WO2013108265A2

WO2013108265A2 - Motor differential

Info

Publication number: WO2013108265A2
Application number: PCT/IN2012/000524
Authority: WO
Inventors: Tejas Krishna Kshatriya; Anup Vitthal SABLE
Original assignee: Kpit Cummins Infosystems Limited
Priority date: 2011-07-29
Filing date: 2012-07-27
Publication date: 2013-07-25
Also published as: WO2013108265A3

Abstract

A method for using an electric motor as differential for a vehicle is disclosed. The electric motor for a hybrid or an electric vehicle is utilized in a split manner in order to provide both, the transmission and the differential required for operating a vehicle. The motor differential allows for rotating a pair of driving wheels at different speeds, mainly while turning of the vehicle. The split AC induction motor comprising of stator windings and two independent rotors is utilized to generate the flux and the torque required for running the vehicle as well as providing the differential action required for turning the vehicle.

Description

MOTOR DIFFERENTIAL

FIELD OF INVENTION:

The present invention relates to the motor vehicle differentials and more specifically to electric motors as differential in a hybrid or electrical vehicle. The invention further relates to a method of combining a motor and a differential without the use of mechanical gears.

BACKGROUND OF INVENTION:

Differential is typically an assembly of gears located between the drive axles of a vehicle. It allows the driving wheels of the vehicle to move at different speeds while maintaining power to both. Differential splits the engine torque in two ways allowing each wheel to spin at different speeds. While making a turn, wheels of a vehicle rotate at different speeds. Fig. 1 illustrates a vehicle turning action. As seen in Fig. 1, each wheel travels different distance through the turn, and that the inside wheels travel shorter distance than the outside wheels.

Speed = distance traveled / time.

The wheels that travel short distance travel at . a lower speed. Also note that the front wheels travel different distance than the rear wheels.

The non-driven wheels of the vehicle - i.e. the front wheels of a rear-wheel drive vehicle, the back wheels of a front-wheel drive vehicle ~ are not an issue. There is no connection between them, so they spin independently. But the driven wheels are linked together so that a single engine and transmission can turn both wheels. If the vehicle did not have a differential, the wheels would have to be locked together, forced to spin at the same speed. This would make turning difficult and hard on the vehicle. The vehicle to be able to turn, one tire would have to slip. With modern tires and concrete roads, a great deal of force is required to make a tire slip. That force would have to be transmitted through the axle from one wheel to another, putting a heavy strain on the axle components. As mentioned above differential is needed because a single machine / engine is providing power to both the wheels of vehicle. In case of Electric vehicles or Hybrid vehicles where the wheels are driven by electric machines (motors) differential action is implemented in multiple ways - If a single motor is used to provide the power to the wheels, a conventional mechanical differential can be used. If each wheel is driven by independent motors, an electronic differential control is implemented. It uses an onboard computer to directly control and adjust the torque split and difference in wheel speed of inside and outside wheels based on the steering wheel angle, to achieve the same effect as a normal mechanical differential.

The patent CN 200953524 discloses a double-rotor differential speed DC motor. The two motors used are DC motor and they are connected in series and packaged in a single housing. The patent US 20090294190 utilizes a DC machine for its electric gearbox with continuous variations.

In order to overcome the shortcomings in the present state of the art with respect to tradeoff between the parameters such as space, weight, efficiency and cost, the applicant proposes a solution as described hereafter.

SUMMARY:

In accordance with the above objects, the present invention discloses a method of utilizing the electric motor of a hybrid or electric vehicle to provide both, power transmission to wheels and the differential action required during the turning of vehicle. Accordingly, an induction motor rotor is split to form two independent rotors within the same motor to allow the slip between the two driving wheels when turning the vehicle. When the vehicle is moving in straight line both the wheels will deliver equal power / torque and speed.

Another aspect of the invention is to eliminate the need of conventional mechanical differential systems in the hybrid or electric vehicles, for generating the torque required to spin the driving wheels. As the differential action is provided by the independent rotor of the electric motor along with the power transmission, it eliminates the need of the conventional mechanical differential systems in the vehicle.

