JPH0667559A - Image froming device - Google Patents

Abstract

PURPOSE:To form a good image without any image deformation or formation of a mark of a paper ejection roller in a transferring process by making the volume resistivity of an elastic body layer used for the paper ejection roller within a specified range. CONSTITUTION:An image carrier 1 is uniformly electrified by a roller 6 in primary electrification, a latent image is formed by laser beam from a scanner 7 after that, the image developed by having the former latent image developed by a developing device 2 has destaticization carried out on it after separating by a destaticizing needle 4 after the image is transferred by a transfer roller 3 onto transfer material 12 which is fed from the outside, made to proceed to a fixing device 9 along a carrying guide 8 and carried and ejected outside by the paper ejection roller 10 and the paper ejection roller 11 after being fixed. The good image can be obtained without generating any mark of the paper ejection roller and electrostatic offsetting by having the paper ejection roller 10 provided with the elastic body layer over core metal and setting the volume resistivity of the elastic body layer which has a fluoro rubber as base to be in range above 10<10>>cm and below 10<13>OMEGAcm.

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 using an electrostatic transfer process such as an electrophotographic apparatus, an electrostatic copying machine and a printer.

[0002]

2. Description of the Related Art FIG. 19 is a diagram showing a conventional example.
In the figure, 1 is an image carrier, 2 is a developing device, 3 is a transfer roller, 4 is a discharging needle, 5 is a cleaning device, 6 is a primary charging roller, 7 is a laser exposure device, 8 is a conveyance guide, and 9 is fixing. Device, 13 is a fixing roller, 14 is a pressure roller, 12
Is a transfer material, 11 is a paper discharge roller, and 19 is a paper discharge roller. In the figure, the image carrier 1 includes a primary charging roller 6
After being uniformly charged by the laser exposure device 7, an electrostatic latent image is drawn, the image is developed by the developing device 7, and the developed image is transferred by the transfer roller 3 by the transfer roller 1.
The image transferred onto the image carrier 2 and remaining on the image carrier is collected by the cleaning device 5. On the other hand, the transfer material 12 on which the image has been transferred is removed of excess charges by the charge elimination needle 4 after being separated from the transfer, and is transferred along the transfer guide 8 into the heat fixing device 9 composed of a pair of rollers. After the fixed image is fixed, it is ejected to the outside of the machine while being sandwiched between the paper ejection roller 19 and the paper ejection roller 11.

By the way, as a recent technical trend, with the demand for smaller size and easier maintenance of the fixing device, a structure without a cleaning mechanism in the fixing roller is becoming indispensable. For that purpose, the toner image on the transfer material is transferred immediately before or in the nip inside the fixing device.
It is indispensable to prevent development called electrostatic offset in which an electrostatic force between the rollers scatters to the fixing roller side and a scattered image appears on the transfer material with a delay of one round of the roller. The electrostatic offset is generated
Usually, the main cause was that the pressure roller side was charged up with the same polarity as the toner.

Therefore, it has been proposed to prevent the electrostatic offset by providing the fixing device with the structure shown in FIG. In the figure, the fixing roller 13 includes a core metal 13A and a fluororesin 13B provided on the core metal 13A.
Is provided with a silicon rubber layer 14B having a low volume resistance of 10 ⁵ Ωcm or less on a core metal 14A, and a fluororesin layer 13C as a surface layer. Here, the pressure roller is provided with the low-resistance silicon rubber layer 14B to increase the electrostatic capacity of the pressure roller itself, thereby preventing charge-up and increasing the effect of the potential operation by the diode. Because of that. The diodes 15 and 16 are connected to the fixing roller side and the pressure roller side in the directions shown in the figure. These effects are obtained when the potential corresponding to the potential of the transfer material 12 is changed to the fixing roller side. A negative potential is induced on the pressure roller side, and a positive potential is induced on the pressure roller side. Due to the potential difference between the upper and lower rollers, an electric field is generated in a direction to hold the toner on the transfer material side, and electrostatic offset is prevented. . In the paper discharge section, a paper discharge roller 11 made of a resin material and a paper discharge roller 19 having a rubber roller made of, for example, CR rubber on the core metal are provided in pairs, and thereby the transfer material 12 is provided. It has the function of discharging it to the outside of the machine. The core of the paper discharging roller 19 is connected to the ground because the rotation of the roller causes electric charges to be accumulated in the core, which causes electrical noise due to leakage due to charge-up and malfunction of the CPU. This is to prevent the induction of.

