JP5964561B2 - Liquid discharge head - Google Patents

Description

  The present invention relates to a liquid discharge head, and more particularly to a liquid discharge head that is mounted on an ink jet recording apparatus and discharges liquid such as ink for forming an image or a quality improving liquid for a recorded image from a nozzle.

  Currently, a liquid discharge head is generally composed of a plurality of nozzles. In addition, liquid is applied to a plurality of nozzles so that they are not easily affected by bubbles generated by continuous recording operations. A large-capacity liquid chamber is also used. Such a liquid discharge head may be shipped while being mounted on the main body of the recording apparatus, or may be distributed, displayed, sold, or stored as a liquid replacement head alone as a regular replacement part. When the liquid discharge head is distributed as described above, the liquid discharge head is stored in a resin or aluminum package. Also, a protective tape should be attached to the discharge surface to protect the surface of the liquid discharge head provided with the nozzle (hereinafter referred to as the discharge surface) from impact and drying, or to prevent liquid leakage from the nozzle. There are many (for example, patent document 1). However, when distribution or the like is performed with the protective tape attached to the discharge surface, the internal pressure of the liquid discharge head increases due to environmental changes such as temperature rise, and the protective tape peels off at some position. In some cases, liquid leakage may occur.

JP 2008-155467 A

Therefore, an object of the present invention is to provide a structure that can quickly mitigate an increase in internal pressure due to environmental changes in a liquid discharge head.

For this purpose, the liquid discharge head according to the present invention is a liquid discharge head connected to a liquid storage section , in which a plurality of nozzles having discharge ports for discharging the liquid are arranged, and is connected to the storage section. the different from the plurality of nozzles, a plurality of first flow path for flowing the liquid, connected to the plurality of first flow path, from the said nozzle flow path resistance is rather smaller than the first flow path a second flow path also small flow resistance, has an opening which communicates with the atmosphere the second flow path, said reservoir, each said plurality of nozzles are connected individually, and the plurality Each of the first flow paths is individually connected .

According to the present invention, it is possible to increase the internal pressure of the liquid discharge head to relax quickly this be caused by environmental changes.

1 is a schematic diagram illustrating an embodiment of an inkjet recording apparatus to which the present invention is applicable. FIG. 2 is a schematic cross-sectional view of the recording head in FIG. It is sectional drawing which expands and shows the one end part of the discharge part in FIG. 2, ie, the part III enclosed with the broken-line circle in the same figure. FIG. 3 is a schematic cross-sectional view of a recording head during distribution. FIG. 5 is a schematic plan view of the recording head of FIG. 4 as viewed from the ejection surface side.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic view showing an embodiment of an ink jet recording apparatus to which the present invention can be applied. An ink jet recording apparatus (hereinafter also referred to as a printer) 10 is connected to a host apparatus 12 in the form of a personal computer, which is an external apparatus that serves as a supply source of image data. The printer 10 has liquid ejection heads 22K, 22C, and 22M for ejecting black (K), cyan (C), magenta (M), and yellow (Y) inks to perform full color recording on the recording medium P. And 22Y are mounted. The internal structure of the liquid discharge heads 22K, 22C, 22M, and 22Y will be described later. It is a so-called line head type having a nozzle. The predetermined range is slightly longer than the maximum effective recording width (the length in the direction perpendicular to the recording surface of the recording medium) on the recording medium that can be recorded by the printer 10. In the present embodiment, the liquid discharge heads 22K, 22C, 22M, and 22Y that discharge the inks of the respective colors are used, and the liquid discharge head that discharges a liquid such as a quality improving liquid for a recorded image is not used. Hereinafter, the “liquid discharge head” is referred to as a “recording head”. However, it goes without saying that the number of print heads and the type of color tone (color, density) are merely examples, and the type of liquid to be ejected may include a print image quality improving liquid. Of course. Further, in the following description, when the color tone is not specified, the recording head is collectively represented by reference numeral 22.

