JPH08314317A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device capable of suppressing curl generated in a recording material smaller and improving a failure in the separation of the recording material. CONSTITUTION: In the image forming device provided with a fixed and supported heater (heating body) 203 and a pressure roller 210 for bringing a fixing film 201 into slidable contact with the heater 203 and pressing the recording material on which a toner image is formed on the surface on a side opposite to the side of the heater 203, of the fixing film 201, to carry it, a lower paper ejecting guide 222 for regulating the carrying direction of the recording material, just after it passes through a fixing nip part N is provided and constituted to be movable up and down (movement). Thus, the lower paper ejecting guide 222 is moved up and down to straighten the curl of the recording material after passing through the fixing nip part N.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner image formed on a recording material by contact-sliding a heat-resistant film on a fixedly supported heating element and applying heat from the heating element to a toner image on a recording material through the film. The present invention relates to an image forming apparatus such as an electrophotographic apparatus, an electrostatic recording apparatus, or the like, which is provided with a fixing device for fixing the above.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic system which is an example of an image forming system, a heating roller controlled at a predetermined temperature and an elastic layer are used as a system for fixing a visualized toner image on a recording material. A method (heat roller method) is generally used in which a recording material is nipped and conveyed while being heated and pressed by a pressure roller that is pressed against the heating roller.

However, recently, in order to save power and shorten the time from power-on to image output, JP-A-63-313182 and JP-A-2-15787.
As disclosed in Japanese Patent Laid-Open No. 8 etc., a fixedly supported heating body (hereinafter referred to as a heater), a heat resistant film (hereinafter referred to as a fixing film) conveyed while being pressed against the heater, and the fixing. The toner image formed on the surface of the recording material is heat-fixed by applying a heat of the heater to the recording material through the fixing film, which has a pressing member that brings the recording material into close contact with the heater through the film. A fixing device (film heating fixing device) adopting a method (film heating fixing system) has been proposed.

An example of such a film heating and fixing device is shown in FIG.
It will be described below based on.

In FIG. 6, reference numeral 101 denotes a cylindrical fixing film, which uses a polyimide film having a thickness of 40 to 60 μm as a base layer and has a thick outer peripheral surface (a surface in contact with the recording material P and the toner image T). 5 to 20 μm PFA and P
It is constituted by forming a release layer in which PTFE is dispersed in FA.

Further, 103 is a heater as a heating element, which has a heater holder 104 made of a low heat capacity ceramic having a long side in the direction orthogonal to the conveying direction of the recording material P and excellent in insulation and heat resistance. The heater holder 104
A resistance heating element 105 printed along the length of the surface of the
The resistance heating element 105 includes a temperature detecting element 106 such as a thermistor provided in contact with the opposite side of the exposed surface.

By the way, the heater 103 is a film guide having a semicircular trough shape in cross section (hereinafter referred to as a heater stay).
The resistance heating element 105 is exposed at 107 and is fixedly supported in a heat insulating state. The temperature control of the heater 103 is performed by controlling energization to the resistance heating element 105 so that the temperature of the heater 103 detected by the temperature detection element 106 becomes constant.

Reference numeral 108 denotes an inverted U-shaped reinforcing metal plate which prevents the heater unit including the heater 103, the temperature detecting element 106 and the heater stay 107 from being deformed when pressed by a pressure roller 110 which will be described later. It is provided to do so. The fixing film 101 is
The inner peripheral diameter is configured to be larger than the outer peripheral length of the heater unit including the reinforcing sheet metal 108.

Further, in FIG. 6, 110 is a pressure roller as a pressure member, which is composed of a core metal 111, an elastic layer 112 made of silicon rubber, and a release layer 113, and the release layer 113 is It is formed by performing a heat drying treatment after performing a fluororesin-based latex coat. The pressure roller 110 is pressed against the heater 103 by a pressure means (not shown) at a total pressure of 5 to 8 kgf.

The pressure roller 110 is driven to rotate in the conveying direction (counterclockwise) of the recording material P by a drive system (not shown). As a result, the cylindrical fixing film 101 closely slides on the surface of the resistance heating element 105 of the heater 103 and rotates around the heater stay 107. The heater 103
In order to reduce the sliding friction on the inner surface of the fixing film 101, heat resistant grease is interposed therebetween.

