JP2003345162A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device that can reduce the occurrences of a fixing failure and paper jams which are caused by wear, and, thereby, can satisfactorily maintain the image quality for a long period of time. <P>SOLUTION: A fixing part 15 has: a thermal fixing roller 29 which heats and fixes unfixed toner T on paper P, a separation claw 37 which separates the paper P from the thermal fixing roller 29, and a separating movable sheet 39 which covers the leading end 38 of the separation claw 37. The leading end 38 of the separation claw 37 is in contact with the thermal fixing roller 29 via the separating movable sheet 39. Also, a releasing layer 45 is formed on the surface of the separating movable sheet 39, which is in contact with the thermal fixing roller 29. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an electrophotographic image forming apparatus such as a copying machine, a facsimile or a laser beam printer, which separates a sheet adhered to a heat fixing member from the heat fixing member. The present invention relates to one having a nail and an image forming apparatus having this fixing device.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus such as a copying machine, a facsimile, a laser beam printer, etc., is provided with a fixing device for melting and fixing unfixed toner electrostatically adhered to a sheet. There is. As shown in FIG. 4, such a fixing device 1 includes a heating fixing roller 2 which heats and fixes the unfixed toner T on the paper P.
A halogen lamp 3 provided inside the heat fixing roller 2 to heat the heat fixing roller 2, a pressure roller 5 for bringing the paper P into close contact with the heat fixing roller 2 by an elastic layer 4 facing the heat fixing roller 2, and a toner fixing In order to prevent the paper jam caused by the paper P adhering to the heat fixing roller 2 later, the separation claw 6 for contacting the heat fixing roller 2 and separating the paper adhered thereto and the surface temperature of the heat fixing roller 2 are set. The thermistor thermometer 7 for detecting is generally comprised.

The heat fixing roller 2 comprises a cored bar 8 usually made of aluminum or iron-based metal, and a release layer 9 provided on the surface of the cored bar. First, the cored bar 8 is subjected to surface roughening such as sandblasting. A base such as a primer layer is formed on the surface, and a fluororesin having excellent releasability, insulation and thermochemical stability (for example, PTFE (polytetrafluoroethylene) or PFA (perfluoroalkoxy fluororesin). (1) with a filler added to (1) to improve wear resistance) is coated and baked, and after cooling, the surface protrusions are removed by tape polishing or the like.

The heating and fixing roller 2 is heated by the halogen lamp 3 and the surface temperature is kept at about 165 to 230 ° C. to melt the unfixed toner T on the paper P, and the pressure roller 5 is applied to the paper P. At the same time, pressure is applied to fix the fused toner (in the figure, the fixed toner is denoted by T '). The thermistor thermometer 7 is in constant contact with the surface of the heat fixing roller 2 to detect and detect the surface temperature of the heat fixing roller 2 so that the surface temperature of the heat fixing roller 2 is maintained in the above-mentioned constant temperature range (165 to 230 ° C.). When the temperature is high, a signal for lowering the output of the halogen lamp 3 is sent to the power supply control unit (not shown) of the halogen lamp 3 for raising the output when the detected temperature is low.

[0005]

By the way, since the releasing layer 9 of the heat fixing roller 2 is usually lower in hardness than the separating claw 6, the separating claw 6 is formed on the surface of the heat fixing roller 2.
Abrasion rapidly progresses only in the portion where the tip portion 10 of the above abuts and the portion where the thermistor thermometer 7 comes into contact, and the surface roughness increases. In such a part, it becomes impossible to transfer sufficient heat to the toner due to the fixation of the molten toner and the generation of steps or protrusions due to the abrasive wear (scratch wear), which is one of the causes of the fixing failure. As a result, there is a problem that the life of the heat fixing roller is shortened.

