JP6427430B2 - Screw compressor - Google Patents

Description

  The present invention relates to a screw compressor having a structure in which a shaft of a screw rotor is connected to a drive shaft via a coupling, and in particular, to a two-stage screw compressor including a low screw rotor and a high screw rotor. is there.

As the prior art of this kind, for example, it is disclosed in Japanese Patent Application Laid-Open Nos. 1-167487 (Patent Document 1), 8-210281 (Patent Document 2), 2001-317480 (Patent Document 3), etc. There is one described.
The above-mentioned Patent Documents 1 and 2 have male and female low-stage screw rotors rotatably supported at predetermined intervals so as to engage with each other in the low-stage casing, and these male and female low-stage screw rotors The shaft portion of one of the low-stage screw rotors of the screw rotors is coupled to the drive shaft of the drive motor via a coupling (gear coupling). The high stage casing is also provided with a pair of male and female high stage screw rotors rotatably supported at predetermined intervals so as to engage with each other, and one of the male and female high stage screw rotors is provided. The shaft of the screw rotor is integrally formed with the drive shaft of the drive motor.

  Further, in the above Patent Document 3, male and female screw rotors are supported by a low pressure side bearing and a high pressure side bearing in a rotor casing, and a shaft portion of a male rotor among the screw rotors and a drive motor are driven. An oil passage is provided, which is connected to the shaft by a coupling and lubricates the high pressure side bearing, and returns the oil to the low pressure side (gas suction side) through the through hole formed at the center of the male rotor. To lubricate.

Unexamined-Japanese-Patent No. 1-167487 JP-A-8-210281 JP 2001-317480 A

  In the two-stage screw compressor described in Patent Document 1 and Patent Document 2, the shaft portion of the low-stage screw rotor and the drive shaft (shaft portion on the high-stage screw rotor side) of the drive motor are connected via a coupling. It is disclosed that. In the case of such a conventional screw compressor, as shown in FIG. 7, the shaft portion 2A 'of the low stage screw rotor and the drive shaft 5c of the drive motor (shaft portion 3A' on the high stage screw rotor side) are assembled Due to an error or the like, an axial misalignment d occurs in which the shaft is displaced at the portion of the coupling 7. Further, during operation of the two-stage screw compressor, each shaft portion is displaced in the radial direction due to the load applied to the screw rotor, so that the shaft misalignment d further increases, and as shown in FIG. When the teeth 7a and 7b are inclined as indicated by the inclination angle θ, there is a problem that the external teeth 7c meshing with the teeth 7a and 7b collide with the teeth 7a and 7b to increase noise and wear of the gear.

  Further, at the time of assembly and maintenance of the screw compressor, the shaft portion 2A 'of the low-stage screw rotor and the drive shaft 5c of the drive motor (shaft portion 3A' at the high-stage screw rotor side) are coupled (gear coupling) 7 The centering of the shaft 2A 'of the low-step screw rotor and the shaft 5c of the drive motor (the shaft 3A' on the high-step screw rotor) is performed by coupling gears (inner teeth 7a and 7b, outside) Must be done with teeth 7c). For this reason, when the shaft misalignment d is large, the meshing of the gears becomes difficult when connecting the internal teeth 7a and 7b and the external teeth 7c of the coupling, and the possibility of damaging the gears increases. In particular, in the two-stage screw compressor described in Patent Document 1 and Patent Document 2, the coupling operation of the coupling portion needs to be performed in a sealed casing and can not be visually connected, so the shaft core The deviation is a factor that greatly reduces the connection workability of the coupling 7 parts.

  The problems of Patent Documents 1 and 2 are the same as those of Patent Document 3 described above. Further, in Patent Document 3, an oil passage for returning the oil after lubricating the high pressure side bearing to the low pressure side through the through hole formed at the center of the screw rotor is provided to lubricate the coupling portion. However, oil discharged from the through hole during operation of the compressor collides with the other axial end face and flows in the outer peripheral direction of the shaft, but due to the inclination of the shaft, it becomes a passage flowing in the outer peripheral direction The gap between the shafts is not constant in the circumferential direction. For this reason, the amount of oil flowing in the outer circumferential direction is not uniform in the circumferential direction but is a uneven flow. In addition, since the tooth grooves of the gear of the coupling 7 are formed in the axial direction (thrust direction), the oil that has flowed in a biased manner flows along the tooth grooves and is discharged as it is. For this reason, since the oil flows in a biased manner with respect to the entire circumference of the coupling 7, the formation of the oil film of the gear is disturbed, and the amount of noise and gear wear increases.

