1. Field of the Invention
The present invention relates to an ink jet head employed for an ink jet recording apparatus that discharges ink droplets to record images on a recording medium.
2. Related Background Art
Conventionally, an ink jet recording apparatus is known that records characters and images on a recording medium by employing an ink jet head that includes a plurality of nozzles from which ink is discharged. The type of ink jet head frequently employed includes, as a single unit, multiple nozzles, pressure generators and ink guide holes, and an ink jet head wherein multiple arrays of nozzles and pressure generator arrays are provided is well known.
As shown in
Ink chamber plates 7 and 10, which form common ink chambers 32 and 33 that communicate with the shallow side ends of the grooves 3, are connected to the sides of the piezoelectric ceramic plates 2 and 5 where the grooves 3 are opened. Thus, two head chips are provided. The piezoelectric ceramic plates 2 and 5 of the two head chips are bonded together to obtain a head chip block 50.
A nozzle plate 15 is adhered to the end face of the head chip block 50, and nozzle holes 16 are formed in the nozzle plate 15 at locations corresponding to the grooves 3. The nozzle plate 15 and the head chip block 50 are fixed together by a head cap 17, and electrodes that are formed on the piezoelectric ceramic plates 2 and 5 are connected to a drive circuit board by a flexible board.
Furthermore, ink flow paths 34 and 35, for supplying ink to the common ink chambers 32 and 35, are secured to the two ink chamber plates 7 and 10, and ink guide joints 39 and 40 are formed in the center of the ink flow paths 34 and 5 in order to introduce ink. Further, pressure relaxing units 41 and 42 are connected to the ink guide joints 39 and 40 to absorb the pressure fluctuation that occurs during printing. In addition, filters 36 and 37 are fixed to the ink flow paths 34 and 35 to prevent foreign substances from entering the nozzle holes 16.
In the thus arranged ink jet head, ink is supplied to the individual grooves 3 via the pressure relaxing units 41 and 42 and the ink flow paths 34 and 35, and when a predetermined drive field is applied, the volumes of the grooves 3 are changed and ink in the grooves 3 is discharged from the nozzle holes 16. That is, the ink flow path 34 and the path along which ink is supplied to the ink chamber plate 7 and the piezoelectric ceramic plate 2 forms a set. Similarly, the ink flow path 35 and the path along which ink is supplied to the ink chamber plate 10 and the piezoelectric ceramic plate 5 forms a set. These sets are independent of each other, i.e., two ink flow paths are provided for the laminated head chip block 50.
However, according to the conventional ink jet head, the ink flow path 34 and the path along which ink is supplied to the ink chamber plate 7 and the piezoelectric ceramic plate 2 form a set, while the ink flow path 35 and the path along which the ink is supplied to the ink chamber plate 10 and the piezoelectric ceramic plate 5 form another set, and these two sets are independent of each other. Thus, two ink flow paths are required for one head chip block 50, and accordingly, two pressure relaxing units must respectively be provided. Therefore, the size of the ink jet head in the direction of thickness is increased, and the weight can not be reduced. Moreover, the number of parts is increased, and the manufacturing cost is increased.
When an ink jet recording apparatus is to be provided by mounting a plurality of such ink jet heads, the attachment area is extended, and also, the weight is increased.
To resolve these shortcomings, the objective of the present invention is to enable the reduction of the size and weight of an ink jet head, and to provide an ink jet head, at a low cost, and an ink jet recording apparatus.
To achieve this objective, according to one aspect of the present invention, an ink jet head comprises:
at least one first head chip, having a first actuator substrate, in which a plurality of parallel grooves are formed that communicate with nozzle holes, a first ink chamber plate, in which a first ink chamber is formed to supply ink to the each grooves; and equal to or greater than one second head chip including an ink flow path for connecting an ink supply portion to the first ink chamber, a second actuator substrate, in which a plurality of parallel grooves are formed to communicate with nozzle holes, a second ink chamber plate, in which a second ink chamber is formed to supply ink to the grooves in the second actuator substrate, and ink supply means for connecting the ink flow path to the second ink chamber. With this arrangement, ink can be supplied to a head chip that is not directly connected to the ink supply means.
