JP2006150745A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent bubbles from being entrained into a recording head from a nozzle during an ink circulatory action and a waste ink from being wastefully discharged from the nozzle during a pressurizing recovery action. <P>SOLUTION: This inkjet recording device comprises a recording head 1 which forms an image by depositing the ink to a recording medium such as paper by discharging the ink from a plurality of the nozzles 1b, an ink supply means such as main pump 5 for supplying the ink to the recording head 1, a buffer tank 4 which is installed in an ink flow path 6b setting the recording head 1 and the ink supply means in a mutually continuity state, a buffer tank 4 with an air buffer 4b, and a pilot pressure means for pilot-pressurizing the inner pressure of the buffer tank 4. When the ink is supplied to the recording head 1 through he buffer tank 4, the inner pressure of the buffer tank 4 is pilot-pressurized beforehand to a specified pressure level by the pilot pressure means, and thereafter, the ink is supplied to the recording head 1 through the buffer tank 4 by the ink supply means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus having an ink supply / recovery mechanism used in an image forming apparatus such as a printer, a FAX, and a copying machine, and an ink supply method used in the apparatus, and more specifically, full line type recording. The present invention relates to an ink jet recording apparatus having a head and an ink circulation system used in the apparatus.

  An ink jet recording apparatus performs image recording such as printing by ejecting ink from a recording head and adhering it to a recording medium. The recording head can be easily made compact and can record high-definition images at high speed. Therefore, the running cost is low, the non-impact method is low in noise, and it is easy to record a color image using multicolor inks. In particular, a full line type ink jet recording apparatus using a line type recording head in which a large number of ejection nozzles are arranged in the width direction of the recording medium can further increase the recording speed.

  However, if the bubbles generated by the ejection of ink droplets are not dissolved in the ink in the liquid chamber inside the recording head but accumulate in the head liquid chamber, the sub tank for temporarily storing the ink supplied to the recording head Therefore, there is a risk that ink discharge may be hindered when ink is supplied to the discharge nozzle of the recording head. In addition, in the case of a thermal type full-line type ink jet recording apparatus that discharges ink droplets by foaming, the recording head may rapidly increase in temperature due to high duty printing in one pass. There arises a problem that the life of the recording head is reduced or the print quality is adversely affected by the thermal expansion of the recording head. Accordingly, the ink is circulated between the ink tank and the recording head as a mechanism for discharging bubbles generated by the ejection to the outside of the head liquid chamber and as a mechanism for cooling the recording head that is heated during printing. In many cases, a so-called ink circulation system is employed (see Patent Document 1).

In an ink supply apparatus employing such an ink circulation system, a buffer tank having an air buffer for absorbing flow rate fluctuations due to pulsation is provided in the ink supply path so that pump pulsation does not cause fluctuations in ink droplet discharge amount. Is provided.
Japanese Patent Laid-Open No. 10-138515

  However, when ink is supplied to the recording head via the buffer tank, for a while after the ink supply starts, the flow rate of the ink flowing into the recording head is reduced due to the effect of absorbing the flow fluctuation by the air buffer. As a result, if the ink flow is gradually increased asymptotically, the flow rate of the outflow ink from the print head exceeds the flow rate of the inflow ink, and bubbles are generated from the nozzles into the printhead. If there is a problem of drawing in, and if it is a pressure recovery operation to eliminate nozzle clogging, the flow of ink flowing into the print head will reach the flow rate required for pressure recovery. In addition, there was a problem that waste ink was discharged from the nozzle.

  The present invention has been conceived in order to solve the above-described technical problem, and an object of the present invention is to rapidly approximate the flow rate of ink supplied to the print head via the buffer tank to the average flow rate of the pump. An ink jet recording apparatus including an ink supply apparatus having a mechanism for the above is provided.

  In order to achieve the above object, an ink jet recording apparatus of the present invention includes an ink jet recording head that forms an image by ejecting ink from a plurality of nozzles to adhere to a recording medium, and an ink for supplying ink to the recording head. In the ink jet recording apparatus having a supply means, a buffer tank having an air buffer provided in an ink flow path that conducts the recording head and the ink supply means, and a preload means for preloading the internal pressure of the buffer tank When the ink is supplied to the recording head via the buffer tank, the internal pressure of the buffer tank is pre-pressurized to a predetermined pressure by the pre-loading means, and then the buffer is supplied by the ink supply means. Ink is supplied to the recording head through a tank.

