Application of the hottest micro energy vector con

2022-08-16
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The application of micro energy vector converter in the energy-saving transformation of injection molding machine

1. Introduction

the plastic products processing industry is one of the industries with rapid development speed in the light industry in recent years. With the increase of the number of plastic enterprises, reducing production costs and improving product competitiveness have become the common concern of many plastic products factories. In the processing cost, electricity accounts for a considerable proportion, and a large number of injection molding machines are the equipment that consumes the most electricity. Therefore, many plastic enterprises have carried out a lot of energy-saving technological transformation on the quantitative pump injection molding machines to save electricity and improve the competitiveness of enterprises. However, many enterprises, including many professional energy-saving companies, are helpless about the variable pump injection molding machines, Therefore, for a large number of variable displacement pump injection molding machines in the market, how to carry out energy-saving transformation has become a hot spot of concern for many plastic enterprises. Through in-depth research on variable displacement pump injection molding machines, Shenzhen Weineng Technology Co., Ltd. successfully realized the energy-saving transformation of variable displacement pump injection molding machines combined with the latest vector control frequency conversion technology, and achieved 10-20% energy-saving effect

2. Introduction to quantitative pump and variable pump injection molding machine

1) quantitative pump injection molding machine

at present, most of the modified injection molding machines belong to hydraulic transmission injection molding machines. The power in the hydraulic transmission system is provided by the motor driven oil pump. The hydraulic oil pump is a vane pump, and its oil supply is proportional to the speed of the oil pump. When the oil pump motor operates at a constant speed of 50Hz, the oil supply of the oil pump is unchanged, so it is called quantitative pump. The system diagram is as follows:

as shown in Figure 1: A1: cylinder rodless cavity piston area F: working load Q1: working flow P1: working pressure △ P: pressure difference at both ends of the proportional speed regulating valve QY: proportional overflow valve flow Pb: oil pump pressure, QB: oil pump flow VB: oil pump displacement n: motor speed

as shown in Figure 1, the system uses quantitative pump oil supply, and the oil pump speed n and oil pump displacement VB are not adjustable, The flow and pressure in the oil circuit are respectively:

oil pump flow QB = VB n is the fixed value

the oil pump pressure Pb is set by the proportional overflow valve

the working flow Q1 is set by the proportional speed regulating valve

working pressure P1 = f/a1 depends on working load f

the production process of general injection molding machines includes the following links: mold locking, glue injection, glue melting, pressure maintaining, cooling and mold opening. The flow and pressure required by the injection molding machine in different processes are different, and the flow and pressure required by different processes must be adjusted by the flow valve and pressure valve. When the flow required for operation is small, the oil supply of the oil pump is greater than that of the actuator, so the oil required for the running elements should be often cleaned at the jaw. The excess hydraulic oil under high pressure is all returned through the overflow valve, and a large amount of energy is consumed through the temperature rise of the oil. This not only aggravates the wear of various valves, but also causes the oil temperature to be too high. In order to reduce the oil temperature, additional cooling water circulation is often required, resulting in further waste of energy. Therefore, in the transformation of the general quantitative pump injection molding machine, the frequency converter is used to control the speed of the oil pump motor to adjust the flow. The amount of oil pumped within the specified time just meets the needs of all action links, and the overflow can be controlled at the minimum state, thus saving energy

2) variable displacement pump injection molding machine

at present, variable displacement pump injection molding machine mostly uses proportional variable displacement pump as the driving element, which belongs to a typical volumetric speed regulation system, and has obvious energy-saving effect compared with the transmission quantitative pump injection molding machine. As shown in Figure 2, the system is composed of load sensitive proportional variable piston pump, proportional overflow valve, proportional speed regulating valve, pressure feedback valve, flow feedback valve, etc

as shown in Figure 1: A1: cylinder rodless piston area F: working load Q1: working flow P1: working pressure △ P: pressure difference at both ends of proportional speed regulating valve QY: proportional overflow valve flow Pb: oil pump pressure, QB: oil pump flow VB: oil pump displacement n: motor speed