With the above structure, the recording material P is guided between the fixing film 101 and the pressure roller 110, and the recording material P passes through the fixing nip portion N, whereby the toner image T on the recording material P is conveyed. Is fixed.

In such a film heating and fixing device, the heat capacity of the heater portion can be reduced to several tens of times as compared with the conventional heat roller type fixing device, and the temperature can be raised. Since it is possible to use a fast heating element,
It is possible to shorten the time required to reach the temperature at which the heated portion can be fixed to several seconds. Therefore, in this film heating and fixing device, so-called on-demand fixing, which was difficult in the heat roller type fixing device, can be performed.

[0013]

By the way, in the film heating and fixing device, ceramics are generally used as the material of the heater holder 104 from the viewpoints of insulation and heat resistance. At this time, in consideration of workability and cost, the ceramic is generally formed in a flat plate shape in mass production as a heater holder.

On the other hand, when paper is used as the recording material, FIG.
As shown in, the paper is conveyed while being sandwiched between the flat surface of the heater 103 and the pressure roller 110 that elastically deforms in the pressure area. Therefore, there is a problem that the output paper is likely to be curled downward with a convex image surface. This problem becomes more serious especially when the image forming apparatus has an automatic double-sided function. That is, when the first side of the paper has a lower curl, the second side reversed in the duplex unit has an upper curl, and a separation failure is likely to occur on the paper after transfer. In particular, for recording materials with a large curl amount, such as hygroscopic paper,
If separation failure occurs and it penetrates into the cleaner, post-processing of paper jam becomes complicated, and not only the operator is contaminated with unfixed toner, but also the cleaner and the photosensitive drum that is the image carrier are damaged. That may be a big problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of suppressing curl generated in a recording material to be small and improving separation failure of the recording material. Especially.

[0016]

In order to achieve the above object, the invention according to claim 1 is a heating body fixedly supported,
An image forming apparatus comprising a fixing device having means for sliding a film on the heating body to press the recording material on which a toner image is formed on the surface of the film opposite to the heating body side and transporting the same. Immediately after the recording material passes through the fixing nip portion, a paper discharge guide for restricting the conveying direction of the recording material is provided, and the paper discharge guide is movable.

According to a second aspect of the present invention, a fixedly supported heating element and a film are brought into contact with the heating element to slide the recording material on which a toner image is formed on the surface of the film opposite to the heating element side. In an image forming apparatus having a fixing device having means for applying pressure to and conveying the recording material, a paper discharge guide for restricting a conveying direction of the recording material is provided immediately after the recording material passes through the fixing nip portion, The feature is that the angle of the surface where the guide contacts the recording material can be changed.

According to a third aspect of the present invention, in the first or second aspect of the invention, the heating element is composed of at least a resistance heating element and a holder for supporting the resistance heating element, and the film of the heating element. Is a flat surface, and the means for pressurizing and conveying the recording material is constituted by an elastic roller that is rotationally driven.

According to a fourth aspect of the invention, in the invention of the first, second or third aspect, the image forming apparatus has an automatic double-sided function capable of forming an image on both sides of the recording material. Characterize.

[0020]

According to the present invention, the curl of the recording material that has passed through the fixing nip portion can be corrected by moving the discharge guide or changing the angle of the surface of the discharge guide that contacts the recording material. Therefore, the separation failure of the recording material is improved. In particular, in an image forming apparatus having an automatic double-sided function, it is possible to improve the separation failure of the recording paper during double-sided printing, and to suppress the curl amount of the recording paper to be small during both single-sided printing and double-sided printing. it can.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a schematic cross-sectional view of a laser printer, and FIGS. 2 to 4 are cross-sectional views of a fixing device and a main portion of a paper discharge unit of the laser printer.

In FIG. 1, reference numeral 1 denotes an organic photosensitive drum, which is an image carrier, which is rotationally driven at a peripheral speed of 75 mm / sec in a direction indicated by an arrow by a driving means (not shown). A charging roller 2 is a charging member, which uniformly charges the surface of the photosensitive drum 1 by a bias applied from a high voltage power source (not shown).

