Patent Application
20080078631
This invention relates to disc brakes in combination with brushless electric motor-generators.
Pancake electric motors typically permit axial compactness while enabling large motor rotor diameters for higher power and torque generation. The pancake electric motor may be operated as a generator using the motor rotor as a mechanical input device. In this mode, current induced in the electromagnets' coils by the rotation of the rotor charges an electricity storage device such as a battery or supercapacitor.
Disc brakes, in typical automotive, rail vehicle, light aircraft and similar applications employ a rotor located on the axle or wheel hub and a caliper mechanism that clamps brake pads against both sides of the rotor, creating friction and generating braking force. Disc brakes may employ annular calipers that clamp annular brake pads, in effect stator discs, into contact with the rotor surfaces to create friction. In most commercial and military aircraft, multiple rotors are splined to the inside of the wheel rim and multiple stators are splined to a torque tube affixed to the undercarriage; a pressure plate compresses the stack of rotor and stator discs against a back plate fitted to the torque tube.
In conventional disc brake usage a vehicle's kinetic energy is dissipated as heat when the brakes are applied. An improvement for vehicles using electricity for motive power, such as electric and hybrid vehicles, is the combination of a disc brake with an electric generator whereby a proportion of the kinetic energy is regenerated as electricity during braking and transferred to a storage device, such as a battery or supercapacitor, for future use. It is advantageous for the generator also to function as an electric motor to provide additional motive power to propel the vehicle via the brake rotor, axle, drive shaft or hub to which it is mounted.
The invention relates to a combination friction brake and kinetic energy regeneration and electric drive mechanism that combines a disc brake and a brushless pancake electric motor-generator in an integrated mechanism for optimum space, weight and component utilization by coupling, combining or integrating the brake rotor and the rotor of the motor, by coupling, combining or integrating the brake caliper with the motor stator, and by coupling, combining or integrating the motor stator with the vehicle hub carrier or suspension upright (sometimes called, when located at steerable wheels, a steering knuckle). Preferred pancake electric motor-generators include, but are not limited to, those disclosed in U.S. Pat. Nos. 6,552,460 and 6,930,433 and US Pat. Application Publication No. US 2006/0119215, a continuation-in-part application to the '460 and '433 patents, which are hereby incorporated by reference in their entirety. The brushless DC electric motor-generators as disclosed in the abovementioned patents and application comprise a disc or ring-like rotor having a plurality of equally spaced permanent magnets of alternating polarity arrayed radially about the rotor periphery that electromagnetically engages with a plurality of electromagnets that form the stator. When energized, the stator electromagnets are triggered to switch polarity in a sequence that attracts and repels the pen anent magnets, causing the rotor to rotate.
The disc brake of the invention comprises at least one rotor and may be actuated by electric, hydraulic, mechanical or pneumatic means. The disc brake may be of the fixed or floating caliper type and may employ fixed or floating rotors. The combination disc brake-motor-generator mechanism may have a) a common rotor, b) the brake rotor and the motor-generator rotor coupled to rotate together, or c) the brake rotor provided with features that enable it to function as an pancake electric motor-generator rotor. Such features may include, but are not limited to, perpendicular, angled, parallel or concentric coaxial annular flanges or projecting elements located on the periphery and/or one or both sides of the rotor, on which is mounted a plurality of equally spaced permanent magnets or magnetic domains mounted in alternating polarity that magnetically engage with the electromagnetic stator elements of the motor-generator. The annular flanges or projecting elements may be affixed to or integral with the rotor. The annular flanges or projecting elements may use different materials and manufacturing processes to that of the rotor, such as, but not limited to, cast, stamped or forged aluminum, steel and titanium, and carbon fiber. The rotor and annular flanges or projecting elements may be vented, vaned, ribbed, drilled and otherwise shaped, formed or featured to dissipate heat and/or cause or assist cooling of the rotor and other brake-motor-generator components, and may incorporate insulation materials to minimize heat transfer from the braking surfaces to the magnets, sensors and other brake and motor-generator components.
