JP2012076834A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer which can alleviates disorder of a printed image.SOLUTION: A controlling section adjusts at least one of a carrying amount by assisting operation of a longitudinal carrying roller 4 assisting a resist roller 5 and a carrying amount by the resist roller 5 so that a sheet reaches a position where a top edge sensor 2 10 detects the sheet in a predetermined period after the sheet is detected by a top edge sensor 1 9 on the basis of information regarding a factor of delay of carrying of the sheet.

Description

  The present invention relates to a printing apparatus that performs printing on a printing medium such as paper.

  2. Description of the Related Art Conventionally, there is known a printing apparatus that prints an image by ejecting ink from an inkjet head onto a sheet while conveying and holding a sheet as a printing medium on a conveyance belt facing the inkjet head. In such a printing apparatus, ink is ejected based on the timing at which the paper is detected by a paper sensor disposed in the vicinity of the upstream side of the paper transport path with respect to the inkjet head.

  As a paper sensor installed in a printing apparatus, in general, an optical transmission sensor in which a light emitting element and a light receiving element are arranged to face each other with a detection target interposed therebetween, or a light emitting element and a light receiving element are used as a detection target. An optical reflective sensor arranged in parallel is used. In order to reliably detect the paper, it is desirable to use a transmissive sensor.

  However, in the printing apparatus using the conveyance belt as described above, there is a conveyance belt in the vicinity of the upstream side of the inkjet head. For this reason, the transmission type sensor cannot be installed at a position near the inkjet head, which is suitable for controlling the ink ejection timing. For this reason, in a printing apparatus using a conveyance belt, a reflective sensor is disposed in the vicinity of the upstream side of the inkjet head. This reflective sensor is arranged above the conveyor belt. The printing apparatus controls the ink ejection timing by the inkjet head based on the paper detection timing of the reflection type sensor.

  However, as described above, the reflective sensor is inferior in paper detection accuracy compared to the transmissive sensor. For example, when the reflectances of the paper and the conveyor belt are close to each other, it is difficult to detect the paper with a reflective sensor.

  On the other hand, a technique is disclosed in which a transmission sensor is provided upstream of the transport belt, and the transmission timing of the ink ejected by the inkjet head is controlled by using this transmission sensor and a reflective sensor in the vicinity of the inkjet head. (For example, refer to Patent Document 1).

  Conventionally, the following ejection control is known in a printing apparatus that performs ink ejection control using a transmission type sensor and a reflection type sensor in combination. The printing apparatus sets a predetermined period (referred to as a window) when a sheet is detected by a transmission type sensor upstream of the conveyance belt. When a sheet is detected by a reflective sensor in the vicinity of the inkjet head at a timing within the window, the printing apparatus controls ink ejection based on the detection timing of the reflective sensor. On the other hand, when no paper is detected by the reflective sensor in the window, the printing apparatus controls ink ejection based on the timing when the paper is detected by the transmissive sensor. Accordingly, even if the paper is not detected by the reflection type sensor in the window, the printing apparatus can eject ink at an appropriate timing on the paper conveyed to the inkjet head.

JP 2006-321066 A

  However, the main case where no paper is detected in the window is a conveyance delay due to an increase in paper conveyance load. In the above-described conventional printing apparatus, for example, even when the paper transport is delayed from the theoretical value due to an increase in paper transport load, even if the paper is not detected by the reflective sensor in the window, the transmission sensor detects the paper. Ink is ejected based on the timing. In such a case, since the distance between the transmissive sensor and the ink jet head is large, there is a case where ink ejection is started even though the paper has not reached the ink jet head. As a result, ink is ejected onto the conveyor belt, and the top and bottom of the printed image is disturbed.

  If a large window is taken, it is possible to reduce the occurrence of problems due to paper conveyance delay as described above. However, when the window is enlarged, there is a high possibility that the paper is erroneously detected by the reflective sensor in the vicinity of the ink jet head, and as a result, the top and bottom of the printed image may be disturbed.

  In addition, if the window is simply enlarged, the time from when the paper is detected by the reflective sensor to when ink ejection starts is insufficient, and ink ejection is in time for the arrival of the paper at the inkjet head. It may disappear. In order to cope with this inconvenience, it is conceivable to increase the interval between the reflective sensor and the ink jet head. However, this causes a large variation in paper conveyance, which becomes a factor that disturbs the top and bottom of the printed image.

  The present invention has been made in view of the above, and an object of the present invention is to provide a printing apparatus that can reduce the disturbance of a printed image.

  In order to achieve the above object, a first feature of a printing apparatus according to the present invention is that a printing unit that performs printing on a print medium that is conveyed on a conveyance path, and an upstream side of the printing unit in the conveyance path. A registration roller that conveys the print medium toward the printing unit, and an upstream side of the conveyance path with respect to the registration roller, conveys the print medium toward the registration roller, and is printed by the registration roller. A vertical conveyance roller that performs an assist operation for assisting conveyance of the medium, and a first detection unit that is disposed between the registration roller and the printing unit in the conveyance path and detects a print medium conveyed on the conveyance path; A second detection unit that is disposed between the first detection unit and the printing unit in the conveyance path and detects a print medium conveyed on the conveyance path; The second control unit controls the operations of the stroller and the vertical conveyance roller, and if the second detection unit detects the print medium in a predetermined period after the detection of the print medium by the first detection unit, the second Printing is performed based on the detection timing of the first detection unit, and printing is performed based on the detection timing of the first detection unit when the second detection unit does not detect the print medium during the predetermined period. A control unit for controlling the printing unit, wherein the control unit is configured to perform the second period in the predetermined period after the detection of the print medium by the first detection unit based on information on a delay factor of the conveyance of the print medium. At least one of the conveyance amount by the assist operation of the vertical conveyance roller and the conveyance amount by the registration roller is adjusted so that the printing medium reaches the detection position by the detection unit. In the door.

