JP2005309316A - Belt fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the durability of the one-way clutch of an anti-belt-slip drive mechanism in a belt fixing device by preventing a change in pressing force on a fixing rotor even when a roller 12 which rotates following the rotation of a belt comes into contact with the fixing rotor 2 via the belt 10 and starts to drive. <P>SOLUTION: The belt fixing device includes drive means 6 and 33 to 35 used for inputting drive force to the roller 12 and disposed via a one-way clutch. The direction in which the driving force is inputted to the roller 12 is the approximately tangential direction of the fixing rotor or roller in the abutting part of the fixing rotor and roller. Alternatively, it is a direction almost parallel to the approximately tangential direction. The belt fixing device also includes means 25 to 27 for conducting switching between a first state in which the fixing rotor 2 and the belt 10 are in contact with each other and a second state in which the fixing rotor 2 and the belt 10 are apart from each other. Whether switching takes place to the first state or second state, the roller drive means 6 and 33 to 35 are capable of transmitting the rotating drive force of the fixing rotor 2 to the roller 12 via the one-way clutch. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt fixing device used in an image forming apparatus.

  The belt fixing device is supported by a fixing roller that is heated by a heating unit and rotated by a driving unit (hereinafter referred to as a fixing roller) and a plurality of belt suspension members. An endless belt (hereinafter referred to as a fixing belt) that rotates in contact with the toner, and a recording material carrying a toner image at a fixing nip portion that is a contact portion between the fixing roller and the fixing belt. It is nipped and conveyed to fix the toner image on the surface of the recording material with heat and pressure.

  In the belt fixing device, the width of the fixing nip portion is adjusted by adjusting the abutting width of the fixing belt with respect to the fixing roller of the fixing roller in comparison with the pressure roller pair type fixing device of the fixing roller and the pressure roller. It can be easily set large. Further, since the fixing nip width can be secured without depending on the diameter of the fixing roller, the fixing roller can have a small diameter and a small heat capacity, and the start-up time can be shortened. Since the fixing nip width can be widened, the toner on the recording material can be melted more, and the fixing device configuration is suitable for an image forming apparatus using a large amount of toner in a color image forming apparatus.

  In the above-described conventional example, even when the image output is not performed and the fixing roller and the fixing belt are not maintained at the specified temperature, the fixing roller and the fixing belt are heated until the specified temperature is reached at the next image output. It takes time to do. For this reason, the fixing roller in the standby state is turned on to rotate the fixing roller so that the fixing belt is driven to rotate and the fixing belt is heated by the heat from the fixing roller. Have taken.

  In a color image forming apparatus, the surface of a recording material (transfer paper) is made of a synthetic resin or the like on the surface of the paper as a recording material for improving the color development and image quality of the toner image by giving the surface gloss. In some cases, a coated paper having a coating layer coated with a thickness of several tens of microns is used. When transferring a toner image onto such coated paper and fixing it with a fixing device, if a heat amount more than necessary is applied to the coated paper, the moisture inside the coated paper will evaporate and a coat made of a synthetic resin or the like applied to the surface of the paper The layer is partially destroyed by water vapor inside the coated paper, resulting in an image with lost smoothness. In particular, in a fixing device using a fixing belt, since the nip width is wide, a large amount of heat is applied to the coated paper, and this problem is likely to occur.

  For this reason, in Patent Document 1, the fixing belt unit is retracted from the fixing roller in a standby state with respect to the state during operation of the image forming apparatus so that the fixing belt does not come into contact with the fixing roller. In this state, the fixing belt is rotated by a driving source, and the fixing belt is heated to a constant temperature by a fixing belt heating roller. Here, by setting the temperature of the fixing belt to a temperature somewhat lower than the temperature of the fixing roller, the amount of heat applied to the back surface of the recording material is reduced, and the occurrence of the above phenomenon is prevented by suppressing the evaporation of moisture inside the paper. doing.

  Further, in the above configuration, the fixing belt is configured to rotate following the fixing roller. In order for the fixing belt to rotate following the fixing roller, the friction coefficient between the fixing roller and the fixing belt surface, and the friction coefficient between the inner surface of the fixing belt and the pressure pad portion that presses the fixing belt against the fixing roller are: The relationship needs to be the friction coefficient of [Friction coefficient between fixing roller and fixing belt surface]> [Fusing belt inner surface and pressure pad portion].

  When the recording material is conveyed at the fixing nip portion, the friction coefficient between the fixing roller and the fixing roller surface of the recording material, the friction coefficient between the fixing belt surface of the recording material and the fixing belt surface, and the fixing belt The relationship between the friction coefficient between the inner surface and the pressure pad portion is [Friction coefficient between the fixing roller and the fixing roller surface of the recording material]> [Friction coefficient between the fixing belt surface of the recording material and the fixing belt surface] ]> [Coefficient of friction between inner surface of fixing belt and pressure pad portion].

  However, with a wide fixing nip portion like a belt fixing device, in a solid image in which a toner is placed on one surface of the recording material, the toner melts at the fixing nip portion at the time of fixing. The friction coefficient with the fixing roller surface of the recording material becomes low. Therefore, [the coefficient of friction between the fixing roller and the fixing roller surface of the recording material], “the coefficient of friction between the fixing belt surface of the recording material and the surface of the fixing belt”, [the inner surface of the fixing belt and the pressure pad portion] [Friction coefficient between the fixing roller and the fixing roller surface of the recording material] <[Friction coefficient between the fixing belt surface of the recording material and the fixing belt surface]> [Fixing belt] Friction coefficient between the inner surface and the pressure pad portion], the conveyance failure of the recording material and the conveyance speed unevenness due to the conveyance failure appear in the image, and problems such as image unevenness occur.

  Therefore, in the configuration of claim 2 of Patent Document 2, the belt is sandwiched between an endless belt, a drive roller that is outside the belt and drives the belt, and the drive roller. In a belt fixing device including a fixing roller for forming a nip portion, a gear arranged on the same axis as the driving roller, and a gear meshing with the gear via a one-way clutch, and a fixing roller An auxiliary mechanism for driving via a one-way clutch by arranging them coaxially has been proposed.

By providing the above configuration in the belt fixing device, it is possible to provide a belt fixing device in which the fixing belt is driven and rotated by a fixing roller and does not cause poor conveyance even in a solid image in which a toner is placed on one surface of the recording material. It becomes like this.
Japanese Patent Application Laid-Open No. 11-194647 JP 2002-287561 A

  However, in order to further melt the toner on the recording material in an image forming apparatus that uses a large amount of toner such as a color image forming apparatus, it is necessary to provide a belt fixing apparatus having a wide fixing nip portion. In order to obtain a good image with this fixing device, the following two items must be combined as in the conventional example.

