LIQUID DISCHARGE HEAD

A liquid discharge unit includes a discharge port which discharges liquid, a supply path which supplies the liquid to the discharge port, and a pressure control unit which controls a pressure of the liquid supplied from a liquid supply source to the supply path. The pressure control unit includes a fluid chamber having an inflow port of the liquid and an outflow port of the liquid, a valve body taking a closed position where the inflow port is closed and an open position where the inflow port is opened, a movable member taking a first position acting on the valve body such that the valve body is located at the closed position and a second position acting on the valve body, and an urging member which applies an urging force to the movable member.

BACKGROUND OF THE INVENTION

Field of the Invention

An art of the present disclosure relates to a liquid discharge head which performs recording by an inkjet method.

Description of the Related Art

In a liquid discharge device, a discharge port of a recording element board (hereinafter, referred to simply as a “chip” in some cases) mounted on a liquid discharge head is open to an atmospheric air, and ink used for the recording forms meniscus by a capillary phenomenon at the discharge port. Here, a pressure applied to the ink at the discharge port is a negative pressure in general. As this negative-pressure generation source, there is a method of using a water head difference between a liquid level of an ink storage tank communicating with the discharge port and a liquid level of the discharge port, but the water head difference is changed in accordance with a positional change of the liquid level of the ink storage tank, and the negative pressure applied to the discharge port also fluctuates. Therefore, since a meniscus surface position in the discharge port fluctuates, a volume of a discharged droplet also fluctuates. When this fluctuation becomes larger, that is, by 3% or more, for example, there is a possibility that an image quality is influenced by generation of image density non-uniformity of the discharged ink.

Thus, for the purpose of stability of the meniscus surface position in the discharge port, as an art of controlling the negative pressure applied to the ink at the discharge port by using a pressure control unit, an art of using a valve lever in a pressure control mechanism is proposed as in Japanese Patent Application Publication

For the purpose of realizing print with high image quality, ink containing a large quantity of solid parts such as pigments is used, and particularly white ink contains pigments such as titanium dioxide or the like which is precipitated and adheres easily. However, in the art in Japanese Patent Application Publication No. 2014-162084, a shaft of a valve and a seal surface of the valve are disposed perpendicularly to a gravity direction (horizontal direction).

In this case, when the aforementioned ink is used, there is a possibility that the ink adheres at an inflow port, which causes occurrence of a defective opening/closing operation of a valve lever, or a flow resistance by the ink flowing in through the inflow port is changed by the adhering ink, which affects fluctuation of the negative pressure in a negative pressure chamber. As a result, there is a possibility that the image quality of recording can deteriorate due to occurrence of image density non-uniformity of the ink or the like.

SUMMARY OF THE INVENTION

In view of the aforementioned problem, the art of this disclosure has an object to provide a liquid discharge head which can reduce adhesion of liquid or malfunction of a valve body at an inflow port of the liquid of a pressure control unit and maintain an image quality of records to which the liquid is discharged.

According to some embodiments, a liquid discharge unit includes a discharge port which discharges liquid; a supply path which supplies the liquid to the discharge port; and a pressure control unit which controls a pressure of the liquid supplied from a liquid supply source to the supply path. The pressure control unit includes a fluid chamber having an inflow port into which the liquid from the liquid supply source flows and an outflow port which causes the liquid having flown in through the inflow port to flow out to the supply path; a valve body configured to be capable of taking a closed position where the inflow port is closed and an open position where the inflow port is opened; a movable member configured to be capable of taking a first position acting on the valve body such that the valve body is located at the closed position and a second position acting on the valve body such that the valve body is located at the open position in the fluid chamber; and an urging member which applies an urging force to the movable member for causing the movable member to be located at the first position. The movable member moves from the first position to the second position when a magnitude of a pressure in the fluid chamber becomes larger than the urging force of the urging member, and in a state where the liquid discharge head is attached to a liquid discharge device which discharges the liquid to recordings by using the liquid discharge head, a direction in which the liquid flows into the inflow port is a direction intersecting with a gravity direction.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, Preferred Embodiments of the art of this disclosure will be explained in detail on the basis of the attached drawings. Note that, in each drawing, the same reference numerals are given to the same members, and duplicated explanation will be omitted. Hereinafter, each of Embodiments will be explained in more detail. Moreover, numerical values shown in each of Examples below are examples, and the art of this disclosure is not limited to them. Furthermore, the art of this disclosure is not limited to each of Embodiments but includes those further combining these Embodiments and those applied to other technical fields.

First Embodiment

Hereinafter, a liquid discharge device according to First Embodiment of the art of this disclosure will be explained. The liquid discharge device according to this Embodiment is an inkjet recording device (recording device) which circulates liquid such as ink between a tank and a liquid discharge head. However, in this Embodiment, a form of supplying ink to the liquid discharge head may be other forms. For example, the following embodiments can be applied to a recording device in which, without circulating the ink, a tank is provided on an upstream side and a downstream side of the liquid discharge head, respectively, and the ink is caused to flow by causing the ink to flow from one of the tanks to the other tank.

Moreover, the liquid discharge device of this Embodiment is assumed to be a liquid discharge device of a so-called line-type head having a liquid discharge head with a length corresponding to a width of a recording medium to which the ink is discharged. However, the liquid discharge device of this Embodiment may be a liquid discharge device having a so-called serial-type liquid discharge head which discharges the ink while scanning the recording medium. As the serial-type liquid discharge head, such a configuration can be cited that a recording element board for black ink and recording element boards for color inks are mounted, respectively, for example. However, not limited to them, such a configuration may be used that a line head with a length shorter than the width of the recording medium on which a plurality of recording element boards are disposed along a discharge-port row direction so that the discharge ports overlap each other is caused to scan the recording medium.

