JP6699184B2 - Fixing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, and a heating type fixing device mounted in such an image forming apparatus.

  In the image forming apparatus, a toner image is formed on an image carrier based on image information, the toner image is transferred onto a recording material such as paper or an OHP sheet, and the recording material carrying the toner image is passed through a fixing device. The toner image is fixed on the recording material by heat and pressure.

  By the way, in recent years, market demands for energy saving and high speed have been increasing.

  On the other hand, by directly heating the endless belt, the energy saving is high and the warm-up time (time required from the normal temperature state to the predetermined printable temperature (reload temperature) such as when the power is turned on) and 2. Description of the Related Art A fixing device is known that can reduce the first print time (the time from the receipt of a print request to the printing operation through the print preparation and the completion of paper discharge) (see, for example, Patent Document 1).

  However, the fixing device described in Patent Document 1 starts the printing operation from a state in which the entire fixing device is cold at the initial stage of sheet passing, so that the temperature sag occurs in the edge portion of the sheet, and the fixing property of the edge portion of the sheet is deteriorated. There is a problem that cannot be secured.

For this, the following measures have been taken conventionally.
The set temperature at the beginning of sheet passing is increased to secure the fixing property at the edge of the sheet (means 1).
The heating area is expanded to secure the fixing property of the edge of the paper (means 2).
By providing the edge heater, the temperature is raised only at the edge to secure the fixability of the edge of the sheet (means 3).

The means 2 has a problem in that the end portion temperature rise in continuous paper feeding after the start of paper feeding is deteriorated and the productivity is lowered.
The means 3 has problems such as cost UP due to the division of heaters and the addition of temperature sensors for controlling the end heaters, and a decrease in heating efficiency due to an increase in heaters.
As shown in FIG. 10, the means 1 can reduce the recovery time, reduce the cost, and reduce the power consumption by raising the set temperature at the initial stage of sheet passing.

  However, as shown in FIG. 11, when a small number of print jobs are repeated many times at short intervals, the fixing device using the means 1 repeats the repeat operation only during the initial period of the sheet passage in which the set temperature is raised. I'm going to make paper. Therefore, there is a problem that the life of the fixing device becomes extremely short.

  Further, in the case of repeating such a small amount of print JOB, it was found that the heat is accumulated in the fixing device as the latter half of the print JOB is repeated, and there is a problem of hot offset of the printed image and deterioration of gloss.

On the other hand, a means has been devised in which a temperature sensor is provided in the fixing device and the sheet passing temperature is lowered based on the detection information of the temperature sensor.
However, the temperature sensor installed in the fixing device measures only the surface temperature of each member and cannot measure the amount of accumulated heat. Therefore, it is difficult to determine the heat storage state of the fixing device from the sensor output.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device having a simple structure that can secure fixing property and long-term life and save energy.

In order to solve the above problems, the fixing device according to claim 1 of the present invention is
A rotatable fixing member,
A heating source for heating the fixing member,
Control means for controlling the heating source so that the temperature of the fixing member becomes a fixing set temperature;
A pressing member that contacts the outer peripheral surface of the fixing member;
A fixing device having a nip forming member located inside the fixing member and contacting the pressure member via the fixing member to form a nip portion between the fixing member and the pressure member. ,
When the printing time of the previous job is longer than the specified time A, and when the next job is started within the specified time B after the end of the previous job, the control means starts the next job. The fixing set temperature lower than the fixing set temperature during the specified time A until the printing paper rushes into the nip part and after the specified time C elapses after the printing paper enters the nip part. Set to
The control means sets the fixing set temperature lower than the fixing set temperature during the specified time C after the specified time C has elapsed .

  According to the present invention, it is possible to provide a fixing device having a simple structure that can secure the fixing property and the long life and save energy.

