Liquid discharge head

There is provided a liquid discharge head including: first and second common channels extending in a first direction; and a plurality of individual channels each including: a supplying part, a descender part, and a returning part. The returning part includes: a throttle part and a wide part. Each of a plurality of nozzles is located at a position at which each of the plurality of nozzles overlaps with the wide part in a second direction. At a throttle-starting position which is a boundary between the throttle part and the wide part, a length in the second direction of the throttle part and a length in the second direction of the wide part are same.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2019-219737, filed on Dec. 4, 2019, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

Field of the Invention

The present disclosure relates to a liquid discharge head which discharges a liquid, such as an ink, toward a medium.

Description of the Related Art

An ink-jet head of a circulation type is known as the liquid discharge head which discharges a liquid. For example, in a publicly-known ink-jet head, an ink flowing out of a common liquid chamber passes through an individual liquid chamber (pressure chamber) and a nozzle passage (descender channel), and is discharged or ejected from a nozzle. On the other hand, the ink which is not discharged from the nozzle passes through a discharge channel and flows into a circulating common liquid chamber. In such a manner, a flow of the ink (ink flow) is generated at a location near to the nozzle to thereby prevent the ink from drying in the vicinity of the nozzle.

In the ink-jet head, the discharge channel has a circulating liquid chamber which is connected to the nozzle passage extending in an up-down direction and which extends in a horizontal direction, and a fluid-resisting part which has channel cross-sectional area smaller than that of the circulating liquid chamber.

SUMMARY

It is known that the ink-jet head of the circulation type not only prevents the ink in the vicinity of the nozzle from drying, but also that, in such a case that any air enters from the nozzle, the ink-jet head is capable of removing the air by using the ink flow. The inventors of the present disclosure found out, as a result of diligent and intensive studies and considerations, that in the above-described ink-jet head, a stepped part in a height direction (difference in height) is formed at the boundary between the circulating liquid chamber and the fluid-resisting part, and thus there is such a possibility that the air might be caught by the stepped part, and thus might become hard to be exhausted or discharged, and the inventors arrived at the present disclosure.

An object of the present disclosure is to provide a liquid discharge head of the circulation type wherein air entered thereinto from a nozzle is easily exhausted or discharged by a flow of ink in the vicinity of the nozzle.

According to an aspect of the present disclosure, there is provided a liquid discharge head including: a first common channel extending in a first direction; a second common channel extending in the first direction; and a plurality of individual channels having a plurality of pressure chambers arranged side by side in the first direction and a plurality of nozzles arranged side by side in the first direction. Each of the plurality of individual channels includes: a supplying part which communicates the first common channel with one of the plurality of pressure chambers; a descender part which extends in a second direction crossing the first direction and which communicates one of the plurality of pressure chambers located on an upstream side in the second direction with one of the plurality of nozzles located on a downstream side in the second direction; and a returning part which branches from the descender part, which extends in a third direction crossing the first direction and the second direction and which communicates with the second common channel. The returning part of each of the plurality of individual channels includes: a throttle part, a downstream end in the third direction of the throttle part being connected to the second common channel; and a wide part, an upstream end in the third direction of the wide part being connected to the descender part, a downstream end in the third direction of the wide part being connected to an upstream end in the third direction of the throttle part, and a cross-sectional area of a surface, of the wide part, which is perpendicular to the third direction is greater than a cross-sectional area of a surface, of the throttle part, which is perpendicular to the third direction. Each of the plurality of nozzles is located at a position at which each of the plurality of nozzles overlaps with the wide part in the second direction. At a throttle-starting position which is a boundary between the throttle part and the wide part, a length in the second direction of the throttle part and a length in the second direction of the wide part are same.

In the above-described configuration, at the throttle-starting position which is the boundary between the throttle part and the wide part, the length in the second direction of the throttle part and the length in the second direction of the wide part are same. That is, at the throttle-starting position, the height of the throttle part and the height of the wide part are same. Therefore, any stepped part in the height direction does not occur between the throttle part and the wide part at the throttle-stating position. As a result, when the ink flows from the wide part to the throttle part, it is possible to suppress such a situation that any air contained in the ink is caught by the stepped part, and it is possible to efficiently remove the air.