The photosensitive drum 1 uniformly charged by the charging roller 2 is scanned by the laser light from the laser exposure device 3 whose intensity is modulated according to the image signal, so that its surface is statically moved. A latent image is formed. Then, the electrostatic latent image includes a developing sleeve, a developing blade, and
The toner image is visualized as a toner image by the developing device 4 including the component magnetic toner, and the toner image is electrostatically transferred onto the recording material (hereinafter referred to as transfer paper) by the transfer roller 6.

By the way, the transfer papers are accommodated in the paper cassette 9, and each transfer paper is fed by the pick-up roller 8 and then conveyed by the registration roller 5 in the arrow direction at a timing coincident with the image forming process. .

Then, the toner image formed on the transfer paper is fixed by the fixing device. The fixing device includes an entrance guide 221, a heating unit 200, and a pressure conveyance roller 2.
10 (hereinafter referred to as a pressure roller), a paper ejection lower guide 222
Etc.

The laser printer according to the present embodiment is equipped with an automatic double-sided unit 300 capable of reversing and conveying the transfer paper, and the transfer paper to be double-sided printed is subjected to image fixing on the first side by the fixing device. After that, the direction of the paper discharge flapper 250 is guided by the automatic double-sided unit 300 by being switched by a driving unit (not shown), and after passing through the conveying roller 301, is guided by the reversing roller 311 to the reversing path 310, according to its size. When the reversing roller 311 reversely rotates at an appropriate timing, the transfer surface is reversed, and the transfer roller 302 or the like conveys the image to form the second surface.

Next, details of the fixing device will be described with reference to FIGS.
It will be described based on.

FIG. 2 shows the states of the fixing device and the main portion of the paper discharge unit when the image is formed and output only on one surface of the transfer paper. At this time, the paper discharge lower guide 222 with respect to the fixing nip surface n. Is set to h ₁ (2 mm in this embodiment).

In the figure, 201 is a cylindrical heat-resistant fixing film, which has a base layer having a thickness of 40 to 60 μm.
The polyimide film of No. 1 is used, and a PFA having a thickness of 5 to 20 μm and a release layer in which PTFE is dispersed in PFA are formed on the outer peripheral surface (the surface in contact with the transfer paper and the toner image). Reference numeral 203 denotes a heater as a heating body, which is a heater holder 204 made of a low heat capacity ceramic having excellent insulation and heat resistance and having a length in a direction orthogonal to the transfer paper conveyance direction, and the heater holder 204.
A resistance heating element 205 printed on the surface of the
The heater holder 204 is composed of a temperature detecting element (thermistor or the like) 206 provided in contact with the exposed surface of the resistance heating element 205 on the opposite side.

The heater 203 is adiabatically supported in a state where a resistance heating element 205 is exposed on a film guide (hereinafter referred to as a heater stay) 207 having a semicircular trough shape in cross section. Note that the energization of the resistance heating element 205 is controlled so that the temperature of the heater 203 detected by the temperature detection element 206 becomes constant.

Numeral 208 is an inverted U-shaped reinforcing sheet metal,
This is to prevent the heater unit 200 including the heater 203, the temperature detecting element 206, the heater stay 207, etc. from being deformed when being pressed by the pressure roller 210 described later. The fixing film 201 has a heater unit 2 whose inner diameter includes the reinforcing sheet metal 208.
It is set to be larger than the outer peripheral length of 00.

Further, in the figure, 210 is a pressure roller as a pressure member, which comprises a core metal 211, an elastic layer 212 made of silicon rubber, and a release layer 213 and having an outer diameter of 18 mm.
And the release layer 213 is the elastic layer 2.
It is formed by applying a fluororesin-based latex coat to 12 and then heating and drying the coat layer. The pressure roller 210 has a total pressure of 5 to 8 kgf by a pressure means (not shown).
The pressure is applied to the heater 203 by the pressure of, and the pressure roller 210 is rotationally driven in the transfer paper conveyance direction (counterclockwise) by a drive system (not shown). As a result, the cylindrical fixing film 201 slides in close contact with the surface of the resistance heating element 205 of the heater 203 and rotates around the heater stay 207. At this time, the heater 203 and the fixing film 201
Heat-resistant grease is interposed between the two in order to reduce the sliding friction on the inner surface.