BRIEF DESCRIPTION OF THE DRAWING; Fig. 1 illustrates a vehicle turning action.

Fig. 2 illustrates application of electric motor in an electric vehicle according to an embodiment of the invention.

Fig. 3 illustrates a motor controller flow chart in part according to an embodiment of the invention.

Fig. 4 illustrates continued motor controller flow chart from Fig, 3 according to an embodiment of the invention

Fig. 5 illustrates a 3-phase induction electric motor according to an embodiment of the invention.

Fig. 6 illustrates an embodiment of the electric motor. DETAILED DESCRIPTION:

Space, weight and cost are critical factors in any electric vehicles and hybrid vehicles with respect to the bulky batteries, complex and expensive motor control systems. There is a need to optimize the components of any Electric / Hybrid vehicle to avoid the problems involved in such factors while maintaining the performance at par with normal vehicles. Thus, the objective of the present invention is to provide a motor vehicle differential system and a method of utilizing the electric motor of a hybrid or electric vehicle to provide both, power transmission to wheels and the differential action required for operating vehicle, without the use of gears to avoid the need of having mechanical differential systems in the hybrid or electric vehicles.

In an embodiment of the present invention, as described in Fig. 2, an Electric Motor 15, which is a split rotor induction motor including two independent .rotors, is used in a hybrid or electric vehicle to achieve optimized efficiency for the motor differential. According to such an embodiment, an Electric Control Unit (ECU) 40 controls various components of the motor differential assembly. A Motor Controller 30 controls said Electric Motor 15. As illustrated in Fig. 2, two RPM Sensors, RPM Sensor 100, which may be a left side sensor and RPM Sensor 200, which may be a right side sensor, along with Steering Position Sensor 50 monitor various events at their respective locations and provide feedback to the ECU 40 with output values Rl, R2 and SPl, respectively. Based on the inputs received from the Steering Position Sensor 50, RPM Sensor 100 and RPM Sensor 200, the resultant action of the ECU 40 is initiated, accordingly.

As seen in Table 1, the ECU 40 controls speed balancing at the wheels of such a hybrid vehicle or electric vehicle based on the rotor RPM values Rl and R2 received from RPM Sensor 100 and RPM Sensor 200, respectively.

Table 1: Speed Balancing Table 2 illustrates the motor controller action based on the turning mode of the vehicle.

Table 2: Turn Mode

The Steering Position Sensor 50 mounted on or near the steering of the vehicle senses position of the steering wheel of the vehicle as being straight or turning left or turning right. Accordingly, the flow chart of Fig. 3 and Fig. 4 illustrate the control logic and actions taken by the ECU 40. At point Ά', when the vehicle is moving in a straight direction, the RPM sensor values Rl and R2 are equal and the ECU 40 directs the Motor Controller 30 to follow both RPM Sensor 100 command and the RPM Sensor 200 command one by one. At point 'B', when the vehicle is turning to the left, Rl value of RPM Sensor 100 is needed to be less than the R2 value of RPM Sensor 200 and the ECU 40 directs the Motor Controller 30 to ignore the left RPM Sensor 100 command while follow the right RPM Sensor 200 command. At point 'C, when the vehicle is turning to the right, Rl value of RPM Sensor 100 is needed to be greater than the R2 value of RPM Sensor 200 and the ECU 40 directs the Motor Controller 30 to ignore right RPM Sensor 200 command while follow ignore^' the left RPM Sensor 100 command. The Steering Position Sensor 50 value SP1 is sensed in a continuous manner as illustrated by the loop Point 'D'. Accordingly, the ECU 40 maintains or modifies the speed of the rotors of the Electric Motor 15. According to an embodiment of the invention, encoders may be used in place of the RPM sensor 100 and the RPM sensor 200 in order to provide the RPM feedback to the ECU 40. Additionally, auto selection of the RPM feedback to the ECU 40 may be provided by means of an appropriate electronic circuitry.

