JP2003076196A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that obtains an image which is free of an image defect or soil on the back even in case offset toner increases as a result of the passage of paper such as recycled paper, thick paper, or OHT. SOLUTION: The image forming device is provided with a fixing device having a fixing roller that contacts unfixed toner on the surface of a recording material and fixes the toner to the surface of the recording material, and a cleaning web that removes offset toner by sliding over the surface of the fixing roller while being wound round a web winding member from a web supply member. In the image forming device, a control means is provided for controlling the abutting pressure of the cleaning web according to the type of the recording material.

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 such as a copying machine or a laser beam printer having a fixing device for cleaning a fixing roller with a cleaning web.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a laser beam printer, in order to make an unfixed toner image formed on a recording material a permanent image, a fixing source heated by a heating source such as a heater is used. A fixing device of a type in which a recording material is nipped and conveyed at a nip portion formed between a roller and a pressure roller that is pressed against the roller and rotates is widely used. In such a fixing device, an offset phenomenon occurs in which a part of the unfixed toner on the recording material adheres to the top roller and the pressure roller during the nip conveyance and is transferred to the next recording material to stain the image. .

In order to prevent the stain and the deterioration and shortening of the life of the fixing roller and the pressure roller due to the offset phenomenon, a release agent such as silicone oil is applied to the fixing roller or toner adhered to the fixing roller is used to prevent the offset. It is known to provide a cleaning mechanism such as a cleaning web for removal.

In this cleaning mechanism, a cleaning web supplied from a cleaning web supply roller which is a web holding means is abutted by a web roller which is a pressure contact member, and toner and the like adhered to the fixing roller are adhered by the cleaning web. It is removed and wound around a web winding roller that is a web winding means. The cleaning web is pressed against the web roller at a constant pressure and wound by a take-up roller. Usually, the drive of the take-up roller is sent by a DC motor, a stepping motor or a solenoid at a feed rate of several mm / 100 sheets. ing.

[0005]

However, these cleaning mechanisms always press the cleaning web against the fixing roller with a constant contact pressure.
Therefore, when the offset amount increases depending on the type of recording material that is passed (generally, when recycled paper or cardboard with rough surface is passed), offset toner cannot be collected and image defects and back stains may occur. It was the cause.

The present invention has been made in view of the above problems, and an object of the present invention is to produce an image free from image defects and back stains even when offset toner increases during the passage of recycled paper, thick paper, and OHT. An object of the present invention is to provide an image forming apparatus that can be obtained.

[0007]

In order to achieve the above object, the present invention provides a fixing roller for contacting unfixed toner on a recording material to fix the unfixed toner on the recording material,
In an image forming apparatus including a fixing device having a cleaning web that removes offset toner by rubbing the surface of the fixing roller while being wound from a web supply member to a web winding member, depending on the type of the recording material. A control means for controlling the contact pressure of the cleaning web is provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a sectional view of a main part of an image forming apparatus according to the present invention. The image forming apparatus shown in the drawing is an electrophotographic full color copying machine using a two-component developer composed of toner and carrier. Is.

In FIG. 1, reference numeral 11 denotes an electrophotographic photosensitive drum (hereinafter referred to as a photosensitive member) as an electrostatic latent image carrier, which has a photosensitive material layer such as OPC or amorphous Si formed of aluminum or nickel. It is formed on a cylindrical substrate and is rotationally driven in the direction of arrow A in the figure at a predetermined process speed.

The photoconductor 11 is uniformly charged by the primary charger 12 and then subjected to image exposure 31 corresponding to an image signal. The image exposure 31 is performed by the LED. The LE
The image exposure emitted by D, after passing through the imaging lens,
An electrostatic latent image is formed by irradiating the photoconductor 11 and attenuating the surface potential of the exposed portion according to the image signal level. Incidentally, as the exposure apparatus of the present embodiment, not only the LED but also a semiconductor laser element or the like can be used.

The latent image formed as described above is developed by a developing device 14 using a two-component developer composed of toner and carrier.
To be developed. Here, the developing device 14 includes a yellow developing device 141, a magenta developing device 142, and a cyan developing device 14.
3 and a black developing device 144 of four colors.
The order of development is that the yellow developing device 141 is first placed on the photoreceptor 1.
Development is carried out in contact with 1, and thereafter development is carried out in the order of magenta, cyan and black. In the developing device 14,
By applying a bias voltage in which an AC voltage and a DC voltage are superimposed, the electrostatic latent image formed on the photoconductor 11 is reversely developed.

As described above, a toner image is formed on the photoconductor 11. Next, a tribo of the toner is optimized by applying a voltage obtained by superimposing the DC voltage and the AC voltage on the toner image by a charger (not shown). Then, the toner image is transferred to a transfer material 16 such as recording paper that is electrostatically attached to a transfer drum 151 that rotates in the direction of arrow B, and the transfer material 16 is charged by a separation charger 152 and the curvature of the transfer drum 151. Is separated from the transfer drum 151. Then, after being conveyed to the fixing device 17 and fixed, it is discharged out of the apparatus.

On the other hand, the photoconductor 11 has a cleaning device 18
After the residual toner is removed by the method, it is subjected to the next image forming process.

Next, the structure of the fixing device 17 will be described with reference to FIG.

FIG. 2 is a sectional view of the fixing device 17. In FIG. 2, 21 is a hollow fixing roller, 22 is a solid pressure roller arranged facing the fixing roller 21, and these are shown in the figure. It is rotationally driven in the arrow direction at a predetermined process speed. The fixing roller 21 includes a halogen heater 28 that heats the fixing roller 21.
By applying pressure to the pressure roller 22, a constant nip is formed.

