JP7654422B2 - Liquid ejection head cleaning method and control method, and liquid ejection apparatus - Google Patents

Description

The present invention relates to a method for cleaning and controlling a liquid ejection head and a liquid ejection device.

In an inkjet recording device, which is a type of liquid ejection device, a recording liquid in which a volatile component such as water, which is a solvent, is added with a solid component such as a coloring material is ejected from the ejection port of a liquid ejection head to the outside to perform recording. When the volatile component of the recording liquid that is in contact with the outside air through the ejection port volatilizes (evaporates) and the viscosity of the recording liquid located near the ejection port increases, the ejection characteristics of the recording liquid, for example, the accuracy with which the droplets land on the recording medium, may decrease, leading to a decrease in recording quality. In particular, recording liquids that contain a larger amount of solid components and have been used in recent years for applications such as commercial printing for album production, may experience a large increase in viscosity (thickening) due to the evaporation of the volatile components, and may not be able to maintain the ejection accuracy of the recording liquid (resulting in liquid ejection failure). As an example of a method for suppressing such thickening of the recording liquid, Patent Document 1 proposes a method of constantly refreshing the recording liquid by circulating the recording liquid through the ejection port and pressure chamber, without allowing the recording liquid to stagnate in the ejection port and pressure chamber.

In addition, in order to remove the recording liquid adhering to the discharge port formation surface of the liquid discharge head and improve the discharge characteristics, various methods of wiping the discharge port formation surface are proposed in Patent Document 2. For example, there is a method of wiping the discharge port formation surface with a flexible plate-like member (rubber blade, etc.), a method of wiping with a flexible tubular member while sucking, a method of wiping with a sponge-like porous body or nonwoven fabric, and a method of sucking the recording liquid by pressing a porous body or nonwoven fabric against it with capillary force. These methods are called the blade wipe method, vacuum wipe method, web wipe method, tack method, etc. However, in a so-called multi-color integrated head in which liquid discharge heads that eject recording liquids of different colors and types are integrally configured, when the above-mentioned wiping is performed, a phenomenon (color mixing) occurs in which recording liquids of different colors (types) mix on the discharge port formation surface. If the mixed recording liquid is pushed into the pressure chamber from the discharge port by wiping, it is no longer possible to record the desired color. Therefore, after wiping and before printing, liquid ejection that is not involved in printing (preliminary ejection) is performed to discharge the mixed printing liquid to the outside.

Special Publication No. 2014-510649 Japanese Unexamined Patent Publication No. 202453/1999

When wiping is performed while the recording liquid is circulating through the ejection port and the pressure chamber as in the method described in Patent Document 1, the mixed recording liquid forced into the ejection port and the pressure chamber by wiping circulates. As a result, the mixed recording liquid spreads throughout the flow path in the liquid ejection head, so that even if preliminary ejection is performed as in the method described in Patent Document 2, the mixed recording liquid cannot be discharged completely, and the desired color cannot be recorded, resulting in a significant decrease in recording quality. In order to prevent such a situation, it is possible to stop the circulation of the recording liquid during wiping, and resume the circulation of the recording liquid after wiping of the entire ejection port formation surface of the liquid ejection head and preliminary ejection are completed. However, even in the short time between wiping and preliminary ejection, the volatile components of the recording liquid near the ejection port volatilize, and the mixed recording liquid due to wiping becomes thicker. When the recording liquid becomes thicker, it becomes difficult to eject the mixed recording liquid due to preliminary ejection. In particular, in a line-type head in which the recording width of the liquid ejection head is the same length as the recording width of the recording medium, it takes a long time from the start to the completion of wiping. If the circulation of the recording liquid is stopped during this wiping, the viscosity of the recording liquid inside the ejection ports and pressure chambers will increase, especially in the areas wiped at the beginning of wiping, which may make it difficult to eject the recording liquid during preliminary ejection.
In this case, in order to remove the thickened recording liquid from the pressure chamber, it becomes necessary to take measures such as increasing the number of preliminary ejections, lengthening the time for which the recording liquid circulates after the preliminary ejection is completed, etc. Such measures increase the consumption of recording liquid that does not contribute to recording, and lengthen the time required for so-called maintenance, from stopping the circulation of the recording liquid to wiping, preliminary ejection, and restarting the circulation.
The present invention aims to provide a liquid ejection head cleaning method and control method, and a liquid ejection device, which consumes less recording liquid during maintenance, removes thickened recording liquid from the pressure chambers, and suppresses color mixing, ejection defects, and deterioration of recording quality. Another aim of the present invention is to provide a liquid ejection head cleaning method and control method, and a liquid ejection device, which can complete maintenance that stops the circulation of the recording liquid in a short time and quickly resume recording operations.

The present invention provides a method for cleaning a liquid ejection head that is provided with a liquid supply path, a supply port, a pressure chamber, a recovery port, and a liquid recovery path so that a recording liquid is circulated , and that has an ejection port formation surface on which a plurality of ejection port rows each consisting of a plurality of ejection ports are formed, and at least one of the ejection port rows ejects a recording liquid different from that of the other ejection port rows, the cleaning method comprising: a circulation stopping step for stopping the circulation of the recording liquid in the liquid ejection head; a wiping step for performing wiping to wipe the ejection port formation surface; a preliminary ejection step for performing a preliminary ejection of the recording liquid from the ejection ports that have already been wiped; and a circulation resumption step for resuming the circulation of the recording liquid after performing the wiping step and the preliminary ejection step, wherein the wiping step involves wiping by moving a wiping member along the ejection port rows that are arranged from one end of the liquid ejection head to the other end , and the preliminary ejection step involves, following the movement of the wiping member, sequentially performing preliminary ejection from the ejection ports that the wiping member has passed, for all the ejection ports in the ejection port formation surface.

According to the present invention, the consumption of recording liquid during maintenance is small, maintenance that stops the circulation of recording liquid can be completed in a short time, the thickened recording liquid can be removed from the pressure chamber, and recording operations can be resumed quickly, while also preventing color mixing, ejection failure, and deterioration of recording quality.

