Vibration evaluation method for printing equipment, and control program

Abstract

To evaluate vibrations in the width direction of a printing device. [Solution] A vibration evaluation method for a printing apparatus includes the steps of: (a) recording at least two line images extending in the transport direction of a recording medium transported by a transport unit; (b) reading the line images recorded in step (a) with a scanner to generate image data; and (c) generating periodic data based on the image data, showing the periodic characteristics of the fluctuation in the transport direction at the interval between the two line images in the width direction perpendicular to the transport direction.

Description

Technical Field

[0001] The present invention relates to a method for evaluating vibrations of a printing apparatus and a control program.

Background Art

[0002] There is known a printing apparatus that discharges ink from a plurality of nozzles and records an image on a sheet. In such a printing apparatus, when vibrations occur between the nozzles and the sheet being conveyed during image recording, periodic unevenness in the image occurs.

[0003] The inkjet printer disclosed in Patent Document 1 simultaneously measures the drive torque of a jetting drum and the grayscale value of a printed image in order to suppress drive fluctuations. Then, frequency domain analysis is performed using Fourier transform, a periodic compensation torque is calculated based on the extracted order components, and the jetting drum is driven and controlled in consideration of the compensation torque.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the printer disclosed in Patent Document 1 compensates for vibrations in the rotational direction of the jetting drum, and no consideration has been given to vibration analysis in the width direction perpendicular to this rotational direction.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to evaluate vibrations in the width direction of a printing apparatus.

Means for Solving the Problems

[0007] The above objectives of the present invention are achieved by the following means.

[0008] (1) A step (a) of recording at least two line images extending in the transport direction of the recording medium on a recording medium transported by a transport unit in a printing apparatus, Step (b) involves reading the line image recorded in step (a) using a scanner to generate image data, A method for evaluating the vibration of a printing apparatus, comprising the step (c) generating periodic data that shows the periodic characteristics of fluctuations in the transport direction at the interval between the two line images in the width direction perpendicular to the transport direction, based on the image data.

[0009] (2) The printing device records an image using an inkjet method, The vibration evaluation method according to (1) above, wherein in step (a), the two line images are recorded by two nozzles separated by a predetermined distance in the transport direction.

[0010] (3) The vibration evaluation method according to (1) or (2) above, wherein the periodic data includes the amplitude component of the variation in the transport direction between the two line images.

[0011] (4) The vibration evaluation method described in (1) or (2) above, wherein the line image is a single dot line.

[0012] (5) The vibration evaluation method according to (1) or (2) above, wherein the distance between the two line images is set to a distance such that the two line images do not overlap when the maximum vibration expected in the printing device occurs.

[0013] (6) The vibration evaluation method according to (2) above, further comprising step (d) prior to step (a), in which the user selects the nozzles that form the two line images, or the user specifies the distance in the transport direction of the nozzles that form the two line images.

[0014] (7) The printing apparatus Step (e) of receiving an input of an oscillation frequency, Based on the oscillation frequency received in step (e) and formula (1), selecting two of the nozzles from the combinations of a plurality of inkjet nozzles, for which the amplitude amplification factor does not become zero, step (f), the vibration evaluation method according to (2) above.

[0015] Amplitude amplification factor = {2 - 2cos(2πfD / v)}^1 / 2 (Formula 1) Here, f: Oscillation frequency [Hz] D: Carrier direction distance between two nozzles [mm] v: Carrier speed [mm / sec] is.

[0016] (8) The vibration evaluation method according to (1) or 2 above, wherein the scanner is provided in the printing apparatus.

[0017] (9) The vibration evaluation method according to (1) or 2 above, wherein the reading resolution of the scanner is higher than the printing resolution of the printing apparatus.

[0018] (10) When two nozzles separated by a predetermined distance in the conveyance direction for recording the two line images are taken as a set, in step (a), a plurality of sets of the two line images are recorded by a plurality of sets of nozzles arranged in the width direction for each set of nozzles, In step (c), based on the intervals between the plurality of sets of the two line images, period data indicating the periodic characteristics of the variations in the conveyance direction is generated, the vibration evaluation method of the printing apparatus according to (2) above.

[0019] (11) Detecting the line center from the density curve of the line image and reading the displacement of the line image in the width direction at a resolution higher than the reading resolution of the scanner, the vibration evaluation method according to (1) or 2 above.

[0020] (12) The vibration evaluation method according to (1) or 2 above, wherein the period data includes a graph showing the variation in the conveyance direction of the intervals between the two line images.

[0021] (13) The vibration evaluation method according to (1) or 2 above, wherein the periodic data includes the numerical value of the period.

[0022] (14) A step (a) of recording at least two line images extending in the conveyance direction of the recording medium with respect to the recording medium conveyed by the conveyance unit in the printing apparatus; A step (b) of reading the line image recorded in the step (a) by a scanner to generate image data; A control program for causing a computer to execute a process including a step (c) of generating periodic data indicating the periodic characteristics of the variation in the conveyance direction in the width direction orthogonal to the conveyance direction based on the image data.