In order to transmit motor and brake torque reaction, the combined disc brake-motor-generator mechanism must be rigidly and robustly affixed to a non-rotatable member of the vehicle, either at the wheel, outboard of the suspension, or on the vehicle inboard of the suspension. In the majority of automotive applications, disc brake calipers are located at the wheel, typically mounted and affixed to a non-rotatable suspension upright, hub carrier or steering knuckle, while the brake rotor is affixed to the wheel hub so as to rotate with the wheel. In a weight, cost and component saving embodiment of the invention, the motor-generator stator housing may be affixed to or combined or integrated with the vehicle suspension upright or hub carrier either inboard or outboard of the upright. The vehicle axle or spindle is rotatably located in the suspension upright. The motor-generator rotor and the brake rotor are coupled or combined coaxially to a common shaft such as an axle, drive-shaft, half-shaft or spindle.
The combined disc brake-motor-generator system may be compatible with various electronic vehicle control and management systems including skid, stability, and traction control systems. The kinetic energy regeneration and reuse brake device is suitably wired to operate during braking, coasting on a trailing throttle and acceleration. The generator function is activated, by appropriate switch devices, when the accelerator is released or the brakes are applied. Applying the accelerator or releasing the brakes disengages the generator function. While the generator function is engaged, the rotation of the vehicle's wheels causes current to be induced in the electromagnets' coils and stored in an electric power storage device such as a battery or supercapacitor. The electric motor function may be engaged, either automatically when the accelerator is applied, or at the driver's discretion by means of a switch device or other engagement mechanism.
The brushless pancake electric motor-generators of the types disclosed in, but not exclusive to the '460 and '433 patents and the '215 application offer advantages of high torque, low weight and axial compactness. The motor-generator rotor's disc-like architecture makes it suitable for combining or coupling with, or forming an integral part of, a disc brake rotor. Similarly, the motor-generator's stator architecture makes it suitable for combining or coupling with, or forming an integral part of, a disc brake caliper and a suspension upright. In addition to savings in reduced complexity, weight and component cost, this combination provides the opportunity for locating the brake-motor-generator mechanism within a conventional vehicle wheel without creating excessive unsprung weight.
The invention may be used to enable full-time or as-needed all-wheel-drive functionality and capability in a two-wheel-drive vehicle by fitting the invention to the front wheels of a rear-wheel-drive vehicle or by fitting the invention to the rear wheels of a front-wheel-drive vehicle.
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of preferred embodiments of the invention which proceed with reference to the accompanying drawings. The same or similar parts are indicated by the same reference numerals.
The '460 and '433 patents disclose a plurality of single-gapped toroidal or “c”-shaped electromagnets that electromagnetically engage with a single ring of equally spaced permanent magnets of alternating polarity radially arrayed about the periphery of the rotor that passes between the single gap formed by the space between the two arms of the “c”. The '215 application discloses a double-gapped version of the pancake motor-generator that employs pairs of half-toroidal or “u”-shaped electromagnets, the pairs of “u”-shaped electromagnets having their arms facing each other and spaced apart to form two gaps through which two rings or rows of equally spaced permanent magnets of alternating polarity radially arrayed about the periphery of the rotor may pass. It is believed that the double-gapped version may offer power and torque advantages over the single-gapped version. Both the single-gapped and double-gapped versions of the pancake motor-generator are compatible with the current invention.
An embodiment of the current invention comprises a disc brake having a conventional hydraulic brake caliper in combination with a brushless pancake electric motor-generator of the type disclosed in the '460 and '433 patents and the '215 application, the rotors of the disc brake and the electric motor-generator coupled to rotate together.
