JPS622692B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for a latching type electromagnetic device, and is most suitable as a drive circuit for driving a latching type electromagnetic device that operates a pinch roller mechanism of a magnetic recording/reproducing device, for example. To provide a driving circuit for a latching type electromagnetic device which can automatically restore the latching type electromagnetic device to its original state when the power supply is cut off or the power supply voltage falls below a predetermined value.

In a magnetic recording/reproducing device, the magnetic tape is fed with a pinch roller pressing the magnetic tape against the capstan shaft, and when the feeding of the magnetic tape is stopped, the pinch roller is released from pressing the magnetic tape against the capstan shaft. Ru. The operation for making the pressure contact or releasing the pressure contact state is to move the pinch roller toward the capstan shaft using an electromagnetic device, or return the pinch roller that is pressed against the capstan shaft via the magnetic tape to its original state. This is done by moving the object into position.

A commonly used electromagnetic device for moving the pinch roller is a continuous excitation type electromagnetic device. Continuously excited electromagnetic devices operate in such a way that when the terminal is energized, the plunger is attracted by a solenoid and moves, and when the terminal is de-energized, it returns to its original position.

By the way, in an apparatus using such a continuous excitation type electromagnetic device, in order to maintain the state in which the magnetic tape is pressed against the capstan shaft by the pinch roller, an excitation current must be continuously supplied to the electromagnetic device during that time. Therefore, there is a problem that power consumption increases. This has been a problem that cannot be overlooked, especially in magnetic recording and reproducing devices that use batteries, because it directly leads to a shortening of the battery usable time. In addition, there is another problem in that the continuously flowing excitation current generates Joule heat from the solenoid, causing a temperature rise, resulting in deterioration of related parts and a decrease in reliability. From this point of view, it is considered more preferable to use a latching type electromagnetic device instead of a continuous excitation type electromagnetic device. This latching type electromagnetic device is shown in Fig. 1A and B.
As shown in the figure, the solenoid 2 that moves the plunger 1 has a terminal pulled out from its midpoint, and that terminal is the common terminal Tc, and one of the two terminals pulled out from both ends of the solenoid 2 is the suction terminal.
Ta and the other terminal is used as a recovery terminal Tr. For example, there is a connection between the common terminal Tc and the attraction terminal Ta in Figure 1B.
When a current is applied in the direction shown by the arrow in , the plunger 1 is attracted to the solenoid 2 and becomes
(The plunger in that state is shown as 1'). Even if the current stops flowing, the plunger 1'
maintains that state. Also, in this state, the common terminal
When a current is passed between Tc and the recovery terminal Tr in the direction shown by the arrow in FIG. 1B, for example, the plunger 1' is moved to its original position, that is, the position shown in FIG. 1A. When such a latching electromagnetic device is used, it is no longer necessary to continue supplying excitation current to the solenoid 2 in order to keep the magnetic tape in pressure contact with the capstan shaft using the pinch roller, so the above-mentioned continuous consumption is eliminated. Problems such as increased power, shortened battery life, and generation of solenoid heat by the solenoid 2 are eliminated.

However, on the other hand, there is a problem in that if the power is cut off while the magnetic tape is being pressed against the capstan shaft by the pinch roller and the magnetic tape is being fed, the pressing state cannot be released and the original state restored. It was hot. In other words, when a continuous excitation type electromagnetic device is used, when the power is cut off, the excitation current naturally stops flowing, so the plunger of the electromagnetic device automatically returns to its original position, but when a latching type electromagnetic device is used, When an electromagnetic device is powered off, it remains in the state it was in when power was cut off. Therefore, if the power is cut off while the pinch roller operated by the latching electromagnetic device presses the magnetic tape against the capstan shaft, the magnetic recording/reproducing device will not be able to connect the pinch roller and the capstan shaft. This results in a state in which they remain pressed together via the magnetic tape. Then, the rubber of the pinch roller is plastically deformed by the pressure, which causes problems such as uneven rotation and changes in the running speed of the magnetic tape. The interruption of the power supply occurs due to, for example, a power outage, a drop in battery voltage, or even the turning off of a power switch. Although such a situation occurs from time to time, it is absolutely necessary to avoid it from causing a significant deterioration of the characteristics of the magnetic recording/reproducing device such as uneven rotation. It is not used very often because it is inappropriate.

