JPH0429176A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the fogging of an image on a transfer sheet by irradiating the outer periphery of a photosensitive drum after toner is transferred by means of a lamp provided on a second fixing part. CONSTITUTION:The fixing part 35 (the second fixing part) is disposed on the upper part of a driving roller 4, in other words, on the upper part of a belt 3 before the transfer sheet 17 is separated from the belt 3, and a toner image on the transfer sheet 17 being carried by the belt 3 is preliminarily fixed with radiation heat. In the fixing part 35. for instance, a tungsten halogen quartz lamp 36 is used as a radiation heat source 36, and the toner image on the transfer sheet 17 is fixed (preliminary fixing) at comparatively gentle speed by accepting the radiation heat from the halogen lamp 36. Thus, the occurrence of the fogging of the image on the transfer sheet 17 after main fixing is carried out, is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is characterized in that a belt is brought into close contact with the outer peripheral surface of a photoreceptor drum on which an electrostatic latent image is formed, and the heald is moved in synchronization with the rotation of the photoreceptor drum. The present invention relates to an image forming apparatus that transfers a toner image on the outer peripheral surface of a photoreceptor drum to a transfer sheet that passes through a contact portion of the belt by running the belt.

[Prior art]

FIG. 2 shows the main parts of a copying machine which is an example of the conventional color image forming apparatus as described above. The copying machine 1' is disclosed in, for example, Japanese Patent Laid-Open No. 63-83774.

In this copying machine 1', an endless belt 3' is disposed near the outer peripheral surface of the photosensitive drum 2.

This belt 3' is connected to drive roller 32. intermediate roller 12,
It is wound around a driven roller 33 and runs in circles between the respective rollers. The belt 3' is brought into close contact with a part of the outer peripheral surface of the photoreceptor drum 2 by an intermediate roller 12, and runs in synchronization with the rotation of the photoreceptor drum 2.

Further, a transfer charger 9 is disposed below the belt 3' in close contact with the photosensitive drum 2.

In order to prevent separation and charging that occurs when the transfer paper 17 separates from the belt 3' after transfer, a static elimination charger 31 is disposed above the end of the belt 3' on the fixing section 5' side. That is, during the static elimination charge 31, at least the amount of charge that can separate the transfer paper 17 from the belt 3' is reduced to the transfer paper 17.
It is configured to give

In such a copying machine 1', for example, when an electrostatic latent image is formed on the outer peripheral surface of the photoreceptor drum 2 by a predetermined image forming process, a toner image corresponding to this electrostatic latent image is developed by the developing section 30. be converted into Then, the transfer paper 17 conveyed by the pair of registration rollers 13 is transferred to the photosensitive drum 2.
When the toner passes through the contact area between the toner and the belt 3', a positive charge is applied via the belt 3' by the discharge of the transfer charger 9, and a toner image made of negatively charged toner is transferred to the transfer surface. . As a result, the toner on the transfer paper 17 and the belt 3' are electrostatically charged in a stable state, so that the transfer paper 17 is electrostatically attracted to the belt 3' and transferred to the fixing section 3'. ’. When separating the transfer paper 17 and the belt 3' which are in an electrostatically stable state, the static elimination charger 31
is transcription 1! Discharge is performed toward E17, and the above transfer IE1
It is designed to provide enough charge to eliminate the separation charge that occurs when the belt 7 is separated from the belt 3'.

This prevents so-called image dust, in which some toner is scattered during separation charging and is fixed as is.

In this manner, in the above-described copying machine 1', the transfer paper 17 and the photosensitive drum 2 are brought into close contact with each other during image transfer, so that the toner image is reliably transferred onto the transfer paper 17. As a result, it is possible to obtain a copy image with less image deviation from a predetermined position, and therefore it is often used in color copying machines that perform overlapping copies several times for each color.

