JP4438555B2 - Droplet ejection state detection method - Google Patents

Description

  The present invention relates to a droplet discharge state detection method in an inkjet apparatus or the like.

  The ink jet apparatus ejects minute liquid droplets from fine nozzles formed on an ink jet head toward an application target such as recording paper, and is used for image recording. In an ink jet device, liquid adhesion such as non-ejection of droplets, change in droplet flying speed, change in droplet flying direction, etc. due to adhesion of dust to the nozzle surface, drying of the nozzle surface, increase in liquid viscosity, etc. Drop ejection may be abnormal. If the use of the ink jet device is continued while the droplet discharge state is abnormal, adverse effects such as inability to accurately record an image appear. Therefore, it is desirable to detect the ejection state and confirm that it is normal before using the ink jet device, and to deal with any abnormalities before using them.

  As a conventional technique for detecting non-ejection of a droplet in an inkjet device, for example, a pair of a light emitting element and a light receiving element is used, and a droplet is ejected so as to pass through a light beam emitted from the light emitting element and reaching the light receiving element. When a decrease in the amount of light received by the light receiving element is not detected, there is one that determines that a droplet is not ejected (see Patent Document 1).

  However, the technique disclosed in Patent Document 1 has a problem that it is merely possible to determine whether or not ink is ejected, and it cannot be determined whether or not the ink ejection state is normal.

  In another prior art, there has been proposed a method for detecting not only a non-ejection of a droplet but also an abnormality in a flying speed and a flying direction in a droplet ejection state (see Patent Document 2).

  In Patent Document 2, a plurality of pairs of light emitting devices that generate an optical beam and light receiving devices that receive the optical beam are provided in parallel, and droplets are ejected so as to sequentially pass through a plurality of light beams formed in parallel. In this case, the abnormality in the flying direction of the droplet is detected from the difference in the amount of light received by each light receiving device, and the flying of the droplet from the time difference that is the time difference at which each light receiving device detects a decrease in the amount of received light. Measure speed.

  However, in the technique disclosed in Patent Document 2, since a plurality of pairs of light emitting elements and light receiving elements are used, there is a problem that a large installation space is required as compared with the case where only one pair is used. In addition, when multiple pairs of light-emitting elements and light-receiving elements are installed in a narrow installation space, the time difference for detecting a decrease in the amount of light received between each pair of light-receiving elements is extremely short, which makes it possible to measure droplet flight speed. There is a problem that high time resolution is required.

JP 9-94946 A JP 2003-276171 A

  An object of the present invention is to provide a droplet discharge state detection method capable of detecting droplet non-discharge, flight speed abnormality, and flight path abnormality using a pair of light-emitting elements and light-receiving elements. It is to be.

The present invention provides a light emitting element that emits a light beam, a light receiving element that receives a light beam emitted from the light emitting element, and a nozzle that is provided in an ink jet apparatus and that discharges ink droplets. Based on a change in the number of droplets in the light beam, the droplets are ejected from the nozzle so that a plurality of ejected droplets exist in the light beam. A method of detecting the discharge state of a droplet based on a change in the amount of received light ,
Maintaining a constant discharge frequency, which is the number of droplets discharged per unit time, and discharging droplets from the nozzle ;
Detecting a light amount of a light beam emitted from the light emitting element with a light receiving element;
Comparing the amount of received light detected by the light receiving element with a predetermined first threshold;
Comparing the amount of received light detected by the light receiving element with a predetermined second threshold;
And a step of determining that the droplet ejection state is normal when the amount of received light is less than the first threshold and greater than the second threshold. .
According to the present invention, when the amount of received light is equal to or greater than the first threshold, it is determined that the liquid droplet is not ejected;
A step of determining that the flying speed of the droplet is reduced when the amount of received light is equal to or less than the second threshold value.

The present invention is characterized in that the step of detecting the amount of light emitted from the light emitting element by the light receiving element is repeated a plurality of times.

In the present invention, the first threshold and the second threshold are
Characterized in that it is determined variably according to the ejection frequency.

