JP2001182680A - Screw compressor - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To improve operation efficiency without lowering volumetric efficiency of a screw compressor. An intermediate pressure chamber (18) is provided in a high pressure seal portion (12) provided near an end face of a high pressure portion of a screw rotor (5), and a bypass (19) communicates the intermediate pressure chamber of the high pressure seal portion with a compression groove of the screw rotor during compression. Is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a screw compressor for compressing a gas.

[0002]

2. Description of the Related Art FIG. 6 is a horizontal sectional view of a conventional screw compressor, FIG. 7 is a vertical sectional view, and FIG. 8 is a sectional view taken along section AA of FIG. FIG. 9 is a conceptual perspective view of the compression mechanism. The configuration of the conventional screw compressor will be described with reference to these drawings. In FIG. 6, 1 is a screw compressor main body, 2 is a casing which forms the main body together with the lateral lid 3, 4 is an electric motor which is inscribed and fixed by the casing, 5 is a screw rotor, which compresses a plurality of spiral strips. A groove 6 is formed, is connected to the electric motor 4 by a screw shaft 7, and is supported by a bearing housing 8 on a suction side bearing 7a and a discharge side bearing 7b on a discharge side. Reference numeral 9 denotes a pair of gate rotors disposed on the left and right of the screw rotor and driven by fitting into the compression grooves 6. The gate rotor body 9 a made of resin is driven by directly contacting the compression grooves 6 of the screw rotor 5. A gate rotor support 9b for supporting the gate rotor main body 9a, bearings 9c and 9e for rotatably supporting the gate rotor support 9b, and housings 9d and 9f for attaching to the casing 2.
Etc. 10 is a suction gas chamber formed by the end faces of the casing 3 and the screw rotor 5;
Reference numeral 1 denotes a space defined by the bearing housing 8, the end face of the discharge-side bearing 7b, and the end face of the screw rotor 5.
12 is the screw rotor 5 and the bearing housing 8
And a high-pressure seal portion formed in a minute gap formed between the high-pressure refrigerant gas and the high-pressure refrigerant gas, thereby suppressing leakage of the high-pressure refrigerant gas. Reference numeral 13 denotes a displacement control piston for driving a displacement control mechanism (not shown).

Further, reference numeral 14 denotes a refrigerant gas suction port provided in the casing 2, 16 denotes a refrigerant gas discharge port compressed by a compression mechanism, and 17 denotes a refrigerant gas discharge port provided in the casing 2.

[0004] For reference, FIG. 10 shows a fitting state of the screw rotor 5 and the gate rotor 9.

The gate rotor 9 and the displacement control piston 13 shown in FIGS. 6 and 7 are drawn only on one side, and irrelevant parts are partially omitted.

Next, the operation will be described. In the figures, arrows indicate the flow of the refrigerant gas. First, when the screw rotor 5 is connected to and supported by the electric motor 4 by the screw shaft 7 and is rotated by the driving force of the electric motor 4, the compression mechanism faces the compression groove 6 of the screw rotor 5 as described above. A pair of gate rotors 9 are fitted and rotate following the rotation of the screw rotor 5.

Next, the rotation of the screw rotor 5 and the gate rotor 2 causes the refrigerant gas inlet 14 and the electric motor 6 to rotate.
The refrigerant gas sucked into the compression mechanism from the suction gas chamber 10 through the suction port is isolated from the suction gas chamber 10 by the teeth of the gate rotor 2 and discharged while being compressed from the suction side to the discharge side. Refrigerant gas outlet 1 through
From 6 is sent to the refrigerant circuit. At this time, a capacity control mechanism (not shown) provided to cope with a start-up stop, a load change, and the like drives the capacity control piston 13 as necessary to change the amount of the compressed refrigerant.

FIG. 10 is a schematic sectional view of a compression mechanism of a conventional screw compressor. During the operation of the compressor, the high-pressure gas discharged from the screw rotor 5 passes through the high-pressure seal portion 12 and enters the space 11, so that the space 11 tends to have a high pressure. However, since the suction gas chamber 10 has a low pressure, when the pressure of the space 11 becomes high, a thrust load is generated in the screw rotor 5 due to a pressure difference, and an excessive load is applied to the bearings 7a and 7b. In order to balance the loads generated at both ends of the screw rotor 5, the pressure equalizing holes 1 communicating the space 11 and the suction gas chamber 10 with the screw rotor 5 are provided.
7 is provided so that the space 11 is maintained at a low pressure.

