JP4792341B2 - Fixing device and warm-up method of image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device used in an image forming apparatus such as an electrophotographic printing apparatus, and more particularly to a warming-up method of a fixing apparatus using a heat roll.

   FIG. 6 is a schematic configuration diagram of the electrophotographic printing apparatus. In the figure, 1 is a charger, 2 is a drum-shaped photoconductor, 3 is a laser beam output from an exposure device (not shown), 4 is a developing machine containing toner, 5 is a recording medium transport unit, and 6 is A recording medium made of continuous paper, 7 is a heat roll for fixing the toner image, 8 is a pressure roll for pressing the recording medium 6 against the heat roll 7 during fixing, 9 is a puller roller for discharging the recording medium 6, and 10 is discharged. A recording medium take-up device for storing the recording medium 6, a corona transfer device 11 for transferring the toner image to the recording medium 6, a retractor 12, and a recording medium supply device 15.

  In this printing apparatus, the electrostatic latent image written by the laser beam 3 onto the photosensitive member 2 charged by the charger 1 is developed by the developing device 4, and the recording medium 6 is sent out from the recording medium transport unit 5, and the retractor 12. The toner on the photoreceptor 2 is transferred to the recording medium 6 by the corona transfer device 11 when passing through the recording medium 6. Thereafter, the sent recording medium 6 passes between the heat roll 7 and the pressure roll 8 to fix the toner, and is sent to the recording medium take-up device 10 by the puller roller 9.

A configuration in the vicinity of the heat roll 7 of such a printing apparatus is shown in FIGS.
FIG. 7 shows a configuration using a thermolite chip as a temperature measuring element. 20a, 20b and 20c are non-contact temperature sensors for detecting the surface temperature of the heat roll 7, and 21 is the temperature of the thermolight chip 22 which is a temperature measuring element. The sensor heads 23 a, 23 b, 23 c and 23 d to be detected are heaters built in the heat roll 7.

  FIG. 8 shows a configuration in which a thermistor sensor 24 is used instead of the sensor head 21 and the thermolite chip 22, and the thermistor sensor 24 is arranged so as to contact both end portions of the heat roll 7.

  As shown in FIGS. 7 and 8, the heater 23 d is a long heating section heater and heater having a heating section over almost the entire length of the fixing area (paper passing area) X extending in the axial direction of the heat roll 7. 23a is a short heating section heater having a heating section on the right end side in the drawing of the fixing area X, the heater 23b is a short heating section heater having a heating section at the center of the fixing area X, and the heater 23c is a fixing area X. This is a short heating section heater having a heating section on the left end side as viewed in the drawing, and in this case, four heaters 23 are incorporated.

  The non-contact temperature sensor 20a corresponds to the heating part of the heater 23a, the non-contact temperature sensor 20b corresponds to the heating part of the heater 23b, and the non-contact temperature sensor 20c corresponds to the heating part of the heater 23c. Is installed. In a high-resolution printing apparatus, a heat-resistant elastic film made of heat-resistant rubber or the like may be formed over almost the entire length of the fixing region X in order to reduce the crushing of the toner image of the fixing apparatus. In the figure, reference numeral 25 denotes an overheat sensor.

  When an infrared detector such as a thermopile is used as the non-contact temperature sensors 20a, 20b, and 20c, the detection temperature varies due to the contamination of the sensor due to scattered toner or paper dust or the change in the emissivity of the measurement object. When the thermistor sensor 24 is used, the detection temperature varies due to variations in the attachment gap.

  In order to correct such variations, the detected value of the sensor head 21 in the case of FIG. 7 and the contact thermistor 24 in the case of FIG. 8 is used as the reference temperature. That is, the standard temperature of each non-contact type temperature sensor 20a, 20b, 20c corresponding to the detected value (reference temperature) of the sensor head 21 or the contact type thermistor 24 and each non-contact type temperature sensor 20a, 20b, 20c are actually used. The difference from the detected temperature to be detected is corrected.

