JP2021066130A - Inkjet recording apparatus - Google Patents

Abstract

To overcome possibility that an inkjet head is damaged by contact with a recording medium.SOLUTION: An inkjet recording apparatus comprises a plurality of recording head units respectively provided for ink colors and respectively including inkjet heads, a conveyance section that includes a placement surface on which a recording medium is placed and conveys the recording medium placed on the placement surface in a conveyance direction along a conveyance path passing through respective image recording positions by the plurality of recording head units, a floating detection unit that detects floating of the recording medium to be conveyed by the conveyance section from the placement surface upstream in the conveyance direction of the image recording positions, a distance change mechanism that can change a conveyance distance between the uppermost stream recording head unit arranged at an uppermost stream side on the conveyance path among the plurality of recording head units and the floating detection unit, and a control unit that controls the conveyance section to change conveyance speed of the recording medium by the conveyance section depending on the conveyance distance.SELECTED DRAWING: Figure 3

Description

The present invention relates to an inkjet recording device.

The inkjet recording apparatus includes a recording head unit having an inkjet head, and ejects ink from the inkjet head to form (record) an image on a recording medium. At that time, since the inkjet head of the recording head unit is arranged close to the recording surface of the recording medium, if the recording medium floats, the recording medium may come into contact with the inkjet head and the inkjet head may be damaged. ..

Patent Document 1 describes a technique for stopping the transport of a recording medium when a transport abnormality due to floating of the recording medium is detected.

JP-A-2002-113910

However, in the technique described in Patent Document 1, even if an attempt is made to immediately stop the transfer of the recording medium by detecting a transfer abnormality due to the floating of the recording medium, the recording medium is caused by the inertial force acting on the recording medium transfer means such as a transfer drum. The movement of the image cannot be stopped immediately, and the recording medium may come into contact with the inkjet head.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an inkjet recording apparatus capable of effectively suppressing damage to an inkjet head due to contact with a recording medium. ..

The present invention has a plurality of recording head units each having an inkjet head and a mounting surface on which a recording medium is mounted, and the recording medium mounted on the mounting surface is provided for each color of ink. , The transport unit that transports in the transport direction along the transport path that passes through the image recording position by the plurality of recording head units, and the floating of the recording medium that is transported by the transport unit from the mounting surface in the transport direction rather than the image recording position. A distance changing mechanism that can change the transport distance between the floating detection unit that detects on the upstream side of the image and the most upstream recording head unit and the floating detection unit that are arranged on the most upstream side of the plurality of recording head units on the transport path. This is an inkjet recording device including a control unit that controls the transport unit so that the transport speed of the recording medium by the transport unit is changed according to the transport distance.

According to the present invention, damage to the inkjet head due to contact with a recording medium can be effectively suppressed.

It is a schematic perspective view of the inkjet recording apparatus which concerns on embodiment of this invention. It is a schematic side view which shows the internal structure of the inkjet recording apparatus shown in FIG. It is a schematic side view which enlarged a part of the image forming part included in the inkjet recording apparatus which concerns on embodiment of this invention. It is a schematic side view which shows the arrangement state when the transport distance between the most upstream recording head unit and a float detection part becomes short. It is a schematic side view which shows the arrangement state when the transport distance between the most upstream recording head unit and a float detection part becomes long. It is a block diagram which shows the structure of the control system of the inkjet recording apparatus which concerns on embodiment of this invention. It is a flowchart which shows the processing procedure of the inkjet recording apparatus which concerns on embodiment of this invention.

<Configuration of inkjet recording device>
FIG. 1 is a schematic perspective view of an inkjet recording device according to an embodiment of the present invention.
As shown in FIG. 1, the inkjet recording device 10 includes a paper feeding unit 11, an image forming unit 12, a paper ejection unit 13, and an ink supply tank 14. The paper feed unit 11 is a unit that supplies paper as a recording medium. The image forming unit 12 is a portion that forms an image on paper using ink. The paper ejection unit 13 is a portion for ejecting the paper after forming the image. The ink supply tank 14 is a tank for storing a predetermined amount of ink and supplying this ink to the image forming unit 12.

FIG. 2 is a schematic side view showing the internal structure of the inkjet recording apparatus shown in FIG.
As shown in FIG. 2, the paper feed unit 11 is provided with a paper feed tray 11a. The paper 15 before forming an image is loaded on the paper feed tray 11a. The paper feed unit 11 separately supplies the paper 15 loaded on the paper feed tray 11a one by one in order from the top.

The image forming unit 12 includes a transport drum 20 as a transport unit, a plurality of recording head units 21W, 21Y, 21M, 21C, 21K, a mist catcher 22, an ultraviolet irradiation unit 23, an in-line sensor 24, and an inversion unit. 25 and two large and small transfer rollers 26a and 26b are provided.