  The recording head 22 is held by a holding unit (not shown) and can be moved up and down in the vertical direction (B direction) together with the holding unit. Further, the recovery unit 40 having the cap 50 corresponding to each recording head 22 is held so as to be movable in the horizontal direction (the direction A and the direction opposite to the A direction).

  At the time of non-recording, such as in a storage state or during recording standby, the cap 50 is applied to the ejection surface 22S of the recording head 22. If the ejection surface 22S of the recording head is exposed to the atmosphere during non-recording, the ink solvent near the ejection port evaporates, causing ink thickening / solidification, or dust adhesion, resulting in ejection failure. Because there is a fear. In addition, the recording head that ejects ink desirably performs a recovery process for maintaining or recovering the ink ejection state in a stable state, and the capping state enables such a recovery process by the recovery unit 40. It is also a state to do. The recovery process of the present embodiment includes a suction recovery operation in which ink is sucked from the ejection port by applying a negative pressure to the cap inner space or the nozzle in the capping state. Further, a preliminary ejection operation for causing the recording head to perform a preliminary ejection operation toward the cap before recording can be included. Further, it can include an operation of wiping the ejection surface 22S of the recording head with a wiper blade made of an elastic member such as rubber to clean it. The recovery unit 40 has components for performing these operations.

  When shifting from the capping state to the recording operation, the holding unit or the recording head 22 is once raised, and then the recovery unit 40 is retracted to the left in FIG. 1, and is further opened in the opening provided between the caps 50 of the recovery unit 40. The recording heads 22 face each other. Then, the holding unit or the recording head 22 is lowered, the recording head 22 protrudes downward from the opening between the caps, and is set to a position facing the recording medium P with a predetermined gap. Then, the recording head 22 is fixed at that position, the recording medium P is conveyed in the A direction, and the recording head 22 is caused to perform an ink ejection operation in the process, thereby performing a recording operation for recording an image. When the recording operation is completed and the state is set to the non-recording state, the reverse operation may be performed.

  The recording medium P in roll paper form is supplied from the supply unit 24 and is conveyed in the direction of arrow A by a conveyance mechanism 26 incorporated in the printer 10. The transport mechanism 26 includes a transport belt 26a for placing and transporting the recording medium P, a transport motor 26b for rotating the transport belt 26a, and a roller 26c for applying tension to the transport belt 26a. Of course, the recording medium P is not limited to the form of roll paper, but may be of cut paper, fanfold paper, or the like.

  In the configuration shown in FIG. 1, when an image is formed on the recording medium P, the recording start position of the recording medium P being conveyed reaches below the recording head 22K for K, and then based on the recording data (image data). Thus, K ink is selectively ejected from the ejection ports of the recording head 22K. Similarly, each color ink is ejected in the order of the recording head 22C, the recording head 22M, and the recording head 22Y to form a color image on the recording medium P.

  The printer 10 includes ink tanks 28K, 28C, 28M, and 28Y that store ink of each color to be replenished when the amount of ink stored in each recording head 22 decreases (hereinafter, when not specified). Are generally referred to by reference numeral 28). Further, a negative pressure generating mechanism (not shown) that places the inside of the recording head 22 in a negative pressure state that balances the holding force of the ink meniscus formed on the nozzles is also arranged. Using this negative pressure generating mechanism, Ink replenishment from the ink tank 28 to the recording head 22 can be performed.

  FIG. 2 is a schematic cross-sectional view of the recording head 22. The recording head 22 applied to the present invention is circulated in a state where a predetermined amount of ink is filled in the recording head 22, that is, the storage portion 22 </ b> L, and is attached to the printer 10. When the amount of ink in the storage unit 22L decreases, ink is replenished from the ink supply port 101 connected to the ink tank 28. The replenishment can be performed by operating the negative pressure generating mechanism and bringing the inside of the recording head 22 into a negative pressure state via the communication port 104 connected to the negative pressure generating mechanism. Note that filters 102 and 103 that prevent entry of dust or the like into the recording head 22 are disposed at the ink supply port 101 and the communication port 104, respectively.

