JP2000206818A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steady fixing operation in a belt fixing unit. SOLUTION: A recording material S with a toner image formed thereon is passed through a pressure-contact part N between a heated endless belt 110 and a pressure roller 120 brought into pressure-contact therewith, so that the toner image is heated and melted and thereby fixed on the surface of the recording material. The oil application width O of an oiling roller 150 is smaller than a belt width B, also smaller than a maximum passage width P for a recording material suppliable for image formation, but larger than the formation width I of the maximum image formable on a recording material. This is particularly effective in the case of the formation of a full-color toner image on both sides of the recording material.

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 such as a printer, a facsimile, a copying machine, etc., capable of forming a toner image on a recording material such as paper by using an electrophotographic technique. More specifically, the present invention relates to a fixing device, and more particularly, to a release oil applying technique in a fixing device using an endless belt.

[0002]

2. Description of the Related Art In general, an image forming apparatus for forming a toner image on a recording material such as paper by using an electrophotographic technique includes a photoconductor which is driven to rotate, and an electrostatic latent image formed on the surface by exposing the photoconductor. Exposure means for forming an image, developing means for developing the electrostatic latent image into a toner image, transfer means for transferring the toner image to a recording material, and a recording material on which the toner image has been transferred by the transfer means And a fixing device for fixing the toner image on the recording material by heating while passing through the recording material.

As a conventional fixing device, a so-called belt fixing type fixing device as shown in FIG. 4 is known (Japanese Patent Laid-Open No. 8-334997).

In this fixing device, a fixing belt 1 is wound and stretched between a rotating fixing roller 2 and a heating roller 3, and a pressure roller 4 is attached to the fixing roller 2 via the fixing belt 1.
The recording material S on which the toner image T is formed is passed through the pressed portion N in the direction of the arrow in the drawing, and the toner image T is heated and melted and fixed on the recording material S.

Further, the fixing device is provided with a fixing belt 1 for preventing the toner on the recording material from being transferred to the surface of the fixing belt 1 (so-called offset phenomenon).
And an oil application roller 5 for applying a release oil such as silicone oil as a release agent to the surface of the roller.

[0006] The oil application width of the oil application roller 5 as the oil application means in the conventional fixing device is formed to be longer than the width of the fixing belt 1, and therefore extends over the entire width of the fixing belt 1. The configuration was such that oil was applied.

[0007]

In the fixing device of the above-described conventional image forming apparatus, the oil application width of the oil application means is larger than the width of the fixing belt 1, so that the surface of the fixing belt 1 The applied oil is
There is a problem that the fixing belt 1 easily wraps around the back surface 1a.

The oil spilled to the back surface 1a of the fixing belt 1 gradually penetrates between the fixing belt 1 and the fixing roller 2 as its driving roller. , The slippage occurs between the fixing roller 2 and the fixing belt 1, and as a result, a stable fixing operation may not be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which solves the above-mentioned problems, hardly causes the slip, and can perform a stable fixing operation.

[0010]

According to an aspect of the present invention, there is provided an image forming apparatus for forming a toner image on a recording material, the recording material comprising: a heated endless belt;
The fixing device includes a rotating body that is pressed against the endless belt, a backup member that supports the endless belt from the inside at the pressed portion, and an oil application unit that applies release oil to the surface of the endless belt. An image forming apparatus, wherein the toner image is heated and melted and fixed on a recording material by passing through the pressure contact portion, wherein an oil application width by the oil application means is smaller than a width of the endless belt.

According to the second aspect of the present invention, there is provided an image forming apparatus according to the first aspect.
In the above image forming apparatus, the oil application width is smaller than a maximum passage width of the recording material that can be used for image formation.

According to a third aspect of the present invention, there is provided an image forming apparatus according to the first aspect.
In the above image forming apparatus, the oil application width is larger than a maximum image formation width that can be formed on a recording material.

[0013] The image forming apparatus according to the fourth aspect is the first aspect.
In the above image forming apparatus, the oil application width is smaller than a maximum passage width of the recording material that can be used for image formation, and larger than a maximum image formation width that can be formed on the recording material. .

According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third or fourth aspect, the image forming apparatus is capable of forming a toner image on both sides of the recording material. It is characterized by.

According to a sixth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth or fifth aspect, the image forming apparatus forms a full-color image by superimposing a plurality of color toners. It is characterized by being possible.

