Claims:WE CLAIM:
1. A hybrid vehicle (10) comprising:
an internal combustion engine (12) configured for generating a driving force during one or more predetermined drive modes for the hybrid vehicle (10);
a traction motor (14) configured for generating a driving force from an energy storage unit (16) during the one or more predetermined drive modes for the hybrid vehicle (10); and
a control unit (100) in communication with an Engine Control Unit (ECU) (18) and the traction motor (14), the control unit (100) configured to:
determine if a state of charge of the energy storage unit (16) is in one or more pre-set threshold range;
determine if a speed of the hybrid vehicle (10) is in one or more pre-set threshold range;
generate a signal indicative of the one or more predetermined drive modes for driving the hybrid vehicle (10) based on the one or more pre-set threshold range of the state of charge of the energy storage unit (16) and the one or more pre-set threshold range of the speed of the hybrid vehicle (10); and
communicate the signal to the traction motor (14) and/or the ECU (18) for driving the hybrid vehicle (10) in the one or more predetermined drive modes.
2. The hybrid vehicle (10) as claimed in claim 1, wherein the one or more predetermined modes comprises a power mode with the traction motor support and an engine mode.

3. The hybrid vehicle (10) as claimed in claim 1, wherein the one or more pre-set threshold range of the state of charge of the energy storage unit (16) comprises a first threshold range between 30% and 40% and a second threshold range between 20% and 30%.

4. The hybrid vehicle (10) as claimed in claim 1 or 3, wherein the one or more pre-set threshold range of the speed of the hybrid vehicle (10) comprises a first threshold range between 0.1 km/h and 30 km/h when the state of charge of the energy storage unit is in the first threshold range of 30% to 40%.

5. The hybrid vehicle (10) as claimed in claim 1 or 3, wherein the one or more pre-set threshold range of the speed of the hybrid vehicle (10) comprises a second threshold range between 0.1 km/h and 20 km/h when the state of charge of the energy storage unit (16) is in the second threshold range of 20% to 30%.

6. The hybrid vehicle (10) as claimed in claim 1 or 4, wherein the control unit (100) is configured to communicate a signal to the traction motor (14) and/or the ECU (18) for driving the hybrid vehicle (10) either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit (16) is in the first threshold range and the pre-set threshold range of the speed of the hybrid vehicle (10) is in the first threshold range.

7. The hybrid vehicle (10) as claimed in claim 1 or 5, wherein the control unit (100) is configured to communicate a signal to the traction motor (14) and/or the ECU (18) for driving the hybrid vehicle (10) either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit (16) is in the second threshold range and the pre-set threshold range of the speed of the hybrid vehicle (10) is in the second threshold range.

8. The hybrid vehicle (10) as claimed in claim 1 or 3, wherein the control unit (100) is configured to communicate a signal to the ECU (18) for driving the hybrid vehicle (10) in the engine mode when the state of charge of the energy storage unit (16) is lesser the second threshold range.

9. The hybrid vehicle (10) as claimed in claim 1, wherein the control unit (100) is configured to communicate a signal to the traction motor (14) and/or the ECU (18) for driving the hybrid vehicle (10) in any one of modes comprising an ECO mode, the power mode with the traction motor support, an electric vehicle mode and the engine mode when the state of charge of the energy storage unit (16) is greater than the first threshold range and the speed of the hybrid vehicle (10) is greater than the first threshold range.

10. A method (200) of operating a hybrid vehicle (10) comprising:
determining (202), by a control unit (100) if a state of charge of an energy storage unit (16) is in one or more pre-set threshold range;
determining (204), by the control unit (100) if a speed of the hybrid vehicle (10) is in one or more pre-set threshold range;
generating (206), a signal indicative of the one or more predetermined drive modes for driving the hybrid vehicle (10) based on the one or more pre-set threshold range of the state of charge of the energy storage unit (16) and the one or more pre-set threshold range of the speed of the hybrid vehicle (10); and
communicating (208), the signal to a traction motor (14) and/or an Engine Control Unit (ECU) (18) for driving the hybrid vehicle (10) in the one or more predetermined drive modes.

11. The method (200) as claimed in claim 10, wherein the one or more predetermined modes comprises a power mode with the traction motor support and an engine mode.

