Method for automatically controlling paint temperature by heating circulating water in color coating unit

Abstract

The invention discloses an automatic circulating water temperature control method for a color coating unit, which comprises the following steps of: establishing a paint / water temperature setting and adjusting module, judging whether the water temperature is enough or not by using paint temperature setting and paint temperature detection, and if the paint temperature is low, raising a water temperature set value; and then the water enters an automatic water temperature control module and is controlled on the basis of a water temperature set value to form a heating control quantity, the heating control quantity is output to a heating controller, and a heater is started to work. The automatic water temperature control module comprises the steps that a water temperature detector is introduced, and when a water temperature set value is larger than a water temperature detection value or smaller than the water temperature detection value, different flow control is started; according to the paint / water temperature setting and adjusting module, water temperature setting is composed of a water temperature reference setting part and a water temperature setting compensation part; water temperature reference setting is obtained by adding 1-3 DEG C to the paint temperature setting, and water temperature setting compensation is generated according to the paint temperature setting and the paint temperature detection value. After the control method is adopted, the paint temperature can be effectively controlled.

Description

Technical Field

[0001] The present invention relates to the field of temperature control, specifically to the core process strip coating of a cold rolling color coating unit and a temperature stability control scheme for related paint coatings. Background Art

[0002] When the paint coatings of the color coating unit enter the production process, they must be heated. Different paints require stable temperatures, neither too high nor too low, otherwise it will affect the product quality. Currently, the heating method used in Baosteel's color coating unit is to heat water through a heater, and then the water heats the paint through a heat exchanger. A typical paint heating system is as Figure 1 shown.

[0003] Since the temperature of the paint directly affects the viscosity of the paint entering the paint tray, and further affects the film thickness, bending and other properties of the color coating product, temperature control accuracy is very important. The current control method is to use the paint temperature as the detection value to control the output power of the heater, and proportional-integral control is adopted. The specific paint temperature control system diagram is as Figure 2 .

[0004] The existing patent retrieval information is as follows:

[0005] Patent Document 1: A pre-coating tray for a color coating unit [utility model], application number: CN201922370618, publication number: CN211678578U. This utility model discloses a pre-coating tray for a color coating unit, including a tray body. A tray baffle is arranged inside the tray body. On one corner of the bottom surface of the tray between the tray baffle and the back of the tray, a section of corrugated pipe is hermetically arranged through threaded connection. On one side wall of the tray beside the corrugated pipe, a vertical groove and a vertically arranged scale are respectively arranged. A slider is slidably arranged up and down in the vertical groove. An L-shaped pull rod is fixedly connected to the side wall of the slider, and the pull rod is connected to the middle of the top surface of the corrugated pipe. Sliding the slider up and down drives the corrugated pipe to stretch up and down, and the height of the liquid level can be conveniently measured through the scale. This utility model not only has clean paint reflux, but also can conveniently adjust the height of the liquid level, and the adjustment of the liquid level height is controllable.

[0006] Patent Document 2: A marine paint heat transfer oil temperature control system [invention]

[0007] Application number: CN201510517823, publication number: CN106468481A

[0008] The marine paint heat-conducting oil temperature control system of the present invention has good temperature control effect, can give out sound and light alarm and command the system to stop working when the temperature is abnormal, and can meet the requirements of actual production and processing. The present invention adopts the fuzzy control principle, including a core controller, an LCD display module, a detection module, a heating module, a sound and light alarm module, and a key module; the detection module includes a reaction kettle, a temperature sensor, and an A / D converter. The output end of the reaction kettle is connected to the input end of the temperature sensor, the output end of the temperature sensor is connected to the input end of the A / D converter, and the output end of the A / D converter is connected to the signal input end of the core controller; the heating module includes a solid-state relay and a heater connected to the solid-state relay. The signal output end of the core controller is connected to the signal input end of the solid-state relay; the signal output end of the core controller is also connected to the LCD display module and the sound and light alarm module, and the signal input end of the core controller is also connected to the key module. This invention focuses more on the construction of hardware.