1 is a schematic perspective view showing a main part of a liquid ejection apparatus including a liquid ejection head to which a cleaning method of the present invention is applied; 2 is a schematic perspective view of the liquid ejection head of the liquid ejection device shown in FIG. 1, as viewed from the ejection port formation surface side. 3 is a schematic perspective view showing a recording element substrate of the liquid ejection head shown in FIG. 2, with a part cut away. FIG. 4(a) is a schematic plan view of the main part of the liquid ejection head shown in FIGS. 2 and 3, and FIG. 4(b) is a cross-sectional view taken along line AA in FIG. 4(a). FIG. 2 is a schematic perspective view showing a cleaning mechanism of the liquid ejection head according to the first embodiment of the present invention. 6A to 6F are schematic front views sequentially showing the steps of the liquid ejection head cleaning method according to the first embodiment of the present invention. FIG. 7(a) is a schematic front view showing a part of a cleaning method for a liquid ejection head of a first embodiment of the present invention, FIG. 7(b) is a cross-sectional view showing an enlarged view of region B in FIG. 7(a), and FIG. 7(c) is a cross-sectional view showing an enlarged view of region C in FIG. 7(a). FIG. 8A is a schematic front view showing a part of a method for cleaning a liquid ejection head according to a first embodiment of the present invention, and FIG. 8B is an enlarged cross-sectional view showing a region B in FIG. 8A. FIG. 9A is a schematic front view showing a liquid circulation state after the liquid ejection head cleaning method according to the first embodiment of the present invention, and FIG. 9B is an enlarged cross-sectional view showing region B of FIG. 9A. FIG. 11 is a schematic perspective view showing a cleaning mechanism of a liquid ejection head according to a second embodiment of the present invention. FIG. 11(a) is a schematic front view showing a liquid ejection head cleaning mechanism of a third embodiment of the present invention, and FIG. 11(b) and FIG. 11(c) are schematic front views showing, in order, each step of a liquid ejection head cleaning method using the mechanism of FIG. 11(a). 12A, 12B and 12C are schematic front views sequentially showing each step of a cleaning method performed using a liquid ejection head cleaning mechanism according to a fourth embodiment of the present invention. 13A, 13B and 13C are schematic front views sequentially showing each step of a cleaning method performed using a liquid ejection head cleaning mechanism according to a fifth embodiment of the present invention. 11 is a graph showing the relationship between the elapsed time after wiping is completed and the ejection speed of droplets ejected from an ejection port. 13 is a schematic front view showing one process of a cleaning method performed using a modified example of a cleaning mechanism for a liquid ejection head according to a fifth embodiment of the present invention. FIG. 1 is a block diagram illustrating an example of a control system of a liquid ejection device to which the present invention is applied.

The following describes an embodiment of the present invention with reference to the drawings. However, the following description does not limit the scope of the present invention. The example described below is a so-called thermal type liquid ejection head that uses a heat generating element as an energy generating element (recording element) that generates energy for ejecting recording liquid. In a thermal type liquid ejection head, thermal energy is generated to generate bubbles in the recording liquid in the pressure chamber, and the recording liquid is ejected from the ejection port. However, the liquid ejection head to which the present invention can be applied is not limited to the thermal type, and the present invention can also be applied to liquid ejection heads that use a piezoelectric type that uses a piezoelectric element, or that employ various other liquid ejection methods.

[First embodiment]
(Inkjet recording device)
FIG. 1 is a schematic perspective view showing some of the components related to recording of an inkjet recording device 10 (hereinafter also referred to as a recording device) which performs recording by discharging liquid ink, as an example of a liquid discharge device to which the present invention is applied. FIG. 2 is a schematic perspective view of a liquid discharge head 3 of the recording device 10 shown in FIG. 1. The recording device 10 includes a conveying unit 1 for conveying a recording medium 2, a liquid discharge head 3 having a recording element substrate 4 shown in FIG. 2, a liquid supply mechanism described later, a cleaning mechanism 30 (see FIG. 5), an outer housing (not shown), a control mechanism 50 (see FIG. 16), and the like. The liquid discharge head 3 is a so-called line-type liquid discharge head 3 in which a plurality of recording element substrates 4 are arranged on a support member 60 in a direction substantially perpendicular to the conveying direction of the recording medium 2 (see FIG. 1) over a width equivalent to the recording width of the recording medium 2, as shown in FIG. 2. A wiring substrate (not shown) for transmitting power and discharge control signals is electrically connected to the liquid discharge head 3. The liquid supply mechanism is a mechanism in which a liquid supply means, which serves as a supply path for supplying the recording liquid (liquid ink) to the liquid ejection head 3, a main tank, and a buffer tank (both not shown) are fluidly connected. The liquid path in the liquid ejection head 3 to which the recording liquid is supplied from the liquid supply mechanism will be described later. The control mechanism 50 controls the driving of the liquid ejection head 3, the driving of each member of the conveying unit 1, the driving of the cleaning mechanism 30, etc. The recording device 10 performs continuous recording in one pass while continuously or intermittently conveying a plurality of recording media 2 by linking these components. Note that the recording media 2 are not limited to cut paper, and may be continuous roll paper. The liquid ejection head 3 of this embodiment is capable of full-color printing using cyan (C), magenta (M), yellow (Y), and black (K) inks as the recording liquid.

As shown in FIG. 1, liquid connection parts 5 provided at both ends of liquid ejection head 3 are parts that connect the supply path of the recording device body and the liquid path of liquid ejection head 3 (not shown). This allows four colors of ink, CMYK, to be supplied from the supply path of the recording device body to liquid ejection head 3, and ink that has passed through the liquid path in liquid ejection head 3 is collected back into the supply path of the recording device body. In this way, ink of each color circulates through the supply path of the recording device body and the liquid path of liquid ejection head 3 (the supply pressure is adjusted along the way by pressure adjustment mechanisms 6a, 6b, 6c, 6d provided on the head).

(Configuration of Liquid Ejection Head)
The configuration of the liquid ejection head 3 according to the first embodiment of the present invention will be described below. FIG. 2 is a schematic perspective view of the liquid ejection head 3 according to this embodiment. The liquid ejection head 3 of this embodiment is a line-type liquid ejection head in which 15 recording element substrates 4 capable of ejecting liquid ink of four colors, C, M, Y, and K, are arranged in a straight line. That is, 15 recording element substrates 4a to 4o are arranged in-line. It should be noted that the recording width can be increased by increasing the number of recording element substrates 4. As shown in FIG. 2, in addition to the recording element substrates 4a to 4o, the liquid ejection head 3 includes an electric wiring substrate 8 electrically connected to a wiring substrate (not shown) of the main body of the recording device via a flexible wiring substrate 7.