  A second feature of the printing apparatus according to the present invention is that the control unit is a motor that drives the vertical conveyance roller during the conveyance operation before the start of the assist operation as information on a delay factor of conveyance of the print medium. At least one of the load current value and the arrival timing of the print medium at a predetermined position near the upstream side with respect to the registration roller is used.

  A third feature of the printing apparatus according to the present invention is that, when the control unit adjusts the transport amount by the assist operation in the vertical transport roller, the control unit of the vertical transport roller before the start of the operation of the registration roller. It is to start the assist operation.

  A fourth feature of the printing apparatus according to the present invention is that when the control unit adjusts the conveyance amount of the registration rollers, the conveyance speed of the registration rollers and the conveyance speed of the vertical conveyance rollers in the assist operation are reduced. It is to make the time spent in the process longer than usual.

  According to the first feature of the printing apparatus of the present invention, the second detection unit performs the predetermined period after the detection of the print medium by the first detection unit based on the information on the delay factor of the conveyance of the print medium. By adjusting at least one of the conveyance amount by the assist operation of the vertical conveyance roller and the conveyance amount by the registration roller so that the print medium reaches the detection position, the print medium can be applied to the print medium at an inappropriate timing. It is possible to prevent the printing operation from being performed and to reduce the disturbance of the printed image.

  According to the second feature of the printing apparatus according to the present invention, as information relating to the delay factor of the conveyance of the printing medium, the load current value of the motor that drives the vertical conveyance roller and the predetermined position near the upstream side with respect to the registration roller. By using at least one of the print medium arrival timings, it is possible to easily detect the magnitude of the print medium conveyance load on the vertical conveyance roller.

  According to the third feature of the printing apparatus according to the present invention, by starting the assist operation of the vertical conveyance roller before the start of the operation of the registration roller, the slack of the paper in the registration roller is greatly formed. The influence of the load on the vertical conveyance roller during driving can be suppressed. Accordingly, it is possible to prevent a delay in the conveyance of the sheet, and to allow the sheet to reach the detection position by the second detection unit in a predetermined period after the print medium is detected by the first detection unit.

  According to the fourth feature of the printing apparatus of the present invention, it is possible to increase the conveyance amount of the sheet by increasing the deceleration time of the vertical conveyance roller in the registration roller and the assist operation longer than usual, and the first detection unit In this case, the sheet can reach the detection position by the second detection unit in a predetermined period after the print medium is detected.

1 is a schematic configuration diagram of a printing apparatus according to a first embodiment. FIG. 3 is a block diagram illustrating a configuration of a control system of the printing apparatus according to the first embodiment. It is a figure which shows an example of the correction value table in 1st Embodiment. 3 is a flowchart illustrating an operation of the printing apparatus according to the first embodiment. 3 is a flowchart illustrating an operation of the printing apparatus according to the first embodiment. (A) is a figure which shows an example of the conveyance speed control waveform of the vertical conveyance roller at the time of normal operation, (b) is a figure which shows an example of the conveyance speed control waveform of a registration roller. (A) is a figure which shows an example of the conveyance speed control waveform of a vertical conveyance roller when the start timing of assist operation | movement is correct | amended, (b) is a figure which shows an example of the conveyance speed control waveform of a registration roller. It is a figure which shows an example of the correction value table in 2nd Embodiment. 6 is a flowchart illustrating an operation of a printing apparatus according to a second embodiment. (A) is a figure which shows an example of the conveyance speed control waveform of a vertical conveyance roller when correcting the deceleration time in assist operation | movement, (b) is an example of the conveyance speed control waveform of a registration roller when correcting deceleration speed. FIG. It is a figure which shows the other example of a correction value table.

  Embodiments of the present invention will be described below 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.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a printing apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the printing apparatus 1 includes an internal paper feeding unit 2, an external paper feeding unit 3, a vertical conveyance roller 4, a registration roller 5, a belt conveyance unit 6, a vertical conveyance sensor 7, and a registration device. A sensor 8, a top edge sensor 19, a top edge sensor 2 10, and a head unit 11 are provided.

  In FIG. 1, a path indicated by a thick line is a transport path through which a sheet as a print medium is transported. Among the transport routes, the route indicated by the solid line is the internal paper feed route RS1, the route indicated by the alternate long and short dash line is the external paper feed route RS2, and the route indicated by the broken line is the normal route RC. Further, the direction indicated by the arrow along the conveyance path in FIG. 1 is the conveyance direction of the paper. In the following description, upstream and downstream mean upstream and downstream in the transport path. In the following description, the up and down direction and the left and right direction respectively indicate the up and down direction and the left and right direction shown in FIG.

  The internal paper feed unit 2 is provided inside a casing (not shown) of the printing apparatus 1, and includes a plurality of internal paper feed trays 21 on which papers are stacked and loaded. A plurality of internal paper feed rollers 22 for picking up and transporting the sheets one by one, and a plurality of internal paper feed transport rollers 23 for transporting the paper picked up from the internal paper feed tray 21 along the internal paper feed path RS1 while nipping the paper. Prepare. The internal paper feeding unit 2 is provided below the belt conveyance unit 6.

