JP2003091205A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent temperature of the induction coil of a fixing device from excessively rising. SOLUTION: This image forming apparatus α is equipped with a CPU 1 centrally controlling respective parts, a RAM 2 in which information is temporarily stored, a ROM 3 in which various kinds of data and programs are stored, a timer 4 for elapsed time, an image forming part 20 forming an image on paper A being recording material and the fixing devices 40A and 40B fixing toner on the paper A on which the image is formed by the image forming part 20. In the device α, the application of a coil current to the induction coils 44A and 44B is changed according to the control temperature of a heating roller 41 corresponding to the elapsed time from the time finishing the printing of a job on a standby control temperature table stored in the ROM 3 and the actual temperature of the heating roller 41, so that the temperature of the roller 41 is controlled.

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 for forming an image on a recording material, fixing the image, and outputting the image.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, an image of an object to be printed is read by a scanner, a toner image of the read image is formed on a recording material in an image forming section, and the formed recording material is printed. It was sent to a fixing device, and the unfixed toner image on the recording material was fixed there to obtain a print image on the recording material.

The fixing device is provided with a heating roller (fixing roller) as a heating member having a heating source inside, and a pressure roller as a pressing member for pressing the heating roller to form a fixing nip. The roller is rotationally driven by a drive source, and the pressure roller is rotated by being driven by the heating roller.
The heating roller and the pressure roller heat and pressurize the recording material while the recording material is nipped and conveyed in the fixing nip to melt and fix the toner image on the recording material.

Conventionally, a halogen lamp has been used as the heating source of the heating roller, but in order to save energy, an induction heating type fixing device using an induction coil is considered as a heating source having high energy efficiency. Has been.

The induction heating type fixing device is provided with an induction coil in the heating roller, and when an alternating current is supplied to the induction coil, a magnetic flux is generated in the induction coil, and the magnetic flux causes an eddy current which is an induction current in the heating roller. An electric current flows, and the heating roller generates heat due to Joule loss of the eddy current.

[0006]

However, in the induction heating type fixing device, in order to efficiently apply the magnetic flux to the heating roller, the induction coil is arranged in the vicinity of the heating roller. The induction coil is also heated by conduction heat or radiant heat from the heated heating roller. In addition, Joule loss due to the resistance of the induction coil itself causes self-heating.

When the induction coil itself is heated, the durability of the induction coil is reduced, so it is not preferable that the coil temperature of the induction coil rises above a predetermined temperature. In some cases, the induction coil may burn out. In particular, the coil temperature tends to increase greatly immediately after printing the recording material continuously. The reason for this is that during continuous printing, the energization duty, which is the ratio of the energization time to the induction coil, increases, so the amount of self-heating due to Joule loss of the resistance of the induction coil itself increases, and the coil temperature rises with respect to the heating roller temperature. It tends to be high.

As another cause, during continuous printing, the discharged recording material absorbs a large amount of heat from the heating roller, so that the temperature of the heating roller often temporarily drops below the control temperature point, and the printing ends. If the heating roller temperature is then returned to the control temperature point, the coil temperature also follows the heating roller temperature, and the coil temperature may further increase.

An example of controlling the heating roller temperature by energizing the conventional induction coil will be described with reference to FIG. FIG. 17 is a graph of the heating roller temperature and the coil temperature with respect to the elapsed time from the end of printing the job in the conventional temperature control procedure. Here, a spring-shaped induction coil is used, and its heat resistant temperature is 220 ° C. In the conventional temperature control procedure, when the heating roller temperature is uniformly lower than 200 ° C. with a cycle of 1 second, the induction coil is energized and when the heating roller temperature is uniformly 200 ° C. or higher,
Control was performed to turn off the power supply to the induction coil.

Since the paper takes heat when printing the job,
The heating roller temperature becomes lower than the coil temperature, and when the heating roller temperature is raised to 200 ° C. after the job execution is completed,
The coil temperature rises excessively to about 235 ° C. and exceeds the heat resistance temperature of the induction coil. Further, a similar problem occurs in a fixing device using a belt.

An object of the present invention is to prevent an excessive rise in the coil temperature of the induction coil of the fixing device.

[0012]

In order to solve the above problems, the invention according to claim 1 supplies an induction coil for generating a magnetic flux by energizing a coil current and the coil current to the induction coil. A power source, a heating member that generates heat with an induction current induced by the magnetic flux generated from the induction coil, a pressing member that pressurizes the recording material, and heating member temperature detection means that detects the heating member temperature of the heating member. An image forming apparatus provided with a fixing device for fixing a developer on a recording material passing through a nip portion of the pressure member by heating and pressurizing, and finishing printing of a job input to the image forming apparatus. Storage means for storing the control temperature of the heating member corresponding to the elapsed time from time, elapsed time detecting means for detecting the elapsed time from the actual end of printing, and the elapsed time detecting means The coil supplied from the power source according to the detected elapsed time from the end of printing, the control temperature of the heating member stored in the storage unit, and the actual heating member temperature detected by the heating member temperature detection unit. An image forming apparatus comprising: a control unit that changes the current to control the temperature of the heating member.

