Liquid discharge apparatus

Abstract

To reduce an error of timing of discharge start by a liquid discharge head.SOLUTION: A liquid discharge apparatus 1 includes: a transportation drum 21 which carries paper P on a peripheral surface thereof and transports the paper P; multiple liquid discharge units 23 which discharge liquid onto the paper P; a paper detection member 56 which detects the paper P; an encoder wheel 51 provided on the shaft of the transportation drum 21; a first encoder sensor 52 which reads the encoder wheel 51; an encoder scale 53 provided on the outer peripheral surface of the transportation drum 21; and head side sensors 54A to 54D and a drum surface sensor 55 serving as second encoder sensors which read the encoder scale 53. The liquid discharge apparatus 1 determines discharge start timing of at least one of the multiple liquid discharge units 23 based on detection results of the paper detection member 56, the first encoder sensor 52, and the second encoder sensors.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a liquid ejection device. [Background technology]

[0002] Among liquid ejection devices, there are those that carry and transport a recording medium on the surface of a transport drum as a rotating member, and form an image by ejecting liquid from liquid ejection heads of each color that face the transport drum.

[0003] In such a liquid ejection device, an encoder sensor or the like detects the position of the transported recording medium, and each liquid ejection head ejects liquid of each color onto the recording medium when the recording medium passes by.

[0004] For example, in the liquid ejection device of Patent Document 1 (JP Patent No. 7016481), after a sheet material position sensor detects the leading edge of the sheet material, an encoder wheel attached to the shaft of the transport drum is read by an encoder sensor to determine the timing for each liquid ejection head to start ejecting liquid. Then, the ejection timing after the liquid ejection head starts ejecting is determined by another encoder sensor provided in the liquid ejection unit reading an encoder scale attached to the circumferential surface of the transport drum. Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration of Patent Document 1, the diameter of the shaft of the transport drum that transports the recording medium is smaller than the outer circumferential surface of the transport drum, so the error of the encoder wheel attached to the shaft of the transport drum is magnified on the transport drum. In other words, the error between the position of the recording medium on the transport drum calculated by reading the encoder wheel and the actual position of the recording medium becomes large, and the error in the ejection start timing from the liquid ejection heads of each color also becomes large. This causes problems such as the ejection start timing of the liquid ejection heads of each color deviating from the target timing, or the error between colors becoming large, affecting the quality of the image.

[0006] An object of the present invention is to suppress errors in the timing at which a liquid ejection head starts ejecting. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a liquid ejection device comprising a rotating member that supports and transports a recording medium on its peripheral surface, a liquid ejection section that ejects liquid onto the recording medium, a recording medium detection member that detects the recording medium, an encoder wheel provided on the axis of the rotating member, a first encoder sensor that reads the encoder wheel, an encoder scale provided on the outer peripheral surface of the rotating member, and one or more second encoder sensors that read the encoder scale, and is characterized in that the ejection start timing of at least one of the liquid ejection sections is determined based on the detection results of the recording medium detection member, the first encoder sensor, and the second encoder sensor. Effect of the Invention

[0008] The present invention can suppress errors in the timing at which liquid is discharged from a liquid discharge head. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of a printing device. [Diagram 2] FIG. [Diagram 3] 1 is a front view showing a printing unit of a printing device according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a plan view of the printing unit in FIG. [Diagram 5] 5A and 5B are conceptual diagrams illustrating ejection start timing and ejection timing of a printing unit according to the first embodiment. [Figure 6] FIG. 4 is a flow diagram of the ejection operation of the printing unit of the first embodiment. [Figure 7] FIG. 2 is a block diagram showing a control configuration relating to ejection of the printing device of the first embodiment. [Figure 8] 13A and 13B are conceptual diagrams illustrating ejection start timing and ejection timing of a printing unit according to a second embodiment. [Figure 9] FIG. 11 is a flow diagram of the ejection operation of a printing unit according to a second embodiment. [Figure 10] 13A and 13B are conceptual diagrams illustrating ejection start timing and ejection timing of a printing unit according to a third embodiment. [Figure 11] FIG. 11 is a flow diagram of the ejection operation of a printing unit according to a third embodiment. [Figure 12] FIG. 11 is a block diagram showing a control configuration relating to ejection of a printing device according to a third embodiment. [Figure 13] 13A and 13B are conceptual diagrams illustrating ejection start timing and ejection timing of a printing unit according to a fourth embodiment. [Figure 14] FIG. 13 is a flow diagram of the ejection operation of a printing unit according to a fourth embodiment. [Figure 15] FIG. 13 is a block diagram showing a control configuration relating to ejection of a printing device according to a fourth embodiment. [Figure 16] 1 is a block diagram showing a hardware configuration of a printing apparatus according to a first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and the duplicated description will be appropriately simplified or omitted.

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, a liquid ejection device according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic explanatory diagram of a printing device as a liquid ejection device according to the same embodiment. This printing device ejects ink as a liquid to form an image on paper as a recording medium.

