JP2018097030A - Fixing device and image forming apparatus - Google Patents

Abstract

Kind Code: A1 An object of the present invention is to prevent image defects and high-temperature slippage due to the effects of edge temperature rise when large-size sheets are passed after successive small-size sheets are passed through a fixing device. In a fixing device (200), when the paper passing width of a succeeding job in successive paper passing jobs is wider than the paper passing width of an immediately preceding job and the driving torque for driving a fixing belt (201) increases, To provide a predetermined waiting time when switching from an immediately preceding job to a succeeding job. The predetermined waiting time is set according to the drive torque increase condition. A predetermined waiting time can be set according to the count value by counting the cumulative number of sheets passed since the start of use of the apparatus. [Selection drawing] Fig. 2

Description

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

In recent years, in the image forming apparatuses such as printers, copiers, and facsimiles, market demands for energy saving and high speed are increasing.
In the above image forming apparatus, a toner image (unfixed toner image) formed by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording is directly or via an intermediate transfer member, a recording material sheet, printing paper, photosensitive. The toner image is transferred onto a recording medium such as paper or electrostatic recording paper, and the recording medium carrying the toner image is passed through a fixing device to fix the toner image on the recording medium.

  As a fixing device for fixing an unfixed toner image, a contact heating method fixing device such as a heat roller method, a film heating method, and an electromagnetic induction heating method is widely used. As an example of such a fixing device, a belt-type fixing device (for example, Patent Document 1) and a surf fixing (film fixing) fixing device (for example, Patent Document 2) using a ceramic heater are known.

  With regard to the belt-type fixing device, it is possible to warm the entire endless belt, shorten the first print time, eliminate the lack of heat during high-speed rotation, and is good even when mounted on a high-production image forming device There has been proposed a fixing device capable of obtaining excellent fixing properties (Patent Document 3).

  In the fixing device shown in FIG. 1 of Patent Document 3, a pipe-shaped metal heat conductor is fixed inside an endless belt so as to be able to guide the movement of the endless belt, and a heat source in the metal heat conductor is obtained. To heat the endless belt through the metal heat conductor. Further, a pressure roller that forms a nip portion in contact with the metal heat conductor via an endless belt is provided, and the endless belt is moved in the circumferential direction so as to rotate along with the rotation of the pressure roller. With this configuration, it is possible to warm the entire endless belt constituting the fixing device, to shorten the first print time from the heating standby time, and to solve the shortage of heat during high-speed rotation. Yes.

  However, in order to further save energy and improve the first print time, it is necessary to further improve the thermal efficiency, and it is not a configuration in which the endless belt is indirectly heated through the metal heat conductor, but not through the metal heat conductor. A configuration in which the endless belt is directly heated is proposed (for example, Patent Document 4). With this configuration, the heat transfer efficiency can be greatly improved to reduce power consumption, and the first print time can be further shortened. In addition, the cost can be reduced because there is no metal heat conductor.

Further, with the downsizing of the fixing device, the diameter of the endless belt is reduced, the distance between the halogen heaters in the cross section of the fixing device is shortened, and the irradiation efficiency is improved.
However, on the other hand, the heat capacity of the endless belt is generally very small, and the temperature at the non-sheet passing portion rises when a small-sized sheet is continuously fed with respect to the heater emission length. It will be greatly affected by the rise. In the large-size sheet passing mode after the small-size continuous sheet passing, the glossiness decreases when the large-size sheet is passed while the temperature of the large-size sheet passing area is increased due to the temperature rise at the edge of the small-sized sheet. In addition to image defects such as hot offset, hot slip occurs.

  As a means to solve this problem, temperature detecting means is arranged in the small size paper passing portion and the non-paper passing portion, and in the large size paper passing mode after the small size continuous paper passing, the passage after the small size continuous paper passing is performed. There has been proposed a fixing device that detects the temperature of a paper portion and a non-sheet passing portion and waits for passing a large size paper until the temperature difference disappears (Patent Document 5).

  Furthermore, instead of setting the waiting time for large-size sheet passing only by temperature, depending on the number of small-sized sheets that are continuously passed (the degree of edge temperature rise) and the image size of the large-sized image after the small size, There has been proposed a fixing device that saves unnecessary waiting time by setting a waiting time (Patent Document 6).

