JPH0460571A - Fixing device for image forming device - Google Patents

Abstract

PURPOSE:To improve the quality of an image at the time of both modes such as a surface mode and a back surface mode by constituting an upper fixing roller of a thin 'Teflon(R)' or a thin silicone rubber and constituting a lower fixing roller of the thick silicone rubber. CONSTITUTION:The upper fixing roller 26 functioning at the time of the surface mode is constituted of a heater 26a, a core bar 26b consisting of aluminum or iron and a mold-released layer 26c. The mold-released layer is constituted of the silicone rubber having high hardness and the core bar 26b is coated therewith. Besides, the lower fixing roller 27 is also constituted of a heater 27a, a core bar 27b and a mold-released layer 27c. Then, the core bar 276 is coated with the layer 27c consisting of the silicone rubber which is comparative ly thick and whose hardness is low. In such a way, the surface of the upper fixing roller contributed to fixation at the time of the surface mode is constitut ed of 'Teflon(R)' or the silicone and the surface of the lower fixing roller con tributed to the fixation at the time of the back surface mode is constituted of the silicone. Thus, the quality of the image in both modes is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device for an image forming apparatus capable of multicolor copying.

[Conventional technology]

During monochrome copying, a mirror image is created on the photoreceptor and this mirror image is directly transferred to transfer paper.For multicolor copying, the normal image on the photoreceptor is sequentially superimposed and transferred onto an intermediate transfer belt, and then,
- In an image forming apparatus having a back mode in which images are transferred all at once to transfer paper, the difference between the front mode and the back mode is as follows:
The copying speed, in other words, the fixing speed is different.

That is, it is necessary to slow down the fixing speed in the back mode.

The reasons for this are: ■The amount of toner adhering to the transfer paper is about 3 to 4 times greater than when using a single color, so sufficient fixing heat and pressure are required; ■Especially when using full color, photographic-like high gloss is desired. Rarely, the above ■
Similarly, sufficient heat and pressure are required for fixing, and the color toner used has high gloss and improves color reproducibility.
One point is that they often use toner with a lower softening temperature than the black toner used in general black-and-white copying machines. Note that since the upper limit temperature for fixing is lower than that for fixing ordinary black toner, it is not possible to increase the amount of heat for fixing by raising the fixing temperature.

Furthermore, in the front mode, there are many text documents, and low gloss is desired from the viewpoint of readability. Even higher speed and higher reliability are desired.

[Problem to be solved by the invention]

In the above conventional technology, the contradictory conditions (1) and (2) described above cannot be satisfied by the same image forming apparatus, and there is a problem that the image quality in either the front side mode or the back side mode must be sacrificed. there were.

The present invention has been made based on this background, and an object of the present invention is to provide a fixing device for an image forming apparatus that can improve image quality in both front mode and back mode.

[Means to solve the problem]

The purpose of the above is to create a mirror image on the photoconductor and transfer the mirror image directly to transfer paper during monochrome copying, and to transfer the M4J on the photoconductor sequentially onto the intermediate transfer belt during multicolor copying. In a fixing device of an image forming apparatus having a back mode in which the image is transferred to transfer paper all at once, the upper fixing roller on the front mode side is high speed and highly reliable, and the upper fixing roller on the back mode side is This is achieved by making the lower fixing roller highly releasable.

More specifically, this is achieved by making the surface of the upper fixing roller made of fluororesin or silicone, and making the surface of the lower fixing roller made of silicone.

[Effect]

The relationship between the material of the pair of fixing rollers that make up the above fixing device, releasability (toner peelability), reliability (stability against deterioration over time, etc.), and high speed performance (reliability at high speed rotation) is approximately as follows. become that way.

Mold releasability: Teflon (product name) <Silicon (HTV) <Silicon (RTV, LTV) Reliability, Teflon ≧ Silicon (HTV)> Silicon (
RTV, LTV) High speed: Teflon ≧ Silicon (HTV) > Si IJ core (
RTV, LTV) Based on the above characteristics, in surface mode, the surface of the upper fixing roller that contributes to fixing is replaced with Teflon, which is a fluororesin, or silicone (
HTV). Furthermore, the surface of the lower fixing roller that contributes to fixing in the back mode is made of silicon (RTV, LTV).

