JPH07319297A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an excellent reproduced image by dealing with the transfer material of various size without being affected by a variation of a transfer material size, and preventing deterioration of the image due to the electric charge history to an image carrier caused by the striping-off discharge. CONSTITUTION:The image forming device is at least provided with the image carrier 1, a developing device 7, a transfer material carrying device 2, a transfer material transporting device 11 for transporting the transfer material 4, a transfer device 12 for transferring the toner image formed on the image carrier 1 to the transfer material and a transfer power source 25 for applying the transfer voltage to the transfer device 12, and more provided with a transfer material trailing end detecting device 3, disposed on the upstream side of the transfer device 12, for detecting the trailing end of the transfer material 4 transported through the transfer material transporting device 11, and a controller 26 for controlling the transfer power source 25 so as to be turned off before the trailing end of the transfer material 4 passes through the transfer device 12 based on the detecting signal of the transfer material trailing end detecting device 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to at least a transfer device for transferring a toner image formed on an image carrier onto a transfer material carried on a transfer material carrier. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine or a printer is provided with an image carrier and a toner developing device, and a transfer material carrier and a transfer device, and the electrostatic latent image formed on the image carrier is developed with the toner. Then, this is transferred to a transfer material (hereinafter, also simply referred to as a sheet) carried on the transfer material carrier by a transfer device to obtain a copy on which a desired image is formed.

The transfer material is carried by a transfer material carrying device by electrostatic attraction or mechanical holding, and a toner is formed on the image carrying device by applying a transfer voltage to the transfer device at a position facing the image carrying body. The image is transferred to the transfer material. In the case of forming a color image, a toner image of a plurality of colors is sequentially formed on the image carrier, and a multicolor image is formed by repeating the transfer operation of the transfer material carried on the transfer material carrier a plurality of times. Get a copy.

As a disclosure of the prior art relating to this type of image forming apparatus, for example, Japanese Patent Laid-Open No. 4-510 is known.
69, JP 4-62580 A, or JP 4-62581 A.

[0005]

In the image forming apparatus as described above, a peeling charger is provided downstream of the transfer device,
After the transfer of the toner image to the transfer material, the peeling charger is driven to remove the electric charge, and the transfer material is peeled from the transfer material carrying device by using the peeling device (nail) and conveyed to the subsequent fixing device. During transfer, the charge history remains on the image carrier due to peeling discharge caused by the accumulation of charges at the rear end of the transfer material in the same area, and the charge uniformity of the image carrier is lost, resulting in a uniform image. There is a problem that cannot be obtained.

In order to solve the above-mentioned problems, in the invention disclosed in Japanese Patent Laid-Open No. 4-51069, a low resistance portion of a transfer improper area is provided in the transfer material rear end area of the transfer material carrier. It is difficult to deal with various transfer material sizes, and it is necessary to provide a large non-transferable area as described above in order to adequately deal with variations in transfer material size, etc., and the transferable area of the image carrier is reduced. There is a drawback that it ends up.

Further, in JP-A-4-62580 or JP-A-4-62581, the transfer material rear end position of the image bearing member is pre-charged or charged,
Although the occurrence of the above-mentioned peeling discharge is suppressed, it is difficult to perform the above-mentioned charge removal or charging while securing a large transferable area. The object of the present invention is to solve the above-mentioned problems of the prior art, to be able to deal with transfer materials of various sizes, and without being affected by variations in the transfer material size, to the image carrier caused by peeling discharge. An object of the present invention is to provide an image forming apparatus capable of preventing deterioration of image quality due to adhesion of toner and obtaining a good reproduced image.

[0008]

In order to achieve the above object, the present invention provides a transfer material trailing edge detecting device on the upstream side of an image transfer portion of a transfer device, and turns off the transfer device based on the detection signal. By controlling the timing, it is possible to obtain a copy of good image quality without leaving a charge history on the image carrier due to peeling discharge.

That is, the invention described in claim 1 is as shown in FIG.
As shown in FIG. 1, the image carrier 1, the developing device 7 for developing the electrostatic latent image formed on the image carrier 1 with toner, the transfer material carrier device 2 for carrying the transfer material, and the transfer material carrier device 2 At least a transfer material conveying device 11 for conveying the transfer material 4, a transfer device 12 for transferring the toner image formed on the image carrier 1 onto the transfer material, and a transfer power supply 25 for applying a transfer voltage to the transfer device. An image forming apparatus provided with the transfer device 12
And a detection signal of the transfer material rear end detection device 3 for detecting the rear end of the transfer material 4 conveyed through the transfer material conveyance device 11 on the upstream side of the transfer material. Based on the above, a control device 26 for controlling the transfer power supply 25 is provided so that the rear end of the transfer material 4 is turned off before passing through the transfer device 12.

