NL2021283B1

NL2021283B1 - Steering knuckle and in-wheel motor for electric vehicle.

Info

Publication number: NL2021283B1
Application number: NL2021283A
Authority: NL
Inventors: Walhout Marko
Original assignee: Atlas Technologies Holding Bv
Priority date: 2018-07-11
Filing date: 2018-07-11
Publication date: 2020-01-20

Abstract

The invention relates to an assembly for an electric or hybrid vehicle, the assembly comprising an in-wheel motor and a steering knuckle, the motor comprising a stator and a rotor, the rotor at least partly surrounding the stator, the rotor rotatable around an axis, the stator comprising a metallic part and a surrounding part connected to the metallic part and surrounding the metallic part, the surrounding part comprising electric coils and magnetizable cores characterized in that the metallic part and the steering knuckle form one integral part.

Description

Technical field of the invention.

[0001] The invention relates to an assembly for an electric or hybrid vehicle, the assembly comprising an in-wheel motor and a steering knuckle, the motor comprising a stator and a rotor, the rotor at least partly surrounding the stator, the rotor rotatable around an axis, the stator comprising a metallic part and a surrounding part connected to the metallic part and surrounding the metallic part, the surrounding part comprising electric coils and magnetizable cores.

Background of the invention.

[0002] Electric and hybrid vehicles, especially electric and hybrid cars with in-wheel motors are known for a long time. As an example the Lohner Porsche shown at the Paris world exhibition showed four in-wheel motors, while the Lohner-Porsche Mixte Hybrid introduced in 1900 was the first hybrid vehicle with in-wheel motors and a combustion engine. Recently the interest in in-wheel motors renewed.

[0003] There are different kinds of in-wheel motors. A common type has a rotor with permanent magnets surrounding a stator comprising electromagnets.

[0004] The rotor rotates around an axis, and bearings, for example ball or cylinder bearings, allow rotation of the rotor around an axle of the stator. The axle of the stator ends at one side of the in-wheel motor, while the other side connects to a steering knuckle (also referred to as the upright), that via a ball joint and a wheel suspension system, for example a double wishbone suspension, connects the in-wheel motor to the rest of the vehicle.

[0005] It is noted that such motors are known from, for example, European Patent application EP2618466 (A1), describing an Axial Field Permanent Magnet motor, although other types, such as the Radial Field Permanent Magnet motor, and the reluctance motor, are known.

[0006] On the in-wheel motor also a brake, either a drum brake of a disk brake, is mounted. The advantages of a disk brake over a drum brake are well known, although space restrictions may trigger the use of a drum brake (see for example Elaphe’s S400, manufactured by Elaphe Propulsion Technologies Ltd, Ljubljana, Slovenia, and disclosed at http://in-wheel.com/product-category/motors/).

[0007] The present in-wheel motors for vehicles often need cooling, preferably by the use of a cooling liquid that is cooled in a central radiator and fed to the stator and/or rotor for cooling, after which it is guided back to the radiator. Such a system is known from, for example, US patent No. US 7,256,526 B1.

[0008] Another such system is known from US patent application publication no. US2014132058 (A1), describing a system with build-in oil pump using a radiator external to the motor.

[0009] It is remarked that the electric coils that generate the electromagnetic fields must be wired to the so-called inverters of the vehicle, the inverters providing the correct AC voltages and currents for the coils. Also sensor wiring must be fed from the motor to the vehicle.

[0010] Mechanically this area is filled with the steering knuckle, as well as suspension and steering components.

[0011] From the above it is clear that the space around the in-wheel motor is rather cluttered with coolant tubes, power wiring and sensor wiring, as well as mechanical components. This results in a complicated design, with many parts and resulting from this a high price for all the parts and joints. Also, the chance of mechanical failure rises when the number of parts and joints increases.

[0012] US patent application US2014159468A1 proposes in its paragraph [0040] to reduce the number of parts in an in-wheel motor assembly by integrating the rim, wheel plate, hub and brake drum as a single piece, thereby providing a strong and lightweight yet simple construction.

[0013] The invention intends to provide a further simplification and reduction in parts of the assembly, resulting in a simpler, cheaper and more reliable assembly.

Disclosure of the invention.

[0014] To that end an assembly according to the invention is characterized in that the metallic part and the steering knuckle form one integral part.

[0015] Inventor realized that, as the central part of the in-wheel motor (often an axle) is stationary, is can be integrated with other parts stationary to that part. The steering knuckle (also named upright) is such a part. By integrating these parts into one integral part, the number of parts is reduced, as well as the number of joints, where parts are welded or bolted together. As known in industry, reduction in parts typically results in reduction of price, and often a higher reliability.

[0016] In an embodiment of the invention the integral part is made using a manufacturing technique from the group of 3D printing techniques, casting and forging.