As described above, according to the invention, when ink is introduced via one ink flow path, this ink can be guided to all the head chips that constitute a head chip block. Thus, the size and weight of the ink jet head can be reduced, and also, the number of parts can be reduced. As a result, an ink jet head at a low price can be provided.
The present invention will now be described in detail by referring to the preferred embodiments.
As shown in these drawings, an ink jet head 1 for the first embodiment includes: a head chip block 50; an ink flow path 12, formed on one side; a circuit board 22, on which a drive circuit for driving a head, for example, is mounted; and a pressure relaxing unit 19, for relaxing the change in the pressure in the head chip block 50. These members are fixed to a base 18. The pressure relaxing unit 19 is connected to the ink flow path 12 via a flow path joint 26 located in the center of the ink flow path 12, and guides ink to the head chip block 50.
The periphery of the head chip block 50, which serves as a pressure generation source for discharging of ink, will now be described in detail. In the following description, reference numerals of elements of a first head chip are preceded by the letter “A” and those of a second head chip are preceded by the letter “B”. A plurality of grooves 3 that communicate with nozzle holes 16 are, formed in piezoelectric ceramic plates A2 and B5, which are actuator substrates that constitute the head chip block 50. The grooves 3 are separated by side walls 6.
One longitudinal end of each groove 3 is extended to and opens at one end face of the piezoelectric ceramic plate A2 or B5, and the other end is not extended to the other end, so that the depth of the grooves 3 is gradually reduced.
Further, on the side walls 6 of the two widthwise sides for each groove 3, electrodes 4 to which a drive electric field is to be applied are formed in the longitudinal direction, near the opening of the groove 3.
A disc-shaped die cutter, for example, is employed to form the grooves 3 in the piezoelectric ceramic plates A2 and B5, and the shape of the die cutter is used to form the portion wherein the depth is gradually reduced. Further, a well known vapor deposition process, for example, is employed in the oblique direction to form the electrodes 4 on the individual grooves 3. After the electrodes 4 are arranged on the two side walls 6 of each groove 3, near the opening, the electrodes 4 are connected to wiring ends on a flexible board 20. The other wiring ends on the flexible board 20 are connected to a drive circuit on the circuit board 22. Thus, the electrodes 4 are electrically connected to the drive circuit.
Ink holes 14 are formed at two locations outside the grooves 3 in the piezoelectric ceramic plates A2 and B5, respectively. Further, ink chamber holes 9 and 11 are also respectively formed at two locations outside ink chamber plates A7 and B10.
Furthermore, the ink chamber plate A7 and the ink chamber plate B10 are respectively bonded to the major faces of the piezoelectric ceramic plates A2 and B5 where the grooves 3 open. Further, an ink chamber A8 and an ink chamber B21 are respectively formed in the ink chamber plates A7 and B10 in the direction of depth so as to cover all the parallel arranged grooves 3. The assembly consisting of the piezoelectric ceramic plate A2 and the ink chamber plate A7 and the assembly consisting of the piezoelectric ceramic plate B5 and the ink chamber plate B10 are laminated, so that the faces of the piezoelectric ceramic plates A2 and B5, in which the grooves 3 have not yet been processed, are aligned. As a result, the head chip block 50 is obtained, and the ink chamber A8 and the ink chamber B21 are externally located.
In this embodiment, the head chip (the piezoelectric ceramic plate A2 and the ink chamber plate A7) adhered to the ink flow path 12 is regarded as a first head chip, and the head chip (the piezoelectric ceramic plate B5 and the ink chamber plate B10) that is not adhered to the ink flow path 12 is regarded as a second head chip.
Furthermore, in this embodiment, the two head chips 15 are coupled together or integrated to form an ink jet head. However, the present invention is not limited to this. The feature of the invention is that a plurality of head chips are integrated and coupled together, and an ink flow path is formed in at least one of the head chips.
