EP1493916A1

EP1493916A1 - Engine fuel injector clamping

Info

Publication number: EP1493916A1
Application number: EP03291630A
Authority: EP
Inventors: Marc Frigo; Philippe Mallet
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2003-07-02
Filing date: 2003-07-02
Publication date: 2005-01-05

Abstract

A clamping arrangement is disclosed for securing a plurality of fuel injectors (16A,16B) to an engine assembly, preferably onto a cylinder head (12) thereof. The clamp (30A) comprises a longitudinally extending beam (32) having at each end thereof an injector clamping member (34) arranged in use to impart a clamping force onto a clamping portion (28) associated with an injector (16A,16B). The beam (32) has defined therethrough and in between said clamping members (34) at least one fixing hole adapted to receive an associated mechanical fixing (36) for imparting said clamping force and the or each said fixing hole and said clamping members (34) are substantially in-line with each other. Each said injector clamping member (34) comprises a closed flange (34) that in use completely surrounds a portion (24) of its associated said fuel injector (16A,16B).

Description

The present invention relates to engines and in particular to an arrangement for clamping fuel injectors in place on an engine assembly.
It is known to provide an engine with fuel injectors and to attach those fuel injectors to the engine using a clamp and a mechanical fastener. A common type of clamping arrangement that has been in use for many years is a simple open forked clamp used one per injector. Examples of such arrangements can be seen for example in US patents 2144861 and 6196194.
With the increasing use of multi-valve overhead camshaft engines, space constraints for injector clamping are becoming ever more restrictive. These problems are recognised in EP-0848158 and EP-0751290 in which are proposed arrangements for clamping down a plurality of injectors using a single clamp. The clamp proposed in each case holds down its outer injectors using a forked end.
The downward force used to fix injector clamps in place tends to splay the fork ends outwards. In order to reduce this effect, such forked clamps have often been made from very thick material and, furthermore, the fingers of the forks tend to be quite wide. The thick material is also necessary to resist the ever higher in-cylinder pressures that try to unseat the injectors, in particular in diesel engine assemblies. Such use of thick and wide members can be inconvenient when trying to install injectors in tight places, such as for example between a pair of overhead camshafts in a multi-valve engine. There is therefore a continuing need to seek compact solutions to injector clamping arrangements.
It is an object of the present invention to provide an improved arrangement for engine fuel injector clamping.
Accordingly, the present invention provides a clamp for securing a plurality of fuel injectors to an engine assembly, preferably onto a cylinder head thereof, said clamp comprising a longitudinally extending beam having at each end thereof an injector clamping member arranged in use to impart a clamping force onto a clamping portion associated with a said injector, said beam having defined therethrough and in between said clamping members at least one fixing hole adapted to receive an associated mechanical fixing for imparting said clamping force and the or each said fixing hole and said clamping members being substantially in-line with each other, characterised in that each said injector clamping member comprises a closed flange that in use completely surrounds a portion of its associated said fuel injector.
Said closed flange may comprise a substantially cylindrical collar adapted to impart a clamping force to its associated said injector by axially directed contact between said collar and said clamping portion.
Said clamp may comprise a double clamp for securing only two neighbouring said injectors to said engine assembly, said clamp preferably being formed by a casting or moulding technique.
Said fixing hole may be defined through a boss disposed substantially in-line and half-way in between two neighbouring said closed flanges. An upper portion of said fixing hole may defined in the form of an at least partially spherical or countersunk recess, preferably adapted to accommodate in use a corresponding part spherical or countersunk washer or a part spherical or countersunk head of a said mechanical fixing.
The present invention also provides a method of fixing a pair of neighbouring fuel injectors into an in-use position on an engine, preferably a direct injection diesel engine and more preferably in between a pair of overhead camshafts thereof, the method including clamping said pair of neighbouring injectors into said in-use position using a clamp according to the present invention.
The present invention also provides a fuel injection sub-assembly comprising a clamp according to the present invention and having captured thereon, through each said closed flange thereof, first and second fuel injectors.
