FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE
Specification
(See section 10 and rule 13)
AN IMPROVED FUEL PUMP OPERATING MECHANISM FOR A
DIESEL ENGINE AND A DIESEL ENGINE COMPRISING THE
SAME HAVING IMPROVED EMISSION CHARACTERISTICS
KIRLOSKAR OIL ENGINES LTD.
an Indian Company
of Laxmanrao Kirloskar Road, Khadki, Pune 411003,
Maharashtra, India.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH JT IS TO BE PERFORMED.

Field of invention:
This invention relates to an improved fuel pump operating mechanism for a
Diesel engine and a diesel engine comprising the same having improved
emission characteristics.
Definitions:
As used in this specification the following words are generally intended to
have a meaning as set forth below, except to the extent that the context in
which they are used indicate otherwise.
'Cam' means a projecting part of a rotating wheel or shaft that strikes a lever
at one or more points on its circular path. The cam may be a simple tooth or
an eccentric disc or other shape that produces a smooth oscillating motion in
a lever.
'Camshaft' means a shaft, which drives cams that are circumferentially fitted
to the camshaft.
'Circumferential' means roughly round or approximately round may also be
elliptical.
'Crank' means a device, which converts reciprocating motion from a source
into rotary motion.
'Crankshaft' means a shaft, which transfers the rotary motion of a crank to a
transmission system.
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Top Dead Centre: In piston engines, the post piston tewl nearest
to the cylinder head and farthest from the crankshaft is known as Top Dead
Centre' (TDC).
'Bottom Dead Centre: In piston engines, the position of the piston head
nearest to the crankshaft and farthest from the cylinder is known as 'Bottom
Dead Centre' (BDC).
Introduction:
In a diesel engine that works on a 4-stroke cycle an as drawn inside the
cylinder due to the motion of the piston, from one end to the other, in the
cylinder. These ends are termed as 'top dead center (TDC)' and 'bottom
dead center (BDC)". Air comes in through a passage in the cylinder head,
generally called as "inlet port" that has a valve at one of its opening at the
cylinder end. This valve is opened at a particular moment during the cycle
and air is admitted into the cylinder-head, this is called the 'suction stroke'
out of the 4-stroke cycle. Further this air is compressed in the next stroke
called as 'compression stroke' due to the motion of the piston from BDC to
TDC. The air gets compressed upto such an extent that temperature of air
rises resulting in spontaneous igniting of the fine droplets, of dieset sprayed
at the end of the compression stroke. These fine droplets are mixed
intimately with the air in the cylinder. Ignition causes violent explosion,
which expands the air and fuel gases resulting ifi motion of the piston from
TDC to BDC, which is called the 'expansion/power stroke' The burnt gases
are then expelled out of the cylinder during the next stroke, called 'exhaust
stroke' during which the piston moves from BDC to TDC, For expelling the
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burnt gases, there is another passage in the cylinder head called as the
'exhaust port', which also has a valve similar to the inlet valve and opens at
a particular moment during the above cycle. The reciprocating motion of the
piston during repetitive and sequential suction, compression, expansion and
exhaust strokes (called as 4-stroke cycle) causes rotation of a crankshaft due
to its connection to the piston by a 'connecting rod1.
In diesel engines the inlet and exhaust ports act as pathway for admitting
fresh air and removing exhaust gases respectively. The design of these ports
has a large effect on the economy and performance of the engine. Two
dimensionless numbers namely 'swirl number and 'flow coefficient' play a
dominant role in engine design, thermodynamic performance and exhaust
emissions. Swirl number relates to the rotation of the fluid in the cylinder
and the flow coefficient is a measure of the pressure loss introduced by the
port/valve combination.
Swirl number is defined as the ratio of the anemometer speed measured by
the stationary flow test and fictitious engine speeds obtained by equating the
mean axial flow velocity to mean piston speed. The swirl number represents
airflow patterns. Swirl number is optimized based on the engine size. The
swirl improves air and fuel mixing which results in efficient combustion in
turn resulting into reduction in exhaust emissions like smoke and particulate
matter.
Flow co-efficient is the ratio of actual flow rate at a certain pressure drop
through a known cross-section to the theoretical mass flow rate at equal
pressure drop through a reference cross-section. Flow coefficient improves
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breathing of the engine and hence improves air to fuel ratio, which reduces
emissions like NOx, HC and CO.
Emission of various types of gases is an important consideration for the
purpose of engine design. It is a mandatory requirement that engine should
meet the national and international emission requirements. Hence it is
necessary that engine components be designed in a manner such that the
emission is below the prescribed limit.