(Configuration of the Printing Element Substrate)
The configuration of the recording element substrate 4 of this embodiment will be described. FIG. 3 is a schematic perspective view of the recording element substrate 4 from the side where the ejection ports 9 are formed (the ejection port forming surface 11a side), with a part of the diagram being cut away. FIG. 4(a) is a schematic plan view showing an enlarged portion of the region P in FIG. 3, with each component being transparently superimposed. FIG. 4(b) shows a schematic cross-sectional view cut along line A-A in FIG. 4(a). The recording element substrate 4 is configured by laminating a substrate 19 made of Si and an ejection port forming member 11 made of a photosensitive resin. As shown in FIG. 3, a plurality of ejection port arrays each consisting of a plurality of ejection ports 9 are formed on the ejection port forming surface 11a of the ejection port forming member 11 of the recording element substrate 4. Specifically, in this embodiment, four ejection port arrays 12M, 12C, 12Y, and 12K corresponding to four colors of ink (M, C, Y, and K) are formed. Hereinafter, the direction in which the ejection port arrays each consisting of a plurality of ejection ports 9 extend will be referred to as the "ejection port arrangement direction." In this manner, in the liquid ejection head 3, a plurality of recording element substrates 4 each having an ejection port forming surface 11a on which a plurality of ejection port arrays 12M, 12C, 12Y, and 12K each consisting of a plurality of ejection ports 9 are formed are arranged in a row.

As shown in FIG. 4(a), pressure chambers 14 partitioned by partitions (flow path walls) 13 are provided at positions corresponding to each ejection port 9. As shown in FIG. 4(b), heating elements (recording elements) 15, which are an example of energy generating elements that generate energy for ejecting the recording liquid, are arranged at positions corresponding to each pressure chamber 14 on the substrate 19. The heating elements 15 are electrically connected to electrical wiring (not shown) provided on the recording element substrate 4. The heating elements 15 generate thermal energy based on an ejection control signal (pulse signal) input from a control circuit of the recording device main body (not shown) via the electrical wiring substrate 8 and the flexible wiring substrate 7, and cause film boiling of the recording liquid. The pressure caused by this film boiling ejects the recording liquid from the ejection port 9 to the outside. As shown in FIG. 3, a liquid supply path 16 is formed on one side of each ejection port row, and a liquid recovery path 17 is formed on the other side, and they extend along the ejection port row. The liquid supply path 16 and the liquid recovery path 17 are made of grooves provided on the surface of the substrate 19 opposite the surface on which the recording elements 15 are formed, and are connected to the pressure chamber 14 and the ejection port 9 via the supply port 18a and the recovery port 18b, respectively. Between the liquid supply path 16 and the liquid recovery path 17, pressure adjustment mechanisms 6a to 6d (see FIG. 1) are provided to generate a pressure difference adjusted for each color.

As shown in FIG. 3, a cover plate 20 is laminated on the surface of the substrate 19 of the recording element substrate 4 opposite the surface that contacts the ejection port forming member 11. The cover plate 20 is provided with a plurality of openings 21 that communicate with the liquid supply path 16 and the liquid recovery path 17. In this embodiment, the cover plate 20 is provided with three openings 21 for one liquid supply path 16, and two openings 21 for one liquid recovery path 17.

Next, the flow of the recording liquid in the recording element substrate 4 will be described. Between the liquid supply path 16 and the liquid recovery path 17, a pressure difference is generated that is adjusted for each color by the pressure adjustment mechanisms 6a to 6d (see FIG. 1). When the recording liquid is being discharged from some of the discharge ports 9 of the liquid discharge head 3, the recording liquid in the liquid supply path 16 of the substrate 19 flows to the liquid recovery path 17 via the supply port 18a, the pressure chamber 14, and the recovery port 18b in the non-discharge discharge port 9 due to the above-mentioned pressure difference. That is, the recording liquid flows in the direction C in FIG. 3. This flow in the direction C allows the recording liquid, bubbles, and foreign matter that have become thickened due to the volatilization of volatile components from the discharge port 9 to be collected in the liquid recovery path 17 in the discharge port 9 and pressure chamber 14 that are not discharging the recording liquid. Since the discharge port 9 and pressure chamber 14 are always supplied with refreshed recording liquid, it is possible to suppress the thickening of the recording liquid inside the discharge port 9 and pressure chamber 14. The recording liquid recovered in the liquid recovery path 17 is eventually recovered to the supply path of the recording device body through the opening 21 in the cover plate 20. This type of flow of the recording liquid is referred to in this specification as the circulation (circulation flow) of the recording liquid.

(Cleaning mechanism)
5 shows a cleaning mechanism 30 that comes into contact with the ejection port forming surface 11a of the ejection port forming member 11 of the recording element substrate 4 to clean the ejection port forming surface 11a. As shown in FIG. 5, the cleaning mechanism 30 has a base 32, an elastic tube 40a fixed to the base 32, a suction tube 33 connected to the elastic tube 40a, and a preliminary ejection receiver 35 arranged adjacent to the base 32. The elastic tube 40a is formed to a size that can cover a plurality of ejection ports 9 in the ejection port arrangement direction and covers all the ejection port arrays 12M, 12C, 12Y, and 12K in a direction intersecting the ejection port arrangement direction. In the wiping process, the open end of the elastic tube 40a is pressed against the ejection port forming surface 11a, and the base 32 is moved in the ejection port arrangement direction by the moving mechanism while operating a suction pump 34 (see FIG. 6A, for example) connected to the elastic tube 40a via the suction tube 33. In this way, the elastic tube 40a is brought into sliding contact with the entire area of the ejection port forming surface 11a, and suction and wiping are performed simultaneously. This operation is called suction wiping. The elastic tube 40a is a tubular member that sucks the recording liquid from the ejection port 9 and wipes the ejection port forming surface 11a with its edge, and is a type of wiping member. By performing suction wiping, it is possible to suck and remove dust adhering to the entire ejection port forming surface 11a including the vicinity of the ejection port 9, solidified and attached recording liquid, air bubbles present inside the ejection port 9 and the pressure chamber 14, and thickened recording liquid. A cleaning mechanism 30 configured in this way is sometimes called a vacuum wiper.

