CN107923395A - Screw compressor - Google Patents

Abstract

Screw compressor (1) includes：Vortex element (6)；Crank mechanism (44)；Shell (2,4), above-mentioned shell (2,4) house for vortex element (6), and have the inhalation port (22) of refrigerant on the periphery wall (2b) positioned at vortex element (6) outer circumferential side；And sealing device (30), above-mentioned sealing device (30) between shell (2,4) and shaft (24) to sealing, shell (2,4) includes crank chamber (48), and above-mentioned crank chamber (48) positions for crank mechanism (44)；Closed chamber (50), above-mentioned closed chamber (50) position for sealing device (30)；Intercommunicating pore (52,58), above-mentioned intercommunicating pore (52,58) make crank chamber (48) be connected with closed chamber (50)；And first guiding groove (54), above-mentioned first guiding groove (54) is from the opening of the intercommunicating pore (52,58) in closed chamber (50) near sealing device (30).

Description

Screw compressor

Technical field

The present invention relates to a kind of screw compressor, more particularly to the whirlpool used in the refrigerating circuit of air conditioner for motor vehicle Revolve compressor.

Background technology

Patent Document 1 discloses a kind of compressor, static vortex disk and movable orbiting scroll are contained in shell by above-mentioned compressor, warp By bearing by shaft support in shell, and the shaft sealing mechanism including being embedded between shaft and shell, and formation makes sealing Room and the access that the suction room side of refrigerant connects are using the lubricating element as shaft sealing mechanism.

Prior art literature

Patent document

Patent document 1：No. 2868998 publication of Japanese Patent Laid

The content of the invention

The technical problems to be solved by the invention

In the case where compressor is construction of the outer circumferential side equipped with inhalation port in the vortex element of the periphery wall of shell, Since the refrigerant imported from inhalation port can be sucked in vortex element immediately, accordingly, it is capable to expect the compression efficiency of refrigerant Improve.On the other hand, in the compressor of such construction, the refrigerant stream at the position of the remote inhalation port in inflow shell Amount can be reduced, and especially all worry the poor lubrication of shaft sealing mechanism or the lippacking as sealing device all the time.

Such as patent document 1 in this way, when only formation makes the access that closed chamber is connected with the suction room side of refrigerant, when In the case that lippacking is away from inhalation port, access can be elongated, so as to be difficult to fully supply lubricating oil to lip Seal.

The present invention in view of above-mentioned technical problem and make, its purpose is to provide a kind of screw compressor, by by lubricating oil actively Ground is guided to sealing device, so that while the compression efficiency of compressor is improved, significantly reduces the abrasion of sealing device, and then Remaining profit margin of the sealing device relative to shaft is ensured, so as to chronically maintain the sealing performance of compressor.

Technical scheme applied to solve the technical problem

To achieve these goals, screw compressor of the invention includes：Vortex element, above-mentioned vortex element is by moving whirlpool Disk is relative to static vortex disk revolution convolution so as to be compressed to refrigerant；Crank mechanism, above-mentioned crank mechanism is by the rotation of shaft Movement is converted into the revolution circumnutation of movable orbiting scroll, and is transmitted；Shell, above-mentioned shell supply whirlpool disk unit housing, and in place In the inhalation port on the periphery wall of the outer circumferential side of whirlpool disk unit with refrigerant；And sealing device, above-mentioned sealing device pair Sealed between shell and shaft, shell has：Crank chamber, above-mentioned crank chamber are positioned for crank mechanism；Closed chamber, it is above-mentioned close Room is sealed to position for sealing device；Intercommunicating pore, above-mentioned intercommunicating pore make crank chamber be connected with closed chamber；And first guiding groove, it is above-mentioned First guiding groove is from the opening of the intercommunicating pore in closed chamber near sealing device.

It is preferable that shell also has the second guiding groove, above-mentioned second guiding groove is opened for the intercommunicating pore of crank chamber Mouth positioning.

It is preferable that above-mentioned crank mechanism includes counterweight, above-mentioned counterweight is installed on shaft, intercommunicating pore be formed at with At the position that the convolution of weight is intermittently covered by counterweight.

It is preferable that intercommunicating pore is tilted relative to the convolution direction radially along counterweight of shaft.

It is preferable that counterweight has inclined plane, above-mentioned inclined plane is tilted relative to the axis of shaft.

