JP3777722B2 - Fixing temperature control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat roller type fixing temperature control method in which unfixed toner adhering to a transfer material is heated and melted and fixed.
[0002]
[Prior art]
The heat roller type fixing device includes a fixing roller having a heat source, a pressure roller in pressure contact with the heat roller, a cleaning member in contact with the fixing roller, and a thermistor in contact with the fixing roller, and a transfer material carrying unfixed toner is the fixing roller. The unfixed roller is heated and melted and fixed to the transfer material. On the other hand, the toner adhering to the fixing roller without being fixed to the transfer material is removed by the cleaning member. The thermistor measures the surface temperature of the cleaned fixing roller, and the heat source is controlled based on the measurement result.
[0003]
[Problems to be solved by the invention]
However, the toner adhering to the fixing roller without being fixed to the transfer material or the paper dust of the transfer paper cannot be completely removed by the above-described cleaning operation, and has passed through the contact portion of the cleaning member without being removed. When a part of the toner, paper powder, or the like adheres to and accumulates on the detection portion of the thermistor and the number of image formation increases, the thermal response of the thermistor decreases and detection deviation occurs. Therefore, there is a problem that the actual surface temperature of the fixing roller becomes higher than the control temperature. Therefore, during periodic inspection, toner, paper dust, and the like that adheres to and accumulates on the detection portion of the thermistor is cleaned, removed, or replaced, and the detection deviation of the thermistor is periodically eliminated.
[0004]
FIG. 13 is a graph showing changes in the detected output of the thermistor and the surface temperature of the fixing roller before and after the periodic inspection.
[0005]
FIG. 13A is a graph showing the detection output transition of the thermistor immediately after completion of the periodic inspection. In the graph shown in FIG. 13A, the vertical axis represents voltage (v) and the horizontal axis represents time (sec). The solid line indicates the detection output from the main thermistor provided in the paper passing portion of the fixing roller, and the alternate long and short dash line indicates the detection output from the sub-thermistor provided in the non-paper passing portion of the fixing roller. The thermistor has the characteristics shown in the graph because the resistance value varies depending on the temperature. Time T₁Indicates the warm-up end time, and the time T₁The output voltage from the main thermistor is Vmain1. In addition, the output voltage from the sub-thermistor has a different rate of temperature rise between the paper passing part and the non-paper passing part (roller end) of the fixing roller (paper passing part temperature rise rate> non-paper passing part temperature rise rate). The voltage Vsub1 is higher than the voltage Vmain1 corresponding to the temperature Tmain1.
[0006]
FIG. 13B is a graph showing the actual surface temperature of the fixing roller immediately after completion of the periodic inspection. In the graph shown in FIG. 13B, the vertical axis represents temperature (° C.) and the horizontal axis represents time (sec). The solid line indicates the actual surface temperature at the sheet passing portion of the fixing roller, and the alternate long and short dash line indicates the actual surface temperature at the non-sheet passing portion of the fixing roller. The actual surface temperature at the sheet passing portion of the fixing roller is the time T₁However, the actual surface temperature in the non-sheet passing portion of the fixing roller is the time T₁It can be seen that the temperature is lower than Tmain1 and increases toward the surface temperature Tmain1 over time. This is time T₁This is because the roller surface temperature converges to Tmain1 as time elapses even when the temperature is lowered at the end of the fixing roller.
[0007]
FIG.13 (c) is a graph which shows the detection output transition of the thermistor just before a periodic inspection. In the graph shown in FIG. 13C, the vertical axis represents voltage (v) and the horizontal axis represents time (sec). The solid line indicates the detection output from the main thermistor provided in the paper passing portion of the fixing roller, and the alternate long and short dash line indicates the detection output from the sub-thermistor provided in the non-paper passing portion of the fixing roller. Time T₂Indicates the warm-up end time, and at this time, the output voltage from the main thermistor is Vmain2. In addition, time T₂The difference between the output voltage Vsub2 from the sub-thermistor and the output voltage from the main thermistor is smaller than that in FIG. In addition, time T₂Is the time T₁It is getting slower. This means that the warm-up period has been extended before the regular inspection. This is because toner, paper powder, and the like adhere to the detection portion of the main thermistor, resulting in a decrease in thermal response and a detection error.
