Patent ID: 8177521
Filing Date: 2012-05-15
Classification: F04B,F25B

Abstract:
1. A method for monitoring and controlling oil return to a compressor, applicable to a monitoring and controlling system for monitoring and controlling a quantity of returned oil in an oil box by controlling a valve opening of an oil return inlet of the oil box, and wherein the system comprises an oil return valve provided at the oil return inlet, a pressure sensor provided at an outlet of the compressor, and an oil level sensor and a temperature sensor provided in the oil box, the method comprising the steps of: setting a lowest oil level of oil in the oil box, a pressure value required for oil return, an initial oil return flag, an oil level of the returned oil corresponding to the initial oil return flag, a maximum temperature value, and a minimum temperature value; detecting an initial oil level value of the oil in the oil box, determining whether the initial oil level value detected exceeds the lowest oil level, and shutting down the compressor upon a negative determination; detecting a temperature value of the oil in the oil box, determining whether the temperature value detected exceeds the minimum temperature value, warming up the oil box upon a negative determination, and heating the oil box to allow the temperature value of the oil in the oil box to fall between the minimum temperature value and the maximum temperature value upon an affirmative determination; detecting a pressure value of the returned oil, determining whether the pressure value detected exceeds the pressure value required for oil return, maintaining full valve opening of the oil return valve upon a negative determination, and controlling the valve opening of the oil return valve upon an affirmative determination; controlling the valve opening of the oil return valve according to a non-segmentation principle calculated with a proportional-integral-derivative (PID) controller algorithm, the controlling comprising: retrieving the initial oil return flag and setting a true value of the oil level value to a first oil level value and a false value of oil level value to a second oil level value; calculating a difference between a measured oil level value and the oil level value of the returned oil, so as to obtain an adjustable range of the valve opening of the oil return valve; determining whether the adjustable range of the valve opening of the oil return valve tends to increase, resetting the oil return flag to the true value upon an affirmative determination, and resetting the oil return flag to the false value upon a negative determination; and converting a range of the valve opening obtained into an electric signal instruction for controlling the valve opening; and determining whether the oil level value is less than or equal to the lowest oil level value, shutting down the compressor upon an affirmative determination, and analyzing the pressure value of the returned oil and the temperature value of the oil box for performing periodical analysis upon a negative determination.