WO2005042954A1

WO2005042954A1 - Improved internal combustion engine working on four stroke principle

Info

Publication number: WO2005042954A1
Application number: PCT/IN2003/000348
Authority: WO
Inventors: A. Joseph
Original assignee: Bajaj Auto Limited
Priority date: 2003-10-30
Filing date: 2003-10-30
Publication date: 2005-05-12
Also published as: BR0318568A; CN1878943A

Abstract

An improved Internal Combustion Engine for efficient burning of lean air fuel mixture used in engines working on four stroke principle. The said Internal Combustion Engine a pair of spark plugs (21, 22), a cylinder head (25), a sleeve (23), a pair of sealing means (24, 24a), a fixing means (26), sleeve cap (27), the said pair of spark plugs (21, 22) are fitted to the said cylinder head (25) to ignite air fuel mixture at predetermined instant; said spark plug (22) is housed within said sleeve (23), said sleeve is detachably fixed to said cylinder head (25) and held in position by said fixing means (26). The said sealing means (24, 24a) are provided between the said cylinder head (25) and the outer periphery of the said sleeve (23) and the said sleeve cap (27) is fitted on to said sleeve (23).

Description

IMPROVED INTERNAL COMBUSTION ENGING WORKING ON FOUR STROKE PRINCIPLE

This invention relates to improvement in the combustion characteristics of an internal combustion engine working on four stroke principle. This invention particularly relates to small displacement engines of cubic capacity ranging from 75 to 250 cc preferably 100 to 200 cc per cylinder employed as prime movers for operation of 2 and 3 wheeled vehicles. Internal combustion engine wherever referred to in this specification means and includes either single cylinder or its duplication thereof.

These engines are provided with two valves namely inlet valve and exhaust valve. These valves open in a cavity in the cylinder head conventionally known as combustion chamber. The valves are actuated by rocker arms. The actuation of the rocker arms is by a cam that is driven by the crankshaft through a timing chain and driving and driven sprockets. Such engines are provided with one spark plug. The spark plug is essential part of the engine that develops a spark inside the combustion chamber of cylinder head that ignites the air-fuel mixture and develops power. This type of arrangement is well known to the prior art and it is not essential to explain the . same in detail. The location of the spark plug inside the combustion chamber is in between the two valves and opposite to the location of the chain and driven sprocket arrangement. The utility of a spark plug in such engines is explained in greater details in the following paragraph.

The air fuel mixture commonly referred to as 'charge' is in the compressed condition at the near end of the compression stroke. This charge is in swirling and tumbling motion inside the combustion chamber so that when the spark produced by the spark plug ignites the charge, power is developed. Due to the swirling and tumbling motion, the flame inside the combustion chamber propagates in a desired manner and the peak of the developed power occurs at an instant as required by the design. In order to achieve optimum performance, the location of spark plug tip, velocity of the charge, the direction of swirl and tumble is some of the important parameters. There are various methods known to improve the engine performance by optimizing the combustion characteristics. Some of these are improved ignition timing, improved combustion chamber design, improved valve timing and valve angles etc.

One of the disadvantages associated with the arrangement explained above is that since there is only one spark plug the process of combustion from initiation of the spark to its completion takes a comparatively longer duration. At higher speeds in order to maintain the time for combustion, the spark timing has to be advanced which can lead to waste of energy.

A further disadvantage of the prior art is the need of a richer or more mixture of fuel and air in the charge to achieve better driveability.

Yet another disadvantage of the prior art is that the flame is not able to propagate adequately in the combustion chamber if the mixture is lean which results in inadequate power.

In order to avoid above difficulty and provide for improved combustion characteristics through rapid completion of the combustion even with a lean air fuel mixture, we have invented an engine wherein there are two spark plugs provided for generating sparks at two predetermined locations at the same time. These spark plugs are located in the cylinder head one on timing chain side and the other plug opposite to the timing chain side. Thus, the twin spark plug arrangement enables the engine to run efficiently which results in decreased emission, decreased fuel consumption and good driveability.

The cavity in which the timing chain is located opens in the crankcase that is filled with oil for lubrication of moving parts. The chain while driving the driven sprocket carries oil with it for lubrication and if the opening for spark plug is provided in this cavity the lubricating oil spreads over the spark plug and affects its function. In order to have the spark plug on the timing chain side and to prevent the above disadvantage we have further invented an arrangement wherein the plug is located on the same side of the timing chain by providing a removable sleeve, which encompasses the spark plug.

This arrangement will now be explained in detail with reference to drawings accompanying this Specification, wherein

Figure 1 shows the cross- section of the prior art engine with one spark plug.

Figure 2 shows the cross-section of the improved engine with two spark plugs.

The invented engine with improved combustion characteristics for efficient air fuel mixture burning, essentially comprises of a pair of spark plugs (21 and 22), sleeve (23), a pair of sealing means (24 and 24a), cylinder head (25), fixing means (26) and sleeve cap (27).

With reference to Figure 1, the spark plug (1) is located in the cylinder head (2) opposite to the timing chain (7) side. The spark plug (1) is fixed to the cylinder head (2) to reach in combustion chamber (3). The inlet (4) and exhaust (5) valves also open in the combustion chamber (3). The cylinder head (2) is having a cavity (6) through which the timing chain (7) drives the driven sprocket (8). The driven sprocket (8) further drives the cam shaft (9) which actuate the valves (4) and (5) through rocker arms (not shown). When the engine runs, the timing chain carries oil from the crankcase (not shown) for the lubrication of the driven sprocket (8) and the cavity (6) is splashed with oil. Any opening made on this side exposes the passage of the oil to outside and the oil starts leaking. When the charge is compressed at the end of the compression stroke in the combustion chamber (3), a spark is initiated by the spark plug (1), and the flame propagates from the tip (la) of the spark plug (1). The combustion of the charge takes place in the combustion chamber (3) to produce power. It is clear from the figure that the flame has to propagate from the tip (la) and ignite the entire mixture in the combustion chamber (3) that needs comparatively more time, particularly at higher speeds of the engine. This results in incomplete combustion and consequent loss of power, fuel wastage, and increase in emissions and poor part throttle efficiency.