  1) A first item includes a fixing belt, a fixing roller, and a grip roller that forms a pressure nip portion with a fixing belt interposed between the fixing roller and the fixing roller. And a drive auxiliary mechanism configuration in which a gear meshed with the gear via a one-way clutch is arranged coaxially with the grip roller.

  2) The second item is that the fixing roller setting temperature and the fixing belt setting temperature are set to different values, and contact / separation means for contacting and separating the fixing roller and the fixing belt are provided and fixing is performed. In other words, a driving means for independently rotating the belt is provided.

  The above two items 1) and 2) are provided in an endless fixing belt as in the prior art, and an entrance roller, a separation roller (grip roller), and a steering roller as a plurality of belt suspension members. In order to construct a belt fixing device in which a fixing belt is provided with a fixing belt and a pressure pad portion is disposed between the entrance roller and the separating roller, the fixing roller is separated from the fixing roller. A driving auxiliary mechanism in which a fixing belt is press-contacted by a roller and a gear arranged coaxially with the fixing roller and a gear meshed with the gear via a one-way clutch are arranged coaxially with the separation roller. A configuration must be provided.

  However, with the above configuration, when the fixing belt slips and driving is input to the separation roller, the reaction force that drives the separation roller escapes from the fixing roller to the separation roller. It will depend on. Therefore, the separation roller pressure with respect to the fixing roller changes depending on whether the fixing belt slides or not. For this reason, the separation ability of the separation roller that separates the recording material front end from the fixing roller varies, resulting in a separation failure problem, or the separation nip portion that is the pressure contact portion between the fixing roller and the separation roller changes. As a result, the fixing property and gloss change to cause an image problem, and further, the separation nip portion changes to cause a problem that the discharged paper curls vary.

  Further, when the fixing roller and the fixing belt are separated from each other, when a driving means for driving the fixing belt is provided independently and the fixing belt is rotated, the one-way clutch of the belt slip prevention driving mechanism must be idled. . Here, when the one-way clutch is idled, the shaft supporting the one-way clutch may be scraped because it slides on the one-way clutch. If the shaft is shaved, a one-way clutch lock failure occurs and belt slip cannot be prevented. In particular, during copy standby, the fixing belt must be rotated for a long time with the fixing roller and the fixing belt being separated from each other, so that the shaft of the one-way clutch is likely to be scraped. Therefore, the problem of shaft durability occurs.

  Needless to say, when the fixing roller and the fixing belt are separated from each other, providing the driving means for driving the fixing belt independently complicates the apparatus configuration, which increases the number of parts of the apparatus. In addition, the device assembly time and maintenance time increase.

  An object of the present invention is to eliminate the above-described problems with belt fixing devices. That is, in the belt fixing device, even if the roller is brought into contact with the fixing rotator with the belt interposed therebetween and driven by the rotation of the belt, the pressure applied to the fixing rotator does not change, and the belt slip prevention drive. The purpose is to endure the one-way clutch of the mechanism.

  The present invention is a belt fixing device having the following configuration.

(1) a fixing rotator heated by a heating unit and driven to rotate by a driving unit;
An endless belt that is supported in a suspended manner between a plurality of belt suspension members and that rotates in contact with the fixing rotator;
A belt fixing device that sandwiches and conveys a recording material carrying a toner image between the fixing rotator and the belt,
One of the plurality of belt suspension members is a roller that abuts on the fixing rotator across the belt and rotates following the rotation of the belt,
Roller drive means for inputting the rotational driving force of the fixing rotator to the roller via a one-way clutch when the belt is slidingly rotating from the fixing rotator,
An input direction of the driving force of the roller is a substantially tangential direction of the fixing rotator or the roller at a contact portion between the fixing rotator and the roller, or substantially parallel to the substantially tangential direction. Belt fixing device characterized in that it is in a different direction.

  (2) The roller driving means applies the rotational driving force of the fixing rotating body until the belt starts to slide from the fixing rotating body and the rotational speed becomes 4% slower than the rotational speed of the fixing rotating body. The belt fixing device according to (1), which is input to a roller.

  (3) a state switching means between a first state in which the fixing rotator and the belt are in contact with each other and a second state in which the fixing rotator and the belt are separated; The roller driving means is in a state in which the rotational driving force of the fixing rotator can be transmitted to the roller via a one-way clutch in any of the switching states of the first state and the second state. The belt fixing device according to (1) or (2).

  (4) The roller driving means includes a first gear arranged coaxially with the fixing rotator, a second gear meshing with the first gear, and coaxial with the second gear. A first belt pulley disposed on the roller, a second belt pulley disposed coaxially with the roller, and a timing belt wound around the first and second belt pulleys, The belt fixing device according to (3), wherein a one-way clutch is interposed in any one of the first gear, the second gear, the first belt pulley, and the second belt pulley. .

  (5) In the second state, when the apparatus is in a standby state, driving is input to the fixing rotator, and the rotational driving force of the fixing rotator is input to the roller by the roller driving means. The belt fixing device according to (3) or (4), wherein the fixing belt is driven.

  (6) The first state and the second state rotate about one axis, and the one axis moves from the center of the second roller to the fixing roller and the second roller. The belt fixing device according to any one of (3) to (5), wherein the belt fixing device is in a direction substantially parallel to a substantially tangential direction.

  That is, in the belt fixing device, a driving means via a one-way clutch that inputs a driving force to a roller as a belt suspension member that is in contact with the fixing rotating body with the belt interposed therebetween and is rotated by the rotation of the belt. The roller driving force is input in a direction substantially tangential to the fixing rotator or roller at the contact portion between the fixing rotator and the roller, or substantially parallel to this tangential direction. Even when the roller is driven, the pressure applied to the fixing rotator of the roller is stable, and there is a large amount of toner such as a solid image on the recording material without deteriorating the fixing performance. It has become possible to provide a fixing device in which image defects do not occur without the belt slipping.

  Further, the roller driving means includes a state switching means between a first state in which the fixing rotator and the belt are in contact with each other and a second state in which the fixing rotator and the belt are separated from each other. Is in a state in which the rotational driving force of the fixing rotator can be transmitted to the roller via a one-way clutch in both the first and second switching states. The belt can be rotated simply by inputting the drive to the fixing rotator, and the belt can be driven with a simple configuration without providing a belt rotation driving means. Since the directional clutch is not idled, the durability of the one-way clutch drive mechanism is improved.

