JP4862549B2 - Liquid detection device and liquid container equipped with the same - Google Patents

Description

  The present invention relates to a liquid detection device and a liquid container including the same, and more particularly, to a liquid detection device suitable for detecting a remaining amount of liquid in a liquid ejecting apparatus and a liquid container including the same.

  A typical example of a conventional liquid ejecting apparatus is an ink jet recording apparatus provided with an ink jet recording head for image recording. Other liquid ejecting apparatuses include, for example, an apparatus having a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an electrode material (conductive page) used for forming an electrode such as an organic EL display and a surface emitting display (FED). Str) An apparatus equipped with an ejection head, an apparatus equipped with a bioorganic matter ejection head used for biochip production, an apparatus equipped with a sample ejection head as a precision pipette, and the like.

  In an ink jet recording apparatus, which is a typical example of a liquid ejecting apparatus, an ink jet recording head having a pressure generating means for pressurizing a pressure generating chamber and a nozzle opening for ejecting the pressurized ink as ink droplets is mounted on a carriage. Has been.

  The ink jet recording apparatus is configured to be able to continue printing by continuously supplying ink in an ink container to a recording head via a flow path. The ink container is configured as a detachable cartridge that can be easily replaced by a user when ink is consumed, for example.

  Conventionally, the ink consumption management method of the ink cartridge includes a method of managing the ink consumption by calculating the number of ink droplets ejected from the recording head and the amount of ink sucked by maintenance, and calculating the ink consumption in the ink cartridge. There is a method of managing a point in time when a predetermined amount of ink is actually consumed by attaching a surface detection electrode.

  However, the method of managing the ink consumption by calculating the number of ink droplet ejections and the amount of ink by software has the following problems. Some heads have variations in weight of ejected ink droplets. Although the weight variation of the ink droplets does not affect the image quality, the ink cartridge is filled with an amount of ink with a margin in consideration of the accumulation of errors in the ink consumption due to the variation. Therefore, depending on the individual, there is a problem that ink is left by the margin.

  On the other hand, the method for managing the point in time when ink is consumed by the electrode can detect the actual amount of ink, so that the remaining amount of ink can be managed with high reliability. However, since the detection of the ink level depends on the conductivity of the ink, there are disadvantages that the types of ink that can be detected are limited and the electrode sealing structure is complicated. In addition, as a material for the electrode, a noble metal having high conductivity and high corrosion resistance is usually used, which increases the manufacturing cost of the ink cartridge. Furthermore, since it is necessary to mount two electrodes, the number of manufacturing steps increases, resulting in an increase in manufacturing cost.

  An apparatus developed to solve the above problems is disclosed as a piezoelectric apparatus in Japanese Patent Application Laid-Open No. 2001-146024. This piezoelectric device can accurately detect the remaining amount of liquid and does not require a complicated seal structure, and can be used by being mounted on a liquid container.

  That is, according to the piezoelectric device described in Japanese Patent Application Laid-Open No. 2001-146024, the drive pulse forcibly oscillates when ink is present in the space facing the vibrating portion of the piezoelectric device and when ink is not present. The remaining amount of ink in the ink cartridge can be monitored by using the fact that the resonance frequency of the residual vibration signal generated due to the residual vibration (free vibration) of the vibration unit of the piezoelectric device later changes.

  FIG. 13 shows an actuator constituting the conventional piezoelectric device described above. The actuator 106 includes a substrate 178 having a circular opening 161 at the substantially center, a diaphragm 176 disposed on one surface (hereinafter referred to as “surface”) of the substrate 178 so as to cover the opening 161, and The piezoelectric layer 160 disposed on the surface side of the vibration plate 176, the upper electrode 164 and the lower electrode 166 sandwiching the piezoelectric layer 160 from both sides, the upper electrode terminal 168 electrically coupled to the upper electrode 164, and the lower electrode 166 And an auxiliary electrode 172 disposed between the upper electrode 164 and the upper electrode terminal 168 to electrically couple them.

  The piezoelectric layer 160, the upper electrode 164, and the lower electrode 166 each have a circular portion as a main body portion. The circular portions of the piezoelectric layer 160, the upper electrode 164, and the lower electrode 166 form a piezoelectric element.

  The diaphragm 176 is formed on the surface of the substrate 178 so as to cover the opening 161. The vibration region of the diaphragm 176 that actually vibrates is determined by the opening 161. The cavity 162 is formed by the portion of the diaphragm 176 that faces the opening 161 and the opening 161 of the substrate (cavity forming member) 178. The surface of the substrate 178 opposite to the piezoelectric element (hereinafter referred to as “back surface”) faces the inside of the ink container. Thereby, the cavity 162 is configured to come into contact with the liquid (ink). Note that the diaphragm 176 is liquid-tightly attached to the substrate 178 so that the liquid does not leak to the surface side of the substrate 178 even if the liquid enters the cavity 162.

  In the actuator 106 according to the conventional technology described above, the residual vibration (free vibration) of the vibration part generated after the drive pulse is applied to the piezoelectric element to forcibly vibrate the vibration part is counter-electromotive force generated by the same piezoelectric element. Detected as mosquitoes. Then, by utilizing the fact that the residual vibration state of the vibration part changes before and after the liquid level in the ink container passes through the installation position of the actuator 106 (strictly, the position of the cavity 162), the ink remaining amount in the ink container is reduced. Can be detected.

Further, FIGS. 6 to 8 of Japanese Patent Application Laid-Open No. 2001-146024 show a configuration in which the length of the cavity in the lead-out direction of the upper electrode and the lower electrode is made longer than the length in the direction orthogonal thereto.
JP 2001-146024 A

  The conventional actuator (piezoelectric device) 106 described above is mounted on the container wall of the container main body 181 of the ink cartridge 180 as shown in FIG. 14, and the cavity 162 for receiving the ink to be detected is provided in the ink storage space inside the ink container 180. It is comprised so that it may be exposed to.

