Liquid discharge apparatus, image forming apparatus, and adjustment method of liquid discharge head unit

Abstract

To provide a liquid discharge apparatus which enables improvement of accuracy of adhesion result of a liquid applied by a head unit and adhering to a medium.SOLUTION: A liquid discharge apparatus comprises: a pair of conveyance guide members which are respectively installed on an upstream side and a downstream side of a liquid discharge head unit in a transport direction of a transported object; an installation part for installing distance measuring means in a position facing the liquid discharge head unit in a discharge direction in which the liquid discharge head unit discharges the liquid; and lifting means which moves up or down the liquid discharge head unit according to a first distance to a transport surface calibration member, which is measured by the distance measuring means in a state where the transport surface calibration member is installed on the transport guide members in stead of the transported object, and a second distance to the liquid discharge head unit, which is measured by the distance measuring means in a state where the transport surface calibration member is not installed. The above problem is solved by the liquid discharge apparatus.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a liquid ejection device, an image forming device, and a method for adjusting a liquid ejection head unit.

Background Art

[0002] A liquid ejection device equipped with a head unit that ejects liquid onto a recording medium is known. Also known is an image forming device that forms an image with the liquid ejected by the head unit onto the recording medium.

[0003] For the purpose of preventing deterioration of image quality due to warping of the recording medium and damage to the head unit, a printing device is disclosed that includes a detection means for detecting the warping height of the recording medium, and a lifting means for raising and lowering a print head according to the warping height detected by the detection means (see Patent Document 1).

Summary of the Invention

Problems to be Solved by the Invention

[0004] A configuration as disclosed in Patent Document 1 is difficult to adjust for accurately assembling the initial position of the head unit in the height direction. When the adjustment accuracy of the height position of the head unit is low, it affects the accuracy of attaching liquid to the recording medium as intended. Therefore, according to the prior art, there is a problem that the accuracy of the attachment result of the liquid attached to the medium by the head unit decreases.

[0005] An object of the present invention is to provide a liquid ejection device capable of improving the accuracy of the attachment result of the liquid attached to the medium by the head unit.

Means for Solving the Problems

[0006] In order to solve the above technical problems, one aspect of the present invention relates to a liquid ejection device that ejects liquid from a liquid ejection head unit onto an object to be conveyed. For the liquid ejection head unit, a pair of conveyance guide members installed on the upstream side and the downstream side in the conveyance direction of the object to be conveyed, and an installation portion for installing distance measurement means at a position facing the liquid ejection head in the ejection direction in which the liquid ejection head unit ejects the liquid, and with a conveyance surface calibration member installed on the conveyance guide member instead of the object to be conveyed, the distance to the conveyance surface calibration member measured by the distance measurement means, and the distance to the liquid ejection head unit measured by the distance measurement means in a state where the conveyance surface calibration member is not installed, and lifting means for lifting the head unit according to these distances.

Advantages of the Invention

[0007] According to the present invention, the accuracy of the adhesion result of the liquid adhered to the medium by the head unit can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same components will be denoted by the same reference numerals, and duplicate descriptions may be omitted.

[0010] [Embodiment of Image Forming Apparatus] First, based on FIGS. 1 and 2, the configuration of an inkjet type image forming apparatus which is an embodiment of the liquid ejection apparatus according to the present invention will be described. FIG. 1 is a diagram showing the overall configuration of the inkjet type image forming apparatus. FIG. 2 is a diagram showing the control system of the inkjet type image forming apparatus.

[0011] As shown in FIG. 1, the image forming apparatus 100 according to this embodiment includes a sheet supply unit 1 that supplies a sheet S as a recording medium for image formation and an object to be conveyed, a conveyance unit 8 that conveys the supplied sheet S, a first image forming unit 3 that forms an image on the front surface of the sheet S, a second image forming unit 4 that forms an image on the back surface of the sheet S, a front-back reversing unit 5 that reverses the front and back of the sheet S, a first drying unit 6 and a second drying unit 7 that dry the sheet S, and a sheet recovery unit 2 that recovers the sheet S on which an image has been formed.

[0012] In addition, the image forming apparatus 100 according to the present embodiment includes a control unit 9 (see FIG. 2) for controlling a sheet supply unit 1, a conveyance unit 8, a first image forming unit 3, a second image forming unit 4, a front-back inversion unit 5, a first drying unit 6, a second drying unit 7, a sheet collection unit 2, and a head unit moving unit 25. Note that the head unit moving unit 25 is not shown in FIG. 1.

[0013] The sheet supply unit 1 has a supply roller 11 around which a long sheet S is wound in a roll shape. The supply roller 11 is configured to be rotatable in the direction of the arrow shown in FIG. 1, and when the supply roller 11 rotates, the sheet S is fed out.

[0014] The conveyance unit 8 includes a conveyance device having a plurality of conveyance rollers 17. The sheet S is wound around each conveyance roller 17, and when each conveyance roller 17 rotates, the sheet S is conveyed. Note that the conveyance roller 17 also includes a pipe having a circular cross section, a shaft, and the like.

