JP6395563B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that fixes an image formed of toner on a recording material.

  2. Description of the Related Art Conventionally, many image forming apparatuses such as copying machines and printers that employ an electrophotographic method employ a thermal fixing method as a means for performing a fixing process on a recording material carrying an unfixed image. A fixing device is provided.

  The fixing device includes a fixing film that rotates along a film guide, a heating source that is provided in the fixing film and that heats the fixing film, and a pressure roller in which a heat-resistant elastic layer is formed on a core metal of aluminum or iron And.

  In such a fixing device, a fixing film provided with a heating source as a heating means is pressed against the pressure roller by a spring or the like. The unfixed toner is fixed on the recording material by passing the recording material carrying the unfixed image (unfixed toner) through the pressure contact width (fixing nip width) formed by the pressure contact and heating and pressing. Is done.

  By the way, an image forming apparatus that employs an electrophotographic process system mainly includes a photosensitive drum unit, a developing device, a transfer device, a fixing device, and the like. These are designed as consumables depending on the model of the image forming apparatus. In this case, in order to always provide a stable and high-quality print image to the user, the lifetime of these consumables is set appropriately, and the user It is important to prompt the service life and replace consumables.

  In the case of a fixing device, if it is used beyond its lifetime, image quality failure and fixing failure occur due to deterioration of each component in the fixing device. In particular, in a fixing film having a release layer on the surface layer, due to the lifetime, the surface layer is scraped off at the edge of the paper (paper edge), the releasability deteriorates, and a paper edge scraping phenomenon occurs in which toner adheres to the film surface layer. The image becomes dirty.

  In order to prevent such a phenomenon in advance, it is necessary to accurately notify the life of the fixing device. As a method for detecting the life of the fixing device used in the apparatus main body, a method for monitoring the number of recording materials to be passed and the time for which the recording material is passed is generally easy. In this method, when a predetermined number of sheets or a sheet passing time is exceeded, a message such as a notice of life or replacement of the fixing device is displayed on the image forming apparatus main body.

Japanese Patent Laid-Open No. 2000-131978

  However, in an image forming apparatus having a plurality of paper passing modes having different fixing temperatures, image forming speeds, and throughputs (such as the time between sheets), thermal damage to the fixing device differs depending on the paper passing mode. For this reason, the number of lifespans of the fixing device may differ depending on the sheet passing mode.

  Since the types of sheet passing modes used in the actual market and the usage ratio thereof vary depending on the user, the lifespan of the fixing device varies greatly. In such a case, there has been a problem that the life of the fixing device cannot be accurately detected by simply monitoring the number of sheets passed as in the prior art for detecting the life of the fixing device.

  In the conventional technology for predicting the life, there is a fixing device that weights the number of sheets to be passed according to the sheet passing mode and the sheet passing state when there is a difference in the number of sheets of the fixing device depending on the sheet passing mode and the sheet passing state ( Patent Document 1). However, since this method weights the relationship between the number of sheets to be fed and the temperature of the fixing temperature control, there is a problem that the variation in the life due to the influence of the paper width cannot be taken into account and the life due to paper edge cutting cannot be corrected accurately. It was.

The present invention is to provide an image forming apparatus capable of accurately predict the lifetime of Fixing device.

In order to achieve this object, an image forming apparatus of the present invention fixes a recording material on which an image is formed by an image forming unit by conveying the recording material through a fixing nip heated by a heating unit, and fixing the recording material. From the temperature detection means for detecting the temperature of the fixing device, the number of recording materials having a predetermined width in the direction orthogonal to the conveyance direction of the recording material, and the detection result of the temperature detection means. sought, and a control means for determining the lifetime of the fixing device based on the temperature of the fixing device corresponding to the position of the end portion in the width direction of the recording material wherein a predetermined width, said control means When there are a plurality of the predetermined widths of the recording material according to the size of the recording material, the fixing device corresponding to the number of sheets passing through the fixing nip portion and the position of the end portion for each size of the recording material to be conveyed Based on the temperature of There characterized by determining the lifetime of the fixing device.

