Ink jet recording device

Abstract

To provide an ink jet recording device which can detect a discharge state of a recording head with configuration that does not use resource such as a recording paper and so on and does not use a special component.SOLUTION: An ink jet recording device has a recording head, a translucent plate, a detection part, a removal part, and a control part. The recording head has a plurality of nozzles for discharging an ink. The translucent plate has light transmissivity, and one face thereof faces each nozzle of the recording head. The detection part has a light detection element which contacts the other face of the translucent plate and reads an image of the ink discharged onto one face of the translucent plate. The removal part removes the ink on one face of the translucent plate. The control part discharges the ink onto one face of the translucent plate from each nozzle of the recording head at timing different from timing contributing to image recording, acquires an ink detection result from the detection part, and confirms the state of the nozzles.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to an inkjet recording apparatus. [Background technology]

[0002] In inkjet printers and other inkjet recording devices, when ink is dried or stuck to the nozzles and the ink ejects poorly, this can appear as streaks in the image. For this reason, methods have been proposed for checking the ink ejection status.

[0003] Patent document 1 discloses a configuration for detecting the ejection state based on the amount of scattered light received when a light beam collides with ink ejected from a head, in order to detect whether ink is being ejected normally.

[0004] Patent Document 2 discloses a configuration in which a discharge defect pattern is printed on a recording sheet, and the presence or absence of a defect is detected by a reading unit provided in the image forming apparatus.

[0005] Patent Document 3 discloses a configuration in which ink is ejected onto a strip of transparent tape and the tape is read multiple times by an encoder sensor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6225517 [Patent Document 2] Patent No. 5473435 [Patent Document 3] JP 2003-127420 A Summary of the Invention [Problem to be solved by the invention]

[0007] The configuration of Patent Document 1 requires special components such as a light emitting element and a light receiving element for emitting a light beam, and the inclusion of a dispersion medium vapor pressure control device may lead to an increase in the size of the device, a more complicated configuration, and increased costs. In addition, there is a possibility that accurate detection may not be possible if the optical axis of the light beam is misaligned.

[0008] In the configuration of Patent Document 2, since the ejection failure pattern is printed on the recording paper, there is a possibility that resources will be wasted.

[0009] Furthermore, the configuration of Patent Document 3 requires a transparent tape that can be printed with ink and cleaned, and therefore requires special members.

[0010] An object of the present disclosure is to provide an inkjet recording apparatus capable of detecting the ejection state of a recording head without using resources such as recording paper or special members. [Means for solving the problem]

[0011] In order to achieve the above object, an inkjet recording apparatus according to one embodiment of the present disclosure includes a recording head having a plurality of nozzles for ejecting ink, a preliminary ejection unit for performing a preliminary ejection operation for checking the state of the nozzles at a timing different from the timing contributing to image recording, and a control unit for controlling the preliminary ejection operation. The preliminary ejection unit includes a light-transmitting plate that is a plate material having translucency and has one surface facing each of the nozzles of the recording head, a detection unit that is arranged in contact with the other surface of the light-transmitting plate and has a light detection element that reads an image of the ink ejected from the nozzles onto the one surface of the light-transmitting plate, and a removal unit that removes the ink after it is detected by the detection unit on the one surface of the light-transmitting plate. When the control unit executes the preliminary ejection operation using the preliminary ejection unit, the control unit ejects the ink from each of the nozzles of the recording head onto the one surface of the light-transmitting plate to form an image of the ink on the light-transmitting plate, obtains a detection result of the image of the ink detected by the detection unit, and checks the state of the nozzles based on the detection result. Effect of the Invention

[0012] The inkjet recording device disclosed herein is configured to eject ink onto a light-transmitting plate and detect the ink in a detection unit through the light-transmitting plate, so that no recording paper is used to inspect the recording head. In addition, the ink adhering to the light-transmitting plate is removed in a removal unit and the light-transmitting plate is reused, so that the state of the nozzles can be inspected without using resources such as recording paper. In addition, special components such as a light-emitting element and a light-receiving element that emit a light beam are not required. Therefore, it is possible to achieve both reduction in the running costs of the inkjet recording device and formation of high-definition images. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a printer as an inkjet recording apparatus. [Diagram 2] FIG. 2 is a block diagram showing the hardware configuration of the main part of the printer. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] 2 is a perspective view showing a schematic configuration of a moving mechanism 22. FIG. [Figure 6] FIG. 2 is a plan view of a light-transmitting plate with ink attached to its upper surface. [Figure 7] 13 is a side view showing a state in which the detection unit detects ink adhering to the upper surface of the light-transmitting plate. FIG. [Figure 8] 4 is a diagram showing an image recording position when a recording unit records an image on a sheet. FIG. [Figure 9] 5A and 5B are diagrams illustrating preliminary ejection positions when the printing unit performs a preliminary ejection operation. [Figure 10] 11A and 11B are diagrams showing capping positions when a cap part is attached to a recording part. [Figure 11] 10 is a flowchart showing a procedure for performing a preliminary ejection operation. [Figure 12] FIG. 13 is a side view of a state in which ink is being detected when it is difficult to accurately detect the ink. [Figure 13]13 is a plan view showing a discharge state of ink discharged by a preliminary discharge operation of a modified example. FIG. [Figure 14] 13 is a side view showing a state in which ink ejected by a preliminary ejection operation of a modified example is read. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 1. Configuration of the Inkjet Recording Apparatus Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an explanatory diagram showing the general configuration of a printer 100 as an inkjet recording device. Fig. 2 is a block diagram showing the hardware configuration of the main parts of the printer. The printer 100 is equipped with a paper feed cassette 2 which is a paper storage section. The paper feed cassette 2 is located at the bottom inside the printer main body 1. Inside the paper feed cassette 2, paper P, which is an example of a recording medium, is stored.

