JP3888349B2 - Liquid ejector - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus, and more particularly to a liquid ejecting apparatus that can suitably perform drive control of a recording head that ejects liquid droplets such as ink droplets from nozzles in accordance with the environmental temperature during use.

  Conventionally, as one type of liquid ejecting apparatus, for example, an ink jet printer that performs printing on a printing medium by ejecting ink droplets from a recording head is known. In this type of printer, the recording head is moved along the main scanning direction and printing paper (a kind of printing medium) is moved along the sub-scanning direction. An image is printed on the printing paper by ejecting ink droplets. Ink droplet ejection is performed, for example, by deforming a piezoelectric vibrator in accordance with a drive pulse supplied to a recording head, thereby expanding and contracting a pressure chamber communicating with a nozzle opening.

  By the way, in recent years, such a printer has been proposed that has a thin box shape that is assumed to be used in a state of being stored in a rack or the like with so-called AV (Audio / Visual) equipment connected to a personal computer (PC). Has been. As described above, in a printer that is used in a state where it is housed in a rack or the like together with other AV equipment, the ambient temperature during use tends to be generally higher than the room temperature due to heat generated in the drive system of the AV equipment. .

Conventionally, in order to cope with such changes in environmental temperature, each pulse waveform of a head drive signal supplied to a recording head according to the environmental temperature detected by a sensor or the like is corrected for potential correction or time correction (hereinafter referred to as “temperature”). By performing “correction”, ink droplets are stably ejected (see, for example, Patent Document 1). This ensures a certain print quality up to a certain temperature (for example, 40 ° C.) even when the environmental temperature becomes high.
Japanese Patent No. 3356204

  By the way, in a printer that is used in a state where it is stored in a rack or the like as described above, the environmental temperature rises to a reasonably high temperature such as exceeding 40 ° C. due to the heat trapped in the rack or the like. Have When a printer is used in such a high temperature environment, ink droplets cannot be stably ejected only by temperature correction as in the prior art, and therefore there is a risk that good print quality cannot be guaranteed. It was. In other words, conventionally, it is not assumed that the printer is used at an environmental temperature exceeding 40 ° C., for example, as described above, and measures are taken to stably eject ink droplets under such a high temperature environment. Absent. For this reason, the ejection stability of the ink drops is lowered under a high temperature environment, and as a result, there has been a problem that good print quality cannot be maintained.

  Here, as a factor that the ejection stability of the ink droplet is lowered, the viscosity of the ink is lowered. The viscosity of the ink decreases as the environmental temperature increases. When the viscosity of the ink decreases in this way, the residual vibration of the meniscus after the ink droplet is ejected increases. Due to the influence of the residual vibration, the ink droplet does not fly straight and the landing position of the ink droplet is displaced, or bubbles are taken into the nozzle and so-called dot missing occurs.

  Another factor is that the frequency of the head driving signal for driving the recording head has been increased in recent years. In other words, by increasing the head drive frequency and ejecting ink droplets with high response, throughput is improved (printing speed is increased). When the ink viscosity decreases as described above, it becomes more difficult to suppress the residual meniscus vibration.

  The present invention has been made in view of such conventional circumstances, and an object of the present invention is to provide a liquid ejecting apparatus capable of stably ejecting liquid droplets even when the use environment is at a high temperature and a driving method thereof. It is to provide.

  In order to achieve the above object, according to a first aspect of the present invention, in a liquid ejecting apparatus that performs printing by ejecting liquid droplets from a recording head that reciprocates in the main scanning direction, the temperature in the peripheral area of the recording head is detected. Temperature detecting means, a first waveform mode for generating a first drive waveform based on the print data, and a discharge operation of the recording head based on the print data so as to be every other pixel or every second pixel. A second waveform mode for generating two drive waveforms is set, and each waveform mode is switched and controlled according to the temperature detected by the temperature detecting means; and the mode switching means outputs the mode. Signal generating means for generating a head drive signal having a drive waveform corresponding to each of the waveform modes based on the mode signal, and in the second waveform mode A head scanning unit that doubles the number of scans of the recording head in the first waveform mode, and a drive waveform corresponding to each waveform mode according to the temperature detected by the temperature detection unit. Correction means for correcting a pulse waveform, wherein the mode switching means is set to the first waveform mode when the temperature detected by the temperature detection means is equal to or lower than a predetermined temperature, and the temperature detected by the temperature detection means. The switching control is performed so that the second waveform mode is set when the temperature exceeds the predetermined temperature, and the first waveform mode or the second waveform mode is set at the start of printing based on one print job. When the mode signal for instructing is output and printing of a plurality of pages is instructed in the one print job, printing based on the one print job is finished. In performs the temperature correction of the pulse waveform according to the temperature detected for each page, in the middle printing based on the single print job does not perform the switching control, and summarized in that.