(Explanation on Inkjet Recording Device)FIG.1illustrates a schematic configuration diagram of a liquid discharge device or particularly an inkjet recording device1000(hereinafter, also referred to as a recording device) which performs recording by discharging ink of this Embodiment. The recording device1000has a conveyance portion1for conveying a recording medium2, and line-type liquid discharge heads3B,3C,3M,3Y (hereinafter, also referred to as a liquid discharge head3) disposed substantially orthogonal to a conveyance direction of the recording medium2. The liquid discharge heads3B,3C,3M,3Y discharge ink for black, ink for cyan, ink for magenta, ink for yellow, respectively. As a result, the recording device1000is capable of full-color print by so-called CMYK ink.

The recording device1000is a line-type recording device which performs continuous recording in one pass while continuously or intermittently conveying a plurality of the recorded mediums2. The recording medium2is not limited to cut paper but may be continuous rolled paper. Moreover, the recording medium2is not limited to paper but may be a film or the like. As will be described later, a supply path for supplying the ink to the liquid discharge head3, a main tank and a buffer tank (seeFIG.2) are fluidly connected. Moreover, to the liquid discharge head3, an electric control portion which transmits electricity and a discharge control signal to the liquid discharge head3is electrically connected. A liquid flow passage and an electric signal path in the liquid discharge head3will be described later.

(Ink Circulation System)FIG.2is a schematic diagram illustrating a circulation flow passage applied to the recording device of this Embodiment. As shown inFIG.2, the liquid discharge head3is fluidly connected to a first circulation pump1002, a buffer tank1003and the like. Note that, inFIG.2, in order to simplify the explanation, only a flow passage through which ink in one color in the CMYK inks flows is illustrated, but in actuality, circulation flow passages in four colors are provided in the liquid discharge head3and the recording device1000. The buffer tank1003as a sub tank connected to a main tank1006as a liquid supply source has an atmospheric-air communication port (not shown) causing an inside and an outside of the tank to communicate with each other and can eject air bubbles in the ink to the outside. The main tank1006stores the ink supplied to the liquid discharge head3, which will be explained below. The buffer tank1003is connected also to a replenishing pump1005. In the liquid discharge head3, ink is consumed by discharging (ejecting) the ink through the discharge port of the liquid discharge head such as recording by discharging the ink, suction recovery or the like. At this time, the replenishing pump1005transfers the ink in an amount according to a consumption amount from the main tank1006to the buffer tank1003.

The first circulation pump1002withdraws the ink from a liquid connecting portion111of the liquid discharge head3and causes it to flow to the buffer tank1003. When the liquid discharge head3is being driven, a certain amount of the ink flows in a common recovery flow-passage212by the first circulation pump1002. A negative-pressure control unit230is provided in a flow passage between a second circulation pump1004and a liquid discharge unit300. The negative-pressure control unit230operates such that, even if a flow rate of a circulation system is fluctuated by a difference in Duty for recording, a pressure on a downstream side (the liquid discharge unit300side) of the negative-pressure control unit230is maintained at a certain pressure set in advance.

As shown inFIG.2, the negative-pressure control unit230includes two pressure adjustment mechanisms for which control pressures different from each other are set, respectively. The negative-pressure control unit230has two negative-pressure control mechanisms, that is, a negative-pressure adjustment mechanism on a relatively high pressure side (a side indicated by “H” inFIG.2) and a negative-pressure adjustment mechanism on a relatively low pressure side (a side indicated by “L” inFIG.2). These two negative-pressure adjustment mechanisms are connected to a common supply flow-passage211and the common recovery flow-passage212of the liquid discharge unit300via a liquid supply unit220, respectively.

In the liquid discharge unit300, the common supply flow-passage211, the common recovery flow-passage212, and an individual supply flow-passage213aand an individual recovery flow-passage213b(hereinafter, also referred to as an individual flow-passage213) communicating with each of the recording element boards are provided. The individual flow-passage213communicates with the common supply flow-passage211and the common recovery flow-passage212. Moreover, since the negative-pressure adjustment mechanism H is connected to the common supply flow-passage211, and the negative-pressure adjustment mechanism L to the common recovery flow-passage212, a differential pressure is generated between the two common flow passages. As a result, the ink flows from the common supply flow-passage211to the common recovery flow-passage212by passing through an internal flow passage of the recording element board10(a flow indicated by an arrow inFIG.2).

As described above, in the liquid discharge unit300, while the ink is caused to flow so as to pass through the common supply flow-passage211and the common recovery flow-passage212, respectively, such a flow that a part of the ink passes through an inside of each of the recording element boards10is generated. Thus, a heat generated in each of the recording element boards10can be ejected to the outside of the recording element boards10by the flows of the common supply flow-passage211and the common recovery flow-passage212. Moreover, by means of the configuration as above, when the recording by the liquid discharge head3is being performed, the flow of the ink can be generated also in the discharge port or a fluid chamber, where the recording is not being performed and thus, thickening of the ink in those parts can be suppressed. Moreover, the thickened ink or foreign substances in the ink can be ejected to the common recovery flow-passage212. Therefore, according to the liquid discharge head3of the recording device1000of this Embodiment, a high-speed and high image-quality recording can be performed for the recording medium.

