JP7516866B2 - Liquid ejection device - Google Patents

Description

The present invention relates to a liquid ejection device equipped with a liquid ejection head that ejects liquid.

An inkjet recording device to which a liquid ejection device is applied is equipped with a liquid ejection head that ejects ink (liquid). The liquid ejection head has a piezoelectric actuator (piezoelectric element) and a liquid ejection hole, and is configured to eject ink from the liquid ejection hole in response to the driving of the piezoelectric actuator.

Ink has the property that its viscosity increases in a low temperature environment. When the viscosity of the ink increases, this can cause poor ejection of the ink from the liquid ejection holes of the liquid ejection head. In order to prevent such poor ejection, it is necessary to warm the ink to a predetermined appropriate temperature before starting ejection through the liquid ejection head.

Patent document 1 discloses a technique for heating the ink in a liquid ejection head in a relatively short time. In this technique, the ink is oscillated in the liquid ejection head by driving a piezoelectric actuator to an extent that does not cause ink to be ejected from the liquid ejection holes. The ink is oscillated in response to the driving of the piezoelectric actuator, allowing the ink to be heated in a short time in the liquid ejection head.

Patent No. 5417240

However, the technology disclosed in Patent Document 1 has the problem that it is not possible to sufficiently suppress ink ejection failures from the liquid ejection holes of the liquid ejection head.

The present invention was made in consideration of these circumstances, and its purpose is to provide a liquid ejection device that can heat the liquid so as to more reliably prevent poor ejection of the liquid from the liquid ejection holes of the liquid ejection head.

According to one aspect of the present invention, there is provided a liquid ejection device including a liquid ejection head having a piezoelectric actuator and a liquid ejection surface formed with liquid ejection holes that eject liquid in response to driving of the piezoelectric actuator, a cap unit having a cap portion that is placed on the liquid ejection surface, a head temperature detection sensor that detects a temperature of the liquid ejection head, and a control unit that controls the liquid ejection head and the cap unit. The control unit is configured to execute, with respect to a power supply state of a power supply unit, power-on control at the time of power-on, and state transition control between a normal state including a liquid ejection state in which liquid is ejected from the liquid ejection holes and a power-saving sleep state, and when a detection result of the head temperature detection sensor indicates a value lower than a predetermined reference temperature during execution of a sleep return control from the sleep state to the normal state in the state transition control, execute cap control to control the cap unit so that the cap portion is placed on the liquid ejection surface, and execute limited drive control to drive the piezoelectric actuator within a range capable of restricting ejection from the liquid ejection holes.

In addition, in the above liquid ejection device, the control unit executes the cap control and the limited drive control until the detection result of the head temperature detection sensor indicates a value equal to or higher than the reference temperature.

According to this liquid ejection device, the temperature of the liquid ejection head, i.e., the temperature of the liquid inside the liquid ejection head, is detected by a head temperature detection sensor. When the detection result of this head temperature detection sensor indicates a value lower than the reference temperature, the control unit executes limited drive control to drive the piezoelectric actuator within a range that can restrict ejection from the liquid ejection hole. Driving the piezoelectric actuator in accordance with the limited drive control causes the liquid inside the liquid ejection hole to oscillate, and the liquid can be heated in a short period of time inside the liquid ejection head.

Here, the liquid in the liquid ejection head is oscillated by driving the piezoelectric actuator so as to repeatedly appear and disappear from the liquid ejection hole. Therefore, during the oscillation in the liquid ejection head, the part of the liquid exposed from the liquid ejection hole is exposed to the outside air. In this case, the liquid exposed to the outside air may become thickened due to drying. Such thickening of the liquid due to drying during the oscillation in the liquid ejection head may cause poor ejection of the liquid from the liquid ejection hole. Therefore, when executing the limit drive control, the control unit executes cap control to control the cap unit so that the cap unit is placed over the liquid ejection surface in which the liquid ejection hole is formed in the liquid ejection head. This makes it possible to prevent the liquid from being exposed to the outside air by the cap unit during the oscillation of the liquid in the liquid ejection head in response to the drive of the piezoelectric actuator. Therefore, it is possible to suppress as much as possible the phenomenon in which the liquid becomes thickened due to drying during the oscillation in the liquid ejection head. As a result, it is possible to heat the liquid in the liquid ejection head in a short time so as to more reliably suppress poor ejection of the liquid from the liquid ejection hole of the liquid ejection head.

In the above liquid ejection device , when the detection result of the head temperature detection sensor indicates a value lower than the reference temperature during execution of the power-on control , the control unit executes the cap control and the limited drive control.

If the power supply unit is in a stopped state or sleep state for a long period of time, there is a high possibility that the temperature of the liquid ejection head, i.e., the temperature of the liquid in the liquid ejection head, will become lower than the reference temperature. Therefore, the control unit executes the cap control and the limited drive control during power-on control when the power supply unit is turned on, and during sleep recovery control from a sleep state to a normal state. This makes it possible to heat the liquid in the liquid ejection head in a state that prevents it from drying out when the power is turned on and when the device is returning from sleep, when the temperature of the liquid ejection head is likely to be lower than the reference temperature.

In the above liquid ejection device, the control unit is configured to execute liquid ejection control for driving the piezoelectric actuator so as to eject liquid from the liquid ejection hole when a liquid ejection request indicating a request for ejection of liquid from the liquid ejection hole is input. Then, when the detection result of the head temperature detection sensor indicates a value lower than the reference temperature during execution of the liquid ejection control, the control unit executes the cap control and the limited drive control in priority to the liquid ejection control, and then executes the cap retraction control for controlling the cap unit so as to position the cap part at a retracted position relative to the liquid ejection surface, and executes the liquid ejection control.

In this aspect, when a liquid ejection request is input, the control unit executes liquid ejection control that drives the piezoelectric actuator so that liquid is ejected from the liquid ejection hole. For example, when a large amount of liquid is ejected from the liquid ejection hole, the entire amount of liquid heated in the liquid ejection head may be consumed during the execution of the liquid ejection control. In this case, if the execution of the liquid ejection control is continued as is, there is a possibility that unheated liquid may be ejected from the liquid ejection hole, and a liquid ejection failure phenomenon may occur. In order to avoid such a phenomenon, when the detection result of the head temperature detection sensor indicates a value lower than the reference temperature during the execution of the liquid ejection control, the control unit executes the cap control and the limit drive control in priority to the liquid ejection control, and then re-executes the liquid ejection control. This makes it possible to more reliably suppress the occurrence of liquid ejection failure from the liquid ejection hole during the execution of the liquid ejection control.

In the above liquid ejection device, the control unit controls the cap unit so that the cap unit is maintained in a state in which it covers the liquid ejection surface after the limit drive control is stopped until the liquid ejection control is started.

In this embodiment, the cap portion prevents the liquid ejection hole from being exposed to the outside air between the stopping of the limit drive control and the start of the liquid ejection control, so that the liquid in the liquid ejection head can be prevented from drying out through the liquid ejection hole during that time.

In the above liquid ejection device, after the limit drive control is stopped, the control unit executes the cap retraction control so that the cap portion covering the liquid ejection surface is positioned at a retracted position relative to the liquid ejection surface before the liquid ejection control is started.