Reference numeral 23 is an inlet guide for conveying the transfer material 16 from the transfer drum 151 to the fixing device 17, 24 is a contact type thermistor whose surface layer is polyimide for temperature measurement, and 25 is an abnormal temperature of the fixing roller 21. When the power is forcibly turned off, the contact surface thermo-switch is made of polyimide, 2
Reference numeral 6 designates the transfer material 16 after passing through the nip.
A separating claw for separating the fixing roller 21 and a cleaning web 27 for cleaning the fixing roller 21.

In the fixing device 17, when the power is turned on, the halogen heater 28 is turned on to heat the fixing roller 21. Then, when the fixing roller 21 reaches a predetermined temperature adjustment temperature, the fixing roller 21 enters a standby state and copying is possible. In this embodiment, the temperature control temperature is 180 ° C.

Transfer material 1 separated from transfer drum 151
6 moves on the entrance guide 27 to rotate the fixing roller 2
1 to the nip portion between the pressure roller 22 and the transfer material 16
The upper toner image is fixed as a permanent image by pressure and heat. After that, the transfer material 16 is separated by the separation claw 76 or the self-weight of the transfer material 16 and is conveyed to the paper discharge unit. The fixing roller 2 used for fixing the toner image at the nip portion
In No. 1, the toner, paper dust and the like offset by the cleaning web 27 are cleaned, and the toner is subjected to the next fixing process.

Next, the cleaning unit of the fixing device 17 will be described with reference to FIG.

In FIG. 3, 31 is a winding roller for winding the cleaning web, 32 is a feed roller for feeding the cleaning web 31, and 33 is the cleaning web 31.
Is a web roller whose contact pressure can be changed to press the fixing roller 35, and 34 is a cleaning web for cleaning the fixing roller 35.

Initially, the cleaning web 34 is wound around the feed roller 32. When the fixing operation is performed a predetermined number of times, the take-up roller 31 is rotated by a predetermined amount, the cleaning web 34 is taken up, and a new web surface is always in contact with the fixing roller 35. In this embodiment, the cleaning web 34 is fed by 0.5 mm every time 10 sheets of A4 size paper are passed.

Next, the contact pressure control of the web roller 33 will be described.

In the present embodiment, the contact pressure of the web roller 33 is set to be controlled when the user specifies the paper type on the operation unit. The types of paper that can be specified on the operation unit are plain paper (not specified), recycled paper, thick paper, and O.
There are four types of HT. The contact pressure of the cleaning web for each paper type is stored in advance. The values are shown in Table 1.

[0025] By using this control, it is possible to control the contact pressure of the cleaning web according to the type of recording material that is passed, and even if the paper type changes, there is no image defect or back stain due to offset toner. Images can be obtained.

<Second Embodiment> Next, a second embodiment of the present invention will be described.

Since the outlines of the image forming apparatus and the fixing apparatus are the same as those described in the first embodiment, their repetitive description will be omitted.

FIG. 4 is a block diagram of the cleaning web unit used in this embodiment. In FIG. 4, 41 is a winding roller for winding the cleaning web 44, and 4 is a winding roller.
2 is a feed roller for feeding the cleaning web 44, 43 is the cleaning web 44 pressed against the fixing roller 45,
A cleaning pad whose contact pressure is variable, and 44 is a cleaning web for cleaning the fixing roller 45.

First, the cleaning web 44 is wound around the feed roller 42. When the fixing operation is performed a predetermined number of times, the take-up roller 41 is rotated by a predetermined amount, the cleaning web 74 is taken up, and a new web surface is always contacted with the fixing roller 45. In the present embodiment, the cleaning web 44 is fed by 0.5 mm every time 10 sheets of A4 size paper are passed.

Since the contact pressure control of the cleaning pad 43 is the same as that described in the first embodiment, the description thereof will be omitted. By using this control, it is possible to control the contact pressure of the cleaning web according to the type of recording material that is passed, and even if the paper type changes, there is no image defect or back stain due to offset toner. Images can be obtained.

[0031]

As is apparent from the above description, according to the present invention, the fixing roller for contacting the unfixed toner on the recording material to fix the unfixed toner on the recording material, and the web supply member. An image forming apparatus including a fixing device having a cleaning web that removes offset toner by rubbing the surface of the fixing roller while being wound on a web winding member from the cleaning web according to the type of the recording material. Since the control means for controlling the contact pressure is provided, it is possible to obtain an image free from image defects and back stains even when the offset toner increases during the passage of recycled paper, thick paper, or OHT.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view of a fixing device of the image forming apparatus according to the present invention.

FIG. 3 is a configuration diagram of a cleaning unit of the image forming apparatus according to the present invention.

FIG. 4 is a configuration diagram showing another form of a cleaning unit of the image forming apparatus according to the present invention.

[Explanation of symbols]

11 Photosensitive drum 12 Primary charger 14 Developer 16 Transfer material 17 Fixing device 21 fixing roller 22 Pressure roller 27,34,44 Cleaning web 151 transfer drum

Claims (3)

[Claims] 1. A fixing roller which contacts unfixed toner on a recording material to fix the unfixed toner on the recording material,
In an image forming apparatus including a fixing device having a cleaning web that removes offset toner by rubbing the surface of the fixing roller while being wound from a web supply member to a web winding member, depending on the type of the recording material. An image forming apparatus comprising a control means for controlling the contact pressure of the cleaning web. 2. The cleaning web contact pressure control means determines the contact pressure of the cleaning web to a preset pressure according to the type of recording material selected by the user on the operation unit. The image forming apparatus according to claim 1. 3. The cleaning web contact pressure control comprises:
The image forming apparatus according to claim 1, wherein the image forming apparatus is activated for each copy operation.