JP6816488B2 - Fixing device and image forming device - Google Patents

Description

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

In recent years, there has been an increasing market demand for energy saving and high speed in image forming devices such as printers, copiers, and facsimiles.
In the above image forming apparatus, a toner image (unfixed toner image) formed by an image forming process such as electrophotographic recording, electrostatic recording, and magnetic recording is directly or via an intermediate transfer body on a recording material sheet, printing paper, and 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 type fixing device such as a thermal roller method, a film heating method, and an electromagnetic induction heating method is widely adopted. 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 using a ceramic heater (for example, Patent Document 2) are known.

With regard to the belt type fixing device, it is possible to heat the entire endless belt, shorten the first print time, eliminate the lack of heat during high-speed rotation, and it is good even if it is mounted on a high-production image forming device. A fixing device that can obtain a good fixing property has been proposed (Patent Document 3).

In the fixing device shown in FIG. 1 of Patent Document 3, a pipe-shaped metal heat conductor is fixed inside the 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 provided. Heats the endless belt through a metal thermal conductor. Further, a pressure roller is provided which is in contact with the metal thermal conductor via the endless belt to form a nip portion, 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 heat the entire endless belt that constitutes the fixing device, shorten the first print time from the standby for heating, and eliminate the lack of heat during high-speed rotation. There is.

However, in order to further save energy and improve the first print time, it is necessary to further improve the thermal efficiency, and the endless belt is not indirectly heated via the metal heat conductor, and the endless belt is not indirectly heated via the metal heat conductor. A configuration in which the endless belt is directly heated has been proposed (for example, Patent Document 4). In this configuration, the heat transfer efficiency can be significantly improved, the power consumption can be reduced, and the first print time can be further shortened. In addition, since there is no metal thermal conductor, cost reduction is possible.

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

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

Furthermore, instead of setting the waiting time for large-sized paper only by temperature, it depends on the number of small-sized papers that are continuously passed (how the edge temperature rises) and the image density of the large-sized paper after the small size. A fixing device that eliminates unnecessary waiting time by setting a waiting time has been proposed (Patent Document 6).

However, as a result of the rise in edge temperature, in addition to large-sized image defects in the large-sized paper passing mode after continuous small-sized paper passing, steam is generated from the paper during heating, which is called high-temperature slip, and the fixing belt and paper A phenomenon occurs in which the paper carrying force is weakened due to the decrease in the frictional force between the sheets, which may cause paper jam. In particular, in an image forming device called a medicine bag machine used in hospitals, a paper bag (medicine bag) equivalent to thick paper for storing medicine and a paper equivalent to plain paper (medicine information) containing information on medicine are printed as a set. A large number of large-sized medicine-passing modes can be performed after continuous passing of small-sized medicine bags. Further, since the medicine bag is equivalent to thick paper, the degree of temperature rise at the end due to continuous paper passing of a small size is large, and therefore, a high temperature slip is likely to occur in the medicine bag machine.

Therefore, an object of the present invention is to provide a fixing device and an image forming device capable of solving the above-mentioned problems in the fixing device and preventing 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 means for heating the fixing member, and a pressurizing member that is pressed against the fixing member to form a nip portion. In the fixing device for fixing the unfixed toner image to the recording material by passing the recording material carrying the unfixed toner image to the recording material, the paper passing width of the succeeding job in the continuous paper passing job is wider than the paper passing width of the immediately preceding job. In addition, when the driving torque for driving the fixing member is increased, a predetermined waiting time is provided when switching from the immediately preceding job to the succeeding job, and the predetermined waiting time is set as the increasing condition for the driving torque. It has a counting means for counting the cumulative paper passing conditions from the start of using the device, and determines that the driving torque is increased when the value counted by the counting means is equal to or higher than a predetermined threshold value. However, the predetermined waiting time is set according to the value counted by the counting means .

