JP2010099920A - Printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer minimizing a medium conveyance error caused by switching of a conveying means, consequently, printing a good image. <P>SOLUTION: The printer includes: a conveying roller (102) that comes in contact with the medium at a position upstream from a printing position and conveys the medium; a discharge roller (103) that comes in contact with the medium at a position downstream from the printing position and conveys the medium; and a sensor (105) that images the image of the surface of the medium and detects movement information about the medium. A control part (90) feeds back the detection result of the sensor (105) and controls the medium conveyance in order to eliminate an influence of a kicking phenomenon when switching from a first state where the same medium is conveyed by the conveying roller (102) and the discharge roller (103) to a second state where the same medium is conveyed only by the discharge roller (103). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technical field of a printer that conveys media and performs printing.

  When printing is performed while transporting print media such as cut sheets (hereinafter referred to as media), if the transport accuracy is low, density unevenness of the halftone image or magnification error may occur, resulting in a printed image. The quality of the product deteriorates. For this reason, high-precision parts are used and a precise transport mechanism is installed, but the demand for print quality is severe and further improvement in accuracy is desired. On the other hand, the demand for cost is strict, and both high accuracy and low cost are required.

Patent Document 1 focuses on the problem that a transport error occurs when a printer having a transport roller and a discharge roller along a transport direction is switched from a state in which a medium is transported by both rollers to a state in which the medium is transported by only a discharge roller. Yes. In order to solve this, an adjustment pattern is printed on a medium before and after switching, and the adjustment amount is read and input as a correction value to the apparatus to correct the feed amount.
JP 2005-7817 A

  However, since the apparatus of Patent Document 1 once prints an adjustment pattern, reads it, and inputs it to the apparatus, it requires labor and time for adjustment, and is not practical. Further, since the adjustment pattern is printed on an unused medium, there is a problem that a useless medium is consumed for adjustment.

  The present invention has been made based on recognition of the above-described problems.

  An object of the present invention is to provide a printer capable of minimizing a medium transport error caused by switching of a transport unit having a plurality of rotating bodies and printing a good image as a result.

  A printer of the present invention that solves the above problems includes a printing unit that prints on a medium at a printing position, a first rotating body that conveys the medium upstream of the printing position, and a downstream side of the printing position. The same rotating medium is transported by the second rotating body that transports the medium, the sensor that detects the movement information of the medium by imaging the surface of the medium, and at least the first rotating body and the second rotating body. When switching from the first state to the second state in which the medium separated from the first rotating body is transported by the second rotating body, the movement information detected by the sensor is fed back to transport the medium. And a control unit for controlling.

  According to the present invention, it is possible to provide a printer capable of minimizing a medium conveyance error caused by switching of a conveyance unit having a plurality of rotating bodies and printing a good image as a result.

  Exemplary embodiments of the present invention will be described below with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

  An embodiment of an inkjet printer will be described as an example of an image forming apparatus to which the present invention is applied. The application range of the present invention is not limited to the ink jet system. For example, the present invention can be applied to various types of printers such as an electrophotographic system, a thermal system, and a dot impact system, or a device including a printer such as a copying machine, a facsimile machine, and a multifunction machine.

[First Embodiment]
FIG. 1 is a perspective view showing the overall configuration of the printer. The print unit 101 includes an ink jet print head and a carriage on which the print head is mounted. The carriage reciprocates in the main scanning direction by a drive mechanism such as a motor, and prints on the medium M facing the print head at the print position. In the conveyance direction of the medium M, the conveyance roller 102 is positioned upstream of the print position, and the discharge roller 103 is positioned downstream.

  A conveyance roller 102 (first rotating body) and a plurality of divided pinch rollers 109 that follow the conveyance roller 102 are a part of a conveyance mechanism that conveys the medium M. The transport roller 102 is made of a metal roller that is processed so as to generate a fine frictional force by forming fine irregularities on the surface. Further, the transport roller 102 includes a rotary encoder 104 that detects the rotation amount. The medium M is conveyed by the rotation of the conveying roller 102 in the sub-scanning direction (arrow F direction in the figure) orthogonal to the main scanning direction.

  The discharge roller 103 (second rotating body) and the spur 110 that follows the discharge roller 103 are also part of the transport mechanism that transports the media. The discharge roller 103 is a rubber roller having a large coefficient of friction. Regarding the rotation of the transport roller 102 and the discharge roller 103, the rotation of the motor 106, which is a common drive source, is transmitted by the transmission mechanism 107 and the transmission mechanism 108, and these rollers are driven synchronously. The medium M printed by the printing unit 101 is discharged in the direction of arrow F by the discharge roller 103.