The transport drum 20 is rotatably provided. The transport drum 20 rotates while winding the paper 15 supplied from the paper feed unit 11 around the outer peripheral surface 20a of the transport drum 20. For example, the transport drum 20 attracts the paper 15 to the outer peripheral surface 20a of the transport drum 20 by suction of air, and rotates in this state to transport the paper 15 in the transport direction A. In order to realize such a transfer method, a large number of air suction holes (not shown) are formed on the outer peripheral surface 20a of the transfer drum 20. The outer peripheral surface 20a of the transport drum 20 corresponds to a mounting surface on which the paper 15 which is a recording medium is placed.

The plurality of recording head units 21W, 21Y, 21M, 21C, and 21K form (record) an image on the paper 15 serving as a recording medium by using inks of corresponding colors. Specifically, the recording head unit 21W forms an image using white (W) ink, and the recording head unit 21Y forms an image using yellow (Y) ink. Further, the recording head unit 21M forms an image using magenta (M) ink, the recording head unit 21C forms an image using cyan (C) ink, and the recording head unit 21K is black (K). An image is formed using ink. In this embodiment, as an example, an ultraviolet curable ink is used.

The recording head units 21W, 21Y, 21M, 21C, and 21K are arranged so as to face the outer peripheral surface 20a on the upper side of the transport drum 20. Further, the respective recording head units 21W, 21Y, 21M, 21C, and 21K are arranged so as to be displaced in the circumferential direction of the transport drum 20. In the present embodiment, as an example, five recording head units 21W, 21Y, 21M, 21C, and 21K are provided in the image forming unit 12.

The mist catcher 22 is arranged on the downstream side of the recording head unit 21K in the transport direction A of the paper 15 by the transport drum 20. The mist catcher 22 collects the mist generated by ejecting ink from the inkjet heads provided in the respective recording head units 21W, 21Y, 21M, 21C, 21K. The ultraviolet irradiation unit 23 is arranged on the downstream side of the mist catcher 22 in the transport direction A of the paper 15. The ultraviolet irradiation unit 23 cures the ink forming an image on the paper 15 by irradiating the paper 15 conveyed by the rotation of the transport drum 20 with ultraviolet rays. The ultraviolet irradiation unit 23 functions as a fixing unit for fixing an image formed on the paper 15 using ink to the paper 15. The fixing of the image by the fixing portion is not limited to the one that irradiates ultraviolet rays, but the one that irradiates energy rays that can cure the ink depending on the properties of the ink, or the one that heats the paper 15 to dry the ink. There may be.

The in-line sensor 24 is arranged on the downstream side of the ultraviolet irradiation unit 23 in the transport direction A of the paper 15. The in-line sensor 24 is a sensor for inspecting the color density, inclination, etc. of the image by reading the image formed on the paper 15 during the transfer by the transfer drum 20. The reversing portion 25 is a portion that reverses the front and back sides of the paper 15 in order to form an image on both sides of the paper 15 or to eject the paper 15 with the image formed on one side of the paper 15 facing downward. The transport rollers 26a and 26b are rollers that transport the paper 15 for which the image has been formed toward the paper ejection unit 13.

The paper ejection unit 13 is provided with a paper ejection tray 13a. Paper 15 that has finished forming an image is sequentially ejected to the output tray 13a.

<Operation of inkjet recording device>
Subsequently, the operation of the inkjet recording apparatus 10 having the above configuration will be described.
The print job performed by the inkjet recording apparatus 10 is roughly classified into three print jobs depending on which color of ink is used to form the image. The first print job is a print job that forms an image on paper 15 using five colors (white, yellow, magenta, cyan, and black) of ink. The second print job is a print job that forms an image on paper 15 using four colors of ink except white. The third print job is a print job that forms an image on paper 15 using only black ink.

Here, the operation of the inkjet recording device 10 when executing the first print job will be described.
First, the paper 15 loaded on the paper feed tray 11a of the paper feed unit 11 is separated one by one in order from the top and supplied to the image forming unit 12. The tip of the paper 15 supplied to the image forming unit 12 is gripped by a transfer claw (not shown). The transport claw feeds the paper 15 to the transport drum 20 at a predetermined timing. As a result, the paper 15 is attracted to the outer peripheral surface 20a of the transport drum 20, and in that state, the paper 15 is transported in the transport direction A according to the rotation of the transport drum 20.

On the other hand, the inkjet heads provided in the respective recording head units 21W, 21Y, 21M, 21C, 21K inject ink into a predetermined position at a predetermined timing with respect to the paper 15 conveyed by the rotation of the transfer drum 20. Discharge. As a result, an image is formed on the paper 15. After that, the paper 15 is irradiated with ultraviolet rays by the ultraviolet irradiation unit 23. When the paper 15 is irradiated with ultraviolet rays, the ink forming the image on the paper 15 is cured.

