Patent Application
20190118534
This application is based upon and claims the benefit of priority from Japanese Patent Applications Nos. 2017-205250, filed Oct. 24, 2017 and 2018-136653, filed Jul. 20, 2018, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a fluid ejection head and a fluid ejection apparatus.
A fluid ejection head, such as an ink jet head, may include a nozzle plate having a plurality of nozzles formed therein, a plurality of pressure chambers facing the nozzle plate and in fluid communication with the nozzles, and a base plate forming a common chamber in fluid communication with the pressure chambers. A voltage is applied to a drive element provided in the pressure chamber to generate a pressure variation and thereby eject fluid from the nozzle. A fluid holding tank is connected to the fluid ejection head, and the fluid is circulated in a circulation path passing through the fluid ejection head and the fluid holding tank.
In such fluid ejection heads, there is a known configuration in which several nozzles communicate with one pressure chamber. For example, if three or more nozzles of the same shape are aligned, an ejection speed of the fluid from the nozzle located at the center will be slowed down. Accordingly, if the fluid is ejected towards an ejection target that moves relative to the fluid ejection head, ejected droplets may hit the ejection target at slightly different locations or ejected droplets may be elongated differently in a particular direction paralleling to the target movement direction.
In general, according to one embodiment, a fluid ejection head includes a pressure chamber and a nozzle plate including a nozzle group. The nozzle plate has a discharge face with an upstream side and a downstream side. The nozzle group is in fluid communication with the pressure chamber and includes a first nozzle on the upstream side of the discharge face, a second nozzle on the downstream side of the discharge face, and a third nozzle between the first and second nozzles. Central axes of the first and second nozzles are inclined with respect to a central axis of the third nozzle such that the central axes of the first and second nozzles intersect the central axis of the third nozzle. A flow channel dimension (such as minimum opening dimension, taper rate, and/or throttle dimension) of the third nozzle is different than corresponding flow channel dimensions of the first and second nozzles.
Hereinafter, an ink jet recording apparatus 1, as an example of a fluid ejection apparatus, according to a first embodiment and an ink jet head 31 as an example of a fluid ejection head, will be described with reference to
As illustrated in
The ink jet recording apparatus 1 is a fluid ejection apparatus that forms an image on paper P by ejecting fluid, such as an ink, onto the paper P while transporting the paper P along a transport path A1. The transport path A1 extends from the medium supply unit 12 to the medium discharge unit 14 and passes through the image forming unit 13.
The housing 11 forms an exterior of the ink jet recording apparatus 1. A discharge hole 11a for discharging the paper P to the outside is provided on the housing 11.
The medium supply unit 12 includes a plurality of paper feeding cassettes 12a in the housing 11. The paper feeding cassettes 12a are each formed in, for example, a box-like shape of a predetermined size having an opening on an upper side and are configured to be able to stack and hold a plurality of sheets of paper P of various sizes.
The medium discharge unit 14 includes a paper discharge tray 14a near the discharge hole 11a of the housing 11. The paper discharge tray 14a is configured to hold the paper P discharged from the discharge hole 11a.
The image forming unit 13 includes a support unit 17 that supports the paper P, and a plurality of head units 30 above the support unit 17.
The support unit 17 includes a transport belt 18 in a loop shape in a region where an image is formed on the paper P, a support plate 19 for supporting the transport belt 18 from a back side, and a plurality of belt rollers 20 provided on the back side of the transport belt 18.
The support unit 17 supports the paper P on a holding surface 18a, which is an upper surface of the transport belt 18, during the image formation process and moves the transport belt 18 at a predetermined speed by rotation of the belt roller 20, and thereby, the paper P is transported through the image forming unit 13 to a downstream side.
The head unit 30 comprises a plurality of ink jet heads 31 for four colors (CMYK), ink tanks 32, as fluid holding tanks, respectively mounted on the ink jet heads 31, a connection flow path 33 connecting the ink jet head 31 to the respective ink tank 32, and a circulation pump 34 that is a circulation unit. The head unit 30 is a circulation type head unit that continuously circulates fluid from the ink tank 32 to a pressure chamber C1 and a common chamber C2 (see
In the example embodiments described herein, the ink jet heads 31C, 31M, 31Y, and 31K for four colors, cyan, magenta, yellow, and black, are provided. Ink tanks 32C, 32M, 31Y, and 31K are provided for these colors. Each ink tank 32 is connected to an ink jet head 31 through a connection flow path 33. The connection flow path 33 includes a supply flow path 33a connected to a supply hole of the ink jet head 31 and a recovery flow path 33b connected to the discharge hole of the ink jet head 31.
In addition, the ink tanks 32 are connected to a negative pressure control apparatus such as a pump (not specifically depicted in the drawings). When the negative pressure control apparatus applies a negative pressure to an ink tank 32 in response to liquid levels in the ink jet head 31 and the ink tank 32, the ink at each of nozzles 41b, 41c, and 41d of the ink jet head 31 is formed into a meniscus of a predetermined shape.
