Liquid discharge head and liquid discharge apparatus

A liquid discharge head includes a recording element board having a first face on which multiple recording elements are provided, and discharge orifices for the recording elements, where pressure chambers are formed for each recording element and liquid is discharged from discharge orifices. A liquid supply channel and a liquid recovery channel are provided in common to the plurality of recording elements, in a second face opposite to the recording element board from the first face. The pressure chambers are each made to communicate with the liquid supply channel and the liquid recovery channel by the supply ports and recovery ports respectively, and a flow from the liquid supply channel through the pressure chambers to the liquid recovery channel is generated. A composited flow resistance of the liquid recovery channel and recovery ports is greater than a composited flow resistance of the liquid supply channel and supply ports.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a liquid discharge head and a liquid discharge apparatus that uses the liquid discharge head.

Description of the Related Art

A liquid discharge apparatus that records by discharging liquid onto a recording medium uses a liquid discharge head having a pressure chamber communicating with a discharge orifice and a recording element that provides energy for discharging to liquid within the pressure chamber. In inkjet recording apparatus, which is representative of liquid discharge apparatuses, discharges recording liquid from discharge orifices. The recording liquid is a color material such as dye or pigment contained in a medium. In a case where the liquid to be discharged is a recording liquid in such a liquid discharge apparatus for example, volatile components in the recording liquid near discharge orifices may evaporate, and the concentration of color material increase accordingly, leading to irregular color in the recorded image. There also are cases where the evaporation of the volatile components raises the viscosity of the liquid near the discharge orifices, which reduces the discharge speed of the liquid, and consequently the liquid cannot accurately reach the intended position on the recording medium. Evaporation of volatile components can also cause clogging of the discharge orifices and pressure chambers or the like.

One known measure to handle such an issue is to circulate liquid through the liquid discharge head, and particularly through the pressure chambers. For example, PCT Japanese Translation Patent Publication No. 2003-505281 discloses providing a discharge orifice and recording element for each pressure chamber, providing channels that branch from a common supply channel, pass through the pressure chambers, and merge at a common recovery channel, and to cause a great amount of recording liquid to flow over this channel.

Although the individual pressure chambers in the liquid discharge head3and the channels connecting thereto are relatively narrow, the configuration described in PCT Japanese Translation Patent Publication No. 2003-505281 causes a greater amount of liquid to flow through narrow channels than that discharged from the discharge orifices, resulting in increased pressure distribution (pressure drip) within the channels. If the variation in pressure distribution or pressure is great, variation will also occur in discharge properties from the discharge orifices, and quality of the recording formed on the recording medium will deteriorate. It is conceivable to flow the liquid to the pressure chambers at a small flow rate to avoid such deterioration in quality. However, if the amount of liquid circulating through the pressure chambers is reduced, there are cases where high-temperature liquid that has passed through the pressure chambers and flowed downstream will back up toward the pressure chambers if the amount of liquid being discharged from the discharge orifices by driving of the recording elements suddenly increases. This heat of the backflow liquid combined with the heat from driving the recording elements will make the temperature of the liquid near the discharge orifices even hotter. On the other hand, if a state where liquid is discharged from the discharge orifices continues, the liquid which has become hot as described above is gradually discharged, and is replaced by supply of cool liquid into the pressure chambers. As a result, the temperature of the liquid near the discharge orifices gradually returns to normal temperature. Thus, in an arrangement where the flow rate of the liquid circulating through the pressure chambers is small, the temperature of the liquid near the discharge orifices temporarily rises as the recording operations start, and thereafter return to a normal state. This temperature change may change the discharge speed or discharge amount of the liquid, and affect recording quality.

SUMMARY OF THE INVENTION

It has been found desirable to provide a liquid discharge head and a liquid discharge apparatus using the liquid discharge head, whereby liquid circulation to pressure chambers can be realized without causing variation in discharge properties, and suppress excessive rise in temperature due to backflow of hot liquid to the pressure chambers.

A liquid discharge head includes a recording element board having a first face on which a plurality of recording elements that generate energy to discharge liquid is provided, partitions disposed between adjacent recording elements, and discharge orifices disposed for each of the recording elements, facing the recording elements, where pressure chambers are formed by the partitions for each recording element and liquid within the pressure chambers is discharged from the discharge orifices by the recording elements. The liquid discharge head includes a liquid supply channel communicating with the plurality of pressure chambers and formed on a second face on the opposite face of the recording element board from the first face, a liquid recovery channel communicating with the plurality of pressure chambers and formed on the second face, supply ports communicating between the pressure chambers and the liquid supply channel, and recovery ports communicating between the pressure chambers and the liquid recovery channel. A flow is formed from the liquid supply channel through the supply ports, pressure chambers, recovery ports, and liquid recovery channel, in a standby state where liquid is not being discharged. A composited flow resistance of the liquid recovery channel and recovery ports is greater than a composited flow resistance of the liquid supply channel and supply ports.

The liquid discharge apparatus according to the present invention includes the liquid discharge head according to the present invention, a storage unit storing liquid, a first circulation system that circulates liquid from the storage unit, and a second circulation system that circulates liquid from the storage unit using a lower pressure than the first circulation system. The liquid supply channel communicates with the first circulation system, and the liquid recovery channel communicates with the second circulation system.

DESCRIPTION OF THE EMBODIMENTS

Configuration examples, embodiments, and examples to which the present invention is applicable will be described below with reference to the drawings. It should be understood that the description that follows does not restrict the scope of the present invention. As one example, an example of a so-called thermal system liquid discharge head, that discharges liquid from a discharge orifice by generating bubbles by heat in liquid in a pressure chamber, using a heat-generating element as a recording element that generates energy to discharge liquid, will be described below. However, liquid discharge heads to which the present invention can be applied is not restricted to thermal systems, and the present invention can be applied to liquid discharge heads employing the piezoelectric system using piezoelectric elements, and various other types of liquid discharge systems. The liquid discharge head according to the present invention that discharges liquid such as ink, and the liquid discharge apparatus having the liquid discharge head, are applicable to apparatuses such as printers, photocopiers, facsimile devices having communication systems, word processors having printer units, and so forth, and further to industrial recording apparatuses combined in a complex manner with various types of processing devices. For example, the present invention can be used in fabricating biochips, printing electronic circuits, fabricating semiconductor substrates, and other such usages.

Although the description below relates to a liquid discharge head3used in a liquid discharge apparatus where a liquid such as recording liquid or the like is circulated between a tank and liquid discharge head, The liquid discharge apparatus using the liquid discharge head according to the present invention is not restricted to this. The present invention may be applied to an arrangement of a liquid discharge apparatus where, instead of circulating liquid, two tanks are provided, one at the upstream side of the liquid discharge head and the other on the downstream side, and liquid within the pressure chamber of the liquid discharge head is caused to flow by running liquid from one tank to the other via the liquid discharge head.

Also, the description below relates to a so-called line head that has a length corresponding to the width of the recording medium, but the present invention can also be applied to a so-called serial liquid discharge head that completes recording on a recording medium by scanning in a main scan direction and sub-scan direction. An example of a serial liquid discharge head is one that has one recording element board each for recording black recording liquid and for recording color recording liquid, but this is not restrictive. An example of a serial liquid discharge head may be an arrangement where short line heads that are shorter than the width of the recording medium are formed, with multiple recording element boards arrayed so that orifices overlap in the discharge orifice row direction, and these being scanned over the recording medium.

Description of Liquid Discharge Head Apparatus According to First Configuration Example

First, description will be made regarding an inkjet recording apparatus1000(hereinafter also referred to simply as “recording apparatus”) that performs recording by discharging a recording liquid as liquid from discharge orifices onto a recording medium, as an example of a liquid discharge apparatus according to the present invention.FIG. 1illustrates a schematic configuration of the recording apparatus1000as a liquid discharge apparatus according to a first configuration example. The recording apparatus1000has a conveyance unit1that conveys a recording medium2, and a line type liquid discharge head3disposed generally orthogonal to the conveyance direction of the recording medium2, and is a line type recording apparatus that performs single-pass continuous recording while continuously or intermittently conveying multiple recording mediums2. The recording medium2is not restricted to cut sheets, and may be continuous roll sheets. The liquid discharge head3is capable of full-color printing by cyan (C), magenta (M), yellow (Y), and black (K) color recording liquid (these colors are also referred together as CMYK). The liquid discharge head3is connected by fluid connection to a liquid supply arrangement that is a supply path for supplying liquid to the liquid discharge head3, a main tank, and a buffer tank (seeFIG. 2), as described later. The liquid discharge head3can be roughly divided into a liquid supply unit220, a negative pressure control unit230, and a liquid discharge unit300, as illustrated inFIG. 2which will be described later. Multiple recording element boards10, and a common supply channel211and common recovery channel212are provided to the liquid discharge unit300, with multiple recording elements provided to each of the recording element boards10. In the liquid discharge unit300, the recording liquid is supplied from the common supply channel211to the recording element boards10as indicated by arrows inFIG. 2, and this recording liquid is recovered by the common recovery channel212. The liquid discharge head3is also electrically connected to an electric control unit that transmits electric power and discharge control signals to the liquid discharge head3. Liquid paths and electric signal paths within the discharge head3will be described in detail later.

