JPH05216312A - Color image forming device - Google Patents

Abstract

PURPOSE:To provide a color image forming device small in size which eliminates the need to increase a distance from a transfer part to a fixing part by carrying out transfer and fixing with decreased processing-speed when forming a color image on a resin film. CONSTITUTION:The distance L from the transfer part of a transfer unit 8 to the fixing part of a fixing unit 13 is shorter than a length in the carrying direction of a prescribed transfer sheet. An image forming means 20 is provided with a film detecting means 21 for detecting that a transfer sheet P is a resin film and a speed varying means 22 for varying the speed of the entire process from electrifying to fixing and sheet ejecting. When the transfer sheet P is a resin film and an image to be recorded is a color image, basing on the detection signal of the film detecting means 21 and the controlled stage of the image forming means 20, a control circuit 50 actuates the speed varying means 22 after the development operations of the plural developing units 4-7 to make the speed of the entire process slow, and makes the device carry out transfer and fixing and sheet ejecting with the decreased processing-speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a color image forming apparatus capable of recording a good image on a resin film.

[0002]

2. Description of the Related Art Conventionally, in many image recording apparatuses, the recorded image is mainly black. Therefore, it suffices to fix the toner not only on the plain paper but also on the resin film such as OHP (Over Head Projector) paper. And, even when a recorded image is colorized in recent years,
Initially, fixing was performed on the transparent resin film in the same manner as conventional fixing. However, when the image thus formed on the transparent resin film was projected on the screen by OHP, a practical color tone was not obtained, and a dark color was projected as a whole (this is a black image. It doesn't matter at all). Such a decrease in color tone is due to the fact that the color toner on the film is fixed in a semi-molten state, an air layer is present inside the toner layer, or the toner surface is rough, which may affect the toner layer. It is considered to be caused by refraction and scattering of light when the light is transmitted. Therefore, in order to improve the color tone of the OHP projected image, the toner layer is made thick and dense when the toner is attached to the film, and the toner layer is sufficiently melted so that the toner particles are fused and the air layer is prevented from entering. Improvements have been made by reducing the amount and flattening the surface of the toner layer.

As a conventional color image forming apparatus for improving this kind, there is, for example, an apparatus for increasing the temperature of the heating roller or an apparatus for decreasing the linear velocity of the heating roller. Further, in the former case, there is a problem that the temperature inside the machine rises, and when a temperature-sensitive toner is used, a so-called offset occurs when the temperature rises. Therefore, the latter method is often adopted.

Specifically, for example, Japanese Patent Laid-Open No. 59-1886.
The one described in Japanese Patent Publication No. 73 is known. In this apparatus, when a fixing process is performed on a transfer material (transfer sheet) carrying a toner image, the fixing time is selectively variable according to the characteristics of the transfer material. In addition, Japanese Patent Laid-Open No. 1-
Japanese Patent No. 131582 describes that the transport speed of the transfer material is made to match the linear speed of image formation before the transfer separation and the variable linear speed of the fixing means after the transfer separation.
In Japanese Utility Model Laid-Open No. 59-192158, the transfer material is moved away from the transfer portion, and the position where the front end of the transfer material is in front of the fixing device is detected to shift the conveying speed and the fixing speed. What you have done is listed.

[0005]

However, in such a conventional color image forming apparatus, only the fixing speed of the fixing device is changed while keeping the speed of the image forming process constant. It is necessary to secure a distance from the transfer unit to the fixing unit to prevent the transfer material from being regulated at different speeds in the front and rear, and the distance between the transfer unit and the fixing unit becomes long, so that the device becomes large. There was a problem.

Further, both the process speed and the fixing speed can be slowed down from the beginning, but in that case, there is a problem that a normal printing process (image recording) requires a very long time. Furthermore, if the timing for slowing down the entire process speed (from charging to fixing and discharging) is set before development, for example, the linear velocity of the photoconductor suddenly changes and the toner replenishment amount changes, resulting in a thin layer on the surface of the developing roller. The thickness of the image changes and appears as jitter on the image, and the contact time between the latent image and toner increases, which increases the leakage of electric charge.
There is a problem that the image density decreases. on the other hand,
If the total process speed is slowed down before exposure, there is a problem that the power becomes excessive and the latent image spreads. On the other hand, it is conceivable to reduce the power, for example, by reducing the rotation speed of the polygon mirror, but this is not practical because it causes control difficulty and high cost.

Therefore, the present invention is applicable to the case where the transfer sheet is a resin film and the recorded image is a color image.
After the final developing operation during the image recording operation for the transfer sheet, the entire process speed is changed to be slower,
It is possible to provide a small-sized color image forming apparatus in which a distance from a transfer unit to a fixing unit is reduced to a length equal to or less than a predetermined transfer sheet conveyance direction length by executing transfer and fixing discharge at the slowed process speed. To aim.

