FR2727719A1 - Mechanism for centring helical return spring in rotary equipment e.g. gas flow control valve, used for i.c. engine carburettor - Google Patents

Abstract

The mechanism comprises a return spring (11) mounted about a longitudinal shaft (4) between a rotary equipment (5) and a valve body (2). Each end of the spring (14,15) is located respectively on one of two support surfaces (18,19) arranged on the rotary equipment and on the body. Each end of the spring extends radially outwardly (16,17) from the main body of the spring, and rests circumferentially against an abutment (20,21) situated on the respective support surface. Each support surface has, at least, one helical ramp surface of the same slope as the ends of the spring. The radial abutments (20,21) are circumferentially arranged on the support surfaces with respect to the helical ramps (18,19) on which the ends of the spring rest.

Description

"DEVICE FOR CENTERING A HELICOIDAL RETURN SPRING IN
TORSION, AND ITS APPLICATION TO GAS COUNT BODIES "
The invention relates to a device for centering a helical torsional return spring of a member rotatably mounted by an axis on a body, the spring being mounted around the axis and between the rotary member and the body.

 With regard to the body, it may in particular, but not limited to, be a gas control body, for an installation for supplying air or carburetted air to an internal combustion engine, in which case the rotary member is preferably, but not limited to, a sector or a cam for controlling the rotation of a throttle element, in the form of a disc and generally called a butterfly, mounted to rotate on a transverse axis in a duct of the body, the latter being equipped outside the body of the sector or of the cam integral in rotation with the axis, and intended to be moved in rotation with the throttling element relative to the body, against '' at least one helical torsion return spring, intended to bring the sector or the cam and the throttle element in a position of rotation relative to the body such that the throttle element is in a corresponding rest position usually at closing at m part of the body duct.

 On such a gas control body, which can be a carburetor body, or a throttle body for an automobile internal combustion engine, the throttle disc or throttle valve, its axis of rotation and the throttle control cam. globally constitute a movable assembly mounted swiveling on the body in order to regulate the passage section in the duct for the carburetted air, in the case of a carburetor, or for the intake air in the intake manifold, in the case of an injection fuel supply installation, as a function of needs expressed, most often by the driver, by action on the accelerator pedal connected to the control cam by a traction cable, causing the movable in rotation against the return spring or springs.

 To recall the moving element in rotation towards its initial rest position, possibly adjustable by the adjustment of appropriate stops, it has already been proposed to use a torsional return helical spring having, at each of its axial ends, a helical end turn bearing against one respectively of two bearing faces opposite one another, and formed one on the rotary member and the other on the body, each turn d end ending with a free end of the spring, which extends radially relative to the longitudinal axis of the latter, to come to bear, in circumferential direction, against one of two radial stops relative to the axis of rotation and presented, on the one hand, by the rotary member, and, on the other hand, by the body.

 In particular, to gain compactness, and because the return to rotation must be ensured by at least two different sources of energy, it has already been proposed that such a torsion return helical spring be double and consist of two strands parallel metal, joined and coiled together in a helix with a substantially constant pitch, the radial ends of the ends turns projecting outwards from the spring.

 Known gas control bodies, equipped with such a helical spring for torsional return of the butterfly rotation control cam, have the disadvantage that the bearing faces receiving the helical turns of the ends of the spring are formed by the bottoms, perpendicular to the axis of rotation, of flats arranged opposite one another in the cam and in the throttle body. As the helical turns of the ends of the spring bear against the flat bottoms of these flats, it follows that the helical spring is curved along and around the axis of rotation, and that its longitudinal axis is curved with respect to the axis of rotation and no longer coaxial with the latter.

 I1 results in mounting difficulties of the spring, and the latter, in operation, works by developing a parasitic radial component of the restoring force.

 The problem underlying the invention is to remedy these drawbacks, and to ensure that the return spring no longer works partially in bending but only in torsion, and furthermore that its mounting is simplified.

 To this end, the invention provides a device for centering a helical torsional return spring of the aforementioned type, which is characterized in that each of the bearing faces of the rotary member and of the body is defined by at least part of a helical ramp with a slope substantially equal to the slope of the corresponding helical end turn of the spring, and in that the radial stops of the body and of the rotary member occupy, in circumferential direction, relative to the ramps helical, indexed positions corresponding to those of the radial ends of the spring end turns, when the end turns rest against the corresponding helical ramps. This advantageously ensures a refocusing of the helical torsion return spring, including the longitudinal axis is thus kept parallel and practically coincident with the geometric axis of rotation of the control cam and of the butterfly on the body , so that the return helical spring works in pure torsion, and can move the moving element on its return stroke with a low hysteresis.

