JP2008253049A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor with a heat dissipating structure capable of preventing short circuit of a control board, without impairing the heat dissipation of electronic components. <P>SOLUTION: An aluminum heat sink 37 is mounted within a synthetic resin case cover 27 so as to face the control board 33. Minute protrusions 41, which are brought into contact with the facing control board 33, to form a space 42 between the heat sink 37 and the control board 33, are formed on the lower surface 37a of the heat sink 37. The minute protrusions 41 are so arranged as to abut against portions other than the conductive parts on the control board 33. The minute protrusions 41 have a clearance secured in between the heat sink 37 and the control board 33, that enables avoiding contact between the heat sink 37 and the conductive parts of the control board, and can prevent short circuiting of the control board. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric motor including a heat radiating unit that cools electronic components on a control board, and more particularly, to an improvement in insulation between the control board and the heat radiating part.

  2. Description of the Related Art Conventionally, as a drive source for a wiper device or the like mounted on an automobile, an electric motor that combines a motor body and a speed reduction mechanism into a single unit has been used. Such an electric motor is provided with a gear case that houses the speed reduction mechanism and a case cover that closes the gear case, and these cases and covers are formed of a synthetic resin material in terms of weight, cost, and the like. There are many. In addition to the speed reduction mechanism, the unitized electric motor is provided with a control board on which electronic components for motor control are mounted, and this control board is housed in the gear case together with the speed reduction mechanism.

  On the other hand, since the electronic components on the control board generate heat due to the energization operation, it is necessary to cool them appropriately. For this reason, in the conventional electric motor, a heat sink made of aluminum is arranged at a portion facing the control board of the case cover, and the heat dissipation of the electronic components is performed by this heat sink. FIG. 8 is an explanatory view showing the heat dissipation structure of such a conventional electronic component. As shown in FIG. 8, an aluminum heat sink 52 is attached to the upper surface of the case cover 51. The heat sink 52 is disposed above the control board 53 so as to face the control board 53. An electronic component 54 such as an FET is mounted on the lower surface side of the control board 53 in the drawing, and a conductive pattern made of copper foil is disposed on the upper surface side of the control board 53 in the drawing.

In the heat dissipation structure of FIG. 8, a thermal conductive sheet 55 is interposed between the control board 53 and the heat sink 52. The thermal conductive sheet 55 is made of a synthetic resin having good thermal conductivity, such as a PPS resin (polyphenylene sulfide) filled with ceramics or a PPS resin filled with carbon fibers. As described above, by sandwiching the heat conductive sheet 55 between the control board 53 and the heat sink 52, the heat generated in the electronic component 54 is transmitted to the heat sink 52 via the heat conductive sheet 55. Then, it travels through the heat sink 52 and is dissipated from the upper surface to the outside of the case cover 51.
JP 2005-168133 A

  However, in the case of the heat dissipation structure as shown in FIG. 8, in order to suppress the stress generated in the control board 53 while maintaining good adhesion to the control board 53 and the heat sink 52, the heat conductive sheet 55 is a thick type. Need to use one. For this reason, in the heat dissipation structure of FIG. 8, although the distance between the heat sink 52 and the control board 53 becomes large and the thermal conductive sheet 55 is sandwiched, the thermal conductivity is lowered and the cooling efficiency is not good. There was a problem. For this reason, in order to improve the cooling efficiency, a method of conducting heat conduction by bringing the heat sink 52 and the control board 53 closer to each other and applying a heat conductive adhesive or silicon grease between them is studied. Used in many motors.

  FIG. 9 is an explanatory view showing a heat dissipation structure by such a proximity arrangement method. As shown in FIG. 9, here, the heat conductive sheet 55 is not interposed between the heat sink 52 and the control board 53, and the heat sink 52 and the control board 53 are arranged close to each other so as not to adhere to each other. . On the other hand, a heat conductive adhesive 56 is applied between the heat sink 52 and the control board 53, and the heat of the electronic component 54 is transmitted to the heat sink 52 by the heat conductive adhesive 56.

