JPH04308418A - Power supply cutting-off device for motor - Google Patents

Abstract

PURPOSE:To provide a power supply cutting-off device for motors which can prevent the burning of a motor when the speed of the motor decreases from a specific value and to realize a fail-safe state by setting the rotation of the motor to a free state. CONSTITUTION:Before the power source of a motor driving section is turned on, the output signal (f) of a photocoupler 4 is set at an 'L' level since the photocoupler 4 is turned off and a signal (f) is set at an 'L' level without rotation pulse. In addition, a signal (e) is set at an 'H' level. Therefore, when the power source is turned on, a motor immediately starts to rotate. When the motor starts to rotate, the output (f) of the photocoupler 4 becomes 'H' in level, but transistors 8 and 9 do not immediately start operation due to a delay circuit 6. While the speed of the motor is higher than a specific value, a monostable multivibrator 3 is re-triggered and its Q output (e) becomes 'L' in level, because a NAND gate 2 trails its operation. When the speed of the motor becomes lower than the specific value and the period during which both signals (b) and (c) become 'H' in level disappears, the multivibrator 3 is not triggered. When such state exceeds the delay setting time tau3 of the circuit 6, the output (h) of an inverter 7 becomes 'L' in level and the transistors 8 and 9 are turned off. As a result, the power supply from the power source to the motor driving section is discontinued.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to cutting off the power supply to the drive part of a motor or the power supply to the control part of the motor. The present invention relates to a power cutoff device suitable for a gate bar drive motor of a dynamically driven opening/closing gate.

0002

2. Description of the Related Art When opening/closing gates are used, objects such as people, cars, trains, etc. may not be able to pass through the gate bar, and the lowering of the gate bar may be temporarily stopped by the body of the person or vehicle. Further, the gate bar may stop lowering due to a failure in the drive circuit of the gate bar drive motor. However, conventionally, no special measures have been taken for this purpose.

0003

[Problem to be Solved by the Invention] However, if the rotational speed (hereinafter referred to as "speed") of the gate bar drive motor decreases or stops rotating due to external or internal factors such as those mentioned above, the motor may burn out. There is a risk. Furthermore, if the motor stops due to an internal factor, the opening/closing gate will not be able to lower the gate bar to prevent danger even in the event of a failure.

[0004] The present invention was made in view of such problems, and when the speed of the motor decreases below a specified value,
It is an object of the present invention to provide a power supply cutoff device for a motor that can prevent the motor from burning out, and can realize fail-safe rotation by allowing the gate bar to lower under its own weight.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a motor power cutoff device as follows (1), (
Configure as per 2).

(1) Low speed detection means for detecting that the rotational speed of the motor is lower than a specified rotational speed, and power supply to the drive section and/or control section of the motor according to the output of the low speed detection means. A power cutoff device for a motor, comprising a cutoff means for cutting off the power. (2) The motor power cutoff device according to (1), further comprising a return means for returning the cutoff means to a state in which power can be supplied.

[0007]

[Operation] With the configurations (1) and (2) above, when the motor speed decreases below the specified speed, the motor drive section and/or
Or cut off the power supply to the control unit. Further, in the configuration (2), the interrupting means is further returned to a state in which power can be supplied by the restoring means.

[0008]

[Examples] The present invention will be explained in detail below using examples. FIG. 1 is a circuit diagram of a "motor power cutoff device" which is an embodiment of the present invention, and FIG. 2 is a timing chart of the same embodiment. In FIG. 1, P1 is a terminal to which a rotation pulse of frequency F, which is proportional to the speed of a brushless motor (not shown), is input, and P2 is a terminal connected to a drive section of the motor. A rotation pulse with a frequency F proportional to the speed of the motor is transmitted by a position detector, an FG (frequency generator),
This is the waveform-shaped output of a PG (pulse generator), etc.

1 is a monostable multi with a set time τ1, 2 is a NAND gate, 3 is a monostable multi with a retriggerable function with a set time τ2, 4 is a photocoupler, 5
is an AND gate, 6 is a delay circuit with a set time τ3, and 7 is an inverter.

Reference numeral 9 denotes a transistor whose emitter is connected to a power source for a motor drive unit and whose collector is connected to a drive unit of the motor. Reference numeral 8 is a transistor that controls transistor 9.

Furthermore, in the above circuit, in order to turn off the transistor 9 when the motor speed becomes below a predetermined value, the time constant τ1 of the monostable multi 3 is set to τ1 = 1/(2Fs ),
Multi 2 to retrigger Monostable Multi 3,
The set times τ1 and τ2 of 3 are selected to be τ2 > 2τ1, and the time margin from turning on the motor driving unit power until the motor reaches the specified speed is selected as τ3.

Next, the operation will be explained. It is now assumed that the power supply voltage VCC of the control section is supplied in advance. Before time t1 when the motor drive power is turned on, the input to the terminal P1 is constant at "L" (or constant at "H"), the Q output c of the monostable multi 1 is "L", and the input of the NAND gate 2 is One side is “L” and the other is “L” (or “H”), the output d is “H”, and the Q bar output e of the monostable multi 3 is “
The input f of the AND gate 5 is "L" because there is no voltage a of the motor drive power supply and the photocoupler 4 is off.The output g of the AND gate 5 is "L", and the output h of the inverter 7 is "H".
is "H", transistor 8 is on, transistor 9 is on, and power can be supplied to the drive section of the motor (not shown).