On the other hand, in order to suppress the abrasion of the release layer due to the contact of the separation claw, a method of lowering the contact pressure of the separation claw with respect to the heat fixing roller has been attempted, but the contact pressure of the separation claw is reduced. Along with this, the separability of the paper from the heat fixing roller also deteriorates, and there is a problem that the heat fixing roller is likely to be damaged due to paper jam (jam) or vibration of the separation claw.

On the other hand, it is well known that firing under a low oxygen concentration is effective for improving the wear resistance of the release layer (see Japanese Patent Laid-Open No. 58-51264), but this method is used. There is a demand for a technique that is costly and difficult to control the oxygen concentration, and that can obtain high wear resistance at a lower cost. Also, by covering the tip of the separating claw with a layer containing a specific copolymer, it is possible to prevent paper jams in high-speed copying machines, and to separate the tip of the separating claw from the heat fixing roller during non-fixing. It is known that the abrasion of the heat fixing roller is suppressed to a minimum by removing the toner adhering to it (Japanese Patent Publication No. 7-86726).
Japanese Patent Application Laid-Open No. 4-282675), the base layer of the separation claw (separation claw exposed when the coating layer is peeled off) due to the coating layer of the separation claw being immediately peeled off or the shape of the tip portion being changed. The base of the above is made of, for example, a polyimide resin.) And its shape causes a problem that the heat fixing roller is damaged and worn.

The present invention has been made in view of the above circumstances, and can prevent the occurrence of fixing failure and paper jam due to abrasion, and thus can maintain good image quality for a long period of time. An object is to provide an apparatus and an image forming apparatus.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 is a heat fixing member for heating and fixing unfixed toner on a sheet, and separating the sheet from the heat fixing member. A separation claw and a separation sheet covering the tip of the separation claw are provided. The tip of the separation claw contacts the heat fixing member via the separation sheet, and the separation claw is attached to the heat fixing member. The fixing device is characterized in that a release layer is formed on the surface of the contact side.

According to the invention of claim 1, the tip of the separation claw comes into contact with the heat fixing member via the separation sheet covering the separation claw, and is separated from the surface of the separation sheet on the side abutting the heat fixing member. Since the mold layer is formed, it is possible to reduce the wear of the separation claw, prevent the deformation of the tip of the separation claw, and prevent the heat fixing member from being scratched or worn due to uneven contact of the separation claw. The surface property of the heat fixing member is maintained. As a result, both poor fixing and paper jam due to wear of the heat fixing member are suppressed, and good image quality is maintained for a long period of time.

According to a second aspect of the invention, in the fixing device according to the first aspect, there is provided a delivery shaft around which the separation sheet is wound and a take-up shaft, and the separation sheet wound around the delivery shaft is It is characterized in that it is sent out, passed through the tip of the separation claw, and then wound around the winding shaft.

According to the second aspect of the present invention, since the separation sheet wound around the delivery shaft is sent out, passes through the tip of the separation claw, and then is wound around the winding shaft, the separation sheet is always attached to the heat fixing member. A new surface can be abutted to prevent solid toner and paper dust pools from sticking to the heat fixing member, resulting in an image defect due to image offset. It adheres to the member and remains,
It is possible to reduce image defects (image defects caused by adhesion to a sheet at the time of fixing the next image). Further, even if abrasion powder is generated by the contact between the heat fixing member and the separation sheet, the abrasion powder is also conveyed by the traveling separation sheet and removed from the abutting position, so that the abrasion due to the existence of the abrasion powder is promoted. Can be prevented and the product life of each component can be extended. The delivery of the separation sheet by the delivery shaft and the take-up shaft is, from the viewpoint of balancing the amount of conveyance of unnecessary substances such as paper dust and abrasion powder and the amount of use (travel amount) of the separation sheet, Considering the speed and wear characteristics, it is preferable to perform a fixed amount at fixed time intervals.

According to a third aspect of the invention, in the fixing device according to the first or second aspect, there is provided a voltage applying device that applies a voltage to the separation sheet.

