KR101004934B1 - Apparatus and method for detecting defect of a printer head - Google Patents

Abstract

The present invention relates to a defect detection apparatus and method of a print head capable of detecting assembly defects or cracks in a print head by detecting vibration frequencies of a print head, in particular a piezoelectric inkjet print head, wherein a driving body is formed on one surface thereof. A defect detection apparatus of a print head in which ink is discharged by vibration of the drive body, the apparatus comprising: a vibration adjusting unit providing an AC power supply for vibration having a predetermined voltage level to the drive body, and one surface of the print head; A measuring unit measuring a displacement of the driving body based on a reference, Fourier transforming the displacement measured by the measuring unit, and a determining unit determining a defect according to a quality index determined by a Fourier transformed frequency value It is to provide a defect detection apparatus of a print head comprising a.

Printer, Printer Head, Actuator, Piezoelectricity, Defect, Crack

Description

Fault detection apparatus and method of the print head {APPARATUS AND METHOD FOR DETECTING DEFECT OF A PRINTER HEAD}

The present invention relates to a defect detecting apparatus and method, and more particularly, to a defect detection apparatus of a print head capable of detecting an assembly defect or crack of a printer head by detecting vibration frequencies of a print head, in particular, a piezoelectric inkjet printer head. It is about a method.

In general, inkjet printers are inexpensive compared to laser printers and are used for general office and home use. Such an inkjet printer employs a head for printing ink, and the inkjet printer head is a device for printing by finely spraying ink droplets for printing at a desired position on a recording sheet.

The ink ejection method of such an inkjet printer uses a heat source to generate droplets in the ink contained in the ink container and discharges the ink with this force, or a piezoelectric element using an electro-thermal transducer (bubble jet method) or a piezoelectric body. There is an electro-mechanical transducer (piezoelectric method) in which ink is ejected through a volume change of the ink container due to the deformation of.

In the case of the inkjet printer head adopting the dual electro-mechanical conversion method, the ink is contained in the inkjet printer head by mounting the actuator on the top plate of the head and deforming the top plate by changing the shape of the piezoelectric body of the actuator by the applied voltage. Change the volume of the chamber.

Such an inkjet printer head forms a thin thickness of a portion of the upper plate in contact with the piezoelectric body of the actuator, and cracks may occur in a portion of the upper plate due to the shape deformation of the piezoelectric body.

In addition, the above-described inkjet printer head constitutes an inkjet printer head by combining a plurality of components to form an ink chamber therein, and the coupling between components may be poor in a product process.

The above structural defects of the inkjet printer head cause a problem that ink ejection is not smooth when using the product.

In order to measure structural defects of the inkjet printer head, a device for measuring defects by detecting vibrations of an actuator and a thin film has been developed. Since it is necessary to designate a large number of inkjet printer heads in the inkjet printer, the defect detection time increases, and thus, the yield of the product decreases.

In order to solve the above-mentioned problems, an object of the present invention is to detect a vibration frequency of the inkjet printer head of the piezoelectric method, in particular, a defect detection apparatus and method of the print head capable of inspecting assembly defects or cracks, etc. of the printer head. To provide.

In order to achieve the above object, one technical aspect of the present invention is a defect detection apparatus of a print head in which a driving body is formed on one surface and ink is discharged by vibration of the driving body. A vibration adjusting unit providing an AC power supply for vibration having a preset voltage level, a measuring unit measuring a displacement of the driving body with reference to one surface of the print head, and a displacement measured by the measuring unit using a Fourier transform ( Fourier Transform, and comprises a determination unit for determining the defect in accordance with the quality index determined by the Fourier transform frequency value.

According to one technical aspect of the present invention, the vibration AC power source may have a power source frequency, and the vibration adjusting unit may vary the power frequency within a preset power source frequency range to drive the vibration AC power source. Can be provided to the sieve.

According to one technical aspect of the present invention, the vibration AC power source may be a pulse type power source, and the vibration adjusting unit may change the power source frequency in a predetermined frequency unit within the power source frequency range and have a variable power source frequency. The vibration AC power may be sequentially provided to the drive body.

