JP2005176451A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the dimensions of switching elements for the reduction of motor size. <P>SOLUTION: A brushless motor comprises a stator 4 and a rotor 5. The stator comprises: a stator core block formed by winding coils 9 on a stator core 6; the switching elements 1 for switching power distribution to the coils 9; a heat radiating member 7 for radiating heat produced in the switching elements 1; and a retaining member 23 formed of a leaf spring for pressing the switching elements 1 against the heat radiating member 7. The rotor comprises a rotor core 13, permanent magnets 14, and a rotating shaft 15 passed through the center of the rotor core 13. The burshless motor is so constructed that the rotor 5 is disposed in the stator 4 with a gap in-between and the rotating shaft 15 is supported in bearings 16 and 17. A thin insulating member 26 is placed between the heat radiating member 7 of metal and at least the back faces of the switching elements 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a structure of a brushless motor, and more particularly to a structure for radiating heat generated from a switching element.

  In general, a brushless motor rotates the motor by switching the energized phase with a switching element such as a MOSFET element. However, since the switching element generates heat when energized, it is pressed against a metal heat radiating member such as aluminum with the pressure of a spring or a screw. It is necessary to transmit heat and dissipate heat. By the way, a package of a switching element such as a MOSFET element usually has a metal radiating fin electrically connected to a drain terminal, and insulation is necessary when a plurality of switching elements are attached to one radiating member. That is, when the switching element is attached to the heat radiating member, it is necessary to insulate the heat radiating member for each switching element or to insulate the switching element and the heat radiating member in order to ensure insulation from other switching elements.

  Conventionally, for this insulation, a switching element 1 'of a packaged product in which a metal part is not exposed by resin molding as shown in FIG. 7 has been used. The switching element 1 ′ has a resin-made continuous portion 2 at the top, and a screw-fastening hole 3 is provided in the continuous portion 2. The switching element 1 ′ is pressed against the heat radiating member by screwing the screw into the heat radiating member through the hole 3 in a state where the switching element 1 ′ is in contact with the heat radiating member. That is, since it is resin-molded so that the metal part is not exposed, heat cannot be dissipated unless it is strongly pressed with screws.

  However, the switching element 1 ′ molded so that the metal part is not exposed must be screwed and the resin element must be molded so that the metal part is not exposed. There is a problem that the size increases and the motor size increases accordingly.

In addition, there is a type in which the switching element 1 ′ is attached by sandwiching the continuous portion 2 and the heat radiating member with a spring clip instead of attaching with a screw as described above (for example, see Patent Document 1). In such a case, the switching element 1 'can be attached without requiring the trouble of screwing. However, the switching element 1' must be the same as that shown in FIG. There is a problem that the size of the motor increases with the increase.
No. 6-46214

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a brushless motor capable of reducing the size of the switching element and reducing the size of the motor.

  In order to solve the above problems, a brushless motor according to the present invention includes a stator core block in which a coil is wound around a stator core, a switching element for switching energization to the coil, and heat generated by the switching element. A stator is composed of a metal heat radiating member with high thermal conductivity for radiating heat and a pressing member made of a leaf spring for pressing the switching element from the front surface of the switching element and pressing the radiating member against pressure. A brushless in which a rotor is constituted by a rotor core and a permanent magnet, and a rotating shaft inserted through the center of the rotor core, and the rotor is disposed in the stator via a gap and the rotating shaft is supported by a bearing. In a motor, a thin insulating member is interposed between a metal heat dissipating member and at least the back surface of the switching element, and a switch is made by a pressing member made of a leaf spring material. Characterized by being pressed from the front of the grayed elements. A thin insulating member interposed between the back surface of the switching element and the heat radiating member can insulate between the switching element and the heat radiating member, and can be fixed by pressing with a holding member made of a leaf spring, so that the switching element can be fixed. Therefore, a small-sized switching element with an exposed metal part can be used, and the motor can be miniaturized.

  It is also preferable that the insulating member has a shape that covers the back surface, top surface, and side surfaces on both sides of the switching element. In this case, not only the back surface of the switching element but also the side surface and the top surface are secured. Thereby, not only the insulation with the heat radiating member but also the insulation with other switching elements and pressing members are ensured, and a safety brushless motor can be formed.

  It is also preferable that the insulating member is made of a material having high thermal conductivity and high elasticity such as silicon rubber. In this case, heat transfer efficiency is good even if an insulating member is interposed, and adhesion with the heat radiating member can be enhanced by the spring pressure of the pressing member. Further, even if vibration is generated in the motor, the contact between the switching element and the heat radiating member is maintained, and heat conduction can be ensured, so that the safety against destruction by heat can be further increased.

  In addition, it is also preferable that a stepped portion in which a metal fin of the switching element is accommodated is provided in an insulating member that covers the back surface, the upper surface, and the four side surfaces on both sides of the switching element. In this case, since the fins of the switching elements are housed in the stepped portions, the switching elements and the insulating member are not easily detached, and a motor that can be easily assembled can be provided.