[0016]

According to the image forming apparatus of the first aspect, a toner image is formed on a recording material, and the recording material is heated by an endless belt, a rotating body pressed against the endless belt, and The toner image is heated and melted and fixed on the recording material by passing through the pressure contact portion of the fixing device provided with a backup member that supports the endless belt from the inside at the pressure contact portion. Since the fixing device includes oil applying means for applying the release oil to the surface of the endless belt, the offset phenomenon hardly occurs.

Since the width of the oil applied by the oil applying means is smaller than the width of the endless belt, there is basically a region where no oil is applied at the surface edge of the endless belt. Since this region acts as a region for preventing the spread of oil, the situation in which the oil applied to the surface of the endless belt goes around to the back surface of the endless belt hardly occurs (at least is significantly reduced).

Therefore, according to the image forming apparatus of the present invention, not only when the endless belt is driven by the driving roller disposed inside but also when the endless belt is driven by the driving roller disposed outside. The presence of the region where oil is not applied enables stable driving, and as a result, stable fixing operation is performed.

According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, the oil application width is smaller than a maximum passage width of the recording material that can be used for image formation. Therefore, when the recording material used for image formation is the recording material having the maximum passage width, the oil applied by the oil applying means is almost absorbed by the recording material or almost transferred to the recording material. Therefore, the amount of oil accumulated on the belt after passing through the recording material becomes zero or significantly reduced. Further, recording materials of various sizes are used for image formation, and therefore, when a recording material having a smaller passing width than the oil application width is provided, oil may accumulate on the belt outside the passing width. Even after that, the recording material having the maximum passage width is used for image formation, and when passing through the fixing device, the oil accumulated earlier is almost absorbed by the recording material having the maximum passage width, or almost completely. Therefore, the amount of oil accumulated on the belt is also zero or significantly reduced.

For this reason, the above-mentioned area where the oil is not applied at the surface edge of the endless belt is well secured, and therefore, the situation where the oil applied to the surface of the endless belt wraps around to the back surface of the endless belt is almost eliminated. This will surely be prevented.

Therefore, according to the image forming apparatus of the second aspect, a more stable fixing operation is performed.

According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the oil application width is larger than a maximum image formation width that can be formed on a recording material. Since the maximum image forming width is smaller than the oil application width, the offset phenomenon is reliably prevented.

According to the image forming apparatus of the fourth aspect, in the image forming apparatus of the first aspect, the oil application width is smaller than the maximum passage width of the recording material that can be used for image formation, and the recording is performed. Since the width is larger than the maximum image forming width that can be formed on the material, the effects of the image forming apparatus according to the second and third aspects can be obtained at the same time.

That is, according to the image forming apparatus of the present invention, the offset phenomenon can be surely prevented while the more stable fixing operation is performed.

According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third or fourth aspect, a toner image can be formed on both surfaces of the recording material. According to the apparatus, the recording material having the toner images formed on both sides may pass through the pressure contact portion of the fixing device.

Since the toner on the recording material interferes with the absorption of oil into the recording material, if the toner image is formed on both sides of the recording material, the toner image is formed only on one side. Oil is less likely to be absorbed by the recording material. For this reason, according to the above-described conventional configuration, when toner images are formed on both surfaces of a recording material, the amount of oil wrapping around the back surface of the belt is increased, and the above-described slip is more likely to occur.

On the other hand, according to the image forming apparatus of the fifth aspect, at least the width of the oil applied by the oil applying means is smaller than the width of the endless belt. Is formed, a stable fixing operation can be performed.

That is, according to the image forming apparatus of the fifth aspect, an image can be formed (fixed) on both surfaces of the recording material by a stable fixing operation.

According to the image forming apparatus of the present invention, a full-color image can be formed by superimposing toners of a plurality of colors in the image forming apparatus of the first, second, third, fourth or fifth aspect. According to this image forming apparatus, the recording material on which the full-color image is formed on at least one side may pass through the pressing portion of the fixing device.

As described above, the toner on the recording material interferes with the absorption of oil into the recording material. Therefore, when a full-color image is formed on the recording material by superimposing a plurality of color toners, Oil is less likely to be absorbed by the recording material than when only a single color toner image is formed. For this reason, according to the conventional configuration described above, when a full-color image is formed by superimposing a plurality of color toners on a recording material, the amount of oil wrapping around the back surface of the belt increases, and the above-described slip occurs more. It will be easier.

