JP2006029918A - Liquid detecting method and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid detecting method and a liquid detecting system capable of surely judging the existence of liquid in a liquid vessel used in a liquid jet device. <P>SOLUTION: The method for detecting liquid inside a liquid vessel used for a liquid jet device, with a liquid detector 60 comprises a first detection process for impressing a drive voltage to a piezoelectric element and detecting at least two kinds of characteristic values from the output signal with reversed electromotive force generated by residual vibration caused later, a second detection process for impressing again the drive voltage to the piezoelectric element after performing the first detection process and detecting again at least two kinds of characteristic values, and a liquid-gas judging process for comparing the two kinds of characteristic values detected in the first process and the two kinds of characteristic values detected in the first detection process, and judging which state of liquid space or gas space the inside of the cavity is, from the variation between the two. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid detection method and a liquid detection system for detecting a liquid inside a liquid container used in a liquid ejecting apparatus.

  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. As other liquid ejecting apparatuses, 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 paste) used for forming an electrode such as an organic EL display, a surface emitting display (FED), etc. ) 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 the user when the 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 the maintenance by software, or an ink cartridge. There is a method of managing a point in time when a predetermined amount of ink is actually consumed by attaching an electrode for detecting a liquid level.

  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 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. 16 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 Piezoelectric layer 160 disposed on the surface side of diaphragm 176, upper electrode 164 and lower electrode 166 sandwiching piezoelectric layer 160 from both sides, upper electrode terminal 168 electrically coupled to upper electrode 164, and lower electrode 166 And an auxiliary electrode 172 disposed between the upper electrode 164 and the upper electrode terminal 168 and electrically coupled to each other.

  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 technique 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 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.

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. 17, 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.
JP 2001-146024 A

  However, when liquid detection is performed using the above-described conventional actuator (piezoelectric device) 106, noise may occur in the back electromotive force signal from the actuator 106. For this reason, for example, if an attempt is made to determine the presence or absence of ink based only on the change in the frequency of the back electromotive force signal, it may be erroneously determined that there is no ink despite the presence of ink, or conversely, there is no ink. In spite of this state, there was a problem that it was erroneously determined that ink was present.

  The present invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a liquid detection method and a liquid detection system that can reliably determine the presence or absence of a liquid.

  In order to solve the above-described problems, the present invention provides a method for detecting a liquid inside a liquid container used in a liquid ejecting apparatus using a liquid detection apparatus, wherein the liquid detection apparatuses are first to face each other. A vibration cavity forming base having a surface and a second surface, wherein a cavity for receiving a medium to be detected is formed to open to the first surface side, and a bottom surface of the cavity is formed to be capable of vibration. A vibrating cavity forming base, a first electrode formed on the second surface side of the vibrating cavity forming base, a piezoelectric layer stacked on the first electrode, and a second electrode stacked on the piezoelectric layer. A liquid detection method comprising: a piezoelectric element; applying a drive voltage to the piezoelectric element, and at least two types of output signals of back electromotive force generated by residual vibration generated thereafter A first detection step for detecting a sex value, and a second detection for detecting again the at least two types of characteristic values by reapplying a driving voltage to the piezoelectric element after the first detection step is performed. And comparing the at least two types of characteristic values detected in the first detection step with the at least two types of characteristic values detected in the second detection step, and based on a change therebetween And a gas-liquid determination step of determining whether the inside of the cavity is in a liquid space or a gas space.

  Preferably, the at least two types of characteristic values include at least one of a frequency or an amplitude of the output signal of the counter electromotive force.

  Preferably, the at least two types of characteristic values include information relating to timing at which the output signal of the back electromotive force crosses a predetermined voltage threshold.

  Preferably, the first detection step is performed when the liquid container is attached to the liquid ejecting apparatus.

  Preferably, the at least two types of characteristic values detected when the liquid container is mounted on the liquid ejecting apparatus are stored in a storage unit provided in the liquid ejecting apparatus.

