JP3925547B2 - Inkjet printer - Google Patents

Description

  The present invention belongs to the technical field of an inkjet printer in which a large number of nozzles are arranged and ink droplets are ejected from the nozzles to perform printing on a recording medium.

  In an ink jet printer, clogging of nozzles of an ink jet head and ejection failure are major issues in reliability. When air bubbles are mixed into the pressure chamber from the nozzle or ink tank, the ink cannot be pressurized properly and ejection becomes unstable, or the ink flow is hindered by solid matter generated by drying the ink, etc. Various adverse effects such as this cause deterioration of the performance of the ink jet printer. Therefore, it is necessary to take some measures against the mixing of bubbles and solid matter inside the inkjet head.

  A method for solving such a problem by performing a so-called purge operation is known. That is, ink is supplied from the ink tank, the ink is circulated through the ink flow path and the nozzle, and the mixed bubbles and solid matter are forcibly discharged to the outside of the nozzle. As a result, nozzle clogging and ejection failure can be prevented, and ink droplets can be ejected stably.

  When performing the above-described purging operation, it is necessary to use a large amount of ink in order to discharge the ink to the outside of the nozzle, and since the discharged ink cannot be reused and is wasted, there is a problem in terms of economy. is there. There is also a concern that the discharged ink may contaminate the recording paper and its surroundings. Therefore, it is desirable to perform the purge operation with the minimum amount of ink without waste as much as possible.

  Accordingly, the present invention has been made in view of such circumstances, and an object thereof is to provide an ink jet printer capable of performing a purge operation using ink in a good state.

In order to solve the above-described problem, an ink jet printer according to claim 1 includes a plurality of head units that distribute and supply ink to a plurality of nozzles from a common manifold communicating with an ink supply port and an ink discharge port, respectively, via pressure chambers. An ink tank that stores ink to be supplied to each head unit, a circulation forward path that is connected to the ink tank and serves as a flow path for circulating ink supplied to each head unit, and A circulation return path serving as a flow path through which ink discharged from the head unit circulates; an ink flow path that directly communicates the circulation forward path and the circulation return path; a communication valve that controls opening and closing of the ink flow path; and the circulation forward path And a plurality of supply paths communicating between the ink supply ports of the head units and the ink supply ports of the head units. A plurality of discharge paths communicating between the discharge outlet and the circulation return path, and the ink stored in the ink tank is fed to the circulation forward path, and the ink is discharged from the circulation return path via the head units. An ink circulation mechanism that collects ink in the tank and circulates the ink, and the flow of ink to the flow path from the connection point on the circulation forward path side of the supply path to the connection point on the circulation return path side of the discharge path the road resistance, the larger if the head unit is arranged close to the ink tank, when disposed distant characterized to Rukoto small.

  According to the present invention, when the purge operation is performed, the ink stored in the ink tank is fed to the circulation forward path by the ink circulation mechanism and reaches each head unit through the plurality of supply paths. Then, the ink is distributed and supplied from the common manifold of each head unit to the plurality of nozzles via the pressure chamber, and the bubbles and solid matter are discharged to the outside together with the ink. Thereafter, the remaining ink flows into the circulation return path through the plurality of discharge paths, and is finally collected in the ink tank by the ink circulation mechanism.

  Therefore, when ink is circulated as described above, when ink is supplied to each head unit, it is hardly affected by the difference in flow path resistance, and purge is performed with a uniform ink amount. In particular, since ink flows into each head unit in parallel, it is possible to avoid a situation in which the ink pressure during purging is lowered many times through a manifold having a large flow path resistance. As a result, an appropriate purge operation for a large number of nozzles is performed without wasting ink.

  According to the present invention, when the communication valve is closed, the ink is circulated and the purge operation is performed as described above. However, when the communication valve is opened, the ink flows directly from the circulation forward path to the circulation return path. It becomes like this.