[0015] A paper feeder 3 is disposed downstream of the paper feed cassette 2 in the paper transport direction, i.e., above the right side of the paper feed cassette 2 in Fig. 1. The paper feeder 3 separates and sends out the paper P one by one toward the upper right of the paper feed cassette 2 in Fig. 1.

[0016] The printer 100 has a first paper transport path 4a inside. The first paper transport path 4a is located in the upper right corner, which is the paper feed direction, of the paper feed cassette 2. The paper P sent out from the paper feed cassette 2 is transported vertically upward along the side of the printer body 1 by the first paper transport path 4a.

[0017] A registration roller pair 13 is provided at the downstream end of the first paper transport path 4a in the paper transport direction A. Furthermore, a first transport unit 5 and a recording unit 9 are arranged immediately downstream of the registration roller pair 13 in the paper transport direction A. The paper P sent out from the paper feed cassette 2 reaches the registration roller pair 13 through the first paper transport path 4a. The registration roller pair 13 corrects skewed feed of the paper P and sends the paper P toward the first transport unit 5 (particularly the first transport roller pair 6a described later) in time with the ink ejection operation performed by the recording unit 9.

[0018] The paper P sent to the first transport unit 5 by the registration roller pair 13 is transported along the paper transport path R1 by the first transport roller pair 6a. Although not shown, the first transport unit 5 is provided with a guide portion for guiding the side of the paper P in the paper width direction B perpendicular to the paper transport direction A. The paper P is transported by the first transport roller pair 6a and reaches the second transport roller pair 6b arranged downstream in the paper transport direction A (left side in FIG. 1). The paper P is moved along the paper transport path R1 by the first transport roller pair 6a and the second transport roller pair 6b. In this embodiment, the configuration has two pairs of transport roller pairs 6a and 6b, but is not limited to this, and three or more pairs may be provided. The transport roller pairs are arranged at positions that do not interfere with the recording unit 9 during a preliminary ejection operation described later.

[0019] The ink Ik is ejected from the recording unit 9 onto the paper P that is moved along the paper transport path R1 by the first transport roller pair 6a and the second transport roller pair 6b. This causes an image to be recorded on the paper P. At this time, the ejection of the ink Ik in the recording unit 9 is controlled by a control device 110 inside the printer 100.

[0020] A second transport unit 12 is disposed downstream (on the left side in FIG. 1) of the first transport unit 5 in the paper transport direction A. The paper P on which an image has been recorded by the recording unit 9 is sent to the second transport unit 12. The ink Ik ejected onto the surface of the paper P is dried while passing through the second transport unit 12.

[0021] A decurler unit 14 is provided downstream of the second transport unit 12 and near the left side surface of the printer body 1 in the paper transport direction A. The paper P on which the ink Ik has been dried by the second transport unit 12 is sent to the decurler unit 14, where any curls in the paper P are straightened out.

[0022] A second paper transport path 4b is provided downstream (upper in FIG. 1) of the decurler unit 14 in the paper transport direction A. When double-sided recording is not performed, the paper P that has passed through the decurler unit 14 passes through the second paper transport path 4b and is discharged to a paper discharge tray 15a provided outside the left side of the printer 100. A sub-discharge tray 15b is provided below the paper discharge tray 15a to discharge unnecessary paper P (broken paper) that has experienced printing defects or the like.

[0023] A reversing transport path 16 for double-sided recording is provided at the top of the printer body 1, above the recording unit 9 and the second transport unit 12. When double-sided recording is performed, after recording on one side (first side) of the paper P is completed and the paper P passes through the second transport unit 12 and the decurler unit 14, it is sent to the reversing transport path 16 via the second paper transport path 4b.

