JPH03995A - Screw fluid machine - Google Patents

Abstract

PURPOSE:To enable the even cooling of a pair of rotors in the circumferential directions by providing a means to rotate the rotors under non-operation condition in an idle manner, in a screw fluid machine housed in a casing while the rotors having spiral land and groove parts are meshed with each other. CONSTITUTION:An oil free screw vacuum pump has therein a pair of male and female rotors 1, 2 which are capable of rotating freely as well as have hull parts with spiral land and goove parts and bearing parts 1A, 1B at the opposed ends. When the pump is turned into inoperative state, a sucking-in closing valve 9 is closed, while a cooling gas sealing-in valve 10 is opened and cooling gas having higher pressure than the atmospheric pressure is sealed in. The paired rotors 1, 2 are rotated with the pressure difference between a discharge port and a sucking in port 4 when the difference exceeds a specified value. Accordingly, the rotors are cooled evenly in the circumferential directions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a rotor cooling method and a cooling device during operation stoppage in a screw fluid machine.

[Conventional technology]

Conventionally, rotor cooling devices for screw fluid machines were developed in Japanese Patent Application Laid-open No. 5
As described in Japanese Patent No. 9-115492, a cooling passage is provided inside the rotor, and a cooling fluid is allowed to flow into the cooling passage to cool the rotor.

Therefore, when the operation is stopped, the rotor remains stopped and is cooled from inside the rotor, or is cooled naturally.

In addition, it is common to cool the rotor of a steam turbine or other device while it is idle by turning while the rotor is not in operation, but in screw fluid machines, cooling the rotor while it is idle is not adopted. It wasn't.

[Problem to be solved by the invention]

The above conventional technology does not take into consideration the uneven thermal deformation of the rotor due to the difference in the cooling effect in the circumferential direction of the rotor during operation and stop. screw fluid machine,
When the rotor is restarted after it has stopped operating before it has sufficiently cooled down, there has been a problem in that rotor vibration increases and rotor contact occurs.

An object of the present invention is to prevent uneven thermal deformation in the circumferential direction of the rotor during cooling.

[Means to solve the problem]

The above problem is solved by a pair of rotors having spiral land portions and grooves, which are housed in a casing in a rotatable state with their axes parallel to each other and meshing with each other. The gas is confined in a working chamber formed by the pair of rotors and the casing, and is discharged from a discharge port formed in the casing as the rotor rotates. This is achieved by providing means for idling the rotor.

The above problem is also solved by the fact that a pair of rotors having a spiral land portion and a groove are housed in a casing in a rotatable state with their axes parallel to each other and meshing with each other, and suction is taken from an inlet formed in the casing. The gas is confined in a working chamber formed by the pair of rotors and the casing, and is discharged from a discharge port formed in the casing as the rotor rotates. This is achieved by providing the suction port with means for supplying gas at a pressure higher than atmospheric pressure and the means for opening the discharge port to the atmosphere.

The above problem is also solved by a pair of rotors having a spiral land portion and a groove being housed in a casing in a rotatable state with their axes parallel and meshing with each other, and an inlet formed in the casing. A screw fluid machine in which the sucked gas is confined in a working chamber formed by the pair of rotors and the casing, and is discharged from a discharge port formed in the casing as the rotor rotates;
means for opening the inlet of the screw fluid machine to the atmosphere;
means for lowering the pressure at the discharge port below the pressure at the suction port;
This can also be achieved by having the following.

The above problem can also be solved by the screw fluid machine according to claim 1, which is provided with means for opening the discharge port and the suction port to the atmosphere at least while the rotor is idling. The present invention is also achieved by the screw fluid machine according to claim 1, comprising means for supplying the cooling gas and means for recovering or releasing the cooling gas from the discharge port to the atmosphere.

The above problem also arises in that the idling means is provided in a cooling passage provided inside the rotor and at least a part of which is concentric with the rotor rotation axis, and in a portion of the cooling passage that is concentric with the rotor rotation axis. The invention is also achieved by a screw fluid machine according to claim 1, comprising a turbine blade fixed to the rotor in a shape and means for supplying fluid to the cooling passage.