[0023] (15) The printing apparatus records an image by an inkjet method, In the step (a), the two line images are recorded by two nozzles spaced apart by a predetermined distance in the conveyance direction. The control program according to (14) above.

[0024] (16) The periodic data includes an amplitude component of the variation in the conveyance direction of the interval between the two line images. The control program according to (14) or (15) above. [Advantages of the Invention]

[0025] The vibration evaluation method according to the present invention includes a step (a) of recording at least two line images extending in the conveyance direction of the recording medium with respect to the recording medium conveyed by the conveyance unit in the printing apparatus; a step (b) of reading the line image recorded in the step (a) by a scanner to generate image data; and a step (c) of generating periodic data indicating the periodic characteristics of the variation in the conveyance direction based on the interval between the two line images in the width direction orthogonal to the conveyance direction based on the image data. By doing so, the vibration in the width direction in the printing apparatus can be appropriately evaluated. [Brief Description of the Drawings]

[0026] The advantages and features provided by one or more embodiments of the present invention will be better understood from the following detailed description and accompanying drawings. However, these are for illustrative purposes only and are not intended to limit the present invention. [Figure 1] This figure shows a schematic configuration of an evaluation system in which the vibration evaluation method of this embodiment is implemented. [Figure 2] This is a diagram showing the configuration of carriage 510. [Figure 3] This figure shows a schematic configuration of an evaluation system in another example. [Figure 4A] This diagram shows an example configuration of the inkjet head 500. [Figure 4B] This is a schematic diagram illustrating the combination and positional relationship of inkjet nozzles used to record two line images. [Figure 4C] This is a schematic diagram illustrating the combination and positional relationship of inkjet nozzles used to record two line images. [Figure 4D] This graph illustrates the vibration amplification factor. [Figure 5] This is an example of multiple pairs of line images recorded on paper. [Figure 6] This is a flowchart showing vibration evaluation methods. [Figure 7] This is an example of an operation screen that accepts the selection of the frequency to be evaluated and the nozzle. [Figure 8A] This graph illustrates the case where the vibration amplification factor is zero. [Figure 8B] This graph illustrates the case where the vibration amplification factor is zero. [Figure 8C] This graph illustrates the case where the vibration amplification factor is zero. [Figure 9A] This is an example of the output screen for periodic data. [Figure 9B] This figure shows the graph displayed on the output screen of Figure 9A. [Figure 10]This is an explanatory diagram showing a modified example of the vibration evaluation method performed in the analysis unit of the terminal device. [Modes for carrying out the invention]

[0027] Embodiments of the present invention will be described below with reference to the attached drawings. However, the scope of the present invention is not limited to the disclosed embodiments. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios. In the drawings, the vertical direction is the Z direction, the front direction of the printing device is the Y direction, and the direction perpendicular to the Z and Y directions is the X direction. The Z direction is also the direction in which ink is ejected onto the recording medium. The Y direction is also the transport direction of the recording medium, and the X direction is also the width direction perpendicular to the transport direction. The width direction is also called the CD direction. In this embodiment, the recording medium includes printing paper (hereinafter simply referred to as paper), cloth, and various films.

[0028] (Overall configuration of evaluation system 1000) Figure 1 shows a schematic configuration of the evaluation system 1000 in which the vibration evaluation method of this embodiment is implemented. The evaluation system 1000 includes a printing device 100, a terminal device 600, and a scanner 700. These devices communicate with each other via a communication interface. The printing device 100 records images on a recording medium using an inkjet method. Details of the configuration of the printing device 100 will be described later.

[0029] The terminal device 600 is a PC (personal computer) and is operated by a user such as an administrator who operates the printing device 100. When conducting vibration evaluation of the printing device 100, the terminal device 600 accepts the user's settings for evaluation conditions. The evaluation results of the vibration evaluation are also displayed on the display of the terminal device 600.

[0030] The scanner 700 optically reads an image on the recording medium and generates image data (also called read data). The generated image data is sent to the terminal device 600. The scanner 700 may be a flatbed scanner that reads original paper placed on a platen glass, or a sheet-fed scanner that reads while transporting the original paper. In both types, the scanner 700 includes a sensor array, a lens optical system, an LED (Light Emitting Diode) light source, and a housing that houses these components. The sensor array is a color or monochrome line sensor in which multiple optical elements (e.g., CCDs (Charge Coupled Devices)) are arranged in a line along the main scanning direction, and the reading area in the main scanning direction corresponds to the entire width of the recording medium. The optical system consists of multiple mirrors and lenses. Light from the LED light source passes through a contact glass that contacts the original (recording medium) at the reading position and illuminates the surface of the recording medium. The image at this reading position is guided by the optical system and formed on the sensor array. It is preferable that the scanner 700 has a higher reading resolution than the printing resolution of the printer 100. For example, if the printing resolution of the printer 100 is 1200 dpi (dots per inch), it is preferable that the scanner 700 has a higher reading resolution of 2400 dpi or 4800 dpi.

[0031] (Printing device 100) Referring to Figures 1 and 2, the printing apparatus 100 in this embodiment includes a paper feeding unit 10, an image forming unit 20, a paper discharge unit 30, and a control unit 40.

