EP3315762A1

EP3315762A1 - Integrated arrangement of a common rail and a pressure sensor

Info

Publication number: EP3315762A1
Application number: EP17198107.9A
Authority: EP
Inventors: Peter Voigt; Christophe Breant
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi Technologies IP Ltd
Priority date: 2016-10-28
Filing date: 2017-10-24
Publication date: 2018-05-02
Anticipated expiration: 2037-10-24
Also published as: GB2555453B; EP3315762B1; GB201618256D0; GB2555453A

Abstract

A common rail (12) adapted to be arranged in a fuel injection equipment and comprising comprises a transverse wall (34) arranged in the vicinity of a first end (16) of the rail, said transverse wall (34) sealingly closing said internal space (S) so that, in use, pressurised fuel retained in the inner space (S) exerts forces on an inner face (36) of said transverse wall (34).

Description

TECHNICAL FIELD

The present invention relates to fuel injection equipment and more particularly to an integrated assembly of a common rail and a pressure sensor.

BACKGROUND OF THE INVENTION

A direct injection fuel equipment comprises a pump which pressurises and delivers fuel to a common rail that stores and distributes it to a plurality of injectors. The common rail typically has an elongated body defining a cylindrical inner space and it is provided with an inlet and several outlets radially arranged in the peripheral wall of the body. At an extremity of the rail is tightly screwed a pressure sensor adapted to send to a command unit a signal dependent on the pressure internal to the rail and, at the opposite end is arranged an electro-valve that receives command signals from said command unit to alternatively open or close a spill orifice thus enabling to regulate the internal pressure.
The inner space, wherein is stored said pressurised fuel, is a through hole opening in both ends of the rail and, specific complex machining operations are required to manufacture the geometrical features enabling complementary arrangement of the pressure limiting valve and of the pressure sensor.
Furthermore, the pressure sensor forms a protruding member larger than the rail and, specific space needs to be reserved for arranging the assembly on the engine block.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a common rail adapted to be arranged in a fuel injection equipment of an internal combustion engine, said common rail having an elongated body extending along a longitudinal axis from a first end wherein is arranged a pressure sensor, to a second end, said body defining a substantially cylindrical peripheral wall surrounding a cylindrical internal space wherein in use, highly pressurised fuel is stored.
Advantageously, the common rail further comprises a transverse wall arranged in the vicinity of said first end, said transverse wall sealingly closing said internal space so that, in use, pressurised fuel retained in the inner space exerts forces on an inner face of said transverse wall.
Also, the transverse wall is arranged slightly inside the first end of the common rail thus defining a recess opening in said first end, the recess being defined between the very end of the peripheral wall and an outer face of the transverse wall that forms the bottom of said recess.
Also, said transverse wall is integral to the peripheral wall.
In a specific embodiment said transverse wall is provided with a thinning feature reducing locally the thickness of the wall.
The invention further extends to an arrangement of a common rail and a pressure sensor, said arrangement comprising a common rail as described above and, a pressure sensor having a force sensing device fixed on the outer face of the transverse wall, said force sensing device being adapted to generate a signal representative of the pressure in the internal space.
More particularly, said force sensing device is a strain gauge.
Also, it is possible, once the force sensing device is fixed on said outer face of the transverse wall, to fill said recess with moulded plastics.
Moreover, the arrangement further comprises an electric connector arranged at the first end of the common rail, said connector having pins electrically connected to the force sensing device.
The invention further extends to an assembly of an arrangement of a common rail and a pressure sensor as described above with a pressure limiting valve.
Also, the invention extends to a fuel injection equipment comprising a common rail and an arrangement with a pressure sensing device as described above.

