JP2019007989A - Image forming apparatus - Google Patents

Abstract

To prevent a trouble in which running torque is initially increased when the use of a new fixing device is started, and a trouble in which running torque of a fixing device is increased over time.SOLUTION: An image forming apparatus 1 comprises: a fixing device 20 that is removably installed in the body of an image forming apparatus; and a cam mechanism 50 (nip pressure varying mechanism) that varies a nip pressure of a nip part between a fixing belt 21 (fixing rotating body) and a pressure roller 31 (pressure rotating body). When the fixing device 20 is recognized to be a new article, an "aging mode" is executed for varying the nip pressure at a timing in a non-image forming period to idle the fixing device 20. Every time the cumulative travel distance (or cumulative drive time) of the fixing device 20 reaches a predetermined value X, an "adjustment mode" is executed for varying the nip pressure at a timing in a non-image forming period to idle the fixing device 20.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines and printers are known in which a fixing device for performing a fixing process is detachably installed (see, for example, Patent Documents 1 and 2).

Specifically, the fixing device of Patent Document 1 is formed by a fixing belt (fixing rotator), a pressure roller (pressure rotator), a heater (heating means) for heating the fixing belt, and the like. The pressure roller is in pressure contact with the fixing belt and forms a nip portion where the sheet is conveyed.
Then, the pressure roller is rotationally driven by the driving means, and the fixing belt is also driven (rotated) with the rotation of the pressure roller due to the frictional resistance with the pressure roller in the nip portion.
The fixing belt is heated by the heater, and the toner image on the sheet conveyed toward the nip portion is fixed on the sheet by receiving heat and pressure at the nip portion.

The conventional image forming apparatus has a problem in that when the new fixing device is driven immediately after the new fixing device is mounted on the image forming apparatus main body, the driving torque is initially increased.
In addition, after a certain period of use has elapsed since the start of use of a new fixing device, there has been a problem that the driving torque of the fixing device increases again.
If the driving torque of the fixing device increases temporarily as described above, damage such as breakage may occur in the fixing device itself and the driving mechanism that drives the fixing device.

  The present invention has been made in order to solve the above-described problems, and there is a problem that the driving torque initially increases when the use of a new fixing device is started, and the driving of the fixing device over time. It is an object of the present invention to provide an image forming apparatus in which a problem of increasing torque is efficiently suppressed.

  The image forming apparatus according to the present invention is detachably installed on the main body of the image forming apparatus, and is configured to form a nip portion where the fixing rotating body and the pressure rotating body are in pressure contact with each other to convey the sheet. A fixing device, and a nip pressure varying mechanism that varies the nip pressure of the nip portion between the fixing rotator and the pressure rotator, and when it is recognized that the fixing device is new, At the time of image formation, an aging mode is executed in which the nip pressure is varied and the fixing device is idly driven. Every time the cumulative travel distance or cumulative driving time of the fixing device reaches a predetermined value, non-image formation is performed. At this timing, an adjustment mode is executed in which the nip pressure is varied to idle the fixing device.

  According to the present invention, the problem that the driving torque initially increases when the use of a new fixing device is started and the problem that the driving torque of the fixing device increases with time can be effectively suppressed. An image forming apparatus can be provided.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. 2 is a configuration diagram illustrating a fixing device. FIG. FIG. 2 is a top view of the fixing device as viewed in the width direction, (A) showing a state where the nip portion forming member forms a nip portion, and (B) showing a state where the nip portion forming member is separated. . It is an enlarged view showing the vicinity of a nip part, (A) a figure showing a state at the time of a fixing process, and (B) a figure showing a state at the time of an aging mode or an adjustment mode. It is the schematic which shows a fixing belt and a guide member in the width direction. It is the schematic which shows the operation | movement by which the contact position of the cam at the time of a fixing process is varied. 3 is a flowchart showing control at startup in the fixing device. FIG. 10 is a diagram illustrating an operation of the fixing device in an aging mode or an adjustment mode as a modification.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the overall configuration and operation of the image forming apparatus 1 will be described with reference to FIG.
As shown in FIG. 1, the image forming apparatus 1 in the present embodiment is a tandem color printer. Four bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceable) installed in the bottle housing portion 101 above the image forming apparatus main body 1. ing.
An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge eliminating unit, and the like are disposed. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the surface of each photoconductive drum 5Y, 5M, 5C, 5K, and each photoconductive drum 5Y, 5M, 5C. An image of each color is formed on the surface of 5K.

The photosensitive drums 5Y, 5M, 5C, and 5K are driven to rotate clockwise in FIG. 1 by a motor. Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (a charging process).
Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (It is an exposure process.)

Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing unit 76, and the electrostatic latent image is developed at this position to form toner images of each color (development process). .)
Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions, the photoconductive drums 5Y, 5M. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K.

Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. 77 is mechanically collected by a cleaning blade (cleaning process).
Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the charge eliminating unit, and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

Thereafter, the toner images of the respective colors formed on the respective photoconductive drums through the development process are transferred onto the surface of the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78.
Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by the three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, thereby forming primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K.
The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78.

Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto the sheet P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 78.
Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

Here, the sheet P conveyed to the position of the secondary transfer nip passes from the sheet feeding unit 12 disposed below the apparatus main body 1 via the sheet feeding roller 97, the registration roller pair 98 (timing roller pair), and the like. Are conveyed.
Specifically, the sheet feeding unit 12 stores a plurality of sheets P such as sheets. When the paper feed roller 97 is driven to rotate counterclockwise in FIG. 1, the uppermost sheet P is fed toward the rollers of the registration roller pair 98.

