JPH0823353B2 - Screw fluid machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a screw fluid machine, and more particularly to a screw fluid machine suitable for reducing thermal deformation of a casing near a high pressure chamber.

[Conventional technology]

Conventional screw fluid machines are generally used, for example, in Japanese Patent Publication
A structure as described in Japanese Laid-Open Patent Publication No. 56-17559 is known.

A twisted crest is engraved on the pair of male and female rotors, and a groove formed between the crests serves as an operating space. The outer peripheral portion and the end portion of the rotor are in contact with the casing through a narrow gap except for the low pressure port and the high pressure port of the gas, and the rotor is substantially wrapped in the casing.

Therefore, the groove carved in the rotor forms a closed space except for the suction stroke and the discharge stroke, and the volume of this space changes with the rotation of the rotor, thereby sucking and discharging the gas, and It is compressed or expanded.

In order to ensure smooth rotation, a narrow gap is provided between the rotor as well as between the rotor and the casing as described above.

However, since high-pressure gas leaks from one groove to another groove through these gaps, resulting in loss of power, it is desirable to make the gaps as small as possible within the range where smooth rotation is not hindered.

By the way, the above internal clearance of the screw fluid machine is
Compared to the assembled state at room temperature, it changes due to various factors during operation. Above all, thermal deformation of the casing and the rotor has the greatest effect on the change in the clearance.

Generally, in an oil-free fluid machine, the fluid temperature on the high-pressure side is very high, and for example, in a single-stage air compressor with a discharge pressure of 0.8 MPa, it becomes 300 ° C. or higher. The rotor and casing exposed to this temperature locally reach the same temperature as this, causing thermal deformation, which greatly affects the internal clearance.

Conventionally, a gap has been designed in consideration of thermal deformation of the rotor and the casing in advance, and a water jacket is provided in the casing to cool the casing in order to minimize the amount of thermal deformation.

[Problems to be Solved by the Invention]

As described above, conventionally, the gap design has been performed in consideration of the thermal deformation of the casing. However, the amount of thermal deformation during operation changes intricately depending on operating conditions, and if a gap is designed in consideration of all possible operating conditions, there will be a larger gap than necessary in normal operation. . In order to fill the extra gap, it is effective to reduce the amount of thermal deformation of the casing, and for that purpose, it is necessary to suppress the heating of the casing by the gas as small as possible.

By the way, among the various parts of the casing, it is the vicinity of the high pressure port that is most exposed to the high temperature gas. Also, since high pressure is applied to the inner wall of the casing near the high pressure port,
In terms of strength, the vicinity of the high pressure port is formed with a thicker wall than other parts. In addition, the mounting seat for the external pipe that connects to the high-pressure chamber is also manufactured firmly.

Therefore, in the thermal deformable body of the casing, the amount of thermal deformation near the high pressure port is dominant. It does not simply mean that the amount of thermal deformation is the largest because this neighborhood has the highest temperature. When the casing is viewed as an elastic structure, since the vicinity of the high-pressure port is firmly formed, the amount of thermal deformation near this area is wide and extends to other parts. Is.

Therefore, cooling near the high pressure port is especially important. However, in addition to the bore for accommodating the male and female rotors, parts such as the rotor shaft and the shaft seal are concentrated in the vicinity of this, the cooling effect due to the water jacket is difficult to reach due to the structure.

On the other hand, in the vicinity of the high pressure port, the pressure difference of the gas between the grooves of the rotor is large, so the leakage from the internal clearance has the greatest effect on the performance, which improves the performance and reliability of the screw fluid machine. In order to do so, it is necessary to reduce the amount of thermal deformation by minimizing the heating near this point. However, in the conventional screw fluid machine, as described above, no measure is taken to suppress the heating near the high pressure port, and the internal clearance during operation was designed to be larger than necessary.

The present invention has been made to solve the above problems in the prior art, reduces heating in the vicinity of the high pressure port of the casing, reduces the amount of thermal deformation in the vicinity to appropriately suppress the internal clearance, and improves the performance of the fluid machine. It is an object of the present invention to provide a screw fluid machine capable of improving the reliability and reliability.