According to the present invention , it is possible to accurately predict the life of the fixing device.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view illustrating a configuration of a fixing unit of an image forming apparatus according to an embodiment of the present invention. 6 is a graph showing the relationship between the surface temperature of the fixing film and the scraping amount at the paper edge position of the image forming apparatus according to the embodiment of the present invention. 6 is a graph showing the relationship between the number of sheets passing through the image forming apparatus according to the embodiment of the present invention and the amount of scraping of the fixing film at the paper edge position. 6 is a graph showing the relationship between the temperature control temperature of the image forming apparatus according to the embodiment of the present invention and the surface temperature of the fixing film at the paper edge position. In the image forming apparatus according to the embodiment of the present invention, a graph showing the relationship between the surface temperature of the fixing film at the paper edge position when two recording materials are intermittently passed in one set at a temperature control temperature of 215 ° C. It is. 6 is a flowchart illustrating a fixing film life prediction operation in the image forming apparatus according to the embodiment of the present invention. 6 is a graph showing a distance from a temperature detection unit to a paper edge position and a temperature difference in an image forming apparatus according to another embodiment of the present invention. It is a flowchart which shows the lifetime prediction operation | movement of the fixing film of other embodiment of this invention. It is a table | surface which shows the correction amount for every temperature of other embodiment of this invention. FIG. 9 is a diagram illustrating a longitudinal paper edge position and a paper edge temperature detection sensor position of a fixing unit according to still another embodiment of the present invention. The paper edge temperature detection sensor of still another embodiment of the present invention is installed at the paper edge position of the maximum paper passing width, and from the position of the paper edge temperature detection sensor when paper of another size is passed to the paper edge. This is a difference between the distance of the paper and the paper edge temperature. It is a flowchart which shows the lifetime prediction operation | movement of further another embodiment of this invention. It is a table | surface which shows the remaining life for every size of further another embodiment of this invention.

<First Embodiment>
An embodiment of an image forming apparatus of the present invention will be described in detail with reference to the drawings.

(Overall configuration of image forming apparatus)
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present embodiment.

  As shown in the figure, the image carrier 3 is charged to a predetermined constant potential from the charging high-voltage power source 1 by the charging roller 2, and a point on the image carrier 3 on which the image is formed is exposed by the exposure means 4. The potential is lowered. Then, the toner in the developing container 5 is uniformly placed on the developing sleeve 6, and the difference between the potential on the image carrier 3 and the potential applied to the developing sleeve 6 where the toner is lowered, that is, the action of the electric field is utilized. Charged toner is deposited on the image carrier 3.

  On the other hand, a recording material such as paper is fed by a paper feeding means and conveyed to a predetermined transfer area along the pre-transfer guide 7. The toner adhering to the image carrier 3 is transferred onto a recording material by the transfer roller 8, and then the recording material onto which the toner has been transferred is conveyed to the fixing unit 12 along the guide 11 and fixed by the fixing unit 12. The paper is discharged.

  The toner that adheres to the image carrier 3 and cannot be transferred is scraped off and collected by the cleaning blade 9 into the waste toner storage space 10.

(Configuration of fixing unit)
FIG. 2 is a schematic cross-sectional view showing the configuration of the fixing unit 12.

  As shown in the figure, the fixing unit 12 is composed of a film unit 20 of a collar 30 and a pressure roller 21 of a collar 25.

  The film unit 20 includes a heating source 19 (heating means), a fixing film 15, a film guide 13, a T-steer 14, and a thermistor 18 (temperature detection element). The heating source 19 is a ceramic heater, which is composed of a heating element in which a heating paste is printed on a ceramic substrate, a glass coating layer for ensuring protection and insulation of the heating element, and the like. A power-controlled AC current is supplied to generate heat. The fixing film 15 is made of polyimide and has a cylindrical shape with a thickness of about 70 μm, and efficiently transfers heat from the heating source 19 to the toner 17 on the recording material 16. The film guide 13 has a number of ribs in the longitudinal direction, thereby assisting sliding of the fixing film 15 while suppressing resistance to the fixing film 15. The T-stay 14 is made of a steel plate and applies a pressing force uniformly. Further, the thermistor 18 on the back side of the ceramic substrate detects a temperature change, determines a target temperature of the heating source 19 based on the detection result, and controls the driving means of the heating source 19 to control the heating source 19. Power control is performed to keep the temperature of the heating source 19 at the target temperature (printing temperature). The heat of the heating source 19 is transmitted to the fixing film 15.

