Image forming device

Abstract

To provide an image formation apparatus which can form a high-quality image even if the temperature of a holding part for holding a plurality of heads changes during image formation.SOLUTION: An image formation apparatus comprises: a plurality of heads which discharge ink to an image formation body to form an image on an image formation body; a holding part 33 which holds the plurality of heads; a temperature determination part which determines the temperature of the holding part 33; and an adjustment part which adjusts the position of the image formed on the image formation body with ink discharged from each head according to the temperature of the holding part 33 determined by the temperature determination part.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2004-321978 (Patent Document 1) discloses a droplet ejection device having an ejection head that ejects a functional liquid from a nozzle and a mounting plate with an opening in which multiple ejection heads are arranged. The multiple ejection heads are arranged in the opening at the mounting position under the same temperature conditions as when the functional liquid is ejected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-321978 Summary of the Invention [Problem to be solved by the invention]

[0004] In an image forming device that forms an image by ejecting ink from multiple heads, the temperature of the holding unit that holds the multiple heads can change due to heat generated during image formation, changes in the ambient temperature, etc. If the positional relationship between the heads changes due to thermal deformation of the holding unit, ink cannot be supplied from each head to the target position, which can result in a decrease in image quality.

[0005] The present disclosure proposes an image forming apparatus that can form high-quality images even if the temperature of the holding unit changes during image formation. [Means for solving the problem]

[0006] The image forming apparatus according to the present disclosure includes a plurality of heads that eject ink onto an image forming body to form an image on the image forming body, a holding unit that holds the plurality of heads, a temperature determination unit that determines the temperature of the holding unit, and an adjustment unit that adjusts the position of the image formed on the image forming body by the ink ejected from each head according to the temperature of the holding unit determined by the temperature determination unit.

[0007] In the image forming apparatus described above, the adjustment section may change the position of each head in the holding section in accordance with the temperature of the holding section.

[0008] In the above-mentioned image forming device, each head may include a plurality of nozzles, and ink may be ejected from some of the plurality of nozzles, and the adjustment unit may change the nozzles in each head that eject ink depending on the temperature of the holding unit.

[0009] In the image forming apparatus, the adjustment unit may change the timing at which ink is ejected from each head onto the image forming body in accordance with the temperature of the holding unit.

[0010] In the image forming apparatus, the temperature determining unit may have a plurality of temperature sensors provided in the holding unit.

[0011] In the image forming apparatus, the temperature determination unit may estimate the temperature of the holding unit based on the amount of ink ejected from each head.

[0012] In the image forming apparatus, the temperature determination unit may determine the temperature distribution of the holding unit, and the adjustment unit may adjust the position of the image formed by each head in accordance with the temperature distribution of the holding unit.

[0013] In the image forming apparatus, the plurality of heads may include heads that eject inks of different colors.

[0014] In the image forming apparatus, the ink may be a water-based ink. [Effects of the Invention]

[0015] According to the image forming apparatus of the present disclosure, even if the temperature of the holding unit changes during image formation, a high-quality image can be formed. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of the inkjet head shown in FIG. [Figure 3] FIG. 10 is a diagram for explaining another example of the temperature determination unit. [Figure 4] FIG. 10 is a schematic diagram showing a state in which the holding portion is thermally deformed. [Figure 5] FIG. 2 is a schematic diagram showing a first example of an adjustment unit. [Figure 6] FIG. 10 is a schematic diagram showing a second example of the adjustment unit. [Figure 7] FIG. 10 is a first schematic diagram showing a third example of the adjustment unit. [Figure 8] FIG. 10 is a second schematic diagram showing a third example of the adjustment unit. [Figure 9] FIG. 10 is a third schematic diagram showing a third example of the adjustment unit. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of an image forming apparatus according to the present disclosure will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[0018] [Configuration of image forming apparatus 1] 1 is a schematic diagram showing a general configuration of an image forming apparatus 1 according to an embodiment. This image forming apparatus 1 is, for example, an inkjet recording apparatus that forms an ink image on a recording medium as an image forming body.

