JP2009288284A - Image heating apparatus and image forming apparatus with the same - Google Patents

Abstract

A belt-type image heating apparatus that suppresses the occurrence of belt damage while suppressing the complexity, size, and cost of the apparatus.
A driving device M that can change the rotation of an endless belt 10 forward and backward, and a regulating member 15 that regulates the movement of the endless belt in the width direction. Rotate in the opposite direction for a predetermined time, or until the position detecting means 54 detects that the endless belt has moved to a predetermined position.
[Selection] Figure 9

Description

  The present invention relates to a belt-type image heating apparatus suitable for use as a fixing device mounted on an image forming apparatus such as a copying machine, a printer, or a fax machine that forms an image by an electrophotographic system or an electrostatic recording system, and the like. The present invention relates to an image forming apparatus including

  Examples of the image heating device include a fixing device that heats and fixes an unfixed toner image formed and supported on a recording material, and a glossiness increasing device that increases the glossiness of an image by heating the image fixed on the recording material. Can be mentioned.

  As a fixing device for heat-melting and fixing an unfixed toner image, a pressure roller is pressed against a fixing roller having a heater inside to form a nip, and a recording material carrying an unfixed toner image is sandwiched and conveyed in the nip In general, a roller fixing method in which fixing is performed is used.

  In recent years, a belt fixing method in which an unfixed toner image on a recording material is fixed via a belt has been used.

  Compared to the roller fixing method, the belt fixing method can form a wide nip without increasing the size of the apparatus, so that it is possible to reduce the wait time, reduce the size of the apparatus, and increase the speed.

  However, in the belt fixing method, the belt moves due to the shifting force toward one end side or the other end side in the belt width direction orthogonal to the belt rotation direction, and the belt end portion repeats sliding with the side plate or the regulating member surface. However, there was a problem that the belt end was cracked or scraped.

  Therefore, as in Patent Document 1, a sensor that detects the movement of the belt in the width direction is provided, and the angle of the roller that stretches the belt is changed in accordance with the detection signal of the sensor, so that the belt is moved in the direction toward the side. Some have a shift control mechanism that moves them in the opposite direction. This mechanism can prevent the end crack of the belt.

Further, Patent Document 2 proposes a deviation restricting means in which an end portion of the belt is abutted and received, and a restricting member that is freely rotated by the movement of the belt is disposed.
Japanese Patent Laid-Open No. 3-209285 JP 2002-323821 A

  In the method of Patent Document 2, scraping due to rubbing between the belt end portion and the regulating member surface can be reduced. However, it is desired to further reduce the damage to the belt end due to the shifting force in the belt width direction. In particular, when the fixing device is warmed up when the fixing device is cold in the morning or the like, a large offset force is generated due to a high viscosity of the lubricant applied to the rubbing portion with the inner surface of the belt. For this reason, it is conceivable that damage such as cracking or buckling of the belt end occurs, and further improvement of this point is desired.

  SUMMARY OF THE INVENTION Accordingly, the present invention is intended to improve the belt-type image heating apparatus and the image formation including the belt-type image heating apparatus that suppress the occurrence of belt breakage while suppressing the complexity, size, and cost of the apparatus. Is to provide a device.

  In order to achieve the above object, an image heating apparatus according to the present invention is an image heating apparatus for heating an image formed on a recording material, wherein the recording material is nipped and conveyed at a nip portion and heated. A driving device for rotating the endless belt, the driving device capable of changing the rotation of the endless belt between a recording material conveyance direction and a direction opposite thereto, and a belt width direction accompanying the rotation of the endless belt. A restricting member that receives and restricts the movement of the endless belt, and a first step of rotating the endless belt in the reverse direction for a predetermined time after the endless rotation of the endless belt in the recording material conveyance direction; And a second step of stopping the rotation of the endless belt after the first step, and a controller that executes a drive device control sequence.

  According to the present invention, in spite of a simple configuration, damage to the belt end at the time of start-up can be reduced, and the occurrence of belt breakage can be suppressed while suppressing complication, enlargement, and cost increase of the device. Longer belt life can be achieved.

  Hereinafter, the present invention will be described more specifically with reference to examples. Although these examples are examples of embodiments to which the present invention can be applied, the present invention is not limited to these examples, and various modifications are possible within the scope of the idea of the present invention.

[First embodiment]
(1) Image Forming Unit FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process.

  Reference numeral 1 denotes a photosensitive drum as an image carrier. A layer of photosensitive material such as OPC, amorphous Se, or amorphous Si is formed on a cylindrical conductive substrate such as aluminum or nickel.

  The photosensitive drum 1 is rotationally driven in a clockwise direction indicated by an arrow with a predetermined peripheral speed (printing speed, process speed). First, the surface is uniformly charged to a predetermined polarity and potential by a charging roller 2 as a charging device.

  Next, scanning exposure 3a is performed on the uniformly charged surface by a laser scanner 3 that is ON / OFF controlled in accordance with image information to form an electrostatic latent image.

  This electrostatic latent image is developed and visualized as a toner image by the developing device 4. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used, and image exposure and reversal development are often used in combination.

  The visualized toner image is transferred from the photosensitive drum 1 onto the recording material P conveyed at a predetermined timing by a transfer roller 5 as a transfer device.