FIG. 1 is a configuration diagram schematically showing an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram schematically showing a fixing device of the image forming apparatus shown in FIG. 1. 2 is an explanatory diagram illustrating a functional configuration of a control unit of the fixing device illustrated in FIG. 1. FIG. 6 is a flowchart illustrating control of a control unit of the fixing device illustrated in FIG. 1. FIG. 3 is an explanatory diagram illustrating a transition of a target fixing temperature of the fixing device illustrated in FIG. 1. FIG. 3 is an explanatory diagram illustrating a transition of a target fixing temperature of the fixing device illustrated in FIG. 1. FIG. 3 is an explanatory diagram illustrating a transition of a target fixing temperature of the fixing device illustrated in FIG. 1. FIG. 3 is an explanatory diagram illustrating a transition of a target fixing temperature of the fixing device illustrated in FIG. 1. FIG. 3 is an explanatory diagram illustrating a transition of a target fixing temperature of the fixing device illustrated in FIG. 1. It is explanatory drawing explaining the transition of the target fixing temperature of the conventional fixing device. It is explanatory drawing explaining the transition of the target fixing temperature of the conventional fixing device. It is a block diagram which shows schematically the fixing device which concerns on another embodiment.

The configuration of the image forming apparatus according to the embodiment of the present invention will be described below with reference to FIG.
The image forming apparatus shown in FIG. 1 is a color printer using a tandem system in which image forming units for forming a plurality of color images are juxtaposed along the belt extending direction. However, the present invention is not limited to this system, and the printer is not limited thereto. It is also possible to apply not only to a copying machine or a facsimile machine.
In the image forming apparatus 100, the photosensitive drums 20Y, 20C, 20M, and 20Bk as image carriers capable of forming images as images corresponding to the colors separated into yellow, cyan, magenta, and black are arranged in parallel. The tandem structure is used.

  In the image forming apparatus 100 having the illustrated configuration, the visible images formed on the photoconductor drums 20Y, 20C, 20M, and 20Bk are transferred to the photoconductor drums 20Y, 20C, 20M, and 20Bk by performing the primary transfer process. The image is superposed and transferred onto an intermediate transfer member (hereinafter, referred to as a transfer belt) 11 using an endless belt that is movable in the direction of arrow A1 while facing each other. After that, the images on the intermediate transfer member are collectively transferred to the recording medium S using a recording sheet or the like by executing the secondary transfer process.

  Around the respective photosensitive drums, a device for performing image forming processing according to the rotation of the photosensitive drums is arranged. The photoconductor drum 20Bk that forms a black image will be described as an example. A charging device 30Bk, a developing device 40Bk, a primary transfer roller 12Bk, and a cleaning device 50Bk that perform image forming processing are arranged along the rotation direction of the photoconductor drum 20Bk. Has been done. The optical writing device 8 is used for writing performed after charging the photosensitive drum.

  Superimposing transfer on the transfer belt 11 is performed by transferring the visible image formed on each of the photoconductor drums 20Y, 20C, 20M, and 20Bk to the same position on the transfer belt 11 while the transfer belt 11 moves in the A1 direction. As described above, the voltage is applied by the primary transfer rollers 12Y, 12C, 12M, and 12Bk, which are arranged to face the photoconductor drums 20Y, 20C, 20M, and 20Bk with the transfer belt 11 interposed therebetween, and the upstream side in the A1 direction. The timing is shifted toward the downstream side from.

  The photoconductor drums 20Y, 20C, 20M, and 20Bk are arranged in this order from the upstream side in the A1 direction. The photoconductor drums 20Y, 20C, 20M, and 20Bk are provided in image stations for forming yellow, cyan, magenta, and black images, respectively.

  The image forming apparatus 100 is arranged so as to face four image stations that perform image forming processing for each color and above the respective photoconductor drums 20Y, 20C, 20M, and 20Bk, and the transfer belt 11 and the primary transfer roller 12Y. , 12C, 12M, and 12Bk, a secondary transfer roller 5 that is a transfer roller as a transfer member that is disposed so as to face the transfer belt 11, is driven by the transfer belt 11, and rotates together with the transfer belt 11. A cleaning device 13 arranged to face the transfer belt 11 for cleaning the transfer belt 11 and an optical writing device 8 serving as an optical writing device arranged below the four image stations are provided. is doing.

  The optical writing device 8 is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, a rotary polygon mirror as a deflecting means, and the like, and each photosensitive drum 20Y, 20C, 20M, The writing light Lb corresponding to each color with respect to 20 Bk is emitted (in FIG. 1, for convenience, the reference numeral is attached only to the image station of the black image, but the other image stations are also the same) to emit the light beam. It is configured to form an electrostatic latent image on 20Y, 20C, 20M, and 20Bk.

