Conveyance device, ink jet recording device, conveyance speed variation detection method, and program

Abstract

To provide a conveyance device, an ink jet recording device, a conveyance speed variation detection method, and a program capable of easily and highly accurately detecting conveyance speed variations of a belt.SOLUTION: A conveyance device 10 includes: an annular conveyance belt 13 that conveys a recording medium M; a drive roller 11 and a driven roller 12 serving as a drive unit that circulates the conveyance belt 13 in a conveyance direction; a movement amount detection unit 33 that is provided at a predetermined position of the conveyance belt 13 that faces ink jet heads 22 which discharge ink onto the recording medium M, and detects a movement amount of the conveyance belt 13; and a control unit 40 functioning as a generation unit that generates data related to a variation in the conveyance speed at the predetermined position of the conveyance belt 13 with respect to a predetermined reference on the basis of the movement amount detected by the movement amount detection unit 33.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a conveying device, an inkjet recording device, a conveying speed unevenness detection method, and a program. [Background technology]

[0002] A belt conveyance system has been known in the past, in which a roller provided inside a circular conveyor belt rotates in the conveyance direction to convey a recording medium placed on the conveyor belt in the conveyance direction. Such a conveyance system is mainly used in inkjet recording devices that form images by ejecting ink from an inkjet head onto a recording medium.

[0003] However, if the conveyor belt has uneven thickness or loose tension, the conveyor belt's conveying speed may become uneven, which may cause deviation in the ink landing position, resulting in low-quality images.

[0004] Therefore, for example, Patent Document 1 describes a configuration in which the ink ejection timing is controlled by measuring the conveyance speed of the conveyor belt using a laser Doppler device or by printing a dedicated chart. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-000910 Summary of the Invention [Problem to be solved by the invention]

[0006] However, laser Doppler devices are expensive, and the measurement precision of laser Doppler devices is insufficient to control the ink landing position of an inkjet recording device, which requires adjustment on the order of microns.

[0007] Furthermore, when printing a dedicated chart, the adjustments can only be made after the inkjet head is installed. Furthermore, if an abnormality is detected, it is impossible to determine whether the cause is the inkjet head or the belt. Furthermore, printing a chart requires a large amount of ink and recording media, and the formed chart must be photographed and compared with other images, resulting in high costs.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conveying device, an inkjet recording device, a conveying speed unevenness detection method, and a program that can easily and accurately detect unevenness in the conveying speed of a conveyor belt. [Means for solving the problem]

[0009] In order to solve the above problems, the invention described in claim 1 is a conveying device, a circular conveyor belt for conveying a recording medium; a drive unit that moves the conveyor belt in a circular movement in a conveyance direction; a movement amount detection unit provided at a predetermined position on the conveyor belt facing an inkjet head that ejects ink onto the recording medium, the movement amount detection unit detecting a movement amount of the conveyor belt; and a generating unit that generates data relating to unevenness in the conveying speed at the predetermined position of the conveyor belt based on the amount of movement detected by the movement amount detecting unit.

[0010] The invention described in claim 2 is the conveying device described in claim 1, The data includes data on the deviation of the conveying speed at a predetermined position of the conveyor belt from a predetermined reference speed.

[0011] The invention described in claim 3 is the conveying device described in claim 1, The data includes data on the deviation of the landing position of the ink ejected by the inkjet head from a reference position.

[0012] The invention described in claim 4 is the conveying device described in claim 1, The movement amount detection unit includes a plurality of the movement amount detection units.

[0013] The invention described in claim 5 is the conveying device described in claim 2, a plurality of the movement amount detection units; the plurality of movement amount detection units detect the movement amounts of the conveyor belt at a plurality of positions on the conveyor belt, respectively; The predetermined reference speed is based on the amount of movement of the conveyor belt detected by any one of the plurality of movement amount detection units.

[0014] The invention described in claim 6 is the conveying device described in claim 4, The plurality of movement amount detection units are provided in the width direction perpendicular to the conveying direction.

[0015] The invention described in claim 7 is the conveying device described in claim 4, The generating unit generates the data by aligning the phases of the plurality of movement amount detecting units by the distance and finding the difference.

[0016] The invention described in claim 8 is the conveying device described in claim 1, The movement amount detection unit is provided on the conveyor belt on the side of the surface on which the recording medium is placed.

[0017] The invention described in claim 9 is the conveying device described in claim 8, A support portion is provided on the surface opposite to the placement surface to support the conveyor belt.

