JPH04166878A - Thermal fixing device and electrophotographic device using this fixing device - Google Patents

Abstract

PURPOSE:To obtain stabilized fixing performance by selectively setting the type of pressurizing roller and the fixing speed in response to the types of recording paper in use so that they are most suitable for fixing of the recording paper. CONSTITUTION:When a toner image formed by black toner grains by using an envelope or an OHP sheet as recording paper 4 is fixed, a first pressurizing roller 11 is pressed against a heating roller 2, and when a toner image formed by color toner grains by using an OHP sheet as recording paper 4 is fixed, a second pressurizing roller 12 is pressed against the heating roller 2. In order to obtain a favorable fixing performance for each fixing, a pressurizing roller supporting base 13 is changed in its angle to select a driving speed. The toner image can thus be stably fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal fixing device and an electrophotographic apparatus using the fixing device.

[Conventional technology]

An electrophotographic device such as an electrophotographic copying machine or an electrophotographic printer has a photosensitive drum at its center, a charger that uniformly charges the surface of the photosensitive drum, and a charger that exposes the charged surface of the photosensitive drum according to image information. an exposure device that forms an electrostatic latent image on the surface of the photoconductor, a developing device that develops the electrostatic latent image formed on the surface of the photoconductor to form a toner image, a paper feeding device that feeds the recording paper, and a paper feeding device that feeds the recording paper. a transfer device that transfers the toner image onto a recording paper;
The apparatus includes a heat fixing device that fixes the toner image onto the recording paper by passing the recording paper onto which the toner image has been transferred, and a control device that controls these devices.

As shown in FIG. 5, a general heat fixing device includes a heating roller 2 having a built-in heating lamp 1, a pressure roller 3 provided to press against the heating roller 2, and the heating roller 2 and the pressure roller. an introduction guide 5 that introduces the recording paper 4=3- between the heating roller 2 and the pressure roller 3, and a paper discharge guide 1< 6, and further includes the heating roller 2
8. A peeling claw 7 for peeling off the recording paper 4 wound on the surface of the heating roller 2; and an oil coating for keeping the surface of the heating roller 2 clean.8. This configuration includes a cleaning roller 9 and the like.

However, this type of electrophotographic apparatus is operated in various environments, and there are many types of recording paper used, and in order to obtain fixing characteristics suitable for these environments and types, for example, Japanese Patent Application Laid-Open No. 1983-1999. As described in Publication No. 9524.6, multiple types of heating rollers and pressure rollers are prepared in consideration of changes in the thickness and moisture content of the recording paper, and these are selectively used depending on the condition of the recording paper. A thermal fixing device for use has been proposed.

Further, the heat fixing device described in Japanese Patent Application Laid-Open No. 63-311373 is devised to stabilize the fixing characteristics by detecting the thickness of the recording paper and controlling the fixing speed.

[Problem to be solved by the invention]

This type of electrophotographic device has recently come to be used for printing color images on OHP sheets and printing addresses on envelopes, and thermal fixing devices are increasingly capable of stably fixing toner images on a variety of recording papers. Increasingly, there is a demand for high fixing performance.

However, the conventional heat fixing device described above was not able to handle such a variety of recording papers. That is, when a color toner image is fixed on an OHP sheet, the light transmittance is so low that the color image cannot be projected, and when a toner image is fixed on an envelope, there is a problem in that the envelope wrinkles.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal fixing device and an electrophotographic device that can stably fix toner images formed on OHP sheets and envelopes.

[Means to solve the problem]

One aspect of the present invention is to provide a heating roller driven by a driving means, a plurality of types of pressure rollers prepared for pressing the back side of recording paper that contacts the outer peripheral surface of the heating roller, and types of recording paper. and a pressure roller selection means for selecting one of the pressure rollers in response to the selection of the heating roller in response to the selection of the roller in contact with the heating roller. Another invention is characterized in that it is provided with a speed control means for changing the speed of the photoreceptor. A developing device that develops the formed electrostatic latent image to form a toner image, a paper feeding device that feeds recording paper, a transfer device that transfers the toner image onto the fed recording paper, and a toner image. The thermal fixing device includes a heat fixing device that fixes the toner image on the recording paper by passing the transferred recording paper, and a control device that controls these. a plurality of types of pressure rollers prepared for pressing the back surface of the recording paper that contacts the outer peripheral surface of the recording paper; and a pressure roller selection means for selecting one of the pressure rollers according to the type of the recording paper. The electrophotographic apparatus is characterized in that the driving means is provided with a speed control means for changing the driving speed of the heating roller in relation to selection of a pressure roller that presses against the heating roller.

