Liquid ejection head and liquid ejection apparatus

In a liquid ejection head and a liquid ejection apparatus capable of reducing the occurrence of ejection malfunction, in a connecting section where a first flow channel and a second flow channel connect, a projecting member is provided on the flow channel wall forming the second flow channel.

BACKGROUND OF THE INVENTION

Field of the Invention

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

Description of the Related Art

The liquid supply system typically used in a liquid ejection apparatus is equipped with a main tank that stores liquid internally, a supply unit to which the main tank is removably attached, and a liquid ejection head connected to the supply unit through a supply tube. The liquid ejection head is equipped with a sub-tank section connected to the supply tube, a filter, a liquid chamber connected to the sub-tank section through the filter, an ejection element board that ejects liquid, and a flow channel that connects the liquid chamber and the ejection element board.

Liquid supplied from the supply tube first enters the sub-tank section, passes through the filter to reach the liquid chamber, and after that, passes through the flow channel to be ejected from the ejection element board. In such a liquid ejection head, bubbles containing gas dissolved in the liquid readily accumulate on the downstream side of the filter. If the bubbles adhere to the filter on the downstream side of the filter, the supply of liquid may be blocked in that portion.

Accordingly, Japanese Patent Laid-Open No. 2002-307709 discloses technology in which a partition section provided with ribs is provided inside the liquid ejection head. By supporting the filter with the partition section, and causing the filter and the ribs to abut, the supply of liquid is ensured.

In the configuration of Japanese Patent Laid-Open No. 2002-307709, depending on the temperature and the pressure of the liquid inside the liquid chamber, bubbles are produced, such as dissolved gas bubbles precipitated from the liquid inside the liquid chamber, and bubbles sucked inside from the ejection ports during the ejection of liquid droplets (ejection bubbles). Bubbles accumulate at the top inside the liquid chamber due to buoyancy of the bubbles themselves, but as the flow rate of liquid increases, such as during high-speed printing, the bubbles overcome buoyancy to move into the flow channel on the downstream side together with the liquid and reach the ejection element board, thereby creating a risk of ejection malfunction.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a liquid ejection head and a liquid ejection apparatus capable of reducing the occurrence of ejection malfunction.

A liquid ejection head according to the present invention is a liquid ejection head including an ejection element board that ejects liquid, wherein a flow channel that guides liquid to the ejection element board includes a first flow channel of wide cross-sectional area, and a second flow channel of narrow cross-sectional area, connected to the first flow channel and downstream to the first flow channel. The liquid ejection head includes at least one projecting member projecting out into the flow channel from a flow channel wall forming the second flow channel.

According to the present invention, a liquid ejection head and a liquid ejection apparatus capable of reducing the occurrence of ejection malfunction may be realized.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Note that in the present embodiment, a connecting section of the flow channel having a different cross-sectional area, such as a curved section, is designated the irregular flow channel connecting section, while the flow channel on the upstream side of the irregular flow channel connecting section is designated the first flow channel, and the flow channel on the downstream side of the flow channel connecting section, having a smaller cross-sectional area than the first flow channel, is designated the second flow channel. Herein, the cross-sectional area refers to the surface area (average cross-sectional area) of a flow channel plane orthogonal to the primary flow direction of the liquid.

In addition, in the liquid ejection head, liquid flows from the first flow channel to the downstream second flow channel, passes through a common liquid chamber, and is supplied to individual ejection ports.

FIG. 1is a perspective view illustrating a liquid ejection apparatus200to which the present embodiment is applicable. A carriage102carrying a liquid ejection head is movably supported on a guide103extending along a main scanning direction, the carriage102being able to move back and forth along the guide103. The carriage102is connected to liquid supply tubes, and is driven by a carriage motor (not illustrated). A print medium such as a sheet of paper is fed by a feed roller (not illustrated) driven by a feed motor of a feed mechanism (not illustrated) via a gear train, and is delivered onto a platen106by a transport roller104and a pinch roller (not illustrated). Printing is conducted by ejecting liquid from ejection ports of the liquid ejection head onto the print medium transported on the platen106by the transport roller104and a delivery roller (not illustrated).

When printing onto the print medium, the carriage102accelerates from a stopped state, and then moves at a constant speed through the scanning range of the print operation. At this point, liquid is ejected from the ejection ports of the liquid ejection head onto the print medium to form an image. After printing for one line is finished by scanning one or multiple times, the carriage102decelerates and stops. Subsequently, the print medium is fed a designated amount by the rotation of the transport roller104and the delivery roller.

