JPH04308492A - Brushless motor - Google Patents

Abstract

PURPOSE:To simplify the total system as compared with a conventional system where power supply voltage is varied by including a PWM control means in a driving circuit thereby providing a variable speed function in a brushless motor incorporating the driving circuit. CONSTITUTION:Driving circuit 6 for a brushless motor comprises a switching power element group 2, means 8 for producing a commutation signal for the switching power element group 2 from the output of a position sensor 5, a switching power element driving means 7, a speed error signal generating means 9 for comparing an externally provided rotational speed command signal with the output from the position sensor 5, and a PWM control means 10 for controlling the ON duty of the switching power element group 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor used as a drive source for a blower fan in a domestic air conditioner or the like.

0002

2. Description of the Related Art In recent years, in air conditioning equipment such as home air conditioners, it has become mainstream to control the capacity of compressors. In response to this, the amount of air blown to the heat exchanger is required to be adjusted widely and in multiple stages.In order to meet these demands, instead of the induction motor as the fan drive source that has traditionally been used, the A method is adopted in which a simple brushless motor is operated using a DC power source. On the other hand, there is a strong demand for this type of motor to be lighter, thinner, and smaller.

A conventional brushless motor drive system has a configuration as shown in the block diagram of FIG. 6, in which a brushless motor A with a built-in drive circuit is operated by a DC power supply B such as a switching power supply, and the output of the DC power supply B is A method is adopted in which the rotation speed of the brushless motor is varied by varying the voltage. An example of a brushless motor driven by such a system is disclosed in Japanese Patent Application Laid-Open No. 61-2514.
Publication No. 62 is mentioned. Note that 5 is a position sensor that detects the rotor position.

Examples of conventional brushless motors will be explained below with reference to the drawings. Figure 7 is Japanese Patent Application Laid-open No. 61-2514.
62 is a vertical cross-sectional view of the brushless motor described in Publication No. 62. FIG. The stator winding 3 is applied to the stator core 14 via an insulating layer 15, while the drive circuit components 28 and the position sensor 5 are mounted on the same surface on the printed circuit board 13, and some or all of the drive circuit components are attached to the printed circuit board 13. All of them are arranged so that they are located between the teeth of the stator core 14, that is, in the space between the windings, and the surface of the printed circuit board 13 on which the drive circuit components are mounted is the end surface of the stator core. The stator core 14, the winding 3, and the printed circuit board 13 are held in a thermosetting resin 27.
The stator 23 is integrally molded and solidified to form the stator 23. A brushless motor is constructed by rotatably supporting the permanent magnet rotor 4 on the thus obtained stator 23 by bearing devices 24a and 24b.

[0005]

[Problems to be Solved by the Invention] However, in the conventional brushless motor as described above, a variable voltage DC power source for driving the motor is indispensable in order to change the speed of the motor. When viewed as a system, this requires space for the DC power supply, and in terms of cost, the DC power supply also increases the cost, making it more expensive than conventional induction motors. As a result, this is a major factor hindering the spread of brushless motors.

SUMMARY OF THE INVENTION An object of the present invention is to provide a brushless motor that can solve the above conventional problems, reduce system costs, and contribute to space saving.

[0007]

[Means for Solving the Problems] In order to achieve this object, the brushless motor of the present invention compares a rotational speed signal obtained by synthesizing the outputs of position sensors with a rotational speed command signal inputted from the outside. a speed error signal generating means for outputting the speed error signal; and a PW for controlling the on-duty of the switching power element according to the speed error signal.
M (pulse width modulation) control means.

[0008]

[Operation] With the above structure, even if the motor drive power supply voltage is constant, the rotational speed of the motor can be varied by controlling the on-duty of the PWM control of the switching element in accordance with the speed command signal.

[0009]

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

FIG. 1 is a system block diagram of a brushless motor according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a rectifier and smoothing circuit section, which includes a bridge diode D1 and a smoothing capacitor C1. 2 is a switching power element group, 6
It consists of six switching power elements and six diodes connected in antiparallel to each switching power element. 3 is a three-phase connected stator winding, 4 is a permanent magnet rotor, and 5 is a position sensor. Reference numeral 6 denotes a drive control circuit section which includes switching power element drive means 7, commutation signal generation means 8, speed error signal generation means 9, and PWM control means 10. This drive control circuit section 6 is implemented as a one-chip IC as a pre-driver IC.

With the above configuration, the output signal of the position sensor 5 is logically processed by the commutation signal generating means 8, and the output signal is transmitted to the switching power element driving means 7 to output a commutation signal to the switching power element group 2. At the same time, the speed error signal generating means 9 compares the speed command signal received from the outside with the rotational speed signal obtained by combining the output signal of the position sensor 5 to obtain a speed error signal,
The M control means 10 controls the on-duty of the switching power element according to the speed error signal, thereby controlling the brushless motor at variable speed while keeping the output voltage of the rectifying and smoothing circuit section 1 constant.

FIG. 2 is a side view of the brushless motor according to the embodiment of the present invention, with the printed circuit board assembled. In FIG. 2, 11 is a pre-driver IC, 12 is a bare chip of the switching power element, 12c is a potting resin for protecting the bare chip 12 of the switching power element from heat and pressure during stator resin molding, and 13 is a printed circuit board. From the viewpoint of heat dissipation, it is advantageous to use a metal base material or a sintered base material for the printed circuit board 13. The predriver IC 11 is surface-mounted on the printed circuit board 13.

