JPH0114873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a charged deflection type inkjet recording device, and in particular, corrects the amount of distortion correction of a deflected droplet according to the amount of deflection of the deflected droplet, that is, the magnitude of the kinetic energy of the deflected droplet. In this way, the printing quality is improved.

Generally, in a charge deflection type inkjet recording device, ink droplets are charged and deflected according to printing information, and are printed on a recording paper. At this time, each ink droplet creates an air flow behind it, and when the subsequent ink droplet enters this airflow, the air resistance of the subsequent ink droplet decreases, so the preceding and following ink droplets approach each other. or they may combine to cause printing distortion. Furthermore, since printing ink droplets are electrically charged, Coulomb force acts between each charged ink droplet, and this Coulomb force disturbs the spacing between each ink droplet, causing printing distortion. Furthermore, the amount of charge of the ink droplet that is about to be charged is reduced by the influence of the preceding charged ink droplet, which also causes printing distortion. For example, US Pat. No. 3,946,399 has been proposed to solve these drawbacks.
The invention of U.S. Pat. No. 3,946,399 detects the printed pattern in advance and corrects the amount of charge according to the pattern in order to compensate for the mutual influence of charged ink droplets due to Coulomb force and deflection distortion due to air resistance. The number of deflection stages is 32.
When the number of steps increases, it becomes ineffective. The reason for this is that as the number of deflection stages increases, the amount of distortion increases because the ink droplets fly close together, and since the time the ink droplets are flying varies depending on the amount of deflection, the amount of distortion increases depending on the amount of deflection. This is because the amounts of
Therefore, in order to perform correction appropriately, it is necessary to add correction according to the number of deflection stages.

1 to 3 are diagrams for explaining an example of an inkjet recording device previously proposed by the applicant. In the figures, 1 is a clock pulse generation circuit, 2 is a frequency dividing circuit, and 3 is a phase shift circuit. , 4 and 5 are amplifiers, 6
7 is a search pulse generation circuit, 7 is a charge correction circuit, 8 is a digital-to-analog (A/D) conversion circuit, and 9 is an amplifier. The excitation frequency of the head is 132kHz.
It is assumed that two guard drops are provided to reduce distortion, but these guard drops are not necessarily required. Therefore, the charging frequency to the ink droplet is 44kHz. In addition, the charging voltage is 50~
It is variable up to 240V depending on the input. In FIG. 1, the clock pulse generated by the clock pulse generation circuit 1 is 1056kHz, and the frequency divider circuit generates a clock pulse of 1056kHz.
The frequency is divided into 1/8, 1/3, and 1/24. Signal ₁ , which is frequency-divided to 1/8, is an excitation pulse with a particleization frequency of 132kHz, 1/8.
Signal ₂ divided by 24 is a 44kHz charging pulse, 1/3
Signal ₃ is a 352kHz correction clock. The charge correction circuit 7 stores correction amounts, sequentially reads out the correction amounts, and controls whether or not to add them depending on the presence or absence of corresponding data.The result of the addition is as follows.
The signal is converted into an analog signal by the D/A conversion circuit 8 and applied to the charged electrode through the amplifier 9. Therefore, the amount of correction is determined by the ROM in the charge correction circuit 7,
It is stored in a binary form in a memory such as RAM, and along with this correction amount, a basic charge code that causes each ink droplet to reach a predetermined position when deflected independently is also stored. This is shown in FIG. 2, where the charge code is 11 bits, divided into 3 bits, 4 bits, and 4 bits and displayed in octal, hexadecimal, and hexadecimal. Therefore, the memory has an 11-bit parallel configuration, 11 (bits) x 8 (dots) x
Any memory having a bit count of 32 (stages) or more may be used. Note that the code of 7FF in the 31st stage _F3 is such that complements are added to implement -1. In addition, the basic charge code is non-linear because air resistance varies depending on the amount of deflection, and the correction amount is determined based on this single ink droplet. is calculated from the simulation results using an electronic computer, and is further determined through experimentation.

FIG. 3 is a detailed diagram of the charge correction circuit 7, in which:
11 is an address counter, 12 is a memory (ROM), 13 is a gate circuit, 14 is an adder, 1
5 is a shift register, 16 is a multiplexer, 1
7 is a latch circuit, 18 is a D/Q flip-flop circuit, and 19 is a gate circuit, which operate as follows.

(1) When the print signal becomes high level, the address counter 11 becomes operational and is counted up by the correction clock signal ₃ . Since the frequency of the correction clock signal ₃ is eight times as high as the frequency of the charging pulse signal ₂ , eight horizontal data items shown in FIG. 2 are read out during one period of the charging pulse.