It is preferable that counterweight has a step surface, above-mentioned step surface is towards the radially projecting of shaft.

Invention effect

Screw compressor according to the present invention, by guiding lubricating oil to sealing device on one's own initiative, so as to be pressed improving While the compression efficiency of contracting machine, significantly reduce the abrasion of sealing device, and then ensure residue of the sealing device for shaft Profit margin, so as to chronically maintain the sealing performance of compressor.

Brief description of the drawings

[figure 1] Fig. 1 is the longitudinal section of the screw compressor of first embodiment of the invention.

Fig. 2 is the longitudinal section of a part of amplified screw compressor by the crank chamber of Fig. 1 and closed chamber.

Fig. 3 is the top view of the front casing of Fig. 1 from the open end side of front casing.

Fig. 4 is the top view for another form for representing Fig. 3.

Fig. 5 is the top view for the another form for representing Fig. 3.

Fig. 6 is the vertical profile of a part of amplified screw compressor by the crank chamber of second embodiment of the invention and closed chamber View.

Fig. 7 is the top view of the front casing of Fig. 6 from the open end side of front casing.

Fig. 8 is the top view of the front casing of third embodiment of the invention from the open end side of front casing.

Fig. 9 is that the counterweight of four embodiment of the invention is being installed on to the side view that is shown in the state of shaft.

Figure 10 is the side view for another form for representing Fig. 9.

Figure 11 is the side view for the another form for representing Fig. 9.

Embodiment

Hereinafter, based on attached drawing, various embodiments of the present invention will be described.

(first embodiment)

Fig. 1 is the longitudinal section of the screw compressor 1 of first embodiment of the invention.Above-mentioned compressor 1 is for example assembled in installing In the refrigerating circuit of the air conditioner for motor vehicle of vehicle, and the compression of the refrigerant for being circulated in refrigerating circuit.

Compressor 1 includes rear casing (shell) 2 and front casing (shell) 4, and vortex element 6 is configured with rear casing 2.Whirlpool Rotation unit 6 is made of static vortex disk 8 and movable orbiting scroll 10, wherein, above-mentioned static vortex disk 8 is fixed on rear casing 2, above-mentioned movable orbiting scroll 10 with The mode that above-mentioned static vortex disk 8 engages is installed.Static vortex disk 8 include end plate 8a and fixed scroll body 8b, above-mentioned fixed scroll body 8b with End plate 8a is molded as one, and movable orbiting scroll 10 includes end plate 10a and movable scroll body 10b, above-mentioned movable scroll body 10b and end plate 10a is molded as one, and fixed scroll body 8b and movable scroll body 10b are engaged with each other.

Formed with discharge room 12 between in rear casing 2, rear casing 2 end wall 2a and static vortex disk 8.Above-mentioned discharge room 12 The tap 14 of the end plate 8a of static vortex disk 8 via the dump valve 16 of leaf-valve type, can be will be formed in and be formed at static vortex disk 8 with moving Discharge chambe 18 between whirlpool disk 10 connects.At position periphery wall 2b, by proximal end wall 2a of rear casing 2, formed with discharge Port 20, discharge room 12 are connected via discharge port 20 with the refrigerant circulating path of refrigerating circuit.

In addition, the outer circumferential side positioned at vortex element 6 of the periphery wall 2b in rear casing 2, the inhalation port equipped with refrigerant 22, promptly sucked from refrigerant circulating path via the refrigerant that inhalation port 22 imports in vortex element 6.

On the other hand, shaft 24 is configured with front casing 4, above-mentioned shaft 24 has big diameter section 24a and small diameter section 24b. In addition, front casing 4 is by making the diameter of the inner circumferential of front casing 4 reduce stepwise, so that from positioned at the openend of 2 side of rear casing 4a is sequentially formed with major diameter inner peripheral surface 4b, central diameter inner peripheral surface 4c and path inner peripheral surface 4d.

Big diameter section 24a is supported to the central diameter inner peripheral surface 4c relative to front casing 4 via needle bearing, i.e. bearing 26 Rotate freely, small diameter section 24b can be rotatably supported in the path of front casing 4 via ball bearing, i.e. bearing 28 Side face 4d.In addition, lippacking (sealing dress is configured between small diameter section 24b and the path inner peripheral surface 4d of front casing 4 Put) 30.The outer circumferential side of lippacking 30 is installed on path inner peripheral surface 4d, because of the path in the lip and rotation of inner circumferential side Axle portion 24b is contacted, and plays the role of sealing device, and hermetic to carrying out zoning in front casing 4.