  The present invention will be described below based on the illustrated embodiments.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration model diagram of an example of an image forming apparatus provided with a belt fixing device according to the present invention. FIG. 2 is an enlarged view of an image forming station portion of the image forming apparatus.

  The image forming apparatus of this example is a four-drum tandem type laser beam printer having a plurality of optical scanning units using an electrophotographic process.

  In this printer, image information of a color original is subjected to color separation reading processing by a photoelectric conversion element such as a CCD in a reader unit 200 disposed on the upper surface side of the printer main body 100. Reference numeral 300 denotes an automatic document feeder or document pressing plate for the document table crow 201 of the reader unit 200. Laser light La, Lb, Lc, Ld modulated corresponding to each color separation read image information in the reader unit 200 is output from a laser scanning unit 400 having a plurality of optical scanning means.

  Pa, Pb, Pc, and Pd are four image forming stations for forming images of each color of magenta, cyan, yellow, and black.

  Referring to FIG. 2, photosensitive drums 101a, 101b, 101c, and 101d are disposed at the image forming stations Pa, Pb, Pc, and Pd, respectively. Each photosensitive drum is driven to rotate in the direction of the arrow. Around each photosensitive drum, chargers 102a, 102b, 102c, and 102d, developing devices 103a, 103b, 103c, and 103d and cleaners 104a, 104b, 104c, and 104d are sequentially arranged along the rotation direction of the photosensitive drum. It is installed.

  A transfer device 105 is disposed below each photosensitive drum. The transfer device 105 includes a transfer belt 106 serving as a recording material conveying means common to each image forming station and transfer chargers 107a, 107b, 107c, and 107d. The transfer belt 106 is an endless belt, and is stretched around three rollers of a drive roller 108 and turn rollers 109 and 110.

  An electrophotographic process including a step of performing scanning exposure with the laser beams La, Lb, Lc, and Ld output from the laser scanning unit 400 is applied to the photosensitive drums 101a, 101b, 101c, and 101d of each image forming station. Magenta, cyan, yellow, and black toner images are formed.

  In FIG. 1, reference numerals 111 and 112 denote first or second paper feed cassettes provided in the printer main body 100. A recording material (paper such as transfer paper, second original paper, OHP sheet) P separated and fed by the recording material supply means from the paper feed cassette 111 or 112 is supported on the transfer belt 106 and is placed on The toner images of the respective colors are sequentially transferred to the image forming stations Pa, Pb, Pc, and Pd, and the toner images of the respective colors formed on the respective photosensitive drums are sequentially superimposed and transferred.

  When this transfer process is completed, the recording material P is separated from the transfer belt 106 and conveyed to the fixing device 1. The fixing device 1 is a belt fixing device according to the present invention. This will be described in detail in the next section (2).

  The toner image transferred to the recording material P is fixed on the recording material P by heat and pressure in the belt fixing device 1 and conveyed to the paper discharge processing device 500 as a full-color image formed product. In the paper discharge processing apparatus 500, the recording material P is discharged onto the paper discharge tray 502 by the transport roller 501. The paper discharge tray moves downward to enable stacking of a large number of sheets. Further, the paper discharge processing apparatus 500 can also process a plurality of recording materials P to be stapled.

  In the mono black image forming mode, the image forming station Pd that forms a black image selectively performs an image forming operation. In the double-sided copy mode, the recording material P that has been copied on one side from the belt fixing device 1 is rerouted to the reversal reconveying mechanism 113 side, reversed by the reversal reconveying mechanism 113, and re-supplied to the transfer belt 106. Paper. As a result, a toner image is transferred and formed on the other side of the recording material P, introduced again into the belt fixing device 1, and the double-sided copy is conveyed to the paper discharge processing device 500.

(2) Belt fixing device 1
FIG. 3 is a schematic configuration model diagram of the belt fixing device 1 in this embodiment. In the belt fixing device 1, reference numeral 2 denotes a fixing roller as a fixing rotating body. Reference numeral 9 denotes a belt unit (fixing belt portion) disposed below the fixing roller 2.

1) Fixing roller 2
The fixing roller 2 is a fixing roller having a hollow body made of a metal such as aluminum as a core metal 2a, an elastic layer 2b made of silicon rubber provided on the outer peripheral surface thereof, and a PFA hub formed on the outer peripheral surface thereof. A release layer 2c that enhances the release property of the toner is provided. The fixing roller 2 is disposed such that both end portions in the longitudinal direction (axial direction) are rotatably supported between bearing side plates (not shown) via a bearing.

  Reference numeral 3 denotes a heater such as a halogen heater as a heating means (heat source) for heating the fixing roller 2, which is disposed in the vicinity of the center of the fixing roller.

  Reference numeral 4 denotes a thermistor as a fixing roller temperature detecting means. The thermistor 4 is arranged in elastic contact with the surface portion of the fixing roller corresponding to the minimum sheet passing area width of the recording material.

  Reference numeral 5 denotes a fixing roller cleaner. A web feed shaft 5b that holds a cleaning web 5a as a cleaning member in a roll form, a web take-up shaft 5c, and a pressing roller that presses the web portion between the shafts 5b and 5c against the outer surface of the fixing roller 2. 5d etc. The toner offset to the surface of the fixing roller 2 is wiped off by the web portion pressed against the fixing roller 2 by the pressing roller 5d, and the fixing roller surface is cleaned. The web portion pressed against the fixing roller 2 is gradually updated as the web 5a is intermittently fed from the feed shaft 5b side to the take-up shaft 5c side.

  Referring to FIG. 6, a fixing roller gear (first gear) 6 is fixedly disposed coaxially with fixing roller 2 at one end in the longitudinal direction of fixing roller 2. The fixing roller gear 6 is meshed with a fixing motor gear 7a of a fixing motor 7 serving as a device driving unit. The fixing motor 7 is fixedly disposed on the apparatus chassis (not shown).

  Referring to FIG. 5, energization of fixing motor 7 from motor driver 51 controlled by control circuit unit 50 causes fixing motor gear 7 a to be rotationally driven in the direction of arrow B in FIG. 6. As a result, the fixing roller gear 6, that is, the fixing roller 2 is rotationally driven in the direction of arrow A at a predetermined speed.