  Further, the pressure roller 21 (pressure member) is formed by coating the core metal 30 made of aluminum of the flange 20 with silicon rubber. The pressure roller 21 is pressed against the heating source 19 with a predetermined pressure (nip pressure) with a fixing film 15 sandwiched by a spring to form a fixing nip portion 22 of 5 to 8 mm by the film unit 20 and the pressure roller 21. ing. The pressure roller 21 is rotationally driven by a pressure roller driving unit, and rotates the fixing film 15 and conveys the recording material 16 introduced into the fixing nip portion 22 in close contact with the fixing film 15. Yes. As the recording material 16 passes through the fixing nip portion 22 in this way, the unfixed toner image formed and supported on the recording material 16 is fixed by the heat of the heating source 19 and the fixing nip pressure. The recording material 16 subjected to the fixing process is discharged out of the apparatus by discharge rollers 23 and 24.

(Relationship between the surface temperature of the fixing film and the amount of scraping at the paper edge position)
FIG. 3 is a graph showing the relationship between the surface temperature of the fixing film 15 and the scraping amount at the paper edge position (the end in the width direction of the recording material 16).

The figure shows the amount of scraping when the surface pressure (about 0.8 Kg / cm ² ) of the fixing unit 12 and the roughness of the paper, which are the same as the paper-passing conditions, are combined with the paper roughness for a time equivalent to paper-passing (about 153,000 seconds) Is shown.

  As shown in the figure, when the temperature of the fixing film 15 is 180 ° C., the scraping amount is 3.8 μm, whereas when the surface temperature of the fixing film 15 is 220 ° C., the scraping amount is 5.5 μm. From this, it can be seen that the amount of scraping increases as the temperature of the fixing film 15 increases. That is, it can be said that the film life decreases as the surface temperature of the fixing film 15 increases. Also, it can be seen from this result that the scraping amount per 1 ° C. is about 0.04 μm. This relationship is defined as the heating member surface layer scraping coefficient.

(Relationship between the number of sheets passed and the amount of fusing film scraped at the paper edge)
FIG. 4 is a graph showing the relationship between the number of sheets to be passed and the amount of scraping of the fixing film 15 at the paper edge position.

  As shown in the figure, the scraping amount is about 0.02 μm when 1000 sheets are passed, and is about 0.11 μm when 5000 sheets are passed, and it can be seen that the shaving amount increases as the number of passing sheets increases. From this result, it can be said that about 0.02 μm can be removed per 1000 sheets. When combined with the result of the amount of chipping per 1 ° C., if the control is continued with a shift of 1 ° C., a life variation of 2000 sheets will occur.

(Temperature control temperature and surface temperature of fixing film at paper edge position)
FIG. 5 is a graph showing the relationship between the temperature control temperature and the surface temperature of the fixing film 15 at the paper edge position.

  As shown in the figure, when the temperature adjustment temperature is controlled at 210 ° C., the surface temperature of the fixing film 15 at the paper edge position is 192 ° C., and when the temperature adjustment temperature is increased to 225 ° C., the fixing film 15 at the paper edge position is The surface temperature also rises to 207 ° C. From this, it can be seen that the surface temperature of the fixing film 15 increases in proportion to the temperature control temperature.

  That is, when the results of FIG. 4 and FIG. 5 are combined, it can be seen that the film life decreases when the temperature control temperature is increased.

