CARBURETOR FOR A TWQ-WHEELED AUTOMOTIVE VEHICLE

FIELD OF INVENTION

[0001] The present invention relates to a carburetor for a two-wheeled automotive vehicle and more particularly to VM type carburetor having an improved throttle return spring.

BACKGROUND OF INVENTION

[0002] A carburetor functions to produce a combustible air-fuel mixture, by mixing fuel with air in a proper ratio, and supplies the mixture to the engine. An ideal air fuel mixture is that which can burn without leaving an excess of fuel or air. Maintaining the ideal air-fuel mixture holds the key to efficient engine operation.

[0003] A conventional carburetor is provided with a low speed fuel system (the pilot system) and a main speed fuel system (the main system). Based on throttle operation, the quantity of air and fuel entering the carburetor is varied. Greater the degree of throttle opening, greater is the amount of fuel that flows into the carburetor chamber. The vehicle rider using the throttle grip provided on the handlebar controls throttle opening. In vehicies having VM type carburetor, actuation of the throttle grip pulís a throttle cable, which in turn controls throttle opening by operating a throttle spring, which actuates a needle jet and jet needle arrangement in the carburetor.

[0004] Fuel efficiency has always remained top priority for both vehicle manufacturers and customers, more so in the recent past due to rising fuel prices. Since fuel consumption increases with increase in throttle opening, for

achieving optimum fuel efficiency, it would be highly desirable to have an improved carburetor, which enables the rider to regúlate throttle operation beyond a particular limit and this forms the principal objective of the present invention.

SUMMARY OF THE INVENTION

[0005] The current invention discloses a carburetor with a variable

pitch throttle spring securely mounted to the throttle valve. The throttle spring has two different portions namely the first portion and the second portion. The second portion is having a spring constant greater than the first portion. Until a certain speed limit, one portion of the throttle spring (the portion with the lower spring constant) operates. Once the vehicle attains a pre-determined speed, and a pre-determined degree of throttle position is achieved, the other portion (the portion with the higher spring constant) of the throttle spring comes under operation. The stiffness on higher throttle degrees limits the rider for further increasing throttle to keep the vehicle under economy range of driving, thus increasing fuel efficiency.

BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 Shows a typical two-wheeler vehicle.

[0007] Figure 2 Shows a carburetor proposed in the invention.

[0008] Figure 3 Shows a variable pitch throttle spring .

[0009] Figure 4 Illustrates block diagram for an indication means.

DETAILED DESCRIPTION OF THE INVENTION

[00010] The present invention is hereinafter described with reference to

the accompanying drawings. It is to be noted that like reference numeráis designate corresponding or identical elements throughout the various drawings. The terms front and rear, and left and right as used indícate the front and rear and the left and right directions when viewed by a rider seated on the vehicle seat.

[00011] A conventional two-wheeled automotive vehicle as illustrated

in Fig. 1, includes an internal combustión engine 41, a front wheel 25, a rear wheel 27, a body frame 19 and a fuel tank 56. Body frame 19 includes a head pipe 12, a main tube 17, a down tube 22, and seat rails 18. The head pipe 12 is provided at the front end of body frame 19 to support a steering shaft 11 disposed within the head pipe 12. The upper and lower ends of the steering shaft 11 are fixed to an upper bracket 13 and a lower bracket 14 respectively. Upper bracket 13 and lower bracket 14 retain front fork 16 that supports front wheel 25. The front wheel 25 is connected at the lower end of the front fork 16, and the upper portion of the front wheel 25 is covered by a front fender 54 mounted to the lower portion of the front fork 16. A handlebar 15 is fixed to upper bracket 13 and can roíate to both sides. A head light 36 is arranged on an upper portion of the front fork 16. Down tube 22 is located in front of the internal combustión engine 41 and stretches slantingly downward from head pipe 12. A bracket 55 is provided at the lower end of down tube 22 for supporting the internal combustión engine 41. Main tube 17 is located above the internal combustión engine 41 and stretches rearward from head pipe 12 and connects the rear of the internal combustión engine 41. A carburetor 30, located above the internal combustión engine 41, and below the main tube 17, is connected to the engine 41 by way of an intake pipe 29. A vertical pipe 28 is joined to the rear end of main tube 17 and stretches downward from the point where the main tube 17 joins the seat rails 18. Seat rails 18 are joined to main tube 17 and stretch rearward to support a seat 57 disposed above seat rails 18. A side stand 58 is arranged towards the lower portion of the internal combustión engine 41. Left and right rear swing arm bracket poitions support a rear swing arm 26 to swing vertically, and a rear wheel 27 is connected to rear end of the rear swing arm 26. A rear wheel suspensión 34 is arranged between rear swing arm 26. A tail light unit 64 is disposed on the rear cover 61. A pillion footrest 31 is connected to the vertical pipe 28. A grab rail 62 is also provided on the rear of the seat rails 18. Rear wheel 27, arranged below the seat 57 is rotated by the driving forcé of the internal combustión engine 41 transmitted through the transmission system.