  The image forming means for forming an unfixed image (unfixed toner image) on the recording material P has been described above.

  Here, the sensor 8 detects the leading edge of the recording material P so that the image forming position of the toner image on the photosensitive drum 1 matches the writing position of the leading edge of the recording material P, and the timing is adjusted. The recording material P conveyed at a predetermined timing is nipped and conveyed between the photosensitive drum 1 and the transfer roller 5, and the toner images on the photosensitive drum 1 are sequentially transferred onto the surface of the recording material P. The recording material P to which the toner image has been transferred is separated from the surface of the photosensitive drum 1 and conveyed to a fixing device 6 as an image heating device, where it is heated and fixed as a fixed image.

  On the other hand, the surface of the photosensitive drum 1 after separation of the recording material is cleaned by removing residual toner remaining after transfer by the cleaning device 7 and is repeatedly used for image formation.

(2) Fixing device 6
In this embodiment, the fixing device 6 that is an image heating device uses a belt (endless belt that heats a recording material carrying an image by nipping and transporting it at a nip portion) as a heating member. Film) A belt fixing device using a heating method and a pressure member driving method.

  In the following description, the width direction of the fixing device 6 or a member constituting the fixing device 6 is a direction parallel to the direction orthogonal to the recording material conveyance direction in the recording material conveyance path surface. Regarding the fixing device 6, the front surface is a surface viewed from the recording material inlet side, and the back surface is the opposite surface (recording material outlet side). Left and right are left (front side) or right (back side) when the apparatus is viewed from the front. The upstream side and the downstream side are the upstream side and the downstream side in the recording material conveyance direction.

  FIG. 2 is a front model view of the fixing device 6 with the middle part omitted, FIG. 3 is a longitudinal front model diagram with the middle part omitted, and FIG. 4 is an enlarged cross-sectional model diagram along line (4)-(4) of FIG. is there. FIG. 5 is an exploded perspective model view of the apparatus, and FIG. 6 is an exploded perspective model view of the heating unit.

  Reference numeral 9 denotes a heating unit (fixing member). Reference numeral 20 denotes an elastic pressure roller as a pressure member (pressure rotator). The heating unit 9 and the pressure roller 20 are held substantially vertically in parallel between the left and right side plates 31 of the apparatus housing (sheet metal frame) 30, and a fixing nip portion N as a heating nip portion is formed by pressure contact between them. I am letting. The heating unit 9 is an assembly (assembly) such as the following a to d.

a: Horizontal heat insulating stay holder 12 having heat resistance and rigidity
b: A heater (heating body) 11 that generates heat by energization, which is fitted and fixedly supported on a lower surface of the heat insulating stay holder 12 in a concave groove 12a provided along the length (width direction) of the member.
c: A cylindrical (endless) fixing belt 10 which is a flexible endless belt as a heating member, which is loosely fitted to a heat insulating stay holder 12 on which a heater 11 is fixedly supported.
d: Flange member 15 as a restricting means for restricting the lateral movement of the fixing belt 10 in the width direction (bus line direction), which is attached to each of the outward extensions 12b on the left and right ends of the heat insulating stay holder 12.
The elastic pressure roller 20 as a pressure member includes a cored bar 21 and an elastic layer 22 formed by foaming heat-resistant rubber such as silicon rubber or fluorine rubber or silicon rubber on the outer side of the cored bar 21. A release layer 23 such as PFA, PTFE, FEP or the like may be formed on the elastic layer 22.

  The left and right side plates 31 of the apparatus housing 30 are each formed with an elongated fitting groove 31a having a width Lb and having an open side on the upper side, in the same shape (symmetrical). A bearing member 32 or a bearing made of a heat-resistant resin such as PEEK, PPS, or liquid crystal polymer is attached to the bottom of each fitting groove 31a with the fitting portion 32a engaged. The left and right bearing members 32 respectively support the left and right end portions of the pressure roller core 21 so that the pressure roller 20 is rotatably held between the left and right side plates 31.

  The heating unit 9 is engaged with the edge portions of the fitting grooves 31a of the left and right side plates 31 by engaging the vertical fitting portions 15c provided on the fixing flanges 15B described later of the left and right flange portions 15 respectively. It is disposed between the left and right side plates 31 above the pressure roller 20. The vertical fitting portion 15c and the fitting groove 31a serve as a guide for sliding the heating unit 9 between the left and right side plates 31 in the direction of the pressure roller 20.

  The pressure spring 17 is contracted between the pressure portions 15 d of the left and right fixing flanges 15 </ b> B and the spring receiving member 40. As a result, the heating unit 9 is pressed against the upper surface of the pressure roller 20 against the elasticity of the fixing belt 10 and the elasticity of the pressure roller 20 with a predetermined pressure to fix the fixing nip having a predetermined width in the recording material conveyance direction. Part N is formed.

  At the fixing nip N, the fixing belt 10 is sandwiched between the lower surface of the heat insulating stay holder 12 holding the heater 11 and the upper surface of the elastic pressure roller 20 by the pressure applied to the pressure roller 20 of the heating unit 9. Then, it bends following the lower surface of the heat insulating stay holder 12. As a result, the inner surface of the fixing belt 10 is in close contact with the lower surface of the heat insulating stay holder 12 and the flat surface of the lower surface of the heater 11.

