JP4514511B2 - Inkjet printer - Google Patents

Description

  The present invention relates to a print head that forms an image on a printing surface by ejecting ink onto a printing medium, a printing stage that is located on the back side of the printing medium and has a large number of holes, and the many The present invention relates to an ink jet printer having an adsorption mechanism for adsorbing a printing medium to a print stage through a hole and a first sensor for detecting a conveyance state of the printing medium and / or an ink landing position. Is.

  Such an ink jet printer sequentially draws paper (corresponding to a printing medium) from a paper magazine in which a paper roll is accommodated, and conveys the paper to a print stage. A print head is provided above the print stage, and ink is ejected onto the paper surface based on image data to form an image on the paper surface (see, for example, Patent Documents 1 and 2 below). A large number of holes are formed in the print stage, and the paper is sucked onto the surface of the print stage by a suction mechanism (suction fan or the like) provided on the back side of the print stage. This prevents the paper from being lifted or distorted carelessly, stabilizes the position of the paper, and ensures image formation. The paper on which the image is formed on the print stage is further conveyed downstream, cut into a print size, and discharged outside the apparatus.

  On the other hand, a sensor (first sensor) is provided in order to perform image formation with high accuracy, and reads a paper conveyance state, an ink landing position, and the like. This reading inspection is performed by forming a predetermined test image with a print head and reading this image with a sensor. The paper transport state inspects whether or not the paper is transported in an inclined state. In addition, the ink landing position is read by checking whether the center of the paper in the width direction matches the center of the image. Based on the inspection result, the paper conveyance state is mechanically corrected, or the image data is electronically corrected so that the center position matches. In addition, since the reading inspection is performed by reading a test image, it is performed at a place different from the image forming area (downstream of the image forming area).

However, in the image forming area, the paper is adsorbed on the surface of the print stage in order to perform image formation with high accuracy, but the paper is not adsorbed in the detection area where the test image is read. Therefore, the paper may be bent or lifted in the detection region. Therefore, there is a possibility that the test image cannot be accurately read by the sensor.
JP 2003-104600 A JP 2003-175655 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an ink jet printer that can accurately perform an image reading inspection by a sensor.

In order to solve the above problems, an ink jet printer according to the present invention provides:
A print head that forms an image on a printing surface by ejecting ink to a substrate;
A print stage located on the back side of the substrate to be printed, on which a large number of holes are formed,
An adsorption mechanism for adsorbing the printing medium to the print stage through the multiple holes;
An inkjet printer comprising a first sensor for reading a test image and detecting a conveyance state of a printing medium and / or a landing position of ink,
The first sensor is disposed downstream of the print head in the conveyance direction of the printing medium,
The upstream side in the transport direction of the print stage is set as an image forming area, and the downstream side in the transport direction is set as a detection area by the first sensor,
The large number of holes are formed in both the image forming area and the detection area, and the print medium is adsorbed to the print stage in both the image formation and the detection operation by the first sensor. It is characterized by.

  The operation and effect of the ink jet printer having this configuration will be described. The print head forms an image on the printing surface by ejecting ink onto the substrate. Ink ejection is performed based on image data. A print stage is provided to perform image formation, and the function can be divided into an image forming area located on the upstream side and a detection area located on the downstream side. In the image forming area, ink is ejected to form an image. In the detection area, the test image is read by the first sensor. A large number of holes are formed in the print stage, and an adsorption action can be performed through the holes, so that the printing medium can be adsorbed on the surface of the print stage. A large number of holes are formed not only in the image forming area but also in the detection area. Therefore, the printing medium can be attracted to the print stage even in the detection region. As a result, it is possible to provide an ink jet printer that can accurately perform an image reading inspection by a sensor.

  The first sensor according to the present invention is preferably provided in a head unit on which a print head is mounted. The head unit can move in the main scanning direction (direction perpendicular to the conveyance direction of the printing medium) in order to print on the printing surface. Therefore, by mounting the first sensor on such a head unit, it is not necessary to provide a dedicated mounting mechanism, and the configuration can be simplified and the cost can be reduced.

