TECHNICAL FIELD

The present disclosure relates to an apparatus, system and method for braking. In particular, but not exclusively it relates to an apparatus, system and method for braking electric and hybrid electric vehicles using an eddy current brake.

Aspects of the invention relate to an eddy current brake, a vehicle braking system, a method for braking a vehicle, a computer program, and a vehicle.

BACKGROUND

Hybrid electric vehicles (HEVs) and electric vehicles (EVs) use electric propulsion systems comprising an electric motor to provide traction. Such motors are sometimes termed electric drive motors, electromechanical generators, electric machines or traction motors. In some examples, hybrid electric vehicles and electric vehicles use one or more batteries as an energy storage means for storing electrical energy that is to be provided to the electric drive motor to provide traction. Such batteries are sometimes termed traction batteries. In some examples, HEVs and EVs alternatively or additionally use one or more capacitors, such as provided by a supercapacitor or bank of capacitors, as an energy storage means. Subsequent examples in this disclosure are described in relation to the use of a battery as an energy storage means, but it is to be understood that such examples may alternatively or additionally employ capacitors as an energy storage means.

In addition, regenerative braking can be provided for such HEVs and EVs, to convert the kinetic energy of the moving vehicle into electrical energy, in order to provide for recharging of the battery and retardation of the vehicle as a consequence. In order to facilitate regenerative braking, the electric motor is operated as a current generating means or current generation means in the form of an electric generator, with the battery providing the load on the electric motor. The electrical energy generated during regenerative braking is stored in the battery.

EVs do not have an internal combustion engine, but have an electric motor to provide motive force to the vehicle when connected to a battery.

HEVs have an internal combustion engine in combination with an electric motor to provide motive force to the vehicle. For example, series HEVs have an electric motor to provide motive force to the vehicle and an internal combustion engine to provide generation of power for the electric motor or to recharge the battery. In another example, parallel HEVs have an electric motor to provide motive force to the vehicle and an internal combustion engine also arranged to provide motive force to the vehicle.

In EVs and series HEVs, the electric motor provides motive power to the vehicle via a drivetrain of the vehicle powertrain. The drivetrain of a vehicle powertrain comprises a transmission and front and rear pairs of wheels. The transmission is arranged to drive a pair of front wheels of the vehicle, a pair of rear wheels of the vehicle, or both the front and rear pairs of wheels of the vehicle.

In parallel HEVs both the electric motor and the internal combustion engine are connected to the transmission of the powertrain and can separately or individually provide motive power to the vehicle.

In one example of a parallel HEV, the powertrain of the vehicle includes an internal combustion engine which is releasably coupled to an electric motor in the form of a crankshaft integrated motor generator (CIMG). The internal combustion engine is releasably coupled to the CIMG by means of a clutch. The CIMG is in turn coupled to a transmission of the vehicle powertrain. The transmission is arranged to drive a pair of front wheels of the powertrain by means of a pair of front drive shafts. The powertrain also has an auxiliary driveline arranged to drive a pair of rear wheels by means of an auxiliary driveshaft and a rear differential.

An energy storage means, such as a battery, may be coupled to the CIMG in order to allow the CIMG to generate motive force in the form of torque when the CIMG is operated as a motor. The battery may be coupled to the CIMG to receive electrical energy in the form of charging current from the CIMG when the CIMG is operated as a generator in order to recharge the battery.

Under high levels of braking, such as under emergency braking conditions, where high levels of braking torque are generated, high levels of electrical energy in the form of charging current are generated by the electric motor. In many HEVs and EVs the battery is not able to accept the high level of charging current generated by the electric motor under such high levels of braking, and so it is necessary to additionally provide friction braking using, for example, conventional friction disc brakes. Furthermore friction braking may be required when the battery is fully charged, and when the vehicle is moving slowly as regenerative braking is less efficient at lower vehicle speeds.

