JP2004148769A - Ink supply mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that there are a method of utilizing a hydraulic head difference by setting a level of ink in an ink tank to be lower than a recording head or a method of utilizing a capillary force by inserting an absorption body into the ink tank as a method of forming a negative pressure in a nozzle section of the recording head in a conventional method, however relative placement is restricted in the former one and the efficiency of usage of the ink tank is lowered in the latter one. <P>SOLUTION: This ink supply mechanism is constituted so as to maintain the negative pressure of the nozzle by attaching a negative pressure maintaining valve and an air buffer between the recording head and the ink tank. As a result, the restriction of the placement of the ink tank and the head is eliminated and the capacity of the ink tank can be increased. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink supply mechanism for supplying ink to a recording head in an ink jet recording apparatus.
[0002]
[Prior art]
Normally, a negative pressure is applied to the nozzle face (meniscus) of the recording head in an ink jet recording apparatus to prevent the influence of the residual droplets on the nozzle plate and the diffusion of the ejected ink. You.
[0003]
As means for generating such a negative pressure, for example, as shown in FIG. 6, a partition 602 having a lower part communicated with an ink tank 601 is provided, and an ink chamber 604 for storing pure ink only and a head 607 are formed by capillary force of an absorber 605. And the like, in which the nozzle section has an absorber chamber 603 for generating a negative pressure.
[0004]
Reference numeral 606 denotes an air communication port.
(See, for example, Patent Document 1).
[0005]
[Patent Document 1]
JP-A-2001-347684 (page 1-5, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, in the absorber method, since the ink is contained in the absorber and stored, the ratio of the pure usable ink to the internal volume of the ink tank (hereinafter referred to as use efficiency) is about 70%. Lower.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the invention according to the present application provides a valve that holds the negative pressure by itself when an external negative pressure is applied between the ink tank and the recording head, and further reduces the negative pressure amount. To provide an ink supply mechanism provided with a buffer for reducing the ink consumption.
[0008]
There is no restriction on the operation of improving the usage efficiency by forming a pure ink storage chamber without an absorber or the like in the ink tank, and the arrangement of the ink tank and the recording head.
In addition, reliability against a minute leak in the negative pressure maintaining valve, a vaporization of a gas dissolved in the ink, and a reduction in a negative pressure amount due to a permeation of an external gas, has been improved.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
<First embodiment>
FIG. 1 shows a first embodiment according to the present invention.
[0010]
The ink tank 120 is filled with the ink 104, and an air opening 121 is provided at the upper part.
[0011]
The atmosphere opening port 121 is sealed during transportation, but is opened in use.
[0012]
Further, at the time of insertion into the recording apparatus, a hollow needle 106 on the recording apparatus main body side penetrates the sealing elastic body 105 which is press-fitted into the ink tank 120, so that a flow path with the recording head 111 is formed. Connected.
[0013]
At this point, a positive pressure is applied to the ink ejection nozzles 112 of the recording head due to a difference in head from the ink 104 in the ink tank 120. However, the negative pressure maintaining valve 107 shuts off the flow path between the ink tank 120 and the recording head 111. The ink 104 does not flow out of the ink tank 120.
[0014]
The negative pressure maintaining valve 107 includes a compression spring 117, a sealing ball 108, and a sealing elastic body 109.
[0015]
Here, the flow rate characteristics of the negative pressure maintaining valve 107 are shown in FIG.
[0016]
That valve when the negative pressure amount reaches P ₀ of the internal liquid chamber 110 (Futomebo - Le 108, a gap between the sealing elastic body 109) ink starts to flow out to the recording head 111 from the ink tank 120 .
[0017]
The amount of negative pressure thereafter increases in proportion to the amount of ink consumed by the print head 111, and corresponds to, for example, the maximum discharge ink flow rate Q _max when ink is discharged from all the discharge nozzles of the print head 111. The amount of negative pressure is defined as _Pmax .
[0018]
Meanwhile, recording its proper value for the negative pressure amount applied to the head nozzle 112 varies by the recording head of interest, but the upper limit negative pressure value 2 is represented by P _2, no more negative pressure amount ink discharge nozzles 112 When the pressure is applied, the meniscus is broken and, specifically, air enters the nozzle.