  As described above, according to the present invention, before the supply of ink to the recording head via the buffer tank is started, the internal pressure of the buffer tank is pre-pressurized, so that the flow rate of ink flowing into the recording head is reduced. The ink supply flow rate of the pump, which is the supply means, can be reached quickly, and an insufficient ink supply amount to the recording head can be prevented. As a result, bubbles can be prevented from being drawn from the nozzles if the ink circulation operation is performed, and wasteful waste ink can be prevented from being discharged if the pressure recovery operation is performed to eliminate clogging of the nozzles.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is an explanatory diagram for explaining an ink supply path of the ink jet recording apparatus according to the first embodiment of the present invention. The present embodiment is mainly an ink supply apparatus including a recording head 1, a main tank 2, a sub tank 3, a buffer tank 4, and a main pump 5.

  An ink supply needle 2a is pierced into the ink supply port of the main tank 2 formed of a flexible ink bag containing ink, and the main tank 5 opens and closes the main tank on-off valve 7a and the ink by forward rotation of the main pump 5. Ink can be supplied to the sub-tank 3 through the flow path 6 a and through the flow meter 8. Since the ink supply port of the main tank 2 is connected to the ink supply needle 2a, the elastic material such as rubber (not shown) is provided so that the ink does not leak when the ink supply needle is inserted and removed. ing.

  Here, the sub-tank 3 includes an opening / closing valve 7d for opening and closing an atmosphere communication port for communicating the atmosphere and the inside of the sub-tank, and a full-tank detection sensor 3a for detecting that the ink in the sub-tank is full. , And an empty detection sensor 3b for detecting that it is empty. One of the on-off valves 7d is provided with an air filter 3c for preventing dust from entering the sub tank.

  In the sub tank, the position where the full tank detection sensor 3a is provided is determined so that the air buffer 3d having a predetermined capacity remains even when the ink is full. As the sky detection sensor 3b and the full tank detection sensor 3a, for example, an optical detection type composed of an LED, an optical prism, and a photo sensor can be considered.

  The ink in the sub tank 3 can be exchanged with the ink in the recording head 1 through the ink flow path 6c, but the ink exchange is blocked by the on-off valve 7c provided in the ink flow path 6c. You can also

  Further, the ink in the sub tank 3 can be supplied to the recording head 1 by reversing the main pump 5 through the ink flow path 6a, the buffer tank 4, and the ink flow path 6b. In this case, the on-off valves 7b and 7e provided in the ink flow path 6b are opened, and the on-off valve 7a of the main tank is closed.

  Here, the buffer tank 4 has a pressure sensor 4a that detects internal pressure, an air buffer 4b that absorbs flow fluctuation due to pulsation of the main pump 5, and an internal pressure that exceeds a certain limit due to abnormality detection of the pressure sensor 4a. An explosion-proof valve 4c that passively vents the air buffer by a spring mechanism or the like to prevent the buffer tank 4 from rupturing, an ink outlet 4d, and an ink outlet 4e provided at a position higher than the ink outlet 4d. And.

  As the on-off valves 7a, 7b, 7c, 7d, and 7e, a solenoid on-off valve that is actively operated with a valve function by providing a solenoid plunger with a sealing function can be considered. In this embodiment, the on-off valve 7a is opened when the solenoid power is on and closed when off, and the on-off valves 7b, 7c, 7d, and 7e are closed when the solenoid power is on and open when off. Each has a configuration. The main pump 5 is optimally a tube pump, a cylinder pump, or the like that can be pumped in both directions by reversing the drive source (motor).

  The recording head 1 is connected to ink flow paths 6b and 6c via filters 1d and 1f for preventing dust from entering the head, respectively. Ink discharged from the nozzles 1b of the recording head 1 by a pressure recovery operation and a circulation operation, which will be described later, is once received by the cap 9 and then recovered by the sub pump 10 to the waste ink recovery tank 11.

  Next, various ink supply operations of the ink jet recording apparatus according to the first embodiment of the present invention will be described with reference to the flowcharts of FIGS. Hereinafter, a tube pump will be described as an example of the main pump 5.

