliary torque by feeding back the motor current and the rotational position of the rotor 6 is provided. Controlling the bridge circuit.

The control device 2 is structurally composed of an aluminum cover 17, a large current substrate 19 that is a main substrate, and an insulating multilayer substrate 18 that is a control substrate, and is made of aluminum of the electric motor 1 that also serves as a heat sink. The motor housing 12 is fixedly attached to the rear end of the motor housing 12, that is, the opposite output shaft side of the electric motor 1.
Each circuit component is mounted on an insulating multilayer substrate 18 and a large current substrate 19 as described later, and is connected by a conductive plate 24 made of a conductive member as described later.

6 is a perspective view of the large current substrate 19 shown in FIG. 5, and FIG. 7 is a front view of the conductive plate 24 constituting the large current substrate 19 shown in FIG.
The large current substrate 19 is manufactured by insert-molding a conductive plate 24 formed of a single metal plate (conductive member) that has been punched and bent with a mold resin 25. Then, by punching the tie bar (connecting member) 27 of the conductive plate 24,
A plurality of wiring patterns are formed. That is, the plurality of wiring patterns include a wiring pattern constituting a bridge circuit, a connection terminal 24a to the electric motor 1, a connection terminal 24b to the insulating multilayer substrate 18, and the like, and is integrated with the large current substrate 19 at the time of insert molding. ing. The connection terminal 24a and the connection terminal 24b are exposed at the surface of the conductive plate 24 from the mold resin 25 for electrical connection.
Further, the terminal 24b for electrical connection with the insulating multilayer substrate 18 is constituted by a protruding portion of the conductive plate 24, and this protruding portion is bent in a direction perpendicular to the mounting surface of the semiconductor switching element 23 to be insulated. The through-hole plating hole of the multilayer board is penetrated and jet soldered to the insulating multilayer board 19.
Further, at the time of the insert molding, the connector 3 for electrically connecting the control device 2 to the external power supply and sensors and a plurality of terminals (support legs) 26 for supporting the insulating multilayer substrate 18 are large by the mold resin 25. It is formed integrally with the current substrate 19. Thereby, the insulating multilayer substrate 18 is fixed to the terminal 26 by screws. For this reason, a support member for coupling the two is not necessary, the number of parts can be reduced, and a reduction in size and cost can be realized.

After the joining of the insulating multilayer substrate 18 and the large current substrate 19 is completed, the control device 2 is screwed to the motor housing 12 that also serves as a heat sink, and the connection terminal 24a to the motor of the large current substrate 19 is connected to the U phase of the electric motor 1. , V-phase and W-phase connection terminals are fixed with screws.
In this configuration, since the distance between the semiconductor switching element 23 constituting the bridge circuit and the electric motor 1 is short, the voltage drop due to the wiring pattern is reduced, and the motor efficiency is improved.

  In addition, electrolytic capacitor 20, shunt resistor 21 and control circuit components, which are part of power circuit components, are mounted on insulating multilayer substrate 18, all of which are surface-mounted components and are reflow soldered. Implemented by appendix. Therefore, in the manufacturing process of the control device 2, all the joining is performed by soldering, and other joining processes such as welding are unnecessary, so that the manufacturing cost can be reduced.

FIG. 8 is an enlarged view of a mounting portion of the semiconductor switching element 23 in the cross-sectional view of the electric power steering apparatus shown in FIG.
The mounting surface 24 c of the semiconductor switching element 23 that is the surface of the conductive plate 24 is provided with an exposed surface in which the surface of the conductive plate 24 is exposed from the mold resin 25 in order to enable reflow soldering. As a result, the semiconductor switching element 23 is mounted on the high-current substrate 19 by the reflow soldering method. Since it is a highly heat-resistant resin that has the strength to withstand temperatures, thermal denaturation does not occur even at the heating temperature of the reflow furnace.

  Further, the exposed surface of the conductive plate 24 exposed from the mold resin 25 is also provided on the opposite mounting surface 24d opposite to the mounting surface 24c, and the large current substrate 19 is placed on the motor housing 12 in the motor housing 12, that is, the heat sink portion. A flat raised portion 29 is formed which comes into thermal contact with the anti-mounting surface 24d, which is the exposed surface of the conductive plate 24, when fixed to the surface. Between the anti-mounting surface 24d and the motor housing 12, an insulating thermal conductive grease 28 in which ceramics such as alumina is dispersed is filled or a heat radiating sheet (heat radiating material) is interposed. As a result, the heat of the semiconductor switching element 23 can be dissipated to the motor housing 12 having a small heat resistance value and a large heat capacity while ensuring electrical insulation between the conductive plate 24 and the motor housing 12. It is possible to reduce the rise.