  However, as a result of the rise in the edge temperature, in addition to the large-size image defect in the large-size sheet passing mode after the small-size continuous sheet passing, water vapor is generated from the sheet during heating, which is called high-temperature slip, and the fixing belt and the paper As a result, the paper conveyance force is weakened due to a decrease in the frictional force between the two, which may cause a paper jam. In particular, in an image forming apparatus called a medicine bag machine used in hospitals or the like, a paper bag (medicine bag) equivalent to cardboard for storing medicine and a paper (medicine information) equivalent to plain paper on which medicine information is written are printed as a set, Many large-sized drug information passing modes after continuous passing of small-sized medicine bags can be performed. In addition, since the medicine bag is equivalent to cardboard, the degree of the end temperature rise due to the small-size continuous paper passing increases, and therefore, the medicine bag machine is likely to generate high temperature slip.

  Accordingly, it is an object of the present invention to provide a fixing device and an image forming apparatus that can solve the above-described problems in the fixing device and can prevent image defects and high-temperature slip due to the influence of an increase in end temperature.

  In order to solve this problem, the present invention includes a rotatable fixing member, a heating unit that heats the fixing member, and a pressure member that is pressed against the fixing member to form a nip portion. In a fixing device that passes a recording material carrying an unfixed toner image on the recording material and fixes the unfixed toner image on the recording material, in a continuous paper passing job, the paper passing width of the subsequent job is wider than the paper passing width of the immediately preceding job, In addition, when the driving torque for driving the fixing member increases, a predetermined waiting time is provided when switching from the immediately preceding job to the succeeding job, and the predetermined waiting time is a condition for increasing the driving torque. It is characterized by being set accordingly.

  According to the present invention, when the force for driving the fixing member correlated with the high temperature slip = the driving torque is increased, the sheet passing waiting time is provided in the large size sheet passing mode after the small size continuous sheet passing, High temperature slip can be prevented by lowering the temperature of the place where the edge temperature rises and then passing large size paper.

1 is a configuration diagram illustrating an outline of a printer as an example of an image forming apparatus equipped with a fixing device according to the present invention. 1 is a diagram illustrating a first embodiment of a fixing device. FIG. It is a flowchart which shows the control in 1st Embodiment. 6 is a graph showing a temperature transition of a fixing belt when small-size paper is continuously fed. It is a figure which shows 2nd Embodiment of a fixing device. It is a figure which shows the rotation detection mechanism with which the fixing device is provided. It is a schematic diagram which shows an example of the detection signal by a rotation detection means.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view showing an example of an image forming apparatus equipped with a fixing device according to the present invention. The image forming apparatus 100 shown in this figure is a tandem color printer in which image forming units for forming a plurality of color images are juxtaposed along the belt extending direction. However, the image forming apparatus is not limited to this method. It is also possible to target not only printers but also copying machines and facsimile machines.

  The image forming apparatus 100 includes photosensitive drums 20Y, 20C, 20M, and 20Bk as image carriers that can form images as images corresponding to colors separated into yellow, cyan, magenta, and black, respectively. The tandem structure is adopted.

  In the image forming apparatus 100, an intermediate transfer member (hereinafter referred to as an endless belt) in which a visible image formed on each of the photosensitive drums 20Y, 20C, 20M, and 20Bk can move in the direction of arrow A1 while facing the respective photosensitive drums. (Referred to as a transfer belt) 11. By executing the primary transfer process, the images of the respective colors are superimposed and transferred, and then transferred to the recording material S on which the recording sheet or the like is used by performing a secondary transfer process.

  Around each photosensitive drum, an apparatus for image forming processing is arranged according to the rotation of the photosensitive drum. The photosensitive drum 20Bk that performs black image formation will be described as a representative. A charging device 30Bk, a developing device 40Bk, a primary transfer roller 12Bk, and a cleaning device 50Bk that perform image forming processing along the rotation direction of the photosensitive drum 20Bk are arranged. ing. The optical writing device 8 is used for writing using the writing light Lb performed after charging.

  In the superimposing transfer on the transfer belt 11, the visible image formed on each of the photosensitive drums 20 </ b> Y, 20 </ b> C, 20 </ b> M, and 20 </ b> Bk is transferred to the same position on the transfer belt 11 while the transfer belt 11 moves in the A1 direction. Is done. For this reason, the transfer is performed in the A1 direction by applying a voltage from the primary transfer rollers 12Y, 12C, 12M, and 12Bk disposed opposite to the photosensitive drums 20Y, 20C, 20M, and 20Bk with the transfer belt 11 interposed therebetween. The timing is shifted from the upstream side toward the downstream side.