  The image forming apparatus 100 includes a sheet feeding device 61 serving as a paper feeding cassette loaded with a recording medium S conveyed between the photoconductor drums 20Y, 20C, 20M, and 20Bk and the transfer belt 11, and a sheet feeding device 61. The recording medium S conveyed from the feeding device 61 is transferred between the photoconductor drums 20Y, 20C, 20M, and 20Bk and the transfer belt 11 at a predetermined timing corresponding to the timing of forming a toner image by the image station. A pair of registration rollers (positioning roller pair) 4 that is fed toward the sheet and a sensor that detects that the leading end of the recording medium S has reached the pair of registration rollers 4 are provided.

  Further, the image forming apparatus 100 includes a roller fixing type fixing device 200 for fixing the toner image on the recording medium S onto which the toner image has been transferred, and a recording medium S on which the toner image has been fixed. A paper discharge roller 7 that discharges the main body of the image forming apparatus 100, and a paper discharge tray 17 that is disposed above the main body of the image forming apparatus 100 and on which the recording medium S discharged to the outside of the main body of the image forming apparatus 100 is stacked. The toner bottles 9Y, 9C, 9M, and 9Bk, which are located below the paper discharge tray 17 and are filled with toners of yellow, cyan, magenta, and black, are provided.

  The transfer belt unit 10 includes a transfer belt 11, primary transfer rollers 12Y, 12C, 12M, and 12Bk, as well as a driving roller 72 and a driven roller 73 around which the transfer belt 11 is wound.

  The driven roller 73 also has a function as a tension urging unit for the transfer belt 11. For this reason, the driven roller 73 is provided with an urging unit using a spring or the like. The transfer belt 71, the primary transfer rollers 12Y, 12C, 12M, and 12Bk, the secondary transfer roller 5, and the cleaning device 13 constitute a transfer device 71.

  The sheet feeding device 61 is disposed in the lower portion of the main body of the image forming apparatus 100, and has the feeding roller 3 as a paper feeding roller that contacts the upper surface of the uppermost recording medium S. Then, the feeding roller 3 is rotationally driven counterclockwise to feed the uppermost recording medium S toward the registration roller pair 4.

  The cleaning device 13 provided in the transfer device 71 has a cleaning brush and a cleaning blade that are arranged so as to face and contact the transfer belt 11, and remove foreign matter such as residual toner on the transfer belt 11. The transfer belt 11 is cleaned by scraping and removing it with a cleaning brush and a cleaning blade.

  The cleaning device 13 also has a discharging means for carrying out and discarding the residual toner removed from the transfer belt 11.

FIG. 2 is a sectional view showing the fixing device according to the embodiment.
The fixing device 200 has a fixing belt 201 as a fixing member and a pressure roller 203 as a pressure member. A halogen heater 202, which is a heat source, is provided in the fixing belt 201, whereby the fixing belt 201 is directly heated by radiant heat from the inner peripheral side. Further, a nip forming member 206 that forms a nip portion N with the pressure roller 203 via the fixing belt 201 is disposed on the side of the fixing belt 201 that faces the pressure roller 203, and is directly or slid on the inner surface of the fixing belt. It is designed to slide indirectly through a moving seat.

  In the configuration of FIG. 2, the shape of the nip portion N is flat, but it may be concave or any other shape. By forming the concave nip portion, the discharge direction of the leading end of the recording medium is closer to the pressure roller, and the separability of the recording medium from the fixing belt is improved, so that the occurrence of jam is suppressed.

  The fixing belt 201 is a metal belt such as nickel or SUS or an endless belt (or film) using a resin material such as polyimide. The surface layer of the belt has a release layer made of tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer resin (PFA) or tetrafluoroethylene resin (PTFE), and has releasability to prevent toner from adhering. I am making it. An elastic layer formed of a silicone rubber layer or the like may be provided between the belt base material and the PFA or PTFE layer. When the silicone rubber layer is not provided, the heat capacity is reduced and the fixing property is improved. However, when the unfixed image is crushed and fixed in the nip portion N, minute unevenness on the belt surface is transferred to the image and the solid image is formed. There is a problem in that a glossy unevenness of a smooth skin (a rough skin image) remains on the area. To improve this, it is necessary to provide a silicone rubber layer of 100 μm or more. Due to the deformation of the silicone rubber layer, minute irregularities are absorbed, and the image of the discolored skin is improved.

