Multispeed gearbox using magnetorheological fluid clutch apparatus for electric vehicle

Abstract

A vehicle powertrain may have: at least an electric motor; a gear assembly configured to couple at least one wheel of the vehicle to the motor for the at least one wheel to be driven by the electric motor, the gear assembly including a positive contact clutch for switching the gear assembly between at least a first gear ratio and a second gear ratio. An actuator controls the switching of the positive contact clutch. A magnetorheological (MR) fluid clutch apparatus is between the motor and the positive contact clutch, the MR fluid clutch apparatus configured to apply a variable amount of slippage between the motor and a component of the positive contact clutch, during coupling of the positive contact clutch in the switching.

Description

MULTISPEED GEARBOX USING MAGNETORHEOLOGICAL FLUIDCLUTCH APPARATUS FOR ELECTRIC VEHICLECROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the priority of United States Patent Application No. 63 / 588,393, filed on October 6, 2024, the contents of which are incorporated herein by reference.TECHNICAL FIELD

[0002] The present application relates generally to magnetorheological (MR) fluid clutch apparatuses and an operation of such MR fluid clutch apparatuses, such as in the context of electrical or hybrid vehicles.BACKGROUND OF THE ART

[0003] Magnetorheological (MR) fluid clutch apparatuses are known as useful apparatuses for transmitting motion / forces from a drive shaft, at a variable degree and with precision and accuracy, among other advantages. Accordingly, an increasing number of applications consider the use of MR fluid clutch apparatuses. In a known configuration, the MR fluid clutch apparatus has shear surfaces such as drums on both the input and the output, with MR fluid located in the annular gaps between the shear surfaces of the input and output. To magnetize the MR fluid located in the annular gaps, a magnetic field passes through the drums. Steel, for example, is commonly used as material for the drums of MR fluid clutch apparatuses.

[0004] There are, in some applications, constraints to maintain torque in the MR fluid clutch apparatus without power. State of the art MR fluid clutch apparatuses with a magnet in the magnetic circuit are able to maintain a fixed torque value when the MR fluid clutch apparatus is not powered as for example shown in PCT Application Publication No. WO 2016168934. In such MR fluid clutch apparatuses, the output starts slipping if the torque applied is larger than the fixed design torque that correspond to the magnetic field maintained in the MR fluid shear interface by the magnetizable component. In this type of MR fluid clutch apparatus, instead of creating a magnetic field in the MR fluid shear interfaces, the coil of the MR fluid clutch apparatus will re-direct the magnetic flux of the magnetizable component installed in parallel into a redirection gap. The control of the magnetic flux in the MR fluid shear interfaces may be controlledwith high bandwidth. When the power is removed from the coil, the magnetizable component may return to its state where it creates a magnetic field in the MR fluid shear area and the MR fluid clutch apparatus returns to a state where it provides its fixed design torque without the electromagnet being powered.

[0005] Electric vehicle powertrains generally employ a motor / generator unit that operate in concert with or without a gearbox to provide driving power to the wheels of a vehicle or equipment. Vehicles employing a multi-speed powertrain are well suited for urban transportation where a significant amount of stop and go driving is undertaken. Some of these vehicles can also include regenerative braking to recharge the electrical power storage devices (batteries), to store energy in a flywheel or to pressurise a fluid in a reservoir, only to name a few examples. During urban travel, the powertrain may take advantage of the power source and a multispeed gearbox to improve, as an example, performance and range. Electrical motors may be easy to control because they may have high bandwidths. On an electrical vehicle where high dynamic response is sought, the most common form of electromechanical actuation is found in direct- drive motors, which may be heavy for such modes of transportation. Device weight can be considerably reduced by providing a reduction ratio between the electric motor and the pedals or the wheel. Indeed, when coupled to reduction gearboxes, lighter and / or less expensive electromechanical actuators may be selected in comparison to direct drive solutions, but their high output inertia, friction and backlash may diminish their dynamic performance. They may not be controlled with the same bandwidth.

[0006] Low bandwidth of the powertrain may be caused by the high inertia of rotating parts that are opposed to speed changes in the system. Usually, the bandwidth of standard powertrains may decrease as the speed of its rotating parts increases, hence their reflected inertia also increases. For that reason, as the speed of rotating parts increases, the powertrain may lose its ability to adapt to the commanded speed.

[0007] Other non-vehicle devices or equipment may also have multispeed powertrains since they need to be able to provide power at various speeds. An example of this is a two-speed chain hoist. In such equipment, in a first operating mode, the hoist reels a chain rapidly with low force capability, while the hoist reels a chain slowly with high force capability in a second operating mode. The operator of the hoist may thus operate the system in the most optimal mode according to the operating load or condition. In order to switch the system from one modeto the other, the operator may need to stop the movement, which is not desirable for efficiency of the operation since time is lost.

[0008] Fine dynamic motion control of mechanical / mechatronic systems fundamentally implies high performance actuators that exhibit rapid dynamics (bandwidth), high torque density (e.g., Nm / kg), low inertia and / or efficiency. Rapid or high dynamics are critical for the actuator to have authority over the system (load). If the dynamics are insufficient, the actuator may not respond fast enough and may lose authority over the system (load). Typical high-dynamic actuators are direct-drive electric motors, that can reach speeds of several thousand RPM’s and have a force bandwidth over 30Hz. For torque density, in most mechanical or mechatronic systems, especially mobile systems that are in movement, such as electric vehicles, a high torque density is also required in order to minimise the system mass. Typical high torque density actuators are geared electric motors. The gearing allows a light weight system to generate high torque output, at the cost of reducing the output speed. The trade-off between torque (density) and dynamics imposed by the user of gearing between the actuator and load is a common and known engineering trade-off. Low inertia actuators are also important to maximise dynamic motion of a system. Lower inertia may translate into higher acceleration for a given force / torque (F = ma), and thus higher reactivity and better dynamics. Low inertia actuators also promote efficiency, as they expend less power fighting their own weight (inertia). Developing low inertia actuators is a major engineering challenge, for any system, as the reflected inertia at actuator output increases by the square of the gearing ratio (lout = x gearing2). Efficient actuators may also be important in order to minimise the weight of the system and the heat that it generates. If a system is not efficient, the system must be made larger (larger motor, power source, batteries, etc.) to compensate this loss of power. Moreover, the lost efficiency is converted to heat, which may require the oversizing of components and the addition of heat dissipation features (fins, cooling, etc.). Thus, gearing is often used to allow the actuator to work in its most efficient zone. For electric motors, gearing may be used to allow electric motors to work at higher speeds.

[0009] Consequently, actuator technologies may face a common fundamental trade-off, that is typically addressed or mitigated through appropriate gearing selection. This engineering challenge can be understood from an energetic perspective, such as shown in Fig. 1 of the prior art. When designing an actuator for a given application, the gearing trade-off between speed and torque limits the design space. When single gearing (A) is used, the size, weight and performance of the system is fixed by the maximum torque (To) and maximum speed (Wo)requirements, as shown in i) by the iso-torque condition. A lower gearing will not match the torque requirement and a higher gearing will not match the speed requirement. This provides a system with generally constant torque, or "iso-torque” output. Since the power is the product of torque and velocity, the power output from an "iso-torque” system linearly increases from zero at stall up to maximal power and the maximal speed, as observed in ii). In this condition, the system mass, size and performance may not be optimal since the same actuator may be oversized for most operating conditions.

[0010] To overcome this challenge, a second gearing (B) may be added to the system in order to change the torque, speed and power output profiles, using a selector (shifter) such as shown in Fig. 2. The actuator may be better suited to meet the maximum speed or torque with different gearings (A or B). The system now has a torque, velocity, and power profile as shown in iii). This strategy is commonly found in transportation vehicles, which may combine any number of gearing stages to better match the maximum speed and torque profile required for various conditions of driving. As the number of gearing ratios tend towards infinity, such as in a continuously variable transmissions, the system tends towards an "iso-power” as in vi) of Fig. 1 , between the larger gearing (A), that matches the maximum torque requirement, and the minimal gearing (B), that matches the maximum speed requirement. A constant power is thus provided between these two operating conditions. Amongst most important advantages, this configuration allows the system to have lower weight and better motor efficiency.

