Rotary compressor

Details Rotary compressor Rotary compressor

2001-02-22

2002-08-20

Denion, Thomas (Department: 3748)

Rotary expansible chamber devices

Working member has planetary or planetating movement

With relatively movable partition member

C418S178000, C418S179000

Reexamination Certificate

active

06435850

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Japanese application serial no. 2000-071619, filed Mar. 15, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to a rotary compressor using a freon without containing chlorine ions, and using polyol ester as a lubricant or plyvinyl ether as a base oil for preventing abnormal abrasion, and more specifically relates to a structure of a vane and a roller of a highly reliable rotary compressor.
2. Description of Related Art
Traditionally, the freon used for most compressors within refrigerators, showcases, vending machines, or air-conditioners for family and businesses are dichrolrodifluoromethane (R
12
) and monochrolrodifluoromethane (R
22
). The traditional freons R
12
and R
22
easily damage the ozone layer when they are released into the atmosphere. Consequently, use of the traditional freon is restricted. Damage to the ozone layer of the atmosphere is due to chlorine components in the freon. Therefore, a natural freon without chlorine ions, such as HFC freon (for example, R
32
, R
125
, and R
134
a
), phytane type freon (for example, propane and butane etc.), carbonic acid gas and ammonia etc, is considered to replace the traditional freon.
FIG. 1
is a cross-sectional view of a rotary compressor with two cylinders,
FIG. 2
is a diagram for showing a structural correlation among a roller, a vane and a cylinder,
FIG. 3
is a diagram for showing a vane structure. As shown in
FIG. 1
, the rotary compressor
1
comprises a sealed container
10
with an electromotor and a compressor both installed within the sealed container
10
. The electromotor
20
includes a stator
22
and a rotor
24
, both of which are fixed on inner walls of the sealed container
10
. A rotary shaft
25
passing through the center of the rotor
24
is freely rotated to support two plates
33
,
34
that are used to seal the openings of the cylinders
31
,
32
. A crank
26
is eccentrically connected to the rotary shaft
25
. The cylinders
31
,
32
are mounted between the two plates
33
,
34
. The axes of the two cylinders
31
,
32
are aligned with the axis of the rotary shaft
25
. Hereinafter, only the cylinder
32
is described for simplification. At the sidewall
32
b
of the cylinder
32
, a freon inlet
23
and a freon outlet
35
are formed respectively.
Within the cylinder
32
, an annular roller
38
is mounted. The inner circumference
38
b
of the roller
38
is in contact with the outer circumference
26
a
of the crank
26
, and the outer circumference
38
a
of the roller
38
is in contact with the inner circumference
32
b
of the cylinder
32
. A vane
40
is mounted on the cylinder
32
and capable of sliding freely. The front end
40
a
of the vane
40
is elastically in contact with the outer circumference
38
a
of the roller
38
. The front end
40
a
of the vane
40
and the roller
38
are securely sealed by introducing a compressed freon from the vane
40
. A compressing room
50
is then encompassed by the roller
38
, the cylinder
32
, and the plate
34
for sealing the cylinder
32
.
When the rotary shaft
25
rotates counterclockwise with respect to
FIG. 2
, the roller
38
rotates eccentrically within the cylinder
32
. Therefore, freon gas is introduced into the compressing room
50
from the inlet
23
, compressed and then exhausted from the outlet
35
. During the cycle, a compressing stress Fv is generated at the contact portion of the vane
40
and the roller
38
.
According to the traditional structure, the contact surface (the front end)
40
a
of the vane
40
in contact with the roller
38
is an arc shape with a radius of curvature Rv. The radius of curvature Rv is substantially equal to the width of the vane
40
, and about {fraction (1/10)} to ⅓ of the radius of the roller
38
. The roller
38
is made of materials such as cast iron or cast iron alloy, and is formed by a quenching process. The vane
40
is made of materials such as stainless steel or tool steel, and can be further coated by nitridation. In general, the vane
40
is characterized by high hardness and malleability.
FIG. 4
shows the contact status between the roller
38
and the vane, however a cylindrical tube with different radius of curvature can be used. As shown in
FIG. 4
, due to the compressing stress Fv of the vane
40
, it is a surface contact, rather than a point contact or a line contact, between the vane
40
and the roller
38
when they squeeze each other. The length of an elastic contact surface between the vane
40
and the roller
38
can be calculated by the following formula:
d
=
4
⁢
(
1
-
v
1
2
π
⁢
 
⁢
E1
+
1
-
v
2
2
π
⁢
 
⁢
E2
)
·
Fv
·
ρ
L
wherein E
1
and E
2
are longitudinal elastic coefficients (kg/cm2) for the vane
40
and the roller
38
respectively, &ngr;
1
and &ngr;
2
are Poisson's ratios for the vane
40
and the roller
38
respectively, L is the height (cm) of the vane
40
, Fv is the compressing stress, &rgr; is a effective radius. At the contact portion, a Hertz stress Pmax (kgfcm2) is exerted and calculated by the following formula:
Pmax=4/&pgr;·Fv/L/d  (9)
As the structure described above, in order to increase the durability of the vane a surface process such as a nitridation process or a CrN ion coating film is performed on the vane of the rotary compressor using a freon without containing chlorine ions and using a polyol ester lubricant or plyvinyl ether as a base oil. However, the durability for nitridation is easily degraded and the CrN ion film is easily stripped. Furthermore, the nitridation process or the CrN ion coating film costs high and therefore the manufacturing cost increases.
SUMMARY OF THE INVENTION
According to the foregoing description, an object of this invention is to provide a high reliable rotary compressor using a freon without containing chlorine ions, and using a polyol ester as a lubricant or plyvinyl ether as a base oil for preventing abnormal abrasion between the vane and the roller.
According to the present invention, it changes the conventional design that the radius of curvature of the contact surface of the vane and the roller is substantially equal to the width of the vane. To maintain the contact surface of the vane and the roller within an acceptable range, by increasing the radius of curvature of the contact surface to be larger than the width of the vane, the Hertz stress is therefore decreased. In addition, the sliding distance increases for diverging the stress such that the temperature at the sliding contact portion between the vane and the roller can be reduced. Accordingly, a coating process with a high cost is not necessary for the surface of the vane. Namely, even though a low cost nitridation (NV nitridation, sulphonyl nitridation or radical nitridation) is used, it can sufficiently reduce the abrasion between the contact area of the roller and the vane, and further prevent abnormal abrasion.
According to the objects mentioned above, the present invention provides a rotary compressor coupled to a freon loop. The freon loop is connected to the rotary compressor, a condenser, an expansion device and an evaporator. The rotary compressor uses a freon without containing chlorine ions and uses a polyol ester as a lubricant or polyvinyl ether as a base oil for the lubricant. The rotary compressor comprises at least a cylinder, a rotary shaft, a roller and a vane. The cylinder has a freon inlet and a freon outlet. The rotary shaft has a crank installed on an axis of the cylinder. The roller is installed between the crank and the cylinder, and capable of eccentrically rotating. The vane is capable of reciprocating within a groove formed in the cylinder, and sliding contact with an outer circumference of the roller. A sliding contact portion is formed between the vane and the roller, having a radius of curvature Rv satisfying the following formula:
T<Rv<Rr  (1)
wherein T is the thickne

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