EP0851124A1

EP0851124A1 - Oldham coupling mechanism of scroll-type fluid displacement apparatus

Info

Publication number: EP0851124A1
Application number: EP97122951A
Authority: EP
Inventors: Akiyoshi Higashiyama
Original assignee: Sanden Corp
Current assignee: Sanden Corp
Priority date: 1996-12-27
Filing date: 1997-12-29
Publication date: 1998-07-01
Also published as: JPH10184570A; JP3274814B2

Abstract

In a scroll-type fluid displacement apparatus, an orbiting scroll has a first and a second grooves formed on a second surface of a second circular end plate, so that the grooves are diametrically opposed to each other. An Oldham coupling is disposed between the orbiting scroll and the housing for preventing the rotation of the orbiting scroll during orbital motion thereby The Oldham coupling has a pair of engaging portions formed thereon for slidably engaging the first and second grooves of the orbiting scroll. A reinforcing device is thus located on the second surface of the second circular end plate of the orbiting scroll and extends across the first groove for reinforcing the circular end plate of the orbiting scroll. Thereby, a scroll-type fluid displacement apparatus may prevent deformation, scuffing and seizures of scroll member while simultaneously maintaining the thickness of the scroll members.

Description

BACKGROUND OF THE INVENTION 1. Technical Field of Invention

The present invention relates to scroll-type fluid displacement apparatus. More particularly, the present invention relates to an Oldham coupling mechanism of a scroll-type refrigerant compressor for use in an automotive air conditioning system.

2. Description of Related Art

The Oldham coupling mechanism of a scroll-type fluid displacement apparatus is known in the art For example, Fig. 1 and 2 depicts an Oldham coupling mechanism used in a scroll-type refrigerant compressor described in U.S. Patent No. 4,767,293.

Ordinarily, a scroll-type fluid displacememt apparatus comprises two scroll members, each having a spiral element. The scroll members are maintained angularly and radially offset, so that their spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces and thereby seal off and define at least a pair of fluid pockets. In operation, the relative orbital motion of the two scroll members shift the line contacts along the spiral curved surfaces and therefore, the fluid pockets change in volume. Because the volume of the fluid pockets increases or decreases dependent on the direction of the orbital motion, this scroll-type fluid displacement apparatus may compress, expand, or pump fluid. One approach for preventing relative angular movement between the scrolls as they orbit with respect to one another involves use of an Oldham coupling between an orbiting scroll and a fixed portion of the apparatus.

Referring to Figs. 1,2, and 3, an orbiting scroll member 50 includes a circular end plate 51, a spiral element 52 formed on one end surface of circular end plate 51 to define an involute curve, and a tubular boss 53 projecting axially outward from a first end surface opposite to a second end surface from which spiral element 52 extends. Further, orbiting scroll member 50 includes a pair of rectangular grooves 51a and 51b formed in the second end surface of circular end plate 51, so as to diametrically opposed to each other. A pair of projections, which are formed in the second end surface of Oldham coupling, slidably disposed in a pair of rectangular grooves 51a and 51b.

Referring to Fig. 4, in this configurations, compression gas forces, which are created by relative orbital motion of orbiting scroll member and fixed scroll member causes thrust load as shown by an arrow 56. The thrust load allows orbiting scroll member 50 to warp spherically in the direction of along the axis of the compressor with displacement 58. Then, orbiting scroll member 50 is supported by a thrust surface 57 of a housing 55. Particularly, portions of circular end plate 51, which are correspond to the bottom of rectangular grooves 51a and 51b, tend to warp significantly. As a result, the scroll members may experience the disadvantages of scuffing and seizures because the thrust load concentrates in those portions of circular end plate 51.

Further, this configuration causes a deterioration in the sealing between the two scroll members. As a result, the compressed gas within a fluid pocket, which is defined by spiral elements of two scrolls, tends to leak from the pockets. This is referred to as the "blow-by phenomenon" which causes a decrease volumetric efficiency.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a scroll-type fluid displacement apparatus which prevents deformation, scuffing, and seizures of scroll members while simultaneously maintaining the thickness of the scroll members.

It is another object of the present invention to provide a scroll-type fluid displacement apparatus which has improved, axial sealing of fluid pockets defined by scroll members and eliminates or lessens reductions in compression efficiency.

It is a further object of the present invention to provide a scroll-type fluid displacement apparatus which has light weight scroll members while simultaneously eliminating or reducing deformation of scroll members.

