JP2004341560A - Thermal fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately detect abnormalities caused at heaters in a thermal fixing device equipped with a plurality of heaters which heat different positions of the axial direction in a fixing member. <P>SOLUTION: When a time t1 has elapsed (S100:YES), whether a temperature TA at the center part of a heating roller 26 which is detected by a first temperature sensor 41 is higher than a fixing lower limit temperature Tl and lower than a fixing upper limit temperature Th or not is judged. When the temperature TA is not within a fixing temperature range, an operation progresses to a step S120, the occurrence of an abnormality in a center heater, that is, a first halogen lamp A is reported and the operation progresses to a step S130. When the TA is within the fixing temperature range, the operation progresses directly to S130. When a time t2 has elapsed (S130:YES), whether a temperature TB at the vicinity of the end part of the heating roller 26 which is detected by a second temperature sensor 42 is within the fixing temperature range or not is judged. When the temperature TB is not within the the fixing temperature range, the operation progresses to a step S150 and the occurrence of an abnormality in a side heater, that is, a second halogen lamp Bis reported and the operation completes. When the temperature TB is within the fixing temperature range, the operation completes as it is. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat fixing device and an image forming apparatus including the heat fixing device.

  2. Description of the Related Art In an image forming apparatus such as a laser printer, a heat fixing device including a heating roller and a pressing roller is generally provided to thermally fix a toner image transferred to a sheet. During the passage, the toner image transferred onto the sheet is thermally fixed.

  The heating roller 26 of the heat fixing device has a generally cylindrical shape as shown in FIG. 10, and has a width corresponding to the maximum size of the paper so that the maximum size of paper allowed by the image forming apparatus can be thermally fixed. It has a length, and a heater composed of a halogen lamp or the like is provided almost entirely in the axial direction, and the heat generated by the heater heats almost the entire length of the heating roller in the axial direction. I have.

  Then, the heater is divided into a first halogen lamp A having a heating peak at the center in the width direction of the heating roller 26 and a second halogen lamp B having heating peaks at both ends of the heating roller 26. Attempts have been made to be adaptable when printing paper.

Further, Patent Document 1 discloses a fixing device including two heaters as described above.
JP-A-64-84273

  However, in the heat fixing device having the heater as described above, if only one of the halogen lamps A and B fails, it is necessary to detect the occurrence of the failure and to determine which of the halogen lamps has failed. Was difficult to identify.

These problems occur not only in an image forming apparatus using such a heat fixing device but also in a device for heating a sheet-like member using a similar heat fixing device, for example, a laminator.
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to appropriately detect an abnormality occurring in a heater in a heat fixing device including a plurality of heaters for heating different positions in an axial direction in a fixing member. And

  The present invention according to claim 1, which has been made to solve such a problem, has a fixing member for thermally fixing a medium to be fixed to a fixing medium, and a side heater for heating the vicinity of an end of the fixing member. Detecting a temperature of the fixing member near an end of the fixing member heated by the side heater in the heat fixing device having a center heater for heating the fixing member in the vicinity of a central portion in the axial direction. An end temperature detection unit, a center temperature detection unit that detects a temperature of the fixing member near a center of the fixing member heated by the center heater, and a detection result obtained by the center temperature detection unit. Diagnostic means for determining the presence or absence of an abnormality in the center heater, and for determining whether or not the side heater is abnormal, based on a detection result by the end temperature detecting means. The thermal fixing device according to symptoms and the gist thereof.

  According to a second aspect of the present invention, in the thermal fixing device according to the first aspect, the diagnostic unit detects the detection result of the end temperature detecting unit or the center temperature when the thermal fixing device starts up. If the detection result by the detection means is not within the predetermined time until the temperature reaches the predetermined temperature, the temperature of the heated portion is detected by the temperature detection means. It is characterized by diagnosing that an abnormality has occurred.

