Printing apparatus

A printing apparatus includes a first head that forms a first dot group and a second head that forms a second dot group. The first head has a first nozzle row for a first chromatic ink and a second nozzle row for a second chromatic ink. The second head has a third nozzle row for the first chromatic ink and a fourth nozzle row for the second chromatic ink. With respect to at least the first chromatic ink or the second chromatic ink, in a case in which the number of dots that configure dot rows that are lined up in the main scanning direction, is 3500 or more, a rational number, which is expressed using a number of dots included in the first dot group and a number of dots included in the second dot group in the dot rows, is a value other than zero.

BACKGROUND

1. Technical Field

The present invention relates to a printing apparatus.

2. Related Art

Ink jet printers that form images configured by groups of ink dots on a print medium by moving a print head that has a plurality of nozzles along a main scanning direction while discharging ink from each nozzle by driving an actuator provided to correspond to each nozzle of the print head are in widespread use.

In ink jet printers, the components for an ink discharge operation such as the nozzle actuator are driven in a period in which the ink discharge operation (image formation operation) from nozzles is executed, and the components and a drive circuit generate heat. Therefore, in a case in which printing is performed at a relatively high resolution on a relatively large print medium (for example, a case in which printing is performed at a resolution of 300 dpi or more on an A3 or larger print medium), there are cases in which excessive loads are applied to the components for the ink discharge operation and the component life is shortened and those in which the amount of heat per unit time is excessive and deteriorations in image quality, which accompany damage to the components and the destabilization of discharge, occur. Conventionally, a technology which detects the temperature of the print head, and stops a print operation in a case in which it seems likely that the temperature of the print head will exceed an upper temperature limit at which correct operation is guaranteed, is known (for example, refer to JP A-2003-341054).

In the abovementioned technology of the related art, although it is possible to prevent the occurrence of a state in which the temperature of the print head exceeds an upper temperature limit, depending on the print resolution and the size of the print medium, there are case in which the print operation is stopped before the formation of images on the print medium is completed, and there is a problem in which the convenience for a user is decreased.

Additionally, this kind of problem is not limited to printing using an ink jet method, but is a problem that is common to printing which forms images on a print medium while moving a print head along a predetermined main scanning direction.

SUMMARY

The invention can be realized in the following forms or application examples.

Application Example 1

According to Application Example 1, there is provided a printing apparatus that is provided with a first head that has a first nozzle row that is configured from a plurality of nozzles that discharge a first chromatic ink and a second nozzle row that is configured from a plurality of nozzles that discharge a second chromatic ink, and forms a first dot group on a print medium by moving along a guide member in a main scanning direction and discharging ink using at least the first nozzle row or the second nozzle row, a second head that is different from the first head, has a third nozzle row that is configured from a plurality of nozzles that discharge the first chromatic ink and a fourth nozzle row that is configured from a plurality of nozzles that discharge the second chromatic ink, and forms a second dot group on the print medium by moving along the guide member in the main scanning direction and discharging ink using at least the third nozzle row or the fourth nozzle row, and a transport mechanism that performs a sub-scan that moves the print medium relatively with respect to the guide member in a sub-scanning direction that intersects the main scanning direction, in which a first straight line, which links a central point of a first line segment that links the nozzles of both ends of the first nozzle row and a central point of a second line segment that links the nozzles of both ends of the second nozzle row, crosses a third line segment that links the nozzles of both ends of the third nozzle row and a fourth line segment that links the nozzles of both ends of the fourth nozzle row, and with respect to at least the first chromatic ink or the second chromatic ink, in a case in which the number of dots that configure dot rows that are lined up in the main scanning direction, which are formed as a result of ink discharge executed between a sub-scan and a subsequent sub-scan, is 3500 or more, a rational number, which is expressed using a number of dots included in the first dot group and a number of dots included in the second dot group in the dot rows, is a value other than zero. In this printing apparatus, in addition to being able to realize image formation on the entire print medium while avoiding situations in which the amount of heat per unit time is excessive and deteriorations in image quality, which accompany damage to the components and the destabilization of discharge, occur irrespective of the contents of target images for printing and the size of the print medium, it is possible to prolong component life since the application of excessive loads to the components for the ink discharge operation is avoided.

Application Example 2

In the printing apparatus according to Application Example 1, a second straight line, which links a central point of the third line segment and a central point of the fourth line segment, crosses the first line segment and the second line segment. In this printing apparatus, since it is possible to execute the print process using 75% or more of the nozzles that configure each nozzle row provided in each print head in a case in which the number of dots that configure dot rows that are lined up in the main scanning direction, which are formed as a result of ink discharge executed between a sub-scan and a subsequent sub-scan, is 3500 or more, it is possible to effectively suppress increases in the time required for the print process.

Application Example 3

In the printing apparatus according to Application Example 1 or 2, the distance between an intersection of the first straight line and the third line segment and the central point of the third line segment is shorter than the distance between the intersection and an end point on the near side of the third line segment. In this printing apparatus, since it is possible to execute the print process using 50% or more of the nozzles that configure each nozzle row provided in each print head in a case in which the number of dots that configure dot rows that are lined up in the main scanning direction, which are formed as a result of ink discharge executed between a sub-scan and a subsequent sub-scan, is 3500 or more, it is possible to suppress increases in the time required for the print process.

Application Example 4

In the printing apparatus according to any one of Application Examples 1 to 3, in a case in which the number of dots that configure dot rows that are lined up in the main scanning direction, which are formed as a result of ink discharge executed between a sub-scan and a subsequent sub-scan, is below 3500, among the dots that configure the dot rows, either a number of dots included in the first dot group or a number of dots included in the second dot group is zero. In this printing apparatus, the print process is simplified and it is possible to realize improvements in the speed of the process and the image quality thereof in cases in which the number of dots that configure dot rows that are lined up in the main scanning direction, which are formed as a result of ink discharge executed between a sub-scan and a subsequent sub-scan, is below 3500.

Application Example 5

In the printing apparatus according to any one of Application Examples 1 to 4, in a case in which the number of dots that configure dot rows that are lined up in the main scanning direction, which are formed as a result of ink discharge executed between a sub-scan and a subsequent sub-scan, is 3500 or more, the ink discharge of the first head and the ink discharge of the second head are executed alternately. In this printing apparatus, it is possible to adopt a simple configuration in which two print heads are mounted in one carriage.

Application Example 6

In the printing apparatus of any one of Application Examples 1 to 4, in a case in which the number of dots that configure dot rows that are lined up in the main scanning direction, which are formed as a result of ink discharge executed between a single sub-scan and a subsequent single sub-scan, is 3500 or more, the ink discharge of the first head and the ink discharge of the second head are executed simultaneously. In this printing apparatus, it is possible to achieve an increase in the speed of the print process.

Additionally, it is possible to realize the invention in various aspects, and for example, the invention can be realized in forms such as a printing method and a printing apparatus, a control method of a printing apparatus and a control apparatus, a computer program for realizing these methods or the functions of these apparatuses, a recordable medium on which the abovementioned computer program is recorded.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Next, aspects of the invention will be described in the following order on the basis of embodiments.A. First EmbodimentA-1. Configuration of the Printing ApparatusA-2. Printing ProcessB. Second EmbodimentC. Modification Examples

A. First Embodiment

A-1. Configuration of the Printing Apparatus

FIG. 1is an explanatory drawing that shows a schematic configuration of a printing apparatus100in the first embodiment of the invention. The printing apparatus100of the present embodiment is an ink jet printer that forms ink dot groups on a print medium PM by discharging ink, and as a result of this, prints images (including characters, diagrams and the like) depending on image data ID supplied from a host computer200.

