JP2002240310A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder having an ink supply system ensuring stabilized ink ejection and exhibiting excellent image quality. SOLUTION: The ink jet recorder comprises a liquid container separated into a first liquid chamber being coupled with an interconnection passage branched from a passage for discharging gas stored in a first ink tank supplying ink to a recording head, and a second liquid chamber coupled with the first liquid chamber through the interconnection passage and having a hole communicating with the atmosphere wherein an appropriate quantity of liquid communicating freely between the first and second liquid chambers is present in the liquid container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus used for a printer or the like.
More specifically, the present invention relates to an ink supply and pressure adjustment mechanism in an ink supply system of an ink jet recording apparatus.

[0002]

2. Description of the Related Art In recent years, ink jet recording apparatuses for recording using ink have become widespread as printers and copiers for personal computers. Since the inkjet recording device is inexpensive and capable of full-color recording,
The demand is growing.

In recent years, ink jet recording apparatuses have been used even for plotters that record photographic images on large-size sheets such as A1 and A0 plates. Further, inkjet recording is being applied to recording of multi-tone images for medical use such as X-ray films and CT scan images. In such a medical image recording apparatus, by recording a plurality of types of inks having different densities twice and three times, it is possible to express much more gradations than the types of inks.

However, the plotter and the recording apparatus for medical images use a large amount of ink as compared with general OA equipment. Therefore, when the ink tank is mounted on the carriage together with the recording head, the ink tank is frequently used. The replacement has to be performed, which is inconvenient and the running cost is high. Therefore, an inkjet recording apparatus that consumes such a large amount of ink includes an ink tank having a large capacity on the main body side other than the carriage, and a mechanism (ink supply system) for supplying ink from the tank to the recording head. is there.

FIG. 5 is a simplified illustration for explaining the configuration of the ink supply system of such an ink jet recording apparatus.

[0006] The nozzle 2 and the ink tank 3 of the recording head 1
And the ink is continuously supplied to the nozzles 2 as the ink is ejected. Reference numeral 5 denotes a spare ink tank installed on the apparatus main body side, and is connected to the ink tank 3 by an ink supply tube 4. By adding the spare ink tank 5 and connecting it with the ink supply tube 4 and arranging it on the apparatus main body side instead of on the carriage, it becomes possible to hold a large amount of ink in the apparatus. Further, when even the ink in the spare ink tank 5 is significantly reduced, the image can be continuously recorded by replacing the spare ink tank 5 with a new one filled with ink. Since the air communication hole 5a is provided, the ink level of the spare ink tank 5 is always set to the atmospheric pressure.

A pump 11 for discharging air from the ink tank 3 for transferring ink from the spare ink tank 5 to the ink tank 3 not filled with ink.
When this is operated, the pressure in the ink tank 3 is reduced, and the ink in the preliminary ink tank 5 is pulled up through the ink supply tube 4. An ink supply valve 9 controls opening and closing of the flow of ink. The ink tank 3 and the pump 11 are connected by an exhaust tube 8,
An exhaust valve 10 necessary for sealing the ink tank 3 is provided. The order of the exhaust valve 10 and the pump 11 may be reversed, and the exhaust valve 10 may be omitted as long as the exhaust path can be sealed when the pump 11 is not operating. The exhaust valve 10 and the pump 11 are often arranged on the apparatus main body side to make the carriage light.

In some cases, the pressure of the ink in the recording head 1 is a negative pressure lower than the atmospheric pressure so as to prevent the ink from leaking from the nozzles 2 and the pressure is too low to record the ink during image recording. It is necessary to keep the pressure within a certain range that does not impose a load on the discharge.

In the conventional recording apparatus, the following measures are taken for that purpose.

(1) A porous resin member is placed inside the ink tank 3, and negative pressure is applied to the ink by utilizing the capillary phenomenon.

(2) During image recording and during standby, the exhaust valve 1
Open 0 and continue operating the exhaust pump 11.

However, since the porous resin member is always immersed in the ink, its durability is considered to be a problem, and it is difficult to use the porous resin member except for a recording apparatus having a structure in which the ink tank 3 can be replaced. On the other hand, the method of continuously operating the exhaust pump generates noise and vibration, which may affect the quality of the recorded image, and increases the energy consumption. In addition, it is necessary to precisely control the exhaust pump in order to generate and maintain a small amount of negative pressure, and the pump and control parts for that purpose require cost.