  According to a third aspect of the present invention, in the thermal fixing apparatus according to the first aspect, the diagnostic unit detects the detection result by the end temperature detecting unit or the center temperature when the thermal fixing device starts up. If the detection result by the detection means is not within a predetermined appropriate temperature range within a predetermined time, an abnormality occurs in the heater in which the temperature of the heated portion is detected by the temperature detection means. It is characterized by the fact that it is diagnosed.

  According to a fourth aspect of the present invention, in the thermal fixing device according to any one of the first to third aspects, the diagnostic unit may determine whether at least one of the detection results of the two temperature detecting units exceeds the upper limit value. Alternatively, when the temperature is lower than the lower limit, the temperature of the heated portion detected by the temperature detecting means is diagnosed as having an abnormality in the heater.

  According to a fifth aspect of the present invention, in the heat fixing device according to any one of the first to third aspects, the difference between the detection results obtained by the diagnosing unit and the two temperature detecting units is the upper limit value and the lower limit value. When the difference exceeds the difference, it is diagnosed that an abnormality has occurred in at least one of the heaters.

  In addition, as a specific example of the position detected by each heater and each temperature detecting means, as described in claim 6, both the side heater and the center heater are halogen lamps, and the end temperature detecting means is a side heater. It is preferable that the temperature at the peak position of the light distribution is detected, and the center temperature detecting means detects the temperature at the peak position of the light distribution of the center heater. Of course, other modes may be adopted.

  According to a seventh aspect of the present invention, in the heat fixing device according to any one of the first to sixth aspects, the fixing member is a heat roller.

  According to an eighth aspect of the present invention, there is provided an image forming apparatus including the heat fixing device according to any one of the first to seventh aspects.

As is apparent from the above description, according to the first aspect of the present invention, the temperature near the center of the fixing member heated by the center heater and the temperature near the end of the fixing member heated by the side heater. Temperature is detected independently by the center temperature detection means and the end temperature detection means, so that the diagnosis means appropriately diagnoses whether an abnormality has occurred in the center heater or the side heater. Can be.

  If there is no abnormality in either the center heater or the side heater when the heat fixing device is started up, the temperature range around the center and the end of the fixing member is within a predetermined appropriate temperature range within a predetermined time. It should get inside. According to the second aspect of the present invention, it is possible to independently detect the abnormality of the heater that occurs when the thermal fixing device is started. Note that the predetermined time and the predetermined appropriate temperature range may be different near the center and near the end. Of course, it may be the same.

  According to the third aspect of the present invention, the same effects as those of the second aspect of the present invention are exhibited. In addition, the following effects are obtained. That is, when an abnormality occurs in the heater, the temperature may not reach a predetermined appropriate temperature. In such a case, diagnosis cannot be performed in the configuration of claim 2 in which the presence or absence of an abnormality is determined based on the time required to reach a predetermined appropriate temperature range. On the other hand, according to the third aspect of the present invention, it is possible to detect occurrence of an abnormality without reaching a predetermined appropriate temperature range.

  According to the present invention, it is possible to independently detect an abnormality occurring in at least one of the center heater and the side heater during fixing.

  That the difference between the detection results by the temperature detecting means exceeds the difference between the predetermined lower limit and the predetermined upper limit means that at least one of the differences is higher than the upper limit or lower than the lower limit. Will be. According to the present invention, it is possible to appropriately diagnose that an abnormality has occurred in at least one of the heaters.

  According to the present invention, the present invention can be easily applied to various heat fixing devices such as an image forming apparatus and a laminator.

  According to the present invention, it is possible to realize an image forming apparatus having the effect of the heat fixing device. For example, according to the image forming apparatus provided with the thermal fixing device according to the first aspect, the image forming apparatus can appropriately diagnose whether an abnormality has occurred in either the center heater or the side heater.

  Hereinafter, a laser printer 1 as an image forming apparatus will be described with reference to FIG. 1 as an embodiment of the present invention. The laser printer 1 includes a feeder unit 4 for feeding paper 3 as a fixing medium and an image forming unit 5 for forming a predetermined image on the fed paper 3 in a main body casing 2. ing.

