Refrigeration Cycle

Abstract

Provided is a refrigeration cycle suitable for an air conditioning system for vehicles, wherein a flow rate of refrigerant which is used to estimate a torque of a compressor can be precisely estimated by accurately detecting a difference between pressures at upstream and downstream sides of an orifice having a high correlation with the refrigerant flow rate, and ultimately, the torque of the compressor can be precisely estimated, and the estimation can be achieved while achieving space saving and cost down. Disclosed is a refrigeration cycle which has a subcool condenser integrally provided with a condensing part for refrigerant, a liquid receiver and a subcooling part, and wherein an orifice for throttling the flow of refrigerant which has passed through the condensing part of the subcool condenser is disposed, a pressure difference detection means capable of detecting a difference between pressures at upstream and downstream sides of the orifice is provided, and provided are a refrigerant flow rate estimation means for estimating a flow rate of the refrigerant with reference to the detected pressure difference and a compressor torque estimation means for estimating a torque of the compressor with reference to the estimated flow rate of the refrigerant.

1 . A refrigeration cycle having a compressor for refrigerant, a subcool condenser which is integrally provided with a condensing part for compressed refrigerant, a liquid receiver for condensed refrigerant and a subcooling part for supercooling refrigerant sent from said liquid receiver, a pressure-reduction and expansion mechanism for reducing in pressure and expanding refrigerant sent from said subcool condenser, and an evaporator for evaporating refrigerant sent from said pressure-reduction and expansion mechanism, characterized in that an orifice for throttling a flow of refrigerant which has passed through said condensing part is disposed in said subcool condenser, a pressure difference detection means capable of detecting a pressure difference between pressures at upstream and downstream positions of said orifice in a refrigerant flow direction is provided, and provided are a refrigerant flow rate estimation means for estimating a flow rate of refrigerant with reference to a pressure difference detected by said pressure difference detection means and a compressor torque estimation means for estimating a torque of said compressor with reference to a flow rate of refrigerant estimated by said refrigerant flow rate estimation means. 
     
     
         2 . The refrigeration cycle according to  claim 1 , wherein said orifice is provided between said condensing part and said liquid receiver in said subcool condenser. 
     
     
         3 . The refrigeration cycle according to  claim 1 , wherein said orifice is provided between said liquid receiver and said subcooling part in said subcool condenser. 
     
     
         4 . The refrigeration cycle according to  claim 1 , wherein detection of a pressure at a downstream position of said orifice in said refrigerant flow direction is carried out at an exit of said subcooling part. 
     
     
         5 . The refrigeration cycle according to  claim 1 , wherein said pressure difference detection means detects said pressure difference by calculating a difference between pressures detected by a first pressure sensor for detecting a pressure at an upstream position of said orifice in said refrigerant flow direction and a second pressure sensor different from said first pressure sensor for detecting a pressure at a downstream position of said orifice in said refrigerant flow direction. 
     
     
         6 . The refrigeration cycle according to  claim 5 , wherein said refrigerant flow rate estimation means estimates a flow rate of refrigerant with reference to a pressure difference detected by said pressure difference detection means and with reference to an amount detected by said first pressure sensor and/or said second pressure sensor. 
     
     
         7 . The refrigeration cycle according to  claim 5 , wherein said compressor torque estimation means estimates a torque of said compressor with reference to a flow rate of refrigerant estimated by said refrigerant flow rate estimation means, a physical amount having a correlation with a suction pressure of said compressor, a physical amount having a correlation with a rotational speed of said compressor, and an amount detected by said first pressure sensor. 
     
     
         8 . The refrigeration cycle according to  claim 1 , wherein said pressure difference detection means detects said pressure difference by a pressure difference sensor which directly detects a pressure difference between pressures at upstream and downstream positions of said orifice in a refrigerant flow direction. 
     
     
         9 . The refrigeration cycle according to  claim 1 , wherein said refrigeration cycle is used for an air conditioning system for vehicles.