For these reasons, a typical negative pressure generating method of a conventional recording apparatus having a main body side ink tank utilizes the height of the ink column. The configuration of the recording apparatus using the liquid column height will be described with reference to FIG.

The pressure in the recording head is set by a height difference Δh0 between the ink level h1 of the main body side ink tank 5 and the height h0 of the nozzle 2, and the height difference is generally about 20 to 100 [mm]. Is considered appropriate. Since the specific gravity of the ink can be considered almost the same as water,
The negative pressure that balances the surface tension of the ink at the nozzles of the recording head is 20 to 100 [mmAq] (= about 19 mmAq).
6 to 980 [Pa]).

The carriage on which the head 1 is mounted reciprocates at the time of image recording, but the carriage is moved by using a flexible material (for example, a silicon tube or a polyethylene tube) for at least a part of the ink supply tube 4. Is not disturbed. The flexible tube material used for the ink supply tube 4 is as follows:
Generally, it is made of rubber or resin and has some gas permeability.

Since the inside of the tube is made to have a negative pressure as well as the inside of the recording head, air gradually enters from the atmosphere through the tube wall into the tube, and bubbles are generated. When the air bubbles flow into the recording head 1, normal ink droplets cannot be ejected, and a printing failure occurs.

Even if it is possible to prevent the air from gradually entering from the atmosphere through the tube wall, the air dissolved in the ink may grow into bubbles in the tube and in the ink tank 3. Therefore, the ink tank 3 has a role of accumulating air generated as bubbles in the ink supply tube 4 and moving to the ink tank 3 to prevent air from entering the recording head 1. Accumulated,
Excess air can be discharged by operating the pump 11 in an ink filling step A11 described later.

The exhaust pump 11 is, for example, a tube pump, and discharges internal air by squeezing a flexible tube having a deformable cross-sectional shape with a roller or the like.
It works to lower the pressure inside the tube. This may be a diaphragm type pump or other types of pumps.However, if the pump is difficult to control delicately, such as suddenly increasing the negative pressure or taking a long time to stop, the recording head may be damaged. There is a risk of giving. It should be noted that if the meniscus of the ink formed in the nozzle 2 is destroyed due to a sudden change in the pressure, the printing cannot be continued. Further, a diaphragm type or a piston type pump or the like has a pulsation in the generation of pressure, which may also damage the recording head or the like. In some cases, a pulsation absorbing means is required.

In FIG. 5, although the ink tank 3 is already sufficiently filled with ink, recording can be performed immediately. However, the recording state is changed from an empty state of the first ink tank immediately after installation of the apparatus. An operation flow for shifting to will be described.

The ink tank 3 has an ink level sensor 1
2 is provided so that it is possible to detect whether at least the amount of ink is sufficient. The term “sufficient amount of ink” as used here means that the ink amount will decrease with the image recording later. The amount determined to be sufficient is appropriately set according to how much ink is consumed by the image handled by the apparatus.

The ink level sensor 12 has at least one
It has an ink detector for detecting whether or not ink is present at predetermined levels, and can determine whether the liquid level is higher or lower than that level. Each of the ink detectors may be an optical sensor, at least two electrodes for detecting by using the energization of the ink, or the like. The greater the number of the ink detectors, the more the ink sensor 12 can grasp the ink amount with a finer resolution. In addition to using the ink detector, even if a float whose height changes according to the ink liquid level is provided inside the ink tank 3 and a means for detecting the position of the float is provided, the same function as the ink level sensor is provided. Fulfill. In FIG. 5, the position of the ink detector 12 corresponds to the position of the ink detector 12. In this apparatus, if the ink level is higher than the level of the ink detector 12, it is determined that there is a sufficient amount of ink, and if the ink level is lower, the ink detector is insufficient.

