JPH09311581A - Fixing temperature controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control fixing temperature with high accuracy by providing a heater driving control circuit and adjusting the conduction time of a heater. SOLUTION: This controller is provided with a temperature sensor arranged at the paper non-passing part of a heating and fixing roller through which a fixing heater is inserted, and estimates the fixing temperature based on a detection signal from the temperature sensor. A CPU 510 judges whether the fixing temperature is within a set temperature range or not and controls the energizing state of the fixing heater. An SRAM 520 sets the upper limit temperature and the lower limit temperature to decide the set temperature range. A fixing temperature control circuit 540 controls the fixing heater to be in a non-conduction state in the case of judging that the fixing temperature is lower than the lower limit temperature set by the SRAM 520, and in a conduction state in the case of judging that the fixing temperature is higher than the temperature set by the SRAM 520, and controls so that the conduction state and the non-conduction state of the fixing heater are repeated in a specified cycle in the case of judging that the fixing temperature is within the temperature range set by the SRAM 520.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing temperature control device for controlling a fixing temperature in a thermal fixing device for permanently fixing a toner image on a transfer material.

[0002]

2. Description of the Related Art As is well known, a fixing device is a device for permanently fixing a toner image on a transfer material by applying heat or heat and pressure to the transfer material carrying the toner image. , A fixing heating roller having a built-in fixing heater, a pressure roller, and a discharge roller for feeding the transfer material. To control the temperature of such a fixing device, a temperature sensor such as a thermistor is provided on the surface of the heating fixing roller, and if it is determined from the detection signal from the temperature sensor that the temperature is lower than the set temperature, the fixing heater is turned on and the temperature sensor If it is determined that the temperature is higher than the set temperature based on the detection signal of, the fixing heater is turned off. Since such a fixing temperature control method is likely to overshoot from the set temperature, it has not been possible to control the fixing temperature to be stable.

In order to eliminate the above-mentioned instability of the fixing temperature, the fixing heater is turned on to control the temperature corresponding to the temperature difference between the detected temperature based on the detection signal from the temperature sensor and the set temperature. A method has been proposed. Such a temperature control method has a problem of poor responsiveness.

In order to eliminate the poor response of the fixing temperature control, an upper limit set temperature and a lower limit set temperature are provided.
If it is determined that the fixing temperature is lower than the lower limit set temperature based on the detection signal from the temperature sensor, the fixing heater is turned on,
A fixing temperature control method has been proposed in which the fixing heater is controlled to be turned off when it is determined that the fixing temperature based on the detection signal from the temperature sensor is higher than the upper limit set temperature.

[0005]

However, even in the fixing temperature control method in which the upper limit set temperature and the lower limit set temperature are set as described above, when the temperature sensor is arranged in the sheet passing portion through which the recording sheet passes. When the recording paper is wrapped around the fixing heating roller, a smoke accident may occur due to an erroneous detection of the temperature sensor. In order to prevent such a smoking accident, a safety device such as a thermostat or a fuse is provided, or a spare temperature sensor is provided at a non-sheet passing portion where the recording sheet does not pass. Such a safety device becomes expensive due to the increase in the number of parts. Therefore, it is desired to propose an appropriate fixing temperature control method only by providing a temperature sensor in the non-sheet passing portion of the heating fixing roller. A technical issue in developing such a fixing temperature control method is a temperature difference between the paper passing portion and the non-paper passing portion of the heating fixing roller, and particularly during continuous printing due to the heat absorbing action of the recording paper. Other than that, the temperature difference between the paper passing portion and the non-paper passing portion changes.

An object of the present invention is to solve the above technical problems,
An object of the present invention is to provide a fixing temperature control device capable of controlling a stable fixing temperature regardless of an operation mode by a temperature sensor provided in a non-sheet passing portion.

[0007]

The above object can be achieved by the following constitutions.

(1) A temperature sensor provided in a non-sheet passing portion of a heating fixing roller having a heater inserted therein is provided, the fixing temperature is estimated based on a detection signal from the temperature sensor, and the fixing temperature is within a set temperature range. A fixing temperature control device for controlling the energization state of the heater by judging either inside or outside,
Fixing temperature setting means for setting an upper limit temperature and a lower limit temperature for determining the set temperature range, and if it is determined that the fixing temperature is lower than the lower limit temperature set by the fixing temperature setting means, the heater is brought into a non-conductive state, If it is determined that the fixing temperature is higher than the upper limit temperature set by the fixing temperature setting means, the heater is made conductive, and if it is determined that the fixing temperature is within the temperature range set by the fixing temperature setting means, the heater is set. 2. A fixing temperature control device, comprising: a heater drive control circuit for controlling so that the conductive state and the non-conductive state are repeated at a predetermined cycle. With such a configuration, the fixing temperature can be controlled with high accuracy by adjusting the conduction time of the heater.

(2) A mode discriminating means for discriminating an operation mode and a heating time changing means for changing a time for conducting a current to the heater according to the print mode discriminated by the mode discriminating means are provided. (1) The fixing temperature control device. With such a configuration, the conduction time of the heater can be adjusted in small increments according to the operation mode, so that the fixing temperature can be controlled to an appropriate fixing temperature in various operation modes.

(3) If the mode discriminating means discriminates the continuous print mode, the fixing temperature setting means for setting the upper limit temperature and the lower limit temperature for determining the set temperature range to a high value is provided ( 1) Fixing temperature control device. By providing such a configuration, it is possible to control to a sufficient fixing temperature even in the continuous print mode.

[0011]

FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus according to the present embodiment, and FIG. 2 is a sectional view showing each cartridge according to the present embodiment.

The image forming apparatus according to the present embodiment has a main body 2 in which a cartridge containing various process members is loaded.
00, a double-sided paper feeding device 400 and a recording paper feeding device 600 are optionally provided.

First, the structure of each cartridge will be described with reference to FIGS.