  The photosensitive drums 20Y, 20C, 20M, and 20Bk are arranged in this order from the upstream side in the A1 direction. Each of the photosensitive drums 20Y, 20C, 20M, and 20Bk is provided in an image station for forming yellow, cyan, magenta, and black images, respectively.

  The image forming apparatus 100 is disposed so as to face four image stations that perform image forming processing for each color and above each of the photosensitive drums 20Y, 20C, 20M, and 20Bk, and includes a transfer belt 11 and a primary transfer roller 12Y. , 12C, 12M, and 12Bk, a secondary transfer roller 5 that is arranged to face the transfer belt 11 and is driven by the transfer belt 11, and is arranged to face the transfer belt 11. A belt cleaning device 13 is provided for cleaning the transfer belt 11, and an optical writing device 8 is provided oppositely below these four image stations.

  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 rotating polygon mirror as a polarizing means, and the like. The optical writing device 8 emits writing light Lb corresponding to each color to each of the photosensitive drums 20Y, 20C, 20M, and 20Bk to form an electrostatic latent image on the photosensitive drums 20Y, 20C, 20M, and 20Bk. It is configured as follows. In FIG. 1, for the sake of convenience, the writing light Lb is labeled only for the image station of the black image, but the same applies to the other image stations.

  The image forming apparatus 100 is provided with a sheet feeding device 61 as a paper feeding cassette on which recording materials S conveyed between the photosensitive drums 20Y, 20C, 20M, and 20Bk and the transfer belt 11 are stacked. Yes. Further, the recording material S conveyed from the sheet feeding device 61 is directed toward the transfer portion between each photosensitive drum and the transfer belt 11 at a predetermined timing in accordance with the toner image formation timing by the image station. A pair of registration rollers 4 is provided. In addition, a sensor that detects that the leading edge of the recording material S has reached the registration roller pair 4 is provided.

  The image forming apparatus 100 also includes a roller fixing type fixing device 200 and a fixed recording material S as the fixing unit for fixing the toner image to the recording material S to which the toner image is transferred. A discharge roller 7 is provided for discharging to the outside of the main body. In addition, a discharge tray 17 on which the recording material S discharged to the outside of the main body of the image forming apparatus 100 by the discharge roller 7 is stacked is provided on the upper part of the main body of the image forming apparatus 100. Further, toner bottles 9Y, 9C, 9M, and 9Bk filled with yellow, cyan, magenta, and black toners are provided below the paper discharge tray 17.

  The transfer belt unit 10 includes a drive roller 72 and a driven roller 73 around which the transfer belt 11 is wound, in addition to the transfer belt 11 and the primary transfer rollers 12Y, 12C, 12M, and 12Bk.

  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. Such a transfer belt unit 10, 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 at the lower part of the main body of the image forming apparatus 100, and has a feeding roller 3 that contacts the upper surface of the uppermost recording material S. The uppermost recording material S is fed toward the registration roller pair 4 by driving the feeding roller 3 counterclockwise in the drawing.

  Although not shown in detail, the cleaning device 13 provided in the transfer device 71 has a cleaning brush and a cleaning blade disposed so as to face and contact the transfer belt 11. The cleaning device 13 cleans the transfer belt 11 by scraping and removing foreign matters such as residual toner on the transfer belt 11 with a cleaning brush and a cleaning blade. The cleaning device 13 also has discharge means for carrying out and discarding the residual toner removed from the transfer belt 11.

FIG. 2 is a schematic configuration diagram illustrating the fixing device according to the first embodiment.
The fixing device 200 includes a fixing belt 201 as a rotatable fixing member and a pressure roller 203 as a pressure member that is disposed opposite to the fixing belt 201 and can rotate, and includes halogen heaters 202A as a plurality of heating units. The fixing belt 201 is directly heated by the radiant heat from the inner peripheral side by 202B.

  A nip forming member 206 that forms a nip portion with the pressure roller 203 via the fixing belt 201 is disposed in the loop of the fixing belt 201, and indirectly through the inner surface of the fixing belt and the heat transfer auxiliary member 216. It comes to slide on. The toner image on the recording material S is fixed by being heated and pressurized at the nip portion.