Further, as shown in FIG. 21, a fixing device in a conventional image forming apparatus has a pair of rollers arranged in pressure contact with each other, and fixing is performed by heating the rollers by a heating means. The fixing roller 130 has a structure in which a fluorine resin layer is provided on the outer surface of a hollow aluminum cored bar, and a halogen heater 131 is provided therein.
Is provided. Reference numeral 132 denotes a silicone oil application / cleaning member, which has a configuration including a cleaning material 132A made of heat-resistant felt impregnated with silicone oil and a holder 132B supporting the cleaning material 132A, and is pressed against the fixing roller. In addition, the pressure roller 1
33 has an elastic layer 133A of, for example, low temperature vulcanizing type silicone rubber (LTV) around the core metal 133B.

In the roller pair, toner increase
The fixing operation is performed by passing the transfer material 135 on which the toner is placed.

[0007]

However, in the conventional example according to FIGS. 19 and 20, if the resistance value of the discharge roller is too low or too high, the following problems occur.

When the resistance is low: For example, when the amount of carbon added in the CR rubber is excessive and a roller having a low resistance is used, the transfer charge retained on the back surface of the transfer material is
By escaping from the roller along the core metal, the potential of the transfer material is lowered, the electric field for holding the toner existing on the surface is weakened, and electrostatic offset is generated.

When the resistance is high: For example, when a high resistance rubber such as fluororubber is used, when the transfer material is discharged, the portion on the back surface of the transfer material, which is in contact with the paper discharge roller, rubs against the roller. As a result, the electric charge generated as a result will accumulate, and when attempting to print again on the back surface of the ejected transfer material during double-sided printing, only the area that touches the paper ejection roller remains on the transfer material. Due to the frictional charge with the roller, the image is disturbed in the transfer process, or there is a problem of so-called sheet ejection roller trace which causes transfer failure. This phenomenon is particularly remarkable in an automatic double-sided machine.

A first object of the present invention is to solve the above-mentioned problems, and an image forming apparatus for forming a good image without disturbing the image in the transfer step or forming a discharge roller trace. To provide.

With respect to the conventional example shown in FIG. 21, further technological trends have made it necessary to further simplify, downsize and extend the life of the device. Along with this, the cleaning padless and the diameter of the roller are reduced, and further, the pressure roller 1
A structure in which a PFA tube layer is provided on the surface layer of 33 is becoming an essential technique. By providing a PFA tube on the surface layer of the pressure roller 133, it is more resistant to dirt and abrasion, but on the other hand, the roller hardness is increased, and the nip is sufficient to guarantee the fixing performance between the fixing roller having a smaller diameter and the pressure roller. In order to have the width, it was necessary to lower the hardness of the rubber that is the elastic layer. For that purpose, a method such as reducing the vulcanization density or the molecular weight of rubber is used.

On the other hand, on the fixing roller 130 side, in determining the light distribution of the halogen heater arranged in the roller, for example, in consideration of heat escape from the bearing, the light distribution at both ends is compared with that at the center. Is set to a higher value to prevent temperature drop at the edge of the fixing roller and to satisfy the fixability at the edge of the image, but the finish roller surface temperature distribution is not always uniform. Not not.