[0008]
FIG. 13D is a graph showing the actual surface temperature of the fixing roller immediately before the periodic inspection. In the graph shown in FIG. 13D, the vertical axis represents temperature (° C.) and the horizontal axis represents time (sec). The solid line indicates the actual surface temperature at the sheet passing portion of the fixing roller, and the alternate long and short dash line indicates the actual surface temperature at the non-sheet passing portion of the fixing roller. The actual surface temperature at the sheet passing portion of the fixing roller is the time T₂Thus, Tmain2 higher than Tmain1 which is the original control temperature is reached. Further, the time T in the non-sheet passing portion of the fixing roller₂Actual surface temperature at time T₁It has reached Tsub2 higher than Tsub1 reached at. Moreover, it turns out that it heats up toward Tmain2 with progress of time.
[0009]
Therefore, from the graphs shown in FIGS. 13A to 13D, if toner, paper dust, or the like adheres to the detection portion of the main temperature sensor, the fixing temperature control cannot be performed accurately.
[0010]
The detected temperature difference between the main thermistor and the sub-thermistor when the warm-up is completed is affected by the temperature state of the fixing roller before the main switch is turned on, and the temperature state of the fixing roller depends on the size of the transfer material at the time of paper passing and the paper passing time. It changes according to the number of sheets. Specifically, if images are continuously formed with a large size transfer material, the heat radiation from both ends of the fixing roller increases, so that the surface temperature of the non-sheet passing portion of the fixing roller is increased in the sheet passing portion of the fixing roller. It becomes a state lower than the surface temperature. On the other hand, if images are continuously formed in a small size typified by a postcard or the like, the heat radiation of the sheet passing portion of the fixing roller is increased, and the fixing roller is heated and controlled accordingly. The surface temperature is higher than the surface temperature at the sheet passing portion of the fixing roller. When the main switch is turned off in this state, if the fixing roller is sufficiently cooled, the temperature difference between the paper passing portion and the non-paper passing portion after warm-up is not affected, but the fixing roller is sufficiently cooled. If the warm-up is performed again in a state where the warm-up is not performed, the temperature difference between the paper passing portion and the non-paper passing portion after the warm-up is affected.
[0011]
On the other hand, as an example of a heating resistor roller, there has been proposed a fixing roller in which a heating conductor formed by baking a heat-resistant resistance heating pattern is formed on a ceramic base, and the heating conductor is covered with a ceramic base and a heat-resistant rubber layer (Japanese Patent Application Laid-Open (JP-A)). (See Japanese Laid-Open Patent Publication Nos. 54-30841 and 56-138766). Further, there has been proposed a fixing roller having a layered heat generating portion on or near the surface of the fixing roller (Japanese Patent Laid-Open No. 3-80279). Since the resistance heating element has a structure in which the heating conductor is embedded in a ceramic body such as alumina having good thermal conductivity, for example, the temperature distribution can be made uniform over the entire roll surface, and the heating resistance element is placed on the roll surface. The temperature rise rate is extremely large compared to the case of heating by conventional radiant heat because it is located in the vicinity and the thermal efficiency is better than that of heating by conventional radiant heat. It is possible to shorten the warm-up time until reaching the value.
[0012]
On the other hand, as described above, since the temperature rise rate of the heating resistor is extremely large, there is a technical problem that when the abnormality occurs in the copying period or idling period, the heating resistor reaches an abnormally high temperature in a short time.
[0013]
In view of the above, the first object of the present invention is to control the fixing roller to a predetermined temperature without being affected by a detection shift due to contamination on the surface of the temperature sensor provided in the sheet passing portion of the fixing roller, and to provide a warm-up period. It is an object of the present invention to provide a fixing temperature control method capable of preventing the extension of the length.
