JP4593839B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present inventionImage forming apparatusIt is about.
[0002]
[Prior art]
Conventionally, as an image forming apparatus, various systems such as an electrophotographic system, a thermal transfer system, and an ink jet system are used. Among these, the electrophotographic method is superior to other methods in terms of high speed, high image quality, and quietness, and is widely used as an image forming engine for copying machines and page printers.
[0003]
In the electrophotographic system, an electrostatic force is used to form an image of toner particles on a transfer material such as paper. A fixing device obtains a stable image by melting and fixing the toner image on a transfer material.
[0004]
Hereinafter, an electrophotographic color image forming apparatus will be described as an example, and a toner image forming principle in an electrophotographic system and a conventional example of a fixing device will be described.
[0005]
FIG. 10 is a schematic configuration diagram of a color image forming apparatus using an electrophotographic system, and the system shown in the figure is a system known as an intermediate transfer system among electrophotographic systems.
[0006]
First, the photosensitive drum 1 is rotationally driven in the direction of the arrow, and the surface thereof is uniformly charged to −600 V by the charger 2. Thereafter, a latent image corresponding to the image is formed on the surface of the photosensitive drum 1 by the scanning light 4 from the laser exposure optical system 3 or the like. The potential of the latent image portion formed by exposure with scanning light is approximately −200V.
[0007]
On the other hand, the color developing devices 5 (black), 6 (magenta), 7 (cyan), and 8 (yellow) containing toner as a developer are arranged on the rotor 21 in the vicinity of the photosensitive drum 1 as shown in the figure. As the rotor revolves every 90 degrees, the rotor is sequentially disposed at the development position facing the photosensitive drum 1.
[0008]
A constant amount of negatively charged toner is supplied onto the developing roller 5a, and a developing bias is applied to the developing roller 12 from a power source (not shown). By setting the developing bias to an appropriate value between the charging potential and the exposure portion potential, it is possible to perform development in which toner is selectively attached to the latent image on the photosensitive drum 1.
[0009]
The monochromatic image formed on the photosensitive drum 1 in this way is sequentially transferred onto the intermediate transfer belt 9 that rotates in the arrow direction at substantially the same speed as the photosensitive drum 1. Reference numeral 10 denotes a transfer roller, to which a positive polarity transfer bias (200 V to 700 V) is applied by a power source 19. After the transfer, the toner remaining on the surface of the photosensitive drum 1 is removed by the cleaner 17.
[0010]
The above-described process is sequentially performed for each of the color developing devices 5 to 8 in synchronization with the rotation of the intermediate transfer belt 9, and when a four-color superimposed color image is formed on the intermediate transfer belt 9, the back surface of the transfer material 18 that is conveyed. Then, the secondary transfer roller 11 is brought into contact with the image, and the color image is secondarily transferred onto the transfer material 18 in a lump by an applied positive polarity bias (1 kV).
[0011]
When the above process is completed, the remaining toner in the secondary transfer is removed by the cleaner 13, and the intermediate transfer belt 9 is discharged by a discharging charger (not shown). As the charge eliminating charger, AC corona charging is often used. In order to increase the charge removal efficiency, an electrode is generally provided on the back surface of the intermediate transfer belt 9. In the drawing, a roller 16 is a tension roller, 15 is a driving roller, and 12 is a secondary transfer counter roller.
[0012]
The intermediate transfer belt 9 usually has a thickness of 70 μm to 200 μm and a volume resistivity of 10^TenΩcm to 10¹⁶A resin film belt of PVdF of about Ωcm, polyamide, polyimide, PET, polycarbonate or the like, and a high resistance resin layer having a good releasability of several tens of μm on a low resistance base layer of rubber having a thickness of about 0.5 to 2 mm. A rubber belt or the like provided with can be used.
[0013]
The full color toner image transferred onto the transfer material is then fixed on the transfer material by passing through the fixing device 21 to become an output image of the device.
[0014]
Next, a schematic configuration of the fixing device in the conventional example will be described with reference to FIG.