12. The method (200) as claimed in claim 10, wherein the one or more pre-set threshold range of the state of charge of the energy storage unit (16) comprises a first threshold range between 30% and 40% and a second threshold range between 20% and 30%.

13. The method (200) as claimed in claim 10 or 12, wherein the one or more pre-set threshold range of the speed of the hybrid vehicle (10) comprises a first threshold range between 0.1 km/h and 30 km/h when the state of charge of the energy storage unit is in the first threshold range of 30% to 40%.

14. The method (200) as claimed in claim 10 or 12, wherein the one or more pre-set threshold range of the speed of the hybrid vehicle (10) comprises a second threshold range between 0.1 km/h and 20 km/h when the state of charge of the energy storage unit (16) is in the second threshold range of 20% to 30%.

15. The method (200) as claimed in claim 10 or 13, wherein a signal from the control unit (100) is communicated to the traction motor (14) and/or the ECU (18) for driving the hybrid vehicle (10) either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit (16) is in the first threshold range and the pre-set threshold range of the speed of the hybrid vehicle (10) is in the first threshold range.

16. The method (200) as claimed in claim 10 or 14, wherein a signal from the control unit (100) is communicated to the traction motor (14) and/or the ECU (18) for driving the hybrid vehicle (10) either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit (16) is in the second threshold range and the pre-set threshold range of the speed of the hybrid vehicle (10) is in the second threshold range.

17. The method (200) as claimed in claim 10 or 12, wherein a signal from the control unit (100) is communicated to the ECU (18) for driving the hybrid vehicle (10) in the engine mode when the state of charge of the energy storage unit (16) is lesser the second threshold range.

18. The method (200) as claimed in claim 10, wherein a signal from the control unit (100) is communicated to the traction motor (14) and/or the ECU (18) for driving the hybrid vehicle (10) in any one of modes comprising an ECO mode, the power mode with the traction motor support, an electric vehicle mode and the engine mode when the state of charge of the energy storage unit (16) is greater than the first threshold range and the speed of the hybrid vehicle (10) is greater than the first threshold range.
, Description:FIELD OF THE INVENTION
[001] The present invention relates to a hybrid vehicle.

BACKGROUND OF THE INVENTION
[002] Due to increasing cost of fossil fuel and to overcome the emission concerns, a hybrid concept has been introduced in two wheelers. In the hybrid concept, a gasoline powered internal combustion engine has been combined with an electric motor which runs on battery power.
[003] Generally, a hybrid electric vehicle (HEV) has two-power sources for propulsion of the vehicle, one with a traction motor and another with an internal combustion (IC) engine. These two sources can be integrated in the vehicle with various combinations for delivery of the power to a rear wheel of the vehicle. In the existing HEV’s, these two power sources are integrated in a parallel combination, with which the HEV can be operated in modes like ECO mode (Economy mode), where at lower speeds tractive force is supplied by the traction motor and at higher speeds tractive force is supplied by the IC engine. In the ECO mode, changeover can happen from the traction motor power supply to the IC engine power supply at a mid-range speed of the vehicle. In another mode like a power mode, a tractive force is supplied by both the traction motor and the IC engine simultaneously. In yet other modes like EV mode, a tractive force is supplied by the traction motor alone, and in the engine mode, a tractive force is supplied by the IC engine alone.
[004] Based on nature of operation of the vehicle, the traction motor provides a maximum torque at zero speed of vehicle, whereas the IC engine provides low torque at low speed of the vehicle, and it raises to its maximum torque at medium speed of the vehicle. In general, the HEV vehicle includes smaller engine in order to reduce the weight of the vehicle. Due to which, in the power mode, when the battery is fully drained, the vehicle performance (like vehicle acceleration) could become completely degraded at low speed, as the vehicle is assisted by the engine alone.
[005] Further, as the HEV has numerous sub-systems when compared to a regular IC vehicle, the engine experiences a very high load during the engine mode and the power mode. The sub-systems of HEV may include, but not limited to, battery packs, traction motor, battery charger, HEV controller and wiring harness as compared over the regular IC engine vehicle. Due to this high load, a clutch plate of the HEV engine could wear out faster as compared to the regular IC engine vehicle. This is because, the high load causes slipping-engaging of the clutch plates with a clutch drum. Also, during a gradient climbing by the vehicle, load on the clutch plates becomes further higher and premature failure can happen with the clutch plates. In addition, the engine gives less mileage at low-speed range of vehicle as it consumes more fuel to overcome the tractive effort demand for the vehicle forward propulsion and for providing more acceleration at low speeds.
[006] Due to this difference in torque characteristics of the traction motor and the IC engine, the vehicle drive feel becomes different at low speed of vehicle (for example around 0~40Kmph). In addition, the difference in the torque feels like a jerk to a rider whenever there is a sudden changeover from the ECO mode. This is because, in the ECO mode, the torque graph switches from traction motor (which provides high torque at low speed) to the engine (which provides low torque at low speed) in within a few seconds.
[007] The existing methods in the hybrid vehicle includes one or more limitations, where the clutch burning can happen at gradient and on plane roads as well. Also, poor drive feeling occurs at a lower speeds and jerks occur during sudden changeover of power sources from the traction motor to the engine, in ECO mode. Further, mileage of the hybrid electric vehicle is poor in the engine mode at low speed of the vehicle. Also, fast discharge of the battery occurs with its non-systematic use in various defined modes of HEV.
[008] Thus, there is a need in the art for a hybrid vehicle which could address at least the aforementioned problems and limitations.