  Further, inside the fixing belt 201, a stay 207, which is a supporting member for supporting the nip portion, is provided to prevent the nip forming member 206 from being bent by the pressure roller 203, thereby preventing the nip forming member 206 from bending. ) So that a uniform nip width can be obtained. The stay 207 is made of a metal material to ensure rigidity. The stay 207 is held and fixed to the side plate at both ends in the axial direction and positioned. Since the nip forming member 206 has a complicated shape, an injection-molded product of a heat-resistant resin is preferable, and as the heat-resistant resin, LCP (heat-resistant temperature of about 330° C.), PEK (heat-resistant temperature of about 350° C.), or the like is preferable. Further, a reflecting member 209 is provided between the halogen heater 202 and the stay 207, and this reflects the radiant heat from the halogen heater 202, thereby suppressing energy waste caused by heating the stay 207 by radiant heat. ..

  Here, instead of providing the reflection member 209, the same effect can be obtained by performing heat insulation treatment or mirror surface treatment on the surface of the stay 207. The heat source may be the halogen heater 202, but may be IH, a resistance heating element, a carbon heater, or the like.

  The pressure roller 203 includes a cored bar 205, an elastic rubber layer 204 provided on the cored bar, and a release layer (PFA or PTFE layer) provided on the surface in order to obtain releasability. The pressure roller 203 is rotated by a driving force transmitted from a driving source such as a motor provided in the image forming apparatus 100 via a gear. The pressure roller 203 is pressed against the fixing belt 201 by a spring or the like, and has a predetermined nip width when the elastic rubber layer 204 is crushed and deformed.

  The pressure roller 203 may be a hollow roller, or may have a heat source such as a halogen heater inside the pressure roller 203. The elastic rubber layer 204 may be solid rubber, but sponge rubber may be used when there is no heater inside the pressure roller 203. The use of sponge rubber is more desirable because the heat insulating property is improved and the heat of the fixing belt 201 is less likely to be taken away.

The fixing belt 201 is rotated together with the pressure roller 203. In the case of the fixing device 200 of FIG. 2, the pressure roller 203 is rotated by a driving source, and the driving force is transmitted to the fixing belt 201 at the nip portion N, whereby the fixing belt 201 is rotated. The fixing belt 201 rotates while being sandwiched between the nip portions N, and is guided by the holding members (flange) 208 at both end portions other than the nip portion and runs. The recording medium S is heated and pressed when passing through the nip portion N, and a fixing process is performed.
With the above configuration, it is possible to realize a fixing device that is inexpensive and that warms up quickly.

Next, the functional configuration of the control unit 90 as the control means will be described.
As shown in FIG. 3, the control unit 90 has a CPU 90a as an arithmetic unit, a ROM 90b as a storage unit, a RAM 90c as a non-volatile memory, and the like. The control unit 90 is connected to the printing time measuring unit 81 and acquires information on the printing time (paper passing time) measured by the printing time measuring unit 81. The control unit 90 is also connected to the timer 82 and acquires information on the time measured by the timer 82. The control unit 90 sets the target fixing temperature (fixing set temperature) of the fixing device 200 based on the print job instruction (print instruction), the print time measured by the print time measuring unit 81, the time measured by the timer 82, and the like. The halogen heater 202 is controlled so that The control unit 90 controls the entire apparatus, and controls the drive of each device based on a control program stored in the RAM 50c or the ROM 50b. Note that the print JOB is a group of image forming processes (or a printing operation output by one print request) performed in response to one print request, and when an image is formed on one sheet. In some cases, an image is formed by continuously passing a plurality of sheets.

  Next, the control of the halogen heater 202 performed by the control unit 90 will be described with reference to the flowchart of FIG. It should be noted that the flow charts are merely explanations of an example of a routine capable of exhibiting the action of the present invention in the present embodiment, and other flow charts can be applied as long as the action of the present invention can be exerted. Needless to say.