In some systems, excess current generated under high levels of regenerative braking is provided to a current dump. For example, excess current generated under high levels of regenerative braking may be provided to braking resistor banks, sometimes called rheostatic brakes.

In some systems, excess current generated under high levels of regenerative braking is provided to heating means, for example heating elements, such as heated windscreens, and heating, ventilation and air conditioning (HVAC) systems, even when such heating means are not required, thus wasting energy that is generated by the electric motor.

It is an aim of the present invention to address disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide an eddy current brake, a vehicle braking system, a method for braking a vehicle, a computer program, and a vehicle, as claimed in the appended claims.

According to an aspect of the invention there is provided an eddy current brake comprising: a rotor; and an electromagnet arranged to receive current from a current generating means during braking of the rotor, and to induce an eddy current within the rotor.

According to an aspect of the invention there is provided an eddy current brake comprising: a rotor; and an electromagnet arranged to receive current from an electromechanical energy generating means during braking of the rotor, and to induce an eddy current within the rotor.

According to an aspect of the invention, there is provided an eddy current brake for a vehicle, the eddy current brake comprising: a rotor; and an electromagnet arranged to receive current from an electromechanical energy generating means during braking of the vehicle and to induce an eddy current within the rotor. This provides the advantage of providing an additional braking component and minimizes the requirements of friction braking.

The electromechanical energy generating means may be an electric motor operating as a generator during braking of the vehicle.

The electromagnet may be separated from the rotor by a small air gap. The air gap may be up to the order of a few millimetres. This provides the advantage of reducing coupling losses between the electromagnet and the rotor when inducing an eddy current in the rotor.

The electromagnet may be located at a radially outer portion of the rotor. This provides the advantage of increased eddy current generation within the rotor, since the outer portion of the rotor moves with higher speed.

According to an aspect of the invention, there is provided a vehicle braking system comprising an eddy current brake as described in any of the preceding paragraphs, and controller means arranged to control the amount of current to be provided to the electromagnet of the eddy current brake from the electromechanical energy generating means.

The controller means may be an electronic controller.

The controller means may arranged to determine an amount of current generation provided by the electromechanical energy generating means.

The controller means may be arranged to determine the amount of current to be provided to the electromagnet of the eddy current brake from the electromechanical energy generating means in dependence, at least in part, upon the current generation provided by the electromechanical energy generating means. This provides the advantage of optimizing the utilization of generated energy, in particular by ensuring that excess current generated by the electromechanical energy generating means is used to provide additional braking torque to decelerate the vehicle.

The controller means may be arranged to determine the amount of current to be provided to an energy storage means from the electromechanical energy generating means in dependence, at least in part, upon the current generation provided by the electromechanical energy generating means. This provides the advantage of optimizing the storage of generated energy within the energy storage means.

The energy storage means may comprise or may be a battery. Alternatively or additionally the energy storage means may comprise one or more capacitors, such as provided by a supercapacitor or bank of capacitors.

The controller means may be arranged to determine the amount of current to be provided to the electromagnet of the eddy current brake from the electromechanical energy generating means in dependence, at least in part, upon a current absorption limit for the energy storage means.

The controller means may be arranged to allow provision of current to the electromagnet of the eddy current brake when the current generation provided by the electromechanical energy generating means exceeds the current absorption limit for the energy storage means.

The controller means may be arranged to receive input from an energy storage state monitor providing an energy storage state value of the energy storage means.

The controller means may be arranged to determine the amount of current to be provided to the electromagnet of the eddy current brake from the electromechanical energy generating means in dependence, at least in part, upon the energy storage state value. This provides the advantage of optimizing the usage of generated energy from the electromechanical energy generating means to minimize energy wastage.

The controller means may be arranged to receive an input from a brake pedal position sensor providing a brake pedal position value corresponding to a driver demanded deceleration and to determine the amount of current to be provided to the electromagnet of the eddy current brake from the electromechanical energy generating means in dependence, at least in part, upon the brake pedal position value.

