JPH08160686A - Recording device and recording method - Google Patents

Abstract

PURPOSE: To keep the resistance to the transfer voltage and the electrification potential of a medium constant when a transfer device applies the transfer voltage to the medium by providing a heating means applying heat to the medium on a conveyance path to nearly unify the temperature and moisture content between hoppers and the transfer device. CONSTITUTION: A heating means 15 is provided between hoppers 2, 3 and an image forming unit 4 on a conveyance path 5. A fixing device 16 is provided between the image forming unit 4 and a feed roller 14b. The heating device 15 is constituted of an upper heat roller 17 and a lower backup roller 18, and the fixing device 16 is constituted of an upper heat roller 19 and a lower pressure roller 20. When a medium is delivered from the hoppers 2, 3 and conveyed on the conveyance path 5, the heating means 15 applies heat to the whole medium, the temperature and moisture content of the medium is made nearly uniform. When a transfer device applies the transfer voltage to the medium, the resistance to the transfer voltage is kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording device such as an electrophotographic printer, and more particularly to heating means for heating a medium.

[0002]

2. Description of the Related Art Conventionally, there is a recording apparatus such as an electrophotographic printer which conveys a medium fed from a hopper to a transfer apparatus and transfers the toner image onto the medium by the transfer apparatus. At the time of transfer, a transfer voltage is applied with the medium sandwiched between the photosensitive drum and the transfer roller, and while the medium is being conveyed, a charge having a polarity opposite to that of the toner is induced on the back side of the medium by the transfer roller. To do. The toner formed on the photosensitive drum is attracted by the opposite charge and adheres to the front side of the sheet, and the toner image is transferred.

When performing double-sided printing in an electrophotographic printer, the medium on which the above-mentioned transfer has been performed is conveyed to a fixing device, and heat and pressure are applied to melt and fix the toner on the medium. After that, the inside and outside of the medium is inverted by the medium inverting means on the transport path. The reversed medium is conveyed again to the transfer device, and similarly, the toner image is transferred while the charge is applied by the transfer roller.

[0004]

In the conventional recording apparatus, an unprinted medium is stored in a place having a different environment such as humidity, or when the back side printing is performed in double-sided printing, the medium is temporarily fixed on the medium by a fixing device. When heat is applied, the water content of each medium, and thus the resistance value of the medium, is different, while the transfer voltage applied to the medium by the transfer roller is constant, so the amount of charge induced in the medium varies, There has been a problem that a constant transfer quality cannot be obtained.

[0005]

In order to solve the above problems, in the recording apparatus of the present invention, heating means for heating the medium is provided on the conveyance path between the hopper and the transfer apparatus.

[0006]

When the medium is fed from the hopper of the recording apparatus constructed as described above and is fed on the feeding path, the heating means applies heat to all the fed medium, so that the temperature and the water content of each medium are almost the same. When the transfer device applies a transfer voltage to the medium, the resistance to the transfer voltage becomes uniform.

[0007]

Embodiments of the present invention will be described with reference to the drawings. The elements common to the drawings are designated by the same reference numerals. FIG. 1 is a schematic side view showing an embodiment of the present invention. In FIG. 1, an electrophotographic printer 1 has hoppers 2 and 3, an image forming unit 4, a conveyance path 5 and the like inside. Unprinted sheets of different sizes are stored in the hoppers 2 and 3, and hopping rollers 6 and 7 are provided above them. The conveyance path 5 indicated by the alternate long and short dash line is composed of a plurality of feed rollers 14a, 14b, 14c, 14d, and communicates with a stacker 5a provided at the top of the electrophotographic printer 1.

On the conveying path 5, heating means 15 is provided between the hoppers 2 and 3 and the image forming unit 4. Further, a fixing device 16 is provided between the image forming unit 4 and the feed roller 14b. The heating means 15 is
Upper heat roller 17 and lower backup roller 1
8 and. The fixing device 16 includes an upper heating roller 19 and a lower pressure roller 20.

The image forming unit 4 includes a charging roller 9, an LED (light emitting diode) array head 10, a developing device 11, a transfer roller 12, and a cleaning device 13 around a photosensitive drum 8 rotatably mounted in the direction of arrow B. Etc. are provided in order and formed. The developing device 11 includes a toner cartridge 21, a toner supply roller 22, and a developing roller 23.

