JPS5932779B2 - Constant output device for fluorescent lamps in diazo copying machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for keeping the light output of a fluorescent lamp constant in a type of diazo copying machine that exposes a document and photosensitive paper while passing through a printing section while superimposing them. be.

In general, the fluorescent lamps used in diazo copying machines are affected by changes in the lamp's ambient temperature, deterioration over time, and even fluctuations in the power supply voltage, and their light output changes significantly. When such a light source is used for a copying machine, even if the original is the same, uniform exposure will not be achieved at the same printing speed, and the printing speed must be changed and adjusted each time, which requires a lot of skill and effort. In short, as a practical matter, it is quite troublesome.

Therefore, an object of the present invention is to obtain constant exposure characteristics by constantly maintaining the light output of the fluorescent lamp constant regardless of variations in power supply voltage, ambient temperature, deterioration over time, etc. Because of that,
In particular, the object is to provide a light-receiving element directly in the vicinity of the fluorescent lamp at all times, thereby obtaining a copied image of average density and simplifying the copying operation.

Hereinafter, the configuration of a specific embodiment will be described in detail with reference to the drawings.

T is a ballast consisting of, for example, a step-up leakage transformer;
Its primary winding is connected to an alternating current power supply, and its secondary winding is connected to each electrode of the fluorescent lamp 1, and each electrode end is connected to a main discharge circuit as shown in the figure to receive the output of the ballast. A bidirectional control element SSS (hereinafter also simply referred to as an element) is inserted into the circuit.

A secondary winding T2 of a pulse transformer Tp, which will be described later, is connected to the gate (control terminal) of the element SSS as shown in the figure, and the element SSS has a predetermined voltage input to its gate. When the value exceeds the predetermined value, the discharge current is ignited, and when the discharge current becomes less than a predetermined value, the discharge current is extinguished and the flow of the discharge current is blocked. Rf is a full-wave rectifier made of, for example, a diode, and its input is connected to an AC power source, and its output is connected to a protective resistor R1 and a Zener diode ZD to form a rectifier circuit. A first series circuit consisting of a light receiving element Pd and a resistor R2, which will be described later, and resistors R5 and R7 are connected to both output ends of the rectifier circuit.
A resistor R3 is connected in series to a bridge circuit constituted by a parallel circuit with a second series circuit consisting of.

Tr is a transistor, for example, and its base is connected to the light receiving element Pd and the resistor R2, and its emitter is connected to the resistor R2.
Its collector is connected to the capacitor C via a resistor R6 at the connection point with the resistor R5 and the resistor R7 via the resistor R6. The capacitor C is charged via the transistor Tr by the output of the rectifier circuit, and in this case, the transistor T
r acts as a control means whose impedance changes in response to the voltage between the connection point between the light receiving element Pd and the resistor R2 of the bridge circuit and the connection point between the resistors R5 and R7 (between the output terminals of the bridge circuit). Eslζ is a unijunction transistor whose emitter (first terminal) is connected to the connection point between the resistor R6 and the capacitor C, and one base (second terminal) connects the protective resistor R8 to the other base (
The third terminal) is connected to both output ends of the rectifier circuit via the primary winding t1 of the pulse transformer Tp, respectively.

When the potential of the capacitor C input to its emitter reaches a predetermined value, the unijunction transistor Es is fired to discharge the capacitor C and drive the pulse transformer, and the pulse transformer Tp connects the gate to the element SSS. A pulse is applied to control the conduction angle of the fluorescent lamp 1. F
is a filter that is interposed between the fluorescent lamp 1 and a light-receiving element Pd (described later) to pass only the wavelengths necessary for copying exposure, and is a filter that allows each spectral spectrum of the light-receiving element Pd (described later) and the photosensitive paper used to pass through. It is adjusted to suit the sensitivity. Pd is, for example, C
ds, a light-receiving element made of a photodiode, etc., specifically, a light-transmitting cylinder made of a transparent material (not shown) loaded with a fluorescent lamp 1 serving as an exposure source, and the conveyor belt is not in contact with the circumferential side of the cylinder. It is arranged so that the light of the lamp 1 is always directly received from the part, and its impedance corresponds in advance to the rated light power of the fluorescent lamp 1, and the bridge circuit maintains a predetermined balanced state. It is set like this. The present invention has the above-mentioned configuration.Next, the operation and effect will be described.First, when the power is turned on, the ballast T activates the fluorescent lamp 1.
lights up.

