JP3414527B2 - Driving method of ink jet recording head and ink jet recording apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / recording method using an on-demand type ink jet recording head.

[0002]

2. Description of the Related Art An on-demand type ink jet recording head is equipped with a nozzle plate having a plurality of nozzle openings on the same substrate, and a spacer forming a pressure generating chamber communicating with each nozzle opening, and is shown in FIG. Like time T0-
At T1, a voltage that changes in one direction in accordance with the print timing signal is applied to the piezoelectric vibrator to expand the pressure generating chamber to suck the ink, and then keep the voltage at a constant voltage for a fixed period T1-T2. After stabilizing the meniscus, the period T2−
At T3, a voltage that changes in the other direction is applied to expand the piezoelectric vibrator, contract the pressure generating chamber to its original state, and eject ink droplets.

Since the pressure of the pressure generating chamber is changed in accordance with the print timing signal as described above, vibration of the pressure generating chamber itself as a mechanical structure and hydrodynamic vibration of the ink itself occur, and the ink After the droplet formation, a meniscus near the nozzle opening causes a reciprocating vibration between the nozzle opening side and the pressure generating chamber side.

As a result, even if the same pressure change is generated in the pressure generating chamber, the position of the meniscus formed in the vicinity of the nozzle opening with respect to the nozzle opening is different due to the driving frequency, so that the ink drop The flight speed, especially the ink droplet ejection amount, changes greatly as shown in FIG. 9, and the dot formation timing, that is, the time from the formation of one dot to the formation of the next dot becomes longer.
Drive frequency lower than the basic drive frequency
If it occurs , there is a problem that the density of the printed dots changes greatly and the print quality deteriorates.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to perform a digital processing with a simple circuit configuration to reduce the speed regardless of the repetition frequency. , A new recording method capable of ejecting ink droplets with a stable ink amount.

[0006]

In order to solve such a problem, in the present invention, a pressure generating chamber communicating with a nozzle opening and a common pressure supplying chamber for supplying ink to the pressure generating chamber via an ink supply port are provided. An ink jet recording head including a flow path forming unit having an ink chamber and a piezoelectric vibrator that expands and contracts the pressure generating chamber is used.
When printing the print data by a number, the first voltage waveform for expanding the pressure generating chamber at a speed suitable for sucking ink from the common ink chamber into the pressure generating chamber, and the pressure generating chamber A second voltage waveform that maintains the inflated state,
A third voltage waveform that contracts the expanded pressure generating chamber at a speed suitable for ejecting an ink droplet from the nozzle opening is applied in the order within the basic drive frequency to record the ink droplet , and , The inkjet recording head
1 / n (where, n is an integer of 2 or more) of the fundamental driving frequency using a draw when printing the print data, the command for sucking ink by expanding said pressure generating chamber to the pressure generating chamber The operation is performed before one cycle of the basic driving frequency, and this state is maintained until the next ink droplet ejection.

[0007]

When the output of the print data is 1 / n of the basic driving frequency, the pressure generating chamber is inflated one cycle before,
This expanded state is held until the print timing comes. This ensures sufficient time for the meniscus vibration that occurs during ink suction to settle, and the fundamental frequency
Even if the driving frequency is lower than
The position where the ink is applied becomes constant, and the decrease in the amount of ink is prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows an embodiment of an ink jet recording head used in the present invention. In the drawing, reference numeral 1 is a nozzle plate having a nozzle opening 2 formed therein, 7 is a pressure generating chamber 3, and a common one. A flow path forming plate that forms an ink chamber 4 and an ink supply port 5 that connects them;
Reference numeral 8 is an elastic plate, which are integrated to form an ink flow path unit.

Reference numeral 9 denotes a piezoelectric vibrator, which is formed by alternately laminating a piezoelectric material and a conductive material, contracts in a direction perpendicular to the stacking direction of the conductive layers in a charged state, and when the charged state is released, the conductive material is conductive. This is a so-called longitudinal vibration mode oscillator that extends in the direction perpendicular to the layers, and the tip of the elastic plate 8 is located in the region of the pressure generating chamber 3.
And the other end is fixed to the base 10.

In the recording head thus constructed, when the drive signal shown in FIG. 8 is applied to the piezoelectric vibrator 9, the ink is sucked from the common ink chamber 4 into the pressure generating chamber 3 through the ink supply port 5. When discharged in this state, the piezoelectric vibrator 9 expands to the original state and presses the elastic plate 8 to eject ink droplets from the nozzle openings 2.