[0012] The printing device 1 includes an input section 10, a printing section 20, a drying section 30, and an output section 40. The printing device 1 applies liquid to paper P as a recording medium input from the input section 10 in the printing section 20 to perform a required printing, dries the liquid adhering to the paper P in the drying section 30, and then discharges the paper P to the output section 40.

[0013] The carry-in section 10 includes an input tray 11 on which a plurality of sheets of paper P are stacked, a feeder 12 that separates and sends out the sheets of paper P one by one from the input tray 11, and a pair of registration rollers 13 that sends the sheets of paper P to the printing section 20.

[0014] Any feeding device can be used as the feeding device 12, such as a device using rollers or a device using air suction. After the leading edge of the paper P sent out from the input tray 11 by the feeding device 12 reaches the pair of registration rollers 13, the pair of registration rollers 13 is driven at a predetermined timing to send the paper P to the printing unit 20.

[0015] The printing section 20 includes a transport drum 21, which is a transport means for supporting and transporting the paper P on its outer circumferential surface, and a plurality of ejection units 23A to 23D for ejecting liquid toward the paper P supported by the transport drum 21.

[0016] The printing section 20 also includes a transfer cylinder 24 that receives the fed paper P and passes it to the transport drum 21 , and a transfer cylinder 25 that passes the paper P transported by the transport drum 21 to the drying section 30 .

[0017] The paper sheet P transported from the carry-in section 10 to the printing section 20 has its leading edge gripped by a sheet gripper provided on the surface of the transfer drum 24, and is transported in the direction of arrow A as the transfer drum 24 rotates. The paper sheet P transported by the transfer drum 24 is delivered to the transport drum 21 at a position opposite to the transport drum 21.

[0018] A sheet gripper is also provided on the surface of the transport drum 21, and the leading edge of the paper P is gripped by the sheet gripper. A plurality of suction holes are formed and dispersed on the surface of the transport drum 21. An adsorption device 26, which is an adsorption means, generates a suction airflow that flows inward from the suction holes of the transport drum 21.

[0019] Then, the paper sheet P transferred from the transfer drum 24 to the transport drum 21 has its leading edge gripped by the sheet gripper, and is adsorbed onto the transport drum 21 by the suction airflow of the adsorption device 26, and is transported as the transport drum 21 rotates.

[0020] The printing section 20 includes a plurality of discharge units as liquid discharge sections. In this embodiment, the four discharge units 23A to 23D are included. The discharge unit 23A is the first discharge section of this embodiment. Hereinafter, the discharge units 23A to 23D are also referred to as discharge units 23. For example, the discharge unit 23A discharges black (K) liquid, the discharge unit 23B discharges cyan (C) liquid, the discharge unit 23C discharges magenta (M) liquid, and the discharge unit 23D discharges yellow (Y) liquid. In addition, a discharge unit that discharges a special liquid such as white or gold (silver) or a treatment liquid such as a surface coating liquid can be provided, and the number of discharge units 23 is not limited to this embodiment. The order of the inks to be discharged is also not limited to this embodiment and can be changed as appropriate.

[0021] The ejection operation of each ejection unit 23 is controlled by a drive signal corresponding to the printing information. When the paper P supported on the transport drum 21 passes through an area facing the ejection units 23, liquid of each color is ejected from each ejection unit 23, and an image corresponding to the printing information is printed.

[0022] The drying section 30 includes a drying mechanism section 31 for drying the liquid adhering to the paper P in the printing section 20, and a suction transport mechanism section 32 for transporting the paper P transported from the printing section 20 under suction (suction transport).

[0023] The paper P conveyed from the printing unit 20 is received by the suction conveying mechanism 32, conveyed so as to pass through the drying mechanism 31, and then delivered to the discharge unit .

[0024] When the paper P passes through the drying mechanism 31, the liquid on the paper P is subjected to a drying process. This causes the water content in the liquid to evaporate, the colorant contained in the liquid to be fixed on the paper P, and curling of the paper P is suppressed.

[0025] The discharge section 40 includes a discharge tray 41 on which a plurality of sheets of paper P are stacked. The sheets of paper P conveyed from the drying section 30 are successively stacked and held on the discharge tray 41.

[0026] In addition, in the printing device 1, for example, a pre-processing unit that performs pre-processing on the paper P can be arranged upstream of the printing unit 20, and a post-processing unit that performs post-processing on the paper P having liquid attached thereto can be arranged between the drying unit 30 and the discharge unit 40.

[0027] An example of the pre-treatment section is a section that performs a pre-coating process in which a treatment liquid that reacts with the liquid to suppress bleeding is applied to the paper P. An example of the post-treatment section is a section that performs a sheet reversing and conveying process in which a sheet printed in the printing section 20 is reversed and sent back to the printing section 20 to print on both sides of the paper P, and a process for binding multiple sheets.