By configuring the fixing roller in accordance with the fixing characteristics in each mode in this way, it is possible to improve the image quality in both modes.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention, which includes an image reading means, a writing means, a developing means, a fixing means, a paper feeding means, a transfer paper conveying means configured.

The image reading means includes a contact glass 1 on which a document is placed.
, illumination lamp 2 for illuminating the document tray, illumination lamp 2
A first mirror 3 that moves in the scanning direction integrally with
The second mirror moves in the same scanning direction in conjunction with the mirror 3. It is composed of a third mirror 4.5, an imaging lens 6 that forms a reflected light image of the document, and a color image sensor 7 that is arranged at the imaging position and reads and photoelectrically converts images for each pixel.

In the above configuration, when the original document is illuminated and scanned, the original image is color-separated pixel by pixel by the color imaging element 7, and then converted into digital signals.

Writing means on the photoreceptor 8 is an imaging optical system 1 including an LD (laser diode) 9, a rotating polygon mirror 10, and an fθ lens.
1. Consists of a mirror 12, which converts the digitized original information into a drive current for the LD 9 for each color, outputs a light output from the LD 9 that substantially matches the density of the original image, and uses the rotating polygon mirror 10 to drive the photoreceptor. 8, optical writing is performed via the imaging optical system 11 and mirror 12. In this case, a color image is written as a normal image, and a black and white image is written as a mirror image in accordance with the scanning of each color. Note that it is also possible to write onto the photoreceptor 8 as a normal image or a mirror image by temporarily storing the order of writing onto the photoreceptor 8 in a buffer (not a frame memory) not shown and changing the order.

The latent image written on the photoreceptor 8 by the writing means is visualized as a toner image by the developing means 13. The developing means I3 consists of four developing devices housed in four partitioned areas within the rotary cylinder 14, and these four developing devices include a developing device 13Y for developing yellow toner and a developing device 13Y for developing magenta toner. The developing device 13M includes a developing device 13M, a developing device 13C1 for developing cyan toner, and a developing device 13B for developing black toner. When a latent image of a color to be visualized arrives in each of these developing devices, the developing device containing toner of that color stops at a position facing the photoreceptor 8, and development is performed. The latent image previously formed on the photoreceptor 8 is, of course, a mirror image for a monochrome original, and a normal image for a color original.

Next, the normal color toner image is transferred by a charger 16 to an intermediate transfer belt 15 disposed opposite to the photoreceptor 8 . This operation is repeated for each color to form a color image on the intermediate transfer belt 15.

At this time, the transfer paper stocked on the cassette 17 (or 18) is sequentially fed from the top by the paper feed roller 19 (or 20), sent out to the registration roller 22 by the feed roller 21, and waited there. .

Next, the registration rollers 22 are driven so that the beginning of the black toner image on the photoreceptor 8 or the color toner image on the intermediate transfer belt 15 coincides with the beginning of the transfer paper, and the black toner image on the photoreceptor 8 is , the color toner image transferred onto the transfer paper by the charger 16 or on the intermediate transfer belt 15 is transferred to the transfer paper by the charger 23, 24, and finally transferred to the intermediate transfer belt 15 by the charger 25.
The upper transfer paper is separated and conveyed to a fixing means.

The fixing means is composed of fixing rollers 26 and 27 arranged opposite each other, and the unfixed toner image on the transfer paper separated from the intermediate transfer belt 15 is fixed after passing between these fixing rollers 26 and 27.

The transfer paper after passing through the fixing means is changed its course by the first switching claw 28. First, at the solid line position, the transfer paper is discharged to the paper discharge tray 30 via the paper discharge rollers 29. Next, at the broken line position, the transfer paper is once conveyed downward. The second switching claw 35 is at the solid line position at this time, and after the trailing edge of the transfer paper passes the paper detection element 36, the conveyance rollers 31 to 34 temporarily stop.
After the first switching pawl 28 returns to the solid line position, it rotates in the opposite direction, whereby the transfer paper is reversely discharged onto the paper discharge tray by the paper discharge roller 29.