On the other hand, according to the image forming apparatus of the present invention, at least the width of the oil applied by the oil applying means is smaller than the width of the endless belt. Even when a full-color image is formed by superimposing toners, a stable fixing operation is performed.

That is, according to the image forming apparatus of the sixth aspect, it is possible to form a stable full-color image, and when combined with the configuration of the fifth aspect, both sides of the recording material can be formed. It is possible to form (fix) a stable full-color image.

[0033]

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

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

First, the outline of the image forming apparatus will be described, and then the fixing device will be described in detail.

This image forming apparatus can form a single-color image and a full-color image using a developing device using four color toners of yellow (Y), cyan (C), magenta (M), and black (K). Device.

In FIG. 1, reference numeral 10 denotes a photoreceptor unit, and the photoreceptor 11 is rotatably driven in a direction indicated by an arrow in FIG.

The photoreceptor 11 has a conductive substrate and a photosensitive layer formed on the surface thereof.

Around the photoreceptor 11, along a rotation direction thereof, a charging roller 12 as a charging unit, an exposure unit 20 as an exposure unit, and a developing unit 30 as a development unit
(Y, C, M, K), an intermediate transfer unit 40 as a transfer unit, and a cleaning unit 13 are arranged. The photoconductor unit 10 includes a photoconductor 11, a charging roller 12, and a cleaning unit 13.

The charging roller 12 contacts the outer peripheral surface of the photoreceptor 11 to uniformly charge the outer peripheral surface. The outer peripheral surface of the uniformly charged photoconductor 11 is selectively exposed L1 according to desired image information by the exposure unit 20, and an electrostatic latent image is formed on the photoconductor 11 by the exposure L1. .

The electrostatic latent image is developed with toner applied by a developing unit 30.

As a developing device, a developing device 30 for yellow is used.
Developing device 30C for Y and cyan, developing device 30 for magenta
A developing unit 30K for M and black is provided. These developing units 30Y, 30C, 30M, 30K are:
Each is configured to be swingable, so that only the developing roller 31 of one developing unit can selectively contact the photoconductor 11. Therefore, these developing devices 30
A toner image is formed by applying any one of yellow, cyan, magenta, and black toners to the surface of the photoconductor 11 and developing the electrostatic latent image on the photoconductor 11.

The toner image is transferred onto an intermediate transfer belt 46 forming an intermediate transfer member of the intermediate transfer unit 40.

After the transfer, the cleaning means 13
The cleaner includes a cleaner blade for scraping off the toner remaining on and adhering to the outer peripheral surface of the photoconductor 11, and a receiving portion for receiving the toner scraped off by the cleaner blade.

The intermediate transfer unit 40 includes a driving roller 41
And four driven rollers 42, 43, 44, 45, and an endless intermediate transfer belt 46 as an intermediate transfer member stretched around these rollers.

The drive roller 41 has a gear (not shown) fixed to the end thereof, which is meshed with a drive gear (not shown) provided at the end of the photosensitive member 11. The intermediate transfer belt 46 is driven to rotate at the same peripheral speed, so that the intermediate transfer belt 46 is driven to circulate at substantially the same peripheral speed as the photosensitive member 11 in the direction of the arrow shown in the figure.

The driven roller 45 is arranged at a position where the intermediate transfer belt 46 is pressed against the photosensitive member 11 by its own tension between the driven roller 45 and the driven roller 41. In the primary transfer section T1
Are formed.

The driving roller 41 includes an intermediate transfer belt 46.
A primary transfer voltage is applied to the intermediate transfer belt 46 via the electrode roller (not shown).

The driven roller 42 is a tension roller, and urges the intermediate transfer belt 46 in the direction of its tension by urging means (not shown).

The driven roller 43 is a backup roller that forms the secondary transfer portion T2. A secondary transfer roller 48 as a secondary transfer unit is opposed to the backup roller 43 via an intermediate transfer belt 46. The secondary transfer roller 48 can be moved toward and away from the intermediate transfer belt 46 by a contact / separation mechanism (not shown). A secondary transfer voltage is applied to the secondary transfer roller 48.