[0019]
Conversely the lower negative pressure is represented by P _1, the ink jet recording apparatus using a line head in which the head is essentially stationary, said value is but negative pressure value close to 0 value, is mounted on a carriage which the recording head moves in serial printers serially scan, also in consideration of inertia due to acceleration and deceleration of the carriage mounting the recording head is set as a lower limit negative pressure P ₁ that does not cause a positive pressure to the nozzle.
[0020]
That is, the range of the amount of negative pressure to be applied to the nozzle is determined within the range of P _{1 to} P _{2. For} these values, the opening / closing point pressure P ₀ is determined by the flow path characteristics of the negative pressure maintaining valve 107. ₁ or more, more negative pressure amount P _max generated during ink flow rate Q _max when ejection of ink from all nozzles provided in the recording head 111 is performed becomes the upper limit negative pressure amount P ₂ less essential conditions, these valves It is set in consideration of the tolerance of the capacity.
[0021]
As a result, the amount of negative pressure applied to the ink ejection nozzles 112 of the recording head 111 during the recording operation varies between P _{0 and} P _max depending on the recorded image (depending on the amount of ink ejected).
[0022]
Here, the amount of negative pressure applied to the ink ejection nozzle 112 based on the control sequence on the actual machine will be described with reference to FIG.
[0023]
First, assume that the default negative pressure amount is zero.
[0024]
Here, first, in order to obtain a necessary amount of negative pressure, ink is ejected from the ink ejection nozzle 112 to the capping mechanism 114 of the recording head 111.
[0025]
Alternatively, the ink may be sucked from the ink discharge nozzle 112 by the suction pump 115 after the nozzle plate 113 is sealed by the capping mechanism 114.
[0026]
These discharged inks are pressure-fed to and stored in a waste ink tank 116 by a suction pump 115.
[0027]
Although the ink in the liquid chamber of the recording head 111 is consumed by such means, the flow of new ink from the ink tank 120 is maintained at a negative pressure (the gap between the sealing ball 108 and the sealing elastic body 109 is closed). Since the valve 107 is shut off, the amount of negative pressure applied to the liquid chamber 110 inside the valve 110 to the ink discharge nozzle 112 increases (a), but the amount of negative pressure exceeds the opening pressure P ₀ of the negative pressure maintaining valve 107. (A gap is formed between the sealing ball 108 and the sealing elastic body 109), and the flow of the ink 104 from the ink tank 120 starts (b).
[0028]
At least after such an inflow of ink has started, the operation of discharging ink from the recording head 111 is stopped.
[0029]
Then although the negative pressure amount turns to decrease (c), at the time when decreased to negative pressure amount P _0, which is the opening and closing points of the negative pressure maintaining valve 107 (Futomebo - Le 108, closing the gap between the sealing elastic body 109 Te) inflow of the ink is blocked, the negative pressure maintaining valve 107 to the ink discharge nozzle 112 is maintained at a negative pressure amount _{P 0} (d).
[0030]
Thereafter, Job (printing operation) is performed, and the value fluctuates according to the flow rate × negative pressure amount graph shown in FIG. 2 according to the ink ejection amount of the print head 111 in Job (e).
[0031]
The After Job ends, while negative pressure maintaining valve 107 to the ink discharge nozzles 112 as described above is maintained after reduction (f) to a negative pressure amount P _0, which is the opening point of the negative pressure maintaining valve 107, the following In preparation for Job, a standby state is set (g).
[0032]
However, if the standby time for the next job is long in the standby state, a minute leak of ink from the sealing portion by the sealing ball 108 and the sealing elastic body 109 or the generation of the negative pressure may occur. valve 107 to vaporization of the ink dissolved gases up to the recording head and, by transmission of an external gas, the negative pressure amount P ₀ is sometimes gradually lost during standby.
[0033]
If the amount of negative pressure decreases to an amount that affects the recording characteristics of the ink discharge nozzle 112 and a predetermined time has elapsed, the automatic sequence forcibly ejects the ink from the ink discharge nozzle 112 before the start of the next Job. by the discharge, it is restored to the negative pressure amount P ₀ again.
[0034]
Incidentally, the opening and closing points pressure P ₀ According to the configuration of the negative pressure maintaining valve according to this embodiment mainly spring pressure of the compression spring 117 and, Futomebo - is set by the flow path cross-sectional area of the Le 108 parts.