FIGS. 2A and 2Bare perspective views illustrating a liquid ejection head100to which the present embodiment is applicable. The liquid ejection head100is equipped with a liquid supply unit120, and an ejection element unit101for receiving a supply of liquid from the liquid supply unit120and ejecting the liquid onto the print medium. The liquid ejection head100is affixed to and supported on the carriage102by positioning means of the carriage102provided in the liquid ejection apparatus200, and in addition, is removable from the carriage102. In an ejection element unit101, two ejection element boards12(12aand12b) are mounted on a support member303, and during ejection, a signal is transmitted to each ejection element board12from an electrical interconnect board304.

In the liquid ejection apparatus200, liquid supply tubes connected to liquid tanks (not illustrated) are provided, and connectors (not illustrated) are provided on the ends of the liquid supply tubes. When the liquid ejection head100is mounted onto the carriage102, an airtight connection is made between the connectors and connector insertion ports112, and liquid inside the liquid tanks is supplied to the liquid ejection head100. Six types of liquid may be mounted onto the liquid ejection head100, and connector insertion ports112ato112fare provided in correspondence with each of the liquid supply tubes to form individual flow channels.

Liquids supplied from the connector insertion ports112ato112cpass through individual flow channels and are supplied to individual liquid chambers on the ejection element board12a. Liquids supplied from the connector insertion ports112dto112fpass through individual flow channels and are supplied to individual liquid chambers on the ejection element board12b.

The ejection element boards12aand12bare equipped with energy-producing elements that produce energy used to eject liquid on one side of a silicon board having a thickness from 0.5 mm to 1 mm. In the present embodiment, heaters are used as the energy-producing elements, and electrical interconnects that supply power to each heater are formed by deposition technology. Additionally, multiple liquid flow channels and multiple nozzles corresponding to these heaters are formed by photolithography, while in addition, liquid chambers (not illustrated) for supplying liquid to the multiple liquid flow channels are formed to open on the back face.

FIGS. 3A and 3Bare cross-section views illustrating respective liquid flow channels inside the liquid supply unit120, in whichFIG. 3Bis a cross-section along the line IIIB inFIG. 2A, andFIG. 3Ais a cross-section along the line IIIA inFIG. 3B.

Herein, the liquid supply system311aincluding the connector insertion port112awill be described primarily, but the five other liquid supply systems have a similar structure. Liquid supplied from the connector insertion port112ais supplied by the liquid supply system311ain communication with the connector insertion port112a. Specifically, liquid passes through a filter pre-chamber202a, a filter203athat prevents the intrusion of foreign substances into the ejection element board12a, a filter post-chamber204a, and a filter chamber outlet205a, and is supplied to the ejection element board12athrough a first flow channel210a, a second flow channel211a(second upstream flow channel), and a second flow channel212a(second downstream flow channel).

One end of the second flow channel211ais connected to the first flow channel210a, while the other end is connected to the second flow channel212a. The cross-sectional area of the second downstream flow channel212aprovided in the support member303is greater than the cross-sectional area of the second upstream flow channel211a. A damper apparatus113ain the upper section of the filter pre-chamber202aabsorbs pressure variations inside the liquid supply system during ejection.

The flow channel up to the second flow channel211ais provided in the liquid supply unit120, while the second flow channel211aand the second flow channel212aof approximately the same shape are provided in the support member303. Consequently, a liquid supply system from the filter203ato the ejection element board12ais formed. Particularly, the pathway from the filter post-chamber204aup to the second flow channel212aconstitutes a main flow channel201ain which ejection bubbles produced during ejection, and flow channel bubbles formed by the union of ejection bubbles, move and accumulate.

As shown inFIG. 3B, the second flow channel211ahas a smaller cross-sectional area than the first flow channel210a, and has the smallest cross-sectional area in the main flow channel201a. The two are connected by an irregular flow channel connecting section213a. The upstream section of the main flow channel201ahas an increased cross-sectional area to decrease the pressure loss of the filter203adue to liquid flow. For this reason, the filter arrangement is provided at the maximum interval allowed by the width of the liquid supply unit120in the X direction. The downstream side of the main flow channel201ahas a decreased cross-sectional area, and by bringing the flow channels close together, a more compact ejection element board12ais realized.

