JP2001153246A - Liquid dripping preventing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid dripping preventing device capable of independently setting a suction period and a suction amount to have a large freedom degree. SOLUTION: This liquid dripping preventing device, preventing liquid dripping by sucking a pressure fluid by displacement based on a pilot pressure of a displacement member, prevents liquid dripping by obtaining a number of control times in a control times arithmetic means 7 dividing the target total displacement set by a displacement up/down indicating switch 1 by a suction period set by a suction period up/down indicating switch 4, counting a sampling clock to a number of control times by an up counter 9, obtaining a change component of the displacement per control times in a displacement arithmetic means 8 dividing the target total displacement by the control times, multiplying a counting value of the up counter 9 and a change component of the displacement per control times in a multiplier 10 to obtain target displacement at each of a number of control times, controlling current carrying of a supply/discharge solenoid valve 13, 14 based on polarity of a deviation of the target displacement and the displacement of the displacement member to adjust the pilot pressure, and follow-up controlling the displacement of the displacement member to the target displacement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying a liquid to be discharged, such as a reagent, onto a target object by discharging the liquid to be discharged from a downwardly opened nozzle when the supply of the liquid to be discharged is stopped. The present invention relates to a dripping prevention device that prevents dripping by sucking the liquid.

[0002]

2. Description of the Related Art A conventional liquid dripping prevention device is provided with a suction valve (hereinafter, referred to as a suction valve) between a liquid supply source to be discharged and a nozzle opened downward.
A suction-back instruction signal supplied based on a supply stop signal of the liquid to be discharged starts suction by the suction valve.

In the suction by the suction valve, the diaphragm is raised by control to increase or decrease the pilot pressure of the pilot pressure chamber of the suction valve provided in the middle of the liquid supply pipe to be ejected, and the liquid to be ejected is substantially supplied to the circulation pipe. The liquid to be ejected is sucked to prevent dripping from the nozzle.

[0004]

However, since the suction amount and the suction period until the end of the suction of the suction amount are different depending on the target process, the suction period of the dripping prevention device is, for example, requested by the process side. Although it is desired that the suction amount is constant, the suction amount during the suction period is set to a different amount, and conversely, the suction amount is constant but the suction period is set to a different period. Are required to be set independently without interfering with each other.

[0005] There has been no such dripping prevention device having a large degree of freedom.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dripping prevention device having a high degree of freedom in which a suction period and a suction amount can be set independently.

[0007]

According to a first aspect of the present invention, there is provided a drip prevention device having a fluid passage for sending a pressurized fluid toward a nozzle and displacing a displacement member which is displaced based on pilot pressure. A dripping prevention device that controls a suction amount of a suck back valve that suctions a pressure fluid in a fluid passage to prevent dripping, a displacement amount detecting unit that detects a displacement amount of a displacement member, and a target total displacement. Target displacement amount setting means for setting the amount, suction period setting means for setting a suction period for sucking the pressure fluid in the fluid passage up to the set target total displacement amount, and the set suction period is predetermined. A control count calculating means for calculating a control count by dividing by a period, a counter for counting the number of pulses supplied in each of the predetermined periods up to the control count, a control target count determined by the set target total displacement and the control count determined. A displacement amount calculating means for calculating a target displacement amount for each of the control times based on the above, and a pilot based on the polarity of the difference between the target displacement amount of the control times based on the count value of the counter and the displacement amount detected by the displacement amount detecting means. Control means for controlling the displacement amount of the displacement member to a target displacement amount of the control number by increasing or decreasing the pressure.

According to the dripping prevention device of the present invention, the number of controls for suctioning up to the target total displacement by dividing the set suction period by the predetermined period is predetermined. The pulse supplied for each of the predetermined periods is counted by the counter until the number of times of control is reached. On the other hand, the displacement amount calculating means obtains the target displacement amount for each control number based on the set target total displacement amount and the control number, and the target displacement amount and the displacement amount detecting means for the control number based on the count value of the counter. The pilot pressure is increased / decreased based on the polarity of the deviation from the detected displacement amount, and the displacement amount of the displacement member is controlled to the target displacement amount of the control number of times, so that the displacement member follows the target displacement amount and displaces. Then, the pressure fluid in the fluid passage is sucked to prevent dripping from the nozzle tip. In this case, the target total displacement amount and the suction period can be set independently, so that the degree of freedom of setting is improved, and it can be applied to a wide range of processes.

