Introduction

Hydraulic drive system is a system of vertical injection molding machine is the most commonly used, vertical injection molding machine energy consumption the main location. So the key energy-saving vertical injection molding machine is the energy utilization efficiency is improved hydraulic power system itself, so that the drive system output power and execution power to achieve the adaptive adjust match, between the energy utilization rate is high, energy saving and efficiency of the system is also higher.

Vertical hydraulic injection molding machine drive system generally has the following two kinds: full hydraulic drive system; electro-hydraulic hybrid drive system. Hydraulic drive system is a vertical injection molding machine is the most widely used in the power drive system, but also energy-saving driving key research object system aspects. From the energy point of view, electric and hydraulic drive system is the innovation and development of the energy utilization rate is not high in the hydraulic drive system, also is the ideal energy-saving driving system.

1 energy saving full hydraulic drive control system

Using the process of processing products of vertical injection molding machine is generally divided into locking, injection, holding pressure, melt, cooling, mold and so on several stages, each stage are required to pressure and different flow. Hydraulic pump and motor, the load state of the injection molding process is always in the change, in the hydraulic system with quantitative pump, hydraulic pump to provide a constant flow at a constant speed, redundant hydraulic oil through the overflow valve reflux, this process is also called high pressure throttle. According to statistics, the energy loss caused by high pressure throttle reaches as high as 36% a 68%. Therefore, reducing throttle loss and improve the efficiency of energy utilization, has become the development direction of J hydraulic driving system and energy saving.

Energy saving system of 1.1 flow pressure double proportional control and quantitative pump consisting of

Double flow ratio and the pressure ratio control energy saving technology is developing along with the performance and control of injection molding technology improvement. Power switch valve and quantitative pump consists of driving system can not meet the performance requirements of injection molding, and the proportional valve can realize flexible stepless regulation, but also has the characteristics of energy saving, in the application process, characteristics of the saving energy has been continuously improved.

Small and medium-sized vertical injection molding machine of P/Q composite electro hydraulic proportional technology and the combination of quantitative pump energy saving power consists of the drive system is widely used in domestic energy saving vertical injection molding machine manufacturers drive system. The hydraulic pump, small vertical injection molding machine is usually a single pump or two pumps, pump discharge flow to adjust the proportion of all through the P/Q valve. The technical characteristics of P/Q composite proportional valve is to control the speed of three formula proportion speed regulating valve, then the superposition of proportion pilot valve pressure control system pressure. Compared with the system composed of separate elements originally adopted, the system greatly reduces the number of components, simplified structure, at the same time, pipelines and throttle can reduce the energy consumption. The application of the system improves the performance of automatic control technology level and vertical injection molding machine injection molding, injection molding process required a longer cooling time in molding products, its energy saving is obvious, has certain advantages in energy saving and cost-effective, therefore in the vertical injection molding machine all use P/Q composite electric liquid proportional technology.

Proportional technology and quantitative pump large vertical injection molding machine is composed of energy-saving power drive system. Large vertical injection molding machine hydraulic pump by multiple dosing pump. In order to meet the need of work flow system. Multi pump and the proportional valve collocation is directly related to the level of energy consumption of the system. The match has two forms: one is the use of small and medium-sized vertical injection molding machine of P/Q composite electro hydraulic proportional technology and quantitative pump combination of energy-saving power driving system composed of form, the total flow of all through the P/Q proportional valve (or near the road P/Q proportional valve). As a result of the work flow of each pump must be approved by the proportional flow valve into the system, thus causing flow pressure difference energy loss, especially under the circumstance of large flow rate, energy loss will be greater; another form only in a small flow pump proportional speed regulation, the rest of the flow rate of the pump according to the flow combination superposition conditions and proportional speed regulation of small pump, forming a flow proportional slash, various conditions needed flow can be selected in the proportion the slash. In addition to the small pump proportional speed regulation, working flow pump to rest in the system, the proportional flow speed is not the first matching forms of energy loss, so as to improve the utilization ratio of energy.