  The sheet P conveyed to the registration roller pair 98 temporarily stops at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotated in synchronization with the color image on the intermediate transfer belt 78, and the sheet P is conveyed toward the secondary transfer nip. Thus, a desired color image is transferred onto the sheet P.

Thereafter, the sheet P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20. At this position, the color image transferred onto the surface is fixed on the sheet P by the heat and pressure of the fixing belt 21 and the pressure roller 31 (this is a fixing step).
Thereafter, the sheet P is discharged out of the apparatus through a pair of paper discharge rollers 99. The sheets P discharged outside the apparatus by the discharge roller pair 99 are sequentially stacked on the stack unit 100 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
The fixing device 20 is a device that conveys the sheet P (a sheet carrying toner in an unfixed state) while heating.
2 to 4 and the like, the fixing device 20 includes a fixing belt 21 as a fixing rotating body, a nip portion forming member 26, a reinforcing member 23 as a moving member, a heater 25 as a heating means (heating source), The reflector 27, a pressure roller 31 as a pressure rotator, a temperature detection sensor 40 (temperature detection means), a sheet-like member 22 (lubricant supply member), an RFID 35 as storage means, and the like.

Here, the fixing belt 21 as a fixing rotator is an endless belt member that circumscribes the pressure roller 31 and that rotates following the rotation of the pressure roller 31. The fixing belt 21 is a thin and flexible endless belt, and rotates (followed rotation) in an arrow direction (counterclockwise direction) in FIG. The fixing belt 21 has a base material layer, an elastic layer, and a release layer sequentially laminated from the inner peripheral surface (sliding contact surface with the nip forming member 26) side, and the total thickness is 1 mm. It is set as follows.
The base material layer of the fixing belt 21 has a layer thickness of 30 to 50 μm and is formed of a metal material such as nickel or stainless steel or a resin material such as polyimide.
The elastic layer of the fixing belt 21 has a layer thickness of 100 to 300 μm and is formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber. By providing the elastic layer, minute irregularities on the surface of the fixing belt 21 in the nip portion are not formed, and heat is uniformly transmitted to the toner image T on the sheet P, so that generation of a scum skin image is suppressed.
The release layer of the fixing belt 21 has a layer thickness of 5 to 50 μm, and includes PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES ( Polyether sulfone) and the like. By providing the release layer, the releasability (peelability) for the toner T (toner image) is secured.

Inside the fixing belt 21 (inner peripheral surface side), a nip portion forming member 26, a heater 25 (heating means), a reinforcing member 23, a sheet-like member 22, a reflecting plate 27, and the like are installed.
Here, the nip portion forming member 26 is in pressure contact with the pressure roller 31 via the fixing belt 21 on the inner side (inner peripheral surface side) of the fixing belt 21 to form a nip portion where the sheet P is conveyed. . That is, the nip portion forming member 26 is installed so as to be in sliding contact with the inner peripheral surface of the fixing belt 21. The nip portion forming member 26 is in pressure contact with the pressure roller 31 via the fixing belt 21 to form a nip portion where the sheet P is conveyed.
2 and 3 and the like, the nip portion forming member 26 is joined to the reinforcing member 23 by screw fastening or the like. The nip portion forming member 26, together with the reinforcing member 23, is configured to be movable in the direction of the black double arrow in FIG. 2 by a cam mechanism 50 (nip pressure variable mechanism), which will be described in detail later.

The fixing belt 21 is directly heated by the radiant heat of the heater 25 (heating means) installed therein. That is, the heater 25 as a heating unit heats the fixing belt 21 in order to heat the sheet P. The heater 25 (heating means) is configured to heat a region in the circumferential direction of the fixing belt 21 different from the nip portion as a heating region.
Specifically, the heater 25 as a heating unit is a halogen heater (or carbon heater), and both ends thereof are fixed to the side plate 43 of the fixing device 20 (see FIG. 3). Then, a heating region (a region facing the heater 25) different from the nip in the fixing belt 21 is mainly heated by the radiant heat of the heater 25 (heating means) whose output is controlled by the control unit 60. Further, heat is applied to the toner image T on the sheet P from the surface of the heated fixing belt 21. The output control of the heater 25 is performed based on the detection result of the belt surface temperature by the temperature detection sensor 40 (temperature detection means) such as a thermopile or thermistor facing the surface of the fixing belt 21. Further, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature by such output control of the heater 25.
In this embodiment, two heaters 25 (heating means) are installed on the inner peripheral surface side of the fixing belt 21, but one or three or more heaters are installed on the inner peripheral surface side of the fixing belt 21. You can also

As described above, in the fixing device 20 in the present embodiment, not only a part of the fixing belt 21 is locally heated, but the fixing belt 21 is heated over a relatively wide range in the circumferential direction. For this reason, even when the speed of the apparatus is increased, the fixing belt 21 is sufficiently heated and the occurrence of fixing failure can be suppressed. That is, since the fixing belt 21 can be efficiently heated with a relatively simple configuration, the warm-up time and the first print time are shortened, and the size of the apparatus is reduced.
In particular, since the fixing device 20 in the present embodiment is configured such that the fixing belt 21 is directly heated by the heater 25 (heating means), the heating efficiency of the fixing belt 21 is further improved and the fixing is performed. The device 20 can be further reduced in cost and size.

Referring to FIG. 5, the guide member 29 guides both ends in the width direction of the fixing belt 21 from the inner peripheral surface side so that the substantially cylindrical posture of the fixing belt 21 is maintained.
Specifically, the two guide members 29 are formed of a heat-resistant resin material or the like, and are fitted into the side plates 43 at both ends in the width direction of the fixing device 20. The guide member 29 includes a guide portion 29a for holding the fixing belt 21 while maintaining the substantially cylindrical posture of the fixing belt 21, and a stopper portion for restricting movement of the fixing belt 21 in the width direction (belt shift). , Etc. are provided.
The guide members 29 are arranged at both ends in the width direction in the circumferential direction excluding the nip portion so as not to prevent the formation of the nip portion by the nip portion forming member 26.