In this embodiment, the cap portion is positioned in a retracted position relative to the liquid ejection surface between the stop of the limit drive control and the start of the liquid ejection control, so there is no waiting time required for the cap portion to be retracted when the liquid ejection control starts, and the time until the liquid ejection control starts can be shortened.

The liquid ejection device may further include a heater for heating the liquid ejection head. In this case, the control unit controls the heater based on the detection result of the head temperature detection sensor so that the temperature of the liquid ejection head in the normal state remains within a predetermined allowable range centered on the reference temperature.

In this embodiment, the temperature of the liquid heated by the limited drive control, which oscillates the liquid within the liquid ejection head in response to the drive of the piezoelectric actuator, can be maintained for a long period of time by the heater.

As described above, the present invention provides a liquid ejection device capable of heating the liquid so as to more reliably prevent liquid ejection failures from the liquid ejection holes of the liquid ejection head.

1 is a diagram illustrating a schematic configuration of a recording apparatus to which a liquid ejection apparatus according to an embodiment of the present invention is applied; FIG. 2 is a block diagram of a recording device. FIG. 2 is an enlarged view showing the periphery of a liquid ejection head provided in the recording apparatus. FIG. 2 is a cross-sectional view showing the internal structure of the liquid ejection head. 2 is an enlarged cross-sectional view showing a main part of the liquid ejection head. FIG. FIG. 2 is a diagram showing a cap unit provided in the recording apparatus. FIG. 4 is a diagram illustrating state transitions of the recording device. 5A and 5B are diagrams for explaining a control operation of a control unit provided in the recording apparatus. 5 is a flowchart showing a control flow of power-on control and sleep return control executed by a control unit. 5 is a flowchart showing a control flow of normal control executed by a control unit. 5 is a flowchart showing a control flow of normal control executed by a control unit.

An inkjet recording device to which a liquid ejection device according to one embodiment of the present invention is applied will be described below with reference to the drawings. Note that in the following, directional relationships will be described using XYZ orthogonal coordinate axes. The X direction corresponds to the front-to-rear direction (+X is rear, -X is front), the Y direction corresponds to the left-to-right direction (+Y is left, -Y is right), and the Z direction corresponds to the up-to-down direction (+Z is up, -Z is down). In the following description, the term "sheet" refers to copy paper, coated paper, overhead projector sheets, cardboard, postcards, tracing paper, or other sheet material that undergoes printing processing.

Figure 1 is a schematic diagram of a recording device 1 to which a liquid ejection device according to one embodiment of the present invention is applied. Figure 2 is a block diagram of the recording device 1. Figure 3 is an enlarged view of the periphery of a liquid ejection head 51 provided in the recording device 1. The recording device 1 is a liquid ejection device that ejects ink as a liquid, and is an inkjet type image forming device that forms (records) an image on a sheet S by ejecting the ink. The recording device 1 includes a device main body 10, a paper feed section 20, a sheet inversion section 30, a sheet transport unit 40, and a recording section 50.

The device body 10 is a box-shaped housing that houses various devices for recording an image on a sheet S. The device body 10 is formed with a first transport path 11, a second transport path 12, and a third transport path 13, which serve as transport paths for the sheet S.

The paper feed unit 20 feeds sheets S to the first transport path 11. The paper feed unit 20 includes a paper feed cassette 21 and a pickup roller 22. The paper feed cassette 21 is detachable from the device body 10 and stores sheets S therein. The pickup roller 22 is disposed on the -Y side of the paper feed cassette 21 and at the end on the +Z side. The pickup roller 22 picks up the topmost sheets S of the stack of sheets stored in the paper feed cassette 21 one by one, and sends them to the first transport path 11.

The sheet S fed to the first transport path 11 is transported by a first transport roller pair 111 provided in the first transport path 11 to a registration roller pair 44 of the sheet transport unit 40 arranged at the downstream end of the first transport path 11. A paper feed tray 25 is also arranged on the -Y side of the device body 10, and the sheet S can be placed on the upper surface of the paper feed tray 25. The sheet S placed on the paper feed tray 25 is sent towards the registration roller pair 44 by the paper feed roller 24.

The registration roller pair 44 is a transport roller pair located at the upstream end of the sheet transport unit 40. The registration roller pair 44 corrects skew of the sheet S, and sends the sheet S toward the transport belt 41 via the sheet introduction guide section 23 in accordance with the timing of the printing process by the recording section 50. The sheet introduction guide section 23 guides the sheet S sent by the registration roller pair 44 toward the outer circumferential surface 411 of the transport belt 41 in the sheet transport unit 40.

When the leading edge of the sheet S guided by the sheet introduction guide section 23 comes into contact with the outer peripheral surface 411 of the conveyor belt 41, the sheet S is conveyed in the sheet conveying direction A while being held on the outer peripheral surface 411 by the drive of the conveyor belt 41. The sheet conveying direction A is the direction from the -Y side to the +Y side in the Y direction.

The sheet transport unit 40 is disposed on the -Z side of the recording section 50 so as to face the liquid ejection head 51. The sheet transport unit 40 transports the sheet S, which has been guided and introduced by the sheet introduction guide section 23, in the sheet transport direction A so that the sheet S passes through the -Z side of the recording section 50. The sheet transport unit 40 includes a transport belt 41 and a suction section 43 in addition to a pair of registration rollers 44.

The conveyor belt 41 is an endless belt that has a width in the X direction and extends in the Y direction. The conveyor belt 41 is disposed opposite the recording unit 50 and conveys the sheet S in the sheet conveying direction A on its outer peripheral surface 411.

The conveying belt 41 is stretched around a first roller 421, a second roller 422, a third roller 423, and a pair of fourth rollers 424. A suction section 43 is disposed inside the stretched conveying belt 41, facing the inner peripheral surface 412. The first roller 421 is driven to rotate by a drive motor (not shown), causing the conveying belt 41 to rotate in a predetermined rotation direction. As the conveying belt 41 rotates, the sheet S held on the outer peripheral surface 411 is conveyed in the sheet conveying direction A.

The second roller 422 is a belt speed detection roller that extends along the X direction, and is disposed upstream of the suction section 43 in the sheet conveying direction A. Here, the area on the outer circumferential surface 411 of the conveying belt 41 that faces the liquid ejection head 51 and is between the first roller 421 and the second roller 422 becomes the predetermined conveying area for holding and conveying the sheet S. The second roller 422 rotates in conjunction with the revolution of the conveying belt 41. A pulse plate (not shown) is attached to the second roller 422, and this pulse plate rotates integrally with the second roller 422. The rotation speed of the conveying belt 41 is detected by measuring the rotation speed of the pulse plate.

The third roller 423 is a tension roller extending along the X direction, and applies tension to the conveyor belt 41 so that the conveyor belt 41 does not sag. The third roller 423 rotates in conjunction with the revolutions of the conveyor belt 41. The pair of fourth rollers 424 are guide rollers extending along the Y direction, and guide the conveyor belt 41 so that the conveyor belt 41 passes through the -Z side of the suction section 43. The pair of fourth rollers 424 rotate in conjunction with the revolutions of the conveyor belt 41.

The conveyor belt 41 has multiple suction holes that run through it in the thickness direction from the outer peripheral surface 411 to the inner peripheral surface 412.

