Patent ID: 12194758

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that each of the drawings is merely illustrative for describing the exemplary embodiment. Since the drawings are illustrative, proportions and shapes may not be precise, match each other, or some may be omitted.

1. Apparatus Configuration

FIG.1illustrates a configuration of a printing apparatus10according to the exemplary embodiment, in a simplified manner.

The printing apparatus10includes a control unit11, a display unit13, an operation receiving unit14, a communication IF15, a printing unit16, a storage unit22, etc. The printing unit16includes a transport unit17, a carriage18, a print head19, a defective nozzle detection unit21, etc. IF is an abbreviation for interface. The control unit11is configured to include, as a processor, one or more ICs including a CPU11a, a ROM11b, a RAM11c, and the like, another non-volatile memory, and the like.

In the control unit11, the processor, that is, the CPU11aexecutes arithmetic processing in accordance with one or more programs12stored in the ROM11b, the other memory, etc., using the RAM11c, etc. as a work area, whereby controlling the printing apparatus10. Note that the processor is not limited to the single CPU, and a configuration may be adopted in which the processing is performed by a hardware circuit such as a plurality of CPUs, an ASIC, or the like, or a configuration may be adopted in which the CPU and the hardware circuit work in concert to perform the processing.

The display unit13is a device for displaying visual information, and is configured, for example, by a liquid crystal display, an organic EL display, or the like. The display unit13may be configured to include a display and a drive circuit for driving the display. The operation receiving unit14is a device for receiving an operation by a user, and is realized, for example, by a physical button, a touch panel, a mouse, a keyboard, or the like. Of course, the touch panel may be realized as a function of the display unit13.

The display unit13and the operation receiving unit14may be part of the configuration of the printing apparatus10, or may be peripheral devices externally coupled to the printing apparatus10. The communication IF15is a generic term for one or a plurality of IFs for coupling the printing apparatus10with the outside in a wired or wireless manner, in accordance with a prescribed communication protocol including a known communication standard provide.

The printing unit16is a mechanism for printing by an inkjet method.

The transport unit17is a means for transporting a printing medium such as paper in a predetermined transport direction, and includes a roller and a motor for rotating the roller, etc. Upstream and downstream in the transport direction are simply referred to below as upstream and downstream.

The print head19has a plurality of nozzles20. The print head19prints an image on the printing medium by discharging or non-discharging dots of ink from the nozzles20based on printing data generated by the control unit11for printing an image with ink. The print head19is capable of discharging a plurality of colors of ink, such as cyan (C) ink, magenta (M) ink, yellow (Y) ink, black (K) ink, for example. Of course, the print head19may also discharge ink or liquid having a color other than CMYK.

The carriage18is a mechanism capable of reciprocating along a predetermined main scanning direction by receiving power from a carriage motor (not illustrated). The carriage18corresponds to a “scanning unit”. The main scanning direction intersects with the transport direction. The intersection referred to here may be understood as orthogonal or almost orthogonal. The print head19is mounted on the carriage18. In other words, the print head19reciprocates along with the carriage18along the main scanning direction.

The storage unit22is constituted by a storage device such as a hard disk drive or a solid state drive, for example. The storage unit22may include a memory included in the control unit11. Furthermore, the storage unit22may be interpreted as a part of the control unit11. The storage unit22stores various information necessary for the control of the printing apparatus10.

FIG.2simply illustrates a relationship between the printing medium30and the print head19, as seen from above. The print head19mounted on the carriage18moves from one end to the other end of a main scanning direction D1(outward movement) and moves from the other end to one end (return movement) together with the carriage18.FIG.2illustrates an example of an array of the nozzles20on a nozzle surface23. The nozzle surface23is a lower surface of the print head19. Each small circle in the nozzle surface23corresponds to the nozzles20.

The print head19includes nozzle rows26at each nozzle row position in a configuration in which ink for each color is supplied from a liquid holding unit (not illustrated) called an ink cartridge, an ink tank, etc. and discharged from the nozzle20.FIG.2illustrates an example of the print head19that discharges CMYK ink. The nozzle row26including the nozzles20for discharging C ink is a nozzle row26C. Similarly, the nozzle row26including the nozzles20for discharging M ink is a nozzle row26M, the nozzle row26including the nozzles20for discharging Y ink is a nozzle row26Y, and the nozzle row26including the nozzles20for discharging K ink is a nozzle row26K.

In the example ofFIG.2, the nozzle rows26C,26M,26Y,26K are aligned along the main scanning direction D1. The print head19having a configuration in which the plurality of nozzle rows26with different colors are arranged along the main scanning direction D1is also referred to as a “horizontal array head”. In the horizontal array head, the plurality of nozzle rows26for each color are disposed at the same position in a transport direction D2. Therefore, in the horizontal array head, the nozzle row position is a different position in the main scanning direction D1. Further, the nozzle row26at each nozzle row position can be said to be the nozzle row26for each ink color. However, each nozzle row26at each nozzle row position may have ink of the same color, specifically, may be the nozzle row26K that discharges the K ink. That is, the print head19may be a head that only corresponds to monochrome printing. Each of the nozzle rows26C,26M,26Y correspond to a “chromatic nozzle row” that each discharge a chromatic color of ink. Furthermore, the nozzle row26K corresponds to a “non-chromatic nozzle row” that discharges a non-chromatic color of ink.

Each of the nozzle rows26is constituted by the plurality of nozzles20for which a nozzle pitch, which is an interval between the nozzles20in the transport direction D2, is constant or substantially constant. The direction in which the plurality of nozzles20constituting the nozzle row26are aligned is referred to as a nozzle row direction D3. In the example ofFIG.2, the nozzle row direction D3is parallel to the transport direction D2. In the configuration in which the nozzle row direction D3is parallel with the transport direction D2, the nozzle row direction D3and the main scanning direction D1are orthogonal. However, the nozzle row direction D3need not necessarily be parallel with the transport direction D2, and a configuration may be adopted in which the nozzle row direction D3obliquely intersects the main scanning direction D1.

The operation in which the print head19discharges ink based on printing data along with movement of the carriage18along the main scanning direction D1is referred to as “main scanning” or a “pass.” The printing unit16completes printing on the printing medium30by combining the pass and transport of the printing medium30by the transport unit17in the transport direction D2.

