EP2316157A2

EP2316157A2 - Interior rotor for a rotary electrical machine and method of assembling it

Info

Publication number: EP2316157A2
Application number: EP09777486A
Authority: EP
Inventors: Maeick Blanc; Frédéric PROGIN
Original assignee: Michelin Recherche et Technique SA Switzerland; Michelin Recherche et Technique SA France; Societe de Technologie Michelin SAS
Current assignee: Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Priority date: 2008-08-20
Filing date: 2009-07-28
Publication date: 2011-05-04
Also published as: JP5793077B2; JP2012500613A; FR2935205A1; WO2010020334A2; FR2935205B1; US20110254399A1; US8723383B2; CN102124635B; CN102124635A; WO2010020334A3

Abstract

The invention relates in particular to an embedded-magnets interior rotor (1) for a rotary electrical machine, the rotor comprising: a shaft (2), a plurality of pole pieces (30) made of a magnetic material, surrounding the shaft, the pole pieces delimiting houses (40) between them, a first lateral flange (5) and a second lateral flange (5') axially on each side of the pole pieces along the shaft (2), the shaft passing through each lateral flange via a central opening in each lateral flange, at least one through bolt (6) per pole piece, the through bolt clamping each pole piece between the lateral flanges, permanent magnets (4) installed in the said housings, the said rotor being characterized in that the shaft comprises, for the first lateral flange (5), an interior shoulder (22) intended to constitute an axial end stop against which the first flange is held axially by an external ring (26) secured to the shaft.

Description

Inner rotor for rotating electrical machine and its method of assembly

The invention relates to rotating electrical machines whose rotor comprises permanent magnets More specifically, the invention relates to machines in which the magnets are disposed in recesses of the rotor is commonly referred to the electrical machines in question by the expression "buried magnets" This principle of rotor arrangement is widely applied for autopiloted synchronous machines with flux concentration

The sizing of a rotating electrical machine depends on its torque name More torque that a motor is capable of delivering is high, the larger the electric motor, all other things being equal There are nevertheless applications for which It is desirable to achieve both significant power and compactness of the engine To simply give a concrete example, when it is desired to implement electric traction motors in the wheels of motor vehicles, it is desirable to be able to develop powers of at least 10 kW per motor, and in most cases at least 25 or 30 kW per motor, for as little weight as possible to limit unsprung masses as far as possible. It is also desirable that the the footprint is also very small, exceeding as little as possible the internal volume of the wheel so as not to interfere with the elements of the vehicle. [0003] These two requirements (high power, compactness and low masses) make it very difficult to install electric traction motors in the vehicle. passenger car wheels, except to radically improve the weight / power ratio of electrical machines currently available on the market

The choice of a high speed for an electric motor during the design of the engine is a solution allowing, at given power, to reduce the torque, so the space requirement In other words, for a given power rating of the engine, more big is his name rotation speed, the lower his clutter will be

The elevation of the rotational speed of a rotating electrical machine poses many problems, however, especially with regard to the centrifugal forces undergone by the rotor elements, in particular the magnets. [0006] The vibrations (mechanical and acoustic) also represent an increasing difficulty as the speed of rotation is increased.

A specific design to achieve high speeds of rotation has already been proposed in the patent application EP 1001507. The speeds referred in this patent application are of the order of 12000 rpm, proposing for this purpose an arrangement particular of the assembly consisting of a polygonal one-piece shaft and polar parts judiciously arranged around this shaft.

An improvement to target speeds of about 20000 rpm has been proposed in the patent application EP 1359657, proposing for this an arrangement using wedges to radially block the magnets in their housing.

An object of the invention is to provide an improved rotor, particularly as regards its dimensional stability.

The invention thus relates to an inner rotor with buried magnets for rotating electrical machine, the rotor comprising: "a shaft, a plurality of pole pieces made of magnetic material, surrounding the shaft, the pole pieces delimiting between them ,

A first lateral flange and a second lateral flange axially on each side of the pole pieces along the shaft, the shaft passing through each lateral flange through a central opening of each lateral flange, at least one pulling piece per pole piece, pulling gripping each pole piece between the lateral flanges,

Permanent magnets installed in said housings, said rotor being characterized in that the shaft comprises, for the first lateral flange, an internal shoulder intended to constitute an axial abutment against which the first flange is held axially by an outer ring integral with the tree.

