JP2012091518A - Device and method for detecting liquid droplet, and inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detecting device for minute liquid droplets which can perform the detecting of liquid droplets using light appropriately even when output fluctuation arises due to variable factors such as environmental variation when detecting the liquid droplet.SOLUTION: The detecting device for minute liquid droplets includes an emission part 51 for emitting a detection light L to intersect the locus of the minute liquid droplet I discharged from each nozzle of a nozzle array wherein a plurality of nozzles are arranged, a light receiving part 52 for receiving the detection light L, a discharge control means for controlling the discharging of minute liquid droplet I from all nozzles to the detection light L serially one by one, and a detection part for detecting the presence or absence of detection light passage of minute liquid droplet I by way of comparing the detection output which is output from the light receiving part 52 with a comparing reference potential and using the comparison result. In the detecting device for minute liquid droplets, the detection part has an amplitude measuring part 106 for measuring the amplitude of detection output which is output from the light receiving part 52. The addition or subtraction of the measured result in the amplitude measuring part 106 is applied to the comparing reference potential, and the comparing reference potential to which the addition or substraction has been applied is compared with the detection output.

Description

  The present invention relates to a microdroplet detection apparatus, a microdroplet detection method, and an ink jet recording apparatus, and more particularly to various conditions such as droplet size, flight state, circuit temperature characteristics, and distance from a light emitting unit. The present invention relates to a microdroplet detection apparatus, a microdroplet detection method, and an ink jet recording apparatus that can detect stably.

  For example, an inkjet recording apparatus that performs image recording by ejecting ink droplets composed of minute droplets from nozzles provided in a recording head onto a recording medium can always maintain high-quality and high-quality image recording. In addition, the ink ejection state is detected by periodically detecting the presence or absence of ejection of ink droplets from each nozzle (the presence or absence of clogging) and the flying speed of the ejected ink droplets.

  As such a detection method, a light-emitting element such as a light-emitting diode or a laser that emits detection light so as to cross the flight trajectory of the ink droplet and a light-receiving element that includes a photodiode or phototransistor that receives the detection light are used. The light receiving element captures the shadow when the ink droplet passes on the optical axis of the detection light, amplifies the detection output of the light receiving element, compares it with a reference potential, and the detection output from the light receiving element is the reference potential. Generally, the method is carried out by determining that there is an ink drop if it exceeds the limit, and that there is no ink drop if it does not exceed the limit. Based on the timing at which the ink droplets are ejected and the timing at which the light receiving element captures the shadow, it is possible to detect the ejection speed of the ink droplets as well as the presence / absence of ejection of the ink droplets (presence / absence of missing nozzles).

  However, the problem here is that the detection output from the light receiving element is easily affected by environmental conditions such as ink droplet size, flight state (bending), and circuit temperature characteristics, and the detection output is not accurate. The problem is that it is difficult to detect correctly. Further, when the light source is diverging light, the magnitude of the shadow of the ink droplet on the light receiving element varies depending on the distance between the ink droplet and the light receiving element, which causes a problem of fluctuation in detection output. Furthermore, there is also a problem that the detection output decreases as the distance from the light receiving element increases due to the problem of a decrease in the light amount detection output associated with the correlation between the light reception distance and the light diffraction. The distance between the light emitting element and the light receiving element becomes longer as the number of nozzles increases so that all the nozzles in the nozzle array can be accommodated on the optical path of the detection light formed between them, and the space for the detection mechanism is reduced. From the viewpoint of achieving the above, the shadow of the ink droplets ejected from the nozzles close to the light emitting element is easily affected by light diffraction while being arranged as close as possible to fit the nozzle row. It becomes difficult to accurately capture shadows. In particular, since the LED emits divergent light, the latter problem is remarkable when the LED is used as a light emitting element.

  In such a case, if the reference potential to be compared with the detection output is set according to the assumed minimum level of the detection output, it is likely to be affected by noise, and accurate detection becomes difficult. On the other hand, if the reference potential is set large in order to avoid the problem of noise, there is a problem that detection errors cannot be dealt with and detection errors increase.

  As described above, the detection output from the light receiving element is not constant for all nozzles and always fluctuates due to environmental conditions and necessary factors, so that it is difficult to accurately detect ink droplets at all nozzles.

  Conventionally, in order to cope with such a problem, in Patent Document 1, two sets of light emitting elements and light receiving elements are provided, and the detection lights are arranged in parallel so that their emission directions are opposite to each other. By stopping each half of the nozzles near the light emitting element in each nozzle row and ejecting ink droplets for each half of the nozzles near the light receiving element whose detection output is higher than a predetermined threshold, A technique for performing detection that is not affected by light diffraction is disclosed.

Further, in Patent Document 2, before detecting an ink droplet, the output signal output from the output signal terminal of the light receiving element is detected while changing the voltage of the variable voltage signal supplied to the gain adjustment terminal of the light receiving element, In accordance with the relationship between the voltage of the variable voltage signal and the output signal, the voltage of the variable voltage signal is set to an appropriate level suitable for detecting ink droplets, so that ink droplets can be reliably detected even when environmental changes occur. Technology is disclosed.
Japanese Patent Laid-Open No. 10-119307 JP 2001-113709 A

  The technique described in Patent Document 1 does not cope with environmental factors, and therefore cannot cope with environmental fluctuations, and it is difficult to always perform accurate detection. In addition, two sets of light emitting elements and light receiving elements must be provided, and there is a problem of increase in size and cost due to a complicated detection mechanism.

  On the other hand, in the technique described in Patent Document 2, since the gain of the light receiving element is only adjusted to an appropriate level in the non-ejection state before the ink droplet is detected, there is a problem of environmental fluctuation during the actual ejection, The variation due to the distance of the ink droplet from the light emitting part or the light receiving part cannot be dealt with at all.