The two negative-pressure adjustment mechanisms disposed in the negative-pressure control unit230do not necessarily have to be controlled to a negative pressure, but the pressure only needs to be controlled such that the negative pressure is maintained at the discharge port. In the control of a pressure value at the discharge port, fluctuation in the pressure in a flow passage from the negative-pressure adjustment mechanism to the discharge port needs to be suppressed and thus, it is preferable that the negative-pressure adjustment mechanism is disposed at a position close to the discharge port. Therefore, it is more preferable that the negative-pressure control unit230is mounted on the liquid discharge head3.

A unit combining the liquid supply unit220and the negative-pressure control unit230shown inFIG.2is called a pressure control assembly2000, here. In order to realize high image-quality print for the recording medium, a pressure difference is held by suppressing fluctuation of a pressure loss generated in the flow passage from the two negative-pressure adjustment mechanisms to the discharge port, and a circulation flow speed flowing through the discharge port is made stable. Thus, it is preferable to have such a configuration that the negative-pressure control unit230is mounted on the liquid discharge head3, and a flow-passage length from the negative-pressure adjustment mechanism of the negative-pressure control unit230to the discharge port is made shorter so as to reduce the pressure loss.

(Explanation on Liquid Discharge Head Configuration) A configuration of the liquid discharge head3according to this Embodiment will be explained.FIGS.3A and3Bare perspective views of the liquid discharge head3according to this Embodiment. The liquid discharge head3is the line-type liquid discharge heads3in which17pieces of the recording element boards10are aligned (in-line disposition) as an example on a straight line.

As shown inFIGS.3A and3B, the liquid discharge head3includes a signal input terminal91and an electricity supply terminal92electrically connected to each of the recording element boards10via a flexible wiring board40and an electric wiring board90. The signal input terminal91and the electricity supply terminal92are electrically connected to a control portion of the recording device1000and supplies electricity required for a discharge drive signal and discharge of the ink to the recording element board10, respectively. By collecting the wirings by an electric circuit in the electric wiring board90, the numbers of the signal input terminals91and the electricity supply terminals92can be made smaller than the number of the recording element boards10. As a result, when the liquid discharge head3is assembled to the recording device1000or when the liquid discharge head3is replaced, the number of electric connection parts required to be removed can be made smaller.

As shown inFIG.3B, the liquid connecting portions111provided on both ends of the liquid discharge head3are connected to a liquid supply system of the recording device1000. As a result, the ink in four colors of CMYK is supplied from the supply system of the recording device1000to the liquid discharge head3, and the ink having passed through the liquid discharge head3is recovered by the supply system of the recording device1000. As described above, the ink in each color can be circulated by the flow passage of the recording device1000and the flow passage of the liquid discharge head3.

FIG.4shows an exploded perspective view of each component or unit constituting the liquid discharge head3. The liquid discharge unit300, the liquid supply unit220, and the electric wiring board90are mounted on a housing80. In the liquid supply unit220, the liquid connecting portion111is provided, and in the liquid supply unit220, in order to remove foreign substances in the supplied ink, a filter221for each color communicating with each opening of the liquid connecting portion111is provided. The two liquid supply units220have the filters221in two colors each, respectively.

The ink having passed through the filter221is supplied to the negative-pressure control unit230disposed on the liquids supply unit220in accordance with the respective colors. The negative-pressure control unit230is a unit constituted by pressure control valves for each of the colors. And by means of operations of the valve, a spring member and the like provided in each of the pressure control valves, a pressure-loss change in the supply system of the recording device1000(supply system on an upstream side of the liquid discharge head3) generated with the fluctuation in the flow rate of the ink attenuates. And the negative-pressure control unit230stabilizes the negative-pressure change on the downstream side (liquid discharge unit300side) of the negative-pressure control unit230within a certain range. In the negative-pressure control unit230in each color, as shown inFIG.2, two pressure control valves are incorporated for each color. The two pressure control valves are set to control pressures, different from each other, and a high-pressure side communicates with the common supply flow-passage211in the liquid discharge unit300, while a low-pressure side with the common recovery flow-passage212via the liquid supply unit220.

The housing80is constituted by a liquid-discharge unit supporting-portion81and an electric-wiring board supporting portion82, supports the liquid discharge unit300and the electric wiring board90, and ensures rigidity of the liquid discharge head3. The electric-wiring board supporting portion82supports the electric wiring board90and is fixed to the liquid-discharge unit supporting-portion81by screwing. The liquid-discharge unit supporting-portion81corrects warping or deformation of the liquid discharge unit300and ensures relative positional accuracy of a plurality of the recording element boards10, thereby suppressing streaks and unevenness in the recording. Thus, the liquid-discharge unit supporting-portion81preferably has sufficient rigidity, and as a material, a metal material such as SUS and aluminum or ceramic such as alumina is preferable. In the liquid-discharge unit supporting-portion81, openings83,84into which a joint rubber100is inserted are provided. The ink to be supplied from the liquid supply unit220is led to a second flow-passage member60constituting the liquid discharge unit300via the joint rubber100.

The liquid discharge unit300is constituted by a plurality of discharge modules200and a flow-passage member210, and a cover member130is mounted on a surface on the recorded medium side of the liquid discharge unit300. Here, the cover member130is, as shown inFIG.4, a member having a frame-like surface in which a lengthy opening131is provided, and from the opening131, the recording element board10and a sealing member110(FIG.7A) included in the discharge module200are exposed. A frame part around the opening131has a function as a contact surface of a cap member which caps the liquid discharge head3during recording stand-by. Thus, it is preferable that a closed space is formed when being capped by applying an adhesive, a sealing material, a filling material or the like along a periphery of the opening131so as to fill irregularity or gaps on a discharge port surface of the liquid discharge unit300.

