JP3888347B2 - Liquid ejecting apparatus and driving method thereof - Google Patents

Description

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

  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 is reduced as described above, it becomes more difficult to suppress the residual vibration of the meniscus.

  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 head drive signal having a first frequency, and a second waveform mode for generating a head drive signal having a second frequency lower than the first frequency Is set, and the mode switching means for switching each waveform mode according to the temperature detected by the temperature detection means, and the head corresponding to each waveform mode based on the mode signal output from the mode switching means A signal generating means for generating a drive signal; and the second waveform mode while moving the recording head at a first speed in the first waveform mode. And a head scanning means for moving the recording head at a second speed slower than the first speed, and each pulse waveform of the drive waveform corresponding to each of the waveform modes according to the temperature detected by the temperature detecting means. And a mode switching unit that sets the first waveform mode when the temperature detected by the temperature detection unit is equal to or lower than a predetermined temperature, and that detects the temperature detected by the temperature detection unit. The switching control is performed so that the second waveform mode is set when a predetermined temperature is exceeded, and the first waveform mode or the second waveform mode is instructed at the start of printing based on one print job. When the mode signal for output is output and printing of a plurality of pages is instructed in the one print job, printing based on the one print job is completed. Performing temperature compensation of the pulse waveform according to the temperature detected for each page until, but during printing based on the single print job does not perform the switching control, and summarized in that.

  According to this configuration, when the temperature in the peripheral area of the recording head detected by the temperature detecting means is equal to or lower than the predetermined temperature, the head driving signal having the first frequency is sent to the recording head while moving the recording head at the first speed. A first waveform mode in which liquid droplets are supplied and discharged is executed. On the other hand, when the temperature in the peripheral area of the recording head detected by the temperature detecting means exceeds a predetermined temperature, the head driving signal having the second frequency is supplied to the recording head while moving the recording head at the second speed. Then, the second waveform mode in which liquid droplets are ejected is executed. At this time, in the second waveform mode, the second speed is set to a speed lower than the first speed, and the second frequency is set to a frequency lower than the first frequency. In such a configuration, when the usage environment of the liquid ejecting apparatus exceeds a predetermined temperature, that is, in a high temperature environment, the head drive signal having a relatively low frequency compared to the normal time (when the recording head is below the predetermined temperature). , The discharge interval of the liquid droplets discharged from the recording head can be extended. Thereby, even in a high temperature environment where the viscosity of the liquid is lowered, it is possible to stably discharge liquid droplets while suitably suppressing residual vibration due to meniscus or the like. As a result, in the liquid ejecting apparatus according to the present invention, the environmental temperature that can be guaranteed during use can be set higher on the higher temperature side than before. In addition, in this configuration, even if one of the above waveform modes is once determined at the start of printing based on one print job, even if the environmental temperature fluctuates between temperature regions corresponding to the respective waveform modes. The frequency of the head drive signal supplied to the recording head and the moving speed of the recording head are not changed until the printing based on the one print job is completed. This is because if the moving speed of the recording head is changed during printing based on one print job, there is a concern that a difference in print image quality, a color difference, or the like may occur due to the change in the moving speed. Therefore, with such a configuration, it is possible to prevent the occurrence of a difference in print image quality, a color difference, and the like in 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 head drive signal 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.

Here, the second frequency of the head drive signal set in the second waveform mode described above is specifically set as follows.
That is, in the second aspect of the present invention, in the first aspect, the frequency of the head drive signal of the second frequency is set lower so that the pulse interval is longer than that of the head drive signal of the first frequency. The gist of this is that the drive signal.

  According to this configuration, in a high temperature environment in which the second waveform mode is executed, the discharge interval of the liquid droplets discharged from the recording head can be made longer than normal (first waveform mode). As a result, liquid droplets can be stably discharged.

  Here, the relationship between the first speed and the first frequency in the first waveform mode described above and the second speed and the second frequency in the second waveform mode is specifically as follows. Set to

  That is, according to a third aspect of the present invention, in the first or second aspect, when the second frequency is set to 1 / N times the first frequency, the second speed is the first speed. The gist is that it is set to 1 / N times as well.