[0011] The problematics described above may be common to various applications where a combination of dynamics, torque density, low inertia and efficiency is required. Some applications may be bi-directional. One such application is an autonomous shuttle bus. Torque density and efficiency are thus a critical feature, which make geared electric motors a common choice for autonomous buses.

[0012] Other applications may be mostly unidirectional, such as electric vehicles. As it is well known for gasoline powered vehicles, electric motors may also be made smaller, lighter, and more efficient if they are combined to one of more gearing. It is common knowledge that vehicles require high torque at low speeds, and low torque at high speeds. When no selector or shifter is used, the motor must be sized for both conditions. Motors are thus oversized for most operating conditions. However, shifters / selectors are not commonly used in electric vehicles, since they provide an interruption in torque during the shifting between gears. Automatic transmissionsmay be a solution, but may be bulky, complex, inefficient, and / or have limited performance vs gain.

[0013] While a multiple gear solution presents several advantages to optimize the size and power of the system, a simple transmission system with adequate performance is desirable. Moreover, fundamental limits still exist in a geared system. For instance, the actuator inertia will still be reflected to the system output according to the instantaneous gearing.

[0014] A dog clutch transmission is a type of manual transmission that is commonly used in small vehicles, such as motorcycles, and heavy vehicles, such as trucks. The transmission uses a set of gears with teeth that engage with slots in a rotating drum, or "dog clutch," in a translational movement, to change the gear ratio.

[0015] One of the advantages of a dog clutch transmission is that it provides quick and precise shifting, which is important for high-performance vehicles. This type of transmission is also relatively simple and lightweight, which may be beneficial for efficiency and robustness.

[0016] While a dog clutch transmission can be an effective choice for some types of vehicles, there are potential drawbacks to using this type of transmission in an electric vehicle with a high- inertia electric motor. One issue is that a dog clutch transmission can create shock and wear on the gears during shifting, particularly when dealing with high inertial loads, when the speed of the motor side of the transmission is different than the speed on the wheel side during gear engagement. This can be especially problematic in an electric vehicle with a high-inertia motor. The shifting of such high-inertial motor may require excessive power consumption and / or unacceptable shifting delay to adjust the motor speed to the wheel speed for smooth shifts. Fast shifts can be performed without speed matching, but at the trade-off of an impact load upon gear engagement leading to loud “klunking” noises, premature wear and / or damage to the transmission, potentially reducing the lifespan of the vehicle and reducing user comfort.

[0017] A proposed solution is to use Powershift Synchronizer Transmissions (PSTs) using oversized cone synchronizers, which lead to bulky and expensive components. In the PST, torque transmission to the wheel may remain partial, due to torque and thermal limitations of the synchronizers and cone wear. Degradation in shift quality over time and challenge in torque control may make PSTs unsuitable as multi-speed transmissions for EVs. Dry or wet clutches may be used but issues regarding the high moment of inertia of electric motors, lining wear andthermal capacity of dry clutches can also be problematic for EVs, because of higher motor rotational speeds.

[0018] Another concern is that the shock and vibration generated by a dog clutch transmission can be more noticeable in an electric vehicle, which tends to be quieter and smoother than traditional combustion engines. This can lead to a less comfortable driving experience for passengers, and may even impact the overall performance of the vehicle.

[0019] Overall, while a dog clutch transmission can be an effective choice for some types of vehicles, it may not be the best choice for an electric vehicle with a high-inertia electric motor. For that reason, there is a need for an innovative solution to have a dog clutch to work in an electric vehicle.SUMMARY

[0020] It is an aim of the present disclosure to provide a novel multi-speed actuator that employs MR fluid coupling in order to connect a power source with a transmission.

[0021] Therefore, in accordance with a first aspect, there is provided a vehicle powertrain, comprising: at least an electric motor; a gear assembly configured to couple at least one wheel of the vehicle to the motor for the at least one wheel to be driven by the electric motor, the gear assembly including a positive contact clutch for switching the gear assembly between at least a first gear ratio and a second gear ratio; an actuator for controlling the switching of the positive contact clutch; and a magnetorheological (MR) fluid clutch apparatus between the motor and the positive contact clutch, the MR fluid clutch apparatus configured to apply a variable amount of slippage between the motor and a component of the positive contact clutch, during coupling of the positive contact clutch in the switching.

[0022] Further in accordance with the first aspect, for instance, the MR fluid clutch apparatus is located between the electric motor and a driving axle of the gear assembly.

[0023] Still further in accordance with the first aspect, for instance, a gear set may be between the electric motor and the MR fluid clutch apparatus to cause a speed reduction.

[0024] Still further in accordance with the first aspect, for instance, the positive contact clutch includes a positive contact component rotating with a driven axle, and translating between engagement with a first gear associated with the first gear ratio, and with a second gearassociated with the second gear ratio, the engagement of the positive contact component resulting in one of the first gear and the second gear to rotate with the driven axle.

[0025] Still further in accordance with the first aspect, for instance, the actuator includes a gear change electric motor.

[0026] Still further in accordance with the first aspect, for instance, the gear change electric motor is coupled to a positive contact component of the positive contact clutch by a rotation-to- translation device.

[0027] Still further in accordance with the first aspect, for instance, two of the motor are included, each of the two motors connected to a driving axle of the gear assembly by a respective one of the MR fluid clutch apparatus, the MR fluid clutch apparatuses apply a variable amount of slippage between the respective motors and the driving axle to control an input of the motors on the driving shaft.

[0028] Still further in accordance with the first aspect, for instance, a gear set may be between each of the motors and the respective MR fluid clutch apparatuses to cause a speed reduction.

[0029] Still further in accordance with the first aspect, for instance, the MR fluid clutch apparatus includes a magnet and is of the normally closed type.

[0030] Still further in accordance with the first aspect, for instance, a controller may be provided for controllably powering the MR fluid clutch apparatus into applying the variable amount of slippage.

[0031] Still further in accordance with the first aspect, for instance, the positive contact clutch is a dog clutch.

[0032] Still further in accordance with the first aspect, for instance, the positive contact clutch is a dog clutch.

[0033] Still further in accordance with the first aspect, for instance, the positive contact clutch is a chain and sprocket drive.

[0034] In accordance with a second aspect, there is provided a vehicle powertrain, comprising: at least a torque source for imparting torque to an input; at least one wheel at anoutput; a positive contact clutch for engagement and disengagement between the input and the output for transmission of the torque to the at least one wheel; and a mechanical clutch actuator for actuating the engagement and / or disengagement of the positive contact clutch by applying a force on at least one component of the positive contact clutch, the mechanical clutch actuator including a motor and a MR fluid clutch apparatus between the motor and the at least one component of the positive contact clutch to control said force by applying a variable amount of slippage between the motor and the at least one component.

[0035] Further in accordance with the second aspect, for instance, the mechanical clutch actuator includes a member pushing the at least one component of the positive contact clutch into engagement, the member connected to an output of the MR fluid clutch apparatus.

[0036] Still further in accordance with the second aspect, for instance, the member is a fork.

[0037] Still further in accordance with the second aspect, for instance, the mechanical clutch actuator includes at least one thrust bearing between the at least one component of the positive contact clutch and the MR fluid clutch apparatus.

[0038] Still further in accordance with the second aspect, for instance, at least one spring may bias the positive contact clutch toward disengagement against an action of the MR fluid clutch apparatus.

[0039] Still further in accordance with the second aspect, for instance, a reduction mechanism may be between the motor and the MR fluid clutch apparatus.

[0040] Still further in accordance with the second aspect, for instance, the reduction mechanism is non backdrivable.

[0041] Still further in accordance with the second aspect, for instance, the MR fluid clutch apparatus includes a magnet and is of the normally closed type.

[0042] Still further in accordance with the second aspect, for instance, the mechanical clutch actuator has a first bi-stable position and a second bi-stable position in which the motor is off, the positive contact clutch in said disengagement in the first bi-stable position, the positive contact clutch in said engagement in the second bi-stable position.

