JPS5845262B2 - DC motor protection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection circuit for a DC motor used in a DC servo recorder.

Generally, when configuring a DC servo type recorder, the output of a potentiometer that detects the position of the recording pen and a command signal to bring the recording pen to the desired position are input, and a servo that outputs a voltage according to the output difference is input. using an amplifier,
The motor for driving the pen is controlled by the output of this servo amplifier.

A signal large enough to cause the pen to overscale is applied as a command signal. Conventionally, a mechanical slip mechanism or electric A widely used method is to detect the scale over condition by using a limit switch or the output of a potentiometer that detects the position of the pen, and then cut off the current supply to the motor.

However, when a slip mechanism is used, there are many unstable factors such as generation of slip noise, abrasion of the slip part, and thermal expansion, and when using the output of a switch or potentiometer, the pen is placed at a position that is not over scale. There was a problem that it would not work even if it was locked.

The present invention eliminates the above-mentioned drawbacks of the conventional technology, and uses an excellent direct current system that completely cuts off the current supply to the motor that drives the pen when a large signal is input as a command signal and the pen scales over. It provides a motor protection circuit.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, A manually outputs a command signal specifying the position of the pen and a potentiometer that detects the position of the pen, and until the output difference reaches a certain value, it outputs a voltage according to the above output difference, and then outputs the above output. A final setting value DC amplifier of the servo amplifier that outputs a predetermined constant saturation voltage when the difference exceeds the above-mentioned certain value, Qa = Q4 is a current amplification transistor controlled by the output of the above-mentioned DC amplifier A, M are the pen drive motors R-1 and R2#C connected in series to the transistors Q3-Q4, respectively.
1 and C2 are a resistor, a capacitor, and Dl, respectively, which constitute an integrating circuit that receives the output of the DC amplifier A as an input.

D2 is a diode constituting a discharge circuit for the capacitors C1 and C2, D3, D4, D7, D8 are diodes for preventing backflow, and D, D are Zener diodes. Qle and Q2 are switching transistors.

In the above embodiment, if the command signal is within a predetermined range, the output of DC amplifier A is also within a predetermined range and does not reach a certain saturation voltage.

Therefore, in this case, even if the output of the DC amplifier A is applied to an integrating circuit consisting of resistors R1 and R2 and capacitors C1 and C2, the capacitor C1.

The voltages V, , V2 across C2 do not exceed a certain level, and both transistors Qt-Q2 are in an off state.

Therefore, transistor Qa'=Q4 is controlled exclusively by the output of DC amplifier A,
A current corresponding to the output of the DC amplifier A is also supplied to the motor M.

Then, when the position of the pen driven by the motor M is brought to the position specified by the command signal and the output of the potentiometer and the command signal completely match, the output of the DC amplifier A becomes zero. Transistors Qs and Q4 turn off, and motor M stops.

Now, if we apply a command signal that exceeds the predetermined range, the difference between the output of the potentiometer that detects the pen position will reach a certain value or more, and the output terminal of DC amplifier A will reach a predetermined saturation level. Voltage output.

Assuming that a positive saturation voltage now appears at the output end of the DC amplifier A, this saturation voltage is first applied to the base of the transistor Qs = Q4 via the resistors R3, R,.

Therefore, transistor Q3 is on, transistor Q
4 is turned off, and current is supplied to the motor M in the forward direction.

The positive saturation voltage appearing at the output end of the DC amplifier is further applied to an integrating circuit comprising resistors R1, R2 and capacitors C1, C.

When the above saturation voltage is applied to the integrating circuit, the capacitor C
1 and C2, and the respective potentials at the connection point between the resistor R1 and the capacitor C1, and the connection point between the resistor R2 and the capacitor C2 approach the saturation voltage in the positive direction.

When the potential at the connection point between resistor R1 and capacitor C1 exceeds the sum of the forward voltage of diode D3, the Zener voltage E of Zener diode D, and the base-emitter voltage of transistor Q1, transistor Q1 turns on. The base potential of transistor Q3 is lowered to completely turn off transistor Q3.

Therefore, the current supplied to the DC motor M through the transistor Q3 is completely cut off, and the DC motor M immediately stops rotating.

Incidentally, when the saturation voltage in the positive direction is applied to the integrating circuit, the potential at the connection point between resistor R2 and capacitor C2 also exceeds a certain value, similar to the potential at the connection point between resistor R1 and capacitor C1. A diode D4 is connected in the opposite direction to the transistor Q2, and this voltage is not applied to the transistor Q2.

