Recording-head position adjustment mechanism and image forming apparatus incorporating same

A recording-head position adjustment mechanism includes a beam to suspend a recording head that discharges droplets so that the recording head is drawable out in a predetermined direction; a first supporter disposed at one end of the beam in the predetermined direction and having a support shaft to support the beam; a second supporter disposed at another end of the beam in the predetermined direction with the beam interposed between the first supporter and the second supporter. The second supporter is attached with an adjuster via which the second supporter supports the beam. The adjuster includes a coarse-adjustment shaft member and a fine-adjustment shaft member that are manually rotatable independent of each other. The coarse-adjustment shaft member coarsely adjusts a rotation angle of the beam at which the beam rotates around the support shaft by manual rotation. The fine-adjustment shaft member finely adjusts the rotation angle of the beam.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2017-164092, filed on Aug. 29, 2017 in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

In an image forming apparatus, such as an inkjet printer, a technique is widely known that adjusts the positions of recording heads (printing modules) to form a good image without positional deviation.

In such an image forming apparatus, for example, recording heads (printing modules) for a plurality of colors are arranged so as to face a sheet conveyed by a conveyor. The recording heads for of the plurality of colors discharge liquid droplets toward the conveyed sheet to form a desired color image on the sheet.

SUMMARY

In an aspect of the present disclosure, there is provided a recording-head position adjustment mechanism that includes a beam, a first supporter, and a second supporter. The beam suspends a recording head that discharges droplets so that the recording head is drawable out in a predetermined direction. The first supporter is disposed at one end of the beam in the predetermined direction and has a support shaft to support the beam so that the beam is rotatable around the support shaft, the support shaft standing in a direction that is perpendicular to the predetermined direction and in which the beam extends. The second supporter is disposed at another end of the beam in the predetermined direction with the beam interposed between the first supporter and the second supporter. The second supporter is attached with an adjuster via which the second supporter supports the beam. The adjuster includes a coarse-adjustment shaft member and a fine-adjustment shaft member that are manually rotatable independent of each other. The coarse-adjustment shaft member is configured to coarsely adjust a rotation angle of the beam at which the beam rotates around the support shaft by manual rotation. The fine-adjustment shaft member is configured to finely adjust the rotation angle of the beam at which the beam rotates around the support shaft by manual rotation.

In another aspect of the present disclosure, there is provided an image forming apparatus that includes the recording-head position adjustment mechanism.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure are described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description thereof are simplified or omitted as appropriate.

First, with reference toFIG. 1, the overall configuration and operation of an image forming apparatus1according to an embodiment of the present disclosure is described below. InFIG. 1, an image forming apparatus1according to the present embodiment is illustrated as an inkjet printer. The image forming apparatus1includes a conveyance drum2to convey a sheet P, a sheet feed tray3on which sheets P to be printed are stacked, and clips5to hold the sheet P on the conveyance drum2. The image forming apparatus1further includes a separator6to separate the sheet P from the conveyance drum2, a conveyance belt7to convey the sheet P separated from the conveyance drum2, and an ejection tray8onto which the printed sheet P is ejected and stacked. The image forming apparatus1further includes recording heads (printing modules)10Y,10M,10C,10K,10S1, and10S2in which image forming units for printing, e.g., letters and images by an ink jet method are unitized, beams20to suspend the recording heads10Y,10M,10C,10K,10S1, and10S2, and a base frame30to hold the beams20and supporters41and42.

Here, as illustrated inFIG. 1, the image forming apparatus1according to the present embodiment forms a color image, and includes the recording head10K for black, the recording heads10Y,10M, and10C for three colors (yellow, magenta, cyan), and the recording heads10S1and10S2for coating (special color). The six recording heads10Y,10M,10C,10K,10S1, and10S2are juxtaposed so as to face the conveyance drum2along the direction of rotation of the conveyance drum2. Since the six recording heads10Y,10M,10C,10K,10S1, and10S2have substantially the same structure except for different colors (types) of ink used for printing, the suffixes (Y, M, C, K, S1, and S2) attached to the reference numeral10of the recording heads may be omitted below as illustrated inFIGS. 2 and 4. As illustrated inFIG. 2, a main part of the recording head10includes a piezoelectric actuator, a thermal actuator, or the like, and includes, for example, nozzles10ato discharge ink as droplets, an ink tank10bfilled with ink, and a control board (controller).

