JP2002086749A - Liquid kind identifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid kind identifying method capable of accurately detecting the kind of a liquid, a liquid container and an ink without the need of a complicated sealing structure, and a liquid container. SOLUTION: A liquid kind identifying method for identifying the kind of a liquid in a liquid container by detecting the frequency of the residual vibration remaining in a piezoelectric device provided in the liquid container, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a change in acoustic impedance, and more particularly, detects a change in resonance frequency to detect the type of liquid in a liquid container containing a liquid such as ink. The present invention relates to a liquid container provided with a piezoelectric device (actuator). More specifically, the present invention relates to an ink cartridge suitable for an ink jet recording apparatus that presses ink in a pressure generating chamber by a pressure generating means in accordance with print data and discharges ink droplets from nozzle openings to perform printing.

[0002]

2. Description of the Related Art As one example of a liquid container, an ink cartridge used in an ink jet recording apparatus for printing by discharging ink droplets from nozzle openings will be described below. The ink jet recording apparatus mounts, on a carriage, an ink jet recording head having a pressure generating means for pressurizing a pressure generating chamber and a nozzle opening for discharging the pressurized ink from the nozzle opening as an ink droplet. The ink jet recording apparatus is configured to be able to continue printing while supplying ink from an ink tank to a recording head via a flow path. The ink tank is configured as a detachable cartridge so that the user can easily replace the ink tank when the ink is consumed.

[0003] Ink cartridges may have different types of ink. For example, a case where a dye-based ink is used, a case where a pigment-based ink is used, or a case where an ink having a more specific composition is used depending on the required characteristics of an image to be recorded is considered. However, it has been difficult to determine the type of ink using a sensor mounted on a conventional ink cartridge.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-mentioned problems.
It is another object of the present invention to provide a liquid type identification method and a liquid container that can accurately detect the type of ink and do not require a complicated seal structure.

[0005]

According to a first aspect of the present invention, there is provided a liquid type identifying method for driving a piezoelectric device mounted on a liquid container and generating a back electromotive force by residual vibration generated by driving the piezoelectric device. This is a liquid type identification method for identifying the type of liquid in the liquid container by generating the liquid type. Furthermore, it is preferable to calculate the frequency of the residual vibration by measuring the time between a plurality of predetermined peaks of the residual vibration of the piezoelectric device, and identify the type of the liquid using the frequency. Further, by measuring the number of peaks of the residual vibration of the piezoelectric device within a predetermined time, the frequency of the residual vibration is calculated,
The type of the liquid may be identified using the frequency. Further, the liquid container may be an ink cartridge used in an ink jet recording apparatus.

The above summary of the present invention does not list all of the necessary features of the present invention, and sub-combinations of these features may also be invented.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the claimed invention and have the features described in the embodiments. Not all combinations are essential to the solution of the invention.

FIG. 1 shows an embodiment of an ink cartridge and an ink jet recording apparatus. Each of the plurality of ink cartridges 180 is
Ink introduction portions 182 and holders 18 corresponding to
4 is attached to the ink jet recording apparatus. The plurality of ink cartridges 180 store inks of different types, for example, colors. The actuator 10 as a means for detecting at least acoustic impedance is provided on the bottom surface of each of the plurality of ink cartridges 180.
6 is mounted. By mounting the actuator 106 on the ink cartridge 180, the type of ink in the ink cartridge 180 can be detected.

FIGS. 2 and 3 show details and an equivalent circuit of the actuator 106 which is one embodiment of the piezoelectric device mounted on the ink cartridge 180 of FIG. The actuator referred to here is used in a method of detecting at least acoustic impedance to detect the type of liquid in the liquid container. In particular, it is used in a method of detecting at least acoustic impedance by detecting a resonance frequency by residual vibration to detect the type of liquid in a liquid container. FIG. 2A is an enlarged plan view of the actuator 106. FIG. 2B shows a BB cross section of the actuator 106. FIG. 2C shows the CC of the actuator 106.
3 shows a cross section. 3A and 3B show an equivalent circuit of the actuator 106. FIG. FIG. 3 (C)
FIG. 3D shows the periphery including the actuator 106 when the ink cartridge is filled with ink, and its equivalent circuit.