[0043] Still further in accordance with the second aspect, for instance, a controller may be provided for controllably powering the MR fluid clutch apparatus into apply the variable amount of slippage.

[0044] Still further in accordance with the second aspect, for instance, the positive contact clutch is a dog clutch.

[0045] Still further in accordance with the second aspect, for instance, the positive contact clutch is a dog clutch.

[0046] Still further in accordance with the second aspect, for instance, the torque source is an electric motor.

[0047] In accordance with another aspect, there is provided an electric vehicle powertrain, comprising: a gearbox including a dog clutch, the gearbox configured to be coupled to a wheel system of an electric vehicle; an electric motor for driving the wheel system of the electric vehicle; and a MR fluid clutch apparatus between the electric motor and the dog clutch, the MR fluid clutch apparatus configured to apply a variable amount of slippage between the electric motor and the dog clutch, during coupling between the electric motor and the dog clutch.

[0048] In accordance with another aspect, there is provided an electric vehicle powertrain, comprising: a gearbox including a dog clutch, the gearbox configured to be coupled to a wheel system of an electric vehicle; an electric motor for driving the wheel system of the electric vehicle via the dog clutch; and a mechanical clutch actuator for actuating an engagement and / or disengagement of the dog clutch, the mechanical clutch actuator including a second motor and a MR fluid clutch apparatus between the second motor and an engagement mechanism of the dog clutch, the MR fluid clutch apparatus configured to apply a variable amount of slippage between the second motor and the engagement mechanism of the dog clutch, during coupling between the input side and the output side of the dog clutch.

[0049] In accordance with another aspect, there is provided an actuator system comprising: a power source; an output member; at least a MR coupling, the MR coupling operable to generate a variable amount of torque transmission; a transmission operatively coupling the at least one MR couplings to the power source and to the multispeed, wherein the MR couplings modulate the torque delivered by the power source..

[0050] These and other objects, features and advantages according to the present invention are provided by a multi-speed or multi-ratio which contains the MR fluid coupling or couplings.

[0051] Control means, such as a microprocessor operating under program control, is preferably operatively connected to the MR fluid force modulation means for causing a predetermined magnetic field strength to be applied to the MR fluid based upon a selected force modulation program that may take into account information from sensors, particularly, user demand, vehicle speed / acceleration, motor speed, and actual gear selection. Accordingly, a desired amount of force or power from the power source can be provided to the powertrain in order to increase or decrease output of the powertrain during the vehicle usage. The system may further comprise a sensor to measure the input of the system in order to control the output required by the power source.

[0052] It is to be noted that the present invention can be used on many other type of components as well as human input power sources like the arms, hands, feet, legs or any other body part. Also, the present invention can be used on various types of vehicle or equipment like moped, push scooter, personal walker, electric car, hand powered cart, plane, bicycle trailer, hoist, only to name a few.

[0053] In equipment, the system may be used to move objects combining power of a single power source connected to multiple speed transmission or multiple sources power. Benefit and principles stay the same than with vehicles. The objectives may still be to increase acceleration, improving control over the equipment or to provide more range or autonomy to the operated equipment.DESCRIPTION OF THE DRAWINGS

[0054] Fig 1 is a series of graphs showing torque vs speed and power vs speed for 2-stage gearing in accordance with the prior art;

[0055] Fig. 2 is a block diagram of an actuation system with a selector / shifter between a power source and load in accordance with the prior art;

[0056] Fig. 3 is a schematic view of a generic magnetorheological (MR) fluid clutch apparatus, incorporating features of the present disclosure;

[0057] Fig. 4 is a sectioned schematic view of a MR fluid clutch apparatus in accordance with an embodiment where the MR fluid clutch apparatus is of normally open type;

[0058] Fig. 5 is a sectioned schematic view of a MR fluid clutch apparatus in accordance with another embodiment where the MR fluid clutch apparatus is of partially or normally closed type;

[0059] Fig. 6 is a sectioned schematic view of a MR fluid clutch apparatus in accordance with another embodiment where the MR fluid clutch apparatus is of programmable type;

[0060] Fig. 7 is a sectioned schematic view of a MR fluid clutch apparatus in accordance with another embodiment where the MR fluid clutch apparatus is of normally closed type without coil;

[0061] Fig. 8 is a sectioned schematic view of a MR fluid clutch apparatus, in accordance with another embodiment where the MR fluid clutch apparatus is of programmable type and uses plates instead of drums;

[0062] Fig. 9 is a sectioned schematic view of a MR fluid clutch apparatus in accordance with another embodiment where the MR fluid clutch apparatus is of normally closed type without coil and using plates instead of drums;

[0063] Fig. 10 is a schematic view of a two-speed electric or hybrid vehicle powertrain from the state of the art;

[0064] Fig. 11 is a schematic view of the powertrain of Fig. 10, modified as per the present disclosure;

[0065] Fig. 12 is a schematic view of an alternative embodiment of the powertrain system of Fig. 10;

[0066] Fig. 13 is a schematic view showing a variation where two motors, each connected to a MR fluid clutch apparatus, power a multi-speed transmission;

[0067] Fig. 14 is a graphic showing the acceleration of a single speed electric vehicle powertrain versus the acceleration of a powertrain of an electric vehicle or hybrid vehicle having a MR fluid actuator(s) in accordance the present disclosure;

[0068] Fig. 15 is schematic view showing a mechanical clutch controlled by a MR fluid actuator;

[0069] Fig. 16 is a schematic view showing a dogbox shifting actuator controlled by a MR fluid actuator in accordance with the present disclosure; and

[0070] Fig. 17 is schematic views of dogbox shifting actuator of Fig. 16 in two positions.DETAILED DESCRIPTION

[0071] Referring to the drawings and more particularly to Fig. 3, there is illustrated a magnetorheological (MR) fluid clutch apparatus 10 configured to provide a mechanical output force based on a received input current and a force based on the remanent magnetization level of a magnetizable component in the magnetic circuit when there is no input current. The MR fluid clutch apparatus 10 is shown as being of the type having collinear input and output shafts 11 and 12. However, the concepts described herein may apply to other configuration of MR fluid clutch apparatuses, for instance some with an input or output outer shell / casing for an output or input shaft, etc. The principles described here can be performed using a MR fluid clutch apparatus of drum type but could also be applied to a disc type MR fluid clutch apparatus.

[0072] The MR fluid clutch apparatus 10 may provide an output force in response to an input current received from an operator or controller, to transmit an output force based on the magnetization level of a magnetizable component in the magnetic circuit when there is no input current. The exemplary MR fluid clutch apparatus 10 may have a stator 10A by which the MR fluid clutch apparatus 10 is connected to a structure. The MR fluid clutch apparatus 10 features driven member 11 and driving member 12 separated by gaps filled with an MR fluid, as explained hereinafter. The driving member 12 may receive rotational energy (torque) from a power device, such as a motor, with or without a transmission, such as a reduction gear box, etc. The MR fluid 19 used to transmit force between the driven member 11 and the driving member 12 is a type of smart fluid that is composed of magnetisable particles disposed in a carrier fluid, usually a type of oil, but the carrier fluid may also be present in gel, a gaseous form (a.k.a., dry MR fluid). Non magnetisable particles may also disposed in a carrier fluid. When subjected to a magnetic field, the fluid may increase its apparent viscosity, potentially to the point of becoming a viscoplastic solid. The apparent viscosity is defined by the ratio between the operating shear stress and the operating shear rate of the MR fluid between opposite shear surfaces. The magnetic field intensity mainly affects the yield shear stress of the MR fluid.

[0073] According to an embodiment, the driving member 12 may be in mechanical communication with a power input (directly or through a transmission), and driven member 11 may be in mechanical communication with a power output (i.e., force output, torque output). The stator 10A, the driven member 11 and the driving member 12 may be interconnected by bearings 12A and 12B, or fewer or more bearings. Bearings of any appropriate type may be used. In the illustrated embodiment, the bearing 12A is between the stator 10A and the driving member 12, whereas the bearing 12B is between the driven member 11 and the driving member12, but this is merely an example. Seal(s) 12C may also be provided at the interface between the stator 10A, the driven member 11 and the driving member 12, to preserve MR fluid between the members 11 and 12. Moreover, the seals 12C are provided to prevent MR fluid from reaching the bearing 12B or to leak out of the apparatus 10.

