Liquid ejecting apparatus

A liquid ejecting apparatus of the invention includes a distance obtaining unit that obtains a distance between the nozzle of the head and a medium to which the liquid is ejected. The driving signal is a periodical signal including a first pulse-wave capable of ejecting a drop of the liquid having a predetermined volume at a relatively low speed, and a second pulse-wave capable of ejecting a drop of the liquid having the predetermined volume at a relatively high speed, the predetermined volume corresponding to a predetermined level data. The driving-pulse generator is adapted to generate, when the selected level data is the predetermined level data: a driving-pulse including only the first pulse-wave when a distance obtained by the distance obtaining unit is not less than a predetermined value; and a driving-pulse including only the second pulse-wave when the distance is less than the predetermined value.

FIELD OF THE INVENTION

This invention relates to a liquid ejecting apparatus having a head member capable of ejecting drops of liquid from nozzles.

BACKGROUND OF THE INVENTION

In a ink-jetting recording apparatus such as an ink-ejecting printer or an ink-jetting plotter (a kind of liquid ejecting apparatus), a recording head (head member) can move in a main scanning direction, and a recording paper (a kind of medium to which liquid is ejected) can move in a sub-scanning direction perpendicular to the main scanning direction. While the recording head moves in the main scanning direction, a drop of ink can be ejected from a nozzle of the recording head onto the recording paper. Thus, an image including a character or the like can be recorded on the recording paper. For example, the drop of ink can be ejected by causing a pressure chamber communicating with the nozzle to expand and/or contract.

The pressure chamber may be caused to expand and/or contract, for example by utilizing deformation of a piezoelectric vibrating member. In such a recording head, the piezoelectric vibrating member can be deformed based on a supplied driving-pulse in order to change a volume of the pressure chamber. When the volume of the pressure chamber is changed, a pressure of the ink in the pressure chamber may be changed. Then, the drop of ink is ejected from the nozzle.

In such a recording apparatus, a driving signal consisting of a series of a plurality of pulse-waves is generated. On the other hand, printing data including level data (gradation data) can be transmitted to the recording head. Then, based on the transmitted printing data, only necessary one or more pulse-waves are selected from the driving signal and supplied to the piezoelectric vibrating member. Thus, a volume of the ink ejected from the nozzle may be changed based on the level data.

It has been proposed that a plurality of ink drops whose speeds are different are joined to each other before they reach a recording paper, when the plurality of ink drops are ejected from the same nozzle based on a level data (JP Laid-Open Publication No. 8-336970 and JP Laid-Open Publication No. 59-133066). This manner can remarkably inhibit generation of ink mist, compared with a case wherein the plurality of ink drops are joined to each other after they reach the recording paper.

Recently, various pigment inks are available on the market. The pigment inks are superior in environmental resistance (water resistance and/or light resistance). On the other hand, the pigment inks have high viscosity. Thus, ink mist is likely to be generated by satellite ink drops, compared with conventional dye inks whose viscosity is low.

The inventors have found that it is effective to decrease the ejecting speed of an ink drop in order to inhibit mist generation of a pigment ink. When the ejecting speed of an ink drop is decreased, the tendency of dissociation of the ink drop is inhibited, and hence generation of satellite ink drops is inhibited.

However, when the ejecting speed of an ink drop is decreased, the ink drop reaches the recording paper less precisely. That is, regarding the ejecting speed of an ink drop, the tendency of the generation of the satellite ink drops and the precision of reach to the recording paper are contradictory.

SUMMARY OF THE INVENTION

The object of this invention is to provide a liquid ejecting apparatus such as an ink-eject recording apparatus that can always achieve more suitable ink-ejecting control taking into consideration both tendency of generation of satellite drops (mist) and precision of reach to a recording paper.

