JP4535909B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile machine, and in particular, a fixing member for fixing a toner image, a separation claw for peeling a sheet from the fixing member, Downstream of the fixing member in the conveyance direction, a remaining sheet detection sensor for detecting the remaining of the wound paper and a sheet conveyance sensor for monitoring the conveyance state of the sheet are provided, and the remaining sheet detection sensor is below the fixing member. And an image forming apparatus equipped with a fixing device arranged to monitor the outer peripheral surface of the fixing member.

  The fixing method of an image forming apparatus using an electrophotographic method such as a copying machine, a printer, and a facsimile is generally a heat fixing method. In the heat fixing method, a heating roller having a heater as a heating source is pressed against it. A heating roller type fixing system for fixing at a nip portion formed by a pressure roller, and a nip portion formed by an endless belt suspended between the heating roller and a fixing roller in pressure contact with the pressure roller. There is known a belt-type fixing method in which fixing is performed by using the above method.

  For example, the conventional fixing device 7 shown in FIG. 3 includes a paper conveyance sensor 25, a remaining paper detection sensor 26, a heating roller 31, a pressure roller 32, an upper conveyance guide 27, a lower conveyance guide 28, a separation claw 29, and a control device 33. Etc. are housed in the housing 34.

  The heating roller 31 includes a heater 35, and a pressure roller 32 is disposed so as to form a nip portion by being in pressure contact with the heating roller 31. An upper transport guide 27 is provided downstream of the heating roller 31 in the transport direction and spaced above the nip portion by a predetermined distance, and a lower transport guide 28 is disposed at a predetermined distance from the nip portion.

  A separation claw 29 configured to be in sliding contact with the surface of the heating roller 31 is provided downstream in the conveying direction of the heating roller 31. The separation claw 29 is made of heat-resistant resin, and is configured to be rotatable in the direction of the arrow about a support shaft 36 provided at a site opposite to the provided portion. A plurality of separation claws 29 are arranged at predetermined intervals in the direction intersecting with the conveyance direction of the paper P in correspondence with the paper P of various sizes.

  The reflected light is received by irradiating light on the surface of the heating roller 31 and on the upper portion of the separation claw 29 downstream of the heating roller 31 in the conveying direction and above the upper conveying guide 27. A remaining paper detection sensor 26 is provided which detects a foreign substance existing on the surface and outputs a detection signal.

  On the other hand, the downstream side of the pressure roller 32 in the conveyance direction and the lower part of the lower conveyance guide 28 are irradiated with light into the sheet conveyance path to receive the reflected light from the sheet P. And a paper conveyance sensor 25 for outputting a detection signal.

  The paper transport sensor 25 and the remaining paper detection sensor 26 are optical sensors having light emitting and receiving portions connected to the control device 33, and detection signals from the paper transport sensor 25 and the remaining paper detection sensor 26 are input to the control device 33. Then, it is configured to be processed and to determine the winding jam.

  Further, the paper P on which the toner image is carried by the image forming unit 6 is conveyed in the direction of the arrow and is carried into the fixing device 7. When a winding jam occurs, the paper transport sensor 25 does not detect the paper, and the remaining paper transport sensor 26 detects the paper P (broken arrow) wound around the surface of the fixing roller 31, so that it may be a winding jam. To be judged. However, there is a problem in that the remaining paper detection sensor 26 is damaged by receiving a heat wave (wavy line) emitted from the heating roller 31 after a predetermined period of use. This is because the sensors are generally vulnerable to heat.

  Therefore, as shown in FIG. 4, a fixing device in which the remaining sheet detection sensor 26 is disposed below the lower conveyance guide 28 has been proposed in order to avoid the influence of the heat wave emitted from the heating roller 31. Note that notches (not shown) configured to allow light emitted from the paper transport sensor 25 and the remaining paper detection sensor 26 to pass through are provided in predetermined portions of the upper transport guide 27 and the lower transport guide 28. Yes.

  In this conventional example, the winding jam is determined as follows. That is, the paper transport sensor 25 does not detect the paper P to be transported after a lapse of a predetermined time, and at the same time, a detection signal of a foreign matter on the surface of the heating roller 31 is input to the control device 33 by the remaining paper detection sensor 26 and wound. Jam is judged. However, when a winding jam is determined, most of the paper P is wound around the heating roller 31.

