WO2021249589A1

WO2021249589A1 - Rotor for a synchronous machine and synchronous machine with such a rotor

Info

Publication number: WO2021249589A1
Application number: PCT/DE2021/100302
Authority: WO
Inventors: Marvin Hofmann; Simon Münster; Frank Frietsch; Miriam Boxriker
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2020-06-10
Filing date: 2021-03-26
Publication date: 2021-12-16
Also published as: DE102020115367B3

Abstract

The invention relates to a rotor for a synchronous machine, having a plurality of permanent magnets arranged in a distributed manner around the rotor circumference, the permanent magnets being arranged so that they can be displaced radially in an axially positionally fixed magnet holder and being mounted directly or indirectly on one or more wedge surfaces of an axially displaceable wedge element, said wedge element can be moved axially in a controlled manner via a hydraulically or pneumatically actuable actuating element.

Description

Rotor for a synchronous machine and synchronous machine with one

rotor

The invention relates to a rotor for a synchronous machine, with a plurality of permanent magnets distributed around the rotor circumference.

A synchronous machine with a rotor on which a plurality of permanent magnets are provided distributed around the circumference is usually also referred to as a manually excited synchronous machine. In addition to the rotor, sometimes also referred to as a rotor, it includes a stator, sometimes also called a stator, via which a rotating magnetic field can be generated that couples with the permanent magnet of the rotor via an air gap. To generate the rotating magnetic rotating field, a three-strand winding operated with a three-phase alternating current is usually provided on the stator. The resulting torque of the machine results from the magnetic interaction between the rotating field and an excitation field generated by the permanent magnet of the rotor.

The synchronous machine is usually controlled via a frequency converter and pulse width modulation, which can be used to regulate a variable speed in a relatively broad speed range. If the speed of the rotor corresponds to the speed of the stator-side rotating field, steady-state operation is given, that is, the rotor speed is synchronous with the stator field speed. The speed is defined by the frequency of the voltage applied to the stator or the alternating current on the stator side. As a result of the interaction of the stator-side rotating field with the rotor-side rotating field, there is a voltage induction in the stator winding, the induced voltage increasing with increasing speed. The voltage induction results from the superposition of the stator flux linkage with the rotor flux linkage. The maximum adjustable voltage that is regulated by the control or power electronics is limited. Above a certain voltage, the required current can no longer be set because the voltage limit has been reached. At high speeds, the machine is therefore in a so-called field weakening range. In order to increase the speed further To be able to increase it, it is necessary to weaken the magnetic field of the rotor so that the stator-side voltage is sufficient to feed in the required current. At the same time, the rotor should nevertheless generate the largest possible rotor or permanent magnet flux linkage so that high basic speed torques can be generated with the same machine volume. However, this leads to comparatively high iron losses in the partial load range and thus to poor efficiency.

In order to achieve the desired field weakening at high speeds, it is known to generate a corresponding opposing field in terms of control technology on the stator, i.e. to impress a negative longitudinal current that generates the opposing field that counteracts the rotor magnetic field. In the field weakening range and in operating points of the lower partial load range, however, the field weakening that can be achieved via the negative longitudinal current is not efficient enough.

The invention is therefore based on the problem of specifying a rotor that enables the aim of a large field weakening at low torque and high speed.

To solve this problem, a rotor for a synchronous machine is provided according to the invention, with several permanent magnets distributed around the rotor circumference, which is characterized in that the permanent magnets are arranged radially in an axially fixed magnet holder and directly or indirectly on wedge surfaces of an axially displaceable wedge element are mounted, which is controlled axially movable bar via a hydraulically or pneumatically actuated adjusting element.

