JPH02168289A - Picture forming device - Google Patents

Abstract

PURPOSE:To display an abnormality message for an operator and to stop the action of a device when film becomes abnormal by providing an abnormal film detecting means on a fixing device fixing through the film. CONSTITUTION:After a motor rotates, the film 11 of a fixing unit is controlled to come to an operator's side. When a film position sensor 16 detects that the film 11 comes to the operator's side, a solenoid 23 is turned on and control is switched to bring the film 11 to the recesses. Similarly, when another sensor 17 detects that the film 11 comes to the recesses, the solenoid 23 is turned off and the control is switched to bring the film 11 to the operator's side. By repeating these actions, the film 11 can be positioned between the sensors 16 and 17. When sensors 24 and 25 detect that the film 112 abnormally comes to one side due to a troubled spring 22, the action of the device is stopped. Thus, the damage of the film 11 is prevented and moreover the abnormality of the fixing unit can be displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus such as a copying machine or a printer that uses a fixing device that fixes images through a film.

(Prior art) In a fixing device that uses an endless belt, it is necessary to prevent the belt from misaligning.The causes of this misalignment include the parallelism and twisting of the two rollers that apply tension to the belt. However, there is a limit to how much accuracy can be improved, and it is extremely difficult to prevent sheet misalignment just by improving accuracy.

Therefore, as a conventional means for controlling the deviation of the belt, at least one of the two rollers that apply tension to the endless belt is made into a crown shape, or a collar is attached to both ends of the roller, and the endless belt is We are adjusting the bias.

(The problem that the invention is trying to solve) However,
In the case of a conventional fixing device misalignment adjustment means using an endless belt, if a thin heat-resistant sheet with a belt thickness of less than 100 μm is used, even if a crown roller or a flange roller is used, the heat-resistant sheet has no elasticity and is thin. As a result, wrinkles and the like occur in the heat-resistant sheet, and it is difficult to correct the deviation.

Therefore, by displacing one of the roller shafts of the rollers that apply tension to this film-like endless belt (hereinafter referred to as "endless film"), it is possible to change the direction of the endless film, and at the same time, the position of the endless film can be changed. Set up a sensor to detect
By controlling the deviation, it becomes possible to correct the deviation. However, in the above-mentioned shifting control mechanism, if the endless film shifts to either end due to a malfunction or other cause, not only the endless film is damaged, but also the fuser is damaged. There was a drawback. In addition, if wrinkles or the like occur in the endless film, not only will it affect the formed image, but it may also become impossible to control the deviation.

[Means and effects for solving the problems] According to the present invention, abnormalities in the film can be detected by providing the above-mentioned film abnormality detection means. Further, when the film is abnormal, an abnormality message is displayed to the operator and the operation of the apparatus is stopped. This not only prevents damage to the film, but also prevents damage to the fixing device and the device including it.

(Example) FIG. 1 is a sectional view of a copying machine which is an example of an image forming apparatus to which the present invention is applied, FIG. 2 is a top view of a fixing device 1, and FIG. 3 is an enlarged sectional view of the fixing device 1. be.

First, the general structure of the image forming apparatus of this embodiment will be described with reference to FIG. 1. Reference numeral 51 denotes a document mounting table made of a transparent member such as glass, which scans the document by reciprocating in the direction of arrow a. A short-focus, small-diameter imaging element array 52 is arranged directly below the document placement table, and the document image placed on the document placement table is illuminated by an illumination lamp 53, and the reflected light image is transferred to the photosensitive drum by the array 52. 54 is slit exposed. Note that this photosensitive drum 54 rotates in the direction of the arrow. A charger 55 uniformly charges the photosensitive drum 4 coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. The drum 4, which is uniformly charged by the charger 5, is subjected to image exposure by the element array 2 to form an electrostatic image. This electrostatic latent image is developed by a developing device 6 using toner made of a resin or the like that softens and melts when heated. On the other hand, the sheet P stored in the cassette S is exposed to light by a pair of conveyance rollers 58 that are rotated while being pressed vertically in synchronization with the image on the feed roller 7 and the photosensitive drum 4. It is fed onto the drum 54. Then, the toner image formed on the photosensitive drum 54 is transferred onto the sheet P by the transfer discharger 59. Thereafter, the sheet P separated from the photosensitive drum 4 by a known separation means is guided to the fixing device 1 by a conveyor belt 60, subjected to heat fixing processing, and then discharged onto a tray 62. Note that after the toner image is transferred, residual toner on the photosensitive drum 54 is removed by a cleaner 63.