1) Ink filling operation to the sub-tank 3 When the sub-tank 3 is filled with ink, the ink capacity of the sub-tank 3 is first checked as shown in FIG. That is, if it is detected that the full tank detection sensor 3a is full (step S2-1), the state of the sky detection sensor 3b is checked (step S2-2), and if it is detected that it is empty. Since either or both of the full tank detection sensor 3a and the sky detection sensor 3b are considered to be erroneously detected, the user is notified that the sensor is abnormal (step S2-3). Stop.

  On the other hand, if it is detected in step S2-1 that the sub tank 3 is not full, ink filling from the main tank 2 to the sub tank 3 is performed according to the following procedure. First, the ink flow path between the main tank 2 and the sub tank 3 is opened by closing the on-off valve 7b and opening the on-off valve 7a (step S2-4). At this time, whether to close the on-off valve 7c and shut off the ink flow path 6c can be selected depending on the mode (SW = ON / OFF). Next, the flow rate of the main pump 5 is set, and the driving of the main pump 5 is started (step S2-5). When the sub tank 3 becomes full, the main pump 5 is stopped and the flow rate setting is returned to the default value (step S2-7). If the on-off valve 7b is immediately opened here, if the pressure in the ink flow path 6a, which has been reduced due to the pressure loss of the ink supply needle 2a, has not recovered to atmospheric pressure, bubbles are generated from the nozzle 1b of the recording head 1 through the ink flow path 6b. Since there is a risk of drawing into the recording head, first, the on-off valve 7a is closed to prevent backflow to the main tank 2 (step S2-8), the tube lock (not shown) of the main pump 5 is released, and the ink flow path 6a. Is communicated with the sub-tank 3 (step S2-9) and waits until the pressure of the flow path 6a is restored to the atmospheric pressure (step S2-10), and the tube is locked (step S3-11). The path 6a is shut off, and the on-off valves 7b and 7c are returned to the default state (step S2-12), and the ink filling operation to the sub tank 3 is completed.

2) Operation during printing During printing, as shown in FIG. 3, the ink supply system confirms the print flag set during printing by a printing sequence (not shown) (step S3-1) and the recording head 1 (not shown). Confirmation of the circulation flag during printing (step S3-3) that is set when the temperature monitoring system determines that the recording head 1 needs to be cooled by circulation during printing (step S3-3), and confirmation of whether the sub tank 3 is empty (step S3). -4).

  First, if the print flag is OFF in step S3-1, it is determined that printing is completed. In step S3-2, the ink filling of the sub tank 4 is switched to the SW = ON mode (the ink supply to the recording head is shut off by the on-off valve 7c. The sub-tank filling is performed and the print mode is terminated. In step S3-4, the state of the sub tank 4 empty detection sensor 3b is checked. If it is detected that the sub tank 4 is empty, it is determined that the ink in the sub tank 4 has become empty by printing, and the sub tank is filled with ink. SW = OFF mode (opening on-off valve 7c and continuing printing while filling subtank).

  On the other hand, if the circulation flag during printing is ON in step S3-3, it is determined that circulation during printing is started, and the state of each on-off valve, the direction of the main pump 5 and the flow rate setting are left as default, and in step S3-6. The drive of the main pump 5 is started. Then, in FIG. 1, the ink in the sub tank 3 is transferred from the main pump 5 through the ink flow path 6c, the large-area filter 1f for refill, the common liquid chamber 1a, the filter 1d, the ink flow path 6b, the buffer tank 4, and the ink flow path 6a. And sucked into the sub tank 3 again. Thus, the bubbles in all the flow paths are collected in the sub tank, and at the same time, the recording head 1 is cooled by the ink flow in the common liquid chamber 1a.

  At this time, since the area of the filter 1f is sufficiently large and the flow resistance combined with the ink flow path 6c is sufficiently small, the internal pressure of the common liquid chamber 1a is not excessively negative, and the meniscus of the nozzle 1b is not broken. Although the ink flowing through the ink flow path 6a is pulsated by the main pump 5, the pulsation of the ink flowing through the ink flow path 6b, the common liquid chamber 1a, and the ink flow path 6c is greatly suppressed through the buffer tank 4. The effect on printing is negligible. In addition, the flow resistance of the filter 1d causes negative pressure in the ink flow path 6b, the buffer tank 4, and the ink flow path 6a, the air buffer 4b expands, and excess air is discharged from the ink outflow inlet 4d to the sub tank 3. Collected. In this ink circulation, the capacity of the air buffer 4b in the steady state when excess air is not discharged becomes the default capacity.

