JP4457637B2 - Head cartridge and liquid ejection device - Google Patents

Description

The present invention relates to a head cartridge that discharges a predetermined liquid to an object from a plurality of liquid discharge nozzles formed in the liquid discharge head, and a liquid discharge apparatus including the head cartridge, and more particularly, generates a negative pressure in the liquid discharge head. When the liquid is circulated between the liquid discharge head and the liquid tank, the discharge time for flowing out the liquid from each liquid discharge port at both ends of the liquid discharge head is the same , and the liquid is replaced in the liquid in a short time. The present invention relates to a head cartridge and a liquid ejection device that attempt to remove bubbles contained therein.

  A conventional liquid ejecting apparatus, for example, an ink jet printer of an ink jet system, applies energy to ejection driving means such as a heat generating element and a piezoelectric element installed in a liquid chamber in a print head, and ink (predetermined liquid in the liquid chamber). ) Are ejected as ink droplets from ink ejection nozzles and attached to recording paper for printing, and the unit price is low, the running cost is low, the image quality is small, and it is generally widespread. .

  The inkjet printer includes a print head that ejects ink from a plurality of ink ejection nozzles formed on a nozzle surface, an ink tank that stores ink to be supplied to a liquid chamber in the print head, and the ink tank that An ink supply line for supplying ink to the print head, an ink reflux line for returning the ink from the print head to the ink tank, and a liquid feed pump for circulating the ink between the print head and the ink tank. The provided head cartridge is held in a removable state with respect to the apparatus main body.

  In such a head cartridge, it is necessary to stably eject, for example, picoliters of ink droplets from the ink ejection nozzle. However, since the ink ejection nozzle is formed to have a fine hole diameter, the ink may be ejected due to various factors. In some cases, the print quality deteriorates due to the discharge failure. One such factor is air bubbles mixed in and near the print head. If air bubbles are mixed in the ink supply pipe or the liquid chamber, not only ink cannot be ejected stably from the ink ejection nozzle, but also ink non-ejection may occur and printing may become impossible.

  The reason why air bubbles are mixed in and in the vicinity of the print head is as follows: when the ink tank that is made detachable from the print head is replaced, the air entering the attachment / detachment opening, the ink due to the change in temperature and pressure, etc. Precipitation of dissolved air in the air, mixing of bubbles from the ink ejection nozzle due to vibration or impact during printing or printing stop, and permeation of air from the pipe member constituting the ink flow path between the ink tank and the print head and so on.

In order to remove the air bubbles mixed in this way, conventionally, the ink is circulated between the ink tank and the print head to remove the air bubbles in the print head and the ink flow path. For example, ink supply ports and ink discharge ports are provided at multiple locations on the print head, an ink supply path is connected between the ink tank and the ink supply port of the print head, and an ink return path is connected between the ink discharge ports An ink circulation system is configured, and a circulation pump for circulating the ink in the liquid chamber of the print head is provided on the ink supply path so that the ink is circulated between the ink tank and the print head. Yes (see, for example, Patent Document 1).
JP-A-6-8467

  However, in the above-described conventional apparatus, ink is circulated while applying a positive pressure to the print head by the circulation pump, and ink may leak from the ink discharge nozzles of the print head during this ink circulation. It was. Therefore, the periphery of the nozzle may be stained with the leaked ink. Further, in a full-line type print head in which the nozzle member is formed long across the width of one side of the recording paper (for example, A4 size), since the number of nozzles is large, the amount of ink pushed out from the ink ejection nozzle is large. As a result, the ink is wasted and uneconomical. In order to cope with this, for example, a head cap may be brought into contact with the ejection port surface of the print head, and an ink circulation system for reusing the leaked ink in the head cap may be provided. Cost.

  In addition, there is a difference in the discharge time of ink flowing out from the plurality of ink discharge ports of the print head. Particularly in the case of a full line type print head, it takes time to circulate and replace the ink in the print head. It took. Therefore, the maintenance time for removing bubbles mixed in and in the vicinity of the print head may be increased.

  Furthermore, if the ink return path from the print head to the ink tank is placed below the print head, bubbles will rise into the print head from the ink tank side through the ink return path, and the ink will not be ejected correctly from the nozzles. It may cause. Also, in the part where the ink return path is downward, the flow of ink circulation from the print head to the ink tank is hindered by bubbles rising due to buoyancy and bubbles remaining inside, and the flow rate between the plurality of ink circulation paths Variation may occur.

Therefore, the present invention addresses such problems and generates negative pressure in the liquid discharge head to circulate the liquid between the liquid discharge head and the liquid tank. It is an object of the present invention to provide a head cartridge and a liquid ejecting apparatus that attempt to remove bubbles contained in a liquid by changing the liquid in a short time by setting the same discharge time for the liquid to flow out from the liquid discharge port.

The head cartridge according to the present invention includes a liquid supply port that receives liquid from a liquid tank that stores a predetermined liquid, and a liquid discharge port at both ends, and a plurality of liquid discharge nozzles formed on the nozzle surface. A liquid discharge head that discharges a predetermined liquid, a liquid supply line that supplies liquid from the liquid tank to the liquid supply port of the liquid discharge head, and a liquid that returns from the liquid discharge port of the liquid discharge head to the liquid tank A liquid reflux line, and a liquid feed pump disposed on the liquid reflux line for circulating the liquid between the liquid discharge head and the liquid tank, and driven by the liquid feed pump . when circulating the liquid between the liquid discharge negative pressure is generated in the head liquid discharge head and the liquid tank, between its two ends a liquid supply port of the liquid discharge head In the state of being arranged in the central part, the flow resistance of each liquid reflux pipe connected to each of both end parts or the pump pressure of each liquid feed pump provided respectively in the middle of each of the above liquid reflux pipes is changed. In the state where the flow rate of the liquid flowing out from the liquid discharge port is the same and the liquid supply port of the liquid discharge head is arranged so as to be deviated from the central portion between the two end portions to either end side, both ends of the liquid discharge head The flow resistance of each liquid reflux pipe connected to both ends according to the ratio of the arrangement distance of the liquid supply port from the section, or the pump pressure of each liquid feed pump provided respectively in the middle of each liquid reflux pipe By changing the ratio of the flow rate of the liquid flowing out from each liquid discharge port at both ends, the discharge time for flowing the liquid from each liquid discharge port at both ends of the liquid discharge head is made the same .

With such a configuration, a liquid discharge head that includes a liquid supply port for receiving a predetermined liquid at one location and has liquid discharge ports at both ends, and discharges the predetermined liquid from a plurality of liquid discharge nozzles formed on the nozzle surface. Liquid is supplied from the liquid tank storing the liquid to be supplied to the liquid supply port of the liquid discharge head via the liquid supply line, and the liquid is returned from the liquid discharge port of the liquid discharge head to the liquid tank via the liquid reflux line. When the liquid feed pump disposed on the liquid reflux pipe is driven to generate a negative pressure in the liquid discharge head and circulate the liquid between the liquid discharge head and the liquid tank, the liquid discharge In a state where the liquid supply port of the head is arranged at the center between the both ends, the flow resistance of each liquid reflux pipe connected to each of both ends or each liquid feed provided in the middle of each liquid reflux pipe Pump The liquid flow rate flowing out from each liquid discharge port at both ends by changing the pump pressure is made the same, and the liquid supply port of the liquid discharge head is arranged so as to be biased from the center between the both ends to either end side In the state, the flow resistances of the liquid reflux pipes connected to the both ends according to the ratio of the arrangement distance of the liquid supply port from the both ends of the liquid discharge head, or provided in the middle of the liquid reflux pipes, respectively. In addition, by changing the pump pressure of each liquid delivery pump and changing the ratio of the liquid flow rate flowing out from each liquid discharge port at both ends, the discharge time for flowing out the liquid from each liquid discharge port at both ends of the liquid discharge head is the same And