  The external paper feed unit 3 is installed so as to be exposed to the outside of a casing (not shown) of the printing apparatus 1, and an external paper feed base 31 on which paper is stacked and placed, and the paper from the external paper feed base 31 is 1 And an external paper feed roller 32 that picks up and conveys the sheets one by one. The external paper feed unit 3 is provided on the left side of the belt conveyance unit 6.

  The vertical conveying roller 4 conveys the sheet conveyed from any of the plurality of internal sheet feeding trays 21 toward the registration roller 5 while nipping the sheet. The vertical conveying roller 4 performs an assist operation when the registration roller 5 operates. The assist operation is an operation in which the vertical conveyance roller 4 assists the conveyance of the sheet by the registration roller 5. In a normal assist operation, the vertical conveyance roller 4 is driven at the same timing and conveyance speed as the registration roller 5 as shown in FIGS. 6A and 6B described later. In the present embodiment, as will be described later, the conveyance amount by the assist operation of the vertical conveyance roller 4 is adjusted based on the load current value I detected by the load current detection unit 20. The vertical conveying roller 4 is arranged on the downstream side of the internal paper feeding unit 2 and upstream of the registration roller 5 along the internal paper feeding path RS1, and corresponds to the conveying roller in the claims.

  The registration roller 5 conveys the sheet conveyed from the internal sheet feeding unit 2 or the external sheet feeding unit 3 while niping it, and sends the sheet toward the belt conveyance unit 6 and the head unit 11. The registration roller 5 is arranged on the upstream side of the normal route RC with respect to the belt conveyance unit 6 and the head unit 11. In other words, the registration roller 5 is disposed in the vicinity of the junction of the internal paper feed path RS1, the external paper feed path RS2, and the normal path RC.

  The belt conveyance unit 6 is provided on the downstream side of the registration roller 5, and includes an annular conveyance belt 61 provided to face the head unit 11, a belt driving roller 62 that drives the conveyance belt 61 to rotate, and a belt drive And driven rollers 63 to 65 driven by the roller 62. The conveyance belt 61 is an endless belt having a large number of holes, and conveys the sheet while adsorbing and holding the sheet with a negative pressure generated when air is sucked from the holes by a suction fan (not shown).

  The vertical conveyance sensor 7 is provided in the vicinity of the downstream side of the vertical conveyance roller 4 and detects a sheet conveyed through the internal paper feed path RS1.

  The registration sensor 8 is provided in the vicinity of the upstream side of the registration roller 5 and detects a sheet entering the registration roller 5.

  The top edge sensor 19 is provided between the head unit 11 and the belt conveyance unit 6 and the registration roller 5, and detects a sheet conveyed on the normal route RC. The top edge sensor 19 corresponds to a first detection unit in the claims.

  The top edge sensor 210 is provided in the vicinity of the upstream side of the head unit 11 between the top edge sensor 19 and the head unit 11, and detects a sheet conveyed on the normal route RC. The top edge sensor 210 corresponds to a second detection unit in the claims.

  The top edge sensor 19 and the top edge sensor 2 10 are used for controlling the timing of ink ejection in the head unit 11.

  As the vertical conveyance sensor 7, the registration sensor 8, the top edge sensor 19, and the top edge sensor 2 10, an optical sensor having a light emitting element and a light receiving element is used.

  The top edge sensor 210 is arranged in an area where the conveyance belt 61 exists in order to detect the sheet immediately before reaching the head unit 11. For this reason, a transmissive sensor cannot be used as the top edge sensor 210. The transmissive sensor is a sensor in which a light emitting element and a light receiving element are arranged to face each other with a conveyance path interposed therebetween. Therefore, as the top edge sensor 210, a reflective sensor in which a light emitting element and a light receiving element are arranged in parallel with respect to the transport path is used. The top edge sensor 210 composed of a reflective sensor is disposed above the conveyor belt 61. The top edge sensor 19 is composed of a transmissive sensor that has better detection accuracy than a reflective sensor. The vertical conveyance sensor 7 is a reflection type sensor, and the registration sensor 8 is a transmission type sensor.

  The head unit 11 has a plurality of line-type inkjet heads 111C, 111K, 111M, and 111Y that are arranged above the belt conveyance unit 6 and in which a plurality of nozzles are arranged in a direction orthogonal to the paper conveyance direction. .

  The inkjet heads 111C, 111K, 111M, and 111Y discharge inks of colors C (cyan), K (black), M (magenta), and Y (yellow), respectively, onto a sheet conveyed by the belt conveyance unit 6. Print the image. Various colors can be formed by printing ink of each color on the same pixel from the inkjet heads 111C, 111K, 111M, and 111Y. The head unit 11 corresponds to a printing unit in claims. In the following description, alphabetical suffixes (C, K, M, Y) indicating colors in the codes of the inkjet heads 111C, 111K, 111M, and 111Y may be omitted and collectively described.

  FIG. 2 is a block diagram illustrating the configuration of the control system of the printing apparatus 1. As shown in FIG. 2, the printing apparatus 1 includes a paper feed motor 12 that rotates and drives an internal paper feed roller 22 and an internal paper feed transport roller 23 of the internal paper feed unit 2, a vertical transport roller 4, and an external paper feed roller 32. A vertical conveyance motor 13 for rotationally driving, a registration motor 14 for rotationally driving the registration roller 5, a belt motor 15 for rotationally driving the belt driving roller 62, a paper feed motor 12, a vertical conveyance motor 13, a registration motor 14, and a belt. Drivers 16 to 19 that respectively drive the drive rollers 62 and a load current detection unit 20 that detects a load current of the vertical conveyance motor 13 are provided.