[0009] The existing control methods and existing invention patents / utility models have the following disadvantages:

[0010] (1). For the original control system, the paint temperature detection is directly used as the control basis (see Figure 2 ), but there is a water tank system, a very long water pipeline, and a heat exchanger between the heater and the paint temperature detection. It takes a long time for the heater to heat the paint through the water in the water tank, the long pipeline, and the heat exchanger. Although the heat conduction of the heater itself is very fast and the water temperature rises and falls quickly, there is a large lag in heating the paint through the long pipeline and then through the heat exchanger. This leads to instability of the control system, and at the same time, the water temperature is easily too high or too low, resulting in the following consequences: the high temperature vaporization of the water in the water tank affects the stability of the water flow in the water pipe, and the heater and heat exchanger are easily deteriorated. Once the external environment changes, it is difficult to control the paint temperature. Summary of the Invention

[0011] Therefore, the technical problem to be solved by the present invention is to provide a stable control method for the paint temperature in view of the poor stability of the paint temperature control in the original system.

[0012] The technical solution of the present invention is a method for automatically controlling the paint temperature of the heating circulating water in a color coating unit,

[0013] The automatic control method includes establishing a paint / water temperature setting and adjustment module, using the paint temperature setting and the paint temperature detection to judge whether the water temperature is sufficient. If the paint temperature is low, the water temperature setting value is raised; if the paint temperature is high, the water temperature setting value is lowered; then it enters the water temperature automatic control module, and based on the water temperature setting value, a heating control quantity is formed and output to the heating controller to start the heater to work;

[0014] The water temperature automatic control module includes:

[0015] (A) Introduce a water temperature detector. When the set water temperature value is greater than the detected water temperature value, start Process 1. Process 1 is as follows: Heat the water temperature for a period of time, stop heating for a period of time, and cycle.

[0016] (B) After Process 1 is started, continue to start Process 2. Process 2 is as follows: Output different grades according to the temperature difference. When the temperature difference is large, the heating control amount is large; when the temperature difference is small, the heating control amount is small.

[0017] (C) When the detected water temperature value is greater than the set water temperature value within a certain range, the heating control amount becomes 0; when the detected water temperature value is greater than the set water temperature value beyond a certain range, the heating control amount becomes 0, and at the same time, drain intermittently and supplement new water to reduce the water temperature to within the permitted range of the set value.

[0018] The paint / water temperature setting adjustment module includes:

[0019] The set water temperature value consists of two parts: "water temperature reference setting" plus "water temperature setting compensation". The "water temperature reference setting" is set with the paint temperature plus 1 - 3°C as the water temperature reference setting. The "water temperature setting compensation" is generated by the difference between the paint temperature setting and the detected actual paint temperature value, and is dynamically adjusted at regular intervals.

[0020] A typical paint heating system is as Figure 1 shown. The heater is controlled by a heating controller. The heater is connected to a water tank, the water tank is connected to a heat exchanger through a pipeline, and the heat exchanger is then connected to a paint tray. The present invention does not change the device structure and solves the existing technical problems from the control method part.

[0021] According to a method for automatically controlling the paint temperature by heating circulating water in a color coating unit of the present invention, preferably, in the water temperature automatic control module, after detecting the water temperature, the heating control amount is intermittently output.

[0022] According to a method for automatically controlling the paint temperature by heating circulating water in a color coating unit of the present invention, preferably, in step (C), draining and water replenishment are carried out intermittently.

[0023] According to a method for automatically controlling the paint temperature by heating circulating water in a color coating unit of the present invention, preferably, a water pump circulation system is provided near the heater.

[0024] According to a method for automatically controlling the paint temperature by heating circulating water in a color coating unit of the present invention, preferably,

[0025] In steps (A) and (B), when the set water temperature value is greater than the detected water temperature value by more than 0°C, start Process 1; after Process 1 is started, continue to start Process 2.

