JPS5855500B2 - Light source device for copying machines - Google Patents

Description

[Detailed description of the invention] The present invention relates to a light source device for a copying machine.

A discharge lamp such as a fluorescent lamp is used as a light source for exposure in a copying machine.

It is common to use an alternating current power source as a lighting power source for this type of discharge lamp, and the lighting is stabilized by a ballast such as a choke coil or a leaky transformer.

By the way, when a discharge lamp is lit by an alternating current power source in this way, the discharge lamp current is naturally an alternating current, so the brightness changes periodically according to its frequency.

Therefore, the occurrence of exposure unevenness due to this cannot be avoided.

Since it required a ballast as mentioned above, it had the disadvantage of being large and heavy as a lighting power source.

It is an object of the present invention to eliminate uneven exposure and to make a lighting power source smaller and lighter.

This invention boosts the voltage obtained from an AC power supply using a voltage doubler rectifier to obtain a DC voltage, and uses this DC voltage to light a discharge lamp with a direct current.Thermal paper is also used as a resistor for stabilizing the discharge necessary for lighting the DC lamp. It is characterized by using a heater for drying or fixing the toner.

According to this, since it is a DC lighting, there is no uneven burning like in the case of AC lighting, and there is no need for a ballast such as a choke coil, which not only makes it lighter and smaller, but also because of the ballast. There is no noise or temperature rise,
Further, by using a heater for part or all of the stabilizing resistor, there are advantages such as the need for a conventional energizing circuit dedicated to the heater.

An embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 denotes a discharge lamp for direct current lighting, which is used as a light source for exposure.

Reference numeral 2 is a commercial AC power supply, and 3 is a voltage doubler rectifier, which is composed of capacitors 4 and 5 and a diode 6.7.

A discharge lamp 1 and a heater 8 used as a resistor for stabilizing discharge are connected in series between output terminals a and b of the voltage doubler rectifier 3.

Reference numeral 9 denotes a cathode heating transformer, the primary coil 10 of which is connected to the power source 2, and the secondary coil 11 connected to each cathode of the discharge lamp 1.

The heater 8 is used for drying the developing paper after development in the case of a diazo copying machine, and for heating for drying or fixing the developing paper in the case of an electrophotographic transfer copying machine.

In the above configuration, when the capacitor 4 is charged via the diode 6 and the capacitor 5 is charged via the diode 7 by the AC power supply 2, the voltage between the output terminals a and b is approximately twice the peak value of the voltage of the AC power supply 2. DC voltage is generated.

This DC voltage is applied to the heater 8 and the discharge lamp 1, and by setting the voltage applied to the discharge lamp 1 to be equal to or higher than its discharge starting voltage, the discharge lamp 1 starts discharging. It will turn on.

This lighting causes a lamp current to flow through the discharge lamp 1, and this current causes a voltage drop in the discharge lamp 1 due to a voltage drop caused by the heater 8. However, by making sure that the voltage at this time is higher than the discharge maintenance voltage, 1 remains lit.

The heater 8 generates heat due to the current flow, and is used for drying or fixing as described above.

According to the above configuration, the voltage doubler rectifier 3 obtains a DC voltage approximately twice as high as the commercial AC power supply voltage, and this is supplied to the heater 8,
Since the discharge lamp 1 is energized, the discharge lamp 10 is lit and the heater 8 generates heat without any trouble.

Furthermore, since the heater 8 is also used as a resistor for stabilizing the discharge, there is no need for a dedicated energizing equipment for the heater, and there is no need for a stabilizer such as a choke coil as in the case of AC lighting.

Note that a nichrome wire or the like can be used as the heater 8, but an incandescent lamp may be used as the heater 8 instead.

If necessary, the nichrome wire and the incandescent lamp may be connected in series or in parallel, and the light from the incandescent lamp may be used as part of the light source for exposure.

If the amount of heat generated by the nichrome wire or incandescent lamp is large, a separate resistor may be connected in series with these.

By the way, although this invention uses a DC lighting method,
In the case of direct current lighting, a dark end phenomenon (a phenomenon in which the tube wall on the positive end side of the discharge lamp turns black) tends to occur after a short period of use.

In order to avoid this, a configuration as shown in FIG. 2 may be used.

In the figure, 12 and 13 are switches that operate in conjunction with each other.

When each switch 12, 13 is in contact with one contact as shown in the figure, the DC voltage from the voltage doubler rectifier 3 is applied to the discharge lamp 1 as shown in the polarity, whereas the switch 12. .13 switches and contacts the other contact, a voltage of the opposite polarity to that shown in the figure is applied to the discharge lamp 1.

Therefore, by switching the switches 12 and 13 at appropriate intervals, the polarity of the voltage applied to the discharge lamp 1 will be constantly reversed, and the period when the dark end phenomenon described above will occur can be extended. become.

In practice, it is preferable to switch the switches 12 and 13 each time the power switch is turned on or each time the document table moves.

As detailed above, according to the present invention, exposure unevenness is eliminated, size and weight can be reduced, and a dedicated energization for the heater is not required, and the heater and a resistor for stabilizing discharge can be used together. The configuration is simple, and since ballasts used in AC lighting are not required, there are effects such as eliminating temperature rise and noise caused by this.

Although the illustrated embodiment uses a double voltage rectifier, a triple or more voltage doubler rectifier may be used instead.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the invention, and FIG. 2 is a circuit diagram showing another embodiment. 1...Discharge lamp, 2...AC power supply, 3.
... Voltage doubler rectifier, 8... Calculator, 11
, 12... switch.

Claims (1)

[Scope of Claims] A light source device for a copying machine comprising a heater for drying or fixing that also serves for stabilizing discharge and a discharge lamp for exposure connected in series between the output terminals of a voltage rectifier. 2. The light source device for a copying machine according to claim 1, wherein part or all of the heater is a nichrome wire. 3. The light source device for a copying machine according to claim 1, wherein part or all of the heater is an incandescent lamp. 2. The light source device for a copying machine according to claim 1, further comprising a switch connected between the output end of the quadruple voltage rectifier and the discharge lamp for reversing the voltage applied to the discharge lamp.