[Problem to be solved by the invention]

However, in the conventional copying machine 1', the resistance of the transfer paper 17 changes depending on the type of transfer paper 17 and the environment (humidity, etc.) at the time, or the charge wire of the static elimination charger 31 deteriorates over time, causing the transfer to fail. Since the amount of charge applied to the IE 17 changes gradually, it is actually extremely difficult to grasp all of these various changes and control them using the static elimination charger 31. Therefore, the amount of electric charge given to the transfer paper 17 from the static elimination charger 31 is set based on the resistance value of the transfer paper 17 used for boat fishing, and also the charge wire is subject to deterioration over time. are often not taken into account.

Therefore, the above-mentioned copying machine 1' was insufficient in preventing image dust in the copied image finally obtained on the transfer paper 17 after fixing.

Therefore, an object of the present invention is to fix the toner image on the transfer sheet before the transfer sheet is separated from the belt, thereby making it possible to prevent the image from becoming dusty on the transfer sheet, and at the same time to fix the toner image on the transfer sheet before the transfer sheet leaves the belt. It is an object of the present invention to provide an image forming apparatus that can perform subsequent static elimination on the outer peripheral surface of a drum.

[Means to solve the problem]

In order to achieve the above object, the main means adopted by the present invention is to bring a belt into close contact with the outer peripheral surface of the photoreceptor drum on which an electrostatic latent image is formed, and to synchronize with the rotation of the photoreceptor drum. By running the belt, the toner image on the outer circumferential surface of the photoreceptor drum is transferred to the transfer sheet passing through the contact portion of the belt, and a first fixing section is placed on the transport path of the transfer sheet after it leaves the belt. In the image forming apparatus, a second fixing section including a lamp is disposed between a close contact portion of the belt and a portion where the transfer sheet leaves the belt, and the transfer sheet is conveyed by the belt. This image forming apparatus fixes a toner image on a certain transfer sheet and irradiates the outer circumferential surface of the photoreceptor drum with the lamp after the toner has been transferred.

[Effect]

According to the present invention, between the close contact portion of the belt where image transfer is performed and the portion where the transfer sheet leaves the belt, the lamp of the second fixing portion fixes the toner image on the transfer sheet by radiant heat, for example. Since pre-fixing is performed, when the transfer sheet is separated from the belt, the toner will not be scattered even if separation charge occurs on the transfer sheet. For example, main fixing is performed by the first fixing unit. Therefore, image dusting on the transfer sheet after main fixing can be prevented.

Furthermore, since the lamp of the second fixing section irradiates the outer peripheral surface of the photoreceptor drum after toner transfer at the same time as fixing, the outer peripheral surface is neutralized by a photoconductive phenomenon.

〔Example〕

Hereinafter, embodiments embodying the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.

In addition, the following example is an example embodying the present invention,
It is not intended to limit the technical scope of the present invention.

Here, FIG. 1 is a block diagram of the main parts of a copying machine according to an embodiment of the present invention.

Further, the same reference numerals are used for elements common to the conventional copying machine 1' shown in FIG. 2, and detailed explanation thereof will be omitted.

As shown in FIG. 1, the copying machine 1 according to this embodiment has a drive roller 4. Driven roller 10. Intermediate rollers (1) 2 are provided, and a belt 3 is wound around each of them. This belt 3 is stretched by the intermediate rollers 11 and 12 and is stretched around the photosensitive drum 2.
The photoreceptor drum 2 is in close contact with a part of the outer peripheral surface of the photoreceptor drum 2, and rotates between the rollers 4, 10, 12, and 11 in synchronization with the rotation of the photoreceptor drum 2 by rotation of the drive roller 4. A transfer charger 9 is provided below the belt 3 in close contact with the photosensitive drum 2.

Further, the belt 3 is connected to the driven roller 10. It is electrically grounded via intermediate rollers 11.12.

The drive roller 4 is made of metal or conductive rubber,
It is connected to a drive source (not shown) so that power can be transmitted.

