Inverter-controlled sealed compressor

Details Inverter-controlled sealed compressor Inverter-controlled sealed compressor

1998-08-11

2001-02-06

Kamen, Noah P. (Department: 3747)

Pumps

Condition responsive control of pump drive motor

By control of electric or magnetic drive motor

C417S423700

Reexamination Certificate

active

06183205

ABSTRACT:

TECHNICAL FIELD
The present invention generally relates to a sealed compressor for use in refrigerating systems and, more particularly, to the sealed reciprocating compressor of a type controlled by an inverter controller to allow the compressor to provide a variable power.
BACKGROUND ART
A reciprocating compressor currently employed in a refrigerator for home use has no variable power feature and is generally operated at a predetermined power source frequency, for example, 50 or 60 Hz in Japan.
Also, the reciprocating compressor is generally of a structure wherein a sealed housing has a low internal pressure and employs a high pressure discharge tube through which a compressed gaseous medium is discharged to the outside of the sealed housing. An example of those reciprocating compressors is disclosed in Japanese Laid-open Patent Publication (unexamined) No. 5-126044.
For further discussion of the prior art reciprocating compressor, reference will be made to
FIG. 3
of the accompanying drawings. The prior art reciprocating compressor shown therein comprises a generally cylindrical sealed housing
1
accommodating therein an electrical element (not shown) including a drive motor and a compressor element
6
. The compressor element
6
comprises a cylinder
2
, a cylinder head
3
, a reciprocating piston
4
and a cranking member
5
. The sealed housing
1
includes an exhaust muffler
7
disposed at a location laterally of the cylinder
2
and a discharge tube
8
extending completely across a wall of the sealed housing
1
and soldered to the sealed housing
1
at a portion thereof which extends through the wall of the sealed housing
1
. The exhaust muffler
7
and the discharge tube
8
are connected with each other by means of a generally tortuous coupling tube
9
disposed inside the sealed housing
1
. The sealed housing
1
also include a coil spring
10
mounted around the tortuous coupling tube
9
for resonance suppression.
In the prior art reciprocating compressor of the structure shown in
FIG. 3
, the electric element is operated at a predetermined power source frequency, for example, 50 or 60 Hz in Japan. Accordingly, the drive motor forming a part of the electric element is driven at a predetermined rotational speed at all times with its rotary drive translated by the cranking member
5
into a reciprocating motion that is assumed by the reciprocating piston
4
within the cylinder
2
. The reciprocating motion of the piston
4
causes a gaseous refrigerant sucked from an external supply system (not shown) to be compressed and subsequently discharged to the exhaust muffler
7
through the cylinder head
3
. The compressed refrigerant in the exhaust muffler
7
flows through the coupling tube
9
and then to the outside of the sealed housing
1
through the discharge tube
8
.
During the flow of the compressed refrigerant through the coupling tube
9
, the coupling tube
9
is apt to generate obnoxious noise in resonance to a pulsating motion of the compressed refrigerant within the coupling tube
9
and the operating frequency of the electric element. However, generation of the obnoxious noise is suppressed by the use of the coil spring
10
.
On the other hand, in the refrigerator for home use, the need has been realized to lower the output capacity during a low load operating condition to thereby minimize a power consumption. In other words, although the coupling tube
9
employed in the prior art reciprocating compressor is designed to successfully suppress resonance when the reciprocating compressor is operated at the specific frequency of 50 or 60 Hz, the prior art reciprocating compressor still has a problem associated with the resonance of the coupling tube
9
when operated at a low frequency. Therefore, no variable-capacity refrigerator for home use has yet been made available in the market.
Accordingly, the present invention is intended to provide an improved compressor having a variable power that is substantially free from the problem associated with resonance.
DISCLOSURE OF THE INVENTION
In accomplishing the above and other objectives, the present invention makes use of an inverter controller with which the electric element of the sealed compressor can be operated at a frequency effective to avoid resonance of the coupling tube. The frequency at which the coupling tube tends to resonate can be determined empirically.
More specifically, the sealed compressor according to the present invention comprises a sealed housing having an interior communicated to outside thereof through a discharge tube, a compressor element accommodated within the sealed housing, an electric element accommodated within the sealed housing for driving the compressor element, and a coupling tube fluid-connecting the compressor element and the discharge tube within the sealed housing. This sealed compressor is characterized by an inverter controller which can operate the electric element at a plurality of operating frequencies other than the frequency at which the coupling tube tends to undergo a resonant motion for operating the electric element at one of these frequencies.
Preferably, at least one of the operating frequencies other than the frequency of resonance of the coupling tube is equal to or substantially equal to the power source frequency, that is, the frequency of the electric power available from a commercial power outlet. This is particularly advantageous in that no design change may be made to the existing coupling tube and the electric element can be driven without being accompanied by the undesirable resonance of the coupling tube.


REFERENCES:
patent: 3691785 (1972-09-01), Ruff et al.
patent: 5493868 (1996-02-01), Kikuiri et al.
patent: 4-270864 (1992-09-01), None
patent: 05126044 (1993-05-01), None
patent: 07337057 (1995-12-01), None
patent: 08086294 (1996-04-01), None

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