Field of the invention:
[0001] The present invention relates to an electric drive unit of a vehicle and further
relates to increasing efficiency and performance of the drive unit of the vehicle.
Background of the invention:
[0002] According to a patent US2015/0171774 discloses a power system for electric vehicle and control method thereof. Disclosed are a power system for an electric vehicle and a control method of a power system for an electric vehicle. The power system may include a first motor and a second motor configured as a power source, first and second reduction gears connected to the first and second motors and having different deceleration ratios a driving shaft transmitting outputs of the first and second reduction gears, and a motor controller configured to determine a first driving point where the first motor responds according to a demand torque of a driver and a driving condition of the vehicle and a second driving point where the second motor responds according to the demand torque of the driver and the driving condition of the vehicle, and control driving by using at least one of an output torque of the first motor and/or an output torque of the second motor according to the determined driving point.
Brief description of the accompanying drawings:
[0003] An embodiment of the disclosure is described with reference to the
following accompanying drawing,
[0004] Fig. 1 illustrates a wheel mounted with a drive unit, according to an
embodiment of the present invention;
[0005] Fig. 2 illustrates a side view of a first side of the wheel mounted with the
drive unit, according to an embodiment of the present invention;
[0006] Fig. 3 illustrates a side view of a second side of the wheel mounted with the
drive unit, according to an embodiment of the present invention.
[0007] Fig. 4 illustrates the drive unit comprising a hub motor, according to an
embodiment of the present invention;

[0008] Fig. 5 illustrates the wheel mounted with the hub motor, according to an
embodiment of the present invention;
[0009] Fig. 6 illustrates a graphical view of efficiency map of a Motor/Generator
(M/G), according to the present invention, and
[0010] Fig. 7 illustrates a flow diagram of a method for operating the drive unit,
according to the present invention.
Detailed description of the embodiments:
[0011] Fig. 1 illustrates a wheel mounted with a drive unit, according to an embodiment of the present invention. The wheel 106, comprising a rim 108 and a tire, refers to either a front wheel or a rear wheel of a vehicle. The electric drive unit 100 for the vehicle comprises two machines 114, namely a first motor-generator (M/G) 102 and a second M/G 104. The drive unit 100 is mounted to the wheel 106 of the vehicle. The drive unit 100 is coupled to the wheel 106 through a gearbox 116. The gearbox 116 is a final reduction gears between the drive unit 100 and the wheel 106. The first M/G 102 is of a power rating higher than that of the second M/G 104. The first M/G 102 is used as the primary driving source for the vehicle. The drive unit 100 is characterized by, the second M/G 104 is mechanically coupled to the first M/G 102, through a transmission unit 402 (shown in Fig. 4). The second M/G 104 is further and selectively actuated in a manner to shift a current operating point of the first M/G (102) to a new operating point at which the efficiency of the first M/G 102 is above a threshold value. The threshold value is calibrated as per the requirement. For example: threshold value for the efficiency of the first M/G 102 is 60%.
[0012] In one embodiment, the gearbox 116 is part of the drive unit 100. Alternatively, the gearbox 116 is part of the rim 108. In yet another alternative, the gearbox 116 is a separate unit and coupled to the wheel 106 or the drive unit 100. The gearbox 116 comprises but not limited to, spur gear arrangement, planetary gear arrangement, and the like.

[0013] In another embodiment, the rim 108 is designed in manner to accommodate the gearbox 116. The rim 108 is displaced to protrude out of the wheel 106 from one side in order to mount the gearbox 116. Alternatively, the gearbox 116 is mounted to a conventional rim 108.
[0014] The drive unit 100 is positioned outside the rim 108 of the wheel 106 and mounted to a first side of the wheel 106. The rim 108 is shown protruding out from a second side of the wheel 106. A drive shaft or output shaft 112 is coupled to the rim 108, which in turn is coupled to the drive unit 100 through the gearbox 116. The drive shaft 112 may or may not protrude out from the rim 108 and the same must not be understood in limiting manner.
[0015] Further, a controller 110 is also provided which controls the working of both the machines 114. The controller 110 receives signal from a wheel speed sensor (not shown) and a vehicle speed sensor (not shown). The controller 110 comprises a memory element which stores the operating characteristics of the first M/G 102 under various conditions as a table or a data map. Thus, the entire operating characteristics of the first M/G 102, comprising the operating points, is categorized into high efficiency and low efficiency regions. Based on the threshold value of the efficiency, the operating points of the first M/G 102 are classified into low and high efficiency operating points.
[0016] By default, the second M/G 104, which is mounted and coupled directly to the first M/G 102, always rotates whenever the first M/G 102 is driven. The second M/G 104 acts as a dead/free load on the first M/G 102. The second M/G 104 is considered as the free load when a field winding of the second M/G 104 is not activated or energized. In other words, the second M/G 104 is not activated/driven when the efficiency of the first M/G 102 is above the threshold value at the current operating point. The second M/G 104 is activated only upon detection of efficiency of the first M/G 102 below the threshold value. Alternatively, the second M/G 104 is activated whenever the first M/G 102 is detected to be functioning in operating