The present invention also provides a light emitting element that emits a light beam, a light receiving element that receives the light beam emitted from the light emitting element, and a nozzle that is provided in the ink jet apparatus and that discharges ink droplets. The flight path and the luminous flux are arranged so that they intersect each other, and droplets are ejected from the nozzle so that a plurality of ejected droplets exist in the luminous flux, thereby changing the number of droplets in the luminous flux. A method for detecting a discharge state of a droplet based on a change in an amount of received light based on :
Maintaining a constant discharge frequency, which is the number of droplets discharged per unit time, and discharging droplets from the nozzle ;
Detecting a light amount of a light beam emitted from the light emitting element with a light receiving element;
Comparing the amount of received light detected by the light receiving element with a predetermined first threshold;
Comparing the amount of received light detected by the light receiving element with a predetermined second threshold;
When the received light amount is less than the first threshold and equal to the second threshold, it is determined that the droplet discharge state is normal, and when the amount of received light is less than the first threshold and exceeds the second threshold, Determining that the flying speed is faster than a predetermined reference speed, and determining that the flying speed of the droplet is slower than the predetermined reference speed when the flying speed is less than the first threshold and less than the second threshold. This is a droplet discharge state detection method characterized by the following.

According to the present invention, a pair of a light emitting element and a light receiving element is used, and the light emitting element, the light receiving element, and the nozzle are arranged so as to pass through a light beam emitted from the light emitting element and received by the light receiving element. The ink droplets are ejected while maintaining the ejection frequency constant, and the amount of light when the droplets pass through the light beam is detected by the light receiving element. The detected amount of received light is less than the first threshold and the second When it exceeds the threshold, it is determined that the droplet discharge state is normal. As described above, since the discharge state of the droplet can be determined by the pair of light emitting / receiving elements, it is possible to solve the problem regarding the installation of the light emitting / receiving elements.
Further, according to the present invention, it is possible to determine that droplets are not ejected using only a pair of light emitting elements and light receiving elements. Furthermore, it is possible to detect that the flying speed of the liquid droplet is reduced by using only a pair of light emitting elements and light receiving elements.

According to the present invention, the step of detecting the light amount of the light beam emitted from the light emitting element by the light receiving element is repeated a plurality of times, so that the detection accuracy of the received light amount can be improved.

  In addition, according to the present invention, the first threshold value and the second threshold value can be variably determined according to the discharge frequency, so that it is possible to determine the droplet discharge state with respect to an arbitrary discharge frequency.

  According to the invention, when the amount of light received by the light receiving element is less than the first threshold and equal to the second threshold, it is determined that the droplet discharge state is normal, is less than the first threshold, and is equal to the second threshold. When the threshold is exceeded, it is determined that the flying speed of the droplet is faster than a predetermined reference speed. When the droplet flying speed is less than the first threshold and less than the second threshold, the flying speed of the droplet is higher than the predetermined reference speed. Determined to be slow. As described above, the normal and abnormal droplet flying speed can be determined by the pair of light emitting and receiving elements, so that the state of the flying speed of the droplet can be accurately detected even in a small installation space. In addition, since a high time resolution is not required for the measurement of the amount of received light, an inexpensive light receiving element can be used.

  FIG. 1 is a system diagram showing a simplified configuration of an ejection state detection apparatus 1 that is preferably used in the droplet ejection state detection method of the present invention.

  The ejection state detection device 1 detects and determines the ejection state of droplets such as ink ejected from an ejection head 2 provided in an ink jet apparatus, and includes a light emitting element 4 that emits a substantially parallel light beam 3, and a light emitting element 4. The light receiving element 5 that receives the light beam 3 emitted from the light receiving device 5 and the computer 6 that performs calculation and determination of the discharge state based on the light reception amount detection result detected by the light receiving element 5.

  The ejection head 2 provided in the ink jet apparatus is mounted on a transport means (not shown) for transporting the ejection head 2 to a desired position with respect to an object to be coated. Inside the head, a piezo element is provided in a liquid chamber communicating with a nozzle. Are provided, and the volume of the liquid chamber is changed by changing the voltage applied to the piezo element, thereby discharging the droplet. The supply of liquid such as ink to the ejection head 2 is performed from an ink tank (not shown) via a tube (not shown) connected to the ejection head 2.

  The ejection head 2 of the inkjet apparatus is not limited to droplet ejection by a piezo method, and a heater is provided in the liquid chamber, and the liquid is ejected by heating the liquid in the liquid chamber to generate bubbles. The method used may be used.