According to the present invention, a scroll-type fluid displacement apparatus includes a housing having an inlet port and outlet port. A fixed scroll is fixedly disposed within the housing and has a circular end plate from which a first spiral element extends into an interior of the housing. An orbiting scroll has a circular end plate, a second spiral element extending from a first surface of the circular end plate. The first and second spiral elements interfit at an angular and radial offset to form a plurality of line contacts defining at least one pair of fluid pockets within the interior of the housing. The orbiting scroll has a first groove and a second groove formed on a second surface of the circular end plate, so as to be diametrically opposed each other. A driving mechanism is operatively connected to the orbiting scroll to effect orbital motion of the orbiting scroll.

An Oldham coupling is disposed between the orbiting scroll and the housing for preventing the rotation of the orbiting scroll during orbital motion thereby enabling the orbital motion to change a volume of said at least one pair of fluid pockets. The Oldham coupling has a pair of engaging portions formed thereon for slidably engaging the first and second grooves ofthe orbiting scroll. Reinforcing means are located on the second surface of the circular end plate of the orbiting scroll and extends across the first groove for reinforcing the circular end plate of the orbiting scroll.

Further objects, features, and advantages of this invention will be understood from the following detailed description of preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a frontal view of an orbiting scroll of a scroll-type refrigerant compressor in accordance with a prior art.

Fig. 2 is a side view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with the prior art.

Fig. 3 is a rear view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with the prior art.

Fig.4 is a longitudinal, cross-sectional partial view of a scroll-type refrigerant compressor in accordance with the prior art.

Fig. 5 is a longitudinal, cross-sectional, partial view of a scroll-type refrigerant compressor in accordance with a first embodiment of the present invention.

Fig. 6 is a frontal view of a orbiting scroll of a scroll-type refrigerant compressor in accordance with the first embodiment of the present invention.

Fig. 7. is a side view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with the first embodiment of the present invention.

Fig. 8 is a rear view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with the first embodiment of the present invention.

Fig. 9 is a front view of an orbiting scroll of a scroll-type refrigerant compressor in accordance with a second embodiment of the present invention.

Fig. 10 is a side view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with the second embodiment of the present invention.

Fig. 11 is a rear view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with the second embodiment of the present invention.

Fig. 12 is a side view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with a third embodiment of the present invention.

Fig. 13 is a rear view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with the third embodiment of the present invention.

Fig. 14 is a side view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with a fourth embodiment of the present invention.

Fig. 15 is a rear view of an orbiting scroll of the scroll-type refrigerant compressor in accordance with the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of the present invention is illustrated in Fig. 5, in which the same numerals are used to denote elements corresponding to similar elements depicted in Figs. 1 and 2 of the prior art. A detailed description of several elements and characteristics of the prior art compressor is provided above, and is, therefore, omitted from this section. Moreover, with reference to Fig. 5, components may be described as positioned or extending to the left or forward or to the right or rearward.

Referring to Fig. 3, compressor includes a compressor housing 20 having a front end plate 22 and a cup-shaped casing 21 which is secured to the rear end surface of front end plate 22 by a plurality of bolts 40. An opening 22a is formed in the center of front end plate 22 for penetration and passage of a steel drive shaft 23. An open end of cup-shaped casing 21 is covered by front end plate 22, and the mating surfaces between front end plate 22 and cup shaped casing 21 are sealed by a first O-ring 41. A first annular sleeve 22b projects from the periphery of opening 22a so as to surround an outer end portion of drive shaft 23 and define a shaft seal cavity 22c therein. A shaft seal mechanism 42 is disposed within shaft seal cavity 22c and is mounted about drive shaft 23. Shaft seal mechanism 42 seals the interior of compressor housing 20 from first annular sleeve 22b, thereby preventing refrigerant and lubricating oil therein from leaking through opening 22a to the exterior of the compressor. Shaft seal mechanism 42 suffers from severe wear and tends to breakdown more frequently than other parts of the compressor.

Drive shaft 23 is rotatably supported by first annular sleeve 22b through a radial needle bearing 43, which is positioned within the from end of first annular sleeve 22b. A second annular sleeve 22d projects rearwardly from the periphery of opening 22a so as to surround an inner end portion of drive shaft 23.

