WO2008151717A2

WO2008151717A2 - Permanently excited rotor for machine tools

Info

Publication number: WO2008151717A2
Application number: PCT/EP2008/004213
Authority: WO
Inventors: Jürgen Gröschel; Gerhard Huth; Sven Urschel
Original assignee: Ksb Aktiengesellschaft
Priority date: 2007-06-15
Filing date: 2008-05-28
Publication date: 2008-12-18
Also published as: WO2008151717A3; EP2156534A2; DE102007028356A1

Abstract

The invention relates to a machine tool (1) that is directly or indirectly connected to a motor (2), force being transmitted from the motor (2) to the machine tool (1) by means of at least one rotor (4), especially a rotor for driving turbo engines, which is driven by magnetic or electromagnetic fields. The rotor (4) is equipped with permanent magnets (3) and is designed to be operated in a chemically aggressive environment. The rotor (4) and a shaft (6, 6.1, 6.2, 6.3) that is connected thereto are monolithically made of a high-quality stainless steel from the group comprising ferritic-austenitic duplex steels, and permanent magnets (3) which are disposed on the rotor are protected against chemical attacks.

Description

K S B A k t i e n g e s e n c e s a t e

Permanently excited rotor for working machines

description

The invention relates to a working machine which is directly or indirectly connected to a motor, wherein a power transmission from the engine to the working machine with at least one driven by magnetic or electromagnetic fields rotor, in particular a rotor for driving turbomachines, wherein the rotor with over the Circumference distributed permanent magnets equipped and designed for operation in a chemically aggressive environment.

Such machines are often used in the chemical industry in the form of a flow machine, often a conveyor in the form of a pump; also with mixers and stirrers. There are equipped with permanent magnets rotors in magnetic clutches, hysteresis clutches or canned motors used. For a hermetic sealing of a working machine which is exposed to aggressive, dangerous or valuable liquids, such rotors are arranged within a containment shell or split tube filled with a conveying medium. This component, referred to below as a gap element, is used for the hermetic sealing between two spaces, firstly for the environment and secondly for a space filled with hazardous fluid and containing the rotor. The stress criteria result from the corrosive, erosive, abrasive, cavitating and tribological factors and / or stresses.

On such a rotor equipped with permanent magnets, a second element, usually an outer element, transmits drive energy. If the rotor is part of an electronically commutated motor, the second element would be a stator with a rotating field winding. Their rotating magnetic fields acting on the rotor equipped with permanent magnets such a drive sits a much higher system efficiency. As a result, the life cycle costs of a machine driven by such a rotor fall more favorably for a plant operator. And if the rotor is designed as part of a magnet or hysteresis clutch, a rotating outer rotor with its permanent magnets transmits its rotational movement to the rotor connected to the working machine. The magnetic forces cause the entrainment effect. In a hermetically sealed coupling, a sealing gap element is arranged between the rotor and the outer rotor.

Such rotors with circumferentially arranged permanent magnets consist of a rotor active part for the magnetic return of the permanent magnets and are connected for torque transmission to a shaft. The rotor active part is encased in a corrosion-resistant metal shell to protect the surfaces of the permanent magnets from attack by the liquid and to absorb centrifugal forces occurring during operation. Such a jacket additionally reduces the hydraulic resistance of the rotor rotating within a gap element in the liquid. The torque of such a rotor is transmitted with the shaft to an element of a work machine, usually an impeller of a pump. The shaft is made of a material resistant to the respective liquid. Due to its function, the rotor consists of a magnetically highly permeable, corrosion-resistant material. Therefore, in addition to the sheath, the end faces of the rotor active part and the transitions to the corrosion-resistant shaft must be sealed by additional means and protected against corrosion. This is done by additional mudguards or potting.

Another solution is shown in EP 1 719 916 A1 for pump units in the form of heating circulation pumps whose electric drive motors are designed as permanent magnet motors. The document criticizes the known permanent magnet motors in that they have a rotor equipped with permanent magnets which is set in rotation by suitable energization of stator coils. These known rotors are rotatably mounted with a rotor shaft in plain bearings in the stator housing or on the stator, wherein the actual rotor with the permanent magnets is fixed on the rotor shaft. The individual permanent magnets are arranged in recesses of a laminated core, in whose central opening the rotor shaft is inserted. As an improvement, it should be possible to surround the entire rotor shaft with a magnetizable material as a rotor and form individual magnetic poles by a targeted magnetization. In order to reduce such a production effort and to save costs, in EP 1 719 916 A1, the rotor is shaftless and completely formed of a magnetizable, ferritic material at least in a partial region of its axial extent and the magnetic poles of the rotor are produced by magnetization of the ferritic material , Such a solution of a rotor made of compressed or sintered material can only be used in the case of the heating circulating pumps designed for a simple conveying medium and having small powers. Such a solution can not be used because of the ferritic material in the chemical field for reasons of lack of corrosion resistance. The stainless steels necessarily used there are usually non-magnetizable austenites.

