FR2759423A1 - FUEL INJECTOR FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

An adapter sleeve (13) having a tapered annular shoulder rests at the pressure chamber against a tapered annular shoulder of the injector body (11) by being clamped against it. The tightening sleeve (13) has a bead (43) at its end (41) on the side of the body (16). After assembly, this bead is pushed back by a drawing ring (49) by a connection by force in a peripheral cavity (46) of the body (16).

Description

STATE OF THE ART The present invention relates to a injector for

  fuel for an internal combustion engine comprising an injector body clamped on a support body, and the bore of which receives in axial sliding a plugging member the bore having a pressure chamber enlarged radially,

  into which at least one feed channel leads

  next to the hole and a tightening sleeve

  by an annular, conical shoulder, applied interior

  the be an annular, conical shoulder of the injector body being located at the pressure chamber, the latter against the support body, Such fuel injectors are known according to document WO 96/19661; these injectors include a fuel supply channel in the body of the injector; this channel is directed at an angle to the axis, passing next to the guide bore of the shutter member

  (needle) which extends coaxially to the axis of the injector.

  This fuel supply channel laterally cuts the pressure chamber produced in the form of an undercut part by an extension of the section of the bore of

  guidance. In this area between the feed channel

  tation and the guide hole, near the mouth of the supply channel in the compression chamber, there is no

  has only a small wall thickness. In addition, the pa-

  King of the injector body which surrounds the pressure chamber is of very reduced thickness and resistance because of the dimension necessary for the distribution of the fuel. For injectors operating up to 400 bar, we do not encounter

  3) no significant damage in such known injectors.

  Recently, no-

  especially in the case of internal combustion engines with injection

  direct tion, which work at a pressure of up to around 1800 bars. There may then be a rupture at the end of the partition between the guide hole and the

  pressure chamber supply channel, which can lead to

  shot at the destruction of the injector body. Such damage

  ges originate in particular from the internal pressure constraints, dynamic, high, in connection with a static tension resulting from the tightening of the body of the injector against the support of the injector by a tightening nut, and from the fact that the injector is itself - even pressed by the clamping nut against a stop in the block of the internal combustion engine. In the case of a fuel injector combined with a high pressure pump, when the pressure is established, the axial pressure of the pump body is transmitted by the retaining member to the injector body. According to document DE 195 23 243, a fuel injector is known which has an annular shoulder of conical shape on the body of the injector at the level of the pressure chamber to reduce the risk of rupture of the body of the injector; the nut which clamps the injector body axially against the fixing body also comprises an annular recess on the side of the annular shoulder of the injector body. Thus, the tightening force of the nut when tightening the body of the injector against the body of the support and the tightening force of the entire injector in the block of the internal combustion engine in the body of the injector, jointly oppose the force generated by

  the very high fuel pressure in the pressure chamber

  sion, especially in the area between the feed channel and the guide hole at the inlet of the feed channel. The angles of the conical surfaces each have two different cone angles, which makes it possible to ensure a determined support and a tightening of the injector body by

  relation to the injector support body by the clamp nut

  rage. This realization allows to induce in an exact way-

  ment localized and concentrated, the forces in the body of the injector to oppose the stresses generated by the pressure. However, the two embodiments have in common the need to tighten the body of the injector on the body of the injector support, to screw the nut onto the support body; in this way, especially when blocking, due to the conical surfaces applied one against

  the other on the body of the injector and the nut, the

  The rotation induces a torsional force in the injector body. So that in particular at the level of the guide bore and the supply channel of the pressure chamber, high voltages are encountered which can cause breakage. In addition, in such fuel injectors, there are gas tightness faults between the cylinder head and the clamping nut because the screwing does not allow the round shape of the nozzle body to be respected. In addition, if the round tolerances are not respected, the nozzle body can be applied

  against the cylinder head and deform the nozzle and cause cracks

  res. Advantages of the invention The present invention proposes to remedy these drawbacks and for this purpose relates to a

  fuel of the type defined above, characterized in that the tightening sleeve has a bead around its end

  mite turned towards the support body, and after the assembly operation, this bead is pushed back by a drawing ring, with a connection by force in a cavity of the support body.

  The fuel injector for engines with com-

  internal bustion according to the invention offers the advantage that at very high pressures, for example of the order of 1800 bars, in the pressure chamber, any rupture of the body of the injector is avoided with certainty. This is obtained in a way

  advantageous by the nature of the fixing of the service sleeve

  rage on the injector support body. A flap link

  kills between a clamping sleeve which clamps the injector body on the support body and the support body

  itself, forms a bond by force which only consists

  Lement of an axial force; it is thus possible to avoid generating other tensions and in particular on the partition, between the guide bore and the supply channel of the pressure chamber. In addition, this connection by force between the support body and the clamping sleeve improves the flat support for a sealing surface of the clamping sleeve on the cylinder head of the engine. In addition, the operation of the valve body can be improved by exclusively axial tightening, since it is not intended to induce forces regularly by conical annular surfaces on the sleeve.

and the valve body.

