JP2851889B2 - Fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used for an image forming apparatus such as a copying machine and an optical printer, and more particularly, to a fixing device for fixing using an endless belt.

(Background Art) Various types of fixing devices for fixing a toner image on a recording material have been conceived and implemented.
No. 3,578,797, JP-B-51-29825, JP-A-63-3131
In Japanese Patent Application Publication No. 82, a fixing device that uses an endless belt, and particularly heats and fuses a toner image via the endless belt is considered.

When fixing is performed using an endless belt in this way, there is a problem that, as the endless belt is driven to rotate, the endless belt is positioned in a direction orthogonal to the rotation direction, so-called deviation occurs.

The cause of this misalignment is the parallelism and twist of the two rollers that apply tension to the belt. However, there is a limit to improving the accuracy of these two rollers. Have difficulty.

For this reason, it is conceivable to provide a rib on the endless belt and regulate the endless belt with this rib to prevent the occurrence of deviation, but as described in JP-A-63-313182, the thickness is 100 μm or less, especially When a heat-resistant film as thin as 50 μm or less is used, the heat-resistant film has no elasticity and is thin, so that wrinkles and the like are generated on the heat-resistant film, and it is difficult to control the deviation.

For this reason, by displacing one of the roller shafts of the rollers applying tension to this film-shaped endless belt (hereinafter referred to as an endless film),
By enabling the direction of movement of the endless film to be switched and simultaneously providing a sensor for detecting the position of the endless film, and alternately controlling the movement direction of the film to perform the leaning control, it is possible to correct the leaning of a thin endless film. .

In addition, when the shift control is started immediately after the power is turned on, if the control is performed in a predetermined shift direction as an initial setting, if the speed difference is large depending on the shift direction, the initial film position is detected from the start of the control and the actual film position is detected. The endless film may move to either end during the time before the shift control starts, in which case not only the endless film is damaged but also the fixing device is damaged. Therefore, it is preferable to provide a non-volatile storage means for storing the direction of the shift of the film when the power is turned off.

(Problems to be Solved by the Invention) However, in an image forming apparatus using such a fixing device, the main motor may be rotated for a short time only when the residual potential of the photoconductor is removed or when paper is initially out of paper.

For this reason, when the endless film is driven by the driving force of the main motor, if the driving time of the short-time main motor is shorter than the time required to detect the position of the endless film and start the actual deviation control, the above-described operation is performed. As described above, in the mechanism in which the direction of the endless film is alternately switched, if the main motor is repeatedly turned on for a short time, it is not possible to detect the deviation of the film, so that the endless film is moved to one end. Sisters,
There is a problem that the endless film may be damaged or the fixing device may be damaged.

(Means for Solving the Problems) In order to solve the above problems, the present invention relates to a fixing device having a film that moves in contact with a recording material carrying an unfixed image. Detecting means for detecting the deviation of the film, and after the movement of the film is started, stopping the film is prohibited until the detecting means detects at least the position of the film.

(Embodiment of the Invention) FIG. 1 is a view showing a first embodiment of the present invention, and is a top view of the fixing device 1 shown in FIG. FIG. 3 is a sectional view of the fixing device.

FIG. 2 shows a copying apparatus which is an image forming apparatus using a fixing device according to the present invention. A document placed on a document 101 is illuminated by an illumination lamp 102, and the reflected light is reflected by a short focus lens array 103. An image is formed on the photosensitive drum 104.

Reference numeral 105 denotes a charger for uniformly charging the photoconductor, 106 denotes a developing device, and 106 denotes a cleaner.

The transfer paper P, which is a recording material accommodated in the paper cassette S, is fed by a paper feed roller 108, and is conveyed to a transfer unit by a registration roller 109 on a photosensitive drum in synchronization with an image.

The unfixed toner image on the photoconductor is transferred onto transfer paper by a transfer charger 110.

The transfer paper on which a toner image made of a resin or the like that is softened and melted by heating is formed is conveyed on a conveyance belt 2 and is fixed to a fixing device
And heat-fixed.

Next, the structure of the fixing unit 1 will be described with reference to FIG. 3. A heat-resistant film 11 having a total thickness of less than 100 μm, preferably less than 40 μm (in this embodiment, polyimide or polyetherimide having a thickness of about 20 μm). , PES, PFA, an endless film in which a release layer of PTFE or the like is coated on the image contact surface by about 10 μm. The drive of the endless film 11 is transmitted to the drive roller 13 by a motor 27 (not shown). The fixing film 1 is configured to move in the direction of arrow a by the tension by the driving roller 13 and the driven roller 12 and the driving thereof. Reference numeral 14 denotes a low heat capacity linear heater (hereinafter referred to as a heater) fixedly supported by the fixing device 11, and reference numeral 15 denotes a pressure roller having a rubber elastic layer having good releasability such as silicon rubber at a total pressure of 4 to 5 kg. The heater is pressurized through the film, and rotates by pressing against the film. With the present fixing device described above, the transfer paper on which the toner image has been formed is guided to the fixing section by the entrance guide 10, enters between the pressure roller 15 and the film 11, and the toner is heated by the heat from the heating body via the film. Is heated and fixed.

