JP2005343100A - Liquid jetting device and controlling method for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a dot formation position at moving forward and backward arranged with higher degree of precision according to a prescribed dot-formation spacing. <P>SOLUTION: A moving-forward delivery spacing td 1 between a delivery timing of a small-dot delivery pulse and the delivery timing of a middle-dot delivery pulse at moving forward and a moving-backward delivery spacing td 2 between the delivery timing of the middle-dot delivery pulse and the delivery timing of the small-dot delivery pulse at moving backward are established so that the difference between a moving-forward formation spacing dd 1 of a small dot S as well as a middle dot M at moving forward and a moving-backward formation spacing dd 2 of the small dot S as well as the middle dot M at moving backward may become less than the prescribed dot-formation spacing at a basic resolution in a recording direction, namely principal scanning direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid ejecting apparatus such as an ink jet printer, and a method for controlling the liquid ejecting apparatus, and more particularly to a liquid ejecting capable of ejecting liquid droplets both when the liquid ejecting head moves forward and when the liquid ejecting head moves backward. The present invention relates to an apparatus control method and a liquid ejecting apparatus.

  The liquid ejecting apparatus is an apparatus that includes a liquid ejecting head capable of ejecting liquid as droplets and ejects various liquids from the liquid ejecting head. A typical example of this liquid ejecting apparatus is, for example, an ink jet printer that performs recording by forming dots by ejecting and landing liquid ink as ink droplets on recording paper or the like as an ejection target. The image recording apparatus can be exemplified. In recent years, it is applied not only to this image recording apparatus but also to various manufacturing apparatuses.

  As an ink jet printer (hereinafter simply referred to as a printer) which is a kind of the above liquid ejecting apparatus, an ink jet recording head (a kind of liquid ejecting head, which is configured so as to be able to eject ink droplets by supplying ejection pulses). And a head scanning mechanism capable of reciprocating the recording head in the width direction of the recording paper (ejection target), that is, the main scanning direction, both during the forward and backward movement of the recording head In addition, a printer capable of so-called bidirectional recording in which ink droplets are ejected for recording has been proposed.

  In a printer capable of bidirectional recording, for example, a drive signal in which a plurality of types of discharge pulses with different amounts of discharged ink are connected in series is generated, and a necessary discharge pulse is selectively selected from the drive signals. When recording is performed by forming dots of different sizes by supplying pressure generating elements such as piezoelectric vibrators, that is, when performing so-called multi-gradation recording, ejection is performed during forward movement and backward movement. By reversing the pulse connection order, the landing positions (dot formation positions) in the main scanning direction in the pixel region are aligned during forward movement and backward movement.

However, in the printer having such a configuration, since the ink droplets are ejected while moving the recording head in the main scanning direction, an inertia component due to the movement of the recording head acts on the ejected ink droplets. The ink droplets fly obliquely with respect to the discharge target such as recording paper. When ejecting ink droplets with different flying speeds, for example, when ejecting ink droplets for forming small dots and ink droplets for forming medium dots, the recording paper is ejected from the nozzle openings. Since the time until landing on each ink drop is different, the flight distance in the main scanning direction is also different. Therefore, in this case, as shown in FIG. 10, the dot formation position in the main scanning direction in the pixel region P is different between forward movement and backward movement.
When such a dot formation position shift occurs, there are problems that banding (streaky noise) and color spots occur in the recorded image, and graininess increases.

  Therefore, by adjusting the waveform interval between the ejection pulses included in the drive signal during forward movement and backward movement according to the difference in the flying speed of ink droplets, the dot formation position during forward movement and backward movement can be adjusted. Those that are arranged are proposed (see, for example, Patent Document 1).

JP 2002-225250 A

  By the way, in this type of printer, a plurality of types of recording modes such as a mode for performing higher-speed recording and a mode for performing higher-definition recording are generally prepared. When the recording mode is switched, the basic resolution (specified dot formation interval) in the main scanning direction may also change. However, the above-mentioned Patent Document 1 is based on the premise that the basic resolution in the main scanning direction is always constant, and the change in the basic resolution in the main scanning direction is not taken into consideration. That is, in Japanese Patent Application Laid-Open No. H10-32077, when the basic resolution in the main scanning direction is changed, there is a problem that the dot forming positions in the main scanning direction are different between forward movement and backward movement.

  The present invention has been made in view of such circumstances, and an object thereof is to align the dot formation positions at the time of forward movement and at the time of backward movement with higher accuracy according to the prescribed dot formation interval.

The liquid ejecting apparatus of the present invention has been proposed in order to achieve the above object, and includes a pressure chamber communicating with a nozzle opening and a pressure generating element that causes a pressure fluctuation in the liquid in the pressure chamber, and the pressure A liquid ejecting head capable of forming a dot on a discharge target by discharging a droplet from a nozzle opening by operation of a generating element;
Drive signal generating means for generating a drive signal including a first discharge pulse capable of forming a first dot and a second discharge pulse capable of forming a second dot having a size different from that of the first dot within one discharge cycle. And
The liquid ejecting head is configured to be capable of reciprocating, and is a liquid ejecting apparatus capable of ejecting liquid droplets both during forward movement and during backward movement,
The drive signal generating means generates a backward drive signal for generating the first discharge pulse and the second discharge pulse in the reverse order of the forward drive signal when the liquid ejecting head moves backward,
The difference between the forward movement formation interval of the first dot and the second dot during the forward movement and the backward movement formation interval of the first dot and the second dot during the backward movement is within the prescribed dot formation interval in the liquid ejecting head moving direction. The forward discharge interval between the discharge timing of the first discharge pulse and the discharge timing of the second discharge pulse during the forward movement, the discharge timing of the second discharge pulse during the backward movement, and the first The backward discharge interval with the discharge timing of one discharge pulse is set.
The “specified dot formation interval” is a distance obtained by multiplying the minimum period (minimum discharge interval) that can be continuously discharged from the same nozzle opening by the moving speed of the liquid ejecting head. Mean interval.

