Patent Publication Number: US-6705283-B1

Title: Throttle body comprising a butterfly with a spot face

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a throttle body for a fuel injection device for an internal combustion engine. 
     More specifically, the invention relates to a throttle body of the type comprising: 
     a housing in which an air inlet duct is formed, and 
     a butterfly in the form of a substantially circular or slightly elliptical disk mounted on a central rotation spindle transversal to the duct, splitting this duct into an upstream part and a downstream part and movable between a minimally open position and a wide open position for which the plane of the butterfly is oriented substantially parallel to the axis of the inlet duct, the part of the butterfly which rotates toward the upstream part of the duct and the part which rotates toward the downstream part, from the minimally open position, being known respectively as the upper wing and the lower wing and having the shape of a flat half-disk having an edge face of small thickness with respect to its area, the upper wing thus having an upstream face and a downstream face, the duct being intended to have passing through it a stream of gas the velocity of which is at a maximum as it passes a portion of the upper wing of the butterfly. 
     2. Background Art 
     The gas deflected by the butterfly has a velocity gradient which reaches a maximum over a certain portion of the upper wing of the butterfly. This may give rise to a whistling effect at certain angles of opening of the butterfly when the stream of gas is deflected sharply downstream of the butterfly, for example by a wall of the inlet manifold positioned in close proximity to the outlet of the housing, this being true irrespective of the known shapes of butterfly. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a throttle body in which this kind of whistling is eliminated irrespective of the angle of opening of the butterfly. 
     To this end, according to the invention, a throttle body of the type in question is essentially characterized in that a recessed relief is formed in the downstream face of the portion of the upper wing of the butterfly which experiences the maximum gas velocity, the recessed relief opening radially into the peripheral lateral face of the butterfly and being delimited by surfaces of which the intersections with the downstream face are sharp edges. 
     By virtue of these provisions, the recessed relief dissipates some of the energy of the stream of gas which flows over the butterfly so that the energy available for producing audible noise is greatly reduced and the whistling is therefore eliminated, whatever the angle of opening of this butterfly. 
     In preferred embodiments of the present invention, recourse is further had to one and/or more of the following arrangements: 
     the recessed relief is delimited by an upper face from which there extend, as far as the downstream face, two substantially radial faces substantially facing each other, and a transverse face connecting the substantially radial faces together and which are such that the intersections of the substantially radial faces and the transverse face with the downstream face are sharp edges, 
     the upper face, the substantially radial faces and the transverse face are substantially flat. 
     the intersections of the transverse face with the substantially radial faces and the upper face are sharp edges, 
     the substantially radial faces are connected to the upper face with a rounded shape, 
     the substantially radial faces diverge from one another from the transverse face and toward the peripheral lateral face of the butterfly, 
     the upper face of the recessed relief is substantially parallel to the downstream face and the upstream face, of which the intersections with the peripheral lateral face of the butterfly are sharp edges, 
     at the recessed relief, the remaining thickness of the butterfly is less than about 1.5 mm, the width of the recessed relief, considered in a substantially circumferential direction, is substantially between 10% and 25% of the diameter of the butterfly, and the length of the recessed relief, considered in a substantially radial direction, is greater than about 50% of the width of said relief, and 
     the length of the recessed relief is less than about 90% of the width of said relief. 
    
