Inkjet recording device and inkjet recording method

Abstract

This invention provides an inkjet recording device capable of automatically determining the excitation voltage of the piezoelectric element most suitable for forming ink droplets. With the deflection electrode de-energized, an excitation voltage value is applied to the piezoelectric element of the nozzle (8) in multiple scans (S11-S15) in a scanning manner from the high voltage side to the low voltage side within a specified voltage range. For ink droplets generated by the applied excitation voltage value, a charged voltage is applied to apply charge according to any number of printing phases, and the amount of charge applied to the ink droplets is detected by a charge sensor (25) to determine the printing phase. For each printing phase detected in each scan, when the relationship between the current printing phase and the previous printing phase reverses from the increasing side to the decreasing side and the determination that the printing phase decreases is true twice consecutively (S16), the excitation voltage value corresponding to the printing phase in the previous scan that was the first to determine the decrease is used as the final excitation voltage value (S17).

Description

Technical Field

[0001] This invention relates to inkjet recording apparatus, and particularly to a continuous jet type electrically controlled inkjet recording apparatus and inkjet recording method. Background Technology

[0002] Typical continuous-jet electrically controlled inkjet recording devices have an ink container inside the main body to store ink, and an ink supply pump supplies ink from this container to the printhead. The ink supplied to the printhead is continuously ejected from the ink nozzles as ink droplets. The ink droplets intended for printing are charged and deflected, causing them to fly to the desired printing position on the object to form characters or marks (hereinafter, referred to as characters). Ink droplets not intended for printing are not charged or deflected; they are captured by an ink reservoir and returned to the ink container by an ink recovery pump.

[0003] In a continuous jet type electrically controlled inkjet recording device, as shown in, for example, Japanese Patent Application Publication No. 2007-136839 (Patent Document 1), ink is ejected from the ink nozzle as ink droplets by driving a piezoelectric element provided in the ink nozzle with a predetermined excitation voltage value.

[0004] However, the excitation voltage that drives the piezoelectric element of the ink nozzle affects ink droplet formation, necessitating the setting of an optimal excitation voltage. In particular, since ink properties vary with ambient temperature, setting the excitation voltage in a way that compensates for this variation is crucial.

[0005] Therefore, methods are known such as: for example, during printing, while adjusting the excitation voltage value of the piezoelectric element of the ink nozzle, visually observing the ink droplets ejected from the ink nozzle with a magnifying glass, and determining the excitation voltage value at which the shape of the ink droplets becomes suitable for printing as the optimal excitation voltage value; or, while adjusting the excitation voltage value of the piezoelectric element and actually printing characters, determining the median of the excitation voltage range that the operator can judge as a good print as the optimal excitation voltage value.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2007-136839 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] When using the above method, it is necessary to visually observe the ink droplets ejected from the ink nozzle using a magnifying glass while changing the excitation voltage value supplied to the piezoelectric element, and determine the optimal excitation voltage value by repeatedly performing test prints. Furthermore, by changing the excitation voltage value according to the "temperature-excitation voltage characteristics" stored in the inkjet recording device, good print quality corresponding to the ambient temperature can be obtained.

[0011] However, visually observing ink droplets with a magnifying glass and accurately determining the suitable droplet shape for printing requires skilled personnel, and because it relies on visual judgment, individual differences can arise. Furthermore, in actual printing and judgment processes, there is a risk of wasting workpieces, and the reliance on visual judgment of print results can also introduce individual variations.

[0012] The purpose of this invention is to provide an inkjet recording device and an inkjet recording method that can automatically determine the excitation voltage value of the piezoelectric element suitable for forming ink droplets.

[0013] Technical means to solve the problem

[0014] This invention provides a continuous-jet, electrically controlled inkjet recording device, comprising: an excitation voltage circuit that applies an excitation voltage to a piezoelectric element disposed in an ink nozzle for ejecting ink droplets; a charged electrode that charges the ejected ink droplets; a deflection electrode that deflects the flight direction of the ink droplets charged by the charged electrode; a charge sensor that measures the amount of charge in the ink droplets charged by the charged electrode; and a control unit that controls the excitation voltage circuit, the charged electrode, the deflection electrode, and the charge sensor.