The control method of the liquid ejecting apparatus of the present invention includes a pressure chamber communicating with the nozzle opening and a pressure generating element that causes a pressure fluctuation in the liquid in the pressure chamber, and the liquid is discharged from the nozzle opening by the operation of the pressure generating element. A liquid ejecting head capable of ejecting droplets to form dots on the ejection target;
Drive signal generating means for generating a drive signal including a first discharge pulse capable of forming a first dot and a second discharge pulse capable of forming a second dot of a size different from the first dot within one discharge cycle; With
A control method for a liquid ejecting apparatus, wherein the liquid ejecting head is configured to eject liquid droplets both in the forward movement and in the backward movement in accordance with the ejection pulse of the drive signal generated by the drive signal generating means. ,
The difference between the forward movement formation interval of the first dot and the second dot during the forward movement and the backward movement formation interval of the first dot and the second dot during the backward movement is within the prescribed dot formation interval in the liquid ejecting head moving direction. The forward discharge interval between the discharge timing of the first discharge pulse and the discharge timing of the second discharge pulse during the forward movement, the discharge timing of the second discharge pulse during the backward movement, and the first A backward discharge interval is set with respect to the discharge timing of one discharge pulse.

  According to the above configuration, since the forward discharge interval and the backward discharge interval are set so that the difference between the forward movement formation interval and the backward movement formation interval is within the prescribed dot formation interval in the head movement direction, the prescribed dot formation It is possible to align the dot formation positions during forward movement and backward movement according to the interval.

  In the above configuration, it is preferable that the forward discharge interval and the backward discharge interval are set in consideration of a distance from the nozzle opening to the discharge target. The forward discharge interval and the backward discharge interval are preferably set in consideration of the moving speed of the liquid ejecting head.

  According to these configurations, even when the distance from the nozzle opening to the discharge target and the moving speed of the liquid ejecting head change, the optimal discharge interval can be set based on the changed value. Therefore, it is possible to align the dot formation positions during forward movement and backward movement with higher accuracy.

Further, in the above-described configuration, an inspection pattern is created on the ejection object using the first ejection pulse and the second ejection pulse at each of forward movement and backward movement,
Based on the forward movement formation interval between the first dot and the second dot in the inspection pattern during the forward movement and the backward movement formation interval between the first dot and the second dot in the inspection pattern during the backward movement. It is also possible to adopt a configuration in which the forward discharge interval and the backward discharge interval are set.

  According to this configuration, the forward discharge interval and the backward discharge interval are set based on the inspection pattern created by actually discharging the droplets, so that the calculation error can be reduced and the setting can be made more accurately. It can be performed. This makes it possible to align the dot formation positions during forward movement and backward movement with higher accuracy.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. In the following, an ink jet printer (hereinafter abbreviated as a printer) shown in FIG. 1 is illustrated as an example of the liquid ejecting apparatus of the present invention.

  FIG. 1 is a perspective view showing the configuration of the printer 1. The printer 1 is equipped with a carriage 4 to which a recording head 2 is attached and an ink cartridge 3 is detachably attached, a platen 5 disposed below the recording head 2, and a carriage 4 (recording head 2). A carriage movement mechanism 7 that reciprocates in the paper width direction of the recording paper 6 as a kind of material, that is, the main scanning direction, and a paper feeding mechanism 8 that conveys the recording paper 6 in the sub-scanning direction that is orthogonal to the main scanning direction. And is schematically configured.

  The carriage 4 is attached while being supported by a guide rod 9 installed in the main scanning direction, and is configured to move in the main scanning direction along the guide rod 9 by the operation of the carriage moving mechanism 7. ing. The position of the carriage 4 in the main scanning direction is detected by the linear encoder 10, and the detection signal, that is, the encoder pulse is transmitted to the control unit 41 (see FIG. 3) of the printer controller. Thus, the control unit 41 can control the recording operation (ejection operation) by the recording head 2 while recognizing the scanning position of the carriage 4 (recording head 2) based on the encoder pulse from the linear encoder 10. .

A home position serving as a scanning base point is set in an end area outside the recording area within the moving range of the carriage 4 (right side in FIG. 1). At the home position in the present embodiment, a capping member 11 for sealing the nozzle forming surface (nozzle plate 21: see FIG. 2) of the recording head 2, a wiper member 12 for wiping the nozzle forming surface, and the recording head 2 And a laser detector 46 (see FIG. 3) capable of detecting the passage of ink droplets ejected from the nozzle openings 27 (see FIG. 2).
The printer 1 moves forward when the carriage 4 (recording head 2) moves from the home position toward the opposite end, and when the carriage 4 returns from the opposite end to the home position. And so-called bidirectional recording in which characters, images, etc. are recorded on the recording paper 6 in both directions.

  FIG. 2 is a cross-sectional view of a main part for explaining the configuration of the recording head 2. The recording head 2 includes a case 13, a vibrator unit 14 housed in the case 13, a flow path unit 15 joined to the bottom surface (tip surface) of the case 13, and the like. The case 13 is made of, for example, an epoxy resin, and a housing empty portion 16 for housing the vibrator unit 14 is formed therein. The vibrator unit 14 includes a piezoelectric vibrator 17 that functions as a kind of pressure generating element, a fixing plate 18 to which the piezoelectric vibrator 17 is joined, and a flexible cable 19 for supplying a drive signal and the like to the piezoelectric vibrator 17. And. The piezoelectric vibrator 17 is a laminated type produced by cutting a piezoelectric plate in which piezoelectric layers and electrode layers are alternately laminated into a comb-like shape, and is capable of expanding and contracting in a direction perpendicular to the laminating direction. This is a piezoelectric vibrator.

