JP2016175361A - Liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform flushing concurrently with sheet supply conducted by a roller to reduce the preparation time, and to perform flushing after checking if the sheet is supplied by the roller.SOLUTION: A printer 1 includes: an ink jet head 26 which discharges an ink toward a recording sheet 100; a pickup roller 24 which supplies the recording sheet 100 placed on a main tray 23a to the ink jet head 26; a paper feeding motor 20 which drives the pickup roller 24; and a control part which controls the ink jet head 26 and the paper feeding motor 20. The control part causes the ink jet head 26 to perform flushing when an electric current of the paper feeding motor 20, which is generated when the pickup roller 24 is driven, exceeds a predetermined threshold value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid ejection apparatus.

  In the field of liquid ejection devices such as inkjet heads, there is a problem in that the liquid in the nozzle dries and the viscosity increases (thickening), resulting in defective ejection at the nozzle. Therefore, conventionally, it is generally performed to discharge a liquid with increased viscosity in advance by discharging a liquid from a nozzle prior to printing on a sheet. The above liquid discharge operation is called flushing or preliminary discharge.

  Patent Document 1 discloses the above flushing. The ink jet printer disclosed in Patent Document 1 includes a carriage that moves in the width direction of a sheet (recording paper), an ink jet head mounted on the carriage, and a pickup roller (paper feed roller) that feeds the sheet placed on the tray to the ink jet head. And. In this inkjet printer, for the purpose of shortening the preparation time until printing is started, the operation related to flushing of the inkjet head is started simultaneously with the driving of the pickup roller.

  Specifically, Patent Document 1 discloses the following two embodiments. In one embodiment, in parallel with the start of driving the pickup roller, the carriage is moved to the flushing position, and the inkjet head is flushed at that position. In another embodiment, the carriage is moved to the flushing position simultaneously with the start of driving of the pickup roller. Unlike the former form, flushing is not performed immediately. After confirming the successful supply of the sheet to the ink jet head by the paper detector, the ink jet head is flushed.

JP 2008-37006 A

  By the way, when the sheet is taken out from the tray by the pickup roller, a slip may occur between the roller and the sheet. In this case, the time from when the driving of the pickup roller is started until the sheet is actually sent to the inkjet head is longer than expected.

  In the former form of Patent Document 1, flushing is performed in parallel with the driving of the pickup roller. However, when slipping occurs on the roller, the sheet supply is not yet completed even if a predetermined amount of flushing is performed. , A situation may occur where only flushing ends first. In this case, after completion of the flushing, the increase in the viscosity in the nozzles may occur before the sheet supply is completed, which may cause a discharge failure. In this regard, the above problem can be avoided if the flushing is terminated when the sheet feeding is confirmed by the paper detector after the flushing is started simultaneously with the driving of the roller. However, in this case, since flushing is performed for a long time including the slip time of the roller from the start of driving of the roller until the sheet is actually supplied, the amount of ink consumed by flushing increases.

  On the other hand, in the latter form of Patent Document 1, flushing is performed after confirming the successful supply of the sheet to the ink jet head. Therefore, even if the roller slips, the above-described problem does not occur. However, since the flushing is performed after the sheet supply is completed, the preparation time until the printing is started is increased accordingly.

  An object of the present invention is to reduce the preparation time by performing flushing in parallel with the sheet supply by the pickup roller, and to perform flushing after confirming that the sheet is supplied by the pickup roller. .

A liquid discharge apparatus according to a first aspect of the present invention includes a liquid discharge head having a nozzle that discharges liquid toward a sheet, a pickup roller that supplies the sheet placed on a tray to the liquid discharge head, and the pickup roller. A motor that drives, a memory that stores a threshold value relating to the current of the motor, the liquid ejection head, and a controller that controls the motor, and
The control unit determines whether or not a current of the motor when driving the pickup roller exceeds the threshold value, and when the current of the motor exceeds the threshold value, Flushing for discharging the liquid from is performed.

  When a sheet is supplied by the pickup roller, a load is applied to the motor, so that the torque increases and the motor current also increases. On the other hand, if slip occurs with the sheet at the start of feeding by the pickup roller, or if there is no sheet and the pickup roller is idle, the load on the motor is small and the motor current remains low. is there. Therefore, in the present invention, when the current value of the motor exceeds a predetermined threshold value stored in the memory, it is determined that the sheet is supplied by the pickup roller, and the liquid ejection head performs flushing.

  In the present invention, since the liquid discharge head is flushed while the sheet is supplied by the pickup roller, it is possible to shorten the preparation time until the liquid discharge onto the sheet is started. The flushing is started after confirming that the sheet is being supplied by the roller based on the current value of the motor that drives the pickup roller. When the amount of flushing is determined in advance, when a roller slip occurs, it is possible to prevent the predetermined amount of flushing from being completed long before the sheet is actually fed. . Further, if the flushing is continued until the supply of the sheet is completed, it is prevented that the flushing is performed wastefully for a long time, and the liquid consumption due to the flushing is suppressed.

