Expander and heat pump using the expander

Abstract

An expander of the present invention includes a plurality of suction ports for guiding a working fluid to a working chamber, and the plurality of suction ports includes a first suction port ( 71 ) and a second suction port ( 73 ) with a differential pressure valve ( 72 ). The ratio R2 of time length of an expansion process of expanding the working fluid in the working chamber to time length of a suction process in which the working fluid is sucked into the working chamber ( 55 a ) from the first suction port ( 71 ) and the second suction port ( 73 ) by opening the differential pressure valve ( 72 ) is smaller than the ratio R1 of the time length of the expansion process to a suction process in which the working fluid is sucked into the working chamber ( 55 a ) only from the first suction port ( 71 ) by closing the differential pressure valve ( 72 ).

1 . A rotary type expander comprising:
 a first cylinder;   a first piston disposed in the first cylinder so as to rotate eccentrically in the first cylinder, and forming a first working chamber between itself and the first cylinder;   a first partition member partitioning the first working chamber into a first suction-side space and a first discharge-side space;   a second cylinder disposed so as to be concentric with the first cylinder;   a second piston disposed in the second cylinder so as to rotate eccentrically in the second cylinder, and forming a second working chamber between itself and the second cylinder, the second working chamber having a greater volume than the first working chamber;   a second partition member partitioning the second working chamber into a second suction-side space and a second discharge-side space;   a communication passage forming a working chamber, for expanding the working fluid, by permitting the first discharge-side space and the second intake-side space to communicate with each other;   a plurality of suction ports for guiding the working fluid to the first suction-side space, comprising a first suction port and a second suction port, the second suction port provided with a differential pressure valve and disposed at a position advanced from a position of the first suction port by a predetermined angle in a direction of rotation of the first piston; and   a control pressure passage connected to the differential pressure valve, for supplying the differential pressure valve with a control pressure for opening and closing the differential pressure valve.   
     
     
         2 . The rotary type expander according to  claim 1 , wherein:
 the control pressure is equal to a pressure (P 1 ) of the working fluid before expansion or a pressure (P 2 ) of the working fluid after expansion; and   the control pressure that is equal to one selected from the pressure (P 1 ) and the pressure (P 2 ) is supplied selectably to the differential pressure valve through the control pressure passage.   
     
     
         3 . The rotary type expander according to  claim 2 , wherein:
 the differential pressure valve closes at least when the control pressure is equal to the pressure (P 1 ); and   the differential pressure valve opens at least when the control pressure is equal to the pressure (P 2 ).   
     
     
         4 . The rotary type expander according to  claim 1 , wherein a time length t2 of a suction process in which the working fluid is sucked into the first suction-side space from the first suction port and the second suction port by opening the differential pressure valve is greater than a time length t1 of a suction process in which the working fluid is sucked into the first suction-side space only from the first suction port by closing the differential pressure valve. 
     
     
         5 . The rotary type expander according to  claim 1 , wherein the differential pressure valve comprises a plunger having one end face to which the pressure in the first working chamber is applied and another end face to which the control pressure is applied, and a spring for pushing the plunger toward the first working chamber. 
     
     
         6 . The rotary type expander according to  claim 1 , wherein the differential pressure valve is disposed within the first cylinder and between an outer circumferential surface of the first cylinder and an inner circumferential surface of the first cylinder. 
     
     
         7 . The rotary type expander according to  claim 1 , further comprising:
 a main passage for guiding the working fluid to the first suction port; and   a sub-passage branching from the main passage and provided along an outer circumference of the first working chamber, for guiding the working fluid to the second suction port.   
     
     
         8 . The rotary type expander according to  claim 7 , wherein:
 the second suction port is provided in the first cylinder or in a closing member closing the first cylinder;   the differential pressure valve comprises (a) a groove following the second suction port and extending outwardly in a radial direction of the first cylinder so that at least a portion thereof overlaps with the sub-passage, and (b) a plunger disposed in the groove and being capable of reciprocating between two positions, one position being an open position for permitting the working fluid to flow through the sub-passage to the second suction port from the main passage and the other position being a close position for prohibiting the working fluid from flowing through the sub-passage to the second suction port from the main passage; and   the reciprocating motion of the plunger is controlled by the control pressure.   
     
     
         9 . The rotary type expander according to  claim 7 , further comprising:
 a shaft for rotating the first piston and the second piston; and   a bearing member closing an end face of the first cylinder on an opposite side to the side where the second cylinder is positioned and supporting the shaft, wherein   the main passage and the sub-passage are provided in the bearing member.   
     
     
         10 . The rotary type expander according to  claim 1 , wherein:
 the plurality of suction ports further comprises a third suction port provided with a differential pressure valve; and   a length t3 of a suction process in which the working fluid is sucked from the first suction port, the second suction port, and the third suction port to the first suction-side space by opening the differential pressure valves of the second suction port and the third suction port is greater than the length t2.   
     
     
         11 . An expander-compressor unit comprising: an expander according to  claim 1 ; a compressor; and a shaft coupling the expander and the compressor. 
     
     
         12 . A heat pump comprising an expander according to  claim 1 . 
     
     
         13 . A heat pump comprising an expander-compressor unit according to  claim 11 . 
     
     
         14 . A heat pump comprising an expander according to  claim 1 , further comprising:
 a compressor;   a high pressure pipe in which a high pressure working fluid compressed by the compressor flows;   a low pressure pipe in which a low pressure working fluid expanded in the expander flows;   a pressure pipe for supplying the control pressure to the differential pressure valve; and   a switching valve connected to the pressure pipe, the high pressure pipe and the low pressure pipe, and wherein:   the control pressure passage comprises the pressure pipe, the high pressure pipe, the low pressure pipe, and the switching valve; and   by switching the switching valve, a pressure of the working fluid in the high pressure pipe or a pressure of the working fluid in the low pressure pipe is applied as the control pressure to the differential pressure valve.   
     
     
         15 . The heat pump according to  claim 14 , wherein the working fluid is carbon dioxide.