JPH09258580A - Device and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a print having the same quality on the front and the back surfaces, by making the transferring current flow changed for the front surface print and the back surface print, in the case of performing the both surface print. SOLUTION: This device provided with a photoreceptor 3 whose surface is uniformly electrified on which an electrostatic latent image of an original is formed by irradiation, a developing device 4 for turning the above mentioned electrostatic latent image to the toner image by feeding the toner on the photoreceptor 3, and a transferring body 6 for transferring the toner image on a paper sheet, is allowed to control the image forming by a controlling device, and moreover in the case of making the changeover between a both surface print mode and the single surface print mode permissible, the applying voltage on the transferring body in the case of the front surface print is changed from that in the case of the back surface print, by the above controlling device controlling the high voltage power source 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrostatic latent image, and more particularly to a technology capable of printing both sides of an image forming apparatus capable of double-sided printing.

[0002]

2. Description of the Related Art When double-sided printing is performed in the above image forming apparatus, the back side is printed after the front side (front side) is printed, but the water content of the paper evaporates due to fixing during the front side printing. It is known that the state of the paper (the resistance increases) due to such changes.

In the case of roller transfer, the back surface is
Transfer must be performed with a large current (or voltage), and the resistance of the paper also increases, so the current must be increased.

Therefore, when the transfer of the front surface and the transfer of the back surface are transferred with the same current, the back surface becomes a strange image when the transfer current is adjusted to the front surface, and the front surface image becomes a strange image when the transfer current is adjusted to the back surface. Therefore, different currents must be transferred on the front surface and the back surface.

[0005]

SUMMARY OF THE INVENTION The present invention has been made based on the above facts. When performing double-sided printing, the transfer current is changed between the front side printing and the back side printing, and a print with the same front and back sides can be obtained. The purpose is to do so.

[0006]

In order to achieve the above object, the present invention provides a photoconductor on which the surface is uniformly charged and an electrostatic latent image of an original is formed by irradiation, and a toner on the photoconductor. It has a developing device for supplying the electrostatic latent image into a toner image and a transfer body for transferring the toner image onto a sheet, and the image formation is controlled by the control device, and the double-sided print mode and the single-sided printing mode are set. In the image forming apparatus capable of switching the print mode, the control device can change the voltage applied to the transfer body between the front side printing and the back side printing.

Further, the configuration provided with a selection switch for manually switching the voltage applied to the transfer member and the control device described above,
It may be configured so that it can be connected to a personal computer or the like, the control device converts a digital signal from the personal computer or the like into an image signal, and the control device switches between front-side printing and back-side printing by a signal from the personal computer.

The image forming method of the present invention forms an electrostatic latent image by forming an image of a document on a photosensitive member whose surface is uniformly charged, and supplies toner to the electrostatic latent image to supply the toner. In the image forming method in which the toner image is transferred to a sheet after the image is formed and double-sided printing is performed, the voltage applied to the transfer body is changed between the front-side printing and the back-side printing.

In addition, when the first printing after the power is turned on and the paper sensor provided in the paper feeding means of the image forming apparatus detects that there is no paper, The printing can be configured to apply a voltage for surface printing to the transfer body.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus of the present invention. As shown in the figure, the image forming apparatus 1 has an operation panel 2 on the upper right side of the figure. This operation panel 2 has a selection switch for paper size, the number of prints, reduction / enlargement ratio, etc., as well as a selection switch for double-sided print mode and single-sided print mode, as in the conventional case, and further, for front side printing and back side printing. It also has a selection switch.

Inside the image forming apparatus 1, there is a photosensitive drum 3 in the shape of a cylindrical drum, around which a developing device 4, a resist roller 5, a transfer member 6, a fixing device 7 and the like are arranged. At the lower part of the apparatus, a paper feeding means 8 including a paper feeding cassette.
There is a paper feed roller 9 for feeding the paper in the paper supply means 8, and the paper supply means 8 is provided with a paper sensor 10 for checking the presence or absence of paper.

Reference numeral 11 indicates a high voltage power supply. As shown in FIG. 2, this high-voltage power supply 11 can apply a high voltage to each of the charger 12, which uniformly charges the surface of the photoconductor 3, the developing device 4, and the transfer body 6.

FIG. 3 shows a block diagram of the present invention. The operation panel 2 includes an engine board 15 via the control device 14.
The engine board 15 is connected to the high-voltage power supply 11, the paper sensor 10, and the selection switch 16. Further, although not shown, a personal computer, a word processor or the like is connected to the control device 14, and a digital signal from these is converted into image information by the control device 14. Engine board 1
5 and the control device 14 are composed of a computer.

The engine board 15 controls the entire drive of the image forming apparatus such as the photoconductor 3, the developing device 4, the registration roller 5, the transfer roller 6, the fixing device 7 and the charging device 12 according to an instruction from the control device 14. Then, the image forming operation is performed.

The selection switch 16 is provided on the operation panel 2 and is used to manually select front side printing or back side printing.

Next, the operation of the image forming apparatus will be described. When a paper feed command is sent from the control device 14, the engine board 15 rotates the paper feed roller 9 in the direction of the arrow in FIG. 1 to convey the paper in the paper feeding means 8 in the direction of the broken arrow.

The conveyed sheet is temporarily stopped by the registration roller 5, and the sheet is conveyed by rotating the registration roller 5 in synchronism with the timing of writing on the photosensitive member 3 by the laser beam shown by the arrow A.

