EP0517584B1 - Throttle valve body for a fuel admission device for an engine - Google Patents

Description

The subject of the present invention is a throttle body for a fuel supply device for an internal combustion engine and it finds a particularly important application in throttle bodies for an injection device comprising electronic means for controlling the quantity of fuel introduced. at each engine operating cycle. However, it can also be used in other cases, and in particular when the throttle body belongs to a carburetion device controlled by electronic means.

A throttle body conventionally comprises a housing in which is formed an intake duct and a substantially circular disc-shaped butterfly, mounted on a median shaft of rotation about an axis transverse to the duct and movable between an open position minimum, possibly zero, and a maximum open position for which the butterfly is oriented parallel to the axis of the duct.

The quantity of fuel injected per cycle must be proportional to the air flow admitted to the engine. Many injection devices used today include electronic means for calculating the air flow from signals indicating the degree of opening of the throttle valve (supplied for example by a potentiometer) and the pressure difference between the 'upstream and downstream of the butterfly, representative of the air speed.

In the usual butterfly bodies the butterfly has a constant thickness and the duct is in the form of a circular cylinder in the area where the butterfly moves. In such a body, the passage section offered to the air increases rapidly during the initial angular displacement of the throttle from its minimum opening position, especially when this minimum opening is practically zero. However, satisfactory control of the motor at low loads (that is to say for small throttle openings) requires that the initial increase in the passage section be very gradual. In particular, driving pleasure is practically obtained, in the case of an electronically controlled injection device, only with an initial variation in the air flow as a function of the throttle opening angle. having the shape shown diagrammatically in thick lines in FIG. 1.

Generally, progressiveness is ensured by substituting the direct control of the throttle valve from the accelerator pedal with a control via a linkage having complex kinematics, the numerous joints of which impair the precision of the control, because from the accumulation of games.

We also use, to make the progressive control, a guide integral with the throttle axis and on which the cable is wound up, connected to the accelerator pedal, this guide being in the form of a sector of variable radius; the improvement obtained by such a technique is generally insufficient.

To provide a throttle body offering to the air a passage section which increases only very gradually during the initial opening of the butterfly, it has already been proposed by JP-A-58 202 338, which is considered to be the closest state of the art, a butterfly body of the kind defined in the second paragraph of the description, which also includes a cover placed in the intake duct, and rotatably mounted around an axis parallel to the axis of rotation of the butterfly and offset from this axis, the cover having an asymmetry with respect to its axis, on one side of which it has a first wing intended to close off a fraction of the cross section of the intake duct, when the position of the butterfly relative to its minimum open position forms an angle less than a determined angle, the cover being linked to the butterfly by a connection mechanical to cause the progressive forced opening of the cover when the movement of the butterfly from its minimum open position exceeds said determined angle.

The present invention aims to provide a throttle body of the type known by JP-A-58 202 338, and using only simple means to vary only very gradually the cross section of the air, in particular during of the initial opening of the butterfly.

To this end, the throttle body is characterized in that the seal is such that the air passing through the intake duct tends to bring its first wing into its position for closing said fraction of the section of the duct, and in that it has, on the other side of its axis housed in the housing, a second wing constituting a cam of shape such that the butterfly comes to bear on it when its movement exceeds said determined angle. Thus the butterfly drives, by a simple press, the cover in the direction of opening when the determined angle is exceeded. Such an embodiment is particularly simple. This is not the only possible: the coupling between butterfly and cover can be achieved by other mechanical means.

The axis around which the cover rotates and the axis of the butterfly shaft advantageously have a relative position such that the butterfly comes to bear against the first wing of the cover and drives it towards its closed position when the throttle returns to its minimum open position. Thus the cover is returned to its closed position not only by the air current, whose action on the first wing is greater than the action on the second wing, but also by positive action of the butterfly. A spring can also be provided to urge the cover towards its closed position.

To further improve the progressiveness, one can give to the intake duct, along the path of the butterfly wing which does not cooperate with the cover, a convergent shape from the location occupied by the edge of the butterfly when the latter is in its minimum open position.

Avoid jamming the cover in the closed position. The cover can be drawn so that, when closed, its plane makes a sufficient angle with a plane orthogonal to the axis of the duct; a stop can be provided to limit the angular displacement of the cover in the closing direction; the sliding of the cover against the wall of the intake duct and / or against the butterfly can be facilitated by constituting the cover in a material with a low coefficient of friction, such as a charged synthetic material.

Finally the two wings of the cover can be drawn so that, by their support against the wings of the butterfly, they limit the angular displacement of the latter from its minimum open position to stop it when it has reached its fully open position.