The arrangement interval of the adjacent second flow channels is approximately the same as the interval of the liquid chambers of the ejection element board12a, and in the liquid supply system, the second flow channel211afarther downstream than the irregular flow channel connecting section213ahas the smallest cross-sectional area. Also, by increasing the volume on the upstream side of the main flow channel201a, a larger amount of ejection bubbles may accumulate without interfering with liquid supply. This is also effective at reducing the frequency of purge operations to discharge the bubbles inside the flow channels that increase with ejection.

The irregular flow channel connecting section213ais the downstream end of the first flow channel210a. Here, at the bottom of the first flow channel210a, an inlet of the second flow channel211ahaving a slot-shaped hole shape smaller than the face of the floor opens out, in a so-called “landing” structure.

In the main flow channel201aof the liquid ejection head100according to the present embodiment, near the center in the Y direction of the second flow channel211a, a projecting member214aoriginating from the irregular flow channel connecting section213aso as to divide the second flow channel211ain half is provided. The adjacent second flow channels211band211care also provided with similar projecting members214band214c. The projecting member214ais a beam-like member that originates from the irregular flow channel connecting section213a, or in other words the inlet of the second flow channel211a, projects out from the inner side face of the second flow channel211a, and goes across the second flow channel211a.

Note that the flow resistance in the second flow channel211aincreases due to the projecting member214a. To equalize this increase in flow resistance, the projecting members in the other adjacent second flow channels are made to have approximately the same length in the Z direction. By providing the projecting member214a, the intrusion of flow channel bubbles into the second flow channel may be prevented, even when a large amount of liquid flows.

FIGS. 5A to 5Dare cross-section views illustrating the main flow channel201bin the liquid supply system311b(seeFIG. 4A). Herein, the liquid supply system311bwill be taken as an example to describe the effect on flow channel bubbles of the projecting member214bin the main flow channel201b.

A flow channel bubble300remaining in the upper section of the main flow channel201bdue to the filter203bin the upper section of the filter post-chamber204bis the combination of the air in the unfilled volume when filling the flow channel with liquid as part of a purge operation, and ejection bubbles301produced near the ejection ports during ejection. During ejection, the ejection bubbles301are released from the vicinity of the ejection ports, float up inside the flow channels in communication with the liquid chambers due to the buoyancy of the ejection bubbles301themselves, and reach the upper section of the main flow channel201b. A large number of ejection bubbles301reaching the upper section unite with the flow channel bubble300in the upper section of the main flow channel201b, and the flow channel bubble300gradually grows in size.

Since a liquid meniscus is formed on the filter203b, air is unable to escape to the filter pre-chamber202b, and as the flow channel bubble300grows, the ratio of the main flow channel201boccupied by the flow channel bubble300increases while the amount of liquid in the main flow channel201bdecreases.

The size of the flow channel bubble300is estimated from the cumulative number of ejections, and when the cumulative number exceeds a designated value, ejection is paused, and the flow channel bubble300is discharged by a purge operation. If the flow channel bubble300is small, liquid supplied from the filter203bside flows around the flow channel bubble300, and the flow channel bubble300does not move downstream much. However, if the flow channel bubble300grows large enough to cover the cross-section of the first flow channel210b, the flow channel bubble300moves downstream together with the flow of supplied liquid (seeFIG. 5B).

Since the force imparted by the flow of liquid also increases as the flow channel bubble300grows, as the flow of liquid becomes stronger, part of the flow channel bubble300enters the second flow channel211b(seeFIG. 5C).

However, in the present embodiment, the projecting member214bis provided from the beginning section of the second flow channel211b. Thus, the flow channel bubble300attempting to enter the second flow channel211babuts the projecting member214b, the projecting member214abdeforms the meniscus302of the flow channel bubble300into a concave shape, and the curvature of the flow channel bubble300increases. As the curvature increases, the flow channel bubble300deforms less readily, and attempts to maintain the current shape. Consequently, the entry of the flow channel bubble300into the second flow channel211bis inhibited. Note that at this time, liquid passes around the flow channel bubble300and is supplied downstream.

If ejection stops, the flow channel bubble300floats up again (seeFIG. 5D), and returns to above the first flow channel210b.

In this way, the projecting member214bis able to prevent the intrusion of the flow channel bubble300into the second flow channel with almost no change in the cross-sectional area of the inlet of the second flow channel211b, or in other words, without significantly increasing the flow resistance.