  In addition, when the heater 3 is energized from the power supply circuit unit 52 controlled by the control circuit unit 50, the heater 3 generates heat. The fixing roller 2 is heated from the inside due to the heat generated by the heater 3 and the temperature rises. The surface temperature of the fixing roller 2 is detected by the thermistor 4, and the electrical detection temperature information is input to the control circuit unit 50. The control circuit unit 50 controls the power supplied from the power supply circuit unit 52 to the heater 3 so that the electrical detection temperature information input from the thermistor 4 is maintained at a substantially constant value corresponding to a predetermined fixing temperature. That is, the control circuit unit 50 controls the surface temperature of the fixing roller 2 to a predetermined fixing temperature.

2) Belt unit 9
Referring to FIG. 3, the belt unit 9 includes an endless and flexible fixing belt 10 as a pressure belt, and a plurality of belt suspension members (a plurality of belt suspension members (a plurality of belt suspension members) on which the fixing belt 10 is suspended. Belt rollers (first to third rollers 11 to 13), a pressure pad portion 14, an oil felt portion 15, a thermistor 16 as fixing belt temperature detecting means, and the like.

  The fixing belt 10 is formed, for example, by molding a heat-resistant resin material such as polyimide into an endless belt shape.

  The first to third rollers 11 to 13 are arranged so as to be freely rotatable and substantially parallel to each other. The first roller 11 is positioned upstream of the fixing roller 2 in the recording material conveyance direction, and is disposed away from the fixing roller 2 in a non-contact manner. Hereinafter, the first roller 11 is referred to as an entrance roller. The second roller 12 is made of a metal such as SUS, and a predetermined mechanism in the direction of the arrow SF with respect to the fixing roller 2 via the fixing belt 10 by a pressurizing mechanism (pressurizing means) described later as a grip roller. It is pressed by pressing force. The second roller 12 has a function of separating the recording material P from the fixing roller 2 as will be described later. Hereinafter, the second roller 12 is referred to as a separation roller. The third roller 13 is disposed below the entrance roller 11 and functions as a misalignment correction roller for the fixing belt 10. Hereinafter, the third roller 13 is referred to as a steering roller.

  The pressure pad portion 14 is disposed on the inner side of the fixing belt 10 and positioned near the separation roller between the entrance roller 11 and the separation roller 12. The pressure pad portion 14 includes a base plate 14a made of SUS or the like, a pressure pad 14b made of silicon rubber or the like disposed on the base plate 14a, and a sliding made of a PI film or the like disposed on the pressure pad 14b. It consists of a sheet 14c and the like. The side of the sliding sheet 14c is opposed to the inner surface of the fixing belt portion between the entrance roller 11 and the separation roller 12. The pressure pad portion 14 is brought into pressure contact with the fixing roller 2 via the fixing belt 10 with a predetermined pressing force in the direction of the arrow PF against the elasticity of the pressure pad 14b through the fixing belt 10. .

  The separation roller 12 and the pressure pad portion 14 are in pressure contact with the fixing roller 2 via the fixing belt 10, so that a fixing portion that is a contact portion between the fixing roller 2 and the fixing belt 10 is obtained. The nip portion N is formed wide in the recording material conveyance direction.

  The fixing belt 10 is driven in the direction of arrow A of the fixing roller 2 to rotate in the direction of arrow C by the contact friction force between the fixing roller 2 and the fixing belt 10 in the fixing nip portion N. Further, following the rotation of the fixing belt 10, the entrance roller 11, the separation roller 12, and the steering roller 13, which suspends the fixing belt 10, rotate.

  The oil felt portion 15 is disposed inside the fixing belt 10 between the entrance roller 11 and the pressure pad portion 14, and the oil felt portion 15 is arranged between the entrance roller 11 and the pressure pad portion 14. It is in contact with the inner surface of the fixing belt portion. The oil felt part 15 is impregnated with silicone oil, and the oil is applied to the inner surface of the fixing belt 10 to reduce the frictional force between the inner surface of the fixing belt 10 and the sliding sheet 14c of the pressure pad part 14. Yes.

  The entrance roller 11 functions as a heat roller that heats the fixing belt 10. That is, the entrance roller 11 is a hollow roller, and a heater 17 such as a halogen heater is inserted into the inner roller thereof. Further, a thyristor 16 as a fixing belt temperature detecting means is arranged in elastic contact with the surface of the fixing belt of the entrance roller 11 where the fixing belt is suspended.

  Referring to FIG. 5, the heater 17 generates heat by energizing the heater 17 from the power supply circuit unit 53 controlled by the control circuit unit 50. The heat generated by the heater 17 heats the entrance roller 11 from the inside. The fixing belt 10 is heated by the heat of the entrance roller 11. The surface temperature of the fixing belt 10 is detected by the thermistor 16, and the electrical detection temperature information is input to the control circuit unit 50. The control circuit unit 50 controls the power supplied from the power supply circuit unit 53 to the heater 17 so that the electrical detection temperature information input from the thermistor 16 is maintained at a substantially constant value corresponding to a predetermined fixing belt temperature. That is, the control circuit unit 50 controls the temperature of the fixing belt 10 to a predetermined fixing belt temperature. The temperature adjustment temperature of the fixing belt 10 is set to a temperature that is somewhat lower than the temperature adjustment temperature (fixing temperature) of the fixing roller 2, so that the amount of heat applied to the back surface of the recording material is reduced, and the evaporation of moisture inside the recording material is reduced. By suppressing, when the recording material is coated paper, the occurrence of poor smoothness of the image due to partial destruction of the coated layer by water vapor inside the coated paper is prevented.

  The fixing roller 2 is rotationally driven, and the fixing belt 10 is rotated following the rotation. The energization of the heaters 3 and 17 heats the fixing roller 2 and the entrance roller 11, and the fixing roller 2. Rises to a predetermined fixing temperature, and the temperature of the fixing belt 10 is adjusted to the predetermined fixing belt temperature by the heat of the inlet roller 11, and the inlet roller 11 side of the belt unit 9 is adjusted. Then, the recording material P carrying the unfixed toner image t enters the belt fixing device 1 from the direction of arrow E with the image surface facing upward, and is introduced into the fixing nip portion N.

