JP4553760B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet by moving a print head in the main scanning direction and moving the sheet in the sub-scanning direction, and more particularly, stains on a conveying belt that conveys the sheet. Is related to the detection of

As described in Patent Documents 1 and 2, etc., in an image forming apparatus, in order to detect the presence or absence of a sheet by a conveyance unit that conveys the sheet, light is emitted to the conveyance unit and light reflected from the sheet is received. In some cases, a sensor having a configuration for detecting the presence of a sheet is mounted.
JP 2004-122681 A Japanese Patent No. 2788905

  However, in the conventional technique, when an abnormal operation such as a paper jam during image formation occurs, a developer or the like may adhere to a conveyance belt as a paper conveyance means, and the above-described paper detection is performed. When performing, there is a possibility that the presence of dirt such as an attached developer is erroneously detected as paper.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of solving the problems of the prior art, preventing erroneous detection of paper detection due to dirt, and improving the reliability of paper detection.

  In order to achieve the above object, an invention according to claim 1 is an image forming apparatus for forming an image on a sheet by moving a print head in a main scanning direction and moving a sheet in a sub scanning direction. A carriage that moves the print head in the main scanning direction, a conveyor belt that moves the paper in a predetermined direction, and a light that is mounted on the carriage and emits light to the conveyor belt and is reflected from the conveyor belt And a belt state determination unit that compares the output from the sheet detection sensor with a preset reference value to determine the state of contamination on the conveyor belt. With this configuration, the paper is sensed on the conveyor belt before paper detection to determine whether the conveyor belt is dirty. It is possible to prevent erroneous detection of sheet presence at transport.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the invention, the belt state determination unit detects a sheet in a portion of the conveyance belt that is determined to be free of dirt, and this configuration is used. In addition, it is possible to detect the presence or absence of a sheet while avoiding a dirty portion during sheet conveyance.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, when the belt state determination unit determines that there is a stain of a reference value or more, the conveyance belt is cleaned. With this configuration, it is possible to transport the paper or detect the presence or absence of the paper after cleaning, and reliably prevent erroneous detection of the paper.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, when the belt state determination unit determines that there is a stain of a reference value or more, a notification signal is output to the outside of the apparatus. With this configuration, for example, it is possible to notify the person who performs maintenance or the service center that the removal of the dirt on the conveyor belt is necessary.

  According to the present invention, a belt state determination unit that compares the output from the sheet detection sensor with a preset reference value and determines the state of dirt on the conveyance belt is provided, thereby conveying the sheet before detecting the sheet. By sensing whether or not the conveyor belt is soiled by sensing on the belt, it is possible to prevent misdetection of paper detection due to contamination, thereby improving the reliability of paper detection. it can.

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

  FIG. 1 is a perspective view showing a main part of an image forming apparatus for explaining an embodiment of the present invention, and FIG. 2 is a plan view showing a control system in the image forming apparatus according to the present embodiment.

  1 and 2, reference numeral 1 denotes a carriage mounted with a print head 2 that moves in the main scanning direction and forms (prints) an image on a sheet. Reference numeral 3 denotes a guide shaft of the carriage 1. Reference numeral 4 denotes an image. In order to achieve this, a conveying belt that moves the paper in the sub-scanning direction, 5 and 6 are a driving roller and a driven roller that drive the conveying belt 4, and the carriage 1 emits detection light to the conveying belt 4. A paper detection sensor 7 that is a reflection type photosensor including an element 7a and a light receiving element 7b that receives reflected light from the conveyor belt 4 is mounted.

  In FIG. 2, reference numeral 11 denotes a head driving unit that controls driving of the print head 2, 12 denotes a carriage driving unit that controls driving of the carriage 1, 13 denotes a roller driving unit that controls driving of the driving roller 5, and 14 denotes from the paper detection sensor 7. It is a CPU (Central Processing Unit) that controls each part in response to a detection signal or the like.

  In this example, the conveyor belt 4 has a black surface. The paper detection sensor 7 has an output that is close to 0 volt with no contamination on the conveyor belt 4 and a constant voltage output such as 3 volt when a paper is detected. It is.

  The output of the paper detection sensor 7 is an analog output, and this output is input to an analog signal / digital signal (A / D) converter such as an ASIC. In the ASIC, a reference value is set in advance at a certain level, and the CPU 14 determines that there is a sheet if the value is equal to or greater than the certain value, and determines that there is no sheet if the value is less than that.

