JP2003307952A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent wrapping around a fixing roller. <P>SOLUTION: Paper and belt are passed together after being attracted to a carrying belt when the paper is passed through a fixing part. Attracting to the carrying belt is carried out with a corona electrifying device. <P>COPYRIGHT: (C)2004,JPO

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, and more particularly to an image forming apparatus having a structure suitable for a color electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, a plurality of image forming sections are provided, toner images of different colors are formed in the respective image forming sections, and the toner images are sequentially superimposed and transferred onto the same recording material to form a color image. Various image forming apparatuses for forming have been proposed.

Under such circumstances, a multicolor electrophotographic color copying machine using an endless recording material carrying member is used for high speed recording.

An example of the color electrophotographic recording apparatus will be briefly described with reference to FIG. 7. First, second, third and fourth image forming sections Pa, Pb, Pc and Pd are provided in the apparatus. , Toner images of different colors are formed through the processes of latent image, development, and transfer.

The image forming portions Pa, Pb, Pc and Pd are respectively dedicated image carriers, in this example, the electrophotographic photosensitive drum 3.
a, 3b, 3c, 3d, and each photosensitive drum 3a, 3
Toner images of respective colors are formed on b, 3c, and 3d. A recording material carrier 130 (hereinafter referred to as a transfer belt 130) is installed adjacent to each of the photosensitive drums 3a, 3b, 3c, 3d, and a toner image of each color formed on each of the photosensitive drums 3a, 3b, 3c, 3d. Are transferred onto the recording material P carried on the transfer belt 130 and conveyed. Further, the recording material P on which the toner images of the respective colors are transferred is heated and pressed by the fixing unit 9 to fix the toner images, and then discharged as a recorded image to the outside of the apparatus.

Drum chargers 2a, 2b, 2c, 2d, are provided on the outer circumferences of the photosensitive drums 3a, 3b, 3c, 3d, respectively.
Potential sensors 113a, 113b, 113c, 113
d, developing devices 1a, 1b, 1c, 1d, transfer charger 24
a, 24b, 24c, 24d and cleaners 4a, 4
b, 4c, and 4d are provided, and a light source device and a polygon mirror 117 (not shown) are further installed in the upper part of the device.

Laser light emitted from a light source device is scanned by rotating a polygon mirror 117, a light flux of the scanning light is deflected by a reflection mirror, and is formed on a generatrix of the photosensitive drums 3a, 3b, 3c, 3d by an fθ lens. By converging and exposing, latent images corresponding to image signals are formed on the photosensitive drums 3a, 3b, 3c, 3d.

The developing devices 1a, 1b, 1c and 1d are filled with a predetermined amount of cyan, magenta, yellow and black toners as a developer by a supply device (not shown). The developing devices 1a, 1b, 1c, 1d develop the latent images on the photosensitive drums 3a, 3b, 3c, 3d, respectively, and visualize them as cyan toner images, magenta toner images, yellow toner images, and black toner images.

The recording material P is accommodated in the recording material cassette 10 and is then supplied onto the transfer belt 130 via a plurality of supporting rollers 68 and registration rollers 12 and is conveyed by the transfer belt 130 to the photosensitive drums 3a, 3b, 3c ,. 3d
It is sequentially sent to the transfer section that opposes.

The transfer belt 130 is made of a dielectric resin sheet such as a polyethylene terephthalate resin sheet (PET resin), a polyvinylidene fluoride resin sheet, or a polyurethane resin sheet. Either endless or non-vertical (seamless) belts are used.

When it is confirmed that the transfer belt 130 is rotated by the driving roller 13 and is in a predetermined position, the recording material P is transferred from the registration roller 12 to the transfer belt 13.
0, and the recording material P is conveyed toward the transfer portion of the first image forming portion Pa. At the same time, the image writing signal is turned on, and the first
An image is formed on the photosensitive drum 3a of the image forming portion Pa. Then, the transfer charger 24a applies an electric field or an electric charge at a transfer portion below the photosensitive drum 3a, so that the toner image of the first color formed on the photosensitive drum 3a is recorded on the recording material P.
Transcribed on.