In the present invention, a windshield disposed on the back side of the print stage and formed with a large number of holes,
A windshield moving mechanism for moving the windshield from the first position to the second position along the direction in which the printing medium is conveyed;
A second sensor for detecting that the substrate to be printed has been conveyed to the print stage;
A windshield control means for controlling the windshield moving mechanism based on the detection result of the second sensor,
In the first position, at least the holes formed in the detection area are shielded, and in the second position, the print stage and the windshield are so opened that the holes formed in the detection area are open. It is preferable that a hole in the plate is formed.

  When a large number of holes are formed on the print stage, the holes can be effectively shielded by the printed material being shielded. However, the substrate to be printed is conveyed from the upstream side to the downstream side, and among the whole holes, there are also open holes. If the suction is performed in a state where such open holes exist, there is a problem that the suction effect is lowered and the power of the suction mechanism must be increased.

  Therefore, a windshield plate having a large number of holes formed on the back side of the print stage is disposed, and a windshield plate moving mechanism is provided for moving the windshield plate from the first position to the second position. In the first position, at least the hole of the print stage formed in the detection area is shielded. Therefore, it is possible to efficiently adsorb the printing medium during image formation. Further, at the second position, since the hole of the print stage formed in the detection area is opened, it is possible to efficiently adsorb the printing medium at the time of reading by the first sensor. The fact that the printing medium has been conveyed to the print stage can be performed by the second sensor. The wind shield control means can perform movement control of the wind shield based on the detection result by the second sensor. Thus, the printing medium can be adsorbed to the print stage in an appropriate state in each of the image forming area and the detection area.

  In the present invention, as the windshield plate moves from the first position to the second position, the positions and sizes of the holes on the print stage and the windshield plate are increased so that the number of holes to be opened gradually increases. It is preferable that it is set.

  As the head of the printing medium advances through the print stage, the number of holes covered by the printing medium gradually changes. Therefore, if the number of holes opened by the wind shielding plate is gradually increased in conjunction with the conveyance of the printing medium from the upstream side to the downstream side, the advanced position of the printing medium Can be adsorbed appropriately.

  A preferred embodiment of an ink jet printer according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating an internal configuration of an inkjet printer.

<Overall configuration of printer>
Paper as an image forming medium (corresponding to a printing medium) is transported along a predetermined transport path, and a paper magazine 1 in which paper is accommodated in a roll shape is provided on the most upstream side of the transport path. The paper magazine 1 may be detachably attached to the apparatus main body, and may be configured to be additionally mountable with another paper magazine containing papers having different width dimensions. As paper, coated paper for ink jet recording based on paper is preferably used, but is not limited thereto.

  The paper drawn from the paper magazine 1 is conveyed downstream by the roller units 2 and 3. The roller units 2 and 3 are driven by a drive motor 4. The roller unit 3 changes the paper transport direction and feeds it to the image forming unit. A head unit 5 is provided in the image forming unit. The head unit 5 is provided with a first head 5a, a second head 5b, and a third head 5c (these correspond to the head unit) along the transport direction. Further, the first sensor 5d is mounted further downstream than the third head 5c, and the first sensor 5d is moved together with the movement of the head unit 5. Each head is provided with a number of nozzles for ejecting ink, and can receive ink supply from the ink supply unit 6. In order to form a color image, seven colors of ink, that is, black, yellow, magenta, cyan, light black, light magenta, and light cyan ink can be ejected, and an ink cartridge for that purpose is provided.

  Each nozzle can print and form an image on the paper surface by discharging liquid ink. As a form for ejecting ink, there are a system for ejecting ink using a piezoelectric element, a bubble jet (registered trademark) system, and the like, but the present invention is not limited to a specific format.

