FR2555489A1 - METHOD FOR MANUFACTURING A SEATING ELEMENT OF A FUEL INJECTION VALVE - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR MANUFACTURING A SEAT-FORMING ELEMENT OF A FUEL INJECTION VALVE. THIS PROCESS CONSISTS OF PRACTICING, IN AN ELEMENT 8 FORMING A VALVE SEAT, A BORE 9, 9 FOR GUIDING A STEM OF THE VALVE; TO MENAGER A SEAT 10, 10 IN THE EXTENSION OF THIS BORE 9, 9; A DRILL A FUEL DELIVERY ORIFICE 11 IN THE EXTENSION OF THE SAID SEAT; TO SUBMIT AT LEAST LEDIT BORE 9, 9 OR LEDIT SEAT 10, 10 TO A BROWNING USING A BRUNISSOR 17; AND TO HARDEN THEIT ELEMENT 8 AFTER THIS BROWNING. APPLICATION IN PARTICULAR TO ELECTRONIC FUEL INJECTION DEVICES.

Description

METHOD FOR MANUFACTURING A SEAT-FORMING ELEMENT

  OF A FUEL INJECTION VALVE

  The present invention relates to a method for producing

  providing a valve seat member in a fuel injection valve of the type comprising a main valve body, a movable core magnetically attracted to a fixed core by an electromagnetic coil located within said main valve body, a valve stem whose end has a shutter and which is

  subject to the mobile core, as well as a strong element

  the seat of the valve and attached to the end of the

  colrps to receive said shank rod

  Pope. FIG. 1 of the accompanying drawings illustrates an embodiment known in the prior art, from which it emerges that an element forming the seat of a fuel injection valve of the type described comprises a bore b for guiding the valve stem in its respective opening and closing movements; a seat c proper, formed at the end of this bore b in the extension of the latter; and a fuel delivery orifice d, made in the extension of said seat c. In this embodiment, it is common practice to polish a bore drilled in a blank of a seat member and to polish a bore formed in the seat of the valve, so as to obtain

  the guide bore b and a bearing surface e of said seat c.

  More specifically, the hole b 'is polished by a grinding tool f which is moved about an axis of rotation 1

  aligned with the axis of the guide bore b, while rotating

  on its own axis of rotation i2 which is parallel to said axis of rotation 1 'The bearing surface e of the seat c of the valve is polished by a grinding tool having

  a shape different from that of the tool f.

  The aforementioned method raises the following difficulties:

lowing:

R555485

  1. When polishing, it is necessary to rigidify the

  polished surface, in a manner well known in the prior art.

  the polishing is preceded by hardening.

  performed between the step of machining the initial hole and the polishing step. Therefore, the draft

  the element forming the seat of the valve is

  removed from the template after machining

  initial drilling, then this blank is hardened

  after which it is readjusted on the template in

  to polish. Thus, the adjustment of the sketch

  on the template and its removal from the latter

kill long interventions ..

  2. Correlatively to the difficulty (1) described above

  when a blank is repetitively adjusted on and removed from the template, the concentricity of the axis of rotation of the tool used to perform the initial drilling (for example a drill) and the axis of rotation ( corresponding to I of the grinding tool is affected, so it is common for drilling

  b 'and the seating surface of the seat are not polished uni-

foment over their entire area.

  3. During a polishing pass, a tolerance of

  relatively large D must be reserved. If an error, even slight, occurs in the positioning of the grinding tool f due, for example, to an offset of the axis of rotation ú2 with respect to the axis of rotation 1

  bore b can not be uniformly polished.

  4. Since the head of the grinding tool f can wear easily, a sharp edge or burr can be formed at. the end of the polished guide bore b or the latter is connected to the seat c. The width of the burr g corresponds to the depth of the grinding tolerance D. In order to avoid the appearance of the burr g, a clearance groove H formed in draft must be machined beforehand in the hole b '; however, this

intervention is difficult.