The invention proposes a rotor with the possibility of changing the air gap between the Ro tor and the stator in a targeted manner and of causing the field to be weakened in a targeted manner by changing the gap. The larger the air gap between rotor and stator, the greater the field weakening. According to the invention it is provided that this Luftspaltver change by means of a hydraulically or pneumatically actuated adjusting element to be controlled in order to achieve a desired acceleration and thus an increase in the Speed and torque to narrow the air gap in a targeted manner and to enlarge the air gap when the speed and torque are reduced. This means that in the event of an increase in speed and the resulting increase in torque, the air gap is deliberately reduced and there is less field weakening and thus also higher field coupling, so that it is possible to accelerate to very high speeds while at the same time low torque and high speed, the gap width is increased again and consequently a large field weakening with a simultaneous reduction in the overall magnetization of the synchronous machine is given.

In order to realize this torque-dependent air gap change, the permanent magnets are arranged according to the invention in an axially fixed Magnethal ter and guided in this radially displaceable, that is, they can be displaced radially relative to the magnet holder. The distance between the permanent magnets and the surrounding stator defines the width of the air gap. According to the invention, a wedge element is provided for radial adjustment of the permanent magnets, which is axially displaceable and has the corresponding wedge surfaces on which the permanent magnets are guided directly or indirectly. If, therefore, the wedge element is axially displaced via the controlled hydraulically or pneumatically actuated adjusting element, the permanent magnets are moved radially out of the magnet holder or in the magnet holder, this radial movement taking place in the range of only a few millimeters. This means that the controlled hydraulic or pneumatic wedge system provided according to the invention in conjunction with the radial permanent magnet displacement can be used to change the air gap in a targeted manner and thus to weaken the field.

The adjusting element can be controlled hydraulically or pneumatically as described. A hydraulic fluid under pressure, or compressed air, is supplied to it in a controlled manner via a control device in order to effect the actuating process. The control device, which for example generally controls the operation of the electric machine, reacts to an acceleration request that is given via a corresponding control signal, and controls a suitable pump or the like. to supply the hydraulic fluid or the compressed air with the necessary pressure and thus actuate the actuating element. term so that the displacement of the wedge element is effected. For this purpose, an axially fixed, concentric slave cylinder with an axially movable piston, which is coupled to the rotor shaft via a release bearing, is preferably used as the adjusting element. Such a slave cylinder, often also called CSC (concentric slave cylinder), is an actuating element used in clutch construction. With such a slave cylinder, the setting task can be carried out very precisely, in particular in connection with the fluid or gas supply controlled via the control device.

The slave cylinder itself is axially fixed, it is attached to the machine housing, for example. Via a line, the slave cylinder is connected to a conveying device controlled via the control device, via which the fluid or gas with the required pressure and the required amount is controlled, depending on which it is controlled how far the piston extends and consequently how far the permanent magnets are displaced radially are fed. The fluid or gas is pressed into a cylinder space so that the piston is moved axially accordingly. With the Kol ben the release bearing is axially displaced, which is firmly connected to the piston with a bearing ring, and the other bearing ring is firmly connected to the component supporting the Keilele element, such as the rotor shaft, which is axially on the bearing ring, for example. The rotating side is connected to the non-rotating side via the release bearing, which is known to be designed as a roller bearing. The displacement of the wedge element is accompanied by the radial displacement of the permanent magnets that run onto the wedge surfaces of the wedge element. This causes the magnetic elements to be displaced radially outwards, and the air gap becomes smaller. The speed can be increased as a result of the changed field coupling until a desired high speed is applied. The permanent magnets are then to be moved back again and the field weakening to be built up, which takes place in that the fluid or gas pressure in the slave cylinder is reduced again so that the piston can return again and with it the wedge element is moved back again, whereby the Permanent magnets are drawn in again and the air gap increases again. The desired field weakening is given again. The permanent magnets are, for example, coupled to the wedge element in such a way that they are automatically taken along as part of the restoring movement, this mechanical coupling also preventing the permanent magnets from moving relative to the magnet due to centrifugal force. net holder can move radially. In this way, a simple, torque-controlled axial displacement can be achieved via the adjusting element provided according to the invention, which is achieved in a simple and quick manner, but can also be reduced again in the same way.

During the backward movement from the disengaged position into the engaged position, the piston can be movable against a spring element, in particular a helical spring, which engages around the slave cylinder. This can be used to dampen the restoring movement, and this spring element can support the disengagement movement. The spring element is expediently supported on the one hand on the slave cylinder and on the other hand on the release bearing.

