FR2745852A1 - FUEL INJECTOR FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

An injector comprising a body (1) receiving an obturator member (13) sliding axially; the injector body is tightened by a nut against a support with the interposition of an intermediate washer (7) whose front faces (47, 49) are tightly sealed respectively against the axial front surface of the body (1) and against the injector support. At least one of the front surfaces (9, 47) which cooperates has a convex shape to achieve the clamping a regular distribution of the forces in the sealing surface. This curved surface is convex.

Description

State of the art.

  The invention relates to a fuel injector for an internal combustion engine comprising an injector body in which a shutter member is guided in axial sliding and which is tightened with a nut,

  axially against an injector support, an inter-

  being clamped between the injector body and the support

  injector port, this washer resting on its faces

  tightly against the axia-

  the injector body and the injector support.

  We already know such an injector according to the docu-

  ment DE 44 08 245 Al; it includes a guiding body,

  axial smoothing, a shutter member, movable, and the end of which protrudes into the combustion chamber of the powered engine. The injector body is tightened axially

  using a cap nut, at its end if-

  killed on the side of the combustion chamber against an injector support; an intermediate washer is interposed between

  the front face of the injector body, opposite the cham-

  combustion bre, and the lower front face of the support

  injector, on the side facing the combustion chamber.

  This intermediate washer is pressed in each case in a sealed manner by its axial front surfaces against the front surface of the injector body and that of the injector support; it has a central through hole to receive a thrust member applied axially against the end of the shutter member, on the side opposite to that

  of the combustion chamber. In addition, a per-

  connecting hole, at an angle, in the intermediate washer, which connects the two parts of the fuel supply hole in the injector body and

in its support.

  The injector support has a bor-

  gene, central, starting from the front face facing the

  combustion chamber, which forms a receiving spring housing

  before the injector spring urging the closure member

in the closing direction.

  The tightness of the corresponding faces of the round

  the intermediate and injector body or injector support is made by applying force against the front faces; this tightening force depends on the tightening force of the nut. This results in a characteristic of inducing forces in the surfaces corresponding to a very high pressure in the radially outer zone and a reduction in forces towards the medium; this is further accentuated by the blind drilling in the support

  injector because at this level you cannot induce any effort.

  This irregular distribution of the induced forces deteriorates the sealing effect at the level of the intermediate washer in its radially inner zone so that the sealing

  known does not meet the high demands, no-

  especially those of injectors using pressures

very important injection.

Advantages of the invention.

  The object of the present invention is to create an

  nozzle to remedy these sealing problems

of the prior art.

  To this end, the invention relates to an injector of the type defined above, characterized in that at least one of the front surfaces of the injector body and of the washer

  intermediate, which cooperates, are convex convex.

  The fuel injector according to the invention, for internal combustion engines, offers the advantage, thanks to the intentionally convex shape of at least one of the front surfaces in cooperation with the intermediate washer and the injector body , to allow a regular distribution of the forces in the sealing section so that even in the area radially inside the injector there is a

  sufficiently high sealing effect.

  As a variant, it is possible to give the front face of the intermediate washer, to the front face of the injector body, on the side opposite to the combustion chamber,

  or on the two front faces, a convex convex shape.

  The apex of the convex shaped surface, turned towards the injector side, must, in the case of a single convex surface, protrude from 0.001 to 0.002 mm, radially outward relative to the annular edge which delimits the

  frontal surface. When the two front surfaces cooperate

  rant are convexly convex, this extra thickness should only represent around 0.0005 to 0.001 mm each time. In the clamped state of the parts, there is elastic deformation of the domed front surfaces giving a flat sealing surface. Alternatively, one can also provide a shape

  convex for the upper front face of the inter-

  medial, on the side of the injector support, and on the front face

  lower plate of the injector support, face which cooperates with

  this front face on the side facing the combustion chamber

  tion; however, due to the large opening for the spring chamber, this shape has only a relatively

  reduced for injector support.

  According to other advantageous features of the invention: - the front face of the injector body, not turned towards the combustion chamber, is curved and the front face of the lower intermediate washer, facing the combustion chamber, cooperating with the front side of the body

injector, is flat.

  - the front face of the injector body, opposite the combustion chamber, is flat and the lower front surface of the intermediate washer, facing the combustion chamber and cooperating with the face of the injector body,

is domed.

  - the front face of the injector body, opposite the chamber

  combustion, and the front face, lower, of the round

  intermediate, facing the combustion chamber and cooperating with the front face of the injector body,

are domed.

  - the rounded front face protrudes at its apex by about

  0.001 to 0.002 mm from the edge delimiting the over-

  front face radially outside.