FIG. 3 shows an enlarged view of the fixing device 1 of this practical example. 11 is a total thickness of 100 μm or less, more preferably 40 μm
A heat-resistant film with a thickness of less than 20 μm in this example
Polyimide, polyetherimide, PES, PF
A is an endless film whose image contacting surface is coated with a release layer such as PTFE to a thickness of about 10 μm), and the endless film 11 is driven by a motor (not shown) transmitting the drive to the drive roller 13 in the direction of the arrow. Due to the tension and drive of the driving roller 13 and the driven roller 12, the fixing film 11 moves in the direction of the arrow. Further, 14 is a low heat capacity positive linear heating element (hereinafter referred to as a heater) that is fixedly supported on the fixing device 1, and 15 is a pressure roller having a rubber elastic layer with good release properties such as silicone rubber, which has a total pressure of 4 to 4.
The heater is pressurized with 7 kg through the film and rotated in pressure contact with the film. With the fixing device described above, the transfer paper on which the toner image has been formed is guided to the fixing section by the population guide 10, enters between the pressure roller 15 and the film 11, and is heated by the heater 14 provided through the film. The device for heating the toner through the film has 20.21 bearings at both ends, and the bearing 20 side is pressed against the side plate by 22 compression springs. Here, in the tree configuration, the drive roller 13. Unless the accuracy of the parallelism (X-axis direction, Y-axis direction, X-axis direction) of the driven roller 12, heater 14, and pressure roller 15 is set to ±0, the drive roller 13 is driven to move the film in the direction of the arrow. As time goes by, this film 11 shifts to the right or left from the initial position of the film 11 shown in FIG. 1 due to the positional relationship of the three rollers and the heater (variations in the directions of the Otherwise, the edges of the film will rub against the side plates 18 and 19, resulting in damage. Therefore, in this embodiment, a solenoid 23 is connected to the bearing 20 so that the position of the driven roller 12 is not variable. Here, solenoid 23 is OFF
In this case, the film 11 is set to be closer to the front side as shown in FIG. 1, and when the solenoid 23 is ON, the film is similarly set to be closer to the back side. 161
Reference numerals 7, 24, and 25 are photosensors that detect the position of the film. The sensor 2425 is installed to detect a position further outside than the detection position of the sensors 16 and 17.

Further, as shown in FIG. 1, both end portions 3 and 3' of the film 11 are masked to block light from the photosensor. In this embodiment, a photointerrupter is used as the photosensor, but if a reflective photosensor is used here, both ends 3.
The 3' portion requires treatment with a reflective member to reflect light. In addition, in this example, masking and other treatments are applied only to both ends, but it goes without saying that the process may be applied to the entire film.

4.5 shows a cleaning member for the edges of the film, which constantly cleans the edges of the film to prevent erroneous readings when using a reflective sensor, for example, due to dirt on the edges of the film. It is. Although felt is used in this embodiment, any type can be used as long as it has a cleaning effect.

Next, FIG. 4 shows a schematic diagram of electrical control.

Here, 26 is a microcomputer, and the photo sensors 16, 17, 24, 25 are connected to the input terminals of INI, IN2, . It is connected to IN3° and IN4. Further, a solenoid 23 is connected to the 0UTI terminal. A motor rotation control signal that also drives the main fixing device is output to the 0UT2 terminal. Although not shown, it is equipped with terminals for other manual signals and output signals of the copying machine using this fixing device, and the microcomputer 26
Built-in is a ROM, RAM, etc. in which sequence programs for copying operations of this copying apparatus are programmed.

FIG. 5 shows a flowchart of the film deviation control program of the present fixing device.

This program is also programmed in the built-in ROM in the microprocessor 26 mentioned above, and is called and executed from the main sequence program at fixed time intervals or as needed. There is.

First, in step 1 after starting, the motor 27 is turned OFF.
NL, we are making a judgment as to whether or not there is.

If the motor 27 is on, step 2
If the shifter 27 is OFF, the film returns to the exit of step 10 without performing shift control and returns to the main program.Next, in step 2, check whether the film is shifted toward the front. I am making a judgment as to whether or not. This sets the contents of a predetermined address on the RAM in the microcomputer 26 as the back side flag, and the state of that memory is 1h10.
I am making a judgment. If the film is about to move toward the front, that is, if the rear side flag is O, the process moves to step 3. In step 3, it is determined whether the sensor 25 is on, and if the sensor 25 is not on, the process moves to step 4.

