JPH07219378A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent flawing of a fixing roller by a cleaning blade and to prevent generation of white lines in output image by pressing this cleaning blade to this fixing roller by inclining the blade to the upstream side in its rotating direction. CONSTITUTION:This fixing device has the fixing roller consisting of a fixing roller 29 provided with an HTV(high-temp. vulcanizing type) silicone rubber layer on its surface and a press roller 30 and the cleaning blade C1 for removing oil and stains on the surface of the press roller 30 by coming into contact with the surface of the press roller. The cleaning blade C1 formed out of a fluororesin, fluororubber or silicone rubber is held pressed in a forward direction to the press roller 30, namely, the cleaning blade C1 comes into contact with the press roller 30 by inclining the blade to the upstream side of the rotating direction of the press roller 30. As a result, the foreign matter on the surface of the press roller 30 is liable to slip off from the contact part of the blade C1 and an edge effect is weak and, therefore, the press roller 30 is made hard to flawing and the transfer of flaws thereto does not arise any more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as an electrophotographic apparatus, and more particularly to a fixing device for fixing a toner image on a recording material.

[0002]

[Related Art] With the recent development of the information industry, higher-definition information output media are required.

Also in image forming apparatuses such as electrophotographic apparatuses, technological development is progressing in the direction of reducing the particle size of the toner and making it into a sharp melt in order to make the output image more fine.

However, there is a problem that the offset of the toner to the fixing roller for fixing the toner image on the recording material occurs more frequently than before due to the decrease in the particle diameter and the sharp melt of the toner. . Therefore, the surface layer of the fixing roller is desired to have more excellent releasability.

As a fixing roller having excellent releasability, one having an addition type silicone rubber layer on its surface has already been put into practical use. Further, there is another method in which silicone oil is applied to the surface of the silicone rubber layer to form an oil film to prevent offset more reliably. However, the offset has not been completely prevented yet. Therefore, offset toner, paper dust, and the like have entered the oil film that has come into contact with the toner image, and it is necessary to remove this oil from the roller surface.

As one means for removing oil, it has been proposed to bring a blade made of fluororubber, silicone rubber or the like into contact with the roller surface in the counter direction with respect to the rotation direction of the roller.

[0007]

However, when the blade is brought into contact with the roller in the counter direction with respect to the rotating direction of the roller, foreign matter such as paper dust is likely to accumulate at the contact portion of the blade,
Further, the edge effect of the blade strongly rubs the foreign matter on the roller surface, so that the roller surface is easily damaged. In particular, when the roller surface layer is relatively soft such as an addition type silicone rubber, the scratches are remarkably exhibited. When the scratches appear on the surface of the fixing roller that is in contact with the toner image, the scratches are transferred to the toner image in the fixing process, resulting in white stripes in the output image.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a fixing roller having an additional silicone rubber layer on its surface, and a cleaning blade for abutting the roller surface to clean the roller surface. In the fixing device having the above, the cleaning blade is inclined to the upstream side with respect to the rotation direction of the roller and abuts on the roller.

[0009]

FIG. 2 shows an electrophotographic color image forming apparatus using the present invention. This color image forming apparatus includes a photosensitive drum 1 as an image bearing member that is rotatably supported in an arrow direction, and a charger that uniformly charges the surface of the photosensitive drum 1 around the photosensitive drum 1. 2 (corona charger in this example), image exposure means 3 for forming an electrostatic latent image on the photosensitive drum 1 according to image information, and the electrostatic latent image formed on the photosensitive drum 1 into a visible image. A developing device 4 for developing, a transfer device 5 including a transfer drum 5a as a recording material carrier, a cleaner 6 for removing the developer remaining on the photosensitive drum 1, and the like are provided.

In the present embodiment, the image exposure means 3 is composed of a polygon mirror, a lens system, etc., and a color image signal for each color is obtained by color-separating a reflected light image obtained from a document scanning unit (not shown) with, for example, a color separation filter. An optical image from the laser output part modulated by
This is a laser beam exposure device that irradiates the photosensitive drum 1 (for example, a diameter of 82 mm) to form an electrostatic latent image corresponding to a color image signal of each color.

