WO2023187806A1

WO2023187806A1 - A method and a system for normalizing position of a piston

Info

Publication number: WO2023187806A1
Application number: PCT/IN2023/050049
Authority: WO
Inventors: Natarajan Krishnakumar NAVEEN; Muralimanohar SATHIAMOORTHY; Prasad Raghavendra; Rajaram Sagare DATTA
Original assignee: Tvs Motor Company Limited
Priority date: 2022-03-31
Filing date: 2023-01-18
Publication date: 2023-10-05

Abstract

The present subject matter provides a method and a system for normalizing position of a piston. The method is implemented by an ISG controller (103B). The method comprises receiving a first signal indicating position of piston (102A). The method further comprises receiving a second signal indicating switching off of engine (102). The method further comprises estimating a position of the piston (102A) at first time instant when engine is turned off. The method further comprises determining position of piston and if position of piston in vicinity of a top dead center then performing forward motoring based on estimated position of piston at first time instant.

Description

A METHOD AND A SYSTEM FOR NORMALIZING POSITION OF A

PISTON

TECHNICAL FIELD

[0001] The present subject matter relates in general to an engine assembly for a vehicle, in particular but not exclusively to a method and system for normalizing position of a piston by an integrated starter generator (ISG) controller for a vehicle. BACKGROUND

[0002] Conventionally, an internal combustion engine has been a main source for powering a vehicle. In recent years, automobile industry has been investigating alternatives to the internal combustion engine to improve fuel efficiency of the internal combustion engines. To meet the requirement of improving fuel efficiency an integrated starter-generator (ISG) is used. The ISG replaces conventional starter motor and conventional alternator (generator). The ISG provides a convenient automatic start-stop system for the vehicle by combining the functions of the starter and the generator. An electronic control system of the vehicle switches off the vehicle during idling or zero load conditions and rapidly automatically restarts the vehicle using ISG when a rider activates the accelerator pedal. The ISG acts as a bi-directional power converter, changing mechanical energy into electrical energy and vice-versa. The ISG functions as an electric motor during motoring mode and the ISG rapidly motors a crankshaft. Whereas, when ISG acts as a generator or during generator mode, the ISG generates electrical energy for various electrical i components of the vehicle from the mechanical energy of the crankshaft. Generally, the ISG is sandwiched between an engine and a transmission system of the vehicle.

[0003] The ISG contributes in start-stop functioning of the vehicle, electricity generation for the vehicle and power assistance for the vehicle. For automatic starting of the vehicle through the ISG, the engine cranking is achieved when ISG provides rotation to the crankshaft using battery power. Once a threshold speed of vehicle is achieved, the ISG drive power is turned off. During braking or retarding force, the ISG regenerates and provides energy back to the battery. For power assistance, the ISG is used to support the engine by supplying additional power for faster acceleration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The detailed description is described with reference to an embodiment of a method and system for normalizing position of a piston by an integrated starter generator (ISG) controller along with the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.

[0005] Figure 1 illustrates a block drawing of an engine assembly, in accordance with an embodiment of the present subject matter.

[0006] Figure 2 illustrates a flow chart for normalizing position of the piston by the ISG controller, in accordance with an embodiment of the present subject matter. [0007] Figure 3 illustrates another flow chart for normalizing position of the piston by the ISG controller, in accordance with an embodiment of the present subject matter.

SUMMARY

[0008] In an aspect of the present invention, a method for normalizing position of a piston by an integrated starter generator (ISG) controller is disclosed. As per the present invention, the method comprises following steps: receiving a first signal by the ISG controller indicating one of a position of piston. Then receiving a second signal by the ISG controller indicating switching off of an engine. Then estimation by the ISG controller about position of piston at a first time instant when engine is turned off. Then the ISG controller is determining one of position of piston by the and if position of piston being in vicinity top dead center (TDC) the ISG controller is performing forward motoring based on estimated position of piston at first time instant.

