JP2023046649A - Printer and method for cleaning discharge head - Google Patents

Abstract

To prevent liquid used in ultrasound cleaning of a discharge head, which discharges ink from a nozzle, from entering the discharge head.SOLUTION: While a supply tank 91a and a recovery tank 92a are supplied with the same pressure P3 and normal liquid feeding operation is stopped, ultrasound cleaning is executed. However, even if the normal liquid feeding operation is stopped, there remains the possibility that the operation of pressure generators 96 and 97 giving pressure P3 to the supply tank 91a and the recovery tank 92a causes ink to be sucked into the supply tank 91a and the recovery tank 92a from a nozzle Hn of a discharge head H. Closing electromagnetic valves 984 and 994 enables the discharge head H to be isolated from each of the pressure generators 96 and 97. In that state, ultrasound cleaning can be executed.SELECTED DRAWING: Figure 6

Description

The present invention relates to a technique for ultrasonically cleaning an ejection head that ejects ink from nozzles.

2. Description of the Related Art A printing apparatus that prints an image using an ejection head that ejects ink from nozzles by an inkjet method is known. Further, such a printing apparatus is provided with a supply tank and a recovery tank communicating with the ejection head, and a circulation pump for feeding ink from the recovery tank to the supply tank. By feeding the ink, the ink can be cyclically supplied to the ejection head.

Further, Patent Documents 1 to 5 disclose techniques for removing ink adhering to an ejection head by ultrasonic cleaning. For example, in Patent Documents 1 and 2, an ultrasonic wave is applied to the cleaning liquid in a state in which the cleaning liquid is in contact with the ejection head while the cleaning liquid is opposed to the ejection head. In Patent Document 3, a cleaning liquid to which ultrasonic waves are applied is jetted from a cleaning liquid nozzle to an ejection head. In Patent Documents 4 and 5, a head cleaning device is used for cleaning the ejection head. This head cleaning device is used by being attached to the ejection head, and supplies cleaning liquid to which ultrasonic waves have been applied to the paths in the ejection head.

JP 2019-171797 A JP 2015-107562 A JP-A-2005-28758 JP 2015-85660 A JP-A-9-254397

According to the methods of Patent Literatures 4 and 5, it is necessary to connect the path in the ejection head to the head cleaning device in order to perform ultrasonic cleaning on the ejection head, resulting in extremely poor working efficiency. On the other hand, according to the methods of Patent Documents 1 to 3, there is an advantage that such a need is eliminated and ultrasonic cleaning can be performed efficiently.

However, the methods of Patent Documents 1 to 3 also have the following problems. In other words, when liquid to which ultrasonic waves have been applied is supplied to the ejection head as in the same method, the pressure of the ultrasonic waves can cause the liquid to enter the ejection head from the nozzles. If the liquid further enters the ejection head along the flow of ink from the supply tank to the recovery tank through the ejection head, there is a risk that the liquid will be mixed throughout the entire interior of the ejection head. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is desirable to suppress the mixing of the liquid used in the ultrasonic cleaning performed on the ejection head that ejects ink from nozzles into the interior of the ejection head. aim.

A printing apparatus according to the present invention includes an ejection head having nozzles that eject ink, a supply tank that stores ink to be supplied to the ejection head, a collection tank that stores ink recovered from the ejection head, a supply tank, and the ejection head. and a supply pipe for feeding ink supplied from the supply tank to the ejection head, and a flow path between the ejection head and the recovery tank, and the ink recovered from the ejection head is delivered to the recovery tank. A recovery pipe, a first pressure generator that generates pressure to be applied to the supply tank, a second pressure generator that generates pressure to be applied to the recovery tank, and the pressure generated by the first pressure generator is supplied. A first pressure transmission pipe that transmits the pressure to the tank, a second pressure transmission pipe that transmits the pressure generated by the second pressure generation unit to the recovery tank, and a liquid that is supplied to the ejection head while applying ultrasonic waves to the liquid. A head cleaning unit that performs ultrasonic cleaning, and a control unit that controls at least the first pressure generation unit and the second pressure generation unit. The first pressure generator and the second pressure generator are controlled so that the pressure applied to the collection tank is lower than the pressure applied to the tank, and the supply tank is discharged through the discharge head to the collection tank. When the ink is sent to the head cleaning unit and the ejection head is ultrasonically cleaned by the head cleaning unit, the pressures applied to the supply tank and the recovery tank are the same. The generator is controlled to stop the normal liquid feeding operation.

In the ejection head cleaning method according to the present invention, the pressure applied to the recovery tank storing ink is lower than the pressure applied to the supply tank storing ink, whereby the ink is sent out from the supply tank and the ink is ejected. Ink is sent to an ejection head having nozzles that are connected to each other, and the ink sent from the ejection head is collected and stored in a recovery tank, and pressure is cut off from the supply tank. At the same time, the application of pressure to the recovery tank is also interrupted, thereby stopping the normal liquid feeding operation step, preparing for the cleaning operation of the ejection head, and applying ultrasonic waves in a state in which the preparation step has been executed. a step of supplying the discharged liquid to the ejection head to clean the ejection head.

In the present invention (printing apparatus and ejection head cleaning method) configured as described above, a supply tank for supplying ink to the ejection head and a recovery tank for recovering ink from the ejection head are provided. Then, by making the pressure generated by the second pressure generation unit and applied to the recovery tank lower than the pressure generated by the first pressure generation unit and applied to the supply tank, Ink is sent to the recovery tank (normal liquid sending operation). If ultrasonic cleaning is performed on the ejection head while such a normal liquid feeding operation is being performed, there is a risk that the liquid used in the ultrasonic cleaning will enter the interior of the ejection head. On the other hand, in the present invention, ultrasonic cleaning is normally performed while the liquid transfer operation is stopped. That is, in the present invention, when performing ultrasonic cleaning of the ejection head, the first pressure generation section and the second pressure generation are controlled so that the same pressure is applied to the supply tank and the recovery tank. Stop the normal liquid feeding operation. This makes it possible to prevent the liquid used in ultrasonic cleaning from entering the interior of the ejection head.

Further, a first valve interposed in the first pressure transmission pipe and a second valve interposed in the second pressure transmission pipe are further provided. When the ink is sent from the supply tank to the collection tank through the ejection head by controlling the valve to be in an open state, while the head cleaning unit performs ultrasonic waves on the ejection head, the first valve and the The printing apparatus is configured to control the second valve so as to be in a closed state, thereby blocking the application of the pressure generated by the first pressure generating unit and the second pressure generating unit to the supply tank and the recovery tank. may In such a configuration, the transmission of pressure from the first pressure generating section to the supply tank is cut off by the first valve, so that the supply of ink from the supply tank to the ejection head can be reliably stopped. By interrupting the transmission of pressure from the pressure generator to the recovery tank, it is possible to reliably stop the transfer of ink from the ejection head to the recovery tank. This makes it possible to prevent the liquid used in ultrasonic cleaning from entering the interior of the ejection head.

In addition, a return pipe for returning the ink stored in the recovery tank to the supply tank by connecting the recovery tank and the supply tank to the supply tank, and a return pipe intervening in the return pipe for returning the ink stored in the recovery tank to the supply tank. The printing device may be configured to further comprise a circulation pump for returning. With such a configuration, the ink collected in the collection tank can be further sent to the supply tank, and the ink can be circulated and ejected from the ejection head for printing.

In addition, a communication pipe provided to communicate the atmosphere between the collection tank and the supply tank, and a third valve interposed in the communication pipe are further provided. When controlling the third valve to close to cut off the atmosphere between the supply tank and the recovery tank and stop the normal liquid feeding operation, the first pressure generating section and the second pressure generating section are controlled. to generate a predetermined pressure, transmit the predetermined pressure to the supply tank and the recovery tank, respectively, and then control the third valve to open to communicate the atmosphere between the supply tank and the recovery tank. The printing apparatus may be configured such that the pressure applied from the first pressure generator to the supply tank is equal to the pressure applied from the second pressure generator to the recovery tank. In such a configuration, the predetermined pressure generated by the first and second pressure generators is applied to the supply/recovery tank, and then the third valve interposed in the communication pipe is opened to allow the supply tank and the recovery tank to communicate with each other. . As a result, it is possible to reliably stop the normal liquid feeding operation and prevent the liquid used in ultrasonic cleaning from entering the interior of the ejection head.

