This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-024388, filed Jan. 31, 2005, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus including a line head which realizes high-speed image formation.
2. Description of the Related Art
In general, there is a printer including a line head, in which a plurality of injection nozzles which eject inks of a black color or a plurality of colors are arranged in a linear state, thereby realizing high-speed image formation. In this line head, a plurality of injection nozzles are arranged face to face over a width of a recording medium to be carried so that an image can be formed along an overall width of the recording medium when the recording medium is transmitted only once. As the line head, there is also a type constituted of one long head which is a so-called line head, but such a head has a bad production yield and a problem of an increase in cost of the head.
As a countermeasure for such a problem, there has been proposed a technology which alternately aligns a plurality of small heads having a relatively low manufacturing cost in a width direction of a recording medium in such a manner that a gap is not generated between ends of these small heads, thereby virtually forming a line head. In Jpn. Pat. Appln. KOKAI Publication No. 2001-322292, small head chips are alternately aligned and arranged (a zigzag arrangement) in a direction orthogonal to a conveying direction of a recording medium and they are covered with a common nozzle plate, thereby constituting a line head. Since the short head chips are connected, a yield of each head chip is improved. Further, the head chips are covered with the common nozzle plate, there is an advantage that a positional accuracy between the respective chips can be determined by a nozzle hole position provided in the nozzle plate. However, when there is a nozzle which cannot eject an ink because of damage or the like caused due to clogging or jam of the nozzle after incorporation in an image forming apparatus, the entire line head must be replaced. Furthermore, the ink has a cartridge configuration which is thrown away together with the line head, and hence the head must be also replaced when the ink is run out. Moreover, Jpn. Pat. Appln. KOKAI Publication No. 2004-306261 discloses an example in which a plurality of heads are alternately aligned and arranged in a zigzag pattern along a direction orthogonal to a conveying direction of a recording medium instead of a line head having a length equal to or larger than a width of the recording medium.
In the above-described image forming apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-322292, the line head is a module having an integral configuration, and the entire line head must be replaced when there is a nozzle which cannot eject an ink because of damage or the like caused due to clogging or jam of the nozzle after incorporation in a printer. Additionally, the ink has the cartridge configuration which is thrown away together with the line head, and hence the head must be also replaced when the ink is run out.
Further, Jpn. Pat. Appln. KOKAI Publication No. 2004-306261 discloses a configuration in which the individual heads are arranged in a zigzag pattern and there are many tubes which supply an ink to the individual heads or control wiring lines which supply an electrical signal, which results in complicated attachment/detachment or adjustment of each head. This publication does not disclose this attachment/detachment or adjustment at all. Furthermore, an ink supply path through which the ink is supplied to a eject opening formed in each head block is not illustrated, and its suggestion is not described either.
According to the present invention, there is provided an image forming apparatus including a recording head portion having a configuration in which a plurality of small heads are alternately arranged in a width direction of a recording medium to have an overlap at each end portion thereof so that a virtual long line head is constituted, and each head can be individually replaced by easy attachment/detachment.
According to the present invention, there is provided an image forming apparatus which has at least one head module group in which a plurality of inkjet type head modules are arranged in a direction substantially orthogonal to a recording medium conveying direction, and has an ink path through which an ink is supplied to the head modules, thereby recording an image on the recording medium, wherein the ink path supplies the ink to the plurality of arranged head modules from one of an upstream side and a downstream side of the recording medium conveying direction.
Furthermore, according to the present invention, there is provided an image forming apparatus which has at least one head module group in which ink head type head modules are arranged in a direction substantially orthogonal to a recording medium conveying direction, and has an ink path through which an ink is supplied to the head modules, thereby forming an image on the recording medium, wherein a part of the common ink path through which the ink is supplied to all the head modules constituting the at least one head module group on one of an upstream side and a downstream side of the recording medium conveying direction is arranged in parallel with the head module group.
Embodiments according to the present invention will now be described hereinafter in detail with reference to the accompanying drawings.
FIGS. 1 to 4 show an appearance configuration of a recording head portion mounted in an image forming apparatus according to a first embodiment of the present invention.
