JP2846065B2 - Liquid injection screw fluid machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the shape of a casing bore in a liquid injection type screw fluid machine.

[Conventional technology]

A screw-type fluid machine that handles gas has two types: a liquid-jet type, in which a liquid such as oil or water is injected into a working chamber to act on a fluid in a gas-liquid mixed phase state, or a gas-jet type, in which no liquid is injected into the working chamber. There is a dry type that operates on a phase-only fluid.

The liquid jet type, which is the object of the present invention, has a function of cooling the jet liquid,
Due to the sealing action or the lubrication action, high efficiency can be obtained even at low speed operation, and it is widely used as a general-purpose air compressor, compressor for air conditioner, vacuum pump, or expander.

A liquid jet type screw fluid machine is disclosed in, for example, Japanese Patent Publication No. 40-12
No. 437, and the detailed structure is, for example,
It is disclosed in Japanese Patent Publication No. 42-10027. Twisted peaks are formed in the pair of male and female rotors, and grooves formed between the peaks serve as working spaces. The outer circumference and end of the rotor are
Except for a part, it contacts the casing through a narrow gap,
The rotor is housed substantially in a casing. Accordingly, each groove formed in the rotor forms a substantially closed space except at the time of fluid inflow and outflow.

In order to ensure a smooth rotation of the rotors, in practice small gaps are provided between both rotors and between the rotor and the casing, from which the working fluid leaks. However, in the liquid injection type, a liquid such as oil is injected into the groove, and this liquid seals the gap, so that high efficiency can be obtained at low speed operation.

[Problems to be solved by the invention]

As described above, the liquid injection type has the feature that high efficiency can be obtained at low speed operation, but on the other hand, from the standpoint of reducing the installation area of the equipment and saving resources such as materials, the speed is increased and the equipment volume per processing air volume is increased. There is an increasing demand for reducing device weight.
However, when the liquid injection type is operated at a high speed, the stirring power of the injected liquid increases, and the efficiency of the fluid machine decreases. This will be described below with reference to FIG. 7 for an oil-cooled compressor.

This figure is a view in which a part of the working chamber on the female rotor side of the oil-cooled screw compressor is cut in a section perpendicular to the rotor axis. In the drawing, reference numeral 1 denotes a casing, 2 denotes a female rotor, and working gas is confined in a working space 5 surrounded by a peak 3 of the female rotor and an inner wall 7 of a bore provided in the casing. Accordingly, the working gas is compressed. The pressure of the working gas is different for each groove. On the other hand, a narrow gap is provided between the mountain 3 and the bore inner wall surface 7 of the casing 4, but a thin layer of oil is formed on the bore inner wall surface 7, and this oil fills the gap, Seal gas leakage from groove to groove. The reason why oil is relatively abundantly present on the bore inner wall surface 7 is that oil is shaken off and collected on the inner wall surface by centrifugal force due to rotation of the rotor.

In order to achieve a sufficient sealing effect, the amount of oil must be increased to some extent. On the other hand, oil adhering to the inner wall surface of the bore is collected by the tip of the rotor, and as shown in FIG. At the same time, there is a resistance to the movement of the rotor.
This is the same on the male rotor side.

The oil mass 8 collected as described above becomes larger as the rotation of the rotor proceeds, and merges with the oil that has been collected by the other rotor at the intersection 10 of the inner wall surfaces 7 and 9 of the casing bores of the male and female rotors. The merged oil has no place in the direction of rotation of the rotor, and is then pushed by the tips of both rotors and moves in the direction of the discharge port along the line of intersection of both bores.
The amount of oil scraped increases as it gets closer to the discharge port, and the resistance against the rotation of the rotor also increases. Such resistance due to oil naturally increases as the rotation speed of the rotor increases.

As described above, in the conventional liquid-injection type screw compressor, no consideration is given to the fact that the oil mass collected at the tip of the rotor becomes a resistance to the rotation of the rotor. There was.