The paper 15 that has finished forming the image is then conveyed by the conveying rollers 26a and 26b and fed to the paper ejection section 13. The paper 15 fed to the paper ejection unit 13 is sequentially ejected onto the paper ejection tray 13a. By the above operation, the image-formed paper 15 is obtained.

FIG. 3 is an enlarged schematic side view of a part of an image forming portion included in the inkjet recording apparatus according to the embodiment of the present invention. In the following description, W, Y, M, C, which represent the color of the ink, unless it is necessary to distinguish each recording head unit 21W, 21Y, 21M, 21C, 21K and its components by the color of the ink. The subscript of K is omitted.

As shown in FIG. 3, a transport path (indicated by a broken line in the figure) 31 for transporting the recording medium is formed on the outer peripheral surface 20a of the transport drum 20. The paper 15 (see FIG. 2) as a recording medium is conveyed according to the rotation of the transfer drum 20 while being attracted to the outer peripheral surface 20a of the transfer drum 20. Therefore, the transport path 31 is formed along the outer peripheral surface 20a of the transport drum 20.

Image recording positions P1, P2, P3, P4, and P5 by the respective recording head units 21W, 21Y, 21M, 21C, and 21K exist in the middle of the transport path 31. The image recording position P1 is a position where the image is recorded (formed) by the recording head unit 21W, and the image recording position P2 is a position where the image is recorded by the recording head unit 21Y. Further, the image recording position P3 is a position where the image is recorded by the recording head unit 21M, and the image recording position P4 is a position where the image is recorded by the recording head unit 21C. Further, the image recording position P5 is a position where the image is recorded by the recording head unit 21K.

When the paper 15 is conveyed along the transport path 31, the tip of the paper 15 first passes through the image recording position P1 by the recording head unit 21W, and then the image is recorded by the other recording head units 21Y, 21M, 21C, 21K. It passes through positions P2, P3, P4 and P5 in order. When the first print job described above is executed, the respective recording head units 21W, 21Y, 21M, 21C, and 21K are located close to the corresponding image recording positions P1, P2, P3, P4, and P5 (hereinafter,). , "Normal position"). Then, when ink is ejected from the five recording head units 21W, 21Y, 21M, 21C, and 21K at predetermined timings, the white ink adheres to the paper 15 at the image recording position P1 and the yellow ink adheres to the paper 15 at the image recording position P2. Adheres to the paper 15 with. Further, the magenta ink adheres to the paper 15 at the image recording position P3, the cyan ink adheres to the paper 15 at the image recording position P4, and the black ink adheres to the paper 15 at the image recording position P5.

The recording head unit 21W includes an inkjet head 32W and a carriage 33W that holds the inkjet head 32W. The inkjet head 32W has an ink ejection surface 34W, and ejects ink from a nozzle (not shown) provided on the ink ejection surface 34W. The ink ejection surface 34W of the inkjet head 32W is arranged so as to face the outer peripheral surface 20a of the transport drum 20. When the recording head unit 21W is arranged at the normal position Pa, a predetermined gap is formed between the ink ejection surface 34W of the inkjet head 32W and the outer peripheral surface 20a of the transport drum 20. The normal position Pa is a position suitable for ejecting ink from the inkjet head 32W to form an image on the paper 15. The predetermined gap is set to, for example, about 1 mm.

Similar to the recording head unit 21W described above, the recording head unit 21Y includes an inkjet head 32Y and a carriage 33Y holding the inkjet head 32Y, and the recording head unit 21M includes an inkjet head 32M and the inkjet head 32M. It is provided with a carriage 33M to be held. Further, the recording head unit 21C includes an inkjet head 32C and a carriage 33C that holds the inkjet head 32C, and the recording head unit 21K includes an inkjet head 32K and a carriage 33K that holds the inkjet head 32K. There is.

Of the five recording head units 21W, 21Y, 21M, 21C, and 21K, the recording head unit 21W is provided so as to be movable in the B direction by the head unit moving mechanism 41. The B direction, which is the moving direction of the recording head unit 21W, is a direction along the radial direction of the transport drum 20. The head unit moving mechanism 41 moves the recording head between the normal position (position indicated by the solid line) Pa close to the image recording position P1 and the retracted position (position indicated by the alternate long and short dash line) Pb retracted from the image recording position P1. It is a mechanism that movably supports the unit 21W. In the present embodiment, as an example, the head unit moving mechanism 41 operates using a motor as a drive source.

In the embodiment of the present invention, when the recording head unit 21W is retracted from the image recording position P1 to the retracted position Pb, the head unit moving mechanism 41 moves the recording head unit 21W in a direction away from the transport path 31. It has become. Therefore, when the recording head unit 21W is retracted to the retracted position Pb, the distance between the ink ejection surface 34W of the inkjet head 32W and the outer peripheral surface 20a of the transport drum 20 is larger than the above-mentioned predetermined gap (for example). , About several tens of mm) is secured.