[0032] The control unit 40 includes a CPU, RAM, ROM, a large-capacity storage unit, a communication interface, and the like. The control unit 40 executes various processes by running programs stored in the ROM and the large-capacity storage unit, and controls various parts of the printing device 100 and performs various calculations according to the programs.

[0033] The paper feeding unit 10 holds the recording medium m on which image formation takes place and supplies it to the image forming unit 20 before image formation. The paper feeding unit 10 includes a paper feeding tray 11 and a transport unit 12.

[0034] The paper feed tray 11 is plate-shaped and can hold one or more recording media m. The paper feed tray 11 moves up and down according to the amount of recording media m placed on it. The paper feed tray 11 is held in a position where the uppermost recording media m is transported by the transport unit 12.

[0035] The transport unit 12 includes a plurality of rollers 121 and 122 (two in this case) and a ring-shaped belt 123. The belt 123 is rotationally driven by the plurality of rollers 121 and 122. The transport unit 12 includes a transport mechanism for transporting recording media m on the belt 123 and a supply unit that transfers the top recording media m from the paper feed tray 11 to the belt 123. The transport unit 12 transports the recording media m transferred to the belt 123 by the supply unit in conjunction with the rotational movement of the belt 123.

[0036] The image forming unit 20 forms an image on the recording medium m by ejecting ink, such as UV ink, onto the recording medium m. The image forming unit 20 includes an image forming drum 21, a transfer unit 22, a paper heating unit 23, an inkjet head 500, an irradiation unit 25, and a delivery unit 26. The inkjet head 500 includes a plurality of carriages 510.

[0037] The image forming drum 21 carries the recording medium m along its cylindrical outer surface and transports the recording medium m as it rotates. The transport surface of the image forming drum 21 faces the paper heating unit 23, a plurality of carriages 510, and the irradiation unit 25. The image forming drum 21 performs image forming processing on the transported recording medium m.

[0038] The transfer unit 22 is provided between the transport unit 12 of the paper feeding unit 10 and the image forming drum 21. The transfer unit 22 transfers the recording medium m transported by the transport unit 12 to the image forming drum 21. The transfer unit 22 includes a swing arm unit 221 and a cylindrical transfer drum 222. The swing arm unit 221 supports one end of the recording medium m transported by the transport unit 12. The transfer drum 222 transfers the recording medium m supported by the swing arm unit 221 to the image forming drum 21. The transfer unit 22 guides the recording medium m in a direction along the outer circumferential surface of the image forming drum 21 by picking up the recording medium m on the transport unit 12 with the swing arm unit 221 and transferring it to the transfer drum 222, thereby transferring the recording medium m to the image forming drum 21.

[0039] The paper heating unit 23 heats the recording medium m supported on the image forming drum 21. The paper heating unit 23 includes, for example, an infrared heater and generates heat in response to the application of electricity. The paper heating unit 23 is located near the outer surface of the image forming drum 21 and upstream of the carriage 510 along the transport direction of the recording medium m due to the rotation of the image forming drum 21. The heat generated by the paper heating unit 23 is controlled by the control unit 40 so that the recording medium m supported on the image forming drum 21 and passing near the paper heating unit 23 reaches a predetermined temperature.

[0040] Each of the multiple carriages 510 of the inkjet head 500 ejects ink of the respective colors: Y (yellow), M (magenta), C (cyan), and K (black). The multiple carriages 510 eject the Y, M, C, and K inks onto the recording medium m supported on the image forming drum 21, thereby forming an image on the recording medium m. A carriage 510 is provided individually for each of the CMYK colors. In Figure 1, the carriages 510 corresponding to each of the YMCK colors are provided in this order along the transport direction of the recording medium m, which is transported as the image forming drum 21 rotates.

[0041] In this embodiment, the carriage 510 is provided with a length (width) that covers the entire recording medium m in the direction perpendicular to the transport direction of the recording medium m (width direction / X direction). In other words, the printing device 100 is a one-pass line-head type inkjet recording device. The carriage 510 can be configured as a line head by arranging multiple heads 521, 522 (see Figure 4A, etc.). The internal configuration of the carriage 510 will be described later.

[0042] The irradiation unit 25 irradiates the ink used in the printing apparatus 100 of this embodiment with energy rays to cure the ink after it has been ejected onto the recording medium m. The irradiation unit 25 includes, for example, a fluorescent tube such as a low-pressure mercury lamp, and irradiates energy rays such as ultraviolet light by emitting light from the fluorescent tube. The irradiation unit 25 is located near the outer surface of the image forming drum 21 and is provided downstream of the carriage 510 in the direction of transport of the recording medium m by the rotation of the image forming drum 21. The irradiation unit 25 irradiates the recording medium m, which is supported on the image forming drum 21 and from which the ink has been ejected, with energy rays, and cures the ink ejected onto the recording medium m by the action of these energy rays.

