JP2013216033A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation in image quality of images formed on a print medium by properly measuring the movement amount of the print medium conveyed by a conveying means.SOLUTION: An image forming apparatus includes: a plurality of imaging parts 61 arranged at intervals that is less than the length of a sheet of paper P in a conveying direction, each part having a light source and imaging; a movement-amount calculating part 62 for calculating plural movement amounts corresponding to the plurality of imaging parts 61, respectively, by comparing plural images obtained from each of the plurality of imaging parts 61 after light intensity of each light source is adjusted; a second top edge sensor 7 for detecting the front end or rear end of the paper P; and a selecting part 15 for selecting one of the plural movement amounts based on the detection result, the movement amount relating to the paper P. The second top edge sensor 7 is disposed between the imaging part 61 arranged on the uppermost stream side and the imaging part 61 arranged on the next upstream side, and disposed at a predetermined distance from the imaging part 61 arranged on the uppermost stream side so that the light intensity adjustment of the imaging part 61 arranged on the uppermost side is completed when detecting the front end of the paper P being conveyed.

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet or the like.

  2. Description of the Related Art Conventionally, there is an image forming apparatus that forms an image on a sheet by ejecting ink from an inkjet head while conveying and holding a sheet (print medium) on a conveying belt. In such an image forming apparatus, an image forming apparatus that captures an image of a transported sheet or transport belt, detects the amount of movement thereof, and forms an image on the sheet according to the detected amount of movement is well known.

  For example, in Patent Document 1, a movement detection sensor that captures reflected light of laser light emitted from a laser diode onto a sheet or a conveyance belt images the sheet or the conveyance belt, and a specific pattern movement in the captured image. An image forming apparatus that detects the amount of movement of a sheet or a sheet conveying unit based on the above and forms an image on a sheet corresponding to the detected amount of movement of the sheet or the sheet conveying unit has been proposed.

  Here, since the reflectance is different between the paper and the conveyor belt, it is necessary to perform light control to adjust the light emission amount of the laser diode depending on which one is imaged. This light control is performed using an AGC (Automatic Gain Control) function of the movement amount detection sensor.

JP 2009-107310 A

  It is desirable that only the sheet is detected by the movement amount detection sensor. This is because slippage or the like may occur between the conveyance belt and the sheet, and when the conveyance belt is detected, a printing position shift occurs, and the image quality of the image formed on the sheet may be deteriorated.

  Further, since the skew correction is performed by the registration means before the sheet enters the conveyance belt, there is a sheet as a detection target of the movement amount detection sensor between the sheets conveyed by the conveyance belt. An area that does not occur (inter-paper area) occurs. In the image forming apparatus disclosed in Patent Document 1, the imaging target in the movement amount detection sensor is switched between the sheet and the conveyance belt before and after the above-described inter-paper area. Dimming is performed by the AGC function at the timing when the imaging target is switched. However, since dimming by the AGC function requires a certain amount of time, the dimming is not in time, and an area that cannot be captured with an appropriate light amount may occur. is there. As a result, there is a non-detection zone in which the amount of movement of the paper or the conveyor belt is not detected, and as a result, the image quality of the image formed on the paper may deteriorate.

  The present invention has been made in view of the above, and an object of the present invention is to provide an image forming apparatus capable of suppressing deterioration in image quality.

  In order to achieve the above object, a first feature of the image forming apparatus according to the present invention is that a printing unit conveys a print medium on a conveyance surface, and an image is printed on the printing medium conveyed by the conveyance unit at a predetermined timing. The image forming unit to be formed is disposed at an interval less than the length in the transport direction of the print medium transported along the transport path, has a light source, and the light from the light source is transported by the transport unit or the transport unit. By comparing a plurality of images obtained by irradiating the print medium with predetermined time intervals and a plurality of images obtained by the plurality of imaging means after the light sources are respectively dimmed A moving amount calculating unit that calculates a plurality of moving amounts corresponding to each of the plurality of imaging units, and an end detecting unit that detects a leading end or a trailing end of a print medium conveyed by the conveying unit. Based on the detection result detected by the edge detection means, a selection means for selecting a movement amount related to the print medium that is one of the plurality of movement amounts, and a movement selected by the selection means Control means for controlling the timing of image formation by the image forming means based on the amount, and the end detection means is the most upstream of the plurality of image pickup means in the transport path with respect to the image forming means. Between the imaging means arranged on the side and the imaging means arranged next on the upstream side, when the leading edge of the print medium conveyed by the conveying means is detected, arranged on the most upstream side In other words, it is arranged at a predetermined distance from the imaging means arranged on the most upstream side so that the light control of the imaging means is completed.

