FR2763379A1 - INJECTOR FIXING FLANGE - Google Patents

Abstract

The invention proposes an arrangement for fixing a fuel injector (10) to a cylinder head of an engine, of the type in which the injector comprises a body (12), a part of which passes axially through a cylindrical housing of the cylinder head. to allow a projection nose (24) of, of the type in which the injector (10) is clamped axially on the cylinder head by a fixing flange (42) which bears on a connecting element (46) integral with the body (12) of the injector (10), and of the type comprising a seal (22) on which the lower end of the body (12) of the injector (10) bears axially to ensure the seal between the housing of the body (12) of the injector (10) and the inlet cavity (26), characterized in that the shape of the complementary contact surfaces (44, 48) between the fixing flange (42) and the 'connecting element (46) is spherical.

Description

B256.DOC 2763379

  The present invention relates to an arrangement for fixing a fuel injector on the cylinder head of a motor vehicle engine, and more particularly the flange of

maintenance of the injector.

  Automotive engines are using more and more injectors instead of carburetors. The injector propels the fuel either directly into the cylinder or into an intake chamber where the air / fuel mixture is made. To bring the fuel from the tank to the cylinder or its intake pipe, the injector passes through part of the cylinder head. The housing of the cylinder head in which the injector is received is substantially perpendicular to the internal face of the cylinder head. The cylinder head housing intended to receive the injector is a stepped housing, which is relatively narrow for precise guidance of the body and more particularly

from the injector nose.

  This arrangement presents a number of problems. The main problem is a sealing problem

  between the intake cavity, constituted either by the cylinder itself

  even, either by its intake pipe, and the housing of the

  cylinder head designed to receive the body and nose of the injector.

  To prevent fuel from leaking into the injector housing, the lower end of the injector body rests on a gasket. Sealing is then ensured by the

  axial clamping of the injector towards the cylinder head and on the seal.

  However, this device requires a perfectly axial force for clamping the lower end of the injector body on

the gasket.

  One of the problems lies in the fact that the housing of the cylinder head which receives the body of the injector is relatively narrow. In particular, the portion of the cylinder head which only allows the nozzle of the injector to protrude is

B256DOC

  relatively long and narrow compared to the diameter of the nose

of the injector.

  As a result, any non-axial force applied to the upper body of the injector risks damaging the part of the body located in the cylinder head housing, and in particular the

injector nose.

  In addition, any non-axial force on the top of the injector body will tend to compress a part of the seal while raising the diametrically opposite part which can therefore no longer adequately ensure its sealing role. To remedy these various problems, it is desirable to apply forces to the body of the injector which

are only axial.

  1 5 For this purpose, it has already been proposed, in particular in patent GB-A2.153.908 to use a clamp for fixing an injector consisting mainly of a lever, the central part of which comprises a hole which is crossed by the part upper part of the injector body, one end of which rests on part of the external surface of the cylinder head, and the other end of which comprises a threaded hole in which a threaded rod is placed, integral with the cylinder head , which receives a tightening nut. The central part of the lever has a bump, generally in the form of a cylinder portion, which bears axially on a flat face of the top of the injector body. The whole of this device thus forms a lever, the axis of which is produced by the free end of the bearing bearing on the cylinder head, and the force is applied by screwing the nut onto the threaded rod, which has for effect of sinking the

  central part including the hump.

  The point of application of the force is on the upper body of the injector through the central part of the bearing and more

B256.DOC 27337

  particularly by the bump mentioned. Due to the cylindrical shape of the bump, the forces on the body of the injector are vertical. However, they are not strictly axial, the hump which is in the center of the bearing being located on a circle whose center is the free end of the bearing resting on the surface of the cylinder head. The bump is therefore likely to be offset and to no longer exert the forces on the very axis of the

injector body.

  According to another known system, a fixing flange o bears on an elastic ring immobilized in a radial groove of a central part of the body of the injector and it is fixed axially by two screws tightened in the holes

threaded from the cylinder head.