[0019] As shown in FIG. 1, the image forming apparatus 1 mainly includes a conveying section 10, an image forming section 30, and an ink drying section 60.

[0020] The transport unit 10 transports the recording medium. The transport unit 10 has a feed roller 11, winding rollers 12 and 13, and a transport belt 14. The feed roller 11 is a roller that feeds out the recording medium. The winding rollers 12 and 13 are rollers that wind up the recording medium. The transport belt 14 is stretched between the feed roller 11 and the winding rollers 12 and 13, and transports the recording medium. The recording medium is transported on the transport belt 14 from the feed roller 11 to the winding rollers 12 and 13 along a transport direction DR indicated by an arrow in FIG. 1.

[0021] Plain paper can be used as the recording medium. The plain paper may be roll paper in which a long piece of paper is wound into a roll, or may be sheets cut to a predetermined size. The recording medium may be a resin film. The resin film may be, for example, a PET film, a PP film, or a PE film. The recording medium may be metal, a wooden board, cloth, or the like.

[0022] The image forming unit 30 ejects ink onto the recording medium transported on the transport belt 14. The image forming unit 30 is of an aqueous inkjet type. The image forming unit 30 has multiple inkjet heads 31. Each inkjet head 31 supplies ink of a respective color to the recording medium. For example, inkjet head 31Y supplies Y (yellow) ink. Inkjet head 31M supplies M (magenta) ink. Inkjet head 31C supplies C (cyan) ink. Inkjet head 31K supplies K (black) ink. The ink ejected from each inkjet head 31 is applied to the recording medium, forming an ink image on the recording medium.

[0023] The ink drying unit 60 heats the recording medium to dry and fix the ink image on the recording medium. The ink drying unit 60 may heat the recording medium from the front side on which the ink image is formed, or from the back side on which the ink image is not formed. The ink drying unit 60 may be equipped with a necessary heater selected from among known heaters such as an infrared heater, an electric heating wire, an ultraviolet lamp, a gas, or a hot air dryer. From the standpoints of safety and energy efficiency, heating using an electric heating wire or an infrared heater is preferred.

[0024] <Ink> The inks used are of various colors including cyan, magenta, yellow, and black (CMYK). By using one or more inks of these colors selected from the CMYK group, primary colors, multiple colors, or halftones can be formed for each of the many unit areas that make up an image. The inks can contain various components such as colorants, resins, aqueous media, surfactants, and other additives.

[0025] (colorant) The coloring material contained in the ink may be a pigment or a dye.

[0026] As the pigment that can be used, any conventionally known pigment can be used without any particular limitation, and both water-dispersible pigments and solvent-dispersible pigments can be used. For example, organic pigments such as insoluble pigments and lake pigments, and inorganic pigments such as carbon black can be preferably used.

[0027] It is preferable to use a dye having an anionic group, and specific examples of the dye include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone dyes.

[0028] Among these, the coloring material is preferably a pigment, and more preferably a resin-dispersible pigment.

[0029] (resin) Examples of resins contained in the ink include acrylic, styrene acrylic, acrylonitrile-acrylic, vinyl acetate acrylic, polyurethane, and polyester.

[0030] Such resins may be obtained by polymerizing a monomer having an acid group. Examples of such monomers include those obtained by radical copolymerization of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and acid derivatives of styrene. Furthermore, copolymerization with other monomers may be performed as needed.

[0031] The amount of ink-soluble resin varies depending on the degree of polymerization of the resin, but is preferably 2 to 10% of the total ink mass, more preferably 3 to 6%. If the amount of resin is too small, the effects of the present invention cannot be obtained, while if the amount is too large, abnormalities occur in inkjet ejection properties and storage stability. Furthermore, the resin may be present in a mixture of multiple resins, in the form of a copolymer, or dispersed in an emulsion state.

[0032] The ink solvent for dissolving and dispersing the solute preferably contains, in addition to water, a solvent component that is soluble in water, for the purpose of improving ejection properties, adjusting ink properties, etc. There are no particular restrictions on the type of solvent, as long as it does not impair the effects of the present invention.

