JP4826244B2 - Liquid container with liquid detection device - Google Patents

Description

The present invention relates to a liquid container provided with a liquid detection device, and particularly relates to a liquid container provided with a liquid detection device suitable for detecting the liquid remaining amount in the 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 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. 12 shows an actuator 106 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, utilizing the fact that the residual vibration state of the vibration part changes before and after the liquid level in the ink container passes the installation position of the actuator 106 (strictly, the position of the cavity 162), the remaining ink amount in the ink container Can be detected.
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. 13, and the cavity 162 that receives the ink to be detected is provided in the ink storage space inside the ink cartridge 180. It is comprised so that it may be exposed to.

  However, since the conventional actuator (piezoelectric device) 106 described above is configured to expose the cavity 162 in the ink storage space inside the ink cartridge 180 as described above, the ink inside the ink cartridge 180 bubbles due to vibration or the like. Then, 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.

  In addition, since the actuator 106 is configured to expose the cavity 162 in the ink storage space inside the ink cartridge 180, the ink pressure in the ink storage space is applied to the vibration plate 176 and the piezoelectric layer 160 of the actuator 106. For example, in the on-carriage ink cartridge 180, the ink in the ink storage space vibrates vigorously due to the reciprocating movement of the carriage during the printing operation, and the pressure of the ink generated by this vibration is directly applied. In other words, there is a problem of erroneous determination due to the influence of the actuator 106.

  Furthermore, it is also considered to form a wave barrier or the like for preventing ink vibration and waves at a position facing the actuator 106, but the spatial structure around the actuator 106 becomes complicated and residual vibration detected by the actuator 106. The vibration mode is complicated so that it becomes difficult to sense and the detection sensitivity may be dulled.

  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.

  The present invention has been made in consideration of the above-described circumstances. The detection mode is improved by simplifying the vibration mode, and the presence or absence of liquid is reliably determined by reducing the influence of vibration received from the liquid. It is an object of the present invention to provide a liquid detection device that can be used and a liquid container including the same.

In order to solve the above problems, a liquid detection device according to the present invention has a first surface and a second surface that face each other, and a cavity for receiving a medium to be detected opens to the first surface side. A vibration cavity forming base formed so that the bottom surface of the cavity can be vibrated, and
A piezoelectric element having a first electrode formed on the second surface side of the vibration cavity forming base, a piezoelectric layer stacked on the first electrode, and a second electrode stacked on the piezoelectric layer;
A flow path formed by laminating on the first surface side of the vibration cavity forming base, a liquid supply path for supplying a liquid to be detected to the cavity, and a liquid discharge path for discharging the liquid to be detected from the cavity. With a forming base,
The flow path formed including the cavity, the liquid supply path, and the liquid discharge path is formed symmetrically with respect to the center of the cavity existing in a region sandwiched between the liquid supply path and the liquid discharge path. And

  That is, the liquid detection device of the present invention is laminated on the first surface side of the vibration cavity forming base, a liquid supply path for supplying the liquid to be detected to the cavity, and a liquid for discharging the liquid to be detected from the cavity. Since a flow path forming base formed with a discharge path is provided, the liquid is supplied to the cavity through the liquid supply path, and the liquid is discharged from the cavity through the liquid discharge path. When mounting the liquid detection device on a liquid container or the like to be detected, the liquid is supplied to the cavity via the liquid supply path without exposing the cavity of the liquid detection device to the liquid storage space to be detected. Can be supplied.

  In this manner, by configuring the liquid to flow inside the liquid supply path and the liquid discharge path of the liquid detection device when the liquid is consumed, even if air bubbles enter the cavity, Bubbles are pushed out from inside. As a result, it is possible to prevent erroneous detection of the liquid detection device due to air bubbles remaining in the cavity, improving detection accuracy, reducing the amount of liquid remaining, and reducing industrial waste.

  In addition, since it is not necessary to expose the cavity to the liquid storage space, it is possible to prevent a meniscus from being formed in the cavity when the liquid surface passes. As a result, it is possible to prevent erroneous detection of the liquid detection device due to liquid remaining in the cavity. Moreover, since the cavity is not a space exposed toward the liquid storage space but a space partitioned from the storage space by the flow path forming base, the bottom surface of the cavity is changed depending on the change in the liquid level or the presence or absence of liquid. The difference in residual vibration remaining on the bottom surface of the cavity when forced vibration is increased, the detection sensitivity is increased, the detection accuracy can be increased, and erroneous detection can be prevented.

  Further, the flow path formed including the cavity, the liquid supply path and the liquid discharge path is formed symmetrically with respect to the center of the cavity existing in the region sandwiched between the liquid supply path and the liquid discharge path. Further, the spatial shape of the flow path formed including the cavity, the liquid supply path, and the liquid discharge path, which is a space through which vibration of the cavity bottom surface propagates, is simplified, and the vibration mode of residual vibration remaining on the cavity bottom surface is also simplified. This makes it easier to simulate residual vibration when the cavity bottom is forced to vibrate, reducing the gap between design and actuality, reducing adjustment work, and improving detection accuracy. It becomes.

  In the present invention, when the cavity is substantially cylindrical, the space shape of the cavity, which is the space through which the vibration of the cavity bottom surface propagates, is further simplified, and the vibration mode of residual vibration remaining on the cavity bottom surface is also simplified. . Further, it becomes extremely easy to simulate residual vibration when the cavity bottom surface is forcibly vibrated, and the difference between the design and the actual is reduced, so that the adjustment work can be reduced and the detection accuracy can be improved.

  In the present invention, the liquid supply path and the liquid discharge path each have a flow path area narrowed with respect to the cavity, and when the length is set so that the fluid mass of the liquid exists inside, the liquid supply path and the liquid discharge path Appropriate flow path resistance is generated in the supply path and the liquid discharge path, so that pressure fluctuations in the cavity caused by vibration at the bottom of the cavity are prevented from diffusing into both buffer chambers, and appropriate residual vibration is generated. It becomes possible to improve and secure the detection accuracy.