The operation of the image forming apparatus1is briefly described with reference toFIG. 1. First, when a print instruction is input from, e.g., a personal computer to the controller of the image forming apparatus1together with image data, the sheet P is fed from the sheet feed tray3by a sheet feed roller. The sheet P fed from the sheet feed tray3is conveyed toward the conveyance drum2by a conveyance roller4. On the other hand, in the recording heads10Y,10M,10C,10K,10S1, and10S2of respective colors, input image data are converted into writing data of respective colors. The sheet P conveyed to the conveyance drum2is positioned on the conveyance drum2in a state of being held by the clips5, and is conveyed along the counterclockwise rotation of the conveyance drum2. Based on writing data, the recording heads10Y,10M,10C,10K,10S1, and10S2of the respective colors sequentially discharge inks as droplets onto the sheet P, which is conveyed in a direction indicated by arrow R1inFIG. 1by the rotation of the conveyance drum2, to form a desired image on the sheet P. The sheet P, on which the desired image has been formed, is separated from the conveyance drum2by the separator6. The sheet P separated from the conveyance drum2is conveyed by the conveyance belt7and ejected onto the ejection tray8.

Hereinafter, a recording-head position adjustment mechanism100to adjust the position of the recording head10for discharging ink (liquid droplets) in the image forming apparatus1thus configured is described below. As illustrated in, e.g.,FIGS. 2 and 4, the image forming apparatus1includes beams20to suspend the recording head10in a state in which the recording head10can be drawn out in a predetermined direction (hereinafter, +Y direction) indicated by arrow Y inFIG. 4. That is, the recording head10is detachably (exchangeably) installed with respect to the image forming apparatus1so that the recording head10can be drawn out from the image forming apparatus1in the +Y direction or installed to the image forming apparatus1in a direction (hereinafter, −Y direction) opposite the +Y direction. When ink stored in the ink tank10bbecomes empty, the existing recording head10is drawn out, and a new recording head10is installed for replacement.

Specifically, the beams20are a pair of beams arranged to sandwich the recording head10in a substantially horizontal direction. As illustrated inFIG. 1, one beam20(excluding the beams20on the most upstream side and the most downstream side in a conveyance direction of the sheet P) is configured to suspend one end side of one of adjacent recording heads10and an opposite end side of the other of the adjacent recording heads10. In addition, each beam20of the pair of beams20is provided with rollers21and22. Specifically, as illustrated inFIG. 2, in the one beam20, two first rollers21are arranged at positions apart from each other in the vertical direction on one end side of the one beam20and two second rollers22are arranged at positions apart from each other in the vertical direction at the opposite end side of the one beam20. The first roller21has a V-shaped groove formed in the circumferential direction. The second roller22is formed in a substantially columnar shape. As illustrated inFIG. 4, the first rollers21are disposed at two positions apart from each other in a drawing direction (+Y direction), and the second rollers22The recording head10is provided with first rail portions11and second rail portions12to engage with the first rollers21and the second rollers22of the beam20. Specifically, as illustrated inFIG. 2, in the recording head10, two, upper and lower, second rail portions12of substantially planar shape to engage with the second rollers22of substantially-columnar shape are disposed on one end side of the recording head10in the conveyance direction of the sheet P. Two, upper and lower, first rail portions11(having a V-shaped protrusion) to engage with the first rollers21having the V-shaped grooves are disposed on the opposite end side of the recording head10in the conveyance direction of the sheet P. The first rail portions11and the second rail portions12are formed so as to extend in the drawing direction (+Y direction). As the first rollers21and the second rollers22relatively move while rotating on the first rail portions11and the second rail portions12, the recording head10is pulled out in a predetermined direction (+Y direction).

With such a configuration, the recording head10is attached to and detached from the image forming apparatus1while the position of the recording head10in ±X directions is restricted by the first rollers21having the V-shaped grooves. Accordingly, attaching and detaching operations of the recording head10can be smoothly performed without causing failures, such as damages to the recording head10by interference with another member in the attachment and detachment operations. In the present embodiment, the V-shaped grooves formed in the first rollers21are engaged with the V-shaped protrusions formed in the first rail portions11, to restrict the position of the recording head10in the ±X directions. However, the shape of the groove provided in the first roller21and the shape of the protrusion provided in the first rail portion11are not limited to the V-shape but may be any other suitable shape that can meet such a function, for example, a W-shape or a shape in which three or more V shapes are arranged.