When the vacuum wiper 30 performs suction wiping, the recording liquids of different colors and types sucked out from the discharge port 9 mix at the contact portion between the vacuum wiper 30 and the discharge port forming member 11 or in the vicinity thereof. A part of the mixed recording liquid (sometimes called mixed recording liquid) may infiltrate into the pressure chamber 14 from the discharge port 9. If the mixed recording liquid is circulated without being discharged from the discharge port 9 and the pressure chamber 14, the mixed recording liquid will flow out into the liquid recovery path 17 and spread throughout the circulation path of the recording liquid. If such color mixing occurs, it will not be possible to reproduce the intended color and the print quality will decrease, so it must be avoided. Conventionally, the circulation of the recording liquid was stopped during wiping, and a preliminary discharge was performed after wiping was completed, and the mixed recording liquid was discharged, and then the circulation of the recording liquid was resumed. A preliminary discharge is a liquid discharge that does not contribute to recording before the original purpose of recording on the recording medium. Wiping takes time, and wiping of the line-type liquid ejection head 3 in particular takes a long time. For this reason, in the ejection port 9 where suction wiping was performed at the beginning of the wiping process, volatilization (evaporation) of the volatile components (e.g., water) contained in the recording liquid progresses, and the viscosity of the recording liquid in the vicinity of the ejection port 9 and inside the pressure chamber 14 increases. When the viscosity of the recording liquid increases, even if the recording element 15 is driven to generate energy, the viscous recording liquid cannot be ejected to the outside (liquid ejection failure occurs). In particular, the recording liquid in commercial printing and the like often has a composition with a water content of less than 71%, and when such a recording liquid is used, the tendency to thicken is significant. When the water content of the recording liquid is less than 66%, the tendency is even more significant, and when the water content of the recording liquid is less than 60%, the tendency is even more significant. In addition, when the content of solid components dispersed in the recording liquid is 7% or more, the tendency to thicken is significant, and when the content of solid components is 10% or more, the tendency is even more significant.

In this embodiment, as shown in Figs. 6(a) to 6(f), without waiting for the completion of wiping of the entire surface of the discharge port formation surface 11a across the multiple recording element substrates 4a to 4o of the liquid discharge head 3, preliminary discharge is sequentially performed from the portion where the vacuum wiper 30 has passed. This preliminary discharge process discharges the recording liquid from the discharge port 9 to the outside before the volatile components of the mixed recording liquid volatilize and the viscosity of the recording liquid in the vicinity of the discharge port 9 and inside the pressure chamber 14 increases, making it difficult to discharge the liquid. In other words, preliminary discharge is performed before liquid discharge failure occurs due to the increase in the viscosity of the recording liquid in the discharge port 9 that has already been wiped. An example of the specific timing of this wiping and preliminary discharge will be described below in order. Before performing the wiping and preliminary discharge operations, the circulation operation of the recording liquid is stopped. After that, as shown in Fig. 6(a), the elastic tube 40a of the vacuum wiper 30 starts wiping by suctioning while sliding against the first recording element substrate 4a of the liquid discharge head 3. Next, the vacuum wiper 30 moves in the A direction, and the elastic tube 40a passes the recording element substrate 4a. Then, the vacuum wiper 30 reaches the position shown in FIG. 6B, that is, the position where the elastic tube 40a faces the second recording element substrate 4b, and while the vacuum wiper 30 is in sliding contact with and sucking the recording element substrate 4b, it starts preliminary ejection of the first recording element substrate 4a. This causes the mixed recording liquid to be discharged toward the preliminary ejection receiver 35 from the vicinity of the ejection port 9 of the recording element substrate 4a and the inside of the pressure chamber 14. After the wiping process of the second recording element substrate 4b and the preliminary ejection process of the first recording element substrate 4a are completed, the vacuum wiper 30 moves further in the A direction as shown in FIG. 6C. As shown in FIG. 6D, the vacuum wiper 30 reaches the position where the elastic tube 40a faces the third recording element substrate 4c. Then, the elastic tube 40a sucks the third recording element substrate 4c while sliding against it, and performs preliminary ejection of the second recording element substrate 4b. In this way, suction wiping of the recording element substrate and preliminary ejection of the recording element substrate that has been suction wiped are performed in parallel. As shown in FIG. 6E, the elastic tube 40a reaches the last recording element substrate 4o of the liquid ejection head 3 and sucks it while sliding against it, and performs preliminary ejection of the previous (upstream) recording element substrate 4n. Then, as shown in FIG. 6F, the elastic tube 40a moves further and passes the last recording element substrate 4o of the liquid ejection head 3, and performs preliminary ejection of the last recording element substrate 4o. In this way, suction wiping and preliminary ejection are performed for all recording element substrates 4a to 4o of the liquid ejection head 3, thereby performing the cleaning operation of the liquid ejection head 3 of this embodiment. In this embodiment, as shown in FIG. 6(a) to FIG. 6(f), without waiting for the completion of suction wiping of the entire surface of the ejection port formation surface 11a of the liquid ejection head 3, preliminary ejection is sequentially performed from the recording element substrate through which the elastic tube 40a has passed. This allows the mixed recording liquid to be discharged to the outside from the ejection port 9 before the volatile components of the mixed recording liquid evaporate and the viscosity of the recording liquid in the vicinity of the ejection port 9 and inside the pressure chamber 14 increases. After the cleaning operation of the liquid ejection head 3 is completed, that is, after the preliminary ejection process is completed, the recording liquid is supplied to each pressure chamber 14 from the supply port 18a, and the recording liquid is recovered from the pressure chamber 14 through the recovery port 18b. In this way, the circulation flow of the recording liquid is started to prepare for the next recording.