  However, the installation of this injector fixing flange poses a problem. In fact, the screws are tightened one after the other in the cylinder head, which has the effect of unbalancing the fixing flange, and causing the injector body to flex, which risks bending it or to damage it. In addition, the fact of tightening one screw before the others involves the risk of seeing the elastic ring being expelled out of the radial groove if the forces are not strictly axial and if, consequently, the support of the fixing flange is not

evenly distributed.

  To overcome all these drawbacks, the present invention provides a new arrangement for fixing an injector which allows an axial distribution of the forces, in particular when mounting the fixing screws on the flange.

  holding the injector body.

  To this end, it is proposed to use an arrangement for fixing a fuel injector to a cylinder head of an engine, of the type in which the injector comprises a body of which

B256.DOC

  a part passes axially through a cylindrical housing in the cylinder head to allow a fuel projection nose, which extends a lower axial end of the injector body, to open into a fuel intake cavity delimited by an internal face of the cylinder head, of the type in which the injector is tightened axially on the cylinder head by a fixing flange which bears on a connecting element integral with the body of the injector, and which is biased axially towards the cylinder head by axial screws screwed in the cylinder head, an axial clearance being arranged between the fixing flange and an external face of the cylinder head, and of the type comprising a gasket on which the lower end of the injector body bears axially to ensure sealing between the housing of the injector body and the fuel intake cavity delimited by the internal face of the cylinder head, characterized in that the shape of the surfaces compl contact elements between the mounting flange and

  the connecting element is spherical.

  According to other characteristics of the invention - the sphere defining the contact surfaces between the fixing flange and the connecting element at its center located on the axis of the injector in order to have an axial distribution of the tightening; - The connecting element between the fixing flange and the injector is an insert, fixed to the body of the injector; The connecting element bears axially, in the tightening direction, against an elastic stop ring immobilized in a radial groove of the injector body - the connecting element between the fixing flange and the body of the injector is generally tubular in shape, traversed by the injector body, has an upper surface

B256.DOC 2763379

  spherical, and has in its lower face a groove for bearing on the elastic stop ring; - The connecting element located between the fixing flange and the body of the injector is made integrally with the body of the injector; - one of the retaining screws of the fixing flange is a shouldered screw which has a head, in axial support on the flange from which extends a first axial section of the body of the screw, extended by a threaded section end of io lower diameter, the two sections being delimited by an annular lower shoulder surface which comes into contact with the external face of the cylinder head, and the length of the first section determines the axial clearance between the cylinder head and the flange fixation; the connecting element is located axially substantially in the middle of the body of the injector, and the body of the injector extends through a hole in the fixing flange of generally conical shape, in order to provide a radial clearance between the flange

  and the injector body when tightening the flange.

  Other characteristics and advantages of the invention

  will appear on reading the detailed description which follows

  for the understanding of which reference will be made to the appended drawings in which: - Figure 1 shows a view, partially in axial section according to a state of the art; - Figure 2 is a view similar to that of Figure 1 which illustrates an arrangement according to the invention during assembly and before tightening; FIG. 3 is a view similar to that of FIG. 2,

  after mounting the various parts and tightening the screws.

  In the description, identical elements will be

  designated by the same reference numbers.

B256.DOC 2763379

  FIGS. 1 to 3 show an injector 10 comprising a cylindrical body 12, a lower part of which

  14 is engaged in a stepped housing 16 of a cylinder head 18.

  The annular lower end face 20 of the end 14 of the body 12 of the injector 10 rests on an annular seal 22, itself resting axially on a

  lower shoulder 17 of housing 16 of cylinder head 18.

  The lower part 14 of the body 12 of the injector 10 is extended at its lower end by an injector nose 24, or injection nozzle, which is used to inject the fuel into the cylinder or into its intake duct. The stepped housing 16 of the cylinder head 18 crosses the latter and opens downwards into an intake cavity 26 delimited in particular by a portion 28 of the internal face of the cylinder head 18. Thus, the nose 24 of the injector 10 can inject fuel into the intake cavity. As can be seen in particular in Figure 1, and according to a known design, the body 12 of the injector 10 comprises substantially in its central part a radial groove 30 in which is fixed an elastic ring 32. On this ring 32 takes axially supporting a flange 34 for fixing the injector 10 on the cylinder head 18. This flange 34 holds the body 12 of the injector 10 in order to tighten it axially in sealed support against the seal 22. The flange 34 for fixing is crossed in its lateral parts by holes 36 of axial orientation which are crossed by screws 38 of

  holding the fixing flange 34.

