JP2017219772A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress overshoot of a fixing belt without damaging another component to prevent damage to the fixing belt.SOLUTION: The present invention is a fixing device comprising: a rotatable fixing belt 70 for fixing an unfixed toner to a sheet; a heater 80 that directly heats the fixing belt 70; and a pressure roller that applies pressure to the sheet with the fixing belt 70. The fixing device includes a driving motor M that rotates the fixing belt 70 in a normal or reverse direction, and rotation control means C2 that, when paper jam occurs, performs a rotation operation having a combination of the normal rotation and reverse rotation of the fixing belt 70 through the drive motor M.SELECTED DRAWING: Figure 2

Description

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

In recent years, market demands for energy saving and high speed are increasing for image forming apparatuses such as printers, copiers, and facsimiles.
In the image forming apparatus described above, an unfixed toner image is transferred to a recording material sheet, printing paper, photosensitive paper, electrostatic recording by an image transfer method or a direct method by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording. It is formed on paper such as paper.

  Incidentally, in the image forming apparatus described above, a fixing device for fixing an unfixed toner image is used. As such a fixing device, a contact heating method such as a heat roller method, a film heating method or an electromagnetic induction heating method is adopted.

As the conventional fixing device, there is a configuration disclosed in Patent Documents 1 and 2.
The fixing device disclosed in Patent Document 1 is of a belt type, but further reduction in warm-up time and first print time is desired (Problem 1).
“Warm-up time” refers to the time required from a normal temperature state to a predetermined printable temperature (reload temperature) such as when the power is turned on.
The “first print time” refers to the time from when a print request is received to when the print operation is performed through the print preparation and the paper discharge is completed.

  Further, as the speed of image forming apparatuses increases, the number of sheets that pass through per unit time increases, and the amount of heat required increases. For this reason, there is a problem that the amount of heat is insufficient (so-called temperature drop) at the beginning of continuous printing (problem 2).

The fixing device disclosed in Patent Document 2 is of the surf fixing (film fixing) type using a ceramic heater. By adopting this surf fixing method, the heat capacity is reduced and the size is reduced as compared with the belt type fixing device described above. Can be realized.
However, in the surf fixing method, since only the nip portion is locally heated, the other portions are not heated, and the belt is in the coldest state at the entrance of the paper or the like in the nip portion, and fixing failure occurs. There is a problem that it becomes easy. In particular, in the high-speed processing in which the belt rotates fast and the heat radiation of the belt outside the nip portion increases, there is a problem that fixing defects are more likely to occur (Problem 3).

For the purpose of solving the above problems 1 to 3, there is a configuration disclosed in Patent Document 3 in the name of a heating device. FIG. 7 is a schematic cross-sectional view showing a schematic configuration of the heating device disclosed in Patent Document 3. As shown in FIG.
The heating device shown in FIG. 7 fixes a pipe-shaped metal heat conductor 2 inside the endless fixing belt 1 so as to guide the movement of the fixing belt 1, The fixing belt 1 is indirectly heated by an internal heat source 3.

  Further, a pressure roller 4 that forms a nip portion N in contact with the metal heat conductor 2 via the fixing belt 1 is provided, and the endless belt 1 is rotated so as to rotate as the pressure roller 4 rotates. Move in the circumferential direction. Reference numeral 5 denotes a metal roller, and reference numeral 6 denotes an elastic layer.

That is, the heating device disclosed in Patent Document 3 is configured to heat the entire fixing belt 1 in the configuration using the fixing belt 1. According to this configuration, it is possible to shorten the first print time from the heating standby time, and to solve the shortage of heat during the high-speed rotation processing.
However, in the heating device disclosed in Patent Document 3, although the above-described first print time can be shortened, it is necessary to further improve the thermal efficiency in order to further improve the energy saving and the first print time. is there.

  In order to further improve the energy saving performance and the first print time, it is necessary to further improve the thermal efficiency. From the configuration in which the fixing belt 1 is indirectly heated through the metal heat conductor, the above-described metal heat conductor is used. A configuration in which the fixing belt 1 is directly heated without being devised is devised. In this configuration, power consumption can be reduced by significantly improving the heat transfer efficiency, and the first print time from the heating standby can be further shortened. Further, the cost can be reduced by eliminating the metal heat conductor.

