JPH11138788A - Inspection method for recording head and recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method for recording head, and a recorder, in which the ink jetting state of a recording head can be detected with high accuracy. SOLUTION: Temperature rise and drop of a recording head jetting no ink incident to heating thereof are measured and temperature rise and drop of the recording head at the time of preliminary ink jet are also measured. A first value indicative of the difference between temperature rise and drop when ink is jetted normally in the preliminary ink jet is determined along with a second value indicative of the difference between temperature rise and drop when ink jet from the recording head is rejectable. Based on these values and a third value indicative of the difference between temperature rise and drop measured at the time of heating the recording head, a threshold value indicative of occurrence of rejectable ink jet is calculated. Subsequently, preliminary ink get is conducted again and the difference between temperature size and drop of the recording head thus obtained is compared with the threshold value. Finally, a decision is made whether ink is jetted normally or not from the recording head based on the comparison results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting a recording head, and more particularly, to a method and an apparatus for inspecting a recording head for performing recording according to an ink jet system.

[0002]

2. Description of the Related Art A recording device incorporated in a printer, a copying machine, a facsimile, or the like, or a recording device used as an output device such as a composite electronic device including a computer or a word processor or a workstation contains character information and the like. Characters and images are recorded on a recording medium such as a recording sheet or a plastic thin plate based on the image information.

[0003] Such recording apparatuses can be classified into an ink jet system, a wire dot system, a thermal system, an electrophotographic system and the like according to the recording system.

[0004] Above all, a recording apparatus employing an ink jet system (ink jet recording apparatus) performs recording by ejecting ink from a recording head to a recording medium, and it is easy to reduce the size of the recording head. High-definition images can be recorded at high speed, and can be recorded on plain paper without requiring special processing.The running cost is low and the non-impact method reduces noise,
In addition, there is an advantage that it is easy to record a color image using multicolor inks. In particular, those using a full-line type recording head in which a large number of ejection ports are arranged in the width direction of the recording paper can further increase the recording speed.

[0005] In a recording head used in an ink jet recording apparatus, the viscosity of ink increases, especially in the ink liquid passage near the discharge port, and normal discharge is performed, for example, when the recording head is left for a long time without discharging. May not be done. Further, when ink is continuously ejected, for example, when printing is performed with a relatively high print duty, fine bubbles generated in the ink in the ink liquid path with the ejection grow, and the grown bubbles are It may remain in the liquid path and affect ink ejection, and similarly, normal ejection may not be performed. Such bubbles may be mixed into the ink from an ink supply system such as a connection portion of an ink supply path or the like, in addition to those generated due to the ink ejection as described above.

When such non-ejection of ink occurs,
Not only does the reliability of the printing apparatus decrease, but in particular, in the bubble jet method in which thermal energy is applied to the ink to discharge the ink, if printing is performed at a high duty with a print head in a state where the ink cannot be normally discharged, the printing is performed. The temperature inside the head rises to a much higher temperature than when the ink is normally ejected, and the recording head itself may be damaged, and its durability may be impaired.

[0007] In order to cope with the ejection failure due to these various causes, a conventional ink jet recording apparatus employs, for example, a capping process for covering the ejection port surface of a recording head to prevent an increase in ink viscosity when ejection is not performed. An ink suction process in which ink with a high viscosity is discharged by sucking ink from the ejection port in a capping state, and ink is ejected to a predetermined ink receiver composed of an ink absorber or the like in the same manner as in normal recording. An ejection recovery process such as a preliminary ejection process for discharging the ink whose height has increased is performed.

Such a discharge recovery process is performed automatically at a predetermined time interval when the apparatus is turned on or during a printing operation, or when the user presses an operation button or the like as necessary. Had been However, in an ink jet recording apparatus that performs an ejection recovery process when the apparatus is powered on, if a user who repeatedly turns on and off the power supply uses the apparatus, the number of times the ejection recovery processing is performed increases unnecessarily,
There is a problem that the amount of consumed ink and the amount of waste ink sucked from the ejection port increase. On the other hand, when the user operates the recovery button in accordance with the determination to perform the recovery processing, the user actually performs printing by determining whether the print head is in a normal state or in a state of ink ejection failure. There is a problem of lack of reliability because it cannot be understood without it.

A comparison between a state in which the recording head normally discharges ink and a state in which the recording head has a defective discharge shows that when the discharge state is normal, part of the heat generated by the preliminary discharge is reduced. The ink is transmitted to the ink, a part of which is used to boil the ink, and a part of the ink goes out of the recording head together with the ink droplet. On the other hand, when the recording head is in an ejection failure state, the temperature difference between the temperature rise and the temperature decrease tends to be larger than that in the case where the ink ejection is performed well. Therefore, taking advantage of such a tendency, in order to solve the above-described problem, the recording head is caused to have an ejection failure in accordance with a temperature rise occurring in the recording head due to the preliminary ejection and a temperature drop occurring in the recording head after the preliminary ejection. (Japanese Patent Laid-Open No. 4-13)
3746 and JP-A-5-293968) are disclosed.

[0010]

However, individual differences in the recording head, such as variations in the heat generation characteristics and storage heat characteristics of the recording head, and individual differences in the recording apparatus main body, such as variations in the power supply voltage supplied from the power supply unit. As a result, there is a variation in the temperature rise occurring in the print head due to the preliminary ejection performed for detecting the ejection state of the print head and the temperature drop occurring in the print head after the preliminary ejection. In addition, when an ink-jet head unit in which a plurality of recording heads for ejecting ink are arranged and integrally formed is used, it is also affected by heat generation and heat generated by neighboring recording heads.

Therefore, in the case where such variation is large or the influence of heat from a neighboring head is present, the conventional example described above has a problem that the ink ejection state of the recording head cannot be detected with sufficient accuracy.