[0028] The ejection unit 23 is, for example, a full-line type head in which multiple liquid ejection heads (hereinafter simply referred to as "heads") 100, each having a nozzle row 101 in which multiple nozzles are arranged, are arranged on a base member 27, as shown in FIG.

[0029] Next, a configuration for controlling the timing of liquid ejection by the liquid ejection head in the printing unit 20 will be described with reference to FIGS.

[0030] 3 and 4, an encoder wheel 51 is provided on the shaft 21a of the transport drum 21. A first encoder sensor 52 that reads the encoder wheel 51 is provided facing the encoder sensor 52. The encoder wheel 51 and the first encoder sensor 52 configure an axial encoder that is a rotary encoder. The axial encoder, that is, the first encoder sensor 52, outputs a first signal corresponding to the amount of rotation of the shaft 21a.

[0031] As shown in Fig. 3, an encoder scale 53 is provided on the outer circumferential surface of the transport drum 21. The encoder scale 53 is provided by attaching a longitudinal scale along the entire circumferential surface of the transport drum 21, and a gap is provided at one point in the circumferential direction of the transport drum 21, which is a gap between both ends of the scale before being attached. The transport drum 21 rotates in the direction of arrow A in Fig. 3, which is the transport direction of the paper P. Hereinafter, the upstream side and downstream side of the transport direction of the paper P will also be simply referred to as the upstream side and the downstream side.

[0032] As a second encoder sensor for reading the encoder scale 53, the head side sensors 54A to 54D are provided corresponding to the discharge units 23A to 23D, and a drum surface sensor 55 is provided at a position not corresponding to the discharge unit 23, separate from the head side sensors 54A to 54D corresponding to the discharge units 23A to 23D. In this embodiment, the head side sensors 54A to 54D are attached to the base members 27 (see FIG. 4) of the discharge units 23A to 23D. Hereinafter, the head side sensors 54A to 54D are also referred to as head side sensors 54. In addition, the position of the drum surface sensor 55 is determined so that the discontinuity of the encoder scale 53 does not come to a position facing the drum surface sensor 55 within the section in which the pulses by the drum surface sensor 55 are counted to determine the discharge start timing (the discharge start timing will be described later). In this embodiment, the drum surface sensor 55 is provided upstream of the most upstream discharge unit 23A in the paper transport direction. The head side encoder is composed of the encoder scale 53 and the head side sensors 54A to 54D. The encoder scale 53 and the drum surface sensor 55 constitute a drum surface encoder. The head side encoder and the drum surface encoder, that is, the head side sensors 54A to 54D and the drum surface sensor 55, output a second signal according to the amount of movement of the outer circumferential surface of the transport drum 21. In other words, the second signal is a signal that correlates with the amount of movement of the paper P transported on the surface of the transport drum 21. However, the encoder scale 53 may be provided in a portion of the outer circumferential surface of the transport drum 21 that has a smaller diameter than the portion that adsorbs and transports the paper P, and does not need to have a completely identical diameter to the portion of the transport drum 21 that adsorbs and transports the paper P. The encoder scale 53 is an encoder that has a larger diameter than the encoder wheel 51 and has a slit at any position in the circumferential direction. In addition, in this embodiment, the head-side sensors 54A to 54D are provided on the base member 27 on which the liquid ejection heads are provided, but the head-side sensors 54A to 54D may be provided on a member other than the member on which the liquid ejection heads are provided.The second encoder sensors corresponding to each of the above-mentioned discharge units 23A to 23D refer to the sensors that read the encoder scale 53 and are provided at the position closest to (or the same as) each of the discharge units 23A to 23D in the circumferential direction, and the second encoder sensors that do not correspond to the discharge units 23 refer to sensors that read the encoder scale 53 and are provided other than the sensors corresponding to each of the discharge units 23A to 23D.

[0033] A paper detection sensor 56 serving as a recording medium detection member is provided upstream of the most upstream ejection unit 23A in the paper transport direction. When the leading edge of the paper P reaches the paper detection sensor 56, the paper detection sensor 56 detects this, and the control unit of the liquid ejection device can recognize that the paper P has reached the paper detection sensor 56. However, the paper detection sensor 56 can also be configured to read a mark affixed to the paper P. This makes it possible to detect a predetermined position other than the leading edge of the recording medium, and also makes it possible to detect continuous recording media such as continuous paper.

[0034] The following describes the hardware configuration of the printing device 1. Fig. 16 is a block diagram showing an example of the hardware configuration of the printing device 1 according to an embodiment of the present invention.

[0035] The main board 61 has a CPU (Center Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, an NVRAM (Non Volatile Random Access Memory) 204, an input / output device (I / O port) 205, an I / F (Interface) 206, etc., each of which is connected by a bus 207.