  Further, there is provided a pressure control means 56 capable of changing the pressure applied to the pressure roller 20 of the heating unit 9, that is, the pressure applied to the fixing nip N by moving the spring receiving member 40 up and down. The pressure control means 56 is controlled by the control unit 54, for example, an eccentric cam mechanism or an electromagnetic solenoid mechanism controlled by the control unit 54. The control unit 54 controls the pressure control means 56 at a predetermined control timing, and the first state in which the spring receiving member 40 is pressed down against the elasticity of the pressure spring 17 and the second state in which the press-down is released. Switch to state. In the first state, the heating unit 9 is pressed against the upper surface of the pressure roller 20 with a predetermined pressure, and a fixing nip portion N having a predetermined width is formed in the recording material conveyance direction. That is, the pressure applied at the fixing nip N is maintained in a pressure application state necessary for nipping and conveying the recording material and fixing it. Further, in the second state, the pressure applied to the fixing nip portion N is reduced or the pressure is released compared to the first state in which the recording material is nipped and conveyed.

  G is a drive gear that is fixedly disposed at one end of the core metal 21 of the pressure roller 20. A rotational force is transmitted from the driving device (driving motor) M to the driving gear G, and the pressure roller 20 is rotated at a predetermined rotational speed (printing speed, process speed) in the counterclockwise direction of the arrow (recording material conveyance direction) in FIG. ). As the pressure roller 20 rotates, a rotational force acts on the fixing belt 10 by the frictional force between the pressure roller 20 and the fixing belt 10 on the heating unit 9 side in the fixing nip portion N. As a result, the fixing belt 10 slides while the inner surface thereof is in close contact with the lower surface of the heater 11, and the outer periphery of the heat insulating stay holder 12 is rotated in the clockwise direction (recording material conveying direction) in FIG. Then, it becomes a rotating state (pressure roller drive type).

  The driving device M is a driving device for rotating the fixing belt 10 which is an endless belt, and is a device capable of changing the rotation of the fixing belt 10 between the recording material conveyance direction and the opposite direction. That is, the rotation of the fixing belt 10 can be changed forward and backward, and is controlled by the control unit (CPU) 54. The control unit 54 performs overall sequence control of the entire image forming operation of the image forming apparatus including the fixing device 6 according to a predetermined control program and a reference table.

  Since the fixing belt 10 rotates while rubbing against the internal heater 11 and the heat insulating stay holder 12, it is necessary to reduce the frictional resistance between the heater 11 and the heat insulating stay holder 12 and the fixing belt 10. For this reason, a small amount of lubricant such as heat-resistant grease is interposed on the surfaces of the heater 11 and the heat insulating stay holder 12. As a result, the fixing belt 10 can rotate smoothly.

  The heater 11 heats the fixing nip portion N that melts and fixes the toner image T on the recording material P.

  In the fixing device 6, the fixing belt 10 is rotated by the rotation of the pressure roller 20 at a predetermined control timing by the control unit 54 based on the print start signal, and the heater 11 is energized so that the temperature of the heater 11 is increased. The temperature rises up to a predetermined temperature.

  In this state, the recording material P carrying the unfixed toner image T is conveyed between the fixing belt 10 and the pressure roller 20 in the fixing nip N along the heat-resistant fixing inlet guide 24. When the recording material P is nipped and conveyed through the fixing nip portion N, the unfixed toner image T is heated and fixed by the heat of the heater 11 via the fixing belt 10. The recording material P that has passed through the fixing nip portion N is separated from the outer surface of the fixing belt 10, guided by a heat-resistant fixing paper discharge guide (not shown), and discharged onto a discharge tray (not shown).

a) Fixing belt 10
The fixing belt 10 as an endless belt is a flexible sleeve having a small heat capacity. More specifically, in order to enable quick start, a metal member such as stainless steel, Al, Ni, Cu, Zn or the like having a total thickness of 500 μm or less and having heat resistance and high thermal conductivity is used alone or an alloy member is used as a base layer. Sleeve. Further, as a metal sleeve having sufficient strength and excellent durability for constituting a long-life fixing device, a total thickness of 30 μm or more is required. Therefore, the total thickness of the fixing belt 10 is optimally 30 μm or more and 500 μm or less.

  Furthermore, the surface is covered with a releasable layer in order to prevent offset and ensure the separation of the recording material. The releasable layer is a mixture or a single material of heat-resistant resin having good releasability such as fluororesin and silicone resin. Examples of the fluororesin are PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene hexafluoropropylene copolymer), and ETFE (ethylene tetrafluoroethylene). Copolymer), CTFE (polychlorotrifluoroethylene), PVDF (polyvinylidene fluoride) and the like.

  As a coating method, the outer surface of the metal sleeve base material is etched, and then the release layer is dipped, applied by powder spraying or the like, or the one formed in a tube shape is the surface of the metal sleeve. It may be of a type that covers the surface. Or after blasting the outer surface of a metal sleeve base material, the primer layer which is an adhesive agent is apply | coated and the method of coat | covering the said release layer may be sufficient.

