Abstract:
A scroll compressor includes a casing, an electric motor and a compressor unit housed in the casing and the compressor unit comprises a movable member having a first scroll blade driven eccentrically by the electric motor and a structural member having a second scroll blade encasing the movable member so that the first scroll blade revolves around a central axis of the compressor with a predetermined radius of revolution, while the first blade is maintained in sliding contact with the second blade. The two scroll blades are formed by drawing a series of semicircles alternately around a first point and a second point spaced apart from the first point. An internal end portion of the first and second scroll blades includes a planar surface disposed perpendicular to a line interconnecting the first and second point.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to scroll compressors, and more particularly to a type thereof wherein the volume of a residual portion of the compressive space formed between a stationary scroll blade and an orbitally movable scroll blade at the final stage of the compressive operation of the compressor is substantially reduced compared to that of an ordinary scroll compressor, thereby improving the efficiency and the compression ratio. 
     Ordinarily, a scroll compressor comprises a stationary scroll blade and an orbitally movable scroll blade, which are formed into equal configurations operable in sliding engagement with each other. A gaseous fluid supplied through a suction port into the compressor is confined in closed spaces formed between the scroll blades in accordance with the progress of the rotation of the orbitally movable blade. The fluid is then delivered through an exhaust port, provided in a central portion of the stationary scroll blade, which is brought into communication with the compressive spaces at the final stage. 
     The stationary and orbitally movable scroll blades of conventional configurations, which are identical to each other, may be formed as shown in FIG. 1. In the shown construction, first and second points A and B are provided in a spaced-apart relation by a distance equal to the sum of e and t, wherein e represents a radius of revolution and t represents the thickness of either one of the two blades. Upper semicircles AC and DE are first drawn around the second point B with radii equal to R 2  =t+e and R 3  =2t+e, respectively. Likewise, lower semicircles CF and EG are drawn around the first point A with radii R 4  =2t +2e and R 5  =3t+2e, respectively. The upper semicircles FH and GI are drawn around the point B with radii R 6  =3t+3e and R 7  =4t+3e, respectively. The internal end of the scroll blade is closed by an arc drawn around the point A with a radius equal to R 1  =t, the arc intersecting with an extension of the semicircle AC at a point J. The outer end of the scroll member is closed by a semicircle HI drawn around the line HI . 
     Relative positions of the stationary scroll blade 1 and the orbitally movable scroll blade 2 during the compression operation of the compressor are shown in FIGS. 2(a), 2(b) and 2(c). In a state shown in FIG. 2(a), a gas is received between the two blades 1 and 2, while in a state shown in FIG. 2(b), the received gas is confined in compressive spaces 3 each having a volume V 1 . In a state shown in FIG. 2(c) corresponding to the last stage of the compression, the volume of each compressive space 3 is reduced to V 2 . 
     In the conventional scroll blades of the above described construction, however, a residual region 4 is formed as shown in FIG. 2(c) at the last stage of the compression, and the gas remaining in the residual region 4 flows back into the compressive spaces 3 when the state of the operation of the compressor returns to that shown in FIG. 2(a), thus deteriorating the efficiency and reducing the compression ratio of the compressor. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a scroll compressor comprising a stationary scroll blade and an orbitally movable scroll blade, the configuration of the internal ends of which is improved such that the residual region formed at the last stage of the compression is reduced, and the compression ratio of the compressor is thereby improved. 
