Liquid ejection head and liquid ejection apparatus with beam-shaped members in flow passage

In a liquid ejection head and a liquid ejection apparatus that can suppress deterioration of image quality, a plurality of second beam-shaped member is provided on the downstream side of a first beam-shaped member in a flow passage connected to an ejection element substrate. The first beam-shaped member divides the flow passage into two flow passages in a liquid-flowing direction and the second beam-shaped member sandwich a line extending from the first beam-shaped member in the liquid-flowing direction.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a liquid ejection head used in a liquid ejection apparatus, and the liquid ejection apparatus.

Description of the Related Art

In the liquid ejection head, there are cases where ejected bubbles are generated from the vicinity of an ejection port along with ejection. The ejected bubbles generated along with ejection float in a flow passage with the aid of their own buoyancy and remain above the flow passage. In the case where the flow rate of liquid in the flow passage is increased by an ejecting operation, the velocity of the liquid in the flow passage is increased, and small bubbles derived from the ejected bubbles which remain above the flow passage are carried away by the flow and fall downward toward an ejection element substrate. In the case where the small bubbles which have fallen downward in this way reach an ejection port, the small bubbles sometimes generate nonejection of not ejecting the liquid. In a case where generation places and generation timing of nonejection are randomly distributed, it is difficult to visually confirm such nonejection, and thus nonejection may rarely deteriorate sensory image quality.

In liquid ejection heads that supply the liquid to the ejection element substrate provided with a comparatively long ejection port array, there is a liquid ejection head having a long-hole flow passage which guides the liquid to a long hole-like liquid supply port of the ejection element substrate and which is widely opened in a long-hole shape. Such a structure makes it possible to supply a large amount of liquid simultaneously and uniformly to the entire ejection element substrate in comparison with a structure of a flow passage accompanied with a steep throttle directly upstream of the ejection element substrate.

In Japanese Patent Laid-Open No. 2011-079246, there is disclosed a liquid ejection head in which a beam-shaped member is provided in the flow passage for reinforcement and the like in order to prevent deformation in the process of manufacturing the long-hole flow passage.

There are cases where flow velocities are different from each other between one side and the other side of the long-hole flow passage in a longitudinal direction depending on the structure of the liquid ejection head. In a case where the beam-shaped member is provided in the flow passage and a difference in flow velocities between the flow passages on the both sides of the beam-shaped member is large as that in Japanese Patent Laid-Open No. 2011-079246, a flow directed from a high-velocity flow passage toward a low-velocity flow passage is generated at a downstream-side terminal of the beam-shaped member.

At this time, also the small bubbles having fallen downward together with the flow of the liquid are carried away toward the low-velocity flow passage side. However, in many cases, the small bubbles are sucked into a flow directed toward the ejection port of the ejection element substrate in the case of passing through the downstream-side terminal of the beam-shaped member. Therefore, there are cases where nonejection frequently occurs in the ejection port located directly under the beam-shaped member and causes deterioration of the image quality.

SUMMARY OF THE INVENTION

Therefore, the present invention aims to provide a liquid ejection head and a liquid ejection apparatus which make it possible to suppress deterioration of the image quality.

According to the present invention, there is provided a liquid ejection head including: an ejection element substrate configured to eject liquid; and a flow passage configured to guide the liquid to the ejection element substrate, wherein the flow passage includes a first beam-shaped member configured to divide the flow passage into a plurality of flow passages and a plurality of second beam-shaped members which are provided on a downstream side of the first beam-shaped member in a liquid-flowing direction so as to sandwich a line extending the first beam-shaped member in the liquid-flowing direction.

According to the present invention, it is possible to achieve the liquid ejection head and the liquid ejection apparatus which make it possible to suppress deterioration of the image quality.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, the first embodiment of the present invention will be described with reference to the drawings.

FIG. 1is a perspective view illustrating a liquid ejection apparatus200to which the present invention is applicable. A carriage102on which a liquid ejection head is to be mounted is supported to be reciprocally movable along a guide103extending in a main scanning direction. The carriage102to which a liquid supply tube has been connected is driven by a carriage motor (not illustrated).