An inner block 27 having a front annular projection 27a and a rear annular projection 27b is disposed within the interior of housing 20. Inner block 27 is fixedly attached to front end plate 22 at its front annular projection 27a by a plurality of bolts 40, so that front annular projection 27a of inner block 27 surrounds second annular sleeve 22d of front end plate 22, and further, so that a front end surface of front annular projection 27a is in contact with the rear end surface of front end plate 22.

Drive shaft 23 has a cylindrical rotor 23a which is integral with and coaxially projects from an inner end surface of drive shaft 23. The diameter of cylindrical rotor 23a is greater than that of drive shaft 23. Cylindrical rotor 23a is rotatably supported by inner block 27 through a radial plane bearing 15 which is fixedly disposed within opening 27c centrally formed through inner block 27. Radial plane bearing IS is fixedly disposed within opening 27c by, for example, forcible insertion. Pin member 24 is integral with, and projects from, a rear end surface of cylindrical rotor 23a. The axis of pin member 24 is radially offset from an axis of cylindrical rotor 23a, i.e. the axis of drive shaft 23, by a predetermined distance.

An electromagnetic clutch 80, which is disposed around first annular sleeve 22b, includes a pulley 80a rotatably supported on sleeve 22b through a ball bearing 80b, an electromagnetic coil 80c disposed within an annular cavity of pulley 80a, and an amateur plate 80d fixed on an outer end of drive shaft 23, which extends from sleeve 22b. Drive shaft 23 is connected to and driven by an external power source (not shown) through electromagnetic clutch 80.

The interior of housing 20 further accommodates a fixed scroll 30, an orbiting scroll 10, and a rotation preventing mechanism 5, such as Oldham coupling mechanism, which prevents rotation of orbiting scroll 10 during operation of the compressor.

Fixed scroll 20 includes a circular end plate 31, a first spiral element 32 affixed to and extending from a side surface of circular end plate 31, and an outer peripheral wall 35 forwardly projecting from an outer peripheral wall 35 forwardly projecting from an outer periphery of circular plate 31. Outer peripheral wall 35 of fixed scroll 30 is fixedly attached to rear annular projection 27b of inner block 27 by a plurality of screws (not shown), so that a rear end surface of rear annular projection 27a of inner block 27 is in contact with a front end surface of outer peripheral wall 35 of fixed scroll 30. Thus fixed, scroll 30 is fixedly disposed within the interior of housing 20.

A second O-ring 90 is elastically disposed between an outer rear peripheral surface of circular end plate 31 and an inner peripheral surface a of cylindrical portion 21a of cup-shaped casing 21 to seal the matching surfaces therebetween. Thus, a first discharge chamber 37 is defined by circular end plate 31 of fixed scroll 30 and rear portion 21b of cup-shaped casing 21. Another O-ring 91 is elastically disposed between an outer rear peripheral surface of rear annular projection 27b of inner block 27 and the inner peripheral surface of cylindrical portion 21a of cup-shaped casing 21 to seal the mating surface therebetween. Thus, a suction chamber 28 is defined by circular end plate 31 of fixed scroll 30, which is a portion of cylindrical portion 21a of cup-shaped cashing 21 and inner block 21, and a second discharge chamber 38 is defined by inner block 27, which is a portion of cylindrical portion 21a of cup-shaped casing 21, and front end plate 22.

An inlet port 128 is formed on cylindrical portion 21a of cup-shaped casing 21 at a position corresponding to suction chamber 28. An outlet port 138 is formed on cylindrical portion 21a of cup-shaped casing 21 at a position corresponding to second discharge chamber 38 in order to place second discharge chamber 38 in communication with the exterior of the compressor.

A plurality of fluid passages 95 are axially formed through outer peripheral wall 35 of fixed scroll 30 and rear annular projection 27b of inner block 27 along the periphery thereof, so as to link first discharge chamber 37 to second discharge chamber 38.

A discharge port 30a is formed through circular end plate 31 of fixed scroll 30 at a position near the center of spiral element 32. A reed valve member 33 cooperates with discharge port 30a at rear end surface of circular end plate 31 of fixed scroll 30 to control the opening and closing of discharge port 30a in response to a pressure differential between first discharge chamber 37 and a central fluid pocket 36. A retainer 39 is provided to prevent excessive bending reed valve member 33 when discharge port 30a is opened. An end of reed valve member 30a, together with one end of retainer 39 is fixedly secured to circular end plate 31 of fixed scroll 30 by a bolt 34.

