JP2003039675A - Ink-jet recorder and method for driving ink-jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recorder and a method for driving a recording head of the same wherein a meniscus behavior at nozzle openings can be controlled properly, and considerably small ink drops cart be discharged stably from nozzle openings having a large opening diameter. SOLUTION: There is provided the recording head which discharges ink by changing in accordance with driving signals the pressure in pressure chambers which communicate with the nozzle openings. At a printing time by micro dots, micro dot driving pulses are used. The driving pulse is constituted by sequentially connecting a charge element Pwc1 for drawing in the meniscus greatly, a discharge element Pwd1 for pressing out the meniscus slightly, and a charge element Pwc2 for drawing in the meniscus slightly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for recording an image, a character and the like on a recording paper by an ink jet recording head, and a method for driving the ink jet recording head, and more particularly to forming microdots. The present invention relates to a device that ejects an extremely small amount of ink droplets.

[0002]

2. Description of the Related Art Ink jet printers are well known as typical ink jet recording apparatuses.
In this printer, the dot diameter on the recording paper, that is, the image quality (resolution) depends on the amount of ink droplets ejected from the recording head.
Is decided. Therefore, it is important to control the amount of ink to be ejected.

Here, if the ejection amount of the ink droplets is controlled by the diameter of the nozzle opening, the resolution can be improved but the recording speed becomes slow when the diameter is narrowed down.
When the aperture is increased, the recording speed can be improved, but a coarse image with low resolution results.

In order to meet such conflicting requirements, there is a printer in which different amounts of ink droplets are ejected from the same nozzle opening by devising the method of driving the recording head, especially the waveform of the driving signal.

When recording extremely small dots (microdots) with this printer, a pressure generating element such as a piezoelectric vibrator is driven by a drive signal containing an appropriate drive pulse for ejecting ink droplets of different ink amounts. To do.

Then, the ink droplets are ejected by utilizing the change in the ink pressure in the pressure chamber due to the expansion and contraction of the pressure chamber.

[0007]

By the way, in recent ink jet recording apparatuses, further improvement in image quality is required. The conventional drive pulse described above can eject a small amount of ink droplets. However, from the viewpoint of improving the image quality, it is required to eject a smaller amount of ink droplets.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an ink jet recording apparatus capable of ejecting an extremely small amount of ink droplets, and an ink jet recording head driving method. To aim.

[0009]

The present invention has been proposed in order to achieve the above object, and the present invention provides a pressure chamber communicating with a nozzle opening and a pressure generating element for expanding and contracting the pressure chamber. An ink jet type recording device having a recording head having the same and a driving signal generating means for generating a series of driving signals having a driving pulse, and activating the pressure generating element by supplying the driving pulse to eject an ink droplet from the nozzle opening. In the device, the drive signal generating means includes a retracting element for expanding the pressure chamber to draw the meniscus into the pressure chamber, and a first contracting member for slightly contracting the pressure chamber expanded by the retracting element.
A drive pulse including a discharge element and a second discharge element that expands the pressure chamber contracted by the first discharge element again is generated, and the drive pulse is supplied to the pressure generating element. The inkjet recording apparatus is characterized in that the pressurized pressure chamber is again decompressed by the supply of the second ejection element to eject ink droplets.

More preferably, the drive signal generating means includes a pull-in hold element for connecting the end of the pull-in element and the start end of the first discharge element at the same potential, and the end of the first discharge element and the start end of the second discharge element. It is characterized in that a drive pulse including an ejection hold element for connecting and at the same potential is generated.

Further, the discharge expansion voltage from the start end potential to the end potential of the second discharge element is set to be equal to or lower than the discharge contraction voltage from the start end potential to the end potential of the first discharge element.

Further, the terminal potential of the second ejection element is set to the first
It is characterized in that the potential is set higher than the terminal potential of the ejection element and lower than the starting potential of the first ejection element.

Further, it is characterized in that the supply time of the retracting element is set to be equal to the natural vibration period of the pressure chamber.

Further, the drive signal generating means is characterized by generating a drive pulse including a contraction element for contracting the pressure chamber expanded by the second ejection element so as not to eject ink droplets.

Further, the contraction element is composed of a plurality of contraction sub-elements and a contraction hold element having a constant potential for connecting an end of the preceding contraction sub-element and a start of the subsequent contraction sub-element. And

Further, it is characterized in that the potential gradient of the subsequent contracting sub-element is set to be gentler than the potential gradient of the previous contracting sub-element.

The drive signal generating means includes a pre-contraction element which is arranged in front of the retracting element and changes the potential from the intermediate potential to the starting potential of the retracting element to contract the pressure chamber of the reference volume. It is characterized by generating a pulse.

The drive signal generating means is disposed after the contracting element, changes the electric potential from the terminal electric potential of the contracting element to the intermediate electric potential, and expands and restores the pressure chamber to the reference volume to stabilize the behavior of the meniscus. It is characterized in that a drive pulse including a damping element to be changed is generated.

Further, the drive signal generating means includes output voltage information holding means for holding output voltage information for defining the shape of the drive signal, change amount information holding means for holding change amount information, and output voltage information. And addition amount information that is obtained by adding the change amount information to the addition amount information, and the addition amount information is added every time the update timing arrives while switching the change amount information output from the change amount information holding unit to the addition unit. Is generated in the output voltage information holding means as new output voltage information, and a drive signal of an arbitrary shape is generated.

Further, the ejected ink droplets are micro dots which are minute ink droplets, and the series of drive signals is a drive for ejecting middle dots which are ink droplets having a larger weight than the micro dots. It is characterized by including a pulse.

More preferably, the series of drive signals includes a drive pulse for ejecting a large dot which is an ink droplet having a weight larger than that of the middle dot.

Further, the series of drive signals are characterized in that drive pulses for ejecting ink droplets of respective ink weights are arranged in the order of the large dot, the micro dot, and the middle dot.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an ink jet recording apparatus of the present invention will be described below with reference to the drawings. Figure 1
7 is the first of the ink jet recording apparatus according to the present invention.
FIG. 1 shows an embodiment, FIG. 1 is a perspective view of an inkjet printer which is a typical inkjet recording device, FIG. 2 is a sectional view showing a recording head, FIG. 3 is a block diagram showing a configuration of a control system of the recording head, and FIG. Is a block diagram showing the configuration of the drive signal generation circuit, FIG. 5 is a timing diagram showing the process of generating a waveform that becomes a drive signal in the drive signal generation circuit, and FIG. 6 is a description of the supply of a series of drive signals and drive pulses. FIG. 7 and FIG. 7 are time charts showing the microdot drive pulse.

In this ink jet printer 1, a carriage 2 is movably attached to a guide member 11, and the carriage 2 is connected to a timing belt 14 which is stretched between a drive pulley 12 and an idle pulley 13. ing. The drive pulley 12 is joined to the rotary shaft of the pulse motor 15, and the carriage 2 is moved (main scanning) in the width direction of the recording paper 3 by driving the pulse motor 15.

A recording head 4 is attached to the surface (lower surface) of the carriage 2 facing the recording paper 3. The recording head 4 causes the ink supplied from the ink cartridge 5 to be ejected as an ink droplet from the nozzle opening 51 (see FIG. 2).

Therefore, at the time of recording, the printer 1 ejects ink droplets from the recording head 4 in synchronization with the main scanning of the carriage 2, rotates the platen 16 in conjunction with the reciprocal movement of the carriage 2, and rotates the recording paper 3 onto the recording paper 3. Move (sub-scan) in the paper feed direction. As a result, images, characters, etc. based on the print data are recorded on the recording paper 3.