DESCRIPTION OF THE EMBODIMENTS

<Overall Configuration of Printer>

As depicted inFIG. 1, a printer1according to an embodiment of the present disclosure mainly includes an ink-jet head2, a head unit3, a platen4, conveying rollers5and6, and a controller7. In the following, a direction in which a recording paper (recording paper sheet, recording sheet) P is conveyed is defined as a conveyance direction, and the upstream side and the downstream side in the conveyance direction are defined, as depicted inFIG. 1. Further, a paper width direction of the recording paper P which is conveyed is defined as a left-right direction, and the right side and the left side of the left-right direction are also defined. The conveyance direction and the left-right direction are each a direction parallel to a horizontal plane and are orthogonal to each other.

The ink-jet head2is an ink-jet head of a so-called line-type, and has eight pieces of the head unit3. Further, as will be described later on, the ink-jet head2is an ink-jet head of a circulation type. As depicted inFIG. 1, the eight head units3are arranged in the staggered manner in the conveyance direction and the left-right direction. Each of the eight head units3discharges or ejects an ink from a plurality of nozzles45formed in the lower surface thereof. The ink-jet head2is provided with a driver IC8. As will be described later, the controller7controls the driver IC8so as to discharge or eject an ink from a desired nozzle45among the plurality of nozzles45.

The platen4is arranged so as to face or to be opposite to the lower surface of the ink-jet head2. The platen4extends in the left-right direction over the entire length in the paper width direction of the recording paper P. The platens4supports the recording paper P from therebelow. The conveying rollers5and6are arranged at the upstream side and the downstream side, respectively, in the conveyance direction of the recording paper P, and convey the recording paper P in the conveyance direction.

In the printer1, the controller7controls a non-illustrated motor (not depicted in the drawings) provided on the conveying rollers5and6so as to cause the conveying rollers5and6to convey the recording paper P in the conveyance direction by a predetermined distance. The controller7discharges or ejects the ink from the plurality of nozzles45of the ink-jet head2each time the recording paper P is conveyed. With this, the printer1executes printing with respect to the recording paper P.

Next, the head unit3of the ink-jet head2will be explained. As depicted inFIGS. 2 and 3A, each of the eight head units3includes a channel unit21in which an ink channel such as the plurality of nozzles45and a plurality of pressure chambers40are formed, and a piezoelectric actuator22which applies pressure to the ink in each of the plurality of pressure chambers40.

As depicted inFIGS. 3A and 3B, the channel unit21has eleven plates101to111which are stacked on one another in the up-down direction. The up-down direction corresponds to a “second direction” of the present disclosure. As depicted inFIG. 2, the channel unit21has six supply manifolds46, six return manifolds47, a plurality of individual channels30, and the plurality of pressure chambers40and the plurality of nozzles45formed in the plurality of individual channels30. The plurality of individual channels30have supplying parts41, descender parts42(seeFIG. 3A), and returning parts43, respectively. Note that, for a purpose that the drawings are seen comprehensively, the returning parts43inFIG. 2are illustrated by a solid line.

The plurality of pressure chambers40are formed in the plate101. Each of the plurality of pressure chambers40has a substantially rectangular shape of which longitudinal direction is the conveyance direction. Further, the plurality of pressure chambers40construct six pressure chamber rows (arrays)119arranged side by side in the conveyance direction. Each of the six pressure chamber arrays119extends in the left-right direction. In two pressure chamber arrays119, included in the six pressure chamber arrays119and which are adjacent to each other, the positions in the left-right direction of the pressure chambers40are shifted.

The plurality of supplying parts41are formed across the plates102and103. Each of the supplying parts41is a channel connecting one of the plurality of pressure chambers40and the supply manifold46to each other. One end of each of the supplying parts41is connected to one of the plurality of pressure chambers40through an opening40aformed in an end part on the upstream side in the conveyance direction of one of the plurality of pressure chambers40. The other end of each of the supplying parts41is connected to the supply manifold46through a supply port41a(an example of a “supply port” of the present disclosure). The cross-sectional area of each of the supplying parts41is smaller than the cross-sectional area of one of the descender parts42. Each of the supplying parts41is connected to an end part on the upstream side in the conveyance direction of one of the plurality of pressure chambers40, and extends from a connection part with respect to one of the plurality of pressure chambers40toward the upstream side in the conveyance direction.