As shown inFIG. 1, the printing apparatus100is provided with a carriage130in which two print heads140(a first print head140A and a second print head140B) are mounted, a movement mechanism that causes the carriage130to reciprocate along a direction (main scanning direction) that is parallel to the axis of a platen176, a transport mechanism that performs a sub-scan that transports the print medium PM in a direction (sub-scanning direction) that is orthogonal to the main scanning direction, an operation panel104that receives various instructions and setting operations that are related to printing, and a control unit110that controls each section of the printing apparatus100. The carriage130that has the print heads140is connected to the control unit110through a flexible flat cable (FFC) which is not shown in the drawing. Additionally, provided the sub-scanning direction is a direction that intersects the main scanning direction, the sub-scanning direction need not necessarily be a direction that is orthogonal to the main scanning direction. In the following description, there are cases in which the first print head140A and the second print head140B are referred to collectively as the print heads140.

The transport mechanism that transports the print medium PM has a paper transfer motor172. The rotation of the paper transfer motor172is transmitted to a print medium transport roller (not shown in the drawing) via a gear train (also not shown in the drawing), and the print medium PM is transported along the sub-scanning direction as a result of the rotation of the print medium transport roller. Additionally, as a sub-scan, a sliding axis (guide member)134may be moved in the sub-scanning direction in place of the print medium PM being transported, or in addition to the print medium PM being transported. That is, a sub-scan is an operation that moves the print medium PM relatively with respect to the sliding axis (guide member)134in the sub-scanning direction.

The movement mechanism that reciprocates the carriage130along the main scanning direction has a carriage motor132, the sliding axis (guide member)134that is installed parallel to the axis of the platen176(that is, in the main scanning direction) and slidably retains the carriage130, and a pulley138on which an endless drive belt136is stretched between the carriage motor132and the pulley138. The rotation of the carriage motor132is transmitted to the carriage130through the drive belt136, and as a result of this, the carriage130in which the two print heads140are mounted reciprocates along the sliding axis134. In addition, the movement mechanism that reciprocates the carriage130controls the rotation of the carriage motor132, and it is possible to stop the carriage130at a desired position along the main scanning direction. Hereinafter, one direction along the main scanning direction (a direction of moving from the home position of the carriage130toward the opposite side) is also referred to as a main scanning travel direction and the other direction (the opposite direction to the main scanning travel direction) is also referred to as the main scanning return direction. Additionally, in order to detect the position along the main scanning direction of the carriage130, the printing apparatus100is provided with an encoder (not shown in the drawing) that outputs a pulsed signal that accompanies the rotation of the carriage motor132to the control unit110. The control unit110generates a timing signal PTS, which defines the input timing of drive signal selection signals SI and SP to a shift register162that will be described later, on the basis of the pulsed signal output from the encoder.

A set of ink cartridges102, in which ink of predetermined colors (for example, cyan (C), magenta (M), yellow (Y) and black (K)) is respectively accommodated, are detachably mounted to the carriage130. The ink that is accommodated in the set of ink cartridges102mounted to the carriage130is supplied to the first print head140A and the second print head140B.

Since the first print head140A and the second print head140B are mounted to the carriage130, the first print head140A and the second print head140B reciprocate along the main scanning direction in a state that accompanies the movement of the carriage130and in which the positional relationship thereof is fixed.

Each print head140has a plurality of nozzles152that discharge ink at a surface (nozzle formation surface) that faces the platen176.FIGS. 2A and 2Bare explanatory drawings that show the configuration of a nozzle formation surface of each print head140. As shown inFIG. 2A, the plurality of nozzles152are formed in the respective nozzle formation surfaces of the first print head140A and the second print head140B. In the respective print heads140, the plurality of nozzles152configure a plurality of nozzle rows154(cyan nozzle row, magenta nozzle row, yellow nozzle row and black nozzle row) that are lined up along the main scanning direction. Each nozzle row154is configured from a plurality of nozzles152that are disposed lined up along the sub-scanning direction. Additionally, it is not necessary for the plurality of nozzles152that configure each nozzle row154to be disposed lined up in linear form along the sub-scanning direction, and for example, the foregoing may be disposed lined up in a zigzag form along the sub-scanning direction.

One ink (for example, set as cyan ink in this instance) from among the cyan ink, magenta ink and yellow ink in the embodiment corresponds to the first chromatic ink in the claims and a different ink (for example, set as magenta ink in this instance) from among the cyan ink, magenta ink and yellow ink corresponds to the second chromatic ink in the claims. In addition, a nozzle row154for the ink (cyan ink) that corresponds to the abovementioned first chromatic ink in the first print head140A corresponds to the first nozzle row in the claims, a nozzle row154for the ink (magenta ink) that corresponds to the abovementioned second chromatic ink in the first print head140A corresponds to the second nozzle row in the claims, a nozzle row154for the ink (cyan ink) that corresponds to the abovementioned first chromatic ink in the second print head140B corresponds to the third nozzle row in the claims, and a nozzle row154for the ink (magenta ink) that corresponds to the abovementioned second chromatic ink in the second print head140B corresponds to the fourth nozzle row in the claims.

In the embodiment, the positions along the sub-scanning direction of each nozzle row154are the same in each print head140. That is, in each print head140, the positions of each nozzle row154overlap in the main scanning direction. In addition, in the embodiment, the positions along the sub-scanning direction of each nozzle row154of the first print head140A and the positions along the sub-scanning direction of each nozzle row154of the second print head140B are the same. That is, in the embodiment the positions along the sub-scanning direction of all of the nozzle rows154formed on the two print heads140are the same. Therefore, in the embodiment, as shown inFIG. 2B, a first straight line SL1, which links a central point MP1of a first line segment LS1that links the nozzles152of both ends of the first nozzle row (set as the cyan ink nozzle row154of the first print head140A in this instance) and a central point MP2of a second line segment LS2that links the nozzles152of both ends of the second nozzle row (set as the magenta ink nozzle row154of the first print head140A in this instance), crosses a third line segment LS3that links the nozzles152of both ends of the third nozzle row (set as the cyan ink nozzle row154of the second print head140B in this instance) and a fourth line segment LS4that links the nozzles152of both ends of the fourth nozzle row (set as the magenta ink nozzle row154of the second print head140B in this instance). In addition, the second straight line SL2, which links a central point MP3of the third line segment LS3and a central point MP4of the fourth line segment LS4, crosses the first line segment LS1and the second line segment LS2. Furthermore, the distance (=zero) between an intersection IP3of the first straight line SL1and the third line segment LS3and the central point MP3of the third line segment LS3is shorter than the distance (=half the length of the third line segment LS3) between the intersection IP3and an end point on the near side of the third line segment LS3.

In addition, each print head140has a nozzle actuator156(refer toFIGS. 3 and 5) that is provided to correspond to each nozzle152. In the embodiment, a piezoelectric element that is a capacitive load may be used as the nozzle actuator156. When a nozzle actuator156is driven by a drive signal that will be described later, a vibration plate inside a cavity (pressure chamber) that communicates with a nozzle152is displaced giving rise to a change in the pressure inside the cavity, and ink is discharged from the corresponding nozzle152as a result of this change in pressure. By adjusting the peak value and the degree of the increase and decrease in voltage inclination of the drive signal used to drive the nozzle actuator156, it is possible to adjust the amount of the ink discharge (that is, the size of dot that is formed). Images are formed on the print medium PM by ink being discharged from the nozzles152of each print head140. Additionally, since the printing apparatus100is an ink jet printer that forms ink dot groups on a print medium PM by discharging ink and prints images as a result of this, it is also possible to refer to an “image” as an “ink dot group”. A dot group formed by the first print head140A in the embodiment corresponds to the first dot group in the claims and a dot group formed by the second print head140B in the embodiment corresponds to the second dot group in the claims.