[0015] The first image forming unit 3 has a plurality of head units 12K, 12C, 12M, 12Y that discharge liquid ink onto the sheet S. Each of the head units 12K, 12C, 12M, 12Y discharges ink onto the front surface of the sheet S based on the image data formed on the front surface of the sheet S among the image data generated by the control unit 9, and forms an image on the sheet S. Here, the ink is a liquid containing a coloring material, a solvent, and crystalline resin particles dispersed in the solvent. The crystalline resin is a resin that undergoes a phase change and melts from a crystalline state to a liquid when heated to a predetermined melting point or higher.

[0016] The first drying unit 6 has a heating drum 13 that heats the sheet S to promote drying of the ink on the sheet S. The heating drum 13 is a cylindrical member that rotates while the sheet S is wound around its outer peripheral surface, and a heating source such as a halogen heater is disposed inside. The heating drum 13 is disposed below (the back side of the sheet S) the conveyance path along which the sheet S is conveyed. For this reason, when the sheet S is conveyed from the first image forming unit 3, the lower surface (the back side surface) of the sheet S contacts the outer peripheral surface of the heating drum 13, and the sheet S is conveyed while being heated by the rotating heating drum 13. Thereby, drying of the ink on the sheet S is promoted. Also, the rotation speed of the heating drum 13 at this time is controlled by the control unit 9 to be substantially the same as the conveyance speeds of the sheet supply unit 1, the sheet collection unit 2, the conveyance unit 8, and the like. For this reason, the sheet S is conveyed without shifting in the sheet conveyance direction with respect to the outer peripheral surface of the heating drum 13.

[0017] The front-back inversion unit 5 is configured by a known device that inverts the positions of the front side and the back side of the sheet S. When the sheet S conveyed from the first drying unit 6 passes through the front-back inversion unit 5, it is front-back inverted and sent to the second image forming unit 4. That is, when the front side surface of the sheet S is conveyed in an upward state, it is inverted by the front-back inversion unit 5 so that the front side surface faces downward (the back side surface faces upward) and conveyed.

[0018] The second image forming unit 4 basically has the same configuration as the first image forming unit 3, and has a plurality of head units 14K, 14C, 14M, 14Y that discharge liquid ink onto the sheet S. However, in the second image forming unit 4, an image is formed on the back side surface of the sheet S. That is, since the sheet S is conveyed to the second image forming unit 4 in a state of being front-back inverted by the front-back inversion unit 5, the second image forming unit 4 discharges ink onto the back side surface of the sheet S based on the image data formed on the back side surface of the sheet S among the image data generated by the control unit 9, and forms an image on the sheet S.

[0019] The second drying unit 7 has a heating drum 15 that heats the sheet S, similar to the first drying unit 6. As shown in FIG. 1, the heating drum 15 of the second drying unit 7 is arranged below the conveyance path, similar to the heating drum 13 of the first drying unit 6. However, since the conveyed sheet S is turned over, it contacts the front side surface of the sheet S. At this time, even if an image is formed on the front side surface of the sheet S, since the drying of the ink has already been promoted by the first drying unit 6, the image will not be disturbed when the heating drum 15 contacts the front side image.

[0020] The sheet collecting unit 2 has a collecting roller 16 that winds up and collects the sheet S. The collecting roller 16 is configured to be rotatable in the direction of the arrow shown in FIG. 1. When the collecting roller 16 rotates, the sheet S is wound up in a roll shape and collected. Note that the sheet collecting unit 2 may include a post-processing unit that performs post-processing such as cutting the sheet S to a predetermined length or aligning the cut sheets S.

[0021] The control unit 9 shown in FIG. 2 is constituted by an information processing device such as a PC (Personal Computer). The control unit 9 generates image data formed on the front side surface and the back side surface of the sheet S, and controls various operations of the sheet supply unit 1, the conveyance unit 8, the first image forming unit 3, the second image forming unit 4, the front-back inversion unit 5, the first drying unit 6, the second drying unit 7, the sheet collecting unit 2, and the head unit moving unit 25. For example, the control unit 9 controls the rotation speeds of the supply roller 11, the collecting roller 16, and each conveyance roller 17, as well as the temperature of the heating source that heats each heating drum 13, 15.

[0022] The control unit 9 includes a CPU (Center Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, and a non-volatile RAM (Non-Volatile Random Access Memory) 94, etc.

[0023] The CPU 91 is an arithmetic unit that controls the operation of the entire image forming apparatus 100. The ROM 92 is a read-only non-volatile storage medium that stores programs such as firmware. The RAM 93 is a volatile storage medium that enables high-speed reading and writing of information and is used as a work area when the CPU 91 processes information. The NVRAM 94 is a non-volatile storage medium that enables reading and writing of information and stores setting values necessary for controlling each part of the image forming apparatus 100. Note that the setting values stored in the NVRAM 94 are, for example, adjustment values for the height position of the head unit 12 according to the type (paper thickness) of the sheet S.