The present invention has been made in view of the above conventional example, and has as its object to provide a recording head inspection method and a recording apparatus capable of detecting the ink discharge state of the recording head with high accuracy.

[0013]

In order to achieve the above object, a method for inspecting a recording head according to the present invention comprises the following steps.

In other words, the present invention is a method of inspecting a recording head for inspecting an ink ejection state of a recording head which performs recording by ejecting ink, wherein the first current pulse which does not cause ink ejection from the recording head is applied to the recording head. Applying a first current pulse to the recording head to heat the recording head, and measuring a temperature rise caused by the application of the first current pulse and a temperature decrease caused by stopping the application of the first current pulse; A second current pulse is applied to the recording head so as to cause ink ejection at a timing different from the operation, and a temperature rise due to the application of the second current pulse and a stop of the application of the second current pulse are caused. A second measurement step of measuring a temperature drop, and the temperature rise measured in the second measurement step when ink is normally ejected from the recording head. A first calculation for obtaining a first value that is a difference from the temperature drop and a second value that is a difference between the temperature rise and the temperature drop when ink ejection from the recording head is defective. A step, the first and second values,
Based on a third value which is a difference between the temperature rise and the temperature fall measured in the first measurement step, a threshold value indicating that an ink ejection failure dependent on the third value occurs is calculated. A second calculation step, in which a second current pulse is applied to the recording head to perform preliminary ejection, and a difference between a temperature rise and a temperature decrease of the recording head obtained from the preliminary ejection is calculated by the second calculation. Printing, comprising: a comparison step of comparing with a threshold value calculated in the step; and a determination step of determining whether ink is normally ejected from the recording head based on a comparison result in the comparison step. A head inspection method is provided.

Further, a monitoring step of monitoring a time during which no current pulse is applied to the recording head, and based on the monitoring, when no current pulse is applied for a predetermined time or more, the first step is performed. And a control step of controlling the measurement step to be performed.

Here, when the recording head includes a plurality of head units each having an ejection port array in which a plurality of ejection ports from which ink is ejected are arranged, the first measuring step sequentially performs the first measurement step on the plurality of head units. One current pulse is applied to perform measurement, and based on the monitoring in the monitoring step, if the application of the current pulse does not occur for a predetermined time or more, the first current pulse is applied to a plurality of head units. The order may be changed so that the measurement is performed.

According to still another aspect of the present invention, there is provided a recording apparatus capable of inspecting an ink discharge state of a recording head which performs recording by discharging ink, wherein the first recording head is of such a degree that ink is not discharged from the recording head. Applying a current pulse to the recording head to heat the recording head, and measuring a temperature rise caused by the application of the first current pulse and a temperature decrease caused by stopping the application of the first current pulse. Measuring means, applying a second current pulse to the recording head so as to cause ink ejection at a timing different from the recording operation, and increasing the temperature by applying the second current pulse;
A second measuring unit for measuring a temperature decrease due to the stop of the application of the second current pulse, and the temperature measured by the second measuring unit when the ink is normally ejected from the recording head. A first value that is a difference between the rise and the temperature decrease and a second value that is a difference between the temperature rise and the temperature decrease when the ink ejection from the recording head is defective. Calculating means, and the first and second
And a third value, which is a difference between the temperature rise and the temperature fall measured by the first measuring means, indicates that an ink ejection failure dependent on the third value occurs. A second calculating means for calculating a threshold value, a preliminary ejection means for applying a second current pulse to the recording head to perform preliminary ejection, and a temperature rise of the recording head obtained from the preliminary ejection by the preliminary ejection means. Comparing means for comparing the difference with the temperature decrease with the threshold value calculated in the second calculation step;
A determining unit for determining whether or not ink is normally ejected from the recording head based on a comparison result by the comparing unit.

Further, monitoring means for monitoring a time during which no current pulse is applied to the recording head, and based on the monitoring, when no current pulse is applied for a predetermined time or more, a first measurement is performed. It is desirable to have control means for controlling the execution of the means.

The recording head may include a plurality of head units each having an ejection port array in which a plurality of ejection ports for ejecting ink are arranged. In this case, the first measuring means sequentially applies the first current pulse to the plurality of head units to perform the measurement, and further, based on the monitoring by the monitoring means, the application of the current pulse is performed for a predetermined time or more. If no such error occurs, it is desirable to further include an order control unit that controls the measurement so as to change the order in which the first current pulses are applied to the plurality of head units.

Further, the average of the measurement result obtained from the first measurement means under the control of the control means and the measurement result obtained previously by the first measurement means may be obtained.

The recording head may be replaceable, and may further include a non-volatile memory for storing the measured values obtained by the first measuring means.

In this case, the control means causes the first measuring means to execute when the recording head is replaced, clears the value stored in the non-volatile memory, and executes the first measuring means. Control is performed to store the newly obtained measurement value in the nonvolatile memory. The control means may further perform control so that the recording head is not at a predetermined position and the first measuring means is executed immediately after power-on.

The recording head is a recording head that uses thermal energy to discharge ink, and preferably includes a thermal energy converter for generating thermal energy to be applied to the ink.

With the above arrangement, the present invention applies a first current pulse to the recording head to the extent that ink is not ejected from the recording head, heats the recording head, and raises the temperature by the application of the first current pulse. And the temperature drop due to the stop of the application of the first current pulse, and the second operation is performed so as to cause ink ejection at a timing different from the recording operation.
Is applied to the recording head, and the temperature rise due to the application of the second current pulse and the temperature decrease due to the stop of the application of the second current pulse are measured, and the ink is normally ejected from the recording head. A first value that is a difference between the temperature rise and the temperature decrease in the case where the recording is performed, and a second value that is a difference between the temperature rise and the temperature decrease when the ink ejection from the recording head is defective. Based on these first and second values and a third value, which is the difference between the temperature rise and the temperature fall measured during the application of the first current pulse, a third value was used. A threshold indicating that an ink ejection failure occurs is calculated, and a second current pulse is applied to the printhead to perform preliminary ejection, and the difference between the temperature rise and temperature decrease of the printhead obtained from the preliminary ejection is calculated. , Compared to the calculated threshold, Based on the compare results to determine whether the ink normally from the recording head is discharged.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

First, the configuration of an ink jet recording apparatus (hereinafter, referred to as a recording apparatus) commonly used in some embodiments described below will be described. (1) Description of Printing Apparatus FIG. 1 is a perspective view showing a main configuration of an ink jet printing apparatus which is a typical embodiment of the present invention.