Subsequently, a configuration of the flow-passage member210included in the liquid discharge unit300will be explained. As shown inFIG.4, the flow-passage member210is constituted by laminating the first flow-passage member50and the second flow-passage member60, and a plurality of the discharge modules200are bonded to a bonding surface53of the first flow-passage member50by an adhesive (not shown). The flow-passage member210is configured to be a flow passage to distribute a liquid supplied from the liquid supply unit220to each of the discharge modules200and to return the liquid circulating from the discharge module200to the liquid supply unit220. The flow-passage member210is fixed to the liquid-discharge unit supporting-portion81by screwing.

FIGS.5A to5Care diagrams for explaining a detailed configuration of the flow-passage member210.FIGS.5A and5Billustrate front/rear surfaces of the first flow-passage member50,FIG.5Cfor a front surface of the second flow-passage member60, respectively.FIG.5Ais a contact surface with the recording element board10, andFIG.5Cis a contact surface with the liquid supply unit220. Moreover, the surface of the first flow-passage member50shown inFIG.5Band a rear surface of the second flow-passage member60shown inFIG.5Care brought into contact with each other.

Communication ports51of a repeated pattern are aligned in the Y-direction in the first flow-passage member50, and one piece of the recording element board10corresponds to the repeated pattern. As shown inFIG.5A, in the surface of the first flow-passage member50to be brought into contact with the recording element board10, the communication port51fluidly connected to the recording element board10and to be the individual supply flow-passage213aand the individual recovery flow-passage213bexplained inFIGS.2A and2Bare formed.

As shown inFIG.5C, a common flow-passage groove62extending in the Y-direction and to be the common supply flow-passage211and the common recovery flow-passage212explained inFIGS.2A and2Bis formed. In both end parts of the common flow-passage groove62, a common communication port61fluidly communicating with the liquid supply unit220is formed.

FIGS.6A and6Bare a perspective view and a sectional view for explaining a flow-passage structure formed inside the flow-passage member210.FIG.6Bis an A-A sectional diagram ofFIG.6A. The common supply flow-passage211and the common recovery flow-passage212extending in a longitudinal direction (Y-direction) of the first flow-passage member50are fluidly connected to the opening21of the recording element board10via the communication port51of the first flow-passage member50and the liquid supply port31of a support member30.

As already explained, the common supply flow-passage211is connected to a first negative-pressure control unit230awith a relatively high pressure, and the common recovery flow-passage212is connected to a second negative-pressure control unit230bwith a relatively low pressure. Thus, an ink supply flow-passage to the recording element board10constituted by the common communication port61(seeFIG.6), the common supply flow-passage211, the communication port51(individual supply flow-passage213a), and the recording element board10is formed. Similarly, an ink recovery flow-passage constituted by the recording element board10, the communication port51(individual recovery flow-passage213b), the common recovery flow-passage212, and the common communication port61(seeFIG.6) is formed. While the ink is circulated as above, in the recording element board10, a discharging operation according to discharge data is performed, and the ink which has not been consumed by the discharging operation in the ink supplied in the ink supply flow-passage is recovered in the ink recovery flow-passage.

(Explanation on Discharge Module)FIG.7Ais a perspective view illustrating one piece of the discharge module200, andFIG.7Bis an exploded view thereof. As a manufacturing method of the discharge module200, first, the recording element board10and the flexible wiring board40are bonded onto the support member30on which the liquid supply port31is provided in advance. After that, a terminal16on the recording element board10and a terminal41on the flexible wiring board40are electrically connected by wire bonding and then, a wiring bonding portion (electric connecting portion) is sealed by covering with the sealing member110. A terminal42on a side opposite to the recording element board10of the flexible wiring board40is electrically connected to a connection terminal93of the electric wiring board90(seeFIG.4). The support member30is a support body for supporting the recording element board10and is also a flow-passage member which causes the recording element board10to fluidly communicate with the flow-passage member210and thus, it is preferably the one which has a high flatness degree and can be bonded with the recording element board with sufficiently high reliability. As a material of the support member30, alumina or a resin material, for example, is preferable.

(Explanation on Structure of Recording Element Board)FIG.8Aillustrates a plan view of a surface on a side where a discharge port13of the recording element board10is formed,FIG.8Billustrates an enlarged view of a part surrounded by a circle indicated by B inFIG.8A, andFIG.8Cillustrates a plan view of a rear surface ofFIG.8A. Here, a configuration of the recording element board10in this Embodiment will be explained.

InFIG.8A, a view when four rows of the discharge-port rows are formed in the discharge-port forming member12of the recording element board10is shown, but the number of the discharge-port rows is not limited to that. Note that, hereinafter, a direction in which the discharge-port row in which a plurality of the discharge ports13are aligned extends will be referred to as a “discharge-port row direction”.

As shown inFIG.8B, at a position corresponding to each of the discharge ports13, a recording element15, which is a heat generating element (pressure generating element) for foaming the ink by using a thermal energy, is disposed. By means of a partition wall22, a fluid chamber23including the recording element15inside is partitioned. The recording element15is electrically connected to the terminal16by an electric wiring (not shown) provided on the recording element board10. And the recording element15generates a heat and boils the ink on the basis of a pulse signal input through the electric wiring board90and the flexible wiring board40from a control circuit of the recording device1000. By means of a force of foaming by this boiling, the ink is discharged from the discharge port13. As shown inFIG.8B, along each of the discharge-port rows, a liquid supply path18extends on one side, while a liquid recovery path19on the other side. The liquid supply path18and the liquid recovery path19are flow passages extending in the discharge-port row direction provided on the recording element board10and communicate with the discharge port13via a supply port17aand a recovery port17b,respectively.