  According to a second aspect of the present invention, there is provided a liquid ejection device according to the first aspect, wherein a cap member that is in close contact with the liquid ejection head and covers the nozzle, a cap member that covers the nozzle and a cap position that covers the nozzle A cap drive unit that moves between the uncap positions, and the control unit starts a discharge operation of the liquid discharge head onto the sheet in a state where the cap member is at the cap position. Is input, the cap drive unit is controlled to move the cap member to the uncapped position, and after the cap member has moved to the uncapped position, the current of the motor exceeds the threshold value. The flushing is performed by the liquid discharge head.

  When the liquid discharge head does not perform the discharge operation to the sheet, the cap member is at the cap position and the nozzle is covered with the cap member. When a signal for starting the discharge operation of the liquid discharge head is input from this state, the cap member first moves from the cap position to the uncapped position and moves away from the liquid discharge head in preparation for the discharge operation. Thereafter, when the motor current exceeds the threshold, the control unit determines that the sheet is being supplied by the pickup roller, and causes the liquid discharge head to perform flushing.

  In the liquid ejection device according to a third aspect of the present invention, in the second aspect of the present invention, the controller is configured to wait until the current of the motor exceeds the threshold value after the cap member has moved to the uncap position. The liquid discharge head is caused to perform liquid agitation in which the liquid in the nozzle is agitated without discharging the liquid.

  In the state immediately before flushing, if the thickening in the nozzle is considerably advanced, the discharge of the liquid in the flushing is not stable, and there is a possibility that the elimination of the thickening due to flushing may be insufficient. Therefore, in the present invention, after the cap member moves to the uncapping position, liquid agitation is performed until the motor current exceeds the threshold value, thereby suppressing the thickening of the liquid in the nozzle. Thereby, the discharge of the liquid in the subsequent flushing is stabilized.

  In the liquid ejection device according to a fourth aspect of the present invention, in the second or third aspect of the invention, the controller may be configured such that, even if a predetermined first time has elapsed since the cap member moved to the uncapping position, When the current of the motor does not exceed the threshold value, the liquid discharge head is caused to perform the flushing.

  When the pick-up roller slips, it takes time for the motor current value to exceed the threshold value. During this time, the liquid in the nozzle increases in viscosity. Therefore, in the present invention, if the motor current value does not exceed the threshold value even after a predetermined first time has elapsed after the cap member has moved to the uncapping position, the nozzle has been subjected to flushing to increase the viscosity in the nozzle. Drain the liquid once.

  According to a fifth aspect of the present invention, in the liquid ejection device according to the first aspect of the invention, the control unit causes the motor current to remain within the threshold value even after a predetermined second time has elapsed after the motor starts driving the pickup roller. In the case where it does not exceed, the liquid discharge head is caused to perform the flushing.

  The pick-up roller is started to be driven. However, when the motor current does not increase due to the slip of the roller, thickening of the liquid in the nozzle proceeds during that time. Therefore, if the motor current does not exceed the threshold value even after a predetermined second time has elapsed after the start of driving the roller, flushing is performed and the thickened liquid in the nozzle is once discharged.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the invention, the control unit is configured so that, even if a predetermined third time has elapsed after the start of driving of the pickup roller by the motor, When the motor current does not exceed the threshold, the motor is stopped.

  If the motor current value does not exceed the threshold value after a certain period of time has elapsed after the motor has started driving, the sheet on the tray has run out, or the roller continues to slip for some reason. Is presumed to be in a state where it cannot be supplied. Therefore, if the motor current does not exceed the threshold value even after the predetermined third time has elapsed, the motor is stopped.

  According to a seventh aspect of the present invention, in the liquid ejecting apparatus according to any one of the first to sixth aspects, the memory stores a plurality of threshold values according to the type of the sheet. Information on the type is acquired, and when the current of the motor exceeds a threshold corresponding to the acquired information on the type of sheet, the liquid discharge head is caused to perform flushing for discharging liquid from the nozzle. It is a feature.

  When a plurality of types of sheets can be used, the way in which the motor current changes varies depending on the type of sheets used. For this reason, if the threshold value of the motor current value is the same regardless of the sheet, it may be erroneously determined whether or not the slip has occurred depending on the type of the sheet. In this regard, in the present invention, since the determination is performed using the threshold value corresponding to the sheet type after recognizing the sheet type, it is possible to perform appropriate determination according to the sheet type.

  According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the control unit is responsive to any one of a temperature of the liquid and a humidity around the liquid discharge head. The amount of liquid ejected by the flushing is changed.

  The ease of thickening the liquid in the nozzle changes depending on the temperature of the liquid and the humidity around the liquid discharge head. Therefore, in the present invention, the amount of liquid ejected by flushing is changed according to temperature and humidity conditions.

  According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the controller performs the flushing of the liquid discharge head when the current of the motor falls below the threshold value. It is characterized by terminating.

  When the sheet supply by the pickup roller is completed, the motor load is reduced and the torque is reduced, so that the current value is also reduced. Therefore, in the present invention, when the current of the motor becomes equal to or less than the threshold value, the flushing of the liquid discharge head is terminated assuming that the sheet supply is terminated. That is, since the flushing is completed almost simultaneously with the completion of the sheet supply, the flushing can be continued until immediately before the completion of the sheet supply.

