CN102884324B

CN102884324B - Screw vacuum pump

Info

Publication number: CN102884324B
Application number: CN201180022605.5A
Authority: CN
Inventors: 托马斯·德赖费特; 马格努斯·亚尼茨基; 彼得·比尔克; 罗兰德·米勒
Original assignee: Oerlikon Leybold Vacuum GmbH
Current assignee: Leybold GmbH
Priority date: 2010-05-04
Filing date: 2011-05-03
Publication date: 2016-06-08
Anticipated expiration: 2031-05-03
Also published as: EP2567096A2; TWI568935B; EP2567096B1; DE102010019402A1; TW201200733A; JP5860035B2; CN102884324A; KR20130100911A; WO2011138318A3; JP2013525690A; KR101855398B1; WO2011138318A2

Abstract

Screw vacuum pump has the screw rotor (12,14) being arranged in pump chamber (10). Screw rotor (12,14) is bearing in pump case respectively through two supporting members (20), and the ratio of the distance (d) of rotor length (l) and rotor axis is more than 3.0. Additionally, screw rotor (12,14) there are variable pitch, at least 7 spiral coils and be at least the machine of 4.5 in compression ratio. Pitch after the spiral coil of half less than the pitch on the rotor outlet (24) on the pressure side of twice.

Description

Screw vacuum pump

Technical field

The present invention relates to a kind of screw vacuum pump.

Background technology

Screw vacuum pump has two screw rotors in the pump chamber consisted of pump case. Screw rotor is typically supported on both sides, and can have the pitch profile being differently composed. That rotor can have a symmetry or asymmetric castellated appearance, for instance at " Wutz ", vacuum technique handbook, 2010 the 10th edition, described in 270-277 page. This kind of rotor is generally of in machine compression ratio, i.e. the cavity volume ratio of the chamber of the suction side less than 4 and chamber on the pressure side. Under high suction pressure, higher compression ratio causes very high power consumption. This needs the driving motor (see " Wutz " ibid, 276 pages) using disproportion ground big. Additionally, the problem producing when compression improves high temperature occurs in the region on the pressure side of screw rotor. In this case, no longer possible by the heat radiation of pump case, to such an extent as to the internal cooling that heat radiation must flow through screw rotor realizes. This is expend technically, and improves manufacturing cost and the maintenance cost of screw vacuum pump.

In order to realize compression ratio in high machine, report in No.19322006 at VDI and illustrate, clearance height is changed. Described herein, by clearance height, say, that especially the distance between screw rotor and pump case is configured to so that described distance in suction side more than on the pressure side. Due to the viscosity according to pressure or the pattern of flow of molecule, it is possible to accept gap bigger in suction side. When suction pressure is high, described gap combines with the reduction of rotor speed can cause the minimizing of internal compression. This causes less compression horsepower, thus results in less heat. But, disadvantageously, the minimizing of internal compression also leads to the reduction of suction capactity.

Furthermore it is known that the rotor supporting on one side or supporting in a floating manner. What this had has the advantages that, only must be provided with a bearing. This arranges on the pressure side or is arranged on the side of actuating device. The second bearing in the suction side in the region being arranged on low pressure can be saved in this case. But, the screw rotor supported in a floating manner must have the rotor constructed shortly, because otherwise producing the danger that operationally rotor contacts with each other. The relatively small structure length of rotor causes that the quantity of spiral coil is few. Additionally, the rotor supported in a floating manner has relatively larger diameter. In this case, rotor length is typically smaller than 2.5 with the ratio of the distance of rotor axis.

Summary of the invention

It is an object of the present invention to provide the screw vacuum pump of " in machine the compression ratio " with at least 4.5, wherein achieve simple heat radiation.

According to the present invention, the solution of described purpose is achieved by a kind of screw vacuum pump, and it has: constitute the pump case of pump chamber; Two screw rotors being arranged in described pump chamber, described screw rotor is bearing in described pump case respectively through two supporting members, and the ratio of the rotor length of described screw rotor and the distance of rotor axis is more than 3.0, wherein, described screw rotor have variable pitch, at least 7 spiral coils and at least 4.5 machine in compression ratio, it is characterized in that, the described pitch in the region of the spiral coil of half is less than the pitch on the rotor outlet on the pressure side of twice.

