FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Dual rotor radial flux BLDC motor and brake combination for driving vehicle wheel
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli,
Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Dr Ekram Samsul, Crompton Greaves Limited, CG Global R&D Centre, Kanjurmarg (East), Mumbai 400042, Maharashtra, India, an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed :

TECHNICAL FIELD OF THE INVENTION
This invention relates to a dual rotor radial flux BLDC motor and brake
combination for driving vehicle wheel.
PRIOR ART DESCRIPTION
A dual motor radial flux BLDC (brushless direct current) motor comprises a rotational shaft rotatable with the inner and outer rotors of the motor. Drive is taken from the shaft of the motor. A vehicle wheel like that of a two wheeler is generally directly driven by a single rotor radial flux BLDC motor comprising a stationary shaft and a rotor located in a motor body and disposed over a stator. The motor body comprises a cylindrical member extending axially from one face of a flat member. The rotor magnets are located at the inner circumference of the cylindrical member. The motor body is rotatably mounted on the shaft and includes a hub axially extending from the opposite face of the flat member and housing a brake to stop the rotation of the motor body and rotor and the vehicle wheel. A single rotor radial flux BLDC motor has a low torque to weight ratio and hence low efficiency and also low speed. The size of the motor increases with the torque and efficiency and also speed requirements of the motor. This increases the cost of the motor and also renders it bulky and heavy. As there is only one air gap between the rotor and stator, short time power delivery of the motor is low. As a result, the acceleration time for the vehicle is increased and pick up speed of the vehicle is reduced. A wheel driving motor is invariably exposed. Unless it is made leak proof, water will seep into the motor and damage the motor. The outer end of the cylindrical

member is prone to cantilever effect. Unless the outer end of the cylindrical member is supported against cantilever effect, the motor body will start wobbling during operation of the motor. This will generate ripple torque and reduce the efficiency of the motor. The air gap between the rotor and stator will become non-uniform and the motor will start malfunctioning. It may also cause the rotor to touch and rub against the stator and damage the stator.
OBJECTS OF THE INVENTION
An object of the invention is to provide a compact, light weight and economical dual rotor radial flux BLDC motor and brake combination for directly driving a vehicle wheel, which combination is leak proof and eliminates the cantilever effect.
Another object of the invention is to provide a compact, light weight and economical dual rotor radial flux BLDC motor and brake combination for directly driving a vehicle wheel, which combination develops increased torque and has improved efficiency and speed and further has improved short time power delivery and acceleration time and pick up speed for the vehicle.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a dual rotor radial flux BLDC motor and brake combination for driving vehicle wheel, the combination comprising a motor body having a flat member having an inner cylinder and an outer cylinder axially extending from one face thereof in spaced apart relationship with each other, the outer end of the outer cylinder protruding

out of the inner cylinder, a non-cantilever support cover supporting the outer end of the outer cylinder leak tight, a shaft axially rotatably supported in the flat member and support cover, the shaft ends protruding outside the flat member and support cover and being adapted to fit the vehicle frame, the motor body further comprising a mounting flange provided around the outer cylinder for mounting the motor to the rim of the vehicle wheel and a hub axially extending from the opposite face of the flat member and housing a brake for arresting the rotational movement of the vehicle wheel, a cylindrical stator disposed in the space between the inner and outer cylinders and mounted on the shaft, an inner rotor mounted on the outer surface of the inner cylinder describing an air gap with the inner circumference of the stator and an outer rotor mounted on the inner circumference of the outer cylinder describing an air gap with the outer circumference of the stator.
The following is a detailed description of the invention with reference to the accompanying drawings, in which
Fig 1 is a schematic crosssectional view of a dual rotor radial flux BLDC motor and brake combination for driving a vehicle wheel according to an embodiment of the invention;
Fig 2 is an enlarged view at X in Fig 1;
Fig 3 is an isometric view of the motor body with the inner and outer rotors; and

