Patent Application
20080291254
1. Field of the Invention
The present invention relates to a liquid ejection apparatus and an image forming apparatus using a liquid ejection apparatus, and more particularly, to air bubble removal technology suitable for removing an air bubble, which is a cause of an ejection defect, from a flow channel in such a liquid ejection apparatus as an inkjet head including a plurality of liquid droplet ejection ports (nozzles).
2. Description of the Related Art
In an inkjet type of recording apparatus, if an air bubble enters inside an ink flow channel, then an ejection defect occurs in that ink ceases to be ejected, or the ink ejection volume (the size of the dot formed by a droplet ejected onto a recording medium) or the droplet ejection position (direction of flight) becomes improper. In response to problems of this kind, in order to improve air bubble removal characteristics inside the ink flow channels, for example, Japanese Patent Application Publication No. 6-115087 discloses a structure in which the ends of the flow channels are formed to fine dimensions.
According to Japanese Patent Application Publication No. 6-115087, the cross-sectional area of an ink supply manifold which supplies ink to each of a plurality of ink supply channels is gradually reduced, the ink flow speed inside the manifold is maintained at or above a prescribed value, and thus the retention of air bubbles on the interior walls of the manifold is suppressed.
It is known that the removal characteristics of air bubbles are greatly dependent on the flow speed (m/s) in the flow channel. Here, the flow speed (m/s) is expressed as follows: “flow speed (m/s)=volume velocity (m3/s)/cross-sectional area of flow channel (m2)”. In other words, the reference to “raising the air bubble removal characteristics” described in Japanese Patent Application Publication No. 6-115087 means to increase the flow speed (m/s) by reducing the cross-sectional area of flow channel.
However, in recent inkjet recording apparatuses, due to demands for increased head length and compatibility with high-viscosity inks, and the like, situations have occurred where the cross-sectional area of the flow channel is inevitably required to increase, and this makes it difficult to remove the air bubbles on the basis of the flow speed.
Considering a case where a high-viscosity ink is used, since the flow channel resistance is directly proportional to the ink viscosity, then if the cross-sectional area of the flow channel is not increased sufficiently, it is not possible to keep the pressure loss inside the head (=flow channel resistance×volumetric speed) to within a specified value (for example, 800 Pa). If the pressure loss rises and exceeds the specified value, then it is difficult that the ink supply to the pressure chambers keeps up with demand, and eventually it becomes impossible to perform ejection.
Furthermore, considering a case where a long head is used, since the flow channel resistance is directly proportional to the length of the flow channel, then if the cross-sectional area of the flow channel is not increased sufficiently, it is not possible to keep the pressure loss inside the head (=flow channel resistance×volumetric speed) to within a specified value (for example, 800 Pa).
For these reasons, according to recent inkjet recording apparatuses, it has become difficult to sufficiently remove the air bubbles on the basis of the flow speed.
The present invention is contrived in view of these circumstances, an object thereof being to provide a liquid ejection apparatus and an image forming apparatus using a liquid ejection apparatus whereby an air bubble inside the flow channel can be removed efficiently.
In order to attain the aforementioned object, the present invention is directed to a liquid ejection apparatus comprising: a plurality of ejection ports which eject liquid; a plurality of pressure chambers which are connected respectively to the ejection ports; pressure generating elements which are provided to correspond respectively to the pressure chambers and create a pressure change in the liquid in the respective pressure chambers; a common flow channel which is connected to the pressure chambers and supplies the liquid to the pressure chambers; a movable member which is disposed inside the common flow channel and can move while making contact with a flow channel wall forming one portion of an internal circumferential surface of the common flow channel; and a movement device which moves the movable member inside the common flow channel.
According to this aspect of the present invention, by making the movable member contact the flow channel wall and moving the movable member by means of the movement device, it is possible to strip off an air bubble adhering to the flow channel wall by means of the movable member. Accordingly, the movement of the air bubble is promoted, and thus air bubble removal characteristics can be improved. The movement device may be driven on the basis of automatic control, or it may be manually controlled.
Each “pressure generating element” in the present invention may be a piezoelectric element or other actuators that can change the volume of the pressure chamber, or may be a heater (heating element) which heats and evaporates the liquid in the pressure chamber.
Preferably, at least a portion of the movable member is constituted by a ferromagnetic body; and the movement device includes a magnetic field generation device which generates a magnetic field.
