Title of Invention

A RECIPROCAING COMPRESSOR FOR COMPRESSING A REFRIGERANT

Abstract A reciprocating compressor includes a driving unit (10) disposed inside a hermetic container (86) and generating a reciprocal motional force, a compression unit (10) for performing a compressing operation or. a refrigerant upon receiving the reciprocal motional force generated from the dnving unit (8); and a lubrication unit (12) for supplying a lubricant to each motional portion of the driving unit (8) and the compression unit (10) to perform a lubrication operation. Hydrocarbon consisting of carbon and hydrogen, a sort of natural refrigerant, is used as the refrigerant. The lubricant is a paraffin-based mineral lubricant, which is a sort of mineral oil and well harmonized with the natural refrigerant used for a refrigerator. Accordingly, a lubricating performance is improved and thus a performance of the reciprocating compressor can be enhanced.
Full Text A Reciprocating Compressoor For Compressing A Refrigerant
TECHNICAL FIELD
The present invention relates to a reciprocating compressor for compressing a refrigerant in a refrigerator, and more particularly, to a reciprocating compressor for compressing a refrigerant that is capable of improving a lubricating performance by using a lubricant with an excellent compatibility with a refrigerant used for a refrigerator and improving a performance of.the refrigerator.
BACKGROUND ART
As chlorofluorocarbon (CFC), a refrigerant used for a refrigerator, an air-conditioner or the like, has been known as a source material damaging an ozone layer of the stratosphere, researches on a substitute refrigerant is being actively
conducted.
The CFC comprises R11 (trichloromonogluoromethane), R12 (dichlorodifluoromethane), R13 and the like, of which R12 mainly used as a refrigerant for a refrigerator is one of regulation-subject materials as being a source material causing an ozone layer reduction and generating a global warming effect. Thus, researches on a natural refrigerant is being actively conducted as a substitute refrigerant.
The natural refrigerant refers to a material used as a refrigerant which naturally exists in the globe such as water, ammonia, nitride, carbon dioxide,

















propane, butane and the like, not an artificial compound. Known that it does not
have a bad influence on the global environment, application of the natural
refrigerant as a refrigerant is positively reviewed.
Among the natural refrigerants, hydrocarbon comprises only carbon and
hydrogen and includes R50 (methane), R170 (ethane), R290 (propane), R600
(butane), R600a (isobutene), R1270 (propylene) or the like. Hydrocarbon is not
toxic and chemically stable and especially exhibits an appropriate solubility in a
mineral oil.
In addition, the hydrocarbon has a zero ozone depletion potential and a
very low global warming index. That is, when a global warming index of carbon
dioxide is admitted as '1', a global warming index of R12 is 7100, R134a is 1200,
while propane is very low, 3.
Especially, isobutane (R600a) is an environmental-friendly natural gas
which does not damage the ozone layer and have no influence on a greenhouse
effect. That is, isobutane (R600a), a sort of a natural gas obtained by refining
hydrocarbon gas created in an oil refining process to a high degree of purity, is
a refrigerant containing no environmentally detrimental factor.
However, with all those advantages, isobutene (R600a) is hardly
combined with refrigerant oil currently used for a refrigerating system due to its
chemical and electrical properties. Therefore, a refrigerant oil suitable for
isobutene (R600a) is in need of development. Especially, necessity of a
refrigerant oil usable for a reciprocating compressor for compressing isobutene

(R600a) comes to the front.
As shown in Figure 1, the currently used reciprocating compressor
includes: a hermetic container 6 having a suction pipe 2 for sucking a refrigerant
and a discharge pipe 4 for discharging a compressed refrigerant each as being
connected thereto; a driving unit 8 disposed inside the case 6 and generating a
reciprocal motional force; a compression unit 10 for receiving the reciprocal
motional force from the driving unit 8 and compressing the refrigerant; and a
lubrication unit 12 for lubricating each motional portion of the driving unit 8 and
the compression unit 10.
In the reciprocating compressor, when the driving unit 8 is driven and the
compression unit 10 makes a compression operation on the refrigerant, the
lubrication unit 12 supplies a lubricant 50 stored at the lower portion of the
hermetic container 6 to the motional portion of the compression unit, thereby
performing a lubricating operation. The refrigerant compressed in the compression
unit is the natural refrigerant.
Since the lubricant used for the reciprocating compressor constructed and
operated as described above is used as a refrigerant oil for the compressor
compressing the natural refrigerant, its physical and chemical properties should
be in good harmony with the natural refrigerant.
Namely, the lubricant used as the refrigerant oil of the reciprocating
compressor needs to have characteristics that it can protect well an oil film even
though the refrigerant is dissolved, should be thermally and chemically stable so
as not to react in spite of being in contact with the refrigerant and an organic