As shown inFIG.8C, on the rear surface of a surface on which the discharge port13is formed in the recording element board10, a sheet-like cover plate20is laminated, and in the cover plate20, a plurality of openings21(opening row) communicating with the liquid supply path18and the liquid recovery path19, which will be described later, are provided. In this Embodiment, three pieces of the openings21with respect to one piece of the liquid supply path18and two pieces of the openings21with respect to one piece of the liquid recovery path19are provided in the cover plate20, respectively. Note that the number of the openings21is not limited to that.

As shown inFIG.8B, the respective openings21in the cover plate20communicate with the plurality of communication ports51shown inFIG.6A. The cover plate20preferably has sufficient corrosion resistance to ink, and from a viewpoint of preventing color-mixing of ink, an opening shape and an opening position of the opening21are required to be disposed with high accuracy. Therefore, it is preferable that a photosensitive resin material or a silicon plate is used as a material for the cover plate20, and the opening21is provided by a photolithographic process.

FIG.9is a perspective view of the recording element board10and a section of the cover plate (lid member)20by a C-C line inFIG.8A. Here, a flow of the ink in the recording element board10will be explained. The cover plate20has a function as a lid which forms parts of walls of the liquid supply path18and the liquid recovery path19formed on a board11of the recording element board10. In the recording element board10, the board11formed by Si and a discharge-port forming member12formed by a photosensitive resin are laminated, and to the rear surface of the board11, the cover plate20is bonded. On one of surface sides of the board11, the recording element15is formed (seeFIG.8B), and on a rear surface side thereof, a groove constituting the liquid supply path18and the liquid recovery path19extending along a nozzle row13ain which a plurality of the discharge ports13are aligned is formed.

The liquid supply path18and the liquid recovery path19formed by the board11and the cover plate20are connected to the common supply flow-passage211and the common recovery flow-passage212in the flow-passage member210, respectively, and a differential pressure is generated between the liquid supply path18and the liquid recovery path19. When recording is performed by discharging the ink from the discharge port13, at the discharge port which is not discharging the ink, the ink in the liquid supply path18provided in the board11flows by this differential pressure to the liquid recovery path19via the supply port17a,the fluid chamber23, and the recovery port17b(arrow D). By means of this flow, in the discharge port13not performing the discharging operation and the fluid chamber23, the thickened ink generated by evaporation from the discharge port13, bubbles, foreign substances and the like can be recovered into the liquid recovery path19. Moreover, thickening of the ink at the discharge port13or the fluid chamber23or an increase in the density of the color material can be suppressed. The ink having been recovered into the liquid recovery path19flows through the opening21of the cover plate20and the liquid supply port31of the support member30as shown inFIG.7B. After that, the ink flows in the order of the liquid supply port31of the support member30, the communication port51of the first flow-passage member50, and the common recovery flow-passage212and is recovered by the supply flow-passage of the recording device1000(FIG.2).

(Detailed Explanation of Negative-Pressure Control Unit) Subsequently, a problem to be solved by the art of this disclosure will be explained in detail.FIGS.10A and10Bare views illustrating a structure of the negative-pressure control unit230a(pressure-reducing valve) on the high-pressure side (H-side) in the negative-pressure control unit230, which is a pressure control unit of ink used in this Embodiment. An operation principle of this negative-pressure control unit230ais similar to the one called a “pressure-reducing regulator” in general. Note that, since the configuration and the operation of the negative-pressure control unit230bon the low-pressure side (L-side) are similar to those of the negative-pressure control unit230a,detailed explanation will be omitted in the following.

FIG.10Ais a view illustrating an appearance of the negative-pressure control unit230a,andFIG.10Billustrates a housing231of the negative-pressure control unit230afor accommodating each of the constituent elements of the negative-pressure control unit230a,which will be explained below. As shown inFIG.10A, the negative-pressure control unit230ahas a pressure-receiving plate2321and a fluid chamber2323. As will be explained below, the pressure-receiving plate2321is a movable member displaced in accordance with pressure fluctuation generated with a change in the ink amount in the fluid chamber2323. By means of an operation of a lever2327, which will be described later, by the operation of the pressure-receiving plate2321, a flow of the ink flowing into the fluid chamber2323, which is a fluid chamber through which the ink flows, and a pressure of the ink in the fluid chamber2323and the liquid supply path18are controlled.

Moreover, as shown inFIG.10B, the housing231of the negative-pressure control unit230ahas a bearing portion2329with which a rotating shaft2328, which will be explained below, is fitted, and an orifice2320, which is an inflow port of the ink. The orifice2320is constituted by a circular opening provided on an upstream side (a liquid communication chamber2324side) through which the ink flows into the fluid chamber2323and a circular opening provided on a downstream side (fluid chamber2323side) thereof, and a cylindrical hole connecting these openings.

FIGS.11and12illustrate a section of the negative-pressure control unit230aby an E-E line inFIG.10A. As shown inFIGS.11and12, the negative-pressure control unit230ahas the pressure-receiving plate2321functioning as a pressure-receiving portion, a flexible film2322which fluidly seals the pressure-receiving plate2321and the housing231, and the fluid chamber2323. Moreover, on an upstream side (paper-surface left side) of the ink flowing through the fluid chamber2323, a movable valve2325, which is a valve body interlocking with the pressure-receiving plate2321and the orifice2320with which the movable valve2325is fitted are provided. The orifice2320is an inflow port through which the ink in the main tank1006, which is a liquid supply source, flows into the fluid chamber2323. Moreover, the ink having flown into the fluid chamber2323from the orifice2320is caused to flow out of an outflow port2331to the common supply flow-passage211(seeFIG.2).