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

It is a block diagram which shows the outline of the printer which is an example of the image forming apparatus which mounts the fixing apparatus which concerns on this invention. It is a figure which shows the 1st Embodiment of a fixing device. It is a flowchart which shows the control in 1st Embodiment. It is a graph which shows the temperature transition of the fixing belt at the time of continuously passing a small size paper. It is a figure which shows the 2nd Embodiment of a fixing device. It is a figure which shows the rotation detection mechanism included in the fixing device. 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 cross-sectional configuration diagram showing an example of an image forming apparatus equipped with the fixing apparatus according to the present invention. The image forming apparatus 100 shown in this figure is a tandem type color printer in which image forming portions forming a plurality of color images are juxtaposed along the extension direction of the belt, but the image forming apparatus is not limited to this type. It is also possible to target not only printers but also copiers and facsimile machines.

The image forming apparatus 100 has photoconductor drums 20Y, 20C, 20M, and 20Bk arranged side by side as an image carrier capable of forming an image as an image corresponding to each of the colors decomposed into yellow, cyan, magenta, and black. The tandem structure is adopted.

In the image forming apparatus 100, the visible image formed on each of the photoconductor drums 20Y, 20C, 20M, and 20Bk is an intermediate transfer body (hereinafter, an intermediate transfer body) which is an endless belt that can move in the direction of arrow A1 while facing each photoconductor drum. , Transfer belt) 11 is primarily transferred. By executing this primary transfer process, images of each color are superimposed and transferred, and then, by executing the secondary transfer process on the recording material S on which a recording sheet or the like is used, batch transfer is performed.

A device for performing image forming processing according to the rotation of the photoconductor drum is arranged around each photoconductor drum. Taking the photoconductor drum 20Bk that forms a black image 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 photoconductor drum 20Bk are arranged. ing. The optical writing device 8 is used for writing using the writing light Lb performed after charging.

In the superimposed transfer to the transfer belt 11, in the process of moving the transfer belt 11 in the A1 direction, the visible images formed on the photoconductor drums 20Y, 20C, 20M, and 20Bk are superimposed and transferred to the same position on the transfer belt 11. Will be done. For this purpose, the transfer is performed in the A1 direction by applying a voltage by the primary transfer rollers 12Y, 12C, 12M, 12Bk arranged to face the photoconductor drums 20Y, 20C, 20M, 20Bk with the transfer belt 11 interposed therebetween. The timing is shifted from the upstream side to the downstream side.

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

The image forming apparatus 100 is arranged so as to face the four image stations that perform image forming processing for each color and above each of the photoconductor drums 20Y, 20C, 20M, and 20Bk, and the transfer belt 11 and the primary transfer roller 12Y. , 12C, 12M, 12Bk, and a secondary transfer roller 5 which is arranged to face the transfer belt 11 and follows the transfer belt 11 to rotate around, and is arranged to face the transfer belt 11. It has a belt cleaning device 13 that is installed and cleans the transfer belt 11, and an optical writing device 8 that is arranged below these four image stations so as to face each other.

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 multifaceted mirror as a polarizing means, and the like. The optical writing device 8 emits writing light Lb corresponding to each color for each of the photoconductor drums 20Y, 20C, 20M, and 20Bk to form an electrostatic latent image on the photoconductor drums 20Y, 20C, 20M, and 20Bk. It is configured as. In FIG. 1, the writing light Lb is coded only for the image station of the black image for convenience, 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 feed cassette loaded with a recording material S conveyed toward between the photoconductor drums 20Y, 20C, 20M, 20Bk and the transfer belt 11. There is. Further, the recording material S conveyed from the sheet feeding device 61 is directed toward the transfer portion between each photoconductor drum and the transfer belt 11 at a predetermined timing in accordance with the formation timing of the toner image by the image station. A pair of resist rollers 4 to be fed are provided. Further, a sensor for detecting that the tip of the recording material S has reached the resist roller pair 4 is provided.