  During ink circulation, it continues to check whether the circulation flag during printing is set (step S3-7) and whether the sub tank 3 is empty (step S3-8). When the sub tank becomes empty during ink circulation, the main pump 5 is temporarily stopped (step S3-9), and the flow path is switched to the main tank 2 by the on-off valves 7a and 7b to fill the sub tank with ink (step S3-10). ) After that, the main pump 5 is driven again to restart the ink circulation.

When the circulation flag during printing is turned off, it is determined that the circulation during printing is finished, the main pump 5 is stopped (step S3-11), the tube lock (not shown) is released, the sub tank 3, the buffer tank 4, and the ink flow path. 6b is made to communicate (step S3-12). When the pressure sensor 4a detects that the internal pressure of the buffer tank has recovered to P _ref− (slightly lower than atmospheric pressure) (step S3-13), the main pump 5 is tube-locked (step S3-14). Complete post-processing of circulation and return to the confirmation sequence during printing.

3) Pressure recovery operation As the printing is repeated, the ink inside the nozzle 1b of the recording head 1 gradually thickens due to evaporation of moisture from the nozzle 1b due to the temperature rise. Vomiting occurs. Further, even if bubbles mixed in the ink from the nozzle 1b are accumulated in the nozzle, an undischarge phenomenon occurs. In order to prevent this discharge failure phenomenon, the pressure recovery operation is performed according to the procedure shown in FIG. 4 to eliminate the discharge failure phenomenon.

First, the sub tank 3 is filled in the SW = ON mode (step S4-1), and a sufficient ink amount is secured in the sub tank 3 for the pressure recovery. Next, as a preparation for preloading the buffer tank 4, the on-off valves 7c and 7e are closed (step S4-2). At this time, the on-off valve 7a is closed and the on-off valves 7b, 7d are opened. Next, set the flow rate of the main pump 5 to Q _pur (pump flow rate for pressure recovery), set the liquid feed direction to reverse (the direction of the buffer tank 4), and drive the main pump 5 to start preloading. (Step S4-3).

When it is detected by the pressure sensor 4a that the internal pressure of the buffer tank has reached the initial pressure P _pur when pressure is restored (step S4-4), only the on-off valve 7e is opened (step S4-5). Recovery time: During the period of T _pur seconds, ink is sent into the recording head 1 through the ink flow path 6b, the ink inlet 1c, and the filter 1d, and at the same time, the ink flows into the buffer tank 4 at a flow rate: Q _pur. to continue. All the ink sent to the recording head 1 is discharged from the nozzle 1b to the cap 9. It is desirable that P _pur be equal to the time average pressure of the buffer tank internal pressure in the steady state when the pressure is restored.

After performing pressure recovery for T _pur seconds in this manner (step S4-6), the main pump 5 is stopped and the liquid feeding direction and flow rate are returned to the default (step S4-7). Then, the opening / closing valve 7c is opened (step S4-8), and the tube lock (not shown) of the main pump 5 is released (step S4-9), so that the buffer tank 4, the ink flow path 6b, and the inside of the recording head 1 are opened to the atmosphere. The sub-tank 3 is communicated, and the pressure of the entire flow path is returned to the pressure of the water head difference from the sub-tank 3. When the pressure sensor 4a detects that the internal pressure of the buffer tank has dropped to P _{ref +} (slightly higher than atmospheric pressure) (step S4-10), the main pump 5 is locked (step S4-11). The post-processing is completed, and the sub tank 3 is replenished with the ink reduced by the pressure recovery (step S4-13), and the pressure recovery operation is completed.

4) Air venting circulation operation When ink is supplied from the sub tank 3 to the recording head 1 during printing, bubbles may be mixed in the supplied ink. If this bubble accumulates in the vicinity of the ink outflow inlet 1e above the filter 1f, the ink refill may be hindered. Therefore, it is necessary to periodically perform an air vent circulation operation as shown in FIG.

