EP3050197A2

EP3050197A2 - Modular system and method for producing an electric machine

Info

Publication number: EP3050197A2
Application number: EP14744120.8A
Authority: EP
Inventors: Norbert Martin
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2013-09-25
Filing date: 2014-07-28
Publication date: 2016-08-03
Also published as: WO2015043799A2; WO2015043799A3; DE102013219309A1; CN105580252A

Abstract

The invention relates to an modular system for forming at least one first electric machine and at least one second electric machine of different outputs. The electric machines are formed as an inner rotor with an external stator (1) and an internal rotor (2) which has permanent magnets (4). The modular system is characterized by stators (1) which are identical at least with respect to the stator internal diameters for the electric machines, whereas the rotor (2) of the first electric machine has ferrite magnets and the rotor (2) of the second electric machine has rare earth magnets.

Description

description

Modular system and method of manufacturing an electric machine Technical field

The present invention relates to a modular system for forming at least a first electric machine and at least one second electric machine of different power and a method for producing an electric machine using such a modular system.

Background Art Battery powered, electrically powered two-wheeled vehicles are legally classified into various type classes that differ in the performance of the electric drive. For example, electrically powered two-wheeled vehicles of the type class L1 e may carry a maximum of up to 4 kW, while those of the type class L3e may have a maximum power of up to 1 1 kW.

Two-wheeled vehicles of the class L1 e are often operated with gearless wheel hub motors in the rear wheel. These are usually brushless, electrically commutated electric motors in a version as PMSM electric motors (with sinusoidal BACK EMF) or BLDC electric motors (with rectangular back EMF). With regard to their construction, these electric motors regularly have an axle-fixed stator with a high number of slots (regularly> 51), while the rotor is an integral part of the rim. The rotor typically has a ring of rare earth permanent magnets mounted on an iron yoke ring (regularly <46). The amount of rare earth magnets used is regularly approx.

450 g, thereby contributing in large part to the total cost of the electricity see drive. Due to the high material costs for the rare earth magnets such designs for electric motors, which are used as a drive for two-wheeled vehicles, limited to regularly 2 kW maximum power.

Alternatively, in battery electric two-wheel drives, there are also those which transmit the drive power to the driven wheel via a reduction gear. In vehicle frame fixed connection of the electric motor, the reduction is done regularly via multi-stage belt or chain drives or combinations of these, possibly even in a further combination with a gear transmission. In Radnaher arrangement of the electric motors, however, often only gear transmission come in versions as Stirnrad- or planetary gear used.

Many electrically powered two-wheeled vehicles are offered with different drive powers, with correspondingly different powerful electric motors are installed in the same vehicle frame. For such two-wheeled vehicles, it would be advantageous to provide correspondingly power-graded electric drives, which also have a substantially identical construction with the same functional concept, so that no or only minimal adjustments of the vehicle frame are required for their integration. Furthermore, it would be advantageous if it were possible to be able to scale the various electric drives in a large torque range, without changing the speed range. An adaptation of the maximum speed of the vehicles equipped with the various electric drives could then take place via changes in the reduction ratios.

There are modular systems for rotating electrical machines in which the performance of the various electric machines that can be formed using the modular system can be scaled up to a factor of approximately 2 over their axial length, ie can be changed. On the other hand, if electrical machines of a series are to have a power scaling going beyond this, adjustments of the machine topology and in particular of the geometric dimensions are required in addition to the adaptation of the axial length. This is usually associated with high investment in tools and manufacturing equipment. It is therefore an object of the present invention to provide a way to provide in cost-effective manner, a series of electric machines, in particular electric motors for the drive of two-wheeled vehicles, in a comparatively large power range, in particular between 1, 5 kW and 1 1 kW , are scalable.

Disclosure of the invention

This object is achieved by a modular system according to claim 1 and by a method according to the independent claim.

Further embodiments are specified in the dependent claims.

According to a first aspect, a modular system for forming at least one first electric machine and at least one second electric machine of different power is provided, wherein the electric machines are designed as internal rotor with an external stator and an internal rotor having permanent magnets. The stators for the electric machines are identical at least in terms of their inner diameter, while the rotor of the first electric machine has ferrite magnets and the rotor of the second electric machine has rare earth magnets.