as shown in Figure 1, the system uses quantitative pump oil supply, and the oil pump speed n and oil pump displacement VB are not adjustable, The flow and pressure in the oil circuit are respectively:

oil pump flow QB = VB n is the fixed value

the oil pump pressure Pb is set by the proportional overflow valve

the working flow Q1 is set by the proportional speed regulating valve

working pressure P1 = f/a1 depends on working load f

the production process of general injection molding machines includes the following links: mold locking, glue injection, glue melting, pressure maintaining, cooling and mold opening. The flow and pressure required by the injection molding machine in different processes are different, and the flow and pressure required by different processes must be adjusted by the flow valve and pressure valve. When the flow required for operation is small, the oil supply volume of the oil pump is greater than the oil volume required by the actuator. The excess hydraulic oil under high pressure is all refluxed through the overflow valve, and a large amount of energy is consumed through the temperature rise of the oil. This not only aggravates the wear of various valves, but also causes the oil temperature to be too high. In order to reduce the oil temperature, additional cooling water circulation is often required, resulting in further waste of energy. Therefore, in the transformation of the general quantitative pump injection molding machine, the frequency converter is used to control the speed of the oil pump motor to adjust the flow. The amount of oil pumped within the specified time just meets the needs of all action links, and the overflow can be controlled at the minimum state, thus saving energy

2) variable displacement pump injection molding machine

at present, variable displacement pump injection molding machine mostly uses proportional variable displacement pump as the driving element, which belongs to a typical volumetric speed regulation system, and has obvious energy-saving effect compared with the transmission quantitative pump injection molding machine. As shown in Figure 2, the system is composed of load sensitive proportional variable piston pump, proportional overflow valve, proportional speed regulating valve, pressure feedback valve, flow feedback valve, etc

as shown in Figure 1: A1: cylinder rodless cavity piston area F: working load Q1: working flow P1: working pressure △ P: pressure difference at both ends of proportional speed regulating valve QY: proportional overflow valve flow Pb: oil pump pressure, so connect the strain gauge into the measuring circuit to force, QB: oil pump flow VB: oil pump displacement n: motor speed

as shown in Figure 1, the system uses quantitative pump oil supply, and the oil pump speed n and oil pump displacement VB are not adjustable, The flow and pressure in the oil circuit are respectively:

oil pump flow QB = VB n is the fixed value

the oil pump pressure Pb is set by the proportional overflow valve

the working flow Q1 is set by the proportional speed regulating valve

working pressure P1 = f/a1 depends on working load f

the production process of general injection molding machines includes the following links: mold locking, glue injection, glue melting, pressure maintaining, cooling and mold opening. The flow and pressure required by the injection molding machine in different processes are different, and the flow and pressure required by different processes must be adjusted by the flow valve and pressure valve. When the flow required for operation is small, the oil supply volume of the oil pump is greater than the oil volume required by the actuator. The excess hydraulic oil under high pressure is all refluxed through the overflow valve, and a large amount of energy is consumed through the temperature rise of the oil. This not only aggravates the wear of various valves, but also causes the oil temperature to be too high. In order to reduce the oil temperature, additional cooling water circulation is often required, resulting in further waste of energy. Therefore, in the transformation of the general quantitative pump injection molding machine, the frequency converter is used to control the speed of the oil pump motor to adjust the flow. The amount of oil pumped within the specified time just meets the needs of all action links, and the overflow can be controlled at the minimum state, thus saving energy

2) variable displacement pump injection molding machine

at present, variable displacement pump injection molding machine mostly uses proportional variable displacement pump as the driving element, which belongs to a typical volumetric speed regulation system, and has obvious energy-saving effect compared with the transmission quantitative pump injection molding machine. As shown in Figure 2, the system is composed of load sensitive proportional variable piston pump, proportional overflow valve, proportional speed regulating valve, pressure feedback valve, flow feedback valve, etc

figure II schematic diagram of oil circuit system

a1: oil cylinder rodless cavity piston area F: working load P1: working pressure Q1: working flow