According to the first aspect of the invention, the elapsed time from the end of actual printing is detected, the detected elapsed time from the end of printing, and the control temperature of the heating member stored in the storage means, In addition, the temperature of the heating member is controlled by changing the coil current supplied from the power source according to the actual heating member temperature.

Therefore, by changing the control temperature of the heating member and controlling the energization of the coil current to the induction coil in accordance with the elapsed time from the end of printing of the input job, the coil of the induction coil is finished after printing. It is possible to prevent an excessive rise in temperature.

According to a second aspect of the present invention, the storage means according to the first aspect stores the control temperature set higher as the elapsed time from the end of printing becomes longer.

According to the second aspect of the invention, the storage means stores the control temperature set higher as the elapsed time from the end of printing becomes longer.

Therefore, after the printing of the input job is completed, the coil temperature that rises during printing is gradually radiated and the temperature decreases, so that the control temperature rises with time and the fixing performance. It is possible to prevent the coil temperature of the induction coil from rising excessively without damaging the coil.

The invention described in claim 3 is the invention according to claim 1 or 2.
The change in the coil current in the control means according to any one of claims 1 to 5 is a change in at least one of a current conduction time ratio of the coil current, a current value, a voltage value, and a frequency value.

According to the third aspect of the invention, the coil current is changed by changing the energizing time ratio of the coil current, the current value,
The change is at least one of a voltage value and a frequency value.

Therefore, the energization of the coil current to the induction coil can be controlled in various ways.

According to a fourth aspect of the present invention, an induction coil for generating a magnetic flux by passing a coil current, a power supply for supplying the coil current to the induction coil, and an induction induced by the magnetic flux generated by the induction coil. On a recording material that passes through a nip portion of the pressing member, a heating member that generates heat with an electric current, a pressing member that pressurizes the recording material, and a heating member temperature detecting unit that detects the heating member temperature of the heating member are provided. An image forming apparatus having a fixing device for fixing the developer by heating and pressurizing, and a storage unit for storing a control temperature of the heating member corresponding to a temperature of the induction coil or a temperature near the induction coil. A coil temperature detecting means for detecting an actual temperature of the induction coil or a temperature near the induction coil, and a temperature of the induction coil detected by the coil temperature detecting means or The coil current supplied from the power source is changed according to the temperature near the induction coil, the control temperature of the heating member stored in the storage unit, and the actual heating member temperature detected by the heating member temperature detection unit. And a control unit that controls the temperature of the heating member.

According to the fourth aspect of the invention, the actual temperature of the induction coil or the temperature near the induction coil is detected, and the detected temperature of the induction coil or the temperature near the induction coil is stored in the storage means. According to the stored control temperature of the heating member and the actual heating member temperature, the coil current supplied from the power source is changed to control the temperature of the heating member.

Therefore, it is possible to prevent the coil temperature of the induction coil from rising excessively by changing the control temperature of the heating member and controlling the energization of the coil current to the induction coil according to the coil temperature or the temperature near the coil. .

According to a fifth aspect of the present invention, the storage means according to the fourth aspect stores the control temperature set lower as the temperature of the induction coil or the temperature near the induction coil increases. It is characterized by

According to the fifth aspect of the present invention, the storage means stores the control temperature set to be lower as the temperature of the induction coil or the temperature near the induction coil becomes higher.

Therefore, according to the coil temperature or the temperature in the vicinity of the coil, a lower control temperature is set as the coil temperature increases to control the energization of the coil current to the induction coil, so that the fixing performance of the induction coil is not impaired. It is possible to prevent the coil temperature from rising excessively.

The invention according to claim 6 is the invention according to claim 4 or 5.
The change of the coil current in the control means according to any one of items 1 to 5 is a change of at least one of a conduction time ratio of the coil current, a current value, a voltage value, and a frequency value.

According to the sixth aspect of the invention, the coil current is changed by changing the energizing time ratio of the coil current, the current value,
The change is at least one of a voltage value and a frequency value.

Therefore, the energization of the coil current to the induction coil can be controlled in various ways.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment and a second embodiment, which are embodiments of the present invention, will be described below in order with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows the present embodiment.
~ It demonstrates with reference to FIG. First, the device features are shown in Fig. 1
This will be described with reference to FIG. 1 is a block configuration diagram of an image forming apparatus α according to the present embodiment, FIG. 2 is a diagram showing configurations of an image forming unit 20 and fixing devices 40A and 40B of the image forming apparatus α, and FIG. FIG. 4 is a cross-sectional view showing the configuration of the fixing device 40A, and FIG.
4A is a diagram showing the shape of 4A, FIG. 5 is a sectional view showing the configuration of the fixing device 40B, and FIG. 6 is a diagram showing the shape of the induction coil 44B of the fixing device 40B.