The circulation pump 34 is a fluid displacement pump configured from, for example, a piezoelectric pump. The circulation pump 34 is connected to the supply flow path 33a. The circulation pump 34 is connected to a drive circuit of the control unit 16 by wiring, such that the circulation pump 34 can be controlled by a central processing unit (CPU) 16a. The circulation pump 34 circulates the fluid in the circulation flow path including the ink jet head 31 and the ink tank 32.
The transport apparatus 15 transports the paper P along the transport path A1 through the image forming unit 13 from the paper feeding cassette 12a to the paper discharge tray 14a. The transport apparatus 15 includes guide plate pairs 21a to 21h disposed along the transport path A1 and a plurality of transport rollers 22a to 22h.
Each of the guide plate pairs 21a to 21h includes a pair of plates disposed so as to face each other with the transported paper P being transported therebetween to guide the paper P along the transport path A1.
The transport rollers 22a to 22h include a paper feeding roller 22a, multiple pairs of transport rollers 22b to 22g, and a pair of discharge rollers 22h. The transport rollers 22a to 22h rotate by being driven under the control of the CPU 16a of the control unit 16 to send the paper P to a downstream side along the transport path A1. Sensors for detecting the transport status of the paper are disposed in various places in the transport path A1.
The control unit 16 includes the CPU 16a which is a controller, a read only memory (ROM) for storing various programs and the like, a random access memory (RAM) for temporarily storing various variable data, image data, and the like, and an interface unit for inputting data from the outside and outputting data to the outside.
As illustrated in
The nozzle plate 41 is formed in a rectangular plate shape. The nozzle plate 41 includes a plurality of nozzle groups 41a, each of which includes a nozzle 41b, a nozzle 41c, and a nozzle 41d communicating with a pressure chamber C1.
In the example embodiments described herein, nozzle groups 41a, each including three nozzles, are formed in parallel for each row of the pressure chambers C1, which are disposed in two parallel rows. Each of the nozzle groups 41a includes nozzles 41b, 41c, and 41d that communicate with one pressure chamber C1. In each of the nozzle groups 41a, the three nozzles 41b, 41c, and 41d are provided in parallel in the X direction.
As illustrated in
Here, when a distance between the nozzles 41b, 41c, and 41d is referred to as a nozzle pitch or a pitch Pt, a distance between the nozzles 41b, 41c, and 41d and the paper P is referred to as G, and an axis angle between an axis of the nozzle at the end and the central axis of the nozzle 41d at the center of the nozzle group 41a is referred to as θ, the relationship
2×Pt/G>tan θ>0 (Equation 1)
will hold. That is, a distance between droplets Id as-landed on the paper P is smaller than the pitch Pt between the nozzles 41b, 41c, and 41d.
In the nozzle group 41a of nozzles 41b, 41c, and 41d disposed to face a common pressure chamber C1, a shape of the nozzle 41d (at the center of the nozzle group 41a) is different from shapes of the nozzles 41b and 41c (which are disposed at either end of the nozzle group 41a), such that an ejection speed of the fluid is adjusted. That is, among the three or more nozzles 41b, 41c, and 41d that are aligned in parallel, the nozzle 41d at the center has a smaller diameter (also referred to as a throttling dimension) than the nozzles 41b and 41c at either of the end portions along the parallel direction such that the ejection speed is uniform among the three or more nozzles. In other words, the nozzle 41d, which is located at a position more distant from a supply path 44a or a recovery path 44b than the nozzles 41b, 41c, is formed to have a smaller diameter than the nozzles 41b and 41c located closer to the supply path 44a or the recovery path 44b.
Specifically, an area of the opening of the nozzle 41d is formed to be smaller than an area of the openings of the nozzles 41b and 41c. That is, a nozzle diameter Dn1 on the ejection surface side (that is the minimum diameter (throttling dimension) of the nozzle 41d of a generally cylindrical shape) is configured to be smaller than a nozzle diameter Dn2 on the ejection surface side (that is the minimum diameter (throttling dimension) of the nozzles 41b and 41c). For example, the diameter of the nozzle 41d is 27 μm and the diameters of the nozzles 41b and 41c are 30 μm. In this example, a ratio between the diameters of nozzles in the nozzle group 41a is the diameter of nozzle at the central portion to the diameter of nozzle at the ends, that is, 9:10.
The base plate 42 is formed in a rectangular shape, and is bonded to face the nozzle plate 41 with the frame 43 interposed therebetween. A common chamber C2 is formed between the base plate 42 and the nozzle plate 41.