  - the domed, cooperating front surfaces,

  pass appreciably, at their apex, from about 0.0005 to 0.001 mm relative to the edge radially to

  the exterior which delimits the corresponding front face.

  - The injector body comprises, to receive the closure member, an axial blind bore, starting from the front face opposite to the combustion chamber, which forms by a section extension, a pressure chamber into which opens a feed hole from the

  front face opposite to the combustion chamber, radial-

  outside the blind hole.

  - the intermediate washer includes, to receive a part

  thrust provided on the side of the shutter op-

  placed on the combustion chamber, a coaxial through hole arriving in the blind bore of the injector body as well as a connecting hole leading to the

feed hole level.

  - the injector support comprises another part of the supply bore which arrives in the connection bore of the intermediate washer as well as a central blind bore forming a spring chamber for receiving an injector spring acting on the member shutter, this piercing

  blind from the frontal surface adjacent to the round

of it intermediate.

  Drawings. The present invention will be described below using three embodiments of a

  fuel according to the invention for internal combustion engines

  dull, shown in the drawings in which: - Figure 1 is a sectional view of the fuel injector in the assembled state,

  - Figure 2 shows a detail in section of the pre-

  mier exemplary embodiment of FIG. 1, the front face

  of the intermediate washer being curved and the face corresponding to

  laying of the injector body, flat,

  - Figure 3 shows a second example of reali-

  sation, similar to that of FIG. 2, according to which the front face of the intermediate washer is planar and the front face of the injector body is curved,

  - Figure 4 shows a third example of a

  reading similar to that of FIGS. 2 and 3, according to which the front faces of the intermediate washer and of the body

  both are domed.

  Description of the exemplary embodiments.

  The fuel injector for engines with com-

  internal bust, shown in the assembled state in FIG. 1, comprises an injector body 1 having rotational symmetry; this body is tightened using a cap nut or tightening nut 3, axially against an injector support; between the injector body 1 and the injector support 5, an intermediate washer 7 has been tightened. The injector body 1, the free end of which projects into a chamber

  not shown in detail of the combustion engine

  internally powered, has a blind bore 11, leaving

  from its front face 9, opposite to that of the control chamber

  bustion, and adjacent to the intermediate washer 7. This per-

  blind hole 11 guides in axial sliding a shutter member 13 in the form of a piston. The blind bore 11 forms, at its closed end, a valve seat 15 turned inwards and which comprises at least one injection orifice 17 opening into the combustion chamber of the internal combustion engine and cooperates with a surface of valve seal 19 provided on the front surface of

the obturation member 13.

  The blind bore 11 functioning as a bore

  guide of the shutter member 13 is widened to a

  right on the side of the pressure chamber 21; at this point, the shutter member 13 has a pressure shoulder

  23 connected by a feed hole 25 axial through-

  the injector body 1 and the injector support 5 in

  communicating with the connection nozzle 27 of the support 5.

  A fuel line, not shown, connected to a

  high pressure injection pump, is connected to this nozzle

  connection stage 27; this high pressure pump provides

  alternatively to the injector a fuel under high pressure

  if we. To receive an injector spring in the form of

  helical spring, support 5 includes a resistor chamber

  comes out 31 in the form of a central blind bore open in the direction of the intermediate washer 7 and the injector spring 29 bears at one end against the bottom of this blind bore via a washer 33. By its other end close to the intermediate washer 7, the injector spring 29 puts the shutter member 13 prestressed by means of a spring cup 35, bearing against the valve seat 15. The member

  shutter 13 has, at its end remote from the cham-

  bre of combustion, a thrust piece 37 of small diameter

  naked compared to that of the injector body; this piece

  thrust protrudes through the central orifice

  slope 39 of the intermediate washer 7.

  To connect the two parts of the supply bore 25 of the injector body 1 and of the injector support 5 there is further provided a connection bore 41 in the intermediate washer 7; this hole is biased

  relative to the axis of the injector.

  The leakage fuel is discharged from the spring chamber 31 by a leakage fuel channel 43

  which leaves this room to arrive at a nozzle of col-

  45 leakage fuel reading at surface level

injector holder cover 5.

  To seal the interior volumes of the injector through which the fuel passes, the front face 47 of the intermediate washer 7, lower on the side of the combustion chamber, and the upper front face 49

  away from the combustion chamber, are applied

  tightly sealed against the front face 9 of the injector body, on the side remote from the combustion chamber and against the lower front face 51 of the injector support 5, on the side

  facing the combustion chamber.

  In order to regularly induce the forces on the sealing surface between the intermediate washer 7 and the injector body 1, at least one of the surfaces

  sealing which cooperates with a convex convex shape.

  According to the simplified views and on an enlarged scale made from FIG. 1 and represented in FIGS. 2

  at 4, there are three possible embodiments.