Here, as illustrated inFIGS. 2 to 4and so on, in the present embodiment, the beam20is held by a housing (the base frame30) of the image forming apparatus1via two supporters (the first supporter41and the second supporter42). As illustrated inFIG. 3and so on, the first supporter41supports the beam20at one end side (the −Y direction side and the right side inFIG. 3) in the predetermined direction so that the beam20is rotatable around support shafts41aand41b. The support shafts41aand41bstand in directions (±Z directions) that are perpendicular to the predetermined direction and the beam20extends. Specifically, the first support shaft41ais formed to stand up in the +Z direction below the first supporter41. The second support shaft41bstands up in the −Z direction above the first supporter41. The beam20has a hole portion20afitted to the first support shaft41aand a hole portion20bfitted to the second support shaft41b. With such a configuration, the beam20is supported by the first supporter41so as to be rotatable around a rotation axis A. The configurations of the support shaft and the hole portions are not limited to the above-described configurations of the present embodiment, but may be any other suitable configurations.

The second supporter42is disposed so as to sandwich the beam20between the first supporter41and the second supporter42. The second supporter42supports the beam20with adjusters50on the opposite end side (the +Y direction side and the left side inFIG. 3) in the predetermined direction. As illustrated inFIG. 5, the adjuster50includes a coarse-adjustment shaft member51and a fine-adjustment shaft member52that are manually rotatable independent of each other. The coarse-adjustment shaft member51is manually rotated to coarsely adjust the angle at which the beam20rotates around the support shafts41aand41b. The fine-adjustment shaft member52is manually rotated to finely adjust the angle at which the beam20rotates around the support shafts41aand41b. In the present embodiment, as illustrated inFIG. 3, the two adjusters50are disposed at positions apart from each other in the ±Z directions.

Such a configuration can efficiently, accurately, and easily adjust the position of the recording head10suspended on the beam20(the perpendicularity of the recording head10with respect to the conveyance direction of the sheet P). That is, in adjusting the perpendicularity of the recording head10with respect to the conveyance direction of the sheet P, first, the coarse-adjustment shaft member51is manually rotated to coarsely adjust the beam20so that the rotation angle of the beam20roughly approaches a target angle. Then, from such a state, the fine-adjustment shaft member52is manually rotated to perform fine adjustment so that the rotation angle of the beam20accurately matches the target angle. Accordingly, the adjustment work can be performed more efficiently, accurately, and easily than the case in which only the coarse adjustment is performed or the case in which only the fine adjustment is performed. The above-described accurate adjustment of the position of the recording head10allows an excellent image to be formed on the sheet P without positional deviation.

As illustrated in, e.g.,FIGS. 5 and 6, in the present embodiment, the coarse-adjustment shaft member51includes a first eccentric boss51bhaving a large amount of eccentricity with respect to a rotation center axis W (indicated by a broken line inFIG. 6) of the adjuster50. The fine-adjustment shaft member52includes a second eccentric boss52chaving a small eccentric amount with respect to the rotation center axis W of the adjuster50. As a result, even if the coarse-adjustment shaft member51and the fine-adjustment shaft member52are manually rotated by the same rotation angle, the coarse-adjustment shaft member51can more rotate the beam20and the fine-adjustment shaft member52can less rotate the beam20. Accordingly, the adjustment of the rotation angle of the beam20(the position adjustment of the recording head10) can be efficiently, accurately, and easily performed. Specifically, in the present embodiment, the eccentric amount of the first eccentric boss51bof the coarse-adjustment shaft member51is set to 2 mm. When the coarse-adjustment shaft member51is rotated by 1°, the beam20is moved by about 0.01 mm in the ±X directions. On the other hand, the amount of eccentricity of the second eccentric boss52cof the fine-adjustment shaft member52is set to 0.2 mm. When the fine-adjustment shaft member52is rotated by 1°, the beam20is moved by about 0.001 mm in the ±X directions.