Further, according to the above configuration, it is possible to prevent the liquid used in the ultrasonic cleaning from entering the ejection head, while reducing the possibility that the liquid remains in the vicinity of the nozzles of the ejection head after the ultrasonic cleaning is performed. remain. Therefore, the head cleaning section may configure the printing apparatus such that ink is discharged from the nozzles of the ejection head after ultrasonic cleaning is performed. With such a configuration, the liquid used in ultrasonic cleaning can be reliably discharged from the ejection head.

A second aspect of the present invention provides an ejection head having nozzles for ejecting ink, a supply tank for storing ink to be supplied to the ejection head, a recovery tank for storing ink recovered from the ejection head, and a supply tank. A supply pipe that connects the tank and the ejection head to flow the ink supplied from the supply tank to the ejection head, and a flow path between the ejection head and the recovery tank that connects the ink recovered from the ejection head to the recovery tank A recovery pipe that sends liquid to, a fourth valve interposed in the supply pipe, a fifth valve interposed in the recovery pipe, a first pressure generation unit that generates pressure to be applied to the supply tank, and a pressure to be applied to the recovery tank. a second pressure generating part that generates a pressure equal to the pressure generated by the first pressure generating part; a first pressure transmission pipe that transmits the pressure generated by the first pressure generating part to the supply tank; and a pressure generated by the second pressure generating part that is transmitted to the recovery tank. a second pressure transmission pipe, a first valve interposed in the first pressure transmission pipe, a second valve interposed in the second pressure transmission pipe, and supplying the liquid to the ejection head while applying ultrasonic waves to the liquid. and a control unit that controls at least the first pressure generation unit, the second pressure generation unit, the first valve, the second valve, the fourth valve, and the fifth valve. , the control unit controls the first, second, fourth and fifth valves to open during normal liquid feeding in which ink is ejected from the nozzles, and the pressure applied to the supply tank is higher than the pressure applied to the recovery tank. While controlling the first pressure generating section and the second pressure generating section so that the pressure applied to the pressure is low, the head cleaning section performs ultrasonic cleaning of the ejection head, the first valve , the second valve, the fourth valve and the fifth valve may be configured to close. According to the above configuration, by closing the first valve and the fourth valve, the supply of ink between the ejection head and the supply tank can be blocked, and by closing the second valve and the fourth valve, the ejection head and the recovery tank can be cut off. It is possible to cut off the ink supply between them. This makes it possible to prevent the liquid used in ultrasonic cleaning from entering the interior of the ejection head.

As described above, according to the present invention, it is possible to prevent the liquid used in the ultrasonic cleaning performed on the ejection head that ejects ink from the nozzles from entering the ejection head.

1 is a front view schematically showing an example of a printing system according to the present invention; FIG. FIG. 2 is a front view schematically showing a printing device included in the printing system of FIG. 1; FIG. 4 is a diagram schematically showing the bottom surface of the ejection head; FIG. 2 is a diagram schematically showing the configuration of an ejection head and an ink supply mechanism that supplies ink to the ejection head; FIG. 2 is a block diagram showing the electrical configuration of the printing device; 4 is a flowchart showing an example of head maintenance; FIG. 7 is a diagram schematically showing the configuration and operation of a maintenance unit used in the head maintenance of FIG. 6; 4 is a diagram schematically showing an ultrasonic cleaning unit included in the maintenance unit; FIG. FIG. 7 is a diagram schematically showing an example of operations performed in the head maintenance of FIG. 6; FIG. 7 is a diagram schematically showing an example of operations performed in the head maintenance of FIG. 6; The figure which shows typically the 1st modification of an ink supply mechanism. The figure which shows typically the 1st modification of an ink supply mechanism. FIG. 11 is a diagram schematically showing a second modification of the ink supply mechanism; FIG. 11 is a diagram schematically showing a third modification of the ink supply mechanism; FIG. 5 is a plan view schematically showing a modification of the maintenance unit; FIG. 5 is a bottom view schematically showing a modification of the ejection head; FIG. 5 is a bottom view schematically showing a modification of the ejection head; FIG. 5 is a bottom view schematically showing a modification of the ejection head; FIG. 5 is a bottom view schematically showing a modification of the ejection head; FIG. 5 is a bottom view schematically showing a modification of the ejection head;

FIG. 1 is a front view schematically showing an example of a printing system according to the invention. In FIG. 1 and the following figures, the horizontal direction X and the vertical direction Z are indicated where appropriate. As shown in FIG. 1, the printing system 1 comprises a printing device 3 and a drying device 6 arranged in the horizontal direction X. As shown in FIG. This printing system 1 transports a long band-shaped print medium M from a delivery roll 11 to a take-up roll 12 in a roll-to-roll manner. The material of the print medium M is a film such as OPP (oriented polypropylene) or PET (polyethylene terephthalate). However, the material of the print medium M is not limited to film, and may be paper or the like. Such a print medium M has flexibility. Further, hereinafter, of the two surfaces of the printing medium M, the surface on which an image is printed is referred to as a surface M1, and the surface opposite to the surface M1 is referred to as a back surface M2.

The printing device 3 prints an image on the surface M1 of the printing medium M by ejecting water-based ink onto the surface M1 of the printing medium M transported from the delivery roll 11 to the take-up roll 12 by an inkjet method. A detailed configuration of the printing device 3 will be described later. The print medium M on which the image is printed in this way is transported in the horizontal direction X from the printing device 3 toward the drying device 6 .

The drying device 6 includes a drying oven 60 and dries the print medium M transported from the printing device 3 as it is transported from the supply roll 11 to the take-up roll 12 . Inside the drying furnace 60, there are two upper blowing units 61u arranged in the horizontal direction X, two middle blowing units 61m arranged in the horizontal direction X below the upper blowing units 61u, and two middle blowing units 61m arranged in the horizontal direction X below the upper blowing units 61u. Two lower blower units 61l arranged in the horizontal direction X below the blower unit 61m are provided.

The print medium M ejected from the ejection port 312 of the printing device 3 passes through the two upper blower units 61u in the horizontal direction X, and then is folded back toward the two middle blower units 61m by the pair of rollers 62. . Subsequently, the print medium M passes through the two middle blower units 61m in the horizontal direction X, and is turned back by the pair of air turn bars 63 toward the second lower blower unit 61l. Further, the print medium M is transported out of the drying device 6 after passing through the two lower blower units 61l in the horizontal direction X. As shown in FIG.

The upper blower unit 61u has two blower chambers 64 arranged so as to sandwich the printing medium M passing in the horizontal direction X from the vertical direction Z. As shown in FIG. Each blowing chamber 64 has a plurality of nozzles 65 arranged in the horizontal direction X, and hot air (gas of 60° C. or higher) is jetted onto the printing medium M from each nozzle 65 . In this way, the print medium M is dried by hot air jetted from the nozzles 65 of the two blowing chambers 64 while passing between the two blowing chambers 64 provided above and below. Each of the middle blowing unit 61m and the lower blowing unit 61l also has two blowing chambers 64 sandwiching the print medium M in the vertical direction Z, similarly to the upper blowing unit 61u.

Incidentally, the specific configuration of the upper blower unit 61u is not limited to this example. For example, a plurality of rollers arranged in the horizontal direction X may be provided instead of the lower blowing chamber 64 of the upper and lower blowing chambers 64 of the upper blowing unit 61u. In such a configuration, hot air can be jetted from the upper air blowing chamber 64 to the front surface M1 of the print medium M while supporting the back surface M2 of the print medium M from below by the plurality of rollers.

FIG. 2 is a front view schematically showing a printing device included in the printing system of FIG. 1. FIG. In FIG. 2, one side X1 and the other side X2 in the horizontal direction X are shown as appropriate. Here, one side X1 is the side facing the drying device 6 from the printing device 3, and the other side X2 is the opposite side of the one side X1. The printing device 3 includes a housing 31, a color printing unit 32 arranged in the housing 31, a white printing unit 33 arranged above the color printing unit 32 in the housing 31, and A transport unit 4 transports the print medium M using a plurality of rollers arranged.

The color printing unit 32 has a plurality of (six) ejection heads arranged above the printing medium M conveyed by the conveying unit 4 in the traveling direction of the printing medium M (the direction from the other side X2 to the one side X1). 321. The plurality of ejection heads 321 has nozzles facing from above the surface M1 of the printing medium M passing below each, and ejects color inks of different colors from the nozzles by an inkjet method. Here, color ink means ink other than white, and includes ink such as cyan, magenta, yellow, and black. In this way, the plurality of ejection heads 321 of the color printing unit 32 eject color ink from above onto the surface M1 of the print medium M passing below them, thereby printing a color image on the surface M1 of the print medium M.

