JP2010156751A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for accurately determining winding or the like of a recording medium by detecting a distance between a temperature detecting means such as a temperature sensor and a clamping body such as a heating roller. <P>SOLUTION: A non-contact type temperature sensor (a non-contact sensor 51) detecting infrared rays radiated from the surface of the heating roller 41 is arranged facing the surface of the heating roller 41. The non-contact sensor 51 is supported by a support member 53 integrally with a distance sensor 52 for detecting a distance to the surface of the heating roller 41. The surface temperature of the heating roller 41 is computed based on the distance measured through the distance sensor 52 and the temperature detected through the non-contact sensor 51. When the measured distance is smaller than a normal-value range, it is determined that paper is wound around the heating roller 41. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a recording medium, and more particularly, includes a fixing unit that thermally fixes the image to the recording medium by conveying the recording medium on which the image is formed. The present invention relates to an image forming apparatus.

  Conventionally, for example, at least one of an image forming unit that forms an image on a recording medium such as paper by a method such as an electrophotographic method and a pair of sandwiching members such as rollers facing each other includes a heating element, and the image forming unit An image forming apparatus including a fixing unit that thermally fixes the image to the recording medium by conveying the recording medium on which the image is formed by nipping the recording medium is considered. In this type of image forming apparatus, it is necessary to appropriately control the temperature of a so-called heating roller provided with the heating element. Therefore, in order to measure the temperature of the heating roller and the like while suppressing wear, it has been considered to dispose a non-contact type temperature sensor opposite the surface of the heating roller or the like.

Since such a non-contact type temperature sensor detects radiant heat, when the paper is wound around the heating roller, the temperature detected by the temperature sensor is lowered. Thus, it has been proposed to detect the surface temperature of the heating roller with a non-contact temperature sensor and determine that a sheet of paper has been wound around the heating roller when the temperature detected by the temperature sensor suddenly decreases (for example, Patent Documents). 1).
JP 2001-125429 A

  However, the distance between the temperature sensor and the heating roller may change due to jam processing or the like, and the temperature detected by the temperature sensor also changes in such a case. For this reason, when the configuration as described in the above publication is adopted, the threshold for judging abnormalities such as paper winding must be increased, and paper winding may not be judged accurately. It was.

  Therefore, the present invention provides an image forming apparatus that can accurately determine the winding of a recording medium by detecting the distance between a temperature detecting unit such as a temperature sensor and a sandwiching member such as a heating roller. It was made as a purpose.

  The image forming apparatus of the present invention made to achieve the above object includes an image forming means for forming an image on a recording medium and at least one of a pair of sandwiching bodies facing each other provided with a heating element, and the image forming means A fixing means for thermally fixing the image to the recording medium by conveying the recording medium on which the image is formed, and a surface of the one sandwiching body that conveys the recording medium in a non-contact manner. The temperature detection means that is provided facing each other, detects the temperature, the distance detection means that detects the distance between the surface of the one sandwiching body and the temperature detection means, and the distance detected by the distance detection means, And a first determination means for determining that a recording medium has entered between the one sandwiching body and the temperature detection means when the allowable range is shorter than a preset allowable range.

  In the image forming apparatus of the present invention configured as described above, a temperature detection unit that detects the temperature is provided so as to face the recording medium conveying surface of the one holding body including the heating element in a non-contact manner. It has been. Further, the distance between the surface of the one sandwiching body and the temperature detecting means is detected by the distance detecting means. For this reason, based on the distance detected by the distance detection means and the temperature detected by the temperature detection means, the temperature of the surface of the one sandwiching body can be accurately estimated.

  Further, the first determination means indicates that the recording medium has entered between the one sandwiching body and the temperature detection means when the distance detected by the distance detection means is shorter than a preset allowable range. Judging. That is, when the recording medium enters between the one sandwiching body and the temperature detecting means, the distance detecting means detects the distance to the recording medium. Or shorter than the error range. Therefore, when the detected distance is shorter than the allowable range, the first determination unit determines that a recording medium has entered between the one sandwiching body and the temperature detection unit. As described above, in the present invention, since the entry of the recording medium is detected by the distance detecting means, it is possible to accurately determine the winding of the recording medium.

