JPS58142857A - Supply element for fluid - Google Patents

Abstract

PURPOSE:To relax the variation of pressure in case of the adjustable speed of a recording head in a fluid injector by interrupting a fluid flow path by moving or bending a sheet when the head is accelerated or decelerated. CONSTITUTION:When the head 1 approaches near a left end, force is applied in the left direction from the right, and the sheets 9, 10 are strained so that the left side is convexed. The sheet 10 clogs an opening 5 at that time, and the flow path of a liquid is interrupted. The flow path is interrupted when force works in an adjustable-speed section, but the flow path is interrupted and the fluid may not be supplied because recording is not executed normally in the section. The variation of pressure propagated to the head 1 can be prevented by interruption the flow path. Consequently, the fluid supply element 4 may be arranged near the head 1 as much as possible. The effect of the fluid supply element 4 is increased because liquid chambers 13, 14 fill the roles of dampers. When the head 1 is positioned near a right end, the sheet 9 is convexed to the right side to clog the opening 5 because force is applied in the right direction from the left, and the flow path is interrupted. Accordingly, the variation of pressure is not transmitted to the head 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluid supply element for a liquid ejecting device such as an inkjet recording device that ejects liquid to record characters and graphics.

For example, in an apparatus such as an X-Y recorder or a line printer in which a recording head' (hereinafter referred to as a head) having an ejection port for ejecting liquid is scanned, the liquid connected to the head is supplied. If the supply pipe moves and the resulting pressure fluctuations in the liquid within the supply pipe are propagated to the head, this will have an adverse effect on the head. In other words, if pressure fluctuations act on the positive side, droplets will be ejected even if no signal is applied to the head, and conversely, if pressure fluctuations act on one side, air will be sucked into the head in the form of bubbles and ejection will fail. This results in stability or inability to eject.

The present invention provides means for alleviating this pressure fluctuation.

In order to alleviate liquid pressure fluctuations within the liquid supply pipe, it is first necessary to consider the movement of the liquid supply pipe.

Figure 1 shows an outline of a liquid supply piping system and its operation generally used for liquid jetting, and Figures B and C show the scanning speed of the head and changes in the pressure of the liquid propagated to the head, respectively. In the figure, 1 is the head 1, 2 is the liquid supply pipe,
3 is a liquid reservoir, the scanning of head 1 is decelerated, accelerated (
C), □ constant speed (b), M speed.

This is done by repeating acceleration (,), usually at a constant velocity (
Recording is performed by injecting two liquids in the section b). In the same figure, there is 1 head (considering the state of a near the left end, 1 head
decelerates to zero speed, changes direction and accelerates. Assuming that the speed when moving to the right from the center is 0, + acceleration always acts in state a. At this time, relative motion (liquid flow) is about to occur between the liquid supply pipe 2 and the liquid,
As shown in Figure C, pressure fluctuations occur on the + side at the entry point.

Conversely, in state C, negative acceleration always acts, so pressure fluctuations at five points occur on one side. In state b, the velocity is constant and no relative movement occurs between the liquid supply pipe 2 and the liquid, so the pressure fluctuation is almost zero. If the distance from point M to the tip of the curved part of liquid supply pipe 2 is l, then the pressure fluctuation P at the five points is PA! ;ρlα 8 where ρ is the density of the liquid and α is the acceleration that the head 1 receives. This was in very good agreement with the experimental value. As the object to be recorded becomes larger, l becomes larger, and if the recording time is set to a single line, α becomes larger, and as a result, P becomes larger. This has been a major obstacle in the development of liquid injection devices that require stability of the meniscus of the liquid injection nozzle.

Figure 2 shows an outline of the liquid supply piping system and its operation (Figure 2 B), where pressure fluctuations are more easily alleviated than those in Figure 1, the scanning speed of the head (Figure 2 B), and the pressure fluctuations propagated to the head. The shape and operation are proposed by E. and STIEMMIE et al. , (Division of Computer Re
5earch, Re5earch Report
N11B1972 0ha1mers Universes
technology).

