A FUEL CONTROL SYSTEM
FIELD OF THE INVENTION
[0001] The subject matter as described herein, relates generally to a fuel .
5 control system operatively connected with an internal combustion engine and more particularly, but not exclusively, to a fuel control system installed in an induction system for an internal combustion engine.
BACKGROUND OF THE INVENTION
10 [0002] A conventional two wheeled vehicle is powered by an internal
combustion engine generally disposed at a lower half of the vehicle. This engine converts chemical energy into mechanical energy by combustion of air-fuel mixture within a combustion chamber of the engine. The said engine, among other components, has a cylinder comprising a cylinder head atop or in front of the
15 cylinder and receiving a reciprocating piston from the bottom or the rear. On combustion of the air-fuel mixture (also called combustible charge), the piston transfers the energy generated during combustion to a crankshaft through a connecting rod thereby driving the crankshaft which then drives the wheel through a transmission system.
20 [0003] The volume of air-fuel mixture going into the engine is controlled
by a metering device. It comprises of a die cast body of complex shape into which a series of carefully machined openings are provided. It provides air-fuel mixture

• to the engine combustion chambers for ignition and works on the basic principle of atmospheric pressure. A typical metering device, made of aluminium or an aluminium alloy, is connected to an intake conduit on one side and an air inlet device on the opposite side through known joining mechanisms. The intake
5 conduit connects the metering device with the cylinder head of the engine. It receives air-fuel mixture from the metering device and supplies it to the combustion chamber of an internal combustion engine with the help of intake valves, the intake valves also situated in the cylinder head. The introduction of the combustible charge into the engine with proper air-fuel ratio is critical for the
10 engine performance.
[0004] It is observed that in high volumetric efficiency engines, a
metering device with a bigger venturi is required to allow more air-fuel mixture into the engine. However in an engine attached to bigger size metering devices, engine stalling or sudden dip in engine rpm takes place during sudden throttle
15 opening. A vehicle user can suddenly open the throttle in various conditions, for instance, when moving from the vehicle from a standstill condition or during overtaking a vehicle on the road. During these conditions, the air-fuel mixture supplied to the engine is lean, that is, the quantity of air is much more than the quantity of fuel which leads to engine stalling as adequate fuel is not available for
20 combustion. The problem is further magnified in an engine where a split type metering device is attached in which only an upper side of a venturi supplies air and lower side supplies air fuel mixture. This improper air fuel ratio during sudden throttle opening results in dip or poor acceleration response. The problem

of improper air fuel ratio is further aggravated in a metering device without auto choke facility.
[0005] Common approaches to overcome this problem either reduce the
power output of the engine or compromise its fuel economy. One of the approaches to tackle this problem is to reduce the venturi size of the metering device. However, the smaller metering device size compromises engine performance in a bigger engine as the power output of the engine decreases. Another approach is to avoid the sudden dip in engine rpm by enriching the combustible charge at lower speeds which means a rich mixture even during lower engine speed. This would result in more fuel consumption by the engine and the fuel economy of the engine is compromised.
SUMMARY OF THE INVENTION
[0006] It is therefore an object of the present invention to enable optimal
engine performance by supplying a rich air-fuel mixture into the engine during sudden throttle conditions. The present invention is aimed at overcoming the challenges associated with a conventional metering device and regulate the air-fuel ratio in the metering device during sudden throttling conditions. In other words, the present invention achieves an easy way of supplying additional fuel into the metering device venturi during such conditions. To this end, the present invention proposes a fuel control system which has rate of change of throttle as input, or change in vacuum of intake conduit as input, or both. The fuel control system comprisesa metering device including a primary fuel supply path and a secondary fuel supply path and operably connected with an internal combustion

