JPS633700A - Coil control circuit for magnetic clutch, brake, or the like - Google Patents

Abstract

PURPOSE:To miniaturize a unit and to cut down the cost required, by controlling in pulse width two transistors connected to the one power supply line and by ON-OFF controlling two transistors connected to the other power source. CONSTITUTION:A transistor 28 is switched ON, while wide pulses are supplied to the base of a transistor 22 and a coil 32 is over-excited. It is detected by the change of current of the coil 32 that the armature of an electromagnetic clutch-brake is attracted to the attracting surface. Narrow pulses are supplied from this attraction point after specified time has passed. Then, a transistor 26 is switched ON and at the same time wide pulses are supplied to the base of a transistor 24 and the coil 32 is inversely excited. When the armature gets to the release point, the inductance of a magnetic circuit rapidly changes. It is detected and at the same time transistors 24 and 26 are interrupted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coil control circuit for an electromagnetic clutch or an electromagnetic brake.

[Conventional technology]

As shown in FIG. 4, this type of conventional control circuit has a dual source of a high-voltage power supply 2 and a lower-voltage steady-state power supply 4, and has five transistors 6.8, 10.12. 14 and two diodes 17.18.

When over-exciting the coil 16 to make the current rise faster, the transistors 8 and 14 are made conductive for a short period of time while the other transistors are off, and the high-voltage power supply 2
is supplied to the coil 16 to over-excite the coil 16. At this time, diode 18 blocks reverse voltage to transistor 6. Next, transistors 6 and 14 are made conductive,
In addition, the transistor 8 is made non-conductive, and the voltage of the low-voltage power supply 4 is supplied to the coil 16, so that the coil 16 is constantly excited.

At this time, diode 17 blocks reverse voltage from being applied to transistor 8. Next, the transistor 6.14 is made non-conductive, and at the same time, the transistor 10.12 is made conductive.
A reverse voltage is applied to the coil 16 to reverse excite the coil 16, and when the magnets of the electromagnetic clutch/brake are separated from the attraction surface, the transistors 10 and 12 are rendered non-conductive, and the high frequency High-precision control is performed.

[Problem that the invention seeks to solve]

The conventional device has two power supplies and 17 reverse blocking diodes.
Since 18 and 5 transistors were required, there was a defect that increased the cost. In addition, the high-pressure overexcitation time and reverse excitation time vary depending on the attraction surface of the clutch brake, wear, etc., and therefore, frequent readjustment is required during long-term use.

The present invention aims to eliminate the above-mentioned defects.

[Means to solve problems]

In order to achieve the above object, the present invention provides a pulse width at the base of two transistors 22, 24 connected to one power supply line 30a among four transistors 22, 24, 26, 28 connected in a bridge type. Transistor on/off control means is connected to the bases of two transistors 26 and 28 connected to the modulation oscillation circuit and connected to the other power supply line 30b, and both ends of the coil 32 are connected to the middle part of the bridge. A current detection means is provided in the power supply circuit to the electromagnetic clutch/brake, and the current detection means detects the attraction point and release point of the armature of the electromagnetic clutch/brake, and the timing of the input signal of the base of the transistor is determined based on the detection signal. is set.

[Effect]

A transistor 26 to which an on/off control means is connected to the base.
．． The coil 32 is connected to one of the transistors 22 and 24 whose bases are connected to the PWM oscillation circuit by controlling the on/off state of the transistor 38 . A wide pulse is supplied to the base of the transistor 22, and due to the wide pulse, a current larger than the rated current is supplied to the coil 32 in the forward direction for a short time until the torque of the electromagnetic clutch/brake increases, causing the coil 32 to overflow. Excited. When the armature of the electromagnetic clutch/brake is attracted to the suction surface,
Since the inductance of the magnetic circuit changes suddenly, the current changes suddenly as shown in Figure 3. The attraction point is detected by a current change in the coil 32, and based on this detection signal, the coil 32 is over-excited for a predetermined period of time from the attraction point. After a predetermined time has elapsed from the attraction point, the PWM oscillation circuit oscillates a rated narrow pulse, and the coil 32 is constantly excited.