  Therefore, the present invention provides a microdroplet detection apparatus, microfluidic, which can appropriately detect droplets using light even when output fluctuations occur due to fluctuation factors such as environmental fluctuations during droplet detection. It is an object of the present invention to provide a droplet detection method and an ink jet recording apparatus.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

The invention according to claim 1 is a light-emitting unit that emits detection light so as to cross the trajectory of a micro droplet discharged from each nozzle of a nozzle row in which a plurality of nozzles are arranged,
A light receiving portion for receiving the detection light;
Discharge control means for sequentially discharging minute droplets from all the nozzles toward the detection light in time series;
A detection device for detecting a microdroplet comprising a detection unit that compares a detection output output from the light receiving unit with a comparison reference potential and detects whether or not the microdroplet has detected light passing through the comparison result. And
The detection unit includes an amplitude measurement unit that measures the amplitude of the detection output output from the light receiving unit, and adds or subtracts the measurement result in the amplitude measurement unit to the comparison reference potential, and the addition or subtraction A microdroplet detection apparatus, wherein a comparison reference potential is compared with the detection output.

  According to a second aspect of the present invention, the discharge control means discharges a dummy liquid droplet prior to the discharge of the detection liquid droplet from the first nozzle. This is a detection device.

  The invention according to claim 3 is characterized in that the detection unit includes an amplitude limiting unit that limits a measurement result of the amplitude measuring unit to be added to or subtracted from the comparison reference potential within a certain level. Or it is a microdroplet detection apparatus of 2 description.

  According to a fourth aspect of the present invention, there is provided a light emitting unit that emits detection light so as to intersect with a trajectory of a minute droplet ejected from each nozzle of a nozzle row in which a plurality of nozzles are arranged, and a light receiving unit that receives the detection light. Comparing the detection output output from the light receiving unit with the comparison reference potential, and the discharge control means for sequentially controlling the liquid droplets in time series from all the nozzles toward the detection light. From the result, a detection device for detecting a microdroplet comprising a detection unit for detecting whether or not the microdroplet has passed through the detection light, wherein the detection unit determines the amplitude of the detection output output from the light receiving unit. Detecting a microdroplet having an amplitude measurement unit for measuring, and feeding back the amplification degree of the detection output from the measurement result in the amplitude measurement unit so that the amplitude of the detection output becomes a constant level Device.

  The invention according to claim 5 is characterized in that the discharge control means discharges a dummy droplet corresponding to the delay time required for the feedback prior to the discharge of the detection droplet from the first nozzle. The microdroplet detection device according to claim 4.

  The invention according to claim 6 is characterized in that the detection unit includes an amplitude limiting unit that limits a measurement result of the amplitude measuring unit fed back to the amplification unit within a certain level. This is a detection device for micro droplets.

  The invention according to claim 7 is characterized in that the discharge control means sequentially discharges the liquid droplets from a nozzle closer to the light emitting portion when detecting the liquid droplets. This is a detection device for micro droplets.

  The invention according to claim 8 is characterized in that the detection unit has switching means for switching the output of the measurement result in the amplitude measurement unit to a constant potential prior to the detection of the droplet. A device for detecting microdroplets according to claim 1.

The invention according to claim 9 forms detection light between the light emitting unit and the light receiving unit so as to intersect with the trajectory of the micro droplets discharged from each nozzle of the nozzle row in which a plurality of nozzles are arranged,
While controlling the ejection of minute droplets sequentially from all the nozzles toward the detection light in a time series, the detection output output from the light receiving unit is compared with a comparison reference potential,
From the comparison result, a detection method for detecting the presence or absence of detection light passing through the microdroplet,
The amplitude of the detection output output from the light receiving unit is measured, the measurement result of the amplitude is added to or subtracted from the comparison reference potential, and the added or subtracted comparison reference potential is compared with the detection output. It is the detection method of the micro droplet.

  The invention described in claim 10 is the method of detecting a micro droplet according to claim 9, wherein the dummy droplet is discharged prior to the discharge of the detection droplet from the first nozzle.

  The invention according to claim 11 is characterized in that, when the measurement result of the amplitude is added to or subtracted from the comparison reference potential, the measurement result to be added or subtracted is limited within a certain level. It is the detection method of the micro droplet described.

  The invention according to claim 12 forms the detection light between the light emitting part and the light receiving part so as to intersect with the trajectory of the micro droplets ejected from each nozzle of the nozzle row in which a plurality of nozzles are arranged. The droplets are sequentially ejected from the nozzle toward the detection light in a time-series manner, and the detection output output from the light receiving unit is compared with a comparison reference potential. A detection method for detecting the presence or absence of passage of detection light, wherein the amplitude of the detection output output from the light receiving unit is measured, and the measurement result of the amplitude measurement is used so that the amplitude of the detection output becomes a constant level. A method of detecting a micro droplet is characterized in that feedback is applied to the amplification degree of the detection output.

  According to a thirteenth aspect of the present invention, prior to the discharge of the detection droplet from the first nozzle, a dummy droplet corresponding to the delay time required for the return is discharged. This is a method for detecting microdroplets.

  According to a fourteenth aspect of the present invention, when the measurement result of the amplitude measurement is fed back to the amplifying unit, the measurement result is limited within a certain level. It is a detection method.

  According to a fifteenth aspect of the present invention, at the time of detecting a liquid droplet, the liquid droplets are sequentially ejected from a nozzle closer to the light emitting unit. Is the method.

  The invention according to claim 16 is characterized in that the output of the measurement result of the amplitude measurement is switched to a constant potential prior to the detection of the droplet, and the method of detecting a micro droplet according to any one of claims 9 to 15 It is.

  The invention described in claim 17 includes the recording head having a nozzle row in which a plurality of nozzles each discharging ink droplets are arranged, and the micro droplet detection device according to any one of claims 1 to 8. This is an ink jet recording apparatus.

  According to the present invention, even when an output fluctuation occurs due to a variation factor such as an environmental fluctuation at the time of detecting a liquid droplet, a micro liquid droplet detection apparatus and a micro liquid that can appropriately detect a liquid droplet using light. A droplet detection method and an ink jet recording apparatus can be provided.