As shown in FIG. 1, an image forming apparatus α according to the present embodiment has a CPU (Central Pr) for centrally controlling each component.
ocessing Unit) 1 and RAM for temporarily storing information
(Random Access Unit) 2, ROM (Read Only Memory) 3 for storing various data and programs, timer 4 for elapsed time, and scanner 1 for reading an image of a print target
0, an image forming unit 20 that forms an image on a paper A that is a recording material, a paper feeding unit 30 that supplies the paper A to the image forming unit 20, and a developer on the paper A formed by the image forming unit 20. And fixing devices 40A and 40B for fixing the toner, and a display unit 50 for displaying various information.
And.

RAM 2, ROM 3, timer 4, scanner 10, image forming unit 20, paper feeding unit 30, fixing devices 40A, 40.
B, the display unit 50 is connected to the CPU 1. Under the control of the CPU 1, the image forming apparatus α reads the information on the print target with the scanner 10 and stores the information on the print target in the RAM 2.
To the image forming unit 20 via the image forming unit 20 to form an image of the paper A supplied from the paper feeding unit 30 based on the information of the print target, and fix the toner on the formed paper A by the fixing devices 40A and 40B. Let

The CPU 1 executes a standby temperature control program. By executing the standby temperature control program, the CPU 1 sets the elapsed time t = 0 from the end of printing after the start of standby due to the end of printing of the job, starts the cycle timer with the timer 4, and sets the elapsed time from the end of printing. The time t is read, the standby control temperature table a1 in the ROM 3 is referred to, the control temperature of the heating roller 41 corresponding to the read time t from the end of printing is set, and the induction coils 44A and 44B are energized and controlled. After the cycle time is up in timer 4, the cycle timer is cleared and the procedure returns to the cycle timer start procedure (see FIG. 8).
reference).

As shown in FIG. 2, the image forming unit 20 includes a rotatable photosensitive drum 21 which is a medium for image formation, a charger 22 for charging the photosensitive drum 21, and an exposing means 23 for exposing the photosensitive drum 21. A developing unit 24 for developing the toner onto the photosensitive drum 21, a transfer unit 25 for transferring the developed toner image onto the paper A, and a cleaner 26 for removing the toner remaining in the development.

When the paper A is conveyed to the image forming unit 20, the surface of the rotating photosensitive drum 21 is charged to a predetermined potential by the charger 22, and the image is exposed by the exposing means 23, so that the surface of the photosensitive drum 21 is exposed. An electrostatic latent image is formed, and this latent image is developed by the developing device 24.
The toner image is visualized as a toner image by developing with a toner, and the obtained toner image is transferred onto the paper A conveyed to the photosensitive drum 21 by the transfer means 25. Photosensitive drum 21 after transfer
Cleans the transfer residual toner remaining on the surface of the cleaner 2
After being removed in 6, the image is prepared for the next image formation.

On the other hand, the paper A carrying the toner image as described above is transferred from the photosensitive drum 21 to the fixing devices 40A and 40B.
And the unfixed toner image on paper A is fixed there,
A print image is obtained on the paper A.

As shown in FIG. 3, the fixing device 40A includes a heating roller 41 which is a rotatable heating member for heating the paper A.
A pressure roller 42 that presses against the heating roller 41 to form a fixing nip and presses against the paper A, a bobbin 43 that is fixed inside the heating roller 41 with the same central axis, and wound around the bobbin 43. An induction coil 44A attached thereto, a fixed heating roller temperature sensor 45 that is in contact with the heating roller 41 to detect the temperature of the heating roller, and a coil power supply 46 that outputs a coil current that is applied to the induction coil 44A are provided.

The heating roller temperature sensor 45 and the coil power supply 46 are connected to the CPU 1. Bobbin 43
For example, PBT (polybutylene terephthalate), PI
It is made of (polyimide), PPS (polyphenylene sulfide), PAI (polyamide imide), or the like.
Although not shown, the bobbin 43 may have a core of ferrite, laminated steel plate or the like inside. The heating roller temperature sensor 45 is, for example, a thermistor, a thermocouple, an infrared radiation temperature sensor, or the like. Further, as shown in FIG. 4, the induction coil 44A is wound around the heating roller 41 in a hairpin shape in the longitudinal direction. The heating roller temperature sensor 45 is provided at the center of the heating roller 41 in the longitudinal direction.

The CPU 1 causes the coil power supply 46 to output an alternating current, which is a coil current, and the alternating magnetic flux to the induction coil 44A induces a periodically changing magnetic flux to heat the periodically changing magnetic flux. By being applied to the roller 41, an eddy current which is an induced current flows on the heating roller 41, and the heating roller 4 is caused by Joule loss of the eddy current.
1 is heated, and the heating roller temperature sensor 45 detects the heating roller temperature of the heating roller 41.

The CPU 1 also rotationally drives the heating roller 41 by a drive source (not shown), and the pressure roller 42 is rotated by being driven by the heating roller 41. By rotating the heating roller 41 and the pressure roller 42, the paper A inserted into the fixing nip is heated and pressed to melt and fix the toner image on the paper A.