[Effect]

Depending on the type of recording paper used, the type of pressure roller and the fixing speed are selectively set to the optimum state for fixing the recording paper, and stable fixing performance can be obtained.

〔Example〕

First, the fixing characteristics of this type of thermal fixing device will be explained with reference to FIG.

FIG. 6 shows changes in fixing characteristics (wrinkle occurrence rate and transmittance) due to differences in the hardness of the surface of the pressure roller used and the type of recording paper (envelope and OHP sheet). According to experimental studies conducted by the inventors, when the envelope is passed between a heating roller and a pressure roller in order to fix the toner image formed on the envelope, the envelope has a structure in which multiple sheets of paper overlap. Therefore, there is a problem that wrinkles occur due to a difference in conveyance speed between the upper and lower sheets of paper, and in order to fix the color toner image formed on the OHP sheet, the OHP sheet is moved between a heating roller and a pressure roller. If the color toner particles are passed through the gap, the color toner particles are insufficiently melted and smoothed, resulting in a problem that a large light transmittance cannot be obtained and a color image cannot be projected. Incidentally, the light transmittance suitable for color image projection is 50% or more.

Reducing the hardness of the pressure roller is effective in preventing wrinkles from forming on envelopes, but reducing the hardness of the pressure roller will reduce the light transmittance of the color I/color image formed on the HP sheet. Therefore, it is impossible to use a pressure roller that is effective for both of these two types of recording paper.

In addition, in order to increase the light transmittance of the color toner image formed on the OHP sheet, it is necessary to increase the length of time the fixing part stays between the heating roller and the pressure roller (slowing down the fixing speed) or heating the sheet. It has been found that increasing the amount of heating by increasing the temperature and increasing the pressure applied to the toner image are effective.

When the above experimental data was obtained, the surface temperature of the heating roller was 200°C, and the elastic layer formed on the outer periphery of the pressure roller was made of silicone rubber with a heat resistance temperature of approximately 240°C. , it can be seen that the solution of increasing the surface temperature of the heating roller cannot be adopted.

Embodiments of the present invention constructed in consideration of the following two situations will be described below with reference to the drawings.

1 to 3 show a heat fixing device according to the present invention, and components equivalent to those of the conventional device are given the same reference numerals, and detailed explanations thereof will be partially omitted.

FIGS. 1 and 2 show a configuration for selectively pressing two pressure rollers against a heating roller. Reference numeral 11 denotes a first pressure roller, which has a pressure roller on its outer peripheral surface so as to have a fixing characteristic suitable for fixing a toner image formed with black toner particles using general PPC recording paper, an envelope, or an OHP sheet as the recording paper 4. An elastic layer having a hardness of 18 degrees is formed. 12 is the second
The outer peripheral surface of the OHP sheet has a hardness of 50 to provide suitable fixing characteristics for fixing a color toner image formed with color toner particles using the OHP sheet as the recording paper 4.
A layer of elastic material is formed.

Reference numeral 13 designates a pair of pressure roller support bases for supporting the two pressure rollers 11 and 12 so as to be able to selectively press against the heating roller 2, which are provided so as to be rotatable about the rotating shaft 14. It is being In order to attach one of the two pressure rollers 11 and 12 to the pressure roller support base 13 so as to selectively press it against the heating roller 2, a support shaft 15 is provided inside each pressure roller support base 13. centered around 2
The pair of attachments is such that one end of each member 16, 17 is rotatably attached and extends in different directions. two pressure rollers 11
, 12 are rotatably mounted to the center of members 15 and 16, and the pressure roller 11 is mounted between each other end of the member 16, 17 and the pressure roller support base 13.
, 12 are interposed to press the heating roller 2 at a predetermined pressure. By the way, the first
The figure shows a state in which the first pressure roller 11 is pressed against the heating roller 2, and FIG.
This shows the state in which they are pressed together.

