JP2001022216A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of the cleaning performance of a fixing device having toner cleaning control, by actively expelling CaCO3 particles together with soiled toner during control of pressure-roller cleaning. SOLUTION: As control for cleaning a pressure roller 17, a proper electric field is generated between the pressure roller 17 and a cleaning sheet after soiled toner is melted by the heat applied to a fixing nip N during a cleaning mode using the cleaning sheet such as a sheet with a solid black image formed on its surface or a blank sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium having an unfixed toner image sandwiched and conveyed to a press contact portion formed by bringing a pair of fixing rotators into pressure contact with each other. A fixing device that heats and fixes an image on the recording material, and an electrophotographic copying machine to which the fixing device is applied;
The present invention relates to an image forming apparatus such as a laser beam printer.

[0002]

2. Description of the Related Art Conventionally, as a fixing device of this type, a heat roller system and an on-demand system are known. A heat roller type fixing device is a press-contact nip portion (fixing nip portion) between a heating roller (fixing roller) maintained at a predetermined heating temperature by a built-in heat source such as a halogen heater and an elastic pressure roller pressed against the heating roller. Then, a recording material having an unfixed toner image (hereinafter abbreviated as toner) is introduced and conveyed, and the unfixed toner image on the recording material surface is heated by the heat from the heating roller. It is to fix it.

[0003] Of the above-mentioned heating roller and pressure roller, the heating roller that comes into contact with the surface of the recording material is a cylindrical roller whose surface is made of a material having good releasability. The heater heats the toner via the heating roller. On the other hand, the pressure roller in contact with the back surface of the recording material is configured by providing an elastic layer on a cored bar, and applies an appropriate pressure to the toner layer.

The fixing device of the on-demand system eliminates the disadvantage of the heat roller system which causes a large amount of energy loss, and enables quick start and power saving. This is because the heat capacity of the fixing device using the heat roller method is reduced by reducing the heat capacity of the fixing device by using a heater such as ceramic and a thin film such as polyimide instead of the halogen heater and the fixing roller in the heat roller method. Is solved.

In such an on-demand type fixing device, since the heat capacity is small and the temperature responsiveness is good, there is no need to preheat the fixing device, and fine temperature control is possible. Can be turned off.

In any of the above-mentioned fixing methods, ideally, all of the toner on the surface of the recording material is heated and melted and fixed on the surface of the recording material. If there is too much toner in the hot offset state, toner that is electrostatically offset to the heating rotator (hereinafter referred to as “toner stain”),
These toner stains adhere to the roller surface of the heating roller and the pressure roller, which is the one having poor releasability.

When the releasability of the heating roller is lower, toner stains adhere to the heating roller.
Since the toner is constantly heated to the toner melting temperature during image formation, the toner stain is in a molten state, and when the next recording material comes, it is mixed with the toner image on its surface and moves to the recording material. There is not much condition that the rollers are continuously dirty.

On the other hand, when the releasability on the pressure roller side is lower, the toner stain once offset on the heating roller is transferred to the pressure roller. The pressure roller has a lower temperature than the heating roller, and the transferred toner stain does not always exist in a completely melted state on the pressure roller. Further, since the toner image on the surface of the recording material does not come into contact with the pressure roller side, dirt rarely moves to the recording material side.

When toner stains on the pressure roller accumulate, the releasability of the pressure roller is further reduced, so that a recording material (especially when the recording material is an OHP film) is wound around the pressure roller. In some cases, however, there is a problem that the accumulated toner stains quickly stain the back surface of the recording material.

In order to solve these problems, that is, the accumulation of toner stains, and the accompanying drawbacks of the recording material and the stains on the back surface of the recording material, it is effective to improve the releasability of the pressure roller. is there. However, when coating a material with good releasability or coating a tube with good releasability to improve the releasability, the hardness of the pressure roller increases or the structure becomes complicated. Therefore, new problems such as an increase in cost arise.