Further, the invention according to claim 2 has an image carrier, a multicolor developing device for sequentially developing an electrostatic latent image formed on the image carrier with multicolor toners, and a transfer material. A transfer material carrying device, a transfer material carrying device for carrying the transfer material to the transfer material carrying device, a transfer device for sequentially transferring the multicolor toner images formed on the image carrier to the transfer material, and a transfer device for transferring to the transfer device. In an image forming apparatus including at least a transfer power source for applying a voltage, a transfer material rear end that is provided on the upstream side of the transfer device and detects the trailing end of the transfer material conveyed through the transfer material conveying device. On the basis of the detection signal in the transfer cycle of each color of the end detection device and the transfer material rear end detection device, the transfer power source is turned off so that the rear end of the transfer material is turned off before the rear end of the transfer material passes through the transfer device when transferring the color. Specially equipped with a control device to control To.

According to a third aspect of the present invention, an image carrier, a multicolor developing device for sequentially developing an electrostatic latent image formed on the image carrier with multicolor toners, and a transfer material are carried. A transfer material carrying device, a transfer material carrying device for carrying the transfer material to the transfer material carrying device, a transfer device for sequentially transferring the multicolor toner images formed on the image carrier to the transfer material, and a transfer device for transferring to the transfer device. In an image forming apparatus including at least a transfer power source for applying a voltage and a control device, the image forming apparatus is provided on the upstream side of the transfer device to detect the trailing end of the transfer material conveyed through the transfer material conveying device. The transfer material trailing edge detection device and the transfer material trailing edge detection device are turned off before the trailing edge of the transfer material passes through the transfer device during the transfer of the first color based on the detection signal in the first color transfer cycle. When the transfer power source is controlled like Based on the detection signal in the first color transfer cycle of the transfer material rear end detection device, the transfer power supply is turned off so that the rear end of the transfer material in the transfer cycles of the second and subsequent colors is turned off before passing through the transfer device. The control device for controlling is provided.

In addition, in the one having a transfer material detecting device for detecting that the transfer material is conveyed to the transfer material carrying member, this transfer material detecting device can be used as the transfer material rear end detecting device. . Further, the transfer material detecting device may be configured to also serve as a transfer material presence / absence detecting means.

[0013]

In the structure according to the above-mentioned claim 1, the electrostatic latent image is formed on the image carrier 1 by the modulated laser beam, and the developing device 7 develops the electrostatic latent image by toner. The transfer material transport device 12 includes a transfer material carrying device 2 for carrying the transfer material and a transfer material 4
The toner image formed on the image carrier 1 is transferred to the transfer material by the transfer device 13. The transfer power supply 25 applies a transfer voltage to the transfer device.

The transfer material trailing edge detection device 3 is the transfer device 1 described above.
3 is provided on the upstream side of 3 to detect the rear end of the transfer material 4 conveyed through the transfer material conveying device 12. Controller 26
Controls the transfer power source 25 based on the detection signal of the transfer material rear end detection device 3 so that the transfer material 4 is turned off before the rear end of the transfer material 4 passes through the transfer device 13.

Further, in the structure described in claim 2, a multicolor electrostatic latent image is sequentially formed on the image carrier by the modulated laser light, and the multicolor developing device forms the electrostatic latent image of each color. The toner is sequentially developed with toner. The transfer material conveying device conveys the transfer material to a transfer material carrying device that carries the transfer material, and sequentially transfers the toner images formed on the image carrier by the transfer device to the toner images of respective colors sequentially formed on the image carrier. Transfer to material. The transfer power source applies a transfer voltage to the transfer device.

The transfer material trailing edge detecting device is provided on the upstream side of the transfer device and detects the trailing edge of the transfer material conveyed through the transfer material conveying device. The control device controls the transfer power source such that the transfer material is turned off before the rear end of the transfer material passes through the transfer device at the time of transfer of the color based on the detection signal in the transfer cycle of each color of the transfer material rear end detection device. To do.

According to the third aspect of the invention, a multicolor electrostatic latent image is sequentially formed on the image carrier by the modulated laser light, and the multicolor developing device forms the electrostatic latent image into toner of each color. The toner is sequentially developed with. The transfer material conveying device conveys the transfer material to a transfer material carrying device that carries the transfer material, and sequentially transfers the toner images formed on the image carrier by the transfer device to the toner images of respective colors sequentially formed on the image carrier. Transfer to material. The transfer power source is
A transfer voltage is applied to the transfer device.