[0036] The CPU 201 is a calculation unit and controls the overall operation of the printing device 1. The ROM 202 is a read-only non-volatile storage medium and stores programs such as firmware. The RAM 203 is a volatile storage medium that allows high-speed reading and writing of information and is used as a working area when the CPU 201 processes information. The NVRAM 204 is a non-volatile storage medium that allows information to be read and written and stores setting values ​​required for controlling each part of the printing device 1. The programs stored in the ROM 202 are read into the RAM 203. The CPU 201 controls each part of the printing device 1 by performing calculations according to the programs loaded into the RAM 203. In addition, at that time, the CPU 201 uses setting values ​​and the like stored in the NVRAM 204.

[0037] The I / O port 205 is connected to the drive units of each part of the printing unit 20 (transfer drum 24, transfer drum 25, suction device 26, ejection units 23A to 23D, transport drum 21, etc.) and a group of sensors (first encoder sensor 52, head side sensors 54A to 54D, drum surface sensor 55, paper detection sensor 56). The CPU 201 controls each part based on the state of the input sensor signal. The CPU 201 also controls the ejection timing of ejection units 23A to 23D, which will be described later, based on a program stored in ROM 202.

[0038] The CPU 201 is also connected to the input unit 10, drying unit 30, and output unit 40 of the printing device 1 via an I / F 206. The CPU 201 controls each unit directly or controls the entire printing device 1 by communicating with separate control units provided in each unit.

[0039] Next, the ejection start timing and ejection timing by the liquid ejection head of each ejection unit will be described with reference to the aforementioned Fig. 3, the conceptual diagram of Fig. 5, and the flow diagram of Fig. 6. In Fig. 5, each ejection unit 23 is indicated by K, C, M, or Y, which is the color of the liquid ejected by each ejection unit 23. That is, in Fig. 5, "K" indicates ejection unit 23A, "C" indicates ejection unit 23B, "M" indicates ejection unit 23C, and "Y" indicates ejection unit 23D. The ejection start timing or ejection timing by the liquid ejection head of the ejection unit is also simply referred to as the ejection start timing or ejection timing of the ejection unit.

[0040] When the paper P reaches the surface of the transport drum 21, the suction device 26 suctions the paper P onto the surface of the transport drum 21 (step S1 in FIG. 6). Then, the transport drum 21 rotates, and the leading edge of the paper P is detected by the paper detection sensor 56 (step S2). At this timing, as shown in FIG. 5, the control unit counts the pulses output by the first encoder sensor 52 after reading the encoder wheel 51. Then, based on the pulses from the first encoder sensor 52, the pre-ejection start timing, which is a predetermined timing before the liquid ejection head starts ejecting, is determined (step S3).

[0041] Thereafter, when the pre-ejection start timing is reached, the control unit starts counting pulses output by the drum surface sensor 55 reading the encoder scale 53, instead of the pulses from the first encoder sensor 52. Then, based on the pulses from the drum surface sensor 55, the control unit determines the ejection start timing of the liquid ejection head of each ejection unit 23 (step S4). In this manner, the ejection start timing of the liquid ejection head of each ejection unit 23 is determined. In other words, the paper detection sensor 56, the first encoder sensor 52, and the drum surface sensor 55 determine the ejection start timing of the liquid ejection head of each ejection unit 23. Note that the ejection start timing of the downstream CMY ejection units 23B to 23D can be set in the same manner by determining the ejection start timing by the pulse count of the drum surface sensor 55 from the ejection start timing of the most upstream K ejection unit 23A.

[0042] After the ejection start timing is reached, the ejection timing after the ejection start by the liquid ejection head of each ejection unit 23 is determined by the pulse of the corresponding head side sensor instead of the drum surface sensor 55, and the ejection operation by each liquid ejection head is started (step S5). Then, when the ejection operations by all the ejection units 23 are completed, the printing operation on the paper P is completed. Note that the ejection start timing of the ejection unit 23 refers to the timing at which each ejection unit 23 ejects liquid onto the recording medium for the first time, and the ejection timing after the ejection start refers to each timing at which each ejection unit 23 ejects liquid onto the recording medium for the second or subsequent times.

[0043] As described above, according to this embodiment, the timing of starting ejection by the liquid ejection heads of each of the ejection units 23A to 23D can be determined based on the pulse of the drum surface sensor 55 that reads the encoder scale 53 provided on the surface of the transport drum 21. As a result, the liquid ejection device can detect the surface movement amount of the transport drum 21, that is, the movement amount of the paper P, without being affected by the rotation accuracy of the transport drum 21 or the dimensional accuracy of the transport drum 21, and can detect the position of the paper P with high accuracy. Therefore, each liquid ejection head can reduce the deviation of the image formation position with respect to the paper P. This also makes it possible to suppress the deviation of the ejection start position between each of the ejection units, and improve the quality of the image formed on the paper P. In addition, the above-mentioned effects can be obtained by the configuration in which the encoder scale 53 is attached to the surface of the transport drum 21, and the cost of the liquid ejection device can be reduced, and it is easily applicable to a large transport drum 21. Furthermore, by using a first encoder which is an encoder on the shaft side of the transport drum 21, a drum surface encoder which is an encoder on the surface side of the transport drum 21, and a head side encoder in combination to determine the ejection start timing, the position of the paper P can be detected without interruption even if there is a gap in the encoder scale 53 on the rotation of the transport drum 21.

