DE202013012760U1 - Rotor arrangement with permanent magnets - Google Patents

Abstract

- wobei ØY ein externer Durchmesser der Mehrzahl von Permanentmagneten ist,
- ØX ein interner Durchmesser des zylindrischen Magnetgehäuses (21; 21a, 21b, 21c) ist und
- IF1 eine erste Presspassung zwischen einem externen Durchmesser der zylindrischen Welle (1) und dem internen Durchmesser des zylindrischen Magnetgehäuses (21; 21a, 21b, 21c) ist.

Permanent magnet rotor assembly having a longitudinal axis of rotation X '-X, first and second ends (11, 12) and at least two poles comprising
a cylindrical shaft (1) having an outer surface extending in the direction of the longitudinal axis X'-X,
a plurality of permanent magnets (22) forming portions of the ring segments and extending in the direction of the longitudinal axis XX ', and an outer cylindrical retaining sleeve (23, 23') surrounding the plurality of permanent magnets (22), characterized
in that it further comprises a cylindrical magnet housing (21; 21a, 21b, 21c) mounted on the cylindrical shaft (1) for supporting the plurality of permanent magnets (22),
wherein the cylindrical magnet housing (21; 21a, 21b, 21c) is formed of a magnetic material, and thereby
in that the cylindrical holding sleeve (23; 23 ') is biased by a resulting interference fit IF2 defined by the following formula: $$IF2=-\varnothing Y+\sqrt{{\left(\varnothing X+IF1\right)}^2+\left(\varnothing Y^2-\varnothing X^2\right)}$$

where ØY is an external diameter of the plurality of permanent magnets,
- ØX is an internal diameter of the cylindrical magnet housing (21; 21a, 21b, 21c) and
IF1 is a first interference fit between an external diameter of the cylindrical shaft (1) and the internal diameter of the cylindrical magnet housing (21; 21a, 21b, 21c).

Description

FIELD OF THE INVENTION

The present invention relates to a rotor assembly with permanent magnets.

BACKGROUND OF THE INVENTION

Permanent magnet rotor assemblies for high speed permanent magnet motors and generators are among others in the documents US 5563463 . US 7872553 B2 . US 2005/0093391 A1 . US 2005/0099079 A1 and US 2009/0261678 A1 disclosed.

In high-speed rotors with permanent magnets, it is necessary to keep the magnets firmly bonded to the shaft in order to transmit the torque coming from the motor via the magnets. At high speed, the centrifugal force becomes too high for ordinary pressure-sensitive adhesives.

To solve the above problem, it has been proposed to use a sleeve or thin-walled retaining sheath stretched around the core and magnets to hold the magnets in place.

In principle, to keep the magnets connected to the rotor via a sleeve, a preload equivalent to the centrifugal force must be exerted, with the limits imposed by the mechanical resistance of the sleeve and the manner in which the preload is exerted is, are given.

A first technical problem resides in the fact that in high-speed engines the required oversize is much higher than the clearance that could be achieved by thermal expansion of the parts for high or low temperature sliding fit without damaging the parts being assembled should risk.

A second technical problem resides in the fact that a thin sleeve could be destroyed or permanently deformed due to a very high axial pressure exerted on the sleeve when this sleeve is inserted by displacement during press-fitting.

DISCLOSURE OF THE INVENTION

The invention has for its object to provide an improved permanent magnet rotor assembly in which in particular the abovementioned technical problems are mitigated or eliminated. In particular, a bias to spend more precise on a sleeve. The permanent magnet rotor assembly should be simple and inexpensive to manufacture.

The object is achieved by a permanent magnet rotor assembly having the features of claim 1 and claim 8. Advantageous embodiments and further developments are the subject of the respective subclaims.

• - wobei ØY ein externer Durchmesser der Mehrzahl von Permanentmagneten ist,
• - ØX ein interner Durchmesser des zylindrischen Magnetgehäuses (21; 21a, 21b, 21c) ist und
• - IF1 eine erste Presspassung zwischen einem externen Durchmesser der zylindrischen Welle (1) und dem internen Durchmesser des zylindrischen Magnetgehäuses (21; 21a, 21b, 21c) ist.