The plurality of descender parts42are formed by allowing through holes formed in the plates102to110, respectively, to overlap with one another in the up-down direction. Each of the descender parts42is a part of a channel connecting one of the plurality of pressure chambers40and one of the plurality of nozzles45and extending downward from an end part on the downstream side in the conveyance direction of one of the plurality of pressure chambers40. A lower end of each of the descender parts42is connected to one of the returning parts43extending in the conveyance direction. Each of the descender parts42is a channel having a substantially cylindrical shape extending in the up-down direction. As depicted inFIG. 4A, an inner diameter D2of each of the descender parts42is greater than a distance L3in the conveyance direction from a throttle starting position P1(to be described later on) to the boundary between a wide part43W and a throttle part43S (to be described later on) (L3<D2). In the present embodiment, the distance L3in the conveyance direction from the throttle starting position P1to the boundary between the wide part43W and the throttle part43S is in a range of approximately 30 μm to approximately 150 μm, and the inner diameter D2of the descender part42is in a range of approximately 150 μm to approximately 180 μm.

The plurality of returning parts43are formed in the plates109and110. Each of the plurality of returning parts43is a channel connecting one of the descender parts42and the return manifold47. Each of the returning parts43extends toward the upstream side in the conveyance direction from a connecting part with respect to one of the descender parts42formed in the plate110. Further, each of the returning parts43is connected to the return manifold47through a return port43a(an example of a “return port” of the present disclosure) formed in the plate109. Each of the returning parts43includes a wide part43W and a throttle part43S. A length H1in the up-down direction (hereinafter also referred to as height H1) of the wide part43W is the same as a height H2of the throttle part43S (seeFIG. 4A). In the present embodiment, the height H1of the wide part43W and the height H2of the throttle part43S are approximately 15 μm.

As depicted inFIGS. 3A and 4A, each of the plurality of nozzles45is formed in the plate111, at a position overlapping with the wide part43W in the up-down direction. As depicted inFIG. 4A, a distance L2in the conveyance direction from the boundary between the wide part43W and the throttle part43S to a center line C1of each of the plurality of nozzles45is shorter than a distance L1in the conveyance direction from the center line C1of each of the plurality of nozzles45to a center line C2of the descender part42(L2<L1). In the present embodiment, the distance L1is set to be approximately two times the distance L2. Note that in the following explanation, the boundary between the wide part43W and the descender part42(or “the throttle part43S”) is referred to as a throttle starting position P1(seeFIG. 4B). A distance L3in the conveyance direction from the throttle starting position P1to the boundary between the wide part43W and the descender part42is greater than an inner diameter D1of each of the plurality of nozzles45(D1<L3). Further, a distance L4from the boundary between the wide part43W and the descender part42to the center line C1of each of the plurality of nozzles45is shorter than the distance L2in the conveyance direction from the throttle starting position P1to the center line C1of each of the plurality of nozzles45(L4<L2). In the present embodiment, the distance L1in the conveyance direction from the center line C1of each of the plurality of nozzles45to the center line C2of the descender part42is set to be two times the distance L2in the conveyance direction from the throttle starting position P1to the center line C1of each of the plurality of nozzles45. Further, the inner diameter D1of each of the plurality of nozzles45is defined as the diameter of an opening of the lower surface of the plate111. In the present embodiment, the inner diameter D1of each of the plurality of nozzles45is approximately 17 μm. As described above, there is no stepped part in the up-down direction (difference in height) at the boundary between the wide part43W and the throttle43S (H1−H2=0). Further, the distance L2in the conveyance direction from the throttle starting position P1to the center line C1of each of the plurality of nozzles45is in a range of 70 μm to 80 μm, the distance L1in the conveyance direction from the center line C1of each of the plurality of nozzles45to the center line C2of the descender part42is in a range of 120 μm to 130 μm, and the distance L4in the conveyance direction from the boundary between the wide part43W and the descender part42to the center line C1of each of the plurality of nozzles45is in a range of 10 μm to 20 μm.

