JPH08298762A - Brushless dc motor - Google Patents

Abstract

PURPOSE: To provide a brushless DC motor whose output is high by increasing the heat-dissipating effect of a semiconductor element or the like which controls the speed of rotation of the motor. CONSTITUTION: A brushless DC motor 1a is provided with a stator 13 in which a wound stator core 3 and a PC board 5a arranged and installed on the surface or the rear surface of the stator core 3 have been molded integrally by a premix 6, with a rotor 7 arranged inside the stator 13 and with a bracket 9 or the like which supports the rotor 7 so as to be freely rotatable via bearings 10a, 10b. In the brushless DC motor, a hole is made in the PC board 5a, a circuit element for motor control is arranged and installed in the hole in the PC board 5a in such a way that its rear is situated in the hole, and the surface and the rear of the circuit element for motor control are sandwiched by a nearly U-shaped metal heat sink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to heat dissipation of a semiconductor device used in a brushless DC motor.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a brushless DC motor having a motor control circuit built into a molded motor and having a controllable rotation speed.

This brushless DC motor uses a magnetic sensor or the like to detect the number of rotations of the rotor of the motor and the rotational position for maintaining the rotation, and is equipped with semiconductor elements such as a power IC and a motor drive IC. This signal is sent to the existing motor control circuit, and the control of the rotation speed of the motor and the switching of the phase by energizing a predetermined coil are performed by this signal and the signal from the set.

The structure of a conventional brushless DC motor is shown in FIG.
It demonstrates using the longitudinal cross-sectional view of FIG. In this figure, the stator core 3 is wound on the winding 4 after the surface is insulated by premolding or the like.
Is given. A PC board 5b is arranged on the stator iron core 3, and a power IC that performs a switching operation and a motor drive I that performs a control operation are provided on the PC board 5b.
C etc. are attached. Some of these two IC devices are packaged in one module. This P
The C plate 5b and the stator core 3 having the windings 4 are integrally molded with the premix 6 to form the stator 13. A permanent magnet 8 is fixed to the outer circumference of the rotor 7 by adhesion or the like. The stator 13, the rotor 7 arranged in the stator 13, the bracket 9, and the bearings 10a, 10
The brushless DC motor 1b is configured by b and the like.

Control of the rotation speed of the motor 1b is performed by the hall I.
The magnetic sensor 14 such as C detects the number of rotations of the rotor 7, and sends a signal to the motor control circuit on the PC board 5b.
This signal and the signal from the set control the switching of the rotation speed and the phase of the motor 1b.

[0006]

The entire brushless DC motor is molded by premixing, and a power IC, a power transistor, a motor drive IC and other IC elements that generate a large amount of heat are used in this motor. The surface area of these IC elements is small and the temperature locally rises. Due to this temperature rise, there is a possibility that the performance of this element may be deteriorated or destroyed. As a result, a large output UP cannot be achieved and the output characteristics of the motor are restricted, which makes it difficult to design an IC circuit built-in high-output motor.

Next, the conventional problems will be described with reference to FIGS.
A brief description will be given based on. By controlling the rotation speed of the brushless DC motor 1b, a current flows through the motor control circuit elements including the IC element 11 such as the motor drive IC, and these elements generate heat.

As a measure against heat generation, measures such as attaching heat sinks (radiating plates) 2b and 2c having the shapes shown in FIGS. 8 to 11 to the upper part of the IC element 11 have been taken. 8,
FIG. 9 is an example of a perspective view and a side view of the PC board 5b in which the heat sink 2b is fixed with the adhesive 17. Also, in FIG.
FIG. 11 is an example of a perspective view and a side view of the PC board 5c in which the heat sink 2c is fixed by the solder 12.

However, in these methods, only heat is dissipated from the front surface of the IC element 11, and the rear surface is the PC board 5b, 5c.
There is a problem that the effect of heat dissipation is low because it is in contact with. Further, since the heat sinks 2b and 2c are fixed by adhesion, soldering, or the like, there is a problem in process such as work time for attachment and detachment from the IC element 11, and reliability.

The present invention has been made in view of the above circumstances, and a hole is formed in an IC element mounting portion of a PC board.
Brushless DC with high output that enhances the effect of dissipating the heat generated from the IC element by changing the shape of the heat sink into a substantially U shape so that the heat sink can be sandwiched from both the front surface and the back surface of the IC element. The challenge is to provide a motor.