The small diameter section 24b of shaft 24 is protruded from front casing 4, above-mentioned jag and the driving cunning for being built-in with electromagnetic clutch The connection of wheel 32.Driving pulley 32 can rotatably be supported in front casing 4 via ball bearing, i.e. bearing 34.Driving pulley 32 are connected via band with the output pulley of the engine side of vehicle, are subject to the power of engine and rotate.

On the other hand, crank-pin 24c from the big diameter section 24a of shaft 24 to can movable orbiting scroll 10 it is prominent.Crank-pin 24c is arranged on From the axle center eccentric position of shaft 24, and it is inserted into the crank pin hole 38 for being arranged in eccentric bush 36 and is fitted.Crank-pin 24c supports eccentric bush 36 using the base end part 24c1 of crank-pin 24c.In addition, eccentric bush 36 is via needle roller axis Hold, i.e. bearing 40 and the axle sleeve 41 of movable orbiting scroll 10 is supported.

In addition, on crank-pin 24c, it is provided with and is matched somebody with somebody in a manner of being clamped between eccentric bush 36 and big diameter section 24a Weigh 42.Counterweight 42 by make the arc-shaped plate 42a of multiple sizes on the axis direction of shaft 24 it is overlapping in a manner of formed, offset companion As the revolution of movable orbiting scroll 10 is circled round and the centrifugal force of shaft 24 is acted on, to obtain the balance that the revolution of movable orbiting scroll 10 is circled round.

In this way, crank mechanism 44, above-mentioned crank are formed by above-mentioned crank-pin 24c, eccentric bush 36, axle sleeve 41 and counterweight 42 The rotary motion of shaft 24 is converted into the revolution circumnutation of movable orbiting scroll 10 by mechanism 44, and is transmitted.

In addition, the rotation resistance of ball-type connector formula is configured between the end plate 10a of movable orbiting scroll 10 and the openend 4a of front casing 4 Locking mechanism 46.Rotation prevent mechanism 46 can without prejudice to movable orbiting scroll 10 relative to the revolution circumnutation of static vortex disk 8 in the case of, Rotation to movable orbiting scroll 10 prevents.

In compressor 1 formed as described above, when in the driving in engine, making electromagnetic clutch in driving pulley 32 Device Operating In Persistent Current Mode, when shaft 24 rotates together with driving pulley 32, the chimeric eccentric bush 36 for having crank-pin 24c can rotate.Companion With in this, in the state of rotation is subject to rotation to prevent mechanism 46 from preventing, public affairs are applied with movable orbiting scroll 10 via axle sleeve 41 Turn circumnutation.

When movable orbiting scroll 10 revolves round the sun circumnutation relative to static vortex disk 8, from refrigerant circulating path via inhalation port 22 The refrigerant of suction can be imported into whirlpool disk unit 6, and static vortex disk 8 cooperates with movable orbiting scroll 10.Thereby, in fixed scroll body 8b Zoning and the discharge chambe 18 formed with the refrigerant containing lubricating oil between movable scroll body 10b.In discharge chambe 18, utilize Movable orbiting scroll 10 relative to static vortex disk 8 revolution circumnutation, while make center from movable scroll body 10b to fixed scroll body 8b move It is dynamic, the volume reducing of one side discharge chambe 18, so as to carry out the compression of refrigerant.Compressed refrigerant is discharged via tap 14 To discharge room 12, and refrigerant circulating path is sent to from discharge port 20.

Here, the medial area in the major diameter inner peripheral surface 4b of front casing 4 marks crank chamber 48.Crank chamber 48 is to supply crank mechanism Space in the front casing 4 of 44 positioning, it is allowed to the convolution of smoothly being revolved round the sun with the rotation of shaft 24 of counterweight 42.This Outside, in crank chamber 48, the seating plane 48a for the ring-band shape being substantially orthogonal formed with the axis with shaft 24, to be used as front casing 4 Major diameter inner peripheral surface 4b and central diameter inner peripheral surface 4c between step surface, the arc-shaped plate 42a of counterweight 42 is close and is positioned at base Face 48a.