Therefore, bubbles and unnecessary objects existing in the circulation forward path and circulation return path can flow via a route different from each head unit having a small ink flow path size, and use ink having a better state. A purge operation can be performed.
Further, according to the present invention, when the purge operation is performed, when the ink fed from the ink tank flows from the circulation forward path to the head unit disposed in the vicinity of the ink tank, the flow return resistance side has a large flow path resistance. When it reaches and flows into the head unit disposed far from the ink tank, it reaches the circulation return path side with a small flow path resistance.
Accordingly, in the ink circulation accompanying the purge operation, the flow resistance of the ink flow path is adjusted so as to reduce the variation in flow path resistance determined by the arrangement and structure of each head unit. Is made uniform, and wasteful consumption of ink during purging can be avoided.

  2. The ink jet printer according to claim 2, wherein the ink circulation mechanism stores ink collected from the circulation return path, and a sub tank communicated with the ink tank, and the ink tank. Stored in the ink tank, a first valve that controls opening and closing of the ink flow path between the sub tank and the sub tank, a second valve that controls opening and closing of the ink flow path between the sub tank and the circulation return path, and And pressurizing means for pressurizing and feeding the ink to the circulation outward path.

  According to the present invention, when performing the purge operation, when the first valve is closed and the second valve is opened and the ink in the ink tank is pressurized by the pressurizing means, the ink is pumped to the circulation forward path. Then, it is collected in the sub tank via each head unit. When the second valve is closed and the first valve is opened, the ink in the sub tank is collected in the ink tank.

  Accordingly, since the ink is smoothly supplied to each head unit and is once stored in the sub tank, the above-described purge operation is executed while efficiently supplying and collecting the ink.

  An ink jet printer according to a third aspect of the invention is the ink jet printer according to the second aspect, wherein the first valve and the communication valve are closed and the second valve is opened, and the pressurizing means opens the ink. The first step of circulating the ink from the ink tank to the sub-tank, the first valve closed, the second valve and the communication valve opened, and the pressurizing means A second step of circulating ink from the ink tank to the sub-tank by pumping ink; and opening the first valve and closing the second valve, and supplying ink from the sub-tank to the ink tank. A purge operation including a third step of collecting is performed.

  According to this invention, when the execution of the purge operation in the ink jet printer is started, the pressure is fed by the pressurizing means for circulating the ink. At this time, the first valve and the communication valve are closed and the second valve is opened, and the process is performed. The first valve is closed, and the second valve and the communication valve is opened and the process is performed. Control is performed as appropriate. Eventually, the first valve is opened, the second valve is closed, and ink is collected from the sub tank to the ink tank.

  Therefore, a series of control procedures for removing bubbles and unnecessary substances from the circulation forward path and the circulation return path, performing a purge operation using a uniform amount of ink between the head units, and then collecting the used ink are easily performed. be able to.

  According to a fourth aspect of the present invention, in the ink jet printer according to the third aspect, the communication valve is opened before the third step from the first step during the purge operation, and the pressurizing means The method further includes the step of circulating ink from the ink tank to the sub tank by pumping the ink.

  According to this invention, bubbles and solids existing in the circulation outward path can be directly poured into the circulation return path together with ink by opening the communication valve prior to the first to third processes.

  Accordingly, since these bubbles and solids are less likely to flow into each head unit, it is possible to perform a purge operation using ink in a better state.

  The ink jet printer according to claim 5 is the ink jet printer according to any one of claims 1 to 4, wherein each of the plurality of supply paths is provided with a filter that passes ink and removes unnecessary substances. It is characterized by being.

  According to this invention, when the ink is circulated and supplied to each head unit, the ink is passed through the filter to remove unnecessary matters such as bubbles and solids in advance.

Thus, for each head unit, without flowing the mixed ink of undesired materials, such as clogging of the nozzles Ru is prevented.