The fixing section 5 (first fixing section) fixes the toner image on the transfer paper 17 as a transfer sheet.
is provided on the conveyance path of the transfer paper 17 after it is separated from the belt 3, that is, on the downstream side of the guide plate 14 in the conveyance direction (arrow D). In this fixing section 5, heat rollers 7 in the form of a cylindrical roll are disposed above the pressure roller 22 with their axes aligned in the same direction, and the transfer paper 17 is brought into pressure contact with the pressure roller 22. ing. A halogen lamp 8 is disposed within the cylinder of the heat roller rough approximately at its axis, and is configured to heat the heat roller 7 to a temperature necessary for fixing the toner. The heat roller 7 is made of fluorine resin (PTFE) on the surface of the aluminum tube, as in the past.
, PFA, etc.) is used.

A cleaning section 44 for cleaning the surface of the belt 3 is disposed downstream of the belt 3 from which the transfer paper 17 has been separated in the belt running direction. The cleaning section 44 includes a cleaning blade 15 that comes into close contact with the surface of the belt 3 and scrapes off dust and the like adhering to the surface, and a collection box 16 that stores the scraped dust and the like.

The belt 3 has a volume resistivity of 106 to 10 Ω.
・cm, a surface layer made of a semiconductor material with a thickness of 40 μm or less, and a base layer made of a semiconductor material with a volume resistivity of 10 Ω·cm or more and a thickness of 40 μm or less. As a specific example of this heald 3, the surface layer is a carbon-containing fluorine coating layer, and the base layer is a polyimide film layer. The belts conventionally used in this type of image forming apparatus are made of, for example, urethane rubber or chloroprene rubber, and their properties such as thermal decomposition temperature and coefficient of linear expansion are similar to those using polyimide as the base layer. Because it is inferior to a belt, the fixing section 3
However, if the belt 3 having the structure of this embodiment as described above is used, the above-mentioned thermal problems can be solved. , stable fixing can be performed using this belt 3.

In the apparatus of this embodiment, a fixing section 35 (second fixing section) is disposed above the drive roller 4, that is, above the belt g before the transfer paper 17 is separated from the belt 3.
The toner image on the transfer paper 17 that is being transported is preliminarily fixed by radiant heat.

The fixing unit 35 uses, for example, a tungsten halogen quartz lamp 36 (hereinafter referred to as a halogen lamp) as a radiant heat source, and a lamp cover 37 having an occluded circular shape facing downward in side view is disposed near the outer periphery of the halogen lamp 36. ing.

A light projecting slit 38 is formed on the photosensitive drum 2 side of the lamp cover 37 so as to be long and open in the axial direction of the photosensitive drum 2. Therefore, the light projection slit 3
The irradiation light from the halogen lamp 36 projected through the photosensitive drum 2 is applied to the image forming area of the outer peripheral surface of the photosensitive drum 2 on the downstream side in the rotational direction of the portion in close contact with the belt 3, for example, the area indicated by l in the figure. irradiated.

Therefore, in the copying machine 1 configured as described above, the first
As shown in the figure, when the transfer paper 17 is conveyed by the pair of registration rollers 13 to the contact portion between the photoreceptor drum 2 and the belt 3, the transfer IL 17 is discharged from the transfer charger 9 while being in close contact with the photoreceptor drum 2. The toner image formed on the outer peripheral surface of the photoreceptor drum 2 is transferred. At this time, the transfer paper 17 is given a positive charge to attract the negatively applied toner, and is transported in the transport direction (arrow D) while being electrostatically attracted to the belt surface.

Then, the transfer paper 17 is guided to a light irradiation position by the halogen lamp 36 on the belt 3, and
6, the toner image on the transfer paper 17 is relatively gently fixed (prefixed) on the transfer paper 17, and the transfer paper 17 with the toner image fixed by this fixing section 35 is , and are conveyed onto the guide plate 14.

Incidentally, since the apparatus of this embodiment is not equipped with a static elimination charge for preventing the above-mentioned separation charge, when the transfer paper 17 separates from the belt 3 in this area, the above-mentioned negative separation charge naturally occurs on the transfer. Print on paper 17.

However, at this time, since the toner image on the transfer paper 17 has already been prefixed by the fixing section 35, these negatively charged toners do not scatter on the transfer 1E17. The transfer paper 17 conveyed to the guide plate 14 undergoes main fixing of the toner image by the subsequent fixing section 5.