According to the invention of claim 3, since the voltage applying device for applying a voltage to the separation sheet is provided,
It is possible to electrically repel the separation sheet and the scattered toner to reduce the adhesion of the scattered toner to the separation sheet, and prevent image stains due to the adhered toner. When the separation sheets are sequentially sent out as in the invention according to claim 2, the electric repulsion prevents the unused surface of the separation sheet from being soiled, and the clean surface is always brought into contact with the heat fixing member. On the other hand, it is possible to prevent the used portion of the separation sheet from being contaminated, and it is possible to prevent the occurrence of image defects due to the fall of the adhered toner. In order to facilitate the charging of the separation sheet by the voltage application device, the release layer of the separation sheet contains conductive particles in an amount of 1.0 to 4
It is desirable that the content is 0% by mass.

According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the release layer contains PTFE or a fluorinated copolymer as a main component. .

According to the invention of claim 4, the release layer is P
Since the main component is TFE or a fluorinated copolymer, the wear coefficient of the surface of the separation sheet is small, the lubricity is good, and the frictional force applied to the heat fixing member is reduced to maintain the surface property. The product life of the heat fixing member can be extended.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, a detection sensor is provided which is provided on a sheet conveyance path and detects a sheet entering the heat fixing member. A moving mechanism for moving the separating claw and the separating sheet between a contact position where the separating claw and the separating sheet contact the heat fixing member and a retracted position where the separating sheet does not contact the heat fixing member. When the sensor does not detect the paper, the separation claw and the separation sheet are moved to the retracted position, and when the detection sensor detects the paper, the separation claw and the separation sheet are moved to the contact position. Characterize.

According to the fifth aspect of the invention, the separation claw and the separation sheet move to the retracted position when the detection sensor does not detect the sheet, and the separation claw and the separation sheet contact when the detection sensor detects the sheet. Since it moves to the contact position, the contact time between the separation sheet and the heat fixing member is shortened by the time when the fixing operation is not performed, such as during standby for preheating, and the scratches and wear on the surface of the heat fixing member are reduced. Become. In addition, by releasing the pressure applied by the contact of the separation sheet during standby at low temperature such as standby for preheating (when the surface temperature of the heat fixing member is equal to or lower than the melting temperature of the toner), immediately after returning from the standby state ( It is possible to avoid a situation in which linear scratches and concave indentations are given to the heating and fixing member by the solidified toner (at the beginning of operation).

The invention according to claim 6 is characterized by an image forming apparatus having the fixing device according to any one of claims 1 to 5.

According to the invention of claim 6, since the fixing device according to any one of claims 1 to 5 is provided in the image forming apparatus, the fixing device according to any one of claims 1 to 5 is provided. The effect of the invention can be obtained in the image forming apparatus.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a copying machine as an image forming apparatus having a fixing device according to the present invention. This copying machine 11
A document reading unit 12 for reading a document to be copied, a paper feeding unit 13 for stocking printing paper, and a toner image on the paper fed from the paper feeding unit 13 based on an image signal from the document reading unit 12. The image forming unit 14 for forming the toner image, the fixing unit 15 as a fixing device for fixing the toner forming the toner image onto the paper, and the paper discharge unit 16 for discharging the paper after the toner fixing to the outside of the machine.

The document reading section 12 is provided with a lamp 17 and mirrors 18a, 1 which run in the direction of arrow A for scanning the document.
8b and a CCD 19 for receiving the reflected light from the original. The paper feeding unit 13 includes a plurality of trays 20a, 20b,
... and different sizes of paper are stocked in each tray.