  Although the present invention is not limited to the following configuration, the temperature of the surface of the one sandwiching body is estimated based on the distance detected by the distance detection unit and the temperature detected by the temperature detection unit. The surface temperature estimation means for performing may be further provided. In this case, as described above, it is preferable to accurately estimate the temperature of the surface based on the temperature detected by the temperature detection unit and the distance from the temperature detection unit to the surface of the one sandwiching body. Can be executed.

  Further, in any one of the above inventions, at least the one sandwiching body conveys the recording medium by rotating itself, and the distance detecting means continuously continues while the one sandwiching body rotates at least once. The distance is detected, and the first determination means determines that the one clamping body and the one clamping body when the distance becomes shorter than the allowable range at any time during one rotation of the one clamping body. It may be determined that a recording medium has entered between the temperature detecting means. In this case, when the edge of the recording medium wound around the one sandwiching body is floating, the portion that is lifted while the one sandwiching body makes one rotation is opposed to the distance detecting means. Since it passes through the position, it is possible to more accurately determine the winding of the recording medium.

  In any one of the above inventions, the distance detection unit and the first determination unit continuously detect and detect the recording medium on which the image is formed by the image forming unit. The above determination may be made. In this case, winding of the recording medium during image formation can be detected immediately.

  In any one of the above-described inventions, the distance detection unit and the first determination unit perform the detection and the determination when the pair of holding bodies are activated before the image formation by the image forming unit is started. May be. In this case, it is possible to detect that the recording medium has been wound around the sandwich body before the start of image formation.

  In the present invention, the distance detection unit and the first determination unit may perform the detection and the determination when the power is turned on before image formation by the image forming unit is started. In this case, it is possible to detect the wrapping of the recording medium in which it is not preferable to activate the sandwiching bodies before the pair of sandwiching bodies is activated.

  In this case, the distance detection unit and the first determination unit perform the detection and the determination even when the recording medium on which the image is formed by the image forming unit is transported by the pair of holding members. 1 judging means makes the judgment by comparing the distance detected by the distance detecting means with the already set allowable range when the power is turned on, and detected by the distance detecting means when the power is turned on during the transporting. The determination may be made by comparing the allowable range set based on the distance with the distance detected by the distance detection means during the conveyance.

  The distance between the one sandwiching body and the temperature detecting means may change depending on the maintenance of the fixing means. Therefore, although the detected distance is compared with a predetermined allowable range when the power is turned on, the detected distance is set based on the distance detected by the distance detecting means when the recording medium is transported. It may be compared with an allowable range. In this case, when the recording medium is transported, the allowable range set based on the distance detected when the power is turned on is used as a comparison target, thereby setting the allowable range more strictly and winding the recording medium. Etc. can be judged more strictly.

  In any one of the above inventions, when the distance detected by the distance detection means is longer than the allowable range, a second determination means for determining that an abnormality has occurred in the temperature detection means or the distance detection means. , May be further provided. When the distance detected by the distance detection means becomes longer than, for example, the range of blur or error, it can be estimated that an abnormal displacement has occurred in the temperature detection means or that the distance detection means itself has failed. Therefore, the second determining means determines that an abnormality has occurred in the temperature detecting means or the distance detecting means when the distance detected by the distance detecting means is longer than the allowable range. In this case, it is possible to determine an abnormal displacement of the temperature detection means, a failure of the distance detection means itself, or the like.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a laser printer 1 as an example of an image forming apparatus to which the present invention is applied. In the following description, the right side in FIG. 1 is the front side of the laser printer 1 and the front side is the left side of the laser printer 1.

1. Overall Configuration of Laser Printer As shown in FIG. 1, the laser printer 1 is configured to form an image on a feeder unit 4 for feeding a sheet 3 as an example of a recording medium into a main body casing 2 and the sheet 3. The image forming unit 5 is provided as an example of the image forming unit. A rear cover 2 a that can be opened and closed is provided on the rear side of the main casing 2.

