Abstract:
A scroll fluid apparatus including two scroll members, with one scroll member having a wrap and an annular portion located outside the wrap and having a height corresponding to the height of the wrap. The annular portion is contiguous at its surface in the form of a land with the surface of the wrap for a circumferential extent of within 180 degrees from the terminating end of the wrap, and a strip-shaped recess is formed in the land, with the strip-shaped form having an end portion maintained in communication with a low pressure zone surrounded by the annular portion of the scroll member.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a scroll fluid apparatus, and, more particularly, to a scroll compressor, a scroll expander, a scroll pump, etc. 
     Generally, a scroll fluid apparatus comprises two scroll members each having an end plate and an upstanding wrap of a vortical form disposed on a surface of the end plate, with the two scroll members being arranged such that the wraps are in meshing engagement with each other. One of the two scroll members is capable of moving in orbiting movement with respect to the other scroll member while the one scroll member is prevented from rotating on its own axis whereby a gas is compressed or expanded to produce a motive force or transfer a liquid. 
     A scroll type fluid apparatus of the aforementioned type is disclosed, for example, in U.S. Pat. No. 801,182. 
     In, for example, U.S. Pat. No. 4,216,661 a fluid scroll apparatus of the aforementioned type is proposed wherein machining of the outer wall surface of the wrap of the stationary scroll member substantially for an extent of 180 degrees is unnecessary. 
     In a construction of the last-mentioned type, the time required for working the stationary scroll member can be shortened since there is no need to machine the outer wall surface of the wrap for an extent substantially of 180 degrees; however, a disadvantage of such construction resides in the fact that the surface normally machined contacts the end plate of the orbiting scroll member and the surface opposite thereto does not contact the end plate of the orbiting scroll member. Thus, the pressure acting on the orbiting scroll member becomes unbalanced, causing an unstable orbiting movement of the orbiting scroll member thereby giving rise to a problem of inducing vibration to occur in the orbiting scroll member. 
     Also, when the orbiting movement of the orbiting scroll member becomes unstable, it is impossible to keep the scroll fluid apparatus functioning at high efficiency for a prolonged period of time because the axial sealing of the orbiting scroll member and the stationary scroll member is adversely affected. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a fluid scroll apparatus in which an evenly distributed pressure can be applied to the orbiting scroll member. 
     Another object of the present invention resides in providing a scroll fluid apparatus in which vibration is minimized. 
     Still another object of the present invention resides in providing a scroll fluid apparatus in which the orbiting movement of the orbiting scroll member is stabilized. 
     A further object of the present invention resides in providing a fluid scroll apparatus having high volumetric efficiency. 
     Yet another object of the present invention resides in providing a scroll fluid apparatus in which the time required for fabricating the two scroll members is shortened. 
     Still another object of the present invention resides in providing a scroll fluid apparatus in which adverse thermal influences exerted on suction gas are small. 
     A further object of the present invention resides in providing a scroll fluid apparatus in which an axial sealing of a high order can be provided to the two scroll members. 