Further, the liquid ejection device according to the present invention holds the head cartridge in a detachable state on the apparatus main body, and ejects a predetermined liquid from each liquid ejection nozzle formed on the liquid ejection head of the head cartridge to produce dots or dots. A liquid ejection device for forming a dot row, wherein the head cartridge has a liquid supply port for receiving liquid from a liquid tank storing a predetermined liquid at one location, and has liquid discharge ports at both ends. A liquid discharge head that discharges a predetermined liquid from a plurality of liquid discharge nozzles formed in the liquid; a liquid supply line that supplies liquid from the liquid tank to a liquid supply port of the liquid discharge head; and a liquid of the liquid discharge head A liquid reflux line for returning liquid from the discharge port to the liquid tank, and a liquid disposed on the liquid reflux line between the liquid discharge head and the liquid tank. And a liquid feed pump for circulating, when circulating the liquid between by generating a negative pressure in the liquid ejecting head liquid ejecting head and the liquid tank by the driving of the liquid feed pump, the In a state where the liquid supply port of the liquid discharge head is disposed at the center between both ends, the flow resistance of each liquid reflux pipe connected to each of both ends or each provided in the middle of each liquid reflux pipe By changing the pump pressure of the liquid feed pump, the liquid flow rate flowing out from each liquid discharge port at both ends is made the same, and the liquid supply port of the liquid discharge head is biased from the center between the both ends to either end. In this state, the flow resistance of each liquid reflux pipe connected to both ends according to the ratio of the arrangement distance of the liquid supply port from the both ends of the liquid discharge head or the middle of each liquid reflux pipe Each liquid feeding pump provided in each By changing the pump pressure to change the ratio of the liquid flow flowing out from the liquid outlet of the ends of the, in which the same discharge time for discharging the liquid from the liquid outlet of the both end portions of the liquid discharge head .

With such a configuration, the head cartridge, which is held in a detachable state from the apparatus main body, has a liquid supply port for receiving a predetermined liquid at one place and a liquid discharge port at both ends, and is formed on the nozzle surface. The liquid discharge head supplies liquid to a liquid supply port of the liquid discharge head from a liquid tank that stores liquid supplied into the liquid discharge head that discharges a predetermined liquid from a plurality of liquid discharge nozzles. The liquid is returned from the liquid discharge port to the liquid tank through the liquid reflux pipe, and a negative pressure is generated in the liquid discharge head by driving a liquid feed pump disposed on the liquid reflux pipe. when circulating the liquid between the liquid tank, in a state of arranging the liquid supply port of the liquid discharge head in the central portion between both end portions, of each liquid return pipe which are respectively connected to both end portions The flow rate of liquid flowing out from each liquid discharge port at both ends is changed by changing the path resistance or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe, and the liquid supply port of the liquid discharge head is In the state of being arranged to be deviated from the central part between the two end parts to either one of the two end parts, the liquid discharge heads are connected to the two end parts according to the ratio of the arrangement distance of the liquid supply port from the both end parts. Change the flow rate resistance of each liquid reflux pipe or the ratio of the liquid flow rate flowing out from each liquid outlet at both ends by changing the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe, The discharge time for the liquid to flow out from the liquid discharge ports at both ends of the liquid discharge head is the same .

Furthermore, another liquid discharge apparatus according to the present invention includes a plurality of liquid discharge ports formed on the nozzle surface, each having a liquid supply port that receives liquid from a liquid tank that stores a predetermined liquid, and liquid discharge ports at both ends. A liquid discharge head for discharging a predetermined liquid from the liquid discharge nozzle, a liquid supply conduit for supplying liquid from the liquid tank to the liquid supply port of the liquid discharge head, and the liquid from the liquid discharge port of the liquid discharge head made comprises a liquid return line for returning the liquid to the tank, and a liquid feed pump for circulating the liquid between the liquid return pipe is disposed on the road the liquid discharge head and the liquid tank, the feed by driving the liquid pump in which circulates the liquid between the liquid discharge head and the liquid tank to generate a negative pressure within the liquid discharge head, at both the liquid supply port of the liquid discharge head In the state of being arranged at the center between the two parts, the flow resistance of each liquid reflux pipe connected to both ends or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe is changed to In the state where the flow rate of liquid flowing out from each liquid discharge port of the unit is the same and the liquid supply port of the liquid discharge head is arranged so as to be deviated from the center between the two ends to either end, the liquid discharge According to the ratio of the arrangement distance of the liquid supply port from the both ends of the head, the flow resistance of each liquid reflux pipe connected to each of the both ends, or each liquid feed pump provided in the middle of each liquid reflux pipe By changing the pump pressure, the ratio of the liquid flow rate flowing out from each liquid discharge port at both ends is changed, and the discharge time for flowing the liquid from each liquid discharge port at both ends of the liquid discharge head is made the same .

With such a configuration, a liquid discharge head that includes a liquid supply port for receiving a predetermined liquid at one location and has liquid discharge ports at both ends, and discharges the predetermined liquid from a plurality of liquid discharge nozzles formed on the nozzle surface. Liquid is supplied from the liquid tank storing the liquid to be supplied to the liquid supply port of the liquid discharge head via the liquid supply line, and the liquid is returned from the liquid discharge port of the liquid discharge head to the liquid tank via the liquid reflux line. When the liquid feed pump disposed on the liquid reflux pipe is driven to generate a negative pressure in the liquid discharge head and circulate the liquid between the liquid discharge head and the liquid tank, the liquid discharge In a state where the liquid supply port of the head is arranged at the center between the both ends, the flow resistance of each liquid reflux pipe connected to each of both ends or each liquid feed provided in the middle of each liquid reflux pipe Pump The liquid flow rate flowing out from each liquid discharge port at both ends by changing the pump pressure is made the same, and the liquid supply port of the liquid discharge head is arranged so as to be biased from the center between the both ends to either end side In the state, the flow resistances of the liquid reflux pipes connected to the both ends according to the ratio of the arrangement distance of the liquid supply port from the both ends of the liquid discharge head, or provided in the middle of the liquid reflux pipes, respectively. In addition, by changing the pump pressure of each liquid delivery pump and changing the ratio of the liquid flow rate flowing out from each liquid discharge port at both ends, the discharge time for flowing out the liquid from each liquid discharge port at both ends of the liquid discharge head is the same And

According to the head cartridge of the first aspect, when the negative pressure is generated in the liquid discharge head and the liquid is circulated between the liquid discharge head and the liquid tank, the liquid supply port of the liquid discharge head is connected to both ends thereof. In the state of being arranged in the central part between the two parts, both end parts are changed by changing the flow resistance of each liquid reflux pipe connected to both end parts or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe. In the state in which the liquid flow rate flowing out from each liquid discharge port is the same and the liquid supply port of the liquid discharge head is arranged so as to be deviated from the central portion between the two end portions to either end side, the liquid discharge head of the liquid discharge head Depending on the ratio of the arrangement distance of the liquid supply port from both ends, the flow resistance of each liquid reflux pipe connected to each end, or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe Change the flow from each liquid outlet at both ends. By varying the proportion of liquid flow rate can be from the liquid outlet of the both end portions of the liquid ejecting head and the same exhaust time for flowing out the liquid. Therefore, without generating a positive pressure in the liquid ejection head and pushing the liquid out of the nozzle, it prevents liquid leakage from the nozzle during liquid circulation, and replaces the liquid in a short time to remove bubbles contained in the liquid can do. Accordingly, it is possible to prevent the periphery of the nozzle from being contaminated with the liquid and to prevent the liquid from being wasted. Further, there is no need for means corresponding to the liquid leaking from the nozzle, and the apparatus can be reduced in size and cost. Furthermore, the maintenance time for removing bubbles can be shortened. The liquid feed pump can circulate the liquid between the liquid discharge head and the liquid tank with a simple configuration.