The actuator 106 includes a substrate 178 having a circular opening 161 substantially at the center, a vibration plate 176 provided on one surface (hereinafter referred to as a surface) of the substrate 178 so as to cover the opening 161, A piezoelectric layer 160 disposed on the side of the surface of the plate 176; and upper and lower electrodes 164 and 166 sandwiching the piezoelectric layer 160 from both sides.
And upper electrode terminal 1 electrically coupled to upper electrode 164
68, a lower electrode terminal 170 electrically coupled to the lower electrode 166, an upper electrode 164 and an upper electrode terminal 168.
And an auxiliary electrode 172 electrically connected therebetween. The piezoelectric layer 160, the upper electrode 164, and the lower electrode 166 each have a circular portion as a main part. Each circular portion of the piezoelectric layer 160, the upper electrode 164, and the lower electrode 166 forms a piezoelectric element.

The vibration plate 176 is formed on the surface of the substrate 178 so as to cover the opening 161. Cavity 162
Is the portion of the diaphragm 176 facing the opening 161 and the substrate 17
8 is formed by the opening 161 on the surface. Substrate 17
The surface opposite to the piezoelectric element 8 (hereinafter referred to as the back surface) faces the liquid container side, and the cavity 162 is configured to be in contact with the liquid. The vibration plate 176 is attached to the substrate 178 in a liquid-tight manner so that the liquid does not leak to the surface side of the substrate 178 even if the liquid enters the cavity 162.

The lower electrode 166 is located on the surface of the vibration plate 176, that is, on the surface opposite to the liquid container.
It is attached so that the center of the circular portion which is the main part of 66 and the center of the opening 161 substantially coincide with each other. The area of the circular portion of the lower electrode 166 is set to be smaller than the area of the opening 161. On the other hand, the lower electrode 1
The piezoelectric layer 160 is formed on the surface side of the substrate 66 such that the center of the circular portion substantially coincides with the center of the opening 161. The area of the circular portion of the piezoelectric layer 160 is
, And larger than the area of the circular portion of the lower electrode 166.

On the other hand, on the front surface side of the piezoelectric layer 160, an upper electrode 164 is provided at the center of the circular portion which is the main portion thereof and the opening 1
61 are formed so as to substantially coincide with the center. The area of the circular portion of the upper electrode 164 is smaller than the area of the circular portion of the opening 161 and the piezoelectric layer 160, and
The area is set to be larger than the area of the circular portion 66.

Therefore, the main part of the piezoelectric layer 160 is sandwiched by the main part of the upper electrode 164 and the main part of the lower electrode 166 from the front side and the back side, respectively. The deformation driving can be performed effectively. The circular portions that are the main parts of the piezoelectric layer 160, the upper electrode 164, and the lower electrode 166 form the piezoelectric element of the actuator 106. As described above, the piezoelectric element is in contact with the vibration plate 176. Of the circular portion of the upper electrode 164, the circular portion of the piezoelectric layer 160, the circular portion of the lower electrode 166, and the opening 161, the opening 161 has the largest area. With this structure, the vibration area of the vibration plate 176 that actually vibrates is determined by the opening 161. The circular portion of the upper electrode 164, the circular portion of the piezoelectric layer 160, and the lower electrode 16
Since the circular portion 6 has a smaller area than the opening 161, the diaphragm 176 is more likely to vibrate. Further, the piezoelectric layer 16
Of the circular portion of the lower electrode 166 and the circular portion of the upper electrode 164 electrically connected to 0, the circular portion of the lower electrode 166 is smaller. Therefore, the circular portion of the lower terminal 166 determines a portion of the piezoelectric layer 160 where the piezoelectric effect occurs.