  However, since the conventional actuator (piezoelectric device) 106 is configured to expose the cavity 162 in the ink storage space inside the ink cartridge 180 as described above, if the ink inside the ink cartridge 180 bubbles due to vibration or the like, Air bubbles easily enter the cavity 162 of the actuator 106. When air bubbles enter the cavity 162 and stay there, the resonance frequency of the residual vibration detected by the actuator 106 becomes faster even though the remaining amount of ink in the ink cartridge 180 is sufficient, and the liquid level becomes higher. There has been a problem in that it is erroneously determined that the amount of ink remaining has passed through the position of the actuator 106.

  Further, if the dimension of the cavity 162 of the actuator 106 is reduced in order to accurately detect the passage timing of the liquid level, an ink meniscus is likely to be formed in the cavity 162. For this reason, even though the liquid level passes through the position of the cavity 162 due to the consumption of ink, the ink remains in the cavity 162, so that the liquid level does not pass through the position of the actuator 106 and the remaining amount of ink. There was a problem of misjudging that there was enough.

  In order to solve the above problem, as proposed in Japanese Patent Application No. 2004-122863 filed by the present applicant, an ink supply path for supplying ink to the cavity, and ink is discharged from the cavity. It is conceivable to provide an ink discharge path for the liquid detection device.

  However, when the planar shape of the cavity of the liquid detection device is circular or square, even if the ink supply path and the ink discharge path are provided, an area in which ink or air bubbles tend to stay is created inside the cavity, and the ink or air bubbles There was a problem that sufficient discharge could not be secured.

  On the other hand, as shown in FIG. 6 to FIG. 8 of Japanese Patent Laid-Open No. 2001-146024, when the planar shape of the cavity is long in one direction, the residual vibration (free vibration) generated in the vibration part after the drive pulse is applied to the piezoelectric element. ) Includes unnecessary vibration different from the residual vibration as the original detection target, and as a result, it is difficult to reliably determine the presence or absence of ink.

The cause of such unnecessary vibration is the vibration between the forced vibration generated in the vibration part when a drive pulse is applied to the piezoelectric element and the residual vibration (free vibration) generated in the vibration part after the forced vibration. This is probably due to the large difference in modes.
The present invention has been made in view of the above situation, and an object thereof is to provide a liquid detection device capable of reliably determining the presence or absence of a liquid and a liquid container including the device.

The above object of the present invention is achieved by the following configuration.
(1) A vibration cavity forming base having a first surface and a second surface facing each other,
A vibrating cavity forming base formed so that a cavity for receiving a medium to be detected is opened to the first surface side, and a bottom surface of the cavity is formed to be capable of vibrating;
A first electrode formed on the second surface side of the vibration cavity forming base, a piezoelectric layer laminated on the first electrode, and a piezoelectric element having a second electrode laminated on the piezoelectric layer,
The planar shape of the cavity has a longitudinal dimension and a widthwise dimension shorter than the longitudinal dimension,
The first electrode is formed so as to cover substantially the entire region corresponding to the cavity,
The second electrode is formed in a substantially cross shape so as to cut out portions corresponding to the four corners of the cavity, and the total width length of the central portion in the longitudinal direction is a quasi-near portion in the vicinity of the longitudinal direction of the central portion. A liquid detection device formed shorter than the total width of the central portion.

(2) The cavity has a first symmetry axis and a second symmetry axis orthogonal to each other, the width direction dimension is a dimension along the first symmetry axis, and the longitudinal dimension is the second symmetry axis. (1) The liquid detection apparatus according to (1).

(3) An entrance / exit forming plate laminated on the first surface side of the vibration cavity forming base,
A liquid supply port for supplying a liquid to be detected to the cavity;
The liquid detection apparatus according to (1) or (2), further including an inlet / outlet forming plate formed with a liquid outlet for discharging the liquid to be detected from the cavity.

(4) The liquid detection device according to (3), wherein the liquid supply port and the liquid discharge port are disposed at positions corresponding to both ends in the longitudinal direction of the cavity.

(5) The liquid detection device according to (3) or (4), wherein the liquid supply port and the liquid discharge port are formed inside a region corresponding to the cavity.

(6) The vibrating cavity forming base includes a cavity plate in which a through-hole forming the cavity is formed, and a vibrating plate laminated on the cavity plate. The liquid detection apparatus according to 1.

(7) The liquid detection device according to any one of (1) to (6), wherein the entire piezoelectric layer is formed inside a region corresponding to the cavity.

(8) The dimension of the piezoelectric layer in the longitudinal direction of the cavity is larger than the longitudinal dimension of the cavity, and the piezoelectric layer is formed to cover the cavity over the entire length in the longitudinal direction of the cavity. The liquid detection device according to any one of (1) to (6).

(9) A liquid container comprising a container body having a liquid delivery port for delivering liquid stored inside to the outside, and a liquid detection device mounted on the container body,
The liquid detection device includes:
A vibration cavity forming base having a first surface and a second surface facing each other, wherein a cavity for receiving a medium to be detected is formed to open to the first surface side, and the bottom surface of the cavity is vibrated. A vibration cavity forming base formed in a possible manner;
A first electrode formed on the second surface side of the vibration cavity forming base, a piezoelectric layer laminated on the first electrode, and a piezoelectric element having a second electrode laminated on the piezoelectric layer,
The planar shape of the cavity has a longitudinal dimension and a widthwise dimension shorter than the longitudinal dimension,
The first electrode is formed so as to cover substantially the entire region corresponding to the cavity,
The second electrode is formed in a substantially cross shape so as to cut out portions corresponding to the four corners of the cavity, and the total width length of the central portion in the longitudinal direction is a quasi-near portion in the vicinity of the longitudinal direction of the central portion. A liquid container formed shorter than the total width of the central portion.

