JP2008225092A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which prevents a fixing film from breaking, requires neither complicated constitution nor control to detect the speed of the fixing film, is inexpensive and precise, and can keep a recorded material carrying speed constant, and to provide an image forming apparatus. <P>SOLUTION: In the fixing device, the strength of both ends of a fixing film is improved by providing projection parts on an inner peripheral surface of both ends of the fixing film, the breakage of the ends part is prevented, and the rotation cycle of the fixing film can be detected by detecting the rotation cycle of the projection parts. Further, the position of the fixing film can be detected by providing a plurality of pressure sensors detecting the cycles of the projection parts, so the fixing film can be prevented from breaking due to friction against a flange cap since the fixing film is one-sided owing to a right-left temperature difference of a fixing nip part etc. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a fixing device and an image forming apparatus.

  Conventionally, for example, in an image forming apparatus such as a copying machine, a laser beam printer, or a facsimile, a heat-meltable developer (toner) is applied by an appropriate image forming process such as an electrophotographic method, an electrostatic recording method, or a magnetic recording method. Used to heat and fix an unfixed toner image formed and supported on the surface of a recording material (transfer material sheet, printing paper, electrofax sheet, electrostatic recording sheet, etc.) by the indirect (transfer) method or the direct method. As a fixing device for this purpose, a heat roller fixing type fixing device composed of a metal roller including a heater and a pressure roller made of an elastic member such as sponge rubber has been widely used.

  This heat roller type fixing device has a pressure nip portion between a heating roller (fixing roller) heated by a built-in heat source such as a halogen heater and maintained at a predetermined temperature and a pressure roller having elasticity pressed against it. The recording material is introduced into the (fixing nip portion) and is nipped and conveyed, whereby the unfixed toner image on the surface of the recording material is thermally fixed by the heat of the fixing roller.

  In addition to these, various systems and configurations such as a flash fixing system, an oven fixing system, and an induction heating system are known and put into practical use.

  Recently, a heating body fixed and supported in place of such a system, a heat resistant film (fixing film) conveyed while being pressed against the heating body, and a recording paper heated through the heat resistant film are heated. Having a pressure member such as an elastic roller that is in close contact with the recording medium, and applying the heat of the heating body to the recording material through the film to heat and fix the unfixed toner image on the recording material to the recording material A film heating method has been proposed and put into practical use.

  In this fixing device, a recording material as a material to be heated is closely attached to a heating body fixedly supported by a supporting member via a film material made of heat-resistant, thin polyimide or the like, and the film material is slid onto the heating body. This is a system / structure that moves and moves the heat of the heating body to the recording material via the film material, and can be used as a device for heat-fixing an unfixed toner image as a fixed image on the recording material surface.

  In such a film heating type fixing device, the heating body has a low heat capacity with a high temperature rise, for example, an insulating / good heat conductive ceramic base material, and energization provided on the surface of the base material. A so-called ceramic heater having a heat generating resistive heating layer as a basic component can be used, and a thin film with a low heat capacity can be used as a film material. There is no need to supply power to the heating element, and the heating element can be sufficiently heated up to a predetermined temperature before the recording material reaches the fixing nip even if the recording material as the material to be heated passes immediately. It has advantages such as shortening the wait time (quick start performance: on-demand operation) and power saving, and suppressing the temperature rise in the image forming apparatus main body. It is ones.

  However, it is a film heating type fixing device, and by driving and rotating a pressure roller that presses the heating body through the film, the film or the film and the recording paper are moved together while sliding the film on the heating body. In the pressure roller driving type heating device that sandwiches and conveys the pressure nip portion between the heating body and the pressure roller, the pressure roller is heated as the temperature of the pressure roller rises with the operation of the device. Due to the subtle expansion, the outer diameter increases.

  The pressure roller is normally driven to rotate at a constant rotational speed. Therefore, when the pressure roller is hot, the thermal expansion increases and the rotational peripheral speed increases, and the heated material sandwiching and conveying speed is faster when the pressure roller is hot. turn into. That is, the heated material clamping and conveying speed varies depending on the temperature state of the pressure roller.

