JP2014052488A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents overheating of a sheet non-passing area in a fixing device caused by the fact that the width of a conveyed sheet is shorter than that of a set sheet.SOLUTION: An image forming apparatus 700 includes: a display unit 620 for setting a size of a sheet P conveyed to a fixing device 190; a printer control unit 380 for controlling the fixing device 190; sensors 501 to 504 for detecting a size of the sheet P conveyed to the fixing device; and determination means Z101 for comparing a width of the detected sheet P with a width of a set sheet so as to determine the presence or absence of an abnormality. The determination means Z101 determines that an abnormality is present, after setting a size of the sheet, when a width of a first sheet P conveyed to the fixing device 190 is smaller than the width of the set sheet, and when sizes of sheets other than a firstly conveyed sheet are different consecutively three times.

Description

  The present invention relates to an image forming apparatus that prevents overheating of a non-sheet passing region in a fixing device that fixes an image transferred onto a transfer material.

  In recent years, as a means for heating the fixing roller in the image forming apparatus, a method of generating an eddy current in an induction heating element provided on the inner surface of the fixing roller with a magnetic field by an exciting coil to generate heat by Joule heat (hereinafter referred to as “IH heater heating”). Is proposed).

  IH heater heating allows the heat generation source to be placed very close to the toner image, so that the surface temperature of the fixing roller is suitable for fixing when the image heating apparatus is started, compared to the conventional heat roller method using a halogen lamp. It has the feature that the time required to reach the desired temperature can be shortened. Further, since the heat transfer path from the heat generation source to the toner is short and simple, there is a feature that the thermal efficiency is high.

  However, in an image heating apparatus employing IH heater heating, when a small size transfer material is continuously passed through a fixing device and a large amount of image heating processing is performed, so-called non-sheet passing portion temperature rise occurs. . That is, in the area where the recording material as the transfer material contacts on the surface of the fixing roller (paper passing area), the heat is taken away by the recording material conveyed, whereas the area where the recording material does not contact (non-paper passing area) Then, the recording material is hard to take heat and accumulates. Further, since the sheet passing area is maintained at a predetermined fixing temperature, the temperature of the non-sheet passing area is excessively increased. Such a phenomenon is called non-sheet passing portion temperature rise.

  Therefore, in order to prevent the temperature rise of the non-sheet passing portion, IH heater heating is proposed in which the magnetic core is divided in the width direction orthogonal to the recording material conveyance direction and is movable in the direction away from the excitation coil by the moving means. (For example, refer to Patent Document 1). By moving the magnetic core in the non-paper passing area, the exciting coil and the magnetic core are separated, thereby reducing the efficiency of the magnetic circuit composed of the magnetic core and the induction heating element formed around the exciting coil, and generating heat. Can be reduced, so that the temperature rise of the non-sheet passing portion is avoided.

  On the other hand, when the size of the paper conveyed on the conveyance path is detected by a sensor provided on the upstream side of the registration roller (hereinafter referred to as a registration roller), and a paper having a size different from the set paper size is detected, Techniques for discharging paper out of the machine have been proposed. At this time, the paper is discharged out of the apparatus through the shortest conveyance path (see, for example, Patent Document 2). According to this technology, it is possible to prevent image defects and jams that may occur when the size of the fed paper is different from the set paper size.

JP 2001-194940 A JP 2008-254399 A

  However, in the technique described in Patent Document 1 in which the movement of the magnetic core is finely performed for each paper size, it is necessary to arrange a considerable number of sensor means in order to detect heat generation in the non-sheet passing area. However, there are practical problems in terms of cost and arrangement space.

  Further, in the technique described in Patent Document 2 that detects whether the paper size is a set size by detecting the paper size on the upstream side of the registration roller, the paper size is set in a state where the paper is stopped in order to improve the accuracy of error detection. It is necessary to detect, and the vicinity of the leading edge of the sheet is a detection target in terms of sensor arrangement. For this reason, there is a problem that the size width is erroneously detected when the leading end portion of the sheet is bent at a corner. In addition, when a large amount of paper is set in the paper feeding unit, there is a risk that the uppermost paper may skew greatly when the storage is closed. In this case, the fed paper is skewed upstream of the registration rollers. There is also a problem that even if a line is taken, an image is formed in a skewed state and the resultant product becomes an oblique image. Furthermore, when trying to shift the sensor placement position for detecting the paper length error to the upstream portion of the registration roller, the point where the paper transport paths from all the paper feed cassettes join is located upstream. Since it is necessary to move, there also exists a subject that the whole apparatus enlarges.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that prevents erroneous detection of a size setting error based on corner bending or skew of a sheet. It is another object of the present invention to provide an image forming apparatus capable of preventing overheating of a non-sheet passing area of a fixing device due to a sheet width being conveyed being smaller than a set sheet width.

  In order to solve the above-mentioned problem, the image forming apparatus according to claim 1, a storage unit that stores paper to be fed, a size setting unit that sets a size of the paper stored in the storage unit, and the storage Conveying means for conveying the paper stored in the means, detecting means for detecting the size of the paper conveyed by the conveying means, and the first detecting means after the paper size is set by the size setting means, and the detecting means When the size of the paper detected by the step is different from the set paper size, it is determined that there is an abnormality. On the other hand, the size of the paper detected by the detection unit other than the first transported paper is the set size. And determining means that does not determine that there is an abnormality when different from the above.

  According to the present invention, it is possible to prevent erroneous detection of a size setting error based on a corner bend or skew of a sheet, and further, in the fixing device caused by the sheet width being conveyed being smaller than the set sheet width. It is possible to prevent overheating of the non-sheet passing area.