In step 4, it is determined whether the sensor 16 is on, and if it is on, the process moves to step 5. In step 5, the film is coming closer to you and the sensor 16
ONL, the solenoid 23 is turned ON to move the film toward the back side, and at the same time, the back side flag is set, and the process moves to the exit of step 10. Further, in step 4, if the sensor 16 is not turned on, the process directly proceeds to the exit of step 10.

Also, in step 3, the sensor 25 is ONL.

In other words, if the film moves further to the back even though the film is controlled to move toward the front side, the process moves to step 9, sets the film abnormality flag, and moves to step 8. and set solenoid 23 to 0.
FFL/, reset the back side flag and go to step 108
and return to the main sequence. Similarly, in step 2, if the film is about to move toward the back side, that is, if the back side flag is 1, the process moves to step 6. In step 6, it is determined whether the sensor 24 is ON or not, and if the sensor 24 is ON, that is, regardless of whether the film is about to move to the back side,
If it moves further to the front side, the process moves to step 9 and returns to the main program in the same manner as described above. Also, in step 6, the sensor 24 is turned off.
If so, move on to step 7 and check the sensor! 7 is ON or not. If the sensor 17 is not ON, go to step 10 for 8 lines and return to the main program. If the sensor 17 is ON, go to step 8 for 8 lines, turn the solenoid 23 to 0FFt, and move the film to the front side. At the same time as the control is switched to move closer, the rear side flag is reset, the process moves to step 10, and the process returns to the main program.

Next, FIG. 6 shows a flowchart of a film abnormality processing program which is a part of the main program. Here, in step 11, it is determined whether or not the film abnormality flag is set. If it is not set, the process moves to the exit of step 12 and the next main sequence program is executed. If the film abnormality flag is set in step 11, the process proceeds to step 13, where all outputs of all devices (in this embodiment, the copying device) are turned off, and then the process proceeds to step 14, where the film is removed. An error message is displayed, and step 14 is set as an endless loop, so that the main program cannot be executed.

As explained above, when the motor rotates, the endless film 11 of this fixing device is first controlled so that the film approaches the front side, and then the film position sensor 16 controls the endless film 11 of the present fixing device.
By turning on the solenoid 23 when it is detected that the film has moved toward the front side, the control is switched to move the film toward the back side. Similarly, when the film moves towards the back side, when the film position sensor 17 detects that the film moves towards the back side, the solenoid 2
3 OF F L, the control will be switched to move the film closer to you. By repeating this operation, it becomes possible to always position the film 11 between the sensors 16, 17, and at the same time
The sensors 24 and 25 located on the outside of the sensor 24 and 25 detect that the film has shifted abnormally due to, for example, a malfunction in the solenoid 23 or a malfunction in the spring 22.
By stopping the operation of this device, it is possible to prevent damage to the film and at the same time to display an abnormality in the fixing device to the operator. Furthermore, by executing the film abnormality processing program shown in FIG. 6 above at the end of one image formation, if an image is being formed when a film abnormality is detected, the film abnormality processing program described above is executed at the end of the image formation. It is also possible that the process is executed, the operation of the apparatus is stopped, and the next new image forming operation is not performed. In this case, it is possible to detect the abnormal position of the film 11 by locating it inside the position where the film 11 is actually damaged by at least the distance that the film 11 moves in the time required to form one image. Even if a film abnormality is detected during formation, the image being formed can be output normally, and no unformed image will remain in the device, so the operator can remove the unformed image from the device. This also has the effect of eliminating the need for this operation.

In addition, in this example, sensor 1617.24
．． Although a transmission type photosensor is used for 25, it goes without saying that a sensor such as a micro SW or a reflection type photosensor may be used as well.

[Other Examples]

FIG. 7 shows a second embodiment of the invention. This embodiment has a configuration in which the sensors 24 and 25 are removed from the configuration of the first embodiment shown in FIG. The outline of the electrical control is the same as the configuration shown in FIG. 4, except that the sensors 24 and 25 are removed (not shown).