[0013] Therefore, when the power to the motor drive section is turned on at time t1, current immediately flows through the transistor 9 and the motor begins to rotate. At the same time, the light emitting diode of the photocoupler 4 is turned on, and the input f of the AND gate 5 becomes "H" and the output g becomes "H". However, due to the delay circuit 6, the output h of the inverter 7 does not become "L" immediately.

As the motor rotates, the terminal P1 changes at time t2.
It rises and falls at time t3, and this falling triggers monostable multi 1, and its Q output c
becomes “H” for time τ1. The output d of the NAND gate 2 becomes "L" because inputs b and c are both "H", but at the falling time t4, the monostable multi 3 is triggered and its Q bar output e becomes "L", and the AND gate The output g of 5 becomes "L".

As described above, the output g of the AND gate 5 is "H" from time t1 to t4, but since this "H" time is less than the delay setting time τ3 of the delay circuit 6, the transistors 8 and 9 are turned on. It remains as it is.

When the motor reaches a specified speed or higher, the monostable multi 3 is retriggered by the output d of the NAND gate 2, and its Q bar output e is maintained in the "L" state.

At time t5, when the speed of the motor decreases for some reason and the frequency F of the rotation pulse at the terminal P1 becomes lower than the threshold frequency FS, the signals b and c
There is no longer a period when both are "H", the output d of the NAND gate 2 stops falling, and the monostable multi 3 is not triggered, and when the set time τ2 elapses in this state, the monostable multi 3 returns and its Q bar output e is “
Therefore, the output g of the AND gate 5 becomes "H", and when the motor speed does not return to the specified speed and the delay time τ3 of the delay circuit 6 elapses at time t7, the output h of the inverter 7 becomes "L". , the transistor 8 is turned off, the transistor 9 is turned off, the output i from the terminal P2 to the motor drive section is cut off, and the motor is free to rotate.The signal h is connected to the reset terminal CD of the monostable multi 3. Therefore, the signal e is maintained at "H" regardless of the signal d.Thereafter, when the limit switch is activated at time t9 due to the free fall of the gate bar, etc., and the power to the motor drive section is turned off, the photocoupler 4 emits light. the diode turns off,
The output f of the photocoupler 4 becomes "L", the input of the inverter 7 immediately becomes "L" due to the diode of the delay circuit 6, the output h of the inverter 7 becomes "H", and the transistor 8 is turned on. At the same time, the signal h is sent to the reset terminal CD of the monostable multi 3, so the reset state of the monostable multi 3 is released and the monostable multi 3 returns to its initial state. If the motor drive power is turned on again in this state, time t
1, power is supplied to the motor drive section and the motor begins to rotate.

[0018] In this manner, when the motor speed becomes lower than the specified speed, the power supply from the motor drive power supply to the motor drive section is cut off, and the motor can be freed from rotation. As a result, the gate bar is lowered under its own weight, and when the limit switch is operated, the state is restored to a state where power can be supplied to the motor drive section.

In the embodiment, the transistors 8 and 9 are turned on again by turning off the power supply to the motor drive unit, but the present invention is not limited to this, and for example, if any of the circuits of the photocoupler 4 It is also possible to insert a push button switch into the switch, thereby momentarily breaking the circuit and returning the transistors 8 and 9 to the on state. In this case, after cutting off the power supply to the motor, the motor can be driven again by operating the push button switch after removing the obstruction or the like.

Further, in the embodiment, the power supply to the motor drive section is cut off, but the present invention is not limited to this, and the motor drive section is cut off by cutting off the power supply to the motor control section. This can be implemented by stopping the motor, or by cutting off power supply to both the motor drive section and the control section.

Although not an embodiment, when the speed of the motor falls below a specified value, a relay or the like is used to turn off circuits such as the windings of the motor to stop driving the motor and prevent burnout of the motor. In addition, the gate bar can be rotated freely so that it can be lowered under its own weight, thereby realizing a failsafe.

[0022]

[Effects of the Invention] As explained above, according to the present invention,
When the motor speed drops below a specified value, the drive of the motor is stopped to prevent motor burnout, and the motor is allowed to rotate freely to achieve a failsafe.

[Brief explanation of drawings]

[Figure 1] Circuit diagram of the embodiment

[Figure 2] Timing chart of the embodiment

[Explanation of symbols]

1 Monostable Multi 2 Nand Gate 3 Monostable Multi 4 with retriggerable function
Photocoupler 5 AND gate 9 Transistor

Claims (2)

[Claims] 1. Low speed detection means for detecting that the rotational speed of the motor is lower than a specified rotational speed, and power supply to the drive section and/or control section of the motor according to the output of the low speed detection means. A power supply cutoff device for a motor, comprising a cutoff means for cutting off the power. 2. The motor power cutoff device according to claim 1, further comprising a return means for returning the cutoff means to a state in which power can be supplied.