Next, an endless film deviation control mechanism of the fixing device of the present embodiment will be described with reference to FIG.

The aforementioned driven roller 12 has 20, 21 bearings,
The side is abutted against the side plate by 22 compression springs. Here, the parallelism of the driving roller 13, the driven roller 12, the heater 14, and the pressure roller 15 (X-axis direction, Y-axis direction, Z-axis direction)
As long as the precision of the film is not ± 0, the drive roller 13 is driven to move the film 11 in the direction of the arrow a. When the film 11 is moved in the direction of the arrow (a direction of X, Y, Z axes) As a result, the film 11 is shifted to the right or left from the initial position of the film 11 shown in FIG. 1, and the ends of the film are rubbed and damaged on the side plates 18 and 19. Therefore, in this embodiment, the bearing 20
Is connected to a solenoid 23 so that the position of the driven roller 12 can be changed. In this case, when the solenoid 23 is OFF, the film 11 is set so as to lean toward the rear side shown in FIG. 1, and when the solenoid 23 is ON, the film 11 is similarly set so as to lean toward the near side. . A photo sensor 16 detects the position of the film.

As shown in FIG. 1, the end portion 3 of the film 11 is subjected to a masking process so as to block light from the photo sensor. In the present embodiment, a photo-interrupter is used for the photo-sensor. However, when a reflection-type photo-sensor is used here, the end portion 3 of the film 11 needs to be subjected to a reflection process for reflecting light. Further, in this embodiment, the processing such as masking is performed only on one side end, but it goes without saying that the processing may be performed on the entire film.
Reference numeral 4 denotes a film edge cleaning member.
The end of the film is always cleaned so that reading is not performed due to contamination of the end of the film. In the present embodiment, felt is used, but the type is not limited as long as it has a cleaning effect.

FIG. 4 shows the external shape of the film 11. This film is an endless belt as described above, and its diameter is ΦM. Also, as shown in the figure, one end of the film 11 is cut diagonally, and the length of the longest part is Lmax,
Assuming that the length of the shortest portion is Lmin, the dimension of the obliquely cut portion (oblique cut portion) of the film 11 is obtained by Lmax-Lmin, and here, it is ΔL (film oblique cut amount).
And As shown in FIG. 1, the oblique cut portion is arranged on the front side of the fixing device, and is configured so that the position of the film 11 is detected by the photo sensor 16.

FIG. 5 is a detailed view of the positional relationship between the photo sensor 16 and the film 11. In this embodiment, a transmission type photointerrupter is used for the photosensor 16, and its detection position is indicated by b. This means that the photo sensor 16 is turned on when the film 11 is on the back side of the position b, and turned off when the film 11 is on the front side of the position b. The oblique cut portion of the film 11 is configured to be at the detection position b. That is, when the film 11 moves (rotates) in the direction of the arrow a shown in FIG. 3, the photo sensor 16 repeats ON / OFF, and the ON / OFF cycle ratio (duty ratio) varies depending on the film position. It will be variable. The film position shown in Fig. 5 is a photo sensor.
The reference position is such that the center of the oblique cut portion of the film 11 is located at the 16 detection positions b. FIG. 6 is a graph showing the relationship between the film position and the OFF time of the photo sensor 16 around the reference position of the film.

As shown in FIG. 6, when the film 11 is at the reference position, the OFF time of the photo sensor 16 is c seconds, and
When 1 is more than 1 / 2ΔL before the reference position, the OFF time of the photo sensor 16 is 0 second. On the other hand, when the film 11 is located at least 1 / 2.DELTA.L behind the reference position, the photo sensor 16 is kept off. Here, when the position of the film 11 is immediately before the position where the photo sensor 16 is kept turned off, the OFF time is d seconds, which can be considered to be substantially equivalent to the time when the film 11 makes one round, and The OFF time c seconds is approximately half of the OFF time d seconds because it is at the center of the film oblique cut portion.

Next, FIG. 7 shows a schematic diagram of the electric control. Here, reference numeral 26 denotes a man-color computer, and the photo sensor 16 is connected to the input terminal IN1. A solenoid 23 is connected to the OUT1 terminal.
An OUT2 terminal outputs a rotation control signal of a motor 27 that also drives the fixing device. The + 5V power supply is connected to the VDD terminal, and the GND terminal is connected to the ground. Although not shown, other input and output signal terminals of the copying apparatus using the fixing device are provided, and a sequence program for the copying operation of the copying apparatus is stored in the mancro computer 26. ROM and RAM
Along with the above, a nonvolatile RAM is provided which does not lose its stored contents even if the power supply to the microcomputer 26 is cut off.