engine,a throttle position sensor,an intake manifold vacuum sensor, wherein the secondary fuel supply path is channelled from a bowl member of the metering device to a venturi member of the metering device and and controlled by a one way valve means,and wherein further the secondary fuel supply path providing additional fuel supply to the metering device.
[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 THE DRAWINGS
[0008] The above and other features, aspects, and advantages of the
subject matter will be better understood with regard to the following description and accompanying drawings where:
[0009] FIG. 1 is a side elevation view of a conventional scooter type
motorcycle.
[00010] FIG. 2 shows a front perspective view of an internal combustion
engine installed in the motorcycle of FIG. 1
[00011] FIG. 3 shows a metering device according to the present invention.
[00012] FIG. 4 shows a schematic illustration of the fuel control system
according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[00013] In order that those skilled in the art can understand the present
invention, the invention is further described below in detail so that various features of the invention thereof proposed here are discernible from the 5 description thereof set out hereunder. However these descriptions and the appended drawings are only used for those skilled in the art to understand the objects, features, and characteristics of the present invention and not to be used to confine the scope and spirit of the present invention. The present subject matter would now be described in greater detail in conjunction with the figures in the 10 following description.The description is to be understood as an exemplary embodiment and reading of the invention is not intended to be taken restrictively.
[00014] FIG. 1 shows a side elevation view of the scooter type vehicle. The
vehicle 1 includes a vehicle frame assembly made up of several tubes welded together supporting the body of said vehicle. The vehicle 1 has a steerable front
15 wheel 2 and a driven rear wheel 25 driven by driving force generated by an internal combustion engine 24. The front wheel 2 of a vehicle 1 is axially supported at a lower end of a front fork 3, and the front fork 3 is pivoted in a steerable manner in a head pipe 58 of the vehicle frame. The frame assembly of the vehicle 1 is covered by a plurality of vehicle body covers including a front
20 panel 17, a leg shield 16, an under seat cover 21, a left side cover 41, a right side cover and a bottom cover 60. The right side cover is substantially symmetrical to the left side cover and hence not shown.

[00015] A handle bar 7 is attached to an upper end of the head pipe 58. A
headlight unit 10 is arranged forwardly of the handle bar 7 and is surrounded by a visor 9. The handle bar 7 and a seat 22 are supported at opposing ends of the frame assembly and a generally open area is defined there between known as
5 floorboard 12 which functions as a step through space. The seat 22 for a driver and a pillion is placed forward to a fuel tank and rearwardly of the floorboard 12. Anarticle storage device(not shown) is provided below the seat 22 for storing useful articles. A side trim member 14 laterally beneath the floorboard 12 is provided to cover the lower frame members from being visible. The side trim
D member 14 has a rearwardly footrest cavity to accommodate a footrest for a pillion rider. The side trim member 14 is laterally present on both sides of the vehicle; however, only one is visible in the side view. A side stand fixed to the left side of the frame supports the vehicle such that vehicle can incline to the left side without falling. A rear fender 27 is accommodated above the engine 24 to
5 partially cover the rear wheel 25. Likewise, the front wheel 2 is covered by a lower member 18 of the front panel 17.
[00016] FIG. 2shows a perspective view of an internal combustion engine
24 according to an embodiment of the present invention. The front of the engine is indicated by an arrow "Fr" and the rear of the engine is indicated by an arrow 0 "Rr", and further the lateral right side of the engine is indicated by an arrow "R" and the lateral left side of the "engine" is indicated by an arrow "L" as necessary. The internal combustion engine shown in ensuing drawings is a four stroke single cylinder swinging internal combustion engine with a forwardly titled cylinder

head generally mounted on a scooter type motorcycle. However, the concepts disclosed in the present invention can be practiced in other engines like a vertical engine. The engine 24 is one made by unitizing a cylinder assembly 42 and a crankcase assembly 44, and rotatably supports a rear wheel of the motorcycle. The rear portion of the crankcase assembly44 includes a power transmission system including a continuously variable transmission made by using a belt and a pulley. The engine 24 has an air cleaner 32 mounted on the upper surface side of the crankcase assembly 44 positioned on the rear side of the engine. The air cleaner 32 exhibits a box shape generally, and has an air inlet pipe 30 extending from the vicinity of an upper portion thereof. Further, the crankcase assembly 44 is covered from a left side by a variator cover 48 which seals the crankcase assembly from the left side and supports the components of the continuously, variable transmission. During operation of the engine 24, the components of the power transmission system become hot and hence are air cooled. The air enters the crankcase assembly 44 from a front portion of the left side thereof through an inlet tube 46. The variator cover 48 comprises of an opening (not shown) for receiving the incoming air.
[00017] A fuel control system is provided in the motorcycle land
comprises of a metering device 38 operably connected to the internal combustion engine 24. An intake hose 34 extends from a right side portion towards the metering device 38 which further carries an air-fuel mixture for combustion through an intake pipe 36. As shown in FIG. 3, the metering device 38 comprises of a venturi member 51 and a bowl member 52. The bowl member 52 is located.