In the present embodiment, the member that contacts the inner peripheral surface of the fixing belt 21 includes a guide member 29 that contacts the looseness at both ends in the width direction, and a nip forming member 26 (actually via the sheet-like member 22). However, there is no other member (belt guide) that contacts the inner peripheral surface and guides the rotation of the fixing belt 21.
As described above, the fixing device 20 according to the present exemplary embodiment removes the pipe-shaped heating member for the purpose of further improving the heating efficiency of the fixing belt 21 and reducing the cost and size of the device, thereby heating the pipe. A configuration in which the fixing belt 21 is directly heated by a heating unit (heater 25) without using a member is employed.

Here, in the present embodiment, the reinforcing member 23 is installed inside the fixing belt 21 so as to come into contact with the pressure roller 31 via the nip portion forming member 26 and the fixing belt 21. The reinforcing member 23 reinforces the strength of the nip portion forming member 26 that forms the nip portion, and is integrated with the nip portion forming member 26 by screw fastening or the like.
Referring to FIG. 3, the reinforcing member 23 is formed so that the length in the width direction is longer than that of the nip portion forming member 26, and both end portions in the width direction are formed on the side plate 43 of the fixing device 20. It is held so as to be movable in the vertical direction (the horizontal direction in FIG. 2).
The reinforcing member 23 comes into contact with the pressure roller 31 via the nip portion forming member 26 and the fixing belt 21, so that the nip portion forming member 26 is greatly deformed by the pressure applied by the pressure roller 31 in the nip portion. Defects are suppressed. In order to satisfy the above-described function, the reinforcing member 23 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron.

In the present embodiment, a reflecting plate 27 is fixed between the reinforcing member 23 and the heater 25. Accordingly, heat from the heater 25 toward the reinforcing member 23 (heat that heats the reinforcing member 23 and is infrared) is reflected by the reflecting plate 27 and used to heat the fixing belt 21. As a result, the heating efficiency of the fixing belt 21 is further improved. In addition, as a material of the reflecting plate, aluminum, stainless steel, or the like can be used.
Note that the same effect can be obtained even when a part of or the entire surface of the reinforcing member 23 facing the heater 25 is mirror-finished or a heat insulating member is provided.

Referring to FIG. 2, a pressure roller 31 as a pressure rotator is provided with an elastic layer 33 on a cored bar 32 (shaft), and is driven in a predetermined direction by a drive motor 61 as drive means. (It is clockwise in FIG. 2).
The cored bar 32 of the pressure roller 31 is a hollow structure formed of a metal material. The elastic layer 33 of the pressure roller 31 is made of a material such as foamable silicone rubber, silicone rubber, or fluorine rubber. A thin release layer made of PFA, PTFE or the like can be provided on the surface layer of the elastic layer 33. The pressure roller 31 is pressed against the fixing belt 21 to form a desired nip portion between both members. 3, the pressure roller 31 is provided with a gear 45 that meshes with the drive gear of the drive motor 61, and the pressure roller 31 is rotationally driven in the direction of the arrow (clockwise) in FIG. Is done. Further, both ends of the pressure roller 31 in the width direction are rotatably supported by the side plates 43 of the fixing device 20 via bearings 42.

  When the elastic layer 33 of the pressure roller 31 is formed of a sponge-like material such as foamable silicone rubber, the applied pressure acting on the nip portion can be reduced, so that the load generated on the nip portion forming member 26 is reduced. Can be reduced. Furthermore, since the heat insulation of the pressure roller 31 is enhanced and the heat of the fixing belt 21 is difficult to move to the pressure roller 31 side, the heating efficiency of the fixing belt 21 is improved.

Referring to FIG. 4A, the nip portion forming member 26 that is in sliding contact with the inner peripheral surface of the fixing belt 21 has a surface facing the pressure roller 31 (sliding contact surface) that has the curvature of the pressure roller 31. It is formed in a concave shape. Thereby, since the sheet P is sent out from the nip portion so as to follow the curvature of the pressure roller 31, it is possible to suppress a problem that the sheet P after the fixing process is not attracted to and separated from the fixing belt 21. it can.
In the present embodiment, the shape of the nip portion forming member 26 that forms the nip portion is formed in a concave shape, but the shape of the nip portion forming member 26 that forms the nip portion can also be formed in a planar shape. That is, the slidable contact surface (the surface facing the pressure roller 31) of the nip portion forming member 26 can be formed to have a planar shape. As a result, the shape of the nip portion is substantially parallel to the image surface of the sheet P, and the adhesion between the fixing belt 21 and the sheet P is increased, so that the fixing property is improved. Further, since the curvature of the fixing belt 21 on the exit side of the nip portion is increased, the sheet P sent from the nip portion can be easily separated from the fixing belt 21.

  As a material for forming the nip portion forming member 26, a resin material or a metal material can be used. However, the nip portion forming member 26 has such rigidity that it does not bend greatly even if it receives pressure applied by the pressure roller 31. And heat insulating resin materials (liquid crystal polymer (LCP), polyamideimide (PAI), polyethersulfone (PES), polyphenylene sulfide (PPS), polyethernitrile (PEN), polyetheretherketone (PEEK), etc. Is preferred). In the present embodiment, a liquid crystal polymer (LCP) is used as the material of the nip portion forming member 26.