  The object of the present invention is to facilitate the coupling operation of the coupling portion even if there is axial misalignment between the shaft portion of the screw rotor and the drive shaft, and the axial misalignment of the screw rotor to be connected is also reduced To provide a low noise and highly reliable screw compressor.

In order to achieve the above object, the present invention comprises a compressor unit having a pair of male and female screw rotors meshing with each other in a casing, and a drive unit having a drive shaft for driving the compressor unit, the screw rotor In the screw compressor in which the shaft end of the drive shaft and the shaft end of the drive shaft are connected via a coupling, the coupling is respectively connected to the shaft end of the screw rotor and the shaft end of the drive shaft. A convex portion is formed at the end of the axial end of the screw rotor or at one end of the axial end of the drive shaft. A concave portion for fitting the convex portion is formed at the center of the end face of the rotor or the other end face of the axial end of the drive shaft, and the convex portion is inserted into the concave portion. It is fitted, and before Wherein a convex portion concave portion is characterized by being fitted with clearance fit so as to be slidable in the axial direction.

Another feature of the present invention is a low-stage compressor unit having a pair of low-stage screw rotors meshing with each other in a low-stage casing, and a pair of high-stage screw rotors meshing with each other in a high-stage casing And a drive unit for driving the low-stage compressor unit and the high-stage compressor unit, one of the rotor shafts of the high-stage screw rotor is a drive shaft of the drive unit, and In the screw compressor which is integrally formed and the shaft end of the low-stage screw rotor and the shaft end of the drive shaft are connected via a coupling, the coupling is the shaft of the low-stage screw rotor An end portion, an internal tooth fixed to each shaft end portion of the drive shaft, and an external tooth meshing with the internal teeth, one of the shaft end portion of the low-step screw rotor or the shaft end portion of the drive shaft A convex part is located at the center of the A concave portion for fitting the convex portion is formed at the shaft end of the low-step screw rotor or at the center of the other end face of the drive shaft, and the convex portion is used as the concave portion. It is inserted and fitted , and the convex portion and the concave portion are fitted in a gap fit so as to be axially slidable .

  According to the present invention, even if there is axial misalignment between the shaft portion of the screw rotor and the drive shaft, the coupling operation of the coupling portion can be easily performed, and the axial misalignment of the screw rotor to be connected is also reduced. Therefore, there is an effect that a low noise and highly reliable screw compressor can be obtained.

It is a longitudinal cross-sectional view which shows Example 1 of the screw compressor of this invention. It is a perspective view explaining the assembly procedure of the coupling connection part shown in FIG. 1, and is a figure which shows the state before an internal tooth is fitted by the axial end of a low stage screw rotor and the axial end of a drive shaft. It is a perspective view explaining the assembly procedure of the coupling connection part shown in FIG. 1, and is a figure which shows the state by which the internal gear was each fitted by the axial end of the low stage screw rotor and the axial end of a drive shaft. It is an enlarged view of the connection part which has connected the axial part of the low stage male rotor of FIG. 1, and both axial end parts of a drive shaft through a coupling, and is a figure which shows a principal part in a cross section. It is a cross-sectional view which expands and shows the low stage compressor part and coupling periphery which are shown in FIG. It is an enlarged view of coupling vicinity shown in FIG. 5, and is a figure which shows the principal part in a cross section. It is an expanded sectional view of the coupling connection part in the conventional screw compressor, and is a figure explaining the axial center offset at the time of an assembly. It is an expanded sectional view of the coupling connection part shown in FIG. 7, and is a figure explaining the state at the time of driving | operation.