[0024] The head unit moving unit 25 includes a motor 42 for moving the head unit 12 between the liquid discharge position 10 and the cleaning position 43. Note that the motor 42 is provided corresponding to each head unit 12 (see FIG. 6). Each head unit 12 can move the head units 12K, 12C, 12M, 12Y independently between the liquid discharge position 10 and the cleaning position 43 by driving the corresponding motor 42 (see FIG. 6).

[0025] [Configuration of Image Forming Unit] Next, based on FIG. 3, the configuration of the image forming unit according to the present embodiment will be described in detail. As described above, the image forming unit in the present embodiment includes the first image forming unit 3 and the second image forming unit 4. Since these configurations are basically the same, only the configuration of the first image forming unit 3 will be described, and the description of the configuration of the second image forming unit 4 will be omitted.

[0026] As shown in FIG. 3, in the first image forming unit 3 according to the present embodiment, four head units 12K, 12C, 12M, and 12Y that discharge ink of black (K), cyan (C), magenta (M), and yellow (Y) are arranged in order from the upstream side in the conveyance direction A in which the sheet S is conveyed. Note that the order of the head units 12K, 12C, 12M, and 12Y of each color may be an order other than that shown in the figure. Also, the color of the ink used may be a color other than black, cyan, magenta, and yellow. Also, the number of head units may be a number other than four.

[0027] Each of the head units 12K, 12C, 12M, and 12Y is a line head type that is longer than the dimension in the width direction of the sheet S having the four liquid ejection heads 18. Each liquid ejection head 18, which is a liquid ejection unit, has a plurality of nozzles 19, and ejects ink (liquid) from each nozzle 19 onto the sheet S. Also, the liquid ejection heads 18 are arranged alternately across the entire width direction of the image forming region on the sheet S, and when the sheet S is conveyed to a position facing each of the head units 12K, 12C, 12M, and 12Y, ink is ejected from each liquid ejection head 18, and an image is formed on the sheet S. Also, the number of liquid ejection heads may be a number other than four.

[0028] Here, the "width direction" of the sheet S means a direction parallel to the conveyance surface on which the sheet S is conveyed and perpendicular to the conveyance direction A. That is, the "width direction" of the sheet S means the direction indicated by the arrow "B" in FIG. 3. Also, the above "conveyance surface" is a surface through which the conveyed sheet S passes, and includes, for example, a virtual surface connecting the contact portions of a plurality of conveyance rollers that convey the sheet S with the sheet S, or the sheet placement surface of a conveyance belt that places and conveys the sheet S. Also, the "sheet width direction" in the following description has the same meaning.

[0029] [First Embodiment of Head Unit 12] Next, the head unit 12 will be further described. FIG. 4 is a diagram for explaining the perspective configuration of the head unit 12. As shown in FIG. 4, the head unit 12 includes four liquid ejection heads 18 and a base member 12a for supporting them. Each of the liquid ejection heads 18 is provided with a lifting mechanism Z0 as an independent lifting means.

[0030] Generally, a manual mechanism such as a feed screw or an eccentric pin is adopted for the lifting mechanism Z0. Note that an electric mechanism such as a servo motor or an actuator may be adopted as the lifting mechanism Z0.

[0031] At the time of assembling the image forming apparatus 100, the lifting mechanism Z0 is temporarily fixed at an appropriate position. Thereafter, fine adjustment is performed by the lifting mechanism Z0. Note that the method of this fine adjustment will be described in detail later because it corresponds to the gist of the present invention.

[0032] Further, the head unit 12 is also provided with a lifting mechanism Z1 as a lifting means for lifting the entire head unit 12. By providing the lifting mechanism Z1, the head unit 12 can keep the gap between the nozzle surface and the sheet S constant by lifting even when the thickness of the sheet S is different. Each of the liquid ejection heads 18 is also provided with a fine adjustment mechanism in the independent A direction, B direction and rotation direction, but this is not the gist of the present invention, so the description thereof will be omitted.

[0033] [Configuration Example of Conveying Unit 8] Subsequently, based on FIG. 5, the configuration of the conveying device 20 (conveying unit 8) disposed in the first image forming unit 3 will be described.

[0034] As shown in FIG. 5, the conveying device 20 (conveying unit 8) has a plurality of conveying rollers 17 as conveying guide members. Among the respective conveying rollers 17 shown in FIG. 5, the driving rollers 17A and 17B on the upstream side and the downstream side (the most upstream and the most downstream in FIG. 5) in the conveying direction A of the sheet S are a pair of driving rollers that sandwich the sheet S from its front side and back side and convey it. The sheet S is conveyed by these driving rollers 17A and 17B, and also by a driving roller 17C (a non-paired conveying roller) arranged on the downstream side of one of the upstream driving rollers 17A.

[0035] Also, between the upstream driving roller 17C and the downstream driving roller 17B, a plurality of driven rollers 17d to 17k as conveying rollers 17 are arranged. Instead of each of the driven rollers 17d to 17k, a plurality of driving rollers may be arranged. Each of the driven rollers 17d to 17k is arranged on the upstream side and the downstream side with the liquid discharge positions 10K, 10C, 10M, and 10Y of each of the head units 12K, 12C, 12M, and 12Y interposed therebetween. In this way, since each of the driven rollers 17d to 17k is arranged on the upstream side and the downstream side with the liquid discharge positions 10K, 10C, 10M, and 10Y interposed therebetween, the fluttering of the sheet S particularly at each of the liquid discharge positions 10K, 10C, 10M, and 10Y is suppressed, and the sheet S can be stably conveyed.