Referring to FIG. 4A, the nip portion forming member 26 is covered with a sheet-like member 22 made of a low friction material such as PTFE in order to reduce the sliding resistance with the fixing belt 21. Yes. Specifically, the sheet-like member 22 is disposed around the nip portion forming member 26 so as to be interposed between the nip portion forming member 26 and the fixing belt 21 at almost the entire width direction (see FIG. 4). It is the circumference | surroundings of the nip part formation member 26 seen in the cross section as shown.) It is installed so that one part or all part may be covered. Further, the sheet-like member 22 in the present embodiment is formed of a fiber material impregnated with a lubricant (a cloth member made of a fluororesin such as PTFE). As a result, the lubricant is held on the surface where the nip portion forming member 26 and the fixing belt 21 abut. Therefore, the problem that both the members 21 and 26 are worn due to the sliding contact between the nip forming member 26 and the fixing belt 21 is reduced.
As the lubricant impregnated in the sheet-like member 22, grease such as fluorine grease or silicone grease, oil such as silicone oil, or the like can be used.

Thus, in the present embodiment, since the sheet-like member 22 impregnated with the lubricant is provided between the nip portion forming member 26 and the fixing belt 21, the fixing belt 21 has the nip portion forming member 26. Therefore, the lubricant is interposed in the portion that is in sliding contact with the nozzle. On the other hand, by directly applying the lubricant between the nip portion forming member 26 and the fixing belt 21 without installing a sheet-like member impregnated with the lubricant, the fixing belt 21 becomes a nip portion. A lubricant may be interposed in a portion that is in direct sliding contact with the forming member 26.
The fixing device 20 according to the present embodiment is also provided with an RFID 35 as a storage unit, which will be described in detail later.

The normal operation of the fixing device 20 configured as described above will be briefly described below.
When the power switch of the apparatus main body 1 is turned on, electric power is supplied to the heater 25, and rotation driving of the pressure roller 31 in the direction of the arrow in FIG. Accordingly, the fixing belt 21 is also driven to rotate (followed) in the direction of the arrow in FIG. 2 by the frictional force with the pressure roller 31 in the nip portion.
Thereafter, the sheet P is fed from the sheet feeding unit 12, and an unfixed color image is carried (transferred) on the sheet P at the position of the secondary transfer roller 89. The sheet P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 while being guided by the guide plate, and is sent to the nip portion of the fixing belt 21 and the pressure roller 31 that are in pressure contact. Entered.
The toner image T is fixed to the surface of the sheet P by the heating by the fixing belt 21 heated by the heater 25 and the pressing force of the nip forming member 26 reinforced by the reinforcing member 23 and the pressure roller 31. The Thereafter, the sheet P sent out from the nip portion is conveyed in the direction of arrow Y11.

Hereinafter, the characteristic configuration and operation of the fixing device 20 according to the present embodiment will be described in detail.
As described above with reference to FIG. 2 and the like, in the fixing device 20 according to the present embodiment, the fixing belt 21 (fixing rotator) and the pressure roller 31 (pressure rotator) are brought into pressure contact with each other, and the sheet P is pressed. A nip portion to be conveyed is formed.
In the present embodiment, the fixing device 20 is detachably (replaceable) installed with respect to the image forming apparatus main body 1. Specifically, as shown in FIG. 1, when the opening / closing cover 110 of the image forming apparatus main body 1 is rotated in the direction of the arrow about the support shaft 110a, the fixing device 20 is exposed in the image forming apparatus main body 1. . In this state, the fixing device 20 is attached and detached in the direction of the white arrow in FIG. 1, and the fixing device 20 is replaced with a new one, or the fixing device 20 is maintained.

2 and 3, in the present embodiment, the image forming apparatus main body 1 includes a nip portion between a fixing belt 21 (fixing rotator) and a pressure roller 31 (pressure rotator). A cam mechanism 50 is provided as a nip pressure variable mechanism that varies the nip pressure.
As shown in FIG. 3, the cam mechanism 50 is a direction in which the nip portion forming member 26 is contacted and separated from the pressure roller 31 by changing the posture of the cam 51 in the rotational direction (the vertical direction in FIG. 3). ) To function as a nip pressure varying mechanism that varies the nip pressure. In particular, the cam mechanism 50 according to the present embodiment abuts on the reinforcing member 23 as a moving member and moves the nip forming member 26 together with the reinforcing member 23 in the contacting / separating direction (contacting / separating direction) described above. It is configured.

Specifically, the cam mechanism 50 includes a pair of cams 51 installed so as to be able to push both ends in the width direction of the reinforcing member 23 in which the nip portion forming member 26 is integrally installed, and a cam motor that rotationally drives the cam 51. And a pair of compression springs 52 that urge the reinforcing member 23 in which the nip portion forming member 26 is integrally installed toward the nip portion.
In the present embodiment, the cam 51 is made of a resin material.

When the cam 51 is rotated to the position shown in FIG. 3A (the position where the reinforcing member 23 is not pushed) by the control of the cam motor by the control unit 60, the biasing force of the compression spring 52 causes the cam 51 to rotate. The reinforcing member 23 is urged toward the pressure roller 31 together with the nip portion forming member 26. As a result, the nip portion forming member 26 is pressed against the pressure roller 31 via the fixing belt 21 with a predetermined nip pressure, and a desired nip portion is formed. In such a state (the states shown in FIGS. 2, 3A, and 4A), the fixing process described above is performed.
On the other hand, when the cam 51 is rotated to the position shown in FIG. 3B (the position to push the reinforcing member 23) by the control of the cam motor by the control unit 60, the compression spring 52 The reinforcing member 23 is pushed together with the nip forming member 26 in the separating direction so as to resist the urging force. Thereby, the nip pressure in the nip portion is reduced. In the present embodiment, the nip portion forming member 26 is completely separated from the fixing belt 21 by such an operation of the cam mechanism 50, so that the nip portion is not formed and the nip pressure is zero. Has been. In such a state (the state shown in FIGS. 3B and 4B), the “aging mode” and the “adjustment mode” are started as described below.