As for this type of fixing device, for example, the following patent documents can be cited.
Japanese Patent No. 3,743,543 JP 2001-242743 A

  In the above-described fixing device, the reference sensor head 21 directly attaches the thermolite chip 22 to the metal surface of the heat roll 7, and the contact type thermistor 24 avoids wear and dirt of the heat roll 7. It is provided on the end side of the heat roll 7 away from the fixing region X in which the heaters 23a, 23b, 23c, and 23d are built.

  For this reason, the sensor head 21 and the contact type thermistor 24 have poor thermal responsiveness compared to the non-contact type temperature sensor 20, and it takes time for the temperature to stabilize. That is, since the output of the sensor head 21 and the contact type thermistor 24 immediately after the warming-up occurs depending on the state of the heating roll 7 during the warming-up (for example, the temperature before the warming up), the correction accuracy of the non-contact temperature sensor 20 Low.

  Further, although Patent Document 2 describes a method of correcting the temperature based on the temperature before warming up of the heat roll 7, there is a problem that it is necessary to wait until the temperature is stabilized to some extent.

  An object of the present invention is to provide a fixing device capable of improving the reliability of temperature control and shortening the warm-up time and a warm-up method of the image forming apparatus.

In order to achieve the above object, the first means of the present invention includes a heat roll provided with a heating means, a pressure roll that is in pressure contact with the heat roll, and a fixing roll that is involved in fixing of the heat roll. Non-contact type first heat roll temperature detecting means arranged in a non-contact state with the roll, and second heat roll temperature detecting means arranged on the area of the heat roll outside the fixing area,
Based on a detection signal from the first heat roll temperature detection means, on / off control of the heating means is performed, and while maintaining the temperature of the heat roll at a predetermined temperature, the heat roll and the pressure roll In a warming-up method of a fixing device for thermally fixing a toner image transferred onto a recording medium at a pressure contact portion to the recording medium,
When the fixing device is warmed up, the first temperature detected by the first heat roll temperature detecting means during a period in which the second temperature detected by the second heat roll temperature detecting means is constant. Obtain the amount of change with time interval of the detected temperature,
From the amount of change with the time interval of the first detection temperature, the predicted convergence temperature of the first detection temperature that is predicted to converge is calculated,
Calculate the difference between the standard temperature stored in advance and the predicted convergence temperature,
By correcting the first detected temperature detected by the first heat roll temperature detecting means by the difference value,
Thereafter, on / off control of the heating means is performed based on the corrected first detected temperature.

According to a second means of the present invention, in the first means, the heating means includes a plurality of short heating section heaters each having a heating section at a different position in the axial direction of the fixing area, and an axis of the fixing area. Having at least one long heating part heater having a heating part over almost the entire length in the direction,
Setting a control temperature higher than a second temperature control set value set to control the second detected temperature to be constant;
At the beginning of warming-up of the fixing device, the short heating unit heater and the long heating unit heater are energized, and the temperature is controlled by the first hot roll temperature detecting means with the control temperature as a target value.
When the second detected temperature reaches the second temperature control set value, the energization to the short heating section heater is stopped, the energization to the long heating section heater is continued, and the second temperature control is performed. The temperature control is switched to the temperature control by the second heat roll temperature detecting means using the set value as a target value.

According to a third means of the present invention, in the first means, the heating means includes a plurality of heaters, each heater having an individual heating unit at a different position in the axial direction of the fixing region,
A plurality of the first heat roll temperature detection means are installed to face each of the heating units,
The first detection temperature is individually corrected for each first heat roll temperature detection means,
The plurality of heaters are individually turned on / off based on the corrected first detected temperature.

  According to a fourth means of the present invention, in the first means, the predicted convergence temperature Y of the first detected temperature is calculated by the following equation.

Y = A * (Pn-P (n-1)) / (Tn-T (n-1)) + Pn
In the formula, A: a constant specific to the first heat roll temperature detection means P: an output of the first heat roll temperature detection means n: number of data acquisitions T: data acquisition time The heating means is controlled to be turned on / off based on the corrected first detected temperature, and warming up is completed when the first detected temperature reaches the control temperature. It is.