[0035]
Although it is desirable to moderate the gradient of the maximum flow rate Q possible characteristic line so as not to exceed the upper limit pressure P ₂ at the time of _max the closing point pressure P ₀ as a start point, which is mainly Futomebo - and Le 108 This is performed by increasing the length of the contact line of the sealing elastic body 109, and is appropriately set as a whole so as to sufficiently satisfy the allowable range P ₁ -P ₂ of the negative pressure amount.
[0036]
In FIG. 3, if the ink discharge operation from the recording head nozzle 112 is stopped after the negative pressure amount exceeds the opening pressure P0 of the negative pressure maintaining valve 107 (b), as a result, the negative pressure maintaining valve 107 to the recording head nozzle During the period 112, the negative pressure amount P0 is maintained (d).
[0037]
In this process, the pressure in the air buffer 101 is similarly reduced to the negative pressure amount P0 via the tubular flow path 103, and the volume of the air 102, which is a compressible fluid, also increases.
[0038]
Here, between Jobs, (d) and (g), due to factors such as minute leakage from the negative pressure maintaining valve 107, vaporization of dissolved gas in ink or permeation of external gas, the negative pressure maintaining valve 107 to When ink and gas flow into the flow path between the recording head nozzles 112, the amount of negative pressure decreases, but the amount of decrease is reduced by the air buffer 101.
[0039]
Specifically, a new volume is added between the negative pressure maintaining valve 107 and the recording head nozzle 112 due to the inflow of ink or air due to the minute leak or the like, but the volume of the expanded air 102 in the air buffer 101 is reduced. The contraction can moderate the decrease in the negative pressure amount.
[0040]
In short, the negative pressure maintaining valve 107 to the recording head nozzle are maintained until the total volume of the inflows of the ink and the gas reaches V, which is the increase amount of the volume of the air 102 in the air buffer 101 during the negative pressure generation process. During the period 112, the negative pressure is maintained.
[0041]
Further, the negative pressure maintaining valve 107 does not have to be provided on the recording head side as described in the present embodiment, and may be, for example, provided on the ink tank side or independent of the recording head and the ink tank.
[0042]
Further, the configuration of the negative pressure maintaining valve is not limited as long as the negative pressure maintaining valve has a flow rate characteristic that satisfies a negative pressure allowable range specific to the recording head employed in the recording apparatus.
[0043]
<Second embodiment>
In the first embodiment, an independent air buffer is provided by a tubular flow path from the liquid chamber inside the valve, but an air reservoir 401 may be directly provided in the liquid chamber 110 inside the valve as shown in FIG.
[0044]
An air chamber 401 for holding a stable amount of air is provided above the negative pressure maintaining valve 107. When ink is discharged from the recording head nozzle 112 as described above to generate a negative pressure, the first embodiment is performed by the negative pressure amount. The air stored in the air chamber 401 expands in volume in the same manner as described in the above, and the amount of expansion causes the flow of ink and gas from outside or the vaporization of gas dissolved in the ink during standby between Jobs. To reduce the decrease in the amount of negative pressure due to.
[0045]
Even more preferably, the ink should have a meniscus shape so that the air in the air chamber 401 does not flow even if the device is turned upside down during transportation.
[0046]
<Third embodiment>
In the first and second embodiments of the present invention, the embodiment in which the negative pressure maintaining valve and the air buffer are combined is described. However, the combination for warming the decrease in the negative pressure amount of the negative pressure maintaining valve is limited to the air buffer type. Not something.
[0047]
FIG. 5 shows an embodiment in which the inside of the flow path is formed only of ink which is an incompressible fluid.
[0048]
In this embodiment, between the negative pressure maintaining valve 107 and the recording head nozzle 112, the elastic member 502 which is deformable and whose internal volume changes by the deformation is removed from the valve internal liquid chamber 110 via the tubular flow path 103. A buffer 501 serving as a membrane is connected.
[0049]
A compression spring 503 is provided in the elastic member 502 and always applies a biasing force to the elastic member 502 in a direction in which the internal volume of the buffer 501 is maximized.
[0050]
Here, it is assumed that the buffer 501 has a maximum internal volume V when the internal pressure of the buffer 501, that is, the pressure of the valve internal liquid chamber 110 is zero.
