WO2021110203A1

WO2021110203A1 - Electric axial-flow machine and drive system

Info

Publication number: WO2021110203A1
Application number: PCT/DE2020/100959
Authority: WO
Inventors: Dennis KUHL; Carsten Angrick; Peter Schwanemann; Wolfgang Reik; Matthias Gramann
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2019-12-04
Filing date: 2020-11-09
Publication date: 2021-06-10
Also published as: DE102020102988A1

Abstract

The invention relates to an electric axial-flow machine and a drive system for a motor vehicle, more particularly an electric axle or a hybrid module. The electric axial-flow machine (1) comprises a stator (20) and a rotor (10) mounted rotatably about an axis of rotation (3) and positioned at an axial distance relative to the stator (20), wherein, according to the invention, the electric axial-flow machine (1) furthermore comprises an adjusting device (31) for setting the axial distance (d) between the rotor (10) and the stator (20). Efficient and optimal operation and an expanded speed range can be ensured with the electric axial-flow machine according to the invention and the drive system for a motor vehicle in a simple design.

Description

Electric axial flux machine and drive system

The invention relates to an electric axial flux machine and a drive system for a motor vehicle.

Electric axial flux machines and drive systems for motor vehicles with electric axial flux machines are known from the prior art. An electric axial flux machine is a motor or generator in which the magnetic flux between a rotor and a stator is implemented parallel to the axis of rotation of the rotor. Other names for electrical axial flux machines are also brushless direct current motors, permanent magnet synchronous motors or pancake motors.

When an electrical axial flux machine is operated, voltages are induced, the strength of which correlates with the speed of the rotor. A higher speed results in a higher induced voltage.

The voltage with which the machine is driven is generally subject to an upper limit. As the induced voltage increases, the difference between the maximum voltage and the induced voltage decreases. This difference is a measure of the maximum current. The current, in turn, is a measure of the torque. This effect restricts the speed range at which torque can still be generated.

To prevent the induced voltage from exerting such an influence, a field weakening is usually implemented in the electrical axial flux machine.

As is known, an additional current is fed into the electrical axial flux machine for this purpose, but this leads to high ohmic losses, which lowers the efficiency of the electrical axial flux machine.

Proceeding from this, the present invention is based on the object of providing an electrical axial flow machine and a drive system equipped therewith To provide, which in a structurally simple manner ensure efficient and optimal operation as well as an extended speed range.

The object is achieved by the electrical axial flux machine according to the invention according to claim 1. Advantageous refinements of the electrical axial flow machine are specified in subclaims 2 to 9. In addition, a drive system for a motor vehicle, in particular an electric axle or a hybrid module, which has the electric axial flux machine, is provided according to claim 10.

The features of the claims can be combined in any technically meaningful manner, in which case the explanations from the following description and features from the figures can also be used, which include additional embodiments of the invention.

In the context of the present invention, the terms “axial” and “radial” always relate to the axis of rotation of the electrical axial flow machine.

The invention relates to an electrical axial flux machine, comprising at least one stator and at least one rotor positioned at an axial distance from the stator and rotatably arranged about an axis of rotation. According to the invention it is provided that the electrical axial flux machine furthermore comprises an adjusting device in order to adjust the axial distance between the rotor and the stator.

The electrical axial flux machine according to the invention is in particular a permanently excited synchronous machine.

This means that the electrical axial flow machine according to the invention is set up to variably set the air gap or the axial distance between rotor and stator.

In particular, a stepless axial adjustability is preferred.

The rotor and / or the stator can be moved axially. In one embodiment of the electric axial flux machine, the rotor has a plurality of permanent magnets, the stator having a plurality of windings of an electrical conductor. If the axial distance between the rotor side and the stator side is increased when the electrical axial flux machine is in operation, this leads to a lower magnetic flux density in the stator or to a field weakening. This makes it possible to dispense with additional currents for realizing an electrically induced field weakening, as a result of which the ohmic losses associated with such currents can be avoided. In addition, the reduced flux density in the stator leads to reduced hysteresis and eddy current losses in the stator.

According to a further aspect of the invention, the setting device is set up to fix the rotor and / or the stator in the set axial position.

In a further advantageous embodiment, the adjusting device only uses mechanical energy to realize a relative movement between the rotor and the stator for the purpose of adjusting the axial distance.

Such a configuration can be implemented, for example, by a centrifugal governor. As an alternative or in addition to a centrifugal governor, a governor unit can also be provided which is set up to regulate the axial distance as a function of an applied torque.

In alternative configurations, however, it is not excluded that the setting device is operated electrically and / or is also operated hydraulically.

According to a further embodiment, the setting device is set up to set the axial distance as a function of the rotational speed of the rotor.

In a further embodiment, the setting device is set up to set the axial distance as a function of the torque applied to the rotor. For this purpose, the setting device comprises a regulator unit which, for the purpose of setting the axial distance between rotor and stator, is coupled to the rotor of the electrical axial flow machine in terms of control technology, so that the torque applied to the regulator unit is the torque of the rotor.

