JPH0888993A - Method for protecting dc brushless motor - Google Patents

Abstract

PURPOSE: To provide a method for protecting a DC brushless motor, which can protect the DC brushless motor from the abnormal operation caused by overload and the like with the simple constitution and can readily monitor the state of the DC brushless motor, by utilizing a Hall element, which has been conventionally used for detecting rotating positions. CONSTITUTION: The number of pulses per unit time is counted based on a pulse signal 4 detected with a Hall element 2, and the pulse signal frequency is obtained. The converting speed is obtained by the conversion from the pulse signal frequency. The converting speed and a preset speed are compared. When the converting speed and the preset speed disagree except the specified time after the starting, a DC brushless motor 1 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting a DC brushless motor, which converts position information obtained by a Hall element to detect rotation and protects the DC brushless motor.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a long-life electric pump, and therefore a DC motor has been used as a drive motor for the electric pump.
Brushless motors are increasingly used. In particular, when the DC brushless motor is used as a drive means of an electric pump, dirt contained in water adheres to cause clogging, or foreign matter is caught, and the DC brushless motor is overloaded. In addition, the operating state of the DC brushless motor is often abnormal, such as the idling operation without water. Therefore, in order to extend the life of the electric pump, it is necessary to monitor whether the DC brushless motor is overloaded. Moreover, since a large current flows through the drive coil of the DC brushless motor at the time of starting the electric pump, it is necessary to control so that an appropriate current flows at the time of starting.

A DC brushless motor uses a hall element, and a rotating magnetic field is formed by a pulse signal detected by the hall element to rotate a rotor. Conventionally, a dedicated control device is used to prevent overload and the like. Had to be attached externally. FIG. 5 is a control circuit diagram of a conventional DC brushless motor.

In FIG. 5, 1 is a DC brushless motor, 2 is a Hall element for detecting the rotational position of the DC brushless motor 1, and 7 is a DC brushless motor 1 driven in response to a speed command signal 8 from a computer 5 for controlling the whole. DC to
It is a brushless motor drive circuit. Then, whether or not the DC brushless motor 1 is overloaded is monitored by using a dedicated circuit C that extracts a current signal from the current transformer T inductively coupled to the stator of the DC brushless motor 1 and outputs the current signal to the computer 5. .

[0005]

However, such a configuration has a problem in that it requires a special element such as a current transformer and a dedicated circuit, which makes the configuration large.

Therefore, the present invention can protect the DC brushless motor from abnormal operation such as overload with a simple structure by utilizing the Hall element which has been conventionally used for detecting the rotational position. An object of the present invention is to provide a method for protecting a DC brushless motor, which makes it easy to monitor the state of the brushless motor.

[0007]

According to the method for protecting a DC brushless motor of the present invention, the pulse signal frequency is obtained by counting the number of pulses per unit time from the pulse signal detected by the hall element, and the converted speed is calculated from the pulse signal frequency. Is converted, the converted speed is compared with the set speed, and the DC brushless motor is stopped if the converted speed and the set speed do not match except for a fixed time after the start.

[0008]

With the above structure, since the state of the DC brushless motor is obtained and monitored from the Hall element already provided for detecting the rotational position, the current transformer or a dedicated circuit for processing the output of the current transformer is not used. The elements can be omitted, and the DC brushless motor can be protected with a simple structure.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. Here, the same components as those in FIG. 5 showing the conventional technique are designated by the same reference numerals,
Description is omitted.

FIG. 1 shows the D according to the first embodiment of the present invention.
It is a control circuit diagram of a C brushless motor. In FIG. 1, reference numeral 3 is a buffer amplifier which is connected to the output terminal of the hall element 2 and receives the pulse signal 4 output from the hall element 2.
Then, the pulse signal 6 is output from the buffer amplifier 3 to the input terminal of the computer 5.

Next, referring to FIG. 2 (a flow chart showing a method of protecting a DC brushless motor in the first embodiment of the present invention), the D in the first embodiment of the present invention is described.
A method of protecting the C brushless motor 1 will be described. First, the speed command signal 8 given from the computer 5 as the control means to the DC brushless motor drive circuit 7 is increased until it reaches a preset speed (step 1), and the speed command signal 8 is changed to the DC brushless motor drive circuit. 7 is output (step 2). As a result, the DC brushless motor 1 is activated.

Next, the Hall element 2 detects the position of the rotor of the DC brushless motor 1 as a pulse signal 4, and the pulse signal 4 is input to the computer 5 as a pulse signal 6 via the buffer amplifier 3. Therefore, the input pulse signal 6 is obtained as a frequency by counting the number of pulses per unit time by the frequency measurement routine of step 3 (step 3). Next, this frequency is converted into the converted speed of the DC brushless motor in consideration of the number of Hall elements 2 and the like by the pulse signal frequency conversion routine of step 4. Then, this converted speed is compared with the set speed (step 5).

Here, when the converted speed and the set speed are substantially equal to each other, it is assumed that the normal operation is performed.
Returning to step 1, the operation is continued.