  As the light emitting element 4, for example, a laser diode is used. The light emitting element 4 may be a light emitting diode (LED) or an arbitrary light source such as a lamp combined with a lens instead of a laser diode so as to emit parallel rays. As the light receiving element 5, a photodiode is used. Note that a phototransistor may be used as the light receiving element 5 instead of the photodiode. Further, a photo interrupter in which the light emitting element 4 and the light receiving element 5 are integrated may be used.

  The computer 6 includes a processing circuit unit 6a on which a central processing unit (CPU) that is a processing circuit is mounted, an input unit 6b including, for example, a keyboard and a mouse, and a display unit 6c such as a liquid crystal display. In accordance with an operation control program stored in advance in a memory (not shown), the overall operation of the inkjet device and the ejection state detection device 1 is controlled. For example, the computer 6 outputs an operation control signal for the conveying means of the ink jet apparatus, and transmits a control signal for ejecting ink droplets from the ejection head 2 to the ejection head 2. 5 receives the electrical signal output from the sensor 5 and detects the amount of received light, and compares the detected amount of received light with each threshold value stored in advance in the memory to determine the droplet discharge state.

  FIG. 2 is a flowchart for explaining an outline of the droplet discharge state detection method of the present invention. At the start of step s0, the power supply switches of the ink jet device and the discharge state detection device 1 are in an operable state. In step s 1, according to the control command of the computer 6, the transport unit of the ink jet apparatus crosses the light beam 3 at a position where the droplet ejected from the ejection head 2 can pass through the light beam 3, that is, the droplet flight path. The ejection head 2 is moved to a position where it can be used. In step s2, the discharge of droplets is started from the nozzles of the discharge head 2 in accordance with the control command of the computer 6.

  In step s 3, the amount of light changed by the liquid droplets ejected from the ejection head 2 partially blocking the light beam 3 emitted from the light emitting element 4 and received by the light receiving element 5. Received light. The amount of received light detected by the light receiving element 5 is transmitted to the computer 6 as an electrical signal. The computer 6 determines the discharge state based on the received light amount, which will be described in detail later, for each embodiment of the present invention.

  In step s4, according to the control command of the computer 6, the ejection head 2 stops ejecting droplets, and the process proceeds to step s5, where the ejection state detection operation ends.

  Step s3 in the flowchart shown in FIG. 2 can take various modes depending on the purpose of determining the discharge state, which is the gist of the present invention, and details of the operation for each mode will be described below.

  FIG. 3 is a flowchart for explaining details of the discharge state detection method according to the first embodiment of the present invention. The first embodiment will be described with reference to FIG.

  In step a1, the light amount of the light beam partially blocked by the droplet ejected so as to pass through the light beam 3 in step s2 of FIG. 2 is detected by the light receiving element, and the detected electrical signal of the received light amount is a computer. 6 and is measured as the amount of received light.

  In step a2, the computer 6 reads the first threshold value T1 stored in advance in the memory, compares the detected light reception amount with the first threshold value T1, and determines whether or not the light reception amount is less than the first threshold value. Is done. Here, the comparison between the received light amount and the threshold value by the computer 6 calculates the difference between the received light amount and the threshold value (= received light amount−threshold value), and if the difference is a positive value, the received light amount exceeds the threshold value. If it is determined that the received light amount is zero (0), it is determined that the received light amount is equal to the threshold value, and if it is a negative value, it is determined that the received light amount is less than the threshold value.

  The first threshold value T1 is the amount of light received when the light beam 3 is applied to the light receiving element 5 without being blocked by the droplet, and the droplet 3 is normally discharged and the beam 3 is blocked by the droplet. In this case, the value is set to a value between the received light amount. Therefore, when the amount of received light is equal to or greater than the first threshold value T1, this means that the droplets do not block the light flux 3, and the computer 6 does not eject droplets from the nozzles of the ejection head 2 (non-ejection). judge.

  When the amount of received light is less than the first threshold value T1, the process proceeds to step a4, and when it is equal to or greater than the first threshold value T1, the process proceeds to step a3. In step a3, the computer 6 determines that the droplet is not ejected, and proceeds to step s4 shown in FIG.

