Oil-flooded screw compressor

Abstract

To reduce the size of a device as a whole, while reducing loss due to oil agitation in a speed increaser, in an oil-cooled screw compressor.SOLUTION: A speed increaser 3 of an oil-cooled screw compressor 1 comprises a pinion gear 11 fixed to a rotor shaft 4a of a male rotor 4, and a bull gear 12 that meshes with the pinion gear 11 and transmits the rotation of a prime mover 10 to the pinion gear 11. The bull gear 12 is arranged so as to overlap a female rotor 5 when viewed from a direction in which the rotor shaft 4a extends, and the lower end of the bull gear 12 is located above the lower end of the male rotor 4.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an oil-flooded screw compressor. [Background technology]

[0002] Patent Document 1 discloses a screw compressor that aims to reduce losses caused by oil agitation in a speed-increasing gear.

[0003] However, the screw compressor disclosed in Patent Document 1 has room for improvement in terms of realizing a compact device as a whole while reducing losses due to oil agitation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-278674 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to reduce the loss caused by oil agitation in a speed increaser in an oil-cooled screw compressor while reducing the size of the entire device. [Means for solving the problem]

[0006] One aspect of the present invention is a speed increaser comprising: a compressor body having a rotor chamber that houses a male rotor and a female rotor arranged side by side, a suction port on the upper side that communicates with a suction port, a first casing having a discharge port on the lower side, air drawn in from the suction port is compressed by the male rotor and the female rotor and discharged from the discharge port, the diameter of the male rotor being larger than the diameter of the female rotor; a pinion gear fixed to a rotor shaft of the male rotor; a bull gear that meshes with the pinion gear and transmits rotation of a prime mover to the pinion gear; and a second casing that houses the pinion gear and the bull gear and has an oil reservoir at its bottom that communicates with the rotor chamber via the suction port, the bull gear being positioned diagonally above the pinion gear and overlapping with the female rotor when viewed from the direction in which the rotor shaft extends, Under The height position of the end of the male rotor Under the height position of the end of the female rotor; Under To provide an oil-cooled screw compressor located between the height positions of the ends.

[0007] The male rotor and female rotor are arranged side by side. Furthermore, the bull gear is not arranged directly above the pinion gear, but is arranged so as to overlap the female rotor when viewed from the direction in which the rotor shaft of the male rotor extends. These features reduce the overall height of the oil-cooled screw compressor, making it possible to reduce the size of the entire device. In particular, by arranging the bull gear so as to overlap the female rotor when viewed from the direction in which the rotor shaft of the male rotor extends, that is, by arranging the bull gear not directly above the male rotor but diagonally above it in a position close to being side by side, it is possible to reduce the overall height of the prime mover connected to the bull gear. Because the prime mover is large and has a high overall height compared to the compressor body, reducing the overall height of the prime mover effectively contributes to reducing the size of the entire oil-cooled screw compressor device by reducing its overall height.

[0008] Although the bull gear is positioned diagonally above and nearly side-by-side with the male rotor, the lower end of the bull gear is located above the lower end of the male rotor, i.e., above the maximum height of the lubricating oil that is expected to collect in the oil sump. Therefore, loss caused by the bull gear stirring the lubricating oil in the oil sump can be avoided or reduced.

[0009] For the above reasons, this embodiment can reduce the loss caused by oil agitation in the speed increaser while also making the device smaller as a whole.

[0013] The prime mover may be an internal combustion engine.

[0014] The speed-increasing ratio of the speed-increasing gear may be 2 or more and 3 or less. [Effects of the Invention]

[0015] According to the present invention, in an oil-cooled screw compressor, it is possible to reduce the loss caused by oil agitation in the speed increaser and to reduce the size of the entire device. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a longitudinal sectional view of an oil-cooled screw compressor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 . [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1 . [Figure 4] FIG. 4 is a cross-sectional view similar to FIG. 3 of a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0018] 1 to 3 show an oil-cooled screw compressor 1 according to an embodiment of the present invention. This oil-cooled screw compressor 1 is a mobile type intended for outdoor use.

[0019] The oil-cooled screw compressor 1 includes a compressor body 2, a speed increaser 3, and an internal combustion engine 10, which is an example of a prime mover. Only the outer shape of the casing of the internal combustion engine 10 is shown schematically. The prime mover may also be an electric motor.