In this embodiment, major faces of the piezoelectric ceramic plates A2 and B10 are bonded together, so that the grooves 3 are arranged in a zigzag manner with their positions staggered or shifted from each other at the same intervals. Further, at the position where these plates A2 and B10 are bonded together, the ink holes 14 and the ink chamber holes 9 and 11 are superimposed and pierce the plates A2 and B10. In this embodiment, the grooves 3 are arranged in a zigzag manner; however, in consonance with the purpose for which used, the piezoelectric ceramic plates A2 and B10 may be bonded together at a position whereat the grooves are superimposed. In addition, in the explanation for this embodiment, the ink holes 14 and the ink chamber holes 9 and 11 have been formed at two places at the ends of the head chip block 50. However, these holes may be formed only at one place, or at more than two locations. The present invention is not limited to the number of through holes. Also, the ink chamber holes 9 and 11 have been formed in one part in the ink chamber plates A8 and B21; however, the holes are not especially limited to these positions.
The ink chamber plates A7 and B10 can be ceramic plates or metal plates; however, while taking into account the deformation that may occur after being bonded to a piezoelectric ceramic plate, a ceramic plate that has a similar thermal expansion coefficient is preferable.
Moreover, the nozzle plate 15 is adhered to the end face of the head chip block 50, which is formed of the piezoelectric ceramic plates A2 and B5 and the ink chamber plates A7 and B10, in which the grooves 3 are opened. And nozzle holes 16 are formed in the nozzle plate 15 at locations corresponding to the grooves 3.
In this embodiment, the nozzle plate 15 is larger than the area of the end face of the head chip block 50 in which the grooves 3 are opened. This nozzle plate 15 is a polyimide film in which the nozzle holes 16 have been formed, for example, by using an excimer laser device. Further, although not shown, a water-repellent film to prevent the attachment of ink is deposited on the face of the nozzle plate 15 opposite the recording material.
A head cap 17 that supports the nozzle plate 15 is adhered to the outer face of the base 18 on the end face side of the head chip block 50 in which the grooves 3 are opened. The head cap 17 is connected to the outer edge of the end face of the assembly that includes the nozzle plate 15, and stably supports the nozzle plate 15. The thus arranged head chip block 50 and the head cap 17 are securely fixed to the base 18.
For the ink chamber plate A7 and the ink chamber plate B10, the ink flow path 12 is bonded to the ink chamber plate A7. A flow path joint 26 is located in the center of the ink flow path 12 and connected to the pressure relaxing unit 19, so that ink is actually supplied through it. Furthermore, in order to remove dust, for example, from ink, a flow path filter 13 having a pore size of eight microns is located along the ink flow path 12, opposite the ink chamber plate A7, in the direction in which the grooves 3 are arranged.
According to the ink jet head of this embodiment, at the initial filling time, for example, ink is supplied to the pressure relaxing unit 19 from an ink tank that serves as an ink supply portion. Further, the ink is guided along the flow path joint 26 to the ink flow path 12. Following this, the ink passes through the flow path filter 13 and reaches the ink chamber plate A7, where part of it is supplied to the ink chamber A8 and is loaded into the grooves 3 in the piezoelectric ceramic plate A2. The other part of the ink passes through the ink chamber holes 9 and the ink holes 14, which are formed at both ends of the ink chamber plate A7, and the ink holes 11, which are formed in both ends of the ink chamber plate B10, and is supplied to the ink chamber plate B21. Thus, the ink is loaded into the grooves 3 in the piezoelectric ceramic plate B5. After the ink has passed through the grooves 3 in the piezoelectric ceramic plates A2 and B5, it reaches the nozzle holes 16. The discharge of ink is then enabled. A detailed method for supplying ink is not described here; however, ink can be supplied either by using pressure-reduction, performed on the nozzle hole 16 side using a suction pump, or by using pressurization, performed on the pressure relaxing unit 19 side using a pressure pump.
