FR2864916A1 - Injection channel producing process for fuel injection device, involves arranging electrode with unsheathed zone in cavity, and applying potential difference between body and electrode using electrolyte to trim periphery of opening - Google Patents

Abstract

The process involves providing an injection channel (32`) opened through an opening into a cavity (33) in a body (30) of a fuel injection device. An electrode (34) having an unsheathed zone (34A`) is arranged in the cavity. A potential difference is applied between the body and the electrode using an electrolyte in the cavity to trim the periphery of the opening by electro-chemical erosion. An independent claim is also included for a fuel injection device including an electrode that implements an injection channel producing process.

Description

The invention relates to the production of channels in a device

  fuel injection, and more particularly the deburring of the mouth of a channel in a cavity.

  As we know, the injection of fuel into an engine is under increasing pressure. Thus, in the field of diesel engines, pressures of the order of 1500 bar are currently used, and it is possible to envisage pressures that may go beyond 2000 bar. Such pressures are particularly sought to improve the performance of engines, including from the point of view impact on the environment.

  In fact, there is a tendency to look for higher pressures for diesel engines (the injection device is then commonly called rail, often made of steel or the like) than for gasoline engines (the injection device is then commonly called ramp, commonly made of aluminum or the like).

  An injection device is in practice a body having channels opening into a cavity, and the pressures used impose that there is a good deburring at the mouth of the channels in the cavity, to avoid any detachment of particles in process. service, such as machining chips.

  Various procedures have been established for this purpose, including a so-called chemical deburring procedure, the principle of which is presented in Figure 1.

  In this figure are shown a body 1 having a channel 2 opening into a larger channel 3. The channel 2 is in practice made by means of a drill bit, and a deburring is useful for rounding or chamfering, the edge to the mouth of this channel 2 in the channel 3. To do this, an electrode 4 is engaged in the channel which has just been made to present its stripped end 4A at the mouth to be deburred. This electrode is brought to a negative potential while the body 1 is a positive potential while the channels 2 and 3 are filled with an electrolyte maintained in recirculation so as to ensure good evacuation of chemical deburring debris.

  This solution gives very good results and is widely used with satisfaction. However, it has drawbacks and limitations.

  Thus, given that the distance between the end of the negative electrode (cathode) and the edge to be deburred must be controlled accurately, it is necessary to have an electrode geometry for each diameter. possible drilling.

  It must also be possible to precisely control the depth at which the end of this electrode is engaged.

  Moreover, and above all, this procedure is valid only above a threshold of channel diameter, since it is necessary to be able to handle with precision an electrode of smaller diameter than that of the channel being finished. However, the tendency to increase the injection pressures is accompanied by a tendency to reduce the diameters of the injection channels (the smaller the diameter, the greater the pressure). As an indication, we are now seeking to achieve channels of diameter substantially less than 4 mm.

  Therefore, there is currently a need for a chemical deburring procedure that is suitable for a wide range of diameters, while being simple and easy to implement, even with very small diameters, taking advantage of as much as possible of the know-how developed with the current procedures.

  To this end, the invention proposes a method for producing a channel in a fuel injection device according to which a channel opening through a mouth in a cavity is provided in the body of this device. the cavity, this electrode being provided with a stripped zone facing this mouth, and a potential difference is applied between this body and this electrode, in the presence of an electrolyte circulating in the cavity so as to deburr by electro chemical erosion the periphery of this mouth.

  It should be noted that, the skilled person used to want to locate the negative electrode in the channel that had just been drilled, taking advantage of what it is in principle easier to position a rod (the electrode) in a small channel than in a large cavity, and it is not necessary to consider the geometry of the channel in which the small channel opens.

  Of course, according to the method according to the invention, it is necessary to use a new electrode geometry, with stripped zones disposed at precise locations of the periphery (it is advantageously of lateral projections).

  However, it appeared that the fact of having the chemical deburring electrode, no longer in the small channel, but in the cavity in which this channel opens, could be done reliably, while ensuring a good positioning of a denuded portion of this electrode facing the mouth of this small channel.