  In FIG. 2, the shape of the heat transfer assisting member 216 is flat, but may be a concave shape or other shapes. In the case of the concave nip portion, the discharge direction of the leading end of the recording material is closer to the pressure roller, and the separation is improved, so that the occurrence of jam is suppressed.

  Inside the loop of the fixing belt 201, a nip forming member 206 disposed opposite to the pressure roller 203, end heaters 226 as end heat sources integrally provided at both ends of the nip forming member 206, a nip A heat transfer assisting member 216 that covers the forming member 206 and a surface of the end heater 226 that faces the inner surface of the fixing belt 201; and a stay member 207 that holds the nip forming member 206 against the pressure applied from the pressure roller 203. have. The end heaters 226a and 226b at both ends in the longitudinal direction are provided independently and do not have a continuous shape.

The nip forming member 206, the heat transfer assisting member 216, and the stay member 207 all have a length that extends in the axial direction of the fixing belt 201 (hereinafter referred to as “longitudinal direction”).
The heat transfer auxiliary member 216 is provided to prevent the heat of the end heater 226 from staying locally, and to positively move the heat in the longitudinal direction to reduce the temperature non-uniformity in the longitudinal direction. .

  For this reason, the heat transfer auxiliary member 216 is preferably a material that can transfer heat in a short time, and is preferably a member such as copper, aluminum, or silver having high thermal conductivity. In consideration of cost, availability, thermal conductivity characteristics, and workability, it is most desirable to use copper.

In the present embodiment, the surface of the heat transfer assisting member 216 that faces the inner surface of the fixing belt 201 is a surface that directly contacts the fixing belt 201 and serves as a nip forming surface.
The fixing belt 201 is composed of 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 such as a PFA or PTFE layer, and has a release property so that toner does not adhere. There may be an elastic layer formed of a silicone rubber layer or the like between the belt substrate and the PFA or PTFE layer. When there is no silicone rubber layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, minute irregularities on the belt surface are transferred to the image, and the image has a crusty skin shape. There may be a problem that the gloss unevenness (skin skin image) remains. In order 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, fine irregularities are absorbed and the skin image is improved.

  The stay member 207 has a shape having an upright portion that is erected on the side opposite to the nip N side. Halogen heaters 202A and 202B serving as fixing heat sources are disposed across the upright portion, and the fixing belt 201 includes the halogen heater 202A, It is directly heated by radiant heat from the inner surface side by 202B.

  A stay 207 as a support member for supporting the nip forming member 206 and the nip portion N is provided inside the fixing belt 201 to prevent the nip forming member 206 that receives pressure from the pressure roller 203 from being bent in the axial direction. A uniform nip width is obtained. The stay 207 is held and fixed and positioned at flanges as holding members at both ends. In addition, a reflection member 209 is provided between the halogen heater 202 and the stay 207, and wasteful energy consumption due to the stay 207 being heated by radiation heat from the halogen heater 202 or the like is suppressed. Here, instead of providing the reflecting member 209, the same effect can be obtained even if the surface of the stay 207 is heat-insulated or mirror-finished.

  In the pressure roller 203, an elastic rubber layer 204 is laminated on a cored bar 205, and a release layer (PFA or PTFE layer) is 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 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, and the pressure roller 203 may have a heating source such as a halogen heater. The elastic rubber layer 204 may be solid rubber, but if there is no heater inside the pressure roller 203, sponge rubber may be used. Sponge rubber is more desirable because it increases heat insulation and makes it difficult for the fixing belt to lose heat.

  The fixing belt 201 rotates along with the pressure roller 203. In the case of FIG. 2, the pressure roller 203 is rotated by a driving source, and the driving force is transmitted to the belt at the nip portion N, whereby the fixing belt 201 is rotated. The fixing belt 201 is sandwiched and rotated at the nip portion N, and travels by being guided by flanges 208 (not shown) at both ends other than the nip portion.

With the above configuration, it is possible to realize a fixing device that is inexpensive and has a fast warm-up.
Next, a specific configuration and control for preventing a large-size high-temperature slip due to an edge temperature rise due to the small-size continuous sheet passing in the large-size sheet passing mode after the small-size continuous sheet passing will be described.

