JP2007076839A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of detecting overlapping feeding accurately even when conveying a paper by passing through any of left and right wall faces of a conveyance passage. <P>SOLUTION: This image forming device has at least two measuring arms attached to both of left and right sides of the conveyance passage 22, at least two energizing means for energizing at least two measuring arms, respectively, to bring tips of the measuring arms into contact with opposing papers, at least two angle sensors 50, 60 for outputting signals corresponding to rotation angles of respective rotary shafts to which at least two measuring arms are attached, and a control part 70 for determining overlapping feeding of papers by outputs of at least two angle sensors 50, 60. Since the angle sensors 50, 60 are provided on both of left and right sides of the conveyance passage 22 in this way, overlapping feeding of papers can be accurately detected even when a paper is conveyed by passing through any of left side and right side wall faces of the conveyance passage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that transports a sheet along a transport path and transfers a toner image onto the sheet to form an image, and more particularly to an image forming apparatus that detects the thickness of the sheet by an angle sensor.

  In an image forming apparatus such as a copy, a FAX, or a printer, an image carrier such as a photosensitive member is charged, and an electrostatic latent image is formed on the surface of the image carrier by irradiating a laser beam. To form a toner image made of powder toner. Then, a sheet such as a sheet is conveyed one by one along the conveyance path, the toner image on the image carrier is transferred to the sheet, and the toner image on the sheet is fixed to form an image.

  In such an image forming apparatus, for example, as shown in FIG. 1, an angle sensor 100 is provided in a conveyance path 110 that conveys a sheet. In the angle sensor 100, the measurement arm 102 is rotatably supported by the support body 104, and the distal end portion 102 </ b> A of the measurement arm 102 is in contact with the wall surface 110 </ b> A on one side of the conveyance path 110. Then, the measurement arm 102 is rotated by the passage of the paper P, thereby detecting the rotation angle, and detecting the double feed of the paper P based on the detected value (for example, Patent Document 1). reference).

JP-A-9-15996

  However, the double feed detection method described in Patent Document 1 has a problem in that when the angle sensor 100 is arranged near the downstream where the conveyance path 110 is curved, the thickness of the paper P is detected to be larger than the actual thickness. In FIG. 1, the conveyance path 110 is curved on the upstream side in the conveyance direction of the angle sensor 100, and curved portions 112 and 114 for conveying and joining the paper P from different directions are provided. When the paper P travels on the conveyance path 110, it travels along the outer wall surfaces of the curved portions 112 and 114, respectively. That is, when the paper P is transported along the curved portion 112 from the left side in FIG. 1, the paper P travels along the wall surface 110A on the right side (curved side) of the transport path 110 as shown in FIG. To do. On the other hand, when the paper P is conveyed along the curved portion 114 from the right side in FIG. 1, the paper P is moved along the wall surface 110B on the left side (curved side) of the conveyance path 110 as shown in FIG. Run. For this reason, in FIGS. 1A and 1B, the rotation angle of the measurement arm 102 when the paper P passes through the tip portion 102A of the measurement arm 102 varies depending on the path through which the paper P is conveyed. . That is, in FIG. 1B, the paper P floats from the wall surface 110A due to the stiffness (rigidity) of the paper P, and the thickness of the paper P is detected to be larger than the actual thickness. For this reason, there is a problem that double feeding of the paper P cannot be accurately detected.

  Further, in order to prevent the paper P from being lifted, it is conceivable to increase the pressing force of the measuring arm. However, the paper P is transported and jammed.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus capable of accurately detecting double feeding even when a sheet is conveyed through either the left or right wall surface of a conveyance path. To do.

In order to achieve such an object, the image forming apparatus of the present invention includes at least two measurement arms attached to the left and right sides of the conveyance path, and the at least two measurement arms so that the leading ends of the measurement arms are in contact with the opposing paper. At least two urging means for respectively urging the at least two urging means, at least two angle sensors for outputting signals corresponding to the rotation angles of the respective rotation shafts to which the at least two measuring arms are attached, and the at least two angle sensors. Is provided with a double feed judging means for judging double feed of paper.
As described above, according to the present invention, the angle sensors are provided on both the left and right sides of the conveyance path, so that even when the sheet is conveyed through the left or right wall surface of the conveyance path, the double feeding of the sheet is accurately detected. be able to.

In the image forming apparatus, the multi-feed determination unit selects one of the outputs of the at least two angle sensors, and when the output of the selected angle sensor is not within a predetermined range, It is good to judge.
The normal sensor output value when no double feed occurs is stored, and if there is no sensor output value within this normal range, it is judged as double feed, so double feed can be detected easily and accurately. can do.