According to an embodiment of the present invention, as illustrated in Fig. 5, an electric motor in a hybrid vehicle or electric vehicle is used to provide the differential action required for operating the vehicle. The Electric Motor 15 of the invention is a split rotor induction motor which includes two independent rotors, Rotor 5a and Rotor 5b which are surrounded by Stator Windings 10. As seen in Fig. 2, a 3-phase Power Supply 35 is provided to the Stator Windings 10. The 3-phase Power Supply 35 generates flux and magnetic field is induced by the Stator Windings 10 in each rotor, Rotor 5a and Rotor 5b. The power supply maybe provided through a battery or inverter. Dual Output Shafts 25 are connected to both the rotors, Rotor 5a and to Rotor 5b, respectively and the other end of the Dual output shafts 25 are connected to a pair of Driving Wheels 20. The two rotors of the split motor, Rotor 5a and Rotor 5b, are independently housed in a separate squirrel cage at either ends along with the Stator Windings 10. The entire assembly of the Stator Windings 10 along with the Rotor 5a and Rotor 5b may be encased in a one single mechanical structure or may be encased separately. The bearings and other mechanical assembly required to provide the drive to the vehicle is connected to the Rotor 5a and Rotor 5b. A single Motor Controller 30 is used to control the motor of the invention, as opposed to the two motor controllers required in the conventional system, which utilize two separate motors.

In another embodiment, the invention provides method of utilizing the electric motor of a hybrid or electric vehicle to provide both, power transmission to wheels and the differential action required for operating vehicle, comprising the steps of: applying A 3- phase AC power to Electric Motor 15 consisting two independent rotors, Rotor 5a and Rotor 5b that are surrounded by Stator Windings 10 , as an input, to generate flux and induce magnetic field into Rotor 5a and Rotors 5b causing rotation of Dual Output Shafts 25 which rotate the Driving Wheels 20; wherein, the vehicle runs with same speed under equal load conditions on output shafts or acts as differential under unequal load conditions on output shafts during turning of the vehicle.

A 3-phase AC power is applied to the Electric Motor 15 as an input, which is converted into the mechanical power and delivered to the two corresponding Dual Output Shafts 25 which rotate the Driving Wheels 20. The 3- phase supply for driving the Electric Motor 15 is applied to the Stator Windings 10. As current flows through the Stator Windings 10, flux is generated and a magnetic field is induced into the Rotor 5a and Rotor 5b, rotating the Dual Output Shafts 25. Under equal load conditions, both the Rotor 5a and Rotor 5b rotate at the same speed. When the load on both the Dual Output Shafts 25 is equal and both the Rotor 5a and Rotor 5b are engaged, the flux generated and the magnetic field induced by the Stator Windings 10 for each Rotor 5a and Rotor 5b is the same. The torque thus generated is provided to both the Dual Output Shafts 25 which drives the Driving Wheels 20 at the same speeds.

When the driving condition changes, say, the load on one Output Shaft 25 is increased during the turning of the vehicle, the split rotors of the motor allow the rpm of the corresponding rotor to reduce without adversely affecting the other rotor. This results in both the Output Shafts 25 and hence the Driving Wheels 20 being driven at different speeds and the Electric Motor 15 acting as a differential. Additionally, under the varying load conditions, one of the Rotor 5a or Rotor 5b may be completely disengaged, in order to provide variable speed of the Driving Wheels 20. Thus, as seen, according to the invention, the Electric Motor 15 of the vehicle is used for providing transmission as well as the differential required for operating the vehicle. The utilization of a 3-phase Electric Motor 15 as a differential eliminates the need for a conventional mechanical differential system in the vehicle. Further, additional auxiliary stator windings may be utilized to provide a quick power boost for the vehicle at zero or lower speeds.