points corresponding to lower efficiency. The activation of the second M/G 104 comprises energization of the field winding. If the controller 110 detects the first M/G 102 is operating with efficiency lower than the threshold value, the controller 110 activates the second M/G 104.
[0017] The second M/G 104 functions or is driven as a generator when the field winding of the second M/G 104 is activated. The second M/G 104 then charges a battery of the vehicle while acting as an active load to the first M/G 102. On activation of the second M/G 104 as an active load, the current operating point of the first M/G 102 shifts to a new operating point where the efficiency is greater than the threshold value.
[0018] In accordance to an embodiment of the present invention, the second M/G 104 is used as a drive motor upon failure of the first M/G 102 to provide limp-home functionality. The second M/G 104 which is coupled to a rotor shaft of the first M/G 102, is operated by the controller 110 to function as the drive motor.
[0019] Fig. 2 illustrates a side view of a first side of the wheel mounted with the drive unit, according to an embodiment of the present invention. A single case is used to enclose the first M/G 102 and the second M/G 104. Further, the size and rating of the machines 114 are so chosen that both the machines 114 comes within the span of the rim 108 of the wheel 106. Thus, providing a compact and optimal drive unit 100. The drive unit 100 is mounted to the rim 108 through the gearbox 116.
[0020] The drive unit 100 is possible to use a different size of the machines 114 for mounting to the wheel 106. The machines 114 are possible to be mounted with the help of more than one case, such as split cases.
[0021] Fig. 3 illustrates a view of a second side of the wheel mounted with the drive unit, according to an embodiment of the present invention. The second side of the

wheel 106 is shown. The first M/G 102 and the second M/G 104 are coupled to the rim 108 of the wheel 106 of the vehicle in any one configuration selected from a same side mount and an opposite side mount. The same side mount corresponds to both the machines 114 mounted to either the first side or the second side. The opposite side mount corresponds to the first M/G 102 mounted to the first side of the wheel 106 and the second M/G 104 mounted to the second side of the wheel 106, and vice-versa.
[0022] Fig. 4 illustrates the drive unit comprising a hub motor, according to an embodiment of the present invention. The first M/G 102 is the hub motor, which is mounted within the rim 108 of the wheel 106. The second M/G 104 is coupled to the drive shaft 112 of the first M/G 102 through the transmission unit 402. The transmission unit 402 is a belt drive or chain drive assembly but not limited thereto. The transmission 402 shown in Fig. 4 is a belt drive and pulley system. A first pulley 404 is coupled to the drive shaft 112 of the first M/G 102. A second pulley 408 is mounted to a rotor shaft of the second M/G 104. The first pulley 404 and the second pulley 408 are coupled to each other via belt 406.
[0023] Fig. 5 illustrates the wheel mounted with the hub motor, according to an embodiment of the present invention. The first M/G 102 is the hub motor, whereas the second M/G 104 is coupled to the drive shaft 112 of the first M/G 102 through the transmission unit 402. The transmission unit 402 is also possible to be spur gear arrangement in addition to belt drive or chain drive assembly.
[0024] Fig. 6 illustrates a graphical view of efficiency map of a Motor/Generator (M/G), according to the present invention. The graph 600 where X-axis 602 denotes speed in rotation per minute (RPM) and Y-axis 604 denotes torque in Newton meter (Nm). A rectangular bar 610 represents a color scale to indicate the efficiency of the motor/generator, specifically for the first M/G 102. The darkest grey color indicates the first M/G 102 at lowest efficiency and the lightest grey color indicates the first M/G 102 at highest efficiency. The data map or the table is derived from