  According to the first aspect of the present invention, since ink flows in parallel to each head unit, it is hardly influenced by the difference in flow path resistance, and each nozzle is purged using a uniform ink amount. Accordingly, it is possible to provide an economical ink jet printer that does not waste ink, can perform an appropriate purge operation for all nozzles, and has few ejection defects.

Further, according to the first aspect of the present invention, it is possible to easily eliminate bubbles and unnecessary substances existing in the circulation forward path and the circulation return path, and to perform the purge operation using the ink in a good state. Therefore, an economical ink jet printer can be provided.
Furthermore, according to the first aspect of the present invention, the flow resistance is adjusted so as to reduce the variation of the flow resistance determined by the arrangement and structure of each head unit in accordance with the purge operation. Thus, an appropriate purge operation can be executed without any need, and a high-performance and economical ink jet printer can be provided.

  According to the second aspect of the present invention, since the above-described purge operation can be executed while efficiently supplying and collecting ink to each head unit, it is economical with few ejection defects and easy control of the purge operation. An ink jet printer can be provided.

  According to the third aspect of the present invention, a series of control procedures accompanying the purge operation can be efficiently performed, and the above-described purge operation can be executed simply and quickly.

  According to the fourth aspect of the present invention, since the communication valve is opened prior to the first to third steps, air bubbles and solids can be directly poured into the circulation return path together with the ink. It is difficult for bubbles and solids to flow into the ink, and a purge operation can be performed using ink in a better state.

According to the invention of claim 5, the filter, the unnecessary matters such as bubbles and solids are preliminarily removed, clogging of the nozzle can be effectively prevented, Ru can provide a highly reliable ink jet printer.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. In the following description, an embodiment in which the present invention is applied to an inkjet printer configured by providing four head units each having a plurality of nozzles will be described.

  FIG. 1 is a diagram showing an overall configuration of an inkjet printer according to an embodiment of the present invention. The ink jet printer shown in FIG. 1 includes four head units 11, 12, 13, and 14, four supply paths 21, 22, 23, and 24 that correspond to the head units 11 to 14, respectively, and four discharge paths 31, 32, 33, 34, circulation forward path 4, circulation return path 5, ink tank 6, sub tank 7, air pump 8, first valve 41, and second valve 42.

  In the configuration of FIG. 1, each of the head units 11 to 14 includes a common manifold, a plurality of pressure chambers, and a plurality of nozzles. Providing the four head units 11 to 14 in this way is an advantageous configuration in that the manufacturing yield is improved as compared to providing a large number of nozzles and pressure chambers in one head unit. In the present embodiment, the case where all the head units 11 to 14 have the same structure will be described.

  Here, the structure of the head unit 11 will be described in more detail with reference to FIGS. Since the head units 12 to 14 are the same as the head unit 11, the head unit 11 will be described as a representative.

  FIG. 2 is an exploded perspective view of the head unit 11. As shown in FIG. 2, the head unit 11 is a unit in which a cavity plate 101, a nozzle plate 102, a piezoelectric element 103, and a diaphragm 104 are bonded and integrated.

  A plurality of pressure chambers 105 partitioned by side walls are formed in the cavity plate 101, and each of them communicates with a common manifold 109 so that ink flows. Each pressure chamber 105 communicates with a plurality of nozzles 106 formed in the nozzle plate 102, and ink pressurized in each pressure chamber 105 is ejected from each nozzle 106.

  Further, a diaphragm 104 is joined to cover the entire opening side of the upper part of the cavity plate 101, and a piezoelectric element 103 is further joined to the diaphragm 104. A supply port 107 and a discharge port 108 are formed in the piezoelectric element 103 and the diaphragm 104 at the upper portion of the manifold 109. The supply port 107 communicates with the supply path 21 and the discharge port 108 communicates with the discharge path 31, respectively. The manifold 109 is part of the ink circulation path.

  In FIG. 2, for simplicity, the head unit 11 is provided with twelve pressure chambers 105 and twelve nozzles 106. However, in reality, the head unit 11 is provided with a larger number of pressure chambers 105 and nozzles 106. Can be configured.

