JP2004105968A - Liquid discharging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always surely apply stable vacuum to a liquid storing vessel regardless of the magnitude of vacuum, and to sufficiently prevent dropping or sucking of liquid by continuously applying vacuum to the vessel at supply stopping of power. <P>SOLUTION: A vacuum system for applying vacuum to the liquid storing vessel 1 is composed of a variable throttle valve 6 mechanically stroking a valve element, a vacuum generating means 5 generating vacuum corresponding to the flow of a pressurizing gas flowing through the valve 6, and a control means 9 controlling the opening of the valve 6. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a liquid ejecting apparatus that ejects a liquid containing a viscous substance such as an adhesive or a paste-like material containing a filler or a filler into a predetermined ejection position according to a predetermined ejection amount, and in particular, During suspension of liquid ejection, the intended negative pressure is always applied accurately to the storage container regardless of the remaining amount of the liquid in the storage container or the physical properties inherent to the liquid.

As a conventional technique for applying a negative pressure to the storage container to improve the cutoff of the liquid and to prevent unexpected dripping during the suspension of the liquid including stoppage of liquid discharge from the storage container, for example, There is one proposed by the applicant as Japanese Patent Application Laid-Open No. 3-217271.
It consists of an air suction source that generates a high negative pressure, an electropneumatic regulator, a negative pressure reducing valve, an accumulator, a suction solenoid valve and a discharge solenoid valve whose opening is controlled by a signal from the control unit. Connected to a syringe as a liquid storage container through a control unit based on the relative relationship between the remaining amount of liquid in the syringe and the degree of negative pressure necessary to offset the liquid weight, obtained by experiments and the like. By adjusting the degree of negative pressure supplied to the syringe in accordance with the pressure setting signal input to the negative pressure reducing valve from, the negative pressure of the liquid in the syringe due to the negative pressure inside the syringe being too high It is intended to prevent suction into the system, while preventing accidental dripping of the liquid in the syringe due to too low a negative pressure.

However, in this prior art, an electropneumatic regulator is used as a negative pressure reducing valve, and many electropneumatic regulators are configured by incorporating an electromagnetic directional switching valve and a diaphragm having a spring force in a housing. Therefore, especially in a negative pressure range close to the atmospheric pressure (around 0 to -10 mmHg), it is difficult to ensure a state of balance with the spring force of the diaphragm, and the stability of the negative pressure becomes low. In addition to the problem that the stability of the amount, the shape of the coating, etc. is also lowered, when the operation of the electromagnetic directional control valve is stopped due to a power failure or the like, the supply of the negative pressure to the syringe is stopped, or the air suction source is stopped. However, there is a problem that the high negative pressure is directly supplied to the syringe without being reduced, and dripping or suction of the liquid in the syringe occurs.

In addition, when the balance between the internal pressure of the syringe and the spring force of the diaphragm is broken, the electropneumatic regulator supplies the negative pressure from the air suction source into the syringe, while the negative pressure in the syringe reaches a predetermined value. Therefore, since the on / off control for stopping the supply of the negative pressure is performed when the two are balanced, pulsation occurs in the syringe internal pressure, which causes a variation in the discharge amount.

In addition, in this prior art, since the electropneumatic regulator as a negative pressure reducing valve is disposed downstream of the air suction source that generates a high negative pressure, a large amount of air can be generated even with a slight opening of the diaphragm. As a result, there is a problem that this causes variation in the discharge amount.

The present invention has been made as a result of studying to solve all such problems of the prior art, and the purpose of the invention is to store liquid regardless of the degree of negative pressure. A stable negative pressure can always be applied to the container, and even when the power supply is stopped due to a power outage or the like, the storage container can be continuously applied with the immediately preceding negative pressure. The dripping and suction of the liquid in the storage container can be more effectively prevented, and furthermore, the generation of pulsation in the storage container and the negative pressure system flow path is prevented, thereby realizing stable control of the discharge amount. Is what you do.
In addition, by disposing the negative pressure generating means on the downstream side of the variable throttle valve, and by eliminating the need for the installation of an air suction source that constantly generates a high negative pressure, stable operation is ensured in any case. It is an object of the present invention to provide a liquid discharge device capable of providing a discharge amount.