  The flow path unit 15 is configured by joining a nozzle plate 21 to one surface of the flow path forming substrate 20 and an elastic plate 22 to the other surface of the flow path forming substrate 20. The flow path unit 15 is provided with a reservoir 23, an ink supply port 24, a pressure chamber 25, a nozzle communication port 26, and a nozzle opening 27. A series of ink flow paths from the ink supply port 24 to the nozzle opening 27 via the pressure chamber 25 and the nozzle communication port 26 are formed corresponding to each nozzle opening 27.

  The nozzle plate 21 is a thin plate made of metal such as stainless steel in which a plurality of nozzle openings 27 are formed in rows at a pitch (for example, 180 dpi) corresponding to the dot formation density. The nozzle plate 21 is provided with a plurality of nozzle openings 27 (nozzle arrays), and one nozzle array is composed of, for example, 180 nozzle openings 27. The recording head 2 in the present embodiment has different colors of ink (one type of liquid in the present invention), specifically cyan (C), magenta (M), yellow (Y), and black (K). Four ink cartridges 3 for storing ink of a total of four colors are configured to be mountable, and a total of four nozzle rows are formed on the nozzle plate 21 corresponding to these colors.

  The elastic plate 22 has a double structure in which an elastic film 29 is laminated on the surface of the support plate 28. In the present embodiment, the elastic plate 22 is manufactured using a composite plate material in which a stainless plate, which is a kind of metal plate, is used as the support plate 28 and a resin film is laminated on the surface of the support plate 28 as an elastic film 29. The elastic plate 22 is provided with a diaphragm portion 30 that changes the volume of the pressure chamber 25. The elastic plate 22 is provided with a compliance portion 31 that seals a part of the reservoir 23.

  The diaphragm portion 30 is produced by partially removing the support plate 28 by etching or the like. That is, the diaphragm portion 30 includes an island portion 32 to which the tip surface of the piezoelectric vibrator 17 is joined and a thin elastic portion 33 that surrounds the island portion 32. The compliance part 31 is produced by removing the support plate 28 in the region facing the opening surface of the reservoir 23 by etching or the like in the same manner as the diaphragm part 30, and reduces the pressure fluctuation of the liquid stored in the reservoir 23. Functions as a damper to absorb.

  Since the tip end surface of the piezoelectric vibrator 17 is joined to the island portion 32, the volume of the pressure chamber 25 can be changed by expanding and contracting the free end portion of the piezoelectric vibrator 17. As the volume changes, pressure fluctuations occur in the ink in the pressure chamber 25. The recording head 2 uses this pressure fluctuation to eject ink droplets from the nozzle openings 27.

  FIG. 3 is a block diagram showing an electrical configuration of the printer 1. The printer 1 is schematically composed of a printer controller 35 and a print engine 36. The printer controller 35 includes an external interface (external I / F) 37 for receiving print data from an external device such as a host computer, a RAM 38 for storing various data, a control routine for various data processing, and the like. The stored ROM 39, a control unit 41 for controlling each unit, an oscillation circuit 42 for generating a clock signal, and a drive signal generation circuit 43 for generating a drive signal to be supplied to the recording head 2 (of the drive signal generating means in the present invention) 1), a timer circuit 44 functioning as a time measuring means, and an internal interface (internal I / F) for outputting ejection data, drive signals, etc. obtained by developing print data for each dot to the recording head 2 45.

In addition to performing various controls, the control unit 41 converts print data input from an external device through the external I / F 37 into ejection data corresponding to a dot pattern. When one row of ejection data that can be printed by one main scan of the recording head 2 is obtained, the control unit 41 sends the ejection data for one row to the recording head 2 through the internal I / F 45. Output.
Further, the control unit 41 is configured to be able to calculate the flying speed of the ink droplet based on the detection signal from the laser detector 46. The calculation of the flying speed of the ink droplet will be described later.

  Further, the control unit 41 functions as a head moving speed calculating unit together with the linear encoder 10, the timer circuit 44, and the carriage moving mechanism 7, and measures a moving time required for the carriage 4 to move a predetermined distance in the recording area. Thus, the moving speed of the carriage 4 (recording head 2) is calculated. When calculating the moving speed, the control unit 41 receives an encoder pulse from the linear encoder 7 in a moving state of the carriage 4 in the recording area and causes the timer circuit 44 to perform a time counting operation, and counts the received encoder pulse. Do. And the control part 41 calculates the moving speed of the carriage 4 by acquiring the time-measured value of the timer circuit 44 when it becomes the encoder pulse number corresponding to 1 inch (= 0.0254m), for example as a moving time. Can do.

  The drive signal generation circuit 43 includes a plurality of ejection pulses that can form dots of different sizes in one recording period (a kind of ejection period in the present invention), and during the forward movement when these ejection pulses are connected in a predetermined order. A drive signal is generated when the recording head 2 is moved forward, and a return drive signal is generated when the recording head 2 is moved backward, in which each ejection pulse is connected in the reverse order of the drive signal during the forward movement. Yes. For example, the forward drive signal COM1 includes, as shown in FIG. 6A, a small dot ejection pulse DP1 for ejecting an ink droplet (small dot ink droplet) of a liquid amount capable of forming a small dot, and a medium dot ejection pulse DP1. It is configured to include a series of signals in which a medium dot ejection pulse DP2 for ejecting an ink droplet (medium dot ink droplet) of a liquid amount capable of forming a dot is connected in order. Further, as shown in FIG. 6B, the backward drive signal COM2 includes a series of signals in which a medium dot ejection pulse DP2 and a small dot ejection pulse DP1 are connected in order. Details of the configuration of these drive signals and drive signal generation circuit 43 will be described later.

