Note: Descriptions are shown in the official language in which they were submitted.
~ACKGROUND OF THE INVENTIOM
Field of the Invention
The present invention relates to a rotary
compressor for use in a refrigerating apparatus.
Description of the Prior Art
In prior refrigerating apparatus, it is common
for a high temperature and high pressure gas in a closed
casing of a compressor to Elow into an evaporator which
is maintained at a low pressure in a refrigerating system
when the operation of a rotary compressor is suspended,
thereby increasing the heat load on the refrigerating
apparatus. Therefore, Japanese Patent Application No.
86447/1981 has proposed a rotary compressor which
incorporates a valve mechanism for cutting off flow of
low-pressure and high-pressure gas and designed to open
during the operation of the rotary compressor and close
~iuring the suspension of the rotary compressor, thereby
attaining reduction in the heat loss generated during
the suspension of the rotary compressor.
In a rotary compressor of the invention of the
above-mentioned application, a slide valve acting as a
valve for cutting off flow of high-pressure gas is
provided at a portion of a cylinder plate which consti-
tutes a compression element of the rotary compressor, and
an inlet port adapted to be opened and closed by means
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1 of a piston-like slider is connected at its one end to a
closed casing and an outlet port is connected to a
discharge pipe which extends through the closed casing.
The rotary compressor of this type also includes a reed
valve type check valve which serves as a valve for
cutting off flow of low-pressure gas, and is disposed
between a suction pipe and a cylinder. In the thus-
arranged rotary compressor, the high-pressure and
low-pressure gas cut-off valves are both closed when
the operation of the compressor is suspended, so that
the high-temperature and high-pressure gas in the closed
casing is prevented from flowing into the evaporator
through the condenser to cause any increase in the heat
load of the refrigerating apparatus. As the compressor
is operated, pressure difference between the closed casing
and the cylinder actuates the slider to communicate the
inlet port with the outlet port, and to open the high
pressure cut-off valve, thereby eeding pressurized gases
to the condenser. The low-pressure gas cut-off valve
is open by this time to afford a normal cooling operation.
The rotary compressors of the prior art suffer
from a problem is that since the high-pressure gas cut-
off valve is of a slide valve type, there is a limit
to its anti-leakage performance when closed. In order
2S to attain an improved anti-leakage performance, the
clearance between the slide valve and a valve cylinder
in which the slide valve moves must be maintained at a
minimal value. However, this requires improved work
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1 accuracy and increases the cost of machining and assembly
work such as matching assembly.
Further, foreign matters such as abrasion powder
generated by the rotating and sliding portions of the
rotary compressor during its operation may enter the
clearance, generating an hydraulic lock which may lead
to disabled operation of the rotary compressor.
In case an effective pressure sur~ace of a
spool valve is increased so as to reduce the pressure
difference required at the time of starting, a larger
space is required to enable mounting a high-pressure gas
cut-off valve, and noise may be generated during the
operation due to the increased weight of the rotary
compressor.
SU~ARY OF THE INVENTION
Accordingly, an object of the present invention
is to provide a rotary compressor which is improved in
anti-leakage performance when flow of a high-pressure
gas is cut off, and which permits cut-off of flow of a
high-pressure gas at a ~ow cost by employing a disc-type
valve.
A further object of the present invention is
to provide a rotary compressor having a high pressure
gas cut-off valve, of which inlet and outlet ports are
arranged to afford positive operation with small pressure
differences and eliminate reduction of the clearancesA
A still further object of the present invention
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1 is to provide a rotary compressor having a compact con-
struction in which a hlgh pressure gas cut~off valve is
incorporated in a compression element of a compressor.
A fur~her object of the present invention is
to provide a rotary compressor having an arrangement of
inlet and outlet ports which can reduce an amount of lap
associated with a high pressure gas cut-off valve and
the outlet port in spite of dispersion produced during
assembly, and having a high pressure yas cut-off valve
which is accommodated in a lim:ited space and has a small
pressure loss.
A further object of the present invention is
to provide a rotary compressor in which a collar-like
member is used to improve an efficiency of asse~bling
operation for a high pressure gas cut-off valve.
Another object of the present invention is to
provide a rotary compressor in which an efficiency of
assembling operation for a low pressure gas cut-off valve
having a bias spring is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a cross-sectional view of a rotary
compressor according to an embodiment of the present
invention;
Figs. 2 and 3 are sectional views taken along
the lines II - II and III - III of Fig. 1, respectively;
Fig. 4 is a sectional views taken along the
line IV - IV of Fig. 3;
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l Fig. 5 is a perspective view or an essential part
of a cylinder plate;
Fig. 6 is a perspective view of a collar;
Fig. 7 is an explodecl sectional view of a high-
pressure gas cut-off valve, illustrating how it is
assembled; and
Fig. 8 is an explodecl sectional view of a low-
pressure gas cut-off valve, illustrating how it is
assembled.
DESCRIPTION OF THE PRE~ERRED EMBODIMENTS
An embodiment of the present invention will be
hereinunder described with reference to the accompanying
drawings.