The suction unit 43 is disposed opposite the recording unit 50 via the conveyor belt 41. The suction unit 43 brings the sheet S into close contact with the outer circumferential surface 411 of the conveyor belt 41 by generating a negative pressure between the sheet S held on the outer circumferential surface 411 of the conveyor belt 41 and the conveyor belt 41. The suction unit 43 includes a belt guide member 431, a suction housing 432, a suction device 433, and an exhaust duct 434.

The belt guide member 431 is disposed opposite the area between the first roller 421 and the second roller 422 on the inner peripheral surface 412 of the conveyor belt 41, and is a plate having a width dimension substantially equal to the length of the conveyor belt 41 in the width direction (Y direction). The belt guide member 431 constitutes the upper surface of the suction housing 432, and has substantially the same shape as the suction housing 432 when viewed from the +Z side. The belt guide member 431 guides the circular movement of the conveyor belt 41 between the first roller 421 and the second roller 422 in conjunction with the rotation of the first roller 421.

The belt guide member 431 also has a number of grooves formed on the belt guide surface facing the inner circumferential surface 412 of the conveyor belt 41. Each groove is formed to correspond to a suction hole in the conveyor belt 41. The belt guide member 431 also has a through hole provided to correspond to each groove. The through hole is a hole that penetrates the belt guide member 431 in the thickness direction within each groove, and communicates with the suction hole in the conveyor belt 41 via each groove.

The suction unit 43 equipped with the belt guide member 431 configured as described above generates a suction force by sucking air from the space on the +Z side of the conveyor belt 41 through the grooves and through holes of the belt guide member 431 and the suction holes of the conveyor belt 41. This suction force generates an airflow (suction wind) toward the suction unit 43 in the space above the conveyor belt 41. When the sheet S is guided onto the conveyor belt 41 by the sheet introduction guide unit 23 and covers part of the outer circumferential surface 411 of the conveyor belt 41, a suction force (negative pressure) acts on the sheet S, causing the sheet S to adhere closely to the outer circumferential surface 411 of the conveyor belt 41.

The suction housing 432 constitutes a support frame that supports the belt guide member 431 from below. The suction housing 432 is a box-shaped housing that is open on the +Z side, and is disposed on the -Z side of the conveyor belt 41 so that the opening on the +Z side is covered by the belt guide member 431. The suction housing 432 cooperates with the belt guide member 431 that constitutes its upper surface to define the suction space 432A. In other words, the space surrounded by the suction housing 432 and the belt guide member 431 becomes the suction space 432A. This suction space 432A communicates with the suction holes of the conveyor belt 41 via the grooves and through holes of the belt guide member 431.

An opening 432B is formed in the bottom wall of the suction housing 432, and a suction device 433 is disposed corresponding to this opening 432B. An exhaust duct 434 is connected to this suction device 433. This exhaust duct 434 is connected to an exhaust port (not shown) provided in the device main body 10.

The sheet transport unit 40 can move up and down in the Z direction. The sheet transport unit 40 moves up and down by a transport lift mechanism 40A (Figure 2). In other words, the transport lift mechanism 40A is a mechanism for moving the sheet transport unit 40 up and down in the Z direction.

The recording unit 50 is disposed on the +Z side of the sheet transport unit 40. Specifically, the recording unit 50 is disposed on the +Z side of the sheet transport unit 40 so as to face the outer peripheral surface 411 of the transport belt 41. The recording unit 50 performs a printing process to record an image on the sheet S that is transported in the sheet transport direction A while being held on the outer peripheral surface 411 of the transport belt 41. In this embodiment, the recording unit 50 uses an inkjet recording method for forming an image, and ejects ink as a liquid to record an image on the sheet S.

The recording unit 50 includes liquid ejection heads 51Bk, 51C, 51M, and 51Y held in a head housing 55. Liquid ejection head 51Bk ejects black ink, liquid ejection head 51C ejects cyan ink, liquid ejection head 51M ejects magenta ink, and liquid ejection head 51Y ejects yellow ink. Liquid ejection heads 51Bk, 51C, 51M, and 51Y are arranged side by side from the upstream side to the downstream side in the sheet conveying direction A. Liquid ejection heads 51Bk, 51C, 51M, and 51Y have the same configuration except for the color of ink they eject, and are therefore sometimes collectively referred to as liquid ejection heads 51.

The liquid ejection head 51 ejects ink onto the sheet S, which is conveyed in the sheet conveying direction A while being held on the outer peripheral surface 411 of the conveyor belt 41, to record an image on the sheet S. In detail, the liquid ejection head 51 ejects ink toward the sheet S, which is conveyed by the conveyor belt 41 and passes a position facing the liquid ejection head 51. This causes an image to be recorded on the sheet S. Details of the liquid ejection head 51 will be described later.

The sheet S on which the image has been recorded is transported by the transport belt 41 and sent to the transport unit 45 arranged downstream of the transport belt 41 in the sheet transport direction A. The transport unit 45 transports the sheet S received from the sheet transport unit 40 further downstream in the sheet transport direction A. A de-curler unit 46 is arranged downstream of this transport unit 45. The de-curler unit 46 transports the sheet S further downstream in the sheet transport direction A while correcting the curl of the sheet S received from the transport unit 45. The sheet S transported by the de-curler unit 46 is sent to the second transport path 12.

The second transport path 12 extends along the side surface on the +Y side of the device body 10. The sheet S sent to the second transport path 12 is transported by a second transport roller pair 121 provided on the second transport path 12 toward the paper discharge port 12A formed on the +Y side of the device body 10, and is discharged from the paper discharge port 12A onto the paper discharge section 47.

On the other hand, if the sheet S sent to the second conveying path 12 is for double-sided printing in which the printing process of the first side (front side) has been completed, the sheet S is sent to the sheet inversion unit 30. The sheet inversion unit 30 is a conveying path branched off in the middle of the second conveying path 12, and is a portion where the sheet S is inverted (switched back). The sheet S inverted by the sheet inversion unit 30 is sent to the third conveying path 13. The sheet S sent to the third conveying path 13 is reversed by the third conveying roller pair 131 provided on the third conveying path 13, and is supplied again on the outer circumferential surface 411 of the conveying belt 41 in an inverted state via the registration roller pair 44 and the sheet introduction guide unit 23. The sheet S supplied to the outer circumferential surface 411 of the conveying belt 41 in an inverted state in this way is conveyed by the conveying belt 41, and the recording unit 50 performs printing on the second side (back side) opposite to the first side. After double-sided printing is completed, the sheet S passes through the second transport path 12 and is discharged onto the discharge section 47 from the discharge outlet 12A.

As shown in FIG. 3, a container mounting section 60 is disposed above the liquid ejection head 51 of the recording section 50 on the +Z side. A plurality of ink containers 61Y, 61M, 61C, and 61Bk, each containing ink of each color, yellow (Y), magenta (M), cyan (C), and black (Bk), are detachably mounted on the container mounting section 60. The ink containers 61Y, 61M, 61C, and 61Bk are liquid storage containers capable of containing ink as liquid, and are connected to the liquid ejection heads 51Y, 51M, 51C, and 51Bk via ink supply tubes 62 and sub-ink tanks 64 of each color. The ink containers 61Y, 61M, 61C, and 61Bk have the same configuration except for the color of ink they contain, and are therefore sometimes collectively referred to as ink containers 61.