A home position is set outside the recording area within the movement range of the carriage 2, and a cleaning mechanism 17 for cleaning the recording head 4 and a capping mechanism 18 for capping are arranged side by side at this home position. It is provided.

In addition to the above, a printer controller 19 for integrally controlling the operation of each part constituting the printer 1 is attached to the housing.

As shown in FIG. 2, the recording head 4 is constructed by joining the flow path unit 7 to the front end surface of the base 40.
Then, the piezoelectric vibrator 6 (a kind of pressure generating element) housed in the base 40 pressurizes the ink in the pressure chamber 71 to eject an ink droplet from the nozzle opening 51 formed in the nozzle plate 50.

The base 40 has a box-like shape in which a housing chamber 43 for housing the transducer unit 46 is formed, and is made of, for example, a resin material. The accommodation chamber 43 is continuous from the opening on the side of the joint surface with the flow path unit 7 to the opposite surface.

The flow path unit 7 is constructed by joining the nozzle plate 50 to one surface of the flow path forming plate 55 and the vibrating plate 60 to the other surface of the flow path forming plate 55.

The flow path forming plate 55 is formed of a silicon wafer or the like, and is divided into a predetermined pattern by etching the silicon wafer or the like. The flow path forming plate 55 communicates with each nozzle opening 51. 72, partition walls forming a plurality of ink supply passages 73 and the like connected from the common ink chamber 72 to each pressure chamber 71 are appropriately formed. The common ink chamber 72 is provided with a connection port connected to the ink supply pipe 48, and the ink stored in the ink cartridge 5 is supplied to the common ink chamber 72 through this connection port.

The nozzle plate 50 has a plurality of (for example, 96) nozzle openings 51 ... Opened in a row at a pitch corresponding to the dot formation density.

The vibrating plate 60 includes a stainless steel plate 61 and a PPS.
A double structure in which an elastic film 62 such as a film is laminated is adopted, and a stainless plate is annularly etched at a portion corresponding to each pressure chamber 71 to form an island portion 70 in the ring.

The vibrator unit 46 is composed of the piezoelectric vibrator 6 (a kind of pressure generating element) and the fixed substrate 42. The piezoelectric vibrator 6 is formed in a comb-like shape by forming slit portions at a predetermined pitch corresponding to each pressure chamber 71 on a single piezoelectric vibrator plate in which piezoelectric bodies and electrode layers are alternately laminated. It Further, the fixed substrate 42 is the comb-shaped oscillator 6
It is fixed to the base end part of.

This vibrator unit 46 includes the piezoelectric vibrator 6
The housing chamber 43 of the base 40 with the tip of the base facing the opening 41
It is accommodated by being inserted into the inside and fixing the fixed substrate 42 to the inner wall of the accommodation chamber 43. In this housed state, each tip of the piezoelectric vibrator 6 is brought into contact with the corresponding island portion 70 of the diaphragm 60.

Each piezoelectric vibrator 6 expands and contracts in the element longitudinal direction orthogonal to the stacking direction by applying a potential difference between the electrodes facing each other, and displaces the elastic film 62 partitioning the pressure chamber 71. That is, in this recording head 4, the piezoelectric vibrator 6 is extended in the element longitudinal direction, so that the island portion 7 is formed.
0 is pushed to the nozzle plate 50 side, and the island portion 70
The peripheral elastic film 62 is deformed and the volume of the pressure chamber 71 is reduced. Further, when the piezoelectric vibrator 6 is contracted in the element longitudinal direction, the displacement of the elastic film 62 expands the volume of the pressure chamber 71. As the pressure chamber 71 expands and contracts, the pressure chamber 71
A pressure fluctuation occurs in the ink filled inside, and an ink droplet is ejected from the nozzle opening 51 of the flow path unit 7.

Next, the electrical configuration of the printer 1 will be described. As shown in FIG. 3, the printer controller 19
Is supplied to the external interface 191, the RAM 192 that temporarily stores various data, the ROM 193 that stores control programs and the like, the control unit 194 that includes a CPU, the oscillation circuit 195 that generates a clock signal, and the recording head 4. A drive signal generation circuit 8 that generates a drive signal COM and functions as a drive signal generation unit of the present invention, various signals such as dot pattern data (bitmap data) developed based on the drive signal and print data, and the recording head 4. And the like, and is provided with an internal interface 196 and the like to be supplied to the drive system side.

The external interface 191 receives print data such as a character code, a graphic function, and image data from a host computer (not shown) or the like. Also, a busy signal (BUSY) and an acknowledge signal (ACK) are sent through the external interface 191.
Are sent to a host computer or the like.

The RAM 192 is a work memory, and includes a reception buffer RB, an intermediate buffer MB, and an output buffer OB.
And so on. That is, the reception buffer RB temporarily stores print data received via the external interface 191, the intermediate buffer MB stores intermediate code data converted by the control unit 194, and the output buffer OB stores dot pattern data. . The dot pattern data is print data obtained by decoding the gradation data.

The ROM 193 stores font data, graphic functions, etc. in addition to a control program (control routine) for performing various data processing.

The control unit 194 performs various controls based on the control program read from the ROM 193, reads the print data in the reception buffer RB, converts the intermediate code data obtained by converting the print data into the intermediate buffer. Store in MB. In addition, the intermediate code data read from the intermediate buffer MB is analyzed, the dot pattern data is developed by referring to the font data and the graphic function stored in the ROM 193, and the necessary decoration processing is performed. Output buffer O
Store in B.

When the dot pattern data for one line which can be printed by one main scan of the print head 4 is obtained, the dot pattern data for one line is output from the output buffer OB through the internal interface 196. The data is sequentially output to the recording head 4. When one line of dot pattern data is output from the output buffer OB, the expanded intermediate code data is erased from the intermediate buffer MB, and expansion processing is performed on the next intermediate code data.

The electric drive system 44 of the recording head 4 includes a shift register 94 (94A to 94N) and a latch circuit 95 (9
5A to 95N), a level shifter 96 which is a voltage amplifier
(96A to 96N), switch 97 (97A to 97)
N) and the piezoelectric vibrator 6 (6A to 6N) are sequentially connected, and these are provided for each nozzle opening 51.

The operation of ejecting ink droplets in the recording head 4 is controlled by the controller 194. In this ejection control, first, the data of the most significant bit string in the print data (SI) array is serially transmitted from the output buffer OB in synchronization with the clock signal (CK) of the oscillator circuit 195, and the shift register elements 94A to 94N are sequentially transferred. To set.
When the print data is set in the shift register elements 94A to 94N for all the nozzle openings 51 ..., Latch signals (LAT) are output to the latch elements 95A to 95N at a predetermined timing to shift register elements 94A to 94N.
The print data set in N is latched by the latch elements 95A to 95A.
Make N latch.

The latched print data is supplied to the level shifter elements 96A to 96N. Each of the level shifters 96A to 96N is configured to boost the print data up to a voltage value that the switches 97A to 97N can drive, for example, several tens of volts when the print data is "1". Switch 9 for the printed data
7A to 97N, so that the switch 97A to
97N is brought into a connected state by the print data. When the print data is, for example, "0", the corresponding level shifter elements 96A to 96N do not boost the voltage.

