Propulsion and braking unit for electric or hybrid vehicles

Abstract

A propulsion and braking unit (10) for electric or hybrid vehicles comprises an outer stator (12), equipped with first (14) and second (16) windings and with an outer wall (18) with an annular cavity (20) adjacent to the second windings (16) in which a magneto-rheological fluid (22) is contained, a first propulsion rotor (24) rotatably arranged in the stator (12) to form with the first windings (14), when powered, an electric motor for the propulsion of the vehicle, and a second braking rotor (26) rotatably arranged in the stator (12), rotationally integral with the first propulsion rotor (24) and having an end (28) rotatably housed in the cavity (20). An outer surface (30) of the end (28) is in contact with the magneto-rheological fluid (22) to form, with the second windings (16) and the magneto-rheological fluid (22), a brake for braking the vehicle when the second windings (16) are powered.

Description

[0001] Propulsion and braking unit for electric or hybrid vehicles

[0002] Technical field

[0003] The present invention relates to propulsion and braking units for electric or hybrid vehicles.

[0004] Prior art

[0005] Many vehicles are currently designed to minimise the production of carbon dioxide (CO2) emissions, nitrogen oxides and their mixtures (NOX), and particulate matter produced during the operation of the vehicle itself, in particular during the braking phase.

[0006] Electric and / or hybrid vehicles are capable of significantly reducing emissions related to internal combustion engines. However, the emissions due to a combustion engine represent only part of the total emissions of a vehicle during its operation. Other non-negligible sources of emissions are, for example, related to the braking systems.

[0007] Typically, the electric motors of electric and / or hybrid vehicles are designed to generate propulsion of the vehicle itself when a user activates the propulsion control, and to generate electric energy, which is stored in the battery of the vehicle, when the user activates the braking control. This energy storage function during braking phase is called regenerative braking, and its efficiency is determined by a plurality of parameters, for example the state of charge of the vehicle battery. In support of the regenerative braking of the electric motor, braking systems with disc brakes are typically used.

[0008] In the art, solutions have been proposed in support of regenerative braking as alternatives to disc brakes, which are designed to reduce emissions during the braking phase. For example, braking systems with pads made of alternative materials having higher percentages of biodegradable components have been proposed, or braking systems equipped with devices adapted to suck in the metallic particulate matter produced by the brake pads during braking.

[0009] In addition, to support regenerative braking, electromagnetic braking systems have also been used, such as eddy-current brakes, Hall effect brakes, and magnetic hysteresis brakes. Although such braking systems do not produce particulate emissions during the braking phase of the vehicle, that is, they are zero-emission, they feature large sizes and masses, and limited performance at low speeds, characteristics that make them unsuitable for use in the automotive sector.

[0010] Also known in the art are braking systems for electric vehicles that use magneto-rheological fluids; however, such solutions present limitations related to the generation of braking torque and to the performance generated in the presence of high temperatures.

[0011] Patent 102022000009272, of the same applicant, describes an electric motor and related magneto-rheological braking system, configured to be arranged on a wheel of the electric vehicle. Such motors are called “in-wheel” motors and, although they are capable of reducing particulate emissions, they have the limitation of being arranged downstream of the suspension system and, therefore, of forming unsprung masses of the vehicle that contribute to increasing the total vibrations of the vehicle, which are transmitted to the user. Moreover, when using in-wheel motors, it is necessary to provide at least one electric motor and related braking system for each driving wheel of the vehicle.

[0012] Summary of the invention

[0013] A main object of the present invention is to make a propulsion and braking unit for electric vehicles capable of minimising particulate emissions.

[0014] Another object of the present invention is to make a propulsion and braking unit capable of increasing comfort for the user during use of the vehicle. In particular, an object of the invention is to reduce the vibrations of the vehicle perceived by the user during use.

[0015] A further object of the present invention is to reduce the structural complexity and the number of components of the braking system, also reducing assembly and maintenance times. The aforementioned and other objects and advantages, which will be better understood below, are achieved according to the present invention having the features set out in independent claim 1. Preferred embodiments of the invention are defined in the dependent claims.