[0024] After the paper P is sent to the reversing transport path 16, the paper transport direction A is switched so that recording can be performed on the other side (second side) of the paper P. The paper P then passes over the top of the printer body 1 and is sent to the right side, and is sent again to the first transport unit 5 with the second side facing up after passing through the pair of registration rollers 13. In the first transport unit 5, the paper P is transported to a position facing the recording unit 9, and an image is recorded on the second side by the ejection of ink Ik from the recording unit 9. After double-sided recording, the paper P passes through the second transport unit 12, the decurler unit 14, and the second paper transport path 4b in that order, and is discharged to the paper discharge tray 15a.

[0025] Moreover, a capping section 28 is disposed above the second transport unit 12. The capping section 28 moves horizontally below the recording section 9 that has moved to a capping position Pc (described later), and then moves further upward to be attached to the lower surface of the recording section 9. This caps the nozzles 19 (described later) provided on the lower surfaces of the recording heads 11Y, 11M, 11C, and 11K.

[0026] Fig. 3 is a plan view of the recording unit 9. As shown in Fig. 3, the recording unit 9 includes a head housing 10, recording heads 11Y, 11M, 11C, and 11K, and a housing drive unit 17 (see Fig. 2). From the recording heads 11Y to 11K, inks Ik of yellow (Y), magenta (M), cyan (C), and black (K) are ejected toward the paper P via nozzles 19 provided in an ejection unit 18.

[0027] 3, the recording heads 11Y-11K extend in a paper width direction B that is perpendicular to the paper transport direction A. Each of the recording heads 11Y-11K has a plurality of nozzles 19 that open to the bottom surface. The nozzles 19 can eject ink Ik onto the paper P transported by the first transport roller pair 6a and the second transport roller pair 6b. In each of the recording heads 11Y-11K, the plurality of nozzles 19 (here, 12) are collectively configured to form an ejection section 18.

[0028] Each of the recording heads 11Y to 11K has a plurality of ejection sections 18, and in each of the recording heads 11Y to 11K, the ejection sections 18 are arranged along the paper width direction B. In addition, in a plan view, adjacent ejection sections 18 are arranged so as to be alternately shifted in the paper transport direction A.

[0029] Here, the details of the ejection unit 18 will be described with reference to the drawings. Fig. 4 is a bottom view of the ejection unit 18. As shown in Fig. 4, the bottom surface of the ejection unit 18 has a plurality of nozzles 19 (here, 12 nozzles) that eject ink Ik. The nozzles 19 are connected to ink tanks (not shown) inside the recording heads 11Y to 11K, and are configured to increase the pressure of the ink Ik inside and spray the ink Ik from the nozzles 19.

[0030] As shown in FIG. 4, the ejection units 18 are longitudinally aligned in the paper width direction B of the paper P, and the nozzles 19 are arranged in two rows of six each. The nozzles 19 in the lower row (first row CL1) shown in FIG. 4 are arranged at equal intervals at a predetermined interval. The nozzles 19 in the upper row (second row CL2) are arranged at the same intervals and in the same direction as the nozzles 19 in the first row CL1, and the positions of the nozzles 19 are shifted in the paper width direction B of the paper P. In other words, when viewed from the paper transport direction A, the nozzles 19 in the first row CL1 and the nozzles 19 in the second row CL2 are arranged alternately. In this way, it is possible to double the resolution compared to a single row.

[0031] The head housing 10 holds a plurality of recording heads 11Y to 11K. The head housing 10 is configured to be movable up and down. The head housing 10 is connected to a housing drive unit 17, and the housing drive unit 17 is capable of moving the head housing 10 up and down.

[0032] A preliminary ejection operation unit 7 is provided below the first transport unit 5. The preliminary ejection operation unit 7 is used when performing a preliminary ejection operation for checking the state of the nozzle 19 at a timing different from the timing contributing to image recording. The preliminary ejection operation unit 7 has a light-transmitting plate 8, a detection unit 20, a removal unit 21, and a movement mechanism 22. The light-transmitting plate 8 is made of a material having light-transmitting properties, such as glass. Although the light-transmitting plate 8 may be made of a resin such as acrylic or epoxy, glass is preferable because its surface is less likely to be scratched and its light-transmitting properties are less likely to decrease over a long period of time. The light-transmitting plate 8 is disposed below the first transport unit 5, and one of its surfaces, the upper surface 8a, is disposed parallel to the paper P transported along the paper transport path R1.

[0033] An upper surface 8a of the light-transmitting plate 8 faces the nozzles 19 arranged on the lower surfaces of the recording heads 11Y to 11K. A detection unit 20 is arranged on the other surface, that is, the lower surface 8b, of the light-transmitting plate 8. The detection unit 20 is a CIS (Contact Image Sensor) that comes into contact with the lower surface of the light-transmitting plate 8 and reads the image of the ink Ik ejected onto the upper surface 8a of the light-transmitting plate 8.