With the above construction, the transfer sheet is guided to the fixing nip portion N by the fixing inlet guide 221, and is nipped and conveyed while being heated and pressed by the fixing film 201 and the pressure roller 210, so that the transfer sheet is transferred onto the transfer sheet. The toner image is fixed.

The transfer sheet on which the toner image is fixed is guided by the lower discharge guide 222 and the upper discharge guide 225 and discharged to the outside of the apparatus. The transfer sheet fixed by the fixing device according to this embodiment is transferred. Since the paper curls downward as described above, the cam 223 is rotated by the drive shaft (not shown).
24, the lower paper ejection guide 222 that abuts against the cam 223 is moved upward as shown in FIG. 2 to lift the transfer paper vertically above the fixing nip surface n by h _1. The curl under the transfer paper can be corrected. The configuration shown in FIG. 2 is 64-105 g /
The conditions are suitable for correcting the curl that occurs when an image is formed on one side of m ² plain paper. In this embodiment, h ₁ in the figure is set to 2 mm.

By the way, in the image forming apparatus having the automatic double-sided function according to the present embodiment, when images are formed on both sides of the transfer paper, if the lower curl remains on the transfer paper after the image fixing on the first side, After the transfer paper is reversed in the reversal path 310 (see FIG. 1), when the toner image formed on the photosensitive drum 1 is transferred onto the transfer paper again, the transfer paper becomes an upper curl and the transfer paper is exposed to light. The separation condition from the drum 1 becomes strict. In particular, when plain paper is used as the transfer paper, the resistance of the transfer paper increases once the transfer paper passes through the fixing device.
Will be even more severe.

Therefore, in the present embodiment, when the print command instructs double-sided printing, the cam 223 shown in the drawing is rotated by the drive means (not shown) to the rotary shaft 224.
By rotating the cam 223 at an appropriate position by changing the height of the lower paper ejection guide 222 to curl the transfer paper at the time of one-sided printing.
It is adapted to switch between one-sided printing and two-sided printing for double-sided printing. This will be described with reference to FIGS. 3 and 4.

FIG. 3 shows the state of the fixing device and the main part of the paper discharge section when the first side is fixed and discharged during double-sided printing, and the cam 223 is rotated about the rotation shaft 224 to make it appropriate. It shows a state in which the height of the lower paper ejection guide 222 is changed by stopping the lower paper ejection guide 222 and the lower paper ejection guide 222 is lifted above the fixing nip surface n by h ₂ (= 3 mm) in the vertical direction.

With the above-mentioned structure, the transfer paper after the toner image is fixed is slightly curled.
The transfer and separation of the toner image on the second surface are favorably performed.
In the fixing of the toner image on the second surface, the transfer paper has passed through the fixing device once, so that the water content thereof is small, and thus the curl amount generated on the transfer paper is also small. Therefore, as shown in FIG. 4, by rotating the cam 223 again and stopping it at an appropriate position, the height of the lower paper ejection guide 222 is set to h ₃ (= 1 mm), and the transfer paper is ejected. .

With the above-mentioned structure, it is possible to improve the separation failure of the transfer paper at the time of double-sided printing, and to suppress the curl amount of the transfer paper to be small both at the time of single-sided printing and at the time of double-sided printing. .

The shape of the members shown in this embodiment,
The size, material or rotation speed, moving method, moving amount, etc. are examples. Further, the paper ejection lower guide 222 shown in the embodiment may be not only moved in the vertical direction, but may also be appropriately rotated to regulate the ejection direction of the transfer paper.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view of the fixing device and the main part of the paper discharge unit according to the second embodiment of the present invention. In this figure, the same elements as those shown in FIGS. There is.

