JP2006212828A - Liquid storage container, liquid ejection device, and liquid quantity detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid storage container or the like capable of accurately detecting the presence or absence of liquid in the fitting position of a piezoelectric element, with application of only one type of a drive signal. <P>SOLUTION: The liquid storage container is provided with a liquid storage section for storing liquid and a piezoelectric element which is provided at a specified position of the liquid storage section, generates residual vibration after the application of n-pieces of pulses of the drive signal and outputs an output signal by the residual vibration. The resonance frequency ν0 of the residual vibration when liquid is not present at the specified position and the resonance frequency ν1 of the residual vibration when liquid is present at the specified position satisfy the relationship: ä(2k+1)×(2n-1)-1/2}/(2n-1)×ν1≤ν0≤ä(2k+1)×(2n-1)+1/2}/(2n-1)×ν1 [wherein k is an optional integer of 1 or more]. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid container, a liquid discharge device, and a liquid amount detection method.

  An ink jet printer as a liquid ejecting apparatus ejects ink as a liquid onto a sheet to form a large number of dots at predetermined positions on the sheet, thereby printing a print image. In such a printer, when the ink is consumed by printing and the ink runs out, the user replaces the ink cartridge as the liquid container.

  As a method for detecting the amount of ink in the ink cartridge, a drive signal is applied to a piezoelectric element attached to the ink cartridge, and an output signal from the piezoelectric element due to residual vibration after the drive signal is applied is detected. A method for detecting the remaining amount of ink based on the result is known.

In this detection method, two types of drive signals are used to accurately detect the presence or absence of ink. The frequency of one drive signal is aligned with the resonance frequency of the residual vibration when there is no ink, thereby greatly exciting the amplitude of the residual vibration when there is no ink, and the frequency of the other drive signal is the same as when the ink is present This matches the resonance frequency of the residual vibration, and thereby greatly excites the amplitude of the residual vibration in the presence of ink. This improves the accuracy of detecting the presence or absence of ink (see Patent Document 1).
JP 2003-112431 A

 However, in this method, first, the piezoelectric element is driven by a drive signal having a resonance frequency of residual vibration in the presence of ink to detect whether ink is present at the mounting position of the piezoelectric element, and then the residual vibration in the absence of ink is detected. The piezoelectric element is driven by the drive signal of the resonance frequency to detect whether there is ink at the mounting position of the piezoelectric element. That is, since two kinds of drive signals are applied, a total of two detection operations are required. Thus, there is a problem that the detection time becomes long.

 The present invention has been made in view of the above problems, and the object of the present invention is to accurately detect any state of the presence or absence of liquid at the mounting position of the piezoelectric element by simply applying one kind of driving signal. It is to realize a liquid storage container, a liquid discharge device, and a liquid amount detection method.

The main invention for achieving the object is as follows:
A liquid container for containing a liquid;
A piezoelectric element that is provided at a predetermined position of the liquid container and generates a residual vibration after n pulses of the drive signal are applied, and that outputs an output signal by the residual vibration,
The liquid container according to claim 1, wherein a resonance frequency ν0 of residual vibration when no liquid is present at the predetermined position and a resonance frequency ν1 of residual vibration when the liquid is present at the predetermined position satisfy the following relationship.

{(2k + 1) × (2n−1) −1/2} / (2n−1) × ν1
≦ ν0 ≦ {(2k + 1) × (2n−1) +1/2} / (2n−1) × ν1
Here, k is an arbitrary integer of 1 or more.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

=== Summary of disclosure ===
At least the following matters will become clear from the description of the present specification and the accompanying drawings.

A liquid container for containing a liquid;
A piezoelectric element that is provided at a predetermined position of the liquid container and generates a residual vibration after n pulses of the drive signal are applied, and that outputs an output signal by the residual vibration,
The liquid container according to claim 1, wherein a resonance frequency ν0 of residual vibration when no liquid is present at the predetermined position and a resonance frequency ν1 of residual vibration when the liquid is present at the predetermined position satisfy the following relationship.
{(2k + 1) × (2n−1) −1/2} / (2n−1) × ν1
≦ ν0 ≦ {(2k + 1) × (2n−1) +1/2} / (2n−1) × ν1
Here, k is an arbitrary integer of 1 or more.

  According to such a liquid container, the resonance frequency ν0 when there is no liquid and the resonance frequency ν1 when there is a liquid are within the range defined by the above relational expression. Therefore, if only one type of drive signal having a predetermined pulse is selected and applied to the piezoelectric element, a large residual vibration can be excited in the piezoelectric element in any state with or without liquid, and as a result, The presence or absence of liquid at the position can be accurately detected. That is, it is possible to accurately detect the presence or absence of liquid using only one type of drive signal without using two types of drive signals.

In such a liquid container, it is desirable that the resonance frequency ν0 and the resonance frequency ν1 satisfy the following relationship.
ν0 = (2k + 1) × ν1
According to such a liquid container, the resonance frequency ν0 when there is no liquid is 2k + 1 times the resonance frequency ν1 when there is liquid. Therefore, if only one type of drive signal having a predetermined pulse is selected and applied to the piezoelectric element, a larger residual vibration can be excited in the piezoelectric element in any state with or without liquid. The presence or absence of liquid at the predetermined position can be detected more accurately. That is, it is possible to more accurately detect the presence or absence of liquid by using only one type of drive signal without using two types of drive signals.

In such a liquid container, it is desirable that the duration of the pulse application period is half of the vibration period of the residual vibration when the liquid is present at the predetermined position.
According to such a liquid container, the amplitude of the residual vibration excited by the drive signal can be reliably increased.

In such a liquid container, when the driving signal has a plurality of pulses, it is desirable that the application period of the pulses is the same as the vibration period of the residual vibration when the liquid is present at the predetermined position.
According to such a liquid container, when the drive signal has a plurality of pulses, the amplitude of the residual vibration excited by the drive signal can be reliably increased.

In such a liquid storage container, it is preferable that a buffer chamber for preventing the piezoelectric element from being affected by the vibration of the liquid in the liquid storage portion is provided in the vicinity of the predetermined position.
According to such a liquid container, residual vibration can be detected without being affected by vibration of the liquid in the liquid container.

In such a liquid container, the liquid container is provided with an opening,
The opening is closed by a diaphragm;
The piezoelectric element is provided on the diaphragm,
A liquid container, wherein the center of the opening and the center of the piezoelectric element coincide.
According to such a liquid container, the resonance frequency of the diaphragm can be detected with high accuracy.

In such a liquid container, the liquid is ink,
The liquid container is preferably an ink cartridge.

 According to such a liquid container, it is possible to provide an ink cartridge capable of accurately detecting the presence or absence of liquid using only one type of drive signal without using two types of drive signals.

An ink containing portion for containing ink;
A piezoelectric element that is provided at a predetermined position of the ink container and generates a residual vibration after n pulses of the drive signal are applied, and that outputs an output signal by the residual vibration,
A buffer chamber for preventing the piezoelectric element from being affected by the vibration of the ink in the ink container is provided in the vicinity of the predetermined position;
The ink container is provided with an opening.
The opening is closed by a diaphragm;
The piezoelectric element is provided on the diaphragm,
The center of the opening coincides with the center of the piezoelectric element;
The application period of the pulse is half of the vibration period of residual vibration when ink is present at the predetermined position,
When the drive signal has a plurality of pulses, the application period of the pulses is the same as the vibration period of the residual vibration when ink is present at the predetermined position;
The liquid container according to claim 1, wherein the resonance frequency ν0 of residual vibration when no ink is present at the predetermined position and the resonance frequency ν1 of residual vibration when ink is present at the predetermined position satisfy the following relationship.
ν0 = (2k + 1) × ν1
Here, k is an arbitrary integer of 1 or more.
According to such a liquid container, since almost all the effects described are exhibited, the object of the present invention is most effectively achieved.

Further, a liquid storage unit that stores liquid for discharging from the nozzle toward the medium,
A piezoelectric element that is provided at a predetermined position of the liquid container and generates a residual vibration after n pulses of the drive signal are applied, and that outputs an output signal by the residual vibration,
A resonance frequency ν0 of residual vibration when there is no liquid at the predetermined position and a resonance frequency ν1 of residual vibration when there is liquid at the predetermined position satisfy the following relationship: Realization is also possible.

{(2k + 1) × (2n−1) −1/2} / (2n−1) × ν1
≦ ν0 ≦ {(2k + 1) × (2n−1) +1/2} / (2n−1) × ν1
Here, k is an arbitrary integer of 1 or more.

Further, n pulses of the drive signal are applied to the piezoelectric element provided at a predetermined position of the liquid storage unit that stores the liquid,
Detecting an output signal from the piezoelectric element due to residual vibration after application of the drive signal;
A liquid amount detection method for detecting presence / absence of liquid at the predetermined position based on the output signal using a difference in resonance frequency of the residual vibration depending on presence / absence of the liquid at the predetermined position,
Resonance frequency ν0 of residual vibration when there is no liquid at the predetermined position and resonance frequency ν1 of residual vibration when there is liquid at the predetermined position satisfy the following relationship: Is also possible.

{(2k + 1) × (2n−1) −1/2} / (2n−1) × ν1
≦ ν0 ≦ {(2k + 1) × (2n−1) +1/2} / (2n−1) × ν1
Here, k is an arbitrary integer of 1 or more.

=== Configuration of Liquid Discharge System 100 ===
<About the overall configuration>
FIG. 1 is a diagram illustrating the configuration of the liquid ejection system 100. The illustrated liquid ejection system 100 includes a printer 1 as a liquid ejection device and a computer 110 as a liquid ejection control device. Specifically, the liquid ejection system 100 includes a printer 1, a computer 110, a display device 120, an input device 130, and a recording / reproducing device 140.

  The printer 1 prints an image on a medium such as paper, cloth, or film. The computer 110 is communicably connected to the printer 1. In order to cause the printer 1 to print an image, the computer 110 outputs print data corresponding to the image to the printer 1. Computer programs such as application programs and printer drivers are installed in the computer 110. The display device 120 has a display. The display device 120 is for displaying a user interface of a computer program, for example. The input device 130 is a keyboard 131 or a mouse 132, for example. The recording / reproducing device 140 is, for example, a flexible disk drive device 141 or a CD-ROM drive device 142.