The transfer material trailing edge detecting device is provided on the upstream side of the transfer device and detects the trailing edge of the transfer material conveyed through the transfer material conveying device. The control device, based on the detection signal in the transfer cycle of the first color of the transfer material rear end detection device, turns off the transfer power source such that the rear end of the transfer material is turned off before passing through the transfer device during the transfer of the first color. In addition to controlling the above, the transfer material rear end detection device is turned off before the rear end of the transfer material in the transfer cycles of the second and subsequent colors is turned off based on the detection signal in the transfer cycle of the first color. Controls the transfer power supply.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 is a schematic view of a color image forming apparatus for explaining the configuration of an embodiment of the image forming apparatus according to the present invention, in which 1 is a photosensitive drum as an image carrier and 2 is a transfer drum as a transfer material carrier. Reference numeral 3 is a transfer material rear end detection device including a reflection type optical sensor, 4 is a transfer material (hereinafter also referred to as a sheet), 5 is a laser writing unit, 6 is a charger, and 7 is a charger.
Is a rotary developing unit as a developing device, 7y is a yellow developing device, 7m is a magenta developing device, 7c is a cyan developing device, 7k is a black developing device, 8 is a transfer film for adsorbing and holding a sheet, 9 is a resist roller, Reference numeral 10 is an adsorption charger, 11 is a transfer material feeding chute, 12 is a transfer charger which is a transfer device, 13 is a photoconductor drum cleaning device, 14 is a peeling charger, 15 is a peeling claw, 16 is a static eliminator,
17 is a transfer sheet cleaning device, 18 is a fixing device, 1
9 is a discharge roller, 20 is a discharge tray, 25 is a transfer power source,
Reference numeral 26 is a control device.

In the copying machine shown in FIG. 1, a sheet 8 is formed by carrying a yellow, magenta, cyan, and black single-color toner image formed every one rotation of the photosensitive drum 1 on a transfer film 8 of a transfer drum 2. The multi-color image is formed by sequentially transferring to the transfer material 4 adsorbed above. The color image forming operation in this image forming apparatus is as follows. The control of this device is performed by the control device 26, and the on / off control of the transfer power supply for applying the transfer voltage to the transfer charger 12 is also executed by this control device 26.

First, image information read by an optical scanning system such as a scanner is processed into each monochromatic component by an image processing means (not shown), and the information of one color is laser-written with a laser light source, a polygon mirror, a lens and the like. Supply to means 5. The laser writing means 5 exposes the photosensitive drum 01 to form an electrostatic latent image. For example, if the image information is a yellow component, the photosensitive drum 1 uniformly charged by the charger 6 has a yellow component. The non-existing areas are exposed and the electrostatic latent image corresponds to yellow in the color image.

The electrostatic latent image is developed by the yellow developing device 7y,
The rotary developing unit 7 having the magenta developing unit 7m, the cyan developing unit 7c, and the black developing unit 7k on the inner circumference sequentially performs the above-mentioned yellow toner image to the yellow developing unit 7y.
To develop toner. On the other hand, the sheet 4 is the registration roller 9
The toner is adsorbed to the transfer film 8 carried on the transfer drum 2 through the transfer material feeding chute 11 at a predetermined timing in synchronization with the formation of the toner image by. This adsorption is performed by the electrostatic charge generated by the adsorption charger 10.

At the position of the transfer charger 12, the toner image formed on the photosensitive drum 01 is transferred to the sheet 4 adsorbed on the transfer film 8. At this time, the sheet trailing edge detection device 3 installed upstream of the transfer charging device 12 detects the trailing edge of the sheet before the transfer operation of the toner image ends. This detection signal is given to the control device 26, and after the transfer of the toner image is completed and the rear end of the sheet 4 is transferred to the transfer charger 1.
Before reaching 2, the transfer power supply 25 is controlled to transfer the toner image, and the transfer voltage applied to the transfer charger 12 is turned off.

Thereafter, the magenta, cyan, and black electrostatic latent images are developed and transferred in the same manner, and one transfer material 0 is transferred.
4, images of yellow, magenta, cyan, and black are superimposed. The sheet 4 on which the transfer of the toner image of the required color is completed is peeled from the transfer film 8 by the peeling charger 14 and the peeling claw 15, is heat-fixed by the fixing device 18, and is then discharged to the discharge tray 20 by the discharge roller 19. .

The photoconductor cleaning device 13 removes the toner remaining on the photoconductor surface after transferring the toner images of the respective colors, and the transfer film 8 similarly removes the toner images after the transfer of the toner images of the respective colors. After the electric charge is removed by the electric device 16, the transfer sheet cleaning device 17 removes the toner attached during the transfer. In this way, a full color image copy is obtained.