[0014]
In view of the above, the second object of the present invention is to fix a fixing roller having a different temperature increase rate without being affected by a detection shift due to contamination on the surface of a temperature sensor provided in a sheet passing portion of the fixing roller. It is an object of the present invention to provide a fixing temperature control method capable of controlling a roller to a predetermined temperature and preventing an extension of a warm-up period.
[0015]
[Means for Solving the Problems]
The above object is achieved by the following configurations.
[0016]
  (1) A main temperature sensor is provided in a sheet passing portion of the fixing roller, a sub temperature sensor is provided in a non-sheet passing portion of the fixing roller, and the fixing roller of the fixing roller is based on detection results from the sub temperature sensor and the main temperature sensor. In a fixing temperature control method for controlling heating,Non-volatile memory Tmain for storing data read in real time including the initial fixing temperature related to the main temperature sensor, and data read in real time including the initial fixing temperature related to the sub-temperature sensor are stored. When the surface temperature of the fixing roller at the start of warm-up is determined to be near room temperature.When the detected temperature from the sub temperature sensor reaches a predetermined temperature Tsub1 during the warm-up, the warm-up is completed, and the detected temperature Tmain1 from the main temperature sensor at that time is set.Non-volatilememoryTmainStore in the warm-up after completionIsThe nonvolatile memory based on a temperature detected from the main temperature sensorTmainHeating control with Tmain1 stored inIf the surface temperature of the fixing roller at the start of warm-up is higher than the room temperature when the power is turned on and heating control is started again after the power supply is shut off and the heating control of the fixing roller is completed. When the warm-up is started from the state where the fixing roller is cooled, the heating control is performed with Tmain1 stored in the nonvolatile memory Tmain based on the temperature detected from the main temperature sensor detected at the time when the warm-up is completed.And a fixing temperature control method.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
A schematic configuration of the fixing device according to the present embodiment will be described with reference to FIG.
[0020]
FIG. 1 is a schematic configuration diagram of a heat roller fixing type fixing device according to the present embodiment. FIG. 1A is a schematic cross-sectional view of the heat roller fixing type fixing device according to the present embodiment. 1 (b) is a perspective view showing the installation location of the temperature detecting means.
[0021]
The fixing device according to the present embodiment is based on a heat roller fixing system. The fixing roller 101 transmits heat to a transfer material onto which a toner image is transferred, a heater 102 that supplies heat to the fixing roller 101, and the fixing roller 101. While pressing the transfer material, the application felt 104 for applying oil to the surfaces of the pressure roller 103 and the fixing roller 101, the thermistors 105 and 106 for detecting the temperature of the fixing roller 101, and the excess oil applied by the application felt 104 are scraped off. The fixing blade 107 and the CPU 5 that controls the energization of the heater 102 and the rotation of the fixing roller 101 by inputting the detection temperature of the fixing claw 108 and the thermistors 105, 106 for separating the transfer material from the fixing roller 101.
[0022]
The heater 102 is a ceramic heater in which a resistance heating element is printed on a ceramic base as an example of a heating resistor. The heater 102 can have a uniform temperature distribution over the entire surface of the fixing roller 101, and the ceramic heater is compared with a halogen lamp or the like. Since the heat generating conductor is located near the roll surface, the temperature rise time is extremely short compared to the case of heating with conventional radiant heat, so the warm-up time to reach the fixable temperature is shortened. be able to.
[0023]
The thermistors 105 and 106 are of the contact type, and the thermistor 105 is arranged at the center of the fixing roller 101. The thermistor 105 corresponds to the main temperature sensor in the claims. The thermistor 106 is the fixing roller 101. The thermistor 106 corresponds to a sub temperature sensor in the claims. The thermistors 105 and 106 have a characteristic that the resistance value changes with respect to the detected temperature. The detected temperature of the thermistor is obtained by converting the resistance value based on characteristics prepared in advance.
[0024]
A schematic configuration of the fixing temperature control apparatus according to the present embodiment will be described with reference to FIG.
[0025]
FIG. 2 is a block diagram of a fixing temperature control circuit in the present embodiment.