Furthermore, the stators of the modular system can also be identical in terms of the geometry of the connection sites, via which the stators can be integrated into supporting structures, for example frames or rear-wheel swing of two-wheeled vehicles. Particularly preferably, it can be provided that the stators of the modular system are completely identical or at least except their axial length completely identical.

The modular system makes it possible to design electric machines of different power without relevant changes to the basic topology and geometry of the stators and rotors used for this purpose. A method for producing an electric machine using such a modular system thus provides that at least the rotor is selected based on the intended power of the electric machine. In a structurally simple and therefore cost-effective embodiment of

Modular system, for example, two electric machines can be provided, the stators are completely identical and their rotors differ only in the use of different permanent magnets. As a result, two differently powerful electric machines can be realized in a simple manner. Since identical stators and with the exception of the permanent magnets used identical rotors is used, the investment in manufacturing facilities and possibly also storage costs compared to the already existing modular systems, in which the different benefits over an axial length scaling of stator and rotor is realized reduced become. In particular, these savings can be so high that additional costs incurred by the use of regularly comparatively expensive rare earths for the permanent magnets of an electric machine are overcompensated. A particularly large and thus advantageous scaling of the power range which can be covered by the electrical machines of the modular system can be achieved by combining the power change based on the use of different types of permanent magnets with a power change via an axial scaling. Accordingly, a plurality of first electric machines and / or a plurality of second electric machines may be provided, which differ in their axial length and thus also have different powers.

Thus, two groups of electric machines differing in the type of permanent magnets used can be provided, with the electric machines of one or preferably both groups again differing in terms of their performance as a result of length scaling. The power adjustment via the length scaling has the advantage of a fundamentally stepless and therefore arbitrary adaptation within the scope of the basic topology and geometry of the stator and rotor as well as by the respective

Type of permanent magnets used limited power ranges. At the same time, the additional production costs associated with the axial length scaling of the stators and rotors are comparatively low. In addition, since no changes are made with respect to the connection sites, the integration of the length-scaled electrical machines into the intended environment, for example a frame or a frame Rear swing arm of a two-wheeled vehicle, possible, without which would be associated with additional effort.

In a preferred embodiment of the modular system, it can be provided that the factor with which the length scaling takes place in the axial direction for the first electric machines and / or second electric machines is between two and three. Thus, the axial length of the longest electric machine of a group (first or second electric machines) is two to three times the axial length of the shortest electric machine of this group. In this factor range, a length scaling of an otherwise (largely) unchanged electric machine with an acceptable difference in efficiency can be realized. In addition, with this Längenskalierungsbereich a meaningful transition can be achieved with respect to the covered by the two groups power ranges. For example, by means of the first, primarily serving as electric motors electric machines, a power range of approx.

1, 5 kW to about 4 kW and by means of the second, also primarily serving as electric motors electric machines, a power range of about 4 kW to about 1 1 kW are covered. Overall, therefore, with the exception of the axial length identical geometry and topology (including the winding pattern of the stator coils) results in a Leistungsskalierbarkeit the electric machines of the modular system with a factor greater than seven. In this case, it may be useful to use the field weakening range of at least some of the electric machines that can be produced from the modular system in order to achieve this (total) power scalability.

A method for producing an electric machine using such a length-scalable modular system can provide that first the type of rotor resulting from the type of permanent magnets used and then a length of the stator and / or the rotor corresponding to the intended power of the electric machine are selected , In a preferred embodiment of the modular system, it can be provided that the rotors of both electric machines have a spoke arrangement of their permanent magnets, wherein the preferably rod-shaped permanent magnets are aligned with a (preferably the largest) longitudinal extent radially relative to the respective axis of rotation of the rotor and the north pole south pole Connections of the permanent magnets perpendicular to the respective radial orientation. It may be particularly preferred that the polarity of adjacent permanent magnets is opposite. Such a spoke arrangement of the permanent magnets can in particular have advantages in the case of a planned length scaling of the electric machines that can be produced from the two groups of the modular system.

The modular system is particularly suitable for the design of electric machines with an operating voltage range of <60 V (DC). If the electric machines are provided as electric motors for driving vehicles, in particular two-wheeled vehicles, they can be designed or used in particular as cooled by a running wind.