When the pressure roller and the halogen heater are used in combination as described above, thermal expansion occurs as the pressure roller 133 is heated by the fixing roller 130, but the surface temperature of the fixing roller is not uniform. Therefore, the expansion of the pressure roller is not evenly performed. At this time,
Regarding the pressure roller used conventionally (rubber hardness is 25 ° or more in JISA), the difference in outer diameter when expanded is small and causes no problem in actual use. On the other hand, in the case of low hardness rubber (rubber hardness is about 10 degrees in JIS),
Since the coefficient of thermal expansion is more than twice that of conventional rubber, the difference in outer diameter due to the temperature difference becomes large, and the problem of wrinkling of the transfer material due to uneven formation of the nip frequently occurs.

A second object of the present invention is to solve the above-mentioned problems, and to provide an image forming apparatus capable of uniformly heating the roller and uniformly forming the nip portion to enable good fixing. To do.

[0015]

According to a second aspect of the present invention, there is provided a means for solving the problems according to the first aspect of the present invention for achieving the first object. To 4 means.

According to the first aspect of the invention, therefore, the electric potential of the paper discharge roller is properly maintained to prevent the image from being disturbed in the transfer process and the formation of the paper discharge roller trace.

According to the second to fourth aspects, by uniformly heating the roller and uniformly forming the nip portion, the wrinkle of the transfer material is prevented and a good image is formed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First to third embodiments according to claim 1 of the present invention will be described with reference to FIGS.

<First Embodiment> FIG. 1 shows a first embodiment of the present invention. In the figure, 1 is an image carrier, 2 is a developing device, 3 is a transfer roller, 4 is a discharging needle, 5 is a cleaning device, 6 is a primary charging roller, 7 is a scanner, 8 is a transfer material conveyance guide, and 9 is a fixing device. Reference numeral 10 is a paper discharge roller, 11 is a paper discharge roller, and 12 is a transfer material. The image carrier 1 is uniformly charged by the primary charging roller 6, then a latent image is formed by the laser beam from the scanner 7, and the electrostatic latent image developed by the developing device 2 is fed from the outside. After being transferred onto the transfer material 12 by the transfer roller 3, the charge is removed by the charge removing needle 4 and then discharged into the fixing device 9 along the conveyance guide 8 and fixed,
The sheet is conveyed by the sheet ejection roller 10 and the sheet ejection roller 11 and ejected to the outside.

Next, FIG. 2 is a diagram showing in detail the fixing device and the vicinity of the paper discharge roller. In the figure, 13 is a fixing roller, and a releasable layer 13B such as PFA or PTFE is provided on a cored bar 13A. A pressure roller 14 has a conductive silicon rubber layer 14B having a volume resistance value of about 10 ⁵ Ωcm on a core metal 14A, and a PFA tube or PFA layer 14C is provided on the surface layer thereof. As a countermeasure against electrostatic offset, a diode 15 is provided on the fixing roller side.
Is connected to the core metal 13A by a sliding contact (not shown), and the diode 16 is connected to the core metal 14A by a sliding contact (not shown) on the pressure roller side. The direction of this diode connection is the one when the image forming apparatus uses the negative toner, and the direction is opposite when the positive toner is used. The paper discharge roller 11 is made of a mold material and is arranged so as to be pressed against the paper discharge roller side by a spring (not shown).

The feature of this embodiment is that the resistance value of the rubber material used for the paper discharge roller is regulated. The paper discharge roller 10 has a structure in which an elastic layer 10B is provided on a core metal 10A. FIG. 3 is a view of the discharge roller in the longitudinal direction. As shown in the figure, a plurality of rollers having a predetermined length are arranged, and the same number of paper discharge rollers are provided to convey the transfer material. The core metal 10A is connected to the ground, for example, via a conductive bearing.