As depicted inFIG. 4B, the descender part42and the wide part43have an oval shape in a top view. The length W1in the conveyance direction of the descender part42is the same as the length W2in the conveyance direction of the wide part43W (W1=W2). Further, both ends in the conveyance direction in an end part, of the wide part43, which is on a side closer to the throttle part43S in the left-right direction have a chamfered shape which is a curved shape in a top view. In the present embodiment, the both ends in the conveyance direction in the end part, of the wide part43, which is on the side closer to the throttle part43S in the left-right direction have a shape which is substantially elliptical in a top view. A length W3in the conveyance direction of the throttle part43S at the throttle starting position P1is smaller than the length W2in the conveyance direction of the wide part43W (W3<W2). In the present embodiment, the length W3in the conveyance direction of the throttle part43S at the throttle starting position P1is not more than half the length W2in the conveyance direction of the wide part43W (W3≤(W2)/2). In the present embodiment, the length W1in the conveyance direction of the descender part42and the length W2in the conveyance direction of the wide part43W are in a range of approximately 150 μm to approximately 180 μm, and the length W3in the conveyance direction of the throttle part43S at the throttle-stating position P1is in a range of approximately 70 μm to approximately 100 μm.

As depicted inFIG. 3A, the supply manifold46is formed in plate104. As depicted inFIG. 2, each of the six supply manifolds46extends in the left-right direction, and the six supply manifolds46are arranged side by side, with spacing distances therebetween, in the conveyance direction. The six supply manifolds46correspond to the six pressure chamber arrays119, and each of the respective supply manifolds46is connected, via the supplying parts41, to pressure chambers40, respectively, constructing a pressure chamber array119, among the six pressure chamber arrays119, corresponding thereto. Supply ports128are formed each at an end part on the left side in the left-right direction of one of the six supply manifolds46. Further, the ink stored in a non-illustrated ink tank is supplied from the supply ports128to the six supply manifolds46, respectively. With this, in each of the six supply manifolds46, the ink flows from the left side to the right side in the left-right direction, and the ink is supplied to each of the pressure chambers40through one of the supplying parts41.

As depicted inFIG. 3A, the return manifold47is formed in plates107and108. As depicted inFIG. 2, each of the six return manifolds47extends in the left-right direction, and the six return manifolds47are arranged side by side, with spacing distances therebetween, in the conveyance direction. Recovery ports129are formed each at an end part on the left side in the left-right direction of one of the six return manifolds47. The non-illustrated ink tank is connected to the recovery ports129. As depicted inFIGS. 3A and 3B, each of the return manifolds47is located at a location below one of the supply manifolds46and overlaps one of the supply manifolds46in the up-down direction. Further, the six return manifolds47correspond to the six pressure chamber arrays119, respectively, and each of the return manifolds47is connected to the pressure chambers40constructing a pressure chamber array119, among the six pressure chamber arrays119and corresponding thereto, via the descender parts42and the returning parts43. In each of the return manifolds47, the ink which is not discharged or ejected from one of the nozzles45flows thereinto from the returning part43of one the individual channels30; the ink flows from the right side toward the left side in the left-right direction; and the ink is recovered from one of the recovery ports129. The ink flowing out from the recovery ports129is returned to the non-illustrated ink tank.

Note that as depicted inFIG. 2, communicating channels50connecting the supply manifolds46and the return manifolds47, respectively, are formed at right ends in the left-right direction of the supply manifolds46and the return manifolds47, respectively. Since each of the communicating channels50has a same shape as one of the plurality of individual channels30except that each of the communicating channels50is not in communication with one of the plurality of nozzles45, a detailed description thereof will be omitted.