FIG. 2 is a vertical sectional view schematically showing the internal configuration of the printer. FIG. 3 is a plan view of the inside of the printer. FIG. 2 is a block diagram schematically illustrating an electrical configuration of a printer. It is operation | movement explanatory drawing of the inkjet head in the flushing before printing. It is a flowchart of flushing before printing. It is a figure which shows the time change of the electric current of a paper feed motor when the slip has not arisen in the roller. It is a figure which shows the time change of the electric current of a paper feeding motor when the slip has arisen in the roller. It is a figure which shows the time change of the electric current of a paper feed motor when there is no recording paper. It is a figure which shows the time change of the electric current of a paper feed motor in a change form. It is a flowchart of flushing before printing. It is a figure which shows the time change of the electric current of the paper feed motor according to the paper type in another modification. It is a figure which shows the relationship between a paper type and a threshold value. It is a flowchart of flushing before printing. FIG. 6 is a block diagram of a printer according to another modification. It is a figure which shows the relationship between temperature and humidity, and the amount of flushing. It is a flowchart of flushing before printing. It is a flowchart of the flushing before printing in another modification. It is operation | movement explanatory drawing of the inkjet head in the flushing before printing of another modification.

  Next, an embodiment of the present invention will be described. FIG. 1 is a vertical sectional view schematically showing the internal configuration of the printer. FIG. 2 is a plan view of the inside of the printer. FIG. 3 is a block diagram schematically showing the electrical configuration of the printer. The front and rear, left and right, and up and down directions shown in FIGS. 1 and 2 are defined as front and rear, left and right, and up and down directions of the printer 1 and will be described below.

  As shown in FIGS. 1 and 2, the inkjet printer 1 includes a printer housing 2 and a cover 3 that is rotatably attached to the printer housing 2.

(Printer housing)
As shown in FIGS. 1 and 2, the printer housing 2 accommodates a printer unit 4, a paper feeding unit 5, a maintenance device 6, a control board 7, and the like.

  As shown in FIGS. 1 and 2, an opening 11 is formed in the front wall portion of the printer housing 2. A paper feeding cassette 23 of the paper feeding unit 5 is mounted below the opening 11. A front inclined surface 12 is provided at an upper portion of the front portion of the printer casing 2, and an operation panel 13 having a display panel, operation buttons, and the like is disposed on the inclined surface 12. An opening / closing lid 14 is attached to the right side of the opening 11 on the front wall of the printer housing 2. A holder 15 is disposed behind the opening / closing lid 14. Four ink cartridges 16 for storing inks of four colors (black, yellow, cyan, magenta) are detachably mounted on the holder. The printer housing 2 includes a substrate support portion 18 that extends horizontally from the inner surface of the front wall portion. The substrate support unit 18 supports a control substrate 7 in which various circuits including a control unit 40 (see FIG. 3) of the printer 1 are incorporated.

(cover)
The cover 3 is disposed on the rear side of the inclined surface 12 of the printer housing 2 and is attached to the printer housing 2 so as to be rotatable up and down around a rotation shaft 17. The cover 3 can be changed in position between a horizontal closed position (position shown by a solid line in FIG. 3) and an open position rotated upward from the closed position (position shown by a two-dot chain line in FIG. 1). is there. Although not described in detail, the cover 3 is provided with a scanner 19 (see FIG. 3) that captures an image recorded on a document.

(Paper Feeder)
As shown in FIG. 1, the paper feed unit 5 includes a paper feed cassette 23 mounted in the opening of the printer housing 2 and a pickup roller 24 that takes out the recording paper 100 from the paper feed cassette 23. The paper feed cassette 23 is provided above the main tray 23a on which the sheet-like recording paper 100 is placed, and the recording paper 100 recorded by the printer unit 4 described later is discharged. It has a paper tray 23b. The pickup roller 24 is disposed above the main tray 23 a and is configured to be rotatable about a rotation shaft provided in the printer housing 2. The pickup roller is driven by a paper feed motor 20 (see FIG. 3) to take out the recording paper 100 one by one from the main tray 23a of the paper feed cassette 23. The recording paper 100 taken out by the pickup roller 24 is pushed upward along the inclined surface 23 c provided at the front end portion of the paper feed cassette 23 and supplied to the printer unit 4. A paper detection sensor 22 for detecting the recording paper 100 sent by the pickup roller 24 is provided in the vicinity of the conveyance roller 33 of the printer unit 4.

(Printer part)
The printer unit 4 is disposed above the paper feeding unit 5. As shown in FIGS. 1 and 2, the printer unit 4 includes a carriage 25 that can reciprocate in the left-right direction (hereinafter also referred to as a scanning direction), an inkjet head 26 mounted on the carriage 25, and a recording paper 100. A transport mechanism 27 that transports forward (hereinafter also referred to as a transport direction) along a horizontal plane is provided.

  A platen 28 that supports the recording paper 100 is installed in the printer casing 2 in a horizontal posture. As shown in FIG. 2, above the platen 28, two guide rails 29 and 30 extending in parallel with the scanning direction are provided. The carriage 25 is driven by a carriage drive motor 32 (see FIG. 3), and moves in the scanning direction along the two guide rails 29 and 30 in a region facing the recording paper 100 on the platen 28.