FIGS. 6A and 6Bare cross-section views illustrating a liquid supply system not provided with a projecting member as a comparative example. If a projecting member is not provided like inFIGS. 6A and 6B, the meniscus302of the flow channel bubble300intruding into the second flow channel211has a comparatively small curvature (seeFIG. 6A). For this reason, compared to the case of providing the projecting member214a, the flow channel bubble300disengages with comparatively little force, and intrudes into the second flow channel211. If the flow channel bubble300intrudes into and obstructs the second flow channel211, negative pressure increases suddenly, the flow channel bubble300flows even farther downstream (seeFIG. 6B), passes through the second flow channel212to reach the ejection element board12as indicated by the dashed line, and causes ejection malfunction. In this way, if a projecting member is not provided, the flow channel bubble300is able to intrude into the second flow channel211aeasily, and may potentially cause ejection malfunction.

Note that as an incidental effect of the present embodiment, the configuration of the present embodiment allows for a larger amount of flow channel bubbles to be accumulated. In other words, it becomes possible to decrease the frequency of the purge operation for discharging flow channel bubbles, improve the utilization rate of the liquid ejection apparatus, and reduce waste liquid due to purge operations.

In this way, in the connecting section where the first flow channel and the second flow channel connect, a projecting member is provided on the flow channel wall forming the second flow channel. Consequently, a liquid ejection head and a liquid ejection apparatus capable of reducing the occurrence of ejection malfunction may be realized.

Second Embodiment

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. Note that since the basic configuration of the present embodiment is similar to the first configuration, only the characteristic parts of the configuration will be described hereinafter.

FIGS. 7A and 7Bare cross-section views illustrating the main flow channel201in the liquid supply system311of the present embodiment. In the present embodiment, the projecting member214extends from the irregular flow channel connecting section213to the downstream side of the second flow channel211. With such a configuration of extending to the downstream end of the second flow channel211, the risk of a flow channel bubble covering a small projecting member214and substantially invalidating the advantageous effects of the projecting member214may be avoided.

Note that in the case of fabricating the liquid supply unit120by plastic molding, there is a risk that a narrow slot-shaped flow channel like the second flow channel of the present embodiment may deform due to shrinkage of the plastic. Specifically, the central area of the slot-shaped cross-section may become narrow and deform into an hourglass shape. In the extreme case, the central area may collapse and impede liquid supply capability. Such deformation of plastic molded components occurs more readily as the length in the Y direction of the ejection element board becomes larger.

According to a structure like the present embodiment, in which a projecting member for restricting the behavior of a flow channel bubble extends to the downstream end of the second flow channel of the liquid supply unit120, the projecting member also acts as a reinforcing member that prevents deformation of the second flow channel. For this reason, such a structure is effective in the case of mounting an ejection element board that is long in the Y direction.

Note that the projecting member214may also be provided up to the second flow channel212where the support member303is provided.

In this way, in the connecting section where the first flow channel and the second flow channel connect, a projecting member that extends to the downstream end of the second flow channel is provided on the flow channel wall forming the second flow channel. Consequently, a liquid ejection head and a liquid ejection apparatus capable of reducing the occurrence of ejection malfunction may be realized.

Third Embodiment

Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. Note that since the basic configuration of the present embodiment is similar to the first configuration, only the characteristic parts of the configuration will be described hereinafter.

FIG. 8is a cross-section view illustrating the main flow channel201in the liquid supply system311of the present embodiment. Although the foregoing embodiments describe a configuration in which one projecting member is provided in the second flow channel, the present embodiment describes a configuration in which multiple projecting members are provided in the second flow channel.

In the second flow channel of the liquid ejection head100according to the present embodiment, two projecting members214are provided. However, the number of projecting members is not limited to two, and two or more projecting members may be provided. The projecting members214are provided so as to approximately trisect the second flow channel211in the Y direction. The projecting members214originate near the irregular flow channel connecting section, and extend to the downstream end of the second flow channel211.

In this way, in the connecting section where the first flow channel and the second flow channel connect, multiple projecting members are provided on the flow channel wall forming the second flow channel. Consequently, a liquid ejection head and a liquid ejection apparatus capable of reducing the occurrence of ejection malfunction may be realized.

Fourth Embodiment

Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings. Note that since the basic configuration of the present embodiment is similar to the first configuration, only the characteristic parts of the configuration will be described hereinafter.

