Air fuel ratio control system

Field of the invention

The present invention relates to an "Air fuel ratio control system" and more particularly to an ultrasonic transceiver that is positioned before the combustion chamber and exercises air-fuel ratio control by correcting the output of an air-fuel ratio sensor in accordance with the output of the transceiver.

Description of the prior art

Motorcycles having electronic fuel ignition system use a close loop air fuel ratio control system. They help determine, in real time, if the air fuel ratio of a combustion engine is rich or lean. Since oxygen sensors are located in the exhaust stream, they do not directly measure the air or the fuel entering the engine. But when information from oxygen sensors is coupled with information from other sources, it can be used to indirectly determine the air-to-fuel ratio. Closed-loop feedback-controlled fuel injection varies the fuel injector output according to real-time sensor data rather than operating with a predetermined (open-loop) fuel map. In addition to enabling electronic fuel injection to work efficiently, this emissions control technique can reduce the amounts of both unburnt fuel and oxides of nitrogen entering the atmosphere. The sensor does not actually measure oxygen concentration, but rather the amount of oxygen needed to completely oxidize any remaining combustibles in the exhaust gas. Modern engines use oxygen sensors and catalytic converters in order to reduce exhaust emissions. Information on oxygen concentration is sent to the ECU, which adjusts the amount of fuel injected into the engine to compensate for excess air or excess fuel. The ECU attempts to maintain, on average, a certain air-fuel ratio by interpreting the information it gains from the oxygen sensor. The primary goal is a compromise between power, fuel economy, and emissions, and in most cases is achieved by an air-fuel-ratio close to stoichiometric. This system is effective mainly for blended fuel systems such as ethanol blended petrol, etc.

However, the above said system is placed after the combustion chamber, and hence fuel supply control is only done after few cycles. Moreover, the above oxygen sensor system is easy to tampered with that can be detrimental to emissions control and can even damage the vehicle.

Hence, a system is required that works as effectively as an oxygen sensor for close loop control system with a better tamper proof structure and reliability. Moreover, the said oxygen sensor is applicable in a narrowband only and requires a temperature of atleast 280-300 degrees.

Another objective of the present invention is to provide a system that is sturdy, less costly, and simple and has longevity.

Brief description of the invention

Accordingly, the present invention describes a system for determining the density of the ethanol-blended fuel by measuring the amplitude of the reflections of an ultrasonic pulse against that of a reference sheet. The present system uses a transducer to transmit ultrasonic interrogation pulses through the fuel. The interrogation pulse is reflected from the fuel to provide return pulses that can be used to determine the density of the fuel. The density is determined as a function of amplitudes of the return pulses.

Brief description of the drawings

Figure 1 illustrates side view of a motorcycle according to the present invention. .

Figure 2 illustrates one embodiment of the present invention.

Detailed description of the invention

A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures 1 and 2.

A motorcycle comprises of a frame 101, front fork 102 attached to a pivot tube 103 of the vehicle frame 101, a front wheel 104 attached to these front forks 102, a handle bar 105 connected to the front forks 102, a fuel tank 106 attached so as to straddle an upper part of the vehicle frame 101, a seat 107 attached to the upper rear portion of the vehicle frame 101, an engine unit 108 attached to the lower front section of the vehicle frame 101, a swing arm 109 attached to a lower rear section of the vehicle frame 101, suspended by a rear shock absorber 110 from the vehicle frame 101 and a rear wheel 111 attached to a rear end of swing arm 109. The intake system of the engine 108 (figure 2, shown partially) comprises of an injector 205, intake duct and an air cleaner. The exhaust system of the engine (not shown in the figure) comprises of exhaust pipe and a muffler.

The motorcycle is also provided with a side cover 112 for covering a side section of the vehicle frame 101, a seat cover (not shown in the figure) for covering a rear section of the vehicle frame 101 below the seat 107, a front fender 113 for covering an upper part of the front wheel 104, and a rear fender 114 for covering an upper part of the rear wheel 111.

According to the first aspect of the present invention is an ultrasonic transceiver 200 that detects the density of the fuel to monitor the ethanol content in it and send the signal to an ECU 201 that in turn operates a close loop air fuel ratio control inside the combustion chamber 203 in the engine 108.
Second aspect of the present invention is the ultrasonic transceiver 200 according to the first aspect, wherein the mounting is arranged pre-combustion chamber and in between the fuel tank 106 and the combustion chamber 203 in the engine 108. Accordingly, the present invention describes a system for determining the density of the ethanol-blended fuel by measuring the amplitude of the reflections of an ultrasonic pulse against that of a reference sheet 204. The present system uses a transducer as a part of transceiver 200 to transmit ultrasonic interrogation pulses through the fuel. The interrogation pulse is reflected from the fuel to provide return pulses that can be used to determine the density of the fuel. The density is determined as a function of amplitudes of the return pulses.

This system is used to determine the ethanol content of ethanol-blended fuel for a better close loop air fuel ratio control. The density of the blended fuel is determined by using the ultrasonic transceiver 200 and compared with previous stored data in the ECU 201 for getting the content of ethanol in the blended fuel. The above system works well just before the fuel is injected through an injector 205 to the combustion chamber 203 in the engine 108 for the real time determination of ethanol content in the fuel. Therefore the transceiver 200 is mounted on a transceiver chamber 202 just before the fuel injector 205 in the connecting pipe 206 between fuel tank 106 and injector 205. This transceiver 202 is in turn located on a suitable place near either the cylinder head of the engine 108 or the fuel tank 106 in the connecting pipe 206. The fuel from the fuel tank 106 passes through the above said transceiver chamber 202 before being sent to the combustion chamber 203 in the engine 108. The transceiver senses the density and sends the data to the ECU 201 for actual determination of ethanol in the fuel: The ECU 201 then directs the injector to inject the fuel in the combustion chamber 203 accordingly.

It should be understood that the foregoing description is that of a preferred embodiment of the invention and that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims. Further any shape and configuration of the extended surface is possible within the ambit of appended claims

Claims: We claim:

1. A fuel intake system for a motorcycle comprising a fuel tank, a fuel injector, a combustion chamber, an electronic control unit (ECU), an ultrasonic transceiver, a transceiver chamber, wherein said ultrasonic transceiver is mounted on the said transceiver chamber which in turn is placed on the pipe connecting the fuel injector to the fuel tank.

2. A fuel system as claimed in claim 1, wherein said transceiver senses the fuel density and sends the information to said ECU, which in turn controls the air fuel ratio in the said combustion chamber.

3. A motorcycle with a fuel intake system as claimed in claim 1.

4. A motorcycle with fuel intake system substantially as herein described with reference to, and as illustrated in, the accompanying drawings.