     In accordance with advantageous features of the invention an outer wall surface of a terminating end portion of the wrap of one scroll member is formed as a land which is contiguous with an annular portion surrounding the wrap, with the contiguous land portion being provided with a recess. Preferably, the recess has a minimal depth so long as the action thereof of rendering the pressure distribution of the fluid uniform is not adversely affected, since the smaller the depth of the recess, the shorter the time required for forming the recess. More importantly when the recess has a small depth, the fluid does not flow in and through the recess thereby avoiding a transfer of heat from the scroll members to the fluid which occur when the fluid flows in and through the recess. By virtue of these features, it is possible to maintain a high level volumetric efficiency. By providing a partition wall midway in the longitudinal direction of the recess it is possible to completely prevent a flow of the fluid in and through the recess. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical cross-sectional view of a first embodiment of a scroll fluid apparatus, taken along the line I--I in FIG. 2; 
     FIG. 2 is a cross-sectional view taken along the line II--II in FIG. 1; 
     FIG. 3 is a cross-sectional view of another embodiment of a scroll fluid apparatus in accordance with the present invention, taken along a line II--II in FIG. 1; and 
     FIG. 4 is a cross-sectional view of yet another embodiment of a scroll fluid apparatus, taken along a line II--II in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numerals are used throughout the various views to designate like parts and, more particularly, to FIGS. 1 and 2, according to these figures, a stationary scroll member generally designated by the reference numeral 1 includes an end plate 1a, and an upstanding vortical wrap 1b located on the surface of the stationary scroll member 1, and an annular portion 1c formed in a manner so as to surround the wrap 1b. An orbiting scroll member generally designated by the reference numeral 2 includes an end plate 2a of the disc form, and an upstanding wrap 2b of the same shape as the wrap 1b located on the surface of the end plate 2a. The wraps 1b, 2b of the scroll members 1, 2 are in the form of an invoulte or a similar curve and have the same thickness and height. The orbiting scroll member 2 has a scroll pin 2c projecting from a back surface thereof. 
     A port 3 is formed in the center of the end plate 1a of the stationary scroll member 1, and another port 4 is formed in an outer peripheral portion thereof. The port 3 serves as an outlet port when the apparatus functions as a compressor and as an inlet port when the apparatus functions as an expander. 
     The two scroll members 1 and 2 are arranged so that the surfaces of the end plates 1a and 2a face each other, and the wraps 1b, 2b are in meshing engagement with each other. With the wraps 1b, 2b in this condition, terminating ends 1b&#39;, 2b&#39;  of the wraps 1b and 2b, respectively, are positioned relative to each other in such a manner that they are spaced apart substantially for a circumferential extent of 180 degrees. 
     A frame 5 is bolted in several positions to an end face of the annular portion 1c of the scroll member 1. A crank shaft 6 is supported by the frame 5 through two sets of bearings 7 and 8 secured to the frame 5. A balance weight 9 is integrally formed with the crank shaft 6; however, the balance weight 9 may also be formed as a separate entity independent of the crank shaft 6. 
     A head of the crank shaft 6 is formed with a hollow boss 10 centered in a position displaced from a center axis O of the crank shaft 6 a distance E, with the scroll pin 2c being accommodated in the hollow boss 10. A needle bearing 11 is mounted between the hollow boss 10 and the scroll pin 2c. 
     A rotation preventing member 12 is mounted between the undersurface of the end plate 2a of the orbiting scroll member 2 and the frame 5. The rotation preventing member 12, is in the form of a ring formed with straight grooves (not shown) on a surface thereof juxtaposed against the end plate 2a and on a surface juxtaposed against the frame 5, respectively. The groove formed on the surface juxtaposed against the frame 5 crosses at a right angle to the groove formed on the surface juxtaposed against the end plate 2a. The groove formed on the surface juxtaposed against the frame 5 has a key 13 fitted therein secured to the frame 5, and the groove formed on the surface juxtaposed against the end plate 2a has a key (not shown) fitted therein which is also secured to the end plate 2a. 
     A conventional mechanical seal 14 is arranged at a portion of the crank shaft 6 extending through and outwardly of the frame 5, with the seal being contained in a seal housing 15. In operation, a rotation of the crank shaft 6, clockwise in FIG. 2, by means of a prime mover (not shown) causes the orbiting scroll member 2 to move in orbiting movement in a clockwise direction while not changing its posture, that is, not apparently rotating on its own axis, with respect to the stationary scroll member 1. As a result, the sealed spaces V 1 , V 2  defined between the two scroll members 1, 2, have their volumes reduced while rotating in the clockwise direction, so as to compress fluid introduced therein through the port 4 and discharge the same through the port 3. 
     When the orbiting scroll member 2 moves in orbiting movement in a counterclockwise direction, as viewed in FIG. 2, the sealed spaces V 1 , V 2  have their volumes gradually increased as they rotate in the counterclockwise direction, so that the gas of high temperature and pressure, as compared with the gas discharged through the port 4, introduced through the port 3 is expanded and discharged through the port 4. At this time, a motive force is generated at the crank shaft 6 and, when the number of turns of the vortices is 1.5, to eliminate any change in the volumes of the sealed spaces, the apparatus functions as a pump. 