[Means for solving the problem]

In order to achieve the above object, the configuration of the screw fluid machine according to the present invention is such that the intersecting 2 communicates with one side of the space formed by the bore to form a low pressure port, and to communicate with the other side to form a high pressure port. Having a casing formed, a pair of male and female screw rotors meshing with each other in the casing,
In the screw fluid machine in which the working space is formed between the pair of male and female screw rotors and the casing, the inner wall of the casing high pressure chamber from the high pressure port to the high pressure external pipe is configured to be covered with a heat insulating layer. It is a thing.

[Action]

The concept of the development of the above technical means and its function will be described below.

As described above, in the screw fluid machine, the hot gas is most exposed to the vicinity of the high pressure chamber, and the heat entering the casing from this part is transmitted through the meat part of the casing, and most of it is provided inside the casing. It is carried away by the water in the water jacket, but partly from the outer surface of the casing to the atmosphere, and partly from the inner wall surface on the low pressure side to the gas on the low pressure side,
Heat it.

The temperature of each part of the casing is determined by the balance between the amount of heat that enters and leaves the casing wall surface and the amount of heat that conducts through the meat part, but even near the high pressure port, the amount of heat that the casing wall receives from the high pressure gas and The internal temperature is determined by the balance with the amount of heat that is transmitted to the low temperature side. Then, if the amount of heat received from the high pressure gas decreases, the temperature of the meat portion decreases.

Therefore, by covering the inner wall of the high-pressure chamber with the heat insulating layer, the temperature of the casing near the high-pressure chamber decreases, and the amount of thermal deformation near this region can be reduced.

As described above, the thermal deformation in the vicinity controls the thermal deformation of the entire casing, and by reducing these, the amount of deformation of the entire casing can be reduced.

By reducing the thermal deformation of the casing in this way, the gap during normal operation can be made smaller than in the past, and the performance of the screw fluid machine is improved.

The performance improvement of the screw fluid machine is due to the following two reasons.

First, the reduction in the amount of thermal deformation of the casing reduces the expansion of the diameter of the bore that houses the rotor, and reduces the gap between the tooth tip of the rotor and the inner wall of the bore.

Secondly, it is possible to reduce the margin width of the gap to be given to the fluid machine in advance, in consideration of various possible operating conditions.

Further, the reduction in the amount of heat transfer from the high-pressure side gas to the casing reduces the heat transfer from the high-pressure side gas to the low-pressure side gas through the casing. Therefore, when the fluid machine is a compressor, heating of the suction gas is reduced, and when the fluid machine is an expander, energy loss of the high-pressure side gas is reduced, and each has an action of improving the property.

Furthermore, when the amount of thermal deformation of the casing is reduced, gap management becomes easier, and reliable operation becomes possible.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.

First, FIG. 1 is a vertical sectional view of a screw compressor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II of FIG.

The embodiment shown in FIGS. 1 and 2 is an example of an oil-free air compressor. In the case of a compressor, the low pressure side is the suction side and the high pressure side is the discharge side.

In FIG. 1, 1 indicates a male rotor of a pair of male and female screw rotors. Reference numeral 3 is a casing, 4 is a suction casing that is in contact with the suction side of the rotor (suction chamber 30, suction port 31), and 5 is a discharge cover that covers the discharge side end of the rotor shaft. A shaft 6 and a shaft 7 are respectively formed on the suction side and the discharge side of the rotor, the shaft 6 on the suction side is formed by a cylindrical roller bearing 8, and the shaft 7 on the discharge side is formed by a cylindrical roller bearing 9 and a combination angular contact ball bearing 10, respectively. It is supported. Further, in order to keep the compression chamber airtight, shafts 11 and 12 are provided respectively on the suction side shaft 6 and the discharge side shaft 7, and further, the lubricating oil of the shaft life leaks from the shaft sealing portion and is compressed space. Oil drains 13 and 14 are installed respectively to prevent entry.

Between the shaft seal 11 and the oil drainer 13, and between the shaft seal 12 and the oil drainer 14, there are gas vent holes so that if the oil leaks from the oil drainer, oil will not enter the shaft seal part. 15 and 16 are provided.

FIG. 2 shows a pair of screw rotors meshing with each other in the casing. That is, the male rotor 1 meshes with the female rotor 2 and two bores intersecting each other like a pair of glasses.
Each rotates in 17,18.

