WO2021191920A1

WO2021191920A1 - A power unit and an intake member thereof

Info

Publication number: WO2021191920A1
Application number: PCT/IN2021/050258
Authority: WO
Inventors: Adiga Vijaya Bhaskar; Johnson Vethanayagam Jayajothi; Aswin SRIDHARAN; Mani Boobalan
Original assignee: Tvs Motor Company Limited
Priority date: 2020-03-26
Filing date: 2021-03-14
Publication date: 2021-09-30
Also published as: CN115298431A; EP4127446A1; BR112022019362A2

Abstract

The present subject matter relates a power unit (200) comprising a cylinder-block (220), and a cylinder-head (225). The cylinder-head (225) is mounted to the cylinder-block (220). The cylinder-block (220) and the cylinder-head (225) defining a combustion chamber (230) for combustion of air-fuel mixture. An intake member (300) is connecting a flow regulator (270) to the cylinder-head (220). The intake member (300) comprises an upstream portion (316) and a downstream portion (317). The upstream portion (316) of the intake member comprises a flow enhancing portion (325) extending radially inward thereat. The present subject matter improves tumble flow without affecting the existing construction of the cylinder-head. The tumble flow improves the mixing of air-fuel mixture thereby improving combustion and reduces emissions.

Description

A POWER UNIT AND AN INTAKE MEMBER THEREOF

TECHNICAL FIELD

[0001] The present invention relates to a power unit like an internal combustion engine, and more particularly to an intake member for the power unit.

BACKGROUND [0002] Conventionally, power units like the internal combustion (IC) engines convert chemical energy into mechanical energy. The IC engines comprise of one or more combustion chambers and air-fuel mixture is sent into the combustion chamber through an intake system. The intake system includes an air cleaner that is used for filtering impurities from atmospheric air before the air is supplied to the power unit. A regulator member like a carburettor or a throttle body is used for regulating flow of air into the power unit. After combustion of the air-fuel mixture, an exhaust system is provided for scavenging exhaust gases created from combustion of air-fuel mixture.

BRIEF DESCRIPTION OF THE DRAWINGS [0003] The detailed description of the present subject matter is described with reference to an embodiment of a two wheeled saddle type motorcycle along with the accompanying figures. Similar reference signs are used throughout the figures to reference like features and components.

[0004] Fig. 1 illustrates a left-side view of an exemplary motor vehicle, in accordance with an embodiment of the present subject matter.

[0005] Fig. 2 illustrates a schematic sectional view of a power unit, in accordance with an embodiment of the present subject matter.

[0006] Fig. 3 depicts a schematic view of a frame assembly and selected components thereon, in accordance with an embodiment of the present subject matter.

[0007] Fig. 4 illustrates an isometric view of an intake member, in accordance with an embodiment of the present subject matter.

[0008] Fig. 5 depicts a schematic sectional view of a portion of an intake path, in accordance with an embodiment of the present subject matter. [0009] Fig. 6 (a) depicts a sectional view of the intake member (section axis shown in Fig. 4), in accordance with an embodiment of the present subject matter.

[00010] Fig. 6 (b) depicts another view of the sectional view of the intake member, in accordance with an embodiment of the present subject matter.

[00011] Fig. 7 (a) depicts a schematic top-view of a portion of the power unit, in accordance with an embodiment of the present subject matter.

[00012] Fig. 7 (b) depicts a schematic cross-sectional view of the power unit, with reference to Fig. 7 (a), in accordance with an embodiment of the present subject matter.

[00013] Fig. 8 depicts a schematic sectional view of an intake passage, in accordance with an embodiment of the present subject matter.

[00014] Fig. 9 depicts a schematic top view of an air cleaner assembly, in accordance with an embodiment of the present subject matter.

[00015] Fig. 10 illustrates a graphical representation of tumble number plotted against valve lift, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION

[00016] Conventionally, a power unit, like a four-cycle engine, is provided with air-fuel mixture, which is drawn into a combustion chamber during an intake stroke. The air-fuel mixture drawn into the combustion chamber undergoes compression during compression stroke. One or more spark plugs are provided in certain type of power units for generating spark. At a pre-determined time during the compression stroke, the spark is generated by the one or more spark plugs to enable combustion. In certain other type of power units, a compression process itself causes combustion of the-fuel mixture without the need for additional spark plugs. Generally, a complete combustion of the fuel is preferred for maximum efficiency of the power unit as the amount of the fuel combusted gets translated into power/ torque, which becomes mechanical output of the power unit. Exhaust gases are generated during the combustion process. However, improper combustion of fuel would result in generation of harmful gases like carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter like soot. The harmful gases are formed and emitted due to incomplete combustion of fuel, due to insufficient or excessive combustion temperatures, due to poor mixing of air and fuel, or due to similar factors. These harmful gases are scavenged by the exhaust system into atmosphere.