  In step a4, the computer 6 reads the second threshold value T2 stored in advance in the memory, compares the detected received light amount with the second threshold value T2, and determines whether the received light amount exceeds the second threshold value. Is done. The second threshold value T2 is a value smaller than the amount of received light when the droplets are normally ejected and the light flux 3 is blocked. When the amount of received light is equal to or smaller than the second threshold value T2, the process proceeds to step a5, where the computer 6 considers that the number of droplets that block the light beam 3 has increased at one time, and the ejection of the droplets is abnormal, that is, the droplet flying speed is It determines with having fallen, and also progresses to previous step s4.

  FIG. 4 is a diagram for explaining a drop in droplet flying speed. A state in which the amount of received light is equal to or smaller than the second threshold value T2 and the droplet flying speed is reduced will be described with reference to FIG. FIG. 4 is a view of a state in which the droplet 11 passes through the light beam 3 as viewed in a cross section perpendicular to the optical axis of the light beam 3. FIG. 4A shows a state in which the droplets 11 ejected from the ejection head 2 have a normal flight speed, and the number of the droplets 11 blocking the light beam 3 is two. FIG. 4B shows a state when the ejection speed of the droplet 11 is half the normal speed although the ejection frequency is the same as FIG. The number of the droplets 11 is four. Here, the ejection frequency is defined as the number of droplets ejected per unit time.

  When the flying speed of the droplets 11 becomes slow, the interval between the continuously ejected droplets becomes narrow, so the number of the droplets 11 that block the light beam 3 at a time increases, and as a result, the light reception detected by the light receiving element 5. The amount decreases. Therefore, it is possible to determine that the amount of received light is equal to or less than the second threshold T2 even though the ejection frequency is maintained constant. In this way, it is possible to detect a drop in the flying speed of the droplet using only the pair of light emitting element 4 and light receiving element 5.

  On the other hand, if it is determined in step a4 that the amount of received light exceeds the second threshold value T2, it is determined that the liquid droplets are ejected normally, and the process proceeds to the previous step s4. After step s4, the process proceeds to the end of step s5 as described above with reference to FIG. 2, the determination of the discharge state of the droplet is confirmed, and the discharge state detection operation ends.

  Alternatively, step a1 for measuring the amount of received light may be repeatedly and continuously executed, and the amount of light received obtained by the computer 6 divided by the number of repetitions may be used as an arithmetic average to be used as the detected amount of received light. By doing so, it is possible to reduce noise included in the measured value of the amount of received light.

  When the ejection state detection operation is completed and ejection abnormality (non-ejection of droplets or drop in flying speed) is detected, forced ejection of liquid, wiping of the nozzle surface, etc. using the abnormality recovery means provided in the inkjet device It is preferable to perform discharge abnormality recovery processing and then detect the discharge state again to confirm whether or not the discharge abnormality has been recovered.

  Further, the first threshold value T1 and the second threshold value T2 can be changed according to the ejection frequency. FIG. 5 is a diagram illustrating a state in which the droplets 11 having the same flight speed and different ejection frequencies block the light beam 3. FIG. 5 is a view seen in a cross section perpendicular to the optical axis of the light beam 3 as in FIG.

  FIG. 5A shows a state where the droplets 11 ejected from the ejection head 2 at the ejection frequency (F) block the light beam 3, and the number of the droplets 11 blocking the light beam 3 at one time is two. FIG. 5B shows a state in which the droplets 11 ejected from the ejection head 2 at the ejection frequency (F / 2) block the light beam 3, and the number of the droplets 11 blocking the light beam 3 at one time is one. is there. FIG. 5C shows a state in which the droplets 11 ejected from the ejection head 2 at the ejection frequency (2F) block the light beam 3, and the number of droplets 11 blocking the light beam 3 at a time is four. As described above, when the ejection frequency is changed, the number of droplets 11 that block the light beam 3 at a time changes according to the ejection frequency. Therefore, the amount of received light when the droplets 11 are ejected normally is the ejection frequency. It depends on.

  Therefore, the first and second threshold values T1 and T2 that are index values indicating the range in which the droplet 11 is normally discharged are variable so as to be in an appropriate range according to the discharge frequency used for discharging the droplet 11. Must be set to That is, when the droplet 11 is discharged at a high discharge frequency, the first threshold T1 and the second threshold T2 are set low, and when the droplet 11 is discharged at a low discharge frequency, the first threshold T1 and the second threshold are set. The discharge state is detected by setting T2 high. This makes it possible to detect the normal ejection state of the droplets at an arbitrary ejection frequency.