  In order to solve the above problems, the present invention provides a liquid detection system for detecting a liquid inside a liquid container used in a liquid ejecting apparatus, and forming a vibrating cavity having a first surface and a second surface facing each other. A vibration cavity forming base, which is a base and is formed so that a cavity for receiving a medium to be detected is opened on the first surface side, and a bottom surface of the cavity is configured to be vibrable; and the vibration cavity A first electrode formed on the second surface side of the formation base, a piezoelectric layer stacked on the first electrode, and a piezoelectric element including a second electrode stacked on the piezoelectric layer, and the liquid A drive voltage is applied to the piezoelectric element at a detection point different from that of the liquid detection device mounted on the container, and an output signal of a counter electromotive force generated by residual vibration generated thereafter is acquired. And detecting at least two types of characteristic values from the body detection control means and the output signal of the back electromotive force, and based on changes in the at least two types of characteristic values between detection points, the interior of the cavity is a liquid space. Alternatively, a gas-liquid determination unit that determines which state is in the gas space and a storage unit that stores the at least two types of characteristic values are provided.

  Preferably, the at least two types of characteristic values include at least one of a frequency or an amplitude of the output signal of the counter electromotive force.

  Preferably, the at least two types of characteristic values include information relating to timing at which the output signal of the back electromotive force crosses a predetermined voltage threshold.

  Preferably, the at least two types of characteristic values are detected when the liquid container is mounted on the liquid ejecting apparatus and stored in the storage unit.

  Preferably, the storage unit is provided in the liquid ejecting apparatus.

  According to the present invention, it is possible to reliably detect the presence or absence of liquid in a liquid container using a liquid detection device having a piezoelectric element.

  Hereinafter, a liquid detection system and a liquid detection method using the liquid detection system according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of an ink jet recording apparatus (liquid ejecting apparatus) to which the liquid detection method according to the present embodiment is applied. Reference numeral 1 in FIG. 1 denotes a carriage. The carriage 1 is driven by a carriage motor 2. It is configured such that it is guided by the guide member 4 via the timing belt 3 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 (object to be processed) 6, and an ink cartridge 7 that supplies ink to the recording head 12 is detachably mounted thereon. . The ink remaining amount in the ink cartridge 7 is detected by the liquid detection system and the liquid detection method according to the present embodiment.

  A cap member 31 is disposed at a home position (right side in the figure) 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 performs recording. It is configured to be pressed against the nozzle forming surface of the head to form a sealed space with 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.

  A wiping means 11 having an elastic plate such as rubber is disposed in the vicinity of the print area side of the cap member 31 so as to be able to advance and retreat in the horizontal direction with respect to the movement trajectory of the recording head. When reciprocating to the cap member 31 side, the nozzle forming surface of the recording head can be wiped off as necessary.

  2 to 7 are views showing a liquid detection device 60 constituting a part of the liquid detection system according to the present embodiment. This liquid detection device 60 vibrates in the cavity plate 41 as shown in FIG. The vibration cavity forming base 40 is configured by laminating the plates 42. The vibration cavity forming base 40 has 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 formed on the vibration plate 42. And can be vibrated. 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. A main body portion 46a, and an extension portion 46b extending from the main body portion 46a toward 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 of the piezoelectric layer 47 except for a portion corresponding to the notch portion 46 c of the lower electrode 46. Laminated on top.

  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. .

  A main body 49 a of an upper electrode (second electrode) 49 is laminated on the piezoelectric layer 47, 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 the liquid detection device 60, as shown in FIGS. 2 and 6B, the upper electrode 49 has a substantially cross shape so that the portions corresponding to the four corners of the cavity 43 are cut out. The first axis of symmetry O1 and the second axis of symmetry O2 formed and common to the cavity 43 are provided.

  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.