=== Computer 110 ===
<Configuration of Computer 110>
FIG. 2 is a block diagram illustrating configurations of the computer 110 and the printer 1. First, the configuration of the computer 110 will be briefly described. The computer 110 includes the recording / reproducing device 140 and the host-side controller 111 described above. The recording / reproducing apparatus 140 is communicably connected to the host-side controller 111, and is attached to the housing of the computer 110, for example. The host-side controller 111 performs various controls in the computer 110, and the display device 120 and the input device 130 described above are also connected to be communicable. The host-side controller 111 includes an interface unit 112, a CPU 113, and a memory 114. The interface unit 112 is interposed between the printer 1 and exchanges data. The CPU 113 is an arithmetic processing unit for performing overall control of the computer 110. The memory 114 is used to secure an area for storing a computer program used by the CPU 113, a work area, and the like, and includes a RAM, an EEPROM, a ROM, a magnetic disk device, and the like. As described above, computer programs stored in the memory 114 include application programs and printer drivers. The CPU 113 performs various controls according to the computer program stored in the memory 114.

  The printer driver causes the computer 110 to convert the image data into print data, and transmits this print data to the printer 1. The print data is data in a format that can be interpreted by the printer 1 and includes various command data and pixel data SI (see FIG. 8 and the like). The command data is data for instructing the printer 1 to execute a specific operation. The command data includes, for example, command data for instructing paper feed, command data for indicating the carry amount, and command data for instructing paper discharge.

=== Printer 1 ===
<About the configuration of the printer 1>
FIG. 3A is a diagram illustrating a configuration of the printer 1 of the present embodiment. FIG. 3B is a side view illustrating the configuration of the printer 1 of the present embodiment. In the following description, FIG. 2 is also referred to.

  The printer 1 includes a paper transport mechanism 20, a carriage moving mechanism 30, a head unit 40, a detector group 50, a printer-side controller 60, and a drive signal generation circuit 70. In the present embodiment, the printer-side controller 60 and the drive signal generation circuit 70 are provided on a common controller board CTR. The head unit 40 includes a head control unit HC and a head 41.

  In the printer 1, the control target unit, that is, the paper transport mechanism 20, the carriage moving mechanism 30, the head unit 40 (head controller HC, head 41), and the drive signal generation circuit 70 are controlled by the printer-side controller 60. As a result, the printer-side controller 60 prints an image on the paper S based on the print data received from the computer 110. Each detector in the detector group 50 monitors the status in the printer 1. Each detector outputs the detection result to the printer-side controller 60. Upon receiving the detection results from each detector, the printer-side controller 60 controls the control target unit based on the detection results.

<Regarding the paper transport mechanism 20>
The paper transport mechanism 20 corresponds to a medium transport unit that transports a medium. The paper transport mechanism 20 feeds the paper S to a printable position, or transports the paper S by a predetermined transport amount in the transport direction. This transport direction is a direction that intersects the carriage movement direction. The paper transport mechanism 20 includes a paper feed roller 21, a transport motor 22, a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for automatically feeding the paper S inserted into the paper insertion opening into the printer 1 and has a D-shaped cross section in this example. The transport motor 22 is a motor for transporting the paper S in the transport direction, and its operation is controlled by the printer-side controller 60. The transport roller 23 is a roller for transporting the paper S sent by the paper feed roller 21 to a printable area. The operation of the transport roller 23 is also controlled by the transport motor 22. The platen 24 is a member that supports the paper S being printed from the back side of the paper S. The paper discharge roller 25 is a roller for carrying the paper S that has been printed.

<About the carriage moving mechanism 30>
The carriage moving mechanism 30 is for moving the carriage CR to which the head unit 40 is attached in the carriage moving direction. The carriage movement direction includes a movement direction from one side to the other side and a movement direction from the other side to the one side. Since the head unit 40 includes the head 41, the carriage movement direction corresponds to the movement direction of the head 41, and the carriage movement mechanism 30 corresponds to a head moving unit that moves the head 41 in the movement direction. The carriage moving mechanism 30 includes a carriage motor 31, a guide shaft 32, a timing belt 33, a driving pulley 34, and a driven pulley 35. The carriage motor 31 corresponds to a drive source for moving the carriage CR. The operation of the carriage motor 31 is controlled by the printer-side controller 60. A drive pulley 34 is attached to the rotation shaft of the carriage motor 31. The drive pulley 34 is disposed on one end side in the carriage movement direction. A driven pulley 35 is disposed on the other end side in the carriage movement direction on the opposite side to the drive pulley 34. The timing belt 33 is connected to the carriage CR and is spanned between a driving pulley 34 and a driven pulley 35. The guide shaft 32 supports the carriage CR in a movable state. The guide shaft 32 is attached along the carriage movement direction. Accordingly, when the carriage motor 31 operates, the carriage CR moves along the guide shaft 32 in the carriage movement direction.

  An ink cartridge 87 is detachably mounted on the carriage CR. The ink cartridge 87 contains ink, and this ink is supplied to the head 41. Note that the ink cartridge 87 of the present embodiment is provided with a liquid level detection unit 90 (described later) for detecting the remaining amount of ink contained therein.

<About the head unit 40>
The head unit 40 is for ejecting ink toward the paper S. The head unit 40 is attached to the carriage CR. The head 41 included in the head unit 40 is provided on the lower surface of the head case 42. The head control unit HC included in the head unit 40 is provided inside the head case 42. The head controller HC will be described in detail later.

  FIG. 4 is a cross-sectional view for explaining the structure of the head 41. The illustrated head 41 includes a flow path unit 41A and an actuator unit 41B. The flow path unit 41A includes a nozzle plate 411 provided with a nozzle Nz, a storage chamber forming substrate 412 in which an opening serving as an ink storage chamber 412a is formed, and a supply port forming substrate 413 in which an ink supply port 413a is formed. Have The actuator unit 41B has a pressure chamber forming substrate 414 in which an opening to be a pressure chamber 414a is formed, a vibration plate 415 that partitions a part of the pressure chamber 414a, and an opening to be a supply side communication port 416a. It has a lid member 416 and a piezoelectric element (piezoelectric element) 417 formed on the surface of the vibration plate 415. In the head 41, a series of flow paths from the ink storage chamber 412a to the nozzle Nz through the pressure chamber 414a is formed. In use, this flow path is filled with ink, and by deforming the piezo element 417, ink can be ejected from the corresponding nozzle Nz. Accordingly, in the head 41, the piezo element 417 corresponds to an element capable of executing an operation for ejecting ink.

  A plurality of types of ink with different amounts can be ejected from each nozzle Nz. For example, from each nozzle Nz, there are three types of ink consisting of large ink droplets capable of forming large dots, medium ink droplets capable of forming medium dots, and small ink droplets capable of forming small dots. Can be discharged. Thereby, the printer 1 can express four gradations of no dots, small dots, medium dots, and large dots in each pixel on the paper S.

<Regarding the detector group 50>
The detector group 50 is for monitoring the status of the printer 1. As shown in FIGS. 3A and 3B, the detector group 50 includes a linear encoder 51, a rotary encoder 52, a paper detector 53, an optical sensor 54, and the like. The linear encoder 51 is for detecting the position of the carriage CR (head 41, nozzle Nz) in the carriage movement direction. The rotary encoder 52 is for detecting the rotation amount of the transport roller 23. The paper detector 53 is for detecting the leading end position of the paper S to be printed. The optical sensor 54 is provided on the carriage CR and can detect the presence or absence of the sheet S at the opposite position. For example, the width of the sheet S can be detected by detecting the end of the sheet S during movement. it can.

<About the printer-side controller 60>
The printer-side controller 60 controls the printer 1. The printer-side controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a control unit 64. The interface unit 61 exchanges data with the computer 110 which is an external device. The CPU 62 is an arithmetic processing unit for performing overall control of the printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and is configured by a storage element such as a RAM, an EEPROM, or a ROM. Then, the CPU 62 controls each control target unit according to the computer program stored in the memory 63. For example, the CPU 62 controls the paper transport mechanism 20 and the carriage moving mechanism 30 via the control unit 64.

  Further, the CPU 62 outputs a head control signal for controlling the operation of the head 41 to the head controller HC, and outputs a control signal for generating the drive signal COM to the drive signal generation circuit 70. The head control signal includes a transfer clock CLK, pixel data SI, a latch signal LAT, a change signal, and the like. The control signal for generating the drive signal COM includes a DAC value to be described later.

<About the drive signal generation circuit 70>
The drive signal generation circuit 70 generates a drive signal for driving the piezo element. In the present embodiment, the drive signal generation circuit 70 is provided for detecting an ejection drive signal COM used in common for a plurality of piezo elements 417 provided for each nozzle or an ink amount described later. A detection drive signal for driving the detection piezo element 911 is generated as a drive signal.

  FIG. 5 is a block diagram illustrating the configuration of the drive signal generation circuit 70. The drive signal generation circuit 70 includes a waveform generation circuit 71 and a current amplification circuit 72. FIG. 6 is a diagram for explaining the relationship between the DAC value input to the waveform generation circuit 71 and the output voltage output from the waveform generation circuit 71.

  The waveform generation circuit 71 includes a D / A converter 711 and a voltage amplification circuit 712. The D / A converter 711 is an electric circuit that outputs a voltage signal corresponding to the DAC value. The DAC value is information for designating a voltage to be output from the voltage amplification circuit 712 (hereinafter also referred to as an output voltage), and is output from the CPU 62 based on the waveform data stored in the memory 63. In the present embodiment, the DAC value is composed of 10-bit data, but for the sake of convenience, it is represented in hexadecimal in the figure.

  The voltage amplification circuit 712 amplifies the output voltage from the D / A converter 711 to a voltage suitable for the operation of the piezo element 417. In the voltage amplification circuit 712 of the present embodiment, the output voltage from the D / A converter 711 is amplified to a maximum of 40 tens V. The amplified output voltage is output to the current amplifier circuit 72 as the control signal S_Q1 and the control signal S_Q2.