Another embodiment of the invention comprises a combination of a coaxial helically actuated disc brake as disclosed in Applicant's US Patent Application Publication No. US 2006/0260886, incorporated by reference, which employs an annular caliper mechanism and annular brake pads, and a brushless electric generator-motor of the type disclosed in '460 and '433 patents and the '215 application.
The motor-generator stator is affixed to brake support element 109 in a stator housing 122 affixed to or integral with brake support element 109. Annular brake pad carriers 105 and 106 are axially slidably mounted on support element 109 which is affixed to the vehicle to transmit the braking torque. Pad carrier 105 is located between pressure plate 108 and floating rotor 102 and pad carrier 106 between floating rotor 102 and fixed rotor 104. Pad carriers 105 and 106 have friction material or suitable friction facings 107 affixed to or integral with their surfaces adjacent to the rotor braking surfaces.
The coaxial helically actuated brake's helical mechanism comprises a series of track rollers 113 running in helical tracks 114 formed in support element 109. Pressure plate 108 is driven by an actuator 116, for example in this embodiment an electric gear motor, by means of pinion 117 meshing with gear rack 118 affixed to pressure plate 108. Alternative actuation means include pneumatic and hydraulic cylinders oriented tangentially to pressure plate 108, and brushless electric motors as disclosed in, but not exclusive to, the '460 and '433 patents and the '215 application and described hereunder with reference to
When the brake is actuated, because pressure plate 108 is rotatably mounted on support element 109 by means of the helical mechanism comprising track rollers 113 running in helically shaped tracks 114, pressure plate 108 moves axially in a helical motion away from stator electromagnets 111 towards pad carrier 105. Pressure plate 108 has a low friction element 115, such as the Diamond-Like Carbon (DLC) coating manufactured by Bekaert Advanced Coating Technologies, on its surface facing adjacent pad carrier 105. Low friction element 115 enables smooth disengagement or decoupling of pressure plate 108 from pad carrier 105 by preventing helically rotating pressure plate 108 from tightening and seizing against adjacent pad carrier 105.
The electric motor-generator may be operated as a motor or as a generator depending on the arrangement of the electronic switching controls employed. When the brake is actuated pressure plate 108 axially pushes pad carrier 105, floating rotor 102 and pad carrier 106 against fixed rotor 104, creating braking friction. Since this embodiment employs both sides of floating rotor 102 and one side of fixed rotor 104 as friction surfaces, one more friction surface than that of a single rotor disc brake, it is able to generate about 50% greater brake torque than a disc brake of equal rotor diameter, or equivalent brake torque with smaller diameter rotors, so permitting reduced overall brake size and weight. The larger friction surface area also provides enhanced heat distribution and dissipation enabling lower friction material and rotor temperatures. To prevent friction generated heat from damaging permanent magnets 112 located on flange 110 of fixed rotor 104, insulating material, vents and other cooling features may be incorporated into flange 110 and rotor 104.
Electronic control devices are arranged to control the operation of the brushless electric motor-generator. In the aforementioned embodiments, when the vehicle is in motion, pushing the brake pedal actuates the brake and simultaneously causes the electric motor-generator to convert a portion of the brake torque to electricity which is transferred to an electricity storage device. The stored electric power may automatically or at the driver's discretion be used to power the electric motor-generator, acting as a motor, to augment the vehicle's main power source. The generator function may be wired to generate electric power while the vehicle is coasting. Releasing the accelerator switches the generator function on, and using the accelerator switches the generator function off. The brushless electric motor-generator of the '460 and '433 patents may be modified to energize the electromagnets in a sequence that is opposite to the direction of rotor rotation so as to retard the rotational speed of the rotor.
In a further embodiment of the invention, brushless electric motors of the type disclosed in, but not exclusive to, the '460 and '433 patents and the '215 application are employed to actuate the pressure plate of a coaxial helical disc brake mechanism such as disclosed in US Patent Application Publication No. US 2006/0260886. The coaxial helical mechanism imparts a helical advance motion (which couples rotational motion to axial motion) to the pressure plate to achieve uniform force across the pressure plate.