A float detection unit 45 and a pressing roller 46 are provided around the transport drum 20. The float detection unit 45 is arranged on the upstream side in the transport direction A from the image recording positions P1, P2, P3, P4, P5 by the respective recording head units 21W, 21Y, 21M, 21C, 21K. When the paper 15 is placed on the outer peripheral surface 20a of the transport drum 20 and transported, the float detection unit 45 measures the float of the paper 15 transported by the transport drum 20 at the image recording positions P1, P2, P3, P4. It is detected on the upstream side of the transport direction A from P5. The floating of the paper 15 is a phenomenon in which the paper 15 is not attracted (adhered) to the outer peripheral surface 20a of the transport drum 20 and the paper 15 floats from the outer peripheral surface 20a.

The float detection unit 45 can be configured by using a contact type sensor (not shown) or a non-contact type sensor. When a contact-type sensor is used, for example, the paper 15 is lifted by making use of a phenomenon in which a contact is brought into contact with the paper 15 carried by the transport drum 20 and the position of the contact changes due to the float of the paper 15. Can be detected. When using a non-contact type sensor, for example, a light emitting element is arranged on one end side in the central axis direction (depth direction in FIG. 3) of the transport drum 20, and a light receiving element is arranged on the other end side, and the light emitting element is directed toward the light receiving element. The floating of the paper 15 can be detected by utilizing the phenomenon that the light emitted from the paper 15 is blocked by the floating of the paper 15.

The pressing roller 46 is arranged on the upstream side in the transport direction A with respect to the float detection unit 45. The pressing roller 46 is pressed against the transport drum 20 with a predetermined pressing force. The pressing roller 46 presses the paper 15 sent from the paper feeding unit 11 to the image forming unit 12 against the transport drum 20, so that the paper 15 is attracted to the outer peripheral surface 20a of the transport drum 20.

The head unit moving mechanism 41 described above corresponds to a distance changing mechanism capable of changing the transport distance between the most upstream recording head unit and the float detection unit 45. This point will be described in detail below. The transport distance between the most upstream recording head unit and the float detection unit 45 is a distance defined by the paper transport direction A along the outer peripheral surface 20a of the transport drum 20.

First, the definition of the most upstream recording head unit will be described.
The “most upstream recording head unit” refers to a recording head unit 21 that satisfies both the following conditions (1) and (2).
(1) The recording head unit 21 is arranged on the transport path 31.
(2) The recording head unit 21 is arranged on the most upstream side in the transport direction A.

The “recording head unit 21 arranged on the transport path 31” described in (1) above refers to the recording head unit 21 arranged in the vicinity of the outer peripheral surface 20a of the transport drum 20 forming the transport path 31. Say. When the recording head unit 21 is arranged close to the outer peripheral surface 20a of the transport drum 20, ink is ejected onto the paper 15 between the inkjet head 32 of the recording head unit 21 and the outer peripheral surface 20a of the transport drum 20. A gap suitable for forming the image is formed. Therefore, the recording head unit 21 arranged at a position suitable for forming an image on the paper 15 by ejecting ink corresponds to the “recording head unit 21 arranged on the transport path 31”.

As shown in FIG. 4, in a state where the recording head unit 21W is arranged at the normal position Pa, five recording head units 21W, 21Y, 21M, 21C, 21K including the recording head unit 21W are arranged on the transport path 31. .. Further, of the five recording head units 21W, 21Y, 21M, 21C, 21K arranged on the transport path 31, the recording head unit 21 arranged on the most upstream side in the transport direction A is the recording head unit 21W. .. Therefore, when the recording head unit 21W is arranged at the normal position Pa, the recording head unit 21W corresponds to the most upstream recording head unit. Further, the transport distance between the recording head unit 21W corresponding to the most upstream recording head unit and the float detection unit 45 is L1.

On the other hand, as shown in FIG. 5, when the recording head unit 21W is arranged at the retracted position Pb, the recording head unit 21W is arranged away from the outer peripheral surface 20a without being close to the outer peripheral surface 20a of the transport drum 20. Therefore, four recording head units 21Y, 21M, 21C, 21K other than the recording head unit 21W are arranged on the transport path 31. Further, of the four recording head units 21Y, 21M, 21C, and 21K arranged on the transport path 31, the recording head unit 21 arranged on the most upstream side in the transport direction A is the recording head unit 21Y. Therefore, when the recording head unit 21W is arranged at the retracted position Pb, the recording head unit 21Y corresponds to the most upstream recording head unit. Further, the transport distance between the recording head unit 21Y corresponding to the most upstream recording head unit and the float detection unit 45 is L2, which is longer than the above L1.