  In each of the conventional fixing devices and the like, by adopting a configuration in which the fixing belt 1 is directly heated, energy saving is high, and the first print time from the heating standby time can be further shortened.

As shown in FIG. 2, if the fixing device is configured to directly heat the fixing belt (details will be described later), the thickness of the fixing belt is reduced as much as possible to achieve higher energy savings and faster first. The print time can be greatly improved.
On the other hand, when a JAM (paper jam) occurs in the fixing device shown in FIG. 2, it is necessary to stop the fixing belt in order to stop the paper conveyance. However, in this case, it has been found that the fixing belt overshoot (overheating) after the rotation of the fixing device is stopped increases, and the fixing belt may be damaged.

The reason why the fixing belt is damaged in the fixing device having the configuration shown in FIG. 2 will be described below.
When rotation is stopped after a paper jam has occurred in the fixing device, overshooting occurs significantly on the surface of the fixing belt facing the heater. On the other hand, overshoot hardly occurs in the vicinity of the nip not facing the heater. This is because the temperature of the heater is high and there is a support member between the heater and the fixing belt in the vicinity of the nip, so that the fixing belt does not directly receive the heat from the heater.

That is, the overshoot is large on the side facing the heater and the temperature is high, whereas the temperature is not high in the vicinity of the nip. As a result, a temperature deviation occurs between the surface of the fixing belt facing the heater and the vicinity of the nip, which is the difference in the thermal expansion amount of the fixing belt as it is.
As described above, although the amount of thermal expansion is different, the longitudinal position of the fixing belt is regulated by the nip, so that the internal stress increases on the side where the amount of thermal expansion is large. The fixing belt is deformed when the internal stress exceeds the yield limit stress. The deformation is a dent toward the inside of the fixing belt, and occurs at the center of the longitudinal position. Once such deformation has occurred, the deformation grows starting from the deformation location, and if it continues to be used as it is, it will eventually be damaged.

In order to solve the above-described problem, conventionally, a countermeasure has been taken in which the fixing belt is rotated by a specified distance after a paper jam occurs.
If the fixing belt is rotated by a specified distance after the paper jam occurs, it is possible to obtain effects such as facilitating the removal of the paper causing the paper jam. However, if the overshoot is still large, overshooting cannot be sufficiently prevented by rotating the fixing belt by a specified distance after the paper jam occurs, and the fixing belt may be damaged.

In order to prevent the above-described overshoot, the fixing belt may be rotated by a long distance, but there are the following problems.
That is, if the paper is rotated for a long time, for example, when a paper jam occurs, there is paper also in the fixing nip, and when the reverse rotation is performed, the paper flows backward, and the upstream side of the fixing device (secondary transfer) The belt will be damaged.
On the other hand, when the forward rotation is performed, problems such as destruction of the sensors disposed in the vicinity of the fixing and discharge of the sheet occur. On the other hand, when the rotation time is short, the overshoot cannot be suppressed and the fixing belt is kinked and broken. Therefore, in realizing a fixing device with a lower heat capacity, even when a paper jam occurs, other parts constituting the image forming apparatus are not damaged, overshoot is suppressed, and the fixing belt is protected from damage. Is required.

  Accordingly, an object of the present invention is to provide a fixing device that suppresses overshoot of the fixing member without damaging other components and does not damage the fixing member.

  The present invention described in claim 1 for solving the above-described problems includes a rotatable fixing member for fixing unfixed toner onto a sheet, a heating source for directly heating the fixing member, and the fixing member. In a fixing device having a pressure member that pressurizes a sheet between the driving source that rotates the fixing member forward and backward, and when the paper is jammed, the fixing member rotates forward via the driving source. And a rotation control means for performing a rotation operation in combination with reverse rotation.

  According to the present invention, it is possible to prevent damage to the fixing member by suppressing overshoot of the fixing member without damaging other components.