[0018] The invention described in claim 10 is the conveying device described in claim 1, The movement amount detection unit is provided on the opposite side of the conveyor belt from the surface on which the recording medium is placed.

[0019] The invention described in claim 11 is the conveying device described in claim 1, The movement amount detection unit is provided at a position within ⅛ of the total length of the conveyor belt in the conveying direction relative to the predetermined position.

[0020] The invention described in claim 12 is the conveying device described in claim 1, The movement amount detection unit is a roller encoder or a non-contact optical sensor.

[0021] The invention described in claim 13 is the conveying device described in claim 1, The generating unit generates the data by calculating the amount of movement of the conveyor belt for a predetermined measurement time.

[0022] The invention described in claim 14 is the conveying device described in claim 1, The generation unit performs low-pass filtering on the movement amount of the conveyor belt detected by the movement amount detection unit.

[0023] The invention described in claim 15 is the conveying device described in claim 1, The generation unit removes a DC component from the amount of movement detected by the movement amount detection unit and extracts an AC component.

[0024] The invention described in claim 16 is the conveying device described in claim 1, the conveyor belt includes a reference portion that serves as a position reference for the conveyor belt; A reference portion detection portion for detecting the reference portion is provided.

[0025] The invention described in claim 17 is the conveying device described in claim 1, the drive unit includes a roller that rotates in the transport direction to move the transport belt in a circular movement in the transport direction; and a rotary encoder that detects the rotation angle of the roller.

[0026] The invention described in claim 18 is an inkjet recording apparatus, A conveying device according to any one of claims 1 to 17; The inkjet head.

[0027] The invention described in claim 19 is the inkjet recording apparatus described in claim 18, a head control unit that controls the ejection of ink from the inkjet head; the inkjet head is a line head type; The head control unit controls the timing of ink ejection by the inkjet head based on the data.

[0028] The invention described in claim 20 is the inkjet recording apparatus described in claim 18, a head control unit that controls the ejection of ink from the inkjet head; the inkjet head is a serial head type; The head control unit shifts the image data based on the data.

[0029] The invention described in claim 21 is the inkjet recording apparatus described in claim 18, a head control unit that controls the ejection of ink from the inkjet head; the inkjet head is a serial head type; The head control unit controls the driving of the drive unit based on the data.

[0030] The invention described in claim 22 is a method for detecting unevenness in conveying speed, comprising: a circular conveyor belt for conveying a recording medium; a drive unit that moves the conveyor belt in a circular movement in a conveyance direction; a movement amount detection unit that is provided at a predetermined position on the conveyor belt facing an inkjet head that ejects ink onto the recording medium, and that detects a movement amount of the conveyor belt, The method further includes a generating step of generating data relating to unevenness in the conveying speed at the predetermined position of the conveyor belt based on the amount of movement detected by the movement amount detecting unit.

[0031] The invention described in claim 23 is a program, a circular conveyor belt for conveying a recording medium; a drive unit that moves the conveyor belt in a circular movement in a conveyance direction; a movement amount detection unit that is provided at a predetermined position on the conveyor belt opposite an inkjet head that ejects ink onto the recording medium, and that detects a movement amount of the conveyor belt; The movement amount detecting unit functions as a generating unit that generates data relating to unevenness in the conveying speed at the predetermined position of the conveyor belt based on the amount of movement detected by the movement amount detecting unit. [Effects of the Invention]

[0032] According to the present invention, unevenness in the belt transport speed can be detected easily and with high accuracy. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a perspective view of an inkjet recording apparatus according to a first embodiment. [Figure 2] 1 is a side cross-sectional view of an inkjet recording apparatus according to a first embodiment. [Figure 3] FIG. 1 is a block diagram of an inkjet recording apparatus. [Figure 4] 10 is a flowchart of a belt profile generation process and a print misalignment correction process. [Figure 5A] FIG. 10 is a diagram illustrating an example of data acquired by a roller encoder. [Figure 5B] FIG. 10 is a diagram illustrating an example of data on a belt movement amount. [Figure 6] FIG. 10 is a cross-sectional top view of an inkjet recording apparatus according to a second embodiment. [Figure 7]10A and 10B are conceptual diagrams illustrating an example of print misalignment correction processing in an inkjet recording apparatus according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, a conveying device according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, components having the same functions and configurations will be given the same reference numerals and their description will be omitted.

[0035] [First embodiment] [Overall configuration of inkjet recording device] Fig. 1 is a perspective view showing a schematic configuration of an inkjet recording apparatus 1 equipped with a conveying device 10 according to the present invention. Fig. 2 is a side cross-sectional view of the inkjet recording apparatus 1. Fig. 3 is a block diagram showing the functional configuration of the inkjet recording apparatus 1.