  According to other features of the invention: e the bead provided at the free end is peripheral and radially projecting relative to a cylindrical segment

  hollow of the adapter sleeve, before the assembly operation

  blocking, * the bead has a peripheral inclined surface, 1 (0 radial before the assembly operation, * the cavity is in the form of a peripheral groove produced

  in the support body, with an annular shoulder

  nique at the junction with the envelope surface of the support body, * the bead has, after the assembly operation, an outside diameter corresponding to that of the hollow cylindrical segment of the clamping sleeve before the assembly operation, * the clamping sleeve is fixed to the support body with pretension. * the connection by force between the clamping sleeve and the

injector body cannot be removed.

  Other characteristics and advantages appear

  will read the description of an embodiment

  an internal combustion engine fuel injector

  shown schematically in the accompanying drawings in the-

  which: - Figure 1 is a section of the part of a fuel injector on the side of the combustion chamber, - Figure 2 shows a detail on an enlarged scale of the fuel injector of Figure 1 at fixing the adapter sleeve to the injector support body.

  Description of the exemplary embodiment

  The fuel injector according to FIG. 1 intended to

  born in internal combustion engines consists of an injector body 11 tightened with the interposition of a washer 12 and a clamping sleeve 13 axially on a support body 16. The injector body 11 has a bore axial 17 in which axially slides a shutter member 18 (needle) in the form of a piston; at one of its ends, this member cooperates in a cup 21 located on the side of the combustion chamber with a valve seat 19 facing inward; downstream of the valve seat 19, the cup 21 has several ejection orifices 22. The body

  injector 11 is a part having a rotational symmetry

  tion with a thicker upper segment 26 and part of

  body 27 elongated, lower, with the end located on the side

  the combustion chamber is closed by the cup 21.

  The part of the hole 17 provided in the upper segment 26 constitutes the guide hole 28 of the guide piece 29 of the closure member 18. The part of the hole 17 passing over the injector body 27 delimits with the rod 17 from the shutter member 18, an annular gap 31 reaching the valve seat 19. In the upper segment 26, at

  proximity of the lower body part 27, between the

  guide hole 28 and annular gap 33 of the hole

  17, there is a pressure chamber 32 with undercut, at dia-

  enlarged meter; the outer wall 33 of this chamber is preferably curved and joins the annular gap 31. A closing spring 34 placed in a blind bore of the injector body 16, holds the shutter member 18 against the

  valve seat 19 via a spring cup

  exit 36 when the injector is closed, in valve position

at the valve seat.

  For the fuel supply, a supply channel 37 passes through the thick upper segment 26 of the

  injector body 11 starting from its upper front surface

  and passing alongside the guide bore 28 to end up with the pressure chamber 32 driven laterally upwards. In order for the diameter of the pressure chamber 32 to be as small as possible and the section of the mouth as large as possible, the supply channel 37 passes at an angle, supplying the drilling of

  guide 28; the distance between its entry and the front surface

  upper tale of the injector body 11 is greater with respect to the axis than the distance from its mouth in the pressure chamber 32; the thickness of the partition 38 near the mouth of the supply channel 37 and near the passage in the guide hole 28 in

  the pressure chamber 32 is small.

  The essential connection for the invention between the clamping sleeve 19 and the support body 16 is shown on an enlarged scale in the detailed view of the injector according to FIG. 2. The clamping sleeve 13 is shown in broken lines before the assembly operation and in solid lines after this operation; the clamping sleeve 13 is connected to the

  support body 16 by a bond by force.

  The clamping sleeve 13 comprises in the non-state

  assembled, at its free end 41, a radial bead 43-

  outside on the hollow cylindrical segment

  42; this bead is of peripheral, radial shape. The bour-

  relet 43 has an inclined surface 44 at the junction with

the hollow cylindrical segment 42.

  To fix the free end 41 of the sleeve

  clamping 13 on the support body 16, there is provided a cavi-

  tee 46. This cavity 46 in the form of a peripheral groove; at its junction with the envelope surface 47 of the support body

  16, has an annular shoulder 48, conical against the

  which applies the bead 14 after assembly, preferably

pre-stressed.