[0017] The aforementioned manufacturing techniques are especially suited for making high strength parts with complicated shapes, such as necessary in automotive applications where axle and steering knuckle are integrated.

[0018] In another embodiment of the invention the integral part is made of one material. [0019] Although not in all cases, often the assembly will be made of one material, such as an aluminium alloy, a steel alloy, or such like.

[0020] In a preferred embodiment the stator shows a part to be cooled by a fluid, the integral part showing channels, the fluid guided through the channels.

[0021] The high-performance in-wheel motors used nowadays need cooling. Although air cooling is used, liquid cooling is more efficient and allows in-wheel motors with a higher power. This implies cooling hoses, and the risk of damage to those hoses. By integrating channels in the integral part, a further reduction in parts is realized and the chance of damage is reduced.

[0022] In an embodiment the integral part shows one or more wiring channels, and wiring for energizing the electric coils is guided through the one or more wiring channels in the integral part.

[0023] An in-wheel motor needs several groups of electric wires to energize the electric coils. By guiding these wires in channels, or at least grooves, in the integral part, dangling wires are avoided and the chance of damage to the wires is minimized.

[0024] In another embodiment a brake disk is mounted on the rotor and a brake caliper on the integral part, brake disk and brake caliper together forming a disk brake, the brake disk situated between the part of the integral part forming the stator and the part of the integral part forming the steering knuckle, the braking disk having a central hole with a diameter sufficiently large that it can be removed over the part of the integral part that forms the steering knuckle.

[0025] As known to the skilled artisan, the braking disk must be exchanged several times in the lifetime of a car. Therefore, it cannot be a part of the integrated part. To enable mounting the braking disk it must fit over the steering knuckle. Replacement over the other side is impossible, as the diameter of the rotor, even when the rim is removed, is typically even larger.

[0026] In yet another embodiment a brake disk is mounted on the rotor and a brake caliper is mounted on the integral part, brake disk and brake caliper together forming a disk brake, the brake disk comprising brake segments on which one or more brake pads of the brake caliper can exert friction.

[0027] This type of braking system is known from heavy duty train and airplane brakes, and described in e.g. US patent US4,155,432. The disk is covered by several brake segments, and the regular replacing of brake parts now involves replacing brake pads of the caliper(s) and replacing the brake segments. As none of these completely surround the integral part between stator and steering knuckle, the exchange does not involve dismounting the in-wheel motor and the moving parts over the steering knuckle, thus greatly reduces maintenance effort.

[0028] In still another embodiment a drum brake is mounted on the rotor and integral part.

[0029] As an alternative to the disk brake a drum brake can be used. Although drum brakes are often associated with overheating problems, electric cars suffer less from this problem as most of the kinetic energy is retrieved by the electric motor acting as a brake. Therefore the drum brake in an electric or hybrid vehicle dissipates less energy than in a non-electric or non-hybrid vehicle.

As for the disk brake, the drum brake should show an inner diameter large enough to fit over the steering knuckle, or the replaceable parts of the drum brake should be formed as segments, both the shoes and the brake drum.

[0030] In yet another embodiment the stator comprises at least three axles on a diameter removed from the center of the motor, each axle equipped with at least one bearing, the rotor rotating on the outside of said bearings or a housing surrounding said outside of the bearing.

[0031] In this embodiment much of the stator material around the axis can be removed, ultimately resulting in a wheel showing a hole at the axis, resulting in a wheel with less mass.

[0032] In still another embodiment the rotor comprises at least three axles on a diameter removed from the axis with one bearing one each of the axles, the stator rotating on the outside of said bearings, and the stator showing a hole around the axis, resulting in a wheel with less mass than a wheel with a central axle.

[0033] This is almost identical to the prior embodiment, but the position of the axles is now in the rotor instead of in the stator. A small disadvantage of this embodiment compared to the embodiment where the axle is in the stator, is that, due to the rotation of the rotor, there is an enlarged chance of imbalance of the wheel.

[0034] In yet another embodiment between the rotor and the stator at least one large diameter bearing is positioned, and the stator shows a hole around the axis, resulting in a wheel with less mass than a wheel with a central axle.

Brief description of the figures.

[0035] The invention is now elucidated using figures, in which identical reference signs indicate corresponding features. To that end:

Figure 1 schematically shows a prior art assembly of in-wheel motor and steering knuckle, with a rim-and-tire fitted to it.

Figure 2 schematically shows an assembly according to the invention,

Figure 3 schematically shows an assembly according to the invention in which the stator is hollow around the axis.

Figure 4 schematically shows a variant of the assembly shown in figure 3.

Detailed description of the invention.

[0036] Figure 1 schematically shows a prior art assembly of in-wheel motor and steering knuckle.