[0034] The detection unit 20 extends in the paper width direction B, and includes a photodetection element 20a (see FIG. 2, etc.). The photodetection element 20a generates an electric charge according to the intensity of incident light, and outputs the electric charge as an electrical signal. As the detection unit 20 moves, the photodetection element 20a receives light, and thereby reads an image of the ink Ik on the upper surface 8a of the light-transmitting plate 8. The detection unit 20 then sends the read image of the ink Ik to the control device 110 as an image signal.

[0035] A white reference portion 8c is formed on the upstream end of the light-transmitting plate 8 in the paper transport direction A. The detection unit 20 moves below the white reference portion 8c and detects light from the white reference portion 8c with the light detection element 20a, thereby adjusting the level of white, thereby performing a so-called calibration operation.

[0036] Fig. 5 is a perspective view showing a schematic configuration of the movement mechanism 22. As shown in Fig. 5, the movement mechanism 22 has a guide unit 23, a drive pulley 24, a driven pulley 25, and a drive belt 26. The guide unit 23 extends along the paper transport direction A. The guide unit 23 is in contact with the detection unit 20, and guides the movement of the detection unit 20 in the paper transport direction A.

[0037] The driving pulley 24 and the driven pulley 25 are disposed in the paper conveying direction A. More specifically, the driving pulley 24 and the driven pulley 25 are disposed at a distance apart that is longer than the length of the guide portion 23. A driving belt 26 is stretched between the driving pulley 24 and the driven pulley 25. A driving motor 27 (see FIG. 2) is connected to the driving pulley 24, and the driving pulley 24 is driven to rotate by the driving motor 27. The driving pulley 24 is driven to rotate in a clockwise direction and a counterclockwise direction. The rotation of the driving pulley 24 also moves the driving belt 26. The detection portion 20 is fixed to the driving belt 26, and the movement of the driving belt 26 causes the detection portion 20 to move toward the upstream side or downstream side in the paper conveying direction A along the guide portion 23.

[0038] Here, detection of the ink Ik adhering to the upper surface 8a of the light-transmitting plate 8 by the detection unit 20 will be described. Fig. 6 is a plan view of the light-transmitting plate 8 with the ink Ik adhering to the upper surface 8a. Fig. 7 is a side view of the detection unit 20 detecting the ink Ik adhering to the upper surface 8a of the light-transmitting plate 8. Note that the image signal Sg1 output in the detection state of the detection unit 20 in Fig. 7 is also shown.

[0039] As shown in FIG. 7, the light detection element 20a of the detection unit 20 has a plurality of detection pixels 20b arranged in the paper width direction B of the paper. The light detection element 20a converts the detected light into an electric charge for each detection pixel 20b. As shown in FIG. 7, the detection pixel 20b reads the ink Ik located directly above it across the light-transmitting plate 8, and outputs an image signal Sg1. The image signal Sg1 has an output value (referred to as Hi level) greater than the threshold value Th when the detection pixel 20b detects the ink Ik, and has an output value (referred to as Lo level) less than the threshold value Th when the detection pixel 20b does not detect the ink Ik. The preliminary ejection control unit 110b of the control device 110, which will be described later, recognizes the Hi level portion and the Lo level portion of the image signal Sg1 and obtains the shape of the ink Ik on the upper surface 8a of the light-transmitting plate 8.

[0040] The ink Ik attached to the upper surface 8a of the light-transmitting plate 8 is no longer necessary after the detection unit 20 has read the ink Ik. Therefore, in the preliminary ejection operation unit 7, the removal unit 21 removes the ink Ik read by the detection unit 20. The removal unit 21 may be, for example, a wiper that extends in the paper width direction B and is made of an elastic plate material. In addition, the removal unit 21 may be any configuration that can reliably remove the attached ink Ik without damaging the upper surface 8a of the light-transmitting plate 8. The removal unit 21 is disposed rearward in the movement direction when the detection unit 20 reads the ink Ik. In this manner, the removal unit 21 can remove the ink Ik after it has been read when moving together with the detection unit 20.

[0041] The removal unit 21 may be connected to the detection unit 20. In this manner, the detection unit 20 can sequentially remove the ink Ik after reading the ink Ik while moving. The removal unit 21 may be fixed to the detection unit 20, or a part of the removal unit 21 may be formed integrally with the detection unit 20.

[0042] Here, the position of the recording unit 9 will be described with reference to the drawings. Fig. 8 is a schematic enlarged view showing an image recording position Pp when the recording unit 9 records an image on the paper P. Fig. 9 is a schematic enlarged view showing a preliminary ejection position Ps when the recording unit 9 performs a preliminary ejection operation. Fig. 10 is a schematic enlarged view showing a capping position Pc when a cap unit 28 is attached to the recording unit 9. In Figs. 8 to 10, the recording unit 9 does not show the recording heads 11M and 11C arranged on the inside in the paper transport direction A, but has a similar configuration to the illustrated recording heads 11Y and 11K.