FIG. 3is an explanatory drawing that shows a schematic configuration of the printing apparatus100focusing on the control unit110and print heads140. The control unit110has a host interface (IF)112for the input of image data ID or the like from the host computer200, a main control section120that executes a predetermined calculation process for the printing of images on the basis of the image data ID input through the host interface112, a paper transfer motor driver114that controls the driving of the paper transfer motor172, a head driver116that controls the driving of each print head140, a carriage motor driver118that controls the driving of the carriage motor132and a main interface (IF)119that is respectively connected to each driver114,116and118, the paper transfer motor172, the print heads140and the carriage motor132.

The main control section120includes a CPU122that executes various calculation processes, a RAM124that temporarily stores and deploys programs and data, and a ROM126that stores programs and the like that the CPU122executes. The various functions of the main control section120are realized by the CPU122reading and executing the programs stored in the ROM126in the RAM124. Additionally, the main control section120may be provided with an electric circuit, at least a portion of the functions of the main control section120may be realized through the electric circuit with which the main control section120is provided operating on the basis of the circuit configuration thereof.

When image data ID from the host computer200is acquired through the host interface112, the main control section120generates nozzle selection data (drive signal selection data), which defines whether or not to discharge ink and the amount of ink to discharge from a certain nozzle152of each print head140, by performing calculation processes for printing execution such as an image development process, a color conversion process, an ink color classification process and a halftone process on the basis of the image data ID, and outputs control signals to each driver114,116and118on the basis of the drive signal selection data and the like. Additionally, since the contents of the various calculation processes for printing execution that the main control section120executes are well-known matters in the technical field of printing apparatuses, the description thereof has been omitted. Each driver114,116and118outputs drive signals for respectively driving the paper transfer motor172, each print head140and the carriage motor132. For example, the head driver116supplies a reference clock signal SCK, a latch signal LAT, drive signal selection signals SI and SP, a channel signal CH and a drive signal COM that will be described later to each print head140. Each print head140(the first print head140A and the second print head140B) has a head interface (IF)142, a thermistor144that detects the temperature of the print head140, a head control section146that is configured from an electric circuit, the abovementioned plurality of nozzles152and a nozzle actuator156that drives the nozzles152. The head control section146includes a switch controller160and a discharge limiting section169. Ink discharge from the nozzles152is executed by the switch controller160operating on the basis of the various signals input from the control unit110through the head interface142. Additionally, either a portion of or all of the functions of the head control section146may be realized using software. The paper transfer motor172and the carriage motor132operate depending on the drive signal supplied from the control unit110. As a result of this, a print process that forms images on the print medium PM is realized.

FIG. 4is an explanatory drawing that shows an example of various signals that are supplied to each print head140. The drive signal COM is for driving the nozzle actuators156provided in each print head140. The drive signal COM is a signal in which drive pulses PCOM (drive pulses PCOM1to PCOM4) are continued in time series as the minimum units (unit drive signals) of the drive signal that drives the nozzle actuators156. The set of the four drive pulses PCOM from the drive pulse PCOM1to PCOM4correspond to one pixel (printing pixel).

Each drive pulse PCOM is configured by a voltage trapezoidal wave. The rise of each drive pulse PCOM increases the capacity of the cavity that communicates with the nozzle152and draws ink in (it could be said that the meniscus is drawn in if considered in terms of the discharge surface of the ink), and the fall of each drive pulse PCOM decreases the capacity of the cavity and pushes ink out (it could be said that the meniscus is pushed out if considered in terms of the discharge surface of the ink). Therefore, ink is discharged from the nozzles152by driving the nozzle actuator156according to the drive pulses PCOM.

In the drive signal COM, the waveforms (the degrees of the increase and decrease in voltage inclination and the peak values) of the drive pulses PCOM2to PCOM4are mutually different. When the waveforms of the drive pulses PCOM that are supplied to the nozzle actuators156are different, the amount by which the ink is drawn in and the speed thereof and the amount by which the ink is pushed out and the speed thereof differ, and the amount of the ink discharge (that is, the size of an ink dot) differs as a result thereof. By selecting either one or a plurality of drive pulses PCOM from among the drive pulses PCOM2to PCOM4and supplying the selected drive pulses to the nozzle actuators156, it is possible to form ink dots of various sizes. Additionally, in the embodiment, the drive pulse PCOM1, which is referred to as a fine vibration, is included in the drive signal COM. The drive pulse PCOM1is used in cases in which ink is only drawn in and not pushed out, for example, a case of suppressing nozzle thickening.

The drive signal selection signals SI and SP determine the connection timing of the nozzle actuators156to the drive signal COM in addition to selecting the nozzles152that discharge ink. The latch signal LAT and the channel signal CH connect the drive signal COM and the nozzle actuators156of each print head140on the basis of the drive signal selection signals SI and SP after nozzle selection data has been input for all of the nozzles152. As shown inFIG. 3, the latch signal LAT and the channel signal CH is synchronized with the drive signal COM. That is, the latch signal LAT becomes a high level in correspondence with the start timing of the drive signal COM, and the channel signal CH becomes a high level in correspondence with the start timing of each drive pulse PCOM that configures the drive signal COM. The output of a successive the drive signal COM is started depending on the latch signal LAT, and each drive pulse PCOM is output depending on the channel signal CH. In addition, the reference clock signal SCK sends the drive signal selection signals SI and SP to each print head140as serial signals. That is, the reference clock signal SCK is used in the determination of the timing with which ink is discharged from the nozzles152of each print head140.

FIG. 5is an explanatory drawing that shows the configuration of a switching controller160of each print head140. The switch controller160is assembled inside the head control section146of each print head140in order to supply the drive signals COM (drive pulses PCOM) to the nozzle actuators156. The switch controller160has a shift register162that saves the drive signal selection signals SI and SP, a latch circuit164that temporarily saves the data of the shift register162, a level shifter166that level converts the output of the latch circuit164and supplies the converted output to a selection switch168and the selection switch168that connects the drive signal COM to the nozzle actuators156.

The drive signal selection signals SI and SP are sequentially input to the shift register162, and the area in which the drive signal selection signals SI and SP are stored is sequentially shifted to a subsequent stage depending on the input pulse of the reference clock signal SCK. Additionally, the input of the drive signal selection signals SI and SP to the shift register162is executed in accordance with the abovementioned timing signal PTS. The latch circuit164latches each output signal of the shift register162in accordance with the input latch signal LAT after drive signal selection signals SI and SP equal to the number of nozzles have been stored in the shift register162. The signal saved in the latch circuit164is converted into a voltage level that can switch (on/off) the selection switch168of the next stage by the level shifter166. A nozzle actuator156that corresponds to a selection switch168that is closed (enters a connected state) by the output signal of the level shifter166is connected to the drive signal COM (drive pulses PCOM) using the connection timing of the drive signal selection signals SI and SP. In addition, after the drive signal selection signals SI and SP that are input into the shift register162have been latched by the latch circuit164, subsequent drive signal selection signals SI and SP are input into the shift register162, and the save data of the latch circuit164is sequentially updated in conformity with the timing of ink discharge. According to this selection switch168, even after the nozzle actuator156has been isolated from the drive signal COM (drive pulses PCOM), the input voltage of the nozzle actuator156is retained as a voltage immediately before isolation. Additionally, the symbol HGND inFIG. 5is a ground end of the nozzle actuator156.