First,
The piezo plates 15 and 16 and the piezo plate 17 have substantially equal degrees of hardness and are made of piezo-electric materials having different electrostatic capacities and piezoelectric constants. In this example, the piezo plates 15 and 16 are set to have a larger piezoelectric constant and electrostatic capacity than the piezo plate 17.
A configuration of a base 2 will now be described with reference to
The piezo structure 18 is attached on both surfaces with the piezo plate 15 side being determined as an outer side while being pressed against the respective bonding reference portions 2c and 2b. A plurality of holes 2d through which the piezo structure 18 attached on both sides are connected and an ink is supplied are formed in a bottom surface of the bonding reference portion 2a. Furthermore, each hole with a bottom 17a is provided to the piezo plate 17 of the piezo structure 18 in such a manner that a position of the hole 17a matches with the hole 2d. A depth of the hole with a bottom 17a is formed in such a manner that it does not deeply pierces beyond at least the surface of the piezo 16.
In this piezo structure 18, such grooves 19 as shown in
Then, as shown in
Next,
After forming these electrodes, as shown in
These covers 20 and 21 are positioned and bonded with respect to open ends 20c and 22c of each groove 16 as shown in
Side surfaces 20b and 21b of the concave portions 20a of the covers 20 and 21 are set at positions apart from the groove open ends 20c and 21c to which a later-described nozzle plate 1 is bonded by N=approximately 1 mm. On the bottom surface of the groove 19, at least a part facing a flat surface portion where the concave portion of the cover is not formed is flat and cut in such a manner that a radius R is not formed by the diamond cutter. A range having a width of 80 μm, a depth of 300 μm and a length of 1 mm surrounded by each groove 19 and the covers 20 and 21 serves as a channel used as a drive portion to eject an ink.
Any other groove portion faces the concave portions 20a and 21a of the covers 20 and 21, and forms a larger space than the channel. This portion functions as a common ink chamber through which an ink is supplied to each channel. A depth of each concave portion 20a or 21a is approximately 0.5 mm. In case of the cover 20a, a distance to the filter 22 facing each groove 19 is a depth of 0.5 mm. A thickness of the cover 20 is 2 mm, and a thickness of the cover 21 is 1.5 mm.
Additionally, in this embodiment, a thermal expansion coefficient of PZT as a material of the piezo structure 18 is substantially equal to that of aluminum nitride as a material of the base 2. Aluminum nitride is hard and has stronger characteristics than PZT in terms of strength. When these different types of materials are attached, aluminum nitride reinforces strength of the piezo structures against an external force, and alleviates a stress of the fragile piezo structures due to a thermal expansion difference at the time of thermal expansion.
Further, the thermal expansion coefficients of these materials are substantial equal to each other. PZT has the thermal expansion coefficient of approximately 5×10−6/° C., and aluminum nitride has the thermal expansion coefficient of approximately 3.5×10−6/° C.
Such a difference results in a small thermal expansion difference of 2.7 μm with a temperature difference of 30° C. even in the piezo structure 18 having a length of 60 mm, which does not lead to a problem in operation. When a material having a thermal expansion coefficient which is not greater than at least 15×10−6/° C. was adopted, damage to the piezo structure experientially did not occur with respect to a temperature change from −20° C. to +60° C.
Then, as shown in
These protruding portions 10a are provided with contact points to supply power or to supply a signal to a head module 57 from the image forming apparatus main body (a printer main body) side. A foamed elastic member is provided in the contact point and functions to press each emboss 10a of the power feed member 10 toward the image forming apparatus main body side by an elastic force.
