JP2007309980A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus where damages to a mechanism caused by an overloading to a fixer is prevented, and the fixer is used to the limit, thus the reducing running cost. <P>SOLUTION: In the image forming apparatus provided with a fixing unit 40 rotatively driven by a fixing/driving motor 47, a CPU 104 measures the driving load of the fixing/driving motor 47 by a torque detector 103 during reverse rotation as a non-paper passing period in which the driving load of the fixing/driving motor 47 is not varied, and based on the measured driving load, whether the fixing unit 40 reaches its end of lifetime, i.e., whether it is time for replacement. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and in particular, in an image forming apparatus such as a copying machine or a printer using an electrophotographic process method, a toner image formed on a recording material (hereinafter referred to as a transfer material) is formed on the transfer material. The present invention relates to an image forming apparatus provided with an image heat fixing device for heat fixing.

  In the prior art, replacement of the fixing device is generally performed from the following viewpoints.

(1) When the predetermined number of sheets has been reached (2) When the predetermined cumulative driving time has been exceeded (3) When the surface property of the fixing belt (or roller) has deteriorated
JP-A-8-95438 Japanese Patent Laid-Open No. 11-305579

  However, there are concerns about the following points in the prior art.

  (1) Even if the fixing device has not reached the end of its service life, the running cost cannot be reduced because the fixing device is replaced when the predetermined number or the predetermined time is exceeded.

  (2) Even if the driving torque is increased due to the deterioration of the surface property, the replacement is not performed unless the predetermined number of sheets or the predetermined time is exceeded, so that the surrounding mechanical mechanisms may be damaged.

  The present invention has been made paying attention to the above points, and prevents damage to the mechanical mechanism due to overload on the fixing device, and it is possible to reduce the running cost by using the fixing device to the limit. An object of the present invention is to provide an image forming apparatus.

  In the present invention, not only the life of the fixing device is determined by a predetermined number of sheets to be passed and the accumulated time, but also the driving load of the fixing device is measured, and the life of the fixing device is determined by the value of the load. Also, as a load measurement timing, the driving load in the fixing device is detected (detecting the driving current of the fixing motor) at times other than when a large load fluctuation is passed (during image adjustment, post-rotation, etc.), and the mechanical mechanism is damaged. When the last load is reached, it is determined that the life of the fixing device is reached. Thereby, it is possible to prevent damage to the mechanical mechanism due to overload and reduce the running cost by using the fixing device to the limit.

  That is, the technical contents of the present invention can solve the above-described problems by including the following configuration.

  (1) A rotating body for fixing a recording material on which a toner image is formed, a pressure rotating body that presses against the rotating body to form a nip portion, and the rotational body and the pressure rotating body are driven to rotate. And an image fixing device for fixing the image on the recording material by sandwiching and transporting the recording material at the nip portion. The image forming apparatus includes a replacement time determining unit that measures the driving load during a non-sheet passing period in which the driving load does not vary, and determines the life of the image fixing device based on the measured value of the driving load. An image forming apparatus.

  (2) a unit for measuring and storing the number of sheets of the image fixing device, and a unit for measuring and storing the driving integration time of the image fixing device, wherein the replacement time determining unit The image forming apparatus according to (1), wherein the life of the image fixing device is determined based on a driving integration time and a driving load measured by the driving load measuring unit.

  (3) The image forming apparatus according to (1), wherein the rotation driving unit is a DC brushless motor.

  (4) The image forming apparatus according to (1), wherein the driving load measuring unit calculates the driving load by detecting a driving current of the rotation driving unit.

  According to the present invention, it is possible to prevent damage to the mechanical mechanism due to overload on the fixing device, and to reduce the running cost by using the fixing device to the limit.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

  FIG. 1 is a schematic sectional view showing the overall configuration of an electrophotographic color copying machine according to an embodiment of the image forming apparatus of the present invention. The electrophotographic color copying machine of the present embodiment is a color image output apparatus in which a plurality of image forming units are arranged in parallel and an intermediate transfer method is adopted, which is considered to be applied particularly effectively.

  In this embodiment, the electrophotographic color copying machine has an image reading unit 1R and an image output unit 1P. The image reading unit 1R optically reads a document image, converts it into an electrical signal, and transmits it to the image output unit 1P. The image output unit 1 </ b> P includes a plurality of image forming units 10 (10 a, 10 b, 10 c, 10 d) arranged in parallel in the present embodiment, and a paper feeding unit 20. The image forming apparatus also includes an intermediate transfer unit 30, a fixing unit 40 (corresponding to an image fixing device), a cleaning unit 50, a cleaning blade 70, a photo sensor 60, and a control unit 80.