In the image forming apparatus, it is preferable that the multifeed determination unit selects multifeed by selecting an output value within a predetermined range from outputs of the at least two angle sensors.
An angle sensor whose output value deviates greatly from the predetermined range can accurately detect double feed by not using it for double feed detection.

In the image forming apparatus, the conveyance path upstream of the measurement position of the angle sensor is branched into a plurality of conveyance paths, and a paper feeding device is provided in each of the branched conveyance paths, and the multifeed determination unit is It is preferable to select an angle sensor to be used for paper multi-feed determination by turning on and off a roller for feeding paper from the tray of the paper feeding device. Further, the double feed determination means may select an angle sensor to be used for paper double feed determination based on the output of a sensor provided in each of the plurality of transport paths. The sensor may be a jam sensor that detects a paper jam that occurs on the conveyance path.
It is possible to determine from which direction of the branched conveyance path the sheet is conveyed, and to select an angle sensor that can detect double feeding.

  In the above image forming apparatus, the conveyance path is branched into a plurality of conveyance paths while being curved upstream from the measurement position of the angle sensor, and the sheet is conveyed at the measurement position of the angle sensor by the conveyance path to be conveyed. It is good to pass through any one wall surface of the said conveyance path.

  The present invention can accurately detect double feeding even when a sheet is conveyed through either the left or right wall surface of the conveyance path.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 2 shows an image forming apparatus 10 of the present embodiment. The image forming apparatus 10 is a laser printer using an electrophotographic system. In the image forming apparatus 10, paper trays 12 </ b> A, 12 </ b> B, and 12 </ b> C that store papers of different sizes are disposed in a lower portion of a housing 11. A paper feed roller 14 and a separating roller 16 are disposed in the feeding direction of the paper trays 12A, 12B, and 12C, respectively, and the paper P is conveyed one by one by the paper feeding roller 14 and the separating roller 16 (conveyance path). The details are shown in FIG. 4) and conveyed by the conveying roller 18.

  A large-capacity paper feeding unit 24 that accommodates a large-capacity paper P is disposed on a side portion of the housing 11. In the feeding direction of the large-capacity paper feeding unit 24, a paper feeding roller 26 and a separating roller 28 are disposed. The paper feeding roller 26 and the separating roller 28 feed the paper P one by one to the transport path 21 (see FIG. 4). Supplied.

  As shown in FIG. 4, the conveyance path 21 and the conveyance path 20 merge on the way to form a conveyance path 22, and the paper P is conveyed to the image forming unit 30 by the conveyance path 22. As shown in FIG. 4, the conveyance path 21 is provided with a curved portion 21 </ b> A that is curved from the left with respect to the sheet conveyance direction on the upstream side of the angle sensors 50 and 60 in the conveyance direction. Further, the conveyance path 20 is provided with a curved portion 20A that is curved from the right side with respect to the conveyance direction of the paper P on the upstream side in the conveyance direction of the angle sensors 50 and 60, as shown in FIG. Then, angle sensors 50 and 60 for detecting the thickness of the paper P are provided on the conveyance path 22 immediately after the conveyance path 20 and the conveyance path 21 merge. Further, the conveyance path 20 is provided with a sensor 76 that detects that a sheet has been fed into the conveyance path 20. Similarly, the conveyance path 21 is provided with a sensor 75 that detects that a sheet has been fed into the conveyance path 21. As the sensors 75 and 76, a jam sensor provided in a jam area where a jam is likely to occur may be used. The control unit 70 inputs the signals of the angle sensors 50 and 60 and the sensors 75 and 76 and determines whether or not the paper P is double fed. The angle sensor 50 and the angle sensor 60 will be described later.

  A photosensitive drum 32 that rotates in the direction of the arrow in FIG. 2 is disposed in the image forming unit 30, and a charger that uniformly charges the photosensitive drum 32 along the rotation direction around the photosensitive drum 32. 34, an optical scanning device 36 for irradiating the surface of the photosensitive drum 32 with laser light to form an electrostatic latent image, a developing device 38 for developing the electrostatic latent image on the photosensitive drum 32 with toner, and a transfer A cleaner 42 for cleaning the subsequent photosensitive drum 32 is provided.

  Further, a transfer roller 40 for transferring the toner image on the photoconductive drum 32 to the paper P is disposed at a position facing the photoconductive drum 32 with the conveyance path 22 interposed therebetween. A fixing device 44 for fixing the toner image on the paper P by heating and pressing is disposed on the downstream side of the transfer roller 40 in the conveyance path 22.

