Refrigeration – Gas compression – heat regeneration and expansion – e.g.,...
Reexamination Certificate
2000-02-15
2002-11-19
Doerrler, William (Department: 3744)
Refrigeration
Gas compression, heat regeneration and expansion, e.g.,...
C060S520000
Reexamination Certificate
active
06481215
ABSTRACT:
TECHNICAL FIELD
The present invention relates to gas compressor-expanders wherein power is generated or refrigeration is effected utilizing the compression and/or expansion of a gas as in Stirling engines or Stirling chillers, and more particularly to gas compressor/expanders having a seal device for preventing lubricating oil from ingressing into a working space wherein a gas is compressed or expanded.
BACKGROUND ART
The fields of cutting-edge technologies, such as biotechnology and electronic devices, in recent years involve a pressing need to develop techniques for preserving various samples of materials at cryogenic temperatures. Attention has been directed especially to gas compressor/expanders, such as Stirling chillers, as means for realizing cryogenic temperatures for wide use in coolers for infrared sensors or superconductive devices, biomedical freezers or chillers, etc.
Such compressor/expanders comprise a piston or displacer (hereinafter referred to collectively as the “piston”) housed in a cylinder, connected to a piston rod and reciprocatingly movable within the cylinder for compressing and/or expanding a working gas, provided around the piston rod is a seal service for preventing lubricating oil in a mechanism chamber (crank chamber) from ingressing into a cylinder space at the rear of the piston.
FIG. 8
shows a gas compressor/expander having a conventional seal device and comprising a housing
112
formed with a crank chamber
111
, a cylinder
101
attached to the housing
112
for compressing or expanding a gas, and a piston
102
housed in the cylinder
101
reciprocatingly movable and connected to a crank mechanism (not shown) within the crank chamber
111
by a piston rod
103
, cross guide
104
and connecting rod
105
. The piston rod
103
extends through a partition wall
99
separating a space
106
at the rear of the piston from the crank chamber
111
and is provided with a seal member
107
for preventing lubricating oil in the crank chamber
111
from ingressing into the rear space
106
.
Used as the seal member
107
is a lip-type seal member having a U-shaped section and a higher sealing property against a flow from the crank chamber
111
to the rear space
106
than against the opposite flow. Unlike seal members having no directionality in sealing property, such as slipper seals having a resin ring on the slidable face, lip-type seal members have an excellent sealing property in one direction and are widely used in hydraulic mechanisms, etc.
However, unlike the hydraulic mechanism wherein one side of the seal member is always in contact with lubricating oil, the gas compressor/expander is not designed to positively supply lubricating oil from the crank chamber toward the seal member so as to prevent ingress of the lubricating oil into the working space to the greatest possible extent, presenting the problem that marked wear occurs on the seal member.
Although countermeasures are therefore taken as by applying grease or like lubricant on the contact face of the seal member in advance, the lubricant applied to the seal member is gradually removed by reciprocating strokes of the piston rod, so that the seal member still wears away markedly to entail the problem of shortening the life of the machine. Especially in the case where the seal member is directional in sealing property, the grease or like lubricant applied initially is scraped off toward the side of lower sealing property with the reciprocating movement of the piston rod to result in a noticeably impaired life.
On the other hand, JP-A No. 87854/1989 discloses a seal device, as shown in
FIG. 9
herein, and comprising a seal member
107
provided, at one side thereof toward a piston
102
, with an intermediate chamber
108
, and a second seal member
109
opposite to the seal member
107
in the directionality of sealing property and positioned between the intermediate chamber
108
and the piston
102
. With this seal device, the intermediate chamber
108
is maintained at an internal pressure equivalent to the lowest pressure of a space
106
at the rear of the piston, so that the internal pressure of a crank chamber
111
is always higher than that of the intermediate chamber
108
, whereby the seal member
107
is tightly pressed into contact with the outer periphery of a piston rod
103
to exhibit a high sealing property.
We have found by experiments that seal members, such as lip-type seal members, having directionality in sealing property act to send gas toward the direction of lower sealing property. With the seal device of
FIG. 9
, accordingly, this action lowers the pressure of the internal chamber
108
further below the lowest pressure of the piston rear space
106
. When the pressure difference between the crank chamber
111
and the intermediate chamber
108
increases considerably during a continuous operation, the seal member
107
is pressed against the outer periphery of the piston rod
103
with an excessive pressure due to the pressure difference to cause marked wear on the seal member
107
. This results in the problem that lubricating oil ingresses into the intermediate chamber
108
from the crank chamber
111
and further into the rear space
106
.
Further, if the pressure difference between the highest pressure of the piston rear space
106
and the pressure of the intermediate chamber
108
increases considerably with a continued operation, the pressure difference causes the working gas to gradually leak out of the rear space
106
onto the crank chamber
111
via the intermediate chamber
108
, consequently entailing the problem of impairing the ability of the gas compressor/expander.
In view of the foregoing problems encountered with the gas compressor/expander including a seal member which has a higher sealing property against a flow from the mechanism chamber (crank chamber) toward the piston rear space than against a flow in the opposite direction, an object of the present invention is to give a longer life to the seal member by minimizing the wear on the seal member and to prevent impairment of the performance of the gas compressor/expander by minimizing the leakage of the working gas from the rear space into the mechanism chamber.
DISCLOSURE OF THE INVENTION
The present invention provides a gas compressor-expander which has a space in the rear of a piston within a cylinder for compressing or expanding a gas, and a mechanism chamber provided with a power transmission disposed therein, a partition wall being provided between the piston rear space and the mechanism chamber and having a rod slidably extending therethrough for interconnecting the piston and the power transmission and a seal device surrounding the rod, the seal device comprising:
a first seal member
93
having a higher sealing property against a flow from the mechanism chamber toward the piston rear space
21
than against a flow in the opposite direction for preventing lubricating oil in the mechanism chamber from ingressing into the piston rear space,
an intermediate chamber
91
provided in the vicinity of the first seal member
93
at one side thereof toward the piston rear space and forming around the rod
22
an annular space having a radial dimension larger than the thickness of a lubricating oil film formed on a surface of the rod,
a second seal member
95
disposed in the vicinity of the intermediate chamber
91
at one side thereof toward the piston rear space for preventing working gas in the piston rear space from ingressing into the intermediate chamber
91
, and
a communication channel
96
for causing the intermediate chamber
91
and the mechanism chamber to communicate with each other.
In the gas compressor-expander of the present invention described, the intermediate chamber
91
and the mechanism chamber are held in communication with each other by the communication channel
96
, whereby the intermediate chamber
91
is maintained at approximately the same pressure as the mechanism chamber. This eliminates the likelihood that the pressure difference between the intermedia
Ikegami Kazuo
Masuda Mitsuhiro
Suzuki Hiroyuki
Armstrong Westerman Hattori McLeland & Naughton LLP
Doerrler William
Sanyo Electric Co,. Ltd.
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