1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a system controller that controls the entire image forming apparatus of FIG. 1. FIG. 2 is a cross-sectional view of a main part when viewed from the front of the fixing device in the image forming apparatus of FIG. 1. FIG. 2 is an enlarged cross-sectional view illustrating a main part of a fixing device in the image forming apparatus of FIG. 1. FIG. 5 is a partially enlarged perspective view showing a movable part of an excitation shielding member in the fixing device of FIG. 4. FIG. 5 is an exploded perspective view of an induction heating device in the fixing device of FIG. 4. It is a figure for demonstrating the function of the excitation shielding member which adjusts the heat_generation | fever area | region of a fixing device. It is a figure for demonstrating the function of the excitation shielding member which adjusts the heat_generation | fever area | region of a fixing device. FIG. 6 is a diagram showing a heat generation area when a sheet of A5R is continuously passed in a state where the sheet width is set to A4 in the fixing device. It is a figure which shows the conveyance direction length and conveyance width (longitudinal direction length) of various paper. 6 is a flowchart illustrating a conveyance paper size detection processing method. It is a figure which shows the relationship between each paper feed stage and a counter. FIG. 5 is a diagram illustrating an example of arrangement of detection sensors that detect a conveyance width of a sheet. FIG. 6 is a diagram illustrating a state where an A4 sheet is stopped by abutting the leading end of the sheet against a registration roller. FIG. 6 is a diagram for explaining a case where a paper feed cassette on which a large amount of paper is set is closed. FIG. 10 is a diagram illustrating a determination logic in paper conveyance width detection. FIG. 2 is a diagram illustrating an operation unit in the image forming apparatus of FIG. 1. It is a figure which shows the paper size setting screen in an operation part. FIG. 9 is a diagram illustrating a method for determining a paper width setting error. It is a figure which shows the display part screen which tells the effect of a paper width setting mistake. It is a flowchart of a job interruption process. 10 is a flowchart of a sheet conveyance direction length error detection process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the overall configuration of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, a copying machine as an image forming apparatus 700 includes an image forming apparatus main body including a printer unit 300 and an image reader 200, a document feeding device 400 and an operation unit 600 disposed on the image forming apparatus main body. Is mainly composed of

  The exposure control unit 301 of the printer unit 300 modulates and outputs a laser beam based on the input video signal. The output laser light is irradiated onto the photosensitive drum 302 while being scanned by a polygon mirror or the like (not shown). An electrostatic latent image corresponding to the scanned laser beam is formed on the photosensitive drum 302.

  The electrostatic latent image on the photosensitive drum 302 is visualized as a developer image by the developer supplied from the developing device 303. A component that performs such a series of image formation is called an image forming unit. On the other hand, a recording material (hereinafter simply referred to as “paper”) as a transfer material led to a conveyance path from a paper feed cassette 311 or 312 or a manual paper feed tray 313 as a transfer material supply unit is provided with a conveyance roller 321. After that, the front end abuts against the registration roller 314 that has stopped, and then stops. The timing of the temporary stop is controlled by the ON edge of the sheet sensor 322 arranged on the upstream side of the registration roller 314. The paper is bent by being conveyed by the conveying roller 321 for a predetermined time while the leading edge of the sheet abuts against the registration roller 314, and skew correction of the leading edge is performed. In a state in which the skew of the sheet is corrected, a length orthogonal to the sheet conveyance direction (hereinafter simply referred to as “width”) is detected.

  The skew-corrected paper is conveyed again between the photosensitive drum 302 and the transfer unit 304 by the registration roller 314 at a timing synchronized with the start of laser beam irradiation. The developer image formed on the photosensitive drum 302 is transferred onto the fed paper by the transfer unit 304.

  The sheet on which the developer image is transferred is conveyed to the fixing device 190. The fixing device 190 fixes the developer image on the paper by heat-pressing the paper. The paper that has passed through the fixing device 190 is determined by the flapper 318 to be conveyed, and is discharged from the printer 300 to, for example, the paper discharge tray 701 via the discharge roller 316.

  Next, a system configuration of a controller that controls the entire image forming apparatus 700 will be described.

  FIG. 2 is a block diagram showing a configuration of a system controller that controls the entire image forming apparatus of FIG.

  In FIG. 2, the system controller has a CPU circuit unit 350. The CPU circuit unit 350 includes a CPU (not shown), a ROM 351, and a RAM 352, and collectively controls the blocks 480, 280, 281, 282, 283, 380, and 680 by a control program stored in the ROM 351. The RAM 352 temporarily stores control data and is used as a work area for arithmetic processing associated with control.

  The document feeder control unit 480 controls driving of the document feeder 400 based on an instruction from the CPU circuit unit 350. The image reader control unit 280 performs drive control on the scanner unit 201 and the image sensor 203 of the image reader 200, and transfers an analog image signal output from the image sensor 203 to the image signal control unit 281.

  The image signal control unit 281 performs each processing after converting the analog image signal from the image sensor 203 into a digital signal, converts the processed digital signal into a video signal, and outputs the video signal to the printer control unit 380. Also, the image signal control unit 281 performs various processes on the digital image signal input from the computer 283 via the external I / F 282, converts the processed digital image signal into a video signal, and outputs the video signal to the printer control unit 380. To do. The processing operation by the image signal control unit 281 is controlled by the CPU circuit unit 350. The printer control unit 380 drives the above-described exposure control unit 301 based on the input video signal, and performs operations of the image forming apparatus 700 such as charging processing, development processing, transfer processing, fixing processing, paper conveyance, and abnormality detection. To control.

  Next, the fixing device 190 in the image forming apparatus 700 of FIG. 1 will be described.

  In the following description, the longitudinal direction of the fixing device 190 or a member constituting the fixing device 190 refers to a direction orthogonal to the sheet conveying direction in the sheet conveying path, that is, the width direction of the sheet. The direction. Regarding the fixing device, the front means the surface of the fixing device viewed from the paper entrance side, the back means the opposite surface, that is, the surface on the paper exit side, and the left and right refer to the left or right toward the front of the fixing device. The upstream side and the downstream side refer to the upstream side and the downstream side in the paper transport direction.