  5. In turn, the clearance groove h constitutes a fuel trap inside the element a forming the seat of the valve, which causes a decrease in the speed of the fuel exerting a negative influence on

the injection of this fuel.

  6. Concurrently with the above mentioned difficulty (4), if the

  wastes produced during the machining of the discharge throat-

  h remain, they can obstruct the delivery port d, or cause fuel leakage. To eliminate this waste, it is necessary to carry out scrupulous cleaning, but it is extremely difficult to completely remove said waste. This results in significant variations in the amount of fuel

  injected and in the performance of the injection device.

  An object of the present invention is to provide a method of manufacturing a guide bore and a valve seat in a fuel injection valve, which

eliminates the aforementioned problems.

  This object is achieved by a method in which the surface finishing is performed by burnishing instead of polishing, which method successively consists in internally digging the seat member of the valve, to bring this internal space to its side. finished by burnishing, then hardening the material on the surface of said

hollow internlme space.

  The method according to the present invention improves the machining

  and produces a fuel injection valve that is highly accurate and suitable for

  electronic fuel injection device.

  In addition, according to the method of the invention, the hollow internal space is constituted by an initial bore for guiding the respective opening and closing movements of the stem of the valve, as well as by a

  seat which is located in the extension of the gui-

  and opens into the fuel delivery port.

  At least the guide bore or the seat of the valve is subjected to burnishing and, preferably, burnishing of

  these two zones occur concomitammnent.

  The guide bore, the seat and the hole are

  preferably by a drill-to which a rotation is printed around a given axis, and an element enclosing

  the seat is kept in a template during the operation

  drill and during the subsequent intervention during

  from which the drilling and the seat are brought by brunis-

  wise to their final rating. In this way, said valve seat member does not need to be removed from the

  template and it can stay in place for both the initial pass and

  only for the subsequent burnishing pass.

  The invention will now be described in more detail by way of non-limitative examples, with reference to the accompanying drawings, in which: FIG. 1 is a longitudinal section showing a conventional method for machining a seat member of a valve ; Figure 2 is a longitudinal sectional view of an embodiment of a fuel injection valve equipped with the valve seat member obtained in accordance with the method according to the present invention; Figure 3 is a flowchart showing the successive steps of the method of the invention; and FIG. 4 is a longitudinal section of the element

  seat, illustrating the step of browning the said

yielded.

  Figure 2 illustrates a main valve body 1

  in which there is an electromagnetic coil 2.

  A fixed core 3 is located inside the winding

  2 and the latter also encloses a movable core 5 in a region situated forward with respect to its axial direction. A spring 4 acts on the movable core to push the latter away from the fixed core 3. A rod 7 of the valve, having a shutter 6 at one end, is connected to the rear end of the movable core 5, and this rod 7 engages in an element 8 forming

  valve seat and secured to the end of the main body 1.

  The element 8 enclosing the seat of the valve comprises a guide bore 9 extending axially; a seat 10 proper formed at the end of the bore 9 in the extension of the latter; as well as an orifice 11

  of fuel delivery, located in the extension of-

  said seat 10. The valve stem 7 passes through the guide bore 9 so that two regions 12 of the

  diameter, provided with grooves 12a for the passage of fuel

  rant along their outer peripheries, can slide along the surface of said bore 9, so that this bore 9 guides the rod 7 in its respective opening and closing movements. The shutter 6, formed at the end of said rod 7, is normally pushed by the spring 4 so that it comes to bear against a surface 10a of the seat 10. When a voltage is applied to the winding electromagnetic 2, the movable core 5 is attracted magnetically towards the fixed core 3 against the force of the spring 4 and, in this case, the movement of the rod 7 raises the shutter 6 away from the surface 10a of the seat, so that fuel, from a sleeve 13 connected to a fuel pipe (not shown), is delivered through the orifice 11. The reference 14

  means an outlet with a connecting pin

  14a supplying the electro-magnetic winding 2.