  Further, each unit will be described in detail.

  Each image forming unit 10 (10a, 10b, 10c, 10d) has the same configuration. In each image forming unit 10 (10a, 10b, 10c, 10d), a drum-shaped electrophotographic photosensitive member as a first image carrier, that is, a photosensitive drum 11 (11a, 11b, 11c, 11d) is freely rotatable. And is rotationally driven in the direction of the arrow. A primary charger 12 (12a, 12b, 12c, 12d) and an optical system 13 (13a, 13b, 13c, 13d) are arranged in the rotational direction opposite to the outer peripheral surfaces of the photosensitive drums 11a to 11d. Further, a folding mirror 16 (16a, 16b, 16c, 16d), a developing device 14 (14a, 14b, 14c, 14d), and a cleaning device 15 (15a, 15b, 15c, 15d) are arranged.

  In the primary chargers 12a to 12d, charges of a uniform charge amount are given to the surfaces of the photosensitive drums 11a to 11d. Next, light beams such as laser beams, which are modulated by the optical systems 13a to 13d in accordance with the recording image signal from the image reading unit 1R which is also a recording image signal output unit, are passed through the folding mirrors 16a to 16d. It exposes on 11a-11d. Thereby, electrostatic latent images are formed on the photosensitive drums 11a to 11d.

  Further, the electrostatic latent images are visualized by developing devices 14a to 14d each containing developer of four colors such as yellow, cyan, magenta and black (hereinafter referred to as “toner”). The visualized visible image is transferred to a belt-like intermediate transfer member as the second image carrier constituting the intermediate transfer unit 30 in the image transfer regions Ta, Tb, Tc, and Td, that is, the intermediate transfer belt 31. To do. The intermediate transfer unit 30 will be described in detail later.

  On the downstream side of the image transfer areas Ta, Tb, Tc, and Td, the toner remaining on the photosensitive drums 11a to 11d without being transferred to the intermediate transfer belt 31 by the cleaning devices 15a, 15b, 15c, and 15d is scraped off. Clean the drum surface. By the process described above, image formation with each toner is sequentially performed.

  The paper feeding unit 20 includes a cassette 21 for storing the transfer material P and a pickup roller 22 for feeding the transfer material P from the cassette 21 one by one. Here, although only the cassette 21 is illustrated in the present embodiment, there may be a plurality of cassettes or a manual feed tray. Further, the sheet feeding roller pair 23 for further conveying the transfer material P fed from the pickup roller 22 and a sheet feeding guide 24 are provided. And it has the registration roller 25 for sending out the transfer material P to the secondary transfer area | region Te according to the image formation timing of each image formation part 10 (10a, 10b, 10c, 10d).

  The intermediate transfer unit 30 will be described in detail.

  The intermediate transfer belt 31 is stretched and wound between a drive roller 32 that transmits driving to the intermediate transfer belt 31, a driven roller 33 that is driven by the rotation of the intermediate transfer belt 31, and a secondary transfer counter roller 34. ing. Here, the driven roller 33 serves as a tension roller that applies an appropriate tension to the intermediate transfer belt 31 by urging a spring (not shown). A primary transfer plane A is formed between the driving roller 32 and the driven roller 33. As the intermediate transfer belt 31, for example, PET (polyethylene terephthalate), PVdF (polyvinylidene fluoride), or the like is used. The drive roller 32 is coated with rubber (urethane or chloroprene) having a thickness of several millimeters on the surface of the metal roller to prevent slippage with the intermediate transfer belt 31. The drive roller 32 is rotationally driven by a pulse motor (not shown).

  Primary transfer chargers 35 (35 a to 35 d) are disposed on the back of the intermediate transfer belt 31 in the primary transfer regions Ta to Td where the photosensitive drums 11 a to 11 d and the intermediate transfer belt 31 face each other. On the other hand, a secondary transfer roller 36 is disposed so as to face the secondary transfer counter roller 34, and a secondary transfer region Te is formed by a nip with the intermediate transfer belt 31. The secondary transfer roller 36 is pressed against the intermediate transfer belt 31 with an appropriate pressure.

