This application is a National Stage filing under 35 U.S.C. § 371 of PCT Application No. PCT/EP2007/007151 filed Aug. 13, 2007, which claims priority from German Application No. DE 10 2006 039 958.7 filed Aug. 25, 2006.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to rotating slide vacuum pumps and compressors as claimed in the precharacterizing clause of claim 1.
2. Description of Related Art
The invention may relate both to rotating slide vacuum pumps and compressors which are lubricated by oil circulation and to those which run dry. These pumps and compressors are normally designed to be horizontal, with the slides, which can move in the rotor, in the case of dry-running rotating slide vacuum pumps and compressors normally being composed of graphite or graphite composite materials while, in the case of rotating slide vacuum pumps and compressors which are lubricated by oil circulation, the slides may also be composed of plastic or plastic composite materials.
Rotating slide vacuum pumps and compressors which are lubricated by oil circulation and which are of block design, that is to say with a rotor which is mounted on flying bearings, are normally operated with single-phase alternating-current motors or three-phase asynchronous motors. Pumps and compressors such as these have been successfully used for decades and are subject to severe competition in the widely differing markets.
Single-shaft rotating slide vacuum pumps and compressors which are lubricated by oil circulation are of block design only for low feed rates, that is to say from about 2 m3/h to a maximum of 100 m3/h. Above these feed rates, the surface area of the pumps and compressors is no longer adequate for thermal emission of the compression heat. Larger vacuum pumps and compressors are therefore designed primarily in a conventional manner with a coupling between the drive motor and the pump or compressor stage.
Prior art throughout the world is the use of alternating-current or three-phase drives which, because of the small gaps that are required between the rotor and the cylindrical housing which is permanently fitted on the drive-end bearing plate of the motor, requires comparatively complex fine tuning of the motor bearing. The drive motors, particularly in the case of high-quality vacuum pumps and compressors, are therefore subject not only to the described fine tuning but, furthermore, they must comply with the required accuracies with the quality remaining unchanged. This results in high costs and a restricted provider market for motors such as these.
Furthermore, particularly in the power range from 80 W to 2 kW that is used here, the relatively low efficiency of alternating-current drives and of three-phase drives not only results in a noticeably larger physical volume but, in addition, the feasible physical space cannot be optimally utilized because of the need for an elongated physical shape.
The described rotating slide vacuum pumps and compressors which are lubricated by oil circulation and are of block design can in principle be subdivided into two further variants, specifically,
1) rotating slide vacuum pumps and compressors which are lubricated by oil circulation and with an oil mist separator arranged at the side of the pump/compressor stage and motor. Owing to the larger external surface area, this embodiment can be used for all physical sizes, that is to say from about 2 m3/h up to a maximum of 100 m3/h. Furthermore, the oil mist separator can use all its external surfaces, except for the inner area of the gas inlet flange to the pump/compressor stage, for heat emission to the outside, and
2) rotating slide vacuum pumps and compressors which are lubricated by oil circulation and have an oil mist separator which is arranged axially with respect to the pump/compressor stage. In the case of this design, one of the axial housing covers is the drive-end motor plate itself, while the other axial housing cover is connected directly to the oil mist separator, as a result of which the drive motor, the pump/compressor stage and the oil mist separator are arranged directly adjacent to one another axially. However, this means that one of the major outer surfaces is not available to the oil mist separator and/or to the pump/compressor stage for heat emission. For this reason, and because this embodiment also has an excessive ratio of length (at its axial extent) to width of the base area, for many applications, machines such as these are produced primarily only in sizes from about 2 m3/h up to a maximum of 12 m3/h.
In the case of small rotating slide vacuum pumps and compressors which are lubricated by oil circulation, one problem that frequently occurs even during production is that, as a consequence of the flying bearings of the rotor, the gaps (of between 0.02 and 0.04 mm) which are narrow and the relatively high radial forces on the rotor during test running, noise is produced which may also be caused, inter alia, by touching between the stationary housing and the rotor, and this noise is unacceptable for the user.
The invention is therefore based on the object of designing rotating slide vacuum pumps and compressors of this generic type in order to overcome the described disadvantages, such that the overall physical size of the machine is minimized, the process reliability during production is increased and, at the same time, the assembly of the machine is lastingly simplified.
SUMMARY OF THE INVENTION
The features of the invention which is being created in order to solve this problem result from claim 1. Advantageous refinements are described in the further claims.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a rotating slide vacuum pump lubricated by oil circulation and having a block design, with a disk-rotor synchronous motor, which is mounted on flying bearings.
