Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Reexamination Certificate
2002-01-23
2002-11-12
Freay, Charles G. (Department: 3746)
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
C417S410500, C417S426000, C417S301000, C417S287000, C417S440000, C417S308000
Reexamination Certificate
active
06478550
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a multi-stage capacity-controlled scroll compressor which enables partial load operation in lower capacity regions.
BACKGROUND ART
Conventionally, as a scroll compressor which enables partial load operation with a bypass hole formed in a scroll, there has been available one as shown in FIG.
8
and
FIG. 9
, which is a sectional view taken along the line X—X of
FIG. 8
(Japanese Patent Laid-Open Publication HEI 9-170573). This scroll compressor is an asymmetrical spiral-type scroll compressor in which a scrolling end of a first scroll
1
is &pgr; (rad) longer in involute angle than a scrolling end of a second scroll
2
. A first fluid working chamber A defined by an inner surface of the first scroll
1
and an outer surface of the second scroll
2
, and a second fluid working chamber B defined by an outer surface of the first scroll
1
and an inner surface of the second scroll
2
are alternately opened and closed to a single low-pressure port
3
. A common bypass hole
4
common to the first fluid working chamber A and the second fluid working chamber B is provided at a point j which is a point about one-scroll inwardly unwound from an outermost side contact point E of the second scroll
2
with the first scroll
1
.
Then, a valve hole
5
communicating with the common bypass hole
4
is formed in the first scroll
1
, and a bypass passage
6
communicating with the low-pressure port
3
is formed in a side portion of the valve hole
5
. In the valve hole
5
, a stepped cylindrical bypass valve
7
for opening and closing the common bypass hole
4
is internally fitted so as to be slidable. Also, a coil spring
8
is engaged with the stepped portion of the bypass valve
7
, and an upper portion of the bypass valve
7
is closed by a lid member
9
and thereby partitioned from a discharge dome
10
to define an operating-pressure chamber
11
. In addition, an operating-pressure line
15
communicated selectively with a low-pressure line
13
or a high-pressure line
14
by a solenoid valve
12
is connected to the operating-pressure chamber
11
via a joint tube
16
. Reference numeral
17
denotes a capillary tube for preventing shortcircuit between the high-pressure line
14
and the low-pressure line
13
, numeral
18
denotes a casing, and numeral
19
denotes a high-pressure port.
As described above, the common bypass hole
4
is formed at the point j, which is a point about one-round inwardly unwound from the outermost side contact point E of the second scroll
2
with the first scroll
1
. Therefore, when high-pressure gas is supplied to the operating-pressure chamber
11
of the bypass valve
7
by closing the solenoid valve
12
and then the bypass valve
7
is closed, discharge capacity becomes the full capacity (100%). On the other hand, when low-pressure gas is supplied to the operating-pressure chamber
11
of the bypass valve
7
by opening the solenoid valve
12
and then the bypass valve
7
is opened, the discharge capacity becomes about 60% of the full capacity because the position of the common bypass hole
4
serves as a compression start point. In this way, the discharge capacity of the scroll compressor is switched between 100% and 60%.
In addition, it is also possible to provide two common bypass holes at a position which is about ¾-round inwardly unwound from the outermost side contact point E of the second scroll
2
with the first scroll
1
, and another position which is a one-round inwardly unwound therefrom, so that three discharge capacities, 100%, 70% and 60%, can be obtained.
However, the above multi-stage capacity-controlled scroll compressor of the prior art has the following problems. First, because its volume ratio Vr considerably lowers during a 50% or lower partial load operation, there is a problem that the operational range is limited.
For example, in the case where the intrinsic volume ratio Vr of the first and second scrolls
1
,
2
is Vr =2.3, since the volume ratio Vr needs to be not less than “1” even with a partial load as a compressor, the critical partial load ratio is 1/2.3=0.44, that is, a 44% operation is a limit. Indeed increasing the intrinsic volume ratio Vr causes the critical partial load ratio to lower so that a 50% or lower partial load operation is enabled, but the efficiency at the full load would be lowered in that case, conversely, so that increasing the intrinsic volume ratio Vr could not be adopted. However, in a multi-type air conditioner in which one outdoor unit serves for a plurality of indoor units, a 20% to 30% load operation is necessarily required so that when the conventional multi-stage capacity-controlled scroll compressor is applied to this multi-type air conditioner, there would arise problems that the compressor runs and stops frequently, or that optimum conditions for air-conditioning cannot be set.
Also, as a load-controlled scroll compressor, there has been available a method using inverter control of motors besides the above scroll compressor. In this case, unfortunately, an inverter circuit is required, leading to a great cost increase. Particularly in large-size inverters, there is a further problem that harmonics would be generated. There is still another problem of lubrication failure during the inverter operation, which causes a reliability deterioration of the compressor as yet another problem.
Furthermore, when a multiplicity of common bypass holes are formed with an aim of a low partial load operation of 50% or lower as described above, machinability or assemblability deterioration maybe incurred or rigidity may deteriorate because of the common bypass holes formed at central portions of the first and second scrolls. Besides, because the gas load within the scrolls of the first and second scrolls decrease to a large extent, the gas load and the centrifugal load of the movable-side second scroll are unbalanced, so that malfunction such as lubrication failures at a pin bearing (not shown) or the like may occur, or that the second scroll. may be turned over, as further problems.
DISCLOSURE OF THE INVENTION
Therefore, an object of the present invention is to provide a multi-stage capacity-controlled scroll compressor which is capable of changing 50% or lower partial load operation in multiple stages and which is low in price and high in reliability.
In order to achieve the aforementioned object, there is provided a multi-stage capacity-controlled scroll compressor comprising:
a first bypass passage formed at a specified position in a compression chamber and serving for returning compressed gas present in a fluid working chamber to a suction port;
first opening/closing means for opening and closing the first bypass passage;
a second bypass passage for communicating discharge side and suction side with each other;
second opening/closing means for opening and closing the second bypass passage and for, with the second bypass passage opened, letting high-pressure gas on the discharge side escape to the suction side by a specified quantity.
With this constitution, the second opening/closing means opens and closes the second bypass passage, by which the load of the compressor can be switched between 100% and a first specified %. On the other hand, the first opening/closing means opens and closes the first bypass passage, by which the discharge capacity of the compressor can be switched between 100% and a second specified %. Accordingly, in combinations of the opening and closing operations of the first opening/closing means and the opening and closing operations of the second opening/closing means, effective load of the compressor can be changed over in four stages. In this case, the discharge capacity of the compressor can be changed over only to the second specified % by the first opening/closing means. Therefore, if the fixed volume ratio for the compressor and the second specified % are so set that the volume ratio at which the discharge capacity of the compressor becomes the second specified % becomes 1 or more, then the
Hagiwara Shigeki
Kuroiwa Hiroyuki
Matsuba Kenji
Shibamoto Yoshitaka
Daikin Industries Ltd.
Freay Charles G.
Solak Timothy P.
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