FIELD OF INVENTION

[0001] The present invention relates to an internal combustion engine and more
particularly to an intake port of an internal combustion engine.

BACKGROUND OF INVENTION

[0002] A three-valve internal combustion engine comprises of two inlet ports and
one exhaust port wherein their respective valves control the intake and exhaust at all the ports. In engines equipped with two intake valves on the two intake ports, one of the intake ports is designed to create swirl motion and the other one is designed to create tumble motion in the charge (air-fuel mixture) entering inside combustion chamber.

[0003] The above two streams created at immediate.downstream of the carburetor
are maintained immiscible by means of a split path intake pipe and a separate port is provided for each valve. Generally, two spark plugs will be disposed off-centered in the cylinder head, opposite to. each other. The swirl motion of the charge is benefitted by this offset in such a way that the ignition starts early so that combustion peak pressure is attained early / optimally in the combustion cycle. In the intake pipe, due to bend at; the partition end, fuel wetting takes place due to collision of charge with the partitign wall. For cost reasons, if single, centered spark plug is used, the same creates noise in the engine due to the late combustion of the charge. Hence an intake system is required which minimizes the fuel wetting thus reduces the intake noise in the engine.

SUMMARY OF THE INVENTION

[0004] To obviate the problems associated with the above design of the intake
port, the current invention discloses the intake path equipped with a short-circuited region by removing a small portion of partition wall separating them right before the valve in the fuel-air intake passage itself. This allows charges to mix efficiently and creates uniform charge distribution to both swirl and tumble ports even during part throttle operation. This makes the start of combustion early and helps in noise reduction.

[0005] The described invention relates to the short-circuiting of the otherwise
separate streams that helps in supplying adequate fuel to the tumble port that is normally non-operational during part throttle condition. This ensures near uniform charge inside the cylinder. In addition, this ensures that the charge flow is adequate near the central spark plug tip. This helps in earlier, faster and complete combustion, thereby reducing chances of knocking and helps to make combustion much leaner by allowing further ignition advances.

BRIEF DESCRIPTION OF DRAWINGS

Figure lillustrates a typical two-wheeler.

Figure 2 illustrates a typical engine and surrounding parts of a two-wheeler.

Figure 3 illustrates intake system of the engine.

Figure 4 illustrates a typical.intake pipe of intake system of the engine.

Figure 5 illustrates the fuel- air intake passage inside intake pipe.

Figure 6 illustrates sectional view of the fuel-air intake passage inside intake pipe.

Figure 7 illustrates the intake manifold of the intake system.

DETAILED DESCRIPTION OF THE INVENTION

[0006] The short circuiting pocket as described in the current invention is located
in the bent portion of intake path so that larger droplets of fuel, due to centrifugal effect enters into the tumble port and make swirl port flow leaner than usual and free of larger droplets, This helps to reduce loss of fuel due to fuel sticking onto cylinder walls and helps in scraping down the fuel to oil sump by oil control ring on the piston, while charge is in swirl motion inside the cylinder, This short circuiting pocket also reduces CO/HC emission, knocking, fuel loss, oil dilution. While tumble port flow, which otherwise gives no flow during part throttle, will carry the reminiscent fuel and burn completely to yield better combustion. The current invention is also applicable where the intake pipe is straight. In internal combustion engine with straight intake pipe, the centrifugal action would be absent, but there also, tumble action is significantly improved.

[0007] The short circuiting pocket created in the intake system is just adequate to
allow a small amount of charge through tumble port and remaining through the swirl port during part throttle condition. This helps achieve / maintain better low-end torque due to sufficient turbulence created inside the cylinder arid combustion efficiency improved.

[0008] Intake port (for swirl motion) has been created from one out of the two
intake ports to create swirl motion in the charge while it enters the combustion chamber. Lower portion of the intake path is connected to this port. Intake port (for tumble motion)

is created out of the other intake port to create tumble motion in the charge. The upper portion of the intake path is connected to this port.

[0009] The intake pipe is disposed between carburetor and intake port face of cylinder head. The splitting wall in the carburetor, separation wall inside pipe intake and cylinder head port separation walls together divide the charge coming out of the carburetor venturi and maintain separate streams of charge until they get mixed inside the cylinder, except for the bypass cut on the separation wall on the pipe intake.

[00010] The contact between the spool inside the carburetor and the separation
wall during lower part throttle conditions ensures that there is no charge flow in the top tumble port. After the throttle position rises past the separation wall, charge is allowed to enter the top port. This effectively ensures that the bottom port alone is operational during lower part throttle conditions and both ports are operational during higher part throttle positions and wide-open throttle positions as well.

[00011] As the proposed short circuiting pocket provides a bypass between those
two streams, the flow may not be completely exclusive of each other. Near the interface of cylinder head ports, the pipe intake is. provided with a cut/passage on its separation .wall. This cut allows the charge to be bypassed from the lower intake path.to upper intake path especially during lower part throttle operation where in.the top.port is^still closed by the spool of the. carburetor. Spark plug is mounted on cylinder head so that the tip of spark plug is central to the combustion chamber. Otherwise, without bypass cut, there have to be two spark plugs offset in the opposite direction to the centre.