The configuration of the printing apparatus10illustrated inFIG.1may be realized by a single printer, or may be realized by a plurality of communicatively coupled devices.

In other words, the printing apparatus10may be the printing system10in actuality. The printing system10includes, for example, a printing control device that functions as the control unit11and the storage unit22, and a printer corresponding to the printing unit16. A printing method according to the exemplary embodiment is realized in this way by the printing apparatus10or the printing system10.

The defective nozzle detection unit21is a means for detecting a “defective nozzle” from the plurality of nozzles20included in the print head19. The defective nozzle is a nozzle20that is not capable of discharging ink due to clogging, etc. even after the operation of ink discharge according to printing data is performed. The inability to discharge the ink includes a state in which the ink cannot be discharged at all, and the amount of liquid to be discharged is too small, etc. Further, the present disclosure includes a case where an amount of liquid to be discharged is normal, but the position where the amount of liquid lands on the printing medium30is shifted with respect to the target position, etc. The defective nozzle may be referred to as an abnormal nozzle, etc. A nozzle20that is not the defective nozzle is also referred to as a “normal nozzle”.

Various types of detection of the defective nozzle by the defective nozzle detection unit21can be adopted as long as it is possible to determine and detect whether each nozzle20is the defective nozzle. The defective nozzle detection unit21adopts a laser method in which, for example, the light emitter and the print head19are aligned so that the laser light emitted from the light emitter and the ink flight path of the nozzle20to be inspected intersect with each other, and determines that the inspection target is the defective nozzle when the light shielding of the laser beam by the dot discharged from the nozzle20cannot be detected by the light receiver. Furthermore, the defective nozzle detection unit21may detect the defective nozzle using the technique disclosed in JP-A-2013-126776. Specifically, whether ink is discharged normally from each nozzle20is detected by measuring the waveform of the residual vibration of a partial configuration of the print head19, such as a so-called vibration plate that bends in conjunction with the deformation of the driving element (piezoelectric element) due to the application of the drive signal in accordance with the printing data.

The defective nozzle detection unit21generates defective nozzle information describing whether the nozzle is a defective nozzle for each of the nozzles20by performing the defective nozzle detection process. The defective nozzle information is stored in the storage unit22. The timing at which the defective nozzle detection unit21executes the defective nozzle detection process is not particularly limited. The defective nozzle detection unit21overwrites the defective nozzle information with the latest defective nozzle information at any time.

2. First Exemplary Embodiment

FIG.3illustrates, by a flowchart, a printing control process according to a first exemplary embodiment executed by the control unit11according to the program12. The printing control process includes a printing method. In the first exemplary embodiment, the print head19is a horizontal array head.

In step S100, the control unit11accesses the storage unit22to acquire the defective nozzle information.

In step S110, the control unit11calculates a “complementary transport amount” for each nozzle row26with reference to the defective nozzle information. The complementary transport amount refers to a one-time transport amount by the transport unit17, and refers to a transport amount at which non-discharge of ink by the defective nozzle is complementable by discharge of ink by the normal nozzle, based on a relationship between the main scanning before the transport and the main scanning after the transport. Note that, in the following, the distance or length refers to the distance or length in the transport direction D2, unless otherwise specified.

In the following, one-time transport by the transport unit17for printing is also referred to as “paper feeding”. Therefore, the one-time transport amount by the transport unit17is a paper feeding amount. In addition, in a relationship of the main scanning for two times performed before the paper feeding and after the paper feeding, the main scanning performed earlier is referred to as a “leading pass”, and the main scanning performed later is referred to as a “backward pass”.

FIG.4is a diagram for describing a method for determining the complementary transport amount for each nozzle row26in step S110. With reference toFIG.4, one pass P1is referred to as a leading pass P1and the next pass2of the pass P1is referred to as a backward pass P2.FIG.4illustrates the nozzle rows26C,26M,26Y,26K when performing the leading pass P1and the nozzle rows26C,26M,26Y,26K when performing the backward pass P2assuming the case where the complementary transport amount for each nozzle row26is applied. In the example ofFIG.4, for convenience of paper space, each of the nozzle rows26C,26M,26Y,26K is indicated by 12 nozzles20. Of course, the number of nozzles that actually constitute the nozzle row26may be greater than 12.FIG.4also illustrates the main scanning direction D1and the transport direction D2in the same manner as inFIG.2.

InFIG.4, for convenience of explanation, each nozzle20constituting the nozzle rows26C,26M,26Y,26K is designated with a nozzle number in order from downstream to upstream, as #1, #2, #3 . . . #12. However, the nozzle number is appropriately omitted for the nozzle rows26C,26M,26Y,26K when performing the backward pass P2. InFIG.4, the nozzle20, which is a normal nozzle in the defective nozzle information, is indicated by a simple open circle, and the nozzle20, which is a defective nozzle in the defective nozzle information, is indicated by a white circle marked with an X.

InFIG.4, for each of the nozzle rows26C,26M,26Y,26K, the position at the time of performing the backward pass P2is offset upstream from the position at the time of performing the leading pass P1, whereby the complementary transport amounts between the leading pass P1and the backward pass P2for each of the nozzle rows26C,26M,26Y,26K are represented. Of course, rather than the nozzle row26actually moving upstream, the printing medium30moves downstream by the paper feeding.

In step S110, the control unit11calculates the maximum complementary transport amount for the nozzle row26based on the positional relationship between the defective nozzle and the normal nozzle included in the nozzle row26in the transport direction D2.

First, attention is given to the nozzle row26C. In the example ofFIG.4, in the nozzle row26C, two nozzles20having a nozzle number #2 and a nozzle number #11 are defective nozzles. In the nozzle row26C, 8 nozzles20of the nozzle numbers #3 to #10 are continuously normal nozzles, and therefore, using 8 nozzles20of the nozzle numbers #3 to #10 in each pass eliminates the use of the defective nozzle. In other words, if a distance of 8 times the nozzle pitch is taken as one-time paper feeding amount, 8 nozzles20of the nozzle numbers #3 to #10 can be used for printing in each pass.