  The feeder unit 4 includes a paper feed tray 6 detachably mounted on the bottom of the main body casing 2, a paper pressing plate 7 provided in the paper feed tray 6, and an upper end of one end of the paper feed tray 6. The paper feed roller 8 and the paper feed pad 9 are provided, and the downstream side in the transport direction of the paper 3 with respect to the paper feed roller 8 (hereinafter, the upstream or downstream side in the transport direction of the paper 3 is simply referred to as the upstream side or the downstream side. ), And a registration roller 12 provided downstream of the transport rollers 10 and 11 in the transport direction of the paper 3.

  The sheet pressing plate 7 is capable of stacking the sheets 3 in a stacked manner, and is supported so as to be swingable at an end farther from the sheet feeding roller 8 to move the end closer to the upper and lower sides in the vertical direction. It is possible, and is urged upward by a spring (not shown) from the back side. Therefore, as the stacking amount of the sheet 3 increases, the sheet pressing plate 7 is swung downward against the urging force of the spring with the end remote from the sheet feeding roller 8 as a fulcrum. The paper feed roller 8 and the paper feed pad 9 are disposed to face each other, and the paper feed pad 9 is pressed toward the paper feed roller 8 by a spring 13 provided on the back side of the paper feed pad 9. . The uppermost sheet 3 on the sheet pressing plate 7 is pressed from the back side of the sheet pressing plate 7 toward the sheet feeding roller 8 by a spring (not shown), and the sheet feeding roller 8 is rotated by the rotation of the sheet feeding roller 8. After being sandwiched between the pads 9, the sheet is fed one by one. The fed sheet 3 is sent to registration rollers 12 by transport rollers 10 and 11. The registration roller 12 is composed of a pair of rollers, and sends the sheet 3 to an image forming position after a predetermined registration.

In the present embodiment, the image forming position is a position where the photosensitive drum 23 contacts the transfer roller 24, that is, a transfer position where the toner image on the photosensitive drum 23 is transferred to the paper 3.
The feeder unit 4 further includes a multi-purpose tray 14, a multi-purpose paper feed roller 15 for feeding paper 3 stacked on the multi-purpose tray 14, and a multi-purpose paper feed pad 15a. The multi-purpose paper feed roller 15 and the multi-purpose paper feed pad 15a are arranged to face each other, and the multi-purpose paper feed pad 15a is arranged by a spring (not shown) arranged on the back side of the multi-purpose paper feed pad 15a. It is pressed toward the multi-purpose paper feed roller 15. The paper 3 stacked on the multi-purpose tray 14 is sandwiched between the multi-purpose paper feed roller 15 and the multi-purpose paper feed pad 15a by the rotation of the multi-purpose paper feed roller 15, and then fed one by one. .

The image forming unit 5 includes a scanner unit 16, a process cartridge 17, a transfer roller 24, a heat fixing device 18, and the like.
The scanner unit 16 is provided at an upper portion in the main body casing 2 and includes a laser light emitting unit (not shown), a polygon mirror 19, lenses 20 and 21, and a reflecting mirror 22 that are driven to rotate. A laser beam based on predetermined image data to be emitted is passed or reflected in the order of a polygon mirror 19, a lens 20, a reflection mirror 22, and a lens 21 as shown by a chain line, and is applied to a photosensitive drum 23 of a process cartridge 17 described later. The surface is irradiated by high-speed scanning.

  The process cartridge 17 is disposed below the scanner unit 16 and is configured to be detachably attached to the main body casing 2. The process cartridge 17 includes a photosensitive drum 23 and a scorotron-type charger, a developing roller, and a toner storage unit (not shown).

The toner accommodating portion is filled with a positively-charged non-magnetic one-component polymerized toner as a developer, and the toner is carried on the developing roller as a thin layer having a constant thickness.
On the other hand, the photosensitive drum 23 is rotatably disposed so as to face the developing roller. The drum main body is grounded, and the surface thereof is formed of a positively charged photosensitive layer made of polycarbonate or the like. .