[0015]
The fixing device is configured such that the transfer material 105 on which the unfixed developer image 104 is placed can pass through the contact nip 110 of two heating rollers (the fixing roller 100 and the pressure roller 101) whose temperatures are adjusted. Yes. The unfixed developer image 104 is heated and pressed to be fixed on the transfer material. The thermistors 120a and 120b are in contact with the surfaces of the rollers 100 and 101, and the temperature is adjusted based on the temperature detected by the thermistor. Each roller 100, 101 has a halogen heater 106a, 106b in the center, and the incident energy generated by the heater 106a, 106b is absorbed by the aluminum core bars 107a, 107b inside the roller 100, 101 and heated. The
[0016]
Elastic layers 108a and 108b made of silicon rubber having a thickness of 2 mm are provided around the aluminum core bars 107a and 107b. Further, PFA and PTFE are used to prevent toner and paper dust from adhering to the outer roller surface. Coating layers 109a and 109b made of a resin having good releasability such as the like are provided.
[0017]
The reason why the rollers 100 and 101 are provided with the elastic layer is as follows.
[0018]
First, the reason is to secure a sufficient fixing nip with a relatively small diameter roller. The second reason is to fix a color toner image cleanly. If there is no elastic layer, unevenness and thickness unevenness on the surface of the transfer material become uneven glossiness of the image, and particularly appear in a color image.
[0019]
On the other hand, in the case of a roller having an elastic layer as in the conventional example, the distance from the portion that generates heat by absorbing the radiation of the heater is increased, resulting in the following disadvantages.
[0020]
That is, when the heat on the roller surface is rapidly taken away by continuous paper feeding, heat supply from the core metal by heat conduction is not in time, and the temperature on the roller surface is lowered, resulting in fixing failure. Further, if strong heating is performed to compensate for the temperature drop on the surface, the temperature of the silicon rubber in the vicinity of the core metal becomes too high and the deterioration is accelerated. Such inconvenience is more severe as the roller diameter is smaller and the elastic layer is thicker when the transfer material supply speed is the same.
[0021]
In order to solve the above problem, a method has been proposed in which a heating member (external heating member) is brought into contact with the outside of the fixing roller to heat the fixing roller from the surface. FIG. 12 shows an example of the configuration of such a fixing device. In FIG. 12, a heating roller (external heating roller) 103 for directly heating the surface of the fixing roller is provided. The heat energy taken from the surface of the fixing roller by the external heating roller can be directly replenished from the surface, and even when the paper is continuously fed, the temperature of the roller surface is hardly lowered. In the figure, 107c is a metal roller, 106c is a heater, and 120c is a thermistor. In addition to such a roller, a ceramic heater or the like can be used as the external heating member.
[0022]
[Problems to be solved by the invention]
The toner is melted in the fixing nip, and the following force relationship is established.
[0023]
Aggregation force between toners> Adhesion force between fixing (pressurizing) roller surface and toner
Adhesive force between toner and transfer material> Adhesive force between fixing (pressurizing) roller surface and toner
As a result, the toner does not adhere to the fixing roller surface 109a and is fixed on the transfer material.
[0024]
On the other hand, when the image forming apparatus detects an abnormality such as a jam, the operation of the apparatus is stopped, and the roller heating by the heater is stopped to ensure safety. At this time, if there is a transfer material loaded with unfixed toner in the fixing nip 110, the above force relationship may be lost due to a decrease in roller temperature, and the toner may adhere (offset) to the surface of the fixing / pressure roller. It is also conceivable that the toner adheres to the roller during jamming by the user.
[0025]
In the case of the conventional fixing device shown in FIG. 11, the surfaces of the fixing roller and the pressure roller may be contaminated with the offset toner for the above reason. However, when the device returns to the normal state, the force relationship is established again. The offset toner on the fixing roller and the pressure roller is fixed again on the transfer material by the first sheet passing and can be removed from the roller.
[0026]
However, in the case of the conventional fixing device shown in FIG. 12, the offset toner due to jam or the like wraps around the external heating roller and does not come into contact with the transfer material even in the first sheet passing after the jam. All of the toner on the surface heating roller cannot be removed. The toner on the external heating roller gradually returns to the fixing roller and is mixed with the image toner on the transfer material and is fixed every time.
[0027]
Even in normal use while maintaining the force relationship, a small amount of offset is unavoidable, and dirt accumulates on the external heating roller due to long-term use, and when there is, it returns to the fixing roller and is mixed with the image and fixed. There was also a problem.
