JP2009012631A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device, in which the assembly work efficiency of a control unit for controlling driving of an electric motor is improved, and the heat radiation function of the control unit is improved to be adaptable to large current size electric motors. <P>SOLUTION: The control unit is provided with a control substrate mounting a control element for controlling driving of the electric motor, a metal substrate mounting a power element through which drive current of the electric motor runs, a mold substrate integrally composed with a resin substrate by insert-molding to electrically connect the control substrate to the metal substrate, a base part to house the control substrate, the metal substrate, and the mold substrate, while functioning as a heat sink, and a cover part to cover the base part. The control substrate, the metal substrate, the mold substrate, the base part, and the cover part are disposed in laminated structure, and part of the mold substrate is connected to part of the base part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus using an electric motor as a generation source of steering assist torque, and more particularly to an improvement in a heat dissipation structure of a control unit (ECU) that controls a drive current of the electric motor.

  In recent years, in this type of electric power steering apparatus, the assisting force of an electric motor for assisting steering of a steering shaft tends to increase with the increase in size and output of a vehicle to be mounted. Therefore, in the control unit (ECU) that controls the driving of the electric motor, the mounted circuit elements, wiring patterns, conductive wires, and other structures have heat resistance and durability that can cope with the increase in electric current of the electric motor. However, there was a problem that the size and complexity were increased.

  Therefore, as an improvement plan for solving such a problem, for example, an electric power steering circuit device disclosed in Patent Document 1 or a control unit of the electric power steering device disclosed in Patent Document 2 is known. .

  In the electric power steering circuit device of Patent Document 1, the conductive plate before insert molding is constituted by a single conductive metal plate on which a wiring pattern is continuously formed, as well as a coil, a power relay, and a motor relay. By forming the portions of the wiring pattern that are electrically connected to each other on the same plane, the cost is reduced and the assembly workability is improved. Also, in this electric power steering circuit device, the amount of heat generated from a large current component or wiring pattern mounted on the metal substrate is transmitted to the heat dissipation case via the metal substrate by bringing the back side of the metal substrate into contact with the heat dissipation case. It has a structure.

  On the other hand, in the control unit of Patent Document 2, a circuit conductor component formed by processing a metal plate is integrated by insert molding, and a part of the circuit conductor component is mounted on a base substrate on which a high-current circuit component is mounted. In this configuration, the current is increased by suppressing the heat generation of the circuit conductor due to a large current while avoiding an increase in size in the substrate surface direction.

Japanese Patent Laid-Open No. 2004-345643 JP 2002-127920 A

  However, in the electric power steering circuit device of Patent Document 1 described above, the heat dissipation function is not sufficient in consideration of further increase in current of the electric motor in the future. That is, as the current increases, the heat generated in the current-carrying metal wiring pattern further increases. Therefore, it is necessary to improve the heat resistance of the current-carrying metal wiring pattern.

  Further, in this electric power steering circuit device, the heat generation of the energized metal wiring pattern due to the increase in current increases the heat generation of the coils and relays mounted on the energized metal wiring pattern, and from the energized metal wiring pattern. There is a problem that the temperature of the mounted parts on the control board and the metal board also rises due to the heat radiation.

  On the other hand, the control unit of Patent Document 2 described above also has a problem that the heat dissipation function is not sufficient with respect to an increase in the amount of heat generated by the heat-generating component due to the increase in current.

  In order to cope with such an increase in the amount of heat generated by heat-generating components, it is conceivable to adopt a structure that can actively dissipate the current-carrying metal wiring pattern. There is a possibility that the conductive metal wiring pattern may be short-circuited on the heat radiating case.

  Therefore, the present invention has been made in view of the above circumstances, and its object is to improve the assembly workability of the control unit that controls the drive of the electric motor and to increase the current of the electric motor. It is an object of the present invention to provide an electric power steering device in which the heat dissipation function of a control unit is improved so that it can be adapted.

