FIELD OF THE INVENTION

[0001] The present invention relates generally to a hybrid vehicle and more particularly, but not exclusively, to a mechanism for starting a hybrid vehicle in emergency conditions.

BACKGROUND OF THE INVENTION

[0002] With dwindling non-renewable energy resources, the need to reduce fossil fuel consumption and emissions from vehicles powered by internal combustion engines is well known. One way to achieve the aforesaid goal is through an electrically driven vehicle. However, such a vehicle has greater body weight and shorter running distance per charge as compared to the conventional vehicles. Such drawbacks are overcome by hybrid vehicles, which utilize the advantages of an internal combustion engine and an electric traction motor into one vehicle. They provide great potential for reducing vehicle fuel consumption and emissions with no serious loss of vehicle performance or drivability.

[0003] The hybrid vehicles are operated through a control apparatus configured according to the engine, traction motor and battery specifications. The control apparatus in hybrid vehicles has a controller which controls the vehicle operation and flow of power in the vehicle based on the inputs available to it and the inbuilt logic. The controller takes power from the battery which, in the case of hybrid vehicles, is usually of high voltage. The controller, in hybrid vehicles, substantially controls the vehicle operations without any manual input including cranking the engine through a starter motor. Battery power is provided to the starter motor. However, there may arise certain undesirable events occuring from an electrical fault or a mechanical fault which cause the controller to malfunction consequently affecting the vehicle operation and causing trouble to the vehicle user.

[0004] For example, the high voltage battery may develop electrical malfunction, or the wires carrying high current from the battery to vehicle components may develop short circuit which would prevent supply of power to the controller. In such situations, the controller would not be able to carry out the vehicle operation as desired. This would also happen if the battery is completely or partially discharged, from where the controller takes the power. Further, if the controller itself is malfunctioned, the self cranking of the engine is disabled and the vehicle would be rendered inoperable. In yet another situation, if the traction motor is short circuited, it would be difficult to even push the vehicle as the traction motor is connected to the rear wheel. Thus, in the case of any fault in controller or battery or motor due to any electrical or mechanical malfunction event, the vehicle operation is affected and the user would be stranded on the road. SUMMARY OF THE INVENTION

[0005] The present subject matter is directed to overcome all or any of the problems as set forth above and thereby to obviate a lacunae in the prior art. It is therefore an object of the present subject matter to provide an emergency mode in a hybrid vehicle in the form of a limp home mechanism so that the vehicle may be manually operated during any emergency or undesirable situation without relying on the battery and the controller. It is another object of the invention to ensure that the limp home mechanism does not interfere in working of the controller in normal situations.

[0006] To this end, the present invention discloses a hybrid vehicle having a limp home mechanism comprising a manually operated kick start lever connected with the engine; an alternator mechanically connected to the kick start lever, the alternator having a stator and a rotor; an RR unit taking input from the alternator; wherein the operation of kick start lever causes the alternator to provide required voltage to an ignition (TCI) unit, the engine being cranked without the help of battery and controller, and wherein further the RR unit regulates the voltage required for the TCI unit. [0007] The foregoing objectives and summary is provided to introduce a selection of concepts in a simplified form, and is not limiting. To fully appreciate these and other objects of the present subject matter as well as the subject matter itself, all of which will become apparent to those skilled in the art, the ensuing detailed description of the subject matter and the claims should be read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0008] The above and other features, aspects and advantages of the subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where: FIG. 1 shows a hybrid vehicle according to the present invention.

FIG. 2 shows a rear portion of the hybrid vehicle without the side covers.

FIG. 3 shows a sectional top view of the engine.

FIG. 4 shows a side view of a kick start lever in the engine case.

FIG. 5 shows the working layout of a limp home mechanim for hybrid vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention discloses a hybrid vehicle with an emergency mode in the form of a limp home mechanism. The limp home mechanism comprises of a manually operated kick start lever connected with the engine, an alternator mechanically connected to the kick start lever, the alternator having a stator and a rotor, an RR unit taking input from the alternator. The limp home mechanism is configured to start the vehicle directly in an engine mode without relying on the battery and the controller. This provision converts the hybrid vehicle into a usual kick start vehicle during emergency, unexpected or undesirable situations. [00010] Further, the controller is configured to work with the limp home mechanism during normal situations when the vehicle is working fine. However, in partial or complete shutdown conditions, the controller allows the vehicle to go into manual mode so that a vehicle user may manually crank the engine and take the vehicle to the nearest service centre. The hybrid vehicle with a limp home mechanism is now explained through an embodiment.