An electromagnetic valve 63 that opens and closes the ink flow path in the ink supply tube 62 is provided in the upstream portion of the ink supply tube 62 with respect to the sub-ink tank 64. The sub-ink tank 64 is disposed between the ink container 61 and the liquid ejection head 51, and is a liquid storage tank that temporarily stores the ink in the ink container 61 before the ink is supplied to the liquid ejection head 51. In this embodiment, the ink stored in the sub-ink tank 64 is supplied to the liquid ejection head 51. The sub-ink tank 64 is provided with an ink sensor (not shown) that detects the amount of ink in the sub-ink tank 64, and the electromagnetic valve 63 is opened according to the amount of ink, and ink is supplied from the ink container 61 to the sub-ink tank 64. The sub-ink tank 64 is disposed at a lower position than the ink container 61, and ink of the corresponding color is supplied from the ink container 61 to the sub-ink tank 64 by the ink pressure generated by the height difference between the sub-ink tank 64 and the ink container 61.

The liquid ejection head 51 provided in the recording unit 50 will be described in detail with reference to Figs. 4 and 5. The liquid ejection head 51 has an elongated shape extending in the X direction. The liquid ejection head 51 is composed of a liquid relay flow path member 52, a liquid ejection flow path member 53, and a piezoelectric actuator substrate 54. In the liquid ejection head 51, the liquid ejection flow path member 53 and the piezoelectric actuator substrate 54 are joined, and the liquid relay flow path member 52 is laminated and bonded to the liquid relay flow path member 52 with the piezoelectric actuator substrate 54 sandwiched between them. However, there is no bond between the piezoelectric actuator substrate 54 and the liquid relay flow path member 52, and a space 524 is appropriately formed.

The liquid relay flow path member 52 has a generally rectangular parallelepiped shape extending in the X direction, and constitutes the +Z side of the liquid ejection head 51. The liquid relay flow path member 52 has a liquid inlet 521 connected to the sub-ink tank 64, a liquid relay port 522 connected to the liquid ejection flow path member 53, and an internal liquid relay flow path 523 that guides the ink flowing in from the liquid inlet 521 to the liquid relay port 522.

The liquid discharge flow path member 53 has a generally rectangular parallelepiped shape extending in the X direction, is located on the -Z side of the liquid relay flow path member 52, and constitutes the -Z side portion of the liquid discharge head 51. The liquid discharge flow path member 53 has a common flow path 531, a plurality of individual supply flow paths 532, a plurality of liquid pressure chambers 533, a plurality of individual discharge flow paths 534, and a plurality of liquid discharge holes 535.

The common flow path 531 is a flow path formed inside the liquid discharge flow path member 53 and connected to the liquid relay port 522 of the liquid relay flow path member 52. The multiple individual supply flow paths 532 are internal flow paths of the liquid discharge flow path member 53 that are connected to the common flow path 531 in a separated state. In the multiple individual supply flow paths 532, the end opposite to the side connected to the common flow path 531 is connected to the corresponding liquid pressure chamber 533. The multiple liquid pressure chambers 533 are hollow areas that open to the upper surface of the liquid discharge flow path member 53. The opening of each of the multiple liquid pressure chambers 533 is closed by bonding the piezoelectric actuator substrate 54 to the upper surface of the liquid discharge flow path member 53. The multiple individual discharge flow paths 534 are internal flow paths of the liquid discharge flow path member 53 that are connected to the corresponding liquid pressure chambers 533 in a separated state. In each of the multiple individual discharge flow paths 534, the end opposite to the side connected to the liquid pressure chamber 533 is connected to the liquid discharge hole 535. The liquid ejection holes 535 are connected to corresponding individual ejection paths 534 in a separated state. The liquid ejection holes 535 open to the lower surface of the liquid ejection path member 53. In other words, the lower surface of the liquid ejection path member 53 constitutes a liquid ejection surface 535S in which the liquid ejection holes 535 are formed.

In the liquid discharge flow path member 53 configured as described above, the multiple liquid pressurizing chambers 533 are connected to a common flow path 531 that is connected to the liquid relay port 522 of the liquid relay flow path member 52 via individual supply flow paths 532. Furthermore, the multiple liquid pressurizing chambers 533 and the multiple liquid discharge holes 535 are connected to each other via individual discharge flow paths 534. Also, as shown in FIG. 4, the liquid discharge surface 535S in which the multiple liquid discharge holes 535 are formed is provided with a protrusion 536 that protrudes to the -Z side.

As shown in FIG. 5, the piezoelectric actuator substrate 54 has a laminated structure in which a first piezoelectric ceramic layer 541 and a second piezoelectric ceramic layer 542 are laminated. The piezoelectric actuator substrate 54 further has a common electrode 543 and an individual electrode 544. The individual electrode 544 is an electrode that is disposed at a position facing the liquid pressure chamber 533 on the upper surface of the piezoelectric actuator substrate 54. The common electrode 543 extends so as to cover all the liquid pressure chambers 533 in the area facing the piezoelectric actuator substrate 54. The common electrode 533 is grounded and held at ground potential.

By selectively supplying the ejection control signal CS2 (see FIG. 8 below), which is a predetermined drive signal, to the individual electrode 544, pressure is applied to the ink in the liquid pressure chamber 533 corresponding to the individual electrode 544. As a result, ink is ejected from the corresponding liquid ejection hole 535 through the individual ejection flow path 534. That is, the portion of the piezoelectric actuator substrate 54 facing each liquid pressure chamber 533 corresponds to each individual piezoelectric actuator 545 (piezoelectric element) corresponding to each liquid pressure chamber 533 and each liquid ejection hole 535. That is, the piezoelectric actuator 545 is built into a laminated structure consisting of the first piezoelectric ceramic layer 541 and the second piezoelectric ceramic layer 542, and is composed of the second piezoelectric ceramic layer 542 located directly above each liquid pressure chamber 533, the common electrode 543, the first piezoelectric ceramic layer 541, and the individual electrode 544.

The drive signal includes, for example, a square wave pulse of a predetermined length. Changing the length of the square wave determines whether ink is ejected, and if it is ejected, the amount of ink changes. For example, by sending a square wave that is shorter than that for normal ejection to the individual electrode 544, the piezoelectric actuator 545 is driven, and the ink in the liquid pressure chamber 533 vibrates but is not ejected.

When the ink in the common flow path 531 decreases in response to the ejection of ink from the liquid ejection hole 535, the ink in the sub-ink tank 64 is replenished to the common flow path 531 through the liquid inlet 521, the liquid relay flow path 523, and the liquid relay port 522 in that order.

As shown in FIG. 1, the recording device 1 further includes a cap unit 70. The cap unit 70 is a unit for capping the liquid ejection surface 535S, in which the liquid ejection holes 535 of the liquid ejection head 51 are formed, during pauses in the printing process in which an image is recorded on the sheet S in response to the ejection of ink by the liquid ejection head 51. The cap unit 70 will be described with reference to FIG. 6.

The cap unit 70 has a flat cap tray 71 and a concave cap portion 72 arranged on the upper surface of the cap tray 71. On the upper surface of the cap tray 71, a number of cap portions 72 corresponding to the number of liquid ejection heads 51 provided in the recording unit 50 are arranged. In other words, four cap portions 72 are arranged on the cap tray 71 corresponding to each of the four liquid ejection heads 51 for each color of Y, M, C, and Bk. In the cap unit 70, the cap portion 72 is a portion that covers the liquid ejection surface 535S in which the liquid ejection holes 535 of the liquid ejection head 51 are formed.