  The ink jet head 26 is attached to the lower portion of the carriage 25 with a gap between the ink jet head 26 and the platen 28. The lower surface of the ink jet head 26 is an ink ejection surface 26a in which a plurality of nozzles 31 are opened. The plurality of nozzles 31 are arranged along the transport direction to form four nozzle rows that respectively eject four colors of ink (black, yellow, cyan, magenta). The ink jet head 26 is connected to the holder 15 by four tubes (not shown). As a result, the four color inks of the four ink cartridges 16 attached to the holder 15 are supplied to the inkjet head 26 via the four tubes, respectively.

  The inkjet head 26 includes a plurality of drive elements (not shown) that apply ejection energy to the ink in the plurality of nozzles 31 and a drive IC 35 (see FIG. 3) that drives the plurality of drive elements. As the driving element, a piezoelectric element or a heating element that heats ink to cause film boiling can be suitably used. The drive IC 35 drives each drive element by supplying a drive signal having a predetermined waveform to each drive element.

  As shown in FIG. 2, the inkjet head 26 can move not only to the area facing the recording paper 100 conveyed on the platen 28 together with the carriage 25, but also to positions on the left and right sides with respect to this facing area. A maintenance device 6 to be described later is disposed on the right side of the facing region. Further, a flushing receiver 38 is disposed on the left side of the facing region. The ink jet head 26 discharges ink thickened in each nozzle 31 by ejecting ink from each nozzle 31 while facing the flushing receiver 38. Hereinafter, the above-described ink ejection operation for suppressing ink thickening is referred to as “flushing”.

  The transport mechanism 27 includes two transport rollers 33 and 34 that are arranged at the front and rear to sandwich the platen 28 and the carriage 25. The two transport rollers 33 and 34 are rotationally driven in synchronization by the transport motor 21 (see FIG. 3), and transport the recording paper 100 forward (transport direction) between the inkjet head 26 and the platen 28.

(Maintenance device)
The maintenance device 6 includes a cap member 36 and a suction pump 37. The cap member 36 is driven up and down by a cap drive motor 39 (see FIG. 3). As a result, the cap member 36 is movable between a cap position that is in close contact with the ink discharge surface 26a of the inkjet head 26 and covers the nozzle 31 and an uncap position that is away from the ink discharge surface 26a (described later). (See FIGS. 4A and 4B). The suction pump 37 is connected to the cap member 36. When the cap member 36 is at the cap position, the suction pump 37 decompresses the inside of the cap member 36, thereby forcibly discharging ink from the plurality of nozzles 31 into the cap member 36. Generally, this ink discharging operation is called suction purge. By this suction purge, it is possible to discharge bubbles and dust mixed in the ink or ink having increased viscosity.

(Control part)
A control unit 40 that controls each unit of the printer 1 is incorporated in the control board 7. As illustrated in FIG. 3, the control unit 40 includes a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, and an ASIC (Application Specific Integrated Circuit) including various control circuits. 44 and the like. The control board 7 includes a scanner 19, a paper feed motor 20 of the paper feed unit 5, an inkjet head 26 of the printer unit 4, a carriage drive motor 32, a transport motor 21, a suction pump 37 of the maintenance device 6, an operation panel 13, and the like. Connected. The control board 7 is electrically connected to an external device 46 such as a PC via the communication unit 45, and image data to be printed is input to the control unit 40 from the external device 46. It has become. Various programs are stored in the ROM 42, and various data for executing these programs are stored. The control unit 40 causes the ASIC 44 to execute processing for controlling operations of the paper feeding unit 5, the printer unit 4, the maintenance device 6, and the like by executing a program stored in the ROM 42 by the CPU 41.

  For example, for printing on the recording paper 100, the control unit 40 executes the following processing. First, when an image print command is input from an external device 46 such as a PC or the operation panel 13, the paper feed motor 20 is controlled to drive the pickup roller 24 and the recording paper placed on the main tray 23a. 100 is supplied to the printer unit 4. In the printer unit 4, the recording motor 100 is transported in the transport direction by controlling the transport motor 21. In addition, ink is ejected from the inkjet head 26 toward the recording paper 100 while the inkjet head 26 is moved in the scanning direction by controlling the carriage drive motor 32 of the printer unit 4. Further, the control unit 40 also controls the raising and lowering operation of the cap member 36 by the cap drive motor 39 and the suction purge by the suction pump 37 with respect to the maintenance device 6.

  In the above description, the control unit 40 performs processing such as printing by the cooperation of the CPU and the ASIC. However, the control unit 40 may include a plurality of CPUs, and the processing may be performed by a plurality of CPUs. Good. Further, the control unit 40 may include a plurality of ASICs, and the processing may be shared by the plurality of ASICs. Alternatively, the processing may be performed by one ASIC alone.

(Control of flushing before printing)
Also, the control unit 40 causes the inkjet head 26 to perform flushing immediately before the printer unit 4 prints an image on the recording paper 100 to discharge the thickened ink in each nozzle 31 (pre-printing flushing).