[0074] As shown with reference to Figs. 4-5 below, drums are located circumferentially about the rotational axis CL. Some support must therefore extend generally radially to support the drums in their circumferential arrangement. In accordance with one embodiment, referring to Fig. 4, a low permeability input drum support 13 (a.k.a., radial wall) projects radially from a shaft of the driving member 12. The input drum support 13 may be connected to an input rotor 14 defining the outer casing or shell of the MR fluid clutch apparatus 10. The input rotor 14 may therefore be rotatably connected to the driven member 11 by the bearing 12B. In an embodiment, the input rotor 14 has an input rotor support 14A which forms a housing for the bearing 12B. According to an embodiment, the input rotor support 14A is an integral part of the input rotor 14, and may be fabricated as a single piece. However, in an embodiment, the input rotor support 14A is ideally made from a low permeability material and the input rotor 14 is made from a high permeability material. As another embodiment, as shown in Fig. 4, the input rotor support 14A may be defined by an annular wall fabricated separately from a remainder of the input rotor 14, though both are interconnected for concurrent rotation. Therefore, the shaft of the driving member 12, the input drum support 13, and the input rotor 14 rotate concurrently. In an embodiment, it is contemplated to have the outer shell of the MR fluid clutch apparatus 10 be part of the stator 10A, or of the driven member 11 .

[0075] The input drum support 13 may support a plurality of concentric annular drums 15, also known as input annular drums. The input annular drums 15 are secured to the input drum support 13 and rotate therewith. In an embodiment, concentric circular channels may be defined (e.g., machined, cast, molded, etc) in the input drum support 13 for insertion therein of the drums 15. A tight fit (e.g., force fit), an adhesive and / or radial pins are some of the mechanical components that may be used to secure the drums 15 to the input drum support 13. In an embodiment, the input drum support 13 is monolithically connected to the shaft of the driving member 12, whereby the various components of the driving member 12 rotate concurrently when receiving the drive from the power source.

[0076] The driven member 11 is represented by an output shaft as a possibility, configured to rotate about axis CL as well. The output shaft 11 may be coupled to various mechanical components that receive the transmitted power output when the clutch apparatus 10 is actuated to transmit at least some of the rotational power input.

[0077] The driven member 11 also has a one or more concentric annular drums 16, also known as output drums, mounted to an output drum support 17. The output drum support 17 may be an integral part of the output shaft, or may be mounted thereon for concurrent rotation. The annular drums 16 are spaced apart in such a way that the sets of output annular drums 16 fit within the annular spaces between the input annular drums 15, in intertwined fashion. When either of both the driven member 11 and the driving member 12 rotate, there is no direct contact between the annular drums 15 and 16, due to the concentricity of the annular drums 15 and 16, about axis CL. In the embodiment of Fig. 2, the driving member 12 or the input rotor 14 may consist of or may include a magnetizable (a.k.a., magnetisable) part (e.g., ferrite). Alternatively, input rotor 14 may be consist of a magnetizable component.

[0078] In the embodiment of Fig. 5, the MR fluid clutch apparatus 10 is similar to the one of Fig. 4, whereby like reference numerals represent like elements. In the embodiment of Fig. 5, a portion of the coil 18 is replaced by a magnetizable component(s) 31 is located in parallel of the magnetic circuit (a.k.a., magnetic path). The magnetizable component 31 is shown as having a form factor but other form factors may also be possible. The magnetizable component 31 is made of a material having the capacity of maintaining a remanent magnetization level, such that the magnetizable component 31 generates a magnetic field itself. The magnetizable component 31 may be annular in shape, for instance by forming a ring integrated into various components of the MR fluid clutch apparatus 10. As another variation, the magnetizable component 31 may be a plurality of discrete magnetizable components 31. Such discrete magnetizable components 31 may be circumferentially distributed around the central axis of the MR fluid clutch apparatus 10, essentially forming a ring around the central axis. The spacing between the magnetizable components 31 may vary. In another variation, the plurality of discrete magnetizable components 31 are arranged in an axisymmetric manner.

[0079] In the embodiment of Fig. 6, the MR fluid clutch apparatus 10 is similar to the one of Fig. 2, whereby like reference numerals represent like elements. In the embodiment of Fig. 3, the driving member 12 is separated in two sections, 12’ and 12”, and a magnetizable part 31 isinstalled in between in the magnetic circuit. The electromagnet unit 18 is used to increase the magnetic field in the magnetic circuit. Since the magnetic circuit includes a magnetizable part 31 , magnetizable part 31 may be magnetized when a current passes through the annular coil 18. When the current is removed, the magnetizable part 31 , because of its hysteretic behaviour, will stay magnetized to a lower level than that of the magnetic field that was applied to the magnetic circuit. When the current in the electromagnetic unit 18 is at lsat level, the effective torque generated by MR fluid clutch apparatus 10 may correspond to Tsat level (maximum level reachable by the MR fluid clutch apparatus 10). When the current is removed in the electromagnetic unit 18, the magnetizable part 31 , because of its hysteresis nature, will decrease but will maintain a magnetization level of the magnetic circuit and the MR fluid clutch apparatus 10 will generate a torque Tsato, even if the current is removed (i.e. l=0 A) in the electromagnetic unit 18. Similarly, when the current in the electromagnetic unit 18 is at Id level, the effective torque generated by MR fluid clutch apparatus 10 may correspond to Td level and when the current is removed in the electromagnetic unit 18, the magnetizable part 31 , because of its hysteresis nature, will decrease but will maintain a magnetization level of the magnetic circuit and the MR fluid clutch apparatus 10 will generate a torque T o, even if the current is removed (i.e., l=0 A) in the electromagnetic unit 18. By using the proper current I in the electromagnetic unit 18, the magnetizable part 31 may be magnetized to any level, and the effective MR fluid clutch apparatus 10 torque when there is no current in the electromagnetic unit 18 may be adjusted to any level between 0 ant Tsat.

[0080] Fig. 7 shows a MR fluid clutch apparatus 10 similar to the MR fluid clutch apparatus 10 of Fig. 2, whereby like reference numerals represent like elements. In Fig. 7, the driving member 12 and the stator 10A are now attached together as non-moving part in order to act as a brake when stator 10A is mounted on a chassis (not illustrated). In this embodiment, electromagnetic unit is replaced by magnet 31. Principle of operation is similar to the MR fluid clutch apparatus of Fig. 5. In this configuration, the magnetic flux created in the shear interface may not be controlled.

[0081] Fig. 8 is a sectioned schematic view of another variant of the MR fluid clutch apparatus, shown as 10. The MR fluid clutch apparatus 10 is of programmable type and uses plates or discs instead of drums. Input disc or discs 71 are connected to driving member 12 while output disc or discs 72 are connected to the stator 10A. The principle of operation of the MR fluid clutchapparatus 10 is similar to that described above. In this configuration, the magnetic flux created in the shear interface by the magnet 31 may be programmed.

[0082] Fig. 9 shows a sectioned schematic view of a MR fluid clutch apparatus 10 in accordance with another embodiment where the MR fluid clutch apparatus 10 is of normally closed type without coil and using plates instead of drums..

[0083] In all embodiments, a controller C may be present to operate the motor and the MR fluid clutch apparatus(es) 10. The controller C may be embodied by a processing unit(s), and a non-transitory computer-readable memory communicatively coupled to the processing unit and comprising computer-readable program instructions executable by the processing unit. While the controller C is shown in only some of the figures for simplicity, any of the embodiments described herein and featuring one or more MR fluid clutch apparatuses 10 may have a controller C. In any of the embodiments, a magnet or magnets may be introduced in the magnetic circuit in order for the MR fluid clutch apparatus 10 to provide a torque when not powered.