  A second feature of the image forming apparatus according to the present invention is that the selection unit sets the movement amount calculated by the movement amount calculation unit from a plurality of images obtained by the upstream imaging unit among the plurality of imaging units. Based on the plurality of images obtained by the downstream imaging means adjacent to the upstream imaging means when it is determined that the dimming of the downstream imaging means is completed among the plurality of imaging means. It is to select the movement amount calculated by the movement amount calculation means.

  According to the first feature of the image forming apparatus according to the present invention, the edge detection means includes an image pickup means arranged on the most upstream side in the transport path with respect to the image formation means, and then the image pickup means. The dimming of the imaging means arranged on the most upstream side is completed when the leading edge of the print medium conveyed by the conveying means is detected between the imaging means arranged on the upstream side Since the image sensor is arranged at a predetermined distance from the image pickup unit arranged on the most upstream side, it is possible to prevent a region where the print medium is not picked up with an appropriate amount of light by the image pickup unit. Thereby, since the moving amount of the printing medium conveyed to the conveying means can be appropriately measured, it is possible to prevent the image quality of the image formed on the printing medium from being deteriorated.

  According to the second feature of the image forming apparatus of the present invention, the selection unit is based on the movement amount calculated by the movement amount calculation unit from the plurality of images obtained by the upstream imaging unit among the plurality of imaging units. When it is determined that the dimming of the downstream imaging means is completed among the plurality of imaging means, the movement amount is calculated from the plurality of images obtained by the downstream imaging means adjacent to the upstream imaging means. Since the movement amount calculated by the means can be selected, it is possible to prevent the image quality of the image formed on the print medium from being deteriorated.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is the figure which showed typically the structure of the imaging part of the 1st movement amount detection sensor with which the image forming apparatus which concerns on embodiment of this invention is provided. 1 is a diagram illustrating a functional configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 5 is a diagram illustrating an example of data obtained by converting a movement amount calculated by a first movement amount detection sensor included in the image forming apparatus according to the embodiment of the present invention into a conveyance speed. 3 is a flowchart illustrating a processing procedure of print processing of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 5 is a diagram schematically illustrating a printing process of the image forming apparatus according to the first exemplary embodiment of the present invention. (A) shows the state after the leading edge of the paper P transported on the transport path R is detected by the second top edge sensor, and (b) shows the paper transported on the transport path R. P shows a state in which the light control of the second movement amount detection sensor is completed. FIG. 6C shows that the paper P conveyed on the conveyance path R is dimmed by the third movement amount detection sensor. Indicates the completed state.

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

  Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones.

  Further, the embodiment described below exemplifies an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention is to arrange the components and the like as follows. It is not something specific. The technical idea of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, an image forming apparatus 1 according to an embodiment of the present invention includes a paper feed unit 2, a belt conveyance unit 3, and an inkjet head unit 4.

  In the following description, the vertical direction and the horizontal direction indicate the vertical direction and the horizontal direction shown in FIG. Further, a path indicated by a broken line in FIG. 1 is a transport path R along which the image forming medium is transported, and a direction from left to right is a transport direction. In the following description, upstream and downstream mean upstream and downstream in the transport path R, respectively.

  The paper feed unit 2 supplies paper to the belt conveyance unit 3. The paper feed unit 2 is provided on the most upstream side of the transport path R. The sheet feeding unit 2 includes a sheet feeding table 21, a sheet feeding roller 22, and a registration roller 23.

  The paper feed table 21 is for stacking paper P that is an image forming medium.