There are several methods for cleaning the surface of the pressure roller against toner contamination in order to solve the above-mentioned problems.

First, a cleaning sheet having a solid black image printed on one side is formed by a heating roller and a pressure roller with the side on which the solid black image is printed facing the pressure roller. The present applicant has previously proposed a method of attaching dirt on the pressure roller to the cleaning sheet by passing the paper through the fixing nip portion.

This is because the adhesive force of the toner stain in a semi-molten state on the pressure roller depends on each member (recording material P, pressure roller R,
The difference is used for the solid black image T). Here, the adhesive force between the toner stain in the semi-molten state on the pressure roller and the recording material P is F _P , the adhesive force between the toner stain and the pressure roller R is F _R , and the toner stain is also Assuming that the adhesive force between the image and the solid black image is F _T ,
The dirt toner on the pressure roller does not adhere to the back surface of the recording material in normal image formation, but adheres to the cleaning sheet due to the adhesive force F _R between the dirt toner and the pressure roller.
It is greater than the adhesive force F _P between the smear-toner and the recording material, the smear-toner and the solid black image (cleaning sheet)
This is because the adhesive force F _T is smaller than the adhesive force F _T.

The above relation can be expressed as follows.

F _P <F _R < _FT Also, a cleaning mode called a cleaning mode is used to effectively remove toner stains without using a cleaning sheet having a solid black image printed on one side of a recording material. The present applicant has previously devised a pressure roller cleaning method using blank paper as a sheet.

A specific pressure roller cleaning method during the operation of the cleaning mode is such that when the cleaning sheet is nipped by the fixing nip portion, the rotation control of the heating roller and the pressure roller is stopped, and the heating control means is simultaneously operated. After the fusing nip is heated, the contaminated toner in the pressure roller portion pressed into contact with the fixing nip is sufficiently melted, and then the heating is stopped, and the recording material portion and the pressing roller portion in the fixing nip are removed. After cooling appropriately,
A series of operations of rotating the heating roller and the pressure roller to the next cleaning portion is defined as one step, and this step is repeated at least for one rotation of the pressure roller.
This is a flow control method.

By using a fixing device having this cleaning mode, toner stains can be effectively removed without using a previous cleaning sheet.

[0018]

In recent years, electrophotographic printers have been widely used all over the world, and accordingly, the recording materials used in the printers have been diversified. For example, in the European and American markets, a recording material having a firmness and a high whiteness is preferred, and CaFc is used as a filler for the recording material.
Recording materials containing a large amount of O ₃ have been produced and are becoming mainstream in the future.

However, when a recording material containing a large amount of CaCO ₃ is passed through the fixing device, the CaCO ₃ particles adhere to the pressure roller at the fixing nip due to electrostatic factors and particle shape factors. . The charging polarity of the CaCO ₃ particles is positive, and is a thermally stable substance, and is contained as 0.1 to several μm fine particle aggregates having various shapes.

Due to the operation of the fixing device, the fluorine-coated pressure roller surface is apt to be negatively charged, and if the CaCO ₃ -containing recording material is passed in this state, it adheres only due to electrostatic factors. Further, when the CaCO ₃ particles have a sharp shape, they adhere so as to bite into the elastic pressure roller surface due to the pressure of the fixing nip portion. Therefore, once they adhere, it is difficult to remove them. Although a heating type cleaning method such as a sheet or cleaning mode is effective for discharging contaminated toner, it is difficult to discharge CaCO ₃ effectively.

The CaCO ₃ particles increase the toner releasability from the recording material and make it difficult to discharge the toner transferred to the pressure roller due to offset or the like to the outside of the apparatus. Therefore, unless CaCO ₃ is removed from the pressure roller, the particles become increasingly dirty. It becomes easier. Therefore, the above-described pressure roller cleaning performance deteriorates with the printing durability of the CaCO ₃ -containing recording material, and the cleaning sheet and the cleaning mode are frequently used. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. By performing control for positively discharging CaCO ₃ particles together with dirty toner during pressure roller cleaning control, toner cleaning is performed. It is possible to prevent the deterioration of the cleaning performance of the fixed fixing device, and to suppress the contamination of the pressure roller, toner particle contamination on the recording material, and the winding of the recording material around the pressure roller in the long term. It is an object to provide a simple fixing device and an image forming apparatus provided with the fixing device.

