CN114109681A

CN114109681A - Fuel injection pump

Info

Publication number: CN114109681A
Application number: CN202111003264.9A
Authority: CN
Inventors: V·苏尼尔库马尔
Original assignee: Robert Bosch GmbH; Bosch Ltd
Current assignee: Robert Bosch GmbH; Bosch Ltd
Priority date: 2020-08-31
Filing date: 2021-08-30
Publication date: 2022-03-01

Abstract

The present invention relates to a fuel injection pump. The present disclosure presents a fuel injection pump (100). The fuel injection pump (100) comprises a low pressure inlet valve (102) and at least one high pressure outlet valve (103). The low pressure inlet valve (102) has a ball (1021) that rests on a low pressure valve seat. The high pressure outlet valve (103) has another ball (1021) that rests on a high pressure valve seat. The fuel pump features a valve seat (1022) having a diamond-like carbon (DLC) coating. In a first embodiment of the invention, the low pressure valve seat (1022) has a diamond-like carbon (DLC) coating. In a second embodiment of the invention, the high pressure valve seat (1022) has a diamond-like carbon (DLC) coating. In a third embodiment of the invention, both the low pressure valve seat (1022) and the high pressure valve seat (1022) have a diamond-like carbon (DLC) coating.

Description

Fuel injection pump

Technical Field

The present disclosure relates to a fuel injection pump for an internal combustion engine. More particularly, it relates to a diesel fuel injection pump with an external drive, known as a PF (pump mit fremdentieb) pump, i.e. the cam driving the pump is a separate part and not part of the pump.

Background

A diesel fuel injection pump with an external actuator is called pf (pumpen mit fremdrintrie) pump, i.e. the cam driving the pump is a separate part and not part of the pump. Most PF pumps are of the single cylinder type. PF pumps are commonly referred to as single cylinder pumps, although there are few multiple cylinder pumps. The operating principle of these pumps is that the spring force balances the force due to the fuel pressure. These forces act on a ball located on a valve seat of the fuel injection pump.

Patent application US20030131473a1 discloses a pre-hardened valve seat insert and a process for forming a pre-hardened valve seat insert for insertion into a cylinder head or engine block of an internal combustion engine. The process comprises the following steps: (a) forming a valve seat insert; (b) precision machining the valve seat insert to precise tolerances such that the valve seat insert can be installed in one of the cylinder head and the engine block without additional valve seat machining; and (c) treating the valve seat insert to form a wear resistant surface layer prior to inserting the valve seat insert into one of the cylinder head and the engine block.

Drawings

Embodiments of the invention are described with reference to the following drawings:

FIG. 1 depicts a fuel injection pump (100);

FIG. 2 depicts a valve seat (1022) inside the fuel injection pump (100); and

fig. 3 analyzes the force acting on the ball (1021) of the low pressure inlet valve (102) of the fuel injection pump (100).

Detailed Description

Fig. 1 depicts a fuel injection pump (100). The fuel injection pump (100) is part of a fuel supply line of an internal combustion engine, which comprises other components, such as a fuel tank, a fuel filter common rail, etc. The fuel injection pump (100) comprises a low pressure inlet valve (102) and at least one high pressure outlet valve (103) among other components known to those skilled in the art, such as a plunger (105) reciprocating in a barrel, a fuel inlet, a fuel outlet, and a spring (106) plate abutting the barrel. The low pressure inlet valve (102) is in fluid communication with an inlet (101) of the fuel pump. The low pressure inlet valve (102) has a ball (1021) that rests on a low pressure valve seat. In an embodiment of the present disclosure, this ball (1021) placed on the low pressure valve seat (1022) is a ceramic ball (1021).

The high pressure outlet valve (103) is in fluid communication with an outlet (104) of the fuel pump. The high pressure outlet valve (103) has another ball (1021) that rests on a high pressure valve seat. Fig. 2 depicts a valve seat (1022) inside the fuel injection pump (100). The fuel pump features a valve seat (1022) having a diamond-like carbon (DLC) coating. DLC coatings are coatings of amorphous hydrocarbons (a-C: H) which are well suited for low lubricant formation of metals. DLC coatings provide significantly higher wear resistance. They have a low coefficient of friction, i.e. approximately 0.1 under standard conditions of unlubrication.