(Surface temperature of fixing film at the edge of paper when intermittent paper is passed)
FIG. 6 is a graph showing the relationship of the surface temperature of the fixing film 15 at the paper edge position when two sheets of recording material 16 are intermittently passed through one set at a temperature control temperature of 215 ° C.

  As shown in the figure, when the paper is continuously fed, the surface temperature of 198 ° C. decreases to 160 ° C. when the paper is passed at intervals of 30 seconds. Therefore, the surface temperature of the fixing film 15 at the paper edge position is most likely to rise during continuous paper passing, and when the interval between operation modes is increased, the surface temperature of the fixing film 15 at the paper edge position decreases, and the film life is shortened. Extend. That is, it can be said that the film life depends on the operation mode.

(Operation for calculating the lifetime of the fixing film)
FIG. 7 is a flowchart showing the life prediction operation of the fixing film 15 in this embodiment.

  As shown in the figure, the lifetime is set for each paper width in advance (step S701). The paper width information is obtained (step S702), and the remaining life time corresponding to the paper width is read (step S703). For example, when a new article is A4L and the lifetime is 160 K at an image forming speed of 220 mm / sec, it is 152727.3 seconds in terms of time. Next, paper length information and image formation speed information are obtained to calculate the paper passing time (steps S704 and S705), and the time for passing one sheet is calculated (step S706, measuring means). For example, when the paper size is A4L and the image forming speed is 220 mm / sec, the paper length is 210 mm, so the time for passing one sheet is 0.955 seconds.

  Next, when the printing operation is not started (step S707), the printing operation is ended (step S707). When the printing operation is started (step S707), the temperature adjustment temperature at the time of paper feeding is obtained from the paper type, paper size, and the like (step S708). . For example, it is 215 ° C. for plain paper and 190 ° C. for thin paper. Note that the relationship between the temperature adjustment temperature at the time of paper feeding and the temperature of the fixing film 15 at the paper edge position is stored in the CPU in advance. For example, in the case of plain paper, when the temperature adjustment temperature is 215 ° C., the temperature of the fixing film 15 at the paper edge position is 197 ° C. Next, the temperature of the fixing film 15 at the paper edge position is determined from the temperature adjustment temperature at the time of paper passing set with respect to the reference temperature. Then, when there is a difference between the reference temperature and the temperature of the fixing film 15 at the paper edge position, the number of differences is calculated (step S709). Here, the reference temperature refers to a temperature when the life of the fixing film 15 is determined based on the paper edge position of the fixing unit 12. For example, when the life is determined by the temperature of plain paper, the reference temperature is 197 ° C. When plain paper is flown, the temperature of the fixing film 15 at the paper edge position during paper passing is 197 ° C. and the reference temperature is 197 ° C., so the difference in reference temperature is 0 ° C. In addition, when thin paper is flowed, the temperature control during paper passing decreases, so the temperature of the fixing film 15 at the paper edge position is determined to be 172 ° C., and the reference temperature is 197 ° C., so the difference from the reference temperature is 25 ° C.

  Next, in order to calculate the sheet passing time, the number of sheets to be passed is integrated with respect to one sheet passing time (step S710), and the obtained time is subtracted from the remaining life time (step S711). Next, if there is a difference caused by the sheet passing condition, the difference is corrected from the remaining life time (step S712). For example, when the condition of passing paper is 100 sheets of plain paper, since the reference temperature 197 ° C. and the paper edge temperature 197 ° C. are the same, the correction amount is zero. However, when the sheet passing condition is 100 sheets of thin paper, the temperature of the fixing film 15 at the paper edge position is 172 ° C. with respect to the reference temperature of 197 ° C., and a state in which a difference of 25 ° C. with respect to the reference temperature is 95.degree. It will last for 5 seconds. Originally, the lifetime is calculated at 197 ° C., so the lifetime is extended if the temperature is low.

