JPH0624348U - Failure detector for DC brushless motor - Google Patents

Abstract

(57) [Summary] [Purpose] To detect the open phase rotation of a DC brushless motor promptly. [Structure] A motor current detection resistor 2 is connected between a DC brushless motor 1 and one end of a power source (not shown) to detect a motor current, and a low-frequency component is taken out by an LPF section 3.
Amplification is performed by the amplification unit 4, and comparison is performed by the comparator unit 5 with a value corresponding to a predetermined value smaller than the lower limit value of the motor current during normal rotation. When the open phase rotation is performed, the motor current intermittently becomes zero and becomes intermittently lower than a value corresponding to a predetermined value smaller than the lower limit value, and the output S1 of the comparator unit 5 is reached.
Repeats "H" and "L", so it can be determined that there is an open phase rotation.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a DC brushless motor (sometimes referred to as a brushless motor), and more particularly to detection of an open phase failure thereof.

[0002]

[Prior art]

 DC brushless motors are brushless, have no sparks, have little electrical noise, and are maintenance-free. They are used in a wide range of fields such as industrial equipment, precision instruments, and home appliances.

By the way, since a DC brushless motor uses a permanent magnet for a rotor and is a brushless motor, there are few electrical failures, and as electrical protection, it is known to perform overload protection based on the motor current. It is only about.

[0004]

[Problems to be solved by the device]

 However, for example, DC brushless motors used to drive the gates of railroad crossing gates and parking lot gates may be out of phase due to lightning strikes, etc., because such gates are installed outdoors. is there.

However, in a multi-phase drive brushless motor such as a three-phase full-wave system, the rotational angle range in which the rotational force is lost even if one phase fails, is small in many cases and apparently normally rotates normally. This is called open-phase rotation.

[0006] This open-phase rotation eventually leads to motor stop depending on the starting position. For example, if the starting position of the DC brushless motor is in a rotation angle range where there is no rotational force when a rise command is issued in a railroad crossing barrier, the balance of the barrier rod is adjusted to descend due to gravity, so the barrier rod is raised. There is a risk that traffic congestion will occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a failure detection device for a DC brushless motor, which quickly detects an open phase rotation of the DC brushless motor. .

[0008]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention detects the open phase rotation by focusing on the waveform of the motor current during the open phase rotation. Specifically, the DC brushless motor failure detection device is described below. It is configured as in 1).

(1) A motor current detection means provided between a DC brushless motor and its power source, a low-pass filter for extracting the low-frequency component from the output of this motor current detection means, and the output value of this low-pass filter A comparator for comparing with a value corresponding to a predetermined value smaller than the lower limit value of the motor current during normal rotation of the DC brushless motor, and a judging means for judging whether or not there is an open phase rotation based on the output of this comparator. DC brushless motor failure detection device equipped with.

[0010]

[Action]

 With the configuration of (1) above, the low frequency component of the motor current is extracted, compared with a predetermined value, and at the time of phase loss rotation, the phase loss rotation is judged by repeating "H" and "L" which are comparison outputs. To do.

[0011]

【Example】

 Hereinafter, the present invention will be described in detail with reference to embodiments. FIG. 1 is a block diagram of an example of a “DC brushless motor failure detection device for a railroad crossing circuit breaker”, and FIG. 2 is a circuit diagram of the LPF (low-pass filter), amplification, and comparator section of FIG. FIG. 3 is a waveform diagram of a main part when the blocking rod normally rises, and FIG. 4 is a waveform diagram of a main part when the blocking rod is lowered.

As shown in FIG. 1, the current of a DC brushless motor (hereinafter referred to as “motor”) 1 is detected by a motor current detection resistor 2 connected between the motor 1 and one end of a power source (not shown), and its low current is detected. The frequency component is extracted by the LPF unit 3, amplified by the amplifying unit 4, and compared by the comparator unit 5 with a value corresponding to a predetermined value smaller than the lower limit value of the motor current during normal motor rotation.

At the time of normal rotation of the motor, the motor current flows as shown in 2a of FIG. 3 or 2b of FIG. 4 (a), and from the LPF unit 3 including the integrating circuit of the resistor 3-1 and the capacitor 3-2. The extracted low frequency component never becomes zero. The positive input terminal of the operational amplifier 5-3 is set to a value corresponding to a predetermined value smaller than the lower limit value of the motor current at the time of normal motor rotation by the resistors 5-1 and 5-2, and the amplification section is connected to the negative input terminal. Since the output of 4 is supplied, during normal rotation, the output terminal of the operational amplifier 5-3 remains "L" and does not invert to "H". It becomes as shown in S1.

When one of the three phases is open, the motor current flows as shown by 2c in FIG. 4 (b) (the waveform varies depending on the motor circuit configuration and the failure point), and the output of the LPF unit 3 is It becomes zero intermittently. As a result, the output terminal of the operational amplifier 5-3 intermittently becomes "H" as shown by S1 in FIG. 4 (b).

The CPU 6 determines the open phase rotation by repeating “H” and “L” of the signal S1 during a predetermined time during motor driving.

In this way, when the CPU 6 detects the phase loss rotation, the CPU 6 displays it and displays an alarm and performs other processing.

In the embodiment, the CPU determines the open-phase rotation by software, but the present invention is not limited to this, and may be performed by hardware.

Further, although the motor current is taken out by the resistance in the embodiment, the present invention is not limited to this, and may be taken out by a current transformer, for example.

[0019]

[Effect of device]

 As described above, according to the present invention, the open phase rotation of the DC brushless motor can be detected quickly.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is a circuit diagram of an LPF, an amplifier and a comparator section in the embodiment.

[Fig. 3] Waveform diagram of main parts when the shutoff rod normally rises

[Fig. 4] Waveform diagram of main parts when the shutoff rod descends

[Explanation of symbols]

 1 DC brushless motor 2 Motor current detection resistor 3 LPF section 5 Comparator section 6 CPU

Continuation of the front page (72) Creator Toshio Takano 1-13-8 Kamikizaki, Urawa-shi, Saitama Nihon Signal Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A motor current detecting means provided between a DC brushless motor and a power source thereof, a low-pass filter for extracting a low-frequency component from the output of the motor current detecting means, and an output value of the low-pass filter for the DC brushless motor. It is provided with a comparator for comparing with a value corresponding to a predetermined value smaller than the lower limit value of the motor current during normal rotation of the motor, and a determination means for determining whether or not there is an open phase rotation based on the output of this comparator. Characteristic DC brushless motor failure detection device.