According to one technical aspect of the present invention, the determining unit (wherein fo is the resonant frequency and the resonant frequency is the frequency having the largest amplitude among the converted frequency, Δf is the amplitude of fo when M, fo The quality index may be calculated according to a range up to a frequency corresponding to an amplitude obtained by dividing the square root of M by reference, and Q is a quality index. .

According to one technical aspect of the present invention, the measuring unit may measure the displacement of a predetermined point of the drive body.

According to one technical aspect of the present invention, the vibration adjusting unit may provide the drive AC with the vibration AC power having a predetermined power frequency.

According to one technical aspect of the present invention, the vibration adjusting unit may provide the vibration AC power in the form of a pulse.

According to one technical aspect of the present invention, the determining unit (wherein fo is the excitation frequency and the excitation frequency is the frequency having the second largest amplitude of the converted frequency, Δf is the amplitude of fo, M, The quality index is calculated according to a range up to a frequency corresponding to an amplitude divided by the square root of M based on fo, Q is a quality index, and if the quality index is less than or equal to a preset reference quality index, it is determined as a defect. Can be.

According to one technical aspect of the present invention, the vibration adjusting unit may provide the vibration AC power to the drive once.

According to another technical aspect of the present invention, in a defect detection method of a print head in which a driving body is formed on one surface and ink is discharged by vibration of the driving body, a voltage level preset in the driving body is set. Providing an oscillating AC power source, measuring the displacement of the driving body with reference to one surface of the printer head, converting the displacement amount according to time measured by the measuring step into a frequency, It is to provide a defect detection method of the print head comprising the step of determining the defect in accordance with the quality index determined by.

According to another technical aspect of the present invention, the vibration AC power source may have a power frequency, and the power supply step may vary the power frequency within a preset power frequency range to provide the vibration AC power. It can be provided to the said drive body.

According to another technical aspect of the present invention, the vibration AC power source may be a pulse type power source, and the power supply step may vary the power frequency in a predetermined frequency unit within the power frequency range and vary the power frequency. The vibration AC power having a may be sequentially provided to the drive body.

According to another technical aspect of the present invention, the determining step (where, fo is the resonant frequency and the resonant frequency is the frequency having the largest amplitude among the converted frequency, Δf is the amplitude of fo, M, The quality index is calculated according to a range up to a frequency corresponding to an amplitude divided by the square root of M based on fo, Q is a quality index, and if the quality index is less than or equal to a preset reference quality index, it is determined as a defect. Can be.

According to another technical aspect of the present invention, the measuring step may measure the displacement of a predetermined point of the driving body.

According to another technical aspect of the present invention, the power supply step may provide the vibration AC power source having a predetermined power frequency to the drive body.

According to another technical aspect of the present invention, the power supply step may provide the vibration AC power in the form of a pulse.

According to another technical aspect of the present invention, the determining step (where, fo is the excitation frequency and the excitation frequency has the second largest amplitude among the converted frequencies, Δf is the amplitude of fo to be M) The quality index is calculated according to a range up to a frequency corresponding to an amplitude of two times the square root of M based on fo, and Q is a quality index, and if the quality index is less than or equal to a preset reference quality index, It can be determined.

According to another technical aspect of the present invention, the power supply step may provide the vibration AC power to the drive once.

According to the present invention, by calculating the quality index according to the vibration frequency of the drive body of the printer head to determine the defect accordingly, it is not necessary to measure the displacement of various positions of the drive body, thereby increasing the efficiency of product inspection, By changing the measuring mode according to the thickness of the sieve, it can be applied to various products.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a top view of a typical printer head.

Referring to FIG. 1, in general, the printer head A includes ink in a chamber formed therein, and the volume of the chamber is changed by changing the shape of the driving body B formed on one surface of the printer head A. It is composed of a structure in which ink is discharged to the outside.

The printer head A is provided with a plurality of drive bodies B on one surface thereof to record various colors on the recording paper.

2 is a configuration diagram of a defect detection apparatus of the print head of the present invention.

Referring to FIG. 2, the defect detecting apparatus 100 of the printhead of the present invention may include a vibration adjusting unit 110, a measuring unit 120, and a determining unit 130.

The vibration adjusting unit 110 provides the AC power for vibration to the drive body B of the printer head A.

