JP2002225250A - Ink jet type recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve quality of a recorded image by arranging a hitting position of ejected ink drops with high precision. SOLUTION: Waveform intervals tA, tB between adjacent ejection pulses DP1-DP3 are set by changing the generation timing of a s mall dot ejection pulse DP2 corresponding to the difference in the flight speed of the ink drops in relation to a forward movement drive signal and a rearward movement drive signal to be generated from a drive signal generating circuit.

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 or the like by ejecting ink droplets from nozzle openings using pressure fluctuations in a pressure chamber.
The present invention relates to an apparatus that performs so-called bidirectional printing by ejecting ink droplets during both forward and backward movements of a print head.

[0002]

2. Description of the Related Art Ink jet recording apparatuses such as printers, plotters, and facsimile apparatuses include a recording head for discharging ink droplets by supplying a driving pulse, and a head for reciprocating the recording head in a main scanning direction. Some include a scanning mechanism. In this recording apparatus, an image is recorded on recording paper by ejecting ink droplets in conjunction with the movement of the recording head in the main scanning direction. This type of recording apparatus is required to improve image quality and recording speed. For this reason, so-called variable dot printing in which a plurality of types of ink droplets having different amounts of ink are ejected from the same nozzle opening, or so-called bidirectional printing in which ink droplets are ejected during both forward and backward movements of the print head, are performed. What has been proposed has been proposed.

In this recording apparatus, a drive signal in which a plurality of types of drive pulses different in the amount of ink to be ejected are connected in series is generated, a necessary drive pulse signal is selected from the drive signal, and a pressure of a piezoelectric vibrator or the like is selected. Supplying to the generating element is performed. For example, in the drive signal of FIG. 11, a drive signal in which the connection order of the drive pulse signal is reversed in the forward movement and the backward movement of the recording head is generated. That is, this drive signal is
A first medium dot ejection pulse M1 used for printing large dots and medium dots, a small dot ejection pulse S used for printing small dots, and a second medium dot ejection pulse M2 used for printing large dots. Are included in one recording cycle T, and each of these ejection pulses is the first medium dot ejection pulse M during the forward movement of the recording head.
1, small dot ejection pulse S, and second medium dot ejection pulse M2 are connected in this order. In addition, when the print head moves backward, as shown in parentheses, the second medium dot ejection pulse M2, the small dot ejection pulse S, and the first medium dot ejection pulse M1 are connected in this order. Since the first medium dot ejection pulse M1 and the second medium dot ejection pulse M2 are drive pulses having the same waveform, when these drive pulses are supplied to the pressure generating element, an amount corresponding to the medium dot is obtained. Are ejected. Further, these three ejection pulses are generated every predetermined period t.

In this printing apparatus, the connection positions of the ink droplets in the main scanning direction are aligned by reversing the connection order of the driving pulse signals at the time of forward movement and at the time of backward movement of the print head, so that the height of the printed image is high. Image quality is being improved. That is, when a small dot is to be printed during the forward movement of the print head, a small dot ejection pulse S that is generated substantially in the middle of the printing cycle T is selected.
When printing medium dots, the first medium dot ejection pulse M1 generated in the first half of the printing cycle T is selected. When printing a large dot, the first medium dot ejection pulse M1 described above and the second medium dot ejection pulse M2 generated in the latter half of the recording cycle are selected. On the other hand, when printing a small dot at the time when the print head moves backward, a small dot ejection pulse S generated almost at the middle of the printing cycle T is selected. The first medium dot ejection pulse M1 generated in the latter half is selected. When printing a large dot, the second medium dot ejection pulse M2 generated in the first half of the printing cycle and the first medium dot ejection pulse M1 are selected.

[0005]

However, since the above-described printing apparatus performs printing while moving the print head in the main scanning direction, the ejected ink droplet has an inertia component caused by the movement of the print head. Vc acts to fly obliquely to the printing surface of the recording paper. This inertial component Vc is
If the ink droplets have different flying speeds, the landing positions of the ink droplets are different between the forward movement and the backward movement when the flying speed of each ink droplet is different, and the landing position is shifted. . For example, as shown in FIG. 12, when the flying speed VmS of the small ink droplet corresponding to the small dot ejection pulse is slower than the flying speed VmM of the medium ink droplet corresponding to the medium dot ejection pulse, The droplet does not land in the middle between adjacent medium ink droplets. For this reason, the landing positions of the small dots in the pixel area W are shifted between the forward movement and the backward movement. When such a displacement of the landing position occurs, the interval between the small dots between the adjacent pixel regions becomes shorter or longer, and thus is not constant, so that the recorded image becomes rough.

[0006] The present invention has been made in view of such circumstances, and the landing positions of ink droplets are aligned with high accuracy.
It is an object of the present invention to further improve the quality of a recorded image.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above object, and the present invention is directed to a pressure chamber communicating with a nozzle opening and a pressure fluctuation in the pressure chamber. A recording head having a pressure generating element capable of causing a reciprocating movement in the main scanning direction, a driving signal generating means for generating a driving signal in which a plurality of ejection pulses capable of ejecting ink droplets are connected in series, A pulse supply unit that selects an ejection pulse from a drive signal generated by the signal generation unit and supplies the selected pulse to the pressure generation element, and is capable of ejecting ink droplets during both forward and backward movements of the printhead. In the apparatus, the drive signal generating unit includes a plurality of types of ejection pulses having different ink amounts in one recording cycle,
A forward drive signal in which a plurality of ejection pulses are connected in a predetermined order is generated during the forward movement of the recording head, and a backward drive signal in which each ejection pulse is connected in the reverse order to the forward drive signal is used for the recording head. An ink jet recording apparatus, which is generated at the time of backward movement, wherein the waveform interval between adjacent ejection pulses in the forward movement drive signal and the backward movement drive signal is determined according to the difference in the flying speed of the ink droplet. is there.

According to a second aspect of the present invention, the interval between the adjacent ejection pulses is determined in consideration of a distance from a nozzle opening to a print medium. It is a recording device.

According to a third aspect of the present invention, there is provided a laser detector capable of detecting passage of an ink droplet ejected from a nozzle opening, and calculating a flying speed of the ink droplet based on a detection signal from the laser detector. 3. The ink jet recording apparatus according to claim 1, further comprising a flight speed calculation unit.

According to a fourth aspect of the present invention, in the inkjet recording apparatus according to the third aspect, the laser detector is disposed at a flushing position at which a recording head moves when performing a flushing operation. It is.

According to a fifth aspect of the present invention, the ejection pulse includes a small dot ejection pulse selected when printing a small dot, and a first medium dot ejection pulse selected when printing a medium dot and a large dot. And a second medium dot ejection pulse selected at the time of printing a large dot, and the small dot ejection pulse is arranged between the first medium dot ejection pulse and the second medium dot ejection pulse. An ink jet recording apparatus according to any one of claims 1 to 4.

According to a sixth aspect of the present invention, the waveform interval between adjacent ejection pulses is determined by changing the timing of generating small dot ejection pulses within one recording cycle. Is an ink jet recording apparatus.

According to a seventh aspect of the present invention, the pressure generating element is constituted by a piezoelectric vibrator arranged so that the volume in the pressure chamber can be changed. An ink jet recording apparatus according to any one of claims 1 to 3.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to an ink jet printer 1 (hereinafter, referred to as a printer 1) which is a typical ink jet recording apparatus.

