field of the invention

This invention relates to a fuel injection system.

Background of the invention

In a fuel injection pump a proper sealing is required for maintaining sufficient contact pressure between the components of the pump as the fuel passes from the inlet to the outlet. The contact pressure is set between the components of the pump by tightening the delivery valve holder to a torque that is required based on the contact pressure requirements.

The fuel Injection pump pressurizes the fuel received from the inlet to a pressure that is required to be delivered at the outlet. During working, the components of the pump are exposed to pressure fluctuations leading to micro movement between the sealing components that lead to wear and tear of the pump components over a prolonged period of time. This wear and tear is commonly called fretting wear and results is minor loss of material of pump components as they experience high pressure. Due to loss of material, a leakage path is created which leads to drop in pressure in fuel injection pump, thereby reducing the performance of the pump.

Hence there is a need to reduce wear and tear between the components of the pump.

Japanese Patent Application number JP2010174751 discloses a fuel feed pump for common-rail fuel-injection apparatus of vehicle. The fretting wear in the prior art is reduced by increasing the tightening torque which in turns increases the contact pressure in the sealing areas there by reducing the micro movement. However there is limit to which tightening torque can be applied in the fuel injection pump. Excessive use of tightening torque can damage the components of the pump.

object of the invention

It is an object of the invention to reduce wear and tear in the components of the fuel injection pump.

Advantages of the invention

The advantage of this invention as claimed in the independent claim is to reduce wear and tear between the components of the pump and to maintain sufficient contact pressure between the components of the pump.

Brief description of the accompanying drawings

Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawings:

Figure 1 illustrates a fuel injection pump in accordance with the present invention.

Detailed description of the embodiments

Figure 1 illustrates a fuel injection pump 100 in accordance with the present invention. The fuel injection pump 100 comprises a housing 101 an inlet valve body 102, and a hollow passage 103 for accommodating a plunger 104. The plunger 104 is adapted to reciprocate in the hollow passage 103 by means of a roller tappet and a cam. One end of the hollow passage 103 opens into and interfaces with the inlet valve body 102.

In the fuel injection pump 100 the cam is rotated by a drive shaft. As the cam rotates, a roller tappet follows the cam and converts rotary motion of the cam into linear motion of the plunger 104. The pressure is built up in the fuel injection pump 100 as plunger 104 moves upwards within the housing 101. The traverse of the plunger 104 within the housing 101 for a single upward and downward movement is stroke of the plunger 104. The fuel that is received from the inlet is pressurized by the plunger 104. The fuel at high pressure may hen be delivered to the cylinders through an injector or delivered to a rail used in a common-rail fuel injection system.

In the fuel injection pump 100 a proper amount of sealing is required to maintain requisite pressure within the pump 100, and to prevent drop in pressure within the housing 101. The main sealing surface is between the inlet valve body 102 and the housing 101. The other sealing surfaces being between the outlet valve body and the inlet valve body 102, and between the outlet valve body and the delivery valve. Sealing in a fuel injection pump 100 is generally achieved by tightening the delivery valve holder to a specified torque. This torque is then transferred to the sealing surfaces. The inlet valve body 102 and the housing 101 are made of different materials; as a result fretting wear is experienced at the interface between the inlet valve body 102 and the housing 101. The fretting wear leads to wear and tear of materials over a period of time, and this causes the pressurized fuel to enter back into the inlet valve body 102 leading to a loss in pump efficiency.

To prevent fretting wear a step 105 is provided at the interface between one end of the hollow passage 103 and the inlet valve body 102. The profile of the inlet valve body 102 is complementary to the step 105. The step 105 results in clearance between the housing 101 and the inlet valve body 102. The clearance thus introduces a leakage path that reduces the frictional contact between the inlet valve body 102 and the plunger 104 thereby reducing the frictional force in the sealing areas that in turn reduces the fretting wear of the pump components. The life of the pump 100 components can be enhanced by the introduction of step 105. The step so provided, may also be implemented in the other sealing surfaces, namely between the outlet valve body and the inlet valve body 102, and between the outlet valve body and the delivery valve.

It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.

WE CLAIM:

1. A fuel injection pump (100), comprising.

a housing (101); an inlet valve body (102) located in said housing (101);

a hollow passage (103) for accommodating a plunger (104), one end of said hollow passage (103) opening into and interfacing with said inlet valve body (102).

characterized in that a step (105) provided at said interface between said one end of said hollow passage (103) and said inlet valve body (102).

2. The fuel injection pump (100) of claim 1, wherein the profile of said inlet valve body (102) is complementary to said step (105).

3. The fuel injection pump (100) of claim 1, said step (105) results in clearance between said housing (101) and said inlet valve body (102).