JP2000318183A - Method and apparatus for detecting filling of recording head in printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eject an ink drop stably by obtaining the resonance point profile of a piezoelectric element for ejecting ink in an ink chamber from a nozzle opening and detecting the ink filling state of a recording head thereby eliminating the problem that a bubble is mixed or generated in an ink channel. SOLUTION: Each ink chamber 38 coupled with an ink supply passage 36 corresponding to each nozzle opening 22 is provided with a piezoelectric element 48 and, under fully replenished state with ink 40, the supply passage 36 and the supply path part 42 thereof, a buffer tank 44, the chamber 38, and the opening 22 are filled with the ink 40. The ink filling detector for a recording head 20 comprises the piezoelectric element 48 connected with a voltage supply section 50, a voltmeter and a reference resistor. Ink filling state of the head 20 is detected based on the fact that the peak value of resonance point profile depends on the ink run out state, stable ejection state or unstable ejection state of the head 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for detecting the filling of a printer recording head such as an ink jet printer.

[0002]

2. Description of the Related Art Conventionally, a recording head of an ink-jet printer has a maintenance station (maintenance processing stage). In order to stabilize the ejection of ink from nozzles, an ink is supplied by a pump during a maintenance operation. , Wiping of the nozzle plate surface with rubber or the like, and flushing by discharging ink droplets from all nozzles are performed. When the power is turned on or when the ink cartridge is replaced, the above-described suction operation by the pump or the wiping operation of the nozzle plate surface by rubber or the like is always performed to fill the recording head with the ink.

[0003]

However, after the maintenance operation is completed, there may be nozzles from which ink droplets have not been ejected when printing is performed. There was a problem that the presence of the nozzle was not noticed. In addition, even when the power is turned on, by performing the maintenance operation in advance,
There is also a problem that a large amount of ink is consumed. Most of these non-ejection nozzles return by repeating the maintenance operation and start ejecting the ink again, but until they can actually print, they have to print and check after the maintenance operation. It had to be repeated. One of the reasons for the non-ejection of ink droplets is the incorporation of air bubbles in the ink flow path or the generation of air bubbles caused by insufficient ink filling in the print head. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems and to provide a recording head filling detection device and a filling detection method for a recording head of a printer which can stably eject ink droplets.

[0004]

According to a first aspect of the present invention, there is provided a nozzle opening for discharging ink droplets, an ink chamber for supplying the ink to the nozzle opening, and a supply of the ink to the ink chamber. And a piezoelectric element for discharging the ink in the ink chamber through the nozzle opening in accordance with an applied voltage. A bubble detecting device for a recording head of a printer, wherein a resonance point profile of the piezoelectric element is obtained to electrically detect a filling state of the ink in the recording head. .

According to the first aspect, when detecting the ink filling state in the recording head of the printer, the resonance point profile of the piezoelectric element is obtained, and the ink filling state in the recording head is electrically detected. This makes it possible to electrically reliably detect whether or not the recording head is filled with ink.

According to a second aspect of the present invention, there is provided the printer according to the first aspect, wherein the ink chamber and the ink supply path of the recording head are filled with the ink. The resonance point profile of the piezoelectric element differs depending on whether the recording head is not sufficiently filled with the ink. According to the second aspect, the resonance point profile of the piezoelectric element is different depending on whether the ink is filled in the ink chamber and the ink supply path of the recording head and the ink is insufficiently filled in the recording head. , The filling state of the ink in the head can be electrically detected.

According to a third aspect of the present invention, there is provided a printer for detecting the ink filling state in a recording head of a printer for discharging ink in an ink chamber through a nozzle opening by operating a piezoelectric element according to an applied voltage. Detecting a filling state of the ink in the recording head by obtaining a resonance point profile of the piezoelectric element and electrically detecting a filling state of the ink in the recording head. Is the way. In the third aspect, when detecting the ink filling state in the recording head of the printer, a resonance point profile of the piezoelectric element is obtained, and the ink filling state in the recording head is electrically detected. This makes it possible to electrically reliably detect whether or not the recording head is filled with ink.