Referring first to Fiys. 1 and 2, reference
numeral 50 designates a rotary compressor which includes
a closed vessel 51, an electrically driven element 52
having a rotor 52a and a stator 52b, and a compression
element 53. Reference numeral 54 denotes a crankshaft
press fitted on the rotor 52a to extend substantially in
the horizontal direction, and rotatably supported by
bearing portions 55a and 56a formed in side plates 55
and 56, respectively. A cylinder plate 57 rotatably
supports a rotor 58 mounted on an eccentric portion 5~a
of the crankshaft 54. A compression chamber 60 defined
by the outer periphery of the rotor 58, the inner
periphery of the cylinder plate 57 and the side plates
55 and 56 is divided into a low-pressure chamber 61 and
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l a high~pressure chamber 62 by a vane 59. Reference
numeral 59a indicates a vane groove. The side plates 55
and 56 and the cylinder plate 57 are secured in a lamin2ted
state by bolts 63. Each bolt 63 is inserted in a bolt
hole 63a wit:-l clearance C provided therebetween, so that
the side plate 55 is allowed to move slightly in its
circumferential direction. A suction pipe 64 for intro-
ducing a refrigerant gas from an evaporator 65 to the
compression chamber 60 is secured in a press-fit bore
65 provided in the side plate 55. The end surface of
the press-fit bore 65 which faces the cylinder plate 57
constitutes a valve seat for a disc-shaped low-pressure
gas cut-off valve 66 which has three leg pieces 66a.
The low-pressure gas cut-off valve 66 is accommodated in
a suction passage 67 which is communicated to the press-
fit bore 65 and is located adjacent to the vane 59, and
which communicates with the compression chamber 60 for
applying a small force on the valve to maintain the same
in a closed position. A stepped portion 69 is provided
to limit the movement of the valve 66 when it is opened.
As shown in Fig. 8, the natural length of the
bias spring 68 is si~ed such that when the bias spring
68 and the low pressure gas cut-off valve 66 are mounted
from above with the cylinder plate 57 and the side plate
56 secured to each other beforehand, the respective
surfaces of the cylinder plate 57 of the valve 66 becomes
substantially flush with one another so as not to cause
the low pressure gas cut-off valve 66 to e~tend ~eyond
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1 the top surEace of the cylinder plate 57.
Re~erence numeral 70 designates a discharge
valve for in-troducing the refrigerant ~as, which has been
compressed in the compression chamber 60, directly or
through the intermediary of a precooler pipe (not shown)
into the closed vessel 51 (see Fig. 2). A high-pressure
gas cut-off valve unit 71 is disposed at substantially
the same level as that of the crankshaft 54, and includes
a high-pressure side inlet port 72 provided in the side
plate 55 to extend in the axial direction of the crank-
shaft 54, and a high-pressure side outlet port 74
connected to a discharge pipe 73 which extends through
the closed vessel 51. The inlet and outlet ports 72
and 74, as shown in ~igs. 3 and 4, are aligned side by
side in the normal direction of the cylinder plate 57
such that the outlet port 74 is disposed inside and the
inlet port 72 is disposed outside. The symbol o shown in
Fig. 3 represents the center of the crankshaft. In the
cylinder plate 57 is provided a valve cylinder 75 which
is common to and corresponds with the adjacent, respective
ports 72, 74, and which is provided at its bottom with
a low pressure side port 76. One end surface of a
disc-shaped circular high-pressure valve 77 is capable
of closing both the inlet and outlet ports 72 and 74,
while the other end surface thereof is capable of closing
- the low-pressure side port 76. Reference numeral 78
designates a bias spring which serves to constantly bias
the pressure side inlet and outlet ports 72, 74 toward
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l the closed position.
A collar 75a is placed insicle the valve cylinder
75, and is cylindrical and has a C-shaped cross-section,
as shown in Fig. 6. Since the collar 75a has a resilient
force tending to expand the collar outward, it can be
held with only its lower portion received in the valve
cylinder 75, as shown in Fig. 7. When assembling the
high-pressure valve 77, the bias spring 78 and the high-
pressure valve 77 are inserted in the collar 75a in that
order, and the collar 75a is then sunk into the valve
cylinder 75 by mounting the side plate 55 on the cylinder
plate 57. The low-pressure side port 76 is communicated
with the low-pressure chamber 61 of the compression
chamber 60 through a pressure passage 79. A channel
79a is mechanically machined or formed by sintering on
one end surface of the cylinder plate 57, and is closed
by the side pla~e 56 to constitute the pressure passage
79.
Although not shown here, a channel may be
alternatively machined on the side plate 56 and then
closed by the cylinder plate 57 to constitute the pressure
passage. In such a case, the low-pressure port 76 must
of course communicate with the pressure passage. A
pressure passage may also be directly drilled in the
cylinder plate 57.
The operation of the rotary compressor arranged
in the above described manner will now be described
below.
