JP2019019738A - Screw compressor - Google Patents

Abstract

To inhibit a leakage flowing from a gap between a discharge side end surface of a screw rotor and a rotor side end surface of a discharge casing to the bearing chamber side via a gap between a rotor shaft and a shaft hole of the discharge casing and further flowing to the suction side to reduce leakage loss.SOLUTION: A screw compressor includes: a screw rotor; a low pressure side bearing and a high pressure side bearing which support a rotor shaft of the screw rotor; a main casing which houses the screw rotor; and a discharge casing having a shaft hole through which the rotor shaft of the screw rotor penetrates, and a bearing chamber which houses a bearing. Further, the screw compressor includes: a ring shaped seal groove formed around the rotor shaft on a rotor side end surface of the discharge casing; a seal ring which is disposed in the seal groove and seals a gap between a discharge side end surface of the screw rotor and the discharge casing; and a ring shaped pressure pocket groove which is formed along an outer periphery of the seal groove and into which a discharge side pressure is introduced.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a screw compressor, and is particularly suitable for a hermetic or semi-hermetic screw compressor used in a refrigeration apparatus such as an air conditioner, a chiller unit, or a refrigerator.

  In the screw compressor, in order to avoid seizure due to contact between the discharge rotor end face and the discharge casing, a gap (hereinafter also referred to as D gap) is provided between the screw rotor discharge end face and the discharge casing. Provided. The D gap is set to an appropriate gap so as to avoid the contact between the screw rotor and the discharge casing, reduce the compressed gas leaking from the discharge side to the suction side, and suppress the reduction in the efficiency of the compressor. Yes.

  Japanese Unexamined Patent Publication No. 62-107285 (Patent Document 1) discloses a technique for making the D gap smaller because the discharge-side end face of the screw rotor does not contact the discharge casing. In this Patent Document 1, a ring-shaped groove is provided on the end face of the discharge casing, and a synthetic resin seal ring and a ring-shaped wave spring are attached to the groove, whereby the seal ring is screwed by the wave spring. It presses against the discharge side end face of the rotor.

JP-A-62-107285

  In a screw compressor, there are thermal fluid loss, mechanical loss, and loss due to an electric motor as losses related to performance. Thermal fluid loss is divided into leakage loss, overcompression loss and suction loss. As main leakage gaps that cause the leakage loss, there are an outer peripheral clearance of the screw rotor, a clearance between the screw rotors, a D gap, a blow hole, and the like.

  The leakage from the D gap is bypassed from the main path that leaks from the gap formed between the discharge-side end face of the screw rotor and the rotor-side end face of the discharge casing to the suction side, and the rotor shaft of the screw rotor. There is a secondary path that leaks from the bearing chamber in which a bearing for supporting the rotor shaft is provided to the suction side via a gap between the shaft hole formed in the discharge casing through which the rotor shaft passes.

  In the thing of the said patent document 1, since the seal ring is always pressed against the discharge side end surface of the screw rotor by the wave spring in the axial direction, it acts also as a seal of the sub path. However, no consideration is given to the fact that if a force due to a pressure difference acts in the radial direction on the seal ring, the seal ring will be displaced downward, making it impossible to seal leakage from the sub-path.

  An object of the present invention is from a gap between a discharge-side end face of a screw rotor and a rotor-side end face of a discharge casing to a bearing chamber side via a gap between a rotor shaft of the screw rotor and a shaft hole of the discharge casing. The purpose is to obtain a screw compressor capable of suppressing leakage and reducing leakage loss from flowing to the suction side.

  To achieve the above object, the present invention provides a pair of male and female screw rotors that mesh with each other, a low-pressure bearing and a high-pressure bearing that support the rotor shaft of the screw rotor, a main casing that houses the screw rotor, A screw compressor comprising: a shaft hole through which a rotor shaft of a screw rotor passes and a discharge casing having a bearing chamber that houses the high-pressure side bearing, wherein the periphery of the rotor shaft on an end surface of the discharge casing on the screw rotor side A ring-shaped seal groove formed in the seal groove, a seal ring which is disposed in the seal groove and seals a gap between the discharge-side end surface of the screw rotor and the discharge casing, and along the outer periphery of the seal groove A ring-shaped pressure pocket groove that is formed and into which pressure on the discharge side is introduced is provided.