  In such an image forming apparatus 10, the surface of the photosensitive drum 32 is charged to a predetermined potential by the charger 34. Then, laser light is irradiated from the optical scanning device 36 to expose the surface of the photosensitive drum 32, and an electrostatic latent image is formed. This electrostatic latent image is developed, for example, when toner adheres to the exposed portion by the developing device 38, and a toner image is formed on the surface of the photosensitive drum 32. The toner image on the surface of the photosensitive drum 32 is transferred to the sheet P conveyed to the position facing the photosensitive drum 32 through the conveying path 22 by the action of the transfer roller 40. Thereafter, the toner image on the paper P is heated and melted by the fixing device 44 installed on the downstream side in the transport direction, the toner image is fixed on the paper P, and the paper P is discharged to the paper discharge tray 46. The toner remaining on the surface of the photosensitive drum 32 without being transferred to the paper P is removed by the cleaner 42.

Here, a detailed configuration of the first angle sensor 50 will be described with reference to FIG. Note that the angle sensor 60 has substantially the same configuration as the angle sensor 50, and therefore the details of the angle sensor 60 are not described.
The angle sensor 50 is disposed in the transport path 22 that transports the paper P. The angle sensor main body 52 is provided with a rotating shaft 53 that is inserted through the support 51, and a measuring arm 54 for detecting the thickness of the paper P is attached to the tip of the rotating shaft 53. A bearing 55 is provided at the tip of the measuring arm 54. A coil spring 56 is wound around the rotary shaft 53, one end 56 </ b> A of the coil spring 56 is locked to one side edge of the measurement arm 54, and the other end 56 </ b> B of the coil spring 56 is provided in a direction perpendicular to the support 51. Locked to the pin 57. The coil spring 56 biases the bearing 55 at the tip of the measurement arm 54 in a direction in contact with the paper P.

  As the paper P passes, the measuring arm 54 rotates in the direction of the arrow shown in FIG. The angle sensor main body 56 outputs a signal corresponding to the rotation angle of the rotary shaft 53, and the rotation output when the paper P passes through the contact position with the bearing 55 and the measurement arm 54 rotates. The thickness of the paper P is detected by the corner. The control unit 70 determines that the paper P has been double fed when the value of the signal output from the angle sensor 50 or 60 is about 1.5 times the value corresponding to the thickness of one paper. It is configured as follows.

  The image forming apparatus according to the present exemplary embodiment includes a plurality of paper feeding devices, and the conveyance paths 20 and 21 that convey the paper fed from each of the paper feeding apparatuses are curved and merge into one conveyance path 22. The conveyance path of the shape to do is provided. Angle sensors 50 and 60 are arranged near the downstream of the portion where the conveyance path is curved.

  The angle sensor 50 is provided upstream of the image forming unit 30 in the transport path 22 in the transport direction and on the left side of the transport path 22 as shown in FIG. Further, the angle sensor 60 is provided on the upstream side in the transport direction from the image forming unit 30 in the transport path 22 and on the right side of the transport path 22 as shown in FIG. In the angle sensor 50, when the paper P does not pass, the bearing 55 is in contact with the right wall surface 22A of the conveyance path as shown in FIG. Similarly, in the angle sensor 60, when the paper P does not pass, the bearing 65 is in contact with the left wall surface 22B of the conveyance path as shown in FIG.

  As shown in FIG. 5A, the paper P fed from the large-capacity paper feeding unit 24 is curved at the curved portion 21A and conveyed through the right wall surface 22A of the conveying path 22. At this time, the angle sensor 60 is largely rotated from the left wall surface 22B as shown in FIG. 5A. Therefore, the double feed of the paper P cannot be accurately detected. Double feed can be detected accurately. Further, the paper P fed from the paper trays 12A, 12B, and 12C is bent by the bending portion 20A as shown in FIG. 5B, and is conveyed through the left wall surface 22B of the conveyance path 22. At this time, the angle sensor 50 is largely rotated from the right wall surface 22A as shown in FIG. 5B. Therefore, the double feed of the paper P cannot be accurately detected. Double feed can be detected accurately.