According to this aspect of the present invention, it is possible to control the position and movement of the movable member, by a non-contact method, by means of the action of a magnetic field generated by the magnetic field generation device, and it is possible to move the movable member on the basis of a simple composition. The magnetic field generation device may be a permanent magnet, an electromagnet, or a combination of these.
Preferably, the movable member includes: an inclined plane section which has an acute angle so as to enter in between the flow channel wall and an air bubble adhering to the flow channel wall and strip the air bubble from the flow channel wall; and a hollow section which retains the air bubble stripped from the flow channel wall.
According to this aspect of the present invention, the acute-angled inclined plane section is inserted in between the flow channel wall and the air bubble, and therefore the air bubble can be stripped more readily from the flow channel wall. Furthermore, the air bubbles stripped from the flow channel wall can be collected into the hollow section of the movable member and moved together with the movable member. By moving the movable member while collecting up the air bubbles in this way, the air bubble removal properties are further improved.
Preferably, the flow channel wall along which the movable member slides has an inclined plane structure wherein height of the flow channel wall gradually increases in a direction of movement of the movable member.
The air bubbles progressively rise upwards inside the flow channel. Therefore, according to this aspect of the present invention, the inclined plane structure is adopted for the flow channel wall, and hence it is possible to lead (collect) the air bubble to the highest position in conjunction with the movement of the movable member. By forming an expulsion port (circulating hole, or the like) for expelling an air bubble at the end toward which the movable member moves (at the highest position in the inclined plane structure, for example), it is possible to expel the collected air bubble to the exterior, with good efficiency.
Preferably, the liquid ejection apparatus further comprises a holding section which is provided in the common flow channel and supports a lower face of the movable member.
According to this aspect of the present invention, a shape (holding section) which is able to hold the movable member in a portion of the common flow channel is formed, and thereby, it is possible to hold the movable member in a stable fashion.
Preferably, the holding section supports the lower face of the movable member in such a manner that the movable member is separated from the flow channel wall.
According to this aspect of the present invention, it is possible to select in a simple fashion between a state where the movable member is in contact with the flow channel wall and a state where it is not in contact with same.
For example, there is a mode in which a first magnetic field generation device forming a movement device for moving the movable member while causing same to make contact with the flow channel wall, and a second magnetic field generation device for moving the movable member while causing same to make contact with the holding section, are provided.
Preferably, the flow channel wall forms a ceiling face of the common flow channel; the flow channel wall has a non-linear shape in which height of the flow channel wall varies when viewed in a direction of movement of the movable member; and the movable member has a non-linear shape when viewed in the direction of movement of the movable member, in such a manner that the non-linear shape of the movable member matches the non-linear shape of the flow channel wall.
The term “non-linear shape” here includes a curved shape, a bent line shape, and a combination of these. According to this aspect of the present invention, since air bubbles are liable to collect in the vicinity of the apex of the non-linear shape (in a case where the shape has a plurality of apices, in the vicinity of each of the apices), then it is possible to expel the collected air bubbles readily.
Preferably, the liquid ejection apparatus further comprises a flow channel which is provided in an end section of the common flow channel in terms of a direction of movement of the movable member and via which an air bubble is expelled to an exterior of the common flow channel.
According to this aspect of the present invention, it is possible to readily expel the air bubble collected by the movable member, from the flow channel for expelling an air bubble, to the exterior of the common flow channel.
Preferably, the movable member has a recess shape which is hollowed in a reverse direction with respect to a direction of movement of the movable member by the movement device.
By forming the shape of the movable member to a recess shape (for example, a V shape which opens in the direction of travel) which is hollowed in the reverse direction to the direction of movement (direction of travel), rather than in a perpendicular shape with respect to the direction of movement, then the air bubble can be collected in the base portion of the recess shape (the rearward portion in terms of the direction of travel), and hence the movable member can be moved while the movable member retains the collected air bubble.
Preferably, the movable member includes: a projecting end section which projects in a direction of movement of the movable member by the movement device; and an end portion which is located posteriorly to the projecting end section in terms of the direction of movement of the movable member by the movement device; and an air bubble removal groove into which an air bubble stripped from the flow channel wall by the movable member is introduced, is provided in an end part of the common liquid chamber which overlaps with the end portion of the movable member.
Since the shape of the movable member is formed in a projecting shape (for example, a V shape having the apex orientated toward the direction of travel) which projects in a forward direction with respect to the direction of movement (direction of travel), rather than in a perpendicular shape with respect to the direction of movement, an air bubble stripped from the flow channel wall by the movable member is moved toward the end portion of the movable member which is situated to the rear side of (namely, in a position behind) the projecting end section of the projecting shape of the movable member. The air bubble moved to the vicinity of the end portion of the movable member in this way is introduced into the air bubble removal groove. In this way, the air bubble can be expelled with good efficiency.
