Single-wheel drive system with combined drive / brake unit

Abstract

The invention relates to a combined drive / brake unit (100), which is integrated into a rim (111) of a wheel (112) and comprises an axial flow machine (118) and an eddy current brake (120), and a common rotor (106) for the axial flow machine (118) and the eddy current brake (120).

Description

[0001] Description

[0002] title

[0003] Single-wheel drive with combined drive / brake unit

[0004] Technical area

[0005] The invention relates to a combined drive / brake unit which can be integrated into a rim of a wheel, wherein the combined drive / brake unit comprises an axial flux machine and an eddy current brake.

[0006] State of the art

[0007] DE 102020200852 A1 describes a recuperatively operable drive system, in particular for motor vehicles, with an electric motor, power electronics, a mechanical brake and an eddy current brake which minimizes the stress on the mechanical brake, wherein it is proposed to generate the braking force by the action of the mechanical brake and / or the eddy current brake on an active unit which is rotatably connected to a rotor of the electric motor along a rotational axis.

[0008] WO 2019101861 A1 describes a drive and deceleration unit comprising a mechanical brake and an electric drive, wherein the mechanical brake and the electric drive are provided as a unit to act on a single wheel connection. Furthermore, a method for controlling or regulating such a drive and deceleration unit is disclosed.

[0009] DE 202005015404 U1 describes a device with a parking brake component, comprising an electric motor, a gearbox, and a spindle unit, which are arranged in series on a common axis. The spindle unit and gearbox are connected via a positive coupling. The electric motors are attached to a cover with a bearing, so that the motor and gearbox are installed as a unit in a common cylindrical housing. A connector for the electric motor is located on the side of the motor-gearbox-spindle unit. An independent claim also relates to a method for performing emergency braking in a combined service and parking brake system.

[0010] Disclosure of the invention

[0011] According to the invention, a combined drive / brake unit is proposed, which is integrated into the rim of a wheel and comprises an axial flux machine and an eddy-current brake, in which a common rotor is provided for the axial flux machine and the eddy-current brake. The axial flux machine can be designed, for example, as a permanently or electrically excited synchronous machine or an asynchronous machine. The invention is explained in the following description using a permanently excited synchronous machine as an example.

[0012] In the context of the invention, a combined drive / brake unit is understood to mean that the rotor of an axial flux machine and a brake drum of a radial eddy current brake are combined in one component, whereby an advantageous size and a lower weight are achieved compared to the prior art.

[0013] An eddy current brake in the sense of the invention is an electromagnetic braking system that provides a braking force, for example for vehicles, that is generated in a very low-wear and material-friendly manner. The eddy current brake uses the eddy current induction principle to generate a braking torque that depends on the speed of a vehicle and the current flow. An eddy current brake typically features an electrical element, which can be designed, for example, as a magnetic coil or as an electromagnet for generating a magnetic field. Alternatively, the electromagnet can have one or more magnetic coils. Furthermore, the eddy current brake has a rotor, wherein the rotor comprises a magnetic, electrically conductive material that is arranged in the immediate vicinity of the electrical element. A rotor is usually in the form of a disk or an annular body.A radial eddy current brake is an eddy current brake that is aligned in such a way that a working air gap is cylindrical to the axis of rotation or the pivot point and a height of the working air gap is measured radially.

[0014] An axial flux machine, as defined by the invention, is a type of electric motor in which the working air gap is oriented as a circular area perpendicular to the motor's rotational axis, and the height of the working air gap is measured in the direction of the rotational axis. Axial flux machines typically comprise a rotor and a stator, with the rotor, which rotates around the rotational axis, and the stator, which generates the rotating magnetic field, arranged axially. With an axial flux machine, electrical energy can be converted into mechanical energy and vice versa.

[0015] According to the invention, the rotor of the eddy current brake and the rotor of the axial flux machine are one and the same component element, which advantageously combines the axial flux machine and the eddy current brake and thus the drive and the braking effect in a combination design and has a space saving and thus a weight reduction compared to a conventional drive / brake unit.

[0016] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the axial flux machine comprises a first stator, a second stator, a third stator, and a rotor arranged axially between the first stator and the second stator and rotatable relative thereto. The axial flux machine is constructed essentially mirror-symmetrically to the rotor.