The liquid discharge device of the present invention discharges the liquid in the storage container by a predetermined amount at a time, and applies a negative pressure to the storage container during a suspension of the liquid discharge including a stop of the liquid discharge. A negative pressure system that applies a negative pressure to the container, a variable throttle valve that mechanically strokes the valve body with, for example, screws, gears, cylinders, and the like, and a negative pressure corresponding to the flow rate of the pressurized gas passing through the variable throttle valve. And a control means for controlling the opening degree of the variable throttle valve based on a previous input relating to the amount of liquid remaining in the storage container and the like.
Here, it goes without saying that valve means such as a regulator and a solenoid valve can be provided downstream of the negative pressure generating means.

In this liquid ejection device, the stroke position of the valve body of the variable throttle valve, and thus the opening of the variable throttle valve, is controlled based on the signal from the control means, and the flow rate of the pressurized fluid passing therethrough is adjusted. Therefore, the degree of negative pressure generated by the negative pressure generating means is always accurate with excellent stability, regardless of the magnitude of the negative pressure, and without having to secure a state of equilibrium with spring force and the like. It can be the expected value. Therefore, the discharge amount of the fluid, the application shape, and the like can also be sufficiently stabilized.

By the way, the mechanically stroked valve body of the variable throttle valve here is advanced and retracted by a motor or the like which is operated by a signal from the control means. Even when the valve stops, the valve body itself is held at the stroke position immediately before the power failure, and the flow rate of the pressurized gas passing through the variable throttle valve is also maintained at the state immediately before the power failure. The fluctuation of the negative pressure generated by the generating means and supplied to the storage container is effectively prevented. Thus, here, no negative pressure is supplied to the storage container due to a power failure or the like, and no excessive negative pressure generated by an air suction source or the like is directly supplied to the storage container. The dripping of the liquid in the container and the suction into the negative pressure system flow path can be effectively prevented.

By the way, also in this discharge device, when a power failure or the like occurs, the operation of, for example, a compressor or the like as a source of the pressurized fluid is stopped. Before the pressurized gas in the accumulator has finished flowing out, take sufficient measures by disconnecting the liquid storage container from the negative pressure system flow path or sealing the storage container. be able to.

Further, since this device continuously applies a negative pressure degree to the storage container in accordance with the flow rate of the pressurized gas passing through the variable throttle valve, on / off control in the storage container and the negative pressure system flow path is performed. , And the variation in the discharge amount due to the generation of the pulsation can be reliably and obviated.

In addition, here, in the case where an air suction source for constantly generating an unnecessarily high negative pressure is provided by generating a desired negative pressure by using a negative pressure generating means disposed downstream of the variable throttle valve. In addition to the above, the apparatus configuration and the circuit configuration of the apparatus are simplified and downsized, and the effect that troubles can be minimized can be achieved.

As is clear from the above description, according to the present invention, the intended negative pressure can be always stably supplied into the liquid storage container regardless of its magnitude, Even if there is a power failure or the like, a negative pressure can be continuously applied to the storage container to effectively prevent the liquid from dripping and sucking. Further, according to the present invention, it is possible to prevent the occurrence of pulsation in the storage container and the negative pressure system flow path, and to stabilize the discharge amount. Further, according to the present invention, it is not necessary to provide an air supply source that constantly generates a high negative pressure, so that a stable discharge amount can be secured, and the apparatus can be simplified, downsized, and reduced in cost.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which a solid line indicates a pressure circuit, and a broken line indicates a signal circuit.
Here, a syringe 1 as a liquid storage container and an air supply source 2 as a pressurized gas supply means are connected via a switching valve 3, and a discharge is performed between the switching valve 3 and the air supply source 2. A pressure setting regulator 4 is interposed, and an ejector 5 as negative pressure generating means is connected to the switching valve 3.
Here, the ejector 5 and the air supply source 2 are connected, for example, with a screw or a gear through a variable throttle valve 6 that mechanically strokes the valve body. , A negative pressure gauge 7 is interposed.
Further, a switching signal is output to the switching valve 3, a set pressure signal is output to the regulator 4, and a set negative pressure signal is output to the motor 8 for the valve body stroke of the variable throttle valve 6. Is provided.

Here, the control means 9 includes, for example, a switching timing and a hold time of the switching valve 3 for a fixed amount discharge of the liquid in the syringe, a pressurizing force according to the amount of liquid in the syringe, and the like. In addition to being able to input in advance in accordance with the empirical rules regarding, the generation of a negative pressure corresponding to the amount of liquid in the syringe is ensured in relation to the pressure of the pressurized air supplied from the air supply source 2. The obtained valve opening of the variable throttle valve 6 can be input in advance, and further, a correction condition of the valve opening based on the feedback signal of the actually measured negative pressure value from the negative pressure gauge 7 can be input.