Description of First Circulation Arrangement

FIG. 2illustrates a first circulation arrangement that is a form of a circulation path configuration applied to the liquid discharge apparatus according to the present invention. In the first circulation arrangement, the liquid discharge head3is connected to a high-pressure side first circulation pump1001, a low-pressure side first circulation pump1002, and a buffer tank1003and the like by fluid connection. AlthoughFIG. 2only illustrates the paths over which one color recording liquid flows, out of the recording liquids of each of the CMYK colors, for the sake of brevity of description, in reality four colors worth of circulation paths are provided to the liquid discharge head3and the recording apparatus main unit. The buffer tank1003, serving as a sub-tank that is connected to a main tank1006, has an atmosphere communication opening (omitted from illustration) whereby the inside and the outside of the tank communicate, and bubbles within the recording liquid can be discharged externally. The buffer tank1003is also connected to a replenishing pump1005. When liquid is consumed at the liquid discharge head3, by discharging (ejecting) recording liquid from the discharge orifices of the liquid discharge head3, to perform recording, suction recovery, or the like, for example, the replenishing pump1005acts to transfer recording liquid of an amount the same as that has been consumed from the main tank1006to the buffer tank1003.

The two first circulation pumps1001and1002serving as a liquid transfer unit act to extract liquid from a fluid connector111of the liquid discharge head3and flow the liquid to the buffer tank1003. The first circulation pumps1001and1002preferably are positive-displacement pumps that have quantitative fluid sending capabilities. Specific examples may include tube pumps, gear pumps, diaphragm pumps, syringe pumps, and so forth. An arrangement may also be used where a constant flow is ensured by disposing a common-use constant-flow valve and relief valve at the outlet of the pump, for example. When the liquid discharge unit300is being driven, the high-pressure side first circulation pump1001and low-pressure side first circulation pump1002each cause a constant amount of recording liquid to flow through a common supply channel211and a common recovery channel212. The amount of flow is preferably set to a level where temperature difference among recording element boards10of the liquid discharge head3does not influence recording image quality on the recording medium2, or higher. On the other hand, if the flow rate is set excessively high, the effects of pressure drop in the channels within a liquid discharge unit300causes excessively large difference in negative pressure among the recording element boards10, resulting in unevenness in density in the recorded image. Accordingly, the flow rate is preferably set taking into consideration temperature difference and negative pressure difference among the recording element boards10. Of the paths that the recording liquid circulate over, the path including the high-pressure side first circulation pump1001makes up a first circulation system in the liquid discharge apparatus, and the path including the low-pressure side first circulation pump1002makes up a second circulation system in the liquid discharge apparatus.

A second circulation pump1004is provided on the path supplying recording liquid from the buffer tank1003toward the liquid discharge head3. The negative pressure control unit230is disposed on the path between the second circulation pump1004and the liquid discharge unit300. The negative pressure control unit230functions such that the pressure downstream from the negative pressure control unit230(i.e., at the liquid discharge unit300side) can be maintained at a present constant pressure even in cases where the flow rate of the circulation system fluctuates due to difference in duty when recording. The negative pressure control unit230has two pressure adjustment mechanisms each set to different control pressures. Any mechanism may be used as these two pressure adjustment mechanisms, as long as pressure downstream from itself can be controlled to fluctuation within a constant range or smaller that is centered on a desired set pressure. As one example, a mechanism equivalent to a so-called “pressure-reducing regulator” can be employed. In a case of using a pressure-reducing regulator as a pressure adjustment mechanism, the upstream side of the negative pressure control unit230is preferably pressurized by the second circulation pump1004via a liquid supply unit220, as illustrated inFIG. 2. This enables the effects of water head pressure as to the liquid discharge head3of the buffer tank1003to be suppressed, giving broader freedom in the layout of the buffer tank1003in the recording apparatus1000. It is sufficient that the second circulation pump1004have a certain lift pressure or greater, within the range of the circulatory flow rate of recording liquid used when driving the liquid discharge head3, and turbo pumps, positive-displacement pumps, and the like can be used. Specifically, diaphragm pumps or the like can be used. Alternatively, a water head tank disposed with a certain water head difference as to the negative pressure control unit230, for example, may be used instead of the second circulation pump1004.

Of the two pressure adjustment mechanisms in the negative pressure control unit230, the relatively high-pressure setting side pressure adjustment mechanism (denoted by H inFIG. 2) is connected to the common supply channel211within the liquid discharge unit300via the liquid supply unit220. In the same way, the relatively low-pressure setting side pressure adjustment mechanism (denoted by L inFIG. 2) is connected to the common recovery channel212within the liquid discharge unit300via the liquid supply unit220. Provided to the liquid discharge unit300, besides the common supply channel211and common recovery channel212, are individual supply channels213and individual recovery channels214each communicating with the recording element boards10. The individual supply channels213and individual recovery channels214provided to each recording element board are collectively referred to as “individual channels”. The individual channels are provided branching from the common supply channel211and merging at the common recovery channel212, and communicating therewith. Accordingly, flows occur where part of the liquid such as recording liquid flows from the common supply channel211through inside of the recording element boards10and to the common recovery channel212(indicated by the outline arrows inFIG. 2). The reason is that the high-pressure side pressure adjustment mechanism H is connected to the common supply channel211, and the low-pressure side pressure adjustment mechanism L to the common recovery channel212, so a pressure difference is generated between the two common channels.

Thus, flows occur within the liquid discharge unit300where a part of the liquid passes through the recording element boards10while liquid flows through each of the common supply channel211and common recovery channel212. Accordingly, heat generated at the recording element boards10can be externally discharged from the recording element boards10by the flows through the common supply channel211and common recovery channel212. This configuration also enables recording liquid flows to be generated at discharge orifices and pressure chambers not being used for recording while recording is being performed by the liquid discharge head3, so higher viscosity of the recording liquid due to evaporation of the medium component of the recording liquid at such portions can be suppressed. Also, thickened recording liquid and foreign substance in the recording liquid can be expelled to the common recovery channel212. Accordingly, using the above-described liquid discharge head3enables recording to be performed at high speed with high image quality.

Description of Second Circulation Arrangement

FIG. 3is a schematic diagram illustrating, of circulation arrangement configurations applied to the liquid discharge apparatus according to the present invention, a second circulation arrangement that is a different circulation arrangement from the above-described first circulation arrangement. The primary points of difference of the second circulation arrangement as to the above-described first circulation arrangement are that both of the two pressure adjustment mechanisms making up the negative pressure control unit230are a mechanism to control pressure at the upstream side from the negative pressure control unit230to fluctuation within a constant range that is centered on a desired set pressure. This sort of pressure adjustment mechanism can be configured as a mechanism part having operations the same as a so-called “backpressure regulator”. The second circulation pump1004acts as a negative pressure source to depressurize the downstream side from the negative pressure control unit230, and the high-pressure side first circulation pump1001and low-pressure side first circulation pump1002are disposed on the upstream side of the liquid discharge head3. Accordingly, the negative pressure control unit230is disposed on the downstream side of the liquid discharge head3.

The negative pressure control unit230according to the second circulation arrangement acts to maintain pressure fluctuation on the upstream side of itself within a constant range centered on a preset pressure, even in cases where the flow rate fluctuates due to difference in recording duty when recording with the liquid discharge head3. The upstream side of the negative pressure control unit230here is the liquid discharge unit300side. The downstream side of the negative pressure control unit230is preferably pressurized by the second circulation pump1004via the liquid supply unit220, as illustrated inFIG. 3. This enables the effects of water head pressure of the buffer tank1003as to the liquid discharge head3to be suppressed, giving a broader range of selection for the layout of the buffer tank1003in the recording apparatus1000. Alternatively, a water head tank disposed with a certain water head difference as to the negative pressure control unit230, for example, may be used instead of the second circulation pump1004.