[0026] A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to the present invention. Preferably, in step (C), when comparing the water temperature detection value with the water temperature set value, when the water temperature set value is less than the water temperature detection value and the temperature difference is between 0 and -2 degrees, start process 3, the heating control amount is 0, and rely on the self-circulation of water and heat exchange with the paint to automatically cool down; when comparing the water temperature detection value with the water temperature set value, when the water temperature set value is less than the water temperature detection value by more than 2 degrees, start process 4, the heating control amount is 0, the drain / fill valve is intermittently opened, once every 5 - 20 seconds, and then closed for 5 - 10 seconds, and the cycle starts until the temperature difference is between 0 and -2 degrees. The above comparison is to subtract the water temperature detection value from the water temperature set value, and the temperature difference is also the water temperature set value minus the water temperature detection value. Figure 4 The difference judgment is to subtract the water temperature detection value from the water temperature set value. The difference is greater than 0 (the water temperature detection value is lower than the water temperature set value), and the difference is less than 0 (the water temperature detection value is greater than the water temperature set value).

[0027] Further, in step (A), process 1 is: heat the water temperature for 10 - 30 seconds, then stop for 5 - 10 seconds, and repeat the cycle.

[0028] Further, the drain / fill valve is intermittently opened, once every 5 - 20 seconds, determined according to the temperature difference. The greater the temperature difference, the shorter the interval time. The greater the temperature difference (here the water temperature detection is higher than the set value), the faster the drainage and filling, and the new water temperature is low to quickly cool down.

[0029] A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to the present invention. Preferably, a. If the difference between the paint temperature set value and the paint temperature detection value is below -2 °C and lasts for 1 - 2 minutes, start process 5, and the water temperature set compensation value decreases by 1 - 2 °C every 5 - 20 seconds, with a lower limit of -10 °C;

[0030] b. If the difference between the paint temperature set value and the paint temperature detection value is within -0.5 to -2 °C and lasts for 1 - 2 minutes, start process 6, and the water temperature set compensation value decreases by 0.5 - 1 °C every 5 - 60 seconds, with a lower limit of -10 °C;

[0031] c. If the difference between the paint temperature set value and the paint temperature detection value is greater than -0.5 °C and less than 0.5 °C, and the duration is less than 1 - 2 minutes, the water temperature set compensation value remains unchanged;

[0032] d. If the difference between the paint temperature set value and the paint temperature detection value is within 0.5 to 2 °C and lasts for 1 - 2 minutes, start process 7, and the water temperature set compensation value increases by 0.5 - 1 °C every 5 - 60 seconds, with an upper limit of 30 °C;

[0033] e. If the difference between the paint temperature set value and the paint temperature detection value is above 2 °C and lasts for 1 - 2 minutes, start process 8, and the water temperature set compensation value increases by 1 - 2 °C every 5 - 20 seconds, with an upper limit of 30 °C.

[0034] Advantages of the present invention:

[0035] The present invention is fundamentally different from existing solutions and inventions in several aspects: (A) The control is simpler and easier to adjust, which is beneficial to the stability of the equipment. (B) The control accuracy is improved.

[0036] By introducing water temperature control, stable control of the paint temperature can be achieved on the basis of effectively controlling the water temperature. For the water system, heat exchanger, the impact brought by environmental changes is reduced to the minimum. The problems existing in the original system are avoided. Description of the drawings

[0037] Figure 1 is a typical paint heating system diagram.

[0038] Figure 2 is a diagram of the existing technology paint temperature control system.

[0039] Figure 3 is a schematic diagram of the overall method of the water temperature control model.

[0040] Figure 4 is a diagram of the water temperature automatic heating module.

[0041] Figure 5 is a diagram of the paint / water temperature setting adjustment module. Detailed implementation manners

[0042] First step: Establish a new paint temperature control model, as shown in Figure 3 . First is the "paint / water temperature setting adjustment module", whose function is to convert the paint temperature control into a water temperature set value. Then is the "water temperature automatic control module" to form a heating output, control the heating controller, and start the heater.

[0043] Second step: Establish the "water temperature automatic control module" in Figure 3 . Its core is: (A) Introduce a water temperature detector to participate in the control to achieve stable water temperature. (B) The heating control quantity output changes from continuous output to intermittent output, that is, heat for a period of time and then stop for a period of time. Utilize the circulation of the water pump to avoid the water temperature near the heater rising too fast and forming vaporization. Instead, utilize the effective cooperation of the water pump circulation and the heater to achieve rapid heating and temperature reduction of the water temperature. (C) When the water temperature detection value is greater than the water temperature set within a certain range, the heating control quantity becomes 0; when the water temperature detection value is greater than the water temperature set beyond a certain range, the heating control quantity becomes 0, and at the same time, drain water intermittently and supplement new water to reduce the water temperature to within the allowable range of the set value; as shown in Figure 4 .

