JPH0475069A - Image forming device - Google Patents

Abstract

PURPOSE:To maximumly increase copying speed while each of copying coditions is satisfied at the time of monochromatic color copying and multicolor copying by almost equalizing the speed of an image forming process to paper carrying speed in a front surface mode, and making the paper carrying speed slower than the speed of the image forming process in a rear surface mode. CONSTITUTION:A latent image for a mirror image formed on a photosensitive body 8 is visualized on a black developing part 13B, and then, transferred on the surface of a transfer sheet P by the control of a system controller, in the front surface mode. In the rear surface mode, the erecting latent images formed on the photosensitive body 8 at every color components are developed by developing for each color 13, and then, sequentially superimposed and transferred on an intermediate transfer body belt 15. After a transfer from the photosensitive body 8 to the intermediate transfer belt 15 is finished, a resist roller 22 is driven in synchronization with an image on the intermediate transfer body belt 15 at the speed slower than that of a working process. The transfer sheet P is carried by the resist roller 22 while the image is transferred on its rear surface, and then, ejected. Thus, while increasing the speed of the multicolor copying, image for satisfying fixing performance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, and particularly relates to a surface mode in which a mirror image is created on a photoconductor and this mirror image is directly transferred to transfer paper during monochrome copying, and The present invention also relates to an image forming apparatus having a back side mode in which, during multicolor copying, normal images on a photoreceptor are sequentially transferred onto an intermediate transfer belt, and then transferred all at once onto a transfer sheet.

C. 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 on an intermediate transfer belt. transcribe and then
- In an image forming apparatus having a back mode in which images are transferred to transfer paper all at once, the copying speed, in other words, the fixing speed, is different between the front mode and the back mode.

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 fixing heat and pressure are required, 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.

In order to satisfy both the conflicting conditions (1) and (2) above, for example, Japanese Utility Model Application No. 59-192158 discloses that the transfer paper leaves the transfer section and the leading edge of the transfer paper is placed at a predetermined position on the front side of the fixing device. A technique has been proposed that detects a certain situation and changes the paper conveyance speed and copying process speed.

Further, Japanese Patent Application Laid-Open No. 60-229041 proposes a technique for making the copying process speed and paper conveyance speed different between monochrome copying and multicolor copying.

[Problem to be solved by the invention]

However, in the former of the above-mentioned conventional techniques, the distance from the transfer section to the fixing device needs to be longer than the maximum paper passing length, which has the disadvantage of increasing the size of the device. Furthermore, the latter method has the disadvantage that the overall copying speed decreases.

The present invention has been made based on this background, and an object of the present invention is to maximize the copying speed while satisfying the respective copying conditions during monochrome copying and multicolor copying.

[Means to solve the problem]

The purpose of the above is to create a mirror image on the photoconductor during monochrome copying and transfer this mirror image directly to transfer paper, and to transfer the normal image on the photoconductor onto the intermediate transfer belt in sequence during monochrome or multicolor copying. In a fixing device of an image forming apparatus that has a back mode in which multiple transfers are performed and then transferred to transfer paper all at once, in the front mode, the image forming process speed and the paper conveyance speed are approximately equal, and in the back mode, This is achieved by a first means comprising a control means for making the paper transport speed slower than the imaging process speed without changing the imaging process speed.

In addition, the above purpose is to create a mirror image on the photoreceptor during monochrome copying and transfer this mirror image directly to transfer paper, and to transfer the normal image on the photoreceptor to the intermediate transfer belt during monochrome or multicolor copying. In the fixing device of an image forming apparatus, which has a back mode in which images are transferred sequentially onto a sheet of paper and then transferred all at once to transfer paper, in the front mode, the image forming process speed and the paper conveyance speed are set to be approximately the same speed, and in the back mode, When copying in multiple colors, the paper transport speed is set lower than the image forming process speed, and when copying in single color in reverse mode, the temperature of the fixing roller on the reverse side mode is increased to adjust the image forming process speed and paper transport speed. This can also be achieved by a second means comprising control means for making the speed substantially constant.

Furthermore, the above purpose is to provide a surface mode in which a mirror image is created on the photoreceptor and transferred directly to transfer paper during monochrome copying, and a surface mode in which the normal image on the photoreceptor is transferred to an intermediate transfer belt during monochrome or multicolor copying. In the fixing device of an image forming apparatus, which has a back mode in which images are transferred sequentially onto a sheet of paper and then transferred all at once to transfer paper, in the front mode, the image forming process speed and the paper conveyance speed are set to be approximately the same speed, and in the back mode, Therefore, during multicolor copying, the paper transport speed is set to v, which is slower than the image forming process speed, and when a signal from the cardboard detection means is received during multicolor copying, the paper transport speed is set to V2, which is even slower than ■. This can also be achieved by a third means including a control means that changes the fixing conditions to make the image forming process speed and the paper conveyance speed substantially equal when performing monochrome copying in the back side mode.