[0043] Examples of fluorescent tubes that emit ultraviolet light include low-pressure mercury lamps, mercury lamps with operating pressures of several hundred Pa to 1 MPa, light sources that can be used as germicidal lamps, cold cathode tubes, ultraviolet laser light sources, metal halide lamps, and light-emitting diodes. Among these, a light source that can irradiate ultraviolet light at a higher intensity and consumes less power (for example, a light-emitting diode) is more desirable. Furthermore, the energy rays are not limited to ultraviolet light; any energy ray that has the property of curing ink depending on the properties of the ink is acceptable, and the light source may be substituted depending on the wavelength of the energy ray.

[0044] The delivery unit 26 transports the recording medium m, which has been irradiated with energy rays by the irradiation unit 25, from the image forming drum 21 to the paper discharge unit 30. The delivery unit 26 includes a plurality of rollers (two in this case) 261 and 262, and a ring-shaped belt 263. The belt 263 is rotationally driven by the plurality of rollers 261 and 262. The delivery unit 26 includes a transport mechanism for transporting the recording medium m on the belt 263, and a cylindrical transfer drum 264 for transferring the recording medium m from the image forming drum 21 to the transport mechanism. The delivery unit 26 transports the recording medium m, which has been transferred to the belt 263 by the transfer drum 264, by the belt 263 and sends it to the paper discharge unit 30.

[0045] The paper output unit 30 stores the recording medium m that has been sent out from the image forming unit 20 by the delivery unit 26. The paper output unit 30 includes a plate-shaped paper output tray 31, and the image-formed recording medium m is placed on the paper output tray 31.

[0046] The ink used in the printing apparatus 100 is, for example, UV ink. When UV light is not irradiated, UV ink undergoes a phase change between a gel state and a liquid (sol) state depending on the temperature. UV ink has a phase change temperature of, for example, about 100°C, and uniformly liquefies (becomes a sol) when heated above this phase change temperature. On the other hand, this ink gels at temperatures below the phase change temperature, including normal room temperature (0°C to 30°C).

[0047] Next, with reference to Figure 2, the configuration of one of the multiple carriages 510 will be described. As shown in Figure 2, the carriage 510 includes multiple modules 520 and an ink heating device 580. Here, as an example, one carriage 510 is composed of eight modules 520 (also called HM (head modules)). Each module 520 consists of a pair of two heads 521 and 522 (see Figure 4A, etc.). Details of the modules 520 will be described later.

[0048] The ink heating device 580 heats the ink, which is in a gel state at room temperature, to a liquid (sol) state in order to stabilize the fluidity of the ink in the ink tank 550 and the amount of ink ejected from the print head, as described above, and supplies the heated ink to each of the multiple print heads 521.

[0049] (Other examples) Figure 3 shows a schematic configuration of evaluation system 1000b in another example. In the explanation of the other example shown in Figure 3, content that overlaps with Figures 1 and 2 will be omitted. In the example shown in Figure 3, the printing device 100b incorporates a sheet-feed scanner 700. The scanner 700 reads the surface of the recording medium m, on which a line image is recorded with ink ejected from the inkjet head 500 as it is transported, and generates image data. Hereafter, the vibration evaluation method will be described assuming that it is performed using evaluation system 1000b shown in Figure 3.

[0050] (A printed chart for vibration evaluation that records two line images) Next, with reference to Figures 4A to 4D and Figure 5, an example configuration of the inkjet head 500 and a print chart for vibration evaluation (hereinafter simply referred to as the print chart) will be described. Figure 4A is a diagram showing an example configuration of the inkjet head 500. Figure 4A is a schematic diagram of the inkjet head 500 viewed from below (Figures 4B and 4C are similar). Each of the heads 521 and 522 contains multiple nozzles n (n1 to n33, etc.). Focusing on one head 521, the multiple nozzles n are exposed on the lower side of the carriage 510 and consist of two rows extending in the X direction. The head 521 ejects ink from the multiple nozzles n and forms an image on the recording medium m supported on the image forming drum 21.

[0051] The eight modules 520 are composed of two columns extending in the X direction, as shown in Figure 4A. Each of the eight modules 520 is arranged in a staggered pattern with respect to the direction perpendicular to the X direction in the two columns.

[0052] Figures 4B and 4C are schematic diagrams illustrating the combination and positional relationship of inkjet nozzles used to record two line images in a printed chart. Figure 4B shows the state in which a line image is formed while the recording medium is transported downwards (the recording medium itself is not shown). Figures 4B and 4C are enlarged views of Figure 4A and show a portion of module 520.

[0053] Module 520 of the inkjet head 500 includes at least two heads 521 and 522, each of which is equipped with a large number of nozzles n (several thousand to tens of thousands, for example, 12,000). The nozzles n are individually controlled, and ink is ejected from the tip of each nozzle n toward the surface of the recording medium.