Preferably, a portion of the movable member which makes contact with the flow channel wall is constituted by an elastic member.
According to this aspect of the present invention, the elastic member can make contact with the flow channel wall while deforming, and hence it is able to apply a force to the flow channel wall without causing damage to the wall.
Preferably, the flow channel wall includes a recess section which forms a projection-shaped space in which a gap is formed between the flow channel wall and the elastic member that is released from a deformed state assumed while the movable member is in contact with the flow channel wall and returns to an original shape of the elastic member.
According to this aspect of the present invention, the surface of the flow channel wall has a projection-recess shape (undulating shape), and the relative distance between the elastic member and the wall surface changes according to the shape (projection section or recess section) of the wall surface. At the recess section in the flow channel wall, the distance from the elastic member to the wall surface increases. In other words, the recess section in the flow channel wall creates a projection-shaped space which projects toward the side opposite to the flow channel (projecting toward the outside of the common flow channel). This projection-shaped space functions as an “escape” space where contact between the wall face and the elastic member is avoided. Consequently, when the elastic member arrives at a position opposing the recess section (escape groove), the elastic member ceases to make contact with the wall surface and it is released from the deformed state that it assumes during the contact. Therefore, the direction of movement of the movable member can be readily reversed without applying excessive force to the elastic member.
Preferably, the liquid ejection apparatus further comprises a guide section which is provided in the common flow channel and restricts a position of the movable member during movement of the movable member, wherein the guide section has a shape which forms a travel path for guiding the movable member to a position where a gap is formed between the flow channel wall and the elastic member that is released from a deformed state assumed while the movable member is in contact with the flow channel wall and returns to an original shape of the elastic member.
According to this aspect of the present invention, a structure is adopted in which the movable member is moved along a path of travel created by the guide section, and a path of travel is formed which causes the movable member to move to a position where it is separated from the flow channel wall.
By separating the movable member from the flow channel wall by guiding same by means of the guide section, the movable member is released from a deformed state which is assumed by the movable member during the contact with flow channel wall, and reverts to its original shape. Therefore, the direction of movement of the movable member can be readily reversed without applying excessive force to the elastic member.
Furthermore, as described above, a structure which allows the relative position (distance) between the movable member and the flow channel wall to be changed by using the guide section does not require the provision of an escape structure in the flow channel wall (undulation of the wall surface) as described above, and a flat flow channel wall which has no positions where air bubbles are liable to stagnate can be formed.
Preferably, the movable member has a columnar shape and relatively lower lyophilic properties than the flow channel wall, and is moved while rolling over the flow channel wall by the movement device.
According to this aspect of the present invention, the air bubble adhering to the flow channel wall readily transfer to the movable member, which has lower lyophilic properties than the flow channel wall, and become attached to the surface of the movable member.
Therefore, it is possible to collect and move the air bubble adhering to the flow channel wall by making it become attached to the movable member. Moreover, since the columnar shaped (round cylindrical) movable member simply rolls over the wall surface, it does not cause any damage to the flow channel wall.
Preferably, the movable member includes a permanent magnet.
According to this aspect of the present invention, it is possible to readily switch between a state where the movable member is made to contact the wall surface and a state where it does not contact same, according to the orientation of an external magnetic field. Furthermore, it is also possible to move the movable member by using the repulsing force created by an external magnetic field.
Preferably, the liquid ejection apparatus further comprises a diaphragm which forms a portion of surfaces of the pressure chambers, wherein the pressure generating elements are formed by piezoelectric elements which are provided on an opposite surface of the diaphragm from the pressure chambers; and the common flow channel is provided on an opposite side of the diaphragm from the pressure chambers.
According to this aspect of the present invention, the common flow channel is formed on the opposite side of the diaphragm to the pressure chambers, and the liquid is supplied to the respective pressure chambers from this common flow channel. By adopting a flow channel structure of this kind, it becomes possible to arrange the pressure generating elements at high density (and hence to achieve a high-density arrangement of the nozzles). Furthermore, it is possible to reduce the flow channel resistance of the liquid supply channels from the common flow channel to the pressure chambers, and a sufficient liquid supply volume can be ensured, even in the case of a high-viscosity liquid.
In order to attain the aforementioned object, the present invention is also directed to an image forming apparatus comprising one of the liquid ejection apparatuses described above, the image forming apparatus forming an image on a recording medium by means of the liquid ejected from the ejection ports.
