JPH09248498A - Flow rate control mechanism of liquid material supply apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flow rate control mechanism capable of keeping and controlling the driving cycle number of a diaphragm pump constant so as to control the emitting amt. from an emitting means to a set objective value from such an aspect that there is quantitativeness in the emitting amt. per one cycle of the diaphragm pump in a liquid material supply apparatus using a reciprocal type diaphragm pump supplying a liquid material such as paint to the emitting means such as a spray gun. SOLUTION: A control circuit detecting the moving quantity of the drive shaft of a reciprocal type diaphragm pump 1 by an optical sensor and measuring the cycle number per the unit time of the diaphragm pump 1 from the detection signal to compare the measured value with a preliminarily set and inputted objective emitting amt. value to operate the same is provided and a compared deviation value is outputted to an electropneumatic converter 13 to be controlled and the controlled air pressure is supplied to a liquid flow rate control valve 5 to control a liquid flow rate not only to control the cycle number of the diaphragm pump l but also to supply a liquid to the emitting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to stabilizing the supply flow rate of a liquid material such as paint, for example, by controlling the flow rate of a coating material supplied to a discharge means such as a spray gun in the field of coating to discharge the spray gun. The amount is kept constant to stabilize the coating quality.

[0002]

2. Description of the Related Art A paint supply device for supplying a liquid material such as paint by pressure to a spray gun by using a double diaphragm pump is widely used in the market as a paint pump. The reciprocating diaphragm pump is a diaphragm that uses compressed air as a drive source and is attached to both sides of the drive shaft of the diaphragm pump to form a pump chamber.By pumping the pump chamber, a liquid material with the same pressure as the working air pressure is generated. It is a positive displacement pump that discharges left and right alternately from the pump chamber. Therefore, the liquid material discharged from the diaphragm pump is discharged at a substantially constant pressure and is supplied to a discharging means such as a spray gun through a pressure regulating valve or the like. The operation of the diaphragm pump is an air pressure control mechanism that operates with the number of cycles that is automatically controlled according to the discharge amount discharged from the spray gun or the like.

In the paint supply device using the above-mentioned reciprocating diaphragm pump, in the case of the conventional spray coating, the pressure of the paint pressure regulating valve or the spray at that time is sensibly adjusted to an appropriate spray pattern suitable for the coating. Painting is performed with the gun paint spray rate control valve fixed. However, when performing painting work, especially when using an automatic painting device that automates painting or a painting robot for a long time, the paint viscosity changes due to changes in environmental temperature such as morning and evening, and the spray gun changes due to the change in paint viscosity. The discharge flow rate may fluctuate due to a change in the discharge amount from the product such as a paint hose, paint supply flow path such as a paint hose, spray gun, etc. There is an aspect of lack of reliability in maintaining stable flow rate.

[0004] Further, in order to improve the stability of coating quality along with the mechanization of coating and to construct a coating system capable of numerically controlling the coating, there is a market demand for a coating supply device capable of continuously and numerically controlling the coating discharge amount. It is rising. In order to meet this demand, a mechanism in which a paint flow meter is attached to the supply flow path and the supply flow rate is controlled by a signal from the flow meter to stabilize the discharge flow rate already exists as a known technique.
For example, Japanese Patent Application Laid-Open No. 7-88408 “Flow Stabilizer” filed by the present applicant is also an example of a flow control mechanism using a flow meter.

However, the flow rate control mechanism in which a flow meter is provided in the fluid material supply passage is the most orthodox control mechanism, but it is a viscous paint containing an extender pigment and a coloring pigment, and the viscosity also depends on the type of paint. When trying to measure different liquid materials with a flow meter, there is a problem that durability of the flow meter and long-term stability of measured values are lacking and reliability is lacking.
Further, if a highly reliable flow meter that can also use the liquid material is used, the price of the flow meter becomes very high, and it is almost difficult to apply it to a general-purpose type paint supply device.

[0006]

As described above,
When supplying a liquid material such as paint to the discharge means such as a spray gun by pumping pressure, discharge due to fluctuations in the discharge flow rate due to changes in the viscosity of the liquid material due to changes in the ambient temperature, or due to obstacles to the paint flow path, etc. Due to flow rate fluctuation,
There is a problem that the discharge amount of the discharge means is not maintained stable.