As shown in FIG. 1, an ink jet head unit 1 having an ejection port array for ejecting ink
1 is mounted on the carriage 13. A recording medium P made of a recording sheet or a thin plastic plate is transported by rollers (not shown).
, And is fed in the direction of arrow B by the driving of a transport motor (not shown).

The carriage 13 is mounted on the guide shaft 1
2, and supported by an encoder (not shown). The carriage 13 reciprocates along the guide shaft 12 by driving a carriage motor 15 via a drive belt 14. A heating element (electric heat energy converter) for generating thermal energy for ink ejection is provided inside each ink ejection port (liquid passage) of the plurality of recording heads constituting the inkjet head unit 11. Then, in accordance with the reading timing of an encoder (not shown), the heating element is driven based on the recording signal.
As a result, an image is formed by ejecting and attaching ink droplets onto the recording medium P.

At the home position (HP) of the carriage 13 provided outside the recording area, a recovery unit having a cap 16 is provided. When recording is not performed, the carriage 13 is moved to the home position (HP) to seal the ink ejection port surface of the ink jet head unit 11 with the cap portion 16 and to fix ink due to evaporation of the ink solvent, dust, or paper dust. Clogging due to adhesion of foreign matter such as

Further, the capping function of the cap section 16 is provided in a state in which the cap section 16 is separated from the ink ejection ports in order to eliminate ink ejection failure or clogging due to an increase in ink viscosity or ink sticking of the ink ejection ports with low ink ejection frequency. It is used to execute a preliminary ejection mode in which ink is ejected to a certain cap unit 16, or operates a pump (not shown) in a capped state to suck ink from the ink ejection port, and to detect the ink ejection port where an ejection failure has occurred. Used for ejection recovery. Also,
By disposing the blade at a position adjacent to the cap section 16, cleaning (wiping) of the ink ejection port surface of the inkjet head unit 11 is possible. (2) Description of Recording Head FIG. 2 is a perspective view schematically showing the configuration of the ejection port forming surface 21 of the inkjet head unit 11 as viewed from the recording medium side.

As is apparent from FIG. 2, the ink-jet head unit 11 is configured so that three recording heads A, B, and C are arranged in the carriage moving direction (the direction of the arrow y in FIG. 2). Have been.
The ink discharge ports 22 of each recording head are arranged so as to be arranged in a direction perpendicular to the y direction.

FIG. 3 is a partial perspective view schematically showing the structure of the ink ejection section of the recording head shown in FIG.

As shown in FIG. 3, an ejection port forming surface 21 having a plurality of ejection ports 22 opened in the print head.
There is provided a heating element 32 for generating heat energy required for discharging ink into a liquid passage 31 communicating with each of the discharge ports 22.

In FIG. 3, reference numeral 33 denotes a sensor for detecting the internal temperature of the recording head. In this embodiment, thermistors are provided at both ends of the discharge port array.
A total of six B heads are arranged, two for each of the B and C heads. The configuration for detecting the internal temperature of the recording head is not particularly limited to this, and other sensors such as a diode sensor may be used, or the head temperature may be calculated from the duty of the recording dots. good.

In this embodiment, an example is described in which three recording heads are integrally formed.
One head, or an inkjet head unit that integrally forms three or more recording heads may be used. (3) Description of Control Configuration FIG. 4 is a block diagram illustrating a control configuration of the printing apparatus.

The control circuit of the recording apparatus shown in FIG. 4 includes an image input unit 403 for accessing the main bus 405, an image signal processing unit 404 corresponding to the image input unit 403, and a C
A circuit group that functions by executing software such as the PU 400, the operation unit 406, and the recovery processing control circuit 40
7, a circuit for performing a mechanical operation such as a printhead temperature control circuit 414 and a printhead drive control circuit 415.

The CPU 400 normally has the ROM 401 and the R
It has an AM 402 and executes control for driving the print head 413 to perform printing by giving appropriate printing conditions to input information. A program for executing a printhead recovery procedure is stored in the RAM 402 in advance, and recovery conditions such as preliminary ejection conditions are given to the recovery processing control circuit 407, the printhead, the heater, and the like as necessary. .
The recovery motor 408 drives the recording head 413, a blade (cleaning) 409 provided opposite to the recording head 413, a cap 410, and a suction pump 411.

The recording head drive control circuit 415 has a CPU
According to the driving conditions given from 400, the recording head 4
By driving the heating element 32, which is an electrothermal transducer of No. 13, the recording head 413 normally performs preliminary ejection and ejection of recording ink.

On the other hand, the substrate on which the electrothermal transducer for ink ejection of the recording head 413 is provided is provided with a heating heater 4.
16 is provided, and the ink temperature in the recording head 413 can be adjusted by heating to a desired set temperature. The thermistor 412 is also provided on the same substrate and is used to measure the ink temperature inside the print head. Note that the thermistor 412 may be provided not on the substrate but on the outside, or near the periphery of the recording head.

Next, a description will be given of a process for detecting a discharge failure of a print head using the printing apparatus having the above configuration as a common apparatus. [First Embodiment] Here, as shown in FIG. 2, the ejection in the case of using an ink jet head unit in which three recording heads A, B and C are arranged integrally in the carriage moving direction. The defect detection processing will be described.