• la figure 1, déjà mentionnée, montre l'allure générale souhaitable d'une courbe de variation du débit d'air Q en fonction de l'angle d'ouverture du papillon, à différence de pression constante entre l'amont et l'aval ;
• la figure 2 est une vue en coupe, suivant la ligne II-II de la figure 3, d'un corps papillon suivant un mode particulier de réalisation de l'invention, le papillon étant représenté en position de ralenti, c'est-à-dire d'ouverture minimum ;
• la figure 3 est une vue de dessus de la figure 2 ;
• les figures 4, 5 et 6, similaires à la figure 2, montrent le papillon respectivement à l'extrémité de la zone d'ouverture sans entraînement de l'opercule, lors de l'entraînement de l'opercule, et en position d'ouverture maximum.

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

• FIG. 1, already mentioned, shows the general desirable appearance of a curve for variation of the air flow rate Q as a function of the opening angle of the butterfly valve, with constant pressure difference between upstream and downstream ;
• Figure 2 is a sectional view along line II-II of Figure 3, a throttle body according to a particular embodiment of the invention, the throttle being shown in the idle position, that is to say - say minimum opening;
• Figure 3 is a top view of Figure 2;
• Figures 4, 5 and 6, similar to Figure 2, show the butterfly respectively at the end of the opening zone without driving the cover, during the drive of the cover, and in the position of maximum opening.

The throttle body shown in Figures 2 and 3 comprises a housing in which is formed a passage constituting a portion of the air intake duct to the engine. A shaft 12 which crosses the intake duct 10 along a diameter carries a butterfly 14 in the form of a flat disc. The butterfly 14 is for example fixed in a slot of the shaft 12 by two screws 16. The butterfly is angularly movable between a minimum open position, practically zero, where it makes an angle α₀ with a plane orthogonal to the axis of the conduit 10, and a maximum open position (Figure 6) where it is oriented parallel to the axis of the duct and the flow of air F along the duct.

The butterfly can be driven by any of the usual linkage types. In the case illustrated in FIG. 3, this linkage comprises a lever 18 fixed to the shaft 12 and connected by a cable to an accelerator pedal. The device is completed by return springs, not shown. The shaft is also fixed, in many cases, to the cursor of a potentiometer constituting a throttle position sensor.

To make the increase in air passage section more progressive during the initial opening of the butterfly valve, the duct shown in FIG. 2 has a converging zone 20, of revolution so that it can be machined easily, from the position that occupies the downstream side of the resting butterfly. This measure further improves progressiveness.

The throttle body according to the invention shown in FIGS. 2 to 6 comprises a cover 22 rotatable about an axis 24 parallel to the axis of rotation of the butterfly, but offset from this axis downstream and also towards the wing of the butterfly which moves upstream during opening. The cover is for example mounted with gentle friction on a rod 26 fitted into the body. It can also include two journals rotating in bearings placed in the housing. At least in the case, which will be described in detail below, where the cover is driven directly by the butterfly, it is desirable to constitute the cover in a material with a low coefficient of friction, such as a charged synthetic material. .

The cover 22 has two wings 28 and 30. These wings are designed so as to fulfill several functions. The wing 28 has a shape such that the cover remains in the rest position where it is shown in Figures 2, 3 and 4 as long as the butterfly has not reached a position making an angle α₁, which will generally be understood between 35 and 55 °, with a plane orthogonal to the axis of the duct. The first wing 28 of the cover (wing rotating upstream in the case of FIG. 2) is provided for closing off a fraction of the intake duct during the initial opening of the butterfly valve. The edge of this first wing 28 is designed to bear against the wall of the intake duct 10 and is dimensioned relative to the butterfly so that the butterfly is in abutment on it when the cover is closed and the butterfly in its minimum opening position (Figure 2).

The second wing 30 of the cover has a profile such that the butterfly 14 comes to rest on it and cause the forced opening of the cover when the angle of the butterfly exceeds α₁. This second wing therefore constitutes an actuating cam. As shown in Figure 6, the profile of the two wings can be chosen so that the cover also constitutes a full opening stop, preventing the rotation of the butterfly beyond the vertical position corresponding to the maximum flow (Figure 6). Grooves 32 can be made in the cover to allow passage at the ends of the screws 16.