  FIG. 3 is a cross-sectional view of the main part when viewed from the front of the fixing device 190 in the image forming apparatus 700 of FIG.

  In FIG. 3, the fixing device 190 mainly includes a fixing belt 1 and a pressure roller 2 that presses against the fixing belt 1 to form a nip portion N. Left and right fixing flanges 10 are provided as restricting members that restrict the longitudinal movement and the circumferential shape of the fixing belt 1. A stay pressurizing spring 9b is contracted between both ends of the stay 4 disposed so as to pass through the fixing flange 10 and a spring receiving member 9a on the apparatus chassis side. A pressing force acting in the direction of the portion N is applied. By applying a pressing force to the stay 4, the lower surface of the pressure applying member 3 supported by the stay 4 and the upper surface of the pressure roller 2 are pressed against each other with the fixing belt 1 interposed therebetween to form a fixing nip portion N having a predetermined width. Is done.

  4 is an enlarged cross-sectional view showing a main part of the fixing device in the image forming apparatus of FIG. 1, FIG. 5 is a partially enlarged perspective view showing a movable part of the excitation shielding member 52 in the fixing device of FIG. FIG. 5 is an exploded perspective view of the induction heating device 100 in the fixing device of FIG. 4. In FIG. 4, a block diagram of the control system is also shown.

  In FIG. 4, the fixing device 190 includes an endless fixing belt 1 having a metal layer (not shown), and a pressure roller 2 as a pressure rotating body disposed so as to be in contact with the outer peripheral surface of the fixing belt 1. And a pressure applying member 3 that presses the fixing belt 1 against the pressure roller 2. The pressure applying member 3 forms a fixing nip portion N by applying a pressing force between the fixing belt 1 and the pressure roller 2.

  The fixing belt 1 rotates at substantially the same speed as the conveyance speed of the sheet P carrying the unfixed toner image T conveyed from the image transfer unit 304 (FIG. 1) side as the pressure roller 2 that rotates is rotated. Rotation drive at speed. That is, the pressure roller 2 is rotationally driven by driving a motor M1 (not shown) as drive means controlled by the control circuit 102, and the fixing belt 1 is rotated in accordance with the rotational driving of the pressure roller 2.

  The pressure applying member 3 is held by a metal stay 4, and the counter pressure applying member side of the stay 4 is protected by a magnetic shielding core 5 as a magnetic shielding member in order to prevent a temperature rise by an induction heating device described later. Covered.

  The pressure applying member 3, the stay 4 and the magnetic shielding core 5 are all disposed in a space surrounded by the fixing belt 1. An induction heating device 100 as a heating source for heating the outer peripheral surface of the fixing belt 1 is disposed on the side opposite to the fixing nip portion of the fixing belt 1. The surface of the induction heating device 100 that faces the fixing belt 1 is a curved surface that fits the outer surface of the fixing belt 1. The induction heating device 100 mainly includes an exciting coil 38, an outer magnetic core 37, and a coil holding member 36 that supports these with an electrically insulating resin.

  For example, a litz wire is used as the electric wire, and the exciting coil 38 is formed so as to face the outer peripheral surface and a part of the side surface of the fixing belt 1 by winding the litz wire and forming it into a horizontally long / bottom shape. . The exciting coil 38 and the fixing belt 1 are separated from each other by a predetermined distance while maintaining an electrical insulation state by a mold having a thickness of about 2 mm, for example. The outer magnetic core 37 covers the exciting coil 38 so that the magnetic field generated by the exciting coil 38 does not substantially leak to other than the metal layer (conductive layer) of the fixing belt 1. It is divided into magnetic cores 37R on both sides. The magnetic core 37T and the magnetic core 37R may be integrally formed.

  For example, a temperature sensor (temperature detection element) TH1 such as a thermistor is disposed so as to contact the inner surface of the center portion in the width direction of the fixing belt 1. The temperature sensor TH1 is attached to the pressure applying member 3 via an elastic support member, and even if a positional variation such as a wave of the temperature sensor TH1 attachment surface of the fixing belt 1 occurs, good contact is made following this. The state is configured to be maintained. The temperature sensor TH1 is connected to the excitation circuit 101 via the control circuit 102. The temperature sensor TH 1 detects the temperature of the sheet passing area of the fixing belt 1, and the detected temperature is fed back to the control circuit 102.

  That is, for example, a high frequency current of 20 to 60 kHz is applied to the excitation coil 38 from the excitation circuit 101 as a power supply device to generate a magnetic field, and the metal layer of the fixing belt 1 is inductively heated by the generated magnetic field. The target temperature of the fixing belt 1 is, for example, 180 ° C., and the power input to the exciting coil 38 is controlled by changing the frequency of the high-frequency current based on the detection value of the temperature sensor TH 1 so as to keep 180 ° C.

  Since the induction heating device 100 including the exciting coil 38 is arranged outside the fixing belt 1 that becomes high in temperature, the exciting coil 38 is unlikely to become high in temperature, the electric resistance does not increase, and a high-frequency current flows. Also, the loss due to Joule heating can be reduced. In addition, since the exciting coil 38 is disposed outside the fixing belt 1, the fixing belt 1 can be reduced in diameter (lower heat capacity), and is excellent in energy saving.

  The heat generation area in the induction heating device 100 is set by a magnetic flux shielding member 52 that slides between the fixing belt 1 and the excitation coil 38 along the longitudinal direction of the induction heating device 100. Since the magnetic flux shielding member 52 is disposed between the fixing belt 1 and the exciting coil 38, the magnetic flux shielding member 52 is held by the slide member 51 so as not to come into contact with the fixing belt 1, and in the longitudinal direction as the slide member 51 moves. Moving. A stopper member 53 that prevents the magnetic flux shielding member 52 from contacting the fixing belt 1 is provided along one end of the coil holding member 36.