FIG. 9is a cross-section view illustrating the main flow channel201in the liquid supply system311of the present embodiment. The origin of the projecting member215according to the present embodiment is provided at a point farther downstream than the irregular flow channel connecting section213b. The origin of the projecting member215may be provided in the second flow channel farther downstream than the irregular flow channel connecting section insofar as a flow channel bubble contacts the projecting member before the flow channel bubble flows into the second flow channel, and the projecting member causes the flow channel bubble to deform.

In this way, in the connecting section where the first flow channel and the second flow channel connect, a projecting member originating farther downstream than the irregular flow channel connecting section is provided on the flow channel wall forming the second flow channel. Consequently, a liquid ejection head and a liquid ejection apparatus capable of reducing the occurrence of ejection malfunction may be realized.

Fifth Embodiment

Hereinafter, a fifth embodiment of the present invention will be described with reference to the drawings. Note that since the basic configuration of the present embodiment is similar to the first configuration, only the characteristic parts of the configuration will be described hereinafter.

FIG. 10is a cross-section view illustrating the main flow channel201in the liquid supply system311of the present embodiment. The origin of the projecting member216according to the present embodiment is provided farther upstream than the irregular flow channel connecting section213b. In other words, the projecting member216is provided projecting towards the first flow channel. The origin of the projecting member216may be provided farther upstream than the irregular flow channel connecting section insofar as a flow channel bubble contacts the projecting member before the flow channel bubble flows into the second flow channel, and the projecting member causes the flow channel bubble to deform.

In this way, in the connecting section where the first flow channel and the second flow channel connect, a projecting member originating farther upstream than the irregular flow channel connecting section is provided on the flow channel wall forming the second flow channel. Consequently, a liquid ejection head and a liquid ejection apparatus capable of reducing the occurrence of ejection malfunction may be realized.

Other Embodiments

FIGS. 11A to 11Care cross-section views illustrating the main flow channel201in the liquid supply system311according to other embodiments. The projecting member may be provided only in some of the liquid supply systems, or the shape of the projecting member, the location where the projecting member is placed, and the number of the projecting member may be modified to fit the characteristics of the individual liquid supply systems. For example, as the volume of the first flow channel becomes smaller, the flow channel bubble reaches the irregular flow channel connecting section more easily, and the amount of flow channel bubbles that may be accumulated becomes smaller.

InFIG. 11A, the projecting member214bis provided only in the second flow channel211bof the liquid supply system (311b) in which the position in the Z direction of the irregular flow channel connecting section213is high and the volume of the first flow channel210is comparatively small. In this way, the projecting member may be provided only in the second flow channel of a liquid supply system in which a flow bubble is considered to reach the irregular flow channel connecting section easily and intrude into the second flow channel easily.

In addition, to decrease flow resistance caused by the projecting member, the projecting member may also not completely extend across the second flow channel.FIGS. 11B and 11Care examples in which the projecting member extending from the inner side face of the second flow channel does not completely extend across the second flow channel. The supply system illustrated inFIG. 11Bis effectively an inclined flow channel structure in which all the filter post-chambers204and the second flow channels211and212immediately above the ejection element board12are shifted away from each other in the X direction, and connected by an inclined first flow channel210.

The projecting member is provided only on the side where the flow channel bubble moves above the first flow channel210, or in other words the side to which the filter post-chamber204is shifted as seen from the second flow channel. Also,FIG. 11Cis an enlarged view of the area near the projecting member214binFIG. 11B. To ensure concave deformation of the flow channel bubble without the flow channel bubble avoiding the projecting member214b, the length Db of the projecting member214bis preferably set to at least 50% of the width Wb of the second flow channel in the X direction, which affects flow resistance the most.

Furthermore, if miniaturization of the liquid supply unit120is required, it is not necessary to provide a face orthogonal to the flow of liquid like with the landing structure.

In the above description, the supply system is a flow channel having a slot-shaped cross-section effective at increasing the density of liquid, but may also include a flow channel with a circular cross-section. For example, a flow channel in which a second flow channel of circular cross-section or elliptical cross-section connects to a first flow channel of slot-shaped cross-section, a flow channel in which a second flow channel of slot-shaped cross-section connects to a first flow channel of circular cross-section or elliptical cross-section, or a flow channel in which a first flow channel and a second flow channel both of circular cross-section or elliptical cross-section are connected is also acceptable.

In addition, the configurations of the projecting member according to the foregoing embodiments may also be combined to form the projecting member in each second flow channel.

This application claims the benefit of Japanese Patent Application No. 2015-104847, filed May 22, 2015, which is hereby incorporated by reference herein in its entirety.