  The ink level 105 of the ink inside the recording head 22, that is, the amount of ink, can be determined by detecting the change in conductivity between the conductive plate 106 and the conductive plate 107 and between the conductive plate 107 and the conductive plate 108. it can. That is, the lower limit position of the ink liquid level 105 is detected by increasing the electric resistance value when ink is exhausted between the conductive plate 106 and the conductive plate 107. Ink replenishment can be performed by operating the negative pressure generating mechanism. On the other hand, the upper limit position of the ink liquid level 105 is detected by a decrease in the electric resistance when ink is present between the ink conduction plate 106 and the conduction plate 108 with the replenishment. Stops the replenishment operation.

  In FIG. 2, what is indicated by reference numeral 109 is a discharge portion in which a plurality of nozzles are formed. The discharge unit 109 includes a member formed with a wall portion that defines a nozzle portion and the like on a silicon substrate and an element that generates energy used for ink discharge by a photolithography process, and a top plate for the member. It is comprised by joining the member which becomes. Note that. In joining these members, ink leakage is prevented from occurring by using a sealing agent (not shown).

  FIG. 3 is an enlarged cross-sectional view showing one end portion of the discharge portion 109 in FIG. 2, that is, a portion III surrounded by a broken-line circle in the same drawing, and shows a liquid channel structure such as a nozzle at the end portion. Here, 201a, 201b,... Are nozzles that are involved in recording by ejecting ink in accordance with image data (hereinafter, these nozzles are referred to as ejection nozzles and are referred to by reference numeral 201 if not specified). ). The discharge nozzle 201 has an electrothermal conversion element (hereinafter referred to as a heater) that generates heat energy that generates heat and generates film boiling in ink as an element that generates energy used for ink discharge. . On the other hand, 202 is a nozzle-shaped flow path (first flow path) that does not participate in recording and has a function of communicating the inside of the recording head 22 or the discharge section 109 to the atmosphere in the vicinity of the discharge nozzle array. The discharge nozzle 201 and the nozzle-shaped channel 202 are each connected to the storage portion 22L, and the ink stored in the storage portion 22L is introduced into the discharge nozzle 201. In this embodiment, a plurality (three in the illustrated example) of nozzle-shaped flow paths 202 are provided in parallel with the discharge nozzles, and none of them has a corresponding heater or electrical connection is not formed. By doing so, it is possible not to be involved in recording. The nozzle-shaped channel 202 has the same shape and size as the discharge nozzle 201 and has the same channel resistance. That is, the flow path resistance of each discharge nozzle 201 from the ink reservoir 22L to the discharge surface 22S is set to be equal to that of each nozzle-shaped flow path 202 from the ink reservoir 22L to a portion connected to a flow path 203 described later. Make the channel resistance equal. Accordingly, for example, excessive ink suction is not performed through the nozzle-shaped flow path 202 during the suction recovery operation.

  Each discharge nozzle 201 has a leading end (discharge port) opened on the discharge surface 22S so as to discharge ink onto the recording medium in accordance with the operation of the heater. On the other hand, the tips of the three nozzle-shaped flow paths 202 are connected in common to a flow path (second flow path) 203 formed inside the recording head 22 or the discharge unit 109 and having a larger cross-sectional area than the nozzle-shaped flow path 202. Has been. The flow path 203 extends from the position away from the discharge nozzle 201a at the end of the discharge nozzle row by a predetermined distance toward the end of the discharge unit 109 in the discharge nozzle arrangement direction. And it bends in the L-shape, for example toward the discharge surface in the vicinity of the end, and has an opening 204 on the discharge surface, thereby communicating with the atmosphere. Thus, by making the flow path 203 have a larger cross-sectional area than the nozzle-shaped flow path 202, dust and the like are difficult to clog. Further, by extending away from the discharge nozzle 201a at the end of the discharge nozzle row and having a L-shaped shape at the tip, it becomes difficult for dust and the like to enter the recording head from the opening 204. ing.

