JP2003098901A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a coil burning by suppressing excessive temperature rise caused by the self-heating of an induction coil provided at the heating member of a fixing device by induction heating and thereby securing the durability of the coil. SOLUTION: The image forming apparatus is provided with the fixing device 40 by induction heating which heats and pressurizes a recording material P inserted into a nip part N, and fixes toner image onto the recording material P. The fixing device 40 by induction heating has a heating member 14 which is induction-heated by the induction coil 13 and a pressurizing member 20 which is pressed to the heating member 10 to form the nip part N. The image forming apparatus is further provided with a heating member temperature detecting means 16 which detects the temperature of the heating member 10, a timer 102 which measures elapsed time from the warm-up of the heating member 10 until a temperature detected by the heating member temperature detecting means 16 reaches a predetermined warm-up temperature, and a change means 100 to change the control temperature of the heating member 10 according to the elapsed time measured by the timer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, the surface of a photosensitive member, such as a photosensitive drum, is charged to a predetermined potential, and an image is exposed on the surface to form an electrostatic latent image. The image is developed with a developer (toner) by a developing means to be visualized as a toner image, and the obtained toner image is transferred to a recording material such as paper conveyed to a photosensitive drum, thus the toner image is formed. The carried recording material is sent to a fixing device, where the unfixed toner image on the recording material is fixed, and a print image is obtained on the recording material.

As shown in FIG. 21, the fixing device 40 includes a heating roller 42 as a heating member having a heating source inside.
And a pressure roller 46 as a pressure member that is in pressure contact with the heating roller 42 to form the nip portion N. The heating roller 42 is rotationally driven by a driving source (not shown), and the pressure roller 46 is heated by the heating roller 42. It is driven and rotated. The heating roller 42 and the pressure roller 46 heat and pressurize the recording material P while sandwiching and conveying the recording material P at the nip portion N to melt and fix the toner image on the recording material P.

Conventionally, a halogen lamp has been used as a heating source for the heating roller 42, but in recent years, an induction heating system using an induction coil is adopted as a heating source with high energy efficiency in order to save energy. Has been done.

As shown in FIG. 21, the induction heating type heating roller 42 includes an induction coil 43 in a cored bar 44, and a coating layer 45 including an elastic layer and a release layer on the cored bar 44.
Is provided. When an alternating current is supplied to the induction coil 43, a magnetic field (magnetic flux) is generated in the induction coil 43 and acts on the cored bar 44 to induce an eddy current in the cored bar 42.
Heats up. The heat generated by the cored bar 42 is transferred to the coating layer 45, and the heating roller 42 is heated. Usually, the induction coil 43 is supplied with an alternating current of several 10 kHz.

[0006]

However, when the heating roller 42 is heated, the induction coil 43 is also heated by the conduction heat and the radiant heat from the heating roller 42. In addition, Joule loss due to the resistance of the induction coil 43 itself causes self-heating. When the temperature of the induction coil is excessively increased, the durability of the induction coil is reduced and the induction coil may be burned out in some cases. Therefore, it is necessary to suppress excessive coil temperature rise due to coil self-heating during printing.

An object of the present invention is to suppress excessive temperature rise of an induction coil provided on a heating member of an induction heating fixing device due to self-heating, ensure the durability of the coil, and prevent burnout.

[0008]

In order to solve the above problems, an invention according to claim 1 is directed to an induction coil, a heating member which is induction-heated by the induction coil, and a nip portion which is pressed against the heating member. An image forming apparatus having an induction heating fixing device for fixing the toner image on the recording material by heating and pressing the recording material inserted into the nip portion. A heating member temperature detecting means for detecting the temperature of the member or the temperature in the vicinity of the heating member, and measuring an elapsed time from warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature. And a changing means for changing the control temperature of the heating member according to the elapsed time measured by the timer.

According to a fifth aspect of the present invention, there is provided an induction coil, a heating member that is induction-heated by the induction coil, and a pressure member that presses against the heating member to form a nip portion. Heating and pressurizing the recording material inserted in
In an image forming apparatus including an induction heating fixing device for fixing a toner image on the recording material, heating member temperature detecting means for detecting a temperature of the heating member or a temperature in the vicinity of the heating member, and detection by the heating member temperature detecting means A timer for measuring the elapsed time after warming up the heating member until the temperature reaches a predetermined warm-up temperature, a print mode time integrating means for integrating print operation time, an elapsed time measured by the timer and the print And a changing unit for changing the control temperature of the heating member according to the print mode integration time integrated by the mode time integration unit.

The invention according to claim 11 is an induction coil,
A heating member that is induction-heated by the induction coil; and a pressing member that presses the heating member to form a nip portion,
An image forming apparatus including an induction heating fixing device that heats and pressurizes a recording material inserted in the nip portion to fix a toner image on the recording material, and detects a temperature of the heating member or a temperature near the heating member. Heating member temperature detecting means, a timer for measuring an elapsed time from warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature, and a timer after the warm-up. Coil energization time integration means for accumulating the energization time of the induction coil, and change for changing the control temperature of the heating member according to the elapsed time measured by the timer and the coil energization integration time integrated by the coil energization time integration means And means.