  According to this configuration, the second waveform mode is executed when the temperature around the recording head detected by the temperature detection means exceeds a predetermined temperature, that is, when the use environment is in a high temperature environment, and the print data The recording head is driven by the head driving signal having the second driving waveform generated so that the ejection operation of the recording head based on the above has a predetermined interval period. In such a configuration, even in a low-viscosity high-temperature environment, the residual vibration of the meniscus that overlaps when liquid droplets are continuously ejected with high response (short ejection intervals) is suitable using a period during which no ejection operation is performed. Can be attenuated. As a result, liquid droplets can be stably ejected, and the environmental temperature that can be guaranteed during use can be set higher on the higher temperature side than before. In addition, once one of the above waveform modes is determined at the start of printing based on one print job, even if the environmental temperature subsequently fluctuates between the temperature ranges corresponding to each waveform mode, The waveform mode is not switched until printing based on one print job is completed. This is because when the waveform mode is switched in the middle of printing based on one print job, the liquid permeation is caused by changing the scanning time (printing time) of the recording head between the first waveform mode and the second waveform mode. This is because there is a concern that the difference in sex may become a color difference. Therefore, with this configuration, it is possible to suppress the occurrence of a color difference during printing based on one print job and to keep the print quality constant. Further, when printing of a plurality of pages is instructed in one print job, each pulse waveform of the drive waveform generated in each waveform mode is corrected according to the environmental temperature detected for each page. As a result, the liquid droplet ejection stability can be further improved.

  In this configuration, in the second waveform mode, the number of scans of the recording head is twice that in the first waveform mode. As a result, the ejection operation for the area in which the liquid droplets are not ejected by the first scan in the recording area corresponding to one scan of the recording head can be interpolated by the second scan. Incidentally, the recording method of the recording head according to this configuration may be a method of performing recording by ejecting liquid droplets when the recording head moves (unidirectional printing), or the recording method of the recording head when the recording head moves. A system (bidirectional printing) may be used in which recording is performed by ejecting liquid droplets both during movement.

Here, specific modes for generating the second drive waveform include, for example, the following modes.
That is, in the second aspect of the present invention, in the first aspect, the second driving waveform is a driving waveform in which a pulse waveform is generated in units of pixels so that the ejection operation of the recording head is performed every other pixel. It is the gist.

  In this configuration, after a liquid droplet is ejected from a certain pixel by one scan of the recording head, the ejection of the liquid droplet is stopped at the next pixel. Therefore, the residual vibration of the meniscus can be damped during this idle period.

  In a third aspect of the present invention, in the first or second aspect, the period of each pulse waveform of the first drive waveform and the second drive waveform is the same, and the moving speed of the recording head is The gist is that it is the same in each waveform mode.

  According to this configuration, since the pulse periods of the first drive waveform and the second drive waveform are the same, the moving speed of the recording head can be made the same in each waveform mode. Thereby, it can suppress that the difference in liquid permeability by changing the discharge timing of a liquid droplet becomes a color difference.

Hereinafter, an embodiment in which a liquid ejecting apparatus of the present invention is embodied in an ink jet printer 1 will be described with reference to FIGS.
FIG. 1 is a perspective view showing an appearance of a printer 1 according to the present embodiment.

  As shown in the figure, the printer 1 has a substantially box shape, and is formed to be about the size of a video tape recorder, assuming that the printer 1 is used in a state of being stored in a television rack, for example. ing.

  The schematic configuration of the printer 1 will be described. A front cover 3 is provided on the front surface of the outer housing 2 having a substantially box shape, and the front cover 3 is opened to the front side (used state) and closed. (Non-use state) is configured to be freely rotatable. A paper feed tray 4 is detachably provided at the lower portion of the front cover 3. By pulling the paper feed tray 4 to the front side and removing it, a printing paper P (see FIG. 2) as a printing medium is obtained. Can be set. An ink cartridge unit 5 is provided above the front cover 3, and a plurality of ink cartridges (not shown) are detachably provided side by side in the width direction of the printer 1.

Next, the internal configuration of the printer 1 will be described with reference to FIG.
FIG. 2 is a perspective view showing the appearance of the printer 1 with the external housing 2 removed.
The printer 1 includes a lower chassis 6, a main frame 7 extending in the main scanning direction that is the width direction of the printer 1, and a sub-scanning direction that is erected on both sides of the main frame 7 and that is the depth direction of the printer 1. And a pair of side frames 8a and 8b parallel to each other. Between the pair of side frames 8a and 8b, a main guide shaft 11 and a sub guide shaft 12 that guide a carriage 10 in which a recording head 9 having a large number of nozzles (not shown) for each color is mounted in the main scanning direction. Are provided at predetermined intervals in the sub-scanning direction. The main guide shaft 11 is inserted into the rear portion of the carriage 10, and the front portion of the carriage 10 is supported from below by the sub guide shaft 12, so that the recording head 9 and the guide member disposed to face the recording head 9 are arranged. A clearance (so-called platen gap) with the platen 13 is defined.

  The carriage 10 is reciprocated along the guide shafts 11 and 12 in the main scanning direction under the rotational driving force of the carriage motor 14 (see FIG. 3). In other words, the carriage head 14 can be reciprocated in the main scanning direction together with the carriage 10 by controlling the rotation of the carriage motor 14.

  The printing paper P set in the paper feed tray 4 includes a conveyance driving roller 21 that is rotated by a conveyance motor 15 (see FIG. 3), and a conveyance driven roller that is driven to rotate as the conveyance driving roller 21 rotates. 22 is guided onto the platen 13 and conveyed below the recording head 9. The conveyed printing paper P is printed by ejecting (jetting) ink droplets from the recording head 9 while being supported from below by the platen 13.

  The recording head 9 is provided at the lower part of the carriage 10, but no ink cartridge is mounted on the carriage 10, and a plurality of ink cartridges are disposed above the main scanning area of the carriage 10 as described above. Are detachably arranged side by side in the main scanning direction. Ink is supplied to the carriage 10 via an ink tube (not shown).