According to the second aspect of the present invention, the liquid reflux conduit is arranged so as to be upward or horizontal between each liquid discharge port of the liquid ejection head and at least the liquid circulation means. It is possible to prevent the bubbles from staying in the pipe and prevent the liquid flow from being obstructed by the bubbles. Accordingly, it is possible to smoothly flow out the liquid from the liquid discharge ports at both ends of the liquid discharge head.

Furthermore, according to the third aspect of the invention, the liquid tank can be attached to and detached from the liquid ejection head, so that the liquid tank can be exchanged according to consumption of a predetermined liquid. Therefore, the head cartridge can be used repeatedly.

According to the fourth aspect of the invention, the liquid circulation means is driven by generating a negative pressure within a range in which the liquid meniscus formed in each liquid discharge nozzle of the liquid discharge head is maintained. The meniscus in each liquid discharge nozzle is not destroyed, and bubbles can be prevented from being mixed from the nozzle.

According to a fifth aspect of the present invention, the valve device is provided on the liquid supply line so that the liquid can be supplied from the liquid tank to the liquid discharge head by opening the internal on-off valve due to the generation of negative pressure in the liquid discharge head. By providing the liquid, it is possible to supply the liquid from the liquid tank to the liquid discharge head when the liquid is discharged from the liquid discharge nozzle of the liquid discharge head. Further, it is possible to prevent the liquid from leaking from the liquid discharge nozzle due to a pressure difference when the liquid discharge head is waiting for operation or when the liquid tank is removed.

According to the sixth aspect of the present invention, the operation of the liquid discharge head is awaited by providing the valve mechanism for preventing the backflow of the liquid from the liquid circulation means side to the liquid discharge head side inside the liquid circulation means. It is possible to prevent the liquid from leaking from the liquid discharge nozzle due to the pressure difference when the inside or the liquid tank is removed.

Furthermore, according to the seventh aspect of the invention, the valve mechanism for preventing the backflow of the liquid from the liquid circulation means side to the liquid discharge head side is provided on the liquid reflux conduit, so that the liquid discharge head is on standby. Alternatively, it is possible to prevent liquid from leaking from the liquid discharge nozzle due to a pressure difference when the liquid tank is removed.

According to the liquid ejection apparatus of the eighth aspect , when the negative pressure is generated in the liquid ejection head and the liquid is circulated between the liquid ejection head and the liquid tank, the liquid supply port of the liquid ejection head In the state of being arranged at the center between both ends, the flow resistance of each liquid reflux pipe connected to each end or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe is changed. In the state where the liquid flow rate flowing out from the liquid discharge ports at both ends is the same, and the liquid supply port of the liquid discharge head is arranged so as to be deviated from the center between the both ends toward either end, the liquid According to the ratio of the arrangement distance of the liquid supply port from both ends of the discharge head, the flow resistance of each liquid reflux pipe connected to both ends or each liquid feed pump provided in the middle of each liquid reflux pipe Change the pump pressure from each liquid outlet at both ends By varying the proportion of liquid and out flow rates, it can be from the liquid outlet of the both end portions of the liquid ejecting head and the same exhaust time for flowing out the liquid. Therefore, without generating a positive pressure in the liquid ejection head and pushing the liquid out of the nozzle, it prevents liquid leakage from the nozzle during liquid circulation, and replaces the liquid in a short time to remove bubbles contained in the liquid can do. Accordingly, it is possible to prevent the periphery of the nozzle from being contaminated with the liquid and to prevent the liquid from being wasted. Further, there is no need for means corresponding to the liquid leaking from the nozzle, and the apparatus can be reduced in size and cost. Furthermore, the maintenance time for removing bubbles can be shortened. The liquid feed pump can circulate the liquid between the liquid discharge head and the liquid tank with a simple configuration.

According to the ninth aspect of the present invention, the liquid reflux conduit is arranged so as to face upward or horizontally between each liquid discharge port of the liquid ejection head and at least the liquid circulation means, so that the liquid reflux conduit is provided. It is possible to prevent the bubbles from staying in the pipe and prevent the liquid flow from being obstructed by the bubbles. Accordingly, it is possible to smoothly flow out the liquid from the liquid discharge ports at both ends of the liquid discharge head.

Furthermore, according to the invention which concerns on Claim 10 , the liquid tank can be replaced | exchanged according to consumption of a predetermined | prescribed liquid because it can be attached or detached with respect to a liquid discharge head. Therefore, the head cartridge can be used repeatedly.

Furthermore, according to the eleventh aspect of the invention, the liquid circulating means is driven by generating a negative pressure within a range in which the liquid meniscus formed in each liquid discharge nozzle of the liquid discharge head is maintained. The meniscus in each liquid discharge nozzle is not destroyed, and bubbles can be prevented from being mixed from the nozzle.

According to the twelfth aspect of the invention, there is provided a valve device capable of supplying liquid from the liquid tank to the liquid discharge head by opening an internal opening / closing valve on the liquid supply pipe line due to generation of negative pressure in the liquid discharge head. By providing the liquid, it is possible to supply the liquid from the liquid tank to the liquid discharge head when the liquid is discharged from the liquid discharge nozzle of the liquid discharge head. Further, it is possible to prevent the liquid from leaking from the liquid discharge nozzle due to a pressure difference when the liquid discharge head is waiting for operation or when the liquid tank is removed.

According to the thirteenth aspect of the present invention, the operation of the liquid discharge head is awaited by providing the valve mechanism for preventing the backflow of the liquid from the liquid circulation means side to the liquid discharge head side inside the liquid circulation means. It is possible to prevent the liquid from leaking from the liquid discharge nozzle due to the pressure difference when the inside or the liquid tank is removed.

According to the fourteenth aspect of the present invention, the operation of the liquid discharge head is awaited by providing the valve mechanism for preventing the reverse flow of the liquid from the liquid circulation means side to the liquid discharge head side on the liquid reflux conduit. Alternatively, it is possible to prevent liquid from leaking from the liquid discharge nozzle due to a pressure difference when the liquid tank is removed.

In addition, according to the liquid discharge apparatus of the fifteenth aspect , when the negative pressure is generated in the liquid discharge head and the liquid is circulated between the liquid discharge head and the liquid tank, the liquid supply port of the liquid discharge head In the state of being arranged at the center between both ends, the flow resistance of each liquid reflux pipe connected to each end or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe is changed. In the state where the liquid flow rate flowing out from the liquid discharge ports at both ends is the same, and the liquid supply port of the liquid discharge head is arranged so as to be deviated from the center between the both ends toward either end, the liquid According to the ratio of the arrangement distance of the liquid supply port from both ends of the discharge head, the flow resistance of each liquid reflux pipe connected to both ends or each liquid feed pump provided in the middle of each liquid reflux pipe Change the pump pressure from each liquid outlet at both ends By varying the proportion of liquid and out flow rates, it can be from the liquid outlet of the both end portions of the liquid ejecting head and the same exhaust time for flowing out the liquid. Therefore, without generating a positive pressure in the liquid ejection head and pushing the liquid out of the nozzle, it prevents liquid leakage from the nozzle during liquid circulation, and replaces the liquid in a short time to remove bubbles contained in the liquid can do. Accordingly, it is possible to prevent the periphery of the nozzle from being contaminated with the liquid and to prevent the liquid from being wasted. Further, there is no need for means corresponding to the liquid leaking from the nozzle, and the apparatus can be reduced in size and cost. Furthermore, the maintenance time for removing bubbles can be shortened. The liquid feed pump can circulate the liquid between the liquid discharge head and the liquid tank with a simple configuration.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of a head cartridge according to the present invention. The head cartridge 1 is a device that ejects ink droplets onto a recording paper that is a discharge target in an ink jet printer as an example of a liquid ejection device. The print head 2, an ink tank 3, and an ink supply pipe 4 And an ink reflux line 5, a liquid feed pump 6, and a valve device 7.