Main part perspective view showing an ink jet recording apparatus The figure explaining the detection operation of the ink droplet by an ink droplet detection apparatus Block diagram showing an example of the internal configuration of the main part of the inkjet recording apparatus Timing chart of each signal at the time of ink droplet detection operation in the ink jet recording apparatus shown in FIG. The block diagram which shows another example of the internal structure of the principal part of an inkjet recording device Timing chart of each signal at the time of ink droplet detection operation in the ink jet recording apparatus shown in FIG. FIG. 3 is a block diagram illustrating an example of a configuration of a main part of a detection unit provided with an amplitude limiting unit in the ink jet recording apparatus illustrated in FIGS. Timing chart of each signal at the time of ink droplet detection operation in the ink jet recording apparatus shown in FIG. Block diagram showing still another example of the internal configuration of the main part of the ink jet recording apparatus Timing chart of each signal at the time of ink droplet detection operation in the ink jet recording apparatus shown in FIG. The block diagram which shows an example of a structure of the principal part of the detection part which provided the amplitude limiting part in the inkjet recording device shown in FIG. Block diagram showing still another example of the internal configuration of the main part of the ink jet recording apparatus Timing chart of each signal at the time of ink droplet detection operation in the ink jet recording apparatus shown in FIG. FIG. 9A is a block diagram illustrating an example of a configuration of a main part of a detection unit provided with a changeover switch in the ink jet recording apparatus illustrated in FIG. 9, and FIG. 11B illustrates a changeover switch provided in the ink jet recording apparatus illustrated in FIG. 11. The block diagram which shows an example of a structure of the principal part of a detection part

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a main part showing an ink jet recording apparatus, and FIG. 2 is a diagram for explaining an ink drop detection operation by an ink drop detection apparatus.

  In FIG. 1, there is one recording head, which is composed of four heads 1 a to 1 d that eject inks of different colors, for example, four colors of YMCK, and are mounted on a common carriage 2. . The carriage 2 is provided so as to be slidable along two parallel guide rails 3 extending in the main scanning direction indicated by A in the figure, and slides along the guide rails 3 by driving a main scanning motor (not shown). Then, it reciprocates at a predetermined speed along the main scanning direction A.

  A conveyor belt 4 is disposed below the carriage 2. The conveyor belt 4 is stretched between two conveyor rollers 4a and 4b arranged at a predetermined interval in the sub-scanning direction indicated by B in the figure. A sub-scanning motor (not shown) is connected to one of the transport rollers 4b so as to be able to transmit a driving force. The sub-scan motor is driven to rotate, so that the transport belt 4 is rotated and placed on the transport belt 4. A recording medium P such as paper, plastic film, cloth or the like is conveyed along the sub-scanning direction B at a predetermined speed.

  In FIG. 1, reference numeral 5 denotes an ink droplet detection device, which is a light emitting unit 51 using a light emitting element (LED), a light receiving unit 52 using a light receiving element (photodiode), and a speed between the light emitting unit 51 and the light receiving unit 52. An ink tray 53 for receiving ink droplets ejected at the time of detection is provided, and these are arranged corresponding to the non-printing position where the carriage 2 is removed from the recording medium P. Here, the ink droplet detection device 5 has a set of light emitting unit 51 and light receiving unit 52 for the four heads 1a to 1d, and performs detection for each of the heads 1a to 1d. However, the number of sets of the light emitting units 51 and the light receiving units 52 may be the same as the number of the heads 1a to 1d.

  In the ink droplet detection device 5, the light emitting unit 51 emits detection light L for detecting the passage of the ink droplet I ejected from each nozzle 11 of the recording head 1 as shown in FIG. 2. The light receiving unit 52 receives the detection light L emitted from the light emitting unit 51. The optical axis of the detection light L is perpendicular to the main scanning direction A of the recording head 1 and is parallel to the arrangement direction of the nozzles 11 of each of the heads 1a to 1d, and the height position along the ejection direction of the ink droplet I Is emitted at a position lower than the position of the nozzle surface 12 of each of the heads 1a to 1d. Thereby, when any nozzle row of the heads 1 a to 1 d is positioned on the optical axis of the detection light L, the flight trajectory of the ink droplet I ejected from the nozzle 11 intersects with the detection light L. Therefore, when the ink droplet I is ejected toward the detection light L by outputting an ejection signal to each nozzle 11, the ejected ink droplet I passes through the detection light L, and the shadow at that time is a light receiving portion. 52.

  FIG. 3 is a block diagram illustrating an example of an internal configuration of a main part of the ink jet recording apparatus.

  In the ink jet recording apparatus, the controller CPU 100 drives a main scanning motor (not shown) to move the carriage 2 along the main scanning direction A, and the controller CPU 100 drives the recording head 1 in the process of this movement. Is driven from the recording head 1 to the recording medium P stopped on the conveying belt 4 by being driven at a predetermined timing and a predetermined driving condition in accordance with image data sent from an image memory (not shown). The droplet I is discharged. The driving circuit 101 is provided for each of the heads 1 a to 1 d of the recording head 1.

  When one main scan of the carriage 2 is completed, the controller CPU 100 drives a sub-scan motor (not shown) to rotate the transport roller 4b, intermittently rotates the transport belt 4 to transport the recording medium P by a predetermined amount, By repeating the operation of performing the next main scanning in the same manner as described above, an image corresponding to the image data is recorded on the recording medium P.

  At the time of printing, the controller CPU 100 drives a main scanning motor and a sub scanning motor (not shown) to control the movement of the carriage 2 and the recording medium P, and outputs the ejection signal Fire to the driving circuit 101 to control the driving of the recording head 1. . The control of the recording head 1 controls the ejection of the ink droplets I according to the image data, and in addition to the ink droplet detection device 5, the ink droplets I are sequentially and time-sequentially detected from all the nozzles constituting the nozzle row. Control is performed so that ink droplets I are discharged or ink droplets I are simultaneously discharged (preliminary discharge) from all nozzles.

  Further, the controller CPU 100 controls the lighting of the light emitting unit 51 so as to detect the ink droplet I using the ink droplet detection device 5. The light emitting unit 51 emits the detection light L by driving the LED driving unit 102 controlled by the controller CPU 100, and the emitted detection light L is received by the light receiving unit 52, and the detection signal at that time is received by the current amplification unit 103. Amplified. The LED driving unit 102 controls driving of the light emitting unit 51 by feeding back an output signal from the current amplification unit 103.