[0015] The control unit is characterized by comprising:

[0016] The excitation voltage scan setting unit applies an excitation voltage value to the piezoelectric element in multiple scans, in a manner that scans from the high voltage side to the low voltage side within a specified voltage range, while the deflection electrode is not energized.

[0017] The printing phase measurement unit applies charge to ink droplets generated by the applied excitation voltage at multiple arbitrary printing phases, and uses a charge sensor to detect the amount of charge applied to the ink droplets to determine the appropriate printing phase; and

[0018] The excitation voltage determination unit, for the printing phase detected in each scan, when the relationship between the current printing phase and the previous printing phase reverses from the increasing side to the decreasing side, and the judgment that the printing phase decreases is true twice consecutively, uses the excitation voltage value corresponding to the printing phase in the previous scan before the first decrease judgment as the final excitation voltage value.

[0019] This invention provides an inkjet recording method in a continuous jet electrically controlled inkjet recording device, characterized in that:

[0020] The inkjet recording device includes: an excitation voltage circuit that applies an excitation voltage to a piezoelectric element disposed in an ink nozzle for ejecting ink droplets; a charged electrode that charges the ejected ink droplets; a deflection electrode that deflects the flight direction of the ink droplets charged by the charged electrode; a charge sensor that measures the amount of charge in the ink droplets charged by the charged electrode; and a control unit that controls the excitation voltage circuit, the charged electrode, the deflection electrode, and the charge sensor.

[0021] Control Department:

[0022] With the deflection electrode unenergized, an excitation voltage value is applied to the piezoelectric element in multiple scans, scanning from the high voltage side to the low voltage side within a specified voltage range.

[0023] For ink droplets generated by the applied excitation voltage, charge is applied by applying a charged voltage at any number of printing phases, and the appropriate printing phase is determined by detecting the amount of charge applied to the ink droplets using a charge sensor.

[0024] For the printing phase detected in each scan, if the relationship between the current printing phase and the previous printing phase reverses from increasing to decreasing, and the judgment that the printing phase decreases is true twice consecutively, the excitation voltage value corresponding to the printing phase in the previous scan before the first decrease judgment is used as the final excitation voltage value.

[0025] Invention Effects

[0026] According to the present invention, the excitation voltage value of the piezoelectric element suitable for forming ink droplets can be automatically determined, so the optimal excitation voltage value can be easily determined without familiarity. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the printing method of an inkjet recording device.

[0028] Figure 2 This is a structural diagram showing the structure of an inkjet recording device.

[0029] Figure 3 This is a block diagram showing the control unit that controls the constituent elements of the inkjet recording device.

[0030] Figure 4 This is an explanatory diagram illustrating the effect of ambient temperature on the excitation voltage of the piezoelectric element of the ink nozzle and the length of the ink column.

[0031] Figure 5This is a block diagram showing the main parts of the control section of an inkjet recording apparatus according to an embodiment of the present invention.

[0032] Figure 6 This is an explanatory diagram illustrating the relationship between the excitation voltage applied to the piezoelectric element of the ink nozzle and the printing phase.

[0033] Figure 7 This is an explanatory diagram used to determine the final excitation voltage value.

[0034] Figure 8 It is used for explanation Figure 5 The flowchart shown is a processing flow chart for the block diagram. Detailed Implementation

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and various modifications and applications are also included within the scope of the technical concept of the present invention.

[0036] First, the structure and operation of a typical continuous-jet electrically controlled inkjet recording device will be briefly explained.

[0037] Figure 1 This describes the external structure of the inkjet recording device. Figure 1 In this inkjet recording device, a display B is provided in the main body A. Ink is supplied to the print head D via cable C, and the determined printing content is sent to the print head D via cable C, based on which ink droplets are continuously ejected, thereby printing on the printing object F transported by a conveyor belt or other transport line E.

[0038] Figure 2 The structure of an inkjet recording device is shown schematically. Figure 2 In the inkjet recording device 100, there is a main ink container 1, which is filled with ink 2a. The main ink container 1 is connected to a supply valve 3, a supply pump 4, a main filter 5, a pressure regulating valve 6, an ejection valve 7, and an ink nozzle 8 via an ink supply pipe 9. A piezoelectric element (not shown) is provided in the ink nozzle 8 to apply vibration to the ink in the ink nozzle 8.