In order to achieve the object, the invention is a liquid ejecting apparatus comprising: a head member having a nozzle; a pressure-changing unit that can cause pressure of liquid in the nozzle to change in such a manner that the liquid is ejected from the nozzle; a level-data setting unit that can set a selected level data from a plurality of level data, based on an ejecting data; a driving-signal generator that can generate a driving signal; a driving-pulse generator that can generate a driving pulse based on the selected level data and the driving signal; a main controller that can cause the pressure-changing unit to operate, based on the driving pulse; and a distance obtaining unit that can obtain a distance between the nozzle of the head and a medium to which the liquid is ejected; wherein the driving signal is a periodical signal including a first pulse-wave capable of ejecting a drop of the liquid having a predetermined volume from the nozzle at a relatively low speed, and a second pulse-wave capable of ejecting a drop of the liquid having the predetermined volume from the nozzle at a relatively high speed, the predetermined volume corresponding to a predetermined level data; the driving-pulse generator is adapted to generate, based on the driving signal, when the selected level data is the predetermined level data: a driving-pulse including only the first pulse-wave when a distance obtained by the distance obtaining unit is not less than a predetermined value, and a driving-pulse including only the second pulse-wave when the distance obtained by the distance obtaining unit is less than the predetermined value.

According to the above feature, based on the distance obtained by the distance obtaining unit, it is determined whether the first pulse-wave capable of ejecting a drop of the liquid having the predetermined volume at the relatively low speed is used or the second pulse-wave capable of ejecting a drop of the liquid having the predetermined volume at the relatively high speed is used. That is, when the distance is not less than the predetermined value so that it is more possible for mist to generate, the liquid is ejected at the relatively low speed. When the distance is less than the predetermined value so that it is less possible for mist to generate, the liquid is ejected at the relatively high speed, giving priority to the precision of reach to the medium. Thus, a suitable ink-ejecting control is always achieved taking into consideration both the tendency of mist generation and the precision of reach to the medium.

For example, the plurality of level data include a small-dot data, a middle-dot data and a large-dot data; the predetermined level data is the middle-dot data; the drop of the liquid having the predetermined volume is a middle-dot drop of the liquid; the driving signal is a periodical signal including a first pulse-wave capable of ejecting the middle-dot drop of the liquid from the nozzle at a relatively low speed, a small pulse-wave capable of ejecting a small-dot drop of the liquid from the nozzle, and a second pulse-wave capable of ejecting the middle-dot drop of the liquid from the nozzle at a relatively high speed, in that order; the driving-pulse generator is adapted to generate, based on the driving signal: a driving-pulse including only the small pulse-wave when the selected level data is the small-dot data, a driving-pulse including the first pulse-wave and the second pulse-wave when the selected level data is the large-dot data, a driving-pulse including only the first pulse-wave when the selected level data is the middle-dot data and the distance obtained by the distance obtaining unit is not less than the predetermined value, and a driving-pulse including only the second pulse-wave when the selected level data is the middle-dot data and the distance obtained by the distance obtaining unit is less than the predetermined value.

In the case, preferably, when the selected level data is the large-dot data, the middle-dot drop of the liquid ejected from the nozzle at the relatively low speed by the first pulse-wave is adapted to be caught up with by the middle-dot drop of the liquid ejected from the nozzle at the relatively high speed by the second pulse-wave and to join the same. In the case, mist generation may be effectively inhibited.

For example, the driving pulse generator is adapted to generate a rectangular-pulse row corresponding to a period of the driving signal based on the selected level data, and generate an AND signal of the rectangular-pulse row and the driving signal as the driving pulse.

In addition, if the distance between the nozzle of the head member and the medium is adapted to be set depending on a kind of the medium, the distance obtaining unit may obtain the distance between the nozzle of the head member and the medium based on the kind of the medium. In general, if the liquid is a kind of ink and the medium is a recording paper, that is, if the liquid ejecting apparatus is an ink-jetting recording apparatus, the distance between the nozzle and the recording paper (PG) is set to 1.2 mm when the recording paper is a special paper, or 1.7 mm when the recording paper is a normal paper.

The predetermined value is for example about 1.5 mm. In the case, in the ink-jetting recording apparatus as described above, the pulse-wave used for the normal paper and the pulse-wave used for the special paper can be switched.