  In FIG. 5, which is a partially enlarged perspective view showing the movable portion of the excitation shielding member 52, the magnetic flux shielding member 52 is held by a slide member 51 that engages with the lead screw member 50 and moves in the longitudinal direction of the induction heating device 100. Yes. The cylindrical portions 51c and 51d of the slide member 51 are fitted on the screw portion 50a (50b) of the lead screw member 50, and the boss portion 51b is engaged with the screw portion 50a (50b). In order to reduce the contact area between the slide member 51 and the lead screw member 50, a three-point contact structure is used, but a configuration in which contact is made at three or more points may be employed.

  In FIG. 6, which is an exploded perspective view of the induction heating device 100, the outer magnetic core 37 composed of the magnetic cores 37 </ b> T and 37 </ b> R is divided in the longitudinal direction of the induction heating device 100.

  The lead screw member 50 is arranged in parallel along the longitudinal direction of the coil holding member 36, and screw portions 50a and 50b that are wound in opposite directions on one side and the other side with respect to the central portion in the longitudinal direction. Is formed. End portions 50c and 50d of the screw portions 50a and 50b are rotatably supported by bearing portions 36a and 36b at both ends of the coil holding member 36, respectively. In addition, it can replace with the bearing parts 36a and 36b, and can provide a durable bearing member separately.

  The two slide members 51 holding the magnetic flux shielding member 52 receive driving force from the lead screw member 50 and move symmetrically with respect to the central reference line of the conveyance width of the paper P. By rotating the lead screw member 50 in the direction of arrow A in FIG. 6, the slide members 51 holding the magnetic flux shielding members 52 arranged at both ends move in the direction of arrow C, respectively. On the other hand, by rotating the lead screw member 50 in the direction of arrow B in FIG. 6, the two slide members 51 holding the magnetic flux shielding members 52 disposed at both ends move in the direction of arrow D, respectively.

  At this time, the drive motor M2 (not shown) for driving the lead screw member 50 is controlled by a control unit (printer control unit 380: see FIG. 2) as a control unit based on a signal from the HP sensor SNS. The HP sensor SNS is a photo interrupter, and the light shielding is turned ON / OFF by a flag portion 51a (see FIG. 5) provided on the slide member 51. In consideration of driving variations such as backlash transmitted from the drive motor M2 to the lead screw member 50, the HP sensor SNS detects the edge of the flag portion 51a, and the position of the magnetic flux shielding member 52 is controlled. Specifically, the position control is performed by changing the pulse amount based on the edge reference of the HP sensor SNS according to the paper width (transfer material width) W to be conveyed. The paper width is set by the operation unit 600. Specific paper width setting will be described later.

  As long as the moving means of the magnetic flux shielding member 52 is a structure that symmetrically moves the magnetic flux shielding member 52 to both ends in the longitudinal direction with respect to the central reference of the conveyance width of the paper P, a structure other than the above, for example, a wire or the like is used. It is also possible to use a moving means having another structure.

  In the fixing device 190 having such a configuration, electric power is supplied from the exciting circuit 101 controlled by the control circuit 102 to the exciting coil 38 of the induction heating device 100 to heat the fixing belt 1 to a predetermined fixing temperature.

  In a state where the temperature of the fixing belt 1 is adjusted, a sheet (recording material) P having an unfixed toner image T is applied to the fixing nip portion N where the fixing belt 1 and the pressure roller 2 are in contact with each other. It is guided and introduced by a guide member so that the side is the fixing belt 1 side. The paper P introduced into the fixing nip N is brought into close contact with the outer peripheral surface of the fixing belt 1 and is conveyed while being sandwiched between the fixing nip N together with the fixing belt 1. As a result, the heat of the fixing belt 1 is applied to the paper P, and the unfixed toner image T is fixed to the surface of the paper P by receiving pressure from the fixing nip N. The sheet P that has passed through the fixing nip N is separated from the outer peripheral surface of the fixing belt 1 along with the deformation of the fixing belt 1 at the exit of the fixing nip N, and is conveyed outside the fixing device.

  By the way, in a fixing device that fixes a transferred image onto the paper P, when a large amount of image heating processing is performed by continuously passing paper having a size smaller than the set paper size, so-called non-paper passing is performed. Part temperature rise occurs. In order to avoid such a temperature increase in the non-sheet passing portion, in the present embodiment, the heat generation area in the longitudinal direction of the fixing device 190 is adjusted using the magnetic flux shielding member 52.

  7A and 7B are views for explaining the function of the excitation shielding member 52 that adjusts the heat generation area of the fixing device 190. FIG.

  7A and 7B, the paper P (not shown) is transported on a central basis with respect to the longitudinal direction orthogonal to the transport direction, and the two slide members 51 holding the magnetic flux shielding member 52 are transported in the transport direction of the paper P. Are arranged symmetrically at both ends of the central reference in the longitudinal direction perpendicular to the axis.

  Hereinafter, a method for adjusting the heat generation area corresponding to the maximum sheet width W1 in the fixing device 190 will be described with reference to FIG. 7A.

  In FIG. 7A, in order to correspond to the maximum sheet width W1 in the longitudinal width of the sheet P, the outer magnetic core 37 is arranged so that the maximum width along the longitudinal direction of the sheet P is W1. The maximum sheet width represents the maximum sheet width that the image forming apparatus permits conveyance. Between the exciting coil 38 and the fixing belt 1, for example, a plate-like copper magnetic flux shielding member 52 is slidably disposed. The magnetic flux shielding member 52 may be made of a nonmagnetic metal such as aluminum, silver, gold, or brass, or an alloy thereof, in addition to copper, as long as it is a material that shields magnetic flux, and is also a high permeability member such as ferrite or permalloy. It may be made of a material such as The magnetic flux shielding member 52 may be disposed between the exciting coil 38 and the outer magnetic core 37 or between the fixing belt 1 and the magnetic shielding core 5 (see FIG. 4).