Therefore, the present invention was developed in view of the above-mentioned circumstances, and is capable of automatically restoring a latching type electromagnetic device to its original state when the power is cut off or when the power supply voltage drops below a predetermined value. The object of the present invention is to provide a driving circuit for a latching type electromagnetic device.

To achieve this object, the drive circuit of the latching type electromagnetic device of the present invention includes a suction solenoid drive signal generation circuit that generates one pulse of the suction solenoid drive signal when a control signal is input, and a suction solenoid drive signal generation circuit that generates one pulse of the suction solenoid drive signal when the control signal is input. At this time, a recovery solenoid drive signal generating circuit that generates a recovery solenoid drive signal, a first switching means that receives a suction solenoid drive signal and switches the current that conducts and excites the suction solenoid, and receives a recovery solenoid drive signal that conducts the solenoid. The second switching means for switching the current that excites the recovery solenoid and the power supply terminal of the recovery solenoid drive signal generation circuit are connected in parallel or in parallel, and when the voltage of the power supply applied between the power supply terminals decreases. , is connected in parallel or in parallel with a circuit consisting of a first capacitor that applies voltage between the power supply terminals, at least a second switching means, and a recovery solenoid, and is connected in parallel to the circuit that applies a voltage between the power supply terminals. This configuration includes a second capacitor that applies voltage to the circuit.

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

Fig. 2 is a circuit diagram showing an embodiment of the present invention. In the figure, PS is a DC power supply circuit, consisting of a power supply E and a switch SW, and a voltage of +12V for exciting the latching type electromagnetic device LEM. This generates +5V voltage to operate the circuit that controls the latching electromagnetic device LEM. AM is a suction solenoid drive signal generation circuit that generates the suction solenoid drive signal Sa. When the signal applied to the input terminal (+) changes from "L" (low level) to "H" (high level), one pulse is generated. Suction solenoid drive signal (for example, the pulse width is about 500mS)
Generate Sa. RM is recovery solenoid drive signal Sr
In the recovery solenoid drive signal generation circuit that generates
The signal applied to the input terminal (-) changes from “H” to “L”
When the change occurs, a one-pulse recovery solenoid drive signal (for example, the pulse width is about 500 mS) Sr is generated.

Note that as the suction solenoid drive signal generation circuit AM and the recovery solenoid drive signal generation circuit RM, for example, a one-shot multivibrator made of a low power consumption CMOSIC (product number: Motorola MC14538B) can be used. It is not necessarily limited to the above types.

Power supply terminal + of suction solenoid drive signal generation circuit AM and recovery solenoid drive signal generation circuit RM
A voltage of +5V from the DC power supply circuit PS is applied to Vc.c. via a charging circuit consisting of a reverse current prevention diode D1 and a capacitor C1.

That is, the anode of a backflow prevention diode D1 is connected to the +5V terminal of the DC power supply circuit PS, the cathode of which is connected to one terminal of the capacitor C1, and the other terminal of the capacitor C1 is connected to the 0V line. The connection point between the capacitor C1 and the backflow prevention diode D1 is connected to the power terminal +Vc.c. of the suction solenoid drive signal generation circuit AM and the recovery solenoid drive signal generation circuit RM. Suction solenoid drive signal generation circuit
The output of an initial reset circuit consisting of a resistor R1, a diode D2, and a capacitor C2 is applied to the AM RESET terminal to prevent malfunctions due to oscillation.