The predetermined volume is for example about 7 ng. In addition, the relatively low speed is for example about 8 m/s, and the relatively high speed is for example about 10 m/s.

For example, the pressure-changing unit may have a piezoelectric vibrating member. The liquid may be a kind of ink, in particular a kind of pigment ink.

In addition, the invention is a controlling unit for controlling a liquid ejecting apparatus including a head member having a nozzle, and a pressure-changing unit that can cause pressure of liquid in the nozzle to change in such a manner that the liquid is ejected from the nozzle, comprising: a level-data setting unit that can set a selected level data from a plurality of level data, based on an ejecting data; a driving-signal generator that can generate a driving signal; a driving-pulse generator that can generate a driving pulse based on the selected level data and the driving signal; a main controller that can cause the pressure-changing unit to operate, based on the driving pulse; and a distance obtaining unit that can obtain a distance between the nozzle of the head and a medium to which the liquid is ejected; wherein the driving signal is a periodical signal including a first pulse-wave capable of ejecting a drop of the liquid having a predetermined volume from the nozzle at a relatively low speed, and a second pulse-wave capable of ejecting a drop of the liquid having the predetermined volume from the nozzle at a relatively high speed, the predetermined volume corresponding to a predetermined level data, the driving-pulse generator is adapted to generate, based on the driving signal, when the selected level data is the predetermined level data, a driving-pulse including only the first pulse-wave when a distance obtained by the distance obtaining unit is not less than a predetermined value, and a driving-pulse including only the second pulse-wave when the distance obtained by the distance obtaining unit is less than the predetermined value.

A computer system can materialize the controlling unit or any element of the above controlling unit.

This invention includes a storage unit capable of being read by a computer, storing a program for materializing the controlling unit or any element in a computer system.

This invention also includes the program itself for materializing the controlling unit or the element in the computer system.

This invention includes a storage unit capable of being read by a computer, storing a program including a command for controlling a second program executed by a computer system including a computer, the program being executed by the computer system to control the second program to materialize the controlling unit or the element.

This invention also includes the program itself including the command for controlling the second program executed by the computer system including the computer, the program being executed by the computer system to control the second program to materialize the controlling unit or the element.

The storage unit may be not only a substantial object such as a floppy disk or the like, but also a network for transmitting various signals.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will now be described in more detail with reference to drawings.

FIG. 1is a schematic perspective view of an ink-jetting printer1as a liquid ejecting apparatus of a first embodiment according to the invention. The ink-jetting printer1includes a carriage5, which has a recording head4(an example of head member) and a cartridge holder3capable of holding a black-ink cartridge2aand a color-ink cartridge2b. The carriage5is adapted to be reciprocated in a main scanning direction by a head-scanning mechanism (an example of moving mechanism).

The head-scanning mechanism is formed by: a guide bar6horizontally extending in a housing, a pulse motor7arranged at a right portion of the housing, a driving pulley8connected to a rotational shaft of the pulse motor7, a free pulley9mounted at a left portion of the housing, a timing belt10connected to the carriage5and going around the driving pulley8and the free pulley9, and a controller11(seeFIG. 4) for controlling the pulse motor7. Thus, the carriage5i.e. the recording head4can be reciprocated in the main scanning direction i.e. in a width direction of a recording paper12, by driving the pulse motor7.

A PG adjusting lever19is mounted to the guide bar6. The PG adjusting lever19is capable of changing the position of the guide bar6in a vertical direction among a plurality of steps. The “PG” means a distance between the nozzle and the recording paper. In the present embodiment, the distance is adapted to be set to 1.7 mm when the recording paper is a normal paper, and 1.2 mm when the recording paper is a special paper. The reason why the “PG” is larger when the recording paper is a normal paper is to secure a margin for the feeding operation.

The printer1includes a paper feeding mechanism for feeding the recording paper12or any other recording medium (a medium onto which the ink is ejected) in a feeding direction (sub-scanning direction). The paper feeding mechanism consists of a paper feeding motor13, a paper feeding roller14or the like. The recording paper12, which is an example of a recording medium, is fed in a subordinate scanning direction in turn by the paper feeding mechanism, in cooperation with the recording operation of the recording head4.