[0054] On the upstream head 521, odd-numbered nozzles n1, n3, n5, n7, n9, n11, n13, etc., are arranged at a predetermined pitch along the X direction. Furthermore, the positions of nozzles n1 to n11 are slightly offset in the Y direction (conveying direction). Also, the Y-direction positions of nozzles n1 to n11 and nozzles n13 to n23 are the same. For example, the Y coordinates of nozzle n1 and nozzle n13 are the same. Figure 4B shows only some of the nozzles on heads 521 and 522. On head 521, the arrangement pattern of nozzles n1 to n11 is repeated up to the last nozzle n (for example, up to the 12000th nozzle n12000). Heads 521 and 522 have the same configuration, although their arrangement in the X direction is offset by one pixel. Head 522 contains even-numbered nozzles n. A pair of heads 521 and 522, along with nozzles n1, n2, n3, n4, etc., form an image with a one-pixel period. The distance in the X direction for one pixel is 21.2 μm. That is, the nozzles n are arranged so that the print resolution in the X direction is 1200 dpi. In the Y direction (transport direction), the same 1200 dpi print resolution is achieved by controlling the ink ejection period from the nozzles n according to the transport speed of the recording medium.

[0055] In Figure 4B, black circles indicate selected nozzles n, and white circles indicate nozzles n that have not been selected. The nozzle selection method will be described later. In Figure 4B, the selected pair of nozzles n2 and n7 constitute one nozzle set. The two nozzles n2 and n7 are separated by a predetermined distance of 24.8 mm in the transport direction (Y direction) (hereinafter referred to as the transport direction distance D (or D1 to D3)). Also, the two nozzles n2 and n7 are separated by 5 pixels (0.106 mm) in the width direction (X direction) (hereinafter referred to as the width direction distance). The nozzles n14 and n19 of set s2, and the nozzles n26 and n31 of the following set s3, have a similar positional relationship.

[0056] In the example shown in Figure 4B, the transport direction distance D1 is set to the distance between the two heads 521 and 522 of the same module 520, but it is not limited to this. As shown in Figure 4A, the transport direction distance D2 between modules can be used by using the two corresponding nozzles n of each of the two modules 520. In this case, for example, the transport direction distance D2 = 70.7 mm. Furthermore, the transport direction distances D3_1 and D3_2 between carriages 510 can be used by using the two corresponding nozzles n of two different carriages 510. For example, the transport direction distance D3_1 between CK carriages 510 is 141.7 mm, and the transport direction distance D3_2 between YK carriages 510 is 425.1 mm. The transport direction distance D can be set in a range of several tens of mm to several hundred mm, for example, from 24.8 mm to 425.1 mm, depending on the selection of nozzles n used in this way.

[0057] Each of the two nozzles in this pair records a pair of line images. Each line image corresponds to a single dot line. The widthwise distance (0.106 mm) of the pair of nozzles n is set to the shortest possible distance while still allowing the two line images to be distinguished. This distance is set so that the two line images do not overlap when the maximum vibration expected in the printing device 100 occurs. The amplitude of the maximum vibration was found to be a maximum of 30 μm based on studies using an external acceleration sensor. In this case, a vibration amplification factor of 60 μm (twice the maximum, see Figure 8A below) is assumed, and this is set to 105 μm or more by adding the ink size of 45 μm for one dot. For example, the widthwise distance is set to 106 μm, which is wider than 105 μm. Here, one dot of ink is ejected at a spacing of 1200 dpi (21 μm), but the ink size of each one dot is larger than this spacing, for example, 45 μm. In this case, a 1200dpi dot pattern (dot spacing) is used, where adjacent ink dots overlap to fill the area completely with ink without any gaps (to create a solid color).

[0058] The transport direction distance D of 24.8 mm for a pair of nozzles n is set within a suitable range depending on the vibration frequency f being analyzed. The transport direction distance D is set so that the vibration amplification factor in equation (1) below is as large as possible.

[0059] Amplitude amplification factor = {2 - 2cos(2πfD / v)}^1 / 2 (Equation 1) Here, f: vibration frequency [Hz] D: Distance in the conveying direction between the two nozzles [mm] v: Conveying speed [mm / sec] The transport speed v is the transport speed of the recording medium and is set by the image forming unit 20. The transport speed v is set to a predetermined value depending on the characteristics of the recording medium.

[0060] Figure 4D is a graph showing the relationship between the wavelength (mm) or vibration frequency (f) of the vibration being analyzed and the amplitude amplification factor when the transport direction distance D is 24.8 mm. In the example in Figure 4D, a transport speed v = 786 mm / s is used. Thus, under these conditions, as shown in the right-hand figure of Figure 4D, the maximum value is obtained at a frequency of 16 Hz, and a high amplitude amplification factor can be obtained in the surrounding frequency range of 8 to 23 Hz.

[0061] The spacing between the two vertical lines is the spacing (in the X direction) between the vertical line recorded by the upstream nozzle (n7 (see Figure 4B)) and the vertical line of the same shape recorded by the downstream nozzle (n2) 24.8 mm later in the transport direction (FD direction / Y direction). The ratio of the vertical line spacing to the displacement of the vibration in the width direction (CD direction / X direction) varies between 0 and 2 depending on the wavelength of the vibration (transport speed / frequency). This method of analysis is suitable for low frequencies of about 25 mm to 400 m (vibration frequencies of 2 Hz to 30 Hz (at a transport speed of 760 mm / s), and 4 Hz to 60 Hz (at a transport speed of 1570.8 mm / s)) (see the left diagram in Figure 4D). It is not very effective for vibration analysis at other frequencies, i.e., wavelengths of 25 mm or less or wavelengths of 400 mm or more.

