JP2008055646A - Inkjet recording apparatus, and ink feeding method for the recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the sinking of a pigment in an ink feeding passage from occurring, to enable the temperature control of an ink in an inkjet head to be surely performed, and in addition, to enable the negative control of the ink of a pressure chamber to be easily performed. <P>SOLUTION: This inkjet recording apparatus is equipped with the inkjet head 5, the first ink feeding passage 8, and the second ink feeding passage 10. In this case, in the inkjet head 5, the pressure chamber 6 having ink tanks 1 and 2 which house the ink and a nozzle is installed. The inkjet head 5 discharges the ink in the pressure chamber from the nozzle when recording, and at the same time, refills the ink in a common ink chamber 7 to the pressure chamber. The first ink feeding passage 8 circulates the ink in the ink tanks by the operation of a circulating pump 9 without making the ink go through the inkjet head, and has a smaller flow passage resistance. The second ink feeding passage 10 takes in a part of the ink from the middle of the first ink feeding passage by branching the flow, and circulates the ink through the common ink chamber of the inkjet head, and has a larger flow passage resistance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that discharges ink from nozzles of an ink jet head while circulating ink, and an ink supply method for the recording apparatus.

Conventionally, an ink jet recording apparatus pressurizes ink in a pressure chamber of an ink jet head provided with a pressure chamber having nozzles, thereby ejecting the ink as ink droplets from the nozzles and attaching the ink droplets to a recording medium to record an image. And an ink supply system for supplying ink from an ink tank to the inkjet head.
Ink used in such an ink jet recording apparatus includes water-based, oil-based, solvent-based, and UV-based inks. Color materials used include pigments and dyes.

  Further, recently, recording media such as ink absorbing media such as paper to non-ink absorbing media such as plastic and metal have been used. Inks used for recording on non-absorbing media are solvent-based and UV-based inks. The ink colors are usually four colors, cyan, magenta, yellow, and black, but white ink is used for printing on the electronic component mounting board.

  White ink uses titanium oxide as a pigment, and has a larger pigment particle size and specific gravity than ordinary cyan, magenta, yellow, and black inks. Further, in order to increase the concealment rate by ink, a large amount of titanium oxide is mixed in the ink, and it is easy to precipitate. For this reason, when the ink is allowed to stand for a certain period of time in the ink tank, in the ink supply path, and in the head, sedimentation of the pigment occurs.

  In order to prevent such sedimentation of the pigment, for example, the ink in the ink tank can be dealt with by stirring using a magnetic stirrer or the like, and the ink in the head is regularly pressurized in the head. This can be dealt with by discharging the ink in the pressure chamber from the nozzle. However, it is difficult to stir the ink in the ink supply path.

For this reason, an ink circulation path that does not pass through an inkjet head is formed to prevent ink from settling by constantly circulating the ink (see, for example, Patent Document 1).
JP 2005-246854 A

  In order to circulate the ink and prevent sedimentation of the pigment, it is preferable that the ink flow rate is large and the flow velocity is high. On the other hand, in order to continue ink ejection stably, it is necessary to maintain the viscosity of the ink within a predetermined range. Usually, the head is provided with a temperature control unit, and the temperature of the ink in the head is within the predetermined temperature range. So that it is controlled.

  However, when the ink is circulated, the ink temperature is easily affected by the environmental temperature. For this reason, if ink circulated at a high flow rate and a high flow rate is supplied as it is to the inkjet head during recording, it becomes difficult to control the ink temperature within a predetermined temperature range by the head temperature control unit. In this case, the ink temperature is controlled within a predetermined temperature range, which causes a problem that energy consumption becomes large. In addition, when ink flows at a high flow rate in the ink jet head, the ink in the pressure chamber is pulled by the circulating ink, which causes a problem that it is difficult to control the negative pressure.

  Therefore, the present invention can prevent sedimentation of the pigment in the ink supply path, can reliably control the temperature of the ink in the ink jet head, can suppress energy consumption, and can further reduce the ink consumption in the pressure chamber of the ink jet head. An ink jet recording apparatus capable of easily controlling negative pressure and an ink supply method for the recording apparatus are provided.