The wedge element itself is attached to a rotor shaft via which the rotor is rotatably mounted in the machine housing, either as a separate element, or the wedge element is formed by the rotor shaft itself, which means that in this case the rotor shaft has corresponding, radially protruding wedge sections has, with which the permanent magnets are coupled. In any case, the rotor shaft, which is coupled to the release bearing, is slightly axially displaceable. This axial displacement requires, on the one hand, a connection between the magnet holder attached to the rotor shaft in such a way that a non-rotatable connection is provided, but at the same time also a connection that enables an axial displacement of the rotor shaft. Appropriately, this connection is implemented in the form of a longitudinal toothing. Correspondingly, a corresponding spline connection between the rotor shaft, which forms the output shaft of the synchronous machine, and a drive shaft connected to it, for example on a vehicle rear axle, is to be seen so that the rotor shaft can also be axially adjusted relative to this.

As described, in the event of an increase in speed and thus an increase in torque, the release bearing coupled to the wedge element or the rotor shaft or the piston is moved axially. When the acceleration is reduced or a constant speed is reached and thus the torque is reduced, the piston is axially reset again. In order to enable or support this restoring movement, the invention also provides that the axial movement of the piston or the rotor shaft or the wedge element takes place against a restoring force, preferably via a spring element, in particular a helical spring. If the axially movable piston or the Ro gate shaft together with the wedge element is axially displaced, a restoring force is built up, that is, the spring element, in particular the helical spring, is compressed. In the event of a reduction in the increase in speed or the torque, the restoring force or the spring element pushes the rotor shaft or the piston back again, so that the radially extended permanent magnets are reset again. A helical spring is particularly suitable as such a spring element; alternatively, the use of a disk spring assembly or the like is also conceivable.

For an appropriate integration of the spring element in the rotor structure, the spring element can be supported on the one hand on the magnet holder or a component connected to it, in particular a bearing ring of a roller bearing supporting the magnet holder, and on the other hand on the axially movable element part. The spring element is thus supported on the one hand on a fixed-position surface, i.e. on the magnet holder or, for example, the bearing ring, and on the other hand on an axially movable surface, i.e. the rotor shaft, which enables integration into an already existing, narrow installation space.

As described, the radial adjustment of the permanent magnets takes place via a wedge surface system in that either a quasi-conical circumferential wedge surface, i.e. a conical surface, is formed on the wedge element, or a number of wedge sections projecting radially on the wedge element corresponding to the number of magnets. With the or these wedge surfaces, the permanent magnets are coupled or directly or indirectly guided on them. It is provided according to a first alternative of the invention that the permanent magnets themselves have wedge surfaces with which they are mounted directly on the wedge surface or surfaces of the wedge element. The permanent magnets therefore have a trapezoidal shape. The outside of the magnet, which faces the stator, runs parallel to the stator surface or parallel to the axis of rotation of the rotor shaft, while the radially inner magnet surface runs at an angle to this, forming a wedge surface. That means that the magnet volume axially changed, the cross-sectional area increases from one end of the magnet to the other. Alternatively, it is conceivable that each permanent magnet is arranged on a magnet carrier which has a wedge surface and is mounted with this on the or a wedge surface of the wedge element. So here each permanent magnet has a constant cross-section over its length, the wedge surface is formed via the interposed magnet carrier, for example a simple plastic component to which the permanent magnet is firmly connected, eg glued.

As described, the permanent magnets are guided radially in the magnet holder.

For this purpose, the magnet holder is expediently designed as a hollow cylinder and has a number of radial recesses corresponding to the number of permanent magnets. It also has on both sides radially inwardly extending radial flanges and adjoining axially extending annular flanges via which the magnet holder rests on the rotor shaft, that is, on these axial, cylindrical annular flanges, the longitudinal toothing is formed, which is integrated into the longitudinal toothing engages on the rotor shaft, and on the one hand forms the non-rotatable connection of the rotor shaft and magnet holder, but on the other hand also enables the rotor shaft to be axially displaced relative to the fixed magnet holder.