  The print engine 36 includes a recording head 2, a carriage moving mechanism 7, a linear encoder 10, a paper feed mechanism 8, a laser detector 46, and a paper gap detector (PG detector) 47. The laser detector 46 is composed of a light emitting element and a light receiving element, and is arranged so that the laser beam intersects the passage area of the ink droplets ejected from the recording head 2. The laser detector 46 functions as a flying speed calculation unit together with the control unit 41 and the timer circuit 44 when measuring the flying speed of the ink droplet. At this time, since the distance from the nozzle opening 27 of the recording head 2 located at the home position to the laser beam is known, the control unit 41 performs the flight time from when the ink droplet is ejected until the ink droplet blocks the laser beam. Is measured, the flying speed of the ink droplet can be calculated.

  The paper gap detector 47 functions as a paper gap detector that detects a distance from the nozzle opening 27 to the recording surface of the recording paper 6 (hereinafter referred to as a paper gap). The paper gap detector 47 includes a distance measuring sensor, detects a paper gap, and outputs a detection signal to the control unit 41. Therefore, in the present embodiment, the control unit 41 is configured to recognize the paper gap based on the detection signal from the paper gap detector 47.

Next, the drive signal generation circuit 43 will be described.
FIG. 4 is a block diagram illustrating the configuration of the drive signal generation circuit 43. The drive signal generation circuit 43 is generally composed of a waveform generation circuit 49 that generates each ejection pulse constituting the drive signal, and a current amplification circuit 50 that performs current amplification on the signal from the waveform generation circuit 49.

  The waveform generation circuit 49 includes a waveform memory 51, a first waveform latch circuit (latch 1) 52, a second waveform latch circuit (latch 2) 53, an adder 54, and a digital / analog converter (D / A converter). ) 55 and a voltage amplifying circuit 56. The waveform memory 51 functions as a change amount data storage unit that individually stores a plurality of types of voltage change amount data. The first waveform latch circuit 52 holds voltage change amount data stored at a predetermined address of the waveform memory 51 in synchronization with the first timing signal. The adder 54 is connected to the first waveform latch circuit 52 and the second waveform latch circuit 53 so that the output of the first waveform latch circuit 52 and the output of the second waveform latch circuit 53 are input. It is configured. The adder 54 functions as change amount data adding means, adds the output signals of the latch circuits 52 and 53, and outputs the result.

  The second waveform latch circuit 53 is output data holding means for holding data (voltage information) output from the adder 54 in synchronization with the second timing signal. The D / A converter 55 is connected to the subsequent stage of the second waveform latch circuit 53, and converts the output signal held by the second waveform latch circuit 53 from a digital signal to an analog signal. The voltage amplification circuit 56 is connected to the output side of the D / A converter 55, and amplifies the analog signal converted by the D / A converter 55 to the voltage of the drive signal.

  The current amplifying circuit 50 is connected to the output side of the voltage amplifying circuit 56, that is, the subsequent stage of the waveform generating circuit 49. The current amplifying circuit 50 amplifies the signal whose voltage has been amplified by the voltage amplifying circuit 56, thereby driving the signal COM (COM1). , COM2).

  In the drive signal generation circuit 48 having the above-described configuration, a plurality of change amount data indicating voltage change amounts are individually stored in the storage area of the waveform memory 51 prior to generation of the drive signal. For example, the control unit 41 outputs change amount data and address data corresponding to the change amount data to the waveform memory 51. Then, the waveform memory 51 stores the change amount data in a storage area specified by the address data. In the present 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.

  In this way, when a plurality of types of change amount data are stored in the waveform memory 51, a drive signal can be generated. The drive signal is generated by setting the change amount data in the first waveform latch circuit 52, and changing the change amount data set in the first waveform latch circuit 52 to the output voltage from the second waveform latch circuit 53 every predetermined update cycle. This is done by adding to.

  In this embodiment, the change amount data set to the first waveform latch circuit 52 is set by the 4-bit address signal input to the waveform memory 51 and the first timing signal input to the first waveform latch circuit 52. Do. That is, the waveform memory 51 selects target change amount data based on the address signal. When the first timing signal is input, the first waveform latch circuit 52 reads the selected change amount data from the waveform memory 51 and holds it.

  The change amount data held in the first waveform latch circuit 52 is input to the adder 54. Since the output voltage held by the second waveform latch circuit 53 is also input to the adder 54, the output data from the adder 54 includes the change amount data held by the first waveform latch circuit 52 and the second data. A voltage value obtained by adding the output voltage held by the waveform latch circuit 53 is obtained. Here, since the change amount data includes positive / negative information, when the change amount data is a positive value, the output data from the adder 54 has a voltage value higher than the output voltage (that is, To increase). On the other hand, when the change amount data is a negative value, the output data from the adder 54 has a voltage value lower than the output voltage (that is, decreases). When the change amount data is “0”, the output data from the adder 54 has the same voltage value as the output voltage. The output data from the adder 54 is captured and held in the second waveform latch circuit 53 in synchronization with the second timing signal. That is, the output voltage from the second waveform latch circuit 53 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, change data of “0” is stored in address A of the waveform memory 51, change data of + ΔV1 is stored in address B, and change data of −ΔV2 is stored in address C. Each is remembered.