  For this reason, the recording material is conveyed in the image forming unit, for example, the image transfer unit, which is a processing unit upstream of the heating device, so that the recording material is kept from the transfer unit to the heating device. When the recording material pressure nip (fixing portion) is reached and the nipping and conveying state is reached, when the pressure roller is in a high temperature state, the recording material is nipped and conveyed in the fixing unit of the heating device rather than the recording material conveying speed in the transfer unit. When the speed is high, the heating device pulls the recording material, and this influence causes image blur in the transfer portion.

  Conversely, when the temperature of the pressure roller is low, an unnecessary loop (sag) is formed in the recording material in the recording material conveyance unit between the transfer unit and the fixing unit of the heating device, and image transfer in the transfer unit Since the separation direction of the recording material later and the incident angle of the recording material to the fixing unit of the heating device become unstable, image scattering during transfer separation, offset at the fixing unit of the heating device, and the like occur.

  In addition, when the recording material used for passing paper is thick, blurring occurs at the transfer portion due to the stiffness of the recording material.

  In order to eliminate the adverse effects caused by the pulling phenomenon of the recording material and the unnecessary loop formation phenomenon due to the fluctuation of the recording material sandwiching and conveying speed of such a heating device, the speed of the fixing film is detected, thereby conveying the recording material A method of predicting the speed and controlling the driving speed of the pressure roller (JP-A-8-190298) has been proposed.

  However, the method of predicting the expansion from the temperature of the pressure roller and controlling the fixing film speed to be constant has a problem in terms of responsiveness to a deviation from the actual rotation speed and a sudden change.

  Further, the speed of the fixing film is detected by a light reflecting portion that reflects the light of the reflective sensor provided on at least one end of the fixing film, and the actual speed of the fixing film detected by the detecting means Based on the above, a system (Japanese Patent Laid-Open No. 2002-31744) has also been proposed which has a control means for controlling the speed of the fixing film in real time.

  However, the reflective plate for detecting the rotation speed of the fixing film with the reflective sensor must be processed on the surface of the very thin fixing film, and a processing or cleaning member that makes the reflective plate on the fixing film difficult to get dirty is provided. Therefore, there is a problem that the cost is high and the detection is performed by the optical reflection type sensor, so that erroneous detection is caused by light leaking into the apparatus.

  Furthermore, a system (Japanese Patent Laid-Open No. 2000-200006) is proposed in which the rotational speed of a roller rotating in contact with a fixing film or a pressure roller is detected to detect a speed change due to expansion of the pressure roller. However, since the parts with high accuracy are added and it is necessary to constantly contact the fixing film and the pressure roller to detect the speed, the surface of the contact portion is damaged, and the damage due to tearing is caused by a very thin fixing film. There are concerns.

  In addition, there has been proposed a method (Japanese Patent Laid-Open No. 2003-337486) in which an opening is provided at the end of the fixing film and a reflection material is provided on a member that supports the fixing film to detect rotation of the fixing film. Even if the opening is provided at the end of the fixing film, which is very thin and difficult in the strength of the end, there is a concern that the end will be broken.

JP-A-8-190298 JP 2002-31744 A JP 2000-200006 A JP 2003-337486 A

  The present invention has been made in view of the above-described problems, and its intended process is to prevent damage to the fixing film, and does not require a complicated configuration or control to detect the speed of the fixing film, and is inexpensive. An object of the present invention is to provide a fixing device and an image forming apparatus capable of keeping a recording material conveyance speed constant with high accuracy.

  The invention of claim 1 includes a heating body, an endless heat-resistant film, a support member that supports the heat-resistant film, and a pressure member that is pressed against and rotated by the heating body across the heat-resistant film. And fixing the toner image on the recording material by heating the recording material carrying an unfixed toner image while sandwiching and transporting the recording material carrying the unfixed toner image to a fixing nip formed by the heat-resistant film and the pressure member. In the apparatus, the heat resistant film has a protrusion on an inner peripheral surface of a longitudinal end portion thereof, and a pressure detection member that detects pressure on the support member at a position where the protrusion contacts the The rotation period of the heat-resistant film is changed in order to achieve a predetermined rotation according to the pressure detection result of detecting the pressure when the protrusion comes into contact with the pressure detection member by rotation. Fixing device to do.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, a plurality of the projecting portions are provided on the same circumference of the inner peripheral surface of the end portion of the heat resistant film.