[00017] Out of aforementioned factors, mixing of the air-fuel mixture plays a critical role in effective and efficient combustion as properly mixed air-fuel mixture can be completely combusted or burnt, subject to precise control of certain parameters like spark time, flame propagation etc. Generally, the air-fuel mixture is supplied to the power unit with a turbulent flow. A swirling motion or a tumbling motion or both is created to the mixture in order to create a desired turbulence. The turbulence improves mixture of the air and fuel and improves flame propagation about the mixture thereby leading to effective combustion. Typically, the power unit has to be modified to obtain desired turbulent motion. Modifying an intake port of a cylinder-head or intake manifold is one such solution known in the art. For example, two or more partitions may be created in an intake passage in order to create a turbulent flow. Some other solutions suggest modification of intake port itself, which may result in complex intake port modification or resulting in a new larger cylinder-head. The aforementioned and other solutions in the art can be adapted in power units that are of higher capacity, say of about lOOOcc or more, which have larger area, in order to perform such modification in the cylinder-head (intake port) or in the intake manifold. However, such solutions cannot be implemented in power units that have a small capacity due to which there exists a challenge of space and compactness as the power unit has to be accommodated in the compact layout of a motor vehicle. One more challenge is to manufacture small engine parts that require high precision, especially parts like intake port of the cylinder-head, in order to obtain desired turbulent flow. Additionally, maintaining dimensional consistency with time in such parts that are subjected to high temperatures is also a major challenge, as even minor variation or deterioration in the dimensions would affect the flow characteristics thereby resulting in poor combustion.

[00018] Generally, in known art for IC engines with small capacity, in order to address the problem related improper combustion, resort to solutions like provision of secondary air injection, exhaust gas re-circulation, or provision of catalytic converter. However, the aforementioned and other solutions in the art are expensive, especially when it demands incorporating above aggregate systems in small capacity engines that have a compact layout. Moreover, incorporation of the aforementioned solutions may necessitate vehicle level modification thereby affecting the existing layout of the vehicle making it an expensive and complex design process.

[00019] Thus, there is a need for an improved & compact power unit that is capable of addressing the aforementioned and other drawbacks in the art. The power unit should be capable of providing improved flow even in small capacity engines. [00020] The power unit as per the present invention comprises a cylinder-block, a cylinder-head, and the cylinder-head mounted to the cylinder-block. The cylinder- block and the cylinder-head define a combustion chamber. An intake member is provided to connect a flow regulator to the cylinder-head for provision of air-fuel mixture. The intake member comprises an upstream portion and a downstream portion and the intake member is configured to have a flow enhancing portion extending radially inward at the upstream portion. A downstream portion of the intake member is connected to the cylinder head.

[00021] The flow enhancing portion of the intake member increases the tumble flow of the air entering the combustion chamber thereby improving charge movement in combustion chamber and improving overall combustion efficiency. Further, the flow enhancing portion is provided at a distal portion from the cylinder head and immediately after the regulating member thereby maintaining sufficient gap between the flow enhancing portion and the combustion chamber to create the tumble flow enhancement/ increase.

[00022] In one embodiment, the flow enhancing portion of the intake member is extending in a radial inward direction with a smooth transition forming a peak point at which the cross-section is minimal. Subsequent to the peak point, the flow enhancing portion recedes in the radial direction (outward). The smooth transition of the flow enhancing portion enables in improving tumble flow with improved mixing thereby resulting in efficient combustion. The efficient combustion of fuel reduces the exhaust emissions. Further, the efficient combustion of fuel improves the torque and power characteristics of the power unit.

[00023] In one embodiment, the intake member comprises a first connection end and a second connection end. The second connection end is connected to the regulating member and the flow enhancing portion is disposed in proximity to the second connection end. Thus, the air flow exiting the regulator member is immediately enhanced to create improved tumble flow, which starts from the upstream portion of the intake member itself.

[00024] In one embodiment, the flow enhancing portion is disposed about a pre determined angular region extending about a first angle. For example, the angular region may extend for about 30 degrees and may be provided for entire 360 degrees. The dedicated intake member is easy to manufacture when compared to modification of complex cylinder-head. Additionally, the intake flow member can be modified to adhere to various driving requirements without modifying the complex cylinder-head that accommodates the camshaft, plurality of valves etc. [00025] In one embodiment, the flow enhancing portion of the intake member comprises a pre-peak portion and a post-peak portion configured at an upstream and a downstream of a peak point, respectively, thereof. The post-peak portion extends in a direction along a central line to flush with an inner periphery of the downstream portion of the intake member. Even subsequent to the peak-portion of the flow enhancing portion, the smooth transition to flush with inner periphery of the intake member helps in retaining the flow rate with improved tumble flow. Further, the smooth receding of peak-portion or smooth increase in diameter creates a necessary direction change for the flow.