  The present invention provides an ink tank containing ink, a pressure chamber having a nozzle, an ink jet head that discharges ink in the pressure chamber from the nozzle during recording, and replenishes the pressure chamber with ink in a common ink chamber, and an ink tank A first ink supply path that circulates the ink without passing through the inkjet head, and a part of the ink from the middle of the first ink supply path, and a common ink chamber of the inkjet head The ink jet recording apparatus includes a second ink supply path having a large flow path resistance to be circulated through the second ink supply path.

  In addition, the present invention provides an ink tank in an ink jet recording apparatus provided with an ink jet head provided with a pressure chamber having a nozzle, and discharging ink from the pressure chamber from the nozzle during recording and replenishing the pressure chamber with ink in the common ink chamber. Are circulated through the first ink supply path having a small flow path resistance without passing through the ink jet head, and a part of the ink is circulated from the middle of the first ink supply path to the second with a large flow path resistance. In the ink supply method, the ink is taken into the ink supply path and circulated through the common ink chamber of the inkjet head, and the ink is stirred by the circulation of the ink through the first ink supply path.

  According to the present invention, the sedimentation of the pigment in the ink supply path can be prevented, the temperature control of the ink in the ink jet head can be reliably performed, the energy consumption can be suppressed, and the ink in the pressure chamber of the ink jet head can be suppressed. An ink jet recording apparatus capable of easily controlling negative pressure and an ink supply method for the recording apparatus can be provided.

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

(First embodiment)
As shown in FIG. 1, a main tank 1 containing ink is provided, an ink supply path 3 is communicated from the main tank 1 to a sub tank 2 functioning as an ink tank, and a liquid feed pump 4 is provided in the middle of the ink supply path 3. Is provided. As the ink, for example, white ink containing a large amount of titanium oxide pigment is used.

  The ink in the main tank 1 is sent through the ink supply path 3 by driving the liquid feed pump 4 when the amount of ink in the sub tank 2 becomes a predetermined amount or less. The detection of whether or not the amount of ink in the sub tank 2 has become a predetermined amount or less can be detected by detecting the weight of the sub tank 2 with a weight sensor, for example. In addition to the weight sensor, it is also possible to detect from the ink level using a liquid level sensor.

  In the figure, reference numeral 5 denotes an ink jet head provided with a number of pressure chambers 6 each having a nozzle, and the ink jet head 5 pressurizes the ink in each pressure chamber 6 by a deformation operation of a piezoelectric element during recording and ejects the ink from the nozzles. In addition, the pressure chamber 6 is replenished with ink in the common ink chamber 7. The ink jet head is not limited to a type in which ink is pressurized by a piezoelectric element and ejected from a nozzle, and a thermal ink jet type in which ink is heated and ejected may be used.

  The sub tank 2 is provided with a first ink supply path 8 having a small flow path resistance for circulating the ink in the sub tank 2 without passing through the ink jet head 5. The first ink supply path 8 has a larger flow path diameter to reduce flow path resistance. In addition, as a method for reducing the flow path resistance, there is a method of using a material having a low flow path resistance as a material for forming the flow path.

  A circulation pump 9 is provided on the upstream side of the first ink supply path 8. By the operation of the circulation pump 9, the ink in the sub tank 2 is sucked up from one end of the first ink supply path 8, and the ink flows through the first ink supply path 8 at a high flow rate and at a high flow rate, and the above-mentioned ink flows from the other end. It is circulated by being returned into the sub tank 2.

  A part of the second ink supply path 10 having a large flow resistance between a portion downstream of the circulation pump 9 disposed in the first ink supply path 8 and one end side of the common ink chamber 7 of the inkjet head 5. 10a is communicated. A part 10 a of the second ink supply path 10 divides a part of the ink flowing through the first ink supply path 8 and supplies it to the common ink chamber 7 of the inkjet head 5.

  The second end side of the common ink chamber 7 of the inkjet head 5 and a portion further downstream of the first ink supply path 8 than the communication portion of the part 10a of the second ink supply path 10 are defined in the second. The remaining part 10b of the ink supply path 10 is communicated. The remaining part 10 b of the second ink supply path 10 returns the ink that has passed through the common ink chamber 7 to the first ink supply path 8.

  Heat generating elements 11 and 12 constituting a temperature control unit are attached around the ink jet head 5 and in the vicinity of the head connecting portion of the part 10a of the second ink supply path 10, and the heat generating elements 11 and 12 generate heat. By controlling, the temperature of the ink in the head 5 is controlled so as to always fall within a predetermined temperature range. The second ink supply path 10 has a smaller flow path diameter and a larger flow path resistance. In addition, as a method for increasing the channel resistance, there is another method in which a material having a large channel resistance is used as a material for forming the channel.