  According to a sixth means of the present invention, in the first or fourth means, the predicted convergence temperature of the first detected temperature is compared with a preset standard temperature, and a range in which the difference is defined is determined. When it comes off, it is judged as an abnormal error of the first heat roll temperature detecting means.

  The seventh means of the present invention notifies the operator of cleaning or replacement of the first heat roll temperature detecting means when the sixth means determines that the first heat roll temperature detecting means is an abnormal error. It is characterized by doing.

According to an eighth means of the present invention, an electrostatic latent image written on a photosensitive member charged by a charger is developed by a developing machine to form a toner image, and a recording medium that has been conveyed is transferred onto the photosensitive member. In the warming-up method of the image forming apparatus, the toner image is transferred by a transfer device, and the toner is thermally fixed to the recording medium by passing the recording medium between a heat roll and a pressure roll of the fixing device.
The fixing device is warmed up by the warming-up method of the fixing device by any one of the first to seventh means.

   The present invention is configured as described above, and can improve the reliability of temperature control and shorten the warm-up time.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a temperature control unit used in the fixing device of FIG. 7 described above. In the figure, the arrangement and configuration of the non-contact temperature sensors 20a, 20b, 20c, sensor head 21, thermolite chip 22, heaters 23a, 23b, 23c, 23d are the same as those described in FIG. Is omitted.

  As shown in the figure, the signal from the sensor head 21 is received by the sensor head signal receiving circuit 31. For example, if the thermolite chip 22 is for 170 ° C. detection, the surface temperature of the heat roll 7 (thermo When the temperature of the light chip 22 is lower than 170 ° C., a “High” signal is output from the sensor head signal receiving circuit 31, and the surface temperature of the heat roll 7 (temperature of the thermolite chip 22) is higher than 170 ° C. The sensor head signal receiving circuit 31 outputs a “Low” signal. This signal is input to the microcomputer 30 and recognized. In the present embodiment, a thermolite chip 22 for detection at 170 ° C. is used, and this set temperature is referred to as a thermolite chip detection temperature K3.

  Analog signals from the non-contact temperature sensors 20a, 20b, and 20c are converted into digital signals by the A / D converter 32, and input to the microcomputer 30 for recognition.

  The microcomputer 30 individually controls the heaters 23a, 23b, 23c, and 23d via the driver 34 based on the signal from the sensor head signal receiving circuit 31 or the signal from the A / D converter 32. . Further, a memory 33 is connected to the microcomputer 30 and can store measurement time, temperature sensor data, and the like, which will be described later.

  An example of a method for warming up the heat roll 7 by the temperature control unit will be described with reference to FIG. The figure shows the temperature transition of any one of the non-contact temperature sensors 20a, 20b, and 20c and the thermolite chip 22 in warming up from the state where the temperature of the heat roll 7 is room temperature.

  The printer is turned on, and temperature control by the non-contact temperature sensor 20 is started at time Ta (warming up start). All the heaters 23a to 23d are energized so that the temperature detected by the non-contact temperature sensor 20 becomes a preset control temperature K1 (set to 200 ° C. in this embodiment), and the temperature of the heat roll 7 is increased. . At this time, the control temperature K1 is sufficiently higher than the thermolite chip detection temperature K3 so that the actual temperature of the thermolite chip 22 reaches the thermolite chip detection temperature K3 (set to 170 ° C. in this embodiment) in a short time. It is set to a very high temperature (a temperature 30 ° C. higher in this embodiment).

  The temperature of the thermolite chip 22 installed on the end side of the heat roll 7 away from the fixing area X is based on the output of the non-contact temperature sensor 20 installed at a position corresponding to the fixing area X of the heat roll 7. Since the responsiveness is poor, first, as a first step, the temperature control by the non-contact temperature sensor 20 is performed with the control temperature K1 as a target value. A region A in the figure indicates a temperature control region by the non-contact temperature sensor 20 with the control temperature K1 in the first step as a target value. A line D indicates the output of the non-contact temperature sensor 20, and a line E indicates the actual temperature of the thermolite chip 22.