7 to 9 are diagrams mainly showing the state around the ejection port 9 and the pressure chamber 14. FIG. 7(a) is a front view showing the state after the state shown in FIG. 6(d) in which suction wiping of a part of the third recording element substrate 4c is completed and preliminary ejection of the second recording element substrate 4b is being performed. FIG. 7(b) is an enlarged cross-sectional view of region B in FIG. 7(a) and is a cross-sectional view showing the main part of the third recording element substrate 4c after suction wiping is completed and before preliminary ejection. FIG. 7(c) is an enlarged cross-sectional view of region C in FIG. 7(a) and is a cross-sectional view showing the main part of the first recording element substrate 4a after suction wiping and preliminary ejection. FIG. 8(a) is a front view showing the state after the state shown in FIG. 6(f) in which suction wiping and preliminary ejection of all recording element substrates 4a to 4o are completed. FIG. 8(b) is an enlarged cross-sectional view of region B in FIG. 8(a), showing the main part of the third recording element substrate 4c that has been left alone after suction wiping and preliminary ejection have been completed. FIG. 9(a) is a front view showing the state after the state shown in FIG. 8(a), in which circulation of the recording liquid has started after suction wiping and preliminary ejection of all recording element substrates 4a to 4o have been completed. FIG. 9(b) is an enlarged cross-sectional view of region B in FIG. 9(a), showing the main part of the third recording element substrate 4c that has started circulation of the recording liquid.

As shown in FIG. 7B, when the suction wiping is completed and the preliminary ejection is not performed, the mixed recording liquid L1 is present in the ejection port 9 and the pressure chamber 14. In the present invention, the mixed recording liquid L1 is discharged to the outside, that is, without waiting for the suction wiping of all the recording element substrates 4a to 4o of the liquid ejection head 3 to be completed, and the mixed recording liquid L1 is no longer present around the ejection port 9 and the pressure chamber 14, as in the state shown in FIG. 7C. If the mixed recording liquid L1 is left in this state until the preliminary ejection of the last recording element substrate 4o of the liquid ejection head 3 is completed, the volatile components of the recording liquid evaporate from the ejection port 9 and thicken. As a result, as shown in FIG. 8B, the thickened recording liquid (concentrated recording liquid) L2 is present in the ejection port 9 and the pressure chamber 14. Therefore, the circulation of the recording liquid is started, and fresh recording liquid is supplied from the supply port 18a to the pressure chamber 14 and the ejection port 9. The thickened recording liquid L2 flows from the ejection port 9 and the pressure chamber 14 to the recovery port 17b, and is diluted with fresh recording liquid on the way there, decreasing its viscosity. In addition, since the mixed recording liquid L1 has already been discharged from the ejection port to the outside by the preliminary ejection, the mixed recording liquid does not flow out from the pressure chamber 14 and the ejection port 9 to the recovery port 18b even if the recording liquid is circulated. Therefore, as shown in FIG. 9B, the ejection port 9 and the pressure chamber 14 are in a state where the recording liquid is not mixed or thickened. According to this embodiment, by starting the circulation of the recording liquid after the cleaning operation (wiping and preliminary ejection), the pressure chamber 14 and the ejection port 9 are in a state where the recording liquid is not mixed or thickened, and the desired color of recording liquid can be ejected, and recording with good recording quality can be performed.

As described above, according to this embodiment, the wiping member 40a is moved along the nozzle rows to wipe the multiple nozzle rows. Then, before wiping of the entire nozzle formation surface 11a across the multiple recording element substrates 4 is completed, preliminary ejection from the wiped nozzles 9 is started. In this way, the wiping process and the preliminary ejection process are performed sequentially from the first recording element substrate 4a located at one end of the row of the recording element substrates 4 to the last recording element substrate 4o located at the other end. Before wiping of the entire nozzle formation surface 11a across all recording element substrates 4 is completed, preliminary ejection is started from the nozzles 9 of the recording element substrate located upstream of the wiping member 40a in the movement direction from the recording element substrate being wiped. This reduces the consumption of recording liquid involved in maintenance, and maintenance that stops the circulation of the recording liquid can be completed in a short time, and the thickened recording liquid can be removed from the pressure chamber, allowing the recording operation to be resumed quickly. This solves the problem of color mixing and thickening of the recording liquid discharged from the liquid discharge head 1 due to suction wiping, etc., and allows for good liquid discharge in the next recording. This method is suitable when the water content of the recording liquid is less than 71%, more suitable when it is less than 66%, and even more suitable when it is less than 60%. This method is also suitable when the content of solid components dispersed in the recording liquid is 7% or more, and even more suitable when the content of solid components is 10% or more. In this embodiment, the recording element substrate during wiping and the recording element substrate during preliminary discharge are adjacent in the movement direction of the wiping member, but are not limited to such a configuration. These operations are mainly controlled by the control mechanism 50 (see FIG. 16).

Second Embodiment
The second embodiment of the present invention will be described below. The same components and methods as those in the first embodiment are indicated by the same reference numerals, and the description may be omitted. The cleaning mechanism of this embodiment shown in FIG. 10 includes a blade wiper 37 having a rubber blade 40b attached to a base 32. A preliminary ejection receiver 35 is provided adjacent to the rubber blade 40b on the base 32. The rubber blade 40b is a flexible plate-like member that wipes the ejection port formation surface 11a with its edge, and is a type of wiping member. By pressing the rubber blade 40b shown in FIG. 10 against the recording element substrate 4 and sliding the surface of the recording element substrate 4, it is possible to wipe off the dust and solidified recording liquid adhering to the vicinity of the ejection port 9 (see FIG. 3). This cleaning mechanism performs each step (wiping and preliminary ejection) of the cleaning method substantially similar to the steps shown in FIG. 6(a) to FIG. 6(f), and sequentially cleans a plurality of recording element substrates 4.

When wiping is performed by the rubber blade 40b of the blade wiper 37, the recording liquids of different colors and types drawn from the discharge port 9 by surface tension and capillary force mix near the contact portion between the rubber blade 40b and the discharge port forming surface 11a. Then, a part of the mixed recording liquid penetrates into the pressure chamber 14 from the discharge port 9. The recording liquid mixed by wiping and penetrated into the pressure chamber 14 is discharged to the preliminary discharge receiver 35 by preliminary discharge performed at the same timing as in the first embodiment. That is, in this embodiment, the mixed recording liquid is discharged from the discharge port 9 by sequentially performing preliminary discharge from the recording element substrate 4 that the rubber blade 40b has passed, without waiting for the wiping of all the recording element substrates 4 of the liquid discharge head 3 to be completed. At this point, the recording liquid is not circulated, so the mixed recording liquid does not flow out to the recovery port 18b and can be discharged to the outside. Since the preliminary ejection is performed immediately after wiping, the volatile components of the mixed recording liquid can be discharged from the ejection port 9 and pressure chamber 14 to the outside before the recording liquid thickens due to evaporation of the mixed recording liquid. Even if the recording liquid is left unattended after wiping and preliminary ejection and thickened, circulation of the recording liquid is started before recording starts and fresh recording liquid is supplied, and the thickened recording liquid is drained to the recovery port 18b and diluted with the fresh recording liquid. Therefore, good recording quality can be obtained when liquid is ejected again. Furthermore, the consumption of recording liquid during maintenance is small, and maintenance that stops the circulation of the recording liquid can be completed in a short time, the thickened recording liquid can be removed from the pressure chamber, and recording operation can be resumed quickly.