The drive signal COM from the drive signal generation circuit 8 is applied to each of the switches 97A to 97N, and when the switches 97A to 97N are in the connected state, the piezoelectric vibrators 6A to 97N connected to the switches 97A to 97N are connected. The drive signal COM is supplied to 6N.

When the drive signal is applied based on the data of the most significant bit string, the control section 194 subsequently serially transmits the bit string data of the lower one bit string and sets it in the shift registers 94. When data is set in the shift registers 94 ..., A latch signal is given to latch the data, and the drive signal is sent to the piezoelectric vibrator 6
... to supply. After that, the same operation is repeatedly performed up to the lowest bit string while shifting the print data to the lower bit string one bit string at a time.

As described above, in the illustrated printer 1, the drive signal C is applied to the piezoelectric vibrator 6 (6A to 6N) of the recording head 4.
Whether or not OM is supplied is controlled by the print data. The drive signal COM is supplied to the piezoelectric vibrator 6 during the period when the print data is "1", and when the print data is "0". The drive signal COM is not supplied.

Next, the drive signal generating circuit 8 will be described. As shown in the block diagram of FIG. 4, the drive signal generation circuit 8 is configured to include a waveform generation circuit 80 and a current amplification circuit 89, and the waveform generation circuit 80 generates a waveform signal to be the drive signal COM. Current amplification circuit 89
It is designed such that it is taken in by, and the current is amplified and output as a drive signal COM.

The waveform generation circuit 80 includes a waveform memory 81,
First waveform latch circuit 82 and second waveform latch circuit 84
, An adder 83, and a digital-analog converter 86 (D /
An A converter 86) and a voltage amplification circuit 88 are provided.

The waveform memory 81 functions as a change amount information storage means for individually storing a plurality of types of voltage change amount data (change amount information) output from the control unit 49 in association with addresses. The waveform memory 81 includes a first waveform latch circuit 82 functioning as a change amount information holding unit of the present invention.
Are electrically connected. This first waveform latch circuit 8
Reference numeral 2 holds the voltage change amount data stored at a predetermined address of the waveform memory 81 in synchronization with the first timing signal. The adder 83 functions as the adding means of the present invention. The adder 83 outputs the output of the first waveform latch circuit 82 and the second waveform latch circuit 82.
The output of the waveform latch circuit 84 is input, and the second waveform latch circuit 84 is electrically connected to the output side of the adder 83. Then, the adder 83 adds the output signals to each other to obtain added voltage information.

The second waveform latch circuit 84 functions as the output voltage information holding means of the present invention, and the data (added voltage information) acquired by the adder 83 in synchronization with the second timing signal.
Is held as output voltage information for defining the waveform shape of the drive signal COM. The D / A converter 86 is electrically connected to the output side of the second waveform latch circuit 84 and converts the data held by the second waveform latch circuit 84 into an analog signal. The voltage amplifier circuit 88 is electrically connected to the output side of the D / A converter 86, and amplifies the analog signal converted by the D / A converter 86 to the voltage of the drive signal.

The current amplification circuit 89 is electrically connected to the output side of the voltage amplification circuit 88, performs current amplification on the signal whose voltage has been amplified by the voltage amplification circuit 88, and outputs it as the drive signal COM.

In the drive signal generation circuit 8 having the above configuration, a plurality of change amount data indicating the voltage change amount are individually stored in the storage area of the waveform memory 81 prior to the generation of the drive signal. For example, the control unit 194 outputs the change amount data and the address data corresponding to the change amount data to the waveform memory 81. Then, the waveform memory 81 stores the change amount data in the storage area designated by the address data. In the present embodiment, the change amount data is composed of data containing positive and negative information (increase / decrease information), and the address data is composed of a 4-bit address signal.

When a plurality of types of variation data are stored in the waveform memory 81 in this way, it becomes possible to generate a drive signal.

The drive signal is generated by the first waveform latch circuit 8
2 is switched to the adder 83, and the adder 83 is switched every time a predetermined update timing arrives.
This is performed by causing the second waveform latch circuit 84 to hold the acquired data as new output voltage information, thereby generating a drive signal of an arbitrary shape.

In this embodiment, the first waveform latch circuit 82
Change amount data set to the first waveform latch circuit 8 and the 4-bit address signal input to the waveform memory 81.
2 and the first timing signal input to the signal line 2. That is, the waveform memory 81 selects target change amount data based on the address signal. Then, when the first timing signal is input, the first waveform latch circuit 82 reads the selected variation data from the waveform memory 81 and holds it.

The change amount data held in the first waveform latch circuit 82 is input to the adder 83. Since the output voltage information held by the second waveform latch circuit 84 is also input to this adder 83, the output data from the adder 83 is the change amount data held by the first waveform latch circuit 82 and the The voltage value is the sum of the output voltage information held by the two-waveform latch circuit 84. Here, since the change amount data includes positive and negative information, when the change amount data has a positive value, the output data from the adder 83 has a voltage value higher than the output voltage information (increase). To). On the other hand, when the change amount data has a negative value, the output data from the adder 83 has a voltage value (decreases) lower than the output voltage information. When the change amount data has the value “0”, the output data from the adder 83 has the same voltage value as the output voltage information.

The output data from the adder 83 is
The second waveform latch circuit 84 is synchronized with the second timing signal.
It is captured and retained in. That is, the output voltage information from the second waveform latch circuit 84 is updated in synchronization with the second timing signal.

Here, the operation of generating the drive signal will be described based on the specific example of FIG. In this example, the waveform memory 8
The change amount data of “0” is stored in the address A of 1,
The change amount data of + ΔV1 is stored in the address B, and the change amount data of −ΔV2 is stored in the address C.

When the first timing signal is input while the address signal indicating the address B is input to the waveform memory 81 (t1), the first waveform latch circuit 82 outputs the signal of + ΔV1 stored at the address B. Waveform memory 8 for variation data
Read from 1 and hold. After that, at the update timing defined by the second timing signal, for example, the second timing
At the rising timing of the timing signal, the second waveform latch circuit 84 takes in and holds the output data from the adder 83 (t2). Here, at the first timing after the supply of the first timing signal, ΔV1 obtained by adding ΔV1 to the GND potential which is the output voltage until then is held as a new output voltage.

After that, when the next update timing arrives after the period ΔT has passed, the second waveform latch circuit 84 adds ΔV1 to the output voltage ΔV1 up to that point, 2 · Δ.
V1 (ΔV1 + ΔV1) is held as new output voltage data (t3).

When the next update timing arrives after the period ΔT further elapses, the second waveform latch circuit 84 outputs V
(2 · ΔV1 + ΔV1) is held as new output voltage data (t4).

With respect to the above address signal, when the change amount data corresponding to the address B is held in the first waveform latch circuit 82, the content of the address signal is switched to the address A after that.

Then, the address signal indicating the address A is referred to by the next input of the first timing signal (t5). That is, the first waveform latch circuit 82 reads the change amount data of the value “0” stored in the address A from the waveform memory 81 in accordance with the input of the first timing signal and holds it.

When the change amount data of the value “0” is held in the first waveform latch circuit 82, the output data from the adder 83 has the same voltage value as the output voltage from the second waveform latch circuit 84. Therefore, while the change amount data of the value “0” is held in the first waveform latch circuit 82, even if the update timing defined by the second timing signal comes, the second waveform latch circuit 84 outputs the data. The output voltage maintains the previous voltage value V (t6, t7).

With the input of the next first timing signal, the change amount data of −ΔV2 corresponding to the address C is held in the first waveform latch circuit 82 (t.
8).

