Patent Grant
11333144
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2019-028314, filed on Feb. 20, 2019, the entire contents of which are incorporated herein by reference.
An embodiment to be described here generally relates to a piezoelectric pump and a liquid ejection device.
For example, there is known a technique of using a piezoelectric pump in a liquid ejection device, the liquid ejection device being used in a recording apparatus of a ink circulating system including an inkjet head, or other apparatuses. The piezoelectric pump changes the volume of a pressure chamber by causing a bending displacement of a diaphragm, suctions liquid from an inlet, and then ejects the liquid from an outlet.
If the liquid contains air bubbles, the air bubbles are possibly accumulated in the pressure chamber. In this regard, there is a demand for a piezoelectric pump capable of suitably discharging air bubbles of a pressure chamber.
According to one embodiment, a piezoelectric pump includes a pressure chamber, a diaphragm, a groove, a first check valve, and a second check valve. The pressure chamber has a variable volume. The diaphragm varies the volume of the pressure chamber by deforming. The groove is provided to a bottom portion of the pressure chamber and includes an inlet and an outlet on a bottom portion of the groove, liquid being caused to flow in the pressure chamber through the inlet and to be discharged from the pressure chamber through the outlet. The first check valve is provided to the inlet and regulates a flow of the liquid. The second check valve is provided to the outlet and regulates the flow of the liquid.
Hereinafter, a piezoelectric pump 100, a liquid ejection device 10, and a recording apparatus 1 using the liquid ejection device 10 including the piezoelectric pump 100 according to an embodiment will be described with reference to
(Piezoelectric Pump 100)
First, the piezoelectric pump 100 according to the embodiment will be described with reference to
As illustrated in
The first port 111 is connected to piping or the like that supplies liquid on a primary side of the piezoelectric pump 100. The first port 111 is connected to the first buffer chamber 112. For example, the first port 111 is formed of a part of the pump main body 101. For example, the first port 111 is formed in a cylinder connectable to the piping.
The first buffer chamber 112 is provided to a secondary side of the first port 111 and also to a primary side of the pressure chamber 114. The first buffer chamber 112 forms a space having a predetermined volume. The first buffer chamber 112 is formed by, for example, partially hollowing the pump main body 101.
The inlet 113 fluidly connects the first buffer chamber 112 and the pressure chamber 114 to each other. The inlet 113 is a hole for fluidly connecting the first buffer chamber 112 and the pressure chamber 114 of the pump main body 101 to each other. For example, the inlet 113 includes a plurality of first holes 124. The first check valve 104 is provided on the pressure chamber 114 side of the inlet 113.
The pressure chamber 114 is configured by the pump main body 101, the diaphragm 102, and the piezoelectric element 103. The pressure chamber 114 is formed to have a predetermined volume. Further, the volume of the pressure chamber 114 varies when the piezoelectric element 103 provided to the diaphragm 102 bends and when the diaphragm 102 deforms (see
As a specific example, the pressure chamber 114 is configured by a recess 121 having a bottomed cylindrical shape, which is formed in the pump main body 101, the diaphragm 102 provided on the opening end side of the recess 121, and the piezoelectric element 103 provided to an outer surface (surface on the opening end side) of the diaphragm 102. In other words, the pressure chamber 114 is formed of the recess 121 of the pump main body 101 and includes the diaphragm 102 provided to the opening end side of the recess 121 and the piezoelectric element 103 provided to the outer surface of the diaphragm 102. Further, the inlet 113 and the outlet 115 are provided to the bottom portion of the pressure chamber 114, that is, a bottom portion 121b of the recess 121 of the pump main body 101, the bottom portion 121b facing the diaphragm 102. The inlet 113 and the outlet 115 include the first check valve 104 and the second check valve 105, respectively. The first check valve 104 and the second check valve 105 regulate a direction of the flow of liquid in the pressure chamber 114. As a specific example, liquid flows in the pressure chamber 114 from the inlet 113. The liquid is then discharged from the outlet 115 to the outside of the pressure chamber 114.
