Dual capacity compressor

Details Dual capacity compressor Dual capacity compressor

2002-02-20

2004-06-29

Yu, Justine (Department: 3746)

Pumps

Condition responsive control of drive transmission or pump...

Adjustable cam or linkage

C092S013300, C092S013000

Reexamination Certificate

active

06755624

ABSTRACT:

TECHNICAL FIELD
The present invention relates to compressors for compressing a working fluid, such as refrigerant, to a required pressure, and more particularly, to a compressor of which compression capacity changes with a direction of rotation.
BACKGROUND ART
The dual capacity compressor is a kind of reciprocating type compressor of which piston stroke as well as a compression capacity vary with an eccentric sleeve rotatably coupled to a crank pin of a crankshaft, a position of which with respect to the crank pin is dependent on a direction of rotation of the motor and the crankshaft. Since the dual capacity compressor has a compression capacity that can be varied with a required load, the dual compressor is used widely in apparatuses which require compression of working fluid, particularly in home appliances operative in a refrigeration cycle, such as a refrigerator, for enhancing an operation efficiency. A U.S. Pat. No. 4,236,874 discloses a general dual capacity compressor, referring to which a related art dual capacity compressor will be explained, briefly.
FIG. 1
illustrates a section of a dual capacity compressor disclosed in U.S. Pat. No. 4,236,874, and
FIG. 2
illustrates operation of the dual capacity compressor, schematically.
Referring to
FIG. 1
, the dual capacity compressor is provided with a piston
7
in a cylinder
8
, a crankshaft
1
, a crank pin
3
having a center
3
a
eccentric from a center of the crankshaft
1
a
, an eccentric ring
4
coupled on the crank pin
3
, and a connecting rod
6
connected to the eccentric ring
4
and the piston
7
, as key components. The eccentric ring and the connecting rod
6
are rotatable both with respect to the other, and the center
3
a
of the crank pin. There are release areas
9
in contact surfaces of the crank pin
3
and the eccentric ring
4
, and a key
5
for coupling the crank pin
3
and the eccentric ring
4
together fitted in the release areas for coupling the crank pin
3
and the eccentric ring
4
. The operation of the dual capacity compressor with respect to the compression capacity will be explained.
Referring to
FIG. 2
, in the dual capacity compressor, a stroke of the piston
7
is regulated by an eccentricity varied with a position of the eccentric ring
4
, and, if a large capacity is required, the crank shaft
1
is rotated in a clockwise direction (regular direction) and, if a small capacity is required, the crank shaft
1
is rotated in a counter clockwise direction (reverse direction). In detail,
FIG. 2A
illustrates a moment the piston
7
is at a top dead center during a clockwise rotation, and
FIG. 2B
illustrates a moment the piston
7
is at a bottom dead center during a clockwise rotation, when the stroke Lmax is the greatest because the eccentricity is the greatest. And,
FIG. 2C
illustrates a moment the piston
7
is at a bottom dead center during a counter clockwise rotation, and
FIG. 2D
illustrates a moment the piston
7
is at a top dead center during a counter clockwise rotation, when the stroke Lmin is the smallest because the eccentricity is the smallest.
However, during the foregoing operation, the crank pin
3
and the eccentric ring
4
are involved in centrifugal forces, respectively caused by their rotation around the center
1
a
of the crank shaft, exerting on a point between the shaft center
1
a
and the pin center
3
a
, and a point on a line extended from the shaft center
1
a
to the a center of gravity of the ring
4
a
, respectively. Therefore, different from
FIGS. 2A and 2B
, as lines of actions are not one the same line, a local rotating moment is occurred at the eccentric ring
4
as a product of a vertical distance ‘d’ to the pin
3
and its own centrifugal force, acting in a direction the same with a direction (counter clockwise direction) of rotation of the crank shaft
1
. Since the crank pin
3
and the eccentric ring
4
are members that can make relative movement to each other, the rotating moment causes a relative rotation of the eccentric ring
4
in a direction of rotation of the crank shaft
1
, releasing the key
5
from the crank pin
3
and the eccentric ring
4
, and leaving the eccentric ring
4
and the key
5
to move together as shown in FIG.
3
.
Moreover, as shown in
FIG. 3
, during operation, for an example, in the clockwise direction, a pressure ‘P’ (a pressure of re-expansion of the working fluid) in the cylinder after compression pushes the eccentric ring
4
to a direction of rotation of the crank shaft
1
, to cause the eccentric ring
4
to make a relative rotation with respect to the crank pin
3
in a rotation direction of the crank shaft. At the end, such a relative rotation makes operation of the compressor unstable, and performance of the compressor poor.
In fact, the relative rotation is occurred because the key
5
can not fix the crank pin
3
and the eccentric ring, perfectly. The key
5
rolls within the release area whenever the direction of rotation of the crank shaft is changed, to cause serious wear at respective contact surfaces, that shortens a lifetime of the compressor.
In the meantime, other than the U.S. Pat. No. 4,236,874, there are many patent publications that disclose technologies of the dual capacity compressors, which will be explained, briefly.
Similarly, U.S. Pat. No. 4,479,419 discloses a dual capacity compressor provided with a crank pin, eccentric cam and a key. The key is fixed to the eccentric cam, and moves along a track in a crank pin when a direction of rotation of the compressor is changed. However, since the key can not fix the crank pin and the eccentric cam perfectly, the U.S. Pat. No. 4,479,419 also has unstable operation caused by the relative rotation.
U.S. Pat. No. 5,951,261 discloses a compressor having an eccentric part with a bore of a fixed inside diameter formed across the eccentric part, and an eccentric cam with another bore with a diameter the same with the eccentric part formed at one side thereof. A pin is provided to the bore in the eccentric part, and a compression spring is provided to the bore in the eccentric sleeve. Accordingly, when the bores are aligned during rotation, the pin moves to the bore in the cam by a centrifugal force, that couples the eccentric part and the eccentric cam, together. However, since the U.S. Pat. No. 5,951,261 is provided with only one bore in the eccentric cam, the U.S. Pat. No. 5,951,261 can couple the eccentric part and the eccentric cam together only when the compressor rotates in a particular direction. Moreover, an operation reliability can not be secured, since an exact movement of the pin from the eccentric part to the cam through respective bores is difficult.
DISCLOSURE OF INVENTION
Accordingly, the present invention is directed to a dual capacity compressor that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a dual capacity compressor which can maintain a fixed eccentricity and make a stable operation even if the compressor is rotated in any directions that have different compression capacity.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
As explained, the inventor understands that the unstable operation of the dual capacity compressor is caused by a local centrifugal force of the eccentric sleeve, and an external load through the connecting rod and etc., during operation. Though such causes are not avoidable as far as an eccentric mechanism is used, the inventor understand that, if the crank pin and the eccentric sleeve can be fixed positively during operation, such a problem can be solve. Taking an idea of a key member that has such a fixing structure, the k

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