  The print head 2 serves as a liquid discharge head that discharges ink (predetermined liquid) onto recording paper. The print head 2 includes a common liquid chamber 9 that accommodates ink 8 to be discharged, and forms a nozzle surface. The thin plate-like nozzle member 10 is formed with a large number of ink discharge nozzles (liquid discharge nozzles) 27, 27,. Here, as an example, a full-line type print head 2 in which a nozzle member 10 is formed in a long length over the width of one side of a recording paper (for example, A4 size) is shown, and one place on the upper surface thereof, for example, at a substantially central portion. In addition to an ink supply port (liquid supply port) 11, left and right ink discharge ports (liquid discharge ports) 12a and 12b are provided at both ends.

  An ink tank 3 is disposed above the print head 2. The ink tank 3 serves as a liquid tank for storing the ink 8 supplied to the common liquid chamber 9 in the print head 2 and is formed in a box shape having a predetermined volume. The air communication hole 13 is formed in the top plate. The ink outlet port 14 is formed on the bottom plate, and the ink reflux port 15 is formed on the side surface. The ink tank 3 can be attached to and detached from the print head 2 by using the ink outlet 14 and the ink reflux port 15 as connection ports with an ink supply channel 4 or an ink reflux channel 5 described later. Yes.

  An ink supply line 4 is connected between the ink outlet 14 of the ink tank 3 and the ink supply port 11 of the print head 2. The ink supply line 4 is a liquid supply line for supplying ink 8 from the ink tank 3 to the print head 2 and is made of, for example, a resin tube such as polyethylene or a metal pipe such as stainless steel.

  An ink return line 5 is connected between the ink discharge ports 12 a and 12 b at both ends of the print head 2 and the ink return port 15 of the ink tank 3. The ink reflux line 5 is a liquid reflux line for returning the ink 8 from the print head 2 to the ink tank 3, and is made of, for example, a resin tube such as polyethylene or a metal pipe such as stainless steel. The first reflux line 5a connected to the discharge port 12a and the second return line 5b connected to the other ink discharge port 12b are connected to each other by a pipe joint 28 in the middle. Yes. In the embodiment of FIG. 1, since the ink tank 3 is disposed above the print head 2, the ink reflux lines 5, 5a, 5b are piped upward.

Further, a liquid feed pump 6 is provided in the middle of the ink reflux pipe 5. The liquid feed pump 6, even because of for circulating ink 8 between the print head 2 and the ink tank 3, for example a tube pump, made like a diaphragm pump or a piston pump, the appropriate one in accordance with the specification Just choose. The ink tank 3, the ink supply line 4, the print head 2, the ink reflux line 5, and the liquid feed pump 6 constitute an ink circulation system in which the ink 8 circulates in the direction indicated by the arrow in FIG. Yes.

  In this case, in the embodiment of FIG. 1, the ink discharge nozzle 27 of the nozzle member 10 has the ink tank 3 due to the height difference H between the liquid level of the ink 8 in the ink tank 3 and the nozzle member 10 of the print head 2. The water head pressure from is always applied. Therefore, the ink 8 accommodated in the common liquid chamber 9 of the print head 2 naturally flows out by the action of the water head pressure. Therefore, a valve device 7 is provided in the middle of the ink supply pipe 4 in order to cope with the outflow of the ink 8. The valve device 7 is closed in a normal state, and an internal on-off valve is opened by generation of a negative pressure in the print head 2 so that ink 8 can be supplied from the ink tank 3 to the print head 2.

  The configuration and operation of the valve device 7 will be described with reference to FIGS. FIG. 2 shows a state in which the on-off valve 16 in the valve device 7 is closed, and FIG. 3 shows a state in which the on-off valve 16 is opened. First, in FIG. 2, the print head 2 shown in FIG. 1 is not performing the ink ejection operation, and the pressure in the ink outflow path 17 connected to the ink supply pipe 4 toward the print head 2 is in a steady state. Thus, it becomes equal to the atmospheric pressure applied to the external communication port 18 formed on the bottom surface of the valve device 7. At this time, the diaphragm 20 stretched in the diaphragm chamber 19 is in a neutral state, and the opening / closing valve 16 connected to the upper end portion of the valve shaft 21 planted upward in the diaphragm 20 is interposed in the upper end surface thereof. The ink spring 22 is pushed downward by the biasing force of the coil spring 22 to close the flow path 17 a of the ink outflow path 17. As a result, the ink chamber 24 is shut off, and the ink 8 contained in the common liquid chamber 9 of the print head 2 does not naturally flow out even when there is a hydraulic head pressure due to the height difference H shown in FIG.

  Next, when the on-off valve 16 in FIG. 2 is closed, if the print head 2 shown in FIG. 1 is operated to discharge the ink 8 from the ink discharge nozzle 27, negative pressure is generated on the print head 2 side. The pressure in the ink outflow path 17 connected to the ink supply line 4 toward the print head 2 decreases. As a result, the pressure in the ink outflow passage 17 becomes lower than the atmospheric pressure applied to the external communication port 18, and the diaphragm 20 in the diaphragm chamber 19 is elastically upward as shown in FIG. Deform. Then, the valve shaft 21 planted in the diaphragm 20 rises against the urging force of the coil spring 22, and the opening / closing valve 16 at the upper end also rises to open the flow path 17 a of the ink outflow path 17. In FIG. 3, the ink inflow path 23 connected to the ink supply line 4 through which ink flows from the ink tank 3 and the ink outflow path 17 communicate with each other in the ink chamber 24. The ink 8 flows into the ink chamber 24 from the ink inflow path 23 by the suction force due to the pressure drop, and the ink 8 flows out of the ink chamber 24 into the ink outflow path 17. Thereby, the ink 8 can be supplied from the ink tank 3 shown in FIG. 1 to the print head 2.

  Next, when the ink 8 is supplied from the ink tank 3 to the print head 2 as described above and the pressure in the ink outflow path 17 shown in FIG. 3 returns to the steady state, the pressure in the ink outflow path 17 is The atmospheric pressure applied to the external communication port 18 becomes equal, and the pressure difference disappears. As shown in FIG. 2, the diaphragm 20 is elastically deformed downward by its restoring force and returns to the neutral state. Then, the valve shaft 21 is lowered by the urging force of the coil spring 22, and the on-off valve 16 at the upper end thereof is also lowered to close the flow path 17a of the ink outflow path 17. Thereby, the supply of the ink 8 from the ink tank 3 to the print head 2 is stopped.

  As described above, the ink supply operation described above is repeated every time the ink 8 is ejected from the ink ejection nozzle 27 of the print head 2 by the valve device 7 shown in FIG. 2 and 3, reference numeral 25 denotes an adjustment screw that adjusts the timing at which the on-off valve 16 opens and closes according to the negative pressure generated on the print head 2 side.

  Next, an ink circulation operation for removing bubbles contained in the ink 8 in the head cartridge 1 configured as described above will be described with reference to FIG. Such an ink circulation operation is performed when the ink jet printer in which the head cartridge 1 is set is started (when power is turned on), before printing starts, every time a predetermined number of sheets are printed on a recording sheet, or when a predetermined time elapses. To be executed.

  First, the liquid feed pump 6 provided in the middle of the ink reflux pipe 5 is driven. Then, the ink 8 in the ink reflux line 5 is sucked as indicated by an arrow A, and the ink 8 in the print head 2 is also sucked from the ink discharge ports 12a and 12b at both ends of the print head 2, and the liquid feed pump. It flows toward 6. Then, by driving the liquid feed pump 6, the ink 8 is sent from the ink reflux port 15 into the ink tank 3 as indicated by the arrow B. As a result, the ink 8 starts to flow from the ink discharge ports 12 a and 12 b of the print head 2 to the ink tank 3 through the ink reflux conduit 5.