[0023]

According to the present invention, there is provided a fixing device and an image forming apparatus having the following constitution.

(1) A recording material having an unfixed toner image is sandwiched and conveyed to a press contact portion formed by bringing a pair of fixing rotators into pressure contact, and the unfixed toner image is recorded by heating and pressing. In a fixing device that heats and fixes the material,
Heating means for heating the pressure contact portion to a temperature equal to or higher than the softening point of the toner, sheet conveying means for passing a cleaning sheet through the pressure contact portion in a heated state, and cleaning control by passing the cleaning sheet through the pressure contact portion A fixing device, further comprising an electric field forming means for forming an electric field in a gap between the fixing rotator and the cleaning sheet.

(2) Rotation control means for stepwise transporting the cleaning sheet by repeating stop and rotation of the fixing rotator, and while the fixing rotator is stopped in a state in which the cleaning sheet is pressed. And a heating amount control means for applying a first heating amount and a second heating amount smaller than the first heating amount to the press contact portion.
The fixing device as described in the above.

(3) Of the pair of fixing rotators, at least the surface layer of the elastic fixing rotator has a volume resistivity of 10 ¹⁰ Ωcm or less, and the cleaning sheet passes through the pressure contact portion while the cleaning sheet passes through the pressure contact portion. The fixing device according to (1) or (2), further comprising a power supply circuit in which a circuit system including a fixing rotator, a cleaning sheet, and a power supply is formed.

(4) An image forming apparatus having image forming means for forming and carrying an unfixed toner image on a recording material, and fixing means for heating and fixing the unfixed toner image formed and carried on the recording material to the recording material. 3. The image forming apparatus according to claim 1, wherein the fixing unit is the fixing device according to any one of (1) to (3).

[0028]

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

Embodiment 1 FIG. 1 is a schematic cross-sectional view of a schematic configuration model of a film heating type fixing device according to the present invention. The fixing device of the first embodiment is a pressure roller drive type, and a heating element (heating roller) 10 is used. The held film supporting means 16 is pressed against the pressure roller 17 with a predetermined suppression force via the cylindrical heat-resistant film 15 to form a fixing nip portion N with the heating element 10.

The heating element 10 includes a heater substrate 12, resistance heating element (electric heating element) patterns 13 a and 13 b formed on one side of the heater substrate 12, and a resistance heating element pattern 13.
It is composed of a surface protection layer 11 covering a and 13b, a power supply electrode pattern (not shown), and the like.

The heater substrate 12 has a horizontally long and thin shape whose longitudinal direction is perpendicular to the conveying / moving direction A of the recording material P as a material to be heated.
It is a heat-resistant, electrically-insulating, and low-heat-capacity ceramic base such as alumina having a thickness of mm, a width of 7.78 mm, and a thickness of 0.635 mm.

The pressure roller 17 uses a metal material having good heat conductivity such as aluminum as the metal core 17a, and its periphery is covered with an elastic body 17b such as silicon rubber. In the first embodiment, a conductive material such as carbon is dispersed in the surface layer of the pressure roller 17 and the surface resistance is set to 10 ¹⁰ Ωcm or less. Also, this is the surface of the pressure roller 17 is connected to an external power source V _R for feeding, except when the cleaning mode is selected feed switch SW
Is configured not to enter.

The fixing guide 24 is 10 ⁹ to 10 ¹¹ Ωc.
It is a member having a volume resistance of about m and is grounded. While the recording material P passes through the fixing device, the recording material P is arranged at a position where the recording material P contacts the non-printing surface side.