First, in order to make the air buffer 3d have a predetermined capacity, the sub tank 3 is filled to the full tank in the SW = ON mode (step S5-1). Next, as a preparation for preloading the buffer tank 4, the on-off valves 7c and 7e are closed (step S5-2). At this time, the on-off valve 7a is closed and the on-off valves 7b, 7d are opened. Next, set the flow rate of the main pump 5 to Q _invcir (pump flow rate for air venting circulation), set the liquid feed direction to reverse (the direction of the buffer tank 4), and drive the main pump 5 to start preloading. (Step S5-3).

When it is detected by the pressure sensor 4a that the internal pressure of the buffer tank has reached the initial pressure: _Pinvcir during the air venting circulation (step S5-4), the main pump 5 is stopped and the liquid feeding direction and flow rate are returned to the default. Then, the preload is finished (step S5-5). In addition, it is desirable that _Pinvcir is made to coincide with the time average pressure of the buffer tank internal pressure in the steady state during the air bleeding circulation. Next, in order to return the air buffer 3d of the sub-tank 3 increased by the preload to a predetermined capacity, the sub-tank 3 is filled to the full tank again in the SW = ON mode (step S5-7).

Since the on-off valve 7c is returned to the default open state in the sub-tank filling sequence, the on-off valve 7c is closed again (step S5-8), and the flow rate of the main pump 5 is set to Q _invcir (pump flow rate for air venting circulation). Then, the liquid feeding direction is set in the reverse direction (the direction of the buffer tank 4), and the main pump 5 is driven to start the air vent circulation circulation (to prevent the backflow from the buffer tank 4) (step S5-9). . After running for about 1 second, the on-off valves 7c and 7e are opened, the on-off valve 7d is closed, the sub-tank 3 is sealed (step S5-11), and air venting circulation is started.

  Then, the flow rate of the ink flowing into the recording head 1 from the pre-pressurized buffer tank 4 via the ink flow path 6b immediately becomes a steady state, whereas recording is performed via the ink flow path 6c in the sub-tank 3 which is not preloaded. The flow rate of ink flowing out of the head increases only gradually at the beginning of the air bleeding circulation due to the buffering action of the air buffer 3d (expansion of the air buffer 3d). For this reason, the ink balance in the recording head 1 shows an excessive inflow tendency and the ink is discharged from the nozzle 1b. In order to suppress the amount of waste ink at this time, it is necessary to suppress the capacity and circulation flow rate of the air buffer 3d and the preload amount of the buffer tank 4 to the minimum necessary. As the expansion of the air buffer 3d subsides, the ink flowing out from the recording head 1 becomes almost equal to the flow rate of the main pump 4, and the internal pressure of the common liquid chamber 1a that is in communication with the atmosphere through the nozzle 1b gradually approaches the atmospheric pressure. As a result, the ink discharged from the nozzle 1b gradually disappears.

In this way, air circulation for _Tinvcir seconds is performed. If the circulation command from the host of the ink jet recording apparatus is withdrawn during that time (step S5-14), the main pump 5 is stopped and the liquid feeding direction and flow rate are returned to the default. The air bleeding circulation is terminated (step S5-15).

At this time, if the inside of the sub-tank 3 is left at a negative pressure, ink flows out of the recording head 1 to the sub-tank 3 due to a pressure difference from the internal pressure of the recording head 1 which is almost atmospheric pressure, and bubbles are recorded from the nozzle 1c. Since there is a risk of being drawn into the head 1, the open / close valve 7d is opened to take in the outside air into the sub tank 3, and at the same time, the open / close valves 7c and 7e are closed to shut off the recording head from the sub tank 3 and the buffer tank 4 ( Step S5-16) The tube lock of the main pump 5 is also released (Step S5-17), and the internal pressure of the sub tank 3 and the buffer tank 4 is reduced to atmospheric pressure by allowing ink to flow from the positive pressure buffer tank 4 to the sub tank 3. Let me recover. After about 2 seconds, the on-off valve 7c is opened (steps S5-18 and S5-19), and the sub-tank 3 recovered to the atmospheric pressure is connected to the recording head 1, and the internal pressure of the buffer tank is adjusted to P _{ref +} ( When it is detected that the pressure has dropped to a pressure slightly higher than the atmospheric pressure (step S5-20), the tube of the main pump 5 is locked (step S5-21). The sub-tank 3 is replenished with the reduced amount of ink (step S5-24), and the air bleed circulation operation is completed.

