The present invention relates to a regulator adapted to regulate the flow of the low pressure side of a fuel injection equipment arranged on an internal combustion engine, said low pressure regulator having a normal operational mode and a flushing operational mode.

BACKGROUND OF THE FNVENTION

In a fuel injection equipment a filter arranged on a low pressure return line, and often on flow regulator, traps debris of any kind such as particles present in the fuel, manufacturing burrs or assembly chips. Said debris remain trapped with a risk to obdurate the filter and are never removed. Means for removing said debris is required.

SUMMARY OF THE FNVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a low pressure regulator adapted to be arranged on the low pressure (hereafter LP) portion of a fuel injection equipment of an internal combustion engine. The LP regulator is provided with a filter and a regulator member moving under the influence of the fuel pressure and controlling the section area of an outlet adapted to be connected to a drain so that, in a normal operational mode, the flow of fuel flowing on an inlet side is regulated as a fraction of the flow goes through the filter and to the outlet and wherein, the LP regulator further defines a flushing operational mode wherein said fuel flowing on an inlet side bypasses the filter and directly flows to the outlet.

Also, the regulator member is provided with an inner channel opening at an end to the inlet of the LP regulator and at another end to the outlet, said fuel flowing on an inlet side flowing in said inner channel in normal operational mode and, bypassing in said inner channel in flushing operational mode.

More precisely, the regulator member is a piston guided in a bore defined in a body of the LP regulator, the inlet to the LP regulator being defined at an open end of the bore, the outlet being an opening provided on a lateral face of the wall of the body, the piston having a front face facing said inlet and a lateral face partially covering the outlet, the inner channel opening in said front face and in said lateral face.

Also, the filter member is fixed to said front face and, the filter member is sized to enter the bore.

Moreover, in said flushing operational mode, the piston is inwardly moved inside the bore to a flush position wherein said front face is beyond at least a portion of the outlet, enabling said fuel flowing on the inlet side to bypass the filter and to directly flow to the outlet.

Also, a spring member is arranged in the bore between the piston and a plug member inserted in a closing end of the bore opposed to the inlet, and wherein, in said flushing operational mode said plug member is partially disengaged from said closed end of the bore enabling the regulator member to move to said flush position.

The invention is also about a flushing operational mode of a LP regulator as described above, said mode comprising the following steps:

a) arranging the LP regulator on a test station adapted to generate on the inlet a fuel flow having a sufficiently high pressure to move the pressure regulator in a flush position wherein said fuel flow bypasses the filter and directly flows to the outlet so that particles trapped in the filter are flushed back the drain,

said step a) comprising the steps:

b) partially disengaging the plug member from the bore so that the piston moves inside the bore;

c) generating said fuel flow on the inlet side so that the piston is inwardly pushed in the bore, the front face and the filter moving beyond at least a portion of the outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

Figure 1 is an axial section of a LP regulator as per the invention when operating in an in-use mode. Figure 2 is the regulator of figure 1 arranged in a flushing operational mode.

Figure 3 is a detailed area of the regulator in the in-use mode.

Figure 4 is a detailed area of the regulator in the flushing operational mode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A diesel fuel injection equipment aims at spraying pressurised fuel in the cylinders of an internal combustion engine and, to do this a high pressure (HP) pump sucks fuel in a low pressure tank and delivers fuel compressed to several thousands of bars to a common rails that feeds several fuel injectors. Part of the diesel fuel is not burnt in the engine and is returned to the tank after lubricating the pump or because the engine does not need it to match the power demand. The injection equipment is further provided with a low pressure (LP) regulator arranged on a return line of the equipment for regulating the LP return flow. Said LP regulator is also provided with a filter that retains debris, burrs, chips and all particles present in the fuel. Said particles can be coming from the fuel itself or can be generated during normal operation as the parts wear or, can also be the consequence of manufacturing and assembly of the equipment.

The LP regulator 10 represented in section on the figures extends along a main axis X and it comprises an elongated body 12 defining a peripheral wall 14 having an outer face 16 and an inner face 18 surrounding a through bore 20 that opens in lower end, defining an inlet 22 to the LP regulator 10, and in an upper end, said upper end being closed by a plug member 24 inserted in the bore. Terms such "lower, upper, above below" are used to ease and clarify the description in reference to the arbitrary orientation of the figure and without any limiting intention. Said body 12 further comprises a lateral opening defining an outlet 26 and extending through the lateral wall between the inner and outer faces 16, 18, said outlet 26 having an axial length L upwardly extending from a first edge 28 to a second edge 30. Between said edges the outlet can have any shape such as a circular section or an elongated slot or any other. Further away from the inlet 22 than where is the outlet 26, the body 12 is provided with calibrated damper orifices 32 radially arranged through the wall. A coil spring 34 is arranged inside the bore 20 between the plug member 24 and a regulator member 36, on the inlet side of the bore, the spring 34 being centered in the bore by its last turns which are wound around cylindrical protrusions of the plug and of the regulator member. The part of the bore wherein is the spring defines a damper chamber 38 wherein open the calibrated orifices 32 and, in use, this damper enable to amortise pressure peaks propagating in the flow.