Therefore, the transport distance between the most upstream recording head unit and the float detection unit 45 can be changed depending on whether the recording head unit 21W is arranged at the normal position Pa or the retracted position Pb. Therefore, the head unit moving mechanism 41 that movably supports the recording head unit 21W between the normal position Pa and the retracted position Pb corresponds to the above-mentioned distance changing mechanism.

FIG. 6 is a block diagram showing a configuration of a control system of the inkjet recording device according to the embodiment of the present invention.
As shown in FIG. 6, in addition to the float detection unit 45 described above, the inkjet recording device 10 includes a control unit 51, an operation display unit 53, a head drive unit 55, a transfer motor 57, and a head unit for moving. It is equipped with a motor 59. When the floating detection unit 45 detects the floating of the paper 15, it gives a detection signal to the control unit 51 informing that the floating of the paper 15 has occurred.

The control unit 51 includes a CPU (Central Processing Unit) 61, a ROM (Read Only Memory) 63, and a RAM (Random Access Memory) 65. The CPU 61 reads a predetermined processing program from the ROM 63, develops it in the RAM 65, and comprehensively controls the operation of each part of the inkjet recording device 10 according to the developed program. The control unit 51 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network (not shown). When the control unit 51 receives a print job from the operation display unit 53 or an external device, the control unit 51 operates each unit of the inkjet recording device 10 so as to form an image on the paper 15 based on the image data specified by the print job. To control.

Further, the control unit 51 has a function of discriminating the color of the ink used for printing the image data in the print job (hereinafter, referred to as “color discriminating function”). The color discrimination function can be given to the control unit 51 by storing the color discrimination program in the ROM 63 and having the CPU 61 read the color discrimination program from the ROM 63 and expand it in the RAM 65.

The operation display unit 53 is composed of, for example, a liquid crystal display with a touch panel, and has a function of displaying various information to the user and a function of receiving various input operations from the user. The information displayed on the operation display unit 53 includes various operation screens, setting screens, error notification screens, and the like. Further, the input operation performed by the user using the operation display unit 53 includes an operation of instructing the execution of the print job, an operation of selecting (designating) the image data to be the target of the print job, and the paper 15 used for the print job. It includes operations to select (specify) the type (size, thickness, paper quality, etc.), and operations to select the conditions to be applied to the print job. Further, the operation of selecting the conditions to be applied to the print job includes an operation of selecting whether or not to execute the transport speed change process described later. That is, the operation display unit 53 has a function as a selection unit. A user who does not want to execute the transfer speed change process does not allow the execution of the transfer speed change process by operating the operation display unit 53 before instructing the execution of the print job (hereinafter, "speed change impossible mode"). ".) Can be selected.

The function as the selection unit can be provided to the control unit 51 instead of the operation display unit 53. Specifically, when the control unit 51 accepts a print job from an external device and the condition applied to the print job includes a condition that the execution of the transport speed change process is not permitted, the condition includes the condition. Therefore, it is possible to adopt a configuration in which the control unit 51 selects the speed changeable mode.

The head drive unit 55 independently drives the respective inkjet heads 32W, 32Y, 32M, 32C, and 32K based on the control command given from the control unit 51. The transport motor 57 is a motor for transporting the paper 15, and serves as a drive source for rotating the transport drum 20. The head unit moving motor 59 is a motor that serves as a drive source for the head unit moving mechanism 41 described above. The drive of the transport motor 57 and the head unit moving motor 59 is individually controlled by the control unit 51.

FIG. 7 is a flowchart showing a processing procedure of the inkjet recording apparatus according to the embodiment of the present invention. The processing shown in this flowchart is performed under the control of the control unit 51.

First, the control unit 51 determines whether or not the print job has been accepted (step S1), and when the print job is accepted via the external device or the operation display unit 53, the process proceeds to step S2. The print job includes image data to be printed, conditions applied when printing the image data on paper 15, and the like.

In step S2, the control unit 51 performs a color discrimination process for discriminating the color of the ink used in the print job. When the print job received in step S1 is the first print job, it is determined that the colors of the ink used for printing the image data are five colors of white, yellow, magenta, cyan, and black. When the print job received in step S1 is the second print job, it is determined that the ink colors used for printing the image data are four colors excluding white, and the third print job In some cases, it is determined that the color of the ink used for printing the image data is only black.

Next, the control unit 51 determines whether or not the white (W) ink is not used in the print job (step S3). This determination is made based on the determination result of the color discrimination process in step S2. Specifically, if the color of the ink used for printing the image data is four colors other than white or only black, it is determined as YES in step S3 and the process proceeds to step S4. If the colors of the ink used for printing the image data are five colors of white, yellow, magenta, cyan, and black, NO is determined in step S3, and the process proceeds to step S5.

In step S4, the control unit 51 moves the recording head unit 21W whose ink color is white (W) from the normal position Pa to the retracted position Pb. At that time, the control unit 51 drives the head unit moving motor 59 to operate the head unit moving mechanism 41.