The negative pressure control unit230illustrated inFIG. 3has two pressure adjustment mechanisms, with different control pressure from each other having been set, in the same way as the first circulation arrangement. The high-pressure setting side (denoted by H inFIG. 3) and the low-pressure setting side (denoted by L inFIG. 3) pressure adjustment mechanisms are respectively connected to the common supply channel211and the common recovery channel212within the liquid discharge unit300via the liquid supply unit220. The pressure of the common supply channel211is made to be relatively higher than the pressure of the common recovery channel212by the two pressure adjustment mechanisms, whereby flows occur where recording liquid flows from the common supply channel211through the individual channels and internal channels in the recording element board10to the common recovery channel212. The flows of recording liquid inFIG. 3are indicated by outline arrows. The second circulation arrangement thus yields a recording liquid flow state the same as that of the first circulation arrangement within the liquid discharge unit300, but has two advantages that are different from the case of the first circulation arrangement.

One advantage is that, with the second circulation arrangement, the negative pressure control unit230is disposed on the downstream side of the liquid discharge head3, so there is little danger that dust and foreign substances generated at the negative pressure control unit230will flow into the liquid discharge head3.

A second advantage is that the maximum value of the necessary flow rate supplied from the buffer tank1003to the liquid discharge head3can be smaller in the second circulation path as compared to the case of the first circulation arrangement. The reason is as follows. The total flow rate within the common supply channel211and common recovery channel212when circulating during recording standby will be represented by A. The value of A is defined as the smallest flow rate necessary to maintain the temperature difference in the liquid discharge unit300within a desired range in a case where temperature adjustment of the liquid discharge head3is performed during recording standby. Also, the discharge flow rate in a case of discharging recording liquid from all discharge orifices of the liquid discharge unit300(full discharge) is defined as F. Accordingly, in the case of the first circulation arrangement (FIG. 2), the set flow rate of the first circulation pump (high-pressure side)1001and the first circulation pump (low-pressure side)1002is A, so the maximum value of the liquid supply amount to the liquid discharge head3necessary for full discharge is A+F. On the other hand, in the case of the second circulation arrangement inFIG. 3, the liquid supply amount to the liquid discharge head3necessary at the time of recording standby is flow rate A. This means that the supply amount to the liquid discharge head3necessary for full discharge is flow rate F. Accordingly, in the case of the second circulation arrangement, the total value of the set flow rate of the high-pressure side and low-pressure side first circulation pumps1001and1002, i.e., the maximum value of the necessary supply amount, is the larger value of A and F. Thus, the maximum value of the necessary supply amount in the second circulation arrangement (A or F) is always smaller than the maximum value of the necessary supply amount in the first circulation arrangement (A+F), as long as the liquid discharge unit300of the same configuration is used. Consequently, the degree of freedom regarding circulatory pumps that can be applied is higher in the case of the second circulation arrangement, and low-cost circulatory pumps having simple structure can be used, the load on a cooler (omitted from illustration) disposed on the main unit side path can be reduced, thereby reducing costs of the recording apparatus main unit. This advantage is more pronounced with line heads where the values of A or F are relatively great, and is more useful the longer the length of the line head is in the longitudinal direction.

However, on the other hand, there are points where the first circulation arrangement is more advantageous than the second circulation arrangement. With the second circulation arrangement, the flow rate flowing through the liquid discharge unit300at the time of recording standby is maximum, so the lower the recording duty of the image is, the greater a negative pressure is applied to the nozzles. Accordingly, particularly in a case where the channel widths of the common supply channel211and common recovery channel212is reduced to reduce the head width, high negative pressure may be applied to the nozzles in low-duty images where unevenness is easy to see, which may increase the influence of satellite droplets. Note that the channel width of the common supply channel211and common recovery channel212is the length in the direction orthogonal to the direction of low of liquid, and the head width is the length in the transverse direction of the liquid discharge head3. On the other hand, high pressure is applied to the nozzles when forming high-duty images in the case of the first circulation arrangement, so any generated satellite droplets are less conspicuous in the recorded image, which is advantageous in that influence on the image quality is small. Which of these two circulation arrangements is more preferable can be selected in light of the specifications of the liquid discharge head3and recording apparatus main unit (discharge flow rate F, smallest circulatory flow rate A, and channel resistance within the liquid discharge head3).

Description of Configuration of Liquid Discharge Head

The configuration of the liquid discharge head3will be described next with reference toFIGS. 4A and 4B.FIG. 4Ais a perspective view of the liquid discharge head3as viewed from the side of the face where the discharge orifices13are formed, andFIG. 4Bis a perspective view from the opposite side fromFIG. 4A. The liquid discharge head3is a line-type liquid discharge head where fifteen recording element boards10capable of discharging recording liquid of the four colors of cyan (C), magenta (M), yellow (Y), and black (K) are arrayed on a straight line (inline layout). The liquid discharge head3includes 15 recording element boards10, flexible printed circuit boards40, and an electric wiring board90, as illustrated inFIG. 4A. The electric wiring board90is provided with input terminals91and power supply terminals92, the input terminals91and power supply terminals92being electrically connected to the recording element boards10via the electric wiring board90and flexible printed circuit boards40. The input terminals91and power supply terminals92are electrically connected to a control circuit of the recording apparatus1000, and respectively supply discharge drive signals and electric power necessary for discharging to the recording element boards10. Consolidating the wiring by electric circuits in the electric wiring board90enables the number of the input terminals91and power supply terminals92to be reduced as compared with the number of recording element boards10. This enables reducing the number of electric connection portions that need to be removed when assembling the liquid discharge head3to the recording apparatus1000or when exchanging the liquid discharge head3. Liquid connection portions111provided to both ends of the liquid discharge head3are connected with the liquid supply system of the recording apparatus1000, as illustrated inFIG. 4B. Thus, recording liquid of the four colors of CMYK is supplied form the supply system of the recording apparatus1000to the liquid discharge head3, and recording liquid that has passed through the liquid discharge head3is recovered to the supply system of the recording apparatus1000such as illustrated inFIG. 2 or 3. In this way, recording liquid of each color can circulate over the path of the recording apparatus1000and the path of the liquid discharge head3.

FIG. 5illustrates a disassembled perspective view of parts and units making up the liquid discharge head3, according to the functions thereof. The liquid discharge head3has a case80, and the liquid discharge unit300, liquid supply units220, and electric wiring board90are attached to this case80. The liquid connection portions111(seeFIGS. 2 through 4B) are provided to the liquid supply unit220, and filters221(seeFIGS. 2 and 3) for each color, that communicate with each opening of the liquid connection portions111to remove foreign substances in the supplied recording liquid, are provided inside the liquid supply units220. Two liquid supply units220and two negative pressure control units230are provided to one liquid discharge head3in the arrangement illustrated inFIG. 5. Two liquid supply units220are each provided with filters221for two colors, in the liquid discharge head3illustrated inFIGS. 2 and 3. The recording liquids that have passed through the filters221are supplied to the respective negative pressure control units230provided on the corresponding liquid supply units220. Each negative pressure control unit230has a pressure adjustment mechanism, and markedly attenuates change in pressure drop in the supply system of the recording apparatus1000(supply system on the upstream side of the liquid discharge head3) occurring due to fluctuation in the flow rate of liquid, by the operations of valve and spring members and the like provided in the pressure adjustment mechanism. Accordingly, the negative pressure control units230are capable of stabilizing change of negative pressure at the downstream side from themselves (liquid discharge unit300side) within a certain range. Each negative pressure control unit230for each color has two pressure adjustment valves built in, as described above, these pressure adjustment valves each being set to different control pressures. The high-pressure side pressure adjustment mechanism communicates with the common supply channel211within the liquid discharge unit300, and the low-pressure side pressure adjustment mechanism communicates with the common recovery channel212.

The case80is configured including a liquid discharge unit support member81and electric wiring board support member82, and supports the liquid discharge unit300and electric wiring board90as well as securing rigidity of the liquid discharge head3. The electric wiring board support member82is for supporting the electric wiring board90, and is fixed by being screwed to the liquid discharge unit support member81. The liquid discharge unit support member81serves to correct warping and deformation of the liquid discharge unit300, and thus serves to secure relative positional accuracy of the multiple recording element boards10, thereby suppressing unevenness in the recorded article. Accordingly, the liquid discharge unit support member81preferably has sufficient rigidity. Examples of suitable materials include metal materials such as stainless steel and aluminum, ceramics such as alumina, and so forth. The liquid discharge unit support member81has openings83and84, at both ends thereof in the longitudinal direction, into which joint rubber members100are inserted. Liquid such as recording liquid supplied from a liquid supply unit220passes through a joint rubber member100and is guided to a third channel member70which is a part making up the liquid discharge unit300described later.

The liquid discharge unit300is made up of multiple discharge modules200and a channel-forming member210, and a cover member130is attached to the face of the liquid discharge unit300that faces the recording medium. The cover member130is a member having a frame-shaped surface where a long opening131is provided as illustrated inFIG. 5, with the recording element boards10included in the discharge module200and a sealing member110(FIG. 9A) being exposed from the opening131. The frame portion on the perimeter of the opening131functions as a contact surface for a cap member that caps off the face of the liquid discharge head3where the discharge orifices are formed, when in recording standby. Accordingly, a closed space is preferably formed when capping, by coating the perimeter of the opening131with an adhesive agent, sealant, filling member, or the like, to fill in roughness and gaps on the discharge orifice face of the liquid discharge unit300.