[0044] Specific process description: (A) When the set water temperature is greater than the detected water temperature, process 1 is started, heating for 10 - 30 seconds, and then stopping for 5 - 10 seconds. This cycle repeats. (B) After process 1 is started, process 2 is started. When the temperature difference is large, the power output to the temperature control module is large; when the temperature difference is small, the output power is small. (C) When the set water temperature is less than the detected water temperature and the temperature difference is between 0 and -1 / -2 degrees, process 3 is started, and the power output of the temperature control module is 0. It relies on the self - circulation of water and heat exchange with paint to automatically cool down. (D) When the set water temperature is less than the detected water temperature and the temperature difference is below -1 / -2 degrees, process 4 is started, and the power output of the temperature control module is 0. The drain / fill valve is intermittently opened, once every 5 - 20 seconds (determined according to the temperature difference size), and then closed for 5 - 10 seconds. This cycle starts until the temperature difference is between 0 and -1 / -2 degrees.

[0045] (3), The third step: Establish Figure 3 the "paint / water temperature setting adjustment module" in. Use the paint temperature setting and paint temperature detection to judge whether the water temperature is sufficient. If the paint temperature is low, then raise the water temperature setting. Due to hysteresis, the detection of the paint temperature also requires time to judge. Such as Figure 5 。

[0046] Specific process description: (A) The set water temperature consists of two parts: "water temperature reference setting" plus "water temperature setting compensation". (B) The "water temperature reference setting" is the paint temperature setting plus 1 - 3 degrees. This is because there is consumption in the water pipeline and heat exchanger, and the ideal water temperature is 1 - 3 degrees higher than the paint temperature. (C) When the water pump stops, the "water temperature setting compensation" is 0. (D) If the difference between the paint temperature setting and the paint temperature detection is below -2 degrees and lasts for 1 - 2 minutes, process 5 is started, and the water temperature setting compensation value decreases by 1 - 2 degrees every 5 - 20 seconds, with a lower limit of -10 degrees. (E) If the difference between the paint temperature setting and the paint temperature detection is within -0.5 to -2 degrees and lasts for 1 - 2 minutes, process 6 is started, and the water temperature setting compensation value decreases by 0.5 - 1 degree every 5 - 60 seconds, with a lower limit of -10 degrees. (F) If the difference between the paint temperature setting value and the paint temperature detection value is greater than -0.5℃ and less than 0.5℃, and the duration is less than 1 - 2 minutes, the water temperature setting compensation value remains unchanged; (G) If the difference between the paint temperature setting and the paint temperature detection is within 0.5 - 2 degrees and lasts for 1 - 2 minutes, process 7 is started, and the water temperature setting compensation value increases by 0.5 - 1 degree every 5 - 60 seconds, with an upper limit of 30 degrees.. (H) If the difference between the paint temperature setting and the paint temperature detection is more than 2 degrees and lasts for 1 - 2 minutes, process 8 is started, and the water temperature setting compensation value increases by 1 - 2 degrees every 5 - 20 seconds, with an upper limit of 30 degrees.

[0047] Through the above control method, after the 2nd fine coating surface coating paint temperature control system of the color coating unit adopts this control model, the original large fluctuation of the paint temperature has now been stabilized.