[0008]

To achieve the above object, the present invention according to claim 1 provides an image forming means in which a plurality of developing devices are arranged around a photoconductor, and a control means for controlling the image forming means. A color image forming apparatus comprising: a toner image formed by repeating predetermined charging, exposing and developing operations, transferring the image to a transfer sheet by a transfer unit, and fixing the image by a fixing device. The distance from the transfer portion of the means to the fixing portion of the fixing device is set to be equal to or less than a predetermined transfer sheet length in the conveying direction, and the image forming means detects that the transfer sheet to be used is a resin film. Film detecting means, and speed varying means for varying the process speed of the entire process from charging to fixing and discharging,
The control means, based on the detection signal of the film detection means and the control state for the image forming means, when the transfer sheet is a resin film and the image to be formed is a color image, a plurality of 3. The method according to claim 2, wherein after the developing operation of the developing device is completed, the speed varying means is operated to slow down the process speed of all processes, and the transfer and fixing operations are executed at the slowed process speed. The invention is characterized in that a switching means for switching the operation of the speed varying means is provided on an operation panel of the apparatus body, and the invention according to claim 3 is characterized in that the film detecting means supplies the film to the apparatus body. The paper portion has a transmitted light amount detecting element, and the resin film is detected by detecting a predetermined transmitted light amount with respect to the sheet in the sheet feeding portion by the transmitted light amount detecting element. Characterized in that it was.

[0009]

According to the present invention, when the transfer sheet is a resin film and the image to be formed is a color image, the control means operates the speed varying means in response to the detection signal of the film detecting means, After the development operation of a plurality of developing devices, that is, after the final development operation is completed, the process speed of the entire process from charging to fixing and discharging the paper is delayed (at this time, the developed color image idles a little), and the delayed process Perform transfer and fusing operations at speed. Therefore, the linear velocities of the transfer portion and the fixing portion do not differ, and it is not necessary to increase the distance between the transfer portion and the fixing portion for changing the speed. Further, even if the process speed is slowed down before the transfer to the transfer sheet, the transfer current can be changed immediately and easily by the control system at a low cost, which is a very practical device.

According to the second aspect of the invention, the process speed can be manually switched by the switching means, and the fixing speed more suitable for the transfer sheet can be selected by the extremely simple structure. According to the third aspect of the present invention, the resin film can be easily detected by detecting the predetermined amount of transmitted light with respect to the sheet in the sheet feeding section by the transmitted light amount detection element, and the structure of the film detection means can be simplified. it can.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of a color image forming apparatus according to the invention described in claims 1 to 3. 1 to 3
In the figure, reference numeral 1 denotes a drum-shaped photosensitive member, and the photosensitive member 1 is rotationally driven by a driving unit (not shown) at the time of image formation to rotate clockwise in the drawing. At the time of this image formation, first, the surface of the photoconductor 1 is uniformly charged by the charger 2, and then the image-modulated laser beam or the like is emitted onto the photoconductor 1 by the exposure device 3 and the surface of the photoconductor 1 is formed. An electrostatic latent image is formed on. The electrostatic latent image is first subjected to yellow toner development by the Y (yellow) developing device 4 to develop the toner on the photoconductor 1, and the formed yellow image is a non-operating transfer device 8 (transfer means). ), Passes through the separator 9 and the cleaning device 10 and reaches the position of the static eliminator 11. The photoconductor 1 is destaticized from the toner image by the static eliminator 11 and reaches the vicinity of the charger 2 again. Below, M (magenta)
For development and C (cyan) development, the same steps (charging, exposure, and development) using the developing devices 5 and 6 are repeatedly executed, and BL (black) is used using the developing device 7 at the bottom.
When developed, a color toner image is formed on the photoconductor 1.

Reference numeral 12 is a paper feed unit having a plurality of rollers and a paper feed guide. The paper feed unit 12 transfers the transfer sheet P (normal transfer paper or a resin film described later) to the photosensitive member 1 side at a predetermined timing. A sheet of paper) is fed and made to enter between the transfer device 8 and the photoconductor 1. When a transfer voltage is applied to the transfer device 8, the color toner image on the photoconductor 1 is transferred to the transfer sheet P, and the transfer sheet P on which the toner image has been transferred is transferred.
Is transported to the fixing device 13 by a transporting means such as a transport belt 14 and enters the nip portion between the fixing roller 13a and the pressure roller 13b of the fixing device 13, and is heated and pressurized between the rollers 13a and 13b. As a result, the toner image on the transfer sheet P becomes a fixed color image.