[0036] The inkjet recording apparatus 1 includes a transport device 10, a head unit 20, a head unit moving section 31, a maintenance section 32, a movement amount detecting section 33, a reference section detecting section 34, an operation display section 35, an input / output interface 36, a bus 37, and a control section 40. Under the control of the control section 40, the inkjet recording apparatus 1 forms an image on a recording medium M transported by the transport device 10 using the head unit 20.

[0037] In the following description, the X direction, Y direction, and Z direction are the directions shown in Fig. 1. In addition, in the following description, the X direction, Y direction, and Z direction are also referred to as the width direction, conveyance direction, and height direction, respectively.

[0038] In addition, in this embodiment, fabric is used as the recording medium M, but this is not limited to this. The recording medium M is not limited to fabric, and various media such as paper and sheet-like resin, on whose surface the ejected ink can be fixed, can be used.

[0039] (Transportation device) The conveying device 10 includes a drive roller 11, a driven roller 12, and a conveying belt 13. Under the control of the control unit 40, the conveying device 10 moves the conveying belt 13 in a circular motion at a speed corresponding to the rotation speed of the drive roller 11, with the recording medium M placed on the conveying surface of the conveying belt 13. In this way, the drive roller 11 and the driven roller 12 function as a drive unit that moves the conveying belt 13 in a circular motion in the conveying direction along a predetermined circular path. The control unit 40 also functions as a drive control unit that controls the driving of the drive unit. In this way, the conveying device 10 performs a conveying operation to convey the recording medium M in the conveying direction, which is the movement direction of the conveying belt 13.

[0040] {Drive roller, driven roller} The drive roller 11 rotates in the conveying direction around a rotation axis extending in the width direction by being driven by a conveying motor (not shown). The driven roller 12 rotates around a rotation axis parallel to the rotation axis of the drive roller 11 as the conveying belt 13 moves around.

[0041] A rotary encoder (not shown) is provided on the drive shaft of the drive roller 11 to measure the circular movement distance of the conveyor belt 13 and transmit the measured distance to the control unit 40. The rotary encoder may be provided on the drive shaft of the driven roller 12 instead of the drive shaft of the drive roller 11.

[0042] {Conveyor belt} The conveyor belt 13 is a circular endless belt whose inner surface is supported by a drive roller 11 and a driven roller 12. The conveyor belt 13 moves in a circular motion as the drive roller 11 rotates. The conveyor belt 13 is made of a material that flexes flexibly at the contact surface with the drive roller 11 and the driven roller 12 and reliably supports the recording medium M. For example, the conveyor belt 13 may be a belt made of resin such as rubber, or a steel belt.

[0043] 2, a reference portion 13a is provided at a predetermined position on the conveyor belt 13. The reference portion 13a is, for example, a hole provided in the conveyor belt 13, a colored tape attached to the conveyor belt 13, or the like.

[0044] {Head Unit} The head units 20 eject ink from nozzles based on image data onto the recording medium M transported by the transport device 10, thereby forming an image on the recording medium M. In the inkjet recording device 1 of this embodiment, the head units 20 are arranged such that four head units 20 eject ink of each color are aligned at predetermined intervals. Note that the arrangement of the multiple head units 20 in the transport direction of the recording medium M does not have to be at equal intervals. Furthermore, in this embodiment, a support unit 14 that supports the transport belt 13 is provided on the opposite side of the head units 20 across the transport belt 13. The support unit 14 is, for example, a known platen roller or platen.

[0045] Each head unit 20 includes a plurality of (seven in this embodiment) recording heads (inkjet heads) 22, each having a plurality of recording elements arranged in a staggered pattern in the width direction, and a head control unit 21 that controls the ink ejection operation of the inkjet heads 22. Each inkjet head 22 has an ink ejection surface on which nozzle openings are provided, and is positioned so that the ink ejection surface faces the conveyance surface of the conveyor belt 13.

[0046] {Inkjet head} Each of the recording elements included in the inkjet head 22 includes a pressure chamber that stores ink, a piezoelectric element provided on the wall of the pressure chamber, and a nozzle that ejects ink. When a drive signal is applied to the piezoelectric element from a drive circuit in the inkjet head 22, the piezoelectric element deforms in response to the drive signal, changing the pressure in the pressure chamber and ejecting ink from the nozzle that communicates with the pressure chamber.

