Liquid ejection head

A liquid ejection head includes a nozzle including an ejection port for ejecting a liquid for performing recording on a recording medium, and a pressure chamber in which an energy generating element that generates energy used for ejecting the liquid from the ejection port is disposed; and a heating unit that heats the liquid. In the liquid ejection head, the liquid in the pressure chamber is circulated to and from the outside of the pressure chamber, and an average number of preliminary ejections per nozzle during an operation period in which the recording is performed is equal to or greater than 0 and equal to or less than 20.

BACKGROUND

Field of the Disclosure

The present disclosure generally relates to a liquid ejection head and a liquid ejection apparatus, including a recording element which ejects a liquid such as ink, for the purpose of recording an image.

Description of the Related Art

A liquid ejection head that applies a voltage pulse to an element generating energy for ejecting a liquid according to recording data, and ejects a liquid such as ink by utilizing the generated energy is widely useful because the liquid ejection head can output an image with high definition and high speed.

In particular, a liquid ejection apparatus including a page-wide type liquid ejection head including a plurality of recording element substrates disposed corresponding to the width of recording paper has been rapidly spread in recent years because higher speed output is possible. Japanese Patent Application Laid-Open No. 2008-526553 discloses a page-wide type liquid ejection head. In a known configuration, the liquid ejection head is provided with a heating unit such as a heater in order to adjust the head temperature to a predetermined temperature during a printing operation (hereinafter, temperature adjustment).

SUMMARY

The disclosure provides a liquid ejection head including a nozzle including an ejection port for ejecting a liquid, and a pressure chamber in which an energy generating element that generates energy used for ejecting the liquid from the ejection port is disposed; and a heating unit that heats the liquid, in which during an operation period in which a recording on a recording medium is performed, the liquid in the pressure chamber is circulated to and from an outside of the pressure chamber, and an average number of preliminary ejections per nozzle of all the nozzles during the operation period is equal to or greater than 0 and equal to or less than 20.

DESCRIPTION OF THE EMBODIMENTS

A liquid ejection head such as an ink jet head may perform an operation called a preliminary ejection that ejects a liquid to a capping member installed in a printer body toward a recording medium during a recording operation separately from original ejection of a liquid for image formation. The preliminary ejection is performed for the purpose of preventing printing failure and deterioration of image quality due to an increase in viscosity of the liquid in the ejection port caused by drying, or the like. However, when a preliminary ejection is performed during the above-described temperature adjusting operation of the liquid ejection head, ink kept at a constant temperature is ejected and the cooled ink flows in, and thus the head temperature temporarily decreases even if the temperature adjusting operation is performed. Further, additional power consumption for raising the temperature again becomes necessary. In particular, in a page-wide type liquid ejection head having a large number of ejection ports, since the amount of ink required for a preliminary ejection is also increased, the influence of these is increased.

The present disclosure has been made to solve the above problems. That is, one aspect of the disclosure is to provide a liquid ejection head and a liquid ejection apparatus, capable of suppressing a temporary temperature change and an increase in power consumption due to preliminary ejections in a liquid ejection head performing a temperature adjusting operation.

Embodiments of the present disclosure will be described below by using the drawings. However, the following description does not limit the scope of the disclosure. For example, although a thermal system for generating air bubbles in the liquid by a heat generating element and ejecting liquid from an ejection port is adopted in the present embodiment, the present disclosure can be applied to a liquid ejection head adopting a piezo system and various other liquid ejection systems.

In the present embodiment, an ink jet liquid ejection apparatus that circulates ink between the buffer tank (liquid container) and the ink jet recording head (liquid ejection head) has been described, but other forms may be used. For example, a form may be used in which tanks are respectively provided on the upstream side and the downstream side of the liquid ejection head, and the ink is made to flow from one tank to the other tank to flow the ink in the pressure chamber.

The so-called page-wide type liquid ejection head having a length corresponding to the width of the recording medium is used in the present embodiment, but the present disclosure can also be applied to a so-called serial liquid ejection head which performs recording while scanning the recording medium. The serial liquid ejection head includes, for example, a configuration in which one recording element substrate for black ink and one recording element substrate for color ink are mounted. However, the serial liquid ejection head is not limited thereto, and there may be adopted a form in which a short line head shorter than the width of the recording medium and having several recording element substrates disposed such that ejection ports overlap each other in an ejection port line direction may be formed to scan the recording medium.

First Embodiment

Description of a Liquid Ejection Apparatus

The schematic configuration of a liquid ejection apparatus of the present disclosure, especially an ink jet recording apparatus1000(hereinafter also referred to as a liquid ejection apparatus) that performs recording by discharging ink is illustrated inFIG. 1. The liquid ejection apparatus1000includes a conveying unit1that conveys a recording medium2and a page-wide type liquid ejection head3disposed approximately orthogonally to the conveying direction of the recording medium. The liquid ejection apparatus is a page-wide type liquid ejection apparatus which performs continuous recording by one pass while continuously or intermittently conveying a plurality of recording media2. The recording medium2may be not only cut paper but also continuous roll paper. The liquid ejection head3can perform full color printing by cyan, magenta, yellow, and black (CMYK) inks. A liquid supply unit which is a supply path for supplying a liquid to a liquid ejection head as described later, a main tank, and a buffer tank (refer toFIG. 2) are fluidly connected to the liquid ejection head. An electric control unit that transmits electrical power and an ejection control signal to the liquid ejection head3is electrically connected to the liquid ejection head3. The liquid path and the electric signal path in the ejection head3will be described later.

Description of First Circulation Path

FIG. 2is a schematic diagram illustrating a first circulation path which is one form of a circulation path applied to a liquid ejection apparatus, and the liquid ejection head3is fluidly connected to a first circulation pump (high pressure side)1001, a first circulation pump (low pressure side)1002, a buffer tank1003, and the like. AlthoughFIG. 2shows only a path through which one color ink of the CMYK inks flows to simplify the description, circulation paths for four colors are actually provided in the liquid ejection head3and the liquid ejection apparatus body. The buffer tank1003as a sub-tank connected to a main tank1006has an ambient air communication port (not illustrated) for communicating the inside of the tank with the outside, and can discharge air bubbles in ink to the outside. The buffer tank1003is also connected to a replenishing pump1005. When the liquid is consumed by the liquid ejection head3by ejecting the ink from the ejection port of the liquid ejection head, such as recording or suction recovery by ejecting the ink, the replenishing pump1005transfers ink of the consumed amount from the main tank1006to the buffer tank1003.

Two first circulation pumps1001,1002as power sources for circulation have the role of flowing the liquid to the buffer tank1003through a liquid connecting part111of the liquid ejection head3. A positive-displacement pump having a quantitative liquid delivery capability can be preferably used as the first circulation pump. Specifically, a tube pump, a gear pump, a diaphragm pump, and a syringe pump can be used, and for example, a general constant flow rate valve or relief valve may be provided at the pump outlet to secure a constant flow rate. When the liquid ejection head3is driven, a fixed amount of ink flows in a common supply flow passage211and a common recovery flow passage212by a first circulation pump (high pressure side)1001and a first circulation pump (low pressure side)1002. The flow rate is preferably set to be equal to or more than a flow rate such that a temperature difference between respective recording element substrates10within the liquid ejection head3does not influence recording image quality. However, when an excessively large flow rate is set, the negative pressure difference in each recording element substrate10is significantly increased due to the effect of pressure loss of a flow passage in the liquid ejection unit300, resulting in uneven density of the image. Therefore, the flow rate is preferably set while considering the temperature difference and the negative pressure difference between the respective recording element substrates10.

