JP5773019B2 - Electric power steering device - Google Patents

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 a vibration isolation structure applied to a control unit (ECU) that controls driving of the electric motor.

  Many of the vehicles in recent years are equipped with an electric power steering device (EPS) that assists the driver's steering by transmitting the driving force of the electric motor to the steering shaft via the speed reduction mechanism. In this electric power steering apparatus, a steering torque signal detected by a torque sensor is input to a control unit (ECU), and the control unit controls a drive current supplied to the electric motor based on the steering torque signal. The drive of the electric motor is controlled.

  In this type of electric power steering device, the operating vibration and sound generated by an electric motor, a speed reduction mechanism, etc. are propagated to the control unit, and the frequency of the natural vibration of the cover member of the ECU housing formed of a thin metal plate or the like. When the number matches, there is a problem that the cover member resonates to generate a large noise.

  In order to solve this problem, for example, in Patent Document 1, by attaching a vibration isolating member to the cover member (main body cover and side cover) of the control unit, the resonance of the control unit is suppressed and noise is reduced. The thing which aimed at is disclosed.

JP 2002-331945 A

  However, as disclosed in Patent Document 1, simply attaching a vibration isolating member to the surface of the cover member of the ECU housing reduces the sound pressure level by several dB with respect to the natural vibration of the cover member. However, there is a problem that a sufficient damping effect cannot be obtained with respect to operating vibration or abnormal noise.

  In the ECU disclosed in Patent Document 1, the vibration isolation effect can be improved by attaching the vibration isolation member over the entire surface of the cover member. However, as the thickness of the vibration isolation member increases. There was a problem that the heat dissipation of the electronic components mounted in the ECU deteriorated.

  Further, as another anti-vibration measure, a method of increasing the rigidity of the cover member and increasing the resonance natural frequency by increasing the plate thickness of the cover member or by performing bead processing on the cover member is used. However, in these anti-vibration measures, there have been problems such as an increase in apparatus weight and material cost due to an increase in the thickness of the cover member, or a decrease in productivity due to an additional process. Therefore, such a method is not a good solution for an electric power steering apparatus that is required to be light and low in cost.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cover member for a control unit that is structurally susceptible to the effects of operating vibration generated by an electric motor, a speed reduction mechanism, etc. It is an object of the present invention to provide an electric power steering apparatus that is attached to a base member in an elevated state to thereby prevent the cover member from vibrating and reducing the generation of abnormal noise.

  An object of the present invention is to provide an electric power steering apparatus including an electric motor that applies a steering assisting force to a steering mechanism and a control unit that controls driving of the electric motor. A base member on which a circuit board for controlling the driving of the electric motor is mounted and a cover member attached to the base member so as to cover the opening; The member includes an auxiliary support portion that protrudes in a vertical direction from the bottom surface toward the opening, and when the cover member is attached to the base member, an upper portion of the auxiliary support portion is an inner surface of the cover member. This is achieved by abutting against.

  Further, the above object is characterized in that the auxiliary support portion has a support column vertically provided from the bottom surface of the base member toward the opening, and an elastic body attached to the upper surface of the support column. When the cover member is attached to the base member, the cover member abuts against the elastic body, thereby effectively achieving the cover member.

  Moreover, the said objective is effectively achieved because the said auxiliary | assistant support part is formed in the center part of the bottom face of the said base member.

  Moreover, the said objective is effectively achieved by the said cover member being fastened by the said auxiliary | assistant support part via the screw | thread.

  Furthermore, the object is effectively achieved by mounting the cover member on the base member so as to be urged by the auxiliary support portion.

  According to the electric power steering apparatus of the present invention, the auxiliary support portion that protrudes in the vertical direction is erected on the bottom surface of the base member constituting the casing of the control unit, and the auxiliary member is attached when the cover member is attached to the base member. The upper part of the support part comes into contact with the inner surface of the cover member. As a result, the rigidity of the cover member can be increased, and the resonance frequency of the cover member can be increased above the natural frequency. As a result, even when a cover member formed of a thin metal material is attached to the base member, the amplitude of the cover member can be suppressed and the occurrence of abnormal noise can be reduced.

  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 3 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. The control unit 11 is supplied with electric power from a battery (power source) 12 and receives an ignition key signal from an ignition key 13. 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 is calculated. The drive current supplied to the electric motor 10 is controlled according to I.