 At least one of the bearing faces, or even each of them, can be defined by a continuous helical ramp over substantially less than one turn of the propeller around the axis of the spring, in order to provide good bearing surface for substantially all of the corresponding helical end turn, without simultaneously complicating the mounting of the spring. But, according to an advantageously economical and lighter embodiment, at least one of the bearing faces, but preferably each of them, is defined by a discontinuous helical ramp, formed by a succession of substantially radial studs, spaced apart in the circumferential direction, and in height, in the axial direction, varying progressively substantially according to the slope of the corresponding end helical turn.

 Advantageously moreover, in order to guarantee proper guidance of the ends of the spring in the position of cooperation with the bearing faces, in order to keep the helical spring centered on the axis of rotation, at least one of the helical end turns of the spring, but advantageously each of them, is housed in an axial chamber of the rotary member or of the body; thus, the bottom of an axial chamber can be at least partially formed by the corresponding helical support ramp, and the axial chamber opens axially towards the other end of the spring.

 In order to further improve the centering and the guiding of the helical spring, said axial chamber, or each of them, is advantageously annular and concentric around the axis of rotation, and delimited around a central core integral with the member rotary or of the body which presents it.

 Advantageously, when at least one of the helical support ramps, but preferably each of them, is discontinuous and formed of studs, the corresponding central core consists of substantially radial ribs, spaced in circumferential direction, and extending axially over a distance greater than the maximum height of the studs of the corresponding support ramp, each stud being in one piece with a respective rib of the central core. This structure has the advantage of facilitating the production of the studs at the base of the ribs of the central core, and therefore of facilitating the production of the discontinuous helical ramp thanks to the presence of such a central core.

 The centering device according to the invention is advantageously used with a double helical spring, constituted, as known and presented above, of two parallel metal strands, joined and coiled together in a helix with a substantially constant pitch, but, of course , a spring with a single metal strand wound in a helix can also be used.

 The invention also relates to a gas control body, for an installation for supplying air or carburetted air to an internal combustion engine, and equipped with a cam for controlling the rotation of a throttling element. , disc-shaped, rotatably mounted on a transverse axis in a conduit of the body, the cam being integral in rotation with the axis outside the body and intended to be moved in rotation with the throttling element relative to the body against at least one helical torsion return spring, intended to bring the cam and the throttle element into a position of rotation relative to the body such that the throttle element is in a at least partial closed position of the body duct, as described above, and which is characterized in that it comprises a centering device according to the invention, as defined above, for centering the helical return spring twisting between the cam e of command and body.

 Advantageously in this application, the control cam can be molded in one piece with the corresponding helical support ramp, as well as with a corresponding central core and the axis of rotation itself, the molding being carried out preferably a synthetic moldable material, such as a thermoplastic preferably loaded with reinforcing fibers, for example glass fibers.

 Likewise, the helical support ramp of the body as well as a corresponding central core can be made in one piece with this body, which can, optionally, also be molded in a synthetic moldable material, preferably also responsible for reinforcing fibers.

Other advantages and characteristics of the invention will emerge from the description given below, without implied limitation, of an exemplary embodiment described with reference to the appended drawings in which
- Figure 1 is an overall perspective view of a throttle body fitted with a throttle control cam, shown partly in section, for an installation for supplying fuel by injection of an engine with automobile internal combustion,
FIG. 2 is a view, partly in side elevation and partly in axial section, of the cam of FIG. 1 secured to the axis of rotation, around which the helical torsion return spring is mounted, and
- Figure 3 is a view similar to Figure 2 showing the spring mounted in the use position on the rotation control cam.

In FIG. 1, the throttle body, generally designated by the reference 1, comprises a body 2 proper, crossed by a cylindrical duct 3, in which a throttle throttle (not visible in FIG. 1) is mounted rotatable on a transverse axis 4, journalling in the body 2 on either side of the conduit 3, and such that its two end parts, only one of which is visible in FIG. 1, are projecting and accessible to the outside of body 2,
A cam 5 is mounted in cantilever on the other axial end of the axis 4, of which it is integral in rotation, to control the rotation of the butterfly in the conduit 3 of the body 2.

 To this end, in a well known manner, the cam 5 has a groove 6 which extends in a circumferential direction over part of its periphery, and opens radially outwards between two flanges 7 and 8 radial relative to axis 4.

 The cam 5 and the axis 4 can be rotated to rotate the butterfly in the conduit 3, by pulling on an accelerator cable (not shown), one end of which is anchored in one end of the groove 6 and one of which part, of variable length, is engaged in this groove 6.