[Third embodiment]
The third embodiment of the present invention will be described below. The same configurations and methods as those of the first and second embodiments are represented by the same reference numerals, and the description may be omitted. The cleaning mechanism of this embodiment shown in FIG. 11A is a so-called web wipe, which includes a nonwoven fabric 40c, fixed rollers 41a and 41b, and a moving roller 42. The nonwoven fabric 40c is a cloth-like member having liquid absorption properties, and is a type of wiping member. As shown in FIG. 11A, the nonwoven fabric 40c is wound around the fixed roller 41a, and is configured to be wound around the fixed roller 41b via the moving roller 42. When wiping is performed, as shown in FIG. 11A, the liquid ejection head and the cleaning mechanism are moved in advance so that they face each other. Then, as shown in FIG. 11B, the moving roller 42 is pressed against the recording element substrate 4, and moved so as to roll on the surface of the recording element substrate 4. In this way, by rubbing the nonwoven fabric 40c against the ejection-orifice forming surface 11a of the ejection orifices 9, it is possible to remove dust and solidified recording liquid adhering to the vicinity of the ejection orifices 9. Then, as shown in Fig. 11C, without waiting for the completion of wiping of all the recording element substrates 4 of the liquid ejection head 3, preliminary ejection can be sequentially performed onto the nonwoven fabric 40c from the recording element substrates 4 that the moving roller 42 has passed. After wiping and preliminary ejection are performed on the entire ejection-orifice forming surface 11a, the soiled nonwoven fabric 40c is taken up by the fixed roller 41b, and a new portion of the nonwoven fabric 40c faces the ejection-orifice forming surface 11a and is prepared for the next wiping operation.

In this embodiment, the mixed recording liquid can be discharged to the outside without flowing out to the recovery port 18b. Since the preliminary ejection is performed immediately after wiping, the mixed recording liquid can be discharged to the outside from the ejection port 9 and the pressure chamber 14 before the volatile components of the mixed recording liquid evaporate and the recording liquid becomes viscous. Even if there is recording liquid that has been left unattended after wiping and preliminary ejection and has become viscous, circulation of the recording liquid is started before recording begins, and fresh recording liquid is supplied, and the viscous recording liquid is caused to flow to the recovery port 18b and is diluted with the fresh recording liquid. Therefore, when liquid is ejected again, good recording quality can be obtained. In this embodiment, preliminary ejection can be performed directly on the nonwoven fabric 40c, and there is no need to provide a preliminary ejection receiver.

In this embodiment, nonwoven fabric 40c is used as the wiping member, but from the viewpoint of absorbing and recovering the recording liquid, it is also possible to use a wiping member made of, for example, a porous body having liquid-absorbency, although this is not shown. When a porous body is used, its shape may be a plate-like shape similar to rubber blade 40b shown in FIG. 10, or a sheet-like shape similar to nonwoven fabric 40c shown in FIG. 11.

[Fourth embodiment]
The fourth embodiment of the present invention will be described below. The same reference numerals are used to denote configurations and methods similar to those of the first to third embodiments, and descriptions thereof may be omitted. In the first to third embodiments, the wiping member 40 completely passes one recording element substrate and performs preliminary ejection of the recording element substrate that has been wiped at the timing when the wiping member 40 is wiping the next recording element substrate. The wiping member 40 here is a general term including the elastic tube 40a, rubber blade 40b, nonwoven fabric 40c, porous body, and the like. In contrast, in this embodiment, as shown in FIG. 12, preliminary ejection is sequentially performed from the ejection port 9 immediately after the wiping member 40 has passed in one recording element substrate 4. For example, as shown in FIG. 12(a), while wiping the first recording element substrate 4a, preliminary ejection is performed for the ejection port 9 that the wiping member 40 of the recording element substrate 4a has passed. As shown in FIG. 12B, when the wiping member 40 is wiping the next recording element substrate 4b, the recording liquid is preliminarily ejected from the ejection port 9 of the recording element substrate 4a through which the wiping member 40 has passed. At the same time, the recording liquid is preliminarily ejected from the ejection port 9 of the recording element substrate 4b through which the wiping member 40 has already passed during wiping. As shown in FIG. 12C, the wiping member 40 and the preliminarily ejected receiver 35 move from one end of the liquid ejection head 3 to the other end. When the cleaning operation of all the recording element substrates 4 of the liquid ejection head 3 is completed, the circulation of the recording liquid is immediately resumed. That is, in this embodiment, the timing from the completion of the cleaning operation to the start of the liquid circulation can be made even faster. In addition, in this embodiment, the mixed recording liquid can be discharged from the ejection port 9 to the outside more quickly, so that it is suitable for the case of using a recording liquid that is more likely to thicken.

In the first to third embodiments, the wiping member 40 and the preliminary ejection receiver 35 are each the same size as each recording element substrate 4 in plan view. In contrast, in this embodiment, the wiping member 40 and the preliminary ejection receiver 35 may each be smaller than each recording element substrate 4 in plan view, and the assembly of the wiping member 40 and the preliminary ejection receiver 35 may be large enough to fit inside one recording element substrate 4 in plan view. This allows the cleaning mechanism to be made compact. The wiping member 40 in this embodiment may be an elastic tube 40a similar to the first embodiment, a rubber blade 40b similar to the second embodiment, a nonwoven fabric 40c similar to the third embodiment, or a porous body.