  Other features of the present invention include a screw rotor, a bearing that supports a rotor shaft of the screw rotor, a casing that houses the screw rotor, a shaft hole through which the rotor shaft of the screw rotor passes, and the bearing. A screw compressor comprising a discharge casing having a bearing chamber, and a ring-shaped seal groove formed around the rotor shaft on an end surface of the discharge casing on the screw rotor side, and disposed in the seal groove A seal ring that seals a gap between the discharge-side end face of the screw rotor and the discharge casing, and a ring-shaped pressure pocket groove that is formed along the outer periphery of the seal groove and into which pressure on the discharge side is introduced. It is to prepare.

  According to the present invention, from the gap between the discharge-side end face of the screw rotor and the rotor-side end face of the discharge casing to the bearing chamber side via the gap between the rotor shaft of the screw rotor and the shaft hole of the discharge casing. There is an effect that it is possible to obtain a screw compressor that can suppress leakage and reduce leakage loss by suppressing leakage flowing from here to the suction side.

The longitudinal cross-sectional view which shows Example 1 of the screw compressor of this invention. The horizontal sectional view which abbreviate | omits and shows a part of screw compressor shown in FIG. The principal part enlarged view of the discharge side end surface vicinity of the screw rotor shown in FIG. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. It is a figure explaining the state of the seal ring in the conventional screw compressor, and is a figure equivalent to FIG. FIG. 6 is a cross-sectional view taken along line B-B in FIG. 5. CC sectional view taken on the line of FIG. The DD sectional view taken on the line of FIG. FIG. 5 is a cross-sectional view taken along line EE in FIG. 4. FIG. 5 is a cross-sectional view taken along line FF in FIG. 4. FIG. 5 is a cross-sectional view taken along line GG in FIG. 4. The top view which shows the shape of the seal ring shown in FIG. The front view of the seal ring shown in FIG.

  Embodiments of the screw compressor of the present invention will be described below with reference to the drawings. In each figure, the part which attached | subjected the same code | symbol has shown the part which is the same or it corresponds. Further, in the following description, the case where the present invention is applied to a hermetic twin screw compressor used in a refrigeration apparatus will be described, but the present invention is limited to a hermetic twin screw compressor used in a refrigeration apparatus. Is not to be done.

A screw compressor according to a first embodiment of the present invention will be described with reference to FIGS.
First, the overall configuration of the screw compressor according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal sectional view showing a screw compressor of the first embodiment, and FIG. 2 is a horizontal sectional view showing a part of the screw compressor shown in FIG.

As shown in FIG. 1, the screw compressor 100 includes a motor casing 1, a main casing 2, and a discharge casing 3 that are connected to each other in a sealing relationship.
The motor casing 1 houses a motor (electric motor) 4 for driving a compression mechanism section described later. The motor 4 includes a stator 4A fixed in the motor casing 1 and a rotor 4B disposed on the inner peripheral side of the stator 4A. The stator 20 is connected via a power cable 53 to a power terminal 52 in a terminal box 51 provided outside the motor casing 1.

  A suction port 18 is provided at one end of the motor casing 1, and a strainer 19 for collecting foreign matter is attached to the suction port 18. The strainer 19 is sandwiched between the fixing flange 65 and the motor casing 1 and fixed to the suction port 18 of the motor casing 1. A refrigerant pipe 64 for sucking refrigerant is fixed to the fixed flange 65.

  The main casing 2 is formed with a cylindrical bore 5 and a suction port 6 for introducing refrigerant gas into the cylindrical bore 5. As shown in FIGS. 1 and 2, a screw rotor 11 is disposed in the cylindrical bore 5, and the screw rotor 11 includes a male rotor 11A and a female rotor 11B meshed with each other. A rotor shaft 11A1 is integrally provided on both sides of the male rotor 11A, and a rotor shaft 11B1 is also integrally provided on both sides of the female rotor 11B.

  The rotor shaft 11A1 of the male rotor 11A is rotatably supported by roller bearings 7A and 8A provided on the motor casing 1, and roller bearings 9A and ball bearings 10A provided on the discharge casing 3. The rotor shaft 11B1 of the female rotor 11B is also rotatably supported by a roller bearing 8B provided in the motor casing 1, a roller bearing 9B and a ball bearing 10B provided in the discharge casing 3.

  The rotor shaft 11A1 of the male rotor 11A is directly connected to the rotor 4B of the motor 4. In addition, an oil separator 12 for integrally separating the oil contained in the refrigerant gas through which the compressed and discharged refrigerant gas passes is integrally provided on the side surface of the main casing 2.