[00026] In one embodiment, the pre-peak portion is provided with an inclination to match an inclination angle of a fuel injector assembly. The intake member that supports the fuel injector assembly enables in maintaining angle of inclination of pre-peak portion and the injector angle thereby avoiding variations due to avoiding mounting on separate parts of the engine assembly. In one embodiment, the flow enhancing portion is having a first diameter at a peak-portion, and a second diameter and a third diameter at a pre-peak portion and a post-peak portion, respectively. The third diameter is smaller than the second diameter, where the third diameter creates the required pre-peak inclination.

[00027] In one embodiment, the first diameter is smaller than the third diameter, where subsequent to the peak point, the air flow experiences a change cross-section with improved tumble flow. Further, the injector axis and the pre-peak axis disposed at a substantial acute angle enables in matching orientation of flow thereby improving the mixing of air and injected fuel.

[00028] In one embodiment, the pre-peak portion and the post-peak portion are disposed substantially within the upstream portion of the intake member. Thus, the effect of engine heat that may cause variations in the flow enhancing portion is kept minimal thereby enabling tumble improvement even upon prolonged usage of the power unit. The pre-peak portion is configured to be in flush with a diameter of the regulating member thereby not causing any disturbances during flow of air from the regulating member to the intake member.

[00029] In one embodiment, the intake member comprises a central line which is at a second angle with respect to a cylinder axis of the power unit. The second angle is in the range of 45 to 135 degrees enabling air flow in a downward direction in to the combustion chamber.

[00030] In one embodiment, the downstream portion of the intake member is disposed to be flush with an intake port and the intake member. The flow enhancing portion and the intake port collectively form an elongated S-profile along at an angular region thereof to create the improved tumble flow. The flow enhancing portion of the intake member creates one curved portion of the elongates S-shaped profile and the downstream portion along with the intake port forms substantially other half of the elongated S-profile thereby cumulatively providing an enhanced tumble flow.

[00031] In one embodiment, the intake member comprises a peak point and a tangential line taken at the peak point cuts through a central line of the intake member at a first point. The first point being within boundary of the intake member. Thus, the effect of the flow enhancing portion with the peak point starts occurring within the intake member even before entering the intake port. [00032] Where arrows are provided in figures, they depicts direction with respect to a motor vehicle, wherein an arrow F denotes front direction, an arrow R indicates rearward direction, an arrow Uw denotes upward direction, an arrow Dw denoted downward direction, an arrow RH denotes right side, an arrow LH denotes left side, as and where applicable.

[00033] Fig. 1 illustrates a left-side schematic view of an exemplary motor vehicle 100, in accordance with an embodiment of the present subject matter. The motor vehicle (hereinafter ‘vehicle’) 100 includes a schematically shown frame assembly 105 that acts a skeleton and a structural member of the vehicle 100. A power unit comprising a power unit 200 is fixedly supported by the frame assembly 105, in the present embodiment. The power unit 200 acts as a power unit of the motor vehicle 100 and hence, the terms are interchangeably used herein; The power unit 200 may also include a traction/electrical motor (not shown) to act independently or to assist the engine assembly. The power unit 200 includes a crankcase 210 for supporting various components thereof and the power unit 200 is secured to the frame assembly 105 through the crankcase 211. The power unit 200 is discussed in detail in the description for Fig. 2.

[00034] Further, the motor vehicle 100 includes a rear wheel 130 that is functionally coupled to the power unit 200 through a transmission system 134. A pair of front forks 132 supports a front wheel 133 and is steerably supported by a head pipe (not shown) of the frame assembly 105. A handlebar assembly 135 is connected to the pair of front forks 132 for maneuvering the motor vehicle 100.

[00035] The motor vehicle 100 of the present embodiment includes a seat assembly 145 that is disposed rearward to a fuel tank 140. The seat assembly 140 and the fuel tank 145 are supported by the frame assembly 105. A rear cover assembly 150 is disposed below the seat assembly 145 and the rear cover assembly 150 extends towards a rear portion of the motor vehicle 100. The vehicle 100 includes an air induction system (not show) and an exhaust system (not shown) connected to the power unit 200 for supply of air and for scavenging of exhaust gases respectively. [00036] Fig. 2 illustrates a schematic sectional view of an engine assembly, in accordance with an embodiment of the present subject matter. The power unit 200 comprises a cylinder-block 220 mounted to the crankcase 210. A piston 215 is slidably disposed in the cylinder-block 220 and a cylinder-head 225 is mounted to the cylinder-block 220. The cylinder-block 220 and the cylinder-head 225 define a combustion chamber 230. The combustion chamber 230 comprises a cylinder axis C-C’, along which the piston 215 slides. A connecting rod 235 connects the piston 215 to a crankshaft 240, which is rotatably supported on the crankcase 210. The cylinder-head 225 comprises an intake port 245, an exhaust port 250, and plurality of valves 255. The intake port 245 is connected to an air induction system 260 through an intake member 300 (shown in Fig. 3) and the exhaust port 250 gets connected to an exhaust system (not shown) for scavenging of burnt exhaust gases. Further, the power unit 200 comprises of a starting system 265 mounted to the crankcase 210 and may have a gear box, a kick-starter assembly, a clutch assembly etc. (not shown).