[0047] The widthwise arrangement range of the recording elements included in the head unit 20 covers the widthwise length of the image formation area of ​​the recording medium M transported by the transport device 10. The head unit 20 is used while its position is fixed relative to the transport device 10 when recording an image. That is, the inkjet recording device 1 records an image by a so-called single-pass method (line head method).

[0048] {Head control section} The head control unit 21 outputs various control signals and image data to the head drive unit of the inkjet head 22. The head control unit 21 outputs these signals at appropriate timing according to the control signal from the control unit 40 and the count number of pulse signals input from the rotary encoder attached to the drive roller 11. The head drive unit of the inkjet head 22 supplies drive signals to the recording elements of the inkjet head 22 to deform the piezoelectric elements in accordance with the control signal and image data input from the head control unit 21, thereby ejecting ink from the openings of each nozzle.

[0049] {Head unit moving part} The head unit moving section 31 raises or lowers the head unit 20 in a height direction perpendicular to the conveyance surface of the conveyor belt 13. After the head unit 20 has risen to a predetermined height position, the head unit moving section 31 moves the head unit 20 in a width direction to a position facing the ink receiving section of the maintenance section 32. The mechanism for raising and lowering the head unit 20 in the height direction is composed of, for example, a support section extending in the height direction and a moving section to which the head unit 20 is fixed and which can move in the height direction along the support section by rotation of a stepping motor. The mechanism for moving the head unit 20 in the width direction is composed of, for example, a guide rail extending in the width direction and a slide member to which the head unit 20 is fixed and which moves along the guide rail. Four head unit moving sections 31 are provided, one for each of the four head units 20.

[0050] {Maintenance Department} The maintenance unit 32 includes an ink receiving unit (not shown) that receives ink ejected by flushing from the nozzles of the head unit 20. Flushing here is an operation of the head unit 20 that ejects ink from the nozzles for the purpose of restoring defective nozzles that can be restored to a normal state in which ink is ejected normally, and for the purpose of suppressing the occurrence of new defective nozzles.

[0051] {Movement amount detection section} The movement amount detection unit 33 detects the amount of movement of the conveyor belt 13 at its installation location and transmits the detection result to the control unit 40. The movement amount detection unit 33 is, for example, a roller encoder. The roller encoder detects the amount of movement of the conveyor belt 13 from the amount of rotation of a roller that contacts the conveyor belt 13 and rotates as the conveyor belt 13 moves.

[0052] The movement amount detection unit 33 is disposed near a position facing the inkjet head 22 of the head unit 20, which will be described later. This arrangement makes it possible to detect deviations in the transport speed of the transport belt 13 relative to the inkjet head 22, in other words, whether or not there is a deviation in the ejection of the inkjet head 22. More specifically, the movement amount detection unit 33 is preferably disposed at a distance of within ⅛ of the circumference of the transport belt 13 from the position of the transport belt 13 facing the inkjet head 22. This arrangement improves the detectability of deviations in the transport speed of the transport belt 13.

[0053] Furthermore, when a roller encoder is disposed in the inkjet recording apparatus 1, it may be located either on the outer periphery or inner periphery of the conveyor belt 13, but it is preferable to locate it on the inner periphery. This is because if a roller encoder is located on the outer periphery of the conveyor belt 13, it may be soiled by ink ejected by the head unit 20. Furthermore, the conveyor belt 13 usually has more unevenness on the inner periphery than on the outer periphery, resulting in greater frictional resistance, making it less likely for the roller to slip, and suppressing the occurrence of detection errors.

[0054] Even when a roller encoder is installed on the outer periphery of the conveying belt 13, roller slippage and detection errors can be suppressed by using a known pressure adjustment mechanism that presses the roller encoder against the inner periphery of the conveying belt 13.

[0055] {Reference part detection part} The reference portion detection unit 34 detects the reference portion 13a provided on the conveyor belt 13. The reference portion detection unit 34 is, for example, a reflective optical sensor. The reference portion detection unit 34 transmits a signal to the control unit 40 each time it detects the reference portion 13a in the belt profile generation process described below. The control unit 40 acquires data related to the position of the conveyor belt 13 based on the timing of receiving the signal, the circumferential length of the conveyor belt 13, the driving speed of the drive roller 11, etc. Similar to the movement amount detection unit 33, the reference portion detection unit 34 is preferably provided on the inner circumferential side of the conveyor belt 13 to prevent contamination by ink ejected by the head unit 20.

[0056] {Operation display section} The operation display unit 35 includes a display device and an input device. The display device is, for example, a liquid crystal display or an organic EL display. The operation display unit 35 displays various information on the display device. The input device is an operation key or a touch panel placed on top of the screen of the display device. The operation display unit 35 converts a user's input operation on the input device into an operation signal and outputs the operation signal to the control unit 40.