  For example, when the DAC value input from the CPU 62 to the D / A converter 711A is “24Eh” in hexadecimal (in the case of “1001001110” in binary), the output voltage after being amplified by the voltage amplification circuit 712 is 25V. It becomes. When the DAC value input from the CPU 62 to the D / A converter 711 is “0h” in hexadecimal (in the case of “0000000” in binary), the output voltage after being amplified by the voltage amplification circuit 712 is 1 When the input DAC value is “3FF” in hexadecimal (in the case of “1111111111” in binary), the output voltage after being amplified by the voltage amplification circuit 712 is 42.32V. That is, the minimum output voltage of the waveform generation circuit 71 is 1.4V, and when the DAC value input from the CPU 62 increases by one, the output voltage of the waveform generation circuit increases by 0.04V.

  The current amplifying circuit 72 is a circuit for supplying a sufficient current so that a large number of piezo elements 417 can operate without trouble. The current amplification circuit 72 includes a transistor pair 721. The transistor pair 721 includes an NPN transistor Q1 and a PNP transistor Q2 whose emitter terminals are connected to each other. The NPN transistor Q1 is a transistor that operates when the voltage of the drive signal increases. The NPN transistor Q1 has a collector connected to a power source and an emitter connected to an output signal line for driving signals. The PNP transistor Q2 is a transistor that operates when the voltage drops. The PNP transistor Q2 has a collector connected to the ground (earth) and an emitter connected to the output signal line of the drive signal. Note that the voltage (drive signal voltage) at the portion where the emitters of the NPN transistor Q1 and the PNP transistor Q2 are connected to each other is fed back to the voltage amplifier circuit 712, as indicated by the symbol FB.

  The operation of the current amplification circuit 72 is controlled by the output voltage from the waveform generation circuit 71. For example, when the output voltage is in the rising state, the NPN transistor Q1 is turned on by the control signal S_Q1. Along with this, the current I1 flows and the voltage of the drive signal also rises. On the other hand, when the output voltage is in a drop state, the PNP transistor Q2 is turned on by the control signal S_Q2. Along with this, the current I2 flows and the voltage of the drive signal also drops. Note that when the output voltage is constant, both the NPN transistor Q1 and the PNP transistor Q2 are turned off. As a result, the drive signal becomes a constant voltage.

<Operation of Drive Signal Generation Circuit 70>
FIG. 7A is a diagram for explaining a part of the drive signal generated by the drive signal generation circuit 70. FIG. 7B is a diagram for explaining the operation of dropping the output voltage of the current amplification circuit 72 from the voltage V1 to the voltage V4.

  The CPU 62 of the printer-side controller 60 first obtains an output voltage for each update period τ based on a parameter for generating a drive signal. Taking the drive pulse PS ′ shown in FIG. 7A as an example, the parameters include a drive voltage Vh, a ratio defining the relationship between the drive voltage Vh and the reference voltage Vc, a time PWh1 for maintaining the intermediate voltage VC, A time PWd1 for dropping the voltage from the intermediate voltage VC to the lowest voltage VL with a constant slope; a time PWh2 for maintaining the lowest voltage VL; a time PWc1 for raising the voltage with a constant slope from the lowest voltage VL to the highest voltage VH; There is a time PWh3 for maintaining the maximum voltage VH, a time PWd2 for dropping the voltage with a constant gradient from the maximum voltage VH to the intermediate voltage VC, and a time PWh4 for maintaining the intermediate voltage VC.

  Here, the drive voltage Vh is a voltage difference between the highest voltage VH and the lowest voltage VL in the drive pulse PS ′. In other words, this corresponds to the difference between the lowest potential (potential determined by the lowest voltage VL) and the highest potential (potential determined by the highest voltage VH) in the piezo element 417. The reference voltage Vc defines a deformation state that serves as a reference for the piezo element 417. In the present embodiment, the reference voltage Vc is 40% of the drive voltage Vh. For this reason, the value “0.4” is stored as a ratio that defines the relationship between the drive voltage Vh and the reference voltage Vc. The intermediate voltage VC is a voltage obtained by adding the reference voltage Vc to the minimum voltage VL. The maximum voltage VH is a voltage obtained by adding the drive voltage Vh to the minimum voltage VL. These parameters are stored in the memory 63.

  The CPU 62 determines the drive voltage Vh based on the parameters stored in the memory 63. When the drive voltage Vh is determined, the CPU 62 calculates a reference voltage Vc, an intermediate voltage VC, and a maximum voltage VH. And CPU62 calculates | requires the output voltage for every update period (tau) using time PWh1-time PWh4 mentioned above. The update period τ is, for example, 0.1 μs (clock CLK = 10 MHz) to 0.05 μs (clock CLK = 20 MHz). Then, based on the obtained output voltage for each update cycle τ, a DAC value for each update cycle τ is determined and stored, for example, in a work area (not shown) of the memory 63.

  When generating the drive signal, the CPU 62 sequentially outputs the DAC value for each update cycle τ to the D / A converter 711A. In the example of FIG. 7B, the DAC value corresponding to the voltage V1 is output at the timing t (n) defined by the clock CLK. Thereby, the voltage V1 is output from the voltage amplification circuit 712 in the cycle τ (n). Until the update period τ (n + 4), the DAC value corresponding to the voltage V1 is sequentially input from the CPU 62 to the D / A converter 711, and the voltage amplifying circuit 712 continues to output the voltage V1. At timing t (n + 5), the DAC value corresponding to the voltage V2 is input from the CPU 62 to the D / A converter 711. As a result, the output of the voltage amplification circuit 712 drops from the voltage V1 to the voltage V2 in the cycle τ (n + 5). Similarly, at timing t (n + 6), the DAC value corresponding to the voltage V3 is input from the CPU 62 to the D / A converter 711, and the output of the voltage amplifier circuit 712 drops from the voltage V2 to the voltage V3. Similarly, since the DAC value is sequentially input to the D / A converter 711, the voltage output from the voltage amplifier circuit 712 gradually decreases. Then, at the period τ (n + 10), the output of the voltage amplification circuit 712 drops to the voltage V4.

  In this way, the signal shown in FIG. 7A is output from the waveform generation circuit 71 and output as a drive signal from the current amplification circuit 72.

<About the head controller HC>
FIG. 8 is a block diagram illustrating the configuration of the head controller HC. FIG. 9 shows the ejection drive signal COM.

  As shown in the drawing, a head control signal is input from the printer-side controller 60 to the head controller HC. The drive signal output from the drive signal generation circuit 70 is input to the selection switch 65 provided on the upstream side of the head controller HC. When the selection switch 65 is connected to a terminal on the head control unit HC side, the drive signal output from the drive signal generation circuit 70 is input to the head control unit HC as an ejection drive signal COM commonly used for a plurality of piezoelectric elements. Is done.

  The head controller HC includes a first shift register 81A, a second shift register 81B, a first latch circuit 82A, a second latch circuit 82B, a decoder 83, a control logic 84, and a switch 85. Yes. Each part excluding the control logic 84, that is, the first shift register 81A, the second shift register 81B, the first latch circuit 82A, the second latch circuit 82B, the decoder 83, and the switch 85 are respectively piezo elements 417. Provided for each. In addition, since the piezo element 417 is provided for each nozzle, in other words, each of these parts is provided for each nozzle.

  The head controller HC performs control for ejecting ink based on print data (pixel data SI) from the printer-side controller 60. In the present embodiment, the pixel data is composed of 2 bits, and this pixel data is sent to the recording head 41 in synchronization with the clock signal CLK. This pixel data is sent in order from the upper bit group to the lower bit group. Each nozzle row of the head 41 of the present embodiment has 180 nozzles from the first nozzle # 1 to the 180th nozzle # 180. Therefore, the pixel data includes the upper bits of nozzle # 1, the upper bits of nozzle # 2,..., The upper bits of nozzle # 179, the upper bits of nozzle # 180, the lower bits of nozzle # 1, and the lower bits of nozzle # 2. ,... Are sent in the order of the lower bits of nozzle # 179 and the lower bits of nozzle # 180. As a result, the upper bit group of each pixel data is set in the first shift register 81A, and the lower bit group is set in the second shift register 81B.

  A first latch circuit 82A is electrically connected to each first shift register 81A, and a second latch circuit 82B is electrically connected to each second shift register 81B. When the latch signal LAT from the printer-side controller 60 becomes H level, that is, when a latch pulse is input to the first latch circuit 82A and the second latch circuit 82B, the first latch circuit 82A is in the first shift register 81A. The second latch circuit 82B latches the lower bits of the second shift register 81B.

  A decoder 83 is electrically connected to the first latch circuit 82A and the second latch circuit 82B. Pixel data (a set of upper bits and lower bits) latched in the first latch circuit 82A and the second latch circuit 82B is input to the decoder 83, respectively.

FIG. 9 shows a latch signal LAT and a change signal CH. Further, in this figure, waveform selection signals q0 to q3 are shown.
A latch signal LAT and a change signal CH are input from the CPU 62 to the control logic 84. The control logic 84 generates the waveform selection signals q0 to q3 shown in FIG. 9 based on the latch signal LAT and the change signal CH. The waveform selection signals q0 to q3 generated by the control logic 84 are input to each decoder 83.

  The decoder 83 outputs a switch control signal SW for controlling on / off of the switch 85 based on the pixel data latched by the first latch circuit 82A and the second latch circuit 82B. When the pixel data is “00”, the decoder 83 outputs the waveform selection signal q0 as the switch control signal SW. When the pixel data is “01”, the decoder 83 outputs the waveform selection signal q1 as the switch control signal SW. When the pixel data is “10”, the decoder 83 outputs the waveform selection signal q2 as the switch control signal SW1. When the pixel data is “11”, the decoder 83 outputs the waveform selection signal q3 as the switch control signal SW. If the switch control signal SW is at H level, the switch 85 is turned on, and if it is at L level, it is turned off.