(2) The print data is delayed by the shift register 15, and the output of _O3 represents the data to be charged. That is, O ₀ , O ₁ , O ₂ indicate trailing charged droplets, corresponding to F ₃ , F ₂ , F ₁ in FIG. 2, respectively, and O ₄ to _{O 7} indicate leading charged droplets, respectively. This corresponds to P ₁ to _{P 4} in Figure 2.

(3) The lower 3 bits of the address counter 11 are introduced into the multiplexer 16, and if the contents of the lower 3 bits are 0, the contents of O ₀ are output, and the lower 3 bits are input to the multiplexer 16.
If the content of the bit is 1, the content of _O1 is controlled to be output. That is, a total of eight pieces of data, seven pieces before and after the printing data, are selected according to the contents of the lower three bits of the address counter.

(4) The output of the multiplexer 16 is sent to the gate circuit 13
The gate circuit 13 controls the output of the memory 12. That is, if the output of the multiplexer 16 indicates "correction is present", the output of the memory 12 is supplied to the adder 14 through the gate circuit 13 and added as a correction value. The output of the adder 14 is delayed by the latch circuit 17 and added to the next correction value. However, the input to the latch circuit 17 is inhibited when the contents of the lower three bits of the address counter 11 become "7", and the contents become "0".

(5) The output of the adder 14 is also supplied to the D/Q flip-flop circuit 18, and is sampled at the rising edge of the charging pulse. As a result, the corrected value is transferred to the D/Q flip-flop circuit 18.
It is controlled depending on the presence or absence of printing data, and when the data indicates "presence", it is sent as a charge code to the D/A conversion circuit 8 through the gate circuit 19, thereby enabling correction. Become.

As described above, according to the above-mentioned prior art, it is possible to perform appropriate distortion correction corresponding to the presence or absence of printing data and the number of deflection stages.
This method has the drawback that the kinetic energy of the flying ink droplets changes, resulting in a change in the amount of deflection, and at the same time, printing distortion increases. In order to solve these drawbacks, for example, the amount of deflection of flying ink droplets can be detected and the amplification factor of the charge amplifier can be controlled. For example, when the gain code is H'80',
A charging voltage of 250V is applied to the charging electrode to obtain a deflection of 5.5mm, and the deflection variation of 5.5mm±1mm is controlled by changing the gain code from H'00' to H'FF'. can do.

FIG. 4 is a schematic diagram of the main parts for explaining an example of a deflection amount control type inkjet recording device, in which 20 is a microcomputer, 21 is an inkjet ejection head, 22 is a piezoelectric vibrator, and 23 is a charging electrode. , 24 is a charge detection electrode, 25 is a deflection electrode, 26 is a gutter, 27 is an upper deflection amount detection electrode,
28 is the lower deflection amount detection electrode, 29 is Qj (charge amount)
Detection integration circuit, 30, droplet cutting phase control circuit, 3
1 is a piezoelectric vibrator drive circuit, 32 is a charge detection circuit,
33 is a charge signal generation circuit, 33a is a reference charge code generation circuit, 33b is a D/A conversion circuit, 33c is an amplification gain control circuit, and 34 is a charge (Vxd) correction code generation circuit, which is an input of the D/A conversion circuit 33b. teeth,
The 32nd stage reference code H'618' is specified, and control is performed to increase the gain code if there is an output to the lower detection electrode 28, and to decrease the gain code if there is an output to the upper detection electrode 27. ,the result,
The output Vda after D/A conversion will be corrected by α _xd . In other words, the reference gain code is α ₀
Then, Vn=Vdan α ₀ (1+α _xd −α ₀ /α ₀ ).

FIG. 5 is a detailed diagram of the deflection position detection electrode section for correcting deflection amount fluctuations. In the detection correction mode, the carriage is stopped at the detection electrode position, and the charge signal generation circuit 33 , the reference charge code (in the standard state, A is shown in Figure 4).
At the paper position shown in , for example, a code such that Xd = 5.5 mm) is input to the D/A conversion circuit 33b, and the ink droplets are continuously charged at a constant cycle of n (for example, 63) guard drops to deflect the ink droplets. , this is electrode 2
7 and 28, and the gain of the amplifier is held constant until the output level of the Qj detection and integration circuit 29 reaches the threshold level. Here, for example, if the deflection amount is smaller than 5.5 mm and the integrating circuit 29
7, the Xd correction code generation circuit 34 is controlled to correct and maintain the amplification gain control circuit 33c in the direction of increasing the gain of the amplification circuit. When the output of the circuit 29 is the output DU from the upper detection electrode 27, the gain of the amplifier circuit is corrected to decrease. Next, the charge is deflected again, and the Qj detection integration circuit 2
9 is repeated, and as shown in Figure 5, the initial correction amount (design value specified by the code) is decreased by 1/2, and the amount of change in gain increase or decrease is reduced by 1. /2, and when the DL and DU outputs are switched with the minimum amount of change (design value), the detection correction ends, and the gain is fixed at that gain and the printing operation begins.

