Rotary expansible chamber devices – With mechanical sealing
Reexamination Certificate
2000-06-07
2001-07-24
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
With mechanical sealing
C418S055400, C418S055600, C418S141000, C418SDIG001, C418S100000, C184S006160
Reexamination Certificate
active
06264448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an open type compressor, and especially relates to an open type compressor which is suitable for a steam compression type cooling cycle using a coolant in the supercritical area of carbon dioxide (CO
2
) and the like.
This application is based on Japanese Patent Application No. Hei 11-1661694, the content of which is incorporated herein by reference.
2. Description of the Related Art
Recently, from the point of view of protection of the environment, a cooling cycle which uses carbon dioxide (CO
2
) as a working gas (coolant gas) has been proposed for steam compression type cooling cycles, as a measures for elimination of fluorocarbons (refer to Japanese Patent Application, First Application No. Hei 7-18602, for example). The operation of this cooling cycle (hereinafter called CO
2
cycle) is similar to the conventional steam compression type cooling cycle. That is, as shown in a line A-B-C-D-A in
FIG. 6
(CO
2
Moller diagram), gaseous CO
2
is compressing by a compressor (A-B), this gaseous CO
2
which is compressed at a high temperature is cooled by a radiator (gas cooler) (B-C), the pressure of the gas is reduced by a decompressor (C-D), the CO
2
which is changed to liquid phase is evaporated (D-A), and an external fluid such as air is cooled by the a latent heat of evaporation.
However, if the external temperature is high, during the sur season or the like, the temperature of the CO
2
at the radiator side becomes higher than the critical temperature of CO
2
, because the critical temperature of CO
2
is about 31° C. which is lower than that of the fluorocarbons used as conventional coolants, and therefore, CO
2
does not condense at the radiator side (the line BC does not cross a saturation line SL in FIG.
6
). Furthermore, the phase of CO
2
at the outlet side of the radiator (point C in
FIG. 6
) is determined by the exhaust pressure of the compressor and the CO
2
temperature at the outlet side of the radiator, and the CO
2
temperature at the outlet side of the radiator is determined by the radiation capacity of the radiator and the external temperature (which cannot be controlled). Hence, the temperature of CO
2
at the outlet side of the radiator is substantially uncontrollable, and the phase of the CO
2
at the outlet side of the radiator is controlled by the exhaust pressure of the compressor (the pressure at the outlet side of the radiator). Consequently, if the outer temperature is high during the summer season or the like, the pressure at the outlet side of the radiator must be increased as shown in line E-F-G-H-E in
FIG. 6
to secure sufficient cooling capacity (difference in enthalpy), and the operation pressure of the compressor must be increased in comparison with the conventional compressor which uses fluorocarbons.
For instance, in the case of an air conditioning unit for a vehicle, the operation pressure of a compressor using CO
2
is increased to 40 kg/cm
2
, as opposed to that of a conventional compressor R134 using fluorocarbon, which is 3 kg/cm
2
. Furthermore, the stopping pressure of the compressor which using CO
2
is increased to 40 kg/cm
2
, as opposed to that of R134, which is 15 kg/cm
2
. Consequently, in the case of the CO
2
cycle, the differential pressure between the internal pressure of the compressor and the atmospheric pressure is increased, and therefore, there is concern of a gas leak from a shaft sealing portion of the compressor during the operation and stopping of the compressor. That is, in the conventional compressor, sufficient lubricating oil is supplied to the compressor, and this lubricating oil is partly supplied to the shaft sealing portion. However, the pressure of the lubricating oil may not be kept at a sufficiently high level, and gas leaks from the shaft sealing portion of the compressor are apt to occur. Especially, when the operation is stopped, the lubricating oil is not sufficiently supplied to the shaft sealing portion, and the gas leak fran the shaft sealing portion can easily occur. Furthermore, the shaft sealing portion may be damaged at the restart of the compressor because lubricating oil is not supplied while it is stopped. For the above reasons, the operation of the CO
2
cycle is not efficient and an improvement is strongly required. Besides, Japanese Patent Application, Second Publication No. Hei 3-6350 discloses a sealing apparatus for a shaft to seal a shaft-end portion of a screw type compressor. In this apparatus, a mechanical seal and a plain bearing which acts as a labyrinth seal are separately arranged on the shaft-end portion to form an enclosed chamber between the seals. A lubricating material is sent into the chamber with a pressure which is higher than the pressure in a pump chamber, and gas leakage from the pump chamber is prevented. However, this apparatus is only for preventing the gas leakage during the operation, and is not for lubricating the machine room (pump chamber) of the compressor.
The present invention is provided in compliance with the above problems of the conventional art, and the object of the present invention is to provide an open type compressor which can secure efficient and appropriate operation during the cooling cycle by improving the lubrication ability during the operation and by preventing the leakage of the working gas when the operation is stopped.
SUMMARY OF THE INVENTION
To achieve the above-described object, the open type compressor of the present invention provides the following features. That is, the open type compressor of the present invention is for compressing an introduced working gas and exhausting the working gas which is compressed by the predetermined pressure, and is characterized by comprising a crank case having a low pressure chamber in which the working gas is introduced, a crank shaft which is rotatively supported by the low pressure chamber by a bearing and compressing the working gas by rotation, a shaft seal which is provided on the crank shaft at the outer side of the bearing along the axial direction, a partition means which is provided between the bearing and the shaft seal for separating a space in which the shaft seal is provided from the low pressure chamber to form a sealing chamber, and a first lubricating agent supply passage which is formed in the crank case and is opened to the sealing chamber for supplying a lubricating agent to the sealing chamber.
In this compressor, the highly compressed lubricating agent is filled in the sealing chamber which is partitioned by the partition means via the first lubricating agent supply passage at the operation of the compressor. As a result, gas leaks from the sealing chamber is surely prevented by this highly compressed lubricating agent.
It is preferable that the partition means is an non-contact type labyrinth seal. The labyrinth seal allows the leakage of a part of the highly compressed lubricating agent which is supplied from the sealing chamber to the low pressure chamber during the operation of the compressor. In this case, the desired leak capacity is provided by a gap between two constituent members which constitute the non-contact type seal. Furthermore, because of the filling of the highly compressed lubricating agent in the sealing chamber via the first lubricating agent supply passage during the operation of the compressor, the pressure of the lubricating agent which is filled in the sealing chamber becomes sufficiently higher than that of the low pressure chamber (machine room). Therefore, a part of the lubricating agent in the sealing chamber is leaked to the low pressure chamber via the labyrinth seal and the low pressure chamber is lubricated by the leaked lubricating agent.
Meanwhile, when the operation is stopped, the pressure in the sealing chamber and the low pressure chamber becomes almost the same. Therefore, the highly compressed lubricating agent which is filled in the sealing chamber is kept by the labyrinth seal and the leakage of the lubricating agent from the sealing chamber
Itoh Takahide
Takeuchi Makoto
Ukai Tetsuzou
Denion Thomas
Mitsubishi Heavy Industries Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Trieu Theresa
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