JPH0452221B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid ejecting apparatus such as an inkjet recording apparatus that ejects liquid to record characters and figures.

Configuration of conventional examples and their problems In devices such as X-Y recorders and serial printers in which a liquid ejecting head (hereinafter referred to as a head) having an ejecting port for ejecting liquid is scanned, a device connected to the head is attached. If the supply pipe that supplies the liquid moves and the pressure fluctuations in the liquid within the supply pipe that occur due to this movement are transmitted to the head, it will have an adverse effect on the head. In other words, when pressure fluctuations act on the sides, droplets are ejected even if no signal is applied to the head, and conversely, when pressure fluctuations act on the sides, air is sucked into the head in the form of bubbles.
This results in unstable discharge or inability to discharge. As a method for alleviating pressure fluctuations within the liquid supply pipe, methods described in Japanese Patent Application Laid-open Nos. 115350/1982 and 120482/1982 are known.

1 and 2 show a liquid supply device known from Japanese Patent Application Laid-Open No. 57-120482.

In Fig. 1, a liquid supply pipe 2 is branched into two routes for a head 1 via a fluid supply element 3, and arranged in a symmetrical shape that looks like two U-shaped liquid supply pipes combined. The length from the left end to the right end of the liquid supply pipe 2 must be at least 2/1 of the moving range of the head 1. In a liquid supply pipe having such a shape, when the head 1 moves from side to side as shown in FIGS. 2B and 2C, the inertial force of the liquid tends to be offset between the left and right sides, so that fluctuations in the pressure of the liquid are easily reduced.

Next, an example of the structure of the fluid supply element 3 is shown in FIG.

The liquid communication passage 4 and the liquid communication passage 5 have orifices 8 and 9 provided in thin orifice plates 6 and 7, respectively, and these two orifices 8 and 9
It communicates with the head via a thin body supply layer 10 formed by orifice plates 6 and 7, and an annular liquid chamber 11 provided around this liquid supply layer 10.

Now, in FIG. 1, head 1 is scanned to the left,
Considering the state shown in Fig. b where the liquid stops at the end, an inertial force is generated in the liquid in the liquid passage 5 in Fig. 2 and in the liquid supply pipe on the right side connected thereto. The inertial force is expressed as the sum of static pressure and dynamic pressure. As shown in FIG.
The velocity of the liquid therein is significantly increased compared to the liquid communication channels 4,5. The dynamic pressure within the orifices 8, 9 therefore increases. Assuming that Bernoulli's equation holds approximately true, dynamic pressure + static pressure = constant, so static pressure will decrease by the amount that dynamic pressure increases. Therefore, the static pressure in the thin liquid supply layer 10 existing between the orifices 8 and 9 exhibits a lower value than the static pressure in the liquid communication passage 5. Since the static pressure in the thin liquid supply layer 10 indicates the pressure propagated to the head, pressure fluctuations in the liquid propagated to the head by the fluid supply element 3 can be alleviated. The same theory as above holds true even when the head 1 in FIG. 1c remains at the right end. Therefore, by using the liquid supply pipe 2 shown in FIG. 1 and the fluid supply element 3 shown in FIG. 2, the pressure fluctuations at both ends b and c in FIG. 1 can be alleviated.

As described above, in the fluid supply element shown in FIG. 2, the pressure propagated to the head 1 can be alleviated by appropriately selecting the diameters of the orifices 8 and 9. To explain this in more detail, the cross-sectional area of the liquid supply pipe 2 and the liquid communication passages 4 and 5 is S _O ,
Let S be the cross-sectional area of the orifices 8 and 9, let α be the acceleration applied to the head 1 at both ends of _{FIG .} Then, the relationship between acceleration α and pressure fluctuation ΔP _H becomes as shown in FIG.

In FIG. 3, when C=S/S _O =1, the pressure fluctuation _ΔPH increases in proportion to the acceleration α, as shown by a straight line 12.

For relatively large values of C<1, curve 13
As shown in , the pressure fluctuation ΔP _H increases in one direction as the acceleration α increases, and then decreases in the other direction.

When C is smaller than 1, as shown by curve 14, pressure fluctuation ΔP _H increases less on the side of curve 13 and decreases faster as the acceleration α increases.