  According to this configuration, the number of liquid droplets ejected per pixel in one scan of the recording head can be made equal in the first waveform mode and the second waveform mode. Depending on the above, the same print image quality can be realized when the recording head is driven in any waveform mode. In this case, in the second waveform mode, the printing time (printing speed) is twice as long as that in the first waveform mode, but in a high temperature environment where the viscosity of the liquid is reduced, The printing speed and the ejection stability of the liquid droplet are in a mutually contradictory relationship. In this aspect, by increasing the discharge interval of the liquid droplets at the expense of the printing speed, the stability of discharging the liquid droplets in a high temperature environment is improved. Good print quality can be ensured even in a high temperature environment, and the environmental temperature that can be guaranteed during use can be set higher on the higher temperature side than before. Therefore, the effect is more than compensated.

  Further, according to a fourth aspect of the present invention, in any one of the first to third aspects, the recording head ejects the liquid droplets both during forward movement and during backward movement. The bidirectional printing is performed, and an adjustment value for adjusting the shift of the printing position for the bidirectional printing is set for each waveform mode, and each waveform is set based on the corresponding adjustment value. The gist of the invention is that it further includes a deviation adjusting means for adjusting the deviation of the printing position in the mode.

  According to this configuration, in printing in each waveform mode in which the frequency of different head drive signals and the moving speed of the recording head are set, the displacement of the printing position for bidirectional printing corresponds to each of these waveform modes. It is adjusted based on the set adjustment value. Therefore, it is possible to suppress a decrease in print quality associated with switching between the waveform modes.

Here, the adjustment value set by the deviation adjusting means is specifically set as follows.
That is, according to a fifth aspect of the present invention, in the fourth aspect, the adjustment value is the waveform corresponding to a gap value between the recording head and a guide member provided facing the recording head. The gist is that it is set for each mode.

  According to this configuration, the adjustment value for adjusting the misalignment for bidirectional printing is set according to the gap value between the recording head and the guide member, so that the misalignment adjustment can be performed with higher accuracy. become. The gap value is set according to, for example, the type of printing medium on which printing is performed. In this case, according to this aspect, the adjustment value is set according to the gap value depending on the type of printing medium. The

  According to a sixth aspect of the present invention, in a method for driving a liquid ejecting apparatus that performs printing by reciprocating a recording head in a main scanning direction and ejecting liquid droplets from the recording head, printing based on one print job is started. Sometimes, it is determined whether or not the temperature in the peripheral area of the recording head is equal to or lower than a predetermined temperature. When the temperature is equal to or lower than the predetermined temperature, the recording head is moved to the recording head while moving at a first speed. A first waveform mode for supplying a head driving signal of one frequency to perform ejection of the liquid droplet is performed, and when the temperature exceeds the predetermined temperature, the recording head is moved to a first speed slower than the first speed. While moving at two speeds, a second waveform mode in which a head driving signal having a second frequency lower than the first frequency is supplied to the recording head to discharge the liquid droplets is performed, and the one printing is performed. When performing printing based on a plurality of pages, each pulse waveform of the head drive signal is corrected according to the temperature in the peripheral area of the recording head for each page. After starting printing based on the first waveform mode or the second waveform mode, switching to another waveform mode is not performed until printing based on the one print job is completed. It is a summary.

  According to this driving method, the same operational effects as those of the first aspect described above can be achieved.

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 substantially box-shaped outer housing 2, 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 by receiving the rotational driving force of the carriage motor 14 (see FIG. 4). 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 is transported by a transport drive roller 21 that is rotated by a transport motor 15 (see FIG. 4), and a transport driven roller that is driven to rotate as the transport drive 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. 3 is a cross-sectional view showing the main part of the recording head 9.