  Then, the surface of the photosensitive drum 23 is uniformly positively charged by a scorotron-type charger with the rotation of the photosensitive drum 23, and is then exposed by high-speed scanning of a laser beam from the scanner unit 16 to obtain predetermined image data. Is formed, and when the toner is opposed to the developing roller, the toner carried on the developing roller and charged positively forms an electrostatic latent image formed on the surface of the photosensitive drum 23, that is, The surface of the photosensitive drum 23, which is uniformly positively charged, is exposed to a laser beam and supplied to a portion where the potential is lowered, and is selectively carried to be visualized by being carried thereon. Is achieved.

  The transfer roller 24 is disposed below the photosensitive drum 23 so as to face the photosensitive drum 23 while being rotatably supported on the main casing 2 side. The transfer roller 24 has a metal roller shaft covered with a roller made of a conductive rubber material, and a predetermined transfer bias is applied to the photosensitive drum 23. Therefore, the visible image composed of the toner image carried on the photosensitive drum 23 is transferred to the sheet 3 while the sheet 3 passes between the photosensitive drum 23 and the transfer roller 24. The sheet 3 onto which the visible image has been transferred is conveyed to a heat fixing device 18 described below via a conveyance belt 25.

  The heat fixing device 18 is disposed on the downstream side of the process cartridge 17, and is disposed opposite to the heating roller 26 as a heat roller with the conveyance path of the sheet 3 interposed therebetween, and presses the heating roller 26. A pressing roller 27 and a transport roller 28 provided downstream of the heating roller 26 and the pressing roller 27 are provided.

The heating roller 26 includes a roller body 32 as a cylindrical heating member made of aluminum, a first halogen lamp A as a center heater, and a second halogen lamp B as a side heater.
As shown in FIG. 1, the first halogen lamp A and the second halogen lamp B are provided in the roller main body 32 in parallel along the axial direction. The roller body 32 is configured to be heated by the heat generated by the halogen lamp B.

The pressing roller 27 has a metal roller shaft covered with an elastic roller, and presses the heating roller 26 with a predetermined pressure.
In the heat fixing device 18, the toner image transferred onto the sheet 3 in the process cartridge 17 is heat-fixed while the sheet 3 passes between the heating roller 26 and the pressing roller 27. .

  The sheet 3 fixed in the heat fixing device 18 is then conveyed to a conveying roller 28 provided downstream of the heat fixing device 18, a conveying roller 29 and a discharge roller 30 arranged downstream of the conveying roller 28. Then, the paper is discharged onto a paper discharge tray 31 by the paper discharge rollers 30.

  The laser printer 1 is configured to be able to print small-sized paper 3 (hereinafter, described as small-sized paper 3a) and large-sized paper 3 (hereinafter, described as large-sized paper 3b). Accordingly, the heat fixing device 18 is also configured to be able to fix the small-sized paper 3a and the large-sized paper 3b correspondingly. Hereinafter, a specific configuration and control for fixing the small-sized paper 3a and the large-sized paper 3b in the heat fixing device 18 will be described in detail.

In the following specific description, small-size paper 3a is A5 vertical size or A6 horizontal size paper (width 148 mm), and large-size paper 3b is A4 vertical size paper (width 209 mm). Is done.
Further, in the heat fixing device 18, the first temperature sensor 41 is located at the peak position of the heating by the first halogen lamp A in the roller body 32, and the second temperature sensor 42 is located at the peak position of the heating by the second halogen lamp B. Is provided. As a result, the control unit C accurately detects the temperature near the center and the end of the roller body 32, and appropriately controls on / off of the first halogen lamp A and the second halogen lamp B. It controls the temperature of the main body 32 and detects abnormality of the halogen lamps A and B.