[0051]
However, at this time, the compression spring 503 has a free length or does not give a resistance to the elastic member 502 by a stopper (not shown).
[0052]
When ink is ejected from the recording head nozzles 112 or ink is sucked by the suction pump 115 in such a configuration, a negative pressure is applied between the liquid chamber 110 inside the valve and the recording head nozzles 112, and the amount of the negative pressure also increases. Although increasing, the elastic member 502 also contracts against the urging force of the compression spring 503, and as a result, the internal volume of the buffer 501 also decreases.
[0053]
As described with reference to FIG. 3, when the operation of discharging ink from the recording head nozzle 112 is stopped after the negative pressure amount exceeds the opening pressure P0 of the negative pressure maintaining valve 107 (b), as a result, the negative pressure maintaining valves 107 to 107 are stopped. The space between the recording head nozzles 112 is maintained at the negative pressure amount P0 (d).
[0054]
In this process, the pressure in the buffer 501 is similarly reduced to the negative pressure amount P0, and the internal volume of the buffer is reduced, for example, from V to x / V.
[0055]
Here, between Jobs, (d) and (g), due to factors such as minute leakage from the negative pressure maintaining valve 107, vaporization of dissolved gas in ink or permeation of external gas, the negative pressure maintaining valve 107 to When ink and gas flow into the flow path between the recording head nozzles 112, the amount of negative pressure decreases. However, the elastic member 502 is pushed and expanded by the compression spring 503, and the pressure between the negative pressure maintaining valve 107 and the recording head is reduced. The volume of the buffer 501 is increased again according to the volume of the ink or the air flowing into the buffer, so that the decrease in the negative pressure amount is moderated.
[0056]
【The invention's effect】
As described above, by providing a valve having flow path characteristics according to the present invention and a buffer filled with a compressive fluid or a buffer formed of an elastic member capable of being deformed by pressure, the use efficiency of ink is high. An ink tank having a pure ink liquid chamber can be realized, and a highly reliable ink supply mechanism can be provided with almost no restrictions on the arrangement of the ink tank and the recording head.
[0057]
In addition, by implementing the present invention, the required negative pressure amount is maintained for a long time over the print head nozzles, and the negative pressure amount due to the discharge of ink from the print head nozzles before the start of a Job (printing operation) after standby. The number of times of restoring (cleaning) operations is expected to be reduced, and the ink consumption is reduced, and the throughput up to the start of the recording operation is improved.
[0058]
[Brief description of the drawings]
FIG. 1 is an ink flow path diagram to which a first embodiment of the present invention is applied.
FIG. 2 is a diagram showing a relationship between a flow rate of a negative pressure maintaining valve and a negative pressure amount.
FIG. 3 is a diagram illustrating a temporal change in the amount of negative pressure applied to nozzles of a recording head.
FIG. 4 is an ink flow path diagram to which a second embodiment of the present invention is applied.
FIG. 5 is an ink flow path diagram to which a third embodiment of the present invention is applied.
FIG. 6 is a diagram illustrating an example of a conventional ink flow path.
[Explanation of symbols]
101 air buffer 102 air 103 tubular flow path 107 negative pressure maintaining valve 108 sealing ball 109 sealing elastic body 111 recording head 112 ink (discharge) nozzle 120 ink tank 121 air opening (communication) port 401 air reservoir 501 buffer 502 elasticity Member 503 compression spring

Claims (7)

When a recording head having a plurality of nozzles for discharging ink, an ink tank for supplying ink to the recording head, and a flow path between the recording head and the ink tank are normally shut off, and a certain negative pressure is generated, An ink supply mechanism comprising: a valve for flowing ink to a recording head; and a pressure buffer between the valve and the recording head. 2. The ink supply mechanism according to claim 1, wherein the pressure buffer is based on a volume change with respect to a pressure fluctuation of the compressible fluid. The ink supply mechanism according to claim 2, wherein the compressible fluid is air. The ink supply mechanism according to claim 1, wherein the pressure buffer is formed by deformation of an elastic member. The ink supply mechanism according to claim 4, wherein the deformation of the elastic member involves a change in volume. The ink supply mechanism according to claim 1, wherein the valve and the pressure buffer are configured in the same mechanism. The ink supply mechanism according to claim 1, wherein the valve and the pressure buffer are connected via a fluid-movable flow path.

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