[0036] In addition, if the heights of the respective liquid discharge heads 18 included in each of the head units 12K, 12C, 12M, and 12Y are different, the landing positions will shift, resulting in density unevenness within the same color or color misregistration between multiple colors. Therefore, it is necessary to assemble and adjust accurately, which is an important part of the present invention and will be described in detail later.

[0037] [Position changing mechanism of head unit 12] Subsequently, with reference to FIG. 6, the position changing mechanism of the head unit 12 will be described. As illustrated in FIG. 6, the head unit 12 is movable to be in either the liquid discharge position 10 or the cleaning position 43.

[0038] <Cleaning position 43> First, the cleaning position 43 will be described with reference to FIG. 6. The cleaning position 43 is an example of the second position. The cleaning position 43 may be the position of the head unit during the execution of the cleaning operation. The cleaning position 43 may be, for example, a position above the discharge receiver of the cleaning unit 45. Also, for example, when the cleaning operation is a wiping operation, it may be the position of the head unit during the execution of the wiping operation.

[0039] The cleaning position 43 includes cleaning positions 43K, 43C, 43M, and 43Y. The cleaning position 43K is the position of the head unit 12K during cleaning. The cleaning position 43C is the position of the head unit 12C during cleaning. The cleaning position 43M is the position of the head unit 12M during cleaning. The cleaning position 43Y is the position of the head unit 12Y during cleaning. The cleaning positions 43K, 43C, 43M, and 43Y are positions deviated from the liquid discharge position 10 in the width direction B of the sheet S. The cleaning positions 43K, 43C, 43M, and 43Y are spaced apart from the liquid discharge position 10 in the width direction B. The liquid discharge position 10 includes liquid discharge positions 10K, 10C, 10M, and 10Y.

[0040] The cleaning positions 43K, 43C, 43M, and 43Y are positions that do not overlap the sheet S. In the conveyance direction A of the sheet S, the cleaning positions 43K, 43C, 43M, and 43Y are arranged at a predetermined interval corresponding to the head units 12K, 12C, 12M, and 12Y.

[0041] <Position changing mechanism 50> The image forming apparatus 100 includes a position changing mechanism 50 that moves the head units 12K, 12C, 12M, and 12Y between the cleaning positions 43K, 43C, 43M, 43Y and the liquid discharge positions 10K, 10C, 10M, 10Y in the width direction B. The position changing mechanism 50 includes position changing mechanisms 50K, 50C, 50M, and 50Y. The position changing mechanism 50K moves the head unit 12K in the width direction B. The position changing mechanism 50C moves the head unit 12C in the width direction B. The position changing mechanism 50M moves the head unit 12M in the width direction B. The position changing mechanism 50Y moves the head unit 12Y in the width direction B. When the position changing mechanisms 50K, 50C, 50M, and 50Y are not distinguished, they may be described as the position changing mechanism 50.

[0042] The position changing mechanism 50 includes a ball screw 40, a linear guide 41, and a motor 42. The ball screw 40 extends along the width direction B. The ball screw 40 is arranged at a position shifted in the conveyance direction A with respect to the head unit 12. The ball screw 40 may be arranged at a position overlapping the head unit 12 in plan view.

[0043] The head unit 12 is supported by the ball screw 40 and the linear guide 41. The motor 42 is provided at one end of the ball screw 40. The motor 42 may be arranged at a position close to the cleaning position 43 in plan view. The motor 42 drives the ball screw 40.

[0044] The linear guide 41 extends along the width direction B. The linear guide 41 extends from the liquid discharge position 10 to the cleaning position 43. The head unit 12 is movable along the linear guide 41. The linear guide 41 is arranged at a position shifted in the conveyance direction A with respect to the head unit 12. The linear guide 41 is arranged on the side opposite to the ball screw 40 with respect to the head unit 12. The linear guide 41 may be arranged at a position overlapping the head unit 12 in a plan view. The linear guide 41 is an example of a guide member. The linear guide 41 guides the movement of the head unit 12 in the width direction B.

[0045] The control unit 9 (see FIG. 2) can drive the ball screw 40 by controlling the operation of the head unit moving unit 25 including the motor 42. The head unit 12 is guided by the ball screw 40 and the linear guide 41 and moves in the width direction B between the liquid discharge position 10 and the cleaning position 43. The motor 42 is provided for each of the plurality of ball screws 40. The head units 12K, 12C, 12M, 12Y can each independently move between the liquid discharge positions 10K, 10C, 10M, 10Y and the cleaning positions 43K, 43C, 43M, 43Y.

