JP6432422B2 - Liquid ejection device - Google Patents

Description

  The present invention relates to a liquid ejection apparatus.

  Patent Document 1 discloses an ink jet head that discharges ink from a plurality of nozzles toward a recording sheet while moving with respect to the recording sheet as a liquid ejecting apparatus. The inkjet head of Patent Document 1 includes a flow path unit in which an ink flow path including nozzles is formed, and a piezoelectric actuator that applies pressure to the ink in the ink flow path. The flow path unit is connected to the ink cartridge by a tube. The piezoelectric actuator discharges ink from the nozzles by applying pressure to the ink in the flow path unit.

  By the way, in such an ink jet head, when ink is ejected from the nozzle, the ink pressure in the flow path unit decreases. Normally, ink flows from the ink cartridge to the flow path unit in response to a drop in the ink pressure in the flow path, so that the ink pressure in the flow path recovers as time passes. However, if the state in which ink is simultaneously ejected from many nozzles continues, the amount of ink ejected within a certain time increases, and the ink supply from the ink cartridge cannot keep up (under refill). Thereby, when the pressure drop in the ink flow path proceeds, the meniscus of the nozzle may be destroyed.

  In this regard, in Patent Document 1, for each one-way movement (pass) of the ink jet head, the ink discharge amount to be discharged in that pass is calculated, and when the ink discharge amount exceeds a threshold value, The printing operation is temporarily suspended. By this pause, the ink pressure in the ink flow path is recovered to prevent meniscus break.

  On the other hand, there is a case where the printing operation of the inkjet head is temporarily stopped for a reason other than the above-described decrease in ink pressure. The ink jet head disclosed in Patent Document 2 includes a piezoelectric actuator that discharges ink from a nozzle and an IC chip that drives the piezoelectric actuator. When the ink is ejected from the nozzle by driving the piezoelectric actuator, heat is generated in the IC chip, and this heat causes a temperature distribution on the nozzle surface of the inkjet head. As a result, a difference in ink temperature occurs between different nozzles, and the ejection characteristics differ between the nozzles. Therefore, in Patent Document 2, when the temperature difference on the nozzle surface becomes larger than a certain level due to heat generation of the IC chip, a delay time is set, and the next printing operation of the inkjet head is delayed by the delay time. Thereby, the temperature difference of a nozzle surface is restrained small.

JP 2010-214727 A JP 2005-335132 A

  However, when it is necessary to temporarily stop the inkjet head due to two different factors, ie, a pressure drop in the ink flow path and heat generated by the IC chip, a pause time is set for each of these two factors. As a result, an excessively long pause time is set. This increases the overall printing time.

  An object of the present invention is to prevent the pause time from being set unnecessarily long when the liquid ejection of the head is temporarily paused due to two factors, ie, a decrease in liquid pressure in the flow path and heat generation of the IC. That is.

The liquid ejection apparatus of the present invention includes a flow channel structure that is connected to a liquid supply unit and has a liquid flow channel including a plurality of nozzles, and a discharge for causing the liquid in the liquid flow channel to be discharged from the nozzles. A liquid ejection head having an energy applying unit that applies energy, a driver IC that drives the energy applying unit, and a control unit that controls the driver IC,
The control unit obtains ejection amount information related to the liquid ejection amount of the liquid ejection head in the scheduled liquid ejection operation before the liquid ejection head performs the scheduled liquid ejection operation. Acquired in the acquisition process, the pressure prediction process for predicting the pressure change of the liquid in the liquid flow path, and the discharge quantity information acquisition process based on the discharge quantity information acquired in the discharge quantity information acquisition process Based on the discharge amount information, the temperature prediction process for predicting the temperature change of the driver IC, the pressure change predicted by the pressure prediction process, and the temperature change of the driver IC predicted by the temperature prediction process A pause period setting process for setting a pause period for the liquid ejection head, and the liquid ejection during the pause period set in the pause period setting process in the liquid ejection operation. It is characterized in performing a pause process and for halting the liquid ejection head.

1 is a schematic plan view of a printer 1 according to an embodiment. 2 is a block diagram schematically showing an electrical configuration of the printer 1. FIG. 4 is a top view of the inkjet head 4. FIG. It is the A section enlarged view of FIG. It is the VV sectional view taken on the line of FIG. (A) is a figure which shows the ink pressure change when the idle period is not provided, (b) is a figure which shows the operating temperature change of the driver IC when the idle period is not provided. It is a flowchart of a printing process. It is a flowchart of an idle period determination process. (A) is a figure which shows the ink pressure change when an idle period is provided, (b) is a figure which shows the operating temperature change of driver IC when an idle period is provided. It is a top view of 4 A of inkjet heads of a change form. It is a top view of the inkjet head 4B of another modification. It is a flowchart of the process regarding the image printing of another modified form. (A) is a diagram showing a change in ink pressure when a pause period is provided, and (b) is a diagram showing a change in operating temperature of the driver IC when a pause period is provided. .

  Next, an embodiment of the present invention will be described. The scanning direction shown in FIG. 1 is defined as the left-right direction of the printer 1. The direction toward the cartridge holder 8 in FIG. 1 is the right side, and the direction toward the side opposite to the cartridge holder 8 is the left side. 1 is defined as the rear side of the printer 1 and the downstream side is defined as the front side of the printer 1. Furthermore, a direction orthogonal to the scanning direction and the conveyance direction (a direction orthogonal to the paper surface of FIG. 1) is defined as the vertical direction of the printer 1. Note that the carriage 3 side on the front side of the page is the upper side, and the platen 2 side on the other side of the page is the lower side. Below, it demonstrates using each direction word of front, back, left, right, up and down suitably.

(Printer configuration)
As shown in FIG. 1, the inkjet printer 1 includes a platen 2, a carriage 3, an inkjet head 4, a transport unit 5, a control unit 6, and the like.