  4 is a schematic cross-sectional view of the recording head 22 during distribution before being mounted on the printer 10, and FIG. 5 is a schematic plan view of the recording head 22 as viewed from the ejection surface side. The protective tape 301 is attached to the discharge surface 22S so as to cover the array range 402 of the discharge nozzles 201, a function of protecting the discharge port of the discharge nozzle 201 from damage, a function of preventing dust from entering from the nozzle opening, and It has a function of protecting the inside of the discharge nozzle from drying. On the other hand, the protective tape 301 does not cover the opening 204 of the flow path 203, and therefore the inside of the recording head 22 or the discharge unit 109 is aired through the opening 204, the flow path 203, and the nozzle-shaped flow path 202 during distribution. Communicated with.

  Here, it is also conceivable to open the inside of the recording head 22 to the atmosphere via the ink storage port 22L, which is a liquid chamber, for example, via the ink supply port 101 or the communication port 104. However, bubbles may be generated in the discharge nozzle 201 or in the vicinity thereof, and the bubbles may expand due to an environmental change, for example, a temperature rise, and the internal pressure of the discharge unit 109 or the discharge nozzle 201 may increase. In such a case, the increase in the internal pressure acts on the discharge nozzle 201 before being mitigated by the ink reservoir 22L communicating with the atmosphere via the ink supply port 101 or the communication port 104, and the protective tape is peeled off. Ink leakage may occur. This becomes more problematic as the ink storage unit 22L has a larger capacity, and the air communication portion is located farther from the discharge unit 109 or the discharge nozzle 201. On the other hand, according to the present embodiment, the inside of the recording head 22 or the discharge unit 109 is communicated with the atmosphere in the vicinity of the array of discharge nozzles. Therefore, the increase in internal pressure is quickly alleviated by the flow path 203 communicating with the atmosphere with a larger cross-sectional area (that is, a smaller flow path resistance) than the discharge nozzle 201 and the nozzle-shaped flow path 202, and the protective tape 301 is peeled off. It is difficult to occur.

  It is also conceivable that what is called a dummy nozzle having no discharge function is provided outside the end of the discharge nozzle arrangement range 402 and the inside of the recording head 22 is opened to the atmosphere via the dummy nozzle. It is done. However, in a configuration in which dummy nozzles are simply provided, the dummy nozzles may be blocked by the protective tape 301 if a sufficient distance between the discharge nozzles 201a at the end of the arrangement range 402 and the dummy nozzles cannot be secured. is there. Then, the desired atmosphere communication effect cannot be obtained, and the protective tape 301 can be peeled off. On the other hand, in this example, the flow path 203 that communicates with the nozzle-shaped flow path 202 extends away from the discharge nozzle 201a at the end of the discharge nozzle row and extends toward the end of the discharge section 109. Is bent in an L shape toward the discharge surface and has an opening 204 on the discharge surface. That is, as shown in FIG. 5, the opening 204 is provided at a distance 404 from the discharge nozzle 201 a at the end of the discharge nozzle array range 402. Accordingly, the degree of freedom in attaching the protective tape 301 is increased, and the opening can be easily performed without the opening 204 of the channel 203 being blocked by the end of the protective tape 301.

  Further, in the configuration in which the dummy nozzle is simply provided, even if the protective tape 301 is accurately attached so as not to block the dummy nozzle, the dummy nozzle is blocked by the intrusion of dust or the like, and the desired atmosphere communication effect is achieved. May not be obtained. In order to cope with this, it is conceivable to increase the size of the dummy nozzle. However, since the flow resistance of the dummy nozzle is reduced by that amount, if the suction recovery operation is performed after being mounted on the printer, the amount of ink discharged from the dummy nozzle increases accordingly, or the discharge nozzle is sufficiently discharged. May not be able to perform proper suction recovery. On the other hand, in the present embodiment, the cross-sectional area of the flow path 203 and the opening area of the opening 204 are made larger than the cross-sectional areas of the nozzle-shaped flow path 202 and the discharge nozzle 201, so that these are caused by intrusion of dust or the like. The possibility of being blocked is reduced. In the present embodiment, the flow path 203 is connected to the nozzle-shaped flow path 202 having the same shape and dimensions as the discharge nozzle 201 and having the same flow resistance. Accordingly, it is possible to prevent the disadvantage that the amount of ink discharged with the suction recovery operation increases or the suction nozzle cannot perform sufficient suction recovery.