  As shown in the figure, the recording head 9 includes a flow path unit 31, a lower electrode 32 disposed on the upper surface of the flow path unit 31, and an actuator stacked on the upper surface so as to be in close contact with the lower electrode 32. And a piezoelectric vibrator 33. Although not shown, an upper electrode is disposed on the upper surface of the piezoelectric vibrator 33. The flow path unit 31 includes a flow path forming substrate 34, and a vibration plate 35 and a nozzle plate 36 that are stacked on both sides with the flow path forming substrate 34 interposed therebetween.

  The flow path forming substrate 34 is connected to the pressure chamber 38 communicating with the nozzle 37 formed on the nozzle plate 36, the ink supply path 39 communicating with the pressure chamber 38, and the pressure chamber 38 via the ink supply path 39. And an ink reservoir 40 for supplying ink. The substrate 34 is formed by, for example, etching a silicon wafer.

  In the recording head 9 configured as described above, when the piezoelectric vibrator 33 is deformed (contracted) by charging, the vibration plate 35 is bent and the pressure chamber 38 contracts. Further, when the piezoelectric vibrator 33 is deformed (extended) by the discharge from the contracted state of the pressure chamber 38, the pressure chamber 38 is expanded by the elasticity of the vibration plate 35. By causing the pressure chamber 38 to expand once and then contract due to the deformation associated with charging and discharging of the piezoelectric vibrator 33, the ink pressure in the pressure chamber 38 is increased, and ink droplets are ejected from the nozzle 37.

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 a carriage motor 14, a conveyance motor 15, and an electric drive system 59 for 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. The ROM 54 corrects the potential (crest value) and time component of the drive signal COM (drive waveform) supplied to each piezoelectric vibrator 33 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 out the print data in the reception buffer, converts the print data into 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. 4, 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 a piezoelectric vibrator 33. 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 33 are provided for each nozzle 37 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 33. When applied, the piezoelectric vibrator 33 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 33 is cut off. As described above, the switch circuit 66 generates a drive waveform (head drive signal SD) to be supplied to each piezoelectric vibrator 33 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) at a frequency depending on the temperature in the peripheral area of the recording head 9 detected by the temperature detection sensor 61. Is set. Each of these waveform modes is switched by a 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, a first waveform mode for generating a drive waveform (head drive signal SD) having a first frequency when the temperature T detected by the temperature detection sensor 61 is equal to or lower than a predetermined temperature, and the temperature T is as described above. A second waveform mode for generating a drive waveform (head drive signal SD) having a second frequency lower than the first frequency when the predetermined temperature is exceeded is set. At this time, in the present embodiment, the predetermined temperature is set to, for example, 40 ° C., and in the first waveform mode (T ≦ 40 ° C.), the driving waveform of the driving frequency f _D (first frequency) ( This drive waveform is hereinafter referred to as “normal waveform”). On the other hand, in the second waveform mode (T> 40 ° C.), the driving frequency is 1 / 2f _D (second frequency), that is, the driving waveform having a frequency that is 1/2 of the first frequency (hereinafter, this driving waveform is referred to as “high temperature”). Waveform ").

  Here, in the present embodiment, when each waveform mode is switched depending on the environmental temperature as described above, the carriage 10 that reciprocates the recording head 9 in the main scanning direction according to each waveform mode. Is moved based on a control signal from a control unit 55 that controls the rotation of the carriage motor 14. In the present embodiment, the carriage motor 14 and the control unit 55 constitute a head scanning unit.

Specifically, in the first waveform mode, the control unit 55 relatively moves the recording head 9 and the printing paper P at the first speed (the moving speed of the carriage 10 at this time is V _CR ). The carriage motor 14 and the conveyance motor 15 are driven and controlled so that On the other hand, in the second waveform mode, the control unit 55 is a second speed that is lower than the first speed, and in the present embodiment, the second speed (1/2 speed of the first speed). that is, controls the driving of the carriage motor 14 and the feeding motor 15 so as to relatively move the recording head 9 and the print paper P moving speed of the carriage 10 in which) to 1 / 2V _CR.