FIG. 4 shows the level of electrostatic offset and the result of evaluation of roller traces when the volume resistance value or the specific resistance of the discharge roller material itself was changed. For the paper discharge roller for this study, we used fluororubber as a base.
A material whose volume resistance was adjusted by appropriately dispersing carbon was used. The electrostatic offset is an evaluation result under normal temperature and normal humidity (20 ° C., 60%), and the discharge roller trace is an evaluation result under low temperature and low humidity (15 ° C., 10%). From the figure, the area where the electrostatic offset is not generated is the volume resistance of the discharge roller of 10 ¹⁰ Ω · cm or more, and the area where the discharge roller trace is not generated is the volume resistance of the discharge roller is 10 ^It was found to be below ¹³ Ω · cm. Therefore, from the above results, it is appropriate that the volume resistance value or the specific resistance of the rubber itself of the discharge roller used in this embodiment is 10 ¹⁰ Ω · cm or more and 10 ¹³ Ω · cm or less.

As described above, according to the present embodiment, the volume resistance value of the rubber of the discharge roller is 10 ¹⁰ Ω · cm or more and 10 ¹³ Ω.
-By setting in the range of cm or less, a good image can be obtained without generating electrostatic offset or paper discharge roller marks.

<Embodiment 2> FIG. 5 is a view best showing the second embodiment of the present invention. A feature of this embodiment is that the resistance value required for the paper discharge roller described in the first embodiment is provided not to the rubber itself of the paper discharge roller but to a resistor provided other than the paper discharge roller. In FIG.
Those with the same number as the above have the same configuration. And the discharge roller 15
Is a roller 1 made of conductive rubber having a low volume resistance of 10 ¹⁰ Ω · cm or less or 10 ⁵ Ω · cm or less on the core metal 15A.
5B is provided. The core metal 15A is electrically connected to the resistor 16 by a sliding contact (not shown).
7, the other side is grounded. The resistor 17 described in this embodiment has a volume resistance of 10 ¹⁰ to 10 ¹³ Ω · cm.
The member 17A controlled within the range of two electrode plates 17B
It is composed by sandwiching.

According to this embodiment, first of all, the resistor 17
The point is that the selection range of the member A is widened. that is,
In order to control the resistance by the paper ejection roller itself, the rubber material used is limited in terms of the transfer material transportability (friction coefficient), abrasion resistance, stain resistance, etc. required for the paper ejection roller. However, in this embodiment, since only the condition of the resistance value needs to be satisfied, it is possible to use the rubber material used in the first embodiment as well as the resin material having a low resistance. Second
Another advantage is that the resistance value is stable. When the discharge roller is used for a long time, the actual resistance value may change due to foreign matter such as paper powder or toner adhering to the roller surface.However, in this embodiment, the resistor serves as a transfer material. Since is not touched, there is a point that a stable resistance value can always be obtained.

<Third Embodiment> FIG. 6 is a view showing a third embodiment of the present invention. The feature of this embodiment is that the shaft material of the paper discharge roller has a required resistance value. In the figure, those having the same numbers as those in FIG. 2 have the same configuration. Then, the paper discharge roller 18 has a volume resistance of 10 ¹⁰ to 10 ¹³ Ω · cm controlled on a paper discharge roller shaft member 18 A made of a material.
A roller 18B made of a conductive rubber having a low volume resistance of 10 ¹⁰ Ω · cm or less or 10 ⁵ Ω · cm or less is provided.
The shaft member 18A is connected to the ground by a sliding contact (not shown). As the material used for the shaft material of this embodiment, since a certain degree of strength as the shaft material is required, it is suitable to use, for example, FRP resin to which an additive such as carbon fiber is added to control the resistance value. . FIG. 7 is a side view of the paper discharge roller used in the third embodiment. The roller 10B made of rubber having a volume resistance value of 10 ⁵ Ω · cm or less has a volume resistance value of 10 ¹⁰ Ω · cm to 1
Shaft material 10A made of material controlled in the range of 0 ¹³ Ω · cm
The aspect provided above is shown.

According to the present embodiment, since the shaft member has the required resistance value, there is no resistance change due to durability, and as in the second embodiment, a space for installing the resistor is provided outside. There is no need to save space.