  The paper feed motor 12 can be connected / released to / from the internal paper feed roller 22 and the internal paper feed / transport roller 23 of the internal paper feed unit 2 via a clutch (not shown). The internal paper feeding roller 22 and the internal paper feeding / conveying roller 23 that are rotationally driven are switched by the clutch.

  The vertical conveyance motor 13 can be connected / released to / from the vertical conveyance roller 4 and the external paper feed roller 32 via a clutch (not shown). The driving of the vertical conveying roller 4 and the external paper feeding roller 32 is switched by the clutch.

  The printing apparatus 1 also includes a head driver 41 that drives the ink jet head 111 of the head unit 11 to eject ink, an encoder 42 that outputs a pulse signal for each predetermined rotation angle of the driven roller 63 of the belt transport unit 6, and A storage unit 43 and a control unit 44.

  The storage unit 43 includes a nonvolatile storage device such as a flash memory, and stores the correction value table 30 shown in FIG. The correction value table 30 associates the load current value I detected by the load current detection unit 20 with the correction value TA for correcting the start timing of the assist operation for assisting the registration roller 5 by the vertical conveyance roller 4. It is to hold. In the first embodiment, as described later, the conveyance amount by the assist operation in the vertical conveyance roller 4 is adjusted by correcting the start timing of the assist operation. The correction value table 30 is used for this adjustment. Each value in the correction value table 30 is experimentally calculated in advance using the printing apparatus 1.

  The control unit 44 includes a CPU, a memory (none of which are shown), and the like, and the CPU performs processing according to the control program, thereby performing overall operations such as paper conveyance and printing in the printing apparatus 1. To control. The outputs of the vertical conveyance sensor 7, the registration sensor 8, the top edge sensor 19, the top edge sensor 2 10, the load current detection unit 20, and the encoder 42 are guided to the control unit 44.

  The control unit 44 controls the ejection timing of the ink in the inkjet head 111 based on the detection timing of the paper by the top edge sensor 19 and the top edge sensor 2 10. Specifically, when the top edge sensor 19 detects the leading edge of the sheet, the control unit 44 sets a predetermined period (called a window). When the paper is transported at a set speed, the top edge sensor 19 detects the front edge of the paper after the top edge sensor 19 detects the front edge of the paper. It is a time width according to the carry amount. The size of the window is set based on the reading accuracy of the top edge sensor 210 and the paper conveyance speed set according to the printing conditions and the like. The controller 44 counts the number of pulses output from the encoder 42 after the top edge sensor 19 detects the leading edge of the paper, and uses the count value to detect the top edge sensor 210 at the timing within the window. It is determined whether the leading edge of the paper has been detected. When the top edge sensor 210 detects the leading edge of the sheet at the timing within the window, the control unit 44 controls ink ejection (printing operation) by the inkjet head 111 based on the detection timing of the top edge sensor 210. . On the other hand, when the top edge sensor 210 does not detect the leading edge of the paper at the timing within the window, the control unit 44 uses the ink from the inkjet head 111 based on the timing at which the top edge sensor 19 detects the leading edge of the paper. To control the discharge.

  Further, the control unit 44 adjusts the transport amount by the assist operation in the vertical transport roller 4 when it is predicted that the top edge sensor 210 will not detect the paper at the timing in the window due to the delay of the paper transport. Thus, the paper is detected by the top edge sensor 210 at the timing within the window. Here, the control unit 44 refers to the correction value table 30 based on the load current value I as information relating to the cause of paper conveyance delay, and adjusts the conveyance amount by the assist operation in the vertical conveyance roller 4. As will be described later, the load current value I is detected at the time of transport speed correction in the transport operation of the vertical transport roller 4 before starting the assist operation.

  Next, the operation of the printing apparatus 1 will be described.

  4 and 5 are flowcharts showing the operation of the printing apparatus 1. The processing of the flowcharts of FIGS. 4 and 5 is started, for example, when a print job is input to the printing apparatus 1 from an external apparatus. Here, a case where paper is fed from the internal paper feeding unit 2 will be described.

  First, in step S <b> 10, the control unit 44 controls the driver 16 to start driving the paper feed motor 12. Here, the control unit 44 switches the clutch (not shown) in order to feed paper from the internal paper feed tray 21 designated by the print job, so that the internal paper feed tray 21 corresponding to the designated internal paper feed tray 21 is switched. The driving force of the paper feeding motor 12 is transmitted to the paper roller 22 and the internal paper feeding / conveying roller 23. As a result, the paper is picked up from the designated internal paper feed tray 21 and sent out to the internal paper feed path RS1.

  Next, in step S <b> 20, the control unit 44 connects the vertical conveyance motor 13 and the vertical conveyance roller 4 via a clutch (not shown) and controls the driver 17 to start driving the vertical conveyance motor 13. As a result, when the vertical conveyance roller 4 is driven to rotate and the paper is conveyed from the internal paper feed unit 2, the vertical conveyance roller 4 conveys the paper along the internal paper feed path RS1.

  Next, in step S <b> 30, the control unit 44 controls the driver 19 to start driving the belt motor 15. As a result, the belt driving roller 62 is driven to rotate, and as a result, the conveyor belt 61 is driven to rotate. The encoder 42 outputs a pulse signal for each predetermined rotation angle of the driven roller 63.

  Next, in step S <b> 40, the control unit 44 determines whether or not the leading edge of the sheet is detected by the vertical conveyance sensor 7.