Thus, in the printer 1 according to the present embodiment, in the first waveform mode (T ≦ 40 ° C.), the normal waveform of the drive frequency f _D is generated, and the moving speed of the carriage 10 at that time is set to V Control to _CR . On the other hand, in the second waveform mode (T> 40 ° C.), a high-temperature waveform with a driving frequency of 1/2 f _D is generated and the moving speed of the carriage 10 at that time is controlled to 1/2 V _CR .

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 input through 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 print data corresponding to the solid filling. 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, based on the print data corresponding to the above-described solid padding, is one cycle of the drive signal COM corresponding to one pixel (hereinafter, this cycle is referred to as “one segment”). ) To generate pulse selection data (1111). On the other hand, in the second waveform mode, pulse selection data (1010) is generated per segment of the drive signal COM. In other words, the decoder 62 generates pulse selection data (10101010) per two segments of the drive signal COM corresponding to one pixel 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. The rectangular pulse train causes the level shifter circuit 65 to be generated. To the switch circuit 66. Then, the switch circuit 66 obtains the drive waveform (head drive signal SD) corresponding to each waveform mode, that is, the drive frequency f _D in the first waveform mode by taking the logical product of the rectangular pulse train and the drive signal COM. the normal waveform, the second waveform mode to generate a high temperature waveform of the driving frequency 1 / 2f _D. 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. 5 is a diagram showing drive waveforms corresponding to the respective waveform modes. Note that, as described above, in this embodiment, it is assumed that a full ejection operation (solid filling) of ink droplets is performed, and therefore, the driving waveform (SD) related to the solid filling control is shown in FIG. Yes.

  In the figure, a drive signal COM is a signal common to each waveform mode generated in the drive signal generation circuit 57 shown in FIG. 4 and includes 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 33 with a voltage that expands the pressure chamber 38 and depressurizes the inside, and a voltage that maintains the depressurized state. The first voltage maintaining unit sa2 supplied to the child 33, the first voltage increasing unit sa3 supplying the piezoelectric vibrator 33 with a voltage that contracts the pressure chamber 38 and pressurizes the inside, and maintains the pressurized state. A second voltage maintaining unit sa4 that supplies such a voltage to the piezoelectric vibrator 33, and a second voltage drop unit sa5 that supplies the piezoelectric vibrator 33 with a voltage that returns the pressure chamber 38 to its original state. Yes. With this single pulse waveform PW, ink droplets having a weight depending on the ink characteristics, the mechanical characteristics of the nozzles 37, manufacturing errors, and the like are ejected for each nozzle 37.

Hereinafter, driving waveforms in each waveform mode will be described.
<First waveform mode>
FIG. 5A 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, the pulse selection data (1111) per segment of the drive signal COM is output from the decoder 62. The switch circuit 66 takes 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 (1111) and the drive signal COM. In other words, in the first waveform mode, the switch circuit 66 captures all the four pulse waveforms PW included in one segment of the drive signal COM, so that the normal frequency of the drive frequency f _D having the same frequency as the drive signal COM is obtained. A waveform (SD) is generated. Thereby, in the first waveform mode, when four ink droplets are ejected from the recording head 9 in one pixel (corresponding to one segment) and the pulse generation period of the drive signal COM is set to 30 μs, for example, the recording head 9 performs image formation by scanning the one pixel at 120 μs.

<Second waveform mode>
FIG. 5B is a waveform diagram showing a high temperature waveform corresponding to the second waveform mode (T> 40 ° C.).

In the second waveform mode, as described above, the pulse selection data (1010) per segment of the drive signal COM is output from the decoder 62. The switch circuit 66 takes 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 (1010) and the drive signal COM. That is, in the second waveform mode, the switch circuit 66 has every other four pulse waveforms PW included in one segment of the drive signal COM, thereby having a frequency half that of the drive signal COM. A high-temperature waveform (SD) having a driving frequency of 1/2 f _D is generated. At this time, as described above, the moving speed of the carriage 10 is controlled to ½ of the moving speed in the first waveform mode. Thus, also in the second waveform mode, four ink droplets are ejected from the recording head 9 in one pixel (corresponding to two segments) as in the first waveform mode, and the pulse of the drive signal COM If the generation cycle is 30 μs, for example, as described above, the recording head 9 performs image formation by scanning the one pixel at 240 μs.