  In the present invention, when a supply-side buffer chamber communicating with the liquid supply path and a discharge-side buffer chamber communicating with the liquid discharge path are provided, the liquid supply path and the liquid discharge path through which liquid enters and exits the cavity Since the paths open to the supply-side buffer chamber and the discharge-side buffer chamber, respectively, and do not directly open to the liquid storage space to be detected, bubbles are generated in the liquid storage space due to vibration of the liquid or the like. Even if the bubbles are generated, the bubbles are once trapped in the supply-side buffer chamber and the discharge-side buffer chamber and are less likely to enter the cavity. Accordingly, it is possible to prevent erroneous detection of the liquid detection device due to air bubbles remaining in the cavity.

  Further, the liquid supply path and the liquid discharge path through which the liquid enters and exits the cavity do not open directly to the liquid storage space, but open to the supply side buffer chamber and the discharge side buffer chamber, respectively. Therefore, since the pressure of the liquid generated in the liquid storage space does not directly act on the cavity, it is possible to prevent erroneous detection of the liquid detection device due to the influence of pressure due to vibration of the liquid or the like.

  In the present invention, when the supply side buffer chamber and the discharge side buffer chamber are formed symmetrically with respect to the center of the cavity, both the supply side buffer chamber and the discharge side buffer chamber are made symmetric. The shape of the members constituting the buffer chamber is simplified, the manufacture is facilitated, and the members can be miniaturized.

  In the present invention, when the supply-side buffer chamber and the discharge-side buffer chamber each have a capacity of at least 10 times the capacity of the cavity, the pressure fluctuation of the liquid generated in the liquid storage space in the liquid container However, the sensor characteristics of the liquid detection device are hardly affected, and erroneous detection of the liquid detection device due to the influence of pressure due to vibration of the liquid or the like can be prevented. Furthermore, since the pressure in the buffer chambers does not increase due to vibrations at the bottom surfaces of the cavities, excess vibrations are not generated, and the vibration mode of residual vibrations remaining on the bottom surfaces of the cavities can be simplified and detection accuracy can be improved. .

In order to solve the above problems, a liquid container according to the present invention includes a container main body having a liquid delivery port for delivering the liquid stored inside to the outside,
A liquid detection device mounted on the container body,
The liquid detection device is
A cavity having a first surface and a second surface facing each other and receiving a medium to be detected is formed so as to open to the first surface side, and a bottom surface of the cavity is formed so as to be able to vibrate. A vibration cavity forming base,
A piezoelectric element having a first electrode formed on the second surface side of the vibration cavity forming base, a piezoelectric layer stacked on the first electrode, and a second electrode stacked on the piezoelectric layer;
A flow path formed by laminating on the first surface side of the vibration cavity forming base, a liquid supply path for supplying a liquid to be detected to the cavity, and a liquid discharge path for discharging the liquid to be detected from the cavity. With a forming base,
The flow path formed including the cavity, the liquid supply path and the liquid discharge path is formed symmetrically with respect to the center of the cavity existing in the region sandwiched between the liquid supply path and the liquid discharge path,
The gist is that the liquid inside the container body is supplied to the cavity through the liquid supply path of the liquid detection device and discharged from the cavity through the liquid discharge path. .

  That is, the liquid container of the present invention is laminated on the first surface side of the vibration cavity forming base, and a liquid supply path for supplying the liquid to be detected to the cavity, and a liquid discharge for discharging the liquid to be detected from the cavity. Since the channel is formed with a flow path forming base, the liquid is supplied to the cavity through the liquid supply path, and the liquid is discharged from the cavity through the liquid discharge path. When mounting the liquid detection device on the liquid container, the liquid in the container body is supplied to the cavity via the liquid supply path without exposing the cavity of the liquid detection device in the liquid storage space in the container body of the liquid container. can do.

  In this way, by configuring the liquid to flow through the liquid supply path and the liquid discharge path of the liquid detection device when the liquid in the liquid container is consumed, even if bubbles enter the cavity, the liquid Bubbles are pushed out of the cavity by the flow of. As a result, it is possible to prevent erroneous detection of the liquid detection device due to air bubbles remaining in the cavity.

  In addition, since it is not necessary to expose the cavity to the liquid storage space in the container body, it is possible to prevent a meniscus from being formed in the cavity when the liquid level passes. As a result, it is possible to prevent erroneous detection of the liquid detection device due to liquid remaining in the cavity. Moreover, since the cavity is not a space exposed toward the liquid storage space but a space partitioned from the storage space by the flow path forming base, the bottom surface of the cavity is changed depending on the change in the liquid level or the presence or absence of liquid. The difference in residual vibration remaining on the bottom surface of the cavity when forced vibration is increased, the detection sensitivity is increased, the detection accuracy can be increased, and erroneous detection can be prevented.

  Further, the flow path formed including the cavity, the liquid supply path and the liquid discharge path is formed symmetrically with respect to the center of the cavity existing in the region sandwiched between the liquid supply path and the liquid discharge path. Further, the spatial shape of the flow path formed including the cavity, the liquid supply path, and the liquid discharge path, which is a space through which vibration of the cavity bottom surface propagates, is simplified, and the vibration mode of residual vibration remaining on the cavity bottom surface is also simplified. This makes it easier to simulate residual vibration when the cavity bottom is forced to vibrate, reducing the gap between design and actuality, reducing adjustment work, and improving detection accuracy. It becomes.

  Further, the flow path formed including the cavity, the liquid supply path and the liquid discharge path is formed symmetrically with respect to the center of the cavity existing in the region sandwiched between the liquid supply path and the liquid discharge path. Further, the spatial shape of the flow path formed including the cavity, the liquid supply path, and the liquid discharge path, which is a space through which vibration of the cavity bottom surface propagates, is simplified, and the vibration mode of residual vibration remaining on the cavity bottom surface is also simplified. This makes it easier to simulate residual vibration when the cavity bottom is forced to vibrate, reducing the gap between design and actuality, reducing adjustment work, and improving detection accuracy. It becomes.