[0017] A stator in the sense of the invention is a stationary, rotationally fixed component of the combined drive / brake unit that surrounds the rotor. The part of the stator radially spaced from the rotor acts as an eddy current brake, while the axially spaced parts act as an axial flux machine. The stator generates a magnetic field that interacts with the magnetic field of the rotor, thus producing a torque on the rotor. In this case, the torque generated by the axial flux machine causes the rotor to accelerate or decelerate, whereby electrical energy is converted into mechanical energy or vice versa. The torque generated by the eddy current brake always has a decelerating effect, whereby the converted energy is converted into heat in the rotor.In the proposed embodiment, the drive / brake combination comprises a first and a second stator, with the rotor arranged centrally between the two stators. In such a design, two magnetically effective air gaps are provided, which, when the rotor is arranged centrally, lead to a cancellation of the forces in the axial direction. The first stator and the second stator, as identical parts, have windings that are mirror images of each other. Windings are, for example, wire coils arranged around slots in the stator, with the slots being, for example, grooves or depressions in the stator. A third stator is arranged around the rotor as part of the eddy current brake.

[0018] An axial arrangement in the sense of the invention comprises an arrangement of the components, for example the rotor, the first stator and the second stator, along the axis of a cylindrical body, for example a drive axis, so that energy is transmitted in the axial direction, i.e. in the direction of said axis.

[0019] In addition, the rotor is relatively rotatable with respect to the first, second and third stators, the possibility of relative rotation of the rotor resulting from the fact that the rotor is not rigidly connected to the stator but has freedom of rotation.

[0020] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the inner region of the rotor has a material with low electrical conductivity or comprises a plurality of individually insulated sheets and the outer region of the rotor has a material with high electrical conductivity.

[0021] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, a thermal separation of the rotor is provided to prevent heat from being introduced from the eddy current brake into the axial flux machine, in particular in the area of ​​magnets attached to the rotor.

[0022] According to the invention, the thermal separation is achieved at the rotor shared by the axial flux machine and the eddy-current brake. This prevents heat transfer between the area of ​​the rotor interacting with the eddy-current brake and heated by the braking energy, and the area of ​​the rotor interacting with the axial flux machine. The thermal separation can, for example, prevent overheating of the combined drive / brake unit, particularly the magnets on the rotor. The improvement is achieved by isolating the heat generated by the eddy-current brake and preventing overheating of the axial flux machine.

[0023] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the thermal separation is achieved by an inserted ring.

[0024] The inserted ring can, for example, be made of a material with low thermal conductivity. The ring can also be made of a perforated or porous material to reduce the cross-section for heat conduction and thus heat transfer. As an alternative to a separate ring, an annular area in the rotor can also be provided with recesses to reduce the cross-section and thus heat transfer.

[0025] In the sense of the invention, the ring which is used for thermal separation comprises, for example, a ceramic material.

[0026] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the inserted ring comprises a plastic material with a low thermal conductivity.

[0027] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the inserted ring comprises a ceramic material with a low thermal conductivity.

[0028] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the inserted ring comprises a porous material. In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the thermal separation is achieved by tapering the material by means of recesses on the rotor.

[0029] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the rotor has at least one cooling channel in the outermost region of the rotor near the eddy current brake.

[0030] This cooling channel can, for example, be realized through flow-optimized openings in the rotor, comparable to a turbine wheel or an internally ventilated brake disc, but with axial flow.

[0031] According to the invention, the rotor has a disk structure, which has two adjacent regions. An inner region which extends from the center of the rotor to a certain diameter and which functionally represents the rotor of the axial flux machine, and an outer region which functionally represents the rotor of the eddy current brake, with the outer region extending from the edge of the inner region to the outermost edge, namely to the diameter of the entire rotor. Furthermore, a width of the inner region of the rotor can be smaller than the width of the outermost region of the rotor. The inner and outer regions of the rotor are preferably thermally decoupled from one another as efficiently as possible.Preferably, the inner region of the rotor is made of a material that is optimal for the axial flux machine and is characterized by low electrical conductivity or is composed of individual insulated sheets, while the outer region of the rotor is made of a material with high electrical conductivity that is optimized for the eddy current brake.

[0032] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the axial flux machine has permanent magnets.

[0033] Alternatively, an electrically excited machine can be constructed in which electromagnets are arranged on the rotor instead of permanent magnets. In another embodiment, it can also be an asynchronous machine, which is magnetless and instead has a squirrel cage.

[0034] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, the eddy current brake has electromagnets.