[0033] (aqueous medium) The ink may be a water-based ink containing water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. Deionized water or ion-exchanged water is preferably used as the water. The water content (mass %) in the ink is preferably 20% to 95% by mass, based on the total mass of the ink. The water-soluble organic solvent content (mass %) in the ink is preferably 3% to 50% by mass, based on the total mass of the ink.

[0034] (surfactant) The surfactant to be used may be any of cationic, anionic, amphoteric, and nonionic. The surfactant or solvent may be used alone or in combination.

[0035] (Other additives) Depending on the purpose of improving ejection stability, compatibility with print heads and ink cartridges, storage stability, image storage stability, and other performances, various known additives, such as polysaccharides, viscosity modifiers, resistivity modifiers, film-forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, anti-mold agents, and anti-rust agents, can be appropriately selected and used.

[0036] [Configuration of inkjet head 31] FIG. 2 is a schematic diagram showing the configuration of the inkjet head 31 shown in FIG. 1. The inkjet head 31 for each color includes multiple heads. While FIG. 2 exemplarily shows a first head 311, a second head 312, and a third head 313, the inkjet head 31 may include four or more heads. The multiple heads are arranged in a staggered pattern. The inkjet head 31 includes a holder 33 that holds the multiple heads. The holder 33 may hold a head group consisting of multiple heads that eject ink of one color, or may hold a multiple head group that each ejects ink of a different color.

[0037] The transport direction DR of the recording medium, which is also shown in FIG. 1, is the vertical direction in FIG. 2. The direction perpendicular to the transport direction DR will be referred to as the width direction hereinafter. The width direction is the horizontal direction in FIG. 2. In the transport direction DR, the first head 311 and the second head 312 are arranged downstream, and the third head 313 is arranged upstream. The first head 311 and the second head 312 are arranged side by side in the width direction. In the width direction, the third head 313 is arranged between the first head 311 and the second head 312. In the width direction, a portion of the first head 311 and a portion of the third head 313 overlap. In the width direction, a portion of the second head 312 and a portion of the third head 313 overlap.

[0038] Each inkjet head 31 has a plurality of nozzles. Nozzles 321 shown in FIG. 2 are the plurality of nozzles of the first head 311, which are shown schematically as straight lines. Nozzles 321 include a plurality of nozzles arranged side by side in the width direction. Nozzles 322 shown in FIG. 2 are the plurality of nozzles of the second head 312, which are shown schematically as straight lines. Nozzles 323 shown in FIG. 2 are the plurality of nozzles of the third head 313, which are shown schematically as straight lines. Each of the nozzles 322 and 323 includes a plurality of nozzles arranged side by side in the width direction.

[0039] The inkjet head 31 further includes a plurality of temperature sensors 34, 35. The temperature sensors 34, 35 are provided in the holding portion 33 and measure the temperature of the holding portion 33. The temperature sensors 34, 35 are an example of a temperature determination portion that determines the temperature of the holding portion 33. The temperature sensors 34, 35 are arranged apart in the width direction. Each temperature sensor 34, 35 measures the temperature of the holding portion 33 at a different position, and the temperature of the holding portion 33 at a position between the temperature sensors 34, 35 is interpolated, thereby making it possible to determine the temperature distribution of the holding portion 33.

[0040] Fig. 3 is a diagram for explaining another example of the temperature determination unit. Fig. 3 shows the first head 311 as a representative, but the other heads have the same configuration. As described above, the nozzle 321 includes a plurality of nozzles arranged side by side in the width direction (the left-right direction in Fig. 3).

[0041] Each nozzle 321 communicates with a cavity 321C. Ink is stored in the cavity 321C. A piezoelectric element 321P is installed adjacent to the cavity 321C. The piezoelectric element 321P is deformed when a voltage is applied from a drive circuit (not shown). When the piezoelectric element 321P deforms, the cavity 321C also deforms, and the volume of the cavity 321C decreases, causing some of the ink in the cavity 321C to be pushed out of the cavity 321C. Then, an ink droplet D is ejected from the nozzle 321.