The setting device can be designed in such a way that it sets the axial distance solely on the basis of the rotational speed or solely on the basis of the torque. In an alternative embodiment, the rotational speed and / or the torque are included in a control or regulation of the setting of the axial distance.

In a structurally advantageous embodiment, the adjusting device has at least one spring device for realizing an adjusting movement for the purpose of adjusting the axial distance, against or with the spring force of which the adjusting device works.

This means that the spring constant of the spring device is included in the characteristic curve of the work effected by the setting device when setting the axial distance.

The spring device can be a single spring or a set of springs made up of several springs connected in parallel and / or in series.

This refinement is implemented in particular when the setting device is set up to adjust the axial distance as a function of the rotational speed of the rotor and / or as a function of the applied torque. In this case, for example, when the air gap is intended to be enlarged or the distance between the rotor and stator is enlarged, work can be carried out against the force or spring constant of a spring device, so that the spring constant is included in a characteristic curve of the movement behavior of the adjusting device.

The spring force would then act against or with a magnetic force of attraction between the respective rotor side and the stator side. Correspondingly, the setting device can also have a spring device with the above-mentioned action options, with no extra drive device for realizing an adjusting movement being present.

In an alternative embodiment, a piston-cylinder device can be provided instead of a spring device, so that instead of the spring constant of the spring device, a pressure realized in the cylinder provides a force via the piston against or with which the adjusting device works when the distance is set. The advantage of this alternative embodiment is that, in contrast to a spring constant, the pressure in the cylinder can be regulated so that a force used to adjust the distance can be flexibly adjusted.

According to a further embodiment, one rotor side of the rotor is arranged axially on both sides of the stator, the setting device being set up to set and fix at least one of the two rotor sides in their distance in relation to the stator.

In particular, provision can be made for both rotor sides to be set and fixed at the same axial spacing in each case.

In this embodiment, the rotor is thus essentially formed from two rotor sides which are axially spaced apart from one another.

A respective rotor side is a carrier of magnets, in particular permanent magnets and / or coils. The stator is also a carrier of magnets and / or coils.

If the distances between the two rotor sides can be set, the setting device can be set up to carry out the setting movement of the two rotor sides synchronously.

This ensures that the distance between a respective rotor side and the stator is always the same.

In an alternative embodiment, the distances between the two rotor sides can be set independently of one another, so that the setting is different Points in time, at different speeds and / or at different intervals.

In a supplementary embodiment, the two rotor sides are arranged axially displaceably on a common shaft.

This can be implemented, for example, by an axial toothing or splined shaft toothing on the shaft, which enables an axial displacement of the rotor sides.

Furthermore, according to the invention, a drive system for a motor vehicle, in particular an electric axle or a hybrid module, is provided which has at least one electric axial flow machine according to the invention.

The hybrid module is used in particular to couple a

Internal combustion engine and comprises a separating clutch with which torque can be transmitted from the internal combustion engine to the hybrid module and with which the hybrid module can be separated from the internal combustion engine, as well as an electrical axial flux machine for generating a drive torque.

Furthermore, the hybrid module can optionally include a double clutch device with which torque can be transmitted from the electric axial flow machine and / or from the separating clutch to a drive train which is provided for coupling to an output element or to a transmission.

The electric axis comprises the electric axial flux machine according to the invention and, coupled with it, likewise a transmission. The electric axle is set up to be connected to an output element, such as a drive axle of a motor vehicle, and in an advantageous embodiment also includes integrated power electronics.

The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way restricted by the purely schematic drawings, it being noted that the exemplary embodiments shown in the drawings are not restricted to the dimensions shown. It is shown in

1: a schematic representation of a rotor and a stator of an electrical axial flow machine in a perspective view,

2: a sectional side view of an electrical axial flow machine according to the invention,

3: a schematic representation of an electrical axial flow machine according to the invention in a first state in a side view and FIG. 4: a schematic representation of the electrical according to the invention

Axial flux machine according to Figure 3 in a second state in side view.

1 is a schematic illustration of a rotor 10 and a stator 20 of an electrical axial flux machine 1 in a perspective view.

The rotor 10 comprises a plurality of permanent magnets 11 distributed around an axis of rotation 3 on a circumference, an alternating sequence of positively polarized permanent magnets and negatively polarized permanent magnets being formed along the circumferential direction.

The stator 20 comprises a plurality of teeth 22 distributed around the circumference.

What can be seen here is an axial distance d between the rotor 10 and the stator 20, which is decisive for the penetration of the stator 20 by the magnetic field of the rotor 10.

2 shows a sectional side view of an electrical axial flow machine 1 according to the invention.

The electric axial flux machine 1 comprises a rotor 10 and a stator 20 equivalent to the rotor 10 and stator 20 from FIG. 1, the electric axial flux machine 1 further comprising a shaft 2 rotatable about the axis of rotation 3 and an adjusting device 31.

The rotor 10 is arranged non-rotatably on the shaft 2, the stator 20 being positioned coaxially to the shaft 2. The axial distance d is realized between the rotor 10 and the stator 20. The stator 20 is carried by a cup-shaped stator carrier 30, the open axial side of the cup shape facing the rotor 10.