  Thus, according to a first embodiment of the invention, the stripped portion of the electrode used has substantially the same dimensions as a stripped end according to conventional procedures, so with in particular a diameter substantially less than that of the channel whose mouth is deburred.

  Indeed, to ensure deburring of the edge defining the mouth of the small channel in the cavity so as to simply round the transition between the surfaces of this channel and this cavity, it is important that the bare portion of the negative electrode is at similar distances from the internal surfaces of the small channel and the cavity connected by this edge.

  However, according to a particularly advantageous characteristic of the invention, the stripped portion of the electrode has dimensions at least equal to those of the channel section that opens.

  It has indeed appeared, contrary to what the skilled person might have thought, that the possible formation of a counterbore around the mouth of the channel in the cavity does not imply a significant deterioration of the resistance to the pressure, or corrosion, of the body in which the cavity and channel are formed. Of course, the resistance to pressure of the body implies that the connection between the counterbore and the surrounding surface of the cavity is also correctly rounded, but experience has confirmed that this was the case when, in the cavity, an electrode having a projection of dimensions at least of the order of those of the mouth to be deburred.

  There was in fact a tendency to consider that it was necessary to minimize all the disturbances on the surface of the cavity likely to lead to degrade the mechanical strength or the resistance to corrosion of the body, but it appeared that the counterbores to which can lead the use of a denuded area of size at least equal to that of the mouth of a canal had no noticeable effect. Of course, it is desirable to maintain the depth of such a counterbore at a low level, for example at a fraction of a millimeter, typically on the order of one tenth of a millimeter. More generally, the depth of this counterbore may be between about one hundredth of a millimeter and a few millimeters.

  An important consequence is that it is therefore possible to choose for stripped portions of various geometries, allowing for example to minimize the manufacturing constraints of these new electrodes. Moreover, it becomes possible, if desired, to use the same electrode geometry for several channel diameters.

  According to another advantageous characteristic of the invention, the same electrode is used to simultaneously chemically deburr several mouths of channels in the same cavity, which leads to a significant reduction in cost.

  This single electrode can thus comprise a longitudinal row of bare zones.

  It may also comprise a ring of such stripped zones for deburring at once the mouths of an annular plurality of channels arranged around the longitudinal axis of the electrode.

  But the single electrode can also include an annular rib, taking advantage of the fact that the geometry of the stripped zone can be defined quite freely, regardless of the precise geometry of the channels; this is how there can be continuity between the stripped zones intended to cooperate with each mouth.

  The cavity may be a channel of constant section, and open at its ends. It may also be a pouch cul-de-sac, whose access may have a smaller section than that of the pocket at the mouths to be deburred. It is then possible to use a laterally extensible electrode, adapted to bring transverse to the axis, the stripped areas of the mouths to be deburred.

  Thus, according to advantageous features of the invention, possibly combined: this stripped zone has dimensions smaller than those of the mouth, this stripped zone has dimensions at least equal to those of the mouth , the electro-erosion of the periphery of this mouth leading to the appearance of a countersink on at least a part of this periphery, - the dimensions of this stripped zone are generally between one and two times that of the mouth to deburr, - the electro-erosion is conducted to a maximum depth of the counterbore of up to several millimeters, for example of the order of a tenth of a millimeter, - the depth of the counterbore is equal to or greater than the order of the hundredth of a millimeter, the electrode is provided with several stripped zones and electro-chemical deburring of several mouths of channels opening into the cavity is simultaneously performed. simultaneously deburring several mouthpieces offset longitudinally in the cavity, - simultaneously deburring of several mouthpieces radially offset about a longitudinal axis of the cavity, - to deburr simultaneously several mouthpieces radially offset the electrode is cleaned an annular rib forming all the stripped areas.

  The invention further provides, for the implementation of the method, an electrode having at least one denuded area in transverse projection.