When this change amount data is held, the output voltage from the second waveform latch circuit 84 decreases by ΔV2 each time the update timing arrives (t9 to t1).
4).

In this way, the exemplified drive signal generation circuit 8
Then, the waveform of the drive signal COM can be set to a free shape only by outputting parameters such as an address signal and a clock signal from the control unit 194.

When the voltage value of the drive signal COM is increased, the piezoelectric vibrator 6 of the recording head 4 is charged and contracts in the element longitudinal direction, so that the volume of the pressure chamber 71 increases. On the contrary, when the voltage value is decreased, the piezoelectric vibrator 6 discharges electric charges and expands in the longitudinal direction of the element to reduce the volume of the pressure chamber 71.

Next, the drive signal COM generated by the drive signal generation circuit 8 and the supply of each drive pulse forming the drive signal COM will be described.

Drive signal C generated by the drive signal generation circuit 8
OM is a signal in which a plurality of types of drive pulses having different ink amounts are connected in series. As shown in FIG. 6, the drive signal COM is a microdot drive pulse DP1 for ejecting an extremely small amount of ink droplets capable of forming microdots from the nozzle openings 51, and a medium ink droplet capable of forming middle dots. Middle dot drive pulse DP2, and
A large dot drive pulse DP3 for ejecting a large ink droplet capable of forming a large dot is provided, and a large dot drive pulse DP3, a microdot drive pulse DP1,
A series of middle dot drive pulses DP2 are connected in this order.

The print data (SI) is composed of 3-bit data corresponding to the drive pulses DP1 to DP3, and the drive pulses DP1 to DP3 are selectively selected according to the contents of the print data. 6 is supplied.
That is, the most significant bit of the print data is the data for selecting the large dot drive pulse DP3, the second bit is the data for selecting the micro dot drive pulse DP1, and the least significant bit is the middle dot drive pulse. The data is used to select DP2.

When a very small ink droplet capable of forming a micro dot is ejected, the print data is set to (010),
By connecting the switch 97 during the period T2, the micro dot drive pulse DP1 is changed from the series of drive signals COM.
Are selectively supplied to the piezoelectric vibrator 6. Similarly, when ejecting the medium ink droplet corresponding to the middle dot, the print data is set to (001) and the switch 97 is connected during the period T3 to supply the middle dot drive pulse DP2 from the drive signal COM. . When a large ink droplet corresponding to a large dot is to be ejected, the print data is set to (100) and the switch 97 is kept connected during the period T1 to supply the large dot drive pulse DP3 from the drive signal COM.

The control unit 194, the shift register 94, the latch circuit 95, and the level shifter 9 which perform such an operation.
The switch 6 and the switch 97 function as a drive pulse supply means, and a required drive pulse D from a series of drive signals COM.
P1 to DP3 are selectively supplied to the piezoelectric vibrator 6.

Next, the above-mentioned microdot drive pulse D
The P1 will be described in detail.

As shown in FIG. 7, the exemplified microdot drive pulse DP1 is applied to the 0th discharge element Pwd0 and the 0th hold element Pw which function as the preliminary contraction element of the present invention.
h0, a first charging element Pwc1 that functions as a pull-in element of the present invention, a first hold element Pwh1 that functions as a pull-in hold element of the present invention, and a first discharge element Pwd1 that functions as a first discharge element of the present invention. , The second hold element P that functions as the discharge hold element of the present invention
wh2, the second charging element Pwh2 that functions as the second discharging element of the present invention, the third holding element Pwh3, the second discharging element Pwd2 that functions as the contracting element of the present invention, the fourth holding element Pwh4, and the 3 discharge element Pwd3
And a fifth hold element Pwh5 and a third charging element Pwc3 that functions as a vibration damping element of the present invention are sequentially connected.

The 0th discharge element Pwd0 is G at a relatively gentle downward slope θ0 from the intermediate potential (bias level) Vm.
The potential is lowered to the ND potential (zero potential, minimum potential). When the zeroth discharge element Pwd0 is supplied to the piezoelectric vibrator 6, the pressure chamber 71 contracts relatively slowly from the reference volume defined by the intermediate potential Vm to the minimum volume defined by the GND potential.

The zeroth hold element Pwh0 maintains the zero potential, which is the immediately preceding potential, for a predetermined time.

The first charging element Pwc1 raises the electric potential from the GND electric potential to the first maximum electric potential VH at the ascending slope θ1 at which ink droplets are not ejected. This first charging element Pw
When c1 is supplied to the piezoelectric vibrator 6, the pressure chamber 71 moves to the first
It rapidly expands to the maximum volume defined by the maximum potential VH. Due to this expansion, the pressure inside the pressure chamber 71 is reduced, and the meniscus (the free surface of the ink exposed at the nozzle opening 51)
Are largely drawn inside the pressure chamber 71.

In this embodiment, the first charging element Pw
Before supplying c1, the 0th discharge element Pwd0 and the 0th hold element Pwh0 are supplied, the pressure chamber 71 is contracted from the reference volume to the minimum volume, and the 0th hold element Pwh is supplied.
It is inflated rapidly after a lapse of time defined by 0.
Therefore, the meniscus is once pushed out in the ink ejection direction and then largely drawn into the pressure chamber 71 side.

By doing so, the behavior of the meniscus can be made more stable than when the meniscus in a stationary state is suddenly drawn into the pressure chamber 71. This is the 0th
It is considered that this meniscus can be largely drawn to the pressure chamber 71 side in accordance with the movement of the meniscus accompanying the supply of the discharge element Pwd0.

Here, the intermediate potential Vm is equal to the pressure chamber 7
It is a potential that defines a reference volume of 1, and is determined based on the drive voltage Vh, that is, the potential difference from the first maximum potential VH (maximum potential) to the GND potential (minimum potential). And
The intermediate potential Vm can be set within a range in which the potential difference Vc0 from the GND potential is 5% to 30% of the drive voltage Vh,
It has been confirmed by experiments that this potential difference Vc0 is optimally set to 15% of the drive voltage Vh.

Regarding the supply time (pulse width) of the first charging element Pwc1, in this embodiment, the supply time is set to be substantially equal to the natural vibration period Tc of the pressure chamber 71. This is to appropriately control the contraction of the pressure chamber 7. That is, by setting the supply time of the first charging element Pwc1 to be substantially equal to the natural vibration period Tc, the residual vibration of the pressure chamber 71 due to the contraction of the piezoelectric vibrator 6 can be prevented. This can prevent a so-called crosstalk phenomenon in which expansion / contraction of a certain pressure chamber 71 is transmitted to the adjacent pressure chamber 71.

The first hold element Pwh1 is an element that maintains the first maximum potential VH, which is the immediately preceding potential, for a predetermined time, and has a pulse width of 1 μsec, for example.

The first discharge element Pwd1 is an element that lowers the potential from the first maximum potential VH to the second maximum potential VH2 with a steep falling gradient θ2. This first discharge element Pwd1
Is supplied to the piezoelectric vibrator 6, the pressure chamber 71 is slightly contracted and the pressure chamber is slightly pressurized. As a result, the meniscus largely drawn by the first charging element Pwc1 is slightly pushed back in the ink ejection direction.

The supply time (pulse width) of the first discharge element Pwd1 can be set within a range of 1 to 3 μsec, for example, but is set to 1 μsec in this embodiment.
This is because the shorter the supply time of the first discharge element Pwd1 is, the higher the flight speed of the ink droplet can be.