The inkjet recording apparatus forming one example of the image forming apparatus described above comprises: a liquid ejection head (recording head) having a high-density arrangement of a plurality of liquid droplet ejection elements (ink chamber units), each comprising an ejection port (nozzle) for ejecting an ink droplet in order to form a dot and a pressure generating device (piezoelectric actuator) which generates an ejection pressure; and an ejection control device which controls the ejection of liquid droplets from the liquid ejection head on the basis of the ink ejection data (dot image data) generated from an input image. An image is formed on a recording medium by means of the liquid droplets ejected from the nozzles.
For example, color conversion or half-toning is carried out on the basis of image data (print data) input via an image input device, thereby generating ink ejection data corresponding to the ink colors. The pressure generating elements corresponding to the respective nozzles of the liquid ejection head are driven and controlled on the basis of this ink ejection data, in such a manner that ink droplets are ejected from the nozzles.
In order to achieve a high-resolution image output, a desirable mode is one using a liquid ejection head (print head) in which a plurality of liquid droplet ejection elements (ink chamber units) are arranged at high density, each liquid droplet ejection element being constituted by a nozzle (ejection port) which ejects ink liquid, and a pressure chamber and pressure generating element corresponding to the nozzle.
A compositional embodiment of a liquid ejection head for printing of this kind is a full line type head having a nozzle row in which a plurality of ejection ports (nozzles) are arranged through a length corresponding to the full width of the recording medium. In this case, a mode may be adopted in which a plurality of relatively short ejection head modules having nozzles rows which do not reach a length corresponding to the full width of the recording medium are combined and joined together, thereby forming nozzle rows of a length that correspond to the full width of the recording medium.
A full line type head is usually disposed in a direction that is perpendicular to the relative feed direction (relative conveyance direction) of the recording medium, but a mode may also be adopted in which the head is disposed following an oblique direction that forms a prescribed angle with respect to the direction perpendicular to the conveyance direction.
The “recording medium” indicates a medium which receives the deposition of ink ejected from the ejection ports of a liquid ejection head (this medium may also be called a print medium, image forming medium, recording medium, image receiving medium, ejection receiving medium, or the like). This term includes various types of media, irrespective of material and size, such as continuous paper, cut paper, sealed paper, resin sheets such as OHP sheets, film, cloth, a printed circuit board on which a wiring pattern, or the like, is formed, and an intermediate transfer medium, and the like.
Modes of the movement device for causing the recording medium and the liquid ejection head to move relatively to each other may include a mode where the recording medium is conveyed with respect to a stationary (fixed) head, a mode where a head is moved with respect to a stationary recording medium, and a mode where both the head and the recording medium are moved. When a color image is formed by means of an inkjet print head, it is possible to provide print heads which each are provided for each color of a plurality of ink colors (recording liquid colors), or it is possible to eject inks of a plurality of colors, from one print head.
According to the present invention, it is possible to strip off an air bubble adhering to the wall surface of the common flow channel, by means of the movable member, and therefore, air bubble removal characteristics can be improved.
The nature of this invention, as well as other objects and benefits thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein:
The head 10 shown in
Furthermore, a supply system connection port 29 for introducing ink into the common flow channel 25 is formed in a suitable position (for example, the left-hand end section in the embodiment in
As shown in
The common flow channel 25 shown in this embodiment is constituted as one large space formed over the whole region in which the pressure chambers 22 are formed, in such a manner that ink is supplied to all of the pressure chambers 22, but it is not limited to being formed as a single space (ink pool) in this way. The common liquid chamber 25 may also be divided into several regions to form a plurality of chambers, and a prescribed flow channel structure capable of restricting the ink flow may be adopted.
Holes for the plurality of nozzles 21 corresponding to the ink ejection ports are formed in the nozzle plate 30. Furthermore, a lyophobic layer (not shown) is provided on the nozzle surface 30A, with a view to improving ejection stability and the cleaning properties of the ejection surface (nozzle surface 30A). There are no particular restrictions on the method for imparting lyophobic properties to the nozzle surface 30A (the lyophobic process method), and possible methods include, for example, a method involving coating of a fluorine-based lyophobic material, and a method involving the formation of a thin layer on the nozzle surface by vapor deposition of a lyophobic material, such as particles of a fluorine-based high polymer (PTFE), in a vacuum.