  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 portion 46a of the lower electrode 46 and the main body portion 49a of the upper electrode 49 that are electrically connected to the piezoelectric layer 47, the main body portion 49a 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 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 for 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 sends out ink stored inside to an ink delivery port (liquid delivery port). A container body 72 having 71 is provided.

  The entire liquid detection device 60 is mounted on the outside of the container main body 72, and a first opening 73 communicating with the ink supply port 51 of the liquid detection device 60 and an ink discharge port 52 are provided on the container wall of the container main body 72. And a second opening 74 communicating therewith.

  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. 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 of the liquid detection device 60 and The ink discharge port 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 of ink is 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 indicates 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 indicates the elapsed time. Show time. Due to the residual vibration of the vibration part 61 of the liquid detection device 60, a waveform of an analog signal of voltage 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.

  Thus, in the liquid detection device 60, the vibration unit 61 of the liquid detection device 60 is forcibly determined as to whether or not the liquid level has passed the mounting position level of the liquid detection device 60 (strictly, the position of the cavity 43). It can be detected by a change in the frequency or amplitude of the residual vibration after the vibration.

  In this embodiment, as described above, the upper electrode 49 is formed in a substantially cross 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 the deformation is forced, the deformation amount 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.

  FIG. 10 is a block diagram for explaining the liquid detection system according to the present embodiment. As shown in FIG. 10, the control device 90 of the ink jet recording apparatus includes a storage unit 80 including a storage element, and a gas-liquid determination unit 81 that determines whether the inside of the cavity 43 is in a liquid space or a gas space. The liquid detection control means 82 for controlling the liquid detection operation by the liquid detection device 60, the carriage motor control means 83 for controlling the carriage motor (CR motor) 2, and the head drive means 13 are controlled to control the operation of the recording head 12. The head control means 84 and the pump control means 85 for controlling the operation of the pump unit 10 by controlling the pump drive means 14 are provided.

  In the present embodiment, using the liquid detection system including the liquid detection device 60, the storage unit 80, the gas-liquid determination unit 81, and the liquid detection control unit 82, the ink inside the ink cartridge 7 is as follows. The remaining amount is detected.

  That is, when the ink cartridge 7 is mounted on the carriage 1 of the ink jet recording apparatus, the liquid detection control means 82 applies a drive voltage to the piezoelectric element of the liquid detection apparatus 60, and the back electromotive force generated by the residual vibration generated thereafter. At least two types of characteristic values are detected from the power output signal (first detection step). The at least two types of characteristic values detected in this way are stored in the storage means 80 provided in the ink jet recording apparatus.

  Here, the frequency and amplitude of the output signal of the back electromotive force can be used as at least two types of characteristic values. Alternatively, information relating to the timing at which the output signal of the back electromotive force exceeds a predetermined voltage threshold can be used.

  Then, at an appropriate timing after the ink cartridge 7 is mounted on the carriage 1, the liquid detection control means 82 reapplies the drive voltage to the piezoelectric element of the liquid detection device 60, and the back electromotive force generated by the residual vibration generated thereafter. At least two types of characteristic values are detected again from the power output signal (second detection step).

  Next, the gas-liquid determination unit 81 includes at least two types of characteristic values detected in the first detection step and stored in the storage unit 80, and at least two types of characteristic values detected in the second detection step. Based on the change between them, it is determined whether the interior of the cavity 43 is in a liquid space or a gas space. That is, the gas-liquid determination unit 81 determines that the inside of the cavity 43 has changed from the liquid space to the gas space when a significant change is recognized in all of the plural types of characteristic values to be monitored.

  Hereinafter, with reference to FIG. 11, the above-described method for detecting at least two types of characteristic values will be described in more detail. In FIG. 11, symbol A indicates a back electromotive force output signal when the inside of the cavity 43 is a liquid space, and symbol B indicates a back electromotive force output signal when the inside of the cavity 43 is a gas space.