  Although not shown here, on the downstream side of the recording head 9, there are a discharge driving roller that is driven to rotate by the conveying motor, and a discharge driven roller that is driven to rotate as the discharge driving roller rotates. The printing paper P is discharged to the outside of the printer 1 by these rollers.

  Further, the printer 1 is provided with a disk tray 23 on which an optical disk D such as a DVD (Digital Versatile Disk) can be set. The disc tray 23 is disposed above the paper feed tray 4. When the optical disc D is set on the disc tray 23 and the tray 23 is transported under the recording head 9, printing can be performed by directly ejecting ink droplets onto the label surface of the optical disc D.

  Next, a configuration example of the recording head 9 used in the printer 1 according to the present embodiment will be described with reference to FIG. FIG. 4 is a cross-sectional view showing the main part of the recording head 9.

  The recording head 9 includes a piezoelectric vibrator 31 as an actuator, an upper electrode 32 provided on the back surface (upper surface) of the piezoelectric vibrator 31, and a lower electrode 33 provided on the front surface (lower surface) of the piezoelectric vibrator 31. The pressure generating unit 34 and the flow path unit 35 are provided.

  The pressure generating unit 34 includes a pressure chamber forming substrate 36, a vibration plate 37 bonded to both sides of the substrate 36, and a flow path forming substrate 38. The pressure chamber forming substrate 36 corresponds to the piezoelectric vibrator 31. A pressure chamber 39 is formed at the position where

  The vibration plate 37 is bonded to the upper surface of the pressure chamber forming substrate 36, and the piezoelectric vibrator 31 is laminated on the upper surface of the vibration plate 37 with the lower electrode 33 interposed therebetween. The flow path forming substrate 38 is joined to the lower surface of the pressure chamber forming substrate 36, and the first ink flow path 40 and the second ink flow path 41 communicating with the pressure chamber 39 are connected to the flow path forming substrate 38. Is formed.

  The flow path unit 35 includes a nozzle plate 42, a reservoir forming substrate 43, and a supply port forming plate 44, with the reservoir forming substrate 43 sandwiched therebetween, the nozzle plate 42 on the lower surface, and the supply port forming plate on the upper surface. 44 are joined to each other. The flow path unit 35 is joined to the lower surface of the pressure generating unit 34.

  The reservoir forming substrate 43 is formed with an ink reservoir 45 that stores ink and a first nozzle communication hole 47 that communicates with the nozzle 46 formed in the nozzle plate 42. The supply port forming plate 44 communicates with the ink reservoir 45 and the first ink flow path 40, and includes an ink supply port 48 for supplying the ink stored in the ink reservoir 45 to the pressure chamber 39, A second nozzle communication hole 49 communicating with the first nozzle communication hole 47 and the second ink flow path 41 is formed.

  In the recording head 9 configured as described above, a series of ink flow paths from the ink reservoir 45 to the nozzle 46 through the pressure chamber 39 is formed. In the recording head 9, the substrates 36, 38, and 43 are formed by, for example, etching a silicon wafer. However, the present invention is not limited to this configuration, and the pressure chamber 39 and the ink flow are not limited to this configuration. The ink flow paths may be formed by forming the paths 40 and 41, the ink reservoir 45, and the like, and laminating and bonding them.

  In the recording head 9 having such a configuration, when the piezoelectric vibrator 31 is deformed (contracted) by charging, the diaphragm 37 is bent and the pressure chamber 39 contracts. Further, when the piezoelectric vibrator 31 is deformed (expanded) by discharge from the contracted state of the pressure chamber 39, the pressure chamber 39 expands due to the elasticity of the vibration plate 37. By causing the pressure chamber 39 to expand once and then contract due to the deformation associated with charging / discharging of the piezoelectric vibrator 31, the ink pressure in the pressure chamber 39 is increased, and ink droplets are ejected from the nozzle 46.

Next, the electrical configuration of the printer 1 will be described with reference to FIG.
As shown in FIG. 1, the printer 1 includes a printer controller 50 and a print engine 51. The printer controller 50 includes an external interface (external I / F) 52, a RAM 53 that temporarily stores various data, a ROM 54 that stores a control program, a control unit 55 that includes a CPU, a clock, and the like. An oscillation circuit 56 that generates a signal CLK, a drive signal generation circuit 57 that generates a drive signal COM to be supplied to the recording head 9, and an internal interface (internal I / F) 58 are provided. On the other hand, the print engine 51 includes the carriage motor 14 that constitutes the head scanning means together with the control unit 55, the conveyance motor 15, and the electric drive system 59 of the recording head 9.

First, the printer controller 50 will be described.
The external I / F 52 receives, for example, print data composed of a character code, a graphic function, image data, and the like from a host computer (for example, a personal computer), a busy signal (BUSY) output from the control unit 55, An acknowledge signal (ACK) or the like is transmitted to the host computer.

  The internal I / F 58 supplies the drive signal COM generated by the drive signal generation circuit 57 and the dot pattern data (also referred to as bitmap data) generated by the control unit 55 to the electric drive system 59 of the recording head 9. The temperature of the peripheral area of the recording head 9 that is transmitted or is detected as an environmental temperature when the printer 1 is used by a temperature detection sensor 61 described later is acquired.