The driven roller 44 is a backup roller for the belt cleaner 49. Belt cleaner 49
Is a cleaner blade 49 which comes into contact with the intermediate transfer belt 46 and scrapes off the toner remaining on and adhering to the outer peripheral surface thereof.
a, and a receiving portion 49b for receiving the toner scraped off by the cleaner blade 49a. The belt cleaner 49 can be moved toward and away from the intermediate transfer belt 46 by a contact / separation mechanism (not shown).

The intermediate transfer belt 46 is composed of a multi-layer belt having a conductive layer and a resistance layer formed on the conductive layer and pressed against the photoconductor 11. The conductive layer is formed on an insulating substrate made of a synthetic resin, and a primary transfer voltage is applied to the conductive layer via the above-described electrode roller.

In the course of circulating the intermediate transfer belt 46, the toner image on the photosensitive member 11 is transferred onto the intermediate transfer belt 46 in the primary transfer portion T1, and the toner image transferred onto the intermediate transfer belt 46 is Is transferred to a sheet (recording material) S such as a sheet supplied between the secondary transfer roller 48 and the secondary transfer unit T2.

The intermediate transfer unit 40 also incorporates the electrode roller, the urging means for the tension roller 42, the secondary transfer roller 48, and the belt cleaner 49.

The recording material S is fed to a sheet feeding device 50 serving as a sheet feeding means.
And is supplied to the secondary transfer portion T2 at a predetermined timing by the gate roller pair G. Reference numeral 51 denotes a paper feed cassette for stacking and holding the recording materials S, and reference numeral 52 denotes a pickup roller.

The recording material S to which the toner image has been transferred in the secondary transfer portion T2 passes through a fixing device 100 serving as a fixing means, and the toner image is fixed on the recording material S.

As will be described later in detail, the fixing device 100 includes an endless belt 110, a pressure roller 120 as a rotating member that is pressed against the endless belt 110, and supports the endless belt 110 from the inside at the pressed portion. A backup roller 130 as a backup member to perform, a heating roller 140 as a heating unit for heating the endless belt,
An oil roller 150 as oil applying means for applying release oil to the surface of the endless belt 110;
The recording material S passing therethrough is heated while being pressed by a pressure contact portion N between the endless belt 110 and the pressure roller 120, so that the toner image is fused and fixed on the recording material S.

The recording material S that has passed through the fixing device 100 is finally discharged through a paper discharge path 60 onto a sheet receiving portion 71 formed on a case 70 of the apparatus main body. The forming apparatus includes a reversing return path 60 ′ that can reverse the recording material S that has passed through the fixing device 100 and return the recording material S to the secondary transfer portion T2 again. That is, the conveying means of the recording material S in this embodiment is:
It has a paper discharge path 60 and a reverse return path 60 ′,
The paper discharge path 60 forms a part of the reverse return path 60 '.

The reversing return path 60 ′ carries the recording material S that has passed through the fixing device 100 and the recording material S once carried in.
And a switchback path 63 having two independent paper discharge paths 61 and 62 capable of reversing the recording material S. The recording material S reversely fed from the switchback path 63 is again directed to the secondary transfer portion T2. And a return path 64 for returning. Therefore, the recording material S returned to the secondary transfer portion T2 again by the reverse return path 60 'is turned upside down and returned to the secondary transfer portion T2.

Such an image forming apparatus can form a toner image only on the surface (first surface) of the recording material S, or can form a toner image on both surfaces (first and second surfaces). It can also be formed.

The outline of the operation of the entire image forming apparatus as described above is as follows.

(I) When a print command signal (image forming signal) from a not-shown host computer or the like (a personal computer or the like) is input to a not-shown control unit of the image forming apparatus, each of the photosensitive member 11 and the developing device 30 The roller 31 and the intermediate transfer belt 46 are driven to rotate.

(Ii) The outer peripheral surface of the photoconductor 11 is uniformly charged by the charging roller 12.

(Iii) The exposure unit 60 selectively exposes the outer peripheral surface of the uniformly charged photoreceptor 11 in accordance with the image information of the first color (for example, yellow). An image is formed.

(Iv) Only the developing roller of the developing device 30Y for the first color (for example, yellow) comes into contact with the photoconductor 11, whereby the electrostatic latent image is developed, and the first color (for example, yellow) is developed. Is formed on the photoconductor 11.