  According to the first embodiment shown

  tee in Figure 2, the front face 9 of the injector body 1, on the opposite side towards the combustion chamber, is flat. The lower front face 47 of the intermediate washer 7, which cooperates with the front face above, has a convex convex shape (facing outwards, that is to say downwards) and the top of this convex surface is located on the axis of the shutter member. The maximum extension X of this vertex of the domed front surface 47 with respect to the edge which delimits the surface radially outside

  frontal 47 is then of the order of 0.001 to 0.002 mm.

  In the case of the second exemplary embodiment,

  presented in FIG. 3, the lower front surface 47 of the intermediate washer 7 is flat and the front surface

  9 of the injection body 1, cooperating with the above surface

  above, facing the opposite side of the combustion chamber,

  is curved convex (curved upwards). In this case also

  the top of the domed front surface 9 is located at the

  level of the axis of the shutter member and the maximum height

  male X of the curved surface is approximately 0.001 to 0.002 mm.

  In the case of the third embodiment shown in Figure 4, the two front surfaces 47, 9, which cooperate, and belong to the intermediate washer 7

  and to the injector body 1, are convex convex; the som-

  put curved surfaces are located on the axis of the shutter member. The maximum height X of the apex of the curved surface, with respect to the edge of the pitch diameter at the level of the radial edges, is in this case only each time

from about 0.0005 to 0.001 mm.

  When mounting the injector and axially tightening the injector body 1 and the intermediate washer 7 against

  the injector support 5, the slightly bom-

  bées undergo an elastic deformation leading to an ap-

  then plane of good sealing between the intermediate washer 7 and the injector body 1. Thanks to the domed embodiment, that is to say in the form of a spherical cap, of the surfaces

  sealing, it is advantageous to induce the forces homogeneously throughout the radial zone; these efforts improve the sealing effect in particular in the inner ra-5 dial area, compared to known fuel injectors.

Claims (7)

R E V E N D I C A T IONS   1) Fuel injector for an internal combustion engine comprising an injector body (1) in which an obturation member (13) is guided in axial sliding and which is tightened with a nut (3), axially against an injector support (5), an intermediate washer (7) being clamped between the injector body (1) and the injector support (5), this washer being supported by its front faces (47, 49) sealingly against the axial front faces (9, 51) of the injector body (1) and of the injector support (5), characterized in that at least one of the front surfaces (9, 47 ) from the body   injector (1) and the intermediate washer (7), which father, are convex convex.   ) Fuel injector according to claim 1, characterized in that the front face (9) of the injector body (1), not turned towards the combustion chamber, is curved and the front face (47) of the intermediate washer ( 7), lower, turned   towards the combustion chamber, cooperating with the front face   tale of the injector body, is flat.   3) Fuel injector according to claim 1, characterized in that the front face (9) of the injector body (1), opposite to the   combustion chamber, is flat and the front surface less   lower (47) of the intermediate washer (7), facing the combustion chamber and cooperating with the face of the body injector, is domed.   4) Fuel injector according to claim 1, characterized in that the front face (9) of the injector body (1), opposite to the combustion chamber, and the front face (47), lower, of the intermediate washer (7), facing the combustion chamber and cooperating with the front face of the body injector, are domed.    ) Fuel injector according to any one of claims 2 or 3, characterized in that the convex front face (9, 47) protrudes, at its top, by about 0.001 to 0.002 mm relative to the delimiting edge   the front surface radially to the outside.   6) Fuel injector according to claim 4, characterized in that   the domed front surfaces (9, 47) which cooperate   rent, protrude appreciably, at their apex, from about 0.0005 to 0.001 mm with respect to the edge radially   on the outside which delimits the corresponding front face.   70) Fuel injector according to claim 1, characterized in that the injector body (1) comprises, to receive the closure member (13), a blind blind bore (11) axial, starting from the front face ( 9) opposite the combustion chamber, which forms, by a section extension, a pressure chamber (21) into which a supply bore (25) opens.   starting from the front face (9) opposite the control chamber   bust, radially outside the blind bore (11).   8) Fuel injector according to claim 7, characterized in that the intermediate washer (7) comprises, for receiving a thrust piece (37) provided on the side of the member   shutter (13) opposite the combustion chamber, a   coaxial through hole (39) arriving in the blind hole (11) of the injector body (1) as well as a connection hole   (41) opening out at the feed hole (25).   9) Fuel injector according to claim 8, characterized in that   the injector support (5) includes another part of the   feed hole (25) which arrives in the hole of connection   its (41) of the intermediate washer (7) as well as a drilling there   central blind forming a spring chamber (31) for receiving   see an injector spring (29) acting on the closure member (13), this blind bore starting from the front surface (51) adjacent to the intermediate washer (7) .5