According to a second aspect of the present invention, there is provided a dripping preventing apparatus according to the first aspect, wherein the displacement calculating means divides the total target displacement by the number of times of control, and the dividing means. And a multiplication means for multiplying the result of the division by the count value of the counter, wherein the multiplication result is set as the target displacement amount.

According to the second embodiment of the present invention, since the division result is a value obtained by dividing the target total displacement by the control count, the target total displacement is a value obtained by equally dividing the target total displacement by the control count. The value multiplied by the count value of the counter becomes the target displacement amount for each control count, and by selecting the predetermined period to a small value, the target displacement amount increases substantially linearly. Therefore, the suckback amount increases substantially linearly by the displacement of the displacement member.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a dripping prevention device according to the present invention will be described with reference to embodiments.

FIG. 1 is a block diagram showing the construction of a dripping prevention device according to an embodiment of the present invention, and FIG. 2 is a sectional view of a suck-back valve to which the dripping preventing device of the present invention is applied. .

A drip prevention device 15 according to one embodiment of the present invention is constituted by a microcomputer, and receives an output of a displacement amount up / down instruction switch 1 to set an up / down target amount of displacement. Down counter 2,
A displacement amount memory 3 for storing the set target total displacement amount based on the count value of the up / down counter 2;
An up / down counter 5 for setting a suction period for receiving the output of the down instruction switch 4 to perform suction to the set target displacement amount, and a suction period memory for storing a set suction period based on the count value of the up / down counter 5. 6 and the number of times of control to obtain the number of control N by dividing the suction period stored in the suction period memory 6 by the period of the sampling clock (also referred to as sampling period) obtained by dividing the operation clock of the microcomputer by a predetermined frequency dividing ratio. There is functionally provided with a calculating means 7 and a displacement calculating means 8 for dividing the total target displacement stored in the displacement memory 3 by the result of calculation by the control number calculating means 7.

Here, a displacement amount up / down instruction switch 1, an up / down counter 2, and a displacement amount memory 3
Constitutes a target displacement amount setting means, and the suction period up / down instruction switch 4, the up / down counter 5, and the suction period memory 6 constitute a suction period setting means.

Further, the drip prevention device 15 according to an embodiment of the present invention includes an up counter 9 for counting the sampling clock by presetting the operation result by the control number operation means 7 and an operation by the displacement amount operation means 8. A multiplier 10 for multiplying the result by the count value of the up counter 9, a switch 11 controlled to be in an off state by an output from the up counter 9 when the count value of the up counter 9 is not within the control count N, and a switch 11. A deviation is calculated by comparing an arithmetic output of the multiplier 10 with the A / D conversion result of a detection output of the displacement amount sensor 33 described later, and based on the polarity of the deviation, the air supply solenoid valve 13 and the exhaust solenoid valve 14 are used. And a deviation detection / control means 12 for selecting and supplying a current.

On the other hand, the displacement amount up / down instruction switch 1 cooperating with the dripping prevention device 15 is provided with a reference to the case where the volume of the flow path of the liquid to be discharged immediately before the supply of the liquid to be discharged is cut off. That is, a displacement amount up / down instruction switch for setting the displacement amount based on the diaphragm displacement amount for suction by the suck back valve 20 immediately before the supply of the liquid to be discharged is shut off.

When the up side is pressed by the displacement amount up / down instruction switch 1, the up / down counter 2 counts up the sampling clock over the pressing period, and when the down side is pressed, the up / down counter 2 is pressed over the pressing period. The down counter 2 counts down the sampling clock, and the target total displacement is set.

The suction period up / down instruction switch 4 cooperating with the dripping prevention device 15 is used to increase the suction period for setting the suction period required for performing suction (suck back) based on the set target total displacement. / Down instruction switch.

If the up side is pressed by the suction period up / down instruction switch 4, the up / down counter 5 counts up the sampling clock over the pressing period, and if the down side is pressed, the up / down counter 5 is up / down over the pressing period. The down counter 5 counts down the sampling clock, and the suction period is set.

