FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
A Novel Twin Cylinder Multipoint Sequential Injection Gas Engine
APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Mr. Dattatraya R. Katkar and Mr. Deepak S. Kulkarni,
both Indian Nationals of TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in
which it is to be performed

FIELD OF INVENTION
This invention relates to Internal Combustion engines (I C engine) and more particularly this relates to twin cylinder multipoint sequential injection gas engine.
BACKGROUND OF THE INVENTION
Use of Natural gas has been an aspiration for automobile industry for a considerable amount of time. The drivers for use of natural gas engines are (i) Environmental aspects (ii) shift to non-conventional fuel (iii) operating economics. Yet another positive aspect of use of natural gas as a fuel in engines is that, it can be produced from Biomass. This has a great significance in Indian context. Currently, automotive engines are adapted to run on natural gas by either of the following two methods:
i) Existing base gasoline engines are made to run on natural gas with no or
cosmetic modifications and add on systems, and
ii) Modifying existing diesel engines with variable degree of design changes to
modify engine components.
Considerable amount of work has been carried out in this field in terms of strategies for conversion of diesel engines to spark ignited natural gas engines. It is worthwhile to note that, most of these patents deal with conversion of a heavy duty D.I. diesel engine into C.N.G. The outcome of design process is disclosed herewith.
US 5,315,981 teaches a method of converting a diesel engine to natural gas fueled engine through following steps -


Cam profiles on the camshaft are modified for valve overlap. Modifications of
cylinder head to adapt spark plugs. Adaptation of natural gas fuel intake system.
Using blower for supplying intake air under pressure. Using an after cooler for
cooling pressurized intake air prior to entering into the engine.
US 6,910, 269 teaches a method of converting a diesel engine into natural gas
fueled engine. The method comprises of following steps -
Inserting a spark plug into diesel fuel injector that opens in to the cylinder head.
Installing a throttle body on diesel engine.
Installing a throttle body adapter between intake manifold and throttle body.
Modifying the piston to reduce the compression ratio. Installation of waste gate,
waste gate adapter and timing mask.
US 5,664,535 teaches the modifications required for converting diesel engine into
a gas engine. These modifications are -
Piston modifications - The hollow in the piston is enlarged in diameter and depth
to a ratio of 30: 11 . This also reduces the compression ratio to 10: 1. Piston top
portion is beveled to take care of extra expansion that occurs on account of extra
gas temperature. The modified piston geometry gives optimum performance in
terms of heat extraction.
The exhaust system is split into two parts, each of which consists of an exhaust
branch piece and a catalyser. The air intake system is made smaller thus reducing
the possibility of backfire.
Apart from the heavy duty diesel engines it is also required to convert small
capacity diesel engines in to C.N.G. which may be D.I. or I.D.I. . The approach
and methods used for conversion of heavy duty engines can not be applied as it
is for small engine conversion.

At this juncture it is vary essential to differentiate the meaning of terms from engine point of view-(i) Conversion and (ii) Design.
Conversion means modifying existing parts, components and assemblies of the engine , primarily intended for one purpose ( end use or application ) to suit another intended purpose keeping existing parts as base. Conversion always leads to a compromise in end performance.
Design of an engine for a particular fuel and, / or application means finalizing critical components, their features, dimensions etc. in such a way the optimum intended performance is achieved.
In order to overcome the above mentioned drawbacks this invention is devised.
OBJECTS OF INVENTION
The main object of this invention is to provide a twin cylinder sequential multipoint gas injection natural gas engine.
Yet another object of this invention is to provide a twin cylinder sequential multipoint gas injection natural gas engine which is able to give the optimum performance
Yet another object of this invention is to provide a twin cylinder sequential multipoint gas injection natural gas engine with combustion chamber which can work with high compression ratio.


Yet another object of this invention is to provide a twin cylinder sequential multipoint gas injection natural gas engine with minimum friction between its various components.
Yet another object of this invention is to provide a twin cylinder sequential multipoint gas injection natural gas engine with intake and exhaust ports and inlet and exhaust manifolds provided on either side of cylinder head.
Yet another object of this invention is to provide a twin cylinder sequential multipoint gas injection natural gas engine which is simple in construction and cost effective.
STATEMENT OF INVENTION
The novel twin cylinder multipoint sequential injection gas engine comprises of Crank train with its housing, combustion chamber, valve train and its housing, manifolds and flywheel, wherein said crank train housing houses crankshaft at its bottom, pistons with rings are connected to the crankshaft by a connecting rod, flywheel having sensor teeth is mounted on one end of said crankshaft, said combustion chamber is provided in the cylinder head, intake and exhaust ports are provided on opposite sides of said cylinder head, intake and exhaust manifolds are connected to said intake and exhaust ports respectively, at least two spark plugs are provided on cylinder head.
BRIEF DESCRIPTION OF INVENTION
The novel twin cylinder sequential multipoint gas injection engine in accordance with this invention basically comprises of crank train with its housing, combustion