  For example, the correction amount (life subtraction time) is calculated by first calculating the temperature difference from the reference temperature, converting the calculated temperature into the amount of scraping from the heating member surface layer scraping coefficient that is the amount of scraping per temperature, The fluctuation of the temperature of the fixing film 15 at the edge position is reduced to a scraping amount (μm). Then, the scraping amount (μm) due to the temperature fluctuation of the paper edge is converted into the number of sheets from the relationship between the scraping amount and the number of sheets. Subsequently, the number of sheets is converted into time to cope with various paper sizes. Finally, a ratio of the time exceeding the reference temperature is calculated to determine how much the time when the deviation from the reference temperature has affected the overall time, and the time is set as the correction time. For example, if 100 sheets of A4L are continuously passed while the difference from the reference temperature is 25 ° C., the correction time is 64909 seconds and the time coefficient exceeding the reference temperature is 0.000625, so the correction amount is +29.8 seconds ( 31.3 sheets in terms of A4L). The obtained correction amount is corrected from the remaining lifetime, and the lifetime is updated and stored (step S713). When the remaining life time corresponding to at least one of a plurality of widths of the stored remaining life time has reached the replacement instruction remaining life time (predetermined time) (step S714), the replacement instruction (predetermined warning) Is displayed (step S715).

Second Embodiment
An image forming apparatus according to another embodiment of the present invention will be described. The basic configuration of the present embodiment is the same as that of the first embodiment, and differences from the first embodiment will be described below.

  In the present embodiment, temperature detection means for detecting the temperature of the fixing film 15 is used separately from the thermistor 18 used for temperature adjustment of the fixing unit 12.

  FIG. 8 is a graph showing the distance from the temperature detecting means to the paper edge position and the temperature difference.

  For example, when the temperature detection means is installed at the end of A4L and A4L size paper is passed, the difference between the temperature of the temperature detection means and the temperature of the fixing film 15 at the paper edge position is about 17 ° C. On the other hand, for example, when A4R width paper is passed, a distance of 38.5 mm from a large size is generated. In this case, an error occurs between the paper edge of about 29 ° C. and the detected temperature of the temperature detecting means, so correction is necessary. As described above, paper edge detection can be predicted by correcting the difference from the temperature detection means.

  FIG. 9 is a flowchart showing the life prediction operation of the fixing film 15 of the present embodiment.

  As shown in the figure, the lifetime is set for each paper width in advance (step S901). The paper width information is obtained (step S902), and the remaining life time corresponding to the paper width is read (step S903). The distance from the temperature detection means is calculated based on the paper width information (step S904), and the correction amount of the temperature detection means is calculated from the calculation result (step S905). For example, as shown in FIG. 8, when there is a temperature detection means at the end of A3 size or A4L, the data value in the case of A3 or A4L is corrected to 17 ° C, and in the case of A4R, the difference from A4L is 38.5 mm. Therefore, 29 ° C. is corrected to the data value.

Next, paper length information is obtained (step S906). For example, in the case of A4L paper passing, it is 210 mm. Then, the image forming speed is obtained (step S907), and the sheet passing time per sheet is calculated from the image forming speed (step S908). For example, it is 0.95 seconds when the image forming speed is 220 mm / sec. A printing operation is started based on the previous information (step S909). Print information such as the life reference temperature during printing (for example, 215 ° C.), the temperature difference between the detection results of the temperature detection means, and the time during which the temperature difference occurs is stored (step S910).
Then, the temperature at which a difference from the reference temperature has occurred is calculated (step S911). Next, based on the stored result, the temperature when the temperature exceeds or falls below the reference temperature and the time in the temperature state are calculated (step S912).

  FIG. 10 is a table showing the correction amount for each temperature. For example, as shown in the figure, when the sheet passing time per sheet is 0.95 seconds, the following is performed. 217 ° C, which exceeded the reference temperature by 2 ° C, for 0.2 seconds, 215 ° C, which is the same as the reference temperature, for 0.1 second, 213 ° C which was 2 ° C below the reference temperature, 0.45 seconds, and the reference temperature was 4 ° C below 211 When the temperature is detected for 0.2 seconds, the difference temperature and the time for the difference temperature are stored.