The fixing device 40B shown in FIGS. 5 and 6 is an induction coil 44A wound in the longitudinal direction of the fixing device 40A.
Is replaced with a spring-shaped induction coil 44B wound around the bobbin 43 in the circumferential direction, and the other configurations are the same.

Now, the standby control temperature table a1 stored in advance in the ROM 3 will be described with reference to FIG. FIG. 7 is a diagram showing an internal configuration of the standby control temperature table a1. Standby control temperature table a1
Stores, as its items, the elapsed time t [seconds] from the end of printing of the input job and the corresponding control temperature [° C.] of the heating roller 41.

Elapsed time t [seconds] from the end of printing
Is 0 ≦ t <200, 200 ≦ t <600, 600 ≦ t
, The control temperature of the heating roller 41 [° C.]
Is 180, 190, 200.

Next, with reference to FIG. 8, a standby temperature control procedure which is an operation of the present embodiment will be described. Figure 8
It is a flowchart of a standby temperature control program. The standby temperature control procedure is an operation procedure that manages the control temperature of the heating roller 41 of the fixing devices 40A and 40B in the image forming apparatus α to prevent the coil temperature of the induction coils 44A and 44B from rising excessively.

The standby is a state in which the printing of the job input to the image forming apparatus α is completed, and the image forming processing of the paper A by the image forming unit 20 in the same job and the fixing by the fixing devices 40A and 40B are performed. In this state, the execution of the process is completed and the next job is waited for.

It is assumed that the ROM 3 previously stores the standby temperature control program, the control cycle, and the standby control temperature table a1. The CPU 1 reads the standby temperature control program from the ROM 3, and the RAM 2
Then, the standby temperature control procedure is started by executing the stored standby temperature control program.

First, the CPU 1 determines whether the standby has started (step S1). When the standby is not started (step S1; NO), the process returns to step S1.

When standby is started (step S
1; YES), the CPU 1 reads the current time from the timer 4 and sets the current time to the elapsed time t from the end of printing.
= 0 is set (step S2). And CPU1
Reads the control cycle from the ROM 3 and starts the timer 4 as a cycle timer (step S3). The period is a value set in advance and is assumed to be 1 second in the present embodiment, but it may be set to another period such as several to several nanoseconds.

Then, the CPU 1 reads the elapsed time t from the end of printing, which is worthy of the current time, from the timer 4 (step S4). Then, the CPU 1 reads out and refers to the standby control temperature table a1 on the ROM 3 (step S5). The CPU 1 then reads the elapsed time t from the end of printing read in step S4 and the step S4.
From the standby control temperature table a1 referred to in 5,
The fixing devices 40A and 40B are set to the control temperature of the heating roller 41 corresponding to the read-out elapsed time t from the end of printing, and the induction coil 4 is set in accordance with the set control temperature.
Energization control of coil current to 4A and 44B is executed (step S6).

Specifically, the CPU 1 transmits an energization control signal corresponding to the set control temperature to the coil power supply 46, and the actual heating roller temperature of the heating roller 41 detected by the heating roller temperature sensor 45 is If the temperature is equal to or higher than the control temperature, the energization control signal is turned off. If the temperature is lower than the control temperature, the energization control signal is turned on, and the energization control signal is turned on.
The energization of the induction coils 44A and 44B is controlled according to the switching between ON and OFF. The coil power supply 46 turns on / off the energization of the alternating current to the induction coils 44A and 44B according to the ON / OFF of the energization control signal.

Then, the CPU 1 determines whether or not the period timer of the timer 4 started in step S3 has timed out (step S7). When the cycle is not up (step S7; NO), the process returns to step S7. When the cycle time is up (step S7; Y
ES), the CPU 1 clears the cycle timer by the timer 4 started in step S3 (step S8).
Then, the process returns to step S3.

When a print job is input to the image forming apparatus α during the execution of the standby temperature control procedure, the processing is immediately stopped and the process returns to step S1.

Here, with reference to FIG. 9, an example of an experimental result of the step standby temperature control procedure will be described. Figure 9
6 is a graph of the heating roller temperature and the coil temperature with respect to the elapsed time from the end of printing the job in the standby temperature control procedure.

The heat resistant temperature of the induction coil differs depending on the type of coil wire. When the coil wire is an enamel wire, there is, for example, one having an endurance temperature of 105 to 240 ° C. In the experiment of FIG. 9, a spring type induction coil 44B is used.
The coil wire is an IMEC wire, and the heat resistant temperature is 220 ° C.

The continuous printing is executed by the job input to the image forming apparatus α, and the standby is started when the continuous printing is completed. The heating roller temperature of the heating roller 41 drops rapidly during printing because the printed paper A takes away heat, but the coil temperature of the induction coil does not drop. The control temperature of the heating roller 41 is set to 180 ° C. (threshold value) until 200 seconds after the start of standby, and when the actual heating roller temperature detected by the heating roller temperature sensor 45 is less than 180 ° C. in a cycle of 1 second, the coil power supply 46 When the actual heating roller temperature detected by the heating roller temperature sensor 45 is 180 ° C. or higher, the energization control signal to the coil power supply 46 is turned off to turn the induction coil 4 on.
Control of energization of AC current to 4B is performed. Similarly, the control temperature is set to 190 ° C. from 200 seconds to 600 seconds, and the control temperature is set to 200 ° C. from 600 seconds to control the energization of the alternating current to the induction coil 44B.