As shown in FIG. 2, the equipment accommodated in the drum stand 30 includes a drum cartridge 40 in which the photosensitive drum 10 and others are incorporated, and a developing cartridge 50 in which each developing device 14 containing Y, M, and C developers is incorporated. Further, it is separately stored into a developing cartridge 50A in which only the developing device 14A containing the K developer is incorporated.

The drum cartridge 40 is the photosensitive drum 1.
In addition to 0, a PCL 11, a charger 12, and a cleaning device 22 are incorporated to cover all the photoconductor surface except for the openings 40A, 40B, and 40C corresponding to the exposure, development, and transfer regions of the photoconductor surface. . In the drum cartridge 40, the bearing 41 of the photosensitive drum 10 is brought into contact with the vertical groove 30 </ b> A of the drum base 30, and the bottom part is brought into contact with a pair of position regulating pins P <b> 1 provided on both inner side surfaces of the drum base 30. In this way, after the rotation is prevented, the horizontal and vertical positions are regulated and each device to be accommodated is set to a predetermined image forming position.

As shown in FIG. 2, the opening 40A, which is the exposure area of the drum cartridge 40, is provided with a slidable shield plate 42 in an elongated slit hole having a width sufficient for a writing beam to pass therethrough. There is no way to get into.

On the other hand, the developing cartridges 50 and 50A
Are biased by the compression springs 52 in a state where the position regulating pins P2 of the respective developing devices projectingly engage with the elongated holes on both side surfaces. The developing cartridges 50 and 50A are pressed leftward by pressing pins P3 or P4 of the side door 34 forming the right side surface of the drum base 30, and abutting rollers (not shown) coaxial with the developing sleeves 141 are pressed. The gap between the peripheral surface of each developing sleeve 141 with respect to the photosensitive member surface, that is, the developing gap value is set by being pressed against the peripheral surface on the photosensitive drum 10.

The drum base 30 is a pedestal 30 installed above.
A plurality of toner replenishing means 300 for replenishing toner to each developing unit are provided integrally on the upper surface of B.

Each toner replenishing means 300 comprises a toner hopper 310 connected to each developing device by a toner carrying pipe (not shown) and a loading section 330 for mounting the toner cartridge 320 in a horizontal position. The toner replenishing means 300 are arranged adjacent to each other on the same plane in the axial direction of the developing sleeve 141 of the developing device 14. The developing sleeve 141 has a power source (not shown) for applying a DC bias and an AC bias set for each color, and the DC bias and the AC bias can be turned on / off individually under the control of the CPU 510.

The connection portion between the toner transport pipe (not shown) and each developing device is released and connected in accordance with the withdrawal and insertion of each developing device. That is, when the drum base 30 is pulled out for jam processing, drum cartridge replacement, or the like, the connecting portion between the toner transport pipe and the developing device does not separate, and the connecting portion (not shown) is only formed when taking out each developing device. The toner stains were reduced because they were separated. Further, when the drum base 30 is taken out, the toner supply means 30
Since it is not necessary to separate 0 from the developing device 14, the construction of those devices is simplified and at the same time the handling operation is simplified.

As shown in FIG. 1, the image forming apparatus is provided with a recording paper passage detection sensor 70 for detecting the recording paper between the transfer roller 216 and the cleaning device 22.

The transfer roller 216 is equipped with a power source (not shown) capable of applying a positive or negative transfer bias.
Switching is performed under the control of the PU 510. When the recording paper exists at the transfer portion, the polarity of the bias voltage to the transfer roller 216 is set to the opposite polarity to the polarity of the toner. When the recording paper passes through the transfer roller 216 and the photosensitive drum 10 and the transfer roller 216 come into direct contact with each other at the transfer portion, the polarity of the bias voltage to the transfer roller 216 is made the same as the charging polarity of the toner. To do. When the recording paper is not present at the transfer portion, the polarity of the bias voltage to the transfer roller 216 is set to be the same as the polarity of the toner. By thus determining the operation of the transfer roller 216, when image formation is continuously performed, the transfer roller 216 can be quickly cleaned in the period between adjacent recording sheets. Such a control method is also effective when the size of the transfer material in the traveling direction is not known in advance, for example, for manual feeding.

As shown in FIG. 1, the main body 200 is provided with a manual paper feed mechanism 270. The manual paper feed mechanism 270 has an insertion hole 271 into which a recording sheet is inserted and a recording paper inserted into the insertion hole 271. A detection member for detecting the paper is provided. The leading end of the inserted recording paper hits the built-in paper feed roller 272 and stops. The recording paper is conveyed by the rotation of the paper feed roller 272, and is conveyed toward the registration rollers 209 via the conveyance path 273. The manual feed mechanism 270 is the main body 2
The shaft is fixed to the shaft at 00 and is slightly movable outward.
Further, a part of the outer member is supported by the shaft, and the insertion hole can be opened.

A paper feed cassette 203 containing a plurality of recording papers in the main body 200 is detachably provided as shown in FIG. A half-moon-shaped paper feed roller 202 for feeding recording paper is provided on the paper feed cassette 203, and the paper feed cassette 2
A push-up plate 204 for pressing the uppermost recording sheet against the separation claw 205 is provided in the inside of the sheet. The recording paper placed on the push-up plate 204 is constantly pushed upward by a spring (not shown), the leading end of the recording paper is locked by the separation claw 205, and the recording paper is fed by the operation of an electromagnetic clutch (not shown). Roller 202
Is driven, and the uppermost sheet of recording paper is separated by the separation claw 205 and fed. The fed recording sheet is driven and conveyed by the intermediate sheet feeding roller 206, and is guided to the registration roller 209. CPU downstream of the registration roller 209
A registration shutter 215 for opening and closing the registration unit in accordance with a control signal from 510 is provided. The detection member 219 is operated by the CPU 510, and when the detection member 219 detects the recording paper, the recording paper directly enters the registration roller 209 and is stopped by the registration shutter 215. Further, a sensor 189 for detecting the transparency of the recording paper surface is provided upstream of the registration roller 209 in the paper feeding. At this time, the leading end of the recording paper abuts on a projection provided on a part of the transmission sensor 189 which is rotatably fixed to a part of the main body 200 on the upper part of the guide member 213, and along the image forming surface of the recording paper. After the transmission sensor 189 is arranged at a predetermined position, the transparency of the image forming surface formed on the recording paper is detected.