[00012] Referring to Fig. 2, the carburetor 30 as per the present invention is characterized by a variable pitch throttle spring 100. The throttle spring 100 is secured to a throttle valve 101. The throttle spring 100 further comprises a first portion 100a and a second portion 100b (as illustrated in Fig. 3). The first portion 100a has a first spring constant and the second portion 100b has a second spring constant such that the second spring constant is greater than the first spring constant. The throttle spring 100 is connected to a throttle grip (not shown in the figures) by way of a throttle cable (not shown in the figures). The throttle grip is rotatably mounted on the handlebar of the vehicle and the rider operates throttle valve 101 by rotating the throttle grip.

[00013] When the rider operates throttle, once the vehicle speed exceeds the speed range 50-60 km/hr and the throttle opening exceeds a particular degree, the second portion 100b of the throttle spring 100 is operated. Since the second spring constant is greater than the first spring constant, operating the throttle when the second portion 100b of the throttle spring 100 is reached, requires the rider to apply greater forcé. This tightness in throttle grip experienced by the rider, enables him to limit throttle operation and vehicle speed within a range wherein máximum fuel effiency is achieved. Therefore fuel consumption is optimized.

[00014] Fig. 4 is a block diagram of an indication means for the present invention. The indication means comprises both visual indication 106 and audio indication 107 and is mounted to the instrument cluster of the vehicle. The indication means receives input from a Throttle Position Sensor (TPS) 104 when throttle position reaches the point wherein the second portion 100b of the throttle spring is operated. As illustrated in Fig. 4, a 12V input is provided to the TPS. When the throttle position reaches the predetermined point based on the vehicle speed, the TPS plunger 105 completes the circuit, which in turn enables the TPS 104 to provide input to the indication means.

[00015] The foregoing description is a specific embodiment of the present invention and has been described for the purpose of illustration only. Persons skilled in the art may practice numerous alterations and modifications of the present invention without departing from its spirit and scope.

We claim:

1. A carburetor for a two-wheeled automotive vehicle, said carburetor comprising a throttle valve and characterized by a variable pitch throttle spring securely mounted to the throttle valve.

2. The carburetor for a two-wheeled automotive vehicle as claimed in claim 1, wherein the throttle spring further comprises a first portion having a first spring constant and a second portion having a second spring constant.

3. The carburetor for a two-wheeled automotive vehicle as claimed in claim 2, wherein the second spring constant is greater than the first spring constant.

4. The carburetor for a two-wheeled automotive vehicle as claimed in claim 1, wherein the throttle spring is connected to a throttle grip through a throttle cable, said throttle grip rotatably mounted on a handlebar of the vehicle.

5. A two wheeled automotive vehicle comprising: a body frame;

an internal combustión engine mounted to the said body frame;

a front fork and a handlebar mounted for rotation on said body frame;

a front wheel mounted to said front fork;

a rear wheel mounted to said body frame;

a carburetor connected to the internal combustión engine, the carburetor

comprising a throttle valve and characterized by a variable pitch throttle

spring securely mounted to the throttle valve.

6. The two-wheeled automotive vehicle as claimed in claim 5, wherein the throttle spring further comprises a first portion having a first spring constant and a second portion having a second spring constant.

7. The two-wheeled automotive vehicle as claimed in claim 6, wherein the second spring constant is greater than the first spring constant.

8. The two-wheeled automotive vehicle as claimed in claim 5, wherein the throttle spring is connected to a throttle grip through a throttle cable, said throttle grip rotatably mounted on the handlebar.

9. The two-wheeled automotive vehicle as claimed in claim 5 further comprising an indication means mounted to an instrument cluster of the vehicle, said indication means actuated on receiving input from a throttle position sensor, said input provided when the second portion of the throttle spring is operated.

10. The two-wheeled automotive vehicle as hereinabove described in the specification and illustrated in the accompanying drawings.
11.