[0039] A charged electrode 23 and a deflection electrode 24 are arranged in the direction of travel of the ink droplets 10 ejected from the ink nozzle 8. The charged electrode 23 imparts a voltage to the ink droplets 10 to be printed, corresponding to the character signal. The charged ink droplets 10 fly in the electric field generated by the deflection electrode 24 and are deflected accordingly to reach the printed object 26, forming characters or marks, etc.

[0040] An ink reservoir 11 for collecting unused ink droplets 10 is provided in the direction of travel of the ink droplets 10 ejected from the ink nozzle 8. The ink reservoir 11 is connected to a charge sensor 25, a recovery pump 12, and a main container 1 via an ink recovery pipe 13, wherein the charge sensor 25 is capable of measuring the charge of the charged ink droplets 10.

[0041] When the ink droplets 10 are recovered through the ink tank 11, the air surrounding the ink droplets 10 is also introduced and transported to the main ink container 1. The air transported to the main ink container 1 is discharged to the outside of the inkjet recording device 100 from the exhaust port (not shown) provided in the inkjet recording device 100 via the external exhaust pipe 22 connected to the main ink container 1.

[0042] Additionally, the inkjet recording device 100 includes a secondary ink container 14, which is filled with ink 2b. The secondary ink container 14 is connected to the replenishment valve 15 and the supply pump 4 via the ink supply pipe 16.

[0043] Furthermore, the inkjet recording device 100 includes a diluent (i.e., "replenishing fluid") container 17, which is replenished with diluent 18. The diluent container 17 is connected to a diluent pump 19 and a dilution valve 20 via a diluent supply pipe 21.

[0044] like Figure 3 As shown, the inkjet recording device 100 includes an MPU32 (microprocessor unit), which functions as a control unit that controls the various components inside the inkjet recording device 100 via the bus 200.

[0045] The MPU32 (microprocessor unit) is connected to a RAM30 (random access memory) that temporarily stores data in the inkjet recording device 100, a ROM29 (read-only memory) that stores pre-stored programs, a graphics RAM31 that stores graphic data that charges the ink droplets 10, a charged signal generating circuit 27 that converts the graphic data into a charged signal, a charge sensor 25, a charge amplification circuit 28 that amplifies the signal from the charge sensor 25, and an excitation voltage application circuit 33 for exciting and driving the ink nozzles 8. These circuits are controlled by the MPU32.

[0046] In addition, the MPU32 (microprocessor unit) is connected to the supply valve 3, nozzle 8, supply pump 4, recovery pump 12, diluent pump 19, supply valve 3, pressure regulating valve 6, spray valve 7, replenishment valve 15, dilution valve 20, charged electrode 23, deflection electrode 24 and operation display unit 300 via bus 200, and controls their operation.

[0047] Next, the operation during printing will be explained. During printing, the supply pump 4, the recovery pump 12, and the diluent pump 19 operate according to the signals input from the operation display unit 300. The supply valve 3 and the ejection valve 7 open, and the pressure is adjusted to any pressure by the pressure regulating valve 6.

[0048] Then, the excitation voltage is applied to the piezoelectric element of the ink nozzle 8 using the excitation voltage application circuit 33, and ink is ejected from the ink nozzle 8. For the ink droplet 10 ejected from the ink nozzle 8, the charging signal generation circuit 27 applies a charging voltage to the charging electrode 23, and the charging electrode 23 charges the ink droplet 10.

[0049] The charged ink droplets 10 are deflected in flight by the electric field generated by the deflection electrode 24 and hit the printed object 26 for printing. The ink droplets 10 not used for printing fly towards the ink tank 11. The ink droplets 10 captured by the ink tank 11 are attracted by the recovery pump 12 and recovered to the main ink container 1 via the recovery pipe 13.

[0050] When the piezoelectric element of the ink nozzle 8 vibrates by applying an excitation voltage, the ink forms droplets due to the pressure pulsation of the ink within the nozzle 8 and the surface tension of the ejected ink. Here, the shape of the ink droplets 10 is affected by the magnitude of the excitation voltage, thus impacting print quality. Furthermore, there exists an appropriate range of excitation voltage values ​​that ensures print quality.