As the transfer charger 24, a contact charger using a transfer charging member such as a blade, a roller or a brush is used.
Compared with the corona transfer method which has been conventionally used, the contact charger has advantages that the amount of ozone generated is small, it is resistant to temperature / humidity environment fluctuations, the size of the device is small, and the cost is easy. In addition, static elimination needles 7a to 7d may be provided for stabilizing transferability. The charge eliminating needles 7a to 7d are the transfer belt 13
Although it is not in contact with 0, it plays the role of discharging a part of the transfer current and letting it escape. With this configuration, it is possible to prevent discharge due to uneven charging after the photosensitive drum and the recording paper are separated.

Image formation and transfer in the second to fourth image forming portions Pb to Pd are performed in the same manner as in the first image forming portion Pa. Next, the recording material P on which the four color toner images have been transferred is removed from the end of the transfer belt 130 by removing the charge by the separation charger 32 at the downstream portion in the transport direction of the transfer belt 130 and attenuating the electrostatic attraction force. .

In particular, in a low humidity environment, the recording material also dries and its electric resistance increases, so that the electrostatic attraction force with the transfer belt increases and the effect of the separating charger increases. Normally, the separation charging device charges the recording material P in a state where the toner image is not fixed, and therefore a non-contact charging device is used.

The separated recording material P is conveyed to the fixing device 9 by the conveying section 62. The separation guide 64 stabilizes the tip behavior of the recording material P.

The fixing device 9 includes a fixing roller 51, a pressure roller 52, heat-resistant cleaning members 54 and 55 for cleaning each of them, roller heaters 56 and 57 installed in the rollers 51 and 52, and a fixing roller. An application roller 50 for applying a release agent oil such as dimethyl silicone oil to 51, a reservoir 53 of the oil, and a pressure roller 5.
2 and the thermistor 58 for detecting the temperature of the surface and controlling the fixing temperature.

The recording material P on which the four color toner images have been transferred is
The toner image is mixed and fixed on the recording material P by fixing, and a full-color copy image is formed.
It is discharged to 3.

Photosensitive drums 3a, 3b and 3 after transfer is completed
c, 3d are cleaners 4a, 4b, 4c,
The residual toner after transfer is cleaned and removed by 4d, and the preparation for the next latent image formation is continued. Transfer belt 1
Toner and other foreign matter remaining on the surface 30 are wiped off by bringing the cleaning blade 20 and the cleaning web (nonwoven fabric) 19 into contact with the surface of the transfer belt 130.

In the cleaner section, the electric charge of the transfer belt remaining after the recording material is separated is removed. Therefore, the discharging roller 21 and the pressing roller 22 are grounded.

Further, not only the high voltage of about 2 to 4 kV is applied to the charge eliminating roller 21 to remove the charge on the transfer belt, but also the charge is applied to the opposite potential so that the potential of the transfer belt at the end of the transfer becomes small. is there.

[0021]

In the above-described conventional example, when an image is formed on the entire surface of the recording material, the recording material winds around the fixing roller 51. This is because the adhesion of the toner to the fixing roller 51 is larger than that of the recording material.

Therefore, it is necessary to set a margin of about 2 to 5 mm at the end of the recording material without forming an image on the entire surface.

However, the image information that can be recorded is reduced by the amount of the blank space, and when used as a copying machine, there is a problem that the image information is lost when the entire image is copied. Therefore, an image may be formed on a recording material larger than the intended size of the recording material, and then the margin portion may be cut, but the number of steps is increased.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a full-color image forming apparatus which does not cause winding of the fixing roller regardless of the size of the margin.