[Effect]

According to the first means, the control means makes the image forming process speed and the paper conveyance speed approximately equal in the front side mode, and sets the paper conveyance speed without changing the image forming process speed in the back side mode. The speed is controlled to be slower than the image processing speed.

According to the second means, the control means makes the image forming process speed and the paper conveyance speed substantially constant in the surface mode;
When performing multi-color copying in reverse side mode, the paper transport speed is set lower than the image forming process speed, and when performing single color copying in reverse side mode, the temperature of the fixing roller on the reverse side mode side is increased to match the image forming process speed. The paper conveyance speed is controlled to be approximately constant.

Further, according to the third means, the control means makes the image forming process speed and the paper conveyance speed substantially equal in the front side mode, and sets the paper conveyance speed to be less than the image forming process speed in the back side mode and in multicolor copying. Similarly, when a signal from the thick paper detection means is received during multicolor copying, the paper conveyance speed is set to ■2, which is even slower than ■1, and when monochrome copying is in reverse side mode, the fixing speed is set to V. The conditions are changed to control the image forming process speed and paper conveyance speed to be approximately equal.

〔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 third mirrors 4 and 5, an imaging lens 6 that forms a reflected light image of the original, and a color image sensor 7 that is placed at an 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 image sensor 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 3. The developing means 13 consists of four developing devices housed in four partitioned areas within the rotating 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 the latent color to be visualized arrives in each developing device, 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 stacked 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 104. 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 (CRGB-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 each of the upper and lower fixing rollers 26 and 27 (FIG. 2).

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 for detecting the presence or absence of transfer paper and the surface temperature of the fixing rollers 26 and 27, and output values are input to the system controller 121. Further, other DC loads 125 include electromagnetic clutches such as paper feed rollers, electromagnetic solenoids such as switching claws, etc., and their operations are controlled by a 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 by the black developing device 13B and then transferred onto the surface of the transfer paper 2.

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 development sections 13 and then transferred onto the intermediate transfer belt 15 one after another, and after the transfer from the photoconductor 8 to the intermediate transfer belt 15 is completed. , Imaging process speed■.

The registration roller 22 is driven in synchronization with the image on the intermediate transfer belt 15 at a lower speed vl. The registration rollers 22 transport the transfer paper P while the image is transferred to the back surface, and after fixing, the paper P is discharged. At this time, it is convenient if the photoreceptor 8 is driven at the above-mentioned low speed V, since there will be no deterioration due to rubbing of the transfer paper P.

Furthermore, when cardboard is detected, the paper conveyance speed is controlled to v2, which is even slower than vl. It should be noted that known techniques can be appropriately applied to the cardboard detection means.

FIG. 6 is an explanatory diagram of an image forming mode for a monochrome original when a transfer paper page alignment mode is selected for an original mixed with a monochrome original and a color original. However, for color originals, the image forming mode is the same as that shown in FIG.

For black and white originals, after forming a positive latent image on the photoreceptor 8, this latent image is visualized by the black developer 13B, and then transferred to the intermediate transfer belt 15.
After this visualized toner image is transferred onto the transfer paper P, according to the first embodiment, the toner image is transferred onto the back surface of the transfer paper P at a speed lower than the image forming process speed.

Further, according to the second embodiment, during transfer, the lower foot landing roller 27
The temperature ranges from low (140℃ to 180℃) to high (185℃).
℃), and then the image on the transfer paper P is fixed (
paper transport speed is the same as the imaging process speed).

FIG. 7 is a longitudinal cross-sectional view showing an example of a fixing device, and the upper fixing roller 26 that functions in the surface mode has a heater 26a,
A core metal 26b made of aluminum or iron and a release layer 2
It consists of 6c. Here, the release layer is Teflon 1
0~50μm, high hardness silicone rubber 0.1~0.5mm
The metal core 26b is coated with the metal core 26b. As mentioned above, in the surface mode for monochrome copying, high-speed and high-reliability fixing performance is required, so Teflon or silicone rubber (HTV) is optimal, and is relatively thin from the point of view of temperature control. 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 a #-type layer 27c, on top of the core bar 27b,
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. 8), 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. 7, monochrome toner TI is on the front side of the transfer paper P, and multicolor toner (toner with monochrome toner loaded) T2 is on the back side.
are listed respectively.

〔Effect of the invention〕

As described above, according to the invention set forth in claim 1, the control means makes the image forming process speed and the paper conveyance speed substantially constant in the front side mode, and changes the image forming process speed in the back side mode. Since the paper conveyance speed is controlled to be slower than the image forming process speed without changing the image forming process speed, the following results can be achieved: 1) Since the image forming process speed is constant, there is no need to change the image forming conditions; 2) The multicolor copying speed can be increased. It is possible to obtain an image that satisfies the fixing performance while increasing the fixing performance.