According to the present invention, the discharge capacity per cycle of the mechanically reliable double-acting diaphragm pump is approximately constant regardless of the density or viscosity of the liquid material in the normal use range. By controlling the number of drive cycles of the diaphragm pump per unit time using the liquid flow rate control valve via the electropneumatic converter, the discharge amount of the discharge means such as the spray gun that fluctuates due to viscosity changes etc. is set. The purpose is to be able to maintain and maintain a constant target value.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a liquid material supply apparatus for supplying a liquid material such as paint to a discharge means such as a spray gun by using a reciprocating diaphragm pump, and a drive shaft of the reciprocating diaphragm pump. A receiver is attached to, and a control circuit having an arithmetic circuit that detects the number of cycles of the drive shaft operating in a unit time by a photoelectric element or a fluid element and compares the number of cycles with a preset stored number is provided. , By supplying a controlled air pressure to a liquid flow rate control valve through an electropneumatic converter that operates according to a command signal from the control circuit to control the liquid flow rate, thereby operating the operation cycle of the backward diaphragm pump. It is a flow rate control mechanism of the liquid material supply apparatus that controls and controls the flow rate to be supplied to the discharge means to be constant.

Further, when detecting the number of cycles of the reciprocating diaphragm pump operating in a unit time, the number of cycles is detected only when the liquid material is discharged from the discharging means operated by air pressure and the discharging means is in an operating state. The control circuit measures a unit time, and when the number of cycles operating in the unit time is detected, the detected number of cycles is set to a unit time that can be integrated at least several times.

Further, the number of cycles per unit time which is preset and stored in the control circuit is determined from the proportional correlation value between the number of operating cycles per unit time of the double diaphragm pump and the liquid material discharge amount, and the target liquid material discharge amount. This is a flow rate control mechanism that can be adjusted by the capacity display value of.

[0011]

The present invention relates to a liquid material supply device for sucking and discharging a liquid material by a reciprocating diaphragm pump using compressed air as a drive source and supplying the liquid material to a supply means such as a spray gun through a liquid material supply passage. In order to detect the reciprocating motion of the drive shaft of the double diaphragm pump, a detector is attached to the drive shaft, the passing amount is detected by the sensor consisting of photoelectric element or fluid element, and the detection signal is stored in the controller. Sent to the control device. The use of the sensor as a photoelectric element or a fluid element requires an explosion-proof function because the diaphragm pump section handles highly flammable dangerous substances such as paint, and is used to avoid using an electric signal. The controller uses a microcomputer to store a counting function that counts the number of cycles per unit time, and a correlation value in which the correlation between the number of cycles of the diaphragm pump and the discharge amount of liquid material is measured in advance. Built-in arithmetic function to compare with the number of cycles. As the stored cycle number, a capacity value obtained by converting the cycle number into a discharge amount is displayed on the controller front panel.

The discharge volume value is displayed by adjusting the discharge volume from the discharge means set in advance by operating the adjuster attached to the panel surface of the controller. When the actual discharge amount fluctuates with respect to the displayed discharge capacity value, the microcomputer function operates, and the command from the microcomputer causes the electropneumatic converter to operate according to the fluctuation amount and send it to the liquid flow control valve. The air pressure to be applied is adjusted according to the fluctuation amount, and the valve opening of the liquid flow rate control valve is adjusted.

When the displacement of the diaphragm pump increases and changes during the adjustment control of the opening of the liquid flow rate control valve, the number of cycles of the diaphragm pump increases. The air pressure decreases, the liquid flow rate control valve operates in the direction of closing, and the discharge amount is reduced. When the discharge volume decreases and fluctuates, it is adjusted in the opposite manner to the above.

The number of cycles is measured by a circuit for counting the unit time only when the solenoid valve, in which the discharge means operating by air pressure is discharging the liquid material, is turned on. Normally, the discharge amount of 10 cycles or more is integrated, and the average value is compared with a preset discharge amount. When a variation error of the discharge amount occurs, a signal corresponding to the error is generated. Sent to the empty converter. Therefore, the unit time for measuring the number of cycles is set long when the discharge amount of the discharge means is small and the operation cycle of the diaphragm pump is slow, and short when it is early.