  According to the liquid detection device of the present invention, a cavity shape suitable for preventing the retention of bubbles and ink in the cavity is adopted, and the occurrence of unnecessary vibration during the residual vibration of the vibration unit is prevented. Thus, it is possible to provide a liquid detection device capable of reliably determining the presence or absence of a liquid and a liquid container including the device.

  According to the liquid container of the present invention, a cavity shape suitable for preventing the retention of bubbles and ink in the cavity is adopted, and the liquid supply port is provided at a position corresponding to both ends in the longitudinal direction of the cavity. In addition, by providing a liquid discharge port, it is possible to prevent air bubbles from remaining in the cavity and ink from remaining, and to reliably determine the presence or absence of liquid, and a liquid container including the same. be able to.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a liquid detection device according to the invention and an ink cartridge (liquid container) including the same will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of an ink jet recording apparatus (liquid ejecting apparatus) in which an ink cartridge according to the present embodiment is used. In FIG. 1, reference numeral 1 denotes a carriage, and the carriage 1 is driven by a carriage motor 2. The belt 3 is guided by the guide member 4 and is reciprocated in the axial direction of the platen 5.

  An ink jet recording head 12 is mounted on the side of the carriage 1 that faces the recording paper 6, and an ink cartridge 7 that supplies ink to the recording head 12 is detachably mounted on the recording head 12.

  A cap member 31 is disposed at a home position (right side in the drawing) which is a non-printing area of the recording apparatus. When the recording head mounted on the carriage 1 moves to the home position, the cap member 31 A sealed space is formed between the nozzle forming surface and the nozzle forming surface. A pump unit 10 is disposed below the cap member 31 for applying a negative pressure to the sealed space formed by the cap member 31 to perform cleaning or the like.

  The wiping means 11 having a resilient plate such as rubber is disposed in the vicinity of the stamping area side of the cap member 31 so that it can advance and retreat in the horizontal direction with respect to the movement trajectory of the recording head, for example. When the carriage 1 reciprocates toward the cap member 31, the nozzle forming surface of the recording head can be wiped as necessary.

  2 to 7 are views showing the liquid detection device 60 according to the present embodiment, and this liquid detection device 60 is configured by laminating the diaphragm 42 on the cavity plate 41 as shown in FIG. The vibration cavity forming base 40 includes a first surface 40a and a second surface 40b that face each other.

  A cavity 43 for receiving a medium (ink) to be detected is formed in the vibration cavity forming base 40 so as to open to the first surface 40 a side, and the bottom surface portion 43 a of the cavity 43 is vibrated by the vibration plate 42. It is made possible. In other words, the contour of the portion of the entire diaphragm 42 that actually vibrates is defined by the cavity 43.

  As shown in FIG. 2, the planar shape of the cavity 43 has a first symmetry axis O1 and a second symmetry axis O2 orthogonal to each other, and a longitudinal dimension along the second symmetry axis O2 is the first symmetry axis O1. It is set longer than the dimension in the width direction along.

  A lower electrode terminal 44 and an upper electrode terminal 45 are formed at both ends of the vibration cavity forming base 40 on the second surface 40b side.

  Further, a lower electrode (first electrode) 46 is formed on the second surface 40 b of the vibration cavity forming base 40, and the lower electrode 46 is formed in a shape substantially the same as the cavity 43 and larger than the cavity 43. It has a main body portion 46 a and an extending portion 46 b extending from the main body portion 46 a in the direction of the lower electrode terminal 44 and connected to the lower electrode terminal 44. The main body 46 a of the lower electrode 46 covers substantially the entire region corresponding to the cavity 43.

  The main body 46 a of the lower electrode 46 includes a notch 46 c formed so as to enter the inside of the position corresponding to the peripheral edge 43 a of the cavity 43.

  A piezoelectric layer 47 is laminated on the lower electrode 46, and the piezoelectric layer 47 is substantially the same shape as the cavity 43 and is smaller in size than the cavity 43. As can be seen from FIG. 2, the entire piezoelectric layer 47 is within the region corresponding to the cavity 43. In other words, the piezoelectric layer 47 does not have any part extending across the position corresponding to the peripheral edge 43 a of the cavity 43.

  The piezoelectric layer 47 has a first symmetry axis O 1 and a second symmetry axis O 2 that are common to the cavity 43, and substantially the whole thereof is on the lower electrode 46 except for a portion corresponding to the notch 46 c of the lower electrode 46. Are stacked.

  An auxiliary electrode 48 is formed on the second surface 40 b side of the vibration cavity forming base 40. The auxiliary electrode 48 extends from the outside of the region corresponding to the cavity 43 to the inside of the region corresponding to the cavity 43 beyond the position corresponding to the peripheral edge 43 a of the cavity 43. A part of the auxiliary electrode 48 is located inside the notch 46 c of the first electrode 46 and supports a part of the piezoelectric layer 47 from the second surface 40 b side of the substrate 40. The auxiliary electrode 48 is preferably made of the same material as the lower electrode 46 and has the same thickness. In this way, by supporting a part of the piezoelectric layer 47 from the second surface 40b side of the substrate 40 by the auxiliary electrode 48, it is possible to prevent the piezoelectric layer 47 from being stepped and prevent the mechanical strength from being lowered. .

  On the piezoelectric layer 47, a main body 49a of an upper electrode (second electrode) 49 is laminated, and the upper electrode 49 is formed with a size smaller than that of the piezoelectric layer 47 as a whole. The upper electrode 49 has an extending portion 49 b that extends from the main body portion 49 a and is connected to the auxiliary electrode 48.