8 to 11 show flowcharts of a film shift control program of the fixing device. This program is also programmed in the built-in ROM in the microcomputer 26 described above, and is called and executed at regular time intervals or as needed by a main sequence program or the like. First step after start 1
In, it is determined whether or not the motor 27 is ON. If the motor 27 is on, the process proceeds to step 2. If the motor 27 is off, the process proceeds to step 1.
Then, the process returns to step S1 and waits until the motor 27 is turned on. Next, in step 2, it is determined whether or not the film has been controlled so as to approach the front side. This is to set the contents of a predetermined address in the nonvolatile RAM in the micro computer 26 as a near side flag, and when the state of the memory is 1, that is, when the memory has been controlled to the near side, go to step 3. Then, the solenoid 23 is turned on, the deviation control is set to the near side, and the routine proceeds to Step 4. If the near side flag is 0 in step 2, the film is controlled so as to be shifted to the far side so that the process proceeds to step 4 as it is. In step 4, it is determined whether or not the sensor 16 is OFF.
In the case of N, the process proceeds to Step 8, and in the case of OFF, the process proceeds to Step 5. At step 5, the value of the error timer is reset to 0, measurement is started, and the routine proceeds to step 6. In step 6, it is determined whether or not the sensor 16 is ON. If not, the process proceeds to step 7. At step 7, an error check routine is executed, and at step 6
Will return to. Here, the content of the error check routine will be described with reference to FIG. 10.First, in step S1, it is determined whether or not the motor 27 is ON.If the motor 27 is ON, the process proceeds to step S2. Step 13
Move to. In step S2, it is determined whether or not the error timer value is greater than d seconds. If the error timer value is less than d seconds, the process proceeds to the exit of this routine. If the error timer value is longer than d seconds in step S2, step S3
Will move to In step S3, an error flag is set, and the routine goes to the exit of this routine. Next, if the sensor 16 is ON in step 6, the process proceeds to step 8, resets the value of the error timer to 0, starts measurement, and proceeds to step 9. In step 9, it is determined whether or not the sensor 16 is OFF. If the sensor 16 is not OFF, the process proceeds to step 10 to execute an error check routine and returns to step 9, and if the sensor 16 is turned off, the process proceeds to step 11. Then, the value of the timer 1 is reset to 0, the measurement is started, and the routine proceeds to step 12. In step 12, it is determined whether or not the motor 27 is ON. If the motor 27 is ON, the process proceeds to step 14. At step 14, it is determined whether or not the sensor 16 is ON. If the sensor 16 is not ON, the process proceeds to step 15 to execute the error check routine and returns to step 14, and if it is ON, the process proceeds to step 16. At step 16, a comparison is made as to whether the measured value of the timer 1 is smaller than 1/4 d second. If it is smaller, it can be determined that the film 11 is located on the near side. Turn off 23 and film 1
The direction of 1 is switched to the back side, the front flag is reset to 0, and the routine proceeds to step 20. If the measured value of the timer 1 is not smaller than 1/4 d second in step 16, the process proceeds to step 18. At step 18, a comparison is made as to whether the measured value of timer 1 is greater than 3/4 dsec. If not, the process proceeds to step 20,
If it is larger, it can be determined that the film 11 is located on the back side.
The direction of the approach 11 is switched to the trouble side, the front flag is set to 1, and the process proceeds to step 20. At step 20, the film flag is set, and the value of the error timer is set to 0.
Then, the measurement is started, and the process proceeds to step 21. In step 21, it is determined whether or not the sensor 16 is OFF. If the sensor 16 is not OFF, the process proceeds to step 22, executes an error check routine, and returns to step 21. If the sensor 16 is OFF in step 21, the process proceeds to step 23, where the value of the timer 1 is reset to 0, measurement is started, and the process returns to step 12. If the motor 27 is turned off in step 12, the process proceeds to step 13, where the timer 1 is stopped and the measured value is reset to zero.
Is turned off, and the process returns to step 1.

Next, FIG. 11 shows a flowchart of a film abnormality processing program which is a part of the main program. Here, it is determined in step 24 whether the error flag has been set. If the error flag has not been set, the process proceeds to the exit and the next main sequence program is executed. If the error flag has been set in step 24, the process proceeds to step 25 to turn off all outputs of all devices (copier in this embodiment), and then to step 26 to display a film abnormality display. The execution step 26 is a permanent loop so that the main program cannot be executed.

Next, FIG. 12 shows a subroutine called when the motor is stopped by a sequence program or the like.