Prior Art:
Figure 1 illustrates a side view of the conventional prior art fuel pump
operating mechanism for a diesel engine and Figure 1A is a top plan view of
the components of figure 1. In figure 1 and figure 1A a lever (13) is used for
operating the fuel pump in cooperation with a cam (12) having a rotating
center (II), which slides on a cam follower (16) of the lever (13). A plunger
(14), which moves up and down, drives the fuel pump and acts on the lever
(13) at the fulcrum point (15). In a diesel engine that works on a 4-stroke
cycle, the spontaneous igniting of fine droplets of diesel sprayed at the end
of the compression stroke is very crucial for low exhaust emission along
with other performance parameters like fuel consumption etc. These fine
droplets need to get mixed intimately with the air in the cylinder. One of the
important features that affect this mixing is the quickness at which the diesel
is pumped into the system. The fuel pump is driven by a camshaft rotating at
a required speed. The camshaft has cam lobes at different locations. The cam
lobe lifts the plunger (14) of the fuel pump through the lever (13). One end
of lever (13) is in contact with the cam (12), and the other end has contact, at
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a fulcrum point (15), with the plunger (14) that drives the fuel pump. The
contact of the lever (13) at the cam side is a sliding type contact. This sliding
contact offers larger friction which gives rise to frictional loses, and diesel
fuel is not quickly pumped into the fuel supply system/cylinder of the diesel
engine, resulting into improper mixing of fuel with air and incomplete
combustion producing higher amount of pollutants in the exhaust emissions.
As such as a limitation of the prior art diesel engines is that the emissions
from the engines are not acceptable.
The main object of this invention is to overcome the said limitation of
the prior art diesel engines and to provide an improved fuel pump operating
mechanism in which the lever operating the fuel pump is modified to have
rolling contact at the cam side to minimize the friction and reducing the
frictional losses so that diesel is pumped very quickly into the system for
proper mixing with air, resulting into complete combustion and low
pollutants in the exhaust emissions, bringing the emissions from the diesel
engines, in acceptable norms.
Brief description of the accompanying drawings:
The invention will be described in detail with reference to a preferred
embodiment. Reference to this embodiment does not limit the scope of the
invention.
In the accompanying drawings:
Figure 1 illustrates a side elevational view of the conventional prior art fuel
pump operating lever component for a diesel engine;
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Figure 1A is a top plan view of the component of figure 1;
Figure 2 illustrates a side elevational view of an improved fuel pump
operating mechanism in accordance with this invention;
Figure 2A is a top plan view of the component of figure 2;
Figure 3 illustrates a tabulated emission report of a water-cooled engine for
an engine incorporating a fuel pump operating lever component known in
the prior art;
Figure 4 illustrates a tabulated emission report of a water-cooled engine for
an engine incorporating a fuel pump operating mechanism in accordance
with this invention;
Figure 5 illustrates a tabulated emission report of an air-cooled engine for an
engine incorporating fuel pump a operating lever component known in the
prior art; and
Figure 6 illustrates a tabulated emission report of an air-cooled engine for an
engine incorporating an improved fuel pump operating mechanism in
accordance with this invention.
Detailed description of the accompanying drawings:
The invention will now be explained with reference to Figures 2 to 6 of the
accompanying drawings.
Accordingly this invention provides
An improved fuel pump operating mechanism for diesel engines comprising
a lever, a roller provided at one end of said lever, a cam adapted to be
mounted on a cam shaft for rotating about its center at desired speed, said
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cam making a rolling point contact with said roller for minimizing the
friction, a fulcrum point provided at the other end of the said lever, a plunger
contacting said fulcrum point of the lever, moving up and down to drive the
fuel pump at a desired speed controlled by the cam rotation, to feed the fuel
quickly for spontaneous ignition and proper mixing with air to achieve diesel
engine emissions of acceptable norm.
Typically, the said lever is sleek with arcuate/rounded off contoures.
Typically, the fulcrum end of the lever is made pointed to reduce friction
between the fulcrum point and the plunger of the plunger of the fuel pump.
Typically, the said cam has a high velocity and high acceleration profile to
feed the fuel quickly in the system.
Typically, the said roller is adapted to with stand relatively higher operating
pressures.
Typically, the said roller follows the cam profile accurately.
Typically, the improved feed pump operating mechanism for diesel engines
substantially as herein described and illustrated in Figures 2 and 2A of the
drawings accompanying the specification.
Typically, the diesel engine incorporated with the improved fuel pump
operating mechanism as claimed in any of the claims 1 to 7.
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Now referring to Figures 2 and 2A, an improved fuel pump operating
mechanism according to an embodiment of this invention comprises a lever
(24) having a sleek design with all the contours curved and rounded off. The
lever (24) is provided with a roller (21) at one end, which remains, is contact
with the cam (23) rolling about its center (22). The cam (23) is adapted to be
mounted on the camshaft, which rotates at a desired speed for operating the
fuel pump. The cam lobe now have a point contact with the roller (21) of the
lever (24) and thus the frictional losses are minimized. The other end (26) of
the lever (24) forming fulcrum point is also now made pointed which
contacts the plunger (25) of the fuel pump. This pointed contact also further
reduces the frictional losses of the fuel pump driving/operating mechanism.