The second maximum potential VH2, which is the terminal potential of the first discharge element Pwd1, is defined based on the drive voltage Vh. The second maximum potential VH2 can be set within a range in which the potential difference Vc1 from the GND potential is 55% to 75% of the drive voltage Vh, and the potential difference Vc1 is set to the drive voltage Vc1.
It has been experimentally confirmed that the optimum value is 70% of h. That is, if the second maximum potential VH2 is set to a high potential, the amount of ink droplets can be reduced, but if the second maximum potential VH2 is too high, the amount of ink droplets fluctuates or the trajectory during flight becomes unstable.

Regarding the first discharge element Pwd1,
From the viewpoint of increasing the flight speed of the ink droplet, it is preferable to supply the ink continuously to the first charging element Pwc1.
However, in the present embodiment, the first charging element Pwc1 and the first charging element Pwc1
The first hold element Pwh1 is arranged between the discharge element Pwd1 and the end of the first charge element Pwc1 and the first discharge element P.
The starting end of wd1 is connected at the same potential. This is to protect the electric drive system 44 of the recording head 4. That is, when the first charging element Pwc1 and the first discharging element Pwd1 are continuously supplied, the potential gradient is rapidly switched and a through current flows through the switch 97 (97A to 97N), deteriorating the stability of the ejection operation. I will end up. Then, if the same potential is maintained for a certain period of time by the first hold element Pwh1, the rapid switching of the potential gradient is alleviated, and the problem that a through current flows through the switch 97 can be prevented.

The second hold element Pwh2 is an element that maintains the second maximum potential VH2, which is the immediately preceding potential, for a predetermined time, and has a pulse width of 1 μsec, for example.

When the second hold element Pwh2 is supplied to the piezoelectric vibrator 6, the contraction operation of the pressure chamber 71 by the first discharge element Pwd1 is stopped. At this time, it is considered that the central portion of the meniscus extends in the shape of a thin column toward the ink ejection direction due to the inertial force.

The second charging element Pwc2 is an element which raises the potential from the second maximum potential VH2 to the third maximum potential VH3 with a steep rising gradient θ3. This second charging element Pwc
When 2 is supplied to the piezoelectric vibrator 6, the pressure chamber 71 expands again. Then, as the pressure chamber 71 expands, 2 pL
A very small amount of ink droplets separate from the column of the meniscus and fly.

This is because if the pressure chamber 71 is expanded while the columnar portion of the meniscus is expanding in the ink ejection direction, the pressure chamber 71 is decompressed and the force to be returned to the pressure chamber 71 side is exerted on the columnar portion. It is thought to work. That is, it is considered that when a force that is pulled back to the pressure chamber 71 side acts on the columnar portion that is extending in the discharge direction, the columnar portion is torn at the tip side as compared with the conventional case due to this pulled back force.

Regarding the third maximum potential VH3 which is the termination potential of the second charging element Pwc2, the third maximum potential VH3 is
The potential difference Vc2 from the GND potential is 70% of the drive voltage Vh
It can be set within a range of up to 120%. Then, in the present embodiment, the third maximum potential VH3 is set to the second maximum potential VH.
The potential is set higher than 2 and equal to or lower than the first maximum potential VH. In other words, the discharge expansion voltage from the start potential to the end potential of the second charging element Pwc2 is calculated as the first discharging element Pwd.
The discharge contraction voltage from the start potential to the end potential of 1 is set to be equal to or lower than the discharge contraction voltage. Specifically, the potential difference Vc2 is the drive voltage Vh.
Is set to 80%. Regarding the supply time (pulse width) of the second charging element Pwc2, this supply time can be set within a range of, for example, 1 to 3 μsec.
In this embodiment, it is set to 1 μsec.

By setting in this way, it is possible to stabilize the ink amount and the trajectory of the ink droplet while keeping the flying speed of the ink droplet high.

Further, regarding the second charging element Pwc2, from the viewpoint of reducing the ink amount, it is preferable to supply the second charging element Pwc2 after the first discharging element Pwd1. However, in this embodiment, the first discharging element Pwd1 and the second charging element Pwd
The second hold element Pwh2 is arranged between the wc2 and
The end of the first discharge element Pwd1 and the start of the second charge element Pwc2 are connected at the same potential.

This is to protect the electric drive system 44 of the recording head 4. That is, when the second charging element Pwc2 is continuously supplied after the first discharging element Pwd1, the potential gradient is rapidly switched and a through current flows through the switch 97 (97A to 97N), which deteriorates the stability of the ejection operation.
Then, when the potential is maintained for a certain period of time by the second hold element Pwh2, the rapid switching of the potential gradient is alleviated, and the problem that a through current flows through the switch 97 can be prevented.

The third hold element Pwh3 is an element that maintains the third maximum potential VH3, which is the immediately preceding potential, for a predetermined time, and has a pulse width of 1 μsec, for example.
The third hold element Pwh3 is the first hold element P
It is an element that performs the same function as wh1, and secures a hold period for stably performing the discharge by the next second discharge element Pwd2.

The second discharge element Pwd2 is a contraction sub-element of the present invention, and has a descending gradient θ4 such that ink drops are not ejected from the third maximum potential VH3 to the contraction hold potential VH4.
The potential down to.

The fourth hold element Pwh4 is the contraction hold element of the present invention, and has the end of the second discharge element Pwd2 (previous contraction sub-element) and the start of the third discharge element Pwd3 (post-contraction sub-element). The contraction hold potential VH4 is used for connection.

The third discharge element Pwd3 is the contraction sub-element of the present invention, and lowers the contraction hold potential VH4 to the GND potential with a descending gradient θ5 such that ink drops are not ejected.

Then, in the present embodiment, the descending gradient θ of the third discharge element Pwd3, which is the potential gradient of the contracting sub-element later.
5 is set to a gentler gradient than the descending gradient θ4 of the second discharge element Pwd2, which is the potential gradient of the contracting subelement.

When the second discharge element Pwd2, the fourth hold element Pwh4, and the third discharge element Pwd3 are sequentially supplied to the piezoelectric vibrator 6, the third hold element Pwh is obtained.
The pressure chamber 71 expanded with the supply of 3 contracts to the minimum volume defined by the GND potential. Here, in the present embodiment, since the fourth hold element Pwh4 having a constant potential is arranged between the second discharge element Pwd2 and the third discharge element Pwd3, the contraction operation of the pressure chamber 71 by the second discharge element Pwd2. And the contraction operation of the pressure chamber 71 by the third discharge element Pwd3, the contraction of the pressure chamber 71 is stopped for a very short time.

If the contraction is temporarily stopped during the operation of contracting the pressure chamber 71, the pressure chamber 71 from the volume defined by the third maximum potential VH3 to the minimum volume is reached.
It is possible to stabilize the ejection of ink droplets as compared with the case where the ink is continuously contracted. For example, it is possible to reduce the difference in the amount of ink droplets and the flying speed between the case where ink droplets are ejected from all the nozzle openings 51 and the case where ink droplets are ejected from several nozzle openings 51.

It is considered that this is because the pressure fluctuation in the pressure chamber 71 at the time of contraction becomes small by contracting the pressure chamber 71 stepwise. Furthermore, the third discharge element Pw
It is considered that the pressure fluctuation in the pressure chamber 71 at the time of contraction can be further reduced by setting the descending gradient θ5 of d3 to be a gentler gradient than the descending gradient θ4 of the second discharge element Pwd2.