  As shown in the flow of FIG. 3, it is first determined whether or not the sheet passing mode is a large size sheet passing mode after small size continuous sheet passing (S1). That is, it is determined whether or not the subsequent sheet passing width is wider than the preceding job passing width in the continuous sheet passing job. If it is the large-size sheet passing mode after the small-size continuous sheet-passing (if the sheet-passing width of the succeeding job is wider than the sheet-passing width of the immediately preceding job), the process proceeds to S2, and is counted by the cumulative sheet passing condition, here the counter mechanism. Read the value of the cumulative number of sheets passed since the start of device use. In S3, it is determined whether or not the read value is equal to or greater than a predetermined value (threshold value).

  If the value of the accumulated paper passing condition that has been read (here, the cumulative number of papers to be passed) is equal to or greater than the threshold value, the fixing belt 201 is idled for a set time after the small-size continuous paper feeding (a predetermined waiting time is provided). Thereafter, large-size paper is fed (S4, S5).

On the other hand, if the read value is less than the threshold value, the process proceeds to S6, and normal paper feeding is performed.
By the above control, high temperature slip can be prevented in this embodiment. The reason why high temperature slip can be prevented by the above configuration and control will be described below.

  It has been found that there is a correlation between the high temperature slip and the torque for driving the fixing member (the fixing belt 201 in the present embodiment). When the driving torque is high, the high temperature slip is likely to occur, and when the driving torque is low, the high temperature slip is unlikely to occur. In addition, this driving torque increases (increases) as the cumulative number of sheets passed increases, so that the higher the cumulative number of sheets passed, the easier the high temperature slip occurs.

  Therefore, by providing a waiting time for large-size paper passing from the normal paper-passing state when high-temperature slip is likely to occur, the waiting time is increased due to an increase in the edge temperature due to small-sized continuous paper feeding. The temperature of the belt 201 is lowered, and high temperature slip can be avoided. Although there is a concern about productivity decline due to the installation of the waiting time, it is considered to be given priority in consideration of the possibility of paper jams due to high temperature slip.

  In this embodiment, the waiting time for large-size sheet passing is changed according to the count value (cumulative sheet passing number) as the driving torque increase condition. Table 1 shows the large-size sheet passing waiting time (time for idling the fixing belt 201) set in accordance with the accumulated sheet passing number in S4 in the above flow.

なお、表１に示す累積通紙枚数および大サイズ通紙待ち時間は一例であり、定着装置の構成等により、適宜設定されるものである。

Note that the accumulated sheet passing number and the large-size sheet passing waiting time shown in Table 1 are examples, and are appropriately set depending on the configuration of the fixing device.

  As explained above, the higher the driving torque = the cumulative number of sheets passed, the greater the possibility of high-temperature slipping. Therefore, when the waiting time is set longer and, on the contrary, when the driving torque = the cumulative number of sheets is low, it is possible to prevent the high temperature slip according to the state of the driving torque by shortening the larger size waiting time.

  Then, a large-size sheet passing waiting time (time for idling the fixing belt 201) set according to the accumulated sheet passing number may be set according to the sheet passing condition of the immediately preceding job. Depending on the degree of edge temperature rise, the waiting time for large-size paper passing is increased when the number of sheets passed in the previous job is large, and the waiting time for large-size paper passing is shortened when the number of sheets passed in the previous job is small. It is possible to prevent paper slip. Control according to the number of continuous sheets in the immediately preceding job will be described.

  FIG. 4 is a graph showing the temperature transition of the fixing belt when small-size paper is continuously passed, and shows the change in belt temperature between the paper passing portion and the non-paper passing portion. As shown in this graph, the temperature of the non-sheet passing portion of the fixing belt 201 when small-size sheets are continuously passed increases as the number of sheets to pass increases (saturated eventually). Therefore, the smaller the number of sheets passed, the smaller the edge temperature rise. Therefore, the possibility of large size high temperature slip is also reduced. That is, since the large-size sheet passing does not wait more than necessary when the degree of the edge temperature rise is small, as shown in Table 2, when the number of small-sized continuous sheet passing is small, the large-size sheet waiting is not waited. Shorten the time and increase the waiting time for large-size sheets when the number of sheets is large. Thereby, it is possible to optimize the waiting time for large-size sheet passing.

なお、表２に示す小サイズ通紙枚数および大サイズ通紙待ち時間は一例であり、定着装置の構成等により、適宜設定されるものである。

Note that the small-size sheet passing number and the large-size sheet passing waiting time shown in Table 2 are examples, and are appropriately set depending on the configuration of the fixing device.