However, such a distance of 8 times the nozzle pitch cannot be said to be the maximum complementary transport amount for the nozzle row26C. According to the example ofFIG.4, for the position of the printing medium30where ink is not discharged due to the defective nozzle of the nozzle number #11 of the nozzle row26C in the leading pass P1, the dot can be complemented by any normal nozzle downstream of this defective nozzle in the backward pass P2. In addition, according to the example ofFIG.4, for the position of the printing medium30where ink is not discharged due to the defective nozzle of the nozzle number #2 of the nozzle row26C in the backward pass P2, the dot can be complemented by any normal nozzle upstream of this defective nozzle in the leading pass P1. Therefore, in the example ofFIG.4, a distance of 10 times the nozzle pitch is the maximum complementary transport amount Fc for the nozzle row26C, which corresponds to the distance from the defective nozzle of the nozzle number #11 to the normal nozzle of nozzle number #1 farthest downstream in the nozzle row26C, and the distance from the defective nozzle of the nozzle number #2 to the normal nozzle of nozzle number #12 farthest upstream in the nozzle row26C.

In the relationship between the leading pass and the backward pass, two nozzles20corresponding to the same position of the printing medium30in the same nozzle row26are referred to as a “paired nozzle”. That is, when the defective nozzle becomes the paired nozzle together with the normal nozzle, complementation is established. When the defective nozzles becomes the paired nozzle, the complementation is not established.

In step S110, the control unit11determines the maximum complementary transport amount for each of the nozzle rows26M,26Y,26K.

In the example ofFIG.4, in the nozzle row26M, two nozzles20of the nozzle number #3 and nozzle number #9 are defective nozzles. In the nozzle row26M, five nozzles20of the nozzle numbers #4 to #8 are continuously normal nozzles, and therefore, if a distance of 5 times the nozzle pitch is taken as one-time paper feeding amount, 5 normal nozzles of the nozzle numbers #4 to #8 can be used for printing in each pass.

However, such a distance of 5 times the nozzle pitch cannot be said to be the maximum complementary transport amount for the nozzle row26M. According to the example ofFIG.4, for the position of the printing medium30where ink is not discharged due to the defective nozzle of the nozzle number #9 of the nozzle row26M in the leading pass P1, the dot can be complemented by the normal nozzle with the nozzle number #1, which is the furthest downstream from this defective nozzle in the backward pass P2. In other words, the two nozzles20of nozzle numbers #1, #9 in the nozzle row26M can be the paired nozzle. In addition, for the position of the printing medium30where ink is not discharged due to the defective nozzle of the nozzle number #3 of the nozzle row26M in the backward pass P2, the dot can be complemented by the normal nozzle with the nozzle number #11 upstream of this defective nozzle in the leading pass P1. Therefore, in the example ofFIG.4, a distance of 8 times the nozzle pitch is the maximum complementary transport amount Fm for the nozzle row26M, which corresponds to the distance from the defective nozzle of the nozzle number #9 to the normal nozzle of the nozzle number #1 downstream in the nozzle row26M, and the distance from the defective nozzle of the nozzle number #3 to the normal nozzle of the nozzle number #11 upstream in the nozzle row26M.

In the example ofFIG.4, in the nozzle row26Y, only the nozzle20of the nozzle number #1 is the defective nozzle. With respect to the nozzle row26Y, for the position of the printing medium30where ink is not discharged due to the defective nozzle of the nozzle number #1 in the backward pass P2, the dot can be simply complemented by the normal nozzle with the nozzle number #12, which is the most upstream from the defective nozzle in the leading pass P1. Therefore, in the example ofFIG.4, a distance of 11 times the nozzle pitch is the maximum complementary transport amount Fy for the nozzle row26Y, which corresponds to the distance from the defective nozzle of the nozzle number #1 to the normal nozzle of the nozzle number #12 upstream in the nozzle row26Y.

In the example ofFIG.4, there is no defective nozzle in the nozzle row26K. The term “complementary” is unnecessary when there is no defective nozzle, but here, the expression of the “complementary transport amount” is used for the nozzle row26K in accordance with the other nozzle rows26C,26M,26Y having defective nozzles. With respect to the nozzle row26K, a distance of 12 times the nozzle pitch is the maximum complementary transport amount Fk, which corresponds to the length of the nozzle row26.

In step S120, the control unit11determines the transport amount common to each nozzle row26at each nozzle row position, based on the complementary transport amount for each nozzle row26calculated in step S110. According toFIG.4, since the maximum complementary transport amount for each of the nozzle rows26C,26M,26Y,26K is the complementary transport amount Fc, Fm, Fy, Fk, the control unit11may determine the smallest complementary transport amount Fm among these complementary transport amounts Fc, Fm, Fy, Fk to the common transport amount.

However, in a case where the smallest complementary transport amount Fm in the complementary transport amounts Fm, Fm, Fy, Fk is set to the common transport amount and where a situation occurs in which the defective nozzles become the paired nozzle in any of the nozzle rows26C,26Y,26K other than the nozzle row26M for which the complementary transport amount Fm is calculated in step S110, the common transport amount needs to be adjusted to a smaller distance. In the nozzle row26C, it is assumed that the three nozzles20of the nozzle numbers #3, #10, #11 are defective nozzles. In this case, the defective nozzles of the nozzle numbers #10, #11 are complemented by the normal nozzles of the nozzle numbers #1, #2, and the defective nozzle of the nozzle number #3 can be complemented by the normal nozzle of the nozzle number #12, so the complementary transport amount Fc of the nozzle row26C is a distance of 9 times the nozzle pitch. In this case, the complementary transport amount Fm, which is the distance of 8 times the nozzle pitch, is still smaller than the complementary transport amount Fc, but when the complementary transport amount Fm is the common transport amount for each nozzle row26, two nozzles20of the nozzle numbers #3, #11, which are defective nozzles, becomes the paired nozzle in the nozzle row26C. Thus, the control unit11determines a common transport amount that is even smaller than the complementary transport amount Fm, and does not generate the paired nozzle of defective nozzles in all of the nozzle rows26C,26Y,26K.

In step S130, the control unit11determines a “used nozzle” in each nozzle row26when printing using the common transport amount determined in step S120. The used nozzle is the nozzle20that is the normal nozzle and is used for printing. By use of printing, it is meant to assign printing data. The nozzle20, which is the normal nozzle and is not used for printing, is referred to as an “unused nozzle”.