The cap unit 70 can move between a retracted position where the cap portion 72 is retracted horizontally (Y direction) relative to the liquid ejection surface 535S of the liquid ejection head 51, and a capping position where the cap portion 72 is located on the -Z side of the Z direction relative to the liquid ejection surface 535S. Furthermore, when the cap unit 70 is placed in the capping position, it can move up and down along the Z direction. The movement of the cap unit 70 between the retracted position and the capping position, and the lifting and lowering along the Z direction are performed by a cap moving mechanism 73 (Figure 2). When the cap unit 70 is placed in the retracted position, the cap portion 72 abuts against a cap abutment member 10A provided on the device main body 10. This makes it possible to prevent foreign matter from adhering to the cap portion 72 when the cap unit 70 is placed in the retracted position.

When the cap portion 72 is to cover the liquid ejection surface 535S of the liquid ejection head 51, the cap moving mechanism 73 moves the cap unit 70 in the Y direction from the retracted position to the capping position. Note that before the cap moving mechanism 73 moves the cap unit 70 in the Y direction, the sheet transport unit 40 is lowered by the transport lift mechanism 40A from a position directly below the liquid ejection head 51 to the -Z side in the Z direction. When the movement of the cap unit 70 to the capping position is completed, the cap moving mechanism 73 raises the cap unit 70 to the +Z side in the Z direction. This causes the cap portion 72 to cover the liquid ejection surface 535S of the liquid ejection head 51.

6, when the cap portion 72 is placed on the liquid ejection surface 535S, the bottom surface 721 of the cap portion 72 facing the liquid ejection surface 535S abuts against the protrusion 536 protruding from the liquid ejection surface 535S. As a result, when the cap portion 72 is placed on the liquid ejection surface 535S, a predetermined gap GP is formed between the bottom surface 721 and the liquid ejection surface 535S according to the ejection amount of the protrusion 536 to the liquid ejection surface 535S. By placing the cap portion 72 on the liquid ejection surface 535S, the cap unit 70 prevents the liquid ejection hole 535 from being exposed to the outside air, and prevents the ink in the liquid ejection head 51 from drying through the liquid ejection hole 535. Note that the bottom surface 721 has an air vent 722 formed therein that is large enough not to hinder the inhibition of drying of the ink in the liquid ejection head 51.

The recording device 1 further includes a head temperature detection sensor 56, a head heater 57, a tank temperature detection sensor 65, and a tank heater 66 as shown in Figs. 2 and 3, and further includes a power supply unit 80, an operation unit 81, a communication unit 82, and a control unit 90 as shown in Fig. 2.

The head temperature detection sensor 56 is a sensor for detecting the temperature of the ink in the liquid ejection head 51 by detecting the temperature of the liquid ejection head 51. The position of the head temperature detection sensor 56 is not particularly limited as long as it can detect the temperature of the liquid ejection head 51. In this embodiment, the head temperature detection sensor 56 is disposed in the liquid relay flow path member 52 that constitutes the +Z side of the liquid ejection head 51. The head heater 57 is a heater for heating the liquid ejection head 51, thereby heating the ink in the liquid ejection head 51.

The tank temperature detection sensor 65 is a sensor for detecting the temperature of the ink in the sub-ink tank 64 by detecting the temperature of the sub-ink tank 64. The tank heater 66 is a heater for heating the ink in the sub-ink tank 64 by heating the sub-ink tank 64.

The power supply unit 80 converts commercial AC power into a DC voltage that can be used by each part of the recording device 1, and supplies the converted DC voltage to each part of the recording device 1 as a power source. The operation unit 81 is composed of various operation keys and a touch panel for performing various settings and operation instructions for the recording device 1. The communication unit 82 has a function of transmitting and receiving various data such as image data used in printing processing between an external device such as a personal computer via a network such as a LAN (Local Area Network). The image data is an example of a liquid ejection request that indicates a request for ejection of ink from the liquid ejection holes 535 of the liquid ejection head 51. The image data is a signal that indicates what size of ink droplets each of the multiple liquid ejection holes 535 in the liquid ejection head 51 will eject on the sheet S to form a pixel. The image data received by the communication unit 82 is input to the control unit 90.

The control unit 90 is an arithmetic processing circuit such as a microcomputer equipped with a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. A control program for controlling the operation of the recording device 1 is stored in the ROM. The control unit 90 reads out the control program stored in the ROM and expands the control program in the RAM to control the entire device including the liquid ejection head 51 and the cap unit 70. The control unit 90 also functions as a memory unit 91 and a timer unit 92. The memory unit 91 stores a predetermined reference temperature ST that indicates the temperature of ink suitable for ejection from the liquid ejection hole 535 of the liquid ejection head 51, that is, the appropriate temperature of the liquid ejection head 51 and the sub-ink tank 64. The timer unit 92 measures the elapsed time after the control unit 90 executes various controls.

Focusing on the power supply state of the power supply unit 80, the control unit 90 supplies power to each part of the recording device 1 via the power supply unit 80, or stops the power supply to each part. Figure 7 is a diagram for explaining the state transition of the recording device 1.

When the power supply unit 80 is turned on (power ON) from a power OFF state, the control unit 90 executes power-on control CA. In the power-on control CA, the control unit 90 does not restrict the destinations to which power is supplied by the power supply unit 80, and controls the power supply unit 80 so that power is supplied to all of the components of the recording device 1. Details of this power-on control CA will be described later.

When the control unit 90 executes the power-on control CA, the power supply state of the power supply unit 80 is set to the normal state. The normal state includes an operating state in which various operations necessary for printing processing are performed, including a liquid ejection state in which ink is ejected from the liquid ejection head 51, and a ready state in which the power supply unit 80 is prepared and waiting to immediately switch to the operating state. In the normal state, there are no restrictions on the destination of the power supply from the power supply unit 80, and the head heater 57 is driven to heat the liquid ejection head 51, and the tank heater 66 is driven to heat the sub-ink tank 64. When the power supply state of the power supply unit 80 is set to the normal state, the control unit 90 executes the normal control CB. Details of this normal control CB will be described later.

The recording device 1 according to this embodiment is capable of state transitions between the normal state and a power-saving sleep state in which the destinations of power supply by the power supply unit 80 are restricted. The control unit 90 executes state transition control for transitioning the power supply state of the power supply unit 80 between the normal state and the sleep state. As the sleep state, a first sleep state and a second sleep state are set according to the degree of restriction on the destinations of power supply by the power supply unit 80. The second sleep state is a state in which the destinations of power supply are more restricted than the first sleep state, and is a so-called deep sleep state.

Assume that the ready state continues in the normal state and a predetermined sleep transition time has elapsed. In this case, the control unit 90 executes sleep transition control CC, which transitions the power supply state of the power supply unit 80 from the normal state to the first sleep state, as state transition control. In the first sleep state, only the power required for operation detection of the operation unit 81 and reception standby of the communication unit 82, as well as the power required for detection by the head temperature detection sensor 56 and the tank temperature detection sensor 65, is supplied. Therefore, in the first sleep state, the supply of power to the head heater 57, the tank heater 66, the liquid ejection head 51, the sheet transport unit 40, the transport lift mechanism 40A, the cap unit 70, the cap moving mechanism 73, etc. is stopped.