  However, when the heat sink 52 and the control board 53 are brought close to each other as in the heat dissipation structure of FIG. 9, there is a problem that the lower surface of the heat sink 52 may come into contact with the copper foil portion of the control board 53. As described above, since the heat sink 52 is formed of aluminum, if the heat sink 52 comes into contact with the copper foil portion, the control board 53 may be short-circuited, and countermeasures are required from the viewpoint of product reliability. It was.

  The objective of this invention is providing the electric motor provided with the heat dissipation structure which can prevent the short circuit of a control board, without impairing the heat dissipation of an electronic component.

  The electric motor of the present invention is an electric motor having a motor body that drives a rotating shaft and a speed reducing mechanism that decelerates and outputs the rotation of the rotating shaft, and is assembled to the motor body and houses the speed reducing mechanism. A gear case, a control board that is housed in the gear case and that outputs a drive signal to the motor body, and a case cover that is assembled to the opening of the gear case and includes a heat dissipation member that releases heat of the control board. The heat radiating member is attached to the case cover so as to face the control board, and contacts at least one of the heat radiating member and the control board with the facing heat radiating member or the control board, A protrusion for forming a gap is provided between the heat dissipation member and the control board.

  In the present invention, a protrusion is provided on at least one side of the heat radiating member or the control board, a gap is formed between the heat radiating member and the control board, and a clearance is secured between them. Thereby, it is possible to prevent a short circuit of the control board without impairing the heat dissipation of the control board. Further, the stress generated in the control board when the gap is secured can be suppressed.

  In the electric motor, a conductive part for forming a circuit is provided on a surface of the control board facing the heat radiating member, and a protrusion formed on the heat radiating member is brought into contact with a part other than the conductive part on the control board. You may arrange as follows. Thereby, the protrusion formed in the heat radiating member does not contact the conductive portion, and the short-circuit of the conductive portion due to the protrusion itself can be avoided.

  Further, a power system electronic component such as a transistor is disposed on a surface opposite to the surface facing the heat dissipation member of the control board, and the power system electronic component back side of the surface facing the heat dissipation member of the control board A heat conductive adhesive may be applied to the portion between the heat radiating member. Thereby, the heat generated in the transistor can be efficiently transmitted to the heat dissipation member via the heat conductive adhesive.

  According to the electric motor of the present invention, at least one of the heat radiating member and the control board is provided with a protrusion that abuts the opposing heat radiating member or control board and forms a gap between the heat radiating member and the control board. Therefore, a predetermined clearance can be ensured between the heat dissipation member and the control board while the heat dissipation member and the control board are arranged close to each other. Therefore, it is possible to prevent a short circuit due to contact between the heat dissipation member and the control board, and to improve product reliability.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a wiper apparatus 11 that uses an electric motor 10 (hereinafter abbreviated as “motor 10”) according to an embodiment of the present invention as a drive source. As shown in FIG. 1, a wiper device 11 is provided below the windshield 13 of the vehicle 12. Wiper blades 16a and 16b are mounted on the wiper device 11, and wipe off rainwater and the like adhering to the windshield 13 to ensure visibility of the driver and the like.

  The wiper device 11 includes two wiper shafts 14 a and 14 b that are rotatably supported by the vehicle 12. The wiper shaft 14a is fixed with a wiper arm 15a on the driver's seat side, and the wiper shaft 14b is fixed with a wiper arm 15b on the passenger seat side. Wiper blades 16a and 16b are attached to the distal ends of the wiper arms 15a and 15b. A spring (not shown) is attached to the base ends of the wiper arms 15a and 15b. The wiper blades 16a and 16b are brought into elastic contact with the windshield 13 by the spring force of the springs.

  The wiper device 11 is provided with a motor 10 as a drive source. A crank arm 18 is connected to the output shaft 17 of the motor 10. The crank arm 18 is connected to a link mechanism 19 having the wiper shafts 14a and 14b as fulcrums. When the crank arm 18 is rotated, the wiper arms 15a and 15b swing within a predetermined angle range. As the wiper arms 15a and 15b swing, the wiper blades 16a and 16b operate in the wiping ranges 20a and 20b between the upper reversal position and the lower reversal position, and rainwater and the like adhering to the windshield 13 is wiped off. .