material metal at a high temperature or at a low temperature, and should have a
high level thermal stability so as not to generate a carbon sludge not to be
oxidized at a high temperature part of the compressor.
In order to satisfy those characteristics, characters of the lubricant, such
as a kinematic viscosity, a pour point, a density, a total acid number, a water
content or the like, work as critical factors.
Therefore, if the lubricant used for the reciprocating compressor
compressing the natural refrigerant is not well harmonized with the refrigerant of
the refrigerator, the oil would be leaked. Then, oil circulation is deteriorated to
degrade a heat transfer performance of the refrigerator and a lubrication
performance, resulting in that frictional portions of each motional part are abraded
and thus each part is damaged.
DISCLOSURE OF THE INVENTION
Therefore, it is an object of the present invention to provide a reciprocating
compressor that is capable of improving a lubrication performance by using a
lubricant in good harmony with a natural refrigerant used for a refrigerator, and
thus enhancing a performance of a reciprocating compressor.
To achieve these objects, there is provided a reciprocating compressor for
compressing a refrigerant including: a hermetic container to which a suction pipe
and a discharge pipe are connected; a driving unit having a stator fixed inside the
hermetic container and a mover disposed spaced apart from the stator and

linearly and reciprocally moved according to an interaction with the stator; an
organic compound refrigerant sucked into the suction pipe, having an
combustibility and explosiveness and consisting of only carbon and hydrogen; a
compression unit for receiving a reciprocal motional force of the driving unit and
making a compression operation on the organic compound refrigerant; and a
mineral-based lubricant filled at a lower portion of the hermetic container; and a
lubrication unit for supplying the mineral-based lubricant to each motional portion
of the driving unit and the compression unit and performing a lubricating operation.
In the reciprocating compressor of the present invention, the stator consists
of an outer stator fixed at the hermetic container; an inner stator disposed with a
certain air gap with an inner circumferential surface of the outer stator; and a
winding coil wound at one of the outer stator and the inner stator, to which power
is applied from an external source, and the mover consists of magnets disposed
at regular intervals between the outer stator and the inner stator and being linearly
and reciprocally moved when power is applied to the winding coil; and a magnet
frame having the magnets mounted thereon and transmitting a linear and
reciprocal motional force to the compression unit.
In the reciprocating compressor of the present invention, the compression
unit includes: a piston connected to the mover and linearly and reciprocally
moved; a cylinder, into whiGh the piston is slidably inserted, for forming a certain
compression chamber; a suction valve mounted at a refrigerant passage formed
at the piston and preventing a backflow of the refrigerant after being introduced
into the compression chamber; and a discharge valve mounted at the front side