As described above, the temperature rise of the print head due to the preliminary discharge executed for detecting the discharge failure of the print head and the temperature change of the temperature drop after the preliminary discharge are caused by the heat generation characteristic and the heat storage characteristic of the print head. It is greatly influenced by such things. The recording heat characteristics of the recording heads differ from one recording head to another due to the degree of joining between the members and variations in the ink discharge amount. Further, even if the same electric energy is applied to the heating element, the recording head that easily heats up heats up to a high temperature, but the recording head that does not easily heat up radiates heat as soon as heat energy is generated, so the temperature does not rise so much. In addition, heat generation characteristics vary from printhead to printhead due to variations in the sheet resistance of the heating elements. In addition, the heat generation characteristic differs for each printing apparatus due to the variation in the driving voltage of the heater driving power supply of the printing apparatus main body.

FIG. 5 is a flowchart showing a process for obtaining the thermal characteristics of the recording head. FIG. 6 is a diagram showing a temporal change in the internal temperature of the recording head (hereinafter referred to as head temperature) when a short pulse is applied to the recording head to acquire the thermal characteristics of the recording head. FIG. 6 shows a temporal change in the average value when the internal temperature of the recording head is measured four times.

Hereinafter, the process of acquiring the thermal characteristics will be described with reference to FIGS.

First, at step S51, the head temperature (T1) before applying a pulse to the recording head is measured. Thereafter, in step S52, the pulse ON time is 0.125.
μsec and a pulse OFF time of 0.375 μsec and a cycle of 0.5 μsec (therefore, the pulse O
(A ratio of N is 25%) for 1 second. By applying such a pulse, the ink in the recording head does not foam.

Next, in step S53, the head temperature (T2) immediately before the end of the application of the pulse is measured. In step S54, the head is left for one second, and in step S55, the head temperature (T3) after being left is measured. Finally, step S56
Then, a thermal characteristic value (ΔTs = ΔT1 + ΔT2) defined by the sum of the temperature change ΔT1 = T2-T1 due to the temperature increase and the temperature change ΔT2 = T2-T3 due to the temperature decrease is acquired.

The reason for adding the temperature difference between the temperature rise and the temperature drop is to minimize the influence of a large change in the temperature of the print head, for example, after high-duty printing. The head temperature is detected every 50 msec, and an average of four times is taken to suppress measurement noise.

In this embodiment, the above-described pulse is applied for one second. However, since the proper value depends on the ink ejection amount, the number of ejection ports of the recording head, and the like,
The pulse application time may be other than this value.

Next, the thermal characteristic value of each recording head included in an ink-jet head unit integrally formed by arranging three recording heads (A head, B head, and C head) as shown in FIG. The process of acquiring will be described with reference to the flowchart shown in FIG.

First, in step S701, a time period during which no pulse application for pre-ejection of the recording head or recording operation occurs is monitored. Here, if it is determined that the time has reached 70 minutes or more, the process proceeds to steps S702 to S7.
At 04, the processing shown in the flowchart of FIG. 5 is executed in the order of the A head, the B head, and the C head, and the thermal characteristics of each head are acquired.

Thereafter, in step S705, a time period during which no pulse is applied to the recording head is monitored as in step S701. Here, if it is determined that the time has reached 70 minutes or more, the process proceeds to step S706, executes the process shown in the flowchart of FIG. 5 for the B head, and acquires the thermal characteristic value for the B head. Then, in step S707, an average of the acquired thermal characteristic value and the previously acquired thermal characteristic value is obtained, and the average value is set as a new thermal characteristic value.

Next, in steps S708 to S709,
Similarly, the thermal characteristic value of the head C is obtained, and the thermal characteristic value of the head A is similarly obtained in steps S710 to S711. Thus, steps S706 to S706
In step 711, the thermal characteristics are acquired in the order of the B head, the C head, and the A head, and the average value of these values and the previously acquired thermal characteristic value of each head is set as a new thermal characteristic value.

Further, the processing in step S712
As in step S701, the time during which no pulse application to the recording head occurs is monitored. If it is determined that the time has reached 70 minutes or more, the process proceeds to step S71.
In step S714, the CPU executes the processing shown in the flowchart of FIG. 5 for the C head to acquire a thermal characteristic value for the C head. Further, in step S714, the acquired thermal characteristic value and the previously updated thermal characteristic value are obtained. An average with the values is obtained, and the average value is set as a new thermal characteristic value.

Next, in steps S715 to S716,
Similarly, the thermal characteristic value for the A head is obtained, and in steps S717 to S718, the thermal characteristic value for the B head is similarly obtained. Thus, steps S713 to S713
At step 718, the thermal characteristics are acquired in the order of the C head, the A head, and the B head, and the average value of these values and the thermal characteristic value of each head updated last time is set as a new thermal characteristic value.

Steps S701, S705, S7
In the monitoring of the time during which no pulse application occurs to the print head in No. 12, the time monitoring threshold is set to 70 minutes, but it goes without saying that another value may be used.

As described above, when the pulse application to the recording head has not been performed for a predetermined time or more, the recording head is warmed by applying a pulse that is short enough not to cause the bubbling of the ink, and its thermal characteristics are constantly obtained. To

In this embodiment, preliminary ejection is performed by using a pulse applied during the printing operation, and the temperature difference between the temperature rise of the print head and the subsequent temperature drop is measured, and the magnitude of the temperature change is measured. Then, a value (△ Ti) indicating the value is calculated. Then, the value (△ Ti) is compared with a threshold value (△ Tth) determined by the thermal characteristic value (△ Ts) of the recording head obtained as described above, and the ejection failure of the recording head is determined.

