AIR FUEL RATIO CONTROL DEVICE FOR AN INTERNAL COMBUSTION
ENGINE
FIELD OF THE INVENTION
The present invention relates to an 'air fuel ratio control device for an internal combustion engine' and more particularly to a mounting arrangement of an air fuel ratio control device for a carburettor of an internal combustion engine.
BACKGROUND OF THE INVENTION
Air fuel mixture gets supplied to an internal combustion engine in numerous ways, the use of carburettor being one of them. The carburettor is where air mixes with fuel to create a flammable mixture or mist that gets ignited in the engine. The carburettor has various circuits / flow paths to route the air flow inside it to achieve desired air fuel mixture to be supplied to the engine at different speeds. The pilot circuit in a carburettor supplies air fuel mixture during idling and during low speeds (around lA throttle opening). The pilot circuit consists of a pilot air screw and a pilot jet. If the pilot airscrew is turned in, amount of air is reduced and the air fuel mixture is made rich and if the screw is turned out, amount of air is increased and the mixture is made lean. The pilot jet provides fuel to the pilot circuit.
Devices for electronic control of airflow in pilot circuit are known in the art. Such systems use an electronic control unit that provides inputs to an actuator, which controls the amount of air flowing into the pilot circuit. In the art, a solenoid arrangement has been used as an actuator. However such systems have the solenoid integrated to the carburettor. Manufacturing such a solenoid carburettor is complex and also increases cost of die component substantially. Further, in such an arrangement, it is inconvenient to clean or replace the solenoid since the entire

carburettor body has to be opened and removed from the intake system. The subsequent re-assembly of the critical solenoid components to the carburettor is often complicated and time consuming. Therefore to obviate defects in the prior art, it would be very convenient to have an alternate arrangement for mounting of a solenoid used for controlling airflow in the pilot circuit of the carburettor.
SUMMARY OF THE INVENTION
A conventional motorcycle includes an engine unit, a front wheel, a rear wheel, a body frame and a fuel tank. Body frame includes a head pipe, a main tube, a down tube and seat rails. The head pipe is provided at the front end of body frame to support a steering shaft disposed "within head pipe. The upper and lower ends of the steering shaft are fixed to an upper bracket and a lower bracket respectively. Upper bracket and lower bracket retain front suspensions that supports front wheel. The front wheel is connected at the lower end of the front fork, and the upper portion of the front wheel is covered by a front fender mounted to a lower portion of the front fork. A handlebar is fixed to upper bracket and can rotate to both sides. A head light is arranged on an upper portion of the front fork. Down tube is located in front of the engine unit and stretches inclined downwards from head pipe. A bracket is provided at the lower end of down tube for supporting the engine unit. Main tube is located above the engine unit and stretches rearward from head pipe and connects the rear of the engine unit. A vertical pipe is joined to the rear end of main tube and stretches upward from the point where it joins to main tube to seat rails. Seat rails are joined to main tube and stretches rearward to support a seat disposed above seat rails. A side stand is arranged on lower portion of engine unit of motorcycle. Left and right rear arm bracket portions support a rear arm to swing vertically, and a rear wheel is connected to rear end of the rear arm. A rear wheel suspension is arranged between rear arms. A tail light unit is disposed on the rear cover. A pillion footrest is connected to the vertical pipe. A grab rail is also provided on the rear of the seat rails. Rear wheel is arranged below seat and rotates by the driving force of engine transmitted through the transmission system.

A rubber boot is mounted on the frame of the vehicle. An air filter is mounted in the rubber boot and also a solenoid is mounted on the said rubber boot. Secondary air injection module also mounted on the said frame. The mounted solenoid on the bracket absorbs the vibration and the vibration originated on the frame is not transmitted to the solenoid. Carburettor is connected to the air filter and to the solenoid through air tubes.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 shows general air fuel ratio controller mounted on frame of a vehicle.
Fig.2 shows the solenoid valve of air fuel ratio controller.
Fig. 3 shows block diagram of air flow through the air filters, solenoid and carburettor.
Fig. 4 shows carburettor connected with secondary air intake valve to solenoid valve
through air tube. Fig. 5 shows the mounting bracket for holding the solenoid valve.