  Hereinafter, specific examples of the screw compressor of the present invention will be described with reference to the drawings. In each of the drawings, the parts denoted by the same reference numerals indicate the same or corresponding parts.

Hereinafter, Example 1 of the screw compressor of this invention is demonstrated using FIGS. 1-6.
First, the overall configuration of the screw compressor according to the first embodiment will be described with reference to FIG. FIG. 1 is a longitudinal sectional view showing a first embodiment of a screw compressor according to the present invention, and shows an example in which the present invention is applied to a two-stage screw compressor as a screw compressor.

  As shown in FIG. 1, the screw compressor 100 of the present embodiment is configured of a two-stage screw compressor including a low-stage compressor unit 25, a motor unit (drive unit) 26, and a high-stage compressor unit 27. . The compressed gas (refrigerant gas in this embodiment) flows from the low stage compressor unit 25 through the motor unit 26 to the high stage compressor unit 27 and is discharged out of the compressor. In the following description, the direction is shown with the low-stage compressor unit 25 side as the upstream side and the high-stage compressor unit 27 side as the downstream side.

  The low-stage compressor unit 25 includes a pair of male and female low-stage screw rotors 2 engaged with each other in a cylindrical bore 1a formed in a low-stage casing (the low-stage main casing 1). That is, the low-stage main casing 1 includes a pair of cylindrical bores 1a extending in the axial direction and intersecting in the circumferential direction, and the male and female low-stage screw rotors 2 are accommodated in the pair of cylindrical bores 1a. It is done.

  Further, a recess 1b extending in the axial direction along the cylindrical bore 1a is formed in the low-stage main casing 1, and a slide valve 17 is accommodated in the recess 1b so as to be movable in the axial direction. The slide valve 17 is for bypassing a portion of the refrigerant gas sucked into the meshing portion of the low-stage screw rotor 2 to the suction side for capacity control, and the shaft formed in the low-stage main casing 1 It is accommodated so as to be movable in the axial direction in the recess 1 b extending in the direction.

  Further, a piston (hydraulic piston) 19 driven hydraulically is connected to the slide valve 17 through a rod 18, and the piston 19 is a cylinder chamber formed in the low stage main casing 1 in the axial direction. 21 is configured to be capable of reciprocating in the axial direction.

  A coil spring 20 is provided in the cylinder chamber 21 on the side opposite to the slide valve of the piston 19. The coil spring 20 applies a force to always press the piston 19 toward the slide valve.

  By introducing high pressure oil into the cylinder chamber 21 in which the coil spring 20 is provided, the piston 19 is moved in the left direction in the drawing, and along with this, the slide valve 17 is also moved in the left direction. Can be reduced. That is, the slide valve 17, the rod 18, the piston 19 and the coil spring 20 constitute a displacement control mechanism.

  Further, a suction port 15 for suctioning the refrigerant gas, a suction chamber 32 and a suction port 33 in the low-stage main casing 1, and a low-stage for discharging the compressed refrigerant gas compressed by the low-stage screw rotor 2. The discharge port 29 and the like are formed.

  The suction port 15, the suction chamber 32 and the suction port 33 form a suction passage to the low-stage screw rotor 2, and the low-stage discharge port 29 forms a discharge passage from the low-stage screw rotor 2. It is. Reference numeral 22 denotes a discharge casing attached so as to cover the discharge side opening of the low pressure main casing 1 so that the compressed refrigerant gas discharged from the low stage discharge port 29 is discharged into the discharge casing 22. It is configured.

  The low-stage screw rotor 2 is composed of a pair of low-stage male rotors 2A and low-stage female rotors 2B (see FIG. 5) engaged with each other. Axial parts are provided on both sides of the low-stage male rotor 2A and the low-stage female rotor, and these axial parts are the roller bearings 8 installed in the bearing chamber 8a of the low-stage main casing 1 and It is supported by the roller bearing 9 and the ball bearing 10 installed in the discharge casing 22. Among the compression reaction forces acting on the screw rotor 2 at the time of compression, radial loads are supported by the roller bearings 8 and 9, and thrust loads are supported by the ball bearing 10.