  The RAM 53 includes a reception buffer, an intermediate buffer, an output buffer, and a work memory (not shown). The reception buffer temporarily stores print data received via the external I / F 52, the intermediate buffer stores intermediate code data converted by the control unit 55, and the output buffer stores dot pattern data. To do. The dot pattern data is print data obtained by decoding (translating) intermediate code data (for example, gradation data).

  The ROM 54 stores font data, graphic functions, etc. in addition to a control program (control routine) for performing various data processing. Further, the ROM 54 corrects the potential (crest value) and time component of the drive signal COM (drive waveform) supplied to each piezoelectric vibrator 31 of the recording head 9 according to the environmental temperature when the printer 1 is used ( A table for performing “temperature correction” (hereinafter referred to as “temperature correction”), and control data for switching a waveform mode to be described later are stored. In the present embodiment, the ROM 54 and the control unit 55 constitute correction means for realizing the temperature correction.

  The control unit 55 performs various controls according to the control program stored in the ROM 54. For example, the control unit 55 reads the print data in the reception buffer, converts the print data to intermediate code data, and stores the intermediate code data in the intermediate buffer. Further, the control unit 55 analyzes the intermediate code data read from the intermediate buffer, and develops (decodes) it into dot pattern data by referring to the font data and graphic functions stored in the ROM 54. Then, the control unit 55 stores the dot pattern data in the output buffer after performing necessary decoration processing.

  When one line of dot pattern data that can be recorded (printed) by one main scan of the recording head 9 is obtained, the control unit 55 reads the dot pattern data for one line from the output buffer. The signals are sequentially output to the electric drive system 59 of the recording head 9 through the internal I / F 58. As a result, the carriage 10 is scanned and printing for one line is performed. When one line of dot pattern data is output from the output buffer, the developed intermediate code data is erased from the intermediate buffer, and the development process for the next intermediate code data is performed.

Next, the print engine 51, particularly the electric drive system 59 of the recording head 9, will be described.
As shown in FIG. 3, the electric drive system 59 includes a temperature detection sensor 61 as a temperature detection means, a decoder 62, a shift register circuit 63, a latch circuit 64, a level shifter circuit 65, a switch circuit 66, and the piezoelectric vibrator 31. I have. Note that the decoder 62, the shift register circuit 63, the latch circuit 64, the level shifter circuit 65, the switch circuit 66, and the piezoelectric vibrator 31 are provided for each nozzle 46 of the recording head 9.

  In this electric drive system 59, when the pulse selection data from the level shifter circuit 65 applied to the switch circuit 66 is “1”, the switch circuit 66 is connected and the pulse waveform in the drive signal COM is directly applied to the piezoelectric vibrator 31. Applied, the piezoelectric vibrator 31 is deformed according to the pulse waveform. On the other hand, when the pulse selection data from the level shifter circuit 65 applied to the switch circuit 66 is “0”, the switch circuit 66 is disconnected and the supply of the drive signal COM to the piezoelectric vibrator 31 is cut off. In this way, the switch circuit 66 generates a drive waveform (head drive signal SD) to be supplied to each piezoelectric vibrator 31 of the recording head 9 based on the drive signal COM and the pulse selection data from the level shifter circuit 65.

  In the present embodiment, two different waveform modes are generated in the ROM 54 in order to generate such a drive waveform (head drive signal SD) as a waveform depending on the temperature in the peripheral area of the recording head 9 detected by the temperature detection sensor 61. These waveform modes are set and switched by the mode signal MODE from the control unit 55. In the present embodiment, the ROM 54 and the control unit 55 constitute mode switching means.

  Specifically, when the temperature T detected by the temperature detection sensor 61 is equal to or lower than a predetermined temperature (for example, 40 ° C.), the control unit 55 generates the drive signal COM based on the dot pattern data read from the output buffer (RAM 53). A first waveform mode for generating a first drive waveform (hereinafter referred to as “normal waveform”) is executed. At this time, the control unit 55 performs temperature correction on each pulse waveform of the drive signal COM according to the temperature T, and generates a normal waveform based on the corrected drive signal COM.

  On the other hand, when the temperature T detected by the temperature detection sensor 61 exceeds the predetermined temperature (40 ° C.), the control unit 55 performs the ejection operation of the recording head 9 based on the dot pattern data at predetermined intervals. In the embodiment, the second waveform mode for generating the second drive waveform (hereinafter referred to as “high temperature waveform”) is executed so that every other pixel is set. Specifically, a high-temperature waveform is generated by generating a pulse train included in one segment of the drive signal COM corresponding to one pixel every two segments. At this time, similarly to the first waveform mode, the control unit 55 performs temperature correction on each pulse waveform of the drive signal COM according to the temperature T, and generates a high-temperature waveform based on the corrected drive signal COM. generate.

  In the present embodiment, the period (pulse period) of each pulse waveform generated for the normal waveform and the high temperature waveform is the same, and the carriage 10 movement speed is the first waveform mode and the second waveform mode. (That is, the moving speed of the recording head 9) is the same. This is because when the moving speed of the recording head 9 is changed, there is a concern that a difference in ink permeability due to a change in ink droplet ejection timing may be caused as a color difference.