[0009] In another aspect, the ISG controller is receiving a signal indicating stroke of the engine before receiving the second signal indicating the switching off of the engine. The ISG controller is determining the type of the stroke of the engine. Then the ISG controller is performing forward motoring only if the determined stroke of the engine is the compression stroke.

[00010] In another aspect of the present invention, an engine assembly comprising: an engine and engine drive system. The engine comprises: a cylinder head and a crankshaft. The engine drive system comprises: an ISG and an ISG controller. The ISG controller is communicatively coupled with the engine and the ISG. The ISG controller is configured to receive plurality of input signal from the engine. The input signal from the engine indicates one of a position of the piston and switching off state of the engine. The ISG controller is configured to determine one of the position of the piston and if the position of the piston is in vicinity a top dead center (TDC) the ISG controller performs forward motoring of the piston.

[00011] In another aspect of the engine assembly, ISG controller is configured to receive a signal indicating stroke of the engine before receiving of the second signal indicating the switching off of the engine. The ISG controller is configured to determines the type of the stroke of the engine. Then the ISG controller performs forward motoring only if the determined stroke of the engine is the compression stroke.

[00012] In an aspect, the forward motoring being assisted by an inertia force of the piston.

[00013] Summary provided above explains the basic features of the present subject matter and does not limit the scope of the invention. The nature and further characteristic features of the present subject matter will be made clearer from the following descriptions made with reference to the accompanying drawings.

[00014] Exemplary embodiments detailing features of the method and system for normalizing position of the piston, in accordance with the present subject matter will be described hereunder with reference to the accompanying drawings. Various aspects of different embodiments of the present subject matter will become discernible from the following description set out hereunder. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the present subject matter. Further, it is to be noted that terms “upper”, “lower”, “right”, “left”, “front”, “forward”, “rearward”, “downward”, “upward”, “top”, “bottom” and like terms are used herein based on the illustrated state or in a standing state of the vehicle with a rider sitting thereon unless otherwise elaborated. Furthermore, a vertical axis refers to a top to bottom axis relative to the vehicle, defining a vehicle vertical direction; while a lateral axis refers to a side to side, or left to right axis relative to said vehicle, defining a vehicle lateral direction. Further, a longitudinal axis refers to a front to rear axis relative to the vehicle, defining the vehicle in a longitudinal direction. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION

[00015] Conventionally, the ISG performs motoring of the crankshaft in an opposite direction to that of the direction of rotation of the crankshaft during normal vehicle running conditions. Therefore, during normal vehicle running conditions, the crankshaft rotates in a forward direction whereas during starting through an ISG the crankshaft is rotated in a reverse direction. Cranking in reverse direction implies that small reverse rotation of engine when it is stopped so as to reduce cranking force during next cycle. Due to this reverse rotation, to overcome such force, the ISG applies excess torque and such phenomenon occurs when engine has switched off abruptly at an intermediate stroke position. [00016] In such scenarios, it is imperative that ISG deploys high energy to transmit high torque for causing rotation of the crankshaft for cranking operation of the engine.

[00017] Typically, during vehicle running conditions, the piston is in a continuous movement between a top dead center (TDC) position and a bottom dead center (BDC) position. However, if an ignition switch of the vehicle is suddenly switched off by the rider, the movement of a piston in the internal combustion engine is suddenly disturbed. During such conditions, the vehicle tends to achieve a standstill position because combustion of the air-fuel mixture in the engine is abruptly suspended. In such a situation, it is desirable that piston shall rest at a BDC position. If the piston is resting at BDC position, relatively less torque is required to restart the engine through the ISG. Whereas, if the piston rests at a TDC position or in the between of TDC and BDC position, a higher torque would be required from the ISG to cause movement of the piston and consequent rotation of the crankshaft. Resultantly, a higher battery power would be necessitated. The present invention aims to avoid a scenario wherein a higher torque is required from the ISG to cause movement of the piston and the subsequent rotation of the crankshaft for re-starting of the vehicle through the ISG.