  Further, a highly lubricious fluororesin layer, polyimide layer, polyamideimide layer or the like may be formed on the inner surface of the metal sleeve in contact with the heater 11.

b) Heater 11
The heater 11 that heats the fixing nip N that melts and fixes the toner image T on the recording material P is, for example, a highly insulating ceramic substrate such as alumina or AlN (aluminum nitride), polyimide, PPS, or liquid crystal polymer. Etc. have a heat resistant resin substrate. Then, along the longitudinal direction of the surface of the substrate, for example, an energization heat generation resistance layer such as Ag / Pd (silver palladium), RuO ₂ , Ta ₂ N is about 10 μm thick and about 1 to 5 mm wide by screen printing or the like. It is a member for energization heating formed by coating in the shape of a line or a thin strip.

  FIG. 7 is a schematic configuration diagram of an example of such a heater (ceramic heater) 11 and includes the following a to e.

a: Ceramic substrate (heater substrate) 11a made of highly insulating ceramics such as horizontally long alumina, aluminum nitride (AlN), silicon carbide, etc.
b: formed on the surface side of the ceramic substrate 11a along the length (width direction) by screen printing or the like, and applied to a linear or narrow strip having a thickness of about 10 μm and a width of about 1 to 5 mm, and fired, for example, Ag / Pd (silver palladium), RuO ₂ , Ta ₂ N, etc. energization heating layer 11b
c: Electrode portion 11c formed of Ag / Pt (silver / platinum) provided to be electrically connected to both ends (width direction) of the energization heating resistor layer 11b.
d: Insulating protective layer 11d, such as a thin glass coat or fluororesin coat, provided on the surface of the energization heating resistor layer 11b, which is electrically insulated and can withstand sliding against the metal fixing belt 10.
e: Temperature sensing element 14 such as a thermistor provided on the back surface (back surface) side of the ceramic substrate 11a.
In the heater 11, the side on which the insulating protective layer 11d is provided is the front side, and the fixing belt 10 slides on the surface of the insulating protective layer 11d. The heater 11 is fitted on a lower surface of the heat insulating stay holder 12 in a groove 12a (FIG. 4) provided along the length of the member, and is adhered and held with a heat resistant adhesive.

  Reference numeral 51 denotes a power supply connector, which is fitted to the electrode portion 11c portion of the heater 11 fixedly supported by the heat insulating stay holder 12, and the electric contact on the power supply connector side is brought into contact with the electrode portion 11c. 52 is a commercial power supply (AC), and 53 is a triac. The heater 11 is heated rapidly and steeply due to the heat generated by the energized heat generating resistance layer 11b by being fed from the commercial power source 52 between the electrode portions 11c via the triac 53. The temperature rise of the heater 11 is detected by the temperature detection element 14 which is a temperature detection body, and electrical analog information of the detected temperature is input to an analog-digital conversion circuit (A / D conversion circuit) 55 and digitized to generate electric power. It inputs into the control part 54 as a control means. DC energization from the temperature detection element 14 to the control unit 54 is performed by a connector (not shown) via a DC energization unit and a DC electrode unit (not shown).

  The control unit 54 appropriately controls the duty ratio, wave number, and the like of the voltage applied from the electrode unit 11c of the heater 11 to the energization heating resistor layer 11b in accordance with a signal from the temperature detection element 14. As a result, the temperature adjustment temperature in the fixing nip portion N is kept substantially constant, and heating necessary for fixing the toner image T on the recording material P is performed. In other words, the control unit 54 to which digital information corresponding to the temperature detected by the temperature detecting element 14 is input is supplied from the commercial power supply 52 so that the temperature detected by the temperature detecting element 14 falls within a predetermined range from the target temperature. The energization to 11b is controlled.

  As control of energization from the commercial power supply 52 to the energization heating resistor layer 11b by the control unit 54, phase control, wave number control, or the like is employed. In the phase control, the phase range used for energization from the commercial power supply 52 to the energization heating resistor layer 11b is changed according to the detected temperature of the temperature sensing element 14 every half-wave period of the AC power output from the commercial power supply 52. Control. The wave number control is a control for switching the energization from the commercial power source 52 to the energization heating resistor layer 11b to either conduction or interruption according to the detected temperature of the temperature detection element 14 every half wave period.

  When AlN or the like having excellent wear resistance and good thermal conductivity is used as the heater substrate 11a, the energization heating resistance layer 11b may be formed on the opposite side of the fixing nip portion N with respect to the substrate. .

  In FIG. 7, W <b> 11 b is the width dimension of the energization heat generation resistance layer 11 b and the effective heat generation area width of the heater 11. In FIG. 2, W10 is the width dimension of the fixing belt 10, and WP is the maximum sheet passing area width. The relationship is W11b> W10> WP.

c) Insulated stay holder 12
The heat insulating stay holder 12 functions as a heat insulating member for supporting the heater 11, serving as a rotation guide member for the fixing belt 10, serving as a pressure member, and preventing heat radiation in a direction opposite to the fixing nip portion N. ing. The holder 12 is a rigid, heat-resistant, heat-insulating member, and is formed of a liquid crystal polymer, a phenol resin, PPS, PEEK, or the like.