A printing medium such as a sheet of paper is fed by a sheet feed roller (not illustrated) driven by a sheet feed motor (not illustrated) of a sheet feed mechanism via a gear train, and is sent out onto a platen106by a conveying roller104and a pinch roller (not illustrated). Liquid is ejected from an ejection port of the liquid ejection head and printing is performed on the printing medium which is conveyed on the platen106by the conveying roller104and a sheet discharge roller (not illustrated).

In the case of performing printing on the printing medium, the carriage102is accelerated from a stopped state, and then is moved at a constant speed throughout a scanning range for a printing operation. At this time, the liquid is ejected from the ejection port of the liquid ejection head onto the printing medium to thereby form an image on the printing medium. After printing for one line has been completed by performing one time or a plurality of times of scanning, the carriage102is decelerated and comes to a standstill. Then, the printing medium is fed by a predetermined amount by rotation of the conveying roller104and the sheet discharge roller.

FIG. 2is an exploded perspective view illustrating a liquid ejection head100according to the first embodiment. The liquid ejection head100includes a liquid supply unit110, an ejection element unit150for accepting supply of the liquid from the liquid supply unit110and ejecting the liquid onto the printing medium. The liquid ejection head100is fixedly supported on the carriage102by a positioning unit and an electric contact of the carriage102provided in the liquid ejection apparatus (not illustrated) and is made to be detachable relative to the carriage102.

The liquid ejection apparatus200is provided with a liquid supply tube connected with a liquid tank (not illustrated), and a leading end of the liquid supply tube is provided with a liquid connector. In the case where the liquid ejection head100is mounted, the liquid connector and a liquid connector insertion port113are air-tightly connected together and the liquid in the liquid tank is supplied to the liquid ejection head100. In the present embodiment, the liquid ejection head100is one capable of mounting six kinds of liquid, liquid connector insertion ports113ato113fare provided respectively corresponding to the liquid supply tubes, and supply paths are individually formed.

The ejection element unit150includes two ejection element substrates155aand155b,a first support member151, a second support member152, an electric wiring tape153, an electric contact substrate154. Although, in the present embodiment, the first support member151and the second support member152are made of calcined alumina, the first support member151and the second support member152may be formed by a resin mold similarly to a housing111.

An ejection element substrate155of the ejection element unit150includes an energy generation element which generates energy utilized for ejecting the liquid onto one surface of a Si substrate having a thickness of 0.5 to 1 mm. In the present embodiment, a plurality of heaters is used as the energy generation element, and electric wiring which supplies electric power to each heater is formed by a film deposition technology. Then, a plurality of liquid flow passages and a plurality of ejection ports which respectively correspond to the heaters are formed by a photolithographic technology, and ejection port liquid chambers (not illustrated) are formed so as to be opened to the back surface in order to supply the liquid to the plurality of liquid flow passages. Note that the energy generation element used may be a piezoelectric element.

The second support member152having an opening for the ejection element substrate is adhesively fixed to the first support member151, and the electric wiring tape153is held so as to be electrically connected to an ejection element substrate155(155a,155b) via the second support member152. The electric wiring tape153is adapted to apply an electric signal for ejecting the liquid to the ejection element substrate155. An electric contact substrate154which includes an external signal input terminal adapted to receive the electric signal from the liquid ejection apparatus200is thermally crimped and electrically connected to an end of the electric wiring tape153, by using an anisotropic electro-conductive film (not illustrated).

The ejection element substrate155is adhesively fixed to the first support member151which includes a liquid supply port156. Six liquid supply ports156ato156fare formed in the first support member151, and the liquid supply ports156ato156fare respectively connected with third liquid chambers123ato123fprovided in the housing111.

FIG. 3is a cross-sectional diagram taken along III-III inFIG. 2illustrating liquid supply from the liquid connector insertion port113cto the ejection element unit150. Other five liquid supply systems such as a liquid supply system which includes the liquid connector insertion port113ahave the same structures as the above. The liquid supplied from the liquid connector insertion port113cpasses through a filter114cwhich prevents mixing of foreign substances into the ejection port, and is supplied to the ejection element unit150through a first liquid chamber121c,a second liquid chamber122cand the third liquid chamber123c.Resin molded parts are adopted as the housing111and a lid member112.