A negative-pressure control unit230is provided in the path between the second circulation pump1004and the liquid ejection unit300. The negative-pressure control unit230has a function of maintaining pressure on the downstream side (that is, on the liquid ejection unit300side) of the negative-pressure control unit230at a preset constant pressure even in a case where the flow rate of the circulation system fluctuates due to the difference in the duty of recording. Any mechanism may be used as two pressure adjusting mechanisms constituting the negative-pressure control unit230, as long as the pressure downstream of the negative-pressure control unit230can be controlled with a fluctuation within a fixed range or less with a desired set pressure as a center. As an example, a mechanism similar to a so-called “pressure reducing regulator” can be adopted. In a case where the pressure reducing regulator is used, the upstream side of the negative-pressure control unit230is preferably pressurized via a liquid supply unit220by the second circulation pump1004as illustrated inFIG. 2. By doing so, the influence of the water head pressure of the buffer tank1003on the liquid ejection head3can be suppressed, and thus the degree of freedom of the layout of the buffer tank1003in the liquid ejection apparatus1000can be widened. The second circulation pump1004may have a head pressure equal to or higher than a fixed pressure within a range of an ink circulation flow rate used when the liquid ejection head3is driven, and a turbo pump, a positive-displacement pump, or the like can be used. Specifically, a diaphragm pump can be applied. Instead of the second circulation pump1004, for example, a head tank disposed with a fixed head difference with respect to the negative-pressure control unit230can also be applied.

As illustrated inFIG. 2, the negative-pressure control unit230includes the two pressure adjusting mechanisms that are respectively set to have mutually different control pressures. A higher-pressure setting side (denoted by H inFIG. 2) and a lower-pressure side (denoted by L inFIG. 2) of the two negative-pressure adjusting mechanisms are respectively connected to the common supply flow passage211and the common recovery flow passage212within the liquid ejection unit300via the inside of the liquid supply unit220. The liquid ejection unit300is provided with the common supply flow passage211, the common recovery flow passage212, and an individual supply flow passage213aand an individual recovery flow passage214bcommunicating with each recording element substrate. Since the individual supply flow passage213communicates with the common supply flow passage211and the common recovery flow passage212, a flow (arrow inFIG. 2) in which a part of the liquid flows from the common supply flow passage211through the internal flow passage of the recording element substrate10to the common recovery flow passage212is generated. This is because, since the pressure adjusting mechanism H is connected to the common supply flow passage211and the pressure adjusting mechanism L is connected to the common recovery flow passage212, differential pressure is generated between the two common flow passages.

Thus, in the liquid ejection unit300, while the liquid is made to flow so as to pass through the common supply flow passage211and the common recovery flow passage212, a flow such that a part of the liquid passes through each recording element substrate10is generated. By such a configuration, ink flow can be generated even at an ejection port and a pressure chamber where no recording is performed when recording is performed by the liquid ejection head3, so the increase in viscosity of ink in the part can be suppressed. The viscosity-increased ink or foreign matter in the ink can be ejected to the common recovery flow passage212. By circulating inside and outside the pressure chamber in this way, the preliminary ejection from the liquid ejection head and the recovery operation of the liquid ejection head can be suppressed, and thus high-quality recording can be performed at high speed. As will be described later in detail, the number of preliminary ejections can be suppressed or eliminated by circulation inside and outside the pressure chamber, a temperature change at the time of temperature adjustment of the liquid ejection head can be suppressed.

Description of Configuration of Liquid Ejection Head

The configuration of the liquid ejection head3according to the first embodiment will be described.FIGS. 3A and 3Bare perspective views of the liquid ejection head3according to the present embodiment. The liquid ejection head3is a page-wide type liquid ejection head in which 15 recording element substrates10each capable of discharging four-color inks of C/M/Y/K are linearly arranged (inline arrangement). The present disclosure is not limited to this aspect, and is also applicable to the liquid ejection head3in which a plurality of recording element substrates10are arranged in staggered manner. As illustrated inFIG. 3A, the liquid ejection head3includes signal input terminals91and electrical power supply terminals92which are electrically connected to the recording element substrates10via a flexible wiring substrate40and an electrical wiring substrate90. The signal input terminals91and the electrical power supply terminals92are electrically connected to the control unit of the body of the liquid ejection apparatus1000, and supply an ejection drive signal and electric power required for discharge to the recording element substrate10, respectively. By collecting the wirings by the electric circuits in the electrical wiring substrate90, the number of signal output terminals91and electrical power supply terminals92can be reduced as compared with the number of recording element substrates10. Thus, the number of electric connection parts required to be removed when the liquid ejection head3is assembled to the liquid ejection apparatus1000or when the liquid ejection head is replaced can be reduced. As illustrated inFIG. 3B, the liquid connecting parts111provided at both ends of the liquid ejection head3are connected to a liquid supply system of the liquid ejection apparatus1000. Thus, the inks of four colors (CMYK) are supplied from the supply system of the liquid ejection apparatus1000to the liquid ejection head3, and the ink passing through the liquid ejection head3is recovered to the supply system of the liquid ejection apparatus1000. Thus, the ink of each color can be circulated through the path of the liquid ejection apparatus1000and the path of the liquid ejection head3. More specifically, ink is circulated through a pressure chamber23(FIGS. 9A to 9C) of the liquid ejection head3.

An exploded perspective view of each component or unit constituting the liquid ejection head3is illustrated inFIG. 4. The liquid ejection unit300, the liquid supply unit220, and the electrical wiring substrate90are attached to a housing80. The liquid supply unit220is provided with the liquid connecting part111(FIG. 2), and a filter221(FIG. 2) of each color communicating with each opening of the liquid connecting part111is provided inside the liquid supply unit220to remove foreign matter in the supplied ink. The two liquid supply units220are respectively provided with filters221of two colors. The liquid passing through the filter221is supplied to the negative-pressure control unit230disposed on the supply unit220corresponding to each color. The negative-pressure control unit230is a unit including a pressure adjusting valve of each color, and largely attenuates a pressure loss change in the supply system of the liquid ejection apparatus1000(the supply system on the upstream side of the liquid ejection head3) caused by the fluctuation of the flow rate of the liquid by the valve or the spring member provided inside. Thus, the negative pressure change on the downstream side (the liquid ejection unit300side) of the pressure control unit is suppressed within a certain fixed range, and the negative pressure can be stabilized. As illustrated inFIG. 2, two pressure adjusting valves of each color are incorporated in the negative-pressure control unit230of each color, and set to different control pressures. The high pressure side communicates with the common supply flow passage211in the liquid ejection unit300and the low pressure side communicates with the common recovery flow passage212through the liquid supply unit220.

The housing80includes a liquid ejection unit support part81and an electrical wiring substrate support part82, supports the liquid ejection unit300and the electrical wiring substrate90, and secures the rigidity of the liquid ejection head3. The electrical wiring substrate support part82supports the electrical wiring substrate90, and is fixed to the liquid ejection unit support part81by screwing. The liquid ejection unit support part81corrects warpage and deformation of the liquid ejection unit300to secure relative position accuracy of the plurality of recording element substrates10, and thereby suppressing stripes and unevenness in the recorded matter. Therefore, the liquid ejection unit support part81preferably has sufficient rigidity, and a metallic material such as SUS and aluminum or ceramic such as alumina is suitably used as a material. The liquid ejection unit support part81is provided with openings83and84into which the joint rubber100is inserted. The liquid supplied from the liquid supply unit220is guided to a third flow passage member70constituting the liquid ejection unit300through the joint rubber.