[0028]
In order to prevent the above inconvenience, a method for removing the offset toner by providing a cleaning member 115 that contacts the fixing roller and the external heating roller as shown in FIG. 13 has been proposed. However, the apparatus becomes larger and complicated. In addition, it is necessary for the apparatus user or a maintenance service person to periodically replace the cleaning member.
[0029]
  The present invention is described above.TaskThe purpose of the process is to remove the offset toner that has wrapped around the external heating means.Image forming apparatusIs to provide.
[0030]
[Means for Solving the Problems]
  The present invention for solving the above-described problems includes an image forming unit that forms an unfixed toner image on a transfer material, a fixing roller, and a rotating body that contacts the surface of the fixing roller, and heats the fixing roller. An external heating unit, and a pressurizing unit that contacts the fixing roller and forms a fixing nip portion together with the fixing roller, and transfers the transfer material carrying an unfixed toner image in the fixing nip portion while nipping and conveying the transfer material. An image forming apparatus having a fixing unit that heat-fixes an unfixed toner image on a material, and transferring the transfer material from the fixing roller to the transfer material by removing the toner by conveying the transfer material through the fixing nip. A cleaning mode, and in the cleaning mode, the temperature difference between the external heating unit and the fixing roller surface is set to be larger than that during normal image formation, and the external heating is performed. Means and the fixing roller surface, characterized in that conveyed by the fixing nip transfer material at a timing that is the temperature difference.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0032]
<Embodiment 1>
The schematic configuration of the image forming apparatus according to the present embodiment is the same as the configuration of the conventional image forming apparatus already shown in FIG. Here, the detailed configuration of the image forming apparatus according to the present embodiment, the differences from the conventional example, and the effects will be described.
[0033]
FIG. 1 is a cross-sectional view of a fixing device according to the present embodiment. In the illustrated fixing device, three heating rollers (fixing roller 100, pressure roller 101, and pressure roller 101, which include halogen heaters 106a, 106b, and 106c inside are shown. The external heating roller 102) is arranged as shown and does not have a cleaning member or the like. The fixing roller 100 and the pressure roller 101, and the fixing roller 100 and the external heating roller 102 are in contact with each other at predetermined pressures (40 kgf and 20 kgf, respectively).
[0034]
Each of the rollers 100, 101, 102 has temperature detection means 120a, 120b, 120c such as a thermistor. The roller temperature control means (not shown) is based on temperature detection information by the thermistor. The lighting of 106c is controlled, and the temperature of the rollers 100, 101, 102 is adjusted.
[0035]
In this embodiment, the diameter of the pressure roller 101 and the fixing roller 100 is both 40 mm, the diameter of the external heating roller 102 is 25 mm, and the roller length is 234 mm for the fixing roller 100, 228 mm for the pressure roller 101, and external heating. The roller 102 is 228. The halogen heaters 106a, 106b, and 106c were all those having a heating value of about 500W.
[0036]
Each of the fixing roller 100 and the pressure roller 101 has silicone rubber elastic layers 103a and 103b having a thickness of about 2 mm outside the hollow aluminum roller cores 107a and 107b (thickness of about 2 mm). High release surface layers 108a and 108b having a thickness of 20 μm are provided on the outside. Additives such as bengara and silica are added to the silicone rubber to improve thermal conductivity, and the rubber hardness is adjusted to 8 ° (test piece hardness JIS A). The external heating roller 102 has a hollow aluminum roller 107c provided with a coating layer 109c having a thickness of 20 μm made of a highly releasable material. As a highly releasable material used for the surface layer of each roller 100, 101, 102, fluorine-based resin such as PFA, PTFE, FEP, fluorine rubber, or the like can be used.
[0037]
During normal image formation, the surface temperature of the fixing roller 100 and the pressure roller 101 are both adjusted to about 180 ° C., and the surface temperature of the external heating roller 102 is adjusted to 185 ° C. The fixing roller 100 is rotationally driven in a direction indicated by an arrow at a peripheral speed of about 120 mm / s by a driving unit (not shown), and the other rollers 101 and 102 are driven to rotate. After the transfer process, the transfer material 105 holding the unfixed toner image 104 on the upper side in FIG. 1 is conveyed in the direction of the arrow by means not shown and enters the fixing device, where the contact roller nip between the fixing roller 100 and the pressure roller 101 110 (about 9 mm). In the nip 110, the transfer material 105 is heated and pressed to fix the image.