  An object of the present invention is to provide an electric power steering apparatus comprising: an electric motor that applies a steering assist force to a steering shaft connected to a steering wheel; and a control unit that controls driving of the electric motor. The unit is configured integrally with a resin base material by insert molding, a control board on which a control element for controlling driving of the electric motor is mounted, a metal board on which a power element through which the driving current of the electric motor flows is mounted, A mold substrate on which a current-carrying metal wiring pattern for electrically connecting the control substrate and the metal substrate is mounted; the control substrate, the metal substrate, and the mold substrate; and a base portion that functions as a heat sink; A cover portion covering the base portion, the control board, the metal Plate, the mold substrate, the base portion, and the cover portion is arranged in a stacked structure, and a portion of the mold substrate, by being connected to a portion of the base portion is achieved.

  Further, the above object is that the mold substrate includes a heat generating component mounted on the mold substrate, a current-carrying metal wiring pattern that electrically connects the heat-generating component to the mold substrate, and the current-carrying metal wiring pattern. This is effectively achieved by having non-current-carrying metal wiring patterns arranged in parallel and a heat-dissipating insulator enclosed between the non-current-carrying metal wiring pattern and the current-carrying metal wiring pattern.

  In addition, the object is to transmit heat from the conductive metal wiring pattern to the heat-dissipating insulator to dissipate heat, and from the heat-dissipating insulator to the base portion through the non-conductive metal wiring pattern. This is achieved effectively by dissipating heat.

  Moreover, the said objective is effectively achieved when the said exothermic component contains at least 1 of a coil, a power supply relay, a motor relay, and a shunt resistance element.

  Further, the object is that the mold substrate is insert-molded integrally with the resin base material so that a space is partially defined between the energized metal wiring pattern and the non-energized metal wiring pattern, and The heat dissipating insulator is effectively achieved by being enclosed in the space.

  According to the control unit of the electric power steering apparatus according to the present invention, a part of the mold substrate that electrically connects the control substrate and the metal substrate is connected to a part of the base portion that functions as a heat sink, thereby energizing The heat of the metal wiring pattern can be transferred to the base portion and dissipated outside the control unit. As a result, the heat generation of the energized metal pattern is suppressed, and the temperature rise of the control board and components mounted on the metal board is also suppressed, so that the heat resistance, durability, and device life of the control unit can be improved. it can.

  In the control unit of the electric power steering apparatus according to the present invention, when mounting exothermic parts such as a coil, a power relay, a motor relay, and a shunt resistor element on the mold substrate, these exothermic parts are electrically connected. The heat conduction metal wiring pattern heat is transferred to the heat dissipating insulator to dissipate heat, and the heat dissipating insulator is transmitted to the base part through the non-conducting metal wiring pattern to dissipate heat to the outside of the control unit. Therefore, it is possible to suppress the temperature rise of the control unit due to these heat generating components while improving the assembly workability of the heat generating components.

  Moreover, according to the said heat dissipation structure which concerns on this invention, since an electricity supply metal wiring pattern is indirectly connected to the base part via a heat-radiating insulator and a non-energization metal wiring pattern, it arises in an electricity supply metal wiring pattern A short circuit can be prevented, and durability against an increase in current of the electric motor can be improved.

  Furthermore, according to the control unit of the electric power steering apparatus according to the present invention, the mold substrate is integrated with the resin base material so that a space is partially defined between the energized metal wiring pattern and the non-energized metal wiring pattern. Insert molding and encapsulating a heat dissipating insulator in the space makes it possible to improve heat dissipation only at a predetermined portion where a coil, a relay or the like that requires heat dissipation is disposed. Thereby, reduction of material costs, such as a heat-radiating insulator, can be aimed at.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a mechanism diagram showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention.