[00037] The cylinder-head 225 comprises a camshaft 251 which consists of at least one inlet cam lobe and at least one outlet cam lobe (not shown) for actuating rocker arms that in turn open and close the valves 255. A cam-chain (not shown) operably connects the crankshaft 240 and camshaft 251 thereby driving the camshaft 251. In one embodiment, the power unit 200 operates in four-cycles namely, intake stroke, compression stroke, power, and exhaust stroke. Combustion of air-fuel mixture occurs at end of the compression stroke and at beginning of the power stroke. The air-fuel mixture is supplied through the intake member 300 that is in turn coupled to an air induction system 260 (shown in Fig. 3).

[00038] Fig. 3 depicts a schematic view of a frame assembly and selected components thereon, in accordance with an embodiment of the present subject matter. The frame assembly 105 comprises of a head tube (not shown) and a main tube 106 extending rearwardly downward from the head tube. One or more rear tubes 107 that have a front portion connected to the main tube 106 and the rear tubes 107 extend in a direction rearward of the vehicle 100. One or more ancillary tubes 108 connect the rear tubes 107 to the main tube 106. In one embodiment, the main tube 106 comprises a rearward portion 106A and a downward portion 106B. The rearward portion 106A extends rearward from the head tube and the downward portion 106B extends downward from the rearward portion 106A. The main tube 106 supports the power unit 200 and at least partially surrounds the power unit 200, in the depicted embodiment.

[00039] An induction system 260 is mounted to the frame assembly 105. Hereinafter, the terms ‘air induction system’ and ‘air cleaner assembly’ are interchangeably used. The air cleaner assembly 260 comprises an inlet 261 and an outlet 262. In one embodiment, the air cleaner assembly 260 comprises an ancillary chamber 263, which is either detachably attached or integrally formed. The outlet 262 of the air cleaner assembly 260 is connected to a regulating member 270, which is in turn connected to the intake member 300. Air from the atmosphere enters the air cleaner assembly 260, where it gets filtered. The filtered air reaches the outlet 262 and passes through the regulating member 270 and then to the intake member 300. The intake member 300 is connected to the intake port 245 of the power unit 200 (shown in Fig. 2). The intake member 300 comprises a second connection end 310 for securing the intake member 300 to the intake port 245. The intake member 300, of the present invention, is configured to improve the turbulent flow and improve mixing of air-fuel that enters the combustion chamber 230. The regulating member 270 comprises a valve control 272, which gets connected to an accelerator (not shown) either directly or through an electrical system. In the current embodiment, a position sensor 274 (shown in Fig 5) is provided on the regulating member 270 supports. The position sensor 274 is also connected to valve control 272 and a valve member 271 (shown in Fig. 5) to identify the position of the valve control 272 and communicate the same to a control unit for regulating fuel injection etc. In one embodiment, the fuel injector assembly is connected to a fuel pump (not shown) which may be used to pump fuel form the fuel tank 140 (shown in Fig. 1) to the fuel injector assembly 275. In another embodiment, the regulating member can be a carburettor for regulating air and for supply of fuel. In yet another embodiment, the regulating member can be an electronic carburettor or a choke member.

[00040] Fig. 4 depicts a perspective view of an intake member, in accordance with an embodiment of the present subject matter. Fig. 5 depicts a schematic sectional view of a portion of an intake path (axis shown in Fig. 3), in accordance with an embodiment of the present subject matter. The outlet 262 of the air cleaner assembly 260 (show in Fig. 3) is connected to the regulating member 270. The regulating member 270 comprises a valve member 271, which is connected to the valve control 272. Rotation of the valve control 272 rotates the valve member 271, which is pivotably disposed, to rotate thereby causing opening/ closing for regulating flow of air. A minimum air flow is always allowed for idling of the power unit 200. The regulating member 270 is connected to the intake member 300 through a first connection end 305 thereof. From the regulating member 270, the air flow reaches the intake member 300. The intake member 300 comprises a hollow region with an inner peripheral region 320 for air flow. Further, in one embodiment, the intake member 300 supports the fuel injector assembly 275 (shown in Fig. 7 (b)) and a mounting portion 303 (shown in Fig 7 (a)) is provided thereon for supporting the fuel injector assembly. The intake member 300 is divided into an upstream portion 316 and a downstream portion 317, in accordance with one embodiment. An imaginary central portion 315 separates the upstream portion 316 and the downstream portion 317. In the depicted embodiment, the imaginary central portion 315 is a plane (shown in dotted line). The imaginary central portion