  When the control unit 44 determines that the leading edge of the sheet is detected by the vertical conveyance sensor 7 (step S40: YES), the control unit 44 proceeds to step S50. When it is determined that the leading edge of the sheet is not detected by the vertical conveyance sensor 7 (step S40: NO), the control unit 44 repeats the process of step S40 until the leading edge of the sheet is detected by the vertical conveyance sensor 7.

  In step S <b> 50, the control unit 44 corrects the conveyance speed of the vertical conveyance roller 4. The control unit 44 corrects the conveyance speed of the vertical conveyance roller 4 to be increased if the timing at which the leading edge of the sheet is detected by the vertical conveyance sensor 7 is delayed from the theoretical value. Correction is performed so as to reduce the conveying speed of the roller 4.

  FIG. 6A is a diagram illustrating an example of a conveyance speed control waveform of the vertical conveyance roller 4 during normal operation. In FIG. 6A, time t <b> 1 indicates the drive start time of the vertical conveyance roller 4 by the vertical conveyance motor 13. FIG. 6A shows that when the timing at which the vertical conveyance sensor 7 detects the paper is later than the theoretical value, the control unit 44 starts the vertical conveyance roller 4 from the time t2 after the vertical conveyance sensor 7 detects the paper. An example of the control for increasing the conveyance speed of the sheet is shown.

  The vertical conveying roller 4 is driven and controlled to stop when the leading edge of the sheet hits the registration roller 5 and a desired amount of slack occurs on the sheet. The slant of the paper is corrected by slackening the paper when it hits the registration roller 5. The control unit 44 determines the conveyance speed, acceleration, drive stop timing (time t4), and the like in the above-described conveyance amount correction so that a desired amount of slackness is generated on the sheet. In the example of FIG. 6A, the sheet hits the registration roller 5 at the timing within the decelerating section (time t3 to t4) after the vertical conveyance roller 4 is accelerated to the predetermined speed Va, and then until the time t4. A slack is formed on the paper.

  In step S60, the control unit 44 acquires the load current value I of the vertical conveyance motor 13 from the load current detection unit 20 when the conveyance speed of the vertical conveyance roller 4 is corrected, that is, from time t2 to t4.

  Next, in step S <b> 70, the control unit 44 controls the driver 17 to stop driving the vertical conveyance motor 13. Thereby, the driving of the vertical conveying roller 4 is stopped at time t4. Here, when the vertical conveying roller 4 is stopped driving, the rear portion of the sheet is nipped by the vertical conveying roller 4.

  Next, in step S80, the control unit 44 determines whether or not the load current value I of the vertical transport motor 13 acquired in step S60 is greater than or equal to a predetermined threshold value I1.

  If it is determined that I <I1 (step S80: NO), the controller 44 starts driving the registration roller 5 in step S90 in order to perform the normal operation of the registration roller 5 and the assist operation of the vertical conveyance roller 4. It is determined whether it is time. When the control unit 44 determines that the driving start timing of the registration roller 5 has been reached (step S90: YES), the control unit 44 proceeds to step S100 and determines that it has not reached the driving start timing of the registration roller 5 (step S90: NO). ), The process of step S90 is repeated until the driving start timing of the registration roller 5 is reached.

  In step S <b> 100, the control unit 44 controls the driver 18 and the driver 17 to start driving the vertical conveyance motor 13 at the same time as starting the driving of the registration motor 14.

  FIG. 6B is a diagram illustrating an example of a conveyance speed control waveform of the registration roller 5. In FIG. 6B, time t <b> 5 indicates the driving start time of the registration roller 5 by the registration motor 14. The controller 44 accelerates the registration roller 5 from time t5. When the conveyance speed of the registration roller 5 reaches the first speed V1 at time t6, the control unit 44 maintains the first speed V1 for a predetermined time until time t7. The driver 18 is controlled. Thereafter, the control unit 44 decelerates the registration roller 5 between time t7 and time t8, and reaches the second speed V2 that is substantially the same speed as the conveyance speed of the conveyance belt 61 at time t8. The driver 18 is controlled to maintain the above. The reason why the registration roller 5 is once accelerated to the first speed V1 is to increase the interval between the fed sheets. The deceleration to the second speed V <b> 2 is performed until the paper reaches the conveyance belt 61. Such acceleration / deceleration control is performed according to a preset schedule.

  Further, at the same time as starting the driving of the registration motor 14 at time t5, the control unit 44 also starts driving the vertical conveying roller 4 by the vertical conveying motor 13 as shown in FIG. The driver 17 is controlled to operate at the same speed as the registration roller 5. Thereby, the vertical conveying roller 4 assists the operation of the registration roller 5.

  After the driving of the registration roller 5 and the assist operation of the vertical conveying roller 4 are started, the control unit 44 determines whether or not the top edge sensor 19 detects the leading edge of the sheet in step S110 of FIG. When the top edge sensor 19 determines that the leading edge of the sheet is detected (step S110: YES), the control unit 44 sets a predetermined window in step S120. Further, the control unit 44 starts counting the number of pulses input from the encoder 42 from the time when the top edge sensor 19 detects the leading edge of the paper. When the leading edge of the sheet that has passed the top edge sensor 19 reaches the conveying belt 61, the sheet is held by the conveying belt 61 and conveyed rightward.

  Next, in step S130, the control unit 44 determines whether the top edge sensor 210 has detected the leading edge of the sheet at the timing within the window set in step S120. When the reflectivity of the sheet and the conveyance belt 61 is close, the sheet may not be detected by the top edge sensor 210 that is a reflective sensor. Here, the control unit 44 uses the count value of the number of pulses from the encoder 42 to determine whether the top edge sensor 210 has detected the leading edge of the sheet at the timing within the window.

