JPS60208254A - Driving circuit of ink jet head - Google Patents

Abstract

PURPOSE:To attain to eliminate the irregularity in the diameter of a recording dot, by storing the past history of printing data and controlling the driving pulse width to an ink jet head on the basis of history information. CONSTITUTION:The printing data signal (b) from the outside is stored in an n-bit shift register 100 by employing a printing timing signal (a) as a shift pulse. The printing timing signal triggers a pulse generation circuit group 101 which in turn simultaneously generates inherent pulses. A data selecting circuit 102 selects one of the output pulses of the pulse generation circuit group 101. By this mechanism, the pulse width can be controlled on the basis of the history information of printing data. The AND of the output of the data select circuit 102 and the printing data signal is taken by an AND circuit 103. This signal is inputted to an ink jet head driving amplifier circuit 104. By this method, the accurate control of a dot diameter can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application on M Beam) The present invention relates to an inkjet head drive circuit, particularly an inkjet head drive circuit of an on-demand type inkjet recording apparatus.

(Prior Art) An inkjet head of an on-demand type inkjet recording device will be described. FIG. 1 is a sectional view showing an example of the configuration of a basic on-demand crab inkjet head. In the figure, one end of an ejection chamber 1 is open to the atmosphere through an orifice 2 for ejecting ink droplets, and the other end communicates with an ink supply hole 3. Ink is supplied to the ejection chamber 1 through the entire ink supply hole 3. A piezoelectric element 5 is attached to a fusible plate 4 formed in a T-groove on a part of the wall of the injection chamber 1 to realize a revival mole 7.

By applying electrical pulses to the piezoelectric element 5.

When the fusible plate 4 is bent in a direction that reduces the volume of the ejection chamber 10, a pressure wave is generated inside, and this pressure wave causes the ink droplet 6 to be ejected from the orifice 2 toward the recording m7. It is possible to make ink droplets fly by applying electric pulses to the inkjet only when recording dots are needed.
This is a characteristic of on-demand type inkjet recording devices, and is the origin of its name.

(Problems with the Prior Art) FIG. 2 is a characteristic diagram showing an example of the droplet generation frequency vs. dot area characteristic in FIG. 1. The inkjet hand shown in FIG. 1 can generate ink droplets even at a frequency of 5 kHz or more, but as shown in FIG. 2, the dot area tends to decrease as the droplet generation frequency increases. This is because the increase in the droplet generation frequency shortens the ink filling time, causing a temporary ink supply shortage in the ink ejection chamber. Therefore, during high-speed printing, there arises an inconvenience that the recording dot diameter is affected by the print data. The phenomenon C becomes more pronounced as the droplet generation frequency increases. In particular, as shown in FIG. 3, which shows an example of recorded dots, there was a noticeable phenomenon in which the first recorded dot 8 became larger than the other recorded dots 9.

In the case of an on-demand inkjet recording apparatus, ink droplets are generated only when necessary, so the ink filling time for each ink droplet differs depending on print data. For example, if the two-droplet generation frequency is 5 kkJz, the ink filling time for each dot will be an integral multiple of 200 μsec. Such variations in ink filling time due to print data are problematic because they cause variations in the diameter of recorded dots during high-speed printing.

Needless to say, such a phenomenon impairs print quality.

(Objective of the Invention) The present invention was made to completely eliminate the variation in recording dot diameter due to print data that occurs during high-speed printing with on-demand inkjet recording devices, and is an inkjet inkjet recording device that enables high-quality printing. The purpose is to provide a head drive circuit.

(Bottom of the Invention) According to the present invention, there is provided an n-bit shift register that uses a print timing signal as a shift pulse to store the past history of print data signals, and a trigger signal that has a unique pulse width for the print timing signal. One of the output pulse signals of the pulse generation circuit, using the n-bit parallel output of the n-bit shift register as a selection signal, and the n-bit parallel output of the n-bit shift register.
a data select circuit that selects one of the two, an AND circuit that takes the logical product of the output signal of the data select circuit and the print data signal, and an incend drive amplifier circuit that receives the output signal of the AND circuit as input. An inkjet head drive circuit can be obtained having the following characteristics.

(Function) In the on-demand type inkjet head, the ink droplet volume can be controlled by the drive pulse width. FIG. 4 is a characteristic diagram showing the drive pulse width versus dot area characteristics when the μ droplet generation frequency is d 2 kHz.

According to the figure, it can be seen that by increasing the pulse width, the dot surface m' can be increased, and conversely, by decreasing the pulse #A, the dot area can be decreased. By checking the history of previous print data, it is possible to estimate the ink filling state of the ink ejection chamber of that nozzle. Therefore, by storing the past history of print data and controlling the drive pulse width for the inkjet head based on the history information of C, it is possible to always obtain a constant dot diameter regardless of the print data.