The upper electrode terminal 168 is formed on the surface of the diaphragm 176 so as to be electrically connected to the upper electrode 164 via the auxiliary electrode 172. On the other hand, the lower electrode terminal 17
0 is formed on the surface side of diaphragm 176 so as to be electrically connected to lower electrode 166. Since the upper electrode 164 is formed on the surface side of the piezoelectric layer 160, the upper electrode terminal 16
8, it is necessary to have a step equal to the sum of the thickness of the piezoelectric layer 160 and the thickness of the lower electrode 166. It is difficult to form this step only with the upper electrode 164, and even if possible, the connection between the upper electrode 164 and the upper electrode terminal 168 is weakened, and there is a risk of disconnection. Therefore, the upper electrode 164 and the upper electrode terminal 16 are formed by using the auxiliary electrode 172 as an auxiliary member.
8 is connected. By doing so, both the piezoelectric layer 160 and the upper electrode 164 have a structure supported by the auxiliary electrode 172, so that a desired mechanical strength can be obtained, and the connection between the upper electrode 164 and the upper electrode terminal 168 is ensured. It becomes possible to.

Note that the piezoelectric element and the vibrating region of the vibrating plate 176 facing the piezoelectric element correspond to the actuator 106.
Is a vibrating part that actually vibrates. Further, the members included in the actuator 106 are preferably integrally formed by firing each other. By forming the actuator 106 integrally, handling of the actuator 106 becomes easy. Further, the vibration characteristics are improved by increasing the strength of the substrate 178. That is, by increasing the strength of the substrate 178, only the vibrating portion of the actuator 106 vibrates, and portions of the actuator 106 other than the vibrating portion do not vibrate. Further, in order to prevent portions other than the vibrating portion of the actuator 106 from vibrating, it is possible to increase the strength of the substrate 178 while making the piezoelectric element of the actuator 106 thinner and smaller and the diaphragm 176 thinner.

As a material of the piezoelectric layer 160, it is preferable to use lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT) or a lead-free piezoelectric film not using lead. Alternatively, it is preferable to use alumina. Further, it is preferable to use the same material as the substrate 178 for the vibration plate 176. For the upper electrode 164, the lower electrode 166, the upper electrode terminal 168, and the lower electrode terminal 170, a conductive material such as a metal such as gold, silver, copper, platinum, aluminum, or nickel can be used.

The actuator 106 configured as described above can be applied to a container for storing a liquid. For example, it can be mounted on an ink cartridge or ink tank used for an ink jet recording apparatus, a container containing a cleaning liquid for cleaning a recording head, or the like.

The actuator 106 shown in FIGS. 2 and 3 has a cavity 162 at a predetermined position in the liquid container.
Is mounted so as to come into contact with the liquid contained in the liquid container. The actuator 106 detects at least the acoustic impedance by contacting the liquid. Actuator 1 by detecting acoustic impedance
Reference numeral 06 can detect the type of liquid in the ink cartridge 180.

Here, the principle of detecting the type of liquid by the actuator 106 will be described.

In order to detect a change in the acoustic impedance of the medium, the impedance characteristic or admittance characteristic of the medium is measured. When measuring the impedance characteristic or the admittance characteristic, for example, a transmission circuit can be used. The transmission circuit applies a constant voltage to the medium, changes the frequency, and measures the current flowing through the medium. Alternatively, the transmission circuit supplies a constant current to the medium, changes the frequency, and measures the voltage applied to the medium. A change in the current value or voltage value measured by the transmission circuit indicates a change in acoustic impedance. Further, a change in the frequency fm at which the current value or the voltage value becomes maximum or minimum also indicates a change in acoustic impedance.

Apart from the above method, the actuator is
A change in the acoustic impedance of the liquid can be detected using only a change in the resonance frequency. As a method utilizing the change in acoustic impedance of the liquid, when using a method of detecting a resonance frequency by measuring a back electromotive force generated by residual vibration remaining in the vibrating portion after the vibrating portion of the actuator vibrates, for example, A piezoelectric element can be used. A piezoelectric element is an element that generates a back electromotive force due to residual vibration remaining in a vibrating part of an actuator, and the magnitude of the back electromotive force changes according to the amplitude of the vibrating part of the actuator. Therefore, the larger the amplitude of the vibrating part of the actuator, the easier it is to detect. Further, a cycle in which the magnitude of the back electromotive force changes according to the frequency of the residual vibration in the vibrating portion of the actuator. Therefore, the frequency of the vibrating part of the actuator corresponds to the frequency of the back electromotive force. Here, the resonance frequency refers to a frequency in a resonance state between the vibrating portion of the actuator and the medium in contact with the vibrating portion.