  FIG. 3 shows a heater abnormality detection process (1) which is an example of such a process. This process is started when the power of the laser printer 1 is turned on. When the present process is started, first, in step (hereinafter referred to as S) 10, it is determined whether or not the temperature TA at the center of the heating roller 26 detected by the first temperature sensor 41 is equal to or higher than the fixing lower limit temperature Tl. The fixing lower limit temperature Tl is a temperature at which the toner is not sufficiently melted, remains in a powder state, and cannot be fixed on the paper 3. If the temperature TA in the central portion does not reach the fixing lower limit temperature Tl, the process returns to S10 and waits until the temperature reaches the fixing lower limit temperature Tl. If the temperature TA at the center is equal to or higher than the fixing lower limit temperature Tl (S10: YES), the process proceeds to S20, and it is determined whether or not the absolute value of the difference between the time t1 and the time t1 since the power is turned on is less than the allowable range ε1. I do. The time t1 is an average of the time required for the first halogen lamp A to reach the fixing lower limit temperature Tl after the power is turned on (that is, the lighting of the first halogen lamp A) (see FIG. 4). If the absolute value of the difference between the elapsed time t and the time t1 is equal to or greater than the allowable range ε1, the process proceeds to S30, where it is notified that an abnormality has occurred in the center heater, that is, the first halogen lamp A, and the process proceeds to S40. If the absolute value of the difference between the elapsed time t and the time t1 is less than the allowable range ε1 (S20: YES), the process directly proceeds to S40.

  In S40, it is determined whether or not the temperature TB near the end of the heating roller 26 is equal to or higher than the fixing lower limit temperature Tl. If the temperature TB near the end does not reach the fixing lower limit temperature Tl, the process returns to S40 and waits until the temperature reaches the fixing lower limit temperature Tl. If the temperature TB near the end is equal to or higher than the fixing lower limit temperature Tl (S40: YES), the process proceeds to S50, and it is determined whether or not the absolute value of the difference between the elapsed time t and the time t2 is less than the allowable range ε2. The time t2 is an average of the time required for the second halogen lamp B to reach the fixing lower limit temperature Tl after the power is turned on (that is, the lighting of the second halogen lamp B) (see FIG. 4). If the absolute value of the difference between the elapsed time t and the time t2 is equal to or larger than the allowable range ε2, the process proceeds to S60, where it is notified that an abnormality has occurred in the side heater, that is, the first halogen lamp A, and the present process ends. If the absolute value of the difference between the elapsed time t and the time t2 is less than the allowable range ε2 (S50: YES), the process ends.

  According to this processing, the abnormalities of the halogen lamps A and B occurring when the laser printer 1 (heat fixing device 18) is started can be detected independently. That is, unlike the related art, only the occurrence of an abnormality in one of the two heaters is detected and notified to the administrator, and the administrator does not need to confirm which of the two heaters caused the abnormality. Further, the energization of one of the heaters is stopped, and the presence or absence of an abnormality in the other heater is detected after the portion heated by the heater has cooled, and if there is no abnormality, the abnormality has occurred in the one heater. There is no need to perform a very time-consuming diagnostic process of determining.

  Since the heat at the end of the heating roller 26 is transmitted to a support member such as a bearing that supports the end of the heating roller 26, the temperature of the end of the heating roller 26 is generally less likely to rise than at the center. Therefore, time t2 is longer than time t1. In the case of this processing, the times t1 and t2 are not always constant values, but may be changed according to the temperature of the heating roller 26 when the power is turned on, so that the allowable ranges ε1 and ε2 are also changed.