The present invention also provides a method of producing a fuel injection sub-assembly according to the present invention, the method including assembling a pair of injectors into said closed flanges of said clamp and capturing said injectors onto said clamp by sliding onto each said injector a sleeve, preferably capturing each said sleeve onto its respective said injector using a captive member such as a snap ring.
The present invention also provides an engine assembly including at least one clamp according to the present invention or at least one fuel injection sub-assembly according to the present invention.
Said engine assembly may comprises a row of cylinders having disposed therealong a pair of overhead camshafts, the or each said clamp or sub-assembly being disposed in use in between and preferably substantially in parallel with said camshafts, said engine assembly preferably comprising a compression ignition internal combustion engine such as a common rail direct injection diesel engine suitable for use in a road-going vehicle.
The present invention will now be described by way of example only and with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a fuel injection sub-assembly;
Figure 2 is a perspective view of a fuel injector hold-down clamp used in the fuel injection sub-assembly of Figure 1;
Figure 3 is similar view to that of Figure 2 of the clamp with the addition of a mechanical fixing;
Figure 4 is a side view of the fuel injector hold-down clamp of Figure 2;
Figure 5 is a side view in section of the fuel injection sub-assembly of Figure 1;
Figure 6 is a side view of an engine assembly including fuel injection sub-assemblies according to Figures 1 and 5.
Referring to the drawings, an engine 10 will be considered as embodied in the non-limiting form of a compression ignition engine, preferably comprising a diesel engine suitable for use in a road-going vehicle such as a passenger car or light commercial vehicle. The engine 10 may comprise one or more banks having defined therein multiple cylinders disposed substantially in-line. For the current and exemplary embodiment, however, the engine 10 will be considered in the form of an in-line arrangement having four cylinders 1-4.
The engine 10 includes a cylinder head 12 having double overhead camshafts (DOHC) 14 arranged in parallel along that cylinder head 12. The engine 10 preferably comprises a common-rail direct injection diesel engine and has a series of fuel injectors 16A-D that is fitted into the cylinder head 12 for injecting fuel directly into the cylinders 1-4. The injectors 16A-D are disposed in between the DOHC 14 and substantially in-line and in parallel with those camshafts 14.
The injectors 16A-D are preferably substantially identical in construction, so as to benefit from commonality between parts and processes. Each injector 16A-D comprises a tubular body assembly 18 having a fuel nozzle 20 in the region of one end and a fuel inlet portion 22 in the region of the opposite end, referred to for convenience as the top and bottom ends of the injector 16A-D. Part way down each injector 16A-D, its body assembly 18 includes an annular portion that steps inwards to a body section 24 of narrowed diameter. This narrow body section is bounded by an upper flange 26 and a lower flange. The lower flange forms part of a clamping sleeve that surrounds the injector body 18, 24 and the lower flange provides a circular and flat working surface at right angles to the injector centre line. This arrangement may be referred to for convenience as that fuel injector's clamping portion 28 and is where a clamping force is applied to clamp that injector 16A-D in place in the cylinder head 12. In the case where the clamping portion 28 comprises such a separate sleeve, the sleeve may be slid onto the injector during assembly and captured in place using a snap ring 28A or equivalent that would stop axial movement of the sleeve 28 in at least one direction and thereby preferably also provide an operative interconnection between the sleeve 28 and the injector 16A-D.
The injectors 16A-D are clamped down into position and are retained there in use by fuel injector hold-down clamps 30A, 30B. Each clamp 30A, 30B is adapted to clamp in place a pair of neighbouring injectors 16A-D. Thus a first clamp 30A clamps in place the injectors 16A, 16B for the first and second cylinders 1, 2 and a second clamp 30B clamps in place the injectors 16C, 16D for the third and fourth cylinders 3, 4.
Each clamp 30A, 30B comprises a longitudinally extending beam 32 having at the each end an injector clamping member 34. The injector clamping members 34 are each embodied in the form of a closed flange that in use completely surrounds a portion 24 of its associated injector 16A-D. The closed flange 34 preferably comprises a substantially cylindrical collar 34 that is adapted to impart a clamping force to its associated injector 16A-D by axially directed contact between the collar 34 and the clamping portion 28 of the injector 16A-D. The clamping force would normally be expected to force the injector 16A-D towards the cylinder head 12.