  The head unit 5 is located on the front side of the paper to be conveyed, and the print stage 7 is located on the back side of the paper. Although details of the print stage 7 will be described later, a large number of small holes are formed on the surface of the print stage 7, and an adsorbing action is performed through the holes to adsorb the paper to the surface of the print stage 7. As a result, the paper is prevented from being bent or lifted, and image formation by ink ejection is performed reliably and accurately. The surface of the print stage 7 is set in an inclined state, and the surface (nozzle arrangement surface) of the head unit 5 is also arranged at the same inclination angle correspondingly.

  The head unit 5 is configured to be movable along the paper width direction (direction perpendicular to the transport direction = main scanning direction = direction perpendicular to the paper surface of FIG. 1), and a guide mechanism 9 for that purpose is provided. Yes. The guide mechanism 9 is configured by a combination of a guide groove 9a and a guide rail 9b. In FIG. 1, the guide groove 9a is provided in the head unit 5, but a configuration in which the guide rail 9b is provided in the head unit 5 may be adopted.

  FIG. 2 is an external perspective view of the head unit 5 as viewed from the nozzle side. Each of the heads 5a, 5b, and 5c is arranged along the conveyance direction, but a plurality (four in the illustrated example) are arranged in the conveyance width direction. The number of sheets arranged in the conveyance width direction can be determined as appropriate. Each head 5a, 5b, 5c is provided with a number of nozzles, and it is possible to appropriately set which color of ink is assigned to which head.

  The paper on which the image is formed is sent to the cutter unit 11 by the roller unit 10 provided on the downstream side of the image forming unit. The cutter unit 11 includes a movable blade 11a and a fixed blade 11b, and cuts long paper so as to have a predetermined print size. A drive motor 12 for driving the roller unit 10 and a drive motor 13 for driving the movable blade 11a are provided. The paper cut to the print size is discharged from the discharge port 16 to the outside of the apparatus by the discharge roller unit 14. The roller unit 14 is driven by a drive motor 15.

<Composition of print stage>
Next, a paper suction mechanism in the print stage 7 will be described. FIG. 3 is a plan view of the print stage 7 and shows a state before the paper arrives at the print stage 7. A large number of holes 7a are formed in the print stage 7, and the holes 7a are circular and all have the same size. As described with reference to FIG. 1, since the suction fan 8 is disposed on the back side of the print stage 7, by operating the suction fan 8, a negative pressure is generated and the paper is sucked onto the stage surface.

  Further, slit holes 7b are formed on the surface of the print stage 7 along the paper conveyance direction. The slit hole 7 b has an elongated long hole shape, and has a function of escaping ink ejected from the head unit 5. That is, when an image is formed on paper, an image may be formed on the entire paper without forming edges on the four sides of the paper. In that case, ink may be ejected to a region where the paper does not exist (a region slightly outside the end surface of the paper in the width direction) on both sides in the width direction of the paper. Since the ink discharge causes the surface of the print stage 7 to become dirty, the back side of the paper transported by the stain is also stained. In order to prevent this, the slit hole 7b is provided so that ink does not adhere to the print stage 7 and remains. The slit holes 7b are formed in advance according to the width dimension of the paper to be used. In the example of FIG. 2, six slit holes 7b are arranged symmetrically with respect to the center in the transport width direction. . This slit hole 7b can be appropriately set according to the number of width dimensions of the paper used.

  The print stage 7 is functionally provided with an image forming region R1 and a detection region R2, and an image is formed in the image forming region R1, and a reading operation by the first sensor 5d is performed in the detection region R2. Is called. The many holes 7a are provided in both the image forming region R1 and the detection region R2, but the slit hole 7b is formed only in the image forming region R1.

  In the detection region R2, the test image printed on the paper surface is read by the first sensor 5d. The first sensor 5d is a reflective optical sensor, and can read a test image. As the test image, a predetermined pattern (such as a line or a lattice pattern) can be printed, but is not limited to a specific image. By reading the test image with the first sensor 5d, it is possible to detect the paper conveyance state (whether or not the paper is conveyed in an oblique state). When the skew amount of the paper is detected, correction is performed so that the paper can be conveyed in a straight state. Such correction can be performed by providing a mechanical correction mechanism (not shown).

