JP2002251087A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent the occurrence of a tailing phenomenon with a simple constitution. SOLUTION: As for the image forming device provided with an image forming part for forming a toner image on a recording paper and a fixing part 20 for fixing the toner image on the recording paper guided from the image forming part, and provided with a thermal fixing roller 21 for heating the recording paper and a press contact roller 22 for bringing the recording paper in press contact with the fixing roller 21 in the fixing part 20, the recording paper is made to enter a nip area 23 formed between the thermal fixing roller 21 and the press contact roller 22 from a position closer to the thermal fixing roller 21 than a reference line L extending toward the tangent direction of the thermal fixing roller 21 after passing through the upstream end part in the recording paper carrying direction in the nip area 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copier, a printer or a printer having an image forming section for forming a toner image on a recording sheet and a fixing section for fixing the toner image on the recording sheet derived from the image forming section. The present invention relates to an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a nip area 2 formed between a heat fixing roller 21 and a pressing roller 22 is formed.
By heating the recording paper P in 3, when the toner image T is fixed on the surface of the recording paper P, the moisture impregnated in the recording paper P evaporates to generate water vapor S, and It is known that the toner particles t constituting the toner image T held in the recording paper P are blown backward by the blowing pressure of the water vapor S and adhere to the recording paper P, that is, a so-called tailing phenomenon occurs. .

In order to prevent the occurrence of the trailing phenomenon, for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-98673,
By applying a bias from a high-voltage power supply to the fixing film constituting the heat fixing roller (heater unit) and grounding the fixing entrance guide, a current flows through the recording paper from the fixing entrance guide through the recording paper when the toner image is fixed. By flowing the film, the holding force of the unfixed toner image on the recording paper is increased, and by providing the protruding portion, the contact pressure between the recording paper and the fixing entrance guide is increased, and the electrical pressure is increased. It has been practiced to reduce contact resistance and increase the holding power of the toner image to prevent toner particles from scattering.

[0004]

According to the image forming apparatus described in the above publication, the toner image T held on the recording paper P by the water vapor S generated when the recording paper is heated in the fixing unit. Can be suppressed to some extent from the tailing phenomenon caused by the toner particles t constituting the toner particles being blown backward.

However, as described above, when the toner image is fixed, the current flows from the fixing entrance guide to the fixing film of the heat fixing roller via the recording paper through the fixing paper, for example, so that the unfixed toner image is retained on the recording paper. In the case where the configuration is designed to increase the power, there are problems that expensive specifications in terms of the system are required, the cost is greatly increased, and the running cost of the apparatus is also high.

In particular, when an image forming apparatus in which the fixing speed of the toner image is set to a high value is used in a high-temperature and high-humidity environment, the recording paper is heated in a fixing unit, and the recording paper is heated. A large amount of water contained in the paper evaporates instantaneously, and the spray pressure of water vapor on the unfixed toner on the recording paper increases, so that there is a problem that it is difficult to avoid the occurrence of the trailing phenomenon.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide an image forming apparatus which can effectively prevent the occurrence of a trailing phenomenon with a simple configuration.

[0008]

According to the first aspect of the present invention,
An image forming unit for forming a toner image on a recording sheet, and a fixing unit for fixing the toner image on a recording sheet derived from the image forming unit, and a heat fixing unit for heating the recording sheet on the fixing unit In an image forming apparatus provided with a roller and a pressure roller that presses the recording paper against the heat fixing roller, an upstream end of a nip region formed between the heat fixing roller and the pressure roller in the recording paper conveyance direction. The recording paper is configured to enter the nip area from a position closer to the heat fixing roller than a reference line extending in a tangential direction of the heat fixing roller through the portion.

According to the above arrangement, when fixing the toner image in the fixing section, most of the water vapor generated by evaporation of the water impregnated on the recording paper flows along the back surface of the recording paper. Therefore, the occurrence of the trailing phenomenon caused by the toner particles constituting the toner image formed on the surface of the recording paper being blown off by the water vapor is effectively prevented.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the angle between the reference line and the recording paper entering direction with respect to the nip area is set to 4 ° to 30 °.
It is set within the range of.