  For example, a non-contact type temperature sensor detects the surface temperature of the heating roller and the surface temperature of the heating roller from the back side of the paper P, and detects the occurrence of jamming of the paper P by the temperature difference between the detected temperatures. Was proposed. (For example, refer to Patent Document 1).

  As a result, although the time for judging the winding jam has been shortened, the surface of the heating roller may be accidentally damaged by the separation claw at the time of the jam handling of the winding jam described later. And the scar appears in an image and there exists a problem that image quality deteriorates remarkably.

  In addition, since the temperature of the paper and the temperature of the heating roller are detected by only one sensor, it may be erroneously detected that a jam has occurred even if the paper is being transported normally. There is a problem that undetectable jams, such as winding around the tip, cannot be detected at an early stage and reliability is lowered.

  Therefore, a fixing device has been proposed in which a winding jam is detected at an early stage and the jam handling operation is facilitated.

  For example, after the front end of the paper fixed at the nip portion passes through two sensors and the paper is detected by the sensors, the tip of the sensor disposed downstream of the nip portion in the paper transport direction is pointed out. When it is detected that there is no paper, the occurrence of paper wrap jams in the fixing means is detected. If the winding jam can be detected at an early stage, the end portion of the sheet protrudes from the fixing device, so that the protruding portion can be grasped and the jam handling operation becomes easy (see, for example, Patent Document 2).

JP-A-10-198216 JP 2000-034038 A

  However, in the above-described conventional example, the winding jam is detected when the time when the leading edge of the sheet should pass through the paper discharge sensor originally provided on the downstream side in the conveyance direction with respect to the nip portion is detected, and the winding jam is detected. At the time of detection, there is a problem that most of the paper is wound around the heating roller, and the jam handling operation becomes difficult. In addition, there is a problem that winding jam is likely to occur due to poor peeling of the paper in the heating roller.

  Accordingly, the present invention solves the problems of the conventional ones as described above, the peeling on the heating roller is good, the sensor is not affected by the heat, and the jam is processed by detecting the jam at an early stage. An object of the present invention is to provide an image forming apparatus that facilitates workability.

  In order to solve the above problem, the invention described in claim 1 is a fixing member for fixing a toner image, a separation claw for separating the paper from the fixing member, and a downstream of the fixing member in the conveying direction. Comprises a remaining sheet detection sensor for detecting the remaining of the wound paper and a sheet conveyance sensor for monitoring the conveyance state of the sheet, and the remaining sheet detection sensor is provided below the fixing member and on the outer peripheral surface of the fixing member. In the fixing device arranged to monitor the above, the sheet conveyance sensor is provided between the remaining sheet detection sensor and the fixing member.

The invention according to claim 2 is the invention according to claim 1, wherein the paper transport sensor is an optical sensor having a light emitting and receiving part, and an optical axis irradiated from the remaining paper detection sensor to the fixing member; The optical axis irradiated to the paper from the paper transport sensor is disposed at a position where it does not cross in the paper transport path.

  According to a third aspect of the present invention, in the second aspect of the present invention, the paper transport path is arranged on the downstream side of the transport direction with respect to the fixing member, and on the lower side of the upper transport guide. It is a space formed between the lower conveyance guide provided.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising the fixing device according to any one of the first to third aspects.

  Since this invention is the above structures, there exists an effect described below.

  In the fixing device according to the first aspect, since the paper transport sensor is disposed upstream of the remaining paper detection sensor in the transport direction, it is possible to reliably determine the winding jam at an earlier stage. In the fixing device according to the second aspect, since the paper is detected by the paper transport sensor before the remaining paper detection sensor detects the paper, the winding jam can be reliably determined at an earlier stage. In the fixing device according to the third aspect, the constituent members of the paper conveyance path are clarified. The image forming apparatus according to the fourth aspect is easy to use because it can easily handle the jam of the winding jam.

  The best mode for carrying out the present invention will be described with reference to the embodiments shown in the accompanying drawings. Since other configurations of the attachment positions of the paper transport sensor and the remaining paper detection sensor are the same as those in the conventional example, the same parts are denoted by the same reference numerals and description thereof is omitted.

  FIG. 1 is a front view showing a schematic overall configuration of an image forming apparatus (full-color copying machine) including a fixing device as a first embodiment of the present invention.