As described above, the print heads140have a thermistor144(FIG. 3) that detects the temperature of the print heads140, and the discharge limiting section169of the head control section146limits the ink discharge operation from the nozzles152on the basis of the temperature detected by the thermistor144.FIG. 6is an explanatory drawing that shows the relationship between the ink discharge operation of the print head140and the temperature T of the print head140on a conceptual basis. InFIG. 6, the relationship between the distance L from a starting position to the position of the carriage130and the temperature T of the first print head140A in a case in which the ink discharge operation is continuously executed at a specific print resolution Rp (a print resolution Rp1or a print resolution Rp2that is lower that the print resolution Rp1) while moving the carriage130in which the first print head140A is mounted along the main scanning direction from one end (starting position) of the print medium PM toward the other end (a case in which the ink discharge operation is executed in all of the printing pixels established by the print resolution Rp), is shown on a conceptual basis. During periods in which the ink discharge operation from the nozzles152is being executed, the temperature of the first print head140A rises as a result of heat being generated from the various elements and drive circuits including the nozzle actuators156. Therefore, as shown inFIG. 6, from an initial temperature Ti of the starting position (a normal temperature when a sufficient amount of time has passed since the completion of the ink discharge operation), the temperature of the first print head140A rises as the distance L, which the ink discharge operation has been continuously executed for, increases. On the other hand, during periods in which the ink discharge operation is not being executed, the temperature of the first print head140A falls toward the initial temperature Ti. In a case in which the movement speed of the carriage130is fixed so that the gradient of a straight line that corresponds to the print resolution Rp1is greater than the gradient of a straight line that corresponds to the print resolution Rp2as inFIG. 6, the ratio of the increase in temperature T to distance L increases by the extent to which the print resolution Rp is a high resolution. Additionally, in the embodiment, since the first print head140A and the second print head140B are the same (same model number) print head, the temperature characteristics of the second print head140B are also the same as the characteristics shown inFIG. 6. In addition, inFIG. 6, the relationship between the distance L and the temperature T is conveniently expressed in linear form, but the relationship between the distance L and the temperature T differs as a result of the configuration of the print heads140and the movement speed of the carriage130, and thus there are cases in which the relationship cannot necessarily be expressed in linear form.

In the embodiment, an upper temperature limit Tth, at which correct operation of the print heads140is guaranteed, is set in advance. The upper temperature limit Tth is determined on the basis of the heatproof temperatures of each component (each element and circuit) that configures the print heads140, the heatproof temperatures of the adhesives that are used in the assembly of each component and the like. The discharge limiting section169(FIG. 3) of the print heads140limits the ink discharge operation from the nozzles152so that the temperature of the print heads140does not exceed the upper temperature limit Tth. More specifically, when the temperature of the print heads140that is detected by the thermistor144reaches the upper temperature limit Tth, the discharge limiting section169changes the drive signal selection signals SI and SP, which are supplied from the control unit110and select the ink discharge nozzles, to signals that represent that ink should not be discharged from any of the nozzles. As a result of this, regardless of the contents of the drive signal selection signals SI and SP that are supplied from the control unit110, the ink discharge operation from the nozzles152is stopped, and the temperature of the print heads140falls. After the limiting of the ink discharge operation has started, when the temperature of the print heads140that is detected by the thermistor144has fallen to a predetermined recovery temperature Tr (FIG. 6), the discharge limiting section169releases the limiting of the ink discharge operation. The recovery temperature Tr is set in advance to be in a range that is greater than or equal to the initial temperature Ti and less than the upper temperature limit Tth. The recovery temperature Tr may be the same as the initial temperature Ti. As a result of the ink discharge operation limitation according to this kind of discharge limiting section169, it is possible to avoid the occurrence of breakdowns that result from excessive temperature increases of the print heads140and printing defects which accompany the destabilization of ink discharge. In addition, it is possible to avoid situations in which the loads that are applied to the components for the discharge operation such as the nozzle actuators156are excessive, and shortening of the component life is suppressed. Additionally, the ink discharge operation limitation according to the discharge limiting section169need not necessarily be executed according to a method that uses the temperature detection result of the thermistor144, and may be executed according to any other method provided it is a method that avoids an ink discharge operation in which the temperature of the print heads140exceeds the upper temperature limit Tth.

A-2. Printing Process

FIG. 7is a flowchart that shows the flow of a print process of the printing apparatus100. The print process of the printing apparatus100forms images depending on image data ID on a print medium PM on the basis of image data ID input from the host computer200under the control of the main control section120.

Firstly, the main control section120(FIG. 3) of the printing apparatus100acquires the print resolution Rp at the time of the print process (Step S110) in addition to acquiring a width Wm along the main scanning direction of the print medium PM to be used in the print process (Step S112). The print resolution Rp and the print medium width Wm are acquired on the basis of information included in a print instruction of the host computer200.

Next, the main control section120calculates a maximum number of dots Nd of one raster (a dot row configured by a plurality of dots lined up along the main scanning direction) (Step S114). The maximum number of dots Nd is, with respect to each ink color, the number of dots that configure one raster that is formed in a case in which a dot is formed in all of the print pixels along the main scanning direction. In the embodiment, since the print resolution Rp is set as the same value for each ink color, the maximum number of dots Nd for each of the ink colors is the same, and is calculated by multiplying the print resolution Rp by the print medium width Wm. For example, in a case in which the size of the print medium PM is A3 (a width of approximately 11.69 inches) and the print resolution Rp is 300 dpi, the maximum number of dots Nd is 11.69×300=approximately 3507 dots. In cases in which the maximum number of dots Nd is large due to the size of the print medium PM being large or the print resolution Rp being a high resolution, when a raster is formed using one print head140, depending on the image data ID, there is a concern that the temperature of the print head140will reach the upper temperature limit Tth.

Next, the main control section120determines whether or not the calculated maximum number of dots Nd is greater than or equal to a predetermined threshold value Tn (Step S120). The threshold value Tn is set as a value that is smaller than the number of dots that it takes for the temperature of the print head140to reach the upper temperature limit Tth in a case in which a raster is formed by continuously discharging ink along the main scanning direction from the nozzles152of one print head140while moving the carriage130at a predetermined speed. In the embodiment, the threshold value Tn is 3500, and thus is a value that is slightly less than the maximum number of dots Nd in a case in which the size of the print medium PM is A3 and the print resolution Rp is 300 dpi (approximately 3507).

In a case in which the maximum number of dots Nd is below the threshold value Tn (Step S120: NO), even if a raster is formed using the nozzles152of one print head140, the temperature of the print heads140does not reach the upper temperature limit Tth. In this case, the main control section120executes a normal print process (Step S130). For example, in a case in which the size of the print medium PM is A4 (a width of approximately 8.27 inches) and the print resolution Rp is 300 dpi or a case in which the size of the print medium PM is A3 and the print resolution Rp is 150 dpi, since the maximum number of dots Nd is below the threshold value Tn, a normal print process is performed.

A normal print process is a process in which images depending on image data ID are printed on the print medium PM by repeating an operation of forming images on the print medium PM by executing an ink discharge operation depending on image data ID using the first print head140A while continuously moving the carriage130in the main scanning travel direction (main scan), a home position return operation of moving the carriage130to the home position in the main scanning return direction without performing ink discharge, and a transport operation of the print medium PM in the sub-scanning direction (sub-scan). In the normal print process, an ink discharge operation (image formation operation) using the second print head140B is not executed. Therefore, all of the plurality of dots that configure each raster (dot row) in images formed using the normal print process are formed by the first print head140A, and dots formed by the second print head140B are not included. That is, in each raster, the number of dots that are included in the second dot group is zero.

Additionally, in the normal print process of the embodiment, image formation on a unit band area (an area with a width along the main scanning direction that is the entire width Wm of the print medium PM and a length along the sub-scanning direction that is the length of the nozzle row of the print head140) is completed in a single image formation operation. Therefore, the transport amount of the print medium PM in the sub-scanning direction is an amount that is equal to the length of the nozzle row.