  The discharge casing 3 is provided with bearing chambers 16 (male rotor side bearing chamber 16A, female rotor side bearing chamber 16B) in which the roller bearings 9A and 9B and the ball bearings 10A and 10B are accommodated. A shielding plate 17 for closing the chamber 16 is attached to the discharge casing 3.

Further, the discharge casing 3 is supplied with a discharge chamber 15 into which refrigerant gas compressed and discharged by the screw rotor 11 is discharged, and the refrigerant gas discharged into the discharge chamber 15 is sent to the oil separator 12. A discharge passage (not shown) is also provided.
The discharge casing 3 is fixed to the main casing 2 with bolts.

Next, the flow of refrigerant gas and oil will be described with reference to FIGS.
The low-temperature and low-pressure refrigerant gas led to the suction port 18 provided in the motor casing 1 from the refrigeration cycle constituting the chiller unit or the like through the refrigerant pipe 64 is trapped by the strainer 19. After being collected, the gas passage 4a provided between the driving motor 4 and the motor casing 1 and the air gap 4b between the stator 4A and the rotor 4B in the motor 4 are passed through, It flows to the suction port 6 side of the main casing 2. When the refrigerant gas passes through the gas passage 4a and the air gap 4b, the motor 4 is cooled by the refrigerant gas.

  The refrigerant gas after cooling the motor 4 is sucked from the suction port 6 formed in the main casing 2 into the meshing tooth surfaces of the male rotor 11A and the female rotor 11B and the compression chamber formed by the main casing 2. Is done. Thereafter, with the rotation of the male rotor 11A driven by the motor 4, the compression chamber is closed and gradually reduced, so that the refrigerant gas in the compression chamber is compressed and becomes a high-temperature and high-pressure refrigerant gas and discharged. It is discharged into a discharge chamber 15 formed in the casing 3, and discharged from the discharge chamber 15 into an oil separator 12 formed integrally with the main casing 2.

  The oil separated from the refrigerant gas in the oil separator 12 is returned to the oil sump 14 formed integrally with the lower portion of the main casing 2. The compressed refrigerant gas after the oil is separated in the oil separator 12 is sent out to the refrigeration cycle from the discharge port 13 provided in the upper part of the oil separator 12.

  In FIG. 2, 20 is an oil supply groove for supplying the oil in the oil sump 14 to the bearings, and 24 is a seal between the discharge side of the screw rotor 11 and the discharge casing 3. It is a seal ring.

  Next, the structure of the seal portion in the vicinity of the discharge side end face of the screw rotor 11 shown in FIG. 1 will be described with reference to FIG. FIG. 3 is an enlarged schematic view showing the vicinity of the discharge-side end face of the screw rotor 11. In FIG. 3, 11a is a discharge side end surface of the rotor 11, 3a is a rotor side end surface of the discharge casing 3, 25 is formed in the discharge casing 3, and a shaft hole through which the rotor shaft 11A1 (or 11B1) of the screw rotor 11 passes. It is.

  21 is a D gap (gap) formed between the discharge-side end surface 11a of the screw rotor 11 and the end surface (rotor-side end surface) 3a of the discharge casing 3 on the screw rotor 11 side, and 26 is the above-mentioned It is a gap formed between the shaft hole 25 of the discharge casing 3 and the rotor shaft 11A1.

  A ring-shaped seal groove (ring-shaped groove) 27 is formed around the rotor shaft 11A1 (11B1) on the rotor-side end surface 3a of the discharge casing 3, and the seal rotor 27 includes the screw rotor. A seal ring 24 is provided for sealing a gap between the discharge side and the discharge casing. The seal ring 24 is pressed against the discharge-side end surface 11a of the screw rotor 11 by a wave spring described later.

  In the D gap 21, the upper pressure is the discharge pressure Pd, and the lower pressure is the suction side pressure Ps. The gap 26 on the outer peripheral side of the rotor shaft 11A1 (11B1) is a pressure (hereinafter also referred to as an intermediate pressure) Pm between the discharge pressure Pd and the suction side pressure Ps.