Transistors Q1 and Q2 are controlled by an attraction solenoid drive signal Sa and are used to switch the excitation current Ia of the attraction solenoid 2a (see FIG. 1B) of the latching type electromagnetic device LEM, and are connected in a Darlington manner. Specifically, the input terminal of the Darlington circuit, that is, the base of the transistor Q1, is connected to the output terminal Q of the suction solenoid drive signal generation circuit Sa through the resistor R3, and one of the output terminals of the Darlington circuit is connected to 0V.
line, the other is connected to the attraction terminal Ta of the electromagnetic device LEM. Transistors Q3 and Q4 are controlled by the recovery solenoid drive signal Sr, and the recovery solenoid 2r of the latching type electromagnetic device LEM is controlled by the recovery solenoid drive signal Sr.
It is for switching the excitation current Ir [see Figure 1B], and is connected by Darlington.
As is clear from the drawing, the connection relationship of this Darlington circuit with other circuit elements is the same as that of the Darlington circuit consisting of transistors Q1 and Q2, so a description thereof will be omitted.

D3 is a backflow prevention diode, and C3 is a capacitor, which are connected in series to each other to form a charging circuit, and the connection point is a latching type electromagnetic device LEM.
, the anode of diode D3 is connected to the +12V terminal of the power supply circuit PS, and the capacitor C
The anti-diode D3 side terminal of No. 3 is connected to the 0V line. Note that diodes D4 and D5 protect transistors Q2 and Q4.

FIG. 3 is a time chart for explaining the operation of the drive circuit of the latching type electromagnetic device shown in FIG. The operation will be explained below with reference to FIG.

(1) First, when the switch SW of the DC power supply circuit PS is turned on (this time is defined as "to"), the capacitor
C ₁ , C ₂ and C ₃ are charged, and as a result, the +Vc.c. terminals of the suction solenoid drive signal generation circuit AM and recovery solenoid drive signal generation circuit RM, that is, line A, and the suction solenoid drive signal generation circuit AM are reset. terminal, i.e. line C
and rises to a potential of approximately +5V, and the common terminal Tc of the electromagnetic device LEM, ie, line B, rises to a potential of approximately +12V. Note that line C is a capacitor
Since C ₂ is charged through the resistor R ₁ , its potential rises at a slower rate than the line A potential rises.

(2) Next, when the control signal Scon is input to the input terminal Tin of the drive circuit of the present invention, the input terminal (+) of the suction solenoid drive signal generation circuit AM becomes "H" (at that point t ₁ ), as a result, the one-pulse suction solenoid drive signal Sa
(its pulse width is T ₁ ). Then, the drive signal Sa turns on the transistors Q1 and Q2, and an exciting current flows through the attraction solenoid 2a of the electromagnetic device LEM, and as a result, the plunger 1 is displaced from the position shown in a to the position shown in b in FIG. do. Therefore, the magnetic tape is brought into pressure contact with the capstan shaft by the pinch roller.

(3) Then, when the control signal Scon is no longer input while the power is not shut off (this time is t ₅
shall be. ), recovery solenoid drive signal generation circuit
RM has its input terminal (-) from “H” to “L”
As a result, a one-pulse recovery solenoid drive signal Sr is generated. Then, the transistors Q3 and Q4 are turned on, and the excitation current Ir flows through the recovery solenoid 2r of the electromagnetic device LEM, and the plunger 1 returns from the position shown in b to the position shown in a in FIG. 2.

By the way, as shown by the broken line in FIG. 3, when the plunger 1 of the electromagnetic device LEM is in the position shown in b, that is, in the attracted state, for example, when the switch SW is shut off (this time is referred to as t ₃ ) becomes as follows. That is, even if the +5V and +12V lines become 0V, in the drive circuit of the present invention, the potentials of the lines A and B are maintained at approximately +5V and +12V.