SUMMARY OF THE INVENTION
[009] In one aspect, the present invention is directed to a hybrid vehicle. The hybrid vehicle includes an internal combustion engine configured for generating a driving force during one or more predetermined drive modes for the hybrid vehicle. The hybrid vehicle further includes a traction motor configured for generating a driving force from an energy storage unit during the one or more predetermined drive modes for the hybrid vehicle. The hybrid vehicle further includes a control unit in communication with an Engine Control Unit (ECU) and the traction motor. The control unit is configured to determine if a state of charge of the energy storage unit is in one or more pre-set threshold range. The control unit is further configured to determine if a speed of the hybrid vehicle is in one or more pre-set threshold range. The control unit is further configured to generate a signal indicative of the one or more predetermined drive modes for driving the hybrid vehicle based on the one or more pre-set threshold range of the state of charge of the energy storage unit and the one or more pre-set threshold range of the speed of the hybrid vehicle. The control unit is further configured to communicate the signal to the traction motor and/or the ECU for driving the hybrid vehicle in the one or more predetermined drive modes.
[010] In an embodiment of the present invention, the one or more predetermined modes includes a power mode with the traction motor support and an engine mode.
[011] In a further embodiment of the present invention, the one or more pre-set threshold range of the state of charge of the energy storage unit includes a first threshold range between 30% and 40% and a second threshold range between 20% and 30%.
[012] In a further embodiment of the present invention, the one or more pre-set threshold range of the speed of the hybrid vehicle includes a first threshold range between 0.1 km/h and 30 km/h when the state of charge of the energy storage unit is in the first threshold range of 30% to 40%.
[013] In a further embodiment of the present invention, the one or more pre-set threshold range of the speed of the hybrid vehicle includes a second threshold range between 0.1 km/h and 20 km/h when the state of charge of the energy storage unit is in the second threshold range of 20% to 30%.
[014] In a further embodiment of the present invention, the control unit is configured to communicate a signal to the traction motor and/or the ECU for driving the hybrid vehicle either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit is in the first threshold range and the pre-set threshold range of the speed of the hybrid vehicle is in the first threshold range.
[015] In a further embodiment of the present invention, the control unit is configured to communicate a signal to the traction motor and/or the ECU for driving the hybrid vehicle either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit is in the second threshold range and the pre-set threshold range of the speed of the hybrid vehicle is in the second threshold range.
[016] In a further embodiment of the present invention, the control unit is configured to communicate a signal to the ECU for driving the hybrid vehicle in the engine mode when the state of charge of the energy storage unit is lesser the second threshold range.
[017] In a further embodiment of the present invention, the control unit is configured to communicate a signal to the traction motor and/or the ECU for driving the hybrid vehicle in any one of modes comprising an ECO mode, the power mode with the traction motor support, an electric vehicle mode and the engine mode when the state of charge of the energy storage unit is greater than the first threshold range and the speed of the hybrid vehicle is greater than the first threshold range.
[018] In another aspect, the present invention is directed to a method of operating a hybrid vehicle. The method includes determining, by a control unit if a state of charge of an energy storage unit is in one or more pre-set threshold range. The method further includes determining, by the control unit if a speed of the hybrid vehicle is in one or more pre-set threshold range. The method further includes generating, a signal indicative of the one or more predetermined drive modes for driving the hybrid vehicle based on the one or more pre-set threshold range of the state of charge of the energy storage unit and the one or more pre-set threshold range of the speed of the hybrid vehicle. The method further includes communicating, the signal to a traction motor and/or an Engine Control Unit (ECU) for driving the hybrid vehicle in the one or more predetermined drive modes.
[019] In an embodiment of the present invention, a signal from the control unit is communicated to the traction motor and/or the ECU for driving the hybrid vehicle either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit is in the first threshold range and the pre-set threshold range of the speed of the hybrid vehicle is in the first threshold range.
[020] In a further embodiment of the present invention, a signal from the control unit is communicated to the traction motor and/or the ECU for driving the hybrid vehicle either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit is in the second threshold range and the pre-set threshold range of the speed of the hybrid vehicle is in the second threshold range.
[021] In a further embodiment of the present invention, a signal from the control unit is communicated to the ECU for driving the hybrid vehicle in the engine mode when the state of charge of the energy storage unit is lesser the second threshold range.
[022] In a further embodiment of the present invention, a signal from the control unit is communicated to the traction motor and/or the ECU for driving the hybrid vehicle in any one of modes comprising an ECO mode, the power mode with the traction motor support, an electric vehicle mode and the engine mode when the state of charge of the energy storage unit is greater than the first threshold range and the speed of the hybrid vehicle is greater than the first threshold range.

