1. Field of the Invention
The present invention relates to a liquid injection type screw compressor comprising a pair of male and female screw rotors that are installed in a space surrounded by a bore face within a casing of the compressor, while a liquid such as oil or water is injected to the bore face; whereby, a lip part is provided so as to prevent the liquid from flowing-back to a working gas inlet side, being placed on the bore face, within a range from a suction seal line (a suction closure line or a suction containment boundary locus) to a line parallel thereto apart from the suction seal line, by a distance equal to one screw pitch (a tooth groove distance in the rotor axis direction) of the rotors.
In hitherto known liquid injection type screw compressors, a pair of a male screw rotor and a female screw rotor within a casing of the compressor are engaged in each other, so as to form a working/operation space inside which a liquid such as oil or water is injected whereby a working substance of a gas-liquid mixing phase is pressurized. The liquid injection brings the screw compressor a cooling function, a sealing function, and a lubricating function; thus, the compressor of the type obtains high efficiency even during a low speed operation, becoming widespread in the industry.
The bore faces forming the working space within the casing of the compressor are important elements so as to secure gas/liquid tightness, when the working space is under a compression process where a gas seal across adjacent tooth spaces is required; consequently, it is a prerequisite to keep the clearance between the addendum circles of the rotors (tooth tip surfaces of the rotors) and the bore faces as small as possible. In this specification, the bore faces in the part as mentioned are called main bore faces.
On the other hand, a gas leakage between adjacent tooth spaces does not effect on the performance of the compressor when working spaces are under gas suction process; therefore, the bore faces in the associated part as mentioned are expanded toward outside in comparison with the main bore faces so that a power consumption is reduced by evading useless possible friction between the bore faces and the tooth tips; thus, the bore faces in the part as mentioned are called expanded bore faces.
In conventional liquid injection type screw compressors as described above, a weir (a lip part) is provided therein so as to prevent oil from scattering through a suction side end face of the rotor casing toward a gas inlet side; thus, it is intended to preserve the compressor volumetric efficiency and reduce the compressor power loss.
Conventional screw compressors with such a weir as mentioned are disclosed, for instance, in a patent literature 1 (JP patent: 1967-10027), a patent literature 2 (JP: 1991-194183) and a patent literature 3 (JP: 1999-13661).
The
On the other hand, the
Moreover, the patent literature 3 discloses that the oil injected into a working space flows back to a gas inhaling space; thereby, an oil mist generated from the back-flow oil suspends in the gas inhaling space, while the oil mist heats up the inhaled gas under a suction process; namely, a phenomenon, what is called inhaled gas heating, occurs; thus, the phenomenon increases a temperature of the gas to be compressed as well as expands a volume thereof; as a result, in a displacement type compressor that needs to inhale a gas of a constant specific volume, not only a reduction of mass-throughput but also a deterioration of volumetric efficiency are brought.
In order to evade the above-mentioned difficulties, according to the patent literature 3, as shown in
a and 9b that are attached to this application shows a casing for conventional screw rotors; for explanatory convenience,
Further, a lip part 04 is provided along a suction side end-face of a casing 01 so that the lip part 04 of the casing 01 protrudes inside, toward screw rotors; on the other hand, a suction seal line (a suction containment boundary locus) 05 is formed on a boundary between the male rotor side main-bore-face 02a and the male rotor side expanded-bore-face 03a as well as between the female rotor side main-bore-face 02b and the female rotor side expanded-bore-face 03b.
In the configuration as stated above, a working space is formed with a tooth space of the male rotor and another working space is formed with a tooth space of the female rotor, the pair of tooth spaces being independent; whereby, the tooth spaces are engraved on an outer periphery of rotors along a screw tooth spiral. While the working spaces are communicated with the expanded-bore-faces 03a or 03b, the working spaces are gradually expanded to a maximum volume, inhaling a gas through a gas inlet; then, the working spaces pass through the suction seal line (the suction containment boundary locus) 05, and the working spaces form a closed space the boundary of which includes a male rotor side main-bore-face 02a and a female rotor side main-bore-face 02b. Thus, after the working space becomes a closed space, the volume of the working spaces is gradually reduced and a confined gas within the space is compressed; at a last stage of compression, the gas inside the spaces is discharged through a discharge opening.