  Hereinafter, the control of flushing before printing will be described in detail. FIG. 4 is an explanatory diagram of the operation of the inkjet head 26 in the pre-printing flushing. FIG. 5 is a flowchart of pre-printing flushing. In FIG. 5, Si (i = 1, 2, 3...) Indicates a step number.

  In a standby state in which printing on the recording paper 100 is not performed, as shown in FIG. 4A, the ink jet head 26 is located on the right side of the platen 28, and the ink discharge surface is formed by the cap member 36 at the cap position. 26a is covered. Thereby, the viscosity increase of the ink in each nozzle 31 is suppressed. When a print command is input from the external device 46 or the operation panel 13 from this state (S1: Yes), the control unit 40 controls the cap drive motor 39 as shown in FIG. Then, the cap member 36 is moved to the uncapping position (S2). As shown in FIG. 4C, the control unit 40 controls the carriage drive motor 32 to move the inkjet head 26 to the flushing position on the left side of the platen 28 and facing the flushing receiver 38 ( S3). Thereafter, the paper feed motor 20 is controlled to rotate the pickup roller 24 (S4).

  The control unit 40 causes the inkjet head 26 to perform flushing as shown in FIG. 4D until the recording paper 100 is sent to the printer unit 4 by the pickup roller 24. Here, when the recording paper 100 is picked up from the main tray 23 a by the pickup roller 24, a slip may occur between the roller 24 and the recording paper 100. Since the roller 24 slips for a while after the driving of the pickup roller 24 is started, the time until the recording paper 100 is actually sent to the printer unit 4 becomes longer than that when there is no slip. For this reason, flushing is performed for a long time, and the amount of ink consumed increases. Therefore, in the present embodiment, the control unit 40 determines whether the recording paper 100 is supplied based on the current value of the paper feed motor 20 that drives the pickup roller 24, and determines that the recording paper 100 is supplied. When this occurs, the inkjet head 26 is flushed.

  6 to 8 are diagrams showing a change with time of the current supplied to the paper feed motor 20. 6 shows a case where no slip occurs in the pickup roller 24, FIG. 7 shows a case where slip occurs, and FIG. 8 shows a case where the recording paper 100 is not present.

  Power is supplied to the paper feed motor 20 from a power supply device (not shown). The paper feed motor 20 drives the pickup roller 24 at a predetermined rotational speed based on a signal from the control unit 40. At this time, the supply current to the paper feed motor 20 changes according to the load applied to the motor 20. As shown in FIG. 6, when there is no slip between the pickup roller 24 and the recording paper 100, the load of the motor 20 increases as the driving of the roller 24 starts, and the torque increases, so the current value increases. . On the other hand, when a slip occurs between the pickup roller 24 and the recording paper 100 as shown in FIG. 7, or there is no recording paper 100 on the main tray 23a as shown in FIG. 8, and the pickup roller 24 is idle. In this case, since the load applied to the paper feed motor 20 is small and the torque is small, the current value of the motor 20 continues to be low.

  Therefore, the control unit 40 compares the current I of the paper feed motor 20 with a predetermined threshold I0 stored in the ROM 42, and determines whether or not the current I exceeds the threshold I0 (S5). When the current I exceeds the threshold I0 (S5: Yes), the control unit 40 determines that the recording paper 100 is supplied by the pickup roller 24, and causes the inkjet head 26 to start flushing (S6).

  After the start of flushing, when the paper detection sensor 22 (see FIG. 1) detects that the recording paper 100 has reached the printer unit 4 (S7: Yes), the control unit 40 stops the paper feed motor 20. (S8). When the supply current of the paper feed motor 20 decreases and the current I becomes equal to or less than the threshold value I0 (S9: Yes), the control unit 40 ends the flushing of the inkjet head 26 (S10).

  On the other hand, when the current I of the paper feed motor 20 does not exceed the threshold value I0 (S11: Yes), the control unit 40 does not perform flushing on the inkjet head 26 until the current I exceeds the threshold value I0. Wait.

  As described above, in the present embodiment, since the inkjet head 26 is flushed while the recording paper 100 is being supplied by the pickup roller 24, the printing command is input until the printing on the recording paper 100 is started. It is possible to shorten the preparation time. Further, after confirming the state in which the recording paper 100 is supplied by the roller 24 from the current value of the paper feed motor 20 that drives the pickup roller 24, the flushing is started. Therefore, when the recording paper 100 is picked up from the main tray 23a, even if a slip occurs between the roller 24 and the recording paper 100, it is prevented that the flushing is performed unnecessarily for a long time, and the ink consumption is suppressed. The

  Further, when the current I of the paper feed motor 20 becomes equal to or less than the threshold value I0, the flushing of the inkjet head 26 is terminated. As a result, the flushing is completed almost simultaneously with the end of the supply of the recording paper 100, so that the flushing can be continued until just before the supply of the recording paper 100 is completed. In addition, compared with the case where flushing is finished simultaneously with the stop command of the paper feed motor 20, the flushing is performed for a short time, but the time from the end of flushing to the start of printing can be shortened.