It has been experimentally confirmed that the supply time of the fourth hold element Pwh4 can be made stable by making the supply time of the fourth hold element Pwh4 as short as possible. Therefore, in the present embodiment, the pulse width is set to 1 μsec which is the minimum time that the electric drive system 44 can control.

The contraction hold potential VH4 is defined based on the drive voltage Vh. This contraction hold potential V
In H4, the potential difference Vc3 from the GND potential is the drive voltage Vh.
It can be set in the range of 20% to 50% of that, and in the present embodiment, it has been confirmed by experiments that it is optimal to set the potential difference Vc3 to 40% of the drive voltage Vh.

The supply time (pulse width) of the second discharge element Pwd2 can be set within the range of 2 to 5 μsec, but is 3.5 μsec in this embodiment in consideration of the contraction hold potential VH4. Similarly, the supply time (pulse width) of the third discharge element Pwd3 is 5 to 8 μsec.
Can be set in the range of, but in the present embodiment, 6.5 μs
It is as ec.

The fifth hold element Pwh5 is the immediately preceding GN.
The D potential is maintained as it is for a predetermined time, and the third charging element Pwc
3 raises the potential from the GND potential to the intermediate potential Vm with a rising gradient θ6.

The third charging element Pwc3 connects the pressure chamber 71 to G
The vibration of the meniscus is converged in a short time by expanding and returning from the minimum volume defined by the ND potential to the reference volume defined by the intermediate potential Vm. The supply time of the third charging element Pwc3 in the present embodiment is set in alignment with the natural vibration cycle Ta of the piezoelectric vibrator 6. Thereby, the residual vibration of the piezoelectric vibrator 6 due to the contraction of the piezoelectric vibrator 6 can be suppressed to a low level, and the pressure chamber 71 can be smoothly expanded.

The fifth hold element Pwh5 is the third hold element Pwh5.
The supply start timing of the charging element Pwc3 is defined. That is, by setting the supply time of the fifth hold element Pwh5, the expansion of the pressure chamber 71 by the third charging element Pwc3 can be started at the optimum timing.

As described above, when the above-mentioned microdot drive pulse DP1 is supplied to the piezoelectric vibrator 6, the first
The pressure in the pressure chamber 71 is rapidly reduced by the charging element Pwc1, and the meniscus is largely drawn inside the pressure chamber 71.
Immediately after this pressure reduction is completed, the pressure chamber 71 is slightly pressurized by the first discharge element Pwd1, and immediately after this pressurization is completed, the pressure chamber 71 is decompressed again by the second charging element Pwc2.

In this series of operations, the first discharge element P
The ink column generated by the pressurization by wd1 (the columnar part formed by the central part of the meniscus) is applied with the pulling force toward the pressure chamber 71 side generated by the pressure reduction of the pressure chamber 71 by the second charging element Pwc2. Therefore, only the tip portion of the ink column separates from the ink column and flies as an ink droplet.

Therefore, it is possible to eject an ink droplet having a smaller amount of ink than before, for example, an ink droplet of 2 pL. Further, in this ejection control, since only the tip portion of the thinly grown ink column can be ejected as an ink droplet, there is little trailing (satellite) of the ejected ink droplet. As a result, it is possible to prevent image quality deterioration and device contamination due to satellite dots (mist).

By the way, the microdot drive pulse according to the present invention is not limited to the above shape. FIG. 8 is a time chart showing a second embodiment of the present invention and showing microdot drive pulses of other shapes.

The second embodiment has the same device configuration and the like as the first embodiment described above, and changes the waveform of the microdot drive pulse by changing the parameters given to the drive signal generating circuit 8.

This microdot drive pulse DP1 '
Are a first charging element Pwc1 ′ that functions as a pull-in element of the present invention, a first hold element Pwh1 that functions as a pull-in hold element of the present invention, and a first discharge element Pwd1 that functions as a first discharge element of the present invention. , The second hold element Pw that functions as the discharge hold element of the present invention
h2, the second charging element Pwc2 that functions as the second discharging element of the present invention, the third hold element Pwh3, the second discharging element Pwd2 that functions as the contracting element of the present invention, and the fourth
Hold element Pwh4 and third discharge element Pwd3 '
It is considered as a signal in which and are sequentially connected.

The difference between the microdot drive pulse DP1 'and the microdot drive pulse DP1 of the first embodiment is that the 0th discharge element Pwd0 and the 0th hold element Pw are included.
h0, the fifth hold element Pwh5 and the third charging element P
There is no wc3, and the starting potential of the first charging element Pwc1 ′ and the ending potential of the third discharging element Pwd3 ′ are the intermediate potential Vm.

Even if this microdot drive pulse DP1 'is supplied to the piezoelectric vibrator 6, the microdot drive pulse D
Similar to P1, the pressure chamber 71 is rapidly depressurized by the first charging element Pwc1 ′, the meniscus is largely drawn to the inside of the pressure chamber 71, and immediately after the depressurization ends, the pressure chamber 71 is slightly pressurized by the first discharging element Pwd1. The pressure chamber 71 is depressurized and the pressure chamber 71 is depressurized again by the second charging element Pwc2 immediately after the pressurization is completed, so that an extremely small amount of ink droplets can be ejected. Then, in the microdot drive pulse DP1 ′, a necessary pulse width (first charging element Pwc1
Since the time from the start end of 'to the end of the third discharge element Pwd3' can be made shorter than the drive pulse DP1, it is suitable for the printer 1 that performs high-speed recording.

FIG. 9 is a time chart showing a third embodiment of the present invention and showing a microdot drive pulse of still another shape. Also in the third embodiment, the configuration of the apparatus is the same as that of the first embodiment described above, and the waveform of the microdot drive pulse DP1 is changed by changing the parameter given to the drive signal generation circuit 8.

This microdot drive pulse DP1 ″
Are a first charging element Pwc1 ′ that functions as a pull-in element of the present invention, a first hold element Pwh1 that functions as a pull-in hold element of the present invention, and a first discharge element Pwd1 that functions as a first discharge element of the present invention. , The second hold element Pw that functions as the discharge hold element of the present invention
h2, the second charging element Pwc2 that functions as the second discharging element of the present invention, the third hold element Pwh3, and the second discharging element Pwd2 ′ that functions as the contracting element of the present invention are sequentially connected as a signal. There is.

The difference between the microdot drive pulse DP1 "and the microdot drive pulse DP1 'of the second embodiment is that the fourth hold element Pwh4 and the third discharge element Pw are different.
The point is that d3 ′ is deleted and the terminal potential of the second discharge element Pwd2 ′ is set to the intermediate potential Vm.

Even if this microdot drive pulse DP1 ″ is supplied to the piezoelectric vibrator 6, the microdot drive pulse D
Similar to P1, the pressure chamber 71 is rapidly depressurized by the first charging element Pwc1 ′, the meniscus is largely drawn to the inside of the pressure chamber 71, and immediately after the depressurization ends, the pressure chamber 71 is slightly pressurized by the first discharging element Pwd1. The pressure chamber 71 is depressurized and the pressure chamber 71 is depressurized again by the second charging element Pwc2 immediately after the pressurization is completed, so that an extremely small amount of ink droplets can be ejected. Then, even with this microdot drive pulse DP1 ″, a necessary pulse width (first charging element Pwc1
Since the time from the start end of 'to the end of the second discharge element Pwd2' can be made shorter than the drive pulse DP1, it is suitable for the printer 1 that performs high-speed recording.