1.1. Structure of Feeder Unit The feeder unit 4 is detachably mounted on the bottom of the main casing 2 and is installed below the paper 3 at the bottom of the paper feed tray 8 to lift the paper 3 during paper feeding. Therefore, a pressure plate 8a is provided so as to be swingable so that the front is lifted, and a lift plate 8b is provided below the pressure plate 8a and lifts the pressure plate 8a from below. The lift plate 8b is supported at the rear end thereof so as to be rotatable on the paper feed tray 8, and is provided with a rotation driving force by a mechanism (not shown) to lift the pressure plate 8a.

  In addition, a paper feed roller 10 that is in contact with the uppermost sheet 3 of the sheets 3 stacked on the paper feed tray 8 from above is disposed above and in front of the paper feed tray 8, and a separation roller 11 is disposed in front thereof. Has been. The separation roller 11 is disposed to face a separation pad 12 made of an elastic material. The separation pad 12 is urged upward by a spring (not shown), and the sheet 3 conveyed by the separation roller 11 is moved from the surface opposite to the surface with which the outer peripheral surface of the separation roller 11 contacts to the outer peripheral surface. Press towards.

  For this reason, the sheet 3 fed out by the sheet feeding roller 10 is sandwiched between the separation roller 11 and the separation pad 12 and further separated. A paper dust removing roller 13 and a counter roller 14 are disposed in front of the separation roller 11 so as to face each other. The direction is changed backward along the conveyance path 19. Further, a registration roller 15 is disposed obliquely above and behind the paper feed roller 10.

  In the feeder unit 4 configured as described above, the sheet 3 in the sheet feed tray 8 is lifted by the lift plate 8b and the pressure plate 8a, and the uppermost sheet 3 is moved to the separation roller 11 side by the sheet feed roller 10. It is paid out. Further, only the uppermost sheet 3 is fed out by the friction between the separation roller 11 and the separation pad 12 and conveyed one by one to the image forming unit 5.

1.2. Configuration of Image Forming Unit The image forming unit 5 provided in the main body casing 2 on the feeder unit 4 includes a scanner unit 20, a process cartridge 30, a fixing device 40 as an example of fixing means, and the like as follows. An image is formed (hereinafter also referred to as printing) on the paper 3 by electrophotography.

1.2.1. Configuration of the Scanner Unit The scanner unit 20 is provided in the upper part of the main body casing 2 and includes a laser light emitting unit (not shown), a polygon mirror 21 that is driven to rotate, lenses 22 and 23, reflecting mirrors 24 and 25, and the like. As indicated by the chain line, the laser beam based on the image data emitted from the laser light emitting section passes or reflects in the order of the polygon mirror 21, the lens 22, the reflecting mirror 24, the lens 23, and the reflecting mirror 25 to process the process cartridge 30. The surface of the photosensitive drum 32 is irradiated with high-speed scanning.

1.2.2. Configuration of Process Cartridge The process cartridge 30 is disposed below the scanner unit 20 and has a structure that is detachably attached to the main body casing 2. The process cartridge 30 includes a photoconductor cartridge 30A that supports a photoconductor drum 32, and a developer cartridge 30B that is detachably attached to the photoconductor cartridge 30A and contains toner T as a developer therein.

  The photoreceptor cartridge 30A includes a photoreceptor drum 32, a scorotron charger 33, and a transfer roller 34 in a photoreceptor case 31 constituting an outer frame. The developer cartridge 30B is detachably attached to the photoreceptor cartridge 30A, and a developer roller 36, a blade 37, a supply roller 38, and an agitator 39 are rotatable on a developer case 35 that accommodates the developer. In preparation. The toner T in the developer case 35 is supplied to the developing roller 36 by the rotation of the supply roller 38 in the counterclockwise direction in FIG. 1. At this time, the toner T is positively supplied between the supply roller 38 and the developing roller 36. Frictional charge. The toner T supplied onto the developing roller 36 enters between the blade 37 and the developing roller 36 for regulating the layer thickness as the developing roller 36 rotates counterclockwise in FIG. It is carried on the developing roller 36 as a thin layer.