  A cleaning unit 50 for cleaning the image forming surface of the intermediate transfer belt 31 is disposed downstream of the secondary transfer region Te of the intermediate transfer belt 31. The cleaning unit 50 includes a cleaning blade 52 for removing toner on the intermediate transfer belt 31 and a waste toner box 53 for storing waste toner.

  A cleaning blade 70 and a pulse motor (not shown) for attaching / detaching the cleaning blade 70 to / from the transfer belt 31 are provided between the driven roller 33 and the secondary transfer counter roller 34 of the intermediate transfer belt 31. The cleaning blade 70 is also for removing toner on the transfer belt 31.

  The fixing unit 40 includes a fixing roller 41a provided with a heat source such as a halogen heater therein, and a pressure roller 41b (which may also include a heat source). The fixing roller 41a and the pressure roller 41b can be separated by a pressure release unit (not shown) (see FIG. 2). Further, a guide 26 for guiding the transfer material P to the nip portion of the roller pair 41a, 41b and a fixing heat insulating cover 51a, 51b for confining the heat of the fixing unit 40 are provided. Further, an inner discharge roller 27 and an outer discharge roller 28 for guiding the transfer material P discharged from the roller pair 41a and 41b to the outside of the image forming apparatus, and a discharge tray 29 on which the transfer material P is stacked. Etc.

  Next, the operation of the electrophotographic color copying machine having the above configuration will be described.

  When an image forming operation start signal is issued by the CPU of the control unit 80, the sheet feeding operation is started from the sheet feeding stage selected according to the selected sheet size or the like.

  For example, the case where paper is fed from the cassette 21 in this embodiment will be described. In FIG. 1, first, the transfer material P is fed one by one from the cassette 21 by the pickup roller 22. The transfer material P is guided between the paper feed guides 24 by the paper feed roller pair 23 and conveyed to the registration rollers 25. At that time, the registration roller 25 is stopped, and the leading edge of the transfer material P hits the nip portion. Thereafter, the registration roller 25 starts rotating in accordance with the timing at which the image forming unit 10 starts image formation. The rotation timing is set so that the transfer material P and the toner image primarily transferred from the image forming unit 10 onto the intermediate transfer belt 31 coincide in the secondary transfer region Te.

  On the other hand, when the image forming operation start signal is issued, the image forming unit 10 starts the image forming operation by the process described above. That is, the toner image formed on the photosensitive drum 11d that is the most upstream in the rotation direction of the intermediate transfer belt 31 (arrow B) is transferred to the primary transfer region Td by the primary transfer charger 35d to which a high voltage is applied. Primary transfer is performed on the intermediate transfer belt 31. The primarily transferred toner image is conveyed to the next primary transfer region Tc. In this case, image formation is performed by delaying the time during which the toner image is conveyed between the image forming portions, and the next toner image is transferred by aligning the resist on the previous image. Thereafter, the same process is repeated, and eventually the four color toner images are primarily transferred onto the intermediate transfer belt 31.

  Thereafter, when the transfer material P enters the secondary transfer region Te and contacts the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in accordance with the passing timing of the transfer material P. As a result, the four color toner images formed on the intermediate transfer belt 31 by the above-described process are transferred onto the surface of the transfer material P. Thereafter, the transfer material P is accurately guided to the fixing roller nip portion by the conveyance guide 26. The toner image is fixed on the surface of the transfer material P by the heat of the roller pair 41a and 41b and the pressure of the nip. Thereafter, the transfer material P is conveyed by the inner and outer discharge rollers 27 and 28, and the transfer material P is discharged out of the image forming apparatus and stacked on the discharge tray 29.

  FIG. 2 is a schematic cross-sectional side view of the fixing unit 40.

  The fixing unit 40 sandwiches the transfer material P between the upper belt unit 41a, which is a rotating body for heating the transfer material P on which the toner image t formed thereon (in the direction of the arrow X) is conveyed to the fixing device. The lower belt unit 41b (corresponding to a pressurizing rotator) is provided. The upper belt unit 41a corresponds to the fixing roller 41a in FIG. 1, and the lower belt unit corresponds to the pressure roller 41b in FIG. Each belt unit 41a, 41b has a flexible endless fixing belt (hereinafter referred to as a belt) 42a, 42b. The belts 42a and 42b are stretched between the driving rollers 43a and 43b and the driven rollers 44a and 44b in a tension state. The upper drive roller 43a and the lower drive roller 43b are connected to a fixing drive motor 47 as a rotational drive means.