The invention according to claim 15 is an induction coil,
A heating member that is induction-heated by the induction coil; and a pressing member that presses the heating member to form a nip portion,
An image forming apparatus including an induction heating fixing device that heats and pressurizes a recording material inserted in the nip portion to fix a toner image on the recording material, and detects a temperature of the heating member or a temperature near the heating member. A heating member temperature detecting means, a timer for measuring an elapsed time after warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature, and after the warming-up, Coil power integration means for integrating the coil power consumed by the induction coil, and changing means for changing the control temperature of the heating member according to the elapsed time measured by the timer and the coil integrated power integrated by the coil power integration means. It is characterized by having.

The invention according to claim 19 is an induction coil,
A heating member that is induction-heated by the induction coil; and a pressing member that presses the heating member to form a nip portion,
An image forming apparatus including an induction heating fixing device that heats and pressurizes a recording material inserted in the nip portion to fix a toner image on the recording material, and detects a temperature of the heating member or a temperature near the heating member. Heating member temperature detecting means, a timer for measuring an elapsed time from warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature, and a timer after the warm-up. It is provided with a print number integrating means for integrating the number of prints, and a changing means for changing the control temperature of the heating member according to the elapsed time measured by the timer and the print integrated number integrated by the print number integrating means. I am trying.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. [Embodiment 1] FIG. 1 is a schematic view showing an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a sectional view showing an induction heating fixing apparatus included in the image forming apparatus of FIG. The image forming apparatus of this embodiment includes a photosensitive drum 30 as shown in FIG. 1, and the surface of the photosensitive drum 30 is charged by a charger 32.
To a predetermined potential by means of image exposure by the exposing means 34 to form an electrostatic latent image on the surface of the photosensitive drum 30, and the latent image is developed by the developing device 36 using a developer (toner). The toner image is visualized as a toner image, and the obtained toner image is transferred to the recording material P such as paper conveyed to the photosensitive drum 30 by the transfer unit 38.
Transfer with. After the transfer, the photosensitive drum 30 is subjected to the next image formation after removing the transfer residual toner remaining on the surface thereof by the cleaner 39.

On the other hand, the recording material P carrying the toner image as described above is sent from the photosensitive drum 30 to the fixing device 40, where the unfixed toner image on the recording material P is fixed and printed on the recording material P. An image is obtained (printed).

The fixing device (induction heating fixing device) 40 is of an induction heating type, and as shown in FIG. 2, the heating roller (heating member) 10 to be induction heated and the nip portion N in pressure contact with the heating roller 10. Pressure roller (pressure member) 2 for forming
With 0 and. The fixing device 40 heats and presses the recording material P inserted into the nip portion N by rotating the heating roller 10 and the pressure roller 20 to fix the toner image on the recording material P.

The heating roller 10 has a coating layer 14 around the cored bar 12 and an induction coil 13 inside the cored bar 12. The coating layer 14 has an elastic layer and a surface release layer.
The coating layer 14 does not include the elastic layer and may be only the release layer. In this example, the induction coil 13 is, for example, as shown in FIG.
It is formed on the cylindrical support 13a by extending the coil wire in the coil axis direction while turning the coil wire at both ends in the roller axis direction in a hairpin shape. As shown in FIGS. 4 and 5, the induction coil 13 arranged in the cored bar 12 of the heating roller 10 may be a so-called spring type in which a coil wire is circumferentially wound on a support 13a. .

An alternating current of, for example, several tens of kHz is supplied to the induction coil 13 from an alternating current power source (not shown). As a result, a magnetic field (magnetic flux) is generated in the induction coil 13 and acts on the cored bar 12 to induce an eddy current in the cored bar 12.
2 heats up. The heat generated by the cored bar 12 is transferred to the coating layer 14, and the heating roller 10 is heated in this manner.

The temperature of the heating roller 10 is
The temperature is detected by the heating member temperature detecting means 16 (FIG. 6), which is a temperature sensor such as a thermistor arranged in contact with the surface. Based on the detection result of the surface temperature of the heating roller 10, the heating roller 10 is maintained at a predetermined control temperature by ON / OFF controlling the alternating current passing through the coil 13.