Then, a plurality of nozzle holes from which an ink is ejected are formed with respect to the nozzle plate 1 by using laser machining. Each of these nozzle holes has a diameter which is approximately 25 μm. The nozzle plate 1 is set in a laser machining device with the outer shape reference surfaces 2e and 2g of the base 2 shown in
According to the above-described manufacturing process, there can be configured a head module having 300 nozzles opened in one of the two lines, i.e., 600 nozzles opened in the two lines. A nozzle interval between these columns is 2.7 mm, and the nozzles are accurately provided in parallel at a pitch of 169 μm with a deviation of 84.5 μm. Furthermore, an ink supplied from the ink port 8 provided on the cover 20 is filled in the concave portion in the cover 20, foreign particles in the ink are filtered by a filter 22 to enter the common ink chamber, and the common ink chamber communicates with the grooves of the piezo structure 18 arranged on the opposite side through the holes 17a and 2d, thereby supplying the ink to each groove 19 provided in each of the piezo structures 18 on both sides.
Moreover, such processing as shown in
A process of attaching the head module 57 to the recording head portion of the image forming apparatus will now be described with reference to
In the head mount 30, an ink path portion 27 is provided at a position apart from the head module inserting direction, on the upstream side of the recording medium conveying direction, and below an insertion opening. This ink path portion 27 is connected with a joint member 35 from an ink bottle 50 through a reservoir 51 shown in
The ink joint 27a is formed of an elastic member such as a rubber. When the ink joint 27a is coupled with the ink port 8, it can supply the ink to the head module without leakage.
As shown in
According to this configuration, a pressure of reservoir 51 can be increased when filling the ink into each head module 57, thereby assuredly filling the ink. Further, when replacing each head module 57, closing the valve 54 can prevent air from entering the ink flow path.
When the head module 57 is inserted, the base convex portion 2K comes off the rib 23b and the surface 2e of the base is positioned in contact with the rib 23b by the spring 25, the ink port 8 is fitted in and coupled with the ink joint 27a. At least the ink joint 27a is formed of an elastic member such as rubber, and hence the ink can be prevented from leaking by the elastic force of the ink joint 27a when the ink port 8 is fitted in the ink joint 27a.
The substrate 24 is provided to the head mount 30 above the ink path portion 27, and the power feed portion 10 of the head module 57 pushed by the spring 25 is pressed against the substrate 24 by this series of head attachment operation, whereby the power supply is connected with a signal line. The power feed portion 10 has an elastic member 10c, and bending this elastic member 10c by the force of the spring 25 allows each emboss 10a to strongly come into contact with the pattern of the substrate, thereby realizing power feeding and connection of the signal line.
A second embodiment according to the present invention will now be described.
In this module, a nozzle array interval is 2.7 mm, and a thickness of the ink port 8 except a protruding portion thereof is 6.5 mm. Each of both end portions of the base 2 is set higher than a central portion and has a thickness of approximately 8 mm. As described above, the nozzle arrays 1b are machined in parallel with a reference surface 2e. Furthermore, a positional accuracy from a reference surface 2g to nozzles in a direction X is set within ±5 μm.
FIGS. 22 to 26 are views showing a structural example of a head mount 30 with which a plurality of head modules 57 can be positioned in a recording medium width direction for attachment. This head mount 30 can hold the plurality of head modules 57 using an ink of one color. Holes 36 for attachment of the head modules 57 are formed at four positions in parallel in a zigzag pattern as seen from a head inserting direction. These holes are set at positions with which end portions of the adjacent head modules 57 overlap each other when the head modules 57 are attached as seen from a conveying direction of the recording medium. As will be described later, since nozzles are arranged without a gap in a direction orthogonal to a recording medium width direction when the head modules 57 are attached in the recording head position, and hence a straight line can be formed without a gap in the recording medium width direction by shifting an ink eject timing of the nozzle arrays.
The head mount 30 is formed by die casting or of an extruded material, and its part requiring an accuracy alone is manufactured by cutting processing. For example, the positioning portions 36a, 36b and 36c used for positioning are simultaneously processed in each of the plurality of hole 36 portions, and they can be processed with an excellent positioning accuracy between these holes.
Furthermore, accurate processing is carried out in such a manner that a line connecting the contact references 36c at both end portions in one hole 36 becomes parallel with all the holes 36c. The head module 57 is also processed in such a manner that the two head arrays become parallel with surfaces 2e at both end portions as contact target. Therefore, all the nozzle arrays 1b included in the plurality of head modules 57 inserted into the head mount and positioned become parallel. When the head modules 57 are arranged in a zigzag pattern in this manner, a distance between the adjacent heads in the recording medium conveying direction can be set as short as 11 mm.