[0037] Assembly 100 shows a symmetry axis 102. The metallic part of the stator 104 and rotor 110 are rotationally symmetric around symmetry axis 102. Rotor 110 is mounted on stator 104 via bearings 112a and 112b. The metallic part of the stator 104 is surrounded by a ring 106 of electrically non-conductive material, in which a number of electromagnets108-n are mounted. The rotor 110 shows a number of permanent magnets 114-m. Typically m is not equal to n, so that not at one moment all permanent magnets can face an electromagnet. However, versions in which equal numbers of permanent magnets and electromagnets are used are known.

[0038] A rim 150 is mounted on the rotor with several screws 154-q. A tire 152 is mounted on the rim.

[0039] The steering knuckle 116, also known as the upright, is bolted on the metallic part of the stator 104 using several bolts 118-p.

[0040] It is noted that the set-up shown here is known as an Axial Field Permanent Magnet motor. Radial Field Permanent Magnet motors are also known, where the coils and magnets have a different position. Literature shows several other types of in-wheel motors, equally relevant to the invention.

It is further noted that, instead of a demountable attachment between stator and steering knuckle using bolts 118-p, other types of joints may be used.

[0041] The force between the permanent magnets and the electromagnets result in a torque between rotor and stator, which in turn results in a rotation of the rotor and the tire (152) mounted on the rotor. By rotating the field generated by the electromagnets the torque between stator and rotor stays present, even when the wheel is rotating, although a torque ripple may occur.

[0042] It is noted that, although the rotor, stator and bearings all show rotational symmetry around the axis, the steering knuckle does not show this symmetry, but has a more complex shape.

[0043] It is further noted that an in-wheel motor assembly typically also shows a brake, either a drum brake or a disk brake. Also sensors, for example ABS (Anti-lock Brake System) are typically integrated in the assembly.

[0044] Figure 2 schematically shows an assembly according to the invention.

[0045] The assembly 200 shown in figure 2 can be thought to be derived from the assembly 100 shown in figure 1. The metallic part of the stator, in figure 1 shown as numeral 104, and the steering knuckle, in figure 1 shown as numeral 116, are integrated in one part 202.

[0046] By integrating the steering knuckle and the metallic part of the stator, also the joint (in figure 1 the screws 118-p or the aforementioned welds) are eliminated. Bearing 112b now shows a larger inner diameter, as it should fit over the steering knuckle. Therefore the inner diameter of the bearing, shown as diameter d, must be larger than the size indicated by size D.

[0047] It is noted that, as an alternative to a large diameter bearing 112b, also one or more bearings at the side of bearing 112a can be used, provided they fulfill the changed demands associated with the one-sided bearing.

It is further noted that the integral part may consist of one uniform material, such as an aluminium alloy or a steel alloy, but that also an integral part with several materials is envisioned, for example an aluminium alloy forming the metallic part of the stator and a titanium alloy forming (part of) the steering knuckle.

Many techniques are known to produce such an integral part, among which 3D printing techniques, casting and forging. In this context one or more pre- and/or postprocessing steps may be included in the production of such an integral part, such as surface finishing steps, the forming of holes, etc.

[0048] A further optimization of the integral part comprises forming channels in the integral part to guide cooling fluid to and from parts in the stator part of the integral part that need to be cooled. Also grooves for guiding electric wiring (power wiring for the electromagnets, and wiring for sensor wiring) can be integrated.

[0049] Integrating cooling channels and electric channels within the stator are known from, for example, US patent no. US7,256,526B1. From this patent the skilled artisan can port the idea to the invention described here, resulting in an integral part with cooling channels for enclosing and guiding cooling fluids (gasses, liquids) and/or electric channels and/or electric grooves for guiding electric power wiring, the power wiring for energizing the electromagnets, and/or guiding sensor wiring.

[0050] An electric or hybrid vehicle can brake and recover electric energy using the electric motor. However, legislation requires another brake as well. Typically, the brake is positioned between the rotor (on which it is mounted) and the steering knuckle. Two types of brakes are used most often, a disk brake or a drum brake.

[0051] As known to the skilled artisan a disk brake typically has a disk of metal connected to the rotor, and one or more braking pads that are actuated by the brake caliper or calipers. Both braking disk and braking pads need replacement during the lifetime of the vehicle. For the brake pads this is not a problem, as they do not enclose part of the integral part, but the brake disk needs to be removed over the steering knuckle. This implies that a disk brake with a relative large central hole needs to be used.