In the present embodiment, the temperature of the heating roller 10 is measured by the heating member temperature detecting means 16 and the heating roller 1 is detected.
When it is detected that the warm-up of 0 is completed (when the heating roller 10 reaches a predetermined warm-up temperature),
The timer 102 measures the elapsed time from the completion of warm-up, and the control temperature of the heating roller 10 is changed according to the elapsed time from the completion of warm-up. More specifically, for example, when the elapsed time measured by the timer 102 becomes a predetermined value (for example, 20 minutes as shown in FIG. 8) or more, the control temperature of the heating roller 10 is lowered. Moreover,
The control temperature of the heating roller 10 is lowered as the elapsed time increases. When the elapsed time from the completion of warm-up increases, the total amount of self-heating of the coil increases, so the coil temperature rises. Therefore, by lowering the control temperature of the heating roller 10, the coil energization on-duty is reduced, the self-heating amount of the coil per unit time is reduced, and as a result, the coil temperature rise can be suppressed. Further, the control temperature of the heating roller 10 may be changed according to the temperature inside the image forming apparatus. That is, in the present embodiment, the in-machine temperature detecting means 103 (FIG. 6) for detecting the in-machine temperature is provided, and the higher the in-machine temperature detected by the in-machine temperature detecting means 103, the lower the control temperature of the heating roller 10. The higher the temperature inside the machine, the lower the heat radiation efficiency from the coil, and as a result, the coil temperature tends to increase. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in coil temperature due to a decrease in radiant heat from the heating roller and a decrease in coil self-heating amount due to a decrease in coil energization duty. Further, the heating member temperature detecting means 1 at the time of starting warm-up
The control temperature of the heating roller 10 may be changed according to the temperature detected by 6. That is, in the present embodiment, the control temperature of the heating roller 10 is lowered as the temperature detected by the heating member temperature detection means 16 at the start of warming up increases.
The control temperature of the heating roller 10 is changed based on a control temperature table as shown in FIG. 8, for example. This control temperature table defines the control temperature of the heating roller 10 according to the elapsed time from the completion of warm-up. In the case of FIG. 8, the heating roller 1 at the start of warming up
The control temperature is also set depending on the temperature of 0. That is,
Specifically, the higher the temperature of the heating roller 10 detected by the heating member detection means 16 at the start of warm-up, the lower the control temperature changed according to the elapsed time from the completion of warm-up. The higher the temperature detected by the heating member at the start of warm-up, the higher the temperature of the coil due to the radiant heat from the heating member. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in coil temperature due to a decrease in the amount of radiant heat from the heating roller and a decrease in the amount of self-heating of the coil due to a decrease in the coil energization duty.

FIG. 6 shows a block diagram of the control system in this embodiment, and FIG. 7 shows a flowchart of the control procedure.
(A) and FIG.7 (b) are shown. The control system mainly includes the control unit 100 of the image forming apparatus. Control unit 100
Is connected to the storage unit 120, the display unit 121 of the image forming apparatus, the image forming unit 122, the image reading unit 123, and the paper feeding unit 124, receives information from these units, determines,
Information such as operation instructions is output to each unit, and each unit is collectively controlled. Further, the control unit 100 is connected to the coil power supply 101 of the fixing device 40 and controls energization of the induction current supplied from the power supply 101 to the induction coil 13. The heating member temperature detecting means 16 is connected to the control unit 100, and the heating roller 10
A signal that detects the surface temperature of is input. In addition, the control unit 1
A timer 102 and an in-machine temperature detection means 103 are connected to 00. As shown in FIG. 7A, when the process starts, whether or not the heating roller 10 has warmed up (completed warming up) until it reaches a predetermined warm-up temperature based on the detection by the temperature detection means 16 in step S1. If the warm-up is not completed (“No”), the process ends. If the warm-up is completed, the elapsed time tw from the completion of the warm-up measured by the timer 102 is read in step S2, the control temperature table is referred to in step S3, and the control temperature of the heating roller 10 is determined in step S4. After setting, the process ends. The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100
It functions as a changing unit of the present invention. In the control of FIG. 7B, it is determined in step S11 whether or not the warm-up of the heating roller 10 is completed, and if the warm-up is not completed (“No”), the process ends. If the warm-up is completed (“Yes”), step S12
Then, the elapsed time tw from the completion of warm-up is read, in step S13 the in-machine temperature Tk of the image forming apparatus detected by the in-machine temperature detecting means 103 is read, and in step S14, the warm-up start detected by the temperature detecting means 1016 is started. The temperature Th of the heating member temperature is read, the control table is referred to in step S15, the control temperature of the heating roller 10 is set in step S16, and the process ends. The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100 functions as the changing unit of the present invention. After that, the temperature of the heating roller 10 is controlled to the set control temperature. In the present embodiment, since the above control is performed, the temperature rise of the coil is suppressed,
It is possible to prevent excessive temperature rise of the coil.

[Second Embodiment] In the second embodiment, a print mode time accumulating means 104 (FIG. 9) for accumulating the print mode time (actual print operation time) is provided, and the print mode time accumulating means 104 integrates the print mode time. The control temperature of the heating roller 10 is changed according to the accumulated print mode time and the elapsed time from the completion of warm-up measured by the timer 102. More specifically, for example, the control temperature of the heating roller 10 is lowered as the elapsed time measured by the timer 102 increases and the print mode integration time integrated by the print mode time integration unit 104 increases. When the print mode integration time after the warm-up is completed and the elapsed time after the warm-up are increased, the total amount of self-heating of the coil is increased and the coil temperature is increased. Therefore, by lowering the control temperature of the heating roller 10, the coil energization on-duty is reduced, the self-heating amount of the coil per unit time is reduced, and as a result, the coil temperature rise can be suppressed.

The control temperature of the heating roller 10 is changed based on a control temperature table as shown in FIG. 11, for example. This control temperature table defines the control temperature of the heating roller 10 according to the elapsed time from the completion of warm-up and the print mode integration time.