[0044] Furthermore, the ejection timing after each ejection unit 23 starts ejecting is also determined by the head side sensors 54A to 54D reading the encoder scale 53. Therefore, the error in the timing, that is, the error in the ejection position with respect to the paper P, can be reduced.

[0045] Next, a block diagram showing a portion of the control section of the liquid ejection device that is related to the control of the ejection timing will be described with reference to FIG.

[0046] As shown in Fig. 7, the liquid ejection device has a main substrate 61 and a head substrate 62. The head substrate 62 is provided in each liquid ejection head 100 of each ejection unit 23, and in Fig. 7, it is referred to as a "KCMY-head substrate" since there is a head substrate 62 provided in each ejection unit 23 of KCMY. The same applies to a "KCMY-head side sensor" or a "KCMY-head".

[0047] Signals from the first encoder sensor 52, the drum surface sensor 55, and the paper detection sensor 56 are input to the main board 61. As described above, the main board 61 determines the ejection start timing of each liquid ejection head 100 based on this information, and inputs it to the head board 62. In this way, the main board 61 is an ejection start timing determination mechanism that determines the ejection start timing of each liquid ejection head. Each head board 62 determines and inputs the ejection timing (hereinafter simply referred to as ejection timing) after the start of ejection by each liquid ejection head based on the ejection start timing input from the main board 61 and the signal input from the head side sensor 54. In this way, the head board 62 is an ejection timing determination mechanism. To be precise, a head board 62 is provided for each of the multiple liquid ejection heads 100 provided in each ejection unit 23, and information is input from the main board 61 to each head board 62. Information is also input from each head side sensor 54 of KCMY to the corresponding head board 62 and then to the corresponding liquid ejection head 100.

[0048] In the above description, the ejection start timings of all the ejection units 23 are determined using the pulses of the second encoder sensor, but this does not necessarily apply to all of them.

[0049] Next, modified examples of the liquid ejection device of the present invention, which change the control configuration or control method for the ejection start timing and the ejection timing after the ejection start, will be described in order. In the following description, the differences from the above embodiment will be mainly described, and common points will be omitted as appropriate.

[0050] Fig. 8 is a conceptual diagram for explaining the ejection start timing and ejection timing of each ejection unit of the liquid ejection device according to the second embodiment, and Fig. 9 is a flow diagram. Note that the configuration of the control unit is the same as that of Fig. 7 in the previous embodiment.

[0051] As shown in FIG. 8, in this embodiment, the ejection start timing of the ejection unit 23A (ejecting K liquid; see FIG. 3) arranged on the most upstream side among the ejection units 23 is determined only by the pulse of the first encoder sensor 52 (step S13) after the leading edge position of the paper P is detected by the paper detection sensor 56 (step S12 in FIG. 9). Then, after the ejection timing of the ejection unit 23A is reached, the ejection start timing of the ejection units 23B to 23D (ejecting CMY liquids, respectively) is determined by the pulse of the drum surface sensor 55 (step S14), as in the previous embodiment. In other words, the ejection start timing of the ejection unit 23A is determined by the paper detection sensor 56 and the first encoder sensor 52. The ejection start timing of the ejection units 23B to 23D is determined by the ejection start timing of the ejection unit 23A, which is a predetermined timing, and the drum surface sensor 55. In other words, the timing at which the discharge units 23B to 23D start discharging is determined by the paper detection sensor 56, the first encoder sensor 52, and the drum surface sensor 55.

[0052] After the ejection start timing of each ejection unit, the ejection timing of each ejection unit is determined based on pulses from the head side sensors 54A to 54D provided in each ejection unit (steps S14 and S15).

[0053] As described above, according to this embodiment, after the ejection start timing of the ejection unit 23A is determined, the ejection start timing of the other ejection units 23B to 23D can be determined based on the timing by the pulse of the drum surface sensor 55. That is, the ejection start timing of the ejection units 23B to 23D can be determined by reading the encoder scale 53 (see FIG. 3) provided on the surface of the conveying drum 21. Therefore, the error of the ejection start timing of the ejection units 23B to 23D relative to the ejection start timing of the ejection unit 23A, that is, the error of the ejection position, can be reduced. Compared with the absolute error of the position of the liquid ejected onto the paper P, the relative error of the position of each color has a large effect on the quality of the image formed on the paper P even if it is slight, and it is particularly important to reduce the error. In this embodiment, the error of the ejection start position between the colors can be reduced, and the quality of the image formed on the paper P can be improved.