The liquid ejection unit300includes a plurality of ejection modules200and a flow passage member210, and a cover member130is attached to the surface of the liquid ejection unit300on the recording medium side. As illustrated inFIG. 4, the cover member130is a member having a frame-like surface provided with a long opening131, and the recording element substrate10and a sealing member110(FIGS. 8A and 8B) included in the ejection module200are exposed from the opening131. A frame part around the opening131has a function as an abutting surface of a cap member capping the liquid ejection head3in the standby state of recording. Therefore, it is preferred that an adhesive, a sealing material, a filler material, or the like is applied along the periphery of the opening131to fill irregularities or gaps on an ejection port surface of the liquid ejection unit300so that a closed space is formed at the time of the capping.

Next, the configuration of the flow passage member210included in the liquid ejection unit300will be described. As illustrated inFIG. 4, the flow passage member210is formed by laminating a first flow passage member50, a second flow passage member60, and a third flow passage member70, and distributes the liquid supplied from the liquid supply unit220to each ejection module200. The flow passage member returns the liquid recirculated from the ejection module200to the liquid supply unit220. The flow passage member210is fixed to the liquid ejection unit support part81by screwing, and thereby, the warpage or deformation of the flow passage member210is suppressed.

FIGS. 5A to 5Fare diagrams illustrating the front and back surfaces of the respective flow passage members of the first to third flow passage members.FIG. 5Ashows the surface of the first flow passage member50on the side where the ejection module200is mounted, andFIG. 5Fshows the surface of the third flow passage member70on the side where it abuts on the liquid ejection unit support part81. The first flow passage member50and the second flow passage member60are joined to each other such that abutting surfaces of respective flow passage members which areFIG. 5BandFIG. 5Care opposed to each other, and the second flow passage member and the third flow passage member are joined to each other such that abutting surfaces of respective flow passage members which areFIG. 5DandFIG. 5Eare opposed to each other. By joining the second flow passage member60and the third flow passage member70to each other, eight common flow passages extending in the longitudinal direction of the flow passage member are formed by common flow passage grooves62,71formed in respective flow passage members. Thus, a set of the common supply flow passage211and the common recovery flow passage212is formed in the flow passage member210for each color (FIG. 6). Communication ports72of the third flow passage member70communicate with respective holes of the joint rubber100, and fluidly communicate with the liquid supply unit220. A plurality of communication ports61is formed on the bottom surfaces of the common flow passage grooves62of the second flow passage member60, and communicates with one ends of individual flow passage grooves52of the first flow passage member50. Communication ports51are formed at the other ends of the individual flow passage grooves52of the first flow passage member50, and the other ends fluidly communicate with the plurality of ejection modules200through the communication ports51. The individual flow passage grooves52enable the flow passages to be collected on the center side of the flow passage member.

It is preferable that the first to third flow passage members have corrosion resistance to the liquid and are made of a material having a low coefficient of linear expansion. As a material, for example, a composite material (resin material) to which an inorganic filler such as silica fine particles and fibers is added using alumina, liquid crystal polymer (LCP), polyphenyl sulfide (PPS), and polysulfone (PSF) as a base material can be suitably used. As the forming method of the flow passage member210, three flow passage members may be laminated and bonded to each other, or in a case where a composite resin material is selected as a material, a bonding method by welding may be used.

Then, the connection relationship of flow passages in the flow passage member210will be described by usingFIG. 6.FIG. 6shows a perspective view in which a part of a flow passage in the flow passage member210formed by joining first to third flow passage members is enlarged from a surface side of the first flow passage member50on which the ejection module200is mounted. The flow passage member210is provided with common supply flow passages211(211a,211b,211c,211d) and common recovery flow passages212(212a,212b,212c,212d) extending in the longitudinal direction of the liquid ejection head3, for respective colors. A plurality of individual supply flow passages (213a,213b,213c,213d) formed by the individual flow passage grooves52is connected to the common supply flow passages211of respective colors through the communication ports61. A plurality of individual recovery flow passages (214a,214b,214c,214d) formed by the individual flow passage grooves52is connected to the common recovery flow passages212of respective colors through the communication ports61. By such a flow passage configuration, ink can be collected on the recording element substrate10positioned at the center of the flow passage member from each common supply flow passage211through the individual supply flow passage213. Additionally, ink can be recovered from the recording element substrate10to each common recovery flow passage212through the individual recovery flow passage214.

FIG. 7is a diagram illustrating a cross section taken along line E-E ofFIG. 6. As illustrated inFIG. 7, the individual recovery flow passages (214a,214c) communicate with the ejection module200through the communication ports51. Only the individual recovery flow passages (214a,214c) are illustrated inFIG. 7, but in another cross section, the individual supply flow passage213communicates with the ejection module200as illustrated inFIG. 6. A flow passage for supplying ink from the first flow passage member50to a recording element15(FIGS. 9A to 9C) provided on the recording element substrate10is formed on a supporting member30and the recording element substrate10included in each ejection module200. Further, a flow passage for recovering (recirculating) a part or the whole of the liquid supplied to the recording element15to the first flow passage member50is formed. Here, the common supply flow passage211of each color is connected to the negative-pressure control unit230(high pressure side) of a corresponding color through the liquid supply unit220, and the common recovery flow passage212is connected to the negative-pressure control unit230(low pressure side) through the liquid supply unit220. The negative-pressure control unit230generates differential pressure (pressure difference) between the common supply flow passage211and the common recovery flow passage212. Therefore, in the liquid ejection head in which flow passages are connected as illustrated inFIGS. 6 and 7according to the present embodiment, a flow flowing through the common supply flow passage211, the individual supply flow passage213a, the recording element substrate10, the individual recovery flow passage214b, and the common recovery flow passage212in this order occurs for each color.

Description of Ejection Module

A perspective view of one ejection module200is illustrated inFIG. 8A, and an exploded view thereof is illustrated inFIG. 8B. As a method of manufacturing the ejection module200, first, the recording element substrate10and the flexible wiring substrate40are bonded on the supporting member30provided with liquid communication ports31in advance. Thereafter, a terminal16on the recording element substrate10and a terminal41on the flexible wiring substrate40are electrically connected to each other by wire bonding, and then a wire bonding part (electric connection part) is covered with the sealing member110to be sealed. A terminal42of the flexible wiring substrate40on the side opposite to the recording element substrate10is electrically connected to a connecting terminal93(seeFIG. 4) of the electrical wiring substrate90. Since the supporting member30is a support that supports the recording element substrate10, and also is a flow passage member for fluidly communicating the recording element substrate10with the flow passage member210, a supporting member, which has high flatness and can be joined to the recording element substrate with sufficiently high reliability, is preferably used. As the material, for example, alumina or a resin material can be preferably used.

Description of Structure of Recording Element Substrate

The configuration of the recording element substrate10in the present embodiment will be described.FIG. 9Aillustrates a plan view of a surface of the recording element substrate10on a side on which the ejection port13is formed,FIG. 9Billustrates an enlarged view of a part indicated by A inFIG. 9A, andFIG. 9Cillustrates the top view of the back surface ofFIG. 9A. As illustrated inFIG. 9A, four ejection port lines corresponding to respective ink colors are formed on the ejection port forming member12of the recording element substrate10. Thereafter, the direction in which the ejection port line including the plurality of ejection ports13disposed therein is extended is called “ejection port line direction”.