According to the above configuration, the occurrence of the trailing phenomenon caused by the spraying of the water vapor on the surface side of the recording paper is effectively suppressed, and before the recording paper reaches the nip area, The occurrence of image disturbance due to the surface contacting the heat fixing roller is effectively prevented.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the recording paper transport direction is deflected to the heat fixing roller side upstream of the nip area in the recording paper transport direction. A deflecting guide is provided, and the conveying direction of the recording sheet deflected by the deflecting guide is set closer to the heat fixing roller than the reference line.

According to the above arrangement, the recording paper is deflected by the deflection guide regardless of the conveyance direction of the recording paper derived from the image forming section.
The entry angle of the recording paper with respect to the nip area is set to an appropriate value, so that the occurrence of the trailing phenomenon is effectively prevented.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the drawing direction of the recording paper drawn from the image forming section is set closer to the heat fixing roller than the reference line. By doing so, the recording paper is configured to enter the nip area from a position near the heat fixing roller.

According to the above arrangement, the angle of entry of the recording sheet with respect to the nip region is set to an appropriate value between the image forming section and the fixing section without changing the conveying direction of the recording sheet. .

[0016]

FIG. 1 shows an embodiment of an image forming apparatus 1 according to the present invention. This image forming apparatus 1
In the copying machine main body 101 constituting the electrostatic copying machine, the surface layer of the photosensitive drum 103 rotating in the direction A in FIG.
The charging unit 102 charges the battery to a predetermined positive potential, and the laser beam emitted from the laser scanning unit (LSU) 105 based on the document image read by the document reading unit 104 loses the charge of the positive potential. A developing unit 10 is added to the electrostatic latent image on the photosensitive drum 103.
An image forming unit 10 for forming a toner image by attaching toner charged to a positive potential supplied from the image forming unit 6; and a fixing unit 20 for fixing the toner image on recording paper derived from the image forming unit 10. ing.

The image forming section 10 performs a negative corona discharge from the back side of the recording paper conveyed from the paper feeding mechanism 200 toward the installation section of the photoconductive drum 103 so that the photoconductive drum 103 Transfer roller 108 for electrostatically transferring the toner image formed on the surface of
Is provided. Then, the recording paper separated from the photosensitive drum 103 is conveyed to the fixing unit 20 where the toner image is fixed, and then as it is (or after being inverted by a switchback unit (not shown) and double-sided copied). Is discharged to a discharge unit 111 by a discharge roller pair 110. Reference numeral 112 denotes a cleaning unit that removes residual toner and the like on the photosensitive drum 103.

The paper feeding mechanism 200 includes a copying machine main body 101.
Paper cassettes 201, 20 detachably attached to
2 and a stack bypass 203 provided thereabove. In the paper feed mechanism 200, a vertical transport path 204 for transporting the recording paper fed from each of the paper feed cassettes 201 and 202 to the photosensitive drum 103 and recording in a direction from the stack bypass 203 to the photosensitive drum 103. A bypass transport path 205 for transporting the paper is provided. The vertical transport path 204 is arranged in a substantially vertical direction at a position deviated to the left side in the figure in the copying machine main body 101, and the stack bypass 203 and the bypass transport path 205 are on the opposite side of the vertical transport path 204, That is, they are arranged substantially horizontally from the right side in the figure to the center position.

Pick-up rollers 206, 20 for taking out recording sheets stored in the paper feed cassettes 201, 202 and the stack bypass 203 are provided in the respective feed cassettes 201, 202 and the stack bypass 203.
7, 208, and a pair of paper feed rollers 209, 210, 211 for feeding (separating) the recording paper one by one to the conveyance path.

The vertical transport path 204 is provided with a pair of transport rollers 212 and 213,
No. 0 merges below the transfer position where the photosensitive drum 103 and the transfer roller 108 face each other. This confluence 205
A is provided with a pair of registration rollers 214 for holding the recording paper at a predetermined position, and the downstream side thereof is the transport route as described above.

In the fixing section 20, as shown in FIG.
A heat fixing roller 21 having a heating power supply, a pressure roller 22 for pressing the recording paper against the heat fixing roller 21 at a predetermined pressure, and a heat fixing roller 21 And a guide guide 24 for guiding to a nip area 23 formed between the pressure roller 22 and the pressing roller 22.