Also, the white printing section 33 has a single ejection head 331 arranged above the print medium M conveyed by the conveying section 4 . The ejection head 331 has nozzles facing from above the surface M1 of the print medium M passing therebelow, and ejects white ink from the nozzles by an inkjet method. In this way, the ejection head 331 of the white printing unit 33 prints a white image on the surface M1 of the printing medium M by ejecting white ink from above onto the surface M1 of the printing medium M passing below.

A carry-in port 311 opens in the side wall of the housing 31 on the other side X2, while a carry-out port 312 opens in the side wall of the housing 31 on the one side X1. Then, the transport unit 4 transports the printing medium M from the inlet 311 to the outlet 312 while passing through the color printing unit 32 and the white printing unit 33 .

The conveying unit 4 includes a carry-in unit 41 provided below the color printing unit 32, an ascending conveying unit 42 provided on one side X1 of the color printing unit 32, and a It has an upper transport section 43 and a lower transport section 44 provided on the other side X<b>2 of the color printing section 32 . The carry-in unit 41 conveys the print medium M carried in from the carry-in port 311 to the one side X1 by the rollers 411, and the ascending transport unit 42 carries the print medium M transported by the carry-in unit 41 upward by the rollers 421. Then, the upper transport section 43 transports the print medium M transported by the ascending transport section 42 to the other side X2 by the rollers 431, and the descending transport section 44 transports the print medium M transported by the upper transport section 43. It is conveyed downward by rollers 441 .

Further, the transport unit 4 has a color transport unit 45 that supports the print medium M facing the color print unit 32 from below. The color conveying unit 45 has a plurality of rollers 451 arranged from the other side X2 to the one side X1, and each roller 451 contacts the back surface M2 of the print medium M from below. Thus, the surface M1 of the print medium M supported by the color transport unit 45 faces upward, and each ejection head 321 of the color printing unit 32 ejects color ink while facing the surface M1 from above.

Further, the transport section 4 has rollers 461, 462, and 463 arranged between the color transport section 45 and the descending transport section 44 in the direction in which the print medium M advances. A roller 461 is a drive roller that drives the print medium M. As shown in FIG. Rollers 462 and 463 are driven rollers that are driven by the print medium M to rotate.

Further, the conveying section 4 has a reversing conveying section 47 that vertically inverts the printing medium M conveyed from the color conveying section 45 to the one side X1 twice. The reversing transport unit 47 has a plurality of rollers 471 to 477 including a driving roller 471, and these rollers 471 to 477 invert the print medium M upside down twice while contacting the back surface M2 of the print medium M. As shown in FIG. That is, the reversing conveying unit 47 conveys the printing medium M conveyed from the color conveying unit 45 downward by the rollers 471 and 472, and further changes the traveling direction of the printing medium M to the other side X2 by the rollers 472. The front surface M1 and the back surface M2 of the print medium M are turned upside down by conveying the print medium M. Subsequently, the reversing conveying unit 47 conveys the print medium M from the one side X1 toward the other side X2 with a plurality of rollers 473, and then conveys the print medium M upward with the rollers 474-476. Further, the reversing conveying unit 47 changes the traveling direction of the printing medium M to the one side X1 by the rollers 476, thereby vertically inverting the front surface M1 and the back surface M2 of the printing medium M again, and the printing medium M by the rollers 477. is conveyed from the other side X2 toward the one side X1.

The transport unit 4 also has a white transport unit 48 that supports the print medium M facing the white print unit 33 from below. enter in. The white conveying unit 48 has a roller 481 that contacts the back surface M2 of the print medium M from below. Thus, the surface M1 of the print medium M supported by the white conveying section 48 faces upward, and the ejection head 331 of the white printing section 33 ejects white ink while facing the surface M1 from above.

Further, the transport section 4 has an unloading section 49 provided above the upper transport section 43 . The carry-out section 49 has a plurality of rollers 491 arranged from the other side X2 in the horizontal direction X to the one side X1. The unloading unit 49 transports the print medium M conveyed by the white conveying unit 48 to the one side X<b>1 with a plurality of rollers 491 , thereby unloading the print medium M from the unloading port 312 of the housing 31 to the drying device 6 .

As described above, the color printing section 32 and the white printing section 33 of the printing device 3 have ejection heads 321 and 331 . Next, the ejection heads 321 and 331 and the ink supply/recovery/circulation mechanism 9 for supplying, recovering, and circulating ink to these will be described. The ink supply/recovery/circulation mechanism 9 includes an ink supply mechanism 9a that supplies ink to the ejection heads 321 and 331, an ink recovery mechanism 9b that recovers ink from the ejection heads 321 and 331, and an ink supply mechanism 9a that recycles the recovered ink. and an ink return mechanism 9c for returning to the original state. The ejection heads 321 and 331 have a common basic configuration, and the basic configuration of the ink supply/recovery/circulation mechanism 9 is also common to the ejection heads 321 and 331 . Therefore, the configuration of the ejection head 331 that ejects white ink will be described. Also, the ejection heads 321 and 331 are hereinafter referred to as an ejection head H as appropriate.

FIG. 3 is a diagram schematically showing the bottom surface of the ejection head, and FIG. 4 shows the ejection head, an ink supply mechanism 9a that supplies ink to the ejection head, an ink recovery mechanism 9b that recovers ink from the ejection head, and an ink recovery mechanism 9b that recovers ink from the ejection head. 4 is a diagram schematically showing the configuration of an ink return mechanism 9c that returns ink to the ink supply mechanism 9a again; FIG. In addition to horizontal direction X and vertical direction Z, horizontal direction Y perpendicular to horizontal direction X is shown in FIG. As shown in FIG. 3, in the printing apparatus 3, a plurality of ejection heads H for ejecting the same color ink (white ink) are arranged in a row in the horizontal direction Y, and each ejection head H is rectangular when viewed from the bottom. have

As shown in FIG. 3, the ejection head H has a housing Ha, and a plurality of nozzles Hn are arranged in a zigzag pattern in the horizontal direction Y and open at the bottom surface of the housing Ha. Inside the housing Ha, there are provided a plurality of cavities Hb communicating with the plurality of nozzles Hn, respectively, and an ink supply chamber Hc communicating with the plurality of cavities Hb. Stored in Hb. A piezoelectric element D is provided in each cavity Hb, and the piezoelectric element D is displaced according to a drive signal (electrical signal) to give pressure fluctuations to the ink in the cavity Hb. This pressure fluctuation pushes the ink out of the cavity Hb and ejects the ink from the nozzle Hn communicating with the cavity Hb. An ink inlet Hd and an ink outlet He are opened in the upper part of the ejection head H, and ink flows from the ink supply mechanism 9a through the ink inlet Hd into the ink supply chamber Hc, whereupon the ink is supplied. The ink flows out from the chamber Hc toward the ink recovery mechanism 9b through the ink outlet He.

The ink supply mechanism 9 a includes an ink supply section 91 that supplies ink toward the ejection head H, and a first pressure generation section 96 that generates supply pressure to be applied to the ink supply section 91 . The ink supply unit 91 includes a supply tank 91 a that stores ink to be supplied to the ejection head H, and a supply pipe 91 b that transfers the ink supplied from the supply tank 91 a to the ejection head H.

The ink recovery mechanism 9 b includes an ink recovery section 92 that recovers ink from the ejection head H and a second pressure generation section 97 that generates pressure to be applied to the ink recovery section 92 . The ink recovery unit 92 includes a recovery tank 92a that stores the ink recovered from the ejection head H, and a recovery pipe 92b that transfers the ink recovered from the ejection head H to the recovery tank 92a.
The supply tank 91a and the recovery tank 92a are arranged above the ejection head H, respectively.

The ink return mechanism 9c includes a return pipe 932 connecting the recovery tank 92a and the supply tank 91a, a circulation pump 93 interposed in the middle of the return pipe 932, and a circulation pump 93 interposed in the middle of the return pipe 932. and a degassing filter 931 arranged between the circulation pump 93 and the supply tank 91a. The circulation pump 93 sends the ink from the collection tank 92 a to the supply tank 91 a , and the degassing filter 931 removes gas from the ink before it flows out of the circulation pump 93 and into the supply tank 91 .

Further, the ink supply/collection/circulation mechanism 9 includes a main tank 951 capable of storing a large amount of ink, a liquid feeding pipe 953 for feeding the ink stored in the main tank 951 to the collecting tank 92a, and the liquid feeding pipe 953. It further includes a main pump 952 that is When the amount of ink stored in the supply tank 91a and the recovery tank 92a decreases as ink is ejected from the nozzles Hn, the main pump 952 supplies ink from the main tank 951 to the recovery tank 92a.