Further, as illustrated in
As illustrated in
As illustrated in
As illustrated in
In other words, the pump main body 101 includes the first port 111, the first buffer chamber 112, the inlet 113, a part of the pressure chamber 114, the outlet 115, the second buffer chamber 116, and the second port 117.
As illustrated in
The pump main body 101 includes the recess 121 having a bottomed cylindrical shape, for example, at one end in an axis direction X illustrated in
As illustrated in
As illustrated in
As illustrated in
For example, as illustrated in
For example, as illustrated in
As a specific example, as illustrated in
As illustrated in
For example, the distance H1 from the surface of the diaphragm 102, which faces the bottom portion 121b, to the surface of the bottom portion 121b, which faces the diaphragm 102, is set to 100 μm. Further, for example, the depth H2 from the surface of the bottom portion 121b, which faces the diaphragm 102, to the surface of the groove 121c, which faces the diaphragm 102, is set to 400 μm. Further, for example, a width W of the groove 121c is set to be larger than the distance H1 from the surface of the diaphragm 102, which faces the bottom portion 121b, to the surface of the bottom portion 121b, which faces the diaphragm 102. Here, the width W of the groove 121c is a width in a direction orthogonal to an axis direction X of the recess 121 and is also a width in a direction orthogonal to a direction in which the groove 121c extends.
The plurality of first holes 124 form the inlet 113. The plurality of second holes 125 form the outlet 115. For example, the plurality of first holes 124 and the plurality of second holes 125 are provided at symmetric positions of the bottom portion 121b.
The diaphragm 102 is, for example, a disc-like metal plate. For example, the diaphragm 102 is made of stainless material. For example, in order to avoid direct contact with liquid, the diaphragm 102 includes a coating layer made of resin material on the surface on the pressure chamber 114 side. The diaphragm 102 is connected to, for example, a device that supplies an alternating-current (AC) voltage via wiring 106. Such a voltage supply device is, for example, a circulation pump drive circuit 74 of the module controller 38 of the recording apparatus 1. The module controller 38 will be described later. Note that the material forming the diaphragm 102 is not limited to the stainless material, and the material may be, for example, a material such as nickel, brass, gold, silver, or copper.
The piezoelectric element 103 is piezoelectric ceramics. The piezoelectric element 103 is formed of, for example, lead zirconate titanate (PZT). The piezoelectric element 103 is, for example, a circular plate having an outer diameter, which is smaller than the outer diameter of the diaphragm 102 and the inner diameter of the wall portion 121a of the recess 121. The piezoelectric element 103 is connected to, for example, the circulation pump drive circuit 74 of the module controller 38 via the wiring 106.
As illustrated in
The piezoelectric element 103 constitutes an actuator together with the diaphragm 102. When an AC voltage is applied to the piezoelectric element 103 in the thickness direction, the electric field is thus applied to the piezoelectric element 103 in the thickness direction, and the piezoelectric element 103 expands and contracts in the surface direction. The diaphragm 102 deforms by deformation (expansion and contraction) of the piezoelectric element 103 to increase or decrease the volume of the pressure chamber 114. Note that the material forming the piezoelectric element 103 is not limited to PZT, and other materials may be used.
As illustrated in
This is because the polyimide material is resistant to various ink materials such as water-based ink, oil-based ink, volatile solvent ink, and ultraviolet (UV) ink, which are liquid to be ejected in the recording apparatus 1. Note that the first check valve 104 may also be made of, in place of polyimide, various materials including resins or metals highly resistant to ink, such as polyethylene terephthalate (PET), ultrahigh molecular weight polyethylene (PE), polypropylene (PP), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), perfluoro alkoxy alkane (PFA), perfluoro ethylene propylene copolymer (FEP), ethylene-tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), aluminum, stainless, and nickel. Note that any material resistant to liquid can be set for the first check valve 104 as appropriate.