Further, the control temperature of the heating roller 10 may be changed according to the temperature inside the image forming apparatus. That is, in the present embodiment, the in-machine temperature detecting means 103 (FIG. 9) for detecting the in-machine temperature is provided, and the in-machine temperature detecting means 10 is provided.
The higher the machine temperature detected by 3, the lower the control temperature of the heating roller 10. The higher the temperature inside the machine, the lower the heat radiation efficiency from the coil, and as a result, the coil temperature tends to increase. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in coil temperature due to a decrease in radiant heat from the heating roller and a decrease in coil self-heating amount due to a decrease in coil energization duty. Further, in the image forming apparatus, a plurality of print modes capable of forming a toner image are set, and the initial control temperature setting of the heating roller 10 is different depending on the type of print mode. A print mode type detection unit 105 (FIG. 9) for detecting the type of mode is provided,
The control temperature of the heating roller 10 may be changed according to the type of print mode detected by the print mode type detection means 105. Here, the print mode includes, for example, a print mode for thick paper, a print mode for thin paper, and the like. In the print mode for thick paper, the initial control temperature of the heating roller 10 is higher than that for the print mode for thin paper. Has become. Since the amount of heat taken from the heating roller 10 varies depending on the type of print mode,
The coil energization on-duty differs, and the coil self-heating amount also differs. As a result, the coil temperature rising speed also differs depending on the type of print mode, so it is preferable to provide a control temperature table for each type of print mode. Further, the heating roller 10 is used depending on the type (size, etc.) of the recording material.
The control temperature may be changed. Since the amount of heat taken from the heating roller 10 differs depending on the type of recording material, the coil energization on-duty differs and the coil self-heating amount also differs. As a result, the coil temperature rising rate also differs depending on the type of recording material, so it is preferable to provide a control temperature table for each type of recording material. Specifically, for example, the control temperature of the heating roller 10 is lowered as the size of the recording material detected by the recording material type detection unit 106 (FIG. 9) increases. Further, the heating member temperature detecting means 1 at the start of warming up
The control temperature of the heating roller 10 may be changed according to the temperature detected by 6. That is, in the present embodiment, the control temperature of the heating roller 10 is lowered as the temperature detected by the heating member temperature detection means 16 at the start of warming up increases.
The higher the temperature detected by the heating member at the start of warm-up, the higher the temperature of the coil due to the radiant heat from the heating member. Therefore, by lowering the control temperature of the heating roller, the amount of radiant heat from the heating roller decreases and the coil self-heating amount decreases due to the reduction of the coil energization duty.
The rise in coil temperature can be suppressed.

FIG. 9 shows a block diagram of the control system in the present embodiment, and FIG. 10 shows a flowchart of the control procedure.
(A), It shows in FIG.10 (b). The control system in the present embodiment is different from the control system shown in FIG. 6 in that the print mode time integrating means 104 and the print mode type detecting means 10 are arranged.
5 and a recording material type detecting means 106 are added. As shown in FIG. 10A, when the process is started, it is determined in step S21 whether or not the warm-up of the heating roller 10 is completed. If the warm-up is not completed, the process is terminated. If the warm-up is completed, the elapsed time tw from the completion of the warm-up measured by the timer 102 is read in step S22, and the print mode time integration means 1 is read in step S23.
The print mode integration time tp integrated in 04 is read, the temperature control table is referred to in step S24, the control temperature of the heating roller 10 is set in step S25, and the process ends. The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100
It functions as a changing unit of the present invention. In the control of FIG. 10B, when the process is started, it is determined in step S31 whether the warm-up of the heating roller 10 is completed,
If the warm-up is not completed, the process ends.
If the warm-up is completed, in step S32,
The elapsed time tw from the completion of warm-up measured by the timer 102 is read, the print mode integrated time tp integrated by the print mode time integration means 104 is read in step S33, and the in-machine temperature detected by the in-machine temperature detection means 103 in step S34. The temperature Tk is read, the heating member temperature Th at the start of warm-up detected by the heating member temperature detecting means 16 is read in step S35, and the print mode information (type) detected by the print mode type detecting means 105 is read in step S36. The recording material information (type) detected by the recording material type detecting means 106 is read in step S37, the temperature control table is referred to in step S38, and the heating roller 10 is read in step S39.
The control temperature is set and the process ends. The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100 functions as the changing unit of the present invention. After that, the temperature of the heating roller 10 is controlled to the set control temperature. In the present embodiment, since the control as described above is performed, it is possible to suppress the temperature rise of the coil and prevent the excessive temperature rise of the coil.

[Third Embodiment] In the third embodiment, the induction coil 13 is provided after the heating roller 10 has warmed up.
Coil energizing time accumulating means 107 for accumulating the energizing time of
(FIG. 12), and the coil energization integrated time and timer 102 integrated by the coil energization time integration means 107.
The control temperature of the heating roller 10 is changed according to the elapsed time from the completion of warm-up measured by. More specifically, for example, the longer the elapsed time measured by the timer 102 is, the more the coil energization time integrating means 107 is provided.
The larger the coil energization cumulative time accumulated by
The control temperature of the heating roller 10 is lowered. When the elapsed time from the completion of warm-up and the cumulative coil energization time increase, the total amount of self-heating of the coil increases and the coil temperature rises. Therefore, by lowering the control temperature of the heating roller 10, the coil energization on-duty is reduced, the self-heating amount of the coil per unit time is reduced, and as a result, the coil temperature rise can be suppressed.

The control temperature of the heating roller 10 is changed based on a control temperature table as shown in FIG. 14, for example. This control temperature table defines the control temperature of the heating roller 10 according to the elapsed time from the completion of warm-up and the coil energization cumulative time.