  The invention of claim 3 is a heating body, an endless heat-resistant film, a support member that supports the heat-resistant film, and a pressure member that is pressed against and rotated by the heating body with the heat-resistant film interposed therebetween. And fixing the toner image on the recording material by heating the recording material carrying an unfixed toner image while sandwiching and transporting the recording material carrying the unfixed toner image to a fixing nip formed by the heat-resistant film and the pressure member. In the apparatus, a protrusion on the inner peripheral surface of the longitudinal end of the heat resistant film, a pressure detection member that detects pressure on the support member at a position where the protrusion contacts, and an end of the heating body A correction heating body for heating the heat-resistant film end portion and changing the end-portion temperature, and detecting the pressure when the protrusion comes into contact with the pressure detection member by the rotation of the heat-resistant film. Depending on the pressure detection result, Controlling the energization of the heating body, fixing device and correcting the longitudinal end positions of the heat-resistant film.

  According to a fourth aspect of the present invention, in the fixing device according to the third aspect, a plurality of the pressure detection members are provided on the support member.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising the fixing device according to any one of the first to fourth aspects, wherein a desired image is formed on a recording material.

As described above, according to the present invention, the protrusions are provided on the inner peripheral surfaces of both ends of the fixing film, thereby increasing the strength of both ends of the fixing film. As a result, damage to the ends can be prevented and the protrusions can be prevented. The rotation cycle of the fixing film can be detected by detecting the rotation cycle.
In addition, since the position of the fixing film can be detected by providing a plurality of pressure sensors that detect the period of the protrusions, the fixing film is moved to one side due to the temperature difference between the right and left of the fixing nip, and the flange cap is It has become possible to prevent damage due to rubbing.

  As described above, an image forming apparatus capable of obtaining a stable image by maintaining a constant change in the film speed is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of an image forming apparatus according to the first embodiment of the present invention. In this embodiment, a laser beam printer will be described as an example of the image forming apparatus according to the present invention.

  However, the present invention is not limited to application to a laser beam printer, and may be a copying machine or a facsimile equipped with the heating device of the present invention.

This laser beam printer includes a photosensitive drum 1 which is an image carrier. The photosensitive drum 1 is rotatably supported by the apparatus main body T, and is driven to rotate at a predetermined speed (for example, a process speed of 131 mm / sec) in the direction of arrow A by the main motor M1.
Around the photosensitive drum 1, a charging roller 2 as a charging device that uniformly charges the photosensitive drum 1 in almost the order along the rotation direction, and a laser scanner that is an exposure means for forming an electrostatic latent image. 3. a developing device 4 for visualizing the electrostatic latent image with toner, a transfer roller 5 which is a transfer device for transferring the toner image on the photosensitive drum 1 to a sheet-like recording material P such as paper, A cleaning device 6 for collecting untransferred toner remaining on the photosensitive drum 1 is provided.

  A paper feed cassette 7 containing a recording material P is disposed at the lower part of the apparatus main body T, and a fixing device 8 according to the present invention is disposed at the upper part of the photosensitive drum 1.

Further, a control board 9 for controlling an image forming operation and the like is disposed on the back surface of the apparatus main body T. On the control board 9, there are mounted a main body CPU 9a that issues a command to execute an image forming operation and the like, a fixing CPU 9b that executes fixing temperature control and the like, and a memory 9c that stores a program and the like. The operation of the printer is realized by these CPUs reading and executing a necessary program from the memory 9c (the same is true of processing according to a flowchart described in detail later).
Next, the operation of the laser beam printer configured as described above will be described.

  The photosensitive drum 1 that is rotationally driven in the direction of arrow A by the main motor M1 is uniformly charged to a predetermined polarity and a predetermined potential (for example, −600 V) by the charging roller 2. The surface of the charged photosensitive drum 1 is subjected to image exposure based on image information by a laser scanner 3 serving as an exposure unit on the surface, and the charge of the exposed portion is removed to form an electrostatic latent image. The electrostatic latent image is developed by the developing device 4.

  The developing device 4 has a developing sleeve 4a whose surface is coated with carbon on an aluminum roller. A predetermined developing bias (for example, AC: 2400 Hz, 1.6 KVpp / DC: −450 V) is applied to the developing sleeve 4a. A toner is attached to the electrostatic latent image on the photosensitive drum 1 and developed (visualized) as a toner image.