315 can be a three-dimensional region with the upstream portion 316 and the downstream portion 317 disposed on either side of the three-dimensional region. [00041] The intake member 300 comprises a flow enhancing portion 325 extending radially inward of the inner peripheral region 320 and the flow enhancing portion 325 is disposed on the upstream portion 316. The flow enhancing portion 325 is disposed at a distal portion from the second connection end 310 that gets connected to the cylinder-head 225 (shown in Fig. 2) and in proximity to the first connection end 305. Thus, the air flow exiting the regulator member 270 is immediately enhanced to create improved tumble flow, which starts from the upstream portion

316 of the intake member 300 itself. In one embodiment, the flow enhancing portion 325 extends about entire angular region (depicted in Fig. 6 (b)). In the depicted embodiment, the flow enhancing portion 325, extending radially inward, is disposed about a pre-determined angular region having a first angle a (shown in Fig. 6 (b)). Further, a central line A-A’ passing about a central axis of the outlet 262, the regulating member 270, and the intake member 300 is shown. In one embodiment, the central line A-A’ is substantially straight to provide undisturbed flow of air into the power unit 200. In another embodiment, the central line A-A’ has a curved profde forming a smooth curve formed for smooth air flow without hindering the flow of air. Thus, the intake member 300 can be modified to adhere to various driving requirements without modifying the complex cylinder-head 225 that accommodates the camshaft, plurality of valves etc.

[00042] The flow enhancing portion 325 of the intake member 300 is extending in the radial inward direction (of the intake member 300) with a smooth transition to a peak point 330 (shown in Fig 7 (b)), forming the peak point at which the cross- section is minimal. Subsequent to the peak point 330, the flow enhancing portion 325 recedes or constricts in the radial direction (outward). The smooth transition of the flow enhancing portion 325 enables in improving tumble flow with improved mixing thereby resulting in efficient combustion.

[00043] The air flow AF that reaches upstream portion 316 of the intake member 300 passes by the flow enhancing portion 325, whereby a tumble flow gets increased due to a gradual reduction in cross-sectional area. The flow enhancing portion 325 forms a radially gradually inward extending to form a smooth profile with a peak point 330 (shown in Fig. 7 (b)) and subsequently extends gradually inward in a radial outward direction thereafter forming a flush continuity interface with rest of inner periphery 320 of the downstream portion 317. In other words, the flow enhancing portion 325 in the intake member 300 forms a gradual reduction in inner cross-sectional area of the intake member whereby the tumble flow is increased subsequent to the flow enhancing portion 325. The air flow AF passing through the intake member 300 experiences an improvement, like increase in tumble flow, and reaches the intake port 245 (shown in Fig. 2) of the power unit 200 thereby forming an improved turbulent flow AF’ due to increased tumble flow. By the time the air flow AF reaches the combustion chamber 230, the turbulent flow AF’ is created with improved swirl and tumble effect in the combustion chamber 230 thereby causing effective air-fuel mixture charge leading to complete & efficient or close to complete combustion. Moreover, the flow enhancing portion 325 disposed immediately after the regulating member 270 acts on the air flow AF path even before the air flow AF reaches the intake port 245.

[00044] Fig. 6 (a) depicts a schematic sectional view of the intake member (section axis shown in Fig. 4), in accordance with an embodiment of the present subject matter. Fig. 6 (b) depicts another schematic sectional view of the intake member, in accordance with an embodiment of the present subject matter. The intake member 300 comprises a mounting aperture 310M for securing the second connection end 310 to the cylinder-head 225. In the depicted embodiment, the inner periphery 320 of the intake member 300 is having a peripheral cross-section PC (also shown in dotted line) that is varying about at least a length of the intake member 300. Especially, the flow enhancing portion 325 extending radially inward causes a change in cross-section of the inner periphery 320, which has a non circular cross-section thereat (where the inner periphery has a circular cross-section at a portion away from the flow enhancing portion 325). However, the ‘circular cross-section’ of the present embodiment is not limiting and the inner periphery may have any preferred geometric profile. A first diameter D1 (inner diameter) of the intake member 300 taken at the flow enhancing portion 325 is substantially smaller than a second diameter D2 or a third diameter D3 (shown in Fig. 7 (b)) taken at a portion away from the flow enhancing portion 325. Thus, the peripheral cross-section PC when axially approaching the flow enhancing region 325 changes into oval profile, in one implementation, and when moving away from the flow enhancing region 325, in axial direction, the peripheral cross-section changes into a circular profile, as per an embodiment. In simple words, the peripheral cross- section of the inner periphery 320 of the intake member 300 at the flow enhancing portion 325 is substantially different from a profile taken at a portion away the flow enhancing region 325. Fig. 6 (b) depicts the angular region denoted by the first angle a about which the flow enhancing region is configured, in accordance with the present embodiment. The flow enhancing region 325 can be configured to extend about entire angular region of the intake member where the first angle can extend till 360 degrees with a minimum angle of about 30 degrees in order to effect a change in cross-sectional area that would cause increase in tumble flow.