The setting device 31 is connected to the stator carrier 30 in such a way that the setting device 31 can set and fix the axial position of the stator carrier 30 and thus the axial position of the stator 20. The setting device 31 is set up accordingly to set the axial distance d between the rotor 10 and the stator 20.

The setting device 31 can be operated electrically or hydraulically, or it can only use mechanical energy for realizing an axial relative movement between the rotor 10 and the stator 20. An input variable, as a function of which the setting device 31 sets the axial distance d, can be the speed of the rotor 10 and / or the torque applied to the rotor 10.

FIG. 3 shows a schematic illustration of an electrical axial flow machine 1 according to the invention in a first state in a side view.

The electric axial flux machine 1 comprises a rotor 10, a stator 20 and a shaft 2, the rotor 10 being formed from two axially spaced apart rotor sides 12, 13 and a rotor side 12, 13 of the rotor 10 being arranged axially on both sides of the stator 20.

The first rotor side 12 and the second rotor side 13 are non-rotatably arranged on the shaft 2 and rotate about a common axis of rotation 3 of the electrical axial flow machine 1. The stator 20 is arranged coaxially to the axis of rotation 3 or the rotor sides 12, 13.

The two rotor sides 12, 13 each carry permanent magnets 11 in their radially outer regions on a respective axial side facing the stator 20, the stator 20 having a plurality of windings 21 of an electrical conductor.

The axial distance between the first rotor side 12 and the stator 20 and between the second rotor side 13 and the stator 20 corresponds to the same distance d.

In the first state of the electrical axial flow machine 1 shown in FIG. 3, the axial distance d is made very small. Starting from this state it can It may be necessary to weaken the field in the electrical axial flow machine 1 by setting the axial distance d.

In addition to FIG. 3, FIG. 4 shows a schematic illustration of the electrical axial flow machine 1 in a second state in a side view.

Compared to the first state according to FIG. 3, in the second state according to FIG. 4 a larger axial distance d is formed between the first rotor side 12 and the stator 20 and between the second rotor side 13 and the stator 20.

For this purpose, the two rotor sides 12, 13 were axially displaced synchronously by means of the adjusting device 31, so that both the first rotor side 12 and the second rotor side 13 are axially further spaced from the stator 20.

As a result of the greater axial distance d here, the magnetic field that is effective during operation of the axial flux machine 1 is reduced. With the electrical axial flow machine according to the invention and the

Drive system for a motor vehicle can ensure efficient and optimal operation and an extended speed range in a structurally simple manner.

Reference list

1 electric axial flow machine

2 shaft 3 axis of rotation

10 rotor

11 permanent magnet

12 first rotor side 13 second rotor side

20 stator

21 winding

22 teeth

30 stator carriers

31 adjusting device d axial distance

Claims

1. Electric axial flux machine (1), comprising a stator (20) and a rotor (10) positioned at an axial distance from the stator (20) and rotatably arranged about an axis of rotation (3), characterized in that the electric axial flux machine (1 ) further comprises an adjusting device (31) in order to adjust the axial distance (d) between the rotor (10) and the stator (20).

2. Electric axial flux machine (1) according to claim 1, characterized in that the adjusting device (31) is set up to fix the rotor (10) and / or the stator (20) in the set axial position.

3. Electric axial flux machine (1) according to one of the preceding claims, characterized in that the adjusting device (31) only uses mechanical energy to realize a relative movement between the rotor (10) and stator (20) for the purpose of adjusting the axial distance (d) .

4. Electric axial flow machine (1) according to one of the preceding claims, characterized in that the adjusting device (31) is set up to adjust the axial distance (d) as a function of the rotational speed of the rotor (10).

5. Electric axial flux machine (1) according to one of the preceding claims, characterized in that the setting device (31) is set up to adjust the axial distance (d) as a function of the torque applied to the rotor (10).

6. Electric axial flow machine (1) according to one of the preceding claims, characterized in that the adjusting device (31) for realizing an adjusting movement for the purpose of adjusting the axial distance is at least one Has spring device, against or with the spring force of which the adjusting device works.

7. Electric axial flux machine (1) according to one of the preceding claims, characterized in that axially on both sides of the stator (20) each one

Rotor side (12, 13) of the rotor (10) is arranged, the adjusting device (31) being set up to adjust at least one of the two rotor sides (12, 13) at its distance (d), in particular at the same axial distances (d) in each case. , to be adjusted and fixed in relation to the stator (20).

8. Electric axial flow machine (1) according to claim 7, characterized in that the adjusting device (31) is set up to carry out the adjusting movement of the two rotor sides (12, 13) synchronously.

9. Electric axial flow machine (1) according to one of claims 7 and 8, characterized in that the two rotor sides (12, 13) are arranged axially displaceably on a common shaft (2).

10. Drive system for a motor vehicle, in particular an electric axle or flybridge module, comprising at least one electric axial flux machine (1) according to one of claims 1 to 9.