  Further, on the conveyance path, the front side (back side) of the medium M is imaged at a position between the printing position of the printing unit 101 and the discharge roller 103, and movement information (movement amount, movement speed, movement direction, etc.) of the medium M A media sensor 105 is provided. The control unit 90 controls various controls of the entire apparatus.

  Next, details of the media sensor 105 will be described. FIG. 2 shows a physical configuration, and FIG. 3 shows an electrical configuration. In FIG. 2, the media sensor 105 is an integrated reading unit including a light emitting element 71, a lens 72, and a photoelectric conversion element 73. As the light emitting element 71, LED, LD, OLED or the like is used. The photoelectric conversion element 73 is a two-dimensional image sensor composed of an image sensor with a CCD or CMOS structure. For example, a cell of 10 μm × 10 μm is arranged by 400 pixels in the transport direction × 200 pixels in the main scanning direction.

  In FIG. 3, the output of the photoelectric conversion element 73 is converted to digital by the A / D conversion circuit 74, and is output as a digital signal to the control unit 90 via the interface 75. Further, light emission of the light emitting element 71 is controlled via the interface 75. In this configuration, the surface of the medium M is spot illuminated with light emitted from the light emitting element 71. The scattered reflected light from the illuminated medium M is collected by the lens 72 and received by the photoelectric conversion element 73. The illuminated area of the medium M and the light receiving surface of the photoelectric conversion element 73 form an imaging relationship by the lens 72, and the photoelectric conversion element 73 acquires precise image information on the surface of the medium M.

  Next, the transport control procedure for the medium M will be described. In the present embodiment, the entire surface of the medium is divided into three regions, and the conveyance / printing operation is changed for each region, whereby a good image can be obtained stably with high throughput.

  FIG. 4 is a diagram showing that the medium M is divided into three areas along the transport direction. The medium is divided into three areas A, B, and C. FIG. 5 is a cross-sectional view of the state of each of the conveyed media as viewed from the side. FIG. 5A shows a state in which the medium is transported only by the transport roller 102. FIG. 5B shows a state in which the medium is being conveyed by the conveyance roller 102 and the discharge roller 103. This state is referred to as a “first state”. FIG. 5C illustrates a state immediately before the medium is switched from a state where the medium is transported by the transport roller 102 and the discharge roller 103 to a state where the medium is transported only by the discharge roller 103. FIG. 5D shows a state immediately after the medium is switched to a state where the medium is conveyed only by the discharge roller 103. FIG. 5E shows a state where the medium is conveyed only by the discharge roller 103. Hereinafter, the state of FIG. 5D and FIG. 5E is referred to as a “second state”.

  In FIG. 4, in the area A, the medium M is transported only by the transport roller 102 (see FIG. 5A) or is transported by the two rollers of the transport roller 102 and the discharge roller 103 (see FIG. 5A). FIG. 5B)). The clamping force between the conveying roller 102 and the pinch roller 109 is sufficiently larger than the clamping force between the discharge roller 103 and the spur 110. Therefore, even if the state is switched from the state shown in FIG. 5A to the state shown in FIG.

  FIG. 6 is a diagram illustrating drive profiles of the conveyance roller 102 and the discharge roller 103 in the area A. A graph G10 is a drive command value for conveying the media, and is driven intermittently in a pulse shape. The maximum conveyance speed is V0. The conveyance amount (the trapezoidal area of one pulse of G10) in one step between time t = t10 and time t = t11 is H. When the media speed becomes zero at intermittent intervals t = t10 and t11, one line is printed.

  In FIG. 4, the area B of the medium is only the discharge roller 103 from the first state (see FIG. 5C) in which the medium is conveyed by the two rollers of the conveyance roller 102 and the discharge roller 103 when printing in this area. This is an area including the moment when the state is switched to the second state (see FIG. 5D). In this region, a so-called kicking phenomenon occurs. The kicking phenomenon is that at the moment when the rear end of the medium to be conveyed comes out of the conveying roller 102 and the pinch roller 109, it is kicked in the conveying direction by the roller, and the urging force momentarily acts to change the conveying amount. It is a phenomenon.

  Further, the medium area C is an area in which the medium is transported only by the discharge roller 103 when the area is printed (see FIGS. 5D and 5E).