Brief description of the drawings

Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Show it:

FIG. 1 shows an electric motor formed from a modular system according to the invention;

Figure 2 is a schematic cross-sectional view through the

Electric motor of Fig. 1; and

Figure 3 shows the course of the difference of the virtual inductances

L _d - L _q (vertical axis) of two electric motors formed from a kit according to the invention over their rotational speeds (horizontal axis). Description of embodiments

Figures 1 and 2 show the structure of an electric motor, which is formed of a stator 1 and a rotor 2 of a modular system according to the invention.

The outer, annular stator 1 has twelve stator slots, which are formed between twelve stator teeth 3. In known manner coils (not shown) wound around the stator teeth 3 in single-tooth windings are arranged in the stator slots.

The rotor 2 has ten rod-shaped permanent magnets 4 in one

Spoke arrangement with five pairs of poles. The largest longitudinal extent of the permanent magnet 4 is thus aligned in each case in a radial direction with respect to the axis of rotation 5 of the rotor 2. This results in a direction perpendicular to the respective radial direction or an imaginary about a rotation axis 5 circle tangential orientation of the North Pole-South pole connections of the individual permanent magnets 4. This arrangement of the permanent magnets 4 leads to a radially with respect to the axis of rotation 5 effective flux concentration and a clearly pronounced salience.

The permanent magnets 4 are in a so-called buried arrangement, i. these are arranged completely in depressions or pockets of a rotor base body 6 consisting of a return material. It may optionally be provided that in the radial direction on at least one side of the permanent magnets 4 between these and the return material air pockets are formed (not shown). As a result, magnetic leakage flux between adjacent permanent magnets 4 can be minimized.

The stator 1 according to FIG. 1 still has a housing 7. This housing 7 is provided with connecting flanges 8, by means of which the electric motor can be connected to a supporting structure in order to support the torque generated thereby. For this purpose, the connection flanges connection points in Have form of holes 9, which can be used for screwing with the supporting structure.

For example, the electric motor is suitable as radnah arranged low-voltage drive motor for a battery-electrically powered two-wheeled vehicle, which may be combined with a transmission, in particular reduction gear that can connect directly to the electric motor. The electric motor is also suitable as an attached to a vehicle frame of the two-wheeled vehicle drive motor, which may be formed in particular without or with integrated partial transmission.

Particularly preferably, the illustrated electric motor is suitable for driving a two-wheeled vehicle with a nominal power located within the legally prescribed homologation limits of 4 kW to 1 1 kW in the European Union. The design of the electric motor with twelve stator slots and five pole pairs has a comparatively high winding factor of 94%. This leads to the intended use sufficiently low cogging torques.

In order to advantageously provide electric motors covering a plurality of power levels within these homologation limits, a modular system is provided that provides various rotors 1 and stators 2 that can be combined with one another to obtain an electric motor of the required rated power.

It is provided that the geometry and the topology (including the winding scheme) for all stators 1 (including the housing 7 and in particular the connection points) of the modular system with the (for at least some of the stators 1 applicable) exception of the axial (ie in the direction of Rotation axis 5 directed) length (in particular of the stator teeth 3 and the wound around these coils) is identical.

The same applies to the rotors 2 of the modular system, which are also identical in terms of their geometry and topology with the (for at least some of the rotors 2 applicable) exception of the axial length. In addition, the rotors 2 are divided into two groups, which differ with respect to the type of permanent magnets 4 used. While in the first group permanent mag- te 4 made of a ferrite material (hereinafter "ferrite") are used for the rotors of the second group permanent magnets 4 from a rare earth comprising material (hereinafter "rare earth magnets"), specifically Nd ₂ Fei ₄ B, provided.

As a result of the stronger magnetic field of rare earth magnets compared to that of ferrite magnets can be achieved by using a rotor 2 with rare earth magnets in comparison to an otherwise identical rotor with ferrite magnet significant performance increase for the electric motor.