(V) A primary transfer voltage having a polarity opposite to that of the toner is applied to the intermediate transfer belt 46, and the toner image formed on the photoconductor 11 is transferred to the intermediate transfer belt 46 at the primary transfer portion T1. Is transferred to At this time, the secondary transfer roller 48 and the belt cleaner 49 are separated from the intermediate transfer belt 46.

(Vi) After the toner remaining on the photoconductor 11 is removed by the cleaning unit 13, the photoconductor 11 is neutralized by the neutralizing light L 2 from the neutralization unit 21.

(Vii) The above operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, the fourth color,
Are repeated on the intermediate transfer belt 46 to form a toner image corresponding to the content of the print command signal.

(Viii) The recording material S is supplied from the paper feeding device 50 at a predetermined timing, and immediately before or after the leading end of the recording material S reaches the secondary transfer portion T2 (in short, a desired portion on the recording material S) (At the timing when the toner image on the intermediate transfer belt 46 is transferred) to the secondary transfer roller 4
8 is pressed against the intermediate transfer belt 46 and a secondary transfer voltage is applied, so that the toner image on the intermediate transfer belt 46 (basically, a full-color image in which four color toner images are superimposed) is formed on the recording material S. Is transferred to Further, the belt cleaner 49 comes into contact with the intermediate transfer belt 46, and the toner remaining on the intermediate transfer belt 46 after the secondary transfer is removed.

(Ix) The toner image is fixed on the recording material S by passing the recording material S through the fixing device 100, and thereafter, the recording material S is directed to a predetermined position (in a case where it is not double-sided printing, a sheet receiving portion). In the case of double-sided printing, the paper is conveyed toward the return path 64 via the switchback path 63.

That is, when an image is formed only on the front surface (first surface), the recording material S fed from the paper feeding device 50 is used.
After the toner image is transferred to the first surface thereof in the secondary transfer portion T2 and fixed by the fixing device 100, the toner image is discharged onto the sheet receiving portion 71 via the paper discharge path 61 or 62. A path switching unit (not shown) is provided at the entrance 60A of each of the paper discharge paths 61 and 62, which determines which of the paper discharge paths (61 and 62) the recording material S is carried in. You.

When an image is formed on both sides (first and second sides), the recording material S fed from the sheet feeding device 50 is used.
After the toner image is transferred to the first surface by the secondary transfer portion T2 and fixed by the fixing device 100, the toner image temporarily enters the paper discharge path 61 or 62 (the switchback path 63), is reversely fed, and is returned. After passing through 64, the sheet is returned to the secondary transfer portion T2 again at a predetermined timing by the gate roller pair G, and the toner image is also transferred to the second surface. Thereafter, the toner image is also fixed on the second surface by the fixing device 100, and the paper ejection path 61 or 6
Then, the sheet is discharged onto the sheet receiving section 71 through the second section.

The outline of the image forming apparatus of this embodiment has been described above. Next, the fixing device 100 will be described in detail.

FIG. 2 is a schematic view showing a main part of the fixing device 100, and FIG. 3 is a schematic side view showing the same main part.

As described above, the fixing device 100 supports the endless belt 110, the pressing roller 120 as a rotating member that is pressed against the endless belt 110, and the endless belt 110 from the inside at the pressure contact portion N. It has a backup roller 130 as a backup member, a heating roller 140 as a heating means for heating the endless belt, and an oil roller 150 as an oil application means for applying release oil to the surface of the endless belt 110, The endless belt 110 includes the backup roller 130 and the heating roller 1.
It is stretched between 40 and 40.

The drive roller for rotating the endless belt 110 and each roller is an oil roller 1
Any roller other than 50 can be used, but in this embodiment, the pressing roller 120 is used as a driving roller.

That is, the pressing roller 120 is driven by a driving unit (not shown) provided in the main body of the image forming apparatus as shown in FIG.
, The backup roller 130, the endless belt 110, and the heating roller 14.
0 and the oil roller 150 are driven. More specifically, since the endless belt 110 and the backup roller 130 are pressed against the pressure roller 120, the endless belt 110 and the backup roller 130 follow the pressure roller 120, and the endless belt 110 , The heating roller 140 is driven by the endless belt 110,
Since the oil roller 150 is pressed against the endless belt 110, the oil roller 150 follows the endless belt 110.