In order to ensure that the radial adjustment of the permanent magnets takes place only in a defined adjustment range, that is, that the permanent magnets can only be adjusted between a defined inner position and a defined outer position, but not beyond that, a development of the invention provides that on the Rotor shaft two axial stops are provided that limit the movement of the rotor shaft Verschiebebe relative to the magnet holder. The axial movement of the rotor shaft is therefore limited by these two stops, but this also limits the maximum adjustment path of the permanent magnets.

Different configurations are conceivable for forming the wedge surfaces on the wedge element. On the one hand, it is possible, as already described, to form a number of longitudinal projections or webs corresponding to the number of permanent magnets on the rotor shaft, on which the radially outer wedge surfaces are formed. This enables a correspondingly light design the rotor shaft, since only the narrow wedge sections have to be provided. The actual radial guidance of the permanent magnets takes place via the magnet holder, which has, for example, corresponding, radially inwardly directed guide surfaces on which the permanent magnets are guided. As an alternative to this embodiment of the wedge element, however, it is also conceivable to design a quasi-cylindrical or conical, radially extending ring section as a wedge element on the rotor shaft, in which corresponding grooves are formed which are each bounded radially inward by a wedge surface, the Permanent magnets and optionally the magnet carriers are received in the grooves. Corresponding longitudinal grooves are formed here in the larger-volume wedge element, in each of which a permanent magnet and, if provided, the magnet holder are inserted, these grooves forming the wedge surfaces in the groove base. Here, the permanent magnets are radially guided via the wedge element or the groove flanks themselves.

In addition to the rotor, the invention also relates to a synchronous machine, comprising a rotor of the type described above. It is therefore a permanently excited synchronous machine.

The invention is explained below using exemplary embodiments with reference to the drawings. The drawings are schematic representations and show:

FIG. 1 shows a basic illustration of a synchronous machine according to the invention with a rotor according to the invention with radially inner or retracted permanent magnets, and FIG

FIG. 2 shows the arrangement from FIG. 1 with radially extended permanent magnets.

FIG. 1 shows a schematic diagram of a synchronous machine 1 according to the invention, with a machine housing 2 in which a stator 3 with a laminated core and stator winding 4 and a rotor 5 according to the invention are accommodated. The rotor 5 can be rotated in the machine housing 2 via corresponding roller bearings 6 in a manner known per se Way stored. The rotor 5 according to the invention has a rotor shaft 7 which is provided with a wedge element 8 or on which a wedge element 8 is integrally formed, the wedge element 8 being formed via a here conical, radially extending shoulder 9 on which a plurality of Grooves 10 is formed, de Ren groove base each having a wedge surface 11, that is, it extends in a wedge shape. In each groove 10 and seated on the respective wedge surface 11, a permanent magnet 12 is arranged, which is movably received on the wedge surface 11. Since the rotor shaft 7 and with it the wedge element 8, as shown by the arrow P1, is axially movable, but the permanent magnets 12 are axially fixed in position, the permanent magnets 12 slide on the wedge surfaces 11, whereby the permanent magnets 12 be moved radially outward.

It is possible, as shown in FIG. 1 on the upper permanent magnet 12, for the permanent magnet 12 itself to have a wedge surface 13, so that a trapezoidal shape results and the magnet cross-section is variable from one end to the other. Alternatively, as shown on the lower permanent magnet 12, it is also conceivable to place a magnet carrier 14 between the permanent magnets 12 and the wedge element 8, in which case a wedge surface 15 is formed on the magnet carrier 14, for example a simple plastic component, which sits on the wedge surface 11. Here the permanent magnet 12 is part of a rectangular construction that has a constant cross section over its length.