  The photoconductor drum 32 is supported by a photoconductor case 31 coupled to the developer cartridge 30B so as to be rotatable in the arrow direction (clockwise). The photosensitive drum 32 has a drum main body grounded and a surface portion formed of a positively chargeable photosensitive layer.

  The scorotron charger 33 is disposed above the photosensitive drum 32 so as to face the photosensitive drum 32 with a predetermined interval therebetween. The scorotron charger 33 is a positive charging charger that generates corona discharge from a charging wire, and is configured to uniformly charge the surface of the photosensitive drum 32 to a positive polarity.

  The transfer roller 34 is disposed below and in contact with the photosensitive drum 32 below the photosensitive drum 32, and is supported by the photosensitive case 31 so as to be rotatable in the direction of the arrow (counterclockwise). . The transfer roller 34 is configured by covering a metal roller shaft with a conductive rubber material. A transfer bias is applied to the transfer roller 34 by constant current control during transfer.

  The surface of the photosensitive drum 32 is uniformly positively charged by the scorotron charger 33 as it rotates, and then exposed by high-speed scanning of the laser beam emitted from the scanner unit 20. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 32.

  Next, when the developing roller 36 rotates, the positively charged toner T carried on the developing roller 36 is formed on the surface of the photoconductive drum 32 when it contacts the photoconductive drum 32. The electrostatic latent image, that is, the surface of the photosensitive drum 32 that is uniformly positively charged is supplied to an exposed portion exposed to a laser beam and having a lowered potential. As a result, the electrostatic latent image on the photosensitive drum 32 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 32. Thereafter, the toner image carried on the surface of the photosensitive drum 32 is transferred to the paper 3 by the transfer bias applied to the transfer roller 34 while the paper 3 passes between the photosensitive drum 32 and the transfer roller 34. Is done.

1.2.3. Configuration of Fixing Unit The fixing unit 40 is disposed on the downstream side of the process cartridge 30 and includes a heating roller 41 (an example of one sandwiching body) that is rotatably provided with a halogen lamp 41A (an example of a heating element) therein. The pressure roller 42 is disposed below the heat roller 41 so as to press the heat roller 41 and is driven to rotate (the heat roller 41 and the pressure roller 42 are an example of a pair of sandwiching bodies). In the fixing device 40, the toner image is thermally fixed to the paper 3 by heating the paper 3 to which the toner T has been transferred while being nipped and conveyed by the heating roller 41 and the pressure roller 42. Then, the sheet 3 on which the toner image is thermally fixed is further conveyed by a pair of conveying rollers 43 disposed obliquely above and rearward of the fixing device 40, and is conveyed to a paper discharge path 44. The paper 3 conveyed to the paper discharge path 44 is discharged onto a paper discharge tray 46 by a paper discharge roller 45.

  The fixing device 40 includes a fixing device cover 47 as an example of a cover that covers the heating roller 41 and the pressure roller 42 from the inside of the rear cover 2a, and the rear conveying roller of the pair of conveying rollers 43 described above. 43 is supported by the fixing device cover 47. The fixing device cover 47 also functions as a guide for guiding the paper 3 that has passed between the heating roller 41 and the pressure roller 42 to the conveyance roller 43.

  Further, as schematically shown in FIG. 2, a non-contact type temperature sensor 51 that detects infrared rays radiated from the surface of the heating roller 41 is located above the heating roller 41 (on the side opposite to the pressure roller 42). (Hereinafter referred to as a non-contact sensor: an example of a temperature detecting means) is disposed to face the surface of the heating roller 41. Further, the non-contact sensor 51 is integrated with a distance sensor 52 as an example of a distance detection unit that detects a distance from the surface of the heating roller 41 with an accuracy of about 0.01 μm by a laser, for example, by a rod-shaped support member 53. It is supported. For this reason, the distance detected by the distance sensor 52 as the distance from itself to the surface of the heating roller 41 coincides with the distance between the non-contact sensor 51 and the surface of the heating roller 41.