  The magnetic flux shielding member 52 is disposed so as to face both end portions of the fixing belt 1 in the longitudinal direction. The longitudinal width 52W of the magnetic flux shielding member 52 corresponds to the longitudinal outer shape portion of the supporting side plate 12 of the fixing belt 1 and the outer magnetic core 37. The width is adjusted to be equal to or smaller than the width that can be arranged at the difference position. This is to ensure a sufficient width for exhibiting the magnetic flux shielding effect, not to reduce the maximum heat generation width (W1) corresponding to the maximum sheet width, and a width that can be arranged without increasing the longitudinal width of the fixing device 190. This is because.

  By providing the magnetic flux shielding member 52, it is possible to weaken the magnetic flux formed by the exciting coil 38 and the outer magnetic core 37 from passing to the fixing belt heat generating layer 1a, thereby controlling the heat generating region.

  In order to fully exhibit the magnetic flux shielding effect, the relationship between the longitudinal width 52W of the magnetic flux shielding member 52 and the longitudinal width 37W of each divided outer magnetic core 37 is adjusted as follows.

52W> 37W (1)
If the above condition is not satisfied, the width at which the temperature rise reduction effect at the edge of the paper P is expressed by the magnetic flux shielding member 52 is smaller than the width of the outer magnetic core 37W. The reduction effect is not fully expressed. Therefore, as shown in equation (1), the width of the magnetic flux shielding member 52 is set to be larger than the width of the outer magnetic core 37W.

  When the sheet having the maximum sheet width W1 is conveyed, the magnetic flux shielding member 52 is disposed outside the area of the maximum sheet width W1, and secures a heat generation area corresponding to the maximum sheet width W1.

  Next, a method for adjusting the heat generation area corresponding to the minimum sheet width W2 will be described with reference to FIG. 7B.

  7B, the magnetic flux shielding member 52 is moved from the position shown in FIG. 7A in the direction of arrow C in order to make the heating area of the induction heating device 100 correspond to the minimum paper width W2. Note that the minimum sheet width represents the minimum width of the sheet that the image forming apparatus permits conveyance. As a result, the magnetic flux shielding member 52 is inserted into both ends of the heat generation width W1 formed by the outer magnetic core 37, and the magnetic flux width passing through the fixing belt 1 is reduced, so that the minimum paper width W2 is reached. A heat generation region corresponding to is formed.

  FIG. 7C is a diagram illustrating a heat generation area when A5R sheets are actually conveyed continuously with the sheet width set to A4 in the fixing device.

  In FIG. 7C, end thermistors 510 and 511 that detect the end temperature of the fixing belt 1 are arranged corresponding to the end on the back side of the fixing belt 1. When A4 paper having the maximum paper width W1 is set, the entire surface of the fixing belt 1 in the width direction becomes a heat generating region, and the temperature rise at the end in the width direction of the fixing belt 1 is detected by the end thermistors 510 and 511. Is done.

  As described above, when an A4R sheet having a maximum sheet width W1 is set and an A5R sheet is passed, both ends of the fixing belt 1 on which the thermistors 510 and 511 are arranged are not passed. Since it becomes a paper region and heat is not taken away by the paper, it becomes an abnormal heat generation region. If such an abnormal heat generation region continues to occur, the fixing belt 1 may be deformed. For example, the temperature of the fixing belt 1 increases by 20 ° C. every second and deforms when the temperature exceeds 300 ° C. For this reason, when the paper width is different from the set width, it is necessary to take measures such as interrupting heat generation before reaching an abnormal temperature and interrupting continuous conveyance.

  Since the fixing temperature of the fixing belt 1 is normally adjusted to 180 ° C., there is a margin of, for example, 120 ° C. (300−180 = 120) until the fixing belt 1 is deformed, and 6 seconds ( There is a margin of 120/20 = 6). Therefore, it is preferable to perform processing for avoiding the abnormality within 6 seconds after the abnormality is detected. In this case, if the image forming apparatus has a capacity of 75 sheets / minute, for example, 800 ms is required for image formation per sheet, so there is a margin for about 7 sheets. In FIG. 7C, it is assumed that A5R paper is passed by the A4 paper setting shown in FIG. 8 and B6R paper is passed by the B5 paper setting.

  On the other hand, when the length in the transport direction is different, such as when the A5R paper is passed in the A4R paper setting, the length in the paper transport direction is separately checked, and the length is compared to the set length. If is short or long, it is forcibly stopped at the registration roller portion. This is to avoid the occurrence of a jam during the downstream conveyance control. For example, the sheet sensor 322 detects the length in the sheet conveyance direction.

  Next, conveyance paper size detection processing using the image forming apparatus according to the present embodiment will be described.

  FIG. 9 is a flowchart illustrating a conveyance paper size detection processing method.

  When the power of the image forming apparatus is turned on and the conveyance sheet size detection process is started for the image formation process, the printer control unit 380 (see FIG. 2) displays counters C for all sheet feed stages such as a sheet feed cassette. The counter D and the size error determination flag are cleared (step S101). The size error determination flag is a flag that is turned ON when it is determined that a paper size setting error has occurred. Next, the printer control unit 380 determines whether or not the storage of any paper feed stage is open (step S102). At this time, the manual feed tray 313 determines that all sheets on the manual feed tray 313 have been removed, or that all sheets have been fed by a printing operation, and a sheet presence / absence detection sensor (not shown) has determined that there is no sheet. If so, it is determined that the storage is open.

  As a result of the determination in step S102, if the storage is open in any of the paper feed stages, the printer control unit 380 clears the counter C of the corresponding paper feed stage (step S103), and then enters the print start state. It is determined whether or not (step S104). Note that the counter of each paper feed stage is as shown in FIG. 10, and has an independent value for each paper feed stage. On the other hand, as a result of the determination in step S102, if the storage is not open in any of the paper feed stages, the printer control unit 380 advances the processing to step S104 and determines whether the print start state has been entered. . The print start state is a state in which the CPU circuit unit 350 (see FIG. 2) notifies the printer control unit 380 of a job start event. Based on the notification of the job start event, the printer control unit 380 determines that it is in the print start state.