  The recording material P introduced into the fixing nip N is nipped between the fixing roller 2 and the fixing belt 10 and conveyed. During the nipping and conveying process of the recording material P at the fixing nip portion N, the unfixed toner image surface of the recording material P comes into close contact with the surface of the fixing roller 2 and is heated by the heat of the fixing roller 2. The back surface of P is heated by the heat of the fixing belt 10, the unfixed toner image t is melted by the heat of the fixing roller 2 and the fixing belt 10, and recording is performed by the pressure of the pressure pad unit 14 and the separation roller 12. Pressed against the material and fixed as a permanently fixed image.

  Then, the recording material P is naturally separated from the surface of the fixing roller 2 by the biting (intrusion) of the separation roller 12 into the elastic layer 2b of the fixing roller 2 at the recording material outlet portion of the fixing nip N. It is discharged and conveyed.

  This will be explained a little further. FIG. 4 is an enlarged view of the vicinity of the separation roller of FIG. The fixing roller 2 has a metal core 2a made of metal such as aluminum and an elastic layer 2b made of silicon rubber or the like on the surface layer thereof. Here, since the separation roller 12 made of metal is pressed against the fixing roller 2 via the fixing belt 10 by a pressurizing mechanism to be described later, the elastic layer 2b of the fixing roller 2 is shown in the drawing. The nip portion 2d is deformed into a depression. The arc shape of the elastic layer 2b is in the opposite direction, particularly at the end 2e of the separation nip 2d that is in contact with the separation roller 12. Since the toner on the recording material is melted and pressed at the fixing nip portion N of the fixing device, the toner and the fixing roller surface layer are stuck to each other due to the surface tension. However, since the arc shape of the elastic layer 2b of the fixing roller 2 is reversed by the separation roller 12, the toner stuck to the fixing roller 2 is peeled off, and the recording material P is separated from the fixing nip. The separation roller 12 bites into the elastic layer 2b of the fixing roller 2 at the recording material outlet of the portion N, and is naturally separated from the surface of the fixing roller 2 and discharged and conveyed in the direction of arrow Y.

  The steering roller 13 also functions as a tension roller that gives tension to the fixing belt 10. Further, one end side of the steering roller 13 is movable in the direction of arrow D in FIG. 3, and the deviation is corrected according to the deviation movement of the fixing belt 10 by a steering roller displacement mechanism (not shown). Displaced in the direction.

  That is, the fixing belt 10 is rotated in the axial direction of the entrance roller 11, the separation roller 12, and the steering roller 13 as a suspension member of the fixing belt 10 (the longitudinal direction of the roller or the belt rotation). A phenomenon occurs in which one side or the other side of the belt width direction crossing the direction moves more or less along the roller. This is due to the parallelism or twist between the plurality of belt suspension members 11, 12, 13 and the like. There is a limit to increasing the accuracy of these, and the above-mentioned belt offset movement can be achieved only by improving the accuracy. Without it, it is difficult to stabilize the running of the belt. Therefore, the relative position of the plurality of belt suspension members 11, 12, 13 with respect to the other belt suspension members 11, 12 is displaced using at least one belt suspension member 13 as a swing member (the degree of parallelism or twist is changed). Thus, the shift movement of the fixing belt 10 during rotation is corrected and controlled. Specifically, when the belt shift position detection sensor (not shown) detects that the shift amount of the fixing belt 10 during rotation exceeds the allowable value, the control circuit unit 50 (FIG. 5) detects the steering roller displacement. The steering roller 13 is displaced in the belt return direction by a mechanism (not shown). By repeating this control, the shifting direction of the fixing belt 10 is alternately corrected so that the shifting movement of the fixing belt 10 is within a predetermined allowable area width.

3) Pressurization Mechanism of Separation Roller 12 and Pressurization Pad Unit 14 A pressurization mechanism of the separation roller 12 and pressurization pad unit 14 for the fixing roller 2 in the belt unit 9 will be described with reference to FIGS. To do.

  With reference to FIGS. 6 and 7, a pressure mechanism 20 is provided on each end of the belt unit 9 in the longitudinal direction. The pressurizing mechanisms 20 on both end sides have substantially the same configuration, and only one side is shown and described in the figure.

  In the pressure mechanism 20, 21 is a first pressure holder, 22 and 23 are second pressure holders (roller pressure holders) arranged in parallel above the first pressure holder 21. It is a 3rd pressurization holder (pad pressurization holder). The first, second, and third pressure holders 21, 22, and 23 are all freely swingable up and down around a common support shaft (rotating shaft of the belt unit 9) 24. The support shaft 24 is fixedly disposed on the apparatus chassis (not shown), and its axis is substantially parallel to the axis of the fixing roller 2.

  Reference numeral 25 denotes a cam follower (roller) provided on the side surface of the first pressure holder 21. Reference numeral 26 denotes a pressure cam (eccentric cam), which is disposed below the cam follower 25 and receives the cam follower 25. Reference numeral 27 denotes a rotating shaft of the pressure cam 26, and 28 denotes a driving device for rotating the rotating shaft 27. The pressurizing cam 26, the rotary shaft 27, and the driving device 28 are fixedly arranged on the device chassis (not shown). The rotary shaft 27 is rotated by the drive device 28, and the pressure cam 26 rotates in a eccentric manner. In conjunction with this, the first pressure holder 21 swings up and down around the support shaft 24 via the cam follower 25.

  Pressurizing coil springs 29 and 30 are disposed (reduced) between the second and third pressure holders 22 and 23, respectively, with the first pressure holder 21. Reference numeral 31 denotes a vertical guide shaft of the second pressure holder 22, which is inserted through the second pressure holder 22 and the pressure coil spring 29. Reference numeral 32 denotes a vertical guide shaft of the third pressure holder 23, which is inserted through the third pressure holder 23 and the pressure coil spring 30.

  As shown in FIG. 8, the lower ends of the guide shafts 31 and 32 are fixed to the first pressure holder 21 and pass through the pressure coil springs 29 and 30, and the upper ends of the guide shafts 31 and 32 are second and second, respectively. The stopper portions (heads) 31a and 32a having a diameter larger than the diameters of the insertion holes 22a and 23a are provided so as to protrude upward from the insertion holes 22a and 23a provided in the three pressure holders 22 and 23. The pressure coil springs 29 and 30 urge the second and third pressure holders 22 and 23 to rotate upward from the first pressure holder 21 around the support shaft 24, respectively.

  Referring to FIGS. 6 and 7, bearings 11a and 12a are respectively provided at the ends of the entrance roller 11 and the separation roller 12 on the belt unit 9 side, and these bearings 11a and 12a are respectively connected to the second roller 11 and the separation roller 12 respectively. Are supported by receiving portions 22b and 22b provided in the pressure holder 22.