  The leakage of the compressed refrigerant gas is bypassed from the main path that leaks from the D gap 21 formed between the discharge-side end face 11a of the screw rotor and the rotor-side end face 3a of the discharge casing 3 to the suction side, and from the main path. A bearing that supports the rotor shaft is provided through the gap 26 between the rotor shaft 11A1 (11B1) of the screw rotor 11 and the shaft hole 25 formed in the discharge casing 3 through which the rotor shaft passes. There is a secondary path that leaks from the bearing chamber 16 (see FIGS. 1 and 2) to the suction side. The seal ring 24 is provided to prevent the refrigerant gas on the discharge side from leaking from the sub-path to the suction side.

Next, the detailed structure of the said seal part in the screw compressor of the present Example 1 is demonstrated using FIGS. Before describing the configuration of the seal portion in the screw compressor of the first embodiment, the configuration of the seal portion in the conventional screw compressor will be described first.
4 is a cross-sectional view taken along the line AA in FIG. 1, and the configuration of the seal portion and the seal ring in the conventional screw compressor will be described with reference to FIG. 5 corresponding to FIG. 4 and FIGS. The state of will be described. 6 is a cross-sectional view taken along line BB in FIG. 5, FIG. 7 is a cross-sectional view taken along line CC in FIG. 5, and FIG. 8 is a cross-sectional view taken along line DD in FIG. In the following description, the configuration of the seal portion around the rotor shaft 11A1 of the male rotor 11A will be described, but the seal portion around the rotor shaft 11B1 of the female rotor 11B has the same configuration.

  As shown in FIGS. 5 to 8, the rotor-side end surface 3 a of the discharge casing 3 is provided with a ring-shaped seal groove 27, and the outer diameter of the seal groove 27 is the tooth bottom 11 b ( The inner diameter is smaller than the diameter of the rotor shaft 11A1. A seal ring 24 and a ring-shaped wave spring 28 are disposed in the seal groove 27. The seal ring 24 is pressed against the discharge-side end surface 11a of the screw rotor 11 by the wave spring 28, and has a secondary path that leaks from the D gap 21 through the gap 26 to the suction side from the bearing chamber 16 (see FIG. 2 and the like). It is sealed.

  In FIG. 6 showing a cross section taken along line B-B in FIG. 5, the seal ring 24 is pressed toward the rotor shaft 11A1 as indicated by the arrow due to the differential pressure between the discharge pressure (high pressure) Pd and the intermediate pressure Pm. Since the seal groove 27 is in contact with the peripheral surface on the inner diameter side of the seal groove 27, the high-pressure refrigerant gas on the discharge side can be prevented from leaking to the intermediate pressure Pm side or the suction side pressure Ps side in the range a shown in FIG.

  In FIG. 7 showing a cross-sectional view taken along the line CC in FIG. 5, the seal ring 24 is placed on the side opposite to the rotor shaft (lower side) as indicated by an arrow due to the differential pressure between the intermediate pressure Pm and the suction side pressure (low pressure) Ps. ) In contact with the outer peripheral surface of the seal groove 27, it is possible to seal the refrigerant gas having the intermediate pressure Pm from leaking to the suction side Ps side even in the range b shown in FIG.

  As shown in FIGS. 6 and 7, the seal ring 24 is pressed downward due to the pressure difference, so that the seal ring 24 hangs down as shown in FIG. 5. Therefore, as shown in FIG. 8 which is a cross-sectional view taken along the line D-D in FIG. 5, the seal ring 24 hangs down in the vicinity of the middle of the seal ring 24 in the vertical direction. Since the seal ring 24 cannot move, a gap 22 is generated between the seal groove 27 on the radially outer side and the inner side. Therefore, as indicated by the arrows, it was found that a leakage flow passing through the clearance 26 on the outer periphery of the rotor shaft 11A1 is generated from the clearance 22, and there is a problem that leakage loss increases.

The structure of the seal part and the state of the seal ring in the screw compressor of the first embodiment for solving the problem of the seal part in the conventional screw compressor will be described with reference to FIGS. 4 and 9 to 11.
4 is a sectional view taken along line AA in FIG. 1, FIG. 9 is a sectional view taken along line EE in FIG. 4, FIG. 10 is a sectional view taken along line FF in FIG. It is a GG arrow directional cross-sectional view. In the following description, the configuration of the seal portion around the rotor shaft 11A1 of the male rotor 11A will be described, but the seal portion around the rotor shaft 11B1 of the female rotor 11B has the same configuration.