[0051] Figure 4 In the diagram, the horizontal axis uses the excitation voltage (denoted as the excitation vibration voltage in the figure) as a parameter, and the vertical axis uses the ink column length as a parameter, representing the variation of the excitation voltage / ink column length characteristics under various ambient temperatures. It shows a trend where longer ink column lengths lead to worse print quality. Dashed line A represents poor print quality caused by errors in the electrical system; print quality is unstable between dashed lines A and B. Therefore, it can be concluded that print quality can be guaranteed when the ink column length is shorter than dashed line B.

[0052] This allows setting the excitation voltage value within a range where the ink column length is shorter than the dashed line B. However, the excitation voltage / ink column length characteristic changes with ambient temperature, and the excitation voltage range also changes accordingly. Figure 4 It can be seen that the following characteristics will occur: the higher the ambient temperature, the longer the ink column, the narrower the excitation voltage range, and the lower the excitation voltage value.

[0053] Therefore, it is difficult for operators to set the appropriate excitation voltage value. To accurately determine the suitable ink droplet shape for printing, skilled personnel are required to visually observe the ink droplets with a magnifying glass. Moreover, due to the reliance on visual judgment, individual differences may arise. Therefore, there is a need for an inkjet recording device that can automatically determine the appropriate excitation voltage value for the piezoelectric element to form ink droplets.

[0054] Based on the results of various experiments and simulations, the inventors discovered that the excitation voltage value for obtaining an appropriate ink droplet can be set to be on the lower side compared to the excitation voltage value with the shortest ink column length, and close to that value. Furthermore, a specific method for obtaining this excitation voltage value was also discovered. Therefore, an appropriate excitation voltage value can be automatically set without visually judging the printing results and without relying on the skills of a skilled operator.

[0055] Hereinafter, specific embodiments of the present invention will be described based on the accompanying drawings. Figure 5 This refers to the automatic excitation voltage setting function unit in this embodiment, which automatically sets the excitation voltage value. This automatic excitation voltage setting function unit is composed of a control program executed by the MPU32 (microprocessor unit).

[0056] Figure 5 In this process, the excitation voltage scanning setting unit 40 has the function of applying an excitation voltage value to the piezoelectric element of the ink nozzle 8 in multiple scans (multiple scan events (scan points)) in a manner that the excitation voltage value is scanned from the high voltage side to the low voltage side within a specified voltage range when the deflection electrode 24 is not energized.

[0057] In addition, the printing phase measurement unit 41 has the function of applying charge to ink droplets generated by the applied excitation voltage value by applying charge voltage from the charged electrode 23 at any number of phases, and using the charge sensor 25 to detect the amount of charge applied to the ink droplets to determine the appropriate printing phase.

[0058] Furthermore, the excitation voltage determination unit 42 has the function of: when the relationship between the current printing phase and the previous printing phase detected by the printing phase measurement unit 41 in each scan is reversed from the increasing side to the decreasing side, and the determination that the printing phase decreases is true twice in a row, the excitation voltage value corresponding to the printing phase of the previous scan before the first decrease determination is used as the final excitation voltage value.

[0059] Next, the specific functions of the excitation voltage scan setting unit 40, the print phase measurement unit 41, and the excitation voltage determination unit 42 will be explained using... Figure 6 To explain. Here, Figure 6 The horizontal axis represents the excitation voltage setting and its scan number. The vertical axis represents the printing phase for each excitation voltage setting. Figure 6 The printed phase shown below corresponds to a phase that divides one cycle of the excitation frequency of the piezoelectric element into 16 equal parts.

[0060] The excitation voltage scan setting unit 40 sets the number of scans and the excitation voltage setting value for the excitation voltage applied to the piezoelectric element provided in the ink nozzle 8. In this embodiment, 20 scans (N=0 to 19) are performed continuously and repeatedly. The excitation time (e.g., 100ms) of each scan (one scan refers to changing the excitation voltage setting value, applying the excitation voltage, and measuring the printing phase) has a predetermined length, and the excitation voltage setting value (Vn) is changed in each scan.

[0061] Furthermore, the difference (ΔV) between the excitation voltage settings of adjacent scans is arbitrary, and the difference (ΔV) is set to approximately 2 [V] to 4 [V]. Thus, the excitation voltage setting [Vn] gradually increases from the low voltage side to the high voltage side according to the difference (ΔV).