  A drive signal COM is input to each switch 85 in common. If the switch 85 is on, the drive signal COM is input to the piezo element 417. If the switch 85 is off, the drive signal COM is not input to the piezo element 417. The output side of the switch 85 is electrically connected to the piezo element 417. When the switch 85 is turned on / off, the waveform portion constituting the drive signal COM is selectively applied to the piezo element 417.

  FIG. 9 shows an applied signal applied to the piezo element 417. As a result, when the pixel data is “00”, none of the six pulses included in the drive signal COM is applied, the piezo element 417 is not driven, and no ink droplet is ejected. When the pixel data is “01”, one pulse included in the drive signal COM is applied, the piezo element 417 is driven according to this pulse, a small ink droplet is ejected, and a small dot is formed on the paper S. . Similarly, when the pixel data is “10”, two pulses included in the drive signal COM are applied, and a medium dot is formed on the paper S. When the pixel data is “11”, six pulses included in the drive signal COM are applied, and a large dot is formed on the paper S.

<About print processing>
FIG. 10 is a flowchart for explaining the printing process. In the printer 1 having the above-described configuration, the printer-side controller 60 controls the control target units (the paper transport mechanism 20, the carriage moving mechanism 30, the head unit 40, and the drive signal generation circuit 70) according to the computer program stored in the memory 63. These processes are performed under control. Therefore, this computer program has a code for controlling the control target unit in order to execute these processes.

  This printing process includes reception of a print command (S10), paper feed operation (S20), dot formation operation (S30), transport operation (S40), paper discharge determination (S50), paper discharge operation (S60), and printing end. It has a judgment (S70). Each process will be briefly described below.

The print command reception (S10) is a process of receiving a print command from the computer 110. In this process, the printer-side controller 60 receives a print command via the interface unit 61.
The paper feeding operation (S20) is an operation for moving the paper S to be printed and positioning it at a printing start position (so-called cueing position). In this operation, the printer-side controller 60 rotates the paper feed roller 21 and the transport roller 23 by driving the transport motor 22 and the like.
The dot forming operation (S30) is an operation for forming dots on the paper S. In this operation, the printer-side controller 60 drives the carriage motor 31 and outputs a control signal to the drive signal generation circuit 70 and the head 41. Thus, ink is ejected from the nozzles Nz while the head 41 is moving, and dots are formed on the paper S.
The transport operation (S40) is an operation for moving the paper S in the transport direction. In this operation, the printer-side controller 60 drives the carry motor 22 to rotate the carry roller 23. By this transport operation, dots can be formed at positions different from the dots formed by the previous dot formation operation.
The paper discharge determination (S50) is an operation for determining whether or not it is necessary to discharge the paper S to be printed. This determination is made by the printer-side controller 60 based on the presence or absence of print data, for example.
The paper discharge process (S60) is a process of discharging the paper S, and is performed on the condition that “discharge” is determined in the previous paper discharge determination. In this case, the printer-side controller 60 rotates the paper discharge roller 25 to discharge the printed paper S to the outside.
The print end determination (S70) is a determination as to whether or not to continue printing. This determination is also made by the printer-side controller 60.

=== Method of detecting ink amount ===
<Overview>
FIG. 11 is a cross-sectional view of the carriage CR and the ink cartridge 87 mounted on the carriage CR.

  The ink cartridge (liquid storage container) 87 is provided with an ink storage portion (liquid storage portion) 871 for storing ink therein. The ink cartridge 87 is provided with a supply portion 872 for supplying ink. The carriage CR is provided with a needle P. When the ink cartridge 87 is mounted on the carriage CR, the needle P sticks into the supply portion 872 and the ink in the ink storage portion 871 is supplied from the supply portion 872 to the head 41. Will come to be.

  When ink is consumed by printing, the amount of ink in the ink containing portion 871 decreases, and the ink level in the ink containing portion 871 falls. Therefore, in the present embodiment, the liquid level detection unit 90 is provided at a predetermined position (referred to as a detection position) in the ink storage unit 871. The liquid level detection unit 90 detects that the ink level in the ink containing portion 871 has reached the detection position by detecting the presence or absence of ink at the detection position. Accordingly, the printer-side controller 60 can detect the remaining amount of ink in the ink containing portion 871 based on the detection result from the liquid level detecting portion 90.

  When the printer-side controller 60 detects that the ink level in the ink containing portion 871 has reached the detection position, the printer-side controller 60 notifies the computer 110 accordingly. The computer 110 displays the remaining amount of ink in the ink cartridge 87 on the display device 120 based on the detection result. Of course, based on the detection result, the printer-side controller 60 or the computer 110 may give a warning to the user or may perform other operations.

  The ink amount detection process is performed when the printer 1 is turned on or when the ink cartridge 87 is replaced. Further, it may be performed before or after a predetermined job. Further, when the printer 1 counts the number of ink ejections and the count value reaches a predetermined value, the ink amount detection process may be performed.

<Configuration of Liquid Level Detection Unit 90>
FIG. 12A is an explanatory diagram of the configuration of the liquid level detection unit 90. The liquid level detection unit 90 includes a vibration unit 91, a buffer chamber 92, a first ink channel 93, and a second ink channel 94. The vibration unit 91 includes a piezo element 911 and a diaphragm 912. The buffer chamber 92 is an ink chamber for preventing the vibration of the ink in the vicinity of the vibration portion 91 from being affected by the state of the ink storage portion 871 and the first ink flow path 93. The buffer chamber 92 and the ink containing portion 871 are connected via a first ink channel 93 and a second ink channel 94. When the liquid level of the ink containing part 871 is lowered and the liquid level of the ink containing part 871 is changed to a position lower than the vibrating part 91, air flows from the first ink flow path 93, and the vibrating part 91 does not come into contact with the ink. If the vibration unit 91 is in direct contact with the ink in the ink storage unit 871, even if the liquid level in the ink storage unit 871 is lower than the vibration unit 91 due to the influence of surface tension, the vibration unit 91 is in contact with the ink. There is a possibility of contact (see FIG. 12B). In the present embodiment, when the liquid level in the ink containing portion 871 becomes lower than the vibration portion 91 by utilizing the capillary phenomenon by the first ink flow path 93 and the second ink flow path 94, the vibration section 91 promptly moves the ink. Therefore, the position of the liquid surface in the ink containing portion 871 can be accurately detected.

  The piezo element 911 is provided on the diaphragm 912. The vibration plate 912 is provided on the side surface of the ink cartridge 87 so as to close the opening 871 a of the ink cartridge 87. That is, the piezoelectric element 911 is provided on one surface of the diaphragm 912, and ink or air is in contact with the other surface. Whether the vibration plate 912 contacts the ink or the air varies depending on the height of the ink surface in the ink containing portion 871.

<Configuration of vibration unit 91>
FIG. 13A is a plan view for explaining the detailed configuration of the vibration section 91. 13B is a cross-sectional view taken along line BB in FIG. 13A, and FIG. 13C is a cross-sectional view taken along line CC in FIG. 13A.

  The piezoelectric element 911 includes a piezoelectric layer 911a, an upper electrode 911b, and a lower electrode 911c. The piezoelectric layer 911a, the upper electrode 911b, and the lower electrode 911c have a circular main part. In this circular portion, the piezoelectric layer 911a is sandwiched between the upper electrode 911b and the lower electrode 911c. The upper electrode terminal 911d is electrically coupled to the upper electrode 911b. Further, the lower electrode terminal 911e is electrically coupled to the lower electrode 911c. The lower electrode terminal 911e is formed on the surface of the diaphragm 912 so as to be electrically connected to the lower electrode 911c. On the other hand, the upper electrode terminal 911d is formed on the surface of the diaphragm 912 so as to be electrically connected to the upper electrode 911b through the auxiliary electrode 911f. Thereby, the piezoelectric layer 911a and the upper electrode 911b are supported by the auxiliary electrode 911f, and the mechanical strength can be improved.

  The lower electrode 911c is located on the surface of the vibration plate 912 opposite to the opening 871a of the ink containing portion 871. The center of the circular portion of the lower electrode 911c substantially coincides with the center of the opening 871a of the ink containing portion 871. Note that the area of the circular portion of the lower electrode 911c is smaller than the area of the opening 871a. On the other hand, the center of the circular portion of the upper electrode 911b substantially coincides with the center of the opening 871a of the ink containing portion 871. Note that the area of the circular portion of the upper electrode 911b is smaller than the area of the opening 871a and larger than the area of the circular portion of the lower electrode 911c. The center of the circular portion of the piezoelectric layer 911a substantially coincides with the center of the opening 871a. Further, the area of the circular portion of the piezoelectric layer 911a is smaller than the area of the opening 871a and larger than the areas of the circular portions of the upper electrode 911b and the lower electrode 911c.

  The centers of the circular portions of the piezoelectric layer 911a, the upper electrode 911b, and the lower electrode 911c constituting the piezo element 911 substantially coincide with the center of the opening 871a. On the other hand, the vibration part of the diaphragm 912 is determined by the opening 871a. Accordingly, the center of the piezo element 911 substantially coincides with the center of the vibration portion of the diaphragm 912. Thereby, when the diaphragm 912 vibrates, the piezo element 911 can output a signal corresponding to the resonance frequency of the diaphragm 912 in a state where the influence of noise is small.

  In the present embodiment, the piezoelectric layer 911a uses lead zirconate titanate (PZT). However, the present invention is not limited to this. Lead lanthanum zirconate titanate (PLZT) may be used, and a lead-less piezoelectric film may be used. In short, any material can be used as long as the piezoelectric effect can be obtained.