A detection member for detecting the recording paper is provided above the paper feed cassette 203. Intermediate paper feed roller 20
Reference numeral 6 denotes a sheet cassette 203 and a curved reversing guide member 212.
It is provided between and.

The recording paper guide member 210 is the registration roller 2
The recording paper having passed through the transfer roller 09 is guided toward the transfer roller 216 which can be pressed and separated from the photosensitive drum 10.

The fixing device 220 is a device for fixing the image transferred on the recording paper, and comprises a fixing heating roller 221 and a pressure roller 222. The heating roller 221 for fixing has a diameter of 245.7 mm and a thickness of 45 on a substrate having an outer diameter of 1.6 mm.
It has a 0 μm silicone rubber layer and a 50 μm thick PFA layer. A fixing heater 224 is inserted into the base of the fixing heating roller 221. The heating roller 221 for fixing is controlled so that the surface temperature is detected by the fixing temperature sensor Th and is always constant. Fixing temperature sensor Th
Is composed of a thermistor or the like, and the fixing heating roller 2
The fixing heater 224 of the fixing heating roller 221 is turned on / off by detecting the surface temperature of the fixing heating roller 22.
When the surface temperature of 1 is detected and it becomes abnormally high,
It is used to stop the power supply to the fixing heater 224. The fixing temperature sensor Th is provided in a non-transfer material region (a region that is not affected by toner, paper dust, etc.) where the transfer material P and the heating roller 221 for fixing do not come into contact with each other when the transfer material P passes, so that the paper passing time is reduced. The initial detection accuracy can be maintained regardless of. The pressure roller 222 has a surface layer such as rubber. The discharge roller 223 is connected to the fixing device 22.
The recording paper is discharged from 0, and the discharged recording paper is conveyed upward by the conveying roller 291. The recording paper conveyed upward by the conveying rollers 224 is ejected from the main body 200 by a paper ejection roller 292 provided in a paper ejection passage formed in the main body 200.
The recording surface is discharged onto a discharge tray 210 provided on almost the entire upper surface with the recording surface facing downward. A paper ejection detection sensor 229 is provided in the paper ejection path of the fixing device 220.

A motor (not shown) transmits a driving force to the sheet feeding roller 202 and the intermediate sheet feeding roller 206 via a reduction mechanism (not shown) via a toothed pulley and an intermediate gear group. It The paper feed roller 202 is intermittently driven by an electromagnetic clutch (not shown). On the other hand, the registration roller 209 and the intermediate sheet supply roller 206 are configured to be driven and rotated at all times.

The above is the schematic mechanism of the image forming apparatus according to the present embodiment.

Next, FIG. 3 shows a schematic configuration of the engine controller 500 used in the image forming apparatus according to the present embodiment.
This will be described with reference to FIG.

FIG. 3 is a block diagram showing a fixing temperature control system of the engine controller 500 in this embodiment.

The engine controller 500 receives page data and print parameters from an external device such as a personal computer mainly via a print controller (not shown), and writes the data into the writing device 230, the scorotron charger 12, and the developing device 14. It controls the drive timings of the transfer roller 216 and the cleaning device 22, and controls the paper feed timing of recording paper from the paper feed device 400, the paper feed cassette 203, and the manual paper feed mechanism 270. Is also in control. Engine controller 50
0 is the CPU 510, SRAM 520, and gate array 5
30 and a fixing temperature control circuit 540. The configuration of each part will be described below.

The CPU 510 executes a sequence program for executing the electrophotographic process from the SRAM 520 by using a reference signal for one round of the drum, which is an external signal, as a trigger, and controls a driving state of a motor driver (not shown). , Passage detection sensors 70, 189, 219,
The conveyance state of the recording paper is controlled based on the detection signal from 229 (see FIG. 1), and the fixing temperature is controlled to a predetermined value for each operation mode via the fixing temperature control circuit 540.

In the present embodiment, the set temperature for fixing the toner image on the plain paper is 165 ° C to 170 ° C.
The set temperature for fixing the toner image on the OHT is set in the range of 180 ° C. to 185 ° C., and the set temperature is 13 when the transfer material is not fed.
The temperature is set in the range of 5 ° C to 145 ° C, and the set temperature in the standby state is set to 120 ° C. Therefore, CP
The U510 sends an ON / OFF signal of the fixing lamp so that the temperature falls within the upper and lower set temperatures of the set temperature range in various modes.

The SRAM 520 has a warm-up process, a multi-color print process, a mono-color print process, a letter size print sequence, a paper feed process including a postcard size print sequence and a purge process, and a manual paper feed. Data and programs for controlling the surface temperature of the fixing heating roller 221 for each mode and the parameters necessary to execute the processing and the program corresponding to the double try sequence and various print sequences are stored. .

The gate array 530 has a developing device drive system, a transfer cleaning drive system, a paper feed drive system, and a fixing temperature control function. The developing device driving system controls the operation of the driving mechanism of the toner supply device by selecting the driving state of the driving mechanism of the developing device. The transfer cleaning drive system instructs the state of pressing / releasing the cleaning blade and the transfer roller 216 to and from the photosensitive drum 10 in the various sequences described above. The paper feed drive system controls the transport speed of the recording paper according to the print size, print mode, and the like.

The gate array 530 inputs a signal indicating the fuse temperature and the open / closed state of the door from the fixing temperature control circuit 540 and forcibly stops the heating operation of the fixing heater 224 by the hardware when the program runs out to fix the fuse. A watchdog function of cooling the heating roller 221 is achieved.
Therefore, when the CPU 510 detects a runaway of the fixing temperature control program based on the input obtained from the gate array 530, the fixing temperature control circuit 540 disconnects the main relay and the AC power source by the operation of hardware. A watchdog function is realized.