  In addition, the ink landing position can be inspected. For example, when the center position of the image is shifted from the center position in the paper width direction, the image data can be corrected so as to match them. Furthermore, it is possible to check whether ink is being ejected from a specific nozzle in the head unit 5. Based on the inspection result, nozzle maintenance, repair and replacement can be performed.

  As described above, in the detection region R2, it is necessary to accurately perform image reading by the first sensor 5d. Therefore, also in the detection region R2, the paper is sucked to prevent the paper from being bent or lifted. Thereby, reading in the detection region R2 can be performed with high accuracy. In addition, since the basic structure of the print stage 7 is the same as that of the prior art and the hole 7a is also formed in the detection region R2, the structure need not be complicated. As for the suction fans 8, the suction fans 8 in the image forming region R1 can be used as they are, so that the number of the suction fans 8 need not be increased.

  Further, only one first sensor 5 d is required to be mounted on the head unit 5. As already described, since the head unit 5 can move along the main scanning direction, the test image can be read by one first sensor 5d. Of course, a plurality of first sensors 5d may be provided as necessary.

<Configuration of wind shield>
Next, the configuration of the wind shield 20 will be described. FIG. 4 is a plan view showing the configuration of the wind shielding plate 20. The wind shield 20 is disposed on the back side of the print stage 7 and is configured to be movable between a first position and a second position along the paper transport direction. FIG. 3 shows a state where the wind shielding plate 20 is in the first position, and FIG. 7 shows a state where the wind shielding plate 20 is in the second position. FIG. 6 shows a state in which the intermediate position is between the first position and the second position. FIG. 5 shows side views of the print stage and the wind shielding plate, and shows (a) a first position, (b) an intermediate position, and (c) a second position, respectively.

  The reason for providing the wind shield 20 will be described. A large number of holes 7 a are formed in the print stage 7. When the holes 7 a are blocked by paper, the paper is sucked through the holes 7 a by the action of the suction fan 8. Therefore, when the hole is blocked by the paper, the suction fan 8 needs to be in a state in which the hole 7a is opened (a state in which the suction action by the suction fan 8 is exerted on the paper). is there. However, since no paper exists on the downstream side (leading side) of the paper, it is preferable to shield the hole 7a of the print stage 7 in this region. Therefore, the wind shield plate 20 is used so that the hole 7a formed in the print stage 7 can be shielded.

  As shown in FIG. 4, a large number of holes 20 a are also formed in the wind shielding plate 20. However, unlike the hole 7a of the print stage 7, the hole 20a formed on the downstream side is circular, but the hole 20a gradually becomes an oval (long hole) shape toward the upstream side. The long hole is formed to be long along the paper transport direction.

  With reference to the schematic diagram of FIG. 5, the moving mechanism of the wind shield 20 (wind shield moving mechanism) will be described. The wind shielding plate 20 is movable along the paper conveyance direction, but is biased by the spring 21 (biasing means) so as to return to the first position (the state shown in FIG. 5A). . The roller unit 10 includes a pressure roller 10a and a drive roller 10b, and the drive motor 12 is coupled to the drive roller 10b via a speed reduction mechanism (not shown). The wind shield 20 is mechanically connected to the drive roller 10b (or drive motor 12) via a torque limiter 22 and a connection mechanism 23 (gear, cam mechanism, etc.). Therefore, when the drive motor 12 is driven, the roller unit 10 is rotated and the wind shielding plate 20 starts to move from the first position to the second position. A stopper 24 for defining the first position and a stopper 25 for defining the second position are provided. The state in which the wind shield 20 abuts against the stopper 25 and cannot be advanced any further is the second position. In order to convey the paper, the roller unit 10 is continuously driven to rotate, but the windshield plate 20 continues to be held at the second position as the torque limiter 22 slides. When the rotation drive of the roller unit 10 is stopped, the wind shielding plate 20 returns from the second position to the first position by the action of the spring 21.