[0038]
The normal image formation described here is a basis weight of 60 to 90 g / m which is generally used.² This refers to the case where paper is used as a transfer material.
[0039]
In the image forming apparatus according to the present embodiment, when the offset toner attached to the surface of the fixing roller 100 wraps around the external heating roller 102, the offset toner is removed by executing the cleaning mode as shown in FIG. Removal is possible.
[0040]
That is, first, the temperature of the external heating roller 102 and the fixing roller 100 is adjusted by the control means so that the fixing device is not driven. The temperature adjustment in this cleaning mode is
Surface temperature of external heating roller-Surface temperature of fixing roller
Is made larger than the value during normal image formation. Specifically, in this embodiment, the (surface) temperature of the fixing roller 100 is the first temperature (160 ° C. in this embodiment), and the surface temperature of the external heating roller 102 is the second temperature (190 in this embodiment). ° C). Although the temperature control of the pressure roller 101 is arbitrary, the temperature is preferably the same as or lower than that of the fixing roller 100. In this embodiment, the temperature is set to 150 ° C.
[0041]
After reaching a predetermined temperature, the rollers 100, 101, 102 are driven. According to the inventor's study, the toner tends to easily move from a roller having a high temperature to a roller having a low temperature, and the tendency becomes stronger as the temperature difference increases. Therefore, the offset toner on the external heating roller 102 gradually moves onto the fixing roller 100 and the pressure roller 101 as the roller rotates.
[0042]
After rotating the roller for a certain time (a certain number of times) (10 seconds in this embodiment), the transfer material was passed through the fixing device, and it was already transferred from the external heating roller 102 to the fixing roller 100 and the pressure roller 101. All of the offset toner is fixed on the transfer material, discharged to the outside of the image forming apparatus, and the cleaning mode ends.
[0043]
The larger the temperature difference between the external heating roller 102 and the fixing roller 100, the easier the toner moves. If the temperature of the external heating roller 102 is raised too much, a hot offset occurs and the toner remains on the external heating roller 102. Also, if the temperature of the fixing roller 100 is too low, the temperature of the fixing nip portion becomes lower than the softening point of the toner, the adhesive force of the toner is lost, and the offset toner cannot be transferred to the transfer material. .
[0044]
For example, when the temperature of the fixing roller 100 and the pressure roller 101 is greatly lowered in the cleaning mode as compared with the normal image formation as in the present embodiment, the offset toner is fixed on the transfer material at the normal speed. It may not be cut.
[0045]
In the present embodiment, in the cleaning mode, the temperatures of the fixing roller 100 and the pressure roller 101 are made lower by rotating the rotation speed of the rollers 100, 101, and 102 slower than that during normal image formation (peripheral speed of about 60 mm / s). Even when the toner is low, the offset toner is easily fixed on the transfer material.
[0046]
In the cleaning mode, after the device detects a jam in the fixing device by means (not shown), the user cleans from the operation panel (not shown) of the main body or a host computer (not shown) connected to the device. It is executed at an arbitrary timing during non-image formation such as when a mode is designated.
[0047]
As described above, by providing a cleaning mode in which the transfer material is passed in a state where the temperature difference between the external heating roller 102 and the fixing roller 100 is kept larger than the temperature difference during normal image formation, the offset toner passes to the external heating unit. Even in such a case, by executing the cleaning mode, it is possible to discharge the offset toner onto the transfer material, and thereafter it is possible to prevent the occurrence of a defective image field due to the offset toner.
[0048]
<Embodiment 2>
The schematic configuration of the image forming apparatus in this embodiment has already been shown in FIG. This is the same as the configuration of the image forming apparatus in the conventional example and the first embodiment, and redundant description is omitted. Here, a detailed configuration of the apparatus according to the present embodiment, differences from the conventional example, and effects will be described.
[0049]
FIG. 3 shows a configuration of related portions of the fixing device and the image forming apparatus according to the present embodiment. In the present embodiment, instead of the pressure roller and the external heating roller, those provided with ceramic heaters 131c and 131b inside the endless thin film films 130c and 130b are employed as the external heating device and the pressure device.