A specific example of step130will be described with reference toFIG.5. InFIG.5, as inFIG.4as well, the relative positions of the nozzle rows26C,26M,26Y,26K in the transport direction D2and the printing medium30vary for each pass. The view ofFIG.5is basically the same asFIG.4. The defective nozzles in the nozzle rows26C,26M,26Y,26K illustrated inFIG.5are the same as inFIG.4. InFIG.5, the pass P1is assumed to be a first pass for the printing medium30. The pass P2is a backward pass when the pass P1is taken as a leading pass, and pass P3is a backward pass when the pass P2is taken as a leading pass.

InFIG.5, the reference sign F denotes the common transport amount F determined in step S120, that is, the amount of paper feeding adopted for printing. Furthermore, the transport amount F is the complementary transport amount Fm illustrated inFIG.4. InFIG.5, the used nozzle is represented by a white circle, and the unused nozzle is represented by a gray color circle.

In a case where the transport amount F is adopted, the control unit11all uses the nozzles20that does not become the paired nozzle with the other nozzles20to be used as the used nozzles. According toFIG.5, each nozzle20of the nozzle numbers #5 to #8 does not become the paired nozzle with other nozzles20, and thus, in each of the nozzle rows26C,26M,26Y,26K, the control unit11sets each nozzle20of the nozzle numbers #5 to #8 to be the used nozzle.

In addition, in the case where the transport amount F is adopted, the control unit11naturally sets the normal nozzle, which becomes the paired nozzle with the defective nozzle, to be the used nozzle. According toFIG.5, for example, the nozzle20of the nozzle number #10 of the nozzle row26C becomes the paired nozzle with the defective nozzle of the nozzle number #2, to be the used nozzle. In addition, for example, the nozzle20of the nozzle number #1 of the nozzle row26M becomes the paired nozzle with the defective nozzle of the nozzle number #9, to be the used nozzle. Further, the control unit11may use either normal nozzle as the used nozzle for the paired nozzle of the normal nozzles when the transport amount F is adopted, but in the example ofFIG.5, the normal nozzle belonging to the backward pass is used as the used nozzle. For example, while the two normal nozzles of the nozzle numbers #11, #3 in the nozzle row26Y have a relationship as the paired nozzle, it is assumed that the nozzle20of the nozzle number #11 serving as a normal nozzle belonging to the leading pass is the unused nozzle, and that the nozzle20of the nozzle number #3 serving as a normal nozzle belonging to the backward pass is the used nozzle.

As a result of this step S130, according to the example inFIG.5, the control unit11determines the 8 nozzles20of the nozzles numbers #1, #3 to #8, #10 in the nozzle row26C to be the used nozzles. Also, in the nozzle row26M, 8 nozzles20of the nozzle numbers #1, #2, #4 to #8, #11 are determined to be the used nozzles. In the nozzle row26Y, 8 nozzles20of the nozzle numbers #2 to #9 are determined to be the used nozzles, and in the nozzle row26K, 8 nozzles20of the nozzle numbers #1 to #8 are determined to be the used nozzles.

Further, in step S130, the control unit11determines the most downstream used nozzles common to each nozzle row26for the pass P1, which is the first pass. In the example inFIG.4,5, due to the defective nozzle of the nozzle number #3 of the nozzle row26M, the most downstream nozzle20that can be commonly used in the nozzle rows26C,26M,26Y,26K in the pass P1, is each nozzle20of the nozzle number #4. Therefore, with respect to the pass P1, the control unit11uses the used nozzles of the nozzle number #4 or higher nozzle numbers among the used nozzles in each nozzle row26determined as described above for printing. That is, in pass P1, each used nozzle located upstream of the dashed line illustrated inFIG.5is used.

In step S140, the control unit11adopts the common transport amount determined in step S120, and performs printing based on the printing data by controlling the transport unit17, the carriage18, and the print head19using the used nozzles determined in each of the nozzle rows26in step S130. In other words, in the pass performed by the carriage18and the print head19, ink discharge is performed from the used nozzle based on the printing data, and the transport unit17executes paper feeding once with the common transport amount between one pass and the next pass, According to this type of printing, the non-discharge of the ink by the defective nozzles is complemented by the normal nozzle, and a high-quality printing result is obtained in which there is no missing of the required dots on the printing medium30.

The printing data is raster data in which an image is represented by a plurality of pixels, and for each pixel, dot discharge (dot on) or dot non-discharge (dot off) for each dot of CMYK ink is specified. In the printing data, a pixel row in which pixels are aligned along the main scanning direction D1is referred to as a raster line. The control unit11can print one raster line on one nozzle20by assigning one raster line of dot data to one nozzle20. Therefore, for the defective nozzle and the used nozzle that relate to the paired nozzle in the leading pass and the backward pass by the paper feeding according to the present exemplary embodiment, the control unit11assigns the raster line data to only the used nozzle, so that a high quality printing result can be output without missing dots due to the defective nozzles.

3. Second Exemplary Embodiment

FIG.6simply illustrates a relationship between the print head19and the printing medium30according to a second exemplary embodiment, as seen from above. The view ofFIG.6is the same as that ofFIG.2. ForFIG.6, only the difference fromFIG.2will be described. In the print head19illustrated inFIG.6, the nozzle rows26C,26M,26Y, which correspond to each of the chromatic nozzle rows, are arranged along the transport direction D2. From a different point of view, it can be said that the three nozzle rows26C,26M,26Y are coupled to form one nozzle row. In the print head19, the nozzle row26K, which is a non-chromatic nozzle row, is arranged side by side with the chromatic nozzle row in the main scanning direction D1. The nozzle row26K inFIG.6has the same length and the same position in the transport direction D2as the nozzle row in which the nozzle rows26C,26M,26Y are coupled. The print head19having a configuration in which the plurality of nozzle rows26C,26M,26Y for each chromatic color are aligned along the transport direction D2is referred to as a “vertical array head”. In the vertical array head, the nozzle row position is a different position in the transport direction D2.