<Principle of liquid level detection>
When a drive signal is applied to the piezo element 911, the piezo element 911 expands and contracts, and the diaphragm 912 vibrates in the direction of the arrow in FIG. 12A. Even when the application of the drive signal to the piezo element 911 is stopped, residual vibration is generated in the diaphragm 912. The nature of this residual vibration varies greatly depending on whether or not the vibration plate 912 is in contact with ink. When the diaphragm 912 is in contact with the ink, the residual vibration frequency is low, and the residual vibration amplitude is small. On the other hand, when the vibration plate 912 is not in contact with the ink, the frequency of the residual vibration is increased and the amplitude of the residual vibration is increased. When the diaphragm 912 vibrates due to residual vibration, the piezo element 911 expands and contracts the diaphragm 912 in accordance with the residual vibration and outputs a signal. That is, when the diaphragm 912 is in contact with ink, the piezo element 911 outputs a signal having a low frequency and a small amplitude. On the other hand, when the diaphragm 912 is not in contact with ink, the piezo element 911 outputs a signal having a high frequency and a large amplitude. Therefore, if the frequency of the signal output from the piezo element 911 can be detected, it can be detected whether or not the liquid level has reached the position of the diaphragm 912 and the amount of ink in the ink containing portion 871 can be detected.

  FIG. 14 is a graph showing the relationship between the amount of ink in the ink containing portion 871 and the frequency of residual vibration. Before the ink amount in the ink containing portion 871 reaches Q, the ink level is higher than the vibration plate 912 and the vibration plate 912 is in contact with the ink, so the frequency of residual vibration is low. On the other hand, when the amount of ink in the ink containing portion 871 becomes Q, the liquid level of the ink is located below the vibration plate 912, and the vibration plate 912 does not contact the ink, so the frequency of residual vibration increases. Incidentally, since the capacity of the ink containing portion 871 and the mounting position of the liquid level detecting unit 90 are determined by design, the ink amount Q in the ink containing portion 871 when the liquid level detecting unit 90 detects the liquid level is also known. Value. For this reason, when the residual vibration frequency changes from a low state to a high state, it is detected that the ink remaining amount of the ink cartridge 87 is the ink amount Q.

<Configuration of Signal Detection Unit 95>
When the selection switch 65 (see FIG. 8) is connected to the terminal on the piezo element 911 side, the drive signal output from the drive signal generation circuit 70 is applied to the piezo element 911. Thereby, the diaphragm 912 vibrates. When the selection switch 65 is turned off, the piezo element 911 outputs a signal according to the residual vibration, and the signal is input to the signal detection unit 95.

  FIG. 15 is an explanatory diagram of the configuration of the signal detection unit 95. The signal detection unit 95 detects the period (or frequency) of the signal output from the piezo element 911 and outputs the detection result to the printer-side controller 60. The signal detection unit 95 includes an amplification unit 951 and a pulse width detection unit 952.

  FIG. 16 is an explanatory diagram of the configuration of the amplifying unit 951. The amplifying unit 951 removes a low-frequency component included in the signal from the piezo element 911 by a high-pass filter composed of a capacitor C1 and a resistor R1, and amplifies it by an operational amplifier 951a. Next, the output of the operational amplifier 951a is passed through a high-pass filter composed of a capacitor C2 and a resistor R2, thereby converting it into a signal that vibrates up and down around the reference voltage Vref. Then, the comparator 951b of the amplifying unit 951 compares it with the reference voltage Vref, and binarizes the signal depending on whether or not it is higher than the reference voltage.

  17A to 17C are explanatory diagrams of signals flowing in the signal detection unit 95. FIG. 17A is a diagram illustrating a signal that the piezo element 911 outputs according to the residual vibration. FIG. 17B is a diagram illustrating a signal after the output of the operational amplifier 951a is passed through a high-pass filter including the capacitor C2 and the resistor R2, and the reference voltage Vref. That is, it is a signal input to the comparator 951b. FIG. 17C is a diagram illustrating an output signal from the comparator. That is, it is a signal input to the pulse width detector 952.

  When the pulse shown in FIG. 17C is input, the pulse width detection unit 952 resets the count value at the rising edge of the pulse, increments the count value for each subsequent clock signal, and counts at the rising edge of the next pulse. Is output to the printer-side controller 60. The printer-side controller 60 can detect the period of the signal output from the piezo element 911 based on the count value output from the pulse width detection unit 952, that is, based on the detection result output from the signal detection unit 95. it can.

<About the drive signal that can improve the detection accuracy of the residual vibration of the diaphragm 912>
Here, the drive signal that can improve the detection accuracy of the residual vibration of the diaphragm 912 will be described. In general, the diaphragm 912 has a unique resonance frequency. When a drive signal having the same frequency as the resonance frequency is applied to the piezo element 911, the amplitude of the diaphragm 912 increases and a signal with a large amplitude is output from the piezo element 911. Is done. For this reason, from the viewpoint of improving the detection accuracy of the residual vibration signal, it is desirable to match the frequency of the drive signal with the resonance frequency of the diaphragm 912.

  On the other hand, the resonance frequency differs greatly between the ink presence state when the diaphragm 912 is in contact with the ink and the ink absence state when the vibration plate 912 is not in contact with the ink. Therefore, unless a drive signal having resonance frequencies ν1 and ν0 corresponding to the states with or without ink is applied, the excitation effect that increases the amplitude of the residual vibration cannot be obtained. Therefore, the signal output from the piezo element 911 Cannot be detected accurately.

  This will be described in detail by taking as an example a case where the resonance frequency ν1 of the vibration plate 912 in the ink state is 30 KHz and the resonance frequency ν0 in the ink absence state is 60 KHz.

  FIG. 18A is a waveform diagram of residual vibration in the presence of ink. FIG. 18B is a waveform diagram of a drive signal in which the frequency is set to 30 KHz, which is the resonance frequency ν1 in the ink presence state. Although the residual vibration waveform diagrams to be described below including FIG. 18A are shown as a sine wave with a constant amplitude for the sake of easy understanding, the waveform amplitude actually attenuates with time. In the following, with respect to the displacement direction of the diaphragm 912 in FIG. 12, the case of displacement toward the inside of the ink containing portion 871 is defined as the positive direction, and the case of displacement toward the opposite outside is defined as the negative direction.

 As shown in FIG. 18B, this drive signal is a rectangular pulse. At the rising time tu, the vibration plate 912 is displaced in the positive direction, which is the inner side of the ink containing portion 871, and during the application period after the rising, the vibration plate 912 stops being displaced and enters the hold state, and at the falling time. At td, the vibration plate 912 is displaced in the negative direction that is the outer side of the ink containing portion 871, and in the non-application state after the falling, the vibration plate 912 stops the displacement and enters the hold state. In this non-applied state, the selection switch 65 is turned off, the diaphragm 912 undergoes residual vibration, and a signal corresponding to the residual vibration is output from the piezo element 911.

Here, when this drive signal is applied to the piezo element 911, the diaphragm 912 is displaced at the rise time tu and the fall time td. The application period corresponding to the time interval between the rising time point tu and the falling time point td is 16.7 μs, which is half the resonance period 33.3 μs of the residual vibration in the ink presence state shown in FIG. 18A. ing.
Therefore, the diaphragm 912 in the ink state is promoted in the positive direction at the rising time point tu, and is displaced in the negative direction at the falling time point td after a half cycle of the resonance period. Since the plate 912 is displaced at the resonance frequency of the residual vibration with ink, the residual vibration after the selection switch 65 is turned off is greatly excited.

  19A and 19B are output signals of the piezo element 911 after this drive signal is applied to the piezo element 911. FIG. 19A shows an output signal in the ink present state, and FIG. 19B shows an ink out state. The output signal is shown.

  As shown in FIG. 19A, when a drive signal is applied to the piezo element 911 in the presence of ink, the vibration plate 912 is displaced at the resonance frequency of 30 KHz as described above, so that the residual vibration of the vibration plate 912 is large. When excited, the amplitude of the output signal of the piezo element 911 increases. As a result, even if noise enters the signal output from the piezo element 911, the printer-side controller 60 can accurately detect the cycle of the signal output from the piezo element 911.

  On the other hand, as shown in FIG. 19B, the amplitude of the output signal of the piezo element 911 is small even when the drive signal is applied to the piezo element 911 in the absence of ink. This is because the resonance frequency of the residual vibration of the diaphragm 912 in the absence of ink is 60 KHz, and even if the drive signal of FIG. 18B for driving the piezo element 911 at 30 KHz is applied, the residual vibration is not easily excited on the diaphragm 912. Because. In this case, if noise enters the signal output from the piezo element 911, the printer-side controller 60 cannot accurately detect the cycle of the signal output from the piezo element 911.

  For this reason, in order to accurately detect the output signal of the piezo element 911 even in the absence of ink, as a drive signal having the same frequency as the resonance frequency 60 KHz of the residual vibration of the diaphragm 912 in the absence of ink, for example, It is necessary to apply to the piezo element 911 an 8.3 μs rectangular pulse whose application period is half of the resonance period 16.7 μs of the residual vibration in the absence of ink.

  That is, in order to accurately detect the presence or absence of ink, first, the piezo element 911 is driven at the resonance frequency ν1 of the residual vibration in the presence of ink to detect whether ink is present at the attachment position of the piezo element 911. After that, it is necessary to perform a detection operation twice, in which the piezo element 911 is driven at the resonance frequency ν0 of the residual vibration in the absence of ink to detect whether ink is present at the attachment position of the piezo element 911. In that case, there arises a problem that the detection time becomes long.

  However, as long as the resonance frequency ν1 in the ink presence state and the resonance frequency ν0 in the ink absence state are set to a predetermined relationship, the residual vibration in the ink absence state is generated by a drive signal that effectively excites the residual vibration in the ink presence state. Therefore, both the presence and absence of ink can be accurately detected by a single detection operation.

  Therefore, in the present embodiment, by setting the resonance frequency ν1 in the ink presence state and the resonance frequency ν0 in the ink absence state to a predetermined relationship described below, the ink is applied by applying one type of drive signal. It effectively excites residual vibration in both states. As a result, the detection time is shortened while maintaining high detection accuracy.