  In the present invention, when the cavity of the liquid detection device is substantially cylindrical, the spatial shape of the cavity, which is the space through which the vibration of the bottom surface of the cavity propagates, is further simplified, and the vibration mode of residual vibration remaining on the bottom surface of the cavity. Also simplify. Further, it becomes extremely easy to simulate residual vibration when the cavity bottom surface is forcibly vibrated, and the difference between the design and the actual is reduced, so that the adjustment work can be reduced and the detection accuracy can be improved.

  In the present invention, the liquid supply path and the liquid discharge path each have a flow path area narrowed with respect to the cavity, and when the length is set so that the fluid mass of the liquid exists inside, the liquid supply path and the liquid discharge path Appropriate flow path resistance is generated in the supply path and the liquid discharge path, so that pressure fluctuations in the cavity caused by vibration at the bottom of the cavity are prevented from diffusing into both buffer chambers, and appropriate residual vibration is generated. It becomes possible to improve and secure the detection accuracy.

  In the present invention, when the liquid detection device includes a supply-side buffer chamber that communicates with the liquid supply path and a discharge-side buffer chamber that communicates with the liquid discharge path, liquid enters and exits the cavity. The liquid supply path and the liquid discharge path open to the supply-side buffer chamber and the discharge-side buffer chamber, respectively, and do not directly open to the liquid storage space of the container body. Even if air bubbles are generated by the above, the air bubbles are once trapped in the supply side buffer chamber or the discharge side buffer chamber and are difficult to enter the cavity. Accordingly, it is possible to prevent erroneous detection of the liquid detection device due to air bubbles remaining in the cavity. In this case, when the liquid detection device is disposed in the vicinity of the bottom of the liquid container, the effect of preventing the invasion of bubbles is further enhanced.

  In addition, the liquid supply path and the liquid discharge path through which liquid enters and exits the cavity do not open directly to the liquid storage space of the container body, but open to the supply side buffer chamber and the discharge side buffer chamber, respectively. Therefore, since the pressure of the liquid generated in the liquid storage space in the liquid container does not directly act on the cavity, it is possible to prevent erroneous detection of the liquid detection device due to the influence of pressure due to vibration of the liquid or the like.

  In the present invention, when the supply side buffer chamber and the discharge side buffer chamber of the liquid detection device are formed symmetrically with respect to the center of the cavity, the supply side buffer chamber and the discharge side buffer chamber are made symmetrical. This simplifies the shape of the members constituting both the buffer chambers, facilitates manufacturing, and allows the members to be miniaturized.

  In the present invention, when the supply-side buffer chamber and the discharge-side buffer chamber of the liquid detection device have a capacity of at least 10 times the capacity of the cavity, they are generated in the liquid storage space in the liquid container. The fluctuation in the pressure of the liquid hardly affects the sensor characteristics of the liquid detection device, and erroneous detection of the liquid detection device due to the influence of pressure due to vibration of the liquid or the like can be prevented. Furthermore, since the pressure in the buffer chambers does not increase due to vibrations at the bottom surfaces of the cavities, excess vibrations are not generated, and the vibration mode of residual vibrations remaining on the bottom surfaces of the cavities can be simplified and detection accuracy can be improved. .

  In the present invention, the supply-side buffer chamber communicates with a liquid storage chamber that constitutes a main portion of the internal space of the container body and stores liquid, and the discharge-side buffer chamber is an interior of the container body. When the liquid stored in the space communicates with the liquid delivery space communicating with the liquid delivery port for delivering the liquid to the outside, the liquid stored in the liquid storage chamber of the container body is While flowing from the inlet of the supply side buffer chamber and discharged from the outlet of the discharge side buffer chamber, it is sent to the liquid delivery port of the container body, and the total amount of liquid sent to the liquid delivery port of the container body is Since the liquid detection apparatus passes through the supply side buffer chamber, the cavity, and the discharge side buffer chamber, the consumption of the liquid can be reliably detected.

  Hereinafter, a liquid detection device according to an embodiment of the present invention and an ink cartridge (liquid container) including the liquid detection device 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. Reference numeral 1 in FIG. 1 denotes a carriage. The carriage 1 is driven by a carriage motor 2. It is configured to be reciprocated in the axial direction of the platen 5 by being guided by the guide member 4 via the timing belt 3.

  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 figure) which is a non-printing area of the recording apparatus. When the recording head 12 mounted on the carriage 1 is moved to the home position, the cap member 31 is The recording head 12 is pressed against the nozzle forming surface 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.

  In the vicinity of the print region side of the cap member 31, a wiping means 11 having an elastic plate such as rubber is disposed so as to be able to advance and retreat in the horizontal direction with respect to the movement locus of the recording head 12. Is configured to be able to wipe the nozzle forming surface of the recording head 12 as necessary when reciprocating toward the cap member 31 side.

  Next, the liquid detection device of the present invention and the ink cartridge including the same will be described.

  FIG. 2 is a cross-sectional view showing the liquid detection device 60 of the present invention. 3 is a diagram showing the detection unit 13 constituting the liquid detection device 60, and FIG. 4 is a diagram showing the buffer unit 14 constituting the liquid detection device 60.

  The liquid detection device 60 includes a detection unit 13 having a cavity 43 and a buffer unit 14 having a supply-side buffer chamber 15 and a discharge-side buffer chamber 16 that communicate with the cavity 43.

  The detection unit 13 is configured by stacking a vibration plate 42 on a cavity plate 41, and includes a vibration cavity forming base 40 having a first surface 40 a and a second surface 40 b facing each other, and the vibration cavity forming base 40. The piezoelectric element 17 is stacked on the second surface 40b side, and the flow path forming plate (flow path forming base) 18 is stacked on the first surface 40a side of the vibration cavity forming base 40.

  A cavity 43 having a cylindrical space shape 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. The portion 43a is formed to be able to vibrate with the diaphragm 42. In other words, the contour of the portion of the entire diaphragm 42 that actually vibrates is defined by the cavity 43. 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.

  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 includes a substantially circular main body 46 a and the lower electrode terminal 44 from the main body 46 a. An extending portion 46 b extending in the direction and connected to the lower electrode terminal 44. The center of the substantially circular main body 46 a of the lower electrode 46 coincides with the central axis C of the cavity 43.