[0050]
Thin film 130c, 130b in the present embodiment has a base layer made of polyimide resin having a thickness of 50 μm and a diameter of φ24 mm, and a surface layer made of a high release material such as PEA, for example. Friction force acting at the contact nip portion of the fixing roller 200 is engaged with the ceramic heater 131c, 131b and the film guides 132c, 132b, and rotates in the direction of the arrow. As the base layer of the thin film, another resin or metal may be used.
[0051]
The ceramic heaters 131c and 131b are both 8 mm wide and 700 W in both the external heating side and the pressure side, and are pressed against the fixing roller 200 by a conventionally known pressurizing means with a total pressure of 15 kg. The thermistors 122c and 122b are provided on the non-contact surfaces of the ceramic heaters 131c and 131b with the film, and the temperatures of the heaters 131c and 131b are monitored.
[0052]
On the other hand, the fixing roller 200 is provided with a 3.5 mm-thick silicone rubber elastic layer 141a on an aluminum cored bar 140a having an outer diameter of φ13 mm and an inner diameter of φ9 mm, and further a PEA coating layer having a thickness of 30 μm as a release layer thereon. What provided 142a was used. The temperature of the fixing roller 200 is monitored by the thermistor 121a.
[0053]
In the fixing device as in the present embodiment, the heaters 122c and 122b directly heat the surface of the fixing roller 200 through the thin film films 130c and 130b having a small heat capacity, so that the fixing roller 200 is brought to a predetermined temperature in a shorter time. It can be heated and the rise time of the apparatus can be shortened.
[0054]
During normal image formation, first, the fixing roller 200 is rotationally driven in a direction indicated by an arrow at a peripheral speed of about 120 mm / s by a driving unit (not shown), and accordingly, the film of the pressure device and the external heating device are at substantially the same speed. The employee is rotated. The fixing roller 200 is heated by the external heating device 202 and the pressure device 201, and the temperature is adjusted so that the surface temperature becomes 180 ° C. In the fixing device as in the present embodiment, in order to uniformly heat the surface of the fixing roller 200, heating and temperature control are always performed in a state where the fixing roller 200 is driven.
[0055]
After the transfer process is completed, the transfer material 105 holding the unfixed toner image 104 on the upper side in the drawing is conveyed in the direction of the arrow by means not shown, enters the fixing device, and the contact roller nip 110 between the fixing roller 200 and the pressure device 201. (About 8 mm). In the nip, the transfer material 105 is heated and pressed to fix the image.
[0056]
In the present embodiment, the normal temperatures of the heater of the external heating device 202 and the fixing roller 200 during normal image formation are 190 ° C. and 180 ° C., respectively.
[0057]
Also in the image forming apparatus according to the present embodiment, when the offset toner adhering to the surface of the fixing roller 200 wraps around the external heating device 202 (film), the cleaning mode as shown in FIG. As a result, the offset toner can be removed.
[0058]
That is, first, temperature adjustment is performed by the heaters 131c and 131b of the external heating device 202 and the pressure device 201 so that the fixing roller 200 becomes the first temperature (150 ° C. in the present embodiment). In this case, since the temperature control temperature is low, the use of the heater of the pressure device 201 is arbitrary and may be OFF. Also, as described above, the temperature adjustment is performed while driving the fixing roller 200 at this time, but if the temperature of the fixing roller 200 is 150 ° C. or higher when the cleaning mode is entered, the roller is first cooled in the stopped state, Thereafter, the temperature adjustment may be started by starting driving.
[0059]
After the fixing roller 200 reaches the first temperature, only the heater temperature of the external heating device 202 is raised to the second temperature (190 ° C. in the present embodiment), and after a very short time (3 in the present embodiment). Second), the transfer material 105 is passed through the fixing device.
[0060]
While the heater temperature of the external heating device 202 immediately reaches the second temperature, the temperature of the fixing roller 200 that does not heat itself is slightly higher than the first temperature for a very short time.
[0061]
In such a state,
Heater temperature of external heating device-surface temperature of fixing roller
Can be made larger than that during normal image formation. As a result, as described in the first embodiment, the offset toner can be moved from the external heating device 202 (film surface) to the fixing roller 200 and the pressure device 201, and the offset toner is transferred to the transfer material by passing paper. It is fixed on 105 and can be discharged out of the apparatus.