[0084] The schematics of Fig. 10 show a state of the art two-speed electric vehicle or hybrid vehicle powertrain 100 with positive clutch engagement, as part of a transmission between torque source and output (e.g., a wheel). The electric motor 101 is connected directly to the gearbox 102, via a driving axle 103 (or driving shaft 103). The gearbox 102 includes a pair of gears 103A and 103B on the driving axle 103. The expression gearbox is used generically, and may also be referred to interchangeably as gear assembly, transmission, gear system, etc. The expression gearbox may generally be described as gears intermeshed with one another in various arrangements. While Figs. 10-13 show an electric motor 101 , the component 101 may be described as a torque source and may include both an electric motor and a combustion engine, such as in hybrid vehicles. For simplicity, the text hereinbelow may refer to the component 101 as an electric motor, but the present disclosure covers scenarios in which 101 may also include a combustion engine, and possibly transmission components to couple the combustion engine to a driven axle or shaft. Moreover, torque-producing component 101 may be shared by two or more wheels. A driven axle 104 (or driven shaft 104) may also be part of the gearbox 102. Gears 104A and 104B are respectively engaged with gears 103A and 103B, for transmission of rotation between the gear sets. The gears 104A and 104B may be coaxially mounted onto the driven axle 104, but may not rotate with it, unless engaged by a dogcomponent 105. The dog component 105 is on the driven axle 104 so as to rotate with it. The dog component 105 may also be referred to as a dog, dogs, dog clutch, clutch, etc, and features axially projecting features configured for engagement with a complementary component (e.g., another dog, dogs, dog clutch device, etc) that is secured to a rotating component, such as found on gears 104A and 104B, and illustrated as 104A’ and 104B’ and illustrated schematically. 104A’ and 104B’ may be complementary dog components. Dog components of a dog clutch in any of the embodiments described herein may be crenellations, i.e., projections between crenels. The dog components described herein may be crown shaped components each with a crenellated end, such that the crenellated ends of adjacent dog components face one another and can mate, by projections of one dog component received into crenels of the other and vice versa. Dog components of a dog clutch are not limited to crenellations, but provide mating engagement between dog components facing one another. In the illustrated embodiment, the dog component 105 may translate along a longitudinal direction of the driven axle 104, while remaining engaged to the driven axle 104 to rotate with it. For example, the driven axle 104 and the dog component 105 may translate together, or the dog component 105 may slide along the driven axle 104, for instance by way of a spline coupling allowing such translation. More importantly, the present disclosure includes other types of similar clutches, referred to as positive contact clutches, as being interchangeable in all systems of the present disclosure, unless stated otherwise. This may include for example jaw clutches, toothed clutches, triangle positive engagement clutch, conical synchro-mesh clutches and variants thereof commonly found in automotive manual transmissions. A positive contact clutch may be generally described as a clutch in which the engaging clutch surfaces interlock to produce a rigid joint, without relying on friction for the engagement of the clutch surfaces. Such positive contact clutches may be referred to as positive engagement clutches. Other positive engagement system used to make multispeed systems, like a chain and sprocket engagement such as commonly found on multispeed bicycles typically using derailleurs, cranted belts and pulleys may also replace the gear and dog clutch engagement, in at least some of the embodiments described herein. Other arrangements are possible. An actuator 106A may be a shifting system 106 or part of it, and is coupled to the dog component 105 to impart a translation to the dog component 105, to cause the dog component 105 to move into engagement with the complementary components 104A’ or 104B’, to switch from one gear ratio to another. For example, the actuator 106A is shown as being a motor (e.g., electric motor) having a ball screw or equivalent rotation-to-translation device, such as a bolt and nut, a pinion and rack, etc. The combination of the actuator 106Aand of the rotation-to-translation device may be referred to as the shifting system 106, through the shifting system 106 may have other components and / or configuration than that shown. The motor is one possible solution among others for displacing the dog component 105, and other types of actuators may be used, such as a linear actuator or cylinder. Moreover, any appropriate power source may be used, such as electric, hydraulic, pneumatic. The gear ratio differs between the gear sets 103A / 104A and 103B / 104B for the gear box 102 to provide at least two speeds to the output. For example, gear ratios of 1.4: 1 and 1 : 1 are shown, but this is merely an example. The output is shown as including a gear 107, mounted to the driven axle 104, and a gear 108A mounted to a wheel axle 108, to impart a rotation to a wheel 108B on the wheel axle 108. Therefore, in use, the electric motor 101 drives the driving axle 103. The gears 103A and 103B may rotate with the driving axle 103, and therefore drive the gears 104A and 104B, respectively. The dog component 105 may be moved into engagement with either one of the gears 104A and 104B by the actuator 106A, to drivingly couple the gear 104A or 104B to the driven axle 104. The rotation of the driven axle 104 then causes a rotation of the wheel 108B. In such a system, when there is a shift between the first and second speed (e.g., gear sets 103A / 104A and 103B / 104B, also referred to as first gear and second gear), the inertia of the motor 101 is high and at the gear change, there may be a significant impact created in the gearbox 102 that may create a jerk and / or NVH. The impact may be particularly important because of the high inertia of the electrical motor 101 and therefore the impact can damage the gearbox components, or cause wear or failure over time.

[0085] The schematic of Fig. 11 shows a positive contact clutch such as in Fig. 10 using a MR fluid clutch apparatus 10 between the motor output and the positive contact clutch, in accordance with the present disclosure. More particularly, the MR fluid clutch apparatus 10 is shown as being on the driving shaft 103 (or motor shaft), though it may be elsewhere. The MR fluid clutch apparatus 10 may be as described in any of Figs. 3 to 9, where appropriate, with combinations of components taken from the various MR fluid clutch apparatuses 10 being possible. Stated differently, Figs. 3 to 9 provide different examples of MR fluid clutch apparatuses that can be used in electric and / or hybrid vehicle powertrains described herein. The utilization of the MR fluid clutch apparatus 10 with low output inertia offers several advantages, including a reduction in impact force on gearbox components and / or a decrease in noise, vibration, and harshness (NVH). During an upshift (i.e., from 1stspeed ratio 1.4:1 (gear set 103A / 104A) to 2ndspeed ratio 1 :1 (gear set 103B / 104B) and shown in Figs. 10-13 in otherarrangements), the driving member 12 of the MR fluid clutch apparatus 10 may rotate at a higher speed than the driven member 11 , as it is coupled to the electric motor 101. This sequence may allow an almost seamless upshift, as fast as the “Electronic gear change” actuator 106A can move the shifting system 106. The energy from the inertia of the motor 101 may be dissipated in the MR fluid clutch apparatus 10 until both the driving member 12 and driven member 11 rotate at the same speed, without significant slippage. When there is no significant slipping, the torque transmission between the driving member 12 and driven member 11 may be very high, increasing the efficiency of the overall powertrain. During a downshift (i.e., from 2ndspeed ratio (gear set 103B / 104B) to 1stspeed ratio (gear set 103A / 104A)), while the system 100 is operated in regenerative braking mode (i.e., negative torque provided at the wheels), the torque transmittable by the MR fluid clutch apparatus 10 may be synchronized and controlled such as by the controller C to match the torque applied to the wheel 108 in the 2nd gear so when the gearbox 102 switches to the 1st gear, the MR fluid clutch apparatus 10 may simultaneously change and reduce its transmissible torque by the same ratio (i.e., reduce by 1.4 the torque if the ratio of the first gear is 1.4:1 and the ratio of the second gear is 1 :1 like shown in Figs. IQ- 12) so the usual “overshoot” of torque at the wheels, and its effect on the instantaneous acceleration of the vehicle, typical from a positive contact clutch transmission (i.e., that may include components 104A’, 104B’, 105, 106 (with 106A), and optionally 104A and 104B), may be prevented. Again, the energy available from the inertia of the motor 101 may be dissipated in the MR fluid clutch apparatus 10 until both the driving member 12 and driven member 11 rotate at the same speed. This sequence may allow an almost seamless downshift, as fast as the “Electronic gear change” actuator 106A can move the shifting system 106.