The object of the invention is to develop a structure for a liquid-flushed rotor that can be used in the chemical sector, whereby a high resistance to corrosive and / or aggressive fluid is given and a high degree of efficiency is ensured for a drive equipped with such a rotor ,

The solution to this problem is that a rotor active part and associated shaft made of a corrosion-resistant stainless steel from the group of ferro-austenitic duplex steels with 40-60% ferrite and that protected in the outer periphery of such a rotor active part integrated permanent magnets from chemical attack are. The formation of rotor active part and shaft made of a corrosion-resistant stainless steel from the group of ferritic-austenitic duplex steels eliminates the previously necessary protective measures in the area between the rotor active part and the transition to the shaft. In the rotor active part, the shaft or shaft parts can be arranged in a manner known per se as separate parts. Similarly, the rotor as a one-piece rotor with integrally formed Shaped wave. For this purpose, the use of a cast or forged preform and its machining has proven to be advantageous. The use of a stainless steel from the group of ferritic-austenitic duplex steels for a rotor with an integrally formed shaft or shaft parts arranged in the rotor active part necessitates a considerable material reduction throughout the entire production process.

The alleged disadvantage of a more difficult processing of such duplex steels is offset by the serious advantage of a single highly corrosion-resistant material. As a result, compared to the previous use of different materials, a component standardization, Matehalminimierung and faster production is achieved. The previously required separate protective measures of individual laminations eliminated completely. And unlike a rotor body made of a magnetically highly permeable material, the rotor active part made of a duplex steel has a significantly lower torque ripple, thereby improving the rotational performance.

Embodiments provide that the rotor active part is composed of a plurality of rotor modules, wherein an axial length of a rotor module is defined by the dimensions of permanent magnets to be arranged therein. The rotor modules are positively secured and / or by means of a shaft or by means of shaft parts to each other. As a result, an adaptation to the respectively required rotor length is possible in a simple manner to obtain the necessary for the particular application, permanent magnetic energy. Also long rotor lengths can be easily realized. Each rotor module consists of a solid stainless steel block from the group of duplex steels. A use of modules in the form of packetized laminations, as known from EP 1 657 800 A1, is eliminated. Since no secure seal between such eggπzeinen, staked sheet metal sections is possible, as a result, no protection of the permanent magnets against the corrosive media is possible. A measure according to which the permanent magnets are arranged below the rotor surface protects the permanent magnets against attack by corrosive or aggressive chemical transport media. The rotor surface may in this case be formed by a thin-walled sleeve of a corrosion-resistant stainless steel from the group of ferritic-austenitic duplex steels. Such a sleeve is sealingly attached to a rotor active body or to a rotor active body composed of rotor modules. This can be done by laser welding or other known means.

In the absence of an additional sleeve for forming the cylindrical rotor surface, the permanent magnets can be arranged directly within the surface of the rotor active body. In this case, the permanent magnets are arranged just below the outer surface or the cylindrical outer peripheral surface within the rotor active body, in order to obtain protection against corrosion attacks on the endangered permanent magnets by the solid rotor surface. Such insertion of the permanent magnets in the rotor, the rotor active body or in a plurality of solid rotor modules provides pockets which extend from a rotor end side in the axial direction close to the outer peripheral surface and receive the permanent magnets. Depending on the type and construction of such pockets, only the receiving openings of the pockets must be sealed after mounting on one or both rotor end faces. For this purpose, arranged on at least one rotor end side receiving openings of the magnetic pockets are closed by separate means. Although DE 10 2005 041 352 A1 discloses a rotor in which permanent magnets are arranged in the tabs of a rotor core. As a result of the laminated structure, the liquid can pass through the gaps between the individual sheets to the permanent magnets and damage them.

When using several rotor modules, the permanent magnets are sealed on each rotor module. A rotor module made of duplex steel with an optimized axial length would be almost fully automatic on a CNC machine tool as a series product. Embodiments of the invention provide that the arranged in pockets of the rotor active part permanent magnets are cup-shaped, rod-shaped, cuboidal or similar.

It is also possible to equip a rotor with or without flow barriers between the arranged in the outer circumference of permanent magnets. A minor increase in production costs for the river barriers is offset by the longer-term advantage of a corresponding reduction in the flux leakage. This ensures long-term energy savings for a machine equipped with it.