  FIG. 3A is a cross-sectional view of the head unit 11 taken along the line XX. A piezoelectric element 103 is arranged on the upper surface side of the lower cavity plate 101 so that the girder portion overlaps each side wall of the cavity plate 101, and the diaphragm 104 is sandwiched therebetween. In addition, an upper portion of each pressure chamber 105 is arranged so that a girder in which the internal electrode 110 of the piezoelectric element 103 is embedded overlaps. Note that at least the girder part of the piezoelectric element 103 is polarized, and in this embodiment, each girder part is polarized in the downward direction of FIG. 3A.

  When a driving voltage is applied to the internal electrode 110 so that an electric field in the same direction as the polarization direction is applied to the beam portion by a driving circuit (not shown), each pressure of the diaphragm 104 is shown in FIG. The upper part of the chamber 105 is deformed downward in a convex shape. Thereby, the volume of each pressure chamber 105 can be reduced and the pressure of ink can be raised, and as a result, ink can be ejected from each nozzle 106.

During the purge operation, the piezoelectric element 103 is not driven, and a part of the large amount of ink that is forcibly supplied via the supply port 107 is discharged from each nozzle 106 via each pressure chamber 105. It is discharged with solids. At this time, maintenance paper or the like may be installed outside each nozzle 106 to wipe out the discharged ink.

  In FIG. 1, an ink tank 6 is a container for storing ink to be used in printing and purging operations by the head units 11 to 14. The ink tank 6 supplies ink to the circulation path 4 connected to the ink tank 6 and communicates with the sub tank 7 via the first valve 41 to collect the circulated ink.

  The air pump 8 is a pressurizing unit that is connected to the ink tank 6 and pressurizes the air layer above the ink tank 6. When pressurization by the air pump 8 is performed, the pressure of the ink in the ink tank 6 increases, and the ink is pumped to the circulation forward path 4 to circulate the ink.

  The circulation forward path 4 is a path through which ink pumped from the ink tank 6 circulates, and communicates with the supply paths 21 to 24 in order to supply ink to the head units 11 to 14. From the circulation forward path 4 to the connection point where the supply paths 21 to 24 communicate with each other, the supply paths 21, 22, 23, and 24 are arranged away from the ink tank 6 in this order.

  The circulation return path 5 is a flow path for recirculating the ink discharged from the head units 11 to 14 and communicates with the discharge paths 31 to 34, respectively. From the circulation return path 5 to the connection point where the discharge paths 31 to 34 communicate with each other, as in the case of the circulation forward path 4, the discharge paths 31, 32, 33, and 34 are arranged away from the ink tank 6 in this order. Yes. The circulation return path 5 is communicated with the sub tank 7 via the second valve 42.

The sub tank 7 is a container that temporarily stores the ink circulated through the head units 11 to 14. Then, the ink stored in the sub tank 7 is returned to the ink tank 6 through the first valve 41 at an appropriate timing, and is supplied to the circulation again.

  As described above, the first valve 41 is inserted between the ink tank 6 and the sub tank 7, and the second valve 42 is inserted between the circulation return path 5 and the sub tank 7, respectively. Opening and closing is controlled by the control means.

  A procedure for performing the purge operation in the ink jet printer configured as described above will be described.

  First, the first valve 41 is closed and the second valve 42 is opened by the control means. As a result, the backflow of ink from the ink tank 6 to the circulation return path 5 side is prevented, and the direction in which the ink is circulated is determined.

  In this state, the air pump 8 is operated to pressurize the ink in the ink tank 6 and feed the ink to the circulation forward path 4. Thereafter, the ink passes through the supply paths 21 to 24 and reaches the head units 11 to 14, and a part of the ink is discharged from the nozzle 106 as described above. The remaining ink passes through each of the discharge paths 31 to 34, passes through the circulation return path 5, and is collected in the sub tank 7 through the second valve 42. In this way, ink circulation from the ink tank 6 to the sub tank 7 is performed.