1 is a front sectional view showing a schematic configuration of an image forming apparatus using a fixing device according to an embodiment of the present invention. It is an enlarged front view showing a main configuration of the fixing device same as above. 6 is a timing chart according to a first example illustrating forward and reverse rotation operations of a drive motor when a paper jam occurs. 10 is a timing chart according to a second example illustrating forward and reverse rotation operations of the drive motor when a paper jam occurs. 12 is a timing chart according to a third example showing forward and reverse rotation operations of the drive motor when a paper jam occurs. 12 is a timing chart according to a fourth example illustrating forward and reverse rotation operations of the drive motor when a paper jam occurs. It is a schematic sectional drawing which shows the schematic structure of the heating apparatus disclosed by patent document 3.

  Hereinafter, an image forming apparatus using a fixing device according to an embodiment of the present invention will be described with reference to the drawings. In addition, about what is the same as that of what was demonstrated in FIG. 1, or the thing equivalent to FIG. 2, the same description is attached | subjected to them and the duplicate description is abbreviate | omitted.

  Hereinafter, a tandem color laser printer (hereinafter simply referred to as “printer”) will be described as an example of the image forming apparatus. The present invention can be applied not only to tandem or other types of printers but also to copying machines, facsimile machines, and the like.

  In the printer A shown in FIG. 1, the bottle storage unit 10, the transfer belt unit 20, the image stations 30 </ b> Y, 30 </ b> M, 30 </ b> C, and 30 </ b> K, the optical writing device 40, the sheet feeding device 50, and the fixing device B are disposed in the main body 9. It has a configuration.

The transfer belt unit 20 is formed by stretching an endless intermediate transfer belt 21 around four primary transfer rollers 22, a secondary transfer backup roller 24, a cleaning backup roller 25, and a tension roller 26. Further, a belt cleaning device 27 is disposed at the left end portion of the intermediate transfer belt 21 in the figure, and the secondary transfer roller 23 is disposed opposite to the secondary transfer backup roller 24.
Here, when the secondary transfer backup roller 24 is driven to rotate, the intermediate transfer belt 21 runs around (rotates) in the direction indicated by the arrow A1 in the figure. The cleaning backup roller 25 includes a spring or the like for applying tension to the intermediate transfer belt 21.

  The four primary transfer rollers 22 form a primary transfer nip by sandwiching the intermediate transfer belt 21 between the photosensitive drums 31 described later. Each primary transfer roller 22 is connected to a power supply (not shown) so that a predetermined DC voltage or AC voltage is applied.

  The secondary transfer roller 23 forms a secondary transfer nip by sandwiching the intermediate transfer belt 21 with the secondary transfer backup roller 24. Similarly to the primary transfer roller 22, a power source (not shown) is connected to the secondary transfer roller 23 so that a predetermined DC voltage or AC voltage is applied.

  The belt cleaning device 27 has a cleaning brush and a cleaning blade (not shown) disposed so as to contact the intermediate transfer belt 21. The cleaning brush and the cleaning blade scrape and remove foreign matters such as residual toner on the intermediate transfer belt 21 to clean the intermediate transfer belt 21. The belt cleaning device 27 has a discharge mechanism (not shown) for carrying out and discarding the residual toner removed from the intermediate transfer belt 21.

Below the transfer belt unit 20, image stations 30 </ b> Y, 30 </ b> M, 30 </ b> C, and 30 </ b> K are juxtaposed along the intermediate transfer belt 21.
The image stations 30Y, 30M, 30C, and 30K, except for creating images of different colors of yellow (Y), magenta (M), cyan (C), and black (BK) corresponding to the color separation components of the color image, respectively. Has the same configuration.

Each of the image stations 30Y, 30M, 30C, and 30K includes a photosensitive drum 31, a charging device 32 that charges the surface of the photosensitive drum 31, the primary transfer roller 22, the developing device 33, a cleaning device 34, and the like.
The developing device 33 supplies toner to the surface of the photoconductive drum 31, and the cleaning device 34 cleans the surface of the photoconductive drum 31.