As described above with reference to FIG. 1, the printer head A has an ink chamber A2 formed therein, and a thin film A1 covering the chamber A2 and forming one surface of the printer head. An actuator is mounted on the thin film A1 of one surface of the printer head A. The actuator is a piezoelectric body B1 coupled between a pair of electrodes B2 and a pair of electrodes B2 that are supplied with AC power for vibration. It is composed.

According to the vibration AC power source, the actuator is deformed and vibrated, and the thin film on which the actuator is mounted is also deformed and vibrated like the actuator. That is, the actuator and the thin film A1 may form the driving body B to discharge the ink inside the printer head A. FIG.

 On the other hand, the width of the vibration may vary according to the thickness of the piezoelectric body B1, and the thicker the thickness of the piezoelectric body B1 is, the more the vibrational AC power having a high voltage level needs to be supplied to obtain the desired vibration that the ink can derive. Can be.

As a result, the vibration unit can provide the driving body B with an AC power supply for vibration having a voltage level set according to the thickness of the piezoelectric body B1, and the driving body B vibrates.

The measuring unit 120 measures the displacement of the driving body B, and measures the displacement of the driving body B based on one surface of the printer head A. FIG. The measuring unit 120 irradiates a laser beam to one point of the vibrating driving body B and measures the displacement of the driving body B through the reflected laser, and uses the Doppler effect to measure the above-described displacement. Measure the displacement of B).

The displacement of the driving body B measured by the measuring unit 120 is transmitted to the determining unit 130. The determination unit 130 converts the displacement of the driving body B, which changes with time, into a frequency domain by Fourier transform. The displacement converted into the frequency domain represents a large amplitude at a specific frequency, and the determination unit 130 calculates a quality index according to the specific frequency and compares the calculated quality index with a preset reference quality index to determine a defect. .

The above-described vibration adjusting unit 110 supplies a vibration AC power having a voltage level set according to the thickness of the piezoelectric body B1, and the vibration AC power has a power source frequency that can be set. Accordingly, the vibration adjusting unit 110 can provide two embodiments. First, FIG. 3 is a flowchart showing the first embodiment of the defect detection method of the print head of the present invention.

Referring to FIG. 3, the vibration adjusting unit 110 provides the AC power for vibration by varying the power frequency at predetermined frequency intervals within a preset power frequency range (S11).

For example, if 0Hz to 1KHz is set as the power frequency range, and the frequency interval is set to 10Hz, the vibration adjusting unit 110, respectively, the vibration AC power having 0Hz, 10Hz, 20Hz ~ 990Hz and 1KHz in the form of a pulse It is provided to the drive body B sequentially. The driving body B vibrates differently depending on the frequency of the AC power source for vibration, and the displacement is the largest at a specific frequency.

Accordingly, the measuring unit 120 measures the displacement of the driving body B for a predetermined time (S12), and the determination unit 130 converts the measured displacement of the driving body B from the time domain to the frequency domain. (S13). Accordingly, the displacement of the driving body B is represented by the largest amplitude at a specific frequency, and the determination unit 130 calculates the quality index according to the specific frequency.

Referring to FIG. 5, the frequency at which the largest amplitude M appears is set to the resonance frequency fo, and the quality index is calculated according to the frequency range Δf of the amplitude M of the resonance frequency fo.

Accordingly, the quality index is calculated according to the following equation.

(Equation)

Here, fo is a resonant frequency and the resonant frequency is the frequency having the largest amplitude among the converted frequencies, and Δf is a frequency corresponding to the amplitude obtained by dividing the square root of M by two times with respect to fo when the amplitude of fo is M. Where Q represents the quality index.

That is, the quality index Q represents the ratio of the energy consumed for the vibration of the driving body B and the attenuated vibration energy per cycle of vibration, and means the amount of attenuated energy compared to the energy consumed for the vibration.

As described above, when the thickness of the piezoelectric body B1 of the driving body B is thin, the vibration adjusting unit 110 vibrates easily even when an AC power supply having a low voltage level is applied, thereby measuring displacement of the driving body B. Because of this ease, it is possible to accurately measure the displacement of the driving body B by varying the power source frequency and supplying the AC power source for vibration.