The movable valve2325has a cylinder-shaped shaft body2325band a projection2325c,which is a circular-shaped annular projection protruding to the orifice2320side on a surface opposed to the orifice2320of the shaft body2325b.The movable valve2325is provided integrally with the lever2327disposed in the fluid chamber2323. The movable valve2325is constituted capable of taking a closed position to close the orifice2320and an open position to open the orifice2320. Moreover, the projection2325cof the movable valve2325is formed so that an inner diameter of the projection2325cis larger than an opening diameter of the orifice2320. When the movable valve2325is at the closed position to close the orifice2320, the projection2325cof the movable valve2325is brought into contact with the housing231so as to surround the orifice2320and to close the orifice2320. It is to be noted that, a shape of the projection2325cof the movable valve2325is not limited to a circular shape but may close a flow passage of the ink by contacting a wall surface2350so as to surround the orifice2320as a rectangular projection, for example.

The lever2327is connected to the movable valve2325on one end and is capable of contacting the pressure-receiving plate2321on the other end and has a rotating shaft2328contacting the fluid chamber2323between the one end and the other end. The lever2327is rotatable around a predetermined rotation axis of the rotating shaft2328with the rotating shaft2328as a fulcrum. Here, as an example, this rotation axis2328ais an axis extending in a direction parallel to the paper surfaces ofFIGS.11and12and is orthogonal to both a first direction D1and a second direction D2.

FIG.11illustrates a state where the movable valve2325blocks the orifice2320, the ink does not flow into the housing231from the liquid communication chamber2324via the orifice2320, and pressure adjustment of the ink pressures of the fluid chamber2323and the common supply flow-passage211is not performed. Moreover,FIG.12illustrates a state where the ink flows into the housing231from the liquid communication chamber2324via the orifice2320, and the pressure control of the ink pressures of the fluid chamber2323and the common supply flow-passage211is performed. Moreover, inFIG.12, the lever227rotates in accordance with displacement of the pressure-receiving plate2321, and the movable valve2325is separated from the orifice2320with the rotation of the lever2327and opens the orifice2320.

As shown inFIG.11, the lever2327is urged to a direction in which the movable valve2325blocks the orifice2320by a spring2330, which is an urging member. The movable valve2325is provided so as to block the orifice2320from a downstream side of the orifice2320, that is, from an inside of the housing231. Regarding the spring2330, one end is fitted with a cylinder-shaped shaft portion2340formed in the housing231, while the other end is fitted with an annular-shaped groove portion2341formed in the lever2327. As a result, a direction in which the urging force of the spring2330acts becomes the second direction D2intersecting with the gravity direction and orthogonal to the first direction D1. Note that, as long as adhesion of the ink in the orifice2320can be avoided, the first direction D1and the second direction D2may be directions intersecting with an angle other than the orthogonal. Moreover, at the closed position where the movable valve2325closes the orifice2320, centers of the orifice2320, the movable valve2325, the groove portion2341, the spring2330, and the shaft portion2340are disposed so as to be aligned on a straight line (line of action1bin the drawing).

Moreover, in a spring2326, one end is fitted with the cylinder-shaped shaft portion2342formed in the housing231, while the other end is fitted with an outer periphery part of the circular-shaped projection portion2343formed on the pressure-receiving plate2321. Moreover, the centers of the spring2326, the shaft portion2342, the projection portion2343are disposed so as to be aligned on a straight line1c.

When the ink flows out of the negative-pressure control unit230ato the common supply flow-passage211, in accordance with the pressure fluctuation in the fluid chamber2323generated with the decrease in the ink amount in the fluid chamber2323, the pressure-receiving plate2321moves to a paper-surface lower direction. And when the pressure-receiving plate2321is brought into contact with the lever2327, the lever2327is rotated in a direction parallel to the paper surface with this contact point2327aas a power point and a contact point2327bbetween the rotating shaft2328and the fluid chamber2323(housing231) as a fulcrum. Moreover, in accordance with the rotation of the lever2327, the movable valve2325, which has blocked the orifice2320, moves in a direction (paper-surface upper side) where a gap is generated from the orifice2320. Then, the ink stored in the liquid communication chamber2324passes through the gap between the movable valve2325and the orifice2320from the orifice2320and flows into the fluid chamber2323. The pressure of the ink having flown into the fluid chamber2323is transmitted to the pressure-receiving plate2321. When the pressure-receiving plate2321receives the pressure of the ink having flown into the fluid chamber2323and is pushed up above the paper surface, the lever2327is rotated in accordance with the displacement of the pressure-receiving plate2321. Moreover, together with the rotation of the lever2327, the movable valve2325moves toward the orifice2320(paper-surface lower side) and blocks the orifice2320again. The ink in the fluid chamber2323is ejected to the common supply flow-passage211on the downstream side via the outflow port2331.

Here, in the fluid chamber2323, a position where the pressure-receiving plate2321acts on the movable valve2325via the lever2327so as to position the movable valve2325to the closed position corresponds to a first position of the pressure-receiving plate2321. Moreover, a position where the pressure-receiving plate2321acts on the movable valve2325via the lever2327so as to position the movable valve2325to the open position corresponds to a second position of the pressure-receiving plate2321. Moreover, the lever2327is a power transmitting member which transmits power by the pressure-receiving plate2321acting on the movable valve2325so as to move the movable valve2325to the open/closed position.