Further, the ink supply mechanism 9a includes a supply-side pressure generator 96 (hereinafter referred to as "pressure generator 96" as appropriate) that applies pressure P1 (negative pressure) to the supply tank 91a. The pressure generation unit 96 includes a pressure tank 961, a pressurization/decompression unit 962 for generating a desired pressure in the pressure tank 961, a flexible tube 963 having one end connected to the pressure tank 961, and a tube 963 a pressure transmission pipe 964 whose one end is communicably connected to the other end of the pressure transmission pipe 964, which is arranged so that the other end faces the atmosphere in the supply tank 91a, and which transmits the pressure generated in the pressure tank 961 to the supply tank 91a; Prepare. The pressurization/decompression unit 962 has an exhaust pump 962a that exhausts the pressure tank 961 and a pressurization pump 962b that pressurizes the pressure tank 961, and selectively operates one of the exhaust pump 962a and the pressurization pump 962b. be able to. In particular, the exhaust pump 962a generates pressure P1 inside the pressure tank 961 by exhausting the pressure tank 961, and the pressure P1 thus generated in the pressure tank 961 is supplied via the tube 963 and the pressure transmission pipe 964. supplied to tank 91a.

On the other hand, in the supply tank 91 a, gas (air) is accumulated above the liquid surface of the ink. That is, in the supply tank 91a, ink is stored below the gas-liquid interface, and gas exists above the gas-liquid interface. Therefore, the pressure generator 96 applies the pressure P1 (negative pressure) to the gas-liquid interface in the supply tank 91a.

In addition, the ink supply mechanism 9 a has an electromagnetic valve 984 provided between the other end of the tube 963 of the pressure generating section 96 and one end of the pressure transmission pipe 964 . The solenoid valve 984 communicates/shuts off the atmosphere between the pressure tank 961 and the supply tank 91a, thereby applying/shutting off the pressure P1 generated in the pressure tank 961 to/from the supply tank 91a. That is, as shown in FIG. 4, when the electromagnetic valve 984 is open, the atmosphere between the pressure tank 961 and the supply tank 91a communicates, and the pressure tank 961, the tube 963, and the pressure transmission pipe 964 flow through the supply tank 91a. An application of pressure P1 to is performed. On the other hand, when the solenoid valve 984 is closed, the atmosphere between the pressure tank 961 and the supply tank 91a is cut off, and the application of the pressure P1 from the pressure tank 961 to the supply tank 91a is stopped.

A check filter 985 is interposed at one end of the pressure transmission pipe 964 of the ink supply mechanism 9a. The non-return filter 985 prohibits passage of ink from the supply tank 91a to the pressure tank 961 while permitting the passage of gas from the supply tank 91a to the pressure tank 961 . Thus, the non-return filter 985 prevents ink from flowing into the tube 963 from the supply tank 91a.

Further, the ink recovery mechanism 9b includes a recovery side pressure generator 97 (hereinafter referred to as “pressure generator 97” as appropriate) that applies pressure P2 (negative pressure) to the recovery tank 92a. The pressure generation unit 97 includes a pressure tank 971, a pressurization/decompression unit 972 for generating a desired pressure in the pressure tank 971, a flexible tube 973 having one end connected to the pressure tank 971, and a 973, one end of which is communicably connected to the other end of the pressure transmission pipe 973, the other end of which is disposed so as to face the atmosphere in the recovery tank 92, and which transmits the pressure generated in the pressure tank 971 to the recovery tank 92a. 974; The pressurization/decompression unit 972 has an exhaust pump 972a that exhausts the pressure tank 971 and a pressurization pump 972b that pressurizes the pressure tank 971, and selectively operates one of the exhaust pump 972a and the pressurization pump 972b. be able to. In particular, the exhaust pump 972a generates pressure P2 inside the pressure tank 971 by exhausting the pressure tank 971, and the pressure P2 thus generated in the pressure tank 971 is recovered via the tube 973 and the pressure transmission pipe 974. supplied to tank 92a.

On the other hand, in the recovery tank 92a, gas (air) is accumulated above the liquid surface of the ink. That is, in the recovery tank 92a, the ink is stored below the gas-liquid interface, and the gas exists above the gas-liquid interface. Therefore, the pressure generator 97 applies a negative pressure P2 (negative pressure) to the gas-liquid interface in the recovery tank 92a.

Further, the ink recovery mechanism 9b has an electromagnetic valve 994 provided between the other end of the tube 973 of the pressure applying section 97 and one end of the pressure transmission pipe 974. As shown in FIG. The electromagnetic valve 994 communicates/shuts off the atmosphere between the pressure tank 971 and the recovery tank 92a, thereby applying/shutting off the pressure P2 generated in the pressure tank 971 to/from the recovery tank 92a. That is, as shown in FIG. 4, when the electromagnetic valve 994 is open, the atmosphere between the pressure tank 971 and the recovery tank 92a is communicated, and the pressure tank 971, the tube 973, and the pressure transmission pipe 974 flow through the recovery tank 92a. Application of pressure P2 to is performed. On the other hand, when the electromagnetic valve 994 is closed, the atmosphere between the pressure tank 971 and the recovery tank 92a is shut off, and the application of the pressure P2 from the pressure tank 971 to the recovery tank 92a is stopped.

In the ink recovery mechanism 9b, a check filter 995 is interposed at one end of the pressure transmission pipe 974. As shown in FIG. The non-return filter 995 prohibits the passage of ink from the collection tank 92a to the pressure tank 971 while permitting the passage of gas from the collection tank 92a to the pressure tank 971 . Thus, the non-return filter 995 prevents the ink from flowing into the tube 973 from the collection tank 92a.

In the state shown in FIG. 4, the pressure P2 applied by the pressure generator 97 to the recovery tank 92a through the tube 973, the solenoid valve 994, and the pressure transmission pipe 974 is It is lower than the pressure P1 applied to the supply tank 91a through the transmission pipe 964. Therefore, according to the pressure difference between the pressure P2 and the pressure P1, the ink is supplied from the supply tank 91 to the ejection head H through the supply pipe 91b, and the ink is recovered from the ejection head H to the recovery tank 92 through the recovery pipe 92b. A normal liquid feeding operation for feeding ink is executed. Further, as shown in FIG. 4, the recovery tank 92a and the supply tank 91a are flow-connected by a return pipe 932. As shown in FIG. A circulation pump 93 is interposed in the return pipe 932 for sending the ink from the collection tank 92a to the supply tank 91a. Here, when the ink in the recovery tank 92a becomes excessive due to the execution of the normal liquid feeding operation, the circulation pump 93 operates to send ink from the recovery tank 92a to the supply tank 91a. In this way, the ink that has reached the collection tank 92a from the supply tank 91a via the ejection head H is circulated through the circulation path C that returns to the supply tank 91a through the return pipe 932. FIG.

A communication pipe 941 is provided between the collection tank 92a and the supply tank 91a to allow communication between the atmosphere of the collection tank 92a and the atmosphere of the supply tank 91a. Further, the communication pipe 941 is interposed with an electromagnetic valve 94 for connecting/disconnecting the atmosphere of the recovery tank 92 and the atmosphere of the supply tank 91 . That is, as shown in FIG. 4, when the solenoid valve 94 is closed, the atmosphere in the supply tank 91 and the atmosphere in the recovery tank 92 are cut off, and the pressure P1 in the supply tank 91a and the pressure P2 in the recovery tank 92a are independent of each other. On the other hand, when the electromagnetic valve 94 is open, the atmosphere in the supply tank 91a and the atmosphere in the recovery tank 92a communicate with each other, and the pressures inside the supply tank 91a and the inside of the recovery tank 92a become equal.

FIG. 5 is a block diagram showing the electrical configuration of the printing apparatus. The electrical configuration of FIG. 5 is provided for the ejection heads 321 and 331 of each color, but here, following the example described above, the configuration of the ejection head 331 that ejects white ink will be described. As shown in FIG. 5, the printing device 3 includes a control unit 300 that controls the entire device. The control unit 300 is a processor composed of, for example, a CPU (Central Processing Unit).

