EP0507652B1 - Method of manufacturing a butterfly valve in a fuel supplying installation - Google Patents

Description

The present invention relates to a method of manufacturing a throttle valve intended to be fixed to a rotary shaft passing through a passage so as to control an air flow in the passage. It finds a particularly important application in supply installations for an internal combustion engine having a carburetor or a body comprising a throttle which is used to regulate the air flow admitted to the engine.

The shaft allows the butterfly to rotate between a fully open position, where it is oriented parallel to the axis of the passage, and a closed position, where it is applied against the wall of the passage and where, in general, it makes an angle of a few degrees with the plane perpendicular to the axis of the passage.

At present, many butterflies are mounted in a slot crossing the rotary shaft: in this case the axis of rotation of the butterfly is merged with a diameter of the butterfly and a diameter of the conduit. The butterfly can then be manufactured in a simple way, because its shape is that of a slice cut obliquely from a straight cylinder. It then suffices to cut out butterfly blanks with a press, to stack them while maintaining them in the appropriate orientation using a spindle and shims, and to machine the cylinder thus formed.

Butterflies are also used fixed, for example by screws, on a flat machined on the rotary shaft. When the diameter of the rotary shaft is large, one can practice a flattened depth such that the plane of the butterfly practically contains the axis of rotation.

When the passage is of small section, the rotary shaft has a diameter too small for it to be possible to machine a deep flat there. In this case, the throttle valve is offset from the axis of rotation: this situation is encountered in particular in many single-point injection supply systems for internal combustion engines.

It is then necessary to give the butterfly a more complex shape than in the previous cases. Figure 1 shows very schematically, by way of example, a throttle body 10 having a housing 12 in which is formed a passage 14 of cylindrical shape. The housing is traversed by a rotary shaft 16, controlled by the driver. On this rotary shaft is formed a flat 17 against which is applied the butterfly 20. The flat being shallow, the butterfly is largely offset from the axis of rotation.

It will be assumed in what follows that the direction of air circulation in the passage 14 is that indicated by the arrow f O. When the butterfly is in the closed position, it is therefore located upstream of the shaft 16. It then makes an angle of a few degrees with the cross section of passage 14.

So that at the same time the butterfly 20 applies well against the wall of the passage 14 in the closed position and does not get caught at the start of its opening movement, it must be scalloped upstream side, on at least a fraction of the periphery of the half which turns in a direction which increases the angle between the butterfly and the cross section of the passage. Figure 1 shows such indentations 22 which constitute in the butterfly thinned peripheral zones limited by a step in the form of an arc of a circle.

Up to now, these thinning operations have been carried out by machining with the individual milling cutter of each butterfly, which considerably increases the cost price.

The present invention aims to provide a butterfly manufacturing process of the above defined type avoiding the need for an additional machining operation performed individually on each butterfly.

For this purpose, the invention proposes in particular a manufacturing method according to claim 1.

It is thus possible to constitute throttle butterflies having peripheral zones thinned by the formation of a circumferential step on at least one face (the operation can however be carried out on both sides, for example for applications where the cross section of the passage varies along its axis).

• la figure 1, déjà mentionnée, montre schématiquement un corps de papillon, en coupe suivant un plan passant par l'axe du passage et perpendiculaire à l'axe de rotation du papillon qu'il contient ;
• la figure 2 est une vue en plan d'un papillon utilisable dans le corps montré en figure 1 ;
• la figure 3 est une vue du papillon depuis le bas de la figure 2 ;
• la figure 4 montre des étapes successives de fabrication lors de la mise en oeuvre du procédé.

The invention will be better understood on reading the following description of a process which constitutes a particular embodiment thereof, given by way of nonlimiting example. The description refers to the accompanying drawings, in which:

• Figure 1, already mentioned, schematically shows a butterfly body, in section along a plane passing through the axis of the passage and perpendicular to the axis of rotation of the butterfly it contains;
• Figure 2 is a plan view of a butterfly usable in the body shown in Figure 1;
• Figure 3 is a view of the butterfly from the bottom of Figure 2;
• Figure 4 shows successive manufacturing steps during the implementation of the process.

The butterfly 20 shown in FIGS. 2 and 3 has a disc shape comprising two thinned zones 22, having for example 0.5 mm thickness when the thickness of the rest of the butterfly is 1.5 mm and the angle of the butterfly with the cross section, in the closed position, is approximately 5 °. In the butterfly are pierced two holes 24 for receiving fixing screws on the rotary shaft. Two notches 26 are provided in the butterfly shown in Figures 2 and 3, to allow the mounting of sealing elements not shown. The thinned zones 22 can be provided over an entire half of the butterfly, except for a central angle a of approximately 40 °.

In Figure 4, we see that during a first step I is cut from a sheet for example of brass, using a punch acting in the direction of the arrow f1, on the one hand a pair of locating holes 28 and on the other hand two notches in an arc of a circle 30 whose internal edge corresponds approximately to a fraction of the final periphery of the butterfly. At a second station II, the thickness of the sheet on the internal edge is reduced using a press (always acting in the direction of arrow f1), to bring it to the final thickness required to constitute the thinned zones 22. This operation makes the metal (brass for example) creep outwards: this creep is authorized due to the width of the notches 30.

At station III a locating hole 34 is drilled, in the zone which will subsequently correspond to the central part of the butterfly, in order to allow locating once the zones which contain the holes 28 have been eliminated.

During stage IV, the periphery of the butterfly in its indented part is formed. During stage V, the other half is formed, which eliminates the zones containing the locating holes 28.

Finally, during step VI, the two holes 24 for the passage of the screws are formed by the press.

All the above operations, as well as the separation of the butterflies by cutting with the press can be carried out on the same tool to be followed. Butterflies set form are stacked at the exit and can be immediately taken up in series of several tens to be threaded on rods, held in place by wedges and transferred to a lathe performing global machining.

It can be seen that the cost of manufacturing the butterflies is very considerably reduced, owing to the fact that the unit rework for machining which was previously necessary is eliminated.

Claims (4)

1. A method of manufacturing a throttle valve (20) comprising peripheral zones (22) of reduced thickness as a result of the formation of a circumferential step on at least one surface,
      characterised in that before machining to give the valves (20) an edge in the form of an oblique section of a right cylinder, valve blanks are made by passing a metal strip along successive forming workstations at which: cutouts (30) are made in such manner that their internal edge corresponds substantially to the shape of the final valve; the said peripheral zones are stamped to reduce their thickness; and the outer shape of the valve is cut out through the reduced thickness zones and through the strip which has retained its original thickness.
2. A method according to claim 1, characterised in that the peripheral zones are so stamped as to cause the metal to flow into the space reserved by the cutouts.
3. A method according to claim 1 or 2, characterised in that lateral holes (28) for locating each blank position are first pressed out and then a locating hole (34) near the centre of the final valve before the external shape of the valve blank is cut out.
4. A method according to claim 1, 2 or 3, characterised in that the part of the valve comprising the reduced-thickness zones and the rest of the valve are successively cut out at two successive stations.

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