Next, when the first switching claw is at the broken line position, after the trailing edge of the transfer paper passes the paper detection element 37, the second switching claw 35 is changed to the broken line position, and the conveyance rollers 31 to 34 are temporarily stopped and then rotated in the reverse direction. As a result, the transfer sheets are stacked on an intermediate tray 38, which is an intermediate stacking means. Thereafter, in response to another copy command, the transfer paper is fed to the registration roller 2 by the paper refeed roller 39.
2. The transfer paper conveying means is configured in this way.

Finally, the accompanying means on the circumference of the photoreceptor 8 and the intermediate transfer belt 15 will be explained.

The charger 40 is a charger for lowering the potential of the photoreceptor 8 under the toner image, and has the effect of increasing the transfer efficiency of the toner image. The charger 41 lowers the potential of the photoreceptor 8 under the residual toner after transfer, and acts so that the cleaning means 42 removes all of this residual toner from the photoreceptor 8.

The static elimination lamp 43 is a lamp for erasing the residual potential on the photoreceptor 8, and the charger 44 is a means for charging the photoreceptor 8. The dustproof glass 45 prevents the writing means from being soiled by toner, paper dust, etc. around the photoreceptor 8.

The charger 46 is a charge eliminating charge for changing the polarity of the surface of the intermediate transfer belt 15, and the charger 47 is a charge eliminating charge for changing the polarity after cleaning.

The cleaning means 48 is a cleaning means for removing toner remaining on the intermediate transfer belt 15 after transfer, and is released when a toner image is held on the intermediate transfer belt 15.

Next, an embodiment of the image data processing block of the image forming apparatus according to the present invention will be described with reference to FIG.

This image data processing block consists of an image reading section, an image processing section, an image writing section, and a storage section.

In the image reading unit 100, a CCD (imaging device) 102 photoelectrically converts original image data. The CCD drive unit 101 is
The CCD 102 is driven according to the resolution (dots/mm). Each color component (R, G, B) converted into an electric signal by the CCD 102 is processed by an analog processing unit 103.
Amplification, dark current correction, shading correction and A/
A D conversion is performed.

The A/D converted image data is subjected to correction of positional deviation of each color component of the reading line in the digital processing unit IO4. In this way, each color component signal is sent to the image processing section without positional deviation.

In the image processing section 105 , a clock generation section 107 generates a basic image frequency and transfers it to the CCD driving section 101 .

The image processing unit 106 performs color processing (RGB-YMC, etc.), magnification processing, and other processing. Here, it can be determined whether the original is a black-and-white original or a color original, and the image data converted into Y, M, C, and B is sent to the writing section 108.

In the writing unit 108, the writing control unit 109
Performs writing speed correction, writing position deviation correction, etc. The LD drive unit 110 converts a digital signal indicating image density into an LD drive current (PWM, power modulation), and
II (LD9 in Figure 2).

Next, the overall electrical configuration of the image forming apparatus according to the present invention will be explained using the blocks shown in FIG.

The fixing heater 120 is a roller heating heater built into the upper and lower fixing rollers 26 and 27 (FIG. 2), respectively.

The system controller (control means) 121 includes a main control section and a key manual control section (not shown) in the operation section. The input various copy modes are processed by the key manual control section and data is output to the image processing section 105. The image processing unit 105 performs processing such as changing magnification based on input data. Further, in the input copy mode, data is outputted to the motor control section 122, process control section 123, etc. through the main control section. The motor control unit 122 controls various motors (scanner, conveyor, developer, intermediate transfer belt, etc.) by predetermined operations. The process control unit 123 controls on/off and output values of illumination lamps, high-voltage power supplies, and the like. The various sensors 124 include elements that detect the presence or absence of transfer paper and the surface temperature of the fixing roller 2627, and output values are input to the system controller 121. Also,
Other DC loads 125 include electromagnetic clutches such as paper feed rollers, etc.
It consists of an electromagnetic solenoid such as a switching pawl, and its operation is controlled by the main control section within the system controller 121. Option 126 consists of an automatic document feeder and the like. Finally, the DC power supply 127 supplies power to various loads.