The brushless electric motor stator, comprising one or more slotted electromagnets 111 in stator housing 122, is fixedly mounted to brake support element 109 or other non-rotatable member and electromagnetically engages a plurality of permanent magnets 112 equally spaced and mounted in alternating polarity in coaxial annular or cylindrical flange 110 affixed to or integral with pressure plate 108. Flange 110 is mounted perpendicular to the rear surface of pressure plate 108 to enable pressure plate 108 to move axially away from electromagnets 111 comprising the motor stator toward brake stator pad carriers 105 and rotors 102 when pressure plate 108 is helically rotated during actuation. Permanent magnets 112 are of sufficient axial length and may be helically oriented so as to maintain electromagnetic engagement with stator electromagnets 111 over the helical axial travel of pressure plate 108. Permanent magnets 112 may be of rectangular, oblong or obround shape in plan view with the longer side corresponding to the helical axial travel of pressure plate 108. Torque tube 123 is mounted on support element 109 and is fitted with a back plate 124. Stator pad carriers 105 are mounted in a splined fashion on torque tube 123 so as to allow them to move axially on torque tube 123. Friction material 107 is affixed to the surfaces of stator pad carriers 105 that are adjacent to the surfaces of rotors 102. Rotors 102 are located in a splined fashion on splines 125 inside wheel rim 126. Pressure plate 108 has a low friction element 115, such as the Diamond-Like Carbon (DLC) coating manufactured by Bekaert Advanced Coating Technologies, on its surface facing adjacent stator pad carrier 105.
When the brake is applied, stator electromagnets 111 rotate pressure plate 108 by means of a triggered sequential electromagnetic engagement with permanent magnets 112 mounted on flange 110 affixed or integral with pressure plate 108. Since pressure plate 108 is rotatably mounted on support element 109 by means of a helical device comprising track rollers 113 running in helically shaped tracks 114, pressure plate 108 moves axially away from stator electromagnets 111 during actuation. A plurality of rectangular or obround permanent magnets 112 of alternating polarity are located length-wise axially on the coaxial annular flange 110 and permit constant electromagnetic engagement between permanent magnets 112 and stator electromagnets 111 as pressure plate 108 moves axially away from stator electromagnets 111 towards the stack of brake stators 105 and rotors 102. Pressure plate 108 axially forces brake stators 105 and rotors 102 against back plate 124 to create braking friction. Low friction element 115 enables smooth disengagement or decoupling of pressure plate 108 from innermost stator pad carrier 105 by preventing helically rotating pressure plate 108 from tightening and seizing against adjacent stator pad carrier 105.
A rear-wheel drive vehicle can similarly be provided with all-wheel drive functionality as well as regenerative braking at the front wheels.
Having described and illustrated the principles of the invention in the preferred embodiments thereof it should be apparent that the invention can be modified in arrangement and detail without departing from such principles. We claim all modifications and variations coming within the spirit and scope of the invention. The foregoing description is only exemplary of the principles of the invention. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, so that one of ordinary skill in the art would recognize that certain modifications and variations would come within the scope of this invention.
This application claims of the benefit of U.S. provisional patent application Ser. No. 60/882,450, filed Dec. 28, 2006, and is a continuation-in-part of U.S. patent application Ser. No. 11/461,912, filed Aug. 2, 2006, which is a continuation-in-part of PCT/US2005/003781, filed Feb. 3, 2005, which claims benefit of U.S. provisional patent application Ser. No. 60/542,523, filed Feb. 5, 2004, all of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60882450 | Dec 2006 | US | |
| 60542523 | Feb 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11461912 | Aug 2006 | US |
| Child | 11937432 | Nov 2007 | US |
| Parent | PCT/US2005/003781 | Feb 2005 | US |
| Child | 11461912 | Aug 2006 | US |