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 optimal in accordance with 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 moving speed of the carriage 10 is also changed), and further, the determined waveform mode is set. It is characterized in that temperature correction is appropriately performed on the corresponding drive waveform. This control routine (FIG. 6) 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 33 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 33 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 in accordance with the newly acquired temperature T (step S114), and is supplied to each piezoelectric vibrator 33 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 33 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 33 of the recording head 9. At this time, the moving speed of the carriage 10 is controlled to ½ as compared with that in the first waveform mode as described above. Printing is performed in the scanning time.

  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 according to the newly acquired temperature T (step S124), and is supplied to each piezoelectric vibrator 33 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 frequency of the recording head 9 and the moving speed of the carriage 10 are not changed during the execution.

  The reason for this control mode is that if the movement speed of the carriage 10 is changed during the execution of printing based on one print job, there is a concern that a difference in image quality, a color difference, etc. will occur due to the change in the carriage speed. Because. It has been experimentally confirmed by the present inventor that the occurrence of the image quality difference, the color difference, and the like is greater when the carriage speed is changed than when the ambient temperature is changed.

  Therefore, as shown in FIG. 7, for example, when printing of four pages is instructed in one received print job, the environmental temperature detected when the first page is printed is 41 ° C. After the first page is printed with the high temperature waveform, printing with the high temperature waveform is performed for four pages regardless of the environmental temperature detected thereafter.

That is, when the environmental temperature detected at the time of printing the first page is, for example, 41 ° C., the printing of the first page is performed by a high-temperature waveform (second waveform mode: with a temperature correction corresponding to 41 ° C.). Carriage speed 1 / 2V _CR , driving frequency 1 / 2f _D ).

Next, when the environmental temperature detected at the time of printing the second page is 41 ° C., the second page is printed at a high temperature waveform (second waveform) that has been subjected to temperature correction corresponding to 41 ° C. as described above. Mode: Carriage speed 1/2 V _CR , driving frequency 1/2 f _D )

Next, when the environmental temperature detected at the time of printing the third page is 40 ° C., the printing of the third page is performed by using a high-temperature waveform (second waveform mode: carriage) subjected to temperature correction corresponding to 40 ° C. Speed 1 / 2V _CR , driving frequency 1 / 2f _D ). That is, even when the environmental temperature is detected as 40 ° C. at the time of printing the third page, the switching to the first waveform mode is not performed, and printing is performed with a high-temperature waveform subjected to only temperature correction.

Next, when the environmental temperature detected at the time of printing the fourth page is 39 ° C., the printing of the fourth page is performed by using a high-temperature waveform (second waveform mode: carriage) subjected to temperature correction corresponding to 39 ° C. Speed 1 / 2V _CR , driving frequency 1 / 2f _D ). That is, even in this case, switching to the first waveform mode is not performed, and printing is performed with a high-temperature waveform subjected to only temperature correction.

Although not described here, similarly, when a plurality of pages are instructed in one print job, the first page is a normal waveform (first waveform mode: carriage speed V _CR , drive frequency f _D ). After printing, printing with a normal waveform is performed for all pages regardless of the environmental temperature detected thereafter.

