EP0878622A1 - Fixing flange of an injector - Google Patents

Abstract

The invention provides an arrangement for fixing a fuel injector (10) on a cylinder head of an engine, of the type in which the injector comprises a body (12) of which a part passes axially through a cylindrical housing of the cylinder head 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 a fuel intake cavity (26) delimited by an internal face (28) of the cylinder head (18), of the type in which the injector (10) is tightened 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 axially bears the lower end of the body (12) of the injector (10) to ensure sealing between the housing of the body (12) of the injector (10) and the intake cavity (26), characterized in that the shape of s complementary contact surfaces (44,48) between the fixing flange (42) and the connecting element (46) is spherical. <IMAGE>

Description

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

Motor vehicle engines also use in addition to injectors instead of carburetors. The injector propels fuel either directly into the cylinder or in an intake chamber where mixing takes place air / fuel. To bring fuel from the tank to the cylinder or its intake pipe, the injector passes through a part of the breech. The cylinder head housing in which is received the injector is substantially perpendicular to the face internal of the cylinder head. The cylinder head housing provided for 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, 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 the injector, the lower end of the injector body rests on a seal. 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 tightening the lower end of the injector body on the gasket.

One of the problems is that the cylinder head housing which accommodates the injector body is relatively narrow. In particular, the portion of the cylinder head which does not allow to exceed only that the net of the injector is relatively long and narrow compared to the diameter of the nose of the injector.

Therefore, any non-axial force applied to the top of the injector body may damage part of the body located in the cylinder head housing, and in particular the injector nose.

In addition, any non-axial force on the upper body of the injector will tend to compress part of the joint while by raising the diametrically opposite part which cannot therefore more adequately ensure its role sealing.

To remedy these various problems, it is desirable to apply forces to the injector body which are only axial.

To this end, it has already been proposed, in particular in the GB-A-2,153,908 patent to use a mounting flange injector consisting mainly of a lever whose part central has a hole which is crossed by the upper part of the injector body, one end of which is in contact on a part of the external surface of the cylinder head, and of which the other end includes a threaded hole in which is placed a threaded rod, integral with the cylinder head, which receives a tightening nut. The central part of the lever has a bump, generally in the shape of a cylinder portion, which takes axially supported on a flat face of the upper body of the injector. The whole of this device thus forms a lever whose axis is produced by the free end of the bearing bearing on the cylinder head, and the force is applied by the screwing of the nut on the threaded rod, which has the effect of driving the central part including the hump.

The point of application of the force is on the top of the injector body through the central part of the bearing and more particularly by the bump mentioned. Due to the shape cylindrical bump, forces on the injector body are vertical. However they are not strictly axial, the hump in the center of the landing 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 no longer exert the forces on the very axis of the injector body.

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

However, the installation of this fixing flange problem with the injector. The screws are tight one after the other in the cylinder head, which has the effect of unbalance the mounting flange, and cause the body to the injector in flexion, which may bend or damage it.

In addition, tightening one screw before the others involves the risk of the elastic ring being forced 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 remedy all these drawbacks, the present invention provides a new arrangement for fixing a injector which allows an axial distribution of the forces, especially 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 on a cylinder head engine, of the type in which the injector comprises a body of which a part passes axially through a cylindrical housing of the cylinder head to allow a fuel projection nose, which extends a lower axial end of the body of the injector, to open into an intake cavity fuel 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 is supported on a connecting element integral with the injector body, and which is stressed axially to the cylinder head by axial screws screwed into the cylinder head, a axial clearance being arranged between the fixing flange and a face external of the cylinder head, and of the type comprising a seal seal on which the end axially bears lower part of the injector body for sealing between the housing of the injector body and the cavity fuel intake demarcated by the internal face of the cylinder head, characterized in that the shape of the surfaces of contact between the fixing flange and the connecting element is spherical.