According to the invention, it has been recognized that the use of a high-grade steel from the group of ferritic-austenitic duplex steels for such permanently excited rotors means virtually no energy-related disadvantage in terms of efficiency. Although corrosion-resistant materials in the form of duplex steels have a lower magnetic permeability, which increases the magnetic voltage drop in a rotor body. As a result, the permanent-magnet air gap induction and the so-called Polradspannung and thus the air gap torque drop only slightly. However, since with decreasing air gap induction at the same time the previous iron losses in a stator surrounding the rotor of a drive motor and also in the rotor go back, the efficiency of such a drive motor with a suitable design of the material and wall thickness changes only insignificantly compared to the previous versions magnetically highly permeable but not corrosion-resistant material.

The use of the rotor as part of a coupling driven by magnetic forces behaves analogously. For magnetic or Hysteresekuppiungen the inner coupling part is also a permanent magnet excited rotor, which is in principle identical in construction as the permanent-magnet pump motor. Thus, a part coupling is possible in principle. Due to the modular design of the rotor, the advantage of t torque distribution for a product series of different drive powers.

Embodiments of the invention provide that the permanent magnets are shell-shaped, rod-shaped, cuboidal or similar.

It is also possible to equip a rotor with or without flow barriers between the arranged in the outer circumference of the permanent magnet, thus preventing this magnetic short circuit.

The ferritic-austenitic duplex stainless steel with 40-60% ferrite is a material known, for example, from the material numbers: 1.4362, 1.4410, 1.4460, 1.4462, 1.4464, 1.4469, 1.4470,

1.4517, 1.4593

Embodiments of the invention are illustrated in the drawings and will be described in more detail below. It show the

1 and 2 show cross sections through directly driven machines,

Fig. 3 shows a working machine with indirect motor drive

Fig. 4 to 6 show different air locks

Fig. 1 shows a cross section through a working machine 1 in the form of a directly driven centrifugal pump. This machine is designed to promote chemically aggressive fluids and designed here with a motor 2 in the form of a canned motor, wherein the permanent magnet 3 provided with rotor 4 is exposed directly to the chemical fluids. The one-piece rotor 4 here consists of a rotor active part 5 and an associated directly molded shaft 6, these parts being made of a corrosion-resistant ferritic-austenitic duplex steel. It has proved to be advantageous to produce such a rotor 4 from a cast or forged preform and abhebender processing to produce the dimensions of the rotor active part 5 and the molded shaft 6 and thus the rotor outer contour.

The rotor active part 5 has distributed over the circumference of several pockets 7, in each of which one or more permanent magnets 3 are arranged. The permanent magnets 3 are protected within the pockets 7 against attacks by an aggressive fluid. The pockets 7 are incorporated below the surface from the outer periphery in the rotor active part 5.

Fig. 2 shows another embodiment of the rotor 4 of Fig. 1, wherein within the one-piece rotor active part 5, two shaft parts 6.1 and 6.2 are attached to the storage thereof. All parts are made of corrosion-resistant ferritic-austenitic duplex steel. As a further modification to FIG. 1, another embodiment of the pockets 7 for receiving the permanent magnets 3 is shown. For reasons of better visibility, the permanent magnets 3 were not drawn in the upper pocket 7 in the section. A separate, consisting of a same corrosion-resistant, ferritic-austenitic duplex steel, 40 - 60% ferrite having sleeve 8 forms the surface of the rotor active part 5. The tight connection of such a sleeve 8 with the rotor active part 5 is carried out by simple circulating welding, soldering -, adhesive, shrink or other sealing compounds. The pockets 7 for receiving permanent magnets 3 are formed by an inner diameter of the sleeve 8 and by grooves which are incorporated into the surface of the Rotoaktivteiles 5.

3 shows a working machine, which is indirectly driven by a motor 3 in the form of a conventional standard motor with the interposition of a magnetic coupling 9 equipped with permanent magnets 3. The inner rotor 10 of the magnetic coupling 9 is a further variant of the rotor structure. The here multi-part rotor active part 5 is composed of two or more rotor modules 5.1, 5.2, which are each made of a solid ferritic-austenitic duplex steel. This composite rotor active part 5 is torque-transmitting connected to a shaft portion 6.3 of the same material. With this shaft part 6 .3 is the rotor active part 5 rotatably supported within the magnetic coupling 9 or a correspondingly formed hysteresis coupling and at the same time connected to the work machine 1 in a force-transmitting manner. The inner rotor 10 may also be constructed analogously to the rotor of FIG. 1 or 2.