Since the discharge roller 103 is a rubber roller, an eccentric error of the roller diameter is likely to occur. In addition, the clamping force between the discharge roller 103 and the spur 110 is small, and slip is likely to occur. Therefore, in the areas B and C that are transported only by the discharge roller 103, the intermittent transport step is reduced (1/4), and the media sensor 105 is used to move the media (transport amount, transport speed, etc.). ) Is detected, and the media is conveyed while feeding back this. Thereby, also in the area | region B and the area | region C, the highly accurate conveyance equivalent to the area | region A can be maintained. In the area A, the conveyance roller 102 and the discharge roller 103 can perform sufficiently stable media conveyance only by feedback control by the rotary encoder 104. Therefore, feedback control by the media sensor 105 is not performed. That is, the feedback control by the media sensor 105 is not performed immediately before the moment of switching from the first state to the second state (switching from the region A to the region B). FIG. FIG. 4 is a diagram showing a driving profile of a roller 102. As shown in the graph G20, in the region B and the region C, the control is intermittently performed by a short step of ¼ that of the previous region A, and conveyance for one line is performed in four steps. At the same time, the media sensor 105 detects the transport amount and performs feedback control.

  FIG. 8 is a flowchart showing the control procedure. FIG. 9 is a diagram for explaining a reading area on the medium by the media sensor 105.

  At time t = t20, the media sensor 105 reads the image data in the area 701 on the medium (step S100). A template pattern 710 is extracted from this image data (step S101). When the conveyance motor is driven between time t = t20 and time t = t21 and the medium is conveyed by one step by H / 4 (step S102), the conveyance motor is stopped (step S103). Next, at different timings and at time t = t21, the image data of the area 701 on the medium after being moved is read again by the media sensor 105 (step S104). Template matching processing is performed in the area 703 in the acquired image data for comparison (step S105). Based on the result, the actual transport amount of the media is calculated (step S106). Then, it is determined whether the target carry amount for one line has been reached (step S107). If not, the process returns to S102 and the media is stepped by H / 4. When the target transport amount for one line is reached at time t = t24, one line is printed (step S108).

  Somewhere between time t = t20 and time t = t24, even if the kicking phenomenon occurs from the first state to the second state, the effect is reduced by feedback control using a media sensor by reducing one step. I try to keep it light.

  In this way, the conveyance of the media is controlled so that the intermittent conveyance step is smaller in the second state than in the first state. At the same time, at the moment of switching from the first state to the second state and in the second state, the conveyance of the media is controlled while feeding back the movement information detected by the media sensor. In this way, by switching the conveyance control for each region, it is possible to stably obtain a good image without reducing the throughput.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, since many apparatus configurations and controls are common to the previous embodiment, a duplicate description is omitted. In the area A, it is the same as the description in FIG. 6, and the control in the areas B and C will be described.

  FIG. 10 is a diagram illustrating drive profiles of the discharge roller 103 and the conveyance roller 102 in the region B and the region C. FIG. 11 is a flowchart showing the control procedure.

  As shown in the graph G30, after the moment of switching to the second state in which the sheet is conveyed only by the discharge roller 103, the conveying roller 102 is temporarily stopped. At the same time, the actual conveyance amount is detected by the media sensor 105, the difference is obtained up to the remaining target conveyance amount, and the step conveyance is performed by the difference amount. That is, after the kicking occurs, the step conveyance is performed by an amount necessary for correction, and the conveyance is controlled so that the target conveyance amount is obtained in total.

  Specifically, at time t = t30, the media sensor 105 reads the image data of the area 701 on the medium (step S200), and extracts the template pattern 710 from this image data (step S201). When the conveyance motor is driven between time t = t30 and time t = t31 and the medium is step-conveyed by H1 (step S202), the conveyance motor is temporarily stopped (step S203). Here, H1 is a value such that H1 <H, and at time t = t31, the first state is surely switched to the second state. At time t = t31, the image data of the area 701 on the medium is read again at different timing after the movement by the media sensor 105 (step S204). Template matching processing is performed within the area 703 in the acquired image data (step S205). Based on the result, the actual transport amount of the medium is calculated (step S206). Between time t = t31 and time t = t32, the transport motor is driven, and the medium M is transported by a transport amount different from the initial amount by (target transport amount) − (media transport amount) (step S207). Then, the conveyance motor is stopped at time t = t32 (step S208). Thereafter, one line is printed (step S209).

  Thus, before and after the moment when the state is switched from the first state to the second state, the amount of movement of the medium 105 is detected by the media sensor, and step transport is performed by an amount that reaches the target transport amount. By switching the conveyance control in each region, a good image can be stably obtained without reducing the throughput.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In addition, since many apparatus configurations and controls are common to the previous embodiment, a duplicate description is omitted.