[0086] The arrangement of Fig. 12 differs from the arrangement of Fig. 11 , in that a first input reduction gearbox 84 is between the electric motor 101 and the MR fluid clutch apparatus 10, the MR fluid clutch apparatus 10 then connected to the multispeed gearbox 102 (i.e., two or more speeds). This arrangement may allow the use of a smaller motor that may turn faster.

[0087] The schematic of Fig. 13 shows a variation where two motors 101 (shown as 101 A and 101 B), each connected to a respective MR fluid clutch apparatus 10 / 10’, can be connected to a common output powering a multi-speed transmission, such as the driving shaft 103. Fig. 13 is schematic, with components removed, such as U-joints or other intermediate gears between the MR fluid clutch apparatuses 10 / 10’ and the driving shaft 103. Various shifting logics can be implemented to control shifting action in multiple motors / clutches configurations, by thecontroller C in a variant. One possible logic is described hereafter and allows relatively low shifting times, appropriate torque interruptions, and suitable (e.g., quasi-perfect) speed matching with little to no impact loads. In the first step of the sequence, the MR fluid clutch apparatus 10 associated with one of the motors 101 A, for example, is opened and motor 101 A is accelerated or decelerated to a speed close to the speed of the next gear to be engaged. Motor 101 B can compensate the torque interruption due to the disconnection of motor 101A. In the second step of the sequence, three events may occur almost simultaneously: (1) the dog clutch transitions from the previous gear ratio to the next gear ratio; (2) the MR fluid clutch apparatus 10’ associated with the motor 101 B may be disengaged and (3) the MR fluid clutch apparatus 10 associated with the motor 101 A may be engaged. Together, the three events bring the driving axle 103 to its expected speed after the shift and connect the new gear almost instantaneously. In the third and last step of the sequence, motor 101 A is reactivated to its desired output torque while motor 101 B is brought to the new driven axle speed after the shift and reconnected using the MR fluid clutch apparatus 10’. Motor 101 B speed setting can be done by controlling the current to the motor 101 and / or by gradually locking MR fluid clutch apparatus 10’.

[0088] At any time during the shifting sequence, the MR fluid clutch apparatuses 10 and 10’ can provide some slipping action to reduce or dampen vibrations or impacts. Also, the desired targeted speed of motor 101 A in the first step of the shifting sequence can be estimated from the conservation of angular momentum such that: IAa>A+ ID)D= (JA+ ID) )ADwhere IAand IDare the rotational inertias of motor A and driven axle, <JJAand a)D, are the angular speeds of motor 101A and driven axle 104 before reconnection; and a)ADis the angular speed of the motor 101 A + driven axle 104 assembly after reconnection. It should be noted that a minimum speed difference between dogs 104A’-104B7105 (or equivalent positive contact engagement surfaces) is typically desired (0 to ~100’s rpm) to provide sufficient dog engagement windows. Also, it should be noted that in most configurations, the rotative inertia of the motor 101 is a few orders of magnitude higher than the rotative inertia of the driven axle 104, so when the MR fluid clutch apparatus 10 is engaged rapidly, the speed of the driven axle 104 will rapidly be brought close to the speed of the motor 101 , without significant motor speed change.

[0089] Live shifting a positive contact clutch such as a dog clutch gearbox may allow the torque output to be maximised. In the case of an arrangement like in Fig. 11 or Fig. 12, this live shifting requires the clutch input driving member 12, a)c, to either increase or decrease speed inorder to match the driven member 11 side with respect to output speed, )a. Controllability may potentially be lost during shifting, if shifting speed is too slow. Assuming that a human can perceive physical inputs up to 20 Hz, shifting times lower than 50 ms should be imperceptible if there are no torque perturbations in the driveline beyond this timeframe.

[0090] Because the MR fluid clutch apparatus 10 generally operates at a frequency range that is higher than a frequency range of the motor assembly (e.g., including motor 101 and a reduction mechanism 84, notably because of inertia, backlash, etc), in some situations force transmission may not be the correct scale when compared to the desired force transmission on the output 11 . For example, in response to perturbations to which the system is exposed during shifting, the controller C may determine that the motor assembly must accelerate or decelerate to a given value (e.g., to a greater or lesser speed). The motor 101 is then controlled to accelerate or decelerate to the given value, but can only do so at its frequency range, lesser than the frequency range of the MR fluid clutch apparatus 10. The MR fluid clutch apparatus 10, transmitting force between input 12 (i.e., the motor 101) and output 11 , may thus react quicker than the motor 101. Accordingly, the controller C may reduce a torque transmission from the MR fluid clutch apparatus 10 during this period in which the torque transmission does not correspond to the desired force, for example to compensate for the mismatch in frequency ranges of operation.

[0091] The MR fluid clutch apparatus 10 allows penalty torque tracking ability of the powertrain to be minimized while maintaining NVH at an acceptable level. It may be useful for a single motor single clutch system similar to the one shown at 100 of Fig. 11-12 or for a system 100 having two motors 101 and two MR fluid clutch apparatuses 10 working in parallel as shown in Fig. 13.

[0092] In normal driving conditions, the MR fluid clutch apparatus 10 may serve to accurately regulate the amount of torque transmitted to the geartrain, such as that shown as gearbox 102 in Figs. 11-13, thereby minimizing the risk of vehicle oscillation (commonly known as jerks) or resonance during abrupt variations in traction torque.

[0093] The MR fluid clutch apparatuses 10, in the disclosed application of Figs. 11 to 13, may have to turn at high speeds (i.e., over 10,000RPM) while having to connect the driving member 12 to the driven member 11 , most of the time. To that effect, shifting time may only represent asmall fraction of the normal operation time of the powertrain. It may thus be advantageous to use a MR fluid clutch apparatus 10 of the type of Fig. 3, with an integrated magnet 31 in parallel with the coil 18, though other configurations of the MR fluid clutch apparatus 10 may be used. Such type of MR fluid clutch apparatus 10 may transmit a significant amount of torque while being unpowered because of the magnetic field from the magnet 31 . In some conditions, electric current generated in coil 18 may be used only when a torque reduction is required, mainly during downshifts, and occasionally during upshifts. The presence of a magnet in the magnetic circuit may also contribute to maximising the ability of the MR fluid clutch apparatus 10 to limit the movement of magnetisable particles under centrifugal effect.

[0094] It may be useful to incorporate a MR fluid clutch apparatus 10 in gearboxes and like transmissions of any number of speeds, including in gearboxes where there is only a single speed. An advantage of having a MR fluid clutch apparatus 10 in association with any of the gearboxes is that the MR fluid clutch apparatus 10 may eliminate the peak load that may happen from time to time in the gearboxes, caused by high load variations at the output of the gearbox. For example, if the wheel of the vehicle is slipping on a surface with low friction coefficient (e.g. wet or icy surfaces only to name a few) and then makes contact with a surface of high friction coefficient (e.g. dry asphalt or concrete to name a few) with high velocity, high inertia, the mismatch of speed between the tire and the road may create a sudden reaction force in the linkages as the accumulated inertia in the electric motor and other rotating parts will be braked rapidly. This kind of situation may create high unwanted mechanical loads in the system. The design of such a transmission will have to take in account those overload condition and oversize the mechanical components for those that may only happen once in a while. The addition of the MR fluid clutch apparatus(es) 10 in such a system may help to shave those peak loads in the system by decoupling the inertia of the output from the inertia of the motor on the output side. With low inertia coupling, the high loads may be eliminated and the component sizes may be reduced.

[0095] In one or more of the configurations from Figs. 11 to 13, it is to be noted that the MR fluid clutch apparatus(es) 10 may be of any types, being normally open when a coil is present as per Fig. 4, normally or partially closed type as per Fig. 5 with a magnet and a coil, or without a coil as per Figs. 7 or 9 if the magnet 31 is strong enough to generate a force high enough to transmit the full torque of the system, or of programmable type, with a magnet and a coil as per Fig. 8.