below the venturi member 51. A primary fuel supply path 56 introduces fuel into the venturi member 51. In an embodiment, the venturi member 51 is of split type comprising an upper portion 53 and a lower portion 54. In the split type metering device, the primary fuel supply path 56 introduces fuel into the lower portion 54 5 of the venturi member 51. The primary fuel supply path 56 is capable to provide sufficient fuel from a fuel tank of the motorcycle to the metering device. However, during sudden throttling conditions, rich air-fuel mixture is required to prevent engine stalling.
[00018] Therefore, the metering device 38 is further provided with a
0 secondary fuel supply path 57 and is configured to receive inputs from a throttle position sensor and an intake manifold vacuum sensor. The secondary fuel supply path 57 is channelled from the bowl member 52of the metering device 38 to a venturi member 51 of the metering device and provides additional fuel supply to the metering device in during pre-defined conditions. In the split type metering 5 device as shown in FIG. 3, the secondary fuel supply path 57 is channelled from the bowl member of the metering device 38 to the upper portion 53 of the venturi member 51. The outlet to the venturi member in the secondary fuel supply path controlled by a valve means which operates one way. In an embodiment, the outlet to the venturi member in the secondary fuel supply path controlled by a :0 diaphragm valve. It only allows the fuel from the bowl member 52to enter the venturi member51. The fuel control system as described herein is. operational during sudden rate of change of throttle opening as detected by the throttle position sensor or sudden change in manifold vacuum as sensed by the intake

manifold vacuum sensor. These changes occur during sudden throttling conditions for instance, when the rider moves the vehicle from a standstill condition suddenly or during overtaking another vehicle on the road.
[00019] In an embodiment, the secondary fuel supply path is substantially
5 parallel to the primary fuel supply path but spaced apart.
[00020] The fuel control system as embodied herein ensures rich air-fuel
mixture to the engine during sudden throttle opening conditions. The secondary fuel supply path supplies the extra amount of fuel required for good response in the venturimember in case of a metering device without split and supplies.the fuel
10 in to the upper portion of the venturi in case of the metering device with split design. The secondary fuel supply path is easy to machine in the metering device with less investment. It is to be noted that the valve means of the secondary fuel supply path 57 operates only when a sudden change in throttle opening or intake manifold vacuum is detected. In any event to the contrary, the primary fuel supply
15 path 56 supplies fuel to the metering device and the secondary fuel supply path 57 remains closed.
[00021] In another embodiment of the metering device, the metering device
also receives input from an engine thermal sensor. In this way, during cold start conditions of the engine 24, the same fuel control system may act as a choke. 20 When the engine temperature is below a predefined temperature as detected by the engine thermal sensor, the valve means control the flow of fuel from the secondary fuel supply path 57 opens and thus the enriched air-fuel mixture facilitates easy start of the. engine during cold start.

[00022] Thus, the present invention provides a transient fuel control circuit
in the metering device which operates with respect to manifold vacuum or rate of change of throttle opening. It uses auto choke system and throttle position sensor to sense the sudden throttle opening and for fuel supply control to optimise air fuel mixture for good acceleration response.
[00023] 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.

We claim:
1. A fuel control system for a vehicle comprising an internal combustion
engine (24) and a metering device (38) operably connected to the engine
(24), the metering device having a primary fuel supply path (56) and
comprising a venturi member (51) and bowl member (52), characterised in
that,
the metering device comprises of a secondary fuel supply path (57) and configured to receive inputs from a throttle position sensor and an intake manifold vacuum sensor,
wherein the secondary fuel supply path (57) is channelled from the bowl member (51) of the metering device to the venturi member (51) of the metering device and provides additional fuel supply to the metering device during pre-defined conditions.
2. The fuel control system as claimed in claim 1, wherein the metering device (38) also receives input from an engine thermal sensor.
3. The fuel control system as claimed in claim 1, wherein an outlet in the secondary fuel supply path (57) toward the venturi member (51) controlled by a one way valve means.
4. The fuel control system as claimed in claim 1, wherein the venturi member (51) is of split type comprising an upper portion (53) and a lower portion (54).

5. The fuel control system as claimed in claim 4, wherein the primary fuel supply path (56) introduces fuel into the lower portion (54) of the venturi member (51) and the secondary fuel supply path (57)introduces fuel into the upper portion (53) of the venturi member (51).
6. A fuel control system comprising:
a metering device (38) including a primary fuel supply path (56) and a secondary fuel supply path (57) and operably connected with an internal combustion engine (24),
a throttle position sensor,
an intake manifold vacuum sensor,
wherein the secondary fuel supply path (57) is channelled from a bowl member (51) of the metering device to a venturi member (51) of the metering device and and controlled by a one way valve means,
and wherein further the secondary fuel supply path (57) providing additional fuel supply to the metering device (38).
7. The fuel control system as claimed in claim 6, wherein the fuel control system further comprises of an engine thermal sensor.
8. The fuel control system as claimed in claim 6, wherein the venturi member (51) is of split type comprising an upper portion (53) and a lower portion (54).

9. The fuel control system as claimed in claim 8, wherein the primary fuel supply path (56) introduces fuel into the lower portion (54) of the venturi member (51) and the secondary fuel supply path (57)introduces fuel into the upper portion (53) of the venturi member (51).