[0042] Heat is generated each time the piezo element 321P is driven. Each time an ink droplet D is ejected from a nozzle 321, the piezo element 321P corresponding to that nozzle 321 is driven and heat is generated. For nozzles 321 that eject ink continuously, the amount of heat generated by the piezo element 321P increases. Heat is generated around the nozzle 321 that ejects ink continuously, causing a localized temperature rise. As a result, a high-temperature region A1, which is an area with a relatively high temperature, and a low-temperature region A2, which is an area with a relatively low temperature, are formed within the inkjet head 31.

[0043] A controller (not shown) receives input of an ink image to be formed on a recording medium by the image forming apparatus 1. Based on the input ink image, the controller sets which of the multiple heads will eject ink and which of the multiple nozzles in that head will eject ink. The controller outputs a control signal to the drive circuit of the piezo element, instructing it to drive the piezo element corresponding to the nozzle set to eject ink. The temperature of the holding unit 33 rises due to the increased amount of heat generated around the nozzles where a large amount of ink is ejected and the piezo element is continuously driven. The controller can estimate the temperature rise of the holding unit 33 based on the amount of ink ejected from each head. Therefore, the controller that controls the image forming apparatus 1 can function as a temperature determination unit that determines the temperature of the holding unit 33.

[0044] [Thermal deformation of the holding portion 33] Fig. 4 is a schematic diagram showing a state in which holding unit 33 has been thermally deformed. In image forming apparatus 1, the temperature of holding unit 33, which holds multiple heads, can change due to heat generated during image formation and changes in the ambient temperature. The temperature of holding unit 33 shown in Fig. 4 has risen compared to the state in Fig. 2, and it has thermally expanded as indicated by the diagonal arrow in Fig. 4.

[0045] The dashed lines in FIG. 4 indicate the positions of the heads before the holding portion 33 shown in FIG. 2 is thermally deformed. The thermal expansion of the holding portion 33 causes the positions of the heads to change. The distance between the first head 311 and the second head 312 in the width direction increases. The distance between the first head 311 and the second head 312 and the third head 313 in the transport direction DR increases. The position of the third head 313 also shifts in the width direction. As the positions of the first head 311, the second head 312, and the third head 313 change, the positions of the nozzles 321, 322, and 323 also change. The positions of the nozzles 321, 322, and 323 change in both the transport direction DR and the width direction.

[0046] Figure 4 shows the holding portion 33 in a thermally expanded state, but the holding portion 33 may also thermally contract due to changes in the ambient temperature, in which case the positions of the first head 311, the second head 312, and the third head 313 change, and the positions of the nozzles 321, 322, and 323 also change.

[0047] [Adjustment section] The image forming apparatus 1 of the embodiment is equipped with an adjustment unit so that ink can be supplied to a target position from each head even if the positional relationship between the heads changes due to thermal deformation of the holding unit 33. The adjustment unit adjusts the position of an image formed on a recording medium by ink ejected from each head in accordance with the temperature of the holding unit 33.

[0048] <First example of adjustment section> Fig. 5 is a schematic diagram showing a first example of the adjustment unit. In the example shown in Fig. 5, the first head 311 is representatively illustrated, and a mechanical mechanism for moving the first head 311 in the width direction is also illustrated.

[0049] Specifically, a stepping motor 361 is attached to the holding unit 33. An output shaft 362 of the stepping motor 361 is provided with an external thread 363. The external thread 363 may be formed by threading the outer circumferential surface of the output shaft 362, or the external thread 363 may be configured by fixing an externally threaded member to the output shaft 362. A swinging member 364 is engaged with and coupled to the external thread 363. The swinging member 364 is provided with an internal thread. The output shaft 362 and the external thread 363 rotate relative to the holding unit 33 when driven by the stepping motor 361. On the other hand, the swinging member 364 is configured to be unable to rotate relative to the holding unit 33.