  When the first timing signal is input in a state where the address signal indicating the address B is input to the waveform memory 51 (t1), the first waveform latch circuit 52 stores the change amount data of + ΔV1 stored in the address B. Is read from the waveform memory 51 and held. Thereafter, at the update timing defined by the second timing signal, for example, at the rising timing of the second timing signal, the second waveform latch circuit 53 captures and holds the output data from the adder 54 (t2). Here, at the rise of the first second timing signal 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.

Thereafter, when the period ΔT elapses and the next update timing comes, the second waveform latch circuit 53 adds 2V1 (= ΔV1 + ΔV1) obtained by adding ΔV1 to the current output voltage ΔV1. Is held as new output voltage data (t3).
When the period ΔT further elapses and the next update timing arrives, the second waveform latch circuit 53 holds V (= 2ΔV1 + ΔV1) as new output voltage data (t4).

  With regard to the above address signal, when the change amount data corresponding to the address B is held in the first waveform latch circuit 52, the contents of the address signal are switched to the address A thereafter. Then, the first waveform latch circuit 52 reads the change amount data of the value “0” stored in the address A from the waveform memory 51 and holds it with the input of the next first timing signal (t5). When the variation data of the value “0” is held in the first waveform latch circuit 52, the output data from the adder 54 has the same voltage value as the output voltage from the second waveform latch circuit 53. For this reason, during the period in which the change amount data of the value “0” is held in the first waveform latch circuit 52, even if the update timing defined by the second timing signal arrives, the change from the second waveform latch circuit 53 The output voltage maintains V which is the previous voltage value (t6, t7).

  Thereafter, with the input of the next first timing signal, the change amount data of −ΔV2 corresponding to the change amount data corresponding to the address C is held in the first waveform latch circuit 52 (t8). When the change amount data is held, the output voltage from the second waveform latch circuit 53 decreases by ΔV2 every time the update timing comes (t9 to t14).

  As described above, in the drive signal generation circuit 48 according to the present embodiment, the waveform of the drive signal COM can be set to a free shape simply by outputting the address signal and the timing signal from the control unit 41.

Next, the drive signal generated by the drive signal generation circuit 43 will be described. In the present embodiment, a drive signal used in a relatively high resolution recording mode is taken as an example.
FIG. 6A is a diagram illustrating the configuration of the forward drive signal COM1, and FIG. 6B is a diagram illustrating the configuration of the reverse drive signal COM2. FIG. 7A is a diagram for explaining the configuration of the small dot ejection pulse DP1, and FIG. 7B is a diagram for explaining the configuration of the medium dot ejection pulse DP2. As described above, the forward drive signal COM1 includes the small dot ejection pulse DP1 (a type of the first ejection pulse in the present invention) that can form a small dot (a type of the first dot in the present invention), and a medium dot (a type of the first ejection pulse in the present invention). This is a drive signal including a medium dot ejection pulse DP2 (a kind of second ejection pulse in the present invention) capable of forming a second dot in the present invention within one recording period (a kind of ejection period in the present invention). . The forward drive signal COM1 and the backward drive signal COM2 are set so that the connection order of the ejection pulses is reversed. That is, the forward drive signal COM1 includes these ejection pulses in the order of the small dot ejection pulse DP1 and the medium dot ejection pulse DP2, and the backward drive signal COM2 includes the medium dot ejection pulse DP2 and the small dot ejection pulse DP2. These ejection pulses are included in the state of being connected in the order of the ejection pulse DP1.

  The small dot ejection pulse DP1 includes a first charging element PE11 that raises the potential with a relatively gentle gradient from the reference potential VB to the first highest potential VH1, and a first hold element that maintains the first highest potential VH1 for a very short time. PE12, a first discharge element PE13 that lowers the potential with a relatively steep slope from the first highest potential VH1 to the first intermediate potential VM1, a second hold element PE14 that maintains the first intermediate potential VM1 for a short time, A second charging element PE15 for slightly increasing the potential from the first intermediate potential VM1 to the second intermediate potential VM2, a third hold element PE16 for maintaining the second intermediate potential VM2 for a short time, and a first lowest from the second intermediate potential VM2. A second discharge element PE17 that drops the potential with a relatively steep gradient to the potential VL1, and a fourth hold element that maintains the first lowest potential VL1 for a predetermined time. And E18, is constituted by a third charge element PE19 for returning the potential from the first minimum potential VL1 to the reference potential VB.

  When this small dot ejection pulse DP1 is supplied to the piezoelectric vibrator 17, it operates as follows. First, when the first charging element PE11 is supplied and the piezoelectric vibrator 17 contracts, the pressure chamber 25 expands from the reference volume to the maximum volume. After the pressure chamber 25 is maintained at the maximum volume for a certain period of time by the first hold element PE12, the first discharge element PE13 is supplied, whereby the piezoelectric vibrator 17 expands and the volume of the pressure chamber 25 contracts. This contracted state is maintained for a short time by the hold element PE14. The volume of the pressure chamber 25 is expanded again by contraction of the piezoelectric vibrator 17 by the second charging element PE15, and the piezoelectric vibrator 17 is expanded by the second discharge element PE17 via the third hold element PE16. The volume of the chamber 25 contracts rapidly again. Along with a series of volume fluctuations of the pressure chamber 25, an ink droplet having a liquid amount capable of forming a small dot (hereinafter referred to as a small dot ink droplet) is ejected from the nozzle opening 27. Thereafter, the fourth hold element PE18 and the third charging element PE19 are sequentially supplied to the piezoelectric vibrator 17, and the pressure chamber 25 returns to the reference volume so as to converge the meniscus vibration accompanying the ejection of the ink droplets in a short time.