  In this embodiment, the downstream portion of the fixing nip portion N of the heat insulating stay holder 12 protrudes toward the pressure roller 20 and has a convex portion K having a height of 1.0 mm (FIG. 4, jaw for changing the curvature of the fixing belt). Part). This is for changing the rotational shape of the fixing belt 10 by the convex portion K and separating the curvature of the recording material P and the fixing belt 10.

d) Flange member 15
The flange member 15 is mounted on each of the left and right end portions of the heat insulating stay holder 12 so that the belt end portion moves in the belt width direction as the fixing belt 10 heats the image on the recording material at the nip portion. It is a member that receives and regulates.

  The flange member 15 is provided at a predetermined distance from the fixing belt 10 and abuts against the end portion of the fixing belt as the fixing belt 10 is moved. The first restricting member 15A. Hereinafter, the first restricting member 15A is referred to as a driven ring.

  The flange member 15 is a second restricting member 15 </ b> B that is a fixed body that is substantially non-rotatably fixed to restrict the movement of the driven ring 15 </ b> A in the width direction by the fixing belt 10. Hereinafter, the second restricting member 15B is referred to as a fixed flange.

a: Fixed flange 15B
The fixing flange 15B as the second restricting member is formed of a heat resistant resin such as PPS, liquid crystal polymer, or phenol resin. The shape is a cap shape, and has an insertion portion 15a having an inner diameter into which a driven ring 15A as a first regulating member can be inserted on the inner surface side. Further, this inner diameter is sufficient so that the outer peripheral surface of the fixing belt 10 does not contact the inner peripheral surface of the insertion portion 15a as shown in FIG. 4 even when the outer peripheral shape of the fixing belt 10 is deformed by forming a nip. It has a size.

  The fixed flange 15B as a regulating member of the driven ring 15A regulates the driven ring 15A in the width direction and regulates the rotational position of the driven ring 15A.

  The fixing flange 15B is fitted to the outward extending portions 12b on the left and right ends of the heat insulating stay holder 12, and the vertical fitting portion 15c of the fixing flange 15B is engaged with the fitting groove 31a of the side plate 31 of the apparatus housing 30. Attach them to the side plate 31 together. Thereby, the movement of the driven ring 15A in the longitudinal direction is restricted by the fixed flange 15B.

  Further, a part of the insertion portion 15a is cut out as 15b so as not to interfere with the heater 11, but the width of the cutout portion 15b is made smaller than the outer diameter of the driven ring 15A. This restricts the rotational position of the driven ring 15A within the insertion portion 15a. That is, by cutting out the fixing nip portion side of the insertion portion 15a, the insertion portion 15a can overlap the fixing nip region in the longitudinal direction of the fixing nip portion.

b: Follower ring 15A
The driven ring 15A as the first restricting member is formed of a heat resistant resin such as PPS, liquid crystal polymer, or phenol resin.

  Its shape is a ring-shaped disk, and its outer diameter is smaller than the inner diameter of the insertion portion 15a of the fixed flange 15 and larger than the notch portion 15b. The inner diameter is such that it does not interfere with the heater 11. The outer extension 12b of the heat insulating stay holder 12 passes through the inner diameter so that the driven ring 15A does not interfere with the outer extension 12b of the heat insulating stay holder 12.

  The endless ring-shaped or disk-shaped driven ring 15 </ b> A as the first regulating member has only a flat surface facing the end in the generatrix direction of the fixing belt 10 that is a rotating body.

  The driven ring 15A regulates the end portion of the fixing belt 10 in the width direction, and the fixing belt 10 receives the force in the width direction and approaches the driven ring 15A. At the same time, the driven ring 15A receives the driving force from the fixing belt 10. , It rotates together with the fixing belt 10. This prevents the end of the fixing belt 10 from rubbing.

  That is, in the rotation process of the fixing belt 10, one end side in the belt width direction perpendicular to the rotation direction of the belt along the longitudinal direction (width direction) of the heat insulating stay holder 12 (the left side of the arrow L in FIGS. 2 and 3). Or the other end side (left side of the arrow R).

  When the fixing belt 10 moves to the left L, the belt end on the left side of the fixing belt 10 abuts against the driven ring 15A of the flange member 15 on the side, and the driven ring 15A receives driving force from the fixing belt 10 at the same time. Receiving and rotating together with the fixing belt 10. The driven ring 15A is restricted in movement in the width direction by the fixing flange 15B and also in the rotational position. In FIG. 8A, as described above, the fixing belt 10 moves to the left L, and the belt end on the left side abuts against the driven ring 15A of the flange member 15 on the left side so that the fixing belt 10 moves to the left. It shows a state where movement is restricted. This prevents the left belt end of the fixing belt 10 from rubbing.

  When the fixing belt 10 moves to the right R, the belt end on the right side of the fixing belt 10 abuts against the driven ring 15A of the flange member 15 on the side, and the driven ring 15A is driven from the fixing belt 10 at the same time. Under the force, it rotates with the fixing belt 10. The driven ring 15A is restricted in movement in the width direction by the fixing flange 15B and is also restricted in rotational position. This prevents the right belt end of the fixing belt 10 from rubbing.