Therefore, it is possible to prevent image dust from occurring on the transfer paper 17 after main fixing.

At the same time, when the image forming area on the outer peripheral surface of the photosensitive drum 2 reaches the position indicated by l in the figure after the toner image transfer, the irradiation light from the fixing section 35 is irradiated to the position. As a result, static electricity is removed from the outer circumferential surface of the photosensitive drum 2 by a photoconductive phenomenon, and the cleaning effect of a subsequent cleaning section (not shown) for cleaning this outer circumferential surface is promoted.

In this manner, the apparatus of this embodiment completes the preliminary fixing of the toner image before the transfer & IE 17 is separated from the belt 3, so it is possible to solve the problem of image dust caused by separation charging. This eliminates the need for the above-mentioned measures to prevent image dust, ie, the static elimination charger 31 in the prior art.

Further, the above-described fixing section 35 can be provided at an appropriate location between the part of the belt 3 that is in close contact with the photoreceptor drum 2 and the part where the transfer paper 17 can be placed on the belt 3. can. For example, it may be the position of the fixing section 35 indicated by the two-dot chain line in the figure.

Furthermore, in such a copying machine, a part of the fixing process is performed by the fixing section 35, so the subsequent fixing section 5 can have a simple configuration, and the pressure for main fixing can be lowered. Furthermore, the copying machine 1 does not strongly fix the toner image in a single fixing process, but rather allows the melted toner to soak into the transfer paper 17 in advance through relatively gentle heating by the fixing section 35. During fixing, for example, character images, etc., do not suffer from image distortion.Furthermore, since the pressure during main fixing can be lowered, the image distortion is further prevented, resulting in clearer copied images. can be obtained.

Since the fixing section 35 removes the charge from the photoreceptor drum 2 after the toner image has been transferred, the capacity of a charge removal charge or the like to be provided near the photoreceptor drum 2 may be small.

〔Effect of the invention〕

According to the present invention, a belt is brought into close contact with the outer peripheral surface of the photoreceptor drum on which an electrostatic latent image is formed, and the belt is run in synchronization with the rotation of the photoreceptor drum to pass through the contact portion of the belt. In an image forming apparatus that transfers a toner image on the outer circumferential surface of a photoreceptor drum onto a transfer sheet and includes a first fixing section in a conveyance path of the transfer sheet after it is separated from the belt, the contact portion of the belt and the first fixing section are provided. a second section comprising a lamp between the transfer sheet and the portion where the transfer sheet leaves the belt;
A fixing section is provided to fix the toner image on the transfer sheet being conveyed by the belt, and the lamp irradiates the outer peripheral surface of the photoreceptor drum after the toner has been transferred. A forming device is provided. Thereby, the toner image on the transfer sheet can be preliminarily fixed, for example, before the transfer sheet is separated from the belt, thereby making it possible to prevent image dust on the transfer sheet. Moreover, static electricity can be removed from the outer peripheral surface of the photoreceptor drum at the same time after the toner image is transferred.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of main parts of a copying machine according to an embodiment of the present invention;
FIG. 2 is a schematic diagram showing the main parts of a conventional copying machine, which is an example of the background of the present invention. [Explanation of symbols] 1.1'... Copying machine 2... Photosensitive drum 3.3'... Belt 5.35.5'... Fixing section 36... Halogen lamp 38... floodlight slit

Claims (1)

[Claims] (1) A belt is brought into close contact with the outer peripheral surface of the photoreceptor drum on which an electrostatic latent image is formed, and by running the belt in synchronization with the rotation of the photoreceptor drum, the transfer sheet that passes through the contact portion of the belt is In an image forming apparatus that transfers a toner image on the outer circumferential surface of a photoreceptor drum and includes a first fixing section in a conveying path of the transfer sheet after it is separated from the belt, the contact portion of the belt and the transfer sheet are connected to each other. A second fixing section including a lamp is disposed between the part separated from the belt, and fixes the toner image on the transfer sheet being conveyed by the belt, and is exposed to light after the toner is transferred by the lamp. An image forming apparatus characterized in that the outer peripheral surface of a body drum is irradiated.