  The motor unit (drive unit) 26 includes a motor casing 23 and a motor cover 24. In the motor casing 23, a motor (drive machine) 5 including a motor stator 5a and a motor rotor 5b is provided. There is. The motor stator 5 is fixed to the inner surface of the motor casing 24, and the motor rotor 6 is rotatably provided in the motor stator 5. A drive shaft 5c is fixed to a motor rotor 5b of the motor 5, and the drive shaft 5c is supported by a ball bearing 11 provided on the motor cover 24 and a roller bearing 12 provided on the motor casing 23.

  The high-stage compressor unit 27 includes a pair of high-stage screw rotors 3 engaged with each other in a cylindrical bore 4a formed in a high-stage casing (high-stage main casing 4). That is, the high stage main casing 4 is also provided with a pair of cylindrical bores 4a extending in the axial direction and intersecting in the circumferential direction, and the male and female high stage screw rotors 3 are provided in the pair of cylindrical bores 4a. It is stored.

  Further, the high-stage main casing 4 receives the compressed refrigerant gas discharged from the low-stage compressor portion 25 and having passed through the discharge casing 22, the motor cover 24 and the motor casing 23 into the high-stage compressor portion 27. A high stage suction port 30 for causing the high stage screw, a high stage discharge port 31 for discharging the compressed refrigerant gas further compressed by the high stage screw rotor 3, and a discharge port 16 are formed.

  The high-stage screw rotor 3 is composed of a pair of high-stage male rotors 3A and high-stage female rotors (not shown) engaged with each other. Shaft portions are respectively provided on both sides of the high stage male rotor 3A and the high stage female rotor, and these axial sections are provided on the roller bearing 12 installed on the motor casing 23 and the high stage main casing 4 It is supported by the installed roller bearings 13 and ball bearings 14. Of the compression reaction force acting on the high stage screw rotor 3 at the time of compression, a radial load is supported by the roller bearings 12 and 13, and a thrust load is supported by the ball bearing 14.

  In the present embodiment, the high stage male rotor 3A is integrally formed with a drive shaft 5c of the motor 5, and the drive shaft 5c is also a shaft portion of the high stage male rotor 3A. Accordingly, the shaft portion of the high stage male rotor 3A is also supported by the ball bearing 11 provided on the motor cover 24.

  The shaft end of the drive shaft 5c of the motor 5 (shaft portion 3A 'of the high stage male rotor 3A) on the low stage compressor portion 25 side is the shaft end of the low stage male rotor 2A of the low stage screw rotor 2 (An end portion of the shaft portion 2A ′) is coupled to the coupling (gear coupling) 7 via the coupling (gear coupling) 7.

  The motor unit 26 is disposed between the low-stage compressor unit 25 and the high-stage compressor unit 27, and the driving force of the motor 5 can be obtained by using the low-stage male rotor 2 A of the low-stage compressor unit 25 and the It is configured to be transmitted to the high stage male rotor 3A of the high stage compressor unit 27. The low stage female rotor 2B is driven by the low stage male rotor, and the high stage female rotor is driven by the high stage male rotor 3A.

Next, the configuration of the connecting portion (coupling 7 portion) between the low stage male rotor 2A and the drive shaft 5c (shaft portion 3A 'of the high stage male rotor 3A) in the two-stage screw compressor shown in FIG. This will be described using FIGS.
2 and 3 are perspective views for explaining the assembly procedure of the coupling connecting portion shown in FIG. 1, and FIG. 2 shows that the internal teeth are fitted to the shaft end of the low-stage screw rotor and the shaft end of the drive shaft. FIG. 3 is a view showing the previous state, FIG. 3 is a view showing the state in which the internal teeth are respectively fitted to the shaft end of the low-step screw rotor and the shaft end of the drive shaft, FIG. 4 is the low-step male rotor 2A of FIG. FIG. 18 is an enlarged view of a connecting portion in which both shaft end portions of the shaft portion 2A 'of the first embodiment and the drive shaft 5c (the shaft portion 3A' of the high stage male rotor) are connected via a coupling.
As shown in FIG. 2, the coupling (gear coupling) 7 is an axis of the internal teeth (high stage side internal teeth) 7a on the drive shaft 5c (shaft portion 3A 'of the high stage male rotor 3A) side and an axis of the low stage male rotor 2A. It is comprised by three components of the internal tooth (low stage side internal tooth) 7b by the side of part 2A ', and the external tooth 7c which meshes with the said internal teeth 7a and 7b. The external teeth 7c are kept at a fixed position so that the internal teeth 7a and 7b and the external teeth 7c always mesh with the internal teeth 7a and 7b during operation of the compressor. A stop ring 7d, which serves as a stopper for the purpose, is fixed.