The collars 34 may be made with no great wall thickness with their outer circumference preferably not exceeding the maximum diameter of the injector 16A-D or more preferably its associated clamping portion 28. This may be achieved because the collars 34 are closed and do not tend to splay open when the clamping load is applied. The clamping load is preferably transmitted from the clamp 30A, 30B into the injector 16A-D by a substantially localised contact surface, e.g. via point loading lobes or knuckles 34A disposed on opposing undersides of each of the collars 34. The closed flanges 34 preferably closely and completely encircle their respective injectors 16A-D, leaving a clearance only sufficient to avoid pinching or hindering the injector 16A-D during storage, fitting or operation and across its operating temperature range.
The beam 32 is preferably of a narrower width/thickness than the injectors 16A-D and/or narrower than the collars 34. The reduced width is possible because there is no longer any need to provide thick and wide fork legs for clamping purposes. This again provides improved packaging, in particular between the DOHC 14, and leads also to a light weight.
The clamps 30A, 30B are each provided with means to introduce the clamping force into their respective pairs of injectors 16A,B; 16C,D. The clamping force may conveniently and cheaply be provided by a mechanical fixing such as a bolt or machine screw 36. Other mechanical fastening systems cab be used, such as a stud and nut arrangement. The mechanical fixing arrangement may also be captive on the clamp 30A, 30B so as to benefit from the possibility of sub-assembly, to keep down the parts count on the production line and to keep down the risk of a fitter dropping loose parts into a cam valley between the DOHC 14.
The clamps 30A, 30B may be formed using a casting or moulding technique and preferably include a dimensionally enlarged portion adapted to co-operate with such a mechanical fixing 36. This may take the form of a boss 38 that both defines a hole 40 therethrough and is adapted to provide on an upper surface 42 thereof a region through which that mechanical fixing 36 can act. The boss 38 is preferably disposed substantially in-line and halfway in between two neighbouring collars 34. An upper portion of the fixing hole 40 is defined in the form of an at least partially spherical and/or countersunk recess 40A, preferably adapted to accommodate in use a part spherical or countersunk washer 36A or a part spherical or countersunk head of the mechanical fixing 36.
The clamps 30A,B; 30C,D are fitted to their respective injector pairs 16A,B; 16C,D by sliding the injectors 16A,B; 16C,D through the collars 34 and then sliding the sleeves 28 onto the injector body below the clamp 30A, 30B and capturing the diverse parts 16A,D, 34, 28 together by fitting their respective snap/stop rings 28A.
Among the further advantages of combined features in the present invention, the fact that the collars 34 completely encircle the injectors 30A, 30B couples with the feature by which each clamp 30A, 30B in the present embodiment is captured onto a plurality of injectors 16A-D, e.g. a pair thereof 16A,B; 16C,D. The interaction between these features means that there is a reduced likelihood of the mechanical fixing 36 from being worked loose by twist of the clamp 30A, 30B or by vibration coming up through the injectors 16A-D. Any turning moment of one injector 16A,C about the fixing 36 is blocked by the presence on the other end of the clamp 30A, 30B of the other injector 16B,D.
By fitting the injectors 16A-D to the clamps 30A, 30B in pairs 16A,B; 16C,D, the parts count at the side of the production line is reduced as they can be supplied already assembled as sub assemblies 30A, 16A,B; 30B, 16C,D. The parts counts being optionally still further reduced if a captive mechanical fixing 36 is employed. This allows a simpler method of clamping the injectors 16A-D in place on the engine 10, in particular between a pair of DOHC 14 and preferably substantially in parallel therewith, where the reduced width of the clamps 30A, 30B provides more handling room and lighter weight. For the same reasoning, servicing and parts exchange is also made easier. By using the fuel injection sub-assemblies 30A, 16A,B; 30B, 16C,D, there is also a reduced risk of encountering assembly problems such as those associated with dropping loose parts into camshaft valleys.
Configurations using the present invention are possible in which, depending on installation constraints or engine configuration, clamping arrangements may be used other than only the double clamps of the non-limiting embodiment described above. For example, in a three cylinder engine, a V-6 or indeed any engine having an odd number of cylinders in line, using only double injector clamp may prove inconvenient. It will be apparent to the skilled man that it is possible to extend the double clamp to form a triple. Such an arrangement would preferably include a boss and mechanical fixing between each pair of neighbouring injectors. As an alternative to a triple array of clamp and injectors, a single collar version can also be envisaged to be used in co-operation with clamps having even numbers of collars.
The present invention can therefore be seen to reduce parts count line-side, reduce overall weight, reduce injector packaging problems and it simplifies assembly procedures. This therefore overcomes or at least alleviates certain problems with some known arrangements for clamping engine fuel injectors in place.