In order to obtain the resonance frequency fs, the waveform obtained by the back electromotive force measurement when the vibrating section and the medium are in a resonance state is subjected to Fourier transform. The vibration of the actuator is not only deformed in one direction but also includes various deformations such as bending and elongation, and thus has various frequencies including the resonance frequency fs. Therefore, the resonance frequency fs is determined by Fourier-transforming the waveform of the back electromotive force when the piezoelectric element and the medium are in a resonance state, and specifying the most dominant frequency component.

The frequency fm is a frequency when the admittance of the medium is maximum or the impedance is minimum. Assuming that the resonance frequency is fs, the frequency fm is equal to the resonance frequency fs due to dielectric loss or mechanical loss of the medium.
Causes a slight error. However, deriving the resonance frequency fs from the actually measured frequency fm is troublesome, so that the frequency fm is generally used instead of the resonance frequency. Here, by inputting the output of the actuator 106 to the transmission circuit, the actuator 106 can detect at least the acoustic impedance.

The frequency fm is measured by measuring the impedance characteristic or the admittance characteristic of the medium, and the resonance frequency fs is measured by measuring the back electromotive force generated by the residual vibration in the vibrating part of the actuator. It has been proved by experiments that there is almost no difference in the resonance frequencies to be obtained.

The vibration region of the actuator 106 is a portion of the vibration plate 176 that forms a cavity 162 determined by the opening 161. When the liquid is sufficiently contained in the liquid container, the cavity 162 is filled with the liquid, and the vibrating region comes into contact with the liquid in the liquid container. On the other hand, if there is not enough liquid in the liquid container, the vibrating region will be in contact with the liquid remaining in the cavity in the liquid container, or will not be in contact with the liquid, but will be in contact with gas or vacuum.

The operation and principle of detecting the type of liquid in the liquid container from the resonance frequency of the medium and the vibrating section of the actuator 106 by measuring the back electromotive force will be described with reference to FIGS. 2 and 3. Actuator 1
At 06, a voltage is applied to the upper electrode 164 and the lower electrode 166 via the upper electrode terminal 168 and the lower electrode terminal 170, respectively. An electric field is generated in a portion of the piezoelectric layer 160 sandwiched between the upper electrode 164 and the lower electrode 166. The piezoelectric layer 160 is deformed by the electric field. When the piezoelectric layer 160 is deformed, the vibration plate 176 is formed.
Vibrating region vibrates flexibly. For a while after the piezoelectric layer 160 is deformed, the flexural vibration is applied to the actuator 10.
6 remains in the vibrating part.

The residual vibration is free vibration between the vibrating portion of the actuator 106 and the medium. Therefore, by setting the voltage applied to the piezoelectric layer 160 to a pulse waveform or a rectangular wave, a resonance state between the vibrating portion and the medium can be easily obtained after the voltage is applied. The residual vibration is
In order to vibrate the vibrating part 06, the piezoelectric layer 160 is also deformed. Therefore, the piezoelectric layer 160 generates a back electromotive force. The back electromotive force is detected via the upper electrode 164, the lower electrode 166, the upper electrode terminal 168, and the lower electrode terminal 170. Since the resonance frequency can be specified by the detected back electromotive force, the type of liquid in the liquid container can be detected.

Generally, the resonance frequency fs is expressed by fs = 1 / (2 * π * (M * Cact) ^1/2 ) (Equation 1). Here, M is the inertance Mact of the vibrating part.
And the additional inertance M ′. Cact is the compliance of the vibrating part.

FIG. 2C shows the actuator 1 according to this embodiment when no ink remains in the cavity.
It is sectional drawing of 06. FIGS. 3A and 3B are equivalent circuits of the vibrating portion of the actuator 106 and the cavity 162 when no ink remains in the cavity.