The regulator member 36 is a cylindrical piston guided and adjusted to slide in the bore. Its cylindrical lateral face 40 axially extends from a front face 42 oriented toward the inlet 22 to an opposed transverse back face 44 provided with said cylindrical protrusion where about is wound an end of the spring. The piston is provided with an inner channel 46 comprising a central channel axially extending from an opening in said front face 40 to a distant blind end and, with two radial channels joining said central channel to an annular groove 48 provided in said cylindrical lateral face 40 and surrounding the piston. Said groove 48 axially extends in said lateral face from a first edge 50, close to the front face 42, to a second edge 52 closer to the back face 44.

In the figures, the axial sections show two radial channels but, another number is also possible. Also, for manufacturing easiness the inner channel 46 comprises said central and radial conduits drilled at right angle but any other path is possible provided that an end opens in the front face and another end opens in said groove 48.

Furthermore, a filter member 54 is fixed on the front face 42, said filter 54 having mesh of approximately 100-150μιη extending over the opening of the inner channel 46. Although the depicted example shows a cup-like filter, any other shape is possible.

In use, the LP regulator 10 is arranged in the low pressure part of the injection equipment, on the return line between the HP pump and the tank. The low pressure of the fuel flowing by the inlet 22 generates on the front face 42 an inwardly oriented force opposed to the spring force pushing the piston toward the inlet 22.

As long as the spring force overcomes the flow inward force, the regulator 10 remains in a stand-by position PI as shown on figures 1 and 3, where the piston 42 is pushed by the spring 34 and the front face 42 lies on the inlet 22 of the regulator. In said stand-by position PI the annular groove 48 slightly intersects with the outlet 26 defining an in-use opening 56 between the second edge 52 of the groove and the first edge 28 of the outlet, t. Under said operational conditions a small fraction, arrow A, of said fuel flow finds a return way through the filter 54, inside the inner channel 46 of the piston, in the groove 48 and, exits the regulator through said in-use opening 56 between said second edge 52 of the groove that is a little above said first edge 28 of the outlet.

In use, the pressure of said inlet fuel flow fluctuates and rises so the inward force overcomes the spring force and the piston further enters the bore and, under said conditions where the piston enters the bore, the filter 54 fixed to the front face also enters the bore. Also, the section area of said in-use opening 56 between the groove 48 and the outlet 26 increases and the exiting fraction of fuel flow raises.

The particles retained by the filter 54 remain on the outside of the mesh. Fortunately said LP regulator 10 can operate under a flushing operational mode P2 shown on the figures 2 and 4. Said flushing operational mode P2 is not a normal in-use operational mode, it is executed at the end of the assembly line or during a service operation where the LP regulator 10 is arranged on a specific machine. The plug member 24 is partially disengaged from the bore, in fact the insertion is minimal and just sufficient to still axially hold the plug, retain the spring 34 and give room to the piston 36 and the filter 54 to inwardly insert in the bore 20. The machine runs a fuel flow to inlet 22 so the piston 36 further moves and reaches a flush position FP wherein the front face 42 and the filter 54 are above the first edge 28 of the outlet thus defining a bypass opening 58 through which a fuel flow can directly exit the regulator without going through the filter 54, cleaning the filter from all retained particles.

This flushing operational mode P2 is executed before the final assembly of the regulator 10 on the injection equipment so that are removed from the filter manufacturing particles and burrs or at a later stage during a service operation, removing all kind of particles and debris. LIST OF REFERENCES

X mam axis

L axial length of the outlet normal operational mode flushing operational mode

A fraction of the flow

FP flush position

10 LP regulator

12 body

14 peripheral wall

16 inner face

18 outer face

20 bore

22 inlet

24 plug member

26 outlet

28 first edge of the outlet

30 second edge of the outlet

32 damper orifices

34 spring

36 regulator member - piston

38 damper chamber

40 lateral face

42 front face

44 back face

46 inner channel

48 annular groove

50 first edge of the groove

52 second edge of the groove

54 filter

56 in-use opening

58 bypass opening