Displacement type compressor having a self-start synchronous motor and start load reducing means

Abstract

In order to make a displacement type compressor be able to reliably start without increasing an outside diameter dimension of the compressor while using a self-start synchronous motor having high energy efficiency, the displacement type compressor according to the invention includes the self-start synchronous motor which starts as an induction-motor and performs synchronous operation by performing synchronization pull-in almost at a synchronous rotational frequency, a compression part having a compression chamber which compresses a working fluid, and a hermetic container which houses the self-start synchronous motor and the compression part. The displacement type compressor is provided with a start load reducing means which reduces a load of the compression part at startup and is placed at the compression part in the hermetic container.

1 . A displacement type compressor, comprising:
 a self-start synchronous motor which starts as an induction-motor, and performs synchronous operation by performing synchronous pull-in approximately at a synchronous rotational frequency;   a compression part which comprises a compression chamber for compressing a working fluid;   a hermetic container which houses the self-start synchronous motor and the compression part; and   a start load reducing means for reducing a load of the compression part at startup, which means is placed at the compression part and located in the hermetic container.   
   
   
       2 . The displacement type compressor according to  claim 1 , wherein the start load reducing means is constructed to include a communication means which allows an intermediate portion of the compression chamber and an inlet side of the compression part to communicate with each other, and a control means which opens and closes the communication means. 
   
   
       3 . The displacement type compressor according to  claim 2 , wherein the control means is composed by a valve which opens and closes the communication means by a differential pressure between the intermediate portion of the compression chamber and the discharge side of said compression part. 
   
   
       4 . The displacement type compressor according to  claim 2 , wherein the communication means is configured to allow intermediate portions at a plurality of positions of the compression chamber and the inlet side of the compression part to communicate with each other. 
   
   
       5 . The displacement type compressor according to  claim 1 , wherein
 the displacement type compressor is a scroll compressor,   the compression part is constructed to include a rotary scroll which has an end plate and a spiral shaped scroll lap vertically provided on the end plate, and rotationally moves in a plane orthogonal to an axial direction corresponding to a direction in which the scroll lap is vertically provided, without performing autorotation, a fixed scroll which has an end plate and a spiral scroll lap vertically provided on the end plate, and is generally restricted in movement at least in an in-plane direction orthogonal to an axial direction corresponding to a direction in which the scroll lap is vertically provided, and a compression chamber constructed between both the scrolls by meshing the rotary scroll and the fixed scroll, and   the start load reducing means is constructed to include a communication passage which is formed in the fixed scroll to allow the intermediate portion of the compression chamber and an inlet space formed in the compression part to communicate with each other, and a check-valve which is provided at the fixed scroll to prevent the working fluid from flowing into the inlet space from the compression chamber through the communication passage.   
   
   
       6 . The displacement type compressor according to  claim 1 , wherein the displacement type compressor is a screw compressor, and wherein
 the compression part is constructed to include a pair of male and female screw rotors meshed with each other, a casing member, and a compression chamber constructed by a meshing portion of both the screw rotors and the casing member, and   the start load reducing means is constructed by providing a slide valve at the meshing portion of both the screw rotors, the slide valve being slidable in an axial direction of the screw rotors.   
   
   
       7 . The displacement type compressor according to  claim 1 , wherein the displacement type compressor is a reciprocating compressor, and wherein
 the compression part is constructed to include a piston, a cylinder having a bore portion in which the piston reciprocates, a valve portion which closes an opening of the bore portion, and a compression chamber constructed by the piston, the bore portion and the valve portion, and   the start load reducing means is constructed to include a communication passage formed in the cylinder to allow an intermediate portion of the compression chamber and an inlet space formed in the hermetic container to communicate with each other, and a check-valve provided at the cylinder to prevent a working fluid from flowing into the cylinder from the inlet space formed in the hermetic container through the communication passage.   
   
   
       8 . The displacement type compressor according to  claim 1 , wherein the displacement type compressor is a rotary compressor, and wherein
 the compression part is constructed to include a cylinder, end plates which close both end portions of the cylinder, a roller portion placed in a space enclosed by the cylinder and the end plates, a vane portion which performs operation of changing a space volume defined by the cylinder, the end plates and the roller portion by movement of the roller portion, and a compression chamber constructed by the cylinder, the end plates, the roller portion and the vane portion, and   the start load reducing means is constructed to include a communication means which allows an intermediate portion of the compression chamber and an inlet side of said compression part to communicate with each other, and a control means which opens and closes the communication means.