  As described above, the present invention can insulate between the switching element and the heat radiating member with a thin insulating member interposed between the back surface of the switching element and the heat radiating member and press the switching element with a pressing member made of a leaf spring. Since it can be fixed, it is possible to use a switching element having a small dimension in which a metal part such as a heat radiating fin is exposed, and the motor can be miniaturized.

  Hereinafter, the present invention will be described based on embodiments shown in the accompanying drawings of FIGS.

  FIG. 1 is an axial cross-sectional view of an embedded magnet type brushless motor, and this motor includes a stator 4 and a rotor 5.

  A heat radiating member 7 made of a metal having good thermal conductivity such as aluminum is disposed on one end side of the stator core 6 on which electromagnetic steel plates or the like are laminated, and the heat radiating member 7 is connected to the stator core 6. A coil frame 8 made of an insulating material such as resin is press-fitted and fixed to the stator core 6, and the stator 4 is assembled by winding a coil 9 on the outside thereof. A circuit board 10 is disposed on one end side of the stator 4, and the circuit board 10 is fixed to the heat radiating member 7 with screws 11. A switching element 1 such as a MOSFET element is mounted on the circuit board 10, and a lead wire 12 for energizing the circuit board 10 is connected to the circuit board 10. The switching element 3 and the heat dissipation member 7 are in contact with each other, and the coil 9 and the circuit board 10 are electrically coupled.

  A rotor core 13 of the rotor 5 is disposed with a gap inside the stator 4, and a permanent magnet 14 is fixed to the rotor core 13 by bonding or the like. A rotating shaft 15 is inserted and integrated in the center of the rotor core 13. Bearings 16 and 17 such as ball bearings are mounted on both ends of the rotating shaft 15, and a pinion 18 is attached to the end of the rotating shaft 15. Is installed. In this manner, the stator 4 and the rotor 5 are housed in a motor case (not shown) with the rotor 5 incorporated in the stator 4, and the bearings 16 and 17 are supported by the motor case.

  In the motor as described above, the current flows in the order of the lead wire 12 → the circuit board 10 → the switching element 1 → the coil 9, and the rotating shaft 15 of the rotor 5 is rotationally driven. That is, the energization to the coil 9 is controlled by the switching element 1 controlled by the switching element control circuit 19 such as a MOSFET element control circuit according to the rotation angle of the rotor 5, and the torque generated between the rotor 5 Thus, the rotary shaft 15 is driven to rotate together with the rotor 5. Although it is rotationally driven in this way, the heat generated in the switching element 1 is radiated from the heat radiation member 7 and the stator core 6. At this time, the stator iron core 6 functions as a heat radiating rib to effectively radiate heat.

  A cooling fan 20 is disposed on the rotating shaft 15 of the rotor 5 at a position opposite to the heat dissipation member 7, and the cooling fan 20 is fixed to the rotating shaft 15 so that the cooling fan 20 rotates together with the rotating shaft 15. It has become. When the rotating shaft 15 of the rotor 5 is driven, the cooling fan 20 is rotated and blown by the cooling fan 20, and the outside air as cooling air is taken in from the heat radiating member 7 side and passes through the switching element 1 → coil 9 in this order. It is discharged | emitted outside and the switching element 1 and the coil 9 are cooled in order.

  The switching element 1 is a package product as shown in FIG. 3, and is not a package product molded with a resin so that the metal portion is not exposed as in the prior art, but a metal radiation fin 21 is exposed. In FIG. 3, G is a gate terminal, D is a drain terminal, S is a source terminal, and the radiation fin 21 is electrically connected to the drain terminal D.

  The heat dissipating member 7 has a rectangular parallelepiped mounting portion 22, and a plurality (six in this example) of switching elements 1 are arranged along the four side surfaces 22 a of the mounting portion 22 as shown in FIG. 4. Is arranged. That is, the two switching elements 1 are arranged along the long side surface 22a of the four side surfaces 22a, and the one switching element 1 is arranged along the short side surface 22a. When the switching element 1 is arranged, it is arranged so that the back surface of the switching element 1 faces the heat radiating member 7 side.

  The pressing member 23 that holds and attaches the switching element 1 is made of a metal (SUS, copper, etc.) leaf spring material having a spring property and excellent heat dissipation, and a plurality of pressings from the periphery of the rectangular main body plate 23a. It protrudes in a direction orthogonal to the piece 23b. The presser member 23 is attached by bringing the main body plate 23a of the presser member 23 into contact with the end face 22b of the attachment portion 22 and screwing a screw 24 such as a screw from the main body plate 23a into the screw hole 25 of the attachment portion. By attaching the pressing member 23 in this way, the pressing piece 23 b is pressed against the front surface of the switching element 1 to hold the switching element 1.

  The switching element 1 is mounted on the circuit board 10 and is connected to the switching element control circuit 19 of the circuit board 10. FIG. 2 is a circuit diagram, in which the switching element control circuit 19 changes the combination of on and off of the six switching elements 1 and changes the direction of the current flowing through the three-phase coil 9 to rotationally drive the rotor 5. be able to. In FIG. 2, HU, HV, and HW are the high-side three-phase switching elements 1, and LU, LV, and LW are the low-side three-phase switching elements 1.