In the present embodiment, the paper discharge section is composed of a paper discharge lower guide 282, a paper discharge upper guide 285, and a guide rotation driving means (not shown), and the paper discharge lower guide 282 and the paper discharge upper guide 285 are long. Are connected at both ends of.
Then, the paper discharge lower guide 282 and the paper discharge upper guide 2
Reference numeral 85 is rotated about the rotation shaft 290 by the rotation driving means, and its setting position is switched between a solid line position and a broken line position in the figure.

By configuring the paper discharge section as described above, the paper discharge lower guide 28 is provided for each of the first side for single-sided printing and the first and second sides for double-sided printing.
It is possible to change the angle between 2 and the paper discharge upper guide 285.

Therefore, for example, in the case of single-sided printing, the angle between the paper ejection lower guide 282 and the paper ejection upper guide 285 is positioned between the solid line and the broken line in the figure. By positioning the transfer paper at each position, it is possible to improve the separation failure of the transfer paper during double-sided printing, and to suppress the curl amount of the transfer paper to be small during both single-sided printing and double-sided printing.

Further, in the present embodiment, since the lower paper ejection guide 282 and the upper paper ejection guide 285 are moved together, it is likely to occur when the upper paper ejection guide is fixed and the lower paper ejection guide is moved and rotated in the lower curl straightening direction. Problems such as rubbing of the upper guide on the image surface of the transfer paper are eliminated.

[0047]

As is apparent from the above description, according to the present invention, a fixedly supported heating member and a recording material on which a toner image is formed by sliding a film on the heating member are used as the film. In an image forming apparatus equipped with a fixing device having means for pressing the surface of the heating body opposite to that of the heating material to convey the recording material, the conveying direction of the recording material is regulated immediately after the recording material passes through the fixing nip portion. Since a paper discharge guide is provided and the paper discharge guide is configured to be movable, or the angle of the surface of the paper discharge guide in contact with the recording material can be changed, curl generated on the recording material can be suppressed to a small value. An effect that the separation failure can be improved can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus (laser printer) according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of a fixing device and a discharge unit of the image forming apparatus (laser printer) according to the first exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view of a main part of a fixing device and a paper discharge unit of the image forming apparatus (laser printer) according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a main part of a fixing device and a paper discharge unit of the image forming apparatus (laser printer) according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of a main part of a fixing device and a paper discharge unit of an image forming apparatus (laser printer) according to a second embodiment of the present invention.

FIG. 6 is a sectional view showing a film heating and fixing device in a conventional image forming apparatus.

[Explanation of symbols]

 200 Heater unit 201 Fixing film (film) 203 Heater (heating body) 204 Heater holder 205 Resistance heating element 210 Pressure roller (elastic roller) 221 Fixing entrance guide 222 Paper ejection lower guide (paper ejection guide) 282 Paper ejection lower guide ( Paper ejection guide) 285 Paper ejection upper guide (paper ejection guide)

Claims (4)

[Claims] 1. A fixedly supported heating element, a film is slid on the heating element, and a recording material on which a toner image is formed is pressed against the surface of the film opposite to the heating element side. An image forming apparatus including a fixing device having a conveying unit is provided with a paper ejection guide for restricting a conveyance direction of the recording material immediately after the recording material passes through a fixing nip portion, and the paper ejection guide is movable. An image forming apparatus characterized by the above. 2. A fixedly supported heating element, a film is slid on the heating element, and the recording material on which a toner image is formed is pressed against the surface of the film opposite to the heating element side. In an image forming apparatus including a fixing device having a conveying unit, a paper discharge guide is provided immediately after the recording material passes through the fixing nip portion, and a paper discharge guide is provided to regulate the conveying direction of the recording material, and the paper discharge guide contacts the recording material. An image forming apparatus characterized in that the angle of the surface to be changed can be changed. 3. The heating element comprises at least a resistance heating element and a holder for supporting the resistance heating element,
The surface of the heating element on which the film contacts and slides is a flat surface,
3. The image forming apparatus according to claim 1, wherein the means for conveying the recording material under pressure is constituted by an elastic roller which is rotationally driven. 4. The image forming apparatus according to claim 1, further comprising an automatic double-sided function capable of forming an image on both sides of the recording material.