The gate array 530 sends the fixing heater 224 control signal according to each operation mode.
The fixing heater 224 is controlled to be turned on / off by sending the fixing heater 224. Specifically, the fixing heater 224 cyclically repeats a heating time of 1.5 sec and a non-heating time of 4 sec in the non-sheet-passing period, and the fixing heater 224 is a plain paper sheet or an OH sheet.
Heating time of 1 sec and 4 sec during the fixing operation of T
The non-heating time of is periodically repeated.

The above is the schematic configuration of the engine controller 500 in the present embodiment.

The printing operation of the image forming apparatus according to the present embodiment will be described with reference to FIGS.

FIG. 4 is a flow chart showing the print sequence of the image forming apparatus in this embodiment.

Upon receiving the print start code, the CPU 510 activates the print start task (step 1). Specifically, as shown in FIG. 2, the CPU 510 (see FIG. 3) grounds the photoconductor drum 10 having the OPC photoconductor coated on the drum, and rotates the drive drum clockwise. CP
U510 rotates a polygon mirror (not shown).
This stabilizes the rotation of the photoconductor drum 10 and the polygon mirror. Further, the CPU 510 initializes the content of the print register α for determining whether continuous printing is performed to 0.

The CPU 510 activates the sequence start task (step 2). As a result, the CPU 51
0 sets various modes.

When the CPU 510 receives the reference interrupt signal in the cycle of one rotation of the photosensitive drum 10, it starts the image start task (step 3).

More specifically, the CPU 510 causes the scorotron charger 12 to uniformly charge VH on the peripheral surface of the photosensitive drum 10 by corona discharge by a grid and a corona discharge wire whose potential is held at VG. Prior to the charging by the scorotron charger 12, in order to eliminate the history of the photoconductor up to the previous print, exposure is performed by the PCL 11 using a light emitting diode or the like to eliminate the charge on the peripheral surface of the photoconductor.

Image exposure means 23 after uniform charging of the photoreceptor
With 0, image exposure based on the image signal is performed. The image exposing means 230 scans by rotating the optical path by a reflecting mirror via a rotating polygon mirror, fθ lens, and the like using a laser diode (not shown) as a light emitting light source. Is formed. In the present embodiment, a character portion is exposed to form a reversal latent image such that the character portion has a lower potential VL.

At the periphery of the photosensitive drum 10, there are provided developing units 14 each containing a developer consisting of toner such as yellow (Y), magenta (M), cyan (C), and black (K) and a carrier. First, the development of the first color is performed by the developing sleeve 141 which contains a magnet and holds the developer and rotates. The developer consists of a carrier in which ferrite is used as a core and is coated with an insulating resin around it, and a toner whose main component is polyester and pigments according to the color and charge control agents, silica, titanium oxide, etc. are added. The agent is regulated by the layer forming means to have a layer thickness (developer) of 100 to 600 μm on the developing sleeve 141 and is conveyed to the developing area. The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is set to 0.2 to 1.0 mm, which is larger than the layer thickness (developer), and the AC bias of VAC and the DC bias of VDC are superposed and applied between them. It Since VDC and VH and the toner are charged in the same polarity, the toner that has been given the opportunity to be separated from the carrier by VAC does not adhere to the VH portion where the potential is higher than VDC, but adheres to the VL portion where the potential is lower than VDC. Then, visualization (reversal development) is performed.

When the CPU 510 receives the reference interrupt signal again after the visualization of the first color is finished, the CPU 510 enters the image forming process of the second color and performs the uniform charging by the scorotron charger 12 again to perform the image of the second color. A latent image based on data is formed by the image exposure means 13. At this time, the charge elimination by the PCL 11 performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to the sudden decrease in the potential around the image. A latent image similar to that of the first color is formed and developed on the portion of the photoconductor having the potential of VH all over the peripheral surface of the photoconductor drum 10 again without the image of the first color. In the portion where the first color image is developed again, a latent image of VM 'is formed by the toner attached to the first color due to the light shielding and the electric charge of the toner itself, and the development according to the potential difference between VDC and VM'. Is done. In the overlapping portion of the images of the first color and the second color, if the development of the first color is performed by forming a latent image of VL, the balance between the first color and the second color is lost, so that the exposure amount of the first color is reduced and VH> The intermediate potential is such that VM> VL. CPU
510 receives the reference interrupt signal for the third and fourth colors as well as the second color, and executes the image forming process,
Visual images of four colors are formed on the peripheral surface of the photosensitive drum 10.

On the other hand, the paper feeding roller 2 from the paper feeding cassette 203
The recording paper conveyed through the sheet No. 02 is temporarily stopped, and is fed to the transfer area by the rotation operation of the registration roller 209 when the transfer timing is adjusted. In the transfer area, a transfer roller 216 is pressed against the peripheral surface of the photosensitive drum 10 in synchronization with the transfer timing, and the fed recording paper is sandwiched to transfer the multicolor image at once. Next, the recording paper is separated into brushes 21 separated from each other at almost the same time as shown in FIG.
7, the charge is removed by the peripheral surface of the photosensitive drum 10, and the charge is conveyed to the fixing device 220.
The toner is fused by heating and pressurizing the pressure roller 1 and the pressure-bonding roller 222, and then the toner is discharged to the outside of the apparatus through the paper discharge roller 223.

After the sequence start task is activated, the CPU 510 activates the image end task after a lapse of a predetermined time specified for each paper size (step 4). Specifically, the CPU 510 stops the rotation of the developing sleeve 141 and turns off the developing bias and the like. The CPU 510 prepares for forming the next toner image by separating the transfer roller 216 and the separation brush 217 from the peripheral surface of the photosensitive drum 10 after passing the recording paper. On the other hand, the CPU 510 presses the photosensitive drum 10 from which the recording paper is separated against the blade of the cleaning device 22. As a result, the residual toner is removed / cleaned, the charge is removed again by the PCL 11 and the charge by the charger 12, and the next image forming process starts. The blade moves immediately after the cleaning of the photoconductor surface and retracts from the peripheral surface of the photoconductor drum 10.

