Refrigeration – Reversible – i.e. – heat pump – With flow control or compressor details
Reexamination Certificate
2001-07-11
2002-05-21
Doerrler, William (Department: 3744)
Refrigeration
Reversible, i.e., heat pump
With flow control or compressor details
C062S160000, C062S505000, C418S055500
Reexamination Certificate
active
06389837
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a scroll compressor incorporated in a reversible refrigerating cycle for an air conditioner, and more specifically, to a technique of switching between an internal high-pressure operation and an internal low-pressure operation and optimizing, during either operation, a thrust force that presses an orbiting scroll against a fixed scroll.
BACKGROUND ART
Scroll compressors comprise a refrigerant compressing section composed of a fixed scroll having a spiral wrap on a base plate and an orbiting scroll driven by an electric motor, the scrolls being engaged with each other. A low-pressure refrigerant that has completed its work during a refrigerating cycle is sucked from an outer peripheral side of the refrigerant compressing section, subsequently compressed as it approaches the center of the spiral, and then discharged as a high-pressure refrigerant from a discharge port formed in the center of the spiral.
During this refrigerant compressing operation, pressure from the interior of the refrigerant compressing section is always exerted on the orbiting scroll in a direction in which the pressure leaves the fixed scroll. Thus, such back pressure as resists the above pressure must be exerted on the orbiting scroll to prevent it from floating. A conventional example will be described with reference to FIG.
12
.
In a basic configuration, the scroll compressor
1
comprises a cylindrical hermetic shell
2
, and its interior is partitioned into a refrigerant discharge chamber
2
a
and a driving chamber
2
b
by means of a frame plate
3
. The refrigerant discharge chamber
2
a
has a refrigerant compressing section
4
housed therein and composed of a fixed scroll
4
a
and an orbiting scroll
4
b
that are engaged with each other.
Although not shown, the driving chamber
2
b
has an electric motor housed therein and contains a predetermined amount of lubricant. A drive shaft
5
of the electric motor is extended through the frame plate
3
to the refrigerant compressing section
4
in such a manner that a crank shaft
5
a
at its tip is connected to the orbiting scroll
4
b
. The drive shaft
5
has a oil filler hole
5
b
drilled therein, and a rear surface of the orbiting scroll
4
b
and the driving chamber
2
b
are in communication with each other via the oil filler hole
5
b.
The scroll compressor
1
as a conventional example is of an internal high-pressure type; the refrigerant discharge chamber
2
a
and the driving chamber
2
b
are in communication with each other via a communication hole
6
that penetrates the fixed scroll
4
a
and the frame plate
3
.
A low-pressure refrigerant that has completed its work during a refrigerating cycle (not shown) is sucked from an outer peripheral side of the refrigerant compressing section
4
through a sucking pipe
7
a
and then discharged as a high-pressure refrigerant from a discharge port
4
c
located in a central portion of the refrigerant compressing section
4
. The refrigerant is guided from the refrigerant discharge chamber
2
a
through a discharge pipe
7
b
to a four-way switching valve (not shown), with part of the refrigerant flowing through the communication hole
6
into the driving chamber
2
b.
Thus, the pressure in the driving chamber
2
b
increases and the pressure on the rear surface of the orbiting scroll
4
b
also increases due to a flow via the oil filler hole
5
b
, but the internal pressure from the interior of the refrigerant compressing section
4
exerted on the orbiting scroll
4
b
is not uniform. That is, the apparatus exhibits a pressure gradient such that the pressure is lower on the outer peripheral side of the spiral (low-pressure refrigerant sucking side) and increases toward the center of the spiral.
To exert back pressure corresponding to this pressure gradient on the orbiting scroll
4
b
, in this conventional example, the rear surface side of the orbiting scroll
4
b
is separated into a main back pressure chamber
8
a
on the central portion side and a secondary back pressure chamber
8
b
on the peripheral portion side by means of a sealing
8
so that the high pressure in the driving chamber
2
b
is exerted in the main back pressure chamber
8
a
, while intermediate pressure, which is lower than the above high pressure, is exerted in the secondary back pressure chamber
8
b
via a throttle valve
9
a.
A check valve
9
b
is provided between the secondary back pressure chamber
8
b
and the outer peripheral side of the spiral of the refrigerant compressing section
4
so as to allow an excess of pressure to escape toward the refrigerant compressing section
4
if the intermediate pressure in the secondary back pressure chamber
8
b
reaches a predetermined value.
In addition to the internal high-pressure type described in the conventional example, the scroll compressor includes an internal low-pressure type that sucks the low-pressure refrigerant having completed its work during the refrigerating cycle, into the driving chamber
2
b
, from which the refrigerant is guided to the refrigerant compressing section
4
.
Both in the internal high- and low-pressure types, the driving chamber (electric-motor chamber) is used as a circulating path for the refrigerant in order to prevent the electric motor from being overheated. Both of these types have the following advantages and disadvantages:
The internal high-pressure type is unlikely to have its performance significantly degraded by an overheated sucked gas, while the internal low-pressure type can be started up fast because an discharged gas is not cooled in the driving chamber during a heating operation.
In the internal low-pressure type, however, the lubricant in the compressor may be discharged to a heat exchanging circuit before being separated from a refrigerant gas, thus degrading the heat exchanging capability. Further, a sliding portion of the scroll may be seized due to an insufficient amount of lubricant in the compressor. In the internal low-pressure type, the sucked refrigerant gas is passed through the electric-motor chamber and overheated therein, so that its density is likely to decrease to degrade the performance.
The applicant has proposed a scroll compressor (for example, Japanese Patent Application published under Publication No. 2000-88386) that includes the advantages of both the internal high- and low-pressure types and that can switch between two operation modes in such a manner that the compressor operates as the internal high-pressure type during a cooling operation and as the internal low-pressure type during a heating operation.
In this scroll compressor, which can switch between the internal high- and low-pressure types, the pressure in the driving chamber varies depending on the operation mode, so that the above conventional method cannot exert a proper back pressure on the orbiting scroll. That is, during the internal low-pressure operation, the pressure in the driving chamber and thus the back pressure exerted on the orbiting scroll are low, possibly causing the orbiting scroll to be separated from the fixed scroll.
SUMMARY OF THE INVENTION
The present invention is adapted to solve the above problems, and its object is to provide a scroll compressor that allows a proper back pressure to be exerted on an orbiting scroll both during an internal high-pressure operation and during an internal low-pressure operation.
To attain this object, the present invention provides a scroll compressor comprising a hermetic shell having an interior partitioned into a refrigerant discharge chamber and a driving chamber by means of a frame plate, the refrigerant discharge chamber having a refrigerant compressing section housed therein and composed of a combination of a fixed scroll and an orbiting scroll, the driving chamber provided with an electric motor for driving the orbiting scroll, the scroll compressor being capable of switching between an internal high-pressure operation mode in which a high-pressure refrigerant generated in the refrigerant compressing section is transferre
Doerrler William
Fujitsu General Limited
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