  On the upper surface of the platen 2, a recording sheet 100 as a recording medium is placed. The carriage 3 is configured to reciprocate in the scanning direction along the two guide rails 10 and 11 in a region facing the platen 2. An endless belt 13 is connected to the carriage 3, and the endless belt 13 is driven by a carriage drive motor 14, so that the carriage 3 reciprocates in the scanning direction.

  The inkjet head 4 is mounted on the carriage 3 and reciprocates in the scanning direction together with the carriage 3. The ink jet head 4 is connected to a cartridge holder 8 to which ink cartridges 16 of four colors (black, yellow, cyan, magenta) are mounted and tubes 15 respectively. The inkjet head 4 has a plurality of nozzles 30 formed on its lower surface (the surface on the other side of the paper surface in FIG. 1). Each nozzle 30 ejects the ink supplied from the ink cartridge 16 toward the recording paper 100 placed on the platen 2. The detailed configuration of the inkjet head 4 will be described later.

  As shown in FIG. 1, the transport unit 5 includes two transport rollers 18 and 19 that are arranged so as to sandwich the platen 2 in the front-rear direction. The two transport rollers 18 and 19 are driven synchronously by a transport motor 17 (see FIG. 2). The transport unit 5 drives the two transport rollers 18 and 19 by the transport motor 17 to transport the recording paper 100 placed on the platen 2 in the transport direction orthogonal to the scanning direction.

  As shown in FIG. 2, the control unit 6 includes a CPU (Central Processing Unit) 20, a ROM (Read Only Memory) 21, a RAM (Random Access Memory) 22, and an ASIC (Application Specific Integrated Circuit) including various control circuits. 23 etc. The control unit 6 is connected to an operation panel 24 that allows the user to perform various operations on the printer 1. The control unit 6 is connected to an external device 26 such as a PC via the communication unit 25 so that data communication is possible.

  The control unit 6 executes various processes such as printing on the recording paper 100 by the CPU 20 and the ASIC 23 according to the program stored in the ROM 21. For example, in the printing process, the control unit 6 controls the driver IC 61 (described later), the carriage drive motor 14, the transport motor 17 and the like of the inkjet head 4 based on a print command input from the external device 26 such as a PC. Control is performed to print an image or the like on the recording paper 100. Specifically, an ink discharge operation for discharging ink while moving the inkjet head 4 in the scanning direction together with the carriage 3 and a transport operation for transporting the recording paper 100 in the transport direction by the transport rollers 18 and 19 alternately. To do.

(Detailed configuration of inkjet head)
Next, the inkjet head 4 will be described in detail with reference to FIGS. In FIG. 3, a COF (Chip On Film) 60 disposed so as to cover the piezoelectric actuator 32 is indicated by a two-dot chain line in order to make the drawing easy to understand. In FIG. 4, the illustration of the COF 60 is omitted.

  As shown in FIGS. 3 to 5, the inkjet head 4 includes a flow path structure 31 and a piezoelectric actuator 32. FIG. 5 shows a state in which ink (shown by symbol I) is filled in the ink flow path formed in the flow path structure 31.

(Channel structure)
As shown in FIG. 5, the flow path structure 31 has a structure in which a plurality of plates 41 to 49 are stacked. The plurality of plates 41 to 49 are bonded to each other by an adhesive in a state where they are stacked on each other. The lowermost plate among the plurality of plates 41 to 49 is a nozzle plate 49 made of a synthetic resin such as polyimide. A plurality of nozzles 30 are formed on the nozzle plate 49. As shown in FIG. 3, the plurality of nozzles 30 are arranged in the transport direction and are divided into four nozzle groups 38 arranged in the scanning direction. The four nozzle groups 38 eject four colors (black, yellow, cyan, magenta) of ink, respectively.

  The plates 41 to 48 other than the nozzle plate 49 constituting the flow path structure 31 are plates made of a metal material such as stainless steel. In these plates 41 to 48, ink flow paths including a manifold 36 and a pressure chamber 37 described below that communicate with the plurality of nozzles 30 are formed.

  As shown in FIG. 3, four ink supply holes 35 are formed side by side in the scanning direction in the uppermost plate 41 constituting the upper surface of the flow path structure 31. The four ink supply holes 35 are supplied with four colors (black, yellow, cyan, magenta) of ink from the four ink cartridges 16 (see FIG. 1) of the holder 8, respectively. In FIG. 5, four manifolds 36 extending in the transport direction are formed on the fourth to seventh plates 44 to 47 from the top. The four ink supply holes 35 and the four manifolds 36 are connected by communication holes (not shown) formed in the plates 42 and 43, respectively.

  A plurality of pressure chambers 37 respectively corresponding to the plurality of nozzles 30 are formed in the uppermost plate 41 of the flow path structure 31. Each pressure chamber 37 has a substantially elliptical planar shape that is long in the scanning direction. The plurality of pressure chambers 37 are arranged in four rows corresponding to the four manifolds 36. The plurality of pressure chambers 37 are covered with the diaphragm 50 of the piezoelectric actuator 32. As shown in FIGS. 3 and 4, a plurality of throttle channels 39 that connect the manifold 36 and the plurality of pressure chambers 37 are formed in the plate 42 that is located second from the top. Further, a total of seven plates 42 to 48 positioned between the uppermost plate 41 and the nozzle plate 49 are formed with a communication channel 33 that connects the pressure chamber 37 and the nozzle 30.

  That is, in the present embodiment, each of the four color manifolds 36 is connected to the nozzles 30 belonging to the corresponding nozzle group 38 via the individual flow paths including the throttle flow path 39, the pressure chamber 37, and the communication flow path 33. Communicate.

(Piezoelectric actuator)
The piezoelectric actuator 32 is disposed on the upper surface of the flow path structure 31 described above. The piezoelectric actuator 32 imparts ejection energy for ejecting from the nozzle 30 to the ink in the pressure chamber 37. As shown in FIGS. 3 to 5, the piezoelectric actuator 32 includes a diaphragm 50, piezoelectric layers 54 and 55, a plurality of individual electrodes 52, and a common electrode 56.