In the first ink supply path 8, the first ink supply path 8 flows between the communication part with the part 10 a of the second ink supply path 10 and the communication part with the remaining part 10 b. A first flow rate adjusting electromagnetic valve 13 for adjusting the flow rate of ink is disposed. Further, a second flow rate adjusting electromagnetic valve 14 for adjusting the flow rate of the ink flowing through the second ink supply path 10 is disposed in the remaining part 10 b of the second ink supply path 10.
The sub tank 2 agitates the ink inside by rotating a rod-shaped iron member 16 disposed at the bottom of the tank using, for example, a magnet stirrer 15.

  In such a configuration, the ink in the sub-tank 2 is agitated by rotating the rod-shaped iron member 16 by the magnet stirrer 15, and the sedimentation of the pigment in the ink is prevented. In addition, the ink in the sub tank 2 is circulated through the first ink supply path 8 by the operation of the circulation pump 9. Before the ink is supplied to the inkjet head 5, the first flow rate adjusting electromagnetic valve 13 is in a fully open state or almost fully open, and the ink has a high flow rate through the first ink supply path 8 having a low flow resistance. It circulates at a high flow rate. Therefore, the pigment in the ink does not settle in the first ink supply path 8.

  When the ink is supplied to the inkjet head 5, the first flow rate adjusting electromagnetic valve 13 is narrowed to 70% or 80%, for example, with respect to the fully open state. Further, the second flow rate adjusting electromagnetic valve 14 is temporarily closed. As a result, the ink is diverted from the first ink supply path 8 to a part 10 a of the second ink supply path 10, and the diverted ink is supplied to the common ink chamber 7 of the inkjet head 5. And since the 2nd flow volume adjustment solenoid valve 14 is closed, the ink of the common ink chamber 7 is sent into each pressure chamber 6, and comes to leak from a nozzle. In this way, the pressure chamber 6 and the nozzle are cleaned.

  Subsequently, the second flow rate adjusting electromagnetic valve 14 is opened, whereby the ink in the common ink chamber 7 passes through the remaining part 10 b of the second ink supply path 10 to the first ink supply path 8. Will come back. In this way, a part of the ink circulating in the first ink supply path 8 becomes part of the second ink supply path 10a → the common ink chamber 7 of the inkjet head 5 → the rest of the second ink supply path 10. It circulates in the route of the part 10b. At this time, the negative pressure applied to the ink in the pressure chamber 6 of the inkjet head 5 is controlled to be constant by adjusting the second flow rate adjusting electromagnetic valve 14 so that the ink does not leak from the nozzle.

  In this way, the inkjet head 5 stands by for the recording operation. Further, the ink in the ink jet head 5 is controlled to enter a predetermined temperature range by temperature control by the heating elements 11 and 12, and the viscosity of the ink is kept substantially constant. At the time of recording, the inkjet head 5 deforms the piezoelectric element in each pressure chamber 6 according to the print data to apply pressure to the ink, and ink droplets are ejected from the nozzles. Then, the ink consumed in each pressure chamber 6 is replenished from the common ink chamber 7.

  In this manner, in the sub tank 2, the rod-shaped iron member 16 is rotated by the magnet stirrer 15 and the ink is agitated, so that precipitation of the pigment in the ink is prevented. In addition, in the first ink supply path 8 through which the ink circulates, the ink flows at a high flow rate and at a high flow rate, so that the state is the same as the stirring state, and the precipitation of the pigment in the ink is prevented.

  The ink supplied to the inkjet head 5 has a part 10 a of the second ink supply path 10 having a large flow path resistance, a common ink chamber 7 of the inkjet head 5, and a remaining part 10 b of the second ink supply path 10. Since it flows via the, it will flow at a low flow rate and at a slow flow rate. For this reason, the temperature management of the ink in an inkjet head can be performed only by the heat generating elements 11 and 12. That is, by controlling the temperature of the heating elements 11 and 12, the temperature of the ink in the ink jet head can be controlled to fall within a predetermined temperature range.