Further, according to the invention set forth in claim 2, the control means:
In front mode, the image forming process speed and paper conveyance speed are approximately the same; in back mode, when making multicolor copies, the paper conveyance speed is slower than the image forming process speed, and in back mode, monochrome copying is performed. During copying, we increased the temperature of the fixing roller on the back side mode and controlled the image forming process speed and paper transport speed to be almost equal. By making the speed approximately the same as the image forming process speed (by increasing the fixing temperature), it is possible to increase the copying speed.

Furthermore, according to the third aspect of the present invention, the control means causes the image forming process speed and the paper transport speed to be set to approximately the same speed in the front mode, and sets the paper transport speed to the image forming process speed during multicolor copying in the back mode. The paper transport speed is set to ■1, which is slower than the process speed, and when a signal from the thick paper detection means is received during multicolor copying, the paper transport speed is set to V, which is even slower than ■2, and when the back side mode is used and monochrome copying is performed. Since the fixing conditions were changed to control the image forming process speed and the paper conveyance speed to be almost constant, in addition to the effect of the invention as claimed in claim 2, it is possible to improve The effect is that sufficient fixing can be performed during multicolor copying and color reproducibility is improved.

[Brief explanation of the drawing]

Figure 1 is an overall block diagram of an image forming apparatus to which the present invention is applied, Figure 2 is a configuration diagram of the image forming apparatus, Figure 3 is a diagram showing an example of an image data processing block, and Figure 4 is in front mode. FIG. 5 is an explanatory diagram of the copying process operation in the back side mode, FIG. 6 is an explanatory diagram of the monochrome original image creation mode when the transfer paper page alignment mode is selected, and FIG. 7 is an explanatory diagram of the copying process operation in the back side mode.
The figure is a longitudinal sectional view of an example of the fixing device, and FIG. 8 is an explanatory diagram showing how the transfer paper is conveyed upward due to the nip shape. 1... Contact glass, 2... Illumination lamp, 3°4.5... 1st. Second. Third mirror 6... Imaging lens, 7... Color image sensor, 9... LD, 10...
... Rotating polygon mirror, 11... Imaging optical system, 12... Mirror 13... Developing means, 15... Intermediate transfer belt, 16.23... Charger, 28.35... 1st. Second switching claw, 38... Intermediate tray, 121...
- System controller (control means), 130... storage unit. Figure 4 Figure 5 Figure 7 Figure 6 Figure 8

Claims (3)

[Claims] (1) During monochrome copying, a mirror image is created on the photoconductor and this mirror image is directly transferred to transfer paper.In monochrome or multicolor copying, the normal image on the photoconductor is sequentially superimposed on the intermediate transfer belt. In a fixing device of an image forming apparatus having a back mode in which images are transferred and then transferred to transfer paper all at once, in the front mode, the image forming process speed and the paper conveyance speed are set to be approximately the same speed,
An image forming apparatus comprising: a control means for setting a paper conveyance speed to a speed lower than an image forming process speed without changing the image forming process speed in a back side mode. (2) During monochrome copying, a mirror image is created on the photoreceptor and this mirror image is directly transferred to transfer paper; and during monochrome or multicolor copying, the normal image on the photoreceptor is sequentially superimposed on the intermediate transfer belt. In a fixing device of an image forming apparatus having a back mode in which images are transferred and then transferred to transfer paper all at once, in the front mode, the image forming process speed and the paper conveyance speed are set to be approximately the same speed,
When performing multi-color copying in reverse mode, the paper transport speed is set lower than the image forming process speed, and when performing monochrome copying in reverse mode, the temperature of the fixing roller on the reverse side mode is increased to match the image forming process speed. An image forming apparatus characterized by comprising a control means for making paper conveyance speed substantially constant. (3) During monochrome copying, a mirror image is created on the photoreceptor and this mirror image is directly transferred to transfer paper; in monochrome or multicolor copying, the normal image on the photoreceptor is sequentially superimposed on the intermediate transfer belt; In a fixing device of an image forming apparatus having a back mode in which images are transferred and then transferred to transfer paper all at once, in the front mode, the image forming process speed and the paper conveyance speed are set to be approximately the same speed,
In the reverse side mode, the paper transport speed is set to v_1, which is slower than the image forming process speed, when making multicolor copies, and when a signal from the cardboard detection means is received during multicolor copying, the paper transport speed is set to a speed that is even slower than v_1. v_2, and further comprising a control unit that changes fixing conditions to make image forming process speed and paper conveyance speed substantially equal when monochrome copying is performed in back side mode.