The endless belt 110 is formed by forming a surface layer (for example, a silicone rubber layer) having excellent releasability on a recording material and toner on the surface of a thin metal (for example, nickel) belt base material. In FIG. 2, 11
Reference numeral 1 denotes a thermistor for detecting a surface temperature of the endless belt 110 at a portion where the endless belt 110 is wound around the backup roller 130. The thermistor 111 is provided on the upstream side of the pressure contact portion N with the pressure roller 120.

The backup roller 130 has a metal core 131 and a relatively thick elastic layer 132 provided on the surface of the core 131.
At 31a, the fixing device 100 is rotatably supported on the side plate 101 of the frame.

The heating roller 140 is formed in a pipe shape from a material having excellent thermal conductivity (eg, aluminum), and a halogen lamp 141 serving as a heat source is disposed inside the heating roller 140. The heating roller 140 is used for the endless belt 11.
It is possible to rapidly heat the endless belt 110 at the zero-wound portion. Heating roller 14 of this embodiment
Reference numeral 0 denotes a tension roller, and the tensioning direction of the endless belt 110 (see FIG.
In the direction of arrow F). In FIG. 3, reference numerals 142, 142 denote flange portions to which the urging means are connected. In FIG. 2, reference numeral 143 denotes a thermistor for detecting the temperature of the heating roller 140.

The pressure roller 120 comprises a pipe-shaped core material 121 having excellent heat conductivity, and a relatively thin elastic layer provided on the surface of the core material 121 and harder than the elastic layer 132 of the backup roller 130. 122 and the elastic layer 122
And a surface layer 122a having excellent releasability from the recording material and the toner formed on the surface thereof, and a halogen lamp 123 as a heat source is disposed inside the core material 121.

The pressure roller 120 is rotatably supported by the frame side plate 101 of the fixing device 100, and is driven to rotate in a direction indicated by an arrow in FIG. 2 by driving means (not shown) provided in the main body of the image forming apparatus. . The pressure roller 120 is attached so as not to move in the radial direction, and the elastic layer 122 and the backup roller 13
The elastic force of the elastic layer 132 of the backup roller 130
Is pressed against. The pressure contact portion N is formed by the elastic layer 132 of the backup roller 130 and the elastic layer 1 of the pressure roller 120.
Since it is thicker and softer than 22, it is formed in a convex shape on the backup roller 130 side. In FIG.
Is a thermistor for detecting the surface temperature of the pressure roller 120.

The oil roller 150 has a shaft 151 and an oil holding layer 152 fixed around the shaft 151 and made of a thick porous or fibrous material.
The oil holding layer 152 is impregnated with a release oil, and the surface thereof is formed of an oil-permeable thin film sheet for uniformizing the amount of applied oil, such as porous PTF.
It is covered with an E sheet 153.

The oil roller 150 is pressed against the endless belt 110 by an appropriate urging means (not shown) and is driven to rotate, and applies a release oil such as silicone oil to the surface of the endless belt 110. In FIG. 2, reference numeral 154 denotes a cleaning member made of felt or the like for cleaning the surface of the oil roller 150;
50 is pressed against the surface.

On the frame 101, the recording material S on which the toner image has been formed (transferred) by the secondary transfer portion T2 (see FIG. 1) is applied to the pressure contact portion (nip portion) N between the endless belt 110 and the pressure roller 120. A guide 102 is provided for guiding. Further, on the downstream side of the pressing portion N, a pair of paper discharge rollers 103 is provided.
And a guide 10 for guiding the recording material S after fixing to the paper discharge path 60.
4 are provided. Each of the thermistors is connected to the above-described control unit (not shown), and the heat source 1 is controlled by the control unit according to the temperature detected from each thermistor.
The amount of current supplied to 23 and 141 is controlled.

Next, the dimensions of the endless belt 110 and each roller will be described with reference to FIG.

B is the width of the endless belt 110, H is the length of the heating portion of the halogen lamp 141, which is the heat source of the heating roller 140, and O is the length of the oil holding layer 152 of the oil roller 150, that is, the oil application width.

P is the maximum width of the recording material S that can be used for image formation. Since the image forming apparatus of this embodiment can pass a recording material of A3 size at the maximum in a vertically placed state, the maximum passing width P of the recording material S is longer than the length of the recording material of A3 size in the lateral direction. (Length in the longitudinal direction of an A4 size recording material).