(Example) Next, the present invention will be described with reference to FIGS. 5 and 6.

FIG. 5 is a block diagram showing one embodiment of the inkjet head driving circuit of the present invention, and FIG. 6 is a circuit diagram showing the simplest example of the circuit in FIG.

In FIG. 5, two signals are applied to the inkjet head drive circuit from the outside. One is a print timing signal with a constant cycle, and the frequency of this pulse is the droplet generation frequency.The other is a print data signal. This signal turns on and off the ejection of ink droplets, and switches in synchronization with the print timing signal. The print data signal is dC1 sent to an n-bit shift register 100 using the print timing signal as a shift pulse. Here, n is an integer of 1 or more. The printing timing signal is generated by the pulse generating circuit group 101t-)IJ, and simultaneously generates and outputs a unique pulse. The data select circuit 1 uses the n-bit parallel output signal of the shift register 100 as a selection signal.
At step 02, one of the output pulses from the pulse generating circuit 101 is selected.

As a result, it is possible to control the pulse width using the history information of the print data. When the print data signal has a logical value of "0", there is no need to generate a ringing pulse, so the output of the data select circuit 102 is ANDed with the print data signal by the AND circuit 103.

This signal is input to the inkjet drive amplifier circuit 104. The inkjet driving amplifier circuit 104 has a function of converting a logic level signal to a piezoelectric element driving level of usually 50 to 150 cm.
8-010282 F Inkjet head drive circuit" is used.

FIG. 6 is a circuit diagram showing the simplest circuit example in FIG. 5, which stores only one bit of past data. In the figure, since the past data is 1 bit, a flip-flop 200 is used instead of the shift register 100 (shown in FIG. 5). The print timing signal 210 triggers the one-shot circuits 201 and 202t, and generates pulse signals 212 and 21 with specific pulse widths, respectively.
Generate 3. Here, the one-shot circuit 202 generates a longer pulse than the one-shot circuit 201. Pulse signal 2 of the above type frig 70 x 200 output
Reference numeral 12 is a selection signal for the data selection circuit 203, which selects the short pulse signal 213t- when it is at a low level, and selects the long pulse signal 214 when it is at a high level.

Therefore, according to this embodiment, a pulse synchronized with the print timing signal is applied to the inkjet head only when the print data No. 8 211 is on, and a long pulse is applied to the inkjet head when the previous print data is on. Otherwise, short pulses can be applied.

Although FIG. 6 shows the simplest circuit example of the present invention, its effect is great and can sufficiently solve the problem that the first dot becomes large during high-speed printing. If necessary, add t2'' one-shot circuits to the D-type Fling 70-bit shift register in this circuit example and change the data select circuit to one that selects 1 signal from 2n signals. , more accurate dot diameter control becomes possible.

(Effects of the Invention) As is clear from the above explanation, according to the inkjet head drive circuit of the present invention, variations in the diameter of recorded dots caused by print data that occur during high-speed printing with an on-demand inkjet recording device can be eliminated. This has the great effect of making high-quality printing possible.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an example of the pathological development of a basic on-demand inkjet head, Fig. 2 is a characteristic diagram showing an example of the droplet generation frequency vs. dot area characteristics in Fig. FIG. 4 is a characteristic diagram showing the drive pulse width versus dot area characteristics; FIG. 5 is a block diagram showing an embodiment of the inkjet head drive circuit of the present invention; and FIG. 6 is a diagram showing an example of the dot area. FIG. 2 is a circuit diagram showing the simplest circuit example. In the figure, 1... injection chamber, 2... orifice. 3... Ink supply hole, 4... Flexible plate, 5... Piezoelectric element, 6... Ink droplet, 7... Recording paper. 8.9... Recording dot, 100... Shift register, 101... Pulse generation circuit group,]
02, 203... Data selection circuit, 103
......Logic product circuit, 104...Inkjet drive amplifier circuit, 200...1] Shun flip 70 tab, 201, 202...One shot circuit, 210...Print timing signal. 211...Print data signal, 212, 213,
214...Pulse signal. α(゛) Agent Patent Attorney Uchiharame, □ 1n Koma 2 to 4 people ship size μm Jiryo J support--Human enemy 73 coarse'l, <Nora %! 5Lノ＼ Child FT tie 'V'Ty,'I; /θθ Kaya 11/1

Claims (1)

[Claims] In an inkjet drive circuit of an on-demand type inkjet recording device, an n-bit shift register stores the past history of print data signals using a print timing signal as a shift pulse, and the print timing signal is used as a trigger signal, each having a unique pulse width. a data selection circuit that selects all of the output pulse signals of the pulse generation circuit using the parallel output of n pins of the n-bit shift register as a selection signal; , 0 of the output signal of the data select circuit and the logic at- of the print data signal.
t-
Characteristic inkjet head drive circuit.