Next, at the same time as the transistor 26 is turned on, a large current exceeding the rated value is supplied to the coil 32 as a reverse current due to a wide pulse supplied to the base of the transistor 24.
Coil 32 is reverse excited.

This eliminates the influence of residual magnetism of the coil 32 on the armature. When the armature reaches the release point, the inductance of the magnetic circuit suddenly changes, and at the same time this is detected, the transistors 24 and 26 are cut off.

〔Example〕

The structure of the present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

In FIG. 1, 20 is a bridge type rectifier to which an AC power source is connected.

22.24, 26.28 are transistors arranged in a bridge type, the collector of the transistor 22.24 is connected to the positive power supply line 30a, and the collector of the transistor 26.24 is connected to the positive power supply line 30a.
．． 28 emitters are connected to the negative power supply line 30b. The emitters of transistors 22, 24 are connected to the collectors of transistors 26, 28. A PWM (pulse width modulation) oscillation circuit (not shown) is connected to the bases of the transistors 22 and 24, and transistor on/off control means (not shown) is connected to the bases of the other transistors 26 and 28. 32 is an electromagnetic clutch/brake coil, the negative end of which is connected between the emitter of the transistor 22 and the collector of the transistor 26 via the current detection resistor 34, and the other end of the coil 32 connected to the emitter of the transistor 26. Emitter and transistor 2
8 collector. Diodes 36 and 38 have their cathodes connected to both ends of the coil 32, and their anodes connected to the negative power line 30b. 40 and 42 are diodes, each of whose cathode side is connected to the positive power supply line 30a, and whose anode side The ends of the coil 32 are connected to both ends of the coil 32.

Next, referring to FIG. 2, the armature suction/release point detection circuit will be described.

4o is a current detection amplifier, 42 is an on/off operation switch for the electromagnetic clutch/brake, and 44 is a sawtooth waveform output generator. When the switch 42 is turned on, a signal of "1" is supplied to the positive input terminal, and this A positive sawtooth waveform output n1 shown in FIG. 3 is output from the positive output end,
Further, when the switch 42 is turned off, a signal of "1" is supplied to the minus input terminal, and thereby a minus sawtooth waveform n2 is output from the minus output terminal. The sawtooth waveform output n1 changes from the state of n 1 < I to the state of n 1 > I at a point near the suction point P1 of the armature with respect to the current detection waveform output of the current detection amplifier 40. It is set. Also, armature release point P2
At one point in the vicinity of n 2 < I, n
The sawtooth waveform output n2 is set as shown in FIG. 3 so that the state changes to 2>I. C1,C
2 is a comparator, 0/S-1 and O/S-2 are one-shot pulse oscillators, 46.48 is a flip-flop circuit, 50°52.54 is an inverter, and 56.58 is an AND gate.

60 is a timer.

Next, the operation of this embodiment will be explained.

With transistors 24 and 26 off, switch 42
When the switch 42 is turned on, a bias voltage is supplied to the base of the transistor 28, and the transistor 28 is turned on. The flip-flop circuit 46 is set by turning on the switch 42, and the 11
171 set signal is output. In response to this set signal of "1", a wide pulse is supplied from the PWM oscillation circuit to the base of the transistor 22 for a short time until the torque of the electromagnetic clutch brake increases.
A current larger than the rated value is supplied to the coil 32 in the forward direction, and the coil 32 is overexcited. Note that when the switch 42 is turned on, the positive sawtooth waveform output n1 is output to the comparator C.
It is supplied to the positive side input terminal of 1. When the armature of the electromagnetic clutch/brake is attracted to the attraction surface, the output level of the comparator C1 changes from "O" to "1" at that point, that is, due to the change in the current at the attraction point P1, from a point near the attraction point P1. ”. When the output level of comparator C1 changes to "1", this "1"
The timer 60 starts a time counting operation in response to the output signal. The timer 60 has a predetermined minute setting time t.
When counting 1, the timer 60 supplies an operating signal to the one-shot pulse oscillator 0/S-1, and the one-shot pulse oscillator sends one pulse to the flip-flop circuit 4.
When one circuit 46 that resets the circuit 46 by supplying it to the reset input terminal of AND gate 5 is reset, the level of its output terminal changes to "'0", and at the same time, the AND gate 5
8 is established, and the AND gate 58 is I(171
Output. The PWM oscillation circuit oscillates a rated narrow pulse by the output of this l(111), and the narrow pulse is supplied to the entire transistor 22, and the coil 32 is constantly excited.