More specifically, as illustrated inFIGS. 5 and 6, the coarse-adjustment shaft member51includes a first operation portion51a, the first eccentric boss51b, and a first through hole51c. The first through hole51cis formed so that the fine-adjustment shaft member52(a boss52b) is rotatably fitted to the first through hole51cand the first through hole51cis not eccentric with respect to the rotational center axis W. The first eccentric boss51bis eccentric with respect to the first through hole51c. The first eccentric boss51bfits into a fitting hole42a, which is a cylindrical through hole, formed in the second supporter42. As illustrated inFIG. 5, the first operation portion51ais exposed so as to be manually operated in a state of being assembled with the apparatus. As illustrated inFIGS. 8 and 9A, the first operation portion51ais formed in a hexagonal nut shape. The first operation portion51ais formed with an outer diameter greater than an outer diameter of the first eccentric boss51b. In the present embodiment, the first operation portion51ais supposed to be manually rotated using a tool, such as a spanner.

On the other hand, the fine-adjustment shaft member52includes a second operation portion52a, the boss52b, the second eccentric boss52c, and a second through hole52d. The boss52bis rotatably fitted in the first through hole51cof the coarse-adjustment shaft member51, and is formed so as not to be eccentric with respect to the rotation center axis W. The second eccentric boss52cis formed to be eccentric with respect to the boss52b. The second eccentric boss52cis fitted into a fitting elongated hole20d(see alsoFIG. 7A) formed in the beam20so as to be rotatable and movable in the ±Z directions. Setting such a fitting hole portion, into which the second eccentric boss52cfits, as the fitting elongated hole20dhaving the ±Z directions as the longitudinal direction can disperse the force applied in the ±Z direction when the adjuster50is manually rotated. The second eccentric boss52cis formed with an outer diameter smaller than an outer diameter of the boss52b. As illustrated inFIG. 5, the second operation portion52ais disposed at a position adjacent to the first operation portion51ain a state of being assembled to the apparatus, and is exposed so as to be manually operated. As illustrated inFIG. 9A, the second operation portion52ais formed in a hexagonal nut shape. The second operation portion52ais formed with an outer diameter larger than an outer diameter of the boss52b. In the present embodiment, the second operation portion52ais supposed to be manually rotated using a tool, such as a spanner. The second through hole52dis formed so that a shaft portion54bof a second locking member54is inserted through the second through hole52d.

Here, the recording head adjuster in the present embodiment includes a first locking member53and a second locking member54. InFIGS. 5 and 8, the first locking member53locks the coarse-adjustment shaft member51so as not to rotate after the turning angle of the beam20is coarsely adjusted. More specifically, the first locking member53includes a locking portion53aand an elongated hole portion53b. The locking portion53ais formed so as to sandwich the first operation portion51ain accordance with the nut shape of the first operation portion51aof the coarse-adjustment shaft member51. The elongated hole portion53bis formed so that the first locking member53can be rotated together with the first operation portion51ain a state in which a screw60is loosened.

As described above, when the adjustment of the rotation angle of the beam20(the position adjustment of the recording head10) is performed, first, the coarse-adjustment shaft member51is manually rotated to perform coarse adjustment. Even if the fine-adjustment shaft member52also rotates together with the coarse-adjustment shaft member51at that time, there is no big influence in the adjustment work. However, in a case in which fine adjustment is performed after coarse adjustment, fine adjustment could not be performed if the coarse-adjustment shaft member51rotates together with the fine-adjustment shaft member52. Therefore, in the fine adjustment, the first locking member53restricts the coarse-adjustment shaft member51so as not to rotate. Specifically, during coarse adjustment, the first locking member53is rotated together with the first operation portion51ain a state in which the screw60is loosened. After the coarse adjustment ends, the screw60is tightly screwed to a female screw portion of the second supporter42. Thus, the first locking member53is fixed, thus restricting rotation of the coarse-adjustment shaft member51.

As illustrated inFIGS. 5 and 6, the second locking member54locks the fine-adjustment shaft member52so as not to rotate after the rotation angle of the beam20is finely adjusted in a state in which the coarse-adjustment shaft member51is locked with the first locking member53. Specifically, the second locking member54has a head portion54aand a shaft portion54bincluding a male screw portion54b1. Until the fine adjustment with the fine-adjustment shaft member52ends, the male screw portion54b1of the second locking member54is loosely screwed against a female screw portion20e(seeFIG. 7A) of the beam20. To prevent the fine-adjustment shaft member52(and the coarse-adjustment shaft member51) from freely rotating after the fine adjustment with the fine-adjustment shaft member52ends, the male screw portion54b1of the second locking member54is firmly screwed to the female screw portion20eof the beam20. Thus, the first operation portion51aand the second operation portion52aare sandwiched between the head portion54aof the second locking member54and the second supporter42.

