JPH0330867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transfer paper separating device for separating a transfer paper onto which a toner image of a photoreceptor has been transferred from a photoreceptor in an electronic copying machine.

Conventionally, a toner image on a photoconductor is transferred to a transfer paper using a transfer charger, the electric charge on the transfer paper is reduced by a separation charger to separate the transfer paper from the photoconductor, and then a fixing process in which flash light is emitted intermittently is used. In an electronic copying machine that heats and fixes a toner image by irradiating flash light from the device onto a toner image on a transfer paper, a transfer paper separation device is known in which a DC voltage and an AC voltage are applied in a superimposed manner to the separation charger. It is being

However, with this transfer paper separation device, if part of the flash light from the fixing device is irradiated to the part of the photoconductor immediately after the transfer paper is separated from the photoconductor, the electrostatic latent image in that part is removed. Therefore, there is a drawback that separation failure of the transfer paper is likely to occur.

Therefore, in an attempt to eliminate the above-mentioned drawbacks, the DC voltage of the DC voltage and AC voltage applied to the corona wire of the separation charger is applied to the photoreceptor both when there is an electrostatic latent image on the photoreceptor and when there is no electrostatic latent image. A transfer paper separation device has been developed that is set to a value that allows the transfer paper to be separated from the transfer paper. However, in this transfer paper separation device, the appropriate value range of the DC voltage applied to the corona wire of the separation charger is very narrow.
If the branch charger current changes due to dirt on the separation charger or changes in the temperature and humidity of the atmosphere, poor separation of the transfer paper is likely to occur, and
There is a drawback that the toner image is easily retransferred to the photoreceptor.

The purpose of the present invention is to achieve good separation of transfer paper,
Another object of the present invention is to provide a transfer paper separation device that can effectively prevent the toner image from being retransferred from the transfer paper to the photoreceptor.

In the present invention, a toner image on a photoreceptor is transferred to a transfer paper using a transfer charger, and the electric charge on the transfer paper is reduced using a separation charger in which a predetermined DC voltage and an AC voltage are superimposed on a corona beam. An electronic copying machine that fixes the toner image on the transfer paper by heating the toner image by irradiating the toner image on the transfer paper with flash light from a fixing device that intermittently emits flash light, An electronic copying machine in which a photoreceptor in a transfer paper separating section is irradiated with a portion of the light, further comprising voltage control means for setting the absolute value of the DC voltage to a small value while the flash light is being emitted. do.

The present invention will be explained in detail based on the embodiments illustrated below.

In FIG. 1, numeral 1 indicates a photoreceptor,
This photoreceptor 1 is rotated in the direction of arrow a by a driving means (not shown). This photoreceptor 1 is formed by forming a photoconductive layer on the surface of a conductive support. A transfer charger 2 is arranged at a predetermined distance from the photoreceptor 1. A pair of registration rollers 3 are arranged at a predetermined distance from the transfer charger 2 and the photoreceptor 1. Transfer paper is fed between these registration rollers 3 by a paper feed roller (not shown). The registration roller 3 temporarily puts this transfer paper on standby, and then sends the transfer paper to the photoreceptor 1 and the transfer charger 2 in synchronization with the toner image on the photoreceptor 1. Two guide plates 4 are arranged between the photoreceptor 1 and the registration roller 3. Above transfer charger 2
An auxiliary roller 6 is arranged between the transfer paper 5 and the photoconductor 1 near the entrance of the transfer paper 5 to bring the transfer paper 5 into contact with the photoconductor 1 .

A separation charger 7 is arranged on the side of the transfer charger 2 in the direction in which the transfer paper 5 moves. A transfer paper conveying means 8 for conveying the transfer paper 5 is arranged on the side of the separation charger 7 in the direction in which the transfer paper 5 travels. The transfer paper conveying means 8 includes a pair of belt pulleys 8a (one not shown) and a plurality of conveyor belts 8b that are attached to these pulleys at predetermined intervals and are moved in the direction of arrow b. , a blower (not shown) that brings the transfer paper 5 into close contact with the conveyor belt 8b by sucking the air above the upper part of the conveyor belt 8b from between the conveyor belts and below.