BRIEF DESCRIPTION OF THE DRAWINGS
[023] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates a schematic block diagram of a hybrid vehicle, in accordance with an embodiment of the present invention.
Figure 2 illustrates a method flowchart, in accordance with an embodiment of the present invention.
Figures 3 - 5 illustrate method flowcharts, in accordance with exemplary embodiments of the present invention.
Figure 6 illustrates a graph of torque characteristics of an internal combustion engine and a traction motor, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[024] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. In the ensuing exemplary embodiments, the vehicle is a hybrid two-wheeled vehicle. However, it is contemplated that the disclosure in the present invention may be applied to any automobile capable of accommodating the present subject matter without defeating the scope of the present invention.
[025] The present invention generally relates to a hybrid vehicle.
[026] Figure 1 illustrates a schematic block diagram of a hybrid vehicle 10, in accordance with an embodiment of the present invention. The terms “hybrid vehicle” and “vehicle” are interchangeably used in this disclosure. It should be understood that both the terms “hybrid vehicle” and “vehicle” are one and the same. The term “vehicle” is used for brevity. As illustrated in Figure 1, the hybrid vehicle 10 includes an internal combustion engine 12 configured for generating a driving force during one or more predetermined drive modes for the hybrid vehicle 10. The hybrid vehicle 10 further includes a traction motor 14 configured for generating a driving force from an energy storage unit 16 during the one or more predetermined drive modes for the hybrid vehicle 10. In an embodiment, the energy storage unit 16 is a battery, including but not limited to a Lithium-ion battery.
[027] As illustrated in Figure 1, the hybrid vehicle 10 further includes a control unit 100. In some embodiments, the control unit 100 includes one or more additional components such as, but not limited to, a memory unit, an input/output module, a pre-processing module etc. In another embodiment, the hybrid vehicle 10 includes more than one of same or similar control unit(s) 100. In another embodiment, the control unit 100 includes only a processor which may be required to process the received instructions / signals from one or more inputs device like energy storage unit 16, speedometer sensor 20, throttle sensor 22 and process the same. In yet another embodiment, the control unit 100 is in communication with an analytic module which is configured to perform additional analysis of the information received from the energy storage unit 16, the speedometer sensor 20, the throttle sensor 22 of the hybrid vehicle 10.
[028] In some embodiments, the memory unit (not shown) in communication with the control unit 100 is capable of storing machine executable instructions. Further, the control unit 100 is capable of executing the machine executable instructions to perform the functions described herein. The control unit 100 is in communication with the components such as the pre-processing module and the analytic module. In another embodiment, the control unit 100 is embodied as a multi-core processor, a single core processor, or a combination of one or more multi-core processors and one or more single core processors. For example, the control unit 100 is embodied as one or more of various processing devices, such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like. In yet another embodiment, the control unit 100 is configured to execute hard-coded functionality. In still another embodiment, the control unit 100 is embodied as an executor of instructions, where the instructions are specifically configured to the control unit 100 to perform the steps or operations described herein for operating the hybrid vehicle 10 in one or more predetermined drive modes. In one embodiment, the one or more predetermined modes includes a power mode with EV support (i.e., traction motor support) and an engine mode.