I is the maximum image forming width that can be formed on the recording material.

As can be seen from the above, in this embodiment, the oil application width O by the oil application means (oil roller) 130 is set smaller than the width B of the endless belt 110 (ie, B> O). ).

The oil application width O is set smaller than the maximum passage width P of the recording material S that can be used for image formation (that is, P> O), and can be formed on the recording material S. The width is set to be larger than the maximum image forming width I (that is, O> I).

Therefore, the relationship between the above lengths is B> P
>O> I.

According to the above-described image forming apparatus, the following operation and effect can be obtained.

(A) A toner image is formed on the recording material S, and the recording material S is
A pressure roller 120 as a rotating body pressed against the endless belt 110 and an endless belt 11
The toner image is heated and melted and fixed on the recording material S by passing through the pressure contact portion N in the fixing device 100 provided with a backup roller 130 as a backup member that supports 0 from the inside. Fixing device 10
In the case of No. 0, since the oil roller 150 as an oil applying means for applying the release oil to the surface of the endless belt 110 is provided, the offset phenomenon hardly occurs.

Since the oil application width O by the oil application means 150 is smaller than the width B of the endless belt 110, the surface edge of the endless belt 110 (B1, B1 in FIG. 3 in this embodiment). Area), there are basically areas B1 and B1 to which the oil is not applied. Since the areas B1 and B1 function as areas for preventing the spread of the oil, the areas B1 and B1 are applied to the surface of the endless belt 110. The situation in which the oil wraps around the back surface of the endless belt 110 hardly occurs (at least is significantly reduced).

For this reason, according to the image forming apparatus of this embodiment, the endless belt 110 is driven by the drive roller disposed inside (for example, the backup roller 13).
0 is used as a drive roller), as well as when driven by a drive roller disposed outside (for example, when the pressure roller 120 is used as a drive roller), stable driving is possible due to the presence of the area where the oil is not applied. As a result, a stable fixing operation is performed.

(B) Since the oil application width O is smaller than the maximum passage width P of the recording material S that can be used for image formation, the recording material S used for image formation has the maximum passage width. In the case of a recording material, the oil applied by the oil applying means is almost absorbed by the recording material S or almost transferred to the recording material S, and thus is accumulated on the belt 110 after passing through the recording material. The oil level will be zero or significantly lower. Further, recording materials of various sizes are used for image formation, and therefore, a recording material having a smaller passage width than the oil application width O (for example, a recording material having a passage width P1 smaller than the oil application width O as shown in FIG. 3). Even if the material S1 (for example, a B5 size recording material in a vertically placed state) is provided, oil may accumulate outside the passage width (the area indicated by A in FIG. 3).
Thereafter, the recording material S having the maximum passage width P is used for image formation, and when the recording material S has passed through the fixing device 100, the oil previously accumulated in the area A is almost absorbed by the recording material S having the maximum passage width. Alternatively, almost all of the oil is transferred to the recording material S, so that the oil amount accumulated on the belt 110 is also zero or significantly reduced.

For this reason, in the above-described regions B1, B on which the oil is not applied on the surface edge of the endless belt 110.
1 is well secured and therefore also the endless belt 110
The situation where the oil applied to the surface of the endless belt 110 goes around the back surface of the endless belt 110 is almost certainly prevented.

Therefore, according to the image forming apparatus of this embodiment, a more stable fixing operation can be performed.

(C) The oil application width O is larger than the maximum image formation width I that can be formed on the recording material S. In other words, the maximum image formation width I is smaller than the oil application width O. Therefore, the offset phenomenon is reliably prevented, and a clear image can be obtained.

(D) The oil application width O is smaller than the maximum passage width P of the recording material S that can be used for image formation and larger than the maximum image formation width I that can be formed on the recording material S. Therefore, the effects (b) and (c) can be obtained at the same time.

That is, according to the image forming apparatus of this embodiment, a more stable fixing operation can be performed, and at the same time, the offset phenomenon can be surely prevented, and a clear image can be obtained.

(E) According to this image forming apparatus, since a toner image can be formed on both surfaces of the recording material S, the recording material S having the toner images formed on both surfaces is pressed into the press contact portion N in the fixing device 100. May pass through.