The image forming section 14 includes a photosensitive drum 21 which rotates in the direction of arrow B, a charging roller 22 which uniformly charges the surface of the photosensitive drum 21, and a surface of the uniformly charged photosensitive drum 21. A laser light source 23 that forms an electrostatic latent image based on the light reception result of the CCD 19, a developing roller 24 that supplies toner to the surface of the photoconductor drum 21 to visualize the electrostatic latent image as a toner image, A transfer roller 25 that transfers the toner image formed on the surface of the body drum 21 to the paper from the paper supply unit 13, and a cleaning mechanism 26 that cleans the surface of the photosensitive drum 21 after the transfer are provided. The paper discharge unit 16 includes a paper discharge port 27 that communicates the inside and the outside of the copying machine 11, and a tray 28 that receives the discharged paper. The paper from the image forming unit 14 is discharged after passing through the fixing unit 15 described below. Paper mouth 2
7 and is discharged onto the tray 28.

As shown in FIG. 2, the fixing unit 15 is configured to feed the paper P.
And a heat fixing roller 2 as a heat fixing member for heating and fixing the unfixed toner T in FIG.
Halogen lamp 3 provided inside 9 to heat it
0, and the pressure roller 3 that brings the sheet P into close contact with the heat fixing roller 29 by the elastic layer 31 facing the heat fixing roller 29.
2, a thermistor thermometer 33 that detects the surface temperature of the heating and fixing roller 29, and a detection sensor 34 that is provided in the sheet conveyance path inside the copying machine 11 and that detects the sheet P that enters the heating and fixing roller 29. .

The heat fixing roller 29 is manufactured by forming the release layer 36 on the surface of the core metal 35, and has the same structure as the heat fixing roller 2 in the fixing device 1. The halogen lamp 30, the pressure roller 32, and the thermistor thermometer 33 are also the same as the halogen lamp 3, the pressure roller 5, and the thermistor thermometer 7 in the fixing device 1, and therefore detailed description thereof will be omitted.

Further, in the fixing section 15, a separating claw 37 for preventing a paper jam caused by the sheet P adhering to the heat fixing roller 29 after toner fixing, and a tip 38 of the separating claw 37.
A separation movable sheet 39 covering the separation movable sheet 39, a delivery shaft 40 and a winding shaft 41 around which the separation movable sheet 39 is wound, and a voltage application device 42 for applying a negative voltage to the separation movable sheet 39 wound around the delivery shaft 40. And a moving mechanism 43 for moving the winding shaft 41 in the direction of arrow C to move the separation movable sheet 39 and the separation claw 37.

The separating claw 37 is urged toward the heat fixing roller 29 by a spring 44 provided on the rear end side. The take-up shaft 41 can rotate by being driven by a motor (not shown), and the rotation of the take-up shaft 41 causes the movable separation sheet 39 wound around the delivery shaft 40 to be drawn out in the direction of arrow D and sent out. . After passing through the tip 38 of the separation claw 37, each part of the separation movable sheet 39 travels in the direction of arrow E and is wound around the winding shaft 41.

The moving mechanism 43 includes a separating movable sheet 39 and
The position where the separation claw 37 contacts the heat fixing roller 29 (contact
Position) and a position that does not contact (retracted position).
When the detection sensor 34 does not detect the paper P,
Moves the separating movable sheet 39 and the separating claw 37 to the retracted position.
(See FIG. 3), the detection sensor 34 causes the edge P of the paper P to
₁When the sheet is detected, the separation movable sheet 39 and the separation claw 3 are detected.
7 is located at the contact position. At this abutting position,
The tip 38 of the release claw 37 is applied via a separation movable sheet 39.
Abuts on the surface of the heat fixing roller 29, but at this time
The pressure is appropriately adjusted by the elastic constant of the spring 44, etc.
It

A release layer 45 containing PTFE or a fluorocopolymer as a main component is formed on the surface of the separation movable sheet 39 which is in contact with the heat fixing roller 29. Generally, the hardness H ₂ of the material to be worn and the hardness H _{1 of the} material to be worn
It is known that the relationship of H ₁ > 1.2 × H ₂ ... Is established, and here, the hardness H _R of the release layer 36 of the heat fixing roller 29 and the separation of the separation movable sheet 39. The relationship of H _R > 1.2 × H _S ... Is established with the hardness H _S of the mold layer 45 and the above equation is satisfied, and when the two abut (sliding contact), not the heat fixing roller 29. The separation movable sheet 39 is worn. However, if the above formula is satisfied, it is necessary to use PTFE when molding the release layer 45.
Alternatively, the wear resistance of the release layer 45 may be improved by adding a filler such as SiO ₂ , Si ₃ N ₄ or carbon together with the fluorinated copolymer.