DETAILED DESCRIPTION OF THE INVENTION
Referring to Figure 1, the air fuel ratio control device for a carburettor 104 of an internal combustion engine for a two wheeled vehicle as per the present invention comprises of a solenoid 100 mounted on the frame 103 of the vehicle. The solenoid 100 controls airflow to a pilot circuit of the carburettor 104 and the operation of the said solenoid is in turn controlled by the electrical signals received from the electronic control unit. The present invention is characterized by the mounting arrangement of the solenoid 100. According to the first embodiment of the invention, the solenoid 100 is mounted on the frame 103 by way of a rubber boot 102. The use of the rubber boot 102 enables easy removal and assembly of the air cleaner 107 which provides air to secondary air injection and solenoid 100, during periodic maintenance and also reduces replacement time. The rubber boot 102 also helps to absorb shock induced in frame 103 and prevents transfer of vibrations to the solenoid 100.
Figure 2 gives an overview of the mounting of solenoid, air filter, and secondary air injection module. This also shows the carburettor and the engine.
Fig. 3 explains the process flow of air taken from atmosphere through the pipe 503 shown in Fig. 5. The air gets filtered in the air filter 107. The air coming out from the air filter gets branched at "T junction such that one branch proceeds to the solenoid and other branch goes to the secondary air injection module. From the secondary air injection module, one branch of the filtered clean air goes to the engine input and other to the inlet of muffler. A second air filter can be used to provide filtered clean air for the carburettor.
As per a second embodiment, the solenoid 100 is mounted to the frame 103 using .a
rubber boot 102 dedicated exclusively for it. In a third embodiment, the solenoid 100 is mounted to the frame 103 by way of a bracket 101(Fig. 1), which also mounts to the

frame 103 the air cleaner for secondary air injection system 105, the bracket 101 being welded to the frame 103. The solenoid is preferably mounted on the main tube of the frame 103 and at a position underneath the fuel tank and above the engine unit 108. Air supply to the solenoid 100 can be provided either from me carburettor air filter or can be branched out from the air cleaner for secondary air injection system 105 using a T-junction 106 or can be provided directly from the air cleaner for secondary air injection system 105 or can be provided from an air filter dedicated exclusively to the solenoid 100. Thus, another embodiment of the invention is that the solenoid can get air from any of the air filters out of the two air filters, which are providing air to the secondary air injection system and to the carburettor for its functioning.
The mounting arrangement as per the present invention therefore makes easier and cost efficient the maintenance and assembly of the solenoid. Further the manufacturing cost and complexity involved in manufacturing of carburettor has been reduced since the solenoid is not integrated to the carburettor.
Fig. 4 shows the tubing for air flow from the solenoid valve to carburettor and from the secondary air injection module to the engine and the exhaust. Air filter supplies air to solenoid through an air tube 401 and another tube 402 supplies air to the secondary air injection system. Carburettor gets the air from me same air filter or any other air filter.
Fig. 5 shows the air inlet tube 503 through which the air enters in the air filter 107.

WE CLAIM:
1. An air fuel ratio control device for a carburettor of an internal combustion
engine, comprising of a
vehicle frame, wherein the said vehicle frame mounts the said internal combustion engine and a carburettor for supplying air and fuel to the said internal combustion engine;
solenoid, wherein the said solenoid is mounted on a frame of a two wheeled vehicle separate from the carburettor and the said solenoid and the said carburettor are connected to each other by means of an air tube;
rubber boot, wherein the said rubber boot is mounted on the said frame of the vehicle and the said rubber boot also holds the said solenoid.
2. The air fuel ratio control device as claimed in claim 1, wherein the said mounting arrangement of the said solenoid includes the solenoid mounted on the frame by way of rubber boot, the rubber boot also mounts an air cleaner for secondary air injection module mounted to the frame.
3. The air fuel ratio control device as claimed in claim 1, wherein the said mounting arrangement includes the solenoid mounted on the frame by way of a bracket which also mounts the air cleaner for secondary air injection system mounted to the frame.
4. The air fuel ratio control device as claimed in claim 1, wherein the solenoid is preferably mounted on a main tube of the frame and at a position underneath a fuel tank and above an engine unit of a two wheeled vehicle.

5. The air fuel ratio control device as claimed in claim 1, wherein air is supplied to the solenoid from a carburettor air filter.
6. The air fuel ratio control device as claimed in claim 1, wherein air is supplied to the solenoid from the air cleaner for secondary air injection system.
7. The air fuel ratio control device as claimed in claim 1, wherein air is supplied to the solenoid from the air cleaner for secondary air injection system using a T-junction.
8. The air fuel ratio control device as claimed in claim 1, wherein air is supplied to the solenoid from an air cleaner exclusively provided for the solenoid.
9. The air fuel ratio control device for a carburettor of an internal combustion engine as hereinabove described in the specification with the drawings.