[0062] The print phase measurement unit 41 measures the print phase during each scan. As is well known, the print phase can be determined using the charge sensor 25. In this embodiment, in order to detect the timing of ink droplet separation (print phase), during the non-printing period, such as... Figure 6 As shown on the vertical axis, the period of the excitation frequency is divided into 16 equal parts (M=0~15) to divide the phase. A phase exploration voltage (pulse voltage) is generated synchronously with the divided phase, which changes the timing of charging the ink droplet, thus charging the ink droplet.

[0063] Then, the charge of each charged ink droplet in each phase is detected using a charge sensor 25. The detected charge is compared with a predetermined threshold, and the phase that can be charged normally is determined as the printing phase. In addition, multiple phases that can be charged normally are usually generated consecutively. Only a representative phase needs to be selected. Generally, the printing phase at the center of multiple consecutive printing phases is selected.

[0064] For example, Figure 6 In the middle, when the excitation voltage setting value (Vn) is "V 15 In the case of “○”, “○” indicates the printed phase “Ph”. 11 ~Ph 15 "This is the phase that can be charged normally. In this printed phase "Ph" 11 ~Ph 15 In the text, the “★” indicates the printed phase “Ph”. 12 "Determine to print the phase for the selected representative."

[0065] Similarly, when the excitation voltage setting (Vn) is "V 11 In the case of “○”, “○” indicates the printed phase “Ph7~Ph”. 11 "This is the phase that can be charged normally. In the printed phase "Ph7~Ph 11In the section, the print phase "Ph9" represented by "★" is selected as the representative print phase. The print phase for each excitation voltage setting (Vn) is the same below.

[0066] Therefore, the excitation voltage setting and the characteristic representing the printing phase are indicated by "★", and this relationship shows the same trend even with changes in ambient temperature. Furthermore, this characteristic is defined within a 16-part phase.

[0067] Ultimately, as Figure 6 The horizontal axis indicates whether printing is possible (○, ×), and the excitation voltage setting value (Vn) is used as the excitation voltage setting value "V3~V". 15 "This is the range of excitation voltages that can be printed. Next, the optimal excitation voltage setting value (Vop) needs to be determined from this range of excitation voltages, which is determined by the excitation voltage determination unit 42 below.

[0068] As described above, based on the results of various experiments and simulations, the inventors discovered that the excitation voltage value that can obtain an appropriate ink droplet can be set to be on the lower voltage side compared to the excitation voltage value with the shortest ink column length, and close to the excitation voltage value with the shortest ink column length.

[0069] Furthermore, it was concluded that the excitation voltage value closest to the excitation voltage value with the shortest ink column length is preferably the excitation voltage value after the direction of increase or decrease of the printing phase value between adjacent scans has just reversed from the increasing side to the decreasing side.

[0070] therefore, Figure 6 In this process, the excitation voltage setting value "V5" is determined as the optimal excitation voltage value. Compared to the excitation voltage value where the direction of increase / decrease of the printing phase value is reversed from the increasing side to the decreasing side, it is closer to the lower voltage side, and also closer to the excitation voltage value where the direction of increase / decrease of the printing phase value is reversed. The method for determining the excitation voltage setting value "V5" is explained below.

[0071] The print phase measurement unit 41 detects an appropriate representative print phase for each scan, and the measurement result is input to the excitation voltage determination unit 42. Here, when detecting the representative print phase for each scan, the scan proceeds from the high voltage side to the low voltage side. That is, according to the excitation voltage setting value "V 19 “V” 18 “V” 17 "...The sequential detection of "V2", "V1", and "V0" represents the printed phase."

[0072] The reason is that the optimal excitation voltage value is located on the lower voltage side than the excitation voltage value where the printing phase value is shortest and the direction of increase / decrease is reversed. Therefore, when scanning the excitation voltage, it is advantageous to detect the printing phase from the high voltage side, where the direction of increase / decrease of the printing phase value can be determined more quickly, towards the low voltage side.

[0073] This is because, assuming scanning from the low-voltage side to the high-voltage side, the optimal excitation voltage setting for the low-voltage side must be determined after reversing the direction of increase or decrease in the printed phase value, which would complicate the regularization of the control program. However, even scanning from the low-voltage side to the high-voltage side, it is still possible to determine the optimal excitation voltage value.