  First, the whole structure of the seal part in the screw compressor of the first embodiment will be described. 3a shows the end surface (rotor side end surface) of the discharge casing 3 on the screw rotor 11 (see FIG. 1) side, and the rotor side end surface 3a of the discharge casing 3 is around the axis (outer peripheral side) of the rotor shaft 11A1. A ring-shaped seal groove (ring-shaped groove) 27 is formed, and a seal ring 24 is disposed in the seal groove 27. The seal ring 24 is for sealing a gap between the discharge side end face 11 a of the screw rotor 11 and the discharge casing 3. Also in this embodiment, the outer diameter of the seal groove 27 is smaller than the diameter of the tooth bottom 11b (see FIG. 2) of the screw rotor 11, and the inner diameter is larger than the diameter of the rotor shaft 11A1.

  Further, as shown in FIGS. 9 to 11, a wave spring 28 is disposed in the seal groove 27 so as to press the seal ring 24 against the discharge-side end face 11 a of the screw rotor 11. Accordingly, since the seal ring 24 is pressed against the discharge side end face 11a of the screw rotor 11 by the wave spring 28, the high-pressure refrigerant gas on the discharge side passes through the gap 26 on the outer periphery of the rotor shaft 11A1 via the D gap 21. A secondary path that leaks from the bearing chamber 16 (see FIG. 2 and the like) to the suction side is sealed.

  In this embodiment, the pressure pocket groove 29 is formed in a ring shape along the outer periphery of the seal groove 27. Further, the discharge casing 3 is provided with a communication passage 30 for introducing pressure on the discharge side (discharge pressure) into the ring-shaped pressure pocket groove 29. In this embodiment, the communication passage 30 is formed on the rotor side end surface 3a of the discharge casing 3 so as to communicate the pressure pocket groove 29 and the discharge chamber 15 (see FIGS. 1 and 4). By the communication passage 30, the discharge pressure (high pressure) Pd of the discharge chamber 15 is introduced into the pressure pocket groove 29, and the pressure in the pressure pocket groove 29 is maintained at a high discharge pressure over the entire circumference. Is done.

  In the present embodiment, the pressure in the discharge chamber 15, that is, the high-pressure refrigerant gas in the discharge chamber 15 is guided to the pressure pocket groove 29, but is not limited to the one that guides the refrigerant gas in the discharge chamber 15, What is necessary is just to comprise so that the high pressure refrigerant gas of a discharge side may be guide | induced to the said pressure pocket groove | channel 29. FIG.

Next, the state of the seal ring 24 at each portion of the seal groove 27 in the screw compressor of this embodiment will be described with reference to FIGS. 9 to 11.
In FIG. 9 showing a cross section taken along line E-E of FIG. 4, the seal ring 24 is caused by the differential pressure between the discharge pressure (high pressure) Pd and the intermediate pressure Pm, as in the conventional case shown in FIG. As indicated by the arrow, it is pressed toward the rotor shaft 11A1 and is in contact with the inner peripheral surface of the seal groove 27, and the high-pressure refrigerant gas on the discharge side leaks to the intermediate pressure Pm side and the suction side pressure Ps side. Is sealed.

  In FIG. 10 showing a cross section taken along line F-F in FIG. 4, the seal ring 24 is pressed to the opposite rotor shaft side (downward side) by the intermediate pressure Pm. However, in the present embodiment, the pressure pocket groove 29 is provided, and the refrigerant gas having the discharge pressure Pd is introduced into the pressure pocket groove 29 from the discharge chamber 15, so that the seal ring 24 is moved upward at the discharge pressure Pd from below. Is also pressed. Therefore, in the section of the FF cross section shown in FIG. 4, the seal ring 24 is subjected to a force that pushes up the rotor shaft side (upward side) as shown by the arrow due to the differential pressure between the discharge pressure Pd and the intermediate pressure Pm. . As a result, the seal ring 24 is pressed toward the rotor shaft 11A1 and comes into contact with the peripheral surface on the inner diameter side of the seal groove 27 to seal the leakage of the gas having the intermediate pressure Pm to the suction side pressure Ps side. it can.

  In the portion shown in FIG. 10, although the pressure pocket groove 29 communicates with the suction side pressure Ps via the D gap 21, the D gap 21 is a very small gap. Leakage of the refrigerant gas from the exhaust gas is very small, and the pressure in the pressure pocket 29 is kept substantially at the discharge pressure Pd.

