FR2576993A1 - Method of clamping a torsion bar - Google Patents

Abstract

The two joined ends of a composite band, formed mainly from roughly longitudinal reinforcing elements bonded in a matrix, are wound around each zone of the bar experiencing a torque. The loop opposite this end is anchored so that the tension on the band resulting from the winding operation causes the band to exert a radial pressure on each of the said zones in the bar, thus clamping it.

Description

l

  The present invention relates to immobilizer systems.

  sation of mechanical elements involved because of their capacity

  cited to undergo high torques, and in particular but not exclusively, torsion bars in the automotive industry. It is known that the effectiveness of these systems is

  linked to their free length between the terminal injection zones

  tion of couples, called "embedding", in this free length exerting variable torsional stresses, by

  example in a suspension. or a drive shaft.

  In known systems with steel torsion bars, the embedding is usually obtained by means of a barbed end or of polygonal section, introduced into a housing with the same geometry of the fixed frame on one side, and in the element of suspension, for example the triangle, on the other. The weight of the assembly is considerable, and of a significant bulk. In addition, the transposition of the grooved embedding structure to a torsion bar made of composite material (for example glass fibers embedded in a plastic matrix) comes up against problems of shearing and compression of the matrix, the consequences of which are generally annoying and / or

  result in unacceptable part dimensions.

  The present invention offers a solution to all of these problems, thanks to:

  - an installation that can be applied effectively without distinction

  tion to steel or composite material bars - a composite torsion bar system, lighter and shorter with equal performance than the equivalent steel system, and therefore more easily integrated for example in

a car.

  The invention therefore relates, first of all, to a process for the introduction of torques at the ends of a torsion bar, characterized in that it consists in winding around each of these zones the two joined ends of a composite tape formed essentially for example of longitudinal glass fibers embedded in a matrix of thermoplastic binder, the loop opposite these two ends being subjected to a restraint, so that the tension on said tape resulting from said winding operation creates a radial pressure of said tape over said area of the bar, allowing later

  to ensure said introduction of couples.

  In practice, the winding of said composite tape is effective as soon as it extends for example over about two

times the periphery of the bar.

  However, to ensure better anchoring of the encasement, still according to the invention, several identical composite ribbons are preferably distributed regularly around the bar and overlapping successively by a fraction of their length equal to their deviation while around the

closed off.

  Similarly, to obtain a damping effect at this embedding, the loop, considered to be immobile, of each composite ribbon, is wound around an axis or pin, preferably sheathed with an elastomeric material, and, in the case where several ribbons are associated, and therefore several axes, each time that, for example, a wheel with which such a suspension system is associated, is raised by a certain height, it causes the articulation to rotate of the suspension element, which in turn drives the torsion bar in rotation: for this, at the suspension / torsion bar interface, a traction is developed tangentially to the torsion bar perpendicular to each of the pins , which, in turn each exert traction on the ribbon associated with them, all of the ribbons, ultimately reflecting on the torsion bar of the torques proportional to the height

wheel lift.

  The ribbons then work in tension and autopressuri-

  centripetal position of the bar like a band brake. This type of operation is particularly favorable in terms of the quality of the stressing of the different parts of the part. Indeed, we work in tension in the fibers of the ribbon, which is ideal. The centripetal pressurization exerted by this tension ensures the adhesion of the interface structure of introduction of the couple / bar, this transmission of the stresses being done by complex phenomenon of friction and bonding under

  high pressure in a fiber matrix continuum.

  The bar being pressurized radially by the

  end structures, is placed in practical-conditions

  ideal for installation and can therefore work at full capacity; in particular, this pressurization effectively locks the core at the ends of the bar and promotes its role as a "prestressing cable", as described in the

  French patent N 80/24491, in the name of one of the applicants.

  It should be noted that the drive tapes can be glued onto the torsion bar not with a "plastic" matrix but by using a layer of vulcanized elastomer (effect

vibration damper).

  The drawing below will allow a better understanding of the invention; in this drawing, - FIG. I diagrammatically represents the basic principle of the invention, - FIG. 2 diagrammatically represents a mode of practical application of the invention, FIG. 3 illustrates the distribution of the elements of a mounting system in accordance with FIG. 2,

  - Figure 4 illustrates a practical mounting of a flush mount-

according to the invention, and

  - Figure 5 is a partial section on a large scale -

  the of a recess according to the invention, in its grooved version.

  The basic principle of the invention consists in joining the two ends substantially of the same length of a ribbon, for example made of mainly longitudinal glass fibers, impregnated with a matrix, for example a thermoplastic material, by winding them in their part. median around an axis 1-optionnellI sheathed with a rubber tube 2 preferably elongated as shown in Figure 1 to form a "head" 5, said ends then constitute a complex ribbon 3, which is wrapped around the bar of torsion 4. After a certain number of turns, generally at least two, the "head" '5 comes into contact with the last layer, and, once immobilized,

  ensures the embedding of the bar 4.

  In practice, several ribbons such as 3 are deposited, preferably distributed equiangularly on the bar 4, as illustrated in FIG. 2. In this case, the heads 5a, 5b, 5c, 5d ... come at the end of winding, in contact with the periphery of all the ribbons wound, in 5a ', 5b', c '5d', .., provided, of course, that the "'tails,'

  ribbons 3 are distributed at the start regularly on the circum-

  fcr - d- e a, a -J 4 (! aS rubaus 3 having senslblemet all the o: -î%: iïoueu 'say manirc that each q4eue is trapped by the

previous head.