Here, in the image forming apparatus 1 according to the present embodiment, when it is recognized that the fixing device 20 is new, as shown in FIG. Thus, an “aging mode (initial mode)” in which the nip pressure is varied and the fixing device 20 is idly driven is executed. Specifically, in the aging mode, the fixing device 20 is idle-driven in the forward direction (the rotation direction shown in FIG. 4) while the heater 25 is kept on with the nip pressure reduced to zero. become.
In addition, every time the cumulative travel distance (or cumulative drive time) of the fixing device 20 reaches a predetermined value X after the use of the new fixing device 20 is started, the cam mechanism 50 performs the timing at the time of non-image formation. An “adjustment mode (condition mode)” is executed in which the nip pressure is varied to idle the fixing device 20. Specifically, in the adjustment mode, with the nip pressure reduced to zero, the fixing device 20 is idly driven in the forward direction (the rotation direction shown in FIG. 4) while the heater 25 is kept on. become.
In particular, in the present embodiment, the “aging mode” and the “adjustment mode” are for idly driving the fixing device 20 under the same conditions except for the execution timing.

Specifically, as shown in FIG. 2, the fixing device 20 is provided with an RFID 35 (Radio frequency identifier) as a storage unit. This RFID 35 (storage means) is executed at least by information relating to whether or not the fixing device 20 is new (new information), information relating to the cumulative travel distance (or cumulative driving time) of the fixing device 20, and the adjustment mode. This is a rewritable communication-type non-volatile memory in which information about the recorded history is stored.
In this way, by installing the RFID 35 as a storage unit in the fixing device 20 itself, the fixing device 20 is attached to another image forming apparatus 1 or another fixing device 20 is temporarily attached to the image forming apparatus 1. Even if it is done, it becomes possible to manage various states of the fixing device 20 itself.
In addition, by using a non-volatile memory as a storage unit that stores information related to the fixing device 20, the stored information is not erased even when the power supply to the storage unit is cut off. Can be managed. Further, by using RFID as the storage means, the storage means can be prevented from coming into contact with the apparatus main body side when the fixing device 20 is attached to or detached from the apparatus main body 1, and the storage means can be prevented from being damaged. It becomes unnecessary and the apparatus can be made compact.

  As shown in FIG. 2, the image forming apparatus main body 1 is provided with a reader / writer 65 as a reading unit capable of reading information stored in the RFID 35 (storage unit). The reader / writer 65 (reading means) is disposed so as to face the RFID 35 of the fixing device 20 mounted on the apparatus main body 1 with a gap. The reader / writer 65 exchanges (reads and writes) information with the RFID 35 of the fixing device 20 mounted on the apparatus main body 1.

  Then, when the fixing device 20 is mounted on the image forming apparatus main body 1, the reader / writer 65 (reading unit) reads information regarding whether or not the product is new in the RFID 35 (storage unit) and reads the fixing device 20. When the control unit 60 recognizes that the product is new, the “aging mode” is executed, and the information indicating that the product is new is stored in the RFID 35 and rewritten as information indicating that the product is not new. Specifically, when the controller 60 recognizes that the fixing device 20 is new, the flag relating to the new information stored in the RFID 35 is erased after the “aging mode” is executed.

Further, when the information related to the cumulative travel distance (or cumulative drive time) stored in the RFID 35 is read by the reader / writer 65 and the cumulative travel distance (or cumulative drive time) has reached the predetermined value X, the control unit When it is recognized by 60, the “adjustment mode” is executed, and the information related to the accumulated travel distance (or accumulated drive time) stored in the RFID 35 is reset to zero, and the adjustment mode is executed. Information (number of executions) is counted up.
The accumulated travel distance (or accumulated drive time) stored in the RFID 35 is obtained based on the time detected by the timer 64 (or counter) in the apparatus main body 1 and is determined by the control unit 60 of the reader / writer 65. It is rewritten from moment to moment by control. The cumulative travel distance (or cumulative drive time) stored in the RFID 35 is rewritten from zero when the use of a new fixing device 20 in the image forming apparatus 1 is started, reaches a predetermined value X, and “adjusts” After the “mode” is executed, it will be reset to zero.

Here, in the present embodiment, as shown in FIG. 4B, the nip portion forming member 26 is separated from the fixing belt 21 so that the nip pressure becomes zero, in the aging mode or the adjustment mode. Thus, the nip portion forming member 26 is moved by the cam mechanism 50 in the separation direction (separation direction) indicated by the white arrow. At this time, the fixing belt 21 is pressed by the guide by the guide member 29 even when the nip portion forming member 26 is not pressed and the nip pressure is almost zero. It will be in the state which contacted the roller 31. FIG. Therefore, when the pressure roller 31 is rotationally driven by the drive motor 61, the fixing belt 21 is also driven to rotate by the frictional resistance with the pressure roller 31.
In order to improve the followability of the fixing belt 21 in a state where no nip portion is formed, it is preferable to configure the sliding resistance between the guide member 29 and the fixing belt 21 to be low. Specifically, it is preferable that the surface roughness of the guide portion 29a of the guide member 29 is set to be rough, or the contact area of the guide portion 29a is set to be small.