  In this embodiment, as shown in FIGS. 2 and 6B, the upper electrode 49 is formed in a substantially cross shape so as to cut out portions corresponding to the four corners of the cavity 43. The first axis of symmetry O1 and the second axis of symmetry O2 are common to the cavity 43.

  A piezoelectric element is formed by the lower electrode 46, the piezoelectric layer 47, and the upper electrode 49. As described above, the piezoelectric layer 47 is sandwiched between the upper electrode 49 and the lower electrode 46, whereby the piezoelectric layer 47 is effectively deformed and driven.

In addition to this, the upper electrode 49 formed in a substantially cross shape has a direction along the second axis of symmetry O2 in a portion not cut out, that is, a portion (substantially central portion) extending along the first axis of symmetry O1. The total width length _WCT of the central portion in the longitudinal direction is shorter than the total width length _WET of the quasi-central portion in the vicinity of the central portion in the longitudinal direction (both sides in the longitudinal direction) (W _CT <W _ET ). . The piezoelectric layer 47 can increase the capacitance and increase the impact resistance by increasing the density of the material. In addition, it is difficult to cause leakage, and moisture resistance can be improved.

  However, in the piezoelectric layer 47 with high density, the amount of deformation increases when a polarization process is performed by applying a voltage (approximately 120 to 130 V) greater than the applied voltage (approximately 34 V) during normal driving in the manufacturing process. In combination with the laminated structure of different materials with the upper electrode 49 having a different linear expansion coefficient, stress may concentrate in the central portion and cracks may occur. If such a crack occurs, it will have a serious effect on the subsequent process, and it will be a factor of reducing the yield.

The upper electrode 49 according to this embodiment, by forming smaller than the total width dimension W _ET quasi central portion located the total width dimension W _CT of the central portion mentioned above in the longitudinal direction near, at the time of polarization voltage applied, The deformation amount in the substantially central portion including the central portion and the quasi-central portion can be controlled to be small, and the stress concentration on the substantially central portion can be reduced. As a result, the stress concentration at the central portion of the piezoelectric layer 47 can be reduced, cracks can be prevented, and the yield can be improved.

  As can be seen from FIGS. 2 and 5, the upper electrode 49 is electrically connected to the upper electrode terminal 45 via the auxiliary electrode 48. By connecting the upper electrode 49 to the upper electrode terminal 45 through the auxiliary electrode 48 in this way, a step caused by the total thickness of the piezoelectric layer 47 and the lower electrode 46 is reduced in both the upper electrode 49 and the auxiliary electrode 48. Can be absorbed by. For this reason, it is possible to prevent the mechanical strength from being lowered due to a large step in the upper electrode 49.

  Of the main body 46 a of the lower electrode 46 and the main body 49 a of the upper electrode 49 that are electrically connected to the piezoelectric layer 47, the main body 49 a of the upper electrode 49 is formed with a smaller size. Therefore, the main body 49a of the upper electrode 49 determines the range of the portion of the piezoelectric layer 47 that generates the piezoelectric effect.

  The centers of the piezoelectric layer 47, the main body portion 49 a of the upper electrode 49, and the main body portion 46 a of the lower electrode 46 coincide with the center of the cavity 43. Further, the center of the cavity 43 that determines the portion of the diaphragm 42 that can vibrate is located at the center of the entire liquid detection device 60.

  The portion of the diaphragm 42 that can be vibrated defined by the cavity 43, the portion corresponding to the cavity 43 in the main body 46a of the lower electrode 46, the portion corresponding to the cavity 43 in the piezoelectric layer 47, and the entire upper electrode 49. Constitutes the vibration part 61 of the liquid detection device 60. The center of the vibration part 61 of the liquid detection device 60 is coincident with the center of the liquid detection device 60.

  Furthermore, as shown in FIGS. 5 and 4, the liquid detection device 60 according to the present embodiment includes an entrance / exit forming plate 50 that is laminated and bonded to the first surface 40 a of the vibration cavity forming base 40. The inlet / outlet forming plate 50 includes an ink supply port (liquid supply port) 51 for supplying ink to be detected to the cavity 43 and an ink discharge port (liquid discharge port) 52 for discharging the ink to be detected from the cavity 43. Is formed.

  The ink supply port 51 and the ink discharge port 52 are disposed at positions corresponding to both ends of the cavity 43 in the longitudinal direction inside the region corresponding to the cavity 43. Further, the edge portions of the ink supply port 51 and the ink discharge port 52 are aligned with each other at the edge portion in the longitudinal direction of the cavity 43. The ink supply port 51 and the ink discharge port 52 are formed in the same shape and size.

  As described above, by disposing the ink supply port 51 and the ink discharge port 52 at positions corresponding to both ends in the longitudinal direction of the cavity 43, the distance between the ink supply port 51 and the ink discharge port 52 is increased. The liquid detector 60 can be easily attached to the container body. Further, by arranging the ink supply port 51 and the ink discharge port 52 inside the region corresponding to the cavity 43, the liquid detection device 60 can be reduced in size.

  The members included in the liquid detection device 60, in particular, the cavity plate 41, the vibration plate 42, and the entrance / exit forming plate 50 are formed of the same material and are integrally formed by firing each other. In this manner, the plurality of substrates are baked and integrated to facilitate handling of the liquid detection device 60. Further, by forming each member with the same material, it is possible to prevent the occurrence of cracks due to the difference in linear expansion coefficient.

  As a material of the piezoelectric layer 47, it is preferable to use lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT), or a lead-less piezoelectric film that does not use lead. As a material of the cavity plate 41, it is preferable to use zirconia or alumina. The diaphragm 42 is preferably made of the same material as the cavity plate 41. For the upper electrode 49, the lower electrode 46, the upper electrode terminal 45, and the lower electrode terminal 44, a conductive material, for example, a metal such as gold, silver, copper, platinum, aluminum, or nickel can be used.