Furthermore, the above-mentioned problem is solved by a pair of rotors having a spiral land portion and a groove portion being housed in a casing in a rotatable state with their axes parallel to each other and meshing with each other, and an inlet formed in the casing. In a method of operating a screw fluid machine, the sucked gas is confined in a working chamber formed by the pair of rotors and the casing, and is discharged from a discharge port formed in the casing as the rotor rotates, After the screw fluid machine stops working,
This can also be achieved by cooling the rotor while it idles.

The above problem is also solved by a pair of rotors having a spiral land portion and a groove being housed in a casing in a rotatable state with their axes parallel and meshing with each other, and an inlet formed in the casing. In a method of operating a screw fluid machine, the sucked gas is confined in a working chamber formed by the pair of rotors and the casing, and is discharged from a discharge port formed in the casing as the rotor rotates, After the screw fluid machine has stopped operating, cooling gas is supplied to the suction port and the discharge port is opened to the atmosphere, and the rotor is rotated by the differential pressure between the cooling gas pressure at the suction port and the pressure at the discharge port. This can also be achieved by cooling the rotor with cooling gas flowing from the suction port through the working chamber to the discharge port as the rotor rotates.

The above problem is further solved by adding a cooling passage provided inside the rotor, at least a portion of which is concentric with the rotor rotation axis, to a rotor used in a screw fluid machine that has a spiral land portion and a groove portion on the outer peripheral surface. This can also be achieved by providing a portion of the cooling passage concentric with the rotor rotation axis with a turbine blade fixed to the rotor concentrically with the rotor rotation axis.

(Function) When the rotor is idled at a low speed while it is being cooled after it has stopped operating, the rotor is cooled uniformly in the circumferential direction, preventing bending of the rotor axis due to uneven rotor temperature distribution and uneven heating. No deformation occurs.

When the rotor is idled in a non-operating state, gas flows from the suction side to the discharge side via the working chamber, and the rotor is also uniformly cooled by the gas.

In addition, when the pressure at the discharge port is maintained low relative to the pressure at the suction port when the operation is stopped, the rotor will slowly move due to the relatively small pressure difference between the suction port and the discharge port due to the principles inherent in screw fluid machines. The rotor rotates, and the rotor is cooled uniformly in the circumferential direction. Furthermore, as the rotor rotates, gas from the suction port flows to the discharge port via the working chamber, and the rotor and casing are also cooled by this gas.

〔Example〕

FIG. 1 shows an oil-free screw vacuum pump to which the present invention is applied. A pair of rotors (consisting of a male rotor 1 and a 1lli rotor 2, one of which is a driving side and the other is a non-active side) having bearing parts IA and IB formed by the rotors 1 and 2. a casing 3 in which the rotors 1 and 2 are rotatably supported by the bearings, bearings 6A and 6B provided in the casing 3 that rotatably support the rotors 1 and 2, and bearings 6A and 6B provided in the bearings on the rotor body side. A shaft seal 7 provided adjacent to the shaft seal 7 is provided.

A suction port 4 is provided in the casing 3 near the left end of the screen of the rotor body, and a discharge port 5 is provided in the casing 3 near the right end of the screen of the rotor body.

The ends of the bearing portions IB (discharge port side) of the rotor tacos 2 protrude outside the casing 3, and timing gears 8 that mesh with each other are mounted on these protrusions. Further, the bearing portion I of each of the rotors 1.2
The end A (suction port side) slightly protrudes from the opposite shaft of the bearing 6A, and an oil ring 20 is attached to this protrusion.

Further, an oil reservoir 21 is formed in a portion of the casing 3 opposite to the copper shaft from the bearing 6A. Furthermore, casing 3
A non-contact displacement sensor 11 is mounted at a position facing the shaft end surface of the bearing portion IA, and detects the amount of thermal expansion of the rotor as the amount of decrease in the gap between the sensor and the shaft end surface.

The shaft seal 7 is connected to the bearing 6 by an oil ring 20 from an oil reservoir 21.
This prevents the lubricating oil supplied to A from leaking into the working chamber formed by the rotors 1 and 2 and the casing 3. The timing gear 8 transmits power from the driving rotor to the non-driving rotor, and adjusts the gap between the two rotors so that they do not come into contact with each other. Bearing part I on the discharge port side
The bearing 6B attached to the bearing 6B receives the radial load of the rotor and fixes the rotor in the axial direction.