The ink path portion 27 is arranged on one of lines of the plurality of head modules arranged in the recording medium conveying direction. An ink joint member 35 which can be coupled with a printer main body is provided at an end portion of the ink path portion 27. An apparatus main body has an ink tube through which an ink is supplied to each head. When the ink tube is connected with this ink joint member 35, the ink can be supplied to all the head modules 57 from the ink joints 27a through the ink path portion 27.
A head drive substrate 38 is arranged on a longitudinal side wall of the head mount 30. Moreover, a lid 37 is arranged on an upper surface of the head mount 30 to cover an upper surface of each head module 57, and provided to be opened and closed with respect to the head mount 30 with a supporting point 37a at the center. Pluralities of hooks 37b are provided on the other end side of the supporting point. When the lid 37 is closed, the hooks 37b engage with non-illustrated concave portions of the head mount 30, thereby maintaining a closed state. The head drive substrate 38 is a flexible substrate, and a part of this substrate is extended toward and fixed at the inside of the lid 37.
In a state where the lid 37 is closed, an electrode of the head drive substrate 38 inside the lid 37 comes into contact with a power feed member 10, and each head module 57 is connected with the head drive substrate 38. As described above, an elastic fore of an elastic member 10c pushes each emboss 10a toward the head drive substrate 38, thereby maintaining normal contact. A contact portion 2m (
A degree of viscosity of the ink in the head ink modules changes depending on a temperature. In order to maintain a eject speed or a eject drop volume of the ink ejected from each head module 57 to appropriate values, a voltage optimized in accordance with a temperature in the vicinity of the nozzles 1a must be applied to each head module 57. As the power supplied to the substrate 38, power of, e.g., 36 volts is supplied to this connector 38b. In order to optimally control characteristics of injection of the ink from each head module 57, a temperature of each head module 57 is detected by a thermistor 23 (
Furthermore, joints 34 of a temperature control pipe are provided above and below the ink joint portion 35. Pure water subjected to temperature control is supplied/discharged from the joints at the two positions by the non-illustrated pump. The joints 34 are coupled with a pipe 39 embedded in the head mount 30. The pipe 39 is formed of a metal such as copper having excellent heat conduction properties, and in contract with the head mount 30 for heat radiation. Pure water flowing through the pipe is subjected to liquid temperature control by a non-illustrated temperature control device such as a chiller.
Usually, thermal conductivity of the piezo structure 18 is as low as 2 to 5 W/(mK), whereas the base 2 is characterized in thermal conductivity which is as high as 170 to 180 W/(mK) since the base 2 is formed of aluminum nitride. Both these members have substantially equal thermal expansion coefficients (5×10−6/° C.), and a crack or a distortion due to a change in temperature is rarely generated even if these members are attached to each other. Moreover, since aluminum nitride is provided with respect to the thin tabular piezo structure 18 in parallel, heat generated in the piezo structures 15, 16 is rapidly absorbed in the base 2 through the piezo structure 18. On the contrary, when the base 2 has a higher temperature, the piezo structure 18 is heated by the base 2.
Heat generated by the head module 57 is mainly heat produced due to deformation of a channel portion and heat generated due to driving of the drive IC 3. In particular, heat generated by the drive IC holds a majority. Heat generated in the channel is also taken by the ink which is driven and ejected, and a temperature is not greatly increased. Heat generated by the drive IC 3 is absorbed in the base 2 with excellent thermal conductivity since the drive IC 3 is directly attached on aluminum nitride. In general, it is said that an allowable temperature limit of the drive IC 3 is not greater than 100° C.