[0062] Figure 4C is a diagram corresponding to Figure 4B, and shows an example where the number of selectable nozzles has been increased. In Figure 4C, nozzles n12 and n24 have been added to the selection compared to Figure 4B. In sets s11 and s12, the transport direction distance is set to 15.2 mm. The width direction distance is set to 5 pixels. In the example shown in Figure 4C, for example, nozzle n7 is used in common in sets s1 and s11.

[0063] Figure 5 shows an example of the output of the evaluation chart shown in Figure 4B. On a recording medium such as paper, under ideal conditions, the image will be a straight line as shown in Figure 5(a), but when the vibration component is large, the image will be a curve corresponding to the vibration period as shown in Figure 5(b).

[0064] (Vibration evaluation method) Referring to Figure 6, the vibration evaluation method according to this embodiment will be explained. Figure 6 is a flowchart of the vibration evaluation method.

[0065] (Step S201) The terminal device 600 accepts input of the frequency to be analyzed. Figure 7 shows an example of the operation screen 601 displayed on the terminal device 600's display. The user inputs the target vibration frequency in field a1. For example, the user inputs the frequency corresponding to the rotation period of the mechanical components that make up the printing device 100b (or printing device 100) as the target frequency.

[0066] (Step S202) Next, in step S202, the terminal device 600 accepts nozzle selection. The user can select a nozzle by entering the nozzle number n in field a2. In the example shown in Figure 7, one pair of nozzles n2 and n7 is selected. Also, since repetition is enabled, nozzles n14, n19, and nozzles n26, n31, etc., which have the same relationship, are automatically selected (see Figure 4B). In this case, the transport direction distance is presented according to the selection of one pair of nozzles. It is also possible to allow the selection of additional pairs of nozzles with different transport distances (see Figure 4C).

[0067] (Step S203) When a pair of nozzles is selected in column a1, the terminal device 600 calculates the amplitude amplification factor using the above-mentioned equation (1). Figure 8 is a graph of the amplitude amplification factor. If the amplitude amplification factor is zero or close to zero (YES), the terminal device 600 proceeds to step S204. On the other hand, if the amplitude amplification factor is not zero or close to zero (NO), the process proceeds to step S205. In this case, column a3 on the operation screen 601 indicates that there is no problem.

[0068] For example, Figures 8A to 8C illustrate the vibration amplification factor for transport direction distances D1 (24.8 mm), D2 (70.7 mm), and D3_1 (141.7 mm), respectively, and the case where the vibration amplification factor is zero. In Figures 8A to 8C, the transport speed v = 786 mm / s is common. Also, although the display range of the horizontal axis is different, Figure 8A corresponds to the left figure of Figure 4D mentioned above. As shown in Figure 8A, for the transport direction distance D1 (24.8 mm) at the two nozzles n selected in step S202, the vibration amplification factor is zero or close to zero when the target frequency is 30 to 34 (especially 32 Hz). Therefore, the process proceeds to step S204. Also, as shown in Figure 8B, for the transport direction distance D2 (70.7 mm) at the two nozzles n selected in step S202, the vibration amplification factor is zero or close to zero when the target frequency is 10 to 12 (especially 11 Hz). Similarly, as shown in Figure 8C, at a transport direction distance D3 (14.7 mm) between the two nozzles n selected in step S202, the vibration amplification factor is zero or close to zero when the target frequency is 10-12 (especially 11 Hz).

[0069] (Step S204) The terminal device 600 issues a warning to the user indicating that they wish to re-select the nozzle and accepts the re-selection of the nozzle (step S202).

[0070] (Steps S205, S206) The inspection is performed in response to the user's operation of the inspection execution button b1 on the operation screen 601. The terminal device 600 creates a vibration evaluation chart based on the specified settings of nozzle n and prints the chart. The printing device 100 records the chart image, which includes multiple pairs of line images, onto a recording medium at the inkjet head 500 position.

[0071] (Step S207) Next, the downstream scanner 700 reads the recorded image and generates image data. The obtained image data is sent to the terminal device 600.

[0072] (Steps S208, S209) The terminal device 600 analyzes the image data to analyze the periodic characteristics that indicate fluctuations in the transport direction, and outputs periodic data that indicates the periodic characteristics.