  FIG. 6 is a flowchart for explaining the details of the discharge state detecting method according to the second embodiment of the present invention. The second embodiment will be described with reference to FIG.

  Step b1 is in the same state as step a1 in FIG. Step b2 is also the same operation as step a2 in FIG. 3, and the computer 6 reads the first threshold value T1 stored in advance in the memory, compares the detected amount of received light with the first threshold value T1, and receives light. It is determined whether the amount is less than a first threshold. If the determination result is negative and the amount of received light is equal to or greater than the first threshold T1, this means that the light beam 3 is not blocked by the droplet, and the process proceeds to step b3, and the computer 6 determines that the droplet is not ejected. When the amount of received light is less than the first threshold value T1, the process proceeds to step b4.

  In step b4, the computer 6 reads another second threshold value T4 stored in the memory in advance, compares the detected light reception amount with the other second threshold value T4, and the received light amount is another second threshold value T4. It is determined whether or not the threshold value is T4 or more. The other second threshold value T4 is a value equal to the amount of received light when the droplets are normally ejected and the light flux 3 is blocked.

  The other second threshold value T4 is preferably set to have a range. This is because if the second threshold value T4 is a point value, the state determined to be normal is restricted more than necessary, which is not suitable for actual operation.

  When the amount of received light is greater than or equal to another second threshold value T4, the process proceeds to step b5, and when it is less than another second threshold value T4, the process proceeds to step b8. In step b8, the computer 6 considers that the number of droplets that block the light beam 3 has increased at one time, and determines that the ejection of the droplets is abnormal, that is, the flying speed of the droplets has decreased, and further step s4. Proceed to

  In step b5, it is further determined whether the amount of received light is equal to another second threshold value T4. When the amount of received light is equal to another second threshold value T4, the process proceeds to step b6, and the computer 6 determines that the droplet ejection is normal, that is, the droplet flying speed is normal, and further proceeds to step s4. When the amount of received light exceeds the second threshold value T4, the process proceeds to step b7, and the computer 6 considers that the number of droplets that block the light beam 3 at a time has decreased, and the ejection of the droplets is abnormal, that is, the flying of the droplets. It is determined that the speed has increased, and the process proceeds further to step s4.

  Here, when the droplet flying speed is normal, the ejected droplet speed is a liquid suitable for application by an ink jet method in accordance with the type of an object to be coated, ink characteristics, nozzle diameter, and the like. It is equal to a reference speed that is set in advance as a droplet discharge speed, and is usually determined with a range, so that it is within the reference range. Therefore, the drop flying speed is lower than the reference speed, and the drop flying speed is higher than the reference speed.

  After step s4, the process proceeds to the end of step s5 as described above with reference to FIG. 2, the determination of the discharge state of the droplet is confirmed, and the discharge state detection operation ends.

  FIG. 7 is a diagram illustrating a state in which droplets 11 ejected from the ejection head 2 at different flight speeds at the same ejection frequency pass the light flux. The determination of the flying speed of the droplet 11 will be described with reference to FIG. FIG. 7A shows a state where the droplet 11 is being ejected at a normal flight speed. In the case of a normal flight speed, the number of droplets that block the light beam 3 at a time is two. FIG. 7B shows a state when the flying speed of the ejected droplet 11 is twice that in the normal case. When the flying speed is twice, the number of droplets 11 that block the light beam 3 at a time is reduced to one. FIG. 7C shows a state when the flying speed of the ejected droplet 11 is halved compared to the normal case. When the flying speed is ½, the number of droplets 11 that block the light beam 3 at a time increases to four.

  Thus, when the flying speed of the droplet 11 changes, the number of droplets 11 that block the light beam 3 at a time changes according to the increase or decrease of the flying speed, so the amount of light beam blocked by the droplet 11 is measured, By comparing with a predetermined threshold value, it is possible to determine whether or not the flying speed of the droplet 11 is normal.

  When the ejection state detection operation is completed and ejection abnormality (non-ejection of droplets or flying speed abnormality) is detected, ejection abnormality recovery processing is executed using abnormality recovery means provided in the ink jet apparatus. For example, when non-ejection of a droplet is detected, processing such as forced extrusion of liquid and wiping of the nozzle surface is performed. When a droplet flying speed abnormality is detected, the ejection head control parameter, for example, a jet head using a piezo element, changes the amplitude by changing the voltage applied to the piezo element so that the flying speed becomes normal. Thus, processing for changing the flight speed is performed. When a drop in the flying speed of the droplet is detected, the flying speed is increased by changing the control parameter so that the amplitude of the piezo element is increased. Conversely, when an increase in the flying speed of the droplet is detected, the flying speed is lowered by changing the control parameter so that the amplitude of the piezo element is reduced.