  FIG. 2 is a perspective view showing the appearance of the motor 10, and FIG. 3 is an explanatory view showing a cross-sectional configuration of the motor 10. As shown in FIG. 2, the motor 10 includes a motor main body 21 and a speed reducer 22. The motor body 21 is a so-called brushed DC motor, and a motor case 23 accommodates a field magnet, an armature coil, a commutator, a brush, and the like (not shown). Here, a DC motor with a brush is used as the motor body 21, but the type of the motor body is not limited to this, and other types of electric motors such as a brushless DC motor may be used.

  On the other hand, the speed reducer 22 includes a gear case 24 assembled to the motor case 23 and a case cover 25 assembled to the opening of the gear case 24. Both the gear case 24 and the case cover 25 are made of synthetic resin. As shown in FIG. 3, a worm gear mechanism 32 and a control board 33 are accommodated in the gear case 24. The gear case 24 is assembled to the case cover 25 via a plurality of clips 26, whereby the inside of the gear case 24 is sealed. A liquid packing or a rubber packing is applied or attached to the mating surface of the gear case 24 and the case cover 25 in order to maintain a sealed state.

  As shown in FIG. 3, a rotation shaft 27 of the motor body 21 extends in the gear case 24. The rotary shaft 27 is rotatably supported via bearings 28 and 29. An output shaft 17 projects from the lower portion of the gear case 24 in the figure. The aforementioned crank arm 18 is fixed to the distal end portion of the output shaft 17. The output shaft 17 is rotatably supported by the boss portion 24a of the gear case 24. A worm 30 is fixed to the rotating shaft 27, and a worm wheel 31 that meshes with the worm 30 is fixed to the output shaft 17. The worm 30 and the worm wheel 31 form a worm gear mechanism 32 that is a reduction mechanism. The rotation of the rotating shaft 27 accompanying the driving of the motor body 21 is decelerated via the worm gear mechanism 32. Thereafter, this rotation is transmitted from the output shaft 17 to the crank arm 18, and the wiper device 11 operates at a predetermined operating speed.

  A control board 33 on which a control circuit is mounted is accommodated inside the gear case 24 so as to cover the worm gear mechanism 32. The control board 33 is composed of a printed board 34 and electronic components mounted thereon. The electronic components include a CPU, a memory, a field effect transistor (FET) 35 that is a power electronic component, and the like. The drive control of the motor body 21 is performed by a drive signal output from the control board 33, that is, a current signal. The control board 33 is further provided with an input terminal connected to the power source and the wiper switch, and an output terminal connected to the motor main body 21. These terminals are electrically connected to a connector portion 25 a provided on the case cover 25. The control board 33 supplies a direct current to the motor main body 21 based on a command signal input from the wiper switch via the connector portion 25a, and executes drive control of the motor main body 21.

  The control board 33 is connected to a rotation sensor and a position sensor (not shown). The control board 33 performs drive control of the motor main body 21 based on the rotation speed of the rotation shaft 27 detected from the rotation sensor and the rotation position of the output shaft 17 detected from the position sensor. The rotation sensor and the position sensor are magnetic sensors, and the rotation speed and rotation position thereof are detected by fixing the magnet 36 to the rotation shaft 27 and the worm wheel 31.

  As described above, the drive control of the motor main body 21 is executed via the control board 33 accommodated in the gear case 24. The FET 35 mounted on the control board 33 generates heat when energized. Therefore, the case cover 25 is provided with an aluminum heat sink (heat radiating member) 37 so as to face the control board 33, and the heat of the FET 35 is released to the outside of the motor through the heat sink 37. FIG. 4 is an explanatory diagram showing an electronic component heat dissipation structure in the motor 10, and FIG. 5 is a bottom view of the heat sink 37.

  As shown in FIGS. 4 and 5, a minute projection 41 protrudes from the lower surface 37 a of the heat sink 37 toward the control board 33 (downward in FIG. 4). The minute protrusions 41 are formed to a height of about 0.1 to 0.5 mm, and a plurality of the minute protrusions 41 are provided on the heat sink lower surface 37a as shown in FIG. Each microprotrusion 41 is arranged at a position where the copper foil pattern (conductive portion) of the control substrate 33 does not exist, and the microprotrusion 41 itself is not in contact with the copper foil pattern. Further, a plurality of heat radiation fins 37b are formed on the surface of the heat sink 37 (upper surface in FIG. 4) in order to improve heat dissipation. The heat sink 37 is insert-molded in the case cover 25 and is fixed in the case cover 25 by retaining portions 37 c formed on both side surfaces of the heat sink 37.