[0074] Then, the excitation voltage determination unit 42 determines the direction of change (increase or decrease) of the measured printing phase and detects the reversal of the increase or decrease of the printing phase value. Figure 7 (and Figure 6 In different examples, for instance, it is possible to compare the printed phase "Ph9" of the previous scan (N=10) with the printed phase "Ph" of the adjacent current scan (N=9). 12 The difference (ΔPh=Ph9-Ph) 12 If the value of the printing phase increases, it indicates that the region is approaching where the direction of increase or decrease in the printing phase is reversed.

[0075] Conversely, for example, it is possible to determine the printing phase "Ph1" of the previous scan (N=4) and the printing phase "Ph" of the adjacent current scan (N=3). 14 The difference between (ΔPh=Ph1-Ph) 14 If the value of the printed phase decreases, it indicates that the region is moving away from the area where the direction of increase or decrease in the printed phase is reversed.

[0076] Furthermore, after the direction of increase or decrease of the printed phase value is reversed, at the printed phase "Ph14" of this scan (N=3), since it has been judged to decrease twice in a row, the excitation voltage setting value "V5" of the previous scan (N=5) of the printed phase "Ph1" of the first scan (N=4) that was judged to decrease is finally determined as the optimal excitation voltage setting value "Vop".

[0077] In addition, depending on the type of ink, viscosity of ink and other conditions, the excitation voltage value has an allowable range. As an allowable range, it can not only automatically set the previous excitation voltage value that is first judged to be reduced, but also automatically set the excitation voltage value between the first two and the last two.

[0078] Next, the process executed by the MPU32 (microprocessor unit) Figure 5 The processing flow shown is based on the automatic excitation voltage setting function unit's operation. Figure 8 A brief explanation is provided. This process flow illustrates the operating principle of the automatic excitation voltage setting function.

[0079] Additionally, in the following description, the voltage of the deflection electrode 24 is set to 0 [V], which prevents the ink droplet from deflecting. This is to prevent a situation where the charged ink droplet 10 is not recovered into the ink tank 11 between the time the ink droplet 10 is charged and the time the ink droplet 10 enters the ink tank 11.

[0080] <<Step S10>>

[0081] In step S10, the excitation voltage setting value "V" is set starting from the high voltage side as the first scan (N=19). 19 The excitation voltage set value "V" is applied to the piezoelectric element of the ink nozzle 8. 19 This causes the piezoelectric element to vibrate. The excitation voltage setting value "V" is set. 19 Then, proceed to step S11.

[0082] <<Step S11>>

[0083] In step S11, ink droplets are charged according to multiple printing phases obtained by dividing the excitation frequency into 16 equal parts. The charge of the charged ink droplets is compared with a threshold to determine whether a printing phase has been detected. This determination is as explained previously. If a printing phase is detected, the process proceeds to step S12. On the other hand, if no printing phase is detected, it is considered that good printing cannot be performed, and the process proceeds to step S13 in order to perform the next scan.

[0084] <<Step S12>>

[0085] In step S12, the value of a representative print phase, composed of the median value, is determined from the multiple detected print phases and stored in the RAM area. The print phase detection process for the first scan ends, and the process proceeds to step S13.

[0086] <<Step S13>>

[0087] In step S13, the excitation voltage setting value "V" is set as the second scan (N=18). 18 Similarly, the excitation voltage setting value "V" is applied to the piezoelectric element of the ink nozzle 8. 18 This causes the piezoelectric element to vibrate. The excitation voltage setting value "V" is set. 18 Then, proceed to step S14.

[0088] <<Step S14>>

[0089] In step S14, ink droplets are charged according to multiple printing phases obtained by dividing the excitation frequency into 16 equal parts. The charge of the charged ink droplets is compared with a threshold to determine whether a printing phase has been detected. This determination is as explained previously. If a printing phase is detected, the process proceeds to step S15. On the other hand, if no printing phase is detected, it is considered that good printing cannot be performed, and the process proceeds to step S13 in order to perform the next scan. In step S13, the number of scans is increased, and the same process is performed thereafter.