Further, the control temperature of the heating roller 10 may be changed according to the temperature inside the image forming apparatus. That is, in the present embodiment, the in-machine temperature detecting means 103 (FIG. 12) for detecting the in-machine temperature is provided, and the in-machine temperature detecting means 1 is provided.
The higher the temperature inside the machine detected by 03, the heating roller 10
Lower the control temperature of. The higher the temperature inside the machine, the lower the heat radiation efficiency from the coil, and as a result, the coil temperature tends to increase. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in coil temperature due to a decrease in radiant heat from the heating roller and a decrease in coil self-heating amount due to a decrease in coil energization duty. Further, the control temperature of the heating roller 10 may be changed according to the temperature detected by the heating member temperature detecting means 16 at the start of warming up. That is, in the present embodiment, the control temperature of the heating roller 10 is lowered as the temperature detected by the heating member temperature detection means 16 at the start of warming up increases. The higher the temperature detected by the heating member at the start of warm-up, the higher the temperature of the coil due to the radiant heat from the heating member. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in the coil temperature due to a decrease in the amount of radiant heat from the heating roller and a decrease in the amount of self-heating of the coil due to a decrease in the coil energization duty.

FIG. 12 shows a block diagram of a control system in this embodiment, and FIG. 13 shows a flowchart of the control procedure.
13 (a) and 13 (b). The control system in the present embodiment is different from the control system shown in FIG. 6 in that a coil energization time integration means 107 is added. FIG.
As shown in (a), when the process is started, it is determined in step S41 whether or not the warm-up of the heating roller 10 is completed. If the warm-up is not completed, the process is terminated. If the warm-up is completed, the elapsed time tw from the completion of the warm-up in step S42.
In step S43, the coil energization time integration unit 107 integrates the coil energization time tc, the temperature control table is referred to in step S44, and the control temperature of the heating roller 10 is set in step S45. finish. The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100
It functions as a changing unit of the present invention. In the control of FIG. 13B, when the process starts, it is determined in step S51 whether or not the warm-up of the heating roller 10 is completed,
If the warm-up is not completed, the process ends.
If the warm-up is completed, the elapsed time tw from the completion of the warm-up is read in step S52, the coil energization cumulative time tc is read in step S53, the machine temperature Tk is read in step S54, and step S55.
The heating member temperature Th at the start of warm-up is read in, the temperature control table is referred to in step S56, and the control temperature of the heating roller 10 is set in step S57.
The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100 functions as the changing unit of the present invention. After that, the temperature of the heating roller 10 is controlled to the set control temperature. In the present embodiment, since the control as described above is performed, it is possible to suppress the temperature rise of the coil and prevent the excessive temperature rise of the coil.

[Embodiment 4] In Embodiment 4, the coil power accumulating means 10 for accumulating the coil power consumed by the induction coil 13 after the heating roller 10 warms up.
8 (FIG. 15), the control temperature of the heating roller 10 is changed according to the coil integrated power integrated by the coil power integration unit 108 and the elapsed time from the completion of warm-up measured by the timer 102. More specifically, for example, the control temperature of the heating roller 10 is lowered as the elapsed time measured by the timer 102 increases and as the coil energization integration time integrated by the coil energization time integration unit 107 increases. When the elapsed time from the completion of warm-up and the integrated power of the coil increase, the total amount of self-heating of the coil increases and the coil temperature rises.
Therefore, by lowering the control temperature of the heating roller 10, the coil energization on-duty is reduced, the self-heating amount of the coil per unit time is reduced, and as a result, the coil temperature rise can be suppressed.

The control temperature of the heating roller 10 is changed based on a control temperature table as shown in FIG. 17, for example. This control temperature table defines the control temperature of the heating roller 10 according to the elapsed time from the completion of warm-up and the coil integrated power.

Further, the control temperature of the heating roller 10 may be changed according to the temperature inside the image forming apparatus. That is, in the present embodiment, the in-machine temperature detecting means 103 (FIG. 15) for detecting the in-machine temperature is provided, and the in-machine temperature detecting means 1 is provided.
The higher the temperature inside the machine detected by 03, the heating roller 10
Lower the control temperature of. The higher the temperature inside the machine, the lower the heat radiation efficiency from the coil, and as a result, the coil temperature tends to increase. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in coil temperature due to a decrease in radiant heat from the heating roller and a decrease in coil self-heating amount due to a decrease in coil energization duty. Further, the control temperature of the heating roller 10 may be changed according to the temperature detected by the heating member temperature detecting means 16 at the start of warming up. That is, in the present embodiment, the control temperature of the heating roller 10 is lowered as the temperature detected by the heating member temperature detection means 16 at the start of warming up increases. The higher the temperature detected by the heating member at the start of warm-up, the higher the temperature of the coil due to the radiant heat from the heating member. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in the coil temperature due to a decrease in the amount of radiant heat from the heating roller and a decrease in the amount of self-heating of the coil due to a decrease in the coil energization duty.