  The reason why such an “aging mode” is performed when the fixing device 20 is new is that when the fixing device 20 is in a new state, lubrication interposed in a portion where the fixing belt 21 and the nip forming member 26 (sheet-like member 22) slide. If the agent is not sufficiently familiar over the entire inner peripheral surface of the fixing belt 21 and the driving of the fixing device 20 is started with the normal nip formed in this state, the fixing device 20 (drive motor 61) is started. ) Is initially increased. If the driving torque of the fixing device 20 increases temporarily as described above, damage such as breakage occurs in the driving mechanism such as the fixing device 20 itself or the driving motor 61.

  In contrast, in the present embodiment, when driving of the new fixing device 20 is started (before the fixing process is started), the nip portion forming member 26 is moved in the separation direction as an aging mode. The pressure roller 31 is driven to rotate and the fixing belt 21 is driven while the fixing belt 21 is in contact with the pressure roller 31 with a small force compared to the normal time (during the fixing process). It is rotating. As a result, the driving torque of the fixing device 20 (drive motor 61) is smaller than that in the case of driving with a normal nip portion formed (an increase in initial driving torque can be reduced). Then, the fixing belt 21 is driven and rotated in such a state that the increase in driving torque is suppressed as described above, so that the fixing belt 21 and the nip portion forming member 26 (sheet-like member 22) are interposed in the sliding portion. The lubricant thus applied is sufficiently adapted to the entire inner peripheral surface of the fixing belt 21. Therefore, after the aging mode, even if the nip pressure is returned to the normal state and the fixing process is performed as shown in FIG. 4A, the problem that the driving torque of the fixing device 20 (drive motor 61) increases is prevented. be able to.

  Further, in the present embodiment, the reason for performing the “adjustment mode” at regular intervals (constant cumulative travel distance) is that when the fixing device 20 is used to some extent, the abrasion powder of the fixing belt 21 and the sheet-like member 22 is worn. Accumulates on the upstream side of the sheet-like member 22, the lubricity of the inner peripheral surface of the fixing belt 21 becomes insufficient, and abrasion powder enters the fibers of the sheet-like member 22, and the fixing belt 21 and the sheet-like member This is because the sliding resistance with the member 22 is increased. If the driving of the fixing device 20 is started while the normal nip portion is formed in such a state, the driving torque of the fixing device 20 (drive motor 61) becomes large. If the driving torque of the fixing device 20 increases temporarily as described above, damage such as breakage occurs in the driving mechanism such as the fixing device 20 itself or the driving motor 61.

  On the other hand, in this embodiment, every time the fixing device 20 is used to some extent, the nip portion forming member 26 is moved in the separation direction as an adjustment mode at the timing when non-image formation is performed. In the state where the fixing belt 21 is in contact with the pressure roller 31 with a smaller force than in the fixing step), the pressure roller 31 is driven to rotate and the fixing belt 21 is driven to rotate. As a result, the driving torque of the fixing device 20 (driving motor 61) becomes smaller than when driving with a normal nip portion formed (an increase in driving torque over time can be reduced). Then, the fixing belt 21 is driven and rotated in such a state that the increase in driving torque is suppressed, so that the wear powder accumulated on the upstream side of the sheet-like member 22 and the fibers of the sheet-like member 22 enter. The wear powder is dispersed over the entire inner peripheral surface of the fixing belt 21 together with the lubricant. Therefore, after the adjustment mode, as shown in FIG. 4A, even when the nip pressure is returned to the normal state and the fixing process is performed, the problem that the driving torque of the fixing device 20 (drive motor 61) increases is prevented. be able to.

Here, in the present embodiment, the RFID 35 (storage unit) may be configured to store information related to the driving torque of the fixing device 20 in addition to newly arrived information. Specifically, as shown in FIG. 2, the apparatus main body 1 is provided with a torque detector 62 that detects a change in drive torque from a change in current flowing in the drive motor 61. The driving torque of the fixing device 20 detected by the torque detector 62 is stored in the RFID 35 while being updated every moment by the control of the reader / writer 65 by the controller 60.
Then, when the information related to the driving torque stored in the RFID 35 is read by the reader / writer 65 and the control unit 60 recognizes that the driving torque has reached the threshold value W, the “adjustment mode” is executed. Information regarding the history of execution of the adjustment mode is counted up.
In such a configuration, the problem that the driving torque of the fixing device 20 (drive motor 61) increases with time is further reduced.

Here, as shown in FIG. 6, in the present embodiment, the cam 51 in the cam mechanism 50 has a reinforcing member 23 on its cam surface for setting the nip pressure during a normal fixing process to a predetermined value. A plurality of contact positions A1 to A3 (top dead center) that can contact the (moving member) are formed. Specifically, the cam 51 in the present embodiment has three contact positions A1 to A3 (top dead center) formed on the cam surface. All of the three contact positions A1 to A3 (top dead center) are formed so that the distances from the central axis 51a of the cam 51 are equal.
When the accumulated usage time of the cam mechanism 50 reaches a predetermined time T, a contact position that has not been used so far is applied to the reinforcing member 23 (moving member) among the plurality of contact positions A1 to A3. The posture of the cam mechanism 50 in the rotational direction is controlled so that the normal fixing process is performed in contact.
Such control is performed when the cam mechanism 50 is used to some extent, and the surface (contact position) of the cam 51 is abraded by sliding contact with the reinforcing member 23, so that the contact from the central axis 51 a of the cam 51 is achieved. This is because the distance to the contact position is shortened and a desired nip pressure cannot be obtained.