As shown in FIG. 1, the printer 1 has a carriage 2 which is movable in a main scanning direction (ie, a recording width direction) by a head scanning mechanism. The carriage 2 has a cartridge holder 4 for detachably holding the ink cartridge 3 and a recording head 6 capable of ejecting ink droplets from a nozzle opening 5 (see FIG. 2).

The head scanning mechanism may have any configuration as long as it can move the carriage 2 in the main scanning direction. In this embodiment, this head scanning mechanism is
A guide member 8 erected in the left-right direction of the housing 7 to movably support the carriage 2, a pulse motor 9 arranged on one side of the left and right sides of the housing 7, a drive pulley 10 rotated by the pulse motor 9, Housing 7
The idler pulley 11 disposed on the left and right side and the other side, and the timing belt 12 laid between the drive pulley 10 and the idler pulley 11 and connected to the carriage 2
The carriage 2 is moved along the guide member 8 by operating the pulse motor 9.

A home position is set in an end area within the moving range of the carriage 2 and outside the printing area, and a capping member 13 for capping the recording head 6 is provided at the home position. . Further, next to the capping member 13, the recording head 6 is provided.
The wiper member 15 for wiping the nozzle surface 27a (see FIG. 2) is disposed.

The above-mentioned capping member 13 is a substantially tray-shaped member in which a concave portion whose upper surface is open is formed.
It is made of a resin material. When the carriage 2 moves to the home position, the capping member 13 moves obliquely upward from the steady position by the cam mechanism to seal the nozzle surface 27a. Then, in the steady position, the capping member 13 is positioned at a position slightly lower than the nozzle surface 27a. Further, in order to prevent the ink from thickening near the nozzle opening 5, a flushing operation is performed using the capping member 13. That is, when the flushing condition is satisfied, the recording head 6 moves to the flushing position, that is, above the capping member 13 in the steady state, and forcibly ejects ink droplets from each nozzle opening 5. Thus, the thickened ink near the nozzle opening 5 is discharged.

At the home position (flushing position), a laser detector 15 (see FIG. 3) capable of detecting the passage of ink droplets ejected from the nozzle opening 5 is provided. The laser detector 15 includes a laser light source and a laser light receiver, and is disposed so that the laser beam intersects the flight trajectory of the ejected ink droplet. In the present embodiment, the laser detector 15 is arranged so that the laser beam is irradiated to the same height as the printing surface of the recording paper 16 (a kind of printing medium). And, this laser detector 15
Is used to detect clogging of the nozzle opening 5 and to measure the flying speed of ink droplets.

That is, when detecting clogging of the nozzle opening 5, ink droplets are ejected and an output signal from the laser light receiver is monitored. That is, when an ink droplet is ejected from the nozzle opening 5, the ink droplet thereafter blocks the laser beam. The laser beam does not reach the laser receiver while the ink droplet is blocking the laser beam. Therefore, when the ink droplet is normally ejected from the nozzle opening 5, every time the ink droplet passes through the laser beam,
The output signal from the laser receiver changes. Therefore, by monitoring the output signal from the laser light receiver at the time of the above-mentioned flushing operation or the like, it is possible to detect whether or not an ink droplet is ejected from the nozzle opening 5.

When measuring the flying speed of the ink droplet, the time from when the ink droplet is discharged to when the laser beam is interrupted is measured. That is, since the distance from the nozzle opening 5 to the laser beam is known, the flying speed of the ink droplet (that is, the average flying speed) can be measured by measuring the time from the time of ejection until the laser beam is blocked. In this case, if the time interval from the supply timing of the ejection element (described later) of the ejection pulse to the timing at which the output signal from the laser light receiver changes is measured, the measurement of the flying speed can be easily performed without using any special device. be able to. Furthermore, when the laser beam is irradiated at the same height as the printing surface of the recording paper 16 as in this embodiment, the flying speed of the ink droplet can be measured with high accuracy. In particular, since a very small amount of ink droplets are greatly affected by the viscous resistance of air, the flying speed at the time of impact is lower than that at the time of ejection, so accurate irradiation is achieved by irradiating the laser beam at the same height as the printing surface. Can measure.

The printer 1 also has a paper feed mechanism for moving the recording paper 16 in the paper feed direction (sub-scan direction). The paper feed mechanism includes, for example, a platen roller 17 (paper feed roller) disposed below the carriage 2 and a paper feed motor 18 as a driving source for rotating the platen roller 17.
, The recording paper 16 can be conveyed by a predetermined amount in a predetermined direction.

When characters and images are recorded on the recording paper 16, the printer 1 ejects ink droplets from the recording head 6 in conjunction with the movement of the carriage 2 in the main scanning direction. The recording paper 16 is moved in the paper feed direction in conjunction with. Further, in the printer 1, so-called bidirectional printing can be performed. That is,
Recording can be performed both at the time of forward movement of the recording head 6 moving from the home position to the opposite end, and at the time of backward movement of the recording head 6 returning to the home position from the opposite end. I have.

Next, the structure of the recording head 6 will be described. In the illustrated recording head 6, as shown in FIG. 2, a channel unit 22 is joined to a tip end surface of a box-shaped case 21. Then, pressure fluctuation is generated in the pressure chamber 24 in the flow path unit 22 by the vibrator unit 23 housed inside the case 21, and the ink droplets are ejected from the nozzle openings 5.

The case 21 has a box shape in which a housing space 25 for housing the vibrator unit 23 is formed, and is made of, for example, a resin material. The storage space 25 is formed in a series from the opening on the side of the joint surface with the flow path unit 22 to the opposite surface.

The flow channel unit 22 has a configuration in which a nozzle plate 27 is bonded to one surface of a flow channel forming substrate 26 and a vibration plate 28 is bonded to the other surface of the flow channel forming substrate 26. The flow path forming substrate 26 is made of, for example, a silicon wafer, and is divided into a predetermined pattern by etching the silicon wafer, and a plurality of pressure chambers 24 communicating with the corresponding nozzle openings 5, a common ink chamber 29, and a common ink chamber 29. Partition walls forming a plurality of ink supply paths 30 and the like from the ink chamber 29 to each pressure chamber 24 are appropriately formed. The common ink chamber 2
9 is provided with a connection port connected to the ink supply pipe 31, and the ink stored in the ink cartridge 3 is supplied to the common ink chamber 29 through this connection port. In the nozzle plate 27, a plurality of nozzle openings 5 are formed in rows at a pitch corresponding to the dot formation density. Diaphragm 2
8 has a double structure in which an elastic film 33 such as a PPS film is laminated on a support plate 32 made of a stainless steel plate or the like, and a portion corresponding to each pressure chamber 24 is formed by etching the support plate 32 in an annular shape. Thus, an island portion 34 is formed in the ring.