Fig 4 is a section at A-A in Fig 1.
The dual rotor radial flux BLDC motor and brake combination 1 as illustrated in Figs 1 to 4 of the accompanying drawings comprises a motor body 2 having a flat member 3 having an inner cylinder 4 and an outer cylinder 5 axially extending from one face of the flat member in spaced apart relationship with each other. The outer end of the outer cylinder protrudes out of the inner cylinder. 6 is a non-cantilever support cover comprising an inwardly extending L-shaped portion 7 around the edge thereof. The cover 6 is fitted leak tight at the outer end of the outer cylinder by tight fitting one limb 7a of the L-shaped portion in an engaging groove 8 provided around the inner circumference of the outer end of the outer cylinder (Fig 2). The other limb 7b of the L-shaped portion extends into the outer end of the outer cylinder in close leak tight contact therewith (Fig 2). The support cover is further fitted at the outer end of the outer cylinder with screws 9 tightened in screw holes 10 at the outer end of the outer cylinder. The contact surfaces between the outer end of the outer cylinder and the support cover are further rendered leak proof by applying a sealant like silica gel (not shown) therebetween. The outer end of the outer cylinder is thus well supported against cantilever effect by the support cover 6. 11 is a hub axially extending from the opposite face of the flat member. 12 is a mounting flange provided around the outer circumference of the outer cylinder. The flange is provided with mounting holes 13. 14 is a shaft axially rotatably supported in the flat member and support cover using bearings 15a and 15b. 16 is a stator body mounted on the shaft. 17 is a cylindrical stator disposed in the space between the inner cylinder and outer cylinder and mounted on the stator body. 18 is an inner rotor mounted on

the outer circumference of the inner cylinder describing an air gap (not marked) against the inner circumference of the stator. 19 is an outer rotor mounted on the inner circumference of the outer cylinder describing an air gap (not marked) against the outer circumference of the stator. The inner rotor magnets are marked 18a and the outer rotor magnets are marked 19a respectively (Fig 3). The wheel mounting forks 20a, 20b of the vehicle frame (not shown) are mounted at the ends of the shaft by nuts 21a and 21b respectively tightened against washers 22a and 22b, respectively. The mounting flange 12 is fitted onto the rim (not shown) of a vehicle wheel by bolts (not shown) tightened in the mounting holes 13. 23 is a drum type brake comprising a pair of semicircular brake shoes 24 axially extending from one face of a flat portion 25. The flat portion is located within the hub against a step 26 at the outer end of the hub with the brake shoes disposed within the hub. A pair of semicircular liners 27, 27 are provided over the brake shoes. The brake shoes are hinged (hinge marked 28) together at one ends thereof. 29 is a brake lever disposed between the other ends of the brake shoes and pivoted (pivot marked 30) at the center thereof and connected to a pulling cord or string or chain or the like (not shown) tied at one end thereof through hole 31 therein.
During operation of the motor, current flows through the windings of the stator. Due to the flow of current through the windings of the stator, a magnetic field is created around the stator and magnetic fluxes flow across the motor radially and cause the inner and outer rotors to rotate. As a result, the motor body rotates around the shaft and transmits rotational movement to the vehicle wheel via the flange 12. On applying a pulling force to the brake lever via the pulling cord, the brake lever rotates about the pivot

thereof and presses or forces apart the other ends of the brake shoes. As a result, the brake shoes with the liners move outwardly and press against the inner circumference of the hub so as to arrest the rotational movement of the motor body and rotor and the vehicle wheel. On releasing the pulling force on the brake lever, the brake lever regains its original position and the brake shoes with the liners also move in and regain their original position so as to allow the vehicle wheel to rotate.
According to the invention maximum use of the current flowing through the windings of the stator is made and the magnetic fluxes generated at the inner and outer circumferences of the stator are utilized to rotate both the inner and outer rotors so as to increase the rotational movement of the rotors and the motor body. As a result, increased torque is developed by the motor and motor efficiency and speed are increased. Due to the double air gap between the stator and the inner and outer rotors, the motor has increased short time power delivery and acceleration time and pick up speed of the vehicle is increased. Because of the increased torque, efficiency and speed of the motor, the motor size can be reduced so as to make it compact and light weight for a given rating of motor. The motor is leak proof and is ideal for external use as damage to the motor due to leakage of water is prevented. As the outer end of the outer cylinder is supported against cantilever effect, problems arising from cantilever effect have been eliminated.
The brake configuration can be different. Instead of the flange with mounting hole, other arrangement may be used for fitting the motor to the rim of the wheel. Instead of the L-shaped portion at the contact surfaces