[0046] <Control of the movement of the head unit in the width direction B in the width direction B> The motor 42 may be a stepping motor that rotates by an amount corresponding to a specified number of pulses. Further, the motor 42 may be a servo motor that detects the rotational position of the rotation shaft of the motor 42 by an encoder and can control the rotational position of the motor 42. Starting from a home position sensor that detects the home position of the head unit 12 (not shown), by controlling the rotation direction and rotation speed of the motor 42, in the image forming apparatus 100, the position of the head unit 12 in the width direction B can be positioned with high accuracy.

[0047] [Embodiment of the method for adjusting the liquid discharge head unit] Next, an embodiment of the method for adjusting a liquid ejection head unit according to the present invention will be described with reference to the flowchart shown in FIG. 12, FIGS. 7 and 8. The method for calibrating the height position of the head unit according to this embodiment includes a method for assembling and adjusting the initial position of the head unit 12 in the height direction and a method for measuring and adjusting the nozzle surface height.

[0048] The flowchart shown in FIG. 12 illustrates the procedure of the method for calibrating the height position of the head unit. Hereinafter, based on the flowchart illustrated in FIG. 12, description will be made with reference to FIGS. 7 and the like. In the following description, the calibration method for the head unit 12K will be described, but basically the same procedure is applicable to other head units 12.

[0049] First, the head unit 12K is retracted to the cleaning position 43 (S1201). At this time, the sheet S is removed.

[0050] Subsequently, as illustrated in FIG. 7, a laser displacement meter 102 as distance measuring means is installed between the upstream driven roller 17d and the downstream driven roller 17e (S1202). The laser displacement meter 102 is installed on a support shaft 22 (see FIG. 10) described later. The installation position of the laser displacement meter 102 is a position corresponding to the position of the elevating mechanism Z0, and the installation direction is such that the laser emission direction faces the conveyance surface. The distance measuring means is not limited to the method using a laser, and an eddy current type, a capacitance type, or other types can also be used. Note that the laser displacement meter 102 has a display unit 1021 for displaying the measured value. The display unit 1021 is configured to display the distance (measured distance Zt) from the laser emission end of the laser displacement meter 102 to the measurement object as a numerical value.

[0051] Also, as shown in FIG. 7, a calibration plate 101 is installed on the conveying surfaces of the driven roller 17d on the upstream side and the driven roller 17e on the downstream side so as to span between them (S1203). The calibration plate 101 as a conveying surface calibration member is made of a plate-like member with high strength and little distortion, such as steel, stainless steel, or aluminum alloy, and at least one side is finished with high-precision flatness. That is, the calibration plate 101 is composed of a material having a strength such that the change (deflection) due to its own weight is below the measurement resolution of the laser displacement meter 102 described later. Note that it is desirable that the flatness of one side (high-precision surface) of the calibration plate 101 is 0.01 mm or less and the surface roughness is polished to Ra 1.6 or less. That is, the flatness of the calibration plate 101 is such that the deflection due to its own weight occurring on the surface on the side placed on the conveying surfaces of the driven roller 17d on the upstream side and the driven roller 17e on the downstream side is below the measurement resolution of the laser displacement meter 102. As illustrated in FIG. 7, when the high-precision surface of the calibration plate 101 is temporarily placed on the conveying roller 17, the high-precision surface coincides with the conveying surface.

[0052] Subsequent to the conveying surface calibration member setting step of step S1203, as a calibration measurement step, the distance detected by the laser displacement meter 102 to the high-precision surface of the calibration plate 101 is measured, and the measured value is defined as the "first distance". This first distance is set as the zero point (S1204). Thereby, the zero point of the laser displacement meter 102 is set (calibrated). Then, the temporarily placed calibration plate 101 is removed (S1205).

[0053] It is also conceivable to calibrate the distance measuring means using the sheet S, but in the case of the sheet S, the surface smoothness is not good, such as the sheet S floating from the conveying surface or wrinkles occurring in a part of the sheet S. Therefore, by using the calibration plate 101, the problems in the case of using the sheet S can be solved.

[0054] Subsequently, the head unit 12K is moved from the cleaning position 43 to the liquid discharge position 10 so that the position of the nozzle surface of the liquid discharge head 18 faces the laser displacement meter 102 (S1206). Step S1206 results in the state illustrated in FIG. 8. Here, the laser displacement meter 102 has been adjusted with the conveyance surface as the zero point in step S1204.

[0055] Subsequent to step S1206, as a liquid discharge head unit measurement process, the distance to the nozzle surface is measured by the laser displacement meter 102 with the zero point set, and the measured value is displayed on the display unit 1021 (S1207). This measured value is defined as the "second distance". This second distance corresponds to the "nozzle surface height".

[0056] Subsequently, based on the second distance, the height position of the liquid discharge head 18 is adjusted by the lifting mechanism Z0 (S1208). As an example, the case where the design value of the nozzle surface height is 1.5 mm and the second measured value displayed on the display unit 1021 is 1.35 mm will be described. In this case, the lifting mechanism Z0 is operated so that the position of the liquid discharge head 18 is moved upward by 0.15 mm. By this operation, the position of the liquid discharge head 18 is adjusted and fixed based on the second distance measured by the laser displacement meter 102. The process of adjusting the height position of each liquid discharge head 18 using this lifting mechanism Z0 is defined as the lifting process.