[0035] In an advantageous embodiment of the combined drive / brake unit proposed according to the invention, a cooling air flow runs through the cooling channel from the inner tire edge through the cooling channel to the outer tire edge of the rim.

[0036] The cooling channel integrated into the rotor effectively cools the rotor through the internal ventilation and the cooling air flow. This effectively prevents the rotor from overheating.

[0037] An outer tire edge is, for example, a vehicle rim visible from the outside or a vehicle wheel with a rim, where the outer tire edge can be viewed from the outside, for example, by a person. An inner tire edge is, for example, a rim invisible from the outside or a vehicle tire with a rim, where the inner tire edge cannot be viewed from the outside, for example, by a person.

[0038] According to the invention, the combined drive / brake unit is used as an individual wheel drive of a vehicle.

[0039] Advantages of the invention

[0040] An advantageous installation space requirement within the rim is realized by the combined drive / brake unit proposed according to the invention. The combined drive / brake unit efficiently utilizes the available installation space within the rim through a compact, combined design.

[0041] In addition, the proposed combined design of the drive / brake unit achieves a weight reduction, which leads to an improvement in the efficiency and range of a vehicle, especially an electric vehicle.

[0042] By using the rotor together with the eddy current brake and the axial flux machine, the number of moving parts, such as rotating parts, is reduced. By reducing the number of moving parts, less wear and maintenance effort is achieved, thereby increasing the potential service life of a vehicle.

[0043] The use of an eddy current brake further reduces wear on the combined drive / brake unit, as the braking effect occurs without physical contact, which also results in a longer service life for the combined drive / brake unit.

[0044] The advantageous stator arrangement enables simple electrical contact between the eddy-current brake and the axial motor using a multi-pin connector. Overall, this enables a highly integrated and cost-effective solution in terms of installation space, mass, assembly, and electrical contacting.

[0045] Short description of the drawings

[0046] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0047] As an axial flux machine, a permanently excited synchronous machine is shown and described as an example, whereby other embodiments of the axial flux machine, such as the electrically excited synchronous machine or an asynchronous machine, are also encompassed by the invention.

[0048] They show:

[0049] Figure 1 is a schematic representation of the combined drive / brake unit

[0050] Figure 2 is a schematic representation of the combined drive / brake unit with thermal separation Figure 3 is a schematic representation of the combined drive / brake unit with an internally ventilated rotor

[0051] Embodiments of the invention

[0052] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0053] Figure 1 shows a schematic representation of the combined drive / brake unit 100, which is integrated into a rim 111 of a wheel 112. From Figure 1, it can be seen that a gear 114, a first drive shaft 116, a second drive shaft 117, an axial flux machine 118, and an eddy current brake 120 are integrated within the rim 111 of the wheel 112. The axial flux machine 118 and the eddy current brake 120 are designed as a combined drive / brake unit 100. From the combined drive / brake unit according to Figure 1, it can be seen that the combined drive / brake unit 100 has a rotor 106, a first stator 102, a second stator 103, the permanent magnets 104 of the rotor 106 and the electromagnets 108 of the eddy current brake 120.

[0054] The rotor 106 is arranged centrally between the two stators 102, 103 in the axial direction, with an axial air gap 124 being present between the rotor 106 and the respective stators 102, 103. The two stators 102, 103 are constructed in a mirror-image manner and have, for example, windings. Depending on the specific design of the axial flux machine 118, the windings can have different winding patterns, such as a concentric winding or skew winding.

[0055] Permanent magnets 104 are arranged on the rotor 106, wherein the number of permanent magnets 104 is variable depending on the design of the rotor 106.

[0056] The rotor 106 is further arranged radially centrally between the eddy current brake 120, wherein a radial air gap 122 is present between the rotor 106, i.e. the outermost diameter of the outer region 208 of the rotor 106, namely the second diameter 208.1, and the eddy current brake 120, or the electromagnets 108 of the eddy current brake 120.

[0057] Figure 2 shows a schematic representation of the combined drive / brake unit 100 with a thermal break 202 integrated into a rim 111 of a wheel 112. Figure 1 shows that a gear 114, a first drive shaft 116, a second drive shaft 117, an axial flux machine 118, and an eddy current brake 120 are integrated within the rim 111 of the wheel 112. The axial flux machine 118 and the eddy current brake 120 are designed as a combined drive / brake unit 100. From the combined drive / brake unit according to Figure 2, it can be seen that the combined drive / brake unit 100 has a rotor 106, a first stator 102, a second stator 103, the permanent magnets 104 of the rotor 106, and the electromagnets 108 of the eddy current brake 120. Furthermore, Figure 2 shows that the rotor 106 is at the outermost diameter of the inner region 206, i.e., at the first diameter 206.1 , which has thermal separation 202 by a ring 204.