FIG.7illustrates, by a flowchart, a printing control process according to the second exemplary embodiment executed by the control unit11according to the program12. In the second exemplary embodiment, the print head19is a vertical array head. In the description of the second exemplary embodiment, the description of the first exemplary embodiment is applied accordingly. Step S200is the same as step S100ofFIG.3.

In step S210, similar to step S110, the control unit11calculates a complementary transport amount for each nozzle row26with reference to the defective nozzle information. However, in step S210, the control unit11calculates the complementary transport amount for each of the nozzle rows26C,26M,26Y, which are chromatic nozzle rows. Here, as a complementary transport amount for each of the nozzle rows26C,26M,26Y, the complementary transport amounts Fc, Fm, Fy described inFIG.4have been calculated.

In step S220, the control unit11determines the common transport amount F based on the complementary transport amount for each of the chromatic nozzle rows calculated in step S210. Similar to the first exemplary embodiment, the control unit11may determine the smallest complementary transport amount Fm among the complementary transport amounts Fc, Fm, Fy to the common transport amount F.

In step230, the control unit11determines the used nozzle when printing using the common transport amount F determined in step S220for the nozzle row26corresponding to the “minimum segment”. The minimum segment is a nozzle row26having a smallest complementary transport amount of the chromatic nozzle row, and here, corresponding to the nozzle row26M. As illustrated inFIG.5, the used nozzles in the nozzle row26M are nozzles20of the nozzle numbers #1, #2, #4 to #8, #11.

In step S240, the control unit11determines whether there is a defective nozzle in a K nozzle adjacent to the used nozzle determined for the minimum segment with reference to the defective nozzle information. The K nozzle is a name for the nozzle20constituting the nozzle row26K. In the second exemplary embodiment, for the used nozzle in the nozzle row26K, the control unit11determines a normal nozzle of the K nozzle adjacent to the used nozzle determined by each of the nozzle rows26C,26M,26Y to be the used nozzle. The term “adjacent” refers to the same position in the transport direction D2. In step S240, the control unit11proceeds to step S250from the determination of “Yes” when there is a defective nozzle in the K nozzle adjacent to the used nozzle determined for the minimum segment, on the other hand, the control unit11proceeds to step S260when there is no defective nozzle in such a K nozzle.

The process ofFIG.7will be described with reference toFIG.8.

FIG.8, similar toFIG.5, illustrates that the relative positions of the nozzle rows26C,26M,26Y,26K in the transport direction D2and the printing medium30vary for each pass by the paper feeding by the common transport amount F. The view ofFIG.8is basically the same asFIG.5. The reference sign26U is a reference sign that refers to the nozzle rows26C,26M,26Y, and is referred to here as a chromatic nozzle row unit26U. Additionally, inFIG.8, the nozzles numbers #1 to 12 of the 12 nozzles20constituting each of the nozzle rows26C,26M,26Y are indicated by adding C, M, Y representing the corresponding ink. For example, the nozzle20of the nozzle number #1 in the nozzle row26C is designated as the nozzle number #1C.

InFIG.8, the 36 K nozzles constituting the nozzle row26K are numbered by the nozzles as nozzle numbers #1K, #2K, #3K . . . #36K from downstream to upstream. In addition, inFIG.8, in the chromatic nozzle row unit26U and the nozzle row26K, a range along the transport direction D2corresponding to the nozzle row26C is a first nozzle range27, a range along the transport direction D2corresponding to the nozzle row26M is a second nozzle range28, and a range along the transport direction D2corresponding to the nozzle row26Y is a third nozzle range29. InFIG.8, the chromatic nozzle row unit26U and the nozzle row26K corresponding to the leading pass are illustrated, while the nozzle row26K of the chromatic nozzle row unit26U and the nozzle row26K corresponding to the backward pass is omitted.

The position of the defective nozzles in each of the nozzle rows26C,26M,26Y illustrated inFIG.8are the same as those in the example ofFIG.4,5. Therefore, the feature wherein the transport amount F determined in step S220is the distance of 8 times the nozzle pitch, and the used nozzle and unused nozzle determined in step S230for the nozzle row26M are the same as in the example ofFIG.5. On the other hand, in the nozzle row26K illustrated inFIG.8, each of the K nozzles of the nozzle numbers #11K, #15K, #23K, #31K are defective nozzles.

According toFIG.8, in step S230, the control unit11determines the nozzles20of the nozzle numbers #1M, #2M, #4M to #8M, #11M of the nozzle row26M, which is the smallest segment, to be the used nozzles. Thus, the K nozzle adjacent to these used nozzles is each K nozzle of nozzle number #13K, #14K, #16 K to #20K, #23K. Then, inFIG.8, among the K nozzles adjacent to these used nozzles, the K nozzle of the nozzle number #23K is the defective nozzle, and thus “Yes” is determined in step S240.

In step S250, for the defective nozzle among the K nozzle adjacent to the used nozzle in the smallest segment, the control unit11determines whether the paired nozzle of the defective nozzle and the normal nozzle having a complementary relationship is established. As described above, the defective nozzle of the K nozzle adjacent to the used nozzle of the minimum segment is the K nozzle of the nozzle number #23K. Furthermore, a K nozzle that can be formed into the paired nozzle with this K nozzle is a K nozzle located at a position that is an integral multiple of the transport amount F from the nozzle number #23K, and specifically, is each K nozzle of the nozzle numbers #31K, #15K, #7K. If all of the K nozzles of the nozzle numbers #31K, #15K, #7K are the defective nozzles, the control unit11determines “No” in step S250because there is no normal nozzle that can complement the K nozzle of the nozzle number #23K.

InFIG.8, among the K nozzles of the nozzle numbers #31K, #15K, #7K, the K nozzle of the nozzle number #7K is the normal nozzle. Therefore, because the pair of the nozzle number #23K and the normal nozzle capable of complementing this nozzle is established, the control unit11determines “Yes” in step S250and proceeds to step S260.