The nip area 23 is formed by the heat fixing roller 21
When the pressure contact roller 22 is pressed against the peripheral surface, the peripheral surfaces of the rollers 21 and 22 are elastically deformed and are in contact with each other. When the recording paper passes through the nip area 23, the recording paper receives a predetermined pressure and
The toner image is fixed on the recording paper by the heat applied from the recording medium.

The guide 24 is provided in the nip area 2
3 at the downstream side in the recording paper transport direction of the pressing roller 2.
2 and a regulating guide 242 disposed below the heat fixing roller 21 so as to face the deflection guide 241.

The deflection guide 241 is connected to the heat fixing roller 2.
1 and an upper guide 241b inclined so as to point toward the upstream end A of the nip region 23. The conveying direction of the recording paper led upward from the image forming unit 10 is deflected toward the heat fixing roller 21 by the lower guide 241a of the deflection guide 241.

The upper portion 24 of the deflection guide 241
1b is the upstream end of the nip area 23 in the recording paper conveyance direction, that is, from the side of the heat fixing roller 21 from a reference line L extending in the tangential direction of the heat fixing roller 21 through the lower end A of the nip area 23. The recording paper is configured to enter the nip area 23. That is, the deflection guide 2
The upper guide 241 b of the deflection guide 241 is disposed closer to the heat fixing roller 21 than the reference line L, and is inclined so as to point toward the upstream end A of the nip region 23. The approach direction B of the recording paper guided along 241b is set closer to the heat fixing roller 21 than the reference line L by a predetermined angle.

The reference line L extending in the tangential direction of the heat fixing roller 21 through the upstream end A of the nip area 23 and the upstream end A of the nip area 23 set by the upper guide 241b of the deflection guide 241. Is not particularly limited as long as the angle θ between the recording paper and the recording paper entering direction B is 0 ° or more. However, if the angle θ is too small, the effect of suppressing the occurrence of the trailing phenomenon tends to decrease as described later, and if the angle θ is too large,
Before the recording paper reaches the nip area 23, the heat fixing roller 2
1 because the image tends to be disturbed by contact with
Is desirably set within a range of 4 ° to 30 °.

On the other hand, the regulation guide 242 is disposed below the heat fixing roller 21 and is installed with its guide surface inclined so as to point toward the nip area 23. Thereby, the regulation guide 241 is provided.
When the recording paper deflected along the lower guide 241a is bent so as to be directed to the heat fixing roller 21 side,
The bending is regulated.

In the above configuration, the recording paper supplied to the image forming section 10 is formed after a toner image is formed on the surface thereof.
It is led upward from the image forming unit 10 and is introduced into the fixing unit 20. At this time, the recording paper led out from the image forming unit 10 is transferred to the lower guide 24 of the deflection guide 241.
1a, the heat fixing roller 21 is moved beyond the reference line L.
After being deflected to the side, the upper guide 241 of the deflection guide
b, and is supplied to the upstream end A of the nip area 23. Then, the recording paper is nipped by the heat fixing roller 21 and the pressure contact and the roller 22 with a predetermined pressure contact force,
The toner image is heated by the heat fixing roller 21 to be fixed on the recording paper.

The image forming section 10 forms a toner image on a recording sheet as described above, and the fixing section 20 fixes the toner image on the recording sheet derived from the image forming section 10. 20 is provided with a heat fixing roller 21 for heating the recording paper and a pressure roller 22 for pressing the recording paper against the heat fixing roller 21 in the image forming apparatus 1. From the position closer to the heat fixing roller 21 than a reference line L extending in the tangential direction of the heat fixing roller 22 through the upstream end portion A of the nip area 23 formed in the nip area 23 in the recording paper conveyance direction. Is set so that the recording paper enters the upstream end portion A of the image forming apparatus, the image forming apparatus 1 in which the fixing speed of the toner image is set to a fast value can be used in an environment of high temperature and high humidity. use Even if it is possible to effectively prevent the tailing phenomenon from occurring.

That is, by setting the direction B of the recording paper entering the nip area 23 closer to the heat fixing roller 21 than the reference line L, the recording paper is brought close to the peripheral surface of the heat fixing roller 21. In the state in which the recording sheet P is made to enter the nip area 23, when the fixing unit 20 fixes the toner image, the moisture impregnated in the recording paper P evaporates as shown in FIG. Most of the generated steam S flows along the back surface of the recording paper P. Therefore, the toner particles constituting the toner image T formed on the surface of the recording paper P are:
It is effectively prevented from being blown off by the water vapor S, and the occurrence of the tailing phenomenon due to the toner particles adhering to the recording paper P is significantly reduced.