Therefore, the transistor Q2 is turned on and the button is turned on, and no change occurs.

When the reduced voltage appearing at the output terminal of DC amplifier A is a negative saturation voltage, this turns on transistor Q4 and turns off transistor Q3.

Therefore, a predetermined current is supplied to the motor M in the negative direction, contrary to the case where the saturation voltage is in the positive direction.

In this case, the capacitor C constituting the integrating circuit is
The voltage across the transistor Q2 turns on the transistor Q2 after a certain period of time and turns off the transistor Q4.

Note that the diode D1. D2 is the output voltage V of the amplifier circuit A.

is the output voltage of the integrating circuit V1. This is to quickly discharge the charges accumulated in the capacitors C1 and C2 when the voltage drops below V2.

In this way, according to the above embodiment, even if a large signal exceeding a certain range is input as a command signal, the current supply to the motor can be completely cut off after a certain period of time determined by the integrating circuit. By determining the scale of the pen so that overscale of the pen does not occur within the fixed time determined by the integration circuit, a large current still flows through the motor even after overscaling of the pen occurs. The inconvenience of interfering with the pen or motor can be completely prevented.

As is clear from the above embodiments, the DC motor protection circuit of the present invention inputs a command signal specifying the position of the pen and the output of a potentiometer that detects the position of the pen, and the output difference between the two reaches a certain value. A servo amplifier is used that outputs a voltage according to the above output difference during the period, and when the above output difference exceeds the above fixed value, a servo amplifier is used that outputs a predetermined constant saturation voltage. The output of the servo amplifier is configured to control a transistor connected in series to the motor that drives the resistor,
The voltage is applied to an integrating circuit consisting of a capacitor, and until the output of this integrating circuit exceeds a certain value, another transistor connected after the integrating circuit does not operate, and the transistor connected in series with the motor does not operate. It is controlled according to the output of the servo amplifier, and only when the output of the integrating circuit becomes equal to or higher than the certain value, the another transistor provided after the integrating circuit operates, and the operation of this another transistor causes the above It is configured so that the transistor connected in series with the motor is completely turned off, and if the command signal is large enough to overscale, the pen is driven for a certain period of time determined by the integration circuit, and the overscale state is reached. This makes it possible to completely block current supply to the motor, which is extremely advantageous in practice.

According to the present invention, while the output of the integrating circuit exceeds a certain value (1), the transistor provided at the latter stage of the integrating circuit does not operate at all, so that the transistor connected in series with the motor The output of the 1 servo amplifier is then applied, and the rotational speed of the motor corresponds to the output of the servo amplifier.

Therefore, if an output large enough to overscale is generated as a command signal, and the output of the servo amplifier reaches the saturation voltage, the current flowing to the motor will also correspond to this saturation voltage, causing the pen to overscale. It has the advantage that the pen is quickly moved by the motor during this time.

[Brief explanation of drawings]

The figure is an electrical wiring diagram of a protection circuit for a DC motor according to an embodiment of the present invention. Person... Servo amplifier, C□, C2...
Capacitor, Dl s D2 s D3 s D4 #
D7s DB...Diode, D5. D6
...Zener diode, Ql, Q2...
...Switching transistor, Qa-Q4...
...Current amplification transistor, M...Motor.

Claims (1)

[Claims] 1 Inputs a command signal that specifies the pen position and the output of a potentiometer that detects the pen position, and outputs a voltage according to the above output difference until the output difference reaches a certain value. When exceeds the above-mentioned certain value, a servo amplifier is used that outputs a predetermined constant saturation voltage, and the output of this amplifier is used to drive the current amplifying transistor connected in series to the motor for driving the pen. and applying the output of the servo amplifier to an integrating circuit consisting of a resistor and a capacitor,
Until the output of this integrating circuit exceeds a certain value, the switching transistor connected to the latter stage of the integrating circuit does not operate, and the current amplifying transistor connected in series to the motor changes to the output of the servo amplifier. The switching transistor provided at the subsequent stage of the integrating circuit operates only when the output of the integrating circuit exceeds the certain value, and the operation of the switching transistor operates the switching transistor connected in series to the motor. A protection circuit for a DC motor used in a DC servo recorder that is configured so that the current amplification transistor is completely turned off.