FIG. 2 shows an embodiment of a drive circuit for driving the above-mentioned recording head. In the figure, reference numerals 9, 9, 9, ... The poles are connected to the drive signal generating means 12 via the semiconductor switching elements 11, 11, 11 ... And the other pole is grounded.

The switching elements 11, 11, 11
Is a solid-state switch capable of conducting in both directions by a signal applied to its gate G, and is sold under the trade name of transmission gate or the like.

Numeral 13 is a data setting means 13, and each output terminal D1, ..., Dn is a switching element 11,11,11.
Is connected to the gate G of the drive signal generating means 1
Piezoelectric vibrators 9, 9, 9 ...
Applied to the piezoelectric vibrators 9, 9, which are in a charged state,
9 is selectively discharged, or a signal for selectively maintaining a charged state is output.

FIG. 3 shows an embodiment of the above-mentioned drive signal generating circuit. In FIG. 3, reference numeral IN1 indicates the first pulse signal defining the charging time Tc (FIG. 8) and IN2. Hold time T after the end of the first pulse signal.
When h has elapsed, a second pulse signal defining the discharge time Td is applied.

A first constant current circuit composed of transistors Q2, Q3 and a resistor R1 is connected to the input terminal IN1 via a level adjusting transistor Q1, and during the input period of the first pulse signal. The capacitor C is charged from the operating voltage supply terminal VH with a time constant determined by R1 and the capacitor C, and a first voltage signal rising at a constant gradient is output to the output terminal OUT.

Then, when the first pulse signal is stopped, the capacitor C maintains the final charging voltage, and the second voltage signal is held for a hold time TH until the second pulse signal described later is input. Is output.

A transistor Q is connected to the input terminal IN2.
A second constant current circuit composed of a transistor 4, a transistor Q5, and a resistor R2 is connected to discharge the capacitor C with a time constant determined by the resistor R2 and the capacitor C during the input period of the second pulse signal. Then, a third voltage signal that drops at a constant gradient is output to the output terminal OUT. In addition, reference numerals Q6 and Q7 in the figure respectively denote the first and
It is a transistor that constitutes a current buffer that amplifies a current according to the second and third voltage signals.

FIG. 4 shows an embodiment of the above-mentioned data setting means 13, which is a piezoelectric vibrator 9 to be driven.
Flip-flops F11, ...
A first shift register 21 composed of 1n and a second shift register 22 composed of flip-flops F21, ... F2n.
Hold print data for two consecutive print cycles, generate a signal for controlling charging and discharging of the piezoelectric vibrators 9, 9, ... A third shift register 23 for serial-parallel conversion composed of F31 ... F3n
Is output to.

A correction circuit 25 is composed of an inverter I1, AND circuits G1, G2, and an OR circuit G3. The correction circuit 25 has print data at the Nth print position stored in the third shift register 23 and the first print data. As shown in FIG. 7, the piezoelectric vibrators 9, 9, ... Are inputted with the print data of the (N + 1) th and the (N + 2) th print positions sent from the data transfer section stored in the shift register 21. Is configured to generate a signal that controls the charging of.

That is, since the piezoelectric vibrators 9, 9 ... Which have ejected ink droplets at the Nth printing cycle are in a discharged state, either the (N + 1) th printing cycle or the (N + 2) th printing cycle that follows. If there is print data that has to eject ink drops, a signal for performing charge control is output in the next (N + 1) th printing cycle (states F, G, and
H).

If the print data at the Nth print position is data that does not require dot formation, (N
Only when there is data required to form dots only at the (+2) th print position, a signal for performing charge control is output in the next (N + 1) th print cycle (state B in FIG. 7). , In other states, control is performed so that charging is not performed. That is, in the case of the states C and D, the above (N
In the -1) th printing cycle, the piezoelectric vibrators 9, 9, ... Are already in the charged state because they were in the state B or the state F, and the switching elements 11, 1 are set so as to be charged again.
This is because erroneous ejection will occur if 1 ...

Reference numeral 26 is a selection circuit, which is an inverter I2,
It is composed of AND circuits G4 and G5 and an OR circuit G6, and selects either the second shift register 22 or the correction circuit 25 according to the data switching signal and outputs the data to the third shift register 23. Is configured.