[0058] Figure 3 shows a schematic representation of the combined drive / brake unit 100 with an internally ventilated rotor 106, which is integrated into a rim 111 of a wheel 112. Figure 3 shows that a gear 114, a first drive shaft 116, a second drive shaft 117, an axial flux machine 118, and an eddy current brake 120 are integrated within the rim 111 of the wheel 112. The axial flux machine 118 and the eddy current brake 120 are designed as a combined drive / brake unit 100. From the combined drive / brake unit according to Figure 3, it can be seen that the combined drive / brake unit 100 comprises a rotor 106, a first stator 102, a second stator 103, the permanent magnets 104 of the rotor 106, and the electromagnets 108 of the eddy current brake 120. Furthermore, Figure 2 shows that the rotor 106 is at the outermost diameter of the inner region, i.e., at the first diameter 206.1, which has thermal separation 202 by a ring 204. Furthermore, the outer region 208 of the rotor 106 has a cooling channel 302.

[0059] The integrated cooling channel 302 in the outer region 208 of the rotor 106 provides internal ventilation of the rotor 106. This can be achieved, for example, by a cooling air flow 304 that runs from the inner tire edge 128 toward the outer tire edge 126. The integrated cooling channel 302 protects the rotor 106 from overheating due to the external heat input of the eddy current brake 120, for example the brake drum of the eddy current brake 120.

[0060] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

Claims

Claims 1 . Combined drive / brake unit (100) integrated into a rim (111) of a wheel (112), comprising an axial flux machine (118) and an eddy current brake (120), wherein a common rotor (106) is provided for the axial flux machine (118) and the eddy current brake (120).

2. Combined drive / brake unit (100) according to claim 1, wherein the axial flux machine (118) comprises a first stator (102), a second stator (103) and a rotor (106) which is arranged axially between the first stator (102) and the second stator (103) and is rotatable relative thereto, and the axial flux machine (118) has a mirror-symmetrical structure.

3. Combined drive / brake unit (100) according to one of claims 1 to 2, wherein the inner region (206) of the rotor (106) comprises a material with low electrical conductivity or comprises a plurality of individually insulated sheets and the outer region (208) of the rotor (106) comprises a material with high electrical conductivity.

4. Combined drive / brake unit (100) according to one of claims 1 to 3, wherein a thermal separation (202) of the rotor (106) is provided to prevent heat input from the eddy current brake (120) into the axial flux machine (118), in particular in the region of magnets attached to the rotor (106).

5. Combined drive / brake unit (100) according to claim 4, wherein the thermal separation (202) is provided by an inserted ring (204).

6. Combined drive / brake unit (100) according to claim 5, wherein the inserted ring (204) comprises a plastic material with a low thermal conductivity.

7. Combined drive / brake unit (100) according to claim 5, wherein the inserted ring (204) comprises a ceramic material with a low thermal conductivity.

8. Combined drive / brake unit (100) according to claim 5, wherein the inserted ring (204) comprises a porous material.

9. Combined drive / brake unit (100) according to claim 4, wherein the thermal separation (202) is achieved by a material taper by means of recesses on the rotor (106).

10. Combined drive / brake unit (100) according to one of claims 1 to 9, wherein the rotor (106) has at least one cooling channel (302) in the outer region (208) of the rotor (106) near the eddy current brake (120).

11. Combined drive / brake unit (100) according to one of claims 1 to 10, wherein the axial flux machine (118) has permanent magnets (104).

12. Combined drive / brake unit (100) according to one of claims 1 to 11, wherein the eddy current brake (120) comprises electromagnets (108).

13. Combined drive / brake unit (100) according to one of claims 1 to 12, wherein the rotor (106) of the axial flux machine (118) has electromagnets (108).

14. Combined drive / brake unit (100) according to one of claims 1 to 13, wherein a cooling air flow (304) runs through the cooling channel (302) from the inner tire edge (128) through the cooling channel (302) to the outer tire edge (126) of the rim (111).

15. Use of the combined drive / brake unit (100) according to one of the preceding claims 1 to 14, as a single-wheel drive.

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