On the other hand, the value A of the pressure fluctuation ΔP _H shown in FIG.
B indicates the range of pressure fluctuation that is allowed to propagate to head 1. If the pressure fluctuation _ΔPH exceeds the value of A, unnecessary ink will be ejected, and if it falls below the value of B, bubbles will appear in the head. is mixed in.

Therefore, for example, when using the fluid supply element 3 having the characteristics shown by the curve 13, stable head scanning is possible in the range of acceleration α such as O≦α<a and C<α<d. , when using the fluid supply element 3 having the characteristics shown by curve 14, stable head scanning is possible in the range of acceleration α of O≦α<b. (However, a, b, c,
d is the acceleration value shown in FIG. ) Since the acceleration that occurs during actual head scanning often has various magnitudes, the characteristics of the fluid supply element 3 that can withstand practical use are selected, for example, as shown by the curve 14. However, in that case, it is necessary to design so that the acceleration α does not exceed the value of b.

Next, in FIG. 2, the pressures in the liquid communication passages 4 and 5 are designated as P _A and P _B , and these pressures will be described.

In the head scanning system shown in FIG. 1b, assuming that the head 1 is at the left end, the lengths from the center of the fluid supply element 3 to the right and left ends of the loop-shaped liquid supply pipe 2 are L _A , respectively. Assuming l _B , the inertial force generated at this time is F _A = S _O l _A ζα when considering only the right side of the fluid supply element 3, and F _B = S _O l _B when considering only the left side. becomes ζα. (However, S _O is the cross-sectional area of the liquid supply pipe, ζ is the density of the liquid, and α is the acceleration.) When such an inertial force is generated on both sides of the fluid supply element 3, the inertial force is applied to the orifice plates 6 and 7. As a result, the liquid pressure in the liquid passages 4 and 5 fluctuates rapidly. Since the orifices 8 and 9 are very small, the magnitude of this variation has been actually measured to be almost the same as when the orifices 8 and 9 are closed, and approximately P _A ≒ F _A /S _O =l _A ζα P _B ≒−F _B /S _O =−l _B ζα ...(1) holds true.

Letting the pressure on the left side of the liquid passages 4 and 5 be ΔP, then ΔP=P _A −P _B = (l _A + l _B )ζα If l=l _A + l _B , then ΔP=lζα ...(2).

Equation (2) shows that the pressure difference ΔP between the liquid passages 4 and 5 is proportional to the acceleration α.

From this, it can be seen that the horizontal axis α in FIG. 3 can be replaced with ΔP according to equation (2). In the case of a liquid supply element having the characteristics shown by curve 13 or 14, the pressure fluctuation ΔP _H increases toward the side in a large part of the acceleration α because the pressure difference ΔP increases,
This can be explained by the fact that the flow velocity of the liquid in the orifices 8 and 9 increases, and _ΔPH , which is a static pressure component, decreases rapidly.

Due to the causes mentioned above, in conventional liquid supply elements, when the acceleration α increases beyond a certain level,
Since the pressure difference ΔP between the liquid passages 4 and 5 increases,
Because excessive negative pressure fluctuations are propagated to the head,
There was a drawback that air bubbles were mixed into the head.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate such drawbacks and to provide a liquid ejecting device capable of high-speed scanning by using a liquid supply device that can withstand even greater acceleration.

Structure of the Invention The present invention provides a liquid ejection head having a scanning function, a liquid supply element connected to the liquid ejection head and configured such that the cross-sectional area of a liquid passage rapidly changes, and a liquid supply element connected to a liquid supply source. and a liquid supply pipe configured in a loop shape, and the liquid supply element is connected to the loop-shaped liquid supply pipe via a viscosity droplet formed by a small-diameter orifice. .

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 4 shows an embodiment of the present invention. In FIG. 4, the loop-shaped distributed liquid supply tube 2 communicates with the liquid supply element 3 via flow resistors 15 and 16. Further, the head 1 and the liquid supply element 3 are connected in the same manner as in FIG.

The flow resistors 15 and 16 are members having a structure that can prevent the flow of liquid, and for example, the flow resistance bodies 15 and 16
A tube having an inner diameter smaller than that of the tube, a tube having a plurality of holes with a fine inner diameter, a porous material, etc. can be used.

FIG. 5 shows a structure in which the flow resistors 15 and 16 shown in FIG. 4 are integrated with the liquid supply element 3 so that the size can be reduced, and the fluid communication passages 4 and 5 shown in FIG.
Orifice plates 19 and 20 having orifices 17 and 18 are provided in the portion 12 to divide the liquid passage, forming liquid chambers 21 and 22 and liquid communication passages 23 and 24, respectively.