As described above, since the threshold value Tn is set as a value that is smaller than the number of dots that it takes for the temperature of the print head140to reach the upper temperature limit Tth in a case in which dots are formed continuously along the main scanning direction using one print head140, in a case in which the maximum number of dots Nd is below the threshold value Tn, even if the image formation operation is performed using the first print head140A while continuously moving the carriage130in the main scanning travel direction across the entire print medium width Wm, the temperature of the first print head140A does not reach the upper temperature limit Tth. In addition, since the ink discharge operation is not performed in periods in which the home position return operation and the transport operation are executed, the temperature of the first print head140A falls. Therefore, even if a normal print process such as that described above is performed, it is possible to complete image formation on the entire print medium PM while avoiding the occurrence of a situation in which the temperature of the first print head140A exceeds the upper temperature limit Tth.

On the other hand, in a case in which the maximum number of dots Nd is greater than or equal to the threshold value Tn (Step S120: YES), there is a concern that, depending on image data ID, the temperature of the print head140will reach the upper temperature limit Tth if a raster is formed using the nozzles152of one print head140. In this case, the main control section120executes a divided print process (Step S140).FIG. 8is a flowchart that shows the flow of a divided print process. In addition,FIGS. 9A to 9Care explanatory drawings that show a summary of the divided print process. InFIGS. 9A to 9C, a print head140that is executing the operations illustrated is shown with a solid line and a print head140that is not contributing to the operations illustrated is shown with a broken line. In addition, images formed by the operations illustrated are shown with single hatching, and images formed before the operations illustrated are shown with cross hatching. The same applies to similar subsequent drawings.

Firstly, the main control section120executes a first image formation operation PA1of forming first images PI1in an area AR1of the print medium PM using the first print head140A while moving the carriage130over a width Wp1in the main scanning travel direction (main scan) (Step S210). Additionally, inFIG. 9A, a number in brackets “(1)” is shown after the symbol “PA1”, but this number in brackets indicates which number unit band area the first image formation operation PA1corresponds to (the same applies to similar subsequent drawings). In the embodiment, image formation on a portion with a width Wp1of a unit band area is completed as a result of the first image formation operation PA1. In such a case, the width Wp1along the main scanning direction of the area AR1is set so that the number of dots that configure each raster (dot row) of each ink color in the first images PI1is less than or equal to the threshold value Tn. Therefore, although the temperature of the first print head140A rises as a result of the first image formation operation PA1, the temperature of the first print head140A does not reach the upper temperature limit Tth. In addition, since ink discharge using the second print head140B is not performed at the time of the first image formation operation PA1, the temperature of the second print head140B does not rise. Additionally, the length along the sub-scanning direction of the area AR1is the same as the length of the nozzle row of the first print head140A.

Next, the main control section120executes a second image formation operation PA2of forming second images PI2in an area AR2of the print medium PM using the second print head140B while moving the carriage130over a width Wp2in the main scanning travel direction (main scan) (Step S230). The first image formation operation PA1and the second image formation operation PA2are executed continuously without the movement of the carriage130being stopped in the interval therebetween. In the embodiment, image formation on a portion with a width Wp2of a unit band area is completed as a result of the second image formation operation PA2. In such a case, the width Wp2along the main scanning direction of the area AR2is set so that the number of dots that configure each raster (dot row) of each ink color in the second images PI2is less than or equal to the threshold value Tn. Therefore, although the temperature T of the second print head140B rises as a result of the second image formation operation PA2, the temperature of the second print head140B does not reach the upper temperature limit Tth. In addition, since ink discharge using the first print head140A is not performed at the time of the second image formation operation PA2, the temperature of the first print head140A, which rose as a result of the first image formation operation PA1falls to the initial temperature Ti. Additionally, the width Wp2along the main scanning direction of the area AR2may be the same as the width Wp1along the main scanning direction of the area AR1, or may differ therefrom. The length along the sub-scanning direction of the area AR2is the same as the length of the nozzle row of the second print head140B.

Next, the main control section120determines whether or not the carriage130has reached the end of the main scanning travel direction side of the print medium PM (Step S232). In a case in which it is determined that the carriage130has not reached the end of the main scanning travel direction side of the print medium PM (Step S232: NO), the main control section120executes the set of the first image formation operation PA1(Step S210) and the second image formation operation PA2(Step S230) again, and performs the determination of Step S232again. Additionally, at the time of a first image formation operation PA1after a second image formation operation PA2, the temperature of the second print head140B, which rose as a result of the second image formation operation PA2, falls to the initial temperature Ti. In this manner, the main control section120repeats the set of the first image formation operation PA1and the second image formation operation PA2until it is determined that the carriage130has reached the end of the main scanning travel direction side of the print medium PM. Additionally, the widths Wp1along the main scanning direction of the area AR1in the first image formation operation PA1and the widths Wp2along the main scanning direction of the area AR2in the second image formation operation PA2may be the same each time or may differ each time. In this manner, even if the first image formation operation PA1and the second image formation operation PA2are executed repeatedly, the temperatures of the first print head140A and the second print head140B do not reach the upper temperature limit Tth.

Once the set of the first image formation operation PA1and the second image formation operation PA2has been executed once or a plurality of times, it is determined that the carriage130has reached the end of the main scanning travel direction side of the print medium PM (Step S232: YES). At this time, as shown inFIG. 9B, image formation of one unit band area is completed.

Among each raster (dot row) of each ink color in the images of a unit band formed by the divided print process, rasters in which the number of dots that configure the raster is greater than or equal to the threshold value Tn (=3500) include both dots formed by the first print head140A and dots formed by the second print head140B. That is, in such rasters, the number of dots that are included in the first dot group is not zero and the number of dots that are included in the second dot group is not zero, and therefore, a rational number, which is expressed using the number of dots included in the first dot group and the number of dots included in the second dot group in the rasters, is a value other than zero.

When it is determined that the carriage130has reached the end of the main scanning travel direction side of the print medium PM, the main control section120determines whether or not image formation on all areas of the print medium PM has been completed (Step S240). In a case in which it is determined that image formation on all areas of the print medium PM has not been completed yet (Step S240: NO), the main control section120executes a home position return operation of moving the carriage130to the end of the main scanning return direction side of the print medium PM without performing ink discharge, and a transport operation of transporting the print medium PM in the sub-scanning direction (sub-scan) (Step S250), and as shown inFIG. 9C, performs the processes from the first image formation operation PA1(Step S210) onwards with the subsequent unit band area (the second unit band area in the example ofFIG. 9C) as the target thereof. The transport amount of the print medium PM in the sub-scanning direction is an amount that is equal to the length of the nozzle row. The above-described processes are repeatedly executed and the divided print process is complete once it is determined that image formation on all areas of the print medium PM has been completed (Step S240: YES).

In the manner described above, the printing apparatus100of the embodiment executes the divided print process (FIG. 8) in cases in which the maximum number of dots Nd of each raster (dot row configured by a plurality of dots lined up along the main scanning direction) of images formed by a single main scan (an image formation operation executed between a sub-scan and a subsequent sub-scan) is greater than or equal to the threshold value Tn (3500 in the embodiment). Among each raster (dot row) of each ink color in the images formed by the divided print process, rasters in which the number of dots that configure the raster is greater than or equal to the threshold value include both dots formed by the first print head140A and dots formed by the second print head140B. That is, in such rasters, the number of dots that are included in the first dot group is not zero and the number of dots that are included in the second dot group is not zero (a rational number, which is expressed using the number of dots included in the first dot group and the number of dots included in the second dot group in the rasters, is a value other than zero). Therefore, it is possible to realize image formation on the entire print medium PM while avoiding a situation in which the temperature of each print head140reaches the upper temperature limit Tth. That is, the printing apparatus100of the embodiment can realize image formation on the entire print medium PM while avoiding situations in which the amount of heat per unit time is excessive and deteriorations in image quality, which accompany damage to the components and the destabilization of discharge, irrespective of the contents of target images for printing and the size of the print medium PM. In addition, in the divided print process of the embodiment, since the number of dots that can be formed continuously by each print head140is limited, it is possible to prolong component life since the application of excessive loads to the components for the ink discharge operation such as the nozzle actuators156is avoided.