  Here, as shown in FIGS. 3A and 3B, when there is a stain A due to ink or the like on the transport belt 4, the output of the paper detection sensor 7 may rise to the detection level of the paper P. There is. As shown in FIG. 3A, when the left end portion of the paper P overlaps with the dirt A portion of the conveying belt 4 and the output state shown in FIG. is there.

  Therefore, in this embodiment, in order to prevent erroneous detection, the carriage 1 is moved in the main scanning direction on the conveying belt 4 before conveying the sheet P as illustrated in the flowchart of FIG. The detection sensor 7 performs detection scanning on the transport belt 4 (S1), detects that the sensor output voltage is less than the reference value (No in S2), that is, is free of dirt (S3), and then the paper. By performing conveyance and paper detection, it is possible to prevent erroneous detection due to contamination as described above. If the sensor output is equal to or higher than the reference value (Yes in S2), normal paper conveyance is stopped because there is a stain, and various processes as described later are performed (S4).

  For example, as shown in FIG. 5, the steps (S1, S2) are similarly performed, and if the sensor output voltage is less than the reference value (No in S2), normal sheet conveyance and sheet detection are performed (S3). If the sensor output is equal to or greater than the reference value (Yes in S2), it is assumed that there is dirt, and the position of the conveyor belt 4 is moved in the sub-scanning direction so that the dirt portion does not overlap the leading edge of the paper P during paper conveyance. By controlling (S5), it is possible to prevent erroneous detection of the leading edge and the sheet width of the sheet by the sheet detection sensor 7.

  Further, as shown in FIG. 6, the steps (S1, S2) are similarly performed, and if the sensor output voltage is less than the reference value (No in S2), normal sheet conveyance and sheet detection are performed (S3). If the sensor output is equal to or higher than the reference value (Yes in S2), it is considered that the conveyance belt 4 is cleaned (S6) to remove or reduce the dirt because there is dirt.

  Further, as shown in FIG. 7, the steps (S1, S2) are similarly performed. If the sensor output voltage is less than the reference value (No in S2), normal sheet conveyance and sheet detection are performed (S3). If the sensor output is equal to or greater than the reference value (Yes in S2), the conveyor belt 3 is cleaned (S6) to remove or reduce the dirt, and at the same time the number of times of cleaning is counted by the count function of the CPU 14. When the predetermined number of cleanings reaches a preset number of times, or when the predetermined number of cleanings are performed continuously (Yes in S7), for example, a maintenance person or a predetermined service A notification signal is output to the outside of the equipment such as the center (S8), and reliable measures (higher cleaning, parts replacement, etc.) are performed. It is also conceivable that way.

  INDUSTRIAL APPLICABILITY The present invention is applied to an image forming apparatus such as an electrophotographic system or an ink jet system that detects a sheet and detects dirt by a conveyance belt that conveys the sheet, and in particular, it is required to improve the reliability of sheet detection. It is effective when applied to an image forming apparatus.

1 is a perspective view showing a main part of an image forming apparatus for explaining an embodiment of the present invention. The top view which shows the control system in the image forming apparatus which is this embodiment (A) is explanatory drawing of the stain | pollution | contamination on a conveyance belt, and a paper, (b) is explanatory drawing of the output of the paper detection sensor by them. Flowchart of operations related to detection of dirt on the conveyor belt according to the present embodiment. Flowchart of operations related to detection of dirt on the conveyor belt according to the present embodiment. Flowchart of operations related to detection of dirt on the conveyor belt according to the present embodiment. Flowchart of operations related to detection of dirt on the conveyor belt according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carriage 2 Print head 4 Conveyor belt 7 Paper detection sensor 12 Carriage drive part 13 Roller drive part 14 CPU

Claims (4)

In an image forming apparatus that forms an image on a sheet by moving the print head in the main scanning direction and moving the sheet in the sub-scanning direction,
A carriage that moves the print head in the main scanning direction, a conveyance belt that moves the paper in a predetermined direction, and a light that is mounted on the carriage and emits light to the conveyance belt and is reflected from the conveyance belt A sheet detection sensor that detects the sheet by receiving light, and a belt state determination unit that compares an output from the sheet detection sensor with a preset reference value to determine the state of dirt on the conveyor belt. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the sheet is detected in a portion of the conveyance belt that is determined to be free of dirt by the belt state determination unit.   The image forming apparatus according to claim 1, wherein when the belt state determination unit determines that there is dirt greater than the reference value, the conveyance belt is cleaned.   The image forming apparatus according to claim 1, wherein a notification signal is output to the outside of the apparatus when the belt state determination unit determines that there is dirt greater than the reference value.

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