Then, the recording head4is explained. As shown inFIG. 2, the recording head4has a plastic box-like case71defining a housing room72. The longitudinal-mode piezoelectric vibrating unit21has a shape of teeth of a comb, and is inserted in the housing room72in such a manner that points of teeth-like portions21aof the piezoelectric vibrating unit21are aligned at an opening of the housing room72. A ink-way unit74is bonded on a surface of the case71on the side of the opening of the housing room72. The points of the teeth-like portions21aare fixed at predetermined positions of the ink-way unit74to function as piezoelectric vibrating members respectively.

The piezoelectric vibrating unit21comprises a plurality of piezoelectric layers21b. As shown inFIG. 2, common inside electrodes21cand individual inside electrodes21dare inserted alternately between each adjacent two of the piezoelectric layers21b. The piezoelectric layers21b, the common inside electrodes21cand the individual inside electrodes21dare integrated and cut into the shape of the teeth of the comb. Thus, when a voltage is provided between the common inside electrodes21cand an individual inside electrode21d, a piezoelectric vibrating member contracts in a longitudinal direction of each of the piezoelectric layers21b.

The ink-way unit74consists of a nozzle plate16, an elastic plate77and an ink-way forming plate75sandwiched between the nozzle plate16and the elastic plate77. The nozzle plate16, the ink-way forming plate75and the elastic plate77are integrated as shown inFIG. 2.

A plurality of nozzles17is formed in the nozzle plate16. A plurality of pressure generating chambers22, a plurality of ink-supplying ways82and a common ink-chamber83are formed in the ink-way forming plate75. Each of the pressure chambers22is defined by partition walls, and is communicated with a corresponding nozzle17at an end portion thereof and with a corresponding ink-supplying way82at the other end portion thereof. The common ink-chamber83is communicated with all the ink-supplying ways82, and has a longitudinal shape. For example, the longitudinal common ink-chamber83may be formed by an etching process when the ink-way forming plate75is a silicon wafer. Then, the pressure chambers22are formed in the longitudinal direction of the common ink-chamber83at the same intervals (pitches) as nozzles17. Then, a groove as an ink-supplying way82is formed between each of the pressure chambers22and the common ink-chamber83. In the case, the ink-supplying way82is connected to an end of the pressure chamber22, while the nozzle17is located near the other end of the pressure chamber22. The common ink-chamber83is adapted to supply ink saved in an ink cartridge to the pressure chambers22. An ink-supplying tube84from the ink cartridge is communicated with a middle portion of the common ink-chamber83.

The elastic plate77is layered on a surface of the ink-way forming plate75opposed to the nozzle plate16. In the case, the elastic plate77consists of two laminated layers that are a stainless plate87and an elastic high-polymer film88such as a PPS film. The stainless plate87is provided with island portions89for fixing the teeth-like portions21aas the piezoelectric vibrating members21in respective portions corresponding to the pressure chambers22, by an etching process.

In the above recording head4, a tooth-like portion21aas a piezoelectric vibrating member can expand in the longitudinal direction. Then, an island portion89is pressed toward the nozzle plate16, the elastic film88is deformed. Thus, a corresponding pressure chamber22contracts. On the other hand, the tooth-like portion21aas the piezoelectric vibrating member can contract from the expanding state in the longitudinal direction. Then, the elastic film88is returned to the original state owing to elasticity thereof. Thus, the corresponding pressure chamber22expands. By causing the pressure chamber22to expand and then causing the pressure chamber22to contract, a pressure of the ink in the pressure chamber22increases so that the ink drop is ejected from a nozzle17.

That is, in the above recording head4, when a tooth-like portion21aas a piezoelectric vibrating member is charged or discharged, the volume of the corresponding pressure chamber22is also changed. Thus, by using the change of the volume of the pressure chamber22, the pressure of the ink in the pressure chamber22can be changed, so that a drop of the ink can be ejected from the corresponding nozzle17or a meniscus at the corresponding nozzle17can be minutely vibrated. The meniscus means a free surface of the ink exposed at an opening of the nozzle17.