  According to preferred characteristics of this electrode, possibly combined: it comprises a plurality of stripped protrusions offset longitudinally along the axis of this electrode, it comprises a plurality of stripped protrusions angularly offset about the longitudinal axis of this electrode the plurality of projections form a continuous annular rib, the angularly offset projections are radially movable.

  The invention further proposes an injection device whose body comprises a cavity into which at least one channel opens, characterized in that the mouth of this channel in the cavity is surrounded, on at least a part of its periphery, by a countersink bordered by rounded areas of connection to the surrounding surfaces.

  According to other preferred characteristics, possibly combined: in this cavity open several longitudinally offset channels whose mouth is surrounded by a counterbore, - in this cavity open several angularly offset channels whose mouth is surrounded by a counterbore, - the With the countersink, the mouth has dimensions of between one and three times the dimensions of the channel; the counterbore has a depth of at most a few millimeters, for example of the order of a tenth of a millimeter; a depth equal to or greater than of the order of a hundredth of a millimeter, the cavity is a channel of constant section, the cavity is a pocket at the end of a bag.

  Objects, features and advantages of the invention will emerge from the description which follows, given by way of nonlimiting illustrative example, with reference to the appended drawings in which: FIG. 1 is a diagrammatic representation of a conventional deburring method FIG. 2 is a schematic representation of a chemical deburring process according to the invention; FIG. 3 is a schematic representation of another chemical deburring method according to the invention, FIG. enlarged mouth of a channel in a cavity, deburred according to the method of Figure 3, Figure 5 is a schematic representation of another method according to the invention for the simultaneous deburring of several mouths, Figure 6 is a variant, and Figure 7 is another variant.

  FIG. 2 represents an embodiment of the method of the invention, according to which, in a body 10 in which a cavity 13 and a channel 12 have been previously made, a negative electrode 14 is placed, either in this channel 12, but in the cavity 13, in principle of larger size than the channel.

  This electrode comprises a stripped zone 14A, preferably consisting of a projection.

  This projection, as shown, is a smaller height than the stripped end 4A of Figure 1, but a barely larger width. Indeed, this projection has dimensions smaller than those of the mouth to be deburred.

  This electrode and the body are put at appropriate potentials for a suitable time, while circulating a given electrolyte under appropriate conditions (all these operating conditions are within the abilities of those skilled in the art, in the light of their know-how developed with the classical procedure). By way of example, these operating conditions are as follows: potential difference: deburring time: nature of the electrolyte: As in the case of FIG. 1, at the periphery of the mouth of the channel, a round of radius R typically of the order of a tenth of a millimeter.

  The body 10 may, depending on the application, be a light alloy, for example an aluminum alloy in the case of an injection device for a gasoline engine, or in particular a steel, in the case of a fuel injection device. injection for diesel engine.

  The realization of the cavity and the channel are made by any suitable known means and will not be detailed here.

  FIG. 3 represents a variant of the method described with reference to FIG. 2, in the sense that an electrode 24 is used whose projection 24A is of dimensions at least equal to those of the mouth to be deburred (the elements of this FIG. 3 which are similar to those of FIG. 2 are designated by reference signs which are deduced therefrom by the addition of the number 10. It may be noted that, unlike the channel 12 which is of constant section, the channel 22 comprises a section of large diameter 22A and a smaller diameter section 22B, typically having the same diameter as the channel 12. For example, the diameter of the section 22A is 4 mm, while that of the section is 1 mm ( to a few tenths).

  The implementation of operating conditions similar to those used for FIG. 3 leads, at the connection between the surface of the channel and that of the cavity, to a recess 26 which is shown on a larger scale in FIG.

  More specifically, it is observed that there is, at the lower end of the channel 22B, a rounded 26A, in principle similar to that of Figure 2 (here it has a radius of curvature of 0.2 mm). This round is connected to a flat or any rounded shape, referred to as the counterbore, 26B which surrounds the mouth flanked by the flare 26A. This countersink is connected to the inner surface of the cavity 23 by a second round 26C, for example of curvature substantially equal to that of the rounded 26A.