 FIGS. 2 and 3 show that the diametrical axis 4, provided, in its part passing through the conduit 3, with a diametrical slot 9 for housing the butterfly fixed to the axis 4 by screws engaged in holes 10 perpendicular to the diametral slot 9, is an axis 4 molded in one piece with the cam 5, for example in a synthetic moldable material, such as a thermoplastic preferably reinforced with reinforcing fibers, in particular glass.

 The butterfly, possibly molded in the same material, constitutes with the axis 4 and the cam 5 a movable assembly rotatably mounted on the body 2 and returned to an initial rest position, which corresponds to a more or less complete closed position. of the conduit 3 by the butterfly, by a helical torsion return spring 11, when no traction is exerted on the connecting cable rator.

 This helical return spring 11 consists of two identical strands 12 and 13 preferably of stainless steel of, for example, 1.5 mm in diameter, which are parallel and joined axially by being wound together in a helix with a substantially constant pitch , forming a helical spring having a diameter of, for example, 30 mm. This helical spring 11 thus has two turns of ends 14 and 15 which are each helical, and which each terminate in a free end 16 or 17 projecting radially outward from the spring 11 relative to its longitudinal axis.

 By its helical end turns 14 and 15, the spring 11 bears axially against bearing faces 18 and 19 facing each other and formed respectively on the cam 5 and on the body 2. The spring 11, thus mounted axially between the cam 5 and the body 2, and radially around the shaft 4, at its free ends 16 and 17 engaged respectively in a radial slot, delimited between two radial stops such as 20 on the face of the cam 5 facing the body 2, and in a slot delimited between two radial stops such as 21 on the face of the body 2 facing the cam 5 (see FIG. 1). These ends 16 and 17 of the spring 11 are thus secured in the circumferential direction respectively of the rotary cam 5 and of the body 2, so that the helical spring 11 ensures a return of the cam 5 to the initial position, when it has been moved away from this position by rotation with the axis 4 by traction on the throttle cable.

 According to the essential characteristic of the invention, each of the bearing surfaces 18 and 19 has, with respect to the axis 4 and the longitudinal axis of the spring 11, an inclination substantially identical to the slope of the helical turn d corresponding end 14 or 15 of the spring 11. In this example, each of the bearing faces 18 and 19 is defined by a discontinuous helical ramp, having substantially the same slope as the corresponding helical end turn 14 or 15 which is supported on it, and more particularly shown in the figures and described below for the bearing face 18. Each discontinuous helical ramp such as 18 is constituted by a succession of radial studs 22, spaced from each other in circumferential direction and having a height, in the axial direction, which varies progressively from one stud 22 to the other of the succession in a manner which corresponds substantially to the slope of the helical end turn corresponding mite 14, thus taking support simultaneously on all these studs 22, without bending the spring 11 radially, the longitudinal axis of which thus remains parallel to the axis 4. Different studs 22 constituting the discontinuous helical ramp 18 are identified at 22a, 22b, 22c and 22d in the figures. Each of the studs 22, the front face of which (towards the spring 11) can be inclined according to a portion of helical surface around the axis of the spring 11, projects radially outwards on the base of one respectively of several radial ribs such as 23a, 23b, 23c and 23d, which are also spaced in circumferential direction from each other, but which extend axially over a distance greater than the maximum height of the studs 22 forming the helical support ramp 18, so that all of these ribs constitute a central core 23 ensuring the centering and guiding of the spring 11 radially inward.

Each of the studs 22 is thus in one piece with a respective rib of the central core 23, and these studs 22 and ribs of the central core 23 project radially outward from a hub connecting the cam 5 at the end corresponding to the axis 4. The studs 22 and the ribs of the central core 23 protrude into a concentric annular chamber 24 formed in the face of the cam 5 which faces the body 2, inside an annular skirt 25 and around the central core 23, and this chamber 24 opens axially towards the other bearing face 19 on the body 2, which can be produced in the same way, by successive studs, spaced circumferentially and of axial height progressively variable, and each projecting on the base of one respectively of several radial ribs extending axially over a distance such that they form a central core to guide and center the corresponding end part of the spring 11 on the body 2, inside a chamber also annular and concentric in the body 2, and opening axially towards the chamber 24. The axial dimension of the ribs such as 23a to 23d of each central core such as 23 and, more generally, the axial depth of each annular chamber such as 24, concentric with the axis of rotation, are such that not only an end turn such as 14 or 15 of the spring 11 is housed in the corresponding axial chamber, such as 24, but also at least one and if possible several turns immediately adjacent to the end turn considered.

The advantage of this arrangement is that the spring 11 is thus protected, centered and guided over practically its entire length between the central cores such as 23, radially inwards, and skirts such as 25 on the cam 5 and on the body 2, with the radial stops such as 20 and 21, radially outward.