[0026]
The fixing temperature control circuit according to the present embodiment includes a heater 102, a triac 2, a commercial AC power source 3, a CPU 5, and a triac drive circuit 6, and is a control circuit that turns on / off the heater 102 by a power supply instruction signal from the CPU 5.
[0027]
The heater unit 1 includes a fixing roller 101, a heater 102, the thermistors 105 and 106, and the like. The heater 102 is a ceramic heater in which a resistance heating element is printed on a ceramic base as described above. The thermistors 105 and 106 are fixedly attached to the front side of the fixing roller 101 and detect the temperature state of the fixing roller 101. The thermistors 105 and 106 are wired electrically independently of the fixing roller 101, and the heater 102 is wired with two connectors. A temperature detection circuit (not shown) detects the divided potential by connecting a fixed resistor (not shown) in series to the thermistors 105 and 106 whose resistance values change according to the temperature change of the heater 102. To the CPU 5.
[0028]
Although the heater 102 is described as a ceramic heater in this embodiment, the present invention is not limited to this and may be a halogen lamp.
[0029]
A commercial AC power source 3 is connected to the heater unit 1 via a triac 2. The triac 2 switches between execution and stop of the power supply to the heater 102, and is provided with a spark killer (not shown) for removing noise generated during switching.
[0030]
While referring to the output voltage from the temperature detection circuit, the CPU 5 turns on the power supply signal if the temperature detected by the thermistors 105 and 106 is lower than the control temperature, and if the temperature detected by the thermistor is higher than the control temperature, The power supply signal is turned off.
[0031]
IP2 is an A / D input port, and can convert an input analog voltage into a digital value and read it. The CPU 5 writes data obtained by converting the thermistor output into temperature in the built-in memory. Therefore, the CPU 5 can accurately detect the temperature of the fixing roller 101 by comparing the value of the A / D input port IP2 with the data in the built-in memory. The CPU 5 includes an external nonvolatile RAM (not shown).
[0032]
OP1 is an output port. The minimum ON / OFF unit of the heater 102 is 10 ms when the commercial AC power supply 3 is 50 Hz, and 8 ms when the commercial AC power supply 3 is 60 Hz.
[0033]
The triac drive circuit 6 performs ON / OFF control of the triac 2 based on a power supply signal from the CPU 5.
[0034]
Next, the control operation in the fixing temperature control circuit of the present embodiment will be described with reference to FIG.
[0035]
FIG. 8 is a time chart showing signals of respective parts of the fixing temperature control circuit according to the present embodiment.
[0036]
The commercial AC power supply 3 is always represented by a sine wave having a fixed period as shown in FIG. First, when the power is turned on, the CPU 5 sets the warm-up state. Thereby, the power supply instruction signal is turned on as shown in FIG. 8B, and when the heater 102 is supplied with power as shown in FIG. 8C, the surface temperature of the heater is raised as shown in FIG. 8D. . This period is called a “warm-up state” and is a preparation period for a recording operation that is positioned as a previous stage for the recording operation.
[0037]
When the surface temperature of the fixing roller 101 reaches the control point temperature through this warm-up state, the power supply to the heater is turned off as shown in FIG. 8B, and the fixing roller 101 is turned off as shown in FIG. When the temperature falls below the control point temperature again, as shown in FIG. 8B, the power supply to the heater is turned on to keep the temperature constantly set.
[0038]
Next, the detailed operation of the fixing temperature control circuit of the present embodiment will be described with reference to FIGS.
[0039]
This control program has a task format and is composed of an aggregate of a plurality of independent control programs. Each subdivided program is grouped by function to form one task. Several such tasks are called as necessary by a monitor program called monitor task control, and a necessary amount of programs are executed and terminated. That is, a small amount of program execution is processed as one unit, and a plurality of tasks are processed one after another. Therefore, one program is executed microscopically, but each task is processed in parallel macroscopically.
[0040]
FIG. 3 is a flowchart showing the control operation of the image forming apparatus employing the fixing device of this embodiment.
[0041]
When the power is turned on, the CPU 5 executes an initial process (step 1). As a result, the memory, the drive input / output system is reset, and the fixing temperature is monitored.