Instead of the above longitudinal-mode piezoelectric vibrating unit21, bending-mode piezoelectric vibrating members can be used. When a bending-mode piezoelectric vibrating member is used, a charging operation causes a pressure chamber to contract, and a discharging operation causes the pressure chamber to expand.

In the case, the recording head4is a many-color-recording head that is capable of recording with a different plurality of colors. Thus, the recording head4has a plurality of head units. Respective predetermined colors are set for and used in the plurality of head units, respectively. In the present embodiment, pigment inks are used for the plurality of colors, respectively.

In detail, the recording head4has: a black head unit capable of ejecting a drop of black ink, a cyan head unit capable of ejecting a drop of cyan ink, a magenta head unit capable of ejecting a drop of magenta ink, and a yellow head unit capable of ejecting a drop of yellow ink. The respective head units are communicated to respective ink chambers in the ink cartridges2aand2b. Each head unit has a structure as explained above with reference toFIG. 2. As shown inFIG. 3, four nozzle rows are formed by the nozzles17, each nozzle row corresponding to each color (BK, C, M and Y).

Then, an electric structure of the printer1is explained. As shown inFIG. 4, the ink-ejecting printer1has a printer controller30and a printing engine31.

The printer controller30has: an outside interface (outside I/F)32, a RAM33which is able to temporarily store various data, a ROM34which stores a controlling program or the like, a controlling part11including CPU or the like, an oscillating circuit35for generating a clock signal, an driving-signal generating part36for generating an driving signal that is supplied into a recording head4, and an inside interface (inside I/F)37that is adapted to send the driving signal, dot-pattern-data (bit-map-data) developed according to printing data (ejecting data) or the like to the print engine31.

The outside I/F32is adapted to receive printing data consisting of character codes, graphic functions, image data or the like from a host computer not shown or the like. In addition, a busy signal (BUSY) or an acknowledge signal (ACK) is adapted to be outputted to the host computer or the like through the outside I/F32.

The RAM33has a receiving buffer, an intermediate buffer, an outputting buffer and a work memory not shown. The receiving buffer is adapted to receive the printing data through the outside I/F32, and temporarily store the printing data. The intermediate buffer is adapted to store intermediate-code-data converted from the printing data by the controlling part11. The outputting buffer is adapted to store dot-pattern-data which are data for printing obtained by decoding (translating) the intermediate-code-data (for example, level data).

The ROM34stores font data, graphic functions or the like in addition to the controlling program (controlling routine) for carrying out various data-processing operations. The ROM34also stores various setting data for maintenance operations.

The controlling part11is adapted to carry out various controlling operations according to the controlling program stored in the ROM34. For example, the controlling part11reads out the printing data from the receiving buffer, converts the printing data into the intermediate-code-data, causes the intermediate buffer to store the intermediate-code-data. Then, the controlling part11analyzes the intermediate-code-data in the intermediate buffer and develops (decodes) the intermediate-code-data into the dot-pattern-data with reference to the font data and the graphic functions or the like stored in the ROM34. Then, the controlling part11carries out necessary decorating operations to the dot-pattern-data, and thereafter causes the outputting buffer to store the dot-pattern-data.

When the dot-pattern-data corresponding to one line recorded by one main scanning of the recording head4are obtained, the dot-pattern-data are outputted to an electric driving system39of the recording head4from the outputting buffer through the inside I/F37in turn. Then, the carriage5is moved in the main scanning direction, that is, the recording operation for the one line is conducted. When the dot-pattern-data corresponding to the one line are outputted from the outputting buffer, the intermediate-code-data that has been developed are deleted from the intermediate buffer, and the next developing operation starts for the next intermediate-code-data.

In addition, the controlling part11controls a maintenance operation (a recovering operation) conducted before the recording operation by the recording head4.