The standby control temperature table a1 is set so that the control temperature is set to be low after the start of the standby state at the end of printing the job, and the control temperature is increased as time passes. Since the energization duty of the induction coil 44B in the standby state is relatively lower than that in the printing state, the coil temperature drops. Therefore, by switching the heating roller temperature of the heating roller 41 to a higher value after the coil temperature decreases, it is possible to prevent the coil temperature from rising excessively without impairing the fixing performance.

According to the graph of the experimental result of the conventional temperature control procedure of FIG. 17, the coil temperature rapidly rises to about 235 ° C. after the start of the standby, and the heat resistant temperature of 220 ° C.
However, according to the experimental result of the standby temperature control procedure of the present embodiment of FIG. 9, the coil temperature is about 215 ° C.
It turns out that it can be suppressed to the following.

Therefore, according to the present embodiment, the control temperature of the heating roller 41 is changed according to the elapsed time from the end of printing of the input job, and the induction coil 44A,
By controlling the heating roller temperature by changing the energization of the coil current to 44B, it is possible to prevent the coil temperature of the induction coils 44A and 44B from rising excessively without impairing the fixing performance.

(Second Embodiment) This embodiment is shown in FIG.
This will be described with reference to FIGS. First, the features of the apparatus will be described with reference to FIGS. FIG. 10 is a block configuration diagram of the image forming apparatus β of the present embodiment, and FIG.
FIG. 12 is a cross-sectional view showing the configuration of the fixing device 40C.
FIG. 6 is a cross-sectional view showing the configuration of the fixing device 40D.

As shown in FIG. 10, the image forming apparatus β of the present embodiment has a structure in which the fixing devices 40A and 40B of the image forming apparatus α of the first embodiment are replaced with fixing devices 40C and 40D. . Therefore, the CPU 1, the fixing devices 40C, 4
0D will be described.

The CPU 1 always executes the temperature control program. By constantly executing the temperature control program, the CPU 1 starts the cycle timer with the timer 4, detects the coil temperature from the coil temperature sensors 47A and 47B, and performs RO
The constant control temperature table a2 of M3 is referred to, the control temperature of the heating roller 41 corresponding to the detected coil temperature is set, the induction coils 44A and 44B are energized, and the period is increased by the timer 4, and then the period timer is set. Is cleared and the procedure returns to the start procedure of the cycle timer (see FIG. 14).

In the fixing device 40C, the coil temperature sensor 47A connected to the CPU 1 is provided between the heating roller 41 and the bobbin 43 and between the coil wires above the induction coil 44A, as shown in FIG. C in the fixing device 40D
As shown in FIG. 12, the coil temperature sensor 47B connected to PU1 is provided between the heating roller 41 and the bobbin 43 and between the coil wires above the induction coil 44B. The coil temperature sensors 47A and 47B respectively include the induction coil 44.
It is provided at the center in the longitudinal direction of A and 44B.

The coil temperature sensors 47A and 47B are, for example, thermistors, thermocouples, infrared radiation temperature sensors and the like. The coil temperature sensors 47A and 47B are configured to contact the induction coils 44A and 44B and detect the coil temperature directly, but may be configured to detect the coil temperature near the induction coils 44A and 44B.

Now, the constant control temperature table a2 stored in advance in the ROM 3 will be described with reference to FIG. FIG. 13 is a diagram showing an internal configuration of the constant control temperature table a2. The constant control temperature table a2 stores, as its items, the coil temperature Tc [° C.] detected by the coil temperature sensors 47A and 47B and the corresponding control temperature [° C.] of the heating roller 41.

Coil temperature Tc [° C.] is 230 ≦ Tc,
When 210 ≦ Tc <230 and Tc <210, the control temperatures [° C.] of the heating roller 41 are 180 and 19, respectively.
It becomes 0,200.

Next, with reference to FIG. 14, an explanation will be given of the constant temperature control procedure which is the operation of the present embodiment. FIG. 14 is a flowchart of the constant temperature control program. The standby temperature control procedure is an operation procedure for managing the control temperature of the heating roller 41 of the fixing devices 40C and 40D in the image forming apparatus β to prevent the coil temperature of the induction coils 44C and 44D from rising excessively. While the standby temperature control procedure of the first embodiment was the temperature control procedure after the standby state, the constant temperature control procedure of the present embodiment is a temperature control procedure that is always performed.

It is assumed that the ROM 3 previously stores the constant temperature control program, the control cycle, and the constant control temperature table a2. The CPU 1 starts the standby temperature control procedure by reading the constant temperature control program from the ROM 3, storing it in the RAM 2, and executing the stored constant temperature control program.