During the mentioned compression process, a liquid such as oil or water is injected into the working space, for the purpose of cooling, sealing, and lubricating.
a and 10b schematically depicts bore faces of a conventional screw rotor casing.
In
The working (operation) spaces formed with the male rotor and the female rotor face the male rotor side expanded-bore-face 03a and the female rotor side expanded-bore-face 03b, while the working spaces gradually increase during a suction process, inhaling a gas through a gas inlet. After the volume of the working spaces reaches a maximum volume and the working spaces cross the suction seal line 05, the spaces form a sealed space, being surrounded by the main-bore-faces 02a and 02b. Subsequently, as the volume of the working spaces is reduced, the gas confined in the spaces is compressed. And the compressed gas is discharged through a discharge opening at a discharge side end face 07 of the rotor casing.
In the above situation, the liquid such as oil or water injected into the working spaces leaks toward a lower pressure suction side and accumulates in the concaved expanded bore faces 03a/03b. The lip part 04 prevents the liquid from leaking and scattering toward the gas suction end face 06 of the rotor casing.
Patent literatures:
In spite of the disclosure according to the configuration such as in the patent literature 3, the conventional technologies are insufficient in sealing a liquid within the working spaces as well as in preventing deterioration as to volumetric efficiency; the insufficiency is caused on the ground that great distances remain between rotor tooth tips and the lip part 04 (04a and 04b in
As just mentioned above, the lip part is provided at the suction side end face of the rotor casings in conventional liquid injection screw compressors; thus, a gas inlet has to be placed outside across the suction side end face; moreover, the lip part lessens a gas inlet passage area (opening area) around the suction side end face of the rotor casings; therefore, in case of manufacturing a mono-block casting of the rotor casings and the gas inlet casing, it becomes difficult to allocate a casting core for rotor casing bores.
Further, in conventional ways, only by means of lengthening rotor space in the axial direction, it is possible to secure a sufficient gas inlet passage for inhaling a gas into the working space; in addition, insufficient inlet passage area enhances suction resistance during a high-speed operation.
Because of the above-mentioned situations, it is conventionally difficult to obtain a mono-block casting of the rotor casings and the gas inlet casing. That is, in casting, it is necessary to manufacture the rotor casing and the gas inlet casing separately; further, it becomes necessary to provide each casing with an essentially useless part such as an additional flange that is needed for assembling the parts. Thus, an increased whole weight and an intricate production process are brought; further, as mentioned above, in a high speed operation, there arise difficulties such as an increased gas suction resistance as well as a lessened volumetric efficiency.
In view of the mentioned subjects in conventional liquid injection type screw compressors, the goals of the present invention are:
Further, the invention aims at realizing a liquid injection type screw compressor provided with a variable compression ratio mechanism, that is, an internal volume ratio adjusting valve; wherein, the compressor has a compact structure so as to not prolong a manipulation mechanism of the internal volume ratio adjusting valve, making manufacturing cost be further reduced.
In order to attain the mentioned goals, the present invention proposes a liquid injection type screw compressor comprising of:
In a screw compressor according to the present invention, a lip part for preventing liquid from back-flowing toward a gas inlet is provided on a casing bores, within a range between a suction seal line and a line that is apart from the suction seal line, by one screw pitch distance of the screw rotors, toward the expanded-bore-face side of the male rotor side casing and/or the female rotor side casing; hence, the lip part is placed nearer to the suction seal line in comparison with conventional ways; as a result, a liquid leakage from the compressed working spaces toward the gas inlet side is effectively prevented; further, the lip part placed nearer to the suction seal line makes it possible to eliminate a part of bore faces that is located at the gas inlet side from the lip part. So can be realized a simplified configuration of rotor casings with a reduced bore surface as well as a reduced suction resistance and a reduced manufacturing cost which are attributable to the simplification.
A preferable configuration of the present invention may comprise:
The above preferable configuration can surely prevent a liquid leakage around a neighborhood along the bore intersection line.
According to a further preferable aspect of the above configuration,
The above configuration can surely prevent a liquid leakage around the bore intersection line.