[00045] Fig. 7 (a) depicts a schematic top-view of a portion of the engine assembly, in accordance with an embodiment of the present subject matter. Fig. 7 (b) depicts a schematic cross-sectional view of the engine assembly, with reference to Fig. 7 (a), in accordance with an embodiment of the present subject matter. In the depicted embodiment, a cylinder-head 225 and a cylinder-head cover 226 are secured to the cylinder-head 225. The cylinder-head 225 houses the intake port 245, the exhaust port, the plurality of valves 255 (corresponding to the intake port 245 and the exhaust port), the cam shaft 251, and other ancillary components. Further, the cylinder-head 225 supports one or more spark plugs 256 (shown in Fig 7 (a)). The present subject with improved air-fuel mixture enables even use of a single spark plug 256 for generation of spark for combustion. In the depicted embodiment, the intake member 300 along with the fuel injector assembly 275 is connected to the cylinder-head 225.

[00046] As discussed, the flow enhancing region 325 is configured to have a first diameter D1 and the first diameter D1 is minimum at a peak point (330). Further the intake member 300 comprises a pre-peak portion 331 and a post-peak portion 332 at upstream and downstream to the peak point 330, respectively. The pre-peak portion 331 is having a second diameter D2 and the post-peak portion 332 is having a third diameter D3. The second diameter D2 and the third diameter D3 are larger than the first diameter Dl, as the first diameter D1 is taken at the peak point 330. In one embodiment, the pre-peak portion 331 and the post-peak portion 332 are disposed substantially within said upstream portion of said intake member 300 thereby keeping the flow enhancing portion 325 substantially away from the cylinder-head 225 thereby reducing any dimensional variations. The post-peak portion 332 extends in a direction along a central line to flush with an inner periphery 320 of the downstream portion 317 of the intake member 300.

[00047] Subsequent to peak point 330, a smooth variation is configured in diameter of the profile of the inner periphery 320 or smooth increase in diameter when moving in a downstream direction of the peak point 330 about the intake member. The flow enhancing portion 325 with the peak point 330 causes a flow change by increasing the tumble flow and the air flow AF. Subsequently, the intake member experiences at least a minor directional change due to increase in diameter D3 at the post-peak portion 332. In other words, certain portion of the air flow AF, subsequent to the peak point 330, takes a smooth deviation away from the central line A-A’ and thereafter the air flow AF experiences a converging flow into the intake port 245. The pre-peak portion 332 is disposed to flush with a diameter of the regulating member 270. Thus, in one embodiment, the intake member 300 is configured to create a desired turbulent flow by first causing increase in flow, then causing change in direction (away from the central line A-A’) and then towards the central line A-A’ causing a turbulent flow. Further, the air flow AF’ entering the combustion chamber 230 with the aforementioned change in direction enters the combustion chamber 230 with turbulence causing effective mixture of air and fuel. In one embodiment, an elongated S-profile ES is configured in the pre peak point (331) for the air to flow thereby creating desired tumble and swirl due to the elongated S-profile ES (shown in Fig 8) that improves tumble flow and the directional change. Moreover, the elongated S-profile ES forms a smooth flow profile for air flow AF entering the intake member 300 and the air flow AF’ exiting the intake member 300. The intake member 300 with the flow enhancing portion 325 is configured to provide smooth transition from a diameter of the regulating member 270 and to a diameter of the intake port 245.

[00048] The intake member 300 supports the fuel injector assembly and the fuel injector assembly is oriented at a pre-determined angle depending on various parameters that include intake port orientation, distance of fuel injector assembly from the intake port etc. In one embodiment, the fuel injector assembly is mounted to the cylinder-head of the engine assembly.