Next, the control unit 51 detects the transport distance L between the most upstream recording head unit and the float detection unit 45 (step S5). This transport distance L can be detected by whether or not the recording head unit 21W has been moved to the retracted position Pb, that is, whether or not the process of step S4 has been executed. Specifically, when the recording head unit 21W is moved to the retracted position Pb by executing the process of step S4, the control unit 51 transfers between the most upstream recording head unit and the floating detection unit 45. It is detected that the distance L is L2 (see FIG. 5). Further, when the control unit 51 does not execute the process of step S4 and does not move the recording head unit 21W to the retracted position Pb, the transport distance L between the most upstream recording head unit and the floating detection unit 45 is increased. It is detected as L1 (see FIG. 4). The case where the recording head unit 21W is not moved to the retracted position Pb means the case where the recording head unit 21W is arranged at the normal position Pa. The transport distance L is detected by a sensor (not shown) that detects whether the recording head unit 21W is located at the normal position Pa or the retracted position Pb, and the control unit 51 determines based on the detection result. It may be adopted.

Next, the control unit 51 determines whether or not to carry out the transfer speed change process in step S7 (step S6). The transport speed changing process is a process performed to change the paper transport speed by the transport drum 20 according to the transport distance L between the most upstream recording head unit and the float detection unit 45 described above. The paper transport speed by the transport drum 20 means the speed at which the paper 15 advances in the transport direction A as the transport drum 20 rotates. If the user operates the operation display unit 53 to select the speed change impossible mode prior to the print job execution instruction, the control unit 51 determines that NO, that is, the transport speed change process is not executed in step S6. To do. Further, if the user has not selected the speed change impossible mode, the control unit 51 determines that YES in step S6, that is, the transport speed change process is executed. Then, if NO is determined in step S6, the process proceeds to step S8, and if YES is determined in step S6, the process proceeds to step S7.

The transport speed change process in step S7 includes three steps S7a, S7b, and S7c.
First, in step S7a, the control unit 51 determines whether or not the transport distance L between the most upstream recording head unit and the float detection unit 45 is L1. In this step S7a, it is determined whether or not L = L1 based on the detection result of step S5 described above. Then, if L = L1, the process proceeds to step S7b, and if L = L1, that is, L = L2, the process proceeds to step S7c.

In step S7b, the control unit 51 sets the paper transport speed V to V1. Further, in step S7c, the control unit 51 sets the paper transport speed V to V2, which is faster than the above V1. As a result, the paper transport speed V set by the control unit 51 becomes faster as the transport distance L between the most upstream recording head unit and the float detection unit 45 becomes longer. If NO is determined in step S6 and the transport speed change process in step S7 is not performed, the paper transport speed V remains set to the initial value. The initial value of the transport speed V is set to the faster speed of V1 and V2 described above, that is, V2.

After that, the control unit 51 drives the transport motor 57 to start transporting the paper 15 (step S8). At this time, the transfer drum 20 rotates according to the drive of the transfer motor 57. Then, when the paper 15 is attracted to the outer peripheral surface 20a of the transport drum 20 through the pressing roller 46, the transport drum 20 transports the paper 15 along the transport path 31 shown in FIG. On the other hand, when the paper transport speed V is set to V1, the control unit 51 controls the drive of the transport motor 57 so that the paper 15 is transported at the speed V1 by the rotation of the transport drum 20. Further, when the paper transport speed V is set to V2, the control unit 51 controls the drive of the transport motor 57 so that the paper 15 is transported at the speed V2 by the rotation of the transport drum 20.

Next, the control unit 51 determines whether or not the float detection unit 45 has detected the float of the paper 15 (step S9). When the float detection unit 45 detects the float of the paper 15, a detection signal to that effect is given to the control unit 51. Therefore, the control unit 51 receives the detection signal and the float detection unit 45 detects the float of the paper 15. Judge that it was done. Then, when the control unit 51 determines that the float detection unit 45 has detected the float of the paper 15, the process proceeds to step S10, and when the float detection unit 45 determines that the float of the paper 15 has not been detected, the process proceeds to step S12.

In step S10, the control unit 51 stops the transfer of the paper 15 by the transfer drum 20 by stopping the drive of the transfer motor 57. At this time, even if the control unit 51 stops driving the transfer motor 57, the transfer drum 20 rotates by a predetermined amount due to the inertial force acting on the drum itself and then stops. Next, the control unit 51 ends a series of processes after executing the notification process for notifying the user that a transport error has occurred (step S11). In the notification process, an error notification screen for notifying the user of the occurrence of a transport error is displayed on the operation display unit 53. On the error notification screen, a message for resolving the transport error may be displayed together with the content of the transport error. As a message for resolving the transport error, for example, a message such as "Please remove the paper in the transport path" can be considered.