First, the CPU 1 reads the control cycle from the ROM 3 and starts the timer 4 as a cycle timer (step T1). The cycle is a preset value,
In the present embodiment, it is set to 1 second, but it may be set to another cycle such as several to several nanoseconds.

Then, the CPU 1 uses the coil temperature sensor 4
The coil temperature Tc is detected from 7A and 47B (step T2). Then, the CPU 1 reads out and refers to the constant control temperature table a2 on the ROM 3 (step T3).
Then, the CPU 1 sets the fixing devices 40C and 40D to the control temperature corresponding to the detected coil temperature Tc from the coil temperature Tc detected in step T2 and the constant control temperature table a2 referred to in step T3, and According to the set control temperature of the heating roller 41, the induction coil 44
A coil current conduction control to A and 44B is executed (step T4).

Specifically, the CPU 1 transmits an energization control signal corresponding to the control temperature set in step T4 to the coil power supply 46, and the actual heating roller temperature of the heating roller 41 detected by the heating roller temperature sensor 45. However, if it is higher than the control temperature, the energization control signal is turned off, and if it is lower than the control temperature, the energization control signal is turned on, and the induction coil 44 is switched according to the on / off switching of the energization control signal.
Energization control to A and 44B is performed. The coil power supply 46 is
Induction coil 44 according to ON / OFF of the energization control signal
Turn on / off AC current supply to A and 44B.

Then, the CPU 1 determines whether or not the period timer of the timer 4 started at step T1 has timed out (step T5). When the cycle is not up (step T5; NO), the process returns to step T5. When the cycle time is up (step T5; Y
ES), the CPU 1 clears the periodic timer by the timer 4 started in step T1 (step T6).
Then, the process returns to step T1.

During execution of this constant temperature control procedure,
When a print job is input to the image forming apparatus β, the process being executed is interrupted and the print job is executed.

Here, with reference to FIG. 15, an example of experimental results of the constant temperature control procedure will be described. FIG. 15 is a graph of the heating roller temperature and the coil temperature with respect to the elapsed time from the end of printing the job in the constant temperature control procedure. 15, in order to compare the result of the constant temperature control procedure of FIG. 14 and the conventional temperature control procedure of FIG. 16, the constant temperature control procedure is executed after the start of the standby. Similar to FIG. 9, an induction coil 44B having a heat resistant temperature of 220 ° C. is used.

The continuous printing is executed by the job input to the image forming apparatus β, and the standby is started when the continuous printing is completed. The heating roller temperature of the heating roller 41 drops sharply during printing because the printed paper absorbs heat, but the coil temperature of the induction coil 44B does not drop. After starting the standby, set the control temperature of the heating roller 41 to 2
If the actual heating roller temperature detected by the heating roller temperature sensor 45 is lower than 200 ° C. at a cycle of 1 second, the energization control signal to the coil power supply 46 is turned on.
If the actual heating roller temperature detected by the heating roller temperature sensor 45 is 200 ° C. or higher, the energization control signal to the coil power supply 46 is turned off, and the energization control of the alternating current to the induction coil 44B is performed. Similarly, when the coil temperature is 210 ° C. or higher, the control temperature is set to 190 ° C., and thereafter, the control temperature is set to 200 ° C. and 190 ° C. according to the coil temperature to control the energization of the alternating current to the induction coil 44B. .

According to the graph of the experimental result of the conventional temperature control procedure of FIG. 17, the coil temperature rapidly rises to about 235 ° C. after the start of standby and exceeds the heat resistant temperature.
According to the experimental result of the constant temperature control procedure of the present embodiment, it is understood that the coil temperature can be suppressed to about 215 ° C. or less.

In the constant control temperature table a2, the control temperature is set lower as the coil temperature increases. Since the energization duty of the induction coils 44A and 44B in the standby state is relatively lower than that in the print state, the coil temperature drops. Therefore, after the start of standby, the coil temperature decreases, the control temperature is switched to a higher value, and when the coil temperature rises, the control temperature is switched to a lower value, and then the control temperature is changed according to the coil temperature, thereby impairing the fixing performance. Without excessively increasing the coil temperature.

Therefore, according to the present embodiment, the fixing temperature is always impaired by changing the control temperature of the heating roller 41 according to the coil temperature to control the energization of the coil current to the induction coils 44A and 44B. Without excessively increasing the coil temperature of the induction coils 44A and 44B.

The standby temperature control program, the control cycle and the standby control temperature table a1 of the first embodiment, and the constant temperature control program, the control cycle and the constant control temperature table a2 of the second embodiment.
May be stored in an external storage unit of the image forming apparatuses α and β, and may be read from the external storage unit when necessary. Further, the image forming apparatuses α and β are provided with an input unit so that the control cycle,
The standby control temperature table a1 and the constant control temperature table a2 may be input and changed by the user at any time.