  Next, the ink 8 flows out of the print head 2 in this way, whereby the pressure in the common liquid chamber 9 decreases. Then, as described with reference to FIG. 3, the on-off valve 16 in the valve device 7 is opened, and the ink 8 in the ink tank 3 flows toward the valve device 7 as indicated by an arrow C, and the ink supply pipe line 4 flows in the direction of the arrow D, and flows into the print head 2 from the center ink supply port 11 as shown by the arrow E. Thus, by driving the liquid feed pump 6, the ink 8 in the print head 2 is sucked as indicated by the arrow A and flows to the ink tank 3 as indicated by the arrow B, and the ink 8 in the ink tank 3 is indicated by the arrows C, D and E flow to the print head 2 and the ink 8 circulates between the print head 2 and the ink tank 3.

At this time, in the print head 2, the ink flows as indicated by arrows E ₁ and E ₂ from the central ink supply port 11 toward both ends, so that the bubbles present in the print head 2 are at both ends. The ink discharge ports 12a and 12b are driven into the ink recirculation pipe 5 to enter the ink tank 3 through the ink recirculation port 15, and are discharged into the air from the air communication holes 13 formed in the top plate. Thereby, bubbles contained in the ink 8 are removed.

  In this case, the ink circulation is a negative pressure method in which the ink 8 in the print head 2 is sucked by driving the liquid feed pump 6, and therefore, unlike the positive pressure method in which the ink is injected into the conventional print head, The ink 8 does not leak from the ink discharge nozzle 27 of the head 2. Therefore, it is possible to prevent the periphery of the nozzle from being stained with the ink 8 and to prevent the ink 8 from being wasted. Further, there is no need for means corresponding to the ink 8 leaking from the nozzle, and the apparatus can be reduced in size and cost.

  Here, in the negative pressure type ink circulation according to the present invention, if the suction pressure of the ink 8 by the drive of the liquid feed pump 6 is too strong, air is drawn from the ink discharge nozzles 27 of the print head 2 and bubbles are mixed. Conversely, it may cause the cause of non-ejection of ink. Therefore, the liquid feed pump 6 may be driven so as to generate a negative pressure within a range in which the ink meniscus formed in each ink discharge nozzle 27 of the print head 2 is maintained.

Generally, when a liquid is stretched in a nozzle having a certain nozzle area, the pressure P at which the meniscus in the nozzle is held is:
P = Liquid surface tension × Nozzle circumference × cos (contact angle of liquid to inner wall of nozzle) ÷ Nozzle area. Assuming that the surface tension of the ink 8 is γ, the contact angle of the ink 8 to the inner wall of the nozzle is θ, and the nozzle diameter is d, the pressure P at which the meniscus in the ink discharge nozzle 27 of the print head 2 is held is
P = 4γ cos θ / d
It becomes.

For example, as an example, if the nozzle diameter d is 17 μm, the surface tension γ of the ink 8 is 30 mN / m, and the contact angle θ is about 5 °, the pressure P at which the meniscus is held is about 740 mmH ₂ O. Become. In this case, in the meniscus in the ink discharge nozzle 27, if the negative pressure due to the driving of the liquid feed pump 6 is about 740 mmH ₂ O or less, the meniscus is not drawn and bubbles are mixed into the print head 2. Absent.

Even if the negative pressure due to the driving of the liquid feeding pump 6 exceeds about 740 mmH ₂ O, the pressure loss due to the flow path resistance of the ink path from the liquid feeding pump 6 to the ink discharge nozzle 27 of the print head 2 in FIG. Accordingly, if the meniscus holding pressure is not exceeded in the ink discharge nozzle 27, the meniscus is not broken and bubbles are not mixed into the print head 2. In this case, when the suction pressure of the liquid feed pump 6 is excessive and air may be drawn from the ink discharge nozzle 27, the ink between the liquid feed pump 6 and the print head 2 is shown in FIG. What is necessary is just to adjust so that the holding | maintenance pressure of a meniscus may not be exceeded in a nozzle by inserting the pressure adjustment part 26 which consists of a throttle device, for example on the reflux conduit 5.

In the present invention, when the ink 8 is circulated between the print head 2 and the ink tank 3 by generating a negative pressure in the print head 2 by driving the liquid feed pump 6, the print head 2. The discharge time for the ink 8 to flow out from the respective ink discharge ports 12a and 12b at the both ends is the same . If the discharge time for the ink 8 to flow out from the ink discharge ports 12a and 12b at both ends is the same , all of the ink 8 in the print head 2 is replaced in a short time to remove bubbles contained in the ink. This is because the maintenance time for removing bubbles can be shortened.

  In the embodiment shown in FIG. 1, one ink supply port 11 is provided at the center of the print head 2, and left and right ink discharge ports 12 a and 12 b are provided at both ends. The shape is symmetrical, but the first reflux conduit 5a connected to the left ink outlet 12a and the second reflux conduit 5b connected to the right ink outlet 12b are the left ink. Since the pipes 28 are connected by a pipe joint 28 at a position biased in the vicinity of the discharge port 12a and are combined into a single ink reflux pipe 5, the shape of the flow path from the left and right ink discharge ports 12a, 12b to the pipe joint 28 Is asymmetrical. Therefore, if the ink 8 is sucked by the liquid feed pump 6 provided downstream of the ink reflux pipe 5 from the pipe joint 28 as it is, the unit time flow rate of the ink 8 flowing out from the left and right ink discharge ports 12a and 12b becomes the same. In addition, the discharge time of the ink 8 flowing out from the ink discharge ports 12a and 12b is not the same.

In this case, the flow resistance of the first reflux pipe 5a from the left ink discharge port 12a to the pipe joint 28 and the flow of the second reflux pipe 5b from the right ink discharge port 12b to the pipe joint 28 are shown. What is necessary is just to design a pipe line so that road resistance may become the same. Here, in the laminar flow of the viscous fluid, the flow path resistance R of the cylindrical pipe line is expressed as follows: the fluid viscosity is μ, the pipe length is l, and the pipe radius is r.
R = 8 μl / πr ⁴
It is represented by Accordingly, the channel resistance R ₁ of the first return line 5a, so that the flow path resistance R ₂ of the second return line 5b are equal, the length l, and in line of each line What is necessary is just to design by adjusting the radius r. At this time, the bent portion of the pipe line and the place where the pipe diameter suddenly expands and contracts cause pressure loss due to the flow path resistance.

  In the case of the embodiment of FIG. 1, the length of the second reflux pipe 5b is made larger than the length of the first reflux pipe 5a up to the pipe joint 28. The radius r of the second reflux conduit 5b may be increased by the following formula.

By adopting such a pipeline design, even if the flow channel shape is asymmetrical, the flow channel resistance of each pipeline becomes equal, and the ink flowing out from the left and right ink discharge ports 12a and 12b. as the same flow rate of 8 units of time, the discharge time of the ink 8 which flows from the ink discharge ports 12a, 12b can be the same.

  FIG. 5 is an explanatory diagram showing the flow of ink in a state where ink 8 is ejected and printed using the head cartridge 1 of the present invention. At the time of printing, the valve device 7 described with reference to FIGS. 2 and 3 causes the internal opening / closing valve 16 to open due to the generation of negative pressure in the print head 2 due to the discharge of the ink 8, and the ink supply pipe 4 is used. Ink 8 is supplied from the ink tank 3 to the print head 2 as indicated by arrows C, D, and E, and discharge driving means such as heating elements and piezoelectric elements installed in the liquid chambers corresponding to the individual ink discharge nozzles 27 are provided. The ink is ejected from each ink ejection nozzle 27 as ink droplets 29, 29,... At this time, every time the ink droplet 29 is ejected from the ink ejection nozzle 27 of the print head 2, the opening / closing valve 16 of the valve device 7 is opened, and the ink 8 is supplied from the ink tank 3 as indicated by arrows C, D, E. Is repeated.