Orbiting scroll 10, which is located in suction chamber 28, includes a circular end plate 11 and a second spiral element 12 affixed to and extending from a rear side surface of end plate 11. Second spiral element 12 of orbiting scroll 10 and first spiral element 32 of fixed scroll 30 interfit at an angular offset of 180° and a predetermined radial offset to make a plurality of line contacts. Therefore, at least one pair of sealed-off fluid pockets 36 are defined between

spiral elements

12 and 32. A baffle 45 is disposed within first discharge chamber 37 to cover discharge port 30a and is secured to circular end plate 31 of fixed scroll 30 by bolt 34. Baffle 45 causes lubricating oil mist flowing from discharge port 30a to condense and to flow to the lower portion of first discharge chamber 37.

Additionally, orbiting scroll 10 further includes an annular boss 13, which projects forwardly from a central region of a front end surface of circular end plate 11. A bushing 17 is rotatably disposed within boss 13 through a radial plane bearing 16. Radial plane bearing 16 is fixedly disposed within boss 13 by, for example, forcible insertion. Bushing 17 has a hole 17a axially formed therethrough, such that the axis of hole 17a is radially offset from an axis of bushing 17. As described above, pin member 24 is integral with and projects from the rear end surface of cylindrical rotor 23a of drive shaft 23. The axis of pin member 24 is radially offset from the axis of cylindrical rotor 23a, i.e., the axis of drive shaft 22, by a predetermined distance.

Pin member 24 is rotatably disposed within hole 17a of bushing 17. A terminal end portion of pin member 24 projects from a rear end of bushing 17, and a snap ring 14 is fixedly secured to the terminal end portion of pin member 24 to prevent axial movement of pin member 24 within hole 24a of bushing 24. Thus, a driving mechanism for orbiting scroll 10 is comprised of drive shaft 23, pin member 24, and bushing 17. A counter-balance weight is disposed within suction chamber 28 at a position forward of circular end plate 11 of orbiting scroll 10, and is connected to a front end of bushing 24. Annular flange 23b may be made of steel and formed at a position which defines a boundary between the inner end portion of drive shaft 23 and cylindrical rotor 23a. The diameter of annular flange 23b is greater than the diameter of cylindrical rotor 23a.

A first thrust plane bearing 46 is fixedly disposed within an outer peripheral region of the rear end surface of second annular sleeve 22d. Second thrust plan bearing 47, which is substantially identical to first thrust plane bearing 46, is fixedly disposed on the front end surface of inner block 27 Second thrust plan bearing 47 faces the rear end surface of annular flange 23b. Thus, second thrust plane bearing 47 also may be in frictional contact with annular flange 23b and may receive a rearward thrust force through annular flange 23b.

Cylinder block 27 includes a conduit 150, which extends longitudinally from a lower end surface to an upper end surface of inner block 27 and is formed in inner block 27 to link second discharge chamber 38 and a hollow space 381. Conduit 150 controls the flow of lubricating oil from second discharge chamber 380 to hollow space 381. In addition, a cylinder 120 is provided with a piston 121 which axially reciprocates within cylinder 120. A coil spring 122 is disposed between one end portion of piston 121 and a snap ring 103 secured to inner wall of cylinder 120 to urge piston 121 toward the other wall of cylinder 120. Piston 121 includes an annular groove formed on the peripheral surface of piston 121. The annular groove regulates the flow of lubricating oil passing through conduit 150, by sliding piston 121.

Referring to Figs. 6, 7, and 8, orbiting scroll 10 includes circular end plate 11, spiral element 12 formed on one end surface of circular end plate 11 to draw involute curve, and tubular boss 13 projecting axially outward from the first end surface, i.e., the end surface opposite to the surface from which spiral element 12 extends. Further, orbiting scroll member 10 includes a pair of rectangular grooves 10a and 10b formed on the first end surface of circular end plate 11 so as to be diametrically opposed to each other and so as to extend from the radial edge to the center of orbiting scroll member 10. The pair of rectangular grooves 10a and 10b are placed on line M which intersects and is offset from line X at 30° angle. Then, the outer and inner side walls of the spiral elements are generally formed by involute curves. The involute curve is drawn based on the involute generating circle. The line X passes through on the center of the involute generating circle. A pair of rectangular grooves 10a and 10b, are respectively formed so as to cross the rear end bottom portion of spiral element 12 twice.

Oldham coupling ring 5, which operates as a rotation preventing device for orbiting scroll 10, is disposed between circular end plate 11 of orbiting scroll 10 and rear annular projection 27d of inner block 27. As a result of the operation of Oldham coupling ring 5, the rotation of drive shaft 23 causes orbiting scroll 10 to orbit without rotating.