And cooperating with a dripping prevention device 15;
A switch 16 for instructing supply of the liquid to be ejected to the nozzles when a power supply Vcc is applied to one end and turned on, and a delay circuit 17 for generating an output with a predetermined time delay after the switch 16 is turned off. Between the supply electromagnetic valve 13 and the exhaust electromagnetic valve 14 that are energized and closed, and the output end of the deviation detection / control means 12 for setting and sucking back the state of the liquid to be ejected before dripping is prevented. And make-before-break type changeover switches 18 and 19 which are connected between them and are switched in conjunction with each other by the output of the delay circuit 17.

The output voltage from the switch 16 is applied to an energized open air supply solenoid valve 75a and an energized closed exhaust solenoid valve 75b, which will be described later, to drive the air supply solenoid valve 75a and the exhaust solenoid valve 75b.

Next, prior to the description of the operation of the drip prevention device 15 of the present invention, a suck back valve 20 to which the drip prevention device 15 of the present invention is applied will be described with reference to FIG.

The suck back valve 20 includes an on / off valve 26 for turning on / off the supply of the liquid to be discharged supplied from the liquid supply source 110 to the nozzle 111 and a suck back mechanism 28 for performing the suck back. Is illustrated by way of example.

The suck back valve 20 includes a tube 22a,
A joint body 40 is detachably and liquid-tightly connected to each end by a joint portion 24, an on / off valve 26 provided on an upper portion of the joint body 40, and a suck back mechanism 2.
8 is included.

Further, the suck back valve 20 has a dripping preventing device 15 for controlling the compressed air (pilot pressure) supplied to the on / off valve 26 and the suck back mechanism 28, respectively, and a sucking amount of the liquid to be discharged. Diaphragm 80 acting as a valve plug for suckback mechanism 28
And a displacement amount sensor 33 as a displacement amount detecting means for detecting a displacement amount (valve lift amount). Joint body 4
The 0, on / off valve 26 and suck back mechanism 28 are integrally assembled.

The joint body 40 has a port 34 at one end.
Is formed, a port 36 is formed at the other end, and a fluid passage 3 for communicating the port 34 with the port 36 is formed.
8 are provided. The joint portion 24 is engaged with the port 34 and the port 36, respectively, and
An inner member 42 inserted into the opening 2b, a lock nut 44 that maintains the liquid tightness of the connection portion of the tubes 22a and 22b by screwing into a thread groove formed in the end of the joint body 40. And the tubes 22a and 22b and the joint body 40 are detachably and liquid-tightly connected.

An on / off valve 26 is provided at an upper portion of the joint body 40 near the port 34.
Is a valve body 46 integrally connected to the joint body 40.
And a diaphragm 50 which is stretched in a chamber 48 formed inside the valve body 46 and is provided so as to be displaceable in the direction of arrow X1 or X2, and a displacement which constitutes a stem which is displaced integrally with the diaphragm 50. The member 51 and the chamber 48
And a cover member 52 for hermetically closing the cover.

The chamber 48 is divided into an upper chamber 48 and a lower chamber 48 by a diaphragm 50. In the following description, the lower chamber 48 to which compressed air is supplied via a pilot passage 64 will be described. Will be described as a first pilot chamber 48.

The displacement member 51 is connected via a hole formed in the center of the diaphragm 50,
Has first and second holding members 55a and 55b for holding the upper surface and the lower surface, respectively. The first seal member 57a and the second seal member 57a are formed on the shaft portion of the second holding body 55b through an annular groove.
The seal member 57b is mounted.

A spring member 54 is interposed between the first holding member 55a and the cover member 52. The resilient force of the spring member 54 causes the displacement member 51 to always move downward (in the direction of arrow X2). It is in an energized state. Therefore, the on / off valve 26 is configured as a normally closed type.

A chamber 58 closed by a diaphragm 56 is formed at the lower end of the displacement member 51. The diaphragm 56 is connected to the lower end of the shaft of the second holding member 55b and is integrated with the displacement member 51. Displace. Here, the diaphragm 56 functions as a valve plug that opens and closes the fluid passage 38 by being separated from or seated on the seating portion 59 that is a valve seat formed on the joint body 40.