[00018] An objective of the present invention is to optimize the torque required for cranking the engine. In a known mechanism, the crankshaft is rotated reverse by a small magnitude at end of every engine off condition to optimize the torque required for cranking of the engine during for vehicle-restarting condition. In such a mechanism, the starter motor is designed in a manner that maximum torque delivered by the motor does not exceed sixty percent of the torque required to overcome a compression stroke. Generally, compression stroke is the stroke where very high torque is required to start the engine. In a situation where the vehicle is abruptly stopped in during the compression stroke, a high power is required to restart the vehicle in such condition. The torque required to restart the vehicle to overcome the compression stroke is significantly higher compared to the torque required in any other stroke. During abrupt stopping of the vehicle in compression stroke, the piston is usually vicinity to the TDC position.

[00019] In another known mechanism, the started motor performs the starting mechanism by controlling the valve movement to a low compression level in the compression stroke and adjusting the valve to a high compression level in an expansion stroke. This necessitates the use of one or more valve actuators which tend to make the assembly complex.

[00020] Therefore, the aim of the present invention is to eliminate high torque requirement and provide an efficient starting system for restarting of the engine without making the engine assembly complex.

[00021] Vicinity vicinity vicinity

[00022] The present subject matter is further described with reference to the accompanying figures. It should be noted that description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.

[00023] Figure 1 illustrates a block drawing of engine assembly 100, in accordance with an implementation of the present invention. The engine assembly 100 comprises an engine 102 and an engine drive system 103. The engine 102 comprises a cylinder head (not shown), a piston 102A and a crankshaft 102B. The crankshaft 102B and the piston 102A operate as per conventional known means. The crankshaft 102B is connected to the piston 102A through a connecting rod (not shown). The movement of the piston from a top dead center (TDC) position to a bottom dead center (BDC) position cause rotational movement of the crankshaft 102B. The engine drive system 103 comprises an integrated starter generator (ISG) 103A and an ISG controller 103B. The ISG controller 103B further comprises a memory unit and a processing unit. The ISG 103 A and the ISG controller 103B are connected to the crankshaft 102B. One or more sensors (not shown) send various input signals to the ISG controller 103B. The input signals include information about the position of the piston 102A, information about the switching on and off state of the engine 102, information about stroke of the engine 102. Further, the ISG 103 A is connected with the crankshaft as per conventionally known means for transfer of torque between the ISG 103 A and the engine 102. The ISG 103 A selectively functions as a starter or a generator or as a starter cum generator and supports the functioning of the crankshaft as per requirement.

[00024] Figure 2 illustrates a flow chart for normalizing position of the piston 102A by the ISG controller 103B, in accordance with an embodiment of the present invention. As per the illustrated embodiment, the method 200 for normalizing position of a piston by ISG controller 103B comprising following steps: At step 201, the ISG controller 103B is determining engine running condition. The engine running condition indicate the combustion in the engine or the speed at which a vehicle using the engine is running. At step 202, the ISG controller 103B is receiving a first signal indicating position of the piston 102Awith respect to the polar or angular orientation of the crankshaft 102B . The position of the piston 102 A is the position at which the piston 102A is rotating based on the combustion stroke of the engine 102. At step 203, the ISG controller is receiving a second signal indicating switching off state of the engine 102. The ISG controller 103B act as brain for the ISG 103 A, therefore the ISG controller 103B receives all the input signals and operates based on the data received from the input signals. At step 204, the ISG controller 103B estimates a position of the piston 102A for a first time instant when engine is turned off. The first time instant occurs after the engine is turned off. The position of the piston 102A is estimated by the ISG controller 103B based on the input signals received from the engine 102. At step 205, the ISG controller 103B is determining position of piston 102A and if position of piston 102A is in vicinity of a bottom dead center (BDC) as per a predetermined limit, the ISG controller 103B does not perform any action. Whereas, at Step 205, if the position of the piston 102A is in vicinity to a top dead center (TDC) i.e. within a predetermined limit, the ISG controller 103 A is configured to perform action as per step 206. At step 206, the ISG controller 103B is performing forward motoring based on estimated position of the piston 102A at the first time instant. As per the illustrated embodiment, the term first time instant implies, the time instant when the engine 102 is in a switched off state. At such time instant, the piston 102A would perform no further action unless the ISG controller 103B performs any action as per the illustrated flow-chart. Therefore, when the engine 102 is turned off or the engine 102 is not preforming any further stroke, at such time instant, the position of the piston 102A would be determined by the ISG controller 103B based on the input signal received from the one or more sensors. The forward motoring of the piston 102A by the ISG controller 103B assists in normalizing the position of the piston 102A to a desired position so that during restarting of the engine, the torque and the power requirement is minimized or optimal.