between the support cover and the outer end of the outer cylinder, other leak tight and supporting arrangement may be used between the contact surfaces of the support cover and outer end of the outer cylinder. Such variations of the invention are to be construed and understood to be within the scope of the invention.

We claim :
1. A dual rotor radial flux BLDC motor and brake combination for driving vehicle wheel, the combination comprising a motor body having a flat member having an inner cylinder and an outer cylinder axially extending from one face thereof in spaced apart relationship with each other, the outer end of the outer cylinder protruding out of the inner cylinder, a non-cantilever support cover supporting the outer end of the outer cylinder leak tight, a shaft axially rotatably supported in the flat member and support cover, the shaft ends protruding outside the flat member and support cover and being adapted to fit the vehicle frame, the motor body further comprising a mounting flange provided around the outer cylinder for mounting the motor to the rim of the vehicle wheel and a hub axially extending from the opposite face of the flat member and housing a brake for arresting the rotational movement of the vehicle wheel, a cylindrical stator disposed in the space between the inner and outer cylinders and mounted on the shaft, an inner rotor mounted on the outer surface of the inner cylinder describing an air gap with the inner circumference of the stator and an outer rotor mounted on the inner circumference of the outer cylinder describing an air gap with the outer circumference of the stator.
2) The combination as claimed in claim 1, wherein the non-cantilever support cover comprises an inwardly extending L-shaped portion around the edge thereof, one limb of the L-shaped portion being tight fitted in an engaging groove provided around the inner circumference of the outer end of the outer cylinder and the other limb of the L-shaped portion extending into the outer end of the outer cylinder in close leak tight contact with the inner circumference thereof, the outer end of the outer cylinder being

supported against cantilever effect by the support cover, the contact surfaces between the outer end of the outer cylinder and the support cover being applied with a sealant therebetween.
3) The combination as claimed in claim 1 or 2, wherein the brake is a drum type brake comprising a pair of semicircular brake shoes extending axially from a flat portion, the flat portion being located in the hub against a step at the outer end of the hub with the brake shoes extending into the hub, a pair of semicircular liners each provided over each of the brake shoes, the brake shoes being hinged together at one ends thereof, a brake lever disposed between the other ends of the brake shoes and pivoted at the center thereof and connected to a pulling cord at one end thereof.
ABSTRACT
A dual rotor radial flux BLDC motor and brake combination (1) for driving vehicle wheel. The combination comprises a motor body (2) having a flat member (3) having an inner cylinder (4) and an outer cylinder (5) axially extending from one face thereof in spaced apart relationship with each other. The outer end of the outer cylinder protrudes out of the inner cylinder. 6 is a non-cantilever support cover supporting the outer end of the outer cylinder leak tight. (14) is a shaft axially rotatably supported in the flat member and support cover. The shaft ends protrude outside the flat member and support cover and is adapted to fit the vehicle frame (not shown). The motor body further comprises a mounting flange (12) provided around the outer cylinder for mounting the motor to the rim of the vehicle wheel and a hub (11) axially extending from the opposite face of the flat member and housing a brake for arresting the rotational movement of the vehicle wheel. (17) is a cylindrical stator disposed in the space between the inner and outer cylinders and mounted on the shaft. 18 is an inner rotor mounted on the outer surface of the inner cylinder describing an air gap with the inner circumference of the stator (16) and (19) is an outer rotor mounted on the inner circumference of the outer cylinder describing an air gap with the outer circumference of the stator (Fig 1).