The compressed air is introduced into the valve body 46 through the pilot passage 64 to the first pilot chamber 48 to turn on / off the valve.
An electromagnetic solenoid valve 75a for controlling the OFF valve 26 to be opened and an exhaust solenoid valve for releasing the compressed air in the first pilot chamber 48 to the atmosphere via the pilot passage 64 and controlling the ON / OFF valve 26 to the closed state. 75b.

Accordingly, by energizing the air supply solenoid valve 75a to open the valve and energizing the exhaust solenoid valve 75b to close the valve, the first solenoid valve 75a
Compressed air (pilot pressure) is supplied into the pilot chamber 48, and the displacement member 51 rises against the elastic force of the spring member 54. As a result, the fluid passage 38 is opened with the diaphragm 56 separated from the seating portion 59 by a predetermined distance, and the port 3 is opened.
The liquid to be discharged flows from 4 toward the port 36 side.

The supply air solenoid valve 75a and the exhaust solenoid valve 75b
To shut off the supply air solenoid valve 75a,
In addition, by opening the exhaust solenoid valve 75b, the compressed air (pilot pressure) in the first pilot chamber 48 is released to the atmosphere through the pilot passage 64, and the displacement member 51 is released by the elastic force of the spring member 54. Descends. As a result, the diaphragm 56 comes into contact with the seating portion 59, the fluid passage 38 is closed, and the flow of the liquid to be discharged is stopped.

In response to the supply instruction of the liquid to be ejected to the nozzle 111, the supply / discharge solenoid valve 75a and the exhaust solenoid valve 75b are energized during the supply instruction period, so that the on / off valve 26 is opened and the fluid passage is opened. The liquid to be discharged is supplied to the nozzle via 38. When the supply instruction of the liquid to be discharged to the nozzle is stopped, the supply of electricity to the supply air solenoid valve 75a and the exhaust solenoid valve 75b is shut off during the supply instruction suspension period, so that the on / off valve 26 is closed and the fluid is stopped. The supply of the liquid to be discharged flowing through the passage 38 to the nozzle is stopped.

On the upper surface of the diaphragm 56, there is provided a ring-shaped buffering member 60 for protecting the thin portion of the diaphragm 56. The buffering member 60 has an L-shaped cross section connected to the lower end of the second holding member 55b. It is held by a holding member 62 in the shape of a circle.

A passage 66 is formed in the valve body 46 to allow the chamber 58 to communicate with the atmosphere.
The air in the diaphragm 8 is supplied and exhausted so that the diaphragm 56 is
Can be operated smoothly. The reference numeral 70
Indicates a buffer member that abuts against the flange of the second holding member 55b and performs a buffer function.

A suck back mechanism 28 is provided at an upper portion of the joint body 40 near the port 36. The suck back mechanism 28 includes a valve body 72 integrally connected to the joint body 40 and the valve body 46, and a valve body 72. X1 or X2 is extended in a chamber 74 formed inside 72.
The diaphragm 76 is provided so as to be displaceable in the direction.
And a displacement member 78 that is displaced integrally with the diaphragm 76
And a cover member 52 that hermetically closes the chamber 74.

The chamber 74 is divided into an upper chamber 74 and a lower chamber 74 by a diaphragm 76. In the following description, the upper chamber to which the pressurized fluid is supplied via the pilot passage 100 will be described. The chamber 74 will be described as a second pilot chamber 74.

The displacement member 78 is connected via a hole formed in the center of the diaphragm 76,
Has first and second holding bodies 77a and 77b for holding the upper surface and the lower surface, respectively. A seal member 57c is mounted on the shaft of the second holding body 77b via an annular groove.

A chamber 79 closed by a diaphragm 80 is formed at the lower end of the displacement member 78. The diaphragm 80 is connected to the lower end of the shaft of the second holding member 77b to be integrated with the displacement member 78. Is provided to be displaced. The diaphragm 80 includes a thick portion formed substantially at the center and a thin portion formed continuously around the thick portion.