  In the above embodiment, the configuration in which the nozzle-shaped flow path 202, the flow path 203, and the opening 204 are provided on one end portion side of the discharge nozzle array range 402 is illustrated. It can also be set as the structure provided also in the part side. In the above-described embodiment, the three nozzle-shaped flow paths 202 are connected to the flow path 203, but the number can be determined as appropriate. Furthermore, the nozzle-shaped flow path 202 has the same shape and dimensions as the discharge nozzle 201 if the desired atmosphere communication effect and the effect of suppressing the increase in the amount of ink discharged with the suction recovery operation can be obtained. You don't have to.

  In addition, in the above embodiment, the case where the present invention is applied to a liquid discharge head in the form of an ink jet recording head has been described. However, it goes without saying that the present invention can be widely applied to a liquid discharge head that discharges a liquid such as a liquid for improving the quality of a recorded image. In the above embodiment, the case where the present invention is applied to a so-called line head type liquid discharge head applied to an ink jet recording apparatus of a line printer type has been described. However, it is needless to say that the present invention can also be applied to a liquid discharge head applied to an ink jet recording apparatus in the form of a serial printer. Further, in the above-described embodiment, the case where the present invention is applied to a liquid discharge head having an element that generates thermal energy as energy used for discharging a liquid has been described. However, the present invention can also be applied to other elements, for example, a liquid ejection head having a piezo element that ejects ink by being deformed or displaced in response to application of a voltage.

22 Recording head 22S Discharge surface 109 Discharge part 201, 201a, 201b Discharge nozzle 202 Nozzle-shaped flow path 203 Flow path 204 Opening 301 Protection tape 402 Discharge nozzle arrangement range

Claims (10)

A liquid discharge head connected to a liquid storage unit and arranged with a plurality of nozzles having discharge ports for discharging the liquid,
Connected to said reservoir, said different from the plurality of nozzles, a plurality of first flow path for flowing the liquid,
Connected to said plurality of first flow path, a small second flow path of the flow path resistance than the said nozzle rather small flow path resistance than the first flow path,
An opening communicating the second flow path with the atmosphere;
Have
Each of the plurality of nozzles is individually connected to the storage unit, and each of the plurality of first flow paths is individually connected to the storage unit .   2. The liquid discharge head according to claim 1, wherein a direction in which the reservoir is connected to the first flow path and a direction in which the reservoir is connected to the nozzle are the same.   The liquid discharge head according to claim 1, wherein the second flow path has a larger cross-sectional area than the first flow path.   The liquid discharge head according to claim 1, wherein the first flow path has a flow path resistance equal to that of the nozzle.   5. The liquid ejection head according to claim 1, wherein the first flow path has the same size and shape as the nozzle. The opening is provided on a surface provided with the discharge port,
6. The first flow path according to claim 1, wherein the second flow path extends in an arrangement direction in which the plurality of nozzles are arranged and is connected to the opening through a bent portion. The liquid discharge head described in 1.   The opening is provided at a position farther from the arrangement range of the plurality of nozzles than the plurality of first flow paths in the arrangement direction in which the plurality of nozzles are arranged. The liquid discharge head according to any one of the above.   8. The liquid ejection head according to claim 6, wherein the first flow path extends in a direction crossing an arrangement direction in which the plurality of nozzles are arranged.   9. The liquid discharge head according to claim 1, wherein the nozzle is provided with an element that generates thermal energy as energy used for discharging the liquid. 10.   The liquid according to any one of claims 1 to 9, wherein a liquid is stored in the storage portion, and a protective tape is attached so as to cover the discharge port and not cover the opening. Liquid discharge head.

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