FIG. 8 is a diagram showing a temporal change of the head temperature when a preliminary ejection for detecting an ejection failure is performed.
FIG. 8 shows the time change of the average value when the measurement of the internal temperature of the recording head was performed four times. Hereinafter, referring to FIG. 8, the magnitude of the temperature change (ΔTi) was measured. The following describes the procedure to be performed.

First, the head temperature (T4) before the preliminary ejection is measured. Subsequently, the same pulse (20,000 KHz) is applied at the same frequency (10 KHz) as used for the recording operation, and the head temperature (T5) immediately before the end of the application is measured. Then, the head temperature (T6) is measured two seconds after the end of the drive pulse application. The head temperature is detected every 50 msec, and an average of four times is taken to suppress measurement noise.

Next, from the measurement results thus obtained, a value indicating the magnitude of the temperature rise and fall of the recording head by the preliminary ejection, ΔTi = (T5−T4) + (T5−T6), is calculated.

Such measurement is performed for a plurality of print heads, and ΔTi and ΔTs obtained in a state where a discharge failure occurs in the print head (solid line in FIG. 8) and a state of normal discharge (dashed line in FIG. 8) are obtained. FIG. 9 plots these relationships.

As can be seen from FIG. 9, the relationship of .DELTA.Ti-.DELTA.Ts is divided into two groups when an ink ejection failure occurs and when ink is ejected normally. Therefore, a threshold value (ΔTth) for determining a discharge failure can be obtained from ΔTs as shown by the solid line in FIG. 9 even when the variation of ΔTs is considered. The threshold value (△ Tth) obtained in this way is written to a nonvolatile memory (EEPROM, NVRAM, etc.) in the main body of the recording apparatus.

The threshold value (△ Tth) shown in FIG.
Expressed as a linear function of s,

ΔTth = 0.5 × ΔTs + 25 (1) Therefore, when ΔTi measured from preliminary ejection is obtained,
Since the obtained thermal characteristic value (ΔTs) and the threshold value from the equation (1) are obtained, it is possible to detect a discharge failure by comparing the threshold value (ΔTth) with the ΔTi.

Here, if △ Ti ≧ △ Tth, it can be determined that there is an ejection failure (no ink), and if △ Ti <△ Tth, it can be determined that normal ejection (ink exists).

As can be seen from FIG. 9, the relationship between .DELTA.Ti-.DELTA.Ts is very clearly divided into two groups when an ink ejection failure occurs and when the ink is ejected normally. It can be said that there is sufficient margin for the determination of.

In this embodiment, the frequency of the pulse for preliminary ejection is 10 KHz, and the number of pulses is 200 KHz.
However, since these values depend on the ink ejection amount, the number of ejection ports, and the like of the target print head, the present invention is not limited to this value, and other values depend on the print head. It goes without saying that the value may be set.

Therefore, according to the above-described embodiment, the recording head is given a pulse which does not actually cause ink bubbling to measure the heat generation characteristic and the heat storage characteristic of the recording head. Based on the characteristic value and the characteristics of the temperature rise and temperature decrease of the print head when the preliminary ejection is performed, a threshold for determining an ink discharge failure unique to the print head is generated, and the ink discharge failure is determined using the threshold. Therefore, even if there is variation due to individual differences of the recording head such as variation in heat / storage heat characteristics of each recording head or variation in the main body of the recording apparatus such as variation in power supply voltage, and even if there is an influence of heat from a neighboring head, these are not affected. By using the threshold value determined in consideration of the above factors, it is possible to detect ejection failure of the recording head with higher accuracy.

Further, when acquiring the heat characteristic value reflecting the heat generation / storage heat characteristic, the timing of acquiring the heat characteristic value is changed one after another, and the average value with the previously acquired heat characteristic value is obtained. There is an advantage that the influence of heat from the recording head can be reduced. [Second Embodiment] Here, a description will be given of a process of detecting an ink ejection failure when two ink jet head units having the configuration shown in FIG. 2 are arranged in the carriage movement direction.

FIG. 10 is a diagram showing a state in which two ink jet head units having the structure shown in FIG. 2 are arranged in the carriage movement direction. As shown in FIG. 10, for convenience, the recording heads included in another inkjet head unit are referred to as a D head, an E head, and an F head.

FIG. 11 is a flowchart showing a process for acquiring the thermal characteristic values of each of the six recording heads included in the ink jet head unit having the configuration shown in FIG.

First, in step S801, a time period during which no pulse application for the preliminary ejection of the print head or the printing operation is performed is monitored. If it is determined that the time has exceeded 70 minutes, the process proceeds to step S802 in which the two inkjet head units are alternately switched in the order of A head, D head, B head, E head, C head, and F head. Then, the processing shown in the flowchart of FIG. 5 is executed to acquire the thermal characteristics of each head.

Thereafter, in step S803, a time period during which no pulse is applied to the recording head is monitored as in step S801. Here, if it is determined that the time has reached 70 minutes or more, the process proceeds to step S804, starting with the D head, and starting with the B head, E head, C head, F head, and A head in the order of the flowchart of FIG. Is performed to obtain a thermal characteristic value. Further, in step S805, an average of the acquired thermal characteristic value and the previously acquired thermal characteristic value is obtained, and the average value is used as a new thermal characteristic value. Value.

Further, in step S806, the time during which no pulse is applied to the recording head is monitored as in step S801. Here, if it is determined that the time has reached 70 minutes or more, the process proceeds to step S807, and the order of B head, E head, C head, F head, A head, and D head is as shown in FIG. To obtain a thermal characteristic value, and further, in step S808,
The average value of the obtained thermal characteristic value and the previously updated thermal characteristic value is set as a new thermal characteristic value.

In the same manner, steps S809 to S8
11, the E head, C head, F head, A head,
In the order of D head and B head, step S81
2 to S814, C head, F head, A head, D head
In steps S815 to S817, the processing shown in FIG. 5 is executed in the order of F head, A head, D head, B head, E head, and C head. Then, a thermal characteristic value is acquired, and an average value of the acquired thermal characteristic value and the previously updated thermal characteristic value is set as a new thermal characteristic value.