Next, description will be made regarding the configuration of the channel-forming member210included in the liquid discharge unit300. The channel-forming member210distributes the liquid such as recording liquid supplied from the liquid supply unit220to each of the discharge modules200, and returns liquid recirculating from the discharge modules200to the liquid supply unit220. The channel-forming member210is an article formed by laminating a first channel member50, a second channel member60, and the third channel member70, in that order, as illustrated inFIG. 5, and is fixed to the liquid discharge unit support member81by screws. This suppresses warping and deformation of the channel-forming member210.

FIGS. 6A through 6Fare diagrams illustrating the front and rear sides of the channel members making up the first through third channel members50,60, and70.FIG. 6Aillustrates the side of the first channel member50on which the discharge modules200are mounted, andFIG. 6Fillustrates the face of the third channel member70that comes in contact with the liquid discharge unit support member81.FIG. 6Billustrates the contact face of the first channel member50as to the second channel member60, whileFIG. 6Cillustrates the contact face of the second channel member60as to the first channel member50. In the same way,FIG. 6Dillustrates the contact face of the second channel member60as to the third channel member70, andFIG. 6Eillustrates the contact face of the third channel member70as to the second channel member60. By adjoining the faces of the second channel member60and third channel member70illustrated inFIG. 6DandFIG. 6Ewith each other form eight common channels extending in the longitudinal direction of the channel members, by common channel grooves62and71formed thereon. This forms a set of common supply channels211and common recovery channels212for each of the CMYK colors within the channel-forming member210(FIG. 7). Communication ports72of the third channel member70communicate with the holes in the joint rubber members100, so as to communicate with the liquid supply unit220by fluid connection. Multiple communication ports61are formed on the bottom face of the common channel grooves62of the second channel member60, communicating with one end of individual channel grooves52of the first channel member50. Communication ports51are formed at the other end of the individual channel grooves52of the first channel member50so as to communicate with the multiple discharge modules200by fluid connection via the communication ports51. These individual channel grooves52allow the channels to be consolidated at the middle of the channel member in the transverse direction of the first channel member50. In the following description, When common supply channels211of individual colors of recording liquid are to be indicated, reference numerals211athrough211dwill be used instead of reference numeral211, and when common recovery channels212of individual colors of recording liquid are to be indicated, reference numerals212athrough212dwill be used instead of reference numeral212. In the same way, when individual supply channels213of individual colors of recording liquid are to be indicated, reference numerals213athrough213dwill be used instead of reference numeral213, and when individual recovery channels214of individual colors of recording liquid are to be indicated, reference numerals214athrough214dwill be used instead of reference numeral214.

The first through third channel members50,60, and70, making up the channel member210, preferably are corrosion-resistant as to the recording liquid, and formed from a material having a low linear expansion coefficient. Examples suitable materials include alumina, liquid crystal polymer (LCP), and composite materials (resin materials) where inorganic filler such as fine particles of silica or fiber or the like has been added to a base material such as polyphenyl sulfide (PPS) or polysulfone (PSF). The channel-forming member210may be formed by laminating the three channel members50,60, and70and adhering to each other using an adhesive agent, or in a case of selecting a composite resin material for the material, the three channel members may be joined by fusing.

Next, the connection relationship of the channels within the channel-forming member210will be described with reference toFIG. 7.FIG. 7is a partially enlarged transparent view of channels within the channel-forming member210formed by joining the first through third channel members50,60, and70, as viewed from the side of the first channel member50on which the discharge modules200are mounted. The regions inFIG. 7surrounded by the single-dot dashed line corresponds to the regions where the recording element boards10are disposed. The channel-forming member210has, for each color, common supply channels211athrough211dand common recovery channels212athrough212dextending in the longitudinal direction of the liquid discharge head3. Multiple individual supply channels213athrough213dof each color formed of the individual channel grooves52are connected to the common supply channels211athrough211dvia the communication ports61. Multiple individual recovery channels214athrough214dof each color formed of the individual channel grooves52are connected to the common recovery channels212athrough212dvia the communication ports61. This channel configuration enables recording liquid to be consolidated at the recording element boards10situated at the middle of the channel-forming member210, from the common supply channels211via the individual supply channels213. Recording liquid can also be recovered from the recording element boards10to the common recovery channels212via the individual recovery channels214.

FIG. 8illustrates the cross-sectional configuration of the channel-forming member210and discharge module200along line VIII-VIII inFIG. 7.FIG. 8illustrates that individual recovery channels214aand214ccommunicate with the discharge module200via the communication ports51. AlthoughFIG. 8only illustrates the individual recovery channels214aand214c, the individual supply channels213and the discharge module200communicate at a different cross-section, as illustrated inFIG. 7. Channels for supplying recording liquid from the first channel member50to recording elements15(FIG. 10B), provided to the recording element board10, are formed in a support member30included in the discharge module200and the recording element boards10. Further, channels for recovering (recirculating) part or all of the liquid supplied to the recording elements15to the first channel member50are formed in the support member30and recording element boards10. The common supply channels211of each color are connected to the high-pressure side pressure adjustment mechanism of the negative pressure control unit230of the corresponding color via its liquid supply unit220. In the same way, the common recovery channels212are connected to the low-pressure side pressure adjustment mechanism of the negative pressure control units230of the corresponding color, via the liquid supply units220. Pressure difference is generated between the common supply channels211and common recovery channels212by these pressure adjustment mechanisms in the negative pressure control units230. Accordingly, a flow occurs for each color in the liquid discharge head3where the channels are connected as illustrated inFIGS. 7 and 8, in the order of common supply channel211→individual supply channels213→recording element board10→individual recovery channels214→common recovery channel212.

Description of Discharge Module

Next, the discharge module200will be described.FIG. 9Aillustrates a perspective view of one discharge module200, andFIG. 9Billustrates a disassembled view thereof. The method of manufacturing the discharge module200is as follows. First, a recording element board10and flexible printed circuit board40are adhered to a support member30in which liquid communication ports31have been formed beforehand. Subsequently, terminals16on the recording element board10are electrically connected to terminals41on the flexible printed circuit board40by wire bonding, following which the wire-bonded portion (electric connection portion) is covered by a sealant110to seal off. Terminals42at the other end of the flexible printed circuit board40from the recording element board10are electrically connected to connection terminals93(FIG. 5) of the electric wiring board90. The support member30is a support member that supports the recording element board10, and also is a channel member communicating between the recording element board10and the channel-forming member210by fluid connection, and accordingly should have a high degree of flatness, and also should be able to be joined to the recording element board10with a high degree of reliability. Examples of suitable materials of the support member30include alumina and resin materials.

Description of Structure of Recording Element Board

The configuration of the recording element board10will be described next.FIG. 10Ais a plan view of the side of the recording element board10on which discharge orifices13have been formed,FIG. 10Bis an enlarged view of the portion indicated by XB inFIG. 10A, andFIG. 10Cis a plan view of the rear face of the recording element board10from that inFIG. 10A. The recording element board10has a discharge orifice forming member12, where multiple discharge orifices13for rows, as illustrated inFIG. 10A. Four discharge orifice rows corresponding to the four colors CMYK that are the colors of the recording liquid are formed on the discharge orifice forming member12. Note that hereinafter, the direction in which the discharge orifice rows, where multiple discharge orifices13are arrayed, extend, will be referred to as “discharge orifice row direction”. The recording elements15that are heat-generating elements to cause the liquid to bubble by thermal energy are disposed at positions corresponding to the discharge orifices13, as illustrated inFIG. 10B. Pressure chambers23that contain the recording elements15are sectioned off by partitions22. The recording elements15are electrically connected to the terminals16inFIG. 10Aby electric wiring (omitted from illustration) provided to the recording element board10. The recording elements15generate heat to cause the liquid to boil, based on pulse signals input from a control circuit of the recording apparatus1000, via the electric wiring board90(FIG. 5) and flexible printed circuit board40(FIG. 9B), causing the liquid in the pressure chambers23to boil. The force of bubbling due to this boiling discharges liquid from the discharge orifices13. A liquid supply channel18extends along one side of each discharge orifice row, and a liquid recovery channel19along the other, as illustrated inFIG. 10B. The liquid supply channels18and liquid recovery channels19are channels extending in the direction of the discharge orifice rows provided on the recording element board10, and communicate with the discharge orifices13via supply ports17aand recovery ports17b, respectively.