     The above-described and other objects of the present invention can be achieved by a scroll compressor which comprises a stationary scroll blade and an orbitally movable scroll blade which are contained in a casing and formed into substantially equal configurations having a thickness t, means for driving the orbitally movable scroll blade eccentrically so that the blade is moved, in contact with the stationary blade, in a revolution following an orbit of a radius e, the stationary and orbitally movable scroll blades being formed in such a manner that a series of semicircles are drawn around two central points spaced apart by (e+t), alternately, and the semicircles thus drawn are connected together into a scroll configuration; the improvement wherein a planar surface is formed in an internal end portion of each scroll blade so as to extend perpendicularly to a straight line interconnecting the two central points. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a plan view showing the configuration of a scroll blade of a conventional scroll compressor; 
     FIGS. 2(al ), 2(b) and 2(c) are plan views showing various stages of the compressing operation of the conventional compressor; 
     FIG. 3 is a vertical sectional view of a scroll compressor according to the present invention; 
     FIG. 4 is a perspective view showing an Oldham&#39;s ring used in FIG. 3; 
     FIG. 5 is a plan view showing a scroll blade used in the present invention; 
     FIGS. 6(a), 6(b) and 6(c) are plan views showing various stages of the compressing operation of the compressor according to the present invention; 
     FIG. 7 is a plan view showing a scroll blade constituting another embodiment of the invention; 
     FIGS. 8(a), 8(b) and 8(c) are plan views showing various stages of the compressing operation of the embodiment shown in FIG. 7; 
     FIG. 9 is a plan view showing a stationary scroll blade constituting still another embodiment of the invention; 
     FIG. 10 is a plan view showing an orbitally movable scroll blade constituting the still another embodiment of the invention; 
     FIGS. 11(a), 11(b) and 11(c) are plan views showing various stages of the compressing operation of the embodiment shown in FIGS. 9 and 10; 
     FIG. 12 is a plan view showing a stationary scroll blade constituting one part of a further embodiment of the invention; and 
     FIG. 13 is a plan view showing an orbitally movable scroll blade constituting another part of the further embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will now be described in detail with reference to FIGS. 3 through 13. 
     In a scroll compressor shown in FIG. 3, there is provided a casing 11 of a totally enclosed type, in which a frame member 12 of the compressor is encased in a force fit manner. In the frame member 12, there are formed a circular recess 13 for receiving a scroll member to be described hereinafter, a head-receiving recess 14 and a bearing hole 15 concentrically in a stepwise manner. 
     An electric motor having a rotor 19 and a stator 20 is also provided in the casing 11 so that the stator 20 is secured to the casing suitably. A driving shaft 16 extending upwardly from the rotor 19 through the bearing hole 15 of the frame member 12 is coupled with a shaft head 17 having a larger diameter than that of the shaft 16 and received in the head receiving recess 14 to rotate freely. The driving shaft 16 also extends downwardly from the rotor 19 so that the lower end of the shaft 16 is submerged into lubricating oil 18 stored in the bottom portion of the casing 11. The underside surface 17a of the shaft head 17 abuts against the bottom of the recess 14 formed in the mounting frame 12 so that the rotor 19 and the shaft 16 are rotatably supported by the frame member 12. A cylindrical hole 21 is formed in the shaft head 17 at a position eccentric with the shaft head. 
     An orbitally movable scroll member 22 having a disc-like portion 24 is received in the circular recess 13 formed in the frame member 12, and a downward projection 23 projecting from the center of the disc-like portion 24 is received rotatably in the hole 21. A scroll blade 25 is formed on the upper surface of the disc-like portion 24. The movable scroll member 22 is supported by an Oldham&#39;s ring 26 provided under side of the disc-like portion 24. The Oldham&#39;s ring 26 has a rectangular cross-section and is provided with radial key grooves 27 and 28 disposed perpendicular to each other on the upper side and lower side thereof, respectively, as shown in FIG. 4. Keys 29 extending diametrically along the bottom surface of the recess 13 are slidably received in the grooves 28, while keys (not shown) extending perpendicularly to the keys 29 along the underside surface of the disc-like portion 24 are slidably received in the grooves 27. As a consequence, when the downward projection 23 of the orbitally movable scroll member 22 is driven by the driving shaft 16 to revolve around the central axis of the driving shaft 16, the orbitally movable scroll blade 25 of the scroll member 22 is revolved by the aid of the Oldham&#39;s ring 26 without being rotated relative to the mounting frame 12. 