The first liquid chamber121c, the second liquid chamber122c, the third liquid chamber123cand the liquid supply port156care all flow passages which are arranged in long hole shapes in an ejection port arrangement direction and form a long-hole communication flow passage130cby mutually communicating them. The communication flow passage130cis a deviated supply path in which the center of a long-hole flow passage located directly downstream of the filter1146cshifts in the ejection port arrangement direction of the ejection element substrate155a. An amount of deviation of the deviated supply path is determined in accordance with a size of the liquid ejection head100and a layout of supply paths for the liquid of a plurality of colors.

In addition, a flow passage (not illustrated) located adjacent to the communication flow passage130chas a structure in which the left and the right are reversed relative to an almost central axis B-B inFIG. 3. Accordingly, the respective flow passages are densely arranged, and miniaturization of the liquid ejection head is achieved. A slope124is for preventing stagnation of liquid flows and the small bubbles in the communication flow passage130c,and has a structure in which the slope is preferably provided in the deviated supply path.

FIG. 4is a diagram illustrating a flow passage region where a first beam-shaped member and a second beam-shaped member of the liquid ejection head100according to the present embodiment are provided. The beam-shaped members are respectively provided in the liquid chamber123cand the liquid supply port156c.A first beam-shaped member131cextending from the upstream (the filter side) to the downstream (the ejection element side) of the flow passage in the liquid chamber123cis arranged approximately at a central part in a width direction of the liquid chamber123cof about 26 mm in width in the ejection port arrangement direction. Consequently, the liquid chamber123cis divided into two chambers of a left-side liquid chamber123pand a right-side liquid chamber123qof the beam-shaped member131c.The left liquid chamber123pis located on the side where the filter114cis provided, and is a deviated-side flow passage.

In addition, the right liquid chamber123qis located on the side where the filter114cis not provided, and is a reversely-deviated-side flow passage. The liquid which has flown into the second liquid chamber122cfrom the oblique upper left-hand side in the drawing is supplied to the third liquid chamber123cthrough the second liquid chamber122c.The flow of the liquid is partially regulated by the beam-shaped member131cwhich vertically extends, and the liquid reaches the ejection element substrate155a.

One set of second beam-shaped members132iand132jis provided in the vicinity of a joint section between the support member151of a liquid supply port156cand the housing111at intervals of about 10 mm so as to sandwich an extension line L of the first beam-shaped member131c.

The first beam-shaped member131cis arranged at a central part of the liquid chamber123cwhich is favorable for reinforcement as a reinforcement member for preventing deformation of the resinous liquid chamber123cin resin molding into a long-hole shape. On the other hand, the second beam-shaped members132iand132jare provided as reinforcement members against deformation in alumina calcination. It is advantageous to reduce the number of the beam-shaped members132from the viewpoint of reducing flow resistance in the liquid supply port156cby providing the second beam-shaped members. However, a problem is generated in the case of one beam-shaped member132. Regarding the point, description will be made in a later-described comparative example.

Next, the behavior of small bubbles140in the flow passage during ejection according to the present embodiment will be described.

The small bubbles140derived from ejected bubbles generated from the ejection port along with ejection float in the communication flow passage130cwith the aid of the buoyancy, and are accumulated by floating above the first liquid chamber121cwhich is located downstream of the filter114cwith the aid of a meniscus stretched over the filter114c. Some of them are accumulated also in the second liquid chamber122c. In a case where the flow rate in the communication flow passage130cin ejection is comparatively small, the small bubbles remain above the first liquid chamber121cand the like. However, in the case where the flow rate of the liquid flowing through the communication flow passage130cis increased in high-speed ejection and force of pushing the small bubbles downstream exceeds the flow power of the small bubbles140, the small bubbles140fall downward toward the downstream through a path such as a flow141. The number of the small bubbles carried toward the downstream becomes larger as the flow velocity becomes larger.

In case of the liquid supply unit110including the deviated supply path as in the present embodiment, even in a case where there is no particular deviation in ejection distribution of liquid droplets ejected from the ejection ports which are arranged just like a belt-shaped pattern in the ejection port arrangement direction, the flow rate in the deviated side flow passage becomes larger than the flow rate in the reversely deviated side flow passage in the deviated flow passage. Accordingly, also the flow velocity becomes higher in the deviated side flow passage. That is, in the third liquid chamber123c,the flow velocity in the left liquid chamber123pbecomes higher than the flow velocity in the right liquid chamber123q.Therefore, a larger number of the small bubbles fall downward in the left liquid chamber123pthan in the right liquid chamber123q.