FIG. 3 shows the first pressure roller 11 and the second pressure roller 1.
This is a heating roller displacement mechanism for selectively pressing one of the heating rollers 2 against the heating roller 2 and controlling the fixing speed (speed change) at the same time. A rotational force transmission gear system is constructed on the pressure roller support base 13 on one side. A base gear 20 rotated by a drive source (not shown) is provided on the rotating shaft 14 so as to be freely rotatable with respect to the rotating shaft 14 . The rotation of the base gear 20 is transmitted to the engagement gear 22 via the idle gear 21, and when the first pressure roller 11 is in pressed contact with the heating roller 2, the engagement gear 22 is transmitted to the heating roller 2. It is configured to engage with a fixed driven gear 23 to complete a first rotational force transmission system for driving the heating roller 2 . The rotation of the base gear 20 is further transmitted to the engagement gear 25 via another idle gear 24 and the second pressure roller 12
When the engagement gear 25 is pressed against the heating roller 2, the engagement gear 25
is configured to engage with the driven gear 23 fixed to the heating roller 2 to complete a second rotational force transmission system for activating the heating roller 2. Incidentally, the speed ratio of the first rotational force transmission system is set to 1:1, and the speed ratio of the second rotational force transmission system is set to 1:0.25.

A transmission system switching means for rotating the pressure roller support base 13 in order to selectively press one of the two pressure rollers 11 and 12 against the heating roller 2 is a control motor 26.
A disk 28 rotated via a worm gear 27 by
and an arm 29 constituting a crank mechanism that connects the disc 28 and the pressure roller support base 13 and rotates the pressure roller support base 13 as described above. The control device 30 controls the rotation of the control motor 26 according to the recording paper 4 to be used and the color of the image to be printed, and presses the first pressure roller 11 against the heating roller 2, and also controls the first rotational force transmission system. Alternatively, the disk 28 is rotated so as to press the second pressure roller 12 against the heating roller 2 and complete the second rotational force transmission system.

In this embodiment, when fixing a toner image formed by black toner particles using PPC recording paper, an envelope, or an HP sheet as the recording paper 4, the first pressure roller 1 is used to fix the toner image formed by black toner particles.
1 is pressed against the heating roller 2, and the pressure roller support base 13 is rotated so as to have a fixing characteristic suitable for fixing these, and the toner image formed of color toner particles is fixed using the OHP sheet as the recording paper 4. At times, control is executed to press the second pressure roller 12 against the heating roller 2 and rotate the pressure roller support base 13 so as to obtain fixing characteristics preferable for fixing the second pressure roller 12 .

Furthermore, when the heat fixing device or the electrophotographic device is heavy, the pressure roller support base 13 is rotated to a position where neither the pressure rollers 11 or 12 come into contact with the heating roller 2, thereby reducing the pressure. Permanent deformation of the rollers 11 and 12 can be reduced.

Furthermore, it is also possible to change the type and number of pressure rollers and the speed ratio of the rotational force transmission system. For example, by using a pressure roller with a hardness of 18 degrees as a dedicated pressure roller for envelopes, and a pressure roller with a hardness of 35 degrees as a pressure roller for fixing monochrome toner images on PPC recording paper and OHP sheets, the pressure roller can be softened. Therefore, the life of the pressure roller whose mold releasability deteriorates rapidly can be extended.

FIG. 4 shows a printer using electrophotographic technology to which this thermal fixing device is applied, which includes a photosensitive tram 31 at the center, a charger 32 that uniformly charges the surface of the photosensitive drum 31, and a charger 32 that uniformly charges the surface of the photosensitive drum 31. An exposure device 33 that forms an electrostatic latent image by exposing according to image information, a developing device 34 that develops the electrostatic latent image formed on the surface of the photoconductor to form a monochrome or color toner image, and a plurality of types of toner images. A paper feeding device 35 that selectively feeds recording paper, a transfer device 36 that transfers a toner image onto the fed recording paper, and a transfer device 36 that transfers a toner image onto the fed recording paper; The image forming apparatus includes the above-described thermal fixing device 37 that performs fixing, and a control device (including the control device 30) 38 that controls these devices.

The paper feeding device 35 has a detection switch 35d that detects whether the cassette installed in the cassette mounting opening 35a is a general paper cassette 35b or an envelope cassette 35c, and a detection switch 35d that detects whether the fed recording paper 4 is an OHP sheet. It is equipped with a transmission type detector 35e for detection, and inputs the detection result to the control device 38.

The control device 38 receives the image data (dot data and color information) to be printed from the upper information processing device and the recording paper 4 to be used.
Enter information on the size and type (PPC recording paper, envelope or ○HP sheet).