Therefore, the measurement unit 120 accurately measures the displacement of the driving body B even when measuring the displacement of one point previously set, without measuring the displacement of several points of the driving body B for accurate displacement measurement. Accordingly, the determination unit 130 can accurately determine the defect of the print head (A).

As described above, a plurality of drive bodies B are formed in the print head A, and thus the transfer unit C may transfer the print heads A to measure displacements of the plurality of drive bodies B. FIG. do.

Next, FIG. 4 is a flowchart showing the second embodiment of the defect detection method of the print head of the present invention.

Referring to FIG. 4, the vibration adjusting unit 110 provides an AC power supply for vibration having a predetermined power source frequency and a predetermined voltage level to the driver B in a pulse form (S21). In this case, the vibration adjusting unit 110 may provide the vibration AC power to the driving body B once.

The measuring unit 120 measures the displacement of the driving body B for a predetermined time (S22), and the determination unit 130 converts the measured displacement of the driving body B from the time domain to the frequency domain (S23). . Accordingly, the displacement of the driving body B is represented as an amplitude at a plurality of specific frequencies, and the determination unit 130 calculates the quality index according to the frequency having the second largest amplitude among the plurality of frequencies.

The determination unit 130 determines that the calculated quality index is a defect if it is less than or equal to a preset reference quality index (S24).

Referring to FIG. 6, the frequency with the second largest amplitude is set as the excitation frequency fo and the quality index is calculated according to the frequency range Δf of the amplitude M of the excitation frequency fo.

에 따라 연산된다.Like the above formula, the quality index is

Is calculated according to

However, unlike the description of the above formula, where fo is the excitation frequency and the excitation frequency has the second largest amplitude among the converted frequencies, Δf is the square root of M with respect to fo when the amplitude of fo is M. Where Q is the quality index.

As described above, when the thickness of the piezoelectric body B1 of the driving body B is thick, the driving body B vibrates only when an AC power having a high voltage level is applied, and the power source frequency and voltage level set in advance in consideration of power consumption. The oscillating AC power supply having the same is provided to the driving body B once.

Accordingly, the driving body B vibrates by the vibration AC power, but the vibration may be divided into main vibration by the vibration AC power and excitation vibration by the main vibration.

When the measured displacement of the driving body B is converted from the time domain to the frequency domain, the main vibration and the excitation vibration described above have different vibration frequencies. The defect of the print head A is determined by calculating the quality index according to the vibration frequency corresponding to the double excitation vibration.

That is, the vibration adjusting unit 110 supplies the AC power for vibration once to the driving body B, and the measuring unit 120 measures the displacement of the driving body B at a set point, and determines the determination unit 130. Can quickly determine the defect of the print head (A).

As described above, a plurality of drive bodies B are formed in the print head A, and thus, the transfer unit C may transfer the print heads A to measure displacements of the plurality of drive bodies B. FIG. To be.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, but is defined by the claims below, and the configuration of the present invention may be modified in various ways without departing from the technical spirit of the present invention. It will be apparent to those skilled in the art that the present invention may be changed and modified.

1 is a top view of a typical print head

2 is a configuration diagram of a defect detection apparatus of the present invention.

3 is a flow chart showing a first embodiment of a defect detection method of the present invention.

4 is a flow chart showing a second embodiment of the defect detection method of the present invention.

FIG. 5 is a frequency characteristic graph shown by the first embodiment shown in FIG.

FIG. 6 is a frequency characteristic graph represented by the second embodiment shown in FIG.

<Detailed Description of Major Symbols in Drawing>

Defect detection device 110 Vibration control unit

120 Measuring unit 130 Determining unit

A ... print head A1 ... thin film

A2 ... Chamber B ... Driver

B1 ... piezoelectric B2 ... electrode

C ... transfer

Claims (20)

In a defect detection apparatus of a print head in which a driving body is formed on one surface and ink is discharged by vibration of the driving body, A vibration adjusting unit for providing an AC power supply for vibration having a voltage level preset to the driving body; A measuring unit measuring a displacement of the driving body with respect to one surface of the printer head; And Fourier transform (Fourier Transform) the displacement measured by the measuring unit, the determination unit for determining the defect in accordance with the quality index determined by the Fourier transform frequency value Defect detection apparatus of the print head comprising a. The method of claim 1, The vibration AC power source has a power source frequency, And the vibration adjusting unit varies the power frequency within a preset power frequency range to provide the vibration AC power to the drive body. The method of claim 2, The vibration AC power is a pulse power supply, Wherein the vibration adjusting unit varies a power frequency in a predetermined frequency unit within the power frequency range, and sequentially provides the oscillating AC power having the variable power frequency to the driving body. . The method of claim 3, The determination unit