  The internal space of the element 8 forming the seat of the

  pape is produced by a method of drilling, in a blank, the guide bore 9, the seat 10 of the valve and the fuel delivery port 11 (step S1 in Fig. 3); subjecting said bore 9 and / or said seat to burnishing (step S2); and curing the blank (step S3) after the browning step. It is this browning step preceding the hardening step that calls for

  in particular a comment and will now be described.

  To proceed with the burnishing, a burnisher 17 is inserted into an initial bore 9 'and a rotation is simultaneously printed with this burnisher relative to the blank, as shown in FIG. 4. Unlike the conventional polishing step, this method eliminates the need to machine a clearance groove in the bore 9 ', so that the latter is configured as

  that rectilinear channel having no clearance throat

  It can be finished to form the guide bore 9. By this method, the burnishing can be performed immediately after the drilling 9 'has been made while the blank remains fixed on the

  same size, which makes it easy to reach the

  of the burnishing tool 17 and the drilling 9 ', where

  results in improved productivity and accuracy.

finishing.

  The burnisher 17 has first and second sur-

  respective burnishing faces 17a and 17b, which respectively come into sliding contact with the bore 9 'and a seat 10' of the valve. A rotation is printed at this burnisher 17 relative to the blank about the same axis as that of the drill, so that the second burnishing surface 17b rectifies the seat 10 'to form the surface 10a whose finishing occurs concomitantly with

  that of the guide bore 9, which improves the technique

  production. According to this method, since only one tool 17 is used, it is possible to improve the concentricity, the uniformity of the surface finishes.

  the bore 9 and the surface 10a, as well as the precision

  injection valve. If necessary, lubrication grooves 17c are made in the surfaces of

burnishing 17a and 17b.

  As described above, since the present invention involves a finish burnishing of the guide bore and the valve seat, it eliminates the need to develop a clearance clearance groove which is otherwise necessary in the case. classic polishing

  and, therefore, it simplifies the intervention by

  any possible negative effects that may result from cutting waste and the clearance throat. Since the machining of the bore and the burnishing can be performed simultaneously, it is not necessary to remove the blank from the jig and reposition it repeatedly, the burnishing may take place while this draft

  remains attached to the template used to form the bore.

  As a result, both production and precision

  finishing can be improved.

  It goes without saying that many modifications can be made to the process described and shown without

depart from the scope of the invention.

Claims (4)

  A method of manufacturing a seat member of a fuel injection valve comprising   a main valve body (1); an electric winding   tromagnetic (2) housed in this body. (1); a fixed core (3) located in said body (1); a movable core (5) magnetically attracted to said fixed core (3) by said winding (2); a valve stem (7) which is secured to said movable core (5) and has a shutter (6) at one end; and an element (8) forming the seat of the valve, which is fixed to said main body (1) and wherein said rod (7) is guided, characterized in that it consists in elaborating, in said element (8) forming a seat of the injection valve, a bore (9) serving to guide   said rod (7) in its respective movements of opening   ture and closure; to provide, in the extension of this guide bore (9), a seat (10) on which said shutter (6) is applied; to drill a   orifice (11) for delivering the fuel in the prolongation   said seat (10); to be burnished   at least one of the surfaces constituted by said   guide guide (9) and said seat (10); and harden   said element (8) after this burnishing.   2. The process according to claim 1, wherein   characterized in that the guide bore (9, 9 ') is machined by a drill rotating about an axis, the burnishing being performed by rotating a tool (17) about the same axis as that of said drill. 3. Method according to claim 2, characterized in that the tool (17) has two surfaces (17a, 17b) for   burn the bore (9, 9 ') and the seat (10, 10').   4. Process according to claim 3, characterized   rised by the fact that the guide bore (9, 9 ') and the   seat (10, 10 ') are concurrently   wise. A method according to claim 2, characterized in that the valve seat member (8) is held in a jig when   machining the bore (9), the seat (10) and the ori-   firing (11), the burnishing taking place while that   ment (8) is maintained in said jig.