As illustrated in
Next, an operation example of the piezoelectric pump 100 thus configured will be described with reference to
As illustrated in
Next, a voltage opposite to the voltage applied in the state illustrated in
If the AC voltage is continuously applied to the piezoelectric element 103, the piezoelectric element 103 repeats a bending displacement to move away from the bottom portion 121b, which is illustrated in
Further, in the pressure chamber 114, part of the liquid moved from the inlet 113 to the pressure chamber 114 flows along the pair of first grooves 121c1 and the pair of second grooves 121c2 as indicated by the arrows in
At that time, the distance H1 from the surface of the diaphragm 102, which faces the bottom portion 121b, to the surface of the bottom portion 121b, which faces the diaphragm 102, is set to be smaller than the depth H2 (the depth of the groove 121c) from the surface of the bottom portion 121b, which faces the diaphragm 102, to the surface of the groove 121c, which faces the diaphragm 102. Therefore, since a flow path friction of the groove 121c is smaller than another flow path friction within the pressure chamber 114, the liquid moved from the inlet 113 to the pressure chamber 114 moves to the outlet 115 through the groove 121c. Thus, as illustrated in
As described above, the piezoelectric pump 100 includes the groove 121c in the bottom portion 121b of the pressure chamber 114. The depth H2 of the groove 121c is set to be larger than the distance H1 between the diaphragm 102 and the bottom portion 121b of the pressure chamber 114. Therefore, in the flow path friction within the pressure chamber 114 from the inlet 113 to the outlet 115, the flow path friction in the groove 121c is smaller than the flow path friction between the diaphragm 102 and the bottom portion 121b.
Accordingly, the liquid moved from the inlet 113 and the air bubbles 190 included in the liquid move through the groove 121c within the pressure chamber 114 and then move from the outlet 115 to the secondary side. In other words, in the flow volume of the liquid passing from the inlet 113 to the outlet 115 through the pressure chamber 114, the proportion of the flow volume of the liquid passing through the groove 121c within the pressure chamber 114 is large. Thus, the air bubbles 190 included in the liquid pass through the groove 121c and are then discharged from the outlet 115. This can prevent the air bubbles from being accumulated within the pressure chamber 114. Further, the air bubbles pre-existing within pressure chamber 114 are also discharged from the outlet 115 after passing through the groove 121c.
More specifically, the groove 121c includes the pair of first grooves 121c1 and the pair of second grooves 121c2. As described above, the first groove 121c1 is a groove provided on the outer circumferential edge side of the bottom portion 121b. In other words, the first groove 121c1 is a groove provided along the inner circumferential surface of the wall portion 121a of the pressure chamber 114. As described above, the second groove 121c2 is a groove provided on the center side of the bottom portion 121b. In other words, the second groove 121c2 is a groove provided close to the center of the bottom portion 121b in the pressure chamber 114. Further, the depth H2 of the groove 121c is set to be larger than the distance H1 between the diaphragm 102 and the surface 121s of the bottom portion 121b in the pressure chamber 114. With this configuration, the groove 121c is disposed over the entire region of the bottom portion 121b of the recess 121, and a cross-sectional area of the flow path of the groove 121c can be ensured. The cross-sectional area of the flow path is a cross-sectional area orthogonal to a direction in which the liquid flows. Therefore, it is possible to help the liquid between the diaphragm 102 and the surface 121s of the bottom portion 121b move to the outlet 115 via the groove 121c and to set the flow volume in the groove 121c to a suitable flow volume.
Thus, for example, the pair of first grooves 121c1 allows the air bubbles 190 existing on the outer side in a radial direction of the pressure chamber 114 to be guided to the outlet 115. Further, the pair of second grooves 121c2 allows the air bubbles 190 existing close to the center of the pressure chamber 114 to be guided to the outlet 115. Therefore, the air bubbles 190 can be prevented from being accumulated within the pressure chamber 114.
In such a manner, the piezoelectric pump 100 can prevent the air bubbles 190 from hindering the pressurization and depressurization within the pressure chamber 114 when the diaphragm 102 bends. Thus, the piezoelectric pump 100 can suppress a reduction in flow volume of the liquid to be ejected from the outlet 115 and can eject a desired amount of liquid.
As described above, the piezoelectric pump 100 according to this embodiment allows the air bubbles within the pressure chamber 114 to be suitably discharged.