As is described above, according to the ink jet head of this embodiment, since the ink supply means constituted by the ink chamber holes 9 and 11 and the ink holes 14 that pierce the head chip block 50 is provided, only one ink flow path 12 need be formed in either the ink chamber plate A7 or the ink chamber plate B10 for ink to be supplied to the grooves 3 in both the piezoelectric ceramic plate A2 and the piezoelectric ceramic plate B5. Therefore, the size and the weight of the ink jet head can be reduced, as can the number of parts, and the ink jet head can be provided at a low cost.
In association with the ink jet head according to the first embodiment, an explanation will be given for a case wherein a greater improvement in printing uniformity is obtained.
In this embodiment, the flow path adjustment plate B24 has been provided on the ink chamber plate B10. However, the face of the ink chamber plate may be bonded directly to the base 18 to eliminate the flow path adjustment plate B24. With this arrangement, no functional problem is encountered.
As shown in
A detailed explanation for this ink jet head will be given. An ink chamber plate A52 and an ink chamber plate B53 are bonded to the piezoelectric ceramic plate A2 and the piezoelectric ceramic plate B5 in which grooves 3 are opened. An ink chamber. A54 and an ink chamber B55 are formed by cutting through the ink chamber plate A52 and the ink chamber plate B53 in the direction of the thickness, so that they cover the parallel grooves 3. A chip side groove A27 and a chip side groove B28 are formed outside the ink chambers A54 and B55 to connect an outer portion.
The assembly composed of the piezoelectric ceramic plate A2 and the ink chamber plate A52 and the assembly composed of the piezoelectric ceramic plate B5 and the ink chamber plate B53 are laminated by aligning the faces of the piezoelectric ceramic plates A2 and B5 in which the grooves 3 are not formed. As a result, the head chip block 51 is obtained and the ink chambers A54 and B55 are open to the outside. In this embodiment, the piezoelectric ceramic plates A2 and B10 are bonded, so that the grooves 3 are arranged in a zigzag manner with their positions shifted relative to each other at the same intervals.
Further, an ink chamber cover A29 and an ink chamber cover B30 are bonded to the ink chamber plate A52 and the ink chamber plate B53, so that both sides of the chip side wall groove A27 and the chip side wall groove B28 are open.
For the ink chamber plate A52 and the ink chamber plate B53, an ink flow path or ink passage 31 is bonded from the ink chamber 25 plate A52 side, and the opening formed by the chip side groove A27 and the chip side groove B28 is covered with the two ends of the ink flow path 31.
According to the ink jet head of this embodiment, at the initial filling time, for example, ink from an ink tank is supplied to the ink flow path or ink passage 31, passes through the flow path filter 13 and reaches the ink chamber cover A29. Further, the ink passes along the ink guide path 56 and enters the chip side groove A27 and the chip side groove B28. Sequentially, the ink is guided to the ink chamber A54 and the ink chamber B55, and fills the grooves 3 in the piezoelectric ceramic plates A2 and B5. Thereafter, the ink reaches the nozzle holes 16 and the discharge of ink is enabled. It should be noted that an ink filling method is not described in detail. Ink filling, however, can be performed either by pressure-reduction, performed on the nozzle hole 16 side using a suction pump, or by pressurization, performed on the pressure relaxing unit 19 side using a pressure pump.
As is described above, according to the ink jet head of this embodiment, only one ink flow path 31 need be formed in either the ink chamber plate A52 or the ink chamber plate B53, for ink to be supplied to the grooves 3 in both the piezoelectric ceramic plate A2 and the piezoelectric ceramic plate B5. Thus, the size and weight of the ink jet head can be reduced, as can the number of parts, and the ink jet head can be provided at a low price.
When the above described ink jet recording apparatus conveys the recording medium S and, at the same time, moves the ink jet head in the direction perpendicular to the direction in which the recording medium S is conveyed, characters or images can be recorded on the recording medium S.
Number | Date | Country | Kind |
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2005-209872 | Jul 2005 | JP | national |
2006-059007 | Mar 2006 | JP | national |
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4443254 | Dec 1995 | DE |
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Number | Date | Country | |
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20070019035 A1 | Jan 2007 | US |