As the developing device 4, a black developing device 4 is used.
K, a cyan developing device 4C, a magenta developing device 4M, and a yellow developing device 4Y are respectively mounted, and a required developing device is rotationally moved to a developing position facing the photoconductor drum 1 to form a latent image on the photoconductor drum 1. A rotary developing device for developing is used.

The operation sequence of the entire color image forming apparatus will be briefly described by taking the case of the full color mode as an example. First, the photosensitive drum 1 is uniformly charged by the charger 2. Next, image exposure is performed on the original with, for example, laser light modulated by a cyan image signal, and an electrostatic latent image is formed on the photosensitive drum 1. This latent image is a cyan development image previously set at the development position. Development is performed by the container 4C, and a cyan visible image (toner image) is formed on the photosensitive drum 1 by the resin-based toner.

On the other hand, the recording material cassette 7a, 7b, or 7
From c (may be manually fed), pickup roller,
A recording material such as a transfer paper fed by a conveying system including a paper feed guide, a paper feed roller and the like along a paper path shown by a dotted line in the drawing is wound around the transfer device 5 in synchronization with a predetermined timing. In this example, the transfer device 5 includes a transfer drum 5a (for example, a diameter of 164 m) as a recording material carrier.
m), a transfer corona charger 5b for transferring the toner image on the photosensitive drum 1 to the recording material, and the transfer drum 5 for the recording material.
An adsorption corona charger 5c which is an adsorption charging means for adsorbing to a and an adsorption (contact) roller 5 as an opposite electrode.
g, an inner corona charger 5d, and an outer corona charger 5e, and the transfer drum 5 is rotatably supported and is rotatably supported.
A recording material carrying sheet 5f, which is a recording material carrying means and is made of a film-shaped dielectric, is integrally stretched in a cylindrical shape in the peripheral opening area of a.

The transfer drum 5a is rotated in the direction of the arrow in the figure in synchronization with the photosensitive drum 1, and the cyan toner image developed by the cyan developing device 4C is transferred to the transfer charger 5b.
Is transferred to the recording material carried on the recording material carrying sheet 5f. The transfer drum 5b continues to rotate,
Prepare to transfer the image of the next color (for example, magenta).

The photosensitive drum 1 to which the toner image has been transferred is cleaned by a cleaner 6 to remove adhering substances such as residual toner, and is uniformly charged again by a charger 2 to be laser light modulated by the next magenta image signal. Receives the image exposure as described above. During this time, the developing device 4 rotates and the magenta developing device 4M is fixed at a predetermined developing position to perform predetermined magenta development.

This magenta toner image is transferred to the recording material carried on the recording material carrying sheet 5f by the transfer charger 5b in the transfer section, and the magenta toner image is transferred onto the cyan toner image. The transfer drum 5a continues to rotate and prepares for transfer of an image of the next color (for example, yellow).

Subsequently, the above-described process is performed for yellow and black image formation and transfer, and when the superimposing transfer of four color toner images is completed, the recording material is discharged by the separation charger 5h and separated. It is separated from the transfer drum 5a by a separating means 8 such as a claw, and is sent to a fixing device (heat roller fixing device in this example) 9 by an appropriate conveying means in accordance with a paper path shown by a dotted line in the drawing, and is collectively fixed. , Are discharged onto the external tray 10. Thus, the series of full-color print sequences is completed, and the required full-color print image is formed.

As described above, since the multicolor toner forms two to four layers in the color image, the electrophotographic apparatus for forming a color image is used for black and white in the following two points. It has different characteristics from the device.

The first feature relates to the toner used.

Since this toner is required to have good meltability and mixability when heat is applied, a sharp melt toner having a low softening point and a low melt viscosity is used. By using the sharp melt toner, the color reproduction range of the copy can be widened and a color copy faithful to the multicolor or full-color image of the original can be obtained.