The pressure chamber forming member 32 is a flow channel forming member which is formed with spaces for pressure chambers 22, connecting channels 40 (nozzle flow channels) which connect the pressure chambers 22 to the nozzles 21, and a portion of the individual supply channels 42 which lead ink from the common flow channel 25 on the ink supply side to the pressure chambers 22.
The pressure chamber forming member 32 may be constituted by a single plate member formed with prescribed flow channel-shaped sections (openings and grooves, etc.), and it may also be constituted by a laminated body in which a plurality of plate members formed with openings and grooves (recess sections) for creating prescribed flow channel-shaped sections are superimposed and bonded together.
The diaphragm 34 is a member which forms a portion of the walls of the pressure chambers 22 (in
Piezoelectric bodies 44 are provided on the surface of the diaphragm 34 on the opposite side of the diaphragm 34 from the side of the pressure chambers 22 (in
The intermediate plate 38 functions as a cover plate and a spacer member which covers the upper portion of the piezoelectric elements 36 and ensures displacement spaces for the respective piezoelectric elements 36, and thus it serves as a protection of the piezoelectric elements 36 against the common flow channel 25 (thereby preventing contact with the ink). The piezoelectric elements 36 produce a warping distortion in the thickness direction or a change in the thickness direction, thereby displacing the diaphragm 34. Hence, a space which permits this deformation is required above each piezoelectric element 36. Therefore, recess sections 38A corresponding to the piezoelectric elements 36 are formed in the intermediate plate 38, each of the piezoelectric elements 36 is accommodated between the diaphragm 34 and each of the recess sections 38A, and hence a prescribed space is ensured about the periphery of each piezoelectric element 36.
There are no particular limitations on the modes of the drive wires for driving the piezoelectric elements 36; for example, the drive wires for driving the piezoelectric elements 36 may be horizontal wires which are formed by patterning electrical wires (internal wires) onto the intermediate plate 38 so as to run in parallel with the surface of the intermediate plate 38.
The intermediate plate 38 in the present embodiment is a member which forms a portion of the surface of the common flow channel 25 (in
From the viewpoint of liquid resistance, an insulating and protective film (not shown) made of resin, or the like, is formed on the portions of the surface of the intermediate plate 38 which make contact with the ink inside the common flow channel 25.
The common flow channel forming member 27 is bonded onto the upper surface of the intermediate plate 38 described above (the surface on the opposite side to the diaphragm 34). The common flow channel forming member 27 is a flow channel forming member (wall member) provided with sections which form side wall portions forming a space for the common flow channel 25 which accumulates ink.
The common flow channel forming member 27 may be constituted by a single plate member formed with prescribed flow channel-shaped sections (openings and grooves, etc.), and it may also be constituted by a laminated body in which a plurality of plate members formed with openings and grooves (recess sections) for creating prescribed flow channel-shaped sections are superimposed and bonded together.
In the composition described above, when a drive voltage is applied between an individual electrode 45 and the common electrode (which the diaphragm 34 serves as), the corresponding piezoelectric element 36 deforms, thereby changing the volume of the corresponding pressure chamber 22. This causes a pressure change which results in ink being ejected from the corresponding nozzle 21. When the displacement of the piezoelectric element 36 returns to its original position after the ejection of ink, the pressure chamber 22 is replenished with new ink from the common flow channel 25, via the ink supply port 24.
As described above, according to the present embodiment, the structure is achieved in which the common flow channel 25 is disposed on the upper side of the diaphragm 34 (the opposite side to the pressure chambers 22), and ink is supplied to the pressure chambers 22 in lower positions by means of the ink flow channels 48 passing in a substantially perpendicular direction through the diaphragm surface. Therefore, it is possible to reduce the flow channel resistance on the supply side, and hence ink refill characteristics can also be improved.
Furthermore, as shown in
The magnetic field generation device 52 is supported movably by a drive mechanism (not shown). The device which moves the magnetic field generation device 52 may be a drive device which uses an electric motor-driven type of power source, such as a motor, and it may also be a device based on the amount of movement of a manual operating member (a lever, dial, or the like). Furthermore, for the device for transmitting the power, it is possible to use a commonly known mechanism, such as a gear transmission mechanism or a wound transmission mechanism, or a suitable combination of these.
As shown in
Desirably, a flow channel for expelling air bubbles to the exterior (for example, a circulating channel, a dummy nozzle, or the like) is provided at a place toward which the movable member 50 advances, in order to expel the air bubbles to the exterior via it.