On the other hand, in step S12, the control unit 51 drives the head drive unit 55 to start printing. At this time, if the ink colors used for printing the image data are five colors of white, yellow, magenta, cyan, and black, the control unit 51 uses all the inkjet heads 32W, 32Y, 32M, 32C, and 32K. The head drive unit 55 is controlled so as to drive the head drive unit 55. Further, if the colors of the ink used for printing the image data are four colors other than white, the control unit 51 controls the head drive unit 55 so as to drive the four inkjet heads 32Y, 32M, 32C, and 32K. However, if the color of the ink used for printing the image data is only black, the control unit 51 controls the head drive unit 55 so as to drive only the inkjet head 32K. As a result, ink is ejected from the inkjet head 32 of the recording head unit 21 used in the print job, and the ink adheres to the paper 15 to form an image on the paper 15.

Next, the control unit 51 determines whether or not the print job has been completed (step S13). The print job ends when printing (image formation) for the print page specified by the print job is completed. In step S13, if it is determined that the print job has not been completed, the control unit 51 returns to step S9 and performs the same processing as described above, and if it is determined that the print job has been completed, the process proceeds to step S14. If the floating detection unit 45 detects the floating of the paper 15 after printing is started in step S12, the control unit 51 stops both the drive of the transport motor 57 and the drive of the head drive unit 55 in step S10. As a result, both the transport of the paper 15 and the printing on the paper 15 are stopped.

In step S14, the control unit 51 determines whether or not the recording head unit 21W is retracted to the retracted position Pb. Then, if the recording head unit 21W is retracted to the retracted position Pb, the process proceeds to step S15, and if the recording head unit 21W is not retracted to the retracted position Pb, a series of processes is completed at that stage.

In step S15, the control unit 51 moves the recording head unit 21W from the retracted position Pb to the normal position Pa by driving the head unit moving motor 59 to operate the head unit moving mechanism 41, and then a series of steps. Finish the process of. As a result, the recording head unit 21W returns to a state close to the outer peripheral surface 20a of the transport drum 20.

As described above, in the embodiment of the present invention, when the transport distance L between the most upstream recording head unit and the floating detection unit 45 is L1, the paper transport speed V is set to V1 and the maximum. When the transport distance L between the upstream recording head unit and the floating detection unit 45 is L2, which is longer than L1, the paper transport speed V is set to V2, which is faster than V1, and printing is performed. It has become. In this way, by changing the paper transport speed V according to the transport distance L between the most upstream recording head unit and the float detection unit 45, the inkjet head 32 is damaged by contact with the paper 15. It can be effectively suppressed. The reason is as follows.

First, when the float detection unit 45 detects the float of the paper 15, and at the same time the control unit 51 stops driving the transfer motor 57, the transfer drum 20 rotates by a predetermined amount due to the inertial force acting on the drum itself. By this rotation, the paper 15 moves by a predetermined distance and then stops. In this case, the distance that the paper 15 travels from the time when the control unit 51 stops driving the transport motor 57 until the rotation of the transport drum 20 stops is defined as the “paper movement distance”.

In the embodiment of the present invention, when the transport distance L between the most upstream recording head unit and the float detection unit 45 is L1 which is shorter than L2, the paper transport speed V is set to V1 which is slower than V2. It is set. When the paper transport speed V is set to be slow in this way, the inertial force acting on the transport drum 20 when the drive of the transport motor 57 is stopped becomes small, so that the paper movement distance becomes short. Therefore, even if the transport distance L between the most upstream recording head unit and the floating detection unit 45 is L1, which is shorter than L2, before the floating portion of the paper 15 comes into contact with the inkjet head 32 of the recording head unit 21. It is possible to stop the movement of the paper 15.

Further, in the embodiment of the present invention, when the transport distance L between the most upstream recording head unit and the float detection unit 45 is L2, which is longer than L1, the paper transport speed V is faster than V1. It is set to V2. When the paper transport speed V is set high in this way, the inertial force acting on the transport drum 20 when the drive of the transport motor 57 is stopped increases, so that the paper movement distance becomes long. However, since the transport distance L between the most upstream recording head unit and the floating detection unit 45 is L2, which is longer than L1, before the floating portion of the paper 15 comes into contact with the inkjet head 32 of the recording head unit 21. , It is possible to stop the movement of the paper 15.

Therefore, regardless of whether the transport distance L between the most upstream recording head unit and the float detection unit 45 is L1 or L2, the paper transport speed V is changed according to the transport distance L (L1 or L2). As a result, damage to the inkjet head 32 due to contact with the paper 15 can be effectively suppressed.