  Thereafter, at an appropriate timing, the control means opens the first valve 41 and closes the second valve 42 to switch the open / close state. Then, the ink circulation as described above is stopped, and the ink collected in the sub tank 7 flows into the ink tank 6 through the first valve 41. Therefore, the consumed ink can be used again.

  In the configuration shown in FIG. 1, the air is circulated by pressurizing the air in the ink tank 6 by using the air pump 8, but the ink is forced by, for example, a gear pump or a tube pump without performing the pressurization. The ink circulation mechanism may be configured by circulation.

  Next, in the ink jet printer according to the present embodiment, the flow path resistance with respect to the ink when the ink is circulated will be described. In order to perform the above-described purge operation optimally, it is necessary to make the ink amounts supplied to the head units 11 to 14 substantially equal. In the following, the flow path resistance design conditions for equalizing the amount of ink flowing between the head units 11 to 14 will be described.

  Here, when the flow resistance of the flow path is R (kgf · s / cm5), the flow rate per unit time is Q (cc / s), and the pressure loss is ΔP (kgf / cm2), ,

(Equation 1)
ΔP = QR
The relationship holds. The channel resistance R is proportional to the channel length. Thus, the channel resistance has the same properties as the electrical resistance in these respects.

  FIG. 4 is a diagram showing the ink flow path of the ink jet printer according to the present embodiment replaced with an equivalent electric circuit. In FIG. 4, pressure is replaced with voltage, ink flow is replaced with current, and flow path resistance is replaced with electrical resistance.

  In FIG. 4, when the pressure V is applied to the ink by the air pump 8, a condition is obtained in which the ink flows flowing through the head units 11 to 14 are all equal to i. At this time, the total ink flow supplied from the ink tank 6 is 4i. Further, since the head units 11 to 14 have the same structure, the flow path resistances from the supply paths 21 to 24 to the discharge paths 31 to 34 are all set to c.

  In the circulation forward path 4, the flow resistance from the connection part to the supply path 21 to the connection part to the supply path 22 is a, and similarly, the connection part to the supply path 22 and the connection part to the supply path 23 are The flow resistance between the two and the flow resistance between the connecting portion to the supply passage 23 and the connecting portion to the supply passage 24 are made to coincide with a. Further, in the circulation return path 5, the flow resistance from the connection part to the discharge path 31 to the connection part to the discharge path 32 is b, and similarly, the connection part to the discharge path 32 and the connection part to the discharge path 33 are And the flow path resistance between the connection part to the discharge path 33 and the connection part to the discharge path 34 are made to coincide with b.

  Further, for the head unit 11, the sum of the flow path resistance of the supply path 21 and the flow path resistance of the discharge path 31 is represented as R1. Similarly, for the head unit 12, the sum of the flow path resistance of the supply path 22 and the flow path resistance of the discharge path 32 is represented as R <b> 2, and for the head unit 13, the flow path resistance of the supply path 23 and the discharge path 33. The sum of the flow path resistances of the supply path 24 and the discharge path 34 for the head unit 14 is represented by R4.

  Using the above values, the circuit equation of FIG. 4 is established as follows.

(Equation 2)
(R1 + c) i = 3ai + (R2 + c) i + 3bi
(R2 + c) i = 2ai + (R3 + c) i + 2bi
(R3 + c) i = ai + (R4 + c) i + bi
From the equation (2), the following equation is further derived.

(Equation 3)
R1 = 3 (a + b) + R2
R2 = 2 (a + b) + R3
R3 = (a + b) + R4
Therefore, the ink flow i flowing through the head units 11 to 14 can be made equal by designing the flow path resistances R1 to R4 so as to satisfy the relationship of Equation 3.