The vibrator unit 23 includes a piezoelectric vibrator 35
(A type of pressure generating element) and a fixed plate 36. The piezoelectric vibrator 35 is provided, for example, on a single laminated piezoelectric body plate in which piezoelectric bodies and electrode layers are alternately laminated, and
2 are formed in a comb shape by forming slit portions at a predetermined pitch corresponding to each of the pressure chambers 24. The fixed plate 36 is fixed to the base end of the comb-shaped vibrator.
The vibrator unit 23 is inserted into the housing space 25 of the case 21 with the tip of the piezoelectric vibrator 35 facing the opening, and is housed by fixing the fixing plate 36 to the inner wall of the housing space 25. . In this housed state, each end of the piezoelectric vibrator 35 comes into contact with the corresponding island 34 of the diaphragm 28. Each piezoelectric vibrator 35 expands and contracts in the element longitudinal direction orthogonal to the stacking direction by applying a potential difference between the opposing electrodes, and displaces the elastic film 33 that partitions the pressure chamber 24. That is, when the potential difference is increased, the piezoelectric vibrator 35 of the recording head 6 is charged and contracts in the element longitudinal direction, and the volume of the pressure chamber 24 increases. Conversely, when the voltage value is reduced, the electric charge of the piezoelectric vibrator 35 is discharged and the piezoelectric vibrator 35 extends in the longitudinal direction of the element, and the volume of the pressure chamber 24 is reduced.

In the recording head 6, the pressure in the pressure chamber 24 fluctuates by changing the volume of the pressure chamber 24 due to expansion and contraction of the piezoelectric vibrator 35. Discharge ink droplets.

Next, the electrical configuration of the printer 1 will be described. As shown in FIG. 3, the printer 1 is schematically constituted by a printer controller 41 and a print engine 42.

The printer controller 41 includes an external interface 43 (hereinafter, referred to as an external I / F 43).
A RAM 44 for temporarily storing various data, a ROM 45 for storing a control program and the like, a control unit 46 including a CPU and the like, an oscillation circuit 47 for generating a clock signal, and a circuit for supplying the recording head 6 Drive signal (CO
M), and an internal interface 49 (hereinafter, referred to as an internal I / F 49) for supplying dot pattern data (gradation data), drive signals, and the like developed based on the print data to the print engine 42. )).

The external I / F 43 receives print data including, for example, character codes, graphic functions, image data, and the like from a host computer (not shown). Also, a busy signal (BUSY) and an acknowledge signal (ACK) are transmitted through the external I / F 43.
Is output to a host computer or the like.

The RAM 44 functions as a receiving buffer, an intermediate buffer, an output buffer, and a work memory (not shown). The reception buffer temporarily stores the print data received via the external I / F 43, the intermediate buffer stores the intermediate code data converted by the control unit 46, and the output buffer stores the dot pattern data.
Note that the dot pattern data in the present embodiment is constituted by gradation data for each dot. Also, R
The OM 45 stores font data, graphic functions, and the like, in addition to a control program (control routine) for performing various data processing.

In addition to performing various controls, the control unit 46 reads print data in the reception buffer, and stores intermediate code data obtained by converting the read print data in the intermediate buffer. Further, it analyzes the intermediate code data read from the intermediate buffer and develops it into dot pattern data by referring to font data and graphic functions stored in the ROM 45. Further, the control unit 46
Performs necessary decoration processing on the developed dot pattern data, and stores the dot pattern data in an output buffer. Then, if one line of dot pattern data that can be printed by one main scan of the print head 6 is obtained,
The control unit 46 converts the dot pattern data for one line into
Output to the recording head 6 through the internal I / F 49. When one line of dot pattern data is output from the output buffer, the expanded intermediate code data is erased from the intermediate buffer, and expansion processing for the next intermediate code data is performed. Further, the control unit 46 also functions as a flight speed calculation unit of the present invention (described later), and calculates the flight speed of the ink droplet based on a detection signal from the laser detector 15.

The drive signal generation circuit 48 functions as drive signal generation means in the present invention, and generates a drive signal in which a plurality of drive pulses capable of discharging ink droplets are connected in series. That is, the drive signal generating circuit 48 includes a plurality of types of ejection pulses having different amounts of ink in one recording cycle, and outputs a forward drive signal in which a plurality of ejection pulses are connected in a predetermined order. When the recording head 6 is moved backward, a drive signal at the time of backward movement in which each ejection pulse is connected in the reverse order to the drive signal at the time of forward movement is generated. For example, the forward drive signal is
As shown in FIG. 7A, the first medium dot ejection pulse D
P1, a small dot ejection pulse DP2, and a second medium dot ejection pulse DP3 are sequentially connected to form a series of signals. As shown in FIG. 8A, the drive signal at the time of the backward movement includes a second medium dot ejection pulse DP3, a small dot ejection pulse DP2, and a first medium dot ejection pulse DP.
1 are sequentially connected to each other. That is, any of the driving signals is the medium dot ejection pulse DP1, D
The small dot ejection pulse DP2 is arranged between P3.

Here, the first medium dot ejection pulse DP1
Is a drive pulse selected at the time of recording medium dots and large dots, and ejects an ink droplet required for forming medium dots, for example, an ink droplet of 12.5 pL (picoliter) from the nozzle opening 5. Small dot ejection pulse D
P2 is a drive pulse selected at the time of recording a small dot, and ejects an ink amount required to form a small dot, for example, an ink droplet of 5.4 pL from the nozzle opening 5. The second medium dot ejection pulse DP3 is a drive pulse selected at the time of printing a large dot. In the present embodiment, the second medium dot ejection pulse DP3 has the same waveform as the first medium dot ejection pulse DP1. Therefore, the second medium dot ejection pulse D
Also at P3, for example, an ink droplet of 12.5 pL is ejected from the nozzle opening 5. The drive signal generation circuit 48
And the respective drive signals generated by the drive signal generation circuit 48 will be described later in detail.

The print engine 42 includes the paper feed motor 1
8, a pulse motor 9, an electric drive system of the recording head 6, and a laser detector 15.

The electric drive system of the recording head 6 includes a shift register including a first shift register 51 and a second shift register 52, a first latch circuit 53 and a second latch circuit 5.
4, a decoder 55, a control logic 56, a level shifter 57, and a switch circuit 58.
And a piezoelectric vibrator 35. Among these, shift registers 51 and 52, latch circuit 53,
The decoder 54, the decoder 55, the level shifter 57, and the switch circuit 58 function as a drive pulse supply unit in the present invention, and appropriately select the ejection pulses DP1 to DP3 from the drive signals as described later, and The pulse is supplied to the corresponding piezoelectric vibrator 35.

Then, each shift register 51, 52, each latch circuit 53, 54, decoder 55, switch circuit 5
8 and a plurality of piezoelectric vibrators 35 are provided corresponding to the respective nozzle openings 5 of the recording head 6. For example,
As shown in FIG. 4, the first shift registers 51A to 51N
, Second shift registers 52A to 52N, first latch circuits 53A to 53N, and second latch circuits 54A to 54N.
, Decoders 55A-55N, and switch circuits 58A-
58N and the piezoelectric vibrators 35A to 35N. In FIG. 4, the level shifter 57 is omitted, but a plurality of the level shifters 57 are also provided.

The recording head 6 is based on the dot pattern data (SI) from the printer controller 41.
Ink droplets having different amounts of ink are ejected appropriately. More specifically, the dot pattern data from the printer controller 41 corresponds to the clock signal (C
K), the data is serially transmitted from the internal I / F 49 to the first shift register 51 and the second shift register 52. The dot pattern data is 2-bit gradation data, and is set for each nozzle opening 5. Then, the data of the lower bits (L) for all the nozzle openings 5 are input to the first shift register 51, and the data of the upper bits (H) for all the nozzle openings 5 are input to the second shift register 52. .