[Fifth embodiment]
The fifth embodiment of the present invention will be described below. The same reference numerals are used to denote configurations and methods similar to those of the first to fourth embodiments, and descriptions thereof may be omitted. In this embodiment, the timing from the completion of wiping to the execution of preliminary ejection is maximized, taking into consideration the evaporation characteristics of the recording liquid used. This allows the distance between the wiping member 40 and the preliminary ejection receiver 35 to be greater than in the first to fourth embodiments. Therefore, a preliminary ejection receiver 35 with a large volume can be used, and the embodiment can also handle a large amount of recording liquid discharged by preliminary ejection. In this embodiment, as shown in FIG. 13(a), the wiping member 40 sequentially performs a wiping operation (wiping) starting from the first recording element substrate 4a. Then, as shown in FIG. 13(b), when the wiping member reaches, for example, the sixth recording element substrate 4f, preliminary ejection is performed for the three recording element substrates 4a, 4b, and 4c, and the discharged recording liquid is collected by the large preliminary ejection receiver 35.

The timing of the start of preliminary ejection from the ejection port 9 after wiping by the wiping member 40 is limited by the thickening state of the recording liquid used, and the thickening state of the recording liquid is determined according to the characteristics of the recording liquid itself and environmental conditions. The timing from the end of wiping to the start of preliminary ejection is described below. FIG. 14 shows the relationship between the elapsed time t after the completion of wiping and the ejection speed vi of the droplets ejected from the ejection port 9. According to this, the ejection speed of the droplets is high immediately after wiping, but as time passes from wiping, the ejection speed decreases because the recording liquid thickens. Then, after a certain amount of time has passed, an ejection speed suitable for ejecting the mixed recording liquid by preliminary ejection cannot be obtained, and the mixed recording liquid cannot be sufficiently ejected from the ejection port 9 and the pressure chamber 14. In other words, liquid ejection failure occurs. The time until the minimum ejection speed (the limit line of the ejection speed) at which the mixed recording liquid can be sufficiently ejected by preliminary ejection after wiping is reached is t1. In other words, if preliminary ejection is performed at each ejection port 9 before the time t1 has elapsed after wiping is completed, the mixed and viscous recording liquid can be discharged to the outside of the liquid ejection head 3.

In this manner, in this embodiment, preliminary ejection is performed at a time t1 at the longest after wiping is completed. At this time, the relative position of the preliminary ejection receiver 35 that receives the preliminary ejected droplets with respect to the wiping member 40 is determined as follows. When the wiping member 40 moves at a moving speed vm, the maximum distance L (see FIG. 13C) from the position of the wiping member 40 to the position of the ejection port 9 where preliminary ejection is performed at that timing is expressed by the following formula.
L≦vm×t1...(Formula 1)
Therefore, the preliminary ejection receiver 35 may be configured to be located within a range of a distance L from the wiping member 40. From another perspective, the position of the rear end of the preliminary ejection receiver 35 that receives the preliminary ejection is located within the range of distance L that satisfies formula 1. Note that the time t1 differs depending on the composition of the recording liquid and the surrounding environment (temperature and humidity) of the liquid ejection head, so it is preferable to determine it by testing under the most severe assumed usage environment conditions. For example, if the speed vm of the wiping member 40 is 20 mm/s and the limit time t1 for good preliminary ejection is 1.5 seconds, L = vm x t1 = 30 mm. Therefore, the maximum distance between the wiping member 40 and the ejection port 9 at which preliminary ejection is performed at that timing is set to within 30 mm. In other words, if the maximum distance from the wiping member 40 to the rear end of the preliminary ejection receiver 35 is 30 mm and it is within a range of 30 mm from the wiping member 40, the preliminary ejection receiver 35 can be made larger. 15, for example, a preliminary ejection receiver 35 having the same size as one recording element substrate 4 can be disposed at a position a distance L away from the wiping member 40. In this case, the preliminary ejection receiver 35 is moved intermittently using the size of the recording element substrate 4 as a unit of movement. This is a configuration in which the wiping member 40 and the preliminary ejection receiver 35 are moved independently, and the distance L can be adjusted according to the characteristics of the recording liquid used and the environmental conditions, and the wiping member 40 and the preliminary ejection receiver 35 can be moved according to that distance L.

The various conditions in each embodiment described above can be controlled by a control mechanism 50 provided in the main body of the recording device 10 as shown in FIG. 16. The control mechanism 50 appropriately controls the timing and speed of the movement of the wiping member 40, the timing and speed of the movement of the preliminary ejection receiver 35, the area where the recording element 15 is operated to eject liquid (specification of the recording element substrate 4 where the preliminary ejection is performed), the ejection timing, etc. In particular, the timing of the preliminary ejection and the timing of the movement of the preliminary ejection receiver are controlled to be synchronized. That is, the control mechanism 50 moves the wiping member 40 along the ejection port row to wipe multiple ejection port rows simultaneously. Before wiping of the entire ejection port formation surface 11a of the main ejection head 3 is completed, the preliminary ejection of the recording liquid from the wiped ejection port 9 is started. Then, the preliminary ejection receiver member 35 sequentially collects the liquid that is preliminary ejected and not used for recording in the order of preliminary ejection. In addition, it is preferable to appropriately control these conditions within a range that satisfies the above-mentioned formula 1 described as the fifth embodiment. In this way, the movement of the wiping member 40 from one end of the liquid ejection head 3 to the other end is controlled to sequentially perform the cleaning operation. After the cleaning operation is completed, the circulation of the recording liquid is promptly performed. The control mechanism 50 stops the circulation flow of the recording liquid that flows from the supply port 18a through the pressure chamber 14 to the recovery port 18b during recording before wiping and preliminary ejection are performed, and resumes the circulation flow after wiping of all ejection ports 9 and preliminary ejection of the recording liquid are completed. Then, the recording operation is performed to eject the recording liquid in response to the input of a recording signal.

According to the cleaning method of the present invention, the recording liquid is sequentially discharged from the discharge ports 9 before wiping of all the recording element substrates 4 of the liquid discharge head 3 is completed and before the mixed recording liquid forced into the discharge ports 9 and pressure chambers 14 of the liquid discharge head 3 thickens. This prevents the mixed recording liquid from circulating, and does not lead to a decrease in recording quality in the subsequent liquid discharge. Note that the present invention is not limited to a configuration in which all discharge port rows discharge different colors or types of liquid, and can be widely applied to a configuration in which at least one discharge port row discharges a recording liquid different from the other discharge port rows. The present invention can also be applied to a configuration in which the liquid discharge head 3 has only one recording element substrate 4.
In addition, according to the present invention, the consumption of recording liquid during maintenance is small, maintenance that stops the circulation of the recording liquid can be completed in a short time, and the thickened recording liquid can be removed from the pressure chamber, allowing the recording operation to be resumed quickly.