In the present embodiment, a non-illustrated pump is provided at an intermediate part or location in a channel between the ink supply ports128and the ink tank, or at an intermediate part or location in a channel between the recovery ports129and the ink tank. The ink is circulated between the ink-jet head2and the non-illustrated ink tank by a flow of ink generated in a case that the non-illustrated pump is driven. Note that in the present embodiment, the pressure applied to the ink flowing through each of the supply manifolds46is made to be greater than the pressure applied to the ink flowing through each of the return manifolds47. This creates a flow of the ink from each of the supply manifolds46to one of the return manifolds47.

Further, in the channel unit21, a damper130is formed. The damper130extends across a lower part of the plate105and an upper part of the plate106, and overlaps with each of the supply manifolds46and each of the return manifolds47in the up-down direction. Further, in a case that a partition wall separating each of the supply manifold46and the damper130and formed by a lower end part of the plate106is deformed, any pressure fluctuation of the ink in each of the supply manifolds46is suppressed. Furthermore, in a case that a partition wall separating each of the return manifold47and the damper130and formed by an upper end part of the plate105is deformed, any pressure fluctuation of the ink in each of the return manifolds47is suppressed.

As depicted inFIG. 3A, the piezoelectric actuator22has two piezoelectric layers141and142, a common electrode143, and a plurality of individual electrodes144. The piezoelectric layers141and142are formed of a piezoelectric material. For example, it is possible to use a piezoelectric material containing, as a main component thereof, lead zirconate titanate (PZT) which is a mixed crystal of lead titanate and lead zirconate. The piezoelectric layer141is arranged on the upper surface of the channel unit21, and the piezoelectric layer142is arranged on the upper surface of the piezoelectric layer141. Note that the piezoelectric layer141may be formed of an insulative material which is different from the piezoelectric material.

The common electrode143is arranged between the piezoelectric layer141and the piezoelectric layer142and extends continuously over the entire areas of the piezoelectric layers141,142. The common electrode143is maintained at the ground potential. The plurality of individual electrodes144are provided individually with respect to the plurality of pressure chambers40, respectively. Each of the plurality of individual electrodes144has a planar shape which is substantially rectangular, and is arranged so as to overlap, in the up-down direction, with a central part of one of the plurality of pressure chambers40corresponding thereto. Connection terminals144aof the plurality of individual electrodes144are connected to the driver IC8(seeFIG. 1) via non-illustrated trace members. The individual electrodes144are selectively provided with either one potential of the ground potential and the driving potential individually by the driver IC8. Further, corresponding to the arrangement of the common electrode143and the plurality of individual electrodes144in such a manner, a part, of the piezoelectric layer142, which is sandwiched by each of the plurality of individual electrodes144and the common electrode143is made to be an active part polarized in a thickness direction thereof.

Here, a method of discharging the ink from each of the plurality of nozzles45by driving the piezoelectric actuator22will be explained. In the present embodiment, the ink(s) is (are) discharged by a so-called pull-strike system as explained below. The control described as below is executed by the controller7(seeFIG. 1) controlling the driver IC8, to thereby control the potentials of the common electrode143and each of the plurality of individual electrodes144. In the piezoelectric actuator22, in a stand-by state in which the ink is not discharged from the nozzle45, the common electrode143is maintained at the ground potential, and all the plurality of individual electrodes144are held at driving potential different from the ground potential. In this situation, parts, of the piezoelectric layer141and142, respectively, which overlap with the pressure chamber40in the up-down direction are deformed so as to project toward the pressure chamber40as a whole.

In a case that the ink is to be ejected or discharged from a certain nozzle45among the plurality of nozzles45, the potential of a certain individual electrode144which is included in the plurality of individual electrodes144and which corresponds to the certain nozzle45is switched to the ground potential. This causes the deformation of the parts, of the piezoelectric layers141and142, overlapping with a certain pressure chamber40, included in the plurality of pressure chambers40and corresponding to the certain nozzle45, in the up-down direction to return to their original shapes, thereby increasing the volume of the certain pressure chamber40. Afterwards, by switching the potential of certain individual electrode144again to the driving potential, the parts, of the piezoelectric layers141,142, overlapping with the certain pressure chamber40in the up-down direction are deformed so as to project toward the certain pressure chamber40. Thus, the pressure of the ink in the certain pressure chamber40is increased, and thus the ink is discharged from the certain nozzle45communicating with the certain pressure chamber40. Even after the ink is ejected from the certain nozzle45, the potential of the certain individual electrode144is maintained at the driving potential.