  By the way, in the second waveform mode as described above, since the ink droplet ejection operation by the recording head 9 is performed every other pixel in the main scanning of the recording head 9, the control unit 55 The number of scans of the recording head 9 in the second waveform mode is changed to twice that in the first waveform mode. In this way, by changing the number of scans of the recording head 9 to twice, the ejection operation for the pixels in which the ink droplets were not ejected in the first scanning in the recording area corresponding to one scanning of the recording head 9 Are interpolated by the second scanning.

  That is, as shown in FIG. 5, for example, when ink droplet ejection is performed four times per pixel, in the second waveform mode, first, the ink droplets are in pixel units during the forward movement of the recording head 9 by the first scanning. Then, every other pixel is discharged. Next, a second scan is performed at the same position as the first scan position, and at the time of forward movement by the second scan, an ink droplet is targeted for each pixel for which no ink droplet was ejected by the first scan described above. Is discharged every other pixel in the same pixel unit. Then, after the second scanning is completed, the printing paper P is fed in the sub-scanning direction.

  As described above, in the printer 1 according to this embodiment, the recording region corresponding to one scan is ejected by two scans of the recording head 9, and the printing paper P is printed every two scans of the recording head 9. The paper feeding operation is performed once.

  The printer 1 according to the present embodiment performs recording by ejecting ink droplets when the recording head 9 moves forward (performs unidirectional printing), but when the recording head 9 moves forward and backward. It is also possible to apply this drive method to a printer that performs recording in both cases (bidirectional printing). In a printer that performs such bidirectional printing, the ejection operation for pixels that were not recorded during the forward movement of the recording head is interpolated during the backward movement.

The specific operation of each circuit of the electric drive system 59 in each waveform mode as described above will be described in detail below.
First, the decoder 62 generates pulse selection data necessary for capturing the pulse waveform in the drive signal COM based on the print data SI input via the internal I / F 58. In the present embodiment, it is assumed that a full ink droplet ejection operation (so-called solid filling) is performed. In this case, the decoder 62 is based on the print data SI corresponding to the solid filling. To generate pulse selection data.

At this time, the decoder 62 generates pulse selection data corresponding to each waveform mode based on the mode signal MODE.
Specifically, in the first waveform mode, the decoder 62 outputs (1111) pulse selection data per segment of the drive signal COM corresponding to one pixel based on the print data SI corresponding to the solid filling. Generate. On the other hand, in the second waveform mode, (1111) pulse selection data and (0000) pulse selection data are alternately generated per segment of the drive signal COM. In other words, the decoder 62 generates (11110000) pulse selection data per two segments of the drive signal COM in the second waveform mode.

  The shift register circuit 63 sequentially outputs each bit of the pulse selection data output from the decoder 62 serially in synchronization with the clock signal CLK output from the oscillation circuit 56. The latch circuit 64 latches each bit of the pulse selection data output from the shift register circuit 63 by a latch signal LAT, thereby generating a rectangular pulse train corresponding to each waveform mode, and this rectangular pulse train causes the level shifter circuit 65 to be generated. To the switch circuit 66. Then, the switch circuit 66 generates a drive waveform corresponding to each waveform mode by taking the logical product of the rectangular pulse train and the drive signal COM. In the present embodiment, the drive signal generating circuit 57, the decoder 62, the shift register circuit 63, the latch circuit 64, the level shifter circuit 65, and the switch circuit 66 constitute a signal generating means.

  FIG. 6 is a diagram showing drive waveforms (head drive signals SD) corresponding to the respective waveform modes. Note that, as described above, the present embodiment assumes a case where a full ejection operation (solid filling) of ink droplets is performed, and in this figure, the drive waveform (SD) related to this solid filling control is taken as an example. It shows.

  In the figure, the drive signal COM is a signal common to each waveform mode generated in the drive signal generation circuit 57 shown in FIG. 3, and is a signal including the same pulse waveform PW at equal intervals.

  Here, the pulse waveform PW includes a first voltage drop unit sa1 that supplies the piezoelectric vibrator 31 with a voltage that expands the pressure chamber 39 and depressurizes the inside, and a voltage that maintains the depressurized state. The first voltage maintaining unit sa2 supplied to the child 31, the first voltage increasing unit sa3 supplying the piezoelectric vibrator 31 with a voltage that contracts the pressure chamber 39 and pressurizes the inside, and maintains the pressurized state. A second voltage maintaining unit sa4 that supplies such a voltage to the piezoelectric vibrator 31, and a second voltage drop unit sa5 that supplies the piezoelectric vibrator 31 with a voltage that returns the pressure chamber 39 to its original state. Yes. With this single pulse waveform PW, an ink droplet having a weight depending on the ink characteristics, the mechanical characteristics of the nozzles 46, manufacturing errors, and the like is ejected for each nozzle 46.

Hereinafter, driving waveforms in each waveform mode will be described.
<First waveform mode>
FIG. 6A is a waveform diagram showing a normal waveform (SD) corresponding to the first waveform mode (T ≦ 40 ° C.).

  In the first waveform mode, as described above, (1111) pulse selection data per segment of the drive signal COM is output from the decoder 62. The switch circuit 66 takes in the pulse waveform PW of the corresponding period from the drive signal COM by taking the logical product of the rectangular pulse train generated based on each bit of the pulse selection data and the drive signal COM. That is, in the first waveform mode, the switch circuit 66 generates a normal waveform (SD) by taking in all the pulse waveforms PW in the drive signal COM.

<Second waveform mode>
FIG. 6B is a waveform diagram showing a high temperature waveform (SD) corresponding to the second waveform mode (T> 40 ° C.).