[0057] {Input / output interface} The input / output interface 36 is a means for transmitting and receiving data to and from the external device 2. The input / output interface 36 is configured, for example, by any one of various serial interfaces, various parallel interfaces, or a combination of these.

[0058] {bus} The bus 37 is a path for transmitting and receiving signals between the control unit 40 and other components.

[0059] (Control unit) The control unit 40 is a processor that controls the overall operation of the inkjet recording apparatus 1. The control unit 40 includes a CPU (Central Processing Unit) 41, a RAM (Random Access Memory) 42, a ROM (Read Only Memory) 43, and a storage unit 44.

[0060] {CPU} The CPU 41 reads out various control programs and setting data stored in the ROM 43, stores the programs in the RAM 42, and performs various arithmetic processing by executing the programs. In this way, the CPU 41 performs overall control of the overall operation of the inkjet recording apparatus 1. For example, while the conveying device 10 conveys the recording medium M, the CPU 41 causes the head unit 20 to eject ink from the nozzles onto the recording medium M based on image data of the image stored in the storage unit 44, thereby recording an image.

[0061] {RAM} The RAM 42 provides a working memory space for the CPU 41 and stores temporary data. The RAM 42 may include a non-volatile memory.

[0062] {ROM} The ROM 43 stores various control programs and setting data executed by the CPU 31. Note that the ROM 43 may be replaced by a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory.

[0063] The storage unit 44 stores print jobs (image recording commands) and image data input from the external device 2 via the input / output interface 36, as well as image data corrected by the CPU 41. As the storage unit 44, for example, an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may also be used in combination.

[0064] (external device) The external device 2 is, for example, a personal computer, and supplies print jobs, image data, and the like to the control unit 40 via an input / output interface 36 .

[0065] [Belt profile generation process, print misalignment correction process] Next, the belt profile generation process and print misalignment correction process performed by the control unit 40 of the inkjet recording apparatus 1 will be described with reference to the flowchart in Fig. 4. The control unit 40 performs the belt profile generation process at a predetermined timing, such as after a predetermined time has elapsed since the previous belt profile generation process.

[0066] The control unit 40 controls the drive roller 11 to move the conveyor belt 13 one revolution and drive the roller encoder (step S101).

[0067] During the circular movement, the control unit 40 sequentially acquires the amount of movement of the conveyor belt 13 from pulses acquired from the roller encoder (step S102). For example, assume that the roller encoder is set to transmit one pulse every 2 μm. Then, as shown in FIG. 5A, if the control unit 40 receives 50 pulses from the roller encoder every 0.1 seconds, the control unit 40 acquires that the amount of movement of the conveyor belt 13 every 0.1 seconds is 100 μm, as shown in FIG. 5B.

[0068] The control unit 40 performs low-pass filtering on the movement amounts sequentially acquired in step S102 (step S103). Specifically, the control unit 40 smooths the data by removing noise from the movement amounts using moving average processing. When the movement amount detection unit 33 is a roller encoder, the detection accuracy of the movement amount may be reduced due to uneven rotation of the roller encoder itself. Therefore, by removing low-accuracy data in this way, highly accurate detection results can be obtained.

[0069] The control unit 40 also uses least squares processing to remove the DC component from the acquired movement amount data and extract the AC component (step S104). Here, the AC component of the movement amount is the deviation of the conveying speed of the conveyor belt 13, i.e., the deviation of the landing position of the ink ejected by the inkjet head 22 from the reference position.

[0070] Through these controls, the control unit 40 functions as a generating unit that generates a belt profile, which is data on the amount of deviation of the conveyor belt 13 for one revolution.

[0071] The control unit 40 determines whether there is a position where the deviation of the landing position is equal to or greater than a predetermined value (step S105). If there is no position where the deviation is equal to or greater than the predetermined value (step S105; No), the process ends. If there is a position where the deviation is equal to or greater than the predetermined value (step S105; Yes), the control unit 40 executes a print deviation correction process (step S106).

[0072] The control unit 40 detects the rotation angle of the drive roller 11 based on pulses obtained from the rotary encoder, and controls the head control unit 21 to eject ink from the inkjet head 22 of the head unit 20 every predetermined number of receptions. Therefore, in the print misalignment correction process, the control unit 40 corrects the print misalignment by correcting the predetermined number of receptions at the position corresponding to the roller encoder according to the amount of misalignment.