Further, at the time of fixing the toner image T, the deflection guide 241 does not employ a complicated structure such as increasing the holding force of the toner image by applying a current to the recording paper P. Since the occurrence of the trailing phenomenon can be prevented with a simple configuration that regulates the approach direction B of P, there is an advantage that the manufacturing cost and the running cost of the image forming apparatus 1 can be reduced.

In particular, the reference line L extending in the tangential direction of the heat fixing roller 21 through the upstream end A of the nip area 23 in the recording paper conveyance direction and the direction B in which the recording paper P enters the nip area 23 are defined. When the angle θ is set in the range of 4 ° to 30 °, the occurrence of the trailing phenomenon caused by spraying the water vapor S on the surface side of the recording paper P is effectively suppressed. There is an advantage that the image can be effectively prevented from being disturbed by the recording paper P coming into contact with the heat fixing roller 21 before reaching the nip area 23.

An experimental example performed to confirm the effect of suppressing the occurrence of the trailing phenomenon will be described below. That is, the angle θ is changed to various values within a range of −12.9 ° to 11.0 °, and the transfer current supplied to the transfer roller 108 is set to 20 μA to 200 μA.
An image was recorded by longitudinally feeding A5 size paper, and an experiment was performed to confirm the occurrence of the trailing phenomenon. As a result, data as shown in Table 1 below was obtained. Note that the angle θ becomes a negative value because the recording paper P
Is located closer to the pressing roller 22 than the reference line L. Further, the transfer voltage is also changed from 0.83 Kv to 2.
It changed within the range of 58 Kv.

[0034]

[Table 1]

From the data shown in Table 1, when the angle θ is a positive value, that is, when the approach direction B of the recording paper P is set closer to the thermal transfer roller 21 than the reference line L, the value is large. Indeed, it was confirmed that the occurrence of the trailing phenomenon was effectively reduced. In particular, the angle θ
Is set to about 4 ° or more, it has been confirmed that the occurrence of the trailing phenomenon is more significantly reduced.

If the angle θ is larger than 30 °, it is difficult to cause the recording paper P to directly enter the nip area 23, and the recording paper P is moved before reaching the nip area 23.
Is inevitable to contact the heat fixing roller 21, and the toner image T formed on the surface of the recording paper P is not nipped by the heat fixing roller 21 and the pressing roller 22, and the toner image T Is likely to be easily disturbed due to the fact that the image is heated and fixed on the recording paper P. Therefore, in order to effectively suppress the disturbance of the image, it is preferable to set the angle θ between the reference line L and the direction in which the recording paper P enters as described above to 30 ° or less.

In the above embodiment, the nip region 23
A deflection guide 241 for deflecting the conveyance direction of the recording paper P toward the heat fixing roller 21 is provided on the upstream side in the recording paper conveyance direction.
By setting the conveyance direction of the recording paper P deflected by the deflection guide 241 to the heat fixing roller 21 side with respect to the reference line L, the nip is moved from a position closer to the heat fixing roller 21 than the reference line L. Since the recording paper P is configured to enter the area 23, the entrance angle of the recording paper P with respect to the nip area 23 can be easily determined regardless of the transport direction of the recording paper P derived from the image forming unit 10. Is set to an appropriate value to prevent the occurrence of the trailing phenomenon.

As shown in FIG. 4, by setting the drawing direction of the recording paper P drawn out from the image forming section 10 to the heat fixing roller 21 side with respect to the reference line L, this heat fixing roller 21 to the nip area 23
May be configured so that the recording paper P enters. In the case of such a configuration, the image forming unit 10 and the fixing unit 2
Since the approach angle of the recording sheet P with respect to the nip area 23 can be set to an appropriate value between 0 and the transport direction of the recording sheet P without changing the transport direction, the approach direction of the recording sheet P can be stabilized. There is an advantage that is.