The toner image visualized on the photoconductor 3 by the developing device 4 is transferred to the paper by the transfer roller 6, fixed by the fixing device 7, and discharged to the paper discharge tray.
In the case of double-sided printing, the sheet is once housed in an intermediate cassette (not shown) and waits for back side printing. Then, it is supplied again from the intermediate cassette to the registration roller 5, and the back surface is printed. Therefore, the controller 14
Always determines whether the next print is a front side print or a back side print.

The high voltage power supply 11 changes the transfer voltage by PWM which changes the duty ratio of the input pulse.
It depends on the control method. The relationship between the duty ratio and the output is shown in FIG.

At the time of transfer of the surface (omoten), the controller 1
According to the instruction from 4, the engine board 15 inputs a pulse with a low duty ratio to the PWM terminal.
By inputting a pulse with a high duty ratio to the WM terminal, an appropriate transfer current can be output. 5 and 6 are diagrams showing this state.

Further, when the image forming apparatus 1 is powered on, the controller 14 inputs a pulse having a low duty ratio to the PWM terminal at the time of the first printing, and sets a transfer current for printing on the front surface. This can be done by software built into the controller 14.

The controller 14 inputs a pulse with a low duty ratio to the PWM terminal when printing on the front side (front side) and a pulse with a high duty ratio when printing on the back side. Since the double-sided print mode is selected on the operation panel 2, the control device 14
However, it is possible to judge whether the next print is the front side or the back side.

In addition to the case where the work is performed as planned once set as described above, it is also possible to manually switch the front surface to the back surface. The selection switch 16 performs this switching. This selection switch 16 is provided on the operation panel 2, and when turned on, the engine board 15 stores it as a back side printing mode and inputs a pulse having a high duty ratio to the PWM terminal during transfer. When it is turned off, the back side print mode is released, the front side print mode is entered, and a pulse with a low duty ratio is input. As described above, an appropriate transfer current can be output.

Further, since the paper in the paper supply means 8 is exhausted, the paper sensor 10 is turned on and the controller 1
In No. 4, it is determined that there is no paper, and the back side print mode is released. 2. Description of the Related Art Conventionally, an image forming apparatus is one in which a personal computer, a word processor, or the like (not shown) is connected to the control device 14, and a digital signal input from these personal computer, a word processor, etc. is converted into an image signal, and a document created by a personal computer or the like Etc. was made into a hard copy. In the present invention, the above-mentioned personal computer or word processor can instruct the control device 14 to switch between the front side print mode and the rear side print mode. When a hard copy is taken from a document created by a personal computer or the like, both front and back instructions can be given from the personal computer or the like.

[0025]

According to the present invention as described above,
When performing double-sided printing, high-quality images can be obtained on both the front and back surfaces because transfer can be performed on the front and back surfaces with appropriate currents. Further, if a switch for switching between the front surface and the back surface is provided, it becomes possible to manually switch, and it becomes possible to perform frequent switching.

Since the front side printing is determined at the first printing after the power is turned on, wastefulness can be eliminated by setting in advance in this way. If the paper sensor is provided, it is possible to detect the absence of the paper in the paper supply means and automatically release the back side print mode, which improves the operability. When the control device is connected to a personal computer or the like, it is easy to use if the front and back sides can be switched from the personal computer or the like.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an image forming apparatus of the present invention.

FIG. 2 is an enlarged view of a transfer portion of FIG.

FIG. 3 is a block diagram of the circuit of the present invention.

FIG. 4 is a diagram showing a relationship between a pulse duty ratio and a high voltage power supply output in PWM control.

5A and 5B are time charts of transfer in the present invention.

FIG. 6 is a time chart explaining a duty in the present invention.

[Explanation of symbols]

 3 Photoconductor 4 Developing Device 6 Transfer Body 8 Paper Supplying Means 10 Paper Sensor 14 Controller 16 Selection Switch

Claims (6)

[Claims] 1. A photoconductor on which a surface is uniformly charged and an electrostatic latent image of an original is formed by irradiation, and a developing process for supplying toner to the photoconductor to convert the electrostatic latent image into a toner image. An image forming apparatus having a container and a transfer body for transferring the toner image onto a sheet, the image forming is controlled by the controller, and the double-sided print mode and the single-sided print mode can be switched. An image forming apparatus characterized in that the voltage applied to the transfer member can be changed during front surface printing and during back surface printing. 2. The image forming apparatus according to claim 1, further comprising a selection switch for manually switching a voltage applied to the transfer body. 3. The control device is connectable to a personal computer or the like, the control device converts a digital signal from the personal computer or the like into an image signal, and the control device uses the signal from the personal computer to print a front surface or a back surface. 3. The image forming method according to claim 1, wherein the switching is performed. 4. An electrostatic latent image is formed by forming an image of a document on a photoconductor whose surface is uniformly charged, and toner is supplied to the electrostatic latent image to form a toner image. An image forming method for transferring a toner image to a sheet and performing double-sided printing, wherein a voltage applied to a transfer body is changed between front-side printing and back-side printing. 5. The image forming method according to claim 4, wherein a voltage for front side printing is applied at the first printing after the power is turned on. 6. A sheet sensor provided in a sheet supply unit of the image forming apparatus detects that there is no sheet, and next printing applies a voltage for surface printing to a transfer body. Item 6. The image forming method according to Item 4 or 5.