Mact is the product of the product of the thickness of the vibrating portion and the density of the vibrating portion divided by the area of the vibrating portion. More specifically, as shown in FIG. 2) is expressed as Here, Mpzt is the product of the thickness of the piezoelectric layer 160 in the vibrating portion and the density of the piezoelectric layer 160,
It is divided by the area of 0. Melectrode1 is obtained by dividing the product of the thickness of the upper electrode 164 and the density of the upper electrode 164 in the vibrating section by the area of the upper electrode 164. M
electrode2 is the product of the product of the thickness of the lower electrode 166 and the density of the lower electrode 166 in the vibrating section divided by the area of the lower electrode 166. Mvib is the diaphragm 1 in the vibrating section.
The product of the thickness of the diaphragm 76 and the density of the diaphragm 176 is
Of the vibration region. However, Mact
In the present embodiment, the piezoelectric layer 160 can be calculated from the thickness, density, and area of the entire vibrating portion.
Although the respective areas of the upper electrode 164, the lower electrode 166, and the vibration region of the diaphragm 176 have the magnitude relationship as described above, it is preferable that the difference between the areas is small. In the present embodiment, it is preferable that portions of the piezoelectric layer 160, the upper electrode 164, and the lower electrode 166 other than the circular portion, which are main portions thereof, are so small as to be negligible with respect to the main portion. Therefore, in the actuator 106, Mact is the upper electrode 164,
The sum of the inertances of the lower electrode 166, the piezoelectric layer 160, and the vibration area of the vibration plate 176. The compliance Cact is the compliance of a portion formed by the vibration region of the upper electrode 164, the lower electrode 166, the piezoelectric layer 160, and the vibration plate 176.

FIG. 3A, FIG. 3B and FIG.
(D) shows an equivalent circuit of the vibrating portion of the actuator 106 and the cavity 162. In these equivalent circuits, Cact indicates compliance of the vibrating portion of the actuator 106. Cpzt, Celectrode1, Celectrode
2 and Cvib are the piezoelectric layers 160 in the vibrating part, respectively.
The compliance of the upper electrode 164, the lower electrode 166, and the diaphragm 176 is shown. Cact is represented by the following equation 3.

1 / Cact = (1 / Cpzt) + (1 / Celectrode1) + (1 / Celectrode2) + (1 / Cvi b) (Equation 3) From Equations 2 and 3, FIG. 3 (B).

The compliance Cact represents a volume that can receive a medium by deformation when pressure is applied to a unit area of the vibrating portion. Further, the compliance Cact may be said to indicate the ease of deformation.

FIG. 3C is a cross-sectional view of the actuator 106 when the liquid is sufficiently contained in the liquid container and the periphery of the vibration region of the actuator 106 is filled with the liquid. M′max in FIG. 3C represents the maximum value of the additional inertance M ′ when the liquid is sufficiently contained in the liquid container and the liquid is filled around the vibration region of the actuator 106. M'max is

M′max = (π * ρ / (2 * k ³ )) * (2 * (2 * k * a) ³ / (3 * π)) / (π * a ² ) ² (Equation 4) (A is the radius of the vibrating part, ρ is the density of the medium, and k is the wave number.)

## EQU3 ## Equation 4 holds when the vibration region of the actuator 106 is a circle having a radius a. The additional inertance M ′ is an amount indicating that the mass of the vibrating part is apparently increased by the action of the medium near the vibrating part. As can be seen from Equation 4, M′max
Varies greatly depending on the radius a of the vibrating portion and the density ρ of the medium. In other words, when the media are liquids of different types, the maximum value of the additional inertance M ′ is different because the density ρ is different.
max changes, and the resonance frequency fs also changes. Therefore, the type of liquid can be specified by specifying the resonance frequency fs.

The wave number k is as follows: k = 2 * π * fact / c (Equation 5) (Fact is the resonance frequency of the vibrating portion when the liquid is not touching. C is the speed of sound propagating in the medium. .)

Is represented by

FIG. 3D shows the actuator 1 in the case of FIG. 3C in which the liquid is sufficiently stored in the liquid container and the liquid is filled around the vibrating region of the actuator 106.
6 shows an equivalent circuit of a vibrating part 06 and a cavity 162.

Since the additional inertance M 'also affects the acoustic impedance characteristic, it can be said that the method of measuring the back electromotive force generated in the actuator 106 due to the residual vibration detects at least a change in the acoustic impedance.