However, when the space 11 communicates with the suction gas chamber 10 through the pressure equalizing hole 17, the high-pressure refrigerant gas discharged from the screw rotor 5 passes through the gap between the screw rotor 5 and the bearing housing 8 and has a low pressure. Then, the gas leaks into the suction gas chamber 10 through the pressure equalizing hole 17 to the space 11. Therefore, this gap is provided with the high-pressure seal portion 12 shown in FIG. 9 to minimize the leakage of the discharge gas into the suction gas chamber 10.

[0010]

As described above, in the conventional screw compressor, it is insufficient to attain a sufficient seal, and a large amount of high-pressure discharge gas leaks into a low-pressure suction gas chamber. The volumetric efficiency of the compressor decreases,
There is a problem that the operation efficiency of the compressor is reduced.

An object of the present invention is to improve the operation efficiency without lowering the volume efficiency of a screw compressor.

[0012]

A screw compressor according to the present invention comprises a compression mechanism comprising a screw rotor and a gate rotor in a casing. The screw compressor compresses gas. An intermediate pressure chamber is provided in the provided high pressure seal portion.

Further, in the screw compressor according to the present invention, a compression mechanism is constituted by a screw rotor and a gate rotor in a casing. A screw compressor provided with a bypass which communicates a compression groove of a screw rotor.

Further, in the screw compressor according to the present invention, a bypass passage communicating the intermediate pressure chamber of the high-pressure seal portion and the compression groove of the screw rotor during compression is provided in a casing which is a non-rotating portion around the screw rotor. It is a thing.

Further, in the screw compressor according to the present invention, the screw rotor is provided with a bypass which communicates the intermediate pressure chamber of the high-pressure seal portion with the compression groove of the screw rotor during compression.

In the screw compressor according to the present invention, a compression mechanism is constituted by a screw rotor and a gate rotor in a casing, and in a two-stage screw compressor for compressing gas, a high-pressure seal portion of a high-stage compression mechanism is provided. An intermediate pressure chamber is provided, and the intermediate pressure chamber and the intermediate pressure chamber for sending gas from the low-stage compression mechanism to the high-stage compression mechanism are provided in communication with each other.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a horizontal sectional view of a screw compressor according to Embodiment 1 of the present invention, and FIG. 2 is a schematic sectional view showing a compression mechanism of the screw compressor. In the figure, 1 is a screw compressor main body, 2 is a casing that forms the main body together with the lateral lid 3, 4 is an electric motor insulated and fixed by the casing, 5 is a screw rotor, and a plurality of spiral grooves are formed. The bearing 6 is connected to the electric motor 4 by a screw shaft 7, and is supported by a bearing housing 8 on a suction side bearing 7a and a discharge side bearing 7b on a discharge side. Reference numeral 9 denotes a pair of gate rotors disposed on the left and right sides of the screw rotor and driven by being fitted into the compression grooves 6.
A gate rotor body 9a made of resin that is driven while directly contacting the compression groove 6, a gate rotor support 9b that supports the gate rotor body 9a, bearings 9c and 9e that rotatably support the gate rotor support 9b, The housing 2 includes housings 9d and 9f to be attached to the casing 2.

Reference numeral 10 denotes a suction gas chamber formed by the casing 3 and the end face of the screw rotor 5, and reference numeral 11 denotes a space formed by the bearing housing 8, the end face of the discharge-side bearing 7b, and the end face of the screw rotor 5. is there. Reference numeral 12 denotes a high-pressure seal formed in a minute gap formed between the screw rotor 5 and the bearing housing 8,
The leakage of high-pressure refrigerant gas is suppressed. Reference numeral 13 denotes a displacement control piston for driving a displacement control mechanism (not shown). Reference numeral 15 denotes a discharge port for the refrigerant gas compressed by the compression mechanism. Reference numeral 17 denotes a pressure equalizing hole communicating the suction gas chamber 10 and the space 11, 18 denotes an intermediate pressure chamber provided in a groove shape on the outer periphery of the screw rotor 5 near the middle of the high-pressure seal portion 13, and 19 denotes the groove and the groove. It is a bypass hole provided in the bearing housing 8 and the casing 2 so as to communicate with the compression groove 6 of the screw rotor 1.

Generally, in the case of supersonic flow, the flow rate leaking through the minute gap is "Opportunity Engineering Handbook" published by the Japan Society of Mechanical Engineers.
According to this, the leak mass flow rate M is represented by “M” Po ”, and is proportional to the square root of the inlet side (high pressure side) pressure Po, and is independent of the outlet side (low pressure side) pressure.