  When the ink droplet I ejected from the recording head 1 through the application of the ejection signal Fire passes through the detection light L, the detection signal received by the light receiving unit 52 is further amplified by the amplifying unit 104 to detect the presence or absence of the ink droplet. Sent to the department. The detection unit compares the received light signal amplified by the amplifying unit 104 with a comparison reference potential ref, and outputs a defect-out signal indicating that there is a received light signal when the received light signal exceeds the comparison reference potential ref; An amplitude measuring unit 106 that measures the amplitude of the signal amplified by the amplifying unit 104 and detects its envelope, and an output signal from the amplitude measuring unit 106 is used as a constant comparison reference potential supplied from the reference potential supplying unit 108. An adder / subtractor 107 for adding or subtracting to / from is provided. When the comparison unit 105 detects a signal having an amplitude exceeding the comparison reference potential ref by comparing the comparison reference potential ref output from the addition / subtraction unit 107 with the detection signal output from the amplification unit 104. When the ink droplet I is detected, a defect-out signal is output to the controller CPU 100.

  Here, the constant comparison reference potential supplied from the reference potential supply unit 108 can be set to about 0.2 V, for example.

  The controller CPU 100 detects the ejection state of the ink droplet I based on the application of the ejection signal Fire and the defect-out signal. For example, whether or not the ink droplet I is ejected from the nozzle can be detected based on the presence or absence of the defect-out signal after the ejection signal Fire is applied to the nozzle. Further, for example, the ejection speed of the ink droplet I from the nozzle can be detected based on the application timing of the ejection signal Fire to the nozzle and the detection timing of the defect-out signal.

  Next, the operation of detecting the ink droplet I by the ink droplet detection device 5 in this ink jet recording apparatus will be described. FIG. 4 shows a timing chart of each signal during the detection operation.

  First, the controller CPU 100 controls the LED driving unit 102 to turn on the light emitting unit 51, forms detection light L between the light receiving unit 52, and further drives a main scanning motor (not shown) to move the carriage 2. Thus, the recording head 1 is moved to the non-printing area along the main scanning direction A, and one of the nozzle rows to be detected is positioned on the detection light L and stopped. In this state, the controller CPU 100 outputs the ejection signal Fire to the nozzle row to be detected, controls the corresponding drive circuit 101 with a predetermined voltage setting, and ejects the ink droplet I from the nozzle.

  Here, the detection of the ink droplet I is sequentially performed in time series from the nozzle No. 1 closest to the light emitting unit 51 in one nozzle row. In addition, the ejection of the ink droplet I controls the ejection signal Fire so as to continuously eject a plurality of ink droplets I per nozzle. In this way, when the continuously ejected ink droplets I pass the detection light L, the light receiving unit 52 can catch them as a shadow of one large droplet, and each droplet is extremely small. Even if it exists, the passage of the ink droplet I can be reliably detected by the light receiving unit 52.

  When the ink droplets I are sequentially ejected from nozzle No. 1 in the nozzle row in time series, the ink droplets I pass through the detection light L, the shadow at that time is captured by the light receiving unit 52, and the light reception signal is amplified. Amplified by the unit 104. Here, the light reception signal a output from the amplifying unit 104 receives the ink droplet I ejected from the nozzle No. 1 closest to the light emitting unit 51 as shown in FIG. 4 due to the influence of light diffraction and light divergence. The signal has a small amplitude and gradually increases as the nozzle moves away from the light emitting unit 51. Nozzle No. 7 is in a state in which a normal light reception signal is not obtained due to a missing nozzle or a discharge bend even though the discharge signal is applied.

  The light reception signal a output from the amplifying unit 104 is sent to the amplitude measuring unit 106. In the amplitude measuring unit 106, the amplitude of the received light signal a is measured in the envelope detecting unit 106a, the envelope as the measurement result is detected, and the envelope detection signal b shown in FIG. 4 is output. The envelope detection signal b output from the amplitude measurement unit 106 is sent to the addition / subtraction unit 107 where it is added or subtracted with the comparison reference potential c supplied from the reference potential supply unit 108. Here, since the circuit configuration is such that the potential decreases when the amplitude of the light reception signal a is high, the comparison reference potential c is subtracted from the detection signal b of the envelope.

  As a result of subtracting the comparison reference potential c from the envelope detection signal b in the addition / subtraction unit 107, a comparison reference potential ref shown in FIG. 4 is generated. The comparison reference potential ref generated by the adder / subtractor 107 in this manner is sent to the comparator 105, and the light receiving signal a output from the amplifier 104 is compared with the comparison signal sent from the adder / subtractor 107. Compare with reference potential ref.

  That is, as a result of comparing the light reception signal a with the comparison reference potential ref, the comparison unit 105 detects the presence or absence of a signal in which the light reception signal a exceeds the level of the comparison reference potential ref. When the comparison unit 105 detects a signal in which the light reception signal a exceeds the level of the comparison reference potential ref, the ink drop I is detected and a defect-out signal shown in FIG. Here, the comparison reference potential ref to be compared with the light reception signal a is a potential reflecting the amplitude of the light reception signal a amplified in the amplification unit 104, and therefore, the light reception signal a is caused by a variation factor such as light diffraction. Even if output fluctuation occurs, accurate detection that is not affected by the output fluctuation can be performed by comparing with the comparison reference potential ref.

  In addition, as shown in FIG. 4, with respect to nozzle No. 1 which is the first nozzle when ink droplet I is detected, ejection of ink droplet I is compared to other nozzles (a plurality of continuous droplets are grouped together). Discharge) is performed twice at a predetermined interval. In this case, the first ejection is ejection of dummy ink droplets, and the second ejection is ejection for detection. This is because the light reception signal a is compared with the comparison reference potential ref generated by reflecting the amplitude of the light reception signal a itself through the amplitude measuring unit 106, and therefore, the comparison reference potential ref is generated compared to the light reception signal a. This is because a slight delay occurs, and the received light signal a from the first nozzle No. 1 cannot be compared with the comparison reference potential ref, making accurate detection difficult. In this way, by discharging the dummy ink droplets prior to detection, the first reference nozzle No. 1 is detected (at the second discharge from nozzle No. 1) and compared with the comparison reference potential ref. It becomes possible.

  FIG. 5 is a block diagram showing another example of the internal configuration of the main part of the ink jet recording apparatus, and FIG. 6 shows a timing chart of each signal during the detection operation. In the block diagram of FIG. 5, the same reference numerals as those in FIG. 3 indicate the same configurations, and detailed descriptions thereof are omitted.