Further, in the embodiment of the present invention, a configuration is adopted in which the user can select whether or not to perform the transport speed change process by operating the operation display unit 53. As a result, the user can select whether or not to execute the transport speed change process according to the type of the paper 15 specified in the print job and the like. Further, when the user who operates the operation display unit 53 selects the speed change impossible mode and executes the print job, the transport speed change process is not performed. In this case, even if the recording head unit 21W is arranged at the normal position Pa and the transport distance L between the most upstream recording head unit and the float detection unit 45 is L1, the paper transport speed V is higher than V1. Is also set to fast V2 (initial value). Therefore, for example, when the print job is executed by designating a type of paper that does not easily float, or when the print job is executed by designating a type of paper that has almost no risk of damaging the inkjet head 32. When the user operates the operation display unit 53 to select the speed change impossible mode in advance, the inkjet recording device 10 can be operated with priority given to printing efficiency.

<Modification example, etc.>
The technical scope of the present invention is not limited to the above-described embodiment, but also includes a form in which various changes and improvements are made to the extent that a specific effect obtained by the constituent requirements of the invention and the combination thereof can be derived.

For example, in the above embodiment, when the recording head unit 21W is movably supported by the head unit moving mechanism 41 and the recording head unit 21W is not used in the print job, only the recording head unit 21W is supported by the head unit moving mechanism 41. The normal position Pa is moved to the retracted position Pb, but the present invention is not limited to this. For example, printing in which four recording head units 21W, 21Y, 21M, and 21C excluding the recording head unit 21K are movably supported by the corresponding head unit moving mechanism 41 and an image is formed using only black ink. When executing the job, the four recording head units 21W, 21Y, 21M, and 21C may be moved from the normal position Pa to the retracted position Pb. In that case, since the recording head unit 21K corresponds to the most upstream recording head unit, the transport distance L between the most upstream recording head unit and the float detection unit 45 is secured longer than the above L2. Therefore, even when the paper transport speed V is set to be faster than the above V2, it is possible to avoid contact between the inkjet head 32 of the recording head unit 21 and the paper 15.

Further, in the above embodiment, as the recording head unit 21 that ejects ink of a predetermined color excluding yellow, magenta, cyan, and black, the recording head unit 21W that ejects white ink has been described as an example. The present invention is not limited to this, and for example, a recording head unit 21 that ejects transparent color ink may be provided instead of the recording head unit 21W. Further, the number of recording head units 21 included in the inkjet recording device 10 is not limited to 5, and may be 6 or more.

Further, in the above embodiment, the configuration in which the paper 15 as the recording medium is conveyed by the conveying drum 20 has been described as an example, but the present invention is not limited to this, and the present invention is not limited to this, and is a flatbed type using a conveying belt (not shown). It can also be applied to inkjet recording devices.

Further, in the above embodiment, paper 15 is mentioned as an example of the recording medium, but the present invention is not limited to this, and can be applied to, for example, an inkjet recording device using a cloth, a resin film, or the like as a recording medium.

10 ... Inkjet recording device 15 ... Paper (recording medium)
20 ... Conveying drum (conveying part)
20a ... Outer peripheral surface (mounting surface)
21W, 21Y, 21M, 21C, 21K ... Recording head unit 31 ... Transport path 32W, 32Y, 32M, 32C, 32K ... Inkjet head 41 ... Head unit moving mechanism (distance changing mechanism)
45 ... Float detection unit 51 ... Control unit (distance detection unit)
53 ... Operation display unit (selection unit)
P1, P2, P3, P4, P5 ... Image recording position L, L1, L2 ... Transport distance Pa ... Normal position Pb ... Evacuation position V, V1, V2 ... Transport speed

Claims (6)

A plurality of recording head units provided for each ink color and each having an inkjet head,
It has a mounting surface on which a recording medium is placed, and the recording medium mounted on the above-mentioned mounting surface is conveyed in a transport direction along a transport path via image recording positions by the plurality of recording head units. Transport section and
A floating detection unit that detects the floating of the recording medium transported by the transport unit from the previously described mounting surface on the upstream side of the image recording position in the transport direction.
A distance changing mechanism capable of changing the transport distance between the most upstream recording head unit arranged on the most upstream side of the transport path and the float detection unit among the plurality of recording head units.
An inkjet recording apparatus including a control unit that controls the transport unit so that the transport speed of the recording medium by the transport unit is changed according to the transport distance. The inkjet according to claim 1, wherein the control unit controls the transport unit so that when the float detection unit detects the float of the recording medium, the transport unit stops the transport of the recording medium. Recording device. The inkjet recording apparatus according to claim 1 or 2, further comprising a distance detection unit that detects the transport distance. The inkjet recording apparatus according to any one of claims 1 to 3, wherein the control unit controls the transport unit so that the transport speed increases as the transport distance increases. The distance changing mechanism according to any one of claims 1 to 4 for changing the transport distance by retracting the recording head unit not used in the print job from the image recording position among the plurality of recording head units. The inkjet recording device described. The inkjet recording apparatus according to any one of claims 1 to 5, further comprising a selection unit capable of selecting whether or not to perform a process of changing the transport speed of the recording medium.

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