  Next, the paper passing time is subtracted from the set remaining life time (step S913). For example, when one sheet is passed as shown in FIG. 10, 0.95 seconds is subtracted from the lifetime. Next, the lifetime correction value for the temperature exceeding the reference temperature 215 ° C. is repeatedly calculated for each temperature (steps S914, S915, S916). For example, when 2 ° C. is exceeded by 0.2 seconds as shown in FIG. 10, when the life correction coefficient is applied, the life correction time is calculated to be 0.005 seconds (step S915), and the time for the temperature difference is cleared (step S916). . Since there is no other data that exceeds the value, it is determined that the correction for the value exceeding has been completed (step S914).

  Next, a life time correction value corresponding to the temperature below the reference temperature of 215 ° C. is repeatedly calculated for each temperature (steps S917, S918, S919). For example, as shown in FIG. 10, when 2 ° C. is lowered by 0.45 seconds, the life correction time is reduced by 0.012 seconds when the life correction coefficient is applied. Subsequently, when the temperature falls below 0.2C for 0.2 seconds, the life correction coefficient is subtracted by 0.01 seconds. Next, the correction time is corrected with respect to the remaining life time after the calculation of the correction amount (step S920), and the corrected remaining life time is stored (step S921). Here, for example, if the corrected remaining life time is less than the replacement instruction time (step S922), the replacement instruction display is instructed on the apparatus body (step S923).

  As described above, by providing the temperature detection means, it is possible to finely correct the time, so that it is possible to accurately detect paper edge scraping.

<Third Embodiment>
An image forming apparatus according to another embodiment of the present invention will be described. The basic configuration of the present embodiment is the same as that of the second embodiment, and differences from the second embodiment will be described below.

  In this embodiment, a paper edge temperature detection sensor 25 is provided in place of the temperature detection means of the second embodiment.

  FIG. 11 is a diagram showing the longitudinal paper edge position of the fixing unit 12 and the position of the paper edge temperature detection sensor 25. For example, in the case of the A3 machine, since A3 or A4L has the maximum sheet passing width, a sheet edge temperature detection sensor 25 for detecting the temperature of the film surface layer in a non-contact manner is provided at the position of the A4L size sheet edge of the maximum sheet of the fixing film. . It is desirable to install the paper edge temperature detection sensor 25 at a position where the most paper passing size is predicted.

  FIG. 12 shows the distance from the position of the paper edge temperature detection sensor 25 to the paper edge when the paper edge temperature detection sensor 25 is installed at the paper edge position of the maximum paper passing width, and the paper edge. It represents the difference from temperature. For example, when the maximum size is passed, there is no difference between the temperature detected by the paper edge temperature detection sensor 25 and the paper edge temperature, but when the A4R width paper is passed, for example, from the large size to the width of 38.5 mm. A distance arises. In this case, since an error occurs between about 11.6 ° C. and the detected temperature of the paper edge and the paper edge temperature detection sensor 25, correction is necessary.

  Providing a plurality of paper edge temperature detection sensors 25 corresponding to the paper edge positions of the paper used in the longitudinal direction makes it possible to cope with each paper size, and it is possible to further improve accuracy by eliminating the need for correction.

As described above, by directly detecting the film surface layer temperature, the paper edge temperature can be detected with high accuracy, and further, paper edge scraping can be detected with high accuracy.
<Fourth embodiment>
An image forming apparatus according to another embodiment of the present invention will be described. The basic configuration of the present embodiment is the same as that of the second embodiment, and differences from the second embodiment will be described below.

  FIG. 13 is a flowchart showing an operation when an operation after the replacement instruction display is added to the life prediction operation of the second embodiment. In addition, the step which shows the operation | movement same as the operation | movement shown in FIG. 9 is attached | subjected the same code | symbol, and the overlapping description is abbreviate | omitted.

  After the A4L remaining life time reaches the replacement display time (step S922) and displays a replacement instruction (step S923), if a substitute can be made with another size (step S924), an instruction to change to another size is displayed. (Step S925). On the other hand, if substitution of another size is impossible (step S924), the process condition is changed (step S926), and the process ends.