When assembling the coupling 7, as shown in FIG. 3, first, the inner teeth 7a are fixed to the shaft end of the drive shaft 5c (shaft portion 3A 'of the high stage male rotor 3A), and the inner teeth 7b are also fixed. It fixes to the axial end part of said low stage | grade male rotor axial part 2A '. Thereafter, as shown in FIG. 4, by meshing the external teeth 7c with the internal teeth 7a and the internal teeth 7b, the axial power of the drive shaft 5c is transmitted to the low speed male rotor 2a side. ing.
The external teeth 7c are attached in a free state in the axial direction, and the low-stage compressor unit 25 side and the motor unit 26 (including the high-stage compressor unit 27) side can be separated. There is.

  In the present embodiment, as shown in FIG. 4, a convex portion 35 is formed at the end face center of the shaft end portion (low step screw rotor shaft end portion) of the low step male rotor shaft portion 2A '. A concave portion 36 is formed at a position opposite to the convex portion 35 at the axial end of the shaft 5c (shaft portion 3A 'of the high stage male rotor). When the coupling 7 is assembled, the convex portion 35 formed at the axial end of the low-step male rotor shaft portion 2A ′ is added to the concave portion 36 formed at the axial end of the drive shaft 5c. By inserting and fitting, the both shaft end portions are formed into a uniaxial shape, and even if there is axial misalignment between the low-step male rotor shaft portion 2A ′ and the drive shaft 5c, this shaft can be obtained. Misalignment can be reduced. Therefore, the coupling operation of the coupling 7 can be easily performed, and a low-noise and highly reliable screw compressor can be obtained.

  In the present embodiment, the convex portion 35 has a distal end side taper portion 35a and a proximal end side parallel shaft portion 35b, and is formed on the drive shaft side by the tapered portion 35a. The insertion into the concave portion 36 is facilitated, and the fitting with the concave portion 36 is properly maintained by the parallel shaft portion 35 b. The taper portion 35a is formed by means such as chamfering.

  Further, during operation of the screw compressor 100, the low level and high level screw rotors 2, 3 are displaced in the axial direction by the internal clearances of the ball bearings 10, 11, 14 supporting the thrust load, and heat is further generated. Since displacement due to deformation is also applied, the fitting portion between the convex portion 35 and the concave portion 36 is a clearance fit so as to be axially slidable to prevent interference between the shafts.

  In the present embodiment, an example in which the taper portion 35a is formed by chamfering is shown, but if the tip side of the convex shape portion 35 is formed as a taper surface, the concave shape of the convex shape portion 35 is further formed. Insertion into the portion 36 can be easily performed. Further, in the present embodiment, the convex portion 35 is provided on the low stage screw rotor 2 side, and the concave portion 36 is provided on the high stage screw rotor 3 side (drive shaft 5 c side). A convex portion may be provided on the side (the drive shaft 5c side), and a concave portion may be provided on the low speed screw rotor 2 side.