3. Laser Printer Control System and Processing FIG. 3 is a block diagram showing the configuration of the laser printer 1 control system. As shown in FIG. 3, the laser printer 1 includes a control circuit 70 (first judgment means, second judgment means, surface temperature estimation) in which a CPU 72, ROM 73, RAM 74, and NVRAM 75 are connected to an ASIC (application specific integrated circuit) 71. An example of means). The ASIC 71 is connected to the fixing device 40 (an example of the fixing unit), the non-contact sensor 51 (an example of the temperature detecting unit), and the distance sensor 52 (an example of the distance detecting unit). The ASIC 71 is also connected to a display unit 81 provided on the surface of the main casing 2 and a transport unit 82 that drives the various rollers 10 to 41 described above.

  Next, processing executed by the control circuit 70 based on a program stored in the ROM 72 will be described. FIG. 4 is a flowchart showing power-on processing executed by the control circuit 70 when the laser printer 1 is powered on.

  As shown in FIG. 4, in this process, first, the distance between the surface of the heating roller 41 and the non-contact sensor 51 is measured via the distance sensor 52 in S1 (S represents a step: the same applies hereinafter). . In subsequent S2, it is determined whether or not the distance is a normal value. The normal value here is a value that is set at the time of shipment from the factory and stored in the NVRAM 75, and is a distance l (for example, 1.0 ± 0.15 mm) between the surface of the heating roller 41 and the non-contact sensor 51. It is expressed by l ± Δl (an example of an allowable range) having a width of an error Δl (for example, 0.3 mm) caused by aging. Further, the magnitude of the error Δl is appropriately set according to the resolution of the distance sensor 52, the specifications of the laser printer 1, and the like.

  If the distance measured in S1 is a normal value (normal range) (S2: Y), the process proceeds to S3. If a wrapping error described later is set at that time, the wrapping is performed. After the error is released, the process proceeds to S4. In S4, the distance measured in S1 is stored in the RAM 74 as the distance L. In the subsequent S5, the process is shifted to a glass turning process described later, and this process ends.

  On the other hand, when the distance measured in S1 is not a normal value (when the distance is not within the allowable range l ± Δl) (S2: N), the process proceeds to S7, and the distance measured in S1 is a normal value. It is determined whether it is larger. When the distance measured in S1 is larger than the normal value (when the distance is larger than the upper limit l + Δl of the allowable range), it is estimated that an abnormal displacement has occurred in the non-contact sensor 51 or the distance sensor 52 itself has failed. can do. Therefore, in that case (S7: Y), in S8, a display indicating the failure of the sensor is made via the display unit 81, and in the subsequent S9, the apparatus is stopped and this processing is terminated.

  When the distance measured in S1 is smaller than the normal value (when the distance is smaller than the lower limit l−Δl of the allowable range), the sheet 3 is wound around the heating roller 41, and the distance to the sheet 3 is set. It can be estimated that the distance sensor 52 is detecting. Therefore, in that case (S7: N), after a display indicating that a winding error of the paper 3 has occurred in S10 is made via the display unit 81, the process proceeds to S9 described above and the apparatus is stopped. , The process ends. In this process, S2 and S7 correspond to examples of the first determination unit and the second determination unit.

  FIG. 5 is a flowchart showing the processing at the time of the glass turning transferred by the processing of S5. Note that at the time of executing the process for rotating the glass, so-called glass rotation is performed by rotating each part of the process cartridge 30 and the heating roller 41 by another routine. As shown in FIG. 5, in this process, first, the rotation counter I is reset to 0 in S21. In subsequent S22, the distance is measured in the same manner as in S1, and in the subsequent S23, the rotation counter I is incremented by one. Further in S24, it is determined whether or not the distance measured in S22 is a normal value. The normal value here is L ± ΔL in which the distance L stored in S4 has a width of error ΔL corresponding to the blur of the heating roller 41 (shaft eccentricity) and the resolution of the distance sensor 52. It is a value (range) represented by (an example of an allowable range). However, ΔL is set sufficiently small with respect to the thickness of the sheet 3 of 60 to 200 μm.