Preferably, the outer ring is shrunk radially on the shaft.

More preferably, the second flange can slide along the shaft.

[0013] More preferably, the central opening of the second flange is such that it can cross the shoulder inside the shaft. More preferably, the shoulder of the shaft cooperates with a counterbore formed in the thickness of the first flange.

More preferably, the pole pieces consist of a stack of magnetic sheets.

More preferably, the shaft comprises a grooved central portion, the inner shoulder being defined by one of the ends of the grooved central portion.

The invention further relates to a rotating electrical machine comprising such a rotor.

The invention also relates to a method for manufacturing such a rotor in which, at first, a subassembly is assembled comprising at least the pole pieces, the side flanges and the tie rods independently of the front shaft. arrange, in a second time, said subset on the shaft.

Preferably, the method further comprises a step of axially fixing said subassembly on the shaft by immobilizing the first lateral flange between the inner shoulder of the shaft and the outer ring made integral with the shaft. .

More preferably, the outer ring is secured to the shaft by radial shrinking.

The invention will be better understood thanks to the following description, which is based on the following figures: • Figure 1 is a sectional view along the axis of a rotor according to the following invention a broken line AA visible in Figures 2 and 3.

FIG. 2 is a partial sectional view perpendicular to the axis of the rotor of FIG. 1 along a line B-B visible in FIG.

FIG. 3 is a sectional view perpendicular to the axis of the rotor of FIG. 1 along a line C-C visible in FIG.

• Figure 4 is a perspective view of the shaft 2.

• Figure 5 is a perspective view of a section along the rotor axis of the embodiment of the flanges and shims magnets.

FIG. 6 is a view similar to FIG. 1 of a second embodiment of the rotor according to the invention. In the accompanying figures, there is shown a rotor 1 for a hexa-polar machine further comprising a not shown stator. The rotor 1 comprises a one-piece shaft 2 resting on bearings 20. Six pole pieces 30 are seen, formed by a stack of ferromagnetic sheets 3. Each sheet 3 is substantially perpendicular to the axis of the shaft. The sheets may have a very small thickness, for example of the order of a few tenths of a millimeter, for example 0.2 mm.

Axially on either side of the shaft 2, we see a side flange 5, 5 '(preferably non-magnetic material), located on each side of the pole pieces 30. In Figure 1, we also see two optional intermediate flanges 7 (preferably also of non-magnetic material). Each lateral flange and optionally each intermediate flange 7 has a central opening. In the nonlimiting example described in FIG. 1, the shape of the central opening of the lateral flanges is circular while that of the central opening of the intermediate flanges is adjusted to that of the shaft 2, ie here grooved.

For each of the pole pieces 30, a tie rod 6 passes through the stack of sheets 3, where appropriate the or the intermediate flanges, and allows to enclose the whole between the side flanges 5 and 5 '. The centrifugal forces experienced by the pole pieces are therefore taken up by the side flanges and if necessary by the intermediate flanges to the exclusion of any other means.

According to the invention, the shaft 2 further comprises an inner shoulder 22 intended to cooperate with a first lateral flange 5 to determine its axial position and therefore the axial position of the pole pieces on the shaft (see in particular the Figures 1, 4, 5 and 6). The shoulder 22 of the shaft preferably bears at the bottom of a countersink 50 of the flange. An outer ring 26 secured to the shaft for example by radial shrinking immobilizes the flange by pressing axially against the shoulder of the shaft. The second flange, which can be described as "floating" does not come to rest on a shoulder of the shaft, it remains on the contrary free to move axially at the discretion of the thermal expansion of the stack. This floating flange 5 'may comprise a countersink substantially identical to the recess 50 of the blocked flange 5 or be on the contrary reamed throughout its thickness as shown here (see bore 50' of the second flange 5 ').

The shoulder (s) 22 preferably correspond to the ends of the grooved central portion 23 of the shaft. Due to the presence of the countersink 50 and the bore 50 ', these ends are then retracted into the flanges 5 and 5'. In this way, the end plates of the stacks can not escape from the grooved central portion 23 of the shaft. This is particularly advantageous during the assembly of the rotor. In the event that the second flange is identical or similar to the first, that is to say with a counterbore and not a bore, an axial clearance must remain between the second flange and the corresponding shoulder on the shaft so to authorize the thermal expansions mentioned above.