Next, the image forming mode will be explained based on FIGS. 4 and 5.

Figure 4 shows the image creation mode (front side mode) for normal black and white originals.
FIG. The mirror latent image formed on the photoreceptor 8 is visualized in the black developing section 13B and then transferred onto the surface of the transfer paper 1.

FIG. 5 is an explanatory diagram of the image forming mode (back side mode) for a normal color original. The normal latent images formed for each color component on the photoconductor 8 are developed by the respective color developing sections 134, and then transferred onto the intermediate transfer belt 15 in a superimposed manner, and finally onto the transfer paper P.
Transferred to the back side.

FIG. 6 is a longitudinal cross-sectional view of a fixing device according to an embodiment of the present invention. The upper fixing roller 26 that functions in the surface mode includes a heater 26a and a core metal 26b made of aluminum or iron.
and a release layer 26c. Here, the release layer is Teflon 10 to 50 μm, high hardness silicone rubber 0.1
~0.5 mm, and coats the core metal 26b. As mentioned above, in surface mode for monochrome copying, high speed and high rotation speed are required for fixing performance, so Teflon or silicone rubber (HTV) is optimal, and from the point of view of temperature control, it is relatively thin. be. The surface temperature of the upper fixing roller 26 is generally controlled to around 185°C.

The lower fixing roller 27 also has a heater 27a and a core metal 27.
b. Consisting of an M-type layer 27c, on the core metal 275,
Relatively thick (1 to 10 mm) low hardness silicone rubber (R
A release layer 27c made of (TV or LTV) is coated. In back mode for multicolor copying, high releasability is required as fixing performance, so silicone rubber with low hardness is optimal. The fact that the silicone rubber is thick has the effect of creating a nip, but since the transfer paper is conveyed upward due to the shape of the nip (see FIG. 7), it has the effect of improving mold release. Although it varies depending on the toner used and the conveyance speed, generally the upper fixing roller 2
The surface temperature of 7 is about 140-180℃ (150-160℃)
℃). In FIG. 6, monochrome toner T1 is on the front side of the transfer paper P, and multicolor toner (toner in which monochrome toner is loaded) T2 is on the back side.
are listed respectively.

〔Effect of the invention〕

As explained above, according to the first and second aspects of the invention, in the surface mode, the upper fixing roller that fixes relatively highly softened single color toner is made of thin Teflon, silicone rubber (HT), etc.
V), and the lower fixing roller, which fixes low-softening multicolor colors (superimposed images) during back side moat, is made of thick silicone rubber (RTV, LTV), which enables high speed when using grass-colored toner. , high reliability (long life), low gloss, and high gloss and high releasability of multicolor toner can be achieved with a single fixing device.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram of an image forming apparatus to which the present invention can be applied, FIG. 2 is a configuration diagram of the image forming apparatus, FIG. 3 is a diagram showing an example of an image data processing block, and FIG. 4 is a diagram in surface mode. FIG. 5 is an explanatory diagram of the copying process operation in the back mode, FIG. 6 is a vertical sectional view of a fixing device according to an embodiment of the present invention, and FIG. 7 is a three-pronged This is a theory FiA threshold indicating how the transfer paper is conveyed upward. 26... Upper fixing roller, 26c... Release layer, 27...
...Lower fixing roller, 27c...Release layer. 111 figure 1144 figure jlj figure

Claims (2)

[Claims] (1) During monochrome copying, a mirror image is created on the photoreceptor and this mirror image is directly transferred to transfer paper; during multicolor copying, the normal image on the photoreceptor is sequentially superimposed and transferred onto the intermediate transfer belt. In a fixing device of an image forming apparatus having a back mode in which the images are transferred to transfer paper in a batch, the upper fixing roller on the front mode side is high speed and highly reliable, and the lower fixing roller on the back mode side is provided with high speed and high reliability. A fixing device for an image forming apparatus, characterized in that the roller has a high release property. (2) A fixing device for an image forming apparatus according to claim 1, wherein the surface of the upper fixing roller is made of fluororesin or silicone, and the surface of the lower fixing roller is made of silicone.