  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) The printer 1 moves the carriage 10 to the carriage speed V _CR 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 is equal to or lower than a predetermined temperature (for example, 40 ° C.). in while moving, to execute a first waveform mode to eject ink droplets by supplying normal waveform of the driving frequency f _D (SD) in the recording head 9. On the other hand, when the temperature T detected by the temperature detection sensor 61 exceeds 40 ° C., the recording head 9 is moved at a high temperature waveform (with a driving frequency of 1/2 f _D while moving the carriage 10 at a carriage speed of 1/2 V _CR. SD) is supplied to execute the second waveform mode in which the ink droplets are ejected. Thereby, when the use environment of the printer 1 is in a high temperature environment exceeding 40 ° C., the recording head 9 is driven by the head drive signal SD having a relatively low frequency compared with the normal time (when it is 40 ° C. or less). Accordingly, the discharge interval of the ink droplets discharged from the recording head 9 can be lengthened. As a result, even in a high temperature environment where the viscosity of the ink is lowered, residual vibration due to meniscus or the like is suitably suppressed (because the vibration attenuation time can be increased), and ink droplets can be stably ejected. It becomes like this. In other words, the environmental temperature that can be guaranteed when the printer 1 is used can be set higher than the conventional one. That is, conventionally, the maximum ambient temperature at which ink droplets can be stably ejected is set to 40 ° C., but in this embodiment, a higher temperature can be set.

  (2) In the present embodiment, the high temperature waveform in the second waveform mode is generated at a relatively low frequency so that the pulse interval is longer than the normal waveform in the first waveform mode. In this way, the pulse interval of the drive waveform generated at high temperature is longer than that at normal time, so that the ink droplet discharge interval is lengthened in a high temperature environment where the ink viscosity decreases, and ink droplets are stably discharged. Will be able to.

  (3) In the present embodiment, the moving speed of the carriage 10 is set to the same as the driving frequency of the recording head 9 in the second waveform mode is set to ½ that in the first waveform mode. Similarly, it was set to 1/2 in the case of the waveform mode 1. Accordingly, the number of ink droplets ejected per pixel in one scan of the recording head 9 can be made equal in the first waveform mode and the second waveform mode. Therefore, the same print image quality can be realized when the recording head 9 is driven in any waveform mode.

  (4) In this embodiment, after the waveform mode is once determined at the start of printing based on one print job, the environmental temperature fluctuates between the temperature ranges corresponding to the respective waveform modes. However, the waveform mode is not switched until printing based on the one print job is completed. According to this, since the moving speed of the recording head 9 is not changed in the middle of printing based on one print job, it is possible to prevent occurrence of a difference in print image quality, a color difference, etc. due to the change in the moving speed.

  (5) 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 these 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 1-1) As a configuration of the recording head 9, the vibration plate 35 is displaced by the deformation of the piezoelectric vibrator 33 as described in the above embodiment, and thereby the capacity in the pressure chamber 38 is changed. For example, the following configuration may be used without being limited to the so-called flexural vibration type driving method in which ink droplets are ejected by the above method. 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 1-2) The configuration of the recording head 9 is not limited to that which is built by etching a silicon wafer as described in the above embodiment. For example, the pressure chamber 38 or ink is formed on a metal plate or the like. A recording head in which an ink flow path is formed by laminating and bonding a supply path 39, an ink reservoir 40, and the like 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. The high temperature waveform may be generated by recording in the ROM 54 so that the drive signal COM for the high temperature waveform has a pulse interval twice as long as the drive signal COM for the normal waveform. . At this time, by changing the pulse interval of the drive signal COM, the frequency is not necessarily limited to a half frequency of the normal waveform, and a high temperature waveform having a frequency of 2/3, 3/4, or the like is used. It can also be generated. For example, in FIG. 8, the pulse interval of the drive signal COM for the high temperature waveform is changed so that the high temperature waveform has a frequency that is 2/3 of the normal waveform (that is, the drive signal COM for the high temperature waveform is for the normal waveform). Generated at a pulse interval 1.5 times the drive signal COM). At this time, the carriage speed is similarly changed to 2/3 as the frequency is reduced to 2/3.

  (Modification 3) In the above embodiment, the frequency of the high-temperature waveform generated in the second waveform mode is set to ½ of the frequency of the normal waveform generated in the first waveform mode. Although the movement speed of the carriage 10 in the waveform mode is half of the movement speed in the first waveform mode, the present invention is not limited to this. That is, when the frequency of the high temperature waveform generated in the second waveform mode is 1 / N (where N is an integer greater than 1) of the frequency of the normal waveform generated in the first waveform mode, Similarly, the moving speed of the carriage 10 may be changed to 1 / N.