There are no particular restrictions on the shape of the movable member 50. For example, as shown in
Desirably, the movable member 50 is formed from a material having high hydrophilic properties, or it is processed with a hydrophilic surface treatment. The device for moving the movable member 50 may be automatically controlled or it may be manually controlled.
In
Furthermore, since the air bubbles 60 travel upward in the flow channel, then as shown in
As shown in
If the magnetic field created by the magnetic field generation device 52 is switched off, then the movable member 50 falls downward under its own weight (due to the force of the gravity), and it is caught and held by the holding sections 64. In other words, if the magnetic field created by the magnetic field generation device 52 is off, the movable member 50 can be held by the holding sections 64. In this embodiment, a composition is adopted in which magnetic field generation devices 66 which each generate a magnetic field is disposed below the holding sections 64, in such a manner that a force can be applied to pull the movable member 50 in the downward direction in
By controlling the generation of the magnetic field by means of the magnetic field generation devices 52 and 66, it is possible to simply switch between a state where the movable member 50 is in contact with the flow channel wall 28A and a state where it is not in contact with same.
The magnetic field generation device 52 situated above the common flow channel 25 is used for moving the movable member 50 while pressing the movable member 50 against the flow channel wall 28A, as shown in
For example, if it is desired to collect and move the air bubbles in one fixed direction (the direction of arrow C in
In
The movable member 50 is also composed in a curved shape in accordance with the curved shape of the flow channel wall 28A, so as to follow the shape of the flow channel wall 28A. When the movable member 50 is made to contact the flow channel wall 28A due to the magnetic field created by the magnetic force generation device 52, the movable member 50 makes tight contact with the flow channel wall 28A because the shape of the movable member 50 coincides with the shape of the flow channel wall 28A.
In the case of the composition shown in
The flow channel wall 28A and the movable member 50 are not limited to having a substantially arc-shaped curved plane shape as shown in
By using this movable member 50 having this shape, the air bubbles 60 are gathered into the most rearward portion of the movable member 50 (the hollow portion 50C of the recess shape), and hence the air bubbles can be collected by the movable member 50. Desirably, a flow channel for removing air bubbles (a circulating flow channel, dummy nozzle, or the like), is formed at the end to which the movable member 50 moves.
By adopting a composition which combines the characteristics of the fourth embodiment and the characteristics of the third embodiment, in such a manner that the flow channel ceiling has a curved shape and the movable member also has a recessed shape in the forward direction of travel (a projecting shape in the direction contrary to the direction of travel), it is possible to collect the air bubbles with even greater efficiency.
With the movement of the movable member 50, the air bubbles 60 stripped from the flow channel wall 28A are moved to the ends of the common flow channel 25 following the oblique edges of the movable member 50, and the air bubbles 60 are moved into the air bubble removal grooves 70.
As shown in
In the embodiment shown in these drawings, a portion of the elastic member 80 has a shape which is previously curved in a rearward direction with respect to the direction of travel (the wiping direction), and the base section 82 which holds the elastic member 80 has a structure with a substantially trapezoid cross-sectional shape which is broad in the bottom face section to stably hold the elastic member 80 so that the direction of the curve is not inversed.
Furthermore, this base section 82 is formed by a ferromagnetic body, and hence the base section 82 creates a section which reacts to the magnetic field. As shown in
The movable member 50 is lifted up and pressed against the flow channel wall 28A by the magnetic field generated by these magnetic force generation devices 52A and 52A, thereby causing the elastic member 80 to make tight contact with the flow channel wall 28A, as shown in
According to this composition, since the distance between each of the portions of the movable member 50 which are attracted by the magnetic field (namely the respective end sections of the base section 82), and each of the magnetic force generation devices 52A, is reduced, then it is possible to pull the movable member 50 strongly.
Furthermore, since the movable member 50 is moved while being fixed at either side of the member, the stability of the member is increased and skewed travel during movement of the member is not liable to occur.
Moreover, similarly to the embodiment shown in
The movable member 50 shown in
According to the elastic member 80 having approximate linear symmetry with respect to the central axis, the direction of deformation (direction of bending) of the elastic member 80 can be reversed in accordance with the direction of movement of the movable member 50.