(3) Backward Control of Fixing Belt 10 In the belt fixing apparatus as in this example, the fixing belt 10 is rotated in the recording material conveyance direction unless the temperature and pressure distribution in the belt width direction is greatly inclined. In most cases, the accompanying movement direction is one direction due to a deviation in positional accuracy such as parallelism between the heater 11 and the pressure roller 20. That is, in FIG. 2 and FIG. 3, the movement phenomenon in one direction of the leftward movement of the arrow L or the leftward movement of the arrow R is almost always the case. Then, the fixing belt 10 in a state in which the shift movement is restricted by abutting against the driven ring 15A of the flange member 15 on the shifted side is rotated in the reverse direction by rotating the fixing belt 10 in the direction opposite to the recording material conveyance direction. You can move back.

  Therefore, in the present embodiment, the control unit 54 has a driving device control sequence having the following first step and second step after the rotation of the fixing belt 10 in the recording material conveyance direction (after completion of printing) is completed. Execute.

  First step: a step of rotating the fixing belt 10 in a direction opposite to the recording material conveyance direction for a predetermined time.

  Second step: A step of stopping the rotation of the fixing belt 10 after the first step.

  This makes it possible to reduce damage to the belt edge during start-up, despite the simple configuration, and to prevent belt damage from occurring while reducing the complexity, size, and cost of the device. Life expectancy can be improved.

  FIG. 9 is a flowchart of the reverse shift control of the fixing belt 10 executed by the control unit 54. In the present embodiment, for the sake of convenience, it is assumed that the shifting direction accompanying the rotation of the fixing belt 10 in the recording material conveyance direction is the shifting to the left of the arrow L in FIGS. Here, the driving device M for rotating the pressure roller 20 and the fixing belt 10 in the recording material conveyance direction is rotated in the forward direction and in the direction opposite to the recording material conveyance direction. The drive is reverse rotation drive.

  The control unit 54 starts the image forming operation of the image forming apparatus based on the input of the print signal (S1: print start).

  As for the fixing device 6, electric power is supplied to the heater 11, heating of the fixing nip N is started, and the driving device M is driven to rotate forward (S2). Then, the heater 11 rises to a predetermined fixing temperature and the temperature is adjusted, and the pressure roller 20 and the fixing belt 10 rise to a speed corresponding to a predetermined printing speed and are stably rotated. The carried recording material P is introduced into the fixing nip N. When the recording material P is nipped and conveyed through the fixing nip portion N, the unfixed toner image T is heated and fixed by the heat of the heater 11 via the fixing belt 10. The recording material P that has passed through the fixing nip N is separated from the outer surface of the fixing belt 10 and discharged to a paper discharge unit, and the paper discharge is detected (S3). The paper discharge is detected by detecting the passage of the rear end of the recording material discharged to the paper discharge unit by a paper discharge sensor (not shown) provided in the paper discharge unit. Heating / temperature control of the heater 11 and forward rotation driving of the driving device M are performed until the print job is completed (printing is completed) (S2 to S4). That is, when the trailing edge of the recording material passes the paper discharge sensor, the presence or absence of the next print signal is determined, and if there is a signal, the rotation is continued as it is.

  As the fixing belt 10 rotates in the recording material conveyance direction by the forward rotation driving of the driving device M during the print job, the fixing belt 10 moves to the left of the arrow L in FIGS. 2 and 3 in this embodiment. Move closer. 8A, the belt end on the left side of the fixing belt 10 abuts against the driven ring 15A of the left flange member 15, and at the same time, the driven ring 15A receives a driving force from the fixing belt 10 and receives the fixing belt. Rotate with 10 The driven ring 15A is restricted in movement in the width direction by the fixing flange 15B and also in the rotational position. This prevents the left belt end of the fixing belt 10 from rubbing.

  After the end of the print job (“next print signal—none” in S4), the power supply to the heater is turned off, and the driving device M is changed to the reverse rotation drive (S5). In this embodiment, the reverse rotation driving of the driving device M is performed at the same speed as the forward rotation driving (the same speed as during printing) for a predetermined time (S5 and S6). That is, the fixing belt 10 is rotated for a predetermined time in the direction opposite to the recording material conveyance direction. In this embodiment, the predetermined time is set to 10 seconds. Then, after the predetermined time has elapsed, the reverse rotation driving of the driving device M is stopped (S7), and the image forming apparatus is held in a standby state until a print signal of the next print job is input (S8).

  By the reverse rotation driving of the driving device M in step S5, the fixing belt 10 is rotated in the direction opposite to the recording material conveyance direction, thereby returning in the reverse direction. That is, until that time, the heater 11 and the pressure roller 20 are moved toward one side due to the positional accuracy deviation such as parallelism, and are in contact with the driven ring 15A of the flange member 15 on the side moving side. The fixing belt 10 is moved back in the reverse direction. By this return movement, the belt end portion is separated from the driven ring 15A. In this embodiment, by executing the print job, as shown in FIG. 8A, the belt L moves to the left of the arrow L and the belt end on that side moves to the driven ring 15A of the left flange member 15. The returning movement in the reverse direction R of the fixing belt 10 in the abutted state is started. By this return movement, the belt end part moves away from the driven ring 15A. In the present embodiment, the reverse rotation time of the fixing belt 10 is set to 10 seconds, so that the belt end that has been in contact with the flange on one side as shown in FIG. As shown in (b), the flange can be brought into a non-contact state.