[0073] For example, suppose the inkjet recording device 1 has a resolution of 720 dpi and the pulse resolution of the rotary encoder is 1 μm. In this case, the ejection interval of the head unit 20 is 35 μm, and the control unit 40 sends an ejection timing signal (FIRE signal) to the head control unit 21 every time it acquires (counts) 35 pulses from the rotary encoder. Therefore, if the control unit 40 determines that the amount of deviation is equal to or greater than a predetermined value, it increases or decreases the count number according to the amount of deviation, thereby offsetting the deviation in the conveyance speed and correcting the printing deviation.

[0074] As described above, the inkjet recording apparatus 1 according to the first embodiment generates data (belt profile) relating to unevenness in the conveying speed at a predetermined position of the conveying belt 13 based on the amount of movement detected by the movement amount detection unit 33 that detects the amount of movement of the conveying belt 13. With this configuration, unevenness in the conveying speed of the conveying belt 13 can be detected with high accuracy based on the amount of movement of the conveying belt 13. Furthermore, with this configuration, it is not necessary to drive the head unit 20, and unevenness in the conveying speed of the conveying belt 13 can be easily detected.

[0075] Although the above example illustrates a configuration in which it is determined whether the amount of impact deviation at the measurement position of the roller encoder is equal to or greater than a predetermined value, the present invention is not limited to this. For example, the conveying speed of the conveyor belt 13 may be calculated based on the measurement time of the roller encoder, and the calculated conveying speed may be compared with a predetermined reference value.

[0076] Although the above example illustrates a configuration in which the measurement value of one roller encoder is compared with a preset reference value, the present invention is not limited to this. For example, multiple roller encoders may be provided, and each measurement value may be compared with a reference value.

[0077] When multiple roller encoders are provided, and one roller encoder is provided in particular near the inkjet head 22 of the reference color, the measurement value of that roller encoder may be used as a reference value to compare with the measurement values ​​of the other roller encoders. However, in this configuration, it goes without saying that the phases must be matched based on the distance between the reference roller encoder and the roller encoder to be compared.

[0078] [Second embodiment] Next, an inkjet recording apparatus 1 according to a second embodiment will be described with reference to Fig. 6. Descriptions of configurations common to the inkjet recording apparatus 1 according to the first embodiment will be omitted. The inkjet recording apparatus 1 according to the second embodiment differs from the first embodiment in that it is a multi-pass type (serial head type).

[0079] A top view of a multi-pass inkjet recording apparatus 1 is shown in Figure 6. The head unit 20 of the second embodiment is made up of multiple inkjet heads 22, each of which has multiple recording elements arranged in a staggered pattern in the transport direction. The inkjet recording apparatus 1 of the second embodiment is equipped with a carriage on which the head units 20 of each color are mounted.

[0080] In this configuration, the head unit 20 forms an image by scanning the carriage from a first end to the opposing second end in the width direction. After the head unit 20 has scanned, the control unit 40 causes the conveyor belt 13 to be intermittently conveyed a predetermined amount in the conveyance direction, and forms an image by scanning the carriage from the second end to the first end.

[0081] In this embodiment, by providing the movement amount detection unit 33 on the conveyor belt 13, the belt profile generation process can be executed in the same manner as in the inkjet recording apparatus 1 according to the first embodiment. On the other hand, as described above, in this embodiment, a plurality of inkjet heads 22 are aligned in the conveyance direction. Therefore, in the print misalignment correction process, it is not possible to correct the print misalignment by controlling the ejection timing as in the first embodiment.

[0082] Therefore, in the print misalignment correction process, the head control unit 21 of this embodiment corrects one line of image data by shifting it by a predetermined number of pixels according to the amount of misalignment, as shown in Fig. 7. Specifically, when the inter-pixel distance is D, the head control unit 21 shifts the image data so as to satisfy the following conditional expression (1) or (2): (1) (n+1)D>Displacement amount ≧ nD ⇒ +n pixel shift (2) -(n+1)D < displacement amount ≦ -nD ⇒ -n pixel shift In the above conditional expression, n is a predetermined positive integer.

[0083] For example, suppose the distance between pixels is 30 μm and the displacement is 35 μm. In this case, the positive integer n that satisfies the conditional expression (1), 30(n+1)>35≧30n, is 1 because 60>35≧30. Therefore, the head control unit 21 corrects the image data so that it is shifted by +1 pixel.

[0084] As described above, the method for detecting unevenness in belt conveyance speed according to the present invention is applicable not only to inkjet recording apparatuses 1 of the line head type but also to inkjet recording apparatuses 1 of the serial head type.