Claims

1. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit, characterized in that: The automatic control method includes establishing a paint / water temperature setting adjustment module, using the paint temperature setting and the paint temperature detection to judge whether the water temperature is sufficient. If the paint temperature is low, the water temperature setting value is raised; if the paint temperature is high, the water temperature setting value is lowered; then it enters the water temperature automatic control module, controls based on the water temperature setting value, forms a heating control amount, outputs it to the heating controller, and starts the heater to work; The water temperature automatic control module includes: (A) Introduce a water temperature detector. When the water temperature setting value is greater than the water temperature detection value, start Process 1. Process 1 is: heat the water temperature for a period of time, stop heating for a period of time, and cycle. (B) After Process 1 is started, continue to start Process 2. Process 2 is: output in grades according to the temperature difference. When the temperature difference is large, the heating control amount is large; when the temperature difference is small, the heating control amount is small; (C) When the water temperature detection value is greater than the water temperature setting value within a certain range, the heating control amount becomes 0; when the water temperature detection value is greater than the water temperature setting value exceeding a certain range, the heating control amount becomes 0, and at the same time, drain water intermittently and supplement new water to lower the water temperature to the permitted range of the setting value; The paint / water temperature setting adjustment module includes: The water temperature setting value consists of two parts: "water temperature reference setting" plus "water temperature setting compensation"; "water temperature reference setting" takes the paint temperature setting plus 1 - 3 °C as the water temperature reference setting; "water temperature setting compensation" is generated by the difference between the paint temperature setting and the actual paint temperature detection value, and is dynamically adjusted at regular intervals.

2. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to claim 1, characterized in that: In the water temperature automatic control module, after detecting the water temperature, the heating control amount is output intermittently.

3. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to claim 1, characterized in that: In step (C), draining and replenishing water are carried out intermittently.

4. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to claim 1, characterized in that: A water pump circulation system is provided near the heater.

5. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to claim 1, characterized in that: In steps (A) and (B), when the water temperature setting value is greater than 0 °C compared with the water temperature detection value, start Process 1; after Process 1 is started, continue to start Process 2.

6. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to claim 1, characterized in that: In step (C), compare the water temperature detection value with the water temperature setting value. When the water temperature setting value is less than the water temperature detection value and the temperature difference is between 0 and -2 degrees, start Process 3, and the heating control amount is 0, relying on the self-circulation of water and the heat exchange of paint to automatically cool down; Compare the water temperature detection value with the water temperature setting value. When the water temperature setting value is less than the water temperature detection value by more than 2 degrees, start Process 4, the heating control amount is 0, the drain / refill valve is opened intermittently, once every 5 - 20 seconds, and then closed for 5 - 10 seconds, and the cycle is started until the temperature difference is between 0 and -2 degrees.

7. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to claim 1 or 5, characterized in that: In step (A), process 1 is: the water temperature is heated for 10 - 30 seconds, then stopped for 5 - 10 seconds, and the cycle is repeated.

8. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to claim 6, characterized in that: The drain / fill valve is intermittently opened, once every 5 - 20 seconds, determined according to the temperature difference. The greater the temperature difference, the shorter the interval time.

9. A method for automatically controlling the paint temperature by the heating circulating water of a color coating unit according to claim 1, characterized in that: In the method of the paint / water temperature setting adjustment module, the paint temperature set value is compared with the paint temperature detected value, and the paint temperature set value minus the paint temperature detected value: a. If the difference between the paint temperature set value and the paint temperature detected value is below -2°C and lasts for 1 - 2 minutes, start process 5, and the water temperature set compensation value decreases by 1 - 2°C every 5 - 20 seconds, with a lower limit of -10°C; b. If the difference between the paint temperature set value and the paint temperature detected value is within -0.5 to -2°C and lasts for 1 - 2 minutes, start process 6, and the water temperature set compensation value decreases by 0.5 - 1°C every 5 - 60 seconds, with a lower limit of -10°C; c. If the difference between the paint temperature set value and the paint temperature detected value is greater than -0.5°C and less than 0.5°C, and the duration is less than 1 - 2 minutes, the water temperature set compensation value remains unchanged; d. If the difference between the paint temperature set value and the paint temperature detected value is within 0.5 to 2°C and lasts for 1 - 2 minutes, start process 7, and the water temperature set compensation value increases by 0.5 - 1°C every 5 - 60 seconds, with an upper limit of 30°C; e. If the difference between the paint temperature set value and the paint temperature detected value is above 2°C and lasts for 1 - 2 minutes, start process 8, and the water temperature set compensation value increases by 1 - 2°C every 5 - 20 seconds, with an upper limit of 30°C.

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