The light-receiving element Pd receives the light from the fluorescent lamp 1 through the filter F and maintains its impedance at a specific value, so the transistor Tr is kept constant by resistors R2, R5, and R7 that maintain a state of equilibrium with this. Since the capacitor C receives a base bias of , and its collector current flows appropriately, the capacitor C is appropriately charged with a time constant determined by the resistors R, and the unijunction transistor Es receives the charging current.
The gate voltage boosted by the pulse transformer Tp that receives the conduction current drives the control element SSS and appropriately controls the phase of the fluorescent lamp 1. At this time, the conduction of the element is The angle shall be set to an appropriate value. Now, when the light output of the fluorescent lamp 1 decreases due to the reasons mentioned above, the impedance of the light receiving element Pd increases, and the impedance and the resistor R7, and the resistor R2 and the same R5.
The equilibrium state of the bridge circuit is disrupted due to
Since the conduction phase of is accelerated, the conduction angle of the control element SSS becomes smaller, and the lamp current to the fluorescent lamp 1 increases, increasing its light output to be equal to the suitably set light output described above. Once the constant output is reached, the bridge circuit returns to its equilibrium state and keeps its optical output constant.

Next, similarly, when the optical output increases, the opposite effect to that in the above case is performed, and the output eventually settles down to a constant value as before. As described above, in the present invention, even if the light output of the fluorescent lamp fluctuates due to the various causes mentioned above, the light receiving element is arranged so as to be able to directly detect it at all times.
The bridge circuit acts to maintain a predetermined equilibrium state in response to the impedance change, and performs compensation control to maintain the optical output at a constant value that is optimal for practical use, so that consistent and even exposure work can be achieved. This not only prevents the wastage of photosensitive paper, but also allows for good continuous copying even when handled by someone with little experience, without the hassle of copying work, and because of the light from a fluorescent lamp. Since changes in the impedance of the light-receiving element that detects the output are detected by a bridge circuit, the detection response to changes in the light output of the fluorescent lamp is good, and the light output of the fluorescent lamp is always maintained constant. Moreover, because of its simple configuration, it can be easily installed on existing copying machines, and it also has the additional effect of making it possible to economically improve older models, as mentioned at the beginning of this section. It produces various excellent effects that can fully achieve the intended purpose.

In addition, in the above explanation, it was stated that a step-up type leakage transformer is used as a stabilizer, but if an appropriate voltage can be obtained, a choke coil may be used, or a unijunction transistor may be used instead. Therefore, this can be replaced with a programmable unijunction transistor.

[Brief explanation of the drawing]

The drawing is an electrical wiring diagram showing an embodiment of the present invention. 1...Fluorescent lamp, SSS...Bidirectional control element, Tp...Pulse transformer, t1...
...Primary winding, T2...Secondary winding, Rf...
... Rectifier, ZD ... Zener diode,
Pd... Light receiving element, R2, R5, R7...
...Resistance, Tr...Transistor, C...
... Capacitor, Es ... Unijunction transistor.

Claims (1)

[Scope of Claims] 1. an AC power source, a fluorescent lamp 1, and an electrode of the fluorescent lamp 1 interposed between the AC power source and the electrode of the fluorescent lamp 1;
The fluorescent lamp 1 has a control terminal, and is turned on when the voltage of the control terminal exceeds a predetermined value, and extinguished when the discharge current of the fluorescent lamp 1 becomes less than a predetermined value in the turned on state. A bidirectional control element SSS that performs full-wave rectification, a light-receiving element Pd having a resistance value corresponding to the amount of light received, a full-wave rectifier Rf that performs full-wave rectification of the output from the AC power supply, and a connection between the output terminal of the full-wave rectifier Rf. a rectifier circuit configured with a Zener diode ZD, and a rectifier circuit configured with a Zener diode ZD;
and a resistor R_2, and a resistor R_2.
Corresponds to the voltage between a bridge circuit configured by connecting a second series circuit consisting of a resistor R_5 and a resistor R_7, a connection point of the light receiving element Pd and a resistor R_2 of the bridge circuit circuit, and a connection point of the resistors R_5 and R_7. a control means Tr whose impedance changes, and a control means Tr whose impedance changes;
a capacitor C connected in series with the control means Tr and arranged to be charged via the control means Tr; and a pulse transformer Tp whose secondary coil output is applied to the control terminal of the bidirectional control element SSS. and the control means T
A first terminal connected to the connection point between r and capacitor C, a second terminal connected to one of the two output ends, and a first terminal connected to the connection point between r and the capacitor C, and a second terminal connected to one of the two output ends, and one of the two output ends and a third terminal connected to the other side of the light receiving element Pd.
A fluorescent lamp for a diazo copying machine, characterized in that the lamp is arranged so as to directly receive the light output of the fluorescent lamp 1 at all times, thereby maintaining the light output of the fluorescent lamp 1 constant. constant output device.