On the other hand, in front casing 4, the medial area of lateral path inner peripheral surface 4d marks close out of central diameter inner peripheral surface 4c Seal room 50.Closed chamber 50 is the space positioned for the lip of lippacking 30, is substantially orthogonal formed with the axis with shaft 24 Ring-band shape seating plane 50a, the step surface using between the central diameter inner peripheral surface 4c as front casing 4 and path inner peripheral surface 4d, peace Bearing 26 loaded on central diameter inner peripheral surface 4c is close and is positioned at above-mentioned seating plane 50a.

Fig. 2 is a part of amplified sectional view by crank chamber 48 and closed chamber 50, and Fig. 3 is the opening from front casing 4 Hold the top view of 4a sides observation front casing 4.As shown in Figures 2 and 3, in the present embodiment, front casing 4, one it is diagonal Clipping at 24 symmetrical symmetric position of shaft on line, through there is two intercommunicating pores connecting crank chamber 48 with closed chamber 50 52.Each intercommunicating pore 52 is tilted relative to the axis of shaft 24 and linearly extended along the radial direction of shaft 24, in crank chamber 48 Seating plane 48a is opened on, and is formed at the convolution with counterweight 42 intermittently by the position of arc-shaped plate 42a coverings.

On the other hand, in closed chamber 50, each intercommunicating pore 52 is open near the seating plane 50a of central diameter inner peripheral surface 4c.Respectively 48 side of crank chamber of intercommunicating pore 52 is located approximately on the diameter line of shaft 24 with the opening of 50 side of closed chamber.In addition, The inner wall of closed chamber 50, i.e. seating plane 50a depressions are provided with guiding groove (the first guiding groove) 54, and above-mentioned guiding groove 54 is from being opened on The depression of intercommunicating pore 52 of central diameter inner peripheral surface 4c is set near the lip of lippacking 30.Guiding groove 54 is formed as having opposite In shaft 24 axis in the inclined bottom in arc-shaped ground, and from being opened on footpath of the intercommunicating pore 52 of central diameter inner peripheral surface 4c along shaft 24 To linearly extending near the lip of lippacking 30.

Here, in refrigerant with the revolution circumnutation of movable orbiting scroll 10 and from inhalation port 22 to 18 side of discharge chambe During flowing, the refrigerant containing lubricating oil is also flowed in the back side 10c sides of the end plate 10a of movable orbiting scroll 10.In addition, with refrigerant one The lubricating oil for playing inflow crank chamber 48 prevents mechanism 46, bearing 40, bearing 26 or even lippacking 30 from being lubricated rotation.

Specifically, as shown in the solid arrow in Fig. 2 and Fig. 3, circled round by counterweight 42 towards two chain-dotted line directions, so that The refrigerant of inflow crank chamber 48, which is temporarily compressed, is being formed at the arc-shaped plate 42a of counterweight 42 with close arc-shaped plate 42a's In minim gap between seating plane 48a.The refrigerant compressed in crank chamber 48 is extruded because of pressure difference from intercommunicating pore 52 To closed chamber 50 at low pressure.

In this way, circulate and drawn in guiding groove 54 from crank chamber 48 via the refrigerant of the inflow closed chamber 50 of intercommunicating pore 52 Lippacking 30 is led, at this time, lippacking 30 is ideally lubricated by the lubricating oil contained by refrigerant.On the other hand, such as In Fig. 2 and Fig. 3 shown in dotted line, the refrigerant for flowing into closed chamber 50 is back to crank chamber 48 by bearing 26, at this time, 26 quilt of bearing Lubricating oil contained by refrigerant ideally lubricates.In this way, formed with lubrication oil circulation road between crank chamber 48 and closed chamber 50 Footpath.

As described above, according to the present embodiment, it is being configured to be equipped with the outer circumferential side of whirlpool disk unit 6 as compressor 1 In the case of inhalation port 22, since the refrigerant imported from inhalation port 22 can be inhaled into vortex element 6 immediately, It can expect the raising of the compression efficiency of refrigerant.On the other hand, in the compressor 1 of said structure, in inflow front casing 4, The refrigerant flow at the position away from inhalation port 22 can be reduced, and especially all worry the profit of lippacking 30 all the time It is sliding to be deteriorated.