The optical writing device 40 described above is disposed below the image stations 30Y, 30M, 30C, and 30K.
The optical writing device 40 includes a semiconductor laser, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, a rotating polygon mirror, and the like as a light source for exposing the surface of each photosensitive drum 31. . With this configuration, writing light Lb corresponding to each color is emitted to each photoconductive drum 31, and an electrostatic latent image is formed on each photoconductive drum 31.

  The bottle housing portion 10 is provided on the upper portion of the main body 9, and four toner bottles 10Y, 10M, 10C, and 10K containing replenishing toner are detachably attached to the bottle housing portion 10.

  A replenishment path (not shown) is provided between each of the toner bottles 10Y, 10M, 10C, and 10K and each of the developing devices 33, and each developing device from each of the toner bottles 10Y, 10M, 10C, and 10K passes through the replenishment path. 33 is supplied with toner.

  The sheet feeding device 50 is disposed at the lower part of the main body 9 and includes a paper feed tray 50 for storing the paper P, a paper feed roller 51 for carrying out the paper P from the paper feed tray 50, and the like. .

  In the main body 9, a conveyance path R is formed through which the paper P of the sheet feeding device 50 passes through the secondary transfer nip and is discharged to the outside. In the transport path R, a pair of registration rollers 35 for transporting the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 23 in the paper transport direction.

Further, a fixing device B, which will be described in detail later, for fixing an unfixed image transferred onto the paper P is disposed downstream of the position of the secondary transfer roller 23 in the paper transport direction.
Further, a pair of paper discharge rollers 36 and 36 for discharging the paper P to the outside of the main body 9 are provided downstream of the fixing device B in the paper transport direction of the transport path R. In addition, a discharge tray 37 for stocking the paper P discharged out of the main body 9 by a pair of discharge rollers 36 and 36 is provided on the upper surface of the main body 9.

  In the above-described configuration, the visible image formed on each photoconductive drum 31 performs the primary transfer process on the intermediate transfer belt 21 that moves in the arrow direction A1 while facing the photoconductive drum 31. Then, each image is superimposed and transferred, and then transferred to the paper P by performing a secondary transfer process.

  In the transfer to the intermediate transfer belt 21, visible images formed on the photosensitive drums 31 are transferred to the same position on the intermediate transfer belt 21 while the intermediate transfer belt 21 moves in the arrow direction A1. I am doing so. That is, the timing is shifted from the upstream side to the downstream side in the moving direction A1 by the voltage application by the primary transfer roller 22 disposed so as to face the respective photosensitive drums 31 with the transfer belt 21 interposed therebetween.

Next, a fixing device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is an enlarged front view showing a main configuration of the fixing device B according to the embodiment of the present invention.
The fixing device B includes a pressure roller 60 as a pressure member, a fixing belt 70 as a fixing member, a heating source (hereinafter referred to as “heater”) 80 for directly heating the fixing belt 70, and a nip forming member 90. Is the main configuration.

  The fixing belt 70 is formed in an endless shape, and the heater 80 and the nip forming member 90 are disposed inside the fixing belt 70. In this configuration, the fixing belt 70 is directly heated by the heater 80 from the inner peripheral side.

  As the fixing belt 70, a belt-like body or film using a metal material such as nickel or SUS or a resin material such as polyimide is used. The surface layer of the fixing belt 70 is coated with a release layer such as PFA (perfluoroalkoxylkane) or PTFE (polytetrafluoroethylene), and has a release property so that toner does not adhere.

  There may be an elastic layer formed of silicone rubber or the like between the base material of the fixing belt 70 and the release layer. In addition, when there is no elastic layer, the heat capacity is reduced and the fixability is improved. However, when the unfixed image is crushed and fixed, minute irregularities on the belt surface are transferred to the image, resulting in a crusty skin on the solid portion of the image. The problem that the uneven glossiness (skin skin image) remains is generated. In order to improve this, it is necessary to provide a silicone rubber layer (elastic layer) with a thickness of 100 [μm] or more. Due to the deformation of the silicone rubber layer, fine irregularities are absorbed and the skin image can be improved.