  The stipulated time A is a paper passing time determination threshold value of the previous print JOB (previous JOB) for determining whether or not to execute this control. The specified time B is the time from the end of the previous job to the start of the next print job (next job), that is, the JOB interval time, when it is determined whether or not this control is performed. The specified time C is the time from the time of entry into the nip portion N, which requires temperature correction for the initial sheet passing temperature of the next JOB.

First, when the print process is started and the print job is completed (step S10), the control unit 90 determines whether or not the print process is completed (step S11).
When it is determined that the print processing is to be ended, the print processing is ended.
On the other hand, when it is determined that the print processing is not ended, the control unit 90 determines whether or not the print time of the previous print JOB (previous JOB)>specified time A is satisfied (step S12).
If it is determined that the print time of the previous job>the specified time A, it proceeds to step S18.
On the other hand, when it is determined that the print time of the previous job>the specified time A, the control unit 90 determines whether or not there is a print job next (step S13).
If it is determined that there is no next print job, the process returns to step S13.
On the other hand, when it is determined that there is the next print job, the control unit 90 determines whether or not the time from the end of the previous job to the start of the next print job (next job) is less than the specified time B (step S14). ).
When it is determined that the time from the end of the previous job to the start of the next job is less than the specified time B, the control unit 90 corrects the target fixing temperature at the initial stage of sheet passing and executes the print job (step S15), and step S16. Proceed to.
On the other hand, when it is determined that the time from the end of the previous job to the start of the next job is not less than the specified time B, the control unit 90 controls the target fixing temperature at the initial stage of sheet passing and executes the print job (step S18), and the step Proceed to S16.
In step S16, when the time after entering the nip portion N=the specified time C, the control unit 90 controls the target fixing temperature in the latter half of the sheet passing and executes print JOB (step S16). That is, the control unit 90 corrects the fixing set temperature after the start of the next JOB until the print sheet rushes into the nip portion N, and until the specified time C elapses after rushing into the nip portion N. To do.
Next, when the print job is completed (step S17), the process returns to step S11, and steps S12 to S18 are repeated until the print is completed.

Next, referring to FIG. 5, the control of the halogen heater 202 performed by the control unit 90 will be described in association with the flowchart.
FIG. 5 shows the transition of the target fixing temperature when the printing operation of the previous job exceeds the specified time A and the printing operation of the next job is started within the specified time B after the printing operation is completed. Step S10→step S11 → Step S12 → Step S13 → Step S14 → Step S15 → Step S16

  In this case, the target fixing temperature is corrected from the start of the next JOB to the time when the print sheet rushes into the nip portion N and from the time when the print sheet rushes into the nip portion N until the specified time C elapses. That is, the target fixing temperature at the beginning of the next job in sheet passing can be lowered within the specified time B because the heat of the previous job is accumulated. As a result, it is possible not to always raise the set temperature at the initial stage of sheet passing. Therefore, deterioration of parts can be suppressed. Further, it is possible to prevent hot offset and deterioration of gloss when a small amount of printing JOB is repeated.

Note that at least one of the specified time A, the specified time B, the specified time C, and the correction amount of the target fixing temperature can be appropriately changed.
For example, as shown in FIG. 6, when the previous job finishes after exceeding the specified time A, the shorter the printing time of the previous job, the shorter the specified time B and the specified time C need to be set. It is necessary to reduce the correction amount of the target fixing temperature at the initial stage of sheet passing.

  On the other hand, as shown in FIG. 7, when the previous job finishes after exceeding the specified time A, the longer the printing time of the previous job, the longer the specified time B and the specified time C can be set, and the next job It is possible to increase the correction amount of the target fixing temperature of.

  Therefore, a plurality of combinations of the specified time A, the specified time B, and the specified time C are prepared in advance, and the optimum combination of the specified time A, the specified time B, and the specified time C is appropriately selected according to the printing time of the previous job. Is desirable.

  By the way, the amount of heat stored in the fixing device changes for each print mode. The print mode refers to a known mode in which printing is performed based on the process linear velocity, paper thickness, color mode, paper size, and the like.