According to a fourth aspect of the present invention, in the method for detecting the filling of the recording head of the printer according to the third aspect, the filling state in which the ink is filled in the ink chamber and the ink supply path of the recording head. The resonance point profile of the piezoelectric element differs depending on whether the recording head is not sufficiently filled with the ink. According to the fourth aspect, the resonance point profile of the piezoelectric element is different depending on the state of filling the ink chamber and the ink supply path of the recording head with ink and the state of insufficient filling of the ink in the recording head. By utilizing the above, the filling state of the ink in the recording head can be reliably detected electrically.

According to a fifth aspect of the present invention, in the method for detecting the filling of the recording head of the printer according to the third aspect, the filling state in which the ink is filled in the ink chamber and the ink supply path of the recording head. The resonance point profile of the piezoelectric element differs depending on whether the recording head is insufficiently filled with the ink or when the recording head does not have the ink. According to the fifth aspect, a filling state in which the ink is filled in the ink chamber and the ink supply path of the recording head, a state in which the ink in the recording head is insufficiently filled,
By utilizing the fact that the resonance point profile of the piezoelectric element differs depending on whether there is no ink in the recording head, it is possible to electrically reliably detect the ink filling state in the recording head. Here, the resonance point profile of the piezoelectric element in the present invention refers to the natural vibration frequency of the piezoelectric element itself and the natural vibration of the vibration system including the piezoelectric element due to filling of the recording head with ink. Including frequency,
In the frequency domain, it is a profile obtained by sweeping a sine wave in the frequency domain and showing a natural oscillation frequency (resonance point) based on gain characteristics, impedance characteristics, phase changes, and the like of the piezoelectric element.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 shows an example of a printer provided with a preferred embodiment of a recording head filling detection device for a printer according to the present invention. 1 is an ink jet printer as an example. Inkjet printer 10
Has a structure as shown in FIG. The paper 12 to be printed is fed by the rollers 14 in the R direction. The roller 14 is connected to an output shaft 17A of a motor 17 via a belt 15. Output shaft 1 of motor 17
As the 7A rotates, the roller 14 rotates by a predetermined amount in the R direction. The recording head 20 includes a head holding unit 18.
Is held in. The head holding unit 18 moves in the X direction along the guide 16 and can be positioned. The movement and positioning of the head holding unit 18 in the X direction are as follows.
This is performed by operating the motor 19. Recording head 20
Is an ink jet recording head that prints or prints by discharging ink onto the paper 12.

FIG. 2 shows an example of a sectional structure of the recording head 20 of FIG. The nozzle plate 24 has a plurality of nozzle openings 22. These nozzle openings 22
Are simply referred to as nozzles, and are arranged at predetermined intervals in the direction perpendicular to the paper surface of FIG. Nozzle plate 24
Are joined to the inner plates 26 and 28, the plate 30, the plate 32, and the diaphragm 34. As a result, the recording head 20 moves the ink supply path 36 and the ink chamber 38
have. The ink supply path 36 has a supply path portion 42 and a buffer tank 44. Buffer tank 44
Are connected to the ink chamber 38 by the supply flow path 46. The supply channel 46 is formed between the nozzle plate 24 and the plate 28. The ink chamber 38 is formed by the vibration plate 34, the inner plate 26, the plate 28, the plate 32, and the nozzle plate 24.

On the vibrating plate 34, a laminated piezoelectric element 48 is provided.
Is set. When an applied voltage (pulse voltage) is supplied from the voltage supply unit 50, the laminated piezoelectric element 48 displaces the diaphragm 34 in the E direction by a predetermined amount according to the magnitude of the applied voltage. Has become. That is, the laminated piezoelectric element 48 is an actuator that expands or contracts the ink chamber 38 according to the voltage applied from the voltage supply unit 50. As the ink chamber 38 expands or contracts in this manner, the ink 40 in the ink chamber 38 forms a predetermined amount of ink droplets 40A from the nozzle opening 22 according to the degree of expansion or contraction of the ink chamber 38. It is designed to exhale.

In FIG. 2, a plurality of ink chambers 38 are connected to an ink supply path 36 via supply paths 46, respectively. Each ink chamber 38 is provided corresponding to each corresponding nozzle opening 22. Each of the ink chambers 38 is provided with a piezoelectric element 40. When the ink 40 is completely filled, the ink 40
Are filled with the supply path portion 42 of the ink supply path 36 and the buffer tank 44, and the supply path 46, the ink chamber 38, and the nozzle opening 22.