In one embodiment, the permanent magnet rotor assembly includes a longitudinal axis of rotation having first and second ends, at least two poles, a cylindrical shaft having an outer surface extending in the direction of the longitudinal axis, a plurality of permanent magnets forming portions of the ring segments, and extending into Direction of the longitudinal axis, and an outer cylindrical holding sleeve, which surrounds the plurality of permanent magnets comprises a cylindrical magnet housing, which is mounted on the cylindrical shaft to support the plurality of permanent magnets, wherein the cylindrical magnet housing is formed of a magnetic material and wherein the cylindrical retaining sleeve is biased by a resultant interference fit IF2 defined by the following formula: $$IF2=-\varnothing Y+\sqrt{{\left(\varnothing X+IF1\right)}^2+\left(\varnothing Y^2-\varnothing X^2\right)}$$

• - in which OY is an external diameter of the plurality of permanent magnets,
• - Ox an internal diameter of the cylindrical magnet housing ( 21 ; 21a . 21b . 21c) is and
• IF1 a first interference fit between an external diameter of the cylindrical shaft ( 1 ) and the internal diameter of the cylindrical magnet housing ( 21 ; 21a . 21b . 21c) is.

• - das zylindrische Magnetgehäuse ist einstückig hergestellt und umfasst einen zylindrischen Abschnitt und zwei Verschlussflansche,
• - das zylindrische Magnetgehäuse umfasst einen zentralen zylindrischen Abschnitt und zwei separate Verschlussflansche umfasst,
• - die zylindrische Haltehülse ist aus einem metallischen Material oder aus einem Verbundmaterial hergestellt,
• - die zylindrische Haltehülse aus einem Verbundmaterial ist um die Anordnung gewickelt, die das zylindrische Magnetgehäuse und die Mehrzahl von Permanentmagneten umfasst,
• - die Permanentmagnete in dem zylindrischen Magnetgehäuse sind durch Kleben, Gießen oder Pressen installiert und damit verbunden.

Preferred embodiments of the permanent magnet rotor assembly comprise individually or in combination in particular the following features:

• the cylindrical magnet housing is made in one piece and comprises a cylindrical section and two closure flanges,
• the cylindrical magnet housing comprises a central cylindrical section and comprises two separate closure flanges,
• the cylindrical holding sleeve is made of a metallic material or of a composite material,
• the cylindrical holding sleeve made of a composite material is wound around the assembly, which comprises the cylindrical magnet housing and the plurality of permanent magnets,
• - The permanent magnets in the cylindrical magnet housing are installed by gluing, casting or pressing and connected.

In another preferred embodiment, the permanent magnet rotor assembly is obtained by forming a cylindrical shaft, forming a cylindrical magnet housing having an inner diameter Ox having an outer diameter of the cylindrical shaft which is less than a press fit IF1 wherein the cylindrical magnet housing is formed of a magnetic material, installing, in the cylindrical magnet housing, a plurality of magnetic or magnetizable elements forming portions of the ring segments, bonding the plurality of magnetic or magnetizable elements into the cylindrical magnet housing, and if necessary Magnetizing such magnetizable members to form permanent magnets, installing an outer cylindrical retainer sleeve surrounding the plurality of permanent magnets installed in the cylindrical magnet housing, the outer cylindrical retainer sleeve surrounding the plurality of permanent magnets installed in the cylindrical magnet housing is installed by simple insertion, inserting the cylindrical shaft in the inner diameter of the cylindrical magnet housing, wherein IF1 a first interference fit between an external diameter of the cylindrical shaft ( 1 ) and the internal diameter of the cylindrical magnet housing.

• - der externe Durchmesser ØY des Magnetgehäuses entspricht dem internen Durchmesser der äußeren zylindrischen Haltehülse,
• - das Einsetzen der zylindrischen Welle in den Innendurchmesser des zylindrischen Magnetgehäuses ist bei gleichzeitigem Vorspannen der äußeren zylindrischen Haltehülse durch eine resultierende Presspassung IF2 erfolgt, wobei die Presspassung IF2 mithilfe der folgenden Formel definiert ist: $$IF2=-\varnothing Y+\sqrt{{\left(\varnothing X+IF1\right)}^2+\left(\varnothing Y^2-\varnothing X^2\right)}$$
  