The surface 2e of the base 2 is pressed against the surface 36c and positioned in a state where the base 2 is attached to the head mount 30 and positioned. As a result, heat generated by the drive IC 3 is transmitted to the head mount 30 from this contact surface. As described above, since the pipe 39 is embedded in the head mount 30 and the temperature-controlled liquid is circulated, heat exchange is performed through the pipe 39. As this circulating liquid, temperature-controlled pure water is circulated in order to maintain the channel portion of the piezo structure 18 at a fixed temperature. For example, when the channel portion should be maintained at 50° C., a temperature of the circulating liquid is controlled in such a manner that the thermistor 23 provided to the head module 57 indicates a resistance value corresponding to 50° C. When a plurality of head modules 57 are provided, control is performed in such a manner that an average value of these heads becomes 50° C. The head modules 57 or the head mount 30 is at the same temperature as, e.g., 25° C. which is a room temperature immediately after the power supply is turned on. In this case, the head mount 30 is heated by the circulating water, the base 2 is heated through the head mount 30, and the piezo structures 18, 16, 15 are finally heated, thereby approximating a target temperature. On the contrary, when image formation is continuously carried out, heat is generated from the drive IC3 or the piezo structure 18. This generated heat is conversely cooled by the circulating water from the base 2 through the head mount 30.
As any other head generation source, there is the head drive substrate 38. Since the head drive substrate 38 is provided with a power supply, heat is likewise generated in this substrate. As described above, the element which generates a large quantity of heat is arranged in a part without the head module 57 of the plurality of head modules 57 alternately arranged in the head mount 30 or a space part excluding the ink port 8 in such a manner that it is embedded in the head mount 30. Actually, the element 40 and the head mount 30 are arranged in such a manner that a gap therebetween is filled with a filling material having excellent thermal conduction properties. Therefore, even if heat is generated from the element 40, it is absorbed in the head mount 30 through the filling material and cooled by the pipe 39 arranged in the vicinity of the element 40.
One head module group is constituted of one head mount 30 having the two head module arrays each having the two head modules 57 which are vertical to the conveying direction of the recording medium 44 and parallel with the width direction of the recording medium 44, the ink path portion 27 which is an ink path through which the ink is supplied to the head module arrays, the head drive substrate 38 and the temperature control pipe 39.
The head mount 30 is independently manufactured in accordance with each of a plurality of colors. In one head mount, a mutual positioning accuracy of the respective head modules 57 is assured by a nozzle position accuracy with respect to the base 2 of each head module 57 and an accuracy of the head mount 30.
However, since a position of each head mount 30 is not guaranteed, adjustment is required. For example, as shown in
Likewise, an adjustment screw 43-2 is also screwed in a hole 32, and an upper side of the hole has a tapered part of five degrees. The entire head mount is pushed by a spring 42 in such a manner that the tapered part of the hole and the adjustment screw 43-2 are pushed. When the adjustment screw 43-2 is likewise fastened or loosened, the head mount 30 can swivel around the adjustment screw 43-1 at the other end and the V-shaped portion, thereby enabling adjustment of an angle. A position of the head mount 30 in the longitudinal direction and an angle of the same around one end can be adjusted by the two adjustment screws 43-1, 43-2, and the head mount 30 can be fixed in the image forming apparatus (the recording head portion) main body.
A line connecting the adjustment screws 43-1 and 43-2 at both end portions is arranged at a position which is substantially parallel with the nozzle arrays 1b of the plurality of alternately arranged heads and runs through the center of the alternately arranged heads. This arrangement can efficiently adjust an angle with respect to a moving distance of the adjustment screw 43-2. Additionally, a concave portion is provided in the projection area of the head mount 30 and the spring 42 is configured to push this concave portion, and hence the spring 42 can be arranged without increasing the width in the short side direction.
In the configuration shown in
Furthermore,
In this configuration, square log bars 47 and 49 each having a block shape are respectively fixed to frames 46 and 48 facing each other in parallel. Each head mount 30 is fixed in such a manner that its both ends in the longitudinal direction are suspended on these bars. The adjustment screws 43-1 and 43-2 are provided at both ends, and each head mount 30 can be adjusted in the longitudinal direction and a rotation direction. The suction belt carrying means 45 is provided at the lower portion, and each head module 57 inserted into each hole 36 from the upper side is positioned by the head mount 30, and the surface of the nozzle plate 1 of the head module 57 faces the suction belt carrying means 45. The ink joint member 35 which supplies the ink can be coupled with the joint 34 which circulates a coolant through a non-illustrated hole from the outside of the frame 48.