The photosensitive drum 8 rotates in the direction of arrow B at a constant speed, and the surface thereof is uniformly charged by the charging roller 9 to be charged. On this charged photosensitive drum 8, L
Image light is emitted from the ED array head 10 to form an electrostatic latent image. This electrostatic latent image reaches a position facing the developing roller 12 in the developing device 11 as the photosensitive drum 8 rotates in the arrow B direction. Here, the developing roller 12
The toner adhered to the surface of the photosensitive drum 8 is charged to the same polarity as the charging potential of the surface of the photosensitive drum 8 and adhered to the electrostatic latent image to be visualized (toner image formation).

On the other hand, the sheets fed one by one from the hopper 2 or 3 by the hopping roller 6 or 7 are conveyed to the upper portion of the transfer roller 12 at the same timing as the rotation of the photosensitive drum 8. Then, the toner image on the photosensitive drum 8 is transferred onto the paper by the transfer roller 12. The sheet having the unfixed toner image is fixed by the fixing device 16
When the toner image is conveyed to and is heated and pressed by the fixing device 16, the toner image is fixed on the sheet and the printing is completed.

After that, the electrostatic latent image on the photosensitive drum 8 is erased by irradiation of light from a light source for neutralization (not shown), and the toner remaining on the photosensitive drum 8 without being transferred to the paper is stored in the cleaning device 13. Are removed and collected by the cleaning roller. Then, in the next image forming step, the photosensitive drum 8 is charged again by the charging roller 9.

An electrophotographic process of the electrophotographic printer 1 by the image forming unit 4 as described above will be described. FIG. 2 is an explanatory diagram showing charges in the electrophotographic process. In FIG. 2, the photosensitive drum 8 and the charging roller 9, and the photosensitive drum 8 and the developing roller 23, which are in pressure contact with each other as shown in FIG. 1, are shown separately from each other, and an electric charge is shown between them.

The charging is performed by rotating the charging roller 9 in pressure contact with the surface of the photosensitive drum 8 in the direction of arrow B '. A high voltage from a power source (not shown) is supplied to the charging roller 9. The (−) electric charge is induced on the surface of the photosensitive drum 8 as the photosensitive drum 8 and the charging roller 9 rotate while being pressed against each other. Due to such charging, the surface of the photosensitive drum 8 is
(-) Charge is retained.

The image light of the LED array head 10 is applied to the surface of the (-) charged photosensitive drum 8 according to the image signal. As a result, a CG (not shown) in the photosensitive drum 8
Positive and negative carriers are generated in the L layer, of which positive carriers are combined with the (-) charge accumulated on the surface of the photosensitive drum 8 to lower the potential. In this way, the potential of the irradiation section is lowered and an electrostatic latent image is formed on the surface of the photosensitive drum 8.

Toner supply roller 22 in the developing device 11
Rotates in the direction of the arrow B ′ while rubbing against the developing roller 23, frictional charging occurs between the developing roller 23 and the toner 28. At this time, the surface of the developing roller 23 is charged (+) and the toner 28 is charged (-), and the toner 28 is charged.
Adheres to the developing roller 23. The toner 28 attached to the developing roller 23 is scraped off by a blade (not shown), and a thin layer of the toner 28 is formed on the surface of the developing roller 23. The toner 28 charged to (−) is the photosensitive drum 8
At the contact portion between the developing roller 23 and the developing roller 23, the electrostatic latent image is made visible by adhering to the exposed portion of the surface of the photosensitive drum 8 having a low electric potential.

A high voltage is supplied to the transfer roller 12 from a power source (not shown) for a predetermined time. The transfer roller 12 is the paper 2
Rotate in the direction of arrow B'while pressing the back surface of paper 7,
7 is conveyed at a constant speed, and a (+) charge is induced on the back surface of the paper 27 at this pressure contact surface. Here, after a lapse of a predetermined time, the voltage supplied from the power supply to the transfer roller 12 is switched to a constant voltage.

The surface of the photosensitive drum 8 is superposed on the surface of the paper 27. At this time, a (−) charge is induced on the surface of the photosensitive drum 8, and the sheet 27 comes into close contact with the photosensitive drum 8. The toner 28 having a (−) charge attached to the surface of the photosensitive drum 8 is attracted by the (+) charge on the back surface of the paper 27 and moves to the paper 27 side. The voltage is switched to the constant voltage and the transfer is performed on the paper 27.