[0050] A biasing spring 366 is disposed at a position facing the swinging member 364 in the width direction. The biasing spring 366 is attached to a support plate 365. The support plate 365 is fixed to the holding portion 33. The biasing spring 366 is disposed so as to be able to expand and contract in the width direction, and one end thereof is supported by the support plate 365. The support plate 365 supports one end of the biasing spring 366 so that it cannot be displaced or is substantially unable to be displaced.

[0051] 5 is held between a swinging member 364 and a biasing spring 366. One end of the first head 311 extending in the width direction receives a biasing force in the width direction from the biasing spring 366, and the other end of the first head 311 is pressed against the swinging member 364. The swinging member 364 and the biasing spring 366 position the first head 311 in the width direction.

[0052] When the stepping motor 361 is driven, the male screw 363 rotates in accordance with the rotation of the output shaft 362. Because the oscillating member 364 does not rotate, the male screw 363 rotates relative to the female screw formed on the oscillating member 364. As a result, stress acts on the oscillating member 364 in the width direction. By driving the stepping motor 361 to rotate in both directions, the oscillating member 364 can be moved back and forth in the width direction. When the oscillating member 364 is moved in a direction approaching the support plate 365, the first head 311 pressed by the oscillating member 364 also moves in a direction approaching the support plate 365. When the oscillating member 364 is moved in a direction away from the support plate 365, the first head 311 receives the biasing force of the biasing spring 366 and also moves in a direction away from the support plate 365.

[0053] 2 and 4, the first head 311, which has been displaced in the width direction due to thermal expansion of the holding unit 33, can be displaced in the width direction by driving the stepping motor 361. By appropriately controlling the drive amount of the stepping motor 361 in accordance with the temperature of the holding unit 33, the displaced first head 311 shown in FIG. 4 can be displaced in the width direction to its original position shown in FIG.

[0054] 5 shows a mechanical mechanism that displaces the first head 311 in the width direction, but a mechanical mechanism that displaces the first head 311 in the transport direction DR is also provided. By appropriately controlling the mechanical mechanism, the first head 311 can be displaced in both the transport direction DR and the width direction, and can be returned to the position shown in FIG.

[0055] Similarly, the second head 312, the third head 313, and other heads are also provided with mechanical mechanisms that displace each head in the transport direction DR and the width direction. By appropriately controlling each mechanical mechanism and using the mechanical mechanisms to correct the head position shift caused by thermal deformation of the holding unit 33, all heads can be positioned as they would be if the holding unit 33 were not thermally deformed, as shown in FIG. 2. Even if the temperature of the holding unit 33 changes and the holding unit 33 is thermally deformed, the amount of head position shift can be predicted from the temperature of the holding unit 33 and the head can be displaced a distance corresponding to that amount of position shift, thereby positioning each head as it would be if the holding unit 33 were not thermally deformed. This allows ink to be supplied from each head to the target position, enabling the image forming device 1 to form high-quality images.

[0056] <Second example of adjustment section> Fig. 6 is a schematic diagram showing a second example of the adjustment unit. Fig. 6 shows a timing chart, with the horizontal axis representing time. Time T01 represents the timing at which ink is ejected from the first head 311 and the second head 312, which are located downstream in the transport direction DR, of the inkjet head 31 before thermal deformation shown in Fig. 2. Time T02 represents the timing at which ink is ejected from the third head 313, which is located upstream in the transport direction DR, of the inkjet head 31 before thermal deformation shown in Fig. 2.

[0057] 4, the positions of the nozzles 321, 322, and 323 in the transport direction DR are shifted due to the thermal expansion of the holding unit 33. Due to the thermal expansion of the holding unit 33, the recording medium arrives at the first head 311 and the second head 312 later than the first head 311. Due to the thermal expansion of the holding unit 33, the recording medium arrives at the third head 313 earlier than the first head 311.

[0058] Therefore, the timing at which ink is ejected from the first head 311 and the second head 312 is set to time T1, which is later than time T01. The timing at which ink is ejected from the third head 313 is set to time T2, which is earlier than time T02.