In the above embodiment, an example in which the present invention is applied to an electrostatic copying machine has been described. However, the present invention is not limited to this, and the present invention relates to an electrophotographic image forming apparatus 1 such as a facsimile or a printer. Can be applied.

[0040]

As described above, according to the first aspect of the present invention, there is provided an image forming section for forming a toner image on a recording sheet, and a fixing for fixing the toner image on the recording sheet derived from the image forming section. An image forming apparatus having a fixing unit, a heat fixing roller for heating the recording paper, and a pressing roller for pressing the recording paper against the heat fixing roller. The recording paper enters the nip area from a position closer to the heat fixing roller than a reference line extending in the tangential direction of the heat fixing roller through the upstream end of the nip area formed between the pressure roller and the nip area in the recording paper conveyance direction. In this configuration, most of the water vapor generated when the toner image is fixed in the fixing section flows along the back surface of the recording paper, so that the toner formed on the surface of the recording paper is formed. That the toner particles are blown off effectively prevented constituting an image, it is possible to the toner particles is reduced significantly the occurrence of trailing phenomenon by adhering to the recording paper. Moreover, at the time of fixing the toner image, a simple configuration that regulates the direction in which the recording paper enters the nip region without adopting a complicated configuration such as increasing the holding force of the toner image by flowing a current to the recording paper. Therefore, since the occurrence of the trailing phenomenon can be prevented, there is an advantage that the manufacturing cost and the running cost of the image forming apparatus can be reduced.

Further, in the invention according to claim 2, the angle formed between the reference line and the direction in which the recording paper enters the nip area is set within a range of 4 ° to 30 °, so that the front side of the recording paper is Along with being able to effectively suppress the occurrence of the trailing phenomenon caused by spraying the steam,
It is possible to effectively prevent image disturbance due to the recording paper P coming into contact with the heat fixing roller before reaching the nip area.

According to a third aspect of the present invention, a deflecting guide for deflecting the conveying direction of the recording paper toward the heat fixing roller is provided upstream of the nip area in the conveying direction of the recording paper. The conveyance direction of the recording paper is set to be closer to the heat fixing roller than the reference line. Therefore, regardless of the conveyance direction of the recording paper derived from the image forming unit, the recording paper can be easily transported to the nip area with a simple configuration. There is an advantage that the trailing phenomenon can be prevented by setting the approach angle to an appropriate value.

According to a fourth aspect of the present invention, the direction in which the recording paper is led out from the image forming section is set closer to the heat fixing roller than the reference line, so that the position closer to the heat fixing roller is set. Since the recording paper is configured to enter the nip area from between the image forming unit and the fixing unit without changing the transport direction of the recording paper,
By setting the entry angle of the recording sheet with respect to the nip area to an appropriate value, the entry direction of the recording sheet can be stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram illustrating a specific configuration of a fixing unit.

FIG. 3 is an explanatory diagram showing the operation of the present invention.

FIG. 4 is an explanatory diagram illustrating a modification of a fixing unit.

FIG. 5 is an explanatory diagram showing a conventional example of an image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming apparatus 10 image forming unit 20 fixing unit 21 heat fixing roller 22 pressure contact roller 23 nip area 241 deflection guide

Claims (4)

[Claims] An image forming section for forming a toner image on a recording sheet; and a fixing section for fixing the toner image on a recording sheet derived from the image forming section. In the image forming apparatus provided with a heat fixing roller that heats the recording paper and a pressure roller that presses the recording paper against the heat fixing roller, a recording paper in a nip region formed between the heat fixing roller and the pressure roller is provided. An image forming apparatus, wherein a recording sheet is made to enter the nip area from a position closer to the heat fixing roller than a reference line extending in a tangential direction of the heat fixing roller through an upstream end portion in a conveying direction. 2. The image forming apparatus according to claim 1, wherein an angle between the reference line and a direction in which the recording paper enters the nip area is set within a range of 4 ° to 30 °. 3. A deflecting guide for deflecting the conveying direction of the recording paper toward the heat fixing roller is provided upstream of the nip area in the conveying direction of the recording paper. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is set closer to the heat fixing roller than the reference line. 4. The recording paper, which is led out of the image forming section, is set on the heat fixing roller side with respect to the reference line, so that the recording paper is moved from a position close to the heat fixing roller to the nip area. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to enter the image forming apparatus.