  The diaphragm 50 is joined to the upper surface of the flow path structure 31 so as to cover the plurality of pressure chambers 37. The diaphragm 50 is made of a metal material such as stainless steel, for example.

  The two piezoelectric layers 54 and 55 are each made of a piezoelectric material. As a piezoelectric material constituting the piezoelectric layers 54 and 55, lead zirconate titanate which is a mixed crystal of lead titanate and lead zirconate can be employed. In addition, a lead-free piezoelectric material such as barium titanate or a niobium-based piezoelectric material may be employed. The piezoelectric layers 54 and 55 are bonded to the upper surface of the diaphragm 50 in a state where they are laminated.

  The plurality of individual electrodes 52 are arranged in the transport direction corresponding to the plurality of pressure chambers 37 on the upper surface of the upper piezoelectric layer 54. The individual electrode 52 has a substantially elliptical planar shape that is slightly smaller than the pressure chamber 37 and is long in the scanning direction, and is arranged to face the central portion of the corresponding pressure chamber 37. A connection terminal 52 a is provided at one end in the longitudinal direction of the individual electrode 52. The connection terminal 52 a extends in the scanning direction from the individual electrode 52 to a region not facing the pressure chamber 37 on the upper surface of the piezoelectric layer 54.

  The common electrode 56 is disposed almost entirely between the two piezoelectric layers 54 and 55. The common electrode 56 is opposed to each of the plurality of individual electrodes 52 with the upper piezoelectric layer 54 interposed therebetween.

  In the above configuration, one piezoelectric element 59 is formed by one individual electrode 52, a portion of the common electrode 56 facing the one pressure chamber 37, and a portion of the piezoelectric layers 54, 55 facing the one pressure chamber 37. Is configured. Further, in each piezoelectric element 59, a portion sandwiched between the individual electrode 52 and the common electrode 56 of the upper piezoelectric layer 54 is hereinafter referred to as an active portion 51. The active portion 51 of each piezoelectric element 59 is polarized downward in the thickness direction, that is, in a direction from the individual electrode 52 toward the common electrode 56.

  As shown in FIGS. 3 and 5, a COF 60 that is a wiring member is disposed on the upper surface of the piezoelectric actuator 32. The COF 60 electrically connects the piezoelectric actuator 32 and the control unit 6. In addition, a driver IC 61 for driving the piezoelectric actuator 32 is mounted on the COF 60.

  In the COF 60, a plurality of input wirings 62a and a plurality of output wirings 62b are formed. The driver IC 61 is electrically connected to the control unit 6 via the input wiring 62a. On the other hand, as shown in FIG. 5, the ends of the plurality of output wirings 62 b are joined to the connection terminals 52 a of the plurality of individual electrodes 52 by bumps 63, respectively. Thereby, the driver IC 61 of the COF 60 and the individual electrodes 52 of the plurality of piezoelectric elements 59 of the piezoelectric actuator 32 are electrically connected.

  Based on the control signal sent from the control unit 6, the driver IC 61 outputs a drive signal to each of the plurality of piezoelectric elements 59 corresponding to the plurality of nozzles 30 of the piezoelectric actuator 32. The potential of the individual electrode 52 of the piezoelectric element 59 to which the drive signal is supplied changes between a predetermined drive potential and a ground potential. The driver IC 61 incorporates a temperature detection circuit 64 (see FIG. 2) that detects the operating temperature.

  Although not shown, the COF 61 is provided with a ground line that is electrically connected to the ground of the printer 1. Since the end of the ground line is electrically connected to the common electrode 56, the common electrode 56 is always maintained at the ground potential.

  The operation of the piezoelectric element 59 when ink is ejected from the nozzle 30 will be described. In a state where no drive signal is supplied from the driver IC 61, the potential of the individual electrode 52 is the ground potential and the same potential as the common electrode 56. From this state, when a drive signal is supplied to the individual electrode 52 of a certain piezoelectric element 59 and a drive potential is applied to the individual electrode 52, the active portion 51 is caused by the potential difference between the individual electrode 52 and the common electrode 56. An electric field parallel to the thickness direction acts. Here, since the polarization direction of the active part 51 and the direction of the electric field coincide with each other, the active part 51 extends in the thickness direction, which is the polarization direction, and contracts in the plane direction. Along with the contraction deformation of the active portion 51, the vibration plate 50 is bent so as to protrude toward the pressure chamber 37, the volume of the pressure chamber 37 is reduced, and a pressure wave is generated in the ink. Thereby, ink is ejected from the nozzle 30 communicating with the pressure chamber 37.

(Outline of inkjet head pause control)
By the way, the printer 1 of the present embodiment performs control for temporarily stopping the ink ejection operation of the inkjet head 4 during printing on the recording paper 100 for the following reasons (1) and (2). As described above, the ink jet head 4 ejects ink while reciprocating in the scanning direction with respect to the recording paper 100 together with the carriage 3, but the carriage 3 moves in one direction in the scanning direction (left or left). The one-way movement to the right is hereinafter referred to as “pass”. The ink-jet head 4 prints an image on the recording paper 100 by ejecting ink during each pass and executing a plurality of passes continuously. Further, the ink jet head 4 causes ink to be ejected from the nozzles 30 in both a pass when the carriage 3 moves to the left and a pass when the carriage 3 moves to the right. That is, the inkjet head 4 of the present embodiment prints an image by so-called bidirectional printing.

(1) Temporary pause for ink pressure recovery As shown in FIG. 6A, when ink is ejected from a nozzle 30 in each pass, the pressure of the ink in the manifold 36 communicating with the nozzle 30 is reduced. descend. The ink pressure P in the manifold 36 decreases more rapidly as the ink discharge amount in each pass increases.