  Thus, by the temperature control by the non-contact temperature sensor 20 with the high control temperature K1 as a target value, the initial rise at the start of warming up can be accelerated.

  When the microcomputer 30 recognizes that the actual temperature of the thermolite chip 22 has reached the thermolite chip detection temperature K3 and the sensor head signal receiving circuit 31 has output a “Low” signal, the sensor head 21 Switch to temperature control (time Tb). At this time, for example, the heaters 23a to 23c are de-energized and the temperature control is performed using only the heater 23d capable of heating the entire width of the heat roll so that the relationship between the heating amount and the heat radiation amount of the heat roll 7 becomes uniform. Do. A region B in the figure indicates a temperature control region by the sensor head 21 with the thermolite chip detection temperature K3 in the second step as a target value.

  As shown in the figure, since the temperature rise of the thermolite chip 22 is delayed from the temperature rise of the non-contact type temperature sensor 20, after switching to the temperature control by the sensor head 21, the non-contact type temperature is gradually increased. The output of the sensor 20 will drop (indicated by a plurality of ● marks in the figure). It is necessary to perform correction based on the output of the non-contact temperature sensor 20 during this period, and the correction method will be described later.

  When the correction is completed, the third step is switched to temperature control by the non-contact temperature sensor 20 (time Tc), and when the non-contact temperature sensor 20 reaches the control temperature K1, the warming up of the heater is completed (time Td). A region C in the figure shows a temperature control region by the non-contact temperature sensor 20 with the control temperature K1 in the third step as a target value, and all the heaters 23a to 23d are energized, Energization on / off control is performed. The energization on / off control of the heaters 23a to 23d is continuously performed during printing.

  The warm-up completion signal output at the time Td is transmitted to the control unit body (not shown) of the printing apparatus, and the control body outputs a print permission signal to each part of the printing apparatus based on the warm-up completion signal. To do.

  On the other hand, for example, when the power is turned off immediately after the printing is finished and turned on immediately, the heat roll 7 is warmed up from a high temperature state. The temperature transition between the non-contact temperature sensor 20 and the thermolite chip 22 in this case is as shown in FIG.

  That is, since the temperature of the thermolite chip 22 (line E) has already exceeded the thermolite chip detection temperature K3, temperature control by the sensor head 21 is performed from the beginning. Since it is delayed from the temperature drop of the contact temperature sensor 20, after switching to the temperature control by the sensor head 21, the output of the non-contact temperature sensor 20 is gradually increased as shown by a plurality of marks ●, contrary to FIG. Will rise.

  As shown in FIGS. 2 and 3, the output of the non-contact temperature sensor 20 varies greatly even when the sensor head 21 serving as a reference exhibits the same temperature depending on the state at the start of warming up. The final convergence temperature Y of the heat roll 7 should be equal, but it takes tens of minutes to several hours to converge. In order to shorten the warm-up time, it is necessary to complete the above-described correction before the output of the non-contact temperature sensor 20 converges, and high accuracy is required for the correction.

  Therefore, a correction method according to an embodiment of the present invention will be described with reference to FIG. This figure shows the time after time Tb in FIG. 3 in more detail. The output P0 of the non-contact temperature sensor 20 (line D) and the time T0 when the temperature control by the non-contact temperature sensor 20 is switched to the temperature control by the sensor head 21 at the time Tb are both stored in the memory 33 and periodically. In addition, the outputs P1, P2, and P3 of the non-contact temperature sensor 20 and the times T1, T2, and T3 at that time are stored in the memory 33. Although four points of data are collected here, the number of points is not limited to four as long as it is a plurality of points. Here, the first output P0 is sampled at time Tb, but may be anywhere after time Tb.