chamber, valve train and its housing, manifolds and flywheel, said crank train primarily comprises of crankshaft connecting rod, piston with piston rings. Said valve train comprises of cam shaft, rocker arm and inlet and exhaust valves. Said valve train housing comprises cylinder head, inlet and exhaust ports and combustion chamber.
Wherein said crank train housing houses crankshaft at its bottom. Piston with rings is connected to the crankshaft by a connecting rod. Flywheel with low inertia having sensor teeth is mounted on the crankshaft end.
Combustion chamber is provided in the cylinder head. Intake and exhaust valves are actuated by an overhead camshaft through rocker arms. Intake and exhaust ports are provided on the opposite sides of the cylinder head. Intake and exhaust manifolds connect ports to intake and exhaust system respectively. Spark plugs are provided on the intake side of the cylinder head.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 shows an assembly of novel twin cylinder sequential multipoint gas
injection engine.
Fig. 2 show connecting rod used in this invention
Fig. 3 shows piston along with piston rings used in this invention
Fig. 4 shows an isometric view of the combustion system used in this invention.
Fig 5 shows an isometric view of the intake manifold used in this invention.
fig. 6 shows the isometric view of exhaust manifold used in this invention.
Fig. 7 shows an arrangement of the intake and exhaust manifolds mounted on the
cylinder head.
Fig. 8 shows low inertia flywheel used in this invention.


Fig. 9 shows camshaft gear with sensor ring used in this invention.
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same
Referring to figs 1 to 9,
The novel twin cylinder sequential multipoint gas injection engine (11)in accordance with this invention basically comprises of Crank train with its housing (12), Combustion chamber (42), Valve train and its housing, Manifolds (51,61) and Flywheel(81), said crank train primarily comprises of crankshaft connecting rod(21), Piston (31)with piston rings (33). Said valve train comprises Cam shaft, rocker arm and inlet and exhaust valves. Said valve train housing comprises of cylinder head (41), inlet and exhaust ports and combustion chamber (42).
Wherein said crank train housing houses crankshaft at its bottom. Piston with rings is connected to the crankshaft by a connecting rod. Flywheel with low inertia having sensor teeth (82) is mounted on the crankshaft end.
Combustion chamber is provided in the cylinder head. Intake and exhaust valves are actuated by an overhead camshaft through rocker arms. Intake and exhaust ports are provided on the opposite sides of the cylinder head. Intake and exhaust manifolds connect ports to intake and exhaust system respectively. Spark plugs are provided on the intake side of the cylinder head.


The small end (22) diameter of said connecting rod (21)is optimized for the
combustion pressure encountered during operation with natural gas. Sufficient
centre distance between the small end (22) and big end (23) of said connecting
rod (21) is provided so that the top surface of the piston is shifted upward further
in order to achieve higher compression ratio which is a prime requirement for
gas engine. Connecting rod is optimized based on peak firing pressure for natural gas.
Said pistons (31) are provided with flat surface (32) at top in order to have lowest
possible combustion chamber volume. The oil ring (33) is optimized for
combustion pressures encountered during natural gas application. Use of
optimized components results in reduction in inertia of moving parts.
Said intake manifold (51) and exhaust manifold (61) are provided on opposite
side of said cylinder head (41) , this results in neat layout and sufficient space
for providing smooth intake runners. This layout also results in minimum heat
transfer from hot exhaust to fresh inlet air charge.
The compression ratio of the engine is increased by reducing the combustion
chamber volume, elevating the piston top surface achieved due to increased
centre distance connecting rod and due to use of flat top pistons. The higher
compression ratio also results in lower valve to piston top clearance. The trade
off is achieved considering valve to piston clearance and diminishing gain
in performance improvement for each incremental unit increase in compression ratio.
The cam shaft is designed for valve overlap and use of roller rocker. The valve
train spring force is optimized to improve valve train friction based on below
mentioned criteria's


i) Cut off speed , valve train is safe if speed of engine is above the cut off
ii) Operating speed range. High chrome alloy steel valves and valve seat material is specially selected for natural gas application considering fuel properties and operating conditions. This material also reduces wear and increase strength at high temperatures encountered during engine operation.
Inlet manifold (51) of the novel engine has curvilinear surfaces to have smooth flow tangential to the ports. The inlet manifold has a provision for mounting combined temperature and pressure sensor (54). Twin cylinder multipoint sequential gas injection engine assembly having uneven firing order poses major difficulties on account of pulsating flow. The manifold air pressure sensor is mounted in such a way that the effect of pulsating flow is minimum. The entry of intake manifold (55) is made in such a way that it the throttle body can directly mounted on the manifold thus eliminating the need of an adapter. Injectors (52) are mounted on the inlet manifold in such a way that , the gas under designed system pressure expands in front of inlet valve and provides the cooling effect. The injectors are fixed on the inlet manifold with the help of fuel rail (53). Exhaust manifold (61) of the novel twin cylinder sequential multipoint gas injection engine assembly is provided in such a way that the exhaust flow is smooth. Exhaust manifold (61) is provided with a provision (62) to mount exhaust gas oxygen sensor. The exhaust manifold is made up of alloy cast iron containing molybdenum so that it can withstand high temperature.
The layout of intake and exhaust manifolds is such that there is minimum heat transfer to the fresh inlet charge.