  FIG. 8 shows an ink cartridge (liquid container) 70 to which the above-described liquid detection device 60 is mounted. This ink cartridge 70 has an ink delivery port (liquid delivery port) 71 for sending the ink stored inside to the outside. A container body 72 is provided.

  The liquid detection device 60 is entirely mounted outside the container main body 72, and the container wall of the container main body 72 communicates with the first opening 73 that communicates with the ink supply port 51 of the liquid detection device 60 and the ink discharge port 52. A second opening 74 is formed so as to penetrate therethrough.

  The inside of the container main body 72 includes a main storage chamber (first chamber) 75 constituting a main portion of the entire internal space of the container main body 72 and a sub storage chamber (first storage chamber) having a smaller volume than the main storage chamber 75. The main storage chamber 75 and the sub storage chamber 76 are separated from each other. The auxiliary storage chamber 76 is located closer to the ink delivery port 71 than the main storage chamber 75 in the direction of ink flow when ink is consumed, and communicates with the ink delivery port 71.

  The second opening 74 formed in the container wall of the container main body 72 communicates with the upper end portion of the sub storage chamber 76. As described above, the outlet 52 b of the ink discharge port 52 of the liquid detection device 60 is connected to the second opening 74.

  A sealed auxiliary flow path 77 is formed inside the main storage chamber 75, and an auxiliary flow path inlet 77 a is formed on the lower end side of the auxiliary flow path 77. The auxiliary flow path inlet 77 a is located at the lower end inside the main storage chamber 75. Further, a first opening 73 formed in the container wall of the container main body 72 communicates with the upper end portion of the auxiliary flow path 77, and the first opening 73 constitutes an outlet of the auxiliary flow path 77.

  As described above, the ink supply port 51 of the liquid detection device 60 communicates with the first opening 73, and the ink discharge port 52 communicates with the second opening 74, whereby the ink supply port 51 and the ink discharge port of the liquid detection device 60 are communicated. The outlet 52 forms a communication channel that connects the main storage chamber 75 and the sub storage chamber 76.

  When the ink in the ink cartridge 70 is consumed, the ink in the main storage chamber 75 flows into the auxiliary channel 77 from the auxiliary channel inlet 77 a and passes through the auxiliary channel 77 to the first. It flows to the opening 73. The ink flowing out from the first opening 73 flows into the cavity 43 from the ink supply port 51 of the liquid detection device 60, flows out from the ink discharge port 52 through the cavity 43. The ink that has flowed out of the ink discharge port 52 flows into the auxiliary storage chamber 76 through the second opening 74. Then, the ink that has flowed into the auxiliary storage chamber 76 is supplied to the recording head 12 of the ink jet recording apparatus via the ink delivery port 71.

  As described above, in the present embodiment, the entire amount of ink sent to the ink delivery port 71 through the sub-storage chamber 76 is configured to pass through the ink supply port 51 and the ink discharge port 52 of the liquid detection device 60 in advance. Has been.

  In the ink cartridge 70 provided with the liquid detection device 60 described above, when the ink remains sufficiently in the container main body 72 and the inside of the auxiliary storage chamber 76 is filled with ink, the inside of the cavity 43 is filled with ink. be satisfied. On the other hand, when the liquid in the container main body 72 of the ink cartridge 7 is consumed and the ink in the main storage chamber 75 is exhausted, the liquid level in the sub storage chamber 76 is lowered, and is higher than the position of the cavity 43 of the liquid detection device 60. When the liquid level falls to the lower side, there is no ink in the cavity 43.

  Therefore, the liquid detection device 60 detects a difference in acoustic impedance caused by the change in this state. Thereby, the liquid detection device 60 can detect whether ink is sufficiently left in the container main body 72 or whether a certain amount or more of ink has been consumed.

  More specifically, in the liquid detection device 60, a voltage is applied between the upper electrode 49 and the lower electrode 46 via the upper electrode terminal 45 and the lower electrode terminal 44. Then, an electric field is generated in a portion of the piezoelectric layer 47 sandwiched between the upper electrode 49 and the lower electrode 46. The piezoelectric layer 47 is deformed by this electric field. When the piezoelectric layer 47 is deformed, a flexural vibration is generated in a vibration region (region corresponding to the bottom surface portion 43 a of the cavity 43) of the vibration plate 42. When the application of voltage is canceled after the piezoelectric layer 47 is forcibly deformed in this way, the flexural vibration remains in the vibration part 61 of the liquid detection device 60 for a while.

  This residual vibration is free vibration between the vibration unit 61 of the liquid detection device 60 and the medium in the cavity 43. Therefore, by setting the voltage applied to the piezoelectric layer 47 to a pulse waveform or a rectangular wave, the resonance state between the vibrating portion 61 and the medium after the voltage is applied can be easily obtained. This residual vibration is a vibration of the vibration part 61 of the liquid detection device 60 and is accompanied by deformation of the piezoelectric layer 47. For this reason, the piezoelectric layer 47 generates a counter electromotive force with the residual vibration. This counter electromotive force is detected via the upper electrode 49, the lower electrode 46, the upper electrode terminal 45 and the lower electrode terminal 44. Since the resonance frequency can be specified by the back electromotive force detected in this way, the presence or absence of ink in the container body 72 of the ink cartridge 7 can be detected based on the resonance frequency.

  9A and 9B show residual vibration (free vibration) of the vibration unit 61 of the liquid detection device 60 when a drive signal is supplied to the liquid detection device 60 and the vibration unit 61 is forced to vibrate. The waveform of this and the measuring method of residual vibration are shown. FIG. 9A shows a waveform when there is ink in the cavity 43 of the liquid detection device 60, while FIG. 9B shows a waveform when there is no ink in the cavity 43 of the liquid detection device 60. .