Image formation by the thus configured recording head portion will now be described.
First, the recording medium 44 is sucked by the suction belt carrying means 45 and transmitted below the head mounts 30 arranged in accordance with the respective colors. The recording medium 44 is first transmitted below the head mounts 30 having the ink of black B (Black) and then the other head mounts 30 in the order of cyan C (Cyan), magenta M (Magenta) and yellow Y (Yellow), and the inks of four colors are sequentially ejected, thereby bringing an image to completion. In regard to heat generated when the head modules 57 are driven, a part of heat in the channel portion is taken by the ink and ejected onto the recording medium 44. Any other heat is transmitted to the attachment reference surface 2a of the base 2.
Moreover, heat generated from the piezo structures 18 attached on both surfaces in order to achieve 300 dpi is transmitted to the base 2 held in the central part. Heat generated in the drive IC 3 flows toward the base 2, and has the minimum thermal resistance. That is, heat flows to the part having a large thickness and is transmitted to the head mount 30 from the contact surface with respect to the head mount 30. The pipe 39 is brought into contact with the head mount 30 through a grease having excellent thermal conduction properties, and the head mount 30 is cooled by circulation of a cooling medium in the pipe 39 so that a problem due to excessive heating does not occur.
A small difference in temperature of the respective head modules 57 is detected by each thermistor 23, and a volume of an ink drop ejected from each head module 57 can be controlled to be a fixed value by controlling a voltage supplied to each head module 57. Assuming that its control range is ±5° C., circulation of the cooling medium is turned on/off in such a manner that this range is not exceeded, thereby controlling a temperature.
The control target is controlled in accordance with each head mount 30 by making reference to an average temperature, a maximum temperature and a minimum temperature of all the head modules 57. That is, when all the head modules 57 fall within the range of ±5° C., the cooling medium is controlled in such a manner that the average temperature becomes the center of this range. When the maximum temperature exceeds this range, control is carried out in such a manner that the maximum temperature falls within the range. On the other when, the temperature is lower than the minimum temperature, the cooling medium is heated, the head mount 30 is heated and a temperature of the base 2 is increased so that each head module 57 falls within the range of ±5° C.
The ink supplied to each head module 57 is coupled with the ink joint portion 35 from the non-illustrated ink bottle through the tube, and supplied to the channel from the ink path portion 27 through the ink port 8 of each head module 57. The ink path portion 27 is extended on the upstream side alone of the recording medium conveying direction with respect to the head modules 57 alternately arranged in the zigzag pattern, and arranged to supply the ink to the ink port provided at the center of each head from the gap of the respective heads. Therefore, each head module 57 has a compact structure. The ink path portion 27 may be extended on the downstream side alone of the recording medium conveying direction with respect to the head modules 57 alternately arranged in the zigzag pattern. In the head module 57, the ink is supplied to the two piezo structures 18 through the holes 17a and 2d connecting the pair of attached piezo structures 18.
Since the reservoir 51 is arranged to apply a negative pressure to the nozzle 1a of the head, the negative pressure is maintained in a part from the ink path portion 27 to the nozzles 1a by a siphon principle, and a meniscus is formed in each nozzle 1a.
As described above, an interval of the head arrays constituting one head module 57 is as small as 2.7 mm. Therefore, even if the recording medium slightly obliquely travels, a deviation of a spotting drop position is ½ of a dot pitch, which does not result in a large error.
The head drive substrate 38 is provided to each of the head modules 57 of four colors, and the element which supplies power to each head module 57 is arranged in the vicinity of each head module 57. Therefore, a voltage rarely drops, and the apparatus is resistant to electromagnetic noise. The element 40 which produces the power source is arranged to be embedded in a part between positions where the respective ink portions 8 of the head mount 30 run. As a result, heat generated by the power supply is also removed from the pipe 39 by the cooling medium.