  The paper feed roller 22 takes out the paper P stacked on the paper feed tray 21 one by one and sends it out toward the registration roller 23.

  The registration roller 23 is provided on the downstream side of the paper feed roller 22. The registration roller 23 sends out the paper P sent from the paper feed roller 22 toward the belt conveyance unit 3 at a predetermined timing.

  The paper feed unit 2 includes a motor that rotationally drives the paper feed roller 22 and a motor (none of which is shown) that rotationally drives the registration roller 23.

  The belt conveyance unit 3 is provided on the downstream side of the registration roller 23. The belt conveyance unit 3 includes an annular conveyance belt 31 provided to face the inkjet head unit 4, a belt driving roller 32 that drives the conveyance belt 31 to rotate, and driven rollers 33 to 35 that are driven by the belt driving roller 32. Is provided. The belt conveyance unit 3 includes a motor (not shown) that rotationally drives the belt driving roller 32.

  The conveyor belt 31 is an endless belt having a large number of holes, and the sheet P is conveyed by negative pressure generated when air is sucked from the holes by a suction fan (not shown), and the conveyor surface 311 is the surface of the conveyor belt 31. Adsorb and hold on to transport. The conveyance belt 31 corresponds to a conveyance unit in claims. The belt conveyance unit 3 is not limited to the configuration in which the paper P is attracted and held on the conveyance surface 311 of the conveyance belt 31 by air suction as described above, and for example, the paper P is held on the conveyance surface 311 by electrostatic adsorption. It is good also as such a structure.

  The inkjet head unit 4 includes a plurality of line-type inkjet heads arranged above the belt conveyance unit 3 and having a plurality of nozzles arranged in a direction orthogonal to the conveyance direction of the paper P. The ink jet head unit 4 forms an image by ejecting ink from the ink jet head onto the paper P transported by the belt transport unit 3.

  On the transport path R, the registration sensor 5, the first top edge sensor 6, the second top edge sensor 7, the first movement amount detection sensor 81, the second movement amount detection sensor 82, and the third movement amount. And a detection sensor 83.

  The registration sensor 5 is disposed on the upstream side of the registration roller 23 and detects the paper P conveyed on the conveyance path R. In the present embodiment, the registration sensor 5 is composed of an optical reflective sensor disposed above the conveyor belt 31 and outputs a signal indicating “ON” when the paper P is passing.

  The first top edge sensor 6 is disposed on the upstream side of the inkjet head unit 4 and detects the leading edge or trailing edge of the paper P that is transported on the transport path R. In the present embodiment, the first top edge sensor 6 is composed of an optical reflective sensor disposed above the conveyor belt 31 and outputs a signal indicating “ON” when the paper P is passing. .

  Thereby, the first top edge sensor 6 can detect the leading edge or the trailing edge of the sheet P conveyed on the conveying path R.

  The first movement amount detection sensor 81 is disposed above the conveyance belt 31 on the downstream side of the first top edge sensor 6 and on the upstream side of the inkjet head unit 4, and calculates the movement amount of the paper P conveyed by the conveyance belt 31. To do. The first movement amount detection sensor 81 includes an imaging unit 61 and a movement amount calculation unit 62. The imaging unit 61 irradiates the moving conveyor belt 31 or the paper P with laser light and images at a predetermined time interval (imaging cycle). The movement amount calculation unit 62 calculates the movement amount of the paper P conveyed by the conveyance belt 31 based on the movement of a specific pattern (uneven pattern on the surface of the paper P) present in the obtained plurality of images.

  FIG. 2 is a diagram schematically illustrating the configuration of the imaging unit 61 of the first movement amount detection sensor 81 provided in the image forming apparatus 1 according to the embodiment of the present invention.

  As shown in FIG. 2, the imaging unit 61 includes a laser diode 611 that is a light source, condenser lenses 612 and 613, and an area sensor 614.

  The laser diode 611 emits laser light that irradiates the conveyance belt 31 or the paper P to be imaged. The laser diode 611 is driven by a drive circuit (not shown) and is configured such that the light emission amount can be adjusted according to the detection target.