We see parallelepiped permanent magnets 4 disposed in the housing 40 between the pole pieces 30. The housing is interrupted by the intermediate flanges 7. In the example of Figure 1, there are 3 magnets per pole while in the example of Figure 6, there are only 2 magnets per pole. Each of the magnet housings is closed by a magnet spacer 51.

Furthermore, as can be seen in FIG. 2, the longitudinal faces 300 of the pole pieces 30 each comprise a groove 31 parallel to the axis of the rotor, hollowed at a radial level close to the outer edge 32 of each pole piece 30 (FIG. and therefore each sheet 3), said pole pieces also having a height (or more exactly a radial dimension) slightly greater than the height of the magnets 4. Each shim 51 thus bears on two grooves 31 disposed on each of the adjacent pole pieces . The magnets 4 are thus made mechanically integral with the pole pieces 30. The essential function of each groove 31 is to form a shoulder to oppose the centrifugation of the wedges and magnets. The pole pieces themselves are integral with each other thanks to the tie rods and side plates and possibly intermediate (s).

The wedges 51 are shaped "T". The "T" is reversed if one looks at a shim placed at the top of the rotor (figure 2). The wings of the "T" and the grooves 31 have flat radial bearing surfaces, that is to say perpendicular to the central radius 41 of the housing 40. This profile of the wedges 51 and grooves 31 allows on the one hand the rotor of resist centrifugation without generating on this occasion an effort to expand housing 40.

The radial portion (the foot) of the "T" fills the other space between the pole pieces which gives the rotor a substantially smooth outer surface (even in the absence of grinding) because the radially outer surface 53 of the wedge is flush with the outer surface 32 of the pole pieces.

The top of the wedge 53 can even be slightly curved (preferably by adopting the same radius as the outside of the rotor) to extend exactly the curvature of the outer edge 32 sheets. In this way, high speed rotation causes even less acoustic vibrations (noise).

The "T" profiles shown here are preferred profiles but other profiles known per se, such as simple flat profiles (rectangular), are used in the context of the present invention.

As detailed in Figure 5, the ends 511 of the wedges extend axially on both sides beyond the pole pieces in notches of the side flanges. Preferably, the ends 511 are refined so as to be folded down in a peripheral groove 52 of the lateral flanges in order to be immobilized axially. This arrangement has also proved favorable in terms of acoustic vibrations (noise) when the rotor is rotating at high speed. To allow their flap in the peripheral groove 52, the ends 511 of the shims are preferably refined by not having the radial portion of the "T" profile. The ends 511 are then in the form of tabs. More preferably the outer wall of the peripheral grooves 52 is inclined relative to the axial direction by an angle substantially less than 90 °, for example of the order of 70 ° in order to create an axial clamping of the wedges when they are folded down. .

Preferably, the pole pieces 30 comprise a stud adapted to cooperate with a groove 21 of the shaft 2. It is this connection which ensures the direct transmission of torque from the pole pieces to the shaft. The grooves 21 are preferably parallel-walled and cooperate with tenons bearing faces also parallel. The pole pieces here being constituted by a stack of ferro-magnetic sheets 3, each sheet has a substantially rectangular radial projection 34 which constitutes a portion of the tenon. Naturally, if only a portion of the plates of a pole piece include this projection, the constraints will be concentrated on these sheets there. It is seen in Figures 2 and 4 that the shaft preferably has as many grooves as poles (here six in number) but it is understood that depending on the efforts involved, we could be limited to only 4, 3 or even 2 grooves.

Weights can also be attached to the flanges to perfect the static and dynamic balancing of the rotor. According to the embodiment of Figures 1, 3 and 6, balancing weights have the form of grub screw 101 that is positioned in holes 102 threaded into the flanges. Of Preferably, the holes are located as here opposite the magnets 4 so that the balancing screws can axially tighten the magnets. Each flange thus comprises six threaded holes 102 in addition to the six passages 61 for the six tie rods 6.

According to a second embodiment balancing weights can also be positioned in recesses 104 in the ends 60 of the tie rods. The weights may for example be in the form of grub screws adapted to threads made in the recesses of the tie rods or even in the heads of the tie rod screws 62.