  The medium dot ejection pulse DP2 includes a fourth charging element PE21 that increases the potential with a relatively gentle gradient from the reference potential VB to the second highest potential VH2, and a fifth hold element PE22 that maintains the second highest potential VH2 for a short time. The third discharge element PE23 that drops the potential with a steep gradient from the second highest potential VH2 to the second lowest potential VL2, the sixth hold element PE24 that maintains the second lowest potential VL2 for a short time, and the second lowest potential VL2 To the third intermediate potential VM3, the fifth charging element PE25 for slightly increasing the potential, the seventh hold element PE26 for maintaining the third intermediate potential VM3 for a predetermined time, and the potential from the third intermediate potential VM3 to the reference potential VB. And a fourth discharge element PE27 to be made.

  When the medium dot ejection pulse DP2 is supplied to the piezoelectric vibrator 17, it operates as follows. First, when the fourth charging element PE21 is supplied and the piezoelectric vibrator 17 contracts, the pressure chamber 25 expands. After the pressure chamber 25 is expanded by the fifth hold element PE22 and maintained for a certain period of time, the third discharge element PE23 is supplied to extend the piezoelectric vibrator 17 so that the volume of the pressure chamber 25 is less than the reference volume. Shrinks rapidly. Thereby, an ink droplet of a liquid amount capable of forming a medium dot (hereinafter referred to as a medium dot ink droplet) is discharged from the nozzle opening 27. Thereafter, the sixth hold element PE24, the fifth charge element PE25, the seventh hold element PE26, and the sixth charge element PE27 are sequentially supplied to the piezoelectric vibrator 17, and the vibration of the meniscus associated with the ejection of the ink droplets is shortened in a short time. In order to converge, the pressure chamber 25 returns to the reference volume.

  Here, the small dot ink droplets ejected by using these ejection pulses DP1 and DP2 and the medium dot ink droplets have different flight speeds. In the present embodiment, the flying speed V1 of the small dot ink droplet is slower than the flying speed V2 of the medium dot ink droplet. As shown in the schematic diagram of FIG. 8, these ink droplets fly in an oblique direction with respect to the recording surface of the recording paper 6 because the inertial component Vcr caused by the movement of the carriage 4 acts. For this reason, if the ejection pulses DP1 and DP2 are arranged (generated) at equal time intervals in the drive signal, the landing position in the pixel region P is shifted between forward movement and backward movement.

  In order to solve such a problem, in the present embodiment, the small dot S and medium dot M formation interval (hereinafter referred to as forward formation interval) dd1 in the same pixel region P during forward movement, The difference between the small dot S and medium dot M formation interval (hereinafter referred to as the backward formation interval) dd2 in the same pixel region P is the dot formation interval at the basic resolution in the moving direction of the recording head 2, that is, the main scanning direction. The discharge timing of the front discharge pulse (that is, small dot discharge pulse) in the forward movement and the discharge pulse of the rear side (that is, medium dot discharge pulse) so that it is within α (hereinafter, the prescribed dot formation interval α). The interval between the discharge timing (hereinafter referred to as the forward discharge interval) td1, the front discharge pulse (medium dot discharge pulse) during the backward movement, and the rear discharge pulse (small dot). Interval (hereinafter referred to as reverse discharge interval) td2 is set.

  In other words, the forward drive interval td1 from the start of the first discharge element PE13 of the small dot discharge pulse DP1 to the start of the third discharge element PE23 of the medium dot discharge pulse DP2 in the forward drive signal COM1, and the drive at the time of backward movement The backward discharge interval td2 from the start end of the third discharge element PE23 of the medium dot discharge pulse DP2 to the start end of the first discharge element PE13 of the small dot discharge pulse DP1 in the signal COM2, the forward formation interval dd1 and the backward formation interval It is determined that the difference from dd2 is within the prescribed dot formation interval α in the main scanning direction.

More specifically, the flying speed of the small dot ink drop s is V1, the flying speed of the medium dot ink drop m is V2, the moving speed of the carriage 4 (recording head 2) is Vcr, the paper gap is PG, and the small dot ink drop is When the flight time of s is t1 (= PG / V1) and the flight time of the medium dot ink droplet m is t2 (= PG / V2), the forward movement formation interval dd1 and the backward movement formation interval dd2 are respectively expressed by the following equations (1) ), (2).
dd1 = {(PG / V2 + td1) −PG / V1} × Vcr
= (Td1−t1 + t2) × Vcr (1)
dd2 = {(PG / V1 + td2) −PG / V2} × Vcr
= (Td2-t2 + t1) * Vcr (2)
The forward ejection satisfying the condition expressed by the following expression (3) so that the difference between the forward movement formation interval dd1 and the backward movement formation interval dd2 is within the prescribed dot formation interval α in the main scanning direction. An interval td1 and a backward discharge interval td2 are determined.
| Dd1-dd2 |
= | (Td1−t1 + t2) × Vcr− (td2−t2 + t1) × Vcr |
= | {Td1-td2 + 2 (t2-t1)} × Vcr | ≦ α (3)

For example, the flying speed V1 of the small dot ink droplet s is 7.0 m / s, the flying speed V2 of the medium dot ink droplet m is 8.0 m / s, and the moving speed Vcr of the carriage 4 (recording head 2) is 20 inches / sec ( Consider a case where the paper gap is 1.0 mm and the basic resolution is 1440 dpi (dot / inch). In this ^{case, t1 = 1.0 × 10 -3 /7≒14.3msec,t2=1.0×10} -3 /8≒12.5msec, defining the dot formation interval α becomes 17.64Myuemu. When td2 = 20 μs is determined, td1 takes a value in the range of 15 to 90 μs based on the above equation (3).