  The condensing lens 612 condenses the laser light emitted from the laser diode 611 on the paper P.

  The condensing lens 613 condenses the reflected light, which is the laser light reflected by the conveyance belt 31 or the paper P, on the area sensor 614.

  The area sensor 614 has an image sensor such as a CCD (Charge Coupled Device), receives the reflected light from the transport belt 31 and the paper P transported by the transport belt 31, converts the received light into an electrical signal, An image is generated based on the electrical signal.

  The movement amount detection sensor 81 can calculate the movement amount of the paper P mainly conveyed by the conveyance belt 31 based on the movement amount of a specific pattern existing in a plurality of images generated by the area sensor 614. Here, the specific pattern obtained from the image obtained by imaging the paper P is unevenness obtained when the paper P is enlarged. This unevenness is caused by fibers such as pulp that is a raw material of the paper P.

  For example, when the movement amount detection sensor 81 compares two images generated at a predetermined time interval (imaging cycle) and the pattern (uneven pattern) of the paper P in the image is displaced, The amount of displacement is calculated as the amount of movement of the paper P, and when the pattern is not displaced at all, the amount of movement of the paper P during this imaging cycle is zero, that is, a conveyance slip has occurred between the conveyance belt 31 and the paper P. to decide.

  In addition, the movement amount calculation unit 62 outputs a pulse signal corresponding to the calculated movement amount to the data processing unit 10.

  The second top edge sensor 7 is disposed on the upstream side of the inkjet head unit 4 and detects the paper P that is transported on the transport path R.

  The second top edge sensor 7 is located between the first movement amount detection sensor 81 and the second movement amount detection sensor 82, and when the leading edge of the paper conveyed by the belt conveyance unit 3 is detected, The dimming of the imaging unit 61 of the first movement amount detection sensor 81 is completed so that generation of movement amount information can be started based on the image captured by the imaging unit 61 of the first movement amount detection sensor 81. As described above, the first movement amount detection sensor 81 is disposed away from the imaging unit 61 by a distance L3. This distance L3 is appropriately determined based on the conveyance speed of the conveyance belt 31 and the time required for light control of the laser diode 611. Details will be described later.

  The second top edge sensor 7 is disposed on the upstream side of the inkjet head unit 4 and detects the paper P that is transported on the transport path R. In the present embodiment, the second top edge sensor 7 is composed of an optical reflective sensor disposed above the conveyor belt 31 and outputs a signal indicating “ON” when the paper P is passing. .

  The second movement amount detection sensor 82 is disposed on the downstream side of the second top edge sensor 7 and on the upstream side of the inkjet head unit 4 and above the conveyance belt 31, and the movement amount of the conveyance belt 31 can also be calculated. The amount of movement of the paper P conveyed by 31 is calculated.

  The third movement amount detection sensor 83 is disposed above the conveyance belt 31 on the downstream side of the inkjet head unit 4 and calculates the movement amount of the paper P conveyed mainly by the conveyance belt 31.

  Similarly to the first movement amount detection sensor 81, the second movement amount detection sensor 82 and the third movement amount detection sensor 83 include an imaging unit 61 and a movement amount calculation unit 62.

  The distance L2 from the first movement amount detection sensor 81 to the second movement amount detection sensor 82 and the distance L3 from the second movement amount detection sensor 82 to the third movement amount detection sensor 83 are determined on the conveyance surface 311 of the conveyance belt 31. The second movement amount detection sensor 82 and the third movement amount detection sensor 83 are arranged so as to be less than the length in the conveyance direction of the conveyed paper P. In addition, a guide rail may be provided so that the position where the second movement amount detection sensor 82 and the third movement amount detection sensor 83 are arranged is displaced by the size of the paper P, and may be slidable in the conveyance direction.

  FIG. 3 is a diagram showing a functional configuration of the image forming apparatus 1 according to the embodiment of the present invention.