That is, the only way to reduce the leakage flow rate is to reduce the inlet-side (high-pressure side) pressure Po when the gap area or the like is unchanged. Therefore, if the pressure in the intermediate pressure chamber 18 can be made lower than the discharge gas pressure by connecting the intermediate pressure chamber 18 to the compression groove 6 through the bypass passage 19, the refrigerant gas from the intermediate pressure chamber 18 to the space 11 can be reduced. It is possible to reduce the leakage flow rate.

At this time, since the discharge gas pressure does not change, the leakage flow rate of the refrigerant gas to the intermediate pressure chamber 18 does not change.
Therefore, the decrease in the leakage flow rate of the refrigerant gas from the intermediate pressure chamber 18 to the space 11 is returned to the compression groove 6.

FIG. 2 shows an example of the pressure fluctuation in the intermediate pressure chamber 18 which is communicated with the compression groove 6 by the bypass passage 19. FIG.
In the compressor of, the pressure of the compression groove 6 at the time when the bypass passage 19 of the casing 2 communicates with the compression groove 6 having the screw rotor 5 during the compressor operation is P1. At this time, the pressure in the intermediate pressure chamber 18 communicating with the compression groove 6 also becomes P1.

Assuming that the compression groove adjacent to the compression groove 6 is 1b, the refrigerant gas in the compression groove 6 is compressed while the bypass path 19 communicates with the compression groove 6, and the compression groove communicating with the bypass path 19 is compressed. If the pressure increases to P2 before the pressure changes from the compression groove 6 to the adjacent compression groove 1b, the pressure of the intermediate pressure chamber 18 communicating with the compression groove 6 increases from P1 to P2.

Next, when the bypass passage 19 communicates with the compression groove 6, the pressure in the compression groove 6 is compressed from P1 to P2 as in the case of the compression groove 6, so that the intermediate pressure chamber 1 connected to the compression groove 6 is compressed.
After the pressure of P8 suddenly drops from P2 to P1,
It rises from 1 to P2. If the screw rotor 5 is 6
If the compression grooves are cut, the above-described pressure fluctuation is repeated six times per rotation of the screw rotor 5, and the pressure fluctuation in the intermediate pressure chamber 18 has a waveform as shown in FIG.

Therefore, the pressure of the intermediate pressure chamber 18 is always lower than the discharge gas pressure and higher than the suction gas pressure, and the leakage flow rate of the refrigerant gas from the intermediate pressure chamber 18 to the space 11 can be reduced.

In the first embodiment, the intermediate pressure chamber 18 is provided in a groove shape on the outer peripheral portion of the screw rotor 5, but the intermediate pressure chamber 18 is provided in the high pressure seal portion 1 on the bearing housing 8 side.
Even if a groove is provided in the middle of 3, the same effect can be obtained.

Embodiment 2 FIG. FIG. 3 is a sectional view of a compression mechanism of a screw compressor according to Embodiment 2 of the present invention.
In the drawing, reference numeral 20 denotes an intermediate pressure chamber 1 provided in a groove shape on the outer periphery of the screw rotor 5 near the middle of the high-pressure seal portion 13.
8 is a second bypass path provided in the screw rotor 5 so that the compression groove 8 communicates with the compression groove 6 of the screw rotor 5.

The compression groove 6 is formed by the second bypass passage 20.
FIG. 4 shows an example of the pressure fluctuation in the intermediate pressure chamber 18 that is communicated with the pressure chamber 18. In order to suck the refrigerant gas, the compression groove 6 is inserted into the suction gas chamber 1.
When opened to zero, the intermediate pressure chamber 18 communicates with the suction gas chamber 10 via the bypass path 20 and the compression groove 6, and the pressure becomes equal to the suction gas pressure.

Next, the teeth of the gate rotor 9 fitted in the compression grooves of the screw rotor 5 are fitted in the compression grooves 6 and
Is separated from the suction gas chamber 10, the compression of the refrigerant gas in the compression groove 6 starts, so that the pressure in the intermediate pressure chamber 18 communicating with the compression groove 6 increases. However, when the teeth of the gate rotor 9 pass through the opening of the second bypass passage 20 in the compression groove 6 during the compression of the refrigerant gas in the compression groove 6, the bypass passage 20
Communicates with the suction gas chamber 10 again, and the pressure in the intermediate pressure chamber 18 decreases from the pressure P3 immediately before the teeth of the gate rotor 9 pass through the opening of the second bypass passage 20 to the suction gas pressure.
Since the above operation is repeated, the pressure fluctuation in the intermediate pressure chamber 18 becomes as shown in FIG.