Assume that in the first sleep state, no operation is detected on the operation unit 81, and no image data is received by the communication unit 82, and a predetermined sleep transition time has elapsed. In this case, the control unit 90 executes sleep transition control CC, which transitions the power supply state of the power supply unit 80 from the first sleep state to the second sleep state, as state transition control. In the second sleep state, only the power required for operation detection on the operation unit 81 and waiting for reception by the communication unit 82, as well as the power required for detection by the tank temperature detection sensor 65, are supplied. In the second sleep state, the power required for detection by the head temperature detection sensor 56 is not supplied, and further, the supply of power to the head heater 57, the tank heater 66, the liquid ejection head 51, the sheet transport unit 40, the transport lift mechanism 40A, the cap unit 70, the cap moving mechanism 73, etc. is stopped.

Assume that in the first or second sleep state, an operation on the operation unit 81 is detected, or image data is received by the communication unit 82. In this case, the control unit 90 executes a sleep recovery control CD as state transition control, which returns the power supply state of the power supply unit 80 from the first or second sleep state to the normal state. In the sleep recovery control CD, the control unit 90, like the power-on control CA, does not restrict the destination of power supply by the power supply unit 80, and controls the power supply unit 80 so that power is supplied to all of the components of the recording device 1. Details of this sleep recovery control CD will be described later.

Next, the control operation of the control unit 90 will be described in detail with reference to the flowcharts of Figures 8, 9, 10A, and 10B. First, the power-on control CA and sleep recovery control CD executed by the control unit 90 will be described with reference to Figures 8 and 9, and then the normal control CB executed by the control unit 90 will be described with reference to Figures 8, 10A, and 10B.

As described above, the power-on control CA and the sleep recovery control CD are both controls for setting the power supply state of the power supply unit 80 to the normal state. In the power-on control CA and the sleep recovery control CD, the control unit 90 controls the power supply unit 80 so that power is supplied to all parts of the recording device 1. Note that in the power OFF state before the power-on control CA is executed, and in the first sleep state or the second sleep state before the sleep recovery control CD is executed, the cap portion 72 of the cap unit 70 is in a state in which it covers the liquid ejection surface 535S of the liquid ejection head 51.

During execution of the power-on control CA and the sleep recovery control CD, the control unit 90 acquires the detection result of the tank temperature of the sub-ink tank 64 by the tank temperature detection sensor 65 (step a1), and controls the tank heater 66 based on the detection result of the tank temperature (step a2). This adjusts the tank temperature of the sub-ink tank 64 to approach the reference temperature ST stored in the memory unit 91.

The control unit 90 further acquires the detection result of the head temperature of the liquid ejection head 51 by the head temperature detection sensor 56 (step a3), and controls the head heater 57 based on the detection result of the head temperature (step a4). This adjusts the head temperature of the liquid ejection head 51 to approach the reference temperature ST stored in the memory unit 91.

Next, the control unit 90 determines whether the detection result of the head temperature detection sensor 56 indicates a value lower than the reference temperature ST, i.e., whether the head temperature is less than the reference temperature ST (step a5). If the head temperature is less than the reference temperature ST (YES in step a5), the control unit 90 executes each process from step a6 to step a9, and then transfers control to normal control CB. On the other hand, if the head temperature is equal to or higher than the reference temperature ST (NO in step a5), the control unit 90 omits execution of each process from step a6 to step a9, and transfers control to normal control CB.

The processes from step a6 to step a9 when the head temperature is below the reference temperature ST will be described with reference to FIG. 8. When the head temperature is below the reference temperature ST, the control unit 90 executes cap control CY1 with the cap unit 70 as the control target (step a6), and executes limited drive control CX1 with the liquid ejection head 51 as the control target (step a7).

In the cap control CY1, the control unit 90 controls the cap unit 70 via the cap moving mechanism 73 so that the cap portion 72 covers the liquid ejection surface 535S of the liquid ejection head 51. As described above, when the cap portion 72 is placed on the liquid ejection surface 535S, a predetermined gap GP is formed between the bottom surface 721 of the cap portion 72 and the liquid ejection surface 535S according to the ejection amount of the protrusion 536 relative to the liquid ejection surface 535S (see FIG. 6). Note that, before the power-on control CA and the sleep recovery control CD are executed, the cap portion 72 is placed on the liquid ejection surface 535S, so the cap control CY1 is controlled to maintain that state.

In the limited drive control CX1, the control unit 90 drives all of the piezoelectric actuators 545 corresponding to each of the liquid ejection holes 535 so that the ink oscillates inside each liquid ejection hole 535 within a range that can regulate the ejection of ink from each liquid ejection hole 535 of the liquid ejection head 51. Specifically, the control unit 90 supplies a limited drive control signal CS1 as a drive signal including a pulse to each individual electrode 544 that constitutes each piezoelectric actuator 545. The limited drive control signal CS1 is a drive signal whose pulse width is set to a range that can regulate the ejection of ink from the liquid ejection hole 535, compared to the ejection control signal CS2 supplied to the individual electrode 544 in the liquid ejection control CX2 described later. The limited drive control signal CS1 may also be a drive signal that reduces the potential of the individual electrode 544 relative to the ejection control signal CS2.

When each piezoelectric actuator 545 is driven by supplying the limited drive control signal CS1 to each individual electrode 544, the drive causes each piezoelectric actuator 545 to generate heat. In addition, the ink oscillates in response to the drive of each piezoelectric actuator, causing the ink itself to generate heat. This heat can warm the ink in the liquid ejection head 51 in a short period of time.

Here, the ink in the liquid ejection head 51 oscillates so as to repeatedly appear and disappear from the liquid ejection hole 535 by driving the piezoelectric actuator 545. Therefore, during the oscillation in the liquid ejection head 51, the ink exposed from the liquid ejection hole 535 is exposed to the outside air. In this case, the ink exposed to the outside air may become thickened due to drying. Such thickening of the ink due to drying during the oscillation in the liquid ejection head 51 may cause poor ejection of the ink from the liquid ejection hole 535. Therefore, when executing the limit drive control CX1, the control unit 90 executes the cap control CY1 that controls the cap unit 70 so that the cap part 72 covers the liquid ejection surface 535S in which the multiple liquid ejection holes 535 are formed in the liquid ejection head 51. As a result, the cap part 72 can prevent the ink from being exposed to the outside air during the oscillation of the ink in the liquid ejection head 1 in response to the drive of the piezoelectric actuator 545. This makes it possible to minimize the phenomenon in which the ink dries and thickens while it is oscillating inside the liquid ejection head 51. As a result, the ink can be heated in a short time inside the liquid ejection head 51, making it possible to more reliably prevent ink ejection problems from the liquid ejection holes 535 of the liquid ejection head 51.

In addition, if the power supply unit 80 is turned off or the first and second sleep states continue for a long period of time, for example in a low-temperature environment such as winter, the temperature of the liquid ejection head 51, i.e., the temperature of the ink in the liquid ejection head 51, is more likely to become lower than the reference temperature ST. Therefore, the control unit 90 executes the cap control CY1 and the limited drive control CX1 during the execution of the power-on control CA when the power supply unit 80 is turned on, and the sleep recovery control CD from the first or second sleep state to the normal state. This makes it possible to warm the ink in the liquid ejection head 51 in a state that suppresses drying when the power is turned on and when the liquid ejection head 51 is returned from sleep, when the temperature of the liquid ejection head 51 is likely to be lower than the reference temperature ST.