A description will now be given on a replacement procedure when a problem has occurred in the head module 57.
As a problem to be generated, there is clogging of each nozzle 1a, electrical disconnection, a damage to the drive IC or the like. First, the hooks 37b are disengaged and swiveled around the supporting point 37a to open the lid 37, and a corresponding head module 57 alone is manually pulled out in an upward direction. When the ink port 8 comes off the ink joint 27a of the ink path portion 27, the head module 57 can be readily pulled out.
Since the inside of the ink path portion 27 has a negative pressure, when even one head module 57 is removed, air enters from the ink joint 27a, and the ink drops. Thus, a supply path valve 54 is provided in a part extending from the ink bottle to the joint portion 35, and the supply path valve 54 is closed to then remove the head module 57. As a result, it is possible to prevent the ink from flowing toward the reservoir 51 side from the inside of the ink path portion 27. Since the joint portion with respect to the ink port 8 is the upper side, the ink does not run into the apparatus from the ink path portion 27 which is ink supplying means irrespective of presence/absence of the valve. Further, the head module 57 can be removed while preventing the ink port 8 from coming into contact with any part without contaminating the periphery.
Furthermore, in the head module 57 in a removing process, as shown in
A description will now be given as to a case where a new head module 57 is inserted.
In the new head module 57, a position of nozzle 1a is produced with a tolerance of approximately 5 μm or below with respect to the surfaces 2e, 2g and 2m (see
Additionally, in a state where the lid 37 is closed, the outer shape reference surface 2m of the head module 57 is pressed against a determining portion 36a of the head mount 30 by the elastic force of the elastic member 10c, thereby determining a position in the height direction. At the same time, each emboss 10a is pressed against the contact point of the head substrate 38 by this elastic force, thus enabling supply of power and supply of a signal. Further, in a process of pushing down and inserting the head module 57, the ink port 8 is fitted in the ink joint 27a of the ink path portion 27. Replacing the head module 57 in this manner enables arrangement of the new head module 57 while maintaining a positional accuracy with respect to any other head module 57.
Then, the atmospheric air opening valve 53 of the reservoir 51 (the ink supply valve 52 is always closed except a supply time of the ink) is closed, and the supply path valve 54 which is precedently closed is opened. As a result, the ink does not drop into the reservoir 51 from the ink path portion 27. When the pressurization pump 55 is pressurized to open the pressurization valve 56 in this state, the inside of the reservoir 51 has a positive pressure, and the ink in the reservoir 51 is supplied into the ink path portion 27.
Then, the ink supplied into the ink path portion pushes out air in the newly replaced and attached head module 57, i.e., air in the joint portion 27a. All air bubbles are pushed from the nozzle 1a of the head module 57. When the ink is filled in the head module 57, the atmospheric air opening electromagnetic valve 53 is opened. Then, a negative pressure is applied to the nozzle 1a portion of the head module 57, and a meniscus is formed, and the apparatus enters a printing enabled state.
The above has described the method of removing air bubbles in the flow path by applying a pressure to the reservoir 51 side. Of course, the present invention is not restricted thereto, and it is possible to adopt a method by which the ink in the ink path portion 27 is filled in the newly replaced head module 57 by known head maintenance means which applies a cap to the nozzle plate 1 side for tight sealing and forms a negative pressure in the cap, thereby sucking the ink from the nozzle 1a. Besides the method of controlling opening/closing by using the electromagnetic valve 54, it is possible to adopt a method in which the valve is opened/closed by a manual operation to prevent the ink in the flow path from dropping into the reservoir 51.
The plurality of head modules 57 are arranged in the zigzag pattern, the ink supply opening of each head module 57 is provided in the vicinity of the center of the eject width, the ink supply path of all the head modules 57 are arranged on only one side of the zigzag arrangement in the recording medium conveying direction in the form of the ink path portion, and the ink can be supplied to the head modules 57 apart from the ink path portion 27 through the gap between the heads close to the ink path portion 27. Therefore, the width of the line head having the plurality of heads in the recording medium conveying direction can be reduced, whereby an interval between the plurality of colors can be shortened.