In the chamber 79, there is provided a spring member 81 which is engaged with the flange of the second holding member 77b and constantly urges the displacement member 78 upward (in the direction of the arrow X1) by its resilient force. Has been established.

The cover member 5 is provided above the displacement member 78.
A screw member 63 is fitted along the through hole 2 and the screw member 63 is fixed to an upper portion of the cover member 52.
5 is locked via a set screw 67. A rod-shaped member 69 made of a ceramic material is fitted in the screw member 63, and a displacement sensor 33 formed by, for example, a Hall element is held by a cap member 71 on the bottom surface of the rod-shaped member 69.

The displacement sensor 33 detects the displacement of the displacement member 78 by detecting the magnetic force of the magnet 73 mounted in the hole on the upper surface of the displacement member 78. Diaphragm 8
Since 0 is displaced integrally with the displacement member 78, the displacement amount of the displacement member 78 corresponds to the displacement amount of the diaphragm 80. Therefore, the displacement member 7 is detected by the displacement sensor 33.
By detecting the displacement amount of 8, the lift amount of the diaphragm 80 for sucking the liquid to be discharged can be directly detected as the lift amount from the position shown in FIG.

On the upper surface of the diaphragm 80, there is provided a ring-shaped buffering member 90 for protecting the thin portion of the diaphragm 80. The buffering member 90 is connected to a lower end of the displacement member 78 and has a holding member having an L-shaped cross section. 92.

A passage 98 is formed in the valve body 72 to allow the chamber 79 to communicate with the atmosphere.
A pilot passage 100 for supplying a pilot pressure to the second pilot chamber 74 is formed.

An electromagnetic valve 13 for supplying compressed air to the second pilot chamber 74 through the pilot passage 100 to control the position of the diaphragm 80 is provided above the cover member 52.
And the second pilot chamber 74 through the pilot passage 100
And an exhaust electromagnetic valve 14 for controlling the position of the diaphragm 80 by releasing the compressed air to the atmosphere.

Accordingly, by energizing the supply air solenoid valve 13 to open the valve and energizing the exhaust solenoid valve 14 to close the valve, the compressed air in the second pilot chamber 74 via the pilot passage 100 is opened. (Pilot pressure) is supplied, the compressed air pressure in the second pilot chamber 74 becomes a predetermined pressure, and the displacement member 7 resists the elastic force of the spring member 81.
As a result, the position of the lower surface of the diaphragm 80 is lowered to a position corresponding to the inner peripheral surface of the fluid passage 38 as shown in FIG. Therefore, the volume of the fluid passage 38 from the seat 59 to the nozzle is minimized.

By shutting off the power supply to the supply electromagnetic valve 13 and the exhaust electromagnetic valve 14 to close the supply electromagnetic valve 13 and open the exhaust electromagnetic valve 14, the pilot electromagnetic valve 13 is opened via the pilot passage 100. The compressed air (pilot pressure) in the second pilot chamber 74 is released to the atmosphere, and the pressure in the second pilot chamber 74 becomes the atmospheric pressure, and the displacement member 78 is moved to a predetermined position by the elastic force of the spring member 81. Rise to
As a result, the lower surface position of the diaphragm 80 rises from the position shown in FIG. 2 to a predetermined position, and the volume of the fluid passage 38 from the seating portion 59 to the nozzle 111 becomes maximum, so that the maximum suckback is performed.

Also, the supply electromagnetic valve 13 and the exhaust electromagnetic valve 1
The pressure in the second pilot chamber 74 is controlled by independently and intermittently energizing the
The position of the displacement member 78 is controlled against the elastic force of the spring member 81 based on the compressed air pressure in the pilot chamber 74, and the position of the lower surface of the diaphragm 80 is shifted from the position where the lower surface of the diaphragm 80 matches the inner peripheral surface of the fluid passage 38. As shown in FIG. 3, the position is controlled based on the compressed air pressure in the second pilot chamber 74 until the pressure in the second pilot chamber 74 is the atmospheric pressure. Therefore, based on the compressed air pressure in the second pilot chamber 74, the volume of the fluid passage 38 from the seating portion 59 to the nozzle 111 is controlled from the minimum to the maximum, and suckback is performed.