<About the predetermined relationship>
The predetermined relationship will be described first from the ideal relationship. This ideal relationship is a relationship in which the resonance frequency ν0 of the residual vibration in the ink-free state and the resonance frequency ν1 of the residual vibration in the ink-present state satisfy the following expression (1). In addition, k in Formula (1) is an arbitrary integer of 1 or more.
ν0 = (2k + 1) × ν1 (1)
If the resonance frequencies ν0 and ν1 are set as described above, the residual vibration in the absence of ink can be most effectively excited using the drive signal that most effectively excites the residual vibration in the presence of ink. It becomes possible to accurately detect the presence or absence of ink with only one detection operation. Incidentally, as a method for setting such resonance frequencies ν0 and ν1, the shapes of the opening 971a, the buffer chamber 92, the first ink flow path 93, and the second ink flow path 94 in FIG. Examples include adjusting the rigidity.

  20A and 20B are waveform diagrams of residual vibration that satisfy Equation (1). FIG. 20A shows a waveform with a resonance frequency ν1 of 30 KHz as an example of residual vibration in the presence of ink, and FIG. 20B below shows an equation ( The waveform of the resonance frequency ν0 of 90 KHz where k = 1 in 1) is shown. FIG. 20C shows a drive signal composed of one rectangular pulse as an example of the drive signal that most effectively excites the residual vibration in the ink presence state of FIG. 20A.

  As shown in FIG. 20C, the magnitude of the rectangular pulse application period is half of the vibration period T1 of the residual vibration in order to most effectively excite the residual vibration in the ink presence state. This is because, in general, vibration is most effectively excited when assisted in the vibration direction at the time when the vibration speed becomes maximum. The rectangular pulse in the illustrated example rises at a time ta at which the residual vibration of 30 KHz in FIG. 20A is displaced with a positive maximum vibration speed (hereinafter, referred to as a positive maximum speed time ta), and reaches the time after a half cycle from there. The residual vibration falls at a time point tb (hereinafter referred to as a negative maximum speed time point tb) where the residual vibration is displaced with a negative maximum vibration speed. Therefore, according to this drive signal, the residual vibration in the presence of ink at 30 KHz is most effectively promoted and excited most effectively.

  On the other hand, looking at the residual vibration in the ink-free state of 90 KHz in FIG. 20B, the residual vibration is also displaced at the positive maximum speed time ta with the maximum positive vibration speed, and at the negative maximum speed time tb. Displace with the maximum negative vibration speed. Accordingly, the rectangular pulse in FIG. 20C acts to promote the vibration without canceling the vibration even in the residual vibration in the ink-free state, and the residual vibration is thereby most effectively excited.

  As described above, the case where k = 1 has been described as an example of the ideal relationship. However, it is needless to say that the above description is valid even when k is an integer other than 1.

Incidentally, as a simple example that does not satisfy the ideal relationship, for example, the case of the following formula (1 ′) can be given. Here, k in the formula (1 ′) is an arbitrary integer of 1 or more.
ν0 = (2k) × ν1 (1 ′)
FIG. 21A to FIG. 21B show waveform diagrams of residual vibration satisfying this equation (1 ′). FIG. 21A shows a waveform having the same resonance frequency ν1 as in FIG. 20A described above as 30 KHz as an example of residual vibration in the presence of ink, and FIG. 21B below shows residual vibration in the absence of ink. As an example, a waveform having a resonance frequency ν0 of 60 KHz where k = 1 in the equation (1 ′) is shown. Further, FIG. 21C below shows a drive signal composed of one rectangular pulse as in FIG. 20C as an example of the drive signal that most effectively excites the residual vibration in the ink presence state of FIG. 21A. .

  As described above, the drive signal most effectively excites the vibration with respect to the residual vibration in the ink presence state of 30 KHz in FIG. 21A. However, it is not possible to effectively excite the residual vibration in the ink-free state of 60 KHz in FIG. 21B. This is because the residual vibration of 60 KHz is displaced at the positive maximum speed time ta with the maximum positive vibration speed, but at the negative maximum speed time tb, it is not negative but has the maximum positive vibration speed. This is because it is displaced.

  That is, as shown in FIG. 21C, since the rectangular pulse of the drive signal falls at the negative maximum speed time tb, if the residual vibration is displaced with a negative vibration speed as shown in FIG. Although the vibration is promoted by the falling edge of the rectangular pulse, the residual vibration of 60 KHz in FIG. 21B is displaced at the maximum positive vibration speed. From this, the rectangular pulse acts in a direction to cancel the residual vibration. Because it will end up.

  Therefore, when the resonance frequencies ν1 and ν0 in the ink presence / absence state are set so as to satisfy the relationship of the above formula (1 ′), the drive signal that effectively excites the residual vibration in the ink presence state causes Residual vibration cannot be excited, that is, effective excitation of residual vibration in both states with and without ink cannot be achieved by applying one drive signal. As a result, the detection time cannot be shortened.

<Acceptable range of ideal relationship>
It is satisfactory if the resonance frequencies ν1 and ν0 in the presence / absence of ink can be set so as to satisfy ν0 = (2k + 1) × ν1 in the above-mentioned ideal relationship (1), but usually this equation (1) It is difficult to pinpoint to the resonance frequencies ν1, ν0 defined by Therefore, it is convenient in design if there is an allowable range in which the above-described excitation effect is recognized.

From the conclusion, the relational expression in consideration of the allowable range is expressed as the following expression (2). That is, the expression (2) is expressed as follows with respect to ν0 defined by the expression (1). Thus, the range of ν0 is expanded by ± ν1 / 2.
{(2k + 1) -1/2} × ν1
≦ ν0 ≦ {(2k + 1) + ½} × ν1 (2)
This allowable range is based on the following concept.

  In general, as shown in FIGS. 22A and 22B, when the residual vibration is displaced at the maximum positive vibration speed at the rising time tu of the rectangular pulse of the drive signal, at the falling time td of the rectangular pulse, Even if the residual vibration is not at the negative maximum speed as shown in FIG. 22B, if the residual vibration is displaced at least at the negative vibration speed as shown in FIG. 22C, the residual vibration is canceled by the falling edge of the rectangular pulse. It is thought that it is excited effectively. On the contrary, if the residual vibration is displaced at a positive vibration speed as shown in FIG. 22D at the falling time td of the rectangular pulse, the residual vibration is canceled by the falling of the rectangular pulse, and is effectively excited. It is not thought to be done.

  Here, as shown in FIG. 22A, the rising time point tu and the falling time point td of the rectangular pulse are set so as to most effectively excite the residual vibration in the ink presence state of FIG. 22E. The falling time td coincides with the positive maximum speed time ta and the negative maximum speed time tb in the residual vibration in the ink presence state, respectively.

  Accordingly, as shown in FIG. 22F, the residual vibration in the ink-free state is displaced at the positive maximum vibration speed ta at the positive maximum speed ta of the residual vibration in the ink-present state, and the negative vibration of the residual vibration in the ink-present state is present. At the maximum speed time tb, if the displacement is not a maximum but a negative vibration speed, the residual vibration in the absence of ink is also excited by the drive signal, that is, an excitation effect should be recognized. And the range where such an excitation effect is recognized is the above-mentioned permissible range.

  With this in mind, first consider the upper limit value ν0max (= {(2k + 1) +1/2} × ν1) of the allowable range. FIG. 23A shows a waveform of residual vibration in the presence of ink having a resonance frequency ν1 of 30 KHz, and FIG. 23B shows a drive signal that most effectively excites this residual vibration of 30 KHz. 23C to 23F show waveforms of residual vibration in the absence of ink. FIG. 23C shows a vibration waveform at an ideal resonance frequency ν0i that satisfies ν0i = (2k + 1) × ν1 that is the ideal relationship described above, and ν0i is 90 KHz because k is 1 as described above. In the following, the frequency of the vibration waveform in the lower figure deviates to a higher side than the ideal resonance frequency ν0i. For example, the frequency of the vibration waveform illustrated in FIG. 23D is 97.5 KHz, which is 1/4 × ν1 higher than 90 KHz of the ideal resonance frequency ν0i, and the frequency of the vibration waveform illustrated in FIG. The frequency of the vibration waveform shown in FIG. 23F below is 105 KHz higher than 90 KHz of the ideal resonance frequency ν0i, and is 3/4 × ν1 higher than 90 KHz of the ideal resonance frequency ν0i. .5 KHz.

  Here, regarding the vibration waveform of FIG. 23D, the vibration speed is a positive maximum speed at the positive maximum speed time ta, and the vibration speed is negative at the negative maximum speed time tb. Accordingly, the drive signal that most effectively excites the residual vibration in the ink presence state shown in FIG. 23B, that is, the residual pulse of FIG. 23D by the rectangular pulse that rises at the maximum speed time ta and falls at the maximum speed time tb. Vibrations are also encouraged and excited, so this frequency is within the acceptable range.

  On the other hand, in the vibration waveform of FIG. 23F, the vibration speed is the positive maximum speed at the positive maximum speed time ta, but the vibration speed is positive at the negative maximum speed time tb. Therefore, this residual vibration is promoted and excited by the rising edge of the rectangular pulse in FIG. 23B at the positive maximum speed time ta, but is canceled by the falling edge of the rectangular pulse at the negative maximum speed time tb. It is not excited. That is, by the rectangular pulse that rises at the maximum speed time ta and falls at the maximum speed time tb as shown in FIG. 23B, the residual vibration of FIG. Out of tolerance.

  Therefore, there is an upper limit value ν0max of the frequency at which the residual vibration in the absence of ink can be effectively excited by the drive signal between the frequency of FIG. 23D and the frequency of FIG. 23F. Is shown in FIG. 23E.