  9A and 9B, the vertical axis represents the drive pulse applied to the liquid detection device 60 and the voltage of the counter electromotive force generated by the residual vibration of the vibration unit 61 of the liquid detection device 60, and the horizontal axis represents the horizontal axis. Indicates elapsed time. Due to residual vibration of the vibration part 61 of the liquid detection device 60, a waveform of an analog voltage signal is generated. Next, the analog signal is converted (binarized) into a digital numerical value corresponding to the frequency of the signal. In the example shown in FIG. 9, the time for generating four pulses from the fourth pulse to the eighth pulse of the analog signal is measured.

  More specifically, after a drive pulse is applied to the liquid detection device 60 to forcibly vibrate the vibration unit 61, a voltage waveform due to residual vibration is changed from a low voltage side to a predetermined reference voltage set in advance. Count the number of crossings to the side. Then, a digital signal is generated with High between 4 counts and 8 counts, and the time from 4 counts to 8 counts is measured by a predetermined clock pulse.

  Comparing FIG. 9A and FIG. 9B, it can be seen that the time from 4 to 8 counts is longer in FIG. 9A than in FIG. 9B. In other words, the required time from 4 counts to 8 counts varies depending on the presence or absence of ink in the cavity 43 of the liquid detection device 60. The consumption state of ink can be detected using the difference in the required time.

  The reason for counting from the fourth count of the analog waveform is to start measurement after the residual vibration (free vibration) of the liquid detection device 60 is stabilized. The count from the fourth count is merely an example, and the count may be counted from an arbitrary count. Here, signals from the 4th count to the 8th count are detected, and the time from the 4th count to the 8th count is measured by a predetermined clock pulse. Based on this time, the resonance frequency can be determined. The clock pulse does not need to be measured until the eighth count, and may be counted up to an arbitrary count.

  Although the time from the 4th count to the 8th count is measured in FIG. 9, the time within different count intervals may be detected according to the circuit configuration for detecting the frequency. For example, when the ink quality is stable and the fluctuation of the peak amplitude is small, the resonance frequency may be obtained by detecting the time from the 4th count to the 6th count in order to increase the detection speed. . When the ink quality is unstable and the fluctuation of the pulse amplitude is large, the time from the 4th count to the 12th count may be detected in order to accurately detect the residual vibration.

  As described above, in the liquid detection device 60 according to the present embodiment, the vibration unit 61 of the liquid detection device 60 determines whether or not the liquid level has passed through the mounting position level of the liquid detection device 60 (strictly, the position of the cavity 43). Can be detected by a change in the frequency or amplitude of the residual vibration after forcibly vibrating.

  In the present embodiment, as described above, the upper electrode 49 is formed in a substantially 10 shape so as to cut out the portions corresponding to the four corners of the cavity 43, so that a drive pulse is applied to the piezoelectric element. Even when forcedly deformed, the amount of deformation of the portions corresponding to the four corners of the cavity 43 is small. Thereby, the vibration mode at the time of forced vibration and the vibration mode at the time of residual vibration (free vibration) after forced vibration become close to each other.

As described above, in the liquid detection device 60 according to the present embodiment, the upper electrode 49 is formed in a substantially cross shape so that the vibration mode during forced vibration and the vibration mode during residual vibration after forced vibration are close to each other. Therefore, although the cavity 43 has a long and narrow shape as described above, the unnecessary vibration component in the detection signal is reduced, so that the presence or absence of ink can be reliably determined.
In addition, since the total width dimension W _CT of the central portion in the notched portion without the top electrode 49 (substantially central portion) is formed smaller than the total width dimension W _ET quasi central portion in the longitudinal direction near the polarization When a voltage is applied, the concentration of stress on the substantially central portion can be alleviated, cracks can be prevented, and the yield can be improved.

  In the present embodiment, ink is supplied to the cavity 43 through the ink supply port 51, and ink is discharged from the cavity 43 through the ink discharge port 52. When the detection device 60 is mounted, the ink in the container main body 72 is passed through the ink supply port 51 without exposing the cavity 43 of the liquid detection device 60 in the ink containing space in the container main body 72 of the ink cartridge 70. It can be supplied to the cavity 43.

  For this reason, when the ink in the ink cartridge 70 is consumed, the ink flow is generated in the cavity 43 via the ink supply port 51 and the ink discharge port 52 of the liquid detection device 60, so that the cavity 43 is temporarily provided. Even if the bubbles enter the inside of the, the bubbles are pushed out of the cavity 43 by the flow of ink. As a result, it is possible to prevent erroneous detection of the liquid detection device 60 due to air bubbles remaining in the cavity 43.

  In addition, according to the present embodiment, since the cavity 43 has an elongated shape instead of a circle or a square, the ink supply port 51 and the ink discharge port 52 are arranged at both ends in the longitudinal direction of the cavity 43, whereby the cavity Ink and bubbles are less likely to stay inside 43. As a result, it is possible to sufficiently ensure the discharge of ink and bubbles, and it is possible to reliably determine the presence or absence of ink.

  Further, in the liquid detection device 60 according to the present embodiment, it is not necessary to expose the cavity 43 to the ink storage space in the container main body 72, so that a meniscus can be prevented from being formed in the cavity 43 when the liquid level passes. As a result, erroneous detection of the liquid detection device 60 due to ink remaining in the cavity 43 can be prevented.

  Further, in the ink cartridge 70 according to the present embodiment, the interior of the container main body 72 is partitioned into a main storage chamber 75 and a sub storage chamber 76 that are separated from each other, and the ink supply port 51 and the ink discharge port of the liquid detection device 60 are separated. The main storage chamber 75 and the sub storage chamber 76 are communicated with each other via the outlet 52, and the cavity 43 of the liquid detection device 60 is disposed at the upper end portion of the sub storage chamber 76.