(Liquid Ejection Device 10 and Recording Apparatus 1)
Next, a liquid ejection device 10 including the piezoelectric pump 100 and a recording apparatus 1 including such a liquid ejection devices 10 will be described with reference to
As illustrated in
As illustrated in
The liquid ejection devices 10 eject respective colors, e.g., cyan ink, magenta ink, yellow ink, black ink, and white ink, but the color or characteristics of the ink I to be used are not limited. The liquid ejection device 10 can eject transparent and glossy ink, special ink whose color comes out when irradiated with infrared rays or ultraviolet rays, or other ink, in place of white ink, for example. The plurality of liquid ejection devices 10 have the same configuration but use different types of ink I, for example.
The liquid ejection head 20 is, for example, an inkjet head. As illustrated in
Next, the circulation device 30 will be described. The circulation device 30 is, for example, integrally coupled to the upper portion of the liquid ejection head 20 by metal coupling parts.
As illustrated in
Further, as illustrated in
The cartridge 51 (liquid tank) can retain the ink I, and the inner space of the cartridge 51 is opened to the atmosphere (released to the atmosphere).
As illustrated in
As illustrated in
The first circulation pump 33 is the piezoelectric pump 100. As illustrated in
As illustrated in
The buffer tank 35 is connected to the bypass flow path 34. Specifically, the bypass flow path 34 includes a first bypass flow path 34a and a second bypass flow path 34b. The first bypass flow path 34a connects a predetermined lower portion of one of a pair of side walls of the buffer tank 35 and the second flow path 31b to each other. The second bypass flow path 34b connects a predetermined lower portion of the other one of the pair of side walls of the buffer tank 35 and the third flow path 31c to each other.
For example, the first bypass flow path 34a and the second bypass flow path 34b have the same length and diameter and each have the diameter smaller than a diameter of the circulation path 31. For example, the diameter of the circulation path 31 is set to approximately twice to five times the diameter of each of the first bypass flow path 34a and the second bypass flow path 34b. For example, in the first bypass flow path 34a and the second bypass flow path 34b, a distance between a position at which the second flow path 31b and the first bypass flow path 34a are connected to each other and the supply port 20a of the liquid ejection head 20 is set to be equal to a distance between a position at which the third flow path 31c and the second bypass flow path 34b are connected to each other and the recovery port 20b of the liquid ejection head 20.
A cross-sectional area of the flow path of the buffer tank 35 is larger than the cross-sectional area of the bypass flow path 34. The buffer tank 35 is formed to be capable of storing liquid. The buffer tank 35 is a rectangular box-like tank including, for example, an upper wall, a lower wall, a rear wall, a front wall, and the pair of right and left side walls, and forms a housing chamber 35a in which liquid is stored.
The position at which the first bypass flow path 34a and the buffer tank 35 are connected to each other and the position at which the second bypass flow path 34b and the buffer tank 35 are connected to each other are set at the same height. Within the buffer tank 35, the lower region of the housing chamber 35a contains the ink I flowing in the bypass flow path 34, and the upper region of the housing chamber 35a forms an air chamber 35b. In other words, the buffer tank 35 is capable of storing a predetermined amount of liquid and air. Further, the buffer tank 35 includes the on-off valve 37 and a pressure sensor 39. The on-off valve 37 can cause the air chamber 35b of the buffer tank 35 to be opened to the atmosphere.
The second circulation pump 36 is the piezoelectric pump 100. As illustrated in
The on-off valve 37 illustrated in
The pressure sensor 39 illustrated in
The pressure sensor 39 outputs the pressure of the air chamber 35b as an electrical signal by using, for example, a semiconductor piezoresistive pressure sensor. The semiconductor piezoresistive pressure sensor includes a diaphragm and a semiconductor strain gauge. The diaphragm receives an external pressure. The semiconductor strain gauge is formed on a surface of the diaphragm. The semiconductor piezoresistive pressure sensor converts a change in electrical resistance into an electrical signal and detects a pressure, the change in electrical resistance being due to the piezoresistive effect produced in the strain gauge along with deformation of the diaphragm by the external pressure.