• - wobei ØY ein externer Durchmesser der Mehrzahl von Permanentmagneten ist und
• - ØX ein interner Durchmesser des zylindrischen Magnetgehäuses ist,
• - beim Installieren der Mehrzahl von magnetischen oder magnetisierbaren Elementen in dem zylindrischen Magnetgehäuse sind die magnetischen oder magnetisierbaren Elemente maschinell bearbeitet und die magnetisierbaren Elemente zum Bilden von Permanentmagneten magnetisiert,
• - die äußere zylindrische Haltehülse, welche die Mehrzahl von Permanentmagneten umgibt, die in dem zylindrischen Magnetgehäuse installiert ist, ist aus einem Verbundmaterial hergestellt und durch Wickeln um das zylindrische Magnetgehäuse installiert ist oder ist aus einem metallischen Material hergestellt,
• - die Permanentmagnete sind in dem zylindrischen Magnetgehäuse durch Kleben, Gießen oder Pressen installiert und damit verbunden,
• - das zylindrische Magnetgehäuse ist einstückig hergestellt und umfasst einen zylindrischen Abschnitt und zwei Verschlussflansche,
• - das zylindrische Magnetgehäuse umfasst einen zentralen zylindrischen Abschnitt und zwei separate Verschlussflansche,
• - die Permanentmagnete sind zuerst eingeführt und mit dem zylindrischen Magnetgehäuse als nicht magnetisierte Elemente verbunden, wonach die resultierende Magnetanordnung maschinell bearbeitet ist und die nicht magnetisierten Elemente magnetisiert sind, um betriebsfähige Permanentmagnete vor der Installation der Hülse zu bilden.

Preferred embodiments of this permanent magnet rotor assembly comprise individually or in combination in particular the following features:

• - the external diameter OY the magnet housing corresponds to the internal diameter of the outer cylindrical holding sleeve,
• - The insertion of the cylindrical shaft in the inner diameter of the cylindrical magnet housing is at the same time biasing the outer cylindrical retaining sleeve by a resulting interference fit IF2 takes place, the press fit IF2 defined by the following formula: $$\mathrm{<figure-callout\; id="2"\; label="I\; F"\; filenames="DE202013012760U1\_0007.png,DE202013012760U1\_0008.png"\; state="\{\{state\}\}">I\; </figure-callout>}F2=-\varnothing Y+\sqrt{{\left(\varnothing X+IF1\right)}^2+\left(\varnothing Y^2-\varnothing X^2\right)}$$
  
• - where ØY is an external diameter of the plurality of permanent magnets and
• ØX is an internal diameter of the cylindrical magnet housing,
• when installing the plurality of magnetic or magnetizable elements in the cylindrical magnet housing, the magnetic or magnetizable elements are machined and the magnetizable elements magnetized to form permanent magnets,
• the outer cylindrical retainer sleeve surrounding the plurality of permanent magnets installed in the cylindrical magnet housing is made of a composite material and installed by winding around the cylindrical magnet housing or is made of a metallic material,
• the permanent magnets are installed in the cylindrical magnet housing by gluing, casting or pressing and connected thereto,
• the cylindrical magnet housing is made in one piece and comprises a cylindrical section and two closure flanges,
• the cylindrical magnet housing comprises a central cylindrical section and two separate closure flanges,
• - The permanent magnets are first inserted and connected to the cylindrical magnet housing as non-magnetized elements, after which the resulting magnet assembly is machined and the non-magnetized elements are magnetized to form operable permanent magnets prior to installation of the sleeve.

Further details and advantages of the invention will become apparent from the following purely exemplary and non-limiting description of an embodiment in conjunction with the drawings.

list of figures

• 1 is a longitudinal sectional view of components of a rotor assembly according to a first embodiment of the invention according to a first step of the manufacturing process,
• 2 is a longitudinal sectional view of components of a rotor assembly according to a second embodiment of the invention according to a first step of the manufacturing process,
• 3 is a longitudinal sectional view of components of a rotor assembly according to the first embodiment of the invention according to a second step of the manufacturing process,
• 4 is a longitudinal sectional view of components of a rotor assembly according to the second embodiment of the invention according to a second step of the manufacturing process,
• 5 is a longitudinal sectional view of components of a rotor assembly according to the first Embodiment of the invention according to a final step of the manufacturing process and
• 6 is a longitudinal sectional view of components of a rotor assembly according to the second embodiment of the invention according to a final step of the manufacturing process.

DESCRIPTION OF PREFERRED EMBODIMENTS

A typical arrangement of a first embodiment of the invention is shown in FIGS 1 . 3 and 5 illustrated.