The cylindrical heat-resistant film 15 is, for example, a thin film cylinder having a thickness of about 30 μm to 100 μm based on polyimide.
A coat of PTFE or the like is applied to keep releasability from the toner. At the same time, by dispersing carbon or ion conductive material in the coating material, the film surface, 10 ⁹ -
It is about 10 ¹⁴ Ωm.

A rotational force acts on the heat-resistant film by a frictional force between the pressure roller and the outer surface of the heat-resistant film 15 due to the rotational drive of the pressure roller 17, and the heat-resistant film 15 causes the heating element 10 to rotate. The held heating element holder 16 is rotated in the direction of arrow A around the outside.

The electric heating of the heating element 10 can be appropriately controlled by the temperature control means 21. The temperature control means 21 uses the side of the heating element 10 where the heating elements 13a and 13b are formed
0 (hereinafter, referred to as a temperature control element 14)
The triac 22 is controlled based on the temperature detected by the thermistor 14 and the heating element 10.
And a CPU 23 for controlling the energization of the

The heat-resistant film 15 is rotated by the rotation of the pressure roller 17, and is electrically heated by the temperature control means 21.
Is heated to a predetermined temperature, the fixing nip N between the heat-resistant film 15 and the pressure roller 17 is
Recording material P holding unfixed toner image T as a material to be heated
Is introduced, the heat of the heating element 10 is applied to the recording material P via the heat-resistant film 15, and the unfixed toner image T
Is thermally fixed on the recording material P surface. The recording material P that has passed through the fixing nip N is conveyed after being separated from the surface of the heat-resistant film 15 by a curvature.

FIG. 2 is a conceptual diagram when the pressure roller cleaning is performed with the cleaning sheet Pc in the fixing device according to the first embodiment. The cleaning sheet Pc used in the first embodiment is a sheet having a solid black image pattern printed on one side as shown in FIG.

The operation will be described below with reference to the operation flow of the cleaning mode shown in FIG. (A) First, in the start state of step 1, the apparatus is in a standby state. (B) In this state, if the user determines that the pressure roller 17 needs to be cleaned, the operation panel or
The control unit (not shown) switches the apparatus to the cleaning mode by a signal from the host computer or the like (step 2). (C) When the cleaning sheet Pc is set in a manual paper feed unit (not shown) with the solid black print surface facing the pressure roller 17 side, feeding of the cleaning sheet Pc starts,
At the same time, the fixing device is driven to heat (step 3). The rotating pressure roller 17 is preheated via the fixing film 15 by the heat generated by the heating element 10 in the fixing nip portion N. In this case, the amount of heat generated per unit of the heating element 10 is controlled to a predetermined first pressurized amount. (D) cleaning sheet Pc is conveyed along the conveying direction A, when it reaches the fixing nip portion N (Step 4), contains the power supply switch, +1 by an external power source V _R
A voltage of kV is applied to the surface of the pressure roller (step 5).

Normally, when the fixing device of the first embodiment is used, when intermittent printing is continued for, for example, about 1 to 2/10 minutes on the recording paper P containing CaCO ₃ or the like, additional printing is performed every several thousand sheets. The dirt on the pressure roller 17 starts to be generated. The soiled toner contains a positively charged substance such as CaCO _{3, and} contains particles that have penetrated the surface layer of the pressure roller.

The charge amount is attenuated with the passage of time from the time of printing. However, by turning on the power supply switch SW and supplying a positive power to the surface of the pressure roller 17, the amount of C
The positively charged polar substance g such as aCO ₃ keeps positively charged again. When the temperature rises above the softening point of the toner in the fixing nip portion N, the surface layer of the pressure roller 17 at that portion thermally expands and CaC
Substances such as O ₃ are easily peeled off, and the toner is also in a semi-molten state.