[0020] The compressor body 2 includes a main body casing (first casing) 2b that is provided with a rotor chamber 2a that houses a male rotor 4 and a female rotor 5. A casing for the speed increaser 3, i.e., a speed increaser casing (second casing) 3a, is attached to the right side of the main body casing 2b in FIG. 1. A bearing casing (not shown) is attached to the left side of the main body casing 2b in FIG. 1.

[0021] 2 and 3, the male rotor 4 and the female rotor 5 are arranged side by side in the rotor chamber 2a. In particular, in this embodiment, as shown in Fig. 3, the rotation axis RAm of the male rotor 4 and the rotation axis RAf of the female rotor 5 are arranged in positions that are horizontal to each other. In other words, the height position Lmc of the rotation axis RAm of the male rotor 4 and the height position Lfc of the rotation axis RAf of the female rotor 5 are located at the same height position.

[0022] 1 and 2, the right side of the rotor shaft 4a of the male rotor 4 in the drawing is rotatably supported by a bearing 6 attached to the main casing 2b and protrudes into the gearbox casing 3a. The right side of the rotor shaft 5a of the female rotor 5 in the drawing is rotatably supported by a female rotor bearing 7 attached to the main casing 2b. Meanwhile, the left sides of the rotor shaft 4a of the male rotor 4 and the rotor shaft 5a of the female rotor 5 in the drawing are each rotatably supported by a bearing (not shown) attached to the bearing casing.

[0023] The main casing 2b has an intake port 2c at the right end of the rotor chamber 2a in the drawing, and an exhaust port 2d (schematically indicated only by an arrow) at the bottom left end of the rotor chamber 2a in the drawing. Also, an intake port 2e communicating with the intake port 2c is provided at the top of the main casing 2b.

[0024] 1 to 3, the speed-increasing gear 3 includes a pinion gear 11, which is a gear, and a bull gear 12, which is a gear that meshes with the pinion gear 11, both of which are housed in a speed-increasing gear casing 3a. The pinion gear 11 is fixed to a portion of the rotor shaft 4a of the male rotor 4 that protrudes into the speed-increasing gear casing 3a. The bull gear 12 is fixed to an input shaft 13. The input shaft 13 is rotatably supported by a bearing 14 attached to the speed-increasing gear casing 3a. The input shaft 13 may be connected to the output shaft of the internal combustion engine 10 via a coupling, or the input shaft 13 itself may be the output shaft of the internal combustion engine 10.

[0025] The rotation of the internal combustion engine 10 is transmitted to the pinion gear 11 via the bull gear 12, and as a result, the male rotor 4 is driven to rotate. The female rotor 5 rotates in response to the male rotor 4. Referring to Figures 2 and 3, in this embodiment, the rotation direction RDb of the input shaft 13, and therefore the bull gear 12, is counterclockwise when viewed from the shaft end of the internal combustion engine 10, so the rotation direction RDp of the pinion gear 11 and the rotation direction RDm of the male rotor 4 are counterclockwise when viewed from the shaft end on the right side in the drawing of the rotor shaft 4a, and the rotation direction RDf of the female rotor 5 is clockwise when viewed from the same direction. In other words, in this embodiment, the male rotor 4 is a right-hand thread type and the female rotor is a left-hand thread type.

[0026] The rotation speed of the internal combustion engine 10 is, for example, 1500 rpm to 2500 rpm, and the rotation speed of the compressor body 2 is, for example, 3000 rpm to 7500 rpm. In this embodiment, the rotation speed of the internal combustion engine 10 is 2000 rpm, the rotation speed of the compressor body 2 is 4200 rpm, and the speed-up ratio of the speed-up gear 3 is 2.1. In other words, the number of teeth of the bull gear 12 is 2.1 times the number of teeth of the pinion gear 11. The speed-up ratio, which is the ratio of the number of teeth of the bull gear 12 to the number of teeth of the pinion gear 11, can be set to be 2 or more and 3 or less.

[0027] The rotational output of the internal combustion engine 10 is transmitted to the male rotor 4 via the bull gear 12 and pinion gear 11 of the speed increaser 3, and when the male rotor 4 and female rotor 5 rotate, air sucked into the suction port 2c via the suction port 2e is trapped and compressed in the confined space defined by the teeth of the male rotor 4 and the tooth grooves of the female rotor 5, and the compressed air is expelled from the discharge port 2d.