  Next, a second embodiment will be described. In the second embodiment, a rotation detection mechanism that detects the rotation state of the fixing belt is provided, and a minute slip of the belt is detected by the rotation detection mechanism so as to prevent high temperature slip.

  As shown in FIG. 5, a rotation detecting unit 238 for detecting the rotation of the fixing belt 201 is disposed in the vicinity of the fixing belt 201. Further, the surface (outer peripheral surface) of the fixing belt 201 is marked 239. In this example, as shown in FIG. 6, the marking 239 is provided in the vicinity of one end of the fixing belt 201 in the axial direction, and the rotation detecting means 238 corresponds to the end of the fixing belt 201 in the axial direction. Located in the vicinity.

  The rotation detection means 238 and the marking 239 constitute a fixing belt rotation detection mechanism. As the rotation detecting means 238, for example, a reflection type photosensor can be used. However, the configuration of the fixing belt rotation detection mechanism is not limited to this, and an appropriate configuration can be adopted.

  In such a configuration, the rotation detection unit 238 detects the marking 239 to detect the rotation state of the fixing belt 201. When a sign that the belt slips is detected, it is recognized that the belt is likely to slip, and control is performed to provide a large-size sheet passing waiting time in order to prevent high temperature slip.

  FIG. 7 is a schematic diagram illustrating an example of a detection signal from the rotation detection unit 238. When there is no belt slip, the rotation detecting means 238 detects the marking 239 at regular intervals. The control means (for example, CPU) that has received the detection signal determines that the rotation is normal. On the other hand, if the detection interval of the marking 239 by the rotation detecting means 238 is extended (becomes longer than normal), it means that the belt is not rotating. Therefore, in this case, the control means determines that the belt is rotating abnormally.

  For example, when it is detected that the detection interval of the marking 239 has been extended while the fixing belt 201 should be rotating, belt slip has started, that is, the belt driving torque has increased. It is. As described above, when the driving torque is high, high-temperature slip is likely to occur. Therefore, when a sign of slip is seen by this rotation detection mechanism (determined as abnormal rotation of the belt), as in the flow of FIG. By providing a waiting time for large-size sheet passing in the large-size sheet passing mode after small-sized continuous sheet passing, high-temperature slip is prevented.

  Further, the magnitude (length) of the waiting time in this case is set according to the rotation state of the fixing belt detected by the rotation detection mechanism. In the case of the configuration of FIG. 7, the waiting time is determined according to the size (length) of the detection interval of the marking 239 by the rotation detection means 238. In other words, based on the detection interval during normal rotation, the waiting time when the degree of extension of the detection interval relative to this reference value is small is set as a small (short) waiting time, and the degree of extension of the detection interval relative to the reference value is large The waiting time is set to a large (long) waiting time.

  This configuration has another advantage, that is, safety is ensured by the rotation detection mechanism. If it is heated during non-rotation, the fixing belt may be deformed and ignited. Therefore, safety can be ensured by adding control to stop heating at the moment when rotation stop is detected during heating.

  In the second embodiment, as in the first embodiment described above, a counting unit that counts the cumulative sheet passing condition is provided, and the count value of the counting unit is added to the setting of a predetermined waiting time. Good.

  In addition, control for setting a large-size sheet passing waiting time according to the sheet passing condition of the immediately preceding job can be performed in the second embodiment. In this case, as shown in Table 2, the waiting time is set according to the number of sheets of the immediately preceding job.

  In the above description, the accumulated sheet passing condition is described as the accumulated sheet passing number. However, the accumulated sheet passing condition is not limited to the accumulated sheet passing number. The accumulated sheet passing condition may be the travel distance of the apparatus or the sheet passing time in addition to the accumulated sheet passing number. In any of these, since it is an index indicating the state of the driving torque, the larger the cumulative number, the longer the cumulative travel distance, the longer the cumulative paper passing time, the higher the driving torque. By detecting the high torque state and inserting the idle rotation of the fixing belt (large-size sheet passing waiting time), high temperature slip can be prevented under any conditions.

  As described above, in the present invention, when the force for driving the fixing member correlated with the high temperature slip = the driving torque is increased, the sheet passing waiting time is reduced in the large size sheet passing mode after the small size continuous sheet passing. The high temperature slip can be prevented by providing a large size paper after providing and lowering the temperature at the end temperature rise.