  Even if the ink pressure in the manifold 36 decreases in one pass, ink is replenished from the ink cartridge 16 during the reversal period in which the carriage 3 reverses the moving direction until the next pass is started. Therefore, the ink pressure is recovered. However, if the amount of ink ejected in the previous pass is large, the pressure does not completely recover during the inversion period, so that the ink pressure is further lowered by the ink ejection in the next pass. When the ink pressure is lower than the predetermined limit pressure PL, the meniscus of the nozzle 30 may be destroyed. Therefore, in this embodiment, before printing on the scheduled recording paper 100, the ink discharge amount in each pass is grasped, and thereby a change in ink pressure in each pass is predicted. Then, the rest period of the inkjet head 4 is set in the inversion period between any of the passes so that the ink pressure predicted in all passes is maintained at the limit pressure PL or higher.

(2) Temporary pause for suppressing temperature rise of driver IC 61 As shown in FIG. 6B, in order to eject ink from the nozzle 30 in each pass, the driver IC 61 drives to the individual electrode 52 of each piezoelectric element 59. When a signal is supplied, the driver IC 61 generates heat and the operating temperature rises. Incidentally, the driving is not performed during the reversal period of the carriage 3, and the operating temperature is somewhat lowered by dissipating the heat of the driver IC 61 during that period. However, when the amount of ink discharged in each pass is large and the driving frequency of the piezoelectric element 59 is high, the operating temperature of the driver IC 61 increases rapidly in each pass. When the operating temperature exceeds a predetermined limit temperature TL, the operation of the driver IC 61 becomes unstable, and further, the driver IC 61 is broken. Therefore, in this embodiment, before printing on the scheduled recording paper 100, the ink discharge amount in each pass is grasped, and thereby the temperature change of the driver IC 61 in each pass is predicted. Then, the rest period of the inkjet head 4 is set in the inversion period between any of the passes so that the predicted operating temperature is equal to or lower than the limit temperature TL.

  The printing process for the recording paper 100 including the setting process for the rest period of the inkjet head 4 will be described with reference to the flowcharts of FIGS. 7 and 8, Si (i = 1, 2, 3,...) Indicates a step number.

  When an image print command is input from the external device 26 to the control unit 6 of the printer 1 (S1: Yes), before starting the image printing, the control unit 6 performs ink in each pass during image printing. Pressure change and driver IC 61 temperature change are predicted. Based on these predictions, the rest period of the inkjet head 4 during image printing is determined (S2). Note that the “pause period” in the present embodiment is a concept including two parameters, “pause timing” indicating which path is paused, and “pause time” indicating how long the pause is performed. Details of the determination of the suspension period will be described later with reference to FIG.

  When the pause period is determined, the control unit 6 calculates the time required for printing the image on the recording paper 100 based on the pause of the inkjet head 4 during the pause period (S3). Also, the calculated printing time information is notified to the external device 26 by the communication unit 25 and displayed on the display of the external device 26 (S4). Alternatively, the printing time may be displayed on the display of the operation panel 24.

  Then, the controller 6 prints an image on the recording paper 100 by ejecting ink from the nozzles 30 of the inkjet head 4 in each pass while reciprocating the carriage 3 in the scanning direction (S5). At that time, when the pass becomes the set pause period, when the carriage 3 is reversed, the inkjet head 4 is stopped at the position on the left side or the right side of the recording paper 100, and is determined by the pause period. Ink ejection from the inkjet head 4 is suspended for a period of time (pause processing). When the pause period ends, the next pass is started and ink ejection of the inkjet head 4 is resumed.

(Determination of suspension period)
Next, the determination of the suspension period in S2 will be specifically described with reference to FIG. First, based on the image data input from the external device 26, information on the ink ejection amount of the inkjet head 4 is acquired for each pass when printing an image. In the present embodiment, the duty is calculated as the information related to the ink discharge amount (S11). The “duty” in the present application is a ratio of the actual ejection amount to the maximum ejection amount (duty 100%) when ink is ejected from all the target nozzles 30 in each pass. The duty is used for ink pressure change prediction (S12) and driver IC 61 temperature prediction (S14), which will be described later. However, for the following reason, it is necessary to separately calculate the duty used for prediction of ink pressure change and the duty used for temperature prediction.

  As described above, the inkjet head 4 has four nozzle groups 38 and four manifolds 36 respectively corresponding to the four nozzle groups 38. The pressure of ink in each manifold 36 is independent of the pressure of ink in other manifolds 36. Therefore, for example, even if the duty of the nozzle group 38 that discharges cyan ink is low and the pressure drop in the cyan manifold 36 is small, the pressure of the black manifold 36 is high if the duty of the nozzle group 38 that discharges black ink is high. In order to suppress the decrease, it may be necessary to pause the inkjet head 4. Therefore, in the duty acquisition process of S11, in order to individually predict the ink pressure change for each of the four manifolds 36, the duty (first duty D1) for each of the four nozzle groups 38 is acquired. That is, the first duty D1 is a ratio of the actual discharge amount to the maximum discharge amount that the target nozzle group 38 discharges in one pass.

  On the other hand, the driver IC 61 drives all of the piezoelectric elements 59 corresponding to the four color nozzles 30. Therefore, in the duty acquisition process of S11, in addition to the first duty D1, the duty (second duty D2) for all the nozzles 30 driven by the driver IC 61 is acquired in order to predict the temperature change of the driver IC 61. To do. That is, the second duty D2 is a ratio of the actual discharge amount to the maximum discharge amount that all the nozzles 30 discharge in one pass.

  The ink pressure P in each manifold 36 depends on the first duty D1 and is a function of the first duty D1 and time t. That is, the ink pressure shown in FIG. 6A is represented by P = f (D1, t) + P0. P0 is an initial pressure in the manifold 36 when the inkjet head 4 is in a standby state. In addition, the actual ink pressure P is calculated using not only the first duty D1 and time t, which are variables, but also a fixed value related to the flow resistance and the like, and this fixed value is incorporated in the above relational expression. . The above relational expression for calculating the ink pressure P is stored in the ROM 21. Then, the control unit 6 refers to the relational expression stored in the ROM 21 and changes the ink pressure in the manifold 36 corresponding to the nozzle group 38 based on the first duty D1 of each nozzle group 38 acquired in S11. Predict (S12).

