JPH04190690A - Brushless motor - Google Patents

Abstract

PURPOSE:To reduce the operating cost of a brushless motor by turning on/off the winding current of the motor with a chopping signal generated by a self-excited oscillator until the motor reaches a prescribed rotating seed after starting and making the full current to flow through a prescribed section on the basis of the signal of a position detector until the motor reaches a steady rotating speed from the prescribed rotating speed. CONSTITUTION:In the stopping or a low rotating speed range of a motor, a rotating speed detection circuit 6 outputs a negative logic signal and a multiplexer 9 outputs the output signal of a self-excited oscillation circuit 7 on the basis of the signal from the circuit 6. AND gates 8 AND the output signals of the circuit 7 and a logic circuit 4 and output the AND to a drive circuit 5. When the motor reaches a prescribed rotating speed, the circuit 6 outputs a positive logic signal and the multiplexer 9 outputs a positive logic signal on the basis of the signal from the circuit 6. Therefore, the stator current and the electric current to a switching element can be reduced at the starting time and while the motor is in a low rotating speed range.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to brushless motors used in vacuum cleaners, blowers, and the like.

Conventional technology In recent years, brushless motors have been developed by taking advantage of their characteristics of large starting torque, easy speed control, and wide range operation.
They are now being used in fields where induction motors and commutator motors have traditionally been used.

Hereinafter, a conventional brushless motor will be explained with reference to FIG.

A is a motor, which is composed of a rotor to which a permanent magnet 1 is attached, a stator winding 2, and a position detector 3. Reference numeral B denotes a drive circuit, which is comprised of a logic circuit section 4 that creates a current pattern to flow through the stator winding 2 based on a signal from the position detector 3, and a switching section 5 that switches the current to the stator winding.

Problems to be Solved by the Invention However, in the configuration described above, a brushless motor with a low motor rotation speed may be used, but when the rotation speed is high, the current flowing through the stator windings and the switching section is high during startup or in the low speed rotation range. In this case, a large current flows, and in a high-speed rotation region, a small current flows. Therefore, the switching elements (power transistors, etc.) of brushless motors that rotate at such high rotational speeds are required to carry not only a small current in the high-speed rotation range that is normally used (but also a large current in the low-speed rotation range). , which was extremely costly.

In view of the above-mentioned problems, the present invention provides a brushless motor in which the switching element of a high-speed rotation brushless motor is designed to have a small current value flowing in the high-speed rotation range where it is normally used, so that it can rotate at startup and in the low-speed rotation range. It is.

Means for Solving Problems In order to solve the above problems, the brushless motor of the present invention detects the rotation speed of the motor, and uses a self-excited oscillator at startup below a predetermined rotation speed and in a low speed rotation range. A signal obtained by an AND gate of the chopping signal obtained by the above and the output signal of the logic circuit 4 is outputted to the switching section, and in a high speed rotation range above a predetermined rotation speed, the signal of the logic circuit 4 is output as is to the switching section. This is how it was done.

Function: By having the above-described structure, only a small amount of current flows through the stator windings even at low speeds, making it possible to use switching elements with small capacitance.

EXAMPLE Hereinafter, a brushless motor according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a motor section 2 circuit section of a brushless motor in a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a permanent magnet which is alternately magnetized to N and S poles. 2 is a stator winding; 3 is a position detector (Hall element) for detecting the position of the permanent magnet 1; Reference numeral 4 denotes a logic circuit section in the drive circuit, which generates a control signal for adjusting the current flowing to the stator winding 2 based on the signal from the position detector 3. 6 is a rotation speed detection circuit, 7 is a self-excited oscillation circuit, 8 is an AND gate, and 9 is a multiplexer, which switches the signal output to the drive circuit 5 according to the rotation speed.

First about the brushless motor configured as above.
The details of the operation will be explained using figures.

When the motor is stopped and in a low rotation range, the rotation speed detection circuit 6 outputs a negative logic signal, and this signal causes the multiplexer 9 to output the output signal of the self-excited oscillation circuit 7. A logical product with the signal is created by the AND gate 8 and output to the drive circuit 5. FIG. 2 shows the voltage waveforms of various parts at that time.

When the rotational speed of the motor reaches a predetermined rotational speed, the rotational speed detection circuit 6 outputs a positive logic signal, and this signal causes the multiplexer 9 to output a positive logic signal. The logical product of this signal and the output signal of logic signal 4 (in this case, the logic signal of 4 remains unchanged) is created by AND gate 8 and output to drive circuit 5. FIG. 3 shows the voltage waveforms of various parts at that time.

By operating as described above, the stator current and switching element current are turned on and off according to the chopping signal of the self-excited oscillator during startup and in the low speed rotation range, making it possible to reduce the current to a small amount. Since the current is sufficiently small, all switching elements need only have a tolerance for this small current value in the rotation range, and can be made inexpensive and small.

Effects of the Invention As described above, the present invention turns the winding current on and off using a chopping signal from a self-excited oscillator from a stopped state to a predetermined number of rotations, and from the predetermined number of rotations to a steady rotation number, the winding current is turned on and off using a chopping signal from a self-excited oscillator. By using a brushless motor that allows the entire current to flow in a predetermined section based on a signal, the switching element that switches the winding current can be designed to have a small current capacity, making it possible to reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a motor section and drive circuit section of a brushless motor according to a first embodiment of the present invention, FIG. 2 is a brushless motor of the present invention, and FIG. 4 is a block diagram showing the motor section of a conventional brushless motor. FIG. 3 is a block diagram showing a drive circuit section. 2... Stator winding, 3... Position detector, 4... Logic circuit, 5... Drive circuit.

Claims (1)

[Claims] The brushless motor turns the winding current on and off using a chopping signal from a self-excited oscillator from a stopped state to a predetermined rotation speed, and from the predetermined rotation speed to a steady rotation speed, the entire current flows in a predetermined section based on the position detector signal. motor.