Another preferable aspect of the invention according to the mentioned configuration is the liquid injection type screw compressor, wherein the rotor casing with the gas inlet casing is formed in one piece or a plurality of divided-pieces from the lip ending edge toward a gas downstream side. Thus, the gas inlet side bore surface of the rotor casing can be omitted in a way that the lip part is located nearer to the suction seal line; as a result, it becomes possible to form a gas inlet casing and a rotor casing in one body.
Consequently, the invention realizes a smaller rotor casing, saving an installation space; in addition, the invention greatly relieves restrictions concerning a position where a gas inlet casing is disposed in a rotor casing; in this regard, the degree of freedom as to the gas inlet casing design can be greatly expanded.
According to a further preferable aspect of the invention, a labyrinth structure is embodied on the inner surface which faces rotor tooth tips in the lip part. For example, a pertinent roughness of the surface (e. g. a pertinent casting surface roughness) or an intended uneven surface can realize lesser liquid leakage.
According to another preferable aspect of the invention, different outer diameters are applied to a pair of the male rotor and the female rotor so that the outer diameter of the male rotor is greater than that of the female rotor, and the number of the male rotor teeth is fewer than that of the male rotor teeth in a case when the same outer diameter is applied to a pair of the male rotor and the female rotor.
In this way, a screw pitch distance of the male rotor can be shortened and the lip part can be located nearer to the suction seal line; thus, the liquid leakage can be further surely prevented; in addition, the geometry of the casings can be simplified.
According to another preferable aspect of the invention, the lip part is provided at the lower side of the casing bore surfaces. In this configuration, the liquid accumulated by gravity at the bottom of the bore surfaces can be easily prevented from scattering toward the gas inlet side; thus, a simple structure can be realized.
Another preferable aspect of the invention according to the mentioned configuration is a liquid injection type screw compressor comprising:
The installation of an internal volume ratio (Ui) adjusting valve makes a whole compressor compact, realizing a compressor of three kinds of compression ratios, namely, of lower/medium/higher compression ratios, without changing a gas inlet casing, only by replacing a rotor casing. Thus, a gas inlet casing can be applied to these kinds of compressors in common.
On the other hand, conventional compressors are apt to be of a large size, as a positioning means to position the internal volume ratio (Ui) adjusting valve is prolonged toward a gas discharge side, penetrating a gas discharging casing so as to be used for setting (positioning) the valve.
In order to solve the difficulty, according to a further preferable aspect of the present invention, the positioning means comprises:
According to the above aspect, there is no need to prolong a positioning means as in conventional approaches; a driving mechanism to position the internal volume ratio-adjusting valve can be formed as a compact one. The mentioned connection part between the hollow shaft and the rotation rod may be a bevel gear pair or a crossed helical gear pair.
In a screw compressor according to the disclosed invention, a lip part for preventing liquid from back-flowing toward a suction inlet is provided on a casing bores, within a range between a suction seal line and a line that is apart from the suction seal line, by one screw pitch distance of the screw rotors, toward the expanded-bore-face side of the male rotor side casing and/or the female rotor side casing.
Therefore, a liquid leakage scattering during a compression process from the compressed working space formed by the screw rotors toward the gas inlet side can be effectively prevented.
Moreover, the lip part placed nearer to the suction seal line makes it possible to eliminate a part of the rotor casing at the gas inlet side from the lip part. So can be realized a simplified configuration of rotor casings with a reduced bore surface as well as a reduced suction resistance of an inhaled gas and an enhanced volumetric efficiency of the compressor.
Further, the lip part placed nearer to the suction seal line makes it possible to eliminate a part of the rotor bore faces at the gas inlet side from the lip part. Hence, the rotor casing can be formed in one body with a gas inlet casing. As a result, manufacturing processes can be simplified and a manufacturing cost can be reduced. Consequently, the disclosed invention greatly relieves restrictions regarding installation position of a gas inlet casing in a rotor casing. Further, the degree of freedom as to the gas inlet casing design can be greatly expanded; in addition, a compact casing can be realized and a compressor installation space can be reduced.
Also as already explained, in a screw compressor according to the disclosed invention, the compressor comprises:
Thus, the above configuration can surely prevent a liquid leakage around a neighborhood along the bore intersection line.