In the above, the example of the oil-injection type screw compressor has been described. However, the same problem occurs when a liquid other than oil is injected or a vacuum pump is used regardless of the compressor.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the efficiency of a screw fluid machine by allowing a mass of oil collected before the tip of the rotor to escape behind the tip of the rotor.

[Means for solving the problem]

According to the present invention, in order to achieve the above object, the inner diameter of the bore near the intersecting line of the male and female bores on the compression side is made larger than other portions.

Further, in order to allow only the jet liquid to efficiently escape to the rear of the rotor tip, the inner wall radius is changed so as to gradually increase toward the intersection of both bores in the direction of travel of the rotor tip.

Further, in order to obtain an effect by simple processing, the sharp portions of both bore intersection lines are flattened off.

[Action]

As described above, the gap between the rotor tip and the bore inner wall is increased by enlarging the bore radius near the compression-side bore intersection line, and the mass of oil collected by the rotor is reduced to the working space. Due to the pressure difference between the working space behind the rotor tip and the working space behind it, it is displaced behind the rotor tip. Therefore, the resistance against the movement of the rotor is reduced, and the rotational power of the rotor is reduced. Since the portion where the bore radius is increased is limited to the vicinity of the line of intersection of both bores on the compression side, the oil film does not break in the gap between the bore inner wall surface and the tooth tip. Therefore, there is no possibility of gas leakage despite the increased clearance, and a highly efficient screw fluid machine particularly suitable for high-speed operation can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the oil-injection screw compressor shown in FIGS.

In FIG. 1, the male rotor 11 is rotatably mounted on the casing 1 and the discharge side casing 17 via bearings 13 and 14, and the female rotor 2 is mounted on bearings 15 and 16 respectively. The casing 1 and the discharge side casing 17 are fixed to each other by bolts (not shown).

As shown in FIG. 2, the male rotor and the female rotor are each carved with teeth 3 and 12, and a working space is formed by grooves between these teeth and a casing 1 covering both rotors. You. When the two rotors rotate in the directions of arrows 6 and 13, respectively, the volume of each groove changes due to the three-dimensional engagement of the two rotors, and operation as a positive displacement fluid machine is performed. Here, the bore intersection 10 on the side where both rotors engage is referred to as the bore intersection on the compression side and the bore intersection 31 on the opposite side.
Is referred to as an expansion-side bore intersection. The same applies to the bore intersection. In FIG. 1, a pulley is attached to the end of the shaft 18 of the male rotor.
19 is attached and driven by an electric motor or the like via a belt (not shown). The drive system may of course be a gear instead of a pulley, or a direct connection with a shaft of a drive source. In this embodiment, the female rotor is directly driven by meshing with the male rotor, but a synchronous gear may be attached to the shaft ends of both rotors, and the rotors may be meshed with each other in specific contact.

A shaft sealing device 20 is attached to the drive shaft 18 so that oil lubricating the bearings 13 and 15 does not leak outside the compressor.
Seal 18 outer surface. Hole 21 in the side wall of casing 1
Is provided, and oil is injected toward the rotor. This oil cools the working gas, seals the gap between the sliding parts, lubricates the meshing part, and is discharged from the discharge port 21 to the outside of the compressor together with the high-pressure gas. After being separated from the gas by a cooler and then injected again into the compressor.

In this embodiment, the oil is directly injected toward the rotor, but the effect of the present invention does not change even if the oil is sucked into the rotor together with the working gas from the low pressure port.

Oil is also supplied from another oil supply port 22, and the suction side bearing 13 and
After lubricating 15, the rotor is sucked into the rotor through gaps 23 and 24 between the shaft hole and the shaft. Further, oil is supplied from another oil supply port 25, part of which enters directly into the bore for accommodating the rotor, and the rest lubricates the discharge-side bearings 14 and 16, and then the hole is formed.
Flows into the bore via 26. These oils mix with the injection oil in the rotor and are discharged to the discharge port together with the gas.