As illustrated in
The processor 71 is an arithmetic element to execute arithmetic processing, for example, a central processing unit (CPU) 71. The CPU 71 performs various types of processing on the basis of data such as programs stored in the memory 72. The CPU 71 executes programs stored in the memory 72 to function as a control circuit capable of executing various types of control.
The memory 72 is storage to store various types of information. The memory 72 includes, for example, a read only memory (ROM) 72a and a random access memory (RAM) 72b.
The ROM 72a is a non-volatile read-only memory. The ROM 72a stores programs, data to be used in the programs, and the like. For example, the ROM 72a stores, as control data to be used for pressure control, a calculation formula for calculating an ink pressure of a nozzle hole, a target pressure range, and various set values such as maximum adjustment values of the respective pumps.
The RAM 72b is a volatile memory, which functions as a working memory. The RAM 72b temporarily stores data being processed by the CPU 71, or the like. Further, the RAM 72b temporarily stores programs to be executed by the CPU 71.
The communication interface 73 is an interface for communicating with another device. The communication interface 73 relays, for example, communication with the host control device 13, which sends print data to the liquid ejection device 10.
The circulation pump drive circuit 74 applies an AC voltage to the piezoelectric element 103 of the piezoelectric pump 100 under the control of the CPU 71 to drive the piezoelectric pump 100. Accordingly, the circulation pump drive circuit 74 causes the ink I to circulate within the circulation path 31. The circulation pump drive circuits 74 are provided in the same number as the number of first circulation pump 33 and second circulation pump 36 and are respectively connected to the first circulation pump 33 and the second circulation pump 36. The circulation pump drive circuit 74 connected to the first circulation pump 33 applies a drive voltage to the piezoelectric element 103 of the first circulation pump 33. The circulation pump drive circuit 74 connected to the second circulation pump 36 applies a drive voltage to the piezoelectric element 103 of the second circulation pump 36.
The valve drive circuit 76 drives the on-off valve 37 under the control of the CPU 71 and causes the air chamber 35b of the buffer tank 35 to be opened to the atmosphere.
The liquid ejection head drive circuit 77 drives the liquid ejection head 20 by applying a voltage to the actuator of the liquid ejection head 20 under the control of the CPU 71. Accordingly, the liquid ejection head drive circuit 77 causes the ink I to be ejected from the nozzle hole of the liquid ejection head 20.
In the configuration described above, the CPU 71 communicates with the host control device 13 through the communication interface 73 to receive various types of information such as operation conditions. Further, various types of information acquired by the CPU 71 are sent to the host control device 13 of the recording apparatus 1 through the communication interface 73.
Further, the CPU 71 acquires a detection result from the pressure sensor 39 and controls the operation of the circulation pump drive circuits 74 and the valve drive circuit 76 on the basis of the acquired detection result. For example, the CPU 71 controls the circulation pump drive circuits 74 on the basis of the detection result of the pressure sensor 39. Accordingly, the CPU 71 controls the liquid pump-out capability of the first circulation pump 33 and the second circulation pump 36. Accordingly, the CPU 71 adjusts the ink pressure of the nozzle hole.
Further, the CPU 71 controls the valve drive circuit 76 to open and close the on-off valve 37. Accordingly, the CPU 71 adjusts the liquid level of the buffer tank 35.
Further, the CPU 71 acquires the detection result from the pressure sensor 39. The CPU 71 controls the liquid ejection head drive circuit 77 on the basis of the acquired detection result. Accordingly, the CPU 71 causes ink droplets to be ejected on a recording medium from the nozzle hole of the liquid ejection head 20. Specifically, the CPU 71 inputs an image signal, which corresponds to image data, to the liquid ejection head drive circuit 77. The liquid ejection head drive circuit drives the actuator of the liquid ejection head 20 corresponding to the image signal. When the liquid ejection head drive circuit 77 drives the actuator of the liquid ejection head 20, the actuator deforms. Accordingly, an ink pressure (nozzle surface pressure) of a nozzle hole located to face the actuator changes. The nozzle surface pressure is a pressure given by the ink I of the pressure chamber 114 to the meniscus formed by the ink I in the nozzle hole. When the nozzle surface pressure exceeds a predetermined value, which is defined by the shape of the nozzle hole, the characteristics of the ink I, and the like, the ink I is ejected from the nozzle hole. Accordingly, the CPU 71 causes an image, which corresponds to the image data, to be formed on a recording medium S.
