In the process of injection molding, it is very important to control the position of moving parts, and its accuracy directly affects the quality of products. Therefore, improving the accuracy of position control is an important aspect of improving the quality of injection molding machine.
Straight lines are currently used Displacement sensor In the injection molding machine system to realize the position control, the straight line Displacement sensor The physical distance from the controller is far, and the commonly used acquisition method is that the analog signal of the sensor is directly transmitted to the controller through the data line, and then the signal acquisition, conversion and calculation are carried out at the controller end. Because the analog signal is easy to be affected by the field environment in the process of long-distance transmission, the data collected by the controller has large error, and the expression of sensor position is not accurate enough, which reduces the control accuracy of injection molding machine.
summary of the invention
The purpose of the utility model is to provide a signal transfer box of a digital linear displacement sensor for an injection molding machine in view of the above shortcomings of the prior art. The utility model has the advantages of low cost, high precision and strong anti-interference ability.
Description of drawings
Figure 1 is the structure diagram of the signal remote transmission junction box of the digital linear displacement sensor.
Specific implementation mode
The embodiment of the utility model is described in detail below in combination with the attached drawings.
As shown in Fig. 1, the utility model adds a dedicated digital linear displacement sensor signal remote transmission junction box on the injection molding machine, which is a transition box with sensor signal acquisition, conversion and transmission, including sensor signal input terminal 1, filter circuit 2, sampling and holding circuit 3, AD conversion circuit 4, isolation circuit 5 and CPU 6. Communication circuit 7, power supply circuit 8, communication bus terminal 10, power supply terminal 9. The junction box is installed near the sensor installation position, and the sensor signal output is connected to the signal input terminal of the junction box to realize the close acquisition of sensor signal. After the sensor signal is connected to the junction box, the interference signal is filtered through the filter circuit. After AD conversion, it is converted into digital signal by the signal conversion circuit inside the junction box, and then transmitted to the remote central controller by bus. The junction box of the utility model can be installed at the same time, and the connecting box can be connected through the bus to form the digital sensor signal remote transmission junction box network.
The signal input terminal of linear displacement sensor is used to connect the sensor. Each sensor is equipped with three terminals, VCC (power supply positive), GND (power negative) and AV (signal). VCC and GND are used to supply power to the sensor. AV is the output of sensor, which is voltage or current signal, indicating the corresponding value of different positions. The range of AV output converted into voltage is between GND and VCC.
The filter circuit uses active low-pass filter to filter the sensor signal.
The sample and hold circuit latch the input value of analog signal during sampling, which is used for AD conversion circuit to convert the voltage signal output from sensor signal filter circuit in real time, and obtain the AD conversion result of more than 16 bits.
The isolation circuit separates the CPU circuit, communication circuit and other digital signals from the analog circuit related to the sensor signal acquisition and amplification through optocoupler to prevent the interference of digital signal on the analog circuit.
The CPU is responsible for reading the results of AD conversion circuit, after digital filtering, the control communication circuit is sent to the remote controller.
The communication circuit adopts can bus communication circuit (also can be Ethernet, etc.), which is controlled by CPU and sends the collected sensor position data to the remote controller through the communication bus terminal. When several junction boxes are installed together, the communication circuit also forms a remote transmission network.
The power supply circuit is used for power supply of the device. The power supply is input from the power supply terminal, which is positive and negative power supply to CPU and communication circuit. A new isolated power supply is generated through the power supply circuit, which is used for the signal input terminal of linear displacement sensor, filter circuit, sampling and holding circuit and AD conversion circuit.