FIG. 3 shows a filling detecting device for detecting the filling of ink in the recording head by detecting the resonance point profile during the operation of the laminated piezoelectric element 48. The piezoelectric element 48 in FIG. 3 is an object to be measured for detecting a resonance point profile.
Is also called a piezo element. This filling detection device 54
Is configured by connecting a resonance point profile detection unit 56 to the piezoelectric element 48. The resonance point profile detection unit 56 includes a reference resistor Rg, a voltmeter 58, and the above-described voltage supply unit 50. Voltage supply unit 5
0 indicates that an AC voltage is applied to the piezoelectric element 48.

FIG. 4 shows the filling detection device 54 of FIG. 3 in more detail. One end of the reference resistor Rg is connected in series to one end of the piezoelectric element 48. The voltmeter 58
Also called network analyzer or servo analyzer. The other end of the reference resistor Rg and the GND of the voltmeter 58 are grounded. Reference resistor Rg and piezoelectric element 48
Is connected to the voltmeter 58. An input sweep waveform Vi can be supplied from a voltmeter 58 to the other end of the piezoelectric element 48. The piezoelectric element 48 and the reference resistor R
g, the output response waveform Vo of the piezoelectric element 48
Is input to the voltmeter 58. The gain characteristic of the voltmeter 58 is obtained by 20 LOG (| Vo | / | Vi |),
The phase characteristics of the input sweep waveform Vi and the output response waveform Vo can be represented by Arctan (| Vo | / | Vi |).

The filling detecting device 54 as shown in FIGS.
A resonance point profile is detected by giving an input sweep waveform Vi to the piezoelectric element 48 and obtaining an output response waveform Vo. Here, the resonance point profile of the piezoelectric element 48 is the natural vibration frequency of the piezoelectric element itself,
And the recording head is filled with ink, including the natural vibration frequency of the vibration system including the piezoelectric element, in the frequency domain, gain characteristics of the piezoelectric element obtained by sweeping a sine wave in that frequency domain, This is a profile indicating the natural vibration frequency (resonance point) based on impedance characteristics, phase change, and the like. In order to obtain such a resonance point profile, as shown in FIG. 5A, a sine wave is swept (swept) as the input sweep waveform Vi, and the change in the value of the current flowing through the reference resistor Rg is changed between the reference resistor Rg. The resonance point profile of the piezoelectric element 48 can be observed by measuring the potential difference of the piezoelectric element 48. When an input sweep waveform Vi having a sine waveform as shown in FIG. 5A is given from the voltmeter 58 of FIG. 4 to the piezoelectric element 48, a sine waveform represented by an output response waveform Vo as shown in FIG. 5B is obtained. Can be.

Next, the filling state of the liquid ink 40 in the recording head 20 of FIG. 2 will be described. As shown in FIG. 6, depending on whether or not the ink supply path 36, the supply flow path 46, the ink chamber 38, and the nozzle opening 22 in the recording head 20 are filled with the ink 40, FIG. , (B) a stable ejection state, and (C) a non-ejection state or an unstable ejection state. 6A means the ink supply path 36, the supply path 46, and the ink chamber 3 of the recording head 20 in FIG.
8 and the case where there is no ink 40 in the nozzle opening 22. The stable ejection state shown in FIG.
0 indicates a state in which the ink supply passage 36, the supply passage 46, the ink chamber 38, and the nozzle opening 22 are sufficiently filled. The non-ejection state or the unstable ejection state shown in FIG. 6C corresponds to the state of the ink 4 in the ink supply path 36, the ink supply
Although 0 is filled, the filling is insufficient and bubbles are mixed in the ink 40 or bubbles are generated.