  In the present embodiment, since four head units are provided, it is only necessary to satisfy the three formulas in Equation 3, but more generally, a case where n head units are provided is considered. At this time, as described above, on the premise that the flow resistance of the connection portion to the supply path is all a adjacent to each other, the flow resistance of the connection portion to the discharge path is all adjacent to b, For any i in the range from 1 to N-1, the following equation is derived:

(Equation 4)
Ri = (ni) (a + b) + Ri + 1
In Equation 4, Ri is the sum of the flow path resistances of the supply path and the discharge path for the i-th head unit. If a plurality of head units are arranged while satisfying Equation 4, a uniform ink flow i can be poured into all the head units regardless of the number of head units.

  In the inkjet head according to the present embodiment, in order to achieve the effect of the present invention more easily, R1 to R4 may be designed to satisfy the following relationships instead of Equation 3. .

(Equation 5)
R1>R2>R3> R4
That is, as the head units 11 to 14 are arranged closer to the ink tank 6, the sum of the flow path resistances of the supply path and the discharge path is increased. In this case, the ink flow i flowing into each head unit does not necessarily match, and the same effect as that in the case of satisfying Equation 3 cannot be obtained. However, compared with the case where R1 to R3 are designed to be the same, for example. Since the difference in the ink flow i decreases, a better purge operation can be performed.

  Note that even in the case of a configuration in which n head units are provided, the relationship of Equation 5 is basically unchanged, and a head unit with a smaller number, that is, a head unit that is disposed closer to the ink tank 6 is supplied. What is necessary is just to design so that the sum of the channel resistance of a path and a discharge path may become large.

  As described above, the ink flow path is designed to satisfy Equation 4 or Equation 5 and the ink jet printer is configured, so that the amount of ink supplied to each head unit during the purge operation can be made uniform or substantially uniform. Thus, the ink pressure discharged from each nozzle 106 can be made constant, and the purge operation is performed using substantially the same amount of ink. Further, when an ink jet printer is configured by further increasing the number of head units, the necessity of making each ink amount uniform is further increased, so that a more remarkable effect can be obtained by applying the present invention.

  In addition, when using a plurality of head units each having the same structure, the flow path resistances of the respective head units themselves are added to the flow path resistances R1 to R4 to satisfy Equation 4 or Equation 5, The same effect as described above can be obtained.

  Further, even if the relationship in Equation 4 or Equation 5 is not satisfied, if the ink jet printer is configured using the ink flow path as shown in FIG. 1, the ink flow of each head unit 11 to 14 is made uniform to some extent. Is possible. That is, in the configuration of FIG. 1, the circulation return path 4 reaches the circulation return path 5 in parallel via the supply paths 21 to 24, the head units 11 to 14, and the discharge paths 31 to 34. Therefore, the ink does not circulate through the plurality of head units in series. The length of the circulation path 4 passing from the ink tank 6 to each of the supply paths 21 to 24 is different for each head unit 11 to 14, but the flow path resistance of the circulation path 4 is different from each head unit 11 to 14. It can be designed to be much smaller than the manifold 109 or the like. Therefore, the influence on the total flow path resistance during ink circulation is small, and the difference in the total flow path resistance when passing through the head units 11 to 14 is not so large. Therefore, in the ink jet printer employing the configuration shown in FIG. 1, the effect of making the ink amounts of the head units 11 to 14 uniform to some extent can be obtained.

  Next, various modifications to the embodiment of the present invention will be described.

(First modification)
The first modification shown in FIG. 5 is configured to allow ink to flow directly from the circulation forward path 4 to the circulation return path 5 in the ink jet printer according to the embodiment, and to provide a communication valve 43 therebetween.

  In the overall configuration of FIG. 5, the head units 11 to 14, the supply paths 21 to 24, the discharge paths 31 to 34, the ink tank 6, the sub tank 7, the air pump 8, the first valve 41, and the second valve 42 are as follows. Since it is the same as that of the embodiment of FIG. 1, description is abbreviate | omitted.