  As can be seen from FIG. 11, when the inside of the cavity 43 is changed from the liquid space to the gas space, the output signal of the back electromotive force increases in both frequency and amplitude. Therefore, in this embodiment, it is determined whether or not the inside of the cavity 43 has changed from the liquid space to the gas space by monitoring both the change in frequency and the change in amplitude in the output signal of the back electromotive force. .

  Further, reference numerals t11 and t12 in FIG. 11 indicate timings when the output signal of the back electromotive force crosses the predetermined voltage threshold Vs when the inside of the cavity 43 is a liquid space, and reference numerals t21 to t26 indicate the cavity. When the inside of 43 is gas space, the output signal of the back electromotive force has crossed the predetermined voltage threshold value Vs.

  As can be seen from FIG. 11, the timing described above changes as the inside of the cavity 43 changes from the liquid space to the gas space. Therefore, information regarding this timing can be set as one of the characteristic values to be monitored.

  As described above, in the present embodiment, a driving voltage is applied to the piezoelectric element of the liquid detection device 60, and at least two types of characteristic values are detected from the output signal of the counter electromotive force generated by the residual vibration generated thereafter, Since it is determined whether or not the inside of the cavity 43 has changed from the liquid space to the gas space based on the change in at least two kinds of characteristic values, the time when the inside of the cavity 43 has changed from the liquid space to the gas space. Can be reliably detected.

  For example, although the noise is added to the output signal from the piezoelectric element, the ink is actually present in the cavity 43 and the frequency of the counter electromotive force signal does not change, but the liquid detection device The apparent frequency detected from the 60 output signals may increase. Even in such a case, the change in not only the frequency but also the amplitude is monitored as in the present embodiment, and the inside of the cavity 43 is removed from the liquid space only when both the frequency and the amplitude change significantly. By determining that the gas space has changed, it is possible to prevent erroneous determination due to noise.

  In this embodiment, when the ink cartridge 7 is mounted on the carriage 1, the first detection process is performed to detect at least two types of characteristic values, and the detected characteristic values are stored in the storage unit 80. Thus, even if there is an individual difference in the characteristic value for each ink cartridge 7, a change in the characteristic value accompanying a change in the state of the cavity 43 can be reliably detected.

  In this embodiment, since the characteristic value is stored in the storage unit 80 provided on the ink jet recording apparatus side, it is not necessary to provide a storage unit on the ink cartridge 7 side, and the structure of the ink cartridge 7 is not required. Simplification and reduction of manufacturing costs can be achieved.

  Further, 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 at the time of forced vibration and the vibration mode at the time of residual vibration after the forced vibration are made close to each other. Even though the cavity 43 has an elongated shape as described above, unnecessary vibration components in the detection signal are reduced, so that the presence / absence of ink can be more reliably determined.

  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 in the present embodiment, it is not necessary to expose the cavity 43 to the ink containing space in the container main body 72, so that it is possible to prevent a meniscus from being formed in the cavity 43 when passing the liquid level. 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 in the present embodiment, the inside 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 previously known amount of ink in the sub-reservoir chamber 76, and the printing paper is wasted because the ink runs out in the middle of one page. Can be prevented.

  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.

  Further, 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 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 in 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.

  In addition, 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, as another embodiment of the present invention, an example in which the configuration of the liquid detection device is changed will be described with reference to FIGS. 12 and 13. In addition, description is abbreviate | omitted about the part which is common in embodiment mentioned above.

  As shown in FIG. 12, in the liquid detection device 60 </ b> A according to this embodiment, the dimension of the piezoelectric layer 47 in the longitudinal direction of the cavity 43 (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.

  Furthermore, 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 (the extending direction of the first symmetry axis O1). The lower electrode 46 and the piezoelectric layer 47 have a common dimension in the longitudinal direction of the cavity 43 (extending direction of the second symmetry axis O2).