[029] In the illustrated embodiment in Figure 1, the control unit 100 is in communication with an Engine Control Unit (ECU) 18 and the traction motor 14. In an embodiment, the control unit 100 is configured to determine a state of charge of the energy storage unit 16. The term “State of Charge” (SOC) is defined as a ratio of available capacity and maximum possible charge that can be stored in a battery. The SOC of a cell indicates the amount of electrical energy in the cell and defines Lithium-ion distribution between a cathode and an anode. In one embodiment of present invention, the control unit 100 is configured to determine if the state of charge of the energy storage unit 16 is in one or more pre-set threshold range. In one exemplary embodiment, the one or more pre-set threshold range of the state of charge of the energy storage unit 16 includes a first threshold range and a second threshold range. The first threshold range of the SOC of the energy storage unit 16 is between 30% and 40% and the second threshold range of the SOC of the energy storage unit 16 is between 20% and 30%.
[030] In an embodiment, the control unit 100 is further configured to determine speed of the hybrid vehicle 10 based on an input received from the speedometer sensor 20. In one embodiment, the control unit 100 is configured to determine if a speed of the hybrid vehicle 10 is in one or more pre-set threshold range. In one exemplary embodiment, the one or more pre-set threshold range of the speed of the hybrid vehicle 10 includes a first threshold range between 0.1 km/h and 30 km/h when the state of charge of the energy storage unit 16 is in the first threshold range of 30% to 40%. In another exemplary embodiment, the one or more pre-set threshold range of the speed of the hybrid vehicle 10 includes a second threshold range between 0.1 km/h and 20 km/h when the state of charge of the energy storage unit 16 is in the second threshold range of 20% to 30%.
[031] Further, in an embodiment of the present invention, the control unit 100 is configured to generate a signal indicative of the one or more predetermined drive modes for driving the hybrid vehicle 10 based on the one or more pre-set threshold range of the state of charge of the energy storage unit 16 and the one or more pre-set threshold range of the speed of the hybrid vehicle 10. Thereafter, the control unit 100 is configured to communicate the signal to the traction motor 14 and/or the ECU 18 for driving the hybrid vehicle 10 in the one or more predetermined drive modes.
[032] In one embodiment, the control unit 100 is configured to communicate a signal to the traction motor 14 and/or the ECU 18 for driving the hybrid vehicle 10 either in the power mode with the traction motor 14 support or in the engine mode when the state of charge of the energy storage unit 16 is in the first threshold range and the pre-set threshold range of the speed of the hybrid vehicle 10 is in the first threshold range.
[033] In another embodiment, the control unit 100 is configured to communicate a signal to the traction motor 14 and/or the ECU 18 for driving the hybrid vehicle 10 either in the power mode with the traction motor support or in the engine mode when the state of charge of the energy storage unit 16 is in the second threshold range and the pre-set threshold range of the speed of the hybrid vehicle 10 is in the second threshold range.
[034] In yet another embodiment, the control unit 100 is configured to communicate a signal to the ECU 18 for driving the hybrid vehicle 10 in the engine mode when the state of charge of the energy storage unit 16 is lesser than the second threshold range.
[035] In still another embodiment, the control unit 100 is configured to communicate a signal to the traction motor 14 and/or the ECU 18 for driving the hybrid vehicle 10 in any one of modes including, but not limited to, an ECO mode, the power mode with the traction motor support, an electric vehicle mode and the engine mode when the state of charge of the energy storage unit 16 is greater than the first threshold range and the speed of the hybrid vehicle 10 is greater than the first threshold range.
[036] Figure 2 illustrates a method flowchart, in accordance with an embodiment of the present invention. The method 200 involves reducing the impact of drive feel that changes by stepping down performance gradually based on state of charge of the vehicle and the speed of the vehicle.
[037] Referring again to Figure 2, the method 200 of operating the hybrid vehicle 10 includes, at a step 202, determining, by the control unit 100 if the state of charge of the energy storage unit 16 is in one or more pre-set threshold range. At a step 204 of the method 200 includes, determining, by the control unit 100 if the speed of the hybrid vehicle 10 is in the one or more pre-set threshold range. Further, at a step 206 of the method 200 includes, generating, by the control unit 100 the signal indicative of the one or more predetermined drive modes for driving the hybrid vehicle 10 based on the one or more pre-set threshold range of the state of charge of the energy storage unit 16 and the one or more pre-set threshold range of the speed of the hybrid vehicle 10. At a step 208 of the method 200 includes, communicating the signal by the control unit 100 to the traction motor 14 and/or the ECU 18 for driving the hybrid vehicle 10 in the one or more predetermined drive modes.