Therefore, in a time period when the compression groove 6 is opened to the low-pressure suction gas chamber 10, the discharge gas passes through the high-pressure seal portion 13, the intermediate pressure chamber 18, the second bypass passage 20, and the compression groove 6. The flow rate leaking to 10 is not different from the conventional one. On the other hand, the flow rate leaking into the suction gas chamber 10 during the time period when the compression groove 6 is at the intermediate pressure,
1, the pressure in the intermediate pressure chamber 18 decreases by an amount smaller than the discharge gas pressure. As a whole, compared with the related art, the leakage amount of the refrigerant gas is reduced by the amount of time during which the compression groove 6 has the intermediate pressure, so that it is possible to contribute to the improvement of the volumetric efficiency of the compressor.

In the second embodiment, the intermediate pressure chamber 18 is provided in a groove shape on the outer peripheral portion of the screw rotor 5, but the intermediate pressure chamber 18 is provided in the high pressure seal portion 1 on the bearing housing 8 side.
Even if a groove is provided in the middle of 3, the same effect can be obtained.

Embodiment 3 FIG. FIG. 5 is a schematic sectional view of a compression mechanism of a two-stage screw compressor according to Embodiment 3 of the present invention. In the figure, 21 is a low-stage screw rotor, 22 is a high-stage screw rotor, 7c is an intermediate bearing, 2
3 is a low-stage discharge port for discharging the gas compressed by the low-stage screw rotor 21 to the high-stage side, 10 is a suction gas chamber, 24
Is a second intermediate pressure chamber that is also a high-stage suction gas chamber, and 26 is a second pressure equalizing hole that connects the space 11 and the suction gas chamber 10.
Reference numeral 25 denotes a third bypass passage opened in the bearing housing 8 and the casing 2 so that the intermediate pressure chamber 18 and the second intermediate pressure chamber 24 communicate with each other.

The operation of the two-stage screw compressor according to Embodiment 3 shown in FIG. 5 will be described. The refrigerant gas sucked into the compressor is sucked through the suction gas chamber 10 and compressed by a low-stage compression mechanism constituted by a low-stage screw rotor 21 and a low-stage gate rotor (not shown) fitted thereto. You.

Next, the refrigerant gas compressed by the low stage compression mechanism is sucked through the low stage discharge port 23 into the second intermediate pressure chamber 24 which is also a high stage suction gas chamber. Further, it is compressed by a high-stage compression mechanism constituted by a high-stage screw rotor 22 and a high-stage gate rotor (not shown) fitted with the high-stage screw rotor 22 and sent to the refrigerant circuit via the discharge port 15. At this time, a pressure difference is generated between the space 11 and the suction gas chamber 10. However, the pressure in the space 11 is equalized by the second equalizing holes 26 to a low-stage suction gas pressure. Refrigerant gas leakage occurs.

In the third embodiment, an intermediate pressure chamber 18 is provided in the high pressure seal portion 13, and the intermediate pressure chamber 18 and the second intermediate pressure chamber 24 are communicated by a third bypass passage 25. Therefore, the pressure in the intermediate pressure chamber 18 becomes the pressure in the second intermediate pressure chamber 24 and becomes smaller than the discharge gas pressure.
The amount of refrigerant gas leaking from the high-pressure seal portion 13 to the space 11 can be reduced.

In the third embodiment, the intermediate pressure chamber 18 is provided in a groove shape on the outer peripheral portion of the high-stage screw rotor 22. However, this intermediate pressure chamber 18 is provided in the middle of the high pressure seal portion 13 on the bearing housing 8 side. Even if it is provided in a groove shape, exactly the same effect can be obtained.

In the third embodiment, the bypass path 2
5 is provided in the bearing housing 8 and the casing 2, but the same effect can be obtained by providing the third bypass passage in the high-stage screw rotor 22.

[0038]

Since the present invention is configured as described above, it has the following effects.

In the screw compressor of the present invention, a compression mechanism is constituted by a screw rotor and a gate rotor in a casing, and in a screw compressor for compressing gas, a high-pressure seal provided near an end face of a high-pressure portion of the screw rotor is provided. Since the intermediate pressure chamber is provided, leakage of high-pressure refrigerant gas from the high-pressure seal portion can be reduced.

In the screw compressor according to the present invention, a compression mechanism is constituted by a screw rotor and a gate rotor in a casing. In the screw compressor for compressing gas, an intermediate pressure chamber of a high pressure seal portion is connected to a screw in the middle of compression. Since the bypass passage communicating the compression groove of the rotor is provided, leakage of the high-pressure refrigerant gas from the high-pressure seal portion can be reduced.