Next, fourth to sixth embodiments according to claims 2 to 4 of the present invention will be described with reference to FIGS.

<Embodiment 4> FIG. 8 is a sectional view of an image forming apparatus which best shows the features of the fourth embodiment of the present invention. In the figure, 101 is a fixing roller, 102 is a pressure roller,
103 is a halogen heater, 104 is a fuser frame, 1
Reference numeral 05 is a temperature detector, 106 is a CPU, 107 is a drive gear, 108 is a pressure roller bearing, 109 is a fixing roller bearing, and 110 is a pressure spring. Fixing roller 10
1 is PTFE or P as a release layer on an aluminum cored bar
A fluororesin layer such as FA is provided and is fixed to the frame 104 via a bearing 109. The drive is performed via the drive gear 107. The pressure roller 102 includes a silicon rubber layer 10 having a thickness t = 5.0 mm on the core metal 102A.
2B, and further, a PFA tube layer 102C having a thickness t = 50 μm is further provided thereon, and the roller hardness is 4
3 ° (ASKER C hardness meter, measured with a total load of 500 g) and a linear expansion coefficient of the roller of about 7.0 × 10 ^-4 ° C ^-1 are used, and the outer diameter of the pressure roller is φ20.0. To do.

[0030] Note that the linear expansion coefficient of the pressure roller referred to here, (dl / dθ) / 1 0 (1: 2t, θ: Temperature, t:
Rubber thickness, 1 _0: the length) at 0 ° C..

As the halogen heater 103, one having a light distribution distribution in the longitudinal direction of 170% at both ends is used as shown in FIG. It should be noted that the light distribution characteristic referred to here is the amount of light emitted when the halogen heater is turned on and is 20 m from the heater.
It shows the amount of light emission at each part in the longitudinal direction when the amount of light emission at the central part is 100 (%), which is detected by the detector in the longitudinal direction of the heater at a position separated by m.
The halogen heater 103 is arranged in the fixing roller 101, and the temperature of the fixing roller 101 is adjusted to a predetermined temperature by a temperature detector 105 that is in contact with the surface of the fixing roller 101 and a CPU 106 that controls the temperature. Then, electricity is supplied. Then, the pressure roller 102 is pressed against the fixing roller 101 with a predetermined pressure by the pressure spring 110 via the bearing 108 to form a nip, and is driven by the rotation of the fixing roller 101, and an unfixed image (not shown) is fed to the nip. The fixing operation is performed by passing through.

In the present embodiment having the above-mentioned structure, the temperature distribution in the longitudinal direction of the surface of the fixing roller and the outer diameter difference with respect to the outer diameter of the central portion of the pressure roller when the temperature controlled temperature during printing is 180 (° C.). Is shown in FIG. In this embodiment, the heater light distribution is 170% at both ends, so that the temperature distribution on the surface of the fixing roller can be made substantially uniform. Therefore, even in the pressure roller that receives heat from the fixing roller and causes thermal expansion, a uniform and uniform nip formation is always maintained, and wrinkles of the transfer material and image disturbance Without causing
Good fixability can be obtained.

On the other hand, FIG. 1 shows a comparative example with respect to this embodiment.
1 and FIG. 12 show the behavior when the heater light distribution is set low at both ends and when it is set high.

FIG. 11 is a diagram showing the behavior when the light distribution at both ends is 110%. In the case of this configuration, the amount of heat supply at the end portion is small, so the temperature difference between the central portion of the fixing roller and both end portions is about 20 ° C. as a result,
Since the pressure roller also undergoes thermal expansion according to temperature, it has a crown shape with an outer diameter difference of about 140 μm between the central portion and both ends, resulting in severe transfer wrinkles.