That is, according to the above equation (3), the distance from the nozzle opening 27 to the recording surface of the recording paper 6, that is, the paper gap PG and the moving speed Vcr of the carriage 4 are taken into account, and the forward discharge interval td1 and the return interval A dynamic discharge interval td2 is determined.
Ideally, it is desirable that the forward movement formation interval dd1 and the backward movement formation interval dd2 are equal, that is, dd1 = dd2. In this case, the following expression (4) is derived based on the above expressions (1) and (2),
td1 = td2-2 (t2-t1) (4)
If td2 = 20 μs is determined in this equation (4), td1 is determined to be 55.7 μs.

Then, the control unit 41 sets the forward discharge interval value of the forward drive signal COM1 and the backward discharge interval value of the backward drive signal COM2 to td1 and td2 obtained as described above, respectively. Set. That is, the control unit 41 adjusts the waveforms of the drive signals COM1 and 2 generated by the drive signal generation circuit 43 by outputting an address signal and a timing signal in accordance with the ejection intervals td1 and td2.
In the present embodiment, since the small dot ink droplet s has a slower flight speed than the medium dot ink droplet m, the forward discharge interval td1 in the forward drive signal COM1 is the reverse drive signal COM2, as shown in FIG. Is set to be longer than the backward discharge interval td2 (the discharge timing of the small dot ink droplet s is earlier than the discharge timing of the medium dot ink droplet m).

Thus, the forward discharge interval td1 and the backward discharge interval td2 are set so that the difference between the forward movement formation interval dd1 and the backward movement formation interval dd2 is within the prescribed dot formation interval α in the main scanning direction. According to the basic resolution, it is possible to align the dot formation positions during forward movement and backward movement. By doing so, it appears to the human eye that the recorded image is recorded at the basic resolution. Thereby, it is possible to improve the image quality of the recorded image.
Further, since the forward discharge interval td1 and the reverse discharge interval td2 are obtained by taking into account the paper gap PG and the moving speed Vcr of the carriage 4, even when these parameters change, Based on this, the optimum discharge intervals dd1 and dd2 can be set. Therefore, it is possible to align the dot formation positions during forward movement and backward movement with higher accuracy.

Next, a second embodiment of the present invention will be described. In the present embodiment, in the adjustment process after assembling the printer 1, an inspection pattern is created on the recording paper 6, and setting is performed based on the inspection pattern.
FIG. 9 shows an example of an inspection pattern, where (a) is a partially enlarged view of the inspection pattern during forward movement, and (b) is a partially enlarged view of the inspection pattern during backward movement. The inspection pattern of the present embodiment is created by recording vertical ruled lines on the recording paper 6 using the small dot ejection pulse DP1 and the medium dot ejection pulse DP2 in each of forward movement and backward movement. That is, the printer 1 fixes the dot formation position in the main scanning direction and forms small dots S and medium dots M in the same pixel area in the sub-scanning direction a predetermined number of times, thereby forming small dots S on the recording paper 6. A medium dot ruled line Lm with dot ruled lines Ls and medium dots M is recorded.

  Next, the forward movement formation interval dd1 and the backward movement formation interval dd2 are acquired based on the created inspection pattern. Specifically, the inspection pattern image is read using an optical reading unit such as a scanner, and the distance between the small dot ruled line Ls and the medium dot ruled line Lm at the time of forward and backward movement of the read image is hosted. By measuring with a computer or the like, they are acquired as the forward movement formation interval dd1 and the backward movement formation interval dd2, respectively.

  Then, the forward discharge interval td1 and the backward discharge interval td2 are set so that the difference between the forward movement formation interval dd1 and the backward movement formation interval dd2 obtained as described above is within the prescribed dot formation interval α in the main scanning direction. Set. According to this method, since the setting is made based on the inspection pattern created by actually ejecting ink droplets, the calculation error can be reduced and the setting can be performed with higher accuracy. This makes it possible to align the dot formation positions during forward movement and backward movement with higher accuracy.

By the way, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the description of the scope of claims.
In each of the above embodiments, an example has been given in which a small dot ink droplet has a slower flight speed than a medium dot ink droplet, but 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 dot ink droplet and the medium dot ink droplet are the same, or the case where the flying speed of the small dot ink droplet is faster than that of the medium dot ink droplet.

  Further, the drive signals are not limited to those exemplified in the above embodiment. For example, the present invention can be applied to a drive signal including three or more types of ejection pulses such as a small dot ejection pulse, a medium dot ejection pulse, and a large dot ejection pulse within one recording period. Also in this case, the discharge interval between the adjacent discharge pulses (that is, the first discharge pulse and the second discharge pulse) can be set by using the above equation (3) or the inspection pattern.

  In the first embodiment, the configuration in which the flying speed of the ink droplet is measured using the laser detector 46 is exemplified, but the present invention is not limited to this. For example, in the adjustment process after assembling the printer 1, the flying speed of each ink droplet is measured and the measurement result is stored as a table in a storage means such as the ROM 39, and this table is used when setting the discharge intervals td1 and td2. It can also be configured to read.

  In the above embodiment, the so-called longitudinal vibration mode piezoelectric vibrator 17 is exemplified as the pressure generating element of the present invention, but the present invention is not limited to this. For example, a piezoelectric vibrator that can vibrate in the electric field direction (the stacking direction of the piezoelectric body and the internal electrode) may be used. In addition, the nozzles are not limited to being unitized, but may be provided for each pressure chamber 25 as in a so-called flexural vibration mode piezoelectric vibrator. Further, not only the piezoelectric vibrator but also other pressure generating elements such as a heating element can be used.