Thus, finally, step S817
The thermal characteristic values obtained in step (1) are determined values for each recording head.

In the above processing, the average value of the newly acquired thermal characteristic value and the previously updated thermal characteristic value is used as the new thermal characteristic value. However, all the thermal characteristic values acquired at each acquisition timing are set. For example, the non-volatile memory (EE
PROM, NVRAM, etc.) and calculate the average value of these later, and use this as a new thermal characteristic value. Alternatively, instead of calculating the average value, a weighted average is calculated according to a predetermined arithmetic expression, and The calculated value may be a thermal characteristic value.

When two ink jet head units are used, a thermal characteristic value is obtained while the two units are alternately shifted as described above, and the thermal value of each recording head obtained by averaging the obtained values is obtained. A threshold value (△ Tth) is obtained based on the characteristic value (△ Ts) in the same manner as in the first embodiment. Hereinafter, similarly to the first embodiment, preliminary discharge is performed to measure ΔTi, and the measured value is compared with a threshold value to determine
An ink ejection failure is determined from the comparison result.

Therefore, according to the above-described embodiment, even when two ink jet head units each having a plurality of recording heads arranged side by side and arranged integrally are arranged, the thermal characteristic value in which the influence of the heat from the adjacent head is further reduced. Therefore, it is possible to detect a discharge failure of the recording head with high accuracy. [Third Embodiment] Here, a process of detecting an ejection failure in a case where the ink jet head unit (hereinafter, referred to as a head unit) shown in FIG. 2 is replaceable with a printing apparatus will be described.

When the head unit is replaceable, the thermal characteristic value of the recording head is obtained when the pulse application to the recording head is not performed for a predetermined time (70 minutes in this embodiment). This is performed after the unit is replaced or when the power of the recording apparatus is turned on without the head unit at a predetermined position such as the home position.

FIG. 12 is a flowchart showing a process for obtaining the thermal characteristic value of each recording head when the head unit shown in FIG. 2 is replaceable.

First, in step S901, it is determined whether the current time is after the replacement of the head unit or whether the power of the recording apparatus is turned on without the head unit at a predetermined position such as the home position. Find out. Here, if the condition of step S901 is satisfied, the process proceeds to step S902, in which the processing shown in FIG. 5 is performed in the order of the A head, the B head, and the C head to obtain a thermal characteristic value, Further, in step S903, all the thermal characteristic values stored in the nonvolatile memory (EEPROM, NVRAM, etc.) of the recording apparatus up to the previous time are discarded, and the value acquired in step S902 this time is used as the thermal characteristic value.

On the other hand, if the condition of step S901 is not satisfied, the process proceeds to step S904,
The time during which no pulse application to the recording head occurs is monitored.

If it is determined that the time has exceeded 70 minutes, the process proceeds to step S706.
If it is less than 0 minutes, the process returns to step S901.

In steps S706 to S711, the thermal characteristics are acquired in the order of the B head, the C head, and the A head, and the average value of these values and the previously acquired thermal characteristic value of each head is calculated as a new thermal characteristic. Value. Note that these processes are the same as those described in the first embodiment, and a description thereof will be omitted. Then, the thermal characteristic value obtained as a result is stored in a non-volatile memory (EEPROM, NVRAM, etc.) of the recording device.
Is written to.

Next, in step S911, it is determined again whether the current time is after the replacement of the head unit or whether the power of the recording apparatus is turned on without the head unit at a predetermined position such as the home position. Find out. Here, when the condition of step S911 is satisfied, the process returns to step S902, and when the condition of step S911 is not satisfied, the process proceeds to step S912. In step S912, the time during which pulse application to the recording head does not occur is monitored again. If it is determined that the time has reached 70 minutes or more, the process proceeds to step S713.
If it is less than 70 minutes, the process proceeds to step S91
Return to 1.

In steps S713 to S718, the thermal characteristics are acquired in the order of the C head, the A head, and the B head, and the average value of these values and the previously acquired thermal characteristic value of each head is calculated as a new thermal characteristic. Value. Note that these processes are the same as those described in the first embodiment, and a description thereof will be omitted. Then, the thermal characteristic value obtained as a result is stored in a non-volatile memory (EEPROM, NVRAM, etc.) of the recording device.
Is written to.

Thereafter, in step S 921, the process proceeds to step S 921 to determine whether the current time is after the head unit is replaced or immediately after the power is turned on to the recording apparatus without the head unit at a predetermined position such as the home position. Find out if. Here, if the condition in step S921 is not satisfied, the process continues in a waiting state in step S921. That is, the thermal characteristic value determined in the processing up to step S718 is used for subsequent determination of ink ejection failure. On the other hand, when the condition in step S921 is satisfied, the process returns to step S921.

According to the above-described processing, when the recording apparatus is powered on after the head unit is replaced or in a state where the head unit is not located at a predetermined position such as a home position, the thermal characteristics of each recording head are updated. And discarding the values of the thermal characteristic values of the respective recording heads up to the previous time, and using the newly acquired values as the thermal characteristic values. The thermal characteristic value (ΔTs) of the recording head can be obtained accurately.

When the thermal characteristic value (ΔTs) of each recording head is obtained in this manner, thereafter, as described in the first embodiment, based on the thermal characteristic value (ΔTs), A threshold value (△ Tth) is obtained, and ejection failure detection is performed.

Therefore, according to the embodiment described above, even when the recording apparatus uses a replaceable ink jet head unit, the influence of heat from the adjacent head is reduced by obtaining the thermal characteristic value at an appropriate timing. Since the thermal characteristic value of each recording head of the ink jet head unit mounted on the recording apparatus can be acquired while performing this, it is possible to detect a discharge failure of the recording head with high accuracy.