Further, in a screw compressor according to the disclosed invention, the compressor comprises:
Thus, the above configuration can surely prevent a liquid leakage around a neighborhood along the bore intersection line.
Further, in a screw compressor according to the disclosed invention, different outer diameters are applied to a pair of the male rotor and the female rotor so that the outer diameter of the male rotor is greater than that of the female rotor, and the number of the male rotor teeth is fewer than that of the male rotor teeth in a case when the same outer diameter is applied to a pair of the male rotor and the female rotor.
In this manner, a screw pitch distance of the male rotor can be shortened and the lip part can be located nearer to the suction seal line; thus, the liquid leakage can be further surely prevented; in addition, the geometry of the casings can be simplified.
Further, in a screw compressor according to the disclosed invention, the compressor comprises:
According to the above disclosure, the installation of an internal volume ratio (Ui) adjusting valve can make a whole compressor compact, realizing a compressor of three kinds of compression ratios, namely, of lower/medium/higher compression ratios, without changing a gas inlet casing, only by replacing a rotor casing. Thus, a gas inlet casing can be applied to these kinds of compressors in common.
Still further, in a screw compressor according to the disclosed invention, the compressor comprises a positioning means for positioning the internal volume ratio-adjusting valve, the positioning means comprising:
According to the above aspect, there is no need to prolong a positioning means as in conventional approaches; a driving mechanism to position the internal volume ratio-adjusting valve can be formed as a compact one.
The present invention will now be described in greater detail with reference to the preferred embodiments of the invention and the accompanying drawings, wherein:
a shows a transparently perspective view seen from a top as to a first embodiment of the present invention;
b is a development view of
a shows a perspective view of an upper side rotor-casing seen from the inside thereof, as to a first embodiment;
b shows a perspective view of a lower side rotor-casing seen from the inside thereof, as to the first embodiment;
a shows a perspective view of an upper side rotor-casing seen from the inside thereof, as to a conventional compressor;
b shows a perspective view of a lower side rotor-casing seen from the inside thereof, as to a conventional compressor;
a shows a transparently perspective view seen from the top as to a conventional compressor in consideration of a schematic explanation for bore faces thereof; and
b is a development view of
Hereafter, the present invention will be described in detail with reference to the embodiments shown in the figures. However, the dimensions, materials, shape, the relative placement and so on of a component described in these embodiments shall not be construed as limiting the scope of the invention thereto, unless especially specific mention is placed.
a shows a transparently perspective view seen from the top as to a first embodiment of the present invention;
a and 1b schematically depict a bore face in a rotor casing of a screw compressor according to the present invention;
In a male rotor side casing la and a female rotor side casing 1b of
The suction seal line 5 includes a curved part 5a that is on a main bore face of the male rotor side casing 1a, a curved part 5b that is on a main bore face of the female rotor side casing 1b, and a curved part 5c that is also on the main bore face of the female rotor side casing 1b; whereby, in the development figures of
On the other hand, in response to the suction seal line 5, the geometry of the lip part 4 comprises:
Liquid such as oil or water injected into a compression working space is apt to leak toward a lower pressure suction side and accumulates in concaved expanded bore faces 3a/3b. The lip part 4 prevents the liquid from leaking and scattering toward a gas inlet side.
According to the first embodiment as described above, the distance between the suction seal line 5 and the lip part 4 is substantially within one screw pitch distance; thus, the lip part 4 is provided at a location closer to the suction seal line 5 in comparison with conventional ways. Therefore, in comparison with conventional ways, is effectively prevented a liquid leakage that scatters, during a compression process, from the compressed working space which is formed by the screw rotors toward the gas inlet side. Moreover, the lip part placed nearer to the suction seal line makes it possible to eliminate a part of the rotor casing, located at the gas inlet side from the lip part. So can be realized a simplified configuration of rotor casings with a reduced bore surface as well as a reduced suction resistance of an inhaled gas and an enhanced volumetric efficiency of the compressor.
Further, in the above embodiment, a straight line portion 5c of the suction seal line 5 is provided in the neighborhood of the bore intersection line, the line lying at right angles with the bore intersection line in a development view. In addition, a thickened lip part 4c is provided, comprising:
In this manner, can be surely prevented a liquid leakage around the neighborhood along the bore intersection line, toward a gas inlet side, from the working (compression) spaces which are formed by the male female rotors.