FIG. 15 shows a block diagram of a control system in the present embodiment, and FIG. 16 shows a flowchart of the control procedure.
16 (a) and 16 (b). The control system according to the present embodiment is different from the control system shown in FIG. 6 in that the coil energization time integration means 107 is not provided and the coil power integration means 108 is added to the control unit 100. Figure 16 (a)
As shown in step S6, when the process starts, step S6
At 1, it is determined whether or not the warm-up of the heating roller 10 is completed, and if the warm-up is not completed, the process ends. If the warm-up is completed, the elapsed time tw from the completion of warm-up is read in step S62, the coil integrated power Wc integrated by the coil power integration means 107 is read in step S63, and step S6
In step S65, the control temperature of the heating roller 10 is set by referring to the temperature control table in step 4, and the process ends. The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100 functions as the changing unit of the present invention. In the control of FIG. 16B, when the control is started, it is determined in step S71 whether or not the warm-up of the heating roller 10 is completed, and if the warm-up is not completed, the process is ended. If the warm-up is completed, the elapsed time tw from the completion of the warm-up is read in step S72, the coil integrated power Wc is read in step S73, and the in-machine temperature T is read in step S74.
k is read, the heating member temperature Th at the start of warm-up is read in step S75, the temperature control table is referred to in step S76, the control temperature of the heating roller 10 is set in step S77, and the process ends. The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100 functions as the changing unit of the present invention. After that, the temperature of the heating roller 10 is controlled to the set control temperature. In the present embodiment, since the control as described above is performed, it is possible to suppress the temperature rise of the coil and prevent the excessive temperature rise of the coil.

[Fifth Embodiment] In the fifth embodiment, a print number accumulating means 109 (FIG. 18) for accumulating the number of prints (the number of print images obtained on the recording material P) after the heating roller 10 warms up. ), The control temperature of the heating roller 10 is changed in accordance with the cumulative number of prints accumulated by the cumulative number of prints 109 and the elapsed time from the completion of warm-up measured by the timer 102. More specifically, for example, the control temperature of the heating roller 10 is lowered as the elapsed time measured by the timer 102 increases and as the print integrated number integrated by the print number integration unit 109 increases. When the elapsed time from the completion of warm-up and the integrated number of prints increase, the total amount of self-heating of the coil increases, so the coil temperature rises. Therefore, by lowering the control temperature of the heating roller 10, the coil energization on-duty is reduced, the self-heating amount of the coil per unit time is reduced, and as a result, the coil temperature rise can be suppressed.

The control temperature of the heating roller 10 is changed based on a control temperature table as shown in FIG. 20, for example. This control temperature table defines the control temperature of the heating roller 10 according to the elapsed time from the completion of warm-up and the cumulative number of prints.

Further, the control temperature of the heating roller 10 may be changed according to the temperature inside the image forming apparatus. That is, in the present embodiment, the in-machine temperature detecting means 103 (FIG. 18) for detecting the in-machine temperature is provided, and the in-machine temperature detecting means 1 is provided.
The higher the temperature inside the machine detected by 03, the heating roller 10
Lower the control temperature of. The higher the temperature inside the machine, the lower the heat radiation efficiency from the coil, and as a result, the coil temperature tends to increase. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in coil temperature due to a decrease in radiant heat from the heating roller and a decrease in coil self-heating amount due to a decrease in coil energization duty. Further, the control temperature of the heating roller 10 may be changed according to the temperature detected by the heating member temperature detecting means 16 at the start of warming up. That is, in the present embodiment, the control temperature of the heating roller 10 is lowered as the temperature detected by the heating member temperature detection means 16 at the start of warming up increases. The higher the temperature detected by the heating member at the start of warm-up, the higher the temperature of the coil due to the radiant heat from the heating member. Therefore, by lowering the control temperature of the heating roller, it is possible to suppress an increase in the coil temperature due to a decrease in the amount of radiant heat from the heating roller and a decrease in the amount of self-heating of the coil due to a decrease in the coil energization duty.

FIG. 18 shows a block diagram of a control system in the present embodiment, and FIG. 19 shows a flowchart of the control procedure.
19 (a) and 19 (b). The control system in the present embodiment is different from the control system shown in FIG. 6 in that a print sheet number accumulating unit 109 is added. FIG. 19
As shown in (a), when the process is started, it is determined in step S81 whether or not the warm-up of the heating roller 10 is completed. If the warm-up is not completed, the process returns to the standby state. If the warm-up is completed, the elapsed time tw from the completion of the warm-up is read in step S82, the print cumulative number Np accumulated by the print number integrating means 109 is read in step S83, and the temperature control table is referred to in step S84. Then, in step S85, the control temperature of the heating roller 10 is set, and the process ends. The above routine is executed every predetermined time
For example, it is repeated every 1 second. Here, the control unit 10
0 functions as the changing means of the present invention. FIG. 19 (b)
In the control of 1, when the process starts, it is determined in step S91 whether or not the warm-up is completed. If the warm-up is not completed, the process ends. If the warm-up is completed, the elapsed time tw from the completion of the warm-up is read in step S92, and step S93
In step S94, the cumulative number of prints Np is read, in-machine temperature Tk is read, in step S95 the heating member temperature Th at the start of warm-up is read, and in step S
The temperature control table is referred to in 96, the control temperature of the heating roller 10 is set in step S97, and the process ends.
The above routine is repeated every predetermined time, for example, every second. Here, the control unit 100 functions as the changing unit of the present invention. After that, the temperature of the heating roller 10 is controlled to the set control temperature. In the present embodiment, since the control as described above is performed, it is possible to suppress the temperature rise of the coil and prevent the excessive temperature rise of the coil.