[0096] The graphic of Fig. 14 shows an exemplary and non-limitative power transmission to the wheels achievable by a single ratio electric vehicle versus a multispeed vehicle using the embodiments of the present disclosure, with MR fluid clutch apparatuses 10. It shows that the power at lower speeds, for the single ratio vehicle, is lower than the multispeed one since the power is proportional to the torque ability of the electric motor multiplied by the speed of the electric motor. A multispeed gearbox allows a better exploitation of the capabilities of the motor (e.g., motor 101), hence better acceleration. In the shown example, the single speed powertrain would reach 70km / h in approximatively 7.6s while a 5-speed powertrain equipped with the disclosed embodiment would allow it 2.6s, in given conditions, these values being merely exemplary.

[0097] The system of Figs. 11-13 may be described as being for a vehicle powertrain and may include: at least an electric motor; a gear assembly configured to couple at least one wheel of the vehicle to the motor for the at least one wheel to be driven by the electric motor, the gear assembly including a positive contact clutch for switching the gear assembly between at least a first gear ratio and a second gear ratio; an actuator for controlling the switching of the positive contact clutch; and a magnetorheological (MR) fluid clutch apparatus between the motor and the positive contact clutch, the MR fluid clutch apparatus configured to apply a variable amount of slippage between the motor and a component of the positive contact clutch, during coupling of the positive contact clutch in the switching.

[0098] A method associated with the system of Figs. 11-13 may include operating a MR fluid clutch apparatus in a transmission between a torque source and at least one wheel in which a positive contact clutch is used by a shifting system, the method comprising adjusting a slippage in the MR fluid clutch apparatus as a function of rotational speeds between positive contact surfaces of the positive contact clutch, with one of the positive contact surfaces being on a wheel side, and the other of the positive contact surfaces being on a torque source side, during shifting.

[0099] Fig. 15 shows a mechanical dry or wet plate type clutch 110 in which the clamping force is controlled by a mechanical clutch actuator system 111 featuring a MR fluid clutch apparatus 10. The MR clutch fluid apparatus 10 may be of any type as described in Figs. 3 to 9, including of programmable type. The mechanical clutch actuator system 111 with MR fluid clutch apparatus 10 may be used as an alternative to any MR fluid clutch apparatus 10 of any transmission of Figs. 11 to 13. In such an arrangement, the transmitted torque by the mechanicalclutch 110 from input shaft 112A to output shaft 113A is a function of the clamping force applied between the input friction plates 112 and the output friction plates 113, by actuator system 111. The actuator system 111 is illustrated as including a motor 114A, a rotation-to-translation device 114B (e.g. a ball screw, a bolt and nut, etc), and an optional linkage mechanism 114C connected to the rotation-to-translation device 114B to apply a force on the plates 113 (or elsewhere such as plates 112, both plates 112 and 113, or other parts of the drive assembly or driven assembly). Different arrangements of the linkage mechanism 114C could be used, including a hydraulic or pneumatic transmission. The rotation-to-translation device 114B could also apply the clamping force directly to the mechanical clutch 110. In such an arrangement, the difference of the inertia of the actuator applying the relative force between the plates 112 and 113 may be reduced substantially by decoupling the inertia of the motor 114A from the actuator output inertia using a MR fluid clutch apparatus 10. For example, for a given torque, the ratio of inertia of a MR fluid clutch apparatus 10 may be 50 times lower (for example) than the inertia of an electrical motor 114A of the same output, combined to the fact that the reduction ratio between the actuator and the mechanical clutch may be 10:1 (for example), the difference of the inertia at the mechanical clutch would be 50x higher without the MR fluid clutch apparatus 10. The presence of a MR fluid clutch apparatus 10 may make the mechanical clutch actuator system 111 more controllable, with higher bandwidth, if a MR fluid clutch apparatus 10 is incorporated in the mechanical clutch actuator system 111. A controller C may be present to operate the mechanical clutch actuator system 111 featuring the MR fluid clutch apparatus 10.

[0100] Fig. 16 shows a gear engagement actuator, that may have components similar to the ones of Fig. 11 to Fig. 13, such as by featuring a dog clutch, and a MR fluid clutch apparatus 10, that may be any of those shown in Figs. 3-9. The gear engagement actuator may need to engage a dog component 161 of a dog clutch (as an example of positive contact clutches that may be used) by sliding or rotating a fork 162 (or other component) thereof that moves the dog component 161 on a drive side powered for example by power motor 163 or other drive source, into engagement with a dog component 164 of a driven side. Thus, while power motor 163 is shown, 163 may be a shaft that is driven, and the dog components 161 and 164, or other clutch components, engage or disengage to selectively transmit torque from the drive side to the driven side. The shaft 163 is thus connected to a power source or torque source (e.g., electric motor, combustion engine, in an EV, a hybrid vehicle, etc) to transfer torque from the shaft 163 to 164 in the transmission, with 161 and 164 potentially being other components than dog components,such as gears, etc, coupling via axial engagement with one another. The expression “dog component(s)” and dog clutch will be used herein. This engagement may be required in any transmission, even in transmission where there is a single speed ratio (e.g. to provide a neutral to the transmission). The gear engagement actuator may need to slide the dog component 161 between a rotating shaft 163 (with which it rotates) and a rotating gear 164 (that has a dog component and may be referred to as dog component 164 for simplicity) that may not turn at the same speed. When both the rotating shaft 163 and the rotating gear 164 are not turning at the same speed, there is statistically a significant probability that the male connectors, dog or dogs of the input side may not be perfectly aligned with the female connectors (between dogs) on gear side so the opposite and complementary dog components (161 and 164) of the dog clutch may not engage instantly. When such a situation happens, it may be necessary to maintain a stable force on the dog clutch so the next time the complementary dog components are aligned with one another, they can engage. Providing a force that is too low may prevent the engagement, while providing too high a force may trigger a jam, or induce unnecessary friction. Moreover, in a dog clutch engagement, the translation speed of the dog clutch during engagement may be important. If the speed is too slow and there is a big speed difference between the input and output side, the dogs of the complementary dog components of the dog clutch may “rattle”, damaging the mechanical components while preventing the transmission of torque between the input and the output. The actuator shown in Fig. 16 uses a motor 165 optionally connected to a reduction ratio system 166 (e.g. a worm gear, a hypoid gear only to name a few) that may be non-reversible to power the MR fluid clutch apparatus 10. The MR fluid clutch apparatus 10 may be connected to a reversible gearbox 166A that displaces a rotary or linear fork 162. A rotary actuator is shown but a rotary or linear fork 162 may also be displaced by a linear actuator, such as a motor with a rotation-to-translation device (e.g., ball screw, bolt and nut), with a MR fluid clutch apparatus 10 between the motor and rotation-to-translation device. The force from the fork 162 to the gear 161 may be transferred using different mechanical components, including optional thrust bearings 168 as shown. The MR fluid clutch apparatus 10 may be of the type that is normally closed, so when the current in the coil 10 of the MR fluid clutch apparatus 10 is removed, the MR fluid clutch apparatus 10 engages without power.

[0101] In such a device, a connecting sequence may be that when a connection is required, the power motor 163 starts its synchronising sequence with the output speed, then a current isapplied to normally closed MR fluid clutch apparatus 10 (if such a normally closed MR fluid clutch apparatus 10 is used) to disengage (ONm) while the motor 165 simultaneously starts to spin.