Moreover, it becomes possible to eliminate a part from the lip part 4 toward a side of the gas inlet 9 in the rotor casing; in addition, a simplified configuration of rotor casings can be realized. Further, since the gas inlet casing can be placed nearer to the rotor casing, the rotor casing can be formed in one body together with the gas inlet casing. As a result, manufacturing processes can be simplified and a manufacturing cost can be reduced.
A second embodiment of the present invention is now detailed with reference to
In
A mechanical seal 24 is provided near a shaft end part 14a of the male rotor shaft 14, the shaft end part 14a being connected to an output shaft of a drive motor (not shown) as a power source.
A gas outlet casing 26 that forms a gas outlet 25 is made of casting; however, the casing 26 is made of different casting from the rotor casing 11, and the casing 26 is fastened thereto with tightening bolts 27. At a lower part of the rotor casing 11, is provided a slide valve (a capacity control valve) 28 that makes it possible to regulate a compressor capacity (an inhaled gas capacity) by means of sliding-manipulation along an axis direction of the rotors; thereby, a pushrod (a driving rod) 29 regulates a length as to the sliding-manipulation of the slide valve 28. In addition, the pushrod 29 is operated through an oil pressure that is supplied to a left cylinder room 30a and a right cylinder room 30b in an oil-hydraulic cylinder 30.
At the middle part of the pushrod 29, is installed a Ui-control device (an internal volume ratio control device) 31 of a manual operation type; hereupon, the device 31 makes it possible to optimize the internal volume ratio Ui. A casing 35 that contains the Ui-control device 31 is fastened to the gas inlet casing 13 with tightening bolts 36, while the oil-hydraulic cylinder 30 is fitted to the casing 35. The reference numeral 37 denotes an internal volume ratio (Ui) adjusting valve; thereby, the Ui-adjusting valve 37 is engaged into a screw part 38a that is provided on an outer face of a hollow shaft 38. Here, the hollow shaft 38 is installed around the pushrod 29 having a round cross-section, so that a round hollow cylinder of the hollow shaft 38 and the round cross-section of the pushrod 29 are concentric, and the hollow shaft 38 can rotate freely around the pushrod 29. Further, the Ui-adjusting valve 37 moves along the rotor axes with a rotational movement of the hollow shaft 38.
On the other hand, the reference numeral 39a denotes a bevel gear that is fitted to a suction-side end part of the hollow shaft 38, while the bevel gear 39a is engaged in a corresponding bevel gear 39b that is fitted to an end part of a rotation-rod 40; hereupon, it is noted that the axes of the hollow shaft 38 and the rotation-rod 40 lie at right angles to each other.
According to the above-mentioned configuration, when the rotation-rod 40 is rotated, either clockwise or counterclockwise, a rotational movement is transmitted to the hollow shaft 38; as a result, the Ui-adjusting valve 37 moves back and forth along an rotor axis, through an engagement of the screw part 38a and the Ui-adjusting valve 37. A steering wheel (not shown) or the like may be fitted to the rotation-rod 40 so as to enable an operator to turn the wheel by hand in case of manual control.
When the internal volume ratio (Ui) is adjusted, the following sequence of manipulations is performed: rotating the rotation-rod 40 under a stop condition of the compressor; making the Ui-adjusting valve 37 move along an rotor axis; as a result, thrusting the slide valve 28 toward the gas outlet 25; adjusting an opening level of a discharge opening 41 that is formed between a cut-out part 28a provided at a discharge-front end side of the slide valve 28, and the gas outlet casing 26; thus, initializing the internal volume ratio (Ui).
In addition, when a capacity of the compressor needs to be adjusted, the slide valve 28 is shifted along the axes of the rotors through a movement of the pushrod 29; thereby, a by-passed gas flow toward the gas inlet side from a gap between the slide valve 28 and the pushrod 29 controls the capacity (the inhaled gas flow quantity).
Incidentally, in
As shown in
Further, the lip part 33 comprises a male casing side lip part 33a on the bore in the male rotor casing 11a, and a female casing side lip part 33b, while the boundary of the lip part 33 comprises a lip-entering-edge and a lip ending (trailing) edge; hereupon, the lip part 33 is away from the suction seal line, within a screw pitch distance.