  The full-color copying machine 1 includes an image forming unit 6 that forms an electrostatic latent image by light writing on a photosensitive member 5 charged by an exposure device 4 and visualizes it with toner t, and a sheet on which an image is formed by the image forming unit 6. A sheet feeding unit 3 having box-shaped sheet feeding cassettes 2 loaded with P in parallel in the vertical direction, a fixing unit 7 for fixing a toner image visualized by the image forming unit 6 to the sheet P, and a fixing unit 7 includes a document transport unit 12 that transports a document of an image fixed in 7 to a document reading unit 11 to be described later, a document reading unit 11 that reflects light on the document transported by the document transport unit 12 and reads a document image. .

  The image forming unit 6 includes an image forming unit 13 that forms a color toner image. The image forming unit 13 includes photoreceptors 5Y, 5M, 5C, and 5K corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K). The image forming unit 13 is different only in the color of the toner t, and other parts have the same configuration. Around the photosensitive member 5, an exposure device 4 including a developing device 14, a laser irradiator 15, a mirror 16 and the like that develop an electrostatic latent image formed on the photosensitive member 5 with toner t, and the photosensitive member 5; A charging roller 17 that generates a corona discharge between them to uniformly charge the surface of the photoconductor 5, a static elimination device (not shown) that returns the surface of the photoconductor 5 to an initial state by applying a predetermined voltage, and a sheet P The primary transfer of the toner image onto the intermediate transfer belt 22 by interposing the intermediate transfer belt 22 between the cleaning device 21 and the photosensitive member 5 that remove the toner t remaining on the surface of the photosensitive member 5 without being completely transferred. A transfer roller 23 and the like are provided.

  The user places a document on the document transport unit 12 and presses a copy switch (not shown). Then, the document is conveyed to the document reading unit 11 and the sheet P is conveyed to the image forming unit 6 from the paper feed cassette 2 selected by the operation unit (not shown). Then, the paper P on which the image is formed by the image forming unit 6 by the electrophotographic process at the correct timing is fixed by the fixing device 7 and discharged to the paper discharge tray 24. Upon completion of copying, the document is discharged to the document transport unit 12.

  A fixing device 7 according to the first embodiment of the present invention shown in FIG. 2 will be described. Since other configurations of the attachment positions of the paper transport sensor 25 and the remaining paper detection sensor 26 are the same as those in the conventional technology, the same parts are denoted by the same reference numerals and description thereof is omitted.

  The sheet conveyance sensor 25 of the fixing device 7 is provided between the remaining sheet detection sensor 26 and the heating roller 31. On the other hand, the remaining sheet detection sensor 26 is disposed downstream of the nip portion in the conveyance direction and on the pressure roller 32 side. The remaining paper detection sensor 26 and the paper transport sensor 25 are connected to a control device 33 provided in the fixing device 7.

The paper transport sensor 25 is arranged at a position where the optical axis irradiated from the remaining paper detection sensor 26 to the heating roller 31 and the optical axis irradiated from the paper transport sensor 25 to the paper P do not intersect in the paper transport path. Established. Here, the optical axis of the remaining sheet detection sensor 26 is configured to irradiate the outer periphery of the heating roller 31 and the downstream portion in the rotation direction from the contact portion between the heating roller 31 and the separation claw 29.

  Further, if the paper transport sensor 25 detects the paper P prior to the remaining paper detection sensor 26, the paper transport sensor 25 is transported normally. On the other hand, the remaining paper detection sensor 26 detects paper before the paper transport sensor 25. If P is detected, the control apparatus 33 will judge immediately as a winding jam.

  When the paper transport sensor 25 outputs a signal for detecting the paper P passing through the paper transport path to the control device 33, the control device 33 determines that the jam is not a winding jam, and the full-color copying machine 1 continues to operate.

  Next, the detection action of the winding jam will be described in detail. The remaining paper detection sensor 26 is arranged with its optical axis directed substantially to the center of the heating roller. As a result, when a paper jam occurs as indicated by the broken line in the figure, the remaining paper detection sensor 26 sets the nip portion to a length of about one-fourth of the circumferential length of the heating roller 31. Is detected, the detection signal is input to the control device 33. On the other hand, the paper transport sensor 25 is arranged with its optical axis facing the upper paper transport path.