Further, in the image forming apparatus 100, as a fixing unit for fixing the toner image on the recording material S on which the toner image is transferred, a roller fixing type fixing device 200 and the fixed recording material S are attached to the image forming apparatus 100. A discharge roller 7 for discharging to the outside of the main body is provided. Further, a paper ejection tray 17 for loading the recording material S ejected to the outside of the main body of the image forming apparatus 100 by the ejection roller 7 is provided on the upper part of the main body of the image forming apparatus 100. Further, on the lower side of the output tray 17, toner bottles 9Y, 9C, 9M, and 9Bk filled with toners of each color of yellow, cyan, magenta, and black are provided.

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

The driven roller 73 also has a function as a tension urging means for the transfer belt 11. Therefore, the driven roller 73 is provided with a urging means using a spring or the like. The transfer device 71 is composed of such a transfer belt unit 10, primary transfer rollers 12Y, 12C, 12M, 12Bk, a secondary transfer roller 5, and a cleaning device 13.

The sheet feeding device 61 is arranged in the lower part of the main body of the image forming device 100, and has a feeding roller 3 that abuts on the upper surface of the uppermost recording material S. By rotationally driving the feeding roller 3 counterclockwise in the drawing, the highest recording material S is fed toward the resist roller pair 4.

Although not shown in detail, the cleaning device 13 mounted on the transfer device 71 has a cleaning brush and a cleaning blade arranged so as to face and abut against the transfer belt 11. The cleaning device 13 cleans the transfer belt 11 by scraping and removing foreign substances such as residual toner on the transfer belt 11 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 schematic configuration diagram showing a fixing device according to the first embodiment.
The fixing device 200 has a fixing belt 201 as a rotatable fixing member and a pressure roller 203 as a rotatable pressure member arranged to face the fixing belt 201, and a halogen heater 202A as a plurality of heating means. The fixing belt 201 is directly heated by radiant heat from the inner peripheral side by 202B.

In the loop of the fixing belt 201, a nip forming member 206 forming a nip portion between the fixing belt 201 and the pressure roller 203 is arranged, and indirectly via the fixing belt inner surface and the heat transfer assisting member 216. It is designed 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 it may be concave or other. In the case of the concave nip portion, the discharge direction of the tip of the recording material is closer to the pressure roller, and the separability is improved, so that the occurrence of jam is suppressed.

Inside the loop of the fixing belt 201, a nip forming member 206 arranged to face the pressure roller 203, an end heater 226 as an end heat source integrally provided at both ends of the nip forming member 206, and a nip. A heat transfer assisting member 216 that covers the surface of the forming member 206 and the fixing belt 201 of the end heater 226 facing the inner surface, and a stay member 207 that holds the nip forming member 206 against the pressing force from the pressurizing 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 extending in the axial direction (hereinafter, referred to as “longitudinal direction”) of the fixing belt 201.
The heat transfer assisting member 216 is provided to prevent the heat of the end heater 226 from staying locally and to positively transfer the heat in the longitudinal direction to reduce the temperature non-uniformity in the longitudinal direction. ..

Therefore, it is desirable that the heat transfer assisting member 216 is a material capable of heat transfer in a short time, and it is desirable that the member is a member such as copper, aluminum, or silver having high thermal conductivity. Considering cost, availability, thermal conductivity characteristics, and workability comprehensively, it is most desirable to use copper.

In the present embodiment, the surface of the heat transfer assisting member 216 facing the inner surface of the fixing belt 201 is a surface that directly contacts the fixing belt 201 and is 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. An elastic layer formed of a layer of silicone rubber or the like may be provided between the base material of the belt and the PFA or PTFE layer. If there is no silicone rubber layer, the heat capacity will be small and the fixability will be improved, but when the unfixed image is crushed and fixed, the minute irregularities on the belt surface will be transferred to the image and the solid part of the image will have a yuzu skin shape. There may be a problem that uneven gloss (Yuzu 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, minute irregularities are absorbed and the yuzu skin image is improved.