A first latch circuit 53 is electrically connected to the first shift register 51, and a second latch circuit 54 is electrically connected to the second shift register 52. Then, a latch signal (LA) from the printer controller 41 is output.
T) is input to each latch circuit, the first latch circuit 5
3 latches the data of the lower bit of the dot pattern data, and the second latch circuit 54 latches the data of the upper bit of the dot pattern data. The set of the first shift register 51 and the first latch circuit 53 and the set of the second shift register 52 and the second latch circuit 54 that operate as described above each constitute a storage circuit and are input to the decoder 55. The previous dot pattern data is temporarily stored.

The dot pattern data latched by each of the latch circuits 53 and 54 is input to a decoder 55. The decoder 55 functions as a translation unit and translates dot pattern data composed of 2-bit gradation data to generate 3-bit print data (pulse selection information). The decoder 55 of the present embodiment includes a waveform selection table, and generates print data based on the waveform selection table. Further, a timing signal from the control logic 56 is also input to the decoder 55. The control logic 56 functions as a timing signal generator together with the control unit 46, and controls the latch signal (LAT) and the channel signal (C
H) to generate a timing signal. That is, the control logic 56 generates a timing signal each time a latch signal or a channel signal is received.

The print data translated by the decoder 55 is sequentially transferred to the level shifter 57 every time the timing specified by the timing signal arrives from the upper bit side.
Is input to The level shifter 57 functions as a voltage amplifier, and outputs an electric signal boosted to a voltage that can drive the switch circuit 58, for example, a voltage of about several tens of volts, when the content of the print data is “1”. The print data of “1” boosted by the level shifter 57 is supplied to a switch circuit 58 functioning as a switch. The drive signal generating circuit 48 is connected to the input side of the switch circuit 58.
, And a piezoelectric vibrator 35 is connected to the output side of the switch circuit 58. And
The print data controls the operation of the switch circuit 58, that is, the supply of the drive signal to the piezoelectric vibrator 35. For example, during a period in which the print data applied to the switch circuit 58 is “1”, the switch circuit 58 is connected and a drive signal is supplied to the piezoelectric vibrator 35. The potential level changes. On the other hand, during a period in which the print data applied to the switch circuit 58 is “0”, the level shifter 57 does not output an electric signal for operating the switch circuit 58. For this reason, the switch circuit 58 is turned off, and no drive signal is supplied to the piezoelectric vibrator 35.

As described above, in the illustrated recording head 6,
Whether or not a drive signal is supplied to the piezoelectric vibrator 35 can be controlled by print data. That is, the drive signal can be supplied to the piezoelectric vibrator 35 by setting the print data to “1”,
By setting the print data to “0”, the supply of the drive signal to the piezoelectric vibrator 35 can be stopped. Therefore, the forward drive signal shown in FIG. 7A and the backward drive signal shown in FIG.
Each of the ejection pulses DP1 to DP included in these drive signals
When each bit of the print data is set corresponding to 3, each of the ejection pulses DP1 to DP3 can be selectively supplied to the piezoelectric vibrator 35. By selecting a discharge pulse to be supplied to the piezoelectric vibrator 35, a plurality of types of ink droplets having different amounts can be discharged from the same nozzle opening 5.

Next, the drive signal generating circuit 48 will be described. The drive signal generation circuit 48 of the present embodiment
As shown in the block diagram of FIG. 5, the circuit is schematically configured by a waveform generation circuit 61 and a current amplification circuit 62.

The waveform generation circuit 61 includes a waveform memory 63,
A first waveform latch circuit 64 and a second waveform latch circuit 65
, An adder 66 and a digital-to-analog converter 67 (D /
A converter 67) and a voltage amplifier circuit 68.

The waveform memory 63 functions as change amount data storage means for individually storing a plurality of types of voltage change amount data output from the control unit 46. This waveform memory 6
3, a first waveform latch circuit 64 is electrically connected. Then, the first waveform latch circuit 64 holds the data of the voltage change amount stored at a predetermined address of the waveform memory 63 in synchronization with the first timing signal. The output of the first waveform latch circuit 64 and the output of the second waveform latch circuit 65 are input to the adder 66, and the output side of the adder 66 is electrically connected to the second waveform latch circuit 65 described above. I have. Then, the adder 66 functions as a change amount data adding unit, and adds and outputs the output signals.

The second waveform latch circuit 65 is output data holding means for holding data (voltage information) output from the adder 66 in synchronization with the second timing signal. D / A
The converter 67 is electrically connected to the output side of the second waveform latch circuit 65, and converts an output signal held by the second waveform latch circuit 65 into an analog signal. Voltage amplification circuit 6
Reference numeral 8 is electrically connected to the output side of the D / A converter 67, and amplifies the analog signal converted by the D / A converter 67 up to the voltage of the drive signal.

The current amplifying circuit 62 is electrically connected to the output side of the voltage amplifying circuit 68. The current amplifying circuit 62 amplifies the current of the signal whose voltage has been amplified by the voltage amplifying circuit 68 to generate the drive signal COM (COM1, COM2). Output as

The drive signal generating circuit 48 having the above configuration
In this example, prior to the generation of the drive signal, a plurality of change amount data indicating the voltage change amount is individually stored in the storage area of the waveform memory 63. For example, the control unit 46 outputs the change amount data and the address data corresponding to the change amount data to the waveform memory 63. Then, the waveform memory 63 stores the change amount data in a storage area specified by the address data. In this embodiment, the change amount data is composed of data including positive / negative information (increase / decrease information), and the address data is composed of a 4-bit address signal.

When a plurality of types of change amount data are stored in the waveform memory 63 in this manner, a drive signal can be generated. To generate the drive signal, the change amount data is set in the first waveform latch circuit 64, and the first waveform latch circuit 64 generates the drive signal every predetermined update period.
This is performed by adding the change amount data set in the waveform latch circuit 64 to the output voltage from the second waveform latch circuit 65.

In this embodiment, the first waveform latch circuit 64
The set of the change amount data to the first waveform latch circuit 6 and the 4-bit address signal input to the waveform memory 63
4 in response to a first timing signal input to the first timing signal. That is, the waveform memory 63 selects the target change amount data based on the address signal. Then, when the first timing signal is input, the first waveform latch circuit 64 reads the selected change amount data from the waveform memory 63 and holds it.

The change amount data held in the first waveform latch circuit 64 is input to the adder 66. Since the output voltage held by the second waveform latch circuit 65 is also input to the adder 66, the output data from the adder 66 is equal to the change amount data held by the first waveform latch circuit 64 and the second data. It becomes a voltage value obtained by adding the output voltage held by the waveform latch circuit 65. 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 66 has a voltage value higher than the output voltage (that is, To increase). On the other hand, when the change amount data has a negative value, the output data from the adder 66 has a voltage value lower than the output voltage (that is, decreases). When the change amount data has the value “0”, the output data from the adder 66 has the same voltage value as the output voltage. Then, the output data from the adder 66 is taken in and held by the second waveform latch circuit 65 in synchronization with the second timing signal. That is, the output voltage from the second waveform latch circuit 65 is updated in synchronization with the second timing signal.