[00049] Fig. 8 depicts a schematic sectional view of a portion of the intake passage, in accordance with an embodiment of the present subject matter. The flow enhancing portion 325 comprises a peak point 330, and in one embodiment, a tangential line T1 taken at the peak point 330 cuts through a central line A-A’ of the intake member 300 at a first point P 1. The fuel injector assembly 275 is disposed a pre-determined angle with respect to the central line A-A\ An injector axis I-G cuts the central line A-A’ at a second point P2. The injector axis I-G is disposed at a higher angle with reference to the angle formed by tangential line T1 with the central line A-A’. The tangential line T1 cutting the central line A-A’ is disposed at a point upstream of the second point P2 causing the air flow AF to be kept towards the central line A-A’ with minor disturbances from the walls of the intake member 300 and the intake port 245. Further, the fuel injector assembly 275 with larger angle with reference to the central line A-A’ is provided to inject fuel into the intake port 245 with a cumulative mixing of fuel with the air flow that is reaching the intake port 245 thereby creating effective mixture before combustion. The intake member 300 that supports the fuel injector assembly 275 enables in maintaining angle of inclination of pre-peak portion 331 and the injector angle I-G thereby avoiding variations that may occur due to mounting on separate parts of the engine assembly. In one embodiment, the injector axis I-G and a pre-peak axis P- P’ (considered by taking a tangent) are disposed at substantially same angles enabling in matching orientation of flow thereby improving the mixing of air and injected fuel. Further, the central line A-A’ is disposed at a second angle b with respect to a cylinder axis C-C’ of the power unit 200. The air flow AF from the intake member 300 flows in a downstream direction to the combustion chamber 230. Thus, in case of a substantially vertically disposed power unit 200, the air flow AF is directed in a gravity direction in addition to the effect provided by the intake member 300 thereby improving tumble flow promoting mixture air and fuel. [00050] Fig. 9 depicts a top view of an air induction system, in accordance with an embodiment of the present subject matter. The air induction system is mounted to a frame assembly 105 (as shown in Fig. 3) that comprises a main frame 106 extending rearward and then downward from a head tube (not shown). The air induction system 460 comprises a body portion 460B that incorporates a filter assembly for filtering the atmospheric air that enters an air inlet 461 to a pre-filter portion (not shown), and filtered air is sent to post-filter portion (not shown), which is connected to an outlet 462. The body portion 460B is at least partially disposed rearward to the main tube 106, when viewed from a top direction. In one embodiment, the body portion 460B is provided with an ancillary chamber 463. The ancillary chamber 463 acts as an additional volume to enable ease of breathing for the power unit 200 even at higher speeds of operation. Further, the ancillary chamber 463 is a triangular region TR, when viewed from a top-direction thereof. The triangular region TR comprises three sides AB, BC, and CA. The side A is disposed at third angle g with respect to a lateral axis RH-LH. The intake passage formed by the outlet 462, a regulating member 470 and the intake member 301 are disposed along a central line A1-AG and the central line A1-AG cuts substantially perpendicularly through the side AB of the triangular region TR. The ancillary chamber 463 comprises a face portion 463F which is disposed at a pre-determined angle, which is third angle g, with respect to a lateral axis RH-LH. The ancillary chamber 463 with the face 463F disposed at the third angle g enables the central line A1-AG to be straight without any curvature thereby improving flow. The ancillary chamber 463 provides as additional volume that is required for supplying air to systems like secondary air injection (SAI) without affecting volume required for the power unit 200. Further, the outlet 462, a regulating member 470 (connected to the outlet 462), and an intake member 301 (connected to a downstream portion of the regulating member 470) comprise a central line A1-AG. In the depicted embodiment, the central line Al-A’ is a substantially straight line whereby it provides a straight flow with minimal disturbances. A fuel injector assembly 275 is mounted to the intake member 301. The regulating member 470 comprises a valve member (not shown) and the valve member is connected to a valve control 472, which is disposed towards one lateral side on the regulating member 470. A position sensor 474 is disposed on other lateral side of the regulating member 470 and the position sensor 474.

[00051] Fig. 10 illustrates a graphical representation of tumble number plotted against valve lift, in accordance with an embodiment of the present subject matter. Line B illustrates a tumble number at various valve lift points taken in millimetres for a conventional system. Line A illustrates a tumble number at similar valve lift in accordance with the present subject matter. The tumble number represents a characteristic of a tumble flow of air. As can be seen, during a smaller valve lift, the tumble number has a minor improvement, which is still significant. Further, with an increase in valve lift, the tumble number in accordance with present invention experiences substantial improvement. Thus, the present subject matter provides an improved tumble flow especially during complete lift of valves as required during end of intake stroke. Thus, the tumble number which represents one of the characteristics of the turbulence is improved thereby improving over turbulence. Thus, the turbulent flow improves the overall mixing of air and fuel. [00052] It is to be understood that the aspects of the embodiments are not necessarily limited to the features described herein. Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.