As described above, the recording apparatus 1 uses the piezoelectric pumps 100 as the first circulation pump 33 and the second circulation pump 36 of the circulation device 30 of the liquid ejection device 10. With this configuration, the cartridge 51 is set to be opened to the atmosphere. Therefore, even if the ink I circulating within the circulation path 31 contains the air bubbles 190, the air bubbles 190 are discharged from the first circulation pump 33 and the second circulation pump 36. Thus, the first circulation pump 33 and the second circulation pump 36 can prevent the flow volume of the ink I, which is supplied to the secondary side, from being reduced. Therefore, the recording apparatus 1 can supply the ink I with a predetermined flow volume to the liquid ejection head 20 and stably control the ink pressure.
As described above, the recording apparatus 1 uses the piezoelectric pumps 100 as the first circulation pump 33 and the second circulation pump 36 and can thus suitably discharge air bubbles within the pressure chamber 114. Therefore, the recording apparatus 1 can stably control the ink pressure of the liquid ejection head 20.
Note that this embodiment is not limited to the example described above and can be embodied while modifying constituent elements without departing from the gist of this embodiment.
For example, in the example described above, the groove 121c of the bottom portion 121b, which is provided to the pressure chamber 114 of the pump main body 101, includes the pair of second grooves 121c2 each having an arc shape curved at a predetermined radius of curvature, but this embodiment is not limited to such an example.
Further, while the above example has described that the piezoelectric pump 100 is used in the recording apparatus 1 that ejects the ink I, but this embodiment is not limited to the example. For example, the piezoelectric pump 100 may be used in a liquid ejection device 10 that ejects liquid other than the ink I. Specifically, the piezoelectric pump 100 can be used in a device that ejects liquid containing conductive particles for forming a wiring pattern of a printed wiring board, for example. Further, the piezoelectric pump 100 can also be used for, for example, 3D printers, industrial production machines, and medical applications.
Further, in the example described above, the recording apparatus 1 includes, as the circulation device 30, the buffer tank 35 including the housing chamber 35a, in the bypass flow path 34, and in order to adjust the liquid level of the buffer tank 35, the on-off valve 37 is opened and closed, but this embodiment is not limited to the example. For example, the recording apparatus 1 does not necessarily include the buffer tank 35 and the on-off valve 37. Further, the recording apparatus 1 may include, for example, a filter and a trap for collecting the air bubbles 190 on the secondary side of the first circulation pump 33 of the circulation device 30.
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 inventions. 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 inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-028314 | Feb 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 8523538 | Kawamura et al. | Sep 2013 | B2 |
| 9611843 | Hsueh et al. | Apr 2017 | B2 |
| 20070065309 | Nakajima | Mar 2007 | A1 |
| 20080095651 | Onishi | Apr 2008 | A1 |
| 20090060762 | Ishikawa | Mar 2009 | A1 |
| 20120301333 | Smirnov | Nov 2012 | A1 |
| 20140010735 | Tanaka | Jan 2014 | A1 |
| 20160159102 | Kaneko | Jun 2016 | A1 |
| 20180333955 | Oikawa | Nov 2018 | A1 |
| Number | Date | Country |
|---|---|---|
| 102165193 | Aug 2011 | CN |
| 104019018 | Sep 2014 | CN |
| 107364234 | Nov 2017 | CN |
| 2008163902 | Jul 2008 | JP |
| 5003154 | Aug 2012 | JP |
| 20120131857 | Dec 2012 | KR |
| 201500151 | Jan 2015 | TW |
| Entry |
|---|
| Chinese Office Action dated Aug. 23, 2021, mailed in counterpart Chinese Application No. 201911328741.1, 19 pages (with translation). |
| Number | Date | Country | |
|---|---|---|---|
| 20200263678 A1 | Aug 2020 | US |