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

Inside the fixing belt 201, a nip forming member 206 and a stay 207 as a supporting member for supporting the nip portion N are provided to prevent the nip forming member 206 receiving pressure from the pressure roller 203 from bending and in the axial direction. We are trying to obtain a uniform nip width. The stay 207 is held and fixed to a flange as a holding member at both ends and is positioned. Further, a reflective member 209 is provided between the halogen heater 202 and the stay 207 to suppress wasteful energy consumption due to the stay 207 being heated by radiant heat from the halogen heater 202 or the like. Here, instead of providing the reflective member 209, the same effect can be obtained by performing heat insulation or mirror surface treatment on the surface of the stay 207.

The pressure roller 203 has an elastic rubber layer 204 laminated on the core metal 205, and a mold release layer (PFA or PTFE layer) is provided on the surface in order to obtain mold releasability. The pressurizing roller 203 rotates by transmitting a driving force from a drive source such as a motor provided in the image forming apparatus via a gear. Further, the pressure roller 203 is pressed against the fixing belt 201 side by a spring or the like, and the elastic rubber layer 204 is crushed and deformed to have a predetermined nip width. The pressurizing roller 203 may be a hollow roller, and the pressurizing 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 preferable because it has higher heat insulating properties and is less likely to take away heat from the fixing belt.

The fixing belt 201 is rotated by the pressure roller 203. In the case of FIG. 2, the pressurizing roller 203 is rotated by the drive source, and the fixing belt 201 is rotated by transmitting the driving force to the belt at the nip portion N. The fixing belt 201 is sandwiched between the nip portions N and rotates, and is guided by flanges 208 (not shown) at both ends except the nip portion to travel.

With the above configuration, it is possible to realize an inexpensive fixing device that warms up quickly.
Next, a specific configuration and control for preventing large-sized high-temperature slip due to an increase in edge temperature due to small-sized continuous paper passing in the large-sized paper passing mode after small-sized continuous paper passing will be described.

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

If the value of the read cumulative paper passing condition (here, the cumulative number of paper passing sheets) is equal to or greater than the threshold value, the fixing belt 201 is idle-rotated for a set time after continuous small size paper passing (providing a predetermined waiting time). After that, a large-sized paper is passed (S4, S5).

On the other hand, if the read value is less than the threshold value, the process proceeds to S6, and the paper is passed as usual.
With 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 is known that there is a correlation between the high temperature slip and the torque for driving the fixing member (fixing belt 201 in the present embodiment), and high temperature slip is likely to occur when the driving torque is high, and high temperature slip is unlikely to occur when the driving torque is low. Further, since this drive torque increases (increases) as the cumulative number of sheets to be passed increases, high-temperature slip is more likely to occur as the cumulative number of sheets to be passed increases.

Therefore, for a state where high-temperature slip is likely to occur, by providing a waiting time for large-sized paper passing compared to normal paper passing, the waiting time is increased due to the rise in edge temperature due to small-sized continuous paper passing. The temperature of the belt 201 is lowered, and high temperature slip can be avoided. There is a concern that productivity will decrease due to the installation of waiting time, but it is considered to be prioritized considering the possibility of paper jam due to high temperature slip.

Further, in the present embodiment, the waiting time for large-sized paper is changed according to the count value (cumulative number of papers) as a condition for increasing the drive torque. Table 1 shows the large-sized paper passing waiting time (time for idling the fixing belt 201) set according to the cumulative number of paper passing sheets 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。

The cumulative number of sheets to be passed and the waiting time for large-sized paper to be passed as shown in Table 1 are examples, and are appropriately set depending on the configuration of the fixing device and the like.

As explained above, the larger the drive torque = cumulative number of sheets, the greater the possibility of high-temperature slip. Therefore, when the drive torque = cumulative number of sheets is large, the temperature at the time of larger size paper is lowered. Therefore, when the waiting time is set long and the drive torque = cumulative number of sheets is low, the large size waiting time can be shortened to prevent high temperature slip according to the state of the driving torque.