  FIG. 14 is a table showing the remaining life for each size.

  For example, if the remaining life of A4L is 0 when the remaining life of A4L is 0, such as the remaining life of each size in FIG. 13, it is determined that other sizes can be used instead of stopping the main body. An A4R change instruction display is issued (recommended for the user). In this way, the operation is enabled by changing to A4R. As a result, the fixing unit can be used up over the entire length, and the running cost can be reduced. If another size cannot be substituted after the replacement instruction is displayed, process conditions such as slowing the image forming speed and lowering the fixing temperature are changed in order to extend the time until replacement. As a result, the amount of paper edge scraping per sheet can be suppressed, the life correction time that can be subtracted is lengthened, and the main body can be operated without stopping.

  As described above, the life of the fixing unit can be accurately determined, so that the fixing unit can be used up and the running cost can be reduced and the stoppage of the operation of the main body can be reduced.

DESCRIPTION OF SYMBOLS 12 ... Fixing unit 15 ... Fixing film 16 ... Recording material 17 ... Toner 18 ... Temperature detection element 19 ... Heating source 21 ... Pressure roller 22 ... Heating nip part 25 ... Paper edge temperature detection sensor

Claims (9)

A fixing device for fixing the recording material on which an image is formed by the image forming unit by passing the recording material through a fixing nip heated by the heating unit;
Temperature detecting means for detecting the temperature of the fixing device;
A recording material having a predetermined width in a direction orthogonal to the conveying direction of the recording material is obtained from the number of sheets that pass through the fixing nip portion and the detection result of the temperature detection unit. Control means for determining the life of the fixing device based on the temperature of the fixing device corresponding to the position of the end in the width direction;
Equipped with a,
When there are a plurality of the predetermined widths of the recording material according to the size of the recording material, the control unit corresponds to the number of sheets passing through the fixing nip portion and the position of the end portion for each size of the recording material to be conveyed. An image forming apparatus that determines the life of the fixing device based on the temperature of the fixing device. When the detection position where the temperature detection means detects the temperature and the position of the fixing device corresponding to the position of the end portion are different,
The control means obtains the temperature of the fixing device corresponding to the position of the end portion from a temperature difference between the detection position and the position of the fixing device corresponding to the position of the end portion stored in advance. The image forming apparatus according to claim 1. When the detection position where the temperature detection means detects the temperature and the position of the fixing device corresponding to the position of the end portion are different and are separated by a predetermined distance,
The control unit obtains a temperature of the fixing device corresponding to the position of the end portion from a temperature difference between the detection position and a position stored at a predetermined distance from the detection position stored in advance. The image forming apparatus according to claim 1.   When the detection position where the temperature detection means detects the temperature is the position of the fixing device corresponding to the position of the end, the temperature of the fixing device corresponding to the temperature detected by the temperature detection means corresponds to the position of the end. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Wherein, when said fixing device is determined to be life image forming apparatus according to any one of claims 1 to 4, characterized in that a predetermined warning. Wherein, when said fixing device is determined to be a life for the recording material of one size even without least is any one of claims 1 to 4, characterized in that a predetermined warning The image forming apparatus described in 1. When the control unit determines that the fixing device has a lifetime for a recording material of a predetermined size, the control means notifies that the recording material that does not pass through the position of the end in the width direction of the recording material of the predetermined size is used. The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. When the control unit determines that the fixing device has a life for a recording material of a predetermined size, the life of the fixing device when the recording material in which the short side and the long side of the recording material are exchanged is conveyed. The image forming and fixing is performed on the replaced recording material when the replaced recording material does not pass through the position of the end portion in the width direction of the recording material of the predetermined size determined to be The image forming apparatus according to any one of 1 to 7 . Wherein, when said fixing device has determined that the predetermined lifetime is one of the claims 1 to 8 the temperature of the fixing nip portion is heated by the heating means and changes to be lower The image forming apparatus according to claim 1.

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