  After pre-positioning and pre-assembly

  components of the injector, slide the clamp sleeve

  rage 13 over the injector body 11 so that the

  hollow cylindrical segment 42 surrounds the intermediate washer

  diary 12 and at least partially the support body 16. The

  support body 16 and injector body 11 are positioned

  born relative to each other by compression in an assembly tool. Then, the peripheral bead 43 is discharged radially inwards with a discharge sleeve 49

  so that the bead is applied against the annular shoulder

  conical ring 48. The sleeve 49 advantageously has also

  LEMENT an inclined surface 41 corresponding substantially to the inclined surface 44 of the bead 43. This allows to stretch the hollow cylindrical segment 42 at least slightly, in the

  axial direction, in the elastic range before the

  reel 43 is not folded back into the cavity 46. This may allow

  be to position the support body 16, the intermediate washer 12 and the injector body 11 relative to each other

  port to others with an appropriate joining force.

  During this assembly operation, according to the invention, an axial force acts through the conical annular shoulder 52 of the clamping sleeve 13 on a conical annular segment 53 of the injector body 11. Due to the clamping force acting exclusively in the axial direction, it is possible to eliminate the radial and complementary forces, such as for example the torsional forces, which prevents the formation of cracks, in particular in the region of the partition 37 between the supply bore 38 and the guide bore 28. In addition, this connection by force allows, thanks to the surfaces 52, 53 of conical shape of the body 11, to ensure the centering with respect to the common median axis with the support body 16

  and the clamping sleeve 13 resulting in precise mounting.

  This also improves the concentricity ensuring

  that the nozzle body is not pressed against the cu-

  tired in the mounted state. In addition, the clamping by force of the

  adapter sleeve 13 relative to the supporting body 16

  liore the flat support for a sealing surface 54 of the

clamp 13.

  This fixing of the clamping sleeve 13 against the support body 16 complies with the specifications of customers according to which the dismantling of the body 11 of an injector should no longer be possible. This integral connection after pushing back by stretching prevents the clamping sleeve 13 from being able to be removed from the support body 16 without destruction,

  thus achieving a very high degree of security because in general

  ral, after exchanging the components, we can no longer

  ter the very tight tolerances for concentricity

of the injector body.

NOMENCLATURE

  11 Injector body 12 Intermediate washer 13 Sleeve 16 Injector support body 17 Axial drilling 18 Sealing member 19 Valve seat 21 Cup 22 Ejection ports 26 Segment 27 Body part 28 Guide drilling 29 Guide piece 31 Annular gap 32 Pressure chamber 33 Outer limit 34 Sealing spring 36 Spring cup 37 Supply channel 38 Intermediate partition 41 Free end 42 Hollow cylindrical segment 43 Bead 44 Inclined surface 46 Cavity 47 Envelope surface 48 Annular shoulder 49 Draw sleeve 51 Inclined surface of 49 52 Annular shoulder of 13 53 Annular segment of 11

54 Sealing surface.

Claims (6)

R E V E N D I C A T I ON S   1) Fuel injector for an internal combustion engine comprising an injector body (11) clamped on a support body (16), and the bore (17) of which receives in axial sliding a shutter member (18), the bore (17) having a radially enlarged pressure chamber (32) into which opens at least one supply channel (37) passing next to the bore (17) as well as a clamping sleeve (13) clamping by a shoulder annular (52), conical, interior applied I () against an annular shoulder (53), conical of the injector body (11), being at the level of the pressure chamber (32), the latter against the body of support (16), characterized in that the tightening sleeve (13) has a bead (43) around its end (41) facing the support body (16), and after the assembly operation, this bead is repelled by a drawing ring (49), with a bond by force   in a cavity (46) of the support body (16).   2) Fuel injector according to claim 1, characterized in that   the bead (43) provided at the free end (41) is peripherally   rique and radially projecting from a cy-   lindrique hollow (42) of the sleeve of clamping (13), before the assembly operation.   3) Fuel injector according to any one of the res-   dications 1 or 2, characterized in that   3 () the bead (43) has an inclined surface (44) peripherally   risk, radial before the assembly operation.   4) Fuel injector according to claim 1, characterized in that the cavity (46) is in the form of a peripheral groove made in the support body (16), with a conical annular shoulder (47) at the junction with the envelope surface (48) from support body (16).   1 () Fuel injector according to claim 1, characterized in that   the bead (43) has, after the assembly operation, an outside diameter corresponding to that of the hollow cylindrical segment (42) of the clamping sleeve (43) before the assembly operation.   6) Fuel injector according to claim 1, I (characterized in that the clamping sleeve (13) is fixed to the support body (16) with prestress.   7) Fuel injector according to claim 1, characterized in that the connection by force between the clamping sleeve (13) and   the injector body (16) is irremovable.