The control unit 300 controls an exhaust pump 962a and a pressurization pump 962b that constitute a part of the pressure generation unit 96 . In particular, the control unit 300 controls the pressure P1 generated in the supply tank 91a by controlling the exhaust amount or the exhaust pressure of the exhaust pump 962a, and controls the opening and closing of the solenoid valve 984 to control the pressure tank 961 to the tube. 963, switches between a state in which the pressure P1 is applied to the supply tank 91a through the pressure transmission pipe 964 and a state in which the application of the pressure P1 is stopped. Further, the control unit 300 controls an exhaust pump 972a and a pressurization pump 972b that constitute a part of the pressure generating unit 97 . In particular, the control unit 300 controls the pressure P2 generated in the recovery tank 92a by controlling the exhaust amount or the exhaust pressure of the exhaust pump 972a, and controls the opening and closing of the electromagnetic valve 994 to control the pressure tank 971 to the tube. 973 , switches between a state in which the pressure P2 is applied to the recovery tank 92 a through the pressure transmission pipe 974 and a state in which the application of the pressure P2 is stopped. As described above, the control unit 300 normally performs the normal liquid feeding operation to send ink from the supply tank 91a to the collection tank 92a via the ejection head H by generating the difference between the pressure P2 and the pressure P1. .

Further, when the amount of ink in the collection tank 92a becomes excessive due to the execution of the normal liquid feeding operation, the control unit 300 operates the circulation pump 93 to return the ink from the collection tank 92a to the supply tank 91a. In this way, the ink circulates in the circulation path C. As shown in FIG.

Further, the control unit 300 opens the electromagnetic valve 94 to eliminate the pressure difference between the pressure in the supply tank 91a and the pressure in the recovery tank 92a, and closes the electromagnetic valve 94 to reduce the pressure in the supply tank 91a. It can be independent of the pressure in the recovery tank 92a. Further, the control unit 300 operates the main pump 952 according to the decrease in the ink in the recovery tank 92a or the supply tank 91a, thereby supplying ink from the main tank 951 to the recovery tank 92a.

Further, the control unit 300 applies a drive signal (voltage signal) generated based on image data representing an image to be printed on the print medium M to the piezoelectric element D, thereby ejecting ink from the nozzles Hn onto the print medium M. Print an image (print operation). In this printing operation, the control unit 300 opens the solenoid valve 984 to apply pressure P1 to the supply tank 91 while the solenoid valve 94 is closed, and opens the solenoid valve 994 to apply pressure P2 to the recovery tank 92 . , the normal liquid feeding operation is performed by the pressure difference between the pressure P1 and the pressure P2.

Further, the control unit 300 controls the maintenance unit 51, the direct-acting mechanism 55y, or the head elevator E that performs operations required for maintenance of the ejection head H, which will be described later. Next, maintenance of the ejection head H will be described.

FIG. 6 is a flow chart showing an example of head maintenance, FIG. 7 is a diagram schematically showing the configuration and operation of a maintenance unit used in the head maintenance of FIG. 6, and FIG. FIG. 9A and FIG. 9B are diagrams schematically showing a unit, and FIGS. 9A and 9B are diagrams schematically showing an example of the operation performed in the head maintenance of FIG. 6; Each step in the flow chart of FIG. 6 is executed under the control of the control unit 300 .

As shown in FIG. 7, the printing apparatus 3 includes a maintenance unit 51 and a linear motion mechanism 55y that drives the maintenance unit 51 in the horizontal direction Y. As shown in FIG. The direct-acting mechanism 55y moves the maintenance unit 51 between the facing position La and a retracted position Lb spaced apart from the facing position La in the horizontal direction Y. As shown in FIG. The maintenance unit 51 positioned at the facing position La faces the plurality of ejection heads H from below, while the maintenance unit 51 positioned at the retracted position Lb does not face the plurality of ejection heads H. FIG. Further, a head elevator E is provided for integrally raising and lowering the plurality of ejection heads H. By raising and lowering the ejection heads H with the head elevator E, interference between the ejection heads H and the maintenance unit 51 can be avoided. can. In particular, the plurality of ejection heads H are positioned at any one of the printing height Hl, the cap height Hm higher than the printing height Hl, and the retraction height Hh higher than the cap height Hm.

This maintenance unit 5 has an ultrasonic cleaning unit 52 . As shown in FIG. 8, this ultrasonic cleaning unit 52 has an ultrasonic cleaning nozzle 521 and a cleaning liquid recovery guide 522 . The ultrasonic cleaning nozzle 521 jets an ultrasonic cleaning liquid, which is a liquid to which ultrasonic waves have been applied, onto the bottom surface of the ejection head H to be cleaned (the surface where the nozzles Hn are open). Water, for example, can be used as this liquid. Also, the cleaning liquid recovery guide 522 receives the liquid dropped from the bottom surface of the ejection head H and guides it to a recovery container (not shown).

In step S101 of head maintenance in FIG. 6, it is determined whether or not the printing operation of printing an image on the print medium M by ejecting ink from the nozzles Hn of the ejection head H is completed. The column of step S101 in FIG. 7 indicates the point in time when the printing operation is completed. In this step S101, the ejection head H is positioned at the printing height Hl, and the maintenance unit 51 is positioned at the retreat position Lb. When the printing operation is completed in this manner, the head elevator E raises the plurality of ejection heads H from the printing height Hl to the retraction height Hh (step S102). Thereby, a space into which the maintenance unit 51 enters is formed below each ejection head H. As shown in FIG.

In addition, in the printing operation, the normal liquid feeding operation is performed by the pressure difference between the pressure P2 and the pressure P1, and the normal liquid feeding operation is continued even after the printing operation ends. On the other hand, in step S103, the control unit 300 applies the same pressure P3 (negative pressure) to the supply tank 91a and the recovery tank 92a, thereby stopping the normal liquid feeding operation. Specifically, the control unit 300 controls the solenoid valve 984 so that the pressure P3 generated in the pressure tank 961 by the exhaust pump 962a is transferred through the tube 963 and the pressure transmission pipe 964 while opening the solenoid valve 984. It is given to the supply tank 91a. Further, the control unit 300 controls the solenoid valve 994 so that the pressure P3 generated in the pressure tank 971 by the exhaust pump 972a is transferred to the recovery tank 92a through the tube 973 and the pressure transmission pipe 974 while opening the solenoid valve 994. Give. This pressure P3 is a negative pressure that forms an ink meniscus at the nozzle Hn while supporting the ink against the head pressure from the gas-liquid interface of the supply tank 91a and the recovery tank 92a to the nozzle Hn. In this way, in a state in which the same pressure P3 is applied to the supply tank 91a and the recovery tank 92a, the control unit 300 controls the solenoid valve 94 to open the solenoid valve 94, thereby separating the supply tank 91 and the recovery tank 92. communicate the atmosphere between them.

When the normal liquid feeding operation stops in this way, the control unit 300 executes control of the electromagnetic valve 984, and as shown in FIG. The atmosphere between the pressure generator 97 (pressure tank 971) and the recovery tank 92a is shut off by closing the electromagnetic valve 994 (blocking in step S104). situation). In this blocked state, the upper side of the gas-liquid interface of the supply tank 91 and the recovery tank 92 is sealed from the outside air.

In step S105, the maintenance unit 51 starts moving from the retracted position Lb to the facing position La, and in step S106, the ultrasonic cleaning nozzle 521 starts spraying the ultrasonic cleaning liquid. As a result, the ultrasonic cleaning nozzle 521 ejects the ultrasonic cleaning liquid onto the bottom surface of the ejection head H (the surface where the nozzle Hn opens) while moving in the horizontal direction Y (ultrasonic cleaning).

When the ultrasonic cleaning nozzle 521 passes below the ejection head H in the horizontal direction Y, the ultrasonic cleaning nozzle 521 finishes ejecting the ultrasonic cleaning liquid (step S107), and the maintenance unit 51 stops at the facing position La (step S108).

In step S109, the ejection heads H are lowered from the retraction height Hh to the cap height Hm and come into contact with the maintenance unit 51 located at the facing position La. As a result, the plurality of ejection heads H are covered and capped by the maintenance unit 51 from below (capping).

With the capping performed in this way, the purge of step 110 is performed. Specifically, as shown in FIG. 9B, the control unit 300 controls the pressurization/decompression unit 962 to generate pressure P4 (positive pressure) in the pressure tank 961 by the pressurization pump 962b. Further, the control unit 300 controls the pressurization/decompression unit 972 to generate the pressure P4 in the pressure tank 971 by the pressurization pump 972b. Then, the control unit 300 controls the solenoid valve 984 to open, and the pressure P4 generated in the pressure tank 961 is applied to the supply tank 91a. Further, the control unit 300 controls the electromagnetic valve 994 to open, and the pressure P4 generated in the pressure tank 971 is applied to the recovery tank 92a. Thus, the insides of the supply tank 91a and the recovery tank 92a are pressurized by the same pressure P4 (positive pressure). As a result, the inflow of ink from the supply tank 91a into the ink supply chamber Hc of the ejection head H and the inflow of ink from the recovery tank 92a into the ink supply chamber Hc of the ejection head H occur simultaneously. Ink is pushed out (purge) from the nozzle Hn. In purging, the control unit 300 controls the electromagnetic valve 94 to open, and the atmosphere in the supply tank 91a and the atmosphere in the recovery tank 92a communicate with each other.