As illustrated inFIG. 9B, the recording element15which is a heat generating element for foaming a liquid by thermal energy is disposed at a position corresponding to each ejection port13. The pressure chamber23provided with the recording element15inside is partitioned by a partition wall22. The recording element15is electrically connected to the terminal16inFIG. 9Aby electric wiring (not illustrated) provided on the recording element substrate10. The recording element15generates heat based on pulse signals input from a control circuit of the liquid ejection apparatus1000through the electrical wiring substrate90(FIG. 4) and the flexible wiring substrate40(FIGS. 8A and 8B), and boils the liquid. The liquid is ejected from the ejection port13by the foaming force by the boiling. As illustrated inFIG. 9B, a liquid supply path18is extended on one side and a liquid recovery path19is extended on the other side along each ejection port line. The liquid supply path18and the liquid recovery path19are flow passages extending in the ejection port line direction provided in the recording element substrate10, and communicate with the ejection port13through a supply port17aand a recovery port17b, respectively. A plurality of supply ports17awhich are through-holes penetrating the substrate is provided to form a supply port line along the line of ejection ports13, and a plurality of recovery ports17bpenetrating the substrate forms a recovery port line along the ejection port line. The liquid supply path18as a common path for supplying liquid to the supply port line is formed along the supply port line, and the liquid recovery path19as a supply recovery path for recovering liquid from the recovery port line is formed along the recovery port line.

As illustrated inFIG. 9CandFIG. 11, a sheet-like lid member20is laminated on the back surface of the surface of the recording element substrate10where the ejection port13is formed, and the lid member20is provided with a plurality of openings21communicating with the liquid supply path18and the liquid recovery path19to be described later. In the present embodiment, the lid member20is provided with three openings21for one liquid supply path18and two openings21for one liquid recovery path19. As illustrated inFIG. 9B, respective openings21of the lid member20communicate with a plurality of communication ports51illustrated inFIG. 5A.

As illustrated inFIG. 10, the lid member20has a function as a lid for forming a part of walls of the liquid supply path18and the liquid recovery path19formed on a substrate11of the recording element substrate10. The lid member20preferably has sufficient corrosion resistance to the liquid, and high accuracy is required for the opening shape and the opening position of the opening21from the viewpoint of color mixing prevention. Therefore, it is preferable that a photosensitive resin material or a silicon plate is used as the material of the lid member20, and the openings21are provided by a photolithographic process. In this way, the lid member20converts the pitch of the flow passages depending on the openings21, preferably has a smaller thickness if pressure loss is taken into consideration, and is preferably made of a film-like member.

Next, the flow of the liquid in the recording element substrate10will be described.FIG. 10is a perspective view illustrating the cross sections of the recording element substrate10and the lid member20on the B-B surface inFIG. 9A. The substrate11formed of Si and the ejection port forming member12formed of a photosensitive resin are laminated on the recording element substrate10, and the lid member20is joined to the back surface of the substrate11. The recording element15is formed on one surface side of the substrate11(FIGS. 9A to 9C), and a groove constituting the liquid supply path18and the liquid recovery path19extending along the ejection port line is formed on the back surface side. The liquid supply path18and the liquid recovery path19formed of the substrate11and the lid member20are respectively connected to the common supply flow passage211and the common recovery flow passage212in the flow passage member210, and differential pressure is generated between the liquid supply path18and the liquid recovery path19. When a liquid is ejected from a plurality of ejection ports13of the liquid ejection head3and recording is performed, a circulation flow flows at the ejection port where no ejection operation is performed. In the circulation flow, the liquid in the liquid supply path18provided in the substrate11flows to the liquid recovery path19through the supply port17a, the pressure chamber23and the recovery port17bby the differential pressure (flow indicated by arrow C inFIGS. 9A to 9C). By this flow, viscosity-increased ink, bubbles, and foreign matters generated by evaporation from the ejection port13in the ejection port13and the pressure chamber23where recording is suspended can be recovered to the liquid recovery path19. Additionally, the increase in viscosity of the ink in the ejection port13and the pressure chamber23can be suppressed. The liquid recovered to the liquid recovery path19is recovered in order of the communication ports51, individual recovery flow passages214and the common recovery flow passages212in the flow passage member210through the openings21of the lid member20and the liquid communication port31of the supporting member30(seeFIG. 8B). The liquid recovered to the liquid recovery path19is finally recovered to the supply path of the liquid ejection apparatus1000.

That is, the liquid supplied from the liquid ejection apparatus body to the liquid ejection head3flows in the following order and is supplied and recovered. First, the liquid flows into the liquid ejection head3from the liquid connecting part111of the liquid supply unit220. Thereafter, the liquid is supplied in the order of the joint rubber100, the communication port72and the common flow passage groove71provided in the third flow passage member, the common flow passage groove62and the communication port61provided in the second flow passage member, and the individual flow passage groove52and the communication port51provided in the first flow passage member. Thereafter, the liquid is supplied to the pressure chamber23through the liquid communication port31provided in the supporting member30, the opening21provided in the lid member, the liquid supply path18and the supply port17aprovided in the substrate11in this order. Among the liquid supplied to the pressure chamber23, the liquid not ejected from the ejection port13flows through the recovery port17band the liquid recovery path19provided in the substrate11, the opening21provided in the lid member, and the liquid communication port31provided in the supporting member30in this order. Thereafter, the liquid flows through the communication port51and the individual flow passage groove52provided in the first flow passage member, the communication port61and the common flow passage groove62provided in the second flow passage member, the common flow passage groove71and the communication port72provided in the third flow passage member70, and the joint rubber100in this order. Thereafter, the liquid flows to the outside of the liquid ejection head3from the liquid connecting part111provided in the liquid supply unit. In the form of the first circulation path illustrated inFIG. 2, the liquid flowing in from the liquid connecting part111is supplied to the joint rubber100after passing through the negative-pressure control unit230. In the form of a second circulation path illustrated inFIG. 2, the liquid recovered from the pressure chamber23passes through the joint rubber100and then flows from the liquid connecting part111to the outside of the liquid ejection head through the negative-pressure control unit230.

As illustrated inFIG. 2, in the present embodiment, a part of the liquid flowing in from one end of the common supply flow passage211of the liquid ejection unit300is ejected from the other end of the common supply flow passage211without flowing in the individual supply flow passage213. However, without being limited thereto, for example, all the liquids may flow into the individual supply flow passage without providing an ejection port at the other end of the common supply flow passage. The number of inlets of the common supply flow passage is not limited to one, and the other end may be provided as an inlet.FIGS. 27A to 27Care views illustrating the structure of the ejection port and an ink flow passage in the vicinity of the ejection port in the liquid ejection head according to the present embodiment.FIG. 27Ais a plan view of an ink flow passage viewed from the side where ink is ejected,FIG. 27Bis a cross sectional view taken along line A-A′ inFIG. 27A, andFIG. 27Cis a perspective view of an A-A′ cross section inFIG. 27A.