  In the figure, the steering mechanism of the electric power steering apparatus 1 includes a steering shaft 3 that rotates in response to a steering operation of a steering wheel 2 attached to a tip portion, and a universal joint 4 on the other end side of the steering shaft 3. 5 and a rack and pinion mechanism 6 that converts the rotational motion of the steering shaft 2 into a linear motion of the rack shaft, and a tie rod 7 that transmits the motion of the rack shaft of the rack and pinion mechanism 6 to the steering wheel. It is composed of

  In addition, the column portion of the electric power steering apparatus 1 includes a torque sensor 8 that detects a steering torque input to the steering shaft 3 via the steering wheel 2 and a steering coupled to the steering shaft 3 via the speed reduction mechanism 9. An auxiliary electric motor 10 is provided.

  Driving of the electric motor 10 is controlled by a control unit (ECU) 11 equipped with a control circuit and the like. Electric power is supplied from the battery 12 to the control unit 11, and an ignition key signal is input from the ignition key 13. Then, the control unit 11 calculates the steering assist command value I based on the steering torque value T detected by the torque sensor 8 and the vehicle speed V detected by the vehicle speed sensor 14, and the calculated steering assist command value I is calculated. The drive current supplied to the electric motor 10 is controlled accordingly.

  The electric power steering device 1 described above is of a column assist type in which the electric motor 10 is disposed in the column portion. However, the present invention is not limited to this, and for example, the electric motor 10 is disposed in the pinion portion. The pinion assist type may be used, or the rack assist type in which the electric motor 10 is disposed in the rack portion.

  2 is an exploded perspective view showing a schematic configuration of the control unit of FIG. 1, and FIG. 3 is a schematic cross-sectional view showing an internal structure of the control unit of FIG.

  As shown in FIG. 2, the box-shaped external housing of the control unit 11 includes a base portion 15 that forms a base portion, and a component that is disposed so as to cover the base portion 15 and is attached to the base portion 15. And a cover portion 16 for shielding. A metal substrate 19 on which power elements such as an FET (field effect transistor) 17 and a relay 18 necessary for driving the electric motor 10 are mounted is fastened and fixed to the base portion 15 with screws or the like.

  The metal substrate 19 is formed of a material such as metal or ceramic having excellent heat transfer properties and heat conductivity, and transfers heat of the power element generated by the drive current of the electric motor 10 to the base portion 15 satisfactorily. It is supposed to be. Thereby, the heat of the power element generated by energization is efficiently dissipated to the outside of the control unit 11 by the function of the base portion 15 as a heat sink (heat radiating plate).

  Above the metal board 19, a control board 20 comprising an insulating printed board on which a control element such as a microcomputer for controlling the drive of the electric motor 10 and its peripheral circuit is mounted is disposed. The control board 20 and the metal board A mold substrate 22 that is integrally formed with the resin base material 21 by insert molding is disposed between the two. That is, the control board 20, the metal board 19, the mold board 22, the base part 15, and the cover part 16 described above are arranged so as to have a laminated structure when assembled.

  The substrate housed in the control unit 11 has a two-sheet structure comprising a metal substrate 19 on which components that generate relatively large heat when energized and a control substrate 20 that mounts components that generate relatively small heat when energized. In addition, each of the substrates 19 and 20 is electrically connected by the mold substrate 22. With this structure, a large current can be supplied to the electric motor 10 and the control unit 11 can be downsized.

  Further, the control unit 11 includes a connector 23 for connecting to the battery 12 or the like at one end of the resin base material 21 formed integrally with the mold substrate 22, and the connector 23 is connected to the control substrate via the mold substrate 22. 20 and the metal substrate 19 are electrically connected. A notch portion 15a to which the connector 23 is attached is formed on one side surface of the base portion 15 disposed when the connector 23 is assembled. A screw groove is formed on a part of the bottom surface of the base portion 15. The engraved boss 15b is erected.

  The mold substrate 22 that is insert-molded integrally with the resin base material 21 includes a coil 24 that is a heat-generating component, an energized metal wiring pattern 25 that electrically connects the coil 24, and the energized metal wiring pattern 25. A non-energized metal wiring pattern 26 arranged in parallel and a heat dissipating insulator 27 enclosed between the non-conductive metal wiring pattern 26 and the conductive metal wiring pattern 25 are provided.