[0028] The speed-increasing gear 3 has an oil sump 3b at the bottom of the speed-increasing gear casing 3a. Lubricating oil is sprayed onto the bull gear 12 and pinion gear 11 from above by a nozzle (not shown) that injects lubricating oil into the speed-increasing gear casing 3a. The lubricating oil sprayed onto the bull gear 12 and pinion gear 11 falls into the oil sump 3b. A communication hole 2f is provided at the bottom of the main casing 2b, connecting the bottom side of the interior of the speed-increasing gear casing 3a with the lower side of the suction port 2c of the main casing 2b. In other words, the oil sump 3b is in communication with the rotor chamber 2a via the suction port 2c. Therefore, the maximum possible height position of the lubricating oil level Lo in the oil sump 3b is the height position Lrc of the lowest end 2g of the rotor chamber 2a. In other words, since the lubricating oil is sucked into the rotor chamber 2a through the lower part of the suction port 2c, the oil level Lo of the lubricating oil collected in the oil reservoir 3b does not exceed the height position Lrc of the lowest end 2g of the rotor chamber 2a.

[0029] 3, in this embodiment, as described above, the height position Lmc of the rotation axis RAm of the male rotor 4 and the height position Lfc of the rotation axis RAf of the female rotor 5 are located at the same height. Next, in this embodiment, the diameter of the male rotor 4 is slightly larger than the diameter of the female rotor 5. Therefore, the height position Lfl of the bottom end 5b of the female rotor 5 is located slightly higher than the height position Lml of the bottom end 4b of the male rotor 4 (the height position Lml of the bottom end 4b of the male rotor 4 is located slightly lower than the height position Lfl of the bottom end 5b of the female rotor 5). The height position Lml of the bottom end 4b of the male rotor 4 is located slightly higher than the height position Lrc of the bottom end 2g of the rotor chamber 2a by an amount corresponding to a slight gap to allow rotation of the male rotor 4 and the female rotor 5. However, in relation to the assumed maximum height position of the height position Lo of the lubricating oil level, the height positions Lml and Lrl can be considered to be the same.

[0030] Continuing to refer to Figure 3, the bull gear 12 is not disposed directly above the pinion gear 11, but is disposed so as to overlap with the female rotor 5 when viewed from the direction in which the rotor shaft 4a of the male rotor 4 extends (or from the direction in which the rotor shaft 5a of the female rotor 5 extends). The height position Lbl of the lowest end 12a of the bull gear 12 is located higher than the height position Lml of the lowest end 4b of the male rotor 4. Specifically, the height position Lbl of the lowest end 12a of the bull gear 12 is located lower than the rotation axis RAf of the female rotor 5. More specifically, in this embodiment, the bull gear 12 is disposed so that the height position Lbl of the lowest end 12a is located slightly higher than the height position Lfl of the lowest end of the female rotor 5.

[0031] In Fig. 3, the symbol Y indicates the difference in height between the height position Lbc of the rotational axis RAb of the bull gear 12 and the height Lfc of the rotational axis RAf of the female rotor 5. Also in Fig. 3, the symbol θ indicates the angle formed by the line connecting the rotational axis RAm of the male rotor 4 and the rotational axis RAb of the bull gear 12 with respect to the line connecting the rotational axis RAm of the male rotor 4 and the rotational axis RAf of the female rotor 5. This angle θ is set, for example, in the range of 5 degrees to 20 degrees.

[0032] In this embodiment, the male rotor 4 and the female rotor 5 are arranged side by side; more specifically, the height position Lmc of the rotational axis RAm of the male rotor 4 and the height position Lfc of the rotational axis RAf of the female rotor 5 are the same. Furthermore, in this embodiment, the bull gear 12 is not arranged directly above the pinion gear 11, but is arranged so as to overlap with the female rotor 5 when viewed from the direction in which the rotor shaft 4a of the male rotor 4 extends. In other words, the bull gear 12 is arranged diagonally above, or nearly side by side with, the male rotor 4. This reduces the overall height of the oil-cooled screw compressor 1 and makes it possible to miniaturize the entire device. In particular, by arranging the bull gear 12 so as to overlap with the female rotor 5 when viewed from the direction in which the rotor shaft 4a of the male rotor 4 extends, that is, by arranging the bull gear 12 not directly above, but diagonally above, the pinion gear 11, it is possible to reduce the overall height of the internal combustion engine 10 connected to the bull gear 12. The internal combustion engine 10 is large compared to the compressor body 2, and in particular has a high overall height, so reducing the overall height of the internal combustion engine 10 effectively contributes to downsizing the entire oil-cooled screw compressor 1 device by reducing its overall height.