Then, the large-sized paper passing waiting time (time for idling the fixing belt 201), which is set according to the cumulative number of paper passing sheets, may be set according to the paper passing conditions of the immediately preceding job. When the number of sheets passed in the previous job is large, the waiting time for large size paper is long, and when the number of sheets passed in the previous job is small, the waiting time for large size paper is shortened according to the degree of edge temperature rise. Paper slip can be prevented. The control according to the number of continuous paper sheets in the immediately preceding job will be described.

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

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。

The number of small-sized sheets and the waiting time for large-sized sheets shown in Table 2 are examples, and are appropriately set depending on the configuration of the fixing device and the like.

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

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

The rotation detecting means 238 and the marking 239 constitute a fixing belt rotation detecting mechanism. The rotation detecting means 238 can use, for example, a reflective photo sensor. 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 means 238 detects the marking 239 to detect the rotation state of the fixing belt 201. Then, when it detects a sign that the belt slips, it recognizes that the belt is in a slip-prone state, and controls so as to provide a large-sized paper passing waiting time in order to prevent high-temperature slip.

FIG. 7 is a schematic diagram showing an example of a detection signal by the rotation detecting means 238. If there is no belt slip, the rotation detecting means 238 detects the marking 239 at regular intervals. The control means (for example, the CPU) that receives the detection signal determines that the rotation is normal. On the other hand, when the detection interval of the marking 239 by the rotation detecting means 238 is extended (longer than usual), it means that the belt is not rotating. Therefore, in this case, the control means determines that the belt is abnormally rotated.

For example, when it is detected that the detection interval of the marking 239 is extended when the fixing belt 201 is supposed to be rotating, the belt starts to slip, that is, the driving torque of the belt is high. Is. As described above, if the drive torque is high, high-temperature slip is likely to occur. Therefore, if a sign of slip is observed by this rotation detection mechanism (determined to be abnormal rotation of the belt), the flow is the same as in FIG. By providing a waiting time for large-sized paper in the large-sized paper-passing mode after continuous small-sized paper, high-temperature slip is prevented.

Further, the size (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 detecting means 238. That is, when the detection interval during normal rotation is used as a reference, the waiting time when the degree of extension of the detection interval with respect to this reference value is small is set to a small (short) waiting time, and when the degree of extension of the detection interval with respect to the reference value is large. Set the waiting time to be large (long).

This configuration has another merit, which is that safety is also ensured by the rotation detection mechanism. If it is heated during non-rotation, it may cause deformation and ignition of the fixing belt. Therefore, safety can be ensured by putting a 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 means for counting the cumulative paper passing conditions may be provided, and the count value of the counting means may be added to the setting of the predetermined waiting time. Good.

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

By the way, in the above description, the cumulative number of sheets to be passed has been described as the cumulative number of sheets to be passed, but the cumulative number of sheets to be passed is not limited to the cumulative number of sheets to be passed. The cumulative paper-passing condition may be the cumulative number of paper-passing sheets, the mileage of the device, or the paper-passing time. In any of these cases, the driving torque is an index indicating the state of the driving torque. Therefore, the larger the cumulative number of sheets, the longer the cumulative mileage, and the longer the cumulative paper passing time, the higher the driving torque. By detecting a high torque state and inserting idle rotation of the fixing belt (waiting time for large-sized paper), high-temperature slip can be prevented under any condition.

As described above, in the present invention, when the force for driving the fixing member correlated with the high temperature slip = the driving torque becomes high, the paper passing waiting time is increased in the large size paper passing mode after the small size continuous paper passing. It is possible to prevent high-temperature slip by providing a large-sized sheet of paper after lowering the temperature of the place where the edge temperature rises.