A timing gear 19 is provided at the shaft end of the male rotor 1 as shown in FIG. 1, and meshes with a timing gear (not shown) on the female rotor 2 side. With this timing gear, the rotation angles of the male and female rotors 1 and 2 are synchronized with each other and rotate without contacting each other through a narrow gap.

The male rotor 1 is driven by a pinion 20 attached to the shaft end from a drive source such as an external electric motor. Bearing on the suction side
8. Lubricating oil is supplied to the bearings 9 and 10 on the discharge side and the timing gear 19 through oil supply holes 21, 22 and 23, respectively. These lubricating oils are discharged from the oil drain holes 24 and 25 after lubricating the bearing or the gear.

A water jacket 26 is formed outside the bores 17 and 18, and cooling water is supplied from the outside through a water inlet and a water outlet (not shown) to cool the casing.

In this embodiment, a heat insulating pipe 34 functioning as a heat insulating layer is inserted into the discharge chamber 33 so as to cover the inner wall 43 of the discharge chamber. A flange 35 is formed on a part of the outside of the heat insulating pipe 34, and the flange 35 is connected via a gasket 36, 37 to a flange 39 of the discharge pipe 38 related to the high pressure external pipe and a pipe mounting seat on the casing. Sandwiched between 40 and bolt 41
It is fixed and supported by.

The casing 3 is generally made of cast iron or aluminum, but the heat insulating pipe 34 is made of ceramics or the like having a lower thermal conductivity. For example, the thermal conductivity of alumina sintered bodies and silicon nitride ceramics is a fraction of the thermal conductivity of ordinary cast iron, and the thermal conductivity of zirconia ceramics is 1/10 that of cast iron. It is as follows and is suitable as a material for the heat insulating pipe of the present embodiment. Moreover, all of these ceramics have high heat resistance,
Even if it is used in an air compressor with a discharge temperature of about 300 ° C, it can withstand enough.

Nickel steel, nickel chrome steel, and the like generally have a thermal conductivity of a fraction or less of that of ordinary cast iron, and are suitable as materials for the heat insulating pipe 34 in this example.

In this embodiment, a slight gap 44 is provided between the outer wall 42 of the heat insulating pipe 34 and the inner wall 43 of the discharge chamber.

Now, in the single-stage air compressor, the temperature of the discharge air becomes close to 300 ° C. as described above, but after this high-temperature and high-pressure gas is discharged from the discharge port 32, it passes through the heat insulating pipe 34 and the discharge pipe 38.
Exit to. Since the conventional compressor does not have such a heat insulating pipe, the discharge gas directly contacts the inner wall 43 of the discharge chamber 33 and heats the casing 3. However, by covering the inner wall 43 with the heat insulating pipe (heat insulating layer) 34 as in the present embodiment, the transfer of heat from the hot discharge gas to the casing 3 is significantly reduced, and the temperature of the casing near the discharge chamber 33 is reduced. To do. Since air stagnates in the gap 44 between the inner wall 43 of the discharge chamber and the heat insulating pipe 34, the amount of heat transferred from the air in the gap 44 to the casing 3 is small.

On the other hand, as described above, the water jacket 26 is provided in the casing 3 to cool the casing. Discharge chamber wall
A slight amount of heat transmitted from the casing 43 through 43 is carried away to this cooling water, and the temperature of the casing 3 is considerably lowered as compared with the case of the conventional screw compressor without the heat insulating pipe.

The cut cross section of the heat insulating pipe 34 is most preferably a circular cross section in order to minimize the contact area with the discharge air. Does not prevent the effect of.

According to the present embodiment, it is possible to reduce the heating of the casing around the discharge chamber (high pressure chamber), which is particularly dominant in the thermal deformation of the casing of the screw compressor. Therefore, the amount of thermal deformation of the casing is reduced, an extra internal clearance for safety during operation can be reduced, and heating of the low-pressure side gas is also reduced, so that the performance of the screw compressor is improved. Further, there is no risk of contact between the rotors or between the rotor and the casing, and there is an effect that reliable operation can be performed.

Next, FIG. 3 is an enlarged cross-sectional view of the vicinity of the discharge chamber of the screw compressor according to another embodiment of the present invention. First in the figure
The parts having the same reference numerals as those in the figure are the same parts as those in the embodiment of FIG.