[0059] By predicting the amount of head positional deviation according to the temperature of the holding unit 33 and changing the timing at which each head ejects ink onto the recording medium, it is possible to supply ink from each head to a target position in the transport direction DR. Therefore, the image forming apparatus 1 can form high-quality images.

[0060] <Third example of adjustment section> Fig. 7 is a first schematic diagram showing a third example of the adjustment unit. Fig. 7 and subsequent Figs. 8 and 9 representatively show the first head 311 and the third head 313 out of the multiple heads of the inkjet head 31. As already mentioned, the nozzles 321 of the first head 311 include multiple nozzles arranged side by side in the width direction. The nozzles 323 of the third head 313 include multiple nozzles arranged side by side in the width direction.

[0061] Each head is controlled so that ink is ejected from only some of its nozzles. The nozzles 321 of the first head 311 include idle nozzles 3210 that do not eject ink, shown in white in the figure, and operating nozzles 3211 that eject ink, shown in hatched in the figure. The nozzles 323 of the third head 313 include idle nozzles 3230 that do not eject ink, shown in white in the figure, and operating nozzles 3231 that eject ink, shown in hatched in the figure.

[0062] In the width direction, the range in which the nozzles 321 of the first head 311 extend overlaps with the range in which the nozzles 323 of the third head 313 extend. More specifically, the operating nozzles 3211 of the first head 311 overlap with the idle nozzles 3230 of the third head 313, and the operating nozzles 3231 of the third head 313 overlap with the idle nozzles 3210 of the first head 311. The operating nozzles 3211 of the first head 311 do not overlap with the operating nozzles 3231 of the third head 313.

[0063] 7, the rightmost nozzle in the diagram among the operating nozzles 3211 of the first head 311 and the leftmost nozzle in the diagram among the operating nozzles 3231 of the third head 313 are adjacent to each other in the width direction. In the width direction, there are no idle nozzles 3210, 3230 between the rightmost nozzle of the operating nozzles 3211 and the leftmost nozzle of the operating nozzles 3231. This allows a desired image to be formed by ink ejection from the operating nozzles 3211, 3231.

[0064] FIG. 8 is a second schematic diagram showing a third example of the adjustment unit. FIG. 8 shows the holding unit 33 thermally expanded as indicated by the diagonal arrow. The thermal expansion of the holding unit 33 causes the positions of the first head 311 and the third head 313 to change in the width direction. The overlap in the width direction between the range in which the nozzles 321 extend and the range in which the nozzles 323 extend becomes smaller. Specifically, in the example shown in FIG. 7, six nozzles are arranged in a range in which they overlap each other in the width direction, whereas in FIG. 8, only two nozzles are arranged in a range in which they overlap each other in the width direction.

[0065] In the inkjet head 31 shown in Fig. 8 in which the holding portion 33 has thermally expanded, the positions of the nozzles that eject ink have been changed. In the example shown in Fig. 7, there are three inactive nozzles 3210 on the right and left of the operating nozzle 3211. There are three inactive nozzles 3230 on the right and left of the operating nozzle 3231. In contrast to this, in Fig. 8, there is one inactive nozzle 3210 on the right of the operating nozzle 3211 and five inactive nozzles 3210 on the left. There are five inactive nozzles 3230 on the right of the operating nozzle 3231 and one inactive nozzle 3230 on the left.

[0066] As a result of changing the positions of the operating nozzles 3211 and 3231 that eject ink, the positions of the operating nozzles 3211 and 3231 before thermal deformation shown in FIG. 7 are the same as those after thermal deformation shown in FIG.

[0067] FIG. 9 is a third schematic diagram showing a third example of the adjustment unit. FIG. 9 shows the holding unit 33 that has been thermally shrunk, as indicated by the diagonal arrow. As the holding unit 33 thermally shrinks, the positions of the first head 311 and the third head 313 change in the width direction. The overlap between the range in which the nozzles 321 extend and the range in which the nozzles 323 extend in the width direction becomes larger. Specifically, in the example shown in FIG. 7, six nozzles are arranged in a range in which they overlap with each other in the width direction, whereas in FIG. 9, eight nozzles are arranged in a range in which they overlap with each other in the width direction.