  FIG. 5 shows a heater abnormality detection process (2), which is another example of the process of detecting a heater abnormality. This process is also started when the power of the laser printer 1 is turned on. When the present process is started, first, in S100, it is determined whether or not the time t1 has elapsed since the power was turned on. If the time t1 has not elapsed, the process returns to S100 and waits for the elapse. When the time t1 has elapsed (S100: YES), it is determined whether or not the temperature TA at the center of the heating roller 26 detected by the first temperature sensor 41 is higher than the fixing lower limit temperature Tl and lower than the fixing upper limit temperature Th. judge. The fixing upper limit temperature Th is a temperature above which hot offset occurs. If the temperature TA at the central portion of the heating roller 26 is not within this range (hereinafter, referred to as a fixing temperature range, which corresponds to an appropriate temperature range in the claims), the process proceeds to S120, and the center heater, The process notifies that an abnormality has occurred in the first halogen lamp A, and proceeds to S130. If the temperature TA at the center of the heating roller 26 is within the fixing temperature range, the process proceeds directly to S130.

  In S130, it is determined whether the time t2 has elapsed since the power was turned on. If the time t2 has not elapsed, the process returns to S130 and waits for the elapse. When the time t2 has elapsed (S130: YES), it is determined whether or not the temperature TB near the end of the heating roller 26 detected by the second temperature sensor 42 is within the fixing temperature range. If the temperature TB near the end of the heating roller 26 is not within the fixing temperature range, the process proceeds to S150, where it is notified that an abnormality has occurred in the side heater, that is, the second halogen lamp B, and the present process ends. If the temperature TB near the end of the heating roller 26 is within the fixing temperature range, the process ends.

  According to this process, it is also possible to independently detect the abnormalities of the halogen lamps A and B occurring when the laser printer 1 (heat fixing device 18) is started. Further, unlike the heater abnormality detection process (1) shown in FIG. 3, even if the temperature TA at the center of the heating roller 26 or the temperature TB near the end of the heating roller 26 does not reach the fixing lower limit temperature Tl, the abnormality is detected. Can be detected. In this process, the times t1 and t2 are not always constant values, but may be changed according to the temperature of the heating roller 26 when the power is turned on.

  FIG. 6 illustrates another example of the heater abnormality detection process (3) performed by the control unit C. This process is interrupted and started at regular intervals while printing (fixing operation) is being performed in the laser printer 1. When this process is started, first, in S200, it is determined whether or not the temperature TA at the center of the heating roller 26 is higher than the fixing upper limit temperature Th. If it is higher, the process proceeds to S210, where it is notified that an abnormality has occurred in the center heater (first halogen lamp A), and the process proceeds to S230. If the temperature TA at the center of the heating roller 26 is equal to or lower than the fixing upper limit temperature Th (S200: NO), the process proceeds to S220 to determine whether the temperature TA at the center of the heating roller 26 is lower than the fixing lower limit temperature Tl. judge. If the temperature TA at the center of the heating roller 26 is lower than the fixing lower limit temperature Tl, the process proceeds to S210, and if not, the process proceeds to S230.

  In S230, it is determined whether the temperature TB near the end of the heating roller 26 is higher than the fixing upper limit temperature Th. If it is higher, the process proceeds to S240, where it is notified that an abnormality has occurred in the side heater (second halogen lamp B), and this process ends. If the temperature TB near the end of the heating roller 26 is equal to or lower than the fixing upper limit temperature Th (S230: NO), the process proceeds to S250 to determine whether the temperature TB near the end of the heating roller 26 is lower than the fixing lower limit temperature Tl. Is determined. If the temperature TB near the end of the heating roller 26 is lower than the fixing lower limit temperature Tl, the process proceeds to S240, and if not, the process ends.

  According to this processing, if any one of the temperature TA near the center of the heating roller 26 and the temperature TB near the end of the heating roller 26 protrudes from the appropriate temperature range, the abnormality is notified, and the halogen lamps A and B are used. Since the occurrence of the abnormality is notified in an identifiable manner, an appropriate response can be taken.