The print engine31includes a paper feeding motor13as a paper feeding mechanism, a pulse motor7as a head scanning mechanism, and an electric driving system39of the recording head4.

Then, the electric driving system39of the recording head4is explained. As shown inFIG. 4, the electric driving system39includes decoders50, shift registers40, latch circuits41, level shifters42and switching units43and the piezoelectric vibrating members21, which are electrically connected in the order. The decoders50correspond to the respective nozzles17of the recording head4, respectively. Similarly, the shift registers40correspond to the respective nozzles17, the latch circuits41correspond to the respective nozzles17, the level shifters42correspond to the respective nozzles17, and the switching units43correspond to the respective nozzles17, respectively. In addition, the piezoelectric vibrating members21also correspond to the respective nozzles17of the recording head4, respectively.

In the electric driving system39, when a pulse-selecting datum (SP datum) supplied to a switching unit43is “1”, the switching unit43is closed (connected) and a pulse-wave in the driving signal is directly supplied to a corresponding piezoelectric vibrating member21. Thus, the piezoelectric vibrating member21deforms according to the pulse-wave of the driving signal. On the other hand, when a pulse-selecting datum (SP datum) supplied to a switching unit43is “0”, the switching unit43is opened (unconnected) and the driving signal is not supplied to a corresponding piezoelectric vibrating member21.

As described above, based on the pulse-selecting data, the driving signal may be selectively supplied to each piezoelectric vibrating member21. Thus, dependently on given pulse-selecting data, a drop of the ink may be ejected from a nozzle17or a meniscus of ink may be caused to minutely vibrate.

Herein, the driving-signal generating circuit36is explained in detail with reference toFIG. 5. As shown inFIG. 5, the driving-signal generating circuit36has a latch-signal outputting part101that outputs a plurality of latch signals synchronizing with passage timings of predetermined passage positions of the recording head4. The latch-signal outputting part101is connected to an encoder102that detects a position or a moving amount of the recording head4, in order to synchronize with the passage timings of the respective passage positions (corresponding to respective pixels) of the recording head4.

In addition, the driving-signal generating circuit36has a channel-signal outputting part103, which outputs a first channel signal after a first set time difference and a second channel signal after a second set time difference, subsequent to each latch signal, based on the predetermined time differences against the latch signal.

Then, the latch-signal outputting part101and the channel-signal outputting part103are connected to a main part105.

The main-part105is adapted to generate a driving signal COM (seeFIG. 6) having: a latch pulse-wave appearing at an outputting timing of each latch signal, a first channel pulse-wave appearing at an outputting timing of each first channel signal by the channel-signal outputting part103, and a second channel pulse-wave appearing at an outputting timing of each second channel signal by the channel-signal outputting part103, in that order.

As shown inFIG. 6, the driving signal COM is a periodical signal having a recording period T. The recording period T is divided into a part T1including a first pulse-wave PS1, a part T2including a small pulse-wave PS3and a part T3including a second pulse-wave PS2. The first pulse-wave PS1, the small pulse-wave PS3and the second pulse-wave PS2are connected in a series manner.

Each of the first pulse-wave PS1, the small pulse-wave PS3and the second pulse-wave PS2can eject a drop of the ink alone.

When the first pulse-wave PS1is supplied to the piezoelectric vibrating member21, a drop of the ink, whose volume corresponds to a middle dot, is ejected from the nozzle17at a relatively low speed. When the small pulse-wave PS3is supplied to the piezoelectric vibrating member21, a drop of the ink, whose volume corresponds to a small dot, is ejected from the nozzle17. When the second pulse-wave PS2is supplied to the piezoelectric vibrating member21, a drop of the ink, whose volume corresponds to a middle dot, is ejected from the nozzle17at a relatively high speed.

As shown inFIG. 7, a level control is conducted by selecting one or more pulse-waves to be supplied to the piezoelectric vibrating member21. That is, a middle dot is formed on the recording paper12by supplying the first pulse-wave PS1or the second pulse-wave PS2, a small dot is formed on the recording paper12by supplying the small pulse-wave PS3, and a large dot is formed on the recording paper12by supplying the first pulse-wave PS1and the second pulse-wave PS2.