[0062]
The heater temperature of the pressure device 201 when the heater temperature of the external heating device 202 is raised to the second temperature is arbitrary, but in order not to raise the temperature of the fixing roller 200 more than necessary, the fixing roller 200 It is desirable that the temperature be equal to or lower than the temperature (in this embodiment, 150 ° C. or lower). When the temperature is equal to or lower than the temperature of the fixing roller 200, a large amount of offset toner is collected by the pressure device 201, which is convenient because the offset toner can be kept away from the external heating device 202.
[0063]
On the other hand, when the transfer material 105 passes through the fixing device, if the temperature of the fixing roller 200 or the pressure device 201 is low, the offset toner may not be sufficiently fixed on the transfer material 105. Therefore, the heater temperature of the pressure device 201 may be raised while the transfer material 105 passes through the fixing device.
[0064]
Further, as described in the first embodiment, the rotation speed of the fixing roller 200 in the cleaning mode may be set slower than that during normal image formation.
[0065]
In this embodiment, since the temperature adjustment of the surface of the fixing roller 200 can be performed in a short time, there is an advantage that the time required for the cleaning mode is shorter than that in the first embodiment. The timing for executing the cleaning mode is the same as in the first embodiment.
[0066]
As described above, by providing the cleaning mode in which the transfer material 105 is passed while maintaining the temperature difference between the heater temperature of the external heating device 202 and the surface temperature of the fixing roller 200 larger than the temperature difference during normal image formation, the offset toner is removed. Even in the case where the external heating device 202 wraps around, it is possible to discharge the offset toner onto the transfer material 105 by executing this cleaning mode, and to prevent the occurrence of image defects due to the offset toner thereafter. it can.
[0067]
<Embodiment 3>
The schematic configuration of the image forming apparatus according to the present embodiment has already been shown in FIG. This is the same as the configuration of the conventional example and the image forming apparatus in the first and second embodiments, and a duplicate description is omitted. Here, a detailed configuration of the apparatus according to the present embodiment, differences from the conventional example, and effects will be described.
[0068]
Among the fixing device and the image forming apparatus according to the present embodiment, the configuration of the related portion is shown in FIG.
[0069]
The configuration of the fixing device according to the present embodiment is substantially the same as the configuration of the device according to the second embodiment, except that the thermistor 121a of the fixing roller 200 is omitted. Other external heating device 202, pressure device 201, and fixing roller 200 are the same as those in the second embodiment.
[0070]
The reason why the thermistor of the fixing roller 200 is omitted in the present embodiment is as follows.
[0071]
That is, in particular, when the thermistor that contacts the fixing roller 200 is used in the second embodiment, the surface of the fixing roller 200 may be scraped by friction with the thermistor, and offset toner or paper dust may be formed on the surface of the thermistor. Is accumulated, and sometimes it peels off and stains the image.
[0072]
During normal image formation in the present embodiment, first, the fixing roller 200 is rotationally driven at a peripheral speed of about 120 mm / s in the direction of the arrow by a driving unit (not shown), and accordingly, the film of the pressure device 201 and the external heating device 202 is driven. Is driven and rotated at almost the same speed. Further, the temperature is adjusted so that the temperatures of the heaters 131c and 131b of the external heating device 202 and the pressure device 201 are both 190 ° C. Although there is no means for directly monitoring the surface temperature of the fixing roller 200, the temperature of the fixing roller 200 settles to around 180 ° C. within several tens of seconds by heating in this way.
[0073]
After the transfer process, the transfer material 105 holding the unfixed toner image 104 on the upper side in the drawing is conveyed in the direction of the arrow by means not shown and enters the fixing device, where the fixing roller 200 and the pressure device 201 abut. Pass through the nip 110 (approximately 8 mm). In the nip, the transfer material 105 is heated and pressed to fix the image.
[0074]
In the image forming apparatus according to the present embodiment, when the offset toner adhering to the surface of the fixing roller 200 wraps around the external heating device 202 (on the film 130c), it is almost the same as in the second embodiment as shown in FIG. The offset toner is removed by executing the cleaning mode, but differs in the following points.