this graph 600. The graph 600 illustrates two-dimensional (2D) contour plot of the efficiency of the first M/G 102 based on speed and torque.
[0025] Now, a first box 606 represents the threshold value. If the controller 110 detects the operating points of the first M/G 102 within the first box 606, then the activation of the second M/G 104 is triggered. The loading of the second M/G 104 on the first M/G 102 shifts the current operating point, which is inside the first box 606, to a new operating point where the efficiency of the first M/G 102 is above the threshold value, such as in a second box 608. The first box 606, the second box 608 and the graph 600 are for explanatory purpose, and must not be understood in limiting manner.
[0026] Fig. 7 illustrates a flow diagram of a method for operating the drive unit, according to the present invention. The drive unit 100 comprising two machines 114, namely the first M/G 102 and a second M/G 104. The drive unit 100 is mounted to the wheel 106 of the vehicle through the transmission unit 402. Also, the power rating of the first M/G 102 is higher than that of the second M/G 104. The method comprising the steps of, a step 702 comprising detecting, by the controller 110, efficiency of the first M/G 102 lower than the threshold value. A next step 704 comprises activating the second M/G 104 to act as active load on the first M/G 102. A next step 706 comprises driving, by the first M/G 102, both of the wheel 106 and the second M/G 104, and shifting the current operating point to a new operating point, where the efficiency is above the threshold value.
[0027] The current operating point is detected by the controller 110 by comparing real-time characteristic signals of the first M/G 102 against the data map stored in the memory element of the controller 110. The second M/G 104 is mounted directly to the first M/G 102. The step 704 of activating the second M/G 104 comprises energizing the field winding of the second M/G 104 by supplying the required current.

[0028] The method further comprises using the second M/G 104 as a drive motor upon failure of the first M/G 102, to provide limp-home functionality.
[0029] According to an embodiment of the present invention, a drive unit 100 and a method to operate the same is provided. The drive unit 100 enables to improve efficiency and performance of the machines 114.
[0030] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.

1. An electric drive unit (100) for a vehicle, said drive unit (100) comprising
a first Motor/Generator (M/G) (102) and a second M/G (104), said drive
unit (100) mounted to a wheel (106) of said vehicle, and said first M/G (102)
is of a power rating higher than that of said second M/G (104), characterized
in that
said second M/G (104) is coupled to said first M/G (102) through a transmission unit (402), said second M/G (104) is selectively activated in a manner to shift a current operating point of said first M/G (102) to a new operating point at which an efficiency of said first M/G (102) is above a threshold value.
2. The drive unit (100) as claimed in claim 1, wherein said second M/G (104) is activated upon detection of said efficiency below said threshold value.
3. The drive unit (100) as claimed in claim 2, wherein said second M/G (104) is driven as a generator by supply of current to a field windings, said second M/G (104) charges a battery of said vehicle.
4. The drive unit (100) as claimed in claim 1, wherein said second M/G (104) is not activated when said efficiency of said first M/G (102) is above said threshold value at said current operating point, said second M/G (104) operates as a free load.
5. The drive unit (100) as claimed in claim 1, wherein said second M/G (104) is driven as a drive motor upon failure of said first M/G (102) to provide limp-home functionality.
6. The drive unit (100) as claimed in claim 1, wherein said first M/G (102) and said second M/G (104) are coupled to said wheel (106) of said vehicle in

any one configuration selected from a same side mount and an opposite side mount.
7. A method for operating a drive unit (100) of a vehicle, said drive unit (100)
comprising a first M/G (102) and a second M/G (104), said drive unit (100)
mounted to a wheel (106) of said vehicle through a transmission unit (402),
and a power rating of said first M/G (102) is higher than that of said second
M/G (104), said method comprising the steps of:
detecting, by a controller (110), efficiency of said first M/G (102)
lower than a threshold value;
activating said second M/G (104) to act as active load on said first
M/G (102), and
driving, by said first M/G (102), both of said wheel (106) and said
second M/G (104), and shifting a current operating point to a new
operating point, where said efficiency is above a threshold value.
8. The method as claimed in claim 7, wherein said current operating point is detected by said controller (110) by comparing real-time characteristic signals of said first M/G (102) against a data map stored in a memory element of said controller (110).
9. The method as claimed in claim 7, wherein activating said second M/G (104) comprises energizing a field winding of said second M/G (104) by supplying a required current.
10. The method as claimed in claim 7, further comprises using said second M/G (104) as a drive motor upon failure of said first M/G (102), to provide limp-home functionality.