Such a sharp melt toner includes a binder resin such as polyester resin or styrene-acrylic ester resin, a colorant (dye, sublimable dye),
It is produced by melt-kneading, pulverizing and classifying a toner forming material such as a charge control agent. If necessary, an external addition step of adding various external additives (for example, hydrophobic colloidal silica) to the toner may be added. As such a color toner, it is particularly preferable to use a polyester resin as the binder resin in consideration of the fixability and the sharp melt property. As the sharp melt polyester resin, a polymer compound having an ester bond in the main chain of a molecule synthesized from a diol compound and a dicarboxylic acid is exemplified. In particular,

[0022]

[Outer 1] (In the formula, R is an ethylene or propylene group, and x, y
Are each a positive integer of 1 or more, and the average value of x + y is 2 to 10. ) And a bisphenol derivative represented by the formula (1) or a substituted product thereof as a diol component, and a carboxylic acid component comprising a carboxylic acid having a valence of 2 or more or an acid anhydride thereof or a lower alkyl ester thereof (for example, fumaric acid, maleic acid, maleic anhydride, Phthalic acid, terephthalic acid,
A polyester resin obtained by copolycondensing at least trimellitic acid or pyromellitic acid) is more preferable because it has sharp melting characteristics.

The softening point of the polyester resin is 75 to 15
0 degreeC, Preferably 80-120 degreeC is good.

FIG. 5 shows an example of the softening characteristics of a sharp melt toner containing this polyester resin as a binder resin. The measurement conditions are as follows.

A flow tester CFT-500A type (manufactured by Shimadzu Corporation) is used, and a die (nozzle) diameter is 0.2 m.
m, thickness 1.0 mm, 20 kg extrusion load, initial temperature 70 ° C., preheating time 300 sec, and constant temperature increase at a rate of 6 ° C./min. A curve (hereinafter referred to as a softened S-shaped curve) was obtained. As a sample toner, fine powder precisely weighed from 1 to 3 g is used, and the cross-sectional area of the plunger is 1.0 cm ² . Softening S
The curved curve is as shown in FIG. As the temperature rises at a constant rate, the toner is gradually heated and begins to flow (plunger descending A → B). When the temperature is further raised, the melted toner largely flows out (B → C → D), and the plunger lowering is stopped and completed (D → E).

The height H of the S-shaped curve indicates the total outflow amount, and H /
The temperature T ₀ corresponding to point C of 2 indicates the softening point of the toner.

Whether or not the toner and the binder resin have a sharp melting property can be determined by measuring the apparent melt viscosity of the toner or the binder resin.

The toner or the binder resin having such a sharp melt property means that the temperature at which the apparent melt viscosity is 103 poise is T1, and the temperature at which the apparent melt viscosity is 5 × 10 ² poise is T _2. , T1 = 90 to 150 ° C. | ΔT | = | T1-T2 | = 5 to 20 ° C.

The sharp-melting resin having these temperature-melt viscosity characteristics is characterized by extremely sharply decreasing the viscosity when heated. Such a decrease in viscosity causes a proper mixing of the uppermost toner layer and the lowermost toner layer, and further sharply increases the transparency of the toner layer itself, thereby causing good color mixture.

The color toner having such a sharp melt property has a large affinity and is easily offset.

Therefore, in the fixing device of the image forming apparatus using the color toner as described above, it is necessary to exhibit high releasability for a long period of time. The fixing device according to the first embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a fixing roller 29, which is a fixing roller for contacting a toner image, is a core metal 3 made of aluminum.
HTV (high temperature vulcanization type) silicone rubber layer 32 having a thickness of 1 mm, a linear polydimethylsiloxane having a terminal vinyl group blocked with a viscosity of 80,000 poise or more, and at least a tetrafunctional group or a trifunctional group. It has a specific addition-type silicone rubber layer 33 formed by curing a polysiloxane mixture containing at least a resinous organopolysiloxane composed of constituent units having one or more vinyl groups and having a thickness of 1 mm and a diameter. It is formed to 60 mm.

On the other hand, the pressure roller 30 which is a fixing roller.
Is a 1 mm thick HTV on an aluminum cored bar 34
Further, the specific additional silicone rubber layer 35 having a thickness of 1 mm is further provided to have a diameter of 60 mm.

The fixing roller 29 is provided with a halogen heater 36 which is a heat generating means, and the pressure roller 30 is also provided with a heater 37 in the core bar to perform heating from both sides. The thermistor 38 in contact with the pressure roller 30
Detects the temperature of the pressure roller, and the controller 39 controls the halogen heaters 36 and 37 based on the detected temperature so that both the temperature of the fixing roller 29 and the temperature of the pressure roller 30 are kept constant at about 170 ° C. Controlled by. The fixing roller 29 and the pressing roller 30 are pressed by a pressing mechanism (not shown) at a total pressure of about 80 kg.