As shown in FIG. 2, the distance L from the transfer portion of the transfer device 8 to the image fixing portion of the fixing device 13 is the length of the transfer sheet P of a predetermined size in the conveying direction, for example, 297 mm which is the A4 size vertical length. It is set below. Therefore, the transfer sheet P whose length in the transport direction is larger than the distance L is
Before the transfer and separation are completed, the tip portion enters the fixing device 13.

The photoconductor 1, the charger 2, the exposure device 3, the developing devices 4 to 7, the transfer device 8, the separator 9, and the cleaning device 1
0, static eliminator 11, paper feed unit 12, fixing device 13, and conveyor belt 14
And the like are image forming means 20 in which a plurality of developing devices 4 to 7 are arranged around the photoconductor 1. The image forming means 20 is controlled by a control circuit 50 (control means), and the above-mentioned predetermined charging, The exposure and development operations are repeated to form and record a color image.

Further, the image forming means 20 has a film detecting means 21 for detecting that the transfer sheet P to be used is a resin film, and a speed variable for varying the process speed of the whole process from charging to fixing and discharging. Means 22 and are provided. The film detecting means 21 is, for example, a changeover switch for manually changing the speed, or has a light emitting element and a light receiving element and automatically detects from the amount of light transmitted to the transfer sheet P that the transfer sheet P is a resin film. A transmitted light amount detecting element can be used.

As the speed varying means 22, the image forming means 20
Examples of the circuit include a circuit for switching and controlling the output of a drive motor (not shown) of each section, and a clutch for intervening in the drive system of each section to switch the speed. The changeover switch as the film detection means 21 can be provided, for example, on an operation panel (not shown) of the image forming apparatus main body, and the transmitted light amount detection element is arranged on the paper feeding path of the paper feeding unit 12 and is a normal transfer device. The resin film can be detected by detecting a predetermined amount of transmitted light that is larger than the amount of transmitted light with respect to the sheet P.

When the transfer sheet P is a resin film and the image to be formed is a color image, based on the detection signal of the film detecting means 21 and the control state of the image forming means 20 in FIG. As shown in the timing chart of FIG. 5, after the developing operation of the plurality of developing devices 4 to 7 is completed (after the final developing operation is completed), the speed changing means 22 is operated to slow down the process speed of the whole process, and then the slow speed is set. The transfer from the photoconductor 1 to the transfer sheet P and the fixing and discharging operation are executed at the above process speed.
When the process speed is changed by the control circuit 50, the color image developed in the above-described developing process is slightly idle.

In the color image forming apparatus of the present embodiment having such a structure, when the transfer sheet P is a resin film and the image to be formed is a color image, the detection signal from the film detecting means 21 is detected. The control circuit 50 operates the speed varying means 22 to reduce the process speed of the whole process from charging to fixing and discharging after the development operation of the plurality of developing devices 4 to 7 is completed, and the transfer and fixing operations are performed at the process speed. Is executed. Therefore, the linear velocity of the transfer portion by the transfer device 8 and the fixing portion (nip portion) of the fixing device 13 can be made equal, and the linear velocity can be different due to the speed change corresponding to the type of the transfer sheet. The conventional problem that the sheet conveying distance between the fixing unit and the fixing unit must be increased to be equal to or longer than the length of a predetermined transfer sheet (for example, a resin film having the maximum size) in the conveying direction is solved. As a result, it is possible to obtain a small-sized color image forming apparatus in which the formed image on the resin film is good and the distance from the transfer portion to the fixing portion is shortened. Further, even if the process speed is slowed down before the transfer to the transfer sheet P made of a resin film in this way, the transfer current of the transfer device 8 can be instantly and easily and cheaply changed by the control circuit 50, which is extremely practical. Color image forming apparatus.

Further, in the present embodiment, the entire process speed can be manually switched by the changeover switch on the operation panel which is a changeover means, and the fixing means suitable for the type of the transfer sheet can be formed by the very simple changeover means. You can select the speed. Further, if the predetermined amount of transmitted light with respect to the transfer sheet P is detected by the transmitted light amount detecting element, the resin film can be automatically detected easily and surely, and the structure of the film detecting means can be simplified.