The heater 80 shown in the present embodiment uses a halogen heater, but is not limited to this, and for example, an IH, a resistance heating element, a carbon heater, or the like can be adopted.
The nip forming member 90 is disposed so as to form a nip with the pressure roller 60 opposed via the fixing belt 70, and is in direct sliding contact with the inner peripheral surface of the fixing belt 70. . In addition, you may make it slide indirectly through the sliding sheet which is not shown in figure.
A temperature detection sensor S for detecting the surface temperature of the fixing belt 70 is disposed adjacent to the left side of the fixing belt 70 in the figure.

  The nip forming member 90 shown in the present embodiment shows a nip portion N formed on a flat surface, but may have a concave shape or other shapes. When the nip is concave, the discharge direction of the leading edge of the paper P is closer to the pressure roller 60 and the separation property is improved, so that the occurrence of paper jam can be suppressed.

A support member (stay) 85 for supporting the nip portion N is provided inside the fixing belt 70 to prevent the nip forming member 90 that receives pressure from the pressure roller 60 from being bent in the axial direction. A uniform nip width is obtained.
The support member 85 is formed in a U-shaped cross section having an opening on the left side in the figure, and is held and fixed to a holding member (flange) 62 at both ends thereof and positioned.
On the inner wall surface side of the support member 85, a reflecting member 100 for blocking radiant heat from the heater 80 is disposed along the inner wall surface. Thereby, useless energy consumption due to the support member 85 being heated by radiant heat from the heater 80 or the like is suppressed. Note that the same effect can be obtained by performing heat insulation or mirror treatment on the inner surface of the support member 85 instead of the reflecting member 100.

The fixing belt 70 described above is rotated by the pressure roller 60.
That is, when the pressure roller 60 shown in FIG. 2 is rotated by the following driving source (hereinafter referred to as “driving motor”) M, the driving force is transmitted to the fixing belt 70 in the nip portion N and the driven roller rotates. Further, the fixing belt 70 rotates while being guided by the holding member 62 at both ends except for the nip portion N. With such a configuration, the fixing device B that is inexpensive and has a fast warm-up is realized.

  The pressure roller 60 is formed by forming an elastic rubber layer 62 on the outer peripheral portion of the cored bar 61, and a release layer (PFA or PTFE layer) is provided on the surface in order to obtain releasability. The pressure roller 60 is connected to a drive motor M provided in the main body 9 via a gear (not shown) and is driven to rotate forward and backward.

The pressure roller 60 is pressed toward the fixing belt 70 by a spring or the like (not shown), and has a predetermined nip width when the elastic rubber layer 62 is crushed and deformed. The pressure roller 60 may have a hollow structure, or a configuration in which a heat source such as a halogen heater is provided inside the pressure roller 60 may be used.
The elastic rubber layer 62 may be solid rubber, but if no heat source is provided inside the pressure roller 60, sponge rubber may be used. Note that it is more preferable to use sponge rubber since heat insulation is enhanced and heat of the fixing belt 70 is hardly taken.

  The light shielding member 63 has a stepped shape provided with a light shielding area corresponding to each paper width, is arranged so as to rotate in a non-contact manner along the inner side of the fixing belt 70, and corresponds to each paper width. Rotate to shield the area unnecessary for heating. As a result, even when narrow-width paper is continuously passed, the non-sheet passing area does not become overheated, and it is necessary to perform control such as reducing productivity in order to cancel the overheated area. Absent.

By the way, the drive motor M and the heater 80 connected to the pressure roller 60 are connected to the output side of the control unit C, respectively, and the temperature detection sensor S is connected to the input side.
The control unit C shown in the present embodiment has the following functions by executing a required program.
A function for determining whether or not the fixing belt 70 has reached a predetermined temperature based on the temperature detected by the temperature detection sensor S. This function is referred to as “belt temperature determination means C1”.
The “predetermined temperature” is a reference temperature for determining whether or not the fixing belt 70 is overheated (overshoot), and is stored in the control unit C in this embodiment.