[0043] 8, when recording an image on paper P, the recording unit 9 is disposed at an image recording position Pp. At the image recording position Pp, the nozzles 19 are in close proximity to the paper P. At the image recording position Pp, the nozzles 19 are in close proximity to the paper P, so that an image can be accurately recorded on the paper P with the ink Ik ejected from the nozzles 19. At the image recording position Pp, the distance between the recording heads 11Y-11K of the recording unit 9 and the upper surface 8a of the light-transmitting plate 8 is an image recording distance L1.

[0044] As shown in Fig. 9, when the preliminary ejection operation is performed, the housing drive unit 17 moves the head housing 10 downward. At the preliminary ejection position Ps, the nozzles 19 come close to the upper surface 8a of the light-transmitting plate 8. At the preliminary ejection position Ps, the nozzles 19 come close to the upper surface 8a of the light-transmitting plate 8, so that the ink Ik ejected from the nozzles 19 can be accurately attached to the upper surface 8a of the light-transmitting plate 8. At the preliminary ejection position Ps, the distance between the recording heads 11Y to 11K of the recording unit 9 and the upper surface 8a of the light-transmitting plate 8 is a preliminary ejection distance L2. Note that the preliminary ejection distance L2 is approximately the same as the distance between the recording heads 11Y to 11K and the paper P at the image recording position Pp.

[0045] As shown in Fig. 10, when performing the capping operation, the housing drive unit 17 moves the head housing 10 above the image recording position Pp. At the capping position Pc, the recording unit 9 is farthest from the upper surface 8a of the light-transmitting plate 8. At the capping position Pc, a cap unit 28 is attached to the lower surface of the recording unit 9. By attaching the cap unit 28 to the lower surface of the recording unit 9, the nozzles 19 on the lower surfaces of the recording heads 11Y to 11K are covered. At the capping position Pc, the distance between the recording heads 11Y to 11K of the recording unit 9 and the upper surface 8a of the light-transmitting plate 8 is a capping distance L3.

[0046] 8 to 10, the position of the head housing 10 to which the recording unit 9 is attached changes with respect to the light-transmitting plate 8 in accordance with the operation of the recording unit 9. The capping distance L3 is the longest, and the preliminary ejection distance L2 is the shortest.

[0047] The housing drive 17 is controlled by a control device 110 .

[0048] The printer 100 further includes an operation panel 29, a storage unit 30, and a communication unit 31. The operation panel 29 is an operation unit for receiving various setting inputs. For example, the user can operate the operation panel 29 to input information on the size of the paper P to be set in the paper feed cassette 2, that is, the size of the paper P to be transported by the first transport unit 5. The user can also operate the operation panel 29 to input the number of sheets of paper P to be printed and to instruct the start of a print job. The operation panel 29 also functions as a notification device that provides notifications regarding the operating status of the printer 100 (image recording and preliminary ejection).

[0049] The storage unit 30 is a memory that stores the operation program of the control device 110 as well as various types of information, and is configured to include a ROM (Read Only Memory), a RAM (Random Access Memory), a non-volatile memory, etc. Information set by the operation panel 29 (e.g., information on the size and number of sheets of paper P) is stored in the storage unit 30.

[0050] The communication unit 31 is a communication interface for transmitting and receiving information to and from an external device (e.g., a personal computer (PC)). For example, when a user operates a PC and sends a print command together with image data to the printer 100, the image data and print command are input to the printer 100 via the communication unit 31. In the printer 100, the main control unit 110a controls the recording heads 11Y to 11K based on the image data to eject ink Ik, thereby recording an image on the paper P.

[0051] The printer 100 of this embodiment also includes a control device 110. The control device 110 includes, for example, a CPU (Central Processing Unit) and a memory. Specifically, the control device 110 includes a main control unit 110a, a preliminary ejection control unit 110b, a paper supply control unit 110c, and a head control unit 110d. Each control unit that constitutes the control device 110 is configured with one CPU, but may of course be configured with separate CPUs.

[0052] The main control unit 110a controls the operation of each unit of the printer 100. For example, the drive of each roller inside the printer 100, the ejection of ink Ik from the recording heads 11Y to 11K during image recording (other than during the preliminary ejection operation), and the like are controlled by the main control unit 110a.

[0053] The preliminary ejection control unit 110b causes the recording heads 11Y to 11K to eject the ink Ik as a preliminary ejection operation. The paper supply control unit 110c is a recording medium supply control unit that controls the pair of registration rollers 13 as a recording medium supply unit.

[0054] The head control unit 110d controls the housing driving unit 17 to control the vertical movement of the head housing 10. When the recording unit 9 moves to the capping position Pc, the head control unit 110d also executes a capping operation in which the cap unit 28 is disposed on the lower surface of the recording unit 9 and caps the lower surfaces of the recording heads 11Y to 11K.