△ P: pressure difference at both ends of proportional speed regulating valve Pb: oil pump pressure QB: oil pump flow n: motor speed

working principle

(1) when the system is in the flow control state, the oil pump pressure Pb is greater than the working pressure P1 and less than the set pressure of the plastic machine, and the proportional overflow valve will be reliably closed. When the load changes, the pressure difference △ p between Pb and P1 will fluctuate accordingly, and the working flow Q1 will change. The above changes are transmitted to the adjusting piston of the variable displacement pump through the flow and pressure feedback valve. The piston then pushes the swashplate of the plunger pump and changes the displacement of the oil pump. The first thing that finally stabilizes the pump is the "Reindustrialization" of developed countries and the accelerated protrusion output flow QB of new economies. It can be seen that the system realizes pressure adaptive control and basically has no overflow loss, but in order to control the working flow Q1, there is still a certain throttling loss on the speed regulating valve

(2) when the system is in the pressure control state, the inclined angle of the swashplate of the variable piston pump is very small, and only a small amount of hydraulic oil flows through the proportional overflow valve to ensure that a certain system pressure is formed. By changing the input signal of the proportional relief valve, the corresponding output pressure of the oil pump can be obtained. Compared with the traditional quantitative pump injection molding machine, this control method reduces the overflow loss to a certain extent

3. Energy saving principle of variable displacement pump injection molding machine

from the above introduction, we can know that compared with quantitative pump injection molding machine, variable displacement pump injection molding machine reduces a lot of overflow loss, making the load of oil pump motor lighter, the current reduced, and it is in a light load state. From the perspective of hydraulic components, variable displacement pump injection molding machine excavates the energy-saving transformation space on the oil circuit, so as to improve the working efficiency of the oil circuit system. However, limited by its control mode, the system can not completely eliminate throttling and overflow losses

1) the variable displacement pump injection molding machine still has a waste of space. The oil from the oil pump still needs to be adjusted by the proportional speed regulating valve and the proportional overflow valve, and there is still a certain power loss on the valve

2) the motor speed of the oil pump still cannot be adjusted. Although its load is much lighter than that of the quantitative pump, it is obvious that the former consumes more energy than adjusting the oil volume by adjusting the speed. Especially when the system is under pressure control, the pressure required by the system is large but the flow is small, and the speed of the oil pump motor cannot be adjusted. If the output flow, output pressure, displacement and speed of the oil pump are expressed as Q, P, VB and N respectively, the output power n of the oil pump is expressed by the formula:

n = Q * P = VB * n * P

the injection molding machine adjusts the displacement VB of the oil pump through mechanical devices. Obviously, its adjustable linear range is limited and zero displacement output cannot be achieved. And in any case, the motor is running at full speed, with a lot of unnecessary energy loss

3) the start of oil pump motor is still star delta start, and the power factor is low

4. Power saving system of micro energy company

micro energy company applies vector frequency conversion technology to the motor drive of injection molding machine, and completes the precise control of injection molding machine through speed regulation and pressure PID closed-loop control function. The proportional speed regulating valve in the oil circuit is manually and rigidly adjusted to the maximum flow and maintained or removed, while cutting off the control of the flow and pressure feedback valve on the piston of the variable displacement pump. The vector variable-frequency PID control is changed to maintain the constant pressure, and the pressure adaptive control is automatically realized. In this way, the system eliminates the throttling and overflow energy loss in the oil circuit from the source, so that the injection molding machine can obtain the best energy-saving effect. The system is as follows:

working principle:

when the oil pump flow QB approaches or reaches the set value of the plastic machine, the oil circuit system enters the flow control state, and the output frequency of the frequency converter is consistent with the set value of the plastic machine flow

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