A function for performing a rotation operation that combines forward rotation and reverse rotation of the fixing belt 70 when a paper jam occurs. This function is referred to as “rotation control means C2”.
In this embodiment, when a paper jam occurs, the rotation of the fixing belt 70 is temporarily stopped, and then the fixing belt 70 is rotated by a specified distance in either the forward or reverse direction to temporarily stop the fixing member. When the temperature reaches a predetermined temperature, the content is that the fixing belt 70 is rotated in a reverse direction by a specified distance and temporarily stopped. Specific rotation control will be described in detail with reference to FIGS. In this embodiment, the “specified distance” is a distance that does not damage components such as a sensor disposed in the vicinity of the fixing device by rotating the fixing belt forward and backward when a paper jam occurs.
A function for controlling the power supplied to the heater 80. This function is referred to as “heater control means C3”.
In the present embodiment, it includes temporarily controlling the heating by the heater 80 when a paper jam occurs.

3 to 6 show the rotation operation of the drive motor after the paper jam occurs, and FIG. 3 shows a first example showing the forward and reverse rotation operation of the drive motor when the paper jam occurs. It is the timing chart which concerns.
In FIG. 3, after the fixing belt 70 is continuously rotated to either one of the forward and reverse directions by a specified distance, the fixing belt 70 is continuously rotated to either the forward or reverse direction by a specified distance. An example is shown.
Specifically, when the paper jam occurs, the rotation of the fixing belt 70 is stopped, and then the fixing belt 70 is rotated by a specified distance in either the forward or reverse direction to stop the fixing belt 70 at a predetermined temperature. An example is shown in which the fixing belt 70 is rotated by a predetermined distance to the other of the forward and reverse directions and stopped when it reaches. The details are as follows.

That is, immediately after the paper jam occurs, the heater 80 and the drive motor M are each temporarily stopped (indicated by “p1” in the figure, the same applies hereinafter). Thereafter, the drive motor M is driven to rotate in the forward direction, whereby the fixing belt 70 is continuously rotated in the forward direction by a specified distance (p2). Then, when the rotation distance of the fixing belt 70 reaches the specified distance, the drive motor M is stopped (p3). In FIG. 3, the time corresponding to the “specified distance” is indicated by T1.
In this case, it is desirable to set the rotation speed of the fixing belt 70 lower than the rotation speed when performing a normal image forming operation. This is because the amount of heat of excessive heating can be uniformly distributed over the entire surface of the fixing belt 70.

When the fixing belt 70 has reached a predetermined temperature when the fixing belt 70 reaches the predetermined temperature after the fixing belt 70 has been rotated by a predetermined distance (p3), this time, the fixing belt 70 is continuously rotated in the reverse direction by a predetermined distance. Thus, the drive motor M is reversely driven (p4).
The linear speed at the time of reverse rotation may be the same as that at the time of forward rotation, or may be a different linear speed. The specified distance at this time needs to be set to the same distance as the specified distance when the forward rotation drive is executed.

Further, when the fixing belt 70 has reached a predetermined temperature at the stop (p5) after the reverse rotation driving, the fixing belt 70 is moved in the forward direction by driving the driving motor M forward rotation. Rotate a specified distance and stop temporarily (p6). Such an operation is appropriately repeated until the detected temperature of the fixing belt 70 does not reach a predetermined temperature.
That is, every time the fixing belt 70 is continuously rotated in the forward and reverse directions by a specified distance, an excessive temperature rise (overshoot) of the fixing belt 70 is detected by the temperature detection sensor S, and the fixing belt 70 is forward and backward as necessary. By rotating, the life is not shortened unnecessarily.

FIG. 4 is a timing chart according to the second example showing the forward / reverse rotation operation of the drive motor when a paper jam occurs.
FIG. 3 shows an example in which the fixing belt 70 is rotated in the forward direction and then rotated in the reverse direction when a paper jam occurs, but in FIG. 4, the paper jam occurs. In some cases, the fixing belt 70 is rotated in the opposite direction to the above and then rotated in the forward direction.