[00012] During lower part throttle conditions, the charge enters the cylinder
through bottom swirl port. Due to the bypass cut, some amount of charge also enters through tumble port. The charge flow from tumble port reaches the central spark plug more easily than the swirling charge does. This ensures that the combustion starts early, flame propagates faster, and combustion is complete because of more uniform air-fuel mixture. In addition, this enables advancing of ignition timing without knocking and lean burning to have lower BSFC etc.

[00013] Figure 1 shows a typical two-wheeled vehicle 1 with a rear wheel 2,
engine 3, air filter 4, front wheel 5, floorboard6, utility box 7, side panel 9, front shock absorber 10, rear shock absorber 11, grab rail 12, tail lamp 13 and rider seat 14. The direction of arrow "F* shows the front direction of the vehicle arid direction of arrow "R" shows the rear direction of the vehicle. The power produced from the engine 3 is transmitted to the wheels. Figure 2 shows engine 3, cylinder head 21 and rear, wheel 2.

[00014] Figure 2 shows rear wheel 2, engine 3, air intake box 4, carburetor 21,
cylinder head 22, spark plug 23 and intake pipe 24. In the current invention, the pipe intake conduit 24 connects carburetor 21 and cylinder head ports with a partition wall inside to carry separate charge stream coming from split wall carburetor towards respective isolated intake valve ports. Said pipe intake has a short circuiting opening on the separation wall near the cylinder head interface.

[00015] Figure 3 shows location for carburetor outlet 31,1st path of intake pipe 32, 2nd path of intake pipe 33, intake partition 34, intake pipe sealing face 35, engine cylinder 36 and exhaust port 37. The venturi type carburetor has the outlet spout split half

by the partition wall 34 along the spout axis to divide the charge coming out of the venturi is created by the carburetor body and a spool actuated by throttle cable. Until the spool opening reaches past the separation wall, no charge flows through the upper portion of the split namely the second path of intake pipe 33. The partition wall portions 341 belong to the intake pipe and 34C belongs to the partition in carburetor outlet. The portion 341 belongs to said intake pipe 24, the portion 34C belonging to said carburetor 21 and the partition in said cylinder head 22 are in tandem meaning that they are in one line and help to create two flow paths for charge.

[00016] Figure 4 shows location for carburetor outlet 31 .and intake pipe sealing
face 35. The intake pipe sealing face 35 is coupled to the cylinder head and carburetor outlet 31 is mated to carburetor outlet. Figure 5 shows carburetor outlet 31, intake partition 34 and intake pipe sealing face 35. The intake pipe has a partition wall 34 inside it that separates the intake pipe inner into two halves namely the first path of intake pipe . 32 and second path of intake pipe 33.

[00017] Figure 6 shows intake partition 34, intake manifold 35, first path of intake
pipe 32, second path of intake pipe 33 and mixing area 63. During lower part throttle conditions, the charge enters the cylinder through bottom swirl port namely the 1st path of intake pipe 32. Due to the bypass cut, some amount of charge also enters through tumble port. The charge flow from tumble port reaches the central spark plug more easily than the swirling charge does. This ensures that the combustion starts early, flame propagates faster, and combustion is complete because of more uniform air-fuel mixture.

[00018] Figure 7 shows location for carburetor outlet 31, 1st path to cylinder 61
and 2nd path to cylinder 62. The first path to cylinder 61 connects to the first path of intake pipe 32 & the second path to cylinder 62 connects to the second path of intake pipe 33. In yet another embodiment of the current invention, a relief 64 is made in the intake pipe sealing face 35 to create an extended mixing region 63.

We claim:
1. A fuel intake system for an internal combustion engine (4) comprising:
a nonlinear intake pipe (24) with two ends namely a first end and a second end; said intake pipe (24) being equipped with a partition wall (341) which divides said intake pipe (24) into two paths namely a first path (32) and a second path (33);
a carburetor (21); wherein said first end of said intake pipe (24) is mated to
the outlet of said carburetor (21) which is further equipped with a partition.
wall(34C); . -
a cylinder head (22) which is equipped with two independent ports separated by a partition wall; wherein said second end of said intake pipe (24) is mated to said cylinder head (22);
wherein the partition wall portion (341) belonging to said intake pipe (24), the portion (34C) belonging to said carburetor (21) and the partition in said cylinder head (22) are in tandem and said intake pipe (24) being provided with a mixing region (63) through at least one relief provided in said partition wall (34).

2. The fuel intake system for the internal combustion engine (4) as claimed in Claim 1 wherein the relief is formed in the intake pipe sealing face (35) to create extended mixing region (63).
3. The fuel intake system for the internal combustion engine (4) as claimed in Claim 1 wherein the mixing region (63) is formed in a linear intake pipe.