[0033] Although the bull gear 12 is disposed diagonally above and nearly side-by-side with the male rotor 4, the lowest end 12a of the bull gear 12 is located above the height position Lml of the lowest end 4b of the male rotor (which can be considered to be the same height as the height position Lrc of the lowest end 2g of the rotor chamber 2a, as described above), that is, above the assumed maximum height of the height position Lo of the lubricating oil level collected in the oil reservoir 3b. Therefore, loss caused by the bull gear 12 stirring the lubricating oil in the oil reservoir 3b can be avoided or reduced.

[0034] As described above, in the oil-cooled screw compressor 1 of this embodiment, it is possible to reduce the loss caused by oil agitation in the speed-increasing gear 3, while also achieving a reduction in the size of the entire device.

[0035] In order to reduce the size of the entire device while avoiding oil agitation in the gearbox 3, it is preferable that the height position Lbl of the lowest end 12a of the bull gear 12 is located slightly above the expected maximum height of the height position Lo of the lubricating oil level collected in the oil reservoir 3b, that is, slightly above the height position Lml of the lowest end 4b of the male rotor in this embodiment. Therefore, for example, the height position Lbl of the lowest end 12a of the bull gear 12 is set to be located between the height position Lml of the lowest end 4b of the male rotor 4 and the height position Lfl of the lowest end 5b of the female rotor 5.

[0036] Fig. 4 shows a modified example of this embodiment. In this embodiment, the gear ratio, which is the ratio of the number of teeth of the bull gear 12 to the number of teeth of the pinion gear 11, is 2.1, whereas in the modified example of Fig. 4, the gear ratio (speed-up ratio) is 3. [Explanation of symbols]

[0037] 1. Oil-flooded screw compressor 2 Compressor body 2a Rotor chamber 2b Main casing (first casing) 2c Intake port 2d outlet 2e Suction port 2f communication hole 2g bottom end 3. Gearbox 3a Gearbox casing (second casing) 3b Oil reservoir 4 Male Rotors 4a Rotor shaft 4b Bottom end 5 female rotors 5a Rotor shaft 5b Bottom end 6,7,14 Bearings 10 Internal combustion engine 11 Pinion gear 12 Burgia 12a Bottom end 13 Input shaft RAm, RAf, RAb rotation axis Lmc, Lfc, Lrc, Lml, Lfl, Lo, Lbl, Lbc height position RDb, RDp, RDm, RDf rotation direction

Claims

1. a compressor body comprising a first casing provided with a rotor chamber accommodating a male rotor and a female rotor arranged side by side, a suction port provided at the upper side communicating with an intake port, and a discharge port provided at the lower side, wherein air drawn in through the intake port is compressed by the male rotor and the female rotor and discharged from the discharge port, and the diameter of the male rotor is larger than the diameter of the female rotor; a speed increaser including: a pinion gear fixed to a rotor shaft of the male rotor; a bull gear meshing with the pinion gear and transmitting rotation of a prime mover to the pinion gear; and a second casing accommodating the pinion gear and the bull gear and having an oil reservoir at its bottom that communicates with the rotor chamber via the suction port. Equipped with the bull gear is disposed obliquely above the pinion gear and overlaps with the female rotor when viewed from the direction in which the rotor shaft extends, an oil-cooled screw compressor, wherein a height position of a lower end of the bull gear is located between a height position of a lower end of the male rotor and a height position of a lower end of the female rotor;

2. 2. The oil-cooled screw compressor according to claim 1, wherein the prime mover is an internal combustion engine.

3. 3. The oil-cooled screw compressor according to claim 1, wherein a speed-increasing ratio of the speed-increasing gear is 2 or more and 3 or less.

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