JPS61272156A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To obtain an ink jet recording apparatus providing excellent printing constantly, by measuring the amount of charge on ink particles by means of video signals, and by setting an exciting voltage in a region charged normally. CONSTITUTION:A video signal VCH1 for detection is impressed on a first dot of an EP character. Thereafter a sensor signal VS1 given on the occasion of the charged ink particle flying is caught. A video signal VCH2 is given to a subsequent dot, and a sensor signal VS2 is obtained. Thereafter this operation is repeated sequentially until VCHn is given. An exciting voltage is not varied during a one-cycle period (T1). Then, a difference between the adjacent sensor signals is calculated. In the case when charging is excellent, the difference between the adjacent sensor signal voltages is fixed constantly. A cycle wherein a value of the voltage difference deviates from an allowable value is determined to be imperfect in charging. Checking is conducted for all cycles in this way, and the exciting voltage is set at the center of an excellent cycle.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention charges ink particles with a voltage proportional to the character size, deflects them with an electrostatic field of a certain strength, and moves the printed object relatively. The present invention relates to an inkjet recording device that forms images, and particularly to an inkjet recording device equipped with a mechanism that detects the amount of charge on ink particles and adjusts the excitation voltage to the nozzles so that the charge is proportional to the size of one character.

[Background of the invention]

The conventional inkjet printer was published in Japanese Patent Application Laid-open No. 57-1315.
It had a function of matching the phases of an excitation signal and a charging signal to perform printing as shown in Japanese Patent Application No. 56-16312. However, although this method can detect the timing of ink cutting, there is no guarantee that proper charging will occur when character signals are charged. In order to ensure proper charging, the mode of ink droplet creation must be well controlled. Conventionally, this control was done in Japanese Patent Application No. 57-61017 and Japanese Unexamined Patent Publication No. 58.
This was done using a method as shown in Japanese Patent No. 179660, in which the excitation voltage was changed depending on the ambient temperature.

In such a method, a temperature correction curve is managed for each nozzle, or a certain excitation-temperature curve is determined and nozzles that match the curve are selected.

The former method becomes almost unmanageable when the number of nozzles manufactured increases. In the latter method, it is necessary to constantly check the temperature characteristics of each nozzle, which requires a great deal of time and effort.

[Purpose of the invention]

An object of the present invention is to provide an inkjet recording apparatus that is equipped with a device that automatically sets the state of particle formation to an optimum value at all times, and that can always perform good printing even if the environmental temperature of the recording apparatus or the physical properties of the ink change.

[Summary of the invention]

The inkjet recording apparatus according to the present invention includes a recording condition optimization device that appropriately sets the following particle creation state. Generate ink particles.

In synchronization with the cutting timing of the ink particles, a step-wave video signal of a size used for actual printing is applied, the amount of charge of the ink particles charged with the video signal is measured, and the charge amount is proportional to the video signal. It is determined whether it is the amount of charge or not and it is stored. Next, the excitation voltage, which is the excitation source, is swept and the same check is performed again. The excitation voltage is sequentially swept from the lower limit to the upper limit, and as a result, the excitation voltage is set in the center of the normally charged region.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention. Ink is supplied under pressure to a nozzle 1 from the direction of the arrow, which shows the overall structure and general operation. The pressure source is not shown. Electrostrictive element 2 is excitation amplifier 1
1, the ink in the nozzle 1 is ejected from the nozzle and becomes an ink column 3. At this time, the tip of the ink column 3 is constricted in synchronization with the excitation signal frequency, and ink particles 22 corresponding to the excitation frequency are generated.

A charging electrode 4 is disposed near where the ink droplet 22 separates from the tip of the ink column, and a video signal is energized from the video amplifier 13 in synchronization with the timing of the ink droplet separation to charge the ink droplet.

The ink particles, which have received a charge proportional to the video signal voltage, are deflected while flying through the electrostatic field formed by the deflection electrodes 5a, 5b. Uncharged ink particles are collected by the gutter 9 and supplied to the nozzle again. In this figure, the ink circulation path after collection is omitted. Further, the charged ink particles 22 cross the backlash and reach the printing object 10, so that printed characters, figures, etc. can be composed of dot matrices. In the example shown in FIG. 1, the ink particles are deflected in the Y direction, and the printing object 10 moves in the X direction to form an image. The high voltage trunk 6 is used to apply a DC high voltage to the deflection electrode 5a, and the high voltage switch is a switch for turning on/off the input to the high voltage transformer 6. The high voltage transformer type-g8 is a power supply for the high voltage transformer 6. High voltage switch driver 17 is Qpu circuit 1
This is to turn on/off the high voltage switch from the microcomputer located at 8.