That is, in the vibration waveform of FIG. 23E, the vibration speed is a positive maximum speed at the positive maximum speed time ta, and the vibration speed is zero at the negative maximum speed time tb. Therefore, the drive signal of FIG. 23B, that is, the rectangular pulse rising at the positive maximum speed time ta and falling at the negative maximum speed time tb, the vibration is effectively promoted at the rising, but at the falling. Is a neutral state in which neither promotion nor cancellation is made, and thus the frequency in FIG. 23E becomes the upper limit value ν0max of the allowable range. The frequency of the vibration waveform in FIG. 23E is a frequency that is higher by ν1 / 2 than the ideal resonance frequency ν0i as described above, and therefore the upper limit value ν0max of the allowable range is expressed as follows.
ν0max = ν0i + ν1 / 2
= {(2k + 1) +1/2} × ν1

  Next, consider the lower limit value ν0min (= {(2k + 1) −1/2} × ν1) of the allowable range. Like FIG. 23A and FIG. 23B described above, FIG. 24A shows a waveform of residual vibration in the presence of ink whose resonance frequency ν1 is 30 KHz, and FIG. 24B shows a drive signal that most effectively excites this residual vibration of 30 KHz. Show. 24C to 24F all show waveforms of residual vibration in the absence of ink. FIG. 24C shows a vibration waveform of an ideal resonance frequency ν0i that satisfies the ideal relationship ν0i = (2k + 1) × ν1. Since k is 1 as described above, ν0i is 90 KHz. In the following, the frequency of the vibration waveform in the lower figure deviates to the side lower than the ideal resonance frequency ν0i. For example, the frequency of the vibration waveform illustrated in FIG. 24D is 82.5 KHz, which is 1/4 × ν1 lower than 90 KHz of the ideal resonance frequency ν0i, and the frequency of the vibration waveform illustrated in FIG. It is 75 KHz which is 1/2 × ν1 lower than 90 KHz of the ideal resonance frequency ν0i, and the frequency of the vibration waveform shown in FIG. 24F below it is 3/4 × ν1 lower than 90 KHz of the ideal resonance frequency ν0i. 67.5 KHz.

  Here, regarding the vibration waveform of FIG. 24D, the vibration speed is a positive maximum speed at the positive maximum speed time ta, and the vibration speed is negative at the negative maximum speed time tb. Accordingly, the drive signal that most effectively excites the residual vibration in the ink presence state shown in FIG. 24B, that is, the residual pulse of FIG. 24D by the rectangular pulse that rises at the maximum speed time ta and falls at the maximum speed time tb. Vibrations are also encouraged and excited, so this frequency is within the acceptable range.

  On the other hand, in the vibration waveform of FIG. 24F, the vibration speed is the positive maximum speed at the positive maximum speed time ta, but the vibration speed is positive at the negative maximum speed time tb. Therefore, this residual vibration is promoted and excited by the rising edge of the rectangular pulse in FIG. 24B at the positive maximum speed time point ta, but is canceled by the falling edge of the rectangular pulse at the negative maximum speed time point tb. It is not excited. That is, by the rectangular pulse that rises at the maximum speed time ta and falls at the maximum speed time tb as shown in FIG. 24B, the residual vibration of FIG. 24F is not effectively excited, and this frequency is Out of tolerance.

  Therefore, there exists a lower limit value ν0min of the frequency at which the residual vibration in the absence of ink can be effectively excited by the drive signal between the frequency of FIG. 24D and the frequency of FIG. 24F. The residual vibration is shown in FIG. 24E.

That is, in the vibration waveform of FIG. 24E, the vibration speed is a positive maximum speed at the positive maximum speed time ta, and the vibration speed is zero at the negative maximum speed time tb. Therefore, depending on the drive signal of FIG. 24B, that is, the rectangular pulse that rises at the positive maximum speed time ta and falls at the negative maximum speed time tb, the vibration is effectively promoted at the rise, but falls. In FIG. 24E, there is a neutral state where neither promotion nor cancellation is made, so the frequency in FIG. 24E becomes the lower limit value ν0min of the allowable range. The frequency of the vibration waveform in FIG. 24E is a frequency lower by ν1 / 2 than the ideal resonance frequency ν0i as described above, and therefore the lower limit value ν0min of the allowable range is expressed as follows.
ν0min = ν0i−ν1 / 2
= {(2k + 1) -1/2} × ν1

<When drive signal has multiple rectangular pulses>
The above explanation is for the case where the drive signal has one rectangular pulse. However, when the drive signal has a plurality of n rectangular pulses, the relational expression in consideration of the allowable range. (2) is expressed by the following equation (3).
{(2k + 1) × (2n−1) −1/2} / (2n−1) × ν1
≦ ν0 ≦ {(2k + 1) × (2n−1) + ½} / (2n−1) × ν1 (3)
The expression (3) means that ± ν1 / {2 × (2n−1) from the ideal resonance frequency ν0i (= (2k + 1) × ν1) defined by the ideal relationship expression (1). )}, The excitation effect of the drive signal against the residual vibration in the absence of ink can be exhibited.

Hereinafter, the expression (3) will be described with reference to FIGS. 25A to 25G.
FIG. 25A shows a vibration waveform having a resonance frequency ν1 of 30 KHz as an example of residual vibration in the presence of ink, as shown above. FIG. 25B below shows the residual vibration in the presence of ink. As an example of the drive signal that is most effectively excited, a drive signal composed of three rectangular pulses, where n = 3 in Equation (3), is shown.

 25C to 25G show three frequencies that fall within the allowable range of Expression (3) and two frequencies that fall outside the allowable range as an example of residual vibration in the absence of ink. That is, FIG. 25E shows a vibration waveform of 90 KHz where k = 1 in Equation (3) as an example of the ideal resonance frequency ν0i that is an intermediate value in the range of Equation (3). Further, FIG. 25D above shows 93 kHz as an example of the upper limit value ν0max of the equation (3), which is 1 / {2 × (2n−1)} × ν1 higher than the ideal resonance frequency ν0i. A vibration waveform of (= {(2 × 1 + 1) × (2 × 3-1) +1/2} / (2 × 3-1) × 30) is shown, and FIG. A vibration waveform of 96 KHz exceeding the value ν0max is shown. FIG. 25F below FIG. 25E shows an example of the lower limit value ν0min of the equation (3), which is a frequency lower than the ideal resonance frequency ν0i by 1 / {2 × (2n−1)} × ν1. , 87 KHz (= {(2 × 1 + 1) × (2 × 3-1) −1/2} / (2 × 3-1) × 30) is shown in FIG. 25G below. A vibration waveform of 84 KHz below the lower limit value ν0 min is shown.

 As shown in FIG. 25B, the rectangular pulse of the drive signal has an application period that is half the vibration period T1 of the residual vibration, and the application period is aligned with the resonance period T1 of the residual vibration. . According to such a drive signal, the residual vibration in the ink presence state can be excited most effectively. This is because, as shown in FIGS. 25A and 25B, the rising edge is aligned with the positive maximum speed point ta of the residual vibration over the three rectangular pulses, and the falling edge is set to the negative maximum of the residual vibration. This is because the speed can be aligned with the time point tb.

 Here, among the residual vibrations in the ink-free state, looking at the residual vibration of 90 KHz, which is the ideal resonance frequency shown in FIG. 25E, the maximum positive vibration speed at all the positive maximum speed time points ta. And at all time points of the negative maximum speed time point tb, it is displaced with a negative maximum vibration speed. Therefore, in the case of the ideal resonance frequency ν0i, the three all rectangular pulses of the drive signal are most effectively excited even with respect to residual vibration in the absence of ink.

 On the other hand, the vibration waveform of 93 kHz, which is the upper limit value ν0max shown in FIG. 25D, is displaced at the positive maximum speed time ta or at the positive maximum speed or at the positive vibration speed. Therefore, the residual vibration is effectively promoted and excited by the rising edge over three all rectangular pulses. However, the first maximum time tb and the next time tb of the negative maximum speed time tb are displaced with at least a negative vibration speed, but the vibration speed is zero at the last time tb. Therefore, except for the last time tb, the residual vibration can be effectively promoted and excited by the rising and falling of the rectangular pulse, but at the last time tb, the vibration speed is zero, so the vibration is not It is a neutral state that is not countered.

 When the frequency becomes higher than this, the residual vibration is displaced at a positive vibration speed at least at the last time tb of the negative maximum speed time tb, as in the frequency of 96 KHz in FIG. 25C. Become. In this case, the last rectangular pulse in FIG. 25B acts so as to cancel out the residual vibration at the falling edge, and the residual vibration of the frequency is effectively excited. However, the frequency of 96 KHz is out of the allowable range, and as a result, 93 KHz in FIG. 25D becomes the upper limit value ν0max of Equation (3).

 On the other hand, the vibration waveform of 87 KHz, which is the lower limit value ν0min shown in FIG. 25F, is displaced at the positive maximum speed time ta with the positive maximum speed or the positive vibration speed. Therefore, the residual vibration is effectively promoted and excited by the rising edge over three all rectangular pulses. However, at the first time point tb and the next time point tb of the negative maximum speed time point tb, the displacement is at least with a negative vibration speed, but at the last time point tb, the vibration speed is zero. Therefore, except for the last time tb, the residual vibration can be effectively promoted and excited by the rising and falling of the rectangular pulse, but at the last time tb, the vibration speed is zero, so the vibration is not It is a neutral state that is not countered.

 When the frequency is lower than this, the residual vibration is displaced at a positive vibration speed at least at the last time tb of the negative maximum speed time tb, such as the frequency of 84 KHz in FIG. 25G. Become. In this case, the last rectangular pulse in FIG. 25B acts so as to cancel out the residual vibration at the falling edge, and the residual vibration of the frequency is effectively excited. However, the frequency of 84 KHz is out of the allowable range, and as a result, 87 KHz in FIG. 25F becomes the lower limit value ν0 min of the equation (3).

  As described above, the case where n = 3 has been described as an example of the case where the drive signal has a plurality of rectangular pulses. However, the above description is valid even when n is an integer other than 3. Needless to say.

=== Other Embodiments ===
The above embodiment mainly describes the ink cartridge 87 as a liquid container and the printer 1 as a liquid ejection device, and includes disclosure of a liquid amount detection method and the like. The above-described embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

  In the above-described embodiment, the printer 1 has been described. However, the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various liquid ejection devices to which inkjet technology such as a device and a DNA chip manufacturing device is applied. These methods and manufacturing methods are also within the scope of application.

  In the above-described embodiment, the drive signal applied to the piezo element 911 is composed of a rectangular pulse, but this drive signal can be any signal that most effectively excites the residual vibration of the diaphragm 912 in the presence of ink. However, the present invention is not limited to this. For example, it may be composed of trapezoidal pulses.

