JPH051983Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a carbon brush wear monitoring device that monitors the wear of carbon brushes that are pressed into contact with a commutator of a motor.

"Prior Art" In a motor, a carbon brush is pressure-welded to a commutator in order to establish an electrical connection with a rotor. When the carbon brush wears out,
Good contact with the commutator cannot be obtained and heat is generated. Conventionally, there was no device for monitoring the wear state of carbon brushes, so it was necessary to replace carbon brushes early. Since the degree of wear varies depending on the carbon brush,
I needed to replace it quickly.

"Means for Solving the Problem" According to this invention, a conductive wire on which a resistive coating is formed is embedded in a carbon brush in the direction of wear, and a constant current is generated between the conductive wire and the carbon brush as a constant current source. The voltage generated between the conductive wire and the carbon brush is compared with a first voltage lower than the constant current source voltage and a second voltage lower thereby, by first and second comparators, respectively. .

``Operation'' Under normal conditions, the voltage drop between the conductor and the carbon brush is mainly caused by the resistance coating of the conductor, but when the carbon brush wears out and the commutator reaches the conductor, the resistance coating is stripped off and the conductor and the carbon brush drops significantly, which is detected by the second comparator. Further, when a break occurs in the wiring, the constant current between the carbon brush and the conducting wire is cut off, and the voltage supplied to the comparator becomes substantially the voltage of the constant current source, which is detected by the first comparator.

"Embodiment" FIG. 1 shows an embodiment of this invention. A carbon brush 12 is pressed against a commutator 11 of the motor by a pressure spring 13. In this invention, the conductive wire 14 is embedded in the carbon brush 12 from the end surface in the wear direction. A resistive coating 15 is formed on the conductive wire 14. For example, the resistive film 15 has a large specific resistance (carbon brush 10
~20 times) carbon can be used. Conductor 1
4 may be a thin copper wire. The carbon brush 12 and the conductor 14 are connected to a monitor 16.

The monitor 16 is connected to a constant current source 17 as shown in FIG.
is provided, and the constant current source 17 is connected to the carbon brush 1.
2 are connected, the conducting wire 14 is connected to a common potential point, and a constant current is passed between the carbon brush 12 and the conducting wire 14. The non-inverting input sides of the first and second comparators 18 and 19 are connected to the carbon brush 12, and the voltage between the carbon brush 12 and the conducting wire 14 is applied to the first and second comparators 18 and 19. .
A first voltage from the power supply 21 is applied as a reference voltage to the inverting input side of the first comparator 18, and a second voltage lower than the first voltage is applied as a reference voltage from the power supply 22 to the inverting input side of the second comparator 19. Applied as a voltage.

The positive output side of the first comparator 18 is connected to the first alarm terminal 23 , and the opposite output side of the second comparator 19 is connected to the second alarm terminal 24 . 1st comparator 1
The reverse polarity output of the second comparator 8 and the positive polarity output of the second comparator 19 are supplied to an AND circuit 25 , and the output side of the AND circuit 25 is connected to a normal terminal 26 .

In the above configuration, under normal conditions, the constant current source 17
The voltage drop of the current flowing from the resistor film 1
5, this value is a relatively high resistance value (several kΩ)
, and this voltage is lower than the first voltage but higher than the second voltage. Therefore, the reverse polarity output of the first comparator 18 is at a high level "1".
Then, the positive polarity output of the second comparator 19 becomes a high level "1", the output of the AND circuit 25 becomes a high level "1", and the normal terminal 2
6 will be notified.

Next, the carbon brush 12 wears out, and the conductor 14
When in contact with the commutator 11, the voltage drop between the carbon brush 12 and the conductor 14 becomes significantly smaller, this value corresponds to a resistance value of several ohms, and this voltage is lower than the second voltage. Therefore, the reverse polarity output of the second comparator 19 becomes a high level "1", the second alarm terminal 24 is notified that the carbon brush 12 is worn, and the normal terminal 26 becomes a low level "0".

When a disconnection occurs on the conductor 14 side connected to the constant current source 17, the voltage input to the first comparator 18 becomes higher than the first voltage, and the positive polarity output of the first comparator 18 becomes a high level "1". , it is reported that a disconnection abnormality has occurred at the first alarm terminal 23, and the normal terminal 26
becomes a low level "0".

"Effects of the invention" As described above, according to this invention, when the wear of the carbon brush 12 reaches a predetermined value, this is notified to the second alarm terminal 24, so that the carbon brush is always kept in the correct usage condition. Tsushi can be exchanged. In addition, in this device, a constant current from a constant current source is constantly passed through the conductor 14, the resistive coating 15, and the carbon brush 12 in series, so even if a disconnection abnormality occurs in the circuit for detecting wear, this will be detected. Therefore, the detection circuit itself can be checked automatically.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an embodiment of this invention.
FIG. 2 is a block diagram showing a specific example of a part thereof.

Claims (1)

[Claims for Utility Model Registration] A conductive wire having a resistive coating formed on its outer circumferential surface and embedded in a carbon brush in the direction of wear, and a constant current source that flows a constant current between the conductive wire and the carbon brush. , a first comparator that compares the voltage generated between the conductive wire and the carbon brush with a first voltage lower than the voltage of the constant current source; A carbon brush wear monitoring device comprising a second comparator that compares the voltage with a second voltage lower than the first voltage.