A sheet-shaped cover20is laminated on the rear face from the face of the recording element board10on which the discharge orifices13are formed, the cover20having multiple openings21communicating with the liquid supply channel18and liquid recovery channel19which will be described later, as illustrated inFIGS. 10C and 11. In the example described here, three openings21are provided in the cover20for each liquid supply channel18, and two openings21are provided for each liquid recovery channel19. The openings21of the cover20communicate with the multiple communication ports51illustrated inFIG. 6A, as illustrated inFIG. 10B. The cover20functions as a lid making up part of the liquid supply channel18and liquid recovery channel19, formed on the substrate11of the recording element board10, as illustrated inFIG. 11. The cover20preferably is sufficiently corrosion-resistant as to liquid such as the recording liquid, and has to have a high degree of precision regarding the opening shapes of the openings21and the positions thereof from the perspective of color mixture prevention. Accordingly, a photosensitive resin material or silicon plate is preferably used as the material for the cover20, with the openings21being formed by photolithography process. The cover20thus is for converting the pitch of channels by the openings21, and the cover20preferably is thin, taking into consideration pressure drop, and preferably is formed of a photosensitive resin film.

Next, the flow of liquid within the recording element board10will be described.FIG. 11is a perspective view, illustrating a cross-section of the recording element board10and cover20taken along plane XI-XI inFIG. 10A. The recording element board10is formed by laminating the substrate11formed of silicon (Si) and the discharge orifice forming member12formed of a photosensitive resin, with the cover20joined on the rear face of the substrate11. The recording elements15are formed on the other face side of the substrate11(seeFIG. 10B) with the grooves making up the liquid supply channels18and liquid recovery channels19extending along the discharge orifice rows being formed at the reverse side thereof. The liquid supply channels18and liquid recovery channels19formed by the substrate11and cover20are respectively connected to the common supply channels211and common recovery channels212within the channel member210, and there is differential pressure between the liquid supply channels18and liquid recovery channels19. Individual supply channels213and individual recovery channels214are formed in the first channel member50. The individual supply channels213connect the liquid supply channel18and common supply channel211, and the individual recovery channels214connect the liquid recovery channel19and common recovery channel212. When multiple discharge orifices13of the liquid discharge head3are discharging liquid and recording, at discharge orifices not performing discharge operations, this differential pressure causes the liquid in the liquid supply channel18to flow in the order of supply port17a→pressure chamber23→recovery port17band to the liquid recovery channel19. This flow is indicated by arrows C inFIG. 11. This flow enables recording liquid that has thickened due to vaporization of the medium from the discharge orifices13, bubbles, foreign substance, and so forth, to be recovered to the liquid recovery channel19from the discharge orifices13and pressure chambers23where recording is not being performed. This also enables thickening of recording liquid at the discharge orifices13and pressure chambers23to be suppressed. Liquid such as recording liquid recovered to the liquid recovery channels19is recovered in the order of the communication ports51in the channel-forming member210, the individual recovery channels214, and the common recovery channel212, via the openings21of the cover20and the liquid communication ports31of the support member30(seeFIG. 9B). This recovered liquid is ultimately recovered to the supply path of the recording apparatus1000.

That is to say, liquid such as recording liquid supplied from the main unit of the recording apparatus1000to the liquid discharge head3is supplied and recovered by flowing in the order described below. First, the liquid flows from the liquid connection portions111of the liquid supply unit220into the liquid discharge head3. This liquid then is supplied to the joint rubber members100, communication ports72and common channel grooves71provided to the third channel member70, common channel grooves62and communication ports61provided to the second channel member60, and individual channel grooves52and communication ports51provided to the first channel member50. Thereafter, the liquid is supplied to the pressure chambers23in the order of the liquid communication ports31provided to the support member30, the openings21provided to the cover20, and the liquid supply channels18and supply ports17aprovided to the substrate11. Liquid that has been supplied to the pressure chambers23but not discharged from the discharge orifices13flows in the order of the recovery ports17band liquid recovery channels19provided to the substrate11, the openings21provided to the cover20, and the liquid communication ports31provided to the support member30. Thereafter, the liquid flows in the order of the communication ports51and individual channel grooves52provided to the first channel member50, the communication ports61and common channel grooves62provided to the second channel member60, the common channel grooves71and communication ports72provided to the third channel member70, and the joint rubber members100. The liquid further flows outside of the liquid discharge head3from the liquid connection portions111provided to the liquid supply unit220. In a case where the first circulation arrangement illustrated inFIG. 2has been employed, liquid that has flowed in from the liquid connection portions111passes through the negative pressure control unit230and then is supplied to the joint rubber members100. On the other hand, in a case where the second circulation arrangement illustrated inFIG. 3has been employed, liquid recovered from the pressure chambers23passes through the joint rubber members100, and then flows out of the liquid discharge head3from the liquid connection portions111via the negative pressure control unit230.

Also, not all liquid flowing in from one end of the common supply channel211of the liquid discharge unit300is supplied to the pressure chamber23via the individual supply channels213a. As illustrated inFIGS. 2 and 3, there is liquid that flows from the other end of the common supply channel211and through the liquid supply unit220without ever entering the individual supply channels213a. Thus, providing channels where liquid flows without going through the recording element board10enables backflow in the circulatory flow of liquid to be suppressed, even in a case where the recording element board10has fine channels where the flow resistance is great. Accordingly, the liquid discharge head3is capable of suppressing thickening of liquid in pressure chambers and portions nearby the discharge orifices, thereby suppressing deviation of discharge and non-discharge, so high image quality recording can be performed as a result.

Description of Positional Relationship Among Recording Element Boards

The liquid discharge head3has multiple discharge modules200, as described above.FIG. 12is a partial enlargement of adjacent portions of recording element boards10in two adjacent discharge modules200. The recording element boards10here are shaped as parallelograms, as illustrated inFIGS. 10A through 10C. The discharge orifice rows14athrough14dwhere discharge orifices13are arrayed on the recording element boards10are disposed inclined to the conveyance direction L of the recording medium by a certain angle, as illustrated inFIG. 12. At least one discharge orifice of discharge orifice rows at adjacent portions of the recording element boards10is made to overlap in the conveyance direction L of the recording medium thereby. InFIG. 12, two discharge orifices13on the lines D are in a mutually overlapping relationship. This layout enables black streaks and blank portions in the recorded image to be made less conspicuous by driving control of the mutually overlapping discharge orifices13, even in a case where the positions of the recording element board10are somewhat deviated from the predetermined position. The configuration illustrated inFIG. 12can be used even in a case where the multiple recording element boards10are laid out in a straight line (inline) instead of in a staggered arrangement. Thus, black streaks and blank portions at overlapping portions between the recording element boards10can be handled while suppressing increased length of the liquid discharge head3in the conveyance direction of the recording medium. Although the shape of the primary face of the recording element board10here is a parallelogram, this is not restrictive. The configuration of the present invention can be suitably applied even in cases where of using recording element boards10of which the shape is a rectangle, a trapezoid, or another shape.

Description of Liquid Discharge Apparatus According to Second Configuration Example

The liquid discharge apparatus to which the present invention can be applied is not restricted to that in the above-described first configuration example. The configuration of an inkjet recording apparatus1000(hereinafter, also referred to as “recording apparatus”) of a second configuration example of the liquid discharge apparatus according to the present invention will be described below.FIG. 13illustrates a schematic configuration of the recording apparatus1000that is the liquid discharge apparatus according to the second configuration example. Note that portions that differ from the first configuration example will primarily be described, and portions that are the same as the first configuration example will be omitted from description.

The recording apparatus1000illustrated inFIG. 13differs from the first configuration example with regard to the point that full-color recording is performed on the recording medium2by arraying in parallel four monochrome liquid discharge heads3, each corresponding to one of the CMYK colors. Although the number of discharge orifice rows usable per color in the first configuration example was one row, the number of discharge orifice rows usable per color in the second configuration example is multiple (20 rows inFIG. 20Adescribed later). This enables extremely high-speed recording to be performed, by allocating recording data to multiple discharge orifice rows. Even if there are discharge orifices that exhibit non-discharge, reliability is improved by a discharge orifice at a corresponding position in the conveyance direction L of the recording medium in another row performing discharge in a complementary manner. Accordingly, the recording apparatus1000according to the second configuration example is suitable for industrial printing and so forth. The supply system of the recording apparatus1000, the buffer tank1003, and the main tank1006are connected to the liquid discharge heads3by fluid connection, in the same way as in the first configuration example. Each liquid discharge head3is also electrically connected to an electric control unit that transmits electric power and discharge control signals to the liquid discharge head3. Either of the first and second circulation arrangements illustrated inFIGS. 2 and 3respectively, may be used in the second configuration example, in the same way as in the first configuration example.