  When this print mode is different, the amount of heat stored in the fixing device is different. For example, the heat storage amount when the paper is passed at a high linear velocity and high temperature for a certain period of time is different from the heat storage amount when the paper is passed at a low linear velocity and a low temperature for a certain period. Therefore, it is desirable that the specified time A and the specified time B are appropriately determined based on the print mode of the previous job, and the specified time C and the correction amount of the fixing set temperature are appropriately determined based on the print mode of the next job. ..

  Further, the target fixing temperature cannot be similarly corrected depending on the combination of the previous JOB and the next JOB print modes. Therefore, the specified time A, the specified time B, the specified time C, and the target fixing temperature correction amount are appropriately selected based on the relationship between the previous JOB and the next JOB print modes. As a result, in the next job, the specified time A, the specified time B, the specified time C, and the correction amount of the target fixing temperature can be set more appropriately.

  It is desirable that the specified time C be specified so as to correspond to a preset set time of the target fixing temperature at the initial stage of sheet passing. The set time of the target fixing temperature in the initial stage of sheet passing is the time required to raise the set temperature in order to secure the fixability of the edge of the paper. Then, the target fixing temperature can be corrected in the next job until the specified time C has elapsed. At this time, the corrected target fixing temperature cannot be lower than the target fixing temperature in the latter half of the sheet passing. Therefore, the upper limit of the correction amount of the target fixing temperature needs to be a temperature obtained by raising the target fixing temperature in the initial stage of sheet passing.

It should be noted that the specified time C and the correction amount of the target fixing temperature may be specified depending on the relationship between the previous job and the next job regardless of the time when the target fixing temperature at the initial stage of sheet passing is increased.
In this case, as shown in FIG. 8, when the specified time C is set shorter than the time (initial temperature correction time) for raising the target fixing temperature at the beginning of paper passing, after the specified time C has elapsed, It is not necessary to raise the temperature until the time for raising the target fixing temperature elapses. Therefore, it is desirable to maintain the same set temperature until the time for raising the target fixing temperature in the initial stage of sheet passing elapses after the stipulated time C has elapsed.

  Further, when the specified time C is set longer than the time for raising the target fixing temperature in the initial passage of the paper, as shown in FIG. It is desirable to finish the temperature correction.

  It is desirable that the printing time be counted, for example, starting from the time when the printing operation of one JOB is started and ending when the printing operation of the JOB is ended. Thereby, the heat storage amount of the fixing device can be determined more accurately. The timing to start lighting the heater may change depending on the image forming apparatus. For this reason, it is desirable to select an appropriate timing for counting the printing time according to the model.

  Further, it is desirable that the counting of the printing time is corrected when the paper interval time changes during the counting of the printing time of JOB. For example, when the paper interval continues for a long time, such as during process control, the paper does not take heat from the fixing device, so that heat storage is promoted. Therefore, the heat storage state cannot be properly predicted. Therefore, if there is a change in the inter-paper time during the counting of the print time of JOB, the count of the print time is corrected more. As a result, the amount of heat stored in the fixing device can be determined more accurately. Since the correction amount of the target fixing temperature depends on the heat storage amount within the specified time, it is desirable to specify it in consideration of the heat capacity of the fixing unit, the target fixing temperature when the paper interval continues for a long time, and the like. .

  It should be noted that if there is a change in the paper interval time during the printing time counting, the method is not limited to the method of correcting the printing time count. For example, the specified time A, the specified time B, the specified time C, and the target fixing temperature correction amount May be changed as appropriate.

Next, a modified example of the fixing device of this embodiment will be described. It should be noted that configurations common to the above-described embodiment are denoted by corresponding reference numerals and detailed description thereof is omitted, and different configurations will be described in detail with reference to the drawings.
FIG. 12 is a configuration diagram schematically showing a modified example of the fixing device according to the present embodiment.
The fixing device of the present modification differs from the fixing devices of the above-described embodiments in that it has a heat transfer assisting member also called a heat equalizing member that moderates the temperature gradient in the longitudinal direction of the fixing belt.

  The heat transfer auxiliary member 311 is provided on the surface of the nip forming member 306 on the nip portion N side. The heat transfer auxiliary member 311 is made of, for example, a metal plate having good heat conductivity such as copper or aluminum. The thickness of the heat transfer assisting member 311 can be appropriately selected, but can be, for example, 0.3 to 0.5 mm. As a result, the heat is positively moved in the width direction of the fixing belt 201, that is, in the longitudinal direction of the heat transfer auxiliary member 311, and the temperature gradient in the longitudinal direction is moderated.