[0090] <<Step S15>>

[0091] In step S15, the value of a representative print phase, composed of the median, is determined from the multiple detected print phases and stored in the RAM area. The print phase detection process for the second scan ends, and the process proceeds to step S16.

[0092] <<Step S16>>

[0093] In step S16, based on the value of the previous printing phase stored in the RAM area and the value of the current printing phase stored in the RAM area, it is determined whether (1) the value of the printing phase is in the increasing direction or in the decreasing direction, and then it is determined whether (2) the phase has decreased twice consecutively after the phase increases (making a decrease judgment). This judgment is as explained above.

[0094] Then, (1) if the value of the printed phase is in the increasing direction or the decreasing direction, the process moves to step S18; (2) if the value is in the increasing direction and then decreases twice consecutively, the process moves to step S17.

[0095] <<Step S17>>

[0096] In step S17, since the value of the printed phase is judged to decrease twice in a row after the direction of increase or decrease is reversed, the excitation voltage setting value of the previous scan of the printed phase of the first scan that makes the decrease judgment is finally determined as the optimal excitation voltage setting value "Vop", and then the process jumps to the end.

[0097] In addition, as mentioned above, depending on the type of ink, the viscosity of the ink, and other conditions, the excitation voltage value has an allowable range. As an allowable range, it is possible not only to automatically set the previous excitation voltage value that is first determined to be a reduced excitation voltage value, but also to automatically set the excitation voltage value between the first two and the last two.

[0098] Here, after determining the optimal excitation voltage setting value "Vop", no further scanning is performed, thus saving unnecessary scanning time and enabling rapid operation.

[0099] <<Step S18>>

[0100] In step S18, it is determined whether (1) the scan has been completed up to N=0 and the direction of increase or decrease of the printed phase value has not been reversed, and is still in the direction of increase or decrease, or (2) whether the scan has not reached N=0.

[0101] If it is determined that (2) the scan has not reached N=0, proceed to step S13 and execute the next scan of the current scan. On the other hand, if it is determined that (1) the scan has been completed to N=0 and the direction of increase or decrease of the printed phase value has not been reversed, and is still in the direction of increase or decrease, proceed to step S19.

[0102] <<Step S19>>

[0103] In step S19, since it is determined that the scan has been completed up to N=0 and the direction of increase or decrease of the printed phase value has not reversed, but is still in the direction of increase or decrease, this is considered an anomaly, and an alarm (warning) is issued. After that, the process jumps to the end. In addition, when the alarm is issued, the operator shall check.

[0104] As described above, the present invention is characterized in that, in the state where the deflection electrode is not energized, an excitation voltage value is applied to the piezoelectric element in multiple scans in a manner that scans from the high voltage side to the low voltage side within a specified voltage range. For the ink droplets generated by the applied excitation voltage value, a charged voltage is applied to apply charge according to any multiple printing phases, and the amount of charge applied to the ink droplets is detected by a charge sensor to obtain the printing phase. For the printing phase detected in each scan, when the relationship between the current printing phase and the previous printing phase reverses from the increasing side to the decreasing side and the judgment that the printing phase decreases is true for two consecutive times, the excitation voltage value corresponding to the printing phase in the previous scan before the first decrease judgment is used as the final excitation voltage value.

[0105] Therefore, the excitation voltage value of the piezoelectric element suitable for forming ink droplets can be automatically determined, so the optimal excitation voltage value can be easily determined without familiarity.

[0106] Furthermore, the present invention is not limited to the above-described embodiments, but includes various modifications. The above embodiments are described in detail for ease of understanding of the present invention and are not limited to having all the structures described. In addition, a part of the structure of one embodiment can be replaced with the structure of another embodiment, and the structure of another embodiment can be added to the structure of one embodiment. For the structures of each embodiment, other structures can also be added, deleted, or replaced.