  Although the convergence temperature is predicted using these data (temperature increase rate data), it has been found that the predicted convergence temperature Y can be predicted by the following formula 1 through various experiments.

Y = A × (Pn−P (n−1)) / (Tn−T (n−1)) + Pn Equation 1
A in the equation is a constant specific to each of the non-contact temperature sensors 20a, 20b, and 20c, and is determined by experiment.

  Therefore, the prediction accuracy can be improved by substituting Pn and Tn recorded in the memory 33 into Equation 1, calculating the convergence temperature Y at three points, and taking the average value thereof.

  The predicted convergence temperature Y obtained in this way is compared with the standard temperature K4 stored in advance in the memory 33, and the correction amount K2 is derived from the difference. Thereafter, when the temperature control is performed by the non-contact temperature sensor 20, the correction amount K2 is reflected on the output of the non-contact temperature sensor 20 (for example, the correction amount K2 is added), and the non-contact temperature is detected. The temperature data of the sensor 20 may be used.

  Here, the standard temperature K4 is a value that is individually measured and set in a new state in which the non-contact temperature sensors 20a, 20b, and 20c are not yet dirty, for example, when the assembly of the printing apparatus is completed.

  Next, an output abnormality detection method of the non-contact temperature sensor 20 will be described with reference to FIG. Information on the effective range obtained in advance by various experiments is stored in the memory 33 in advance. As shown in the figure, the effective range is set within a range of ± 5 ° C. to ± 10 ° C., for example, centered on the standard temperature K4. The predicted convergence temperature Y calculated as described above is the effective temperature. If it is within the range, it is determined that the correction amount K2 is valid, and the above-described correction processing is executed. On the other hand, when the calculated predicted convergence temperature Y is out of the effective range, the predicted convergence temperature Y is determined to be invalid, and the correction process is not executed, and an abnormal error is detected on the operation surface of the printing apparatus, for example. The operator is notified by an appropriate means such as display with characters or pictures, notification by sound, etc., and the cleaning or replacement of the non-contact temperature sensor 20 is urged.

  As described above, according to the present invention, the warm-up of the fixing device can be completed in a short time, and temperature correction and abnormality detection of the non-contact temperature sensor can be realized with high accuracy by simple calculation.

  Although the configuration of FIG. 7 has been described in the above embodiment, the configuration shown in FIG. 8 can also be applied. In this case, the output can be easily applied by replacing the output of the sensor head 21 with the output of the contact thermistor 24.

FIG. 3 is a schematic configuration diagram of a temperature control unit of a fixing device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a first example of temperature transition during warming up of a heater in the fixing device. It is a figure which shows the 2nd example of the temperature transition at the time of warming up of the heater in the fixing device. It is a figure for demonstrating the temperature correction method which concerns on embodiment of this invention. It is a figure for demonstrating the abnormality detection method of the non-contact-type temperature sensor which concerns on embodiment of this invention. 1 is a schematic configuration diagram of an electrophotographic printing apparatus. It is a perspective view showing the 1st example of composition near the heat roll in the printer. It is a perspective view showing the 2nd example of composition near the heat roll in the printer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Charger, 2 ... Photoconductor, 3 ... Laser beam, 4 ... Developing machine, 5 ... Recording medium conveyance unit, 6 ... Recording medium, 7 ... Heat roll, 8 ... Pressure roll, 9 ... Puller roller, 10 ... Recording Medium take-up device, 11 ... Corona transfer device, 12 ... Retractor, 15 ... Recording medium supply device, 20a, 20b, 20c ... Non-contact temperature sensor, 21 ... Sensor head, 22 ... Thermolite chip, 23a, 23b, 23c , 23d ... heater, 24 ... contact thermistor, 30 ... microcomputer, 31 ... sensor head signal receiving circuit, 32 ... A / D converter, 33 ... memory, 34 ... driver, X ... fixing area (paper passing area) .