of the cylinder and performing an opening and closing operation on the
compressed refrigerant.
In the reciprocating compressor of the present invention, the lubrication unit
includes: a lubricant pumping unit for pumping the lubricant filled as much as a
certain amount at a lower portion of the hermetic container; and a lubricant supply
passage for supplying the lubricant pumped by the lubricant pumping unit to a
frictional portion between the piston and the cylinder.
In the reciprocating compressor of the present invention, the refrigerant is
isobutane (R600a) which is hydrocarbon-based and has a molecular formula of
CH(CH3)3.
In the reciprocating compressor of the present invention, the lubricant is
a paraffin-based lubricant.
In the reciprocating compressor of the present invention, the lubricant has
a density of 0.866~0.880 g/cm3 at a temperature of 15°C and a flash point of
above 140°C.
In the reciprocating compressor of the present invention, the lubricant has
a kinematic viscosity of 7.2-21.8 mm2/s at a temperature of 40°C and a viscosity
index of 73-99.
In the reciprocating compressor of the present invention, the lubricant has
a flow point of below -25°C and a total acid number of below 0.01 mgKOH/g.
In the reciprocating compressor of the present invention, the lubricant has
a water content of below 20 ppm and a breakdown voltage of above 30kV.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1 is a sectional view of a general reciprocating compressor for
compressing a refrigerant.
MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS
Figure 1 is a sectional view of a general reciprocating compressor for
compressing a refrigerant.
As shown in Figure 1, the general reciprocating compressor includes: a
hermetic container 6 to which a suction pipe 2 for sucking a refrigerant and a
discharge pipe 4 for discharging a compressed refrigerant are connected, a
driving unit 8 disposed inside the case 6 and generating a reciprocal motional
force; a compression unit 10 for receiving a reciprocal motional force generated
from the driving unit 8 and performing a compressing operation on the refrigerant;
and a lubrication unit 12 for performing a lubricating operation on each motional
portion of the driving unit 8 and the compression unit 10.
The driving unit 8 includes: a cylindrical outer stator 16 fixed by a support
frame 14 fixed inside the hermetic container 6; an inner stator 18 disposed with
a certain air gap with an inner circumferential surface of the outer stator 16; a
winding coil 20 wound at the outer stator 16, to which power is applied from an
external source; and magnets 22 disposed at regular intervals between the outer
stator 16 and the inner stator 18 and linearly and reciprocally moved when power
is applied to the winding coil 20.


The magnets 22 are fixed at an outer circumferential surface of the magnet
holder 24 at equal intervals, and the magnet holder 24 is connected to the piston
26 of the compression unit 10.
The compression unit 10 includes a piston 26 connected to the magnet
i holder 24 and linearly and reciprocally moved; a cylinder 28, into which the piston
26 is slidably inserted, forming a compression chamber 36; a suction-valve 32
mounted at a suction opening 30 formed at the piston 26 and preventing a
backflow of the refrigerant after being introduced into the compression chamber
36; and a discharge valve 34 mounted at a front side of the cylinder 28 and performing an opening and closing operation on a compressed refrigerant.
The lubrication unit 12 includes: a lubricant 50 filled as much as a certain
amount at a lower portion of the hermetic container; a lubricant pumping unit 40
for pumping the lubricant 50; and a lubricant supply passage 42 for supplying the
lubricant 50 pumped by the lubricant pumping unit 40 to a frictional portion between the piston 26 and the cylinder 28.
The operation of the general reciprocating compressor constructed as
described above will now be explained.
When power is applied to the winding coil 20, a flux is formed around the
winding coil 2, a flux is formed around the winding coil 20, forming a closed loop along the outer stator 16 and the inner stator 18. By the interaction of the flux
formed between the outer stator 16 and the inner stator 18 and the flux formed
by the magnet 22, the magnet 22 is linearly moved in an axial direction. When the
direction of a current applied to the winding coil 20 is changed in turn, the magnet

22 is linearly and reciprocally moved as the direction of the flux of the winding coil
20 is changed.
Then, as the motion of the magnet 22 is transferred to the piston 26 by the
magnet holder 24, the piston 26 is linearly and reciprocally moved inside the
cylinder 28, thereby compressing a refrigerant.
That is, when the piston 26 is retreated, the refrigerant is supplied to the
compression chamber 36 through the suction opening 30 formed at the piston 26.
When the piston 26 advances, the suction opening 30 is closed by the suction
valve 32 and the refrigerant inside the compression chamber 36 is compressed,
which is then discharged through the discharge pipe 4.
The lubricant 50 filled in the hermetic container 6 is pumped by the
operation of the lubricant pumping unit 40 and supplied to the frictional portion
between the piston 26 and the cylinder 28 through the lubricant supply passage
42, thereby performing a lubricating operation.
The refrigerant compressed by the reciprocating compressor constructed
and operated as described above is a natural refrigerant which is environment-
friendly and has combustibility and explosiveness.
As the natural refrigerant, an organic compound refrigerant consisting of
only carbon and hydrogen is mainly used. Among organic compound refrigerants,
hydrocarbon, consisting of only carbon and hydrogen, has no toxicity, is
chemically stable, has a zero ozone depletion potential and a very low global
warming index. Hydrocarbon includes R50 (methane), R170 (ethane), R290
(propane), R600 (butane), R600a (isobutene), R1270 (prophylene), etc.