  Thereby, the viscosity of the ink can always be maintained within a predetermined range, and stable ink discharge can be performed. Further, it is only necessary to manage the temperature of the ink in the inkjet head. For example, the energy consumption by the heating element can be sufficiently suppressed as compared with the case where the temperature of the ink in the sub tank 2 is managed. Further, since the ink flowing into the common ink chamber 7 has a small flow rate and a low speed, the negative pressure of the ink in the pressure chamber 6 can be easily controlled to be constant by adjusting the second flow rate adjusting electromagnetic valve 14. it can.

  For the ink in the second ink supply path 10, if the first flow rate adjusting electromagnetic valve 13 is narrowed down and the second flow rate adjusting electromagnetic valve 14 is closed, a part 10 a of the second ink supply path 10 and the ink jet are arranged. Ink can be discharged from the nozzles via the head 5, and if the second flow rate adjusting electromagnetic valve 14 is fully opened, a part 10 a of the second ink supply path 10, the inkjet head 5, and the second ink supply path 10 circulates ink through the remaining part 10b, and the flow rate can be increased to some extent by the degree of throttling of the first flow rate adjusting electromagnetic valve 13, so that sedimentation of the pigment in the ink is prevented as much as possible. Is possible.

  Further, since the volume in the second ink supply path 10 and the inkjet head 5 is not so large, it can be periodically cleaned using a separate cleaning liquid.

(Second Embodiment)
In addition, the same code | symbol is attached | subjected to the part same as embodiment mentioned above, and detailed description is abbreviate | omitted.
As shown in FIG. 2, the second ink supply path 101 is used as the second ink supply path having a large flow path resistance. Other configurations are the same as those of the first embodiment.

  The second ink supply path 101 has the same part 101a as the part 10a of the first embodiment. The difference is that the remaining part 101 b of the second ink supply path 101 is directly connected to the sub tank 2 without connecting the remaining part 101 b to the first ink supply path 8.

  In such a configuration, the negative pressure of the ink in each pressure chamber 6 of the inkjet head 5 can be controlled to be constant by controlling the flow rate of the ink flowing through the second ink supply path 101 to be always constant. it can. Thereby, the ink discharge from the nozzle of the inkjet head 5 can be stabilized.

  Since the other configuration is the same as that of the first embodiment, this embodiment can provide the same operational effects as those of the first embodiment described above.

(Third embodiment)
In addition, the same code | symbol is attached | subjected to the part same as embodiment mentioned above, and detailed description is abbreviate | omitted.
As shown in FIG. 3, the second ink supply path 102 is used as the second ink supply path having a large flow path resistance. The electromagnetic valve disposed in the second ink supply path 102 is an open / close electromagnetic valve 141 that only opens and closes the supply path.

  The part 102a of the second ink supply path 102 is the same as the part 10a of the first embodiment. The remaining part of the second ink supply path 102 is separated into two supply paths 102b1 and 102b2, the open / close electromagnetic valve 141 is arranged in the middle of the supply path 102b1, and circulates in the middle of the supply path 102b2. A pump 17 is arranged.

  One end of the supply path 102b1 communicates with the common ink chamber 7 of the ink jet head 5, and the other end communicates with a pressure adjusting mechanism 18 including a sealed tank. The supply path 102b2 has one end communicating with the pressure adjusting mechanism 18 and the other end communicating with the sub tank 2. The pressure in the tank of the pressure adjusting mechanism 18 is measured by a pressure gauge 19, and the circulation pump 17 is controlled according to the measured value to control the amount of ink to be circulated.

  Also in the pressure adjusting mechanism 18, the ink in the tank is agitated by rotating a rod-shaped iron member 21 using a magnetic stirrer 20. Other configurations are the same as those of the first embodiment.

  In such a configuration, the flow rate of the ink diverted from the first ink supply path 8 and flowing in the second ink supply path 102 and the inkjet head 5 is the negative flow of the ink in each pressure chamber 6 of the inkjet head 5. It is automatically controlled by the pressure adjusting mechanism 18 so that the pressure becomes constant.