When the ink supply valve 9 and the exhaust valve 10 are opened and the pump 11 is operated, the ink in the ink tank 5 is guided to the ink tank 3 through the supply tube 4. When a sufficient amount of ink has been replenished, the pump 11 is stopped and the exhaust valve 10
When is closed, recording preparation is completed. In the multi-head type as shown in the figure, if only the ink supply valve 9 corresponding to the sub-tank to be replenished is opened, unnecessary ink is not sent to the sub-tank which does not need to be replenished (the ink filling step A11). .

Here, when the ink supply valve 9 is kept open, the pressure inside the recording head 1 is represented by a height difference Δh2 between the ink level h1 of the second ink tank 5 and the height h0 of the nozzle 2. Is maintained in a negative pressure state. Therefore, if Δh2 is within the range of an appropriate value, ink does not leak from the nozzle 2 during standby.
Further, even when the image recording is started and the ink is ejected from the nozzle 2, the ink amount in the ink tank 3 does not usually decrease because the ink is automatically guided from the ink tank 5.

However, as described above, as the air generated as air bubbles accumulates in the first ink tank 3, the ink liquid level may drop. When the liquid level in the first ink tank drops significantly and air reaches the tip of the supply tube 4, automatic ink replenishment is not performed, and it is necessary to refill the ink. If the ink level sensor 12 detects that the ink level is insufficient, the time may be used as the timing, or the time when the number of ejection dots is counted and the count reaches a predetermined value may be used as the timing.

When there is no more ink to be supplied in the spare ink tank 5, the following processing may be performed. If the ink level sensor 12 does not detect an increase in the ink level even after the pump 11 has been operated for a certain period of time in the ink filling step A11, this is determined to be the ink tank 5 empty. In such a case, the pump 11 is stopped and an error message is displayed to prompt the user to replenish the ink in the spare ink tank 5. If the user replenishes the ink in the spare ink tank or replaces the spare ink tank, subsequent image recording becomes possible.

[0026]

In the above conventional example,
The pressure inside the recording head is determined by the height difference between the ink level h1 of the main tank 5 and the height h0 of the nozzle 2, and is assumed to be maintained at a constant negative pressure. However, the recording head 1 and the sub tank 3 are mounted on a carriage (not shown), and reciprocate with the carriage. Therefore, the ink inside the recording head 1 and the sub-tank 3 constantly exerts an inertial force. The reciprocating movement of the carriage repeats a fine go-and-stop operation, and each time the ink tries to move alternately in the supply path in both directions of the head and the main tank. As a result, a remarkable pressure fluctuation occurs inside the print head 1 and the sub tank 3 during printing, which increases or decreases the load for ink ejection, and may adversely affect print image quality.

An object of the present invention is to provide an ink jet recording apparatus having an ink supply system capable of discharging ink stably with reduced pressure fluctuation inside the recording head.

[0028]

In order to achieve the above object, an ink jet recording apparatus according to the present invention is directed to an ink jet recording apparatus which performs recording by discharging ink from a recording head onto a recording medium. And a first ink tank mounted on a carriage together with the recording head, and ink supplied to the first ink tank via an on-off valve, and a second ink tank provided on the recording apparatus main body side. The first ink tank, the first ink tank and the second ink tank, a continuous pipe member, and a pressure holding container having a capacity larger than the void volume of the first ink tank. Is characterized in that the ink tank is a closed container, and the cavity of the ink tank and the pressure holding container are connected by a pipe member.

Further, in the ink jet recording apparatus according to the present invention, the pressure holding container may be a single container provided with a liquid communication passage and a partition for restricting the inflow and outflow of air, or at least two containers connected partially by a pipe member or the like. In the container, the liquid is stored so as to be able to flow through both chambers inside the container, at least two liquid levels are formed, a gap in contact with the first liquid level is sealed, and the gap is sealed with the first ink. It is characterized in that it is communicated with the gap of the tank and the gap in contact with the second liquid surface is opened to the atmosphere.

The liquid contained in the pressure holding container may be water, ink for recording, or a highly viscous liquid, or may be volatile. Liquid may be used.

Further, the ink jet recording apparatus of the present invention is of a multi-head type.