[00011] FIG. 1 shows a side view of the concerned hybrid vehicle. The vehicle has body frame assembly made up of several tubes welded together which usually supports the body of the said vehicle. The vehicle has a steerable front wheel 101 and a driven rear wheel 102. The body frame assembly of the vehicle is an elongated structure, which typically extends from a forward end to a rearward end of the vehicle. It is generally convex in shape, as viewed from a side elevational view. The said frame assembly includes a head tube (not shown), a main frame 108 and may also have a sub-frame. The sub-frame is attached to the main frame using appropriate joining mechanism. The frame assembly is covered by a plurality of vehicle body covers including a front panel 105, a leg shield 141, an under seat cover 143 and a side panel 106. [00012] A handlebar assembly 150 and a seat assembly 142 are supported at opposing ends of the frame assembly and a generally open area is defined there between known as floorboard 140 which functions as a step through space. The seat for a driver and a pillion is placed forward to a fuel tank and rearwardly of the floorboard 140. A front fender 103 is provided above the front wheel 101 to avoid the said vehicle and its occupants from being splashed with mud. Likewise a rear fender 104 is placed between fuel tank and rear wheel 102, and to the outer side in the radial direction of rear wheel 102. Rear fender 104 inhibits rain water or the like from being thrown up by rear wheel 102. [00013] Suspensions are provided for comfortable steering of the vehicle on the road. A front suspension assembly (not shown) is connected to a front fork 107 while the rear suspension assembly is a hydraulic damped arrangement and is connected to the body frame. The rear suspension assembly comprises of at least one rear suspension 131 preferably on the left side of the vehicle. However, a vehicle with two rear suspensions, namely on the left side and the right side is also possible. For the safety of the user and in conformance with the traffic rules, a headlight 136 in the front portion of the vehicle and a taillight 137 in the rear portion of the vehicle is also provided. [00014] The vehicle has an electromechanical powertrain including an internal combustion engine 120 and an electrical traction motor 122 as drive sources. The engine 120 is disposed forwardly of the rear wheel 102 and supported on the vehicle frame. As shown in FIG. 2, the traction motor 122 is powered by a battery 126 whereas the engine is cranked by a starter motor (not shown) powered by the battery. A controller 125 controls the flow of power in the vehicle. In an embodiment, the engine is a four stroke single cylinder engine. The rear wheel 102 is driven by driving force generated by either the engine 120 or the traction motor 122 or both. The power from the engine is delivered to the rear wheel 102 through a transmission system. The engine 120 is arranged horizontally, that is, its crankshaft is placed at right angles to the longitudinal direction of the vehicle body. The traction motor 122 derives power from the battery 126. In a preferred embodiment as shown in FIG. 3, the traction motor 122 is located within a hub 127 of a rear wheel 102. The hub 127 moves around a wheel shaft 27 passing axially through the hub. The direct coupling of traction motor 122 to the rear wheel hub 127 outside the engine crankcase saves space and prevents transmission losses due to gear reduction.

[00015] As shown in FIG. 3, the engine 120 has a piston operated crankshaft 22 which rotates to transmit power to the rear wheel 102 through a transmission system. The crankshaft 22 is operably engaged with and drives an intermediate shaft 24. According to an embodiment of the present invention, the power transmission from the crankshaft 22 to the intermediate shaft 24 is through a wet type chain transmission. The chain is shown through the reference numeral 23. A centrifugal clutch 32 disposed at an end portion of the crankshaft 22 helps in engagement and disengagement of the crankshaft 22 with the intermediate shaft 24. A sprocket 26 disposed at an end portion of the intermediate shaft 24 transfers the power received from the crankshaft to a wheel shaft 27 through a dry type chain/belt transmission. The sprocket and chain mechanism reduces rotational force of intermediate shaft and transmits reduced rotational force to rear wheel 102.

[00016] The hybrid vehicle further comprises a plurality of user-selectable operating modes. The user can select any of the operating modes for operating the vehicle and/or switch between the operating modes through a mode selection switch (not shown) provided for this purpose. The selected mode is displayed on a display panel of the hybrid vehicle. The controller 125 starts the motor or the engine or both according to the mode selected by the user. In case no mode is selected, the controller starts the vehicle in default mode. In a preferred embodiment, the hybrid vehicle is provided with atleast four operating modes for optimizing the fuel efficiency, range of the vehicle and to provide more control and discretion to the vehicle user regarding the vehicle operation.