[0055] The second transport unit 12 has a second transport belt 12a and a dryer 12b. The second transport belt 12a is stretched around two drive rollers 12c and a driven roller 12d. The paper P transported by the first transport unit 5 and having an image recorded thereon by the ink Ik ejected by the recording unit 9 is transported by the second transport belt 12a, dried by the dryer 12b during transport, and transported to the decurler unit 14 described above.

[0056] [2. Preliminary ejection operation] Next, a description will be given of the preliminary ejection operation in the printer 100 of this embodiment. In the printer 100 of this embodiment, a preliminary ejection operation is performed in which ink Ik is ejected from the nozzles 19 onto the upper surface 8a of the light-transmitting plate 8 at a timing different from the timing of image recording, and the image of the ink Ik on the upper surface 8a of the light-transmitting plate 8 is read by the detection unit 20.

[0057] For example, the ink Ik is stored in a tank (not shown) arranged inside the recording heads 11Y to 11K. The ink Ik in the tank dries over time. When the ink Ik dries, the nozzles 19 are blocked, and the amount of ink ejected and the shape of the ejected ink Ik adhering to the paper P change. Therefore, in the printer 100 of this embodiment, a preliminary ejection operation is performed to check the state of the nozzles 19 at a timing different from image recording.

[0058] Details of the preliminary ejection operation will be described below with reference to the drawings. Fig. 11 is a flow chart showing the procedure for executing the preliminary ejection operation. The main control unit 110a judges whether it is time to execute the preliminary ejection operation (step S101). The timing for executing the preliminary ejection operation can be determined by recording the ejection history of each nozzle 19 and determining, for example, the elapsed time, the number of ink ejections, and the amount of ink ejected. The elapsed time, the number of ink ejections, and the amount of ink ejected refer to the time elapsed since the previous preliminary ejection operation, the number of ink ejections, and the amount of ink ejected.

[0059] If it is determined that it is not the timing for the preliminary ejection operation (No in step S101), the main control unit 110a returns to step S101 and determines whether it is the timing to perform the preliminary ejection operation. If the main control unit 110a determines that it is the timing to perform the preliminary ejection operation (Yes in step S101), the main control unit 110a determines whether paper P is currently being printed (step S102). If paper P is currently being printed (Yes in step S102), the main control unit 110a repeats step S102 and waits for the printing of paper P to finish.

[0060] If the paper P is not being printed (No in step S102), the head control unit 110d confirms that the paper P is not in the printing area, and controls the housing drive unit 17 to move the head housing 10 downward (step S103). Then, it is determined whether the head housing 10 has moved to the preliminary ejection position Ps (step S104). If it is determined that the head housing 10 has not moved to the preliminary ejection position Ps (No in step S104), the process returns to step S103, where the movement of the head housing 10 continues, and the determination of whether to move to the preliminary ejection position Ps is repeated.

[0061] When it is determined that the head housing 10 has moved to the preliminary ejection position Ps (Yes in step S104), the preliminary ejection control unit 110b ejects a determined amount of ink Ik from all the nozzles 19 of the recording heads 11Y to 11K of the recording unit 9 (step S105). The detection unit 20 and the removal unit 21 are positioned at the upstream end of the light-transmitting plate 8 in the paper conveying direction A before all the nozzles 19 of the recording heads 11Y to 11K eject the ink Ik. Then, when the ejection of the ink Ik starts, the preliminary ejection control unit 110b detects light from the white reference portion 8c with the photodetection element 20a of the detection unit 20, and calibrates the photodetection element 20a (step S106).

[0062] Thereafter, when ejection of the ink Ik from all the nozzles 19 of the recording heads 11Y to 11K is completed, the preliminary ejection control unit 110b drives the drive motor 27 to move the detection unit 20 to directly below the ink Ik ejected from the first recording head (here, the recording head 11K) (step S107). The preliminary ejection control unit 110b instructs the detection unit 20 to read the image of the ink Ik attached to the upper surface 8a of the light-transmitting plate 8 (step S108).

[0063] The detection unit 20 reads the ink Ik adhering to the upper surface 8a of the light-transmitting plate 8 and sends the result as an image signal Sg1 (see FIG. 7) to the preliminary ejection control unit 110b (step S109). The preliminary ejection control unit 110b determines whether or not there is a portion where the ejection amount of the ink Ik differs from a specified amount based on the image signal Sg1 (step S110). The ejection amount of the ink Ik can be determined by the area of ​​the ink Ik adhering to the light-transmitting plate 8. More specifically, the preliminary ejection control unit 110b obtains the shape of the ink Ik based on the output value of the image signal Sg1. Calculating the shape of the ink Ik includes cases where the shape is obtained purely, and also cases where the area of ​​the ink Ik is obtained. The specified amount may not only be a specific numerical value, but may be a value having a certain range.