  This counterbore may have a depth ranging from a hundredth of a millimeter to a few millimeters.

  The detail of Figure 4 is taken parallel to the axis of the cavity; it is clear that, depending on the shape chosen for the protrusion 24A of the electrode, this shape is more or less modified in other sectional planes of the body 20 passing through the axis of the channel 22.

  It may be noted that the counterbore 26B is of shallow depth, especially with respect to the diameter of the channel, and that it is not bordered by any sharp edge. This is why it can be understood that tests have led to the conclusion that these countersinks do not affect the pressure resistance or corrosion of the injection body 20.

  Figures 1 to 3 correspond to cases where the cavity is a channel of constant section, in which the channels are offset longituditunalement.

  It is easy to understand that, unlike in the case of FIG. 1, the configurations of FIGS. 2 and 3 allow simultaneous deburring of the mouths of several longitudinal staggers: it suffices to have several stripped protrusions on the electrode, according to the same geometrical arrangement. as the mouths to deburr. This is schematized in dotted line on the left-hand side of FIG. 3. Similarly, if several mouths are arranged in the body, at the same longitudinal level (in other words, if there are several mouthpieces simply angularly offset one screw to the others) it is sufficient to have bare projections on the electrode, according to the same annular arrangement as the mouths.

  This is shown in Figure 5, in a configuration where the cavity 33 is a bag pouch, whose access, in the lower part is of smaller section than the central portion of this cavity. Elements similar to those of Figure 3 are designated by reference signs which are deduced from those of Figure 3 by adding the number 10.

  The cavity 33 being of short length, the various channels are arranged radially with respect to the longitudinal axis of this cavity (vertical in this FIG. 5); Thus, in this figure, there are two channels arranged diametrically opposite, respectively designated 32 and 32 '.

  The production of such an injection device body, with a dead-end cavity and radially arranged channels, is known per se from WO-99/60263 or its equivalent US-6196192 and will not be detailed. right here.

  According to the invention, an electrode 34, provided with stripped zones 34A and 34A ', is engaged in the cavity until these stripped zones, here constituted by projections, are positioned as precisely as possible facing the mouths of the channels (it can therefore there is in front and behind the plane of the figure).

  A negative potential is applied to the electrode 34 while the body 30 is set to a positive potential while circulating a suitable electrolyte in the cavity around the electrode 34: a deburring of all the mouths of the channels opposite which have been arranged protrusions 34A or 34A '...

  FIG. 6 represents an embodiment variant of the electrode, all the other elements of the body being identical.

  This electrode, denoted 44, has opposite channels mouths, no longer an annular plurality of individual stripped protrusions, but a continuous stripped rib 44A. In this way, it is no longer necessary to seek to position with great angular precision this electrode. However, it has appeared that the deburring phenomenon obtained is quite similar to that obtained with the electrode 34 of FIG.

  FIG. 7 represents an alternative embodiment of the electrode, all the other elements of the body being identical.

  This electrode 54 is transversely deformable, in that the projections 54A and 54A 'are radially movable, here in opposition to a return spring 55. More specifically, each projection is disposed at the end of a link and by action on the end 56 common to these rods, for example by means of a slider movable along the body 57 of this electrode, it can force the spacing of the projections. An electrode thus makes it possible to arrange the projections at any suitable distance from the mouths to be deburred, independently of the passage section of the access orifice to the cavity.

  As before, the simultaneous deburring of the mouths of the various channels is carried out, by adopting the appropriate operating conditions.

  The above has been presented about the production of injection channels within a fuel injection device, but this is generalized to any other channel in an injection device, and even to the realization at any device having a channel whose mouth in a cavity must be deburred carefully.

  It will be appreciated that the dimensions of the stripped protrusions are preferably between one and two times (advantageously between one and one and a half times) that of the mouths to be deburred, and that the mouth, after deburring, has a dimension equal to countersink, between one and a half times and three times the size before deburring (in Figure 4, the ratio is barely greater than 2).