  In the present embodiment as well, in the same manner as in the above-described embodiment, it is possible to prevent occurrence of unnecessary vibrations, to prevent bubbles and ink from staying, and to prevent ink from adhering to the cavity 43. By detecting the presence or absence of ink, the remaining amount of ink in the ink cartridge 7 can be reliably detected.

  Furthermore, according to the present embodiment, since the longitudinal dimension of the piezoelectric layer 47 is set 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 this configuration, the first opening 73 and the second opening 74 formed in the container body 72 constitute part of the ink cartridge 70 and part of the liquid detection devices 60 and 60A.

  FIG. 14 shows an ink cartridge (liquid container) 70A in which the liquid detection device 60 is mounted as a modification of the above-described embodiment. The ink cartridge 70A is an ink that sends ink stored inside to the outside. A container main body 72 having a delivery port (liquid delivery port) 71 on the front surface is provided.

  The liquid detection device 60 is entirely disposed outside the container main body 72 and mounted on the upper surface of the container main body 72. A container wall that forms the upper surface of the container body 72 is formed with a first opening 73 that communicates with the ink supply port 51 of the liquid detection device 60 and a second opening 74 that communicates with the ink discharge port 52.

  An ink storage chamber 75 is formed inside the container body 72, and the ink storage chamber 75 and the first opening 73 are connected via the first communication channel 76, and the second opening 74 and the ink delivery port 71 are connected. Are connected via a second communication channel 77.

  FIG. 15 shows an ink cartridge (liquid container) 70B to which the liquid detection device 60 is mounted as another modification of the above-described embodiment. In this ink cartridge 70B, the inside of the container main body 72 is the first. The storage chamber 75a and the second storage chamber 75b are partitioned, and the first storage chamber 75a and the second storage chamber 75b are separated from each other. The second storage chamber 75b is located closer to the ink delivery port 71 than the first storage chamber 75a in the direction of ink flow when ink is consumed, and communicates with the ink delivery port 71.

  The liquid detection device 60 is mounted on the upper surface of the container main body 72. A container wall that forms the upper surface of the container body 72 is formed with a first opening 73 that communicates with the ink supply port 51 of the liquid detection device 60 and a second opening 74 that communicates with the ink discharge port 52. The first storage chamber 75a and the first opening 73 are connected via a communication channel 76, and the second opening 74 communicates with the second storage chamber 75b. The ink delivery port 71 is provided on the bottom surface of the container main body 72.

  Thus, the first storage chamber 75a and the second storage chamber 75b communicate with each other via the liquid detection device 60, and the total amount of ink sent from the first storage chamber 75a to the second storage chamber 75b is the liquid detection device. 60.

  In each of the modifications shown in FIGS. 14 and 15, the remaining amount of ink in the ink cartridge 7 can be reliably detected as in the above-described embodiment.

1 is a perspective view showing a schematic configuration of an ink jet recording apparatus to which a liquid detection method according to an embodiment of the present invention is applied. The top view which showed the liquid detection apparatus which comprises some liquid detection systems 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 shown in FIG. 2, (a) shows a pattern of electrode terminals, (b) shows a pattern of an upper electrode, and (c) shows a pattern of the piezoelectric layer. 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 block diagram for demonstrating the liquid detection system by one Embodiment of this invention. The graph for demonstrating the liquid detection method by one Embodiment of this invention. The top view which showed the liquid detection apparatus in 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. 12, (a) shows the pattern of an electrode terminal, (b) shows the pattern of an upper electrode, (c) shows the pattern of a piezoelectric layer. A pattern is shown, (d) shows the pattern of a lower electrode and an auxiliary electrode. The side view provided with the ink cartridge in the modification of the said embodiment. The side view provided with the ink cartridge in the other modification of the said embodiment. 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. 17 is a cross-sectional view of a conventional ink cartridge provided with the conventional liquid detection device shown in FIG. 16.