In this subroutine, when the motor is stopped, it is checked in step 30 whether or not the film flag is set. If it is not set, wait until it is set, and when it is set, turn off the motor,
This subroutine ends. This film flag is set when the position of the film 11 is first detected after the motor is turned on. For this reason, even in the pre-rotation process or when there is no paper by this subroutine, the stop of the motor is prohibited until the position of the film 11 is first detected, so that the film position is always cleared to the correct value.

As described above, the endless film 11 of the present fixing device controls the solenoid 23 in accordance with the contents of the non-volatile RAM which stores the shift direction previously controlled before the rotation of the motor. Next, when the sensor 16 is ON when the motor is rotating, wait until the sensor 16 turns OFF, and when the sensor 16 is OFF, wait until the sensor 16 turns ON and then wait until the sensor 16 turns OFF. Detects the timing of switching to OFF and ends the initial setting. Then, the position of the film 11 is detected only by measuring the OFF time of the sensor 16 until the sensor 16 switches from OFF to ON. That is, since the control of the film 11 is disabled until the time when the OFF time of the first sensor 16 is measured, the film 11 is set to the direction in which the control was performed up to that time, and the motor stop is prohibited during that time.
Then, it reaches the point of time when the OFF time of the first sensor 16 is measured,
When the measurement time is smaller than 1 / 4d or larger than 3 / 4d, the inhibition of the stop of the motor is released after controlling the solenoid. As a result, even if the process of rotating the motor for a shorter time than the time required for the pre-rotation process or the position detection of the endless film such as the absence of paper is repeated, the film is abnormally abnormal during the above-mentioned uncontrollable state. It can be prevented from approaching the end. And from the timing when the sensor 16 switches from ON to OFF,
The OFF time of the sensor 16 until the switch from FF to ON is measured, and the film position is controlled so as to be within a predetermined control range.

In the present embodiment, a transmission type photo sensor is used as the sensor 16, but a sensor such as a micro SW or a reflection type photo sensor may be used.

Further, as the storage means for storing the direction of the endless film even when the power is turned off, a nonvolatile RAM is used in the above-described embodiment. May be used.

However, it is preferable to use a non-volatile RAM from the viewpoint of preventing the device from being enlarged.

 Next, another embodiment of the present invention will be described.

In the above-described embodiment, the stop of the rotation of the endless film is prohibited until the film flag is set. However, in the present embodiment, the stop of the motor is prohibited for a predetermined time after the start of the rotation of the endless film.

In the film shift control shown in FIGS. 8 to 11, when the sensor 16 is ON during the rotation of the motor, wait until the sensor 16 is OFF, and when the sensor 16 is OFF, wait until the sensor 16 is ON and then wait until the sensor 16 is OFF. And then the sensor 16 turns from OFF to ON
Then, the position of the film 11 is detected by measuring the OFF time of the sensor 16 until the switch is made. This means that the film
The position of the film 11 can be detected during the circumferential rotation. In other words, the position of the film can be detected by prohibiting the motor from stopping for two rotations (2d) of the film from the start of the rotation of the motor. The subroutine is shown in FIG.

FIG. 13 is a subroutine called when the motor stops, and the timer T is a timer that is reset when the motor starts rotating. This timer T is determined in advance
It is smaller than a long time T ₀ than 2d waiting for longer than the T ₀ to stop the motor. Other processes are the same as those in the above-described embodiment.

[Effects of the Invention] According to the present invention, it is possible to prevent the endless belt from leaning to one side even when the drive motor is repeatedly turned on only for a short time.

[Brief description of the drawings]

1 is a top view illustrating a fixing device according to an embodiment of the present invention, FIG. 2 is a side view of a main body illustrating an image forming apparatus using the fixing device according to the embodiment of the present invention, and FIG. FIG. 4 is an external view of an endless film, FIG. 5 is a diagram showing a relationship between a film sensor and a film position, FIG. 6 is a graph showing a relationship between a film position and a film sensor output, FIG. The drawings are schematic diagrams of the electric control of the first embodiment. FIGS. 8 to 11 are flowcharts of the shift control program of the first embodiment, respectively. FIG. 12 is the control of the first embodiment of the present invention. FIG. 13 is a flowchart showing control of another embodiment of the present invention. 11 ... Fixing sheet for endless film 12 ... Driving roller 13 ... Drive roller 14 ... Fixing heater 15 ... Pressurizing roller 16 ... Photo sensor 23 ... Solenoid 26,28,32 ... Microcomputer 27 ... Motor

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kursunori Tsunori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-59-97168 (JP, A) JP-A-63 -12570 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/20 G03G 15/20 B65H 5/02 B65G 43/02

Claims (1)

(57) [Claims] 1. A fixing device having a film that moves in contact with a recording material bearing an unfixed image, comprising: a detection unit configured to detect a deviation of the film in a direction orthogonal to a direction in which the film moves. The fixing device according to claim 1, wherein after the movement of the film is started, the stop of the film is prohibited until the detecting means detects at least the position of the film.