In the present embodiment, the nozzle45is provided on the wide part43W. In other words, at least a part of the nozzle45is arranged at a position overlapping the wide part43W in the up-down direction. For example, there is such a case, for example, that after the ink is discharged, the meniscus of the ink in the nozzle45is vibrated and that any air enters from the nozzle45, in some cases. In such a case that an air bubble, generated by the air which has entered, is present in the inside of the channel, a part of the pressure applied from the piezoelectric actuator22so as to discharge the ink is consequently consumed to shrink the air bubble. In such a situation, there is such a fear that the pressure for discharging the ink might become insufficient, and any discharge failure or unsatisfactory discharge might occur. Therefore, it is preferable to remove the air bubble of the air, which has entered from the nozzle45, as quickly as possible. In particular, in such a case that the air bubble is present in the vicinity of the nozzle45, there is a high possibility that any discharge failure or unsatisfactory discharge might occur in the nozzle45, and thus the air bubble is required to be removed quickly.

The ink-jet head2of the present embodiment is the ink-jet head of the so-called circulation type. In the ink-jet head2of the present embodiment, the air bubble of the air entering from the nozzle45can be pushed away toward the return manifold47by the ink flowing through the returning part43(the wide part43W).

In the present embodiment, since the height H1of the wide part43W is same as the height H2of the throttle part43S, there is no stepped part in the height direction (difference in height), at the throttle starting position P1, between the wide part43W and the throttle part43S. Therefore, there is no fear that the air bubble of the air might be caught by and remain in any stepped part (difference in height) at the boundary between the wide part43W and the throttle part43S, and it is possible to push the air bubble of the air, by the ink flowing through the returning part43(the wide part43W), reliably toward the return manifold47.

Further, in the present embodiment, the height H2of the throttle part43S is uniform in the longitudinal direction (the left-right direction) of the throttle part43S, and there is not any stepped part in the up-down direction (difference in height), in the inside of the throttle part43S, at which that the air bubble of the air might be otherwise caught. Therefore, there is no fear that the air bubble of the air might be caught by and might remain at the stepped part also in the inside of the throttle part43S.

As described above, the both ends in the conveyance direction in the end part, of the wide part43, which is on the side closer to the throttle part43S in the left-right direction have a shape which is substantially elliptical in a top view. The both ends in the conveyance direction in the end part, of the wide part43, which is on the side closer to the throttle part43S in the left-right direction have a chamfered shape which is a curved shape in a top view. Thus, there is no such a fear that the air bubble of the air might be caught at the both ends in the conveyance direction in the end part, of the wide part43, which is on the side closer to the throttle part43S in the left-right direction. Therefore, the air bubble of the air can be reliably pushed toward the return manifold47by the ink flowing through the returning part43(the wide part43W).

In the present embodiment, as described above, the distance L2in the conveyance direction from the boundary between the wide part43W and the throttle part43S (throttle starting position P1) to the center line C1of the nozzle45is shorter than the distance L1in the conveyance direction from the center line C1of the nozzle45to the center line C2of the descender part42(L2<L1). Namely, the center of the nozzle45is located at a position closer to the throttle starting position P1than the center of the descender part of42. As depicted inFIG. 4B, the length in the conveyance direction of the wide part43W is narrowed further as approaching closer, in the left-right direction, toward the throttle part43S, and thus the flow rate of the ink flowing through the wide part43W becomes faster as the ink approaches closer to the throttle part43S. Therefore, the center of the nozzle45is arranged at the position closer to the throttle starting position P1than the center of the descender part42, thereby making the flow rate of the ink flowing in the vicinity of the nozzle45to be greater, and allowing the air bubble of the air to be reliably pushed toward the return manifold47.