The controller means may be arranged to receive an input from a speed sensor providing a vehicle speed value, and to determine the amount of current to be provided to the electromagnet of the eddy current brake from the electromechanical energy generating means in dependence, at least in part, upon the vehicle speed value.

The vehicle braking system may comprise electromechanical energy generating means arranged to provide current to the electromagnet of the eddy current brake.

The vehicle braking system may comprise energy storage means for receiving current from the electromechanical energy generating means.

The controller means may be arranged to determine the amount of braking torque to be provided by a friction brake. The friction brake may be a hydraulic friction brake.

The friction brake may be arranged to be actuated during a braking event, prior to the eddy current brake receiving current from the electromechanical energy generating means. Alternatively or additionally, the friction brake may be actuated when the vehicle speed is below a threshold speed.

The friction brake may be actuated when the vehicle speed is less than 16 kilometres per hour (km/h). In other examples, the friction brake may be actuated at a different low vehicle speed, for example at a vehicle speed between 0 km/h and 20 km/h. In some examples the vehicle speed at which the friction brake may be actuated may be 10 km/h or 20 km/h. The speed at which the friction brake may be actuated may be dependent on the configuration of the eddy current brake arrangement.

The vehicle braking system may comprise a hydraulic friction brake comprising a caliper and brake pad, the caliper arranged to move the brake pad to be in contact with a brake disc when the hydraulic friction brake is actuated. Other mechanical vehicle braking systems may be alternatively or additionally employed to decelerate the vehicle at low vehicle speeds and/or to hold the vehicle in a stationary position.

The electromechanical energy generating means may be provided on a first vehicle axle and the eddy current brake may be provided on a second vehicle axle. This provides the advantage of providing a level of frictionless braking on a plurality of axles simultaneously, for example on both axles of a two axle vehicle.

According to an aspect of the invention, there is provided a vehicle comprising an eddy current brake as described in any of the preceding paragraphs, or a vehicle braking system as described in any of the preceding paragraphs.

According to an aspect of the invention, there is provided a method for braking a vehicle, comprising: controlling the amount of current to be provided to an electromagnet of an eddy current brake from an electromechanical energy generating means during braking of the vehicle.

The method may comprise determining an amount of current generation provided by the electromechanical energy generating means.

The method may comprise determining the amount of current to be provided to the electromagnet of the eddy current brake from the electromechanical energy generating means in dependence, at least in part, upon the current generation provided by the electromechanical energy generating means.

According to an aspect of the invention, there is provided a computer program comprising instructions that, when executed by one or more processors, cause a system to perform, at least, controlling the amount of current to be provided to an electromagnet of an eddy current brake from an electromechanical energy generating means during braking of the vehicle.

The computer program may comprise instructions that, when executed by one or more processors, cause a system to perform, at least, a method as described in any of the preceding paragraphs.

According to an aspect of the invention, there is provided a non-transitory computer readable media comprising a computer program as described in any of the preceding paragraphs.

According to an aspect of the invention, there is provided a controller means arranged to control the amount of current to be provided to an electromagnet of an eddy current brake from an electromechanical energy generating means. The current may be provided to the electromagnet of the eddy current brake from the electromechanical energy generating means without being stored in an energy storage means.

According to an aspect of the invention, there is provided a method for braking a vehicle, comprising: determining the amount of current generation provided by electromechanical energy generating means during braking of the vehicle; supplying a first portion of generated current to energy storage means; and supplying a second portion of generated current to an eddy current brake.

The current supplied to the eddy current brake may be supplied directly and/or exclusively from the electromechanical energy generating means.

According to an aspect of the invention, there is provided a method for braking a vehicle, comprising: detecting current generated by electromechanical energy generating means, which may be in the form of a motor generator, during regenerative braking of the vehicle; supplying a first portion of the detected current to energy storage means, which may be in the form of a battery, such as a traction battery; and supplying a second portion of the detected current to an eddy current brake.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