  Further, the end portion 14 d of the base plate 14 a of the pressure pad portion 14 on the belt unit 9 side is supported by a receiving portion 23 b provided in the third pressure holder 23.

  Further, an end portion of the steering roller 13 and a displacement mechanism (not shown) of the steering roller 13 are disposed and supported by the first pressure holder 21.

  In this way, both end sides of the belt unit 9 are supported by the pressurizing mechanism 20 as described above, and the belt unit 9 is freely rotatable around the support shaft (one axis) 24.

  The pressure mechanism 20 applies a pressure state to the fixing roller 2 of the belt unit 9 (first state in which the fixing roller 2 and the fixing belt 10 are in contact) and a pressure release state (fixing). Switching between the state in which the roller 2 and the fixing belt 10 are separated from each other) is performed by a driver 54 controlled by the control circuit unit 50 (FIG. 5), such as an intermittent rotation clutch mechanism. Is done by controlling.

  6, 7, and 9 (a) show the pressurized state. This pressurization state is a rotation angle state in which the drive device 28 is activated by the driver 54 controlled by the control circuit unit 50, the pressurization cam 26 rotates, and the long diameter portion 26a of the cam is positioned corresponding to the cam follower 25. This appears when the rotation of the pressure cam 26 is stopped.

  That is, the cam follower 25 is lifted as the long-diameter portion 26a of the cam is directed upward by the rotation of the pressure cam 26, and the first pressure holder 21 is centered on the support shaft 24 as shown in FIG. It is raised and rotated in the direction of arrow V. Accordingly, the second and third pressure holders 22 and 23 mounted on the first pressure holder 21 are also supported by the pressure coil springs 29 and 30 and rotated upward about the support shaft 24. The During the upward rotation of the first pressure holder 21, the separation roller 12 supported by the second pressure holder 22 contacts the lower surface of the fixing roller 2 through the fixing belt 10. In addition, the pressure pad portion 14 supported by the third pressure holder 23 also contacts the lower surface of the fixing roller 2 via the fixing belt 10. In the further upward rotation process of the first pressure holder 21, the pressure coil spring 29 of the second pressure holder 22 and the pressure coil spring 30 of the third pressure holder 23 are respectively the first pressure holder 21 and the second pressure holder 21. And the third pressure holders 22 and 23 are compressed and compressed, and the compression reaction force of the pressure coil springs 29 and 30 applies the separation roller 12 and the pressure pad portion 14 to the fixing roller 2. The pressure, that is, the pressure applied to the fixing roller 2 of the fixing belt 10 increases. The pressure cam 26 is stopped in a rotation angle state corresponding to the cam follower 25 with the long-diameter portion 26 a of the cam facing upward, so that the separation roller 12 and the pressure pad portion 14 are interposed via the fixing belt 10. Thus, the compression reaction force of the pressure coil springs 29 and 30 is held in a state of being pressed against the fixing roller 2 with a predetermined pressure.

  FIG. 8A shows a state in which the pressure coil springs 29 and 30 are compressed between the first pressure holder 21 and the second and third pressure holders 22 and 23 in the above-described pressure state. Is shown.

  FIG. 9B shows the pressure release state (when retracted). In this pressure release state, the drive device 28 is activated by the driver 54 controlled by the control circuit unit 50, the pressure cam 26 rotates, and the rotation angle at which the short diameter portion 26 b of the cam is positioned corresponding to the cam follower 25. It appears when the rotation of the pressure cam 26 is stopped in this state.

  That is, in the pressurized state of FIGS. 6, 7, and 9 (a), the cam follower 25 is lifted as the long diameter portion 26 a of the cam is directed downward by the rotation of the pressure cam 26, and the first The pressure holder 21 rotates downward in the direction of arrow W about the support shaft 24. Accordingly, the compression of the pressure coil spring 29 of the second pressure holder 22 and the pressure coil spring 30 of the third pressure holder 23 is relaxed, and the separation roller 12 and the fixing roller 2 of the pressure pad portion 14 are relaxed. The pressurizing force against is decreasing. Then, as shown in FIG. 9B, the second and third pressure holders 22 and 23 are respectively engaged with the stopper portions 31a and 32a of the guide shafts 31 and 32, whereby the pressure coil spring 29 is obtained. The urging force of 30 is not applied to the fixing roller 2. In the further downward rotation process of the first pressure holder 21, the second and third pressure holders 22 and 23 are also hooked on the stopper portions 31 a and 32 a of the guide shafts 31 and 32 to be subjected to the first pressure. The separation roller 12 and the pressure pad 14 are separated downward from the fixing roller 2 by rotating downward along the support shaft 24 together with the holder 21. Then, the pressure cam 26 is stopped in a rotation angle state in which the short-diameter portion 26b of the cam corresponds to the cam follower 25, and the belt unit 9 is removed from the fixing roller 2 as shown in FIGS. The fixing belt 10 is retracted in a separated state, and the pressure state of the belt unit 9 against the fixing roller 2 is switched and held in a completely released state.

  In the image forming sequence control of the image forming apparatus, the control circuit unit 50 determines the state of the belt fixing apparatus 1 when the recording material does not come into the belt fixing apparatus 1 or in a standby state such as waiting for image output. As described above, the fixing roller 2 and the fixing belt 10 are switched and held in the pressure release state (second state) in which they are separated. In this case, when the fixing belt 10 stops rotating, only the fixing belt portion that is wound around the entrance roller 11 by the heat from the heater 17 provided in the entrance roller 11 has a high temperature. Therefore, the fixing belt 10 is rotated by rotating the separation roller 12 in the direction of arrow J in FIGS. At this time, if the fixing roller 2 is also rotated, temperature unevenness of the fixing roller 2 does not occur. Further, in recent high-power fixing devices, an external heating roller (non-heating roller) that heats the fixing roller from the outside in order to prevent a temperature drop of the fixing roller that occurs when the recording material is deprived of temperature during fixing. A fixing arrangement with the figure) has been proposed. In the fixing device having such a configuration, if the fixing roller does not rotate during standby, the fixing roller is locally heated by the heat of the external heating roller. The roller is also rotated to prevent uneven temperature of the fixing roller.