The above-described embodiment is particularly provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging ink, even in an ink jet recording system. By using a method in which a change in the state of the ink is caused by energy, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method can be applied to both the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, liquid (ink)
By applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise exceeding the film boiling to the electrothermal transducer arranged corresponding to the sheet or the liquid path holding the Since thermal energy is generated in the electrothermal transducer and film boiling occurs on the heat-acting surface of the recording head, bubbles in the liquid (ink) corresponding to this drive signal on a one-to-one basis can be formed. It is valid. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of the liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable.

As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

The configuration of the recording head may be a combination of a discharge port, a liquid path, and an electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above-mentioned specifications. A configuration using U.S. Pat. No. 4,558,333 or U.S. Pat. No. 4,459,600, which discloses a configuration in which a heat acting surface is arranged in a bent region, is also included in the present invention. In addition, for multiple electrothermal transducers,
JP-A-59-123670 which discloses a configuration in which a common slot is used as a discharge part of an electrothermal transducer, and JP-A-59-123670 which discloses a configuration in which an opening for absorbing a pressure wave of thermal energy corresponds to a discharge part. A configuration based on 138461 may be adopted.

Further, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is determined by combining a plurality of recording heads as disclosed in the above specification. This may be either a configuration satisfying the above requirements or a configuration as a single recording head formed integrally.

In addition to the cartridge type recording head in which the ink tank is provided integrally with the recording head itself described in the above embodiment, the recording head is electrically connected to the apparatus main body by being mounted on the apparatus main body. A replaceable chip-type recording head, which enables a simple connection and supply of ink from the apparatus main body, may be used.

It is preferable to add recovery means for the print head, preliminary auxiliary means, and the like to the configuration of the printing apparatus described above, since the printing operation can be further stabilized. Specific examples thereof include capping means for the recording head, cleaning means, pressurizing or suction means, preheating means using an electrothermal transducer or another heating element or a combination thereof. It is also effective to provide a preliminary ejection mode for performing ejection that is different from printing, in order to perform stable printing.

Further, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but may be a single recording head or a combination of plural recording heads. Alternatively, the apparatus may be provided with at least one of full colors by color mixture.

In the embodiments described above, the description is made on the assumption that the ink is a liquid. However, even if the ink solidifies at room temperature or lower, it is possible to use an ink that softens or liquefies at room temperature. Or, in the ink jet method, generally, the temperature of the ink itself is controlled within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range.
It is sufficient that the ink is in a liquid state when the use recording signal is applied.

In addition, in order to positively prevent the temperature rise due to thermal energy as energy for changing the state of the ink from the solid state to the liquid state,
Alternatively, in order to prevent evaporation of the ink, an ink which solidifies in a standing state and liquefies by heating may be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy recording signal and the liquid ink to be ejected, or by the time the ink reaches the recording medium, the solidification of the ink already begun. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, as described in JP-A-54-56847 or JP-A-60-71260, the ink is held in a liquid state or a solid state in the concave portion or through hole of the porous sheet. It is good also as a form which opposes an electrothermal transducer. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition to the above, the recording apparatus according to the present invention may be provided not only as an image output terminal of an information processing apparatus such as a computer but also integrally or separately, a copying apparatus combined with a reader, etc. It may take the form of a facsimile machine having functions.

The present invention can be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), and can be applied to a single device (for example, a copying machine, a facsimile machine) Etc.).

Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and to provide a computer (or CPU) of the system or apparatus.
And MPU) read and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0108]

As described above, according to the present invention, ink ejection failure is considered in consideration of factors such as variations in the heat generation characteristics / storage heat characteristics of each print head and variations in the power supply voltage applied to the print head. Is determined, a more accurate detection of an ink ejection failure can be performed that reflects the unique state of the print head or the printing apparatus.

Further, even in a recording head having a plurality of head units for ejecting ink, accurate detection of an ink ejection failure should be performed in consideration of the influence of heat generation and heat generation by an adjacent head unit. Can be.

[0110]

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a main configuration of an inkjet recording apparatus according to a representative embodiment of the invention.

FIG. 2 is a perspective view schematically showing a configuration of a discharge port forming surface 21 of the inkjet head unit 11 as viewed from a recording medium side.

FIG. 3 is a partial perspective view schematically illustrating a structure of an ink ejection unit of the recording head illustrated in FIG. 2;

FIG. 4 is a block diagram illustrating a control configuration of the printing apparatus.

FIG. 5 is a flowchart illustrating a process of acquiring a thermal characteristic of a recording head.

FIG. 6 is a diagram illustrating a change over time in the internal temperature of the print head when a short pulse is applied to the print head in order to acquire the thermal characteristics of the print head.

FIG. 7 is a flowchart illustrating a process for acquiring a thermal characteristic value of each recording head included in the inkjet head unit illustrated in FIG. 2;

FIG. 8 is a diagram showing a temporal change in head temperature when a preliminary ejection for detecting an ejection failure is performed.

FIG. 9 is a diagram plotting the relationship between △ Ti and △ Ts obtained for each of a plurality of print heads in a state in which discharge failure occurs in the print heads and a state of normal discharge.

FIG. 10 is a diagram illustrating a state in which two inkjet head units having the configuration illustrated in FIG. 2 are arranged in the carriage movement direction.

FIG. 11 is a flowchart illustrating a process of acquiring thermal characteristic values of each of six print heads included in the inkjet head unit having the configuration illustrated in FIG.