FIG. 3 is a main part operation waveform diagram for explaining the operation of the image forming apparatus according to the present invention. FIG. 3A is a reference signal output in synchronization with the rotation of the photosensitive drum, and FIG.
Is a sheet detection signal, (c) is a sheet trailing edge detection signal,
(D) is a transfer voltage. In the figure, the reference signal (a) is output at a rate of one pulse for one rotation of the photosensitive drum, and serves as a reference when the transfer voltage to the transfer charger is turned on.

The sheet 4 is transferred from the sheet conveying device 11 by a registration roller 9 at a timing.
And is conveyed toward the transfer charger 12. When the sheet 4 reaches the position of the transfer charger 12, the above-mentioned reference signal (a)
When the time t ₀ is counted from the transfer voltage to the transfer charger 12 is turned on. As a result, the transfer of the toner image of the first color from the photosensitive drum 1 to the sheet 4 is started.

The supply standard of the sheet 4 is its tip,
The trailing edge of the sheet changes due to variations in the size of the sheet that is supplied. Therefore, the on-point of the transfer voltage to the transfer charger 12 is set to t ₀ time after the reference signal (a). Before the transfer operation is completed, the sheet trailing edge detection device 3 detects the trailing edge of the sheet 4. Detection of the rear edge of the seat
As shown in (b), it is detected at a predetermined threshold value L, and the transfer voltage to the transfer charger 12 is turned off after t ₁ hours from the time when this signal is detected.

The transfer of the toner image of the second color is similarly started, and the transfer voltage is turned off after t ₁ 'after the sheet trailing edge detection signal (c). The transfer time of the transfer voltage for the first color is t ₂ hours after the reference signal, and the transfer time of the transfer voltage for the second color is t ₂ ′ time after the reference signal. The above is to detect the trailing edge of the sheet for each transfer of each toner image, and is applied not only to the formation of a multicolor image but also to the case of forming a single color image on each sheet.

When a multicolor toner image is transferred onto the same sheet, the change in the sheet size can be ignored after the second rotation of the photosensitive drum, so that the reference signal ( The time t ₂ from a) to the transfer voltage OFF time can also be used as the transfer voltage OFF time for the second and subsequent colors. FIG. 4 is a flow chart for explaining an operation example of the control device for explaining the operation of the image forming apparatus according to the present invention.

In the figure, when the image forming apparatus starts an image forming operation, first, a toner image is formed on the photosensitive drum (S-1). At this time, a reference signal is generated as the photosensitive drum rotates. After the toner image is formed, the old material of the transfer material (sheet) is performed (S-2), and when the sheet enters the installation position in the transfer charger, the transfer voltage is changed after counting t ₀ time from the reference signal. Turned on (S
-3).

When the transfer operation progresses and the sheet trailing edge detection device detects the sheet trailing edge, the transfer voltage is turned off after a count of t ₁ hours (S-5) from this detection time (S-).
6). When the transfer of the required toner image is not completed (N of S-7), the process returns to S-1 and the same operation is repeated, and when the transfer of all toner images is completed (Y of S-7). ,
The image forming operation ends.

FIG. 5 is a flow chart for explaining another operation example of the control device for explaining the operation of the image forming apparatus according to the present invention. In the figure, when the image forming apparatus starts the image forming operation, first, a toner image is formed on the photosensitive drum (S-11). At this time, a reference signal is generated as the photosensitive drum rotates.

After the formation of the toner image, the old material of the transfer material (sheet) is performed (S-12), and when the sheet enters the installation position in the transfer charger, after counting t ₀ time from the reference signal. The transfer voltage is turned on (S-13). If the transfer is the first color (Y of S-14), the sheet trailing edge detection device obtains the output of the sheet trailing edge detection signal (Y of S-15) as in the case of FIG. , T from this detection time
After counting for _one hour (S-16), the transfer voltage is turned off (S-17).

When the transfer of the required toner image is not completed (N of S-18), the process returns to S-1 and the same operation is repeated until S-13 and the transfer cycle of two or more colors is reached. (N in S-14), subjected to t ₂ counts from the reference signal (S-19), turns off the transfer voltage after t ₂ counts (S-17). If the transfer of the required toner image is not completed (N of S-18), the process returns to S-11 and the same operation is repeated, and when the transfer of all toner images is completed (Y of S-18). The image forming operation ends.