[038] In an embodiment, when the state of charge of the energy storage unit 16 is in the first threshold range and the pre-set threshold range of the speed of the hybrid vehicle 10 is in the first threshold range, a signal from the control unit 100 is communicated to the traction motor 14 and/or the ECU 18 for driving the hybrid vehicle 10 either in the power mode with the traction motor support or in the engine mode.
[039] In another embodiment, when the state of charge of the energy storage unit 16 is in the second threshold range and the pre-set threshold range of the speed of the hybrid vehicle 10 is in the second threshold range, a signal from the control unit 100 is communicated to the traction motor 14 and/or the ECU 18 for driving the hybrid vehicle 10 either in the power mode with the traction motor support or in the engine mode.
[040] In yet another embodiment, when the state of charge of the energy storage unit 16 is lesser the second threshold range, a signal from the control unit 100 is communicated to the ECU 18 for driving the hybrid vehicle 10 in the engine mode.
[041] In still another embodiment of the present invention, when the state of charge of the energy storage unit 16 is greater than the first threshold range and the speed of the hybrid vehicle 10 is greater than the first threshold range, a signal from the control unit 100 is communicated to the traction motor 14 and/or the ECU 18 for driving the hybrid vehicle 10 in any one of modes comprising an ECO mode, the power mode with the traction motor support, an electric vehicle mode and the engine mode. That is to say, when the SOC of the energy storage unit 16 (battery) is more than 40%, the hybrid vehicle 10 can be operated in all the modes including, but not limited to, ECO mode, power mode, EV mode and power mode with EV support up to the maximum speed of the traction motor.
[042] In one exemplary embodiment as shown in Figure 3, the method 300 of operating the hybrid vehicle 10 at a step 302 includes, determining, by the control unit 100 if the state of charge of the energy storage unit 16 is in the first threshold range between 30% and 40%. At a step 304 of the method 300, the control unit 100 determines if the speed of the hybrid vehicle 10 is in the first threshold range between 0.1 km/h and 30 km/h. Then, at a step 306, the control unit 100, generates the signal for driving the hybrid vehicle 10 in power mode with EV support and not to operate the hybrid vehicle 10 in the ECO and EV modes. At step 308, the signal is communicated by the control unit 100 to the traction motor 14 and the ECU 18 for driving the hybrid vehicle 10 in the power mode with EV support up to 30 Km/h and to reduce the support of EV to 65% of the maximum speed up to 30 Km/h.
[043] In another exemplary embodiment as shown in Figure 4, the method 400 of operating the hybrid vehicle 10 at a step 402 includes, determining, by the control unit 100 if the state of charge of the energy storage unit 16 is in the second threshold range between 20% and 30%. At a step 404 of the method 400, the control unit 100 determines if the speed of the hybrid vehicle 10 is in the second threshold range between 0.1 km/h and 20 km/h. Then, at a step 406, the control unit 100, generates the signal for driving the hybrid vehicle 10 in power mode with EV support and not to operate the hybrid vehicle 10 in the ECO and EV modes. At step 408, the signal is communicated by the control unit 100 to the traction motor 14 and the ECU 18 for driving the hybrid vehicle 10 in the power mode with EV support up to 20 Km/h and to reduce the support of EV to 45% of the maximum speed up to 20 Km/h.
[044] In yet another exemplary embodiment as shown in Figure 5, the method 500 of operating the hybrid vehicle 10 at a step 502 includes, determining, by the control unit 100 if the state of charge of the energy storage unit 16 is below 20%. At a step 504, the control unit 100 generates a signal to the ECU to operate the hybrid vehicle 10 only in the engine mode with the assistance of the reserved SOC from the battery 16 of the hybrid vehicle 10. At a step 506, the control unit 100 communicates the signal to the ECU to operate the hybrid vehicle 10 only in the engine mode with the assistance of the reserved SOC from the battery 16. The step-down performance avoids sudden change in performance and therefore, allows the rider to adjust with the performance over a period of time.