  In the configuration shown in FIG. 5, unlike the overall configuration shown in FIG. 1, the circulation forward path 4 and the circulation return path 5 are provided with a flow path for allowing ink to pass without passing through the head units 11 to 14. The communication valve 43 is connected. The opening and closing of the communication valve 43 is also controlled by a control means (not shown), like the first valve 41 and the second valve 42. By opening the communication valve 43, the ink can be circulated even when the head units 11 to 14 are not passed.

In the ink jet printer having the configuration shown in FIG. 5, bubbles and solids existing in the circulation forward path 4 can be directly passed through the circulation return path 5 by opening the communication valve 43 and can be poured into the sub tank 7 together with the ink. . That is, since it is difficult for these bubbles and solids to flow into each of the head units 11 to 14, it is possible to perform a purge operation using ink in a better state.

(Second modification)
The second modification shown in FIG. 6 has a configuration in which filters 51 to 54 are provided in the middle of the supply paths of the head units 11 to 14 in the ink jet printer according to the first modification of FIG. . Other configurations are the same as those shown in FIG.

  In the configuration shown in FIG. 6, before ink circulates from the circulation path 4 to the head units 11 to 14, only the ink passes through the filters 51 to 54, but unnecessary matters such as bubbles and solids are removed. Is done. As a result, it is possible to supply good ink with a small amount of unnecessary materials to each of the head units 11 to 14, so that clogging and ejection failure of each nozzle 106 can be made difficult to occur.

  Next, a procedure for performing a purge operation in the inkjet printer having the overall configuration shown in FIG. 5 or FIG. 6 will be described.

  First, the first valve 41 is closed and the second valve 42 and the communication valve 43 are opened by a control means (not shown). In this state, the air pump 8 is operated to pressurize the ink in the ink tank 6 and feed the ink to the circulation forward path 4. As a result, the ink reaches the sub tank 7 in any one of a flow path that passes through the head units 11 to 14 and a flow path that flows directly from the circulation forward path 4 to the circulation return path 5. At this time, when flowing directly from the circulation forward path 4 to the circulation return path 5, the flow path is thick and easy to flow. Therefore, if there are bubbles or solids present in the circulation forward path 4, most of them go directly to the circulation return path 5 together with ink. Into the sub tank 7.

  Then, the control means maintains the state of the first valve 41 and the second valve 42 and switches the communication valve 43 to the closed state. Then, the circulating ink flows through one of the head units 11 to 14, and a part of the ink is discharged from the plurality of nozzles 106 as described above, and the remaining ink passes through the circulation return path 5. And collected in the sub tank 7.

  Next, the control means maintains the state of the first valve 41 and the second valve 42 and switches the communication valve 43 to the opened state again. As a result, the ink discharged to the circulation return path 5 by the purge operation can be poured into the sub tank 7 together with the remaining bubbles and solids at a larger flow rate.

  Finally, at an appropriate timing, the control means opens the first valve 41 and switches the second valve 42 to the closed state. Then, the ink circulation as described above is stopped, and the ink collected in the sub tank 7 flows into the ink tank 6 through the first valve 41. Therefore, the consumed ink can be used again.

  By appropriately performing the purge operation in the above procedure, the ejection state from each nozzle 106 of each head unit 11 to 14 can be maintained and recovered. At this time, the amount of ink used can be made uniform between the head units 11 to 14, so that the ink is used without waste, and the ink is sufficiently supplied to all the nozzles 106 to perform an optimum purge operation. Done.

  Not limited to the above-described procedure, the purge operation performed by opening the communication valve 43 and the purge operation performed by closing the communication valve 43 are appropriately combined, so that the circulation forward path 4, the circulation return path 5, and each manifold 109 Any procedure can be used as long as it can eliminate bubbles and solids.

  In the embodiment described above, the case where each of the head units 11 to 14 is physically separated has been described. However, in the integrated head unit, an ink flow path such as a manifold is divided and each ink unit is formed. The present invention can also be applied to an ink jet printer configured to distribute and supply ink from a flow path to a plurality of pressure chambers and nozzles.