As in 1 For example, to form a permanent magnet rotor assembly having at least two poles, a cylindrical shaft is formed 1 manufactured with a longitudinal axis of rotation. The wave 1 has an outer surface extending in the direction of the longitudinal axis, and has first and second ends 11 . 12 with a reduced cross section.

1 further shows a plurality of elements 22 which are to be magnetized to become permanent magnets or a plurality of already existing permanent magnets 22 , The elements or permanent magnets to be magnetized 22 form sections of ring segments and are in a cylindrical magnet housing 21 mounted, which is formed of a magnetic material and an inner diameter Ox having an outer diameter of the cylindrical shaft 1 which is less than a press fit IF1 is. The outer diameter of the cylindrical shaft 1 is thus equal to ØX + IF1.

The majority of permanent magnets or elements to be magnetized 22 is in the cylindrical magnet housing 21 connected, which may be made in one piece and may comprise a cylindrical portion and two closure flanges. The permanent magnets or elements to be magnetized 22 can in the case 21 be installed by gluing, casting, pressing or any other method that allows the elements or magnets 22 in the case 21 to bond.

If at this stage to be magnetized elements 22 instead of already being used magnetic permanent magnets, the magnet assembly, the housing 21 and the elements 22 and having an outer diameter ØY, can be machined at this location, if necessary, without the inconvenience of magnetized chips or particles likely to adhere to other magnetic material.

Once the magnet assembly, the housing 21 and the elements 22 Once completed, it can be magnetized for its final function.

An outer cylindrical retaining sleeve 23 then becomes the plurality of permanent magnets 22 used in the cylindrical magnet housing 21 is installed.

The next step of a method of manufacturing a rotor motor assembly is in FIG 3 illustrated. An end 12 the wave 1 will be in a fixed frame 13 held, whereas the other end 11 the magnetic ring arrangement 2 facing in the step of 1 was produced and the permanent magnets 22 that covers itself in its housing 21 are located and through the sleeve 23 being held.

wobei ØY ein externer Durchmesser der Mehrzahl von Permanentmagneten 22 ist, ØX ein interner Durchmesser des zylindrischen Magnetgehäuses 21 ist und IF1 eine erste Presspassung zwischen einem externen Durchmesser der zylindrischen Welle 1 und dem internen Durchmesser des zylindrischen Magnetgehäuses 21 ist.The order 2 will then move forward in the direction of the shaft 1 moves in the inner diameter of the cylindrical magnet housing 21 while simultaneously biasing the outer retaining sleeve 23 by a resulting interference fit IF2 which is defined using the following formula: $$\mathrm{<figure-callout\; id="2"\; label="I\; F"\; filenames="DE202013012760U1\_0007.png,DE202013012760U1\_0008.png"\; state="\{\{state\}\}">I\; </figure-callout>}F2=-\varnothing Y+\sqrt{{\left(\varnothing X+IF1\right)}^2+\left(\varnothing Y^2-\varnothing X^2\right)}$$

in which OY an external diameter of the plurality of permanent magnets 22 is Ox an internal diameter of the cylindrical magnet housing 21 is and IF1 a first interference fit between an external diameter of the cylindrical shaft 1 and the internal diameter of the cylindrical magnet housing 21 is.

In 3 the arrows indicate the direction of application of the force acting on a flange of the magnetic ring arrangement 2 is exercised to him on the shaft 1 sit up.

The required preload on the sleeve 23 depends on the application, but can be ensured with high precision by the resulting interference fit, which is given by the above-mentioned formula (1).

5 illustrates the resulting rotor assembly 10 with the permanent magnets 22 , which the magnetic ring arrangement 2 that covers the shaft 1 is attached, with the first press fit IF1 and a resulting interference fit IF2 are shown in the drawing, as well as the longitudinal axis X-X ' the rotor assembly 10 ,

The two-step process of creating an interference fit, including the second step of suspending preassembled magnetic rings 2 on a wave 1 , allows to obtain the required high excess, without having to apply the excessively high or low temperatures, according to the known methods for assembling permanent magnet rotors of the prior art using the coefficient of thermal expansion of the parts for a high or low temperature sliding fit required are.

The 2 . 4 and 6 illustrate a variant of the embodiment of the embodiment of 1 . 3 and 5 is generally similar and not described in detail, but which is a cylindrical magnet housing 21a . 21b . 21c includes a central cylindrical section 21a and two separate closure flanges 21b . 21c includes. In the embodiment of the 2 . 4 and 6 bear the elements that are the elements of the embodiment of the 1 . 3 and 5 are identical, the same reference numerals and will not be described again.