  In the second waveform mode, as described above, (1111) pulse selection data and (0000) pulse selection data per segment of the drive signal COM are alternately output from the decoder 62. The switch circuit 66 takes in the pulse waveform PW of the corresponding period from the drive signal COM by taking the logical product of the rectangular pulse train generated based on each bit of the pulse selection data and the drive signal COM. That is, in the second waveform mode, the switch circuit 66 generates a high temperature waveform (SD) by taking each pulse waveform in the drive signal COM every other segment. At this time, as described above, the number of scans of the recording head 9 is controlled to be twice (2n times) the number of scans (n times) in the first waveform mode. Therefore, in the second waveform mode, recording is performed in twice the scanning time (printing time) as in the first waveform mode.

Next, the head drive control of the printer 1 will be described with reference to FIG.
Here, the head drive control is a control for making the drive waveform supplied to the recording head 9 more appropriate according to the environmental temperature. Specifically, as described below, the waveform mode is changed according to the environmental temperature during use of the printer 1 (at this time, the number of scans of the recording head 9 is also changed), and further, the determined waveform mode It is characterized in that temperature correction is appropriately performed on the drive waveform corresponding to. This control routine (FIG. 7) is stored in the ROM 54 and executed by the control unit 55 when print data is received.

  That is, when the control unit 55 receives print data from the host computer or the like via the external I / F 52 (step S100), the control unit 55 shifts the processing to this routine and executes the head drive control according to the present embodiment. . At this time, the print data received by the control unit 55 is print data in units of jobs.

  When the control unit 55 receives the print data (print job) for each job, the temperature in the peripheral area of the recording head 9 (environmental temperature) detected by the temperature detection sensor 61 when printing is started based on the print job. ) T is acquired via the internal I / F 58, and it is determined whether or not the temperature T is 40 ° C. or less, and the waveform mode is determined (step S101).

  At this time, when determining that the temperature T is equal to or lower than 40 ° C., the control unit 55 sets the waveform mode to the first waveform mode, and thereafter executes printing in the first waveform mode (step S110). ). On the other hand, when determining that the temperature T exceeds 40 ° C., the control unit 55 sets the waveform mode to the second waveform mode, and subsequently executes printing in the second waveform mode (step S120). ).

  Here, when T ≦ 40 ° C. and the first waveform mode is executed, the control unit 55 generates a normal waveform in the electric drive system 59 and supplies it to each piezoelectric vibrator 31 of the recording head 9. Then, printing is executed by ejecting ink droplets (step S111). At this time, the drive signal COM, which is an original signal for generating a normal waveform, is controlled based on a table stored in the ROM 54 for temperature correction such as potential correction and time correction according to the environmental temperature (temperature T). A normal waveform generated by the unit 55 and generated based on the drive signal COM to which the temperature correction is applied is supplied to each piezoelectric vibrator 31 of the recording head 9.

  When printing on the printing paper P for one page is completed by the normal waveform subjected to such temperature correction, the control unit 55 should then confirm the content of the print job and execute printing of the next page for the print job. It is determined whether there is an instruction to that effect (step S112). That is, the control unit 55 determines whether or not the print job instructs to print a plurality of pages.

  If it is determined that there is no next page, the control unit 55 ends printing. On the other hand, when determining that there is a next page, the control unit 55 acquires again the temperature T in the peripheral area of the recording head 9 detected by the temperature detection sensor 61 when starting the printing of the second page. (Step S113). Then, a normal waveform is generated again based on the drive signal COM subjected to temperature correction according to the newly acquired temperature T (step S114), and is supplied to each piezoelectric vibrator 31 of the recording head 9. By causing ink droplets to be ejected, the second page is printed.

  Thereafter, the control unit 55 proceeds to step S112 to confirm the print job again, and if it is determined that there is a print instruction for the next page in the determination process here, the control unit 55 performs the process in steps S113 and S114. Processing is performed in the same manner. The control unit 55 executes printing in the first waveform mode by repeating such a series of processes for a plurality of pages designated by the job.

  On the other hand, when T> 40 ° C. and the second waveform mode is executed, the control unit 55 generates a high temperature waveform in the electric drive system 59 and supplies it to each piezoelectric vibrator 31 of the recording head 9. Printing is executed by ejecting ink droplets (step S121). At this time, the drive signal COM serving as an original signal for generating a high temperature waveform is a temperature such as potential correction or time correction corresponding to the environmental temperature (temperature T), as in the first waveform mode. Correction is performed by the control unit 55, and a high-temperature waveform generated based on the drive signal COM with this temperature correction is supplied to each piezoelectric vibrator 31 of the recording head 9. At this time, since the number of scans of the recording head 9 is doubled in the first waveform mode as described above, the scan time (printing time) is twice as long as that in the first waveform mode. Printing is started.

  When printing on the printing paper P for one page is completed by the high-temperature waveform subjected to such temperature correction, the control unit 55 should then confirm the contents of the print job and execute printing of the next page for the print job. It is determined whether there is an instruction to that effect (step S122).

  If it is determined that there is no next page, the control unit 55 ends printing. On the other hand, when determining that there is a next page, the control unit 55 acquires again the temperature T in the peripheral area of the recording head 9 detected by the temperature detection sensor 61 when starting the printing of the second page. (Step S123). Then, a high temperature waveform is generated again based on the drive signal COM subjected to temperature correction in accordance with the newly acquired temperature T (step S124), and is supplied to each piezoelectric vibrator 31 of the recording head 9. By causing ink droplets to be ejected, the second page is printed.