  The substantially circular main body 46 a of the lower electrode 46 is formed with a larger diameter than the circular cavity 43 and covers substantially the entire region corresponding to the cavity 43. The substantially circular main body 46 a of the lower electrode 46 includes a notch 46 c formed so as to enter the inner side of the position corresponding to the peripheral edge 43 b of the cavity 43.

  A piezoelectric layer 47 is laminated on the lower electrode 46, and the piezoelectric layer 47 has a circular main body portion 47 a formed with a smaller diameter than the cavity 43 and a main body portion within a range corresponding to the cavity 43. And a protruding portion 47b protruding from 47a. 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 b of the cavity 43.

  The center of the main body portion 47a of the piezoelectric layer 47 coincides with the central axis C of the cavity 43, and the main body portion 47a of the piezoelectric layer 47 is substantially entirely excluding the portion corresponding to the notch portion 46c of the lower electrode 46. It is laminated on the lower electrode 46.

  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 b of the cavity 43. A part of the auxiliary electrode 48 is located inside the notch 46 c of the lower electrode (first electrode) 46, and the protruding portion 47 b of the piezoelectric layer 47 and the vicinity thereof from the second surface 40 b side of the vibration cavity forming base 40. I support it. The auxiliary electrode 48 is preferably made of the same material as the lower electrode 46 and has the same thickness. As described above, the auxiliary electrode 48 supports the protruding portion 47b of the piezoelectric layer 47 and the vicinity thereof from the second surface 40b side of the vibration cavity forming base 40, thereby preventing the piezoelectric layer 47 from having a step and providing a mechanical strength. A decrease can be prevented.

  A circular 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 to have a smaller diameter than the main body 47 a of the piezoelectric layer 47. 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. As can be seen from FIG. 2, the position P at which the connection between the extended portion 49 b of the upper electrode 49 and the auxiliary electrode 48 starts is located within the region corresponding to the cavity 43.

  The piezoelectric element 17 is formed by the main body portions of the lower electrode 46, the piezoelectric layer 47, and the upper electrode 49.

  As can be seen from FIG. 3, 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, the 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.

  The main body 49 a of the upper electrode 49 has a circular shape, and the center thereof coincides with the central axis C of the cavity 43. The main body 49 a of the upper electrode 49 is formed with a smaller diameter than both the main body 47 a of the piezoelectric layer 47 and the cavity 43.

  Thus, the main body portion 47 a of the piezoelectric layer 47 has a structure sandwiched between the main body portion 49 a of the upper electrode 49 and the main body portion 46 a of the lower electrode 46. Thereby, the piezoelectric layer 47 can be effectively deformed and driven.

  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 to have a smaller diameter. 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 main body portion 47 a 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 central axis C of the cavity 43. In addition, the central axis C of the cylindrical cavity 43 that determines the portion of the vibration plate 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 of the main body 46 a of the lower electrode 46 that corresponds to the cavity 43, the main body 47 a and the protrusion 47 b of the piezoelectric layer 47, and the main body of the upper electrode 49. Portions corresponding to the cavity 43 of the portion 49 a and the extension portion 49 b constitute a vibrating portion 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.

  Further, the main body portion 47 a of the piezoelectric layer 47, the main body portion 49 a of the upper electrode 49, the main body portion 46 a of the lower electrode 46, and the vibrating portion of the diaphragm 42 (that is, the portion corresponding to the bottom surface portion 43 a of the cavity 43) are circular. In addition, since the entire piezoelectric layer 47, that is, the main body portion 47 a and the protruding portion 47 b of the piezoelectric layer 47 are disposed inside the region corresponding to the cavity 43, the vibrating portion of the liquid detection device 60 Reference numeral 61 denotes a shape that is substantially symmetrical with respect to the center of the liquid detection device 60.

  Furthermore, the liquid detection device 60 according to the present embodiment includes a flow path forming plate (flow path forming base) 18 that is laminated and bonded to the first surface 40 a of the vibration cavity forming base 40.

  The flow path forming plate 18 includes an ink supply path (liquid supply path) 19 for supplying ink to be detected to the cavity 43, and an ink discharge path (liquid discharge path) 20 for discharging the ink to be detected from the cavity 43. Is formed. The ink supply path 19 and the ink discharge path 20 are formed in the same size and shape, and both have a cylindrical space shape.

  The ink supply path 19 and the ink discharge path 20 formed in the flow path forming plate 18 are both formed in a region corresponding to the circular cavity 43, and the ink supply path 19 and the ink discharge path 20 are They are arranged symmetrically with respect to the central axis C of the cavity 43. Thereby, the space formed including the cavity 43, the ink supply path 19, and the ink discharge path 20 is in relation to the central axis C of the cavity 43 existing in the region sandwiched between the ink supply path 19 and the ink discharge path 20. Are formed symmetrically.

  In addition, the ink supply path 19 and the ink discharge path 20 each have a flow path area narrowed with respect to the cavity 43. That is, in this example, one ink supply path 19 and one ink discharge path 20 are formed for one cavity 43, but the flow path of one flow path (ink supply path 19 or ink discharge path 20). The area is set to be smaller than at least half of the area of the cavity 43. The ink supply path 19 and the ink discharge path 20 are set to have a certain length so that a fluid mass of the liquid exists inside, and preferably the flow paths of the ink supply path 19 and the ink discharge path 20. Each length is set to be twice or more the flow path diameter.

  On the other hand, the liquid detection device 60 includes a buffer unit 14 having a supply side buffer chamber 15 communicating with the ink supply path 19 and a discharge side buffer chamber 16 communicating with the ink discharge path 20.

  In this example, the buffer unit 14 has a rectangular shape that is slightly larger than the liquid detection device 60 in plan view, and is formed in a rectangular parallelepiped shape as a whole. The inside of the buffer unit 14 is divided into two spaces (flow paths) having the same size and shape by a single partition wall 21 disposed in the center, and one side is connected to the supply side buffer chamber 15 and the other side. Is the discharge-side buffer chamber 16.

