Linear compressor

Details Linear compressor Linear compressor

2002-07-24

2004-06-29

Yu, Justine R. (Department: 3746)

Pumps

Motor driven

Electric or magnetic motor

Reexamination Certificate

active

06755627

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 2002-5865, filed Feb. 1, 2002, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to linear compressors and, more particularly, to a linear compressor provided with an anti-collision device for preventing a piston from excessively moving past an upper dead center position of the linear compressor inside a cylinder to collide against the cylinder head having a suction valve.
2. Description of the Related Art
As well known to those skilled in the art, a compressor is a machine that sucks and compresses gas refrigerant in a refrigerating system or an air conditioning system, such as a refrigerator or an air conditioner, by performing a refrigeration cycle. Such compressors have been typically classified into three types: reciprocating compressors, rotary compressors and linear compressors. In the linear compressors, a linear motor is used as a drive unit linearly reciprocating a piston to compress gas refrigerant and is low in energy loss for the drive unit, thus being high in energy efficiency in comparison with the other types of compressors.
FIG. 1
is a view, showing the construction of a conventional linear compressor.
As shown in
FIG. 1
, the conventional linear compressor comprises a drive unit
2
and a compressing unit
3
, which are housed in a hermetic casing
1
. The drive unit
2
generates drive power when supplied by electricity, while the compressing unit
3
sucks gas refrigerant and compresses the gas refrigerant using the drive power transmitted from the drive unit
2
.
The compressing unit
3
comprises a cylinder block
3
a
having a cylinder
3
b
, with a cylinder head
3
c
assembled with a lower end of the cylinder block
3
a
and provided with a suction valve
8
a
and an exhaust valve
8
b
guiding inlet and outlet gas refrigerant. A piston
3
d
is movably received in the cylinder
3
b
such that the piston
3
d
linearly reciprocates in the cylinder
3
b
using the drive power transmitted from the drive unit
2
.
The drive unit
2
, which is a linear motor, comprises a cylindrical inside stator
4
fitted over the cylinder
3
b
, and a cylindrical outer stator
5
which is arranged such that the cylindrical outside stator
5
surrounds the cylindrical inside stator
4
with an annular gap defined between the two stators
4
and
5
. A magnet
6
is positioned in the gap formed between the two stators
4
and
5
such that the magnet
6
vertically reciprocates in the gap.
The cylindrical outside stator
5
is fabricated by closely layering a plurality of steel sheets
5
a
in a radial direction, thus forming a cylindrical shape. A coil
5
b
is wound in the cylindrical outside stator
5
, and so the cylindrical outside stator
5
generates a magnetic flux when an alternating current AC is applied to the coil
5
b
of the cylindrical outside stator
5
. The lower end of the cylindrical outside stator
5
is seated on a first support frame
3
e
, which extends outward in a radial direction from a lower end of the cylinder block
3
a
. An upper end of the cylindrical outside stator
5
is supported by a second support frame
3
f
, which is assembled with the first support frame
3
e
using a plurality of bolts
9
.
The cylindrical inner stator
4
is fabricated by regularly arranging a plurality of steel sheets
4
b
in a radial direction around a cylindrical holder
4
a
. This cylindrical inside stator
4
is positioned outside the cylinder
3
b
, and forms a complete electromagnetic circuit of the linear motor in combination with the cylindrical outside stator
5
having the coil
5
b.
The magnet
6
is arranged such that the magnet
6
vertically reciprocates in the gap between the two stators
4
and
5
, and is connected to the piston
3
d
. Therefore, the piston
3
d
linearly reciprocates in the cylinder
3
b
at the same time as a linear reciprocating action of the magnet
6
. A resonant spring
7
, as shown in
FIG. 1
, is used to enhance a reciprocating force of the piston
3
d.
When the alternating current AC is applied to the coil
5
b
of the cylindrical outside stator
5
, the coil
5
b
generates a magnetic flux. This magnetic flux of the coil
5
b
cooperates with the magnetic field of the magnet
6
, thus allowing the magnet
6
and the piston
3
d
to reciprocate in a vertical direction at the same time.
When the piston
3
d
moves from a stop position to a lower dead center position, as shown by the arrow “B” of
FIG. 1
, during a reciprocating action of the piston
3
d
, the suction valve
8
a
is opened, while the exhaust valve
8
b
is closed. Gas refrigerant is sucked from a suction chamber into the cylinder
3
b
. When the piston
3
d
moves to the upper dead center position, as shown by the arrow “A” of
FIG. 1
, the suction valve
8
a
is closed, while the exhaust valve
8
b
is opened to discharge the compressed gas refrigerant from the hermetic casing
1
.
In a conventional linear compressor, a natural frequency of the resonant spring
7
, according to a mass of both the piston
3
d
and the magnet
6
, is set to be substantially equal to a frequency of the alternating current AC applied to the coil
5
b
of the cylindrical outside stator
5
, and the drive unit
2
can therefore generate high drive power by resonance of the piston
3
d
, magnet
6
and resonant spring
7
. An amplitude of both the reciprocating piston
3
d
and the magnet
6
is regulated by controlling an applied voltage. To allow the piston
3
d
to stably reciprocate with a predetermined amplitude, a separate control unit (not shown) is provided, which is capable of stably controlling the amplitude of the piston
3
d.
In the conventional linear compressor, a volumetric efficiency of the compressor varies in accordance with a clearance volume determined by a minimum gap between the cylinder head
3
c
and the upper dead center position of the piston
3
d
. Accordingly, higher volumetric efficiency of the linear compressor can be obtained as the minimum gap distance is reduced. Therefore, when high volumetric efficiency of the linear compressor is desired, the clearance volume should be reduced as much as possible by controlling the amplitude of the piston
3
d
such that the piston
3
d
can closely approach the cylinder head
3
c
and the suction valve
8
a
during an operation of the linear compressor.
However, during a linear reciprocating action of the piston
3
d
in the cylinder
3
b
of the conventional linear compressor, behavior of the piston
3
d
may unexpectedly become unstable, thus abruptly and rapidly increasing the amplitude of the piston
3
d
due to unexpected internal or external causes, such as unexpected rapid variation in the applied voltage or unexpected rapid variation in a pressure of a refrigeration cycle.
When the amplitude of the piston
3
d
rapidly increases as described above, the end of the piston
3
d
may collide with the suction valve
8
a
and/or the cylinder head
3
c
, thus generating operational noise, as well as causing serious damage or breakage of the cylinder head
3
c
, the suction valve
8
a
, and/or the piston
3
d.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a linear compressor, which is provided with an anti-collision device for preventing a movement of a piston past an upper dead center position of the piston in a cylinder, thereby preventing the piston from colliding with a suction valve and/or a cylinder head, and attenuates impacts resulting from an excessive movement of the piston.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To accomplish the above and other

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