When the ink path portion 27 is seen in a distance from the recording medium, the ink path portion is arranged between the nozzle 1a of the head module 57 and the ink port 8, and the ink path portion 27 and the head module 57 match with each other by inserting the head module 57 from the upper side. Therefore, at the time of removable/attachment of the head module 57, the head module 57 can be readily removed/attached without interference of the ink supply path.
The distance between the ink port 8 opening and the nozzle 1a is set to 4 cm or below and the ink path portion 27 is arranged at the position where the inside diameter of the ink port 8 is not greater than φ4 mm. Therefore, at the time of removal/attachment of the head module 57, the ink can be prevented from sweeping down from the opening of the ink port 8 or the nozzle 1a of the head module 57.
The pressurizing or sucking means for filling the replaced head ink is provided with respect to the plurality of head modules 57 replaceably arranged in the head mount 30, and the head module 57 is replaced with the supply path valve 54 for the head mount 30 being closed. After replacement, the supply path valve 54 is controlled to be opened in a state where a pressure for supplying the ink to the nozzle 1a is generated by the pressurizing or sucking means. As a result, an amount of air mixed in the ink path portion 27 which is coupled with the plurality of head modules 57 can be suppressed to the minimum level, and the ink can be filled in the replaced head module 57 with the minimum amount of a waste liquid.
When the supply path valve 54 is opened after the atmospheric air opening electromagnetic valve 53 of the reservoir 51 is closed, the ink in the ink path portion 27 can be prevented from dropping into the reservoir 51 side, the ink can be efficiently filled in the replaced head module 57, and the ink can be filled in the replaced head module 57 with the minimum amount of the waste liquid.
This embodiment is different from the constitution shown in
In an intermediate position of the head mount 30, the ink pass portion 61 extends in a line in a width direction of a recording medium. On the uppermost surface of the ink path portion 61, an opening portion 61a is disposed. An end portion of an ink port 62 of the head module 57 is provided with a tube made of a resin, a rubber or the like having elasticity. The ink port 62 is inserted into the opening portion 61a, whereby the head module 57 can be linked with the ink path portion without any leakage of the ink.
That is to say, when the head module 57 is inserted as shown in
The opening portion 61a is provided on the uppermost surface of the ink path portion 61, and therefore, attachment operation is easy, and bubbles can easily be discharged and constitution can easily be realized. Needless to say, such a joint constitution as in the above embodiment may also be employed.
According to the above-described structure, the following effects can be obtained.
1. Since the plurality of head modules 57 are arranged in the direction orthogonal to the recording medium conveying direction and the ink supplying means for the plurality of head modules 57 is arranged on one of the upstream side and the downstream side of the recording medium conveying direction, the width of the line head having the plurality of heads in the recording medium conveying direction can be reduced, thereby shortening an interval between a plurality of colors.
2. When the ink path portion is seen in a distance from the recording medium, arranging the ink path portion between the nozzles of the head module 57 and the ink port and inserting the head modules 57 from the upper side allows the ink path portion and the head modules 57 to match with each other. Therefore, at the time of removal/attachment of the head module 57, the head can be readily removed/attached without interference of the ink supply path.
3. The pressurizing or sucking means for filling the head ink 57 in a replaced head is provided with respect to the plurality of head modules 57 replaceably arranged in the head mount 30, the ink supply valve of the head mount 30 is closed to replace the head module 57, and the valve is controlled to be opened in a state where a pressure for supplying the ink to the nozzles is generated by the pressurizing or sucking means after replacement. As a result, an amount of air mixed in the ink path portion coupled with the plurality of head modules 57 can be suppressed to the minimum level, and the ink can be filled in the replaced head with the minimum amount of a waste liquid.
According to the present invention, it is possible to provide image formation including the recording head portion in which the plurality of small heads are alternately arranged in such a manner that their end portions overlap each other to constitute the virtual elongated line head and each head can be individually replaced by easy removal/attachment.
Number | Date | Country | Kind |
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2005-024388 | Jan 2005 | JP | national |