Although FIGS. 4 and 5 show similar effects in principle, a detailed explanation will be given here using FIG. 5. Assume now that the liquid supply element having the configuration shown in FIG. 5 is turned back at the left end as shown in FIG. 1b due to head scanning. The acceleration at this time is α,
The distances between the center of the liquid supply element and the right and left ends of the liquid supply pipe 2 are l _A and l _B , the length of the loop of the liquid supply pipe 2 is l = l _A + l _B , and the density of the liquid is ζ. Furthermore, it is assumed that the cross-sectional areas of the liquid chambers 21 and 22 and the liquid passages 23 and 24 and the internal cross-sectional area of the liquid supply pipe 2 are equal to S _O.

The liquid pressure in the liquid chambers 21, 22 is expressed by the above equation (1) when the orifice plates 19, 20 are not present, but when the orifice plates 19, 20 are present, the liquid pressure is the value obtained by subtracting the pressure loss here. In other words, the inertial force generated on the left and right sides of the liquid supply pipe, l _A ζαS _O ,
-l _B ζαS _O is not transmitted as it is to the liquid chambers 21 and 22, but only n% of it is transmitted. Then,
The liquid pressures P _A ′, P _B ′ in the liquid chambers 21 and 22 are P _A ′=n/100l _A ζα P _B ′=−n/100ζα ……(3), and the differential pressure ΔP′=P _A ′ −P _B ′ becomes ΔP′=n/100lζα ……(4). Comparing equations (2) and (4), we find that ΔP'=n/100ΔP, and the configuration shown in Figure 5 is n% lower for the same acceleration than the conventional configuration shown in Figure 2. It can be seen that only a pressure difference ΔP' of .

FIG. 6 is a graph in which the horizontal axis is the acceleration α, and the vertical axis is the pressure fluctuation _ΔPH of the liquid propagated to the head. Curve 25 shows the characteristics when using a liquid supply element with a conventional configuration, and when the acceleration α increases beyond b, a large negative pressure is generated and bubbles are mixed into the head. Curve 26 shows the characteristics of the liquid supply element of the present invention, and even at a large acceleration α greater than b, the absolute value of the pressure fluctuation ΔP _H can be made small. This is because, as described above, the pressure difference between the liquids in the liquid chambers 21 and 22 does not occur much.

In the example, a detailed explanation was given of an example in which the present invention was applied to a liquid supply element having the configuration shown in FIG. Of course, the present invention can also be applied to liquid supply elements.

Effects of the Invention As described above, the present invention provides a liquid ejecting device in which a liquid ejecting head is connected to a liquid supply element, and a liquid pipe is connected to this liquid supply element in a loop through a viscous resistor. Even if the acceleration α applied to the turn of the head provided in the liquid supply pipe is increased, the pressure fluctuation of the liquid propagated to the head ΔP _H
Since the head can be made small, the head can be scanned at high speed, and high-speed recording is possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the configuration of a conventional liquid ejecting device, Fig. 2 is a sectional view of a conventional liquid supply element, and Fig.
The figure is a graph showing the characteristics of a conventional liquid ejecting device, FIG. 4 is a schematic diagram showing the configuration of the liquid ejecting device of the present invention, FIG. 5 is a cross-sectional view of a liquid supply element used in the present invention, and FIG. 6 is a graph showing the characteristics of the liquid ejecting device of the present invention. DESCRIPTION OF SYMBOLS 1... Head, 2... Liquid supply pipe, 3... Liquid supply element, 4, 5... Liquid passage, 8, 9... Orifice, 15, 16... Viscous resistance body, 17, 18
...orifice, 19,20...orifice plate,
21, 22...Liquid chamber, 23, 24...Liquid communication passage.

Claims (1)

[Claims] 1. A liquid ejection head having a scanning function, a liquid supply element connected to the liquid ejection head and configured such that the cross-sectional area of the liquid passage changes rapidly, and a liquid supply element connected to the liquid supply source and configured in a loop shape. A liquid ejecting device comprising: a liquid supply pipe; wherein the liquid supply element is connected to the loop-shaped liquid supply pipe via a viscous resistor formed by a small-diameter orifice.