In the case, the decoder50generates pulse-selecting data consisting of three bits, based on the non-ejecting dot-pattern data (level data00), the small-dot dot-pattern data (level data01), the middle-dot dot-pattern data (level data10) and the large-dot dot-pattern data (level data11), respectively.

As shown inFIG. 7, each of the three bits corresponds to each of the pulse-waves. That is, the first bit of the pulse-selecting data corresponds to the first pulse-wave PS1. The second bit of the pulse-selecting data corresponds to the small pulse-wave PS3. The third bit of the pulse-selecting data corresponds to the second pulse-wave PS2.

In the case, the pulse-selecting data generated based on the non-ejecting dot-pattern data (level data00) is “000”. Similarly, the pulse-selecting data generated based on the small-dot dot-pattern data (level data01) is “010”, and the pulse-selecting data generated based on the large-dot dot-pattern data (level data11) is “101”.

Then, as the feature of the present invention, the pulse-selecting data generated based on the middle-dot dot-pattern data (level data10) depends on the distance (PG) between the nozzle17and the recording paper12.

Specifically, a distance obtaining unit206(seeFIG. 4) is adapted to obtain the distance between the nozzle17and the recording paper12. Then, the distance obtaining unit206judges whether the distance is less than a predetermined value or not, and sends the result to the decoder50. In the case, the predetermined value is 1.5 mm.

The decoder50generates the pulse-selecting data (100) based on the middle-dot dot-pattern data (level data10) when the judgment result sent from the distance obtaining unit206is not less than the predetermined value (when the recording paper12is a normal paper).

On the other hand, the decoder50generates the pulse-selecting data (001) based on the middle-dot dot-pattern data (level data10) when the judgment result sent from the distance obtaining unit206is less than the predetermined value (when the recording paper12is a special paper).

When the first bit of the pulse-selecting data is “1”, the switching circuit45(driving-pulse generator) is closed (connected) from a first timing signal (LAT signal), which is generated when the part T1of the period T starts, to a second timing signal (CH signal), which is generated when the part T2of the period T starts. In addition, when the second bit of the pulse-selecting data is “1”, the switching circuit45is closed from the second timing signal to a third timing signal (CH signal), which is generated when the part T3of the period T starts. Similarly, when the third bit of the pulse-selecting data is “1”, the switching circuit45is closed from the third timing signal to a timing signal (LAT signal) which is generated when the part T1of the next period T starts.

Thus, based on the small-dot dot-pattern data, only the small pulse-wave PS3is supplied to the corresponding piezoelectric vibrating member21. As a result, correspondingly to the small-dot dot-pattern data, a small-dot drop of the ink is ejected from the nozzle17. Thus, a small dot is formed on the recording paper12.

In addition, when the judgment result sent from the distance obtaining unit206is not less than the predetermined value, that is, when the “PG” is larger (when the recording paper12is a normal paper), based on the middle-dot dot-pattern data, only the first pulse-wave PS1is supplied to the corresponding piezoelectric vibrating member21. As a result, correspondingly to the middle-dot dot-pattern data, a middle-dot drop of the ink is ejected from the nozzle17at the relatively low speed. Thus, a middle dot is formed on the recording paper12.

On the other hand, when the judgment result sent from the distance obtaining unit206is less than the predetermined value, that is, when the “PG” is smaller (when the recording paper12is a special paper), based on the middle-dot dot-pattern data, only the second pulse-wave PS2is supplied to the corresponding piezoelectric vibrating member21. As a result, correspondingly to the middle-dot dot-pattern data, a middle-dot drop of the ink is ejected from the nozzle17at the relatively high speed. Thus, a middle dot is formed on the recording paper12.

Then, based on the large-dot dot-pattern data, the first pulse-wave PS1and the second pulse-wave PS2are supplied to the corresponding piezoelectric vibrating member21. As a result, correspondingly to the large-dot dot-pattern data, two middle-dot drops of the ink are ejected from the nozzle17. Thus, a large dot is formed on the recording paper12.