Then, the data held in the third shift register 23 is latched by the latch circuit 24 by the latch signal, and the switching elements 11, 1 as parallel signals.
It is output to the gate G of 1 ... and controls the charging / discharging of the piezoelectric vibrators 9, 9.

Next, the operation of the thus constructed apparatus will be described with reference to the timing charts shown in FIGS. When a print start command is issued and the carriage equipped with the print head is traveling in a section two print cycles before the print start position, first a first and second clock signals having the same phase and cycle from a data transfer unit (not shown). Then, in synchronization with this, n bits of the print data at the print start position are transferred.

The print data for n bits is stored in the first shift register 21, and at the same time, the print data previously stored in the first shift register 21 is moved to the second shift register 22.

In the initial state, each shift register 21, 2
The flip-flops F11, ...
Since F21 ... F2n, F31 ... F3n are all cleared, all the data of "0" is output from the first shift register 21 when the first print data is transferred, and each of the second shift register 22 is output. Flip-flops F21, F22,
.... F2n will memorize all "0".

During the print data transfer period from the data transfer unit, the data switching signal is set to HIGH level, and the selecting circuit 26 operates so as to store the data from the correction circuit 25 in the third shift register 23 in parallel. .

In this way, each shift register 21, 2
After the predetermined data is stored in Nos. 2 and 23, the drive voltage generating unit 12 controls the charging of the piezoelectric vibrators 9, 9, ... From the next printing cycle, that is, the printing cycle immediately before the printing start position. The data stored in the third shift register 23 during the period when the drive signal of
Latched by and output to the gate G of the switching elements 11, 11, ....

Then, when the print timing signal one printing cycle before the print start position is generated and the drive voltage generating means 12 outputs the first voltage signal (FIG. 8), the above-mentioned charge control is performed. During this charging control period, the data switching signal is switched to LOW, the second clock signal is output for n clocks, and the second shift register that stores the print data in the printing cycle through the selection circuit 24 is stored. The print data is transferred from 22 to the third shift register 23.
Then, while the drive voltage signal generating means 12 is outputting the second voltage signal, the latch signal causes the latch circuit 24 to latch the print data of the printing cycle, in preparation for the subsequent ink droplet ejection operation.

Since the data initially stored in the flip-flops F11, ..., F1n of the second shift register 22 is "0", it is stored in the third shift register 23 via the selection circuit 26. Since the print data to be printed is also “0”, ink droplets are not ejected even if the piezoelectric vibrators 9, 9, ... 9 are charged in the print cycle immediately before the print start position. .

After the print data in the print cycle is latched in the latch circuit 24, the first and second clock signals having the same phase and cycle are sent from the data transfer unit as described above.
In synchronization with this, the next print data is transferred by n bits.

The newly transferred n-bit print data is stored in the first shift register 21, and at the same time, the print data previously stored in the first shift register 21 is moved to the second shift register 22. . Thereafter, the same operation is repeated until the print end position.

That is, as shown in FIG. 6, for example, the print data from the print start position is 1, 0, 1, ... (1 is data for forming dots, 0 is data for which dot formation is not required). when output in the order, that is in a situation which must be ink ejected at half or less of the driving frequency of the fundamental drive frequency, in advance at the time of the printing cycle of the prior one from the print period (T1, T2) Since the piezoelectric vibrator 9 is charged and the pressure generating chamber 3 is expanded, a sufficient time (Th) for allowing the meniscus to settle at a predetermined position is secured, and thus the nozzle of the meniscus. Insufficiency of the ink amount of the ink droplets due to the non-uniform position with respect to the openings does not occur. Needless to say, the basic driving cycle
In dot formation at wave number, the meniscus vibrates
In that state, the next ink drop will be ejected.
Originally, the basic drive frequency should be the proper amount of ink.
Designed for, the meniscus must be flat
There is no.

[0034]

As described above, according to the present invention,
It is possible to secure a sufficient time for the movement of the meniscus that occurs during ink suction to settle, and to prevent fluctuations in the amount of ejected ink due to fluctuations in the drive frequency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an ink jet recording head used in the present invention.

FIG. 2 is a block diagram showing an embodiment of a driving device for driving the same device.

FIG. 3 is a circuit diagram showing an embodiment of a drive signal generating means in the same apparatus.

FIG. 4 is a circuit diagram showing an embodiment of data setting means in the same apparatus.

FIG. 5 is a timing chart showing the operation of the above apparatus.

FIG. 6 is a timing diagram showing an operation of the same device at a frequency which is ½ of a basic drive frequency.