When the converted speed is higher than the set speed, the speed of the DC brushless motor 1 is excessive,
The set speed indicated by the speed command signal 8 of the computer 5 is set to 0, and the DC brushless motor 1 is stopped (step 9).

Further, when the comparison result that the converted speed is lower than the set speed is obtained in step 5, it is checked in step 6 whether or not the engine is being started. If it is not started, it is determined to be abnormal and the stop operation of step 9 is performed. On the other hand, when the engine is being started, the timer counting for the time required to shift from the starting to the steady state is started in step 7, and the process returns to step 1. When the converted speed is still lower than the set speed even after the count-up, the stop processing of step 9 is performed.

If the electric pump or the like driven by the DC brushless motor 1 is clogged, the converted speed remains lower than the set speed even after a lapse of a certain time after startup, so step 8 The DC brushless motor 1 is stopped by the route from to. Next, when the foreign matter is caught in the electric pump during the steady operation of the electric pump, the DC brushless motor 1 is stopped by the routes of step 5, step 6, and step 9.

In the above two cases, the operator performs the work of removing the clogging or foreign matter from the electric pump and then restarting the electric pump.

Further, when water is not introduced into the electric pump and the electric pump is in idle operation, the DC brushless motor 1 is in a state of almost no load operation, and the rotation of the DC brushless motor 1 becomes abnormally high. Therefore, the DC brushless motor 1 is stopped along the route of step 5 and step 9.

Of course, if there is no abnormality in the DC brushless motor 1, steady rotation is continued (step 5, step 1).

In this embodiment, the Hall element 2 and the buffer amplifier 3 are constructed as separate bodies, but electronic components in which these are integrated may be used, or the buffer amplifier 3 in FIG. Alternatively, a transistor switch may be used. Further, in the present embodiment, the conversion speed and the set speed are directly compared, but the comparison result may be evaluated by comparing the function values depending on these.

As described above, in the present embodiment, D
In order to detect the rotational position of the C brushless motor 1, D
The load state of the DC brushless motor 1 is monitored by using the Hall element 2 attached to the C brushless motor 1, and the additional elements such as the buffer amplifier 3 should have a simple structure with a few parts. You can

Next, please refer to FIG. 3 (control circuit diagram of the DC brushless motor in the second embodiment of the present invention) and FIG. 4 (flow chart showing a method for protecting the DC brushless motor in the second embodiment of the present invention). However, the second aspect of the present invention
An example will be described.

In the second embodiment, a display device 9 is connected to the computer 5, as shown in FIG. And Figure 4
As shown in FIG. 7, in the second embodiment, in contrast to the first embodiment, during the process from step 5 to step 9, the abnormal high rotation is displayed (step 10), and from the process from step 6 to step 9. Then, the abnormal low rotation display at the steady time (step 11) is displayed during the process from step 8 to step 9 and the abnormal low rotation display at the start time (step 1).
2) The difference is that they are performed respectively. Others are the same as those in the first embodiment.

In this way, the display device 9 informs the operator of the details of the abnormality, so that the maintenance work of the operator can be facilitated. Of course, it is needless to say that the notification may be given by voice instead of the display by the display device 9.

By performing the above-mentioned monitoring, DC
By detecting the abnormality of the brushless motor 1 promptly and without increasing the scale of the DC brushless motor 1 and protecting the DC brushless motor 1, the life of the DC brushless motor 1 can be extended.

[0026]

The DC brushless motor protection method of the present invention obtains the pulse signal frequency from the pulse signal detected by the Hall element, converts it to a converted speed, and compares the converted speed with the set speed to determine the DC brushless motor. To protect,
The DC brushless motor can be protected without using a special element such as a current transformer or a dedicated circuit. Further, since the abnormality is displayed, maintenance work becomes easy.

[Brief description of drawings]

FIG. 1 is a control circuit diagram of a DC brushless motor according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a method for protecting a DC brushless motor according to the first embodiment of the present invention.

FIG. 3 is a control circuit diagram of a DC brushless motor according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing a method for protecting a DC brushless motor according to a second embodiment of the present invention.

FIG. 5 is a control circuit diagram of a conventional DC brushless motor.

[Explanation of reference symbols] 1 DC brushless motor 2 Hall element 4 Pulse signal 5 Computer 7 DC brushless motor drive circuit 8 Speed command signal

Claims (2)

[Claims] 1. A DC brushless motor, a DC brushless motor drive circuit for driving the DC brushless motor, and control means for giving a speed command signal to the DC brushless motor drive circuit, and the position of the rotor by a hall element. Is a method for protecting a DC brushless motor that is detected as a pulse signal, the number of pulses per unit time is counted from the pulse signal detected by the Hall element to obtain a pulse signal frequency, and the converted speed is calculated from the pulse signal frequency. Converting, comparing the converted speed with the set speed, and stopping the DC brushless motor if the converted speed and the set speed do not match except for a certain time after starting, protection of the DC brushless motor Method. 2. The D according to claim 1, wherein an abnormality is displayed when the converted speed and the set speed do not match.
C Brushless motor protection method.