  Further, the control unit 6 receives the detection signal from the temperature detection circuit 64 of the driver IC 61, and detects the current operating temperature T0 of the driver IC 61 (S13). The operating temperature T of the driver IC 61 depends on the second duty D2 and is a function of the second duty D2 and time t. That is, the operating temperature shown in FIG. 6B is represented by T = g (D2, t) + T0. The actual operating temperature T is calculated using not only the variable second duty D2 and time t but also a fixed value related to the capacitance of the piezoelectric element 59, etc., and this fixed value is included in the above relational expression. It has been incorporated. The above relational expression for calculating the operating temperature T is stored in the ROM 21. Then, the control unit 6 refers to the relational expression stored in the ROM 21 and predicts a change in the operating temperature of the driver IC 61 based on the second duty D2 acquired in S11 (S14).

  Next, the rest period of the inkjet head 4 is set in the inversion period of the carriage 3 during image printing from the pressure change predicted in S12 and the temperature change predicted in S14 (S15 to S23). By setting a pause period between passes, the inkjet head 4 can be paused frequently during printing on one sheet of recording paper. This can reliably prevent the ink pressure from falling below the limit pressure PL or the operating temperature of the driver IC 61 from exceeding the limit temperature TL.

  First, based on the pressure change predicted in S12, a period (first period p1) in which the ejection of the inkjet head 4 is temporarily stopped so that the pressure in each manifold 36 is maintained below a predetermined limit pressure PL. Calculate (S15). The value of the limit pressure PL is, for example, −8 kPa. In the example of FIG. 6A, the ink pressure P is lower than the limit pressure PL during the third pass. Therefore, a first period p1 having a predetermined time length is set in the inversion period between the second pass and the third pass.

  Next, based on the temperature change predicted in S14, a period (second period p2) in which the ejection of the inkjet head 4 is temporarily stopped so that the operating temperature of the driver IC 61 is maintained below a predetermined limit temperature TL. Calculate (S16). The value of the limit temperature TL is 80 ° C., for example. In the example of FIG. 6B, the temperature T exceeds the limit temperature TL during the fourth pass. Therefore, a second period p2 having a predetermined time length is set in the inversion period between the third pass and the fourth pass.

  In addition, the time length (rest time) of the first period p1 and the second period p2 is the value of the pressure P and the temperature T immediately before those periods, and the value of the duty of the path after those periods have elapsed. It calculates according to etc. For example, in FIG. 6A, when the pressure P at the end of the second pass is very close to the limit pressure PL, if the pause time of the first period p1 is short, the limit is limited in the third pass. Even if it does not fall below the pressure, it must fall below the limit pressure PL again in the fourth and subsequent passes, and a rest period must be provided again. Therefore, in such a case, it is preferable to increase the pause time of the first period p1.

  Next, an appropriate pause period is set from the first period p1 for suppressing the decrease in ink pressure and the second period p2 for suppressing the temperature rise of the driver IC 61. First, the first period p1 and the second period p2 may have the same pause timing (S17: Yes), that is, the first period p1 and the second period p2 may be set in the same inversion period. In this case, the pause time is compared between the first period p1 and the second period p2, and the longer pause period is set as the pause period (S18).

  When the timings of the first period p1 and the second period p2 are different (S17; No), the period with the earlier pause timing is set as the pause period. On the other hand, the period during which the pause timing is later is handled as follows.

  When one of the first period p1 and the second period p2 is selected as the actual pause period, the factor corresponding to the selected one period (decrease in ink pressure or temperature increase in the driver IC 61) is suppressed without any problem. The On the other hand, as to the factor corresponding to the other non-selected period, whether it is suppressed or not depends on the situation, but it is certain that it will be relaxed to some extent at least by the suspension of the one period. It is.

  For example, from the pressure change in FIG. 6A, the first period p1 for suppressing the ink pressure drop is set to the inversion period between the second pass and the third pass. On the other hand, from the temperature change of FIG. 6B, the second period p2 for suppressing the temperature rise of the driver IC 61 is set to an inversion period between the third pass and the fourth pass. That is, since the first period p1 is earlier in the pause timing than the second period p2, the first period p1 is set as the pause period.

  As shown in FIG. 9A, when a pause period is provided between the second pass and the third pass, the ink pressure greatly recovers during that period, and the ink pressure is the limit pressure after the third pass. It is possible not to fall below PL. At this time, as shown in FIG. 9B, the temperature of the driver IC 61 also decreases during the pause period. Therefore, it is desirable that the second period p2 for suppressing the subsequent temperature increase of the driver IC 61 is recalculated on the condition that the ejection of the inkjet head 4 is suspended during the first period p1.

  Specifically, when the first period p1 is set at a timing earlier than the second period p2 (S19: Yes), the first period p1 is set on the condition that the discharge is suspended during the first period p1. Two periods p2 are recalculated (S20). Then, the first period p1 and the second period p2 after recalculation are set as a pause period (S21). In the recalculation of the second period p2, the second period p2 is not necessary when it is determined that the temperature of the driver IC 61 does not exceed the limit temperature TL only after the pause of the first period p1. Therefore, the rest time of the second period p2 may be set to zero.

  Conversely, when the second period p2 is set at an earlier timing than the first period p1 (S19: No), the first period is set on the condition that the discharge is suspended during the second period p2. p1 is recalculated (S22). Then, the second period p2 and the first period p1 after recalculation are set as a pause period (S23). In addition, in the recalculation of the first period p1, if it is determined that the first period p1 is unnecessary only after the second period p2 is paused, the pause time of the first period p1 may be set to zero.