In addition, the printing apparatus100of the embodiment executes the normal print process in cases in which the maximum number of dots Nd of each raster of images formed by a single main scan is below the threshold value Tn. In the normal print process, all of the plurality of dots that configure each raster are formed by the first print head140A, and there are no dots that are formed by the second print head140B. Therefore, in this case, the print process is simplified and it is possible to realize improvements in the speed of the process and the image quality thereof.

In addition, since the printing apparatus100of the embodiment alternately executes the image formation operation of the first print head140A and the image formation operation of the second print head140B at the time of performing the divided print process, it is possible to adopt a simple configuration in which two print heads140are mounted in one carriage130.

Additionally, the printing apparatus100can execute the abovementioned divided print process by determining the number of times of the first image formation operation PA1and the second image formation operation PA2that are executed at the time of performing the divided print process and the positions (areas AR1and AR2) on the print medium PM, dividing the image data ID (or print data) on the basis of the abovementioned number of times and positions and using the divided data.

B. Second Embodiment

FIG. 10is an explanatory drawing that shows a schematic configuration of a printing apparatus100ain a second embodiment. The printing apparatus100ain the second embodiment differs from the printing apparatus100of the first embodiment that is shown inFIG. 1in that the printing apparatus100ais provided with two carriages130(a first carriage130A and a second carriage130B) that correspond to the two print heads140(the first print head140A and the second print head140B). The remaining configuration of the printing apparatus100ain the second embodiment is the same as that of the first embodiment. In the following description, there are cases in which the first carriage130A and the second carriage130B are referred to collectively as the carriages130.

The two carriages130are slidably retained by a common sliding axis134. When the rotation of the carriage motor132is transmitted to the two carriages130through the drive belt136, the two carriages130reciprocate along the sliding axis134in a state in which the mutual positional relationship thereof is fixed. Since the first print head140A is mounted in the first carriage130A and the second print head140B is mounted in the second carriage130B, the two print heads140also reciprocate along the main scanning direction in a state that accompanies the movement of the two carriages130and in which the positional relationship thereof is also fixed. In the present embodiment, at the time of performing a print process on a print medium PM of the maximum width that the printing apparatus100acan accommodate, the area of the print medium PM is split in half along the main scanning direction, an image formation operation on the first split area is executed using the first print head140A and an image formation operation on the second split area is executed using the second print head140B at the same time. Therefore, the two carriages130(the two print heads140) reciprocate along the main scanning direction for approximately half of the maximum width of print medium PM that the printing apparatus100acan accommodate in states in which a positional relationship in which there is an interval is retained. That is, the scanning range of the two print heads140does not overlap.

A set of ink cartridges102is detachably mounted to each carriage130. The ink that is accommodated in the set of ink cartridges102mounted each carriage130is supplied to the corresponding print head140. That is, in the embodiment, a dedicated set of ink cartridges102is prepared for each print head140. Additionally, in the embodiment although the two print heads140are separated, the configuration of the disposal of the plurality of nozzles152in each print head140is the same as that of the first embodiment that is shown inFIG. 2. That is, the positions along the sub-scanning direction of all the nozzle rows154that are formed in the two print heads140is the same.

In the same manner as the first embodiment that is shown inFIG. 7, in the print process of the printing apparatus100aof the second embodiment, the normal print process is executed in cases in which the maximum number of dots Nd of a raster (a dot row configured by a plurality of dots lined up along the main scanning direction) is below the threshold value Tn (Step S130inFIG. 7). The normal print process in the second embodiment is a process in which images depending on image data ID are printed on the print medium PM by repeating an operation of forming images on the print medium PM by executing an ink discharge operation depending on image data ID using the first print head140A while continuously moving the two carriages130in the main scanning travel direction (main scan), a home position return operation of moving the two carriages130to the home position in the main scanning return direction without performing ink discharge, and a transport operation of the print medium PM in the sub-scanning direction (sub-scan). In the normal print process, an ink discharge operation (image formation operation) using the second print head140B is not executed. Therefore, all of the plurality of dots that configure each raster (dot row) in images formed using the normal print process are formed by the first print head140A, and dots formed by the second print head140B are not included. That is, in each raster, the number of dots that are included in the second dot group is zero.

In the same manner as the first embodiment, the threshold value Tn of the maximum number of dots Nd is set as a value that is smaller than the number of dots that it takes for the temperature of the first print head140A to reach the upper temperature limit Tth in a case in which dots are formed continuously along the main scanning direction using the first print head140A. Therefore, in a case in which the maximum number of dots Nd is below the threshold value Tn, even if the image formation operation is performed across the entire print medium width Wm using the first print head140A, the temperature of the first print head140A does not reach the upper temperature limit Tth. In addition, since the ink discharge operation is not performed in periods in which the home position return operation and the transport operation are executed, the temperature of the first print head140A falls. Therefore, even if a normal print process such as that described above is performed, it is possible to complete image formation on the entire print medium PM while avoiding the occurrence of a situation in which the temperature of the first print head140A exceeds the upper temperature limit Tth.

On the other hand, in a case in which the maximum number of dots Nd is greater than or equal to the threshold value Tn, a divided print process is executed (Step S140inFIG. 7).FIG. 11is a flowchart that shows the flow of a divided print process in the second embodiment. In addition,FIGS. 12A and 12Bare explanatory drawings that show summaries of the divided printing process in the second embodiment. InFIGS. 12A and 12B, a print head140that is executing the operations illustrated is shown with a solid line, and a print head140that is not contributing to the operations illustrated is shown with a broken line. In addition, images formed by the operations illustrated are shown with single hatching, and images formed before the operations illustrated are shown with cross hatching. The same applies to similar subsequent drawings.

Firstly, the main control section120executes a first image formation operation PA1of forming first images PI1in an area AR1of the print medium PM using the first print head140A (main scan) in addition to executing a second image formation operation PA2of forming second images PI2in an area AR2of the print medium PM using the second print head140B (main scan) while moving the two carriages130over a width Wp in the main scanning travel direction (Step S212). In the embodiment, the width Wp that each carriage130moves is half the maximum width of print medium PM that the printing apparatus100acan accommodate. Therefore, in a case in which the width of the print medium PM that is to be used is the maximum width, the widths along the main scanning direction of the area AR1that the first images PI1form and the area AR2that the second images PI2form are both the width Wp. On the other hand, in cases in which the width of the print medium PM that is to be used is less than the maximum width, the width along the main scanning direction of the area AR1that the first images PI1form is the width Wp, but the width along the main scanning direction of the area AR2that the second images PI2form is less than the width Wp. Image formation on one unit band area is completed as a result of the first image formation operation PA1and the second image formation operation PA2.

Among each raster (dot row) of each ink color in the images of a unit band formed by the divided print process, rasters in which the number of dots that configure the raster is greater than or equal to the threshold value Tn (=3500) include both dots formed by the first print head140A and dots formed by the second print head140B. That is, in such rasters, the number of dots that are included in the first dot group is not zero and the number of dots that are included in the second dot group is not zero, and therefore, a rational number, which is expressed using the number of dots included in the first dot group and the number of dots included in the second dot group in the rasters, is a value other than zero.

In such a case, each the width Wp that each carriage130moves is set so that the number of dots that configure each raster (dot row) of each ink in the first images PI1and the second images PI2is less than or equal to the maximum number of dots Nd. Therefore, although the temperatures of the first print head140A and the second print head140B rise as a result of the first image formation operation PA1and the second image formation operation PA2, the temperatures of the first print head140A and the second print head140B do not reach the upper temperature limit Tth.