The CPU 510 activates the check task (step 5). As a result, the CPU 510 determines whether or not the start command is received from the print controller (not shown). The CPU 510 increments the register α (step 8). When the CPU 510 receives the start command from the print controller (not shown) (step 6), the operations after step 2 are executed again. If the CPU 510 does not receive the start command for the next print from the print controller (not shown) (step 6), it executes the print end task (step 7). Specifically, the CPU 510 causes the polygon mirror to rotate at a half speed, and the photoconductor drum 10 to rotate.
Stop rotating. This ends the print sequence.

The CPU 510 drives the standby task upon completion of the print end task (step 1).
0). As a result, the CPU 510 reduces the rotation speed of the fan to lower the temperature of the fixing heating roller 221.

Next, the fixing control task will be described with reference to FIGS.

5 and 6 are flowcharts showing the fixing control task.

The CPU 510 activates the fixing control task in parallel with the print start task shown in FIG. The fixing control task is activated every predetermined time. An example of such a predetermined time is 250 msec.

Whether the CPU 510 is warming up control (step 110), idling mode control (step 120), plain paper print mode control (step 140), or OHT print mode control (step 160). ), It is determined whether the task is a standby mode control task (step 180) or an abnormality occurrence stop mode (step 190).

If the CPU 510 determines in step 110 that the warm-up is being performed, the gate array 530 is selected.
The fixing temperature control circuit 540 refers to the fuse temperature to confirm whether the fixing temperature is 145 ° C. or lower (step 111). When the CPU 510 detects in step 111 that the fixing temperature is 145 ° C. or lower, it turns on the fixing heater 224 (step 112). CPU510
Counts up the warming-up abnormality detection (F38) counter (step 113). Thereby, the CP
U510 ends this task. On the other hand, if the CPU 510 determines in step 11 that the fixing temperature is higher than 145 ° C., it turns off the fixing heater 224 (step 114),
Set the warm-up completion flag (step 1
15) Set the idling mode (step 1
16). This ends the task.

When the fixing control task is activated again, the CPU 510 sets the idling mode in step 116, so that a positive determination is made in step 120, and the fixing temperature control circuit 54 via the gate array 530.
The fuse temperature is checked from 0 to confirm whether the fixing temperature is 145 ° C. or higher (step 121). CPU510
If it is determined in step 121 that the fixing temperature is 145 ° C. or higher, the fixing heater 224 is turned off and the present task is ended. The CPU 510 determines that the fixing temperature is 1 in step 121.
If it is determined that the temperature is lower than 45 ° C, it is determined whether the fixing temperature is 135 ° C or lower (step 123). CPU51
If 0 determines that the fixing temperature is 135 ° C. or lower in step 123, the fixing heater 224 is turned on (step 124), and this task ends. Such Step 121
Therefore, step 124 is a normal control in the idling mode. As a result, the set temperature during the idling period when the transfer material is not passed is in the range of 135 ° C to 145 ° C.

If the CPU 510 determines in step 123 that the fixing temperature is 135 ° C. or higher, the fixing heater 22
It is judged whether or not the on-time of 4 is finished (step 12).
5). If the CPU 510 determines in step 125 that the ON period has ended, it turns off the fixing heater 224 (step 127), and if it determines in step 125 that the ON period has not ended, it turns on the fixing heater 224. (Step 126). The CPU 510 executes step 12
6 and 127, the fixing heater 224 is set to OFF time 1
It is determined whether or not sec has been reached (step 128). CPU
If the OFF time of the fixing heater 224 has been reached in step 128, 510 clears the fixing heater 224 ON time counter (step 129) and ends this task. On the other hand, if the OFF time of the fixing heater 224 has not been reached in step 128, the CPU 510 increments the fixing heater 224 ON time counter (step 131) and ends this task. Thus, if the lower limit of the set temperature during the idling period is exceeded, the fixing heater 2
The ON period of 24 is lengthened to raise the temperature.

Again, if the plain paper print mode is set by the sequence start task of step 2 shown in FIG. 4 when the fixing control task is activated, the CPU 510 makes a positive determination in step 140, and the gate It is confirmed whether the fixing temperature is 175 ° C. or higher by referring to the fuse temperature from the fixing control circuit 540 via the array 530 (step 141). The CPU 510 executes step 141.
If it is determined that the fixing temperature is 175 ° C. or higher, the fixing heater 224 is turned off (step 142), and this task ends. If the CPU 510 determines in step 141 that the fixing temperature is lower than 175 ° C., the fixing temperature is 170 ° C.
It is determined whether or not the following (step 143). CPU5
When determining in step 143 that the fixing temperature is 170 ° C. or less, 10 turns on the fixing heater 224 (step 144) and ends this task. Such Step 14
Steps 1 to 144 are normal control in the plain paper print mode. As a result, the set temperature during the plain paper print mode period is in the range of 170 ° C to 175 ° C.

If the CPU 510 determines in step 143 that the fixing temperature is 170 ° C. or higher, the fixing heater 22
It is determined whether or not the on-time of 4 has ended (step 14
5). If the CPU 510 determines in step 145 that the ON period has ended, it turns off the fixing heater 224 (step 147), and if it determines in step 145 that the ON period has not ended, it turns on the fixing heater 224. (Step 146). The CPU 510 proceeds to step 14
6 and 147, the fixing heater 224 is set to OFF time 1
It is determined whether or not sec has been reached (step 148). CPU
If the OFF time of the fixing heater 224 has been reached in step 148, 510 clears the fixing heater 224 ON time counter (step 149) and ends this task. On the other hand, if the OFF setting time of the fixing heater 224 has not been reached in step 148, the CPU 510 increments the fixing heater 224 ON time counter (step 151) and ends this task. As described above, when the temperature is lower than the lower limit of the set temperature during the plain paper print mode period, the ON period of the fixing heater 224 is lengthened to raise the temperature.