  As shown in FIG. 3, the image forming apparatus 1 includes a data processing unit 10, an inkjet head unit 4, a display panel 55, a first top edge sensor 6, a second top edge sensor 7, and a first movement amount. A detection sensor 81, a second movement amount detection sensor 82, a third movement amount detection sensor 83, a mechanical control unit 90, an actuator 100, and a registration sensor 5 are provided. Among these configurations, the inkjet head unit 4, the first top edge sensor 6, the second top edge sensor 7, the first movement amount detection sensor 81, the second movement amount detection sensor 82, and the third movement amount. Since the detection sensor 83 and the registration sensor 5 have been described above, description thereof will be omitted.

  The display panel 55 includes an image output device such as an organic EL (electroluminescence) display or a liquid crystal display, and displays an image based on an output signal supplied from the data processing unit 10.

  The actuator 100 is various drive devices such as a motor for a conveyance roller.

  The data processing unit 10 includes a CPU 11, an external I / F (interface) 12, a memory 13, an internal I / F (interface) 14, a selection unit 15, and a drive driver 16.

  The CPU 11 executes various data processing in the image forming apparatus 1.

  The external I / F (interface) 12 is supplied with a print job from an external terminal via a network, for example.

  The memory 13 is composed of, for example, a volatile semiconductor and stores data necessary for the CPU 11 to execute various processes.

  The internal I / F (interface) 14 is a communication interface with the mechanical control unit 90. For example, the internal I / F (interface) 14 transmits a print job to the mechanical control unit 90 and receives a result for the print job.

  Based on the detection result detected by the second top edge sensor 7, the selection unit 15 selects a movement amount related to the paper P that is one of a plurality of movement amounts. Specifically, the selection unit 15 includes a plurality of movement amounts calculated by the movement amount calculation unit 62 of the first movement amount detection sensor 81, the second movement amount detection sensor 82, and the third movement amount detection sensor 83; Based on the detection result detected by the second top edge sensor 7, a movement amount calculated after the light control of the imaging unit 61 is selected from the calculated movement amounts.

  The drive driver 16 controls the inkjet head unit 4 based on the movement amount selected by the selection unit 15.

  The mechanical control unit 90 includes a CPU 91, a memory 92, an internal I / F (interface) 93, an actuator control I / F (interface) 94, and a sensor control I / F (interface) 95.

  The CPU 91 performs central control of various devices constituting the image forming apparatus 1.

  The memory 92 is composed of, for example, a volatile semiconductor, and stores data and the like necessary for the CPU 91 to execute various processes.

  An internal I / F (interface) 93 is a communication interface with the data processing unit 10 and transmits, for example, a result for a print job to the data processing unit 10 and receives a print job.

  An actuator control I / F (interface) 94 supplies a control signal to the actuator 100.

  A sensor control I / F (interface) 95 supplies a detection result detected by the registration sensor 5 to the CPU 91.

  FIG. 4 is a diagram illustrating an example of data obtained by converting the movement amount calculated by the first movement amount detection sensor 81 included in the image forming apparatus 1 according to the embodiment of the present invention into a conveyance speed.

  As shown in FIG. 4, when the transport operation starts at time t1, the first sheet P is transported and detected until time t2.

  Then, during the period from time t2 to time t3, the value of the conveyance speed converted from the calculated movement amount is an unstable value.

  Since the sheet P and the conveyance surface 311 of the conveyance belt 31 have different reflectances, it is necessary to perform dimming to adjust the light emission amount of the laser diode 611 depending on which one is imaged.

  Therefore, the first movement amount detection sensor 81 adjusts the light emission amount of the laser diode 611 using an AGC (Automatic Gain Control) function.

  When the object to be imaged by the first movement amount detection sensor 81 is switched between the paper P and the transport surface 311 of the transport belt 31, light control is performed by the AGC function. A certain amount of time is required for dimming by this AGC function.

  For this reason, there is a region where the dimming is not in time and an image is not captured with an appropriate amount of light on the transport surface 311 of the paper P or the transport belt 31, that is, there is a portion where the waveform is greatly lowered from the time t2 to the time t3. This indicates that a non-detection zone in which the movement amount (conveyance speed) is not detected between the sheets P has occurred. Such a non-detection zone occurs because the AGC function cannot adjust the light in time, and an area that cannot be imaged with an appropriate amount of light is generated.