[0016] In summary, a propulsion and braking unit for electric or hybrid vehicles adapted to allow propulsion or braking of electric or hybrid vehicles according to a request by a user comprises an outer stator, equipped with first and second windings, and having an outer wall in which an annular cavity is provided, arranged adjacent to said second windings and wherein a magneto-rheological fluid is contained. The propulsion and braking unit further comprises a first propulsion rotor equipped with at least one permanent magnet or third windings and rotatably arranged within said stator so as to form with the first windings an electric motor for propulsion of the electric or hybrid vehicle when said first windings are powered, and also comprises a second braking rotor arranged within said stator, rotationally integral with the first propulsion rotor and configured such that the second braking rotor has an end rotatably housed in the cavity of the stator and an outer surface of said end is in contact with the magneto-rheological fluid contained in the cavity to form with the second windings and with the magneto-rheological fluid a brake for braking the electric or hybrid vehicle when said second windings are powered.

[0017] Brief description of the drawings

[0018] The features and advantages of the present invention will be evident from the following description, provided by way of example and not limitation. Reference is made to the accompanying drawings, in which:

[0019] Figure 1 is a perspective view of the propulsion and braking unit,

[0020] Figure 2 is a lateral sectional view of one embodiment of the propulsion and braking unit,

[0021] Figure 3 is an enlarged- scale lateral sectional view of part of the embodiment of the propulsion and braking unit of Figure 2, and

[0022] Figure 4 is a lateral sectional view of an alternative embodiment of the propulsion and braking unit. Detailed description

[0023] The figures illustrate a propulsion and braking unit 10 suitable to be mounted on board electric or hybrid vehicles to allow propulsion and / or braking thereof according to a request by a user. Such propulsion and braking unit is suitable to be mounted to the chassis of the electric or hybrid vehicle, upstream of the suspensions, so as to limit the vibrations deriving from the unsprung masses, that is, the masses of the wheels and of the bodies connected thereto, so as to advantageously increase the comfort of the user during use of the electric or hybrid vehicle.

[0024] The propulsion and braking unit 10 comprises an outer stator 12, a first propulsion rotor 24 and a second braking rotor 26 rotatably arranged within the stator 12.

[0025] Preferably, the propulsion and braking unit 10 defines a longitudinal axis x around which the first propulsion rotor 24 and the second braking rotor 26 rotate. In the following of the present description, terms and references indicating directions such as “axial”, “radial” and “transverse” are to be interpreted with reference to the longitudinal axis x, unless otherwise indicated.

[0026] The stator 12 of the propulsion and braking unit 10 is an outer stator of substantially cylindrical shape that defines an internal cylindrical cavity in which the first propulsion rotor 24 and the second braking rotor 26 are rotatably housed.

[0027] The stator 12 comprises an outer wall 18 that delimits the stator, and is provided with first windings or coils 14 and second windings or coils 16 which may be axially spaced from each other. Preferably, the outer wall 18 of the stator 12 has a predetermined thickness and the first windings 14 and / or the second windings 16 may be arranged within the thickness of the outer wall 18, for example in respective niches or housing seats, so as to be axially spaced from one another. In the outer wall 18 of the stator 12 an annular cavity 20 is also provided, arranged adjacent to the second windings 16 and wherein a magneto-rheological fluid 22 is contained. A magneto-rheological fluid is a fluid that typically comprises a carrier fluid, for example a mineral, silicone or synthetic oil, magnetic particles, for example carbonyl iron particles, dispersed in the carrier fluid, and additives to prevent sedimentation or agglomeration of the particles in the carrier fluid. The magneto-rheological fluid is capable of varying its properties, for example its viscosity, when subjected to a magnetic field. In particular, in the absence of a magnetic field the magneto-rheological fluid has low apparent viscosity and behaves like an oil, while in the presence of a magnetic field the magneto-rheological fluid has high apparent viscosity and behaves like a semi-solid.

[0028] The annular cavity 20 may be provided so as to have at least one side wall, for example a radially outer wall and / or a radially inner wall, in proximity to the second windings 16 such that when the second windings 16 are traversed by electric current they generate a magnetic field capable of varying the properties of the magneto-rheological fluid 22 contained within the cavity 20 and of maximising the effect of the magnetic field on the magneto-rheological fluid 22.

[0029] In one embodiment, the stator 12 may comprise a first portion 36 wherein the first windings 14 are arranged and a second portion 38 wherein the cavity 20 and the second windings 16 are present. The first portion 36 may have a first outer diameter and the second portion 38 may have a second outer diameter, different from the first outer diameter. The difference in diameter between the first 36 and second 38 portion advantageously allows the two portions 36, 38 of the propulsion and braking unit to be designed independently from each other so as to optimise their overall dimensions according to requirements.