FIG. 6A shows a state without ink, and FIG.
It should be noted that the peak value (kHz) of the resonance point profile of the piezoelectric element 48 differs between the stable ejection state and the (C) non-ejection state or unstable ejection state. That is, FIG.
The resonance mode of the piezoelectric element 48 differs depending on the state of each of FIGS. 6A, 6B, and 6C. The reason why the peak value of the resonance point profile is different, that is, the resonance mode is different, is that the flow path of the recording head 20, that is, the ink supply path 36, the supply path 46, the ink chamber 38, and the nozzle opening 22 It is considered that this is due to a change in inertance (a constant representing the inertia of the acoustic system) and a change in flow path resistance due to ink. Inertance uses electromechanical acoustic similarity to solve the coupling problem between the fluid system flowing through the flow path and the mechanical system of the vibrating part such as a piezoelectric element or diaphragm, and equivalent elements are equivalent electric circuit elements And the whole can be represented by a lumped constant circuit model. The inertance is an acoustic element that resists a change in volume flow, and has an inertance of M [g / cm
⁴ ], the rate of change of the volume flow is expressed as dU / dt [cm ³ / se
c ² ] and the driving pressure is p [dyne / cm ² ], which is determined by p = M · dU / dt.

In the state where the ink in the recording head 20 in FIG. 2 is sufficiently filled, the state where the ink is insufficiently filled, and the state where the ink is not filled, the peak value of the resonance point profile is apparent. Thus, it is possible to detect the state of the ink in each nozzle opening 22 in FIG. The peak value of the resonance point profile is a peak value that appears in the gain characteristics and impedance characteristics of the piezoelectric element. (The value of the peak in the phase change is
The values slightly differ from the values that appear in the gain characteristics and impedance characteristics of the piezoelectric element. In the example of FIG. 6, the peak value of the resonance point profile is 115 (kHz) in the absence of ink in FIG.
In the stable ejection state shown in FIG. 6B, the peak values of the resonance point profile are 73 (kHz) and 130 (kHz). Further, in the non-ejection state or the unstable ejection state shown in FIG. 6C, the peak value of the resonance point profile is 107 (kHz).
It is. Thus, FIGS. 6A, 6B and 6
In (C), the peak values of the resonance point profile are clearly different.

FIGS. 7 and 8 show the gain characteristics of the resonance point profile in the absence of ink of FIG.
(| V |) and examples of phase characteristics. 7 and 8
In the graph in, the horizontal axis indicates frequency (Hz). The vertical axis of FIG. 7 indicates the gain (dB), and the vertical axis of FIG. 8 indicates the phase (deg.). Thus, FIG.
In the state of (A) with no ink, the peak value P of the resonance point profile is 115 kHz.

FIGS. 9 and 10 show the gain characteristics of the resonance point profile in the stable ejection state shown in FIG.
V |) and examples of phase characteristics. Referring to FIGS. 9 and 10, in the stable ejection state shown in FIG. 6B, the peak values P1 and P2 of the resonance point profile are 73 kHz and 130 kHz.
kHz.

FIGS. 11 and 12 show the gain characteristics of the resonance point profile in the non-ejection state shown in FIG.
(| V |) and examples of phase characteristics. Figures 11 and 1
2, the peak value P3 of the resonance point profile is 107 k
Hz.

FIGS. 13 and 14 show the gain characteristics of the resonance point profile in the unstable ejection state shown in FIG.
An example of G (| V |) and phase characteristics is shown. 13 and 14, the peak value P4 of the resonance point profile is 10
7 kHz.

As can be seen from the above results, there are a state where the liquid ink is sufficiently filled in the flow path of the recording head and a state where the ink is insufficiently filled. And the peak value of the resonance point profile differs between the stable ejection state in FIG. 6B and the non-ejection state or unstable ejection state in FIG. 6C. By paying attention to such a peak value difference of the resonance point profile, it is possible to detect the ink filling state in the recording head 20 at the present time. If the filling is insufficient, bubbles may be mixed in or generated in the ink filled in the ink flow path. It is possible to reliably distinguish between a case where such bubbles are mixed in the ink or a bubble is generated in the ink, and a case where there is no ink or the case where the ink is sufficiently filled. That is, the filling detecting device 54 can also detect a state in which bubbles are generated in the ink or bubbles are mixed in the ink, and can be used as a bubble detecting device.
Thereby, the bubble detection method can be performed.