[00025] Figure 3 illustrates a flow chart for normalizing position of the piston 102A by the ISG controller 103B, in accordance with an embodiment of the present invention. As per the illustrated embodiment, the method for normalizing position of the piston 102A by the ISG controller 103Bcomprising following steps: At step 201, the ISG controller 103B is determining the engine 103 running condition. At step 202, the ISG controller 103B is receiving signal indicating position of the piston 102Awith respect to the polar or angular orientation of the crankshaft 102B. At step 202A, the ISG controller 103B is receiving signal indicating stroke of the engine 102. At step 202B, the ISG controller 103B is determining stroke of the engine 102 being either a compression stroke or expansion stroke. If the stroke of the engine 102 is a compression stroke, the ISG controller 103B proceeds as per step 203, else if the stroke is not a compression stroke then the ISG controller 103B stops to operate and allows a normal restarting of the engine 102 as per known means. At step 203, the ISG controller 103B is receiving signal from one or more sensors, indicating switching off state of engine 102. At step 204, the ISG controller 103B estimates position of the piston 102A at the first time instant when engine 102 is turned off. At step 205, the ISG controller 103B is determining position of the piston 102A and if position of piston is vicinity bottom dead center (BDC) as per a predetermined limit, the ISG controller 103B does not perform any action. Whereas, at Step 205, if the position of the piston 102A being vicinity top dead center (TDC) as per a predetermined limit, the ISG controller 103B is configured to perform action as per step 206. At step 206, the ISG controller 103B is performing forward motoring based on estimated position of the piston 102A at the first time instant. As per the illustrated embodiment, the term first time instant implies, the time instant when the engine 102 is in a switched off state. At such time instant, the piston 102A would perform no further action unless the ISG controller 103B performs any action as per the illustrated flow-chart. Therefore, when the engine 102 is turned off or engine is not performing any further stroke, , the position of the piston 102A at the first time instant would be estimated by the ISG controller 103B before the engine 102 is turned off based on the input signal received from the one or more sensors. The forward motoring ofthe piston 102A by the ISG 103A assists in normalizing the position of the piston 102A to a desired position so that during restarting of the engine, the torque and the power requirement is minimized.

[00026] As per an embodiment, the piston position is detected by magnetic signals from the crankshaft 102B or one or more sensors which determine the piston 102A position from the working conditions ofthe crankshaft 102B. [00027] Further, in an embodiment, the forward motoring by the ISG controller (103B) is performed before a predetermined time of turning off of the engine, wherein the predetermined of turning off of the engine, wherein the predetermined time being in range of 5 millisecond to 200 milliseconds.

[00028] The claimed steps as discussed herein are not routine, conventional, or well understood in the art, as the claimed steps enable the following solutions to the existing problems in conventional technologies. Prior to the present invention, a high torque and power was required to restart the engine 102 in such circumstances when the engine was abruptly turned off. Therefore, the present invention normalizes the piston 102A position to a desired position by forward motoring of the engine 102, based on determination of position of the piston 102A in an off state. This results in less torque and energy requirement during restarting of the engine. Also, the present invention utilizes the inertia of the piston when the engine is abruptly switched off. This further reduces the energy required for forward motoring by the ISG controller 103B. the Hence, the present invention optimizes the torque and energy requirement based on the engine conditions.