  When it is determined that the leading edge of the sheet is detected by the top edge sensor 210 at the timing within the window (step S130: YES), in step S140, the control unit 44 detects the leading edge of the sheet by the top edge sensor 210. From the time, counting of the number of pulses input from the encoder 42 is started, and control is performed so that printing is performed by ejecting ink from the inkjet head 111 at a timing based on the count value.

  If it is determined at the timing within the window that the top edge sensor 210 has not detected the leading edge of the sheet (step S130: NO), the control unit 44 detects the leading edge of the sheet by the top edge sensor 19 in step S150. At a timing based on the count value of the number of pulses from the encoder 42 that has started counting from the point in time, control is performed so that printing is performed by ejecting ink from the inkjet head 111.

  When the trailing edge of the sheet is detected by the vertical conveyance sensor 7 after the start of the assist operation of the vertical conveyance roller 4, the control unit 44 decelerates the vertical conveyance roller 4 by the vertical conveyance motor 13 via the driver 17. To stop. In FIG. 6A, it is assumed that the trailing edge of the sheet is detected by the vertical conveyance sensor 7 at time t9. The controller 44 controls the driver 17 to decelerate the vertical transport roller 4 from time t9 and then stop driving at time t10.

  When the trailing edge of the sheet is detected by the registration sensor 8 after the operation of the registration roller 5 is started, the control unit 44 decelerates and stops the registration roller 5 by the registration motor 14 via the driver 18. In FIG. 6B, it is assumed that the trailing edge of the sheet is detected by the registration sensor 8 at time t11. The controller 44 controls the driver 18 to decelerate the registration roller 5 from time t11 and then stop driving at time t12.

  On the other hand, when it is determined in step S80 of FIG. 4 that I ≧ I1 (step S80: YES), in step S160, the control unit 44 sets the correction value TA corresponding to the load current value I acquired in step S60. Obtained from the correction value table 30. Then, using this correction value TA, the control unit 44 corrects the start timing of the assist operation by the vertical conveyance roller 4. The start timing of the assist operation after correction is the time point before the correction roller TA from the drive start timing of the registration roller 5.

  Next, in step S <b> 170, the control unit 44 determines whether or not the start timing after correction of the assist operation of the vertical conveyance roller 4 has come. When it is determined that the start timing after correction of the assist operation of the vertical conveyance roller 4 has been reached (step S170: YES), the control unit 44 controls the driver 17 to start driving the vertical conveyance motor 13 in step S180. . When determining that it is not the start timing of the assist operation (step S170: NO), the control unit 44 repeats the process of step S170 until the start timing of the assist operation is reached.

  Next, in step S <b> 190, the control unit 44 determines whether or not it is time to start driving the registration rollers 5. When it is determined that the driving start timing of the registration roller 5 is reached (step S190: YES), the control unit 44 controls the driver 18 to start driving the registration motor 14 in step S200. Thereafter, the control unit 44 proceeds to the process of step S110 in FIG. When it is determined that the driving start timing of the registration roller 5 is not reached (step S190: NO), the control unit 44 repeats the process of step S190 until the driving start timing of the registration roller 5 is reached.

  FIG. 7A is a diagram illustrating an example of a conveyance speed control waveform of the vertical conveyance roller 4 when the start timing of the assist operation is corrected. FIG. 7B shows a conveyance speed control waveform of the registration roller 5, which is the same waveform as FIG. When I ≧ I1, the control unit 44, as shown in FIG. 7A, the vertical conveying roller 4 at time t13, which is a correction value TA before time t5 that is the driving start timing of the registration roller 5 by the registration motor 14. Is started, and the driver 17 is controlled to reach the same first speed V1 as that of the registration roller 5 at time t6. The conveyance speed control after time t6 is the same as that in FIG.

  When the load current value I ≧ I1, the sheet conveyance load on the vertical conveyance roller 4 is large. As a factor that increases the conveyance load, it is conceivable that the vertical conveyance roller 4 slips. Due to the occurrence of paper slip, the load current value I increases as a result of attempting to increase the transport speed in the transport speed correction operation of the vertical transport roller 4 described above.

  When the conveyance load is large, the conveyance amount becomes smaller than the theoretical value, and the conveyance of the sheet is delayed. Even when the conveyance speed of the vertical conveyance roller 4 is corrected, the registration roller 5 may not form a desired slack on the sheet. In this case, when the normal conveyance speed control as shown in FIGS. 6A and 6B is performed during the driving of the registration roller 5 and the assist operation by the vertical conveyance roller 4, the influence of the load on the vertical conveyance roller 4 causes A so-called back tension (paper tension) may occur on the paper, and the amount of conveyance by the registration roller 5 may be smaller than the theoretical value. As a result, the conveyance of the sheet is delayed, and the sheet may not reach the detection position of the top edge sensor 210 in the window.

  Therefore, in the first embodiment, as described above, the driving in the assist operation of the vertical transport roller 4 is started earlier than the driving of the registration roller 5, and the sheet transport amount by the assist operation of the vertical transport roller 4 is started. Adjust so that becomes larger. As a result, the slack of the paper is greatly formed in the registration roller 5. Thereby, when the registration roller 5 is driven, it is possible to reduce the influence of the load of the vertical conveyance roller 4 and convey the sheet so that the sheet reaches the detection position by the top edge sensor 210 in the window.