Specifically, it is as follows.
That is, immediately after the paper jam occurs, the heater 80 and the drive motor M are each temporarily stopped (p1). Thereafter, the drive motor M is reversely driven so as to continuously rotate the fixing belt 70 by a specified distance in the reverse direction (p2). Then, when the rotation distance of the fixing belt 70 reaches the specified distance, the drive motor M is stopped (p3).
When the fixing belt 70 has reached a predetermined temperature when the fixing belt 70 has stopped after the fixing belt 70 has been rotated by a specified distance (p3), this time, the fixing belt 70 is continuously rotated in the forward direction by a specified distance. Thus, the drive motor M is driven to rotate forward (p4).

  Further, when the fixing belt 70 reaches the predetermined temperature again at the stop after the forward rotation driving (p5), this time, the fixing belt 70 is continuously rotated in the reverse direction by a specified distance. The drive motor M is driven in reverse rotation.

FIG. 5 is a timing chart according to the third example showing the forward / reverse rotation operation of the drive motor when a paper jam occurs.
FIGS. 3 and 4 show an example in which either the forward or reverse rotational driving operation is continuously performed until the rotational distance of the fixing belt 70 reaches the specified distance.
In this example, until the total rotation distance of the fixing belt 70 reaches the specified distance, the rotation and stop in one of the forward and reverse directions are repeated for each rotation distance shorter than the specified distance, and the total rotation distance of the fixing belt 70 is After reaching the specified distance, until the rotation distance of the fixing belt 70 reaches the specified distance, the rotation and stop in the other direction, either forward or reverse, are repeated for each rotation distance shorter than the specified distance.

Specifically, it is as follows.
That is, immediately after the paper jam occurs, the heater 80 and the drive motor M are each temporarily stopped (indicated by p1 in the figure, and so on). Thereafter, the drive motor M is driven to rotate forward so that the fixing belt 70 is rotated in the forward direction by a predetermined distance shorter than the specified distance (p2). Then, when the total rotational distance of the fixing belt 70 reaches the specified distance, the drive motor M is temporarily stopped (p3). When the fixing belt 70 has reached a predetermined temperature at the time of this stop, this time, the drive motor M is driven in reverse rotation so as to rotate the fixing belt 70 in the reverse direction by a predetermined distance shorter than the specified distance. (P4). This operation is repeated in the same manner as described above until the detected temperature of the fixing belt 70 does not reach a predetermined temperature. In FIG. 5, the time corresponding to “distance shorter than the prescribed distance” is indicated by T2.

FIG. 6 is a timing chart according to the fourth example illustrating the forward / reverse rotation operation of the drive motor when a paper jam occurs.
In the rotating operation shown in FIG. 5, the fixing belt 70 is intermittently rotated in the same direction by a distance shorter than the specified distance until the total rotation distance of the fixing belt 70 reaches the specified distance. After that, it was rotated intermittently by a distance shorter than the specified distance in the direction opposite to the above rotation direction. On the other hand, the rotation operation shown in FIG. 6 is as follows.

  That is, until the total rotation distance of the fixing belt 70 reaches the specified distance, rotation and stop in the same direction are repeated by a rotation distance shorter than the specified distance. After the total rotation distance of the fixing belt 70 reaches the specified distance, the fixing belt 70 is moved back to the initial rotation position when the paper jam occurs, and then the rotation distance of the fixing belt 70 is specified. Until the distance is reached, a rotation operation is repeated in which the rotation and stop of the rotation distance shorter than the specified distance in one direction are repeated.

Specifically, it is as follows.
That is, immediately after the paper jam occurs, the heater 80 and the drive motor M are each stopped (indicated by p1 in the figure, the same applies hereinafter). Thereafter, the drive motor M is driven to rotate forward so that the fixing belt 70 is rotated in the forward direction by a predetermined rotation distance shorter than the specified distance (p2).
And if it reaches | attains the predetermined | prescribed rotation distance shorter than a regulation distance, it will stop (p3). At the time of the stop, it is determined whether or not the fixing belt 70 has reached a predetermined temperature. If the fixing belt 70 has reached the predetermined temperature, the operation of rotating again by a predetermined rotation distance shorter than the specified distance is repeated (p4). . Then, when the total rotation distance of the fixing belt 70 reaches the specified distance, the drive motor M is stopped (p5).