Again, if the OHT print mode is set in the sequence start task of step 2 shown in FIG. 4 when the fixing control task is activated, the CPU 510 makes a positive determination in step 160, and the gate array It is confirmed whether the fixing temperature is 185 ° C. or higher by referring to the fuse temperature from the fixing control circuit 540 via 530 (step 161). The CPU 510 executes step 161.
If it is determined that the fixing temperature is 185 ° C. or higher, the fixing heater 224 is turned off (step 162) and this task is ended. If the CPU 510 determines in step 161 that the fixing temperature is lower than 185 ° C., the fixing temperature is 180 ° C.
It is determined whether or not the following (step 163). CPU5
If the fixing temperature is determined to be 185 ° C. or lower in step 163, the ten turns on the fixing heater 224 (step 164) and ends this task. Such Step 16
Steps 1 to 164 are normal control in the OHT print mode. As a result, the set temperature during the plain paper print mode period is in the range of 180 ° C to 185 ° C.

If the CPU 510 determines in step 163 that the fixing temperature is 180 ° C. or higher, the fixing heater 22
It is determined whether or not the ON time of 4 has ended (step 16).
5). If the CPU 510 determines in step 165 that the ON period has ended, it turns off the fixing heater 224 (step 167), and if it determines in step 165 that the ON period has not ended, it turns on the fixing heater 224. (Step 166). The CPU 510 executes step 16
6 and 167, followed by the fixing heater 224 OFF setting time 1
It is determined whether or not sec has been reached (step 168). CPU
If the OFF setting time of the fixing heater 224 has been reached in step 168, 510 clears the fixing heater 224 ON time counter (step 169) and ends this task. On the other hand, if the OFF time of the fixing heater 224 has not been reached in step 168, the CPU 510 increments the fixing heater 224 ON time counter (step 171) and ends this task. As described above, if the temperature is below the lower limit of the set temperature during the OHT print mode, the ON period of the fixing heater 224 is lengthened to raise the temperature.

Again, when the fixing control task is started, the CPU 510 makes a positive determination in step 180 if the standby task of step 10 shown in FIG. 4 is being started, and the fixing is performed via the gate array 530. Referring to the fuse temperature from the temperature control circuit 540, the fixing temperature is 120
It is confirmed whether the temperature is equal to or higher than ° C (step 181). CPU
If it is determined in step 181 that the fixing temperature is 120 ° C. or higher, 510 turns off the fixing heater 224 (step 183) and ends this task. When the CPU 510 determines in step 181 that the fixing temperature is lower than 120 ° C., it turns off the fixing heater 224 (step 18
2) End this task. Steps 181 to 183 are control in the standby mode. As a result, the set temperature during the standby mode is 12
Control at around 0 ° C.

Again, when the CPU 510 is in the abnormal occurrence stop mode such as the occurrence of a jam when the fixing control task is started, the affirmative judgment is made in Step 190, and the fixing heater 224 is turned off (Step 193). End this task.

Again, when the CPU 510 is in the cooling mode due to the occurrence of the fixing abnormality when the fixing control task is started, the steps 510, 120, 140, 160 and 18 are executed.
When 0 and 190 are all negative, the cooling counter is incremented (step 191), and it is confirmed whether 15 minutes have passed (step 192). The CPU 510
If 15 minutes have not elapsed in step 192, the fixing heater 224 is turned off (step 193), and this task ends. If the CPU 510 determines in step 192 that 15 minutes have elapsed, it clears the fixing abnormality occurrence status set in the nonvolatile RAM (step 1
94), the fixing abnormality cancellation (F39) flag is set (step 195), the abnormality occurrence stop mode is set (step 196), and this routine is ended. Such steps 191 to 196 are the fixing abnormality occurrence cooling mode, and when the fixing abnormality occurs, the fixing heater 224 is stopped for at least 15 minutes and then a cooling completion message is issued.
As a result, it is possible to reduce the chance of accidents due to abnormal fixing control. The above is the fixing control task in the present embodiment.

FIG. 7 is a time chart showing the fixing temperature control in this embodiment.

FIG. 7A is a time chart showing a paper discharge signal from the paper discharge detection sensor. Such an output signal is
Although there is a slight time lag, the high level indicates the paper passing period, and the low level corresponds to the non-paper passing period. Therefore, the paper discharge signal indicates continuous printing.

FIG. 7B shows a control signal for the fixing heater 224. The fixing heater 224 control signal has a high level for a heating period and a low level for a non-heating period.

The fixing heater 224 cyclically repeats a heating time of 1.5 sec and a non-heating time of 4 sec during the non-sheet passing period as indicated by a normal dotted line, and during the fixing operation of plain paper and OHT. A heating time of 1 sec and a non-heating time of 4 sec are periodically repeated. In this embodiment, the heating time is extended when printing a predetermined number of sheets or more continuously as shown by the straight line.

FIG. 7C is a graph showing the control state of the fuse temperature.

The alternate long and short dash line SH indicates the upper limit set temperature, and the alternate long and short dash line SL indicates the lower limit set temperature. Such an alternate long and short dash line S
The fixing temperature is controlled within the range of H and SL.

The dotted line shows the locus of the fixing temperature in the case where the heating time and the non-heating time are periodically repeated, and rises and falls in the vicinity of the lower limit fixing temperature from the third print in continuous printing. This shows that the fixing temperature is slightly insufficient. In case of 3 or more continuous prints, SH 'and SL' are newly higher than SH and SL.
Is set to control the fixing temperature. As described above, the present embodiment shows that even continuous printing can be fixed at a good fixing temperature.

Next, the abnormal fixing task when the fixing control program runs out of control will be described with reference to FIGS.

FIG. 8 is a flowchart showing the fixing abnormality detection task.

The fixing abnormality detection task is started by the CPU 510 repeatedly at a predetermined cycle when the power is turned on.

Since the CPU 510 repeatedly activates the fixing abnormality detection task at a predetermined cycle, whether the warming-up control is being performed (step 201) or the idling mode control is being performed in order to know which operation mode the operation is in. In step 202, it is confirmed whether the print start mode control (printing state from standby) is in progress (step 203) or the normal print mode control is in progress (step 204). Therefore, the following processing is performed according to the operation mode at the time when this task is activated.