Next, the anti-drip device 15 according to the present invention will be described.
4 to 6 together with the operation of the suck back valve 20.
It will be explained by.

When the switch 16 is depressed, the switch 16 is closed and an instruction to supply the liquid to be ejected is issued as shown in FIG. 4 (a). Valve 75a and exhaust solenoid valve 75
4B is applied during the period shown in FIG. As a result, during the target liquid supply instruction period, the supply air solenoid valve 75a opens,
The exhaust solenoid valve 75b is closed.

As a result, the compressed air passes through the pilot passage 64
The air pressure in the first pilot chamber 48 is increased to a predetermined pressure, and the pressure is maintained, and the pressure in the first pilot chamber 48 causes the spring member 54 to operate. On / off valve 26 against elasticity
During the period shown in FIG. 4C, the valve is opened, that is, the diaphragm 56 is separated from the seating portion 59, and the liquid to be discharged supplied from the liquid supply source 110 flows to the nozzle 111 through the fluid passage 38.

In this state, the changeover switches 18 and 19 are in the state of being switched to the normally closed contact side, and the power supply voltage is supplied to the air supply solenoid valve 13 and the exhaust solenoid valve 14 through the closed switch 16. Vcc is applied during the period between a and b in FIG. 4D including a delay period d by the delay circuit 17 to be described later during the supply period of the liquid to be discharged, and the air supply solenoid valve 13 is opened and the exhaust solenoid valve is opened. 14 is closed.

As a result, the compressed air is
0, is supplied to the second pilot chamber 74, and the air pressure in the second pilot chamber 74 increases to a predetermined pressure.
In addition, the pressure is maintained, and the pressure in the second pilot chamber 74 opposes the resilience of the spring member 81 so that the diaphragm 8
0 is the period a to b in FIG. 4E including the delay period d, and FIG.
, The volume of the fluid passage 38 is controlled to the minimum volume, and the liquid to be supplied supplied from the liquid supply source 110 is passed through the fluid passage 38 and the nozzle 11
It will flow to 1.

Next, when the switch 16 is opened by releasing the pressing of the switch 16, that is, when the supply instruction of the liquid to be discharged is stopped, the energization to the supply air solenoid valve 75 a and the exhaust solenoid valve 75 b is cut off. Therefore, the air supply solenoid valve 75a is closed, the exhaust solenoid valve 75b is opened, the air pressure in the first pilot chamber 48 is reduced to the atmospheric pressure, the diaphragm 56 is lowered, and the seating portion 59
, And the on / off valve 26 is closed.

As a result, the fluid passage 38 is closed, and the flow of the liquid to be discharged supplied from the liquid supply source 110 to the fluid passage 38 is blocked by the on / off valve 26.

In this state, the liquid to be discharged remaining in the fluid passage 38 on the nozzle side from the seating portion 59 drips through the nozzle 111, but the dripping prevention device 15 prevents the liquid to be discharged. Will be.

Next, the operation of the dripping prevention device 15 to prevent dripping will be described.

The drip prevention device 15 cooperates with the up / down counter 2 by operating the displacement amount up / down instruction switch 1 in the program mode before the control mode for performing the suck-back operation. The amount Q is set, and the set target total displacement Q is stored in the displacement memory 3. Similarly, in the program mode, the suction period T / T is operated in cooperation with the up / down counter 5 by operating the suction period up / down instruction switch 4.
Is instructed, and the instructed suction period T is stored in the displacement amount memory 3.

A control mode instruction signal for entering the control mode is supplied to the dripping preventing device 15 with a delay of the delay time d set in the delay circuit 17 by an output by releasing the switch 16 from being pressed. At the same time, the switches 18 and 19 are switched to the normally open contact side in conjunction with the output from the delay circuit 17.

In the dripping prevention device 15 which has received the control mode instruction signal, the control frequency calculating means 7 performs an operation of dividing the suction period T by the sampling period SP obtained by dividing the operation clock of the dripping prevention device 15. The control count N is determined, and the determined control count N is set in the up counter 9 (step S1). By the calculation in step S1, the control number N indicating how many times the control reaches the target total displacement amount in units of the sampling period is obtained.