Claims

A clamp for securing a plurality of fuel injectors (16A-D) to an engine assembly (10), preferably onto a cylinder head (12) thereof, said clamp (30A, 30B) comprising a longitudinally extending beam (32) having at each end thereof an injector clamping member (34) arranged in use to impart a clamping force onto a clamping portion (28) associated with a said injector, said beam having defined therethrough and in between said clamping members at least one fixing hole (40) adapted to receive an associated mechanical fixing (36) for imparting said clamping force and the or each said fixing hole and said clamping members being substantially in-line with each other, characterised in that each said injector clamping member (34) comprises a closed flange (34) that in use completely surrounds a portion (24) of its associated said fuel injector (16A-D).
A clamp according to claim 1, wherein each said closed flange (34) comprises a substantially cylindrical collar adapted to impart a clamping force to its associated said injector (16A-D) by axially directed contact between said collar and said clamping portion (28).
A clamp according to claim 1 or claim 2, wherein said clamp (30A, 30B) comprises a double clamp for securing only two neighbouring said injectors (16A,B; 16C,D) to said engine assembly (10), said clamp preferably being formed by a casting or moulding technique.
A clamp according to any preceding claim, wherein said fixing hole (40) is defined through a boss (38) disposed substantially in-line and half-way in between two neighbouring said closed flanges (34).
A clamp according to any preceding claim, wherein an upper portion of said fixing hole (40) is defined in the form of an at least partially spherical or countersunk recess, preferably adapted to accommodate in use a corresponding part spherical or countersunk washer or a part spherical or countersunk head of a said mechanical fixing (36).
A method of fixing a pair of neighbouring fuel injectors (16A,B; 16C,D) into an in-use position on an engine (10), preferably a direct injection diesel engine and more preferably in between a pair of overhead camshafts (14) thereof, the method including clamping said pair of neighbouring injectors into said in-use position using a clamp (30A, 30B) according to any preceding claim.
A fuel injection sub-assembly comprising a clamp (30A, 30B) according to any one of claims 1 to 5 and having captured thereon, through each said closed flange (34) thereof, first and second fuel injectors (16A,B; 16C,D).
A method of producing a fuel injection sub-assembly according to claim 7, the method including assembling a pair of injectors (16A,B; 16C,D) into said closed flanges (34) of said clamp (30A, 30B) and capturing said injectors onto said clamp by sliding onto each said injector a sleeve 28, preferably capturing each said sleeve onto its respective said injector using a captive member such as a snap or stop ring (28A).
An engine assembly including at least one clamp (30A, 30B) according to any one of claims 1 to 5 or at least one fuel injection sub-assembly (30A, 16A,B; 30B, 16C,D) according to claim 7.
An engine assembly according to claim 9, wherein said engine assembly (10) comprises a row of cylinders (1-4) having disposed therealong a pair of overhead camshafts (14), the or each said clamp (30A, 30B) or sub-assembly (30A, 30B, 16A,B; 16C,d) being disposed in use in between and preferably substantially in parallel with said camshafts, said engine assembly preferably comprising a compression ignition internal combustion engine such as a common rail direct injection diesel engine suitable for use in a road-going vehicle.