 It should be noted that the radial stops such as 20 and 21 occupy indexed positions relative to the studs such as 22 of the corresponding helical ramp, so as to define a slot receiving the end 16 or 17 of the spring 11 in the position corresponding to the end of the corresponding end turn 14 or 15, that is to say immediately near the studs such as 22 of lower axial height, therefore at the base of the corresponding discontinuous helical ramp. The advantage of such an embodiment is that the studs 22 and ribs of the central core 23, as well as the skirt 25 and the radial stops 20 of the cam 5 are obtained during the same molding operation, during the production in one piece of the axis 4 with the cam 5, while allowing a saving in weight and material.

 Of course, it can be the same for the body 2, which can be molded in one piece with the helical support ramp 19 and the corresponding central body.

Claims (10)

 1. Device for centering a helical spring (11) for torsional return of a member (5), such as a sector or a gas control cam, rotatably mounted by an axis (4) on a body ( 2), such as a throttle body, the spring (11) being mounted around the axis (4) between the rotary member (5) and the body (2), and having, at each of its axial ends , a helical end turn (14, 15) bearing against one respectively of two bearing faces (18, 19) facing one another and formed one (18) on the 'rotary member (5) and the other (19) on the body (2), each end turn (14, 15) ending in a free end (16, 17) of the spring (11), which s' extends radially relative to the longitudinal axis of the latter, to come to bear, in circumferential direction, against one of two radial stops (20, 21) relative to the axis of rotation (4) and presented, d on the one hand, by the rotary member (5), and, on the other hand, by the co rps (2), in order to return the rotary member (5) in rotation to an initial position relative to the body, (2) characterized in that each of the bearing faces (18, 19) of the rotary member ( 5) and of the body (2) is defined by at least part of a helical ramp with a slope substantially equal to the slope of the corresponding helical end turn (14, 15) of the spring (11), and in that the radial stops (20, 21) of the body (2) and of the rotary member (5) occupy, in circumferential direction, relative to the helical ramps (18, 19), positions indexed in correspondence with those of the radial ends ( 16, 17) of the end turns (14, 15) of the spring (11), when the end turns rest against the corresponding helical ramps.  2. Device according to claim 1, characterized in that at least one of the bearing faces (18, 19) is defined by a continuous helical ramp over substantially less than one revolution.  3. Device according to one of claims 1 and 2, characterized in that at least one of the bearing faces (18, 19) is defined by a discontinuous helical ramp, formed by a succession (22a, 22b, 22c , 22d) of pads, substantially radial, spaced in the circumferential direction, and of height, in the axial direction, varying progressively substantially according to the slope of the corresponding end helical turn (14, 15).  4. Device according to any one of claims 1 to 3, characterized in that at least one of the turns (14, 15) of helical end of the spring (11) is housed in an axial chamber (24) of the 'rotary organ (5) or body (2).  5. Device according to claim 4, characterized in that said axial chamber (24) is annular and concentric around the axis of rotation (4), and delimited around a central core (23) integral with the rotary member (5) or of the body (2), in order to center and guide the helical spring (11).  6. Device according to claim 5, as attached to claim 3, characterized in that the central core (23) consists of substantially radial ribs (23a, 23b, 23c, 23d), spaced in circumferential direction, and s' extending axially over a distance greater than the maximum height of the studs (22) of the corresponding support ramp (18, 19), each stud (22) being in one piece with a respective rib of the central core (23).  7. Device according to any one of claims 1 to 6, characterized in that the helical spring (11) is double and consists of two parallel metallic strands (12, 13) joined and coiled together helically with a pitch substantially constant.  8. Gas control body (1), for air or carburetted air supply installation of an internal combustion engine, and equipped with a cam (5) for controlling the rotation of a throttling element, disc-shaped, rotatably mounted on a transverse axis (4) in a conduit (3) of the body (2), the cam (5) being integral in rotation with the axis (4) outside the body (2 ) and intended to be moved in rotation with the throttling element relative to the body (2) against at least one helical spring (11) for torsional return, intended to bring the cam (5) and the throttling element in a position of rotation relative to the body (2) such that the throttling element is in an at least partial closed position of the conduit (3) of the body (2), characterized in that '' it comprises a centering device according to one of the preceding claims 1 to 7, for centering the helical spring (11) for torsional return between the cam control (5) and the body (2).  9. Body according to claim 8, characterized in that the control cam (5) is molded in one piece with the corresponding helical ramp (18), a corresponding central core (23) and the axis of rotation (4), preferably made of a synthetic moldable material, such as a thermoplastic preferably loaded with reinforcing fibers.  10. Body according to one of claims 8 and 9, characterized in that the helical support ramp (19) of the body (2) and a corresponding central core are made in one piece with this body (2 ).