4) Fixing belt drive configuration (belt slip prevention drive mechanism)
In FIG. 6, a one-way clutch gear (second gear) 33 is engaged with the fixing roller gear (first gear) 6, and the first belt pulley is coaxial with the one-way clutch gear 33. 34 is provided. The one-way clutch gear 33 and the first belt pulley 34 are disposed on a device chassis (not shown). A second belt pulley 35 is provided at the end of the separation roller 12, and the first belt pulley 34 and the second belt pulley 35 are driven and connected by a timing belt 36. I am letting. The timing belt 36 is maintained at an appropriate belt tension by a tensioner 37. The tensioner 37 is disposed on the device chassis side (not shown).

  Here, in the drive trains 6 and 33 to 36 between the fixing roller 2 and the separation roller 12, the fixing belt 10 is driven to rotate with the fixing roller 2 in a pressurized state. At this time, the one-way clutch of the one-way clutch gear 33 is not input to the separation roller 12. When the fixing belt 10 starts to slide with respect to the fixing roller 2, the driving force from the fixing roller 2 is separated before the speed of the fixing belt 10 slips 4% or more with respect to the speed of the fixing roller 2. The gear ratio is set so as to be input to the ring 12.

  The gear ratio is based on the experimental result of the relationship between the fixing belt slip rate and the image shift when the solid image shown in Table 1 is fixed.

表１は横列に定着ベルト１０のすべり率を示し、縦列に記録材の紙種としてコ−ト紙と普通紙の結果を表している。表１から分かるように、画像ずれは定着ベルト１０の滑り率が４％を超えると認識できるようになる。ここで、普通紙とコ−ト紙では、コ−ト紙のほうが定着ベルト１０の滑り率が低いときから画像ずれが認識できるようになっているが、これは、紙の表面性が普通紙よりコ−ト紙のほうが平滑であるためである。

Table 1 shows the slip ratio of the fixing belt 10 in the horizontal row, and the results of the coated paper and the plain paper as the paper type of the recording material in the vertical row. As can be seen from Table 1, the image shift can be recognized when the slip rate of the fixing belt 10 exceeds 4%. Here, with plain paper and coated paper, the coated paper can recognize image misalignment from when the slip rate of the fixing belt 10 is low. This is because the surface property of the paper is plain paper. This is because the coated paper is smoother.

  In this example, the one-way clutch is interposed in the gear 33 as the second gear, but the same thing can be achieved even if the one-way clutch is interposed in the first belt pulley 34 or the second belt pulley 35. An effect is obtained.

  Next, the details of the unidirectional drive mechanism will be described with reference to FIG. FIG. 11A shows a state in which the belt unit 9 is pressed against the fixing roller 2 by the pressure mechanism 20, and FIG. 11B shows a state in which the pressure is released, that is, the fixing roller. The belt unit 9 is retracted from the roller 2.

  As shown in FIG. 11A, in the pressurized state, the shaft center of the separation roller 12 (the shaft center of the second belt pulley 35), the shaft center of the first belt pulley 34, The center of the support shaft 24 of the first to third pressure holders 21 to 23, which is the rotation center of the belt unit 9, is aligned on a substantially straight line Z, and the fixing roller 2 and the separation roller are aligned. 12 on the nip tangent line. That is, the straight line Z is substantially parallel to the tangent line at the nip portion between the fixing roller 2 and the separation roller 12.

  With the above configuration, the fixing belt 10 starts to slide relative to the fixing roller 2 when fixing the recording material P having a large toner paste amount such as a solid image, and the fixing roller 2 and the separation roller 12 Even if drive is input to the separation roller 12 by the drive trains 6, 33 to 36, the reaction force of the drive acts in the direction of the arrow K, so the pressure applied to the fixing roller 2 by the separation roller 12 Does not affect the SF. Therefore, even when the second belt pulley 35 is driven, the separation roller pressure does not change, the fixing performance is not deteriorated, and the fixing belt 10 has a large amount of toner such as a solid image. Therefore, it is possible to provide a belt fixing device in which image defects do not occur without slipping.

  Further, with the above configuration, when the fixing belt 10 starts to slide, the driving torque for rotating the fixing roller 2 becomes light. On the other hand, when the fixing belt 10 slides with respect to the fixing roller 2, the separation roller 2 rotates. The driving torque for rotating the fixing belt 10 from the roller 12 becomes heavy. For this reason, if a driving motor for rotating the fixing roller 2 and a driving motor for rotating the fixing belt 10 are provided separately, when the fixing belt 10 starts to slide, uneven rotation occurs due to a change in the driving force of each motor. There is a risk that a gloss level difference occurs in the image. When the fixing roller 2 and the fixing belt 10 are rotated by the single fixing motor 7 as in the above configuration, the driving torque for rotating the fixing roller 2 becomes light even if the fixing belt 10 starts to slide. Since the driving torque for rotating the fixing belt 10 is canceled out and the driving torque for rotating the fixing motor 7 does not change, the fixing roller 2 and the fixing belt 10 do not cause uneven rotation, and a good image is obtained. It becomes possible to fix with.

  FIG. 11B shows a state in which the belt unit 9 is released from the fixing roller 2 by being depressurized, and the first and first belts 9 are also retracted from the fixing roller 2. The second belt pulleys 34 and 35 are drivingly connected by a timing belt 36.

  Here, the distance between the first belt pulley 34 and the second belt pulley 35 differs between when the belt unit 9 is pressed against the fixing roller 2 and when the pressure is released (when retracted). The distance difference is configured by adjusting the lengths of the belt tensioner 37 and the timing belt 36.

  Even in the state where the belt unit 9 is retracted from the fixing roller 2 with the above configuration, when the fixing motor gear 7a is rotated in the arrow B direction by the fixing motor 7 (FIG. 6), the fixing roller 2 is moved in the arrow A direction. The separation roller 12 rotates in the direction of arrow J. Further, by rotating the fixing belt 10 with the above-described configuration, the one-way clutch can always be kept locked. Therefore, it is possible to rotate the fixing belt 10 by the drive trains 6 and 33 to 36 between the fixing roller 2 and the separation roller 12 only by inputting driving to the fixing roller 2. With a simple configuration, the fixing belt 10 can be driven without providing a rotation driving means for the fixing belt 10, and the one-way clutch is not idled in order to rotate the fixing belt 10, so that the one-way clutch is driven. The durability of the mechanism is improved.

  Example 2 will be described with reference to FIG. 12A shows a state in which the belt unit 9 is pressed against the fixing roller 2 by the pressurizing mechanism 20, and FIG. 12B shows a state in which the pressure is released, that is, the fixing roller. The belt unit 9 is retracted from the roller 2.