Screw vacuum pump according to the present invention has the pump case constituting pump chamber. Pump case is provided with two screw rotors. Because being long according to the screw rotor of the present invention, referring to the screw rotor of supporting on both sides respectively, to such an extent as to each screw rotor is provided with two supporting members. Additionally, screw rotor has a relatively small diameter, to such an extent as to the ratio of the length of screw rotor and the distance of rotor axis is more than 3.0, is especially greater than 3.5, and is particularly preferably more than 4.0. Additionally, have variable pitch according to the screw rotor of the present invention, and to have be at least 7, especially at least 9 and especially preferred at least 11 spiral coils. Compression ratio according to the present invention is at least 4.5, it is preferable that at least 5. In order to avoid the overheated of rotor when the big compression ratio according to the present invention, rotor has multiple spiral coil on the pressure side, and the pitch of described spiral coil only slight changes or constant. Therefore, according to the present invention, the pitch after the spiral coil of half is less than the pitch on rotor outlet of twice. Especially, the pitch less than 2 times of the pitch after the spiral coil of half, be particularly preferably less than the pitch on rotor outlet of 1.5 times. Due to the little pitch change with the clearance height preferably correspondingly selected on the pressure side gone up at rotor according to the present invention, the longer region of rotor is compressed. This having the advantages that according to the present invention having, better heat radiation is possible. Such reason for this is that, work done during compression and thus used heat substantially occurs in the region of high pressure, and due to region that produce high pressure, that be obviously prolonged according to the present invention, housing area becomes big, for heat absorption. A preferred improvement project of the screw vacuum pump according to the present invention proposes to be respectively provided with the screw rotor of only one threaded line.

The region of the length on the pressure side owing to proposing according to the present invention, in this region, screw rotor has little pitch change such that it is able to realizes the compression ratio of at least 4.5, and can be shed by the heat in this generation, to such an extent as to avoids rotor overheated. At this, it has to be noted that, heat radiation be merely able to carry out in region on the pressure side because low pressure or in the region of fine vacuum, due to little gas density, it is impossible for being sufficiently transferred on housing by heat.

Additionally, the expansion scheme according to the present invention with the screw rotor of high self-contained volume ratio this have the advantage that, under little pressure, power consumption is little. Accordingly, for the initial pressure lower than 10mbar, it is possible to realize relative to suction capactity, lower than 12W/ (m³H) power consumption.

In particularly preferred form of implementation, heat radiation is only undertaken by pump case. Therefore, except the heat radiation undertaken by medium itself, heat radiation is preferably only undertaken by pump case. Therefore, it is not necessary to be provided with the internal rotor cooling expended technically.

Additionally, according to the present invention, the setting of the multiple spiral coils in region on the pressure side at rotor with little pitch change this have the advantage that, hence it is evident that reduce noise and produce. Such reason for this is that, longer region is compressed, and therefore pressure differential between last chamber and the region of gas outlet is less. Therefore, reducing inverted ventilation, wherein, form pressure wave when inverted ventilation, described pressure wave causes noise to be produced. Due to less inverted ventilation, when free exhaust, noise produces also to reduce 3 to 6dB (A). This major advantage having it is possible to be provided with less silencer element. Owing to reducing the probability of architectural volume of deafener such that it is able to again compensate at least in part vacuum pump due to the structure length of longer screw rotor.

It is furthermore preferred that the profile of screw rotor symmetry substantially. In this case preferred that such as trapezoidal profile, cycloid profile or evolvent profile. Preferably, clearance height, say, that the distance between screw rotor and inner walls is especially chosen as so that be compressed on the longer region on the outlet side of rotor and extend. It is particularly preferred here that, under the cold conditions of turbomolecular pump, the ratio of cold clearance height/axial line distance > 2/1000. Moreover it is preferred that under operation, say, that when reaching running temperature, produce the ratio of cold clearance height/axial line distance > 12/1000. According to the present invention, clearance height is preferably chosen as so that when final pressure runs, and only just average cavity chamber pressure lower than 100mbar after about the 20% of rotor length, measures from entrance side.

In preferred form of implementation, there is according to the screw vacuum pump of the present invention rated speed of rotating speed more than 5000 turns per minute. Additionally, in order to avoid overcompression, it is possible in the region on the pressure side of screw rotor, it is provided with excess pressure valve. Replace or except excess pressure valve is set, it is possible to be provided with rotating speed control. By rotating speed is correspondingly reduced, same it can be avoided that overcompression. By two measures, it is possible to be effectively reduced the power consumption under high suction pressure, and thus reduce machine inner motor power.

Accompanying drawing explanation

Below, the present invention is elaborated by means of a preferred form of implementation with reference to accompanying drawing. Shown in accompanying drawing:

Fig. 1 illustrates the diagrammatic top view of two screw rotors constructed according to the invention, and

The signal chart of Fig. 2 and pressure distribution curve illustrates and schematic diagram compared with the screw rotor of the present invention, according to the screw rotor of prior art explicitly.