When the purge is continued for a predetermined time, the controller 300 controls the solenoid valve 94 to close, and after the atmosphere in the supply tank 91a and the atmosphere in the recovery tank 92a is cut off, the supply tank 91a and the recovery tank 92a are closed. are supplied with the pressure P1 and the pressure P2, respectively (FIG. 4), and the normal liquid feeding operation is started (step S111).

In the embodiment described above, the discharge head H is provided with a supply tank 91a that is flow-connected via a supply pipe 91b and a recovery tank 92a that is flow-connected via a recovery pipe 92b. By making the pressure P2 applied to the recovery tank 92a by the pressure generator 97 (second pressure generator) lower than the pressure P1 applied to the supply tank 91a by the pressure generator 96 (first pressure generator), The ink is sent from the supply tank 91a to the ejection head H through the supply pipe 91b, and the ink is sent from the ejection head H to the recovery tank 92a through the recovery pipe 92b and recovered (normal liquid delivery operation). If ultrasonic cleaning is performed on the ejection head H while such a normal liquid feeding operation is being performed, there is a risk that the liquid used in the ultrasonic cleaning will enter the ejection head H. In contrast, in the above-described embodiment, the same pressure P3 is applied to the supply tank 91a and the recovery tank 92a, and ultrasonic cleaning is performed in a state where the normal liquid feeding operation is stopped (steps S103, S106, S107). However, even if the normal liquid feeding operation is stopped, the pressure generating unit 96 and the pressure generating unit 97 apply the pressure P3 to the supply tank 91a and the recovery tank 92a. And there remains a possibility that the ink will be sucked into the collection tank 92a. Therefore, in the above embodiment, by closing the solenoid valve 984 and the solenoid valve 994, the atmosphere between the pressure generator 96 and the supply tank 91a is cut off, and the atmosphere between the pressure generator 97 and the recovery tank 92a is cut off. Ultrasonic cleaning is performed with the atmosphere shut off (FIG. 9A, steps S104, S106, and S107). As a result, it is possible to prevent the liquid used in ultrasonic cleaning from entering the ejection head H. As shown in FIG.

Specifically, an electromagnetic valve 984 (first valve) is provided between the other end of the tube 963 and one end of the pressure transmission pipe 964, and an electromagnetic valve 984 (first valve) is provided between the other end of the tube 973 and one end of the pressure transmission pipe 974. A valve 994 (second valve) is provided. Then, the control unit 300 controls the electromagnetic valve 984 so that the electromagnetic valve 984 is opened, thereby communicating the atmosphere between the pressure generating unit 96 and the supply tank 91a. Thereby, the pressure generated by the pressure generator 96 is applied to the supply tank 91a. On the other hand, the controller 300 shuts off the atmosphere between the pressure generator 96 and the supply tank 91a by controlling the electromagnetic valve 984 so that the electromagnetic valve 984 is closed. As a result, application of pressure from the pressure generator 96 to the supply tank 91a is stopped. Further, the controller 300 controls the electromagnetic valve 984 so that the electromagnetic valve 994 is opened, thereby communicating the atmosphere between the pressure generator 97 and the collection tank 92a. As a result, pressure is applied from the pressure generator 97 to the recovery tank 92a. On the other hand, the controller 300 controls the electromagnetic valve 984 so that the electromagnetic valve 994 is closed, thereby blocking the atmosphere between the pressure generator 97 and the collection tank 92a. As a result, application of pressure from the pressure generator 97 to the recovery tank 92a is stopped. The control unit 300 shuts off the atmosphere between the pressure applying unit 96 and the supply tank 91 with the electromagnetic valve 984 , and shuts off the atmosphere between the pressure applying unit 97 and the recovery tank 92 with the electromagnetic valve 994 . In such a configuration, the electromagnetic valve 984 shuts off the atmosphere between the pressure generator 96 and the supply tank 91a, thereby reliably shutting off the influence of pressure applied to the supply tank 91a. In addition, by blocking the atmosphere between the pressure generator 97 and the collection tank 92a by the electromagnetic valve 994, the application of pressure to the collection tank 92a is cut off, and the influence of the application of pressure to the collection tank 91a is reliably cut off. be. As a result, it is possible to prevent the liquid used in ultrasonic cleaning from entering the ejection head H. As shown in FIG.

Further, the control unit 300 equalizes the pressures of the supply tank 91a and the recovery tank 92a, thereby stopping the normal liquid feeding operation (FIG. 9A, step S103). In such a configuration, the normal liquid feeding operation is stopped by simple control such as equalizing the pressures of the supply tank 91a and the recovery tank 92a, thereby suppressing the mixing of the liquid used in the ultrasonic cleaning into the inside of the ejection head H. can do.

In addition, an electromagnetic valve 94 is interposed in a communication pipe 941 provided to communicate the atmosphere between the supply tank 91 and the recovery tank 92 . When the normal liquid feeding operation is executed, the control unit 300 controls the electromagnetic valve 94 so that the electromagnetic valve 94 shuts off the atmosphere between the supply tank 91a and the recovery tank 92a. On the other hand, the control unit 300 controls the pressure generation unit 96 and the pressure generation unit 97 so that the pressure generation unit 96 applies pressure P3 (predetermined pressure) to the supply tank 91a and the pressure generation unit 97 causes the recovery tank to After the pressure P3 is applied to 92a, control of the solenoid valve 94 is executed. That is, the control unit 300 controls the electromagnetic valve 94 so that the electromagnetic valve 94 is opened, and communicates the atmosphere between the supply tank 91a and the recovery tank 92a, thereby increasing the pressure in the supply tank 91a and the recovery tank 92a. equalize the pressure inside. That is, pressure P3 is applied to the supply tank 91a and the recovery tank 92a by the pressure generator 96 and the pressure generator 97, and then the atmosphere between the supply tank 91a and the recovery tank 92a is communicated by the electromagnetic valve 94. As a result, it is possible to reliably stop the normal liquid feeding operation and prevent the liquid used in the ultrasonic cleaning from entering the ejection head H. FIG.

By the way, according to the above configuration, it is possible to prevent the liquid used in the ultrasonic cleaning from entering the inside of the ejection head H, while the liquid remains in the vicinity of the nozzles Hn of the ejection head H after the ultrasonic cleaning is performed. Possibilities remain. Therefore, the control unit 300 executes control of the pressure generation unit 96 and the pressure generation unit 97 after executing ultrasonic cleaning, and purge is executed to discharge ink from the nozzles Hn of the ejection head H ( FIG. 9B , step S110). With such a configuration, the liquid used for ultrasonic cleaning can be reliably discharged from the ejection head H.

In the embodiment described above, the printing apparatus 3 corresponds to an example of the "printing apparatus" of the present invention, the control section 300 corresponds to an example of the "control section" of the present invention, and the maintenance unit 51 corresponds to the "control section" of the present invention. The supply tank 91a corresponds to an example of the "supply tank" of the present invention, the collection tank 92a corresponds to an example of the "collection tank" of the present invention, and the supply pipe 91b corresponds to an example of the "collection tank" of the present invention. The recovery pipe 92b corresponds to an example of the "recovery pipe" of the present invention, the return pipe 932 corresponds to an example of the "return pipe" of the present invention, and the circulation pump 93 corresponds to an example of the "return pipe" of the present invention. The communication pipe 941 corresponds to an example of the "communication pipe" of the present invention, and the solenoid valve 94 corresponds to an example of the "third valve" of the present invention. 96 corresponds to an example of the "first pressure generation section" of the present invention, the pressure generation section 97 corresponds to an example of the "second pressure generation section" of the present invention, and the tube 963 and the pressure transmission piping 964 of the present invention. The tube 973 and the pressure transmission pipe 974 correspond to an example of the "second pressure transmission pipe" of the present invention, and the solenoid valve 984 corresponds to the "first valve" of the present invention. The solenoid valve 994 corresponds to an example of the "second valve" of the present invention, the ejection head H corresponds to an example of the "ejection head" of the present invention, and the nozzle Hn corresponds to the "nozzle" of the present invention. It corresponds to an example.