As shown in
In the state represented by (1) in
Thereupon, as in the state represented by (3) in
The lines marked by reference numeral 64 in
Furthermore, in the embodiment in
The projection-shaped space described above (hereinafter, also called “reversal space”) may be provided in one position or in a plurality of positions in the common flow channel 25. For example, as shown in
A mode is also possible in which a pump 74 is used as a device for removing air bubbles collected in the escape holes 88 and 88 for air bubble removal, as shown in
The embodiment shown in
In a state represented by (1) in
Thereupon, as shown in (3) in
The composition shown in
According to the composition described above, as shown in
Furthermore, according to the present embodiment, since a round bar-shaped movable member 50 rolls over the wall face, benefits are obtained in that less damage is caused to the wall face in comparison with a composition based on a sliding system as described in
By successively controlling the polarity of the electromagnets 92 indicated by (1) to (5) in
In the embodiments shown in
By changing the direction of the magnetic field generated by a magnetic field generation device 52 situated externally (external magnetic field), it is possible to select between a state where the movable member 50 is in contact with the flow channel wall 28A as shown in
In other words, as shown in
Furthermore, as shown in
In a state where the movable member 50 is held by the holding section 64, as shown in
In other words, even if the movable member 50 is not in contact with the flow channel wall 28A, it can still be moved. According to this composition, benefits are obtained in that the movable member 50 can be controlled only from one side (here, the upper side) of the flow channel wall 28A.
In addition to the compositions explained in the first to eleventh embodiments described above, it is also desirable to circulate the ink in the common flow channel 25, in accordance with the direction of travel of the movable member 50. By making the direction of circulation of the ink (flow direction) coincide with the direction of travel of the movable member 50 (the direction in which the movable member 50 moves while making contact with the flow channel wall 28A), it is easier to remove the air bubbles in the direction of ink circulation.
Moreover, a more desirable composition is one in which the flow channel wall is inclined upwards in the direction in which it is sought to move the air bubbles (see
Next, an embodiment of an image forming apparatus using a liquid ejection head having the structure described in the first to twelfth embodiments is described below.
The liquid ejection head 10 according to any one of the first to twelfth embodiments described above is used as each of the heads 112K, 112C, 112M and 112Y of the print unit 112.
The ink storing and loading unit 114 shown in
In
In the case of a configuration in which a plurality of types of recording medium (media) can be used, it is preferable that an information recording medium such as a bar code and a wireless tag containing information about the type of media is attached to the magazine, and by reading the information contained in the information recording medium with a predetermined reading device, the type of recording medium to be used (type of media) is automatically determined, and ink-droplet ejection is controlled so that the ink-droplets are ejected in an appropriate manner in accordance with the type of medium.
The recording paper 116 delivered from the paper supply unit 118 retains curl due to having been loaded in the magazine. In order to remove the curl, heat is applied to the recording paper 116 in the decurling unit 120 by a heating drum 130 in the direction opposite from the curl direction in the magazine. The heating temperature at this time is preferably controlled so that the recording paper 116 has a curl in which the surface on which the print is to be made is slightly round outward.
In the case of the configuration in which roll paper is used, a cutter (first cutter) 128 is provided as shown in
The decurled and cut recording paper 116 is delivered to the suction belt conveyance unit 122. The suction belt conveyance unit 122 has a configuration in which an endless belt 133 is set around rollers 131 and 132 so that the portion of the endless belt 133 facing at least the nozzle face of the printing unit 112 and the sensor face of the print determination unit 124 forms a horizontal plane (flat plane).
The belt 133 has a width that is greater than the width of the recording paper 116, and a plurality of suction apertures (not shown) are formed on the belt surface. A suction chamber 134 is disposed in a position facing the sensor surface of the print determination unit 124 and the nozzle surface of the printing unit 112 on the interior side of the belt 133, which is set around the rollers 131 and 132, as shown in
The belt 133 is driven in the clockwise direction in
Since ink adheres to the belt 133 when a marginless print job or the like is performed, a belt-cleaning unit 136 is disposed in a predetermined position (a suitable position outside the printing area) on the exterior side of the belt 133. Although the details of the configuration of the belt-cleaning unit 136 are not shown, embodiments thereof include a configuration of nipping cleaning rollers such as a brush roller and a water absorbent roller, an air blow configuration in which clean air is blown onto the belt 133, or a combination of these. In the case of the configuration of nipping the cleaning rollers, it is preferable to make the line velocity of the cleaning rollers different than that of the belt 133 to improve the cleaning effect.
The inkjet recording apparatus 110 can comprise a roller nip conveyance mechanism, instead of the suction belt conveyance unit 122. However, there is a drawback in the roller nip conveyance mechanism that the print tends to be smeared when the printing area is conveyed by the roller nip action because the nip roller makes contact with the printed surface of the paper immediately after printing. Therefore, the suction belt conveyance in which nothing comes into contact with the image surface in the printing area is preferable.