The CPU circuit 18 contains a microcomputer that controls the entire inkjet recording apparatus of the present invention, and the ROM 19 is a read-only storage element that holds programs and data for the operation of the microcomputer. Further, the RAM 20 is a readable/writable storage element, and is used by the microcomputer when running a program. Further, the CPU circuit 18 can freely drive circuits connected to the bus via the pass line 21. The excitation signal circuit receives the magnitude of the excitation voltage as a digital signal from the CPU circuit 18, converts it into an analog signal, and passes it to the excitation amplifier 11. The video signal circuit 14 is for receiving a digital video signal from the CPU circuit 18, converting it into an analog signal, and passing it to the video amplifier 13. The auto phase sensor 23 is a sensor for measuring the amount of charge on ink particles.The weak signal detected by the sensor is amplified by the sensor amplifier 15, and converted from an analog signal to a digital signal by the sensor signal processing circuit 16. into the circuit 18. The above is the general configuration of the present invention.

Next, detailed operation of the present invention will be described. As stated in the previous object section, the purpose of the present invention is to check the state of ink droplet formation and always maintain it in an optimal state. What is necessary for this purpose is to stably apply electric charges to the ink particles 22. FIG. 2 shows the waveforms of the detection video signal and sensor signal during one cycle of check execution. Naturally, when the ink particles are being charged by the detection video signal, it is necessary to turn off the high voltage switch 7 to prevent ink particles from flying out from the gutter 9. Therefore, it is necessary for the inkjet to perform a check while not printing. First, the excitation voltage is kept constant and the timing of particle creation is detected. The method for detecting the timing of particle creation has already been explained in detail in Japanese Patent Application No. 16312/1982 and Japanese Patent Application Laid-Open No. 131570/1983, so it will not be described here in 22.

Once the particle creation timing is determined, select the vol on the left end of Figure 2.
ll is applied to the charging electrode 4. Vc+11 is a voltage corresponding to the lowest dot level of printed characters. The ink particles are electrically charged. The charged ink droplets 22 then fly over the autophase sensor 23. During this flight, a waveform as shown in the sensor signal in FIG. 2 can be caught by the output of the sensor amplifier 15. This value is V
aI, and convert from analog to digital quantity using the sensor signal processing circuit. In this embodiment, this digital value is set to the needle side of the peak voltage of the sensor signal. It is assumed that this digital value is stored in the RAM 20. Then c
A detection video signal V Ck 2 is provided from the pu circuit 18 to the video signal circuit 14 . This voltage corresponds to the second dot level from the bottom of the printed character*
The sensor signal corresponding to Vchz is Vo. Following the same procedure, sequentially v08. This is repeated until. This completes one cycle of checking. It is assumed that the excitation voltage is not changed during one cycle period (T1). FIG. 3 shows each signal waveform when such one cycle is repeated once. The excitation signal is T2.・
...Ti is shown to be changed sequentially. Based on the sampling data collected after the end of i cycle, it is checked whether charging was performed properly in the corresponding cycle. FIG. 4 shows an example of a waveform (a) in the case of good charging and a waveform (b) in the case of inappropriate charging in the sensor signal for one cycle. On the right side of each waveform is shown one row of dot patterns when actually printed. Good printing has a uniform dot pitch in the vertical direction as shown in the figure. In contrast, in the case of defective printing, the vertical dots overlap. A defect in which the amount of charge charged to the ink droplets is inappropriate will hereinafter be referred to as a drop in level. This level drop phenomenon can be eliminated by changing the ink droplet generation mode by sequentially sweeping the excitation voltage. As is clear from FIG. 4, when charging is good, the difference between adjacent sensor signal voltages is always constant. In other words, ΔV1=V,, -V,,,A
V,=V,.

-v,,,av,=v,4. -v, 3,... and Ruto, AV.

If =AV, ==7jV3=AV, =aV, =76, it can be determined that the pitch between the dots in the vertical direction is uniform. Taking FIG. 4(b) as an example, since the third dot from the bottom is insufficiently charged, ΔV,
, =V, , -V, , and ΔV,2=V, , -V,2 have different values. In this way, in each cycle 1,
The relative voltage difference between the dots is calculated, and a cycle in which the value of the voltage difference deviates from the allowable value can be determined to be a charging failure. In this way, a check is made over the entire cycle and the excitation voltage is determined in the middle of a good cycle.

