JP2012000846A - Inkjet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To feed ink bi-directionally between an ink tank and a recording head only with one unidirectional pump for feeding unidirectionally.SOLUTION: An apparatus includes: a unidirectional pump 7 provided midway of an ink supply tube 4 for feeding unidirectionally; a third three-way valve 8A provided on an upstream side of the unidirectional pump; a second three-way valve 8B provided on the downstream side; a first communication passage 9A for making the first three-way valve and a site on a recording head side than the second three-way valve communicate each other; and a second communication passage 9B for making the second three-way valve and a site on an ink tank 6 side than the first three-way valve communicate each other. By driving the unidirectional pump and switching the passages of the first three-way valve and the second three-way valve, the feeding direction of ink of an outward passage for feeding ink in the ink tank toward the recording head without passing through the first communication passage and the second communication passage and a return path for returning ink from the recording head side toward the ink tank after passing through the first communication passage and the second communication passage is controlled.

Description

  The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus in which bidirectional liquid feeding of ink between an ink tank and a recording head is performed by only one unidirectional pump for feeding liquid in one direction. .

  An ink jet recording apparatus that forms an image by ejecting ink droplets from a nozzle of a recording head toward a recording medium is configured such that an ink is supplied toward the recording head via an ink supply pipe by driving a pump from an ink tank that stores ink. The liquid is being delivered.

  In addition to feeding a predetermined amount of ink from the ink tank to the recording head during image formation, the ink feeding between the recording head and the ink tank may be directed from the recording head to the ink tank in some situations. You may need to return ink. For example, an intermediate tank for storing ink is provided between the ink tank and the recording head, and a predetermined amount of ink is fed back from the intermediate tank to the ink tank side to maintain a predetermined negative pressure in the intermediate tank. Inkjet recording apparatuses that control the back pressure applied to the recording head are known, and in this case, ink is fed between the ink tank and the recording head in both forward and reverse directions. Need to be able to. Therefore, it is preferable that the pump for feeding the ink is capable of both forward feeding from the ink tank side to the recording head and reverse feeding from the recording head side to the ink tank. Tube pumps, plunger pumps, and the like are known as pumps that can forward and reverse ink as a single unit.

  For example, Patent Document 1 provides a circulation forward path and a circulation return path between the recording head and the reservoir tank, and a relief valve that opens when a predetermined pressure is reached between the circulation forward path and the circulation return path. A liquid droplet ejection device that provides a bypass path, sends liquid from the reservoir tank to the recording head by a tube pump provided on the circulation outward path, and returns excess ink from the recording head to the reservoir tank via the circulation return path. It is disclosed. It also discloses that the tube pump is rotated in the reverse direction to feed the circulation path in the reverse direction.

  In Patent Document 2, an ink bypass circuit is formed in an ink supply pipe between an ink container and a recording head via a valve mechanism including a three-way valve, a tube pump is provided on the ink bypass circuit, By switching the mechanism and switching the forward or reverse rotation of the tube pump, the liquid supply flow path from the ink container is different depending on whether the recording head is filled with ink or the ink supply pipe is filled with ink. A droplet jet recording apparatus is disclosed which is adapted to switch to the above.

JP 2007-33281 A JP 2004-284027 A

  Inkjet recording devices are now used not only for general image recording, but also for various industrial fields such as color filter manufacturing and semiconductor manufacturing. Along with this, the types of ink used are diverse. Across. For this reason, the ink jet recording apparatus needs to cope with various types of ink. Specific examples include cationic UV ink and radical UV ink. For this reason, in particular, ink resistance is required for the ink supply path that is in direct contact with the ink.

  However, the conventional tube pump is not suitable for applications requiring ink resistance such as using a multi-layer tube because a flexible resin tube is used in the ink supply path. In addition, due to the characteristics of the plunger pump, a shear load is generated in the ink when the liquid is fed. For example, in the case of a high viscosity ink such as radical UV ink, there is a problem that the ink gels, and it is also suitable for use. Absent.