  A coil 24 is electrically connected to a part of the current-carrying metal wiring pattern 25 formed on the surface of the resin base material 21 (upper surface in FIG. 3) by soldering. The energized metal wiring pattern 25 has a sufficient cross-sectional area so that it can cope with a large current flowing through the coil. Here, although the coil 24 is mounted on the mold substrate 22 as a heat-generating component, the present invention is not limited to this, and may be, for example, a power relay, a motor relay, a shunt resistor, or the like.

  A heat dissipating insulator 27 is joined to a part of the back surface (lower surface in FIG. 3) of the energizing metal wiring pattern 25, and a non-energizing metal wiring is connected to the back surface (lower surface in FIG. 3) of the heat dissipating insulator 27. The pattern 26 is joined. A part of the non-energized wiring pattern 26 and the heat dissipating insulator 27 are insert-molded integrally with the energizing metal wiring pattern 25 and the resin base material 21 in the above-described joined state, while the non-energized wiring pattern 26 and the heat dissipating insulation. The other part of the object 27 extends outward (left side in FIG. 2) from the resin base material 21. A hole 26h through which the screw 26s is inserted is formed at the center of the other end (left side in FIG. 2) of the non-energized wiring pattern 26, and the screw 26s inserted through the hole 26h is formed in the screw groove of the boss 15b. Screwed. By fastening the screws 26s, the mold substrate 22 is fixed to the case 15, and the non-energized wiring pattern 26 is connected to the base portion 15 that is a heat sink member. Note that the heat dissipating insulator 27 is preferably an insulator excellent in heat dissipating property, heat transfer property, and heat conductivity, and is made of, for example, a silicon-based resin.

  Although not shown, a part of the energized metal wiring pattern 25 of the mold substrate 22 extends into the connector 23 to form a terminal of the connector 23 and is connected to the battery 12 or the like.

  In the mold substrate 22 having such a configuration, the heat of the energized metal wiring pattern 25 generated by energizing the coil 24 is transmitted to the heat dissipating insulator 27 to be dissipated, and is not energized from the heat dissipating insulator 27. It has a heat dissipation structure that is transmitted to the base portion 15 through the metal wiring pattern 26 to dissipate heat. That is, in this heat dissipation structure, the current-carrying metal wiring pattern 25 connected to the heat-generating component such as the coil 24 is indirectly connected to the base portion 15 via the heat-dissipating insulator 27 and the non-current-carrying metal wiring pattern 26. ing. Therefore, even when a large current flows through a heat-generating component such as the coil 24 in order to increase the output of the electric motor 10, the energized metal wiring pattern 25 is not directly connected to the base portion 15 that is a heat sink. Since the heat of 25 can be satisfactorily transmitted to the base portion 15, it is possible to prevent a short circuit of the conductive metal wiring pattern 25 and adapt to the increase in current of the electric motor 10.

  FIG. 4 is a schematic cross-sectional view showing a modification of the mold substrate 22 in the above-described embodiment. In this modification, the same members as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, the mold substrate 22 'is insert-molded integrally with the resin base material 21' so that a space is partially defined between the energized metal wiring pattern 25 'and the non-energized metal wiring pattern 26'. The heat dissipating insulator 27 'is enclosed in the space. Above the portion where the heat dissipating insulator 27 'is disposed, a coil 24' which is a heat generating member is disposed. In this modification, a coil 24 'that generates particularly high heat is disposed as a heat-generating component that is mounted above the enclosed heat-dissipating insulator 27'. However, the present invention is not limited to this. For example, a capacitor, a relay, a shunt resistor, or the like may be used.