Further, in FIG. 1, O is an oil applying device as a releasing agent applying means, C is a cleaning device, and C1 is a cleaning blade for removing oil and dirt of the pressure roller. The cleaning blade is made of fluorine resin, fluorine rubber, or silicone rubber. Only the pressure roller contact portion may be made of the above material.

The oil application device O is a dimethyl silicone oil 41 (KF963 manufactured by Shin-Etsu Chemical Co., Ltd.) in an oil pan 40.
00 cs) is passed through the oil pumping rollers 50 and 42 and the oil application roller 43, and the oil application amount adjusting blade 44 regulates the oil application amount to apply it on the fixing roller 29. In the apparatus shown in FIG. 1, the amount of application is 0.02 g / A4 by the measuring method described later. The oil application roller 43 can be brought into contact with and separated from the fixing roller 42 and is located in front of the leading end of the recording material. 5mm to 5mm from the rear end
Oil is applied to.

The fixing device as described above is as shown in FIG. In FIG. 4, the fixing device 13
0 is a fixing roller 131 having a halogen heater 131a as a heating source therein, and a pressure roller 132 having a halogen heater 132a as a heating source therein and rotatably pressed against the fixing roller (inside Halogen heater 1
32a) may not be provided), an oil application device 133 that applies silicone oil as a release agent to the surface of the fixing roller 131, the fixing roller 131, and the pressure roller 132.
Cleaning device 13 for removing toner adhering to the surface
4 and 135.

The fixing roller 131 and the pressure roller 13
2 is HTV (high temperature vulcanization type) on an aluminum cored bar
A lower layer made of silicone rubber, an intermediate layer made of fluororubber on the outside for preventing oil intrusion, and LTV (low temperature vulcanization type) or RTV (room temperature vulcanization type) on the outside, which is well compatible with silicone oil as a release agent. ) The fixing roller 131 is composed of a surface layer made of silicone rubber.
The surface layer of the pressure roller 132 is preferably made of the same material in order to ensure releasability. The fixing roller 131 and the pressure roller 132 are arranged so as to cooperate with each other to form a nip portion for conveying the recording material under pressure.

Further, each halogen heater 131a, 132
The heating operation of a is controlled by the temperature control means (not shown). That is, the temperature control means is the thermistor 136a,
The fixing roller 131 and the pressure roller 1 detected by 136b
Based on the surface temperature of 32, each halogen heater 131a, 1
The ON / OFF state of 32a is controlled.

Further, the oil applying device 133 can be brought into contact with and separated from the fixing roller 131, and the oil sump 133a.
Silicone oil pumping rollers 133b, 133 inside
The coating roller 133d is moved toward the coating roller 133d by c, and silicone oil is coated on the surface of the fixing roller 131 by the coating roller 133d. The oil applying device 13
The contact / separation of the fixing roller 131 and the fixing roller 131 is controlled by turning on / off a solenoid (not shown), and the application of silicone oil to the fixing roller 131 is controlled by the control blade 13.
It is controlled by 3e.

The amount of silicone oil applied by the oil applying device O and the oil applying device 133 is determined as follows.

First, the weight of 50 sheets of A4 size blank paper is A
1 (g), without transferring the image onto the blank sheet and without applying silicone oil to the rubber layer of the fixing roller,
Blank sheet 50 after passing between the fixing roller and the pressure roller
Let the weight of the sheet be B (g). Next, similarly, another 50 sheets of A4 size blank paper are set to A2 (g), and the image is not transferred onto this blank paper, but the silicone oil is applied to the rubber layer of the fixing roller to fix it. Let C (g) be the weight of 50 blank sheets after passing between the roller and the pressure roller. When the above A1, B, A2, and C are used, the amount of silicone oil applied per white sheet of A4 size X (g)
Is calculated by the following equation.

X = (C + A1-B-A2) / 50

On the other hand, in the fixing device shown in FIG. 3, the cleaning device C performs cleaning by pressing the non-woven fabric web 46 made of Nomex (product name) against the fixing roller 29 by the pressing roller 45. The web 46 is appropriately wound by a winding device (not shown) so that toner or the like does not accumulate on the contact portion.