Detailed description of the invention

Two screw rotors that figure 1 illustrates are arranged in unshowned pump case. Constitute pump chamber 10 by pump case, described pump chamber is provided with two screw rotors 12,14. Two screw rotors have the shaft shoulder 16,18 on both sides, and the described shaft shoulder is rotatably supported in pump case respectively through supporting member 20. In order to drive two screw rotors 12,14, generally by the shaft shoulder 18 or as an alternative by the shaft shoulder 16 directly or by actuating device with drive motor be connected. Second screw rotor, so that two screw rotors 12,14 are synchronized with each other and is rotated by identical drive motor in a reverse direction by corresponding teeth portion (not shown). Pass through screw rotor, it is achieved the suction of the medium to be conveyed in suction side (arrow 22), and realize the discharge of the medium on (arrow 24) on the pressure side.

The pitch of screw rotor illustrates by tilting the line 26 extended. It can be seen from figure 1 that pitch changes on the length l of rotor. In region 28 on the pressure side, pitch is significantly less than in the region 30 of suction side. At this, according to the present invention, the pitch in region 28 on the pressure side is configured to so that the twice of the pitch that the pitch in region 31 in the spiral coil of half is up on rotor outlet 24. This causes, constructs long region 28 on the pressure side by only slightly changing pitch. In region 28 on the pressure side, it is achieved the compression of most pressure differential between the inlet. Therefore, most work done during compression is also conducted in region 28. This causes, produces heat to be discharged substantially in this region. At this, according to the present invention, the housing of the screw rotor 12,14 by being enclosed in region on the pressure side realizes the discharge of heat.

According to the present invention, refer to the screw rotor 12,14 of long structure. Therefore, according to the present invention, the ratio of the length l of screw rotor 12, the 14 and distance d of rotor axis is more than 3.0.

In fig. 2, screw rotor 12 according to the present invention shown in upper area, described screw rotor is corresponding to screw rotor 12,14 in FIG. In its lower section, it is shown that the screw rotor 32 according to prior art. Screw rotor 32 is shorter, and has small number of spiral coil in region on the pressure side, wherein a slight variations pitch. In the rotor 32 according to prior art, obtain pressure distribution curve, as schematically illustrated by line 34. Therefrom visible, the region 36 on the pressure side of screw rotor 32 realizes violent pressure and rises.

Based on the expansion scheme according to the present invention of rotor 12, region 28 on the pressure side is considerably longer. Additionally, correspondingly select clearance height (cold clearance height/axial line distance > 2/1000 and temperature gap height/axial line distance > 12/1000). Therefore, obtaining rising corresponding to the pressure of line 38 in the graph, described pressure rises and is flatly distributed.

Claims

1. screw vacuum pump, has:

Constitute the pump case of pump chamber;

Two screw rotors being arranged in described pump chamber, described screw rotor is bearing in described pump case respectively through two supporting members, and the ratio of the rotor length of described screw rotor and the distance of rotor axis is more than 3.0,

Wherein, described screw rotor have variable pitch, at least 7 spiral coils and at least 4.5 machine in compression ratio,

It is characterized in that, the described pitch in the region of the spiral coil of half is less than the pitch on the rotor outlet on the pressure side of twice.

2. screw vacuum pump according to claim 1, it is characterised in that each screw rotor has only one threaded line.

3. screw vacuum pump according to claim 1, it is characterised in that the profile substantial symmetry or asymmetric of described screw rotor.

4. screw vacuum pump according to claim 1, it is characterised in that only effectively cool down described pump case, to dispel the heat.

5. screw vacuum pump according to claim 1, it is characterised in that the described ratio of rotor length and the distance of rotor axis is more than 3.5.

6. screw vacuum pump according to claim 1, it is characterised in that the described ratio of rotor length and the distance of rotor axis is more than 4.

7. screw vacuum pump according to claim 1, it is characterised in that each screw vacuum pump is provided with at least 9 spiral coils.

8. screw vacuum pump according to claim 1, it is characterised in that each screw vacuum pump is provided with at least 11 spiral coils.

9. screw vacuum pump according to claim 1, it is characterised in that described compression ratio is at least 5.

10. screw vacuum pump according to claim 1, it is characterised in that described compression ratio is at least 6.

11. screw vacuum pump according to claim 1, it is characterised in that clearance height is chosen as so that obtain the final pressure of at least 5Pa of vacuum pump, wherein, described clearance height is the distance between screw rotor and inner walls.

12. screw vacuum pump according to claim 1, it is characterised in that rated speed is more than 5000 turns per minute.

13. screw vacuum pump according to claim 1, it is provided with one or more excess pressure valve and/or rotor speed can be controlled by rotating speed, to avoid the overcompression in region on the pressure side.