[0054] Next, regarding a liquid ejection device according to a third embodiment of the present invention, FIG. 10 is a conceptual diagram explaining the ejection start timing and ejection timing, FIG. 11 is a flow diagram, and FIG. 12 is a block diagram explaining the configuration of the part related to the control of the ejection timing of the control unit.

[0055] In this embodiment, as shown in FIG. 10, when the leading edge position of the paper P is detected by the paper detection sensor 56, the counting of pulses of the first encoder sensor 52 is started, and the ejection start timing of the ejection unit 23A is determined (steps S22 and S23 in FIG. 11). This is the same as in the second embodiment. Then, a difference from the second embodiment is that after the ejection start timing of the ejection unit 23A is reached, the ejection start timing of the other ejection units 23B to 23D is determined by the counting of pulses of the head side sensor 54 of the ejection unit 23A (step S24). That is, the ejection start timing of the ejection units 23B to 23D is determined by the ejection start timing of the ejection unit 23A and the head side sensor 54 of the ejection unit 23A. In other words, the ejection start timing of the ejection units 23B to 23D is determined by the paper detection sensor 56, the first encoder sensor 52, and the head side sensor 54 of the ejection unit 23A.

[0056] As shown in Fig. 12, unlike the first and second embodiments described above, the liquid ejection device of this embodiment does not have a drum surface sensor 55 (see Fig. 3). Also, this embodiment differs from the above-described embodiments in that pulse information from a head side sensor 54A provided in an ejection unit 23A is input to each of the head substrates 62A-62D. The head substrates 62A-62D and heads 100A-100D correspond to the ejection units 23A-23D, respectively.

[0057] As described above, in this embodiment, after the ejection start timing of the ejection unit 23A is determined, the ejection start timing of the other ejection units 23B to 23D can be determined based on that timing by the pulse of the head side sensor 54A of the ejection unit 23A. Therefore, as in the second embodiment, the error in the ejection start timing of the ejection units 23B to 23D relative to the ejection start timing of the ejection unit 23A, that is, the ejection position error, can be reduced. This makes it possible to improve the quality of the image formed on the paper P. Particularly in this embodiment, such an effect can be obtained without providing a drum surface sensor 55 that does not correspond to each ejection unit 23.

[0058] In the above second and third embodiments, the ejection start timings of all the ejection units 23B to 23D downstream from the most upstream ejection unit 23A are determined by the pulse of the second encoder sensor from the ejection start timing of the most upstream ejection unit 23A. However, it is not necessary to determine all the downstream ejection units, and it may be some of them. Also, it is not necessary to determine the ejection start timing of the ejection units 23 downstream from the most upstream ejection unit 23A. For example, the ejection start timing of the third and subsequent ejection units 23 may be determined by the pulse of the second encoder sensor from the ejection start timing of the second most upstream side. In this way, it is not necessary to apply the configuration of this embodiment to all the ejection units.

[0059] Next, regarding a liquid ejection device according to a fourth embodiment of the present invention, FIG. 13 is a conceptual diagram explaining the ejection start timing and ejection timing, FIG. 14 is a flow diagram, and FIG. 15 is a block diagram explaining the configuration of the part related to the control of the ejection timing of the control unit.

[0060] As shown in FIG. 13, in this embodiment, after the ejection start timing of the most upstream ejection unit 23A is reached, the ejection start timing of the next downstream ejection unit 23B is determined by counting the pulses of the head side sensor 54A of the ejection unit 23A (step S34 in FIG. 14). Similarly, after the ejection start timing of the ejection unit 23B is reached, the ejection start timing of the next downstream ejection unit 23C is determined by counting the pulses of the head side sensor 54B of the ejection unit 23B (step S35). Then, after the ejection start timing of the ejection unit 23C is reached, the ejection start timing of the next downstream ejection unit 23D is determined by counting the pulses of the head side sensor 54A of the ejection unit 23C (step S36). In other words, the ejection start timing of the most upstream ejection unit 23A is determined by the paper detection sensor 56 and the first encoder sensor 52. The ejection start timing of the ejection units 23B to 23D is determined by the ejection start timing of the ejection unit 23 one upstream and the head side sensor 54 of that ejection unit 23. In other words, the ejection start timing of the ejection units 23B to 23D is determined by the paper detection sensor 56, the first encoder sensor 52, and the head side sensor 54 of the ejection unit 23 one upstream.

[0061] As described above, in this embodiment, the ejection start timing of the ejection unit 23 is determined by the ejection start timing of the ejection unit 23 one upstream and the pulse of the head side sensor 54 of this ejection unit 23. Therefore, it is possible to reduce the error of the ejection start timing of each of the ejection units 23B to 23D relative to the ejection start timing of the ejection unit 23 one upstream, that is, the ejection position error. This makes it possible to improve the quality of the image formed on the paper P. Particularly in this embodiment, such an effect can be obtained without providing a drum surface sensor 55 that does not correspond to each ejection unit 23.