A fixing device 9 is arranged on the conveyor belt 8b at a predetermined interval. This fixing device 9
consists of a light emitter, such as a xenon lamp 9a, which intermittently emits flash light, and a reflector 9b with a lower opening surrounding the xenon lamp 9a. The fixing device 9 intermittently irradiates the toner image on the transfer paper 5 with flash light to heat and melt the toner image, thereby fixing the toner image on the transfer paper 5. A part of the flash light emitted from the xenon lamp 9a of the fixing device 9 is irradiated onto the photoreceptor 1 immediately after the transfer paper 5 is separated, as shown by a dashed line A. An actuator 10a of a paper detection switch 10 for detecting the presence or absence of the transfer paper 5 is disposed between the photoreceptor 1 of the transfer paper conveying means 8 and the fixing device 9. protrudes from between and above the conveyor belt 8b, and is adapted to be pushed and rotated by the transfer paper 5.

A separation claw 11 is arranged on the side of the separation charger 7 in the direction in which the transfer paper 5 moves. This separation claw 11 is used to auxiliarily move the transfer paper 5 from the photoconductor 1 when the separation of the transfer paper 5 by the separation charger 7 is insufficient.
Separate from. A cleaning device 12 is arranged near the separating claw 11 to remove toner remaining on the photoreceptor 1 after the toner image is transferred.

Around the photoreceptor 1, a charging device, an exposure device, a developing device, a static elimination device (not shown), etc., which constitute an electronic copying machine, are arranged at predetermined positions. The steps of separation, fixing, cleaning, and static elimination can be repeated.

Next, the principle of separation of the transfer paper 5 by the separation charger 7 will be explained, and the present invention will be explained based on this.

The polarity of the electrostatic latent image formed on the photoreceptor 1 is determined as either positive or negative depending on the type of photoreceptor 1. A case where a positive electrostatic latent image is formed with the photoreceptor 1 will be described as an example.

The photoreceptor 1 is positively charged by a charging device,
An exposure device irradiates image light onto the photoreceptor 1 to form a positive electrostatic latent image, and a negatively charged toner is applied to the positive electrostatic latent image on the photoreceptor 1 at a development position to generate an electrostatic charge. A negative toner image is formed by being attached to the electrostatic latent image by attraction.

The transfer charger 2 is connected to a transfer paper 5 that is in contact with a portion of the photoreceptor 1 on which a toner image is formed.
A charge of opposite polarity to that of the toner image, that is, a positive charge is given to the back surface of the toner image. When the electrostatic attraction between the charge applied to the back surface of the transfer paper 5 and the toner charge is greater than the electrostatic attraction between the electrostatic latent image and the toner charge, the toner moves and adheres to the transfer paper 5. At the same time, charges are applied to the back surface of the transfer paper 5 by the transfer charger 2, and charges are induced in the conductive support of the photoreceptor 1. Due to the electrostatic attraction of these charges, the transfer paper 5 is attracted to the photoreceptor 1. Being brought into close contact.

Next, a separate charger 7 applies an electric charge to the back surface of the transfer paper 5 that is in close contact with the photoreceptor 1 to reduce the electric charge on the back surface of the transfer paper 5. In this case, the electrostatic attraction between the charge on the back side of the transfer paper 5 and the charge induced on the conductive support of the photoreceptor 1 by this charge causes the elastic stress of the transfer paper 5 and the gravitational force acting on the transfer paper 5 to The transfer paper 5 is separated from the photoreceptor 1 when the separation force becomes smaller than the separation force, which is approximately the combined force of . At this time, if the charge on the back surface of the transfer paper 5 is reduced too much by the separation charger 7, the electrostatic attraction between the charge on the back surface of the transfer paper 5 and the charge on the toner will cause the electrostatic latent image on the photoreceptor 1 and the charge on the toner. Since the electrostatic attraction force is smaller than the electrostatic attraction between the photoreceptor 1 and the photoreceptor 1, the toner that has been transferred to the transfer paper 5 moves again to the photoreceptor 1, causing a transfer defect. In order to prevent defective toner image transfer, a DC voltage and an AC voltage are applied in a superimposed manner to the corona wire 7a of the separation charger 7, so that the potential on the back side of the transfer paper 5 becomes positive after static electricity is removed by the separation charger 7. I try to keep it within a certain range.