The heating member temperature detecting means 16 is, for example, a thermistor, but the present invention is not limited to this. For example, a thermocouple,
Any infrared sensor such as an infrared sensor that can detect the temperature of the heating roller 10 or the temperature in the vicinity of the heating roller 10 may be used.

[0038]

As described above, according to the image forming apparatus of the present invention, the induction coil provided in the heating member of the fixing device is prevented from excessive temperature rise due to self-heating, and the durability of the coil is ensured. It is possible to prevent burning.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a sectional view showing a fixing device installed in the image forming apparatus of FIG.

FIG. 3 is a perspective view showing an induction coil arranged in a heating roller of the fixing device of FIG.

FIG. 4 is a sectional view showing another example of a fixing device that can be used in the present invention.

5 is a perspective view showing an induction coil arranged in a heating roller of the fixing device of FIG.

FIG. 6 is a block diagram showing a control system according to the first embodiment of the present invention.

FIG. 7 is a flowchart showing a control procedure in the first embodiment.

FIG. 8 is a table showing a control temperature table used in the control of the first embodiment.

FIG. 9 is a block diagram showing a control system in the second embodiment.

FIG. 10 is a flowchart showing a control procedure in the second embodiment.

FIG. 11 is a table showing a control temperature table used in the control of the second embodiment.

FIG. 12 is a block diagram showing a control system in the third embodiment.

FIG. 13 is a flowchart showing a control procedure in the third embodiment.

FIG. 14 is a table showing a control temperature table used in the control of the third embodiment.

FIG. 15 is a block diagram showing a control system in the fourth embodiment.

FIG. 16 is a flowchart showing a control procedure in the fourth embodiment.

FIG. 17 is a table showing a control temperature table used in the control of the fourth embodiment.

FIG. 18 is a block diagram showing a control system in the fifth embodiment.

FIG. 19 is a flowchart showing a control procedure in the fifth embodiment.

FIG. 20 is a table showing a control temperature table used in the control of the fifth embodiment.

FIG. 21 is a cross-sectional view showing a conventional fixing device.

[Explanation of symbols]

10 Heating roller (heating member) 13 induction coil 16 Heating member temperature detection means 20 Pressure roller (pressure member) 40 Fixing device (Induction heating fixing device) 100 control unit (changing means) 102 timer 103 In-machine temperature detection means 104 Print mode time integration means 105 Print mode type detection means 106 recording material type detecting means 107 Coil energizing time integrating means 108 Coil power integrating means 109 print quantity accumulating means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miho Toyoda             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             Inside the company F term (reference) 2H033 AA23 BA25 BA26 BA31 BB14                       BB18 BB21 BB28 BE06 CA05                       CA07 CA08 CA16 CA23 CA30                 3K059 AB19 AC33 AC35 CD03

Claims (22)