[0025]

SUMMARY OF THE INVENTION The present invention comprises an image forming section,
In the image forming apparatus including a fixing unit, a conveying unit that conveys the recording material P from the image forming unit through the fixing unit, and an adsorption unit that adsorbs the recording material P to the conveyance manual throwing unit, The hand stroke is provided between the image forming unit and the fixing unit,
In addition, the end portion of the transport hand striker is provided after the exit of the fixing unit, and the recording material P after the image fixing is released from the transport unit at a position after the exit of the fixing unit. It is characterized by

In this case, the carrying means is constructed as a carrying device having an endless belt-like carrying body supported by a plurality of rollers.

Further, the carrying means is constituted as a carrying device having an endless belt-like carrying body, and the supporting roller of the carrying body is provided at a position after the exit of the fixing section.

Further, the supporting roller of the carrier may also serve as the pressure roller of the fixing section.

Further, the adsorption means is a corona charger.

In this case, the output current of the corona charger is preferably opposite in polarity to the toner.

As an invention close to the present invention, for example, Japanese Patent Laid-Open No. 5-313531 can be cited. That is, an invention is disclosed in which, in a multiple transfer system using a transfer belt, a fixing step is performed before a recording material, which has been transferred, is separated from the transfer belt.

The object of the present invention is to prevent image defects when the recording material is separated from the transfer belt. However, since the fixing step is performed while the recording material is electrostatically strongly attracted to the transfer belt,
It is also effective for winding around the fixing roller, which is a problem of the present invention.

However, according to the present invention, the transfer belt and the transport belt are independent, and therefore, JP-A-5-313353 is used.
This is different from the invention disclosed in Japanese Patent Publication No.

In the structure of Japanese Patent Laid-Open No. 5-313531, since the transfer belt that has passed through the fixing unit returns to the image forming unit, a new problem arises in that fixing oil adheres to the photosensitive drum to cause an image defect. . Further, since the heat of the fixing roller is transferred to the image forming section through the transfer belt, there arises a problem that toner fusion occurs near the developing device.

Further, in the conventional image forming apparatus, an invention has been proposed in which the fixing speed is changed depending on the thickness of the recording material (for example, Japanese Patent Application Laid-Open No. 7-311506). Since the fixing speed does not change independently of the image forming speed, the image forming speed must be changed in order to change the fixing speed, which causes a problem that the control of the image forming unit becomes complicated. To do.

[0036]

In the image forming apparatus according to the present invention, since the recording material P is adsorbed by the conveying means, it does not wind around the fixing roller even if the toner increases the adhesive force to the fixing roller.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of an image forming apparatus according to the present invention will be described below with reference to FIG.

FIG. 1 is a sectional view of a color electrophotographic printer showing a first embodiment of the image forming apparatus of the invention, and FIG.
The same parts as those of the above are given the same numbers, and the description thereof will be omitted.

The carrying section of the image forming apparatus shown in this embodiment will be described.

The conveyor belt 65 includes support rollers 66, 67,
It is supported by 68. The support roller 68 is connected to a motor, and the conveyor belt 65 is rotated in the arrow direction.
The conveyor belt 65 is made of a dielectric resin sheet such as a polyethylene terephthalate resin sheet or a polyvinylidene fluoride resin sheet.

Further, an adsorption charger 70 for adsorbing the recording material P on the conveyor belt 65 is provided. Adsorption charger 7
0 is connected to a high voltage power source (not shown), and a DC negative current having the same polarity as the toner is output. The support roller 67 is connected to the ground and serves as a counter electrode of the adsorption charger 70.

When the image forming process is completed and the recording material P is separated from the transfer belt 130, the adsorption charger 70 is turned off.
Due to the electrostatic attraction force generated as N, the toner is conveyed to the fixing unit while being attracted and held by the conveyor belt 65. The toner on the recording material P is heated by the fixing roller 51 and the pressure roller 5 in the fixing unit.
The color is mixed by the pressure generated between the two and is fixed on the recording material. When the fixing of the toner onto the recording material is completed, the recording material P is discharged from the conveyance belt 65 on the supporting roller 68 by curvature separation.

Here, the output current of the adsorption charger 70 was determined by conducting an image formation without a margin and changing the output current.