To give an example of separating the transfer paper 5 from the photoreceptor 1 and preventing the toner from being retransferred from the separated transfer paper 5 to the photoreceptor 1, a positive predetermined amount is applied to the corona line 2a of the transfer charger 2. A voltage is applied to increase the transfer current to +70 μA, and the effective value of the alternating current component of the separation current is applied to the corona wire 7a of the separation charger 7.
When applying an AC voltage such that it is 90μA,
When the image area ratio is about 10 to 20%, it is sufficient to apply a DC voltage to the corona wire 7a of the separation charger 7 so that the separation current becomes +10 μA to +50 μA, and when the image area ratio is about 100 %, a DC voltage may be applied to the corona wire 7a of the separation charger 7 so that the DC component of the separation current is +20 μA to +60 μA. Therefore, when the DC voltage applied to the corona wire 7a of the separation charger 7 is set so that the DC component of the separation current is approximately +30 μA, the photoreceptor 1 is irradiated with the flash light of the xenon lamp 9a of the fixing device 9. In this case, the surface potential of the photoreceptor 1 becomes almost 0, so the electrical charge on the back surface of the transfer paper 5 after reducing the charge on the back surface of the transfer paper 5 by the separation charger 7 increases the electrical charge on the conductive support of the photoreceptor 1. As the number of charges induced increases, the electrostatic attraction of these charges becomes greater than the force that separates the transfer paper 5 from the photoreceptor 1, resulting in defective separation of the transfer paper 5. In this case, the fixing device 9
If the DC voltage applied to the corona wire 7a of the separation charger 7 is lowered so that the DC component of the separation current is reduced by about 10 μA during the time when the photoreceptor 1 is irradiated with the flash light, the transfer from the photoreceptor 1 can be achieved. The paper 5 is well separated and the toner image is not retransferred from the transfer paper 5 to the photoreceptor 1.

The present invention is directed to the corona wire 7a of the separation charger 7.
A DC voltage and an AC voltage are superimposed on each other to ignite, and the DC voltage applied to the corona wire 7a of the separation charger 7 is changed depending on the time when the flash light is emitted by the fixing device 9 and the time other than this time. It is something.

Next, a voltage control means for changing the DC voltage between the DC voltage and the AC voltage applied to the corona wire 7a of the separation charger 7 in synchronization with the emission time of the flash light of the xenon lamp 9a of the fixing device 9 is shown in FIG. This will be explained based on FIGS.

The photoreceptor 1 of the transfer paper conveying means 8 and the fixing device 9
Turn on the paper detection switch 10 located between
(closed) and OFF (opened) to control the output state of the timer circuit 13.
The output of No. 3 is given to the timing pulse generation circuit 14. The output of this timing pulse generation circuit 14 is given to a trigger pulse generation circuit 15, the output of this trigger pulse generation circuit 15 is given to a xenon lamp power supply circuit 16, and the output of this xenon lamp power supply circuit 16 is given to a xenon lamp power supply circuit 16. applied to lamp 9a.

The output of the timing pulse circuit 14 is also given to a separation voltage switching timer circuit 17. The output of this separate voltage switching timer circuit 17 is given to a separate charger power supply circuit 18, and the output of this separate charger power supply circuit 18 is given to the corona wire 7a of the separate charger 7. The separation charger power supply circuit 18 includes an AC power supply circuit 18a that applies an AC voltage to the corona wire 7a of the separation charger 7, and a DC power supply circuit 18b that applies a DC voltage. The DC power supply circuit 18b is provided with a changeover switch 18c that changes the DC voltage applied to the separation charger 7, and this changeover switch 18c is connected to the separation voltage changeover timer circuit 1.
It is operated by the level of the output voltage of 7.