  In the printing operation shown in FIG. 5, in order to prevent the ink 8 from flowing back from the liquid feed pump 6 side to the print head 2 side, a valve mechanism, for example, a check valve, for preventing the ink from flowing back in the liquid feed pump 6 is provided. It has. In the case where the check valve is not provided in the liquid feed pump 6, a check valve 48 is provided on the ink reflux line 5 between the liquid feed pump 6 and the print head 2, as shown in FIG. Just do it. This backflow prevention valve mechanism may use an electromagnetic valve or the like, or may use a mechanical valve that passively opens and closes in accordance with the pressure of the ink 8 in the pipe line, such as a so-called duckbill valve. Good.

  The above-described backflow prevention valve mechanism is necessary even during printing standby or when the ink tank 3 is removed. During printing standby, the water head pressure is always applied to the ink discharge nozzles 27 of the print head 2 due to the height difference H between the ink tank 3 and the print head 2, and when the ink tank 3 is removed, Since the connection port to the ink tank 3 (part of the ink recirculation port 15) is opened to the atmosphere and atmospheric pressure is applied, the ink 8 leaks from the ink discharge nozzle 27 of the print head 2 unless the valve mechanism for preventing backflow is provided. Because it will come out.

  FIG. 7 is a cross-sectional view showing another embodiment of the head cartridge of the present invention. In this embodiment, the ink supply port 11 at the center of the print head 2 and the ink discharge ports 12a and 12b at both ends are the same as in FIG. 1, and the first reflux line 5a connected to the left ink discharge port 12a. Is connected to the first ink return port 15a of the ink tank 3, and the second return line 5b connected to the right ink discharge port 12b is connected to the second ink return port 15b of the ink tank 3 to A first liquid feed pump 6a and a second liquid feed pump 6b that are symmetrical and have the same pump pressure are provided in the middle of the respective reflux lines 5a and 5b.

In this case, as shown in FIG. 7, since the flow path shapes of the print head 2 and the first and second reflux pipes 5a and 5b are symmetrical, the first and second reflux pipes 5a. 5b, the length l of the pipe line, the radius r of the pipe line, the bending method, the materials used, the parts, etc. are made the same, so that the first liquid feed pump 6a side and the second liquid feed pump 6b side , The flow resistance of the ink 8 flowing out from the left and right ink discharge ports 12a and 12b is the same , and the discharge time of the ink 8 flowing out from each of the ink discharge ports 12a and 12b is the same. It becomes.

  FIG. 8 is a sectional view showing still another embodiment of the head cartridge of the present invention. This embodiment is different from the embodiment of FIG. 7 in that the pump pressure of the first liquid pump 6a and the pump pressure of the second liquid pump 6b are different, for example, from the first liquid pump 6a. Also, the pump pressure of the second liquid feeding pump 6b is increased. In this case, as shown in FIG. 7, the unit of the ink 8 flowing out from the right ink discharge port 12b when the flow path resistances of the pipes on the first liquid feed pump 6a side and the second liquid feed pump 6b side are equal. The flow of time will increase.

Therefore, in the case of FIG. 8, the flow path resistance of the pipe line on the second liquid feed pump 6b side where the pump pressure is high is increased, and the flow path resistance of the pipe line on the first liquid feed pump 6a side where the pump pressure is low. Should be made smaller. For example, the length l of the conduit of the second reflux conduit 5b may be increased or the radius r of the conduit may be decreased according to the above-described equation of the channel resistance R. In the example of FIG. 8, the case where the radius r of the pipe line of the second reflux pipe line 5b is reduced to increase the flow path resistance is shown. Thus, the left and right of the ink discharge port 12a, as the same flow rate per unit time of the ink 8 flowing out of the 12b, the discharge time of the ink 8 which flows from the ink discharge ports 12a, 12b are the same.

FIG. 9 is a cross-sectional view showing still another embodiment of the head cartridge of the present invention. In this embodiment, the ink supply port 11 of the print head 2 is arranged so as to be deviated from the center portion to either end side with respect to the embodiment of FIG. 7, and the ink supply from both ends of the print head 2 is performed. The ratio of the flow rate of the ink 8 flowing out from the ink discharge ports 12a and 12b at both ends is changed according to the ratio of the arrangement distance of the ports 11. In FIG. 9, it is assumed that the ink supply port 11 is disposed at a position where the distance from the left end of the print head 2 is D ₁ and the distance from the right end is D ₂ . When the ratio of the arrangement distance from both ends of the ink supply port 11 is, for example, D ₁ : D ₂ = 1: 2, the ink capacity on the left side of the ink supply port 11 in the print head 2 and the right ink The ratio to the capacity is 1: 2.

In this case, if the first liquid pump 6a and the second liquid pump 6b have the same pump pressure as shown in FIG. 7, the discharge time of the ink 8 flowing out from the right ink discharge port 12b is used. Will become longer. Therefore, in the case of FIG. 9, the pump pressure of the second liquid feed pump 6 b with respect to the first liquid feed pump 6 a according to the ratio D ₁ : D ₂ of the arrangement distance from both ends of the ink supply port 11. For example, the value may be doubled. At this time, the flow rate of the ink 8 flowing out from the left ink discharge port 12a becomes 1, whereas the flow rate of the ink 8 flowing out from the right ink discharge port 12b becomes 2, and as a result, the left and right ink discharge ports 12a and 12b The discharge time of the outflowing ink 8 is the same .

  7 to 9, the check valves 48a and 48b are provided on the first and second reflux pipes 5a and 5b. However, the first and second liquid feed pumps are used. If the 6a and 6b have a check valve function, the check valves 48a and 48b can be omitted. Also in the embodiment of FIGS. 7 to 9, the pressure adjusting unit 26 may be inserted on each of the reflux lines 5 a and 5 b as shown in FIG. 4.

  Furthermore, in the above description, the ink tank 3 is disposed above the print head 2, and all the ink return lines 5 between the ink discharge ports 12 a, 12 b of the print head 2 and the ink tank 3 are provided. However, the present invention is not limited to this, and the pipes are arranged so as to be upward or horizontal from each ink discharge port 12a, 12b of the print head 2 to at least the liquid feed pump 6. Just do it. This is because suction is performed at a relatively weak pressure such as generating a negative pressure within a range in which the meniscus of ink formed in each ink discharge nozzle 27 of the print head 2 is maintained on the suction side of the liquid feed pump 6. This is because, in particular, bubbles do not stay in the ink reflux line 5 during this period, and the flow of ink is not hindered.

  In the above description, the print head 2 is a full-line type in which the nozzle member 10 is formed to be long over the width of one side of the recording paper. However, the present invention is not limited to this, and the nozzle member 10 The present invention is also applicable to a serial type that is formed shorter than the width of one side of the recording paper and reciprocates in the width direction of the recording paper. In FIG. 1, when the ink tank 3 is disposed below the print head 2, the valve device 7 may be omitted.

  Next, an embodiment of an ink jet printer as an example of a liquid ejection apparatus according to the present invention will be described with reference to FIGS. This ink jet printer 30 forms an image by ejecting ink droplets onto a predetermined position of a recording paper, which is an ejection target, with the head cartridge 1 described above. The printer main body 31, the head cartridge 1, the recording And a paper tray 32.