[0057] Subsequently, the motor 42 is driven to retract the head unit 12 to the cleaning position 43 (S1209). Subsequently, the laser displacement meter 102 is removed (S1210). If the processes from step S1201 to step S1210 have not been executed for all the liquid discharge heads 18 of all colors (S1211: NO), the process returns to step S1201 to perform calibration on the unadjusted liquid discharge heads 18. If it has been executed for all the liquid discharge heads 18 of all colors (S1211: YES), the calibration of the height position of the liquid discharge head 18 is completed.

[0058] As described above, calibration is performed to determine the zero point based on the first distance. Then, the distance to the nozzle surface (second distance) is measured using the laser displacement meter 102 in the calibrated state. The height of the nozzle surface is adjusted using the elevating mechanism Z0 based on the measured second distance. As described above, by performing the above adjustment and fixing operations for each liquid ejection head 18, the initial positions of all the liquid ejection heads 18 in the height direction can be accurately assembled and adjusted.

[0059] Note that in the calibration process of the height position of the liquid ejection head 18 described in the above flowchart, the distance measuring means (laser displacement meter 102) is not permanently installed inside the image forming apparatus 100, but is installed at a predetermined position and orientation when the calibration process is executed and removed at the end. However, the image forming apparatus 100 may be provided with distance measuring means, for example, a laser displacement meter 102, inside.

[0060] When the laser displacement meter 102 is provided, in step S1202, instead of installing the laser displacement meter 102, a moving mechanism for moving the position of the laser displacement meter 102 may be operated to move the laser displacement meter 102 from the standby position to a predetermined measurement position. Further, in step S1210, the moving mechanism may be operated to move the laser displacement meter 102 to the standby position.

[0061] Also, when measuring at a plurality of locations, the moving mechanism may be operated each time to move the laser displacement meter 102 to the measurement position.

[0062] [Second Embodiment of Head Unit 12] FIG. 9 is a diagram for explaining a perspective configuration of another embodiment of the head unit 12. The head unit 12 includes four liquid ejection heads 18, a flat plate 12b for supporting them, and a base member 12a.

[0063] The flat plate 12b is manufactured with high precision, and since the four liquid ejection heads are fixed thereto, the nozzle surfaces of the four liquid ejection heads are ensured to be on the same plane. The flat plate 12b is provided with three independent elevating mechanisms Z0(a), Z0(b), and Z0(c).

[0064] Generally, a manual mechanism such as a feed screw or an eccentric pin is adopted for the elevating mechanism Z0, but an electric mechanism such as a servo motor or an actuator may also be used. By adjusting the three independent elevating mechanisms, the four head units can be lifted and lowered collectively. This configuration enables simplification of the adjustment work when the number of mounted head units is large (for example, 10). When assembling the image forming apparatus, the elevating mechanism Z0 is temporarily fixed at an appropriate position. This adjustment method is as described above.

[0065] Also, the head unit 12 is also provided with an elevating mechanism Z1 for lifting and lowering the whole, and as described above, even if the thickness of the sheet S is different, the gap between the nozzle surface and the sheet S can be kept constant by lifting and lowering the head unit 12.

[0066] Since the head unit 12 is held at both ends, it tends to bend due to its own weight. Therefore, as illustrated in FIG. 9, elevating mechanisms Z0 may be provided at three locations, i.e., both ends and substantially the center of the head unit 12, and laser displacement meters 102 may be installed at corresponding positions for measurement at three locations. The measurement at the three locations may be configured to use three laser displacement meters 102 for measurement at one time, or may be configured to use one laser displacement meter 102 for measurement in three separate times.

[0067] [Support portion of laser displacement meter 102] FIG. 10 is a perspective view showing a support portion of the laser displacement meter 102 according to the present embodiment. As shown in FIG. 10, a pair of side plates 21A and 21B are roller support members that support both ends (both ends or the vicinity thereof) of a plurality of transport rollers 17, and are arranged in parallel with a space therebetween. Each support shaft 22 that supports the laser displacement meter 102 is attached between the pair of side plates 21A and 21B. Fixing members 24 for fixing the support shaft 22 are provided on each of the pair of side plates 21A and 21B. That is, both ends of the support shaft 22 are attached to the side plates 21A and 21B via the fixing members 24, respectively.

[0068] [Mounting Structure of Laser Displacement Meter 102] FIG. 11 is a perspective view showing the mounting structure of the laser displacement meter 102 according to the present embodiment. As shown in FIG. 11, the bracket 104 is provided with three V-blocks 103 at the lower part, and is configured to be supported by a support shaft 22 (see FIG. 10) as an installation part. The laser displacement meter 102 is slidably supported on the support shaft 22. That is, the laser displacement meter 102 is configured to be slidably installed at a predetermined position without steps in the aforementioned B direction. Two laser displacement meters 102 are provided on the bracket 104. They are positioned so as to face the liquid ejection heads 18 on the upstream side and the downstream side in the transport direction (A direction) of the sheet S, respectively.