[0107] Explanation of reference numerals in the attached figures

[0108] 1…Main ink container, 2…Ink, 3…Supply valve, 4…Supply pump, 5…Main filter, 6…Pressure regulating valve, 7…Ejection valve, 8…Nozzle, 9…Supply pipe, 10…Ink droplet, 11…Ink tank, 12…Recovery pump, 13…Recovery pipe, 14…Secondary ink container, 15…Replenishment valve, 16…Replenishment pipe, 17…Diluent container, 18…Diluent, 19…Diluent pump, 20…Dilution valve, 21…Dilution replenishment pipe, 22…Exhaust pipe, 23…Civilized electrode, 24…Deflection electrode, 25…Charge sensor, 26…Printed object, 27…Civilized signal generation circuit, 28…Charge amplification circuit, 29…ROM, 30…RAM, 31…Graphics RAM, 32…MPU, 33…Excitation voltage application circuit, 100…Inkjet recording device, 200…Bus.

Claims

1. A continuous-jet, electrically controlled inkjet recording device, comprising: An excitation voltage circuit applies an excitation voltage to a piezoelectric element disposed in an ink nozzle for ejecting ink droplets. A charged electrode, disposed downstream of the ink nozzle in the direction of ink droplet travel, is used to charge the ejected ink droplet; a deflection electrode, disposed downstream of the charged electrode in the direction of ink droplet travel, is used to deflect the flight direction of the ink droplet charged by the charged electrode; a charge sensor measures the amount of charge in the ink droplet charged by the charged electrode; and a control unit controls the excitation voltage circuit, the charged electrode, the deflection electrode, and the charge sensor. The control unit is characterized in that it includes: The excitation voltage scanning setting unit applies an excitation voltage value to the piezoelectric element in multiple scans, in a manner that scans from the high voltage side to the low voltage side within a specified voltage range, while the deflection electrode is not energized. A printing phase measurement unit applies charge to ink droplets generated by an applied excitation voltage at multiple arbitrary printing phases, and uses a charge sensor to detect the amount of charge applied to the ink droplets to determine the appropriate printing phase; and The excitation voltage determination unit, for the printing phase detected in each scan, when the relationship between the current printing phase and the previous printing phase reverses from the increasing side to the decreasing side, and the judgment that the printing phase decreases is true twice consecutively, uses the excitation voltage value corresponding to the printing phase in the scans between the two before and two after the first decrease judgment as the final excitation voltage value.

2. The inkjet recording device as claimed in claim 1, characterized in that: The excitation voltage determination unit uses the excitation voltage value corresponding to the printing phase in the previous scan before the first reduction judgment as the final excitation voltage value.

3. The inkjet recording device as described in claim 2, characterized in that: After the excitation voltage determination unit calculates the final excitation voltage value, the control unit no longer executes the scan of the excitation voltage scan setting unit.

4. The inkjet recording device as described in claim 2, characterized in that: If, during all scans, the excitation voltage determination unit determines that the relationship between the current printing phase and the previous printing phase has reversed from increasing to decreasing and the printing phase has decreased, the control unit issues an alarm if this determination is met twice consecutively.

5. An inkjet recording method in a continuous jet electrically controlled inkjet recording device, characterized in that: The inkjet recording device includes: an excitation voltage circuit that applies an excitation voltage to a piezoelectric element disposed in an ink nozzle for ejecting ink droplets; a charged electrode disposed downstream of the ink nozzle in the direction of ink droplet travel for charging the ejected ink droplets; a deflection electrode disposed downstream of the charged electrode in the direction of ink droplet travel for deflecting the flight direction of the ink droplets charged by the charged electrode; a charge sensor that measures the amount of charge in the ink droplets charged by the charged electrode; and a control unit that controls the excitation voltage circuit, the charged electrode, the deflection electrode, and the charge sensor. The control unit: With the deflection electrode unenergized, an excitation voltage value is applied to the piezoelectric element in multiple scans, scanning from the high voltage side to the low voltage side within a specified voltage range. For ink droplets generated by the applied excitation voltage, charge is applied by applying a charged voltage at any number of printing phases, and the appropriate printing phase is determined by detecting the amount of charge applied to the ink droplets using a charge sensor. For the printing phase detected in each scan, if the relationship between the current printing phase and the previous printing phase reverses from increasing to decreasing, and the judgment that the printing phase decreases is true for two consecutive times, the excitation voltage value corresponding to the printing phase in the scans between the two before and two after the first decrease judgment is used as the final excitation voltage value.

6. The inkjet recording method in the inkjet recording apparatus as described in claim 5, characterized in that: The excitation voltage value corresponding to the printed phase in the previous scan before the first reduction judgment is used as the final excitation voltage value.

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