Even in this case, by forming intercommunicating pore 52 and guiding groove 54 in front casing 4, and crank chamber 48 with it is close Envelope forms lubrication oil circulation path between room 50, so as to guide lubricating oil on one's own initiative to lippacking 30.Thus, can be While improving the compression efficiency of compressor 1, the abrasion of lippacking 30 is greatly reduced, and then can ensure that lippacking 30 relative to small diameter section 24b remaining profit margin, so as to chronically maintain the sealing performance of compressor 1.In addition, intercommunicating pore 52 and the quantity of guiding groove 54 be not particularly limited, for example, both shaft 24 can be clipped on two diagonal as shown in Figure 4 Symmetric position at respectively form two groups of intercommunicating pores 52 and guiding groove 54, can also only form one group of 52 He of intercommunicating pore as shown in Figure 5 Guiding groove 54.

(second embodiment)

Fig. 6 is a part of amplified sectional view by the crank chamber 48 of second embodiment of the invention and closed chamber 50, and Fig. 7 is From the top view of the front casing 4 of openend 4a unilateral observations Fig. 6 of front casing 4.In addition, for identical with first embodiment Structure, uses identical title, identical symbol in the description or in attached drawing, and omits the description.

As shown in FIG. 6 and 7, present embodiment front casing 4 it is seating plane 48a, with the guiding groove of seating plane 50a 54 at the position for clipping shaft 24 on same diagonal, and depression is provided with two guiding grooves (the second guiding groove) 56.Respectively Guiding groove 56 is linearly extended up near central diameter inner peripheral surface 4c near major diameter inner peripheral surface 4b along the radial direction of shaft 24, connection Hole 52 is formed at the bottom of guiding groove 56.

In this way, in the present embodiment, due on seating plane 48a, the guiding identical with the guiding groove 54 of seating plane 50a Groove 56 is formed at the aperture position of intercommunicating pore 52, therefore, as shown in the solid arrow in Fig. 6 and Fig. 7, can efficiently will attach to The lubricating oil of seating plane 48a is guided to intercommunicating pore 52 from guiding groove 56, and more initiatively can be guided lubricating oil to lip packing Part 30.Thus, it can realize the drop by a larger margin of the abrasion of lippacking 30 while the compression efficiency of compressor 1 is improved It is low, and realize the remaining profit margin for ensuring lippacking 30, so as to longer-term maintain the sealing performance of compressor 1.

(the 3rd embodiment)

Fig. 8 is the top view from the front casing 4 of the openend 4a unilateral observation third embodiment of the invention of front casing 4.In addition, Present embodiment is illustrated as the another form of the Fig. 5 shown in first embodiment, for first embodiment phase Same structure, marks identical title, identical symbol, and omit the description in the description or in attached drawing.

As shown in figure 8, front casing 4 makes crank chamber 48 and closed chamber 50 formed with an intercommunicating pore 58, above-mentioned intercommunicating pore 58 Connection.Above-mentioned intercommunicating pore 58 axis and radial direction shown in dotted line relative to shaft 24 is tilted and linearly extended.Shaft 24 relative to the direction that the inclination of radial direction is along the convolution direction of counterweight 42.That is, the opening of 48 side of crank chamber of intercommunicating pore 58 It is positioned to tilt with the diameter line of shaft 24 with the opening of 50 side of closed chamber.

As described above, in the present embodiment, by forming the intercommunicating pore with first embodiment and second embodiment 52 intercommunicating pores 58 of different shapes, so that as shown in the solid arrow in Fig. 8, utilize the refrigerant for acting on inflow intercommunicating pore 58 With the power in the convolution direction of the counterweight 42 on lubricating oil, energy is more efficient and promptly guides lubricating oil to lippacking 30. Thus, it can realize the reduction by a larger margin of the abrasion of lippacking 30 while the compression efficiency of compressor 1 is improved, and Realizing ensures the remaining profit margin of lippacking 30, so as to longer-term maintains the sealing performance of compressor 1.

(the 4th embodiment)

Fig. 9 is that counterweight 60 is being installed on the side view that is shown in the state of shaft 24 by four embodiment of the invention.In addition, For with first embodiment to any of the 3rd embodiment identical structure, mark in the description or in attached drawing identical Title, identical symbol, and omit the description.

As shown in figure 9, the radial end face 60a1 of each arc-shaped plate 60a of the counterweight 60 of present embodiment is relative to shaft 24 Axis tilt, and formed be in conplane inclined plane 62.Above-mentioned inclined plane 62 is from the lateral major diameter axle portions of crank-pin 24c mono- 24a is tilted towards close to the direction in axle center, with the convolution of counterweight 60, will attach to each arc-shaped plate as depicted by the solid-line arrows The lubricating oil of the radial end face 60a1 of 60a is guided to intercommunicating pore 52 or intercommunicating pore 58.