Sensor plate ( 92) is bolted to Camshaft gear (91). Cam sensor is essential to for adapting non wasted spark type of ignition system. The present design of novel to twin cylinder multipoint sequential gas injection engine assembly is provided with the features such that it can adapt to full fledge natural gas Engine Management System. However, the lower level systems can also be adapted on this engine.
The novel twin cylinder multipoint sequential injection gas engine wherein said crank shaft is provided with 180 degree firing separation and said cam shaft is provided with respective orientation of cam lobes to have un even firing. The other configuration is with 360 degree firing separation for crankshaft and said cam shaft is provided with respective orientation of cam lobes to have even firing.
Twin cylinder engine poses a unique design challenges in either of the above configurations . These are -
a) Intake manifold pulsating flow
b) High crankcase pressure
These design challenges are addressed by suitably designing intake system, locating TMAP sensor and by providing adequate crankcase volumes. The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.


WE CLAIM
1 The novel twin cylinder multipoint sequential injection gas engine comprises of Crank train with its housing, Combustion chamber, Valve train and its housing, Manifolds and Flywheel, wherein said crank train housing houses crankshaft at its bottom, pistons with rings are connected to the crankshaft by a connecting rod, flywheel having sensor teeth is mounted on one end of said crankshaft, said combustion chamber is provided in the cylinder head, intake and exhaust ports are provided on opposite sides of said cylinder head, intake and exhaust manifolds are connected to said intake and exhaust ports respectively, at least two spark plugs are provided on cylinder head.
2 The novel twin cylinder multipoint sequential injection gas engine as claimed in claim 1 wherein said valve train comprises Cam shaft, rocker arm and inlet and exhaust valves.
3 The novel twin cylinder multipoint sequential injection gas engine as claimed in claims 1 and 2 wherein sufficient centre distance between the small end and big end of said connecting rod is provided so that the top surface of the piston is shifted upward further in order to achieve higher compression ratio.
4 The novel twin cylinder multipoint sequential injection gas engine as claimed in claims 1 to 3 wherein said pistons are provided with flat surface at top in order to have lowest possible combustion chamber volume.
5 The novel twin cylinder multipoint sequential injection gas engine as claimed in claims 1 to 4 wherein said cam shaft is overhead camshaft and is provided in cylinder head to actuate intake and exhaust valves through rocker arms.


6 The novel twin cylinder multipoint sequential injection gas engine as claimed in claims 1 to 5 wherein said crank shaft is provided with 180 degree firing separation and said cam shaft is provided with respective orientation of cam lobes to have un even firing.
7 The novel twin cylinder multipoint sequential injection gas engine as claimed in claims 1 to 5 wherein said crank shaft is provided with 360 degree firing separation and said cam shaft is provided with respective orientation of cam lobes to have even firing.
8 The novel twin cylinder multipoint sequential injection gas engine as claimed in claims 1 to 7 wherein said gas is either natural gas or LPG.
9 The novel twin cylinder multipoint sequential injection gas engine as claimed in claims 1 to 8 having a provision to mount gas engine management system for automotive application.
10 The novel twin cylinder multipoint sequential injection gas engine substantially as herein described with reference to accompanying drawings.




ABSTRACT
A Novel Twin Cylinder Multipoint Sequential Injection Gas Engine
This invention related to novel twin cylinder sequential multipoint gas injection engine which comprises of Crank train with its housing , Combustion chamber, Valve train and its housing, Manifolds and Flywheel, said crank train primarily comprises of crankshaft connecting rod, Piston with piston rings. Said valve train comprises Cam shaft, rocker arm and inlet and exhaust valves. Said valve train housing comprises cylinder head, inlet and exhaust ports and combustion chamber. Wherein said crank train housing houses crankshaft at its bottom. Piston with rings is connected to the crankshaft by a connecting rod. Flywheel with low inertia having sensor teeth is mounted on the crankshaft end. Combustion chamber is provided in the cylinder head. Intake and exhaust valves are actuated by an overhead camshaft through rocker arms. Intake and exhaust ports are provided on the opposite sides of the cylinder head. Intake and exhaust manifolds connect ports to intake and exhaust system respectively. Spark plugs are provided on the intake side of the cylinder head.
Fig. 1