As illustrated inFIGS. 27A to 27C, ink flows17are generated in the pressure chamber23provided with the recording element15on the substrate11of the liquid ejection head and the flow passage24before and after the pressure chamber23by the above-described circulation of ink. That is, the ink is supplied from the liquid supply path (supply flow passage)18through the supply port17aprovided on the substrate11by a differential pressure generating ink circulation. The ink flows through a supply-side flow passage24, the pressure chamber23, and a recovery-side flow passage24, and a flow to the liquid recovery path (recovery flow passage)19through the recovery port17bis generated.

When the ink is not ejected, together with the flow of the ink described above, a space from the recording element (energy generating element)15to the ejection port13above it is filled with the ink, and a meniscus of ink (ink interface13a) is formed in the vicinity of an end on the ejection direction side of the ejection port13. Although the ink interface is represented by a straight line (plane) inFIG. 27B, its shape is determined according to a member forming the wall of the ejection port13and the ink surface tension, and is usually a concave or convex curve (curved surface). The ink interface is represented by a straight line in order to simplify illustration. By driving an electrothermal conversion element (heater) which is the energy generating element15in a state where the meniscus is formed, air bubbles are generated in the ink by utilizing the generated heat, and the ink can be ejected from the ejection port13. Further, in the present embodiment, a heater is applied as an energy generating element, but the present disclosure is not limited thereto, and various energy generating elements such as piezoelectric elements can be applied, for example. In the present embodiment, the speed of the ink flow flowing through the supply-side flow passage24is, for example, about 0.1 to 100 mm/s, and even if the ejection operation is performed in a state where the ink flows, the influence on the landing accuracy and the like can be made relatively small.

In the liquid ejection head of the present embodiment, the relationship between the height H of the supply-side flow passage24, the thickness P of an orifice plate (ejection port forming member12), and the length (diameter) W of the ejection port is defined as described below. InFIG. 27B, the upstream-side height of the supply-side flow passage24is indicated as H at the lower end (communication part between the ejection port part and the flow passage) of the part (hereinafter referred to as ejection port part13b) having the thickness P of the orifice plate of the ejection port13. The length of the ejection port part13bis indicated as P. Further, the length of the ejection port part13bin the flow direction of the liquid in the flow passage24is indicated as W. In the liquid ejection head of the present embodiment, H is 3 to 30 μm, P is 3 to 30 μm, and W is 6 to 30 μm. The ink has a nonvolatile solvent concentration of 30% and a coloring material concentration of 3%, and its viscosity is adjusted to 0.002 to 0.01 Pa·s.

In the present embodiment, the following is performed in order to suppress the increase in viscosity of ink due to the evaporation of ink from the ejection port13.FIG. 28Ashows the flow state of the ink flow17in the ejection port13, the ejection port part13b, and the flow passage24when the ink flow17(seeFIGS. 27A to 27C) of the ink flowing in the flow passage24and the pressure chamber23of the liquid ejection head is in a steady state. InFIG. 28A, the length of the arrow does not indicate the magnitude of the speed of the ink flow.FIG. 28Bshows a flow when ink flows in from the liquid supply path18to the flow passage24at a flow rate of 1.26×10−4ml/min in the liquid ejection head having a height H of the supply-side flow passage24of 14 μm, a length P of the ejection port part13bof 10 μm and a length (diameter) W of the ejection port of 17 μm.

In the present embodiment, the height H [μm] of the flow passage24, the length P [μm] of the ejection port part13b, and the length W [μm] of the ejection port part13bin the ink flowing direction has a relationship satisfying the following Expression (1).
H−0.34×P−0.66×W>1.5  (1)

When this condition is satisfied, as illustrated inFIG. 28A, the ink flow17flowing in the flow passage24flows into the ejection port part13b, reaches at least a half of the thickness of the orifice plate of the ejection port part13b, and then returns to the flow passage24again. The ink returned to the flow passage24flows through the liquid recovery path19to the common recovery flow passage212described above. That is, at least a part of the ink flow17reaches a position of ½ or more of the ejection port part13bin a direction toward the ink interface13afrom the pressure chamber23, and then returns to the flow passage24. The flow can suppress the increase in viscosity of the ink in many regions in the ejection port part13b. Since such an ink flow in the liquid ejection head is generated, the ink not only in the flow passage24but also in the ejection port part13bcan flow out to the flow passage24. As a result, an increase in viscosity of ink and an increase in the ink coloring material concentration at the ejection port13and the ejection port part13bcan be suppressed. The liquid droplets of the ink ejected from the ejection port are ejected in a state where the ink of the ejection port part13band the ink of the pressure chamber23(flow passage24) are mixed. In the present embodiment, it is preferable that the ratio of the ink of the pressure chamber23(flow passage24) is larger among the ejected liquid droplets. For example, it is preferable that air bubbles generated for ejection communicate with the ambient air. In particular, the liquid ejection head having H of 20 μm or less, P of 20 μm or less, and W of 30 μm or less is preferably used because it can perform higher-definition recording.

In order to further suppress the increase in viscosity of the ink in the ejection port part13b, it is preferable that the flow of the ink flowing into the ejection port part13breaches closer to the ink interface13aon the ejection port surface, as illustrated inFIG. 28B. This is achieved by satisfying the following Expression (2).
H−0.34×P−0.66×W>1.7  (2)

In the case of a configuration satisfying Expression (2), since the ink flows further to the vicinity of the meniscus of the ejection port13, the increase in viscosity of the ink near the ink interface13acan be suppressed as compared with the case ofFIG. 28A. Thus, the number of preliminary ejections can be suppressed, and preliminary ejections during recording on the recording medium can be eliminated as described later.

Thus, by circulating the ink inside and outside the pressure chamber23as in the present embodiment, an increase in viscosity of the ink inside the pressure chamber23and the ejection port part13bcan be suppressed, and as a result, the number of preliminary ejections can be reduced. In particular, since the increase in viscosity of ink can be further suppressed by satisfying Expression (1) and more preferably Expression (2), the number of preliminary ejections can be further reduced.

The shapes of the ejection port13and the ejection port part13bare not limited to the shapes illustrated inFIGS. 28A and 28B. For example, as illustrated inFIGS. 25A and 25B and 26A and 26B, it is also applicable to a ejection port shape in which a plurality of projections extend from the periphery of the ejection port13toward the center of the ejection port13. InFIGS. 25A, 25BandFIGS. 26A and 26B, plan views and cross-sectional views of a nozzle part around the ejection port13are respectively illustrated. By providing projections in the ejection port13in this way, the satellite and mist accompanying the liquid droplets ejected can be suppressed. In the case of the ejection ports having such a shape, W is a part having a maximum ejection port diameter as illustrated inFIGS. 25A, 25BandFIGS. 26A and 26B. The present disclosure can be applied even when the ejection port part13bhas a tapered shape such that the cross-sectional area is enlarged or reduced from the pressure chamber23to the ejection port13or has a stepped shape.

FIGS. 25A and 25Billustrate an example in which two projections are formed along a circulation flow in the ejection port13, andFIGS. 26A and 26Billustrate an example in which two projections extend in a direction intersecting (orthogonal to) the flow of the circulation flow.

Description of Positional Relationship Between Recording Element Substrates

FIG. 11is a plan view partially enlarging and illustrating the adjacent parts of the recording element substrates in two adjacent ejection modules. As illustrated inFIGS. 9A to 9C, in the present embodiment, a recording element substrate of an approximately parallelogram shape is used. As illustrated inFIG. 11, ejection port lines (14a-14d) having ejection ports13disposed in each recording element substrate10are disposed so as to incline at a fixed angle with respect to the conveying direction of the recording medium. Consequently, on the ejection lines in the adjacent parts of the recording element substrates10, at least one ejection port is overlapped in the conveying direction of the recording medium.