  FIG. 7 shows a temperature control process which is an example of still another process executed by the control unit C. This processing is also interrupted and started at regular intervals while the laser printer 1 is performing printing (fixing operation). When this process is started, first, in S300, it is determined whether or not the temperature difference between the temperature TA at the center of the heating roller 26 and the temperature TB near the end (hereinafter, also simply referred to as the temperature difference) exceeds 15 ° C. judge. Here, the value of 15 ° C. is a difference between the fixing upper limit temperature Th and the fixing lower limit temperature Tl (hereinafter also referred to as an appropriate temperature range, which is smaller than the fixing temperature range). If the temperature difference does not exceed the appropriate temperature difference range (S300: NO), the process ends, and if it exceeds (S300: YES), the process proceeds to S310. In S310, a temperature farther from the center temperature Tm is selected from the temperature TA at the center of the heating roller 26 and the temperature TB near the end. The center temperature Tm is an average value of the fixing upper limit temperature Th and the fixing lower limit temperature Tl. In the case of FIG. 8, the temperature TA at the center is farther from the center temperature Tm than the temperature TB near the end of the heating roller 26, so that the temperature TA at the center is selected.

  In subsequent S320, the farther halogen lamp (the first halogen lamp in FIG. 8) is selected so that the selected one (the temperature TA in the center in FIG. 8) approaches the closer one (the temperature TB in the vicinity of the end in FIG. 8). Change the control value of A). Then, in S330, it is determined whether or not the temperature difference has become 10 ° C. or less. If the temperature difference has become 10 ° C. or less, the present process is terminated. If not, the process returns to S320 to further change the control value.

  According to this process, the temperature of one of the vicinity of the end and the center of the heating roller 26 can be made closer to the other. By repeating this process, if the other becomes farther than the center temperature Tm than the one, the other approaches the one. Accordingly, both the vicinity of the end and the vicinity of the center of the heating roller 26 can be set to a temperature between the fixing upper limit temperature Th and the fixing lower limit temperature Tl.

  The abnormality of the first halogen lamps A and B may be detected by using a process similar to this process. FIG. 9 shows an example of the heater abnormality detection process (4). This processing is also interrupted and started at regular intervals while the laser printer 1 is performing printing (fixing operation). When the present process is started, first, in S400, it is determined whether or not the temperature difference between the temperature TA at the center of the heating roller 26 and the temperature TB near the end thereof exceeds the fixing temperature range (Th-Tl). If the temperature difference does not exceed the fixing temperature range, the present process ends, and if it exceeds (S400: YES), the process proceeds to S410. In S410, it is notified that an abnormality has occurred in at least one of the heaters, that is, at least one of the first halogen lamp A and the second halogen lamp B, and the process ends.

  The fact that the detected temperature difference exceeds the fixing temperature range means that at least one of the temperature TA at the center and the temperature TB near the end is above the upper limit or below the lower limit. Become. According to such processing, it can be appropriately diagnosed that an abnormality has occurred in at least one of the lamps. According to the characteristics described above, if only one is above the upper limit, it is usually a portion heated by the center heater, and if only one is below the lower limit, it is usually This is the portion heated by the side heater.

As described above, the heat fixing device 18 and the laser printer 1 to which the present invention is applied have been described. However, the present invention is not limited to this embodiment and can be implemented in various modes.
(Modification 1)

For example, the present invention may be applied to a heat fixing device of a laminator instead of the laser printer 1.
(Modification 2)

In the above-described processing (3), specific numerical values such as 15 ° C. and 10 ° C. are shown, but these are merely examples, and variously change depending on the characteristics of the toner and the structure of the heat fixing device 18. An appropriate temperature should be set according to these characteristics and structure.
(Modification 3)

In the heater abnormality detection process (3), an abnormality is reported when the temperature TA at the center of the heating roller 26 or the temperature TB near the end thereof exceeds the fixing upper limit temperature Th or falls below the fixing lower limit temperature Tl. The abnormality may be notified only by approaching these thresholds. If it is determined that “approached” when the difference from each threshold value is 50% or less of the appropriate temperature range, control is theoretically established, but preferably “approached” when it is 20 to 30%. ".
(Modification 4)

Further, in the heater abnormality detection processing (4), the temperature difference between the temperature TA at the center of the heating roller 26 and the temperature TB near the end is compared with the fixing temperature range. It may be compared with the appropriate temperature difference range of 3).
(Modification 5)

  The time t1 is different from the time t2, but may be the same value. The appropriate temperature difference range may be different between the vicinity of the center and the vicinity of the end. Further, the time may be a predetermined temperature before t1 and t2 reach the fixing lower limit temperature Tl.