FIG. 10 shows a fourth embodiment of the present invention. In this embodiment, an example in which a drive signal COM different from that in FIG. 6 is adopted is shown. For example, in the example shown in FIG.
It is composed of bit data D1, D2, D3,
The print data D1 is associated with the intra-print micro-vibration pulse 1013, the print data D2 is associated with the micro dot pulse 1014, and the print data D3 is associated with the middle dot drive pulse 1015. Then, by appropriately changing the respective data D1, D2, D3, it is possible to eject a plurality of types of ink droplets having different amounts from the nozzle opening 51.

For example, the print data is D1 = 1, D2 =
1 and D3 = 0, fine vibration pulse in print 1013
And the microdot drive pulse 1014
, And ink droplets of microdots are ejected from the nozzle openings 51. In addition, each data is D1 = 1, D2
= 0, D3 = 1, fine vibration pulse in print 10
13 and the middle dot drive pulse 1015 are applied to the piezoelectric vibrator 6, and ink droplets of middle dots are ejected from the nozzle openings 51. Similarly, each data is D1 = 1, D2
= 1 and D3 = 1, the minute vibration pulse in printing 1
013, the micro dot drive pulse 1014, and the middle dot drive pulse 1015 are applied to the piezoelectric vibrator 6,
Ink droplets generated by the micro dot drive pulse 1014 and ink droplets generated by the middle dot drive pulse 1015 are ejected to form a large dot. In addition, each data is D1
= 1, D2 = 0, D3 = 0, the in-print micro-vibration pulse 1013 is applied to the piezoelectric vibrator 6, and the meniscus at the nozzle opening 51, that is, the free surface of the ink exposed at the nozzle opening 51. Vibrates slightly. As a result, the ink in the nozzle openings 51 is agitated, and the thickening of the ink is prevented.

In this embodiment, the micro dot drive pulse 1014 and the middle dot drive pulse 1015 are used.
By continuously applying and discharging the piezoelectric vibrator 6, the large dots are discharged. As for the micro dots and the middle dots, by applying the respective driving waveforms to the piezoelectric vibrator 6 as described above, for example, ink droplets of 4 ng and 11 ng are ejected from the nozzle openings 51.

Further, the drive signal COM of FIG. 10 is provided with the in-print micro-vibration pulse 1013 prior to each drive waveform for ejecting ink droplets. By applying the micro-vibration pulse 1013 in the print to the piezoelectric vibrator 6, the piezoelectric vibrator 6 slightly contracts and extends,
The pressure chamber 71 slightly expands and contracts. This small expansion
The meniscus slightly vibrates to the extent that the ink is not ejected due to the contraction, and the thickening of the ink can be prevented.

Next, the microdot drive pulse 1014 shown in FIG. 10 will be described in detail with reference to FIG. In the microdot drive pulse 1014 shown in FIG. 11, the upward gradient portion of the upward convex waveform charges the piezoelectric vibrator 6 of the recording head and serves as the pull-in element P1 that draws ink into the pressure chamber, and the downward gradient gradient The portions are the first contraction element P2 and the second contraction element P4 that contract the pressure chamber by discharging the piezoelectric vibrator 6. Further, a first hold element Ph that connects the end of the retracting element P1 and the start end of the first contraction element P2 at a constant potential, the end of the first contraction element P2 and the second contraction element P4.
And a second hold element P3 having a constant potential.

Microdot drive pulse 101 of FIG.
4, the first contraction element P2 for expanding the piezoelectric vibrator 6
A second hold element P3 that temporarily stops the expansion is applied between the second contraction element P4 and the second contraction element P4. In this case, by applying the second hold element P3 while the ink column is formed by the first contraction element P2, the ink droplet is separated and a minute ink droplet is ejected. When the ink droplet is ejected, the meniscus is largely drawn in the direction opposite to the nozzle opening 51. Here, the second hold element P
3 is maintained for a predetermined time, and is lowered toward the lower limit potential at an appropriate timing. The second contraction element P4 expands the piezoelectric vibrator 6, and thus acts in the direction of pushing the meniscus toward the nozzle opening.

Therefore, by appropriately adjusting the time for maintaining P3, the force of returning the meniscus in the direction of the pressure chamber after ejecting the ink droplets and the force of the piezoelectric vibrator 6 for contracting the pressure generating chamber are offset, and The amount of meniscus drawn after the droplet is discharged is reduced. Therefore, it is possible to reduce the residual vibration of the meniscus after the ink droplets are ejected.

For example, the time from the moment when the ink droplet is ejected to the maximum amount of pulling in the meniscus after the ink droplet is ejected is about 3.5 μs to 5.5 μs. In this case, according to the experiment conducted by the inventor, the time for maintaining P3 was appropriately in the range of 0.8 μs to 1.2 μs.

Furthermore, the inclination of the first contraction element P2 is adjusted,
Residual vibration of the piezoelectric vibrator can be reduced by adjusting the sum of the application times of the signals of the first contraction element P2 and the second hold element P3 to 1/2 of the natural vibration cycle of the piezoelectric vibrator.

Further, the inclination of the second contraction element P4 for reducing the residual vibration of the ink in the pressure generating chamber after the ink droplet is ejected is from the start of the first contraction element P2 to the second contraction element P4.
The time to the end of is set to be approximately equal to the natural vibration period Tc of the pressure generating chamber. That is, the pulse width of the second contraction element P4 = natural oscillation period Tc of the pressure generating chamber− (pulse width of the first contraction element P2 + pulse width of the second hold element P3). By setting the sum of the pulse widths of the first contraction element P2, the second hold element P3, and the second contraction element P4 as the natural vibration period Tc of the pressure generation chamber, it is possible to damp the residual vibration of the pressure generation chamber. .

According to the result of the experiment conducted by the inventor,
The potential of the second hold element P3 is set to the potential Vh of the charging element P1.
By setting the value from 45% to 70%, it was possible to realize a drive waveform capable of stably ejecting very small ink droplets having an appropriate ejection speed. This is set so that the time from the start of the discharge pulse P2 to the end of the second contraction element P4 is substantially equal to the natural vibration period Tc of the pressure generating chamber, so that, for example, the second hold element P
When the potential of 3 is low, the inclination of the discharge pulse P2 becomes large and the inclination of the second contraction element P4 becomes small, so that sufficient vibration damping action cannot be obtained with respect to the ejection energy and ink ejection becomes unstable. Because. On the other hand, the second hold element P
When the potential of 3 is high, the slope of the discharge pulse P2 becomes small. This means that the inclination of P2 becomes small and the second contraction element P4
As a result, the appropriate ink ejection speed cannot be obtained. The application time of the second hold element P3 is constant here.

The microdot drive pulse shown above does not limit the included drive signal COM. For example, in FIG.
11 may be applied to the drive signal COM shown in FIG. 11, or the microdot drive pulse DP1 shown in FIGS. 7 to 10 may be included in the drive signal COM shown in FIG. I don't mind.

In each of the above-described embodiments, the piezoelectric vibrator 6 that expands the pressure chamber 71 by charging and contracts the pressure chamber 71 by discharging is illustrated, but the pressure chamber 71 contracts by charging and the pressure chamber 71 expands by discharging. A similar configuration can be achieved by using a piezoelectric vibrator.