  In this ink jet recording apparatus, a comparison reference potential c as shown in FIG. 6 that is subtracted from the envelope detection signal b in the adder / subtractor 107 is applied to the received light signal a output from the amplifier 104 with a low-pass filter 109. Is generated. Also in this case, the comparison reference potential ref to be compared with the light reception signal a in the comparison unit 105 is a potential reflecting the amplitude of the light reception signal a amplified in the amplification unit 104. Therefore, even if the output fluctuation occurs in the light reception signal a, by comparing with the comparison reference potential ref, accurate detection that is not affected by the output fluctuation becomes possible.

  In this case, since the average potential of the detection output from the amplifying unit 104 is the output of the low-pass filter 109 as compared with the mode shown in FIG. 3, the reference potential shown in FIG. There is an effect that it is not necessary to adjust the supply unit 108.

  Note that the light reception signal from the light receiving unit 52 may be subject to extreme fluctuations due to factors such as being affected by noise such as disturbance light and reflected light. As a result, the envelope that is the measurement result of the amplitude measuring unit 106 is generated. The line detection signal b may be smaller or larger than a certain level. In the inkjet recording apparatus having the configuration shown in FIGS. 3 and 5, the comparison reference potential ref for comparison with the light reception signal a in the comparison unit 105 is input to the comparison unit 105 with a delay from the light reception signal a. Therefore, in such a case, if the addition / subtraction unit 107 directly adds or subtracts the envelope detection signal b with the comparison reference signal c, the comparison unit 105 compares the received light signal a with the comparison reference signal ref. There is a problem of false detection such as a defect-out signal is not output even though a normal light reception signal is output, or a defect-out signal is output even though an abnormal light reception signal is output. There is a fear.

  For this reason, in the ink jet recording apparatus having the configuration shown in FIGS. 3 and 5, when the envelope detection signal b, which is the measurement result of the amplitude measuring unit 106, is smaller or larger than a certain level, the certain level It is preferable that the addition / subtraction unit 107 does not add or subtract portions that are smaller or larger than.

  An example of the configuration of the main part of the detection unit for this purpose is shown in FIG. Here, an amplitude limiting unit 110 that limits the detection signal output from the amplitude measuring unit 106 to a potential within a certain range is provided at the subsequent stage of the amplitude measuring unit 106, as shown in FIG. And different from that shown in FIG. That is, after detecting the envelope of the received light signal a output from the amplification unit 104 (see FIGS. 3 and 5) in the amplitude measurement unit 106, the amplitude limiter 110 detects a constant potential with respect to the detection signal b ′. The envelope detection signal b output to the adder / subtractor 107 is set to be within a certain level by limiting the small or large portion beyond the limit.

  FIG. 8 is a timing chart showing the relationship between the light reception signal a output from the amplification unit 104 and the envelope detection signal b output from the amplitude limiting unit 110. Here, a case is shown in which the amplitude of the light reception signal a at nozzle No. n is extremely large beyond a certain potential due to the influence of noise or the like. At this time, the envelope detection signal b ′ output from the amplitude measurement unit 106 greatly exceeds a certain potential as shown by the dotted line, but the envelope detection signal b ′ in the amplitude limiter 110 at the next stage. , The envelope detection signal b as shown by a solid line is output to the adder / subtractor 107, and an extremely large amplitude portion in the light reception signal a is added or subtracted. Not subtracted. Therefore, it is possible to avoid the problem of erroneous detection due to the influence of noise or the like.

  The constant potential when the amplitude limiter 110 limits the envelope detection signal b 'can be set to, for example, 0.2V for the lower one and 1.0V for the higher one.

  FIG. 9 is a block diagram showing still another example of the internal configuration of the main part of the ink jet recording apparatus, and FIG. 10 shows a timing chart of each signal during the detection operation. In the block diagram of FIG. 9, the same reference numerals as those in FIGS. 3 and 5 indicate the same configuration, and detailed description thereof will be omitted.

  In this ink jet recording apparatus, the light reception signal a received by the light receiving unit 52 and amplified by the amplification unit 111 is sent to the comparison unit 105 and compared with the comparison reference potential ref generated through the low-pass filter 109. It has become. On the other hand, the amplitude measurement unit 106 generates an envelope detection signal b from the light reception signal a output from the amplification unit 111, and feeds back the envelope detection signal b to the amplification unit 111 again.

  The feedback of the envelope detection signal b to the amplification unit 111 is feedback so that the amplitude of the light reception signal a output from the amplification unit 111 is constant, and the envelope detection signal b is fed back. In the amplifying unit 111, a small amplitude increases the amplification degree, and a large amplitude reduces the amplification degree, thereby amplifying the light according to the amplitude of the light reception signal received by the light receiving unit 52 and outputting the received light reception signal. The amplitude of a is made constant as shown by the dotted line in FIG.

  Therefore, the comparison unit 105 compares the light reception signal a amplified by the amplification unit 111 so that the amplitude is constant and the comparison reference potential ref generated through the low-pass filter 109 based on the light reception signal a. Therefore, even if the output fluctuation occurs in the light reception signal a, the amplitude of the light reception signal a is constant, and accurate detection can be performed without being affected by the output fluctuation.

  Here, as shown in FIG. 10, since the amplitude of the received light signal is small due to the effects of light diffraction and light divergence, the envelope from the amplitude measuring unit 106 is detected for the nozzle near the light emitting unit 51 at the initial detection stage. Due to the delay time required for feedback of the line detection signal b, it takes time until the light reception signal for the nozzle in the initial detection stage becomes constant. For this reason, dummy discharge is repeatedly performed (three times in the example shown in FIG. 10) for the first nozzle No. 1 for a predetermined time. The predetermined time is a time comparable to the delay time (pull-in time) required for the light reception signal a output from the amplifying unit 110 to be fed back to the amplifying unit 111 and the amplitude to be constant.

  By the dummy ejection from nozzle No. 1 repeated for a predetermined time, the light reception signal received by the light receiving unit 52 is amplified by the amplification unit 111, and the envelope detection signal b generated by the amplitude measurement unit 106 is further generated. By returning to the amplifying unit 111, the amplitude of the light reception signal a from the nozzle No. 1 output from the amplifying unit 111 is made constant over time. Therefore, stable detection is possible even with detection from nozzle No. 1 where the amplitude of the received light signal is small due to the influence of light diffraction or the like.