[0075]
That is, in this embodiment, when the temperature adjustment is performed so that the fixing roller 200 becomes the first temperature in the cleaning mode, only the heater 131c of the external heating device is used instead of the heater 131b of the pressure device 201, or The thermistor 122b of the pressure device 201 is used for monitoring the temperature of the fixing roller 200.
[0076]
Since the heat capacities of the ceramic heaters 131 c and 131 b and the thin film films 130 c and 130 b are smaller than those of the fixing roller 200, the temperature of the heater 131 b of the pressure device 201 is the temperature of the fixing roller 200 unless the heater 131 b of the pressure device 201 is operated. Close to. That is, the thermistor 122 b of the pressure device 201 can be used for monitoring the temperature of the fixing roller 200.
[0077]
In the present embodiment, the heater 131b of the external heating device 201 is first driven in the cleaning mode so that the heater temperature of the pressure device 201 becomes the third temperature (130 ° C. in the present embodiment) while driving the fixing roller 200. Then, the temperature of the external heating device 201 is raised to a second temperature (180 ° C. in this embodiment) and the transfer material 105 is passed through the fixing device, as in the second embodiment.
[0078]
As described above, according to the present embodiment, even when the thermistor of the fixing roller 200 is omitted, the same cleaning mode as in the second embodiment can be performed, and the same effect can be obtained.
[0079]
<Embodiment 4>
In this embodiment, the configurations of the image forming apparatus and the fixing apparatus are the same as those in the second embodiment, but only the operation in the cleaning mode is different. Here, the apparatus will be described with reference to FIG. 3 in the second embodiment, and the cleaning mode in the present embodiment is shown in FIG.
[0080]
In the cleaning mode of the present embodiment, it is first confirmed that the fixing roller 200 is below a certain fourth temperature (120 ° C. in the present embodiment). When the temperature of the fixing roller 200 is higher than that, the roller is cooled without operating the heater. Thereafter, the temperature of the heater 131c of the external heating device 201 is adjusted to the second temperature (190 ° C. in the present embodiment) while the fixing roller 200 is driven. The temperature rise of the fixing roller 200 is monitored by the thermistor 121a of the fixing roller 200. When the temperature of the fixing roller 200 reaches the first temperature (150 ° C. in this embodiment), the transfer material 105 is passed through the fixing device. The heater temperature of the pressurizing device 201 is arbitrary, but is desirably equal to or lower than the fourth temperature.
[0081]
By executing the cleaning mode as described above, the same effect as that of the second embodiment can be obtained.
[0082]
<Embodiment 5>
In the present embodiment, the configurations of the image forming apparatus and the fixing apparatus are the same as those in the third embodiment, and only the operation in the cleaning mode is different. Here, the description will be made with reference to FIG. 5 in the third embodiment, and the cleaning mode in the present embodiment is shown in FIG.
[0083]
In the cleaning mode of this embodiment, first, the temperature of one or both of the heaters 131c and 131b of the external heating device 202 and the pressurizing device 201 is equal to or lower than a fifth temperature (120 ° C. in this embodiment). Confirm. When the temperature of the heaters 131c and 131b is higher than that, the heaters 131c and 131b are cooled without being operated. Thereafter, the temperature of the heater 131c of the external heating device 202 is adjusted to the second temperature (190 ° C. in this embodiment) while the fixing roller 200 is driven. The heater 131b of the pressure device 201 is not operated, and the temperature rise of the heater 131b is monitored by the thermistor 122b of the pressure device 201, and the heater temperature of the pressure device 201 is the third temperature (140 ° C. in the present embodiment). Is reached, the transfer material 105 is passed through the fixing device.
[0084]
The same effect as in the third embodiment can be obtained by executing the cleaning mode as described above.
[0085]
<Embodiment 6>
In the present embodiment, the configurations of the image forming apparatus and the fixing apparatus are the same as those in the third embodiment, and only the operation in the cleaning mode is different. Here, the description will be made with reference to FIG. 5 in the third embodiment, and the cleaning mode in the present embodiment is shown in FIG.