The suction port 4 is equipped with a suction shutoff valve 9 and a cooling gas filling valve 10 (not shown) connected to a cooling gas source with a pressure higher than atmospheric pressure. Both of them are automatically opened and closed by an external electrical signal. It is a valve. The output side of the non-contact displacement sensor 11 is connected to a cooling gas filling valve 10. Furthermore, cooling passages 22 are formed inside the rotors 1 and 2, and cooling oil is flowed through the rotors 1 and 2 to cool them.

When this oil-free screw vacuum pump is in operation.

The suction shutoff valve 9 is open, and the cooling gas filling valve 10 is closed.

The gas flowing into the suction port 4 through the suction shutoff valve 9 is confined in a working chamber formed by a male/female rotor 1.2 and a casing 3 driven by an external drive device, and is
, 2 is compressed and discharged from the discharge port 5. On the other hand, when a stop command is issued to the externally driven prime mover and the vacuum pump is brought to a halt state, the suction shutoff valve 9 is closed, the cooling gas filling valve 10 is opened, and the cooling gas at a pressure higher than atmospheric pressure is supplied to the suction port 4. will be enclosed in. In this embodiment, which is a vacuum pump, the discharge port 5 is open to the atmosphere, so the pressure at the suction port 4 is higher than the pressure at the discharge port 5, and there is a pressure difference between the two due to the principle unique to screw fluid machines. When the value is exceeded, this pressure difference causes the male and female rotors to rotate.
Since the rotor rotates, the rotor is cooled uniformly in the circumferential direction, and bending of the rotor shaft during cooling and non-uniform thermal deformation do not occur. Further, as the rotor rotates, cooling gas flows from the suction port through the working chamber toward the discharge port, and this flow also provides a cooling effect for the rotor and the casing.

In a compressor or the like whose discharge port is not open to the atmosphere, a means for opening the discharge port to the atmosphere, such as an air discharge pipe, may be provided. Note that the pressure difference required to rotate the rotor is the smallest in the case of a screw expander, and in the case of a compressor, the larger the built-in pressure ratio, the larger the pressure difference is required.

As the rotor cools down and the rotor temperature decreases,
Since the amount of thermal expansion of the rotor in the axial direction decreases, the amount of gap detected by the non-contact displacement sensor 11 increases. When the gap amount reaches a preset value, a closing command is issued to the cooling gas filling valve 10, the cooling gas filling valve 10 is closed, and the rotor also stops idling. Note that if it is not desirable to release the cooling gas into the atmosphere, a pipe for recovering the cooling gas may be connected to the discharge port, and the cooling gas may be collected as appropriate while being careful not to increase the pressure at the discharge port beyond the permissible limit.

According to this embodiment, the rotor can be uniformly cooled simply by injecting cooling gas into the suction port without providing a separate drive device for idling the rotor. Furthermore, according to this embodiment, a decrease in the amount of thermal expansion of the rotor is detected, and the supply of cooling gas is stopped based on this detection result.
Cooling gas supply amount is minimized. Furthermore, when the rotor is restarted while the rotor is idling, the motor current required at startup can be reduced. Furthermore, since the pressure within the working chamber is higher than atmospheric pressure while the rotor is idling, there is no fear that lubricating oil will leak into the working chamber through the shaft seal 7.

In addition, by connecting the drive side rotor and the drive motor via a clutch (for example, an electromagnetic clutch) and releasing the connection of the clutch at the same time as the drive motor stops, rotational resistance when the rotor is idling is reduced. The pressure of the cooling gas supplied to the suction port 4 may be lowered.

In the above embodiment, a decrease in the amount of thermal expansion of the rotor is detected by a change in the gap detected by the non-contact displacement sensor 11,
Although the injection of cooling gas to the rotor is stopped, it is also possible to provide a rotor temperature detection means in place of the non-contact displacement sensor 11 and stop the injection of cooling gas when the rotor temperature drops to a predetermined value. good. Also, in advance,
Measure the time required to inject cooling gas and cool the rotor to a predetermined temperature while idling the rotor, and then start injecting cooling gas once the predetermined time has elapsed after starting the cooling gas injection. It may be configured to stop.