The present invention is not limited to the above-described embodiments, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, the ink supply/recovery/circulation mechanism 9 can be modified as described below. In the following description, differences from the ink supply/recovery/circulation mechanism 9 shown in FIG. 4 will be mainly described, and common parts will be denoted by corresponding reference numerals and description thereof will be omitted as appropriate.

10A and 10B are diagrams schematically showing a first modification of the ink supply mechanism. In this modification, a supply pipe 91b connecting the supply tank 91a and the ink inlet Hd of the ejection head H is provided with an electromagnetic valve 986 to allow the ink outlet He of the ejection head H to flow through the collection tank 92a. A solenoid valve 996 is provided on the connecting recovery pipe 92b. Then, the control unit 300 controls the electromagnetic valve 986 to open the electromagnetic valve 986 to allow the flow path between the supply tank 91a and the ejection head H to communicate, while controlling the electromagnetic valve 986 to close. The flow path between the supply tank 91a and the ejection head H is blocked. Further, the control unit 300 controls the solenoid valve 996 to open the solenoid valve 996 to allow communication between the collection tank 92a and the ejection head H, and controls the solenoid valve 996 to close. The flow path between the recovery tank 92a and the ejection head H is blocked.

In particular, during the normal liquid feeding operation, the control unit 300 opens the electromagnetic valves 986 and 996 to send ink from the supply tank 91 through the supply pipe 91b to the ejection head H as shown in FIG. The ink is recovered in the recovery tank 92 from the head H through the recovery pipe 92b. On the other hand, when stopping the normal liquid feeding operation, as shown in FIG. 10B, the control unit 300 controls the solenoid valves 986 and 996 to close. As a result, a blocked state in which the flow path between the recovery tank 92a and the ejection head H is blocked while the flow path between the supply tank 91 and the ejection head H is blocked can be realized.

10A and 10B, the solenoid valve 986 (fourth valve) provided between the ejection head H and the supply tank 91a and the solenoid valve 986 (fourth valve) provided between the ejection head H and the collection tank 92 A solenoid valve 996 (fifth valve) is provided. Then, when the normal liquid feeding operation is executed, the control unit 300 controls the electromagnetic valve 986 to open, communicates the flow path between the ejection head H and the supply tank 91, and opens the electromagnetic valve 996. , and the flow path between the ejection head H and the recovery tank 92a is communicated. Further, the control unit 300 controls the solenoid valve 986 to close, blocks the flow path between the supply tank 91a and the ejection head H, controls the solenoid valve 996 to close, and controls the collection tank 92a and the ejection head H to close. The flow path between H is cut off. As a result, it is possible to prevent the liquid used in ultrasonic cleaning from entering the ejection head H. As shown in FIG.

FIG. 11A is a diagram schematically showing a second modification of the ink supply mechanism. In this modification, a pressurization tank 901 is connected to the atmosphere of the supply tank 91a and the atmosphere of the recovery tank 92a via a pressurization pipe 905, and a pressurization pump 902 that pressurizes the pressurization tank 901 is provided. . Further, an electromagnetic valve 903 is interposed in this pressurization pipe 905 for communicating/shutting off the atmosphere of the pressurization tank 901 and the atmosphere of the supply tank 91a. A solenoid valve 904 is interposed to communicate/shut off atmosphere. Then, the control unit 300 controls the solenoid valve 903 to open, communicates the atmosphere of the pressurization tank 901 and the atmosphere of the supply tank 91a, and supplies the pressure (positive pressure) generated in the pressurization tank 901. While supplying to the tank 91a, control is performed so that the electromagnetic valve 903 is closed to cut off the atmosphere in the pressurized tank 901 and the atmosphere in the supply tank 91a. Further, the control unit 300 controls the electromagnetic valve 904 to open, communicates the atmosphere of the pressurized tank 901 and the atmosphere of the recovery tank 92a, and recovers the pressure (positive pressure) generated in the pressurized tank 901. While supplying to the tank 92a, control is performed so that the electromagnetic valve 904 is closed to cut off the atmosphere of the pressurized tank 901 and the atmosphere of the recovery tank 92a.

In this modification, the control unit 300 closes the solenoid valves 903 and 904 by controlling the solenoid valves 903 and 904 during the period in which the purge is not performed. on the other hand. Control unit 300 executes control of solenoid valve 984, solenoid valve 994, solenoid valve 903, and solenoid valve 904 to close solenoid valve 984 and solenoid valve 994, open solenoid valve 903 and solenoid valve 904, and perform heating. The inside of the supply tank 91a and the recovery tank 92a is pressurized by the pressure (positive pressure) of the pressure tank 901, and purging can be performed to cause the ink to flow out from the nozzle Hn (step S110).

FIG. 11B is a diagram schematically showing a third modification of the ink supply mechanism. In this modification, solenoid valve 984 is a three-way valve that also functions as solenoid valve 903 in FIG. 11A. That is, the solenoid valve 984 is
・Negative pressure application operation for communicating the atmosphere of the pressure tank 961 and the atmosphere of the supply tank 91a ・Interruption operation of isolating the atmosphere of the pressure tank 901 and the atmosphere of the pressure tank 961 from the atmosphere of the supply tank 91a ・Pressure tank Any one of the positive pressure application operations for communicating the atmosphere of 901 and the atmosphere of supply tank 91 can be selectively performed.

Also, the solenoid valve 994 is a three-way valve that also functions as the solenoid valve 904 in FIG. 11A. That is, the solenoid valve 994 is
・Negative pressure applying operation for communicating the atmosphere of the pressure tank 971 and the atmosphere of the recovery tank 92a ・Blocking operation of isolating the atmosphere of the pressure tank 901 and the atmosphere of the pressure tank 971 from the atmosphere of the recovery tank 92a ・Pressure tank Any one of the positive pressure applying operations for communicating the atmosphere of the tank 901 and the atmosphere of the recovery tank 92a can be selectively executed.

Therefore, the above-described normal liquid feeding operation can be performed or stopped while the electromagnetic valve 984 and the electromagnetic valve 994 are performing the negative pressure applying operation. In addition, the shutoff state (step S104) described above can be achieved by the electromagnetic valves 984 and 994 performing shutoff operations. Furthermore, the above-described purge (step S110) can be performed by the solenoid valve 984 and the solenoid valve 994 performing the positive pressure application operation.

Also, the contents of the flowchart in FIG. 10 may be changed as appropriate. For example, the purge in step S110 may be performed by opening the supply tank 91a and recovery tank 92a to atmospheric pressure rather than pressurizing them. Also, the purge in step S110 is not essential and may be omitted.

Furthermore, the configuration of the maintenance unit 51 that performs ultrasonic cleaning may be modified as follows. FIG. 12 is a plan view schematically showing a modification of the maintenance unit. Here, the difference from the above maintenance unit 51 will be mainly described, and the common parts will be denoted by corresponding reference numerals, and the description thereof will be omitted as appropriate. This maintenance unit 51 has a linear motion mechanism 55x that drives the ultrasonic cleaning unit 52 in the horizontal direction X. As shown in FIG.

When cleaning the nozzle Hn, the control unit 300 drives the linear motion mechanism 55y while maintaining the ultrasonic cleaning nozzle 521 that injects the ultrasonic cleaning liquid at a position facing the nozzle Hn by the linear motion mechanism 55x. to move the maintenance unit 51 in the horizontal direction Y (nozzle cleaning mode). Thereby, the ultrasonic cleaning nozzle 521 moves in the horizontal direction Y along the arrangement of the nozzles Hn. On the other hand, when cleaning the gap between two ejection heads H adjacent to each other in the horizontal direction Y, the maintenance unit 51 causes the direct-acting mechanism 55x and the direct-acting mechanism 55y to cooperate to eject the ultrasonic cleaning liquid. The ultrasonic cleaning nozzle 521 is moved along the gap (gap cleaning mode). As a result, dirt in the gap between the two adjacent ejection heads H can be reliably removed. At this time, the ultrasonic cleaning nozzle 521 may be reciprocated a predetermined number of times along the gap.

By the way, the ink that has entered the gap tends to concentrate at one end or both ends of the transport direction (X direction) in which the print medium M is transported for the following reasons. That is, when the ejection head H is inclined with respect to the horizontal direction X as illustrated in FIG. Further, in the ejection head H in which the periphery of the nozzle Hn is water-repellent, the ink repelled from the periphery of the nozzle Hn tends to gather at the end in the horizontal direction X. FIG. In addition, the coffee ring phenomenon, in which the density near the air-liquid interface increases during the drying process of the ink that has entered the gap, tends to leave solid ink deposits at the edges in the horizontal direction X of the gap.