In the fixing section 15 of the copying machine 11 according to this embodiment, the tip 38 of the separating claw 37 abuts on the heat fixing roller 29 via the separating movable sheet 39 that covers the separating claw 37 and the separating movable sheet 39. Heating fixing roller 29
Since the release layer 45 is formed on the surface contacting the
The wear of the separation claw 37 can be reduced, and the deformation of the tip portion 38 thereof can be prevented. Therefore, the heat fixing roller 29 is prevented from being scratched or abraded due to uneven contact of the separation claw 37, and the fixing failure and the paper jam caused by this are both suppressed, and the image quality is kept good for a long time. It

Further, since the new surface of the movable separation sheet 39 is always in contact with the heating and fixing roller 29 by the winding mechanism composed of the sending shaft 40 and the winding shaft 41, toner, paper dust and abrasion powder are in contact with each other. Etc. do not stay for a long time, and the possibility of image defects is reduced. In particular, the separation movable sheet 39 is sent out at a constant amount at a constant time interval in consideration of the linear velocity and wear characteristics, thereby suppressing the occurrence of image defects without excessively moving the separation movable sheet 39. be able to.

Furthermore, since the voltage application device 42 for applying a voltage to the separation movable sheet 39 is provided, the separation movable sheet 39 and the scattered toner are electrically repelled, and the image defect caused by the scattered toner is generated. Since the moving mechanism 43 is provided that can suppress the separation movable sheet 39 and the separation claw 37 between the contact position and the retracted position, the contact time with the heat fixing roller 29 is the minimum necessary. Therefore, the product life of the heat fixing roller 29 can be extended.

The effects of the present invention will be described below with reference to more specific examples.

A tape-shaped polyimide resin substrate having a width of 5 mm and a thickness of 40 μm was coated with PFA to a thickness of 20 μm.
A release layer of m was formed to obtain a separation movable sheet 39. One end of the separation movable sheet 39 is attached to the delivery shaft 40 having an outer diameter of φ10, the separation movable sheet 39 is wound around the delivery shaft 40, and the other end is passed through the tip 38 of the separation claw 37, and then the take-up shaft 41. I installed it. In this embodiment, the separation claw 3
The width of 7 (width in the direction perpendicular to the paper surface in FIGS. 2 and 3) is 4 m.
m, and the angle θ of the tip as viewed from the side is 45 °. Further, the winding shaft 41 is a drive shaft connected to the motor as described above and rotates by itself, the feeding shaft 40 is driven in accordance with the pulling out of the separation movable sheet 39, and the winding by the winding shaft is 1 mm / It is performed at a constant time interval of 30 sec (constant winding frequency).

The voltage application device 42 was brought into contact with the surface of the delivery shaft 40, thereby applying a voltage of about -10 V to the movable separation sheet 39. By the operation of the moving mechanism 43 linked to the detection sensor 34, the separation movable sheet 39 and the separation claw 37
Has moved as described above between the contact position and the retracted position.

The fixing unit 15 thus constructed or a modified fixing unit (for example, the fixing unit without the moving mechanism 43, the fixing unit without the voltage applying device 42 and the winding mechanism: see below). "Experimental conditions" in Table 1) was set in a digital copying machine, and 10 sheets were continuously fed for 6 minutes until a total of 20,000 sheets were reached. At this time, the image pattern was so-called black solid, and the pressing force of the separation member (separation claw 37 or separation movable sheet 39) to the heat fixing roller 29 was constant at 45 gf (4.4 × 10 ⁻³ N).
Note that the linear velocity of the copying machine is 230 mm / sec, and the toner in the digital copying machine is negatively charged, and therefore repels the separation movable sheet 39 to which a voltage is applied.