Next, the main control section120determines whether or not image formation on all areas of the print medium PM has been completed (Step S240). In a case in which it is determined that image formation on all areas of the print medium PM has not been completed yet (Step S240: NO), the main control section120executes a home position return operation of moving the two carriages130in the main scanning return direction without performing ink discharge, and a transport operation of transporting the print medium PM in the sub-scanning direction (sub-scan) (Step S250), and as shown inFIG. 12B, performs the first image formation operation PA1and the second image formation operation PA2with the subsequent unit band area (the second unit band area in the example ofFIG. 12B) as the target thereof (Step S212). The transport amount of the print medium PM in the sub-scanning direction is an amount that is equal to the length of the nozzle row. These processes are repeatedly executed and the divided print process is complete once it is determined that image formation on all areas of the print medium PM has been completed (Step S240: YES).

In the manner described above, the printing apparatus100aof the second embodiment executes the divided print process (FIG. 11) in cases in which the maximum number of dots Nd of each raster (dot row configured by a plurality of dots lined up along the main scanning direction) of images formed by a single main scan (an image formation operation executed between a sub-scan and a subsequent sub-scan) is greater than or equal to the threshold value Tn (3500 in the embodiment). Among each raster (dot row) of each ink color in the images formed by the divided print process, rasters in which the number of dots that configure the raster is greater than or equal to the threshold value Tn include both dots formed by the first print head140A and dots formed by the second print head140B. That is, in such rasters, the number of dots that are included in the first dot group is not zero and the number of dots that are included in the second dot group is not zero (a rational number, which is expressed using the number of dots included in the first dot group and the number of dots included in the second dot group in the rasters, is a value other than zero). Therefore, it is possible to realize image formation on the entire print medium PM while avoiding a situation in which the temperature of each print head140reaches the upper temperature limit Tth. That is, the printing apparatus100aof the second embodiment can realize image formation on the entire print medium PM while avoiding situations in which the amount of heat per unit time is excessive and deteriorations in image quality, which accompany damage to the components and the destabilization of discharge, irrespective of the contents of target images for printing and the size of the print medium PM. In addition, in the divided print process of the second embodiment, since the number of dots that can be formed continuously by each print head140is limited, it is possible to prolong component life since the application of excessive loads to the components for the ink discharge operation such as the nozzle actuators156is avoided.

In addition, the printing apparatus100aof the second embodiment executes the normal print process in cases in which the maximum number of dots Nd of each raster of images formed by a single main scan is below the threshold value Tn. In the normal print process, all of the plurality of dots that configure each raster are formed by the first print head140A, and there are no dots that are formed by the second print head140B. Therefore, in this case, the print process is simplified and it is possible to realize improvements in the speed of the process and the image quality thereof.

In addition, since the printing apparatus100aof the second embodiment simultaneously executes the image formation operation of the first print head140A and the image formation operation of the second print head140B at the time of performing the divided print process, it is possible to achieve an increase in the speed of the print process.

Additionally, the printing apparatus100acan execute the abovementioned divided print process by determining the number of times of the first image formation operation PA1and the second image formation operation PA2that are executed at the time of performing the divided print process and the positions (areas AR1and AR2) on the print medium PM, dividing the image data ID (or print data) on the basis of the abovementioned number of times and positions and using the divided data.

C. Modification Examples

Additionally, the invention is not limited to the abovementioned embodiments and examples, and can be implemented in various forms within a range that does not depart from the scope thereof. For example, the invention can be implemented as the following modification examples.

The configuration of the printing apparatus100in the abovementioned embodiments is merely an example and various modifications are possible. For example, in the abovementioned embodiments, the printing apparatus100performs the print process by receiving image data ID from a host computer200, but instead of this, the printing apparatus100may, for example, perform the print process on the basis of image data acquired from a memory card, image data acquired from a digital camera through a predetermined interface or image data acquired using a scanner.

In addition, in the abovementioned embodiments, the main control section120of the printing apparatus100that had received image data ID performs calculation processes for printing execution such as an image development process, a color conversion process, an ink color classification process and a halftone process, but these calculation processes may be executed by the host computer200. In such a case, the printing apparatus100receives a print command that has been generated by the calculation processes of the host computer200, and performs a print process according to the print command. In this case also, the printing apparatus100can execute the same print process as that described in the abovementioned embodiments.

In addition, in the abovementioned embodiments, the print head140has the discharge limiting section169, but the print head140may be provided without the discharge limiting section169, and the control unit110may have a functional section that is the same as the discharge limiting section169. In such as case, the detection result of the temperature of the print head140using the thermistor144is sent to the control unit110, and the control unit110limits the ink discharge operation in the same manner as that in the abovementioned embodiments on the basis of the received temperature detection result.

In addition, in the abovementioned embodiments, since the occurrence of a situation in which the temperature of the print head140exceeds the upper temperature limit Tth is avoided as a result of the control of the main control section120, it is possible to achieve simplification and a reduction in cost of the configuration of the apparatus by omitting the thermistor144and the discharge limiting section169. Alternatively, it is possible to use the control of the main control section120as a backup in a case in which there is a defect with the operation of the thermistor144and the discharge limiting section169.

In addition, in the abovementioned embodiments, the printing apparatus100performs the print process using the four ink colors of cyan, magenta, yellow and black, but the number and type of ink colors that the printing apparatus100uses in the print process is not limited thereto. For example, the printing apparatus100may perform the print process using a total of six colors of ink by adding light cyan and light magenta to the four colors of cyan, magenta, yellow and black.

In addition, in the abovementioned embodiments, the printing apparatus100is a so-called on carriage type printer in which the ink cartridges102reciprocate in the main scanning direction along with the carriage130, but the invention may also be applied to a so-called off-carriage type printer in which a holder that attaches the ink cartridges102is provided in a different location to that of the carriage130, and ink is supplied from the ink cartridges102to the print head140through a flexible tube or the like. In addition, in the abovementioned first embodiment, one common set of ink cartridges102respectively supplies ink to both the first print head140A and the second print head140B, but a designated set of ink cartridges102may be respectively prepared for first print head140A and the second print head140B, and ink may be supplied from the designated ink cartridges102to the corresponding print head140. In addition, in the abovementioned second embodiment, a designated set of ink cartridges102is respectively prepared for first print head140A and the second print head140B, but one set of ink cartridges102may respectively provide ink to the both the first print head140A and the second print head140B. In addition, the invention may be applied to printing apparatuses that form images on a print medium PM using fluid other than ink (including liquid bodies in which particles of functional materials are dispersed and fluid bodies such as gel).

In addition, in the abovementioned embodiments, the first print head140A and the second print head140B are the same (same model number), but the first print head140A and the second print head140B may be print heads that differ (in model number). In addition, in the abovementioned embodiments, the printing apparatus100is provided with two print heads140, but the printing apparatus100may be provided with three or more print heads140. In a case in which the printing apparatus100is provided with three or more print heads140, it is possible to realize the divided print process that executes image formation operations using the 3 or more print heads140in order in the same manner as the first embodiment. Alternatively, in a case in which the printing apparatus100is provided with three or more print heads140, it is possible to realize the divided print process that executes image formation operations using the 3 or more print heads140at the same time in the same manner as the second embodiment.