  Therefore, in the image forming apparatus 1 according to the embodiment of the present invention, the first movement amount detection sensor 81 and the second movement amount for which dimming is completed are performed so as not to use such a movement amount of the non-detection band. By selecting and using any one of the movement amounts calculated by the detection sensor 82 and the third movement amount detection sensor 83, the movement amount of the paper P can be acquired more accurately, and the acquired movement can be obtained. The inkjet head unit 4 is controlled based on the amount.

<Operation of Image Forming Apparatus>
Next, the operation of the image forming apparatus 1 according to the first embodiment of the invention will be described.

  FIG. 5 is a flowchart showing the processing procedure of the printing process of the image forming apparatus 1 according to the first embodiment of the invention.

  When the paper P is supplied and the leading edge of the paper P transported on the transport path R is detected by the first top edge sensor 5, the imaging target changes from the transport belt 31 to the paper P. Dimming of the laser diode 611 corresponding to P is started.

  Thereafter, as shown in FIG. 5, the selection unit 15 of the data processing unit 10 determines whether or not the second top edge sensor 7 has detected the leading edge of the sheet P conveyed on the conveyance path R (step). S101).

  When it is determined in step S101 that the leading edge of the paper P has been detected (in the case of YES), the selection unit 15 uses the movement amount of the first movement amount detection sensor 81 for which dimming has been completed as the movement amount of the paper P. Is selected (adopted) to represent (step S103). Specifically, the imaging unit 61 of the first movement amount detection sensor 81 irradiates the moving conveyor belt 31 or the paper P with a laser beam to capture images at predetermined time intervals, and the movement amount calculation unit 62 is obtained. Based on the movement of the specific pattern between the plurality of images, the movement amount of the paper P conveyed by the conveyance belt 31 is calculated. Then, the selection unit 15 selects the movement amount calculated by the movement amount calculation unit 62 of the first movement amount detection sensor 81 as the movement amount of the paper P.

  Next, the selection unit 15 determines whether or not the movement amount has exceeded the first specified pulse count (step S105). Here, as shown in FIG. 1, the first prescribed pulse count S <b> 1 includes the distance S <b> 2 from the second top edge sensor 7 to the second movement amount detection sensor 82 on the transport path R, and the second movement amount detection sensor 82. Corresponds to the sum of the distance S3 corresponding to the time for dimming. Therefore, the selection unit 15 determines whether or not the number of pulses (the movement amount of the paper P) from the first movement amount detection sensor 81 calculated by the movement amount calculation unit 62 has exceeded the first specified pulse count S1. .

  If it is determined in step S105 that the movement amount of the paper P has exceeded the first specified pulse count (in the case of YES), the selection unit 15 sets the movement amount of the paper P by the movement amount by the second movement amount detection sensor 82. It selects as what to represent (step S107). Specifically, the imaging unit 61 of the second movement amount detection sensor 82 irradiates the paper P conveyed by the conveyance belt 31 with a laser beam and picks up images at a predetermined time interval, and the movement amount calculation unit 62 obtains the images. Based on the movement of the specific pattern in the obtained image, the movement amount of the paper P conveyed by the conveyance belt 31 is calculated. Then, the selection unit 15 selects the movement amount calculated by the movement amount calculation unit 62 of the second movement amount detection sensor 82.

  Next, the selection unit 15 determines whether or not the movement amount has exceeded the second specified pulse count (step S109). Here, as shown in FIG. 1, the second specified pulse count V1 includes the distance V2 from the second movement amount detection sensor 82 to the third movement amount detection sensor 83 on the transport path R, and the third movement amount detection sensor. 83 corresponds to the sum of the distance V3 corresponding to the time for dimming. Therefore, the selection unit 15 determines whether or not the number of pulses (movement amount of the paper P) from the second movement amount detection sensor 82 calculated by the movement amount calculation unit 62 has exceeded the second specified pulse count V1. .

