JPH05168280A - Brushless motor - Google Patents

Abstract

PURPOSE:To improve safety, reliability of a system by informing a malfunction of a motor for generating a lock alarm sound when the motor is locked in the brushless motor having a current limiter as overcurrent protecting means. CONSTITUTION:A brushless motor 6 generates an electromagnetic sound as lock alarm sound by opening or closing a switching power element group 5 by an audible frequency if a motor current flowing to the switching power element 5 becomes larger than a predetermined value due to a motor lock.

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 blower fan drive source for an air conditioner or the like, and more particularly to a brushless motor provided with a motor lock countermeasure.

[0002]

2. Description of the Related Art A conventional brushless motor drive system has a structure shown in the block diagram of FIG. 2, in which a motor unit A having a drive circuit unit 7 is operated by a DC power source unit B such as a switching power source, and a DC power source unit B. The rotation speed of the brushless motor is changed by changing the output voltage of the brushless motor. An example of a conventional brushless motor drive system will be described below with reference to the drawings. The DC power supply unit B converts the commercial power supply 1 into the rectifying / smoothing unit 3
After rectifying and smoothing with, transformer 4 and switching power element 10
The DC-DC converter unit composed of the voltage control unit 11 and the DC voltage is used as a variable DC voltage, and the driving circuit unit
The rotation speed of the motor 6 connected to the power element group 5 which is opened / closed is controlled by the energization switching signal. The voltage control unit 11 of the DC-DC converter controls the output voltage according to the rotation speed command signal from the rotation speed command unit 2. However, the output voltage of the current detection unit 9 is further input to cause an overcurrent. The switching power element 10 is controlled so that it does not flow, and when a current exceeding the overcurrent setting flows, the switching power element 10 is turned off so that the DC output voltage is throttled so that a current exceeding the set value does not flow. .

[0003]

In the conventional brushless motor drive system as described above, when the motor is locked due to a bearing failure or the like, a current of the overcurrent set value continues to flow to the motor, and The driving circuit generates a large amount of heat. In order to prevent this, motor lock detection means is provided to cut off the output of the DC power supply when the motor is locked to suppress heat generation of the motor and drive circuit. However, in such a system, it is not known whether the motor has locked and the system has stopped, so the system remains stopped until the user of the air conditioner notices an abnormality in the room temperature. Further, when the microcomputer of the system runs out of control, the lock of the motor cannot be detected, the heat generation becomes large, and the life of the motor is shortened.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a brushless motor which is provided with safety measures by taking measures against motor lock while reducing system cost.

[0005]

In order to achieve this object, the brushless motor of the present invention comprises a means for detecting a motor current and an output of the current detecting means by comparing the output voltage of the motor current detecting means with a reference voltage. An opening / closing type current limiting means having an opening / closing cycle of an audible frequency is provided, in which when the voltage is higher, the energization to the motor is interrupted and the motor is energized again after a lapse of a certain time.

[0006]

With the above configuration, when the motor is locked, the motor current is chopped at the audible frequency by the open / close type current limiting means, and the electromagnetic noise of the audible frequency is generated from the motor.
Notify that the motor is locked.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a brushless motor drive system according to the present invention. The driving DC power supply unit B controls the output voltage in the DC-DC converter unit including the transformer 4, the switching power element 10, and the voltage control unit 11 after the commercial power supply 1 is rectified and smoothed by the rectification smoothing unit 3. ing. In the motor unit A, the signal from the rotor position sensor is logically processed by the drive circuit unit 7 to open / close the switching power element group 5. In the overcurrent protection, the motor current is detected by the current detection resistor 9, the current limit circuit 8 compares the output voltage of the current detection resistor 9 with the current limit level, and when the output voltage of the current detection resistor 9 is higher, the switching power is increased. The element group 5 is turned off, the energization of the motor is cut off, and the energization is restarted after a certain period of time. That is, the current limiting circuit 8 includes an open / close type current limiting means for opening / closing the switching power element group 5 in such a manner. Here, by setting the switching time of energization so that the switching frequency of the switching power element group 5 during overcurrent operation is in the audible range, when the motor is locked, the motor is electromagnetically vibrated by the switching current and electromagnetic noise is generated. The alarm sounds for the motor lock. Furthermore, if the frequency of the electromagnetic sound is made to match the resonance frequency of the motor, the sound becomes louder and the effect as a lock warning sound becomes larger. As an embodiment of the present invention, the switching power element group 5, the drive circuit section 7 and the open / close type current limiting means are
It is integrated into a chip IC, and further, the rotor position sensor, the printed board on which the one-chip IC and the current detecting means are mounted, the stator core, and the stator winding are integrally resin-molded to form a stator. However, all are effective forms for improving reliability.

[0008]

As described above, by adopting the configuration of the present invention, the following effects can be obtained.

1. When the motor is locked, the electromagnetic noise generated by the motor current serves as a lock alarm to notify the user that an abnormal condition has occurred, so that the system can be detected quickly and the safety and reliability of the system can be improved.

2. Since the DC power supply section does not need a current detecting means, the power supply section is low in cost, and the space and cost of the system can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a drive system for a brushless motor according to the present invention.

FIG. 2 is a block diagram of a drive system for a brushless motor according to a conventional example.

[Explanation of symbols]

 5 Switching Power Element Group 6 Motor 7 Drive Circuit Section 8 Current Limiting Circuit (Switching Type Current Limiting Means) 9 Current Detection Resistor (Motor Current Detection Means)

Claims (3)

[Claims] 1. A motor current detection means, a switching power element group for supplying a motor current, a drive circuit section for opening and closing the switching power element group according to a signal from a rotor position sensor, and a motor current larger than a predetermined value. In this case, the switching power element group is closed and the switching power element group is opened again after a fixed time, and the switching frequency of the switching power element group by the opening and closing current limiting means is an audible frequency. 2. A brushless motor according to claim 1, further comprising a one-chip IC containing a switching power element group, a drive circuit section, and an open / close type current limiting means. 3. A printed circuit board on which a rotor position sensor, the one-chip IC according to claim 2 and a motor current detection means are mounted, a stator core, and a stator winding are integrally molded and solidified with a thermosetting resin. The brushless motor according to claim 1, further comprising a stator formed by the above.