Here, the operation of generating the drive signal will be described based on a specific example of FIG. In this example, the waveform memory 6
The change amount data of “0” is stored in the address A of No. 3,
The address B stores the change amount data of + ΔV1, and the address C stores the change amount data of −ΔV2.

When the first timing signal is input in the state where the address signal indicating the address B is input to the waveform memory 63 (t1), the first waveform latch circuit 64 causes the + ΔV1 stored in the address B to be applied. Change amount data in waveform memory 6
3 and hold. Thereafter, at the update timing defined by the second timing signal, for example, the second
At the rising edge of the timing signal, the second waveform latch circuit 65 captures and holds the output data from the adder 66 (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 up to that time is held as a new output voltage. Thereafter, when the next update timing arrives after the period ΔT has elapsed, the second waveform latch circuit 65 adds 2ΔV1 (ΔV1 + ΔV1) obtained by adding ΔV1 to ΔV1 which is the output voltage up to that time. It is held as new output voltage data (t3). When the next update timing comes after the period ΔT has further elapsed, the second waveform latch circuit 65 holds V (2 △ V1 + △ V1) 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 64, then the content of the address signal is switched to the address A. Then, the address signal indicating the address A is referred to by the input of the next first timing signal (t5). That is, the first waveform latch circuit 64 reads out the change amount data of the value “0” stored at the address A from the waveform memory 63 and stores it in accordance with the input of the first timing signal. When the change amount data of the value “0” is held in the first waveform latch circuit 64, the output data from the adder 66 has the same voltage value as the output voltage from the second waveform latch circuit 65. Therefore, during the period when the change amount data of the value “0” is held in the first waveform latch circuit 64, even if the update timing specified by the second timing signal arrives, the second waveform latch circuit 65 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, which is the change amount data corresponding to the address C, is held in the first waveform latch circuit 64 (t8). Then, when this change amount data is held, the second
The output voltage from the waveform latch circuit 65 decreases by ΔV2 (t9 to t14).

As described above, the illustrated drive signal generation circuit 4
In 8, the waveform of the drive signal COM can be set to any shape only by outputting the address signal and the timing signal from the control unit 46.

Next, the drive signal generated by drive signal generation circuit 48 will be described.

The forward drive signal shown in FIG. 7A and FIG.
The return drive signal shown in (a) is the first drive signal as described above.
Medium dot ejection pulse DP1 and small dot ejection pulse D
This is a signal in which P2 and the second medium dot ejection pulse DP3 are connected in series. The forward drive signal COM1 and the backward drive signal COM2 are different in that the connection order of the drive pulses is reversed. That is, in the forward movement drive signal COM1, the first middle dot ejection pulse DP1, the micro dot drive pulse DP2, and the second middle dot ejection pulse DP3 are connected in series in this order.
In OM2, the second medium dot ejection pulse DP3, the micro dot drive pulse DP2, and the first medium dot ejection pulse DP1 are connected in series in this order.

The above-mentioned medium dot ejection pulses DP1 and DP3
Have the same waveform shape. That is, these ejection pulses DP1 and DP3 are composed of an expansion element P1 that increases the potential from the intermediate potential VM to the first maximum potential VH1 at a constant gradient that does not eject ink droplets, and a first maximum potential VH.
An expansion hold element P2 for holding H1 for a predetermined time;
An ejection element P3 that drops (discharges) the potential at a steep gradient from the maximum potential VH1 to the first lowest potential VL1, a contraction hold element P4 that holds the first lowest potential VL1 for a predetermined time, and an intermediate potential VM from the first lowest potential VL. And a damping element P5 that raises the potential to the maximum.

In these ejection pulses DP1 and DP3, the supply of the expansion element P1 and the expansion hold element P2 causes the pressure chamber 24 to expand from the volume defined by the intermediate potential VM to the volume defined by the first maximum potential VH1. . Next, the supply of the ejection element P3 causes the pressure chamber 24 to contract rapidly to a volume defined by the first lowest potential VL1, and an ink droplet is ejected from the nozzle opening 5. Then, during the period in which the contraction hold element P4 is supplied, the pressure chamber 24
Is maintained, the damping element P5 is supplied to expand the pressure chamber 24 to the reference volume so as to suppress the vibration of the meniscus (the free surface of the ink exposed at the nozzle opening 5).

The above-mentioned small dot ejection pulse DP2
Are an expansion element P6 for increasing the potential at a constant gradient from the intermediate potential VM to the second maximum potential VH2 such that ink droplets are not ejected; an expansion hold element P7 for holding the second maximum potential VH2 for a predetermined time; A discharge element P8 that drops (discharges) the potential steeply from the potential VH2 to the discharge potential VM ', a discharge hold element P9 that holds the discharge potential VM' for a very short time, and a second lowest potential V from the discharge potential VM '.
A contraction element P10 that lowers the potential at a constant gradient that does not eject ink droplets to L2, a contraction hold element P11 that holds the second lowest potential VL2 for a predetermined time, and a potential rises from the second lowest potential VL to the intermediate potential VM. And a return element P12.

In this ejection pulse DP2, the expansion element P6
And the supply of the expansion hold element P7 causes the pressure chamber 24 to move from the volume defined by the intermediate potential VM to the second maximum potential VH2.
Expand to the volume specified in. Next, the supply of the ejection element P8 causes the pressure chamber 24 to rapidly contract to a volume defined by the ejection potential VM ′, and an ink droplet is ejected from the nozzle opening 5. Thereafter, the pressure chamber 24 is contracted by the supply of the contraction element P10, the contracted state of the pressure chamber 24 is maintained during the period in which the contraction hold element P11 is supplied, and the pressure chamber 24 is set to the reference by the supply of the return element P12. Expanded to volume.

As shown in FIG. 7B, in the forward drive signal COM1, the data D1 is the first medium dot ejection pulse DP1, the data D2 is the microdot drive pulse DP2, and the data D3 is the first drive pulse DP2. 2 data D1 and D of three bits respectively corresponding to the medium dot ejection pulse DP3.
2 and D3, the print data is constituted, and the amount of ink to be ejected is set by appropriately changing the data D1, D2 and D3.

That is, in the case of non-printing dot pattern data (gradation value 1 (00)), the decoder 55 sets the print data to D1 = 0, D2 = 0, and D3 = 0, respectively.
Thus, the ejection pulse signal is not supplied to the piezoelectric vibrator 35 in the recording cycle, and no ink droplet is ejected from the nozzle opening 5. In the case of small dot pattern data (gradation value 2 (01)), the decoder 55
The print data is set to D1 = 0, D2 = 1, D3 = 0, respectively. Thereby, only the small dot ejection pulse DP2 is supplied to the piezoelectric vibrator 35 in the recording cycle,
Small ink droplets are ejected from the nozzle openings 5. Further, in the case of dot pattern data of medium dots (gradation value 3 (10)), the decoder 55 sets the print data to D1 = 1, D2 =
0 and D3 = 0. As a result, only the first medium dot ejection pulse DP1 is supplied to the piezoelectric vibrator 35 in the recording cycle, and medium ink droplets are ejected from the nozzle openings 5. Further, in the case of large dot pattern data (gradation value 4 (11)), the decoder 55
The print data is set to D1 = 1, D2 = 0, and D3 = 1. As a result, the first medium dot ejection pulse and the second medium dot ejection pulse are supplied to the piezoelectric vibrator 35 within the recording cycle, and medium ink droplets are ejected twice successively from the nozzle openings 5. Large dots are formed on the top.