In addition, in the abovementioned embodiments, the positions along the sub-scanning direction of all the nozzle rows154that are formed in the two print heads140is the same, but the invention is not limited to this configuration.FIG. 13is an explanatory drawing that shows a configuration of a nozzle formation surface of each print head140in a modification example. In the modification example shown inFIG. 13, since the positions along the sub-scanning direction of the two print heads140are shifted, the positions along the sub-scanning direction of the nozzle rows154that are formed in the first print head140A and the positions along the sub-scanning direction of the nozzle rows154that are formed in the second print head140B are shifted. In this regard, in the modification example shown inFIG. 13, a portion of 75% or more of the nozzle rows154that are formed in the first print head140A and the nozzle rows154that are formed in the second print head140B respectively overlap in the main scanning direction. That is, in the modification example shown inFIG. 13, a first straight line SL1, which links a central point MP1of a first line segment LS1that links the nozzles152of both ends of the first nozzle row (the cyan ink nozzle row154of the first print head140A) and a central point MP2of a second line segment LS2that links the nozzles152of both ends of the second nozzle row (the magenta ink nozzle row154of the first print head140A), crosses a third line segment LS3that links the nozzles152of both ends of the third nozzle row (the cyan ink nozzle row154of the second print head140B) and a fourth line segment LS4that links the nozzles152of both ends of the fourth nozzle row (the magenta ink nozzle row154of the second print head140B). In addition, the second straight line SL2, which links a central point MP3of the third line segment LS3and a central point MP4of the fourth line segment LS4, crosses the first line segment LS1and the second line segment LS2. Furthermore, the distance between an intersection IP3of the first straight line SL1and the third line segment LS3and the central point MP3of the third line segment LS3is shorter than the distance between the intersection IP3and an end point on the near side of the third line segment LS3. In the modification example shown inFIG. 13, at the time of the divided print process (Step S140inFIG. 7), among each of the nozzle rows154respectively provided in the first print head140A and the second print head140B, only nozzles152of portions that overlap the nozzle rows154of the other print head140in the main scanning direction are used, and the remaining nozzles152are not used. In the modification example shown inFIG. 13, since the divided print process can be executed using 75% or more of the nozzles152that configure each nozzle row154provided in each print head140, it is possible to effectively suppress increases in the time required for the divided print process.

FIG. 14is an explanatory drawing that shows a configuration of a nozzle formation surface of each print head140in a different modification example. In the modification example shown inFIG. 14, since the positions along the sub-scanning direction of the two print heads140are shifted to a greater extent than the modification example shown inFIG. 13, the positions along the sub-scanning direction of the nozzle rows154that are formed in the first print head140A and the positions along the sub-scanning direction of the nozzle rows154that are formed in the second print head140B are shifted to a greater extent than that of the modification example shown inFIG. 13. In this regard, in the modification example shown inFIG. 14, 50% or more of the nozzle rows154that are formed in the first print head140A and the nozzle rows154that are formed in the second print head140B respectively overlap in the main scanning direction. That is, in the modification example shown inFIG. 14, a first straight line SL1, which links a central point MP1of a first line segment LS1that links the nozzles152of both ends of the first nozzle row (the cyan ink nozzle row154of the first print head140A) and a central point MP2of a second line segment LS2that links the nozzles152of both ends of the second nozzle row (the magenta ink nozzle row154of the first print head140A), crosses a third line segment LS3that links the nozzles152of both ends of the third nozzle row (the cyan ink nozzle row154of the second print head140B) and a fourth line segment LS4that links the nozzles152of both ends of the fourth nozzle row (the magenta ink nozzle row154of the second print head140B). In addition, the second straight line SL2, which links a central point MP3of the third line segment LS3and a central point MP4of the fourth line segment LS4, crosses the first line segment LS1and the second line segment LS2. In this regard, the distance between an intersection IP3of the first straight line SL1and the third line segment LS3and the central point MP3of the third line segment LS3is longer than the distance between the intersection IP3and an end point on the near side of the third line segment LS3. In the modification example shown inFIG. 14, at the time of the divided print process (Step S140inFIG. 7), among each of the nozzle rows154respectively provided in the first print head140A and the second print head140B, only nozzles152of portions that overlap the nozzle rows154of the other print head140in the main scanning direction are used, and the remaining nozzles152are not used. In the modification example shown inFIG. 14, since the divided print process can be executed using 50% or more of the nozzles152that configure each nozzle row154provided in each print head140, it is possible to effectively suppress increases in the time required for the divided print process.

In addition, in the abovementioned embodiments, the portion of the configuration that is realized using hardware may be substituted with software and conversely, the portion of the configuration that is realized using software may be substituted with hardware.

In addition, in a case in which either a portion of or all of the functions of the invention are realized using software, the software (computer program) can be provided in a format of being stored on a recordable medium that is readable by a computer. In this invention, “a recordable medium that is readable by a computer” is not limited to portable recordable media such as flexible discs and CD-ROMs, and also includes computer internal storage units such as various types of RAM and ROM and external storage units that are fixed to a computer such as hard disks.

In the abovementioned first embodiment, the normal print process is executed in a case in which the maximum number of dots Nd is below the threshold value Tn, but the divided print process may be performed even in cases in which the maximum number of dots Nd is below the threshold value Tn. According to this configuration, it is possible to suppress bias in the frequency of use of each print head140, and it is possible to realize prolongation of the life of the printing apparatus100as a whole by avoiding common occurrence of specific print head140breakdowns.

In the abovementioned embodiments, the printing apparatus100acquires the print resolution Rp and a width Wm along the main scanning direction of the print medium PM, and calculates the maximum number of dots Nd by multiplying the print resolution Rp by the print medium width Wm, but in a case in which the print resolution Rp of the printing apparatus100is fixed, the printing apparatus100may calculate the maximum number of dots Nd on the basis of the width Wm along the main scanning direction of the print medium PM without acquiring the print resolution Rp for each print process. In addition, the printing apparatus100may save a table that shows a correspondence between a combination of the print resolution Rp and width Wm of the print medium PM (or the width Wm of the print medium PM only) and a result of the determination of whether or not the maximum number of dots Nd is greater than or equal to the threshold value Tn (Step S120inFIG. 7), and may perform the abovementioned determination by referring to the table when a combination of the print resolution Rp and width Wm of the print medium PM (or the width Wm of the print medium PM only) is specified in the table.

In addition, in the abovementioned embodiments, the determination of whether to execute normal printing or divided printing (the determination of whether or not the number of dots that configure each raster of each ink color is greater than to equal to the threshold value Tn or not) is performed using the maximum number of dots Nd, but the abovementioned determination may be performed using image data ID in addition to the maximum number of dots Nd. For example, the abovementioned determination may be performed by calculating the number of dots that configure each raster that is formed in practical terms on the basis of the maximum number of dots Nd and the image data ID, and a comparing the calculated number of dots and the threshold value Tn.

In the abovementioned embodiments, at the time of normal printing, only the ink discharge operation (image formation operation) of the first print head140A is executed and the ink discharge operation of the second print head140B is not executed, but conversely, normal printing may be performed by only executing the ink discharge operation (image formation operation) of the second print head140B and not executing the ink discharge operation of the first print head140A.

In the divided print process in the abovementioned embodiments, image formation in an area that is scanned is completed by a single first image formation operation PA1and single second image formation operation PA2, but the divided print process is not necessarily limited to this configuration. For example, only a portion of the rasters (lines configured by a plurality of dots lined up along the main scanning direction) that form images that are to be formed in an area that is scanned may be formed by a single first image formation operation PA1and single second image formation operation PA2, and different rasters that form images that are to be formed in the area may be formed by a different single first image formation operation PA1and single second image formation operation PA2. That is, the print process may be performed using a so-called interlaced method.

In the divided print process in the abovementioned embodiments, the movement direction of the carriage130in the first image formation operation PA1and the second image formation operation PA2is the main scanning travel direction at all times (that is, so called one-way printing is performed), but so-called two-way printing, in which an operation of performing image formation while moving the carriage130in the main scanning travel direction and an operation of performing image formation while moving the carriage130in the main scanning return direction are repeatedly executed, may be performed.

The entire disclosure of Japanese Patent Application No. 2012-154353, filed Jul. 10, 2012 is expressly incorporated by reference herein.