The apparatus configured as described above discharges a fixed amount of liquid in the syringe in a state where the syringe 1 is positioned at a required position with respect to the work, for example, under the action of the regulator 4 based on a signal from the control means 9. While reducing the pressurized air from the air supply source 2 to a predetermined pressure, the switching valve 3 is also shifted from the position shown in the figure by a signal from the control means 9, and the air pressure passed through the regulator 4 is transferred into the syringe. The operation is carried out for a required time, and as a result, the liquid in the syringe is discharged by a predetermined amount from the nozzle 1a provided at the tip under the action of its own weight and pressure.

On the other hand, the stop of the discharge of the liquid is performed by shifting the switching valve 3 to the position shown in the drawing based on the signal from the control means 9, and is generated by the ejector 5 simultaneously with this shift of the switching valve 3. The negative pressure will be supplied into the syringe.

Here, the degree of negative pressure generated by the ejector 5 is specified by a valve opening signal output from the control means 9 to the motor 8 of the variable throttle valve 6 according to the amount of liquid remaining in the syringe, When the amount of liquid is large, the valve opening is increased, and a large amount of pressurized air is passed through the variable throttle valve to generate a large negative pressure. Thus, a small negative pressure is generated. Then, the measured value of the negative pressure generated in this way is fed back from the negative pressure gauge 7 to the control means 9, and when there is a difference between the measured value and the expected negative pressure, the control means 9 A valve opening correction signal is output to the motor 8 again to make them match with high accuracy.
Therefore, when the switching valve 3 is shifted to the illustrated position as described above, the pressure in the syringe is quickly discharged, and the inside thereof is set to a negative pressure corresponding to the remaining amount of liquid. Therefore, excellent running out of liquid is realized, and accidental dripping of liquid is effectively prevented. Here, when the required negative pressure to be supplied into the syringe also becomes small due to the small amount of liquid remaining in the syringe, the flow rate of pressurized air passing through the variable throttle valve 6 is reduced by reducing the flow rate. Since a negative pressure close to the atmospheric pressure can be supplied stably, the discharge amount of the liquid, the application shape, and the like can always be as expected regardless of the remaining amount of the liquid.

By the way, in this device, even if the operation of the control means 9, the motor 8, etc. is stopped due to a power failure or the like, the opening degree of the variable throttle valve 6 is maintained as it is. As long as the supply is continued, a negative pressure can be applied to the syringe 1, so that it is possible to secure a sufficient time for taking a good or bad measure before the liquid dripping or the like occurs.
Moreover, the negative pressure here is generated under the continuous flow of the pressurized air to the variable throttle valve 6 regardless of the magnitude thereof, and pulsation occurs in both the syringe 1 and the negative pressure system flow path. As a result, variations in the discharge amount can be effectively suppressed.
In addition, here, by providing the ejector 5 for generating a required negative pressure, it is not necessary to install an air supply source for always preparing a high negative pressure, so that the structure of the apparatus, especially the circuit configuration, is simplified. In addition, it is possible to reduce the size and contribute to maintenance free and cost reduction.

Although the embodiment of the present invention has been described with reference to the drawings, valve means such as a regulator solenoid valve may be provided downstream of the ejector 5, for example, between the ejector 5 and the switching valve 3. According to this, when it is desired to more quickly supply the negative pressure into the syringe, the negative pressure generated in the ejector 5 is set to a relatively large value in advance, and the shift and the timing of the switching valve 3 are adjusted. A large negative pressure can be applied to the syringe 1.

Although it is not clear from the drawing, it is not clear that the length of the pipeline between the ejector 5 and the syringe 1 is as short as possible to reduce the amount of air in the pipeline and reduce the pipeline resistance. As a result, the desired negative pressure can be applied more quickly to the syringe.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Syringe 1a Nozzle 2 Air supply source 3 Switching valve 4 Regulator 5 Ejector 6 Variable throttle valve 7 Negative pressure gauge 8 Motor 9 Control means

Claims (1)

A liquid discharge device that discharges a predetermined amount of liquid in a storage container and applies a negative pressure to the storage container during suspension of liquid discharge,
A negative pressure system that applies a negative pressure to the storage container, a variable throttle valve that mechanically strokes the valve body, and a negative pressure generating unit that generates a negative pressure according to a flow rate of the pressurized gas passing through the variable throttle valve, A liquid discharging apparatus comprising: a control unit that controls an opening degree of a variable throttle valve based on a previous input.

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