[0069] The image forming apparatus 100 according to the present embodiment described above can measure the height of any liquid ejection head 18 in order to accurately assemble and adjust the initial position in the height direction of the liquid ejection head 18.

[0070] Note that, in the image forming apparatus 100, in measuring the height of the liquid ejection head 18, the initial position in the height direction of the liquid ejection head 18 can be accurately assembled and adjusted by raising and lowering the liquid ejection head 18 according to the distance between the calibration plate 101 and the liquid ejection head 18.

[0071] Note that the above configuration is an example. For example, the bracket 104 may have the same width as the sheet S, and a laser displacement meter may be installed at a necessary part.

[0072] Also, the laser displacement meter may be installed on the image forming apparatus, or may be attached only when assembling and adjusting the initial position in the height direction of the head unit. Generally, it is necessary to assemble and adjust the initial position when the liquid ejection head is shipped from the factory or when the liquid ejection head is replaced in the market.

[0073] Note that the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist thereof. All technical matters included in the technical idea described in the claims are the subject of the present invention. The above embodiments show preferred examples, but those skilled in the art can realize various modified examples from the disclosed content. Such modified examples are also included in the technical scope described in the claims.

[0074] The content of the present invention is as follows, for example. <1> A liquid ejection device that ejects liquid from a liquid ejection head unit onto an object to be conveyed, a pair of conveyance guide members installed upstream and downstream in the conveyance direction of the object to be conveyed with respect to the liquid ejection head unit; an installation part for installing distance measurement means at a position facing the liquid ejection head unit in the ejection direction in which the liquid ejection head unit ejects the liquid; lifting means for lifting and lowering the liquid ejection head unit according to a first distance to the conveyance surface calibration member measured by the distance measurement means with the conveyance surface calibration member installed on the conveyance guide member instead of the object to be conveyed, and a second distance to the liquid ejection head unit measured by the distance measurement means without installing the conveyance surface calibration member; A liquid ejection device, comprising: <2> A liquid ejection device that ejects liquid from a liquid ejection head unit onto an object to be conveyed, a pair of conveyance guide members installed upstream and downstream in the conveyance direction of the object to be conveyed with respect to the liquid ejection head unit, distance measuring means installed at a position facing the liquid ejection head unit in the ejection direction in which the liquid ejection head unit ejects the liquid, with a conveyance surface calibration member installed on the conveyance guide member instead of the object to be conveyed, a first distance to the conveyance surface calibration member measured by the distance measuring means, and a second distance to the liquid ejection head unit measured by the distance measuring means in a state where the conveyance surface calibration member is not installed, and lifting means for lifting and lowering the liquid ejection head unit according to the above, A liquid ejection device characterized by comprising the above. <3> The conveyance surface calibration member is a plate-like member made of a material with a strength such that the change due to its own weight is equal to or less than the resolution of the measurement by the distance measuring means, and the deflection due to its own weight of the surface on the side placed on the conveyance guide member is equal to or less than the resolution of the measurement. The liquid ejection device according to <1> or <2> above. <4> The installation position of the distance measuring means is any one of a position corresponding to the position of the lifting means, both ends of the liquid ejection head unit, or substantially the center of the liquid ejection head unit. The liquid ejection device according to any one of <1> to <3> above. <5> An image forming apparatus having a conveyance unit that conveys a sheet-like object to be conveyed and an image forming unit that forms an image on the object to be conveyed, The image forming unit has a liquid ejection head unit, and is the liquid ejection device according to any one of <1> to <4> above, in which the liquid ejection head unit ejects liquid onto the object to be conveyed. This is an image forming apparatus characterized by this. <6> A liquid ejection head unit adjustment method for adjusting the distance between the liquid ejection head unit and the object to be conveyed, A conveyance surface calibration member setting step of installing a conveyance surface calibration member on a pair of conveyance guide members installed upstream and downstream in the conveyance direction of the object to be conveyed, in place of the object to be conveyed, with respect to the liquid discharge head unit; A calibration measurement step of measuring the distance to the conveyance surface calibration member by distance measurement means installed at a position facing the liquid discharge head unit; A liquid discharge head unit measurement step of measuring the distance to the nozzle surface of the liquid discharge head unit with the conveyance surface calibration member removed; A lifting step of lifting and lowering the liquid discharge head unit by lifting means according to the distances between the conveyance surface calibration member and the liquid discharge head unit measured in the calibration measurement step and the liquid discharge head unit measurement step; A liquid discharge head unit adjustment method characterized by comprising the above steps. <7> A liquid discharge head unit adjustment method for adjusting the distance between a liquid discharge head unit and an object to be conveyed, the method comprising: A conveyance surface calibration member setting step of installing a conveyance surface calibration member on a pair of conveyance guide members installed upstream and downstream in the conveyance direction of the object to be conveyed, in place of the object to be conveyed, with respect to the liquid discharge head unit; An installation step of installing position distance measurement means facing the liquid discharge head unit; A calibration measurement step of measuring the distance to the conveyance surface calibration member by the installed distance measurement means; A liquid discharge head unit measurement step of measuring the distance to the nozzle surface of the liquid discharge head unit with the conveyance surface calibration member removed; A lifting step of lifting and lowering the liquid discharge head unit by lifting means according to the distances between the conveyance surface calibration member and the liquid discharge head unit measured in the calibration measurement step and the liquid discharge head unit measurement step; A liquid discharge head unit adjustment method characterized by comprising the above steps.