[00017] The four operating modes are named as a hybrid economy mode, a hybrid power mode, an engine mode and an electric mode. The hybrid economy mode is the default mode for the vehicle i.e., except in case of any user selection otherwise, the controller starts and runs the vehicle in hybrid economy mode. In this mode, the controller operates the vehicle by initially powering the traction motor 122 and then once the vehicle reaches a pre-defined operating point, the ■

controller 125 cranks the internal combustion engine 120 and stops the traction motor 122. In the hybrid power mode the controller operates the vehicle in such a way that the vehicle gets power from the engine 120 and the traction motor 122 simultaneously. In the engine mode, the controller cranks the engine 120 and the vehicle runs only on the engine whereas in the electric mode, the vehicle is powered with traction motor 122 only.

[00018] As shown in FIG. 5, the user for operating the vehicle firstly switches on the ignition switch 10 through an ignition key provided in the vehicle which provides the voltage to a DC/DC converter 11. The output of the DC/DC converter 11 is connected to all lighting loads including the display panel. The battery 126 is a single battery used to provide power across all vehicle components like starter motor for engine cranking, display panel, all lighting loads, controller and for powering traction motor. In an embodiment of the hybrid vehicle, the battery 126 includes a lithium ion battery and provides 48V of electromotive force. The battery works under dual voltage system. The battey supplies 48V of electromotive force to the electric motor through the controller 125 whereas it supplies 12V to all other loads through the DC-DC converter 11. The battery can be charged either through direct charging or using the traction motor.

[00019] Once the user selects a particular operating mode, the controller 125 switches on the traction motor 122 or the internal combustion engine 120 depending upon the input obtained from the mode selection switch. For initiating the traction motor 122, the controller 125 receives power from the battery 126 and supplies it to the traction motor 122. For initiating the engine 120, the controller 125 cranks a starter motor (not shown) by supplying required voltage to a starter relay (not shown). The starter relay supplies required voltage to the starter motor. In a preferred embodiment, the controller supplies 12 V to the starter relay and the starter relay further supplies 48 V to the starter motor. The controller simultaneously powers an ignition (TCI) unit 12 for spark plug ignition. In order to switch off the engine automatically (when the vehicle speed reaches to zero), the controller cuts off the power supply using an ignition cut off relay (TCI relay) 17. It stops the power supply to the ignition (TCI) unit 12 and thus stops the internal combustion engine 120.

[00020] In the case of any fault in controller or battery or motor due to any electrical or mechanical malfunction event, the vehicle operation is affected and the user would be stranded on the road. The battery 126 may develop a fault or wires may fail to supply current to the controller. Therefore, an emergency mode in the form of a limp home mechanism is provided in the vehicle to assist the vehicle user in emergency situations. It comprises of a manually operated kick start lever 31 connected with the engine 120; an alternator 33 mechanically connected to the kick start lever 31; and a regulation and rectifier unit (RR unit) 9 taking input from the alternator 33. The kick start lever 31 is placed external to the engine laterally, and is operatively connected to the transmission system further connected to the crankshaft. The alternator enables the kick start in the vehicle. The vehicle user can manually operate the kick start lever 31 to start the vehicle when the battery faces complete or partial shutdown, or even otherwise.

[00021] The limp home mechanism starts the vehicle directly in an engine mode during any electrical or mechanical malfunction event. Its presence converts the hybrid vehicle into a vehicle having an engine with battery-less ignition system. To use the vehicle in emergency mode, the user first switches on the ignition key i.e. the ignition switch 10 must be ON. As shown in FIG. 4, when manual force is applied, the kick start lever 31 operates the kick start drive gear 36 which is meshed with an idler gear 34. The idler gear 34 passes the drive to the kick start driven gear 35 which powers the crankshaft 22. As shown in FIG. 5, the rotation of crankshaft causes the alternator 33 to provide required voltage to the TCI unit 12 through the TCI cut off relay 17. A pulser coil connected to the alternator generates rpm signal which is sensed by the TCI unit (signal flow). The TCI unit 12 powers the ignition coil 14 which further powers the spark plug. The TCI unit thus provides the spark and activates ignition when the rpm signal is adequate. In this way, the engine 120 is cranked without the help of battery and controller.