  At this time, if there is no paper P passing through the paper conveyance path, the detection signal is not input from the paper conveyance sensor 25 to the control device 33, and the control device 33 determines that the paper jam has occurred. Then, the information is displayed on the display device (not shown) provided in the full-color copying machine 1 from the control device 33, and the user is prompted to perform jam processing. Then, the user immediately stops the full-color copying machine 1 and performs jam handling work. When the user finishes the work after jamming, the full-color copying machine is restored by pressing a reset button (not shown) of the apparatus main body.

  Next, the state of occurrence of winding jam will be described. When the sheet P adheres to the outer peripheral surface of the heating member 31 due to the action of the carried molten toner and rubs between the separation claw 29 and the heating roller 31, the curvature is the same as that of the heating roller 31 and integrated. Wrap around. Then, the tip of the separation claw 29 cannot be interrupted between the heating roller 31 and the paper P, and the separation claw 29 is pushed up and overlaps the paper P that is wound around the heat roller 31 first. When the trailing edge of the paper P passes through the nip portion, there is no portion around the fixing roller 31.

  In the present invention, it is an eye that the detection result of the paper transport sensor 25 is not used as a judgment material for winding jam. That is, the position at which the paper transport sensor 25 intersects the optical axis irradiated from the remaining paper detection sensor 26 to the fixing roller 31 and the optical axis irradiated from the remaining paper detection sensor 26 to the paper P in the paper transport path. Since it is unclear which of the remaining paper detection sensor 26 and the paper transport sensor 25 is detected first, and which is the detection first, it is unknown whether the detection is a winding jam or not. It becomes difficult to determine whether. Further, when the remaining paper detection sensor 26 detects the paper P before the remaining paper detection sensor 26, it takes a predetermined time for the paper transport sensor 25 to determine that the paper P is not transported. The timing for stopping the full-color copying machine 1 is delayed by that time. The paper P wraps around the fixing roller 31 only during this feeding time.

  Further, the heat roller fixing method, which is a fixing device of the image forming apparatus shown in the embodiment, is merely a preferable example, and in the implementation, these components are within the scope of the claims, for example, pressurization. Needless to say, the fixing method, the heat belt fixing method, and the like can be appropriately changed and corrected.

1 is a front view showing a schematic overall configuration of an image forming apparatus according to the present invention. 1 is a schematic side view of a fixing device showing an overall configuration of a first embodiment of the present invention. It is a schematic side view of a conventional fixing device. It is a schematic side view of a conventional fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Full color copying machine (image forming apparatus) 2 Paper feed cassette 3 Paper feed part 4 Exposure apparatus 5 Photoconductor 6 Image forming part 7 Fixing apparatus 11 Document reading part 12 Document conveyance part 13 Image forming unit 14 Developing apparatus 15 Laser irradiator 16 Mirror 17 Charging roller 21 Cleaning device 22 Intermediate transfer belt 23 Primary transfer roller 24 Paper discharge tray 25 Paper transport sensor 26 Remaining paper detection sensor 27 Upper transport guide 28 Lower transport guide 29 Separation claw 31 Heating roller (fixing member)
32 Pressure roller 33 Controller 34 Housing 35 Heater 36 Support shaft t Toner

Claims (4)

A fixing member for fixing the toner image, a separation claw for separating the paper from the fixing member, a remaining paper detection sensor and paper for detecting the remaining of the paper wound around the fixing member in the transport direction A sheet conveyance sensor for monitoring the conveyance state of the fixing member, wherein the remaining sheet detection sensor is arranged below the fixing member and arranged to monitor the outer peripheral surface of the fixing member.
The fixing device, wherein the sheet conveyance sensor is provided between the remaining sheet detection sensor and a fixing member. The paper transport sensor is an optical sensor having a light emitting / receiving unit, and an optical axis irradiated from the remaining paper detection sensor to the fixing member and an optical axis irradiated from the paper transport sensor to the paper are within the paper transport path. The fixing device according to claim 1, wherein the fixing device is disposed at a position where the crossing is not performed. The sheet conveyance path is a space formed between an upper conveyance guide disposed on the downstream side in the conveyance direction with respect to the fixing member and a lower conveyance guide disposed on the lower side of the upper conveyance guide. Item 3. The fixing device according to Item 2. An image forming apparatus comprising the fixing device according to claim 1.

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