InFIG. 11, two ejection ports on the D line are in a mutually overlapped relationship. By such arrangement, even in a case where the position of the recording element substrate10is shifted slightly from the predetermined position, the black stripe and void of the recording image can be made inconspicuous by the driving control of the overlapping ejection ports. Even in a case where a plurality of recording element substrates10are not arranged in staggered manner but arranged on a straight line (inline), an increase in the length of the liquid ejection head3in the conveying direction of the recoding medium can be suppressed by the configuration illustrated inFIG. 11. Further, countermeasures can be taken against black stripes and void in the connecting portion between the recording element substrates10. Although the main plane of the recording element substrate is a parallelogram in the present embodiment, the present disclosure is not limited to this, and the configuration of the present disclosure can be preferably applied even in a case where, for example, a recording element substrate of a rectangle, a trapezoid or other shapes is used.

Specifically, the configuration of the present disclosure can be applied to an example in which parallelogram recording element substrates10are disposed in a line as illustrated inFIG. 23A, and an example in which rectangular recording element substrates are arranged in a staggered manner as illustrated inFIG. 23B. Further, as illustrated inFIG. 24, the configuration of the present disclosure can be applied to an aspect in which rectangular recording element substrates10each discharging one type of ink are arranged in a staggered manner. In this case, in order to configure a color liquid ejection apparatus, it is necessary to provide four liquid ejection heads. In this way, liquid ejection heads in various forms can be applied, as long as they are of the form in which a liquid circulates inside and outside the pressure chamber23.

Description of Temperature Adjustment

FIGS. 20A and 20Bare diagrams schematically illustrating the positional relationship between the opening21, a heater102, and a temperature sensor103measuring the temperature of a liquid (substrate), in the recording element substrate according to the first embodiment.FIG. 20Aillustrates, in a transparent manner, the ejection port forming member12(FIG. 10) in order to describe the arrangement of the openings21along the ejection port line in which ejection ports13are disposed on the recording element substrate10. As illustrated inFIGS. 9A to 9CandFIG. 10, the opening21is an opening, formed on the back surface of the recording element substrate10, through which a liquid is conducted, and is disposed for each of the liquid supply path18and the liquid recovery path19extending along the ejection port line on both sides. InFIGS. 20A and 20B, respective openings21are arranged on straight lines for simplifying illustration and description. The opening21ais an opening, disposed in the liquid supply path18(FIGS. 9A to 9C), for supplying liquid from the outside of the recording element substrate10to the liquid supply path18. The opening21bis disposed in the liquid recovery path19(FIGS. 9A to 9C), and recovers ink in the liquid recovery path19to the outside of the recording element substrate10. The sizes of the respective openings21inFIGS. 20A and 20Bare schematically illustrated, and the number of openings21is schematically indicated without specifying three for one liquid supply path18and two for one liquid recovery path19inFIG. 10.

FIG. 20Bschematically illustrates the state of removing the ejection port forming member12fromFIG. 20A. The positional relationship of the heater102(and the line of heaters) and the temperature sensor103(and the line of temperature sensors) relative to the positions of the openings21aand21balong the ejection port lines is illustrated. As will be described below, the heater102is provided separately from the recording element15(FIGS. 9A to 9C) for ejection, and is used to warm the ink to be ejected and/or the recording element substrate (to adjust temperature (hereinafter, temperature adjustment)). The numbers of openings21aand21bare an example, and two openings21amay be used for one liquid supply path18and one opening21bmay be used for one liquid recovery path19. The number of openings21a,21bmay be the same.

In the present embodiment, as illustrated inFIG. 20A, areas near the opening21aor the opening21bare defined as temperature adjustment areas101. The temperature sensor103and the temperature adjusting heater102are disposed in each of these areas as illustrated inFIG. 20B. Specifically, the temperature adjusting heater102and the temperature sensor103are provided around the recording element15which is an element for ejection at a distance not affecting each other. As a specific example of the temperature sensor, a diode sensor or the like can be cited.

The shape of the temperature sensor103is long in the direction of the ejection port line inFIG. 20B, but the shape is not particularly limited and may be circular, square, or the like. The temperature adjusting heater102is not limited to the form illustrated inFIG. 20B. For example, in a case where the recording element15for ejection is a heat generating element, temperature adjustment may be performed by inputting to the recording element15a pulse current which is so shorter than that for ejection that liquid is not to be ejected and utilizing the recording element15as a temperature adjusting heater. Further, the temperature adjusting heater102and the temperature sensor103may not be provided for each temperature adjustment area101, and at least one temperature adjusting heater102may be provided on the recording element substrate10. The temperature adjusting heater102may not be in an individual form, and may be configured to adjust the temperature by disposing, for example, a conductive member (wiring member) on the recording element substrate10.

The temperature adjustment control of the liquid ejection head will be described below, but the example illustrated below is an example, and the present disclosure can be applied to various forms of temperature adjustment controls, without being limited thereto. In each area101, when the temperature sensor103provided in this area measures a temperature equal to or lower than a fixed threshold temperature (a predetermined temperature), the heater102heats ink. That is, a temperature adjustment control unit (not illustrated) provided in the apparatus body or the like drives the heater102in the area based on the value measured by the temperature sensor103to heat the ink (substrate). When a temperature higher than the threshold which is a predetermined temperature is detected, heating by the heater102is stopped. Generally, since ink of relatively low temperature flows in the vicinity of the opening21athrough which the ink flows into the recording element substrate10, a corresponding temperature sensor103detects a relatively low temperature. As a result, by temperature control, heating by the corresponding heater102increases the frequency of heating or increases the heating time.

On the other hand, since the temperature of the ink near the opening21bthrough which the ink flows out is relatively high, the corresponding temperature sensor103detects a relatively high temperature. As a result, by temperature control, heating by the corresponding heater102is performed with a small frequency of heating or a short heating time, or the heating is not performed. As a result, the temperature fluctuation of the ink along the ejection port line which may be caused by the circulation of the ink can be suppressed. In the present embodiment, the number of openings and the number of temperature adjusted areas can be made equal, and the number of temperature sensors and the number of temperature adjusting heaters can be reduced.FIG. 21illustrates power consumption of the whole head at the time of preliminary ejection for each difference ΔT between the temperature of ink supplied to the head and the adjusted temperature which is the target temperature of the head.

The ink temperature is equal to the temperature in the printer unless a special ink temperature adjusting mechanism is used. The horizontal axis indicates the number of dots per square area with one side of 600 dpi (=about 42 μm), and the vertical axis indicates the power consumption of the whole head of the present embodiment at that time. Since the flow rate of ink passing through the head increases as the number of driven dots increases, power consumption for maintaining the adjusted temperature increases. The larger the temperature difference ΔT between the adjusted temperature and the ink temperature, the larger the power consumption becomes. For example, when the adjusted temperature as the target temperature is 40° C., ΔT=35° C. in a case where the ink temperature is 5° C., and ΔT=10° C. in a case where the ink temperature is 30° C. When the number of driven dots is zero, the power consumption represents the power consumption required to maintain the adjusted temperature by compensating for heat lost due to ink circulation and heat radiation to the surroundings. The number of driven dots of the horizontal axis can be regarded as the driving frequency at the time of preliminary ejection, and the power consumption of the vertical axis can be regarded as the instantaneous temperature change at the time of ejection, and the instantaneous temperature change of the head tends to become larger as ΔT becomes larger and the driving frequency of the preliminary ejection becomes larger. Therefore, the number of preliminary ejections is ideally zero, but in a case where it is necessary to perform preliminary ejection, for example, in a case of ink with a small amount of moisture, or a case where ink around the ejection port tends to dry after being left unattended for a long time, by limiting the number of preliminary ejections per ejection port to 200 or less, the influence on printing can be prevented. In the present embodiment, during a printing operation, by controlling the number of preliminary ejections to 0 or more to 20 or less while controlling the temperature while circulating the ink, the influence of temperature change on printing is suppressed.