In step S260, the control unit11determines the used nozzle for each of the other segments that are not the minimum segment, that is, in the example ofFIG.8, for each of the nozzle rows26C and26Y. In each of the chromatic nozzle rows, the control unit11may determine the used nozzle so that the printing result of the nozzles20having the same color corresponding to the common transport amount F is coupled to the transport direction D2. For example, as the nozzles20of nozzle numbers #1, #3 to #8, #10 are determined in the nozzle row26C to be the used nozzles in the first exemplary embodiment, also in step S260, each nozzle20of the nozzle numbers #1C, #3C to #8C, #10C can be determined as the used nozzle in the nozzle row26C. Similarly, as the nozzles20of the nozzle numbers #2 to #9 in the nozzle row26Y are determined to be the used nozzles in the first exemplary embodiment, also in step S260, each nozzle20of the nozzle numbers #2 Y to #9 Y can be determined as the used nozzle in the nozzle row26Y.

Note that in step S260, the control unit11determines the used nozzle so that the normal nozzle that complements the defective nozzle adjacent to the used nozzle of the minimum segment falls within the range of the used nozzle. In the example ofFIG.8, the K nozzle of the nozzle number #23K should be complemented by the K nozzle of the nozzle number #7K of the third nozzle range29. Thus, with respect to the nozzle row26Y, the control unit11determines the used nozzle so that the nozzles20of the nozzle number #7Y, which are adjacent to the nozzle number #7K, are included in the used nozzle. Further, in step S260, the control unit11determines the used nozzle so that the defective nozzle of the K nozzle does not fall within the range of the used nozzle as possible. In the example ofFIG.8, the K nozzle of the nozzle number #11K in the third nozzle range29is the defective nozzle, so that with regard to the nozzle row26Y, the control unit11may preferably determine the used nozzle separately from the nozzle20of the nozzle number #11Y that is adjacent to the nozzle number #11K.

When “No” is determined in step S240, no matter how many defective nozzles are included in the K nozzles corresponding to the other segments, those defective nozzles can be complemented with the K nozzles corresponding to the minimum segment. Therefore, in step S260of determining “No” in step S240and executing, when determining the used nozzle in each of the other segments, there is a low need to determine the used nozzle in consideration of the K nozzle as described above, and the degree of freedom of determination of the used nozzle is increased.

In step S270, the control unit11adopts the common transport amount determined in step S220, and performs printing based on the printing data by controlling the transport unit17, the carriage18, and the print head19using the used nozzle determined in each nozzle row26C,26M,26Y in steps S230and S260, and the K nozzle which is the normal nozzle adjacent to these used nozzles. According to this type of printing, the non-discharge of the ink by the defective nozzles is complemented by the normal nozzle, and a high-quality printing result is obtained in which there is no missing of the required dots on the printing medium30.

As illustrated inFIG.7, when the control unit11determines “No” in step S250, the control unit11returns to step S220. In step S220, returning from step S250, the common transport amount is adjusted. In step S220in this case, the control unit11determines a transport amount smaller than the common transport amount determined in the previous step S220as a common transport amount. In addition, the common transport amount is determined so that the paired nozzle of the defective nozzles does not occur in each of the nozzle rows26C,26M,26Y. The control unit11may determine the used nozzle having the minimum segment in step S230in accordance with the adjusted transport amount, and perform step S240and subsequent steps. In this way, in the flowchart ofFIG.7, the control unit11determines the common transport amount based on the complementary transport amount for each of the chromatic nozzle rows and the position of the defective nozzles in the non-chromatic nozzle row.

FIG.9is a diagram for describing step S270executed after step S260.FIG.9illustrates a vertical array head according to the chromatic nozzle row unit26U and the nozzle row26K as inFIG.8. In the nozzle rows26C and26Y illustrated inFIG.9, the used nozzle is determined. In the example ofFIG.9, 8 continuous normal nozzles of the nozzle numbers #3C to #10C in the nozzle row26C are the used nozzles. In addition, in the example ofFIG.9, in the nozzle row26Y, the 8 continuous normal nozzles of the nozzle numbers #3Y to #10Y are the used nozzles. Also, in each of the first nozzle range27, second nozzle range28, and third nozzle range29, the normal nozzle, which is the K nozzle adjacent to the used nozzle determined by the chromatic nozzle row, is determined to be the used nozzle in the nozzle row26K.

Further,FIG.9illustrates a part of the printing medium30transported downstream at the common transport amount F each time the pass ends by receiving ink discharge in accordance with the printing data in each pass such as passes P1, P2, P3, P4. Each rectangle in the printing medium30inFIG.9indicates each dot discharged from the nozzle20. Of course, the actual dots are not rectangular, but are illustrated here simply as rectangular. Additionally, inFIG.9, the dots for each KCMY ink can be identified by changing the concentration of the rectangle. In the actual printing, each dot in the KCMY ink overlaps in the printing medium30, but inFIG.9, the dots for each ink does not overlap and are shifted to the main scanning direction D1.

Attention is given to a region A in the printing medium30. According to the example ofFIG.9, in the first pass P1, dots of the K ink and dots of the C ink are discharged into the region A by the used nozzle of the K nozzles in the first nozzle range27and the used nozzle of the nozzle row26C. As a result, there is no missing dot in the C ink in the region A, and the printing medium30is paper-fed with the transport amount F and receives the pass P2in a state where there is no dot missing corresponding to the defective nozzle of the nozzle number #31K. In the pass P2, among the used nozzles in the nozzle row26M, the dots of the M ink are discharged into the region A by each of the nozzles20of the nozzle numbers #7M, #8M, #11M.

In the pass P3that has passed the paper feeding after the pass P2, among the used nozzles in the nozzle row26M, the dots of the M ink are discharged into the region A by each of the nozzles20of the nozzle numbers #1M, #2M, #4M to #6M. In other words, the pass P2and the pass P3complete the discharge of the M ink relative to the region A. At this time, ink non-discharge by the defective nozzle of the nozzle number #9M is complemented by the used nozzle of the nozzle number #1M, and ink non-discharge by the defective nozzle of the nozzle number #3M is complemented by the used nozzle of the nozzle number #11M.

In the pass P4that has passed the paper feeding after the pass P3, the dots of the K ink and the dots of the Y ink are discharged into the region A by the K nozzles of the nozzle number #7K of the third nozzle region29and the used nozzle of the nozzle row26Y. As a result, in the region A, the missing dot corresponding to the defective nozzle of the nozzle number #31K is filled, and all of the KCMY ink printing is completed. Needless to say, rather than focusing almost all of the timing of the pass P1as in the example ofFIG.9, discharge of the K ink to the region A may be distributed to each pass by using the used nozzles by the K nozzles in the second nozzle range28and the third nozzle range29.