  As described above, in this embodiment, the duty (first duty D1, second duty D2) of each pass in the scheduled printing on the recording paper 100 is calculated, and each pass is calculated based on this duty. The change in the pressure of the ink in the manifold 36 and the change in the operating temperature of the driver IC 61 are predicted. Based on the predicted ink pressure change and the driver IC 61 temperature change, the rest period of the inkjet head 4 is set. In other words, since it is possible to set the optimum rest period in consideration of both the ink pressure change and the temperature change of the driver IC 61, it is possible to prevent the rest time from becoming unnecessarily long.

  In the setting of the pause period, first, the first period p1 is set as a period for stopping the ejection so that the ink pressure is maintained at a predetermined limit pressure PL or higher. Further, the second period p2 is set as a period for stopping the discharge so that the temperature of the driver IC 61 is maintained at a predetermined limit temperature TL or lower.

  When the pause timing is the same in the first period p1 and the second period p2, the longer pause time is selected as the pause period. Thereby, it is possible to set the shortest pause time in which both the ink pressure drop and the temperature rise of the driver IC 61 can be reliably suppressed.

  When the pause timings of the first period p1 and the second period p2 are different, the earlier pause timing is adopted as the pause period. Thus, both the ink pressure drop and the driver IC 61 temperature rise can be efficiently suppressed by the set pause period.

  Further, of the first period p1 and the second period p2, the period after the pause timing is recalculated on the condition that the pause timing is the pause of the previous period, and a new period obtained by the recalculation is paused. Include in the period. That is, it is possible to optimally reset the subsequent period in consideration of the influence of the suspension in the previous period.

  In the embodiment described above, the ink jet printer 1 corresponds to the “liquid ejecting apparatus” of the invention. The inkjet head 4 corresponds to the “liquid discharge head” of the present invention. The ink cartridge 16 corresponds to the “liquid supply unit” of the present invention. The recording paper 100 corresponds to the “subject” of the present invention. The piezoelectric actuator 32 corresponds to the “energy applying unit” of the present invention. The manifold 36 corresponds to the “common liquid chamber” of the present invention. The driver IC 61 corresponds to the “driver” of the present invention. The first duty D1 corresponds to “first discharge amount information” of the present invention. The second duty D2 corresponds to “second discharge amount information” of the present invention. The printing time corresponds to the “operation time” of the present invention. The communication unit 25 that transmits the printing time to the external device 26 or the operation panel 24 that displays the printing time corresponds to the “notification unit” of the present invention.

  Next, modified embodiments in which various modifications are made to the embodiment will be described. However, components having the same configuration as in the above embodiment are given the same reference numerals and description thereof is omitted as appropriate.

1] When the number of passes during image printing is large, even if the decrease in ink pressure (or the temperature rise in the driver IC 61) is temporarily suppressed by setting the pause period, the number of passes thereafter By repeating the above, the limit value may be approached again. In such a case, a plurality of pause periods may be set during image printing. As can be understood from FIGS. 6 and 9, the lower the ink pressure is, and the higher the temperature of the driver IC 61 is, the greater the pressure is recovered in a shorter pause time, and the temperature is greatly decreased. Therefore, it is preferable that the ink jet head 4 is paused for a short time when the ink pressure is lowered to the extent that it does not fall below the limit pressure PL and the temperature of the driver IC 61 has risen to the extent that the limit temperature TL is not exceeded. Thereby, pressure recovery and temperature drop can be effectively performed in one pause. The total pause time can be shortened by frequently performing the pauses for a short time.

2] In the above embodiment, one manifold 36 is provided for one color ink, but a plurality of manifolds 36 may be provided for one color ink. For example, the inkjet head 4A of FIG. 10 has two manifolds 36k1 and 36k2 for black ink. The nozzles 30 that discharge black ink constitute two nozzle groups 38k1 and 38k2 that communicate with the two manifolds 36k1 and 36k2, respectively. Although the two manifolds 36k1 and 36k2 communicate with the common ink supply hole 35k, there is almost no mutual interference of ink pressure between the two manifolds 36k1 and 36k2, and it can be said that the ink pressures are independent of each other. In this case, in the duty acquisition process of S11 of FIG. 8, the first duty D1 is calculated for each of the two black manifolds 36k1 and 36k2.

3] In the above-described embodiment, one driver IC 61 is configured to drive all the piezoelectric elements 59 of the piezoelectric actuator 32. In contrast, a configuration in which the piezoelectric actuator 32 is driven by two or more driver ICs 61 may be employed. For example, two driver ICs 61 a and 61 b are mounted on the front and rear sides of the inkjet head 4 in the COF 60 connected to the inkjet head 4 </ b> B in FIG. 11. The front driver IC 61 a drives the piezoelectric element 59 corresponding to the nozzle 30 located in the front half of the plurality of nozzles 30. The rear driver IC 61 b drives the piezoelectric element 59 corresponding to the nozzle 30 located in the rear half of the plurality of nozzles 30. In this case, in the duty acquisition process of S11 of FIG. 8, the second duty D2 for the front half nozzle 30 corresponding to the front driver IC 61a and the second duty for the second half nozzle 30 corresponding to the rear driver IC 61b. The duty D2 is calculated.

4] In the above embodiment, the ink pressure change prediction and the driver IC 61 temperature change prediction are performed for all passes before printing on one recording paper 100, and the rest period is based on these predictions. Is set. In this case, in the first pass, both the pressure prediction and the temperature prediction can obtain a prediction result that is close to the actual result, but in the latter pass, the difference between the prediction and the actual may be large. Therefore, when setting the rest period in the earlier path, the rest period calculated from the pressure prediction and the temperature prediction is used as it is, and when setting the rest period in the later path, it is calculated. You may perform the process which lengthens time a little with respect to a stop time. For example, when a pause period is provided after the end of the third pass, the pause time is increased by multiplying the calculated pause time by a weighting factor (for example, 1.1 times).