Further, according to the present embodiment, the back electromotive force generated in the actuator 106 due to the vibration generated by the actuator 106 and subsequent residual vibration is measured. However, it is not always necessary for the vibrating section of the actuator 106 to vibrate the liquid by its own vibration due to the drive voltage. That is, even if the vibrating portion does not oscillate by itself, it vibrates with a certain range of liquid in contact therewith, so that the piezoelectric layer 160 bends and deforms. This residual vibration generates a back electromotive force voltage in the piezoelectric layer 160, and the upper electrode 164
And the lower electromotive force voltage to lower electrode 166.
The state of the medium may be detected by utilizing this phenomenon. For example, in an ink jet recording apparatus, even if the state of the ink tank or the ink inside the ink tank is detected by using the vibration around the vibration part of the actuator generated by the vibration due to the reciprocation of the carriage due to the scan of the print head during printing. Good.

The frequency at which the actuator 106 oscillates is preferably in the non-audible range. For example, the frequency is preferably between 100 kHz and 500 kHz. In recent years, inkjet recording devices have
When the sound generated during operation is extremely low and the frequency generated when the actuator 106 is driven is in the audible range, the sound generated by the actuator 106 becomes relatively prominent, and the user of the recording apparatus is uncomfortable. You may feel it. Therefore, by setting the frequency at which the actuator 106 oscillates to a frequency in the non-audible region,
It is desirable that the user of the recording apparatus does not feel the vibration generated by the actuator 106 uncomfortable.

FIG. 4 shows the relationship between the ink density and the resonance frequency fs of the ink and the vibrating section. As shown in FIG. 4, when the ink density increases, the additional inertance increases, so that the resonance frequency fs decreases. That is, the resonance frequency fs differs depending on the type of ink. Therefore, by measuring the resonance frequency fs, it is possible to determine the type of ink contained in the ink cartridge mounted on the recording apparatus.

The purpose of determining the type of ink is, for example,
Depending on the country and region where the ink cartridge is used,
This is because the type of ink suitable for the country and region may be different. For example, it is necessary to use a high-viscosity ink, for example, a dye-based ink in a high-temperature area, and to use a low-viscosity ink, for example, a pigment-based ink in a low-temperature country. Therefore, by determining the type of ink by measuring the resonance frequency, it can be determined whether the ink cartridge is suitable for the country or region where the ink cartridge is used. Further, in some countries and regions, the use of a specific material, for example, sodium or the like in the ink is regulated. By measuring the resonance frequency, a warning can be given to the user of the ink cartridge when an ink using a material whose use is restricted is mounted on the recording apparatus.

FIG. 5 shows a waveform of the residual vibration of the actuator 106 after the actuator 106 is vibrated and a method of measuring the residual vibration. 5, the vertical axis indicates the voltage of the back electromotive force generated by the residual vibration of the actuator 106, and the horizontal axis indicates the time. Actuator 106
5 generates a waveform of a voltage analog signal as shown in FIG. Next, the analog signal is converted into a digital numerical value corresponding to the frequency of the signal.

In the example shown in FIG. 5, the resonance frequency is calculated by measuring the time during which four pulses from the fourth pulse to the eighth pulse of the analog signal occur.

More specifically, the number of times the actuator 106 oscillates and crosses a predetermined reference voltage from a low voltage side to a high voltage side is counted. A digital signal between 4 and 8 counts is defined as High,
The time from 4 counts to 8 counts is measured by a predetermined clock pulse.

The counting from the fourth count of the analog waveform is for starting the measurement after the vibration of the actuator 106 is stabilized. Starting from the fourth count is merely an example, and counting from an arbitrary count may be performed.
Here, the signals from the fourth count to the eighth count are detected, and the time from the fourth count to the eighth count is measured by a predetermined clock pulse. Thereby,
Find the resonance frequency. The clock pulse is preferably a clock pulse equal to a clock for controlling a semiconductor memory device and the like attached to the ink cartridge. It is not necessary to measure the time up to the eighth count, and the time may be counted up to an arbitrary count. In FIG. 5, the time from the fourth count to the eighth count is measured, but the time within a different count interval 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 is obtained by detecting the time from the fourth count to the sixth count in order to increase the detection speed. You may. Further, when the quality of the ink is unstable and the fluctuation of the amplitude of the pulse is large, the time from the fourth count to the twelfth count may be detected in order to accurately detect the residual vibration.