Then, the control device 38 determines whether the set or fed recording paper 4 is a predetermined one based on the detection signal from the detection switch 35d and the detector 35e, and further,
The rotation of the control motor 26 of the fixing device 37 is controlled by referring to the color information of the image to be printed, and the rotation of the control motor 26 of the fixing device 37 is controlled.
An optimal one of the first and second pressure rollers 12 is selected and pressed against the heating roller 2. With this selection, naturally one of the two rotational force transmission systems for driving the heating roller 2 is selected. Further, the exposure device 33 and the developing device 34 are controlled to form a toner image on the surface of the photosensitive drum 31.

If the electrophotographic apparatus is an electronic copying apparatus, the operator inputs the size, type, and color information of the recording paper 4 from the operation panel, and the control device 38 refers to the input information to control the pressure rollers 11 and 12. Executing selection control and control of the developing device 34 [Effects of the Invention] As described above, the present invention allows the type and fixing speed of the pressure roller to be adjusted to fix the toner image on the recording paper depending on the type of paper used. It is possible to provide a thermal fixing device and an electrophotographic device that are set in an optimal state and can obtain stable fixing performance, and can therefore stably fix toner images formed on OHP sheets and envelopes.

[Brief explanation of drawings]

1 to 4 show embodiments of the present invention. FIGS. 1 and 2 are side views of the heat fixing device, FIG. 3 is a side view of the heating roller drive mechanism, and FIG. 4 is a side view of the heat fixing device. 1 is a side view of a printer using electrophotographic technology to which a heat fixing device is applied; FIG. FIG. 5 is a side view of a conventional heat fixing device, and FIG. 6 is a diagram showing fixing characteristics. 2...Heat fixing roller, 11...First pressure roller, 12...Second pressure roller, 13...
・Pressure roller support base, 20...Base gear,
21゜24・・・Idle gear, 22.24・
... Engagement gear, 23 ... Driven gear, 26.
...Control motor, 30°38...Control device.

Claims (1)

[Claims] 1. A heating roller driven by a driving means, a plurality of pressure rollers prepared for pressing the back side of the recording paper that contacts the outer peripheral surface of the heating roller, and a and a pressure roller selection means for selecting one of the pressure rollers according to the type, the drive means selects one of the pressure rollers according to the type of the heating roller, and the driving means selects one of the pressure rollers according to the type of the heating roller. A heat fixing device comprising a speed control means for changing the driving speed of the heat fixing device. 2. The thermal fixing device according to claim 1, wherein the speed control means includes transmission system switching means for a plurality of rotational force transmission systems from a drive source to a heating roller. 3. The heat fixing device according to claim 2, wherein the transmission system switching means is linked to a pressure roller selection means. 4. A recording paper type detection means for detecting the type of recording paper, a heating roller driven by a driving means, and a plurality of types prepared for pressing the back surface of the recording paper that contacts the outer peripheral surface of the heating roller. In a thermal fixing device comprising a pressure roller, and a pressure roller selection means for selecting one of the pressure rollers according to the type of recording paper, the drive means detects the detection result of the recording paper type detection means. A heat fixing device comprising a speed control means for changing the driving speed of the heating roller in response to the heating roller. 5. A photoreceptor, an exposure device that exposes the surface of the photoreceptor according to image information to form an electrostatic latent image, and develops the electrostatic latent image formed on the surface of the photoreceptor to form a toner image. a developing device that feeds multiple types of recording paper selectively, a paper feeding device that selectively feeds multiple types of recording paper;
It includes a transfer device that transfers the toner image onto the fed recording paper, a heat fixing device that fixes the toner image on the recording paper by passing the recording paper on which the toner image has been transferred, and a control device that controls these. The heat fixing device includes a heating roller driven by a driving means, a plurality of pressure rollers prepared for pressing the back side of the recording paper that contacts the outer peripheral surface of the heating roller, and a plurality of pressure rollers according to the type of recording paper. and a pressure roller selection means for selecting one of the pressure rollers according to the selection of the pressure roller, wherein the drive means drives the heating roller in connection with selection of the pressure roller that presses against the heating roller. An electrophotographic apparatus characterized by comprising speed control means for changing speed. 6. An electrophotographic apparatus according to claim 5, wherein the control device selects the pressure roller and controls the speed of the heating roller depending on the type of recording paper fed from the paper feeder. 7. In claim 5, the developing device includes a color developing device, and the control device selects the pressure roller and the speed of the heating roller according to the type of recording paper fed from the paper feeding device and the developed color. An electrophotographic device characterized by performing control.