FIG. 7 is a diagram schematically showing a relationship between print data and a charged / uncharged state of the piezoelectric vibrator in the same apparatus.

FIG. 8 is a diagram showing an example of a drive signal of an inkjet recording head using a piezoelectric vibrator as an actuator.

FIG. 9 is a diagram showing a relationship between a drive frequency and an ink ejection amount.

[Explanation of symbols]

1 nozzle plate 2 nozzle openings 3 Pressure generation chamber 4 common ink chamber 5 Ink supply port 8 diaphragm 9 Piezoelectric vibrator 11 Switching element 21, 22, 23 shift registers G Gate

Claims (5)

(57) [Claims] 1. A flow path forming unit having a pressure generating chamber communicating with a nozzle opening and a common ink chamber for supplying ink to the pressure generating chamber via an ink supply port; and expanding the pressure generating chamber. Print data at a basic drive frequency using an inkjet recording head consisting of a piezoelectric vibrator that contracts.
When printing the data, the first voltage waveform for expanding the pressure generating chamber at a speed suitable for sucking ink from the common ink chamber to the pressure generating chamber, and the pressure generating chamber in the expanded state. And a third voltage waveform for contracting the expanded pressure generating chamber at a speed suitable for ejecting an ink droplet from the nozzle opening in the basic driving frequency in the order described above. The ink is applied to record with ink droplets, and the ink jet recording head is used to print at a driving frequency of 1 / n (where n is an integer of 2 or more)
When printing data, set a command for inhalation by expanding the ink the pressure generating chamber to the pressure generating chamber, performs one cycle earlier the fundamental drive frequency, of the state next ink drop ejection A method for driving an ink jet recording head, characterized in that the method is maintained until a certain point. 2. A (N + 1) th piezoelectric vibrator which continuously ejects ink droplets at the Nth printing cycle, or (N +)
When the ink droplets are ejected in any of the 2) th printing cycles, the piezoelectric vibrator that has not ejected the ink droplets in the (N + 1) th printing cycle or the Nth printing cycle is (N + 2). The method for driving an ink jet recording head according to claim 1, wherein, when the ink droplets are ejected in the second printing cycle, the ink is sucked into the pressure generating chamber in the (N + 1) th printing cycle. 3. A flow path forming unit including a pressure generating chamber communicating with a nozzle opening and a common ink chamber for supplying ink to the pressure generating chamber via an ink supply port, and the pressure generating chamber is expanded. An inkjet recording head comprising a piezoelectric vibrator for contracting, and expanding the pressure generating chamber at a speed suitable for sucking ink from the common ink chamber into the pressure generating chamber,
Voltage waveform of the pressure generation chamber, a second voltage waveform for maintaining the pressure generation chamber in an expanded state, and the pressure generation chamber at a speed suitable for ejecting ink droplets from the nozzle opening in the expanded pressure generation chamber. a switching element which connects the drive signal generating means for outputting on the basis of the clock signal to the order in the basic driving frequency of the third voltage waveform for contracting the, and said drive signal generating means and the piezoelectric vibrator, the basic drive When printing print data with frequency, first
Based on the voltage waveform of, the second voltage waveform, and the third voltage waveform
Output in the above order within the main drive frequency, and basic drive using the inkjet recording head
Print data at 1 / n of frequency (where n is an integer of 2 or more)
When printing the data, the first voltage waveform is output to the switching element before one cycle of the basic drive frequency, and then the second voltage waveform is maintained until the next ink droplet ejection. An ink jet recording apparatus comprising: a data setting unit that outputs a third voltage waveform at the time of ejection. 4. When ink droplets are ejected at either the (N + 1) th or (N + 2) th printing cycle that is followed by the piezoelectric vibrator that has ejected the ink droplets at the Nth printing cycle, N + 1) th print cycle, again N
In the case where the piezoelectric vibrator that has not ejected the ink droplets in the (n + 1) th printing cycle ejects the ink droplets in the (N + 2) th printing cycle, the first voltage waveform is applied to the data in the (N + 1) th printing cycle. The ink jet recording apparatus according to claim 3, wherein the setting means outputs the data. 5. The data setting means stores the print data for each of the piezoelectric vibrators and stores the print data according to the drive frequency, and serial - parallel converts the data from the storage means. The ink jet recording apparatus according to claim 3, wherein the ink jet recording apparatus comprises a means for outputting to the switching element.