  When it is determined in step S109 that the movement amount has exceeded the second specified pulse count (in the case of YES), the selection unit 15 represents the movement amount by the third movement amount detection sensor 83 as the movement amount of the paper P. Select (step S111). Specifically, the image pickup unit 61 of the third movement amount detection sensor 83 irradiates the moving conveyor belt 31 or the paper P with laser light and picks up images at a predetermined time interval, and the movement amount calculation unit 62 is obtained. The amount of movement of the paper P conveyed by the conveyance belt 31 is calculated based on the movement of a specific pattern in the obtained image. Then, the selection unit 15 selects the movement amount calculated by the movement amount calculation unit 62 of the third movement amount detection sensor 83.

  Next, the selection unit 15 determines whether or not the rear end of the paper P has passed through the third movement amount detection sensor 83 (step S113). Specifically, the selection unit 15 determines that the trailing edge of the paper P is the first based on the movement amount calculated by the movement amount calculation unit 62 of the third movement amount detection sensor 83 and the length in the conveyance direction of the paper P. It is determined whether or not the three movement amount detection sensor 83 has passed.

  Then, the selection unit 15 determines whether printing is completed based on the print job (step S115). If the print job includes an instruction to print a plurality of sheets, the processes of steps S101 to S115 are repeatedly executed for the number of sheets.

  FIG. 6 is a diagram schematically illustrating the printing process of the image forming apparatus 1 according to the first embodiment of the invention. 6A shows a state after the leading edge of the paper P transported on the transport path R is detected by the second top edge sensor 7, and FIG. 6B shows the state on the transport path R. 6 shows a state in which the dimming of the second movement amount detection sensor 82 has been completed, and FIG. 6C shows the third movement amount of the paper P conveyed on the conveyance path R. The state where the light control of the detection sensor 83 is completed is shown.

  As shown in FIG. 6A, when the leading edge of the sheet P conveyed on the conveyance path R exceeds the position detected by the second top edge sensor 7 (P1 position), the first movement is performed at this time. Since the light control of the amount detection sensor 81 is completed, the selection unit 15 selects the movement amount calculated by the first movement amount detection sensor 81.

  As described above, the second top edge sensor 7 is between the first movement amount detection sensor 81 and the second movement amount detection sensor 82 and detects the leading edge of the paper P conveyed by the conveyance belt 31. Since the distance L3 is provided from the imaging unit 61 of the first movement amount detection sensor 81 so that the light control of the imaging unit 61 of the first movement amount detection sensor 81 is completed, the first movement amount detection is performed. It is possible to prevent the sensor 81 from generating a region that is not imaged with an appropriate amount of light. As a result, the amount of movement of the paper P being transported by the transport belt 31 can be measured appropriately, so that it is possible to prevent the image quality of the image formed on the paper P from being degraded.

  The sheet P is further conveyed, and when the leading end of the sheet P is conveyed from the second movement amount detection sensor 82 by a distance S3 corresponding to the time required for dimming as shown in FIG. Since the dimming of the two movement amount detection sensor 82 is completed, the selection unit 15 selects the movement amount calculated by the second movement amount detection sensor 82.

  In this manner, the selection unit 15 adjusts the imaging unit 61 of the second movement amount detection sensor 82 based on the movement amount calculated based on the image captured by the imaging unit 61 of the first movement amount detection sensor 81. When it is determined that the light has been completed, the movement amount calculated based on the image captured by the imaging unit 61 of the second movement amount detection sensor 82 is selected. It is possible to prevent a region that is not imaged from occurring. As a result, the amount of movement of the paper P being transported by the transport belt 31 can be measured appropriately, so that it is possible to prevent the image quality of the image formed on the paper P from being degraded.

  When the paper P is further transported and the leading edge of the paper P is transported by the distance V3 corresponding to the time required for dimming from the third movement amount detection sensor 83, as shown in FIG. Since the light control of the third movement amount detection sensor 83 has been completed, the selection unit 15 selects the movement amount calculated by the third movement amount detection sensor 83.