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1 When the operation of the rotary compressor is
suspended, as shown in Fig. 1, the low-pressure gas cut-off
valve 66 acting as a check valve is closed, and the
high-pressure gas cut-off valve 77 closes both the high-
pressure side inlet and outlet ports 72 and 7~. The
high-pressure gas cut-off valve 77 is closed by virtue
of the difference in pressure generated at the upstream
and downstream sides of the high-pressure side outlet port
74, i.e., the difference between .he condensing saturation
pressure at the temperature of the cooling chamber
containing the evaporator 65 and the sa-turation pressure
at the temperature of the closed vessel 51, as well as
by the slight amount of force of the bias spring 78.
Therefore, the high-temperature and high-pressure
gas contained in the closed vessel 51 is prevented from
flowing into the condenser 80 and evaporator 65, thereby
reducing the heat load on the evaporator 65.
When the operation of the rotary compressor is
started and the electrically driven element 52 is
electrically energized, the crankshaft 54 is rotated
so as to cause gas pressure drop in the low-pressure
chamber 61 of the compression chamber 60. This pressure
drop is produced positively in a very short period of
time despite the relatively loose clearance (amounting to
about 0.1 to 0.2 mm) provided between the high-pressure
gas cut-off valve 77 and the collar 75a mounted inside
of the valve cylinder 75, since the high-pressure side
inlet port 72 is closed. This pressure drop naturally
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1 leads to pressure drop in the pressure passage 79, the
low-pressure side port 76 and the valve cylinder 75, so
that pressure difference between the pressure in the high
pressure side inlet port 72, hence in the closed vessel
51 and the pressure in the valve cylinder 75 is applied
on the high pressure gas cut-ofE valve 77 to separate
the same from the high pressure side outlet port 72,
to which the valve 77 has strongly adhered. The high-
pressure gas cut-off valve 77, after the initial
separation thereof from the high-pressure side outlet
port 72, then closed the low-pressure side port 76
against the resilient force of the bias spring 78 with
the aid of the dynamic pressure of the gas fiow as well
as this pressure difference. Such closed position of the
low pressure side port 76 is maintained during the
operation of the compressor 50 by pressure difference
between the high pressure in the closed vessel 51 and
the low pressure in the low pressure chamber 61. At
this time, the high-pressure side inlet and outlet
ports 72 and 74 communicate with each other, so that
the high-pressure refrigerant gas flows from the closed
vessel 51 to the condenser 80. On the other hand, the
low-pressure gas cut-off valve 66 is also opened to
afford a normal cooling operation.
When the operation of the rotar~ compressor
is suspended and the crankshaft 54 stops its rotation,
the flow of gases through the suction pipe 64 is stopped,
so that the suction gas cut-off valve 66 is closed by
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1 the blas ~orce of the bias spring 8. The oil seal which
divides the compression chamber 60 into the high-pressure
and low-pressure chambers 63 and 61 is also broken, so
that the high-pressure gas in the closed vessel 51 builds
pressure in the low-pressure chamber 61 through~ for
example, the clearance between the vane 59 and the vane
groove 59a. This action eventually extends to the low-
pressure port 76 through the pressure passage 79. Such
extent of rise in pressure is attained in a relatively
short period of time (for example, about 10 to 20 seconds)
since the pressure passage 79 can be made small in volume.
As the gas pressures in the lo~-pressure side port 76 and
in the closed vessel 51 becomes substantially equal to
each other, the high-pressure gas cut-off valve 77 is
separated from the low-pressure side port 76 by means
of the resilient force of the bias spring 78 to close
both the high-pressure side inlet and outlet ports 72
and 74.
In consequence, during the suspension of the
operation of the rota.ry compressor, the high-temperature
and high-pressure gas contained in the closed vessel 51
is prevented from flowing into the condenser 80 and the
evaporator 65.
In addition, since the high-pressure side inlet
and outlet ports 72 and 74 are arranged side by side in
the normal direction of the cylinder plate 57, the change
which occurs in the amount by which the high-pressure
gas cut-off valve 77 overlaps the ports 72 and 74 can
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1 be reduced remarkably even if the cylinder plate 57 is
radially moved during the assembly as compared with the
case in which the inlet and outlet ports 72 and 7a were
arranged side by side in the circumferential direction of
the plate 57.
Assembly of the compression element 53 will be
described below with reference to Figs. 7 and 8. The
compression element 53 is assembled by successively
placing on the side plate 56 the cylinder plate 57 and
the side plate 55.
At this time, the natuxal length of the bias
spring 68 of the low-pressure gas cut-off valve 66 is
sized that the low-pressure gas cut-off valve 66 does
not extend beyond the upper surface of the cylinder plate
1~ 57 when set on the bias spring 68. On the other hand,
the high-pressure gas cut-off valve 77 is first assemble~
by setting the collar 75a in the valve cylinder 75 with
its upper portion extending beyond the upper surface o~
the cylinder plate S7 and then inserting in the collar
75a the bias spring 78 and the high-pressure gas cut-off
valve 77. The high-pressure gas cut-off valve 77 can
be prevented from moving in the collar 75a by the
presence of the bias spring 78 which requires to be
preloaded. The siae plate 55 is then placed on the
cylinder plate 57 from above to complete the assembly
of the collar 75a, high-pressure gas cut-off valve 77
and bias spring 78.
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