[0042]
The CPU 5 confirms whether or not the warm-up has been completed (step 2). If the CPU 5 confirms the completion of the warm-up, it confirms that the copy button is turned on (step 3). If the CPU 5 confirms that the copy button is turned on, it executes a copy process (step 4). As a result, on / off control of the drive motor, on / off control of paper feed, on / off control of charging, on / off control of developing bias, on / off control of transfer / separation, control of optical exposure system, etc. Is made.
[0043]
FIG. 4 is a flowchart showing the fixing temperature processing task.
[0044]
The fixing temperature processing task is called and started every 350 msec by the monitor program.
[0045]
When the fixing temperature processing task is activated, the CPU 5 stores, in Tmain, data converted into the sheet passing portion temperature of the fixing roller 101 from the detection result of the thermistor 105 provided in the sheet passing portion (step 11). Here, the data stored in Tmain is data read in real time including the fixing temperature at the initial stage of warm-up. The CPU 5 stores, in Tsub, data converted from the detection result of the thermistor 106 provided in the non-sheet passing portion into the non-sheet passing portion temperature of the fixing roller 101 (step 12). Here, the data stored in Tsub is data read in real time including the fixing temperature at the initial stage of warm-up. The CPU 5 checks whether or not the warm-up completion flag is on (step 13). If the CPU 5 determines in step 13 that the warm-up completion flag is off, the CPU 5 activates the fixing drive processing task during the warm-up (step 14). If the CPU 5 determines in step 13 that the warm-up completion flag is on, it starts the fixing drive processing task after warm-up (step 15).
[0046]
FIG. 5 is a flowchart showing a fixing drive processing task during warm-up.
[0047]
If the CPU 5 activates the fixing drive processing task during warm-up in step 14 shown in FIG. 4, it is determined whether or not Tsub <Tsub1 is satisfied (step 141). Here, Tsub1 is control temperature data for the thermistor 106 that determines the fixing drive ON / OFF state during warm-up.
[0048]
If the CPU 5 determines in step 141 that Tsub <Tsub1, the fixing drive is turned on (step 142).
[0049]
If the CPU 5 determines that Tsub ≧ Tsub1 in step 141, the fixing drive is turned off (step 143), the warm-up completion flag is turned on, and the value of the detection result Tmain of the thermistor 105 described above in the RAM MEM (Tmain1). (Step 144), and the fixing driving process task during the warm-up is ended (step 145). The MEM (Tmain1) of the RAM may be a nonvolatile RAM.
[0050]
FIG. 6 is a flowchart showing the fixing drive processing task after warm-up.
[0051]
If the CPU 5 starts the fixing drive processing task after warm-up in step 15 shown in FIG. 4, it is determined whether or not Tmain <mem (Tmain1) (step 151). Here, mem (Tmain1) is the detection data from the thermistor 105 provided in the paper passing section at the time of completion of warm-up stored in step 144 described above.
[0052]
If the CPU 5 determines in step 151 that Tmain <mem (Tmain1), it turns on the fixing drive (step 152).
[0053]
If the CPU 5 determines that Tmain ≧ mem (Tmain1) in step 151, it turns off the fixing drive (step 153) and turns on the warm-up completion flag (step 154).
[0054]
FIG. 7 is a graph showing the transition of the thermistor detection output during the warm-up and the surface temperature transition of the fixing roller 101 before the regular inspection in the present embodiment.
[0055]
FIG. 7A is a graph showing the transition of the thermistor detection output during the warm-up before the periodic inspection. In the graph shown in FIG. 7A, the vertical axis represents voltage (v) and the horizontal axis represents time (sec). The solid line shows the detection output transition from the main thermistor provided in the paper passing portion of the fixing roller 101, and the alternate long and short dash line shows the detection output transition from the sub-thermistor provided in the non-paper passing portion of the fixing roller 101. is there. Since the CPU 5 ends the warm-up when the detection result from the thermistor 106 reaches a predetermined value Vsub1 (the same value as that immediately after the periodic inspection), the warm-up end time is the warm-up end time T immediately after the periodic inspection.₁And the same time. Time T₁The detection result from the thermistor 105 is Vmain1, which is also the same value as the detection value from the thermistor 105 at the time of warm-up immediately after the periodic inspection.