  In this way, the selection unit 15 adjusts the imaging unit 61 of the third movement amount detection sensor 83 based on the movement amount calculated based on the image captured by the imaging unit 61 of the second movement amount detection sensor 82. When it is determined that the light has been completed, the movement amount calculated based on the image captured by the imaging unit 61 of the third movement amount detection sensor 83 is selected. It is possible to prevent a region that is not imaged from occurring. As a result, the amount of movement of the paper P being transported by the transport belt 31 can be measured appropriately, so that it is possible to prevent the image quality of the image formed on the paper P from being degraded.

  As described above, according to the image forming apparatus 1 according to the first embodiment of the present invention, it is possible to suppress deterioration in image quality.

  In the first embodiment of the present invention, the first movement amount detection sensor 81, the second movement amount detection sensor 82, and the third movement amount detection sensor 83 each including the imaging unit 61 and the movement amount calculation unit 62 are provided. Although the image forming apparatus 1 provided is described as an example, the present invention is not limited to this, and the movement amount calculation common to the first movement amount detection sensor 81, the second movement amount detection sensor 82, and the third movement amount detection sensor 83 is not limited thereto. 1 unit 62, common based on images captured by the imaging unit 61 provided in each of the first movement amount detection sensor 81, the second movement amount detection sensor 82, and the third movement amount detection sensor 83. The movement amount calculation unit 62 may calculate each movement amount.

  The present invention can also be applied to an image forming apparatus in which a print medium is conveyed and image formation is performed by an installed image forming unit, such as a tandem copying machine.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Paper feed part 3 ... Belt conveyance part 4 ... Inkjet head part 5 ... Registration sensor 6 ... 1st top edge sensor 7 ... 2nd top edge sensor 10 ... Data processing part 11 ... CPU
DESCRIPTION OF SYMBOLS 13 ... Memory 15 ... Selection part 16 ... Drive driver 31 ... Conveyance belt 32 ... Belt drive roller 33-35 ... Driven roller 61 ... Imaging part 62 ... Movement amount calculation part 81 ... 1st movement amount detection sensor 82 ... 2nd movement amount Detection sensor 83 ... third movement amount detection sensor 90 ... mechanical control unit 91 ... CPU
92 ... Memory 100 ... Actuator 311 ... Conveying surface 611 ... Laser diode 612, 613 ... Condensing lens 614 ... Area sensor

Claims (2)

Conveying means for conveying the print medium on the conveying surface;
Image forming means for forming an image on the printing medium conveyed by the conveying means at a predetermined timing;
The print medium that is transported along the transport path is disposed at an interval less than the length in the transport direction, has a light source, and the light from the light source is transmitted to the transport means or the print medium transported by the transport means to a predetermined amount. A plurality of imaging means for imaging by irradiating at time intervals;
A movement amount calculating means for calculating a plurality of movement amounts corresponding to each of the plurality of imaging means by comparing a plurality of images obtained by the plurality of imaging means after the light sources are respectively dimmed; ,
End detection means for detecting the leading edge or the trailing edge of the print medium conveyed by the conveying means;
Selection means for selecting a movement amount related to the print medium, which is one of the plurality of movement amounts, based on a detection result detected by the edge detection means;
Control means for controlling the timing of image formation by the image forming means based on the amount of movement selected by the selection means,
The end detection means is
Among the plurality of imaging units, the imaging unit is disposed between the imaging unit disposed on the most upstream side in the conveyance path with respect to the image forming unit and the imaging unit disposed next on the upstream side, and is conveyed by the conveyance unit. Arranged at a predetermined distance from the imaging means arranged on the most upstream side so that the light control of the imaging means arranged on the most upstream side is completed when the leading edge of the print medium to be detected is detected An image forming apparatus characterized by that. The selection means includes
Based on the movement amount calculated by the movement amount calculation unit from the plurality of images obtained by the upstream imaging unit among the plurality of imaging units, the dimming of the downstream imaging unit among the plurality of imaging units is adjusted. The movement amount calculated by the movement amount calculation unit is selected from a plurality of images obtained by a downstream imaging unit adjacent to the upstream imaging unit when it is determined that the movement is completed. The image forming apparatus according to 1.

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