(Second Embodiment)
FIG. 6 is a diagram showing the configuration of the ink supply path of the ink jet recording apparatus according to the second embodiment of the present invention.

  In the configuration of the ink supply path of the ink jet recording apparatus of the first embodiment shown in FIG. 1, the pressure sensor 4a is used to detect the preload level of the buffer tank 4, but in this embodiment, the ink in the buffer tank 4 is used. The liquid level is detected by the liquid level detection sensor 4f and the capacity of the air buffer 4b is monitored to determine the preload level.

  The structure of components other than the preload level detection method is the same as that shown in FIG. Also, the sequence of various ink supply operations in the present embodiment is the same as in FIGS. 2 to 5 representing the various ink supply operations in the first embodiment. Omit.

  By using the preload level detection system as described above, the full tank / empty detection sensors 3a and 3b of the sub tank 3 can be used in common, and the cost of the ink supply device can be reduced.

(Third embodiment)
FIG. 7 is a diagram showing the configuration of the ink supply path of the ink jet recording apparatus according to the third embodiment of the present invention.

  Unlike the configuration of the ink supply path of the ink jet recording apparatus according to the first embodiment shown in FIG. 1 or the second embodiment shown in FIG. 6, the present embodiment does not have a means for detecting the preload level of the buffer tank 4. In some cases, the preload level is determined by determining the volume of ink that the main pump 5 has sent to the buffer tank 4 by pump flow rate × pump drive time.

  The structure of components other than the preload level detection method is the same as that shown in FIG. Further, the sequence of various ink supply operations in the present embodiment is basically the same as the steps for detecting the preload level in FIGS. 2 to 5 representing the various ink supply operations in the first embodiment, but the weight processing for a predetermined time is changed. I won't change the explanation because it doesn't change.

  By adopting the preload level determination method as described above, the sensor for detecting the preload level can be eliminated, and the cost of the ink supply device can be reduced.

  Finally, characteristics of the ink jet recording apparatus based on the first to third embodiments will be described.

  The ink jet recording apparatus based on the first to third embodiments described above has, as a first configuration, a recording head 1 that forms an image by ejecting ink from a plurality of nozzles 1b and attaching it to a recording medium such as paper. And an ink supply means such as a main pump 5 for supplying ink to the recording head 1, provided in an ink flow path 6 b that connects the recording head 1 and the ink supply means. When the ink is supplied to the recording head 1 through the buffer tank 4, the buffer tank 4 having the air buffer 4b and the preloading means for preloading the internal pressure of the buffer tank 4 are preliminarily provided by the preloading means. The internal pressure of the ink is preloaded to a predetermined pressure, and then recording is performed via the buffer tank 4 by the ink supply means. And supplying ink to the head 1.

  According to the recording apparatus having such a first configuration, the internal pressure of the buffer tank 4 is pre-pressurized before the ink supply to the recording head 1 via the buffer tank 4 is started, so that the recording head 1 is supplied. The inflow ink flow rate can quickly reach the ink supply flow rate of the main pump 5 serving as the ink supply means, and the shortage of the ink supply amount to the recording head 1 can be prevented.

  In the ink jet recording apparatus having the first configuration, the preload means has an opening / closing valve 7e provided in the ink flow path 6b between the buffer tank 4 and the recording head 1, and closes the opening / closing valve 7e. In addition, the internal pressure of the buffer tank 4 is preloaded by flowing ink into the buffer tank 4 by the ink supply means.

  According to this, since the preloading means of the buffer tank 4 can be realized with the existing configuration except that one on-off valve 7e is added, the preloading means can be added at low cost.