The improved lever (24) having rolling point contact with cam and also a
point contact with plunger, instead of sliding contacts in prior art, provides
desired quickness at which the diesel fuel is pumped into the system for
achieving better mixing with air and spontaneous ignition of fine droplets of
diesel sprayed in the combustion chamber resulting into complete
combustion with low pollutants emissions.
Further reduction in friction results in lower temperature and lower
lubrication requirements lesser wear and tear. As the roller (21) withstands
relatively high operating pressures cam (23) with a high velocity &
acceleration profile may be used. The roller (21) also has a better ability to
follow the cam (23) profile accurately.
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The diesel engine incorporated with improved fuel pump operating
mechanism according to this invention complies with the acceptance norms
for emissions/pollution control.
The diesel engine may also be incorporated with an improved piston having
off-set 're-entrant cavity' in the piston head, relieved skirt and 'keystone
ring' in the top groove, for better acceptance.
The diesel engine may also be incorporated with improved cylinder head
having helical inlet port and rectangular airport opening with inlet and outlet
ports placed opposite to each other, for better performance.
For the purpose of testing a test rig was set up to determine the smoke and
exhaust emissions for different types of water cooled and air cooled engines
as known in the prior and in accordance with this invention. Similar engines
were selected as known in the prior art and in accordance with this invention
with respect to bore x stroke values. Three representative engines of each
type having an inlet port of length 145mm were selected in the trials, all
engines were set up at a uniform speed of 1500 rpm, the following parameter
namely specific fuel consumption (SFC), exhaust temperature, rub oil
pressure and temperature, smoke and exhaust emissions were noted for all
the engines except that the volume of smoke generated was not checked for
engine of the prior art. The results were tabulated and are shown in figures 3
to 6 of the accompanying drawings. The specific fuel consumption for all
bore x stroke values was found to be consistently lower in engines in
accordance with the present invention as compared to engines known in the
prior art.
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The smoke generated in the exhaust emissions measured in BOSCH was
significantly lower in engines in accordance with the present invention as
compared to engines known in the prior art.
Similarly values of NOx, HC, CO and participate matter in the exhaust
emissions was found to be consistently and significantly lower in engines in
accordance with this invention as compared to engines known in the prior
art. These test results therefore confirm the adoption of the features of the
present invention, which on one hand improves the fuel consumption and
also concomitantly improves the quality of the emissions including smoke,
HC, CO, NOx and participate matter.
A diesel engine used for gensets, incorporating an operating lever
component in accordance with this invention was tested, the data tabulated
below was obtained as a result of the tests. The improvements achieved in
the emission levels are as below:

Parameter Unit % Improvement
(reduction in emission
parameter)
Nox gm/kW-hr 50 to 60
CO gm/kW-hr 60 to 63
HC gm/kW-hr 82 to 88
PM gm/kW-hr 76 to 80
Smoke Bosch No. 58 to 60
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While considerable emphasis has been placed herein on the structures and
structural interrelationships between the component parts of the preferred
embodiments, it will be appreciated that many embodiments can be made
and that many changes can be made in the preferred embodiments without
departing from the principles of the invention. These and other changes in
the preferred embodiment as well as other embodiments of the invention will
be apparent to those skilled in the art from the disclosure herein, whereby it
is to be distinctly understood that the foregoing descriptive matter is to be
interpreted merely as illustrative of the invention and not as a limitation.
We Claim:
1. An improved fuel pump operating mechanism for diesel engines
comprising a lever, a roller provided at one end of said lever, a cam
adapted to be mounted on a cam shaft for rotating about its center at
desired speed, said cam making a rolling point contact with said roller
for minimizing the friction, a fulcrum point provided at the other end
of the said lever, a plunger contacting said fulcrum point of the lever,
moving up and down to drive the fuel pump at a desired speed
controlled by the cam rotation, to feed the fuel quickly for
spontaneous ignition and proper mixing with air to achieve diesel
engine emissions of acceptable norm.
2. The mechanism according to claim 1, in which the said lever is sleek
with arcuate/rounded off contoures.
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3. The mechanism, according to claim 1, in which the fulcrum end of the
lever is made pointed to reduce friction between the fulcrum point and
the plunger of the plunger of the fuel pump.
4. The mechanism, according to claim 1, in which the said cam has a
high velocity and high acceleration profile to feed the fuel quickly in
the system.
5. The mechanism, according to claim 1, in which the said roller is
adapted to with stand relatively higher operating pressures.
6. The mechanism, according to claim 1, in which the said roller follows
the cam profile accurately.
7. An improved feed pump operating mechanism for dieseJ engines
substantially as herein described and illustrated in Figures 2 and 2A of
the drawings accompanying the specification.
8. A diesel engine incorporated with the improved fuel pump operating
mechanism as claimed in any of the claims I to 7.
13
Dated this 3rd day of April, 2006.