[0030] Within the stator 12, preferably in the first portion 36 of the stator 12, the first propulsion rotor 24 is rotatably housed, which is equipped with at least one permanent magnet or third windings 25 so as to form with the first windings 14 of the stator 12 an electric motor for the propulsion of the electric or hybrid vehicle when the first windings 14 are powered. The first windings 14 may be powered by actuation by the user of a propulsion control, for example an accelerator pedal, present in a passenger compartment of the electric or hybrid vehicle in order to move the vehicle forward.

[0031] Within the stator 12, preferably in the second portion 38 of the stator 12, the second braking rotor 26 is also rotatably housed, which is rotationally integral with the first propulsion rotor 24.

[0032] In one embodiment, the first propulsion rotor 24 and the second braking rotor 26 may be two separate elements joined together by a mechanical joint, for example by a rigid joint or an elastic joint.

[0033] In an alternative embodiment, the first propulsion rotor 24 and the second braking rotor 26 may be two parts of a single rotor or rotating element.

[0034] The second braking rotor 26 has an end 28 that is rotatably housed in the cavity 20 of the stator 12. This end 28 has an outer surface 30 that is in contact with the magneto-rheological fluid 22 contained in the cavity 20 (Figure 3) so as to form, with the second windings 16 and the magneto-rheological fluid 22, a brake for braking the electric or hybrid vehicle when the second windings 16 are powered. The second windings 16 may be powered by actuation by the user of a brake control, for example a brake pedal, present in a passenger compartment of the electric or hybrid vehicle in order to slow down or stop the vehicle.

[0035] The first part 36 of the stator 12 equipped with the first windings 14 and the first rotor 24 equipped with the at least one permanent magnet or third windings 25 may together form an electric motor. The second part 38 of the stator 12 equipped with the second windings 16 and the cavity 20, the second rotor 26 and the magneto-rheological fluid 22 contained in the cavity 20 may together form a magneto-rheological brake. Advantageously, the propulsion and braking unit 10 of the present invention comprises in a single solution or compact device an electric motor and a magneto-rheological brake, allowing the number of components on board the electric or hybrid vehicle to be reduced. According to one embodiment, the annular cavity 20 provided in the stator 12 may have an inner wall 32 that may form with the outer surface 30 of the end 28 of the second braking rotor 26 a gap 34 (Figure 3), which preferably has a constant height and is configured to contain the magneto-rheological fluid 22. In other words, the gap 34, in which the magneto- rheological fluid 22 is contained, may be delimited by the inner wall 32 of the cavity 20 and by the outer surface 30 of the end 28 of the second braking rotor 26.

[0036] An inlet opening of the cavity 20 for the entry of the second braking rotor 26 may comprise sealing means, for example a gasket, so as to prevent leakage of the magneto-rheological fluid 22 from the cavity 20 and / or the inlet of dust or polluting particles into the cavity 20.

[0037] With reference to the second braking rotor 26, it may preferably comprise a radially inner hub part 40 mechanically connected to the first propulsion rotor 24, a radially outer tubular part 42 arranged in the cavity 20 of the stator 12, and a connecting part 44 extending in the radial direction from the hub part 40 to the tubular part 42 (Figures 2 and 4).

[0038] In one embodiment, the connecting part 44, which connects the tubular part 42 to the hub part 40 of the second braking rotor 26, may be discoidal. In other words, the second braking rotor 26 may be connected to the first propulsion rotor 24 by means of the hub part 40, the connecting part 44 may be a disc having two opposite transverse faces, flat, circular and solid, and the connecting part 44 terminates with the tubular part 42 which may rotate in the cavity 20 of the stator 12.

[0039] In an alternative embodiment, the connecting part 44, which connects the tubular part 42 to the hub part 40 of the second braking rotor 26, may comprise a plurality of elements angularly spaced from each other. In other words, the connecting part 44 may comprise a plurality of spokes extending in the radially outer direction from the hub part 40 to the tubular part 42 so as to connect the tubular part 42 to the hub part 40.

[0040] Preferably, the connecting part 44 and the tubular part 42 of the second braking rotor 26 may together have a T-shape in axial section (Figure 3). In other words, the connecting part 44 and the tubular part 42 may be perpendicular to each other and the tubular part 42 may be parallel to the longitudinal axis x of the propulsion and braking unit 10.

[0041] In an alternative embodiment not illustrated in the figures, the tubular part 42 may be inclined and form a predetermined angle with the longitudinal axis x of the propulsion and braking unit 10.