  The vertical position of the radial groove 30 relative to a portion 40 of the external face 40 of the cylinder head 18 determines an axial clearance necessary for the tightening, between the

  mounting flange 34 and cylinder head 18.

B256.DOC 2763379

  According to the invention, and as can be seen more particularly in Figures 2 and 3, a fixing flange 42 has a lower face 44 of concave spherical shape. This spherical lower face is complementary to the convex spherical upper face 48 of an element of

  link 46, of generally tubular shape.

  The spherical surfaces 44 and 48 which come to bear one on the other have a center which, as can be seen more particularly in FIG. 3, is located on the axis XX of the injector 10. Advantageously, the sphere which defines the surfaces 44 and 48, has a diameter of about sixty millimeters. It is here the connecting element 46 which rests on

  the elastic ring 32 housed in the radial groove 30.

  The fixing flange 42 with a spherical surface is, as previously, crossed in its center by the body 12 of the injector 10. However, the internal wall 50 of the central hole of the spherical fixing flange 42 is shaped

  similar to an inverted truncated cone.

  As before, the lateral parts of the spherical fixing flange 42 are crossed axially by

  the holes which accommodate the clamping screws.

  According to the invention, one of the clamping screws is modified. It is a shouldered screw 52 comprising a head 54 in axial support on the flat upper face 45 of the spherical fixing flange 42. This head 54 is extended by a first smooth axial section 56, itself extended by a threaded section 58 of smaller diameter. The second threaded section

  58 is provided to be screwed a tapped hole in the cylinder head 18.

  The difference in diameter between the two sections 56 and 58 of the screw 52 defines an annular shoulder surface 60

  which is supported on the external face 40 of the cylinder head 18.

B256.DOC 2763379

B256.DEC 2 7 6 3 3 7 9

  Tightening is completed by at least a second screw

  62, which is a conventional non-shouldered screw.

  The shouldered screw 52 can, of course, be replaced by a conventional screw, similar to the second screw 62, to which is added an additional element forming

  spacer and acting as a shoulder. This additional element

  then is tubular, it is crossed axially over its entire length by the threaded part of the screw, on which it is tightened, and it is in axial support on the lower part of the head of the screw 62. Thus, the element additional is clamped between the head of the screw 62, and the outer face 40 of the cylinder head 18. This element can be made from any material, rigid enough to withstand the force applied to it. Advantageously, and for reasons of lower costs, it can be made of plastic material,

especially in polyamide.

  For the assembly of the assembly and in accordance with the invention, the spherical fixing flange 42 is then placed axially by the free lower end 20 of the body 12 of the injector 10, then the piece of link 46 whose upper face 48 is spherical, then the elastic ring 32 in the groove 30 of the body 12 of the injector 10. On

  then sets up the shouldered screw 52 before the other screws.

  We then put everything in place on the cylinder head with

  interposition of the seal 22.

  Having contact surfaces 44 and 48 between the connecting piece 46 and the fixing flange 42, which are spherical in shape and which cooperate with each other, allows an axial distribution of the forces tightening applied to the body 12 of the injector 10 via the connecting piece 46, and this regardless of the inclination of the flange

B256.DOC 2763379

  spherical attachment 42, with respect to the axis X-X of the injector. The shouldered screw 52 is put in place first, and when the other screw 62 is screwed in, the forces on the body 12 of the injector 10 remain axial, without risk of deformation of the injector 10 or other problems. . This method of installation is facilitated by the central hole of the spherical fixing flange 42, the wall 50 of which has a general shape of an inverted truncated cone which makes it possible to keep a certain inclination of the spherical fixing flange 42 in relation to to the body 12 of the injector 10, without risking damaging

this last.