  Thereafter, the control unit 55 proceeds to step S122 to confirm the print job again, and if it is determined that there is a print instruction for the next page in the determination process here, the control unit 55 performs the process in steps S123 and S124. Processing is performed in the same manner. The control unit 55 executes printing in the second waveform mode by repeating such a series of processes for a plurality of pages designated by the job.

  As can be seen from the above description, in the head drive control according to the present embodiment, temperature correction is performed for each page until printing based on one received print job is completed, but the waveform mode is first The determined waveform mode is not changed. In other words, once the waveform mode is determined in the execution of printing based on one print job, the drive waveform of the recording head 9 is not changed during the execution.

  The control mode is such that when the waveform mode (driving waveform) is switched during printing based on one print job, the difference in ink permeability due to the change in scanning time (printing time) is the color difference. This is because there are concerns that occur. It has been experimentally confirmed by the present inventor that the occurrence of such a color difference is more dependent on the ink permeability (that is, the time difference) than on the environmental temperature.

  Therefore, when printing of multiple pages is instructed in one print job, if the first page is printed with a high temperature waveform, the high temperature waveform is applied to all pages regardless of the environmental temperature detected thereafter. Is executed (temperature correction of each pulse waveform is performed for each page). In addition, when the first page is printed with a normal waveform, printing with the normal waveform is executed for all pages regardless of the environmental temperature detected thereafter (temperature correction of each pulse waveform for each page). Do).

  Incidentally, in the printer 1 of the present embodiment used in a state of being stored in a rack or the like, even when the environmental temperature exceeds 40 ° C. at the time of use (at the start of printing of the first page), The heat trapped in the rack or the like is released by driving a cooling fan (not shown) provided in the printer 1, and the temperature tends to gradually decrease. Therefore, after starting the printing of the first page with the normal waveform in the first waveform mode, it is considered unlikely that the temperature will rise beyond 40 ° C. after that. It is assumed that it is unlikely that it will be necessary to switch to the second waveform mode.

As described above, according to the present embodiment, the following effects can be obtained.
(1) When the temperature T in the peripheral area of the recording head 9 detected by the temperature detection sensor 61 as the environmental temperature during use of the printer 1 is equal to or lower than a predetermined temperature (for example, 40 ° C.), A first waveform mode is executed in which each waveform is captured and a normal waveform is generated. On the other hand, when the temperature T detected by the temperature detection sensor 61 exceeds 40 ° C., each pulse waveform in the drive signal COM is set to 1 so that the ink droplet ejection operation by the recording head 9 is performed every other pixel. A second waveform mode is executed that takes in every other segment and generates a high temperature waveform (SD). In general, the residual vibration of the meniscus after the ink droplets are ejected increases in a high temperature environment where the viscosity decreases, and the ink droplets are superimposed by being continuously ejected with a high response (short ejection interval). Become. In the present embodiment, when the usage environment of the printer 1 is in a high temperature environment exceeding 40 ° C., for example, as described above, the discharge operation by the recording head 9 is performed every other pixel, so that the viscosity becomes low. However, the residual vibration of the meniscus that overlaps when ink droplets are continuously ejected can be suitably damped using a period during which no ejection operation is performed. As a result, ink droplets can be stably ejected, and the environmental temperature that can be guaranteed when the printer 1 is used can be set higher than the conventional temperature. That is, conventionally, the maximum ambient temperature at which ink droplets can be stably ejected is set to 40 ° C., but in the present embodiment, a higher temperature can be set.

  (2) In the present embodiment, since the moving speed of the carriage 10 (moving speed of the recording head 9) is constant in each waveform mode, the difference in ink permeability due to the change in the ink droplet ejection timing. It is possible to suppress the occurrence of color differences and the occurrence of ink droplet landing position errors as image quality differences.

  (3) In the present embodiment, after the waveform mode is once determined at the start of printing based on one print job, it is assumed that the environmental temperature subsequently fluctuates between temperature regions corresponding to each waveform mode. However, the waveform mode is not switched until printing based on the one print job is completed. According to this, it is possible to suppress the occurrence of a difference in ink permeability due to a change in scanning time (printing time) due to a change in waveform mode as a color difference.

  (4) In this embodiment, in addition to executing switching control of each waveform mode in accordance with the environmental temperature, each pulse waveform of the drive waveform generated in each of the waveform modes is also in accordance with the environmental temperature. Temperature correction was applied. At this time, if the print job includes an instruction to execute printing of a plurality of pages, temperature correction corresponding to the environmental temperature is appropriately performed for each page. According to this, the ejection stability of ink droplets can be further improved.

In the above-described embodiment, a modified example changed to the following aspect may be adopted.
(Modification 1) As a configuration of the recording head 9, the vibration plate 37 is displaced by the deformation of the piezoelectric vibrator 31 as described in the above-described embodiment, thereby changing the capacity in the pressure chamber 39 to change the ink. For example, the following configuration may be used instead of a so-called flexural vibration type drive system that ejects droplets. That is, the pressure chamber is expanded by deformation (shrinkage) due to charging of the piezoelectric vibrator, while the pressure chamber is contracted by deformation (extension) due to discharge, thereby changing the capacity in the pressure chamber, thereby discharging ink droplets. A longitudinal vibration type drive type recording head may be used.