  If it is determined in step S104 that the print start state has not been reached, the printer control unit 380 returns the process to step S102. On the other hand, in the print start state, the printer control unit 380 determines whether paper feed data for starting paper feed is sent from the image signal control unit 281 (step S105). If not, wait until it is sent. Here, the paper feed data is data indicating from which paper feed stage the paper is fed, and is data in units of one page. FIG. 10 shows that five pages have already been fed from the cassette 1.

  If the paper feed data is sent from the image signal control unit 281 as a result of the determination in step S105, the printer control unit 380 controls to feed paper from the corresponding paper feed stage based on the paper feed data. (Step S106). Next, the printer control unit 380 waits for the fed paper to reach before registration (step S107), and after reaching the sheet sensor 322, feeds the paper in the paper feed stage. The counter C is incremented by 1 (step S108).

  Next, the printer control unit 380 advances the process to step S109, detects the paper width, and determines whether there is a paper width setting error (abnormal) (step S109).

  A paper width setting error is performed using a paper width detection sensor.

  FIG. 11 is a diagram illustrating an arrangement example of detection sensors that detect the width of a sheet.

  In FIG. 11, four detection sensors 501 to 504 of width detection sensors in a conveyance path 100 mm between the conveyance roller 321 and the registration roller 314 have a position of 103 mm on the left and right with respect to the center in the width direction of the paper. , 143.2 mm are arranged in plural. The distance between the registration roller 314 and the width detection sensors 501 to 504 is, for example, 15 mm. Each width detection sensor can detect a sheet within a range of ± 2.5 mm with respect to the sensor center. The sheet sensor 322 is used when determining the timing at which the leading edge of the sheet hits the registration roller 314.

  The width detection sensors 501 to 504 detect the width of the sheet at the timing after the leading edge of the sheet hits the registration roller 314 and is conveyed by the conveyance roller 321 for a certain period of time depending on the combination. When the conveyance of the sheet by the conveyance roller 321 is stopped, the skew of the leading end of the sheet is corrected, so that the width of the sheet can be detected correctly.

  By the way, when the paper is bent, the paper width is not accurately detected. FIG. 12 is a diagram illustrating a state where the A4 sheet is stopped by abutting the leading edge of the sheet against the registration roller 314.

  In FIG. 12A, the sheet width detection sensor 504 is not turned ON because the sheet is bent at a corner. In FIG. 12B, since the A4 sheet is skewed greatly, the width detection sensor 501 that should normally be turned on as in the case of corner breakage is not turned on.

  As a cause of the large skew of the paper, for example, as shown in FIG. 13, there is a stacking failure when a large amount of paper is set. FIGS. 13A and 13B are diagrams for explaining a case where a paper feeding cassette in which a large amount of paper is set is closed, FIG. 13A is a side view thereof, and FIG. 13B is a view seen from above. . In FIG. 13A, the sheet 593 is the uppermost sheet when a large amount of sheets are set, and it can be seen that the sheet 593 is shifted compared to other sheets. In FIG. 13B, since a large number of sheets are set, the uppermost sheet 593 exceeds the height of the side regulating plates 590 and 591 and the trailing edge regulating plate 592 for regulating the sheets. Is off. Here, a side regulating plate 590, which is arranged on the back side and regulates the left end of the paper when being carried into the fixing device, is arranged on the near side, and is a side regulating plate that regulates the right end of the paper when being carried into the fixing device. Is 591. Such a large skew of the sheet is likely to occur when, for example, the sheet feeding cassette is closed with a large amount of sheets set in the sheet feeding cassette.

  Next, criteria for determining the width of the paper will be described.

  FIG. 14 is a diagram showing a definition for determining whether or not the set paper width matches the detected paper width, and this data Z101 is stored in the ROM 351.

  In the paper width detection, the width detection sensors 501, 502, 503, and 504 are selectively used. When the width detection sensor is ON, it is determined that there is a sheet, and when it is OFF, it is determined that there is no sheet. In the figure, “-” indicates that the sensor is not used for determination of a size setting error. For example, when A4 paper is set (= paper width is 297 mm), if any of the width detection sensors 501, 502, 503, and 504 is not ON, the paper is actually passed through the set paper. Judge the paper is small. That is, in FIG. 14, an abnormality is detected when a detection result that cannot be obtained when the set sheet is conveyed as set is obtained.

  In FIG. 14, in the case of * 1, the paper having a width of 202 mm to 212 mm is sure to have the width detection sensor 502 or 503 turned on. Therefore, when the four sensors are turned off, it is determined that the actual paper is small. It is recognized as abnormal. Since the interval between the width detection sensors 502 and 503 is 206 mm and the detection range of the width detection sensor is ± 2.5 mm from the sensor center, the width direction center of the 202 mm width sheet and the width direction center of the conveyance path are If they match, the sensors 502 and 503 are turned on.

  In the case of * 2 and * 3, even if the center of the paper width with respect to the center in the width direction varies somewhat, the sensors 502 and 503 are always turned on. In other cases, it is determined that the paper is small. To do. Further, in the case of * 4, since the three sensors are sure to be turned on, it is determined that there is an abnormality if the two sensors are turned off. In the case of * 5, as described above, the four sensors should be turned on as described above. In other cases, it is determined that there is an abnormality.

  By the way, in the present embodiment, it is premised that a case where the length in the conveyance direction of the paper is the same and the paper width is different is detected as a misset paper. This is because the length in the transport direction of the paper is separately detected, and if the length in the transport direction is different from the set length, it is determined that the sheet is misset. Cases where the lengths in the transport direction of the paper are the same and the paper widths are different include the case where A5R is passed while A4 is set, and the case where B6R is passed while B5 is set. . Considering this case, the sensor setting when the paper width is short only needs to detect 257 mm or more. On the other hand, assuming that the misset detection in the length in the transport direction is not detected due to the mechanical crossing although it is a case that is easy to be mistaken like the case of A4R and LTRR (paper width is 215.9 mm), 212 mm The sensor is arranged so that it can be separated by. The paper width of A4R is 210 mm, and the paper width of LTRR is 215.9 mm.