  Each belt unit 41a, 41b includes pressure pads 45a, 45b. Each pressure pad 45 is fixed to the driving roller 43 and the driven roller 44 of each belt unit 41. Therefore, as shown in FIG. 2, the nip portion N can be formed by the pressure pad 45 and the drive roller 43 when the lower belt unit 41 b is in a wearing (pressure contact) state. In the nip portion N, the transfer material P can be nipped and pressed via the upper and lower belts 42a and 42b. Further, oil is applied between the pressure pad 45 and the belt 42. For this purpose, the sliding resistance between the pressure pad 45 and the belt 42 is reduced, the rotational drive torque applied to the fixing drive motor 47 is reduced, the tension applied to the belt 42 is reduced, and the life of the belt 42 is extended. effective.

  A halogen lamp heater (not shown) (hereinafter referred to as a heater) is arranged as a heating means inside the driving roller 43a and the driven roller 44a of the upper belt unit 41a. When the transfer material P passes through the nip portion N, the toner image t on the transfer material P can be heated and fixed through the belt 42.

  A detachable motor 46 is connected to the upper belt unit 41a and the lower belt unit 41b, and each belt unit 41 is configured to rotate. When each belt unit 41 rotates, the upper belt 42a and the lower belt 42b are separated from each other and are in a detached (separated) state. Accordingly, the nip portion N is eliminated and the binding force to the transfer material P is eliminated (see FIG. 3).

  The fixing unit 40 includes an upper cover 51a so as to cover the upper belt unit 41a and a lower cover 51b so as to cover the lower belt unit 41b. Since these are fixed, the clearance between the cover 51 and the belt 42 becomes small when the belt unit 41 is removed. The upper and lower covers 51a and 51b correspond to the fixing heat insulating covers 51a and 51b in FIG. 1, respectively.

  Further, an inner paper discharge roller pair 27 is provided on the downstream side, and assists the discharge of the transfer material P discharged from between the upper and lower belt units 41. The inner discharge roller pair 27 is fixed to the upper belt unit 41a and the lower belt unit 41b, respectively, and when the belt unit 41 is in the detached state, the inner discharge roller pair 27 is separated.

  Further, as a sensor for detecting the transfer material P, a fixing inlet sensor 48 is provided on the upstream side, and an internal paper discharge sensor 49 is provided on the downstream side. The fixing entrance sensor 48 detects that the transfer material P has entered the fixing unit 40, and the inner paper discharge sensor 49 detects that the transfer material P is discharged from the fixing unit 40. FIG. 3 illustrates the detached state in which the fixing belt 42 is separated.

  FIG. 4 shows the fixing unit 40 of the image forming apparatus and its driving. The fixing unit 40 is driven by a fixing drive motor 47 via the speed reduction unit 101. A signal from an after-mentioned fixing drive motor 47 or an external drive load measuring means 103 (for example, drive current detecting means, torque converter, etc.) is sent to the CPU 104 (exchange) via an A / D converter (not shown) if necessary. Equivalent to time determination means). A signal from the driving load measuring means input to the CPU 104 is converted into a load size as necessary. In that case, a conversion table prepared in advance is used.

FIG. 5 shows an example of a specific torque detecting device 103 as a driving load measuring means. The DC brushless motor consumes a current corresponding to the driving load. Therefore, when a DC brushless motor is used for fixing driving, the current supplied to the fixing driving motor 47 can be calculated by the CPU 104. For example, the current detection resistor 103a is first connected in series to the power supply line (VDD in FIG. 5) of the fixing drive motor 47, and V is the difference between the voltages V _A and V _B across the current detection resistor 103a. the _a -V _B is calculated by the difference circuit 103b. And it can calculate by inputting into CPU104 or an A / D converter. Further, if a conversion table created from a graph showing the relationship between the detected voltage (V _A -V _B ) (or detected current) and the drive load (torque) as shown in FIG. 6 is used, the drive load on the motor shaft can be easily obtained. Can be detected.

  In the case of a fixing device in which the fixing belt 42 (or roller) can be separated, generally, when the fixing device is in the attached state, friction between the rollers is added to the torque in the detached state. The driving load becomes larger in the wearing state. Further, when the paper is passed through the fixing device, the load fluctuation becomes large due to a paper rush shock or the like.