[0056]
FIG. 7B is a graph showing the actual surface temperature transition of the fixing roller 101 immediately before the periodic inspection. In the graph shown in FIG. 7B, the vertical axis represents temperature (° C.) and the horizontal axis represents time (sec). The solid line indicates the actual surface temperature at the sheet passing portion of the fixing roller 101, and the alternate long and short dash line indicates the actual surface temperature at the non-sheet passing portion of the fixing roller 101. The actual surface temperature at the sheet passing portion of the fixing roller 101 is the time T₁Thereafter, the temperature is controlled at the same temperature as the control temperature Tmain1 immediately after the periodic inspection, and the actual surface temperature in the non-sheet passing portion of the fixing roller 101 is also the time T.₁Thus, the temperature Tsub1 at the end of the warm-up immediately after the periodic inspection is reached.
[0057]
As described above, according to the present embodiment, the warm-up time is not extended without being affected by sensitivity reduction due to detection deviation caused by toner, paper dust, or the like attached to the detection unit of the main thermistor immediately before the periodic inspection. . Therefore, the actual temperature of the fixing roller 101 can be controlled to a predetermined temperature, high temperature offset can be prevented, and safety can be enhanced.
[0058]
(Embodiment 2)
Since the present embodiment has substantially the same device configuration and the same circuit configuration as those of the first embodiment described above, the same components are denoted by the same reference numerals and detailed description thereof is omitted. Since the operation of the fixing temperature control circuit of this embodiment is different from that of the first embodiment, it will be described with reference to FIGS.
[0059]
If the fixing temperature control is executed from the state where the surface temperature of the fixing roller 101 is cooled to the vicinity of the environmental temperature, the first embodiment can sufficiently cope with it. However, as described above, if images are continuously formed with a large size transfer material, the heat radiation from the end portion of the fixing roller 101 increases compared to the central portion. The surface temperature is lower than the surface temperature of the sheet passing portion of the fixing roller 101. On the other hand, if images are continuously formed in a small size represented by a postcard or the like, the heat radiation from the non-sheet passing portion of the fixing roller 101 is reduced. When the main switch is turned off in such a state that the main switch is turned off and the fixing roller 101 is not sufficiently cooled, the temperature of the fixing roller 101 is changed. Power supply control that is easily affected by the distribution, is difficult to accurately control the temperature of the fixing roller 101, and is not affected by these states is necessary.
[0060]
FIG. 9 is a flowchart showing the control operation of the image forming apparatus employing the fixing device of this embodiment.
[0061]
When the power is turned on, the CPU 5 executes an initial process (step 31). Thereby, resetting of the memory and the drive input / output system is executed.
[0062]
The CPU 5 stores the data converted from the detection result of the thermistor 105 into the temperature of the sheet passing portion of the fixing roller 101 in Tmain0 (step 32). Here, the data stored in Tmain0 is data read at power-on.
[0063]
The CPU 5 checks whether or not Tmain0 ≦ 50 ° C. and Tsub0 ≦ 50 ° C. (step 33). If the CPU 5 determines in step 33 that Tmain0 <50 ° C. and Tsub0 ≦ 50 ° C., the CPU 5 turns on the ASA flag (step 34). If the CPU 5 determines in step 33 that Tmain0> 50 ° C. or Tsub0> 50 ° C., the CPU 5 turns off the ASA flag (step 35). Here, it is determined whether or not the fixing roller 101 is cooled based on the detection data from the thermistors 105 and 106, but it may be determined based on the single detection data from the thermistor 105 or the thermistor 106. Further, it is not necessary to limit to the two thermistors 105 and 106 described above. An in-machine temperature sensor may be used in combination with the thermistors 105, 106, and the like.
[0064]
The CPU 5 starts a fixing temperature processing task following Step 34 or Step 35 (Step 36).