  Compared to the allowable range l ± Δl in the process of FIG. 4, the allowable range L ± ΔL in the process of rotating the glass in FIG. 5 is a stricter allowable range based on the measured distance. In the time processing, the winding of the paper 3 can be detected more accurately.

  When the distance measured in S22 is a normal value (when the distance is within the allowable range L ± ΔL) (S24: Y), the process proceeds to S25, and the value of the rotation counter I is 1 of the heating roller 41. It is determined whether or not the value is greater than the value corresponding to the circumference, and if it is equal to or less than the value corresponding to one revolution (S25: N), the process proceeds to S22 described above. That is, the rotation counter I corresponding to one rotation of the heating roller 41 is divided by dividing the time required for one rotation of the heating roller 41 by the monitoring cycle in which the distance measurement (S22) is repeated by the loop processing of S22 to S25. Can be calculated. In S25, it is determined whether or not the value of the rotation counter I exceeds a value corresponding to one turn of the heating roller 41. Then, the distance measured repeatedly in S22 does not deviate from the normal value (allowable range L ± ΔL) (S24: Y), and the heating roller 41 makes one round (S25: Y), the process is continued in S26. After the transition to the standby state, this process ends. The standby state is a well-known processing state that waits until image data is input.

  On the other hand, when the distance measured in S22 is not a normal value (when the distance is not within the allowable range L ± ΔL) (S24: N), the process proceeds to S33, and the distance measured in S22 is normal. It is determined whether or not it is larger than a value (the upper limit L + ΔL of the allowable range). When the distance measured in S22 becomes larger than the normal value, it can be estimated that an abnormal displacement has occurred in the non-contact sensor 51 or that the distance sensor 52 itself has failed. Therefore, in that case (S33: Y), in S34, a display indicating the failure of the sensor is made via the display unit 81, and in the subsequent S35, the apparatus is stopped and this processing is terminated.

  Further, when the distance measured in S22 is smaller than the normal value (when the distance is smaller than the lower limit L−ΔL of the allowable range), the sheet 3 is wound around the heating roller 41, and the distance to the sheet 3 is set. It can be estimated that the distance sensor 52 is detecting. Therefore, in that case (S33: N), a display indicating that a paper 3 winding error has occurred is made via the display unit 81 in S37, and in S38, the apparatus is stopped and an error release waiting state is entered. The process is shifted to end the present process. This error release waiting state is a processing state in which the apparatus waits until a well-known reset is performed, for example, the sheet 3 wound around the heating roller 41 is removed. In this process, S24 and S33 correspond to an example of the first determination unit and the second determination unit.

  Further, when the laser printer 1 is powered on, the control circuit 70 executes the following temperature control process in parallel with the above processes based on the program stored in the ROM 72. FIG. 6 is a flowchart showing the temperature control process. As shown in FIG. 6, in this process, first, in S41, the detected temperature of the non-contact sensor 51 is set to x, and in S42, the distance detected through the distance sensor 52 at that time is set to l. Is done. In S43 as an example of the subsequent surface temperature estimation means, the temperature of the heating roller 41 is calculated by substituting x and l into the function f (x, l), and in S44, the calculated temperature is set to the calculated temperature. Accordingly, the control of the fixing device 40 (particularly the halogen lamp 41A) is executed, and the process proceeds to S41 described above.

  Note that the process of S44 is changed as needed depending on the accuracy of the temperature required for the heating roller 41. For example, relatively rough control is performed in the standby state described above, and when the apparatus is stopped (S9, S35, In S38), the energization of the halogen lamp 41A is stopped, and precise control is performed during printing described later. By repeatedly executing the processing of S41 to S44, the temperature of the heating roller 41 is controlled with accuracy as required.