  There exists a diaphragm pump as a pump which can eliminate such a problem. Compared to other pumps, diaphragm pumps can use expensive perfluoroelastomers with excellent ink resistance for the liquid transfer film, do not generate a shear load on the ink during liquid transfer, and can easily manage the liquid supply volume. It has certain advantages.

  However, since the diaphragm pump is a unidirectional pump that sends liquid in only one direction, it has a drawback that it can only send liquid in one direction. For this reason, in order to feed the ink supply pipe in both the forward and reverse directions, two diaphragm pumps for forward and reverse feeding must be arranged in parallel in the ink supply pipe. In other words, the size of the apparatus is increased, and the cost is very disadvantageous.

  Moreover, since separate pumps are driven for progressive feeding and reverse feeding, even if the same type of pump is used, even if slight variations occur between the pumps, the reverse of the forward feeding will occur. There has been a problem that an error occurs in the amount of liquid to be fed at the time of feeding, and the management of the liquid feeding amount becomes very complicated.

  Such an error in the liquid feeding amount becomes a problem particularly when the back pressure of the recording head is controlled by the intermediate tank. In other words, the back pressure control of the print head is performed so that the ink meniscus in the nozzle of the print head is at an optimum position for ink ejection. Therefore, even a slight error in the amount of liquid delivered by driving the pump causes a serious problem such as breakage of the ink meniscus, and there is a problem that hinders image forming work.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus that can perform bi-directional liquid feeding of ink between an ink tank and a recording head with only one unidirectional pump for feeding liquid in one direction. There is to do.

  Another object of the present invention is to control the back pressure of the print head by performing bi-directional liquid feed of ink between the ink tank and the print head with only one unidirectional pump that feeds in one direction. It is an object of the present invention to provide an ink jet recording apparatus capable of accurately performing the above.

  The other subject of this invention becomes clear by the following description.

  The above problems are solved by the following inventions.

According to a first aspect of the present invention, an ink tank that stores ink, a recording head that discharges ink droplets from nozzles to form an image on a recording medium, and the ink in the ink tank through the ink supply pipe are recorded in the recording medium. In an ink jet recording apparatus comprising an ink supply means for supplying toward the head,
The ink supply means
One unidirectional pump for feeding in one direction provided in the middle of the ink supply pipe;
A first three-way valve provided upstream of the unidirectional pump in the ink supply pipe;
A second three-way valve provided downstream of the unidirectional pump in the ink supply pipe;
A first communication path that communicates between the first three-way valve and a portion of the ink supply pipe that is closer to the recording head than the second three-way valve;
A second communication path that communicates between the second three-way valve and a portion of the ink supply pipe that is closer to the ink tank than the first three-way valve;
By driving the unidirectional pump and switching the flow paths of the first three-way valve and the second three-way valve, ink in the ink tank is supplied to the first communication path and the second communication path. The forward path for sending liquid toward the recording head without passing through the path, and the ink from the recording head side return to the ink tank through the first communication path and the second communication path. An ink jet recording apparatus comprising: control means for controlling the ink feeding direction in any of the return path.

According to a second aspect of the present invention, the ink supplied from the ink tank toward the recording head is temporarily stored between the connection portion of the ink supply pipe connected to the first communication path and the recording head. Have an intermediate tank,
The control means switches the flow path of the first three-way valve and the second three-way valve to the return path, and reversely feeds the ink in the intermediate tank to the ink tank by driving the unidirectional pump. 2. The ink jet recording apparatus according to claim 1, further comprising back pressure control means for controlling a back pressure applied to the recording head by adjusting a pressure inside the intermediate tank.

  According to a third aspect of the present invention, a connection portion between the connection portion of the ink supply pipe with the first communication path and the second three-way valve, and a connection portion of the ink supply pipe with the second communication passage. Between the first three-way valve and the unidirectional pump, between the second three-way valve and the unidirectional pump, and on the first communication path. 3. An ink jet recording apparatus according to claim 1, wherein a filter is provided on any of the second communication paths.