Next, when the switch 42 is turned off, a signal of 11111 is supplied to the negative input terminal of the sawtooth waveform generator 44.
The generator 44 outputs a negative sawtooth waveform, the output of which is fed to the positive input of comparator C2. On the other hand, at the same time as the switch 42 is turned off, the flip-flop circuit 48 is set, and the circuit outputs 51''.
By turning off the switch 42, the AND gate 58 becomes +4 Q.
I+, which stops supplying the narrow pulse to the base of transistor 22. Furthermore, when the switch 42 is turned off, the transistor 28 is turned off and the transistor 26 is turned on. In addition, a wide pulse is supplied to the base of the transistor 24 by the set signal of "1" of the flip-flop circuit 48, and a large current exceeding the rated value due to the wide pulse is passed through the coil 32 as a reverse current.
The coil 32 is reversely excited. This results in
The influence of residual magnetism of the coil 32 on the armature is eliminated. When the armature separates from the attraction surface, the inductance of the magnetic circuit changes suddenly. Assuming that the time of this amateur separation is the release point P2, the sawtooth waveform and the current detection waveform ■ intersect at a point near the release point P2, as shown in FIG. 3, and at this time, the output terminal of the comparator C2 is , 1101Jy, changes to "1". This level change causes the one-shot pulse oscillator 0/S-2 to output one pulse, which resets the flip-flop circuit 48 and stops supplying the wide pulse to the base of the transistor 24. Transistor 26 is turned off.

〔effect〕

Since the present invention is configured as described above, it is possible to perform overexcitation, steady excitation, and reverse excitation control using a power source and four transistors, and it is possible to miniaturize the device and reduce costs. The suction point and release point of the armature are detected by current changes, and the coil current is controlled based on this detection signal, so highly accurate control is possible regardless of gap variations due to lining wear between the armature and suction surface. Furthermore, since the energy stored in the coil is regenerated to the DC power supply, there are advantages such as there being no restriction on operating frequency as in the varistor system.

[Brief explanation of drawings]

FIG. 1 is an electronic circuit diagram, FIG. 2 is an electronic circuit block diagram, FIG. 3 is a timing diagram, and FIG. 4 is a conventional electronic circuit diagram. 2...High voltage power supply, 4...Standard power supply, 6,
8゜10.12.14...Transistor, 16
... Coil, 20 ... Bridge type rectifier,
22゜24.26.28...transistor,
30a...Positive power line, 30b...Minus power line, 32...Coil, 34...
··resistance. 36.38...Diode, 40.42...
・Diode patent applicant Miki Pulley Co., Ltd. Figure 3 0/S-I L C2 Dual Sword”-m- 〇/S-2-Knee

Claims (1)

[Claims] (1) Four transistors 22 connected in a bridge configuration
, 24, 26, and 28, a pulse width modulation oscillation circuit is connected to the bases of two transistors 22 and 24 connected to one power supply line 30a, and two transistors 26 connected to the other power supply line 30b. A transistor on/off control means is connected to the base of the coil 32, both ends of the coil 32 are connected to the middle part of the bridge, a current detection means is provided in the power supply circuit to the coil 32, and the current detection means controls the electromagnetic clutch/brake. 1. A coil control circuit for an electromagnetic clutch, brake, etc., characterized in that a suction point and a release point with respect to a suction surface of an armature are detected, and the timing of a base input signal of the transistor is set based on the detection signal.