Especially, isobutene (R600a) is hydrocarbon-based, has a molecular
formula of CH (CH3)3, and is environment-friendly natural gas which does neither
damage an ozone layer nor affect a greenhouse effect, and as such it is used as
a refrigerant compressed by the reciprocating compressor of the present
invention.
As the lubricant 50 for making a lubricating operation for the reciprocating
compressor of the present invention, a mineral oil is used which has a favorable
compatibility with hydrocarbon and satisfies physical and chemical characteristics.
The mineral oil is divided into a paraffin-based one and a naphtan-based
one. In the present invention, the paraffin-based mineral lubricant is used.
It is preferred that the paraffin-based lubricant has a density of
0.866-0.880 g/cm3 at a temperature of 15°C.
A flash point of the paraffin-based lubricant varies depending on a size and
a type of the reciprocating compressor. Preferably, it is above 140°C, and it can
be below 165°C, below 175°C, below 185°C and below 200°C according to the
type of an adopted compressor.
A kinematic viscosity of the paraffin-based lubricant is preferably 7.2-21.8
mm2/s at a temperature of 40°C, and most preferably, it is 8.29 mm2/s and 10.3
mm2/s depending on the size and type of an adopted reciprocating compressor.
A viscosity index of the paraffin-based lubricant is preferably 73-99.
A flow point of the paraffin-basedjubricant is preferably below -25°C.
A total acid number of the paraffin-based lubricant is below 0.01 mgKOH/g.

The total acid number of the lubricant, representing an amount of an acid
component contained in an oil, indicates an amount of potassium hydroxide
required for neutralizing an acid component contained in 1 g of sample oil by the
number of mg.
A water content of the paraffin-based lubricant is preferably below 20 ppm.
A breakdown voltage of the paraffin-based lubricant is preferably above 30
kV.
As so far described, the reciprocating compressor for compressing a
refrigerator of the present invention has such an advantage that since it uses the
paraffin-based lubricant, a sort of the mineral oil with an excellent compatibility
with the hydrocarbon, a natural refrigerant, compressed by the reciprocating
compressor, the lubricating performance is improved and a life span of the
reciprocating compressor is lengthened.
It will be apparent to those skilled in the art that various modifications and
variations can be made in the reciprocating compressor of the present invention
without departing from the spirit or scope of the invention. Thus, it is intended that
the present invention cover modifications and variations of this invention provided
they come within the scope of the appended claims and their equivalents.

WE CLAIM :
1. A reciprocating compressor for compressing a refrigerant comprising:
a hermetic container to which a suction pipe and a discharge pipe are
connected;
a driving unit having a stator fixed inside the hermetic container and a
mover disposed spaced apart from the stator and linearly and reciprocally moved
according to an interaction with the stator;
an organic compound refrigerant sucked into the suction pipe, having a
combustibility and expressiveness and consisting of only carbon and hydrogen;
a compression unit for receiving a reciprocal motional force of the driving
unit and making a compression operation on the organic compound refrigerant;
a mineral-based lubricant filled at a lower portion of the hermetic
container; and
a lubrication unit for supplying the mineral-based lubricant to each
motional portion of the driving unit and the compression unit and performing a
lubricating operation,
characterized in that the lubricant has a water content of below 20 ppm.
2. The reciprocating compressor as claimed in claim 1, wherein the stator
comprises:
an outer stator fixed at the hermetic container;
an inner stator disposed with a certain air gap with an inner circumferential
surface of the outer stator; and
a winding coil would at one end of the outer stator and the inner stator, to
which power is applied from an external source, and
the mover comprises:
magnets disposed at regular intervals between the outer stator and the
inner stator and being linearly and reciprocally moved when power is applied to
the winding coil; and
a magnet frame having the magnets mounted thereon and transmitting a
linear and reciprocal motional force to the compression unit.