  As shown in FIG. 8, if the current value of the paper feed motor 20 does not exceed the threshold value I0 even after a certain time has elapsed after the drive of the paper feed motor 20 is started, the recording paper 100 is placed on the main tray 23a. It is presumed that the recording paper 100 cannot be supplied to the printer unit 4 such as a state where there is no recording or a state where the pickup roller 24 continues to slip for some reason. Therefore, if the current I of the motor 20 does not exceed the threshold value I0 even if the elapsed time Ta since the feeding motor 20 is driven exceeds the predetermined time Ta1 (S11: Yes), the control unit 40 20 is stopped (S12).

  If slip occurs between the pickup roller 24 and the recording paper 100, as shown in FIG. 7, the state where the current I of the paper feed motor 20 is equal to or less than the threshold value I0 (S5: No) continues for a while. Therefore, there is a possibility that the viscosity increase of the ink in the nozzle 31 proceeds during this time. Therefore, if the current I of the motor 20 does not exceed the threshold value I0 even if the elapsed time Tb after the cap member 36 moves to the uncapping position exceeds the predetermined time Tb1 (S13: Yes), the inkjet head 26 Flushing is performed (S14), and the thickened ink in the nozzle 31 is once discharged. After the flushing, the apparatus waits again until the current I of the paper feed motor 20 exceeds the threshold value I0. At this time, the amount of ejection in the flushing may not be so large, and may be less than that in S10. After flushing, the time Tb is reset (S15), and the process returns to S5.

  The time Ta1 used for the determination in S11 and the time Tb1 used for the determination in S13 are stored in advance in the ROM 42 of the control unit 40. For example, Ta1 = 3s and Tb1 = 4s.

  When the paper feeding by the pickup roller 24 and the flushing of the inkjet head 26 are completed, the control unit 40 controls each unit of the printer unit 4 based on the input image data, as shown in FIG. Then, an image is printed on the recording paper 100 by the inkjet head 26.

  In the embodiment described above, the printer 1 corresponds to the “liquid ejecting apparatus” of the invention. The recording paper 100 corresponds to the “sheet” of the present invention. The inkjet head 26 corresponds to the “liquid ejection head” of the present invention. The paper feed motor 20 corresponds to the “motor” of the present invention. The main tray 23a corresponds to the “tray” of the present invention. The ROM 42 corresponds to the “memory” of the present invention. The cap drive motor 39 corresponds to the “cap drive unit” of the present invention. The time Tb1 used for the determination of S13 in FIG. 5 corresponds to the “first time” of the present invention. The time Ta1 used in S11 of FIG. 5 corresponds to the “third time” 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] In the above embodiment, not only the start of flushing (S6 in FIG. 5) but also the end of flushing (S10) are performed by the current value of the paper feed motor 20. On the other hand, the end of the flushing may be performed under conditions different from the current of the paper feed motor 20. For example, flushing may be terminated when the recording paper 100 is supplied to the printer unit 4 by the paper detection sensor 22.

  Alternatively, the ink amount to be ejected by the flushing may be stored in the ROM 42 in advance, and the flushing may be terminated when the ejection amount from the start of the flushing reaches the amount stored in the ROM 42. Conventionally, when the flushing amount is predetermined, if the flushing is performed in parallel with the driving of the paper feed motor 20, the supply of the recording paper 100 is completed when the pickup roller 24 slips. There is a possibility that the flushing may be terminated long before. In this regard, by starting flushing when the current value of the paper feed motor 20 exceeds the predetermined threshold value I0, it is possible to prevent the predetermined amount of flushing from being terminated prematurely.

2] In the above-described embodiment, when the current I of the paper feed motor 20 is equal to or less than the threshold value I0, is flushing performed to suppress ink thickening during standby based on the elapsed time Tb from the transition to the uncapping state? It was determined (see S13 in FIG. 5). Instead of this, whether or not to perform the flushing during standby may be determined based on the elapsed time Ta from the start of driving of the paper feed motor 20. That is, when the elapsed time Ta exceeds the predetermined time Ta2, the thickening suppression flushing may be performed. The predetermined time Ta2 corresponds to the “second time” of the present invention.

3] In the above-described embodiment, after the cap member 36 is separated from the ink jet head 26 and is in the uncapping state, the ink jet head 26 is in the uncapping state until the current value of the paper feed motor 20 exceeds the threshold value I0. doing. However, if the pick-up roller 24 slips or the like and the uncapping state continues for a while, the ink in the nozzle 31 increases in viscosity.

  Therefore, as shown in FIGS. 9 and 10, the nozzles are not ejected until the current of the paper feed motor 20 exceeds the threshold value I0 after the cap member 36 moves to the uncapping position (S23). The ink in the ink 31 may be agitated, or ink agitation may be performed (S24). The flowchart of FIG. 10 differs from that of FIG. 5 of the above embodiment only in that an ink stirring start step (S24) is included, and the other steps are the same as those in FIG. Is omitted.

  The ink agitation in S24 is performed by applying a smaller energy to the ink as compared with the case of discharging from the nozzle 31. Specifically, a drive signal different from the case where ink is ejected is supplied from the drive IC 35 (see FIG. 3) to each drive element, and pressure waves that are not ejected are generated in the ink. By this pressure wave, the meniscus of the ink formed on the nozzle 31 slightly vibrates, so that the ink in the nozzle 31 is agitated and viscosity increase is suppressed. In this way, by performing ink agitation (meniscus fine vibration) before the flushing to suppress the increase in the viscosity of the ink in the nozzles 31, the ink ejection in the subsequent flushing is stabilized. In addition, unlike flushing, since ink is not ejected from the nozzles 31, ink is not consumed by this stirring operation.