Explanation of Reference Numerals

[0075] 8: Conveyor section 9: Control section 10: Liquid ejection position 11: Supply roller 12: Head unit 12a: Base member 12b: Flat plate 13: Heating drum 15: Heating drum 16: Recovery roller 17: Conveyor roller 18: Liquid ejection head 19: Nozzle 20: Conveyor device 50: Position changing mechanism 100: Image forming apparatus 101: Calibration plate 102: Laser displacement meter 103: V-block 104: Bracket S: Sheet Z0: Lifting mechanism Z1: Lifting mechanism

Prior art documents

Patent documents

[0076]

Patent Document 1

Claims

1. A liquid ejection device that ejects liquid onto an object to be conveyed from a liquid ejection head unit, comprising: a pair of conveyance guide members installed upstream and downstream of the liquid ejection head unit in the conveyance direction of the object to be conveyed; an installation portion for installing distance measurement means at a position facing the liquid ejection head unit in the ejection direction in which the liquid ejection head unit ejects the liquid; lifting means for lifting and lowering the liquid ejection head unit according to a first distance to the conveyance surface calibration member measured by the distance measurement means with the conveyance surface calibration member installed on the conveyance guide member in place of the object to be conveyed, and a second distance to the liquid ejection head unit measured by the distance measurement means without the conveyance surface calibration member installed; A liquid ejection device, characterized by comprising the above.

2. A liquid ejection device that ejects liquid onto an object to be conveyed from a liquid ejection head unit, comprising: a pair of conveyance guide members installed upstream and downstream of the liquid ejection head unit in the conveyance direction of the object to be conveyed; distance measurement means installed at a position facing the liquid ejection head unit in the ejection direction in which the liquid ejection head unit ejects the liquid; lifting means for lifting and lowering the liquid ejection head unit according to a first distance to the conveyance surface calibration member measured by the distance measurement means with the conveyance surface calibration member installed on the conveyance guide member in place of the object to be conveyed, and a second distance to the liquid ejection head unit measured by the distance measurement means without the conveyance surface calibration member installed; A liquid ejection device, characterized by comprising the above.

3. The conveyance surface calibration member is a plate-like member made of a material with a strength such that the change due to its own weight is equal to or less than the resolution of the measurement by the distance measurement means, and the deflection due to its own weight of the surface on the side placed on the conveyance guide member is equal to or less than the resolution of the measurement. The liquid ejection device according to Claim 1 or 2.

4. The installation position of the distance measurement means is any one of a position corresponding to the position of the lifting means, both ends of the liquid ejection head unit, or substantially the center of the liquid ejection head unit. The liquid ejection device according to Claim 1.

5. An image forming apparatus having a conveyance unit that conveys a sheet-like object to be conveyed and an image forming unit that forms an image on the object to be conveyed. The image forming unit has a liquid ejection head unit, and the liquid ejection head unit ejects liquid onto an object to be conveyed, which is the liquid ejection device according to claim 1. An image forming apparatus characterized by this.

6. A method for adjusting the distance of a liquid ejection head unit with respect to an object to be conveyed, comprising: a conveyance surface calibration member setting step of installing a conveyance surface calibration member in place of the object to be conveyed on a pair of conveyance guide members installed upstream and downstream in the conveyance direction of the object to be conveyed with respect to the liquid ejection head unit; a calibration measurement step of measuring the distance to the conveyance surface calibration member by distance measurement means installed at a position facing the liquid ejection head unit; a liquid ejection head unit measurement step of measuring the distance to the nozzle surface of the liquid ejection head unit with the conveyance surface calibration member removed; a lifting step of lifting and lowering the liquid ejection head unit by lifting means according to the distances between the conveyance surface calibration member and the liquid ejection head unit measured in the calibration measurement step and the liquid ejection head unit measurement step; A method for adjusting a liquid ejection head unit, characterized by comprising the above steps.

7. A method for adjusting the distance of a liquid ejection head unit with respect to an object to be conveyed, comprising: a conveyance surface calibration member setting step of installing a conveyance surface calibration member in place of the object to be conveyed on a pair of conveyance guide members installed upstream and downstream of the object to be conveyed with respect to the liquid ejection head unit; an installation step of installing distance measurement means at a position facing the liquid ejection head unit; a calibration measurement step of measuring the distance to the conveyance surface calibration member by the installed distance measurement means; a liquid ejection head unit measurement step of measuring the distance to the nozzle surface of the liquid ejection head unit with the conveyance surface calibration member removed; a lifting step of lifting and lowering the liquid ejection head unit by lifting means according to the distances between the conveyance surface calibration member and the liquid ejection head unit measured in the calibration measurement step and the liquid ejection head unit measurement step; A method for adjusting a liquid ejection head unit, characterized by comprising the above steps.

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