  When the control board 33 is attached to the case cover 25 having such a heat sink 37, the minute projections 41 abut on the upper surface 33a of the control board 33, and a gap 42 is formed between the heat sink lower surface 37a and the control board upper surface 33a. Is done. At this time, since the minute protrusion 41 is formed at a position where the copper foil pattern of the control board 33 does not exist, the minute protrusion 41 comes into contact with the insulating substrate portion of the control board 33. For this reason, the microprotrusions 41 made of aluminum as in the heat sink 37 do not come into contact with the copper foil pattern, and a short circuit due to the microprotrusions 41 themselves does not occur.

  In addition, as in the case of FIG. 9, a heat conductive adhesive 43 is applied to the control substrate 33 on the mounting portion of the FET 35. That is, the FET 35 is mounted on the surface of the control board 33 that does not face the heat sink 37, and the thermally conductive adhesive 43 is applied to the back side (the surface that faces the heat sink 37) of the FET 35. The adhesive 43 is also accommodated in the gap 42. Accordingly, the heat of the FET 35 is transmitted to the heat sink 37 through the adhesive 43 and is radiated from the heat radiation fins 37b to the outside of the motor. At that time, in the motor 10, since the heat sink lower surface 37a and the control board upper surface 33a are close to each other, the thermal conductivity from the control board 33 side to the heat sink 37 side is high. Cooling efficiency is improved.

  In the case of the heat dissipation structure of the motor 10, although the distance between the heat sink 37 and the control board 33 is small, a gap 42 is formed between the two by the fine protrusion 41. That is, a slight clearance is secured between the heat sink 37 and the control board 33. In addition, since the minute protrusion 41 is also arranged at the central portion of the heat sink lower surface 37a, the deflection of the control board 33 is suppressed, and the clearance between the heat sink 37 and the control board 33 is securely held. For this reason, it is possible to avoid contact between the heat sink 37 and the control board conductive portion, and it is possible to prevent a short circuit due to contact between the two. Further, in this structure, when the board is attached or the gap is formed, a large external force is not applied to the control board 33, so that the stress generated in the control board 33 can be suppressed.

  Thus, in the motor 10 of the present embodiment, the minute protrusion 41 is provided on the heat sink lower surface 37a, and the gap 42 is secured between the heat sink 37 and the control board 33. Therefore, the heat sink 37 and the control board 33 are arranged close to each other. However, a predetermined clearance is ensured between the heat sink 37 and the control board 33. For this reason, it is possible to prevent the heat sink lower surface 37a from coming into contact with the control board conductive portion due to the vibration or impact of the vehicle, and the control board 33 can be prevented from being short-circuited. Therefore, it is possible to prevent a short circuit and improve product reliability without impairing the heat dissipation of the control board. Further, since the stress generated in the control board 33 can be suppressed when the gap 42 is secured, the board itself is not forced, and the product reliability can be improved also in this respect.

  In this embodiment, the fixing hole 45 of the screw 44 that fixes the control board 33 to the heat sink 37 is also provided with a pedestal 46 having the same height as the minute protrusion 41, and this pedestal 46 is also the same as the minute protrusion 41. Plays the function.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, the minute protrusion 41 is provided on the heat sink lower surface 37a to form the gap 42. However, as shown in FIG. 6, the minute protrusion 41 is provided on the control board 33 side to form the gap 42. May be. Of course, it is also possible to provide the minute projections 41 on both the heat sink 37 and the control board 33. In FIG. 6, when the heat sink 37 is insert-molded into the case cover 25, synthetic resin is turned from the outer periphery of the heat sink 37 to the vicinity of the outer edge of the lower surface 37a to form the outer edge portion 47, which helps to form the gap.