Oldham ring 5 has a ring portion 6 and a pair of first projections 7 extending from the outer peripheral of ring portion 6. A pair of projections 7 are axially offset from the one end surface of ring portion 6 and are further diametrically opposed to each other. A pair of second projections 8 are further diametrically opposed to each other and angularly spaced from a pair of first projections 7 by about 90° degrees. Pair of first projections 7 are slidably disposed in grooves 10a and 10b which are formed in the axial end of orbiting scroll 10. Pair ofprojections 8 are slidably disposed in grooves 27d which are formed in the rear end of inner block 27 so as to be diametrically opposed to each other.

In operation of the compressor, as orbiting scroll 10 orbits, the line contacts between

spiral elements

12 and 32 converge. This causes fluid pockets 36 to move toward the center with a consequent reduction in volume and compression of the fluid (e.g. refrigerant) within fluid pockets 36. Refrigerant gas, which may be introduced from a component, such as an evaporator (not shown), of a refrigerant circuit (not shown), through fluid inlet port 28, is taken into fluid pockets 36 formed between spiral elements and from the outer end portion of these

spiral elements

12 and 32.

When Oldham coupling ring 5 prevents rotation of orbiting scroll 10, orbiting scroll 10 linearly slides along projections 7 with respect to Oldham coupling ring 5, so that grooves 10a and 10b slidably engage with projections 7 while projections 8 reciprocately slide in grooves 27d formed on inner block 27. Thus, orbiting scroll 10 orbits fixed scroll member 30 through these two movements.

The refrigerant gas taken into fluid pockets 36 then is compressed and discharged through discharge port 30a into first chamber section 37 from central fluid pockets of

spiral elements

12 and 32. Thereafter, the refrigerant gas in first discharge chamber 37 flows to second discharge chamber 38 through fluid passages 95, which are axially formed through outer periphery wall 35 of fixed scroll 30 and rear annular projection 27b of inner block 27. The refrigerant gas flowing into second discharge chamber 38 then may flow through outlet portion 138 to another component, such as a condenser (not shown) of the refrigerant circuit (not shown).

Thereby, the bottom portions of pair of rectangular grooves 10a and 10b are respectively reinforced in mechanical strength because the rear end bottom portion of spiral element 12 acts to substantially increase the thickness of circular end plate 11. As a result, this configuration prevent a part of circular end plate 11, which are corresponding to the bottom of rectangular grooves 10a and 10b, from deforming. The scroll members do not incur the disadvantages of scuffing and seizures even if the through load concentrates to the above portions of circular end plate 11.

Further, this configuration improves sealing between the two scroll members As a result, the compression gas within the fluid pocket, which is defined by the spiral elements of two scrolls, does not leak from the pockets, and, thus, prevents the "blow-by phenomenon." Therefore, the configuration may increase volumetric efficiency of the compressor.

Figs. 9, 10, and 11 illustrate a second embodiment of the present invention. Elements in Figs. 9, 10, and 11 are similar to those in Figs. 6, 7, and 8 are designated by the same reference numerals.

Orbiting scroll 10 includes a reinforced portion 101 formed on one end surface of circular end plate 11. Reinforced portion 101 extends from the root of terminal end 12a of spiral element 12 to draw involute curve substantially the same as the involute curve of spiral element 12. Further, reinforced portion 101 has an axial height "h," which is designed to be preferably smaller than a height "H" of spiral element 12, in step-like fashion.

Reinforced portion 101 is not directly involved in the creation of fluid pockets 36. A pair of

rectangular grooves

10c and 10d are formed substantially on line X. Rectangular groove 10c is located so as to cross the rear end of bottom portion of reinforced portion 101 and the rear end of bottom portion of spiral element 12. Rectangular groove 10d is also located so as to cross the rear end of bottom portion of spiral element and is formed so as to cross the rear end bottom portion of spiral element 12 at least twice.

Figs. 12 and 13 illustrates a third embodiment of the present invention. Elements in Figs. 12 and 13 are similar to those in Figs. 10 and 11 and are designated by the same reference numerals. Reinforced portion 102 extends from terminal end 12a of spiral element 12 to draw involute curve substantially the same as the involute curve of spiral element 12. Further, reinforced portion 102 has an axial height that gradually decreases along the radial outside of orbiting scroll 10 in slope-like fashion. Rectangular groove 10c is located to cross the rear end of bottom portion of reinforced portion 102 and the rear end of bottom portion of spiral element 12.