Description of Structure of Liquid Discharge Head

Description will be made regarding the structure of the liquid discharge head3according to the second configuration example with reference toFIGS. 14A and 14B.FIG. 14Ais a perspective diagram of the liquid discharge head3as viewed from the side of the face where discharge orifices are formed.FIG. 14Bis a perspective view from the opposite side fromFIG. 14A. The liquid discharge head3has 16 recording element boards10arrayed in a straight line in the longitudinal direction thereof, and is an inkjet line liquid discharge head (page-wide) that can record with recording liquid of one color. The liquid discharge head3has the liquid connection portions111, signal input terminals91, and power supply terminals92in the same way as the first configuration example. However, the input terminals91and power supply terminals92are disposed on both sides of the liquid discharge head3, since the number of discharge orifice rows is greater than that in the first configuration example. This is to reduce voltage drop and signal transmission delay that occurs at wiring portions provided to the recording element boards10.

FIG. 15is a disassembled perspective view of the liquid discharge head3according to the second configuration example, illustrating each part or unit making up the liquid discharge head3disassembled according to function. The roles of the units and members, and the order of liquid flow through the liquid discharge head3, are basically the same as in the first configuration example, but the function by which the rigidity of the liquid discharge head is guaranteed is different. The rigidity of the liquid discharge head was primarily guaranteed in the first configuration example by the liquid discharge unit support member81, but the rigidity of the liquid discharge head is guaranteed in the second configuration example by the second channel member60included in the liquid discharge unit300. There are liquid discharge unit support members81connected to both ends of the second channel member60in the present second configuration example. This liquid discharge unit300is mechanically enjoined to a carriage of the recording apparatus1000, whereby the liquid discharge head3is positioned. Liquid supply units220having negative pressure control units230, and the electric wiring board90, are joined to the liquid discharge unit support members81. Filters (omitted from illustration) are built into the two liquid supply units220. The second configuration example is not arranged for each negative pressure control unit230to perform two types of pressure control. One of the two negative pressure control units230is set to control pressure at a relatively high negative pressure, serving as a high-pressure side negative pressure control unit, and the other is set to control pressure at a relatively low negative pressure, serving as a low-pressure side negative pressure control unit. When the high-pressure side and low-pressure side negative pressure control units230are disposed on both ends in the longitudinal direction of the liquid discharge head3as illustrated inFIG. 15, the flow of liquid on the common supply channel211and the common recovery channel212that extend in the longitudinal direction of the liquid discharge head3are mutually opposite. This promotes heat exchange between the common supply channel211and common recovery channel212, so that the temperature difference between the two common channels can be reduced. This is advantageous in that temperature difference does not readily occur among the multiple recording element boards10disposed along the common supply channel211and common recovery channel212, and accordingly unevenness in recording due to temperature difference does not readily occur.

The channel-forming member210of the liquid discharge unit300will be described in detail next. The channel-forming member210is the first channel member50and second channel member60that have been laminated as illustrated inFIG. 15, and distributes liquid such as recording liquid supplied from the liquid supply unit220to the discharge modules200. The channel-forming member210also serves as a recovery channel member for returning liquid recirculating from the discharge modules200to the liquid supply unit220. The second channel member60of the channel-forming member210is a member in which the common supply channel211and common recovery channel212have been formed, and also primary undertakes the rigidity of the liquid discharge head3. Accordingly, the material of the second channel member60preferably is sufficiently corrosion-resistant as to the liquid such as recording liquid and has high mechanical strength. Examples of suitably-used materials include stainless steel, titanium (Ti), alumina, or the like.

Next, details of the first channel member50and second channel member60will be described with reference toFIGS. 16A through 16E.FIG. 16Aillustrates the face of the first channel member50on the side where the discharge modules200are attached, andFIG. 16Bis a diagram illustrating the reverse face therefrom, that comes into contact with the second channel member60. Unlike the case in the first configuration example, the first channel member50according to the second configuration example is an arrangement where multiple members corresponding to the discharge modules200are arrayed adjacently. Employing this divided structure enables a length corresponding to the length required for the liquid discharge head3to be realized, by arraying multiple such modules. This configuration can particularly be suitably used in relatively long-scale liquid discharge heads corresponding to sheets of JIS (Japanese Industrial Standards) B2 size and even larger dimensions, for example. The communication ports51of the first channel member50communicate with the discharge modules200by fluid connection as illustrated inFIG. 16A, and individual communication ports53of the first channel member50communicate with the communication ports61of the second channel member60by fluid connection as illustrated inFIG. 16B.FIG. 16Cillustrates the face of the second channel member60that comes in contact with the first channel member50,FIG. 16Dillustrates a cross-section of the middle portion of the second channel member60taken in the thickness direction, andFIG. 16Eis a diagram illustrating the face of the second channel member60that comes into contact with the liquid supply unit220. The functions of the channels and communication ports of the second channel member60are the same as in with one color worth of recording liquid in the first configuration example. One of the common channel grooves71of the second channel member60is the common supply channel211illustrated inFIG. 17and the other is the common recovery channel212, each being supplied with liquid from one end side to the other end side in the longitudinal direction of the liquid discharge head3. Unlike the case in the first configuration example, the directions of the flow or liquid for the common supply channel211and common recovery channel212are mutually opposite directions in the longitudinal direction of the liquid discharge head3in this configuration example.

FIG. 17illustrates the connection relationship regarding the channels between the recording element boards10and the channel-forming member210. The set of the common supply channel211and common recovery channel212extending in the longitudinal direction of the liquid discharge head3is provided within the channel-forming member210, as illustrated inFIG. 17. The communication ports61of the second channel member60are each positioned with and connected to the individual communication ports53of the first channel member50, thereby forming a liquid supply path from the communication ports72of the second channel member60to the communication ports51of the first channel member50via the common supply channel211. In the same way, a liquid supply path from the communication ports72of the second channel member60to the communication ports51of the first channel member50via the common recovery channel212is also formed.

FIG. 18is a diagram illustrating a cross-section taken along XVIII-XVIII inFIG. 17.FIG. 18shows how the common supply channel211connects to the discharge module200through the communication port61, individual communication port53, and communication port51. Although omitted from illustration inFIG. 18, it can be clearly seen fromFIG. 17that another cross-section would show the common recovery channel212connected to the discharge module200through a similar path. Channels are formed on the discharge modules200and recording element boards10to communicate with the pressure chambers23where the discharge orifices13are formed in the same way as in the first configuration example. Part or all of the supplied liquid recirculates through the pressure chambers23corresponding to the discharge orifices13that are not performing discharging operations, by these channels. The common supply channel211is connected to the high-pressure side negative pressure control unit230, and the common recovery channel212to the low-pressure side negative pressure control unit230, via the liquid supply unit220, in the same way as in the first configuration example. Accordingly, a flow is generated by the differential pressure generated by the negative pressure control units230, that flows from the common supply channel211through the pressure chambers23of the recording element board10to the common recovery channel212.

Description of Discharge Module

Next, the discharge module200according to the second configuration example will be described.FIG. 19Ais a perspective view of a discharge module200, andFIG. 19Bis a disassembled view thereof. The difference as to the first configuration example is the point that multiple terminals16are disposed arrayed on both sides (the long side portions of the recording element board10) following the direction of the multiple discharge orifice rows of the recording element board10. Another point is that two flexible printed circuit boards40are provided to one recording element board10and are electrically connected to the terminals16. The reason is that the number of discharge orifice rows provided on the recording element board10is 20 rows, for example, which is an increase over the four rows in the first configuration example. That is to say, the object is to keep the maximum distance from the terminals16to the recording elements15provided corresponding to the discharge orifice row short, thereby reducing voltage drop and signal transmission delay that occurs at wiring portions provided within the recording element board10. Liquid communication ports31of the support member30are provided to the recording element board10, and are opened so as to span all discharge orifice rows. Other points are the same as in the first configuration example.

Description of Structure of Recording Element Board

Next, the configuration of the recording element board10according to the second configuration example will be described.FIG. 20Ais a plan view illustrating the face of the recording element board10on the side where the discharge orifices13are disposed,FIG. 20Bis a diagram illustrating a portion where liquid supply channels18and liquid recovery channels19are formed, andFIG. 20Cis a plan view illustrating the reverse face of that illustrated inFIG. 20A.FIG. 20Bis a schematic diagram illustrating the face of the recording element board10in a state where the cover20provided on the rear face side of the recording element board10is removed inFIG. 20C. Liquid supply channels18and liquid recovery channels19are alternately provided on the rear face of the recording element board10following the discharge orifice row direction, as illustrated inFIG. 20B. Despite the number of discharge orifice rows being much greater than that in the first configuration example, a substantial difference from the first configuration example is that the terminals16are disposed on both side portions of the recording element board10following the discharge orifice row direction, as described above. The basic configuration is the same as that in the first configuration example, such as one set of a liquid supply channel18and liquid recovery channel19being provided for each discharge orifice row, openings21that communicate with the liquid communication ports31of the support member30being provided to the cover20, and so forth.