By the operation described above, a stable and constant discharge amount can be maintained by controlling the number of cycles of the diaphragm pump that is directly linked to the discharge capacity from the discharge means. In addition, this mechanism controls the liquid flow rate control valve without providing a flow meter, which is unreliable in reliability, in the fluid material supply passage, so that the control is highly reliable and stable mechanical performance can be maintained for a long period of time. It is a thing.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a structure in which a flow rate control mechanism is arranged in a liquid material supply device for supplying a liquid material to a spray gun by using a backward movement diaphragm pump of the present invention. And the flow rate control mechanism of this liquid material supply device is not limited to paints in the field of coating, but it is a liquid material that quantitatively discharges and supplies a viscous liquid such as chemical liquid, food, oil that can be easily sucked and discharged by the diaphragm pump. It is a flow rate control mechanism adaptable to a supply device.

In FIG. 1, a liquid material is sucked up from a suction pipe 2 attached to a reciprocating diaphragm pump 1,
It is alternately discharged from the left and right pump chambers of the double-acting diaphragm pump 1. Then, a liquid material supply flow path 4 is provided via a paint pressure regulator 3 which is used to roughly adjust the paint pressure supplied to the spray gun 6 and to eliminate discharge pulsation that occurs at the left and right dead points of the diaphragm pump 1. And is supplied to the spray gun 6. An air operated liquid flow rate control valve 5 is arranged in the liquid material supply flow path 4.
The spray gun 6 is interlocked with the opening / closing drive of the electromagnetic valve 7 instructed by the spray gun control panel 9, and the operating needle valve of the spray gun 6 is driven by the air pressure, and the paint is sprayed from the spray gun 6 accordingly. Is turned on / off. In addition, the spray gun 6 is linked with the opening / closing drive of the solenoid valve 7.
The spray air is also turned on / off. Further, the opening / closing drive control signal of the solenoid valve 7 is simultaneously transmitted from the control panel 9 to the controller 10 having an arithmetic function.

In the above, in order to measure the number of drive cycles of the reciprocating diaphragm pump 1, a receiver is attached to the drive shaft of the pump 1, and the amount of movement of the receiver is detected by a photoelectric element or a fluid element, It is transmitted to the microcomputer housed in the controller 10. The transmitted signal is preset and input, and the discharge volume value displayed on the panel display plate 14 is compared with the input value from the counting function 11, and when the comparison value is different, an error signal is output. The output signal is transmitted to the electropneumatic converter 13. The electro-pneumatic converter 13 adjusts the flow rate of the compressed air supplied from the air source via the pressure adjusting valve according to the output signal level from the arithmetic function of the microcomputer, and the air operated liquid flow rate control valve 5 As control air. Then, the liquid flow rate control valve 5
Adjusts the valve opening according to the air pressure of the control air supplied, and adjusts the operation of the double-acting diaphragm pump 1.
The number of cycles of the diaphragm pump is controlled so that the deviation from the set value is minimized.

The liquid material in the liquid flow path 4 controlled by the liquid flow rate control valve 5 controls the number of cycles of the diaphragm pump 1 and is supplied to the spray gun 6 at a controlled flow rate and discharged. When the injection of the spray gun 6 is stopped, the operation of the diaphragm pump 1 is automatically stopped, but when the injection of the spray gun 6 is stopped, the OFF signal of the solenoid valve 7 is input to the control circuit of the controller 10 for a unit time. Counting is stopped.

FIG. 2 is a sectional view showing an example of a known liquid flow rate control valve 5, in which the air pressure controlled by the electropneumatic converter 13 is supplied from the supply port 51 and enters the upper chamber of the diaphragm 52. Is pressing. And the valve rod 5 for adjusting the opening degree of the ball valve 54 to the diaphragm 52.
3 is screwed. The liquid material from the double-acting diaphragm pump 1 enters from the inlet 55, enters the lower chamber of the diaphragm 52 from the adjusted opening of the ball valve 54, balances with the control air pressure from the electropneumatic converter 13, and the liquid pressure. Is adjusted. The adjusted liquid material is supplied to the spray gun from the discharge port 56 by a flexible paint hose or the like.

