Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
2001-02-07
2002-04-09
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S150000
Reexamination Certificate
active
06368087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scroll-type fluid displacement apparatus, and more particularly, to a spiral starting portion of a fixed scroll and an orbiting scroll.
2. Description of Related Art
Scroll-type fluid displacement apparatus are known in the art. For example, U.S. Pat. No. 5,037,279, which is incorporated herein by reference, describes spiral portions of a fixed scroll and an orbiting scroll.
Referring to
FIGS. 5
to
7
a-d,
an orbiting scroll
50
has an end plate
50
a
; an involute spiral wrap element
50
b
, which extends from a first side of end plate
50
a
; and an annular boss
50
c
, which extends from a second side of end plate
50
a
. An involute spiral wrap element
40
b
of a fixed scroll (not shown) is formed on an end plate of the fixed scroll and is symmetrical to spiral element
50
b
of orbiting scroll
50
. Orbiting scroll
50
is supported on a housing by an Oldham coupling mechanism consisting of an Oldham coupling ring and Oldham coupling keys. The Oldham coupling mechanism prevents the rotation of orbiting scroll
50
on its axis and generates an orbital motion with respect to the fixed scroll.
As shown in
FIGS. 5 and 6
, a widened-starting portion
500
c
of spiral element
50
b
of orbiting scroll
50
has a cross-sectional shape, in which the thickness is greater at the base surface and less at the tip surface (i.e., the thickness decreases or tapers from the base surface to the tip surface). An exterior curve
506
, which is a radially exterior curve between a first tip point
501
at the tip and a first widened-starting point
503
at the base surface, is an involute curve. An interior curve
507
, which is a radially interior curve between a second tip point
502
at the tip surface and a second widened-starting point
505
at the base surface, also is an involute curve. A spiral base portion between point
503
and point
505
is composed of the curved line, described below. A region between point
503
and a point
504
is defined by a first convex arc
509
. A radius r of the convex arc
509
is defined by the following equation:
r
=
4
a
2
(
λ
1
2
+
1
)
-
ϵ
2
4
(
ϵ
+
2
a
λ
1
)
where:
a is a radius of an involute base circle;
&lgr;
1
is a widened-starting angle; and
&egr; is an orbit radius.
A region between point
504
and point
505
is defined by a second concave arc
510
. A radius R of the concave arc
510
is defined by the following equation:
R=r+&egr;
On the other hand, the region between point
501
and point
502
at the tip of spiral element
50
b
is defined by an arc
508
, the diameter of which substantially corresponds to a distance between opposed walls of the involute curve of spiral element
50
b
. A curve along the base from point
503
to point
505
and a curve along the tip from point
501
to point
502
are connected through a smooth inclined wall.
Referring to the compression and discharge strokes of the known scroll-type compressor,
FIG. 7
a
shows the known compressor in a condition, in which the suction stroke has been completed and the compression stroke has just begun. Thereafter, the strokes proceed in sequence, as shown
FIGS. 7
b,
7
c
and
7
d,
and a compression chamber
60
gradually moves towards the center like a compression chamber
60
′, as shown in
FIG. 7
a
, while its volume decreases. Consequently, compressed gas is discharged through a discharge port
61
.
In the known scroll-type fluid displacement apparatus, however, as shown in a central portion of
FIG. 7
d
, when compression is completed, fluid remains in a dead volume, which is defined by an inclined wall of spiral element
50
b
of orbiting scroll
50
and an inclined wall of spiral element
40
b
of the fixed scroll. The fluid in this dead volume expands, and interupts the drawing of new fluid into compression chamber
60
. As a result, the compression efficiency of the scroll-type fluid displacement apparatus may be reduced.
Further, each of the tip points of spiral element
50
b
of orbiting scroll
50
and of spiral element
40
b
of the fixed scroll has a sharp edge shape. Therefore, when orbiting scroll
50
and the fixed scroll are operated in the compression and discharge strokes, defects may be created in the tip points of each spiral elements because both spiral element engage each other.
SUMMARY OF THE INVENTION
A technical advantage of the present invention is to reduce or eliminate the above-mentioned defects encountered in the spiral elements of the known scroll-type fluid displacement apparatus.
Another technical advantage of the present invention is to provide a scroll-type fluid displacement apparatus, which has increased strength in the central portions of spiral elements of an orbiting scroll and a fixed scroll.
A further technical advantage of the present invention is to provide the scroll-type fluid displacement apparatus, which has increased volmetric efficiency, e.g., compression efficiency, expansion efficiency, and discharge efficiency.
In an embodiment of this invention, a scroll-type fluid displacement apparatus comprises a rear housing and a front housing, a fixed scroll and an orbiting scroll, a driving mechanism, and a rotation preventing mechanism. The rear housing has an open end and an inlet port and an outlet port. A front housing closes the open end of the rear housing. The fixed scroll has a first end plate and a spiral element formed on and extending from a first side of the first end plate. The fixed scroll is attached to the rear housing. The orbiting scroll has a second end plate and a spiral element formed on and extending from a first side of the second end plate. Each of the spiral elements interfits with the other at an angular and a radial offset to form a plurality of line contacts defining at least one pair of sealed-off fluid pockets. A driving mechanism includes a drive shaft rotatably supported by the front housing to effect the orbital motion of the orbiting scroll by rotation of the drive shaft to thereby change the volume of the fluid pockets. A rotation preventing mechanism prevents the orbiting scroll from rotating. An interior wall of a widened-starting portion of each of the spiral elements is inclined, such that the thickness of a base surface of the widened-starting portion is greater than the thickness at a tip surface and the thickness of the widened-starting portion gradually decreases towards the tip surface of the widened-starting portion. A first transition line between the interior wall and the tip surface comprises a first upper arc ending at an upper, interior involute wall starting point and a second upper arc beginning at an upper, exterior involute wall starting point. A second transition line between the interior wall and the base surface comprises a first lower arc ending at the lower, interior involute wall starting point and a second lower small arc beginning at the lower, exterior involute wall starting point.
Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings.
REFERENCES:
patent: 4457674 (1984-07-01), Kawano et al.
patent: 4457676 (1984-07-01), Hiraga
patent: 4477238 (1984-10-01), Terauchi
patent: 4499099 (1985-02-01), Terauchi et al.
patent: 4547137 (1985-10-01), Terauchi et al.
patent: 4548555 (1985-10-01), Hiraga et al.
patent: 4594061 (1986-06-01), Terauchi
patent: 4627800 (1986-12-01), Matsudaira et al.
patent: 4666380 (1987-05-01), Hirano et al.
patent: 4824345 (1989-04-01), Fukuhara et al.
patent: 5037279 (1991-08-01), Suefuji et al.
patent: 5370512 (1994-12-01), Fujitani et al.
patent: 6132179 (2000-10-01), Higashiyama
patent: 0761971 (1997-03-01), None
patent: 2161218 (1986-01-01), None
patent: 59079090 (1984-08-01), None
patent: 62-107283 (1987-05-01), None
patent: 01-130083 (1989-05-01), None
patent: 04350378 (1992-04-01), None
Kikuchi Toshiyuki
Tsukamoto Ko
Denion Thomas
Sanden Corporation
Trieu Theresa
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