  Next, FIG. 7 is a flowchart showing a printing process executed when image data is input in the standby state. At the time of image data input, a well-known print process for driving the paper feed roller 10, the scanner unit 20 and the like is executed in parallel with this process.

  As shown in FIG. 7, in this process, first, in S52, the distance is measured in the same manner as in S1, and in subsequent S54, it is determined whether or not the distance measured in S52 is a normal value. Note that the normal value here is the same as that used in S24.

  When the distance measured in S52 is a normal value (when the distance is within the allowable range L ± ΔL) (S54: Y), the process proceeds to S55, and whether or not the printing of the image data is completed. Is judged. If printing has not been completed (S55: N), the process proceeds to S52 described above. Note that the loop processing of S52 to S55 repeatedly executed during printing is executed at a sufficiently fine cycle as compared with the processing of S22 to S25 in the processing during the rotation. Then, the distance measured repeatedly in S52 does not deviate from the normal value (S54: Y). When the printing is completed (S55: Y), the process is shifted to the standby state in the subsequent S56, and then the present process. Ends.

  On the other hand, when the distance measured in S52 is not a normal value (when the distance is not within the allowable range L ± ΔL) (S54: N), the process proceeds to S63, and the same processes as in S33 to S38 described above. Is executed. That is, it is determined whether or not the distance measured in S52 is larger than the normal value (allowable range upper limit L + ΔL) (S63). If the distance is larger than the normal value (if the distance is larger than the allowable range upper limit L + ΔL), S63: Y), a display indicating a failure of the sensor is made (S64), the apparatus is stopped (S65), and the process ends. When the distance measured in S52 is smaller than the normal value (when the distance is smaller than the lower limit L-ΔL of the allowable range) (S63: N), a display indicating that a winding error has occurred is made ( In S67, the apparatus is stopped and the process shifts to an error release waiting state (S68), and this process ends. In this process, S54 and S63 correspond to an example of the first determination unit and the second determination unit.

4). Effects of the present embodiment and modifications thereof As described above, in the present embodiment, when the distance measured via the distance sensor 52 becomes smaller than the normal value range (S7: N, S33: N, S63: N), it is determined that the paper 3 has a winding error (S10, S37, S67). For this reason, the winding error of the paper 3 can be accurately determined.

  Moreover, since the above determination is made before the fixing device 40 is started when the power is turned on (S2, S7), the winding of the paper 3 that is not preferable to rotate the heating roller 41 is also detected well. The apparatus can be stopped (S9). In addition, since the above determination is continuously performed while the heating roller 41 makes one revolution when the glass is rotated (S22 to S25), the sheet 3 may be attached to a part of the heating roller 41 before the start of printing. It can be detected well. Further, when the edge of the sheet 3 is lifted from the surface of the heating roller 41, the lifted portion passes through the position facing the distance sensor 52 while the heating roller 41 makes one round. The winding of the paper 3 can be determined more accurately by the processing. Furthermore, since the above determination is performed while rotating the heating roller 41 during printing (S52 to S55), even if the paper 3 is wound during printing, it can be immediately detected. .

  Moreover, in the said embodiment, when the distance measured via the distance sensor 52 becomes smaller than the range of a normal value (S7: Y, S33: Y, S63: Y), it is judged as a sensor failure. (S8, S34, S64). For this reason, it is possible to satisfactorily determine that an abnormal displacement has occurred in the non-contact sensor 51 or that the distance sensor 52 itself has failed. In addition, in the processing at the time of turning the glass and at the time of printing, the range of the normal value is set narrower than that at the time of power-on based on the distance measured at the time of power-on (S24, S54). Winding and sensor failure can be determined more precisely.

  Furthermore, in the above-described embodiment, the fixing device 40 is controlled based on the distance measured via the distance sensor 52 and the temperature detected via the non-contact sensor 51 (FIG. 6). The surface temperature of the toner 41 can be accurately controlled, and the toner image can be fixed stably.