  A fourth aspect of the present invention is the ink jet recording apparatus according to the first, second or third aspect, wherein the unidirectional pump is a diaphragm pump.

  According to the present invention, there is provided an ink jet recording apparatus which can perform bidirectional ink feeding between an ink tank and a recording head with only one unidirectional pump for feeding in one direction. Can do.

  In addition, according to the present invention, the back pressure control of the print head can be accurately performed by performing bi-directional liquid feed of ink between the ink tank and the print head with only one unidirectional pump that feeds in one direction. An ink jet recording apparatus that can perform well can be provided.

1 is a schematic configuration diagram showing an example of an ink jet recording apparatus according to the present invention. 1 is a block diagram showing a control configuration of an ink jet recording apparatus according to the present invention. (A) is a figure which shows the mode of the ink feeding at the time of the progressive feeding of the inkjet recording device which concerns on this invention, (b) is a figure which shows the mode of the ink feeding at the time of reverse feeding The figure which shows the aspect of the arrangement position of a filter The figure which shows the aspect of the arrangement position of a filter The figure which shows the aspect of the arrangement position of a filter The figure which shows the aspect of the arrangement position of a filter The figure which shows the aspect of the arrangement position of a filter

  An ink jet recording apparatus according to the present invention includes an ink tank that stores ink, a recording head that ejects ink droplets from nozzles to form an image on a recording medium, and a recording head that supplies ink in the ink tank via an ink supply pipe. And an ink supply means for supplying the ink toward the head. The ink supply pipe in the present invention is a pipe that can supply ink from the ink tank toward the recording head.

  The ink supply means includes one unidirectional pump that feeds liquid only in one direction provided in the middle of the ink supply pipe. The unidirectional pump feeds ink only in one direction in the ink supply pipe by driving, and a diaphragm pump is preferably used from the viewpoint of excellent ink resistance.

  The ink supply pipe is provided with a total of two three-way valves, one on each of the upstream side of the unidirectional pump (the suction side of the unidirectional pump) and the downstream side (the discharge side of the unidirectional pump). In the present invention, the upstream side is the first three-way valve and the downstream side is the second three-way valve, and these also constitute the ink supply means in the present invention. Each three-way valve is connected to three flow paths, and selectively switches the outflow destination of ink flowing from one of the flow paths to one of the other two flow paths.

  A first communication path is provided between the first three-way valve in the ink supply pipe and a portion closer to the recording head than a portion where the second three-way valve is provided. . As a result, the first three-way valve is connected to three flow paths: a flow path connected to the unidirectional pump, a flow path connected to the ink tank, and the first communication path. In addition, a second communication path is provided between the second three-way valve and a portion closer to the ink tank than the portion of the ink supply pipe where the first three-way valve is provided. Yes. As a result, the second three-way valve is connected to three flow paths: a flow path connected to the unidirectional pump, a flow path connected to the recording head side, and a second communication path. These first communication path and second communication path also constitute the ink supply means in the present invention.

  The driving of these unidirectional pumps and the switching operation of the first and second three-way valves are controlled by the control means. The control means for controlling the driving of the unidirectional pump and the switching operation of each of the first and second three-way valves constitutes an ink supply means in the present invention, and drives the unidirectional pump as well as the first and first By selectively switching the flow path of each of the three-way valves 2, the ink in the ink tank does not pass through the first communication path and the second communication path, and passes through the unidirectional pump to the recording head. Either the forward path for sending the liquid toward the head or the return path for passing the ink from the recording head side through the first communication path and the second communication path and returning the ink toward the ink tank via the unidirectional pump To control the ink feed direction.

  That is, when the ink is sent in the forward path, the control means switches the first three-way valve so that the flow path connected to the ink tank and the flow path connected to the unidirectional pump communicate with each other. The three-way valve is switched so that the flow path connected to the unidirectional pump communicates with the flow path connected to the recording head. As a result, the ink passes through the ink supply pipe from the inside of the ink tank, flows into the unidirectional pump by the first three-way valve, and is driven from the second three-way valve toward the recording head by driving the unidirectional pump. And sent to the recording head. At this time, the ink does not pass through the first communication path and the second communication path.