     Above the frame member 12, there is provided a shroud (or otherwise termed a stationary scroll member) 31. The shroud 31 is fixed to the mounting frame 12 with the movable scroll member 22 interposed therebetween. A stationary scroll blade 33 of an equal configulation with the orbitally movable scroll blade 25 is formed integrally on the surface of the shroud 31 facing the orbitally movable scroll member 22 at a position slidably engageable with the movable scroll blade 25. 
     A suction pipe 36 is introduced through the casing 11 into the suction chamber 32 formed circumferentially of the stationary scroll blade 33, while an outlet pipe 37 passed through the casing 11 into a space communicating with a delivery port 34 formed through a central part of the shroud 31. 
     FIG. 5 shows a configuration commonly utilized for the stationary scroll blade 33 and the orbitally movable scroll blade 25 of the present invention, which is substantially equal to that of the conventional blades described hereinbefore. 
     More specifically, assuming that the thicknesses of the two blades 25 and 33 are equal to t, and that the radius of the revolution of the orbitally movable blade 33 is equal to e, two points A and B are determined at positions spaced apart by a distance h=e+t. An arc PC and a semicircle DE are drawn around the point B with radii equal to R 2  =t+e and R 3  =2t+e, respectively. Likewise, lower semicircles CF and EG are drawn around the point A with radii R 4  =2t+2e and R 5  =3t+2e, respectively. Then upper semicircles FH and GI are drawn around the point B with radii R 6  =3t+3e and R 7  =4t+3e, respectively. 
     According to the present invention, the internal (or central) end of the scroll blade is configured as follows. 
     An arc is drawn around the point A with a radius R 1  =t (thickness of the blade). A point K is selected on the line AB so that DK= ##EQU1## and a line perpendicular to the line AB is drawn through the point K so that the line intersects with the arc drawn around the point A at a point J. Furthermore, an arc CP is drawn around the point B with a radius R 2  =t+e, and the point P and the perpendicular line are connected together with a radius of curvature R 0  =e which smoothly joins the perpendicular lines as shown in FIG. 6(a). The outer end of the scroll blade is closed by a semicircle HI. 
     FIGS. 6(a), 6(b) and 6(c) illustrate various stages of the operation of the compressor utilizing the scroll blades shown in FIG. 5. Among these drawings, FIG. 6(a) indicates a stage wherein a gaseous fluid is received between the stationary blade 33 and the movable blade 25, while FIG. 6(b) indicates a stage wherein the gas is compressed to a volume V 1  in each of the two spaces between the stationary blade 33 and the movable blade 25. FIG. 6(c) indicates the last stage of the compression wherein the volume of the gas in each space is reduced to V 2 , whereafter the compressed gas is permitted to leave the compressor through discharge port 34, shown in phantom in FIG. 6(c). 
     FIG. 7 illustrates another embodiment of the present invention wherein the stationary scroll blade 33 and the movable scroll blade 25 are both formed into a configuration as follows. 
     Points A and B are spaced apart by a distance h=t+e as in the previous embodiment, while points M and N are positioned on the line segment AB such that AN=BM=l, wherein l is selected in a range of 0&lt;l&lt; ##EQU2## 
     An arc PC of a radius R 2  =h+l=t+e+l is drawn around the point M, and then a semicircle DE of a radius R 3  =h+t=2t+e is drawn around the point B. Then, semicircles CF and EG are drawn around the point A with radii R 4  =2h=2t+2e and R 5  =3t+2e, respectively. Furthermore, semicircles FH and GI are drawn around the point B with radii R 6  =3t+3e and R 7  =4t+3e, respectively. 
     In addition, a point K is selected on the line segment AB so that DK= ##EQU3## and a line perpendicular to the line AB is drawn through the point K. An arc is drawn around the point N with a radius R 1  =t+l so that the arc intersects the perpendicular line at a point J. The perpendicular line passing through the point K is smoothly connected at a point Q with the arc PC with a radius of curvature R 0  =e. The outer end of the scroll blade is terminated with a semicircle HI. 