  Further, by determining the condition for increasing the driving torque based on the counting means for counting the cumulative sheet passing condition, it is possible to appropriately prevent high temperature slip with a simple and low cost configuration.

Moreover, it is possible to appropriately prevent high-temperature slip by a simple and low-cost configuration by determining the condition for increasing the drive torque based on the detection output of the rotation detection mechanism.
In addition, by setting the sheet passing waiting time in accordance with the marking detection interval by the detecting means, it is possible to detect a minute slip of the fixing member and to reliably determine the high torque state.

Moreover, high temperature slip can be more reliably prevented by adding the accumulated sheet passing condition to the setting of the waiting time.
Further, by rotating the fixing member while keeping the heating means in a non-heated state for a predetermined waiting time, the temperature of the non-sheet passing portion of the fixing member can be reliably reduced, and high temperature slip can be reliably prevented. .

In addition, by setting the sheet passing waiting time according to the sheet passing condition of the immediately preceding job, it is possible to prevent the high temperature slip according to the degree of the temperature rise in the non-sheet passing portion.
Further, by determining the accumulated sheet passing condition based on the sheet passing number, the apparatus travel distance, or the sheet passing time, the high torque state can be determined with a simple and low-cost configuration.

Although the present invention has been described based on the illustrated examples, the present invention is not limited to this and can be appropriately changed within the scope of the present invention.
As the fixing device and the image forming apparatus, any configuration can be adopted as long as the present invention is applicable. The image forming apparatus is not limited to a printer, and may be a copying machine, a facsimile machine, or a multifunction machine having a plurality of functions.

DESCRIPTION OF SYMBOLS 10 Transfer belt unit 20 Photosensitive drum 100 Image forming apparatus 200 Fixing apparatus 201 Fixing belt (fixing member)
202 Halogen heater (heating means)
203 Pressure roller (Pressure member)
206 Nip forming member 216 Heat transfer auxiliary member 238 Rotation detecting means 239 Marking N Fixing nip S Paper (recording material)

JP 2004-286922 A Japanese Patent No. 2861280 JP 2007-334205 A Japanese Patent Laid-Open No. 2007-233011 JP 2004-322284 A JP 2007-193165 A

Claims (11)

A recording material that includes a rotatable fixing member, a heating unit that heats the fixing member, and a pressure member that is pressed against the fixing member to form a nip portion, and carries an unfixed toner image in the nip portion. In a fixing device that passes and fixes an unfixed toner image on a recording material,
In a continuous sheet passing job, when the sheet passing width of the succeeding job is wider than the sheet passing width of the immediately preceding job and the driving torque for driving the fixing member is increased, when switching from the immediately preceding job to the succeeding job, While providing a predetermined waiting time,
The fixing device according to claim 1, wherein the predetermined waiting time is set according to an increase condition of the driving torque. It has a counting unit that counts the cumulative sheet passing condition from the start of use of the apparatus, and determines that the driving torque increases when the value counted by the counting unit is equal to or greater than a predetermined threshold,
The fixing device according to claim 1, wherein the predetermined waiting time is set according to a value counted by the counting unit.   The fixing device according to claim 1, further comprising: a rotation detection mechanism that detects a rotation state of the fixing member, wherein a condition for increasing the driving torque is determined based on a detection output of the rotation detection mechanism. . The rotation detection mechanism comprises a marking provided on the surface of the fixing member, and a detection means for detecting the marking,
When the detection interval of the marking detected by the detecting means is longer than a predetermined threshold, the driving torque is increased.
The fixing device according to claim 3, wherein the predetermined waiting time is set according to a detection interval of the marking detected by the detection unit. Having a counting means for counting the cumulative sheet passing conditions from the start of use of the apparatus;
The fixing device according to claim 3, wherein a count value of the counting unit is added to the setting of the predetermined waiting time.   6. The fixing device according to claim 1, wherein the fixing member is rotated while the heating unit is in a non-heated state during the predetermined waiting time.   The fixing device according to claim 1, wherein the predetermined waiting time is set according to a sheet passing condition of the immediately preceding job.   The fixing device according to claim 2, wherein the cumulative sheet passing condition is a sheet passing number.   The fixing device according to claim 2, wherein the cumulative sheet passing condition is an apparatus travel distance.   The fixing device according to claim 2, wherein the cumulative sheet passing condition is a sheet passing time. An image forming apparatus comprising the fixing device according to claim 1.

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