[0064] If there are any portions where the amount of ink Ik ejected differs from the specified amount (Yes in step S110), the preliminary ejection control unit 110b identifies the nozzles 19 from which the amount of ink Ik ejected differs from the specified amount (step S111). The preliminary ejection control unit 110b acquires information on the operating state of the drive motor 27 and the timing of reading the ink Ik, and identifies the nozzles 19 from which the amount of ink Ik ejected differs from the specified amount based on this information.

[0065] Then, the preliminary ejection control unit 110b performs a cleaning operation on the nozzles 19 that eject the amount of ink Ik different from the specified amount (step S112). The cleaning of the nozzles 19 is performed, for example, by ejecting the amount of ink specified for cleaning from the nozzles 19. When performing the cleaning operation, the ink Ik may be ejected only from the nozzles 19 to be cleaned, or the ink Ik may be ejected from all the nozzles 19 of each of the recording heads 11Y to 11K. When the cleaning operation is completed, it is confirmed whether the ink Ik ejected from the nozzles 19 of all the recording heads 11Y to 11K has been read (step S113).

[0066] When the reading of the images of the ink Ik ejected from the nozzles 19 of all the recording heads 11Y to 11K is completed (Yes in step S113), the preliminary ejection control unit 110b completes the process. On the other hand, when the reading of the images of the ink Ik ejected from the nozzles 19 of all the recording heads 11Y to 11K is not completed (No in step S113), the process proceeds to step S107 and the reading operation of the ink Ik is continued.

[0067] Furthermore, if the ejection amount of the ink Ik is the specified amount (No in step S110), the process proceeds to step S113. The process from step S113 onwards is the same as described above, and will therefore be omitted.

[0068] In the printer 100 according to the present embodiment, the state of the nozzles 19 of each of the recording heads 11Y to 11K is checked using an abnormality procedure, and problems such as stains on the paper P and poor recording can be prevented. This can eliminate waste of the paper P and contribute to energy savings.

[0069] It should be noted that, when a cleaning operation has been performed, a preliminary ejection operation may be performed only on the ejection unit 18 that includes the nozzle 19 for which the cleaning operation has been performed. Furthermore, if the malfunction of the nozzle 19 is not corrected even after performing the cleaning operation multiple times, the preliminary ejection control unit 110b may be configured to send information about the malfunctioning nozzle 19 as well as information about the need for repair to an external device via the communication unit 31.

[0070] 3. Modifications In the above-described embodiment, the detection unit 20 has a resolution higher than that of the recording heads 11Y to 11K. Therefore, the light detection element 20a can accurately obtain the size of the ink Ik attached to the upper surface 8a of the light-transmitting plate 8. On the other hand, as shown in FIG. 12, if the resolution of the nozzle 19 is higher than the resolution of the light detection element 20a, the image of the ink Ik may be read by all the detection pixels 20b. In this case, the image signal Sg2 does not have a Lo level area, and the preliminary ejection control unit 110b cannot accurately obtain the position and shape of the ink Ik on the upper surface 8a of the light-transmitting plate 8.

[0071] Therefore, the preliminary ejection control unit 110b executes a preliminary ejection operation in which the photodetector element 20a reads the image of the ink Ik on the upper surface 8a of the light-transmitting plate 8 and accurately detects the shape of the ink Ik. Here, a modified preliminary ejection operation that can accurately read the ink Ik will be described with reference to the drawings.

[0072] Fig. 13 is a plan view showing a discharge state of the ink Ik discharged by the preliminary discharge operation of the modified example, and Fig. 14 is a side view showing a state in which the ink Ik discharged by the preliminary discharge operation of the modified example is read.

[0073] The preliminary ejection control unit 110b sets the odd-numbered nozzles 19 from the left in each stage included in the ejection unit 18 as a first set, and the even-numbered nozzles as a second set. The first and second sets are set in the same manner in all the ejection units 18. Then, the ink Ik is ejected from the nozzles 19 of the first set of each ejection unit 18 onto the upper surface 8a of the light-transmitting plate 8. At this time, the preliminary ejection control unit 110b controls the nozzles 19 to eject a larger amount of the ink Ik than when ejected from all the nozzles 19. By doing so, it is possible to reduce the effective resolution of the recording heads 11Y to 11K when ejecting the ink Ik.

[0074] The ink Ik ejected from each set of nozzles 19 onto the upper surface 8a of the light-transmitting plate 8 is detected by the detection unit 20. Because the effective resolution of the recording heads 11Y to 11K is reduced, an image signal Sg3 as shown in FIG. 14 is output from the detection unit 20. The image signal Sg3 is a signal that has a Hi level and a Lo level, and the preliminary ejection control unit 110b can accurately read the position and shape of the ink Ik on the upper surface 8a of the light-transmitting plate 8. As a result, the preliminary ejection control unit 110b can accurately obtain the state of the nozzles 19.