  A sliding sheet 312 may be provided on the nip forming member 306. Specifically, the sliding sheet 312 is provided on the surface of the nip forming member 306 facing the inner peripheral surface of the fixing belt 201. The sliding sheet 312 is a sheet-shaped member provided to reduce the sliding resistance between the fixing belt 201 and the nip forming member 306.

  The sliding sheet 312 is preferably impregnated with a lubricant in order to reduce the load due to friction. As a result, it is possible to reduce friction, suppress an increase in torque, reduce the load on the drive source, and prevent damage to the drive source. In addition, slippage can be prevented and abnormal images can be prevented from occurring.

  The method of attaching the sliding sheet 312 to the nip forming member 306 is not limited, but for example, the sliding sheet 312 is wound around the nip forming member 306 and an adhesive means (for example, double-sided tape) and a fastening means (for example, screw) are attached to the nip forming member 306. The method of fixing by any at least one is mentioned.

  By fixing the sliding sheet 312 so as to be in close contact with the nip forming member 306, it is possible to prevent the generation of gaps and wrinkles due to deformation and displacement, and to prevent the impregnated lubricant from leaking due to breakage or expansion and contraction. it can.

  Also in such a fixing device 300, the control of the halogen heater 202 performed by the control unit 90 described in the above-described embodiment can be executed, and it is possible not to always increase the set temperature in the initial stage of sheet passing. Therefore, deterioration of parts can be suppressed, and hot offset and gloss reduction can be prevented when a small number of printing jobs are repeated.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, in the above-described embodiment, the number of printed sheets may be specified instead of the specified time A and the specified time C. In this case, instead of counting the print time of the previous job, the number of printed sheets of the previous job is counted. Further, instead of correcting the printing time count when the paper interval continues for a long time, the number of printed sheets is corrected.

  The materials and dimensions of the components introduced in the above-described embodiments are merely examples, and it goes without saying that various materials and dimensions can be selected within the range in which the effects of the present invention can be exerted.

201 fixing belt (an example of fixing member)
202 Halogen heater (an example of heat source)
203 pressure roller (an example of pressure member)
90 control unit (an example of control means)
206 Nip forming member N Nip part

JP, 2007-233011, A

Claims (7)

A rotatable fixing member,
A heating source for heating the fixing member,
Control means for controlling the heating source so that the temperature of the fixing member reaches a fixing set temperature;
A pressing member that contacts the outer peripheral surface of the fixing member;
A fixing device having a nip forming member located inside the fixing member and contacting the pressure member via the fixing member to form a nip portion between the fixing member and the pressure member. ,
When the printing time of the previous job is longer than the specified time A, and the next job is started within the specified time B after the end of the previous job, the control means starts the next job. The fixing set temperature lower than the fixing set temperature during the specified time A until after the printing paper rushes into the nip part and after the specified time C has elapsed after entering the nip part. Set to
The fixing device is characterized in that the control means sets a fixing set temperature lower than a fixing set temperature during the specified time C after the specified time C has elapsed . The fixing device according to claim 1, wherein at least one of the specified time A, the specified time B, the specified time C, and the amount of decrease in the set fixing temperature can be appropriately changed. The specified time A and the specified time B are appropriately determined based on the print mode of the previous job,
The fixing device according to claim 2, wherein the prescribed time C and the amount of decrease in the set fixing temperature are appropriately determined based on the print mode of the next job. The prescribed time A, the prescribed time B, the prescribed time C, and the amount of decrease in the set fixing temperature are appropriately determined based on the relationship between the print mode of the previous JOB and the print mode of the next JOB. The fixing device described in 1.   5. The printing time of the previous job starts counting from the time when the previous job starts the printing operation, and ends counting when the previous job finishes the printing operation. The fixing device according to item 1.   The fixing device according to claim 5, wherein when there is a change in the inter-paper time during the previous job, the printing time of the previous job is corrected.   An image forming apparatus comprising the fixing device according to claim 1.

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