  In addition, when the ink is sent through the return path, the control unit switches the first three-way valve so that the first communication path and the flow path connected to the unidirectional pump communicate with each other. The three-way valve is switched so that the flow path connected to the unidirectional pump communicates with the flow path connected to the second communication path. As a result, the ink passes through the ink supply pipe from the recording head side, flows into the unidirectional pump by the first three-way valve, and is driven from the second three-way valve to the recording head side by driving the unidirectional pump. And sent to the recording head.

  Therefore, according to the present invention, with only one unidirectional pump that feeds liquid in one direction, bidirectional ink feeding between the forward path from the ink tank toward the recording head and the backward path from the recording head to the ink tank is performed. It can be performed. Since only one pump is required, the apparatus does not increase in size and does not cause a significant increase in cost. In addition, since a single pump is used for both forward and backward liquid feeding, there is no error in the amount of liquid delivered between the forward and backward paths, and liquid feeding can be performed with high accuracy.

  In particular, according to the present invention, the connection portion of the ink supply pipe with the first communication path, that is, the portion of the ink supply pipe where the recording head side and the first communication path are connected with respect to the second three-way valve is recorded. An intermediate tank that temporarily stores ink supplied from the ink tank toward the recording head is provided between the head and the control unit, and the control unit returns the flow path of the first three-way valve and the second three-way valve. The back pressure applied to the recording head is controlled by adjusting the internal pressure of the intermediate tank by reversely sending the ink in the intermediate tank to the ink tank by driving a unidirectional pump that sends liquid in one direction. It is preferable to constitute a back pressure control means.

  Even in the case of the ink jet recording apparatus in which the back pressure of the recording head is controlled by the intermediate tank as described above, according to the present invention, there is no occurrence of an error in the liquid feeding amount between the forward path and the backward path. Since the liquid feeding amount can be managed with high accuracy, the pressure in the intermediate tank can be controlled with high accuracy, and the ink meniscus position in the nozzles of the recording head can be easily set to the specified position.

  An ink jet recording apparatus may be provided with a filter on an ink supply pipe in order to remove dust or the like in ink sent from an ink tank to a recording head. In the present invention, when such a filter is provided, a connection portion between the connection portion of the ink supply pipe and the first communication path and the second three-way valve, and a connection portion of the ink supply pipe and the second communication passage are provided. Between the first three-way valve, between the first three-way valve and the unidirectional pump, between the second three-way valve and the unidirectional pump, on the first communication path, or on the second communication It is preferable to intervene anywhere on the road.

  According to this, the ink can always pass through the filter from one direction.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an example of an ink jet recording apparatus according to the present invention, and FIG. 2 is a block diagram showing a control configuration.

  The ink jet recording apparatus includes a plurality of recording heads 1A to 1F and a common flow path member 2 that supplies ink in common to the recording heads 1A to 1F.

  The common flow path member 2 is connected to the inside of the ink tank 6 by the ink supply pipe 4 constituted by the pipe portions 41 to 47. An intermediate tank 3 that temporarily stores ink is interposed between the ink tank 6 and the recording heads 1 </ b> A to 1 </ b> F in the middle of the ink supply pipe 4, and ink that connects the common flow path member 2 and the intermediate tank 3. The ink in the intermediate tank 3 can be supplied to the common flow path member 2 through the opening / closing valve V1 formed of an electromagnetic valve by the piping portion 47 of the supply pipe 4. SP2 in the ink tank 6 is an ink non-detection sensor for detecting the absence of ink provided in the ink tank 6.