In another embodiment, the wave number of the voltage waveform of the back electromotive force within a predetermined period may be counted (not shown). The resonance frequency can also be obtained by this method. More specifically, after the actuator 106 oscillates, the digital signal is set to High only for a predetermined period, and the number of times the predetermined reference voltage crosses from the low voltage side to the high voltage side is counted. By measuring the count, the presence or absence of ink can be detected.

The residual vibration of the actuator 106 is preferably measured when the carriage is not moving or when the recording head is not printing. When the residual vibration is measured during printing of the recording head, the central processing unit (CPU) of the ink cartridge recording device is used for measuring the residual vibration.
The time that the PU can be used for printing decreases, and the printing speed decreases. Therefore, the printing speed is prevented from lowering by measuring the residual vibration during non-printing of the recording head where the CPU is not used. Furthermore, in the case of an ink container that is mounted on the carriage and moves together with the carriage, when the residual vibration is measured during printing by the recording head, the ink in the ink container shakes due to the movement of the ink container. Cannot be measured. Therefore, it is preferable to measure the residual vibration during non-printing.
Further, during non-printing, the motor for driving the carriage is stopped, and the measurement can be performed while avoiding noise when the recording head and the carriage are driven by the motor, so that the residual vibration can be measured more accurately. The non-printing time of the recording head includes times such as a page break, cleaning, power-on, and immediately before power-off, that is, a time from when the power is turned off to when the recording apparatus actually stops.

As described above, the present invention has been described using the embodiments. However, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes or improvements can be added to the above embodiment. It should be noted that such modified or improved embodiments may be included in the technical scope of the present invention.
It is clear from the description of the claims.

[0054]

The liquid consumption state detecting method and liquid container of the present invention can accurately detect the remaining amount of liquid and do not require a complicated sealing structure. Further, the liquid consumption state detection method of the present invention is not affected by an unstable measurement signal generated at the beginning of the measurement of the liquid consumption state. Further, the liquid consumption state detecting method of the present invention can reduce the time for detecting the liquid consumption state.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of an ink cartridge and an ink jet recording apparatus.

FIG. 2 is a diagram illustrating details of an actuator 106 that is an embodiment of a piezoelectric device mounted on the ink cartridge 180 of FIG.

FIG. 3 is a diagram showing an equivalent circuit of an actuator 106 which is one embodiment of a piezoelectric device mounted on the ink cartridge 180 of FIG.

FIG. 4 is a diagram illustrating the relationship between the density of ink and the resonance frequency fs of the ink and the vibrating section.

FIG. 5 is a diagram illustrating a waveform of a residual vibration of the actuator and a method of measuring the residual vibration after the actuator is vibrated.

[Explanation of symbols]

 106 Actuator 160 Piezoelectric layer 162 Cavity 164 Upper electrode 166 Lower electrode 168 Upper electrode terminal 170 Lower electrode terminal 172 Auxiliary electrode 176 Vibrating plate 178 Substrate 180 Ink cartridge 182 Ink introducing section 184 Holder

Claims (4)

[Claims] 1. A liquid type identification method for identifying a type of a liquid in a liquid container by detecting a frequency of a residual vibration remaining in a piezoelectric device mounted on the liquid container. 2. The method according to claim 1, wherein a frequency of the residual vibration is calculated by measuring a time between a plurality of predetermined peaks of the residual vibration of the piezoelectric device, and a type of the liquid is identified using the frequency. The method for identifying a liquid type according to claim 1, wherein 3. The frequency of the residual vibration is calculated by measuring the number of peaks of the residual vibration of the piezoelectric device within a predetermined time, and the type of the liquid is identified using the frequency. The liquid type identification method according to claim 1. 4. The method according to claim 1, wherein the liquid container is an ink cartridge used in an ink jet recording apparatus.