In this system, the liquid supply pipe 2 is branched into two paths with respect to the head 1, and the liquid supply pipe 2 is arranged symmetrically like two U-shaped pipes put together. The length to the right end must be at least as long as the movement range of the head.

It is said that in the liquid supply pipe 2 having such a shape, the inertial force of the liquid is canceled out on the left and right sides, so that pressure fluctuations in the liquid propagated to the head are significantly reduced. But in reality,
Due to the flow resistance on the inner wall of the liquid supply pipe 2 and the flow resistance at the curved part of the liquid supply pipe 20, the rate at which the flow of liquid is converted into pressure fluctuation is large, and the liquid as shown in Figure 2 Even the supply pipe 2 cannot sufficiently alleviate pressure fluctuations, and as shown in FIG. 2C, pressure fluctuations on the positive side occur even when the acceleration is positive or negative (although it is small compared to that shown in FIG. 1).

As a practical matter, no pressure fluctuations in liquids at all.

It is not necessary to keep the temperature constant as long as the meniscus of the liquid jet nozzle can be kept stable. FIG. 3 shows the state of the meniscus 26 of the liquid jet nozzle 26. The holding force ΔP of the meniscus 26 is expressed by the following formula.

ΔPA: 2 T cotta/r where T represents the surface tension, α represents the contact angle, and γ represents the radius of the nozzle 26.

The meniscus 26 becomes unstable due to fluid pressure fluctuations,
In a critical state in which droplets are ejected, α=π; conversely, in a critical state in which the meniscus 26 is torn and air bubbles enter the head, α=0. That is, ΔPmu>2T/γ (droplet ejection) ΔPmu(-2T/γ (bubble suction). In the case of the liquid (black ink) used by the inventor, the surface tension is T = 40 dyn/ca+, The radius of the injection nozzle 26 is still γ = 26 μm, but in order to maintain the stable state of the meniscus 260 at this time, the pressure fluctuation of the liquid is -o o 3 s kg7a!!<ΔPa, <0,
It is sufficient to keep it within the range of 0.03 s kg/1 yrr.

As shown in Figures 1 and 2, liquid pressure fluctuations occur only in the acceleration/deceleration sections (a, c) of head scanning, and hardly occur in the constant velocity sections. Therefore, the pressure in the acceleration/deceleration sections It is necessary to reduce the fluctuation to a range in which the meniscus 26 shown above can be stably maintained.

The present invention has been made from this point of view, and provides a device for alleviating pressure fluctuations during acceleration and deceleration of head scanning in a liquid ejecting device. An embodiment of the present invention will be described in detail below.

The present invention provides a fluid supply element that is characterized in that it closes the passage of the liquid supply pipe when the head accelerates or decelerates, thereby blocking the propagation of pressure fluctuations. As a first embodiment of the present invention, its structure and operation are shown in FIGS. 4, 6, and 6. The fluid supply element 4 according to the invention is installed in the vicinity of the head 1 of the liquid supply pipe system shown in FIG. The scanning of the head 1 is the same as in FIG. 1, and the positions indicated by a, b, and c correspond to a, b, and c in FIG. 1, respectively. Also a,
Enlarged sectional views of the fluid supply element 4 in states b and c are shown at the bottom of each of FIGS. 4 to 6.

The structure of the fluid supply element 4 will be explained using FIG. 6B. Thin plates 9 and 1o with removed portions 7 and 8 provided on the periphery are attached to both sides of a partition plate 6 having an opening 6. The thickness of the partition plate 6 is very slightly thinner in the peripheral area including the opening 5, and thin layers 11° and 12 are formed between the thin plate 9 and the partition plate 60 and between the partition plate 6 and the thin plate 1o. ing. Also thin plate 9,1o
The structure is such that the removed portion 7.8 and the opening 6 of the partition plate 6 do not overlap. The liquid is transferred from the liquid reservoir 3 to the liquid supply pipe 2, the liquid chamber 14, the removal section 8, the thin layer 12, and the opening 6.
, the thin layer 11 , the removal section 7 , the liquid chamber 13 , and the liquid supply pipe 2 before being supplied to the head 1 . This is shown in Figure 6,
When the head 1 is in state b, that is, scanning at a constant speed, no force (acceleration) is applied. Since recording is normally performed in this constant velocity section, the above-mentioned liquid flow is necessary.