[0073] The analysis unit (program) of the terminal device 600 identifies the positions of multiple line images extending in the transport direction from the image data by performing binarization and edge processing. It then calculates the variation in the spacing in the transport direction of the widthwise distance between two line images recorded by a pair of nozzles. This calculation can be performed using processing such as FFT. For example, in the chart of Figure 4B, the widthwise distance between two line images recorded by nozzles n2 and n7 of the pair is analyzed. Alternatively, the widthwise distance between other pairs of line images that are aligned in the widthwise direction and have the same position (Y coordinate) in the transport direction may be used. For example, in the example shown in Figure 4B, with respect to pair s1, pairs s2 and s3 correspond to pairs of line images recorded by nozzles that are aligned in the widthwise direction with respect to pair s1 and have the same position (Y coordinate) in the transport direction. In this case, the analysis unit of the terminal device 600 averages the spacing between the two line images of each pair s1, s2, and s3 for each coordinate in the transport direction, and uses this average value to calculate the variation in the spacing of a pair of line images in the transport direction. Note that while Figure 4B shows an example of three sets of line images, in reality, many more sets (e.g., several hundred sets) of line images are formed. In this case, the analysis unit uses the average value of the interval between two line images from several hundred sets to analyze the periodic characteristics based on the interval variation in the transport direction. By using the average value, the periodic characteristics related to the interval variation in the transport direction can be analyzed with high accuracy.

[0074] Alternatively, in this case, the wide pitch (inter-line distance of 7 pixels in Figure 4B) and narrow pitch (inter-line distance of 5 pixels in Figure 4B) for several hundred sets of head widths may be averaged, and half of the deviation of the difference from the theoretical value may be used as the interval variation value.

[0075] Figures 9A and 9B show examples of periodic data output in step S209. Figure 9A is an example of the display screen 602 shown on the terminal device 600. Area a11 of the display screen shows the period and amplitude (intensity) of the frequency components as examples of periodic data. In addition, the graph display area of ​​area a11 displays a profile as periodic data, as shown in Figure 9B. In the graph of Figure 9B, the X axis (horizontal axis) is the position in the transport direction of the recording medium, and the Y axis (vertical axis) is the interval (mm) between a pair of line images. Zero (0) is the ideal distance (for example, 0.106 mm for 5 pixels), and the vertical axis shows the difference value from the ideal distance.

[0076] As described above, the vibration evaluation method in this embodiment includes the steps of: (a) recording at least two line images extending in the transport direction of a recording medium transported by a transport unit in a printing apparatus; (b) reading the line images recorded in step (a) with a scanner to generate image data; and (c) generating periodic data indicating the periodic characteristics of fluctuations in the transport direction based on the distance between the two line images in the width direction perpendicular to the transport direction, based on the image data. In this way, vibrations in the width direction in the printing apparatus can be appropriately evaluated.

[0077] In particular, in this embodiment, the printing apparatus records images using an inkjet method, and in step (a), two line images are recorded by two nozzles separated by a predetermined distance in the transport direction. In this way, in a pair of line images arranged in the width direction on the recording medium, the timing at which images at the same position in the transport direction are recorded differs by the transport direction distance D / transport speed V. As a result, the vibration in the width direction component of the vibration that occurs between those timings is recorded as a variation in the spacing between the two line images. By analyzing the variation in the spacing between the line images, periodic data showing periodic characteristics can be generated.

[0078] (modified version) Figure 10 is an explanatory diagram showing a modified example of the vibration evaluation method performed in the analysis unit of the terminal device 600. As described below, the analysis unit detects the line center from the density curve of the line image and reads the displacement of the line image in the width direction at a resolution higher than the reading resolution of the scanner. In this way, the periodic characteristics related to the spacing variation in the transport direction can be analyzed with high accuracy.

[0079] Figure 10 shows the scan values ​​obtained from the scanner at 2400 dpi, 8 bits (256 gradations), and the calculated maximum values ​​derived from those scan values. Figure 10(b) is a magnified view of a portion of Figure 10(a). The maximum values ​​are obtained by cubic interpolation of the scan values, with the maximum point being the center position (X-direction center position) of the vertical line (Y-direction line). The wide pitch (inter-line distance of 7 pixels in Figure 4B) and the narrow pitch (inter-line distance of 5 pixels in Figure 4B) are averaged, and half of the difference from the theoretical value is taken as the interval variation value.

[0080] Cubic interpolation is performed using the following method. (1) Scan data scanned at 2400 dpi with 10.6 μm intervals is subjected to cubic interpolation, and the x-coordinate of the local maximum is set to the center position of the black line. (2) The cubic equation passing through the two maximum points of the scan value and the two points on either side of them, a total of four points (see Figure 10(b)), y = ax 3 + bx 2 + cx + d Let's assume that the x-coordinates of the four scan points are -1, 0, 1, and 2 for convenience. When x = -1, y1 = -a + b - c + d When x = 0, y² = d When x = 1, y³ = a + b + c + d When x = 2, y4 = 8a + 4b + 2c + d Solving this, d = y² b = (y1 + y3 -2d) / 2 a = (y₄ - 2y₃ - 2b + d) / 6 c = y³ - a - b - d Let Xc be the x-coordinate of the local maximum. y' = 3aXc 2 + 2bXc + c = 0 (Equation 2-1) Xc = (-2b ± (4b 2 - 12ac) 1 / 2 ) / 6a... (Equation 2-2) Of the two Xc values ​​in equations 2-1 and 2, the second derivative value y'' = 6aXc + 2b < 0 Xc was defined as the local maximum point and the center position of the black line. Note that when a=0, Xc = ∞ in equation 2-1, so it becomes a quadratic expression. y = bx 2 + cx + d Let Xc be the x-coordinate of the local maximum. y' = 2bXc + c = 0 Xc = -c / 2b This was set as the center position of the black line.