On the other hand, when the switch SW is cut off and the voltage of the power supply E is not applied to the circuit, the control signal Scon naturally becomes "L" as shown by the broken line.
Therefore, the recovery solenoid drive signal generation circuit RM
The potential of its input terminal (-) changes from "H" to "L" and accordingly generates a suction solenoid drive signal Sr. Of course, the recovery solenoid drive signal generating circuit RM receives the charging voltage of the capacitor _C1 as the power supply voltage Vc.c., so it can operate satisfactorily. Then, transistors Q3 and Q4 are turned on by the restoration solenoid drive signal Sr. Then, a charging current flows from the capacitor _C3 to the recovery solenoid 2r, and the plunger 1 returns from position b to position a. Therefore, the pinch roller, which had been pressed against the capstan shaft via the magnetic tape, returns to a state where it is separated from the capstan shaft.

As described above, the drive circuit of the latching type electromagnetic device of the present invention includes a suction solenoid drive signal generation circuit that generates one pulse of the suction solenoid drive signal when a control signal is input, and a recovery solenoid drive signal that generates one pulse of the suction solenoid drive signal when the control signal disappears. a recovery solenoid drive signal generating circuit that generates a drive signal; a first switching means that receives a suction solenoid drive signal and switches a current that conducts and excites the suction solenoid; A second switching means for switching an exciting current and a power supply terminal of the recovery solenoid drive signal generating circuit are connected in parallel or in parallel, and when the voltage of the power supply applied between the power supply terminals decreases, the power supply terminal A first capacitor that applies a voltage between the two, at least a second switching means, and a recovery solenoid. Since the recovery solenoid drive signal generating circuit is equipped with an additional second capacitor, even if the power is cut off, the recovery solenoid drive signal generating circuit remains operable by the charging voltage of the first capacitor. Then, when the control signal naturally disappears due to the cutoff of the power supply, a recovery solenoid signal is generated and the second switching means becomes conductive. Then, due to conduction of the second switching means, a discharge current flows from the second capacitor to the recovery solenoid, and the recovery solenoid is excited. As a result, the plunger of the latching electromagnetic device is restored to its original state. As described above, according to the present invention, when the power is cut off, even if the electromagnetic device is in an attracted state, it can be automatically restored to its original state by cutting off the power. Therefore, it is possible to apply the latching type electromagnetic device to the operation of the pinch roller of a magnetic recording/reproducing device without any problem.

[Brief explanation of the drawing]

Figures 1A and B show a latching type electromagnetic device, where A is a front view, B is its internal circuit diagram, Figure 2 is a circuit diagram showing the configuration of an embodiment of the present invention, and Figure 3 is a timer diagram. It is a chart diagram. AM……Suction solenoid drive signal generation circuit,
RM……Recovery solenoid drive signal generation circuit, Q
1, Q2...first switching means, Q3, Q
4...Second switching means, E...Power supply,
C ₁ , C ₂ , C ₃ ... Capacitor, D1, D2, D3
……diode.

Claims (1)

[Claims] 1 A suction solenoid drive signal generation circuit that generates one pulse of a suction solenoid drive signal when a control signal is input, a recovery solenoid drive signal generation circuit that generates a recovery solenoid drive signal when the control signal disappears, and a suction solenoid drive a first switching means that receives a signal and switches a current that conducts and excites the attraction solenoid; a second switching device that receives a restoration solenoid drive signal and switches a current that conducts and excites the restoration solenoid; and the restoration solenoid. A first capacitor connected in parallel or in parallel between the power supply terminals of the drive signal generation circuit and applying voltage between the power supply terminals when the voltage of the power supply applied between the power supply terminals decreases; and at least a second switching capacitor; A second circuit that is connected in parallel or parallel to the circuit consisting of the means and the recovery solenoid and applies voltage to the circuit when the voltage of the power supply applied to the circuit decreases.
1. A drive circuit for a latching electromagnetic device, comprising a capacitor.