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 a schematic representation of a fuel injection equipment comprising a common rail and pressure sensor arrangement as per the invention.
Figure 2 is a 3D view of the rail and sensor arrangement of figure 1.
Figure 3 is an axial section of a first embodiment of the the rail and a force sensing device arrangement of figures 1 or 2.
Figure 4 is the arrangement of figure 3 further provided with a connector arranged to electrically connect the force sensing device.
Figure 5 is a second embodiment of a rail and sensor arrangement.
Figure 6 is an alternative to the second embodiment of figure 5.
Figure 7 is a third embodiment of a rail and sensor arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 generally presents a fuel injection equipment 10 of an internal combustion engine. The equipment 10 comprises a pumping device that draws fuel from a tank, pressurises and delivers it to a common rail 12, wherefrom said pressurised fuel is distributed to fuel injectors, only one being shown, adapted to alternatively spray said fuel in the pistons of the engine. A pressure sensor 14 is arranged at a first end 16 of the common rail 12 and, a pressure limiting valve 18 is arranged at an opposite distant end.
A command unit 20 controls the overall operation of the equipment 10 and, in particular it regulates the rail internal pressure by receiving from the pressure sensor 14 a signal representative of the fuel pressure inside the rail 12 and, by sending to the pressure limiting valve 18 a signal to command opening or closing of a spill orifice enabling fuel in excess in the rail to return to the tank.
The magnified view of figure 2 presents an arrangement 22 comprising the common rail 12 and the pressure sensor 14 arranged at the first end 16 of the rail, a connector 24 is also arranged protruding from said first end 16.
The rail 12 has an elongated shape extending along a longitudinal axis X from said first end 16 to said opposite distant end. The rail 12 presented is machined from a forged blank and it comprises a radially extending inlet 26 for enabling connection to a high pressure pipe, several radially extending outlets 28, four are shown on the figure, also for connecting pipes joining the injectors and, two ear members 30 for fixing the rail on the engine block. This embodiment is shown as an illustration and many other embodiments are known with other numbers of outlets or other orientations of the inlet and outlets.
A more detailed integration of the arrangement of the pressure sensor 14 into the rail 12 is now presented in reference to the figures 3 to 7 presenting axial sections of the first end 16 of the rail. The rail 12 has a cylindrical peripheral wall 32 surrounding an inner space S in which opens the inlet and outlets, not shown on said figures. In said first end 16, the rail 12 is further provided with a transverse wall 34 arranged inside said peripheral wall 32 and sealingly closing the space S, said transverse wall 34 having an inner face 36 oriented toward the inner space S opposed to an outer face 38 oriented toward the opening of the first end. Also as shown, the transverse wall 34 being arranged slightly inside the rail 12, it defines along with the very end portion of the peripheral wall 32 a recess 40 that opens in said first end 16 of the rail. The transverse wall 34 can be integral to the peripheral wall or can be added afterward and sealingly fixed to it by screwing, welding, laser welding, friction welding or any other known means. The embodiment of figure 3 presents a transverse wall 34 having a constant thickness with planar inner 36 and outer 38 faces while, a transverse wall 34 having nonplanar inner and outer faces is possible. The transverse wall 34 could also be non-symmetric with, for instance a flat outer face 38 and a non-flat inner face 36.
In use, the inner face 36 of the transverse wall 34 is in contact with the fuel and is directly subject to the fuel pressure in the inner space S and, under said pressure which in the case of diesel fuel can reach up to 2500 bars and much more under testing conditions, the transverse wall 34 slightly deflects. A force sensing device 42, for instance a strain gauge intimately fixed on the outer face 38 follows and senses said resilient deformation of the transverse wall 34. Strain gauge are generally fixed on a larger ceramic wafer 43 which is intimately glued to the transverse wall.
More precisely and without limiting the invention to the following dimensions, considering the common rail application and the fuel pressure that can rise to several thousands of bars, the central bore of the rail is about 10 mm diameter, the transverse wall 34 has a thickness of about 1mm, the strain gauge 42 being of about 1 mm² and the wafer 43 is about 5 mm in diameter.
As shown in figure 4 the electric connector 24, previously introduced, has a small profile and is provided with electrical pins 44 adapted to complementary connect to another connector, not shown, linked to the command unit 20. In this context "small profile" is to be understood as having the minimum necessary size enabling said complementary connection. The connector 24 may axially extend as shown in figure 2 or make an angle as in figure 4 where it is represented provided with an engagement cylindrical feature arranged around the end of the rail. Other connection type are possible such as an engagement inside the recess.
Internally, said connector 24 is provided with electrical leads 46 linking said force sensing device 42 to the pins 44 so that, the fuel pressure in the inner space S deforms the transverse wall 34, said deformation is sensed by the force sensing device 42 which can transmits to the command unit a signal indicative of the fuel pressure.
Thanks to this integrated arrangement 22, the required manufacturing is limited and the necessary space to accommodate the rail and the sensor on the engine is reduced.
As indicated on the figure, the pressure sensor 14 that is in the prior art a separate component integrating in a body fixed to the rail, the wall, the sensing device, the leads and the connector, is now divided in individual components better integrated with the rail 12.
In a second embodiment presented on figure 5, for mechanical resistance purposes the transverse wall 34 is much thicker than in figures 3 and 4. The force sensing device 42 remains glued on the outer face 38 and, to enable proper sensing, a thinning recess 48 is arranged in the transverse wall 14. Said recess 48 axially extends in the wall 34 from the inner face 36 to a bottom face 50 so that, the remaining thickness between said bottom face 50 and the outer face 38 is about 1mm.
In an alternative to the second embodiment, presented on figure 6 the outer recess 40 opening at the first end 16 of the common rail is enlarged defining an annular groove 52 surrounding the central area of the wall 34 where is fixed the force sensing device 42.
In a third embodiment, shown on figure 7, the transverse wall 34 is provided with a central through aperture 54 axially extending between the inner 36 and outer 38 faces. The force sensing device 42 fixed on its wafer 43 is glued to a metallic plug 56 of about 1mm thickness, said plug 56 being fixed on the outer face 38 over the opening of the aperture 54. The plug 56 can be welded, laser welded or any other fixation means can be used provided it resists to the pressure in the inner space S.
In alternative embodiments not shown, the transverse wall 34 can be arranged closer to the very end of the rail 12, the resulting recess 40 being shallow or, said transverse wall 34 can even be arranged at the very end of the rail without defining a recess 40, the force sensing device 42 still being fixed to the outer face 38 of the transverse wall and, the connector 24 with an appropriate design would also be fixed to the rail and would provide the required protection to the sensing device.
Furthermore, the volume inside the connector, whether with a recess 40 or with a flush end wall, may be filled with moulding plastics that would provide further protection to the sensing device.