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

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

Further, by adding the cumulative paper passing condition to the setting of the waiting time, high temperature slip can be prevented more reliably.
Further, by rotating the fixing member while the heating means is not heated during a predetermined waiting time, the temperature of the non-passing portion of the fixing member can be surely lowered and high temperature slip can be surely prevented. ..

Further, by setting the paper passing waiting time according to the paper passing condition of the immediately preceding job, it is possible to prevent high temperature slip according to the degree of temperature rise of the non-paper passing portion.
Further, by determining the cumulative paper passing condition based on the number of sheets to be passed, the mileage of the device, or the passing time, the high torque state can be determined with a simple and low-cost configuration.

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

10 Transfer belt unit 20 Photoreceptor drum 100 Image forming device 200 Fixing device 201 Fixing belt (fixing member)
202 Halogen heater (heating means)
203 Pressurizing roller (pressurizing member)
206 Nip forming member 216 Heat transfer assisting member 238 Rotation detecting means 239 Marking N Fixing nip S Paper (recording material)

Japanese Unexamined Patent Publication No. 2004-286922 Japanese Patent No. 2861280 JP-A-2007-334205 Japanese Unexamined Patent Publication No. 2007-23301 Japanese Patent Application Laid-Open No. 4-322284 JP-A-2007-193165

Claims (10)

A recording material provided with a rotatable fixing member, a heating means for heating the fixing member, and a pressure member for forming a nip portion by being pressed against the fixing member, and carrying an unfixed toner image on the nip portion. In a fixing device that allows an unfixed toner image to pass through and fixes it to a recording material.
In a continuous paper-passing job, when the paper-passing width of the succeeding job is wider than the paper-passing width of the immediately preceding job and the driving torque for driving the fixing member increases, when switching from the immediately preceding job to the succeeding job. Along with setting a predetermined waiting time
The predetermined waiting time is set according to the conditions for increasing the drive torque .
It has a counting means for counting the cumulative paper passing conditions from the start of using the device, and determines that the driving torque increases when the value counted by the counting means is equal to or higher than a predetermined threshold value.
A fixing device , wherein the predetermined waiting time is set according to a value counted by the counting means . A recording material provided with a rotatable fixing member, a heating means for heating the fixing member, and a pressure member for forming a nip portion by being pressed against the fixing member, and carrying an unfixed toner image on the nip portion. In a fixing device that allows an unfixed toner image to pass through and fixes it to a recording material.
In a continuous paper-passing job, when the paper-passing width of the succeeding job is wider than the paper-passing width of the immediately preceding job and the driving torque for driving the fixing member increases, when switching from the immediately preceding job to the succeeding job. Along with setting a predetermined waiting time
The predetermined waiting time is set according to the conditions for increasing the drive torque.
Rotation has a detection mechanism, a constant Chakusochi you and judging condition in which the driving torque is increased based on the detection output of the rotation detection mechanism for detecting a rotational state of the fixing member. The rotation detection mechanism comprises a marking provided on the surface of the fixing member and a detection means for detecting the marking.
The condition is that the drive torque increases when the detection interval of the markings detected by the detection means becomes longer than a predetermined threshold value.
The fixing device according to claim 2 , wherein the predetermined waiting time is set according to the detection interval of the marking detected by the detection means. It has a counting means to count the cumulative paper passing conditions from the start of using the device.
The fixing device according to claim 2 or 3 , wherein the count value of the counting means is added to the setting of the predetermined waiting time. The fixing device according to any one of claims 1 to 4 , wherein the fixing member is rotated while the heating means is not heated during the predetermined waiting time. The fixing device according to any one of claims 1 to 5 , wherein the predetermined waiting time is set according to the paper passing condition of the immediately preceding job. The fixing device according to claim 1 , wherein the cumulative paper passing condition is the number of sheets to be passed. The fixing device according to claim 1 , wherein the cumulative paper passing condition is the device mileage. The fixing device according to claim 1 , wherein the cumulative paper passing condition is a paper passing time. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 9 .

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