If this task is activated during the warm-up control, the CPU 510 activates the high-temperature abnormality detection module (step 205), activates the sensor short-circuit abnormality detection module (step 206), and activates the warm-up low-temperature abnormality detection module. (Step 20
7) Then, the abnormality detection counter is incremented and this task is terminated.

If the CPU 510 starts this task during the idling mode control, the CPU 510 sets the watchdog time to 15
Seconds (step 208), the high temperature abnormality detection module is activated (step 209), the low temperature abnormality detection module is activated (step 210), the sensor short circuit abnormality detection module is activated (step 211), and this task is executed. finish.

If the CPU 510 activates this task during the control of the print start mode, the watchdog time is set to 40
Seconds (step 212), the high temperature abnormality detection module is activated (step 213), the low temperature abnormality detection module is activated (step 214), and the sensor short circuit abnormality detection module is activated (step 215). finish.

If the task is activated during the normal print mode control, the CPU 510 sets the watchdog time to 15
Set to seconds (step 216), activate the high temperature abnormality detection module (step 217), activate the low temperature abnormality detection module (step 218), activate the sensor short circuit abnormality detection module (step 219), and execute this task. finish.

Next, the operation of each detection module will be described below.

FIG. 9 is a flowchart showing the high temperature abnormality detecting module.

The high-temperature abnormality detection module sets a high-temperature abnormality code F34 and executes stop processing if it detects a state where the fixing temperature is 205 ° C. or higher continuously for 2 seconds or longer. The algorithm is as shown below.

The CPU 510 executes step 20 shown in FIG.
When the detection module is activated in Nos. 5,209, 213, and 217, the fixing temperature is set to 205 by referring to the fuse temperature from the fixing control circuit 540 via the gate array 530.
It is confirmed whether or not the temperature is equal to or higher than ° C (step 301). CPU
If it is determined in step 301 that the fixing temperature is 205 ° C. or higher, 510 increments the high temperature abnormality counter (step 302) and confirms whether 2 seconds have passed (step 303).

When the CPU 510 detects that 2 seconds have elapsed in step 303, it determines that a high temperature abnormality has occurred (step 304), sets an abnormality code in the nonvolatile RAM (step 305), and executes stop processing. This module is terminated and steps 205, 209 and 21 shown in FIG.
Return to 3,217.

On the other hand, when the CPU 510 determines in step 301 that the fixing temperature is 205 ° C. or lower, it clears the high temperature abnormality counter (step 307) and terminates the process to steps 205, 209, 213 and 217 shown in FIG. Return. Furthermore, if the CPU 510 determines in step 303 that 2 seconds have not elapsed, the CPU 510 ends this module and returns to steps 205, 209, 213, and 217 shown in FIG.

As described above, since the high temperature abnormality detecting module does not continue the abnormal heating state, it is possible to prevent the recording paper from burning.

FIG. 10 is a flowchart showing the low temperature abnormality detecting module.

The low temperature abnormality detection module has a fixing temperature of 10
If it detects that the temperature is below -30 ° C for more than 2 seconds (thermistor is disconnected), the low temperature error code F35
Is set and stop processing is executed, and the detection algorithm is as follows.

The CPU 510 executes step 21 shown in FIG.
If the detection module is activated at 0, 214, and 218, the fixing control circuit 540 is passed through the gate array 530.
Then, it is confirmed whether the fixing temperature is −30 ° C. or lower by referring to the fuse temperature (step 401). When the CPU 510 determines in step 401 that the fixing temperature is −30 ° C. or lower, it increments the low temperature abnormality counter (step 402) and confirms whether 10 seconds have elapsed (step 4).
03).

When the CPU 510 detects that 10 seconds have elapsed in step 403, it determines that a low temperature abnormality has occurred (step 404), sets an abnormality code in the nonvolatile RAM (step 405), and executes stop processing. This module is terminated and steps 210, 214 shown in FIG.
Return to 218.

On the other hand, if the CPU 510 determines in step 401 that the fixing temperature is -30 ° C. or higher, it clears the low temperature abnormality counter (step 407) and terminates this module, and steps 210, 214 shown in FIG. Return to 218. Further, the CPU 510 makes 10 in step 403.
If it is determined that the second has not elapsed, this module is terminated and the process returns to steps 210, 214 and 218 shown in FIG.

As described above, the abnormality detecting module can prevent the failure from spreading by detecting the failure of the sensor by detecting the state that the fixing temperature does not rise below -30 ° C.

FIG. 11 is a flowchart showing the sensor short circuit abnormality detection module.

The sensor short-circuit abnormality detection module detects a sensor short-circuit abnormality code F if it detects that the fixing temperature is 270 ° C. or higher for 500 msec or longer.
37 is set and the stop process is executed, and the detection algorithm is as follows.

The CPU 510 executes step 20 shown in FIG.
6, 211, 215, and 219, when the detection module is activated, the fixing temperature is controlled by the fixing temperature control circuit 540 through the gate array 530 and the fixing temperature is set to 2
It is confirmed whether the temperature is 70 ° C. or higher (step 501). C
If the PU 510 determines in step 501 that the fixing temperature is 270 ° C. or higher, it increments the sensor short-circuit abnormality counter (step 502) and confirms whether 500 msec has elapsed (step 503).

The CPU 510 makes 500 in step 503.
If it is detected that msec has elapsed, it is determined that a sensor short has occurred (step 504), an abnormal code is set in the non-volatile RAM (step 505), a stop process is executed, the module is terminated, and the process shown in FIG. Step 20 to show
Return to 6, 211, 215, and 219.

On the other hand, if the CPU 510 determines in step 501 that the fixing temperature is 270 ° C. or lower, it clears the sensor short-circuit abnormality counter (step 507) and terminates this module to execute steps 206 and 21 shown in FIG.
Return to 1, 215 and 219. Furthermore, if the CPU 510 determines in step 503 that 500 msec has not elapsed, it terminates this module and executes step 2 shown in FIG.
Return to 06, 211, 215 and 219.