  As shown in FIG. 3, a pair of second sensors 17 are provided at the upstream end of the print stage 7, and it is possible to detect that the top of the paper has arrived. Based on this detection result, the drive timing of the roller unit 10 can be controlled. Similarly to the first sensor 5d, the second sensor 17 can be a reflective photosensor.

<Control block diagram>
The control block configuration of the ink jet printer according to this embodiment will be described with reference to FIG. However, only the main part will be described. The head unit 5 is driven by the head driving unit 30, and the head driving unit 30 is controlled by the head control unit 31. Image data to be formed by the head unit 5 is input via the image data input unit 32. The image data input unit 32 includes a film scanner that reads a frame image of a developed photographic film, a storage medium such as a digital camera, and a device that acquires image data from a storage medium such as a CD-R or MO disk. The The image processing unit 33 has a function of performing image processing (color / density correction, data enlargement processing, etc.) on input image data. The image data after the image processing is transmitted to the head unit 5 via the image transmission unit 34. Control for image data transmission is also performed by the head controller 31, and control in the sub-scanning direction and main scanning direction in image formation is performed. The sub-scanning direction is the same as the paper transport direction, and can be performed by driving control on the roller unit 3.

  The wind shield control means 35 controls the roller unit 10 and the wind shield 20. These drive timings can be performed based on an input signal from the second sensor 17. That is, when it is detected by the second sensor 17 that paper has arrived, the drive motor 12 is started to drive after a predetermined timing with reference to this. The predetermined timing can be set based on, for example, a timer unit 36 provided. The timer means 36 may count a preset time or may count pulses having a predetermined period.

  The fan drive unit 37 drives the suction fan 8 and starts rotating the suction fan 8 when the second sensor 17 detects the arrival of paper. The controller 38 has a function of performing overall control of each part of the ink jet printer.

<Operation description>
Next, the operation of the wind shielding plate 20 will be described with reference to FIGS. The state in which the paper P has not arrived at the print stage 7 is the state shown in FIGS. 3 and 5A, and the wind shield 20 is in the first position. As shown in FIG. 3, in the region A upstream of the image forming region R1 (the region where the wind shielding plate 20 does not exist in plan view), the holes 7a are not shielded, but all the other holes 7a are not covered. It is shielded by the wind shield 20. Therefore, in the state of FIG. 3, the suction action of the suction fan 8 reaches only the region A.

  When the paper P is conveyed and the leading edge of the paper P is detected by the second sensor 17, a command is given to the fan drive unit 37 and the suction fan 8 starts to be driven. As a result, the conveyed paper P is attracted to the surface of the print stage 7, and ink ejection and image formation by the head unit 5 are started. When the paper P is detected by the second sensor 17, the timer means 36 starts counting. While this count is being performed, the paper P is continuously conveyed, but the wind shield 20 is still held in the first position.

  When the count value by the timer means 36 reaches a predetermined value, a command is issued to the drive motor 12 by the wind shield control means 35, and the driving of the roller unit 10 and the movement of the wind shield 20 are started. FIG. 6 and FIG. 5B show a state where the wind shielding plate 20 has moved from the first position (an intermediate position between the first position and the second position). In this state, the state shielded by the wind shielding plate 20 is released on the upstream side, and the state where the hole 7a is gradually opened is shown. 7 and 5C, the holes 7a in the detection region R2 are all open. Since the hole 20a formed in the windshield 20 is formed in an oval shape as it goes upstream, the hole 7a can be gradually opened and the hole 7a once opened is the second hole. It is prevented from being shielded again until reaching the position.

  As can be seen from the above figures, the number of open holes 7a is gradually increased in accordance with the progress of the paper P. The conveyance of the paper P and the movement of the wind shielding plate 20 are interlocked so that the hole 7a on the upstream side of the front end of the paper P is opened, and the hole on the downstream side of the front end is closed. As you can see, both are linked. Thereby, the hole 7a is opened only in a necessary area so that the paper P can be adsorbed appropriately. As a result, the paper P can be appropriately adsorbed not only in the image forming region R1 but also in the detection region R2, so that the image reading by the first sensor 5d can be performed with high accuracy.