The liquid flowing through the left liquid chamber123pis divided into two flows141aand141bby the beam-shaped member132i.In the two flows, one flow141bmerges with a flow141dfrom the right liquid chamber123qdirectly under a lower end of a beam-shaped member131c,and flows through a region158bbetween the beam-shaped member132iand the beam-shaped member132jof the liquid supply port156cby more reducing the flow velocity than that of the flow in the left liquid chamber123p.The other flow141ain the left liquid chamber123ppasses on the left side of the beam-shaped member132iand reduces its flow velocity due to a spread157at an end of the liquid supply port156c.

The liquid flowing through the right liquid chamber123qis divided into two flows141cand141dby the beam-shaped member132j.In the two flows, one flow141dmerges with the flow141bfrom the left liquid chamber123pflowing under the beam-shaped member131c,and flows through the region158bbetween the beam-shaped member132iand the beam-shaped member132jof the liquid supply port156cby more increasing the flow velocity than that of the flow in the right liquid chamber123q.The other flow141cof the liquid in the right liquid chamber123qpasses on the left side of the beam-shaped member132jand reduces its flow velocity due to the spread157at the end of the liquid supply port156c.

As a result, a difference in flow velocity between adjacent regions in three regions158a,158band158cof the liquid supply port156cdivided by the beam-shaped members132iand132jis made smaller than the difference in flow velocity of the liquid between the left liquid chamber123pand the right liquid chamber123q.Since the difference in flow velocity between the adjacent regions is small, almost no flow of the liquid flowing between the respective regions is generated in parts at the lower end portions of the beam-shaped member132iand the beam-shaped member132j.Consequently, the small bubbles140carried to the three regions of the liquid supply port156care distributedly carried to the vicinity of the ejection ports via ejection port liquid chambers located downstream of the respective regions without concentrating on the parts under the beam-shaped members.

The amount of the small bubbles carried from each of the left and right liquid chambers of the beam-shaped member131to the region158bis changed depending on the flow rate in each of the left and right liquid chambers of the third liquid chamber123c,associated with details of ejection. Supposing that the liquid droplets are continuously ejected from all of the ejection ports, the flow rate in the left liquid chamber123pis larger than that in the right liquid chamber123q.In addition, the flow rate of the liquid flowing from the left liquid chamber123pinto the region158bis larger than the flow rate of the liquid flowing from the right liquid chamber123qinto the region158b.Therefore, the amount of the small bubbles carried from the left liquid chamber123pinto the region158bbecomes larger than that of the small bubbles carried from the right liquid chamber123qinto the region158b.

As described above, the small bubbles carried to the liquid supply port156cfall downward by being distributed in the three regions divided by one set of beam-shaped members132, thereby not concentrating on a specific place. Accordingly, although there is the possibility that the fallen small bubbles may jump into the ejection ports, the places are distributed in the ejection port arrangement direction, and thus a visible ejection failure is hardly generated.

FIG. 5Ais a diagram illustrating a flow passage region in which the beam-shaped member of a liquid ejection head of a comparative example of the present embodiment is provided. In the liquid ejection head of the comparative example, the reinforcement beam-shaped member131to be provided in the third liquid chamber123chas the same structure as the liquid ejection head according to the embodiment of the present invention inFIG. 4and one beam-shaped member132kis provided in the liquid supply port156capart from the ejection element substrate155aby the distance which is the same as that in the example inFIG. 4. The beam-shaped member132kis provided at a central part of the liquid supply port156cwhich is a favorable position for preventing deformation of the long-hole liquid supply port156cby one beam-shaped member, that is, directly downstream of the beam-shaped member131c.

FIG. 5Bis for describing a moving state of the small bubbles in the liquid ejection head in the comparative example. At this time, the small bubbles carried by the liquid flow fall downward toward the downstream through the path such as the flow141. Since a gap between a lower end of the beam-shaped member131cand the beam-shaped member132kis smaller than a space under the beam-shaped member132k,the liquid flow from the left liquid chamber123pto the region158e moves along a path141bpassing through a lower end of the beam-shaped member132k.