  A one-way clutch gear 33 is engaged with the fixing roller gear 6, and this one-way clutch gear 33 is separated through idler gears 38, 39, and 40 in the pressurized state of FIG. The drive input gear 41 provided at the end of the roller 12 is drivingly connected.

  Here, in the drive trains 6, 33, and 38 to 41 of the fixing roller 2 and the separation roller 12, the fixing belt 10 is driven and rotated by the fixing roller 2 as in the case of the first embodiment. When the vehicle is on, the one-way clutch interposed in the one-way clutch gear 33 prevents the drive from being input to the separation roller 12. When the fixing belt 10 starts to slide with respect to the fixing roller 2, the drive trains 6, 33, 38-before the speed of the fixing belt 10 slips 4% or more with respect to the speed of the fixing roller 2. 41, the gear ratio is set so that the driving force from the fixing roller 2 is input to the separation roller 12.

  As shown in FIG. 12A, in the pressurized state, the shaft center of the separation roller 12 (the shaft center of the drive input gear 41), the shaft center of the one-way clutch gear 33, and the rotation of the belt unit 9 are obtained. The axial centers of the support shafts 24 of the first to third pressure holders 21 to 23, which are dynamic centers, are aligned on a substantially straight line Z, and the nip contact between the fixing roller 2 and the separation roller 12. Located on the line. That is, the straight line Z is substantially parallel to the tangent line at the nip portion between the fixing roller 2 and the separation roller 12.

  That is, the rotation shaft 24 of the belt unit 9 is located on the nip tangent line between the fixing roller 2 and the separation roller 12, and the driving force of the idler gear 40 to the drive input gear 41 acts in the arrow X direction. In this manner, the nip tangent direction between the fixing roller and the separation roller 12 is provided.

  With the above configuration, the fixing belt 10 starts to slide relative to the fixing roller 2 when fixing a recording material having a large amount of toner, such as a solid image, and is driven by the drive trains 6, 33, 38 to 41. Even if driving is input to the separation roller 12, the driving force acts in the direction of the arrow X, so that the applied pressure SF of the separation roller 12 is not affected. Therefore, it is possible to provide a belt fixing device that obtains the same effects as those of the first embodiment.

  FIG. 12B shows a state in which the belt unit 9 is released from the pressure by the fixing roller 2 and is retracted. In this retracted state, the idler gear 42 connects the one-way clutch gear 33 and the drive input gear 41. Therefore, even when the fixing belt 10 is retracted from the fixing roller 2, the drive input gear 41 of the separation roller 12 is drivingly connected by the idler gear 42.

  Even in a state where the belt unit 9 is retracted from the fixing roller 2 with the above configuration, when the fixing motor gear 7a is rotated in the arrow B direction by the fixing motor 7 of the fixing motor 7, the fixing roller 2 is moved to the arrow A. The separation roller 12 rotates in the direction of arrow J. Therefore, it is possible to provide a belt fixing device that obtains the same effects as those of the first embodiment.

  In this description, the one-way clutch is used for the gear 33. However, the same effect can be obtained by using the one-way clutch for the drive input gear 41 or the idler gear.

1 is a schematic configuration diagram of an example of an image forming apparatus in Embodiment 1. FIG. It is an enlarged view of an image forming station part. FIG. 3 is an enlarged view of a belt fixing device when a belt unit is pressed. It is an enlarged view of a separation roller part. It is a block diagram of a control system. It is a perspective view of a pressurization mechanism part. It is a partially cutaway perspective view of a pressurizing mechanism portion. It is explanatory drawing of a pressurization coil spring and a guide shaft. It is operation | movement explanatory drawing of a pressurization mechanism. FIG. 3 is an enlarged view of a belt fixing device in a belt unit pressure release state. It is operation | movement explanatory drawing of a belt slip prevention drive mechanism. FIG. 6 is an operation explanatory diagram of a belt slip prevention drive mechanism of the belt fixing device in Embodiment 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Belt fixing apparatus, 2 ... Fixing roller (fixing rotating body), 9 ... Belt unit (fixing belt part), 10 ... Fixing belt, 11 ... Entrance roller, 12 ... Separation roller, 13 ... Steering roller, 14 ... Pressure pad

Claims (6)

A fixing rotator heated by a heating means and driven to rotate by a driving means;
An endless belt that is supported in a suspended manner between a plurality of belt suspension members and that rotates in contact with the fixing rotator;
A belt fixing device that sandwiches and conveys a recording material carrying a toner image between the fixing rotator and the belt,
One of the plurality of belt suspension members is a roller that abuts on the fixing rotator across the belt and rotates following the rotation of the belt,
Roller drive means for inputting the rotational driving force of the fixing rotator to the roller via a one-way clutch when the belt is slidingly rotating from the fixing rotator,
An input direction of the driving force of the roller is a substantially tangential direction of the fixing rotator or the roller at a contact portion between the fixing rotator and the roller, or substantially parallel to the substantially tangential direction. Belt fixing device characterized in that it is in a different direction.   The roller driving means reduces the rotation driving force of the fixing rotator until the belt starts to slide from the fixing rotator and the rotation speed becomes 4% slower than the rotation speed of the fixing rotator. The belt fixing device according to claim 1, wherein the belt fixing device is input to the belt fixing device.   The roller drive includes state switching means between a first state in which the fixing rotator and the belt are in contact with each other and a second state in which the fixing rotator and the belt are separated from each other. The means is capable of transmitting the rotational driving force of the fixing rotator to the roller via a one-way clutch in any of the switching states of the first state and the second state. Item 3. The belt fixing device according to Item 1 or 2.   The roller driving means is arranged coaxially with the first gear arranged on the same axis of the fixing rotating body, a second gear meshing with the first gear, and the second gear. A first belt pulley; a second belt pulley disposed coaxially with the roller; and a timing belt wound around the first and second belt pulleys. 4. The belt fixing device according to claim 3, wherein a one-way clutch is interposed in any one of the gear, the second gear, the first belt pulley, and the second belt pulley.   In the second state, when the apparatus is in a standby state, driving is input to the fixing rotator, and the rotational driving force of the fixing rotator is input to the roller by the roller driving means. The belt fixing device according to claim 3, wherein the belt fixing device is driven.   The first state and the second state rotate about one axis, and the one axis is substantially tangent to the fixing roller and the second roller from the center of the second roller. 6. The belt fixing device according to claim 3, wherein the belt fixing device is in a direction substantially parallel to the direction.

Images