[0011]

According to the present invention, a stator in which a wound stator core and a PC plate are integrally molded with a premix, a rotor arranged in the stator, and a bearing are provided. It is composed of a bracket that rotatably supports the rotor, has a hole in the PC board, and is arranged so that the back surface of the motor control circuit element comes into the hole of the PC board. The problem is solved by sandwiching the back surface and the back surface with a metal plate material (heat sink) having a substantially U-shape to enhance the effect of dissipating heat generated from a semiconductor element such as an IC element through the plate material.

[0012]

The IC element mounted on the PC board is sandwiched by a heat sink made of a metal plate and having a substantially U-shape having a spring property. Due to this sandwiching, the heat sink is IC
Since it adheres to the front surface and the back surface of the element and fits into the hole of the PC board, it does not come off.

The PC board and the wound stator core are integrally molded with a premix to form a stator.
By energizing the brushless DC motor assembled using this stator, a magnetic field is generated and the rotor rotates. The rotation speed is detected by a magnetic sensor such as a Hall IC, and a signal is transmitted to the motor control circuit element mounted on the PC board. The rotation speed is controlled and the phase is switched by this signal and the signal from the set. Be done. Due to this action, a current flows through the control circuit element such as an IC element to generate heat. IC
The heat generated in the element is conducted to the heat sink which is in contact with the element, and further the heat is conducted from the heat sink to the premix and dissipated in the air.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on an embodiment shown in the drawings. FIG. 1 is a vertical sectional view of a brushless DC motor according to an embodiment of the present invention, and FIG. 2 is an embodiment of the present invention. 5 is a perspective view of a PC board, an IC element and a heat sink according to FIG. 3, FIG. 3 is a perspective view of a heat sink according to an embodiment of the present invention, FIG. 4 is a perspective view of the IC element mounted on the PC board, and FIG. FIG. 7 is a perspective view of a PC board in which an IC element according to an embodiment of the present invention is sandwiched by heat sinks, and FIG.
FIG. 7 is a partial vertical cross-sectional view of the C plate, and FIG. 7 is a partial vertical cross-sectional view of the PC plate before the IC element according to the embodiment of the present invention is sandwiched by heat sinks.

In FIG. 1, the winding 4 is provided after the surface of the stator iron core 3 is insulated by premolding or the like. A PC plate 5a is arranged on the upper surface or the lower surface of the stator iron core 3.
The stator core 3 having the windings 4 and the PC plate 5a are integrally molded with the premix 6 to form the stator 13. A permanent magnet 8 is fixed to the outer circumference of the rotor 7 by adhesion or the like. A brushless DC motor 1a is composed of the stator 13, the rotor 7 arranged in the stator 13, the bracket 9, the bearings 10a, 10b, and the like.

2 to 5, the hole 1 is formed in the PC board 5a.
5 is formed. The back surface of the IC element 11 such as a power IC, a power transistor, or a motor drive IC is P
It is mounted so as to come into the hole 15 of the C plate 5a, and further, other control circuit elements, capacitors, resistors, etc. are mounted on the PC plate 5a and then soldered. After that, the heat sink 2a having a substantially U-shape is inserted from the side surface of the PC plate 5a to sandwich the front surface and the back surface of the IC element 11 in a sandwich shape. The heat sink 2a uses a spring material so as to sandwich the front and back surfaces of the IC element 11 and prevent the heat sink 2a from coming off the hole 15.

In such a structure, the brushless D
A magnetic field is generated by energizing the C motor 1a, and the electromagnetic force causes the rotor 7 to rotate. The magnetic sensor 14 such as a Hall IC detects the number of rotations and detects the PC board 5a.
The signal is transmitted to the motor control circuit element mounted on the. The rotation speed is controlled by this signal and the signal from the set. Due to the function of this motor control, a current flows through the control circuit element such as the IC element 11 to generate heat. If the heat is generated above a certain temperature, the performance and reliability of the motor control circuit will be degraded, and the semiconductor element will be broken.

Therefore, according to the present invention, as a method of dissipating the heat, the heat generated by the IC element or the like is sandwiched by sandwiching the IC element or the like from the front surface and the back surface of the IC element with a substantially U-shaped metal heat sink. Is transmitted to the heat sink and then to the premix to dissipate the heat into the air.