  An inflow opening 22 through which ink flows into the supply-side buffer chamber 15 and an outflow opening 23 through which ink flows out from the discharge-side buffer chamber 16 are formed on the opposite side of the surface of the buffer unit 14 to which the detection unit 13 is joined. Is formed. Further, on the surface to which the detection unit 13 of the buffer unit 14 is joined, the inflow channel 24 that supplies the ink flowing into the supply side buffer chamber 15 to the cavity 43 through the ink supply channel 19, and the ink in the cavity 43 And an outflow passage 25 through which the ink flows out to the supply-side buffer chamber 15 through the ink discharge passage 20.

  The inflow channel 24 and the outflow channel 25 are formed in a substantially cylindrical channel space, and are formed in the same size. In addition, the openings of the inflow channel 24 and the outflow channel 25 coincide with the openings of the ink supply path 19 and the ink discharge path 20, respectively. In this example, the ink supply path 19 and the inflow path 24 are the same as those of the present invention. A liquid supply path is formed, and the ink discharge path 20 and the outflow path 25 form the liquid discharge path of the present invention.

  The supply-side buffer chamber 15 and the discharge-side buffer chamber 16 of the liquid detection device 60 are formed symmetrically with respect to the central axis C of the cavity 43. In other words, the space formed by the cavity 43, the ink supply path 19, the ink discharge path 20, the inflow channel 24, the outflow channel 25, the supply side buffer chamber 15, and the discharge side buffer chamber 16 is the center of the cavity 43. It is formed symmetrically with respect to the axis C.

  Further, the capacities of the supply-side buffer chamber 15 and the discharge-side buffer chamber 16 of the liquid detection device 60 are set to have at least 10 times the capacity of the cavity 43, respectively.

  With such a configuration, the ink inside the cartridge to be detected flows into the supply-side buffer chamber 15 from the inflow opening 22 and is supplied to the cavity 43 through the inflow channel 24 and the ink supply channel 19. The ink supplied to the cavity 43 is discharged to the discharge side buffer chamber 16 through the ink discharge path 20 and the outflow path 25, and is further discharged from the discharge side buffer chamber 16 through the outflow opening 23.

  The members included in the liquid detection device 60, in particular the cavity plate 41, the vibration plate 42, and the flow path forming plate 18, 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. 5 is a view showing an ink cartridge 70 of the present invention provided with the liquid detection device, and FIG. 6 is a view showing an example of an attachment portion of the liquid detection device to the ink cartridge 70.

  FIG. 5 shows an ink cartridge (liquid container) 70 to which the above-described liquid detection device 60 is mounted. The ink cartridge 70 is an ink delivery port (liquid delivery port) for sending the ink stored inside to the outside. A container body 72 having 71 is provided.

  As shown in FIG. 6, the entire liquid detection device 60 is mounted on a container body 72, and the buffer portion 14 is attached to the rectangular opening 26 formed on the wall surface 27 of the container body 72 by an adhesive 28 or the like. It is attached in a liquid-tight manner. At this time, the detection unit 13 of the liquid detection device 60 is arranged outside the container main body 72, and the inflow opening 22 and the outflow opening 23 of the buffer unit 14 are arranged to open inside the container main body 72.

  The inside of the container main body 72 (returning to FIG. 5) constitutes a main portion of the entire internal space of the container main body 72 and stores a main storage chamber (liquid storage chamber) 75 for storing ink, and this main storage. The main storage chamber 75 and the sub storage chamber 76 are separated from each other. The sub storage chamber (liquid delivery space) 76 has a smaller volume than the chamber 75. 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.

  The inflow opening 22 of the liquid detection device 60 is opened at a position communicating with the main storage chamber 75, and the outflow opening 23 is arranged to open to the sub storage chamber 76 that is the liquid delivery space. Thus, the supply-side buffer chamber 15 communicates with the main storage chamber 75 that constitutes a main portion of the internal space of the container main body 72 and stores the liquid, and the discharge-side buffer chamber 16 is connected to the container Of the internal space of the main body 72, the liquid stored inside is communicated with a liquid delivery space communicating with an ink delivery port 71 for delivering the liquid to the outside.

  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. In addition, the inflow opening 22 of the liquid detection device 60 communicates with the upper end portion of the auxiliary flow path 77, and the inflow opening 22 constitutes the outlet of the auxiliary flow path 77.

  As described above, the inflow opening 22 of the liquid detection device 60 communicates with the main storage chamber 75 through the auxiliary flow path 77, and the outflow opening 23 communicates with the ink delivery port 71 through the sub storage chamber 76. As a result, the ink stored in the main storage chamber 75 flows into the supply-side buffer chamber 15 from the inflow opening 22 through the auxiliary flow path 77 and is supplied to the cavity 43 through the inflow flow path 24 and the ink supply path 19. The Then, the ink supplied to the cavity 43 is discharged to the discharge side buffer chamber 16 through the ink discharge path 20 and the outflow path 25, and further passes through the outflow opening 23 and the auxiliary storage chamber 76 from the discharge side buffer chamber 16. The ink is discharged from the ink outlet 71 and supplied to the recording head 12.

  As described above, in this embodiment, the entire amount of ink sent to the ink delivery port 71 through the sub-reservoir chamber 76 passes through the ink supply path 19 and the ink discharge path 20 of the liquid detection device 60 in advance. Has been.

  Next, the operation for detecting the liquid in the liquid container will be described.

  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.

  7A and 7B show residual vibrations (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 to forcibly vibrate the vibration unit 61. FIG. The waveform of this and the measuring method of residual vibration are shown. FIG. 7A shows a waveform when ink is present in the cavity 43 of the liquid detection device 60, while FIG. 7B shows a waveform when ink is not present in the cavity 43 of the liquid detection device 60. .

  7A and 7B, the vertical axis indicates the drive pulse applied to the liquid detection device 60 and the voltage of the back 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 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. 7, 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. 7A and FIG. 7B, it can be seen that the time from 4 to 8 counts is longer in FIG. 7A than in FIG. 7B. 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.

  In FIG. 7, the time from the 4th count to the 8th count is measured, but 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 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.