The spring2326applies an urging force to position the pressure-receiving plate2321to the first position to the pressure-receiving plate2321. And the pressure-receiving plate2321is configured to displace from the first position to the second position in the second direction D2against the urging force by a magnitude of the pressure (negative pressure) in the fluid chamber2323increasing larger than the urging force of the spring2326. As described above, the second position of the pressure-receiving plate2321changes in accordance with the pressure in the fluid chamber2323. Moreover, the orifice2320is formed such that, in a state where the liquid discharge head3is attached to the recording device1000, the direction in which the ink flows into the orifice2320is the direction intersecting with the gravity direction.

The fluid chamber2323is filled with the ink, and a balance of forces applied to respective parts in the housing231is determined by the following relational equation (1). As indicated in the equation (1), the principle of leverage is used for this balance of forces. At this time, as shown inFIGS.11and12, L1is a length obtained by suspending vertically downward from a fulcrum (2327bin the drawing), which is a contact point between the rotating shaft2328and the housing231, to the line of action (1ain the drawing) of the force of the pressure-receiving plate2321pressing the lever2327. Moreover, L2indicates a length obtained by suspending vertically downward from the fulcrum (2327bin the drawing) to the line of action (1bin the drawing) of the force pressing the center of the movable valve2325. At this time, by changing a spring constant of a spring2326, which is the urging member, a pressure by the ink on the upstream side when viewed from the orifice2320, that is, a pressure P1by the ink in the liquid communication chamber2324can be set to a desired pressure.

Here, on a plane on which the lever2327is rotationally moved, shown inFIG.11,FIG.12, each value in the equation (1) is as follows.

L1: Length obtained by suspending vertically downward from the fulcrum to the line of action of force of the pressure-receiving plate pressing the lever

L2: Length obtained by suspending vertically downward from the fulcrum to the line of action of force pressing the center of the movable valve

P1: Pressure by the ink on the orifice upstream side

P2: Pressure by the ink in the fluid chamber

kd: Spring constant of the spring2326in the fluid chamber

xd: Spring displacement of the spring2326in the fluid chamber

kv: Spring constant of the spring2330urging the movable valve

xv: Spring displacement of the spring2330urging the movable valve

Sd: Pressure-receiving area from the ink of the pressure-receiving plate

Sv: Pressure-receiving area from the ink of the movable valve

Here, the pressure-receiving area Sa from the ink of the pressure-receiving plate2321is a pressure-receiving area which the pressure-receiving plate2321receives from the ink in the fluid chamber2323and corresponds to an area of the pressure-receiving plate2321on a top view when the pressure-receiving plate2321is viewed in a displacement direction of the pressure-receiving plate2321inFIG.10A. Moreover, the pressure-receiving area Svfrom the ink of the movable valve2325is a pressure-receiving area which the movable valve2325receives from the ink flowing in from the orifice2320and corresponds to the opening area of the orifice2320inFIG.10B.

Moreover, from the equation (1), P2can be expressed by the following equation (2).

Moreover, assuming that valve resistance against the ink by the movable valve2325is R, and a flow rate of the ink passing through the orifice2320is Q, the following equation (3) is established.

Here, the valve resistance R and the valve opening degree in the movable valve2325are designed to have such a relation shown in a graph inFIG.13, for example. That is, as the valve opening degree of the movable valve2325increases, the valve resistance R lowers. Moreover, by determining the valve position so that the equation (2) and the equation (3) are established at the same time, P2is determined.

A pressure of a pressurization source (not shown) connected to an upstream of the negative-pressure control unit230ais constant. Therefore, when the flow rate Q of the ink flowing into the negative-pressure control unit230aincreases, P1decreases by an increase part of the resistance between the negative-pressure control unit230aand the buffer tank1003caused by the increase in the flow rate Q. As a result, a force P1Svfor opening the movable valve2325is decreased, and as calculated from the equation (2), P2instantaneously increases.

Moreover, from the equation (3), the following equation (4) is derived.

At this time, Q, P2increase, while P1decreases and thus, R decreases. When R decreases, the valve opening degree of the movable valve2325increases. As shown inFIG.11, when the valve opening degree of the movable valve2325increases, the length of the spring2330becomes shorter and thus, x, which is displacement from a free length, increases. Therefore, an action force kx of the spring2330becomes larger, and as calculated from the equation (2), P2instantaneously decreases.

Moreover, when P2instantaneously decreases, P2increases by an action opposite to the aforementioned. As described above, by means of the repetition of the instantaneous increase and decrease of P2, the valve opening degree of the movable valve2325changes in accordance with the flow rate Q of the ink. And since the equation (2) and the equation (3) are established, as the result of substantially constant control of P2, the pressure by the ink in the fluid chamber2323and thus, in the common supply flow-passage211is also controlled substantially constant.

In this Embodiment, as shown inFIG.10B, a valve contact surface2325abrought into contact with the housing231when the movable valve2325blocks the orifice2320and a placement surface2329aof the rotating shaft2328of the bearing portion2329are disposed in parallel to the gravity direction. As a result, a malfunction of the movable valve2325caused by settlement, adhesion of a solid part such as pigment components and the like contained in the ink at the orifice2320or a gap between the movable valve2325and the orifice2320can be suppressed. At this time, the closer to parallel with respect to the gravity direction the valve contact surface2325aor the placement surface2329aof the rotating shaft2328is, the more the settlement, adhesion of the ink can be suppressed. Moreover, by opening a through hole at a part of the placement surface2329a,a configuration to cause the ink settled in the bearing portion2329to flow outside the bearing portion2329may be provided. Moreover, in this Embodiment, if the ink is ink containing titanium oxide, the effect of suppressing settlement, adhesion of the ink by the negative-pressure control unit230can be obtained more greatly. However, the ink used for this Embodiment may be various types of ink, not limited to the ink containing titanium oxide.