• la sphère définissant les surfaces de contact entre la bride de fixation et l'élément de liaison a son centre situé sur l'axe de l'injecteur afin d'avoir une répartition axiale du serrage ;
• l'élément de liaison entre la bride de fixation et l'injecteur est une pièce rapportée, fixée sur le corps de l'injecteur ;
• l'élément de liaison prend appui axialement, dans le sens du serrage, contre un anneau élastique d'arrêt immobilisé dans une gorge radiale du corps de l'injecteur ;
• l'élément de liaison entre la bride de fixation et le corps de l'injecteur est de forme générale tubulaire, traversé par le corps de l'injecteur, comporte une surface supérieure sphérique, et possède dans sa face inférieure une gorge pour prendre appui sur l'anneau élastique d'arrêt ;
• l'élément de liaison situé entre la bride de fixation et le corps de l'injecteur est réalisé venu de matière avec le corps de l'injecteur ;
• l'une des vis de maintien de la bride de fixation est une vis épaulée qui comporte une tête, en appui axial sur la bride à partir de laquelle s'étend un premier tronçon axial du corps de la vis, prolongé par un tronçon fileté d'extrémité de diamètre inférieur, les deux tronçons étant délimités par une surface inférieure annulaire d'épaulement qui vient au contact de la face externe de la culasse, et la longueur du premier tronçon détermine le jeu axial entre la culasse et la bride de fixation ;
• l'élément de liaison est situé axialement sensiblement au milieu du corps de l'injecteur, et le corps de l'injecteur s étend à travers un trou de la bride de fixation de forme générale conique, afin de ménager un jeu radial entre la bride de fixation et le corps de l'injecteur lors du serrage de la bride.

According to other characteristics of the invention:

• the sphere defining the contact surfaces between the fixing flange and the connecting element at its center situated on the axis of the injector so as 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 body of the injector;
• the connecting element between the fixing flange and the injector body is of generally tubular shape, traversed by the injector body, has a spherical upper surface, and has a groove in its lower face to bear on the elastic stop ring;
• the connecting element located between the fixing flange and the injector body is made integrally with the injector body;
• 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 d end of smaller 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 play between the cylinder head and the fixing flange;
• 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, so as to leave a radial clearance between the flange and the injector body when tightening the flange.

• la figure 1 représente une vue, partiellement en coupe axiale selon un état de la technique ;
• la figure 2 est une vue similaire à celle de la figure 1 qui illustre un agencement conforme à l'invention en cours de montage et avant le serrage ;
• la figure 3 est une vue similaire à celle de la figure 2, après le montage des différentes pièces et le serrage des vis.

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:

• FIG. 1 represents 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;
• Figure 3 is a view similar to that of Figure 2, after mounting the various parts and tightening the screws.

In the description, identical elements will be designated by the same reference numbers.

FIGS. 1 to 3 show an injector 10 comprising a cylindrical body 12 of which a lower part 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 injector 10 rests on an annular seal 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 fuel into the cylinder or in its intake duct. Storied accommodation 16 of the cylinder head 18 crosses it and opens downwards in an intake cavity 26 delimited in particular by a portion 28 of the internal face of the cylinder head 18. Thus, the nose 24 injector 10 can inject fuel into the cavity of admission.

As can be seen in particular in Figure 1, and according to a known design, the body 12 of the injector 10 substantially comprises in its central part a radial groove 30 in which is fixed an elastic ring 32. On this ring 32 axially bears a flange 34 for fixing the injector 10 on the cylinder head 18. This flange 34 maintains the body 12 of injector 10 to tighten it axially in support waterproof against the gasket 22. The fixing flange 34 is crossed in its lateral parts by holes 36 axial orientation which are crossed by screws 38 of holding the fixing flange 34.

The vertical position of the radial groove 30 relative to to a portion 40 of the external face 40 of the cylinder head 18 determines an axial clearance required for tightening, between the mounting flange 34 and cylinder head 18.