     FIGS. 8(a), 8(b) and 8(c) illustrate compression stages of a compressor utilizing the stationary scroll blade 33 and the movable scroll blade 25 both formed in accordance with the second embodiment of the invention shown in FIG. 7. As is apparent from FIG. 8(c), at the last stage of the compression, the linear edge at the internal end of the blade 33 abuts against the linear edge at the internal end of the blade 25, thus eliminating the residual region tending to be created at the last stage of the conventional compressor. 
     In still another embodiment of the present invention, the stationary scroll blade 33 is formed as shown in FIG. 9 and the movable scroll blade 25 is formed as shown in FIG. 10. 
     In the configuration shown in FIG. 9, points A and B are assumed as in the previous embodiment, and a semicircle CD is drawn around the point A with a radius R 1  =t, and a line perpendicular to the line AB is drawn through the point D. Then an arc GF is drawn around the point B with a radius R 2  =t+e, and the arc GF and the perpendicular line are connected together smoothly through an arc EG of a radius R 0  =e. Furthermore, a semicircle CH is drawn around the point B with a radius R 3  =2t+e, and semicircles FI and HJ are drawn around the point A with radii R 4  =2t+2e and R 5  =3t+2e, respectively. Then semicircles IK and JM are drawn around the point B with radii R 6  =3t+3e and R 7  =4t+3e. The outer end of the scroll blade is closed by a semicircle KM. 
     Likewise, the orbitally movable scroll blade 25 is formed as follows. Points O and P are assumed to be spaced apart by a distance h=t+e. An arc with a radius R 8  =t is drawn around the point P so that the arc intersects at a point Q with a line drawn perpendicular to the line OP through the point P. Then, semicircles PS and RT are drawn around the point O with radii R 9  =t+e and R 10  =2t+e, respectively. Semicircles SU and TV are drawn around the point P with radii R 11  =2t+2e and R 12  =3t+2e, respectively, and then semicircles UW and VX are drawn around the point O with radii R 13  =3t+3e and R 14  =4t+3e, respectively. The outer end of the scroll blade 25 is closed with a semicircle XW. 
     FIGS. 11(a), 11(b) and 11(c) illustrate compression stages of the compressor including the stationary scroll blade 33 and the orbitally movable scroll blade 25 formed in accordance with the embodiment shown in FIGS. 9 and 10. In the stage shown in FIG. 11(a), a gaseous fluid is received between the two scroll blades, while in the stage shown in FIG. 11(b), the fluid of a volume V 1  is confined in each of compression spaces formed between the two blades. In the last stage of the compression shown in FIG. 11(c), the volume of the fluid in each compression space is reduced to V 2 . 
     In the embodiment shown in FIGS. 9 and 10, the inner end of stationary scroll blade 33 has been formed into a semicircle CD, this may otherwise be formed such that a central angle θ subtended by the arc CD is not 180°, but less than 180° as shown in FIG. 12. In this case, the orbitally movable scroll blade 25 shown in FIG. 10 must be slightly modified as shown in FIG. 13 so that the semicircle formed around the point O with the radius R 9  is reduced to an arc less than the semicircle. 
     Furthermore, it should be noted that the different configurations of the stationary scroll blade 33 and the orbitally movable scroll blade 25 in either of the embodiments shown in FIGS. 9 and 10, and 12 and 13 may be interchanged between the stationary blade 33 and the movable blade 25 without causing any discrepancy. 
     According to the present invention, linear portions are provided at the inner end of both of the stationary blade 33 and the movable blade 25 in a manner that the portions are disposed perpendicularly to the line drawn through two central points such as A, B and O, P, and the linear portions are brought into contact with each other at the end of the compression stage of the compressor. Thus, the residual portion of the compressive space formed in the conventional scroll type compressor can be substantially eliminated, and the size of the delivery port of the compressor can be increased as desired. Furthermore, since the volume of the compression spaces at the end of the compressive stage can be far reduced from that of the conventional scroll type compressor, the compression ratio of the compressor can be much improved, and the size of the compressor as well as the frictional loss thereof can be reduced remarkably.