The heating means 15 used in the electrophotographic printer 1 as described above will be described. FIG. 3 is a schematic side view showing the heating means of one embodiment. In FIG. 3, the heat roller 17 of the heating means 15 is attached so as to be rotatable in the arrow B direction. The surface of the heat roller 17 is Teflon processed. Further, a halogen lamp 24 which is a 400 W heater is inserted inside the heat roller 17, and heat is generated on the surface of the heat roller 17 by applying a predetermined current to the halogen lamp 24.

A thermistor 25 as a temperature sensor is in contact with the surface of the heat roller 17. A control unit (not shown) controls the current applied to the halogen lamp 24 based on the surface temperature of the heat roller 17 measured by the thermistor 25 to keep the surface temperature of the heat roller 17 constant.
Here, it is kept at 120 ° C.

The backup roller 18 rotating in the direction of the arrow B'is constantly pressed against the heat roller 17 by a spring 26 having one end attached to a casing (not shown). When the sheet 27 is conveyed to the heating unit 15, the backup roller 18 sandwiches the sheet 27 with the heat roller 17, and conveys the sheet 27 while pressing the sheet 27 against the heat roller 17. The heat roller 17 applies heat to the paper 27 to make its temperature and water content substantially uniform.

The printing operation of the above electrophotographic printer will be described with reference to FIGS. 1 and 4. FIG.
6 is a flowchart showing a printing operation of one embodiment. 4, in step 1, the hopping roller 6 or 7 in FIG. 1 rotates in the direction of the arrow B, and the unprinted sheets stacked in the hopper 2 or 3 are fed to the transport path 5.

In step 2, the paper is sandwiched between the heat roller 17 and the backup roller 18, and the heat roller 17
Heat the paper at 120 ° C. As a result, the temperature and the water content of all the sheets become substantially uniform regardless of the storage state of the sheets, for example, the humidity of the environment in which the sheets were stored. Also, heat applied to the paper is 100 ° C to 13 ° C.
By setting it to 0 ° C, preferably 120 ° C,
The water content can be set to an appropriate value. In step 3, the toner image is transferred to the paper. At this time, the transfer roller 12 applies an electric charge having a polarity opposite to that of the toner to the back side of the paper, but since the water content of all the paper is substantially uniform,
The resistance value and charging potential of all the sheets are constant.

In step 4, the fixing device 16 melts and fixes the toner on the paper. In step 5, it is determined whether or not back side printing is to be performed. If yes, in step 6, the sheet is reversed by a reversing unit (not shown). The inverted paper is
In step 2, heat is again applied by the heat roller 17 to make the temperature and the water content substantially uniform. When the back side printing is not performed, the paper is discharged to the stacker 5a in step 7.

As described above, when the transfer roller applies a transfer voltage to the paper by applying heat to all the paper on the conveying path between the hopper and the transfer device to make the temperature and the water content substantially uniform. Moreover, since the resistance to the transfer voltage and the charging potential of the paper are constant, uniform and stable transfer quality can be obtained.

[0026]

Since the present invention is configured as described above, it has the following effects.

That is, the transfer device applies a transfer voltage to the medium by providing heating means for applying heat to the medium on the conveying path between the hopper and the transfer device to make the temperature and the water content substantially uniform. At this time, since the resistance to the transfer voltage and the charging potential of the medium are constant, it is possible to obtain a uniform and stable transfer quality.

[Brief description of drawings]

FIG. 1 is a schematic side view showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing charges in an electrophotographic process.

FIG. 3 is a schematic side view showing a heating means of an embodiment.

FIG. 4 is a flowchart illustrating a printing operation according to an embodiment.

[Explanation of symbols]

 1 Electrophotographic Printer 2, 3 Hopper 5 Conveying Path 12 Transfer Roller 15 Heating Means

Claims (3)

[Claims] 1. A recording apparatus which conveys a medium fed from a hopper to a transfer device and transfers a toner image onto the medium by the transfer device, wherein the medium is provided on a medium conveying path between the hopper and the transfer device. A recording apparatus comprising a heating means for heating the recording medium. 2. The recording apparatus according to claim 1, wherein the temperature of the heating means is about 120 ° C. 3. A recording method in which a medium is fed from a hopper, conveyed to a transfer device, and a toner image is transferred onto the medium. In the recording method, the medium is heated on a conveyance path to the transfer device so that temperature and water content are substantially uniform. And a toner image is transferred by applying a transfer voltage to the medium in which the temperature and the water content are substantially uniform.