  Since the above-described embodiment is an embodiment of the printer 1, liquid dye ink or pigment ink is ejected from the nozzle Nz. However, the ink ejected from the nozzles Nz is not limited to such ink as long as it is liquid.

  In the above-described embodiment, the signal generated by the drive signal generation circuit 70 is applied to one of the piezo element 417 or the piezo element 911 by switching the selection switch 65 (see FIG. 8). It is not restricted to such a configuration.

1 is a diagram illustrating a configuration of a liquid ejection system 100. FIG. 2 is a block diagram illustrating configurations of a computer 110 and a printer 1. FIG. FIG. 3A is a diagram illustrating a configuration of the printer 1 of the present embodiment. FIG. 3B is a side view illustrating the configuration of the printer 1 of the present embodiment. 4 is a cross-sectional view for explaining the structure of a head 41. FIG. 3 is a block diagram illustrating a configuration of a drive signal generation circuit 70. FIG. 7 is a diagram for explaining a relationship between an input of a waveform generation circuit 71 and an output of the waveform generation circuit 71. FIG. FIG. 7A is a diagram for explaining a part of the drive signal generated by the drive signal generation circuit 70. FIG. 7B is a diagram for explaining the operation of dropping the output voltage of the current amplification circuit 72 from the voltage V1 to the voltage V4. It is a block diagram explaining the structure of the head control part HC. A discharge drive signal COM is shown. 6 is a flowchart for explaining print processing. 4 is a cross-sectional view of a carriage CR and an ink cartridge 87. FIG. FIG. 12A is an explanatory diagram of the configuration of the liquid level detection unit 90. FIG. 12B is an explanatory diagram of the influence of surface tension. FIG. 13A is a plan view for explaining the detailed configuration of the vibration section 91. 13B is a cross-sectional view taken along the line BB in FIG. 13A. 13C is a cross-sectional view taken along the line CC in FIG. 13A. It is a graph which shows the relationship between the ink amount and the frequency of residual vibration. 7 is an explanatory diagram of a configuration of a signal detection unit 95. FIG. It is explanatory drawing of a structure of the amplification part 951. FIG. FIG. 17A is a diagram illustrating an output signal of the piezo element 911. FIG. 17B is a diagram illustrating the reference signal Vref. FIG. 17C is a diagram illustrating an output signal from the comparator 951b. FIG. 18A is a waveform diagram of residual vibration in the presence of ink. FIG. 18B is a waveform diagram of a drive signal in which the frequency is set to 30 KHz, which is the resonance frequency ν1 in the presence of ink. This is an output signal of the piezo element 911 after a drive signal is applied to the piezo element 911. FIG. 19A shows an output signal in the presence of ink, and FIG. 19B shows an output signal in the absence of ink. FIG. 20A is a waveform diagram of a resonance frequency ν1 of 30 KHz as an example of residual vibration in a state where ink is present. FIG. 20B is a waveform diagram of a resonance frequency ν0 of 90 KHz where k = 1 in Equation (1) as an example of residual vibration in the absence of ink. FIG. 20C is a drive signal composed of one rectangular pulse as an example of a drive signal that most effectively excites the residual vibration in the ink presence state of FIG. 20A. FIG. 21A is a waveform diagram of a resonance frequency ν1 of 30 KHz as an example of residual vibration in the presence of ink. FIG. 21B is a waveform diagram of a resonance frequency ν0 of 60 KHz where k = 1 in equation (1 ′) as an example of residual vibration in the absence of ink. FIG. 21C is a drive signal composed of one rectangular pulse as an example of a drive signal that most effectively excites the residual vibration in the ink presence state of FIG. 21A. It is a figure for demonstrating the tolerance | permissible_range of an ideal relationship. It is a figure for demonstrating the upper limit (nu) 0max of the said tolerance | permissible_range. It is a figure for demonstrating the minimum value (nu) 0min of the said tolerance | permissible_range. It is a figure for demonstrating the tolerance | permissible_range of the said ideal relationship in case a drive signal has a some rectangular pulse.

Explanation of symbols

1 printer,
20 paper transport mechanism, 21 paper feed roller, 22 transport motor, 23 transport roller,
24 platen, 25 paper discharge roller,
30 Carriage moving mechanism, 31 Carriage motor, 32 Guide shaft,
33 Timing belt, 34 Drive pulley, 35 Drive pulley,
40 head unit, 41 head, 41A channel unit,
411 Nozzle plate, 412 storage chamber forming substrate, 412a ink storage chamber,
413 supply port forming substrate, 413a ink supply port,
41B Actuator unit, 414 Pressure chamber forming substrate, 414a Pressure chamber,
415 diaphragm, 416 lid member, 416a supply side communication port, 417 piezo element,
42 head case,
50 detector groups, 51 linear encoder, 52 rotary encoder,
53 Paper detector, 54 Optical sensor,
60 printer-side controller, 61 interface unit, 62 CPU,
63 memory, 64 control unit, 65 selection switch 70 drive signal generation circuit, 71 waveform generation circuit, 72 current amplification circuit 81A first shift register, 81B second shift register,
82A first latch circuit, 82B second latch circuit, 83 decoder,
84 control logic, 85 switches,
87 ink cartridge, 871 ink storage portion, 871a opening,
90 liquid level detection unit, 91 vibration unit, 911 piezo element, 912 vibration plate,
92 buffer chamber, 93 first ink flow path, 94 second ink flow path,
95 signal detector, 951 amplifier, 952 pulse width detector,
100 liquid ejection system, 110 computer, 111 host side controller,
112 interface unit, 113 CPU, 114 memory, 120 display device,
130 input device, 131 keyboard, 132 mouse, 140 recording / reproducing device,
141 flexible disk drive device, 142 CD-ROM drive device,
S paper, HC head controller, CR carriage, Nz nozzle

Claims (10)

A liquid container for containing a liquid;
A piezoelectric element that is provided at a predetermined position of the liquid container and generates a residual vibration after n pulses of the drive signal are applied, and that outputs an output signal by the residual vibration,
The liquid container according to claim 1, wherein a resonance frequency ν0 of residual vibration when no liquid is present at the predetermined position and a resonance frequency ν1 of residual vibration when the liquid is present at the predetermined position satisfy the following relationship.
{(2k + 1) × (2n−1) −1/2} / (2n−1) × ν1
≦ ν0 ≦ {(2k + 1) × (2n−1) +1/2} / (2n−1) × ν1
Here, k is an arbitrary integer of 1 or more. The liquid container according to claim 1,
The liquid container, wherein the resonance frequency ν0 and the resonance frequency ν1 satisfy the following relationship.
ν0 = (2k + 1) × ν1 The liquid container according to claim 1 or 2,
The size of the pulse application period is half of the vibration period of residual vibration when the liquid is present at the predetermined position. The liquid container according to any one of claims 1 to 3,
When the drive signal has a plurality of pulses, the application period of the pulses is the same as the vibration period of residual vibration when the liquid is present at the predetermined position. The liquid container according to any one of claims 1 to 4,
A liquid storage container, wherein a buffer chamber for preventing the piezoelectric element from being affected by vibration of the liquid in the liquid storage section is provided in the vicinity of the predetermined position. The liquid container according to claim 5,
The liquid container is provided with an opening,
The opening is closed by a diaphragm;
The piezoelectric element is provided on the diaphragm,
A liquid container, wherein the center of the opening and the center of the piezoelectric element coincide. The liquid container according to any one of claims 1 to 6,
The liquid is ink;
The liquid container is an ink cartridge. An ink containing portion for containing ink;
A piezoelectric element that is provided at a predetermined position of the ink container and generates a residual vibration after n pulses of the drive signal are applied, and that outputs an output signal by the residual vibration,
A buffer chamber for preventing the piezoelectric element from being affected by the vibration of the ink in the ink container is provided in the vicinity of the predetermined position;
The ink container is provided with an opening.
The opening is closed by a diaphragm;
The piezoelectric element is provided on the diaphragm,
The center of the opening coincides with the center of the piezoelectric element;
The application period of the pulse is half of the vibration period of residual vibration when ink is present at the predetermined position,
When the drive signal has a plurality of pulses, the application period of the pulses is the same as the vibration period of the residual vibration when ink is present at the predetermined position;
The liquid container according to claim 1, wherein the resonance frequency ν0 of residual vibration when no ink is present at the predetermined position and the resonance frequency ν1 of residual vibration when ink is present at the predetermined position satisfy the following relationship.
ν0 = (2k + 1) × ν1
Here, k is an arbitrary integer of 1 or more. A liquid storage portion for storing a liquid for discharging from the nozzle toward the medium;
A piezoelectric element that is provided at a predetermined position of the liquid container and generates a residual vibration after n pulses of the drive signal are applied, and that outputs an output signal by the residual vibration,
The liquid ejection apparatus according to claim 1, wherein a resonance frequency ν0 of residual vibration when no liquid is present at the predetermined position and a resonance frequency ν1 of residual vibration when the liquid is present at the predetermined position satisfy the following relationship.
{(2k + 1) × (2n−1) −1/2} / (2n−1) × ν1
≦ ν0 ≦ {(2k + 1) × (2n−1) +1/2} / (2n−1) × ν1
Here, k is an arbitrary integer of 1 or more. N pulses of the drive signal are applied to the piezoelectric element provided at a predetermined position of the liquid storage unit for storing the liquid,
Detecting an output signal from the piezoelectric element due to residual vibration after application of the drive signal;
A liquid amount detection method for detecting presence / absence of liquid at the predetermined position based on the output signal using a difference in resonance frequency of the residual vibration depending on presence / absence of the liquid at the predetermined position,
Resonance frequency ν0 of residual vibration when there is no liquid at the predetermined position and resonance frequency ν1 of residual vibration when there is liquid at the predetermined position satisfy the following relationship: .
{(2k + 1) × (2n−1) −1/2} / (2n−1) × ν1
≦ ν0 ≦ {(2k + 1) × (2n−1) +1/2} / (2n−1) × ν1
Here, k is an arbitrary integer of 1 or more.

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