[0062] As shown in Figure 15, information is input from the K head substrate 62A to the C head substrate 62B one downstream, information is input from the C head substrate 62B to the M head substrate 62C, and information is input from the M head substrate 62C to the Y head substrate 62D. In other words, information is input from the head substrate 62 of the upstream ejection unit 23 to the downstream head substrate 62.

[0063] In the above fourth embodiment, the ejection start timing is determined for all the ejection units 23 downstream of the most upstream ejection unit 23A, based on the ejection start timing of the ejection unit 23 one upstream and the pulse of the head side sensor 54 of this ejection unit 23, but this may be the case for only some of the downstream ejection units. Also, the ejection start timing of the second ejection unit 23 from the upstream side or further downstream may be determined based on the pulse of the first encoder sensor 52, and the ejection start timing of the third ejection unit 23 from the upstream side or further downstream may be determined based on the ejection start timing of the ejection unit 23 one upstream and the pulse of the head side sensor 54 of this ejection unit 23. In this way, it is not necessary to apply the configuration of this embodiment to all the ejection units.

[0064] Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0065] In the present application, the liquid to be ejected may have a viscosity and surface tension that allows it to be ejected from the head, and is not particularly limited, but it is preferable that the viscosity of the liquid is 30 mPa·s or less at room temperature and pressure, or by heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, etc., containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a functionalizing material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, or calcium, an edible material such as a natural colorant, etc., and these can be used for applications such as inkjet ink, surface treatment liquid, a liquid for forming a component of an electronic element or a light-emitting element, an electronic circuit resist pattern, a material liquid for three-dimensional modeling, etc.

[0066] "Liquid" includes not only ink but also paint, pretreatment liquid, binder, and overcoat liquid.

[0067] In this application, a "liquid ejection device" is a device that includes a carriage having a liquid ejection head and ejects liquid by driving the liquid ejection head. Liquid ejection devices include not only devices that can eject liquid onto a recording medium to which the liquid can adhere, but also devices that eject liquid into air or liquid.

[0068] This "liquid ejection device" can also include means for feeding, transporting, and discharging objects onto which liquid can be attached, as well as pre-processing devices and post-processing devices.

[0069] For example, examples of "liquid ejection devices" include image forming devices that eject ink to form an image on paper, and three-dimensional modeling devices that eject modeling liquid onto a powder layer formed by layering powder in order to create a three-dimensional object (a three-dimensional model).

[0070] Furthermore, the term "liquid ejection device" is not limited to devices that visualize meaningful images such as characters and figures by ejecting liquid. For example, the term also includes devices that form patterns that have no meaning in themselves and devices that create three-dimensional images.

[0071] The above-mentioned "object to which liquid can adhere" means an object to which liquid can adhere at least temporarily, and to which the liquid adheres and sticks, or to which the liquid adheres and penetrates, etc. Specific examples include media such as paper, recording paper, film, cloth, and other recording media, electronic boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all objects to which liquid can adhere.

[0072] The material of the above-mentioned "object to which liquid can adhere" may be any material to which liquid can adhere even temporarily, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, and ceramics.

[0073] Other examples of "liquid ejection devices" include a treatment liquid application device that ejects a treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and an injection granulation device that ejects a composition liquid in which raw materials are dispersed through a nozzle to granulate fine particles of the raw materials.

[0074] In the present application, the terms image formation, recording, printing, imprinting, printing, modeling, and the like are all synonymous.

