JP3728998B2 - Ink supply device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for forming a fine film by discharging ink, a semiconductor liquid material, or the like onto an object, and more particularly to an ink supply apparatus for controlling the height position of a container of liquid material.
[0002]
[Prior art]
So-called inkjet technology is employed for printing on paper and manufacturing color filters for liquid crystals. Since printing on large paper and manufacturing color filters consumes a large amount of ink, they are replenished using aluminum sealed packs or cartridge-type ink packs.
[0003]
[Problems to be solved by the invention]
However, for products that consume a large amount of ink and have a high unit price, long-term reliability and a reduction in ink replacement frequency are desired. In this respect, the capacity of the conventional aluminum sealed pack (for example, 200 ml and 300 ml) is insufficient.
[0004]
Therefore, it is conceivable to make the ink container with a larger capacity. In such a case, the fluctuation range of the ink liquid level becomes large. This is because the difference between the liquid level of the ink and the height of the nozzle portion (water head difference) becomes large, which is not preferable because the ink cannot be ejected or becomes unstable. In addition, when used in a range where the water head difference does not become large, useless waste ink is generated, which is a problem.
[0005]
Conventionally, ink is replaced in advance from the viewpoint of process management. However, since the replacement time is determined by counting the number of ejections, it does not necessarily correspond to the actual ink remaining amount. For this reason, a lot of ink is wasted due to replacement and wasted.
[0006]
Accordingly, an object of the present invention is to provide an ink supply device that is provided with a mechanism for keeping the ink liquid level constant, thereby keeping the water head difference constant and stabilizing ink ejection.
[0007]
It is another object of the present invention to provide an ink supply apparatus that can discharge with high reliability over a long period of time using a large-capacity container such as an ink bottle.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an ink supply apparatus according to the present invention includes a container portion that stores ink to be supplied to an inkjet head, a lifting mechanism that moves the container portion in the vertical direction, and a position of a liquid surface of the ink. A liquid level detecting unit for detecting, an ink weight detecting unit for detecting the weight of the ink, a nozzle level of the inkjet head based on at least the detected liquid level of the ink and the weight of the ink, and the liquid level of the ink And a control unit that controls the lifting mechanism so that the ink level is maintained at a target position where the difference between the head and the head is a predetermined water head difference .
[0009]
With such a configuration, the water head difference of a large amount of ink can be kept constant, so that a good meniscus can be secured over a long period of time, and the occurrence of ejection omission is suppressed.
[0010]
Preferably, the control unit further detects an ink discharge abnormality by monitoring a change in the weight of the ink with respect to the number of ink discharges.
[0011]
According to this configuration, it is possible to grasp the weight (weight change / number of ejections) of the ink droplets ejected by the ink supply device. Since the weight of the ink droplet can be grasped in a state where the water head difference and the liquid surface position of the ink can be adjusted, the weight of the ink can be grasped more accurately. It is possible to determine the state of ink supply (oversupply of ink, insufficient supply, ink clogging, etc.) based on the slope of the weight change characteristic (weight of ink droplet) with respect to the number of ink ejections .
[0012]
Preferably, the control unit further operates the lifting mechanism at a first speed so that the liquid level of the ink is in the vicinity of the target position based on the weight of the ink after replacement or replenishment. The elevating mechanism is moved at a second speed until the liquid level of the ink reaches the target position from the vicinity .
[0013]
With this configuration, it is possible to move the elevating mechanism in two stages of relatively high speed movement and low speed movement, and the liquid level alignment time after ink replenishment is shortened.
[0014]
Preferably, the control unit further notifies ink replacement when the weight of the ink falls below a replacement reference value.
[0015]
Preferably, a liquid material used in a semiconductor process is used instead of the ink.
[0016]
Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram for explaining the outline of the ink supply apparatus of the present invention. As shown in the figure, the ink supply device is roughly constituted by an ink bottle 9 as an ink storage container, a liquid level detector 21, a weight detector 23, an elevating mechanism 8, a control unit 24, and the like. The ink bottle 9 has a larger capacity than conventional ones, and stores, for example, about 1000 ml of ink. A liquid level detector 21 is disposed on the side surface of the ink bottle 9, and the position of the liquid level is detected by, for example, the light emitter 21a and the light receiver 22b. It is also possible to use a float that floats on the liquid surface or a magnet. Further, the liquid level may be read by a CCD line sensor provided on the side of a transparent bottle or a transparent window. The ink bottle 9 is placed on a weight detector 23 that measures the ink weight. The weight detector 23 is a so-called electronic balance and is disposed on the upper surface of the lifting table 10. The lifting table 10 is moved in the vertical direction by the lifting mechanism 8. The elevating mechanism 8 includes a pulse motor 16 that generates a driving force, a spiral shaft 14 that is rotatably mounted between the upper and lower frames 11, and a guide rail 12 that reciprocally moves the table 10 linearly. 13. A belt 17 that transmits the driving force of the motor 16 to the spiral shaft 14, a potentiometer 15 that is attached to the end of the spiral shaft 14 and detects the rotational angle of the shaft. Preferably, the spiral shaft 14 is a ball screw having the table 10 as a slider.
