Air Conditioning System for Vehicle

Abstract

Provided is an air conditioning system for vehicles wherein a flow rate of refrigerant used for estimating a compressor torque can be accurately estimated by accurately detecting a difference between pressures at upstream and downstream sides of an orifice, which has a high correlation with the flow rate of refrigerant, and ultimately, the compressor torque can be accurately estimated, and this estimation can be performed while space saving and cost down can be achieved. The air conditioning system for vehicles having a refrigeration cycle provided with a refrigerant compressor, a condenser, a pressure reduction/expansion mechanism and an evaporator is characterized in that an orifice for throttling a refrigerant flow is disposed in a refrigerant path between the condenser and the pressure reduction/expansion mechanism, a pressure difference detection means capable of detecting a difference between pressures at upstream and downstream positions of the orifice is provided, and provided are a refrigerant flow rate estimation means for estimating a refrigerant flow rate with reference to the detected pressure difference and a compressor torque estimation means for estimating a compressor torque with reference to the estimated refrigerant flow rate.

1 . An air conditioning system for vehicles having a refrigeration cycle provided with a refrigerant compressor, a condenser for condensing compressed refrigerant, a pressure reduction/expansion mechanism for reducing in pressure and expanding refrigerant sent from said condenser and an evaporator for evaporating refrigerant sent from said pressure reduction/expansion mechanism, characterized in that an orifice for throttling a refrigerant flow is disposed in a refrigerant path between said condenser and said pressure reduction/expansion mechanism, 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 refrigerant flow rate with reference to a pressure difference detected by said pressure difference detection means and a compressor torque estimation means for estimating a compressor torque with reference to a refrigerant flow rate estimated by said refrigerant flow rate estimation means. 
     
     
         2 . The air conditioning system for vehicles according to  claim 1 , wherein a tube for forming a part of said refrigerant path between said condenser and said pressure reduction/expansion mechanism and said pressure difference detection means are formed as an integrated unit, and said orifice is disposed in said unit. 
     
     
         3 . The air conditioning system for vehicles according to  claim 2 , wherein a sight glass capable of observing an inside of said refrigerant path is provided to said unit. 
     
     
         4 . The air conditioning system for vehicles 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. 
     
     
         5 . The air conditioning system for vehicles according to  claim 4 , wherein said refrigerant flow rate estimation means estimates said refrigerant flow rate with reference to said pressure difference detected by said pressure difference detection means and with reference to amounts detected by said first pressure sensor and/or said second pressure sensor. 
     
     
         6 . The air conditioning system for vehicles according to  claim 4 , wherein said compressor torque estimation means estimates said compressor torque with reference to a refrigerant flow rate 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. 
     
     
         7 . The air conditioning system for vehicles according to  claim 1 , wherein said pressure difference detection means detects said pressure difference by a pressure difference sensor for directly detecting a pressure difference between pressures at upstream and downstream positions of said orifice in said refrigerant flow direction. 
     
     
         8 . The air conditioning system for vehicles according to  claim 1 , wherein a signal of said compressor torque estimated by said compressor torque estimation means is sent to a control unit for a drive source of said compressor.