In the embodiment shown in FIG. 3, one end of the heat insulating pipe 34A that functions as a heat insulating layer that covers the inner wall 43 of the discharge chamber is fitted into a hole 51 provided in the flange 39 of the discharge pipe 38, and is pushed toward the casing side by the spring 52. It is fixed. The discharge pipe 38 is fitted with a gasket between the flange 39 and the pipe mounting seat 40 on the casing.
It is sandwiched between 36 and fixed with bolts 41.

According to the embodiment shown in FIG. 3, the same effect as that of the previous embodiment is expected, and the structure of the heat insulating pipe is simple and easy to install.

Next, FIG. 4 is an enlarged cross-sectional view of the vicinity of the discharge chamber of the screw compressor according to still another embodiment of the present invention. In the figure, those having the same reference numerals as those in FIG. 1 are the same parts as those in the embodiment of FIG.

In the embodiment of FIG. 4, the heat insulating pipe 34B that functions as a heat insulating layer that covers the inner wall 43 of the discharge chamber is attached to the inner wall 43 of the discharge chamber, that is, the wall of the casing, by an adhesive material 53. When there is a large difference in the coefficient of linear expansion between the material of the heat insulating tube 34B and the material of the casing, a wall made of a third material is sandwiched between them to absorb the difference in the amount of thermal deformation between them. , Stable attachment is possible.

Further, in the embodiment shown in FIG. 4, the discharge gas flow passage area inside the heat insulating pipe 54 gradually changes along the flow passage to minimize the flow passage resistance and guide the gas to the discharge pipe 38. Further, by gradually increasing the flow passage area from the discharge port 32 toward the discharge port pipe 38, the adiabatic pipe 34B also serves as a diff user, and the velocity of the gas discharged at high speed is effectively converted into pressure. can do.

With the structure in which the heat insulating pipe 34B is attached to the casing with the adhesive material 53 as in the present embodiment, the assembly of the device is particularly easy.

It should be noted that although the above embodiments have been described by taking the compressor as an example, it goes without saying that the present invention is not limited to the compressor and can be applied to an expander or a vacuum pump.

Also, in the above-mentioned screen compressor, the structure of cooling the casing with water was explained, but instead of providing a water jacket, a heat dissipation fin is provided outside the bore to cool the casing with air, or forced The present invention can also be applied to the case of a screw compressor of a type in which cooling is not performed and natural heat is radiated from the outer wall of the bore, and the same effects as those described above are expected.

〔The invention's effect〕

As described above, according to the present invention, the heating in the vicinity of the high pressure port of the casing is reduced, the amount of thermal deformation in the vicinity is reduced, the internal clearance is appropriately suppressed, and the performance and reliability of the fluid machine are improved. It is possible to provide a clear fluid machine.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a screw compressor according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II of FIG. 1, and FIG.
FIG. 4 is an enlarged sectional view near a discharge chamber of a screw compressor according to another embodiment of the present invention, and FIG. 4 is an enlarged sectional view near a discharge chamber of a screw compressor according to still another embodiment of the present invention. Is. 1 ... Male rotor, 2 ... Female rotor, 3 ... Casing,
17,18 …… Bore, 30 …… Suction chamber, 31 …… Suction port, 32 ……
Discharge port, 33 …… Discharge chamber, 34, 34A, 34B …… Insulation pipe, 35 ……
Flange, 36,37 …… Gasket, 38 …… Discharge pipe, 39
...... Flange, 40 ...... Piping mount, 42 …… Outer wall, 43 ……
Inner wall, 44 …… Gap, 51 …… Hole, 52 …… Spring, 53 …… Adhesive material, 54 …… Insulation pipe inside.

Claims (1)

[Claims] 1. A casing having a low-pressure port communicating with one side of a space formed by two intersecting bores and a high-pressure port communicating with the other side of the space. In a screw fluid machine including a pair of male and female screw rotors meshing with each other, and an operating space is formed between the male and female screw rotors and a casing, an inner wall of a casing high pressure chamber from the high pressure port to a high pressure external pipe The screw fluid machine is characterized in that it is configured so as to be covered with a heat insulating layer.