In addition, in the above embodiment, a cooling passage is formed in the rotor, and coolant is injected into the rotor, but as the rotor rotates,
The coolant uniformly contacts the circumferential direction of the wall surface of the cooling passage, and cooling from the inner surface is also performed uniformly.

Figures 2A and 2B illustrate a second embodiment of the invention. The oil-free screw compressor 12 has an electric motor 13
Driven by. The structure of the compressor main body is almost the same as that in FIG. 1, so it will be omitted. A discharge shutoff valve 14 is provided at the discharge port 5.
A discharge port exhaust valve 15 is provided, and a discharge port exhaust valve 1 is provided.
A vacuum pump 16 is provided on the downstream side of the pump 5 as a means for lowering the pressure at the discharge port below the pressure at the suction port. Since the suction port 4 is an air compressor, it is open to the atmosphere. In the case of a compressor that compresses a gas other than air, a means for opening the suction port to the atmosphere when the operation is stopped may be provided between the suction shutoff valve and the suction port.

FIG. 2A shows the oil-free screw compressor when it is in operation, and FIG. 2B shows the state when it is not in operation. Discharge shutoff valve 14. The discharge port exhaust valve 15 and the vacuum pump 16 operate in conjunction with the operation of starting and stopping the electric motor 13.

When the compressor is in operation, gas sucked through the suction port 4 is compressed within the compressor 12 and is discharged from the discharge port 5 through the discharge shutoff valve 14 which is in an open state. At this time, the discharge port exhaust valve 15 is closed and the vacuum pump 16 is stopped. When a stop command is issued to the electric motor 13, the discharge stop valve 14 is simultaneously closed, the discharge outlet exhaust valve 15 is opened, and the vacuum pump 16 starts evacuation. Therefore, a pressure difference is created between the inlet port 4 which is open to the atmosphere and the outlet port 5 which is exhausted, and the gas (air in this case) flowing in from the inlet port 4 causes the rotor to idle and cools the rotor.

Note that in this embodiment as well, similar to the embodiment shown in FIG.
When the amount of thermal expansion of the rotor is detected and the rotor temperature has decreased, the vacuum pump 16 may be stopped to stop rotor cooling.

According to this embodiment, there is no need to forcibly supply cooling gas from the outside, and no cooling gas pressure feeding equipment is required.

In the third embodiment shown in FIG.
The number of revolutions can be varied by 7. The discharge port 5 is provided with an atmosphere release valve 23.

While the compressor is not operating, the electric motor 13 is rotated at a very low speed, the atmosphere release valve 23 is opened, and as the rotor rotates, gas is sucked in through the suction port 4 and the rotor is cooled.

According to this embodiment, there is no need for a cooling gas sealing device or a means for lowering the pressure at the discharge port below the pressure at the suction port, thereby simplifying the apparatus.

Further, in this embodiment, an inverter-driven electric motor is used as the drive motor, but a pole-changing electric motor, an expander, a turbine, etc. may also be used.

Further, as a rotor idling device, a rotor turning device may be provided separately from the driving motor.

Further, as another embodiment of the present invention, a rotor cooling passage is provided inside the rotor, at least a part of which is concentric with the rotor rotation axis, and a small The turbine blades (stator vanes) of the rotor are fixed concentrically with the rotor rotation axis, and cooling fluid is injected into the cooling passage at high speed by a fluid supply means connected to the cooling passage inlet at the end of the rotor, so that the rotor is connected to the turbine. The blade may be idled by the rotational force generated in the blade, and at the same time, the blade may be cooled from the inside using a cooling fluid. In addition, by providing fins on the upstream side of the turbine blades in this cooling passage, it is possible to increase the heat transfer area and improve the cooling effect, and to make the incident angle of the cooling fluid flowing into the turbine blades appropriate. .