  In addition, as a second configuration, the ink jet recording apparatus according to the first to third embodiments includes a recording head 1 that forms an image by ejecting ink from a plurality of nozzles 1b and attaching the ink to a recording medium; A sub-tank 3 for temporarily storing ink to be supplied to the recording head 1, and a main pump 5 for supplying ink in the sub-tank 3 to the recording head 1. In the ink jet recording apparatus having an ink circulation mechanism in which ink is sucked and ink flows from the sub tank 3 into the recording head 1 and the ink sucked from the recording head 1 is collected again in the sub tank 3. An open / close valve 7d serving as an air release valve is provided, and air is provided in the ink flow paths 6a and 6b that connect the recording head 1 and the main pump 5. A buffer tank 4 having a buffer 4 b is provided, and a first on-off valve 7 e is provided in the ink flow path 6 b between the buffer tank 4 and the print head 1, and an ink flow path between the sub tank 3 and the print head 1. 6c is provided with a second on-off valve 7c, respectively, and the first and second on-off valves 7e are opened by opening the atmosphere release valve 7d in a circulation mode opposite to the circulation by the ink circulation mechanism. 7c are closed, the main pump 5 is operated to cause the ink in the sub tank 3 to flow into the buffer tank 4 to preload the internal pressure of the buffer tank 4 to a predetermined pressure, and then the atmospheric release valve 7d. Is closed, both the first and second on-off valves 7e and 7c are opened, and ink circulation is started.

  According to the ink jet recording apparatus having the second configuration, the internal pressure of the buffer tank 4 is pre-pressurized before the ink circulation operation for supplying ink to the recording head 1 via the buffer tank 4 is performed, thereby 1 can quickly reach the ink supply flow rate of the pump, and the ink supply amount to the recording head 1 can be prevented from being insufficient to prevent bubbles from being drawn from the nozzles.

  In the ink jet recording apparatus having the second configuration, the predetermined pressure substantially matches a time average pressure of the buffer tank internal pressure when the circulation in the reverse circulation mode becomes a steady state.

  According to this, since the internal pressure of the buffer tank 4 has already become a steady state pressure immediately after the start of ink circulation, the flow rate of ink flowing into the recording head 1 reaches the ink supply flow rate of the main pump 5 in the shortest time. The amount of waste ink from the nozzle 1b after the start of ink circulation can be minimized.

  In addition, as a third configuration, the ink jet recording apparatus according to the first to third embodiments includes a recording head 1 that forms an image by ejecting ink from a plurality of nozzles 1b and attaching the ink to a recording medium; A sub-tank 3 for temporarily storing ink to be supplied to the recording head 1, and a main pump 5 for supplying ink in the sub-tank 3 to the recording head 1. In the ink jet recording apparatus having an ink circulation mechanism in which ink is sucked and ink flows from the sub tank 3 into the recording head 1 and the ink sucked from the recording head 1 is collected again in the sub tank 3. An open / close valve 7d serving as an air release valve is provided, and air is provided in the ink flow paths 6a and 6b that connect the recording head 1 and the main pump 5. A buffer tank 4 having a buffer 4 b is provided, and a first on-off valve 7 e is provided in the ink flow path 6 b between the buffer tank 4 and the print head 1, and an ink flow path between the sub tank 3 and the print head 1. 6c is provided with a second on-off valve 7c. In the pressure recovery mode in which ink is discharged from the nozzle 1b by pressurizing the ink in the recording head 1, the air release valve 7d is opened to open the air release valve 7d. With the first and second on-off valves 7e and 7c both closed, the main pump 5 is operated to cause the ink in the sub tank 3 to flow into the buffer tank 4 to preload the internal pressure of the buffer tank 4 to a predetermined pressure. Thereafter, the first on-off valve 7e is opened to recover the pressure.

  According to the ink jet recording apparatus having the third configuration, the internal pressure of the buffer tank 4 is pre-pressurized before the start of the pressure recovery operation for supplying ink to the recording head 1 via the buffer tank 4. The inflow ink flow rate to the head 1 can quickly reach the ink supply flow rate of the pump, and wasteful waste ink discharge can be suppressed.

  In the ink jet recording apparatus having the third configuration, the predetermined pressure substantially matches a time average pressure of the buffer tank internal pressure when the pressurization operation in the pressurization recovery mode becomes a steady state. .

  According to this, since the internal pressure of the buffer tank 4 has already become a steady state pressure immediately after the start of pressure recovery, the flow rate of the ink flowing into the recording head 1 can reach the ink supply flow rate of the pump in the shortest time. It is possible to minimize the waste ink discharge.