  After performing the discharge abnormality recovery process in this manner, it is preferable to detect the discharge state again and confirm whether or not the discharge abnormality has been recovered.

  FIG. 8 is a flowchart for explaining the details of the discharge state detecting method according to the third embodiment of the present invention. A third embodiment will be described with reference to FIG.

  Step c1 is in the same state as step a1 in FIG. However, the first light amount detected by the light receiving element 5 in this step c1 is referred to as a first received light amount I1. In step c2, the ejection head is moved by a predetermined distance in a direction parallel to the droplet ejection direction. The droplet discharge direction here refers to a droplet flight path determined by design in the discharge head, and corresponds to an extension direction of the nozzle directing direction.

  In step c3, after the ejection head is moved, the second light amount is measured by ejecting the droplets so as to pass through the light flux again. The second light quantity detected by the light receiving element 5 at this time is referred to as a second received light quantity I2. In step c4, the computer 6 compares the first received light amount I1 and the second received light amount I2, and determines whether or not they are equal. When the first received light amount I1 and the second received light amount I2 are equal, the process proceeds to step c5, and in step c5, the computer 6 determines that the droplet flying direction is normal. When the first received light amount I1 and the second received light amount I2 are not equal, the process proceeds to step c6, where the computer 6 determines that the droplet flying direction is abnormal.

  FIG. 9 is a diagram showing a state in which the droplets 11 having the same ejection frequency and the same flight speed block the light beam 3 in the normal flight path, and FIG. 10 shows the droplets 11 having the same ejection frequency and the same flight speed. It is a figure which shows the state which interrupts the light beam 3 with an abnormal flight path | route. The determination of the droplet flight path will be described with reference to FIGS. Note that the imaginary line 12 shown in FIGS. 9 and 10 is an axis indicating the above-described normal flight path of the droplet.

  FIG. 9A shows a case where the droplets 11 are ejected in the normal flight direction, and the number of droplets that block the light beam 3 at a time is four. On the other hand, FIG. 10A shows a case where the droplet 11 is ejected in an abnormal flight direction, but the number of droplets that block the light beam 3 at a time is four, and the droplets are ejected in the normal flight direction. It is not different from the case where it is done. Therefore, when the amount of received light is measured in the case of FIG. 9A and the case of FIG. 10A, the value is the same, and in any case, the ejection state is determined to be normal. Therefore, in this embodiment, the ejection state detection accuracy is improved by moving the ejection head 2 in the normal flight path direction (the direction in which the shaft 12 extends).

  That is, FIG. 9B and FIG. 10B show a state where the ejection head 2 is moved in the direction away from the light beam 3 in the direction of the axis 12 from the state of FIG. 9A and FIG. FIG. In FIG. 9B where the flight path of the droplet 11 is normal, the number of droplets that block the light beam 3 at a time is four, which is the same as in FIG. 9A, and the ejection head 2 is moved. Even if it is used, the amount of received light does not change. However, in FIG. 10B in which the flight path of the droplet 11 is abnormal, the number of droplets that block the light beam 3 at a time is reduced to two compared to the case of FIG. When the head 2 is moved, the amount of received light that is measured increases.

  As described above, when the flying direction of the droplet 11 is normal, the measured light reception amount before and after the movement of the ejection head 2 does not change, but when the flying direction of the droplet 11 is abnormal, the measurement before and after the movement of the ejection head 2 is performed. The amount of received light changes. Accordingly, when the ejection head 2 is moved to a plurality of positions in the direction of the axis 12 and the amount of received light is measured at each position, if there is no change in the amount of received light at each measurement position, the ejection is performed in the normal flight direction. If there is a change in the amount of received light according to the measurement position, it can be determined that the discharge is in an abnormal flight direction.