With reference to Figure 2, the engine with improved combustion characteristics for lean air fuel mixture burning has two spark plugs (21 and 22) are fitted to the cylinder head (25). These spark plugs are located in the cylinder head (25) opposite to each other. One of the spark plugs (21) is located in the same location as in the prior art and the other spark plug (22) is located on the same side as the timing chain (7). The sleeve (23) is detachably fitted in the cylinder portion of the cylinder head (25). Between the outer periphery of the sleeve and the inner periphery of the cylinder portion, a pair of sealing means (24 and 24a) are provided. The sleeve (23) is retained in position by fixing means (26) and this arrangement is closed by a sleeve cap (27) snugly fitted on to the sleeve (23) with its other lip covering the opening in the cylinder head (25), which provides protection from entry of dust, water etc. The sleeve cap (27) is made of resilient materials such as nylon, PVC, rubber.

The energy for spark, in case of twin spark plug engine is provided through the similar system as single spark plug where the conventional components line H.T. coil, H.T. cable, etc. are provided in duplicate.

By providing two spark plugs, the initiation of the spark starts at two places, ie. tips (21a and 22a) in the combustion chamber. These places are opposite to each other. Due to this, the combustion is completed in a comparatively shorter duration of time leading to reduction in emission and improved fuel consumption while maintaining the desired level of performance. This reduced time of achieving near complete combustion permits use of less amount of fuel air mixture or lean mixture without affecting the performance for the same power output, especially at part throttle condition.

The applicants have developed 150 cc capacity engines with invented features of this application and the same has been evaluated. The table given below indicates the comparative test values of the engines with and without the invented feature. The emission, fuel consumption values are as tested with statutorily applicable Indian Driving Cycle on Chassis dynamometer.

Test results conducted on a 150 cc engine.

It can be concluded from the above test values that there is a significant reduction in CO emissions from 1 g/km to 0.6 g/km and HC emissions from 0.7 g/km to 0.5 g/km. There is significant increase in fuel efficiency from 55 km/litre to 62 km/litre. The advantages mentioned above are obtained along with an improvement in peak power of the engine. As can be seen from the figures, when the engine runs, the oil carried by the timing chain (3) when splashed, falls on the outer periphery of the sleeve (23) and leads its way back to the crankcase without being exposed to outside and causing leakage.

Usage of this sleeve (23) enables the use of a conventional closed type timing chain without any difficulty. Inner diameter of the sleeve (23) is so chosen that the spark plug can be removed with a spark plug spanner without any difficulty.

The description and the figures provided in this specification, indicate the location of spark plugs opposite to each other. However, depending upon the design requirements, it may be necessary to change the locations at predetermined angular positions.

It will be appreciated that the invented engine with improved combustion characteristics for efficient air fuel mixture burning as described and illustrated in the drawings, it would be within the knowledge of a person skilled in the art and such would not be deviating from the scope of the invention. The applicant intends to include those modifications and variations within the scope and the ambit of this invention.

Claims

CLAIMS:

1. An improved Internal Combustion Engine for efficient burning of lean air fuel mixture used in engines working on four stroke principle, characterized in that said Internal Combustion Engine comprising a pair of spark plugs (21 and 22), a cylinder head (25), a sleeve (23), a pair of sealing means (24 and 24a), a fixing means (26) and sleeve cap (27); the said pair of spark plugs (21 and 22) being fitted to the said cylinder head (25) to ignite air fuel mixture at predetermined instant; said spark plug (22) being housed within said sleeve (23), said sleeve (23) being detachably fixed to said cylinder head (25) and held in position by said fixing means (26), said sealing means (24 and 24a) being provided between the said cylinder head (25) and the outer periphery of the said sleeve (23) and the said sleeve cap (27) being fitted on to said sleeve (23).

2. An improved Internal Combustion Engine as claimed in Claim 1 wherein the said pair of spark plugs (21 and 22) are fitted opposite preferably diametrically to each other.

3. An improved Internal Combustion Engine as claimed in Claims 1 and 2 wherein the said fixing means (26) is a circlip or a screw.

4. An improved Internal Combustion Engine as claimed in Claims 1 and 2 wherein the said pair of sealing means (24 and 24a) is an O ring or an oil seal.

5. An improved Internal Combustion Engine as claimed in any of the preceding claims wherein the sleeve cap (27) is made of resilient material such as Nylon, PVC, rubber.

6. An improved Internal Combustion working on four stroke principle, characterized in that said Internal Combustion Engines comprising of a spark plug (22), a cylinder head (25), a sleeve (23), a pair of sealing means (24 and 24a), a fixing means (26) and sleeve cap (27); the said spark plug (22) being housed within said sleeve (23) and being fitted to the said cylinder head (25) on timing chain side (7) so as to provide spark at predetermined instant to ignite air fuel mixture; the said sleeve (23) being detachably fixed to said cylinder head (25) and held in position by said fixing means (26), the said pair of sealing means (24 and 24a) being provided between the said cylinder head (25) and the outer periphery of the said sleeve (23) and the said sleeve cap (27), made of resilient material such as Nylon, PVC_> rubber being fitted on said cylinder head (25).

7. A single cylinder Internal Combustion Engines with improved combustion characteristics for use in two or three wheeled vehicles working on four stroke principle as claimed in any one of the preceding claims and as described herein above and illustrated.

Dated this 27^th day of October 2003.