Here, fo is a resonant frequency and the resonant frequency corresponds to a frequency having the largest amplitude among Fourier transformed frequency values, Δf corresponds to an amplitude obtained by dividing the square root of M with respect to fo when the amplitude of fo is M. Wherein the quality index is calculated according to a range up to a frequency, Q is a quality index, and if the quality index is equal to or less than a preset reference quality index, it is determined as a defect. The method of claim 4, wherein And the measuring unit measures a displacement of one point previously set among the driving bodies. The method of claim 1, And the vibration adjusting unit provides the vibration AC power having a predetermined power frequency to the drive body. The method of claim 6, And the vibration adjusting unit provides the vibration AC power in the form of a pulse. The method of claim 7, wherein The determination unit

(Where, fo is the excitation frequency and the excitation frequency has the second largest amplitude among the Fourier transformed frequency values, and Δf is the amplitude obtained by dividing the square root of M with respect to fo when the amplitude of fo is M. Wherein the quality index is calculated according to a range up to a frequency corresponding to Q, and Q is a quality index, and if the quality index is equal to or less than a preset reference quality index, the defect is determined as a defect. The method of claim 8, And the measuring unit measures a displacement of one point previously set among the driving bodies. 10. The method of claim 9, And the vibration adjusting unit provides the vibration alternating current power supply to the drive body once. In the defect detection method of the print head in which a driving body is formed on one surface and ink is discharged by the vibration of the driving body, Providing a power supply for supplying vibration AC power having a predetermined voltage level to the driving body; A measuring step of measuring a displacement of the driving body with respect to one surface of the printer head; And Fourier transform (Fourier Transform) the displacement measured by the measuring step, and determining the defect according to the quality index determined by the Fourier transform frequency value Defect detection method of the print head comprising a. The method of claim 11, The vibration AC power source has a power source frequency, The power supply step is a defect detection method of the print head, characterized in that for supplying the vibration AC power to the drive body by varying the power frequency within a predetermined power frequency range. The method of claim 12, The vibration AC power is a pulse power supply, In the power supply step, a defect detection method of a print head, characterized in that the power supply frequency is varied in a predetermined frequency unit within the power supply frequency range and the oscillating AC power having a variable power supply frequency is sequentially provided to the driving body. . The method of claim 13, The determining step (where fo is the resonant frequency and the resonant frequency is the frequency having the largest amplitude among the Fourier transformed frequency values, Δf is the square root of M by dividing the square root of M with respect to fo when the amplitude of fo is M). The quality index is calculated according to a range up to a frequency corresponding to one amplitude, Q is a quality index, and if the quality index is equal to or less than a preset reference quality index, a defect is detected in the print head. . The method of claim 14, The measuring step is a defect detection method of the print head, characterized in that for measuring the displacement of a predetermined point of the drive body. The method of claim 11, The power supply step is a defect detection method of the print head, characterized in that for providing the vibration AC power having a predetermined power frequency to the drive body. The method of claim 16, The power supply step is a defect detection method of the print head, characterized in that for providing the vibration AC power in the form of a pulse. The method of claim 17, The determining step (where fo is the excitation frequency and the excitation frequency is the frequency having the second largest amplitude among the Fourier transformed frequency values, Δf is the square root of M with respect to fo when the amplitude of fo is M). A defect of the print head characterized in that the quality index is calculated according to a range up to a frequency corresponding to the amplitude equal to two amplitudes, Q is a quality index, and the quality index is determined to be a defect if the quality index is equal to or less than a preset reference quality index. Detection method. The method of claim 18, The measuring step is a defect detection method of the print head, characterized in that for measuring the displacement of a predetermined point of the drive body. The method of claim 19, The power supply step is a defect detection method of the print head, characterized in that for providing the vibration AC power to the drive once.

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