[0075] Then, after the preliminary ejection operation of the first set of nozzles 19 is completed, the second set of nozzles 19 is used to perform the preliminary ejection operation. This allows the preliminary ejection control unit 110b to accurately obtain the state of the second set of nozzles 19 as well. In this manner, even the detection unit 20, which has a lower resolution than the recording heads 11Y to 11K, can accurately obtain the state of all the nozzles 19 of the recording heads 11Y to 11K. In this modified example, the multiple nozzles 19 are divided into two sets to perform the preliminary ejection operation, but the number of sets is not limited to two. Three or more sets may be used, and the number of sets that allows the resolution of the recording heads 11Y to 11K to be accurately detected by the detection unit 20 can be adopted.

[0076] [4. Other] The present invention is not limited to the above embodiment, and various modifications are possible within the scope of the present invention. As a method for ejecting the ink Ik from the recording heads 11Y to 11K, a piezoelectric method in which a piezoelectric element is used to push out the ink Ik can be mentioned, but is not limited to this. Various methods can be used, such as a thermal inkjet method in which air bubbles are generated by a heating element and pressure is applied to eject the ink Ik.

[0077] In the above embodiment, the preliminary ejection unit 7 is provided below the first transport unit 5, and when the preliminary ejection operation is performed, the head housing 10 is moved downward so that the nozzles 19 approach the upper surface 8a of the light-transmitting plate 8, but the present invention is not limited to this configuration. For example, the light-transmitting plate 8, the detection unit 20, the removal unit 21, and the movement mechanism 22 may be configured to approach the recording unit 9. Furthermore, the preliminary ejection unit 7 may be horizontally movable between a retracted position where it does not overlap with the head housing 10 and a preliminary ejection position directly below the head housing 10, and when the preliminary ejection operation is performed, the first transport unit 5 may be moved downward to move the preliminary ejection unit 7 to the preliminary ejection position.

[0078] In addition, in the above embodiment, an example was described in which the printer 100 that records color images using four colors of ink was used as the inkjet recording device, but it is also possible to use the driving waveform switching control of this embodiment when using a monochrome printer that records monochrome images using black ink. [Industrial Applicability]

[0079] The present invention can be used in inkjet recording devices such as inkjet printers. [Explanation of symbols]

[0080] 9. Recording Section 10 Head housing 11Y~11K recording head 17 Housing drive unit 18 Discharge part 19 Nozzle 20 Detection unit 21 Removal part 110 Control device 110a Main control unit 110b Pre-ejection control section

Claims

1. a recording head having a plurality of nozzles for ejecting ink; a preliminary ejection unit that performs a preliminary ejection operation for checking the state of the nozzles at a timing different from a timing that contributes to image recording; A control unit that controls the preliminary ejection operation, The preliminary ejection operation unit includes: a light-transmitting plate, one surface of which faces each of the nozzles of the recording head; a detection unit that is disposed in contact with the other surface of the light-transmitting plate and has a light detection element that reads an image of the ink ejected from the nozzle onto one surface of the light-transmitting plate; a removal unit that removes the ink after the ink is detected by the detection unit on the one surface of the light-transmitting plate, When the control unit performs the preliminary ejection operation using the preliminary ejection operation unit, the control unit ejects the ink from each nozzle of the recording head onto one side of the light-transmitting plate to form an ink image on the light-transmitting plate, obtains a detection result of the ink image detected by the detection unit, and checks the state of the nozzles based on the detection result.

2. the control unit divides the plurality of nozzles into a plurality of groups and executes the preliminary ejection operation for each group, and makes an amount of ink ejected from one nozzle in each group greater than an amount of ink ejected from one nozzle when the ink is ejected from all of the nozzles simultaneously; 2. The ink jet recording apparatus according to claim 1, wherein one ink image is read by a plurality of adjacent light detection elements of the detection section.

3. 2. The inkjet recording apparatus according to claim 1, wherein the detection section detects the ink ejected onto one surface of the light-transmitting plate while moving in a direction along a transport direction of the printing sheet.

4. The inkjet recording apparatus according to claim 3 , wherein the remover is connected to the detector and moves together with the movement of the light detection element to remove the ink read by the detector on the one surface of the light-transmitting plate.

5. 2. The inkjet recording apparatus according to claim 1, wherein the distance between said recording head and said light-transmitting plate is changeable between an image recording distance when performing image recording and a preliminary ejection distance which is shorter than said image recording distance.

6. 6. The ink jet recording apparatus according to claim 5, wherein the recording head is capable of approaching and receding from the light-transmitting plate.

Images