  Here, the correction value TA for correcting the driving start timing of the assist operation of the vertical conveying roller 4 is set so that the paper reaches the detection position by the top edge sensor 210 in the window according to the load current value I. As a value indicating the correction amount necessary for this, it is experimentally obtained in advance using the printing apparatus 1. In the printing apparatus 1, the correction value table 30 of FIG. 3 in which the load current value I and the correction value TA are associated with each other is stored in the storage unit 43 in advance.

  As described above, in the printing apparatus 1 according to the first embodiment, the paper reaches the position detected by the top edge sensor 210 in the window based on the load current value I as information relating to the paper conveyance delay factor. Thus, the conveyance amount by the assist operation in the vertical conveyance roller 4 is adjusted. Thus, even when the top edge sensor 210 does not detect the paper in the window and the ink is discharged based on the detection timing of the top edge sensor 19, the paper reaches the inkjet head 111. .

  Here, as described above, the printing apparatus 1 corrects the assist operation of the vertical conveying roller 4 so that the paper reaches the detection position of the top edge sensor 210 within the window. Therefore, the top edge sensor 210 does not detect the leading edge of the paper in the window due to the paper not reaching. However, for example, since the reflectances of the paper and the conveyor belt 61 are close to each other, the top edge sensor 210 that is a reflection type sensor may not be detected. In such a case, ink is ejected with reference to the detection timing of the top edge sensor 19.

  As described above, even when ink is ejected with reference to the detection timing of the top edge sensor 19, the paper has reached the inkjet head 111, and therefore, in the printing apparatus 1, the paper has not reached the inkjet head 111. It is possible to prevent the ink from being ejected at an improper timing such that the ejection of the ink is started despite being present. Thereby, according to the printing apparatus 1, disorder of a printing image can be reduced.

  In the printing apparatus 1, the window is enlarged so that the paper is detected by the top edge sensor 2 10 in the window, and the interval between the top edge sensor 2 10 and the inkjet head 111 is increased accordingly. There is no need to For this reason, in the printing apparatus 1, it is possible to prevent the print image from being disturbed due to the erroneous detection of the paper by the top edge sensor 210 and the influence of the paper conveyance variation.

  Further, by using the load current value I of the vertical conveyance motor 13 to correct the start timing of the assist operation, the magnitude of the paper conveyance load on the vertical conveyance roller 4 can be easily detected.

  Further, by starting the assist operation of the vertical conveyance roller 4 before the operation of the registration roller 5 is started, the slack of the paper in the registration roller 5 is greatly formed, and the load on the vertical conveyance roller 4 when the registration roller 5 is driven is increased. The influence of can be suppressed. Accordingly, it is possible to prevent a delay in the conveyance of the sheet and to allow the sheet to reach the detection position by the top edge sensor 210 in the window.

(Second Embodiment)
Since the printing apparatus according to the second embodiment has the same configuration as that of the printing apparatus 1 according to the first embodiment shown in FIGS. 1 and 2, the printing apparatus according to the second embodiment also has the same structure as FIG. This will be described with reference to FIG. However, in the second embodiment, the printing apparatus 1 stores the correction value table 30A shown in FIG. 8 in the storage unit 43 instead of the correction value table 30 in FIG. 3 in the first embodiment. ing.

  As shown in FIG. 8, the correction value table 30 </ b> A includes a load current value I detected by the load current detection unit 20, and a time (deceleration time) required for deceleration in driving of the registration roller 5 and assist operation by the vertical conveying roller 4. Is stored in correspondence with the correction value TB for correcting.

  FIG. 9 is a flowchart illustrating the operation of the printing apparatus 1 according to the second embodiment. In FIG. 9, steps similar to those in the flowchart of FIG. 4 described in the first embodiment are denoted by the same step numbers, and description thereof is omitted or simplified.

  As shown in FIG. 9, first, the control unit 44 performs the processes of steps S <b> 10 to S <b> 70 described in the first embodiment.

  Next, in step S310, the control unit 44 acquires the correction value TB corresponding to the load current value I acquired in step S60 from the correction value table 30A.

  Next, in step S320, the control unit 44 sets the acceleration during deceleration of the registration roller 5 using the correction value TB acquired in step S310.

  In the second embodiment, as will be described later, during the driving of the registration roller 5 and the assist operation by the vertical conveying roller 4, after accelerating to the first speed V <b> 1 and decelerating to the second speed V <b> 2. By adjusting the time (deceleration time) from the start of deceleration until the second speed V2 is reached, the conveyance amount of the paper is adjusted. The correction value TB is a value used for adjusting the deceleration time, that is, adjusting the acceleration during deceleration. The control unit 44 sets the acceleration at the time of deceleration of the registration roller 5 using the deceleration time corrected with the correction value TB.

  Next, the control unit 44 performs the processes of steps S90 and S100 described in the first embodiment, and starts the driving of the registration roller 5 and the assist operation by the vertical conveyance roller 4. After that, the control unit 44 performs the processing after step S110 in FIG. 5 as in the first embodiment.

  FIG. 10A is a diagram illustrating an example of a conveyance speed control waveform of the vertical conveyance roller 4 when the deceleration time in the assist operation is corrected. FIG. 10B is a diagram illustrating an example of a conveyance speed control waveform of the registration roller 5 when the deceleration time is corrected. When I ≧ I1, as shown in FIGS. 10 (a) and 10 (b), the control unit 44 starts the deceleration of the vertical conveying roller 4 and the registration roller 5 at time t7, and FIGS. The drivers 17 and 18 are controlled so as to reach the second speed V2 and finish the deceleration at a time t14 after the correction value TB after the time t8. The conveyance speed control waveforms at times t5 to t7 in FIGS. 10A and 10B are the same as those at times t5 to t7 in FIGS. 6A and 6B. In the case of I <I1, as shown in FIG. 8, the correction value TB = 0, and the deceleration time is not corrected.