[0075] For example, aspects of the present invention are as follows. <1> A rotating member that carries and transports a recording medium on its circumferential surface; a liquid ejection unit that ejects liquid onto the recording medium; a recording medium detection member for detecting the recording medium; An encoder wheel provided on the shaft of the rotating member; a first encoder sensor that reads the encoder wheel; an encoder scale provided on an outer circumferential surface of the rotating member; a second encoder sensor that reads the encoder scale, The liquid ejection device is characterized in that the ejection start timing of at least one of the liquid ejection sections is determined based on the detection results of the recording medium detection member, the first encoder sensor, and the second encoder sensor. <2> A discharge start timing of a liquid discharge unit downstream of the first liquid discharge unit in a recording medium transport direction is determined based on a discharge start timing of a first liquid discharge unit, which is one of the liquid discharge units, and a detection result of the second encoder sensor. <1> The liquid ejection apparatus is as described above. <3> the second encoder sensor corresponding to the liquid ejection unit; the second encoder sensor not corresponding to the liquid ejection unit, The ejection start timing of one or more of the liquid ejection units downstream of the first liquid ejection unit in a recording medium transport direction is determined based on the ejection start timing of the first liquid ejection unit and the detection result of the second encoder sensor that does not correspond to the liquid ejection unit. <2> The liquid ejection apparatus is as described above. <4> A discharge start timing of the first liquid discharge unit is determined based on detection results of the recording medium detection member, the first encoder sensor, and the second encoder sensor that does not correspond to the liquid discharge unit. <3> The liquid ejection apparatus is as described above. <5> the second encoder sensor corresponding to the first liquid ejection unit; determining a discharge start timing of one or more liquid discharge units downstream of the first liquid discharge unit in a recording medium transport direction based on the discharge start timing of the first liquid discharge unit and a detection result of the second encoder sensor corresponding to the first liquid discharge unit; <2> The liquid ejection apparatus is as described above. <6> the second encoder sensor corresponding to each of the first liquid ejection unit and a plurality of the liquid ejection units downstream of the first liquid ejection unit; The ejection start timings of the plurality of liquid ejection units are determined based on the ejection start timings of the liquid ejection units arranged one unit upstream of the liquid ejection units in the recording medium transport direction and the detection result of the second encoder sensor corresponding to the liquid ejection units arranged one unit upstream of the liquid ejection units in the recording medium transport direction. <2> The liquid ejection apparatus is as described above. <7> A discharge start timing of the first liquid discharge unit is determined based on the detection results of the recording medium detection member and the first encoder sensor. <2> , <3> , <5> , <6> 1 is a liquid ejection apparatus according to any one of the above items. <8> the second encoder sensors are provided corresponding to the plurality of liquid ejection units, The ejection timing after the ejection start of each of the liquid ejection units is determined based on the detection result of the second encoder sensor corresponding to each of the liquid ejection units and the ejection start timing of each of the liquid ejection units. <2> ~ <7> The liquid ejection apparatus according to any one of the above aspects is provided. [Explanation of symbols]

[0076] 1 Printing device (liquid ejection device) 21 Conveyor drum (rotating member) 23 Discharge unit (liquid discharge unit) 23A Discharge unit (first liquid discharge part) 51 Encoder Wheel 52 1st Encoder Sensor 53 Encoder scale 54A~54D Head side sensor (second encoder sensor) 55 Drum surface sensor (second encoder sensor) 56 Paper detection sensor (recording medium detection member) 100 Liquid ejection head A Paper transport direction (recording medium transport direction) P Paper (recording medium) [Prior art documents] [Patent documents]

[0077] [Patent Document 1] Patent No. 7016481

Claims

1. A rotating member that carries and transports a recording medium on its circumferential surface; a liquid ejection unit that ejects liquid onto the recording medium; a recording medium detection member for detecting the recording medium; An encoder wheel provided on the shaft of the rotating member; a first encoder sensor that reads the encoder wheel; an encoder scale provided on an outer circumferential surface of the rotating member; and one or more second encoder sensors that read the encoder scale. a first encoder sensor for detecting a discharge of the liquid from the recording medium; and a second encoder sensor for detecting a discharge of the liquid from the recording medium.

2. When one of the liquid ejection units is a first liquid ejection unit, A liquid ejection device according to claim 1 , further comprising: a detection result of the second encoder sensor from a predetermined timing, which is used to determine the ejection start timing of one or more of the liquid ejection sections downstream of the first liquid ejection section in the recording medium transport direction.

3. the second encoder sensor corresponding to the liquid ejection unit; the second encoder sensor not corresponding to the liquid ejection unit, A liquid ejection device as described in claim 2, wherein the ejection start timing of one or more of the liquid ejection units downstream in the recording medium transport direction from the first liquid ejection unit is determined using the detection result of the second encoder sensor that does not correspond to the liquid ejection unit.

4. 4. The liquid ejection device according to claim 3, wherein the ejection start timing of the first liquid ejection portion is determined based on the detection results of the recording medium detection member, the first encoder sensor, and the second encoder sensor that does not correspond to the liquid ejection portion.

5. the second encoder sensor corresponding to the first liquid ejection unit; A liquid ejection device as described in claim 2, wherein the ejection start timing of one or more of the liquid ejection units downstream of the first liquid ejection unit in the recording medium transport direction is determined based on the ejection start timing of the first liquid ejection unit and the detection result of the second encoder sensor corresponding to the first liquid ejection unit.

6. The second encoder sensor is provided corresponding to each liquid ejection unit, A liquid ejection device as described in claim 2, wherein the ejection start timing of the multiple liquid ejection units is determined based on the ejection start timing of the liquid ejection unit that is located one unit upstream of the liquid ejection unit in the recording medium transport direction and the detection result of the second encoder sensor corresponding to the liquid ejection unit that is located one unit upstream of the liquid ejection unit in the recording medium transport direction.

7. 7. The liquid ejection apparatus according to claim 2, wherein the ejection start timing of the first liquid ejection section is determined based on the detection results of the recording medium detection member and the first encoder sensor.

8. the second encoder sensors are provided corresponding to the plurality of liquid ejection units, A liquid ejection device according to any one of claims 2 to 6, wherein the ejection timing after each liquid ejection section starts ejection is determined based on the detection result of the second encoder sensor corresponding to each liquid ejection section and the ejection start timing of each liquid ejection section.

Images