In the bore inner wall, a portion facing the rotor groove during the suction stroke is provided with a relief portion shown as 27 and 28 in FIGS. This is to eliminate the sliding loss between the tooth tip and the bore inner wall via oil, and since the pressure of each groove is almost equal to each other during the suction stroke, the gap between the tooth tip and the bore inner wall is reduced. Such relief is conventionally provided because it does not cause leakage loss even if it is large.

In most areas of the bore inner wall facing the grooves of the compression stroke and discharge stroke, the gap between the rotor tip and the bore inner wall can be made in a range where safe operation is ensured to reduce leakage loss. It is set to be as small as possible. However, in the present embodiment, as shown in FIG.
The bore radius between the point 27 of the male bore and the intersection 10 and between the point 28 of the female bore and the intersection 10 is larger than the other portions.

The area of the portion where the bore radius is enlarged is shown on the developed bore diagram of FIG. In this figure, the bore inner wall surfaces 7 and 9 of FIG. 2 are cut open at the expansion side bore intersection 31. In the figure, the closed section surrounded by the line from 32 to 32 through 33, 37, 38, and 39 is surrounded by the bore wall surface on the male rotor side, and the line from 34 to 34 through 33, 37, 36, and 35 to 34. The closed section corresponds to the bore wall surface on the female rotor side. Reference numeral 21 denotes a discharge port, which is provided on the discharge end face of the bore between 38 and 39 on the male rotor side and between 36 and 35 on the female rotor side, and between 32 and 33 on the male rotor side and the female rotor side. The side from 33 to 34 corresponds to the suction end face of the bore. Further, a straight line 49 connecting 33 and 37 is a compression side intersection line of both bores. Two-dot chain lines represented by 40 and 41 are development lines of the helix of the tip of the rotor at a certain rotation angle.

Section surrounded by a line from 42 to 42 through 33, 45 and 46
47 and section 48 from 43 to 43 via 33, 45 and 44
Are the bore radius enlarged portions in the present invention. In the present embodiment, the bore enlarged portion is distributed in the male and female bores across the compression-side bore intersection line 49, and starts in the axial direction from the suction end side and extends in the discharge port direction. It does not reach the end and ends on the way.

The suction end side does not necessarily start from the suction end, but may extend from the position somewhat away from the suction end to the discharge port side as shown in FIG. 4 which is a second embodiment of the present invention. .

According to this embodiment, the oil collected by the male rotor tip 12 and the female rotor tip 3 near the compression side intersection line 49 of both bores passes through the space of the radially enlarged portion of the bore. Since the oil is released to the rear of the tooth tip, the oil in front of the tooth tip is reduced, and the resistance against rotation of the rotor can be reduced. The amount of collected oil is not sufficient in a portion of the two bores away from the compression side intersection line 49. If the bore inner wall radius is large, the oil film is cut, causing gas leakage and reducing the efficiency of the compressor. But,
In the present embodiment, since the enlarged portion of the bore inner wall radius is limited to the vicinity of the compression side intersection line 49 of both bores, there is no possibility that the oil film will be cut in this way.

Further, in a place close to the discharge port, since the pressure difference between the adjacent grooves is large, the oil film may be cut off when the bore radius is large, and in this embodiment, the enlarged portion of the bore radius is on the suction side. It is limited to the approach. However, when the amount of oil is sufficient and the rotation speed is high, the leakage near the discharge port may not significantly affect the performance. In such a case, the enlarged portion of the bore radius is extended to reach the discharge port. You can also. Since the oil resistance exerted on the rotor becomes smaller as the enlarged portion of the bore radius becomes wider, it is better to increase the enlarged portion of the bore radius as long as the oil film is not broken.

As shown in FIG. 4, if the enlarged bore is separated from the suction end by any distance, there is no change in the radius near the suction end face, so that the bore diameter can be easily measured, which is convenient for processing accuracy control. It is sufficient if the distance from the enlarged bore to the suction end is in the range of about 3mm to 5mm.

