Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
2002-07-22
2003-12-09
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S055400
Reexamination Certificate
active
06659745
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scroll compressor which is installed in an air conditioner, a refrigerator, or the like, and in particular, a scroll compressor comprising characteristic scroll members.
2. Description of the Related Art
In conventional scroll compressors, a fixed scroll and an orbiting scroll are provided by engaging their spiral wall bodies, and fluid inside a compression chamber, which has a crescent shape and is formed between the spiral wall bodies, is compressed by gradually reducing the volume of the compression chamber as the orbiting scroll revolves around the fixed scroll.
The compression ratio in the design of the scroll compressor is determined based on the ratio of the maximum volume of the compression chamber (the volume at the point when the compression chamber is formed by the engaging of the spiral wall bodies) with respect to the minimum volume of the compression chamber (the volume immediately before the spiral wall bodies become unengaged and the compression chamber disappears). Conventionally, in order to increase the compression ability of the scroll compressor, the number of windings of the spiral wall bodies of both scrolls is increased, and thereby the cross-sectional area of the compression chamber at maximum volume is increased. However, in the conventional method of increasing the number of windings of the spiral wall bodies, the external shape of the scrolls is enlarged, increasing the size of the compressor; for this reason, it is difficult to use this method in an air conditioner for vehicles and the like which have strict size limitations.
In an attempt to solve the problem, the publication of Japanese Patent No. 1296431 proposes the following scroll compressor comprising stepwise scroll members.
FIG. 4A
shows a fixed scroll
1
of the above patent comprising an end plate
1
a
and a spiral wall body
1
b
provided on one side surface of the end plate
1
a
.
FIG. 4B
shows an orbiting scroll
2
similarly comprising an end plate
2
a
and a spiral wall body
2
b
provided on one side surface of the end plate
2
a.
A step portion
3
is provided on the surface of the end plate
1
a
of the fixed scroll
1
. The step portion
3
has two parts in which one is a high part at the center of the surface of the end plate
1
a
and the other is a low part at the outer end of the end plate
1
a
. Furthermore, a step portion
4
, corresponding to the step portion
3
of the end plate
1
a
, is provided in the spiral wall body
1
b
of the fixed scroll
1
. The step portion
4
has two parts in which one is a low part at the center of the spiral wall body
1
b
and the other is a high part at the outer end of the spiral wall body
1
b
. Similarly, a step portion
3
is provided on the surface of the end plate
2
a
of the orbiting scroll
2
. The step portion
3
has two parts in which one is a high part at the center of the surface of the end plate
2
a
and the other is a low part at the outer end of the end plate
2
a
. Furthermore, a step portion
4
, corresponding to the step portion
3
, is provided in the spiral wall body
2
b
of the orbiting scroll
2
. The step portion
4
has two parts in which one is a low part at the center of the spiral wall body
2
b
and the other is a high part at the outer end of the spiral wall body
2
b.
FIG. 5
shows the state when the spiral wall body
1
b
of the fixed scroll
1
and the spiral wall body
2
b
of the orbiting scroll
2
are engaged. While this engagement state is maintained, the orbiting scroll
2
is revolved eccentrically with respect to the fixed scroll
1
, and the volume of compression chambers C
1
to C
5
, which are formed by the spiral wall bodies
1
b
and
2
b
, gradually decreases. Thereby, fluid in the compression chambers C
1
to C
5
is gradually compressed, and finally the fluid is discharged at a high pressure from a discharge port
5
provided at the center of the end plate
1
a
of the fixed scroll
1
. In the scroll compressor comprising such a structure, since the volume of the compression chamber suddenly decreases because of the existence of the step portions
3
and
3
, the minimum volume in the compression chambers can be reduced. Thereby, without an increase in the size of both the fixed scroll
1
and the orbiting scroll
2
, the compression ratio can be improved.
However, in the scroll compressor comprising the fixed scroll
1
and the orbiting scroll
2
comprising the step portions
3
and
3
, a tip clearance (not shown in figures) is formed between the end plate
1
a
of the fixed scroll
1
and the top edge of the spiral wall body
2
b
of the orbiting scroll
2
, and between the end plate
2
a
of the orbiting scroll
2
and the top edge of the spiral wall body
1
b
of the fixed scroll
1
. If the tip clearance is too small, the smooth revolution of the orbiting scroll
2
with respect to the fixed scroll
1
is inhibited, and a power increase may be caused. In addition, when the scroll compressor is operated at high temperatures, the spiral wall bodies
1
b
and
2
b
of the fixed scroll
1
and the orbiting scroll
2
expand, the top edge of the spiral wall bodies
1
b
and
2
b
and the end plates
1
a
and
2
a
make firmly contact, and thereby, abrasion or seizure may occur.
Furthermore, as described above, since the volume of the compression chambers suddenly decreases due to the existence of the step portions
3
and
3
, the differential pressure between in the compression chambers at the center and the compression chambers at the outer end, with respect to the step portions
3
and
3
is relatively large.
In contrast, if the tip clearance is too large, the amount of leakage of the compressed gas, which flows via the tip clearance between the adjacent compression chambers increases, and there are cases in which the compression ability of the scroll compressor is degraded.
Therefore, it is necessary for the tip clearance to be adjusted in a suitable range. In conventional scroll compressors, a tip clearance at any position in the spiral direction of the spiral wall bodies
1
b
and
2
b
is adjusted to a substantially fixed value. In other words, if the tip clearance between the end plates
1
a
and
2
a
and the top edge of the spiral wall bodies
1
b
and
2
b
at the low part of the end plates
1
a
and
2
a
(outer end of the end plates
1
a
and
2
a
with respect to the step portions
3
and
3
) is defined as &dgr;1, and the tip clearance between the end plates
1
a
and
2
a
and the top edge of the spiral wall bodies
1
b
and
2
b
at the high part of the end plates
1
a
and
2
a
(center position of the end plates
1
a
and
2
a
with respect to the step portions
3
and
3
) is defined as &dgr;2, in conventional scroll compressors, the relation &dgr;1=&dgr;2 is established.
However, in order to satisfy the relation &dgr;1=&dgr;2, it is necessary to improve the working precision of the fixed scroll
1
and the orbiting scroll
2
, and measure &dgr;1 and &dgr;2 during the assembly processes. A large number of man-hours is required, and an increase in the cost cannot be avoided.
In consideration of the above-described problems, it is an object of the present invention to provide a scroll compressor which can improve the decrease in the compression ratio due to the leakage of compressed gas via the tip clearance between the adjacent compression chambers, which can be assembled with a fewer processes, and which can be manufactured at a low cost.
SUMMARY OF THE INVENTION
One aspect of the present invention is a scroll compressor comprising a fixed scroll member which is fixed in position and has a spiral wall body provided on one surface of an end plate; an orbiting scroll member which has a spiral wall body provided on one surface of an end plate, being supported by engaging the spiral wall bodies so as to orbit and revolve around the fixed scroll member without rotation; the spiral wall bodies of the fixed scroll member and the orbiting scroll member each compr
Fujita Katsuhiro
Takeuchi Makoto
Mitsubishi Heavy Industries Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Vrablik John J.
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