In this way, in the present embodiment, since counterweight 60 has inclined plane 62, accordingly, it is capable to efficiently will attach to each circle The lubricating oil of the radial end face 60a1 of arc shape board 60a is guided to intercommunicating pore 52 or intercommunicating pore 58, and can be more initiatively by lubricating oil Guide to lippacking 30.Thus, it can realize the mill of lippacking 30 while the compression efficiency of compressor 1 is improved The reduction by a larger margin of damage, and realize the remaining profit margin for ensuring lippacking 30, so as to longer-term maintain compressor 1 Sealing performance.

In addition, it is not limited to the above embodiment, such as inclined plane 64, above-mentioned inclination can also be formed as shown in Figure 10 Face 64 only tilts the radial end face 60a1 of an arc-shaped plate 60a near big diameter section 24a.In addition, as shown in figure 11, It can also make one in each circular plate 60a towards the radially projecting of shaft 24, with from the radial end face of each circular plate 60a 60a1 forms step surface 66.In such cases, as shown in solid arrow in Figure 10 and Figure 11, the profit for being attached to counterweight 60 can be made Lubricating oil efficiently flows or drips to intercommunicating pore 52 or intercommunicating pore 58 and guides.

The present invention is not limited to the respective embodiments described above, can carry out various modifications.

For example, in the respective embodiments described above, the engine-driven screw compressor 1 for being assembled into air conditioner for motor vehicle is carried out Explanation.However, the present invention is applicable to the screw compressor of integral motor driving and uses various working fluids Different field all screw compressors in.

(symbol description)

1 screw compressor；

2 rear casings (shell)；

2b periphery walls；

4 front casings (shell)；

6 vortex elements；

8 static vortex disks；

10 movable orbiting scrolls；

22 inhalation ports；

24 shafts；

30 lippackings (sealing device)；

42nd, 60 counterweight；

44 crank mechanisms；

48 crank chambers；

50 closed chambers；

52 intercommunicating pores；

54 guiding grooves (the first guiding groove)；

56 guiding grooves (the second guiding groove)；

62nd, 64 inclined plane；

66 step surfaces.

Claims (6)

1. A kind of 1. compressor, it is characterised in that including：

   Vortex element, the vortex element is by movable orbiting scroll relative to static vortex disk revolution convolution so as to be compressed to refrigerant；

   The rotary motion of shaft is converted into the revolution circumnutation of the movable orbiting scroll, gone forward side by side by crank mechanism, the crank mechanism Row transmits；

   Shell, the shell supplies the whirlpool disk unit housing, and has on the periphery wall positioned at the outer circumferential side of the whirlpool disk unit There is the inhalation port of refrigerant；And

   Sealing device, the sealing device to being sealed between the shell and the shaft,

   The shell has：

   Crank chamber, the crank chamber are positioned for the crank mechanism；

   Closed chamber, the closed chamber are positioned for the sealing device；

   Intercommunicating pore, the intercommunicating pore make the crank chamber be connected with the closed chamber；And

   First guiding groove, first guiding groove is from the opening of the intercommunicating pore in the closed chamber up to the sealing device Near.
2. 2. screw compressor as claimed in claim 1, it is characterised in that

   The shell also has the second guiding groove, and the opening for the intercommunicating pore that second guiding groove is supplied in the crank chamber is determined Position.
3. 3. screw compressor as claimed in claim 1 or 2, it is characterised in that

   The crank mechanism includes counterweight, and the counterweight is installed on the shaft,

   The intercommunicating pore is formed at the position intermittently covered by the counterweight with the convolution of the counterweight.
4. 4. screw compressor as claimed in claim 3, it is characterised in that

   The intercommunicating pore is tilted relative to the convolution direction radially along the counterweight of the shaft.
5. 5. the screw compressor as described in claim 3 or 4, it is characterised in that

   The counterweight has inclined plane, and the inclined plane is tilted relative to the axis of the shaft.
6. 6. the screw compressor as any one of claim 3 to 5, it is characterised in that

   The counterweight has step surface, and the step surface is radially projecting towards the shaft.