FIG. 12 is a flowchart showing a process for acquiring a thermal characteristic value of each recording head when the head unit shown in FIG. 2 is replaceable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Ink jet head unit 12 Guide shaft 13 Carriage 14 Drive belt 15 Carriage motor 16 Cap part 17 Discharge roller 21 Ink discharge port formation surface 22 Discharge port 31 Liquid path 32 Heating element 33 Thermistor 400 CPU 401 ROM 402 RAM 403 Image input part 404 Image signal processing unit 405 Main bus 406 Operation unit 407 Recovery processing control unit 408 Recovery processing motor 409 Blade 410 Cap 411 Pump 412 Thermistor 413 Print head 414 Print head temperature control circuit 415 Print head drive control circuit

Claims (13)

[Claims] 1. A recording head inspection method for inspecting an ink ejection state of a recording head that performs recording by ejecting ink, wherein the first current pulse that does not cause ink ejection from the recording head is applied to the recording head. Applying a first current pulse to the recording head to heat the recording head, and measuring a temperature rise caused by the application of the first current pulse and a temperature decrease caused by stopping the application of the first current pulse; Applying a second current pulse to the recording head so as to cause ink ejection at a timing different from the operation,
A second measurement step of measuring a temperature rise due to the application of the second current pulse and a temperature decrease due to the stop of the application of the second current pulse; and the recording measured in the second measurement step. A first value that is a difference between the temperature increase and the temperature decrease when the ink is normally ejected from the head, and the temperature increase and the temperature decrease when the ink ejection from the recording head is defective. A first calculation step for obtaining a second value that is a difference between the first and second values, and a third calculation step that is a difference between the temperature rise and the temperature decrease measured in the first measurement step. A second calculation step of calculating a threshold value indicating the occurrence of an ink ejection failure dependent on the third value based on the value of the third value, and applying a second current pulse to the recording head to perform preliminary ejection. And obtained from the preliminary discharge. A comparing step of comparing the difference between the temperature rise and the temperature drop of the recording head with the threshold value calculated in the second calculating step; and based on the comparison result in the comparing step, ink is normally ejected from the recording head. And a determining step of determining whether or not the recording has been performed. A monitoring step of monitoring a time during which no current pulse is applied to the recording head; and a monitoring step for a predetermined time or more based on the monitoring in the monitoring step.
2. The method according to claim 1, further comprising a control step of performing control so as to execute the first measurement step when no current pulse is applied. 3. When the recording head includes a plurality of head units each having an ejection port array in which a plurality of ejection ports from which ink is ejected are arranged, the first measuring step includes sequentially setting the plurality of head units in the plurality of head units. Performing the measurement by applying a first current pulse;
Further, based on the monitoring in the monitoring step, when the application of the current pulse does not occur for a predetermined time or more, the order of applying the first current pulse to the plurality of head units is changed to perform the measurement. 3. The printhead inspection method according to claim 2, further comprising an order control step of performing control as described above. 4. A recording apparatus capable of inspecting an ink discharge state of a recording head that performs recording by discharging ink, wherein the recording head supplies a first current pulse that does not cause ink to be discharged from the recording head. A first measuring unit for heating the recording head by applying the first current pulse to measure a temperature rise caused by the application of the first current pulse and a temperature decrease caused by stopping the application of the first current pulse; Applying a second current pulse to the recording head so as to cause ink ejection at a timing different from
A second measuring unit that measures a temperature rise due to the application of the second current pulse and a temperature decrease due to the stop of the application of the second current pulse; and the recording measured by the second measuring unit. A first value that is a difference between the temperature increase and the temperature decrease when the ink is normally ejected from the head, and the temperature increase and the temperature decrease when the ink ejection from the recording head is defective. A first calculating means for obtaining a second value which is a difference between the first and second values; and a third calculating means which is a difference between a temperature rise and a temperature decrease measured by the first and second values and the first measuring means. And a second calculating means for calculating a threshold value indicating that an ink ejection failure dependent on the third value is generated, based on the third value, and applying a second current pulse to the recording head to perform preliminary ejection. Preliminary discharge means for performing A comparing unit that compares a difference between a temperature rise and a temperature decrease of the print head obtained from the preliminary ejection by the ejection unit with a threshold value calculated in the second calculation step, based on a comparison result by the comparison unit, A determining unit for determining whether or not ink is normally ejected from the recording head. 5. A monitoring means for monitoring a time during which no current pulse is applied to the recording head, and when the current pulse is not applied for a predetermined time or more based on monitoring by the monitoring means, 5. The recording apparatus according to claim 4, further comprising control means for controlling the first measuring means to execute. 6. The recording apparatus according to claim 5, wherein the recording head includes a plurality of head units each having an ejection port array in which a plurality of ejection ports for ejecting ink are arranged. 7. The first measuring means performs the measurement by sequentially applying the first current pulse to the plurality of head units, and further, based on monitoring by the monitoring means, for a predetermined time or more. And an order control means for changing the order in which the first current pulse is applied to the plurality of head units when the application of the current pulse does not occur, and controlling the head unit to perform the measurement. The recording apparatus according to claim 6, wherein: 8. An averaging means for averaging a measurement result obtained from the first measurement means under the control of the control means with a measurement result previously obtained by the first measurement means. The recording apparatus according to claim 5, wherein: 9. The recording apparatus according to claim 5, wherein the recording head is replaceable. 10. The recording apparatus according to claim 9, further comprising a non-volatile memory for storing a measured value obtained by said first measuring means. 11. The control unit executes the first measurement unit when the recording head is replaced, clears a value stored in the nonvolatile memory, and controls the first measurement unit. 11. The recording apparatus according to claim 10, wherein control is performed such that a measurement value newly obtained by execution is stored in the nonvolatile memory. 12. The control means further comprises: the first recording head is not located at a predetermined position, and the first recording head is turned on immediately after power is turned on.
12. The recording apparatus according to claim 11, wherein the measuring unit is executed. 13. The recording head according to claim 1, wherein the recording head ejects ink by using thermal energy, and includes a thermal energy converter for generating thermal energy to be applied to the ink. Item 5. The recording device according to Item 4.