FIG. 12 is a diagram showing the behavior when the light distribution at both ends is 210%. In the case of this configuration, the fixing roller surface temperature distribution has a two-peaked distribution having a peak temperature near the heater light distribution peak position and a temperature difference of about 30% from the central portion. The outer diameter of the pressure roller also causes thermal expansion according to the surface temperature of the fixing roller, and has a two-peak shape in which the outer diameter difference from the outer diameter of the central portion of the pressure roller is about 200 μm, so that a uniform nip is no longer formed. You can't do that, and wrinkles will occur on the transfer material.

Therefore, as described above, when a pressure roller having a low hardness and a large coefficient of thermal expansion is used, it is necessary to set an appropriate heater light distribution so as not to cause a wrinkle on the transfer material.

FIG. 13 shows the level of paper wrinkles when the heater light distribution is changed in this embodiment. In this study, under a normal temperature and normal humidity environment of a room temperature of 20 ° C. and a temperature of 60%, a fixing roller having an outer diameter of φ20 was used, and the total pressure between fixing and pressurization was 8.5 kg.
It was performed using RY (registered trademark). If the linear expansion coefficient of the pressure roller used in this embodiment is 1.0 × 10 ⁻⁴ ° C. ⁻¹ or more, the hardness will be low enough to obtain a sufficient nip width. From the results shown in FIG. 13, it can be seen that in this embodiment, it is appropriate to set the halogen heater light distribution within the range of 120% to 190%.

As described above, a pressure roller using a solid rubber having a PFA tube as a surface layer as an elastic body and having a linear expansion coefficient of 1.0 × 10 ^-4 ° C ^-1 or more is used. In image formation, by setting the light distribution of the halogen heater used for the image formation in the range of 120% or more and 190% or less, good fixing property can be obtained without causing wrinkles of the transfer material.

<Fifth Embodiment> FIG. 14 shows a fifth embodiment of the present invention.
Shown in. This embodiment differs from the fourth embodiment in that a silicone sponge is used for the elastic layer of the pressure roller. In the figure, reference numeral 111 denotes a fixing roller 112 having a releasable layer such as PFA or PTFE on the surface layer, and a fixing roller 112. Specifically, the silicon sponge layer 1 is provided on the core metal 112A.
12B, and a PFA tube layer 112C further thereon, and an axial through hole 1 as an air vent hole for suppressing thermal expansion to some extent in the silicon sponge layer 112B.
12D is provided. 113 is a halogen heater, 114
Is a temperature detector, 115 is a frame, 116 is a transfer material inlet guide, 117 is a pressure roller bearing, and 118 is a pressure spring.

A feature of the pressure roller used in the present embodiment is that the sponge is used for the elastic layer and therefore the heat capacity is small. Therefore, by using this pressure roller, the heat taken from the fixing roller to the pressure roller is reduced and the thermal efficiency is improved, and the fixability, especially immediately after the machine is started up, is more advantageous than when solid rubber is used. Become.

Also in the pressure roller in this embodiment,
Although the through hole 112D for air vent is provided, the coefficient of thermal expansion tends to be larger than that of solid rubber. Therefore, the appropriate heater light distribution range in this embodiment tends to be slightly narrower than that in the fourth embodiment. FIG. 15 shows the generation level of the transfer material wrinkle when the heater light distribution was changed in the fifth embodiment. In addition, in the case of the pressure roller used in the present embodiment, the linear expansion coefficient that can be taken is larger than that in the case of using solid rubber, 1.0 × 1.
A temperature of 0 ^-3 ° C ^-1 or higher is suitable. From the figure, the proper heater light distribution range in this embodiment is 130% or more and 190% or more.
It becomes the following.

As described above, according to this embodiment, the PF
A pressure roller having an A tube layer as a surface layer and a sponge as an elastic body, the linear expansion coefficient of which is 1.0 × 10.
^{In the} image forming apparatus using the one whose temperature is ⁻³ ° C. ⁻¹ or more,
The light distribution of the halogen heater used for that is 130% or more 19
By setting the content in the range of 0% or less, good fixing property can be obtained without causing wrinkles of the transfer material.