For example, with the topology shown in FIGS. 1 and 2, an electric motor with ferrite magnets can be formed, which has an operating voltage of 50.5 V, an outer diameter of the stator of 120 mm, an outer diameter of the rotor of 65 mm and an axial packet length

(ie, the axial length in which the rotor 2 is covered by the coils of the stator 1) outputs a rated power of about 4 kW at a maximum torque of about 15.1 Nm. For an identical with the exception of the use of rare earth magnet electric motor, however, a power of about 1 1 kW with a maximum torque of about 41, 2 Nm can be achieved. This corresponds to a power increase by a factor of 2.75 and a torque increase by a factor of about 2.73. Both electric motors would also have approximately the same engine mass (about 7410 g), active mass (about 5630 g) and mass of copper used (about 1490 g). Only the masses of magnetic material used would be different, using 450 grams of ferrite material and 350 grams of rare earth material. The smaller dimensions of the rare earth magnets also resulting from the lower mass of rare earth material used compared to the ferrite magnets can be compensated for by the use of a filling material, so that the total weight is the same for both electric motors. A significant advantage of using the filling material is that the dimensions of the pockets of the rotor base body 6 can be identical for all rotors 2 present in the modular system. Accordingly, only one embodiment of the rotor base body 6 must be provided for the modular system. If in the modular system also a length scaling over a factor of about two for the stator and both versions of the rotor (ferrite and rare earth magnets) is provided, can for the above-described embodiment of the electric motors with the dimensions shown, a power range for on ferrite based electric motors of 1, 5 kW at one

(minimum) package length of about 37 mm up to the already described 4 kW and for rare earth magnet based electric motors a power range from 4 kW up to the already described 1 1 kW are covered. Overall, this results in a coverable power range from 1, 5 kW to 1 1 kW for all electric motors that can be formed from the modular system

Scaling factor of about 7.33, without this would be associated with significant, the manufacturing costs increasing changes to the stators 1 and 2 rotors. The selection of the type of permanent magnets 4 to be used in each case as well as the configuration of stator 1 and rotor 2 with the respectively required axial length is possible without significantly increasing the production costs and in particular without additionally required investment in tools and machines. Furthermore, it may be advantageous that the power scaling is achieved only by adjusting the torque, while the usable speed band and the commutation frequencies can remain the same.

A peculiarity of the geometry and topology of the electric motors which can be formed from the modular system is the pronounced salience, ie the pronounced difference of the virtual inductances L _d and L _q with respect to a rotor-fixed coordinate system the difference of the virtual

Inductances (L _d - L _q ) in the area of the transition from the armature positioning operation to the field weakening operation for the ferrite magnet-based electric motors, as shown in FIG. 3. FIG. 3 shows a diagram which, by way of example, represents the course of the inductance L of the electric motor over the rotational speed n.

Usually applies to electric motors with buried magnets that

(L _d - L _q ) <0. Since a pre-commutation negative by definition, l _d and positive lq generated results for the torque due to pre-commutation ( "phase advancing") a usable additional torque from (L _d - L _q) ^■ ^■ l _d l _q. An electric motor with ferrite magnets formed from the modular system (see solid line in FIG. 3) has a significantly greater contribution in reluctance mode (L _d -L _q )> 0 than in the case of electric motors with rare-earth magnets (see dashed line in FIG. on. This makes it possible to use a considerable reluctance torque by means of "phase retarding", which can be used both to improve the efficiency in this area and to achieve a temporary power increase, a so-called boost power Electric motor driven two-wheeled vehicle to climb on a curb are used.

Claims

claims

1 . Modular system for forming at least a first electric machine and at least a second electric machine of different power, the electric machines are designed as internal rotor with an outer stator (1) and an internal, permanent magnets (4) having rotor (2), characterized by stators (1 ), which are identical for the electric machines at least in terms of their inner diameter, while the rotor (2) of the first electric machine has ferrite magnets and the rotor (2) of the second electric machine has rare earth magnets.

2. Modular system according to claim 1, characterized in that the rotors (2) of the electric machines have a spoke arrangement of their permanent magnets (4).

3. Modular system according to one of the preceding claims, characterized by a plurality of first electric machines and / or a plurality of second electric machines, which differ in their axial length and thereby have different benefits.

4. Modular system according to claim 3, characterized in that the factor with which the axial lengths of the first electric machines and / or the second electric machines differ, is between 2 and 3.

5. A method for producing an electric machine using a modular system according to one of the preceding claims, wherein the rotor (2) is selected based on a predetermined power of the electric machine. A method for producing an electric machine using a modular system according to one of claims 3 or 4, wherein first of the type of permanent magnets used (4) resulting type of rotor (2) and then one of the intended power of the electric machine corresponding axial length of the stator (1) and / or the rotor (2) is selected.