During the execution of the cap control CY1 and the limited drive control CX1, the control unit 90 judges whether the detection result of the head temperature detection sensor 56 indicates a value equal to or higher than the reference temperature ST, i.e., whether the head temperature of the liquid ejection head 51 has reached the reference temperature ST, based on the detection result of the head temperature detection sensor 56 (step a8). If the head temperature of the liquid ejection head 51 has reached the reference temperature ST (YES in step a8), the control unit 90 stops the limited drive control CX1 (step a9). In other words, the control unit 90 executes the limited drive control CX1 until the detection result of the head temperature detection sensor 56 indicates a value equal to or higher than the reference temperature ST. As a result, when the limited drive control CX1 is ended and the power supply state of the power supply unit 80 is switched to the normal state and the control transitions to the normal control CB, the temperature of the liquid ejection head 51 is set to the reference temperature ST suitable for ejecting ink from each liquid ejection hole 535.

After the limit drive control CX1 is stopped, the control unit 90 controls the cap unit 70 so that the cap unit 72 is maintained covering the liquid ejection surface 535S of the liquid ejection head 51 until the liquid ejection control CX2 in the normal control CB described later is started. In this case, the cap unit 72 can prevent the liquid ejection hole 535 of the liquid ejection head 51 from being exposed to the outside air between the stop of the limit drive control CX1 and the start of the liquid ejection control CX2, so that the ink in the liquid ejection head 51 can be prevented from drying through the liquid ejection hole 535 during that time. In addition, the control unit 90 may execute a cap retraction control CY2 with the cap unit 70 as the control target so that the cap unit 72 covering the liquid ejection surface 535S is positioned at a retracted position relative to the liquid ejection surface 535S between the stop of the limit drive control CX1 and the start of the liquid ejection control CX2. In this case, when image data is input to the control unit 90 via the communication unit 82 during normal control CB, there is no waiting time required for the cap unit 72 to retract when starting liquid ejection control CX2 corresponding to that image data, and the time until liquid ejection control CX2 starts can be shortened.

When the power supply state of the power supply unit 80 is set to the normal state, the control unit 90 executes the normal control CB shown in FIG. 8 and FIGS. 10A and 10B. In the normal control CB, the control unit 90 acquires the detection result of the tank temperature of the sub-ink tank 64 by the tank temperature detection sensor 65 (step b1), and controls the tank heater 66 based on the detection result of the tank temperature (step b2). Specifically, the control unit 90 controls the tank heater 66 based on the detection result of the tank temperature detection sensor 65 so that the tank temperature of the sub-ink tank 64 fluctuates within a predetermined allowable range centered on the reference temperature ST. This allows the tank temperature of the sub-ink tank 64 to fluctuate near the reference temperature ST in the normal state.

Furthermore, the control unit 90 obtains the detection result of the head temperature of the liquid ejection head 51 by the head temperature detection sensor 56 (step b3), and controls the head heater 57 based on the detection result of the head temperature (step b4). Specifically, the control unit 90 controls the head heater 57 based on the detection result of the head temperature detection sensor 56 so that the head temperature of the liquid ejection head 51 varies within a predetermined allowable range centered on the reference temperature ST. This allows the head temperature of the liquid ejection head 51 to vary around the reference temperature ST in a normal state. Therefore, the temperature of the ink heated in the limit drive control CX1 that oscillates the ink in the liquid ejection head 51 in response to the drive of the piezoelectric actuator 545 can be maintained for a long period of time by the head heater 57.

Next, the control unit 90 determines whether image data has been input via the communication unit 82 (step b5). If image data has been input (YES in step b5), the control unit 90 executes cap retraction control CY2 with the cap unit 70 as the control target (step b6) and executes liquid ejection control CX2 with the liquid ejection head 51 as the control target (step b7).

In the cap retraction control CY2, the control unit 90 controls the cap unit 70 via the cap moving mechanism 73 so that the cap portion 72 is positioned at a retracted position retracted in the Y direction relative to the liquid ejection surface 535S of the liquid ejection head 51. As described above, when the cap unit 70 is positioned at the retracted position, the cap portion 72 abuts against the cap abutment member 10A provided on the device main body 10 (see FIG. 8). This makes it possible to prevent foreign matter from adhering to the cap portion 72 when the cap unit 70 is positioned at the retracted position.

In the liquid ejection control CX2, the control unit 90 drives the piezoelectric actuator 545 so that ink is ejected from the liquid ejection holes 535 of the liquid ejection head 51 in accordance with the image data. Specifically, as shown in FIG. 8, the control unit 90 supplies an ejection control signal CS2 as a drive signal including a pulse to the individual electrodes 544 constituting the piezoelectric actuator 545. The ejection control signal CS2 is a drive signal in which the potential and pulse width of the individual electrodes 544 are set so that ink can be ejected from the liquid ejection holes 535. There are multiple types of ejection control signal CS2 depending on how the piezoelectric actuator 545 is driven. For example, depending on which size of pixel each of the multiple liquid ejection holes 535 ejects ink droplets to form on the sheet S, the corresponding ejection control signal CS2 is supplied to the individual electrodes 544 of the piezoelectric actuators 545 corresponding to each of the multiple liquid ejection holes 535.

When the piezoelectric actuator 545 is driven by supplying the ejection control signal CS2 to the individual electrode 544, the first piezoelectric ceramic layer 541 and the second piezoelectric ceramic layer 542 constituting the piezoelectric actuator 545 are displaced accordingly, causing a change in pressure within the liquid pressure chamber 533, and ink is ejected from the liquid ejection hole 535 corresponding to that liquid pressure chamber 533. As a result, an image corresponding to the image data is recorded on the sheet S transported by the sheet transport unit 40.

For example, when a large amount of ink is discharged from the liquid discharge hole 535 of the liquid discharge head 51, the entire amount of ink heated in the liquid discharge head 51 may be consumed during the execution of the liquid discharge control CX2. In this case, if the execution of the liquid discharge control CX2 is continued, unheated ink may be discharged from the liquid discharge hole 535, and a liquid discharge defect may occur. In order to avoid such a phenomenon, the control unit 90 judges whether or not the detection result of the head temperature detection sensor 56 indicates a value lower than the reference temperature ST during the execution of the liquid discharge control CX2, that is, whether or not the head temperature of the liquid discharge head 51 is lower than the reference temperature ST (step b8). If the head temperature is lower than the reference temperature ST (YES in step b8), the control unit 90 executes each process from step b9 to step b15. On the other hand, if the head temperature is equal to or higher than the reference temperature ST (NO in step b8), the control unit 90 skips the execution of steps b9 to b15 and proceeds to the next step b16.

If the head temperature is lower than the reference temperature ST, the control unit 90 temporarily suspends the liquid ejection control CX2 (step b9), and in priority to the liquid ejection control CX2, executes the cap control CY1 with the cap unit 70 as the control target (step b10), and executes the limited drive control CX1 with the liquid ejection head 51 as the control target (step b11).