  Here, even if the fixing belt 10 returns too much during reverse rotation and the opposite belt end hits the flange on that side, the fixing belt temperature remains at a certain level regardless of whether or not the heater temperature is adjusted. It is. For this reason, there is no problem because a large offset force is not generated, and there is no possibility that breakage such as cracking or buckling of the belt end portion may occur.

  After that, when the fixing device is not used for a while and the warming-up operation is started after the fixing device is cooled, the shifting force becomes the largest due to the high viscosity of the grease as the lubricant. However, since the end of the belt on which the fixing belt 10 approaches is not in contact with the flange (FIG. 8B), there is no force applied to the end of the belt, and the end of the belt is broken. To prevent buckling.

  In this way, when the printing is completed, the fixing belt 10 is reversely rotated, and the belt end is returned to a position where it does not come into contact with the deviation regulating member. Since it is not in contact with the member, damage to the belt end can be reduced, and the life of the belt can be extended.

  Further, the drive device M is configured to be able to change its rotation speed (rotation speed per unit time) so that the rotation speed during reverse rotation drive is higher than the rotation speed during forward rotation drive (during printing). By controlling so, it is possible to shorten the rotation time after the end of printing.

  Further, when the driving device M is driven in reverse rotation, the pressure control means 56 is switched to the second state. That is, the pressure applied to the fixing nip N is reduced as compared with the time when the recording material is nipped and conveyed (during fixing), or the pressure is released to release the pressure on the fixing belt 11 and the pressure roller 20 to rotate in the light pressure state. As a result, it is possible to suppress wear and the like between the inner surface of the fixing belt and the rubbing member. As a result, the life of the fixing belt is not shortened due to an increase in the rotational speed.

[Second Embodiment]
Since the apparatus configuration of the present embodiment is substantially the same as that of the apparatus of the first embodiment, only the main differences will be described.

  In this embodiment, as shown in FIG. 10A, a position detecting means 58 for detecting a shift position in the belt width direction accompanying the rotation of the fixing belt 11 is provided. Then, after the rotation of the fixing belt 10 in the recording material conveyance direction (after the end of printing) is completed, the control unit 54 executes a drive device control sequence having the following first step and second step.

  First step: a step of rotating the fixing belt 10 in the direction opposite to the recording material conveyance direction.

  Second step: A step of stopping the rotation of the fixing belt 11 when the position detecting means 58 detects that the fixing belt shifted by the first step rotation has moved to a predetermined position.

  Also in this embodiment, the shifting direction along with the rotation of the fixing belt 10 in the recording material conveyance direction is shifted to the left of the arrow L in FIGS. 2 and 3 for convenience, as in the first embodiment. Suppose it is a move. The position detecting means 58 for detecting the shift position of the fixing belt 11 is a photo sensor (photo interrupter) having a light emitting portion 58a and a light receiving portion 58b, and is arranged on the left side of the fixing device as shown in FIG. .

  FIG. 11 is a flowchart of the retraction control of the fixing belt 10 executed by the control unit 54. The control unit 54 starts the image forming operation of the image forming apparatus based on the input of the print signal (S1: print start). Thereafter, up to step S5 is the same as step S5 in the flowchart of FIG. 9 in the first embodiment.

  Also in this embodiment, as shown in FIG. 10A, the fixing belt 10 moves to the left of the arrow L as a result of the execution of the print job, and the left belt end is the flange member on that side. It will be in the state regulated by hitting 15 follower rings 15A. The driven ring 15A is restricted in movement in the width direction by the fixing flange 15B and also in the rotational position. This prevents the left belt end of the fixing belt 10 from rubbing.

  In this case, the optical path between the light emitting portion 58a and the light receiving portion 58b of the photosensor 58 is blocked by the belt end on the side of the fixing belt that has moved to the left L, and the photosensor 58 is turned off. It becomes the state of. The control unit 54 determines that the fixing belt 10 is moving to the left by the photo sensor 58 being off. In addition, when the photosensor 58 is on because the optical path between the light emitting unit 58a and the light receiving unit 58b is open, the control unit 54 detects that the belt end on the left side of the fixing belt 10 is in FIG. As shown in (b), it is determined that it is in a state of being separated from the driven ring 15A by a predetermined distance.

  After the end of the print job (“next print signal—none” in S4), the power supply to the heater is turned off (S5). At this time, if the photosensor 58 is in an off state, the driving device M is changed to reverse rotation driving (S6 and S7). The reverse rotation driving of the driving device M is continued until the photosensor 58 is turned on from the off state (S7 and S8). When the photosensor 58 is turned on, the reverse rotation drive of the drive device M is stopped based on the signal (S9), and the image forming apparatus is in a standby state until a print signal for the next print job is input. It is held (S10).

  If it is determined in step S6 that the photosensor 58 is on, the forward rotation drive of the drive device M is stopped (S9), and the image forming apparatus is on standby until a print signal for the next print job is input. The state is maintained (S10).