[0068] In the inkjet head 31 in which the holding portion 33 has been thermally shrunk as shown in Fig. 9, the positions of the nozzles that eject ink have been changed. In Fig. 9, there are four idle nozzles 3210 to the right of the operating nozzle 3211 and two idle nozzles 3210 to the left. There are two idle nozzles 3230 to the right of the operating nozzle 3231 and four idle nozzles 3230 to the left.

[0069] As a result of changing the positions of the operating nozzles 3211 and 3231 that eject ink, the positions of the operating nozzles 3211 and 3231 before thermal deformation shown in FIG. 7 are the same as those after thermal deformation shown in FIG.

[0070] By predicting the amount of head positional deviation based on the temperature of the holding unit 33 and changing the position of the nozzles that eject ink from each head onto the recording medium, it is possible to supply ink from each head to a targeted position in the width direction. Therefore, the image forming device 1 can form high-quality images.

[0071] [Action and effect] Although some of the description overlaps with the above description, the characteristic configuration and effects of the image forming apparatus 1 of the embodiment can be summarized as follows.

[0072] 5 to 9, image forming apparatus 1 adjusts the position of an image formed on a recording medium by ink ejected from each head in accordance with the temperature of holding unit 33. Even if the temperature of holding unit 33 changes and the position of the head changes due to thermal deformation of holding unit 33, the amount of change in head position is predicted from the temperature of holding unit 33, and the position of the image formed on a recording medium by each head is adjusted for each head based on the amount of change in head position, thereby making it possible to supply ink from each head to the target position. Therefore, image forming apparatus 1 can form high-quality images.

[0073] 5, the position of each head in the holding unit 33 may be changed depending on the temperature of the holding unit 33. By changing the position of the head, it is possible to appropriately adjust the position of the image in the transport direction DR and the width direction, and it is possible to supply ink from each head to the target position. By making the position of the head changeable, it is possible to reduce the overlap of the ranges in which the nozzles extend in the width direction, and therefore it is possible to reduce the number of nozzles in each head.

[0074] As shown in Figures 7 to 9, the nozzles that eject ink in each head may be changed depending on the temperature of the holding unit 33. By changing the position of the nozzles to be used, the position of the image in the width direction can be appropriately adjusted, and ink can be supplied to the target position from each head. Compared to the example shown in Figure 5, in which the position of the head is changed, there is no need to provide a stepping motor 361, etc., and therefore the position of the image can be adjusted with a simple configuration.

[0075] As shown in Fig. 6, the timing at which ink is ejected from each head onto the recording medium may be changed depending on the temperature of the holding unit 33. By changing the timing at which ink is ejected, the position of the image in the transport direction DR can be appropriately adjusted, and ink can be supplied to the target position from each head. Compared to the example shown in Fig. 5, in which the position of the head is changed, there is no need to include a stepping motor 361, etc., and therefore the position of the image can be adjusted with a simple configuration.

[0076] 2, the holder 33 may be provided with a plurality of temperature sensors 34, 35 that measure the temperature of the holder 33. In this way, the temperature distribution of the holder 33 can be determined based on the measurement results of the temperature sensors, and the position of the image can be adjusted accurately according to the temperature of the holder 33.

[0077] 3, the temperature of holding unit 33 may be estimated based on the amount of ink ejected from each head. Since the temperature of holding unit 33 can be estimated by processing by the controller that controls image forming apparatus 1, the temperature of holding unit 33 can be determined without providing multiple temperature sensors.

[0078] The position of the image formed by each head can be adjusted according to the temperature distribution of the holding unit 33. The adjustment amount can be increased for heads in high-temperature positions and decreased for heads in low-temperature positions. The image position can be appropriately adjusted for each head according to the temperature change of the holding unit 33, and ink can be supplied from each head to the target position with high precision.