When the power supply switch SW is turned on, current flows through the fixing guide 24 or the fixing film 15 via the cleaning sheet Pc.
An electric field is generated between the surface layer 7 and the cleaning sheet Pc, and the positively charged substance moves to the cleaning sheet Pc. The dirt toner on the pressure roller 17 is peeled off from the pressure roller I7 due to the adhesive force with the solid black portion on the cleaning sheet. At the same time, the charged substance g such as CaCO ₃ is attracted and discharged out of the apparatus.

FIG. 10 is a conceptual diagram of the cleaning mode using the cleaning sheet during execution of the cleaning mode. Conventionally, the electric field control as described above is not performed during cleaning, and only the dirty toner is to be cleaned. Therefore, the charged substance g such as CaCO ₃ attached to the surface of the pressure roller cannot be effectively removed, and the cleaning performance deteriorates while the intermittent printing of the CaCO ₃ -containing paper is continued. Usability was not good because of the frequent use.

However, according to the first embodiment, by performing the pressure roller cleaning by applying the electric field during the above-described cleaning mode, the cleaning performance is deteriorated along with the dirty toner on the cleaning sheet. Since the charged substance g such as CaCO _3, which is the cause, can be effectively fixed and discharged, the cleaning performance can be maintained as a high-quality fixing device for a long time without deterioration in cleaning performance.

In the first embodiment, the case of the on-demand fixing method has been described. However, the same effect as described above can be obtained in the heat roller fixing method.

Embodiment 2 In the fixing device according to the second embodiment, as a means for applying an electric field to the fixing nip portion N during the cleaning mode using the cleaning sheet according to the first embodiment, voltage application from outside the fixing device is performed from the film 15 side. It is characterized by.

The fixing guide 24 is an insulating member having a volume resistance of 10 ¹⁴ Ωcm or more, and the other configuration is the same as that of the first embodiment. However, in order to form an electric field between the cleaning sheet Pc and the pressure roller 17, the cleaning sheet Pc is desirably a sheet having a volume resistance of 10 ¹² Ωcm or less.

[0048] FIG. 5 shows a fixing device schematic cross-sectional view of a cleaning mode during execution by the fixing device in the second embodiment, the conductive layer in the film 15 from the second embodiment in the external power supply V _R of this embodiment, cleaning An electric field is formed in the same direction as in the first embodiment by flowing a current through the inside of the sheet Pc into the pressure contact portion N with the pressure roller 17. The timing of voltage application is the same as in the first embodiment. With the fixing device having the configuration and control as in the second embodiment, the same effects as in the first embodiment can be obtained, the performance degradation of the cleaning mode can be prevented, and a high-quality fixing device can be maintained for a long time. .

The surface resistance of the pressure roller in the fixing device according to the second embodiment is the same as that in the first embodiment.
0 ¹⁰ Ωcm or less, and an electric field is formed by passing an electric current between the cleaning sheet and the pressure roller. However, even if the pressure roller surface is floated with an insulating member,
The negative potential on the surface of the film makes it possible to negatively polarize the potential of the cleaning sheet Pc on the pressure roller side.
The cleaning effect of the charged substance g such as ₃ can be obtained.

Embodiment 3 The fixing device according to the third embodiment is particularly effective in the on-demand fixing method, and includes a cleaning mode control using blank paper. As a fixing control different from the first embodiment, when the cleaning mode is selected, the pressure roller 1
7 can be driven stepwise.

The pressure roller 17 is driven to rotate in the direction of arrow A by the rotation control means 18.
The motor 8 has a motor 19 for rotating the pressure roller 17 and a CPU 20 for controlling the rotation of the motor 19. As the motor 19, for example, a stepping motor or the like can be used. It is driven intermittently by a predetermined angle in the direction of arrow A. That is, the cleaning sheet Pc is step-conveyed for a predetermined length and time, and the other configuration is the same as that of the first embodiment.