In the configuration in which the two beam-shaped members are provided according to the embodiment of the present invention, the small bubbles are distributed in the ejection port arrangement direction, whereas, in the comparative example, a constant flow is generated along the ejection element substrate155adirectly under the beam-shaped member132k.A constant ratio of the small bubbles contained in the flow is sucked into the flow toward the ejection port located directly under the beam-shaped member132k,and causes sudden nonejection in the ejection port in the vicinity of the beam-shaped member132k.Since the sudden nonejection concentrates on some regions, visible ejection failures are generated.

Note that the shapes of the one set of the beam-shaped members132iand132jmay be different from each other. For example, the vertical length of the deviated-side beam-shaped member132imay be made longer than that of the beam-shaped member132j,and thus flow regulation of the liquid flow from the left liquid chamber123pin which the flow rate is comparatively large may be performed.

FIG. 6is a diagram illustrating a modification of the liquid ejection head according to the present embodiment. Although, in the present embodiment, an example of the communication flow passage having a deviated liquid supply structure has been described, the present invention is not limited to the deviated liquid supply structure. For example, even in a long-hole communication flow passage through which the liquid is supplied without deviation as illustrated inFIG. 6, the difference in flow velocity is generated between left and right regions of the beam-shaped member131cdepending on the liquid to be ejected. In this case, it is possible to distribute the positions where the small bubbles jump into the ejection ports as in the present embodiment by setting a positional relation among the beam-shaped member131c,the beam-shaped member132iand the beam-shaped member132jas illustrated inFIG. 6.

In this way, the plurality of second beam-shaped members is arranged downstream of the first beam-shaped member which divides the flow passage connected to the ejection element substrate into two flow passages in the liquid-flowing direction so as to sandwich the line extending the first beam-shaped member in the liquid-flowing direction. Accordingly, it becomes possible to achieve the liquid ejection head and the liquid ejection apparatus which make it possible to suppress deterioration of the image quality.

Hereinafter, other embodiments of the present invention will be described with reference to the drawings. Note that, since the basic configurations of the embodiments are the same as that of the first embodiment, hereinafter, only characteristic configurations will be described.

FIG. 7AtoFIG. 7Care diagrams illustrating flow passages of liquid ejection heads according to other embodiments of the present invention.FIG. 7Ais an example in which the distance L1between the beam-shaped member132jand the extension line L has been made longer than the distance L2between the beam-shaped member132iand the extension line L, and thus the region158bhas been made wider than the region158a.Accordingly, the difference in flow velocity between the adjacent regions is reduced, and the small bubbles fall downward by being distributed in the three regions, thereby not concentrating on the specific place.

In addition, the positions in the height direction of the beam-shaped members132iand132jmay be different from each other.FIG. 7Bis an example that a vertical distance d between the lower end of beam-shaped member131and the beam-shaped member132jhas been made larger than the distance between the lower end of the beam-shaped member131and the beam-shaped member132i,and thus an inlet of the liquid from the right liquid chamber123qinto the region158bhas been made large.

In addition, the beam-shaped member131may be shifted to one side of the liquid chamber123if there is no hindrance in reinforcement of the flow passage as illustrated inFIG. 7C. At that time, the three beam-shaped members132i,132jand132kare provided in the liquid supply port156cas illustrated in the drawing.

As described above, the plurality of second beam-shaped members is provided on the downstream side of the first beam-shaped member which divides the flow passage into the two flow passages in the liquid-flowing direction so as to sandwich the line extending the first beam-shaped member in the liquid-flowing direction. Accordingly, the difference in flow velocity between the adjacent regions becomes smaller, and the small bubbles fall downward by being distributed to the three regions to thereby not concentrate on the specific place, with the result that it becomes possible to achieve the liquid ejection head and the liquid ejection apparatus which make it possible to suppress deterioration of the image quality.

This application claims the benefit of Japanese Patent Application No. 2015-107269, filed May 27, 2015, which is hereby incorporated by reference herein in its entirety.