In the cap control CY1, the control unit 90 controls the cap unit 70 via the cap moving mechanism 73 so that the cap unit 72 covers the liquid ejection surface 535S of the liquid ejection head 51. In the limited drive control CX1, the control unit 90 drives all of the multiple piezoelectric actuators 545 corresponding to each of the multiple liquid ejection holes 535 so that the ink oscillates inside each liquid ejection hole 535 within a range that can regulate the ejection of ink from each liquid ejection hole 535 of the liquid ejection head 51. Specifically, the control unit 90 supplies the limited drive control signal CS1 as a drive signal including a pulse to each individual electrode 544 constituting each piezoelectric actuator 545. As described above, when the piezoelectric actuator 545 is driven by supplying the limited drive control signal CS1 to the individual electrode 544, the piezoelectric actuator 545 generates heat due to the drive. In addition, the ink itself generates heat due to the oscillation of the ink in response to the drive of the piezoelectric actuator. This heat can heat the ink inside the liquid ejection head 51 in a short period of time.

While the cap control CY1 and the limited drive control CX1 are being executed, the control unit 90 determines whether the detection result of the head temperature detection sensor 56 indicates a value equal to or higher than the reference temperature ST, i.e., whether the head temperature of the liquid ejection head 51 has reached the reference temperature ST (step b12). If the head temperature of the liquid ejection head 51 has reached the reference temperature ST (YES in step b12), the control unit 90 stops the limited drive control CX1 (step b13). In other words, the control unit 90 executes the limited drive control CX1 until the detection result of the head temperature detection sensor 56 indicates a value equal to or higher than the reference temperature ST.

After the limit drive control CX1 is stopped, the control unit 90 executes the cap retraction control CY2 (step b14). In the cap retraction control CY2, the control unit 90 controls the cap unit 70 via the cap moving mechanism 73 so that the cap unit 72 is positioned at a retracted position retracted in the Y direction relative to the liquid ejection surface 535S of the liquid ejection head 51. When the cap unit 70 is positioned at the retracted position, the control unit 90 re-executes the liquid ejection control CX2 that was temporarily suspended in step b9 (step b15).

As described above, if the head temperature of the liquid ejection head 51 is below the reference temperature ST while the liquid ejection control CX2 is being executed, the control unit 90 executes the cap control CY1 and the limited drive control CX1 in priority to the liquid ejection control CX2, and then executes the liquid ejection control CX2 again. This makes it possible to more reliably prevent poor ink ejection from the liquid ejection holes 535 of the liquid ejection head 51 while the liquid ejection control CX2 is being executed.

Next, the control unit 90 determines whether the printing process (the ink ejection process by the liquid ejection head 51) corresponding to the image data input via the communication unit 82 has been completed (step b16). If the printing process has not been completed (NO in step b16), the control unit 90 returns the process to step b7 and continues executing the liquid ejection control CX2. On the other hand, if the printing process has been completed (YES in step b16), the control unit 90 stops the liquid ejection control CX2 (step b17). Then, the control unit 90 determines whether a predetermined reference waiting time has elapsed while the communication unit 82 continues not to receive new image data (step b18). The reference waiting time is set to, for example, one minute.

When the reference waiting time has elapsed (YES in step b18), the control unit 90 executes cap control CY1 with the cap unit 70 as the control target (step b19). In cap control CY1, the control unit 90 controls the cap unit 70 via the cap moving mechanism 73 so that the cap part 72 covers the liquid ejection surface 535S of the liquid ejection head 51. This allows the cap part 72 to prevent the ink in the liquid ejection head 51 from being exposed to the outside air through the liquid ejection hole 535 during standby. This makes it possible to prevent the ink in the liquid ejection head 51 from becoming thicker due to drying.

After executing the cap control CY1, the control unit 90 determines whether the state in which new image data is not received by the communication unit 82 continues and a predetermined sleep transition time has elapsed (step b20). If the sleep transition time has elapsed (YES in step b20), the control unit 90 executes the sleep transition control CC so that the power supply state of the power supply unit 80 transitions from the normal state to the first sleep state. This allows the recording device 1 to save power.

1. Recording device (liquid ejection device)
50 Recording section 51 Liquid ejection head 535 Liquid ejection hole 535S Liquid ejection surface 54 Piezoelectric actuator substrate 545 Piezoelectric actuator 56 Head temperature detection sensor 57 Head heater 70 Cap unit 71 Cap tray 72 Cap section 80 Power supply section 90 Control section CA Power-on control CB Normal control CC Sleep transition control CD Sleep recovery control CX1 Limited drive control CX2 Liquid ejection control CY1 Cap control CY2 Cap retraction control

Claims (7)

a liquid ejection head having a piezoelectric actuator and a liquid ejection surface in which liquid ejection holes are formed to eject liquid in response to driving of the piezoelectric actuator;
a cap unit having a cap portion that is adapted to cover the liquid ejection surface;
a head temperature detection sensor that detects the temperature of the liquid ejection head;
a control unit for controlling the liquid ejection head and the cap unit,
The control unit is
With respect to the power supply state of the power supply unit, the power supply unit is configured to execute a power-on control at the time of power-on, and a state transition control between a normal state including a liquid ejection state in which liquid is ejected from the liquid ejection holes and a power-saving sleep state,
A liquid ejection device in which, when a detection result of the head temperature detection sensor indicates a value lower than a predetermined reference temperature during execution of sleep return control from the sleep state to the normal state in the state transition control, a cap control is executed to control the cap unit so that the cap portion covers the liquid ejection surface, and a limited drive control is executed to drive the piezoelectric actuator within a range capable of regulating ejection from the liquid ejection hole. The liquid ejection device according to claim 1, wherein the control unit executes the cap control and the limited drive control until the detection result of the head temperature detection sensor indicates a value equal to or higher than the reference temperature. The liquid ejection device according to claim 1 , wherein the control unit executes the cap control and the limited drive control when the detection result of the head temperature detection sensor indicates a value lower than the reference temperature during execution of the power-on control . The control unit is
when a liquid ejection request indicating a request for ejection of liquid from the liquid ejection hole is input, a liquid ejection control is executed to drive the piezoelectric actuator so that liquid is ejected from the liquid ejection hole,
A liquid ejection device as described in any one of claims 1 to 3, wherein when the detection result of the head temperature detection sensor indicates a value lower than the reference temperature during execution of the liquid ejection control, the cap control and the limited drive control are executed in priority to the liquid ejection control, and then the liquid ejection control is executed while executing a cap retraction control that controls the cap unit so that the cap portion is positioned in a retracted position relative to the liquid ejection surface. The liquid ejection device according to claim 4, wherein the control unit controls the cap unit so that the cap unit is maintained in a state in which it covers the liquid ejection surface until the liquid ejection control is started after the limit drive control is stopped. The liquid ejection device according to claim 4, wherein the control unit executes the cap retraction control so that the cap portion covering the liquid ejection surface is positioned at a retracted position relative to the liquid ejection surface after the limit drive control is stopped and before the liquid ejection control is started. The liquid ejection head further includes a heater for heating the liquid ejection head.
A liquid ejection device described in any one of claims 1 to 6, wherein the control unit controls the heater based on the detection result of the head temperature detection sensor so that the temperature of the liquid ejection head remains within a predetermined allowable range centered on the reference temperature.

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