It is understood that by adjusting the position, the length and / or the material chosen for each balance weight, one can adjust the balance of the rotor. The number of threads being limited, it is often necessary to combine the effect of two weights, each positioned in a clean bore to obtain a sufficiently fine balance. To obtain a satisfactory dynamic balance, it is often useful to place weights on each of the two side flanges.

Preferably, the weights are further immobilized by gluing in their threads to ensure the maintenance of their axial position.

Alternatively, instead of fixing weights on the flanges, we can proceed to one or more machining localized flanges by removal of material.

The figures also show tie rods 6 and tie rods 62 specific. The heads of the tie rods are pressed into one of the flanges (here on the right side of the figure) and are simply stopped by a rod 63 cooperating with a shoulder 64 of the flange. Tie screws 62 are screws whose countersunk heads are retracted into the thickness of the flange (left in the figure).

This design allows on the one hand to reduce the axial size of the rotor and on the other hand to obtain substantially smooth flanges and therefore little noise generators.

The central opening of the intermediate flange 7 of the rotor of Figure 6 is circular, that is to say, it does not transmit rotational force to the shaft. In this example, the entire torque is transmitted to the shaft by the projections 34 of the plates since all the flanges (lateral and intermediate) are slidably mounted in rotation on the shaft. The configuration shown in FIG. 1 in which the intermediate flanges also comprises tenons However, it can be chosen to further facilitate the transmission of the torque and the alignment of the passages 61 for the tie rods during assembly of the rotor.

In the preferred embodiment in which the second flange (the floating flange 5 ') is bored so as to slide without hindrance on the grooved portion 23 of the shaft and thus cross the inner shoulder cooperating with the first flange, it is possible to assemble a first subassembly comprising at least the pole pieces, side flanges and tie rods independently of the rotor shaft, for example on an assembly mandrel, before transferring this subassembly on the tree and fix it with the ring 26.

The rotor withstands without damage very high speeds of rotation, much higher than 10000 rpm, namely speeds of the order of 20000 rev / min at least. The high dimensional stability of the rotor according to the invention makes it possible to adopt a very small gap.

The figures show a hexa-polar rotor, that is to say having 3 pairs of poles, but the person skilled in the art knows how to transpose the technical teachings of the present application to rotors comprising for example 2, 4 or 5 pairs of poles. poles instead of three.

Claims

1. Inner rotor (1) with buried magnets for rotating electrical machine, the rotor comprising: "a shaft (2), a plurality of pole pieces (30) made of magnetic material, surrounding the shaft, the pole pieces delimiting between them housing (40),

A first lateral flange (5) and a second lateral flange (5 ') axially on each side of the pole pieces along the shaft (2), the shaft passing through each lateral flange through a central opening of each lateral flange, At least one tie rod (6) per pole piece, the pulling gripping each pole piece between the lateral flanges,

Permanent magnets (4) installed in said housings, said rotor being characterized in that the shaft comprises, for the first lateral flange (5), an internal shoulder (22) intended to constitute an axial abutment against which the first flange is held axially by an outer ring (26) integral with the shaft.

2. Rotor according to claim 1 wherein the outer ring (26) is shrunk radially on the shaft.

3. Rotor according to one of the preceding claims wherein the second flange (5 ') can slide along the shaft.

4. Rotor according to claim 3 wherein the central opening (50 ') of the second flange is such that it can cross the inner shoulder (22) of the shaft.

5. Rotor according to one of the preceding claims wherein the shoulder of the shaft cooperates with a counterbore (50) formed in the thickness of the first flange.

6. Rotor according to one of the preceding claims wherein the pole pieces consist of a stack of magnetic sheets (3).

7. Rotor according to one of the preceding claims wherein the shaft comprises a grooved central portion (23), the inner shoulder (22) being defined by one end of the grooved central portion.

8. Rotating electrical machine comprising a rotor (1) according to one of the preceding claims.

9. A method of manufacturing a rotor according to one of claims 1 to 7 wherein, is first assembled a subassembly comprising at least the pole pieces (30), the side flanges (5, 5 '). and the tie rods (6) independently of the shaft (2) before disposing, in a second step, said subassembly on the shaft.

The method of claim 9 further comprising a step of axially securing said subassembly to the shaft by immobilizing the first side flange (5) between the inner shoulder (22) of the shaft and the outer ring ( 26) made integral with the tree.

11. The method of claim 10 wherein the outer ring is secured to the shaft by radial shrinking.