The number of preliminary ejections here indicates the number of preliminary ejections during an operation period for printing (recording). That is, when the liquid ejection head is in a non-recording operation period (standby state), the ejection port of the liquid ejection head is covered with a cap. In this state, when a recording signal is sent from the liquid ejection apparatus to the liquid ejection head and the cap is removed from the liquid ejection head, the liquid ejection head is shifted to the recording operation. Thereafter, after a predetermined recording operation is performed on the recording medium according to the recording signal, the liquid ejection head is covered with a cap, so the liquid ejection head is in a standby state again. The definition that the number of preliminary ejections during the recording operation period described above is 20 or less per ejection port indicates the number of preliminary ejections in the period from when the cap is removed from the liquid ejection head in the standby state until the liquid ejection head is capped again. That is, the number of preliminary ejections for performing preliminary ejection in the cap is not counted. The preliminary ejection during the recording operation period is performed on a recording medium including a recording area and a non-recording area in the case of continuous paper such as roll paper. In the case of cut paper, the preliminary ejection is performed on the recording medium, similarly to continuous paper, and/or a preliminary ejection receiver provided in a recording apparatus provided in an area (inter-page) between recording media. The number of preliminary ejections is set to 20 or less per one ejection port because it is the average value of number of all ejection ports provided in the liquid ejection head3.

By this constitution, the number of preliminary ejections during the printing operation can be suppressed to 20 or less by circulating the ink inside and outside the pressure chamber in the liquid ejection head performing temperature adjustment. Thus, the temperature change of the liquid ejection head caused by the preliminary ejection can be suppressed, and the power consumption for raising the lowered temperature can be suppressed. Thus, the liquid ejection head and the printer having high image quality and low power consumption can be provided. In particular, in the case of a page-wide type liquid ejection head as in the present embodiment, since a plurality of recording element substrates are disposed and a considerable number of ejection ports are formed in the whole liquid ejection head, the effect of preliminary discharge is particularly great. Therefore, in a page-wide type including a plurality of recording element substrates, the number of preliminary ejections during the recording operation period described above is preferably set to 9 or less (zero or more to 9 or less) per nozzle.

In the present embodiment, an example in which a temperature sensor and a temperature adjusting heater are provided in each ejection port line is illustrated inFIGS. 20A and 20B, but the number of ejection port lines and the arrangement of the temperature sensors and the temperature adjusting heaters corresponding thereto are not limited. An example of a recording element substrate is shown inFIG. 22in which four lines of K and two lines of each of CMY are provided as ejection port lines, and a temperature sensor and a temperature adjusted area are provided in a line for each color. In a case where a plurality of ejection port lines are provided for the same color, when one line of temperature sensors and one line of temperature adjusting heaters are used for control of the plurality of ejection port lines as illustrated, it is possible to suppress an increase in the area of the recording element substrate more than the case where temperature sensors and temperature adjusting heaters are provided for each ejection port line.

Second Embodiment

The configurations of an ink jet recording apparatus1000which is a liquid ejection apparatus according to a second embodiment of the present disclosure and a liquid ejection head3will be described. In the following description, only a part different from the first embodiment is mainly described, and a description is omitted for parts similar to the first embodiment.

Description of Ink Jet Liquid Ejection Apparatus

An ink jet liquid ejection apparatus according to a second embodiment of the present disclosure is illustrated inFIG. 19. The liquid ejection apparatus1000of the second embodiment is different from the first embodiment in that four monochromatic liquid ejection heads3corresponding to inks of CMYK are disposed in parallel to perform full color recording on a recording medium. While the number of ejection port lines that can be used for one color in the first embodiment is one, the number of ejection port lines that can be used for one color in the present embodiment is 20 (FIG. 18A). Thus, recording is performed by appropriately assigning the recording data to a plurality of ejection port lines, so the recording can be performed very fast. Further, even if there is an ejection port which is in a state of non-ejection, interpolating ejection is performed from the ejection ports in another line which is disposed at the position corresponding to the conveying direction of the recording medium with respect to the ejection port, so reliability is improved, which is suitable for commercial printing. Similar to the first embodiment, a supply system of the liquid ejection apparatus1000, the buffer tank1003, and the main tank1006(FIG. 2) are fluidly connected to each liquid ejection head3. An electric control unit that transmits electrical power and an ejection control signal to the liquid ejection head3is electrically connected to each liquid ejection head3.

Description of Liquid Ejection Head Structure

The structure of the liquid ejection head3according to the second embodiment of the present disclosure will be described.FIGS. 12A and 12Bare perspective views of the liquid ejection head3according to the present embodiment. The liquid ejection head3is an ink jet type page-wide type recording head including 16 recording element substrates10arranged linearly in the longitudinal direction of the liquid ejection head3and capable of recording with one color of liquid. As in the first embodiment, the liquid ejection head3includes the liquid connecting part111, the signal input terminals91, and the electrical power supply terminals92. However, in the liquid ejection head3of the present embodiment, since there are more ejection port lines than in the first embodiment, the signal output terminals91and the electrical power supply terminals92are disposed on both sides of the liquid ejection head3. This is to reduce voltage drop and signal transmission delay generated in a wiring part provided on the recording element substrate10.

FIG. 13is a perspective exploded view of the liquid ejection head3, in which each component or unit constituting the liquid ejection head3is separately displayed for each function. The roles of the respective units and members and the order of the liquid circulation in the liquid ejection head are basically the same as the first embodiment, but the function of securing the rigidity of the liquid ejection head is different from the first embodiment. Although the rigidity of the liquid ejection head is secured mainly by the liquid ejection unit support part81in the first embodiment, the rigidity of the liquid ejection head is secured by the second flow passage member60included in the liquid ejection unit300in the second embodiment. The liquid ejection unit support part81in the present embodiment is connected to both ends of the second flow passage member60, and the liquid ejection unit300is mechanically coupled with a carriage of the liquid ejection apparatus1000to position the liquid ejection head3.

The liquid supply unit220including the negative-pressure control unit230and the electrical wiring substrate90are coupled with the liquid ejection unit support part81. Filters (not illustrated) are respectively incorporated in the two liquid supply units220. The two negative-pressure control units230are respectively set to control the pressure with relatively high and low different negative pressures. In a case where the negative-pressure control units230on the high pressure side and the low pressure side are installed at both ends of the liquid ejection head3as illustrated, the flows of the liquid in the common supply flow passage211and the common recovery flow passage212extending in the longitudinal direction of the liquid ejection head3face each other. Thus, heat exchange is promoted between the common supply flow passage211and the common recovery flow passage212, and the temperature difference in the two common flow passages is reduced. Thus, there is an advantage that the temperature difference between the plurality of recording element substrates10provided along the common flow passages does not easily occur, and the recording unevenness due to the temperature difference does not easily occur.