A piezoelectric block 45 including a plurality of piezoelectric elements 45a which acts as drive elements is provided on a surface of the base plate 42 facing the nozzle plate 41. The piezoelectric block 45 has an elongated shape in which a longitudinal direction extends in the first direction, and includes a plurality of piezoelectric elements 45a in parallel in the second direction. In the second direction, a groove for forming the pressure chamber C1 is formed between adjacent piezoelectric elements 45a. The piezoelectric element 45a is formed of a piezoelectric ceramic material such as lead zirconate titanate (PZT). Electrode 47 are formed on both end surfaces of the piezoelectric elements 45a in the parallel direction. The electrodes 47 are electrically connected to a circuit board 50 via a wiring pattern 48.
In the pair of piezoelectric blocks 45, positions of the respective piezoelectric elements 45a are shifted in the second direction by one-half of the arrangement pitch of the piezoelectric elements 45a. That is, as illustrated in
The base plate 42 has a supply hole 46a and a recovery hole 46b. The supply hole 46a is a through-hole penetrating the base plate 42 in a thickness direction, and communicates with the supply path 44a of the manifold 44. The recovery hole 46b is a through-hole penetrating the base plate 42 in the thickness direction, and communicates with the recovery path 44b of the manifold 44. That is, the supply hole 46a and the recovery hole 46b are connected to an external side of the nozzle group 41a in the first direction that is a juxtaposed direction in which the nozzles 41b, 41c, and 41d are disposed.
The frame 43 is formed in a rectangular frame shape and is disposed between the base plate 42 and the nozzle plate 41. The frame 43 has a predetermined thickness and forms the common chamber C2 between the base plate 42 and the nozzle plate 41.
The manifold 44 is a rectangular block shape and is bonded to the base plate 42. The manifold 44 has ink flow channels that communicate with the common chamber C2. Each ink flow channel includes supply path 44a and the recovery path 44b. The supply path 44a is fluidly connected to the supply flow path 33a, and the recovery path 44b is fluidly connected to the recovery flow path 33b. The circuit board 50 is provided on the outer surface of the manifold 44. The circuit board 50 has a drive IC 51 mounted thereon. The drive IC 51 is electrically connected to the electrode 47 of the piezoelectric element 45a via flexible printed circuits (FPC) 52 and the wiring pattern 48.
When the nozzle plate 41, the base plate 42, the frame 43, and the manifold 44 are assembled together as described, the ink jet head 31 is formed and provides a plurality of pressure chambers C1 therein and ink flow channels connecting these pressure chambers. The pressure chambers C1 are separated from one another by the piezoelectric elements 45a serving as dividing walls.
An operation of the ink jet recording apparatus 1 configured as described above will be described below. The CPU 16a detects a print instruction made by an operation of a user form input unit, for example, via an interface. Then, if the print instruction is detected, the CPU 16a controls the transport apparatus 15 to transport the paper P and outputs a print signal to the head unit 30 at a predetermined timing to drive the ink jet head 31. Based on an image signal corresponding to image data, the piezoelectric elements 45a are selectively drive such that ink is discharged from the nozzles 41b, 41c, and 41d adjacent to each piezoelectric element 45a, and thereby an image is formed on the paper P held on the transport belt 18.
During a fluid ejection operation, the CPU 16a controls the drive circuit to apply a drive voltage to the electrode 47 on the piezoelectric element 45a via the wiring pattern 48 to deform the piezoelectric elements 45. For example, when the piezoelectric element 45a is driven so as to increase the volume of the pressure chamber C1 and create a negative pressure in the pressure chamber C1, ink is guided back into the pressure chamber C1. When the piezoelectric element 45a is driven as to decrease the volume of the pressure chamber C1 and apply pressure to the inside of the pressure chamber C1, ink droplets are ejected from the nozzles 41b, 41c, and 41d disposed to face the pressure chamber C1. Then, the droplets Id are ejected onto the paper P disposed to face the nozzles.
The CPU 16a controls the circulation pump 34 to circulate the fluid in a circulation flow path passing through the ink tank 32 and the ink jet head 31. Through the circulation operation, the ink in the ink tank 32 flows into the common chamber C2 having a flow path portion through a supply hole (not specifically depicted in the drawings), and is supplied to the plurality of pressure chambers C1.
In the ejection operation, a distance G (see
The distance G between the ejection surface and the paper P is set to 2 mm to 3 mm and the transport speed of the paper P is set to 0.4 m/sec for the fluid ejection operations illustrated in
As illustrated in
In the first comparative examples, as illustrated in
For example, as illustrated in
As illustrated in
In contrast, in the ink jet head 31 according to the present embodiment, the nozzle 41d at the center portion has a smaller in diameter than the nozzles (41b, 41c) at the ends of the nozzle group. As a result, the ejection speed from the nozzle 41d increases, and as a result, the ejection speeds of the nozzles 41b, 41c, and 41d can be made more uniformed. Accordingly, the landing timing of droplets from the nozzle group can be adjusted as compared to the comparative examples, and thereby, the landing positions of droplets from each nozzle in the nozzle group 41 are gathered more closely at desirable places and a more desirable landing shape is obtained as compared to the comparative examples. Among the three nozzles 41b, 41c, and 41d in the ink jet head 31, the pressure of the nozzle 41d at the central portion is higher than pressures of the nozzles 41b and 41c when ejecting the ink. Therefore, the desirable landing shape can be obtained.