  (Modification 2) In the above embodiment, the normal waveform generated in the first waveform mode and the high temperature waveform generated in the second waveform mode are generated using the common drive signal COM. The method for generating a high temperature waveform is not limited to this method. For example, in the second waveform mode, the same pulse selection data (1111) as in the first waveform mode is output from the decoder 62, and the drive signal COM is divided into a normal waveform and a high temperature waveform in advance. As shown in FIG. 8, the high temperature waveform is generated by generating the drive signal COM for the high temperature waveform so that the recording operation of the ink droplets by the recording head 9 is performed every other pixel. You may do it.

  (Modification 3) In the above embodiment, the high temperature waveform is generated so that the ink droplets are ejected by the recording head 9 every other pixel, but it is not always necessary that every other pixel. For example, after performing the ejection operation for two pixels, the ejection operation may be stopped for the next two pixels. Further, it is not always necessary to eject ink droplets in units of pixels. In other words, in the present invention, the discharge operation of the recording head 9 is set to have a predetermined interval period in order to attenuate residual meniscus vibration caused by continuous discharge of ink droplets in a high temperature environment with low viscosity. To generate a high temperature waveform.

  (Modification 4) In the above embodiment, the period (pulse period) of each pulse waveform of the normal waveform and the high temperature waveform is the same, and the carriage speed (movement speed of the recording head 9) is the same in each waveform mode. It is also possible to change the moving speed of the recording head 9 in the second waveform mode along with changing the pulse period in the high temperature waveform. For example, when the pulse period in the high temperature waveform is changed to double, the moving speed of the recording head 9 in the second waveform mode is changed to ½.

  (Modification 5) In the above embodiment, the first waveform mode and the second waveform mode are switched and controlled using 40 ° C. as a reference (predetermined temperature). Of course, the temperature is limited to this temperature. is not.

(Modification 6) In the above embodiment, ink is used as the liquid, but other liquids may be used.
(Modification 7) In the above-described embodiment, the liquid ejecting apparatus is applied to the box-type printer 1 that is assumed to be used in a state of being stored in a rack or the like. It may be a shape.

1 is a schematic perspective view illustrating an appearance of a printer (liquid ejecting apparatus) according to an embodiment. FIG. 2 is a schematic perspective view showing the appearance (internal configuration) of the printer with an external housing removed. FIG. 2 is a block diagram illustrating an electrical configuration of the printer. FIG. 3 is a schematic cross-sectional view illustrating a configuration example of a recording head. FIG. 9 is a principle explanatory view showing an ejection operation of a recording head according to a second waveform mode. It is explanatory drawing which shows the drive waveform corresponding to each waveform mode, (a) shows the normal waveform corresponding to 1st waveform mode, (b) shows the high temperature waveform corresponding to 2nd waveform mode. 7 is a flowchart showing a control routine for head drive control. Explanatory drawing which shows an example of the normal waveform concerning a modification 2, and a high temperature waveform.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Printer, 9 ... Recording head, 13 ... Platen, 14 ... Carriage motor, 54 ... ROM, 55 ... Control part, 57 ... Drive signal generation circuit, 61 ... Temperature detection sensor, 62 ... Decoder, 63 ... Shift register circuit, 64: Latch circuit, 65: Level shifter circuit, 66: Switch circuit, T: Temperature, COM ... Drive signal, PW ... Pulse waveform, MODE ... Mode signal, SD ... Head drive signal, SI ... Print data.

Claims (3)

In a liquid ejecting apparatus that performs printing by ejecting liquid droplets from a recording head that reciprocates in the main scanning direction,
Temperature detecting means for detecting the temperature of the peripheral area of the recording head;
A first waveform mode for generating the first drive waveform based on the print data and a second drive waveform are generated so that the ejection operation of the recording head based on the print data is performed every other pixel or every two pixels. A second waveform mode for setting, and mode switching means for switching and controlling each waveform mode according to the temperature detected by the temperature detection means,
Based on the mode signal output from the mode switching means, signal generating means for generating a head drive signal having a drive waveform corresponding to each waveform mode;
Head scanning means for doubling the number of scans of the recording head in the second waveform mode to that in the first waveform mode;
Correction means for correcting each pulse waveform of the drive waveform corresponding to each waveform mode according to the temperature detected by the temperature detection means,
The mode switching means is
The first waveform mode is set when the temperature detected by the temperature detection means is equal to or lower than a predetermined temperature, and the second waveform mode is set when the temperature detected by the temperature detection means exceeds the predetermined temperature. It is configured to perform the switching control, and outputs the mode signal for instructing the first waveform mode or the second waveform mode at the start of printing based on one print job,
When printing of a plurality of pages is instructed in the one print job, the temperature correction of the pulse waveform corresponding to the temperature detected for each page is performed until the printing based on the one print job is completed. The switching control is not performed during printing based on the print job.
A liquid ejecting apparatus. The liquid ejecting apparatus according to claim 1, wherein the second drive waveform is a drive waveform in which a pulse waveform is generated in units of pixels so that the ejection operation of the recording head is performed every other pixel. 3. The liquid ejection according to claim 1, wherein the pulse waveforms of the first drive waveform and the second drive waveform have the same period, and the moving speed of the recording head is the same in each of the waveform modes. apparatus.

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