With the mold clamping force is vertical injection molding machine of 8000kN as an example, the pump source five sets quantitative pump group, respectively is the displacement of 76L proportional small pump, the other two groups for displacement of 76U152L double pump. Four pump two sets of double pump flow according to the working condition and proportional small pump combination and superposition, the formation of a flow proportional slash, various conditions needed flow can be selected in proportion of the slash, small pumps in addition to proportional speed regulation of work flow, the rest of the pump must enter the system, the proportional flow speed without energy loss and flow related to basically, thus its energy utilization rate is increased. The system also can reduce the number of pump according to the need, do not affect the performance of speed regulation system.

1.2 load sensing control system application

Energy saving measures of vertical injection molding machine is the most effective traffic adaptive between dynamic mechanism and executing mechanism, both regulation. Composition combined by variable pump and electro-hydraulic proportional valve load sensing pump energy saving control system of the whole control mechanism is composed of a differential pressure control type radial piston pump, variable with position closed loop speed proportional valve and the pressure sensor and the displacement sensor, the dynamic response speed of the system thus improved. Position closed-loop system flow control consists of a displacement sensor proportional valve and detection of variable pump eccentric quantity to achieve; variation proportional pressure sensor control variable displacement pump can compensate for the loss caused by the leakage flow, so that the pump output flow in O within a 10V signal and the setting value is linearly proportional to the electric control closed loop control system; pressure is composed of proportional valve with the pressure sensor to realize the conversion of the pressure and flow separation; and two control state by the electronic amplifier according to the set signal automatically. The output flow by. Increases to 90%, the response time is about 50ms; the output flow rate decreases from 90% to O, the response time is about 30m,. Dynamic response time of the system pressure in the load chamber is 4L, less than 200ms, the proportional valve it with the high performance fairly, so the process is completely suitable for vertical injection molding machine control. Hydraulic power output loading sensitive proportional pump energy saving hydraulic system and load synchronous, because the minimum value, so basically no waste of energy. Compared with the quantitative system, energy saving achieved 30~60%, is an ideal energy-saving hydraulic system.

The set load sensitive pump output flow can not and need to precisely adjust the flow matching, this system must be added a flow regulating valve, thus will cause the throttle loss of energy consumption. Can eliminate the energy loss of throttling and line load sensitive pump closed loop control system and servo valve components, and can greatly improve the performance of the whole machine. Most of the domestic manufacturers only consider from the aspect of energy conservation, replace the quantitative pump and P/Q double proportional valve with a load sensing pump, and no further from the load sensing pump can improve the performance of the whole machine as a test the filter, thus failing to make the control performance and energy saving characteristics of the system into full play. The international advanced load sensing pump control system in plasticizing injection oil part are installed the servo valve is designed with a load sensing pump consists of a closed loop control system with high performance and energy saving. The system in energy saving at the same time, but also can improve the injection performance, but in the domestic plastics machinery manufacturing is not popularized by industry basically. In early 1985, the author has successfully design of vertical injection molding machine equipped with a closed loop control system composed of a load sensing pump and servo valve. After the actual use proof, the machine in the two aspects of energy saving and performance are achieved good results.

1.3 quantitative pump with frequency conversion motor system

Use of frequency adjustment technology by adjusting the hydraulic pump speed to make the dynamic mechanism has properties similar to proportional pump energy saving system, to realize the dynamic mechanism of output flow and execution mechanism of flow matching, so as to reduce the flow loss. Inverter control technology is the use of vertical injection molding machine synchronous signal and electric control system and electro-hydraulic proportional control system simulation load tracking control system according to the requirements of injection molding process, so that the hydraulic pump motor speed and vertical injection molding machine work required hydraulic flow and pressure is proportional to the product of the transformation of traditional, quantitative pump a variable frequency variable drive system, so that the oil return flow relief valve is reduced to a minimum, and no pressure throttling loss of energy, and then will traditional high pressure throttle "energy" vertical injection molding machine upgrade for the non pressure throttling "energy saving" vertical injection molding machine. In the control mode of vertical injection molding machine and oil original unchanged, the original machine through the transformation of frequency conversion energy-saving device installed in the vertical injection molding machine, single machine energy saving effect reached 30% a 60%. Cixi City, more than 200 vertical injection molding machine enterprises every year can save 6000000 kwh.

The pressure holding time and cooling time long thick wall products required, using frequency control equipment should be the first choice for the.