FIG. 8 shows a control flowchart of the second embodiment. This control program is also called and executed from the main sequence program, etc., as explained in the first embodiment. First, after the start, in step 20, it is determined whether the motor 27 is turned on. If the motor 27 is not turned on, the process moves to step 29, sets the solenoid 23 to 0FFL, resets the rear side flag, and moves to the exit of step 24. If the motor 27 is turned on in step 20, the process moves to step 21 and the approach control program is executed. Next, in step 21, it is determined whether the film 11 is moving towards the back side or towards the front side, and here the back side flag is checked. If the back side flag is O, that is, if the film 11 is about to move toward the front side, the process moves to step 22, where it is determined whether the sensor 16 is ON or not. Here, if the sensor 16 is ONL, that is, the film 1
If 1 approaches sensor 16, step 2
13 lines to 3.

In step 23, first, a timer 1 is started to measure a predetermined timer time T4 seconds, and then the solenoid 23 is turned ONL and controlled to move the film toward the back side. Next, the back side flag is set, the process moves to the exit of step 24, and the process returns to the main program. Next, if the sensor 16 is not turned on in step 22, the process moves to step 25. In step 25, it is determined whether or not the timer time quantum of 2 seconds measured by timer 2 has elapsed. If it has not elapsed, the process moves to the exit of step 24, and if it has elapsed, the process moves to step 26. The sensor 17 is turned ON and judged. Here, if the sensor 17 is OFF, the process moves to the exit of step 24, but if the sensor 17 is ON, that is, even though the film 11 is controlled to move toward the front side, the predetermined time 1
If the film 11 is still present in the rear sensor 17 after 2 seconds have elapsed, the process moves to step 32, sets a film abnormality flag, moves to the exit of step 24 via step 29, and returns to the main program.

Next, in step 21, if the back side flag is 1, that is, if the film 11 is about to move to the back side,
It will take 8 lines to proceed to step 27. In step 27, it is determined whether the sensor 17 is ON or not. If the sensor 17 is ON, that is, the film 1
1 has moved to the position of the rear sensor 17, the process moves to step 28. In step 28, the timer 2 which measures a predetermined timer time T2 seconds is started, and the process proceeds to step 29, where the solenoid 23 is set to 0FFL,
The film 11 is controlled to move toward the front, the back side flag is reset to O, and the process moves to the exit in step 24. Also, in step 27, the sensor 17 is ONL.
/ If not, go to step 30 for 8 lines. In step 30, it is determined whether or not the timer time T1 seconds measured by timer 1 has elapsed. If the timer time T1 seconds has not elapsed, the process moves to the exit of step 24, and if it has passed, the process moves to step 31. -Sensor 16 is O
NL, we are making a judgment as to whether or not there is. Step 31
If the sensor 16 is not ON, the process moves to the exit of step 24, and if the sensor 16 is ON, that is, even though the film 11 is controlled to move toward the back side, it moves to the exit of step 24. If there is film in the front sensor 16 even after the time T1 second has elapsed, the process moves to step 32, sets a film abnormality flag, and steps 29
8 lines go to the exit of step 24, and the process returns to the main program.

The processing in the main program is the same as in the first embodiment shown in FIG.
It is possible to disable the operation of the main body sequence and at the same time notify the operator of the abnormality by displaying a film abnormality display.

As explained above, when the motor rotates, the endless film 11 of this fixing device is first moved toward the front side.
When the film position sensor 16 detects that the film 11 has moved toward the front side, the solenoid 23 is turned on to move the film 11 toward the front side.
The control must be switched in order to move the object closer to the back. At this time, a timer 1 is started to measure a predetermined time TI seconds. Next, the film 11 tries to move toward the back side, but until the back side sensor 17 is turned on, the timer 1
Wait until 13 seconds have elapsed at It will be detected. Similarly, when the film 11 moves toward the back side and the back side sensor 17 turns on, the solenoid 23 is controlled to move the 0FFL film 11 toward the front side, and at the same time, a predetermined time of 12 seconds is measured. Start timer 2.

As the film 11 is kneaded, it tries to move towards the front side, but just like when moving towards the back side, wait for 12 seconds on the timer 2 until the near side sensor 16 turns on. If 17 seconds have passed, sensor 17
Checks whether sensor 1 is on.
If the film 11 does not move toward the front at step 7, a film abnormality is detected. Of course, if there is no abnormality in the fixing device, the position of the film 11 will be controlled between the sensors 16 and 17. Here, the predetermined time T1 seconds,
Regarding the setting of T2 seconds, after the front side sensor 16 or the rear side sensor 17 detects the film 11, control is performed in the opposite direction, and the time is set longer than the time until the film becomes undetectable from each sensor. , When the sensors 16 and 17 are in an uncontrollable state after detecting the film, the film moves toward the front and back, respectively, and the time is set to be shorter than the time before it is damaged by the side plate, etc. According to the embodiment, it is possible to control the deviation of the endless film and detect the abnormal position of the film.