[0085] Although the above describes an example of a method for correcting the landing misalignment by correcting the image data, the present invention is not limited to this. That is, in this embodiment, the control unit 40 may correct the landing misalignment by controlling the driving of the drive roller 11 so as to correct the deviation in the conveying speed based on the generated belt profile.

[0086] [Variations] Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above-described embodiments. Of course, the present invention can be modified in various ways within the scope of the invention described in the claims and its equivalents.

[0087] For example, the above example illustrates a configuration for detecting the deviation in the conveying speed of the conveyor belt 13 of the conveyor device 10 in the inkjet recording device 1 equipped with the head unit 20, but the present invention is not limited to this. As described above, in the present invention, the movement amount detection unit 33, which is a roller encoder, detects the deviation in the conveying speed of the conveyor belt 13 without printing. Therefore, the present invention is also applicable to a conveyor device 10 that does not have a head unit 20. Note that in this configuration, since the head unit 20 is not equipped, the movement amount detection unit 33 is attached to a predetermined position on the conveyor belt 13 that faces the intended mounting position of the head unit 20.

[0088] In the above, it has been described that the roller encoder is preferably installed on the inner periphery side in the inkjet recording device 1, but for ease of installation, it may be installed on the outer periphery side of the conveyor belt 13 in this configuration. However, if the roller encoder is installed on the outer periphery side of the conveyor belt 13, there is a risk that the conveyor belt 13 will bend toward the inner periphery side, so it is particularly preferable to provide a support portion 14.

[0089] Furthermore, if a deviation in the conveying speed is detected in this configuration, the deviation in the conveying speed can be eliminated by adjusting the tension of the conveying belt 13 to make it taut or by replacing the conveying belt 13.

[0090] In the above example, the movement amount detection unit 33 is a roller encoder, but the movement amount detection unit 33 is not limited to this. For example, a known non-contact optical sensor may be used, which acquires image data of the conveyor belt 13 using a line sensor and detects the movement amount of the conveyor belt 13 by matching a pattern that changes with the displacement.

[0091] The movement amount detection unit 33, which is a non-contact optical sensor, is configured by a sensor unit (a so-called reflective optical sensor unit) equipped with a light source such as an LED (Light Emitting Diode) and an optical sensor. The movement amount detection unit 33 detects the amount of movement of the conveyor belt 13 in the conveying direction using the principle of an optical mouse, and outputs the result to the head control unit 21 of the corresponding head unit 20.

[0092] However, if the movement amount detection unit 33 is an optical sensor, an error in the tilt when the optical sensor is attached may cause an error in the detection result of the movement amount of the conveyor belt 13. Therefore, it is preferable to adjust the tilt of the optical sensor in advance so that the circumference becomes a known length.

[0093] Furthermore, if the movement amount detection unit 33 is an optical sensor, fluctuations in the height direction of the conveyor belt 13 may cause errors in the detection result of the movement amount of the conveyor belt 13. Therefore, for example, it is preferable to provide a mechanism such as a known belt restraint that suppresses fluctuations in the height direction of the conveyor belt 13. Alternatively, it is preferable to provide an optical sensor at a position corresponding to the support unit 14. Alternatively, it is preferable to use a sensor that detects fluctuations in the belt surface height of the conveyor belt 13, and correct the detection result of the movement amount of the conveyor belt 13 using a coefficient corresponding to the detected fluctuations in the belt surface height.

[0094] In the above description, it is possible to provide a configuration in which multiple movement amount detectors 33 are installed, but the conveying speed of the conveyor belt 13 may vary not only in the conveying direction but also in the width direction. Therefore, it is possible to provide multiple movement amount detectors 33 in the width direction.

[0095] Although the above describes an example in which a hard disk or a semiconductor nonvolatile memory is used as a computer-readable medium for the program according to the present invention, the present invention is not limited to this example. Other computer-readable media include portable recording media such as CD-ROMs. Furthermore, a carrier wave can also be used as a medium for providing the program data according to the present invention via a communication line. [Explanation of symbols]

[0096] 1. Inkjet recording device 10. Conveyor 11 Drive roller (drive part, roller) 12 Driven roller (drive part, roller) 13 Conveyor belt 13a Reference part 14 Support part 20 Head Unit 21 Head control unit 22 Inkjet head 33 Movement amount detection unit 34 Reference part detection part 40 Control unit (generation unit) M Recording medium

Claims

1. a circular conveyor belt for conveying a recording medium; a drive unit that moves the conveyor belt in a circular movement in a conveyance direction; a movement amount detection unit provided at a predetermined position on the conveyor belt facing an inkjet head that ejects ink onto the recording medium, the movement amount detection unit detecting a movement amount of the conveyor belt; a generating unit that generates data relating to unevenness in the conveying speed at the predetermined position of the conveyor belt based on the amount of movement detected by the movement amount detecting unit.