[0032]

FIG. 4 is a schematic diagram of a multi-head type ink jet recording apparatus provided with an ink supply system according to the present invention. In FIG. 4, 1a, 1b, 1
Reference numerals c and 1d denote recording heads, and nozzles for discharging ink are formed at portions facing the recording sheet S. Different types of ink can be ejected for each head, and multicolor recording is generally possible by sorting the inks into four colors of cyan, magenta, yellow, and black. Further, in a printing apparatus that requires more tones with similar colors, a larger number of heads may be prepared. In the case of a multi-head recording device as shown,
In the ink supply system, the same number of heads are prepared for each ink type.

Reference numeral 31 denotes a carriage on which the recording heads 1a to 1d are mounted; 32, a guide shaft for guiding the carriage 31; 33, both ends of which are fixed to the carriage 31; The driving belt 34 to be moved is a carriage motor for driving the driving belt 33.

Recording heads 1a to 1d on carriage 31
Is reciprocally scanned in the direction of arrow A along the guide shaft 32 by the drive belt 33, and discharges ink from the ink discharge port to the recording sheet S held at the opposite position from the ink discharge port at a predetermined timing during the scan. An image is formed by discharging separately.

The recording sheet S is not particularly limited to plain paper. The recording sheet S is fed from a feeding unit (not shown) to a printing position in the direction of arrow B, and is fed every time one scan of printing is performed. Is discharged to

The recording heads 1a to 1
The sub-tanks 3a, 3b, 3c, and 3d as the first ink tanks connected to the nozzles are respectively mounted on the sub-tanks 3a to 3d.
Are connected to ink supply tubes 4a, 4b, 4c, and 4d as ink supply paths for supplying ink from a main tank (not shown) as an ink tank. Reference numerals 6a, 6b, 6c, and 6d denote sub-tank exhaust tubes serving as exhaust passages for exhausting air from the sub-tank. A plurality of tubes are joined by a joint 7 on a carriage, and a single exhaust tube is provided. Tube 8
And head for the device body. This is for the purpose of not increasing the number of tubes connecting the carriage and the main body.

Reference numeral 35 denotes a caterpillar for accommodating the ink supply tubes 4a to 4d connecting the apparatus main body and the carriage and the exhaust tube 8. The ink supply tubes 4a to 4d reaching the apparatus main body side are connected to a main tank (not shown) in FIG. 4, and the exhaust tube 8 is also connected to an exhaust pump (not shown).

Next, the ink supply system of the present invention will be described in detail below. FIG. 1 is a block diagram showing a configuration of an ink supply system according to the present invention.

The characteristic feature of FIG. 1 is that the exhaust tube 8 continuing from the ink tank 3 is branched by the flow path branch 13, passes through the pressure holding liquid chamber valve 15 by the communication path 14, and is connected to the liquid container 16. It is that you are.

The liquid container 16 is separated by a partition wall into an ink tank communication chamber 17 and an atmosphere communication chamber 18. The two chambers are communicated only by a communication passage 20 between the liquid chambers. Air entry and exit is restricted. The ink tank communication chamber 17 communicates with the air in the ink tank 3 through the communication path 14, and the atmosphere communication chamber 18 is opened to the atmosphere through an atmosphere communication hole 19. As the liquid 21,
The use of various substances is conceivable. When water is used, handling becomes very easy. When ink for use in image recording is used, it is easy to obtain because it is always held in the apparatus.

The negative pressure is generated by the operation of an exhaust pump 11 as an exhaust means.
The value of the required negative pressure within 20 to 100 [m
[mAq] (approximately 196 to 980 [Pa]), so it is very difficult to make fine adjustments with a normal pump. The negative pressure in the recording head 1 is not equal to the negative pressure in the air chamber above the sub-tank 3 because the water pressure due to the ink in the sub-tank 3 is applied. That is, assuming that the specific gravity of the ink is equal to water and the height difference between the liquid level height h2 of the sub-tank 3 and the height h0 of the nozzle 2 is Δh2, the negative pressure pH near the nozzle 2 of the recording head 1 is PH = pST-Δh2 for the negative pressure pST in 3
[MmAq], which is 20 to 100 [mmAq] (approximately 196 to 980 [P
For a)), it is necessary to set pST higher (that is, lower pressure).