[0081] The configurations of the evaluation systems 1000, 1000b, the printing devices 100, 100b, and the vibration evaluation methods performed by these devices, as described above, represent the main configurations described in order to explain the features of the above embodiments. The configurations are not limited to those described above and can be modified in various ways within the scope of the claims.

[0082] Furthermore, the means and methods for performing various processing in the evaluation systems 1000 and 1000b according to the above-described embodiment can be implemented by either a dedicated hardware circuit or a programmed computer. The program may be provided, for example, on a computer-readable recording medium such as a USB memory stick or a DVD (Digital Versatile Disc)-ROM, or it may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. The program may also be provided as a standalone application software, or it may be incorporated into the software of the device as a function of the device.

[0083] While embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are for illustrative purposes only and are not limiting. The scope of the present invention should be interpreted in accordance with the language of the appended claims. [Explanation of Symbols]

[0084] 1000, 1000b evaluation system 100, 100b printing device 10 Paper feed section 20 Image forming unit 21 Image forming drum 22 Transfer Unit 23 Paper heating section 25 Irradiation area 26 Delivery Department 500 inkjet heads 510 Carriage 520 modules 521, 522 head n, n1~n33 nozzles 30 Paper output section 600 terminal devices 700 Scanners

Claims

1. (a) A step of recording at least two line images extending in the transport direction of the recording medium on a recording medium transported by a transport unit in a printing apparatus, Step (b) involves reading the line image recorded in step (a) using a scanner to generate image data, A method for evaluating the vibration of a printing apparatus, comprising the step (c) of generating periodic data showing the periodic characteristics of fluctuations in the transport direction at the interval between the two line images in the width direction perpendicular to the transport direction, based on the image data.

2. The aforementioned printing device records images using an inkjet method, The vibration evaluation method according to claim 1, wherein in step (a), the two line images are recorded by two nozzles separated by a predetermined distance in the transport direction.

3. The vibration evaluation method according to claim 1 or claim 2, wherein the periodic data includes the amplitude component of the variation in the transport direction between the two line images.

4. The vibration evaluation method according to claim 1 or claim 2, wherein the line image is a single-dot line.

5. The vibration evaluation method according to claim 1 or 2, wherein the distance between the two line images is set to a distance such that the two line images do not overlap when the maximum vibration expected to occur in the printing device occurs.

6. The vibration evaluation method according to claim 2, further comprising step (d) prior to step (a), in which the user selects the nozzles that form the two line images, or the user specifies the distance in the transport direction of the nozzles that form the two line images.

7. The aforementioned printing apparatus Step (e) of receiving an input of vibration frequency, The vibration evaluation method according to claim 2, comprising the step (f) of selecting two nozzles from a plurality of inkjet nozzle combinations such that the amplitude amplification factor is not zero, based on the vibration frequency received in step (e) and formula (1). Amplitude amplification factor = {2 - 2cos(2πfD / v)}^1 / 2 (Equation 1) Here, f: vibration frequency [Hz] D: Distance in the transport direction between the two nozzles [mm] v: Conveying speed [mm / sec] That is the case.

8. The vibration evaluation method according to claim 1 or 2, wherein the scanner is provided in the printing device.

9. The vibration evaluation method according to claim 1 or 2, wherein the reading resolution of the scanner is higher than the print resolution of the printing device.

10. When two nozzles separated by a predetermined distance in the transport direction to record the two line images are considered as a pair, in step (a), multiple sets of the two line images are recorded by multiple sets of nozzles arranged in the width direction, The vibration evaluation method according to claim 2, wherein in step (c), periodic data indicating the periodic characteristics of the fluctuation in the transport direction is generated based on the interval between the multiple sets of two line images.

11. The vibration evaluation method according to claim 1 or 2, comprising detecting the line center from the density curve of the line image and reading the displacement of the line image in the width direction at a resolution higher than the reading resolution of the scanner.

12. The vibration evaluation method according to claim 1 or 2, wherein the periodic data includes a graph showing the variation in the distance between the two line images in the transport direction.

13. The vibration evaluation method according to claim 1 or 2, wherein the period data includes a numerical value of the period of the fluctuation.

14. (a) A step of recording at least two line images extending in the transport direction of the recording medium on a recording medium transported by a transport unit in a printing apparatus, Step (b) involves reading the line image recorded in step (a) using a scanner to generate image data, A control program for causing a computer to perform a process that includes (c) generating periodic data showing the periodic characteristics of the variation in the transport direction at the interval between the two line images in the width direction perpendicular to the transport direction, based on the image data.

15. The aforementioned printing device records images using an inkjet method, The control program according to claim 14, wherein in step (a), the two line images are recorded by two nozzles separated by a predetermined distance in the transport direction.

16. The control program according to claim 14 or claim 15, wherein the periodic data includes the amplitude component of the variation in the transport direction of the interval between the two line images.

Images