  The toner image is transferred to the recording material P such as paper by the transfer roller 5. The recording material P is stored in a paper feed cassette 7, and is transported by a paper feed roller and a transport roller (not shown), and is transported to a transfer nip portion N between the photosensitive drum 1 and the transfer roller 5.

  The recording material P carrying the unfixed toner image on the surface by transfer is transported to the fixing device 8 along a transport guide (not shown). In the fixing device 8, the unfixed toner image is heated and pressurized to melt the toner, and is fixed on the surface of the recording material P. The specific configuration of the fixing device 8 will be described in detail later.

  On the other hand, after the toner image is transferred, the toner remaining on the surface of the photosensitive drum 1 without being transferred to the recording material P is removed by the cleaning blade 6a of the cleaning device 6 and used for the next image formation.

  By repeating the above operation, image formation can be performed one after another.

FIG. 2 shows a schematic configuration of the fixing device according to the first embodiment of the present invention.
The fixing device 8 includes a ceramic heater 20 as a heating body that heats toner, a fixing film 21 that is an endless heat-resistant film member that encloses the ceramic heater 20, and a heating member that is in contact with the fixing film 21. A pressure roller 22 as a pressure member, a fixing film rotation detecting member 23 for detecting the rotation speed of the fixing film 21, a fixing drive motor M2 for driving the fixing device 8, and a fixing rotation control for controlling the rotation speed of the fixing drive motor M2. The temperature control means 25 which controls the temperature of the means 24 and the ceramic heater 20 is comprised as a main structural member.
The temperature control means 25 includes a thermistor (temperature detection element) 26 attached to the back surface of the ceramic heater 20, a fixing CPU 9 b that controls the triac 27 based on the temperature detected by the thermistor 26 and controls the energization of the ceramic heater 20. Consists of.

  The ceramic heater 20 is formed by forming a resistor pattern 20b on a heat-resistant base material 20a such as alumina by printing, for example, and covering the surface with a glass layer 20c. It is longer in the direction, that is, longer than the width of the recording material P.

  The ceramic heater 20 is supported by a heater guide (also referred to as a heater holder) 28 attached to the apparatus main body T. The heater guide 28 is a member formed in a semi-cylindrical shape by a heat-resistant resin such as a liquid crystal polymer, and acts as a guide member for guiding the rotation together with a support member for supporting the fixing film 21.

  The fixing film 21 is formed by forming a heat-resistant resin such as a polyimide layer 21a into a cylindrical film shape, and is loosely fitted to the ceramic heater 20 and the heater guide 28 described above.

  The fixing film 21 is pressed against the ceramic heater 20 by a pressure roller 22 described later, whereby the back surface of the fixing film 21 is brought into contact with the lower surface of the ceramic heater 20.

  The fixing film 21 is configured to rotate in the direction of arrow D as the recording material P is conveyed in the direction of arrow B by the rotation of the pressure roller 22 in the direction of arrow C.

  The left and right end portions of the fixing film 21 are regulated by the flange cap 30 of the guide portion of the heater guide 28 so as not to be displaced in the longitudinal direction of the ceramic heater 20. In order to reduce the sliding resistance between the ceramic heater 20 and the heater guide 28, grease is applied.

  In addition, as shown in FIG. 2, the fixing film 21 of this embodiment has protrusions 21d on the inner peripheral surfaces of both ends of the non-image area, and the protrusions 21d on the inner peripheral surface of the fixing film of the heater guide portion 28. A sheet-type pressure sensor is provided as a pressure detection member 23 at the rubbing position.

  As the fixing film 21 rotates, the protrusion 21d on the inner peripheral surface of the fixing film periodically passes over the pressure sensor, and the speed of the fixing film 21 is detected by detecting this period.

  The pressure roller 22 is provided with a heat-resistant release layer 22b having elasticity such as silicon rubber on the outer peripheral surface of a metal cored bar 22a, and a fixing film from below by the outer peripheral surface of the release layer 22b. 21 is pressed against the ceramic heater 20 to form a fixing nip portion N with the fixing film 21.

  The width (nip width) in the fixing nip portion N in the rotation direction of the pressure roller 22 is defined as a. The nip width a is set so that the toner on the recording material P can be appropriately heated and pressurized.

  When the control of the fixing device 8 receives a print signal, the fixing CPU 9b supports the temperature control means 25 with a predetermined temperature setting (190 ° C. in this embodiment).