Subsequent to step S1, a calculation for dividing the target total displacement Q by the control count N is performed by the displacement calculating means 8 (step S2). By the calculation in step S2, the variation ΔQi of the target total displacement that increases in each sampling cycle is obtained. As is clear from this, the present example is an example in which the displacement amount of the diaphragm 80 is linearly controlled.

Next, the process waits for the input of a sampling clock (step S3). When the sampling clock is input in step S3, the count value of the up counter 9 is incremented to n = n + 1 (step S4), and it is checked whether the count value n is within the control count N (step S5). If it is determined in step S5 that the count value n is within the control count N, the calculation of the target displacement amount (ΔQi × n) is performed by the multiplier 10.
Is calculated (step S6). Multiplier 10
Indicates the target displacement amount for each input sampling clock.

Step S6 is executed when the count value n of the up-counter 9 is within the control count N, and the switch 11 is controlled to be in the ON state. The output is sent to the control means 12, and the output of the displacement sensor 33 is compared with the value obtained by A / D conversion to detect the polarity of the deviation (step S).
7).

If the polarity of the deviation calculated in step S7 is the polarity of (the target displacement (ΔQi × n)> the output value of the displacement sensor 33), only the exhaust solenoid valve 14 is energized and the exhaust solenoid valve 14 is energized. Only the second pilot chamber 74 is opened to reduce the pressure in the second pilot chamber 74 (step S8), and then step S3 is executed. Step S8 is executed when the position of the diaphragm 80 has not risen to the calculated target displacement amount, the supply electromagnetic valve 13 is closed, the exhaust electromagnetic valve 14 is opened, and the second pilot valve is opened. The pressure in the chamber 74 is led to the atmosphere and reduced, the position of the diaphragm 80 rises, the suckback amount is increased, and the target displacement is controlled. This period is performed until the next sampling clock is input, that is, over the period of the sampling cycle.

When the polarity of the deviation calculated in step S7 is the polarity of (the target displacement (ΔQi × n) <the output value of the displacement sensor 33), only the air supply solenoid valve 13 is energized and the second pilot The pressure in the chamber 74 is increased (Step S9), and then Step S3 is executed. When the step S9 is executed, the position of the diaphragm 80 has risen beyond the target displacement amount, the exhaust solenoid valve 14 is closed, and the air supply solenoid valve 13 is opened and the second The pressure in the pilot chamber 74 is increased, the position of the diaphragm 80 is lowered, the suckback amount is reduced, and the target displacement (ΔQi × n) is controlled. This period is performed until the next sampling clock is input, that is, over the period of the sampling cycle.

In step S7, the calculated polarity of the deviation is (target displacement (ΔQi × n) = displacement sensor 33).
If the output value has the polarity of (), step S3 is executed following step S7. Therefore, in this case, since the diaphragm 80 is located at the position of the target displacement amount, the supply solenoid valve 13 and the exhaust solenoid valve 14 are controlled in the previous control state by the sampling period until the next sampling clock is input. For a period of time.

When it is determined in step S5 that the count value n of the up counter 9 is not within the control count N, that is, when the control count N is exceeded, step S5
Subsequently, the switch 11 is turned off (step S10), and the suck-back ends.

As described above, these steps S1 to S9 are executed until the count value n of the up counter 9 does not fall within the control count N, that is, until the set target displacement amount Q is reached. By executing steps 1 to S9, the diaphragm 80 rises from the position shown in FIG. 2 during the period a to b in FIG. 4E as shown in the period b to c in FIG. Done. As a result, since the diaphragm 80 is controlled to the position of the target total displacement amount Q,
The suckback amount is controlled to the target suckback amount, so that dripping is prevented.

The suck-back state will be further described. The target total displacement (Q) of the diaphragm 80 set by the displacement up / down instruction switch 1 is set on the vertical axis, and the suction period up / down instruction switch 4 is used. As shown by a solid line in FIG. 6 in which the set suction period (T) is plotted on the horizontal axis, the target displacement to which the displacement amount (ΔQi) per control number is added for each sampling cycle (SP). The diaphragm 8 is positioned at a position based on the quantity Qi (Qi × n).
Suckback is performed by controlling the displacement amount of zero. The target displacement amount Qi when the n-th sampling clock is input is represented by Qi = nΔQi = Q. Since the sampling period is short, for example, 5 msec, suckback is performed substantially as shown by a dashed line in FIG.