In a first embodiment of the invention, the low pressure valve seat (1022) has a diamond-like carbon (DLC) coating. In a second embodiment of the invention, the high pressure valve seat (1022) has a diamond-like carbon (DLC) coating. In a third embodiment of the invention, both the low pressure valve seat (1022) and the high pressure valve seat (1022) have a diamond-like carbon (DLC) coating.

In an operating configuration of the fuel injection pump (100), fuel enters through the inlet and fills a gallery (gallery) around the low pressure inlet valve (102). Once the force due to this fuel is greater than the spring (106) force acting on the inlet valve (102), the ball (1021) (conventionally the ceramic ball (1021)) rises and fuel is fed down into the element chamber with the plunger (105). The plunger (105) is raised, and moving the plunger (105) causes fuel to be pressurized in the element chamber. The fuel rises through a path provided in the body of the inlet valve (102) and fills the area below the high pressure outlet valve (103). When the force due to this pressurized fuel is greater than the force acting on the outlet valve (103), the ball (1021) (conventionally, steel ball (1021)) in the outlet valve (103) lifts and fuel flows into the common rail due to the pressure from the common rail and spring (106). Excess fuel is returned to the fuel tank in the low-pressure circuit of the internal combustion engine via the overflow connection.

Fig. 3 illustrates a free body diagram of the forces acting on the ball (1021) of the low-pressure inlet valve (102) of the fuel injection pump (100). The forces depicted in the figures are listed below:

f: spring (106) force due to compression

a: angle of spring (106) force action due to bias

N: normal reaction force

μ: coefficient of friction

Fa: component of F along the x-axis

Fb: component of F along the y-axis

Phi: 90-valve cone angle/2.

Parameters such as "a" (the angle at which the spring (106) acts due to biasing), μ (coefficient of friction), and Φ (90-valve cone angle/2) affect seal loss. If Fa > μ N when the ball (1021) is in the lifted state, the ball (1021) will return to its sealing position. In case a Diamond Like Carbon (DLC) coating is used, this μ value is reduced, whereby μ N will be much lower than Fa, which ultimately ensures a better sealing and reduces sealing losses.

This concept of developing a fuel injection pump (100) with the coating on the valve seat (1022) improves quality and reduces complaints about unwanted (non-start) capabilities. Further, the coated valve seat has improved service life due to its higher wear resistance. In addition, there is a reasonable cost reduction because the ceramic balls (1021) at the inlet can be replaced with steel balls (1021) due to the use of such low friction coatings. Diamond Like Carbon (DLC) coatings improve wear resistance and robustness against particles.

It must be understood that the embodiments explained in the above detailed description are illustrative only and do not limit the scope of the present invention. Any modification of the fuel injection pump (100) is contemplated and forms part of the present invention. The scope of the invention is limited only by the claims.

Claims

1. A fuel injection pump (100) for an internal combustion engine, the fuel injection pump (100) comprising a low pressure inlet valve (102) and at least a high pressure outlet valve (103), the low pressure inlet valve (102) being in fluid communication with an inlet (101) of a fuel pump, the low pressure inlet valve (102) having a ball (1021) placed on a low pressure valve seat, the high pressure outlet valve (103) being in fluid communication with an outlet (104) of the fuel pump, the high pressure outlet valve (103) having another ball (1021) placed on a high pressure valve seat, the fuel pump characterized by: the valve seat (1022) has a diamond-like carbon (DLC) coating.

2. The fuel injection pump (100) for an internal combustion engine according to claim 1, wherein the low pressure valve seat (1022) has a diamond-like carbon (DLC) coating.

3. The fuel injection pump (100) for an internal combustion engine according to claim 1, wherein the high pressure valve seat (1022) has a diamond-like carbon (DLC) coating.

4. The fuel injection pump (100) for an internal combustion engine according to claim 1, wherein both the low pressure valve seat (1022) and the high pressure valve seat (1022) have a diamond-like carbon (DLC) coating.