JP2670786B2 - DC motor automatic stop circuit - Google Patents

Description

The present invention relates to an automatic stop circuit for a DC motor. [Summary of the Invention] A rotation detection transistor that is connected to a terminal of a DC motor and is turned on by an induced electromotive voltage, and is momentarily turned off by a pulse generated in an armature winding of the DC motor,
The output current of the rotation detecting transistor becomes a control current, and when the rotation detecting transistor is turned on, a driving transistor that supplies a driving voltage to the DC motor is provided to cut off the power supply when restrained. In addition, by adding a Zener diode that cuts off the control current when the power supply voltage drops below a predetermined value between the rotation detection transistor and the drive transistor, it is possible to cut off the power supply when the voltage is reduced with a simple configuration. It is an automatic stop circuit of a DC motor that can be operated. [Prior Art] For example, in an electric radio control airplane,
Once the propeller is rotated, the drive voltage supplied to the DC motor for propeller rotation should be shut off unless the switch is turned off. Therefore, if the propeller is restrained due to a collision during flight, or if the propeller is restrained due to a fall or the like, an excessive restraint current flows to the electric motor for propeller rotation, which is uneconomical, and the motor and other mechanisms are not subject to inorganic loads To shorten the life of the electric radio control airplane, or there is a risk of fire due to the heat generated by the DC motor and the battery. In addition, when the electric energy of the battery is excessively consumed during the flight, the servo motor for flight control cannot be driven, and the radio control airplane cannot be landed. A conventional automatic stop circuit uses a fuse to cut off power supply when the electric motor is restrained. Further, a magnet relay is arranged in a circuit that supplies a power supply voltage to the electric motor, and the power supply to the electric motor is cut off when the power supply voltage drops below a certain voltage by utilizing its reduced voltage recovery characteristic. [Problems to be Solved by the Invention] When the restriction of the electric motor is detected by using the fuse, the supply voltage is cut off by blowing the fuse by the restriction current. Therefore, the electric energy of the battery is wasted during the restraint, and the fuse must be replaced every time the restraint is detected. Further, if the restricted current does not reach the rated current of the fuse, the power supply to the DC motor cannot be cut off. Further, since the magnet relay used to cut off the power supply to the electric motor when the power supply voltage is reduced is heavy, it has been an obstacle in reducing the weight of a radio control airplane or the like. In view of the above problems, it is an object of the present invention to obtain the function of interrupting power supply during restraint and during voltage reduction with a simple circuit configuration without using a fuse or a magnet relay. [Means for Solving the Problems] The automatic stop circuit of the DC motor of the present invention is turned on by an induced electromotive voltage generated at the terminals of the DC motor, and the armature winding is provided for each polarity switching point of the commutator of the motor. A rotation detecting transistor Q1 having a control input terminal connected to one terminal of the electric motor is provided so as to be momentarily turned off periodically by a pulse generated in the line. Further, the output current of the rotation detecting transistor Q1 is coupled so as to become a control current, and when the rotation detecting transistor is turned on, it is turned on to supply a drive voltage to the terminal of the DC motor. A driving transistor Q2 is provided which is turned off in accordance with the periodic turning off of the rotation detection transistor. Zener diode between the control input terminal of the driving transistor Q2 and the output terminal of the rotation detecting transistor Q1.
When D1 is connected and the reverse voltage applied to it drops below a predetermined voltage, the Zener diode turns off,
The configuration is such that the control current of the driving transistor Q2 is cut off. [Operation] Every time the rotation detecting transistor Q1 is momentarily turned off, an induced electromotive voltage accompanying the rotation of the motor M is detected, and the induced electromotive voltage turns the rotation detecting transistor Q1 on again. When the motor M is constrained, the induced electromotive voltage becomes extremely small immediately before stopping, and once the detection transistor Q1 is turned off, it cannot be turned on again. When the reverse voltage applied to the Zener diode D1 becomes equal to or lower than the Zener voltage due to the decrease in the power supply voltage, the control current stops flowing, so that the driving transistor is turned off and the power supply to the DC motor M is stopped. [Embodiment] FIG. 1 shows an automatic stop circuit for a DC motor according to an embodiment of the present invention. This automatic stop circuit is incorporated in, for example, a toy electric radio control airplane, and the electric motor M is