The same applies to the case where the target total displacement (Q) is set to a low value. This case is indicated by a broken line in FIG. 6, and the suck back in this case is indicated by two points corresponding to the dashed line. Shown by chain lines.

The setting of the displacement amount by operating the displacement amount up / down instruction switch 1 and the suction period up / down instruction switch 4 and the setting of the suction period (T) required to perform the displacement of the set target displacement amount are as follows. It is performed by the user, and the suction period (T) and the target total displacement amount (Q) can be set independently by the displacement amount up / down instruction switch 1 and the suction period up / down instruction switch 4. It is also possible to set such that the suckback time can be kept constant regardless of the set amount of displacement, such that one is fixed and the other is variable,
The setting can be made irrespective of the type and viscosity of the liquid to be discharged flowing through the suck back valve 20, the degree of freedom is improved, and it is possible to cope with a wide range of processes.

In the above-described embodiment, the case where the displacement amount of the diaphragm 80 is controlled linearly, that is, the case where the change amount (ΔQi) of the displacement amount is fixed, is exemplified. By changing the component (ΔQi) for each sampling period, the control can be performed in a polygonal manner, and by increasing the number of polygons, the control can be performed substantially along a predetermined curve.

[0075]

As described above, according to the anti-drip device of the present invention, the target total displacement and the suction period can be freely set, and the target suction amount is set by the suction in the set suction period. Suckback of the target total displacement can be performed and dripping can be prevented. Further, the target total displacement and the suction period can be freely set, and the degree of freedom is increased, so that the present invention can be applied to a wide range of processes.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a configuration of a dripping prevention device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a suck-back valve to which the dripping prevention device according to one embodiment of the present invention is applied.

FIG. 3 is a cross-sectional view for explaining an operation of a suck-back valve to which the dripping prevention device according to the embodiment of the present invention is applied.

FIG. 4 is a timing chart for explaining the operation of the dripping prevention device according to the embodiment of the present invention;

FIG. 5 is a flowchart for explaining the operation of the dripping prevention device according to the embodiment of the present invention.

FIG. 6 is a diagram provided for describing an operation of the dripping prevention device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Displacement amount up / down instruction switch 2 and 5 Up / down counter 3 Displacement amount memory 4 Suction period up / down instruction switch 6 Suction period memory 7 Control frequency calculation means 8 Displacement amount calculation means 9 Up counter 10 Multiplier 11 Switch 12 Deviation detection and control means 13 and 75a Supply air solenoid valve 14 and 75b Exhaust solenoid valve 20 Suck back valve 26 On / off valve 28 Suck back mechanism 33 Displacement sensor 74 Room 78 Displacement member 80 Diaphragm 100 Pilot passage

Claims (2)

[Claims] A suction amount is controlled by a suck-back valve that has a fluid passage for delivering a pressure fluid to a nozzle and that sucks the pressure fluid in the fluid passage by displacement of a displacement member that is displaced based on pilot pressure. A displacement detecting device for detecting a displacement of a displacement member, a target displacement setting device for setting a target total displacement, and a set target total displacement. A suction period setting means for setting a suction period for suctioning the pressure fluid in the fluid passage, a control number calculation means for calculating the control number by dividing the set suction period by a predetermined period,
A counter for counting the number of pulses supplied for each predetermined period up to the control count, and a displacement calculating means for calculating a target displacement for each control count based on the set target total displacement and the determined control count. And the pilot pressure is increased or decreased based on the polarity of the deviation between the target displacement at the control count based on the count value of the counter and the displacement detected by the displacement detector, and the displacement of the displacement member is set at the target displacement at the control count. A drip prevention device comprising: 2. The drip prevention device according to claim 1, wherein
The displacement amount calculating means includes a dividing means for dividing the total target displacement amount by the number of times of control, and a multiplying means for multiplying the result of the division by the dividing means and the count value of the counter. Features a dripping prevention device.