EP0507652A1 - Method of manufacturing a butterfly valve in a fuel supplying installation - Google Patents

Abstract

The method is intended for manufacturing throttle butterfly valves comprising thinned peripheral zones by forming a circumferential baffle (step) (22) on at least one face. A metal strip is made to pass through successive shaping workstations at which: curved cut-outs (30) are made corresponding to zones of the perimeter to be thinned, these zones of the perimeter (32) are stamped in order to reduce their thickness and the external shape of the butterfly valve is cut out through the thinned zones with the strip having maintained its original thickness. <IMAGE>

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 in 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. In this case, the throttle 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 the butterfly 20 is applied. The flat being shallow, the butterfly is largely offset from the axis of rotation.

In the following, it will be assumed 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 on the 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 method of manufacturing a butterfly of the kind defined above avoiding the need for an additional machining operation performed individually on each butterfly.

To this end, the invention notably proposes a manufacturing method according to which, before machining a stack of butterflies to give them an edge in the form of an oblique slice of a straight cylinder, a metal strip is passed through successive work stations of forming which: notches are cut corresponding to zones of the periphery to be thinned on butterflies; said perimeter zones are stamped to reduce their thickness; the outer shape of the butterfly is cut through the thinning and through the strip having retained its original thickness.

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;
• FIG. 4 shows successive manufacturing steps during the implementation of the method.

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 locating holes 28 and on the other hand two indentations 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 causes the metal (brass for example) to 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)

Method for manufacturing a throttle valve comprising thinned peripheral zones by forming a circumferential step on at least one face,
characterized in that, before machining to give the butterflies an edge in the form of an oblique slice of a straight cylinder, butterfly blanks are made by passing a metal strip through successive forming work stations to which: cut notches (30 ) corresponding to peripheral areas to be thinned; said peripheral zones are stamped to reduce their thickness; and the outer shape of the butterfly is cut through the zones of reduced thickness and through the strip having retained its original thickness. Method according to claim 1, characterized in that the notches are cut so that their internal edge corresponds substantially to the shape of the final butterfly and in that the peripheral zones are stamped so as to creep the metal in space reserved by the notches. Method according to claim 1 or 2, characterized in that first press holes are cut (28) for locating each blank location, then a locating hole (34) near the center of the butterfly final before cutting of the external shape of the butterfly blank. Method according to claim 1, 2 or 3, characterized in that the portion of the butterfly comprising the thinned zones and the rest of the butterfly is cut successively, at two successive positions.

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