Explanation of symbols

1 Carriage 6 Recording paper (processed object)
7 Ink cartridge 12 Recording head 13 Head drive means 14 Pump drive means 40 Vibration cavity forming base 41 Cavity plate 42 Vibration plate 43 Cavity 43a Cavity bottom face portion 46 Lower electrode (first electrode)
47 Piezoelectric layer 49 Upper electrode (second electrode)
50 Inlet / outlet forming plate 51 Ink supply port (liquid supply port)
52 Ink outlet (liquid outlet)
60, 60A Liquid detection device 61 Vibrating portions 70, 70A, 70B of 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 storage chamber (first chamber)
76 Secondary storage chamber (second chamber)
77 Auxiliary flow path 77a Auxiliary flow path inlet 80 Storage means 81 Gas-liquid determination means 82 Liquid detection control means 83 CR motor control means 84 Head control means 85 Pump control means 90 Controller O1 First symmetry axis O2 of cavity Second of cavity Axis of symmetry

Claims (10)

A method for detecting a liquid inside a liquid container used in a liquid ejecting apparatus using a liquid detection device, wherein the liquid detection device is a vibration cavity forming base having a first surface and a second surface facing each other. A vibration 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 vibration; and the vibration cavity forming base A liquid detection method comprising: a first electrode formed on the second surface side of the first electrode; a piezoelectric layer stacked on the first electrode; and a piezoelectric element including the second electrode stacked on the piezoelectric layer. In
A first detection step of applying a driving voltage to the piezoelectric element and detecting at least two types of characteristic values from an output signal of a counter electromotive force generated by a residual vibration generated thereafter;
A second detection step in which, after the first detection step is performed, a drive voltage is again applied to the piezoelectric element to detect the at least two types of characteristic values again;
The at least two types of characteristic values detected in the first detection step and the at least two types of characteristic values detected in the second detection step are compared, and based on the change between them, the A gas-liquid determination step of determining whether the interior of the cavity is in a liquid space or a gas space.   The liquid detection method according to claim 1, wherein the at least two types of characteristic values include at least one of a frequency and an amplitude of the output signal of the back electromotive force.   The liquid detection method according to claim 1, wherein the at least two types of characteristic values include information related to timing at which the output signal of the back electromotive force crosses a predetermined voltage threshold.   The liquid detection method according to claim 1, wherein the first detection step is performed when the liquid container is attached to the liquid ejecting apparatus.   The liquid detection method according to claim 4, wherein the at least two types of characteristic values detected when the liquid container is mounted on the liquid ejecting apparatus are stored in a storage unit provided in the liquid ejecting apparatus. In a liquid detection system for detecting a liquid inside a liquid container used in a liquid ejecting apparatus,
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. An oscillating cavity forming base that can be formed, a first electrode formed on the second surface side of the oscillating cavity forming base, a piezoelectric layer stacked on the first electrode, and stacked on the piezoelectric layer A piezoelectric element having a second electrode, and a liquid detection device mounted on the liquid container;
A liquid detection control means for applying a driving voltage to the piezoelectric element at different detection time points and obtaining an output signal of a counter electromotive force generated by a residual vibration generated thereafter;
At least two types of characteristic values are detected from the output signal of the back electromotive force, and the inside of the cavity is either a liquid space or a gas space based on a change in the at least two types of characteristic values between detection points. A gas-liquid determination means for determining whether the state is present;
And a storage means for storing the at least two types of characteristic values.   The liquid detection system according to claim 6, wherein the at least two types of characteristic values include at least one of a frequency and an amplitude of the output signal of the back electromotive force.   The liquid detection system according to claim 6 or 7, wherein the at least two types of characteristic values include information related to a timing at which the output signal of the back electromotive force crosses a predetermined voltage threshold.   The liquid detection system according to claim 6, wherein the at least two kinds of characteristic values are detected when the liquid container is mounted on the liquid ejecting apparatus and stored in the storage unit.   The liquid detection system according to claim 6, wherein the storage unit is provided in the liquid ejecting apparatus.

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