The central cylindrical section 21a is like the cylindrical magnet housing 21 made of magnetic material. The separate closure flanges 21b . 21c can be made of either magnetic material or non-magnetic material.

In the embodiment of the 2 . 4 and 6 can the outer holding sleeve 23 ' containing the plurality of permanent magnets 22 surrounding in the cylindrical magnet housing 21a . 21b . 21c installed, can be made of a composite material and can be wound around the cylindrical section 21a of the cylindrical magnet housing are installed.

The method and resulting rotor assembly with preassembled rings described herein have a number of advantages.

A simple in situ magnetization of the magnetic ring arrangement 21 . 22 or 21a . 21b . 21c . 22 can before inserting the retaining sleeve 23 . 23 ' done as the mass of the full wave 1 does not exist, so the assembly and machining of the magnets 22 that are not yet magnetized, can be simplified. In particular, the risks of damage during the transport of the arrangements are reduced since there is no magnetic field during transport and this only later before inserting a retaining sleeve 23 ; 23 ' is produced.

When using the above-described press-in process, only radial loads act on a sleeve 23 . 23 ' because the force is on the surface of the complete arrangement 2 . 2 ' (eg on the flange 21b) is exercised, which has a larger surface and is better able to withstand axial forces.

In an arrangement according to the invention, the magnets on another arrangement 2 . 2 ' as the wave 1 be prepared, so a complete arrangement 2 . 2 ' on a wave 1 can be put on and various steps of assembling and machining the shaft 1 which have been used in the prior art, omitted, whereby the production cycle time is reduced and a series production is facilitated.

Finally, the invention enables a preload precisely on the sleeve 23 ; 23 ' exercise. Thus, the invention allows to simplify the manufacturing process with increased performance and reduced costs.

Although preferred embodiments have been illustrated and described, it should be understood that any changes and modifications may be made thereto without departing from the scope of the invention as defined in the appended claims. Thus, the features of the various embodiments can be combined.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5563463 [0002]
• US 7872553 B2 [0002]
• US 2005/0093391 A1 [0002]
• US 2005/0099079 A1 [0002]
• US 2009/0261678 A1 [0002]

Claims (16)

A permanent magnet rotor assembly having a longitudinal axis of rotation X'-X, first and second ends (11, 12) and at least two poles, comprising - a cylindrical shaft (1) having an outer surface extending in the direction of the longitudinal axis X'-X , - a plurality of permanent magnets (22) forming portions of the ring segments and extending in the direction of the longitudinal axis XX ', and an outer cylindrical retaining sleeve (23, 23') surrounding the plurality of permanent magnets (22) characterized in that it further comprises a cylindrical magnet housing (21; 21a, 21b, 21c) mounted on the cylindrical shaft (1) for supporting the plurality of permanent magnets (22), the cylindrical magnet housing (21; 21b, 21c) is formed from a magnetic material, and in that - the cylindrical retainer sleeve (23; 23 ') is biased by a resultant interference fit IF2 defined by the following formula: $$IF2=-\varnothing Y+\sqrt{{\left(\varnothing X+IF1\right)}^2+\left(\varnothing Y^2-\varnothing X^2\right)}$$