  In addition, when the width of the fed paper (detected paper width) is larger than the set paper width, it is not regarded as a size setting error, and the above-described counter D is not updated. This is because even if the width of the actually transported paper is wider than the width of the heating area of the fixing device, the fixing device will not be heated abnormally due to the difference in size, and the fixing device will not be damaged. is there.

  Here, a paper width setting operation, which is a precondition for paper width detection, will be described.

  FIG. 15 is a diagram showing the operation unit 600 in the image forming apparatus 700 of FIG.

  15A, the operation unit 600 includes a start key 602 for starting an image forming operation, a stop key 603 for interrupting the image forming operation, and numeric keys 604 to 612 and 614 for setting a numerical value. Has been placed. The operation unit 600 includes a user setting mode key 613, a clear key 615, a reset key 616, and the like. In addition, a display unit 620 formed with a touch panel is disposed on the operation unit 600, and a soft key can be created on the screen.

  When the screen as shown in FIG. 15A is displayed on the operation unit 600, the user sets the paper size stored in the paper cassette from the menu displayed by pressing the user setting mode key 613. When the paper size setting is selected, a paper size setting screen as shown in FIG. 16 is displayed on the display unit 620. The paper size is set using this screen. That is, the paper size is set by inputting the paper width Y and the conveyance direction length X in units of 1 mm on the paper size setting screen of FIG. When the printing operation is being executed, a screen for pop-up displaying the number of prints and the like is displayed on the display unit 620 as shown in FIG. 15B.

  Returning to FIG. 9, when it is determined that there is no abnormality (paper width setting error) as a result of the determination in step S109, the printer control unit 380 clears the counter D of the paper feed stage of the fed paper (step S110). ).

  Here, the paper width setting error means that the paper width in the set paper size is different from the width of the conveyed paper. However, in the present embodiment, when the first sheet is fed from the sheet feeding stage immediately after the sheet size is set, there is a high possibility of a size setting error, so as shown in FIG. For the size difference immediately after the size setting, the abnormality is notified at the first abnormality detection, and the image formation is stopped. The sheet feeding immediately after the size setting is a sheet feeding immediately after the power is turned on or when an opened sheet feeding stage is closed. On the other hand, if a paper width setting error occurs after the second sheet is fed, there is a high possibility that the paper will be bent or skewed. Is not notified, an abnormality is notified when it is detected that a predetermined number of images are continuously different, and image formation is stopped. The predetermined number of times is, for example, three times. Accordingly, for example, as shown in FIG. 17B, in the count data of the paper feed cassette 1 in FIG. 10, for example, the sheet due to the corners of the fourth and fifth page sheets being folded. Even if a width setting error occurs, it is not judged abnormal. In this case, since the 6th page paper other than the 4th and 5th page paper is conveyed in a normal state, the abnormalities on the 4th and 5th pages may be erroneously detected. is there. As a result, the accuracy in detecting a true sheet width setting error can be increased.

  In step S109 and step 110 in FIG. 9, after the paper width setting error is not detected and the paper feed stage counter D of the fed paper is cleared, the printer control unit 380 advances the process to step S111. That is, the printer control unit 380 waits for the re-conveying of the temporarily stopped paper in a state where the front end of the paper is abutted against the registration roller 314 (step S111). Then, after the re-conveyance is performed, a length error in the paper conveyance direction described later is detected (step S121).

  Next, the printer control unit 380 determines whether or not a job completion notification is received from the image signal control unit 281 (step S112). If the result of determination in step S112 is that no notification of job completion has been received from the image signal control unit 281, the process returns to step S105. On the other hand, if it is determined in step S112 that the image signal control unit 281 has received a notification that the job has ended, the printer control unit 380 advances the process to step S113. That is, the printer control unit 380 waits for all sheets being conveyed to be discharged from the apparatus to the discharge tray 701, and after all the sheets have been discharged to the discharge tray 701, the size error determination flag. It is determined whether or not is ON (step S114). If the size error determination flag is not ON as a result of the determination in step S114, the printer control unit 380 returns the process to step S102. On the other hand, as a result of the determination in step S114, if the size error determination flag is ON, the printer control unit 380 informs the display unit 620 of the operation display unit control unit 680 that a paper width setting error has occurred as shown in FIG. A communication screen is displayed (step S115).

  In the example of FIG. 18, a message for confirming the paper size of the cassette 311 in which a paper size different from the set size is contained is displayed. When the paper setting key is pressed in the screen of FIG. 18, the screen changes as shown in FIG. 16, and the paper size can be set. When the OK key is pressed on the screen of FIG. 16, the screen returns to the screen of FIG. Further, when the cancel key is pressed in the screen of FIG. 18, the temporarily suspended job is cancelled, and the display unit 620 returns to the normal screen of FIG. Also, when the resume key is pressed on the screen of FIG. 18, the temporarily suspended job is resumed from the page on which no image is formed yet. The job is restarted by the CPU circuit unit 350 notifying the printer control unit 380 of a job start event, as described in the process of step S104. Thereafter, the display unit 620 returns to the display screen during printing shown in FIG.

  In step S115, after the setting error is displayed on the operation unit, the printer control unit 380 clears the counter D of the paper determined to have a setting error (abnormality), and clears the size error determination flag (step S116). The process returns to step S101.

  On the other hand, as a result of the determination in step S109, if there is a mistake in setting the paper width, the printer control unit 380 determines whether the storage counter C for the fed paper is 1 (step S117). As a result of the determination in step S117, if the storage counter C for the fed paper is not 1, the printer control unit 380 adds 1 to the storage counter D for the fed paper (step S118). Next, the printer control unit 380 determines whether or not the storage counter D of the fed paper is 3 (step S119). As a result of the determination in step S119, if the storage counter D of the fed paper is not 3, the printer control unit 380 advances the process to step S111. On the other hand, as a result of the determination in step S119, if the storage counter D of the fed paper is 3, the printer control unit 380 executes a job interruption process described later (step S120), and then the process proceeds to step S112. And proceed.