[0086]
In the cleaning mode of this embodiment, first, the temperature of one or both of the heaters 131c and 131b of the external heating device 202 and the pressurizing device 201 is equal to or lower than a fifth temperature (120 ° C. in this embodiment). Confirm. When the temperature of the heaters 131c and 131b is higher than that, the heaters 131c and 131b are cooled without being operated. Thereafter, with the fixing roller 200 driven, the temperature of one or both of the heaters 131c and 131b of the external heating device 202 and the pressure device 201 is adjusted to the second temperature (190 ° C. in this embodiment). Then, after a certain period of time has passed, the transfer material 105 is passed through the fixing device.
[0087]
The same effect as in the third embodiment can be obtained by executing the cleaning mode as described above.
[0088]
【The invention's effect】
As is apparent from the above description, according to the present invention, at least a fixing member that is in contact with an unfixed developer carrying side of a transfer material carrying an unfixed developer image and can heat the transfer material, and a transfer material In the image forming apparatus comprising a fixing device having an external heating member that contacts the surface of the fixing member and heats the fixing member, and a pressure member that presses the transfer material against the fixing member. A mode in which the transfer material is passed through the fixing device (cleaning mode) in a state where the difference between the surface temperatures of the heating member and the fixing member is large (cleanable state) due to the difference in the surface temperature during normal image formation. Since it is sometimes feasible, it is possible to remove the offset toner that has wrapped around the external heating means.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a fixing device according to a first embodiment of the present invention.
FIG. 2 is a flowchart illustrating an operation procedure of a cleaning mode in the fixing device and the image forming apparatus according to the first embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating a schematic configuration of a fixing device according to a second embodiment of the present invention.
FIG. 4 is a flowchart showing an operation procedure of a cleaning mode in the fixing device and the image forming apparatus according to Embodiment 2 of the present invention.
FIG. 5 is a cross-sectional view illustrating a schematic configuration of a fixing device according to a third embodiment of the present invention.
FIG. 6 is a flowchart illustrating an operation procedure of a cleaning mode in the fixing device and the image forming apparatus according to Embodiment 3 of the present invention.
FIG. 7 is a flowchart showing an operation procedure of a cleaning mode in the fixing device and the image forming apparatus according to Embodiment 4 of the present invention.
FIG. 8 is a flowchart illustrating an operation procedure of a cleaning mode in the fixing device and the image forming apparatus according to Embodiment 5 of the present invention.
FIG. 9 is a flowchart showing an operation procedure of a cleaning mode in the fixing device and the image forming apparatus according to Embodiment 6 of the present invention.
FIG. 10 is a cross-sectional view illustrating a schematic configuration of a conventional image forming apparatus.
FIG. 11 is a cross-sectional view illustrating a schematic configuration of a conventional fixing device.
FIG. 12 is a cross-sectional view illustrating a schematic configuration of a conventional fixing device.
FIG. 13 is a cross-sectional view illustrating a schematic configuration of a conventional fixing device.
[Explanation of symbols]
100 Fixing roller (fixing member)
101 Pressure roller (pressure member)
102 External heating roller (external heating member)
105 Transfer material
120a-120c temperature detection means

Claims (3)

An image forming unit that forms an unfixed toner image on a transfer material, a fixing roller, an external heating unit that has a rotating body that contacts the surface of the fixing roller, and that heats the fixing roller; A fixing unit that heats and fixes the unfixed toner image on the transfer material while sandwiching and transporting the transfer material carrying the unfixed toner image at the fixing nip portion. An image forming apparatus having:
A cleaning mode in which toner is transferred from the fixing roller to the transfer material by removing the toner by conveying the transfer material at the fixing nip, and in the cleaning mode, the temperature of the external heating unit and the surface of the fixing roller The difference is set to be larger than that at the time of normal image formation, and the transfer material is conveyed by the fixing nip portion at a timing when the temperature of the external heating unit and the fixing roller is the temperature difference. Image forming apparatus. The external heating unit includes a heater that is in non-contact with the peripheral surface of the rotating body inside the rotating body, and in the cleaning mode, the difference between the surface temperature of the rotating body and the temperature of the fixing roller is a normal image. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to be larger than that at the time of formation. The external heating unit includes a heater that contacts the outer circumferential surface of the rotating body inside the rotating body, and in the cleaning mode, the temperature difference between the heater and the fixing roller is set higher than that during normal image formation. The image forming apparatus according to claim 1, wherein the image forming apparatus is set large.

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