  In FIG. 5C, the wind shield 20 abuts against the stopper 25 and cannot move further forward, but the roller unit 10 continues to be driven, so that the paper P is sent out in the direction of the cutter unit 11. Can do. Further, while the roller unit 10 is being driven, the wind shield plate 20 is held at the second position because the wind shield plate 20 is also subjected to a force for moving in the downstream direction. While the roller unit 10 is continuously driven, the torque limiter 22 operates.

<Another embodiment>
The configuration of the print head is not limited to the configuration of the present embodiment, and various modifications are possible. In the present embodiment, the first head to the third head are provided along the transport direction, but the number of heads can be set as appropriate. The arrangement of the nozzles can be modified as appropriate. Various modifications of the mounting position of the first sensor 5d on the head unit 5 are possible. Also, the number of ink colors is not limited to seven, and may be four colors, for example.

  The inspection by the first sensor may be performed only in the paper conveyance state or only in the ink landing position. Both of these may be performed. Of course, in addition to these, other types of inspections may be performed.

Schematic diagram showing the internal configuration of an inkjet printer External perspective view of the head unit viewed from the nozzle side Plan view showing the configuration of the print stage and wind shield (first position) Plan view showing the configuration of only the wind shield Side view showing the configuration of the print stage and windshield Plan view showing the configuration of the print stage and wind shield (intermediate position) Plan view showing the configuration of the print stage and wind shield (second position) Diagram showing control block configuration

Explanation of symbols

5 Head unit 5a 1st head 5b 2nd head 5c 3rd head 5d 1st sensor 7 Print stage 7a Hole 7b Slit hole 8 Suction fan 9 Guide mechanism 10 Roller unit 17 2nd sensor 20 Wind shield 20a Hole 21 Spring 22 Torque Limiter 30 Head drive unit 31 Head control unit 35 Wind shield control unit 36 Timer unit 37 Fan drive unit P Paper R1 Image formation region R2 Detection region

Claims (3)

A print head that forms an image on a printing surface by ejecting ink to a substrate;
A print stage located on the back side of the substrate to be printed, on which a large number of holes are formed,
An adsorption mechanism for adsorbing the printing medium to the print stage through the multiple holes;
An inkjet printer comprising a first sensor for reading a test image and detecting a conveyance state of a printing medium and / or a landing position of ink,
The first sensor is disposed downstream of the print head in the conveyance direction of the printing medium,
The upstream side in the transport direction of the print stage is set as an image forming area, and the downstream side in the transport direction is set as a detection area by the first sensor,
The plurality of holes are formed in both the image forming region and the detection region, and configured to adsorb the printing medium on the print stage both in the case of performing image formation and the detection operation by the first sensor , further,
A drive roller for transporting the substrate to be printed along the transport direction;
A windshield plate arranged on the back side of the print stage and formed with numerous holes;
In order to move the windshield plate from the first position to the second position along the direction in which the printing medium is conveyed , the windshield plate is coupled to the drive roller via a torque limiter and a coupling mechanism. A moving mechanism;
A second sensor for detecting that the substrate to be printed has been conveyed to the print stage;
A windshield control means for controlling the windshield moving mechanism based on the detection result of the second sensor,
In the first position, at least the holes formed in the detection area are shielded, and in the second position, the print stage and the windshield are so opened that the holes formed in the detection area are open. An ink jet printer , wherein a hole in the plate is formed and the wind shield plate can be kept in contact with the stopper by the action of the torque limiter in the second position . The inkjet printer according to claim 1, wherein the first sensor is provided in a head unit on which a print head is mounted. As the wind shield moves from the first position to the second position, the positions and sizes of the holes on the print stage and wind shield are set so that the number of holes to be opened gradually increases. The inkjet printer according to claim 1 .

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