    
     Other features and advantages of the invention will become apparent in the course of the following description of one of its embodiments, which is given by way of nonlimiting example, with reference to the appended drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view in longitudinal section of a throttle body comprising a butterfly according to the present invention, 
     FIG. 2 is a view from beneath of the butterfly of FIG. 1, and 
     FIG. 3 is an enlarged partial schematic view, on arrow III of FIG. 2, of the butterfly in side elevation facing onto the opening of the recessed relief in the peripheral lateral face of the butterfly. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     FIG. 1 depicts a throttle body  1  which comprises a housing  2  in which an inlet duct  3  of longitudinal axis X—X is formed. The housing  2  is, for example, manufactured by molding in a synthetic material such as a thermoplastic, and obtained in its definitive shape without additional machining or additional deburring. This housing may alternatively be made of aluminum. 
     In the housing  2 , a pivot  5 , of axis Y—Y perpendicular to the longitudinal axis X—X of the duct  3  and intersecting this axis X—X, is mounted so that it can rotate and constitutes a central rotation spindle for a butterfly  6  in the form of a flat disk of cross section (perpendicular to the axis of the disk) approximately circular or slightly elliptical, with an upper face and a lower face which are substantially flat and substantially parallel to one another, and of which the intersections with a peripheral lateral face that connects them to each other are sharp edges. 
     The central rotation spindle  5  is mounted to rotate, for example, mid-way up the duct  3  and splits this duct into two portions  8  and  9 . As the duct  3  has a stream of gas passing through it in the direction of the arrow F, for example, the portion  8  is, by convention, known as the upstream portion and the portion  9  is known as the downstream portion. 
     The butterfly  6  depicted in FIGS. 1 to  3  is advantageously made of a synthetic material such as a thermoplastic. It consists of a flat disk which in plan view is of substantially circular or slightly elliptical shape, of generally constant thickness which means that it has an edge face  11  of substantially constant height around the entire periphery of the disk. Because of technological constraints and because of the pressure exerted by the gases on the butterfly  6 , its thickness is, for example, substantially equal to 3 mm at least. 
     The butterfly  6  pivots about its central rotation spindle  5  in the direction of the double-headed arrow R depicted in FIG. 1, between a minimally open position and a wide open position. In FIG. 1, the butterfly  6  is depicted in an intermediate position of openness. This butterfly may thus be considered as consisting of two half-disks  12  and  13 , the half-disk  12  rotating toward the upstream part  8  of the duct  3  being known as the upper wing and the half-disk  13  rotating toward the downstream part  9  of this duct being known as the lower wing. The upper wing  12  has a face  15  known as the upstream face, facing toward the incoming stream, and an opposite face  16  known as the downstream face which faces toward the outgoing stream. 
     The distribution of the gas velocity gradient across the duct  3  dictates that a portion  20  of the trailing edge of the upper wing  12  experiences a maximum gas velocity. In this portion, the energy of the stream is therefore very high. 
     According to the present invention, at this portion  20 , a single recessed relief  21  is made in the downstream face  16  of the upper wing  12 . This relief  21  opens into the downstream face  16  and into the peripheral lateral face of the butterfly  6 , extending through part of the thickness of this butterfly. 
     The recessed relief  21  is in the form of a spot face of substantially rectangular shape and extending substantially radially. Its axis of symmetry Z—Z coincides for example with the diameter of the butterfly and is perpendicular to the axis Y—Y. This is because when no obstacle lies upstream of the butterfly  6  in the duct  3 , the plane of maximum gas velocities passes along the diameter of the butterfly  6  which is perpendicular to the axis of rotation Y—Y. However, when the duct  3  has an obstacle upstream of this butterfly  6 , the plane of maximum velocities passes through a different place which means that the recessed relief  21  then lies in a different region of the downstream face  16  of the upper wing  12  of the butterfly  6 . An essential characteristic is that this relief  21  always lies in the plane of maximum velocity. 
     In this instance, the depth of the recessed relief  21  is such that the remaining thickness e of the butterfly  6  in the region  20  is less than 1.5 mm. 
     Furthermore, the recessed relief  21  is delimited by an upper face  24  which is substantially flat and substantially parallel to the downstream face  16 , and from which there extend, as far as the downstream face  16 , two substantially radial faces  25 ,  26  substantially facing each other, and a transverse face  27 , which are also substantially flat, this face  27  connecting the radial faces  25  and  26  together and being substantially parallel to the axis of rotation Y—Y. 
     The intersections of the faces known as the radial faces  25 ,  26  and of the transverse face  27  with the downstream face  16  are all sharp edges  25   a ,  26   a  and  27   a . Likewise, the intersections of the transverse face  27  with the faces known as the radial faces  25 ,  26  and with the upper face  24  may be sharp edges  27   c ,  27   d  and  27   b.    
     The width l of the recessed relief  21 , considered in a substantially circumferential direction, that is to say its dimension along the transverse face  27 , is substantially between 10% and 25% of the value of the diameter of the butterfly  6 . As to the length L of this relief  21 , considered in the substantially radial direction, that is to say its dimension along the faces known as the radial faces  25 ,  26 , this is between about 50% and 90% of the width l. Typically, the width l is approximately equal to 6 mm and the length L is approximately equal to 5 mm while the depth of this relief  21  is substantially constant and approximately equal to 1 mm. The portion  20  of the upper wing  12  is of greatly reduced thickness by comparison with the thickness of the remainder of the butterfly  6 , and in this instance of the order of two-thirds to half the thickness of the remainder of the butterfly  6 . 
     Thus, the presence of the recessed relief  21  as defined hereinabove causes a reduction in the energy of the gas stream flowing over the butterfly  6  so that any whistling, which would typically arise at an angle of opening α of the butterfly  6  of between 13° and 21°, is eliminated. 
     As an alternative, the faces  25  and  26  may be substantially parallel to one another, alternatively may diverge, to an extent different than the divergence resulting from strictly radial faces, from the transverse face  27  and toward the periphery of the butterfly. 
     In yet another alternative form, the faces known as the radial faces  25  and  26  are connected to the upper face  24  of the relief  21  with rounded edges. This goes even further toward eliminating the whistling. 
     Sometimes, for space reasons, obstacles are located in the downstream part  9  of the duct  3 . It is then preferable for the butterfly  6  to be situated away from these obstacles by a distance equal at least to its diameter and preferably to 1.5 times its diameter.