The pressure generating element that changes the volume of the pressure chamber 71 is not limited to the piezoelectric vibrator. For example, it may be a magnetostrictive element. Furthermore, the microdot described above means that the ink weight is, for example, 1 ng (nanogram) to
6 ng, a middle dot is a dot having a larger weight than a micro dot, for example, an ink weight is 7 ng to 11 ng,
Similarly, a large dot has an ink droplet of 11 ng or more, but since the weight of the ejected ink changes depending on the characteristics of the ink used, it is not particularly limited to this numerical range.

[0139]

As described above, the present invention has the following effects.

That is, since the pressure chamber is expanded to draw in the meniscus, the pressure chamber is slightly pressurized, and the pressure chamber is expanded again after the pressurization to eject the ink droplets, so that an extremely small amount from the nozzle opening. Ink droplets can be ejected. As a result, the size of the dots formed can be made smaller than in the conventional case, and the image quality can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of an ink jet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a recording head.

FIG. 3 is a block diagram showing a configuration of a control system.

FIG. 4 is a block diagram showing a configuration of a drive signal generation circuit.

5 is a timing diagram showing a process of generating a waveform of a drive signal in the drive signal generation circuit of FIG.

FIG. 6 is a diagram illustrating a drive signal and a drive pulse.

FIG. 7 is a time chart showing microdot drive pulses.

FIG. 8 is a time chart showing a microdot drive pulse according to the second embodiment of the present invention.

FIG. 9 is a time chart showing a microdot drive pulse according to the third embodiment of the invention.

FIG. 10 is a diagram illustrating a drive signal and a drive pulse according to the fourth embodiment of the present invention.

FIG. 11 is a time chart showing a microdot drive pulse according to the fourth embodiment of the present invention.

[Explanation of symbols]

1 Inkjet recording device 2 carriage 3 recording paper 4 recording head 5 ink cartridges 6 Piezoelectric vibrator 7 flow path unit 8 Drive signal generation circuit 11 Guide member 12 Drive pulley 13 Idler pulley 14 Timing belt 15 Drive motor 16 Platen 17 Cleaning mechanism 18 Capping mechanism 19 Controller 40 base 41 opening 42 unit board 43 accommodation room 44 Electric drive system 46 oscillator unit 48 ink supply pipe 50 nozzle plate 51 nozzle opening 55 Spacer 60 diaphragm 61 stainless steel plate 62 Elastic membrane 70 Island 71 Pressure chamber 72 common ink chamber 73 ink supply path 80 Wave forming circuit 81 Waveform memory 82 First Waveform Latch Circuit 83 adder 84 Second Waveform Latch Circuit 86 Digital-to-analog converter 88 voltage amplifier circuit 89 Current amplification circuit 94 shift register 95 Latch 96 level shifter 97 switch 191 External interface 192 RAM 193 ROM 194 Control unit 195 oscillator circuit 196 Internal interface 1013 Micro vibration pulse An example of 1014 microdot drive pulse 1015 Example of large dot drive pulse

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C057 AF33 AG12 AG44 AG47 AM03                       AM15 AM16 AM18 AM21 AM22                       AM40 AN01 BA04 BA14

Claims (15)

[Claims] 1. A drive comprising: a recording head having a pressure chamber communicating with a nozzle opening and a pressure generating element for expanding and contracting the pressure chamber; and drive signal generating means for generating a series of drive signals having drive pulses. In an ink jet recording apparatus in which a pressure generating element is operated by supplying a pulse to eject an ink droplet from a nozzle opening, the drive signal generating unit is a pulling element that expands a pressure chamber to pull a meniscus into the pressure chamber. Generating a drive pulse including a first discharge element that contracts the pressure chamber expanded by the retracting element and a second discharge element that expands the pressure chamber contracted by the first discharging element again. The pressure chamber supplied to the generating element and pressurized by the supply of the first discharge element is decompressed again by the supply of the second discharge element. An ink jet recording apparatus characterized by ejecting ink droplets by. 2. The drive signal generating means connects a pull-in hold element that connects the end of the pull-in element and the start end of the first ejection element at the same potential, and the end of the first ejection element and the start end of the second ejection element. The ink jet recording apparatus according to claim 1, wherein a drive pulse including an ejection hold element connected at the same potential is generated. 3. The ejection expansion voltage from the starting potential to the termination potential of the second ejection element is set to be equal to or lower than the ejection contraction voltage from the starting potential to the termination potential of the first ejection element. The ink jet recording apparatus according to claim 2. 4. The terminal potential of the second ejection element is set to a potential higher than the terminal potential of the first ejection element and lower than the starting potential of the first ejection element.
The ink jet recording apparatus according to item 1. 5. The supply time of the retracting element is set so as to be aligned with the natural vibration period of the pressure chamber.
5. The inkjet recording device according to any one of 4 to 4. 6. The drive signal generating means generates a drive pulse including a contraction element for contracting the pressure chamber expanded by the second ejection element so as not to eject ink droplets. 5. The inkjet recording device according to any one of 5 above. 7. The contraction element comprises a plurality of contraction sub-elements and a contraction hold element having a constant potential that connects the end of the preceding contraction sub-element and the start of the subsequent contraction sub-element. The inkjet recording apparatus according to claim 6. 8. The ink jet recording apparatus according to claim 7, wherein the potential gradient of the subsequent contraction subelement is set to be gentler than the potential gradient of the previous contraction subelement. 9. The drive including a pre-contraction element, which is disposed in front of the retracting element and changes the potential from an intermediate potential to a starting potential of the retracting element to contract the pressure chamber of the reference volume. The ink jet recording apparatus according to claim 1, wherein a pulse is generated. 10. The driving signal generating means is disposed after the contracting element, changes the electric potential from the terminal electric potential of the contracting element to the intermediate electric potential, and expands and restores the pressure chamber to the reference volume to stabilize the behavior of the meniscus. 10. A drive pulse including a damping element to be converted is generated.
5. The inkjet recording device according to any one of 1. 11. The drive signal generation means includes output voltage information holding means for holding output voltage information for defining the shape of the drive signal, change amount information holding means for holding change amount information, and output voltage information. And addition amount information that is obtained by adding the change amount information to the addition amount information, and the addition amount information is added every time the update timing arrives while switching the change amount information output from the change amount information holding unit to the addition unit. 11. The ink jet recording apparatus according to claim 1, wherein the drive voltage having an arbitrary shape is generated by holding the output voltage information as new output voltage information in the output voltage information holding means. 12. In a method of driving an ink jet recording head, wherein a pressure in a pressure chamber communicating with a nozzle opening is changed, and an ink droplet is ejected from the nozzle opening due to the pressure change in the pressure opening, a pressure is applied to draw a meniscus into the pressure chamber. A method for driving an ink jet recording head, characterized in that the inside of the chamber is decompressed, the pressure chamber is slightly pressurized after the decompression, and then the pressure chamber is decompressed again to eject ink droplets. 13. The ejected ink droplet is a micro dot which is a minute ink droplet, and the series of drive signals is a drive for ejecting a middle dot which is an ink droplet having a larger weight than the micro dot. The method for driving an inkjet recording head according to claim 12, further comprising a pulse. 14. The ink jet recording head according to claim 13, wherein the series of drive signals includes a drive pulse for ejecting a large dot, which is an ink droplet having a larger weight than the middle dot. Driving method. 15. The drive pulse for ejecting ink droplets of respective ink weights is arranged in the order of the large dot, the micro dot, and the middle dot in the series of drive signals. 7. A method for driving an ink jet recording head according to [4].