1.  Field of the Invention
The present invention relates to scroll compressors, and in particular to scroll compressors known as xe2x80x9cdouble rotational compressors,xe2x80x9d in which a drive scroll rotates in synchronism with a driven scroll about respective rotational axes that are offset with respect to each other. 
2.  Description of Related Art
Japanese Laid-open Patent Publication No.  7-229480 discloses a double rotational scroll compressor, in which a drive scroll and a driven scroll oppose each other and define a compression chamber therebetween.  The drive and driven scrolls are disposed within a rotor of an electric motor and the drive scroll is secured to the rotor.  Further, the rotor and the drive scroll are rotatably and coaxially supported within a housing, i.e., a sealed chamber that accommodates the scrolls.  The driven scroll is rotatably supported by an eccentric mechanism that is mounted on a shaft and the shaft extends though the rotor.  An Oldham""s coupling serves to transmit the rotation of the rotor or the drive scroll to the driven scroll. 
Therefore, during the operation of the compressor, refrigerant (cooling medium) is drawn into the compression chamber via a suction channel defined within the drive scroll.  The refrigerant is then compressed within the compression chamber and is highly pressurized.  The compressed refrigerant is thereafter discharged into the sealed chamber within the housing via a discharge channel defined within the drive scroll. 
Because the highly pressurized refrigerant is discharged into the sealed chamber of the known double rotation compressor, the pressure of the discharged refrigerant is applied to the entire rear surface of the driven scroll.  Therefore, the driven scroll is forcibly pressed against the drive scroll and a possibility exists that the tip ends of the scroll walls will be damaged due to the driven scroll being forcibly pressed against the drive scroll. 
Therefore, it is one object of the present teachings to provide improved scroll compressors.  In one aspect of the present teachings, scroll compressors are taught that include means for preventing scroll walls from being damaged. 
In another aspect of the present teachings, scroll compressors are taught that have a drive scroll opposing a driven scroll.  One or more compression chambers may be defined between the drive scroll and the driven scroll.  A first scroll selected from the drive and driven scrolls may be rotatably supported in a straddle manner.  That is, both ends of the first scroll are rotatably supported, e.g., by a housing.  A second scroll selected from the other of the drive and driven scrolls may be rotatably supported in a cantilever manner and in a manner that permits the second scroll to move or slide along its axial direction.  A discharge chamber may be defined on the side of the second scroll that is opposite to the compression chamber.  Therefore, when refrigerant (cooling medium) is compressed within the compression chamber(s) and is discharged into the discharge chamber, the pressure of the discharged refrigerant will apply a thrust force against the second scroll and urge the second scroll towards the first scroll.  Such a thrust force may depend upon the volume and/or the surface area of the discharge chamber onto which the thrust force is applied.  By appropriately applying the thrust force against the pressure receiving area defined on the second scroll, the scroll walls of the respective drive and drive scrolls may be prevented from being damaged. 
In another aspect of the present teachings, the drive and driven scrolls may be disposed within an enclosed chamber that defines a refrigerant suction area.  An electric motor also may be disposed within the same enclosed chamber and the electric motor may rotatably drive the drive scroll.  Because the drawn refrigerant disposed within the enclosed chamber has a relatively low pressure, the thickness of the walls of the enclosed chamber may be relatively thin.  Therefore, the entire compressor may have a relatively lightweight construction.  In addition, refrigerant that enters into the enclosed chamber may be utilized to effectively cool the electric motor, as well as bearings that may support the drive and driven scrolls.  Optionally, the refrigerant may contain a lubricant (e.g., a lubrication oil) that serves to lubricate the rotational support portions of the electric motor and the bearings. 
In another aspect of the present teachings, a transmission or other means for rotating the driven scroll in synchronism with the drive scroll may be provided.  For example, the transmission may include a first torque transmission member disposed on the drive scroll and a second torque transmission member disposed on the driven scroll.  The first torque transmission member may slidably contact the second torque transmission member, so that the rotation of the drive scroll is transmitted to the driven scroll.  Therefore, the driven scroll can synchronously rotate with the drive scroll and the rotational axis of the driven scroll is preferably offset with respect to the rotational axis of the drive scroll. 
Preferably, the first transmission member can rotate relative to and around the second torque transmission member.  Further, the radius of rotation of the first transmission member may be equal to the distance between the rotational axes of the drive scroll and the driven scroll.  Therefore, rotational torque may be smoothly transmitted. 
In another aspect of the present teachings, the first transmission member may comprise one of a pin or a ring and the second transmission member may comprise the other of a pin or a ring.  In that case, the pin can slidably rotate along the inner circumferential surface of the ring.  In another aspect, the first transmission member and the second transmission member may comprise respective pins, and a ring may couple the respective pins.  In that case, the pins can slidably rotate along the inner circumferential surface of the ring.  In another aspect, the first and second torque transmission members may respectively comprise a first pin and a second pin.  In that case, the first pin can slidably contact and rotate around the second pin.  Further, a ring may be rotatably mounted on one of the first pin or the second pin, so that the first pin or the second pin can slidably rotate around the ring. 
Additional objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.