Scroll compressor having wraps of varying thickness

Details Scroll compressor having wraps of varying thickness Scroll compressor having wraps of varying thickness

2001-08-02

2003-03-04

Vrablik, John J. (Department: 3748)

Rotary expansible chamber devices

Working member has planetary or planetating movement

Helical working member, e.g., scroll

Reexamination Certificate

active

06527526

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to scroll compressors, and more particularly, to a wrap structure of each scroll in the scroll compressor for compressing refrigerant as an orbiting scroll orbits a fixed scroll.
2. Background of the Related Art
In general, the scroll compressors are mostly used in room air conditioners or car air conditioners as the scroll compressors have low noise, and small sized and light weighted, in which one pair of opposite scrolls form a compression chamber, in which the refrigerant is compressed.
FIG. 1
illustrates a section of a related art scroll compressor, referring to which the related art scroll compressor will be explained.
Referring to
FIG. 1
, there is an enclosed shell of a body
1
having an inlet tube
11
and an outlet tube
15
connected thereto for drawing and discharging the refrigerant, respectively. There is a fixed scroll
8
in an upper part of the body
1
having an outlet
12
at a central part
12
thereof and a wrap
8
a
of an involute curve projected downward from a bottom thereof. Also, there is an orbiting scroll
7
under the fixed scroll
8
orbitably coupled with the fixed scroll
8
in correspondence thereto having a wrap
7
a
of an involute curve projected upward. Side surfaces of the wraps
8
a
and
7
a
on the fixed, and orbiting scrolls
8
and
7
are made to be brought into contact as well as fore ends of the wraps
8
a
and
7
a
and scroll dish plates (disks the wraps are formed thereon), to form a compression chamber (a space which encloses refrigerant therein and is involved in gradual reduction for implementing compression).
The orbiting scroll
7
has a crank shaft
6
fixed to a bottom thereof for orbiting the orbiting scroll
7
as the crank shaft
6
transmits a rotating force from a motor part
5
, provided in a lower part of the body
1
, to the orbiting scroll
7
via an Oldham ring
9
that prevents rotation of the orbiting scroll
7
, to reduce a volume of the compression chamber gradually to compress the refrigerant trapped between the two scrolls
7
and
8
and discharge through the outlet tube
15
.
FIGS.
2
A~
2
D illustrate the steps of a process for compressing refrigerant in a related art scroll compressor, referring to which the operation of the related art scroll compressor will be explained in detail.
Upon application of power to the motor part
5
, the crank shaft
6
rotates to rotate the orbiting scroll
7
fixed on a top thereof. In this instance, the orbiting scroll
7
is made to orbit spaced from a center of the crank shaft
6
by a preset orbiting radius in a state rotation is prevented by the Oldham ring
9
. As shown in
FIG. 2B
, low temperature and low pressure refrigerant
20
drawn into the body
1
through the inlet tube
11
after being heat exchanged at an evaporator during the foregoing process is the compression chamber through refrigerant inlets
21
and
22
formed by the wraps
8
a
and
7
a
on the fixed scroll
8
and the orbiting scroll
7
, respectively.
Then, as shown in
FIGS. 2C and 2D
, as the orbiting scroll
7
keeps to orbit, the refrigerant is involved in gradual decrease of a volume thereof and flows toward a central portion of the compression chamber, i.e., to a location where the outlet
12
of the fixed scroll
8
is formed. It can be known that, as explained, the refrigerant is compressed to high temperature and pressure as the refrigerant is involved in gradual decrease of volume during the refrigerant flows toward the central portion of the compression chamber.
At the end, as shown in
FIG. 2D
, the refrigerant compressed thus is discharged through the outlet
12
passed through the fixed scroll
8
, and, therefrom, to a condenser through the outlet tube
15