  The intermediate tank 3 is connected to the common flow path member 2 by a pipe portion 47 that constitutes the ink supply pipe 4, and has a predetermined amount with respect to each of the recording heads 1 </ b> A to 1 </ b> F by the liquid level of the ink stored inside. Applying back pressure. SH1 is a liquid level reference position sensor, and SH2 is a liquid level upper limit sensor. The inside of the intermediate tank 3 is connected to an air release pipe 5 that is opened and closed by an on-off valve V3 that is an electromagnetic valve. Further, the pressure in the intermediate tank 3 is detected by the back pressure air pressure sensor SP1 by opening the on-off valve V4 made of an electromagnetic valve.

  In the middle of the ink supply pipe 4 connecting the intermediate tank 3 and the ink tank 6, a unidirectional pump 7 including a diaphragm pump for feeding in one direction is provided, and a predetermined amount of ink in the ink tank 6 is supplied by a predetermined amount. It can be supplied inside.

  The ink supply pipe 4 is provided with a first three-way valve 8A on the upstream side (suction side) of the unidirectional pump 7 and a second three-way valve 8B on the downstream side (discharge side). .

  Further, the first communication passage 9A can circulate ink between the first three-way valve 8A and the portion of the ink supply pipe 4 closer to the intermediate tank 3 than the second three-way valve 8B. The second communication path 9B is provided between the second three-way valve 8B and a portion of the ink supply pipe 4 closer to the ink tank 6 than the first three-way valve 8A. It is provided so that it can be distributed.

  Reference numeral 9a in FIG. 1 is a connection part between the first communication path 9A and the ink supply pipe 4B, and 9b is a connection part between the second communication path 9B and the ink supply pipe 4B. Reference numeral 41 denotes a pipe portion of the ink supply pipe 4 that connects between the connection part 9b and the inside of the ink tank 6, and reference numeral 42 denotes an ink supply pipe that connects between the connection part 9b and the first three-way valve 8A. 4 is a piping portion of the ink supply pipe 4 connecting the unidirectional pump 7 and the first three-way valve 8A, and 44 is a unidirectional pump 7 and a second three-way valve 8B. 45 is a pipe portion of the ink supply pipe 4 that connects between the second three-way valve 8B and the connection portion 9a, and 46 is an intermediate portion between the connection portion 9a and the connection portion 9a. This is a piping portion of the ink supply pipe 4 connecting the tank 3.

  The flow path of the first three-way valve 8A and the second three-way valve 8B is selectively switched by the control unit 100 shown in FIG. That is, the first three-way valve 8A is connected to the piping portion 42, the piping portion 43, and the first communication passage 9A of the ink supply tube 4, and the piping portion 43 on the suction side of the unidirectional pump 7 is connected to the ink tank. 6 is selectively communicated with one of the piping portion 42 and the first communication passage 9A. The second three-way valve 8B is connected to the piping part 45, the piping part 44, and the second communication passage 9B of the ink supply pipe 4, and the discharge-side piping part 44 of the unidirectional pump 7 is connected to the intermediate tank. 3 is selectively communicated with one of the pipe portion 45 and the second communication passage 9B.

  A filter 10 is provided in a piping portion 42 of the ink supply pipe 4 that connects between the first three-way valve 8A and the connection portion 9b, and the liquid is being fed from the ink tank 6 toward the intermediate tank 3. Thus, dust and the like in the ink are removed.

  On the other hand, an ink discharge pipe 11 is connected to the common flow path member 2. The discharge path of the ink discharge pipe 11 can be opened and closed by an on-off valve V2 made of an electromagnetic valve, and its discharge end is open to the atmosphere.

  An ink tray 12 is disposed at a position facing the nozzle surface of each of the recording heads 1A to 1F, and receives ink droplets that are forcibly discharged from the nozzles of the recording heads 1A to 1F by a maintenance operation, and discharges the ink. It is made to flow into the waste liquid tank 14 via the path 13. Ink discharged from the common flow path member 2 is also sent into the waste liquid tank 14 via the ink discharge pipe 11.

  The on-off valves V1 to V4 are controlled to be opened and closed by the control unit 100 shown in FIG.

