JPH0129580Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a rotation speed measuring device for a brushed DC motor.

This applicant first detects a pulsating current generated in a DC power circuit of a brushed DC motor due to contact and separation between brushes and a commutator of the DC motor, and converts the detection signal into pulses. A rotation speed measuring device for a brushed DC motor, characterized in that a waveform conversion circuit for conversion is connected, pulses output from the circuit are counted by a counter, and the counted value is taken as a function of the rotation speed of the DC motor. (Jitsugan No. 57-201574).

However, this embodiment of the device cannot detect the inertial rotation of the motor after the power is cut off, so it is not possible to accurately detect the rotation angle until the motor rotation completely stops from the rotation speed measurement value. It was enough.

This invention is an improvement in view of the above points, and includes not only the number of rotations while the motor is energized, but also
It is also possible to measure the rotation speed due to inertial rotation after the power is turned off.
It is an object of the present invention to provide a rotation speed measuring device that can accurately detect the rotation angle when the rotation of the motor has completely stopped.

Next, an embodiment of this invention will be described based on the drawings.

As shown in Fig. 1, the rotation speed measuring device according to this invention has a power supply circuit 2 of a brushed DC motor (hereinafter simply referred to as the motor) 1, a DC power supply 3, and a switch that turns on and off current to the motor. A capacitor 6 is connected in parallel to a series circuit 5 including 4, a waveform conversion circuit 7 is connected in series to the parallel circuits 5 and 6 to the power supply circuit 2, and the output pulse is connected to the waveform conversion circuit. It is constructed by connecting a counter 8 for counting.

The waveform conversion circuit 7 detects the pulsating current generated in the power supply circuit 2 due to the repeated contact and separation between the brushes of the motor and the commutator as the motor rotates, and converts it into pulses corresponding to the pulsating current. This is what is output. Therefore, basically a monostable multivibrator, a Schmitt circuit, a clip circuit, etc. can be used as the waveform conversion circuit. If the waveform of the pulsating current is gentle because the motor has a small number of rotor slots and the rotational speed is relatively slow, a differentiating circuit, an amplifier circuit, etc. may be used in the waveform conversion circuit to shape the pulses into pulses that can reliably operate the counter. They may be used in combination as necessary.

FIG. 2 shows and explains a specific example of the waveform conversion circuit. A waveform conversion circuit 7 is coupled to the power supply circuit 2 between the terminal 1b and the parallel circuit via a bias resistor _R1 , and is formed by sequentially connecting a differentiator circuit 7a, an amplifier circuit 7b, a rectifier circuit 7c, and a limiter 7d. There is.

Here, to show an example of the ratings of each element in Figure 2, motor 1 is 24V, 100mA, and capacitor C ₁ =
20μF, C ₂ = 0.1μF, resistance R ₁ = 20Ω, R ₂ , R ₃ =
100kΩ, cathode voltage of diode _D2 E = 1.5V
It is.

With the above configuration, when the switch 4 is closed, the capacitor 6 does not pass direct current, so the power supply circuit 2 supplies direct current power to the motor 1, causing the motor to rotate. Then, a pulsating current flows through the power supply circuit 2 due to the contact and separation of the motor brushes and the commutator (FIG. 3a). The differentiating circuit 7a obtains a sharp waveform output (Fig. 3b) corresponding to each slot of the motor rotor from the pulsating current, and the amplifying circuit 7b amplifies the output to the level necessary to operate the counter 8 reliably. Then, only the positive portion is extracted from the amplified output by the rectifier circuit 7c, and finally the waveform is manipulated by the limiter 7d to output a rectangular wave for operating the counter 8 (FIG. 3d).

If the rotor of the motor has, for example, three slots, six pulses are outputted from the waveform conversion circuit 7 and applied to the counter 8 during one revolution of the motor.

Furthermore, when the switch 4 is opened, the motor rotates due to inertia, so it becomes a generator. and,
Since capacitor 6 is inserted in power supply circuit 2,
Due to the inertial rotation of the motor and the contact and separation of the brush and commutator, one terminal 1b, resistor R ₁ , capacitor 6,
A pulsating current is generated in the circuit connecting the other terminal 1a. This continues until the motor stops rotating completely. Therefore, this pulsating current is detected by the waveform conversion circuit 7 in the same manner as in the above case, converted into pulses corresponding to the rotation of the motor, and provided to the counter 8. In this way, even after the switch 4 is turned off, the number of rotations of the motor can be measured.

As mentioned above, according to this invention, a capacitor is connected in parallel to the series circuit of a switch and a DC power supply in the motor power supply circuit, a pulsating current is detected in the power supply circuit, and the detection signal is converted into a pulse. It is made by combining a waveform conversion circuit that outputs a waveform conversion circuit, and a counter that counts the output pulses from the waveform conversion circuit.
Even when the power is turned off, pulses corresponding to the actual rotation speed are generated and counted until the motor rotation completely stops, so it is possible to accurately calculate the rotation angle until the motor completely stops rotation after the power is turned off. can be detected.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the basic configuration of this invention, Figure 2 is a circuit diagram showing a specific example, and Figure 3 is a of Figure 2.
It is a figure which shows the output waveform at each point of -d. 1...DC motor, 2...Power circuit, 3...DC power supply, 4...Switch, 6...Capacitor, 7
...Waveform conversion circuit, 8...Counter.

Claims (1)

[Scope of utility model registration request] In the power supply circuit of a brushed DC motor having a rotor with a small number of slots, the pulsating current generated in the power supply circuit due to the contact and separation between the brushes of the DC motor and the commutator is detected, and the detection signal is converted into pulses. A rotational speed measuring device comprising: a waveform converting circuit for converting; a counter for counting the output pulses of the waveform converting circuit;
A rotation speed measuring device for a brushed DC motor, characterized in that a capacitor is connected in parallel to a DC power source in the power supply circuit.