  FIG. 7 shows the load fluctuation of the fixing device. Since section a is in a standby state in which no printing operation is performed, the fixing device is in a detached state, so that the current value, that is, the load is light. In the section b, since the printing operation is performed, the load is increased because the fixing device shifts from the detached state to the worn state. In section c, the load is constant when the fixing device is worn. Since the section d is in the paper passing state, the load fluctuation is large due to a paper rush shock or the like, and the current value is not constant. The section e is a post-rotation period after the end of paper passing, and this period is a constant load period when the fixing device is worn and the paper is not passed. In the section f, since the printing operation ends and returns to the standby state, the fixing device shifts from wearing to unloading, and the load is lightened.

  In order to perform accurate load measurement with the fixing device in a worn state, it is not suitable when a paper having a large load fluctuation is passed, and is preferably performed when a paper is not passed. It is also important to measure without affecting the print sequence. For example, since the wearing state (section c) before passing paper may affect FCOT (First Copy Out Time), it is not preferable as the measurement period. Therefore, in the present embodiment, load measurement is performed during the section e in which the load fluctuation is small and the print sequence is not affected, that is, during post-rotation. However, if it is clear that the print sequence is not affected, the measurement may be performed in the wearing state (section c) before passing the paper.

  FIG. 8 shows how the driving load of the fixing device changes with time. Over time, the load will increase, and if the load exceeds a certain value, the surrounding mechanical mechanism will be damaged, so replacing the fixing device immediately before reaching that value also reduces the running cost. desirable.

  FIG. 9 shows a flowchart for determining the life in this embodiment. When the power is turned on in step S201, a standby state is set in step S202. When the printing operation is started in step S203, the fixing device is changed from the detached state to the wearing state in step S204. In step S205, printing is performed, that is, the sheet is in a passing state. In step S206, it is determined whether or not the vehicle is in the post-rotation state. If the post-rotation is in progress, the process proceeds to step S207. If the post-rotation is not in progress, the next printing (paper passing) is performed (step S205). If post-rotation is in progress, the load on the fixing device is measured in step S207. If the load measured in step S208 exceeds the threshold, the process proceeds to step S209. If not, the process proceeds to step S210. In step S209, since the measured value exceeds the threshold value, it is determined that the fixing device has reached the end of its life. In step S211, the print sequence is terminated and error display is performed. In step S210, since the measured value does not exceed the threshold value, it is determined that the fixing device has not reached the end of its life. In step S212, the print sequence is terminated and the operation is continued.

  As described above, by measuring the load on the fuser during post-rotation, it is possible to accurately measure the load on the fuser, and to determine the life with high accuracy, thereby reducing running costs. In addition, the reliability of the product can be improved.

  As a second embodiment, a conventional method for determining the life of a fixing device, which uses a predetermined number of sheets to be passed and a predetermined drive integration time together, will be described.

  The subsequent operation is determined based on the measured load of the fixing device and the number of sheets passed at that time, or the drive integration time. For example, let us consider a case where the measured load (current value) of the fixing device is within a certain range, that is, within a range of 90 to 95% of the value regarded as the fixing device lifetime. If the number of sheets to be passed is 200,000 sheets or less and the accumulated driving time is 4000 hours or less, the user is notified of a warning, that is, a message such as “Fixer replacement time is approaching”. Even with the same load (current value), if the number of sheets to be passed is 200,000 sheets or more, or if the drive integration time is 4000 hours or more, it is determined that the life of the fixing device has been reached, and an error, that is, “fixing” Please replace the device ”message. However, the measured load (current value) range of the fixing device, the number of sheets passed, and the drive integration time do not have to be the range, the number of sheets, and the time described in the present embodiment.

  FIG. 10 shows a flowchart.