Also, in the example ofFIG.9, the entire region A is filled with dots for each of the KCMY inks, but in practice, whether each used nozzle actually discharges dots depends on the contents of the printing data. In any case, according to the present exemplary embodiment, it is avoided that the dots specified as the printing data to be discharged are not discharged due to the defective nozzle and that the dots are missing in the printing result.

4. Summary

As described above, according to the present exemplary embodiment, the printing apparatus10includes the transport unit17configured to transport the printing medium30in the transport direction D2, the print head19including the nozzle row26at each of the plurality of nozzle row positions, the nozzle row26being constituted by the plurality of nozzles20configured to discharge ink onto the printing medium30, the scanning unit configured to move the print head19in the main scanning direction D1that intersects with the transport direction D2, the control unit11configured to control the transport unit17, the print head19, and the scanning unit, and the defective nozzle detection unit21configured to detect the defective nozzle failing to discharge ink from the plurality of nozzles20included in the print head19. Then, the printing apparatus10performs printing on the printing medium30by the combination of the transport by the transport unit17and the main scanning for discharging the ink by the print head19based on the printing data in association with the movement of the scanning unit. The control unit11is configured to calculate, based on a positional relationship between the defective nozzle and a normal nozzle that is not the defective nozzle included in the nozzle row26in the transport direction D2, a one-time transport amount by the transport unit17for each nozzle row26at each of the nozzle row positions, the one-time transport amount being a complementary transport amount at which non-discharge of ink by the defective nozzle is complementable by discharge of ink by the normal nozzle, based on a relationship between the main scanning before the transport and the main scanning after the transport, determine a common transport amount to the nozzle rows26at the respective nozzle row positions based on the complementary transport amount for each nozzle row26, and perform the printing by adopting the determined common transport amount as the one-time transport amount by the transport unit17.

According to this configuration, the control unit11calculates the complementary transport amount for each nozzle row26at each of the nozzle row positions, and determines the common transport amount to each nozzle row26based on the complementary transport amount thereof. This makes it easy to ensure a large transport amount as possible as a common transport amount. Therefore, an increase in the number of passes required for printing completion by limiting the range of the used nozzles can be suppressed as much as possible, and a decrease in the printing speed is easily avoided.

In particular, in the present exemplary embodiment, when the complementary transport amount is calculated for each nozzle row26at each of the nozzle row positions, the maximum complementary transport amount is calculated for each nozzle row26. Therefore, the common transport amount to each nozzle row26determined based on the complementary transport amount for each nozzle row26is also the largest possible transport amount, and it is possible to suppress an increase in the number of passes in a situation where printing is performed while complementing the defective nozzles with the normal nozzles.

In addition, according to the present exemplary embodiment, the print head19may be the horizontal array head or the vertical array head.

At the vertical array head, each chromatic nozzle row serving as each nozzle row at each of the plurality of chromatic inks is arranged along the transport direction D2, and the non-chromatic nozzle row corresponding to the non-chromatic ink is arranged side by side with the chromatic nozzle row in the main scanning direction D1.

Then, the control unit11may calculate the complementary transport amount for each chromatic nozzle row, and determine the common transport amount based on the complementary transport amount for each chromatic nozzle row and the position of the defective nozzles in the non-chromatic nozzle row.

According to the configuration, in the case where the vertical array head is used, it is possible to determine an appropriate transport amount that can complement or avoid ink non-discharge due to the defective nozzles in both the chromatic nozzle row and the non-chromatic nozzle row.

The present exemplary embodiment is not limited to the printing apparatus10and the system, and discloses inventions of various categories such as a method executed by the apparatus and the system and the program12for causing the processor to execute the method.

A printing method for performing printing on the printing medium30by the combination of the transport of the printing medium30in the transport direction D2and the main scanning for discharging ink by the print head19based on the printing data in association with the movement of the print head19in the main scanning direction D1that intersects with the transport direction D2, the print head19including the nozzle row26at each of the plurality of nozzle row positions, the nozzle row26being constituted by the plurality of nozzles20configured to discharge ink onto the printing medium,30the method including a defective nozzle detection step for detecting the defective nozzle failing to discharge ink from the plurality of nozzles20included in the print head19, a calculation step for calculating, based on a positional relationship between the defective nozzle and the normal nozzle that is not the defective nozzle included in the nozzle row in the transport direction D2, a one-time transport amount of the printing medium30for each nozzle row26at each of the nozzle row positions, the one-time transport amount being a complementary transport amount at which non-discharge of ink by the defective nozzle is complementable by discharge of ink by the normal nozzle, based on a relationship between the main scanning before the transport and the main scanning after the transport, a determination step for determining a common transport amount to the nozzle rows26at the respective nozzle row positions based on the complementary transport amount for each nozzle row26, and a printing step for performing the printing by adopting the determined common transport amount as the one-time transport amount. According to the above description, the defective nozzle detection step is performed by the defective nozzle detection unit21. Furthermore, step S110inFIG.3or step S210inFIG.7corresponds to the calculation step, and step S120and step S220correspond to the determination step, and step S140and step S270correspond to the printing step.

5. Other Exemplary Embodiments

The control unit11may cause the normal nozzle adjacent to the defective nozzle in the nozzle row26to discharge ink that complements at least part of the ink non-discharge by the defective nozzle. Such a process is referred to as neighbor complementation. The term “adjacent” referred to here means the neighbor in the transport direction D2. The control unit11may perform the neighbor complementation in step S140or step S270. As an example, attention is given to the defective nozzle of the nozzle number #2 in the nozzle row26C inFIG.5. According toFIG.5, in order to complement the non-discharge of ink by the defective nozzle, the control unit11assigns the printing data for one raster line to the normal nozzle of the nozzle number #10 of the nozzle row26C, which is the paired nozzle with the defective nozzle. At this time, the control unit11further assigns the printing data for discharging ink to the normal nozzle of the nozzle number #1 near the defective nozzle of the nozzle number #2, and the normal nozzle of the nozzle number #3.