Next, as shown in FIG. 4, when the head 1 comes to the vicinity of the left end, a force is applied from the right to the left, and the thin plate 9.degree. 1o is distorted so that its left side becomes convex. At this time, the thin plate 1o closes the opening 6 and the liquid flow path is blocked.

The flow path is blocked during the acceleration/deceleration section when force is applied, but since no recording is normally performed during this section, it is not necessary to block the flow path and supply no liquid.

By blocking the flow path, pressure fluctuations propagated to the head 1 can be prevented. Therefore, the fluid supply element 4
It is better to place it as close to head 1 as possible. Also, liquid chamber 1
3 and 14 serve as dampers, increasing the effectiveness of the fluid supply element 4.

Next, FIG. 6 shows a state C when the head 1 is near the right end. This time, force (acceleration) is applied from left to right, so
The thin plate 9 is convex to the right and blocks the opening 6, blocking the flow path. Therefore, pressure fluctuations are not transmitted to the head 1.

As a practical matter, it takes a certain amount of time for the flow path to be blocked due to acceleration, and therefore it is not possible to completely prevent the propagation of pressure fluctuations, but it is less severe than when this fluid supply element 4 is not installed. Next, the dimensions of the fluid supply element 4 will be described. The major parameters that affect the performance of this fluid supply element 4 are the thin plate 9,
1o thickness, the thickness of the thin layer 11.12, the large area of the opening 5), and the large area of the removed portions 7, 8). The dimensions of the grooves further vary depending on the size and inner diameter of the liquid supply tube 2. The following description will be based on the liquid supply pipe having an inner diameter of 1 mIn.

The thin plates 9 and 10 are elastic bodies that can easily bend even with a small amount of force, and are required to have strength. From the point of view of flexibility, it is better to be as thin as possible, but from the point of view of strength, thicker is better. The amount of deflection is also highly dependent on the thickness of the thin layer 11.12. The thin plate 9.10 and the thin layer 11.12 have approximately the same thickness, preferably about 30 μm to 60 μm. The removed parts 7 and 8 need to have the same area and also the opening 5. This is to keep the amount of liquid supplied constant. The diameter of the opening 6 is within an effective range of SOO μm to 700 μm. Although the removed portions 7 and 8 vary depending on the diameter, it is more effective to provide a large number of removed portions with a smaller area around the thin plates 9 and 1o. Further, the shapes of the removed portions 7 and 8 do not need to be circular either.

The removed portions 7, 8 and the opening 6 can be easily processed by etching. The thin layers 11, 12 can also be easily formed by half etching.

The important conditions for the material are that the liquid used should have good corrosion resistance, be strong, and be easily etched (if processing is done by etching instead of micro-drilling).
Stainless steel is one of the materials that satisfies these conditions.

Only the partition plate 6 and the thin plates 9 and 10 need to be made of stainless steel, and the body 16, which can be relatively thick, is preferably made of plastic material (for example, BS, polycarbonate) from the viewpoint of weight. Of course, it is not necessary to limit it to these materials. Furthermore, regarding the dimensions, the sizes of important parameters change depending on the size of the liquid supply pipe system and the size of the fluid supply element itself, so it is necessary to select optimal values.

A second embodiment of the invention is shown in FIGS. 7, 8, and 9. States a, b, and c in FIG. 1 correspond to FIGS. 7, 8, and 9, respectively. 4, 6, and the same parts as in FIG. This embodiment is characterized in that one movable thin plate 23 is used instead of the two thin plates 9 and 1o shown in FIGS. 4 to 4E, and the flow path is blocked by this. The movable thin plate 23 is provided in a partition plate 6' having openings D20, 21.

The operation is the same as in the first embodiment, and the acceleration is
When the pressure is applied to the pressure, the movable thin plate 23 blocks the opening 2o or the opening 21 to prevent pressure fluctuations from propagating. Opening 20.
The size of 21 and the thickness of the movable thin plate conform to the embodiments shown in FIGS. 4, 6, and 6.