This is a well-known DC 3-pole (phase) type commutator motor (micromotor). To the terminal T1 of the electric motor M, the emitter-collector of the driving transistor Q2 that supplies the power supply voltage E is coupled in series, and the zener diode D1 is connected to the pace of this transistor Q2. The Zener diode D1 has one end connected to the base of Q2 in the direction in which the power supply voltage E is applied as a reverse voltage, and the other end thereof connected in series with the collector-emitter of the rotation detection transistor Q1. The base of the detecting transistor Q1 is connected to the terminal T1 of the electric motor M via the resistor R1, and the emitter is connected to the terminal T2 (ground potential) of the electric motor M via the resistor R2. Therefore, the emitter-base of the transistor Q2, the Zener diode D1, the collector-emitter of the transistor Q1 and the resistor R2 are connected in series, and the power supply voltage E is applied to this series circuit when the switch S1 is closed. These transistors Q1 and Q2 are connected so that the ON state is self-held. That is, once Q1 turns on, its collector current becomes the base current of Q2 and Q2 turns on. Therefore, the collector voltage of Q2 rises and the drive voltage is supplied to the motor M. At this time, since the base current is supplied from the collector of Q2 to Q1 via the resistor R1, the ON state of Q1 is maintained. The automatic stop circuit of the electric motor of FIG. 1 is kept off in the stationary state. Here, the terminal T1 of the electric motor M is positive, the terminal
The electric motor M is rotated by an external force so that a negative voltage is generated in T2 (this direction is forward rotation). Induced electromotive force E _n is proportional to the rotational speed N of the armature. E _n = A · N (A is a constant) the base-emitter forward voltage V of E _n is the transistor Q1
_{When BE1} is exceeded, base current flows through resistors R1 and R2, turning on Q1. Therefore, the transistor Q2 is also turned on and the positive rotation continues. After the electric motor M is started in this manner, when the electric motor M is stopped by being restrained by, for example, the electric airplane crashing and the propeller being restrained, the automatic stop circuit of FIG. 1 automatically operates according to the following principle. Turn off. Figure 2 a~c shows the armature circuit of the motor M of Figure 1, the commutator C ₁ three-pole of the delta winding L ₁ of the three phases in the example, L _2, L _3, C _2, C ₃ and a pair of brushes B ₁ and B ₂ .
The rotational position of (a), the series of winding L ₂ and L ₃ is in parallel with winding L ₁ between the brush B _1, B _2. The rotational position of (b), in the winding L ₃ is short-circuited, the windings L _1, L ₂ and are parallel and (c)
The rotational position series between winding L ₁ and L ₃ is in parallel with winding L _2. Therefore, at the rotational position (b), steep positive and negative pulse voltages due to the reactance voltage are generated between the terminals T1 and T2 of the motor M as shown in the waveform diagram of FIG. Since the connection state similar to that shown in FIG. 2B occurs six times per rotation of the armature, this pulse voltage is generated every 60 degrees. Therefore, in FIG. 1, for example, when the automatic stop circuit is turned on and the electric motor M is rotating normally, the terminals T1 and T2 are
Since the base and the emitter of the detection transistor Q1 are reverse-biased by the negative pulse generated therebetween, these transistors are momentarily turned off every 60 ° rotation of the motor M.
However, as long as the electric motor M is rotating, the automatic stop circuit is kept on even with the positive induced electromotive voltage. When the motor M is restrained by an external force, the restraining current generally tends to continue to flow, but the transistor Q1 is turned off by a negative pulse generated in the connection state as shown in FIG. . At this point, if the rotation speed is close to a stop, the induced electromotive force E _{n at} the terminals T1 and T2 is remarkably small, E _{n ≤V BE1} , and the detection transistor Q1 can no longer be turned on. . Therefore, the control circuit is turned off. In addition, in the automatic stop circuit of FIG.
The resistor R2 inserted in the emitter of Q acts as a negative feedback to the collector current of Q1. That is, when the base current of Q1 increases and the collector current attempts to increase, the emitter voltage increases and the base current decreases. Therefore, the transistor Q1 can be operated in the active region, the excess minority carriers in the base region can be eliminated, and the turn-off delay time can be reduced. For this reason, the transistor Q1 can be completely and instantaneously turned off by a pulse generated in the armature winding by the polarity switching of the commutator with the rotation of the motor M. Therefore, the constraint detection is performed reliably. Therefore, according to the automatic stop circuit shown in FIG. 1, when the electric motor M is constrained, the turn-off does not fail and the detection of the confinement and the interruption of the power supply are reliably performed. When the automatic stop circuit of the embodiment is applied to an electric radio control airplane, if the propeller is normally rotated by an external force, the circuit is turned on and continues to rotate normally, and the propeller is restrained by a collision or a crash during flight. Then the circuit turns off instantly. Therefore, since the starting current and the restraining current of the DC motor (both are larger than those during flight) do not flow, the energy of the battery or the like is wasted little. Further electric motor,
Trouble is reduced because the mechanism is not overloaded, and the life of the radio-controlled airplane can be extended. Also, because the rotation is simple, these functions can be obtained easily at low cost, and unlike the fuses that are blown out by overcurrent, it does not take time to replace the parts each time an overcurrent flows, and it also operates. Is certain. Also, since the electric motor rotates in only one direction, the circuit will not turn on even if the propeller is rotated in the reverse direction. The terminal voltage (power supply voltage) E of the battery 1 that drives the DC motor M decreases. The voltage E of the battery 1 is also supplied to a receiving circuit that receives a remote control signal transmitted from the remote controller, and a flight control servomotor whose operation is controlled by the receiving circuit. Therefore, while driving the electric motor M, the battery 1