[0065]
The CPU 5 confirms whether or not the warm-up has been completed (step 37). If the CPU 5 confirms the completion of the warm-up, it confirms that the copy button is turned on (step 38). If the CPU 5 confirms that the copy button is turned on, it executes a copy process (step 39). As a result, on / off control of the drive motor, on / off control of paper feed, on / off control of charging, on / off control of developing bias, on / off control of transfer / separation, control of optical exposure system, etc. Is made.
[0066]
FIG. 10 is a flowchart showing the fixing temperature processing task.
[0067]
The fixing temperature processing task is called and started every 350 msec by the monitor program.
[0068]
When the fixing temperature processing task is activated, the CPU 5 stores, in Tmain, data converted from the detection result of the thermistor 105 into the temperature of the sheet passing portion of the fixing roller 101 (step 41). Here, the data stored in Tmain of the RAM is data read in real time including the fixing temperature at the initial stage of warm-up. The CPU 5 stores the data converted from the detection result of the thermistor 106 into the temperature of the non-sheet passing portion of the fixing roller 101 in the Tsub of the RAM (step 42). Here, the data stored in the Tsub of the RAM is data read in real time including the fixing temperature at the initial warm-up. The CPU 5 checks whether or not the warm-up completion flag is on (step 43). If the CPU 5 determines in step 43 that the warm-up completion flag is ON, the CPU 5 activates the fixing drive processing task when the fixing is not cold (step 46). If the CPU 5 determines in step 43 that the warm-up completion flag is OFF, the CPU 5 determines whether or not the ASA flag = 1 (ON state) (step 44).
[0069]
If the CPU 5 determines in step 44 that the ASA flag is not 1 (ON state), it starts a processing task when the fixing is not cold (step 46).
[0070]
If the CPU 5 determines in step 44 that the ASA flag = 1 (ON state), it starts a processing task when the fixing is cold (step 45).
[0071]
FIG. 11 is a flowchart showing processing tasks when the fixing is cold.
[0072]
  The CPU 5 performs the steps shown in FIG.45If the processing task when the fixing is cold is started, it is determined whether Tsub <Tsub1 is satisfied (step 451). Here, Tsub is temperature data detected in real time from the thermistor 106, and Tsub1 is control temperature data for the thermistor 106 that determines the fixing drive ON / OFF state during warm-up from when the fixing roller 101 is cold. .
[0073]
If the CPU 5 determines in step 451 that Tsub <Tsub1, the fixing drive is turned on (step 452).
[0074]
If the CPU 5 determines that Tsub ≧ Tsub1 in step 451, the fixing drive is turned off (step 453), the warm-up completion flag is turned on, and the value of Tmain is stored in the nonvolatile SRAM 1 (Tmain1) (step 454). ).
[0075]
FIG. 12 is a flowchart showing processing tasks when the fixing is not cold.
[0076]
  The CPU 5 fixes and cools in step 46 shown in FIG.Not inIf the current processing task is activated, it is determined whether or not Tmain <SRAM1 (Tmain1) (step 461). Here, Tmain is temperature data detected in real time from the thermistor 105, and the non-volatile SRAM (Tmain1) is from the thermistor 105 when the warm-up is completed when the warm-up is started from the state where the fixing roller 101 is cooled. This is detected temperature data.
[0077]
If CPU 5 determines in step 461 that Tmain <SRAM1 (Tmain1), it turns on the fixing drive (step 462).
[0078]
If the CPU 5 determines in step 461 that Tmain ≧ SRAM1 (Tmain1), it turns off the fixing drive (step 463) and turns on the warm-up completion flag (step 464).
[0079]
According to the present embodiment, the detection deviation due to a decrease in the thermal response of the thermistor 105 due to toner, paper dust, or the like adhering to the detection unit of the main thermistor immediately before periodic inspection affects the temperature distribution of the fixing roller 101 before and after the main switch is turned on. Accordingly, the temperature of the fixing roller 101 can be accurately controlled until just before the periodic inspection, and the warm-up time is not extended. Therefore, high temperature offset can be prevented and safety can be enhanced.