A heating fan 140 is disposed on the upstream side of the printing unit 112 in the conveyance pathway formed by the suction belt conveyance unit 122. The heating fan 140 blows heated air onto the recording paper 116 to heat the recording paper 116 immediately before printing so that the ink deposited on the recording paper 116 dries more easily.
The heads 112K, 112C, 112M and 112Y of the printing unit 112 are full line heads having a length corresponding to the maximum width of the recording paper 116 used with the inkjet recording apparatus 110, and comprising a plurality of nozzles for ejecting ink arranged on a nozzle face through a length exceeding at least one edge of the maximum-size recording medium (namely, the full width of the printable range).
The print heads 112K, 112C, 112M and 112Y are arranged in color order (black (K), cyan (C), magenta (M) and yellow (Y)) from the upstream side in the feed direction of the recording paper 116, and these respective heads 112K, 112C, 112M and 112Y are fixed extending in a direction substantially perpendicular to the conveyance direction of the recording paper 116.
A color image can be formed on the recording paper 116 by ejecting inks of different colors from the heads 112K, 112C, 112M and 112Y, respectively, onto the recording paper 116 while the recording paper 116 is conveyed by the suction belt conveyance unit 122.
By adopting a configuration in which the full line heads 112K, 112C, 112M and 112Y having nozzle rows covering the full paper width are provided for the respective colors in this way, it is possible to record an image on the full surface of the recording paper 116 by performing just one operation (one sub-scanning operation) of relatively moving the recording paper 116 and the printing unit 112 in the paper conveyance direction (the sub-scanning direction), in other words, by means of a single sub-scanning action. Higher-speed printing is thereby made possible and productivity can be improved in comparison with a shuttle type head configuration in which a recording head reciprocates in the main scanning direction.
Although the configuration with the KCMY standard colors (four colors) is described in the present embodiment, combinations of the ink colors and the number of colors are not limited to those. Light inks, dark inks or special color inks can be added as required. For example, a configuration is possible in which inkjet heads for ejecting light-colored inks such as light cyan and light magenta are added. Furthermore, there are no particular restrictions of the sequence in which the heads of respective colors are arranged.
The print determination unit 124 illustrated in
A post-drying unit 142 is disposed following the print determination unit 124. The post-drying unit 142 is a device to dry the printed image surface, and includes a heating fan, for example. It is preferable to avoid contact with the printed surface until the printed ink dries, and a device that blows heated air onto the printed surface is preferable.
In cases in which printing is performed with dye-based ink on porous paper, blocking the pores of the paper by the application of pressure prevents the ink from coming contact with ozone and other substance that cause dye molecules to break down, and has the effect of increasing the durability of the print.
A heating/pressurizing unit 144 is disposed following the post-drying unit 142. The heating/pressurizing unit 144 is a device to control the glossiness of the image surface, and the image surface is pressed with a pressure roller 145 having a predetermined uneven surface shape while the image surface is heated, and the uneven shape is transferred to the image surface.
The printed matter generated in this manner is outputted from the paper output unit 126. The target print (i.e., the result of printing the target image) and the test print are preferably outputted separately. In the inkjet recording apparatus 110, a sorting device (not shown) is provided for switching the outputting pathways in order to sort the printed matter with the target print and the printed matter with the test print, and to send them to paper output units 126A and 126B, respectively. When the target print and the test print are simultaneously formed in parallel on the same large sheet of paper, the test print portion is cut and separated by a cutter (second cutter) 148. Although not shown in
In the present embodiment, an inkjet recording apparatus having a full line type head is described, but the scope of application of the present invention is not limited to this. For example, the present invention may also be applied to a case where images are formed by using a head of a length which is shorter than the width dimension of the recording medium (the recording paper 116 or other print media), and scanning the head a plurality of times, as in a shuttle scanning method.
Moreover, in the foregoing explanation, an inkjet recording apparatus is described, but the scope of application of the present invention is not limited to this. For example, the liquid ejection apparatus according to the present invention may also be applied to a photographic image forming apparatus having a liquid ejection head which applies developing solution, or the like, onto a printing paper by means of a non-contact method. Furthermore, the scope of application of the present invention is not limited to an image forming apparatus, and the present invention may also be applied to various other types of apparatuses which spray various types of liquids, toward an ejection receiving medium, by means of a liquid ejection head (such as a coating device, an application device, wiring pattern printing device, or the like).
It should be understood that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the invention is to cover all modifications, alternate constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-292654 | Oct 2005 | JP | national |