Next, the flow of oil will be described with reference to FIGS. 5 and 6. 5 is an enlarged cross-sectional view showing the periphery of the low-stage compressor portion 25 and the coupling 7 shown in FIG. 1, and FIG. 6 is an enlarged view of the vicinity of the coupling 7 shown in FIG. FIG.
Oil for lubrication and cooling of bearings may be transferred from, for example, an oil separator (not shown) installed separately from the compressor to the roller bearings 8, 9, 12, 13 and the ball bearings 10, 11, 14. It is supplied by differential pressure through an oil passage. Further, as shown in FIG. 5, the bearing chamber 8a is in communication with the gear coupling 7 by an oil passage 34 formed at the center of the shaft portion 2A 'of the low-stage male rotor 2A. The oil supplied to the roller bearing 8 which is the upstream side bearing of the low stage male rotor 2A and the low stage female rotor 2B through the oil passage 37 flows into the bearing chamber 8a, and from here the low stage male rotor 2A The gear coupling 7 is lubricated through the oil passage 34 opened at the center of the shaft portion 2A '. The oil which lubricated the gear coupling 7 is mixed with the refrigerant gas of the intermediate pressure which is discharged from the gear coupling 7 and discharged from the low-stage compressor unit 25, and the high-stage suction port 30 (see FIG. 1) side The gas flows into the groove of the high-stage screw rotor 3 and is discharged from the discharge port 16 together with the compressed gas.

  The oil supplied to the roller bearings 12 and 13 of the high-stage screw rotor 3 and the ball bearing 14 is discharged to the meshing portion of the high-stage screw rotor, and the roller bearings 8 of the low-stage screw rotor 2 on the upstream side The oil is discharged from the discharge port 16 together with the oil supplied to the ball bearing 10 and the ball bearing 10.

The detailed configuration of the oil passage 34 formed in the low stage male rotor 2A in this embodiment will be described with reference to FIG.
In the present embodiment, a communication hole 34a is provided to connect the oil passage 34 and the outer peripheral surface of the convex portion 35, and the oil supplied from the oil passage 34 is passed through the communication hole 34a. It is configured to lead to the coupling 7. Further, the communication hole 34a is formed in the inter-axial gap 38 between the shaft end of the shaft portion 2A 'of the high stage male rotor 2A and the shaft end of the drive shaft 5c. Furthermore, a plurality of the communication holes 34a communicating the oil passage 34 and the outer peripheral surface of the convex portion 35 in the radial direction (four in the present embodiment at equal intervals in the circumferential direction) are provided. The hole 34a is formed in a circular hole.

  With this configuration, the oil flowing from the bearing chamber 8a into the oil passage 34 is injected from the communication hole 34a into the inter-shaft gap 38 and injected toward the external teeth 7c of the gear coupling 7. And lubricate the engagement portion between the internal teeth 7a, 7b and the external teeth 7c.

  With the above-described configuration, according to the present embodiment, between the shaft portion 2A 'of the low-stage male rotor 2A and the drive shaft 5c (shaft portion 3A' of the high-stage screw rotor) with a simple structure. Even when there is axial misalignment, the coupling work of the coupling 7 can be easily performed, and axial misalignment between the coupled drive shaft 5c and the shaft portion 2A 'of the low-stage screw rotor 2A is also reduced. Thus, a low-noise and highly reliable screw compressor can be obtained.

  In the above embodiment, although the present invention is applied to a two-stage screw compressor, the present invention can be applied to a single-stage screw compressor as well. That is, in the case of a single-stage screw compressor, although the high-stage compressor unit 27 shown in FIG. 1 is not provided, the other configuration is almost the same. The drive shaft 5c of the motor 5 and the shaft portion of the male rotor of the screw rotor When the coupling 7 to be coupled is similarly provided, the coupling 7 may be configured in the same manner as the embodiment described above.

  Furthermore, the present invention is not limited to the above-described embodiments, and includes various modifications. Further, the above-described embodiments are described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described.

1: Low-stage main casing 1a: cylindrical bore 1b: recess
2: Low-stage screw rotor 2A: Low-stage male rotor 2A ′: Shaft,
2B: Low-stage female rotor,
3: High-stage screw rotor, 3A: High-stage male rotor, 3A ': Shaft,
4: High stage main casing 4a: Cylindrical bore,
5: motor (drive machine), 5a: motor stator, 5b: motor rotor, 5c: drive shaft,
7: Coupling (gear coupling),
7a, 7b: internal teeth, 7c: external teeth, 7d: stop ring,
8, 9, 12, 13: Roller bearings, 8a: Bearing chamber 8a,
10, 11, 14: Ball bearings,
15: inlet, 16: outlet,
17: slide valve, 18: rod, 19: piston,
20: coil spring, 21: cylinder,
22: Discharge casing 23: Motor casing, 24: Motor cover,
25: low-stage compressor unit, 26: motor unit (drive unit), 27: high-stage compressor unit,
29: low stage discharge port, 30: high stage suction port, 31: high stage discharge port,
32: suction chamber, 33: lower stage suction port,
34: oil passage, 34a: communication hole,
35: convex shape portion 35a: taper portion 35b: parallel shaft portion 36: concave shape portion
37: oil passage, 38: inter-shaft gap, 100: screw compressor,
d: axis misalignment, θ: tilt angle.