  For this reason, the time when the ink in the main storage chamber 75 runs out can be reliably detected by the liquid detection device 60, so that the user can be notified that the ink end is approaching. Further, it is possible to notify the user of the number of printable sheets with the remaining ink based on the amount of ink in the sub-reservoir chamber 76 that is known in advance. This can prevent waste.

  Further, in the ink cartridge 70 according to the present embodiment, the sealed auxiliary flow path 77 is formed inside the main storage chamber 75, and the auxiliary flow path inlet 77 a of the auxiliary flow path 77 is positioned at the lower end of the main storage chamber 75. At the same time, the inlet 51 b of the ink supply port 51 of the liquid detection device 60 is communicated with the upper end of the auxiliary channel 77. For this reason, bubbles generated in the main storage chamber 75 are unlikely to enter the auxiliary flow port 77, and bubbles can be prevented from entering the cavity 43 of the liquid detection device 60.

  Furthermore, in the ink cartridge 70 according to the present embodiment, the sub-reservoir chamber 76 is filled with ink until all the ink in the main reservoir chamber 75 is consumed, so that vibration is applied to the ink cartridge 70. Even if the liquid level is changed, the liquid level does not fluctuate in the auxiliary storage chamber 76 as long as the ink remains in the main storage chamber 75. Accordingly, it is possible to prevent the liquid detection device 60 from erroneously detecting due to the fluctuation of the liquid level.

  Further, according to the liquid detection device 60 according to the present embodiment, the range in which the vibrating unit 61 and the liquid are in contact is limited to the range in which the cavity 43 exists, so that the liquid can be detected pinpointed. Thus, the ink level can be detected with high accuracy.

  In addition, since the substantially entire region corresponding to the cavity 43 is covered with the main body 46a of the lower electrode 46, the difference between the deformation mode during forced vibration and the deformation mode during free vibration is reduced. Further, since the vibration part 61 of the liquid detection device 60 has a symmetrical shape with respect to the center of the liquid detection device 60, the rigidity of the vibration part 61 is substantially isotropic when viewed from the center.

  For this reason, generation | occurrence | production of the unnecessary vibration which may arise from the asymmetry of a structure is suppressed, and the output fall of the counter electromotive force by the difference in the deformation mode between the time of forced vibration and free vibration is prevented. Thereby, the detection accuracy of the resonance frequency of the residual vibration in the vibration unit 61 of the liquid detection device 60 is improved, and the detection of the residual vibration of the vibration unit 61 is facilitated.

  In addition, since substantially the entire region corresponding to the cavity 43 is covered with the main body portion 46a of the lower electrode 46 having a size larger than that of the cavity 43, generation of unnecessary vibration due to the positional deviation of the lower electrode 46 at the time of manufacture occurs. It is prevented, and the fall of detection accuracy can be prevented.

  Further, the entire hard but fragile piezoelectric layer 47 is disposed inside the region corresponding to the cavity 43, and the piezoelectric layer 47 does not exist at a position corresponding to the peripheral edge 43 a of the cavity 43. For this reason, there is no problem of a crack of the piezoelectric layer at a position corresponding to the peripheral edge of the cavity.

  Next, a liquid detection device according to another embodiment of the present invention will be described with reference to FIGS. In addition, description is abbreviate | omitted about the part which is common in embodiment mentioned above.

  As shown in FIG. 10, in the liquid detection device 60 </ b> A according to the present embodiment, the dimension of the piezoelectric layer 47 in the longitudinal direction of the cavity 43 (the extending direction of the second symmetry axis O <b> 2) is larger than the length of the cavity 43 in the longitudinal direction. Is also set longer. The piezoelectric layer 47 is formed so as to cover the cavity 43 over its entire length in the longitudinal direction of the cavity 43. In the width direction of the cavity 43 (the extending direction of the first symmetry axis O <b> 1), the piezoelectric layer 47 is formed inside the cavity 43 with a smaller dimension than the cavity 43.

  Further, in the present embodiment, the lower electrode 46 is formed in a substantially rectangular shape, and the lower electrode 46 has a size larger than that of the piezoelectric layer 47 in the width direction of the cavity 43 (extending direction of the first symmetry axis O1). In the longitudinal direction of the cavity 43 (extending direction of the second axis of symmetry O2), the lower electrode 46 and the piezoelectric layer 47 have a common dimension.

  In the present embodiment, similarly to the above-described embodiment, it is possible to prevent occurrence of unnecessary vibrations and to prevent air bubbles and ink from staying.

  Furthermore, according to the present embodiment, since the longitudinal dimension of the piezoelectric layer 47 is set to be larger than the longitudinal dimension of the cavity 43, the formation position of the piezoelectric layer 47 is shifted in the longitudinal direction of the cavity 43. However, the size of the part contributing to vibration in the entire piezoelectric layer 47 does not change. For this reason, generation | occurrence | production of the unnecessary vibration by the shift | offset | difference of the formation position of the piezoelectric layer 47 can be prevented.

  As a modification of each embodiment described above, the inlet / outlet forming plate 50 is omitted in the liquid detection devices 60 and 60A, and the first opening 73 and the second opening 74 formed in the container main body 72 of the ink cartridge 70 are provided. The liquid detection devices 60 and 60A can be configured to be used as an ink supply port and an ink discharge port to the cavity 43.