The ink jet head 31 according to the first embodiment includes a nozzle plate including a nozzle group 41a including three nozzles 41b, 41c, and 41d communicating with the common pressure chamber C1, and thereby, a large amount of the fluid can be ejected in one ejection drive. That is, in the ink jet head 31 according to the first embodiment, a large amount of fluid can be ejected, and the landing positions are gathered to obtain a desirable landing shape.
The ink tank 32 for storing fluid is connected to the ink jet head 31 according to the first embodiment, and the fluid is circulated through a circulation path that passes through the ink jet head 31 and the fluid tank. That is, in the ink jet head 31 according to the first embodiment, even if the fluid has a high specific gravity or the fluid has a high viscosity, a large amount of fluid can still be ejected, and the landing positions are gathered to obtain a desirable landing shape.
The present disclosure is not limited to the example embodiments described above, and the configuration elements can be modified without departing from the gist of the present disclosure.
For example, in the first embodiment, nozzle diameters on the ejection surfaces of the nozzles 41b, 41c, and 41d are made different from each other such that different nozzle shapes are provided to adjust the ejection speed from each nozzle, but the present disclosure is not limited to this particular example. For example, as depicted in
In addition, the position at which the nozzle diameters (throttling dimensions) are different from each other is not limited to the ejection surface, but may instead be at an intermediate portion of the nozzle. For example, in a nozzle plate 241 illustrated in
A shape of an opening of a nozzle is not limited to a circular shape, and other shapes may be used.
The nozzle 341d having a circle-like shape has a faster ejection speed than the nozzles 341b, 341c having an elliptical shape, thus the ejection speed of the nozzle 341d can be increased and the ejection speeds of the three nozzles 341b, 341c, and 341d can be made equal by making the nozzle 341d have a shape close to a circle. Therefore, in the same manner as in the first embodiment, a landing position can be adjusted and a desirable landing shape obtained. Among the three nozzles 341b, 341c, and 341d in the nozzle plate 341, a pressure of the nozzle 341d at the central portion is higher than pressures of the nozzles 341b and 341c when ejecting the ink. Therefore, a desirable landing shape is obtained.
In example embodiments described above, the nozzles 341b and 341c have a long elliptical axis along the X direction, and thereby, there are effects in which the nozzles 341b and 341c can be prevented from being too close to an edge portion of a groove, and the amount of flow and the ejection speed can be adjusted efficiently in a narrow space. The major axis of the elliptical shape for the nozzles may be along in the X direction and the minor axis along in Y second direction or vice versa.
The number of nozzles in each nozzle group is not limited to three, and may be four or more. For example, a nozzle plate 441 illustrated in
The ink jet recording apparatus 1 according to the example embodiments described above is an ink jet printer which forms a two-dimensional image on an image forming medium S by using ink. However, the ink jet recording apparatus is not limited to this particular example. The ink jet recording apparatus may be, for example, a 3D printer, an industrial manufacturing machine, a medical machine (e.g., a liquid dispensing apparatus), or the like. When the ink jet recording apparatus according to an embodiment is a 3D printer, the ink jet recording apparatus ejects a binder or the like for solidifying a material to become a harden substance for forming a three-dimensional object.
The ejection method is not also limited to the above examples. For example, other methods such as a bubble method and a Kaiser method, which uses piezoelectric elements, can also be applied.
The ink jet recording apparatus 1 according to the example embodiments described above includes four ink jet heads 31, and colors of ink used by each ink jet head 31 are cyan, magenta, yellow, and black. However, the number of ink jet heads 31 included in the ink jet recording apparatus is not limited to four, and may be any number. The colors and characteristics of the ink used by each ink jet head 31 are not limited. An ink jet head 31 can also eject transparent gloss ink, ink that develops color when irradiated with infrared rays or ultraviolet rays, or other special inks. Furthermore, the ink jet heads 31 may be able to eject fluids other than the ink. The fluid ejected by the ink jet head 31 may be dispersion fluid such as suspension. Fluid other than the ink ejected by the ink jet head 31 includes fluid such as a resist material for forming a wiring pattern of a printed wiring board, a fluid including a cell for artificially forming a tissue or an organ, binder such as adhesive, wax, a fluid resin precursor, and the like.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-205250 | Oct 2017 | JP | national |
| 2018-136653 | Jul 2018 | JP | national |