  FIG. 12 is a diagram illustrating drive control of the discharge roller 103 and the conveyance roller 102 in the region B and the region C. FIG. 13 is a flowchart showing the control procedure.

  As shown in the graph G40, the medium is conveyed at a speed V1 that is lower than the maximum speed V0 in the area A. Instead of intermittent step feed for each line as in the above example, the medium is continuously conveyed in each region. G41 indicates a sampling period f in which the media sensor 105 images the surface of the medium and calculates the conveyance amount, and the actual conveyance amount is calculated at this interval to perform feedback control.

  Specifically, at time t = t40, the media sensor 105 reads the image data of the area 701 on the medium (step S300), and extracts the template pattern 710 from this image data (step S301). Between time t = t40 and time t = t41, the transport motor is driven at a constant speed V1 to transport the medium (step S302). During this period, image data in the area 701 on the medium is read by the media sensor 105 at every sampling period f (step S303), and template matching processing is performed in the area 703 (step S304). It is determined whether or not there is the same pattern as the template pattern (step S305), and if not, the process returns to step S302. If there is the same pattern, the media transport amount is calculated (step S306), and it is determined whether the target transport amount has been reached (step S307). If not, the process returns to step S302 again. Somewhere in the meantime, the state is switched to the second state where the sheet is conveyed only by the discharge roller 103. When the target transport amount is reached at time t = t41, the transport motor is stopped (step S308). Then, one line is printed (step S309).

  In this way, the conveyance of the media is controlled so that the conveyance speed is lower in the second state than in the first state. At the same time, at the moment of switching from the first state to the second state and in the second state, the conveyance of the media is controlled while feeding back the movement information detected by the media sensor 105. By switching the conveyance control in each region, a good image can be stably obtained without reducing the throughput.

  In each of the above embodiments, the transport roller 102 and the discharge roller 103 which are rotating bodies do not necessarily have the form of a roller. For example, the belt conveyance may be such that the belt rotates on a plurality of rollers so that the belt rotates and a part of the belt is in contact with the medium to convey the medium. That is, in this case, the belt is a rotating body.

Perspective view showing the overall configuration of the printer Schematic diagram of media sensor Media sensor block diagram Diagram showing three areas on the media Cross-sectional view showing each process of media transport The figure which shows the drive profile in the area | region A The figure which shows the drive profile in the area | region B and the area | region C Flowchart diagram showing the control procedure Diagram explaining the reading area on the media The figure explaining the drive profile in 2nd Embodiment Flow chart showing the control procedure The figure explaining the drive profile in 3rd Embodiment Flow chart showing the control procedure

Explanation of symbols

101 Print head 102 Conveying roller (corresponding to the first rotating body)
103 discharge roller (corresponding to the second rotating body)
105 Media sensor 106 Transport motor M Media

Claims (8)

A print unit for printing on the medium at the print position;
A first rotating body that conveys media upstream of the print position;
A second rotating body that conveys media downstream of the print position;
A sensor that detects the movement information of the media by imaging the surface of the media;
At least a second state in which a medium separated from the first rotating body is transported by the second rotating body from a first state in which the same medium is transported by the first rotating body and the second rotating body. And a control unit that feeds back movement information detected by the sensor and controls the conveyance of the media when switching to the printer.   The printer according to claim 1, wherein the sensor images the surface of the medium at a position between the print position and the second rotating body in the conveyance path.   The control unit conveys the medium so that the intermittent conveyance step is smaller in the second state than in the first state, and at the moment when the first state is switched to the second state, and 3. The printer according to claim 1, wherein in the second state, the conveyance of the medium is controlled while feeding back the movement information detected by the sensor.   The control unit detects the moving amount of the medium with the sensor before and after the moment when the first state is switched to the second state, and performs step transport by an amount that reaches a target transport amount. The printer according to claim 1 or 2.   The control unit controls the conveyance of the media so that the conveyance speed is lower in the second state than in the first state, and at the moment when the first state is switched to the second state and the second state. 3. The printer according to claim 1, wherein in the state, the conveyance of the medium is controlled while feeding back the movement information detected by the sensor.   6. The control unit according to claim 1, wherein the control unit does not perform feedback control by the sensor in the first state until immediately before the moment of switching from the first state to the second state. Printer.   The printer according to claim 1, wherein the movement information of the medium is detected by comparing a plurality of pieces of image data acquired at different timings using the sensor.   8. The printer according to claim 1, wherein printing is performed by an ink jet method.

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