As shown in FIG. 4A, the paper detection switch 1
When the actuator 10a of No. 0 is rotated by the transfer paper 5 and the paper detection switch 10 is turned on, the output voltage of the timer circuit 13 remains high for a predetermined period of time as shown in FIG. 4B. During the time when the output voltage of this timer circuit is high, the leading edge of the transfer paper 5 reaches the actuator 1 of the paper detection switch 10.
It is determined by the time it takes to move to a predetermined position within the fixing device 9 after pressing 0a. When the output voltage of the timer circuit 13 falls, the timing pulse generating circuit 14 periodically generates timing pulses as shown in FIG. 4C. The trigger pulse generating circuit 15 that receives the timing pulse from the timing pulse generating circuit 14 periodically generates a trigger pulse as shown in FIG. 4D. Xenon lamp power supply circuit 16 that received this trigger pulse
As shown in FIG. 4E, a high voltage is intermittently applied to the xenon lamp 9a in synchronization with the trigger pulse to cause the xenon lamp 9a to emit light.

Separated voltage switching timer circuit 1 receiving timing pulses from the timing pulse generation circuit 14
7 outputs a high voltage intermittently for a predetermined period of time in synchronization with the timing pulse, as shown in FIG. 4F. As shown in FIG. 4G, the DC voltage applied to the corona wire 7a of the separation charger 7 is high or low when the output voltage of the separation voltage switching timer circuit 17 is low, and When the output voltage of is high, it becomes a low state. Therefore, when the output voltage of the separation voltage switching timer circuit 17 is low, the separation charger power supply circuit 18 superimposes a high DC voltage and a predetermined AC voltage to the corona wire 7a of the separation charger 7.
and separate voltage switching timer circuit 17
When the output voltage is high, the separation charger power supply circuit 18 superimposes a low DC voltage and a predetermined AC voltage and applies it to the corona wire 7a of the separation charger 7.

The output voltage of the separate charger power supply circuit 18 is generally obtained by replacing the output of the DC power supply circuit with an inverter or the like, and superimposing the DC voltage of another DC voltage circuit on the approximately 500 Hz AC voltage, as shown in the diagram, or by using a diode and a diode. The DC component may be substantially changed by changing the positive and negative peak values of the AC voltage using a high-voltage varistor or the like.

Note that when a negative electrostatic latent image is formed on the photoreceptor 1, the polarity of the charge applied to the transfer paper 5 by the transfer charger 2 and the DC voltage of the voltage applied to the corona wire 7a of the separation charger 7. The polarity of can be reversed from the above example.

The transfer paper separation device of the present invention changes the DC voltage between the AC voltage and the DC voltage applied to the separation charger depending on the time when the photoreceptor is irradiated with the flash light of the fixing device and the time other than this time. Paper can be separated from the photoreceptor well, and the appropriate range of DC voltage applied to the corona wire of the separation charger is wide, so the divided current will not change due to dirt on the separation charger or changes in the temperature and humidity of the atmosphere. can also maintain good separation of transfer paper,
In addition, it is possible to effectively prevent the toner image from being retransferred from the transfer paper to the photoreceptor.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the main parts of an electronic copying machine having a transfer paper separating device of the present invention, and FIG. 2 is a block diagram showing voltage control means of the transfer paper separating device of the present invention.
FIG. 3 is a circuit diagram showing the main parts of the voltage control means as above;
FIG. 4 is a timing chart for explaining the operation of the voltage control means. 1...Photoreceptor, 2...Transfer charger, 5...
... Transfer paper, 7 ... Separation charger, 8 ... Transfer paper transport means, 9 ... Fixing device, 9a ... Xenon lamp, 10 ... Paper detection switch, 13 ... Timer circuit, 14 ... Timing pulse generation circuit ,
15...Trigger pulse generation circuit, 16...Xenon lamp power supply circuit, 17...Separation voltage switching timer circuit, 18...Separation charger power supply circuit.

Claims (1)

[Claims] 1. The toner image on the photoreceptor is transferred to a transfer paper using a transfer charger, and the charge on the transfer paper is reduced using a separation charger in which a predetermined DC voltage and an AC voltage are superimposed on a corona beam to separate the transfer paper from the photoreceptor. ,
Next, the toner image on the transfer paper is irradiated with flash light from a fixing device that intermittently emits flash light, and the toner image is heated and fixed on the transfer paper. In an electronic copying machine in which a photoreceptor of a transfer paper separation section is irradiated with a photoconductor, the transfer paper separation device includes voltage control means for setting the absolute value of the DC voltage to a small value while the flash light is being emitted.