However, when the amount of deflection is controlled as described above, it has been found that if the amount of deflection is controlled when the amount of deflection is large, the quality of printed characters is significantly degraded. At the same time, since the amount of deflection is controlled by reducing the amount of charge on the ink droplet to compensate for the decrease in the kinetic energy of the ink droplet, the distortion that the ink droplet receives while flying is increased. I also found out that it was for the sake of becoming.

The present invention has been made in view of the above-mentioned circumstances, and is particularly applicable to a charged deflection type inkjet recording device in which deflection amount control is performed, in which the distortion correction amount is changed according to the magnitude of the control amount (correction amount). This is intended to improve printing quality.

FIG. 6 is a main part configuration diagram for explaining one embodiment of the inkjet recording device according to the present invention, and FIG.
The figure is a flowchart for explaining the operation of the present invention, and in the figure, 21 is an inkjet head;
3 is a charged electrode, 24 is a charged phase search electrode, 25 is a deflection electrode, 26 is a gutter, 27 is an upper deflection amount detection electrode, and 28 is a lower deflection amount detection electrode. Now, when a print command is generated, deflection amount control is first performed, a gain code is determined, and then this gain code is compared with a predetermined deflection amount code, for example, H'40'. As a result, when the gain code is greater than H'40', that is, when the kinetic energy of the ink droplet is large, the low correction table shown in Figure 8a is selected; ', that is, when the kinetic energy of the ink droplet is small, the High correction table shown in FIG. 8b is selected, and then,
A printing operation is started, distortion correction is performed according to the correction table selected as described above, and printing is performed. Note that the correction table shown in FIG. 8 is created so as to correct the influence of the preceding five drops S ₁ to S ₅ and the following two drops K ₁ and K ₂ .

As is clear from the above description, according to the present invention, the distortion correction table is switched according to the kinetic energy of the flying ink droplets and appropriate correction is performed, making it possible to perform high-quality printing.

[Brief explanation of drawings]

1 to 3 are diagrams for explaining an example of the prior art of the present invention, in which FIG. 1 is an electrical circuit diagram of a main part of an inkjet recording device, and FIG. 2 is a correction table (memory contents). FIG. 3 is a detailed electrical circuit diagram of the charge correction circuit shown in FIG. 1, and FIG. 4 is a schematic diagram of the main part for explaining an example of the deflection amount control type inkjet recording device. , FIG. 5 is a detailed view of the deflection amount detection electrode section shown in FIG. 4, FIG. 6 is a diagram showing the main part of the ink jet recording apparatus according to the present invention, and FIG. Flowcharts for explaining the operation, FIGS. 8a and 8b, each show an example of a correction table (memory contents) used in implementing the present invention. DESCRIPTION OF SYMBOLS 1... Clock pulse generation circuit, 2... Frequency division circuit, 3... Phase shift circuit, 6... Search pulse generation circuit, 7... Charge correction circuit, 8... D/A conversion circuit, 11... Address counter , 12...Memory, 13...Gate circuit, 14...Adder, 15
...Shift register, 16...Multiplexer,
17... Latch circuit, 18... D/Q flip-flop circuit, 21... Inkjet head, 2
3... Charged electrode, 24... Charged phase search electrode, 2
5... Deflection electrode, 26... Gutter, 27, 28...
...Deflection amount detection electrode.

Claims (1)

[Claims] 1. In an inkjet recording device that selectively charges ink droplets continuously ejected from an inkjet head depending on the presence or absence of printing data, and prints them on recording paper by deflecting them according to the amount of charge, A control means for detecting the amount of deflection of the deflected droplet in the deflection stage and controlling the amount of charge on the deflected droplet so that the deflected droplet flies to a predetermined position, and a distortion correction amount for correcting printing distortion of the deflected droplet. An inkjet recording apparatus comprising: a storage means for storing the distortion; and a correction means for selecting and correcting the distortion correction amount in accordance with a control amount of the deflection amount of the deflected droplet.