FIG. 5 is a diagram showing another embodiment of the color image forming apparatus according to the present invention. Since the basic image forming method is the same, members that are the same as or equivalent to those in the above-described example are designated by the same reference numerals and redundant description will be omitted. In FIG. 5, reference numeral 30 denotes an image forming means in which a plurality of developing devices 4 to 7 are arranged around the photoconductor 1 which rotates counterclockwise, and the image forming means 30 is controlled by a control means (not shown). Predetermined charging similar to the example,
The exposure and development operations are repeated to form a toner image. In this embodiment, the transfer means for transferring the toner image onto the transfer sheet is different from that in the above example. That is, the color toner image formed on the photoconductor 1 is temporarily
The image is transferred to the endless belt-shaped intermediate transfer member 31 by the first charger 28A, and transferred from the intermediate transfer member 31 to the transfer sheet P by the second charger 28B. The distance between the transfer portion of the charger 28B from the intermediate transfer member 31 to the transfer sheet P and the fixing portion of the fixing device 13 is
As shown in the figure, it is set to a value shorter than the length of the predetermined transfer sheet in the conveyance direction. Other configurations are the same as the above-mentioned example.

Also in this embodiment, when the transfer sheet P is a resin film and the image to be formed is a color image, the control means operates the speed varying means 22 according to the detection signal of the film detecting means 21. By doing so, after the development operation of the plurality of developing devices 4 to 7 is completed, the process speed of the whole process from charging to fixing and discharging is slowed down, and the transfer and fixing operations are executed at the process speed. Therefore, the linear velocities of the transfer portion of the transfer device 28B and the fixing portion of the fixing device 13 do not differ, and the same effect as the above example can be obtained.

[0022]

According to the invention of claim 1, when the transfer sheet is a resin film and the image to be formed is a color image, the speed varying means is operated by the control means according to the detection signal of the film detecting means. Since the process speed is slowed down after the development operation of a plurality of developing devices is completed and the transfer and fixing operations are executed at the slowed process speed, the linear speeds of the transfer portion by the transfer means and the fixing portion of the fixing means can be adjusted. They can be the same, and the need to increase the distance between the transfer section and the fixing section can be eliminated. As a result, it is possible to provide a small-sized color image forming apparatus in which the formed image on the resin film is excellent and the distance from the transfer portion to the fixing portion is shortened to the length in the conveying direction of the predetermined transfer sheet or less.

According to the second aspect of the present invention, by providing the switching means on the operation panel, the process speed can be easily switched manually, and the fixing means suitable for the transfer sheet can be realized by the switching means having an extremely simple structure. You can select the speed. According to the third aspect of the invention, the resin film can be automatically detected easily and surely by detecting the predetermined amount of transmitted light by the transmitted light amount detecting element, and the structure of the film detecting means can be simplified.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of a color image forming apparatus according to the present invention.

FIG. 2 is a partial front view showing the relationship between the distance from the transfer unit to the fixing unit and the length of the transfer sheet in the conveyance direction in one embodiment.

FIG. 3 is a conceptual diagram of a control system according to an embodiment.

FIG. 4 is a timing chart of each process of an example.

FIG. 5 is an overall configuration diagram of another embodiment of the color image forming apparatus according to the present invention.

[Explanation of symbols]

 1 Photoreceptor 2 Charging Device 3 Exposure Device 4 to 7 Developing Device 8 Transfer Device (Transfer Means) 12 Paper Feeding Section 13 Fixing Machine 20 Image Forming Means 21 Film Detecting Means 22 Speed Changing Means 28A First Charging 28B Second Charger 30 Image forming means 31 Intermediate transfer body 50 Control circuit (control means) P Transfer sheet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03G 15/01 114 B 7818-2H 15/20 107

Claims (3)

[Claims] 1. An image forming means in which a plurality of developing devices are arranged around a photoconductor, and a control means for controlling the image forming means.
A color image forming apparatus comprising: a toner image formed by repeating predetermined charging, exposing, and developing operations, transferring the image to a transfer sheet by a transfer unit, and fixing the image by a fixing device. A film in which the distance from the transfer portion to the fixing portion of the fixing device is set to be equal to or less than a predetermined transfer sheet length in the conveyance direction, and the image forming unit detects that the transfer sheet to be used is a resin film. A detection unit and a speed changing unit that changes the process speed of the entire process from charging to fixing and discharging, and the control unit is based on a detection signal of the film detection unit and a control state for the image forming unit. When the transfer sheet is a resin film and the image to be formed is a color image, the speed changing means is activated after the developing operation of the plurality of developing devices is completed. Allowed to slow down the process speed of the entire process, the color image forming apparatus, characterized in that to execute the transfer and fixing operation in slow-comb was process speed. 2. A color image forming apparatus according to claim 1, wherein a switching means for switching whether or not the speed varying means is operated is provided on an operation panel of the apparatus main body. 3. The film detecting means has a transmitted light amount detecting element in a sheet feeding portion of the apparatus main body, and is made of resin by detecting a predetermined transmitted light amount with respect to a sheet in the sheet feeding portion by the transmitted light amount detecting element. The color image forming apparatus according to claim 1, wherein a film is detected.