[0017]
The detection outputs of the liquid level detector 21 and the weight detector 23 are supplied to the control unit 24 as a liquid level detection signal and a weight detection signal, respectively. The output signal of the potentiometer 15 is also supplied to the control unit 24. The control unit 24 adjusts the height position of the turntable by appropriately controlling the rotation of the motor 16 to maintain the ink liquid level at a predetermined position where a predetermined water head difference is obtained.
[0018]
2 and 3 are explanatory diagrams for explaining liquid level detection and height control. In FIG. 2, the light emitter 21a is constituted by an LED, and the light beam emitted from the LED is adjusted to an appropriate width, passes through the bottle 9, and enters the phototransistor of the light receiver 21b. The phototransistor outputs a current corresponding to the amount of received light and is converted into a voltage signal by a resistor. This voltage output is amplified to an appropriate level by an amplifier 21c having a noise removal filter having an LPF characteristic, and converted to voltage data by a D / A converter in the control unit 21. As shown in FIG. 3, the sensor output varies depending on the position of the ink surface. When the liquid level is at the center position of the sensor beam, the output voltage of the amplifier 21c is Vo. When the liquid level is lowered and positioned below the light beam width, the phototransistor receives all the light beam, and the output voltage becomes a large value (maximum). When the liquid level rises and is positioned above the light beam width, all the light beam passes through or is blocked by the ink, so that the light received by the phototransistor decreases and the output voltage becomes a small value (minimum). The determination unit 24b compares the current voltage value V ′ with the reference value Vo, and calculates a difference ΔV between the current voltage value V ′ and the reference value Vo. When the difference ΔV exceeds a predetermined range, the rotation direction of the motor 16 is determined in accordance with the sign of the difference ΔV, and the rotation amount of the motor is determined in accordance with the value of the difference ΔV. This is supplied to the motor drive circuit 24c. The motor drive circuit 24c supplies a number of drive pulses corresponding to ΔV to the motor 16 in a phase order so as to be in the determined rotation direction. As the motor 16 operates, the table moves up and down so that the liquid level is at the center position of the light beam. By such a control loop, the ink level is maintained at a certain position. Here, if the difference between the height position of the liquid level detector 21 and the height position of the nozzle 19 of the inkjet head 18 is set to a predetermined water head difference, the water head difference is maintained to be constant.
[0019]
FIG. 4 is an explanatory diagram for explaining another operation of the control unit 24. As described above, the control unit 24 monitors the output signal of the weight detector 23 and grasps the change in the ink weight in the bottle 9. Further, the control unit 24 grasps the number of ink ejections from the nozzles 19 by counting nozzle drive pulses. Therefore, when the bottle is replaced, the control unit 24 stores the weight of the ink (or ink and bottle) in the memory table for each predetermined number of ejections as shown in FIG. When the ejection number versus weight change characteristic follows a standard change pattern stored in advance, it can be determined that ink supply is normally performed in the ejection process. When the inclination of the measurement pattern is steeper than the inclination of the standard change pattern, it is estimated that ink is excessively supplied, when the inclination is gentle, ink supply is insufficient, and when there is no inclination, ink clogging is estimated. When the ink weight falls below the replacement determination reference value, it is determined that it is time to replace the ink (or ink bottle). The determination result of the abnormality based on the weight and the replacement time is reported to, for example, a process computer (not shown) managing the process via the LAN, and a warning is displayed.
[0020]
FIG. 5 is a flowchart for explaining an example in which the liquid level is controlled by using a liquid level detector, a weight detector, and a potentiometer. In this example, after replacing the ink, the table 10 is moved relatively fast until the ink level is near the level detector, and when it is near, the table is moved relatively slowly, The liquid level detector 21 is positioned as fast as possible at the detection center position.