Claims (23)

  A method of producing a channel in a fuel injection device in which a channel (12, 22, 32, 32 ') emerging through the body (10, 20, 30) of the device is provided. a mouth in a cavity (13, 23, 33), there is an electrode (14, 24, 34, 44, 54 in the cavity, this electrode being provided with a stripped zone (14A, 24A, 34A, 34A ', 44A, 54A, 54A '), opposite this mouth, and a potential difference is applied between this body and this electrode, in the presence of an electrolyte circulating in the cavity so as to deburr by electro-chemical erosion. periphery of this mouth.   2. Method according to claim 1, characterized in that this denuded area has dimensions smaller than those of the mouth.   3. Method according to claim 1, characterized in that this stripped zone has dimensions at least equal to those of the mouth, the electro-erosion of the periphery of this mouth leading to the appearance of a countersink (26). ) on at least a part of this periphery.   4. Method according to claim 3, characterized in that the dimensions of this denuded zone are generally between one and two times that of the mouth to be deburred.   5. Method according to claim 3 or claim 4, characterized in that the electro-erosion is conducted to a depth of the counterbore of between one hundredth of a millimeter and a few millimeters.   6. Method according to claim 5, characterized in that the depth of the counterbore is of the order of a hundredth of a millimeter.   7. Method according to any one of claims 1 to 6, characterized in that, the electrode is provided with several stripped areas (24A, 34A, 34A ', 44A, 54A, 54A') and is simultaneously performed deburring electrochemical of several mouths of channels opening into the cavity.   8. A method according to claim 7, characterized in that simultaneously performs (24A) the deburring of several mouths offset longitudinally in the cavity.   9. A method according to claim 7 or claim 8, characterized in that simultaneously deburring (34A, 34A ', 44A, 54A, 54A') of several mouths offset radially about a longitudinal axis of the cavity .   10. The method of claim 9, characterized in that for deburring simultaneously several radially offset mouths is provided on the electrode an annular rib (44A) forming all bare areas.   11. Electrode (14, 24, 34, 44, 54) adapted to the implementation of the method according to any one of claims 1 to 10, comprising at least one stripped zone projecting transversely (14A, 24A, 34A, 34A 44A, 54A, 54A ').   12. Electrode according to claim 11, characterized in that it comprises a plurality of stripped protrusions (24A) offset longitudinally along the axis of this electrode.   13. Electrode according to claim 11 or claim 12, characterized in that it comprises a plurality of stripped protrusions (34A, 34A ', 44A, 54A, 54A') angularly offset about the longitudinal axis of this electrode.   14. Electrode according to claim 13, characterized in that the plurality of projections form a continuous annular rib (44A).   15. Electrode according to claim 13, characterized in that the angularly offset projections (54A, 54A ') are radially movable.   16. Injection device comprising, in a body (20, 30), a cavity (23, 33) into which at least one channel opens, this channel being surrounded, on at least a part of its periphery, by a countersink ( 26) bordered with rounded contours.   17. Device according to claim 16, characterized in that in this cavity open several channels (22) offset longitudinally whose mouth is surrounded by a counterbore.   18. Device according to claim 16 or claim 17, characterized in that in this cavity open a plurality of channels (32, 32 ') angularly offset whose mouth is surrounded by a counterbore (26).   19. Device according to any one of claims 16 to 18, characterized in that the mouth has, with the countersink, dimensions between one and three times the dimensions of the channel.   20. Device according to any one of claims 16 to 19, characterized in that the counterbore has a depth of between one hundredth of a millimeter and a few millimeters.   21. Device according to claim 20, characterized in that the counterbore has a depth of about one hundredth of a millimeter.   22. Device according to any one of claims 16 to 21, characterized in that the cavity (23) is a channel of constant section.   23. Device according to any one of claims 16 to 21, characterized in that the cavity (33) is a bag pouch.