- where ØY is an external diameter of the plurality of permanent magnets, - ØX is an internal diameter of the cylindrical magnet housing (21; 21a, 21b, 21c), and - IF1 is a first interference fit between an external diameter of the cylindrical shaft (1) and the internal diameter of the cylindrical magnet housing (21; 21a, 21b, 21c). Permanent magnet rotor assembly according to Claim 1 wherein the cylindrical magnet housing (21) is made in one piece and comprises a cylindrical portion and two closure flanges. Permanent magnet rotor assembly according to Claim 1 wherein the cylindrical magnet housing (21a, 21b, 21c) comprises a central cylindrical portion (21a) and two separate closure flanges (21b, 21c). Permanent magnet rotor assembly according to one of Claims 1 to 3 wherein the cylindrical retaining sleeve (23) is made of a metallic material. Permanent magnet rotor assembly according to one of Claims 1 to 3 wherein the cylindrical retaining sleeve (23 ') is made of a composite material. Permanent magnet rotor assembly according to Claim 5 wherein the cylindrical support sleeve (23 ') of composite material is wound around the assembly comprising the cylindrical magnet housing (21a, 21b, 21c) and the plurality of permanent magnets (22). Permanent magnet rotor assembly according to one of Claims 1 to 6 wherein the permanent magnets (22) are installed in and bonded to the cylindrical magnet housing (21; 21a, 21b, 21c) by gluing, casting or pressing. Permanent magnet rotor assembly, in particular according to one of Claims 1 to 7 characterized in that the permanent magnet rotor assembly is obtained by - forming a cylindrical shaft (1) - forming a cylindrical magnet housing (21; 21a, 21b, 21c) having an inner diameter ØX corresponding to an outer diameter of the cylindrical shaft (1) which is smaller than a press fit IF1, wherein the cylindrical magnet housing (21; 21a, 21b, 21c) is formed of a magnetic material, - installing, in the cylindrical magnet housing (21; 21a, 21b, 21c), a plurality of magnetic or magnetizable elements (22) forming portions of the ring segments, bonding the plurality of magnetic or magnetizable elements (22) into the cylindrical magnet housing (21; 21a, 21b, 21c) and, if necessary, magnetizing such magnetizable elements to form of permanent magnets (22), - installing an outer cylindrical retaining sleeve (23, 23 ') which surrounds the plurality of permanent magnets (22) formed in the cylindrical magnet housing (21; 21a, 21b, 21c), wherein the outer cylindrical holding sleeve (23) surrounding the plurality of permanent magnets (22) installed in the cylindrical magnet housing (21) is installed by simple insertion, inserting the cylindrical shaft (1) into the inner diameter of the cylindrical magnet housing (21; 21a, 21b, 21c), IF1 having a first interference fit between an external diameter of the cylindrical shaft (1) and the internal diameter of the cylindrical magnet housing (21; 21a, 21b, 21c ). Permanent magnet rotor assembly according to Claim 8 , wherein the external diameter ØY of the magnet housing (21) corresponds to the internal diameter of the external cylindrical retaining sleeve (23, 23 '). Permanent magnet rotor assembly according to Claim 8 in which the insertion of the cylindrical shaft (1) into the inner diameter of the cylindrical magnet housing (21; 21a, 21b, 21c) while simultaneously biasing the outer cylindrical retaining sleeve (23, 23 ') by a resulting Press fit IF2 is done, with press fit IF2 defined by the following formula: $$IF2=-\varnothing Y+\sqrt{{\left(\varnothing X+IF1\right)}^2+\left(\varnothing Y^2-\varnothing X^2\right)}$$

- where ØY is an external diameter of the plurality of permanent magnets and - ØX is an internal diameter of the cylindrical magnet housing (21; 21a, 21b, 21c). Permanent magnet rotor assembly according to one of Claims 8 to 10 wherein the permanent magnet rotor assembly is obtained by machining the magnetic or magnetizable elements (22) and the magnetizable elements when installing the plurality of magnetic or magnetizable elements (22) in the cylindrical magnet housing (21; 21a, 21b, 21c) are magnetized to form permanent magnets. Permanent magnet rotor assembly according to one of Claims 8 to 11 in which the outer cylindrical holding sleeve (23 ') surrounding the plurality of permanent magnets (22) installed in the cylindrical magnet housing (21a, 21b, 21c) is made of a composite material and wound around the cylindrical magnet housing (11) 21a, 21b, 21c) is installed or - wherein the cylindrical holding sleeve (23) is made of a metallic material. Permanent magnet rotor assembly according to one of Claims 8 to 12 wherein the permanent magnets (22) are installed in and bonded to the cylindrical magnet housing (21; 21a, 21b, 21c) by gluing, casting or pressing. Permanent magnet rotor assembly according to one of Claims 8 to 13 wherein the cylindrical magnet housing (21) is made in one piece and comprises a cylindrical portion and two closure flanges. Permanent magnet rotor assembly according to one of Claims 8 to 13 wherein the cylindrical magnet housing (21a, 21b, 21c) comprises a central cylindrical portion (21a) and two separate closure flanges (21b, 21c). Permanent magnet rotor assembly according to one of Claims 8 to 15 wherein the permanent magnets (22) are first inserted and connected to the cylindrical magnet housing (21; 21a, 21b, 21c) as non-magnetized elements, after which the resulting magnet assembly (21,22; 21a, 21b, 21c, 22) is machined and the non-magnetized elements are magnetized to form operative permanent magnets (22) prior to installation of the sleeve (23; 23 ').

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