As described above, when the abnormality detecting module detects that the fixing temperature is 270 ° C. or higher and continues for 500 msec or more, it is determined that the sensor is short-circuited and the stop process is executed. Can be prevented from expanding.

FIG. 12 is a flowchart showing the warming-up low temperature abnormality detecting module.

The warm-up low-temperature abnormality detecting module sets a warm-up low-temperature abnormality code F38 and executes a stop process if a low-temperature abnormality during warm-up is detected. The detection algorithm is as follows.

The CPU 510 executes step 20 shown in FIG.
7, when the detection module is activated, an abnormality detection time calculated based on the initial fixing temperature obtained by referring to the fuse temperature from the fixing temperature control circuit 540 via the gate array 530 is set (step 601). Further, the watchdog time calculated based on the initial fixing temperature is set (step 602).

The CPU 510 refers to the counter value of the abnormality detection counter and confirms whether the set time has been exceeded (step 603).

If the CPU 510 determines in step 603 that the set time has elapsed, it determines that there is a warming-up low temperature abnormality (step 604), sets a warming-up low temperature abnormality code in the non-volatile RAM (step 605), and executes stop processing. Execute and step 2 shown in FIG.
Returning to 07, the detection module is terminated.

On the other hand, if the CPU 510 determines in step 603 that the set time has not elapsed, it terminates this module and returns to step 207 shown in FIG.

As described above, the present detection module can detect the warm-up low temperature abnormality and prevent the failure from spreading.

The image forming apparatus in this embodiment is provided with the temperature sensor Th provided in the non-sheet passing portion of the heating fixing roller 221 having the fixing heater 224 inserted therein, as described above.
The CPU 5 that estimates the fixing temperature based on the detection signal from the temperature sensor Th, determines whether the fixing temperature is within the set temperature range, and controls the energization state of the fixing heater 224.
10, the SRAM 520 that sets the upper limit temperature and the lower limit temperature that determine the set temperature range, and if it is determined that the fixing temperature is lower than the lower limit temperature set by the SRAM 520, the fixing heater 224 is made non-conductive and the upper limit temperature set by the SRAM 520 is set. If it is determined that the fixing temperature is higher, the fixing heater 22
When the fixing temperature is determined to be within the temperature range set by the SRAM 520 and the fixing temperature is set in the SRAM 520, a fixing temperature control circuit 540 is provided to control the fixing heater 224 to repeat the conductive state and the non-conductive state at a predetermined cycle. Therefore, the fixing temperature can be controlled with high accuracy by adjusting the conduction time of the fixing heater 224.

Further, the image forming apparatus according to the present embodiment has the CPU 5 for discriminating the operation mode as described above.
10 (see FIGS. 5 and 6) and the CPU 510 (see FIG. 5).
And FIG. 6), by changing the time for conducting the current to the fixing heater 224 according to the operation mode determined by
Since the conduction time of the heater can be adjusted in small increments according to the operation mode, it is possible to control the fixing temperature to be appropriate in various operation modes.

If the CPU 510 (see FIGS. 5 and 6) determines that the image forming apparatus according to the present embodiment is in the continuous print mode, the upper limit temperature and the lower limit temperature that determine the set temperature range are set high. By providing the SRAM 520, a sufficient fixing temperature can be controlled even in the continuous print mode.

Therefore, in the image forming apparatus according to the present embodiment, the temperature sensor provided in the non-sheet passing portion can control the stable fixing temperature regardless of the operation mode.

[0112]

As described above, according to the present invention, the temperature sensor provided in the non-sheet passing portion can control the fixing temperature to be stable regardless of the operation mode.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment.

FIG. 2 is a cross-sectional view showing each cartridge according to the embodiment.

FIG. 3 is a block diagram showing a fixing temperature control system of the engine controller in the present embodiment.

FIG. 4 is a flowchart showing a print sequence of the image forming apparatus according to the present embodiment.

FIG. 5 is a flowchart showing a fixing control task.

FIG. 6 is a flowchart showing a fixing control task.

FIG. 7 is a time chart showing the fixing temperature control in the present embodiment.

FIG. 8 is a flowchart showing a fixing abnormality detection task.

FIG. 9 is a flowchart showing a high temperature abnormality detection module.

FIG. 10 is a flowchart showing a low temperature abnormality detection module.

FIG. 11 is a flowchart showing a sensor short circuit abnormality detection module.

FIG. 12 is a flowchart showing a warm-up low temperature abnormality detection module.

[Explanation of symbols]

 500 engine controller 510 CPU 520 SRAM 530 gate array 540 fixing temperature control circuit Th temperature sensor

Claims (3)

[Claims] 1. A temperature sensor provided in a non-sheet passing portion of a heating fixing roller having a heater inserted therein, the fixing temperature is estimated based on a detection signal from the temperature sensor, and the fixing temperature is within a set temperature range. In the fixing temperature control device for controlling the energization state of the heater by judging either of the above, the fixing temperature setting means for setting the upper limit temperature and the lower limit temperature for determining the set temperature range, and the fixing temperature setting means If it is determined that the fixing temperature is lower than the lower limit temperature, the heater is made non-conductive, and if it is determined that the fixing temperature is higher than the upper limit temperature set by the fixing temperature setting means, the heater is made conductive and the fixing temperature is set. If it is determined that the fixing temperature is within the temperature range set by the setting means, the heater drive is controlled to repeat the conduction state and the non-conduction state of the heater at a predetermined cycle. A fixing temperature control device comprising a dynamic control circuit. 2. A mode discriminating means for discriminating an operation mode, and a heating time changing means for changing a time for conducting a current to the heater according to the operation mode discriminated by the mode discriminating means. The fixing temperature control device according to claim 1. 3. The fixing temperature setting means for setting the upper limit temperature and the lower limit temperature for determining the set temperature range to be high when the mode determining means determines that the continuous print mode is set. 1. The fixing temperature control device according to 1.