  The controller 70 determines whether the paper P is fed from the large-capacity paper feed unit 24 or conveyed from the paper trays 12A, 12B, and 12C by the sensors 75 and 76 shown in FIG. The angle sensors 50 and 60 to be turned on are selected according to the determination result. That is, the angle sensor 50 is turned on when paper is fed from the large-capacity paper feeding unit 24, and the angle sensor 60 is turned on when paper is fed from the paper trays 12A, 12B, and 12C. Alternatively, both the angle sensors 50 and 60 may be always turned on, and the output of either one of the angle sensors 50 and 60 may be selected based on the output of the sensors 75 and 76.

  In addition, as shown in FIG. 5A, the paper P that has been transported along the transport path 21 is transported along the right wall surface 22A in the transport path 22, and therefore the output of the angle sensor 60 is determined from a normal measurement value. It is greatly shifted. Similarly, as shown in FIG. 5B, since the paper P that has been transported along the transport path 20 is transported along the left wall surface 22B in the transport path 22, the output of the angle sensor 50 is determined from a normal measurement value. It is greatly shifted. For this reason, the value of the measurement range including the case where double feed occurs can be set in advance, and the output of the angle sensor greatly exceeding this value can be prevented from being used. In this case, the sensors 75 and 76 are unnecessary. This determination method is suitable when thick paper is used as printing paper. In the case of thin paper, the rigidity of the paper may be defeated by the spring force of the angle sensor, and the thickness of the paper may be detected correctly.

  In the embodiment shown in FIG. 2, the sensors 75 and 76 are newly provided to specify the paper transport direction. However, the on / off signal of the large-capacity paper feed unit 24 and the paper trays 12A, 12B, and 12C is provided. It is also possible to determine the sheet conveyance direction. When the large-capacity paper feed unit 24 is turned on, the paper feed roller 26 is driven, so that the feed from the large-capacity paper feed unit 24 can be determined by turning on the paper feed roller 26. When the paper trays 12A, 12B, and 12C are turned on, the paper feed roller 14 is driven, so that the paper feed from the paper trays 12A, 12B, and 12C can be determined by turning on the paper feed roller 14.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

It is a figure for demonstrating the double feed determination method using the conventional angle sensor. 1 is a diagram illustrating a configuration of an image forming apparatus. 2 is a diagram illustrating a configuration of an angle sensor 50. FIG. It is a figure which shows the attachment position of the angle sensors 50 and 60. FIG. (A) is a diagram showing a conveyance path of a sheet fed from a large-capacity paper feeding unit, and (B) is a diagram showing a conveyance path of a sheet fed from a sheet tray.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12A, 12B, 12C Paper tray 18 Conveyance roller 20, 21, 22 Conveyance path 20A, 21A Curved part 22A Right wall surface 22B Left wall surface 24 Large capacity paper feed unit 26 Paper feed roller 28 Rolling roller 30 Image forming part 50 , 60 Angle sensor 52 Angle sensor body 53 Rotating shaft 54 Measuring arm 55 Bearing 70 Controller 75, 76 Sensor

Claims (7)

At least two measuring arms attached to the left and right sides of the transport path;
At least two urging means for urging each of the at least two measurement arms so that the leading ends of the measurement arms are in contact with opposing paper;
At least two angle sensors that output signals corresponding to the rotation angles of the respective rotation axes to which the at least two measurement arms are attached;
A double feed determining means for determining double feed of paper based on outputs of the at least two angle sensors;
An image forming apparatus comprising:   The double feed determining means selects one of the outputs of the at least two angle sensors, and determines that the paper is double fed when the output of the selected angle sensor is not within a predetermined range. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 2, wherein the double feed determination unit selects a double feed by selecting an output value within a predetermined range from outputs of the at least two angle sensors. The conveyance path upstream of the measurement position of the angle sensor is branched into a plurality of conveyance paths, and a paper feeding device is provided in each of the branched conveyance paths,
The image forming apparatus according to claim 1, wherein the multi-feed determining unit selects an angle sensor used for determining multi-feed of paper by turning on and off a roller that feeds the paper from the tray of the paper feeding device. The conveyance path upstream from the measurement position of the angle sensor branches into a plurality of conveyance paths,
The image forming apparatus according to claim 1, wherein the multi-feed determining unit selects an angle sensor to be used for determining multi-feed of paper based on an output of a sensor provided in each of the plurality of transport paths.   The image forming apparatus according to claim 5, wherein the sensor is a jam sensor that detects a paper jam occurring on a conveyance path. The conveyance path is branched into a plurality of conveyance paths while being curved upstream from the measurement position of the angle sensor,
The image forming apparatus according to claim 1, wherein the sheet passes through one of the left and right wall surfaces of the conveyance path at a measurement position of the angle sensor, depending on a conveyance path to be conveyed. .

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