  When the power is turned on in step S301, a standby state is set in step S302. When the printing operation is started in step S303, the fixing device is changed from the detached state to the wearing state in step S304. In step S305, printing is performed, that is, a sheet is being passed. In step S306, it is determined whether or not the vehicle is in the post-rotation state. If the post-rotation is in progress, the process proceeds to step S307. If the post-rotation is not in progress, the next printing (paper passing) is performed (step S305). If post-rotation is in progress, the load on the fixing device is measured in step S307. If the load measured in step S308 is smaller than a certain range, the process proceeds to step S309, and if not smaller, the process proceeds to step S310. In step S309, since the measured value is smaller than a certain range, it is determined that the fixing device has not yet reached the end of its life. In step S311, the print sequence is terminated and the operation is continued. In step S310, if the measured value is larger than a certain range, the process proceeds to step S312 and if not larger, the process proceeds to step S313. In step S312, since the measured value is larger than a certain range, it is determined that the fixing unit has reached the end of its life. In step S314, the print sequence is terminated and an error is displayed. Step S313 is excluded from steps S308 and S310, that is, the measured load of the fixing device is within a predetermined range. Therefore, if the number of sheets to be passed is equal to or less than the predetermined number and the accumulated driving time is equal to or shorter than the predetermined time, the process proceeds to step S315. Since it exceeds, it progresses to step S312. In step S315, it is determined that the life of the fixing device is approaching because the load on the fixing device is within a predetermined range, the number of sheets to be passed is not more than the predetermined number, and the drive integration time is not more than a predetermined time. Exit and display a warning.

  For example, the CPU 104 is used as a means for measuring and storing the number of sheets passing through the fixing unit 40. At this time, the measured number of sheets to be passed may be stored in a register inside the CPU 104 or a non-volatile memory outside the CPU 104. Similarly, for example, the CPU 104 can be used as means for measuring and storing the accumulated driving time of the fixing unit 40. As in the case of the number of sheets to be passed, the measured drive integration time may be stored in a register inside the CPU 104 or in a nonvolatile memory outside the CPU 104.

  As described above, the load of the fixing device is measured, and the life of the fixing device is determined from both the value, the number of sheets to be passed, and the accumulated operation time, thereby determining the life according to the usage state of the image forming apparatus. Will be able to.

1 is a schematic cross-sectional view of an image forming apparatus according to the present invention. Schematic cross-sectional side view showing the fixing (pressing) state of the fixing unit in the present invention FIG. 3 is a schematic cross-sectional side view showing a state where the fixing unit is removed (separated) in the present invention. The block diagram which shows the fixing unit and torque detection apparatus in this invention Detailed block diagram of torque detector in the present invention Graph showing the correlation between the detection voltage for generating a conversion table (V A _{-V B)} and the drive load (torque) A graph showing the state of load (pressure contact) and removal (separation) of the fixing unit and load fluctuation Graph showing the change over time of the driving load in the fixing unit Flowchart for determining the life of a fixing unit in Embodiment 1. Flowchart for determining the life of a fixing unit in Embodiment 2.

Explanation of symbols

1R image reading unit 1P image output unit 10 image forming unit 11 photoconductor drum 12 primary charger 20 sheet feeding unit 30 intermediate transfer unit 40 fixing unit (corresponding to image fixing device)
41a Upper belt unit (equivalent to rotating body)
41b Lower belt unit (equivalent to a pressure rotating body)
42a Upper fixing belt 42b Lower fixing belt 43a Upper driving roller 43b Lower driving roller 44a Upper driven roller 44b Lower driven roller 45a Upper pressure pad 45b Lower pressure pad 46 Removable motor 47 Fixing drive motor (corresponding to rotation drive means)
48 Fixing entrance sensor 49 Internal paper discharge sensor 103 Torque detection device (corresponding to driving load measuring means)
104 CPU (corresponding to replacement time determining means) (corresponding to means for measuring and storing the number of sheets passing through the image fixing device and means for measuring and storing the driving integration time of the image fixing device)
P transfer material (equivalent to recording material)

Claims (4)

  A rotating body for fixing a recording material on which a toner image is formed, a pressure rotating body that presses against the rotating body to form a nip portion, and a rotational drive that rotationally drives the rotating body and the pressure rotating body. And an image fixing device for fixing the image on the recording material by sandwiching and transporting the recording material at the nip portion. The apparatus further comprises a replacement time determining means for measuring the driving load during a non-paper passing period in which the driving load does not vary and determining the life of the image fixing device based on the measured value of the driving load. Image forming apparatus.   Means for measuring and storing the number of sheets passing through the image fixing device, and means for measuring and storing the cumulative driving time of the image fixing device, wherein the replacement time determining means comprises the number of passing sheets and the cumulative driving time. 2. The image forming apparatus according to claim 1, wherein the life of the image fixing device is determined based on the driving load measured by the driving load measuring unit.   The image forming apparatus according to claim 1, wherein the rotation driving unit is a DC brushless motor.   The image forming apparatus according to claim 1, wherein the driving load measuring unit calculates the driving load by detecting a driving current of the rotation driving unit.

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