The following is a description of a configuration according to the present invention regarding a liquid discharge head or liquid discharge apparatus that can control temperature rise due to backflow of hot liquid to the pressure chambers, without variation in discharge properties.FIG. 21illustrates the liquid discharge unit300of a liquid discharge head3according to an embodiment of the present invention. The case80, electric wiring board90, liquid supply unit220, and like configurations of the liquid discharge head3according to the present embodiment are the same as those already described inFIGS. 1 through 20C, so description will be omitted below. Control of negative pressure is performed by using water head pressure instead of providing a negative pressure control unit, as described later. The liquid discharge head3will be described as having two discharge orifice rows that discharge liquid of the same color, to facilitate description.

In the liquid discharge unit300illustrated inFIG. 21, multiple support members30are joined to the channel member210, and further, a recording element board10is joined for each support member30, as described above.FIG. 22is a disassembled perspective view illustrating the liquid discharge unit300in detail, illustrating a discharge module made up of the support member30and recording element board10.FIG. 22illustrates the substrate11making up the recording element board10divided in two, in the thickness direction thereof. One divided part is illustrated in a state joined to the discharge orifice forming member12in (a) inFIG. 22, and the other is illustrated in (b) in a state where liquid supply channels18and liquid recovery channels19are exposed. InFIG. 22, (c) illustrates the cover20, and (d) illustrates the support member30.

The support member30according to the present embodiment supports the recording element board10as to the channel member210, and also functions to distribute liquid such as recording liquid from the channel member210to the recording element boards10. The cover20is provided on the face of the recording element board10opposite to the face on which the discharge orifices13are formed, but in a case where the molding precision of the support member30is high, the cover20may be molded integrally with the support member30. The cover20has multiple fine openings functioning to convert the pitch of the liquid channels from the support member30to the recording element boards10. Of these openings, those openings that communicate with the liquid supply channel18will be referred to as supply-side openings21a, and those openings that communicate with the liquid recovery channel19as recovery-side openings21b. In the arrangement illustrated inFIG. 21, one channel member210is provided to all recording element boards10provided to the liquid discharge head3, but an arrangement may be made wherein multiple channel members210are provided with each corresponding to multiple or one recording element board10. Also, while a support member30is provided for each recording element board10, one support member30may be provided for multiple recording element boards10.

Slit-shaped supply-side distribution channels318and recovery-side distribution channels319are formed on the support member30in a direction orthogonal to the direction in which the discharge orifice rows extend. The distribution channels318and319correspond to the liquid communication ports31in the configurations illustrated inFIGS. 9B and 19B. The supply-side distribution channels318are paths that distribute and supply liquid from the common supply channel211within the channel member210to the recording element board10, and communicate with the common supply channel211. In the same way, the recovery-side distribution channels319are paths that recover liquid from the recording element board10to the common recovery channel212within the channel member210, and communicate with the common recovery channel212. The supply-side openings21aprovided in the cover20are provided at positions where the supply-side distribution channels318and liquid supply channel18intersect, so that these communicate. In the same way, the recovery-side openings21bare provided at positions where the recovery-side distribution channels319and the liquid recovery channel19intersect, so that these communicate. The liquid supply channel18and liquid recovery channel19are formed as mutually parallel grooves extending in the direction in which the discharge orifice rows extend, on the face of the substrate11opposite to the face where the discharge orifices13are formed.

FIGS. 23A through 23Care disassembled perspective views describing the recording element board10in detail.FIG. 23Aillustrates a portion where discharge orifices13are formed,FIG. 23Billustrates a portion where pressure chambers23, supply ports17a, and recovery ports17bare formed, andFIG. 23Cillustrates the substrate11where the liquid supply channel18and liquid recovery channel19are formed. Only one discharge orifice row is illustrated here for wake of description.FIGS. 24A and 24Bare for describing a pressure chamber23and discharge orifice13.FIG. 24Ais a plan view illustrating a state of inside the recording element board10as viewed from the discharge orifice13, andFIG. 24Bis a cross-sectional view taken along line XXIVB-XXIVB inFIG. 24A. The liquid discharge head3according to the present embodiment will be described with reference toFIGS. 22 through 24B. A recording element15is provided on the surface of the substrate11so as to face the discharge orifices13as illustrated inFIGS. 23A through 24B, with the region between the discharge orifice13and recording element15being the pressure chamber23. Although multiple recording elements15are provided on the substrate11, partitions22are disposed between adjacent recording elements15, partitioning off between pressure chambers23. Accordingly, one recording element15and one discharge orifice13correspond to one pressure chamber23. The supply ports17aand recovery ports17brespectively communicate with the liquid supply channel18and liquid recovery channel19formed as grooves on the opposite face of the substrate11.

Multiple supply-side openings21acommunicating with the liquid supply channel18are formed on the cover20in a row, and multiple recovery-side openings21bcommunicating with the liquid recovery channel19are formed on the cover20in a row, as illustrated in (c)FIG. 22. Slit-shaped supply-side distribution channels318and recovery-side distribution channels319are formed on the support member30, communicating with the supply-side openings21aand recovery-side openings21b, respectively. These communicate with the common supply channel211and common recovery channel212formed on the channel member210. In the following description the supply-side openings21aof the cover20are also included in the supply-side distribution channels318, and the recovery-side openings21bare also included in the recovery-side distribution channels319.

The flow of liquid such as recording liquid at the liquid discharge head3according to the present embodiment will be described. Prior to describing the flow of liquid at the liquid discharge head3, an overview of the configuration of the liquid discharge apparatus according to the present embodiment will be described with reference toFIG. 25. Provided to the liquid discharge head3are a high-pressure side inlet port307aand outlet port310a, and low-pressure side inlet port307band outlet port310b. The common supply channel211is connected between the inlet port307aand outlet port310ain the liquid discharge head3, and the common recovery channel212is connected between the inlet port307band outlet port310b. The inlet ports307aand307beach are connected to buffer tanks308aand308bcommunicating with the atmosphere. On the other hand, the outlet port310aand outlet port310beach are connected to the buffer tanks308aand308bvia constant flow pumps311aand311b. The buffer tanks308aand308beach function as storage units storing liquid (recording liquid in this case). Paths where liquid circulates are formed for each of the buffer tanks308aand308bin this liquid discharge apparatus, these paths being connected to the common supply channel211and common recovery channel212, respectively, which will be described later. Accordingly, the path connecting to the common supply channel211will be referred to as a first circulation system, and the path connecting to the common recovery channel212will be referred to as a second circulation system.

A main tank314is provided to supply liquid to the buffer tanks308aand308b. A pump312aand valve313aare serially provided between the main tank314and buffer tank308a, and a pump312band valve313bare serially provided between the main tank314and buffer tank308b. Liquid level sensors309aand309bare attached to the buffer tanks308aand308b, and a controller315controls pumps312aand312band valves313aand313bbased on sensor signals. The pressure difference between the inlet port307aand inlet port307bcan be controlled to a desired value by control by the controller315, and functions equivalent to the negative pressure control units230in the liquid discharge head3illustrated inFIGS. 1 through 20Ccan be realized. The pressure difference between the inlet port307aand inlet port307bis set such that the recording liquid flows through the pressure chambers23at a flow velocity of several mm/s to several tens of mm/s.

FIGS. 26A and 26Billustrate the flow of liquid in the common supply channel211, common recovery channel212, and the distribution channels318and319, as viewed from the common supply channel211side and common recovery channel212side, by arrows.FIG. 26Ashows that the flow of liquid flowing through the pressure chambers23flows from the common supply channel211through the supply-side distribution channels318, circulates within the pressure chambers23, and through the recovery-side distribution channels319to be expelled to the common recovery channel212. In a recording state where the recording elements15are driven with the liquid being circulated to the pressure chambers23in this way, the flow of liquid heads from the supply ports17aand recovery ports17btoward the pressure chambers23for discharge from the discharge orifices13, as illustrated inFIG. 26B. At this time, liquid that has passed through the pressure chambers23due to circulation and flowed out to the recovery-side distribution channels319flows toward the discharge orifices13, and is discharged. Accordingly, the amount of liquid within the recovery-side distribution channels319decreases, but liquid is supplied from the common recovery channel212to the recovery-side distribution channels319to compensate for this phenomenon.

