[0001] The present disclosure relates a fuel injection pump for an
internal combustion engine.
Background of the invention
[0002] Fuel injection pumps are both oil lubricated and fuel lubricated. The fuel pumps are connected to a roller tappet which makes plunger to reciprocate which in turn increases fuel pressure. For the functioning of fuel injection pumps, there should be continuous supply of lube oil to roller tappet when system is running. The oil used in the lubrication enters from the engine cylinder to components of roller tappet. The plunger drags the oil from the surface of the roller tappet and this gets mixed with fuel. The Oil in fuel leads to nozzle coking and higher emissions. Oil sticking to plunger should be reduced by coating the plunger which should be slippery. Oil lubricated Fuel injection pumps are with coating on the plunger to reduce the effect of oil in fuel.
[0002] Patent application US20160222959A1 "Pump with plunger
having tribological coating" discloses a pump having at least one pumping mechanism. The at least one pumping mechanism may include a barrel formed of a substrate having a bore and a plunger formed of a substrate and slidably disposed within the bore in the barrel. The pump may further include a coating disposed on the plunger. The coating may include a main

layer containing a tribological material and a sacrificial break-in layer disposed on the main layer, the break-in layer containing a tribological material.
Brief description of the accompanying drawings
[0003] An embodiment of the invention is described with
reference to the following accompanying drawings:
[0004] Figure 1 depicts a fuel injection pump (100) for an internal
combustion engine.
[0005] Figure 2 depicts the interface (200) between the fuel injection
pump (100), the roller tappet (109) and the engine cylinder (108).
Detailed description of the drawings
[0006] Figure 1 depicts a fuel injection pump (100) for internal combustion engine. The fuel injection pump (100) comprises a plate (101) abutted on to a roller tappet (109), a spring (102), a barrel (103) and at last a plunger (104). The plate (101) is biased against the spring (102). The spring (102) is attached to the barrel (103). One of the most important non-limiting feature of this invention is the barrel (103) and the plunger (104). The barrel (103) has a coating of Aluminum magnesium boride on its inner walls. The plunger (104) reciprocates within the barrel (103). The plunger (104) is coated with Aluminum magnesium boride on its outer walls.

[0006] In an embodiment the Aluminum magnesium boride coating
is applied only on the inner walls of the barrel (103) and not on the plunger (104). In another embodiment the Aluminum magnesium boride coating is applied only on the plunger (104) and not on the inner walls of the barrel (103). Aluminum magnesium boride coating can be applied using one of the many methods known in the art. One such method is Physical Vapor Deposition (PVD) using Aluminum Magnesium Boride as a target. Physical Vapor Deposition (PVD) is a technique where a high-power pulsed laser beam is focused inside a vacuum chamber to strike a target of the material that is to be deposited. This material is vaporized from the target which deposits it as a thin film on a substrate. Aluminum magnesium boride has a coefficient of friction of approximately 0.02 or even less.
[0007] Figure 2 depicts an interface (200) between engine cylinder
(108) and roller tappet (109) with fuel injection pump (100). Roller tappet components are Oil lubricated in few fuel injection pumps. Due to the clearance between the engine cylinder (108) and the roller tappet (109), some quantity of fuel gets leaked from the engine cylinder (108). The arrow (110) reflects the direction of oil drip, when it leaks through the clearance. This oil drips on to the surface of the roller tappet (109) and also drips upwards towards the barrel (103) of the fuel injection pump (100). The plunger (104) during its operative action drags this oil onto its

outer surface. Due to the presence of Aluminum magnesium boride coating on its outer surface, the oil instead of being further dragged upwards towards the outlet (106) of the fuel injection pump (100) falls down on to the surface of the roller tappet (109).
[0008] This Aluminum magnesium boride coating repels the oil
droplets on the surface of the plunger (104) and by the action of gravity the oil droplets end up falling on the surface of the roller tappet (109). Similarly oil particles that drip inside the barrel (103) are repelled by the Aluminum magnesium boride coating on the inner walls of the barrel (103). In absence of this oil repelling Aluminum magnesium boride coating, the oil particles during the operative movement of the plunger (104) get dragged upwards towards the outlet (106) of the fuel injection of the pump (100). The Aluminum magnesium boride coating on plunger (104) and the inner walls of the barrel (103) avoids this drag. Therefore it avoids the mixing of oil particles with fuel that is delivered to the other fuel injection components.
[0009] This idea to develop a fuel injection pump (100) for an
internal combustion engine is aimed at reducing the oil in fuel content. In absence of the coating on the plunger (104) or the barrel (103), the plunger (104) drags oil from the surface of the roller tappet (109) and this oil mixes with fuel that is delivered to the other fuel injection components. This content of oil in fuel damages fuel injection equipment's like the common rail and injector. Further oil in fuel also increases emissions from exhaust

pipe. Oil content in fuel is not properly burnt during the process of combustion and comes out of the exhaust gas pipe as black soot leading to unwanted emissions. Further applying Aluminum magnesium boride coating on the surface of plunger (104) also reduces the losses that occur due to friction as Aluminum magnesium boride has a coefficient of friction which is least amongst the known materials of the world.
[0010] It must be understood that the embodiments explained in the
above detailed description are only illustrative and do not limit the scope of this invention. Any modification to the fuel injection pump (100) for an internal combustion engine are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.

A fuel injection pump (100) for an internal combustion engine, the fuel injection pump (100) comprising a plate (101) abutted on to a roller tappet (109), the plate (101) biased against a spring (102), the spring (102) attached to a barrel (103), characterized in that fuel injection pump (100):
the barrel (103) having a coating of Aluminum magnesium
boride on its inner walls;
a plunger (104) reciprocating within the barrel (103), the
plunger (104) coated with Aluminum magnesium boride on
its outer walls.