JPH06121509A - Brushless motor - Google Patents

Abstract

PURPOSE:To provide a light and compact brushless motor excellent in heat dissipation properties in which a drive circuit including a power element is formed on a printed board. CONSTITUTION:A part of a metal base printed board 18 mounting a drive circuit including a power element 19 is bent oppositely to the power element mounting face. The bent part is exposed through a notch made in the end face of bracket 1 in the axial direction thereof thus fitting the inner face of the bracket tightly to the rear of the power element mounting face of the printed board. Consequently, the printed board 18, the bracket 1, the stator 5, and the winding 3 can be utilized as a heat spreader for the drive circuit. When forcible air cooling is carried out by means of convection through the bent part of the printed board including the interior of the motor or an outer fan and/or an inner fan, heat generated from the circuit can be dissipated efficiently. This constitution realizes a light and compact brushless motor having long service life and excellent in reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor including a power element and incorporating a drive circuit.

[0002]

2. Description of the Related Art In recent years, electric appliances have been rapidly replaced by brushless motors, which are efficient and easy to change gears, in place of high functionality electric appliances, instead of induction motors.

A conventional brushless motor will be described below. FIG. 2 shows the structure of a conventional brushless motor. In FIG. 2, 1 is a bracket, 2 is a bearing, 3 is a winding wire, 4 is a holding base having a built-in position sensor, 5
Is a stator, 6 is a rotor, 7 is a cable, and 8 is a motor drive circuit. In a conventional brushless motor, a rotor 6 having a bearing 2 mounted as a motor portion is housed in a stator 5 having a winding 3, and is rotatably held by a bracket 1. A position sensor for detecting the rotor position is built in the holding table mounted on the bracket 1 and is mounted so as to face the rotor magnet. On the other hand, the drive circuit 8 is provided outside the motor, and the drive circuit 8 and the motor section are connected by ten or more lead wires.

[0004]

However, in the above-mentioned conventional configuration, the position detection signal line is externally provided in a large installation space, so that it is affected by noise. On the other hand, if an attempt is made to incorporate a circuit into the motor in order to solve this problem, the heat generation of the circuit will become an obstacle, and the number of parts will increase and the number of assembly steps will increase.

The present invention solves the above problems,
An object of the present invention is to provide a compact circuit-integrated brushless motor having good heat dissipation.

[0006]

In order to achieve this object, the brushless motor of the present invention is such that a metal-based printed circuit board is partially bent and a notch is provided on the axial end face of the bracket. Further, the bent portion of the printed circuit board is exposed, the back surface of the power element mounting surface of the printed circuit board is closely attached to the inner surface of the bracket, and the bracket notch is used as a ventilation hole.

[0007]

With this configuration, the heat of the circuit is transferred to the metal-based printed circuit board, the bracket, the stator and the windings by heat conduction by (1) mounting the metal-based printed circuit board in close contact with the bracket. Is
(2) A part of the bent portion of the printed circuit board is exposed from the notch provided on the axial end face of the bracket, that is, the printed circuit board is used as a heat radiation fin directly exposed to the outside air, and the inside and outside air of the motor are exposed through the notched hole. By causing convection, the heat generated in the circuit can be efficiently dissipated.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a bracket, 2 is a bearing, 3 is a winding wire, 4 is a holding base having a built-in position sensor,
Reference numeral 5 is a stator, 6 is a rotor, 17 is a cable, and 18 is a metal-based printed circuit board on which a drive circuit including a power element 19 is mounted. As a motor structure, a rotor 6 having a bearing 2 mounted therein is housed in a stator 5 having a winding 3, and is rotatably held by a bracket 1. And
The position sensor for detecting the rotor position is built in the holding table 4 attached to the bracket 1 and is attached so as to face the rotor magnet.

The axial end surface of the bracket 1 is shown in FIG.
1A, a cutout is provided, and a part of the metal-based printed circuit board 18 is bent to the side opposite to the surface on which the power element 19 is mounted.
As shown in FIG. 3, the bracket 1 is configured so as to be exposed from the cutout portion, and the back surface of the metal base printed board 18 on which the power element 19 is mounted is in close contact with the inner surface of the bracket 1.

In the brushless motor configured as described above, heat dissipation of heat generated during driving will be described below.

Since the metal-based printed circuit board 18 on which the power element 19 is mounted is closely attached to the bracket 1, the heat generated in the drive circuit, particularly the power element 19, is conducted by heat conduction to the printed circuit board 18, the bracket 1, and the stator. 5, the motor can be used as a radiator to radiate heat. Further, by exposing the bent portion of the printed circuit board 18 from the cutout portion of the end face in the axial direction of the bracket 1, the printed circuit board can have a function as a heat radiation fin, and the inside and outside air of the motor can be exposed through the cutout hole. By causing convection, the heat generated in the circuit can be efficiently dissipated.

It is needless to say that if one or both of the external fan fan and the internal fan fan are forcibly air-cooled, the heat dissipation will be further increased.

Further, the shape of the bent portion of the printed circuit board 18 exposed from the notch portion of the bracket 1 is such that both end surfaces are bent outward, but only one of them may be bent.

In order to secure heat dissipation, the printed circuit board 18 may be attached to the bracket 1 by applying a compound having good thermal conductivity.

[0016]

As described above, according to the present invention, the printed circuit board, the bracket, the stator, and the winding of the metal base are used as a radiator, and the metal base is removed from the cutout portion provided on the axial end face of the bracket. By exposing the bent portion of the printed circuit board, the heat radiation area is expanded and heat is radiated by convection. In addition, forcible air cooling enables efficient heat dissipation, such as attaching a dedicated heat sink to the power element and avoiding the use of a compound when mounting the printed circuit board.
It can contribute to reducing the number of parts. Further, since the drive circuit is integrally built in the motor, the position detection signal line is not provided outside, so that it is not affected by noise and complicated wiring is not required outside. Therefore, the configuration of the present invention can realize a brushless motor that is easy to handle, compact, and lightweight.

[Brief description of drawings]

FIG. 1A is a structural diagram of a brushless motor according to an embodiment of the present invention. FIG. 1B is a detailed structural diagram of a portion A in FIG. 1A.

FIG. 2 is a structural diagram of a conventional brushless motor.

[Explanation of symbols]

 1 bracket 2 bearing 3 winding 4 holding base 5 stator 6 rotor 7, 17 cable 8 drive circuit 18 printed circuit board 19 power element

Claims (1)

[Claims] 1. A brushless motor including a stator having a winding, a rotor having a bearing mounted thereon, a bracket holding the bearing, and a drive circuit,
A drive circuit including a power element is formed on a metal-based printed circuit board, and a structure in which a part of the printed circuit board is bent is provided, and the bent portion is provided with a cutout portion on an axial end surface of the bracket from the cutout portion. A circuit-integrated brushless motor in which the back surface of the power element mounting surface of the printed circuit board is mounted in close contact with the inner surface of the bracket while being exposed.