  FIG. 8 is an equivalent circuit diagram that can be simulated by approximating the vibration of the vibration part 61 of the liquid detection device 60 as described above.

  In this figure, the inertance (Mc) of the vibration part 61 (Sensor Chip), the inertances (Ms1, Ms2) of the ink supply path 19 and the ink discharge path 20 (Hole) are coils, and the compliance of the vibration part 61 (Sensor Chip) ( Cc), the compliance of the ink (Ci) is a capacitor, the resistance (Rs1, Rs2) of the ink supply path 19 and the ink discharge path 20 (Hole) is the resistance, and the supply side where the ink supply path 19 and the ink discharge path 20 communicate with each other The buffer chamber 15 and the discharge side buffer chamber 16 are represented by grounds.

And the compliance (Cc) of the vibration part 61 is calculated | required by the structural finite element method. Further, the inertance (Mc) of the vibration unit 61 is approximated by a series system of inertance and compliance, and an approximate value can be calculated by the following approximate expression.

Mc = 1 / (4π ² ) × 1 / (f ² ) × 1 / Cc

Here, f is a natural period of the vibration part 61 and can be obtained by a structural finite element method or actual measurement.

The ink compliance (Ci) can be obtained by the following equation.

Ci = C × Vi

Here, C is the ink compression ratio, and Vi is the ink volume. The compressibility of water is 4.5e-10 / Pa.

Further, the inertance (Ms) of the ink supply path 19 and the ink discharge path 20 (Hole) can be obtained by the fluid finite element method, or when the flow path (Hole) is a cylinder, it can be obtained by the following simplified formula.

Ms = ρ × L / π / r ²

Here, ρ is the viscosity of the ink, L is the length of the flow path (Hole), and r is the radius of the flow path (Hole).

  By using the value obtained as described above, the vibration of the vibration part 61 can be simulated by approximating with the equivalent circuit of FIG.

  As a result of simulating the vibration of the vibration part 61 with such an equivalent circuit, it can be seen that when Ms1 and Ms2 and Rs1 and Rs2 are approximately equal, vibration is simple and no extra vibration mode occurs. Therefore, in the present invention, the space formed by the cavity 43, the ink supply path 19, and the ink discharge path 20 is formed symmetrically with respect to the central axis C of the cavity 43.

  In addition, the requirement that the supply side buffer chamber 15 and the discharge side buffer chamber 16 function as buffers is that the buffer chambers 15, 16 are configured so that the pressure in the buffer chambers 15, 16 is hardly increased by the vibration of the vibration part 61. It is preferable that the compliance of 16 is 10 times or more the compliance (Cc) of the vibration part 61. In order not to generate extra vibration, the inertance of the buffer chambers 15 and 16 is preferably set to 1/10 or less of the inertance (Ms) of the flow path (Hole).

  As described above, according to the liquid detection device 60 and the ink cartridge 70 according to the present embodiment, the ink supply path 19 that supplies ink to the cavity 43 and the ink discharge path 20 that discharges ink from the cavity 43. Therefore, the ink is supplied to the cavity 43 through the ink supply path 19, and the ink is discharged from the cavity 43 through the ink discharge path 20. Therefore, when the liquid detection device 60 is attached to the ink cartridge 70 or the like, the ink is supplied to the cavity 43 via the ink supply path 19 without directly exposing the cavity 43 of the liquid detection device 60 to the ink containing space. can do.

  As described above, by configuring the ink to flow through the ink supply path 19 and the ink discharge path 20 of the liquid detection device 60 when the ink is consumed, even if bubbles enter the cavity 43, the ink The air bubbles are pushed out of the cavity 43 by the flow of. 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 this way, the detection accuracy of the liquid detection device 60 is improved, and the remaining liquid is reduced, leading to a reduction in industrial waste.

  Further, since it is not necessary to expose the cavity 43 to the ink containing space, it is possible to prevent a meniscus from being formed in the cavity 43 when the liquid surface passes. As a result, erroneous detection of the liquid detection device 60 due to ink remaining in the cavity 43 can be prevented. In addition, since the cavity 43 is not a space exposed toward the ink storage space but a space partitioned from the storage space by the flow path forming plate 18, depending on the change in the ink liquid level, the presence or absence of ink, and the like, The difference in residual vibration remaining in the vibration part 61 when the vibration part 61 is forcibly vibrated is increased, the detection sensitivity is increased, the detection accuracy can be increased, and erroneous detection can be prevented.

  The flow path (space) formed including the cavity 43, the ink supply path 19, and the ink discharge path 20 is a central axis of the cavity 43 existing in a region sandwiched between the ink supply path 19 and the ink discharge path 20. Since it is formed symmetrically with respect to C, the space shape of the space formed including the cavity 43, the ink supply path 19 and the ink discharge path 20 through which the vibration of the bottom surface of the cavity 43 propagates is simplified. The vibration mode of residual vibration remaining on the bottom surface 43 is also simplified. This makes it easier to simulate residual vibration when the bottom surface of the cavity 43 is forcibly vibrated, reducing the difference between the design and actuality, reducing the adjustment work, and improving the detection accuracy. It becomes possible.

  Further, since the space forming the cavity 43 is substantially cylindrical, the shape of the cavity 43, which is the space through which the vibration of the bottom surface of the cavity 43 propagates, is further simplified, and the vibration mode of residual vibration remaining on the bottom surface of the cavity 43. Also simplify. Then, it becomes extremely easy to simulate residual vibration when the bottom surface of the cavity 43 is forcibly vibrated, the deviation between the design and the actual is reduced, adjustment work is reduced, and the detection accuracy can be improved. .

  Further, the ink supply path 19 and the ink discharge path 20 are each narrowed in flow path area with respect to the cavity 43 and set in length so that the fluid mass of the ink exists therein. Appropriate flow path resistance is generated in the path 19 and the ink discharge path 20, so that the pressure fluctuation in the cavity 43 caused by the vibration of the bottom surface of the cavity 43 is prevented from diffusing into both the buffer chambers 15 and 16. Residual vibration can be generated to improve and secure detection accuracy. In particular, the effect becomes conspicuous by setting the flow path lengths of the ink supply path 19 and the ink discharge path 20 to be not less than twice the flow path diameter.