FIG. 5 shows a third embodiment of the present invention. 1 in the figure
Is the casing, 9 and 7 are the inner wall surfaces of the male and female bores, respectively, and 10 is the intersection of the compression side of both bores. The illustration of the rotor is omitted. In the present embodiment, the bore radius gradually increases from 52 to 51 of the bore inner wall surface 9 on the male rotor side.
Similarly, the bore radius gradually increases from 50 to 51 of the bore inner wall surface 7 on the female rotor side. According to this embodiment, the amount of increase in the bore radius is the largest on the bore intersection line where the amount of collected oil is the largest, and there is no waste in the passage area where oil escapes. Therefore, the possibility that the oil film breaks under various refueling conditions and operating conditions is greatly reduced.

Further, in this embodiment, when the tip of the rotor reaches the enlarged bore radius portion, there is no sharp increase in the tip clearance, so that the impact applied to the rotor is small and quiet operation can be performed.

FIG. 6 shows a fourth embodiment of the present invention. 1 in the figure
Is the casing, 9 and 7 are the inner wall surfaces of the male and female bores, respectively, and 10 is the intersection of the bosses on the compression side. In this embodiment, the male side 53 and the female side near the compression side intersection 10 of both bosses.
Make a cut on a straight line or arc between 53 and 53. This method is easy to process and can exert the effects of the present invention, and is industrially very effective.

5 and 6, similarly to the embodiment of FIG. 2, the axial distribution range of the bore radius enlarged portion is shown in FIGS.
It is effective to approach the suction end side as shown in the figure.

The above is an example in which the present invention is applied to an oil-cooled screw compressor, but the present invention can be applied not only to a compressor but also to a vacuum pump. The effect is the same in the case of a liquid.

[Effects of the Invention] According to the present invention, the oil mass that collects at the front of the rotor tip that rotates and moves along the casing bore wall is effectively eliminated at the rear of the rotor tip, so that the oil resistance against the rotor rotation is reduced. Is reduced. In addition, since the enlarged portion of the bore radius for releasing the oil lumps is limited to the portion having a large amount of oil lumps, there is no possibility that the working gas escapes from the enlarged portion, and a screw fluid machine with less energy loss can be obtained.

[Brief description of the drawings]

1 is a longitudinal sectional view of an oil-cooled screw compressor according to one embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. FIG. 4 is a developed view of the inner wall surface of the bore of the second embodiment of the present invention, and FIGS. 5 and 6 are enlarged cross-sectional views of the main part of the casing in the third and fourth embodiments of the present invention, respectively. FIG. 7 is an explanatory view of a conventional screw fluid machine. DESCRIPTION OF SYMBOLS 1 ... Casing, 2 ... Female rotor, 3 ... Female rotor tooth tip, 7 ... Female rotor side bore inner wall surface, 9 ... Male rotor side bore inner wall surface, 10 ... Compression side intersection of both bores, 11 … Male rotor, 12… Male rotor tip, 47… Male rotor side bore radius enlarged part, 48… Female rotor side bore radius enlarged part, 49… Compression side intersection of both bores.

Claims (1)

(57) [Claims] A casing having a space formed by two intersecting bores, a low pressure port formed in communication with one side of the space, and a high pressure port formed in communication with the other side; And a pair of male and female rotors in which a plurality of grooves existing between the peaks and between the peaks are formed in a spiral shape, and the pair of rotors are fitted in the bore so as to be engaged with each other. A screw fluid machine in which a plurality of working spaces are formed between a rotor and the casing, wherein a compression is performed on the bore inner wall surface facing the groove in a stroke not communicating with any of the low-pressure port and the high-pressure port. A bore radius near the line of intersection of the two bores on the side is larger than a bore radius of another portion of the inner wall surface of the bore.