Since the thickness of the conductive plate 24 constituting the wiring pattern is about 800 μm, the generation of Joule heat due to the wiring resistance and the case where a metal substrate using a copper foil of about 100 μm thickness as the wiring pattern is adopted. The voltage drop can be reduced. For this reason, it becomes possible to flow a larger motor current.
Furthermore, since the plate thickness of the conductive plate 24 can be increased, the heat generated by the semiconductor switching element 23 can be easily diffused in the plane direction of the conductive plate 24 and the heat capacity of the conductive plate 24 is increased. And functions as a thermal buffer that suppresses the temperature rise of the semiconductor switching element 23.
In addition, compared with a copper foil of a general metal substrate, the conductive plate 24 has a large degree of freedom in changing the plate thickness, and the width can be reduced by increasing the plate thickness. The apparatus can be reduced in size under the same cross-sectional area.

1 is a cross-sectional view showing an electric power steering device according to Embodiment 1 of the present invention. It is a disassembled perspective view which shows the electric power steering apparatus of FIG. It is a disassembled perspective view which shows the control apparatus of the electric power steering apparatus of FIG. FIG. 4 is a front view showing the insulating multilayer substrate of FIG. 3. It is a front view which shows the high current board | substrate of FIG. FIG. 6 is a perspective view of the large current substrate shown in FIG. 5. FIG. 6 is a front view of a conductive plate constituting the large current substrate shown in FIG. 5. It is an enlarged view which shows the mounting part of the semiconductor switching element of the electric power steering apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Control apparatus 3 Connector 4 Output shaft 5 Permanent magnet 6 Rotor 7 Stator 8 Salient pole 9 Insulator 10 Armature winding 11 Reduction gear 12 Motor housing (heat sink part)
13 Gear Case 14 Worm Gear 15 Worm Wheel 16 Coupling 17 Aluminum Cover 18 Insulating Multilayer Board (Control Board)
DESCRIPTION OF SYMBOLS 19 Large current board | substrate (main board | substrate) 20 Large-capacity electrolytic capacitor 21 Shunt resistor 22 Coil 23 Semiconductor switching element 24 Conductive plate 24a Connection terminal with electric motor 1 24b Connection terminal with insulating multilayer board 18 24c Mounting of semiconductor switching element 23 Surface 24d Anti-mounting surface 25 Mold resin 26 Terminal (support leg)
27 Tie bar (connecting member) 28 Thermally conductive grease 29 Raised portion of heat sink.

Claims (11)

In an electric power steering device including an electric motor that outputs an auxiliary torque to a steering wheel of a vehicle, and a control device that controls driving of the electric motor,
A main board on which a plurality of semiconductor switching elements for switching the electric motor current are mounted;
A control board for generating a drive signal for controlling the plurality of semiconductor switching elements;
A conductive member that constitutes a wiring pattern of the plurality of semiconductor switching elements and electrically connects the main board and the control board;
A connector for electrically connecting the control board to an external power source is provided in the control device,
An electric power steering apparatus, wherein the main board, the conductive member, and the connector are integrally formed of a mold resin.   2. The electric power steering apparatus according to claim 1, wherein the control device is attached to a motor housing of the electric motor that also serves as a heat sink portion of the control device.   2. The electric power steering apparatus according to claim 1, wherein each connection terminal of the main board is integrated with the main board by insert molding.   2. The electric power steering apparatus according to claim 1, wherein a mounting surface of the semiconductor switching element is provided on an exposed surface of the conductive member exposed from the mold resin.   5. The electric power steering apparatus according to claim 4, wherein the semiconductor switching element is mounted on the main board by a reflow soldering method.   2. The heat sink portion according to claim 1, further comprising a raised portion that is in thermal conduction contact with an exposed surface of the conductive member exposed from the mold resin on the opposite side of the semiconductor switching element mounting surface. The electric power steering apparatus as described.   The electric power steering apparatus according to claim 6, wherein a heat conductive grease is filled or a heat dissipation material is interposed between the raised portion of the heat sink portion and the conductive member.   2. The electric power steering apparatus according to claim 1, wherein the main board is formed by integrally molding a plurality of support legs that support the control board with the molding resin. 3.   2. The electric power steering apparatus according to claim 1, wherein the mold resin is a high heat resistant resin having a strength that can withstand a reflow temperature of solder.   The terminal for electrically connecting the main board and the control board is formed by bending a protruding portion of the conductive member formed exposed from the mold resin. The electric power steering apparatus according to 1.   The electric power steering apparatus according to claim 1, wherein the main board is fixed to a side opposite to the output shaft of the electric motor via the heat sink portion.

Images