As described above, according to the above-described embodiment, various sizes of sheets can be dealt with, and the toner adheres to the image carrier due to the peeling discharge without being affected by the variation in sheet size. It is possible to provide an image forming apparatus capable of preventing deterioration of image quality and obtaining a good reproduced image.

[0037]

As described above, according to the present invention,
An image that can be applied to transfer materials of various sizes and that is not affected by variations in transfer material size and that prevents deterioration of image quality due to charge history on the image carrier due to peeling discharge and obtains a good reproduced image A forming device can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a basic configuration of the present invention.

FIG. 2 is a schematic diagram of a color image forming apparatus for explaining the configuration of an embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a main part operation waveform diagram for explaining the operation of the image forming apparatus according to the present invention.

FIG. 4 is a flowchart illustrating an operation example of a control device for explaining the operation of the image forming apparatus according to the present invention.

FIG. 5 is a flowchart illustrating another operation example of the control device for explaining the operation of the image forming apparatus according to the present invention.

[Explanation of symbols]

1 ... Image carrier (photosensitive drum), 2 ... Transfer material carrier (transfer drum), 3 ... Transfer material trailing edge detector (sheet trailing edge detector), 4 ... ..Transfer material (sheet), 5 ... Laser writing means, 6 ..., Charging device, 7 ... Developing device (rotary developing unit),
7y ... Yellow developing device, 7m ... Magenta developing device, 7c ... Cyan developing device, 7k ... Black developing device, 8 ... Transfer film for adsorbing and holding sheets , 9 ・ ・ ・ ・ Registration roller, 10 ・ ・ ・ ・ Suction charging device, 11 ・ ・ ・ ・ Transfer material feeding chute, 12 ・ ・
..Transfer device (transfer charger), 13 Photosensitive drum cleaning device, 14 ... Separation charger, 15
... Stripping claws, 16 ... static eliminator, 17 ... Transfer sheet cleaning device, 18 ... Fixing device, 19 ...
... Ejection rollers, 20 ... Ejection trays, 25 ...
..Transfer power supply, 26 ... Control device

Claims (3)

[Claims] 1. An image carrier, a developing device that develops an electrostatic latent image formed on the image carrier with toner, a transfer material carrier that carries a transfer material, and a transfer material is conveyed to the transfer material carrier. An image forming apparatus comprising at least a transfer material conveying device, a transfer device for transferring a toner image formed on an image carrier onto a transfer material, and a transfer power source for applying a transfer voltage to the transfer device. A transfer material trailing edge detecting device for detecting the trailing edge of the transfer material conveyed through the transfer material conveying device to the upstream side, and the transfer material trailing edge detecting device based on the detection signal of the transfer material trailing edge detecting device. An image forming apparatus comprising a control device for controlling the transfer power source so that the transfer power is turned off before the end passes through the transfer device. 2. An image carrier, a multicolor developing device for sequentially developing an electrostatic latent image formed on the image carrier with multicolor toners, a transfer material carrier device for carrying a transfer material, and a transfer material carrier. A transfer material conveying device that conveys the transfer material to the device, and a transfer device that sequentially transfers the multicolor toner images formed on the image carrier to the transfer material,
An image forming apparatus having at least a transfer power supply for applying a transfer voltage to the transfer device, wherein the transfer device is provided on the upstream side of the transfer device and detects the rear end of the transfer material conveyed through the transfer material conveying device. And a transfer material trailing edge detection device for turning off the transfer material trailing edge detection device before the trailing edge of the transfer material passes through the transfer device at the time of transferring the color based on the detection signal in the transfer cycle of each color. An image forming apparatus comprising: a control device for controlling the transfer power source. 3. An image carrier, a multicolor developing device for sequentially developing an electrostatic latent image formed on the image carrier with multicolor toners, a transfer material carrier device for carrying a transfer material, and a transfer material carrier. A transfer material conveying device that conveys the transfer material to the device, and a transfer device that sequentially transfers the multicolor toner images formed on the image carrier to the transfer material,
An image forming apparatus having at least a transfer power supply for applying a transfer voltage to the transfer device, wherein the transfer device is provided on the upstream side of the transfer device and detects the rear end of the transfer material conveyed through the transfer material conveying device. And a transfer material trailing edge detection device for performing the transfer material trailing edge detection device before the trailing edge of the transfer material passes through the transfer device during the transfer of the first color based on the detection signal in the first color transfer cycle. The transfer power source is controlled as if it is turned off.
Based on the detection signal in the transfer cycle of the first end of the transfer material rear end detection device, the transfer power source is controlled so that the rear end of the transfer material in the transfer cycles of the second and subsequent colors is turned off before passing through the transfer device. An image forming apparatus comprising a control device.