5] In the above embodiment, before printing on one sheet of recording paper 100, the ink pressure change prediction and the driver IC 61 temperature change prediction are performed for all passes, and based on these predictions, It is determined how long a pause is provided between which passes. On the other hand, during printing, before each pass, for example, while ink is ejected in the previous pass, the ink pressure change and temperature change in the next pass are predicted, and the rest period is based on the prediction. May be provided.

  As shown in FIG. 12, during printing of an image, the control unit 6 obtains a duty for the next pass (S31), pressure prediction (S32), temperature prediction based on temperature detection (S33) (S34), And a rest period setting (S35-S37) is performed. In the rest period setting process, first, based on the pressure change predicted in S32, the third period p3 is calculated as a period for delaying the next pass so that the ink pressure is maintained at or above the predetermined limit pressure PL ( S35). Further, based on the temperature change predicted in S34, the fourth period p4 is calculated as a period for delaying the next pass so that the temperature of the driver IC 61 is maintained below the predetermined limit temperature TL (S36). Then, the period having the longer pause time of the third period p3 and the fourth period p4 is set as the pause period (S37). Depending on the path, there may be a case where no pause is required. In this case, the pause time is set to zero.

  After the setting of the pause period, at the time of inversion before the start of the next pass, during the set pause period, the start of the next pass of the inkjet head 4 is delayed and ink ejection is paused (S38). When the pause period ends, the next pass is started (S39). The above processing is performed for each pass, and when all passes are completed (S40: Yes), printing of the image is finished. In the embodiment, before printing on one sheet of recording paper 100, the ink pressure in each pass and the operating temperature of the driver IC 61 are predicted, and based on those predictions, a pause period is set between which passes. It is decided whether to set. However, it can be said that the temperature of the driver IC 61 can be predicted more accurately if the temperature information detected by the temperature detection circuit 64 is frequently acquired and predicted. In this regard, in the modification of FIG. 12, the ink pressure change and temperature change in each pass are predicted for each pass. That is, immediately before each pass, the temperature information of the driver IC 61 is predicted using the temperature information (S33) detected by the temperature detection circuit 64. Therefore, the temperature change is predicted with higher accuracy than the above embodiment. Is possible.

6] In the above-described embodiment, a pause period is set in the inversion period of the carriage 3 between passes when an image is printed on one sheet of recording paper 100, but printing is continued on a plurality of recording sheets 100. In this case, a pause period may be applied while the next recording sheet 100 is conveyed. That is, as shown in FIG. 13, when printing (ink ejection) on one recording sheet 100 is completed and the next recording sheet 100 is transported to the inkjet head 4 by the transport unit, a pause period is set. . Specifically, the start of conveyance of the next recording sheet 100 may be delayed, or the start of ink ejection by the inkjet head 4 may be delayed after the next recording sheet 100 is conveyed to the inkjet head 4. .

  In general, the time required to transport the next recording paper 100 is longer than the time required to reverse the carriage 3. Therefore, when comparing the configuration of the above-described modified example in which a pause period is set during sheet conveyance with the configuration of the embodiment in which a pause period is set between passes, the time required for pressure recovery and temperature drop is compared. Assuming that they are the same, the configuration of this modified embodiment requires less time for stopping the ink-jet head 4 excessively. Further, there may be a case where pressure recovery and a temperature drop can be achieved only by the time required for paper conveyance (when it is not necessary to provide a pause period separately from paper conveyance).

  The ink jet head 4 of the above embodiment is a so-called serial type head that has a plurality of nozzles 30 arranged in the transport direction and ejects ink onto the recording paper 100 while moving in the scanning direction. On the other hand, the present invention can also be applied to a so-called line head in which a plurality of nozzles are arranged in the width direction of the recording paper (direction perpendicular to the transport direction). In particular, when the present invention is applied to this line head, the above-described form in which a pause period is set when a recording sheet is conveyed can be suitably employed.

7] In the embodiment, the first period p1 is determined from the predicted ink pressure change, the second period p2 is determined from the predicted temperature change of the driver IC 61, and the pause timings of the first period p1 and the second period p2 are determined. The rest period is compared to determine the rest period. On the other hand, a relational expression between the ink pressure and the temperature of the driver IC 61 and the pause period is acquired in advance and stored in the ROM 21. By this relational expression, the predicted pressure and temperature values are calculated at a time. A rest period may be set.

8] In the above embodiment, the control unit 6 of the printer 1 calculates the duty from the image data. However, after the duty is calculated in advance by the external device 26 such as a PC, the calculated duty is calculated by the external device 26. From the printer to the control unit 6 of the printer.

9] The discharge amount information used for pressure prediction and temperature prediction is not limited to the duty of the embodiment. For example, information related to the discharge amount such as the number of nozzles 30 to be discharged at one discharge timing (discharge cycle), the drive frequency (reciprocal of the discharge cycle), and the like may be acquired.

10] The energy applying unit that applies the ejection energy to the ink is not limited to the piezoelectric actuator. For example, a heater substrate provided with a plurality of heating elements for heating the ink to cause film boiling can be employed as the drive element.

11] In the above embodiment, the image is printed by bidirectional printing in which the inkjet head 4 ejects ink both when the carriage 3 moves to the left and when it moves to the right. On the other hand, the present invention can also be applied to image printing by so-called unidirectional printing in which ink is ejected only when the carriage 3 moves in one direction and ink is not ejected when the carriage 3 moves in the other direction. It is. In unidirectional printing, ink pressure recovery and driver IC heat dissipation are performed during the return path that does not eject ink, so compared to bi-directional printing, ink pressure drop and driver IC temperature rise are problems. However, depending on the duty of each path and the time required for the return, it may be better to set a pause period.