, when new refrigerant to be compressed is drawn through the refrigerant inlets
21
and
22
of the compression chamber formed as the scrolls
7
and
8
are engaged.
The foregoing related art scroll compressor is required to compress the refrigerant gradually as the refrigerant goes toward the central portion of the compression chamber, for which it is very important that the wraps
7
a
and
8
a
of the orbiting scroll
7
and the fixed scroll
8
are required to be designed to come into a close contact at appropriate positions.
FIGS.
3
A~
3
C illustrate the steps of a process for forming an orbiting scroll wrap of a related art scroll compressor, referring to which structures of the orbiting scroll wrap
7
a
and a fixed scroll wrap
8
a
of the related art scroll compressor will be explained.
Referring to
FIG. 3A
, a base circle
30
with a radius ‘a’ is drawn on a center on an X-, and Y-axes. Then, an involute curve is drawn, taking one point on a circumference of the base circle
30
at a starting angle ‘a’ from the X-axis as a starting point, i.e., an inner involute curve is drawn. One point on the inner involute curve
31
for the base circle
30
may be expressed with a parameter ‘&thgr;’ as follows.
X
i
=a
×{cos(&thgr;
i
−&agr;)+&thgr;
i
×sin(&thgr;
i
−&agr;)},
and
Y
i
=a
×{sin(&thgr;
i
−&agr;)−&thgr;
i
×cos(&thgr;
i
−&agr;)}
Then, as shown in
FIG. 3B
, in order to form a thickness of the wrap
7
a
of the orbiting scroll
7
, another involute curve started from a point at ‘−&agr;’ angle to the X-axis on the circumference of the base circle
30
, i.e., an outer involute curve
32
, is drawn. One point on the outer involute curve
32
for the base circle
30
may be expressed with a parameter ‘&thgr;’ as follows.
X
o
=a×{cos(&thgr;
o
+&agr;)+&thgr;
o
×sin(&thgr;
o
+&agr;)},
and
Y
i
=a×{sin(&thgr;
o
+&agr;)−&thgr;
o
×cos(&thgr;
o
+&agr;)}
A distance of the inner involute curve
31
and the outer involute curve form a thickness ‘t’ for forming the wrap. Thus, as shown in
FIG. 3C
, upon completion of formation of involute curves, the orbiting scroll
7
a
can be formed by using the involute curves.
FIGS.
4
A~
4
C illustrate the steps of a process for forming a fixed scroll wrap of a related art scroll compressor, the fixed scroll wrap
8
a
is formed in a form having a 180° phase difference from the orbiting scroll wrap
7
a
. That is, a base circle
40
with a radius ‘a’ is drawn in a method identical to the base circle
30
drawn for the orbiting scroll wrap
7
a
, inner and outer involute curves
41
and
42
are drawn starting from points on the circumference of the base circle
40
, and the fixed scroll wrap
8
a
is formed based on the involute curves
41
and
42
of the scroll compressor, of which detailed explanation will be omitted.
For making appropriate points of the wraps
7
a
and
8
a
of the orbiting scroll
7
and the fixed scroll
8
being brought into contact, orbiting radiuses of the involute curves are required to have a relation of (P−2t)/2, where P=2&pgr;a, i.e., a pitch of the wraps
7
a
and
8
a
on the scrolls, and ‘t’=2a&agr;, i.e., the thickness of the wrap. Accordingly, the compression chamber is formed as the orbiting scroll
7
is made to orbit along an orbiting radius by the motor
5
, and the refrigerant drawn into the compression chamber is compressed.
However, the foregoing scroll wrap structures have the following problems in light of the present trend in which the scroll compressor is made smaller while capacity and efficiency are enhanced.
That is, in order to increase a capacity of the related art scroll compressor, there is no way, but to increase a height of the wrap on the scroll, or to increase an overall size of the scroll compressor, which, not only is against the recent trend of making the scroll compressor smaller, but also makes a reliability of the scroll compressor poor, if the heights of the wraps on the scrolls are increased, that makes points of action of a pressure occurred as the refrigerant is compressed higher as much as the increased height of the wrap.
The increas

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