Further, in controlling the energization of the coil current to the induction coils 44A and 44B corresponding to the control temperature in each of the above-described embodiments, the control temperature of the heating roller 41 is set as a threshold and the control temperature and the actual heating roller temperature are set. By comparison, the energization of the coil current is ON / OFF controlled according to the result of the comparison, but the energization duty of the coil current is changed depending on the difference between the control temperature and the actual heating roller temperature and the operating state of the image forming apparatus. Or the current value of coil current, voltage value,
The frequency value or the like may be changed to perform control such that the electric power supplied to the induction coils 44A and 44B is switched to a plurality of levels.

Further, although each of the above-described embodiments has been described as a configuration using a roller type fixing device using a heating roller and a pressure roller, each embodiment is applied to a belt type fixing device using a belt. It may be configured. here,
An example of the belt type fixing device will be described with reference to FIG. Figure 1
6 is a sectional view of the belt type fixing device 40E.

As shown in FIG. 16, the belt type fixing device 4
Reference numeral 0E denotes a heating roller 41A, a bobbin 43, an induction coil 44A, a heating roller temperature sensor 45, and a coil temperature sensor 47A, and pressure rollers 42A and 42B that are in pressure contact with each other to form a nip portion, and a heating roller 41A. And a belt 48 wound around the pressure roller 42A and rotated at the same speed.

The belt-type fixing device 40E includes the induction coil 4
Heating roller 4 generated by passing coil current to 4A
The heat on 1A is transferred to the pressure roller 42A via the belt 48, and the nip portion of the pressure rollers 42A and 42B is made to pass the recording material imaged by the image forming section to fix the toner image. . Other than this, each embodiment can be applied to a belt-type fixing device in which the belt itself is induction-heated by the magnetic flux from the induction coil.

Further, the image forming apparatuses α and β in each of the above-described embodiments are used as a so-called copy machine or the like in the scanner 1
Although the configuration uses 0, a configuration such as a printer for a computer that does not include a reading unit such as a scanner may be used. In this case, print data is received from the outside, an image is formed on the recording material by the image forming unit using the print data, and the recording material is fixed by the fixing device.

In the second embodiment, the constant temperature control procedure is always executed by using the constant temperature control table a2. A configuration may be used in which the control temperature in the standby state at the end of execution is set differently.

The induction coil according to claim 1 or 4 is, for example, the induction coils 44A and 44B shown in FIG. 1, and the heating member according to claim 1 or 4 is, for example, the heating roller 41 or the drawing shown in FIG. 16 is a heating roller 41A,
The pressure member according to claim 1 or 4 is, for example, the pressure roller 42 shown in FIG. 1 or the pressure rollers 42A, 4 shown in FIG.
2B, the power source according to claim 1 or 4 is the coil power source 46 shown in FIG. 1, and the heating member temperature detecting means according to claim 1 or 4 is the heating roller temperature sensor 45 shown in FIG. Is.

The storage means according to claim 1 is, for example, the ROM 3 shown in FIG. 1 for storing the standby control temperature table a1 shown in FIG. 7, and the control means according to claim 1 is shown in FIG. It is CPU1 shown in FIG. 1 which performs the shown steps S4 to S6.

The storage means according to claim 4 is, for example, the ROM 3 shown in FIG. 10 for storing the constant control temperature table a2 shown in FIG. 13, and the coil temperature detecting means according to claim 4 is, for example, as shown in FIG. Coil temperature sensor 4 shown in 13
7A and 47B, and the control means according to claim 4 executes, for example, steps T2 to T4 shown in FIG.
CPU 1 shown in FIG.

Although the embodiments of the present invention have been described above, the present invention is not necessarily limited to the above-described means and techniques, and the objects referred to in the present invention can be achieved and the effects referred to in the present invention can be achieved. Modifications can be appropriately made within the range.

[0090]

According to the first aspect of the present invention, the control temperature of the heating member is changed according to the elapsed time from the end of printing of the input job to control the energization of the coil current to the induction coil. After the completion of job execution,
It is possible to prevent the coil temperature of the induction coil from rising excessively.

According to the second aspect of the present invention, after the printing of the input job is completed, the coil temperature increased during printing is gradually radiated with time and the temperature decreases. Will be raised,
It is possible to prevent the coil temperature of the induction coil from rising excessively without impairing the fixing performance.

According to the third aspect of the present invention, it is possible to variously control the passage of the coil current to the induction coil.

According to claim 4 of the present invention, the coil temperature of the induction coil can be controlled by changing the control temperature of the heating member according to the coil temperature or the temperature in the vicinity of the coil to control the supply of the coil current to the induction coil. It is possible to prevent an excessive rise.

According to the fifth aspect of the present invention, the fixing performance is controlled by setting the control temperature lower as the coil temperature increases according to the coil temperature or the coil vicinity temperature to control the energization of the coil current to the induction coil. It is possible to prevent the coil temperature of the induction coil from rising excessively without damaging the coil.

According to the sixth aspect of the present invention, it is possible to variously control the energization of the coil current to the induction coil.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an image forming apparatus α according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an image forming unit 20 and fixing devices 40A and 40B of the image forming apparatus α in FIG.

FIG. 3 is a cross-sectional view showing a configuration of a fixing device 40A in FIG.