<Sixth Embodiment> FIG. 16 is a diagram showing a sixth embodiment of the present invention. The feature of the present embodiment is that in a film type fixing device using a flat plate heating element, by keeping the calorific value distribution of the flat plate heating element within an appropriate range when a pressure roller having a large coefficient of thermal expansion is used, This is a point that good fixing property can be obtained without causing the warpage.

In FIG. 16, 119 is a flat plate heating element having a heating portion printed on a ceramic support, 120 is a pressure roller consisting of a single layer of silicon rubber, 121 is a film having a releasing layer on the surface of a polyimide substrate, 122 is a drive roller for driving the film, 123 is a tension roller for properly stretching the film, 124 is a transfer material inlet guide, and 125 is a frame. FIG. 17 shows 119
It is a figure showing the heater of. The heat generating portion 119A is provided on a ceramic holder 119B, and heat is generated by energizing both ends thereof.
In this heater, there is a place (especially the end portion) where heat is greatly released due to the shape of the holder, etc. Therefore, in order to give uniform heat to the transfer material, the heat generation amount of the end heater is increased. There was a need. On the other hand, also for the pressure roller, since low hardness silicon rubber is used to secure a sufficient nip, the coefficient of thermal expansion is inevitably high. Therefore, if the sequence for warming the pressure roller side sufficiently is continued as in the case of intermittent sheet feeding, the outer diameter of the end portion of the pressure roller becomes larger than that at the center. Then, as a result of the uneven state of the nip, the film cannot be fed normally,
Wrinkles and twists occur on the film itself. Therefore,
Also in this embodiment, there is an appropriate range in the calorific value distribution in the flat plate heating element.

FIG. 18 shows the result of examination of the feeding condition of the film when the heat generation amount at both ends of the heater was changed in this example. In this study, the pressure roller has an outer diameter of φ2.
0, the thickness of the elastic silicon rubber layer is 5 m
m and roller hardness of 25 ° (JISA) are used.
The linear expansion coefficient of this pressure roller is 1.0.
A temperature of × 10 ^-4 ° C ^-1 or more is suitable. Further, the heater was monitored by a temperature detector (not shown) attached to the heater so that the nip temperature was 160 ° C., and an experiment was conducted while controlling the temperature. It should be noted that the heater heat generation distribution referred to here is a comparison value when the heat generation amount per unit length of the heat generation portion shown in FIG. 17 is 100 (%). It can be seen from FIG. 18 that the film is fed without any trouble when the both ends of the heater heat distribution are 90% or more and 110% or less.

As described above, according to this embodiment, in the film type fixing device using the flat plate heating element, the linear expansion coefficient of the pressure roller is 1.0 × 10 ^-4 ° C. ^-1 or more. When using, the heating value distribution of the heating part is 90% at both ends.
As described above, when the content is 110% or less, the film can be reliably fed and a good fixing operation can be obtained.

[0047]

As described above, according to the present invention, in the paper discharge roller installed after the fixing device, the volume resistance value of the material used for the roller is 10 ¹⁰ Ω · cm or more,
By setting it within the range of 10 ¹³ Ω · cm or less, a good image can be obtained without causing problems such as electrostatic offset or paper discharge roller marks.

A pressure roller having a PFA tube on its surface layer, having a linear expansion coefficient of 1.0 × 10 ^-4 ° C ^-1
In the heat fixing device using the above, in the case of the roller heat fixing device using the halogen heater as the heat source, the light distribution of the halogen heater is 130% or more at both ends, and 190%.
In the following range, and in the case of a film type heat fixing device using a flat plate heating element, the heating value distribution of the heating element is 90% or more,
By setting the range to 110% or less, good fixing property can be obtained without causing wrinkles of the transfer material.

[Brief description of drawings]

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

FIG. 2 is a diagram showing details of a fixing device and a paper discharge unit in the image forming apparatus of FIG.

FIG. 3 is a diagram showing a paper discharge roller in the image forming apparatus of FIG.