As mentioned above, the length W1in the conveyance direction of the descender part42is same as the length W2in the conveyance direction of the wide part43W (W1=W2). Therefore, there is no stepped part (difference in height) in the conveyance direction between the descender part42and the wide part43W, and thus there is no such a fear that the air bubble of the air might be caught by the stepped part. Further, the length W3in the conveyance direction of the throttle part43S at the throttle starting position P1is not more than half the length W2in the conveyance direction of the wide part43W (W3≤(W2)/2). Note that in the present embodiment, the height H1of the wide part43W and the height H2of the throttle part43S are same. Therefore, in such a case that the difference between the length W3in the conveyance direction of the throttle part43S at the throttle starting position P1and the length W2in the conveyance direction of the wide part43W is small, most of the pressure wave advancing or proceeding to the wide part43W escapes through the throttle part43S. From the viewpoint of improving the discharge force of the ink from the nozzle45provided on the wide part43W, it is preferable to set the length W2in the conveyance direction of the wide part43W to be not less than two times the length W3in the conveyance direction of the throttle part43S. With this, it is possible to suppress any loss of the discharge force of the ink from the nozzle45provided on the wide part43W.

Further, in such a case that a part of the nozzle45is at a position overlapping with the descender part42in the top plan view, the ink flowing downward through the descender part42imparts the downward pressure to the air bubble of the air entering from the nozzle45, thereby causing the air bubble of the air to be less likely to flow leftward toward the return manifold47. On the other hand, in the present embodiment, as described above, the distance L3in the conveyance direction from the throttle starting position P1to the boundary between the wide part43W and the descender part42is greater than the inner diameter D1of the nozzle45(D1<L3). Therefore, it is possible to arrange the nozzle45so that the entirety of the nozzle45overlaps reliably with the wide part43W in the up-down direction. In the wide part43W, since a component of the ink flow directed to the left side is greater than a component of the ink flow directed to the lower side, the air bubble of the air entered from the nozzle45can be reliably pushed toward the return manifold47.

The pressure wave generated in the pressure chamber40becomes weaker as the pressure wave moves farther from the pressure chamber40. The wide part43W is connected, at the downstream side thereof in the conveyance direction, to the descender part42, having a cross-sectional area greater than that of the wide part43W, and is connected, at the upstream side thereof in the conveyance direction, to the throttle part43S, having a cross-sectional area smaller than that of the wide part43W. In the wide part43W, the pressure wave is not weakened on the downstream side in the conveyance direction which is close to the pressure chamber40and the descender part42, as compared with the upstream side in the conveyance direction close to the throttle part43S. In the present embodiment, as described above, the distance L4from the boundary between the wide part43W and the descender part42to the center line C1of the nozzle45is shorter than the distance L2from the boundary between the wide part43W and the throttle part43S (throttle starting position P1) to the center line C1of the nozzle45(L4<L2). With this, it is possible to prevent the pressure wave at a position immediately above the nozzle45from becoming too weak, thereby making it possible to prevent any discharge failure of the ink from the nozzle45.

The embodiment as explained above is merely an example, and may be changed as appropriate. For example, it is allowable to set the number, arrangement, shape, pitch, etc., of the pressure chambers arbitrary or optionally, and according to this, it is allowable to adjust the number, arrangement, shape, pitch, etc., of the individual electrodes and the nozzles. Further, the inner diameter of the nozzle45, the height of the wide part43W, the height of the throttle part43S, etc., in the above-described embodiment are described as examples only, and the present disclosure is not limited thereto or restricted thereby, and may be changed as appropriate. For example, in the above-described embodiment, the height H2of the throttle part43S is uniform in the longitudinal direction (the left-right direction) of the throttle part43S. However, under a condition that any stepped part in the up-down direction at which the air bubble of the air might be caught is not provided in the inside of the throttle part43S, it is not necessarily indispensable that the height H2of the throttle part43S is uniform in the longitudinal direction (the left-right direction) of the throttle part43S. For example, as depicted inFIG. 5, a height H2of a throttle part143S may be gradually increased toward the downstream side (left side inFIG. 5) of the flow of the ink.