The electropneumatic converter 13 is also a well-known control device, which converts a signal input from a control circuit into a mechanical operation by using a piezoelectric element to control the air pressure supplied from the air source. The air volume control of is almost the same as the principle of FIG.
The pressure applied to the diaphragm of the diaphragm type valve is
The flapper valve composed of the piezoelectric element is used for adjustment.

An automatic spray gun is taken as an example of the liquid material discharging means of the present invention, and a method of operating ON / OFF of the needle valve of the spray gun by air pressure from the solenoid valve is used, and a signal input to the solenoid valve is sent to the control circuit. Although the circuits are input at the same time, the input method to the control circuit is not limited to the above. For example, when the discharging means performs on / off operation by the discharging means itself like a hand-blown spray gun, the discharging means does not A method of converting ON / OFF of the signal into a signal and inputting the signal into the control circuit of the controller is adopted.

[0023]

Since the present invention is constructed as described above, it has the following effects.

Utilizing the quantitativeness of the discharge capacity, which is not affected by the density and viscosity of the liquid material of the reciprocating diaphragm pump,
By controlling the operation cycle of the diaphragm pump itself, it becomes possible to perform quantitative discharge with numerical control without providing a flow meter in the fluid material supply passage, and to provide a highly reliable and inexpensive liquid material supply device. Become.

By using the flow rate control mechanism using the reciprocating diaphragm pump, as compared with other positive displacement pumps such as gear pumps or plunger pumps, wear of the gear due to paint pigment of the gear pump and plunger The liquid material supply device has high reliability and can maintain long-term stability without problems such as sliding wear of the packing of the pump.

The unit time only when the discharge means discharges the flow rate of the diaphragm pump is relatively long, and the discharge capacity value averaged over several cycles is used, so that the reliability is high and stable. The discharge amount can be obtained.

The flow rate control mechanism is a simple mechanism controlled by a liquid flow rate control valve via a control circuit using a microcomputer and an electropneumatic converter, and becomes a liquid material supply device capable of controlling the discharge flow rate at low cost.

Since the target discharge volume is displayed on the front panel of the controller and the target value can be easily adjusted and set, the flow rate control mechanism is easy to handle.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a flow rate control mechanism of a liquid material supply apparatus of the present invention.

FIG. 2 is a cross-sectional view of a liquid flow rate control valve used in the present invention.

[Explanation of symbols]

 1 Reciprocating diaphragm pump 3 Paint pressure regulator 4 Liquid material supply flow path 5 Liquid flow rate control valve 6 Spray gun 7 Control panel solenoid valve 10 Controller 12 Microcomputer 13 Electro-pneumatic converter 14 Display panel

Claims (4)

[Claims] 1. In a liquid material supply device for supplying a liquid material such as paint to a discharge means such as a spray gun by using a reciprocating diaphragm pump, a receiver is attached to a drive shaft of the reciprocating diaphragm pump, and a photoelectric converter is provided. A control circuit having an arithmetic circuit for detecting the number of cycles of the drive shaft operating in a unit time by an element or a fluid element and comparing it with the number of cycles set and stored in advance is provided, and a command signal from the control circuit is provided. By controlling the liquid flow rate by supplying a controlled air pressure to the liquid flow rate control valve via the electropneumatic converter operated by, the operation cycle of the double-acting diaphragm pump is controlled, and A flow rate control mechanism of a liquid material supply device that controls a constant supply flow rate. 2. When detecting the number of cycles of the reciprocating diaphragm pump operating in a unit time, the number of cycles is detected only when the liquid material is being discharged from the discharging means operated by air pressure and the discharging means is operating. The flow rate control mechanism of the liquid material supply device according to claim 1, which is a control circuit for measuring a unit time. 3. The control circuit, wherein when detecting the number of cycles of the double-acting diaphragm pump operating in a unit time, the detected number of cycles is set to a unit time that can be integrated at least several times. A flow rate control mechanism of the liquid material supply apparatus described. 4. The number of cycles per unit time preset and stored in the control circuit is a target liquid material discharge amount based on a proportional correlation value between the number of operation cycles per unit time of the reciprocating diaphragm pump and the liquid material discharge amount. The flow rate control mechanism of the liquid material supply apparatus according to claim 1, wherein the flow rate control mechanism can be set so as to be adjustable by the capacity display value.