[0052] A drum brake is typically positioned between rotor and steering knuckle. Here as well care should be taken that all parts should fit over the steering knuckle, in figure 2 indicated by diameter D. An alternative, proposed in previously mentioned US patent application US2014159468A1, is to place the drum brake between rotor 110 and rim 150, although this implies that at least parts of the integral part must extend to a diameter where the drum brake can be mounted (the drum brake needs to be fixed between stator and rotor), and that the rotor, and thus the motor, has a smaller diameter, as the drum brake takes up space between the rotor and the rim. This might have a negative impact on power and torque of the motor, or more precise, the tire 152. By integrating the braking drum and the rim, a further reduction of parts is reached. However, from a thermal point of view it might be preferred to form the (exchangeable) braking drum as a cylinder surrounding the rotor and mounted on the rotor, so that heating of the tire by the brake drum is prevented or at least minimized.

[0053] Figure 3 schematically shows an assembly according to the invention in which the stator is hollow around the axis.

[0054] Assembly 300 shows an integral unit of which parts 302, 304 and 306 do not show rotational symmetry round axis 102, while the other parts to a large degree do show symmetry round axis 102. By using bearings 112a, 112b with a large inner diameter, the center of the stator can be eliminated. This elimination of material reduces weight, and results ultimately in a hollow stator 308. However, large diameter bearings are often heavy, counteracting the weight reduction by the removal of material of the stator. It is worth mentioning that part 302 may be superfluous, but in other cases be necessary for robustness.

[0055] Figure 4 schematically shows a variant of the assembly shown in figure 3.

[0056] Figure 4 shows a variant 400 of the assembly shown in figure 3 with a lighter construction. This is achieved by replacing the two large diameter bearings 112a, 112b by several smaller bearings. The stator (the integral part) comprises several axles 402a, each of the axles connected with the inner shell of a bearing 404a. Preferably at least three or more bearings on one side of the stator and an identical number on the other side of the stator. The rotor ‘rolls’ over the outside of the bearings, or a housing surrounding this outer shell of the bearings.

[0057] It is noted that other configurations than two planes of three bearings can be used. A configuration of two planes with two bearings each (rotated by preferably 90 degrees) is possible. It should however be kept in mind that the bearings must withstand high static and dynamic loads, as well as a combination of radial and axial loads.

[0058] It is also possible to mount the axles on the rotor and have the outer shells of the bearing contact the stator. However, this is less attractive because there is a risk of unbalance due to the rotating bearings, something that does not occur when the bearing’s axle is located in the stator. It is also possible to form the axles as a number of axles penetrating through the stator, each axle showing a bearing on each side of said axle.

Claims

Conclusions.

An assembly for an electric or hybrid vehicle, the assembly comprising an in-wheel motor and a stub axle, the motor comprising a stator and a rotor, the rotor at least partially surrounding the stator, the rotor rotatable about an axis, the stator comprising a metal part containing a metal part and a surrounding part connected to the metal part and surrounding the metal part;

2. The assembly of claim 1 where the integrated part is fabricated using a manufacturing technique from the group of 3D printing, casting and forging.

3. The assembly according to any one of the preceding claims, wherein the integrated part consists of one material.

The assembly according to any one of the preceding claims, wherein the stator has a part that is to be cooled by a gas or a liquid, the integrated part having channels through which the gas or the liquid can be passed.

The assembly according to any of the preceding claims, wherein the integrated component displays one or more wiring channels and / or wiring slots, and wherein wiring for driving the electrical coils is guided through the wiring channels and / or the wiring slots in the integrated component

The assembly of any one of the preceding claims wherein a brake disc is mounted on the rotor and a brake caliper is mounted on the integrated component, brake disc and brake caliper together forming a disc brake, the disc brake disposed between the part of the integrated component forming the stator and the part of the integrated part that forms the swivel, and wherein the brake disc has an inner diameter that is sufficiently large for the brake disc to be removed over the swivel.

The assembly according to any of claims 1-5 wherein a brake disc is mounted on the rotor and a caliper is mounted on the integrated component, brake disc and brake caliper together forming a disc brake, wherein the brake disc comprises brake segments on which the caliper can exert friction, and wherein the brake segments can be replaced while the integrated component remains connected to the vehicle.

The assembly of any one of claims 1-5 wherein a drum brake is mounted on rotor and integrated component.

The assembly according to any of the preceding claims, wherein the stator has at least three shafts on which bearings are mounted, the rotor rotating on said bearings, and the stator shows a hole around the shaft, resulting in an assembly with less mass than an assembly with material on the shaft.

The assembly of any one of the preceding claims wherein the rotor has at least three shafts on which bearings are mounted, the stator rotating on said bearings, and the stator showing a hole around the shaft, resulting in an assembly with less mass than an assembly with material on the shaft.

The assembly of any one of claims 1-8 wherein there is at least one bearing with a large inner diameter between rotor and stator and the stator has a hole around the shaft, resulting in an assembly with less mass than an assembly with material on the shaft .