  The temperature control means 25 energizes the ceramic heater 20 until the thermistor 26 detects a predetermined temperature, and heats the recording material P that is nipped and conveyed by the rotation of the pressure roller 22 in the direction of arrow C at the fixing nip N. The toner is fixed on the recording material P.

  Next, a detailed view of the fixing film 21 and the pressure detecting member 23 of the fixing device 8 in this embodiment is shown in FIG.

  The fixing film 21 has a total thickness of about 40 to 70 μm in order to reduce the heat capacity and improve the quick start property, and a primer on the outer peripheral surface of the polyimide layer 21a having heat resistance, releasability, strength, durability and the like. A layer 21b is provided, and a PFA layer 21c obtained by adding a conductive agent to a fluororesin is provided on the outer peripheral surface of the layer 21b.

  At both ends of the non-image area of the fixing film 21, polyimide pieces are dispersed on the inner peripheral surface side of the polyimide layer 21 a so that protrusions having a diameter of 2 mm and a height of 2 mm are formed on the inner peripheral surface side of the fixing film 21. The protrusions 21d are formed in four places (this example) in the circumferential direction.

  A heater guide 28 that supports the fixing film 21 and the ceramic heater 20 is formed of a liquid crystal polymer made of a heat-resistant material in a substantially semicircular arc shape, and a protrusion 21 d formed on the inner peripheral surface of the fixing film of the heater guide 28. A sheet-type pressure sensor having a thickness of 100 μm is provided as a pressure detection member 23 at a position where the contact is made, and by detecting a pressure change caused by the protrusion 21 d of the fixing film 21 passing over the pressure detection member 23. The rotation period of the fixing film 21 can be detected.

  Then, the fixing CPU 9b can calculate the time required for the fixing film 21 to make one rotation from the rotation period detected by the pressure detection member 23 and the circumference of the fixing film 21, and can determine the rotation speed.

  FIG. 4 is a diagram illustrating changes in the conveyance speed of the recording material P and the rotation speed of the fixing film 21. According to the experiment, as shown in FIG. 4, there is a correlation between the conveyance speed of the recording material P and the rotation speed of the fixing film 21.

  Therefore, the actual conveyance speed of the recording material P can be predicted from the rotation speed of the fixing film 21.

  Therefore, when the rotation period of the fixing film 21 is faster than the predetermined period, the speed of the fixing motor M2 is reduced, and when the rotation period of the fixing film 21 is slower than the predetermined period, the speed of the fixing motor M2 is increased. Control is performed so that the conveyance speed of the recording material P is constant.

  Next, the detailed operation of the image forming apparatus in the present embodiment will be described based on the flowchart of FIG.

  When the image forming apparatus receives a copy signal by a user operation, a print signal from a host computer (not shown) or a facsimile reception operation, the image forming operation is started (S1).

  At the same time, the fixing CPU 9b controls the power supply to the ceramic heater 20 by controlling the triac 27 based on the temperature detected by the thermistor 26 so that the temperature control means 25 reaches a predetermined temperature (190 ° C. in this embodiment). S2).

  Thereafter, when the thermistor 26 detects a predetermined temperature (100 ° C. in the present embodiment), the fixing CPU 9b instructs the rotation control means 24 to specify a predetermined rotation speed, and rotates the fixing motor M2 (S3).

  When the rotation speed of the fixing motor M2 reaches the set value, the fixing CPU 9b starts monitoring the rotation cycle through which the projection 21d of the fixing film 21 detected by the pressure detection member 23 passes (S4).

  When the value to be monitored is faster than the preset value, the conveyance speed of the recording material P increases and the magnification of the image to be formed increases, so the rotation period of the fixing film 21 is a predetermined value. The setting value is changed so that the rotation speed of the rotation control unit 24 of the fixing motor M2 becomes slower so that the value becomes equal.

On the contrary, when the value to be monitored is slower than the preset value, the magnification of the image to be formed is increased. Therefore, the fixing motor M2 is set so that the rotation period of the fixing film 21 becomes a predetermined value. The set value is changed so as to increase the rotation speed by the rotation control means 24 (S5).
By performing the above setting, the image forming operation can be terminated in a stable state without any adverse effects of image and paper conveyance by fixing the recording material P through the fixing material 21 while the rotation speed of the fixing film 21 is always constant. Yes (S6).