  The above-described electric power steering apparatus 1 is 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 provided in the pinion portion of the rack and pinion mechanism. May be a pinion assist type in which is provided, or a rack assist type in which the electric motor 10 is provided in the rack portion.

[First Embodiment]
FIG. 2 is a schematic cross-sectional view showing the internal configuration of the control unit according to the first embodiment of the present invention. In the figure, a housing 15 of the control unit 11 is composed of a box-shaped base member 16 having an open top surface, and a cover member 17 attached so as to cover the opening of the base member 16. Are detachably attached to the base member 16 by fitting with caulking or fastening with bolts. Although not shown here, the control unit 11 includes a power connector and a signal connector, and is electrically connected to the battery 12, the torque sensor 8, the vehicle speed sensor 14, the ignition key 13, and the like through these various connectors. ing.

  The control unit 11 includes a drive circuit board 18 that supplies a drive current to the electric motor 10, an insert molding module 20 that is electrically connected to the drive circuit board 18 via a wire-bonded metal wire 19, and leads. A control circuit board 22 electrically connected to the drive circuit board 18 via the terminal 21 is provided inside the base member 16.

  The drive circuit board 18 is made of a metal material having excellent heat transfer properties and heat conductivity, and a heat generating component such as an FET (field effect transistor) 23 is mounted on the surface thereof. When the drive current supplied to the electric motor 10 flows to the drive circuit board 18, the temperature of the drive circuit board 18 increases with the heat generation of the FET 23. Therefore, the drive circuit board 18 is mounted so as to be in contact with the bottom surface of the base member 16 that functions as a heat sink.

  The insert molding module 20 includes a wiring pattern 25 that is insert-molded integrally with the resin base material 24, a coil 26 that is electrically connected to the wiring pattern 25, and a wiring pattern 25 that protrudes from the resin base material 24. A bus bar terminal 27 formed at one end is provided, and is electrically connected to the electric motor 10 via the bus bar terminal 27. Further, similarly to the drive circuit board 18 described above, a heat-generating component such as a coil 26 is mounted on the insert molding module 20. Therefore, the insert molding module 20 is mounted so as to be in contact with the bottom surface of the base member 16 in consideration of heat dissipation, and the bus bar terminal 27 protrudes from a notch formed in a part of the side wall of the base member 16. It is arranged in.

  The control circuit board 22 is a printed board formed of an insulating resin material or the like, and a control element such as a microcomputer chip 28 that generates relatively little heat due to energization is mounted on the surface thereof. Since the heat generating components such as the FET 23 and the coil 26 are not mounted on the control circuit board 22, the temperature of the control circuit board 22 when energized is lower than the drive circuit board 18 and the insert molding module 20 described above. . For this reason, the control circuit board 22 is disposed above the drive circuit board 18 and the insert molding module 20 by the support of the step 16a formed at the opening peripheral edge of the base member 16.

  Since the base member 16 is required to function as a heat sink as described above, the base member 16 is formed of a thick metal material (for example, an aluminum alloy) excellent in thermal conductivity and durability. In particular, the location where the drive circuit board 18 that generates high heat is mounted is thicker than the other portions. On the other hand, the cover member 17 has a structural purpose to cover the upper surface opening of the base member 16 and prevent dust and the like from entering the inside of the control unit 11. It is made from a relatively thin material in consideration.

  The control unit 11 having the casing 15 having such a configuration is a position where the operating vibration of the electric motor 10 or the speed reduction mechanism 9 is easily transmitted, for example, a part of a steering column that rotatably supports the steering shaft 3. Is attached. When the control unit 11 is arranged at such a position, since the cover member 17 constituting the housing 15 has a thin-walled structure as described above, there is a high possibility that it will resonate due to this operating vibration.

  Therefore, in the present embodiment, the auxiliary support portion 29 that protrudes in the vertical direction from the bottom surface toward the opening on the top surface at the center portion of the bottom surface of the base member 16, that is, between the drive circuit board 18 and the insert molding module 20. When the cover member 17 is mounted on the base member 16, the upper portion of the auxiliary support portion 29 and the inner surface central portion of the cover member 17 are brought into contact with each other. The auxiliary support portion 29 includes a support column 30 that is erected vertically from the center of the bottom surface of the base member 16 toward the upper opening, and an elastic body 31 that is attached to the upper surface of the support column 30 with an adhesive or the like. Have

  An insertion hole 22a through which the auxiliary support portion 29 is inserted is formed near the center of the control circuit substrate 22 disposed above the drive circuit board 18 and the insert molding module 20, that is, at a position corresponding to the auxiliary support portion 29. Has been. After the drive control circuit 18 and the insert molding module 20 are mounted on the bottom surface of the base member 16, the control circuit board 22 has a step 16a of the base member 16 in a state where the upper portion of the auxiliary support portion 29 protrudes from the insertion hole 22a. It is fixed by screw fastening or the like.