  As described in the first embodiment, when the load current value I ≧ I1, the conveyance amount by the registration roller 5 may be smaller than the theoretical value. In the second embodiment, as shown in FIGS. 10 (a) and 10 (b), the deceleration time (time t7 to t14) is changed to the normal deceleration time (time t7) shown in FIGS. 6 (a) and 6 (b). -T8), the paper conveyance amount by the registration roller 5 and the vertical conveyance roller 4 is increased. As a result, when the registration roller 5 is driven, the sheet can reach the detection position by the top edge sensor 210 at the timing within the window.

  Here, the correction value TB for correcting the deceleration time in the registration roller 5 and the vertical conveyance roller 4 is set so that the paper reaches the detection position by the top edge sensor 210 in the window according to the load current value I. As a value indicating the correction amount necessary for this, it is experimentally obtained in advance using the printing apparatus 1. In the printing apparatus 1, the correction value table 30 shown in FIG. 8 in which the load current value I and the correction value TB are associated with each other is stored in the storage unit 43 in advance.

  As described above, in the second embodiment, based on the load current value I, the assist operation in the registration roller 5 and the vertical conveyance roller 4 is performed so that the sheet reaches the detection position by the top edge sensor 210 within the window. The conveyance amount is adjusted by correcting the deceleration time. As a result, as in the first embodiment, ink discharge is performed at an improper timing such that ink discharge starts even though the paper has not reached the inkjet head 111. This can prevent the disturbance of the printed image.

(Other embodiments)
As described above, the present invention has been described according to the first and second embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the first and second embodiments, the load current value I is used as information relating to the paper conveyance delay factor, but the paper to the registration sensor 8 provided at a predetermined position near the upstream side of the registration roller 5 is used. May be used. For example, the delay time TD with respect to the theoretical value of the arrival timing of the sheet to the registration sensor 8 is used instead of the load current value I. In the first embodiment, the delay time TD and the correction value TA as shown in FIG. And a correction value table 30B that holds them in correspondence with each other. It is considered that the arrival timing of the sheet to the registration sensor 8 is delayed with respect to the theoretical value, indicating that the sheet conveyance load on the vertical conveyance roller 4 is increased. For this reason, the delay time TD can be used instead of the load current value I. Further, both the load current value I and the delay time TD may be used as information relating to the paper conveyance delay factor.

  In the first embodiment, the start timing of the assist operation in the vertical conveyance roller 4 is corrected. In the second embodiment, the deceleration time in the registration roller 5 and the vertical conveyance roller 4 is corrected. You may combine correction | amendment of the start timing of the assist operation | movement in the roller 4, and correction | amendment of the deceleration time in the registration roller 5 and the vertical conveyance roller 4. FIG.

  In the first and second embodiments, the case where paper is fed from the internal paper feed unit 2 has been described. However, the present invention can also be applied to the case where paper is fed from the external paper feed unit 3.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 Printing apparatus 2 Internal paper feed part 3 External paper feed part 4 Vertical conveyance roller 5 Registration roller 6 Belt conveyance part 7 Vertical conveyance sensor 8 Registration sensor 9 Top edge sensor 1
10 Top edge sensor 2
DESCRIPTION OF SYMBOLS 11 Head unit 12 Paper feed motor 13 Vertical conveyance motor 14 Registration motor 15 Belt motor 16-19 Driver 20 Load current detection part 30, 30A, 30B Correction value table 43 Storage part 44 Control part

Claims (4)

A printing unit for printing on a print medium conveyed on the conveyance path;
A registration roller that is arranged on the upstream side in the transport path with respect to the printing unit, and that transports a print medium toward the printing unit;
A transport roller that is disposed upstream of the registration roller in the transport path, transports the print medium toward the registration roller, and performs an assist operation for assisting the transport of the print medium by the registration roller;
A first detection unit that is disposed between the registration roller and the printing unit in a conveyance path and detects a print medium conveyed on the conveyance path;
A second detection unit that is disposed between the first detection unit and the printing unit in the conveyance path and detects a print medium conveyed on the conveyance path;
While controlling the operation of the registration roller and the transport roller, and when the print medium is detected by the second detection unit in a predetermined period after the print medium is detected by the first detection unit, Printing is performed based on the detection timing of the second detection unit, and if the print medium is not detected by the second detection unit during the predetermined period, printing is performed based on the detection timing of the first detection unit. A control unit for controlling the printing unit,
The control unit arrives at a detection position by the second detection unit during the predetermined period after the detection of the print medium by the first detection unit based on information on a delay factor of conveyance of the print medium. As described above, at least one of a conveyance amount by the assist operation in the conveyance roller and a conveyance amount by the registration roller is adjusted.   The control unit, as information on the delay factor of the conveyance of the print medium, the load current value of the motor that drives the conveyance roller during the conveyance operation before the start of the assist operation, and the vicinity of the upstream side with respect to the registration roller The printing apparatus according to claim 1, wherein at least one of the arrival timings of the print medium at a predetermined position is used.   3. The control unit according to claim 1, wherein the controller starts the assist operation of the transport roller before the operation of the registration roller when adjusting the transport amount of the transport roller by the assist operation. The printing apparatus as described in.   The control unit, when adjusting a conveyance amount in the registration roller, makes a time required for decelerating the conveyance speed of the registration roller and the conveyance speed of the conveyance roller in the assist operation longer than usual. Item 4. The printing apparatus according to any one of Items 1 to 3.

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