JPS59204483A - Intermittent drive unit of dc motor - Google Patents

Abstract

PURPOSE:To enable to brake a DC motor with less rotating angle error by calculating a reverse polarity voltage necessary for stopping the motor at the prescribed rotating angle, and applying the reverse polarity voltage in response to the calculated result. CONSTITUTION:When the application of a positive polarity voltage to a DC motor 1 is interrupted, a current induced during the interial rotation of the motor 1 is detected by a current detector 12. The current detected by the detector 12 is proportional to the inertial rotation speed of the motor 1. This detector 12 is connected through an applied voltage controller 13 to a drive circuit 4. The controller 13 variably controls the applied voltage level of reverse polarity to be applied to the motor 1 in response to the current value detected by the detector 12. The voltage detected by the controller 13 is applied to a drive circuit 4.

Description

[Detailed Description of the Invention] The technical field of the invention relates to an intermittent drive device for a DC motor that is capable of accurately controlling the intermittent rotation angle of a DC motor. Background Art 1/- Financial institutions, etc. require 24I hour monitoring When a security camera is installed at a certain location and the images taken by the security camera are recorded on a video recorder, etc., it is best to record for a long time while moving frame by frame like a videotape. In that case,
When recording with a video chip recorder, it is necessary to drive the cab stan motor intermittently, so a direct current motor that can rotate forward or reverse depending on the polarity of the applied voltage is often used as the cab stan motor.

Conventionally, an intermittent drive device for intermittently driving this type of DC motor has been designed to adjust the output of a pulse generator, which generates a number of pulses according to the rotation angle of the DC motor, in advance to correspond to the amount of intermittent feed. How many pulses? When the pulses generated by the pulse generator reach the set number of pulses in the control circuit, the power to the DC motor is cut off and at the same time a reverse polarity voltage is applied to stop the inertial rotation of the DC motor. It is configured to brake.

However, in the above conventional intermittent drive device, the reverse polarity voltage applied to brake inertial rotation is constant at normal pressure, so the reverse polarity voltage may change due to fluctuations in the tape feeding load applied to the capstan. Disclosure of the Invention The present invention eliminates the above-mentioned drawbacks, such as the rotation angle required for braking f from application to the actual stop of rotation of the DC motor, which tends to vary, and therefore, the intermittent feed accuracy is not very good. After cutting off the application of positive polarity electrons to the DC motor, a current proportional to the rotational speed induced in the DC motor is detected, and a reverse polarity voltage is applied according to the detection result to correct the rotation angle error. An object of the present invention is to provide an intermittent drive device for a DC motor that enables braking with less friction.

In order to achieve this object, the present invention provides a DC motor that rotates forward or reverse depending on the polarity of the applied voltage applied by a drive circuit, and a DC motor that rotates when the application of positive polarity electrons to the rotating DC motor is cut off. A current detection circuit detects the current induced in the motor, and from the induced current detected by this current detection circuit, calculates the reverse polarity I'F required to stop the DC motor at a predetermined rotation angle v7. L ~, reverse polarity voltage according to the equation [1 J]! The gist is that a control circuit is provided to take out an output that controls the oil circuit.

According to the present invention, when the application of positive polarity electrons to a DC motor is interrupted, a current induced in proportion to the rotational speed of the DC motor is detected, and the DC motor is stopped at a predetermined rotation angle based on this induced current. Since the configuration is such that the opposite polarity electrons, which are essential for the operation of It is possible to control the rotation angle required for braking until it comes to a stop with great precision, and as a result, it is possible to drive the DC motor intermittently at a constant rotation angle without being affected by load fluctuations. It has excellent effects such as:

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, practical examples of the present invention will be described with reference to the drawings. FIG. 7 is a schematic circuit diagram showing an embodiment of an intermittent drive device for a DC motor according to the present invention. In FIG.
Used as a capstan motor for video tape recorders. This DC motor is capable of forward and reverse rotation depending on the polarity of the applied voltage, and is therefore provided with a polarity reversal circuit for reversing the polarity of the applied voltage. The polarity reversing circuit 2 is connected to a DC motor via a changeover switch 3, and is connected to a drive circuit in front of it, and is supplied with a drive current of an appropriate voltage from the drive circuit.

There is an adder in the front stage of the drive circuit! A free-lag frog circuit g for intermittent feed control is connected through the . A sending signal is supplied to the set input terminal g8 of this flip-flop circuit, and a sending stop signal from the counter circuit 2 is supplied to the reset input terminal r.

The counter circuit 2 is supplied with pulses from a pulse generator ♂ consisting of a rotary encoder that detects the rotation angle of a DC motor after being amplified to a predetermined level by an amplifier. When the number of pulses reaches a set number of pulses corresponding to the frame feed amount of the videotape, a feed stop signal is output. This counter circuit 7 is connected not only to the flip-flop circuit, but also to the cascade-connected single-base multivibrator 10. It is also possible to contact Kajiya via //. Each monostable multivibrator 10. The operation time of // is set to an appropriate value. The first stage monostable multivibrator 10 is connected to a light bending switch 3 provided between the DC motor and the polarity reversing circuit.

The changeover switch 3 can selectively switch between the DC motor/polarity reversing circuit and the current detection circuit 1.2 described later, and is used to change the operating period of the seventh stage monostable multivibrator 10. Inside, selector switch 3 is set to '[
The li current detection circuit is switched to the t2 side.