  By the reverse rotation driving of the driving device M in step S7, the fixing belt 10 is rotated in the direction opposite to the recording material conveyance direction, thereby returning in the reverse direction. That is, until that time, the heater 11 and the pressure roller 20 are moved toward one side due to the positional accuracy deviation such as parallelism, and are in contact with the driven ring 15A of the flange member 15 on the side moving side. The fixing belt 10 is moved back in the reverse direction. By this return movement, the belt end portion is separated from the driven ring 15A. In this embodiment, as shown in FIG. 10 (a), the left belt end is in contact with the driven ring 15A of the left flange member 15 as the arrow L moves toward the left. The return movement of the fixing belt 10 in the reverse direction R is started. By this return movement, the belt end part moves away from the driven ring 15A. In the present embodiment, the reverse rotation drive of the driving device M is executed until the photosensor 58 is turned on from the off state. And when it will be in an ON state, the reverse rotation drive of the drive device M will be stopped. As a result, the fixing belt 11 that has moved to the left is moved back to the right R in a state in which the belt end of the fixing belt 11 is separated from the driven ring 15A by a predetermined distance.

  That is, after the end of the print job, the rotation of the pressure roller is stopped when the end of the fixing belt returns to a predetermined position based on the detection result of the photo sensor 58 which is a belt position detection sensor. This position is set to a position where the fixing belt does not come into contact with the regulating member at the end when the biasing force when starting up is large.

  In this state, when the warm-up operation is started from a state in which the fixing device is not used for a long time, the shifting force becomes the largest. However, since the belt end is not in contact with the flange, there is no force applied to the belt end, and the belt end is prevented from cracking or buckling.

  In this way, the belt position is not returned to the position where the belt does not come in contact with the belt position detection sensor, and the belt end is not in contact with the restricting member, so damage to the belt end is reduced. This can extend the life of the belt.

  The image heating device of the present invention is not limited to the fixing device of the embodiment, and is effective as a glossiness increasing device that increases the glossiness of an image by heating an image fixed on a recording material, and other image heating devices. is there.

  The driving of the endless belt is not limited to the pressure member driving method. A system in which an endless belt is suspended between a plurality of suspension members including a driving roller and is rotated by the driving roller may be employed.

  The image forming means (image forming system) for forming an unfixed image on the recording material of the image forming apparatus is not limited to the electrophotographic system. An electrostatic recording system, a magnetic recording system, or the like may be used.

Schematic configuration diagram of an image forming apparatus in an embodiment Front model diagram of the heating fixing device (image heating device) in the embodiment with part omitted in the middle Similarly, a vertical front view of the middle part is omitted. Enlarged cross-sectional model view along line (4)-(4) in FIG. Exploded perspective view of the device Exploded perspective view of heating unit Schematic diagram of an example of a heater (ceramic heater) Explanatory drawing of displacement of fixing belt and regulating member Flowchart of fixing belt retraction control in the first embodiment Explanatory drawing of the movement of the fixing belt and the regulating member in the second embodiment Flow chart of fixing belt retraction control in the second embodiment

Explanation of symbols

  6: belt-type fixing device (image heating device), 10: fixing belt (endless belt), 11: heater for heating, 12: heat-resistant stay holder, 15: fixing flange (regulating member), 20: pressure roller, M : Driving device, N: fixing nip, P: recording material, T: toner image, 54: controller, 56: pressure control means, 58: position detection means

Claims (5)

An image heating apparatus for heating an image formed on a recording material,
An endless belt for nipping and conveying the recording material at the nip and heating;
A driving device for rotating the endless belt, the driving device capable of changing the rotation of the endless belt in a recording material conveyance direction and a direction opposite thereto;
A regulating member that receives and regulates the belt end portion in the belt width direction accompanying rotation of the endless belt;
After the rotation of the endless belt in the recording material conveyance direction is completed, a first step of rotating the endless belt in the reverse direction for a predetermined time, and after the first step, a rotation of the endless belt is stopped. A controller that executes a drive device control sequence having two steps;
An image heating apparatus comprising: An image heating apparatus for heating an image formed on a recording material,
An endless belt for nipping and conveying the recording material at the nip and heating;
A driving device for rotating the endless belt, the driving device capable of changing the rotation of the endless belt in a recording material conveyance direction and a direction opposite thereto;
A regulating member that receives and regulates the belt end portion in the belt width direction accompanying rotation of the endless belt;
Position detecting means for detecting a shift position in the belt width direction accompanying rotation of the endless belt;
After the rotation of the endless belt in the recording material conveyance direction is completed, the first step of rotating the endless belt in the reverse direction, and the endless belt moved by the rotation of the first step moved to a predetermined position A second step of stopping the rotation of the endless belt when the position detecting means detects that, a controller that executes a drive device control sequence,
An image heating apparatus comprising:   The image heating apparatus according to claim 1, wherein a rotation speed of the endless belt in the reverse direction is higher than a rotation speed of the endless belt in the recording material conveyance direction.   4. The image heating apparatus according to claim 1, wherein, in the first step, the pressure applied to the nip portion is reduced or the pressure is released compared to when the recording material is nipped and conveyed.   5. An image forming apparatus comprising: an image forming unit that forms an unfixed image on a recording material; and a fixing device that heat-fixes the unfixed image formed on the recording material, wherein the fixing device is any one of claims 1 to 4. An image forming apparatus according to claim 1.

Images