Table 1 shows the experimental results under the above conditions.

[0039]

[Table 1]

The items and marks (evaluation) of the experimental results in Table 1 are as follows.

Wear of the heat fixing roller: This is the wear of the heat fixing roller due to the contact of the separating member, and the examiner visually judges the wear state (scratch) of the surface of the heat fixing roller.

Contamination of the separation member: Contamination of the separation claw or the separation movable sheet due to adhesion of toner, etc., and is visually judged by an examiner.

Image defect: The print image is defective and judged by an examiner visually.

Adhesion of foreign matter: The adherence of foreign matter (unnecessary matter) on the surface of the heat fixing roller, which is visually judged by the examiner.

◯ ... Excellent Δ ... Good (image defects occurred several times until 20,000 sheets were passed, but were not confirmed after 20,000 sheets were passed.) × ... In the defective table 1, No. 3, No. 4 and No. Each trial of No. 5 is for the fixing device according to the present invention, and by adopting the separation movable sheet 39 having the release layer 45, the wear of the heat fixing roller 29 and the image defect due to the contact of the separation member are improved (No. .3), by adding the voltage applying device 42 and the winding mechanism, the dirt of the separating member and the adhesion of foreign matter (unnecessary matter) on the heat fixing roller 29 are improved (N
o. 4) Further, the image defect was further improved by adding the moving mechanism 43 (No. 5).

The embodiment of the present invention is not limited to the above-mentioned embodiment. For example, in the above embodiment, the hardness H _R of the release layer 36 of the heat fixing roller 29 and the separation movable sheet 3 are used.
Although the relationship expression holds between the hardness H _S of the releasing layer 45 of 9, just lower than the surface hardness H _Rs hardness H _S of the releasing layer 45 of the isolation movable sheet 39 is heated fixing roller 29 Even if only (H _S <H _Rs ), the wear of the heat fixing roller 29 can be suppressed to some extent, which is acceptable. Also,
In the above embodiment, the running direction of the movable separation sheet 39 (direction of arrow D) and the rotating direction of the heat fixing roller 29 (direction of arrow B) are opposite to each other at the contact point, but the delivery shaft 4
The traveling direction of the separation movable sheet 39 may be set in the forward direction of the rotation direction of the heat fixing roller 29 by changing the positional relationship between 0 and the winding shaft 41. However, in this forward direction, the heat fixing roller 29 and the separable movable sheet 39 are rotated together, but if this is done, free toner or the like at the contact point will adhere and remain on the surface of the heat fixing roller 29. Since there is a high possibility, it is desirable that the directions are opposite as in the above-described embodiment.

[0047]

As described above, according to the invention of claim 1, the tip of the separation claw comes into contact with the heat fixing member via the separation sheet covering the separation claw and the heat fixing member of the separation sheet. Since the release layer is formed on the surface of the separation claw, the wear of the separation claw can be reduced and the tip of the separation claw is prevented from being deformed. The scratches and abrasion of the heat fixing member are prevented and the surface property of the heat fixing member is maintained. As a result, both poor fixing and paper jam due to wear of the heat fixing member are suppressed, and good image quality is maintained for a long period of time.

According to the second aspect of the invention, the separation sheet wound around the delivery shaft is sent out, passes through the tip of the separation claw, and then is wound around the winding shaft. It is possible to bring the new surface of the sheet into contact with the sheet and prevent solidification of toner solids and paper dust accumulation on the heating and fixing member to reduce image defects due to image offset. Further, even if abrasion powder is generated by the contact between the heat fixing member and the separation sheet, the abrasion powder is also conveyed by the traveling separation sheet and removed from the abutting position, so that the abrasion due to the existence of the abrasion powder is promoted. Can be prevented and the product life of each component can be extended.