Since the toner on the recording material S inhibits the absorption of oil into the recording material S, if a toner image is formed on both sides of the recording material S, the toner image is formed on only one side. Oil is less likely to be absorbed by the recording material S than in the case where Therefore, according to the above-described conventional configuration, when toner images are formed on both surfaces of the recording material S,
The amount of oil spilled to the back surface of the belt is increased, and the above-mentioned slip is more likely to occur.

On the other hand, according to the image forming apparatus of this embodiment, the oil application width O by the oil application means is:
Since it is smaller than the width B of the endless belt 110,
Even when toner images are formed on both sides of the recording material S, a stable fixing operation is performed.

That is, according to the image forming apparatus of this embodiment, an image can be formed (fixed) on both surfaces of the recording material S by a stable fixing operation.

(F) According to this image forming apparatus, since a full-color image can be formed by superimposing a plurality of color toners, the recording material S on which the full-color image is formed on at least one side is fixed. 100 may pass through the pressure contact portion N.

As described above, the toner on the recording material S interferes with the absorption of oil into the recording material S, so that a full-color image is formed on the recording material S by superimposing a plurality of color toners. In this case, the oil is less likely to be absorbed by the recording material S than when only a single color toner image is formed. For this reason, according to the above-described conventional configuration, when a full-color image is formed by superimposing toners of a plurality of colors on the recording material S, the amount of oil wrapping around the back surface of the belt is increased, and the slip described above is further increased. It is easy to occur.

On the other hand, according to the image forming apparatus of this embodiment, the oil application width O by the oil application means is
Since it is smaller than the width B of the endless belt 110,
Even when a full-color image is formed on the recording material S by superimposing toners of a plurality of colors, a stable fixing operation can be performed.

That is, according to the image forming apparatus of this embodiment, it is possible to form a stable full-color image, and to form (fix) a stable full-color image on both sides of the recording material S. It becomes possible.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the present invention.

[0112]

According to any of the image forming apparatuses of the first to sixth aspects, a stable fixing operation can be performed.

Further, according to the image forming apparatus of the second aspect, a more stable fixing operation can be performed.

According to the image forming apparatus of the third aspect, the offset phenomenon is reliably prevented.

According to the image forming apparatus of the fourth aspect, the offset phenomenon can be surely prevented while the more stable fixing operation is performed.

According to the image forming apparatus of the fifth aspect, an image can be formed (fixed) on both surfaces of the recording material by a stable fixing operation.

According to the image forming apparatus of the present invention, a stable full-color image can be formed.

[0118]

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing a main part of the fixing device 100.

FIG. 3 is a schematic side view showing a main part of the fixing device 100.

FIG. 4 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 S Recording Material 100 Fixing Unit 110 Endless Belt 120 Pressure Roller (Rotating Body) 130 Backup Roller (Backup Member) 150 Oil Roller (Oil Application Means) N Pressure Contact Area O Oil Application Width P Maximum Passage Width of Recording Material I Maximum Image Formation width

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazutoshi Fujisawa 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation F-term (reference) 2H030 AD04 2H033 AA11 BA02 BA11 BA46 BA59

Claims (6)

[Claims] 1. A toner image is formed on a recording material, and the recording material is heated by an endless belt, a rotating body is pressed against the endless belt, and the endless belt is supported from the inside by a press contact portion. Image forming apparatus which passes through a pressure contact portion of a fixing device provided with a backup member to be applied and an oil applying means for applying release oil to the surface of the endless belt, heats and melts the toner image, and fixes the toner image on a recording material. An image forming apparatus, wherein an oil application width by the oil application unit is smaller than a width of the endless belt. 2. The image forming apparatus according to claim 1, wherein the oil application width is smaller than a maximum passage width of the recording material that can be used for image formation. 3. The image forming apparatus according to claim 1, wherein the oil application width is larger than a maximum image formation width that can be formed on a recording material. 4. The image forming apparatus according to claim 1, wherein the oil application width is smaller than a maximum passage width of the recording material that can be used for image formation and larger than a maximum image formation width that can be formed on the recording material. 2. The image forming apparatus according to 1. 5. The image forming apparatus according to claim 1, wherein the image forming apparatus is capable of forming a toner image on both sides of the recording material. 6. The image forming apparatus according to claim 1, wherein said image forming apparatus is capable of forming a full-color image by superimposing toners of a plurality of colors.