[0079] 1, the inkjet head 31 may include inkjet heads 31Y, 31M, 31C, and 31K that eject inks of different colors. The adjustment of the image position according to the temperature of the holding unit 33 in this embodiment can also be applied to color printers.

[0080] The ink ejected from each head may be water-based ink. In an image forming apparatus 1 using water-based ink, temperature control of the ink is not required, so there is no temperature adjustment mechanism within the apparatus, and the temperature of the holding unit 33 in standby mode follows the ambient temperature. When image formation begins, the head generates heat as ink is ejected from the nozzles, causing the temperature of the surrounding holding unit 33 to rise, resulting in thermal expansion of the holding unit 33. Thus, by applying the configuration of the embodiment, in which the position of the image formed by each head on the recording medium is adjusted for each head according to the temperature of the holding unit 33, to an image forming apparatus 1 using water-based ink, which experiences large temperature changes in the holding unit 33, the image forming apparatus 1 can form high-quality images.

[0081] 1 is configured to directly form an ink image on a recording medium as an image forming body. The image forming apparatus is not limited to this configuration, and may be configured to eject ink from image forming unit 30 onto an intermediate transfer body, form an ink image on the intermediate transfer body as an image forming body, and transfer the image from the intermediate transfer body to the recording medium.

[0082] Although the embodiments have been described above, configurations that can be combined with each other among the configurations described in the embodiments may be appropriately combined. Furthermore, the embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0083] 1 image forming apparatus, 10 conveying section, 11 feeding roller, 12, 13 winding roller, 14 conveying belt, 30 image forming section, 31, 31C, 31K, 31M, 31Y inkjet head, 33 holding section, 34, 35 temperature sensor, 60 ink drying section, 311 first head, 312 second head, 313 third head, 321, 322, 323 nozzle, 321C cavity, 321P piezoelectric element, 361 stepping motor, 362 output shaft, 363 male screw, 364 swinging member, 365 support plate, 366 biasing spring, 3210, 3230 idle nozzle, 3211, 3231 operating nozzle, A1 high temperature area, A2 low temperature area, D droplet, DR Conveying direction, T01,T1,T2,T02 time.

Claims

1. a plurality of heads that eject ink onto an image forming body to form an image on the image forming body; a holding unit that holds a plurality of the heads; a temperature determination unit that determines the temperature of the holding unit; an adjustment unit that adjusts a position of an image formed on the image forming body by ink ejected from each of the heads in accordance with the temperature of the holding unit determined by the temperature determination unit, Each of the heads includes a plurality of nozzles arranged side by side in a width direction perpendicular to the conveyance direction of the image forming body, and ejects ink from some of the plurality of nozzles that are in operation and some of the plurality of nozzles that are inactive, without ejecting ink; the adjustment unit changes positions of the operating nozzles and the idle nozzles in each of the heads in accordance with the temperature of the holding unit; Each of the heads is controlled so as to eject ink from only some of the nozzles of the plurality of nozzles of each head, an inactive nozzle is located on the right and left sides of the active nozzle in the width direction;

2. The image forming apparatus according to claim 1 , wherein the adjustment unit changes the position of each of the heads in the holding unit in accordance with the temperature of the holding unit.

3. 3. The image forming apparatus according to claim 1, wherein the adjustment section changes the timing at which ink is ejected from each of the heads onto the image forming body in accordance with the temperature of the holding section.

4. 4. The image forming apparatus according to claim 1, wherein the temperature determining unit includes a plurality of temperature sensors provided in the holding unit.

5. 4. The image forming apparatus according to claim 1, wherein the temperature determination unit estimates the temperature of the holding unit based on the amount of ink ejected from each of the heads.

6. the temperature determination unit determines a temperature distribution of the holding unit, 6. The image forming apparatus according to claim 4, wherein the adjustment section adjusts the position of the image formed by each of the heads in accordance with the temperature distribution of the holding section.

7. 7. The image forming apparatus according to claim 1, wherein the plurality of heads include heads that eject inks of different colors.

8. 8. The image forming apparatus according to claim 1, wherein the ink is a water-based ink.

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