The second stage monostable multivibrator 10 is triggered by the trailing edge of the output pulse of the first stage monostable multivibrator 10, and during its operation period it is connected to the drive circuit 4t via the adder j. In addition to supplying a sending signal, a signal for inverting the polarity of the applied voltage is supplied to the polarity inverting circuit.

By the way, the current detection circuit /:2 connected to the DC motor / via the changeover switch 3 detects the current induced by the DC motor / during inertial rotation. The current detected by is proportional to the inertial rotational speed of the DC motor. This current detection circuit/! is connected to the drive circuit G via the applied voltage control circuit/3. The applied voltage control circuit 13 variably controls the applied voltage level of the opposite polarity to be applied to the DC motor according to the current value detected by the current detection circuit 2. The calculated voltage is applied to the drive circuit/
applied to l.

When starting the DC motor, a sending signal is supplied to the set input terminal ≦8 of the free-lag flop circuit B. As a result, the flip-flop circuit B is set, and the drive circuit G is operated by the output of the flip-flop circuit B, and applies a positive polarity voltage of a predetermined level to the DC motor via the polarity inverting circuit B and the changeover switch 3. . As a result, the DC motor begins to rotate squarely, and a number of pulses corresponding to the rotation angle are supplied from the pulse generator to the counter circuit 7 via the multiplier. When the same number of pulses as the preset setting pulses are counted, a feed stop signal F is supplied to the reset input terminal Ar of the flip-flop circuit g and the monostable multivibrator 10. As a result, the flip-flop circuit g is reset and stops outputting to the drive circuit da, and the seventh stage multivibrator lO is triggered and becomes operational.

In this way, the drive circuit temporarily stops operating, the DC motor 11 is cut off, and the 7th stage motor 11 is cut off. With the multivibrator 10 constant, the current detection circuit 12 is activated. Therefore, at the same time that the DC motor / enters the inertial rotation state, the current induced in the DC motor / will be detected by the current detection circuit 12.0 The current detected by the current detection circuit 12 will be 1α The reverse polarity voltage that the applied voltage control circuit 13 applies to the drive circuit 11A is proportional to the inertial rotation speed of the current motor.
The voltage value is necessary and sufficient to stop the DC motor at a constant rotation angle due to its inertial rotation.

In this way, during the operation period of the first stage monostable multivibrator 10, the applied voltage of the opposite polarity is set which is necessary for braking and stopping the DC motor at a predetermined rotation angle of inertial rotation. Therefore, when the first stage monostable multivibrator 10 stops operating, the second stage monostable multivibrator l/ starts operating in its place. When the second-stage monostable multivibrator // operates, the drive circuit DA operates with the polarity inverting circuit inverting the polarity of the applied voltage. Therefore, in this case, a reverse polarity voltage is applied to the DC motor according to the inertial rotational speed at the time of idle rotation, and the motor stops at a constant rotational angle regardless of the magnitude of the inertial rotational speed.

That is, according to the DC motor/intermittent drive device/l having the above configuration, when the DC motor/ is rotated by a predetermined rotation angle, a voltage of opposite polarity corresponding to the rotational speed at that time is generated. is applied, the rotation angle required for braking the DC motor is
, -1 is approximately constant regardless of the load, and as a result, the rotation angle from when the DC motor is started to when it is completely stopped can be precisely controlled to a predetermined angle.

Note that the once stopped DC motor is restarted by supplying a feed signal to the set input terminal of the flip-flop circuit g, and the above-mentioned intermittent driving is repeated.

In the embodiment described above, the voltage level of the applied voltage of opposite polarity was varied in accordance with the inertial rotation speed of the DC motor, but instead of changing the voltage level of the applied voltage, the application time was varied. A configuration may also be adopted in which the optimum voltage application is set. DC motor/intermittent drive device 15 shown in FIG.
is a circuit in which an application time control circuit 16 is connected to the current detection circuit 12, and the operating time of the second stage monostable multivibrator // is controlled according to the application time set by the application time control circuit /A. Therefore, for example, if the inertial rotation speed of the DC motor l is large, the operating time of the second stage monostable multivibrator // is extended, and 10
− The voltage will be applied for a longer period of time.

[Brief explanation of the drawing]

FIG. 7 is a schematic circuit diagram showing an embodiment of the intermittent drive device for a DC motor according to the present invention, and FIG. 2 is a schematic circuit diagram showing a modified example of the intermittent drive device for a DC motor. /...DC motor, G...drive circuit, 12...current detection circuit, /,? ... Applied voltage control circuit, /Q,
/,! ;... Intermittent drive device, /l... Application time control circuit. −／／ −

Claims (1)

[Claims] A DC motor that rotates forward or reverse depending on the polarity of the applied voltage applied by the drive circuit, and detects the current induced in the DC motor when the application of positive polarity voltage to the rotating DC motor is cut off. A current detection circuit calculates a reverse polarity voltage necessary to stop the DC motor at a predetermined rotation angle from the induced current detected by the current detection circuit, and calculates the reverse polarity voltage necessary to stop the DC motor at a predetermined rotation angle based on the reverse polarity voltage according to the calculation result. An intermittent drive device for a DC motor, which is provided with a control circuit that takes out an output that controls a drive circuit.