FIG. 3 is an assembled state diagram of the stator of the brushless motor according to the embodiment of the present invention. In FIG. 3, a stator winding 3 is provided on a stator core 14 with a core insulation 15 interposed therebetween. On the other hand, the printed circuit board 13 is formed into a substantially donut shape, and the main components of the predriver IC 11 and bare chip groups 12a and 12b of switching power devices potted with resin are arranged at substantially equal pitches and in a substantially radial pattern. It is located.

The position sensor 5 is surface mounted on the printed circuit board 13 with a pitch of 120 degrees in electrical angle. In addition, when the fixed resistor 16, jumper wire 17, capacitor 18, winding end connection pin 19, etc. are attached to the stator core 14, the fixed resistor 16, jumper wire 17, capacitor 18, winding end connection pin 19, etc. Surface mounted in a position where there is no contact or interference.

The printed circuit board 13 is provided with mold pins that hold the printed circuit board 13 in a fixed position in the mold during resin molding and that form holes for inserting through bolts, rivets, etc. when assembling the motor after molding. A hole 13c is provided for insertion.

Further, a group of lead wires 20 for supplying power or transmitting speed command signals is attached to the printed circuit board 13, and a bushing 21 for protecting the group of lead wires 20 from heat and pressure during resin molding is attached to the lead wire group 20. line group 2
Fixed to 0. At this time, a groove 13d for positioning with the core insulation 15 is also provided.

The wound stator core 14 and the component-mounted printed circuit board 13 configured as described above are placed between one shroud part and the adjacent shroud part, as shown in the side view of the completed stator winding in FIG. Bare chip groups 12a and 12b of the pre-driver IC 11 and switching power elements are located,
The shroud parts 15a and 15b are combined so that the axial ends of the shroud parts 15a and 15b are brought into contact with the printed circuit board surface to form a completed stator winding product 22.

FIG. 5 is a perspective view of this state, in which the winding end 3a is wound around a winding connection pin 19 and is electrically fixed with solder or the like. The completed stator winding product configured as described above is resin molded and combined with a permanent magnet rotor to form a completed motor product.

[0019]

As is clear from the above description, the brushless motor of the present invention has the following advantages.

(1) Since a constant voltage is sufficient for the driving DC power supply, there is no need for a DC-DC converter section to vary the voltage, and the cost of the power supply section is low, making it possible to save space and reduce the cost of the system. .

(2) Mounting of the drive circuit By using a metal base material or a sintered base material as the printed circuit board and surface mounting the drive circuit components and the position sensor, the space of the drive circuit section can be saved. Since the leads of the circuit components do not protrude from the surface of the printed circuit board opposite to the component mounting surface, the size of the motor can be reduced to the same size as before, resulting in a space-saving system.

(3) Since it has a built-in speed control circuit,
There is no need to provide a speed control circuit outside the motor, making it possible to control the motor rotation speed with high accuracy at low cost.

[Brief explanation of drawings]

[Fig. 1] System block diagram of a brushless motor in an embodiment of the present invention

FIG. 2 is a side view of the printed circuit board assembly state of the brushless motor in the embodiment of the present invention.

[Fig. 3] Stator assembly state diagram of a brushless motor in an embodiment of the present invention.

FIG. 4: Completed side view of the stator winding of the brushless motor in the embodiment of the present invention.

[Fig. 5] Completed perspective view of the stator winding of the brushless motor in the embodiment of the present invention.

[Figure 6] System block diagram of conventional brushless motor

[Figure 7] Longitudinal cross-sectional view of a conventional brushless motor

[Explanation of symbols]

2 Switching power element group 3
Stator winding 4 Permanent magnet rotor 5 Position sensor 6 Drive control circuit section (drive circuit) 7
Switching power element driving means 8 Commutation signal generating means 9 Speed error signal generating means 10 PWM control means

Claims (3)

[Claims] Claim 1: A permanent magnet rotor is rotatably held by a bearing device on a stator in which a stator winding, a printed circuit board on which a position sensor, and a drive circuit are mounted are integrally molded and solidified with synthetic resin having electrical insulation properties. In the brushless motor, the drive circuit includes a switching power element group that switches the drive current flowing to the stator winding, and a commutation circuit that logic-processes the output of the position sensor to generate a commutation signal for the switching power element group. A rotational speed signal obtained by combining the outputs of the signal generation means, the switching power element driving means for driving the switching power element group with a commutation signal, and the position sensor is compared with the rotational speed command signal inputted from the outside. A brushless motor comprising: speed error signal generating means for outputting a speed error signal thereof; and PWM (pulse width modulation) control means for controlling on-duty of the switching power element group according to the speed error signal. 2. The brushless motor according to claim 1, wherein a metal base material or a sintered base material is used as the printed circuit board on which the drive circuit is mounted, and the drive circuit components and the position sensor are surface-mounted. 3. The brushless motor according to claim 2, wherein the switching power element is mounted and wired in a bare chip state.