  In addition, since the liquid detection device 60 includes the supply-side buffer chamber 15 that communicates with the ink supply path 19 and the discharge-side buffer chamber 16 that communicates with the ink discharge path 20, ink is supplied to the cavity 43. The ink supply path 19 and the ink discharge path 20 through which the ink enters and exits open to the supply-side buffer chamber 15 and the discharge-side buffer chamber 16, respectively, and do not open directly to the ink storage space of the container body 72. Even if bubbles are generated due to ink vibration or the like in the ink storage space, the bubbles are temporarily trapped in the supply-side buffer chamber 15 and the discharge-side buffer chamber 16 and are unlikely to enter the cavity 43. Therefore, erroneous detection of the liquid detection device 60 due to air bubbles remaining in the cavity 43 can be prevented. In addition, since the liquid detection device 60 is disposed near the bottom of the ink cartridge 70, the effect of preventing bubbles from entering is further enhanced.

  Further, the ink supply path 19 and the ink discharge path 20 through which ink enters and exits the cavity 43 do not directly open to the ink storage space of the container body 72, but supply side buffer chamber 15 and discharge side buffer chamber, respectively. 16, since the ink pressure generated in the ink storage space in the ink cartridge 70 does not directly act on the cavity 43, erroneous detection of the liquid detection device 60 due to the influence of pressure due to ink vibration or the like is detected. Can be prevented.

  Furthermore, since the supply side buffer chamber 15 and the discharge side buffer chamber 16 of the liquid detection device 60 are formed symmetrically with respect to the central axis C of the cavity 43, the supply side buffer chamber 15 and the discharge side buffer chamber 16. Are simplified, the shapes of the members constituting both the buffer chambers 15 and 16 are simplified, the manufacture is facilitated, and the members can be miniaturized.

  Moreover, the supply-side buffer chamber 15 and the discharge-side buffer chamber 16 of the liquid detection device 60 each have a capacity at least 10 times the capacity of the cavity 43, so that the ink storage space in the ink cartridge 70 is obtained. The ink pressure fluctuation generated in the ink hardly affects the sensor characteristics of the liquid detection device 60, and the erroneous detection of the liquid detection device 60 due to the influence of pressure due to ink vibration or the like can be prevented. Further, since the pressure in the buffer chambers 15 and 16 does not increase due to the vibration of the bottom surface of the cavity 43, no extra vibration is generated, and the vibration mode of the residual vibration remaining on the bottom surface of the cavity 43 is simplified and the detection accuracy is improved. It becomes possible to make it.

  Further, the supply-side buffer chamber 15 communicates with a main storage chamber 75 that constitutes a main portion of the internal space of the container main body 72 and stores ink, and the discharge-side buffer chamber 16 includes the container main body 72. Since the ink stored in the internal space 72 is communicated with the auxiliary storage chamber 76 which is a liquid delivery space communicating with the ink delivery port 71 for delivering the ink to the outside, the ink is stored in the main storage chamber 75 of the container body 72. The discharged ink flows from the inlet of the supply-side buffer chamber 15 of the liquid detection device 60, is discharged from the outlet of the discharge-side buffer chamber 16, and is sent to the ink delivery port 71 of the container main body 72. 72, the total amount of ink sent to the ink delivery port 71 of the liquid 72 passes through the supply side buffer chamber 15, the cavity 43 and the discharge side buffer chamber 16 of the liquid detection device 60 in advance. To, can be detected reliably ink consumption.

  Further, according to the liquid detection device 60, since the ink discharge path 20 is formed in accordance with the region corresponding to the cavity 43, the bubbles that have entered the cavity 43 can be reliably discharged.

  Further, in the ink cartridge 70, 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 main body 72 is separated via the inflow opening 22 and the outflow opening 23 of the liquid detection device 60. The storage chamber 75 and the sub storage chamber 76 are connected to each other, 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, according to the ink cartridge 70, the sealed auxiliary flow path 77 is formed inside the main storage chamber 75, and the auxiliary flow path inlet 77a of the auxiliary flow path 77 is positioned at the lower end of the main storage chamber 75. The inflow opening 22 of the liquid detection device 60 is communicated with the upper end portion of the auxiliary flow path 77. For this reason, bubbles generated in the main storage chamber 75 are unlikely to enter the auxiliary flow path 77, and bubbles can be prevented from entering the cavity 43 of the liquid detection device 60.

  Furthermore, according to the ink cartridge 70, since the inside of the sub storage chamber 76 is filled with ink until all the ink in the main storage chamber 75 is consumed, vibration is applied to the ink cartridge 70. Even in this case, as long as ink remains in the main storage chamber 75, the liquid level does not shake in the sub storage chamber 76. 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, since the range in which the vibrating unit 61 and the ink are in contact is limited to the range in which the cavity 43 exists, it is possible to pinpoint ink detection. Thereby, 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 46a of the lower electrode 46 having a diameter larger than that of the cavity 43, generation of unnecessary vibration due to the positional deviation of the lower electrode 46 during manufacturing is generated. 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 b of the cavity 43. For this reason, there is no problem of a crack of the piezoelectric film at a position corresponding to the peripheral edge of the cavity.

  FIG. 9 shows a second embodiment of the ink cartridge of the present invention.

  In the ink cartridge 70 </ b> A, a protruding portion 76 a that protrudes upward is formed in the upper portion of the sub-reservoir chamber 76 formed inside the container main body 72. The outflow opening 23 of the liquid detection device 60 is disposed at a position corresponding to the protrusion 76 a and communicates with the protrusion 76 a of the sub-storage chamber 76. The rest is the same as in the first embodiment, and the same reference numerals are given to the same parts. Also in this embodiment, the same effects as those of the first embodiment are achieved.

  10 and 11 show a third embodiment of the liquid detection device 60A of the present invention.

  In the liquid detection device 60A, a flow path forming base 50 laminated and bonded to the first surface 40a of the vibration cavity forming base 40 is formed by stacking and bonding the flow path plate 51 and the inlet / outlet plate 52.