FIGS. 9 and 10 show separate flowcharts of the third embodiment of the present invention. The other configuration is the same as the second embodiment, and its operation will be explained with reference to FIGS. 9 and 10. First, in step 40 of FIG. 9, it is determined whether the motor is ON or not. If not, the first
Move to step 29 in Figure 0 and turn off the solenoid 23.
However, the process of resetting the back side flag and proceeding to the exit in step 24 is the same as in the previous embodiment. If the motor is ON in step 40, proceed to step 418
go In step 41, the measured flag is checked, and if the measured flag is 0, step 42
Move to. In step 42, it is determined whether the film 11 is moving towards the front side or towards the back side, and here the back side flag is checked. If the rear side flag is O, that is, if the film 11 is about to move toward the front side, the process moves to step 43.

In step 43, it is determined whether the sensor 16 is ON or not. If it is not ON, step 24 in FIG.
Move to the exit. If the sensor 16 is turned on here, the process moves to step 44. In step 44, the second time flag is checked, and if the second time flag is O, that is, if the film 11 approaches the front sensor for the first time, the process goes to step 45 for eight lines. In step 45, a back side measurement timer is started, then a second flag is set to 1, and the process moves to step 46. In step 46, the control is switched so that the solenoid 23 is ONL, the shifting direction of the film 11 is changed to the back side, and the back side flag is set to 1.
8 lines to step 24 in FIG. 10, which is the exit.

Next, in step 42, if it is determined that the film is closer to the back side, that is, if the back side flag is 1, the process moves to step 48. In step 48, sensor 17
It is determined whether or not the film 11 is ONL, and if the film 11 has not come close to the sensor 17, the process moves to the exit of step 24 in FIG. Also, if the sensor 17 is ONL, that is, the film 1
If 1 moves toward the back side, the process moves to step 49. In step 49, the front side measurement timer is started, the solenoid 23 is set to 0FFL, the control is switched to move the film 11 closer to the front side, and the rear side flag is reset to O.

Next, the back side measurement timer is stopped, the value of the timer is read and written to a predetermined location in the RAM of the microcomputer 26, and then the process moves to the exit of step 24 in FIG.

Next, in step 44, if the second time flag is 1, that is, after the film 11 comes to the front to the position of the sensor 16 in the first time, the control is switched so that it comes to the back side, and then the back side sensor 2 after moving the film 11 to position 17 and switching the control to move the film 11 toward the front again.
If the film comes to the position of the sensor 16 for the second time, the process moves to step 47. In step 47,
Stop the front side measurement timer and read the timer value. The timer value at this time is the time it takes for the film 11 to move toward you from the position of the sensor 17 to the position of the sensor 16, and the unit time is determined from the distance of the sensor 18, 17 and the length of the film 11 in the width direction. The distance by which the hit film 11 moves toward the front side can be measured. Similarly, it is possible to measure 34 distances that the film 11 moves toward the back side per unit time based on the back side measurement timer value. Then, based on the distance traveled per unit time, the distance between the position where the sensors 16 and 17 detect the film 11 and the position where the film becomes undetectable by each sensor when control is performed in the opposite direction is determined. The detection time of each sensor can be calculated, and the sensor 1
The abnormality detection time for each film can be calculated from the position where the film is detected by 6.17 and the distance from which the film approaches the front and back sides until it is damaged by a side plate or the like. Here, we calculate the set times that are longer than the above-mentioned detection time and shorter than the abnormality detection time, and timer 1
The set time TI of the timer 2 and the set time T2 of the timer 2 are set. In this embodiment, the timer value T1T2
are set to intermediate values between the detection time and the abnormality detection time, respectively. Next, after setting the timer values T, T2, the measured flag is set to 1, and the process moves to step 46, where the solenoid 23 is set to ONL,
After switching the control of the film 11 to the rear side, set the rear side flag to 1 and proceed to step 2 in FIG.
You will move to Exit 4.