  As a result of the determination in step S117, if the storage counter C of the fed paper is 1, and the paper is the paper that is fed first after the size setting in the paper feed stage, the printer control unit In step 380, the process proceeds to step S120. As a case where it is determined in step S117 that the storage counter C in the fed paper cassette is 1, for example, the case shown in FIG. FIG. 17A shows a case where the first sheet fed after the size is set is a sheet having a shorter width than the heat generation area of the fixing device. When the power is turned on or when the size of the first paper fed after opening / closing the storage is different from the set size, there is a high possibility that the paper size is wrongly set, so the processing is shifted to the job interruption processing in step S120. And proceed.

  Next, the job interruption process in step S120 in FIG. 9 will be described with reference to FIG.

  FIG. 19 is a flowchart of job interruption processing.

  In FIG. 19, when the job interruption process is started, the printer control unit 380 sets a size setting error determination flag to ON (step S201). Next, the printer control unit 380 determines whether there is next paper feed data (step S202). If it is determined in step S202 that there is next paper feed data, the printer control unit 380 suspends the job (step S203). Thereafter, the printer control unit 380 waits for the paper that has reached the registration roller 314 to be re-conveyed (step S204), and if the paper that has reached the registration roller 314 has been re-conveyed, the printer control unit 380 exits the process. (RETURN). On the other hand, if the result of determination in step S202 is that there is no next paper feed data, the printer control unit 380 advances the process to step S204, and then exits the process (RETURN).

  Next, the sheet conveyance direction length error detection in step S121 in FIG. 9 will be described with reference to FIG. FIG. 20 is a flowchart of a sheet conveyance direction length error detection process.

  First, the printer control unit 380 determines whether or not the sheet sensor 322 has detected the trailing edge of the sheet (ON → OFF). If not, the printer control unit 380 waits until OFF is detected (step S301). When the sheet sensor 322 detects OFF, the trailing edge of the sheet is detected. After the trailing edge of the paper is detected, the printer control unit 380 advances the process to step S302. In step S302, the length of the paper in the conveyance direction is determined. The length in the paper transport direction is determined by the following calculation.

  That is, the distance from the registration roller 314 to the sheet sensor 322 corresponds to the number of clocks from when the registration motor (not shown) that drives the registration roller 314 is re-driven until the sheet sensor 322 detects the trailing edge of the sheet. Add length. Thereby, the length of the sheet in the conveyance direction is obtained. Next, the printer control unit 380 determines whether or not the difference between the length in the paper transport direction and the length in the paper transport direction set in FIG. 18 is, for example, 15 mm or more (step S303). If the difference in length is 15 mm or more, it is determined that a setting error has occurred, the job is interrupted (step S304), and then the process is exited. As a result of the determination in step S303, if the difference between the length in the paper transport direction and the length in the paper transport direction set in FIG.

  According to the processing of FIG. 9, FIG. 19, and FIG. 20, the paper size is detected by preventing erroneous detection based on corner bending or skew of the paper, and when the paper width is shorter than the paper setting size, It is possible to prevent an increase in temperature at the end of fixing by guiding a sheet setting error on the operation unit. Further, when a plurality of sheets are largely skewed due to overloading of sheets in the sheet feeding cassette, it is possible to prevent misprinting in which image formation is performed while keeping skewing.

DESCRIPTION OF SYMBOLS 1 Fixing belt 2 Pressure roller 37 Outer magnetic body core 38 Excitation coil 52 Magnetic flux shielding member 100 Induction heating apparatus 190 Fixing apparatus 300 Printer part 380 Printer control part 501-504 Width detection sensor 600 Operation part 700 Image forming apparatus

Claims (8)

Storage means for storing paper to be fed;
Size setting means for setting the size of the paper stored in the storage means;
Conveying means for conveying the paper stored in the storage means;
Detecting means for detecting the size of the paper conveyed by the conveying means;
The paper is first transported after setting the paper size by the size setting means, and when the paper size detected by the detection means is different from the set paper size, it is determined as abnormal, while the paper is transported first. Determination means that does not determine that there is an abnormality when the size of the paper detected by the detection means is other than the set size,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the determination unit determines that an abnormality occurs when a predetermined number of sheets other than the first sheet to be conveyed continuously differ in size. A fixing unit that heats and fixes the toner image formed on the sheet conveyed by the conveying unit to the sheet;
The fixing unit determines a heat generation area according to the width of the sheet set by the size setting unit, and the determination unit sets the sheet width detected by the detection unit by the size setting unit. 3. The image forming apparatus according to claim 1, wherein an abnormality is determined when a non-sheet-passing portion in which the sheet does not pass is formed in the heat generating area that is smaller than the width of the image forming area.   4. The image forming apparatus according to claim 3, wherein the determination unit does not determine that there is an abnormality when the width of the sheet detected by the detection unit is larger than the width of the sheet set by the size setting unit. apparatus.   The determination unit determines that an abnormality occurs when a length of the paper in the conveyance direction detected by the detection unit is different from a length of the paper in the conveyance direction set by the setting unit. The image forming apparatus according to 3 or 4.   A selection unit configured to select change of the set paper size, stop or restart of image formation when the size of the paper detected by the detection unit is different from the size of the paper set by the size setting unit; The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 6, wherein when the selection unit selects to stop image formation, all the sheets being conveyed by the conveyance unit are discharged.   The detection unit includes a plurality of sensors arranged along a width direction orthogonal to a sheet conveyance direction, and detects a sheet size in the width direction by a combination of the plurality of sensors. Item 8. The image forming apparatus according to any one of Items 1 to 7.

Images