Displacement control mechanism of variable displacement type compressor

Abstract

A displacement control mechanism controls displacement of a variable displacement type compressor that forms a refrigerant circulation circuit for an air conditioning apparatus. The displacement is decreased as a pressure in a crank chamber rises while being increased as the pressure in the crank chamber falls. The displacement control mechanism includes a bleed passage, a supply passage, a first control valve and a second control valve. The second control valve includes a back pressure chamber, a valve chamber, a valve body, a spring and a second valve portion. The second valve portion is provided with the back surface of the valve body. The second valve portion closes an opening of an introduction passage in the back pressure chamber when the first valve portion maximizes the opening of the bleed passage.

What is claimed is:  
     
         1 . A displacement control mechanism for controlling displacement of a variable displacement type compressor that forms a refrigerant circulation circuit for an air conditioning apparatus, the displacement being decreased as a pressure in a crank chamber rises while being increased as the pressure in the crank chamber falls, the refrigerant circulation circuit having a suction pressure region and a discharge pressure region, the displacement control mechanism comprising: 
 a bleed passage interconnecting the crank chamber with the suction pressure region;    a supply passage interconnecting the crank chamber with the discharge pressure region;    a first control valve located on the supply passage for adjusting an opening of the supply passage at a position of valve opening adjustment;    a second control valve comprising; 
 a back pressure chamber to which a pressure on a downstream side of the position of valve opening adjustment of the first control valve in the supply passage is introduced through an introduction passage;  
 a valve chamber forming a part of the bleed passage;  
 a valve body having a first valve portion located in the valve chamber and a back surface located in the back pressure chamber, the first valve portion decreasing an opening of the bleed passage as a pressure in the back pressure chamber which is applied to the back surface rises;  
 a spring for urging the valve body so that the first valve portion increases the opening of the bleed passage; and  
 a second valve portion provided with the back surface of the valve body, the second valve portion closing an opening of the introduction passage in the back pressure chamber when the first valve portion maximizes the opening of the bleed passage.  
   
     
     
         2 . The displacement control mechanism according to  claim 1 , wherein the second valve portion is so shaped as to protrude and taper from the back surface toward the opening of the introduction passage, the second valve portion closing the opening of the introduction passage by entering the introduction passage.  
     
     
         3 . The displacement control mechanism according to  claim 1 , wherein the introduction passage and the back pressure chamber form a part of the supply passage.  
     
     
         4 . The displacement control mechanism according to  claim 3 , wherein the second control valve opens and closes the supply passage at a plurality of places.  
     
     
         5 . The displacement control mechanism according to  claim 1 , wherein the second valve portion is made of resilient material.  
     
     
         6 . The displacement control mechanism according to  claim 1 , wherein the first valve portion of the second control valve opens and closes the bleed passage at a plurality of places.  
     
     
         7 . The displacement control mechanism according to  claim 1 , wherein the variable displacement type compressor is of a clutchless type, the variable displacement type compressor of clutchless type is such a variable displacement type compressor that continues to rotate a drive shaft in a state that a minimum inclination angle of a cam plate is maintained such that a refrigerant is not substantially flowed into an external refrigerant circuit while a refrigeration cycle stops.