According to the third aspect of the invention, since the voltage applying device for applying a voltage is provided on the separation sheet,
It is possible to electrically repel the separation sheet and the scattered toner to reduce the adhesion of the scattered toner to the separation sheet, and prevent image stains due to the adhered toner. When the separation sheets are sequentially sent out as in the invention according to claim 2, the electric repulsion prevents the unused surface of the separation sheet from being soiled, and the clean surface is always brought into contact with the heat fixing member. On the other hand, it is possible to prevent the used portion of the separation sheet from being contaminated, and it is possible to prevent the occurrence of image defects due to the fall of the adhered toner.

According to the invention of claim 4, the release layer is P
Since the main component is TFE or a fluorinated copolymer, the wear coefficient of the surface of the separation sheet is small, the lubricity is good, and the frictional force applied to the heat fixing member is reduced to maintain the surface property. The product life of the heat fixing member can be extended.

According to the invention of claim 5, the separation claw and the separation sheet move to the retracted position when the detection sensor does not detect the sheet, and the separation claw and the separation sheet contact when the detection sensor detects the sheet. Since it moves to the contact position, the contact time between the separation sheet and the heat fixing member is shortened by the time when the fixing operation is not performed, such as during standby for preheating, and the scratches and wear on the surface of the heat fixing member are reduced. Become. In addition, by releasing the pressure applied by the contact of the separation sheet during standby at low temperature such as standby for preheating, linear scratches and concave indentations are heated and fixed by the solidified toner immediately after returning from the standby state. A situation given to the member can be avoided.

According to the invention of claim 6, since the fixing device according to any one of claims 1 to 5 is provided in the image forming apparatus, the fixing device according to any one of claims 1 to 5 is provided. The effect of the invention can be obtained in the image forming apparatus.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a fixing unit of the image forming apparatus of FIG.

FIG. 3 is an explanatory diagram showing a state in which a separation movable sheet and a separation claw are in a retracted position in the fixing unit in FIG.

FIG. 4 is an explanatory diagram showing a conventional fixing device.

[Explanation of symbols]

11 Copier (image forming device) 15 Fixing unit (fixing device) 29 Heat fixing roller (heat fixing member) 34 Detection sensor 37 Separated nail 38 Tip 39 Separable movable sheet (separable sheet) 40 sending axis 41 winding shaft 42 Voltage application device 43 Moving mechanism 45 Release layer P paper T Unfixed toner

Claims (6)

[Claims] 1. A heat fixing member for heating and fixing unfixed toner on a sheet, a separation claw for separating the sheet from the heat fixing member, and a separation sheet for covering the tip of the separation claw. The tip of the separation claw is in contact with the heat fixing member via the separation sheet, and a release layer is formed on the surface of the separation sheet on the side in contact with the heat fixing member. Fixing device. 2. A take-up shaft having a delivery shaft and a take-up shaft around which the separation sheet is wound, and the take-up shaft after the separation sheet wound around the delivery shaft is sent out and passes through the tip of the separation pawl. The fixing device according to claim 1, wherein the fixing device is wound around. 3. The fixing device according to claim 1, further comprising a voltage applying device that applies a voltage to the separation sheet. 4. The release layer comprises PTFE or a fluorinated copolymer as a main component.
The fixing device according to any one of 1. 5. A detection sensor provided on a sheet conveyance path for detecting a sheet entering the heat fixing member, a contact position at which the separation claw and the separation sheet are in contact with the heat fixing member, and the heat fixing. A moving mechanism that moves the member between a retracted position that does not contact the member, and moves the separating claw and the separating sheet to the retracted position when the detection sensor does not detect a sheet. The fixing device according to any one of claims 1 to 4, wherein the separation claw and the separation sheet are moved to the contact position when the detection sensor detects a sheet. 6. An image forming apparatus comprising the fixing device according to any one of claims 1 to 5.