According to the invention, and as can be seen more particularly in FIGS. 2 and 3, a flange of attachment 42 has a spherical bottom face 44 concave. This spherical underside is complementary of 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 we can see more particularly in Figure 3, is located on the X-X axis 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, same as before, crossed in its center by the body 12 of the injector 10. However, the internal wall 50 of the hole center of the spherical mounting 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 flange spherical attachment 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 screw 52 defines an annular shoulder surface 60 which is supported on the external face 40 of the cylinder head 18.

Tightening is completed by at least a second screw 62, which is a conventional non-shouldered screw.

Shoulder screw 52 can, of course, be replaced by a conventional screw, similar to the second screw 62, to which is added a complementary element forming spacer and acting as a shoulder. This additional element is then tubular, it is crossed axially on its entire length by the threaded part of the screw, on which it is tight, and it is in axial support on the lower part of the screw head 62. Thus, the additional element is tightened between the head of the screw 62, and the external face 40 of the cylinder head 18.

This element can be made from a material arbitrary, rigid enough to withstand the force which is applied. Advantageously, and for cost reasons lower, it can be made of plastic material, especially in polyamide.

For mounting the assembly and in accordance with the invention, it is axially put in place, by the end lower free 20 of the body 12 of the injector 10, first the spherical fixing flange 42, then the connecting piece 46 of which the upper face 48 is spherical, then the ring elastic 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 between the connecting piece 46 and the flange of fixing 42 of the contact surfaces 44 and 48, which are shaped spherical and which cooperate with each other, allows to have an axial distribution of the clamping forces applied to the body 12 of injector 10 via the part of link 46, regardless of the inclination of the flange of spherical attachment 42, with respect to the axis X-X of the injector. The shoulder screw 52 is put in place first, and when screwing on the other screw 62, the forces on the body 12 of the injector 10 remain axial, without risk of deformation of the injector 10 or Other problems.

This installation method 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 that keeps a certain inclination of the spherical fixing flange 42 relative to the body 12 of the injector 10, without risking damage 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 entire axial clamping allows a distribution of the equal tightness over the entire circumference of the seal 22, thus preventing any impurity from entering the housing 16 of cylinder head 18. This tightening allows more remove the risk of the elastic ring 32 being expelled out of the radial groove 30, and to avoid any bending of the body 12 of injector 10 caused by other efforts than axial.

Alternatively, the elastic ring 32 immobilized in the radial groove 30 of the body 12 of the injector and the element link 46 can be replaced by another element of bond of material with the injector body and one of which part of the upper side would have a spherical shape.

Claims (8)

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 nose (24) of fuel projection, which extends a lower axial end (20) of the body (12) of the injector (10), to open into an intake cavity (26) of fuel delimited by an internal face (28) of the cylinder head (18), of the type in which the injector (10) is tightened axially on the cylinder head (18) by a fixing flange (42) which is supported on an element connecting (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 flange of fixing (42) and an external face (40) of the cylinder head (18), and of the type comprising a seal (22) on which bears axially t 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. 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. 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). 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 groove radial (30) of the body (12) of the injector (10). Arrangement for fixing an injector (10) according to claim 4, characterized in that the connecting element (46) between the mounting flange and the injector body (12) (10) is generally tubular in shape, crossed by the body (12) of the injector (10), has an upper surface (48) spherical, and has on its underside a groove for press on the elastic stop ring (32). 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). 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 comprises a head (54), in abutment axial on the flange (42) from which extends a first axial section (56) of the screw body, extended by a section threaded (58) end of smaller diameter, the two sections being delimited by an annular lower surface (60) shoulder which comes into contact with the external face (40) of the cylinder head (18), and in that the length of the first section determines the axial play between the cylinder head (18) and the flange fixing (42). 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 this that the body (12) of the injector (10) extends through a hole (50) of the generally conical fixing flange, in order to leave a radial clearance between the fixing flange (42) and the body (12) of the injector (10) when tightening the flange (42).

Images