  Even in the ink jet recording apparatus having the configuration shown in FIG. 9, the light reception signal from the light receiving unit 52 may be subject to extreme fluctuations due to factors such as being affected by noise such as disturbance light and reflected light. Thus, there may occur a case where the envelope detection signal b, which is the measurement result of the amplitude measuring unit 106, becomes smaller or larger than a certain level. Also in the ink jet recording apparatus having the configuration shown in FIG. 9, the comparison reference potential ref for comparison with the light reception signal a in the comparison unit 105 is input to the comparison unit 105 with a delay from the light reception signal a. In such a case, if the amplification unit 111 performs amplification based on the envelope detection signal b as it is, when the light reception signal a is compared with the comparison reference signal ref in the comparison unit 105, a normal light reception signal is obtained. There is a possibility that a defect-out signal may not be output even though is output, or a false detection problem such as a defect-out signal being output even though an abnormal received light signal is output. The

  Therefore, even in the ink jet recording apparatus having the configuration shown in FIG. 9, when the detection signal b of the envelope, which is the measurement result of the amplitude measuring unit 106, is smaller or larger than a certain level, the certain level is exceeded. It is preferable that the small or large portion is not returned to the amplification unit 111.

  An example of the configuration of the main part of the detection unit for this purpose is shown in FIG. Here, an amplitude limiting unit 110 that limits the detection signal output from the amplitude measuring unit 106 to a potential within a certain range is provided at the subsequent stage of the amplitude measuring unit 106, as shown in FIG. It is different from what is shown in. That is, after detecting the envelope of the received light signal a output from the amplifying unit 111 in the amplitude measuring unit 106, the amplitude limiting unit 112 detects a small or large portion exceeding a certain potential with respect to the detection signal b ′. The envelope detection signal b fed back to the amplifier 111 is within a certain level.

  In this case, from the amplitude limiting unit 112, even when the envelope detection signal b ′ output from the amplitude measuring unit 106 greatly exceeds a certain potential as shown by the dotted line, as shown in FIG. In the next-stage amplitude limiting unit 112, the envelope detection signal b ′ is limited so as to be within a certain potential, so that the envelope detection signal b as shown by a solid line is output to the amplification unit 111. Then, an extremely large amplitude portion in the light reception signal a is not fed back to the amplification unit 111. Therefore, it is possible to avoid the problem of erroneous detection due to the influence of noise or the like.

  The constant potential when the amplitude limiter 112 limits the envelope detection signal b 'can be set, for example, to 0.2V for the lower one and 1.0V for the higher one.

  FIG. 12 is a block diagram showing still another example of the internal configuration of the main part of the ink jet recording apparatus, and FIG. 13 shows a timing chart of each signal during the detection operation. In the block diagram of FIG. 12, the same reference numerals as those in FIGS. 3 and 5 indicate the same configuration, and detailed description thereof will be omitted.

  This inkjet recording apparatus is an inkjet recording apparatus configured as shown in FIG. 5 for switching the output of the envelope detection signal b from the amplitude measuring unit 106 to the addition / subtraction unit 107 to a constant potential (V-level). A changeover switch 113 is provided. The constant potential here is a potential at a level where the light emitting unit 51 is lit but the light receiving unit 52 does not capture the shadow of the ink droplet I. Here, the selector switch 113 includes a selector switch 113a that switches the output from the amplitude measurement unit 106 to a constant potential, and a selector switch 113b that switches the output from the low-pass filter 109 to a constant potential. On / off control can be performed by a reset signal RST from the controller CPU 100.

  This changeover switch 113 is effective in the following cases. For example, after the light emitting unit 51 is turned on, as shown in FIG. 13, prior to the ink droplet I detecting operation, a predetermined number of ink droplets are ejected from all the nozzles, and preliminary ejection is performed to homogenize all the nozzles. In this case, the shade of the ink droplet I due to the preliminary ejection is captured by the light receiving unit 52, so that the light receiving signal a related to the preliminary ejection is output from the amplifying unit 104, and the preliminary amplitude measuring unit 106 and the addition / subtraction unit 107 Processing based on the received light signal a related to ejection is also executed. As a result, the comparison reference potential ref output from the addition / subtraction unit 107 to the comparison unit 105 reflects the amplitude of the light reception signal a related to the preliminary ejection, and at the time of detection from the nozzle No. 1 executed after this preliminary ejection. There is a risk of false detection. The same problem of output fluctuation of the light receiving unit 52 before detection is not limited to the case of performing preliminary ejection, but when the light receiving unit 52 receives a signal at the time of the lighting operation of the light emitting unit 51 or when disturbing light is detected before detection. This also occurs when light is received.

  The controller CPU 100 outputs the reset signal RST to the change-over switch 113 to turn on the change-over switch 113 before discharging the ink droplet I from the nozzle No. 1 which is the first nozzle to perform detection, and the addition / subtraction unit The output of the envelope detection signal b from the amplitude measuring unit 106 input to the 107 is set to a constant potential (V-level). As a result, as shown in FIG. 13, the output of the envelope detection signal b from the amplitude measuring unit 106 input to the adder / subtractor 107 is set to a constant potential (V-level) by the rising edge of the reset signal RST. The signal a is not affected by the preliminary ejection, and similarly, the output from the amplitude measuring unit 106 before detection is also maintained at a constant potential (V-level).

  Thereafter, the changeover switch 113 is restored by the falling edge of the reset signal RST, and only the output of the envelope detection signal b from the amplitude measuring unit 106 can be input to the adder / subtractor 107.

  Therefore, the influence of the output fluctuation of the light receiving unit 52 before detection can be eliminated, and detection from the nozzle No. 1 which is the first nozzle at the time of detection can be stably performed.

  The changeover switch 113 can be applied to the preceding stage of the adder / subtractor 107 in the same manner in the case of each inkjet recording apparatus having the configuration shown in FIGS. 3 and 7.

  In the case of the ink jet recording apparatus having the configuration shown in FIG. 9, as shown in FIG. 14A, and in the case of the ink jet recording apparatus having the configuration shown in FIG. 11, as shown in FIG. A changeover switch 114 may be provided in each stage before the detection signal b of the envelope output via the amplitude measuring unit 106 is input to the amplifying unit 111. The changeover switch 114 uses the reset signal RST from the controller CPU 100 to set the signal input to the amplifier 111 as the envelope detection signal b output via the amplitude measuring unit 106 or to a constant potential (V-level). The switching is controlled.