[0102] When the synchronisation of the power motor 163 and the output side is within an acceptable range, the current in the normally closed MR fluid clutch apparatus 10 (if such a normally closed MR fluid clutch apparatus 10 is used) is lowered so the torque can flow from the actuator motor 165 to the fork 162. In such a device, the inertia of the output side of the MR fluid clutch apparatus 10 may be several orders to magnitude lower than the reflected inertia of the input side so the output of the actuator, composed of the motor 160, the gearbox 166 and the fork 162, is accelerated at a high bandwidth. In addition, the limited reflected inertia of the MR fluid clutch apparatus 10 and the dog component 161 of the dog clutch does not create a big shock when it hits the dog component 164 on the output side so parts engage smoothly. Simultaneously, when the dog component 161 of the dog clutch and the dog component 164 are fully engaged, the motor 165 may be stopped and the actuator may be locked in a bi-stable position without any power consumption. The power motor 163 driving the input shaft may then be activated to transfer torque through the dog clutch. To disengage the dog component 161 of the dog clutch and the dog component 164, the sequence may be that the torque from the power motor 163 is removed in order to unload the dog clutch, and subsequently a current is applied to the normally closed MR fluid clutch apparatus 10 (or otherwise reduced if another type of MR fluid clutch apparatus 10 is used) so the force applied by the MR fluid actuator 160 on the dog component 161 is reduced. Spring(s) 167 may backdrive the dog component 161 until disengagement from the dog component 164. Spring(s) 167 may be a coil spring, a bushing, a leaf spring, or any other biasing member. When the dog component 161 is fully disengaged from of the dog component 164, the current may be removed if a normally closed MR fluid clutch apparatus 10 is used (though optional) to lock it in the position where the dog clutch is in bistable position 1 without any power consumption. Bi-stable states 1 and 2 are shown in Fig. 17.

[0103] The normally closed MR fluid clutch apparatus 10 may also be a non-controllable one, where a magnet is present but no coil 18. In such an embodiment, the sequence may need to be different. When the synchronisation of the power motor 163 and the output is within an acceptable range, the motor 165 may be activated so the torque from the actuator motor 165 can displace the fork 162 through the normally closed MR fluid clutch apparatus 10. During the connection sequence, the actuator motor 165 has to accelerate so clamping time may beincreased. However, the system using a non-controllable MR fluid clutch apparatus 10 may still offer the advantage of producing little reflected inertia and the dog component 161 of the dog clutch does not create a big shock when it contacts the dog component 164 on the output side so parts engage smoothly. Simultaneously, when the dog component 161 of the dog clutch and the dog component 164 are fully engaged, the actuator motor 165 may be stopped and the actuator may be locked in a bi-stable position 2 without any power consumption. The power motor 163 connected to the input shaft may then be activated to transfer torque through the dog clutch. To disengage the dog clutch in the system where the MR fluid clutch apparatus 10 is of non-controllable type, the power motor torque may be reduced and the actuator motor 165 may be activated in the reverse direction so the actuator may “pull” on the system, allowing the spring(s) 167 to separate the dog components 161 and 164. In such a system, the spring(s) 167 may also be removed if the thrust bearings 168 are of a type that may transfer the force in two directions. When the dog component 161 is fully disengaged from of the dog component 164, the current may be removed if a normally closed MR clutch apparatus 10 is used, to lock it in the position where the dog clutch is in bi-stable position 1 without any power consumption.

[0104] The system of Figs. 16 and 17 may generally be described as being for a vehicle powertrain and may include at least a torque source for imparting torque to an input; at least one wheel at an output; a positive contact clutch for engagement and disengagement between the input and the output for transmission of the torque to the at least one wheel; and a mechanical clutch actuator for actuating the engagement and / or disengagement of the positive contact clutch by applying a force on at least one component of the positive contact clutch, the mechanical clutch actuator including a motor and a MR fluid clutch apparatus between the motor and the at least one component of the positive contact clutch to control said force by applying a variable amount of slippage between the motor and the at least one component.

Claims

CLAIMS:

1. A vehicle powertrain comprising: at least an electric motor; a gear assembly configured to couple at least one wheel of the vehicle to the motor for the at least one wheel to be driven by the electric motor, the gear assembly including a positive contact clutch for switching the gear assembly between at least a first gear ratio and a second gear ratio; an actuator for controlling the switching of the positive contact clutch; and a magnetorheological (MR) fluid clutch apparatus between the motor and the positive contact clutch, the MR fluid clutch apparatus configured to apply a variable amount of slippage between the motor and a component of the positive contact clutch, during coupling of the positive contact clutch in the switching.

2. The vehicle powertrain according to claim 1 , wherein the MR fluid clutch apparatus is located between the electric motor and a driving axle of the gear assembly.

3. The vehicle powertrain according to claim 2, further including a gear set between the electric motor and the MR fluid clutch apparatus to cause a speed reduction.

4. The vehicle powertrain according to any one of claims 1 to 3, wherein the positive contact clutch includes a positive contact component rotating with a driven axle, and translating between engagement with a first gear associated with the first gear ratio, and with a second gear associated with the second gear ratio, the engagement of the positive contact component resulting in one of the first gear and the second gear to rotate with the driven axle.

5. The vehicle powertrain according to any one of claims 1 to 4, wherein the actuator includes a gear change electric motor.

6. The vehicle powertrain according to claim 5, wherein the gear change electric motor is coupled to a positive contact component of the positive contact clutch by a rotation-to-translation device.

7. The vehicle powertrain according to claim 1 , including two of the motor, each of the two motors connected to a driving axle of the gear assembly by a respective one of the MR fluidclutch apparatus, the MR fluid clutch apparatuses apply a variable amount of slippage between the respective motors and the driving axle to control an input of the motors on the driving shaft.

8. The vehicle powertrain according to claim 7, further including a gear set between each of the motors and the respective MR fluid clutch apparatuses to cause a speed reduction.

9. The vehicle powertrain according to any one of claims 1 to 8, wherein the MR fluid clutch apparatus includes a magnet and is of the normally closed type.

10. The vehicle powertrain according to any one of claims 1 to 9, further including a controller for controllably powering the MR fluid clutch apparatus into applying the variable amount of slippage.

11. The vehicle powertrain according to any one of claims 1 to 10, wherein the positive contact clutch is a dog clutch.The vehicle powertrain according to any one of claims 1 to 10, wherein the positive contact clutch is a dog clutch.

13. The vehicle powertrain according to any one of claims 1 to 10, wherein the positive contact clutch is a chain and sprocket drive.

14. A vehicle powertrain comprising: at least a torque source for imparting torque to an input; at least one wheel at an output; a positive contact clutch for engagement and disengagement between the input and the output for transmission of the torque to the at least one wheel; and a mechanical clutch actuator for actuating the engagement and / or disengagement of the positive contact clutch by applying a force on at least one component of the positive contact clutch, the mechanical clutch actuator including a motor and a MR fluid clutch apparatus between the motor and the at least one component of the positive contact clutch to control said force by applying a variable amount of slippage between the motor and the at least one component.

15. The vehicle powertrain according to claim 14, wherein the mechanical clutch actuator includes a member pushing the at least one component of the positive contact clutch into engagement, the member connected to an output of the MR fluid clutch apparatus.

16. The vehicle powertrain according to claim 15, wherein the member is a fork.

17. The vehicle powertrain according to any one of claims 15 to 16, wherein the mechanical clutch actuator includes at least one thrust bearing between the at least one component of the positive contact clutch and the MR fluid clutch apparatus.

18. The vehicle powertrain according to any one of claims 14 to 17, including at least one spring biasing the positive contact clutch toward disengagement against an action of the MR fluid clutch apparatus.

19. The vehicle powertrain according to any one of claims 14 to 18, including a reduction mechanism between the motor and the MR fluid clutch apparatus.

20. The vehicle powertrain according to claim 19, wherein the reduction mechanism is non backdrivable.

21. The vehicle powertrain according to any one of claims 14 to 20, wherein the MR fluid clutch apparatus includes a magnet and is of the normally closed type.

22. The vehicle powertrain according to claim 21 , wherein the mechanical clutch actuator has a first bi-stable position and a second bi-stable position in which the motor is off, the positive contact clutch in said disengagement in the first bi-stable position, the positive contact clutch in said engagement in the second bi-stable position.

23. The vehicle powertrain according to claims 14 to 22, further including a controller for controllably powering the MR fluid clutch apparatus into apply the variable amount of slippage.

24. The vehicle powertrain according to any one of claims 14 to 23, wherein the positive contact clutch is a dog clutch.

25. The vehicle powertrain according to any one of claims 14 to 23, wherein the positive contact clutch is a dog clutch.

26. The vehicle powertrain according to any one of claims 14 to 23, wherein the torque source is an electric motor.

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