2. The conveying device according to claim 1 , wherein the data includes data on a deviation of the conveying speed of the conveying belt at a predetermined position from a predetermined reference speed.

3. The transport device according to claim 1 , wherein the data includes data on a deviation of a landing position of ink ejected from the inkjet head from a reference position.

4. The transport device according to claim 1 , further comprising a plurality of the movement amount detectors.

5. a plurality of the movement amount detection units; the plurality of movement amount detection units detect the movement amounts of the conveyor belt at a plurality of positions on the conveyor belt, respectively; The conveying device according to claim 2 , wherein the predetermined reference speed is based on a movement amount of the conveying belt detected by any one of the plurality of movement amount detecting units.

6. The conveying device according to claim 4 , wherein the plurality of movement amount detecting units are provided in a width direction perpendicular to the conveying direction.

7. The transport device according to claim 4 , wherein the generation unit generates the data by aligning phases of the plurality of movement amount detection units by distance and calculating a difference.

8. The conveying device according to claim 1 , wherein the movement amount detection unit is provided on the conveying belt on a side of the conveying belt where the recording medium is placed.

9. The conveying device according to claim 8 , further comprising a support portion that supports the conveying belt on a surface opposite to the placement surface.

10. The conveying device according to claim 1 , wherein the movement amount detection unit is provided on the opposite side of the conveying belt from a surface on which the recording medium is placed.

11. The conveying device according to claim 1 , wherein the movement amount detecting unit is provided at a position that is within ⅛ of the total length of the conveying belt in the conveying direction with respect to the predetermined position.

12. The conveying device according to claim 1 , wherein the movement amount detection unit is a roller encoder or a non-contact optical sensor.

13. The conveying device according to claim 1 , wherein the generating unit generates the data by calculating a movement amount of the conveying belt for a predetermined measurement time.

14. The conveying device according to claim 1 , wherein the generating unit performs low-pass filtering on the movement amount of the conveying belt detected by the movement amount detecting unit.

15. The conveying device according to claim 1 , wherein the generating unit extracts an AC component by removing a DC component from the movement amount detected by the movement amount detecting unit.

16. the conveyor belt includes a reference portion that serves as a position reference for the conveyor belt; The conveying device according to claim 1 , further comprising a reference portion detection unit for detecting the reference portion.

17. the drive unit includes a roller that rotates in the transport direction to move the transport belt in a circular movement in the transport direction; The conveying device according to claim 1 , further comprising: a rotary encoder that detects a rotation angle of the roller.

18. A conveying device according to any one of claims 1 to 17; An inkjet recording apparatus comprising the inkjet head.

19. a head control unit that controls the ejection of ink from the inkjet head; the inkjet head is a line head type; 19. The inkjet recording apparatus according to claim 18, wherein the head control unit controls the timing of ink ejection by the inkjet head based on the data.

20. a head control unit that controls the ejection of ink from the inkjet head; the inkjet head is a serial head type; The inkjet recording apparatus according to claim 18, wherein the head control unit shifts the image data based on the data.

21. a head control unit that controls the ejection of ink from the inkjet head; the inkjet head is a serial head type; The inkjet recording apparatus according to claim 18, wherein the head control unit controls the driving of the driving unit based on the data.

22. a circular conveyor belt for conveying a recording medium; a drive unit that moves the conveyor belt in a circular movement in a conveyance direction; a movement amount detection unit that is provided at a predetermined position on the conveyor belt facing an inkjet head that ejects ink onto the recording medium, and that detects a movement amount of the conveyor belt, A conveying speed unevenness detection method comprising: a generating step of generating data relating to unevenness in conveying speed at the predetermined position of the conveying belt based on the amount of movement detected by the movement amount detection unit.

23. a circular conveyor belt for conveying a recording medium; a drive unit that moves the conveyor belt in a circular movement in a conveyance direction; a movement amount detection unit that is provided at a predetermined position on the conveyor belt opposite an inkjet head that ejects ink onto the recording medium, and that detects a movement amount of the conveyor belt; a program that functions as a generating unit that generates data relating to unevenness in the conveying speed at the predetermined position of the conveyor belt based on the amount of movement detected by the movement amount detecting unit;

Images