  Further, as described above, a part of the non-energized metal wiring pattern 26 ′ is insert-molded integrally with the resin base material 21 ′ with the heat dissipating insulator 27 ′ enclosed between the conductive metal wiring pattern 25 ′. On the other hand, the other part of the non-energized metal wiring pattern 26 ′ extends outward (left side in FIG. 4) from the resin base material 21 ′. A hole 26h through which a screw 26s is inserted is formed in the center of the end of the extended non-energized metal wiring pattern 26 '. The screw 26s inserted through the hole 26h is screwed to the boss 15b provided in the same manner as in the above-described embodiment, whereby the non-energized metal wiring pattern 26 'is connected to the base portion 15 which is a heat sink member. The

  According to the mold substrate 22 ′ according to the present modification having such a configuration, the same effect as that of the above-described embodiment can be obtained, and the portion where the heat dissipating insulator 27 ′ is disposed can be dissipated. Since it can be limited only to the lower part of the part where the exothermic parts are required, it is possible to reduce the material cost of the heat dissipating insulator 27 'when manufacturing the control unit.

  Further, according to the mold substrate 22 'according to this modification, the heat dissipating insulator 27' is enclosed by the resin base material 21 'filled between the energized metal wiring pattern 25' and the non-energized metal wiring pattern 26 '. As a result, the installation space can be saved.

  In the above-described embodiment, the non-energized wiring pattern 26 and the base portion 15 are connected by the screw 26s. However, this connection means is not limited to this and has excellent thermal conductivity. If it is what. Therefore, for example, even if the non-energized wiring pattern 26 and the base portion 15 are connected by welding, the same operational effects as in the present embodiment can be obtained.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to this, In the range which does not deviate from the meaning, it can change suitably.

It is a mechanism figure showing a schematic structure of an electric power steering device concerning an embodiment of the present invention. It is a disassembled perspective view which shows schematic structure of the control unit of FIG. It is a schematic sectional drawing which shows the internal structure of the control unit of FIG. It is a principal part perspective view which shows the modification of the mold substrate which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 2 Steering wheel 3 Steering shaft 11 Control unit (ECU)
15 Base 16 Cover 17 FET (Field Effect Transistor)
18 Relay 19 Metal substrate 20 Control substrate 21, 21 ′ Resin base material 22, 22 ′ Mold substrate 24, 24 ′ Coil 25, 25 ′ Energized metal wiring pattern 26, 26 ′ Non-energized metal wiring pattern 27, 27 ′ object

Claims (5)

An electric power steering apparatus comprising: an electric motor that applies a steering assist force to a steering shaft coupled to a steering wheel; and a control unit that controls driving of the electric motor,
The control unit is configured integrally with a resin base material by insert molding, a control board on which a control element for controlling driving of the electric motor is mounted, a metal board on which a power element through which the driving current of the electric motor flows is mounted. , A mold substrate that electrically connects the control substrate and the metal substrate, a base portion that houses the control substrate, the metal substrate, and the mold substrate, and that functions as a heat sink, and covers the base portion A cover portion,
The control board, the metal board, the mold board, the base part, and the cover part are arranged in a laminated structure, and
An electric power steering apparatus, wherein a part of the mold substrate is connected to a part of the base part.   The mold substrate includes a heat generating component mounted on the mold substrate, a conductive metal wiring pattern for electrically connecting the heat generating component, and a non-conductive metal wiring pattern arranged in parallel with the conductive metal wiring pattern. The electric power steering apparatus according to claim 1, further comprising: a non-energized metal wiring pattern; and a heat dissipating insulator enclosed between the conductive metal wiring pattern.   The heat of the current-carrying metal wiring pattern is transmitted to the heat-dissipating insulator and dissipated, and is also transmitted from the heat-dissipating insulator to the base portion through the non-energized metal wiring pattern and dissipated. 2. The electric power steering apparatus according to 2.   The electric power steering apparatus according to claim 2 or 3, wherein the heat-generating component includes at least one of a coil, a power supply relay, a motor relay, and a shunt resistance element. The mold substrate is insert-molded integrally with the resin base material so that a space is partially defined between the energized metal wiring pattern and the non-energized metal wiring pattern, and
The electric power steering apparatus according to claim 2, wherein the heat dissipating insulator is sealed in the space.

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