FIG. 4 is a diagram showing a relationship between a discharge roller resistance value, an electrostatic offset, and a discharge roller trace.

FIG. 5 is a diagram showing a second embodiment of the present invention.

FIG. 6 is a diagram showing a third embodiment of the present invention.

FIG. 7 is a diagram showing the paper discharge roller of FIG. 6;

FIG. 8 is a diagram showing a fourth embodiment of the present invention.

FIG. 9 is a diagram showing a heater light distribution according to a fourth embodiment of the present invention.

FIG. 10 is a graph showing the relationship between the roller surface temperature and the pressure roller outer diameter difference according to the fourth embodiment of the present invention.

FIG. 11 is a diagram showing Comparative Example 1 regarding heater light distribution, roller surface temperature, and pressure roller outer diameter difference.

FIG. 12 is a diagram showing Comparative Example 2 regarding heater light distribution, roller surface temperature, and pressure roller outer diameter difference.

FIG. 13 is a diagram showing the relationship between heater light distribution and transfer material wrinkle level in the fourth embodiment of the present invention.

FIG. 14 is a diagram showing a fifth embodiment of the present invention.

FIG. 15 is a diagram showing the relationship between heater light distribution and wrinkle level of transfer material in the fifth embodiment of the present invention.

FIG. 16 is a diagram showing a sixth embodiment of the present invention.

FIG. 17 is an enlarged view of a heating element according to a sixth embodiment of the present invention.

FIG. 18 is a diagram showing a relationship between heater heat generation amount distribution and film feeding in the sixth embodiment of the present invention.

FIG. 19 is a diagram showing an example of a conventional image forming apparatus.

FIG. 20 is a diagram showing a fixing device and a paper discharge unit in a conventional image forming apparatus.

FIG. 21 is a diagram showing a conventional fixing device.

[Explanation of Codes] 1 ... Image bearing member 2 ... Developing device 3 ... Transfer roller 4 ... Discharge needle 5 ... Cleaning device 6 ... Primary charging roller 7 ... Laser exposure device 8 ... Conveying guide 9 ... Fixing device 10 ... Paper discharge roller 11 ... Paper discharge roller 12 ... Transfer material 15, 16 ... Diode 101 ... Fixing roller 102 ... Pressure roller 103 ... Heater 104 ... Frame 105 ... Temperature detector 106 ... CPU 107 ... Drive gear 108 ... Pressure roller bearing 109 ... Fixing Roller bearing 110 ... Pressure spring

Claims (4)

[Claims] 1. A latent image carrier rotatably disposed, and a charging unit, a developing device, and a charging unit, which are disposed around the latent image carrier so as to face each other along the rotation direction of the latent image carrier. Transfer means,
In an image forming apparatus having a fixing device including a fixing roller having a heating unit therein and a pressure roller in pressure contact with the fixing roller, and a discharge roller arranged after the fixing device, the discharge roller is , Volume resistance is 10 ¹⁰ Ωcm to 10 ¹³
An image forming apparatus using a material of Ωcm. 2. A fixing device comprising a pressure roller and a fixing roller, wherein the pressure roller comprises an elastic layer and a P on the surface side thereof.
In an image forming apparatus having an FA layer and having a linear expansion coefficient of 1.0 × 10 ⁻⁴ ° C. ⁻¹ or more, the light distribution of a halogen heater arranged in the fixing roller is
An image forming apparatus characterized in that both ends are set to 120% to 190%. 3. The image forming apparatus according to claim 2, wherein silicon rubber is used for the elastic layer of the pressure roller. 4. An image forming device comprising a flat plate heating element and a pressure roller facing the flat plate heating element with a film interposed therebetween, and the linear expansion coefficient of the pressure roller is 1.0 × 10 ⁻⁴ ° C. ⁻¹ or more. In the device, the heating value distribution of the flat plate heating element is 90% to 11% at both ends.
An image forming apparatus characterized by being set in a range of 0%.