Now, the liquid discharge head3performs temperature control where the recording element boards10are warmed to a constant temperature, to suppress temperature change of the head due to driving, and maintain good recording quality. In a state where the temperature of the liquid discharge head3is raised and controlled, the liquid is warmed by flowing through the channels in the recording element boards10, and warmed liquid flows into the recovery-side distribution channels319. Once the liquid discharge head3enters recording operations, liquid that has been warmed during circulation is supplied from the recovery-side distribution channels319to the discharge orifices13as described above, so the temperature near the discharge orifices13rises. In a case where a state of continuously discharging is prolonged, the heated ink within the recovery-side distribution channels319is gradually discharged from the recording element boards10and unheated ink is supplied from the recovery-side distribution channels319. Accordingly, the temperature of the liquid in the recovery-side distribution channels319decreases, and the temperature near the discharge orifices13also decreases, finally reaching a normal temperature.

In order to suppress this phenomenon, The flow resistance of the liquid recovery channels19formed as grooves in the substrates11of the recording element boards10is made to be larger than the flow resistance of the liquid supply channels18. Now, the amount of liquid supplied to the pressure chambers23will be considered. In the following description, Rinrepresents the composted flow resistance of the supply ports17aand liquid supply channel18, and Routrepresents the composited resistance of the recovery ports17band liquid recovery channel19. Q represents the amount discharged in a full-discharge state where liquid is discharged from all discharge orifices13, converted in to flow rate, and q represents the flow rate of the liquid circulating through the pressure chambers23when not discharging. Expression (1) below shows the flow rate Quotaof liquid supplied from the liquid recovery channel19to the pressure chambers23when the driving state of the liquid discharge head3changes from non-discharging to discharging.

It can be seen from Expression (1) that if a configuration is made where the flow resistance of the liquid recovery channel19is larger than the flow resistance of the liquid supply channel18, the amount of liquid supplied from the liquid recovery channel19to the pressure chambers23when discharging decreases. Accordingly, the backflow of liquid within the liquid recovery channel19accompanying change in the driving state of the liquid discharge head3can be reduced, a state where the temperature of liquid within the pressure chambers23temporarily becomes excessively high can be suppressed, and recording quality can be maintained at a high level. The flow resistance of the liquid recovery channel19can be set higher than the flow resistance of the liquid supply channel18by making the cross-sectional area of a plane perpendicular to the flow direction of liquid in the liquid supply channel18to be larger than the cross-sectional area of a plane perpendicular to the flow direction of liquid in the liquid recovery channel19, for example.

The following is a description of the liquid discharge head3according to the present embodiment, based on several examples and comparative examples.FIG. 27schematically illustrates a cross-section of the substrate11of the recording element board10orthogonal the flow direction of the liquid supply channel18, in a first example.FIG. 28schematically illustrates the cross-section of the recording element board10as a first comparative example.

First Example and First Comparative Example

A recording element board10where the cross-sectional area of the liquid recovery channel19is one-third the cross-sectional area of the liquid supply channel18was fabricated, by changing the width of the channels, as illustrated inFIG. 27, as a first example. Thus, the composited flow resistance of the recovery ports17band liquid recovery channel19is four times as compared to the composited flow resistance of the supply ports17aand liquid supply channel18.

As a first comparative example, a recording element board10was fabricated where the cross-sectional area of the liquid recovery channel19and the liquid supply channel18were the same, by making the width and depth of the channels to be the same, as illustrated inFIG. 28.

The pressure difference between the buffer tanks308aand308bwas set to around 300 Pa, so that the liquid would flow at a flow velocity of 10 mm/s through the pressure chambers23that were 30 μm wide and 15 μm high. Recording liquid for inkjet recording was used as the liquid supplied to the liquid discharge head3. The temperature of the supplied recording liquid was controlled to 35° C., temperature control was performed for the recording element board10so that the temperature sensors (omitted from illustration) disposed near the pressure chambers23all read 60° C., and the temperature distribution at the liquid discharge head3was brought to a state of equilibrium. In this state of equilibrium, the liquid discharge heads3according to the first example and first comparative example were driven at a driving frequency of 8000 Hz for a discharge amount of 5×10−15m3, and temporal change of the average temperature of recording liquid within the pressure chambers23was calculated. The results are shown inFIG. 29, where the solid line represents the first example, and the dotted line represents the first comparative example.

In the first comparative example, around recording liquid of about four times the amount of recording liquid circulating due to pressure difference is discharged, so hot recording liquid in the liquid recovery channel19backs up into the pressure chambers23, and so the temperature within the pressure chambers23temporarily becomes excessively high. On the other hand, the composited flow resistance of the recovery ports17band liquid recovery channel19is around four times the composted flow resistance of the supply ports17aand liquid supply channel18, so the flow rate of hot recording liquid backing up from the liquid recovery channel19is reduced to around two fifths, from Expression (1). Accordingly, the first example suppresses temperature rise of the recording liquid within the pressure chambers23as compared to the first comparative example.

Thus, changing the shape of the liquid recovery channel19formed in the substrate11so as to increase the flow resistance enables the temperature rise of liquid in the pressure chambers23to be suppressed, so a liquid discharge head3with high recording quality can be fabricated. In the present embodiment, the flow resistance of the liquid recovery channel19was made to be around four times that of the liquid supply channel18, but the present invention is not restricted to this, and it is sufficient as long as the relationship is satisfied where the composited flow resistance of the recovery ports and the liquid recovery channel is larger than the composited flow resistance of the supply ports and the liquid supply channel.

Second Example

The second example takes note of the relationship between the composited flow resistance of the supply ports17aand liquid supply channel18, the composited flow resistance of the recovery ports17band the liquid recovery channel19, the discharge amount Q, and the flow rate q of liquid circulating the through the pressure chambers23when not discharging. The flow rate of hot liquid backing up from the liquid recovery channel19is markedly reduced by these flows satisfying a later-described Expression (4). Note that the discharge amount Q here indicates the total sum of droplet amounts of droplets discharged from all discharge orifices13included in the liquid discharge head3.

Based on Expression (1), the conditions for the flow rate of liquid supplied from the liquid recovery channel19to the pressure chambers23at the time of discharge to become substantially zero, i.e., the conditions for no backflow, are as in the following Expression (2).

However, in a situation where more liquid circulates through the pressure chambers23when not discharging, than the amount of liquid discharged, there are cases where imbalance in pressure distribution in the channels increases due to pressure drop, leading to unevenness in discharge properties. Accordingly, the circulation amount of liquid needs to be smaller than the flow rate of liquid that is discharged, as illustrated in Expression (3) below.
q<Q  (3)

Accordingly, it can be seen from Expressions (2) and (3) that the following Expression (4) heeds to hold as conditions for avoiding unevenness in discharge properties due to pressure drop, while markedly reducing the flow rate of hot liquid backing up from the liquid recovery channel19.

In the second embodiment, a liquid discharge unit300the same as the first embodiment illustrated inFIG. 27was used. The flow velocity within the pressure chambers23was set to 60 mm/s to satisfy the conditions of Expression (4), and the pressure difference between the buffer tanks308aand308bwas set to around 1800 Pa to achieve this flow velocity. In the state of equilibrium under the same conditions as in the first example, the liquid discharge heads3according to the second example and first comparative example were driven at a driving frequency of 8000 Hz for a discharge amount of 5×10−15m3, and temporal change of the average temperature of recording liquid within the pressure chambers23was calculated. The results are shown inFIG. 30, where the solid line represents the second example, and the dotted line represents the first comparative example.

In the second example, the flow rate of liquid circulating through the pressure chambers23when not discharging satisfies the conditions of Expression (4), so there is hardly any hot liquid backing up from the liquid recovery channel19. On the other hand, in the first comparative example, the flow rate q of liquid circulating through the pressure chambers23when not discharging is around half the value at the right side in Expression (4), so the conditions of Expression (4) are not satisfied. It can be seen fromFIG. 30the second example suppresses temperature rise within the pressure chambers23in comparison with the first comparative example, and further in comparison with the first example as well. Accordingly, a liquid discharge head with high recording quality can be fabricated.

Although water head difference has been described as being used in the present embodiment to generate negative pressure between the high-pressure side and low-pressure side, arrangements for generating and controlling negative pressure are not restricted to this. A negative pressure control unit such as illustrated inFIGS. 1 through 20Cmay be used. Also, though an arrangement has been described where temperature near the pressure chambers23is monitor to suppress change in discharge properties due to temperature change in the pressure chambers23, thereby maintaining the temperature of the liquid within the pressure chamber23within a set range, the present invention is effective in cases of using other heating arrangements, as well.

According to the present invention, a liquid discharge head and a liquid discharge apparatus using the liquid discharge head, can be provided, whereby liquid circulation to pressure chambers can be realized without causing variation in discharge properties, and excessive rise in temperature due to backflow of hot liquid to the pressure chambers is suppressed.

This application claims the benefit of Japanese Patent Application No. 2016-002946, filed Jan. 8, 2016 and No. 2016-236072 filed Dec. 5, 2016, which are hereby incorporated by reference herein in their entirety.