FIG. 3 shows an example of a heat sink. Such a heat sink 2a having a spring property is used as shown in FIG. 6 for a power IC, a power transistor, and a motor drive IC.
The IC element 11 such as is sandwiched. This allows the IC
The heat generated in the element 11 is conducted from the front surface and the back surface to the heat sink 2a which is in contact with the element 11, and the heat is further transmitted to the premix 6 and dissipated in the air. The heat sink 2a of the present invention is a conventional heat sink 2b,
The surface area is larger than that of 2c, and the surface of the IC element 11 is
The IC element 1
The heat generated in 1 is transmitted to the heat sink 2a from the front and back surfaces of the element 11, and the heat is further transmitted to the premix. Further, since this heat sink 2a is U-shaped, it does not take much space.

As shown in FIG. 3, the shape of the heat sink 2a is such that both ends thereof are bent so that they can be easily inserted into the PC board 5a. Further, the shape of the heat sink 2a may be determined so that the position of the heat sink 2a does not vary after the insertion so that the position is determined by the side surface of the PC plate 5a or the hole 15. And the heat sink 2a
It goes without saying that the dimension is designed in consideration of the creepage distance with the pattern 16 arranged on the PC board 5a.
The plate material used for the heat sink 2a may be spring steel, stainless steel, hard steel, pure aluminum, aluminum alloy, or copper alloy such as phosphor bronze or brass. If an aluminum alloy is used, a drawing material may be used.

The PC board 5a having such a shape with good heat dissipation.
By inventing, it has become possible to design a high output motor with a built-in IC circuit.

[0022]

As described above, the brushless DC motor of the present invention enhances the heat dissipation effect of IC elements such as power ICs, power transistors, and motor drive ICs, thereby lowering the performance of these elements due to temperature rise, and It is possible to prevent the destruction. In addition, since the temperature rise of IC elements can be derated, brushless DC
Motor reliability is improved. Further, the steps such as bonding and soldering are unnecessary, and a stable PC board can be obtained.

As described above, since the heat radiation efficiency is high, the high output brushless DC motor of the IC circuit built-in type can be manufactured without being restricted by the restriction of the temperature rise as compared with the conventional case.

[0024]

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a brushless DC motor according to an embodiment of the present invention.

FIG. 2 is a perspective view of a PC board, an IC device and a heat sink according to an embodiment of the present invention.

FIG. 3 is a perspective view of a heat sink according to an exemplary embodiment of the present invention.

FIG. 4 is a perspective view in which an IC element is mounted on a PC board.

FIG. 5 is a perspective view of a PC board in which an IC element according to an embodiment of the present invention is sandwiched by heat sinks.

FIG. 6 is a partial vertical cross-sectional view of a PC board in which an IC element according to an embodiment of the present invention is sandwiched by heat sinks.

FIG. 7 is a partial vertical cross-sectional view of a PC plate before an IC element according to an embodiment of the present invention is sandwiched by heat sinks.

FIG. 8 is a perspective view of a PC board in which a heat sink is fixed to a conventional IC element by adhesion.

FIG. 9 is a side view of a PC board in which a heat sink is fixed to a conventional IC element by adhesion.

FIG. 10 is a perspective view of a PC board in which a heat sink is fixed to a conventional IC element by soldering.

FIG. 11 is a side view of a PC board in which a heat sink is fixed to a conventional IC element by soldering.

FIG. 12 is a vertical sectional view of a conventional brushless DC motor.

[Explanation of symbols]

 1a, 1b ..... Brushless DC motors 2a, 2b, 2c ... Heat sink 3 ..... Stator iron core 4 .....・ ・ ・ ・ ・ ・ ・ ・ Winding 5a, 5b, 5c ・ ・ ・ PC board 6 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Premix 7 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ Rotor 8 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Permanent magnet 9 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Brackets 10a, 10b ・ ・ ・ Bearing 11 ・ ・ ・IC element 13 Stator 14 Magnetic sensor

Claims (1)

[Claims] 1. A stator in which a wound stator core and a PC plate disposed on an upper surface or a lower surface of the stator core are integrally molded with a premix, and the stator is disposed in the stator. In a brushless DC motor including a rotor and a bracket that rotatably supports the rotor via a bearing, a hole is provided in the PC plate, and the back surface of the motor control circuit element is provided in the hole of the PC plate. A brushless DC motor, characterized in that the front and back surfaces of the motor control circuit element are sandwiched between substantially U-shaped metal plate members.