Next, a third embodiment is shown in FIGS. 10, 11, and 12. This is an example in which the fluid supply element 16 of the present invention is applied to the liquid supply pipe system shown in FIG.
The state of each is shown in Figure 10.

This corresponds to FIGS. 11 and 12. Figures 4 to 9 in the diagram
Components that are the same as those in the drawings are given the same reference numerals and their explanations will be omitted. This embodiment has a structure in which the fluid supply element 4 shown in FIGS. 4, 6, and 6 is divided in half at the center to form a thin layer 26, in which a movable thin plate 23' is arranged. . The liquid is divided from the liquid reservoir 3 into two liquid supply pipes 2, one of which is connected to the liquid chamber 1.
3, through the removal section 7, the thin layer 11, the opening 2σ to the thin layer 26; 6, which communicates with the head 1 via a liquid chamber 17 formed by the body 24.
In FIG. 11, where the head 1 is scanning at a constant speed, no force (acceleration) is applied, so the thin plate 9,
1o is not distorted and the movable thin plate 23' does not move, so the flow path is not blocked. However, in the state shown in Fig. 10a (head 1 is near the left end), the thin plates 9 and 1o are distorted on the left side and opening 2.
At the same time as the opening 20' is blocked, the movable thin plate 23' also sticks to the partition plate 18 and blocks the opening 20', so that the flow path leading to the head 1 is blocked. The same thing can be seen in Figure 12.
This also occurs in state C, where the head 1 is near the right side.

The ring 22 prevents the movable thin plate 23' from moving in the vertical direction. The width between the rings 22 is narrower than the thickness of the movable thin plate 23'. This part has the effect of reducing pressure loss due to the viscous resistance of the liquid and further promotes pressure fluctuation mitigation. As shown in FIGS. 10 to 12, the liquid chamber 17 is more likely to exert its damper effect if it is arranged so as to surround the partition plates M 8 and 19.

FIG. 13 is an exploded perspective view of parts of the thin plate partition plate portion. Epoxy adhesive may be used to assemble this part, but in order to obtain the correct width of the thin layer, 1. It is preferable to use a metal diffusion bonding method.

If adhesive is used, an adhesive layer (from 10 μm) is formed, which makes the width of the thin layer unstable.

Although three embodiments of the present invention have been described above, the present invention is not limited to these.
A similar effect can be obtained if a part of the liquid supply pipe is provided with an element that moves when acceleration is applied to block the flow path.

As described above, the present invention is designed to block the flow path only when acceleration is applied to a part of the liquid supply pipe connected to the head. It can alleviate pressure fluctuations and is extremely useful for use in inkjet recording heads and the like.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams of conventional liquid supply pipe systems, B and O are diagrams showing their speed and pressure fluctuations, and Figure 3 shows the state of the meniscus of the liquid jet nozzle of the head. Figures 4 to 6, 7 to 9, and 10 to 12 are views showing the positions of the fluid supply elements of the first to third embodiments of the present invention, respectively. 13 is a sectional view showing its structure and operation, and FIG. 13 is an exploded perspective view of the components of the embodiment shown in FIGS. 10 to 12. 1...Head, 2...Liquid supply pipe, 3
...Liquid reservoir, 4,16...Fluid supply element, 5,20°21.20', 21'...
Opening, 6.6', 18.19... Partition plate, 7,
8... Removal part, 9, 10... Thin plate, 1
1.12...thin layer, 13,14.17...
...Liquid chamber, 15.24...Body, 22...
...Ring, 23...Movable thin plate, 26...
...Liquid injection nozzle, 26...Meniscus. Name of agent: Patent attorney Toshio Nakao and 1 other person31
0- 311- 31 2-

Claims (1)

[Claims] (1) A first opening communicating with the recording head, a second opening communicating with the liquid reservoir, and at least one sheet disposed in a fluid flow path connecting the first opening and the second opening. A fluid supply element comprising: a thin plate, the thin plate being moved or deflected to block the fluid flow path when the recording head is accelerated or decelerated.