When the fixing belt 70 has reached a predetermined temperature at the time of the stop (p5), this time, the fixing belt 70 is rotated in the reverse direction by a specified distance, and the fixing belt 70 is returned to the initial rotation position. (P6).
Thereafter, the drive motor M is driven to rotate forward from the initial rotation position so that the fixing belt 70 is rotated in the forward direction by a predetermined rotation distance shorter than a specified distance. Then, when the total rotation distance of the fixing belt 70 reaches the specified distance, the drive motor M is stopped. Such an operation is repeated in the same manner as described above until the detected temperature of the fixing belt 70 does not reach a predetermined temperature.

Note that the present invention is not limited to the above-described embodiments, and the following rotation operation may be performed.
In the above-described embodiment, an example in which “distance shorter than the prescribed distance” is the same distance as each other has been described, but the distance may be different from each other.
Furthermore, in the above-described embodiment, an example in which one heater is disposed inside the fixing belt is illustrated, but the present invention is not limited to this, and a configuration in which two or three heaters are used may be employed. Further, the support member and the reflection member inside the fixing belt are not limited to those in the form shown in FIG. 2, and an optimum form can be selected depending on the image forming apparatus.

9 Body 10Y, 10M, 10C, 10K Toner bottle 21 Transfer belt 22 Primary transfer roller 23 Secondary transfer roller 25 Cleaning backup roller 27 Belt cleaning device 30Y, 30M, 30C, 30K Image station 31 Photosensitive drum 33 Developing device 34 Cleaning device 35 registration roller 36 paper discharge roller 37 paper discharge tray 50 paper feed tray 51 paper feed roller 61 cored bar 62 holding member 70 fixing belt (fixing member)
80 Heater (heating source)
85 Support member 90 Nip forming member 100 Reflective member A Printer M Drive motor (drive source)
N Nip part R Transport path S Temperature sensor

JP 2004-286922 A Japanese Patent No. 2861280 JP 2007-334205 A

Claims (6)

A rotatable fixing member for fixing unfixed toner to the paper;
A heating source for directly heating the fixing member;
In a fixing device having a pressure member that pressurizes a sheet between the fixing member,
A drive source for rotating the fixing member forward and backward;
A fixing device, comprising: a rotation control unit that performs a rotation operation combining forward rotation and reverse rotation of the fixing member via the driving source when the paper jam occurs.   The rotation control unit continuously rotates the fixing member in one of the forward and reverse directions by a predetermined distance, and then continuously rotates the fixing member in the forward and reverse directions by the predetermined distance. The fixing device according to claim 1, wherein:   The rotation control means stops whenever the fixing member is rotated in both forward and reverse directions, and at this time, the fixing member is moved in both forward and reverse directions until the temperature of the fixing member does not reach a predetermined temperature. The fixing device according to claim 1, wherein the fixing device is repeatedly rotated.   The rotation control unit repeats rotation and stop in the same direction by a rotation distance shorter than the specified distance until the total rotation distance of the fixing member reaches a specified distance, and the total rotation distance of the fixing member becomes the specified distance. 4. The rotation of the fixing member in the direction opposite to the one direction is repeated and stopped until the rotation distance of the fixing member reaches a specified distance after reaching the specified distance. Fixing device.   The rotation control unit repeats rotation and stop in the same direction by a rotation distance shorter than the specified distance until the total rotation distance of the fixing member reaches a specified distance, and the total rotation distance of the fixing member becomes the specified distance. After reaching the fixing member, the fixing member is moved back to the initial rotation position when the paper jam occurs, and thereafter, the rotation distance of the fixing member is shorter than the specified distance until the rotation distance reaches the specified distance. The fixing device according to claim 3, wherein the fixing device repeats rotation and stop in the same direction as the one direction.   An image forming apparatus comprising the fixing device according to claim 1.