The permanent magnets 12 are accommodated in a magnet holder 16, which is a hollow cylindrical component and has a number of slot-shaped recesses 17 corresponding to the number of permanent magnets 12. Through these recesses 17, each permanent magnet 12 can be moved slightly radially outward in the direction of the stator 3, so that the air gap 18 between stator 3 and rotor 5 is reduced in width and enlarged again when the permanent magnets 12 are moved back. The guidance of each permanent magnet 12 in the context of the radial movement can either take place via the corresponding, longitudinal flanks of the respective groove 10, in which the permanent magnets 12 and possibly the magnet carrier 14 are received, or via ent- speaking, radially inwardly directed wall-like guide sections on the magnet holder 16 itself.

The magnet holder 16, preferably a plastic component, has, as described, a hollow cylindrical shape. On the cylindrical, with the recesses 17 versehe NEN section closes at each end a radially inwardly extending radial flange 19 and to this a hollow cylindrical, axially extending annular flange 20, the magnet holder 16 via a formed on the annular flanges 20, on the inner circumference provided longitudinal toothing engages in a corresponding, formed on the Ro gate shaft 7 outer longitudinal toothing. On the one hand, a non-rotatable connection is realized via this toothing engagement, so that consequently the entire unit of rotor shaft 7 and magnet holder 16 rotates together; on the other hand, rotor shaft 7 can also be axially displaced relative to magnet holder 16, which is fixed in position.

As FIG. 1 also shows, the two roller bearings 6 with their respective inner ring 21 sit on the outside of the annular flanges 20, while the outer ring 22 is received in a corresponding bearing seat 23 of the machine housing 2.

As described, the rotor shaft 7 and with it the wedge element 8 is axially displaceable, as shown by the arrow P1, in order to push the permanent magnets 12 radially outwards and to reduce the air gap 18, or to move them back radially inwards to close the air gap enlarge. So that this radial adjustment is precisely limited in terms of travel, two axial stops 24 in the form of annular collars are provided on the rotor shaft 7, which run against the neighboring inner ring 21 of the adjacent roller bearing 6 depending on the adjustment movement.

The axial adjustment takes place in the synchronous machine 1 according to the invention via a hydraulically, alternatively also pneumatically controlled or actuatable Stellele element 25. This adjusting element 25 comprises a concentric slave cylinder 26 or is designed as such. The slave cylinder 26 has a cylinder 27 and a piston 28 guided therein. It can be moved in the cylinder 27 in which it is controlled by means of a control device not shown in detail Conveying device 29 via a line 30, a hydraulic fluid, or a gas, is supplied under pressure and in a controlled manner in a suitable amount. The fluid or gas is pressed into a cylinder space 34, which results in the piston shifting to the left. The piston 28 is coupled to a release bearing 35 which has two bearing rings 36, 37, between which rolling elements in the form of balls 38 roll. The piston is connected to the bearing ring 36. The bearing ring 37, on the other hand, is connected to the rotor shaft 7, which has a radial flange 39 with which it is supported on the bearing ring 37.

Furthermore, a spring element 31 is provided in the form of a helical spring 32, which is supported with its right end on the radial flange 39 and with its left end on the outer ring 21 of the adjacent, stationary roller bearing 6. On the opposite side of the release bearing 35 there is a further spring element 40, also here a helical spring 41, which is supported on the one hand on the bearing ring 36 and on the other hand on the cylinder 27. This spring element 40 supports on the one hand the release movement, on the other hand it dampens the return movement when a move.

If the piston 28 is disengaged, as a result of the coupling of the piston 28 to the rotor shaft 7 via the release bearing 35, the rotor shaft 7 is also axially displaced, as shown by the arrow P1. This in turn results in the permanent magnets 12, which are axially fixed in position, are pushed radially outward from the magnet holder 16 through the radial recesses 17 (see arrow P3 in FIG. 1), and are consequently positioned closer to the stator 3, which is shown in FIG a narrowing of the air gap 18 leads. This adjustment movement begins when the speed is to be increased, which is controlled via the control device, not shown in detail, by activating the conveying device for the axial adjustment.

The adjustment situation is shown in FIG. 2, where it can be seen that the piston 28, including the release bearing 35 and the rotor shaft 7, have been pushed to the left as a maximum, the stop 24 rests on the inner ring 21 of the right-hand roller bearing 6. The permanent magnets 12 are visibly pushed slightly radially outward, the air gap 18 is reduced. In this way, the field- Reduced weakening, there is a changed field coupling between stator field and rotor field, which enables start-up even at very high speeds.