1 is an overall configuration diagram of an inkjet printer according to an embodiment of the present invention. It is a disassembled perspective view of the head unit which concerns on embodiment of this invention. FIG. 3 is a cross-sectional view taken along line XX of FIG. 2 of the head unit according to the embodiment of the present invention, where (a) shows a case where no driving voltage is applied to the piezoelectric element, and (b) shows a case where a driving voltage is applied to the piezoelectric element. It is. It is a figure which replaces the ink flow path of the ink jet printer which concerns on embodiment of this invention, and is replaced with an equivalent electric circuit. It is a whole block diagram which shows the 1st modification of the inkjet printer which concerns on embodiment of this invention. It is a whole block diagram which shows the 2nd modification of the inkjet printer which concerns on embodiment of this invention.

Explanation of symbols

4 ... circulation forward path 5 ... circulation return path 6 ... ink tank 7 ... sub tank 8 ... air pumps 11, 12, 13, 14 ... head units 21, 22, 23, 24 ... supply paths 31, 32, 33, 34 ... discharge paths 41 ... first valve 42 ... second valve 43 ... communication valves 51, 52, 53, 54 ... filter 101 ... cavity plate 102 ... nozzle plate 103 ... piezoelectric element 104 ... diaphragm 105 ... pressure chamber 106 ... nozzle 107 ... supply port 108 ... Exhaust port 109 ... Manifold 110 ... Internal electrode

Claims (5)

An inkjet printer comprising a plurality of head units for distributing and supplying ink to a plurality of nozzles from a common manifold communicating with an ink supply port and an ink discharge port, respectively, via a pressure chamber,
An ink tank for storing ink to be supplied to each head unit;
A circulation forward path connected to the ink tank and serving as a flow path for the ink supplied to each head unit;
A circulation return path serving as a flow path through which ink discharged from each head unit circulates;
An ink flow path that directly communicates the circulation forward path and the circulation return path;
A communication valve for opening and closing the ink flow path;
A plurality of supply paths that communicate between the circulation path and the ink supply ports of the head units;
A plurality of discharge paths communicating between the ink discharge port of each head unit and the circulation return path;
With feeds the ink stored in said ink tank to said circulation forward, the recovered ink to the ink tank from the circulation return via the respective head units, and a ink circulation mechanism for circulating the ink ,
When the head unit is disposed close to the ink tank in terms of flow path resistance to ink in a flow path from the connection point on the circulation forward path side of the supply path to the connection point on the circulation return path side of the discharge path. significantly, the ink jet printer, wherein to Rukoto small when placed distant. The ink circulation mechanism is
Storing the ink collected from the circulation return path, and a sub-tank communicating with the ink tank;
A first valve that controls opening and closing of an ink flow path between the ink tank and the sub tank;
A second valve that controls opening and closing of an ink flow path between the sub tank and the circulation return path;
Pressurizing means for pressurizing the ink stored in the ink tank and pumping the ink to the circulation path;
The inkjet printer according to claim 1, comprising: A first step of circulating ink from the ink tank to the sub-tank by pumping ink by the pressurizing means in a state where the first valve and the communication valve are closed and the second valve is opened; ,
A second step of circulating ink from the ink tank to the sub tank by pumping ink by the pressurizing means in a state where the first valve is closed and the second valve and the communication valve are opened; ,
A third step of collecting ink from the sub tank to the ink tank with the first valve opened and the second valve closed;
The inkjet printer according to claim 2, wherein a purge operation is performed.   A step of opening the communication valve prior to the first step to the third step during the purge operation, and feeding the ink by the pressurizing means to circulate the ink from the ink tank to the sub tank; The inkjet printer according to claim 3, further comprising:   5. The ink jet printer according to claim 1, wherein each of the plurality of supply paths is provided with a filter that passes ink and removes unnecessary substances.

Images