  Further, the mounting of the cover member 17 and the base member 16 is set such that the distance between the inner surface of the cover member 17 and the bottom surface of the base member 16 has a minus tolerance than the height of the auxiliary support portion 29. That is, the cover member 17 is attached to the base member in a bent state due to the contact between the inner surface central portion and the auxiliary support portion 29. As a result, the center portion of the cover member 17 attached to the base member 16 is biased toward the auxiliary support portion 29, and as a result, the rigidity of the cover member 17 is increased.

  As described above, according to the electric power steering apparatus 1 according to the present embodiment, the base member 16 constituting the casing 15 of the control unit 11 is vertically projected from the central portion of the bottom surface toward the opening of the upper surface. 29, the elastic body 31 is attached to the upper surface of the support column 29, and the elastic body 31 is brought into contact with the center of the inner surface of the cover member 17 when the cover member 17 is attached to the base member 16. As a result, the amplitude of the cover member 17 is suppressed and the rigidity of the cover member 17 is increased, so that it is possible to reduce the occurrence of abnormal noise caused by the resonance of the cover member 17.

[Second Embodiment]
FIG. 3 is a schematic cross-sectional view showing the internal configuration of the control unit according to the second embodiment of the present invention. In the figure, the same members as those in the embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 3, in the case 15A of the control unit 11A according to the present embodiment, the central portion of the cover member 17A that contacts the elastic body 31A of the auxiliary support portion 29A when mounted is connected to the base member 16A via a screw 32. This is different from the above-described first embodiment in that it is fastened and fixed to. The screw 32 used for fastening and fixing passes through the cover member 17 and the elastic body 31A and is screwed into a screw hole formed on the upper surface of the support 30A. By adjusting the tightening degree of the screw 32, The rigidity of the cover member 17A can be arbitrarily adjusted.

  According to the control unit 11A according to the present embodiment having the above-described configuration, the cover member that comes into contact with the elastic body 31A of the auxiliary support portion 29A at the time of mounting as well as obtaining the same effect as the first embodiment described above. By fastening and fixing the central portion of 17A with the screw 32, the amplitude suppressing effect and the rigidity improving effect of the cover member 17A can be further enhanced.

  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 schematic sectional drawing which shows the internal structure of the control unit which concerns on 1st Embodiment of this invention. It is a schematic sectional drawing which shows the internal structure of the control unit which concerns on 2nd Embodiment of this invention.

DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus 2 ... Steering wheel 3 ... Steering shaft 10 ... Electric motor 11, 11A ... Control unit (ECU)
15, 15A ... casing 16, 16A ... base members 17, 17A ... cover members 29, 29A ... auxiliary support portions 30, 30A ... struts 31, 31A ... elastic bodies 32 ··screw

Claims (3)

An electric motor for applying a steering assist force to the steering mechanism;
An electric power steering apparatus comprising a control unit for controlling the drive of the electric motor,
It has a box shape with an opening on the top surface,
A base member that controls the driving of the electric motor and on which a circuit board having an insertion hole in the center is mounted;
A housing of the control unit is configured from a cover member attached to the base member so as to cover the opening,
The base member includes an auxiliary support portion protruding in a vertical direction from the bottom surface toward the opening,
The auxiliary support portion is inserted through the insertion hole of the circuit board, and a support column vertically erected from the bottom surface of the base member toward the opening;
An elastic body attached to the upper surface of the column;
And,
When the cover member is attached to the base member, the elastic body attached to the upper surface of the column is
Abutting only on the inner surface of the cover member;
The electric power steering apparatus according to claim 1, wherein the cover member is attached to the base member so as to be urged by the auxiliary support portion.   2. The electric power steering apparatus according to claim 1, wherein the cover member is attached to the base member in a bent state by contact between an inner surface central portion of the cover member and the auxiliary support portion. . The electric power steering apparatus according to claim 1, wherein the cover member is fastened to the auxiliary support portion via a screw.

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