On the other hand, as shown in FIG. 8B, in the backward drive signal COM2, the data D1 is the second medium dot ejection pulse DP3, the data D2 is the micro dot drive pulse DP2, and the data D3 is the second drive pulse DP2. 1 medium dot ejection pulse D
3-bit data D1, D respectively corresponding to P1
2 and D3 constitute print data. And
The amount of ink to be ejected is set by appropriately changing the data D1, D2, and D3.

That is, when non-printing is performed, the decoder 55
The print data is set to D1 = 0, D2 = 0, D3 = 0, respectively, and in the case of small dots, the print data is set to D1 = 0, D3
2 = 1 and D3 = 0, respectively, and in the case of a large dot, the print data is set to D1 = 1, D2 = 0 and D3 = 1, respectively. In these cases, the operation is the same as that in the forward movement. In the case of non-printing, no ink droplet is ejected. In the case of a small dot, only the small dot ejection pulse DP2 is supplied to the piezoelectric vibrator 35 and Ink droplets are ejected. Then, in the case of a large dot, a second medium dot ejection pulse DP3,
The first medium dot ejection pulse DP1 is supplied to the piezoelectric vibrator 35, and medium ink droplets are successively ejected twice. Also,
The decoder 55 converts the print data to D1 in the case of a medium dot.
= 0, D2 = 0, and D3 = 1. As a result, only the first medium dot ejection pulse DP1 is supplied to the piezoelectric vibrator 35 in the recording cycle, and medium ink droplets are ejected from the nozzle openings 5.

By the way, the medium ink droplet and the small ink droplet ejected by the above-mentioned ejection pulse have different flying speeds.
The flying speed of the small ink droplet is lower than the flying speed of the medium ink droplet. These ink droplets fly obliquely because an inertial component (Vc in FIG. 9) due to the movement of the recording head acts thereon. For this reason, if each of the ejection pulses DP1 to DP3 is arranged (that is, generated) at equal time intervals, the small ink droplets do not land in the middle between adjacent medium ink droplets, and land in the pixel area. Is shifted between the forward movement and the backward movement. Under such circumstances, in the present embodiment, the waveform interval between adjacent ejection pulses in the forward drive signal and the backward drive signal is determined according to the difference in the flying speed of the ink droplet. In the present embodiment, the generation timing of the small dot ejection pulse DP2 is determined according to the flying speed of the ink droplet. In other words,
A first adjustment element P13 that connects the first ejection pulse and the second ejection pulse in the recording cycle T with the intermediate potential VM.
And the time width of the second adjustment element P14 connecting the second ejection pulse and the third ejection pulse at the intermediate potential VM are determined according to the difference in the flying speed of the ink droplet.
This is because changing the timing at which the small dot ejection pulse DP2 is generated can be achieved by changing the two medium dot ejection pulses DP1 and DP3.
This is because it is easier than changing the generation timing.

In the present embodiment, since the flying speed of the small ink droplet is slower than that of the medium ink droplet, the small dot ejection pulse DP2 is arranged at the front (earlier timing) just in between the ejection pulses DP1 and DP3. That is, the first ejection pulse in the recording cycle T (ejection pulse DP1 in the forward drive signal, ejection pulse DP3 in the backward drive signal).
The interval tA from the second ejection pulse (ejection pulse DP2) to the second ejection pulse (ejection pulse DP2) is from the third ejection pulse (ejection pulse DP3 in the forward drive signal, in the backward drive signal). Discharge pulse DP
The interval is set to be shorter than the interval tB up to 1).

In this way, as shown in FIG. 9, small ink droplets whose flying speed Vms is lower than the flying speed VmM of medium ink droplets are ejected at an earlier timing. Can be landed at an intermediate position. As a result, the pixel region W can be used both in the forward movement and the backward movement.
The landing positions of the ink droplets in the inside can be aligned with high accuracy, and the image quality of the recorded image can be further improved. further,
These intervals tA and tB can be set to the same time width for the forward drive signal and the backward drive signal. In the present embodiment, since the middle dot ejection pulses DP1 and DP3 have the same waveform, the forward drive signal and the backward drive signal can be constituted by drive signals having the same shape.
Therefore, parameters for generating the drive signal (such as the address signal described above) can be reduced, and the control unit 4
6 can be reduced, and the storage capacity of a storage device (for example, the ROM 45) for storing parameters can be saved. As a result, the speed of processing during operation can be increased.

In the above example, the small ink droplet has a lower flying speed than the medium ink droplet. However, the present invention is not limited to this example. The present invention can also be applied to the case where the flying speed of the small ink droplet is the same as the flying speed of the medium ink droplet, or the case where the flying speed of the small ink droplet is higher than that of the middle ink droplet. For example, if the ink droplets ejected by the ejection pulses DP1 to DP3 have the same flying speed, the ejection pulses are arranged at equal intervals (interval tA = interval tB), that is, medium dot ejection pulses DP1 and DP3. By arranging the small dot ejection pulse DP2 just halfway between the ink droplets, the landing intervals between the ink droplets become uniform. For this reason, the landing positions of the ink droplets in the pixel area can be aligned with high accuracy, and the image quality of the recorded image can be further improved. If the flying speed VmS of the small ink droplet is faster than the flying speed VmM of the medium ink droplet, the interval tA is set to the interval tB.
By setting the length to be longer than the above, it is possible to make the landing intervals of each ink droplet uniform.

This will be described with reference to a specific example of FIG. In this specific example, the recording cycle T is 115.7 microseconds (hereinafter, referred to as μs), and the medium dot ejection pulse D
The supply time of P1 and DP3, that is, the time from the beginning of the expansion element P1 to the end of the damping element P5 is 16 μs,
The supply time of the small dot ejection pulse DP2, that is, the time from the start of the expansion element P6 to the end of the return element P12 is 2
1.5 μs. Further, each of the ejection pulses DP1 to DP3
, Ie, the intervals tA and tB described above.
Is set equal to 48.85 μs, the time width (reference time width) of the first adjustment element P13 is 31.3.
5 μs, and the time width (reference time width) of the second adjustment element P14 is 27.85 μs. Then, the distance from the nozzle opening 5 to the printing surface of the recording paper 16 (paper gap)
Is 1.1 mm, and the scanning speed of the carriage 2 when ejecting ink droplets is 24 inches / sec (about 0.6 m / sec.).
s), and the flying speed VmM of the medium ink droplet is 7.0 m / s.
(Landing time = 157 μs).

In this specific example, the flying speed VmS of the small ink droplet is increased from 5.0 m / s to 9.
The landing time difference Δt (μs) and the landing position deviation ΔL (μm) between the small ink droplet and the medium ink droplet were calculated by changing the distance from 0 m / s to 0.5 m / s every 0.5 m / s.

When the flying speed VmS of the small ink droplet is equal to the flying speed VmM of the medium ink droplet and both are 7.0 m / s, the landing time of both ink droplets is 157 μs, and the landing time difference Δt and the landing time The displacement ΔL is both 0.0.
Therefore, in this case, by setting the above-mentioned intervals tA and tB equal, in other words, the first adjustment element P1
By setting both the third adjustment element P14 and the second adjustment element P14 to the reference time width, each ink droplet can be landed at a desired landing position.