  In the case of FIG. 14B, the changeover switch 114 may be provided between the amplitude measuring unit 106 and the amplitude limiting unit 112.

  In the above description, the detection of the ink droplet I is performed from the nozzle closest to the light emitting unit 51, but conversely, the nozzle closest to the light emitting unit 51 sequentially from the nozzle closest to the light receiving unit 52. You may make it perform toward. In particular, as described above, when the process is performed from the nozzle closest to the light emitting unit 51, the light reception signal gradually increases and stabilizes as the nozzle moves away from the light emitting unit 51 due to the effects of light diffraction and light divergence. Therefore, it is preferable because it is possible to stably detect the envelope in the amplitude measurement unit 106 in the subsequent stage.

  The microdroplet detection apparatus and microdroplet detection method according to the present invention are not limited to those applied to the ink jet recording apparatus described above, and are ejected from each nozzle of a nozzle array in which a plurality of nozzles are arranged. The present invention can be widely applied to the case where the discharge state of micro droplets is detected using detection light formed between a light emitting unit and a light receiving unit.

1: Recording head 1a to 1d: Head 11: Nozzle 12: Nozzle surface 2: Carriage 3: Guide rail 4: Transport belt 4a, 4b: Transport roller 5: Ink drop detection device 51: Light emitting unit 52: Light receiving unit 53: Ink Sauce pan 100: Controller CPU
DESCRIPTION OF SYMBOLS 101: Drive circuit 102: LED drive part 103: Current amplification part 104: Amplification part 105: Comparison part 106: Amplitude measurement part 107: Addition / subtraction part 108: Reference potential supply part 109: Low-pass filter 110: Amplitude restriction part 111: Amplification Part 112: Amplitude limiting part 113, 114: Changeover switch

The present invention relates to a droplet detection device, a droplet detection method, and an ink jet recording apparatus, and more specifically, regardless of various conditions such as droplet size, flight state, circuit temperature characteristics, distance from a light emitting unit, and the like. detection device of droplets can be stably detected, for the detection method and an ink jet recording apparatus of the droplet.

The present invention, even when the output fluctuation by the fluctuation factors environmental fluctuation during drop detection occurs, the detection device of droplets which can appropriately perform detection of droplets using light, the droplet It is an object to provide a detection method and an ink jet recording apparatus.

The invention according to claim 1 is a light emitting unit that emits detection light that intersects with the trajectory of droplets ejected from each nozzle of a nozzle row in which a plurality of nozzles are arranged and is affected by light diffraction or light divergence ;
A light receiving portion for receiving the detection light;
A discharge control unit that sequentially discharges droplets in time-series from all the nozzles including a plurality of nozzles having different distances from the light emitting unit toward the detection light;
Compared comparison reference potential detection output outputted from the light receiving portion, from the comparison result, a detection device of a droplet comprising a detector for detecting the presence or absence of the detection light passing the droplets,
The detection unit is an amplitude that measures a relatively small detection output amplitude at a nozzle close to the light emitting unit output from the light receiving unit and a relatively large detection output at a distant nozzle by detecting whether or not the detection light passes through the droplet. A measurement unit is included, and the measurement result in the amplitude measurement unit is added to or subtracted from the comparison reference potential, and the addition or subtraction reflecting the amplitude of the detection output itself output from the light receiving unit by the addition or subtraction. The liquid droplet detection apparatus is characterized in that a comparison reference potential is compared with the detection output.

According to a second aspect of the invention, the discharge control means, prior to the discharge of the detection of droplets from the first nozzle, have rows ejection of dummy droplet,
The detection unit adds or subtracts the measurement result in the amplitude measurement unit of the amplitude of the detection output when the dummy droplet passes through the detection light to the comparison reference potential, and compares the addition or subtraction 2. The droplet detection device according to claim 1 , wherein a reference potential is compared with the detection output when the droplet discharged from the first nozzle passes the detection light .

The invention according to claim 3 is characterized in that the detection unit includes an amplitude limiting unit that limits a measurement result of the amplitude measuring unit to be added to or subtracted from the comparison reference potential within a certain level. Or it is a droplet detection apparatus of 2 description.

Invention of claim 4, wherein said discharge control means, upon detection of the droplet, the liquid of claim 1, 2 or 3, wherein the discharging sequentially droplets from the side of the nozzle close to the light emitting portion It is a drop detection device.

According to a fifth aspect of the invention, the detector is either prior to the detection of droplets, according to claim 1-4, characterized in that it comprises a switching means for switching the output of the measurement results in the amplitude measurement section at a constant potential A droplet detection apparatus according to claim 1.

According to the sixth aspect of the present invention, there is an effect of light diffraction or light divergence between the light emitting unit and the light receiving unit so as to intersect with the trajectory of droplets ejected from each nozzle of a nozzle row in which a plurality of nozzles are arranged. the detection light to receive forms,
The droplets are sequentially ejected from all the nozzles including a plurality of nozzles having different distances from the light emitting unit toward the detection light in a time-series manner, and the detection output output from the light receiving unit is used as a comparison reference potential. Compare and
From the comparison result, a detection method for detecting the presence or absence of detection light passing through the droplet ,
A detection result of the amplitude is measured by measuring the amplitude of the detection output that is relatively small at the nozzle close to the light emitting unit output from the light receiving unit by detecting whether the detection light passes through the droplet, and relatively large at the far nozzle. Is added to or subtracted from the comparison reference potential, and the added or subtracted comparison reference potential reflecting the amplitude of the detection output itself output from the light receiving unit by the addition or subtraction is compared with the detection output. This is a characteristic droplet detection method.

According to the seventh aspect of the invention, prior to the discharge of the detection droplet from the first nozzle, a dummy droplet is discharged, and the detection output when the dummy droplet passes the detection light is detected. The amplitude measurement result is added to or subtracted from the comparison reference potential, and the added or subtracted comparison reference potential is compared with the detection output when the droplet ejected from the first nozzle passes the detection light. The method of detecting a droplet according to claim 6 .

The invention of claim 8, wherein, at the time of adding or subtracting a measurement result of said amplitude to said comparison reference potential, according to claim 6 or 7, characterized in that to limit the measurement result to the addition or subtraction in a constant level It is the detection method of the described droplet .