Here, in the present embodiment, as illustrated inFIG. 9A(andFIG. 5), the first operation portion51aand the second operation portion52ahave nut-shaped outer peripheral surfaces of different outer diameters from each other. Specifically, the outer diameter D1of the first operation portion51ais greater than the outer diameter D2of the second operation portion52a(D1>D2). Such a configuration facilitates visual distinction between the first operation portion51aand the second operation portion52aand reduces a failure that the coarse adjustment and the fine adjustment are mistaken for each other.

In the present embodiment, as illustrated inFIG. 9B, the first operation portion51aand the second operation portion52amay have nut-shaped outer peripheral surfaces having the same outer diameter D1. In such a case, the first operation portion51aand the second operation portion52acan be manually rotated using the same tool (spanner), thus enhancing the efficiency of the adjustment operation.

Further, in the present embodiment, the recording head10is opposed to the sheet P conveyed in the +X direction, which is the direction perpendicular to the predetermined direction in which the recording head10is drawn out. The recording head10is configured to be drawn from the side of the first supporter41to the side of the second supporter42. Accordingly, the position adjustment of the beam20(the recording head10) can be performed on the front side in the operation direction in which the recording head10is attached or detached. Therefore, the workability of the position adjustment with the adjuster50is enhanced as compared with the case in which the position adjustment is performed on the back side in the operation direction.

Here, as illustrated inFIGS. 3 and 7B, in the present embodiment, the beam20has an elongated hole20cextended in a longitudinal direction along a direction (±X directions) in which the beam20rotates around the support shafts41aand41b. The elongated hole20cis disposed at a position between the two adjusters50in the Z direction. The second supporter42has a pin42cstanding upright in the −Y direction, to fit in the elongated hole20c. With such a configuration, even when the position of the beam20is adjusted by the adjusters50, the beam20is supported by the second supporter42via the pin42c. That is, the pin42cfunctions as a member to receive the weight of the beam20. Such a configuration can reduce a failure that the second supporter42is deformed or the adjustment work is hampered by the weight of the beam20in the adjustment of the beam20. Further, the longitudinal direction of the elongated hole20c, into which the pin42cfits, is along the ±X directions. Such a configuration prevents the fitting of the pin42cinto the elongated hole20cfrom hampering the rotation of the beam20caused by the operation of the adjuster50. In the present embodiment, the pin42cis disposed directly on the second supporter42. In some embodiments, another component having the pin42cmay be fixed on the second supporter42by, e.g., screw fastening.

As described above, in the recording-head position adjustment mechanism100(of the image forming apparatus1) according to the present embodiment, the beam20that suspends the recording head10in a drawable manner includes the first supporter41at one end side and the second supporter42at the other end side. The first supporter41supports the beam20so that the beam20is rotatable around the support shafts41aand41b. The second supporter42supports the beam20via the adjusters50. The adjuster50includes the coarse-adjustment shaft member51and the fine-adjustment shaft member52that can be manually rotated independent of each other. The coarse-adjustment shaft member51is configured to coarsely adjust the angle at which the beam20rotates around the support shafts41aand41bby manual rotation. The fine-adjustment shaft member52is configured to finely adjust the angle at which the beam20rotates about the support shafts41aand41bby manual rotation. Thus, the position of the recording head10can be efficiently and easily adjusted with high accuracy.

In the present embodiment, the image forming apparatus1includes the six recording heads10Y,10M,10C,10K,10S1, and10S2. Note that the number of recording heads is limited to six but may be any suitable number. Even in such cases, the same effects as the effects of the present embodiment can be obtained.

Note that embodiments of the present invention are not limited to the above-described embodiments and it is apparent that the above-described embodiments can be appropriately modified within the scope of the technical idea of the present invention in addition to what is suggested in the above-described embodiments. Further, the number, position, shape, and so on of components are not limited to those of the present embodiment, and may be the number, position, shape, and so on that are suitable for implementing the present invention.