  The printer main body 31 houses a recording paper transport mechanism and an electric circuit for proper printing on the recording paper as an apparatus main body, and houses the head cartridge 1 on the upper surface. A storage portion 33 is opened, and an upper lid 34 for opening and closing the storage portion 33 is provided at an upper end portion thereof. In addition, a tray insertion opening 35 for mounting a recording paper tray 32 described later is provided at the lower front portion of the printer main body 31. The tray insertion port 35 also serves as a recording paper discharge port. Further, a display panel 31 a for displaying an overall operation state of the ink jet printer 30 is provided on the upper front surface of the printer main body 31.

  In the storage portion 33 of the printer main body 31, the head cartridge 1 configured as shown in FIGS. 1 to 9 is stored as indicated by an arrow Z and is held in a detachable state. The head cartridge 1 includes a print head 2 that discharges ink from a plurality of ink discharge nozzles 27 formed on the nozzle surface, and, for example, yellow Y, magenta M, cyan C, and black supplied to a liquid chamber in the print head 2. And four ink tanks K of four colors. A head cap 41 is attached to the lower surface side of the print head 2. Here, as an example, a full-line type print head 2 in which a nozzle member is formed in a long length over the width of one side of recording paper (for example, A4 size) is shown.

  A recording paper tray 32 is detachably attached to the tray insertion port 35 of the printer main body 31. The recording paper tray 32 stores recording paper in an overlapping manner, and a recording paper discharge receiving portion 32 a for discharging the recording paper from the printer main body 31 is provided on the upper surface of the recording paper tray 32.

  11A and 11B are cross-sectional views showing a specific example of the internal structure of the printer main body 31. FIG. 11A shows a printing stop state, and FIG. 11B shows a printing operation state. As shown in FIG. 11A, the printer main body 31 includes a roller at a lower portion of the printer main body 31 and in an upper portion corresponding to the side end portion in the insertion direction of the recording paper tray 32. A paper feeding means 36 is provided so that recording paper 37 can be supplied from the recording paper tray 32 at any time. In addition, a separating unit 38 is provided in the supply direction of the recording paper 37 so that the recording paper 37 stored in an overlapping manner can be separated and fed one by one. Further, a reversing roller 39 that reverses the conveyance direction of the recording paper 37 is provided above the printer main body 31 in the conveyance direction of the recording paper 37 separated by the separation means 38.

  A belt conveying means 40 is provided at the tip of the recording sheet 37 reversed by the reversing roller 39 in the conveying direction. As shown in FIG. The end 40a is lowered in the direction of arrow F, and a large gap is formed between the lower surface of the head cartridge 1. On the other hand, in the printing operation state shown in FIG. 11B, the end 40a is raised in the direction of arrow G to be in a horizontal state, and a recording paper path having a predetermined small gap is formed between the lower surface of the head cartridge 1. To be formed.

  Further, in the printing stop state, as shown in FIG. 11A, the lower surface of the head cartridge 1 is closed by the head cap 41 to prevent the ink of the ink discharge nozzle 27 from being dried and clogged. . Further, the head cap 41 is provided with a cleaning unit 42, and the ink discharge nozzle 27 is moved along with the operation of the head cap 41 retracting to a predetermined position (see FIG. 11B) before starting the printing operation. Is supposed to be cleaned.

  Next, the operation of the ink jet printer 30 configured as described above will be described. First, the upper lid 34 of the upper surface of the printer main body 31 shown in FIG. Further, the recording paper tray 32 is inserted into a tray insertion opening 35 provided at the lower front of the printer main body 31. At this time, as shown in FIG. 11A, the end 40a of the belt conveying means 40 is lowered in the arrow F direction inside the printer main body 31, and the lower surface of the head cartridge 1 is closed by the head cap 41. The print is stopped.

  Next, when a print start control signal is input, the head cap 41 moves as shown by an arrow H in FIG. At this time, as the head cap 41 is retracted, the cleaning means 42 slides on the surface of the nozzle member 10 (see FIG. 1) of the print head 2 to clean the ink discharge nozzles 27.

  When the head cap 41 is retracted to a predetermined position, the end 40a of the belt conveying means 40 rises in the direction of arrow G in FIG. Then, a recording paper path having a predetermined small gap is formed between the head cartridge 1 and the head cartridge 1 (see FIG. 11B).

  Then, in the printing operation state shown in FIG. 11B, the paper feeding unit 36 is driven, and the recording paper 37 stored in the recording paper tray 32 is supplied in the direction of arrow I. At this time, the recording paper 37 is separated one by one by the separating means 38 and is fed as needed in the direction of arrow J.

  The fed recording paper 37 is conveyed to the belt conveying means 40 with its conveying direction reversed by the reverse roller 39. Then, the recording paper 37 is carried to the lower part of the head cartridge 1 by the belt conveying means 40.

  Further, when the recording paper 37 reaches the lower part of the head cartridge 1, a print signal is input, and the heating element of the print head 2 is driven in accordance with the print signal. For example, ink droplets 29 (see FIG. 5) are ejected from a row of ink ejection nozzles 27 corresponding to four colors of ink onto the recording paper 37 fed at a constant speed, and a color print image is printed on the recording paper 37. Is formed.

  When all the printing on the recording paper 37 is completed in this way, the recording paper 37 is conveyed in the direction of the arrow K from the lower part of the head cartridge 1 as shown in FIG. The paper is discharged from the tray insertion opening 35 (see FIG. 10) to the paper discharge receiving portion 32a of the recording paper tray 32. Then, as shown in FIG. 11A, the end 40a of the belt conveying means 40 is lowered in the direction of arrow F, the head cap 41 closes the lower surface of the head cartridge 1 and returns to the printing stop state, and the inkjet printer 30 Operation stops.

  In the description of FIGS. 10 to 11, the ink jet printer 30 is provided with the head cartridge 1 detachably attached to the printer main body 31. However, the present invention is not limited to this, and the printer main body without using the head cartridge 1. The print head 2 may be provided in the portion 31.

  In the above description, an example applied to an ink jet printer has been described. However, the present invention is not limited to this, and any device that discharges a predetermined liquid as liquid droplets from a liquid discharge nozzle may be used. Good. For example, the present invention can also be applied to an image forming apparatus such as a facsimile apparatus or a copying machine whose recording system is an inkjet system.

  Furthermore, the liquid ejected from the liquid ejection nozzle is not limited to ink, and other liquids may be ejected if the liquid ejection head (2) is driven to eject a predetermined liquid to form a dot row or dot. It can also be applied to devices. For example, a liquid ejecting apparatus for ejecting a DNA-containing solution onto a pallet in DNA identification or a liquid ejecting apparatus for ejecting a liquid containing conductive particles for forming a wiring pattern of a printed wiring board Can be applied.