The invention according to claim 9 is the droplet detection method according to claim 6 or 8 , wherein the droplets are sequentially ejected from a nozzle closer to the light emitting portion when the droplet is detected.

The invention of claim 10 wherein, prior to the detection of a droplet, in the method for detecting droplets of any of claims 6-9 which the output of the measurement results of amplitude measurement and switches to a constant potential is there.

The invention according to claim 11 is a recording head having a nozzle row in which a plurality of nozzles each ejecting ink droplets are arranged;
An ink jet recording apparatus characterized by comprising a detection device of the droplet according to any one of claims 1-5.

According to the present invention, even when the output fluctuation by the fluctuation factors environmental fluctuation during drop detection occurs, the detection device of droplets which can appropriately perform detection of droplets using light, the droplet A detection method and an ink jet recording apparatus can be provided.

The droplet detection apparatus and the droplet detection method according to the present invention are not limited to those applied to the ink jet recording apparatus described above, but are droplets ejected from each nozzle in a nozzle array in which a plurality of nozzles are arranged. Can be widely applied to the case where the discharge state is detected using detection light formed between the light emitting portion and the light receiving portion.

Claims (17)

A light emitting unit that emits detection light so as to intersect with the trajectory of a micro droplet discharged from each nozzle of a nozzle row in which a plurality of nozzles are arranged;
A light receiving portion for receiving the detection light;
Discharge control means for sequentially discharging minute droplets from all the nozzles toward the detection light in time series;
A detection device for detecting a microdroplet comprising a detection unit that compares a detection output output from the light receiving unit with a comparison reference potential and detects whether or not the microdroplet has detected light passing through the comparison result. And
The detection unit includes an amplitude measurement unit that measures the amplitude of the detection output output from the light receiving unit, and adds or subtracts the measurement result in the amplitude measurement unit to the comparison reference potential, and the addition or subtraction A device for detecting a microdroplet, wherein a comparison reference potential is compared with the detection output.   2. The micro droplet detection apparatus according to claim 1, wherein the ejection control unit ejects a dummy droplet prior to ejection of the detection droplet from the first nozzle.   3. The microdroplet according to claim 1, wherein the detection unit includes an amplitude limiting unit that limits a measurement result of the amplitude measuring unit to be added to or subtracted from the comparison reference potential within a certain level. Detection device. A light emitting unit that emits detection light so as to intersect with the trajectory of a micro droplet discharged from each nozzle of a nozzle row in which a plurality of nozzles are arranged;
A light receiving portion for receiving the detection light;
Discharge control means for sequentially discharging minute droplets from all the nozzles toward the detection light in time series;
A detection device for detecting a microdroplet comprising a detection unit that compares a detection output output from the light receiving unit with a comparison reference potential and detects whether or not the microdroplet has detected light passing through the comparison result. And
The detection unit includes an amplitude measurement unit that measures the amplitude of the detection output output from the light receiving unit, and the detection output is obtained from the measurement result of the amplitude measurement unit so that the amplitude of the detection output is at a constant level. A device for detecting microdroplets, wherein feedback is applied to the degree of amplification.   5. The micro liquid according to claim 4, wherein the ejection control unit ejects a dummy droplet corresponding to a delay time required for the feedback prior to ejection of the detection droplet from the first nozzle. Drop detection device.   6. The micro droplet detection device according to claim 4, wherein the detection unit includes an amplitude limiting unit that limits a measurement result of the amplitude measurement unit that feeds back to the amplification unit within a certain level.   6. The micro droplet detection apparatus according to claim 1, wherein the ejection control unit sequentially ejects droplets from a nozzle closer to the light emitting unit when detecting the droplets.   8. The microdroplet according to claim 1, wherein the detection unit includes switching means for switching an output of a measurement result from the amplitude measurement unit to a constant potential prior to detection of the droplet. Detection device. A detection light is formed between the light emitting unit and the light receiving unit so as to intersect with the trajectory of the micro droplet ejected from each nozzle of the nozzle row in which a plurality of nozzles are arranged,
While controlling the ejection of minute droplets sequentially from all the nozzles toward the detection light in a time series, the detection output output from the light receiving unit is compared with a comparison reference potential,
From the comparison result, a detection method for detecting the presence or absence of detection light passing through the microdroplet,
The amplitude of the detection output output from the light receiving unit is measured, the measurement result of the amplitude is added to or subtracted from the comparison reference potential, and the added or subtracted comparison reference potential is compared with the detection output. A method for detecting microdroplets.   10. The method for detecting micro droplets according to claim 9, wherein the dummy droplets are discharged prior to the discharge of the detection droplets from the first nozzle.   11. The method for detecting a microdroplet according to claim 9 or 10, wherein when adding or subtracting the amplitude measurement result to or from the comparison reference potential, the measurement result to be added or subtracted is limited to a certain level. . A detection light is formed between the light emitting unit and the light receiving unit so as to intersect with the trajectory of the micro droplet ejected from each nozzle of the nozzle row in which a plurality of nozzles are arranged,
While controlling the ejection of minute droplets sequentially from all the nozzles toward the detection light in a time series, the detection output output from the light receiving unit is compared with a comparison reference potential,
From the comparison result, a detection method for detecting the presence or absence of detection light passing through the microdroplet,
The amplitude of the detection output output from the light receiving unit is measured, and feedback is applied to the amplification degree of the detection output from the measurement result of the amplitude measurement so that the amplitude of the detection output becomes a constant level. Detection method of micro droplets.   13. The method for detecting micro droplets according to claim 12, wherein dummy droplets corresponding to the delay time required for the return are ejected prior to ejection of the detection droplets from the first nozzle.   14. The method of detecting a micro droplet according to claim 12, wherein when the measurement result of the amplitude measurement is fed back to the amplifying unit, the measurement result is limited to a certain level.   15. The method for detecting micro droplets according to claim 9, wherein when detecting the droplets, the droplets are sequentially ejected from a nozzle closer to the light emitting unit.   The method for detecting a micro droplet according to any one of claims 9 to 15, wherein the output of the measurement result of the amplitude measurement is switched to a constant potential prior to detecting the droplet. A recording head having a nozzle row in which a plurality of nozzles each ejecting ink droplets are arranged;
An ink jet recording apparatus comprising the microdroplet detection device according to claim 1.

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