The working machine can here - as shown - be a pump 1 or a stirrer, a mixer or other device. The rotor modules 5.1, 5.2 are positively connected to each other and the joints sealed form-fitting and cohesive. The rotor modules 5.1, 5.2 of the multi-part rotor active part 5 have below the rotor surface in the axial direction extending pockets 7, in which permanent magnets 3 are stored firmly and liquid-tight. The storage of such permanent magnets 3 takes place by known means. The sealing of the pockets 7 is carried out by separate means, thus precluding access of the chemical liquid to the permanent magnet 3. The connection between the sealing center and the rotor active part 5 or the rotor modules 5.1, 5.2 must in this case be resistant to the respective chemical aggressive liquids. Welded joints have proven to be very beneficial.

If such pockets 7 are designed in the manner of blind bores, which can take place by simple machining, this reduces the use of the sealing means and also the expense of arranging them.

In FIGS. 4 to 6, three cross sections through rotors are shown as cutouts, in which the pockets 7 with permanent magnets 3 inserted therein and the use of flow locks 11 are shown. In FIG. 4, the flow barriers 11 are shown as closed air barriers in the form of slots. The river barriers are here below the rotor surface. Another embodiment is shown in FIG. 5, in which the flow barriers 11 are installed as slotted open air barriers in the surface of the rotor active part 5. And Fig. 6 shows a form of round, drilled air locks 11. Here is another form of permanent magnet 7 application. These are cuboid and arranged side by side.

Claims

claims

1. work machine (1) which is directly or indirectly connected to a motor (2), wherein a power transmission from the motor (2) to the working machine (1) with at least one driven by magnetic or electromagnetic fields rotor (4), in particular a rotor for driving turbomachines, wherein the rotor (4) is provided with circumferentially distributed permanent magnets (3) and adapted for operation in a chemically aggressive environment, characterized in that a rotor active part (5) and an associated Shaft (6, 6.1, 6.2, 6.3) is made of a corrosion-resistant stainless steel from the group of ferritic-austenic duplex steels with 40-60% ferrite and that in the outer periphery of such a rotor active part (5) integrated permanent magnets (3) are protected from chemical attack ,

2. Work machine according to claim 1, characterized in that rotor active part (5) and shaft (6) as a one-piece rotor (4) is formed with integrally formed shaft (6).

3. Work machine according to claim 2, characterized in that the one-piece rotor (5) with integrally formed shaft (6) is made of a cast or forged preform and machined.

4. Work machine according to claim 1, characterized in that a shaft (6.3) or two shaft parts (6.1, 6.2) in the rotor active part (5) is attached or are.

5. Work machine according to one of claims 1 to 4, characterized in that the rotor active part (5) from a plurality of rotor modules (5.1, 5.2) is put together.

6. A working machine according to claim 5, characterized in that an axial length of a rotor module (5.1, 5.2) is defined by the dimensions of permanent magnets to be arranged (3).

7. Work machine according to claim 5 or 6, characterized in that the rotor modules (5.1, 5.2) are positively secured and / or by means of a shaft (6.3) or by means of shaft parts (6.1, 6.2) to each other.

8. Machine according to one or more of claims 1 to 7, characterized in that the permanent magnets (3) on the rotor active part (5) and below a sealingly mounted sleeve (8) are arranged.

9. Work machine according to one or more of claims 1 to 7, characterized in that the permanent magnets (3) in the rotor active part (5, 5.1, 5.2) are arranged below the rotor surface.

10. Work machine according to claim 9, characterized in that in the rotor, in the rotor active part (5) or in the rotor modules (5.1, 5.2) the permanent magnets (3) receiving, in the axial direction below the outer peripheral surface extending pockets (7) are arranged.

11. Work machine according to claim 9 or 10, characterized in that arranged on at least one rotor end side receiving openings of the pockets (7) are closed by separate means.

12. Work machine according to one of claims 1 to 11, characterized in that the permanent magnets (3) for a high packing density shell-shaped, rod-shaped, cuboid or similar are formed.

13. Work machine according to one of claims 1 to 12, characterized in that the rotor (4) with or without flow locks (11) between the in the Au ßenumfang arranged permanent magnet (3) is provided.

14. Work machine according to one of claims 1 to 13, characterized in that the flow locks (11) are designed as open or closed air locks in the form of slots, grooves, holes or the like.

15. Work machine according to one of claims 1 to 14, characterized in that the rotor (4) is part of a magnetic or hysteresis (9).

16. Work machine according to one of claims 1 to 15, characterized in that the rotor (4) is part of an electronically commutated motor (3).

17. Work machine according to one of claims 1 to 16, characterized in that the rotor (4) is part of a canned motor.