Claims (8)

A heat roll provided with heating means;
A pressure roll in pressure contact with the heat roll;
Non-contact type first heat roll temperature detecting means arranged in a non-contact state with the heat roll so as to face the fixing region involved in the fixing of the heat roll;
A second heat roll temperature detecting means disposed on the heat roll area outside the fixing area,
Based on a detection signal from the first heat roll temperature detection means, on / off control of the heating means is performed, and while maintaining the temperature of the heat roll at a predetermined temperature, the heat roll and the pressure roll In a warming-up method of a fixing device for thermally fixing a toner image transferred onto a recording medium at a pressure contact portion to the recording medium,
When the fixing device is warmed up, the first temperature detected by the first heat roll temperature detecting means during a period in which the second temperature detected by the second heat roll temperature detecting means is constant. Obtain the amount of change with time interval of the detected temperature,
From the amount of change with the time interval of the first detection temperature, the predicted convergence temperature of the first detection temperature that is predicted to converge is calculated,
Calculate the difference between the standard temperature stored in advance and the predicted convergence temperature,
By correcting the first detected temperature detected by the first heat roll temperature detecting means by the difference value,
A fixing apparatus warming-up method, wherein the heating means is turned on / off based on the corrected first detected temperature. The fixing device warm-up method according to claim 1,
The heating means includes a plurality of short heating unit heaters having heating units individually at different positions in the axial direction of the fixing region, and at least one heating unit having substantially the entire length in the axial direction of the fixing region. A long heating part heater,
Setting a control temperature higher than a second temperature control set value set to control the second detected temperature to be constant;
At the beginning of warming-up of the fixing device, the short heating unit heater and the long heating unit heater are energized, and the temperature is controlled by the first hot roll temperature detecting means with the control temperature as a target value.
When the second detected temperature reaches the second temperature control set value, the energization to the short heating section heater is stopped, the energization to the long heating section heater is continued, and the second temperature control is performed. A method for warming up the fixing device, wherein the temperature control is performed by the second heat roll temperature detecting means using the set value as a target value. The fixing device warm-up method according to claim 1,
The heating means includes a plurality of heaters, and each heater has a heating unit individually at a different position in the axial direction of the fixing region,
A plurality of the first heat roll temperature detection means are installed to face each of the heating units,
The first detection temperature is individually corrected for each first heat roll temperature detection means,
A fixing apparatus warming-up method, wherein the plurality of heaters are individually turned on / off based on the corrected first detected temperature. The fixing device warm-up method according to claim 1,
A fixing apparatus warming-up method, wherein the predicted convergence temperature Y of the first detected temperature is calculated by the following equation.
Y = A * (Pn-P (n-1)) / (Tn-T (n-1)) + Pn
In the formula, A: constant specific to the first heat roll temperature detection means P: output of the first heat roll temperature detection means n: number of data acquisitions T: time of data acquisition The fixing device warming-up method according to claim 2.
A warming-up method for a fixing device, wherein on / off control of the heating means is performed based on the corrected first detected temperature, and the warm-up is completed when the first detected temperature reaches the control temperature. . In the fixing device warming-up method according to claim 1 or 4,
The predicted convergence temperature of the first detected temperature is compared with a preset standard temperature, and when the difference is outside the specified range, it is determined as an abnormal error of the first heat roll temperature detecting means. A method for warming up a fixing device. The method of warming up a fixing device according to claim 6.
A warming-up method for a fixing device, comprising: notifying an operator of cleaning or replacement of the first heat roll temperature detecting means when it is determined that the first heat roll temperature detecting means is abnormal. The electrostatic latent image written on the photoconductor charged by the charger is developed by a developing machine to form a toner image, and the toner image on the photoconductor is transferred to the conveyed recording medium by a transfer device. In the warm-up method of the image forming apparatus, the toner is thermally fixed to the recording medium by passing the recording medium between the heat roll and the pressure roll of the fixing device.
8. A method for warming up an image forming apparatus, wherein the warming up of the fixing device is executed by the method for warming up the fixing device according to claim 1.

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