Therefore, in the ultrasonic cleaning mode, the energy applied by the ultrasonic cleaning liquid to at least one of the ends of the gap may be made larger than the energy applied by the ultrasonic cleaning liquid to the central portion between the ends of the gap. As a specific method to increase the energy,
・Increase the output (amplitude) of the ultrasonic waves applied to the liquid ・Bring the ultrasonic cleaning nozzle 521 closer to the ejection head H ・Reduce the speed at which the ultrasonic cleaning nozzle 521 is moved with respect to the ejection head H . By changing the conditions at the center and the end of the gap in this way, the nozzles Hn adjacent to the center of the gap of the ejection head H are prevented from being damaged by the impact caused by the ejection of the ultrasonic cleaning liquid. The edge of the gap of the ejection head H can be reliably cleaned.

Also, the energy applied to the ejection head H by the ultrasonic cleaning liquid in the nozzle cleaning mode can be the same or smaller than the energy applied to the central portion of the gap in the gap cleaning mode. As a result, it is possible to reliably prevent the nozzles Hn of the ejection head H from being damaged.

The ejection head H and the gaps to be subjected to the ultrasonic cleaning using the nozzle cleaning mode and the gap cleaning mode may be configured so that the operator can select them through a UI (User Interface). Alternatively, all the ejection heads H and the gaps may be subjected to the above-described ultrasonic cleaning regardless of the instructions of the operator.

Note that the configuration of the ejection head H that can be cleaned by the maintenance unit 51 in FIG. 12 is not limited to the configuration illustrated in FIG. 3. For example, the ejection head H illustrated in FIGS. Here, FIGS. 13A to 13E are bottom views schematically showing modifications of the ejection head. In FIG. 13A the ejection head H has a trapezoidal shape and in FIG. 13B the ejection head H has a parallelogram shape. 13C and 13D, both ends of the ejection head H in the horizontal direction Y have a stepped shape that combines a portion parallel to the horizontal direction X and a portion parallel to the horizontal direction Y, and in FIG. The head H has a stepped shape in which a portion parallel to the horizontal direction X and a portion inclined to the horizontal direction Y are combined.

Further, in ultrasonic cleaning, by moving the ejection head H in the horizontal direction Y, the ejection head H and the maintenance unit 51 may be moved relative to each other.

Further, when printing an image on the print medium M, the ejection head H may be moved to move the ejection head H and the print medium M relative to each other.

INDUSTRIAL APPLICABILITY The present invention is applicable to all techniques for performing ultrasonic cleaning on ejection heads that eject ink from nozzles.

3...Printing device 300...Control unit 51...Maintenance unit (head cleaning unit)
91a... Supply tank 91b... Supply pipe 92a... Recovery tank 92b... Recovery pipe 93... Circulation pump 94... Solenoid valve 96... Pressure generator (first pressure generator)
97... Pressure generator (second pressure generator)
932... Return pipe 941... Communication pipe 963, 973... Tube
964, 974... Pressure transmission piping 984... Solenoid valve (first valve)
994... Solenoid valve (second valve)
986... Solenoid valve (fourth valve)
996... Solenoid valve (fifth valve)
H...Ejection head Hn...Nozzle

Claims (7)

an ejection head having nozzles for ejecting ink;
a supply tank that stores ink to be supplied to the ejection head;
a recovery tank that stores the ink recovered from the ejection head;
a supply pipe that connects the supply tank and the ejection head in a flow path and sends ink supplied from the supply tank to the ejection head;
a recovery pipe that connects the ejection head and the recovery tank to a flow path and sends the ink recovered from the ejection head to the recovery tank;
a first pressure generator that generates pressure to be applied to the supply tank;
a second pressure generator that generates pressure to be applied to the recovery tank;
a first pressure transmission pipe for transmitting the pressure generated by the first pressure generation unit to the supply tank;
a second pressure transmission pipe for transmitting the pressure generated by the second pressure generation unit to the recovery tank;
a head cleaning unit that applies ultrasonic waves to the liquid and supplies the liquid to the ejection head to perform ultrasonic cleaning;
A control unit that controls at least the first pressure generation unit and the second pressure generation unit,
The control unit
The first pressure generator and the second pressure are arranged so that the pressure applied to the recovery tank is lower than the pressure applied to the supply tank during a normal liquid feeding operation for ejecting ink from the nozzle. controlling a generation unit to send ink from the supply tank to the recovery tank through the ejection head;
When performing ultrasonic cleaning of the ejection head by the head cleaning unit, the first pressure generating unit and the second pressure generating unit are arranged so that the same pressure is applied to the supply tank and the recovery tank. controlling the unit to stop the normal liquid feeding operation;
printer. a first valve interposed in the first pressure transmission pipe;
a second valve interposed in the second pressure transmission pipe;
further comprising
The control unit controls the first valve and the second valve to be in an open state during the normal liquid feeding operation, and feeds ink from the supply tank to the recovery tank through the ejection head. On the other hand, when ultrasonic waves are applied to the ejection head by the head cleaning section, the first valve and the second valve are controlled to be in a closed state, and the first pressure generating section and the blocking the application of the pressure generated by the second pressure generation unit to the supply tank and the recovery tank;
The printing device according to claim 1. a return pipe for connecting the recovery tank and the supply tank in a flow path to return the ink stored in the recovery tank to the supply tank;
a circulation pump that is interposed in the return pipe and functions to return the ink stored in the recovery tank to the supply tank;
further comprising
3. A printing device according to claim 1 or 2. a communicating pipe provided so as to communicate the atmosphere between the recovery tank and the supply tank;
a third valve interposed in the communication pipe,
The control unit
When the normal liquid feeding operation is executed, the third valve is controlled to close to cut off the atmosphere between the supply tank and the recovery tank,
When stopping the normal liquid feeding operation, the first pressure generating section and the second pressure generating section are controlled to generate predetermined pressures respectively, and the predetermined pressures are applied to the supply tank and the recovery tank, respectively. The pressure is transmitted, and then the third valve is controlled to open, the atmosphere between the supply tank and the recovery tank is communicated, and the atmosphere is applied from the first pressure generator to the supply tank. 4. The printing apparatus according to any one of claims 1 to 3, wherein the pressure is equal to the pressure applied from the second pressure generator to the recovery tank. 5. The printing apparatus according to claim 1, wherein the head cleaning section discharges ink from the nozzles of the ejection head after performing the ultrasonic cleaning. an ejection head having nozzles for ejecting ink;
a supply tank that stores ink to be supplied to the ejection head;
a recovery tank that stores the ink recovered from the ejection head;
a supply pipe that connects the supply tank and the ejection head in a flow path and sends ink supplied from the supply tank to the ejection head;
a recovery pipe that connects the ejection head and the recovery tank to a flow path and sends the ink recovered from the ejection head to the recovery tank;
a fourth valve interposed in the supply pipe;
a fifth valve interposed in the recovery pipe;
a first pressure generator that generates pressure to be applied to the supply tank;
a second pressure generator that generates pressure to be applied to the recovery tank;
a first pressure transmission pipe for transmitting the pressure generated by the first pressure generation unit to the supply tank;
a second pressure transmission pipe for transmitting the pressure generated by the second pressure generation unit to the recovery tank;
a first valve interposed in the first pressure transmission pipe;
a second valve interposed in the second pressure transmission pipe;
a head cleaning unit that performs ultrasonic cleaning for supplying the liquid to the ejection head while applying ultrasonic waves to the liquid;
a controller that controls at least the first pressure generator, the second pressure generator, the first valve, the second valve, the fourth valve, and the fifth valve;
with
The control unit
During normal liquid feeding for ejecting ink from the nozzle, control is performed so that the first valve, the second valve, the fourth valve, and the fifth valve are opened, and the pressure applied to the supply tank is lower than the pressure applied to the supply tank. While controlling the first pressure generation unit and the second pressure generation unit so that the pressure applied to the recovery tank is low,
A printing apparatus configured to control the first, second, fourth and fifth valves to close when ultrasonically cleaning the ejection head by the head cleaning unit. By making the pressure applied to the collection tank storing ink lower than the pressure applied to the supply tank storing ink, the ink is sent from the supply tank to the ejection head having nozzles for ejecting the ink. a normal liquid sending operation step of liquidating and further collecting and storing the ink sent from the ejection head in the recovery tank;
a preparation step of interrupting the application of pressure to the supply tank and also interrupting the application of pressure to the recovery tank to stop the normal liquid feeding operation step and prepare for the cleaning operation of the ejection head;
and a step of supplying liquid to which ultrasonic waves have been applied to the ejection head to clean the ejection head in a state in which the preparation step has been performed.

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