[045] In some embodiments of the present invention, the EV support reduces as the battery SOC falls and thus the method in the present invention helps the battery 16 to retain the SOC for a longer period of time.
[046] Figure 6 illustrates a graph of torque characteristics of an internal combustion engine and a traction motor, in accordance with an embodiment of the present invention. In Figure 6, the torque difference is shown where the two lines intersect each other. Initially, the traction motor is “ON”, and the IC engine is switched “ON”, since both the power source is “ON”, the torque will be slightly high, which will further smoothen the transition of the power source. In order to smoothen the changeover, both the power source has to work together for some time. This will improve the rider feel during the changeover of the power sources.
[047] In yet another exemplary embodiment in the present invention the transition speed zone lies in the range of 25 to 50 Kmph. In the ECO mode, the jerk is reduced during switchover of the power source from the traction motor to the IC engine with the transition speed zone. As during the transition speed zone, the traction motor will assist the engine during the mid-speed zone before giving the complete authority to the engine for further propulsion. Therefore, the method in the present invention having the changeover, the transition of power source will be smooth, as there will be no sudden torque characteristics change of the vehicle with the sudden change of power source in ECO mode.
[048] When the vehicle is in the ECO mode of operation, the power supply is given to the traction motor based on the throttle position sensor output, which is based on the throttle opening operated by the rider of the vehicle. If the vehicle speed is equal to or more than the starting point of the transition speed zone i.e., 25 Kmph, then the control unit switches the engine “ON”. If the previous condition is not met, the control unit continues to supply power to the traction motor. The control unit further checks, if the vehicle speed is greater than the transition speed zone, the power supply to the traction motor is stopped. If the previous condition is not met, the control unit checks, if the vehicle speed is less than the starting point of the transition speed zone, if the condition is met, the engine is switched “OFF”, and the control unit keeps on checking for the vehicle speed. If the previous condition is not met, then the power supply to the engine and the traction motor is continued, based on the throttle position sensor.
[049] Advantageously, present invention provides good drive feel at lower speeds and provides a good power pick-up for the hybrid vehicle. The present invention avoids clutch burning at gradient and thus increases durability and the life of the engine clutch. In other words, the present invention eliminates the premature failure of clutch plates during engine and ECO modes caused due to the high load on the engine, and thus provides better acceleration in the engine mode when the battery capacity becomes zero.
[050] In the present invention, initial assist approach with the traction motor in the engine mode will reduce the impact onto the engine clutch, thereby increasing the life of the clutch. Thus, the load carried by the engine will reduce and will be shared by the traction motor. Therefore, it also helps to improve durability of the engine clutch in gradient condition, especially in hilly regions.
[051] Further, the present invention reduces jerks during sudden changeover of power source from the traction motor to the engine in ECO mode and thus increases the comfort level of the rider. The present invention achieves good mileage of hybrid electric vehicle in engine mode (at low speed of vehicle), improves performance of the vehicle and also reduces the emission. The present invention reserves SOC of the battery with its systematic use in various different modes of the hybrid electric vehicle.
[052] The power assist approach with the traction motor in the engine mode helps to propel the vehicle from standstill (the most in-efficient zone of the engine) to any speed less than 50 km/h. This will improve the initial acceleration of the vehicle and the drive feel in the engine mode. Moreover, this will also improve the fuel mileage of the engine, as the engine power requirements get reduced.
[053] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.