〔Effect of the invention〕

According to the present invention, since the rotor that is not in operation is cooled while being idled, the rotor is cooled uniformly in the circumferential direction, and the occurrence of bending of the rotor shaft and uneven thermal deformation during cooling is prevented. This enables stable startup without increased shaft vibration or rotor contact even if the screw fluid machine is restarted after it has stopped operating but before the rotor has finished cooling.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention. 2A and 2B are system diagrams showing a second embodiment of the invention, and FIG. 3 is a system diagram showing a third embodiment of the invention. 1.2... Rotor, 3... Casing, 4... Inlet. 5... Discharge port, 10... Cooling gas filling valve (means for supplying gas at a pressure higher than atmospheric pressure to the suction port). 16... Vacuum pump (means for lowering the pressure at the discharge port than the pressure at the suction port), 23... Atmospheric release valve (means for opening the discharge port to the atmosphere)
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Claims (1)

[Claims] 1. A pair of rotors having a spiral land portion and a groove are housed in a casing in a rotatable state with their axes parallel to each other and meshing with each other, and an inlet is formed in the casing. In a screw fluid machine, gas sucked in from the rotor is confined in a working chamber formed by the pair of rotors and the casing, and is discharged from a discharge port formed in the casing as the rotor rotates. A screw fluid machine characterized by comprising means for idling the rotor therein. 2. A pair of rotors having a spiral land portion and a groove are housed in a casing with their axes parallel to each other so that they can rotate while meshing with each other, and the gas sucked in from the inlet formed in the casing In a screw fluid machine that is confined in a working chamber formed by the pair of rotors and the casing, and is discharged from a discharge port formed in the casing as the rotor rotates, an inlet of the screw fluid machine, A screw fluid machine characterized by comprising means for supplying gas at a pressure higher than atmospheric pressure and means for opening a discharge port to the atmosphere. 3. A pair of rotors having spiral land portions and grooves are housed in a casing in a rotatable state with their axes parallel and meshing with each other, and the gas sucked in from the inlet formed in the casing is In a screw fluid machine that is confined in a working chamber formed by the pair of rotors and the casing, and discharges from a discharge port formed in the casing as the rotor rotates, the suction port of the screw fluid machine is connected to the atmosphere. 1. A screw fluid machine characterized by comprising: means for opening the discharge port to lower pressure than the suction port pressure; 4. The screw fluid machine according to claim 1, further comprising means for opening the discharge port and the suction port to the atmosphere at least while the rotor is idling. 5. The screw fluid machine according to claim 1, further comprising means for supplying cooling gas to the suction port, and means for recovering or releasing the cooling gas from the discharge port to the atmosphere. 6. The idling means is fixed to the rotor in a cooling passage provided inside the rotor and at least a part of which is concentric with the rotor rotation axis, and in a portion of the cooling passage concentric with the rotor rotation axis so as to be concentric with the rotor rotation axis. 2. The screw fluid machine according to claim 1, further comprising: a turbine blade having a cylindrical shape, and means for supplying fluid to the cooling passage. 7. A pair of rotors having a spiral land portion and a groove are housed in a casing in a rotatable state with their axes parallel to each other and meshing with each other, and the gas sucked in from the inlet formed in the casing is In a method of operating a screw fluid machine, which is confined in a working chamber formed by the pair of rotors and the casing, and discharges fluid from a discharge port formed in the casing as the rotor rotates,
A method for operating a screw fluid machine, which comprises cooling the rotor while idling the rotor after the screw fluid machine stops operating. 8. A pair of rotors having a spiral land portion and a groove portion are housed in a casing in a rotatable state with their axes parallel to each other and meshing with each other, and the gas sucked in from the inlet formed in the casing is In a method of operating a screw fluid machine, which is confined in a working chamber formed by the pair of rotors and the casing, and discharges fluid from a discharge port formed in the casing as the rotor rotates,
After the screw fluid machine has stopped operating, cooling gas is supplied to the suction port and the discharge port is opened to the atmosphere, and the rotor is rotated by the differential pressure between the cooling gas pressure at the suction port and the pressure at the discharge port. A method of operating a screw fluid machine, characterized in that the rotor is cooled by cooling gas flowing from the suction port through the working chamber to the discharge port as the rotor rotates. 9. In a rotor used in a screw fluid machine having a spiral land portion and a groove portion on the outer peripheral surface, a cooling passage provided inside the rotor and at least a part of which is concentric with the rotor rotation axis, and a cooling passage of the cooling passage. A rotor comprising: a turbine blade fixed to the rotor concentrically with the rotor rotation axis in a portion concentric with the rotor rotation axis.