FIG. 6 is a conceptual diagram during execution of the cleaning mode according to the third embodiment. Here, plain paper of about 60 to 80 g / m ² is used as the cleaning sheet Pc, but an OHP sheet having an antistatic agent (conductive) applied on the surface may be used.

The operation will be described below with reference to the operation flow of the cleaning mode shown in FIG. (A) First, in the start state of step 31, the apparatus is in a standby state. (B) In this state, if the user determines that the pressure roller 17 needs to be cleaned, the operation panel or
A control unit (not shown) with a signal from a host computer or the like,
Switch the device to cleaning mode (Step 3
2). (C) The device in the cleaning mode is set in step 3
At 3, the feeding of the cleaning sheet Pc is started, and at the same time, the fixing device is driven to heat. Rotating pressure roller 17
Is preheated in the fixing nip N through the fixing film 15 by the heat generated by the heating element 10. Heating body 1 in this case
The heat value per unit of 0 is controlled to a predetermined first heating value. (D) When the cleaning sheet Pc is transported along the transport direction A, reaches the fixing nip N, and reaches the predetermined position at the leading end (step 34), the fixing drive motor 1
9 is stopped. The sensor at the leading edge of the sheet may be upstream or downstream of the fixing nip N. (E) When the heating element 10 is turned on in step 36, the first
The fixing nip portion N is heated with a predetermined second heating amount larger than the heating amount. By the second heating amount and the predetermined heating time, the pressure roller 17 in the fixing nip portion N rises to a temperature equal to or higher than the softening point of the soil toner adhered on the surface. At this time, the power supply switch SW is turned on (step 3).
7), the voltage of + 1 kV by the external power source V _R is applied to the pressure roller surface layer.

When the temperature of the fixing nip N is higher than the softening point of the toner, the surface of the pressure roller 17 at that portion expands thermally, and the CaCO
Substances such as ₃ are easily peeled, and the toner is sufficiently melted. When the power supply switch SW is turned on, the current flows through the fixing sheet 2 via the cleaning sheet Pc.
4 or the fixing film 15, but at this time, an electric field is generated between the surface layer of the pressure roller 17 and the cleaning sheet Pc as in the first embodiment, and the positively charged substance g moves to the cleaning sheet Pc side. Transition. (F) Thermistor 14 has a predetermined heating temperature, for example, 220 ° C.
Is detected (step 38), the power supply to the heating element 10 is turned off (step 39), and the fixing nip N is cooled. At this point, power supply to the pressure roller 17 is continued. (G) When the thermistor 14 detects a predetermined temperature, for example, 180 ° C. (step 40), the power supply switch SW to the pressure roller 17 is turned off (snub 41). At this time, the contaminated toner adheres to the cleaning sheet Pc side, and simultaneously, the CaCO
The charged material g such as _{3 is} also fixed while being attracted to the sheet side. (H) The cleaning sheet Pc is transported stepwise by the width of the fixing nip by the fixing drive motor 19 (step 42), and the operation cycle of steps 35 to 42 is repeated until the cleaning sheet Pc transports a predetermined length. Execute (step 43). (I) The cleaning sheet Pc is discharged (step 44), and the cleaning mode ends.

In the above description, the voltage applied to the pressure roller 17 is turned on when the toner temperature has reached its softening point or higher, and the voltage has been set to 0 after the toner has cooled down to the softening point or lower.
FF was controlled, for example, the pressing roller bias is turned on at the time of step 33, and the sheet is discharged (step 4).
The application timing may be changed as long as the temperature of the fixing nip portion N includes a range equal to or higher than the softening point of the toner, such as the control for turning off in 4).

FIG. 11 is a conceptual diagram of a conventional fixing device during execution of a cleaning mode using a blank cleaning sheet Pc. Conventionally, the above-described electric field control was not performed in the cleaning mode. Since only the soiled toner was targeted for cleaning, the charged material g such as CaCO ₃ adhered to the surface of the pressure roller could not be effectively removed, and the cleaning performance was deteriorated while the intermittent printing of the CaCO ₃ -containing paper was continued. Deteriorating,
Since the use of the cleaning mode becomes more frequent, the usability is not good.