An example of this judgment is shown in FIG. 5. Seven cycles from T to T7 are checked and favorable cycles are marked with a circle.

In this example, it is determined that the T4 cycle is optimal. FIG. 6 shows a schematic flowchart of the present invention. Box 5 is for initializing various registers. Here, high pressure switch 7 is turned OFF.
, includes initialization of counters. In BOXIO, vIl, □ is first applied to the charged electrode 4, and then V is applied in BOX15 after a certain time delay.

, take in. Update to the next step with BOX20.

Determine whether one cycle has been completed. Box if incomplete
Return to IO and perform the same test. After completing one cycle B
Exit OX20 and enter BOX25.

In BOX 25, the excitation voltage is updated to the next value, and the cycle is updated at the same time. BOX 30 determines whether all cycles are complete, and if not completed, returns to Box 10 and starts checking from vawt again. When all cycle checks are completed in this way, the process enters the box 35 and calculates the difference between adjacent sensor signals. BOX 40 performs a step update and at the same time determines whether one cycle has been completed. After completing the difference calculation for one cycle, go to Box 45. Here, the next cycle is updated, and the box 50 determines whether all cycles have been completed. BO if not finished
Return to X35 and perform the difference calculation again. When all cycles are completed, determine the optimum excitation voltage using BOX55,
The voltage is applied to the electrostrictive element 2. The above is the software processing method according to the present invention.

In addition, when installing the auto phase sensor 23 as shown in FIG. 1 of the present invention, the high voltage transformer 6 is turned off.
The particle creation status cannot be checked until after that. When carrying out the check as in the present invention while the high voltage transformer 6 is kept on, a method as shown in FIG. 7 can be considered. In the case of the present invention, when checking, the same voltage as the printing character signal is applied, so the ink particles wobble as shown in A and B. The auto phase sensor 23 detects ink particles A and B so that even if the ink particles are vertically deflected, they can be sufficiently detected.
and the autophase sensor so that the distance α between them is constant. With such a configuration, detection can be performed while the high voltage transformer 6 is being applied.

〔Effect of the invention〕

According to the present invention, since the ink droplet creation state can always be set to the optimum value, the ink droplets can be reliably charged, and good recording can always be performed even if the environmental temperature of the recording device or the physical properties of the ink change. It is possible to realize an inkjet recording apparatus that can perform

[Brief explanation of drawings]

Fig. 1 is an overall block diagram of an embodiment of the present invention, Fig. 2 is a signal waveform diagram for one cycle, Fig. 3 is a signal waveform diagram for all cycles, Fig. 4 is a detailed diagram of the sensor signal, and Fig. 5 is an optimum diagram. A setting diagram of the excitation voltage, FIG. 6 is a processing flowchart of the present invention, and FIG.
The figure shows an example of application of the present invention. [Explanation of symbols] 1... Nozzle, 2... Electrostrictive element, 3... Ink column, 4... Charging electrode, 5a... Deflection electrode ■, 5b...
・Deflection electrode ○, 6... High voltage transformer, 7... High voltage switch, 8... Power supply for high voltage transformer, 9... Gutter, 10... Printed object, 11... Excitation amplifier, 12・
...Excitation signal circuit, 13...Video amplifier, 14...
・Video signal circuit, 15...Sensor amplifier, 16...
・Sensor signal processing circuit, 17... High voltage switch driver, 18... CPU circuit, 19... ROM, 20
...RAM, 21...pass line, 22...ink particles, 23...auto phase\sensor, 30-
Gutter for detection.

Claims (1)

[Claims] 1. Excite the nozzle, guide ink to the nozzle, eject the ink from the nozzle, separate it into regular ink particles, fly in the direction of the recording medium, charge these particles according to the recording signal, In an inkjet recording device that performs recording by deflecting the recording material and depositing it on a predetermined position on a recording medium, the first means for sweeping the excitation voltage and the same voltage range and number of steps as the staircase-wave recording signal and the same pulse width are used. a second means for continuously generating a monitor signal for an arbitrary period of time; a third means for measuring the amount of charge of the ink particles charged with the monitor signal; and a fourth means for storing the measured value. , using the difference between adjacent charge amounts among the charge amounts relative to the monitor signals arranged in ascending order or descending order in the charge amount data of the group measured at the same excitation voltage from among the stored charge amounts, An inkjet recording apparatus comprising: a fifth means for determining whether the excitation voltage is appropriate; and a sixth means for setting the excitation voltage to the center of the excitation voltage determined to be appropriate.