An example of an Electric Motor 15 according to any of the embodiments as mentioned herein above is illustrated in Fig. 6. Stator (1001), Rotor 1 (501a) and Rotor 2 (501b) are enclosed between covers L-Cover (601) and R-Cover (603). An Intermediate Plate (602) is placed between the Rotor (501a) and Rotor (501b). RPM Sensor Rl and RPM Sensor R2 are mounted alongside Rotor 1 (501a) and Rotor 2 (501b), respectively. A 3-phase Power Supply 35 is provided to the Stator (1001) by an Input Wire A. The specifications for the Electric Motor 15 of the embodiment are as mentioned below:

Rated Voltage-28 Volt

Rated Frequency-75 Hz

No Load Current- 100 Amp

No Load RPM -2245/min

Load Torque-9.7 N-m POT-35 N-m per rotor

Starting Torque-23 N-m/rotor

The specifications of the Electric Motor 15 for the example mentioned herein above are only for illustrative purposes and it may be noted that the specifications may be varied depending upon the requirements of the application. While the examples of the embodiments of the present invention are described with particular values, a person skilled in the art may appreciate that they may be suitably modified as per the efficiency requirement of the system. These values, examples and figures in no way limit the execution of the embodiments.

As such, the present invention finds great utility in the area of hybrid or electric vehicles in order to achieve maximum motor differential efficiency required in the vehicles with respect to space, motor parameters and ratings, speed and torque requirements 6f the vehicles, bulk/weight tolerance capacity of the vehicle, etc.

Claims

We claim,

1. A motor differential system to provide both, power transmission to wheels and the differential action required for operating the hybrid or electric vehicle comprises: a) an Electric Motor 15 , a split' rotor induction motor having two independent rotors Rotor 5a and Rotor 5b surrounded by Stator Windings 10, controlled by a single Motor Controller 30;

b) a 3-phase Power Supply 35 provided to the Stator Windings 10 via the Electric Motor 15, as an input to generate flux and to induce the magnetic field into Rotor 5a and Rotor 5b;

c) a Dual Output Shaft 25 connected to the two rotors, Rotor 5a and Rotor 5b, respectively and the other end of the Dual Output Shaft 25 connected to a pair of Driving Wheels 20, wherein, the two rotors of the split motor, Rotor 5a and Rotor 5b are independently housed in a separate squirrel cage at either ends along with the Stator Windings 10

and

d) at least two Sensors RPM Sensor 100 and RPM Sensor 200, placed at least on one side of Rotor 5a and Rotor 5b each, and at least one Steering Position Sensor 50, to provide feedback to an ECU 40;

wherein, the motor differential system is controlled by said Electric control unit (ECU) 40.

2. The motor differential system according to Claim 1, wherein, the power supply is provided through a battery connected to a motor controller / inverter.

3. The motor differential system according to Claim 1 , wherein, the ECU 40 determines speed and orientation of the vehicle based on outputs of RPM Sensor 100, RPM Sensor 200 and Steering Position Sensor 50.

4. The motor differential system according to Claim 1, wherein, the bearings and other mechanical assembly required to provide the drive to the vehicle are connected to Rotor 5a and Rotor 5b.

5. The motor differential system according to Claim 1, wherein, the Output Shafts 25 rotate the Driving Wheels 20 with same speed under equal load conditions on output shafts or acts as differential under unequal load conditions on output shafts during the turning of the vehicle.

6. The motor differential system according to Claim 1, wherein, one of the rotors, Rotor 5a or Rotor 5b is completely disengaged to provide variable speed under varying load conditions.

7. A method of utilizing the electric motor of a hybrid or electric vehicle to provide both, power transmission to wheels and the differential action required for operating vehicle, comprising the steps of:

a. applying A 3-phase AC power supply to Electric Motor 15, consisting two independent rotors Rotor 5a and Rotor 5b surrounded by Stator Windings 10 , as an input to generate flux and induce magnetic field into Rotor 5a and Rotor 5b causing rotation of Output Shafts 25 to rotate Driving Wheels 20;

b. controlling the Electric Motor 15 by Motor Controller 30, in turn controlled by Electric control Unit (ECU) 40;

and

c. providing at least two Sensors RPM Sensor 100 and RPM Sensor 200 at least on one side of Rotor 5a and Rotor 5b each, and at least one Steering Position Sensor 50, to enable said ECU 40 to receive feedback as output values Rl, R2 and SP1 respectively, wherein, the ECU 40 maintains same speed at said driving wheels 20 when the vehicle moves straight, or enables electric motor 15 to act as differential under unequal load conditions to follow the RPM Sensor 100 when the vehicle turns right or to follow the RPM Sensor 200 when the vehicle turns left.