  However, in the stirring of the ink, the meniscus vibrates and the air outside the nozzle 31 comes into contact with the ink. Therefore, when ink stirring is performed for a long time, the frequency of contact between the ink and air increases, and on the contrary, the viscosity of the ink proceeds. From this point of view, as in the previous embodiment, when the motor current I does not exceed the threshold I0 even if the elapsed time Tb after the cap member 36 moves to the uncapping position exceeds the predetermined time Tb1. (S34: Yes), it is preferable to cause the inkjet head 26 to perform flushing (S35). Thereby, the thickened ink in the nozzle 31 is once discharged. After the flushing in S35, the ink agitation is performed again until the current I of the paper feed motor 20 exceeds the threshold value I0.

4] When the printer 1 can use a plurality of types of recording paper 100, depending on the type (size, weight, surface contact resistance, etc.) of the recording paper 100 used, as shown in FIGS. In addition, the current change of the paper feed motor 20 changes. For example, when a sheet having a large size or weight per unit area is used, a torque necessary for feeding the recording sheet 100 is larger than that of a sheet having a small size or weight, and the current of the sheet feeding motor 20 is also increased. There is a tendency to grow. Therefore, the threshold I0 used for the determination may be made different depending on the type of the recording paper 100.

  A plurality of threshold values corresponding to the type of the recording paper 100 are stored in the ROM 42. For example, as shown in FIG. 12A, even if three threshold values (Ia, Ib, Ic) are set for three types of recording paper 100 (plain paper, matte paper, glossy paper) having different paper qualities. Good. For example, Ia (plain paper) <Ib (matte paper) <Ic (glossy paper). Alternatively, as shown in FIG. 12B, even if three threshold values (Id, Ie, If) are set for three types of recording papers 100 (A4, A3, L-size photographic papers) having different sizes. Good. The magnitude relationship between these threshold values is, for example, If (L-size photographic paper) <Id (A4) <Ie (A3).

  The flowchart of this modification is as shown in FIG. When a print command is input from the external device 46 or the like (S41: Yes), the control unit 40 acquires information regarding the type of the recording paper 100 input together with the print command (S42). Next, the threshold I0 is determined from the information acquired in S42 and the threshold information stored in the ROM 42 (S43). The subsequent steps are the same as those after S2 in FIG. 5 of the above embodiment, and flushing is executed when the current of the paper feed motor 20 exceeds the threshold value I0 determined in S43 in S5. In this modified embodiment, the type of the recording paper 100 to be used is recognized, and the determination is performed using the threshold value corresponding to the type of the recording paper 100. Therefore, an appropriate determination according to the type of the recording paper 100 is performed. Can do.

5] The ease of thickening the ink in the nozzle 31 varies depending on the temperature of the ink and the humidity around the inkjet head 26. That is, the higher the ink temperature, the easier the ink thickening in the nozzle 31 proceeds. Further, as the humidity around the inkjet head 26 is lower, the viscosity of the ink in the nozzles 31 is more likely to proceed. Therefore, the amount of ink ejected by flushing may be changed according to temperature and humidity conditions.

  As shown in FIG. 14, the printer 1 </ b> A in this modified form includes a temperature sensor 50 that detects the temperature of ink in the inkjet head 26, and a humidity sensor 51 that detects the humidity around the inkjet head 26. The temperature sensor 50 may directly measure the temperature of the ink, but may be attached to a part of the inkjet head 26 and measure the temperature of the part instead of the ink temperature. The humidity sensor 51 is preferably attached to the inkjet head 26, and more preferably provided near the nozzle 31.

  As shown in FIG. 15, the ROM 42 of the control unit 40 has four flushing amounts (Va, Vb, Vc, Vd) corresponding to four temperature ranges and five flushing amounts (Ve) corresponding to five humidity ranges. , Vf, Vg, Vh, Vi) are stored. Note that the flushing amounts Va to Vi shown in FIG. 15 indicate the ink discharge amount per unit time for each nozzle 31. The flushing amount of each nozzle 31 can be varied by changing the drive signal supplied from the drive IC 35 to the drive element corresponding to each nozzle 31.

  The higher the temperature, the easier the drying of the ink progresses, but conversely, the viscosity of the ink becomes lower and works favorably for ejection. Therefore, the higher the temperature, the more the flushing amount should be increased. For example, the magnitude relationship of the flushing amount with respect to temperature is Va = Vb = Vd> Vc, and only the flushing amount Vc when the temperature is in the optimum temperature range (20 to 30 ° C.) is reduced. On the other hand, as the humidity decreases, the ink viscosity increases more easily as the humidity decreases. Therefore, the flushing amount is preferably increased as the humidity decreases. That is, Ve> Vf> Vg> Vh> Vi. Further, when the humidity is considerably high (for example, humidity of 60 to 100%), the speed of ink thickening is slow, so that it is only necessary to perform ink stirring without performing flushing and stirring without ejecting ink.