[0042] The second braking rotor 26 may comprise a plurality of tubular parts 42 coaxially arranged to one another and contained in the cavity 20 of the stator 12 (Figure 4). The plurality of tubular parts 42 may be radially spaced from each other so as to allow the magneto- rheological fluid contained within the cavity 20 to contact the outer surface 30 of each tubular part 42 and increase the braking force applied to the second braking rotor 26 when the second windings 16 are actuated and the apparent viscosity of the magneto-rheological fluid 22 increases.

[0043] In one embodiment, the cavity 20 may be shaped correspondingly to the plurality of tubular parts 42 so as to minimise the amount of magneto-rheological fluid contained in the brake.

[0044] The propulsion and braking unit 10 may comprise a single cooling system arranged adjacent to the stator 12, to the first propulsion rotor 24 and / or to the second braking rotor 26 and is configured to cool the first windings 14, the second windings 16 and the magneto- rheological fluid 22 so as to advantageously reduce the consumption related to the cooling of the system and maximise its efficiency.

[0045] For example, the single cooling system of the propulsion and braking unit 10 may comprise a duct having a single inlet and a single outlet and comprising one or more coils arranged adjacent to the first windings 14 and the second windings 16 of the stator 12 and adjacent to the cavity 20 in which the magneto-rheological fluid 22 is contained. The duct may for example be made of copper or aluminium.

[0046] Various aspects and embodiments of the propulsion and braking unit have been described. It is understood that each embodiment may be combined with any other embodiment. Furthermore, the invention is not limited to the described embodiments, but may be varied within the scope defined by the appended claims.

Claims

CLAIMS1. A propulsion and braking unit (10) for electric or hybrid vehicles adapted to allow propulsion or braking of electric or hybrid vehicles according to a request of a user, said propulsion and braking unit (10) comprising:- an outer stator (12) equipped with first (14) and second (16) windings and having an outer wall (18) wherein an annular cavity (20) is provided, wherein the cavity (20) is arranged adjacent to said second windings (16) and wherein a magneto-rheological fluid (22) is contained in the cavity (20),- a first propulsion rotor (24), equipped with at least one permanent magnet or third windings (25), is rotatably arranged within said stator (12) so as to form with the first windings (14) an electric motor for propulsion of the electric or hybrid vehicle when said first windings (14) are powered,- a second braking rotor (26) rotatably arranged within said stator (12), rotationally integral with the first propulsion rotor (24) and configured such that the second braking rotor (26) has an end (28) rotatably housed in the cavity (20) of the stator (12), and an outer surface (30) of said end (28) is in contact with the magneto-rheological fluid (22) contained in the cavity (20) to form with the second windings (16) and with the magneto-rheological fluid (22), a brake for braking the electric or hybrid vehicle when said second windings (16) are powered.

2. The propulsion and braking unit (10) according to claim 1, wherein the cavity (20) has an inner wall (32) forming with the outer surface (30) of the end (28) of the second braking rotor (26) a gap (34) having a constant height and configured to contain the magneto- rheological fluid (22).

3. The propulsion and braking unit (10) according to claim 1 or 2, wherein the stator (12) comprises a first portion (36) wherein the first windings (14) are provided and having a first diameter, and a second portion (38) wherein the cavity (20) and the second windings (16) are provided and having a second diameter, different from the first diameter.

4. The propulsion and braking unit (10) according to any one of the preceding claims, defining a longitudinal axis (x) around which the first propulsion rotor (24) and second braking rotor (26) rotate, wherein the second braking rotor (26) comprises a radially inner hub part (40) mechanically connected to the first propulsion rotor (24), a radially outer tubular part (42) arranged in the cavity (20) of the stator (12) and a connecting part (44) extending in radial direction from the hub part (40) to the tubular part (42).

5. The propulsion and braking unit (10) according to claim 4, wherein the connecting part (44) is discoidal.

6. The propulsion and braking unit (10) according to claim 4, wherein the connecting part (44) comprises a plurality of elements angularly spaced apart.

7. The propulsion and braking unit (10) according to any one of claims 4 to 6, wherein the connecting part (44) and the tubular part (42) together have a T-shape in axial section.

8. The propulsion and braking unit (10) according to any one of the preceding claims, wherein the second braking rotor (26) comprises a plurality of tubular parts (42) coaxial to each other and contained in the cavity (20) of the stator (12).

9. The propulsion and braking unit (10) according to any one of the preceding claims, comprising a single cooling system arranged adjacent to the stator (12), the first propulsion rotor (24) and / or the second braking rotor (26) and configured to cool the first windings (14), the second windings (16) and the magneto-rheological fluid (22).

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