The printing data that causes excess ink to be discharged is, in the example described above, data that causes a large amount of dots to be discharged than the raster line data originally assigned to each normal nozzle of the nozzle numbers #1, #3 of the nozzle row26C. By performing such neighbor complementation, non-discharge of the ink by the defective nozzle can be complemented by the plurality of normal nozzles as well as the normal nozzle that is the paired nozzle with the defective nozzle. Additionally, by using the combination of the neighbor complementation, the amount of ink discharged for the complementation of the defective nozzle can be reduced in the normal nozzle that is the paired nozzle with the defective nozzle.

The control unit11may be configured to cause, in the nozzle row26, a plurality of the normal nozzles to perform overlap printing of a common raster line to the main scanning before the transport and the main scanning after the transport, the plurality of the normal nozzles being in a positional relationship in which the plurality of the normal nozzles are configured to perform printing of the common raster line extending in the main scanning direction D1and configured to constitute the printing data. As is known, overlap printing is a process in which one raster line is shared and printed with the plurality of nozzles20. The control unit11may perform the overlap printing in step S140and step S270. The plurality of the normal nozzles being in a positional relationship in which the plurality of the normal nozzles are configured to perform printing of the common raster line, are the paired nozzles of the normal nozzles, as illustrated in the previous description.

For example, the normal nozzle of the nozzle number #10 (#10M) and the normal nozzle of the nozzle number #2 (#2M) in the nozzle row26M form the paired nozzle. Also, for example, in the nozzle row K inFIG.5, the normal nozzles of the nozzle numbers #9, #1, the normal nozzles of the nozzle numbers #10, #2, the normal nozzles of the nozzle numbers #11, #3, and the normal nozzle of the nozzle numbers #12, #4 respectively form the paired nozzles. With respect to such a paired nozzle, the control unit11performs overlap printing by assigning data of some pixels out of data of the plurality of pixels constituting the raster line for allocation to the pair of used nozzles to the normal nozzles that have been used as the unused nozzles in the previous description.

In the overlap printing, the allocation ratio of pixels in the raster line to two normal nozzles forming the paired nozzle may not be 50% to 50%, for example 20% to 80%, 60% to 40%, etc. In addition, the control unit11may have such an allocation ratio different for each raster line to be overlap-printed. By making the allocation ratio different from each raster line to be overlap-printed, the image quality can be improved by ensuring gradation in a region where the raster lines to be overlap-printed are continuous in the transport direction D2.

Note that the complementation of the defective nozzle by the normal nozzle does not need to be executed if it is not necessary to discharge the ink with the defective nozzle.

Thus, the control unit11is configured to perform the printing by adopting a common transport amount based on the complementary transport amount as a one-time transport amount by the transport unit17, when a raster line assigned to the defective nozzle includes data of ink to be discharged, the raster line extending in the main scanning direction D1and configured to constitute the printing data. On the other hand, the control unit11may be configured to perform the printing by adopting a transport amount at which non-discharge of ink by the defective nozzle cannot be complemented by discharging ink by the normal nozzle as the one-time transport amount by the transport unit17, the transport amount being greater than a common transport amount based on the complementary transport amount, when a raster line assigned to the defective nozzle does not include data of ink to be discharged.

FIG.10is a representation similar to that illustrated inFIG.5to indicate that the relative positions of the nozzle rows26C,26M,26Y,26K in the transport direction D2and the printing medium30vary for each pass. Also, inFIG.10, part of the printing data40is also illustrated together. The individual rectangles constituting the printing data40are individual pixels, each pixel having dot on data and dot off data for each CMYK ink.

InFIG.10, a transport amount F0corresponds to the length of the nozzle row26, and is greatest as the one-time paper feeding amount. The transport amount F0is an example of a transport amount that cannot complement the ink non-discharge by the defective nozzles due to the discharge of the ink of the normal nozzle, and is an example of a transport amount greater than the common transport amount F determined in step S120or step S220. The control unit11is configured to analyze the printing data, and determine whether the raster line assigned to the defective nozzle does not have the data of ink to be discharged if the transport amount F0is adopted as the paper feeding amount.

In the printing data40, a raster line formed from a pixel that describes “0” is a raster line that does not have dot on data. In a case where the raster line assigned to each of the defective nozzles is a raster line that does not have dot on data when the paper feeding amount between the pass P1and the pass P2is set as the transport amount F0as illustrated inFIG.10, in actual printing, the control unit11may set the paper feeding amount between the pass P1and the pass P2to the transport amount F0. By adopting the transport amount F0, the number of passes required for completion of printing can be reduced, and the printing speed can be improved. In the example ofFIG.10, the raster line assigned to the defective nozzle when the paper feeding amount between the pass P2and the pass3is the transport amount F0is the raster line having the dot on data, so that the paper feeding amount between the pass P2and the pass P3is the common transport amount F described above.

Such control of the transport amount is also possible in the vertical array head of the second exemplary embodiment. In the vertical array head, the individual lengths of the nozzle rows26C,26M,26Y constituting the chromatic nozzle row unit26U are the maximum value of the one-time paper feeding amount. Accordingly, when the control unit11executes paper feeding between passes with such maximum paper feeding amount, in a case where the raster line assigned to the defective nozzle is a raster line that does not have dot on data, the control unit11may adopt this maximum paper feeding amount in actual printing.

Further, the control of the transport amount can be performed in accordance with a correspondence relationship between the defective nozzles and the printing data at each nozzle row position. Referring toFIG.10, it is assumed, for example, that the raster line assigned to the nozzle20of the nozzle number #9 in the pass P1is data that defines the dot for the CYK ink, but does not define the dots of the M ink in all the pixels. In addition, it is assumed that the raster line assigned to the nozzle20of the nozzle number #11 in the pass P1is data that defines a dot for the C ink. In this case, in the relationship between the pass P1and the pass P2, the paper feeding to complement the defective nozzle of the nozzle number #9 of the nozzle row26M by the normal nozzle is not required, but the paper feeding to complement the defective nozzle of the nozzle number #11 of the nozzle row26C is required. Therefore, in accordance with the contents of the printing data, the control unit11may determine the transport amount that can complement the defective nozzle that needs to be complemented by the normal nozzle for each of the passes, and may adopt it in actual printing.