  In addition, this invention is not limited to the said embodiment at all, It can implement with a various form in the range which does not deviate from the summary of this invention. For example, the distance sensor 52 is not limited to one using a laser, and various sensors such as one using an ultrasonic wave can be used. Moreover, it is not always necessary to execute all the processes in FIGS. 4 to 7, and only some of them may be executed. Further, the fixing means in the present invention is not limited to the one provided with the heating roller 41 and the pressure roller 42 as described above, and various types of fixing means such as one having a platen shape may be applied. Can do.

1 is a longitudinal sectional view illustrating a schematic configuration of a laser printer to which the present invention is applied. 2 is a perspective view schematically showing a configuration in the vicinity of a fixing unit of the laser printer. FIG. It is a block diagram showing the structure of the control system of the said laser printer. It is a flowchart showing the process at the time of power-on which the control system performs. It is a flowchart showing the processing at the time of the glass rotation which the control system performs. It is a flowchart showing the temperature control process which the control system performs. It is a flowchart showing the process at the time of printing which the control system performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer 3 ... Paper 5 ... Image forming part 20 ... Scanner part 30 ... Process cartridge 40 ... Fixing device 41 ... Heating roller 41A ... Halogen lamp 42 ... Pressure roller 51 ... Non-contact sensor 52 ... Distance sensor 53 ... Support member 70 ... Control circuit 81 ... Display unit

Claims (8)

Image forming means for forming an image on a recording medium;
Fixing means for heat-fixing the image on the recording medium by transporting the recording medium on which at least one of the pair of sandwiching bodies facing each other includes a heating element and sandwiching the recording medium on which the image is formed by the image forming means When,
A temperature detecting means for detecting the temperature provided in a non-contact manner on the surface of the one sandwiching body that conveys the recording medium;
Distance detecting means for detecting a distance between the surface of the one sandwiching body and the temperature detecting means;
When the distance detected by the distance detecting means is shorter than a preset allowable range, a first judging means for judging that a recording medium has entered between the one sandwiching body and the temperature detecting means. When,
An image forming apparatus comprising: Surface temperature estimation means for estimating the temperature of the surface of the one sandwiching body based on the distance detected by the distance detection means and the temperature detected by the temperature detection means,
The image forming apparatus according to claim 1, further comprising: At least the one sandwiching body conveys the recording medium by rotating itself,
The distance detection means continuously detects the distance while the one clamping body rotates at least once,
The first determination means determines whether the one clamping body and the temperature detection means are used when the distance becomes shorter than the allowable range at any point during the one rotation of the one clamping body. 3. The image forming apparatus according to claim 1, wherein it is determined that a recording medium has entered between them.   The distance detection unit and the first determination unit continuously perform the detection and the determination while the recording medium on which the image is formed by the image forming unit is conveyed by the pair of sandwiching members. The image forming apparatus according to claim 1.   The distance detection unit and the first determination unit perform the detection and the determination when the pair of holding bodies are activated before image formation by the image forming unit is started. 5. The image forming apparatus according to any one of 4 above.   The image forming apparatus according to claim 1, wherein the distance detection unit and the first determination unit perform the detection and the determination when the power is turned on before image formation by the image forming unit is started. The distance detection unit and the first determination unit perform the detection and the determination even when the recording medium on which the image is formed by the image forming unit is transported by the pair of sandwiching bodies.
The first determination means makes the determination by comparing the distance detected by the distance detection means when the power is turned on with an already set allowable range, and during the transport, the distance detection means is turned on when the power is turned on. The image forming apparatus according to claim 6, wherein the determination is performed by comparing an allowable range set based on the detected distance with a distance detected by the distance detecting unit during the conveyance. When the distance detected by the distance detection means is longer than the allowable range, a second determination means for determining that an abnormality has occurred in the temperature detection means or the distance detection means,
The image forming apparatus according to claim 1, further comprising:

Images