List of reference numerals:

100 motor vehicle 261/461 inlet

106 main frame 262/462 outlet

106A rearward portion 263/463 ancillary chamber 106B downward portion 35 air cleaner assembly

107 reartube(s) 463F face portion

108 ancillary tube (s) 265 starter system

130 rear wheel 270/470 regulating member

132 front forks 271 valve member 133 front wheel 40 272/472 valve control

134 transmission system 274/474 position sensor

135 handlebar assembly 275 fuel injector assembly

140 fuel tank 300/ 301 intake member

145 seat assembly 302 fastening portion 150 rear cover assembly 45 303 mounting portion

200 engine assembly 305 first connection end

210 crankcase 310 second connection end

220 cylinder-block 310M mounting aperture

225 cylinder-head 315 imaginary central portion 226 cylinder-head cover 50 316 upstream portion

230 combustion chamber 317 downstream portion 235 connecting rod 320 inner peripheral region

240 crankshaft 325 flow enhancing portion

245 intake port 330 peak point 250 exhaust port 55 331 pre-peak portion

251 cam shaft 332 post-peak portion

255 valves A-A7 A1-AG central line

256 spark plug AF/ AF’ Air flow

260/460 induction system/ D 1 first diameter air cleaner assembly 60 D2 second diameter

460B body portion D3 third diameter ES elongated S-profile TR triangular region

I-G injector axis PI/ P2 point

PC peripheral cross-section a first angle

P-P’ pre-peak axis b second angle T1 tangential line 10 g third angle

Claims

We Claim:

1. A power unit (200) comprising: a cylinder-block (220); a cylinder-head (225), said cylinder-head (225) mounted to said cylinder-block (220), said cylinder-block (220) and said cylinder-head (225) defining a combustion chamber (230); and an intake member (300), said intake member (300) connecting a flow regulator (270) to said cylinder-head (220), said intake member (300) comprises an upstream portion (316) and a downstream portion (317), and said upstream portion (316) comprises a flow enhancing portion (325) extending radially inward thereat.

2. The power unit (200) as claimed in claim 1, wherein said flow enhancing portion (325) extending in said radial direction with a smooth transition forming a peak point (330), and subsequent to said peak point (330) the flow enhancing portion (325) recedes in said radial direction.

3. The power unit (200) as claimed in claim 1, wherein said intake member (300) comprise a first connection end (305) and a second connection end (310), said second connection end (310) connected to said regulating member (270) and said flow enhancing portion (270) disposed in proximity to said second connection end (310).

4. The power unit (200) as claimed in claim 1, wherein said flow enhancing portion (325), extending radially inward, extends a pre -determined angular region having a first angle (a), wherein said first angle (a) is in the range of 30 to 360 degrees.

5. The power unit (200) as claimed in claim 1, wherein said flow enhancing portion (325) comprises a pre-peak portion (331) and a post-peak portion (332) at an upstream and a downstream of a peak point (330) thereof, and said post-peak portion (332) extends in a direction along a central line (A-A’) to flush with an inner periphery (320) of said downstream portion (316) of said intake member (300).

6. The power unit (200) as claimed in claim 5, wherein said flow enhancing portion (325) is having a first diameter D1 at said peak-portion, said a second diameter D2 and a third diameter D3 at a pre-peak portion (331) and a post-peak portion (332) respectively, said third diameter (D3) is smaller than said second diameter (D2) and said first diameter (Dl) is smaller than said third diameter (D3).

7. The power unit (200) as claimed in claim 5, wherein said pre-peak portion (331) and said post-peak portion (332) are disposed substantially within said upstream portion (316) of the intake member (300) and said pre-peak portion (332) is in flush with a diameter of said regulating member (270).

8. The power unit (200) as claimed in claim 5, wherein said intake member (300, 301) comprises an central line (A-A’) disposed at a second angle (b) with respect to a cylinder axis (C-C’) of said power unit (200) and an air flow (AF) from said intake member (300, 301) flows in a downstream direction to said combustion chamber (230).

9. The power unit (200) as claimed in claim 1, wherein said downstream portion (317) of said intake member (300, 301) is disposed to be in flush with an intake port (245) and said intake member (300, 301) with said flow enhancing portion (325) and said intake port (245) collectively form an elongated S-profile (ES) along at a angular region of said intake member (300).

10. The power unit (200) as claimed in claim 1, wherein said intake member (300, 301) comprises apeak point (330) and a tangential line (Tl) taken at the peak point (330) cuts through a central line (A-A’) of the intake member (300) at a first point (PI) which is within said intake member (300, 301).

11. The power unit (200) as claimed in claim 10, wherein said intake member (300, 301) supports a fuel injector assembly (275) mounted thereon at an injector axis (I-G) with respect to a central line (A-A’) of said intake member (300, 301) and said injector axis (I-G) cuts through the central line (A-A’) at a second point (P2), wherein said first point (PI) is upstream of said second point (P2).

12. The power unit (200) as claimed in claim 11, wherein said regulating member (270) connected to an air cleaner assembly (260, 460), said air cleaner assembly (260) comprises an ancillary chamber (263, 463) disposed within a triangular region (TR), having a side (AB) disposed at third angle (g) with respect to a lateral axis (RH-LH), and an intake passage formed by an outlet (462), said regulating member (270, 470) and said intake member (301) are disposed along a central line (A1-AG) and said central line (A1-AG) cuts substantially perpendicularly through said side (AB).