  The embodiments described above and the modifications thereof are applied to an ink jet printer that prints an image or the like by ejecting ink onto a recording sheet, but can be used for various purposes other than printing an image or the like. The present invention can also be applied to a liquid ejecting apparatus. For example, the present invention can also be applied to an industrial liquid discharge apparatus that discharges a conductive liquid onto a substrate to form a conductive pattern on the substrate surface. In the above example, the substrate on which the conductive liquid is discharged corresponds to the “discharged body” of the present invention.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 4 Inkjet head 5 Conveyance part 6 Control part 16 Ink cartridge 24 Operation panel 25 Communication part 30 Nozzle 31 Flow path structure 32 Piezoelectric actuator 36 Manifold 37 Pressure chamber 38 Nozzle group 59 Piezoelectric element 61 Driver IC
100 recording paper

Claims (9)

A flow path structure that is connected to the liquid supply section and has a liquid flow path including a plurality of nozzles, and an energy applying section that applies discharge energy for discharging the liquid in the liquid flow path from the nozzles. A liquid ejection head having
A driver for driving the energy application unit;
A control unit for controlling the driver,
The controller is
A discharge amount information acquisition process for acquiring discharge amount information related to the liquid discharge amount of the liquid discharge head in the scheduled liquid discharge operation before the liquid discharge head performs the scheduled liquid discharge operation;
A pressure prediction process for predicting a change in pressure of the liquid in the liquid channel based on the discharge amount information acquired in the discharge amount information acquisition process;
A temperature prediction process for predicting a temperature change of the driver based on the discharge amount information acquired in the discharge amount information acquisition process;
A pause period setting process for setting a pause period of the liquid ejection head from the pressure change predicted in the pressure prediction process and a temperature change of the driver predicted in the temperature prediction process;
In the liquid ejection operation, a pause process for pausing the liquid ejection of the liquid ejection head during the pause period set in the pause period setting process;
A liquid ejecting apparatus characterized in that: The control unit, in the suspension period setting process,
Based on the pressure change of the liquid predicted in the pressure prediction process, the first period is determined as a period for temporarily stopping the discharge so that the pressure of the liquid is maintained at a predetermined pressure or higher,
Based on the temperature change of the driver predicted in the temperature prediction process, the second period is determined as a period for temporarily stopping the discharge so that the temperature of the driver is maintained at a predetermined temperature or lower.
If the pause timing of the first period is earlier than the pause timing of the second period, the first period is set to the pause period,
2. The liquid ejection apparatus according to claim 1, wherein the second period is set to the pause period when the pause timing of the second period is earlier than the pause timing of the first period. The controller is
If the pause timing of the first period is earlier than the pause timing of the second period, the second period is recalculated under the condition that the ejection is paused during the first period, and the first period is calculated. Set the period and the second period after recalculation to the pause period;
If the pause timing of the second period is earlier than the pause timing of the first period, the first period is recalculated under the condition that the ejection is paused during the second period, and the second period The liquid ejection apparatus according to claim 2, wherein the period and the first period after recalculation are set as the pause period. The control unit, in the suspension period setting process,
If the pause timing of the first period and the pause timing of the second period are the same, the period of the longer pause time of the first period and the second period is set as the pause period. The liquid discharge apparatus according to claim 2 , wherein the liquid discharge apparatus is a liquid discharge apparatus. The liquid discharge head performs the scheduled liquid discharge operation several times in succession,
The controller is
Before performing each liquid discharge operation, perform the discharge amount information acquisition process, the pressure prediction process, the temperature prediction process, and the pause period setting process for the next liquid discharge operation,
In the pause process, during the pause period set in the pause period setting process, the start of the next liquid ejection operation of the liquid ejection head is delayed,
In the suspension period setting process,
Based on the change in pressure of the liquid predicted in the pressure prediction process, a third period is determined as a period for delaying the next liquid discharge operation so that the pressure of the liquid is maintained at a predetermined pressure or higher,
Based on the temperature change of the driver predicted in the temperature prediction process, the fourth period is determined as a period for delaying the next liquid discharge operation so that the temperature of the driver is maintained at a predetermined temperature or lower.
2. The liquid ejection apparatus according to claim 1, wherein a period of a longer pause time of the third period and the fourth period is set as the pause period. The flow path structure has a plurality of common liquid chambers connected to the liquid supply unit,
The plurality of nozzles are divided into a plurality of nozzle groups corresponding respectively to the plurality of common liquid chambers, and the nozzles belonging to the corresponding nozzle group communicate with each common liquid chamber,
The energy applying unit has a plurality of driving elements respectively corresponding to the plurality of nozzles,
Comprising one or more drivers for driving the plurality of drive elements;
The controller is
In the discharge amount information acquisition process, first discharge amount information that is discharge amount information for each nozzle group and second discharge amount that is discharge amount information for the nozzles corresponding to the drive elements driven by the drivers. Get information and
In the pressure prediction process, the pressure change of the liquid in each common liquid chamber is predicted based on the first discharge amount information,
The liquid ejection apparatus according to claim 1, wherein the temperature prediction process predicts a temperature change of each driver based on the second ejection amount information. The liquid discharge head discharges liquid from the nozzle while reciprocating in a predetermined scanning direction.
7. The control unit according to claim 1, wherein the controller sets the pause period in an inversion period in which the liquid ejection head completes one movement in the scanning direction and reverses the movement direction. The liquid discharge apparatus according to 1. A transport unit that transports the discharge target body in a predetermined transport direction with respect to the liquid discharge head;
The liquid discharge head discharges liquid from the nozzle to the discharge target transported in the transport direction by the transport unit,
The said control part sets the said rest period when the liquid discharge with respect to one said to-be-discharged body is complete | finished and the said to-be-discharged body is conveyed to the said liquid discharge head. The liquid ejection apparatus according to any one of 1 to 6. The controller is
Further executing an operation time calculation process for calculating an operation time required for the scheduled liquid ejection operation of the liquid ejection head based on the pause period set in the pause period setting process;
The liquid ejecting apparatus according to claim 1, further comprising a notification unit that notifies the operation time calculated in the operation time calculation process.

Images