  That is, when the flow rate of the ink flowing in the second ink supply path 102b1 and the ink jet head 5 increases, the pressure in the tank of the pressure adjusting mechanism 18 increases, so the pressure gauge 19 measures the pressure and the operation of the circulation pump 17 is performed. The pressure in the tank of the pressure adjusting mechanism 18 is lowered. Conversely, when the flow rate of the ink flowing through the second ink supply path 102b1 and the inkjet head 5 decreases, the pressure in the tank of the pressure adjusting mechanism 18 decreases, so the pressure gauge 19 measures it and the circulation pump 17 The operation is suppressed and the pressure in the tank of the pressure adjusting mechanism 18 is increased.

In this way, even if the flow rate of the ink flowing through the second ink supply path 102b1 and the inkjet head 5 changes, the pressure in the tank of the pressure adjusting mechanism 18 is controlled to be always constant, and each pressure chamber of the inkjet head 5 is controlled. The negative pressure of the ink in 6 is kept substantially constant. Thereby, the ink discharge from the nozzle of the inkjet head 5 can be stabilized.
Since the other configuration is the same as that of the first embodiment, this embodiment can provide the same operational effects as those of the first embodiment described above.

1 is a schematic configuration diagram of an ink jet recording apparatus according to a first embodiment of the present invention. FIG. 5 is a schematic configuration diagram of an ink jet recording apparatus according to a second embodiment of the present invention. FIG. 5 is a schematic configuration diagram of an ink jet recording apparatus according to a third embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Sub tank, 5 ... Inkjet head, 6 ... Pressure chamber, 7 ... Common ink chamber, 8 ... 1st ink supply path, 9 ... Circulation pump, 10 ... 2nd ink supply path, 11, 12 ... Heat generating body, 13 ... 1st flow control solenoid valve, 14 ... 2nd flow control solenoid valve.

Claims (9)

An ink tank containing ink;
An ink jet head for providing a pressure chamber having a nozzle, discharging ink from the pressure chamber from the nozzle during recording, and replenishing the pressure chamber with ink in a common ink chamber;
A first ink supply path having a small flow path resistance for circulating the ink in the ink tank without passing through the inkjet head;
An ink jet comprising a second ink supply path having a large flow resistance that takes in part of the ink from the middle of the first ink supply path and circulates it through the common ink chamber of the ink jet head. Recording device. The inkjet recording apparatus according to claim 1, wherein
The ink jet recording apparatus according to claim 1, wherein the first ink supply path includes a first flow rate adjusting valve that adjusts an ink flow rate on a downstream side of an ink diverting portion to the second ink supply path. The inkjet recording apparatus according to claim 2.
The inkjet recording apparatus, wherein the second ink supply path is provided with a second flow rate adjusting valve for adjusting an ink flow rate in the middle. The inkjet recording apparatus according to claim 1 or 2,
The ink jet recording apparatus according to claim 1, wherein the second ink supply path is provided with a pressure adjusting mechanism for adjusting a negative pressure applied to the ink in the pressure chamber of the ink jet head to be constant. The inkjet recording apparatus according to any one of claims 1 to 4,
The ink jet recording apparatus, wherein the second ink supply path is provided with a temperature control unit for controlling the temperature of the circulating ink to a predetermined temperature. In an ink jet recording apparatus comprising a pressure chamber having a nozzle, and having an ink jet head for discharging ink in the pressure chamber from the nozzle during recording and replenishing the pressure chamber with ink in a common ink chamber,
Circulating the ink in the ink tank through the first ink supply path having a low flow path resistance without passing through the inkjet head;
A portion of the ink from the middle of the first ink supply path is taken into a second ink supply path having a large flow path resistance and circulated through the common ink chamber of the inkjet head;
An ink supply method for an ink jet recording apparatus, wherein the ink is agitated by circulation of ink through the first ink supply path. The ink supply method for an ink jet recording apparatus according to claim 6.
An ink supply method for an ink jet recording apparatus, comprising: controlling an ink flow rate to be diverted to the second ink supply path by suppressing an ink flow rate flowing to the first ink supply path. The ink supply method for an ink jet recording apparatus according to claim 6 or 7,
An ink supply method for an ink jet recording apparatus, wherein a negative pressure applied to ink in a pressure chamber of the ink jet head is adjusted to be constant by controlling a flow rate of ink flowing in the second ink supply path. The ink supply method for an ink jet recording apparatus according to any one of claims 6 to 8,
An ink supply method for an ink jet recording apparatus, wherein the ink flow is forcibly discharged from the nozzles of the ink jet head by controlling the flow rate of ink flowing in the second ink supply path.

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