In the above-described embodiment, the length W1in the conveyance direction of the descender part42is same as the length W2in the conveyance direction of the wide part43W. However, the present disclosure is not limited to such an aspect. For example, as depicted inFIG. 6, a length W2in the conveyance direction of a wide part143W may be smaller than the length W1in the conveyance direction of the descender part42(W2<W1). Also in this case, at the boundary between the descender part42and the wide part143W, there is no stepped part (height in difference) in the conveyance direction and the left-right direction at which the air bubble of the air might be caught. Therefore, the air bubble of the air can be reliably pushed toward the return manifold47. Note that the diameter D1of the nozzle45is smaller than the length W2in the conveyance direction of the wide part143W (D1<W2). Since the diameter D1of the nozzle45is smaller than the length W2in the conveyance direction of the wide part143W, the nozzle45can be arranged to ensure that the entirety of the nozzle45overlaps with the wide part143W in the up-down direction. Thus, it is possible to reliably push the air bubble of the air entering from the nozzle45toward the return manifold47.

In the above-described embodiment, the wide part43W and the throttle part43S extend parallel to the left-right direction, but the present disclosure is not limited to such an aspect. For example, as depicted inFIG. 7, a wide part243W and a throttle part243S may extend so as to be inclined toward one side (e.g., the upstream side) in the conveyance direction, rather than extending parallel to the left-right direction. In such a case, as compared to the case wherein the wide part43W and the throttle part43S extend parallel to the left-right direction, the sum total of the lengths in the extending direction of the wide part243W and the throttle part243S can be made longer. This makes it possible to increase the channel resistance in the returning part (the wide part243W and the throttle part243S) as compared with the case wherein the wide part43W and the throttle part43S extend parallel to the left-right direction. Therefore, it is possible to reduce such a situation that the pressure wave generated in the pressure chamber40escapes through the returning part. Further, inFIG. 7, the wide part243W and the throttle243S extend in a same directions. Therefore, there is no bent part or curve part at the boundary between the wide part243W and the throttle243S, and the air bubble of air is less likely to be caught. Note that inFIG. 7, both the wide part243W and the throttle243S extend so as to be inclined toward one side (e.g., the upstream side) in the conveyance direction with respect to the left-right direction, but the present disclosure is not limited to such an aspect. For example, one of the wide part243W and the throttle243S may extend so as to be inclined toward one side (e.g., the upstream side) in the conveyance direction with respect to the left-right direction. Also in this case, the channel resistance in the returning part (the wide part243W and the throttle part243S) can be made greater than in the case wherein the wide part43W and the throttle part43S extend parallel to the left-right direction.

In the above-described embodiment, the length in the conveyance direction of the throttle part43S is uniform in the extending direction (left-right direction). However, the present disclosure is not limited to such an aspect. For example, as depicted inFIG. 8, a length W4in the conveyance direction of an end part, in the left-right direction of a throttle343S, on a side opposite to the throttle-stating position P1may be greater than a length W3in the conveyance direction of the throttle part343S at the throttle-stating position P1(W4>W3). In this case, in a case that the plate110and the plate109are positioned with respect to each other, it is easy to position the return port43aformed in the plate109and the throttle part343S formed in the plate110to each other. Note that the shape of the throttle part343S is not limited to such an aspect; it is allowable, for example, that the throttle part343S is formed to have such a shape in which the length in the conveyance direction of the throttle343S becomes gradually longer toward the left side in the left-right direction. Further, note that the length W4in the conveyance direction of the end part, of the throttle343S, on the side opposite to the throttle starting position P1in the left-right direction may be a length in a range of approximately 100 μm to approximately 130 μm.

The above-described embodiment and modifications are not limited to the above-described aspects, and may be combined as appropriate.

In the above-described embodiment, although the ink-jet head is the ink-jet head of the so-called line-type, the present disclosure is not limited to this; the present disclosure is applicable also to an ink-jet head of a so-called serial-type. Further, the present disclosure is not limited to being applicable to the ink-jet head which discharge an ink. The present disclosure is also applicable to a liquid discharge apparatus usable in a variety of kinds of usages or applications other than printing image, etc. For example, it is possible to apply the present disclosure also to a liquid discharge apparatus configured to form a conductive pattern on a surface of a substrate by discharging a conductive liquid onto the substrate.