3. The reciprocating compressor as claimed in claim 1, wherein the
compression unit comprises:
a piston connected to the mover and linearly and reciprocally moved;
a cylinder, into which the piston is slidably inserted, for forming a certain
compression chamber;
a suction valve mounted at a refrigerant passage formed at the piston and
preventing a backflow of the refrigerant after being introduced into the
compression chamber; and
a discharge valve mounted at the front side of the cylinder and performing
an opening and closing operation of the compressed refrigerant.
4. The reciprocating compressor as claimed in claim 1, wherein the
lubrication unit comprises:
a lubricant pumping unit for pumping the lubricant filled as much as a
certain amount at a lower portion of the hermetic container; and
a lubricant supply passage for supplying the lubricant pumped by the
lubricant pumping unit to a frictional portion between the piston and the cylinder.
5. The reciprocating compressor as claimed in claim 1, wherein the
refrigerant is isobutane (R600a) which is hydrocarbon-based and has a
molecular formula of CH (CH3)3.
6. The reciprocating compressor as claimed in claim 1, wherein the lubricant
is a paraffin-based lubricant.
7. The reciprocating compressor as claimed in claim 1, wherein the lubricant
has a density of 0.866-0.880 g/cm3at a temperature of 15°C and a flash point of
above 140°C.

8. The reciprocating compressor as claimed in claim 1, wherein the lubricant
has a kinematic viscosity of 7.2-21.8 mm2/s at a temperature of 40°C and a
viscosity of 73~79.
9. The reciprocating compressor as claimed in claim 1, wherein the lubricant
has a flow point of below -25°C and a total acid number of below 0.01 mgKOH/g.
10. The reciprocating compressor as claimed in claim 1, wherein the lubricant
has a breakdown voltage of above 30kv.

A reciprocating compressor includes a driving unit (10) disposed inside a hermetic container (86) and generating
a reciprocal motional force, a compression unit (10) for performing a compressing operation or. a refrigerant upon receiving the
reciprocal motional force generated from the dnving unit (8); and a lubrication unit (12) for supplying a lubricant to each motional
portion of the driving unit (8) and the compression unit (10) to perform a lubrication operation. Hydrocarbon consisting of carbon
and hydrogen, a sort of natural refrigerant, is used as the refrigerant. The lubricant is a paraffin-based mineral lubricant, which is a
sort of mineral oil and well harmonized with the natural refrigerant used for a refrigerator. Accordingly, a lubricating performance
is improved and thus a performance of the reciprocating compressor can be enhanced.

Documents:

1102-KOLNP-2005-CORRESPONDENCE.pdf

1102-KOLNP-2005-FORM-27.pdf

1102-kolnp-2005-granted-abstract.pdf

1102-kolnp-2005-granted-assignment.pdf

1102-kolnp-2005-granted-claims.pdf

1102-kolnp-2005-granted-correspondence.pdf

1102-kolnp-2005-granted-description (complete).pdf

1102-kolnp-2005-granted-drawings.pdf

1102-kolnp-2005-granted-examination report.pdf

1102-kolnp-2005-granted-form 1.pdf

1102-kolnp-2005-granted-form 18.pdf

1102-kolnp-2005-granted-form 3.pdf

1102-kolnp-2005-granted-form 5.pdf

1102-kolnp-2005-granted-gpa.pdf

1102-kolnp-2005-granted-reply to examination report.pdf

1102-kolnp-2005-granted-specification.pdf

1102-KOLNP-2005-PA.pdf


Patent Number 228051
Indian Patent Application Number 1102/KOLNP/2005
PG Journal Number 05/2009
Publication Date 30-Jan-2009
Grant Date 28-Jan-2009
Date of Filing 08-Jun-2005
Name of Patentee LG ELECTRONICS INC.
Applicant Address 20, YOIDO-DONG, YOUNGDUNGPO-GU, SEOUL 150-010
Inventors:
# Inventor's Name Inventor's Address
1 KWON GI-BONG DAEDONG APT. 608-1301, SEOKBONGMAEUL, SAMMOON-LI, JANGYU-MYEON, GIMHAE, GYUNGSANGNAM-DO 621-831
2 JUNG WON-HYUN SEONGWON 1ST APT. 106-404, NAMYANG-DONG, CHANGWON, GYUNGSANGNAM-DO 641-751
3 LEE SU-WON SEONGWON 1ST APT. 113-1302, NAMYANG-DONG, CHANGWON, GYUNGSANGNAM-DO 641-751
4 LEE DONG-WON DAEDONG APT. 107-1204, SANGNAM-DONG, CHANGWON, GYUNGSANGNAM-DO 641-777
PCT International Classification Number F04B 39/02
PCT International Application Number PCTKR2003/001374
PCT International Filing date 2003-07-10
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10-2002-0081897 2002-12-20 Republic of Korea