| 摘要 |
<p>The invention relates to a valve assembly for a refrigeration plant of the kind used for controlling the flow of refrigerant from the evaporator to the compressor. The closure member for the valve unit is controlled directly or indirectly by a reference pressure generator having an expansible chamber filled with a refrigerant medium having vapor and liquid phases. The pressure exerted by the vapor phase of the medium provides a bias for controlling the valve and is directly related to the temperature of the liquid phase. A heat transfer element such as a heating resistor in the liquid phase is heated or allowed to cool in a controlled manner by an external control unit. A temperature responsive sensor element in the liquid phase of the medium is part of a feedback system for the control unit which allows a selected temperature to be maintained in the chamber which results in a desired constant pressure in a valve opening direction to be maintained in a chamber. A control circuit has an evaporator parameter input branch and a second input branch for the feedback temperature sensing element. The control unit has an output for heating the heating resistor in the expansible chamber and a summating section for varying the relative effects of the input branches on the output.</p> |