InFIG.11, the springs2326,2330, which are urging members, are configured as two coupled springs. However, since there is no problem with the pressure adjustment function of the negative-pressure control unit230, as long as a resultant spring force satisfies a desired negative pressure value, it may be so configured that either one of the two springs2326,2330is used. Moreover, the orifice2320is opened so that, by causing the ink to flow in the direction orthogonal to the gravity direction, the ink is caused to flow into the fluid chamber2323. As shown inFIG.11, the orifice2320is opened in the wall surface2350extending along the first direction D1intersecting with the gravity direction in the wall surfaces forming the fluid chamber2323. Note that, within a range capable of avoiding adhesion of the ink in the orifice2320, the direction in which the ink flows into the orifice2320may have an angle with respect to the direction orthogonal to the gravity direction, that is, the direction intersecting with the gravity direction.

Subsequently, a variation of the negative-pressure control unit according to the aforementioned Embodiment will be explained. Note that, in the following explanation, configurations similar to the configuration in the aforementioned Embodiment are given the same reference numerals, and detailed explanation will be omitted.FIG.14illustrates a section corresponding toFIGS.11and12of a negative-pressure control unit3000according to a first variation. As shown inFIG.14, in a state where the liquid discharge head3is attached to the recording device1000, the negative-pressure control unit3000has such a configuration that a plurality of (two in the case of the drawing) the aforementioned negative-pressure control units230aare coupled in the direction orthogonal to the gravity direction.

The negative-pressure control unit3000shown inFIG.14has two negative-pressure control units240,250. The negative-pressure control units240,250have the same configuration as that of the negative-pressure control unit230ashown inFIGS.11and12. Moreover, the negative-pressure control units240,250are coupled in such a manner that they are vertically inverted with respect to each other on the section shown inFIG.14. In the negative-pressure control unit3000, in each of the negative-pressure control units240,250, it may be so configured that the pressures of ink in different colors are controlled. Alternatively, in the negative-pressure control unit3000, it may be so configured that the negative-pressure control units240,250are controlled to different negative pressures, respectively, for the ink in the same color. Note that, the operation of each of the negative-pressure control units240,250is similar to that of the aforementioned negative-pressure control unit230aand thus, detailed explanation will be omitted here.

Moreover, inFIG.14, the negative-pressure control unit240and the negative-pressure control unit250are coupled in such a manner that the configuration of the section shown inFIG.14is vertically inverted with respect to each other, but the negative-pressure control units240,250may be configured to be vertically matched.

Subsequently, a negative-pressure control unit according to a second variation will be explained.FIG.15illustrates a section corresponding toFIG.10Bof a negative-pressure control unit4000according to the second variation. Note that, inFIG.15, the pressure-receiving plate2321of the negative-pressure control unit4000is also illustrated. Moreover,FIG.15illustrates the negative-pressure control unit4000in a state where the liquid discharge head3is attached to the recording device1000. Each constituent element of the negative-pressure control unit4000is the same as each constituent element of the aforementioned negative-pressure control unit230. In a state where the liquid discharge head3is attached to the recording device1000, the pressure-receiving plate2321of the negative-pressure control unit4000is displaced in a direction orthogonal to the gravity direction. Moreover, in accordance with the displacement of the pressure-receiving plate2321, the lever2327is rotated in a plane orthogonal to the gravity direction. Moreover, the orifice2320is opened so that, by causing the ink to flow in the direction orthogonal to the gravity direction, the ink is caused to flow into the fluid chamber2323.

At this time, as shown inFIG.15, on a plan view by a plane parallel to the gravity direction, that is, when the negative-pressure control unit4000is viewed in the second direction D2, an opening center2320aof the orifice2320is located below in the gravity direction of a center2321aof the pressure-receiving plate2321. By configuring the orifice2320and the pressure-receiving plate2321as above, even if air bubbles are mixed in the ink, the air bubbles hardly remain in the orifice2320, and the malfunction of the movable valve2325caused by the adhesion of the ink at a gas-liquid interface is reduced. Note that, a separation distance D3between the opening center2320aof the orifice2320and the center2321aof the pressure-receiving plate2321can be changed as appropriate depending on a material of the ink in use, contents of the pressure control of the ink by the negative-pressure control unit4000or the like.

Subsequently, a negative-pressure control unit according to a third variation will be explained. In the aforementioned Embodiments and variations, it may be so configured that the liquid discharge head3has a plurality of the recording element boards, and the negative-pressure control unit executes the pressure control of the ink as above for these recording element boards. In this case, the common supply flow-passage211connected to the negative-pressure control unit230is connected to the plurality of recording element boards having a nozzle row13aconstituted by the discharge port13. By providing the plurality of recording element boards in the liquid discharge head3, the number of discharge ports (nozzle rows) discharging the ink is also increased and thus, the fluctuation in the ink amount supplied to the discharge port also becomes larger by the density of the print to the recordings of the like. In the pressure control of the ink executed in accordance with the fluctuation in the ink supply amount which becomes larger by the increase in the number of recording element boards of the liquid discharge head3, by using the aforementioned pressure control unit, the inflow control of the ink by the movable valve according to the fluctuation of the ink in the fluid chamber can be executed appropriately.

According to the art of this disclosure, adhesion of the liquid at the inflow port of the liquid or malfunction of the valve body of the pressure control unit is reduced, whereby the image quality of the recordings to which the liquid is discharged can be maintained.

This application claims the benefit of Japanese Patent Application No. 2023-114629, filed on July 12, 2023. which is hereby incorporated by reference herein in its entirety.