  Further, as shown in FIG. 7, the gear case 24 is formed of a heat conductive material such as aluminum, the heat dissipating fins 48 are formed on the outer wall surface thereof, and the minute protrusions 41 are formed on the inner wall surface of the gear case 24. The control board 33 may be disposed there. In this case, the minute protrusion 41 forms a gap 49 between the gear case 24 and the printed board 34, and a clearance between the two is ensured. Further, the heat generated from the FET 35 is radiated from the radiation fin 48. Therefore, even in the configuration of FIG. 7, short-circuiting of the control board 33 can be prevented without impairing the heat dissipation of the control board. The case cover 25 may further be provided with a heat radiating member formed of a heat conductive material, thereby improving the heat radiating property.

  On the other hand, in the above-described embodiment, the motor 10 is used as the drive source of the wiper device 11. However, the use of the electric motor according to the present invention is not limited to the wiper device, and the present invention is applied to a power window device, a door opening / closing device, and the like. The electric motor may be applied. Moreover, although the heat sink 37 is formed of aluminum which is one of materials having good thermal conductivity, the material is not limited to aluminum, and the thermal conductivity of other metal materials or resin materials having heat conductivity. A material may be used. Furthermore, although the heat sink 37b is formed on the heat sink 37, it may be reduced when the heat generation amount of the control board 33 is small. In addition, although the worm gear mechanism 32 is used as the speed reduction mechanism in the motor 10, the speed reduction mechanism is not limited to this, and other types of speed reduction mechanisms such as a speed reduction gear train composed of a plurality of spur gears may be used. .

It is the schematic which shows the structure of the wiper apparatus which uses the electric motor which is one embodiment of this invention as a drive source. It is a perspective view which shows the external appearance of the electric motor of FIG. It is explanatory drawing which shows the cross-sectional structure of the electric motor of FIG. It is explanatory drawing which shows the electronic component thermal radiation structure in the electric motor of FIG. It is a bottom view of a heat sink. It is explanatory drawing which shows the modification of an electronic component thermal radiation structure. It is explanatory drawing which shows the other modification of an electronic component thermal radiation structure. It is explanatory drawing which shows the thermal radiation structure of the electronic component in the conventional electric motor. It is explanatory drawing which shows the other electronic component thermal radiation structure in the conventional electric motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric motor 11 Wiper apparatus 12 Vehicle 13 Front glass 14a, 14b Wiper shaft 15a, 15b Wiper arm 16a, 16b Wiper blade 17 Output shaft 18 Crank arm 19 Link mechanism 20a, 20b Wiping range 21 Motor main body 22 Reduction gear 23 Motor case 24 Gear case 24a Boss portion 25 Case cover 25a Connector portion 26 Clip 27 Rotating shaft 28 Bearing 29 Bearing 30 Worm 31 Worm wheel 32 Worm gear mechanism 33 Control board 33a Top face 34 Printed board 35 Field effect transistor (FET)
36 Magnet 37 Heat sink 37a Lower surface 37b Radiation fin 37c Retaining prevention part 41 Small protrusion 42 Gap 43 Thermal conductive adhesive 44 Screw 45 Fixing hole 46 Base 47 Outer edge 48 Radiation fin 51 Case cover 52 Heat sink 53 Control board 54 Electronic component 55 Heat Conductive sheet 56 Thermally conductive adhesive

Claims (3)

An electric motor having a motor body that drives a rotating shaft, and a speed reducing mechanism that decelerates and outputs the rotation of the rotating shaft,
A gear case that is assembled to the motor body and houses the speed reduction mechanism;
A control board housed in the gear case and outputting a drive signal to the motor body;
A case cover that is assembled to the opening of the gear case and includes a heat dissipation member that releases heat of the control board;
The heat dissipating member is attached to the case cover so as to face the control board,
Protruding that forms a gap between the heat dissipation member and the control board is provided on at least one side of the heat dissipation member or the control board, which is in contact with the opposing heat dissipation member or the control board. Electric motor.   2. The electric motor according to claim 1, wherein the control board has a conductive part for forming a circuit on a surface facing the heat radiating member, and a protrusion formed on the heat radiating member is formed on the control board. An electric motor characterized by being arranged so as to abut against other parts.   3. The electric motor according to claim 1, wherein a power electronic component is disposed on a surface opposite to the surface facing the heat radiating member on the control board, and on the surface facing the heat radiating member of the control board. An electric motor, wherein a heat conductive adhesive is applied to a portion on the back side of the power electronic component between the heat dissipation member.

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