Next, the details of the flow passage member210of the liquid ejection unit300will be described. As illustrated inFIG. 13, the flow passage member210is formed by laminating the first flow passage member50and the second flow passage member60, and distributes liquid supplied from the liquid supply unit220to each ejection module200. The flow passage member210functions as a flow passage member for returning the liquid recirculated from the ejection module200to the liquid supply unit220. The second flow passage member60of the flow passage member210is a flow passage member in which the common supply flow passage211and the common recovery flow passage212are formed, and has a function of mainly bearing rigidity of the liquid ejection head3. Therefore, the material of the second flow passage member60is preferably one having sufficient corrosion resistance to the liquid and high mechanical strength. Specifically, SUS, Ti, or alumina can be preferably used.

FIG. 14Ais a diagram illustrating the surface of the first flow passage member50on the side where the ejection module200is mounted, andFIG. 14Bis a diagram illustrating the back surface of the first flow passage member50on the side where it abuts on the second flow passage member60. Different from the first embodiment, in the second embodiment, the first flow passage members50are obtained by adjacently arranging a plurality of members that correspond to the ejection modules200, respectively. By taking the structure divided in this way, the plurality of modules can be arranged so as to correspond to the length of the liquid ejection head. Thus, for example, the disclosure can be particularly preferably applied to a liquid ejection head of comparatively long scales corresponding to B2 size and a length equal to or larger than the B2 size. As illustrated inFIG. 14A, the communication port51of the first flow passage member50fluidly communicates with the ejection module200, and as illustrated inFIG. 14B, an individual communication port53of the first flow passage member50fluidly communicates with the communication port61of the second flow passage member60.FIG. 14Cillustrates the surface of the second flow passage member60abutting on the first flow passage member50,FIG. 14Dillustrates the cross section of the central part in the thickness direction of the second flow passage member60, andFIG. 14Eillustrates the surface of the second flow passage member60abutting on the liquid supply unit220. Functions of a flow passage and a communication port of the second flow passage member60are similar to those of one color in the first embodiment. One of the common flow passage grooves71of the second flow passage member60is the common supply flow passage211shown inFIG. 15, and the other is the common recovery flow passage212, and each supplies liquid from one end side to the other end side along the longitudinal direction of the liquid ejection head3. In the present embodiment, unlike the first embodiment, the longitudinal directions of the liquid in the common supply flow passage211and the common recovery flow passage212are opposite to each other.

FIG. 15is a perspective view illustrating a liquid connection relationship between the recording element substrate10and the flow passage member210. As illustrated inFIG. 15, a pair of the common supply flow passage211and the common recovery flow passage212extending in the longitudinal direction of the liquid ejection head3is provided in the flow passage member210. The communication port61of the second flow passage member60is connected in alignment with the individual communication port53of each first flow passage member50, and a liquid supply path communicating with the communication port51of the first flow passage member50through the common supply flow passage211from the communication port72of the second flow passage member60is formed. Similarly, a liquid supply path communicating with the communication port51of the first flow passage member50through the common recovery flow passage212from the communication port72of the second flow passage member60is also formed.

FIG. 16is a diagram illustrating a cross section taken along line F-F ofFIG. 15. As illustrated inFIG. 16, the common supply flow passage is connected to the ejection module200through the communication port61, the individual communication port53, and the communication port51. It is clear that the individual recovery flow passage is connected to the ejection module200through the same path with reference toFIG. 15. Similar to the first embodiment, a flow passage communicating with each ejection port13is formed in each ejection module200and recording element substrate10, and a part or the whole of the supplied liquid can be recirculated through the ejection port13(pressure chamber23) where the discharge operation is suspended. Similar to the first example, the common supply flow passage211is connected to the negative-pressure control unit230(high pressure side) and the common recovery flow passage212is connected to the negative-pressure control unit230(low pressure side) through the liquid supply unit220. Therefore, by this differential pressure, a flow flowing from the common supply flow passage211to the common recovery flow passage212through the ejection port13(pressure chamber23) of the recording element substrate10is generated.

Description of Ejection Module

FIG. 17Aillustrates a perspective view of one ejection module200, andFIG. 17Billustrates an exploded view thereof. It is different from the first embodiment in the following points. A plurality of terminals16are disposed on both sides along the direction of a plurality of ejection port lines of the recording element substrate10(long sides of each recording element substrate10). Two flexible wiring substrates40electrically connected to the terminals16are also disposed on one recording element substrate10. This is because the number of ejection port lines provided on the recording element substrate10is 20, which is significantly increased more than eight lines in the first embodiment. That is, an object is to suppress the maximum distance from the terminal16to the recording element15provided corresponding to the ejection port line short, to thereby reduce voltage drop and signal transmission delay caused in the wiring part in the recording element substrate10. The liquid communication port31of the supporting member30is opened so as to straddle all the ejection port lines provided on the recording element substrate10. Other aspects are similar to those in the first embodiment.

Description of Structure of a Recording Element Substrate

FIG. 18Ais a schematic diagram of the surface of the recording element substrate10on which the ejection port13is disposed, andFIG. 18Cis a schematic diagram illustrating the back surface of the surface ofFIG. 18A.FIG. 18Bis a schematic diagram illustrating the surface of the recording element substrate10when a lid member20, illustrated inFIG. 18C, provided on the back surface side of the recording element substrate10is removed. As illustrated inFIG. 18B, the liquid supply path18and the liquid recovery path19are alternately provided along the ejection port line direction on the back surface of the recording element substrate10. Although the number of ejection port lines is greatly increased from that of the first embodiment, the essential difference from the first embodiment is that the terminals16are disposed on both sides along the ejection port line direction of the recording element substrate as described above. A basic configuration is similar to the first embodiment, such as providing a set of the liquid supply path18and the liquid recovery path19for each ejection port line, and providing on the lid member20the opening21communicating with the liquid communication port31of the supporting member30.

Other Configurations

In each embodiment described above, an example in which a pump as a power source for circulation is provided in the liquid ejection apparatus body which is outside of the liquid ejection head is illustrated, but the power source may be provided on the liquid ejection head3. In particular, a micropump (micro actuator) including a heat generating element, a piezoelectric element or the like may be provided on the recording element substrate10(FIGS. 8A and 8B) including the recording element, and a pump on the apparatus body side and a micropump may be used in combination.

In a case where the micropump is provided on the recording element substrate, a common liquid chamber (not illustrated) for holding liquid, a first flow passage (not illustrated) communicating the pressure chamber23with the common liquid chamber, and a second flow passage (not illustrated) communicating the pressure chamber23with the common liquid chamber are provided. A configuration in which the micropump is provided in the second flow passage can be applied. The second flow passage may be a substantially U-shaped flow passage having a bent part.

As described in the above embodiments, in the liquid ejection head performing temperature adjustment, the average number of preliminary ejections during a recording operation period per ejection port of the liquid ejection head can be suppressed to 20 or less, by ink circulating inside and outside the pressure chamber23. Thus, temperature change and increase in power consumption caused by preliminary ejections are prevented, and the liquid ejection head and the liquid ejection apparatus having high image quality and low power consumption can be provided.

This application claims the benefit of priority from Japanese Patent Application No. 2018-190400, filed Oct. 5, 2018, which is hereby incorporated by reference herein in its entirety.