As a result of the examination, as the output current is increased, the number of times of winding around the fixing roller 51 decreases, and
It has been found that the output frequency of μA is less than once per 5000 sheets. Further, when the output is further increased, when the output current exceeds 1400 μA, the separation of the recording material P from the support roller 68 becomes unstable.

Therefore, the output current of the adsorption charger 70 is set to -400 μA.

With the above-described structure, even when the recording material P has no margin, it is not wound around the fixing roller 51.

In this embodiment, the curvature separation is applied to separate the recording material from the conveyor belt. However, if the separation claw 17 is used as shown in FIG. It is stable and preferable.

Further, although the color image forming apparatus is used, it is needless to say that the same effect can be obtained also in the monochrome image forming apparatus.

The transport belt 65 has a volume resistivity of 10e16 or more. However, the value is not limited to this value, and even if the volume resistivity is as low as about 10e9, a sufficient effect can be obtained by changing the output of the adsorption charger 70.

Further, although the color image forming apparatus is used in the present embodiment, it is needless to say that the same effect can be obtained also in the monochrome image forming apparatus.

Although the curvature separation is applied to separate the recording material from the conveyor belt, the separation claw 69 as shown in FIG. 2 is preferable because the separation is further stable.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
It is a schematic configuration diagram of the image forming apparatus according to the first embodiment, and its basic operation is the same as that shown in the conventional example.

In this embodiment, as shown in FIG. 3, in the image forming apparatus shown in the first embodiment, the support roller 68 of the conveying device is also used as the pressure roller 52 which is in pressure contact with the fixing roller 51. And At this time, since the support roller 68 and the drive are not required, the cost can be significantly reduced.

Also in this configuration, even when the recording material P has no margin, it is not wrapped around the fixing roller 51.

(Embodiment 3) In this embodiment shown in FIG. 4, a fixing device 80 having an endless fixing film is used instead of the heating roller type fixing device.

Next, the fixing device 80 will be described with reference to FIG.

In FIG. 5, reference numeral 81 denotes an endless belt-shaped fixing film, which has a left driving roller 82, a right driven roller 83, and a low heating element disposed below the driving roller 2 and the driven roller 83. Heat capacity linear heating element 8
5 are suspended between the four parallel members 81.82.83.84.

The driven roller 83 also serves as a tension roller for the endless belt-shaped fixing film 81. The fixing film 81 is rotated at a predetermined peripheral speed in the clockwise direction with the clockwise rotation of the driving roller 25, that is, the image forming portion. The unfixed toner image conveyed from the side is rotationally driven at the same peripheral speed as the conveying speed of the recording material P carrying the upper surface without wrinkles, meandering, or speed delay.

The low-heat-capacity linear heating element 85 as a heating element in this example is the fixing film crossing direction (fixing film 2
Rigidity of the lateral hand with the longitudinal direction of 4)
A heater substrate 88 having a heater support 84 having high heat resistance and heat insulation and a heating element 86, a temperature measuring element 87, etc. integrally attached and held on the lower surface side of the heater support 84 along the lower surface length. To have.

The fixing film 81 has heat resistance, releasability and durability, and is generally 100 μm or less, preferably 40 μm.
Single-layer or composite-layer films of m or less can be used.

Next, the operation of the apparatus of this embodiment has been described in each of the above-mentioned embodiments, and therefore the description thereof is omitted.

In this embodiment, an image was formed without a margin, but when the output of the adsorption charger was turned off, it was wrapped around the fixing film 81. However, this time, the output of the adsorption charger is about -50 μA. However, the sufficient effect was obtained.

Therefore, also in this embodiment, the fixing roller 51 is not wound around.

Further, as the value of θ in FIG. 5 is increased, the separability is improved, and it has been clarified that the separation can be performed without the adsorption charger. In this case, the fixing film 81 is used.
A new problem was clarified that the torso would be torn because it was greatly bent.