If all the electric energy is consumed, the receiving circuit and the flight control servomotor cannot be operated. In order to eliminate such inconvenience, in this embodiment, as described above, the base-emitter of the driving transistor Q2,
The zener diode D1, the collector-emitter of the detection transistor Q1 and the resistor R2 are connected in series, and the terminal voltage E of the battery 1 is applied to both ends of this series circuit. As a result, the terminal voltage E drops and E ≤ V _BE2 + V _D1 + V _CE1 (V _BE2 : Q2 base-emitter forward voltage, V _D1 : D1 Zener voltage, V _CE1 : Q1 collector-emitter saturation voltage )
Then, no current flows through the series circuit of Q2, D1, and Q1, so that Q2 is turned off and the drive voltage E supplied to the DC motor M is cut off. The power supply voltage value when the power supply to the DC motor M is cut off can be changed by changing the Zener voltage V _D1 of the Zener diode D1. Therefore, the zener diode D1 having an appropriate zener voltage value is arranged in consideration of the discharge characteristic of the battery 1 and the final discharge voltage, so that the DC motor M can be operated before the terminal voltage of the battery 1 drops to the final discharge voltage. The power supply to can be cut off. With this, without mounting a heavy magnet relay on the airplane,
It is possible to secure electric power for driving the altitude and direction control servo motors of the airplane. This start / stop circuit can be used not only for radio control airplanes but also for various applications in which the power supply to the DC motor is cut off when the DC motor is restrained or before the battery voltage drops to the final discharge voltage. For example, when used in video tape recorders and video cameras, it is possible to stop driving the DC motor for tape running when the winding / rewinding of the tape is completed and the DC motor is restrained or when the battery voltage drops. In addition, it is possible to secure electric power for rewinding the tape wound around the rotary head into the cassette. A start switch or a stop switch may be added to the control circuit shown in FIG. 1 if necessary. The start switch is the first
Transistor Q1 (or Q2) as shown by the broken line in the figure
Push switch S2 that short-circuits between collector and emitter of
It may be. The stop switch is, for example, transistor Q1
Alternatively, it may be a push switch that short-circuits the base and emitter of Q2. If these start switches or stop switches are provided, in addition to the start and stop by the external force of the electric motor M, the start / stop by the switches can be controlled. Further, the control circuit may be stopped by providing a switch that short-circuits both ends of the electric motor M. [Advantages of the Invention] As described above, the present invention outputs the output of the rotation detecting transistor which is connected to the terminals of the DC motor to be turned on by the induced electromotive voltage and which is momentarily turned off by the pulse generated in the armature winding of the DC motor. Between the electrode and the output current of the rotation detection transistor becomes a control current, and when the rotation detection transistor is turned on, the control electrode of the drive transistor that is turned on to supply a drive voltage to the DC motor, Since a Zener diode that cuts off the drive current when the reverse voltage applied falls below a predetermined voltage is provided, it is possible to detect the devoltage when the power supply voltage drops to a predetermined value and control the cutoff of power supply to the motor. Can be done with a single component Zener diode. Therefore, the configuration is simpler than that of the conventional method using the reduced voltage recovery characteristic of the magnet relay, and the circuit can be made smaller and lighter. Further, since the voltage reduction detection and the power supply cutoff control are performed at the minute current level targeted for the control current of the transistor, the voltage loss and the power consumption are small and the operation is reliable. on the other hand,
A Zener diode is provided in the control current path of the drive transistor, and the Zener diode is on when the power supply voltage is above a predetermined value. Since it is cut off, no restraint failure occurs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an automatic stop circuit diagram of a DC motor showing an embodiment of the present invention, FIGS. 2A to 2C are armature circuit diagrams of the motor, and FIG. 3 is a terminal voltage waveform of the motor. It is a figure. In still code used in the drawings, 1 ...... battery E ...... supply voltage M ...... motor Q1 ...... rotation detecting transistor Q2 ...... driving transistor R1, R2 ...... resistance L ₁ ~L ₃ ...... armature Lines C _{1 to} C ₃ ... commutator B ₁ , B ₂ ... brushes T ₁ , T ₂ ... terminals.

Claims (1)

(57) [Claims] One of the DC motors is turned on by an induced electromotive voltage generated at the terminals of the DC motor and is turned off momentarily periodically by a pulse generated in the armature winding at each polarity switching point of the commutator of the DC motor. A rotation detection transistor whose control input terminal is connected to the terminal is coupled to the rotation detection transistor so that the output current of the rotation detection transistor becomes a control current. When the rotation detection transistor is turned on, the rotation detection transistor is connected to the terminal of the DC motor. A driving transistor which is turned on to supply a driving voltage and which is turned off with the periodic turning off of the rotation detecting transistor; a control input terminal of the driving transistor and the rotation detecting transistor Connected to the output terminal of the drive transistor, and when the reverse voltage applied falls below a specified voltage, the drive transistor Auto-stop circuit of the DC motor comprising a Zener diode for interrupting the control current of.