Specifically, as shown in FIG. 6A, in the present embodiment, the first first abutting position A1 among the three abutting positions A1 to A3 is first used as the reinforcing member 23 in the fixing process. The cam motor of the cam mechanism 50 is controlled so as to make contact. Then, when the accumulated usage time of the cam mechanism 50 is detected by the timer 64 and the accumulated usage time reaches the predetermined time T, as shown in FIG. Of A1 to A3, the cam motor of the cam mechanism 50 is controlled so that the second contact position A2 that has not been used so far contacts the reinforcing member 23. At this time, the accumulated usage time of the cam mechanism 50 is reset to zero.
When the accumulated use time of the cam mechanism 50 further reaches a predetermined time T, the three contact positions A1 to A3 have been used so far in the fixing process, as shown in FIG. 6C. The cam motor of the cam mechanism 50 is controlled so that the third contact position A3 that does not exist contacts the reinforcing member 23.
By performing such control, the nip pressure at the nip portion hardly changes even over time, and a good fixed image can be formed.

In the present embodiment, when the accumulated usage time of the cam mechanism 50 has reached the predetermined time T, after the “adjustment mode” is executed, out of the plurality of contact positions A1 to A3. The cam mechanism 50 is controlled so that a normal fixing process is performed by bringing a contact position that is not used in the process into contact with the reinforcing member 23.
When the adjustment mode is executed, the cam mechanism 50 is operated once in order to reduce the nip pressure. Therefore, the contact positions A1 to A3 are changed in accordance with the operation in which the adjustment mode ends and the normal nip pressure is restored. Can be performed. Therefore, the time required for both operations can be used efficiently.

Finally, the characteristic control of the fixing device 20 described above will be collectively described with reference to the flowchart of FIG.
First, when a print command is input to the control unit 60, it is determined whether or not the fixing device 20 set in the apparatus main body 1 is new by reading information on the RFID 35 by the reader / writer 65 (step S1). As a result, when it is determined that the fixing device 20 is new, the aging mode is executed (step S2), and the new information flag is turned off (step S3).
Thereafter, it is determined whether or not the cumulative travel distance of the fixing device 20 is equal to or greater than the predetermined value X by reading the information of the RFID 35 by the reader / writer 65 (step S4). As a result, when it is determined that the cumulative travel distance is equal to or greater than the predetermined value X, the adjustment mode is executed (step S5), the cumulative travel distance is cleared, and the adjustment mode execution history is updated (step S5). S6).
Thereafter, based on the detection result of the timer 64, it is determined whether the accumulated usage time of the cam mechanism 50 is equal to or longer than the predetermined time T (step S7). As a result, when it is determined that the accumulated usage time is equal to or longer than the predetermined time T, the contact positions A1 to A3 of the cam 51 are changed (step S8).
Then, the printing operation is started (step S9), and this flow is finished.
If it is determined in step S1 that the fixing device 20 is not new, the flow after step S4 is performed. If it is determined in step S4 that the cumulative travel distance of the fixing device 20 is not equal to or greater than the predetermined value X, the flow after step S7 is performed. Furthermore, when it is determined in step S7 that the accumulated usage time of the cam mechanism 50 is not equal to or longer than the predetermined time T, the flow after step S9 is performed.

<Modification>
FIG. 8 is a diagram illustrating an operation of the fixing device in the aging mode or the adjustment mode as a modified example.
In the modification, the “aging mode” and the “adjustment mode” are respectively set to the nip pressure, the heating temperature of the fixing belt 21 by the heater 25 (heating means), and the direction in which the fixing belt 21 and the pressure roller 31 are rotated. , The 20 fixing device is idle driven.
Specifically, in the modified example, when the “aging mode” or “adjustment mode” is executed, as shown in FIG. 8A, the same nip pressure (normal nip pressure) as that in the fixing process is used. An operation in which the fixing device 20 is idly driven at the same heating temperature (normal heating temperature) of the heater 25 in the same rotation direction (forward rotation direction) as in the fixing process, and from the fixing process as shown in FIG. The operation of idly driving the fixing device 20 in the reverse rotation direction (reverse rotation direction) at the time of the fixing process at the heating temperature of the heater 25 higher than that at the time of the fixing process at a low nip pressure is alternately repeated. .
In particular, as shown in FIG. 8B, when the nip portion forming member 26 (and the reinforcing member 23) is moved in the separation direction (to the left in FIG. 8) by the cam mechanism 50, the nip portion. The forming member 26 is not completely separated from the inner peripheral surface of the fixing belt 21, but the corner portion of the nip forming member 26 is in partial contact with the inner peripheral surface of the fixing belt 21 (lightly pressurized state). ).

By executing the “aging mode” as in the modified example, the lubricant interposed in the portion where the fixing belt 21 and the sheet-like member 22 slide is moved so as to be squeezed out from the portion when new. As a result, the lubricant quickly and sufficiently becomes familiar over the entire inner peripheral surface of the fixing belt 21. Therefore, even if the nip pressure is returned to the normal state and the fixing process is performed after the aging mode, it is possible to prevent a problem that the driving torque of the fixing device 20 (drive motor 61) increases.
Further, by executing the “adjustment mode” as in the modification, the wear powder that has accumulated on the upstream side of the sheet-like member 22 and the wear powder that has entered the fibers of the sheet-like member 22 over time are removed from that portion. Since it moves so as to be squeezed out, it is quickly dispersed over the entire inner peripheral surface of the fixing belt 21 together with the lubricant. Therefore, even if the nip pressure is returned to the normal state after the adjustment mode and the fixing process is performed, it is possible to prevent a problem that the driving torque of the fixing device 20 (drive motor 61) increases.
The combination of the nip pressure, the heating temperature, and the rotation direction is not limited to this modified example, and various combinations are possible.