  Further, by providing the projections 21d in the non-image areas at both ends of the fixing film 21, it becomes possible to increase the strength of the end of the fixing film 21 by about three times (this example). It has become possible to suppress the occurrence rate of the end portion damage of the fixing film 21 as thin as 60 μm (this example) to about 1/10 of this (this example).

  As described above, the protrusion 21d is provided on the inner peripheral surface of the non-image area at both ends of the fixing film 21 to increase the strength of the end of the very thin fixing film 21, and the heater at a position opposed to the protrusion 21d. By providing the guide 28 with a sheet-type pressure sensor, which is a pressure detection member 23 for detecting the rotation speed of the protrusion 21d, and detecting the rotation cycle of the fixing film 21, erroneous detection can be performed without complicated control and configuration. As a result, the number of rotations of the fixing film 21 can be kept constant.

  FIG. 6A shows a schematic configuration of a heating apparatus according to the second embodiment of the present invention. The configuration of the fixing device 8 is substantially the same as that of the first embodiment, and a duplicate description of the same parts is omitted.

  The difference from the first embodiment is that a sheet-type pressure sensor, which is a rotation detecting member 23 for detecting the number of rotations of the protrusion 21d, is fixed to the heater guide 28 at a position opposed to the protrusion 21d of the fixing film 21. A plurality of devices 8 are provided in the longitudinal direction of the apparatus 8, and correction heaters as correction heaters are provided at both end portions 29a and 29b (FIG. 6-2) of the ceramic heater.

  Next, the detailed operation of the image forming apparatus according to the second embodiment will be described based on the flowchart of FIG.

  When the image forming apparatus receives a copy signal by a user operation, a print signal from a host computer (not shown), or a print signal by a facsimile reception operation, the image forming operation is started (S10).

  At the same time, the fixing CPU 9b controls the power supply to the ceramic heater 20 by controlling the triac 27 based on the temperature detected by the thermistor 26 so that the temperature control means 25 reaches a predetermined temperature (190 ° C. in this embodiment). S11).

  Thereafter, when the thermistor 26 detects a predetermined temperature (100 ° C. in the present embodiment), the fixing CPU 9b instructs the rotation control means 24 to specify a predetermined rotation speed, and rotates the fixing motor M2 (S12).

  When the rotation speed of the fixing motor M2 reaches the set value, the fixing CPU 9b starts monitoring the rotation cycle through which the projection 21d of the fixing film 21 detected by the pressure detection member 23 passes (S13).

  When the value to be monitored is faster than the preset value, the conveyance speed of the recording material P increases and the magnification of the image to be formed increases, so the rotation period of the fixing film 21 is a predetermined value. The setting value is changed so that the rotation speed of the rotation control unit 24 of the fixing motor M2 becomes slower so that the value becomes equal.

  On the contrary, when the value to be monitored is slower than the preset value, the magnification of the image to be formed is increased. Therefore, the fixing motor M2 is set so that the rotation period of the fixing film 21 becomes a predetermined value. The set value is changed so as to increase the rotational speed of the rotation control means 24 (S14).

  Further, since a plurality of pressure detection members 23 are provided in the longitudinal direction (three in one embodiment, a total of six), the fixing CPU 9b determines which position the pressure detection member 23 is from (S15). When detecting the signal from the outermost end position, the fixing CPU 9b instructs the correction heater 29 opposite to the direction in which the outermost end position is detected to be energized (S16).

When the detection signals from the plurality of pressure detection members 23 are not the detection signals from the outermost end position, the fixing CPU 9b stops energizing the correction heater 29 (S17).
By performing the above setting, the recording material P can be passed with the rotation speed of the fixing film 21 always constant, and the fixing film 21 is shifted to either one so that the fixing film 21 is not damaged. By fixing the recording material P in a state where there is no image, the image forming operation can be completed in a stable state without any trouble of image and paper conveyance while preventing damage to the fixing film (S18).

  Further, by providing the protrusions 21d in the non-image areas on the inner peripheral surfaces of both ends of the fixing film, the strength of the end of the fixing film 21 is increased by about three times (this example), and then the fixing film 21 is used. The position of the fixing film 21 can always be kept constant in the longitudinal direction, so that the fixing film 21 is moved to one side due to a difference in temperature between the left and right sides, and a machine failure occurs due to damage to the end of the fixing film 21 by rubbing against the flange cap 30. Can now be almost completely eliminated.