The present invention is directed to, in a first aspect, a rotating slide vacuum pump or compressor including a rotor, which can rotate in a housing and is driven by a drive shaft, and slides which can be moved outward in the circumferential direction herein in slots in the rotor, which separate individual feed chambers of a working area, which is provided with an induction opening and an outlet opening, from one another and, driven by centrifugal force, each occupy a maximum outer position on the housing inner wall, comprising a brushless disk-rotor synchronous motor which is fitted in the axial direction on the rotor shaft, wherein thermal isolation is incorporated in the form of a housing constriction between the pump/compressor stage and the disk-rotor synchronous motor or is provided by the housing shape itself.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention will be explained in more detail in the following text with reference to the drawing, in which:
FIG. 1 shows a rotating slide vacuum pump which is designed according to the invention, is lubricated by oil circulation and has a block design, with a disk-rotor synchronous motor, which is mounted on flying bearings, schematically in the form of a longitudinal section, and
FIG. 2 shows a cross section along the line II-II in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
In describing the preferred embodiment of the present invention, reference will be made herein to FIGS. 1-2 of the drawings in which like numerals refer to like features of the invention.
The invention covers rotating slide vacuum pumps and compressors of block design which are mounted on flying bearings, run dry or, preferably, are lubricated by oil circulation, with an oil mist separator which is fitted parallel, that is to say at the side or axially, with respect to the common motor and pump/compressor shaft.
According to the invention, the bearing is moved from the motor to the pump/compressor stage, that is to say the motor itself is mounted either by a plain bearing or by needle bearings directly in the housing covers of the pump/compressor stage, with a disk-rotor synchronous motor, which is mounted on flying bearings, and has a brushless rotor, being used as the drive. The arrangement with two stator disks, in each case one on one of the end faces of the disk rotor which is fitted with permanent magnets compensate virtually completely for the axial forces, thus rendering support by an axial bearing superfluous.
This surprisingly simple arrangement according to the invention not only significantly minimizes the overall physical size of the pump or of the compressor and achieves the required accuracy for rotor guidance, but also achieves an efficiency improvement of the motor from about 75 to 80% to 85 to 95%. This means that there is no need for direct cooling of the motor by a motor fan.
Finally, the arrangement according to the invention results in a simplification of the logistic handling of the vacuum pumps and compressors, to be precise in that as a result of the use of simple electronic closed-loop control and so-called multi-voltage power supply units, the complexity, that is to say the range of variants of motors for each physical size, is reduced from more than 20 variants in the past down to one variant.
The invention is thus based on the idea of fitting a brushless disk-rotor synchronous motor in the axial direction on the rotor shaft. In one refinement of the invention, this may either have a stator which is fitted on both sides with respect to the disk rotor, for the purpose of axial force compensation, or else may be provided with only one stator which is fitted on one side with respect to the disk rotor, and in which the axial forces which occur are then absorbed by an axial bearing.
Particular advantages are achieved when, according to the invention, thermal isolation is incorporated in the form of a housing constriction between the pump/compressor stage and the disk-rotor synchronous motor or is provided by the housing shape itself.
It is within the scope of the invention that a Hall sensor is provided for position identification for closed-loop control.
In a development of the invention, it is possible to provide that an oil mist separator is arranged around the housing of the pump/compressor stage so as to achieve a minimal physical space overall, with a square base area.
Finally, according to the invention, it is possible to provide a fan to be arranged opposite the disk-rotor synchronous motor on the rotor shaft, by means of which the compression heat is dissipated from the machine.
Alternatively or additionally, a fan impeller is fitted on the rotor shaft, on the side opposite the disk-rotor synchronous motor, with respect to the pump/compressor stage, and is used for cooling the pump/compressor stage with cooling air.
As can be seen from the drawing, in the case of the illustrated rotating slide vacuum pump which is lubricated by oil circulation, the feed medium is inducted via an induction opening 1 tangentially into the working area 9 of a housing 2, and is fed axially through one or more holes 3 to an oil mist separator 4.
This oil mist separator 4 is flange-connected directly to the pump/compressor stage via a housing intermediate cover 5. In the oil mist separator 4, the feed medium is passed to an air oil-extraction element 15 and then to the gas outlet 16.
A rotor 6, which is arranged in the housing 2, is provided with a plurality of slide slots 7 which, as can be seen in FIG. 2, are incorporated radially or else off-axis, externally in the rotor 6. Slides 8 are arranged such that they can be moved in the slide slots 7. These slides 8 separate individual feed chambers of the working area 9 from one another.
The housing 2 is bounded by the intermediate cover 5 on its left-hand side as shown in FIG. 1, and is bounded by a further cover 10 on its right-hand side as shown in FIG. 1. The housing of a brushless disk-rotor motor is fitted to the outside of the housing cover 10 and has a brushless disk rotor 11, which is fitted with permanent magnets, as well as two stator disks 12 in which multipole electrical windings are located. The position sensor which is required for the motor regulator for driving the motor windings is not illustrated in any more detail in the drawing.
The single bearing for the entire rotor 6 is provided by needle bearings 13 in the illustrated example embodiment. Instead of this, it is, of course, also possible to use plain bearings instead of the needle bearings 13.
The motor area is sealed by a conventional radial shaft sealing ring 14.
With regard to features of the invention which are not explained in any more detail above, reference is furthermore expressly made to the drawing and to the claims.