As described above, the image forming apparatus according to the present embodiment includes the fixing device 20 that is detachably installed on the image forming apparatus main body 1, the fixing belt 21 (fixing rotating body), and the pressure roller 31 (pressing member). And a cam mechanism 50 (nip pressure variable mechanism) that varies the nip pressure of the nip portion with the pressure rotator. Then, when it is recognized that the fixing device 20 is new, an “aging mode” in which the nip pressure is varied and the fixing device 20 is idly driven is executed at the timing of non-image formation. In addition, every time the cumulative travel distance (or cumulative drive time) of the fixing device 20 reaches the predetermined value X, an “adjustment mode” in which the nip pressure is varied and the fixing device 20 is idly driven at the timing of non-image formation. Executed.
As a result, the problem that the driving torque initially increases when the use of the new fixing device 20 is started and the problem that the driving torque of the fixing device 20 increases with time are efficiently suppressed. The

In this embodiment, the heater 25 is used as a heating unit (heating source) for heating the fixing belt 21. However, the heating unit (heating source) for heating the fixing belt is not limited to this, and for example, An electromagnetic induction coil can be used as the heating means, and a resistance heating element can be used as the heating means.
In such a case, the same effect as that of the present embodiment can be obtained.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

  In the present specification and the like, the “width direction” is defined as a direction orthogonal to the sheet conveyance direction and the same direction as the rotation axis direction of the fixing belt and the pressure roller.

1 image forming apparatus (image forming apparatus main body),
20 fixing device,
21 fixing belt (fixing rotating body),
22 sheet-like members,
23 Reinforcing member (moving member),
25 heater (heating means),
26 nip forming member,
29 Guide member (flange),
31 Pressure roller (pressure rotating body),
35 RFID (storage means),
40 Temperature detection sensor (temperature detection means),
50 Cam mechanism (nip pressure variable mechanism),
51 cam (cam mechanism),
52 compression spring (cam mechanism),
61 Drive motor (drive means),
65 Reader / writer (reading means),
A1-A3 contact position,
P sheet (recording medium).

JP 2012-32472 A Japanese Patent Laid-Open No. 2006-75839

Claims (9)

A fixing device that is detachably installed on the image forming apparatus main body, and is configured to form a nip portion where the fixing rotating body and the pressure rotating body are in pressure contact with each other to convey a sheet;
A nip pressure variable mechanism that varies the nip pressure of the nip portion between the fixing rotator and the pressure rotator;
With
When it is recognized that the fixing device is new, an aging mode is executed in which the nip pressure is varied and the fixing device is idlely driven at a timing during non-image formation.
Each time the cumulative travel distance or cumulative drive time of the fixing device reaches a predetermined value, an adjustment mode is executed in which the nip pressure is varied and the fixing device is idlely driven at a timing during non-image formation. An image forming apparatus. The fixing device includes a heating unit that heats the fixing rotator,
The aging mode and the adjustment mode vary the nip pressure, the heating temperature of the fixing rotator by the heating means, and the direction in which the fixing rotator and the pressure rotator are rotated. The image forming apparatus according to claim 1, wherein the fixing device is idle-driven.   3. The image forming apparatus according to claim 1, wherein the aging mode and the adjustment mode are configured to idle-drive the fixing device under the same conditions except for execution timing. 4. . The fixing device is a rewritable storage in which at least information on whether or not it is new, information on the cumulative travel distance or the cumulative drive time, and information on a history of execution of the adjustment mode are stored. Comprising means,
The image forming apparatus main body includes a reading unit capable of reading information stored in the storage unit,
When the fixing device is attached to the image forming apparatus main body, the reading unit reads information on whether or not the new product is stored in the storage unit, and recognizes that the fixing device is new. When the aging mode is executed, the information indicating that it is new and stored in the storage means is rewritten to information indicating that it is not new,
When the information relating to the cumulative travel distance or the cumulative drive time stored in the storage means is read by the reading means and it is recognized that the cumulative travel distance or the cumulative drive time has reached the predetermined value The adjustment mode is executed, and the information on the cumulative travel distance or the cumulative drive time stored in the storage unit is reset, and the information on the history of the adjustment mode being executed is counted up. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The storage means stores information related to the driving torque of the fixing device,
When the information relating to the driving torque stored in the storage means is read by the reading means and it is recognized that the driving torque has reached a threshold value, the adjustment mode is executed, and the adjustment mode is The image forming apparatus according to claim 4, wherein information relating to the executed history is counted up.   The image forming apparatus according to claim 4, wherein the storage unit is a non-volatile memory or an RFID. The pressure rotator is a pressure roller that is driven to rotate in a predetermined direction by a driving means,
The fixing rotator is a fixing belt that is heated by a heating unit and that rotates following the rotation of the pressure roller,
The fixing device includes a nip portion forming member that forms the nip portion in pressure contact with the pressure roller via the fixing belt inside the fixing belt,
A lubricant is interposed in a portion where the fixing belt is in direct or indirect sliding contact with the nip portion forming member,
The nip pressure variable mechanism is a cam mechanism that varies the nip pressure by moving the nip portion forming member in a direction to contact or separate the pressure roller by changing a posture of a cam in a rotation direction. The image forming apparatus according to claim 1, wherein: The cam has a plurality of contact positions on the cam surface that can contact the moving member in order to set the nip pressure in a normal fixing process to a predetermined value.
When the accumulated use time of the cam mechanism reaches a predetermined time, a normal fixing process is performed by bringing a contact position that has not been used so far among the plurality of contact positions into contact with the moving member. The image forming apparatus according to claim 7, wherein the cam mechanism is controlled.   When the cumulative use time of the cam mechanism reaches a predetermined time, and after the adjustment mode is executed, a contact position that has not been used so far is selected from the plurality of contact positions. The image forming apparatus according to claim 8, wherein the cam mechanism is controlled such that a normal fixing process is performed by contacting the cam mechanism.

Images