Still further, the lip-ending-edge comprises:
In the above-mentioned manner, a thickened lip part 33c is formed with the bent curve portion 33d and the line portion 33e, in response to the straight line portion 32c of the suction seal line 32. So can be surely prevented a liquid leakage around the neighborhood along the bore intersection line, toward a gas inlet side, from the working (compression) spaces in the rotor casing 11.
According to the second embodiment, in the same way as the first embodiment, the lip part 33 is provided apart from the suction seal line 5, by a screw pitch distance, toward the gas inlet side; thus, can be surely prevented a liquid leakage around the neighborhood along the bore intersection line, toward a gas inlet side, from the working (compression) spaces. Further, since the lip part is provided around the neighborhood along the bore intersection line as mentioned above, a liquid leakage around the bore intersection line can be surely prevented.
Moreover, can be eliminated a part of the rotor casing on the gas inlet side of the lip part 33. Thus, can be secured a satisfactory space that communicates the bore faces of the rotor casing to the gas inlet 12, the space reducing a suction resistance of the gas inhaled from the gas inlet 12. As a result, a volumetric efficiency of the compressor can be enhanced.
On the other hand, by means of eliminating a part of the rotor casing the part which is located on the gas inlet side of the lip part, the location of the gas inlet 12 can be shifted toward the rotor casing 11. Thus, the rotor casing 11 together with a gas inlet casing 13 that forms a gas inlet 12 can be made of mono casting. In this way, a compact casing can be realized and a compressor installation space can be reduced. Consequently, a compact casing can be realized, a compressor installation space can be reduced, a compressor manufacturing cost can be greatly lowered, and the degree of freedom as to the gas inlet casing design about the rotor axis direction can be expanded.
Further, it becomes possible to design a compressor casing of the same kind compressors so that a distance L between an axis “i” of the gas inlet 12 and an axis “o” of the gas outlet 25 can be kept constant. Therefore, a manufacturing line of the compressor casings can be streamlined so as to mechanized and robotized.
The installation of an internal volume ratio (Ui) adjusting valve makes a whole compressor compact, realizing a compressor with three kinds of compression ratios , namely, of lower/medium/higher compression ratios, without changing sorts of a gas inlet casing, only by replacing a rotor casing. Thus, a gas inlet casing can be applied to these kinds of compressors in common. Namely, even if the rotor-casing is replaced by another one for constituting a different kind (capacity) of the compressor, it is not necessary to exchange the gas inlet casing.
Further, conventional compressors are apt to be of a large size, as a positioning means to position the internal volume ratio (Ui) adjusting valve is prolonged toward a gas discharge side, penetrating a gas outlet casing so as to be used for positioning the valve. Contrary to the above, the second embodiment comprises a positioning means for positioning the internal volume ratio-adjusting valve including:
a hollow shaft 38 , and
According to the above configuration, there is no need to prolong a positioning means as in conventional approaches; a driving mechanism to position the internal volume ratio-adjusting valve 37 can be formed as a compact one.
Incidentally, for the connection part between the rotation rod 40 and the hollow shaft 38, a crossed helical gear pair may be applied instead of a bevel gear pair; a bevel gear pair tends to have a play to some extent between meeting gears, while a crossed helical gear has little play.
According to the present invention regarding a liquid injection type screw compressor, a liquid leakage, such as an oil leakage or a water leakage, that flows back to a gas inlet side from a compression room which is formed screw rotors is further effectively prevented in comparison with conventional compressors of the same kind. In addition, suction resistance of the gas inhaled from the gas inlet can be lowered, and volumetric efficiency as to the inhaled gas can be improved; further, cast modeling of a rotor casing can be simplified and a manufacturing cost can be reduced.
Thus, the invention greatly contributes to a practical compressor industry.
This is a continuation of International Application PCT/JP2005/0020041 (published as WO 2007-0542322) having an international filing date of Oct. 31, 2005. The disclosure of the priority application, in its entirety, including the drawings, claims, and the specification thereof, is incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/JP2005/020041 | Oct 2005 | US |
Child | 12111624 | US |