  (Modification 4) 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 5) The printer 1 of the above embodiment may have the following functions.
Adjusting the displacement of the printing position (the deviation of the landing position of the ink droplet) when performing bidirectional printing by ejecting ink droplets both when the recording head 9 moves forward and backward (so-called Bi-d adjustment) You may provide the deviation adjustment means to do. This deviation adjusting means is constituted by a ROM 54 and a control unit 55, for example. Specifically, the control unit 55 sets an adjustment value (Bi-d adjustment value) for performing Bi-d adjustment for each waveform mode, and stores it in the ROM 54. The method for setting the Bi-d adjustment value may be a method for setting a value selected by the user, or a method for the printer 1 to set automatically. Based on such Bi-d adjustment value, the control unit 55 performs Bi-d adjustment for each waveform mode, thereby adjusting the displacement of the printing position for bidirectional printing. In the printer 1 including such a deviation adjustment unit, it is possible to suppress a decrease in print quality associated with switching between the waveform modes for each waveform mode in which different driving frequencies and moving speeds are set.

  In the printer 1 having such a deviation adjusting means, the Bi-d adjustment value is set according to the gap value (platen gap) between the recording head 9 and the platen 13, for example, Bi. The −d adjustment can be performed with higher accuracy.

(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. 3 is a schematic cross-sectional view illustrating a configuration example of a recording head. FIG. 2 is a block diagram illustrating an electrical configuration of the printer. 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. FIG. 3 is an explanatory diagram illustrating an example of printing according to the 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.

Claims (6)

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 a head drive signal having a first frequency and a second waveform mode for generating a head drive signal having a second frequency lower than the first frequency are set. Mode switching means for switching and controlling the 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 the head drive signal corresponding to each waveform mode, and
Head scanning means for moving the recording head at a first speed in the first waveform mode, and moving the recording head at a second speed slower than the first speed in the second 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. 2. The liquid ejecting apparatus according to claim 1, wherein the second frequency head driving signal is a driving signal whose frequency is set low so that a pulse interval is longer than the first frequency head driving signal. . 3. The second speed is set to 1 / N times the first speed when the second frequency is set to 1 / N times the first frequency. Liquid ejector. The recording head performs bidirectional printing by ejecting the liquid droplets both during forward movement and during backward movement.
An adjustment value for adjusting the displacement of the printing position for the bidirectional printing is set for each waveform mode, and the displacement of the printing position in each waveform mode is adjusted based on the corresponding adjustment value. The liquid ejecting apparatus according to claim 1, further comprising a displacement adjusting unit. 5. The liquid jet according to claim 4, wherein the adjustment value is set for each of the waveform modes in accordance with a gap value between the recording head and a guide member provided to face the recording head. apparatus. In a driving method of a liquid ejecting apparatus for performing printing by reciprocating a recording head in a main scanning direction and discharging liquid droplets from the recording head,
At the start of printing based on one print job, it is determined whether the temperature of the peripheral area of the recording head is equal to or lower than a predetermined temperature,
A first waveform mode in which when the temperature is equal to or lower than the predetermined temperature, the recording head is moved at a first speed, and a head driving signal having a first frequency is supplied to the recording head to discharge the liquid droplets. And
When the temperature exceeds the predetermined temperature, a head driving signal having a second frequency lower than the first frequency is sent to the recording head while moving the recording head at a second speed that is slower than the first speed. Performing a second waveform mode for supplying and discharging the liquid droplets;
When printing based on the one print job is performed over a plurality of pages, each pulse waveform of the head drive signal is corrected according to the temperature in the peripheral area of the recording head for each page. After printing based on a print job is started in the first waveform mode or the second waveform mode, switching to another waveform mode is not performed until printing based on the one print job is completed. A method for driving a liquid ejecting apparatus.

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