  Incidentally, as shown in FIG. 2, the drain terminals of the low-side three-phase switching element 1 indicated by LU, LV, and LW are DU, DV, and DW, and the high-side three-phase switching indicated by HU, HV, and HW. The potential of each terminal changes depending on whether the element 1 is on or off. When the low-side three-phase switching element 1 indicated by LU, LV, and LW is attached to the heat radiating member 7 without being electrically insulated, the drain terminal indicated by DU, DV, and DW is short-circuited. The switching element 1 is turned on and flows through the switched switching element 1 without passing through the coil 9. At this time, since the resistance of the switching element 1 such as a MOSFET element is smaller than that of the coil 9, a large current flows and the switching element 1 is destroyed. Therefore, at least the three switching elements 1 on the low side need to be insulated from the heat radiating member 7. Since all the drain terminals of the switching element 1 on the high side are connected to the power supply voltage Vh, insulation between the switching elements 1 on the high side is not necessary.

  In the present invention, a thin insulating member 26 is interposed between at least the back surface of the switching element 1 and the heat radiating member 7 in order to insulate and contact the switching element 1 with the heat radiating member 7. In this example, an insulating member 26 is interposed between the three switching elements 1 on the low side and the heat dissipating member 7 that are at least insulated. This insulating member 26 is formed of a highly conductive and highly elastic insulating material such as silicon rubber, and the heat radiating member 7, the insulating member 26, and the switching element 1 are brought into close contact with each other by pressing of the pressing piece 23 b of the pressing member 23. As a result, the thermal conductivity increases. Further, even if vibration occurs, it is absorbed by elasticity and becomes difficult to come off. By providing the switching element 1 through the insulating member 26 in this way, the switching element 1 having a small size with exposed metal parts such as the radiation fins 21 can be used, and the motor can be reduced in size.

  In the case of this example, the insulating member 26 is formed in a box shape that covers not only the back surface of the switching element 1 but also the top surface and the side surfaces on both sides as shown in FIG. If the insulating member 26 covers the upper surface and both side surfaces of the switching element 1 in this way, it is possible to ensure insulation for the switching elements 1 arranged adjacent to each other and also ensure insulation for the pressing member 23. it can. As described above, the insulating member 26 is formed in a box shape that covers the back surface, the upper surface, and the side surfaces of both sides of the switching element 1, and a stepped portion 27 is provided in the box-shaped insulating member 26 as shown in FIG. 6. The heat dissipating fin 21 is accommodated in the stepped portion 27 when the insulating member 26 is attached to the switching element 1. If it does in this way, it can stop so that the insulating member 26 may not be removed from the switching element 1 at the time of an assembly, and an assembly property can be improved.

  Further, as shown in FIG. 5, the front surface of the switching element 1 is directly pressed and attached by the pressing piece 23b of the pressing member 23 (the front surface of the switching element 1 is insulated by the package). Since the front surface is not covered, heat dissipation from the pressing member 23 is promoted.

It is sectional drawing of the brushless motor of an example of embodiment of this invention. It is a circuit diagram explaining the circuit which drives a motor same as the above. The switching element same as the above is shown (a) is a front view, (b) is a side view, and (c) is a bottom view. It is a perspective view which shows the state which attaches a switching element same as the above. It is a perspective view of the state which attached the pressing member from the state of FIG. It is sectional drawing of the state of FIG. The conventional switching element is shown, (a) is a front view, (b) is a side view, (c) is a bottom view.

Explanation of symbols

1 Switching element
4 Stator
5 Rotor 6 Stator Core 7 Heat Dissipation Member 9 Coil 13 Rotor Core
14 Permanent magnet
DESCRIPTION OF SYMBOLS 15 Rotating shaft 16 Bearing 17 Bearing 21 Radiation fin 23 Holding member 26 Insulating member 27 Step part

Claims (4)

A stator core block in which a coil is wound around a stator core, a switching element for switching energization to the coil, and a metal heat dissipating member with high thermal conductivity for dissipating heat generated in the switching element; The stator is constituted by a pressing member made of a leaf spring for pressing the switching element from the front surface of the switching element and pressing the heat radiating member against the heat radiating member, and at the center of the rotor core and permanent magnet and the rotor core. In a brushless motor in which a rotor is configured with the inserted rotation shaft, the rotor is disposed in the stator via a gap, and the rotation shaft is supported by a bearing, a metal heat dissipation member and at least the back surface of the switching element, The brushless motor is characterized in that a thin insulating member is interposed between them and pressed from the front surface of the switching element by a pressing member made of a leaf spring material. . 2. The brushless motor according to claim 1, wherein the insulating member is formed to cover four surfaces of the back surface, the top surface, and both side surfaces of the switching element. 3. The brushless motor according to claim 1, wherein the insulating member is made of a material having high thermal conductivity and high elasticity such as silicon rubber. 3. The brushless motor according to claim 2, further comprising a step portion in which a metal fin of the switching element is accommodated inside an insulating member that covers the back surface, the top surface, and the four side surfaces on both sides of the switching device.

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