In its part close to the axis, the periphery of the second wing is generally designed so as to avoid or reduce air leaks along the shaft 12. The part of the second wing more distant from the axis 24 has a plan shape chosen according to the desired variation in flow characteristics. To obtain a particularly slow variation, the second wing can be given a strip shape extending over the entire width of the duct, as indicated in dashes in FIG. 3. In the case on the contrary, the part remote from the axis of the second wing 30 can be limited to a tongue 34 (in phantom in Figure 3).

The operation of the device which has just been described is as follows.

When the butterfly valve 14 is ajar from the minimum open position shown in FIG. 2, the air only begins to pass between the edge of the butterfly valve which opens downstream and the wall of the duct. Indeed, as shown in Figure 4, the seal continues to close substantially half of the passage section offered by the conduit.

There is also no passage along the shaft 12, because the central part of the cover 22 is in contact with the shaft itself.

When the degree of opening of the butterfly 14 exceeds that shown in FIG. 4, the wing of the butterfly which opens downstream pushes the second wing of the cover and drives the latter, causing a progressive opening.

Finally, when the butterfly reaches its fully open position (Figure 6) the cover itself takes a position in which it creates a minimum pressure drop, being applied against the butterfly.

When the butterfly closes, it pushes the cover back. This forced closure is a safety factor.

The invention is susceptible of numerous variants. For example, the housing can carry a stop intended to limit the rotation of the cover towards its closed position and to avoid jamming. The relative arrangement of the butterfly and the lid in the direction of flow can be reversed.

Claims (10)

1. A throttle valve body for a fuel feed device for an internal combustion engine, said body comprising a casing formed with an intake conduit (10) containing a throttle valve (14) in the form of a substantially circular disc mounted on a central shaft (12) rotatable about an axis extending transversely to the conduit (10), said throttle valve being movable between a minimum and possibly zero open position and a maximum open position in which the throttle valve (14) extends substantially parallel to the axis of the conduit (10), and also comprising a valve member (22) disposed in the intake conduit (10) and mounted for rotation about an axis (24) parallel to the axis of rotation of the throttle valve (14) and offset from said axis, the valve member (22) being asymmetrical with respect to its axis (24), on one side of which it has a first flange (28) adapted to close a fraction of the section of the intake conduit (10) when the position of the throttle valve (14) with respect to its minimum open position (α O) forms an angle less than a specific angle (α 1), the valve member (22) being connected to the throttle valve (14) by a mechanical link to cause progressive forced opening of the valve member (22) when the movement of the throttle valve (14) from its minimum open position (α O) exceeds said specific angle (α 1), characterised in that the valve member (22) is such that the air flowing through the intake conduit (10) tends to bring its first flange (28) into its position in which it closes the said fraction of the section of the conduit (10) and in that on the other side of its axis (24) it has, contained in the casing, a second flange (30) which constitutes a cam of a shape such that the throttle valve (14) bears thereon when its movement exceeds the said specific angle (α 1).
2. A throttle valve body according to claim 1, characterised in that the valve member (22) is mounted with an easy fit on a rod (26) fixed across the conduit (10).
3. A throttle valve body according to claim 1 or 2, characterised in that the axes of rotation of the throttle valve (14) and of the valve member (22) have a relative position such that the throttle valve (14) bears against the first flange (28) of the valve member (22) to drive it towards its closed position on closure of the throttle valve (14).
4. A throttle valve body according to any one of the preceding claims, characterised in that the axis of rotation (24) of the valve member (22) is offset downstream and on the side of the flange (28) of the throttle member (14) which moves upstream on opening.
5. A throttle valve body according to any one of the preceding claims, characterised in that the valve member (22) is made of a plastic having a low coefficient of friction.
6. A throttle valve body according to any one of the preceding claims, characterised in that the throttle valve (14) in its minimum open position forms an angle (α O) with a plane at right angles to the axis of the intake conduit (10), said angle (α O) being sufficient to obviate any jamming.
7. A throttle valve body according to any one of the preceding claims, characterised in that the second flange (30) of the valve member (22) has a periphery which closes the intake conduit (10) in a part of the cross-section contained between the axis of rotation (12) of the throttle valve (14) and the axis of rotation (24) of the valve member (22) at least.
8. A throttle valve body according to any one of the preceding claims, characterised in that the valve member (22) has a shape such that it forms a stop which limits the opening movement of the throttle valve (14) in its fully open position.
9. A throttle valve body according to any one of the preceding claims, characterised in that it comprises a spring returning the valve member (22) to its closed position.
10. A throttle valve body according to any one of the preceding claims, characterised in that the conduit (10) has a convergent shape (20) from the position occupied by the downstream section of the throttle valve (14) in the minimum open position (α O) of the latter.

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