It is sectional drawing which shows embodiment of the head cartridge by this invention. It is sectional drawing explaining the internal structure and operation | movement of the valve apparatus shown in FIG. 1, and is a figure which shows the state which the internal on-off valve closed. It is sectional drawing which similarly illustrates the internal structure and operation | movement of a valve apparatus, and is a figure which shows the state which the internal on-off valve opened. It is sectional drawing which shows 2nd embodiment of the head cartridge of this invention. It is explanatory drawing which shows the flow of the ink in the state which discharges and prints ink using the head cartridge of this invention. It is sectional drawing which shows 3rd embodiment of the head cartridge of this invention. It is sectional drawing which shows 4th embodiment of the head cartridge of this invention. It is sectional drawing which shows 5th embodiment of the head cartridge of this invention. It is sectional drawing which shows 6th embodiment of the head cartridge of this invention. 1 is a perspective view showing an embodiment of an ink jet printer as an example of a liquid ejection apparatus according to the present invention. FIG. 11 is a cross-sectional view illustrating an internal configuration of the ink jet printer illustrated in FIG. 10, in which (a) illustrates a printing stop state and (b) illustrates a printing operation state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Head cartridge 2 ... Print head 3 ... Ink tank 4 ... Ink supply line 5, 5a, 5b ... Ink return line 6, 6a, 6b ... Liquid feed pump 7 ... Valve apparatus 8 ... Ink 9 ... Common liquid chamber 10 ... Nozzle member 11 ... Ink supply port 12a, 12b ... Ink discharge port 13 ... Atmospheric communication hole 14 ... Ink outlet 15, 15a, 15b ... Ink return port 26 ... Pressure adjusting unit 27 ... Ink ejection nozzle 30 ... Inkjet printer 31 ... Printer main body 32 ... Recording paper tray 48, 48a, 48b ... Check valve

Claims (15)

Liquid that discharges a predetermined liquid from a plurality of liquid discharge nozzles formed on the nozzle surface, provided with a liquid supply port for receiving liquid from a liquid tank that stores the predetermined liquid at one location and liquid discharge ports at both ends. A discharge head;
A liquid supply line for supplying liquid from the liquid tank to the liquid supply port of the liquid discharge head;
A liquid reflux line for returning liquid from the liquid discharge port of the liquid discharge head to the liquid tank;
A liquid feed pump disposed on the liquid reflux line for circulating the liquid between the liquid discharge head and the liquid tank;
When the liquid feed pump is driven to generate a negative pressure in the liquid discharge head and circulate the liquid between the liquid discharge head and the liquid tank, the liquid supply port of the liquid discharge head is connected to both ends thereof. In the state of being arranged in the central part between the two ends, the flow resistance of each liquid reflux pipe connected to each of both ends or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe is changed. In the state in which the liquid flow rate flowing out from each liquid discharge port is the same, and the liquid supply port of the liquid discharge head is arranged so as to be deviated from the central portion between the two end portions to either end side, the liquid discharge head The flow resistance of each liquid reflux pipe connected to both ends according to the ratio of the arrangement distance of the liquid supply port from the both ends of each liquid pump or the pump of each liquid feed pump provided in the middle of each liquid reflux pipe Discharge each liquid at both ends by changing pressure Varying the proportion of liquid flow flowing out of the head cartridge, characterized in that the same discharge time for discharging the liquid from the liquid outlet of the both end portions of the liquid discharge head. 2. The head cartridge according to claim 1, wherein the liquid reflux pipe is piped upward or horizontally between each liquid discharge port of the liquid discharge head and at least the liquid feed pump .   2. The head cartridge according to claim 1, wherein the liquid tank is detachable from the liquid discharge head. 2. The head cartridge according to claim 1, wherein the liquid feed pump is driven to generate a negative pressure within a range in which a liquid meniscus formed in each liquid discharge nozzle of the liquid discharge head is maintained.   A valve device is provided on the liquid supply line so that a liquid can be supplied from the liquid tank to the liquid discharge head by opening an internal on-off valve when negative pressure is generated in the liquid discharge head. The head cartridge according to claim 1. The inside of the liquid feed pump, a head cartridge according to claim 1, wherein the from the liquid feed pump side provided with a valve mechanism for preventing backflow of the liquid to the liquid ejecting head side. 2. The head cartridge according to claim 1, wherein a valve mechanism for preventing a reverse flow of liquid from the liquid feed pump side to the liquid discharge head side is provided on the liquid reflux conduit. A liquid ejection device that holds a head cartridge in a detachable state on the apparatus main body and ejects a predetermined liquid from each liquid ejection nozzle formed on the liquid ejection head of the head cartridge to form a dot or a dot row. And
The head cartridge is provided with a liquid supply port for receiving liquid from a liquid tank storing a predetermined liquid at one location and with liquid discharge ports at both ends, and a plurality of liquid discharge nozzles formed on the nozzle surface. A liquid discharge head for discharging liquid, a liquid supply line for supplying liquid from the liquid tank to the liquid supply port of the liquid discharge head, and a liquid reflux pipe for returning the liquid from the liquid discharge port of the liquid discharge head to the liquid tank And a liquid feed pump disposed on the liquid reflux pipe for circulating the liquid between the liquid discharge head and the liquid tank, and is driven into the liquid discharge head by driving the liquid feed pump. when circulating the liquid between the negative pressure is generated in the liquid discharge head and the liquid tank, like placing the liquid supply port of the liquid discharge head in the central portion between both end portions Then, the flow resistance of each liquid reflux pipe connected to each end part or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe is changed to flow out from each liquid discharge port at both ends. In a state where the liquid flow rate is the same and the liquid supply port of the liquid discharge head is arranged so as to be deviated from the central portion between the two end portions to one of the end portions, The flow resistance of each liquid reflux pipe connected to both ends according to the ratio of the arrangement distance of each of the liquid reflux pipes or the pump pressure of each liquid feed pump provided respectively in the middle of each liquid reflux pipe is changed. A liquid discharge apparatus characterized in that the ratio of the liquid flow rate flowing out from the liquid discharge port is changed, and the discharge time for flowing out the liquid from each liquid discharge port at both ends of the liquid discharge head is the same . 9. The liquid discharge apparatus according to claim 8 , wherein the liquid reflux pipe is piped upward or horizontally between the liquid discharge port of the liquid discharge head and at least the liquid feed pump . 9. The liquid ejection apparatus according to claim 8 , wherein the liquid tank is detachable from the liquid ejection head. 9. The liquid discharge apparatus according to claim 8 , wherein the liquid feed pump is driven to generate a negative pressure within a range in which a liquid meniscus formed in each liquid discharge nozzle of the liquid discharge head is maintained. . A valve device is provided on the liquid supply line so that a liquid can be supplied from the liquid tank to the liquid discharge head by opening an internal on-off valve when negative pressure is generated in the liquid discharge head. The liquid ejection apparatus according to claim 8 . The inside of the liquid feed pump, the liquid discharge apparatus according to claim 8, wherein the from the liquid feed pump side provided with a valve mechanism for preventing backflow of the liquid to the liquid ejecting head side. 9. The liquid ejection apparatus according to claim 8, wherein a valve mechanism for preventing a back flow of liquid from the liquid feed pump side to the liquid ejection head side is provided on the liquid reflux conduit. Liquid that discharges a predetermined liquid from a plurality of liquid discharge nozzles formed on the nozzle surface, provided with a liquid supply port for receiving liquid from a liquid tank that stores the predetermined liquid at one location and liquid discharge ports at both ends. A discharge head;
A liquid supply line for supplying liquid from the liquid tank to the liquid supply port of the liquid discharge head;
A liquid reflux line for returning liquid from the liquid discharge port of the liquid discharge head to the liquid tank;
A liquid feed pump disposed on the liquid reflux line for circulating the liquid between the liquid discharge head and the liquid tank;
When the liquid feed pump is driven to generate a negative pressure in the liquid discharge head and circulate the liquid between the liquid discharge head and the liquid tank, the liquid supply port of the liquid discharge head is connected to both ends thereof. In the state of being arranged in the central part between the two ends, the flow resistance of each liquid reflux pipe connected to each of both ends or the pump pressure of each liquid feed pump provided in the middle of each liquid reflux pipe is changed. In the state in which the liquid flow rate flowing out from each liquid discharge port is the same, and the liquid supply port of the liquid discharge head is arranged so as to be deviated from the central portion between the two end portions to either end side, the liquid discharge head The flow resistance of each liquid reflux pipe connected to both ends according to the ratio of the arrangement distance of the liquid supply port from the both ends of each liquid pump or the pump of each liquid feed pump provided in the middle of each liquid reflux pipe Discharge each liquid at both ends by changing pressure Varying the proportion of liquid flow flowing out of the liquid ejecting apparatus characterized by the same exhaust time for flowing out the liquid from the liquid outlet of the both end portions of the liquid discharge head.

Images