Further, in the screw compressor according to the present invention, a bypass passage communicating the intermediate pressure chamber of the high-pressure seal portion with the compression groove of the screw rotor during compression is provided in the casing which is a non-rotating portion around the screw rotor. With this configuration, the intermediate pressure chamber of the high pressure seal portion always has an intermediate pressure and is lower than the discharge gas pressure, so that leakage of the high pressure refrigerant gas from the high pressure seal portion can be reduced.

Further, the screw compressor of the present invention has a structure in which the screw rotor is provided with a bypass which communicates the intermediate pressure chamber of the high pressure seal with the compression groove of the screw rotor during compression. An intermediate pressure is intermittently obtained in the intermediate pressure chamber, and leakage of the high-pressure refrigerant gas from the high-pressure seal portion can be reduced during a time period when the intermediate pressure chamber is at the intermediate pressure.

Further, in the screw compressor of the present invention, a compression mechanism is constituted by a screw rotor and a gate rotor in a casing, and in a two-stage screw compressor for compressing gas, an intermediate portion is provided at a high-pressure seal portion of a high-stage compression mechanism. Since the pressure chamber is provided and the intermediate pressure chamber communicates with the intermediate pressure chamber that sends gas from the low-stage compression mechanism to the high-stage compression mechanism, the pressure of the intermediate pressure chamber can be easily made smaller than the discharge pressure. Can,
Further, since the high-pressure refrigerant gas that is leaking from the high-pressure seal portion to the low-pressure side can be guided to the high-stage compression mechanism and recompressed, leakage of the high-pressure refrigerant gas from the high-pressure seal portion can be reduced.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional view of a screw compressor according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of a compression mechanism of the screw compressor according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example of a pressure fluctuation of a compression groove in FIG.

FIG. 4 is a schematic sectional view of a compression mechanism of a screw compressor according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an example of a pressure fluctuation of a compression groove in FIG. 3;

FIG. 6 is a schematic sectional view of a compression mechanism of a two-stage screw compressor according to Embodiment 3 of the present invention.

FIG. 7 is a horizontal sectional view of a conventional screw compressor.

FIG. 8 is a vertical sectional view of a conventional screw compressor.

FIG. 9 is a sectional view of a gate rotor section of a conventional screw compressor.

FIG. 10 is a schematic sectional view of a compression mechanism of a conventional screw compressor.

FIG. 11 is a conceptual perspective view of a compression mechanism of a conventional screw compressor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Screw compressor main body, 2 Casing, 5 screw rotors, 6 compression grooves, 7 screw shaft, 8 bearing housing, 9 gate rotor, 10 suction gas chamber, 1
1 space, 13 high-pressure seal, 14 refrigerant gas inlet, 15 discharge port, 16 refrigerant gas discharge, 17
Equalizing hole, 18 intermediate pressure chamber, 19 bypass passage, 20 second bypass passage, 21 low-stage screw rotor, 22 high-stage screw rotor, 23 low-stage discharge port, 24 second intermediate pressure chamber, 25 third bypass passage, 26 Second equalizing hole.

Claims (5)

[Claims] 1. A compression mechanism comprising a screw rotor and a gate rotor in a casing, and in a screw compressor for compressing gas, an intermediate pressure chamber is provided in a high pressure seal portion provided near an end face of a high pressure portion of the screw rotor. A screw compressor, characterized in that: 2. A compression mechanism comprising a screw rotor and a gate rotor in a casing, wherein in a screw compressor for compressing gas, a bypass communicating between an intermediate pressure chamber of a high pressure seal portion and a compression groove of the screw rotor during compression. A screw compressor characterized by having a passage. 3. A casing which is a non-rotatable casing around the screw rotor, wherein a bypass passage communicating the intermediate pressure chamber of the high-pressure seal portion and the compression groove of the screw rotor during compression is provided. 3. The screw compressor according to 2. 4. The screw compressor according to claim 1, wherein a bypass path is provided in said screw rotor for communicating the intermediate pressure chamber of the high-pressure seal portion with the compression groove of the screw rotor during compression. 5. A two-stage screw compressor for compressing gas, wherein a compression mechanism is constituted by a screw rotor and a gate rotor in a casing, and an intermediate pressure chamber is provided in a high pressure seal portion of the high stage compression mechanism. A two-stage screw compressor characterized by communicating a chamber and an intermediate pressure chamber for sending gas from a low-stage compression mechanism to a high-stage compression mechanism.