[00022] The alternator 33 is a magneto having a rotor and a stator and is mounted near an end portion of the crankshaft 22 of the engine opposite to the centrifugal clutch 32. It provides the electromotive force to the RR unit 9 which provides the required regulated voltage (12 V) to the ignition unit 12 and to all the loads along with the DC/DC converter output. The RR unit has a full bridge configuration and a capacitor arrangement in order to regulate the voltage output to acceptable limits in the absence of a 12 V battery as the main battery 126 is of very high power. The output of the DC/DC converter 11 is connected to all lighting loads including the display panel. Thus, the limp home mechanism is capable to start the vehicle in engine mode manually without battery power and without taking input from the controller. On manually operating the kick lever, the mechanism cranks the engine and ensures vehicle movement during emergency situations.

[00023] It is possible that during the operation of the hybrid vehicle, the battery may face complete, partial or no shutdown. All battery related activities in the vehicle are routed through the controller during normal conditions and therefore, the limp home mechanism is configured to work during the complete or partial shutdown conditions caused by battery discharge or any electrical malfunction event. As shown in FIG. 5, when the battery and other vehicular systems are working fine in 'no shutdown' condition, the controller works normally according to the user selected mode and switches off the TCI unit 12 to disable the engine initially. In the default hybrid economy mode, the traction motor 122 initially powers the vehicle as the TCI unit 12 is disabled and when the vehicle reaches a threshold speed, the controller 125 cranks the engine through the starter motor. If the user manually selects engine mode, the engine is cranked by controller with the help of starter motor. In no shutdown condition, even if the user manually cranks the engine through the kick start lever 31, the controller 125 detects it and stops the power to the TCI unit 12 thus switching off the ignition to the engine. The engine will thus stop when not required. [00024] In 'complete shutdown' condition, no electrical input is available to the controller 125 and the battery 126 is completely dead, or the connection to the controller is broken. During this time, the engine 120 is cranked by the vehicle user using the limp home mechanism as explained above but only after the ignition key is switched ON. Thus, the vehicle starts in the engine mode. Here, the alternator 33 provides power to the TCI unit 12 rather than the battery 126 and the entire operation is devoid of any controller or battery. Once the engine is started, the electrical system keeps providing sufficient voltage for operating all vehicle loads. Since a secondary 12 V battery is not used in the vehicle and the main battery is dead, the RR unit 9 provides the output voltage without any ripples. To enable this, the RR unit comprises of the full bridge rectifier and capacitor arrangement providing full DC current.

[00025] During 'partial shutdown' condition, the vehicle ignition key is switched ON and the instrument cluster is also ON but shows a severe malfunction indication. This condition occurs when the controller is ON but because of some, safety critical parameters going wrong on the battery, the controller is disabling the high current battery discharge. It is to be noted that the battery is a lithium ion battery with an internal BMS (battery management system) which provides safety critical parameters to the controller. The controller is supposed to keep the TCI unit 12 switched off but during partial shutdown conditions, the controller logic changes and the TCI cut off relay 17 is enabled even in zero speed for enabling the manual cranking of the engine. It also disables starter motor to stop self-cranking. Previously in prior art, the engine would start only when the controller cranks the starter motor or when the user itself selects the engine mode or hybrid power mode. Thus, with limp home mechanism, the kick start lever 31 cranks the engine and the controller would power the TCI unit for ignition.

[00026] Because of provision of the limp home mechanism, the controller logic is configured taking into account different situations as explained as well as giving it more flexibility to shut down the electric self-start and avoiding deep discharge of the battery. This is because there is another option available to start the vehicle by using the kick start lever. This flexibility increases the safety parameter of the vehicle as lithium ion batteries must be monitored continuously. [00027] The present subject matter and its equivalent thereof offer many advantages, including those which have been described henceforth. The present invention discloses a hybrid vehicle with user selectable modes and a limp home mechanism to start the hybrid vehicle during any electrical or mechanical malfunction event. The limp home mechanism improves convenience of the user and converts the hybrid vehicle into a normal manually cranked vehicle.

[00028] The present subject matter is thus described. The description is not intended to be exhaustive nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiments may be modified in light of the above description. The embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore the forgoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the appended claims.