The flying speed VmS of the small ink droplet is lower than the flying speed VmM of the medium ink droplet, for example, 6.0 m / s.
, The landing time t1 of the small ink droplet is 183
μs, the landing time difference Δt is 26.2 μs, and the landing position deviation ΔL is 16.0 μm. Therefore, in this case, by setting the interval tA to be shorter than tB and ejecting the small ink droplets at an earlier timing, each ink droplet can be landed at a desired landing position.
More specifically, the first adjustment element P13 is:
Eliminating the landing position deviation by setting the time width obtained by subtracting the landing time difference Δt from the reference time width and setting the second adjustment element P14 to the time width obtained by adding the landing time difference Δt to the reference time width Thus, each ink droplet can be landed at a desired landing position.

On the other hand, the flying speed VmS of the small ink droplet is faster than the flying speed VmM of the medium ink droplet, for example, 8.0 m / s.
, The landing time t1 of the small ink droplet is 138.
μs, the landing time difference Δt is −19.6 μs, and
The landing position shift ΔL is −12.0 μm. Therefore, in this case, by setting the interval tA to be longer than tB and ejecting small ink droplets at a later timing, each ink droplet can be landed at a desired landing position. More specifically, the first adjustment element P13 is set to a time width obtained by subtracting the landing time difference Δt from the reference time width, that is, a time width obtained by adding the absolute value of the landing time difference Δt to the reference time width. The second adjustment element P14 is set to a time width obtained by adding the landing time difference Δt to the reference time width, that is, a time width obtained by subtracting the absolute value of the landing time difference Δt from the reference time width. Accordingly, it is possible to eliminate a landing position shift, and to cause each ink droplet to land at a desired landing position.

In this specific example, the first adjustment element P
13 and the reference time width of the second adjustment element P14,
The flying speed VmS of the small ink droplet is from 6.0 m / s to 8.5 m
The landing position deviation can be adjusted in the range of / s.

Next, a method of adjusting the displacement of the landing position of the ink droplet, that is, a method of setting the forward drive signal and the backward drive signal will be described.

As the adjustment method, for example, a first method of recording a vertical ruled line and the like based on the recording result,
A second method of measuring the flying speed of each ink droplet in a single state of the recording head 6 and measuring the flying speed of the ink droplet in a state where the recording head 6 is assembled in the printer 1,
A third method performed based on the measurement result is considered. Hereinafter, each method will be described.

First, the first method will be described. This method is performed in an adjustment process after the printer 1 is assembled. In this method, first, the position of the medium dot is adjusted.
For example, by changing the generation timing of the drive signal based on the encoder output indicating the position of the carriage 2, the formation position of the medium dot (the landing position of the medium ink droplet) is aligned between the forward movement and the backward movement. That is, an adjustment pattern such as a vertical ruled line is actually recorded, a shift in the main scanning direction is observed, and the generation timing of the drive signal is adjusted so as to eliminate the shift. Once the medium dot formation position has been adjusted,
Adjust the position of small dots. Also here, the adjustment pattern is actually recorded using small dots, and the shift in the main scanning direction is observed. Then, the time width between the first adjustment element P13 and the second adjustment element P14 is set so that this deviation is eliminated.
That is, a supply pattern of an address signal for generating a drive waveform is set. According to this method, since the dot misalignment can be adjusted in the last step of the manufacturing process of the printer 1, the dot misalignment hardly occurs thereafter. Therefore, a high-quality image can be recorded even after shipment.

Next, the second method will be described. This method is performed in an inspection process of the recording head 6. In this method, after assembling the recording head 6, ink droplets are actually ejected in an inspection process, and the flying speed is measured. The measured flying speed is converted into identification information (ID) and stored in an information storage element such as a ROM with contacts (not shown) provided in the recording head 6. In this case, the control unit 46 functions as waveform data generation means, reads the identification information stored in the information storage element, and generates waveform data for generating a drive signal, that is, a series of address signal groups and the like. I do.
For example, in the above embodiment, the flying speed VmM of the medium dot
Adjustment element P13 and second adjustment element P based on the identification information indicating the flying speed VmS of the small dot and the identification information indicating the flying speed VmS of the small dot.
14, a time width is determined, and waveform data is generated from the determined waveform. Then, the control unit 46 outputs the generated waveform data to the drive signal generation circuit 48. As the identification information in this method, information indicating the ratio between the flying speed VmM of the medium dot and the flying speed VmS of the small dot may be used.

Next, the third method will be described. This method can be performed in an adjustment process after the printer 1 is assembled, and can also be performed after the printer 1 has been delivered to the user. In this method, a laser detector 15 disposed at a flushing position is used.
That is, the control unit 46 functions as the flying speed calculating unit of the present invention, and calculates the flying speed of the ink droplet based on the detection signal from the laser detector 15. For example, the ejection pulse DP
The time interval from the timing of starting supply of the ejection elements P3 and P8 of 1 to DP3 to the timing of changing the output signal from the laser light receiver is measured, and the flying speed is calculated based on this time interval. That is, since the distance from the nozzle surface 27a to the laser beam is known, the flying speed of the ink droplet can be calculated if the above time interval is known. After calculating the flying speed of each ink droplet, the control unit 46 functions as a waveform data generating unit, generates waveform data for generating a drive signal, and generates the generated waveform data, as in the second method. The waveform data is output to the drive signal generation circuit 48. According to this method, the flying speed can be easily measured without using a dedicated device, and the waveform of the drive signal can be automatically adjusted even after the purchase of the printer 1. That is, the state where the waveform interval is adjusted can be maintained for a long period of time.

Incidentally, the present invention is not limited to the above-described embodiment, and can be modified based on the description in the claims.

For example, the waveform interval between ejection pulses may be determined in consideration of the distance (paper gap) from the nozzle opening 5 to the printing surface of the recording paper 16. This type of printer 1 can use a plurality of types of printing media having different thicknesses, such as board paper, plain paper, photo paper, and postcards. For this reason, the paper gap slightly varies depending on the printing medium used. This variation in the paper gap may have some influence on the landing position. Therefore, if the waveform interval between the ejection pulses is determined in consideration of the paper gap, the landing positions of the ink droplets can be aligned with higher accuracy. In this case, a paper gap may be set for each type of print medium that can be used, or the paper gap may be measured by a distance measuring sensor that functions as a gap detecting unit.

In the above-described embodiment, the drive signal including two types of ejection pulses, that is, a small dot ejection pulse and a medium dot ejection pulse, has been described as an example. However, a drive signal including three or more types of ejection pulses is described. The present invention can be applied to a device that generates a signal. For example, the present invention can be applied to an apparatus that generates a drive signal including three types of ejection pulses including a small dot ejection pulse, a medium dot ejection pulse, and a large dot ejection pulse.

In the above embodiment, one recording cycle T
Although three ejection pulses were included in the
It is not limited to this number. For example, one recording cycle T may include two ejection pulses, or may include four or more ejection pulses.

The pressure generating element is not limited to the piezoelectric vibrator 35 that changes the volume in the pressure chamber 24. For example, a heating element or a magnetostrictive element may be used.

The present invention can be applied not only to the printer 1 but also to an ink jet recording apparatus such as a plotter or a facsimile apparatus.