4 is an induction coil 44 of the fixing device 40A in FIG.
It is a figure which shows the shape of A.

5 is a cross-sectional view showing a configuration of a fixing device 40B in FIG.

6 is an induction coil 44 of the fixing device 40B in FIG.
It is a figure which shows the shape of B.

FIG. 7 is a diagram showing an internal configuration of a standby control temperature table a1.

FIG. 8 is a flowchart of a standby temperature control program.

FIG. 9 is a graph of the heating roller temperature and the coil temperature with respect to the elapsed time from the end of printing the job in the standby temperature control procedure.

FIG. 10 is an image forming apparatus β according to the second embodiment of the present invention.
It is a block configuration diagram of.

11 is a cross-sectional view showing a configuration of a fixing device 40C in FIG.

12 is a cross-sectional view showing the configuration of the fixing device 40D in FIG.

FIG. 13 is a diagram showing an internal configuration of a constant control temperature table a2.

FIG. 14 is a flowchart of a constant temperature control program.

FIG. 15 is a graph of heating roller temperature and coil temperature with respect to the elapsed time from the end of printing a job in the constant temperature control procedure.

FIG. 16 is a sectional view showing the structure of a belt-type fixing device 40E.

FIG. 17 is a graph of heating roller temperature and coil temperature with respect to the elapsed time from the end of printing a job in the conventional temperature control procedure.

[Explanation of symbols]

α, β ... Image forming device 1 ... CPU 2 ... RAM 3 ... ROM 4 ... Timer 10 ... Scanner 20 ... Imaging department 21 ... Photosensitive drum 22 ... Charger 23 ... Exposure means 24 ... Developer 25 ... Transferring means 26 ... Cleaner 30 ... Paper feeder 40A, 40B, 40C, 40D, 40E ... Fixing device 40E ... Belt type fixing device 41, 41A ... Heating roller 42, 42A, 42B ... Pressure roller 43 ... Bobbin 44A, 44B ... Induction coil 45 ... Heating roller temperature sensor 46 ... Power supply for coil 47A, 47B ... Coil temperature sensor 50 ... Display A ... paper

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miho Toyoda             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             Inside the company F-term (reference) 2H027 DA12 DA38 DA40 EA12 EC20                       ED25 EE02 EE07 EE08 EF12                 2H033 AA24 AA42 BA25 BA30 BB18                       CA05 CA07 CA21 CA30 CA32                       CA48                 3K059 AA08 AB19 AC33 AD26 CD03                       CD05 CD18

Claims (6)

[Claims] 1. An induction coil that generates a magnetic flux by passing a coil current, a power supply that supplies the coil current to the induction coil, and a heating member that generates heat with an induction current induced by the magnetic flux generated from the induction coil. A pressure member for pressing the recording material and a heating member temperature detecting means for detecting the heating member temperature of the heating member are provided to heat and apply the developer on the recording material passing through the nip portion of the pressing member. An image forming apparatus having a fixing device for fixing by pressure, the storage means storing a control temperature of the heating member corresponding to an elapsed time from the end of printing of a job input to the image forming apparatus, and Elapsed time detection means for detecting the elapsed time from the end of printing, the elapsed time from the end of printing detected by the elapsed time detection means, and stored in the storage means. Control temperature of the heating member, and control means for controlling the temperature of the heating member by changing the coil current supplied from the power source according to the actual heating member temperature detected by the heating member temperature detecting means, An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the storage means stores a control temperature that is set higher as the elapsed time from the end of printing becomes longer. 3. The change of the coil current in the control means is a change of at least one of an energization time ratio of the coil current, a current value, a voltage value, and a frequency value. The image forming apparatus according to any one of 1 and 2. 4. An induction coil that generates a magnetic flux by passing a coil current, a power supply that supplies the coil current to the induction coil, and a heating member that generates heat with the induction current induced by the magnetic flux generated from the induction coil. A pressure member for pressing the recording material and a heating member temperature detecting means for detecting the heating member temperature of the heating member are provided to heat and apply the developer on the recording material passing through the nip portion of the pressing member. An image forming apparatus having a fixing device for fixing by pressure, comprising: a storage unit that stores a control temperature of the heating member corresponding to a temperature of the induction coil or a temperature in the vicinity of the induction coil; Coil temperature detecting means for detecting temperature or temperature near the induction coil, and temperature of the induction coil detected by the coil temperature detecting means or temperature near the induction coil According to the control temperature of the heating member stored in the storage means, and the actual heating member temperature detected by the heating member temperature detecting means, the coil current supplied from the power source is changed to change the coil temperature of the heating member. An image forming apparatus comprising: a control unit that controls temperature. 5. The image forming apparatus according to claim 4, wherein the storage unit stores the control temperature set lower as the temperature of the induction coil or the temperature near the induction coil increases. apparatus. 6. The change of the coil current in the control means is a change of at least one of a conduction time ratio of the coil current, a current value, a voltage value, and a frequency value.
The image forming apparatus according to claim 4, wherein the image forming apparatus is an image forming apparatus.