     As shown in FIG. 2, a relief 16 is provided which extends from the terminating end 1b&#39; of the wrap 1b of the stationary scroll member 1 for a circumferential extent of about 180 degrees, so that there is no interference in the orbiting movement of the orbiting scroll member 2 nor does the wrap 2b strike an inner wall surface of the annular portion 1c. The relief 16 serves as a passage of a low pressure and low temperature gas when the apparatus functions as a compressor or an expander. A recess 17 of a strip form and a small depth, and communicating with the reflief 16, is provided and extends through a circumferential extent of 180 degrees which makes up a complete circle with the aforesaid circumferential extent of 180 degrees while leaving alone the wrap 1b of the stationary scroll member 1. The proper depth of the shallow recess 17 is less than 2 mm. By this construction, the fluid acting on the orbiting scroll member 2 has a pressure distribution which is of a point symmetry, thereby enabling a moment applied to the orbiting scroll member 2 by a biased pressure distribution to be reduced. The fluid flowing in and through the shallow recess 17 leaks into the relief 16 under the influences exerted by heat from the wall. Since the volume of such leaking fluid is very small as compared with the flow rate of fluid drawn by suction and discharged, a rise in the temperature of gas within the relief 16 caused to occur by the gas flowing in and through the recess 17 and leaking into the relief 16 is so small that it is negligible. Thus, the fluid machine obtained is advantageously low in vibration and thermal loss. 
     As shown in FIG. 3 shallow recess 17&#39; is provided which is of an arcuate form with curves KF and IJ being arranged as concentric arcs. The outer involute curve of the stationary scroll member 101 terminates at a point 101d, and a curve 101d, with the curve being of any form as desired. Thus, the construction of FIG. 3 differs from the embodiment of FIGS. 1 and 2 in that the curve IJ is arcuate in shape. The construction of FIG. 3 offers the advantage that a working of the scroll member 1 to form the recess 17&#39; is facilitated. 
     In FIG. 4 a partition wall 18 is provided midway in a strip-shaped recess formed on the outer side of circumferential extent of 180 degrees extending from the terminating end of the wrap of the stationary scroll member 201, with the partition wall 18 serving to break up or divide the recess into two recess sections 17&#34; and 17&#39;&#34;. The partition wall 18 connects the wrap 201b of the stationary scroll member 201 to the annular portion 201c. In this case, the depth of the recess sections 17&#34; and, 17&#39;&#34; may be over 2 mm. Also, the recess sections 17&#34; and, 17&#39;&#34; may have a depth which corresponds to the height of the wrap 201b, and the recess sections 17&#34; and, 17&#39;&#34; may have different depths. In this embodiment, wherein the recess sections 17&#34; and, 17&#39;&#34; may have many modifications, the fluid acting on the surface of the end plate of the orbiting scroll member on which the wrap is located has a pressure distribution which is substantially of point symmetry. In this respect, the point on which the point symmetry is based is located on the line connecting a center of the stationary scroll member 201 to a center of the orbiting scroll member 2 and in a position on such line which is equidistantly spaced apart from the two centers. 
     Thus, an axially oriented force acts substantially uniformly on the orbiting scroll member, so that the orbiting scroll member is capable of moving in orbiting movement in stable condition. As a result, vibration is eliminated. The existence of the partition wall 18 has the effect of preventing the flow of the fluid in and through the recess toward the sealed spaces V 1 , V 2 , so that the path of flow of gas through the port 4 to the sealed spaces V 1 , V 2  is by way of the relief 16. This minimizes the length of flow of the gas, and hence it is possible to minimize the amount of heat transferred from the wall surfaces of the relief 16 and the recess 17&#34;, 17&#39;&#34;, thereby enabling volumetric efficiency to be maintained at a high level.