LIST OF REFERENCES

X: longitudinal axis
S: internal space

10: fuel injection equipment
12: common rail
14: pressure sensor
16: first end of the common rail
18: pressure limiting valve
20: command unit
22: arrangement of a common rail and a pressure sensor
24: connector
26: inlet
28: outlet
30: ear member
32: peripheral wall of the common rail
34: transverse wall of the common rail
36: inner face
38: outer face
40: recess
42: force sensing device
43: wafer
44: pins
46: electrical leads
48: recess
50: bottom of the recess
52: annular groove
54: aperture
56: plug

Claims

Common rail (12) adapted to be arranged in a fuel injection equipment (10) of an internal combustion engine, said common rail (12) having an elongated body extending along a longitudinal axis (X) from a first end (16) wherein is arranged a pressure sensor (42) to a second end, said body defining a substantially cylindrical peripheral wall (32) surrounding a cylindrical internal space (S) wherein in use, highly pressurised fuel is stored, characterised in that
the common rail (12) further comprises a transverse wall (34) arranged in the vicinity of said first end (16), said transverse wall (34) sealingly closing said internal space (S) so that, in use, pressurised fuel retained in the inner space (S) exerts forces on an inner face (36) of said transverse wall (34) and wherein the transverse wall (34) is arranged slightly inside the first end (16) of the common rail thus defining a recess (40) opening in said first end, the recess being defined between the very end of the peripheral wall and an outer face (38) of the transverse wall (34) that forms the bottom of said recess (40) and wherein said transverse wall (34) is integral to the peripheral wall (32).
Common rail (12) as claimed in claim 1 wherein said transverse wall (34) is provided with a thinning feature (48) reducing locally the thickness of the wall.
Arrangement (22) of a common rail and a pressure sensor, said arrangement comprising a common rail (12) as claimed in any one of the preceding claims and, a pressure sensor having a force sensing device (42) fixed on the outer face of the transverse wall (34), said force sensing device (42) being adapted to generate a signal representative of the pressure in the internal space (S).
Arrangement (22) as claimed in claim 3 wherein said force sensing device (42) is a strain gauge.
Arrangement (22) as claimed in claim 3 or 4, the force sensing device (42) being fixed on said outer face (38) of the transverse wall (34) and, said recess (40) being filled with moulded plastics.
Arrangement (22) as claimed in any one of the claims 3 to 5 further comprising an electric connector (24) arranged at the first end (16) of the common rail, said connector (24) having pins (44) electrically connected to the force sensing device (42).
Assembly of an arrangement of a common rail and a pressure sensor as claimed in claim 6 and, a pressure limiting valve (18).
Fuel injection equipment (10) comprising a common rail (12) as claimed in any of the claims 1 or 2.