[0080]
In the present embodiment described above, the fixing roller 101 is described using a ceramic heater as an example of the heating resistor. However, the present invention is not limited to this, and a fixing roller 101 as shown in FIG. There may be. FIG. 14 is a cross-sectional view showing another example of the fixing roller 101 in the present embodiment.
[0081]
21 is a metal core, 22 is an insulator layer, 23 is a resistance heating element layer fired after being fitted with an epoxy primer, and 24 is a PFA tube as a release material. (Refer to Unexamined-Japanese-Patent No. 3-80279).
[0082]
The fixing roller 101 using a halogen lamp as a heat source may be used.
[0083]
【The invention's effect】
  According to the first aspect of the present invention, by providing the above configuration, the fixing roller can be controlled to a predetermined temperature without being affected by detection deviation due to contamination on the surface of the temperature sensor provided in the sheet passing portion of the fixing roller, Also, since there is no extension of the warm-up time, it is excellent in prevention of high temperature offset and safetyIn addition, it is possible to provide a fixing temperature control method capable of controlling the fixing roller to a predetermined temperature without being affected by a detection shift caused by the surface temperature distribution of the fixing roller when the power is turned on.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a heat roller fixing type fixing device according to an exemplary embodiment;
FIG. 2 is a block diagram of a fixing temperature control circuit in the present embodiment.
FIG. 3 is a flowchart illustrating a control operation of an image forming apparatus employing the fixing device according to the present exemplary embodiment.
FIG. 4 is a flowchart illustrating a fixing temperature processing task.
FIG. 5 is a flowchart illustrating a fixing drive processing task during warm-up.
FIG. 6 is a flowchart illustrating a fixing drive processing task after warm-up.
7 is a graph showing a thermistor detection output transition and a surface temperature transition of the fixing roller 101 during warm-up before regular inspection in the present embodiment. FIG.
FIG. 8 is a time chart showing signals of respective parts of the fixing temperature control circuit of the present embodiment.
FIG. 9 is a flowchart illustrating a control operation of the image forming apparatus employing the fixing device according to the present exemplary embodiment.
FIG. 10 is a flowchart illustrating a fixing temperature processing task.
FIG. 11 is a flowchart showing processing tasks when the fixing is cold;
FIG. 12 is a flowchart showing processing tasks when the fixing is not cold;
13 is a graph showing the relationship between the detection output of the thermistor before and after periodic inspection and the surface temperature of the fixing roller 101. FIG.
FIG. 14 is a cross-sectional view showing another example of a fixing roller in the present embodiment.
[Explanation of symbols]
5 CPU
101 Fixing roller
102 Heater
103 Pressure roller
105,106 thermistor

Claims (1)

A main temperature sensor is provided in a sheet passing portion of the fixing roller, a sub temperature sensor is provided in a non-sheet passing portion of the fixing roller, and heating control of the fixing roller is performed based on detection results from the sub temperature sensor and the main temperature sensor In the fixing temperature control method, non-volatile memory Tmain for storing data read in real time including a fixing temperature in the initial warm-up relating to the main temperature sensor, and reading in real time including the fixing temperature in the initial warm-up relating to the sub-temperature sensor. A non-volatile memory Tsub in which the stored data is stored, and when it is determined that the surface temperature of the fixing roller at the start of warm-up is near room temperature, the temperature detected from the sub-temperature sensor is a predetermined temperature during warm-up When Tsub1 is reached, the warm-up is completed and Stores the detected temperature Tmain1 from the main temperature sensor of the point in the non-volatile memory Tmain, after completion of warm-up is heated controlled Tmain1 wherein are stored in the nonvolatile memory Tmain based on the detected temperature from the main temperature sensor, the power If the surface temperature of the fixing roller at the start of warm-up is higher than the room temperature when the heating control is started by turning on the power again after shutting off and finishing the heating control of the fixing roller, the fixing roller The heating control is performed with Tmain1 stored in the non-volatile memory Tmain based on the temperature detected from the main temperature sensor detected at the time of completion of warming up when the warming up is started from a state where the battery is cold. Fixing temperature control method.

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