Claims (9)

And a drive unit having a drive shaft for driving the compressor unit, the compressor unit including a screw rotor having a pair of male and female screw members engaged with each other in a casing, and a shaft end of the screw rotor and a shaft of the drive shaft. In a screw compressor in which the ends are connected via a coupling:
The coupling includes an axial end of the screw rotor and an internal tooth fixed to the axial end of the drive shaft, and an external tooth meshing with the internal tooth.
A convex portion is formed at the center of one end face of the shaft end of the screw rotor or the shaft end of the drive shaft,
A concave portion for fitting the convex portion is formed at the center of the other end face of the shaft end of the screw rotor or the shaft end of the drive shaft,
The convex portion is inserted into and fitted to the concave portion , and
A screw compressor characterized in that the convex portion and the concave portion are fitted with clearance fit so as to be axially slidable . A low-stage compressor unit including a pair of low-stage screw rotors meshing with each other in a low-stage casing; and a high-stage compressor unit including a pair of high-stage screw rotors meshing together within a high-stage casing; The low-stage compressor unit and a driver for driving the high-stage compressor unit are provided, and one of the rotor shafts of the high-stage screw rotor is integrally formed with a drive shaft of the driver, the low-stage compressor unit In a screw compressor in which a shaft end of a screw rotor and a shaft end of the drive shaft are connected via a coupling,
The coupling includes an inner end fixed to the shaft end of the low-stage screw rotor and the shaft end of the drive shaft, and an outer gear engaged with the inner teeth.
A convex portion is formed at the center of one end face of the shaft end of the low-step screw rotor or the shaft end of the drive shaft,
A concave portion for fitting the convex portion is formed at the shaft end of the low-stage screw rotor or at the center of the other end face of the drive shaft,
The convex portion is inserted into and fitted to the concave portion , and
A screw compressor characterized in that the convex portion and the concave portion are fitted with clearance fit so as to be axially slidable . The screw compressor according to claim 1 or 2 , wherein the convex portion has a tapered portion on the tip end side and a parallel shaft portion on the base end side. The screw compressor according to claim 3 , wherein the tapered portion is formed by chamfering. The screw compressor according to claim 3 , wherein the taper portion is formed by a taper surface formed on the tip end side of the convex portion. The screw compressor according to any one of claims 1 to 5 , wherein the convex portion is provided at the end face center of the shaft end of the screw rotor, and the coupling oil is provided at the screw rotor shaft center. Forming an oil passage for supplying oil, providing a communication hole connecting the oil passage and the outer peripheral surface of the convex portion, and guiding oil supplied from the oil passage to the coupling through the communication hole A screw compressor characterized by having a configuration. The screw compressor according to claim 6 , wherein the communication hole is formed in an inter-axial gap between an axial end of the screw rotor and an axial end of the drive shaft. Screw compressor. The screw compressor according to claim 7 , wherein a plurality of the communication holes communicating the oil passage and the outer peripheral surface of the convex portion are provided in the radial direction, and each communication hole is formed in a circular hole. A screw compressor characterized by The screw compressor according to any one of claims 6 to 8 , wherein the convex portion is formed at the end face center of an axial end portion of a male rotor of the screw rotor, and the concave portion is of the drive shaft. The shaft end portion is formed at a position opposite to the convex shape portion, and when the coupling is assembled, the convex shape portion is inserted into and fitted to the concave shape portion to configure the both shaft end portions in a uniaxial shape. A screw compressor characterized by having.

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