  During assembly, the length of the first smooth section 56 of the shouldered screw 52, in accordance with the vertical position of the elastic ring 32, defines the clearance required for tightening between the upper face 40 of the cylinder head 18 and the flange of

ball mount 52.

  The assembly of the axial clamping allows an equal distribution of the clamping over the entire circumference of the seal 22, which thus prevents any impurity from entering the housing 16 of the cylinder head 18. This clamping also makes it possible to eliminate the risk of see the elastic ring 32 be expelled from the radial groove 30, and to avoid any flexing of the body 12 of the injector 10 caused by forces other than axial. As a variant, the elastic ring 32 immobilized in the radial groove 30 of the body 12 of the injector and the connecting element 46 can be replaced by another connecting element made integrally with the body of the injector and one

  part of the upper side would have a spherical shape.

B256.DOC 2763379

Claims (8)

  1. Arrangement for fixing a fuel injector (10) on a cylinder head (18) of an engine, of the type in which the injector comprises a body (12), a part of which passes axially through a cylindrical housing (16) of the cylinder head (18) to allow a fuel projection nose (24), which extends a lower axial end (20) of the body (12) of the injector (10), to open into an intake cavity io (26) of fuel delimited by an internal face (28) of the cylinder head (18), of the type in which the injector (10) is clamped axially on the cylinder head (18) by a fixing flange (42) which is supported on a connecting element (46) integral with the body (12) of the injector (10), and which is biased axially towards the cylinder head (18) by axial screws screwed into the cylinder head (18), an axial clearance being arranged between the fixing flange (42) and an external face (40) of the cylinder head (18), and of the type comprising a gasket (22) on which is supported axi alement the lower end (20) of the body (12) of the injector (10) to seal between the housing (16) of the body (12) of the injector (10) and the intake cavity ( 26) of fuel delimited by the internal face (28) of the cylinder head (18), characterized in that the shape of the complementary contact surfaces (44, 48) between the fixing flange   (42) and the connecting element (46) is spherical.   2. Arrangement for fixing an injector (10) according to claim 1, characterized in that the sphere defining the contact surfaces (44, 48) between the fixing flange (42) and the connecting element (46 ) has its center located on the axis of   the injector (10) in order to have an axial distribution of the clamping. B256.DOC 2763379   he 3. Arrangement for fixing an injector (10) according to claim 2, characterized in that the connecting element (46) between the fixing flange (42) and the injector (10) is a   insert, fixed to the body (12) of the injector (10).   4. Arrangement for fixing an injector (10) according to claim 3, characterized in that the connecting element (46) bears axially, in the tightening direction, against an elastic stop ring (32) immobilized in a throat   radial (30) of the body (12) of the injector (10).   5. Arrangement for fixing an injector (10) according to claim 4, characterized in that the connecting element (46) between the fixing flange and the body (12) of the injector (10) is generally tubular in shape, crossed by the body (12) of the injector (10), has a spherical upper surface (48) 1s, and has a groove in its lower face for   press on the elastic stop ring (32).   6. Arrangement for fixing an injector (10) according to claim 1, characterized in that the connecting element (46) located between the fixing flange (42) and the body (12) of the injector ( 10) is made integrally with the body (12) of the injector (10).   7. Arrangement for fixing an injector (10) according to   any one of the preceding claims, characterized   in that one of the screws (52) holding the fixing flange (42) is a shouldered screw which has a head (54), in axial support on the flange (42) from which extends a first axial section (56) of the body of the screw, extended by a threaded section (58) of end of smaller diameter, the two sections being delimited by an annular lower surface (60) of shoulder which comes into contact with the face external (40) of the cylinder head (18), and in that the length of the first section B256.DQC 2 7 63379   determines the axial play between the cylinder head (18) and the flange fixing (42).   8. Arrangement for fixing an injector (10) according to   any one of the preceding claims, characterized   in that the connecting element (46) is located axially substantially in the middle of the body (12) of the injector, and in that the body (12) of the injector (10) extends through a hole (50) of the generally conical fixing flange, in order to provide a radial clearance between the fixing flange (42) and the body   io (12) of the injector (10) when tightening the flange (42).