As described above, according to the present embodiment, regarding the middle-dot drop of the ink, when the “PG” is not less than the predetermined value and hence it is more possible for mist to be generated, for example when the recording paper12is a normal paper, a middle-dot drop of the ink is ejected from the nozzle17at the relatively low speed. On the other hand, when the “PG” is less than the predetermined value and hence it is less possible for mist to be generated, for example when the recording paper12is a special paper, a middle-dot drop of the ink is ejected from the nozzle17at the relatively high speed, giving priority to the precision of reach to the recording paper12. Thus, a suitable ejecting control of the middle-dot drop of the ink can be achieved taking into consideration balance of the tendency of mist generation and the precision of reach to the recording paper12.

Specifically, it is preferable that each middle-dot drop of the ink has a volume of about 7 ng, the relatively low speed is about 8 m/s, and the relatively high speed is about 10 m/s. Actually, when the volume of a drop of the ink is about 7 ng and the “PG” is not less than 1.5 mm, if the ejecting speed of the drop of the ink is not larger than 9 m/s, the apparatus is badly befouled with ink mist. However, according to the present embodiment, such befoulment can be avoided. The volume of a small-dot drop of the ink is for example 3 ng.

In the case, preferably, when the selected level data is the large-dot data, the middle-dot drop of the ink ejected from the nozzle17at the relatively low speed by the first pulse-wave PS1is adapted to be caught up with by the middle-dot drop of the ink ejected from the nozzle17at the relatively high speed by the second pulse-wave PS2and to join the same. In the case, mist generation may be remarkably inhibited.

In the above suitable case, that is, if each middle-dot drop of the ink has a volume of about 7 ng, the relatively low speed is about 8 m/s, and the relatively high speed is about 10 m/s, two middle-dot drops of the ink can join to each other in the air, which is preferable.

In addition, the distance obtaining unit206may obtain the distance between the nozzle17and the recording paper12in any known manner. For example, a set position of the PG adjusting lever19can be detected. Alternatively, the distance between the nozzle17and the recording paper12can be actually measured.

If the distance between the nozzle17and the recording paper12is adapted to be automatically set depending on a kind of the recording paper12, the distance between the nozzle17and the recording paper12may be obtained from information of the recording paper12inputted from a recording-paper-information inputting part205. The information of the recording paper12may be information about a product-type or the like of the recording paper12. In the case, the distance obtaining unit206has stored table data associating the product-types or the like with respective “PG”.

The above embodiment can be variously modified in a scope of claimed invention.

For example, a pressure-generating member for changing the volume of the pressure chamber22is not limited to the piezoelectric vibrating member21. For example, a pressure-generating member can consist of a magnetostrictive device. In the case, the magnetostrictive device causes the pressure chamber22to expand and contract, thus, changes the pressure of the ink in the pressure chamber22. Alternatively, a pressure-generating member can consist of a heating device. In the case, the heating device causes an air bubble in the pressure chamber22to expand and contract, thus, changes the pressure of the ink in the pressure chamber22.

In addition, as described above, the printer controller30can be materialized by a computer system. A program for materializing the above one or more components in a computer system, and a storage unit201storing the program and capable of being read by a computer, are intended to be protected by this application.

In addition, when the above one or more components may be materialized in a computer system by using a general program such as an OS, a program including a command or commands for controlling the general program, and a storage unit202storing the program and capable of being read by a computer, are intended to be protected by this application.

Each of the storage units201and202can be not only a substantial object such as a floppy disk (flexible disk) or the like, but also a network for transmitting various signals.

The above description is given for the ink-jetting printer as a liquid ejecting apparatus of the embodiment according to the invention. However, this invention is intended to apply to general liquid ejecting apparatuses widely. A liquid may be glue, bonding agent, nail polish, liquid metal for forming an electric circuit, organic liquid or the like, instead of the ink. In addition, this invention can be also applied to an apparatus for manufacturing color filters of a display member such as a liquid crystal display.