  The flowchart of this modification is as shown in FIG. When a print command is input from the external device 46 or the like (S51: Yes), the control unit 40 acquires information about the ink temperature from the temperature sensor 50, and acquires information about humidity from the humidity sensor 51 (S52). . Further, the flushing amount is determined with reference to the information stored in the ROM 42 of FIG. 15 (S53). For example, when the temperature is 25 ° C. and the humidity is 50%, the flushing amount of each nozzle 31 is calculated from the values of Vc and Vg stored in the ROM 42. The subsequent steps are the same as those after S2 in FIG. 5 of the above embodiment, and when the current of the paper feed motor 20 exceeds the threshold value I0, the amount of flushing determined in S53 is executed. In FIG. 16, the flushing amount is changed based on both the temperature and humidity conditions. However, the flushing amount may be changed only on one of the temperature and humidity conditions.

6] In the above embodiment, when the current of the paper feeding motor 20 does not exceed the threshold value I0, the motor 20 is stopped according to the elapsed time Ta from the start of driving of the motor 20 (S11, S12), and unloaded Flushing is performed according to the elapsed time Tb since the transition to the capping state (S13, S14). These processes are not essential. As shown in FIG. 17, when the current of the paper feed motor 20 does not exceed the threshold value I0 (S65: No), the inkjet head 26 is simply kept waiting until the threshold value I0 is exceeded. But you can.

7] In the above embodiment, after the cap member 36 is set to the uncapped position, the ink jet head 26 is moved to the flushing position facing the flushing receiver 38 to perform the flushing. On the other hand, as shown in FIG. 18, after moving the cap member 36 from the standby state (a) to the uncapped position as shown in (b), the carriage 25 is not moved in the scanning direction. You may flush as it is toward the cap member 36 like (c) as it is. That is, the cap member 36 may be used as a flushing receptacle.

8] The above embodiment is an example in which a so-called serial type printer Japanese invention in which the ink jet head 26 is moved in the scanning direction together with the carriage 25 and ejects ink onto the recording paper 100 is applied. Is not limited to this. That is, the present invention can also be applied to a printer having a so-called line-type inkjet head in which a plurality of nozzles are arranged in the width direction of the recording paper.

  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.

1, 1A Inkjet printer 20 Paper feed motor 23a Main tray 24 Pickup roller 26 Inkjet head 26a Ink discharge surface 31 Nozzle 36 Cap member 39 Cap drive motor 40 Control unit 100 Recording paper

Claims (9)

A liquid discharge head having a nozzle for discharging liquid toward the sheet;
A pickup roller for supplying the sheet placed on a tray to the liquid discharge head;
A motor for driving the pickup roller;
Including a memory that stores a threshold value relating to the current of the motor, the liquid ejection head, and a control unit that controls the motor, and
The controller is
It is determined whether the current of the motor when driving the pickup roller exceeds the threshold value, and when the current of the motor exceeds the threshold value, the liquid ejection head causes the liquid to be ejected from the nozzle. A liquid ejecting apparatus that performs flushing. A cap member that is in close contact with the liquid discharge head and covers the nozzle;
A cap drive unit that moves the cap member between a cap position that covers the nozzle and an uncap position that is distant from the liquid ejection head;
The controller is
When the signal for starting the discharge operation of the liquid discharge head to the sheet is input in a state where the cap member is at the cap position, the cap drive unit is controlled to remove the cap member from the uncap. Move it to the position
2. The liquid ejection apparatus according to claim 1, wherein the liquid ejection head performs the flushing when the current of the motor exceeds the threshold after the cap member has moved to the uncapping position. 3. . The controller is
Liquid agitation in which the liquid ejection head agitates the liquid in the nozzle without ejecting the liquid after the cap member moves to the uncapping position until the current of the motor exceeds the threshold value. The liquid ejecting apparatus according to claim 2, wherein The controller is
If the current of the motor does not exceed the threshold value even after a predetermined first time has elapsed since the cap member moved to the uncapping position, the flushing is performed by the liquid ejection head. The liquid ejection apparatus according to claim 2, wherein: The controller is
If the motor current does not exceed the threshold value even after a predetermined second time has elapsed after the pickup roller starts to be driven by the motor, the flushing is performed by the liquid discharge head. The liquid ejection device according to claim 1. The controller is
6. The motor is stopped if the current of the motor does not exceed the threshold value even after a predetermined third time has elapsed after the pickup roller starts to be driven by the motor. The liquid ejection apparatus according to any one of the above. The memory stores a plurality of threshold values according to the type of the sheet,
The controller is
Obtaining information about the type of sheet,
The flushing for causing the liquid discharge head to discharge liquid from the nozzle is performed when the current of the motor exceeds a threshold value according to the acquired information on the sheet type. 7. The liquid ejection device according to any one of 6.   The control unit changes the amount of liquid ejected by the flushing according to any one of a temperature of the liquid and a humidity around the liquid ejection head. The liquid ejection apparatus according to any one of the above. The controller is
The liquid ejection apparatus according to claim 1, wherein the flushing of the liquid ejection head is terminated when the current of the motor becomes equal to or less than the threshold value.

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