It is explanatory drawing for demonstrating the ink supply path | route of the inkjet recording device of 1st Embodiment of this invention. 3 is a flowchart for explaining an ink filling operation to a sub tank in the ink jet recording apparatus according to the first embodiment of the present invention. 3 is a flowchart for explaining an operation during printing in the ink jet recording apparatus according to the first embodiment of the present invention. 3 is a flowchart for explaining a pressure recovery operation in the ink jet recording apparatus according to the first embodiment of the present invention. 3 is a flowchart for explaining an air bleeding / circulating operation in the ink jet recording apparatus according to the first embodiment of the present invention. It is explanatory drawing for demonstrating the ink supply path | route of the inkjet recording device of 2nd Embodiment of this invention. It is explanatory drawing for demonstrating the ink supply path | route of the inkjet recording device of 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording head 2 Main tank 3 Sub tank 4 Buffer tank 5 Main pump 6a, 6b, 6c Ink flow path 7a, 7b, 7c, 7d, 7e On-off valve

Claims (6)

An ink jet recording head that forms an image by ejecting ink from a plurality of nozzles to adhere to the recording medium; and
An ink jet recording apparatus having ink supply means for supplying ink to the recording head;
A buffer tank having an air buffer provided in an ink flow path communicating with the recording head and the ink supply means; and a preload means for preloading the internal pressure of the buffer tank; When the ink is supplied to the recording head, the internal pressure of the buffer tank is pre-pressurized to the predetermined pressure in advance by the preloading means, and then the ink is supplied to the recording head via the buffer tank by the ink supply means. An ink jet recording apparatus.   The preload means has an open / close valve provided in an ink flow path between the buffer tank and the recording head, and closes the open / close valve and causes ink to flow into the buffer tank by the ink supply means. 2. The ink jet recording apparatus according to claim 1, wherein the internal pressure of the buffer tank is preloaded. An ink jet recording head that forms an image by ejecting ink from a plurality of nozzles to adhere to the recording medium; and
A sub tank for temporarily storing ink to be supplied to the recording head;
A pump for supplying ink in the sub tank to the recording head,
Ink jet equipped with an ink circulation mechanism in which ink in the recording head is sucked by the pump and ink flows from the sub tank into the recording head, and the ink sucked from the recording head is again collected in the sub tank. In the recording device,
The sub tank includes an air release valve, and a buffer tank having an air buffer is provided in an ink flow path that communicates the recording head and the pump, and an ink flow path between the buffer tank and the recording head. Are provided with a first on-off valve, and a second on-off valve is provided in the ink flow path between the sub tank and the recording head, respectively.
When the circulation operation in the direction opposite to the circulation by the ink circulation mechanism is performed, the pump is operated in a state in which both the first and second on-off valves are closed by opening the atmosphere release valve, and the inside of the sub tank The ink is poured into the buffer tank to preload the internal pressure of the buffer tank to a predetermined pressure, and then the atmosphere release valve is closed and both the first and second on-off valves are opened to start ink circulation. An ink jet recording apparatus.   4. The ink jet recording apparatus according to claim 3, wherein the predetermined pressure substantially coincides with a time average pressure of the buffer tank internal pressure when the reverse circulation operation becomes a steady state. An ink jet recording head that forms an image by ejecting ink from a plurality of nozzles to adhere to the recording medium; and
A sub tank for temporarily storing ink to be supplied to the recording head;
A pump for supplying ink in the sub tank to the recording head,
Ink jet equipped with an ink circulation mechanism in which ink in the recording head is sucked by the pump and ink flows from the sub tank into the recording head, and the ink sucked from the recording head is again collected in the sub tank. In the recording device,
The sub-tank includes an air release valve, and includes a buffer tank having an air buffer in an ink flow path communicating the recording head and the pump, and an ink flow path between the buffer tank and the recording head. Are provided with a first on-off valve, and a second on-off valve is provided in the ink flow path between the sub tank and the recording head, respectively.
When performing a pressure recovery operation for discharging ink from the nozzles by pressurizing the ink in the recording head, the air release valve is opened and the first and second on-off valves are both closed. The pump is operated to cause the ink in the sub-tank to flow into the buffer tank so that the internal pressure of the buffer tank is preloaded to a predetermined pressure, and then the first on-off valve is opened to recover the pressure. An inkjet recording apparatus.   6. The ink jet recording apparatus according to claim 5, wherein the predetermined pressure substantially coincides with a time average pressure of the buffer tank internal pressure when the pressure recovery operation is in a steady state.

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