  In such an ink jet recording apparatus, when the ink in the ink tank 6 is sent toward the recording heads 1A to 1F and is sent in the forward path (sequential feeding) to be stored in the intermediate tank 3, it is shown in FIG. As described above, the control unit 100 switches the first three-way valve 8A so that the pipe part 42 connected to the ink tank 6 and the pipe part 43 connected to the unidirectional pump 7 are communicated with each other, and the second three-way valve 8B. Are switched so that the piping portion 44 and the piping portion 45 are communicated with each other. As a result, the ink in the ink tank 6 passes through the piping part 41 of the ink supply pipe 4, the filter 10, and the piping part 42, flows into the piping part 43 by the first three-way valve 8 </ b> A, and is driven by the unidirectional pump 7. It is sent from the second three-way valve 8B into the intermediate tank 3 through the piping parts 45 and 46. At this time, the ink does not pass through the first communication path 9A and the second communication path 9B.

  On the other hand, in order to adjust the amount of ink liquid in the intermediate tank 3 or the like, when returning the liquid from the intermediate tank 3 to the ink tank 6 side (reverse feeding), it is shown in FIG. As described above, the control unit 100 switches the first three-way valve 8A so that the first communication passage 9A and the pipe portion 43 connected to the unidirectional pump 7 communicate with each other, and the second three-way valve 8B It switches so that the piping part 44 connected to the unidirectional pump 7 and the 2nd communicating path 9B may be connected. As a result, the ink in the intermediate tank 3 passes through the piping part 46 of the ink supply pipe 4 and the first communication path 9A, flows into the piping part 43 by the first three-way valve 8A, and is driven by the unidirectional pump 7. The ink is sent from the second three-way valve 8B into the ink tank 6 through the second communication passage 9B and the piping portion 41. At this time, the ink does not pass through the piping part 42 and the piping part 45 of the ink supply pipe 4.

  In this way, by only switching the flow path of the first three-way valve 8A and the second three-way valve 8B, the ink is fed from the ink tank 6 to the intermediate tank 3 by driving the unidirectional pump 7. Can be performed in both directions, and the reverse feed from the intermediate tank 3 to the ink tank 6. Since these forward and reverse feeds are performed by a single unidirectional pump 7 that feeds in one direction, the ink in the intermediate tank 3 is moved to the ink tank 6 side in order to control the back pressure of the recording heads 1A to 1F. Even when it is necessary to reversely feed and finely adjust the inside of the intermediate tank 3 to a predetermined negative pressure side, ink can be fed without error in the amount of liquid feeding, and the back pressure control of the recording heads 1A to 1F can be performed. It can be performed with high accuracy.

  In addition, since the ink passes through the filter 10 only at the time of progressive feeding, the ink always passes through the filter 10 only in one direction toward the intermediate tank 3 side (recording heads 1A to 1F side). It is possible to reliably prevent the entry of dust and the like.

  FIGS. 4 to 8 show other modes of the arrangement position of the filter 10 when the ink is always allowed to pass through the filter 10 from one direction.

  FIG. 4 shows a case where the arrangement position of the filter 10 is the piping portion 45 of the ink supply pipe 4. In this case, the ink passes through the film 10 when the ink liquid is sequentially transferred from the ink tank 6 to the intermediate tank 3 (FIG. 4A), but the ink liquid is transferred from the intermediate tank 3 to the ink tank 6. At the time of reverse feeding, the ink does not pass through the film 10 (FIG. 4B).

  FIG. 5 shows a case where the arrangement position of the filter 10 is the second communication path 9B. In this case, when the ink liquid is sequentially transferred from the ink tank 6 to the intermediate tank 3, the ink does not pass through the film 10 (FIG. 5A), but the ink liquid is transferred from the intermediate tank 3 to the ink tank 6. At the time of reverse feeding, the ink passes through the film 10 (FIG. 5B).