The exhaust tube 6 continuing from the sub tank 3 is
A portion of the head that passes through the caterpillar 35 and reaches the main body of the apparatus is branched by the flow path branch 13, passes through the pressure holding liquid chamber valve 15 as an on-off valve via the communication path 14, and then moves through the pressure holding container. It is connected to a certain liquid container 16. The configuration when the pressure holding liquid chamber valve 15 is closed is the same as the configuration of the ink supply system shown in FIG. 5, and similar operations such as ink supply can be performed. Note that the pressure holding container may have any configuration as long as it can absorb pressure, but in consideration of its structure, size, and the like, is a liquid container 16 having a configuration described in detail below. Is preferred.

The liquid container 16 includes an ink tank communication chamber 17 as a first liquid chamber to which the communication path 14 is connected, and an air communication chamber 18 as a second liquid tank provided with an air communication hole 19. And is divided into: An appropriate amount of liquid 21 is stored in the liquid container 16, and the liquid 21 is communicated with the ink tank communication chamber 17 and the atmosphere communication chamber 1 via the inter-liquid chamber communication path 20.
You can go back and forth between 8 freely. The appropriate amount of the liquid 21 is such that an air chamber is always formed as an air reservoir above the ink tank communication chamber 17.

Reference numeral 22 denotes a liquid level sensor provided in the ink tank communication chamber 17. When the liquid level reaches the set height, detection is performed and an electric signal is generated. The liquid level sensor 22 has a liquid level detector for detecting whether or not the liquid 21 exists at at least one predetermined level. The liquid level detector may be an optical sensor or at least two electrodes for detecting by using the energization of the liquid. As the number of liquid level detectors increases, the liquid level sensor 22
Can ascertain the liquid level with a fine resolution. In addition to the use of the liquid level detector, even if a float for changing the height in accordance with the liquid level is provided inside the ink tank communication chamber 17 and a means for detecting the position of the float is provided, the liquid level sensor is used. Performs the same function as

The function of the liquid 21 in the liquid container 16 will be described with reference to FIG. When the exhaust valve 10 is opened and the inside of the ink tank communication chamber 17 is equal to the atmospheric pressure, when the pressure holding liquid chamber valve 15 is opened, the ink tank communication chamber 1 is opened.
The liquid surface height of 7 and the air communication chamber 18 are in the same state as shown in FIG. 2A (hA = hB = hLE).

When the exhaust pump 11 is operated to reduce the pressure in the tube to a negative pressure state, the ink tank communication chamber 1
7, the liquid level height hA rises, and the liquid level height hB of the atmosphere communication chamber 18 decreases (FIG. 2-B). Here, the negative pressure pST of the air in the sub tank 3 has a value indicated by the height difference Δh1 between hA and hB (see FIG. 1). For example, liquid 2
When 1 is water, pST = Δh1 [mmAq].

When it is considered that the specific gravities of water and ink are substantially equal, when the ink supply valve 9 is opened after the end of the ink filling process, Δh1 = Δh0 + Δh2, but Δh0 is 2
Since the value of 0 to 100 [mm] is an appropriate value, Δh1 is a larger value, and the size of the liquid container 16 is inevitably increased. Therefore, in order to make the liquid container 16 compact, it is effective to use a liquid having a large specific gravity as the liquid 21.

Further, the exhaust pump 11 is continuously operated, and hA is the height hL of the liquid level sensor 22 as shown in FIG.
When S exceeds S, the exhaust pump 11 is stopped in response to the detection signal, and the exhaust valve 10 is closed. In this state, the inside of the recording head 1 has a proper negative pressure, for example, a value close to the lower limit of the proper negative pressure range (20 [mmAq] = about 196 [P
a]), hLS is set. Therefore, stable image recording can be performed by shifting the liquid surface of the liquid 21 in the liquid container 16 by the exhaust pump 11 so as to achieve such a state.

As the image recording progresses and the ink in the sub-tank 3 is consumed and the volume occupied by the air above the sub-tank 3 increases, the air pressure in the upper air chamber in the sub-tank 3 and the air chamber in the ink tank communication chamber 17 increases. Start to drop (negative pressure starts to increase). If the negative pressure exceeds an appropriate range, image recording will be hindered. Therefore, it is necessary to supply ink while the negative pressure is within the appropriate range and reset the negative pressure.