[00029] Although the subject matter has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. It is to be understood that the appended claims are not necessarily limited to the features described herein. Rather, the features are disclosed as embodiments of the present subject matter. LIST OF REFERENCE SIGNS

100: Engine Assembly

102: Engine

102A: Piston 102B: Crankshaft

103: Engine Drive System

103 A: Integrated Starter Generator

(ISG)

103B: ISG Controller

Claims

I/We claim:

1. A method for normalizing position of a piston ( 102A) of an engine assembly (100), the method comprising steps of: receiving (step 202), by an ISG controller (103B) a first signal indicating a position of a piston (102A); receiving (step 203), by the ISG controller (103B), a second signal indicating switching off state of the engine (102); estimating (step 204), by the ISG controller (103B), a position of the piston (102A) the estimation being about a first time instant, said first time instant occurs after the engine (102) being turned off; performing (step 206), by the ISG controller (103B), a forward motoring of the engine (102) based on the estimated position of piston (102A) for the first time instant.

2. The method as claimed in claim 1, comprising step of determining, by the ISG controller (103B), an engine (102) running conditions before receiving the first signal indicating a position of the piston (102A).

3. The method as claimed in claim 1, comprising step of determining position of the piston (102A) by the ISG controller (103B) and if the position of the piston (102A) is in vicinity of a top dead center (TDC), the ISG controller (103B) is performing a forward motoring of the engine (102).

4. The method as claimed in claim 1, comprising step of determining, by the

ISG controller (103B), atype of stroke of the engine (102) when the engine (102) is in a running condition; The method as claimed in claim 4, wherein the forward motoring being performed before the first time instant based on the estimated position of piston (102A) at first time instant (206) and the determined type of stroke. The method as claimed in claim 1 , wherein the forward motoring being assisted by an inertia force of the piston (102A). The method as claimed in claim 1 , wherein the first signal being based on one or more of a magnetic flux from the engine (102). The method as claimed in claim 1 , wherein the first signal being based on inputs received from one or more sensors on a crankcase. The method as claimed in claim 1, wherein the forward motoring by the ISG controller (103B) is performed before a predetermined time of turning off of the engine, wherein the predetermined time being in range of 5 millisecond to 200 milliseconds. The method as claimed in claim 4, wherein the forward motoring is performed based on the estimated position of the piston (102A) and the stroke type, wherein the stroke of the engine corresponds to a compression stroke. An engine assembly (100) comprising: an engine (102), the engine (102) comprising: a cylinder head, the cylinder head including a piston (102A); a crankshaft (102B); an engine drive system (103), the engine drive system (103) comprising: an integrated starter generator (ISG) (103A); an ISG controller (103B), the ISG controller (103) being communicatively coupled with the engine (102) and the ISG (103A), the ISG controller (103B) being configured for : receiving a plurality of input signals from the engine (102), the input signal from the engine (102) indicating one of aposition of the piston (102A) and a switching off state of the engine (102), determining one of the position of the piston ( 102A), and if the position of the piston being vicinity a top dead center (TDC), performing a forward motoring of the piston (102A) for achieving a desired position of the piston (102A). The engine (100) as claimed in claim 11, wherein the ISG controller (103B) is configured to receive an input from the engine (102) indicating a type of stroke of the engine (102). The engine (100) as claimed in claim 12, wherein the ISG controller (103B) is configured to perform forward motoring if the stroke of the engine (102) is a compression stroke. The engine (100) as claimed in claim 11, wherein the forward motoring of the piston (102A) being assisted by inertia force of the piston (102A). The engine (100) as claimed in claim 11, wherein one of the plurality of signals being s based on magnetic flux from the engine (102). The engine (100) as claimed in claim 11, wherein one of the plurality signals received by the ISG controller (103B) indicating the position of the piston (102A) being based on one or more sensors on the crankshaft (102B).