  In the above method, when the flying direction of the liquid droplet is shifted in the same direction as the direction in which the optical axis of the light beam 3 extends, an abnormality cannot be detected. In such a case, the ejection head 2 is angularly displaced by 90 degrees around the axis 12, the ejection state of the droplet 11 is detected again, and the presence or absence of an abnormality in the flight direction is confirmed to further increase the determination accuracy. Can do.

  Further, in the present embodiment, although the ejection head is moved, the light beam, that is, the light emitting element and the light receiving element that form a pair, on the contrary, can be moved or angularly displaced while facing each other. There is an effect.

1 is a system diagram showing a simplified configuration of a discharge state detection apparatus 1 that is preferably used in a droplet discharge state detection method of the present invention. It is a flowchart explaining the outline | summary of the discharge state detection method of the droplet of this invention. It is a flowchart explaining the detail of the discharge state detection method which is the 1st aspect of implementation of this invention. It is a figure explaining the flying speed fall of a droplet. It is a figure which shows the state in which the droplet 11 with the same flight speed and different discharge frequency blocks the light beam 3. FIG. It is a flowchart explaining the detail of the discharge state detection method which is the 2nd aspect of implementation of this invention. FIG. 6 is a diagram illustrating a state in which droplets 11 ejected from the ejection head 2 at different flight speeds at the same ejection frequency pass the light flux. It is a flowchart explaining the detail of the discharge state detection method which is the 3rd aspect of implementation of this invention. It is a figure which shows the state which the droplet 11 of the same discharge frequency and the same flight speed blocks the light beam 3 by a normal flight path. It is a figure which shows the state which the droplet 11 of the same discharge frequency and the same flight speed blocks the light beam 3 by an abnormal flight path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge state detection apparatus 2 Discharge head 3 Light beam 4 Light emitting element 5 Light receiving element 6 Computer 11 Droplet

Claims (5)

A light emitting element that emits a light beam, a light receiving element that receives a light beam emitted from the light emitting element, a nozzle that is provided in the ink jet apparatus and that discharges ink droplets, a flight path of the discharged liquid droplets, and the light flux Change in the amount of received light based on the change in the number of droplets in the light beam, by discharging the droplets from the nozzle so that a plurality of discharged droplets exist in the light beam. A method for detecting the discharge state of a droplet based on
Maintaining a constant discharge frequency, which is the number of droplets discharged per unit time, and discharging droplets from the nozzle ;
Detecting a light amount of a light beam emitted from the light emitting element with a light receiving element;
Comparing the amount of received light detected by the light receiving element with a predetermined first threshold;
Comparing the amount of received light detected by the light receiving element with a predetermined second threshold;
And a step of determining that the droplet ejection state is normal when the amount of received light is less than the first threshold and greater than the second threshold. Determining that a droplet is non-ejection when the amount of received light is equal to or greater than the first threshold;
2. The droplet discharge state detection method according to claim 1, further comprising a step of determining that the flying speed of the droplet is reduced when the amount of received light is equal to or less than the second threshold value. 3. The droplet discharge state detection method according to claim 1, wherein the step of detecting the light amount of the light beam emitted from the light emitting element by the light receiving element is repeated a plurality of times. The first threshold and the second threshold are:
Discharge state detecting methods of drops according to any one of claims 1-3, characterized in that it is determined variably according to the ejection frequency. A light emitting element that emits a light beam, a light receiving element that receives a light beam emitted from the light emitting element, a nozzle that is provided in the ink jet apparatus and that ejects ink droplets, a flight path of the ejected droplets, and the light flux Change in the amount of received light based on the change in the number of droplets in the light beam, by discharging the droplets from the nozzle so that a plurality of discharged droplets exist in the light beam. A method for detecting the discharge state of a droplet based on
Maintaining a constant discharge frequency, which is the number of droplets discharged per unit time, and discharging droplets from the nozzle ;
Detecting a light amount of a light beam emitted from the light emitting element with a light receiving element;
Comparing the amount of received light detected by the light receiving element with a predetermined first threshold;
Comparing the amount of received light detected by the light receiving element with a predetermined second threshold;
When the received light amount is less than the first threshold and equal to the second threshold, it is determined that the droplet discharge state is normal, and when the amount of received light is less than the first threshold and exceeds the second threshold, Determining that the flying speed is faster than a predetermined reference speed, and determining that the flying speed of the droplet is slower than the predetermined reference speed when the flying speed is less than the first threshold and less than the second threshold. A method for detecting a discharge state of droplets.

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