In the fixing device shown in FIG. 4, the cleaning devices 134 and 135 are heat-resistant non-woven cloth Nomex (trade name) or webs 134a and 135 in which Nomex is plated with nickel by electroless plating.
a, rollers 134b and 135b for pressing the cleaning webs 134a and 135a toward the fixing roller 131 and the pressure roller 132, and the cleaning web 134
unwinding roller 134 for feeding out a and 135a
c, 135c and cleaning webs 134a, 135a
And winding rollers 134d and 135d for sequentially winding.

In such an apparatus, when the recording material is conveyed to the fixing device 130, the fixing roller 131 and the pressure roller 132 rotate at a constant speed, and the recording material is the roller 13.
When passing between Nos. 1 and 132, the unfixed toner carried by being pressed and heated from both the front and back sides is melted and fixed. At this time, the fixing roller 131 and the pressure roller 13
The toner adhered to 2 is cleaned by the cleaning devices 134 and 13
5 to be cleaned.

In the electrophotographic apparatus for forming a color image described above, the recording material is left as it is or reversed so that the visible image formed as described above can be formed on both the front surface and the back surface of the recording material, and a series of full-color images is reproduced again. The print sequence is performed and the desired duplex image is obtained. Specifically, it can be re-executed from the manual feed or re-fed by the reversing mechanism. Therefore, the toner image also contacts the pressure roller.

The cleaning blade C1 in the fixing device 9 is in contact with the roller in the forward direction, that is, the cleaning blade is inclined to the upstream side with respect to the rotation direction of the roller and contacts the roller, and is made of fluorine rubber. The amount of penetration is 1 mm ± 0.5 mm. Since the contact is made in the forward direction, foreign matter easily slips through the contact portion of the blade,
Also, since the edge effect is weak, the pressure roller is less likely to be scratched, and even if the full color image toner amount of 0.05 g / A4 is used for 100,000 sheets or more, the scratches will not be transferred to the first side of the double-sided image. It was The double-sided image was checked with a uniform image on the first side with a toner amount of 0.05 g / A4.

<Second Embodiment> In the second embodiment, as shown in FIG. 3, unlike the first embodiment, the cleaning blade C1 is attachable / detachable by an attaching / detaching device (not shown). It is worn during image formation and jam processing, and is removed in the mode where it is not necessary to clean the pressure roller. The other conditions were the same as in Example 1, and even after the durability of 200,000 sheets or more, scratches were not transferred to the first side of the double-sided image.

<Embodiment 3> As shown in FIG. 4, Embodiment 3 is different from Embodiment 1 in that the cleaning function of the pressure roller is separated, the cleaning device 135 is added, and the intrusion amount of the cleaning blade is reduced to 0. The contact force was weakened by setting it to 5 mm ± 0.1 mm. The other conditions were the same as in Example 1, and scratches were not transferred to the first side of the double-sided image even after being durable for 150,000 or more.

The effects are summarized in Table 1.

[0052]

[Table 1]

[0053]

As described above, since the cleaning blade contacting the fixing roller is contacted in the forward direction, the pressure roller is rubbed on the flat portion, and the pressure roller is damaged. Less likely to occur.

Therefore, since the scar of the roller is not transferred to the toner image at the time of fixing, white streak does not occur in the output image, and good fixing property can be maintained.

[Brief description of drawings]

FIG. 1 is a sectional view of a fixing device according to a first embodiment of the invention.

FIG. 2 is a sectional view of an image forming apparatus using the fixing device of the present invention.

FIG. 3 is a sectional view of a fixing device according to a second embodiment of the invention.

FIG. 4 is a sectional view of a fixing device according to a third embodiment of the invention.

FIG. 5 is a view showing softening characteristics of a sharp melt toner containing a polyester resin as a binder resin.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 1'Photoconductor belt 2 Charging device 3 Image exposure means 4Y, 4M, 4C, 4K Developing device 5 Transfer device 5a Transfer drum 6 Cleaner 9 Fixing device 11 Pre-exposure lamp O Oil applying device C1 Cleaning blade

Claims (1)

[Claims] 1. A fixing device comprising: a fixing roller having an addition type silicone rubber layer on the surface thereof; and a cleaning blade for contacting the roller surface to clean the roller surface, wherein the cleaning blade has a rotation direction of the roller. The fixing device is characterized in that it is inclined to the upstream side and comes into contact with the roller.