As described above, according to the third embodiment, by performing the pressure roller cleaning in the cleaning mode described above, the cleaning performance is deteriorated together with the stained toner on the cleaning sheet. Since a charged substance such as CaCO ₃ can also be effectively fixed and discharged, the cleaning performance does not deteriorate and a high quality fixing device can be maintained for a long time.

In the third embodiment, the case of the on-demand fixing method has been described. However, the same effect as described above can be obtained in the heat roller fixing method.

Embodiment 4 FIG. The fixing device according to the fourth embodiment is characterized in that voltage is applied from the outside of the fixing device from the film 15 side as means for applying an electric field to the fixing nip portion N in the cleaning mode according to the third embodiment. . The fixing guide 24 is 10 ¹⁴
This is an insulating member having a volume resistance of Ωcm or more, and other configurations are common to the third embodiment. However, in order to form an electric field between the blank cleaning sheet Pc and the pressure roller 17, the cleaning sheet Pc is desirably a sheet having a volume resistance of 10 ¹² Ωcm or less.

[0060] by the fixing device in the fourth embodiment in FIG. 8, shows a fixing device schematic cross-sectional view of the cleaning mode is executed, the conductive layer in the film 15 from an external power source V _R in the fourth embodiment, cleaning Sheet Pc
An electric field is formed in the same direction as in the third embodiment by flowing a current through the inside of the pressure contact portion N with the pressure roller 17. The timing of voltage application is the same as in the third embodiment.

With the fixing device having the configuration and control as in the fourth embodiment, the same effects as in the third embodiment can be obtained, and the performance degradation of the cleaning mode can be prevented.
The fixing device can be maintained as a good-quality fixing device for a long time. Further, the surface resistance of the pressure roller in the fixing device according to the fourth embodiment is equal to or less than 10 ¹⁰ Ωcm as in the first embodiment, and by applying a current between the cleaning sheet Pc and the pressure roller 17, Although the electric field is formed, even if the pressure roller surface is an insulating member and floats, the cleaning sheet Pc is generated by the negative potential of the film surface.
Can be negatively polarized, and an effect similar to the above, that is, a cleaning effect of a charged substance such as CaCO ₃ can be obtained.

Embodiment 5 FIG. 9 is a configuration diagram of an image forming apparatus to which the heat fixing device according to the present invention is applied. In FIG. 9, reference numeral 51 denotes a photosensitive drum on which a photosensitive material such as OPC, amorphous Se, or amorphous Si is formed on a cylindrical base such as aluminum or nickel. The photosensitive drum 51 is driven to rotate in the direction of the arrow, and the surface thereof is first charged with a charging roller 52 as a charging device.
Is charged uniformly. Next, turn on according to the image information
Scanning exposure is performed by the / OFF controlled laser beam 53 to form an electrostatic latent image. This electrostatic latent image is developed and visualized by the developing device 54. As a development method, a jumping development method, a two-component development method, an FEED development method, or the like is used, and a combination of image exposure and reversal development is often used.

The visualized unfixed toner image is transferred from the photosensitive drum 51 onto the recording material P conveyed at a predetermined timing by a transfer roller 55 as a transfer device. At this time, the recording material P includes the photosensitive drum 1 and the transfer roller 55.
Is conveyed by a constant pressure. The recording material P to which the unfixed toner image has been transferred is conveyed to a fixing device (any one of the fixing devices in the above embodiments) 56 and fixed as a permanent image.

On the other hand, the transfer residual toner remaining on the photosensitive drum 51 is removed from the surface of the photosensitive drum 1 by the cleaning device 57.