[Claims] 1. A recording material having an induction coil, a heating member that is induction-heated by the induction coil, and a pressure member that is in pressure contact with the heating member to form a nip portion, and is inserted into the nip portion. In an image forming apparatus including an induction heating fixing device for heating and pressurizing a toner image on the recording material, a heating member temperature detecting means for detecting a temperature of the heating member or a temperature in the vicinity of the heating member; A timer for measuring the elapsed time after warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature, and a control temperature of the heating member according to the elapsed time measured by the timer An image forming apparatus comprising: a changing unit configured to change the image forming apparatus. 2. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the changing unit lowers the control temperature of the heating member as the elapsed time measured by the timer increases. 3. The image forming apparatus according to claim 1, further comprising an in-machine temperature detecting means for detecting an in-machine temperature of the image forming apparatus, wherein the changing means sets the in-machine temperature detected by the in-machine temperature detecting means. An image forming apparatus, wherein the control temperature of the heating member is changed in accordance with the above. 4. The image forming apparatus according to claim 1, wherein the changing unit controls the heating member according to a temperature detected by the heating member temperature detecting unit at the start of warming up. An image forming apparatus characterized by changing a temperature. 5. A recording material having an induction coil, a heating member that is induction-heated by the induction coil, and a pressure member that presses against the heating member to form a nip portion, and is inserted into the nip portion. In an image forming apparatus including an induction heating fixing device for heating and pressurizing a toner image on the recording material, a heating member temperature detecting means for detecting a temperature of the heating member or a temperature in the vicinity of the heating member; A timer for measuring the elapsed time after warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature, and a print mode time accumulating means for accumulating the print mode time which is the print operation time. According to the elapsed time measured by the timer and the print mode total time accumulated by the print mode time accumulating means. An image forming apparatus, comprising: a changing unit that changes the control temperature of the heating member. 6. The image forming apparatus according to claim 5,
The image forming method, wherein the changing unit lowers the control temperature of the heating member as the elapsed time measured by the timer increases and as the print mode integration time integrated by the print mode time integration unit increases. apparatus. 7. The image forming apparatus according to claim 5, further comprising an in-machine temperature detecting means for detecting an in-machine temperature of the image forming apparatus, wherein the changing means sets the in-machine temperature detected by the in-machine temperature detecting means. An image forming apparatus, wherein the control temperature of the heating member is changed in accordance with the above. 8. The print mode for forming a toner image is set to a plurality of types, and the initial control temperature setting of the heating member is different depending on the type of print mode. Image forming apparatus includes a print mode type detecting means for detecting the type of print mode, and the changing means changes the control temperature of the heating member according to the type of print mode detected by the print mode type detecting means. An image forming apparatus comprising: 9. The image forming apparatus according to claim 5, further comprising a recording material type detecting means for detecting a recording material type, and the changing means detects the recording material type detecting means. An image forming apparatus, wherein the control temperature of the heating member is changed according to the type of recording material. 10. The image forming apparatus according to claim 5, wherein the changing unit controls the heating member in accordance with a temperature detected by the heating member temperature detecting unit at the time of starting warm-up. An image forming apparatus characterized by changing a temperature. 11. A recording material having an induction coil, a heating member that is induction-heated by the induction coil, and a pressure member that presses against the heating member to form a nip portion, and is inserted into the nip portion. In an image forming apparatus including an induction heating fixing device for heating and pressurizing a toner image on the recording material, a heating member temperature detecting means for detecting a temperature of the heating member or a temperature in the vicinity of the heating member; A timer for measuring the elapsed time after warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature and an energization time of the induction coil after the warm-up are integrated. Depending on the coil energization time integration means, the elapsed time measured by the timer and the coil energization integration time integrated by the coil energization time integration means An image forming apparatus comprising: a changing unit that changes a control temperature of the heating member. 12. The image forming apparatus according to claim 11, wherein the changing unit increases as the elapsed time measured by the timer increases, and as the coil energization integration time integrated by the coil energization time integration unit increases. An image forming apparatus, wherein a control temperature of the heating member is lowered. 13. The image forming apparatus according to claim 11, further comprising an in-machine temperature detecting means for detecting an in-machine temperature of the image forming apparatus, wherein the changing means sets the in-machine temperature detected by the in-machine temperature detecting means. An image forming apparatus, wherein the control temperature of the heating member is changed in accordance with the above. 14. The image forming apparatus according to claim 11, wherein the changing unit controls the heating member according to a temperature detected by the heating member temperature detecting unit at the start of warming up. An image forming apparatus characterized by changing a temperature. 15. A recording material having an induction coil, a heating member that is induction-heated by the induction coil, and a pressure member that is in pressure contact with the heating member to form a nip portion, and is inserted into the nip portion. In an image forming apparatus including an induction heating fixing device for heating and pressurizing a toner image on the recording material, a heating member temperature detecting means for detecting a temperature of the heating member or a temperature in the vicinity of the heating member; A timer that measures the elapsed time after warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature, and the coil power consumed by the induction coil after warming up are integrated. Coil power accumulating means, and the coil power integrating means integrated according to the elapsed time measured by the timer and the coil integrated power integrated by the coil power integrating means. An image forming apparatus comprising: a changing unit that changes a control temperature of a heating member. 16. The image forming apparatus according to claim 15, wherein the changing unit increases the heating time as the elapsed time measured by the timer increases and the coil integrated power integrated by the coil power integrating unit increases. An image forming apparatus characterized by lowering a control temperature of a member. 17. The image forming apparatus according to claim 15, further comprising an in-machine temperature detecting means for detecting an in-machine temperature of the image forming apparatus, wherein the changing means sets the in-machine temperature detected by the in-machine temperature detecting means. An image forming apparatus, wherein the control temperature of the heating member is changed in accordance with the above. 18. The image forming apparatus according to claim 15, wherein the changing unit controls the heating member according to a temperature detected by the heating member temperature detecting unit at the start of warming up. An image forming apparatus characterized by changing a temperature. 19. A recording material having an induction coil, a heating member that is induction-heated by the induction coil, and a pressure member that presses against the heating member to form a nip portion, and is inserted into the nip portion. In an image forming apparatus including an induction heating fixing device for heating and pressurizing a toner image on the recording material, a heating member temperature detecting means for detecting a temperature of the heating member or a temperature in the vicinity of the heating member; A timer for measuring the elapsed time after warming up the heating member until the temperature detected by the heating member temperature detecting means reaches a predetermined warm-up temperature, and a print number accumulating means for accumulating the number of prints after the warm-up. And the control temperature of the heating member according to the elapsed time measured by the timer and the print integrated number integrated by the print number integrating means. An image forming apparatus comprising: a changing unit that changes a degree. 20. The image forming apparatus according to claim 19, wherein the changing unit increases the heating time as the elapsed time measured by the timer increases and the print integration number integrated by the print number integration unit increases. An image forming apparatus characterized by lowering a control temperature of a member. 21. The image forming apparatus according to claim 19 or 20, further comprising an in-machine temperature detecting means for detecting an in-machine temperature of the image forming apparatus, wherein the changing means sets the in-machine temperature detected by the in-machine temperature detecting means. An image forming apparatus, wherein the control temperature of the heating member is changed in accordance with the above. 22. The image forming apparatus according to claim 19, wherein the changing unit controls the heating member in accordance with a temperature detected by the heating member temperature detecting unit at the time of starting warm-up. An image forming apparatus characterized by changing a temperature.