That is, as described later, the pressure holding liquid chamber valve 15 is closed, the ink supply valve 9 and the exhaust valve 10 are opened, and then the exhaust pump 11 is operated.
Ink is supplied from the main tank 5 to the sub tank 3. At the same time, the air accumulated above the sub tank 3 is discharged. When the replenishment of the ink is completed, the ink supply valve 9 is closed, the pressure holding liquid chamber valve 15 is opened to establish the set negative pressure state, and then the exhaust pump 11 and the exhaust valve 10 are closed.

Here, with respect to the liquid surface area of the sub-tank 3 (total of all sub-tanks), the ink tank communication chamber 17
When the tank is configured such that the liquid level of the atmosphere communication chamber 18 is sufficiently large, the upper limit of the appropriate negative pressure range (1
00 [mmAq]) (relative to the speed of ink consumption), and the frequency of negative pressure setting can be reduced.

Further, if the height of the hLM is set to the upper limit of the appropriate range of the negative pressure, the negative pressure in the exhaust tube 6 and the sub-tank 3 can always be maintained within an appropriate constant range. Image recording can be continued without resetting the negative pressure. In this case, it is only necessary to stop recording and fill the ink only when the amount of ink in the sub tank 3 is reduced. Ink replenishment into the sub-tank 3 is performed at the time when the ink level sensor 12 detects that the amount of ink is insufficient, or when the number of ejected dots is counted and the counted number reaches a predetermined value. Time
The timing of ink supply may be used.

As described above, the liquid contained in the liquid container 16 may be water or recording ink.
It is not preferable that the liquid amount is changed from a predetermined amount. This is because if the amount changes, the negative pressure set value changes. Therefore, it is desirable that the liquid 21 is as volatile as possible in the environment where the device is placed. Examples of the liquid having low volatility include glycerin. Even if the liquid volume is reduced due to volatilization, other liquids are also possible if the liquid is replenished by some method.

Even if the height difference Δh1 is the same, the magnitude of the negative pressure is not equal due to the specific gravity of the liquid 21. Therefore, for example, when it is desired to increase the resolution of the negative pressure set value, a liquid having a small specific gravity may be used, and when it is desired to make the liquid container 16 compact, a liquid having a large specific gravity may be used.

Here, it is assumed that the above-mentioned pressure fluctuation in the recording head due to the movement of the carriage at the start of image recording has occurred. The amount of ink in the ink tank 3 increases and decreases, and the fluctuation in the atmospheric pressure transmitted from the ink tank 3 to the liquid container 16 is transmitted to the liquid 21. The liquid 21 is in the ink tank communication chamber 1
Since the air chamber 7 can freely move between the air communication chamber 7 and the atmosphere communication chamber 18, the volume of the air chamber above the ink tank communication chamber 17 is variable.
Further, since the liquid 21 has a higher viscosity than air, it has an effect of attenuating the pressure fluctuation and has an effect of stabilizing the air pressure in the ink tank 3.

Even during the operation of the exhaust pump 11, it is possible to absorb a pressure fluctuation such as a sudden generation of a negative pressure, thereby avoiding the danger of destroying the meniscus of the recording head. The pulsation can be attenuated even when the exhaust pump 11 is a type of pump that generates pressure pulsation.

If a highly viscous liquid such as silicon oil is used as the liquid 21, the damping effect can be further enhanced. Providing a throttle in the inter-liquid chamber communication passage 20 is also effective in increasing the damping effect. If an aperture adjustment mechanism is provided, an appropriate attenuation rate can be set.

By the way, Boyle's law (pV = constant)
(When the temperature is constant), the larger the volume of the air chamber portion above the ink tank communication chamber 17 is, the smaller the fluctuation of the air pressure (p) when the volume (V) of the air chamber is changed becomes. . Therefore, this is an effective means for stabilizing the negative pressure applied to the recording head. Further, even when the exhaust pump 11 operates, the air buffer serves as an air buffer, which can suppress rapid fluctuations and pulsations in the pressure inside the recording head.