[0065]

As described above, according to the present invention, as the control for cleaning the pressure roller,
When performing a cleaning mode using a sheet having a solid black image formed on the surface or a cleaning sheet for blank paper, the fixing nip is heated to melt the contaminated toner, and then the pressure roller and the cleaning sheet are used. Since an appropriate electric field is formed in the gap, the charged material such as CaCO _3, which is a cause of the deterioration of the cleaning performance, can be discharged from the surface of the pressure roller to the outside of the apparatus via the cleaning sheet. As a result, it is possible to prevent deterioration of the cleaning performance of the fixing device having the cleaning control, and suppress the occurrence of contamination of the pressure roller, toner particle contamination on the recording material due to the long term, and the winding of the recording material around the pressure roller in the long term. There is an effect that a fixing device that can perform the fixing is selected.

Further, by applying this fixing device, it is possible to obtain an image forming apparatus capable of forming a high quality image.

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram of a cleaning mode of the fixing device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a cleaning sheet used in the first embodiment of the present invention.

FIG. 4 is an operation flowchart of a cleaning mode in the fixing device according to the first embodiment of the present invention.

FIG. 5 is a conceptual diagram of a cleaning mode in a fixing device according to a second embodiment of the present invention.

FIG. 6 is a conceptual diagram of a cleaning mode in a fixing device according to a third embodiment of the present invention.

FIG. 7 is an operation flowchart of a cleaning mode in a fixing device according to a third embodiment of the present invention.

FIG. 8 is a conceptual diagram of a cleaning mode in a fixing device according to a third embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of an image forming apparatus to which the fixing device of the present invention is applied.

FIG. 10 is a conceptual diagram of a cleaning mode of a conventional fixing device.

FIG. 11 is a conceptual diagram of cleaning with a cleaning sheet in a conventional fixing device.

[Explanation of symbols]

10 heating element (heating means), 11 heating element surface protective layer,
12 heating element substrate, 13 resistance heating element, 13a / 13b
Reciprocating resistance heating element, 14 temperature detection bare hands, 15 heat resistant film, 16 film support means, 17 pressure roller (sheet transport means), 18 rotation control means, 21 temperature control means, T toner P recording material, Pc cleaning sheet , N fixing nip portion (pressure contact portion), SW switches (electric field forming means), V _R power (electric field forming means), 18
Rotation control means, 21 heating amount control means, 51 photosensitive drum (image forming means), 52 charging roller (image forming means), 53
Laser beam (image forming means), 54 developing device (image forming means), 56 fixing device.

Claims (4)

[Claims] 1. A recording material having an unfixed toner image is nipped and conveyed to a pressing portion formed by bringing a pair of fixing rotators into pressure contact with each other, and the unfixed toner image is heated and pressurized to transfer the recording material. A heating unit for heating the pressure-contact portion to a temperature equal to or higher than the softening point of the toner,
A sheet conveying means for passing the cleaning sheet through the pressure contact portion in a heating state; and an electric field in the gap between the fixing rotating body and the cleaning sheet during execution of cleaning control by passing the cleaning sheet through the pressure contact portion. A fixing device, comprising: an electric field forming unit for forming the electric field. 2. A rotation control unit for stepwise transporting a cleaning sheet by repeating stop and rotation of a fixing rotator, and while the fixing rotator is stopped in a state where the cleaning sheet is pressed. 2. A heating amount control means for applying a first heating amount and a second heating amount smaller than the first heating amount to the press-contact portion.
The fixing device as described in the above. 3. A revolving fixing rotator having at least a surface layer having a volume resistivity of 10 ¹⁰ Ωcm or less among a pair of fixing rotators. Fusing rotator, cleaning sheet,
3. The fixing device according to claim 1, further comprising a power supply circuit in which a circuit system including a power supply is formed. 4. An image forming apparatus comprising: image forming means for forming and carrying an unfixed toner image on a recording material; and fixing means for heating and fixing the unfixed toner image formed and carried on the recording material to the recording material. An image forming apparatus, wherein the fixing unit is the fixing device according to any one of claims 1 to 3.