Next, in step 41 described above, if the measured flag is 1, that is, the travel time for the front side and the back side is measured, and the timer values T, , T2 are calculated and set.
The process will move on to step 21 in Figure 0. Step 2
The operations after step 1 are the same as in the second embodiment, and the explanation will be omitted here.

As explained above, by measuring the speed at which the film 11 moves toward the back and the front at the beginning, the abnormality detection timing can be optimally set. Reliable shift control and film position abnormality detection are possible without significantly increasing the assembly accuracy of the heater 14 and pressure roller 15.

FIG. 11 shows a control flowchart of the fourth embodiment of the present invention. This embodiment is a partially modified version of the second embodiment shown in FIG. 8, and the other configurations are the same as the second embodiment.

First, after the start, in step 20 it is determined whether the motor 27 is at 0tlL, and if the motor 27 is not turned on, the process moves to step 29, the solenoid 23 is set to 0FFL, and the back side flag is set to 0FFL. It is reset and moves to the exit of step 24. If the motor 27 is ONL in step 20, step 2
1, and the shift control program is executed.

Next, in step 21, it is determined whether the film 11 is moving towards the back side or towards the front side, and here the back side flag is checked. When the back side flag is 0, that is, when the film 11 is about to move toward the front side, the process moves to step 22, where it is determined whether the sensor 16 is on. Here, if the sensor 16 is ONL, that is, the film 1
If 1 is close to sensor 16, step 2
Move to 3. In step 23, first, a timer 1 is started to measure a predetermined timer time TI seconds, and then the solenoid 23 is turned ON and the film is controlled to move toward the back side. Next, the back side flag is set and the process moves to the exit of step 24 to return to the main program.If the sensor 16 is not turned on at next step 22, the process moves to step 25. In step 25, it is determined whether or not the timer time of 2 seconds measured by the timer 2 has elapsed. If it has not elapsed, the process moves to the exit of step 24, and after the elapse, that is, the film 11 is If the film 11 does not reach the position of the front sensor 16 even after a predetermined time of 12 seconds has elapsed even though the film 11 is controlled to move closer to the front side, the process moves to step 32, and a film abnormality flag is set. 8 lines pass through step 29 to the exit of step 24, and the process returns to the main program.

Next, in step 21, if the back side flag is 1, that is, if the film 11 is about to move toward the back side, the process moves to step 27. In step 27, it is determined whether the sensor 17 is ON or not. If the sensor 17 is ON, that is, the film 11
has moved to the position of the rear sensor 17, the process moves to step 28. In step 28, first, timer 2 is started to measure a predetermined timer time T2 seconds,
Proceed to step 29 and set the solenoid 23 to 0FFL.
The film 11 is controlled to move toward the front, the back side flag is reset to 0, and the process moves to the exit in step 24. Also, in step 27, sensor 1 is ON.
, otherwise the process goes to step 30 for eight lines.

In step 30, it is determined whether or not the timer time TI seconds measured by the timer 1 has elapsed. If the timer time TI seconds has not elapsed, the process moves to the exit of step 24; if it has elapsed, that is, the film 11 is If the film does not move to the position of the rear sensor 17 even after the predetermined time T1 seconds have elapsed even though the film is controlled to move to the side, the process moves to step 32, a film abnormality flag is set, and step 29 After that, the program moves to the exit of step 24 and returns to the main program.

The processing in the main program is the same as that of the first embodiment shown in FIG. 6, and the film abnormality flag can disable the sequence operation of the main body and at the same time notify the operator of the abnormality by displaying the film abnormality. .