If the negative pressure rises too much, hB further decreases and air enters the ink tank communication chamber 17 from the inter-liquid chamber communication passage 20. (FIG. 2-D) This means that air is automatically replenished to the exhaust tube 8 side, and the air pressure in the exhaust tube 8 and the ink tank 3 does not further decrease. Thus, the mechanism of the present invention can also function as a negative pressure limiter. Even if a delicate pressure control pump is used as the pump 11, the limiter operates before the ink meniscus of the recording head is destroyed, so that the recording performance is not adversely affected.

Further, the liquid container divided into two chambers of the ink tank communication chamber 17 and the air communication chamber 18 in FIG.
One container provided with a liquid communication passage and a partition for restricting the inflow and outflow of air, or at least two containers partially connected by a pipe member or the like, storing the liquid so that both chambers can flow inside the container, At least two liquid levels are formed, a gap in contact with the first liquid level is sealed, the gap is communicated with the gap in the first ink tank, and the gap in contact with the second liquid level is opened to the atmosphere. It is doing. First
Is the liquid level of the ink tank communication chamber 17, and the second liquid level is the liquid level of the atmosphere communication chamber 18. Here, the procedure of the operation in the supply system of the present invention will be described using a flowchart. FIG. 3 shows an operation for preparing for recording before starting image recording.

After closing all the ink supply valves 9, the exhaust valves 10, and the pressure holding liquid chamber valves 15, it is checked whether the ink amounts in all the sub-tanks 3 are sufficient. When the ink level sensors 12 of all the sub-tanks 3 detect that the ink is sufficient, the process proceeds to the subsequent negative pressure generation step. On the other hand, if there is at least one sub-tank 3 with an insufficient amount of ink, the process proceeds to an ink filling step to replenish the sub-tank 3 with ink.

The method of filling the ink in the supply system of the present invention, that is, the method of supplying ink from the main tank 5 to the sub-tank 3, is the same as the conventional example, but will be described again. Open all the ink supply valves 9 connected to the sub-tank 3 where the insufficient ink is detected. Then, the exhaust valve 10 is opened, the exhaust pump 11 is operated, and the ink in the main tank 5 is supplied to the sub tank 3.
Invite to Then, the ink supply valves 9 corresponding to the sub-tanks 3 to which a sufficient amount of ink has been supplied are sequentially closed, and when the filling of all the sub-tanks 3 is completed, the exhaust pump 10 is stopped. Move on to the generation process.

However, a fixed time T from the start of the pump operation
When the filling of the sub-tank 3 is not completed even after the elapse of (when the ink level sensor 12 does not detect the ink level), it means that the ink in the main tank 5 is empty. Is stopped and all valves are closed, an error is displayed, and the user is urged to refill the main tank 5 with ink (or to replace the main tank 5).

Next, the negative pressure generating step will be described. Immediately after all the sub-tanks 3 are filled with ink, the process enters the negative pressure generation step. The pressure holding liquid chamber valve 15 is opened, and the exhaust pump 10 is operated. The liquid level sensor 22 is the liquid 21
When the liquid level is detected, the exhaust pump 11 is stopped and the exhaust valve 10 is closed. At this time, the sub tank 3 and the recording head 1
The inside is in an appropriate negative pressure state, and preparation for image recording is completed.

[0065]

As described above, according to the present invention,
A first ink tank that supplies ink to the recording head;
A second ink tank that supplies ink to the first ink tank, an exhaust path connected to an exhaust hole provided in the first ink tank, and an exhaust pump connected to the exhaust path; In the ink jet recording apparatus for discharging gas accumulated in the first ink tank from the above, at least one container provided with a liquid communication path and a partition for restricting the entrance and exit of air, or at least a part of which is connected by a pipe member or the like In two containers, storing the liquid so that both chambers can be circulated inside the container, forming at least two liquid levels,
By providing a liquid container in which a gap in contact with the first liquid surface is sealed, the gap is communicated with the gap in the first ink tank, and the gap in contact with the second liquid surface is open to the atmosphere. The negative pressure in the head can be appropriately maintained, the movement of the ink in the supply tube can be eliminated, the pressure fluctuation in the recording head can be reduced, and stable image recording can be performed.