[0021]
When the ink (bottle) is replaced or the ink is replenished, the control unit 24 performs the process shown in FIG. First, the control unit 24 reads the placed ink weight (or ink and bottle weight) W ′ (S22). The control unit 24 stores the value of the potentiometer 15 (the height of the table 10) when the liquid level of the ink (or ink and bottle) weight W is previously positioned in the memory at the target height (center position of the light beam). ) Are stored in a table. With reference to this table, the target height Ho corresponding to the weight W ′ is read (S24). The current value of the potentiometer 15 is read to know the current height H ′ (S26). A difference ΔH between the target height Ho and the current height H ′ is obtained (S28). The amount of rotation angle of the motor corresponding to this difference is calculated (S30). The motor 16 is driven by applying a pulse train that gives the motor 16 rotation of the corresponding angle amount, and the table 10 is moved (S32). The value of the potentiometer 15 is read (S34), and it is determined whether or not the target height (reference position) Ho has been reached (S36) (S36; No). When the value of the potentiometer 15 is close to the target height position (S36; Yes), the rotation of the motor 16 is switched to a low speed (S38). The low speed rotation of the motor 16 is continued until the liquid level detector 21 detects the liquid level (S38, S40). When the liquid level detector 21 detects the liquid level (S40; Yes), the output of the potentiometer is read and set as the detected liquid level height Hs (S42). As a result, the liquid surface position after replacement of the bottle 9 or after ink replenishment is set as the reference position. The weight W ′ and the corresponding liquid level height position Hs are written in the above-mentioned table of the memory, and the data of the table weight to the liquid level height position is enriched. The motor is stopped (S46). Thereafter, as described with reference to FIGS. 2 and 3, the lowering of the liquid level is detected and the height of the table is controlled to slightly increase.
[0022]
In this way, using the ink weight as a guide, the table is moved quickly, and then the ink liquid level is positioned at the target position so that the liquid level does not wave at a low speed. This speeds up the process restart after ink replacement (replenishment).
[0023]
If the ink container has a shape in which the volume and the height are in direct proportion, the liquid level decreases in proportion to the decrease in the ink weight. Therefore, the motor moves up the table in response to the decrease in the ink weight. May be controlled. The control may be switched when the output of the liquid level sensor is defective due to some cause.
[0024]
The ink container is not limited to a bottle. Any shape may be used as long as it is suitable for storing ink. The container and the weight sensor may be integrated, or the weight sensor and the table may be integrated.
[0025]
【The invention's effect】
As described above, according to the ink supply device of the present invention, the water head difference of a large amount of ink can be kept constant, so that a good meniscus can be secured over a long period of time, and the occurrence of discharge omission is suppressed. Is done.
[0026]
In addition, since the ink weight is monitored, the weight of the ink droplet can be grasped, and the occurrence of ejection failure can be detected early.
[0027]
Since the ink weight is monitored, it is possible to know the ink replacement time with little ink waste.
[0028]
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration of the present invention.
FIG. 2 is a block diagram for explaining liquid level detection and motor control.
FIG. 3 is an explanatory diagram for explaining a relationship between a liquid level position of ink and a detection output.
FIG. 4 is a graph illustrating the relationship between the number of ink ejections and the ink weight.
FIG. 5 is a flowchart illustrating an example in which control is further performed using detected weight and potentiometer output.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Lifting table 11 Frame 12, 13 Guide rail 16 Motor 18 Inkjet head 21 Liquid level detector 23 Weight detector 24 Control part

Claims (5)

A container portion containing ink to be supplied to the inkjet head;
An elevating mechanism for moving the container part in the vertical direction;
A liquid level detection unit for detecting the position of the liquid level of the ink;
An ink weight detector for detecting the weight of the ink;
Based on at least the detected liquid level of the ink and the weight of the ink, the liquid level of the ink is maintained at a target position where the difference between the nozzle portion of the inkjet head and the liquid level of the ink becomes a predetermined water head difference. A control unit for controlling the elevating mechanism so that,
An ink supply device comprising: The ink supply apparatus according to claim 1, wherein the control unit further detects an abnormality in ink discharge by monitoring a change in the weight of the ink with respect to the number of ink discharges . The control unit further operates the elevating mechanism at a first speed so that the liquid level of the ink is in the vicinity of the target position based on the weight of the ink after replacement or replenishment . the ink supply device according to claim 1 or 2 liquid surface and wherein the moving the lifting mechanism at a second speed from the vicinity until the target position. Wherein the control unit further, the ink supply device according to any one of claims 1 to 3, wherein the notifying the exchange of the ink when the weight of the ink falls below the replacement reference value. Apparatus according to any one of claims 1 to 4, characterized by using a liquid material used for the semiconductor process instead of the ink.

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