[0088]

As described above, according to the present invention, the following effects can be obtained. That is, the drive signal generating means includes a plurality of ejection pulses having different ink amounts in one recording cycle, and generates a forward drive signal in which a plurality of ejection pulses are connected in a predetermined order when the print head moves forward. A reverse drive signal in which each discharge pulse is connected in the reverse order to the forward drive signal generates a reverse drive signal when the print head moves backward, and a waveform between adjacent discharge pulses in the forward drive signal and the reverse drive signal. Since the interval is determined according to the difference in the flying speed of the ink droplet, it is possible to prevent the displacement of the landing position of the ink droplet caused by the difference in the flying speed. That is, the landing positions of the ink droplets discharged during the forward movement and the landing positions of the ink droplets discharged during the backward movement can be aligned with high accuracy. As a result, the quality of the recorded image can be further improved.

When the waveform interval between adjacent ejection pulses is determined in consideration of the distance from the nozzle opening to the print medium, the optimum waveform interval for a plurality of types of print media having different thicknesses is determined. Can be set, so that higher image quality can be achieved.

Further, there is provided a laser detector capable of detecting the passage of ink droplets ejected from the nozzle opening, and a flying speed calculating means for calculating the flying speed of the ink droplet based on a detection signal from the laser detector. In this case, the flying speed of the ink droplets can be automatically measured, so that the efficiency of the adjustment operation can be increased. Furthermore, since the flying speed of the ink droplets can be calculated even after the apparatus reaches the hand of the user, the state where the waveform interval is adjusted can be maintained for a long time.

When the laser detector is arranged at the flushing position where the recording head moves when performing the flushing operation, the laser detector can be used for detecting clogging of the nozzle opening. The apparatus configuration can be simplified, the number of parts can be reduced, and the efficiency of manufacturing can be improved.

Further, the ejection pulse includes a small dot ejection pulse selected when printing a small dot, a first medium dot ejection pulse selected when printing a medium dot and a large dot, and
When a small dot ejection pulse is arranged between the first medium dot ejection pulse and the second medium dot ejection pulse, the second medium dot ejection pulse is selected when printing a large dot. The forward drive signal and the backward drive signal can have the same waveform shape, and the parameters for generating the drive signal can be reduced. Therefore, the load on the control unit can be reduced, and the storage capacity of the storage device that stores the parameters can be saved. as a result,
The processing speed during operation can be increased.

Also, by changing the generation timing of the small dot ejection pulse within one recording cycle, when the waveform interval between adjacent ejection pulses is determined, the generation timing can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating the structure of an ink jet printer.

FIG. 2 is a cross-sectional view illustrating a structure of a recording head.

FIG. 3 is a block diagram illustrating an electrical configuration of the printer.

FIG. 4 is a block diagram illustrating an electric drive system of the recording head.

FIG. 5 is a block diagram illustrating an electrical configuration of a drive signal generation circuit.

FIG. 6 is a diagram illustrating a procedure for generating a drive signal by a drive signal generation circuit.

FIG. 7A is a waveform diagram of a forward drive signal, and FIG. 7B is a diagram illustrating a gradation value and a pulse selection pattern.

8A is a diagram illustrating a waveform of a drive signal at the time of a backward movement, and FIG. 8B is a diagram illustrating a gradation value and a pulse selection pattern.

FIG. 9 is a schematic diagram for explaining an ink droplet ejection state;
(A) shows the forward movement, and (b) shows the backward movement.

FIG. 10 is a diagram illustrating a specific example of waveform interval adjustment.

FIG. 11 is an example of a conventional drive signal.

FIG. 12 is a schematic diagram illustrating a state of ejection of ink droplets by a conventional drive signal.

DESCRIPTION OF SYMBOLS 1 Ink jet printer 2 Carriage 3 Ink cartridge 4 Cartridge holder part 5 Nozzle opening 6 Recording head 7 Housing 8 Guide member 9 Pulse motor 10 Driving pulley 11 Idling pulley 12 Timing belt 13 Capping member 14 Wiper member 15 Laser Detector 16 Recording paper 17 Platen roller 18 Paper feed motor 21 Case 22 Flow path unit 23 Vibrator unit 24 Pressure chamber 25 Housing empty space 26 Flow path forming board 27 Nozzle plate 28 Vibration plate 29 Common ink chamber 30 Ink supply path 31 Ink Supply pipe 32 Support plate 33 Elastic film 34 Island part 35 Piezoelectric vibrator 36 Fixed plate 41 Printer controller 42 Print engine 43 External interface 44 RAM 45 ROM 46 Control 47 Oscillation circuit 48 Drive signal generation circuit 49 Internal interface 51 First shift register 52 Second shift register 53 First latch circuit 54 Second latch circuit 55 Decoder 56 Control logic 57 Level shifter 58 Switch circuit 61 Waveform generation circuit 62 Current amplification circuit 63 Waveform memory 64 First waveform latch circuit 65 Second waveform latch circuit 66 Adder 67 Digital-to-analog converter 68 Voltage amplifier circuit

Claims (7)

[Claims] 1. A pressure chamber communicating with a nozzle opening, and a pressure generating element capable of causing pressure fluctuation in the pressure chamber,
A recording head capable of reciprocating in the main scanning direction, a driving signal generating means for generating a driving signal in which a plurality of discharging pulses capable of discharging ink droplets are connected in series, and a discharging pulse from the driving signal generated by the driving signal generating means And a pulse supply means for selecting and supplying a pressure generating element to the pressure generating element, wherein the drive signal generating means comprises an ink A plurality of ejection pulses having different amounts are included in one recording cycle, and a forward drive signal in which a plurality of ejection pulses are connected in a predetermined order is generated when the print head moves forward, and each ejection pulse is driven during the forward movement. A reverse drive signal, which is connected in the reverse order to the signal, is generated when the print head moves backward, and the waveform interval between adjacent ejection pulses in the forward drive signal and the reverse drive signal is determined by the ink drop. An ink jet recording apparatus characterized by determined in accordance with the difference Xiang speed. 2. The ink jet recording apparatus according to claim 1, wherein a waveform interval between the adjacent ejection pulses is determined in consideration of a distance from a nozzle opening to a print medium. 3. A laser detector capable of detecting passage of an ink droplet ejected from a nozzle opening, and a flying speed calculating means for calculating a flying speed of the ink droplet based on a detection signal from the laser detector. The ink jet recording apparatus according to claim 1 or 2, wherein: 4. The ink jet recording apparatus according to claim 3, wherein the laser detector is disposed at a flushing position where a recording head moves when performing a flushing operation. 5. The ejection pulse includes a small dot ejection pulse selected when printing a small dot, a first medium dot ejection pulse selected when printing a medium dot and a large dot, and
A second medium-dot ejection pulse selected at the time of printing a large dot;
The ink jet recording apparatus according to any one of claims 1 to 4, wherein the ink jet recording apparatus is disposed between the medium ejection pulse and the medium ejection pulse. 6. The ink jet recording apparatus according to claim 5, wherein the timing of generating small dot ejection pulses within one recording cycle is changed to determine the waveform interval between adjacent ejection pulses. 7. The ink jet recording according to claim 1, wherein the pressure generating element is constituted by a piezoelectric vibrator arranged so that the volume in the pressure chamber can be changed. apparatus.