In the above, the liquid ejection head is described as being applied to a so-called multi-color integrated line head configuration. However, the cleaning method of the present invention can also be applied to a liquid ejection head that employs a method of circulating the recording liquid, for example, a monochromatic line-type liquid ejection head. In this case, there is no problem of color mixing, but the maintenance time can be shortened.
It goes without saying that the cleaning method of the present invention can also be applied to a configuration in which multiple monochromatic line-type liquid ejection heads that eject liquids of different colors are arranged in parallel to enable color recording as a whole, and multiple liquid ejection heads are wiped at once.

3 Liquid ejection heads 4, 4a to 4o Recording element substrate 9 Ejection port 11a Ejection port forming surfaces 12M, 12C, 12Y, 12K Ejection port arrays 40, 40a to 40c Wiping member

Claims (6)

A method for cleaning a liquid ejection head which is configured to include a liquid supply path, a supply port, a pressure chamber, a recovery port, and a liquid recovery path so that a recording liquid is circulated , and which has an ejection port formation surface on which a plurality of ejection port arrays each consisting of a plurality of ejection ports are formed, and at least one of the ejection port arrays ejects a different recording liquid from the other ejection port arrays, comprising:
the cleaning method includes a circulation stopping step of stopping circulation of the recording liquid in the liquid ejection head, a wiping step of wiping the ejection orifice formation surface, a preliminary ejection step of preliminary ejection of the recording liquid from the ejection orifices that have already been wiped, and a circulation resumption step of resuming circulation of the recording liquid after the wiping step and the preliminary ejection step are performed ;
the wiping step is a step of wiping the liquid ejection head by moving a wiping member along the ejection port row arranged from one end to the other end of the liquid ejection head ;
the preliminary ejection step is a step of sequentially ejecting preliminary ink from the ejection ports that have been passed by the wiping member, for all the ejection ports in the ejection port formation surface , following the movement of the wiping member ;
A method for cleaning a liquid ejection head, comprising: the liquid ejection head is configured by arranging a plurality of recording element substrates in a row from one end to the other end of the liquid ejection head, the recording element substrates having an ejection port formation surface on which a plurality of ejection port arrays each having a plurality of ejection ports are formed,
2. The method for cleaning a liquid ejection head according to claim 1, characterized in that, when, of the multiple arranged recording element substrates, the recording element substrate arranged on the one end side is defined as a first recording element substrate, and the recording element substrate arranged adjacent to the first recording element substrate on the other end side is defined as a second recording element substrate, after performing the wiping process on the first recording element substrate, preliminary ejection is performed from the ejection openings of the first recording element substrate while the wiping process is being performed on the second recording element substrate. the liquid ejection head is configured by arranging a plurality of recording element substrates in a row from one end to the other end of the liquid ejection head, the recording element substrates having an ejection port formation surface on which a plurality of ejection port arrays each having a plurality of ejection ports are formed,
2. The method for cleaning a liquid ejection head according to claim 1, characterized in that, when, among the multiple arranged recording element substrates, the recording element substrate arranged on the one end side is defined as a first recording element substrate, and the recording element substrate arranged adjacent to the first recording element substrate on the other end side is defined as a second recording element substrate, while the wiping process is being performed on the first recording element substrate, a preliminary ejection is performed from the ejection port of the first recording element substrate through which the wiping member has passed. the liquid ejection head is configured by arranging a plurality of recording element substrates in a row from one end to the other end of the liquid ejection head, the recording element substrates having an ejection port formation surface on which a plurality of ejection port arrays each having a plurality of ejection ports are formed,
2. The method for cleaning a liquid ejection head according to claim 1, characterized in that, when, among the multiple arranged recording element substrates, the recording element substrate arranged on the one end side is defined as a first recording element substrate, and the recording element substrate arranged adjacent to the first recording element substrate on the other end side is defined as a second recording element substrate, while the wiping process is being performed on the second recording element substrate, preliminary ejection is performed from the ejection openings of the first recording element substrate through which the wiping member has passed and the ejection openings of the second recording element substrate through which the wiping member has passed. a moving speed vm of the wiping member, a time t1 from when wiping is performed until a liquid ejection failure occurs due to an increase in the viscosity of the recording liquid caused by volatilization of a volatile component at the ejection port where wiping is performed, and a distance L between the ejection port being wiped and the ejection port at which preliminary ejection is started,
L≦vm×t1
5. The method for cleaning a liquid ejection head according to claim 1, wherein the following relationship is satisfied: a liquid ejection head that is configured to include a liquid supply path, a supply port, a pressure chamber, a recovery port, and a liquid recovery path so that the recording liquid is circulated, and that is configured to include an ejection port forming surface on which a plurality of ejection port arrays each consisting of a plurality of ejection ports are formed , and at least one of the ejection port arrays ejects a different recording liquid from the other ejection port arrays;
a wiping member that wipes the ejection port surface;
a preliminary ejection receiving member for receiving the liquid ejected by the preliminary ejection from the ejection port after the wiping;
a control mechanism for controlling each of the operations of circulating the recording liquid to the liquid ejection head, ejecting the recording liquid from the ejection openings, moving the wiping member, and moving the preliminary ejection receiving member,
the control mechanism performs a circulation stop for stopping the circulation of the recording liquid in the liquid ejection head; a wiping for simultaneously wiping a plurality of the ejection port rows by moving the wiping member from one end of the liquid ejection head toward the other end along the ejection port rows ; a preliminary ejection for ejecting recording liquid that is not used for recording from the wiped ejection ports ; an operation for receiving the preliminary ejected recording liquid in the preliminary ejection receiving member; and a circulation restart for restarting the circulation of the recording liquid after performing the wiping and the preliminary ejection.
the operation of receiving the preliminary ejection with the preliminary ejection receiving member is to move the preliminary ejection receiving member so as to face the ejection port from which the preliminary ejection is being performed in synchronization with the ejection of the recording liquid from all the ejection ports of the ejection port formation surface through which the wiping member has passed, following the movement of the wiping member;
A liquid ejection device comprising:

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