  FIG. 6 shows a case where the filter 10 is disposed at the piping portion 43 of the ink supply pipe 4 that connects the first three-way valve 8 </ b> A and the unidirectional pump 7. In this case, the ink passes through the film 10 at the time when the ink liquid is sequentially fed from the ink tank 6 to the intermediate tank 3 (FIG. 6A), and the ink liquid is fed from the intermediate tank 3 to the ink tank 6. The ink also passes through the film 10 during reverse feeding toward the head (FIG. 6B). However, since the filter 10 is located on the suction side of the unidirectional pump 7, the ink always passes only in one direction in both forward and reverse feeding.

  FIG. 7 shows a case where the filter 10 is disposed at the piping portion 44 of the ink supply pipe 4 that connects the second three-way valve 8 </ b> B and the unidirectional pump 7. Also in this case, since the filter 10 is located on the discharge side of the unidirectional pump 7, as in the case of FIG. 6, the ink passes through the film 10 during the forward feeding of the ink liquid from the ink tank 6 to the intermediate tank 3. The ink also passes through the film 10 (FIG. 7B) when the ink passes through (FIG. 7A) and when the ink is fed back from the intermediate tank 3 to the ink tank 6.

  FIG. 8 shows a case where the arrangement position of the filter 10 is the first communication path 9A. In this case, when the ink liquid is sequentially fed from the ink tank 6 toward the intermediate tank 3, the ink does not pass through the film 10 (FIG. 8A), but the ink liquid is transferred from the intermediate tank 3 to the ink tank 6. At the time of reverse feeding, the ink passes through the film 10 (FIG. 8B).

1: Recording head 2: Common flow path member 3: Intermediate tank 4: Ink supply pipe 41-47: Piping portion 5: Atmospheric release pipe 6: Ink tank 7: Unidirectional pump 8A: First three-way valve 8B: First 2 three-way valve 9A: first communication path 9B: second communication path 10: filter 11: ink discharge pipe 12: ink tray 13: discharge flow path 14: waste liquid tank 100: control unit SH1: liquid level reference position Sensor SH2: Liquid level upper limit sensor SP1: Back pressure air pressure sensor SP2: No ink detection sensor V1 to V4: Open / close valve

Claims (4)

An ink tank that stores ink; a recording head that ejects ink droplets from nozzles to form an image on a recording medium; and an ink supply that supplies ink in the ink tank toward the recording head via an ink supply pipe An ink jet recording apparatus comprising:
The ink supply means
One unidirectional pump for feeding in one direction provided in the middle of the ink supply pipe;
A first three-way valve provided upstream of the unidirectional pump in the ink supply pipe;
A second three-way valve provided downstream of the unidirectional pump in the ink supply pipe;
A first communication path that communicates between the first three-way valve and a portion of the ink supply pipe that is closer to the recording head than the second three-way valve;
A second communication path that communicates between the second three-way valve and a portion of the ink supply pipe that is closer to the ink tank than the first three-way valve;
By driving the unidirectional pump and switching the flow paths of the first three-way valve and the second three-way valve, ink in the ink tank is supplied to the first communication path and the second communication path. The forward path for sending liquid toward the recording head without passing through the path, and the ink from the recording head side return to the ink tank through the first communication path and the second communication path. An ink jet recording apparatus comprising: control means for controlling the ink feeding direction in any of the return path. An intermediate tank for temporarily storing ink supplied from the ink tank toward the recording head between the connection portion of the ink supply pipe to the first communication path and the recording head;
The control means switches the flow path of the first three-way valve and the second three-way valve to the return path, and reversely feeds the ink in the intermediate tank to the ink tank by driving the unidirectional pump. 2. The ink jet recording apparatus according to claim 1, further comprising back pressure control means for controlling a back pressure applied to the recording head by adjusting a pressure inside the intermediate tank.   Between the connection part of the ink supply pipe with the first communication path and the second three-way valve, between the connection part of the ink supply pipe with the second communication path and the first three-way valve. Between the first three-way valve and the unidirectional pump, between the second three-way valve and the unidirectional pump, on the first communication path, or on the second communication The ink jet recording apparatus according to claim 1, wherein a filter is provided on any of the roads. 4. The ink jet recording apparatus according to claim 1, wherein the unidirectional pump is a diaphragm pump.

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