Figs. 14 and 15 illustrate a fourth embodiment of the present invention. Elements in Figs. 14 and 15 are similar to those in Figs. 10 and 11 are designated by the same reference numerals. Reinforced rib 103 as formed on one end surface of circular end plate 11 so as to be located on the rear surface of bottom of rectangular groove 10c. Reinforced rib 103 is formed on one end surface of circular end plate 11 so as to be located on the rear surface ofbottom of rectangular groove 10c. Reinforced rib 103 has a rectangular shape so as to cross the width of groove 10c. Reinforced rib 103 is further located on the radial outside of radial inner side line of spiral element 12 to prevent orbiting and fixed scrolls from biting into each other. Substantially the same advantages as those achieved in the first embodiment are realized in this fourth embodiment.

Although the present invention has been described in connection with preferred embodiments, the invention is not limited thereto. It will be understood by those of ordinary skill in art that variations and modifications may be made within the scope of this invention as defined by the appended claims.

Claims

A scroll-type fluid displacement apparatus comprising:

a housing having an inlet port and an outlet port;

a fixed scroll fixedly disposed within said housing and having a first circular end plate from which a first spiral element extends into an interior of said housing;

an orbiting scroll having a second circular end plate, a second spiral element extending from a first surface of said second circular end plate, said first and second spiral elements interfitting at an angular and radial offset to form a plurality of line contacts defining at least one pair of fluid pockets within said interior of said housing, said orbiting scroll having a first groove and a second groove formed on a second surface of said second circular end plate, so that said grooves are diametrically opposed each other;

a driving mechanism operatively connected to said orbiting scroll to produce orbital motion of said orbiting scroll;

an Oldham coupling disposed between said orbiting scroll and said housing for preventing rotation of said orbiting scroll during orbital motion thereby enabling said orbital motion to change a volume of said at least one pair of fluid pockets, said Oldham coupling having a pair of engaging portions formed thereon for slidably engaging said first and second grooves of said orbiting scroll; and

reinforcing means located on said second surface of said second circular end plate of said orbiting scroll and extends across said first groove for reinforcing said circular end plate of said orbiting scroll.
The scroll-type fluid displacement apparatus of claim 1, wherein said reinforcing means extends across a radial width of said first groove.
The scroll-type fluid displacement apparatus of claim 1, wherein said reinforcing means is a supporting portion integrally formed with and extending from a terminal end of said second spiral element of said orbiting scroll.
The scroll-type fluid displacement apparatus of claim 3, wherein said supporting portion has an axial height less than that of said second spiral element of said orbiting scroll.
The scroll-type fluid displacement apparatus of claim 1, wherein said reinforcing means is a rib formed integrally on said second surface of said circular end plate of said orbiting scroll.
The scroll-type fluid displacement apparatus of claim 5, wherein said rib is located radially outside of a radial inner wall of said spiral element.
The scroll-type fluid displacement apparatus of claim 5, wherein said rib has an axial height less than that of said second spiral element of said orbiting scroll.
A scroll-type fluid displacement apparatus comprising:

a housing having an inlet port and an outlet port;

a fixed scroll fixedly disposed within said housing and having a first circular end plate from which a first spiral element extends into an interior of said housing;

an orbiting scroll having a second circular end plate, a second spiral element extending from a first surface of said second circular end plate, said first and second spiral elements interfitting at an angular and radial offset to form a plurality of line contacts defining at least one pair of fluid pockets within said interior of said housing, said orbiting scroll having a first groove and a second grooves formed on a second surface of said second circular end plate, so that said grooves are diametrically opposed each other;

a driving mechanism operatively connected to said orbiting scroll to produce orbital motion of said orbiting scroll;

an Oldham coupling disposed between said orbiting scroll and said housing for preventing rotation of said orbiting scroll during orbital motion thereby enabling said orbital motion to change a volume of said at least one pair of fluid pockets, said Oldham coupling having a pair of engaging portions formed thereon for slidably engaging a pair of said grooves of said orbiting scroll; and

a pair of said grooves formed, so that said pair of said grooves respectively extend across said spiral element of said orbiting scroll at least twice.
The scroll-type fluid displacement apparatus of claim 8, wherein said first and second grooves are rectangular in shape and extend from a radial end toward a radial center said second circular end plate of said orbiting scroll.