As described above, by observing the resonance point profile of the vibrating portion of the ink jet recording head, the filling state of the ink in the head flow path can be determined. Non-ejection or unstable ejection nozzles in the print head can be detected without printing. Therefore, the maintenance operation of the recording head may be performed only when the ink filling is defective. Further, the maintenance operation when the power is turned on can be simplified, and the amount of ink consumption can be reduced. That is, when the ink is properly filled, the suction operation by the pump can be omitted. Here, the present invention is not limited to the above embodiment. In the above-described embodiment, the nozzle openings are provided in the nozzle plate for ejecting ink droplets. However, an ink nozzle opening for discharging ink to a nozzle plate and a diluting liquid nozzle opening for discharging a diluting liquid for diluting the ink are provided. However, the present invention can be applied. Further, the printer of the present invention is not limited to the ink jet type recording head, and the present invention can be applied to any head using a piezoelectric element.

[0027]

As described above, according to the present invention,
By detecting the ink filling status, it is possible to stably eject ink droplets.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an ink jet printer as an example of a printer according to the invention.

FIG. 2 is a cross-sectional view illustrating a configuration example of a recording head of the inkjet printer in FIG.

FIG. 3 is a diagram illustrating an example of an ink filling detection device.

FIG. 4 is another view showing the filling detection device of FIG. 3 in more detail;

FIG. 5 is a time chart showing a relationship example between an input sweep waveform and an output response waveform given to a piezoelectric element in the filling detection device.

FIG. 6 is a diagram illustrating an example of a peak value of a resonance point profile in an ink-out state, a stable ejection state, a non-ejection state, and an unstable ejection state.

FIG. 7 is a diagram illustrating an example of a gain characteristic of a resonance point profile in an ink-out state.

FIG. 8 is a diagram illustrating an example of a phase characteristic of a resonance point profile in an ink-out state.

FIG. 9 is a diagram showing an example of a gain characteristic of a resonance point profile in a stable ejection state.

FIG. 10 is a diagram illustrating an example of a phase characteristic of a resonance point profile in a stable ejection state.

FIG. 11 is a diagram illustrating an example of a gain characteristic of a resonance point profile in a non-ejection state.

FIG. 12 is a diagram illustrating an example of a phase characteristic of a resonance point profile in a non-ejection state.

FIG. 13 is a diagram illustrating an example of a gain characteristic of a resonance point profile in an unstable ejection state.

FIG. 14 is a diagram showing an example of a phase characteristic of a resonance point profile in an unstable ejection state.

[Explanation of symbols]

10 ... inkjet printer (printer), 20
... Recording head, 22 ... Nozzle opening, 36 ...
・ Ink supply path, 38 ・ ・ ・ Ink chamber, 40 ・ ・ ・ Ink, 48 ・ ・ ・ Piezoelectric element, 54 ・ ・ ・ Filling detector

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C056 EB08 EB33 EB40 EC07 EC53 EC62 FA04 FA10 2C057 AF72 AF76 AG44 AL17 AL18 AM31 BA04 BA14

Claims (5)

[Claims] A nozzle opening for discharging ink droplets; an ink chamber for supplying the ink to the nozzle opening; an ink supply path for supplying the ink to the ink chamber; A piezoelectric element for discharging the ink in the ink chamber through the nozzle opening; and a printer recording head filling detection device for detecting a filling state of the ink in the recording head of the printer, the piezoelectric element comprising: Wherein the ink filling state in the recording head is electrically detected by obtaining the above resonance point profile. 2. The method according to claim 1, wherein the ink chamber and the ink supply path of the recording head are filled with the ink and the recording head is insufficiently filled with the ink. The apparatus according to claim 1, wherein the resonance point profiles are different. 3. A printer recording head for detecting a filling state of the ink in a printer recording head for discharging ink in an ink chamber through a nozzle opening by operating a piezoelectric element according to an applied voltage. A method for detecting the filling of a recording head of a printer, comprising: obtaining a resonance point profile of the piezoelectric element; and electrically detecting a filling state of the ink in the recording head. 4. A method according to claim 1, wherein the ink chamber and the ink supply path of the recording head are filled with the ink, and the recording head is insufficiently filled with the ink. 4. The method according to claim 3, wherein the resonance point profiles are different. 5. A state where the ink is filled in the ink chamber and the ink supply path of the recording head, a state where the ink is insufficiently filled in the recording head, and a state where the ink is insufficient in the recording head. 4. The method according to claim 3, wherein a resonance point profile of the piezoelectric element is different depending on whether the ink is empty.