When a constant speed is reached again, the acceleration-related increased torque decreases again. The speed is recorded and the fluid or gas pressure in the slave cylinder is reduced again by the control device. The spring element 31 sets the piston 28 together with the release bearing 35 back again. At the same time, however, the rotor shaft 7 is moved back to the right again, as shown by the arrow P2, the permanent magnets 12 run off the wedge surfaces 11 again and are guided radially inward into the magnet holder 16, as the arrow P4 again indicates. In this case, of course, there is a corresponding forced guidance of the permanent magnets 12 with the rotor shaft 7 or the wedge element 8, i.e. a corresponding mechanical coupling is provided, for example via a groove engagement or the like, which ensures that the permanent magnets 12 also define despite the higher speed are moved inward again, and at the same time also ensures that the permanent magnets 12 are not guided radially outward due to centrifugal force alone.

LIST OF REFERENCE NUMERALS synchronous machine machine housing stator stator winding rotor roller bearing rotor shaft wedge element shoulder groove wedge surface permanent magnet wedge surface magnet carrier wedge surface magnet holder recess air gap radial flange ring flange inner ring outer ring bearing seat axial stop adjusting element slave cylinder cylinder piston conveyor line 31 spring element

32 coil spring

33 -

34 cylinder space

35 release bearings

36 bearing ring

37 bearing ring

38 bullets

39 radial flange

40 spring element

41 coil spring

P1 arrow

P2 arrow

P3 arrow

P4 arrow

Claims

1. Rotor for a synchronous machine, with several permanent magnets (12) distributed around the rotor circumference, characterized in that the permanent magnets (12) are arranged radially displaceably in an axially fixed magnet holder (16) and directly or indirectly on one or more wedge surfaces (11 ) an axially displaceable wedge element (8) are mounted which is axially movable steered via a hydraulically or pneumatically actuated adjusting element (25).

2. Rotor according to claim 1, characterized in that an axially fixed, concentric slave cylinder (26) with an axially movable piston (28) which is coupled to the rotor shaft (7) via a release bearing is provided as the adjusting element (25) .

3. Rotor according to claim 2, characterized in that the piston is movable against a spring element (40), in particular a helical spring (41) from the disengaged into the engaged position.

4. Rotor according to one of the preceding claims, characterized in that the wedge element (8) is attached to a rotor shaft (7) or is formed by the rotor shaft (8) itself.

5. Rotor according to one of the preceding claims, characterized in that the axial movement of the axially movable element part (27) or the wedge element (8) against a, preferably via a spring element (31), in particular a special helical spring (32) generated, restoring force he follows.

6. Rotor according to one of the preceding claims, characterized in that the permanent magnets (12) themselves have wedge surfaces (13) with which they are mounted directly on the wedge surface or surfaces (11) of the wedge element (8), or that each permanent magnet ( 12) arranged on a magnet carrier (14) is net, which has a wedge surface (15) and is mounted with this on the or a wedge surface (11) of the wedge element (8).

7. Rotor according to one of the preceding claims, characterized in that the magnet holder (16) is hollow cylindrical and has a number of radial recesses (17) corresponding to the number of permanent magnets (12), and radial flanges (19) extending radially inward on both sides and has axially extending annular flanges (20) adjoining this, via which the magnet holder (16) rests on the rotor shaft (8).

8. Rotor according to claim 7, characterized in that two axial stops (24) are provided on the rotor shaft (7), which limit the displacement movement of the rotor shaft (7) relative to the magnet holder (16).

9. Rotor according to one of the preceding claims, characterized in that the wedge element (8) has grooves (10) which are bounded radially inward by a wedge surface (11), the permanent magnets (12) and, if appropriate, the magnet carriers ( 15) are received in the grooves (10).

10. Synchronous machine, comprising a rotor (5) according to one of the preceding claims.