  In addition, the present invention can be applied even if the third and fourth ejection pulses are added as ejection pulses. The present invention can also be applied to liquid ejecting apparatuses other than the printer as long as landing position accuracy is required. For example, the present invention can be applied to a display manufacturing apparatus, an electrode manufacturing apparatus, a chip manufacturing apparatus, and the like.

FIG. 2 is a perspective view illustrating a configuration of a printer. FIG. 3 is a cross-sectional view of a main part illustrating the configuration of a recording head. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a block diagram explaining the electrical structure of a drive signal generation circuit. It is a figure explaining the production | generation process of a drive signal. (A) is a waveform diagram for explaining the configuration of the forward drive signal, and (b) is a waveform diagram for explaining the configuration of the backward drive signal. (A) is a waveform diagram illustrating the configuration of a small dot ejection pulse, and (b) is a waveform diagram illustrating the configuration of a medium dot ejection pulse. (A) is a schematic diagram for explaining the ejection state of ink droplets during forward movement, and (b) is a schematic diagram for explaining the ejection state of ink droplets during backward movement. (A) is a figure which shows an example of the test pattern at the time of forward movement, (b) is a figure which shows an example of the test pattern at the time of backward movement. FIG. 5 is a schematic diagram for explaining a shift in dot formation position in the main scanning direction during forward movement and backward movement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Printer, 2 Recording head, 3 Ink cartridge, 4 Carriage, 5 Platen, 6 Recording paper, 7 Carriage moving mechanism, 8 Paper feed mechanism, 9 Guide rod, 10 Linear encoder, 11 Capping member, 12 Wiper member, 13 Case, 14 vibrator unit, 15 flow path unit, 16 storage space, 17 piezoelectric vibrator, 18 fixing plate, 19 flexible cable, 20 flow path forming substrate, 21 nozzle plate, 22 elastic plate, 23 reservoir, 24 ink supply port, 25 Pressure chamber, 26 Nozzle communication port, 27 Nozzle opening, 28 Support plate, 29 Elastic membrane, 30 Diaphragm part, 31 Compliance part, 32 Island part, 33 Thin elastic part, 35 Printer controller, 36 Print engine, 37 External interface , 38 AM, 39 ROM, 41 control unit, 42 oscillation circuit, 43 drive signal generation circuit, 44 timer circuit, 45 internal interface, 46 laser detector, 49 waveform generation circuit, 50 current amplification circuit, 51 waveform memory, 52 first waveform Latch circuit, 53 Second waveform latch circuit, 54 Adder, 55 D / A converter, 56 Voltage amplification circuit, 57 Current amplification circuit

Claims (5)

It has a pressure chamber that communicates with the nozzle opening and a pressure generating element that generates pressure fluctuations in the liquid in the pressure chamber. By operating the pressure generating element, droplets are discharged from the nozzle opening to form dots on the discharge target. Possible liquid jet heads,
Drive signal generating means for generating a drive signal including a first discharge pulse capable of forming a first dot and a second discharge pulse capable of forming a second dot having a size different from that of the first dot within one discharge cycle. And
The liquid ejecting head is configured to be capable of reciprocating, and is a liquid ejecting apparatus capable of ejecting liquid droplets both during forward movement and during backward movement,
The drive signal generating means generates a backward drive signal for generating the first discharge pulse and the second discharge pulse in the reverse order of the forward drive signal when the liquid ejecting head moves backward,
The difference between the forward movement formation interval of the first dot and the second dot during the forward movement and the backward movement formation interval of the first dot and the second dot during the backward movement is within the prescribed dot formation interval in the liquid ejecting head moving direction. The forward discharge interval between the discharge timing of the first discharge pulse and the discharge timing of the second discharge pulse during the forward movement, the discharge timing of the second discharge pulse during the backward movement, and the first A liquid ejecting apparatus, wherein a backward discharge interval with respect to a discharge timing of one discharge pulse is set.   The liquid ejecting apparatus according to claim 1, wherein the forward discharge interval and the backward discharge interval are set in consideration of a distance from the nozzle opening to the discharge target.   The liquid ejecting apparatus according to claim 1, wherein the forward ejection interval and the backward ejection interval are set in consideration of a moving speed of the liquid ejecting head. In each of the forward movement and the backward movement, an inspection pattern is created on the discharge object using the first discharge pulse and the second discharge pulse,
Based on the forward movement formation interval between the first dot and the second dot in the inspection pattern during the forward movement and the backward movement formation interval between the first dot and the second dot in the inspection pattern during the backward movement. The liquid ejecting apparatus according to claim 1, wherein the forward discharge interval and the backward discharge interval are set. It has a pressure chamber that communicates with the nozzle opening and a pressure generating element that generates pressure fluctuations in the liquid in the pressure chamber. By operating the pressure generating element, droplets are discharged from the nozzle opening to form dots on the discharge target. Possible liquid jet heads,
Drive signal generating means for generating a drive signal including a first discharge pulse capable of forming a first dot and a second discharge pulse capable of forming a second dot of a size different from the first dot within one discharge cycle; With
A control method for a liquid ejecting apparatus, wherein the liquid ejecting head is configured to eject liquid droplets both in the forward movement and in the backward movement in accordance with the ejection pulse of the drive signal generated by the drive signal generating means. ,
The difference between the forward movement formation interval of the first dot and the second dot during the forward movement and the backward movement formation interval of the first dot and the second dot during the backward movement is within the prescribed dot formation interval in the liquid ejecting head moving direction. The forward discharge interval between the discharge timing of the first discharge pulse and the discharge timing of the second discharge pulse during the forward movement, the discharge timing of the second discharge pulse during the backward movement, and the first A control method of a liquid ejecting apparatus, comprising setting a backward discharge interval with a discharge timing of one discharge pulse.

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