  In FIG. 11 showing a cross section taken along the line G-G in FIG. 4, the seal ring 24 is pressed to the opposite rotor shaft side (outward side) by the intermediate pressure Pm. However, in the present embodiment, the pressure pocket groove 29 is provided, and the refrigerant gas having the discharge pressure Pd is introduced into the pressure pocket groove 29 from the discharge chamber 15, so that the seal ring 24 is discharged from the side at the discharge pressure Pd. It is also pressed to the rotor shaft 11A1 side. Therefore, also in the portion of the GG cross section shown in FIG. 4, the seal ring 24 has a differential pressure between the discharge pressure Pd and the intermediate pressure Pm to the rotor shaft side (inward side) as shown by the arrow. The pressing force works. As a result, the seal ring 24 is pressed toward the rotor shaft 11A1 and comes into contact with the inner peripheral surface of the seal groove 27 to seal the discharge pressure Pd gas from leaking toward the intermediate pressure Pm.

  As described above, according to the present embodiment, by providing the pressure pocket groove 29, the discharge pressure Pd can be applied over the entire circumference of the outer peripheral surface of the seal ring 24. Thus, the seal ring 24 is pressed inward over the entire circumference, and the inner peripheral surface of the seal ring 24 contacts the peripheral surface on the inner diameter side of the seal groove 27 over the entire periphery. Therefore, the refrigerant gas on the discharge side with the discharge pressure Pd can be prevented from leaking to the intermediate pressure Pm side or the suction pressure Ps side.

  That is, in the conventional one, as the seal ring 24 hangs down, gaps 22 are formed on both the radially outer side and the inner side of the seal ring 24 as shown in FIG. Leakage to the intermediate pressure Pm side could not be sealed, and leakage occurred. On the other hand, by adopting the configuration of the present embodiment, it is possible to prevent the seal ring 24 from hanging down and to prevent a gap from being formed on both the radially outer side and the inner side of the seal ring 24. As a result, the refrigerant gas having the discharge pressure Pd can be sealed from leaking to the intermediate pressure Pm side, and the high-pressure side refrigerant gas can pass through the gap 26 on the outer periphery of the rotor shaft 11A1 to the suction pressure Ps side. Since leakage can be suppressed, leakage loss can be greatly reduced. Therefore, according to the present Example, the performance improvement of a screw compressor can be aimed at.

  Next, the shape of the seal ring 24 will be described with reference to FIGS. 12 is a plan view showing the shape of the seal ring 24 shown in FIGS. 2 to 4 and the like, and FIG. 13 is a front view of the seal ring shown in FIG. 12, viewed from the direction indicated by the arrow H in FIG.

  In the first embodiment, as shown in FIG. 12, the sealing ring 24 is cut in the radial direction at one place in the circumferential direction of the seal ring 24, and an abutment (cut portion) 24a that divides in the circumferential direction is provided. Provided. By providing the mating port 24 a in the seal ring 24 in this way, the seal ring 24 can be easily enlarged and reduced in the radial direction, so that the inner peripheral surface 24 b of the seal ring 24 is formed in the seal groove 27. It is easily pressed against the rotor shaft 11A1 side, that is, the inner peripheral surface. Therefore, the sealing performance of the seal portion can be further improved.

  As shown in FIG. 13, the shape of the abutment 24a is preferably a stepped shape (step cut shape), that is, a configuration having a radial cut surface and a circumferential cut surface. The radial cut surface that cuts the seal ring in the radial direction makes the seal ring 24 easily expand and contract in the radial direction. In addition, the circumferential cut surface that cuts the seal ring in the circumferential direction is formed on the inner diameter side of the seal ring 24 by a portion that overlaps in the radial direction of the abutment 24a even when the seal ring 24 is expanded in the radial direction. The sealing performance on the outer diameter side can be maintained and pressure leakage can be suppressed.

  According to the screw compressor of the present embodiment described above, the ring-shaped pressure pocket groove 29 that is formed along the outer periphery of the seal groove 27 and into which the pressure on the discharge side is introduced is provided. The bearing chamber passes through the gap between the rotor shaft 11A1, 11B1 of the screw rotor 11 and the shaft hole 25 formed in the discharge casing 3 from the gap between the discharge side end surface 11a and the rotor side end surface 3a of the discharge casing 3. It is possible to obtain a screw compressor that seals a sub-path that leaks from the 16 side to the suction side, reduces leakage loss, and improves performance.