  As described above, the protrusion 21d is provided in the non-image area on the inner peripheral surface of both ends of the fixing film 21, thereby increasing the strength of the end of the very thin fixing film 21, and the heater guide at a position opposed to the protrusion 21d. 28 is provided with a sheet-type pressure sensor, which is a pressure detection member 23 for detecting the rotation speed of the protrusion 21d, and detects the rotation period of the fixing film 21, thereby reducing erroneous detection without complicated control and configuration. As a result, the rotation speed of the fixing film 21 can be kept constant with high accuracy.

1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to a first invention of the present invention. 1 is a longitudinal sectional view showing a schematic configuration of a fixing device according to a first invention of the present invention. The figure which shows schematic structure of the fixing film and pressure detection member which concern on 1st invention of this invention Diagram showing changes in paper transport speed and fixing film rotation speed FIG. 3 is a flowchart of the image forming apparatus according to the first aspect of the present invention. 6-1 shows a schematic configuration of a pressure detection member for a fixing film according to the second invention of the present invention. FIG. 6-2 is a schematic diagram of a fixing film according to the second invention of the present invention. FIG. 7 is a flowchart of the image forming apparatus according to the second aspect of the present invention.

Explanation of symbols

1 Photosensitive drum (image carrier)
2 Charging roller 3 Laser scanner 4 Developing device 4a Developing sleeve 5 Transfer roller 6 Cleaning device 6a Cleaning blade 7 Paper feed cassette
8 Fixing device 9 Control board 9a Main body CPU
9b Fixing CPU
9c Memory 20 Ceramic heater (heating body)
20a substrate 20b resistor pattern 20c glass layer 21 fixing film (heat resistant film)
21a Polyimide layer 21b Primer layer 21c PFA coating layer 21d Protrusion 22 Pressure roller 22a Core metal 22b Release layer 23 including elastic layer Pressure detection member 24 Rotation control means 25 Temperature control means 26 Thermistor 27 Triac 28 Heater guide (supporting member) )
29a, 29b Correction heater (correction heating element)
30 Flange cap T Main unit N Fixing nip pressure P Recording material M1 Main unit driving motor M2 Fixing driving motor

Claims (5)

A heating member, an endless heat-resistant film, a support member that supports the heat-resistant film, and a pressure member that is pressed against and rotated by the heating member with the heat-resistant film interposed therebetween. In a fixing device for fixing a toner image to the recording material by heating while sandwiching and conveying a recording material carrying an unfixed toner image to a fixing nip formed by a film and the pressure member,
A protrusion on the inner peripheral surface of the longitudinal end of the heat-resistant film, and a pressure detection member that detects pressure on the support member at a position where the protrusion contacts, and by rotation of the heat-resistant film, A fixing device that changes a rotation period of the heat-resistant film in order to achieve a predetermined rotation in accordance with a pressure detection result of detecting a pressure when the protrusion comes into contact with the pressure detection member. .   The fixing device according to claim 1, wherein a plurality of the protruding portions are provided on the same circumference of the inner peripheral surface of the end portion of the heat resistant film. A heating member, an endless heat-resistant film, a support member that supports the heat-resistant film, and a pressure member that is pressed against and rotated by the heating member with the heat-resistant film interposed therebetween. In a fixing device for fixing a toner image to the recording material by heating while sandwiching and conveying a recording material carrying an unfixed toner image to a fixing nip formed by a film and the pressure member,
A protrusion on the inner peripheral surface of the longitudinal end of the heat-resistant film, a pressure detection member for detecting pressure on the support member at a position where the protrusion contacts, and the heat-resistant film at the end of the heating body A pressure detection result of detecting a pressure when the protrusion comes into contact with the pressure detection member by rotation of the heat-resistant film, and a correction heating body for heating the end and changing the temperature of the end In accordance with the fixing device, the energization to the correction heating body is controlled to correct the longitudinal end position of the heat resistant film.   The fixing device according to claim 3, wherein the support member includes a plurality of the pressure detection members.   An image forming apparatus comprising the fixing device according to claim 1 and forming a desired image on a recording material.

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