FIG. 1 is a side sectional view of a main part showing an embodiment of a laser printer as an image forming apparatus of the present invention. FIG. 3 is a front sectional view of a main part of a heating roller used in the laser printer of the embodiment. It is a flowchart of a heater abnormality detection process (1). 6 is a graph showing how the temperature TA at the center of the heating roller 26 and the temperature TB near the end of the heating roller 26 change after power is turned on. It is a flowchart of a heater abnormality detection process (2). It is a flowchart of a heater abnormality detection process (3). It is a flowchart of a temperature control process. 6 is a graph showing a change in a temperature TA at a center portion and a temperature TB near an end portion of the heating roller 26 during printing. It is a flowchart of a heater abnormality detection process (4). FIG. 10 is a front sectional view of a main part of a heating roller used in a conventional laser printer.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Laser printer 18 ... Thermal fixing device 25 ... Conveying belt 26 ... Heating roller 27 ... Pressing roller 41 ... 1st temperature sensor 42 ... 2nd temperature sensor A .. .First halogen lamp B ... Second halogen lamp

Claims (8)

A fixing member for thermally fixing the medium to be fixed to the fixing medium, a side heater for heating the vicinity of the end of the fixing member, and a center heater for heating the vicinity of the axial center of the fixing member. Equipped with a heat fixing device,
End temperature detecting means for detecting a temperature near an end of the fixing member heated by the side heater,
A central part temperature detecting means for detecting a temperature near a central part of the fixing member heated by the center heater of the fixing member;
Diagnostic means for determining the presence or absence of an abnormality in the center heater based on the detection result by the center temperature detection means, and determining whether or not the side heater is abnormal based on the detection result by the end temperature detection means. A heat fixing device comprising: The heat fixing device according to claim 1,
The diagnostic means,
When the heat fixing device is started up, the time required for the detection result by the end temperature detection means or the detection result by the center temperature detection means to reach a predetermined temperature is within a predetermined time. A heat fixing device for diagnosing that an abnormality has occurred in the heater in which the temperature of the portion heated by the temperature detecting means is detected. The heat fixing device according to claim 1,
The diagnostic means,
At the time of startup of the heat fixing device, when the detection result by the end temperature detection unit or the detection result by the center temperature detection unit is not within a predetermined appropriate temperature range within a predetermined time, A heat fixing device for diagnosing that an abnormality has occurred in the heater in which the temperature of the portion heated by the temperature detecting means is detected. The thermal fixing device according to claim 1, wherein
The diagnostic means,
If at least one of the detection results by the two temperature detecting means exceeds the upper limit value or falls below the lower limit value, an abnormality occurs in the heater in which the temperature of the heated portion is detected by the temperature detecting means. A heat fixing device characterized in that the heat fixing device diagnoses that the temperature is low. The thermal fixing device according to claim 1, wherein
The diagnostic means,
When the difference between the detection results by the two temperature detecting means exceeds the difference between the upper limit value and the lower limit value, it is diagnosed that an abnormality has occurred in at least one of the heaters. apparatus. The thermal fixing device according to claim 1, wherein
Both the side heater and the center heater are halogen lamps,
The end temperature detection means detects the temperature of the peak position of the light distribution of the side heater,
The heat fixing device, wherein the center temperature detecting means detects a temperature at a peak position of light distribution of the center heater. 9. The heat fixing device according to claim 1, wherein:
The fixing member is a heat roller,
A heat fixing device, comprising: An image forming apparatus comprising the heat fixing device according to claim 1.

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