In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, in the above description of the first embodiment, an example in which the present invention is applied to a twin screw compressor having a pair of male and female screw rotors in which the male rotor 11A and the female rotor 11B are engaged with each other has been described. The present invention is not limited to the twin screw compressor, and can be similarly applied to a single screw compressor or the like.
The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

1 ... motor casing, 2 ... main casing,
3 ... discharge casing, 3a ... rotor side end face,
4 ... Motor (electric motor), 4A ... Stator, 4B ... Rotor,
4a ... gas passage, 4b ... air gap,
5 ... cylindrical bore, 6 ... suction port,
7A, 8A, 8B ... Roller bearing (low pressure side bearing),
9A, 9B ... Roller bearing (high pressure side bearing), 10A, 10B ... Ball bearing (high pressure side bearing),
11 ... Screw rotor (11A ... male rotor, 11B ... female rotor),
11A1, 11B1 ... rotor shaft, 11a ... discharge end face of the rotor, 11b ... tooth bottom,
12 ... oil separator, 13 ... discharge port,
14 ... Oil sump, 15 ... Discharge chamber,
16 ... Bearing chamber (16A ... Male rotor side bearing chamber, 16B ... Female rotor side bearing chamber),
17 ... Shield plate, 18 ... Suction port, 19 ... Strainer,
20 ... oil supply groove, 21 ... D gap, 22 ... gap,
24 ... Seal ring, 24a ... Joint (cut part), 24b ... Inner peripheral surface,
25 ... shaft hole, 26 ... gap,
27 ... Seal groove (ring-shaped groove), 28 ... Wave spring, 29 ... Pressure pocket groove,
30 ... Communication passage,
51 ... Terminal box, 52 ... Power terminal, 53 ... Power cable,
64 ... refrigerant piping, 65 ... fixing flange,
100: Screw compressor.

Claims (9)

A pair of male and female screw rotors that mesh with each other, a low-pressure bearing and a high-pressure bearing that support the rotor shaft of the screw rotor, a main casing that houses the screw rotor, and a shaft hole through which the rotor shaft of the screw rotor penetrates And a discharge casing having a bearing chamber that houses the high-pressure side bearing, and a screw compressor comprising:
A ring-shaped seal groove formed around the rotor shaft at the screw rotor side end surface of the discharge casing, and a gap between the discharge side end surface of the screw rotor and the discharge casing disposed in the seal groove A screw compressor, comprising: a seal ring that seals the ring, and a ring-shaped pressure pocket groove that is formed along the outer periphery of the seal groove and into which pressure on the discharge side is introduced.   2. The screw compressor according to claim 1, wherein a communication passage for introducing a discharge-side pressure into the pressure pocket groove is provided in the discharge casing.   3. The screw compressor according to claim 2, wherein a discharge chamber for discharging compressed gas is formed in the discharge casing, and the communication passage communicates the pressure pocket groove and the discharge chamber. A screw compressor characterized by that.   4. The screw compressor according to claim 3, wherein the communication passage is formed on the rotor-side end surface of the discharge casing so as to communicate the pressure pocket groove and the discharge chamber. 5. Screw compressor.   2. The screw compressor according to claim 1, wherein a wave spring is disposed in the seal groove so as to press the seal ring against a discharge side end face of the screw rotor. 3. Compressor.   The screw compressor according to claim 1, wherein the seal ring is provided with an abutment for dividing the seal ring in a circumferential direction.   The screw compressor according to claim 6, wherein the abutment is configured in a stepped shape having a radial cut surface that cuts the seal ring in the radial direction and a circumferential cut surface that cuts in the circumferential direction. A screw compressor characterized by that.   The screw compressor according to any one of claims 1 to 7, wherein the screw compressor is a hermetic screw compressor used in a refrigeration apparatus. A screw rotor, a bearing that supports the rotor shaft of the screw rotor, a casing that houses the screw rotor, a shaft hole through which the rotor shaft of the screw rotor passes, and a discharge casing that has a bearing chamber that houses the bearing; A screw compressor comprising:
A ring-shaped seal groove formed around the rotor shaft at the screw rotor side end surface of the discharge casing, and a gap between the discharge side end surface of the screw rotor and the discharge casing disposed in the seal groove A screw compressor, comprising: a seal ring that seals the ring, and a ring-shaped pressure pocket groove that is formed along the outer periphery of the seal groove and into which pressure on the discharge side is introduced.

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