As explained above, when the motor rotates, the endless film 11 of this fixing device is first controlled so that the film 11 approaches the front side, and then the film position sensor 16 detects that the film 11 has moved towards the front side. At this time, by turning on the solenoid 23, the control is switched to move the film 11 toward the back side. At this time, a timer 1 for measuring a predetermined time T1 seconds is started. Next, the film 11 moves to the back side, but even after 13 seconds have elapsed according to timer 1, the back side sensor 17 remains ON.
If not, a film abnormality will be detected. Also, before T1 seconds have elapsed, the film 11 is removed from the rear sensor 17.
When the sensor 17 is turned on after reaching the position, the solenoid 23 is set to 0FFL, and the timer 2, which measures a predetermined time of 12 seconds, is started to move the film 11 toward the front side. This allows film 1
1 moves to the front side, but at the same time as it moves to the back side, if the front side sensor 16 is not ON even after 12 seconds have elapsed according to the timer 2, an abnormality in the film will be detected. Here, regarding the setting of the predetermined time of 11 seconds and 12 seconds, first set 11 seconds, which is longer than the back side moving time for the film 11 to move from the position of the front sensor 16 to the position of the rear sensor 17, and similarly set the film 11 to the position of the rear sensor 17. It is sufficient to set the film 11 to move from the position of the rear sensor 17 to the position of the front sensor 16 < 72 seconds, which is longer than the time required for the film 11 to move from the position of the front sensor 16 to the position of the front sensor 16. Set the film to be shorter than the travel time until it moves further forward than the position of , and is damaged by the side plate on the front side.
The moving time may be set to be shorter than the moving time required for the sensor to move further back than the position of the back sensor 17 and be damaged by the side plate or the like on the back side. Figure 12 shows the positional relationship between the sensor positions and the film etc. that enable the time setting of T, T2, and the position indicated by A here is the 8th shift limit position of the film on the near side. If the film 11 were to move forward eight times from this position, the film 11 would be damaged. Next, B indicates the film detection position of the front sensor 16.

Similarly, C is the film detection position of the back side sensor 17, and D is the film B limit position on the back side.

Here, the width of the film is Ll, the distance of the film movement control range, that is, the distance between B and C, is L2, and the distance from the film detection position of the front sensor 16 to the film movement limit position on the front side, that is, between A and 8. Let the distance be LJ,
Similarly, if the distance from the film detection position of the back sensor 17 to the back film movement limit position, that is, the distance between C-0, is LJ, the positional relationship that enables the above-mentioned time setting of T and T2 is as follows. If the speed at which the film 11 moves toward the front is ■1, and conversely, the speed at which the film 11 moves toward the back is ■2, and if the film length and the positional relationship of each sensor etc. satisfy the above formula, then good.

According to this embodiment, in addition to controlling the shifting of the endless film and detecting the abnormal position of the film, it is also possible to detect abnormalities when an abnormality such as wrinkles occurs on the film and its length changes or the moving speed changes. is possible.

Although this embodiment has been described using a copying machine as an example, the present invention is not limited to this, and can also be applied to devices that perform heat fixing via a film, such as facsimile machines, laser beam printers, etc. It is.

(Effects of the Invention) As explained above, by providing the film abnormality detection means, it becomes possible to detect film abnormalities, display the film abnormality to the operator, and cancel the image forming operation or restart the new image forming operation. By discontinuing the
This has the effect of preventing damage to the film. At the same time, this has the effect of preventing damage to the entire device.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of an image forming apparatus that is an embodiment of the present invention, FIG. 2 is a top view of a fixing device, FIG. 3 is an enlarged view of the fixing device, and FIG. 4 is a first embodiment. Electrical control schematic diagram, Fig. 5, showing
6 is a control flowchart showing the first embodiment, FIG. 7 is a top view showing the second embodiment, FIG. 8 is a control flowchart showing the second embodiment, FIGS. 9 and 10 FIG. 11 is a control flowchart showing the third embodiment, FIG. 11 is a control flowchart showing the fourth embodiment, and FIG. 12 is a partial top view of the fourth embodiment. 4.5... End cleaner Sumire 1... Endless film fixing sheet 12... Driven roller 13... Drive roller 14... Fixing heater 15... Pressure roller 16.17... Photo Sensor 23...Solenoid 24.25...Photo sensor

Claims (4)

[Claims] (1) An image forming apparatus having a fixing device that performs fixing via a film, characterized in that the image forming apparatus includes a means for detecting an abnormality of the film. (2) An image forming apparatus having a fixing device that performs fixing via a film, further comprising a film abnormality detecting means, and displaying a film abnormality display in response to a film abnormality detection signal from the abnormality detecting means. image forming device. (3) An image forming apparatus having a fixing device that performs fixing via a film, comprising an abnormality detection means for the film, and forms an image in response to an endless film abnormality detection signal from the film abnormality detection means. An image forming apparatus characterized by having means for stopping operation of the apparatus. (4) In an image forming apparatus having a fixing device that fixes through a film, if an image forming operation is in progress when the film abnormality detection signal is generated from the film abnormality detection means, a new image after the image forming operation is completed. An image forming apparatus characterized by having means for stopping a forming operation.