  In the flow path plate 51 of the flow path forming base 50, an ink supply path (liquid supply path) 19A for supplying the detection target ink to the cavity 43 and an ink discharge path (liquid discharge) for discharging the detection target ink from the cavity 43 are provided. Road) 20A. The inlet / outlet plate 52 is formed with an inlet 53b of the ink supply path 19A and an outlet 54b of the ink discharge path 20A. The inlet 53 b of the ink supply path 19 </ b> A and the outlet 54 b of the ink discharge path 20 </ b> A are arranged so as to exclude the area corresponding to the cavity 43.

  According to this embodiment, the outlet 54b of the ink discharge path 20A is disposed at a position opposite to the inlet 53b of the ink supply path 20A with the cavity 43 interposed therebetween, and the gap between the inlet 53b and the outlet 54b is increased. Therefore, the operation for mounting the liquid detection device 60A on the predetermined position of the container main body 72 of the ink cartridge 70 is facilitated, and the degree of freedom in designing the ink cartridge 70 is improved. The rest is the same as in the first embodiment, and the same reference numerals are given to the same parts. Also in this embodiment, the same effects as those of the first embodiment are achieved.

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. It is sectional drawing along the AA in FIG. 3 of the liquid detection apparatus by one Embodiment of this invention. It is a figure which shows the detection part of the said liquid detection apparatus, (a) is a top view, (b) is the bottom view. It is a top view which shows the buffer part of the said liquid detection apparatus. It is a figure which shows the ink cartridge provided with the said liquid detection apparatus, (a) is a side view, (b) is the front view. It is an expanded sectional view which shows the attachment part of the liquid detection apparatus of the said ink cartridge. 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. It is a figure which shows an example of the equivalent circuit which approximates and simulates the vibration of a vibration part. It is 2nd Example of the ink cartridge provided with the liquid detection apparatus of this invention, (a) is a side view, (b) is the front view. FIG. 13 is a third embodiment of the liquid detection device of the present invention, and is a cross-sectional view taken along line BB in FIG. 11. It is a figure which shows the detection part of the said liquid detection apparatus, (a) is a top view, (b) is the bottom view. 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. 13 is a cross-sectional view of a conventional ink cartridge including the conventional liquid detection device shown in FIG. 12.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Carriage 2: Carriage motor 3: Timing belt 4: Guide member 5: Platen 6: Recording paper 7: Ink cartridge 10: Pump unit 11: Wiping means 12: Recording head 13 Detection part 14: Buffer part 15: Supply side buffer Chamber 16: Discharge-side buffer chamber 17: Piezoelectric element 18: Flow path forming plate 19: Ink supply path 19A Ink supply path 20: Ink discharge path 20A: Ink discharge path 21: Partition wall 22: Inflow opening 23: Outflow opening 24: Inflow channel 25: Outflow channel 26: Opening 27: Wall surface 28: Adhesive 31: Cap member 40: Vibration cavity forming base 40a: First surface 40b: Second surface 41: Cavity plate 42: Vibration plate 43: Cavity 43a : Bottom part 43b: peripheral edge 44: lower electrode terminal 45: upper electrode terminal 46: lower electrode 46 : Main body part 46b: Extension part 46c: Notch part 47: Piezoelectric layer 47a: Main body part 47b: Protrusion part 48: Auxiliary electrode 49: Upper electrode 49a: Main body part 49b Extension part 50: Flow path forming base 51: Flow Road plate 52: Entrance / exit plate 53b: Inlet 54b: Outlet 60: Liquid detection device 60A: Liquid detection device 61: Vibration unit 70: Ink cartridge 70A: Ink cartridge 71: Ink delivery port 72: Container main body 75: Main storage chamber 76: Auxiliary storage chamber 76a: protrusion 77: auxiliary channel 77a: auxiliary channel inlet 106: actuator 160: piezoelectric layer 161: opening 162: cavity 164: upper electrode 166: lower electrode 168: upper electrode terminal 170: lower electrode terminal 172 : Auxiliary electrode 176: Diaphragm 178: Substrate 180: Ink cartridge 181: Container body

Claims (4)

A cavity having a first surface and a second surface facing each other and receiving a medium to be detected is formed so as to open to the first surface side, and a bottom surface of the cavity is formed so as to be able to vibrate. A vibration cavity forming base,
A piezoelectric element having a first electrode formed on the second surface side of the vibration cavity forming base, a piezoelectric layer stacked on the first electrode, and a second electrode stacked on the piezoelectric layer;
A liquid supply path that is stacked on the first surface side of the vibration cavity forming base and supplies a liquid to be detected to the cavity;
A flow path forming base formed with a liquid discharge path for discharging the liquid to be detected from the cavity ;
A supply-side buffer chamber communicating with the liquid supply path;
And a discharge side buffer chamber communicating with the liquid discharge passage, and the liquid detection device Ru provided with,
The liquid detection device is mounted and has a liquid delivery port for delivering the liquid stored inside to the outside, and the liquid inside is supplied to the cavity via the liquid supply path of the liquid detection device. A container body configured to be discharged from the cavity through a discharge path,
The space formed by including the cavity, the liquid supply path and the liquid discharge path in the liquid detection device is formed symmetrically with respect to the center of the cavity existing in the region sandwiched between the liquid supply path and the liquid discharge path. The supply-side buffer chamber constitutes a main portion of the internal space of the container body and communicates with a liquid storage chamber for storing liquid, and the discharge-side buffer chamber is formed in the internal space of the container body. A liquid container characterized in that the liquid container communicates with a liquid delivery space communicating with the liquid delivery port . The liquid container according to claim 1, wherein the space forming the cavity is substantially cylindrical. The supply side buffer chamber and the discharge side buffer chamber, the liquid container according to claim 1, wherein are formed symmetrically with respect to the center of the cavity. The liquid container according to any one of claims 1 to 3 , wherein each of the supply-side buffer chamber and the discharge-side buffer chamber has a capacity of at least 10 times the capacity of the cavity.

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