Furthermore, since the system of the exhaust path can be provided with a function of a negative pressure limiter, the negative pressure in the recording head is not unnecessarily increased even if an exhaust pump difficult to control delicately is used. There is little risk of breaking the head.

Further, since the recording head and the main tank can be arranged without concern for the height difference for maintaining the negative pressure, the degree of freedom in the apparatus configuration is increased, which is effective for realizing a compact and low-cost apparatus. is there.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an ink supply system of the present invention.

FIG. 2 is a diagram showing an operation state of a liquid container of the ink supply system of the present invention.

FIG. 3 is a flowchart illustrating an operation of an ink supply system when preparing for recording before starting image recording.

FIG. 4 is a schematic diagram of a sub-tank exhaust type ink jet recording apparatus.

FIG. 5 is a schematic diagram of a conventional sub-tank exhaust type ink supply system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording head 2 Nozzle 3 Sub tank 4 Ink supply tube 5 Main tank 8 Exhaust tube 9 Ink supply valve 10 Exhaust valve 11 Exhaust pump 12 Ink level sensor 15 Pressure holding liquid chamber valve 16 Liquid container 17 Ink tank communication chamber 18 Air communication chamber 19 Atmospheric communication hole 20 Communication passage between liquid chambers 21 Liquid 22 Liquid level sensor

Claims (13)

[Claims] 1. An ink jet recording apparatus which performs recording by discharging ink from a recording head onto a recording medium, a first ink tank which supplies ink to the recording head and is mounted on a carriage together with the recording head, A second ink tank which supplies ink to the first ink tank and is provided on the recording apparatus main body side, a pipe member which connects the first ink tank and the second ink tank, A pressure holding container having a larger capacity than the gap volume of the first ink tank, wherein the first ink tank is a sealed container, and the gap portion of the ink tank and the pressure holding container are connected by a pipe member. An ink jet recording apparatus characterized by the above-mentioned. 2. An ink jet recording apparatus which performs recording by discharging ink on a recording medium, wherein the first ink tank is supplied to the recording head and mounted on a carriage together with the recording head; A second ink tank provided on the recording apparatus main body side, a pipe member connecting the first ink tank and the second ink tank, and a variable gap volume. Wherein the first ink tank is a sealed container, and the gap of the ink tank and the pressure holding container are connected by a pipe member. 3. The ink jet recording apparatus according to claim 2, wherein the pressure holding container having a variable gap volume is a liquid container storing a liquid, and the gap volume can be enlarged and reduced by raising and lowering the liquid level of the liquid. 4. The liquid container may be a single container provided with a liquid communication passage and a partition for restricting the inflow and outflow of air, or at least two containers partially connected by a pipe member or the like. Storing the liquid so that the chamber can be circulated, forming at least two liquid levels, sealing a gap in contact with the first liquid level, and communicating the gap with the gap of the first ink tank; 4. The ink jet recording apparatus according to claim 3, wherein a gap portion in contact with the liquid surface of No. 2 is opened to the atmosphere. 5. The ink jet recording apparatus according to claim 4, wherein the liquid stored in the liquid container is water. 6. The ink jet recording apparatus according to claim 4, wherein the liquid stored in the liquid container is the ink. 7. The ink jet recording apparatus according to claim 4, wherein the liquid stored in the liquid container is a liquid having a lower volatility than water and ink. 8. The ink jet recording apparatus according to claim 4, wherein the viscosity of the liquid stored in the liquid container is equal to or higher than the liquid viscosity of the ink. 9. The ink jet recording apparatus according to claim 4, further comprising means for controlling the flow rate of the liquid at a connection portion of at least two successive liquid containers. 10. The ink jet recording apparatus according to claim 1, wherein an opening / closing valve is provided in a pipe member connecting the first ink tank and the second ink tank. 11. The ink jet recording apparatus according to claim 1, wherein an opening / closing valve is provided in a pipe member that connects the gap portion of the first ink tank and the pressure holding container. 12. The ink jet recording apparatus according to claim 1, further comprising an exhaust unit between the gap of the pressure holding container and the gap of the first ink tank. 13. An opening / closing valve is provided between a pipe member extending from the gap of the pressure holding container to the gap of the first ink tank and the exhaust means. 3. The ink jet recording apparatus according to claim 1.