In the above embodiments, the substantially central portion in the longitudinal direction of the upper electrode 49 formed in a substantially cross shape, shortening the total width dimension W _CT of the central portion than the total width dimension W _ET quasi central portion formed However, in the liquid detection device according to the present invention, as shown in FIG. 12A, the edge portions 80 of the rectangular four corners of the upper electrode 49 are removed, and the substantially central portion of the upper electrode 49 is formed in a so-called bowl shape. May be. Further, as a shape that makes the total width length _WCT of the central portion in the longitudinal direction shorter than the total width length _WE of the quasi-central portion, as shown in FIG. 81 and 81 may be formed. Furthermore, as a shape in which the total width length _WCT of the central portion in the longitudinal direction is shorter than the total width length _WE of the quasi-central portion, as shown in FIG. 12C, a hole 83 is formed in the central portion of the upper electrode 49. The total width length W _CT (W _C1 + W _C2 ) from the hole 83 to each of the long side portions of the substantially central portion is made shorter than the total width length W _ET of the quasi-central portion where the hole 83 is not provided. It may be a thing.

1 is a perspective view illustrating a schematic configuration of an ink jet recording apparatus in which an ink cartridge including a liquid detection device according to an embodiment of the present invention is used. The top view which showed the liquid detection apparatus by one Embodiment of this invention. The bottom view which showed the liquid detection apparatus shown in FIG. Sectional drawing along the AA line of the liquid detection apparatus shown in FIG. Sectional drawing along the BB line of the liquid detection apparatus shown in FIG. FIG. 3 is an exploded view of a portion of an electrode and a piezoelectric layer of the liquid detection device illustrated in FIG. A pattern is shown, (d) shows the pattern of a lower electrode and an auxiliary electrode. FIG. 3 is an exploded view of a portion of the substrate of the liquid detection device shown in FIG. 2, (a) showing a diaphragm, (b) showing a cavity plate, and (c) showing an entrance / exit forming plate. FIG. 3 is a diagram illustrating an ink cartridge including the liquid detection device illustrated in FIG. 2, in which (a) is a side view and (b) is a front view. It is a figure which shows the drive pulse waveform and back electromotive force waveform in the liquid detection apparatus by one Embodiment of this invention, (a) is a wave form diagram in case ink exists in a cavity, (b) is ink in a cavity. Waveform diagram when it does not exist. The top view which showed the liquid detection apparatus by other embodiment of this invention. It is an exploded view of the part of the electrode and piezoelectric layer of the liquid detection apparatus shown in FIG. 10, (a) shows the pattern of an electrode terminal, (b) shows the pattern of an upper electrode, (c) is the piezoelectric layer A pattern is shown, (d) shows the pattern of a lower electrode and an auxiliary electrode. Plan view showing a modification of the upper electrode It is the figure which showed the conventional liquid detection apparatus, (a) is a top view, (b) is sectional drawing along the BB line of (a), (c) is CC line of (a). FIG. FIG. 14 is a cross-sectional view of a conventional ink cartridge including the conventional liquid detection device shown in FIG. 13.

Explanation of symbols

40 ... vibration cavity forming base 41 ... cavity plate 42 ... vibration plate 43 ... cavity 43a ... bottom surface 46 of cavity ... lower electrode (first electrode)
47: Piezoelectric layers 49, 49A, 49B, 49C: Upper electrode (second electrode)
50: Entrance / exit forming plate 51 ... Ink supply port (liquid supply port)
52 ... Ink discharge port (liquid discharge port)
60, 60A ... Liquid detection device 61 ... Vibrating portion 70 of the liquid detection device ... Ink cartridge (liquid container)
71: Ink delivery port (liquid delivery port)
72 ... Container body 73 ... First opening 74 ... Second opening 75 ... Main reservoir (first chamber)
76 ... Sub-reservoir (second chamber)
77 ... supplementary passage 77a ... auxiliary flow path inlet O1 ... first symmetry axis O2 ... second axis of symmetry W _{CT ...} longitudinal total width length direction central portion W _{ET ...} total width dimension of the longitudinal ends of the cavity of the cavity

Claims (5)

A vibration cavity forming base having a first surface and a second surface facing each other, wherein a cavity for receiving a medium to be detected is formed to open to the first surface side, and the bottom surface of the cavity is vibrated. A vibration cavity forming base formed in a possible manner;
The vibration cavity forming base portion first electrode said is found provided on the second side of, and a piezoelectric element having a piezoelectric layer laminated on the first electrode, and a second electrode laminated on the piezoelectric layer ,
The shape of the bottom surface of the cavity has a lengthwise dimension along a first axis and a widthwise dimension along a second axis perpendicular to the first axis, and has a widthwise dimension shorter than the lengthwise dimension. ,
The area of the piezoelectric layer is smaller than the area of the bottom surface of the cavity,
The first electrode includes a large first body part of the area than the bottom surface of the cavity has covering substantially the entire area corresponding to the bottom surface of the cavity, for connecting the first body portion to the first electrode terminal A first extension part ,
The second electrode includes a second main body portion having a smaller area than the piezoelectric layer, and a second extending portion for connecting the second main body portion to a second electrode terminal,
The liquid detecting device , wherein the second body portion of the second electrode has a width direction dimension on the second axis shorter than a width direction dimension in the vicinity of the second axis .   2. The liquid detection device according to claim 1, wherein the second main body portion of the second electrode has concave portions at both end portions on the second axis.   The liquid detection device according to claim 1, wherein a shape of the second main body portion of the second electrode is substantially cross-shaped. A liquid supply port for supplying the liquid to be detected to said cavity, and a liquid discharge port for discharging the liquid from the cavity is formed, laminated on the first surface of the vibration cavity forming base portion liquid detector according to any one of claims 1 to 3, further comprising a doorway formed plate. 5. A liquid detection device according to claim 1 , comprising: a container main body having a liquid delivery port for sending the liquid stored inside to the outside; and a liquid detection device mounted on the container main body. And a liquid container comprising the device .

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