(Fourth Embodiment) An image forming apparatus according to a fourth embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 is a sectional view of a color electrophotographic printer showing a fourth embodiment of the image forming apparatus of the invention, and FIG.
The same parts as those of the above are given the same numbers, and the description thereof will be omitted.

The image forming apparatus shown in this embodiment will be described.

The image forming apparatus shown in the present embodiment is provided with developing units 108 and 109 for forming images of yellow, magenta, cyan and black on the photoconductor 101. The yellow image formed on the photoconductor 101 forms an image and is transferred not on the recording material P but on the intermediate transfer body 102. As a power source for performing this primary transfer, 121
Are connected. This primary transfer process is sequentially performed for yellow, magenta, cyan, and black, and then the secondary transfer roller 122 collectively transfers to the recording material P.

The recording material P on which the secondary transfer has been completed is sent to the transport section.

The structure of the transport unit is basically the same as that of the first embodiment.

However, depending on the layout of the inside of the image forming apparatus main body, as shown in FIG.
The book is supported by supporting rollers 91 to 94.

In the present embodiment, the output current of the adsorption charger 70 is -300 μA.

With such a structure, the recording material P
Even when there is no blank space, the fixing roller 51 is not wrapped around.

[0074]

According to the apparatus of the present invention, by adsorbing the recording material to the conveying device 62 by the adsorbing device, it is possible to provide a full-color image forming device which does not cause the fixing roller to wrap regardless of the size of the margin. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a first embodiment of an image forming apparatus of the present invention.

FIG. 2 is a view showing a part of a modified embodiment of the apparatus of FIG.

FIG. 3 is a schematic diagram showing a configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic view showing the arrangement of an image forming apparatus according to a third embodiment of the present invention.

5 shows a variant embodiment of a part of the device shown in FIG.

FIG. 6 is a schematic view showing the arrangement of an image forming apparatus according to the fourth embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a conventional image forming apparatus.

[Explanation of symbols]

1-1d developing device 2a to 2d drum charger 3a to 3d electrophotographic photosensitive drum 4a-4d cleaner 5 Adsorption charger 7a-7d Static elimination needle 9 Fixing device 10 Recording material cassette 12 Registration roller 13 Drive roller 18 Cleaning means 19 Cleaning web (nonwoven fabric) 20 cleaning blade 21 Static elimination roller 22 Pressing roller 24a to 24d Transfer charger 26a-26d concentration sensor 32 separate charger 50 coating roller 51 fixing roller 52 Pressure roller 53 Oil sump 54, 55 Heat-resistant cleaning member 57 Roller heater 58 Thermistor 62 Transport section 63 Output tray 64 Separation guide 65 conveyor belt 70 Adsorption charger 81 Fixing film 85 heating body 87 Temperature sensor 88 heat board 101 photoconductor 102 Intermediate transfer body 113a-113d electric potential sensor 117 polygon mirror 122 Secondary transfer roller 130 recording material carrier P Recording material P Pa to Pd First, second, third, and fourth image forming units

Claims (6)

[Claims] 1. An image forming unit, a fixing unit, a conveying unit that conveys the recording material P from the image forming unit to the fixing unit, and a suction handle that adsorbs the recording material P to the conveying unit. In the image forming apparatus, the suction unit is provided between the image forming unit and the fixing unit, and the end of the conveying unit is provided after the exit of the fixing unit, and the recording material after the image fixing is performed. An image forming apparatus, wherein P is released from the conveying means at a position after the exit of the fixing unit. 2. The image forming apparatus according to claim 1, wherein the conveying means is configured as a conveying device having an endless belt-shaped conveying body supported by a plurality of rollers. 3. The supporting roller of the conveying member is provided at a position after the exit of the fixing unit.
Image forming device. 4. The image forming apparatus according to claim 2, wherein the supporting roller of the conveyance body also serves as a pressure roller of the fixing section. 5. The image forming apparatus according to claim 1, wherein the suction means is a corona charger. 6. The image forming apparatus according to claim 5, wherein the output current of the corona charger has a polarity opposite to that of the toner.