  It is this distribution that he illustrates by way of example in FIG. 3. Each of the four ribbons 3a, 3b, 3c, 3d, having the same length L equal to twice the perimeter of the bar 4, and the winding is doing in the direction of arrow F, each ribbon will be deposited on the bar with, with respect to the previous one, an offset 1 equal to a quarter of said perimeter. After winding, the total number of layers of ribbon 3 superimposed will be eight, with four heads distributed 9angularly around the

0 bars.

  According to a variant, before the ribbons 3 are wound,

  you can wrap a round of rubber band around the bar

  cabbage or other elastomer (not shown). The advantage of this strip and / or of the elastomer sheath has the advantage of better supporting the shocks and also of making up for defects.

  possible alignment of the bar.

  This system advantageously applies to the fitting of steel torsion bars. It applies even better to

  the installation of torsion bars made of agglomerated fibers

  earned in a matrix, as described in particular in the patent

French above.

  In this case the material of the ribbons and that of the

  bar itself constitute a unitary whole like the illus-

be figure 4.

  In this figure, the bar 6 is embedded at its ex-

  left end 7 by a system according to the invention comprising

  (visible in the drawing) eight heads constituted by axes 8-

  8 'immobilized by grooved washers, integral with the frame 9 after winding of the ribbons shown as forming a mass

  unitary with said end 7-of the bar.

  Such an assembly has a whole series of advantages: Thus, for example, the built-in bar of FIG. 4 can undergo torsion angles of more than 60. She spends a couple of 90

  M.Da N. (meter-dica-Newton) .The overall diameter of the casing-

  very much is 38 mm; the thickness of the ribbon is 0.2 mm, its width 15 mm. The diameter of the pins is 3 mm. There are 8 pins. The mass of the bar is 454 g of composite and 428 g of steel, as drawn. It can be reduced with a different design to 454 g of composite and 110 g of steel, or 564 g compared to 2.3 kg of an equivalent steel bar. So the bar

  composite weighs only 24% of the equivalent steel bar.

  On the other hand, for the same properties, it measures 440 mm overall length against 982 mm for its steel counterpart (i.e. 44% of the steel bar). It is therefore more easily integrated into a car. As thermoplastic material, the

  polyamides, poly-ethylenes, polypropylenes, polysty-

  reins, modified or not, and the like.

  Although the invention has been described with reference to the preferred example of ribbons constituted by glass fibers agglomerated by a matrix of thermoplastic resin, many variants can be envisaged; for example, the threads may more generally be conventional reinforcing fibers, such as glass, metal, carbon, textile, boron, aramid fibers and the like, and the dies

  can be, not only thermoplastic, but also ther-

  curable, or even be constituted for example by elastomers or even suitable metals, in particular light metals such as aluminum or magnesium. The fact that a matrix is used, for example made of elastomer, makes it possible to produce torsion bar heads having a certain angular compliance, which allows an alignment take-up which is not possible.

  could get with rigid heads.

  Likewise, while it has been specified that the system according to the invention is monodirectional, it is easy to deposit two series of side-by-side tapes wound in opposite directions, which will allow the system to be bidirectional, for example of

  be able to be used for drive shafts.

  Conversely, the ribbons being all wound in the same direction, the system is normally monodirectional, but it can be made bi-directional by surrounding all of the ribbons by a winding covering them ensuring the strapping of the heads, which gives to the system its reverse operating capacity. Instead of or in addition to fibers, the tapes may include (not exclusively) as reinforcing material one or more very thin metal strips, for example

  foils, for example steel, 0.1 to 0.01 mm thick.

6 2576993

  In the case of the direct installation of a torsion bar in a grooved part, for example a suspension element of a vehicle. The pins of the ribbons wound on said bar constitute the male groove which comes to cooperate with the female groove made in said element, and transmit the torque to the bar. Pin 1 can then be

  both in steel and in short fiber composite.

  Thus, if we refer to Figure 5, we have represented

  felt, in very enlarged schematic section, a sector of a bar 10, similar to bar 6 of FIG. 4, and on the embedding zone from which are wound equiangularly, on

  two towers each, eight ribbons, 11, 11 '..., made up of the ma-

  niere indicated for the tape 3 in Figure 1, that is to say each comprising two thicknesses of composite and a head

  5.5 '... The installation area of the bar is thus covered

  te of 32 strata S (8 ribbons X 2 thicknesses X 2 layers), which, for a unit thickness of 0.2 mm represents a radial thickness e of 6.4 mm, ensuring grooved embedding, each head 5 representing a 3.2 mm male spline (pin 1 of

  3 mm in diameter, covered with a thickness of 0.2 mm of compound

  site), cooperating with the female grooves 13 of the chassis or of the suspension 12, the "tail" of each strip being immobilized by jamming the head of the previous one, as illustrated in FIG. 3. The direction of drive of the bar 10 being indicated by the arrow F ', the male splines 5 transmit the torque to the frame 12 by the corresponding female splines 13 of the latter. Such a construction is as effective as the system

  metallic, and in many cases has additional advantages

  for a much lower cost price

Student.

Claims (11)

  1. Method for embedding a torsion bar, characterized in that it consists in winding around each torque injection zone the two ends joined together with a composite tape formed essentially of substantially reinforcing elements longitudinal agglomerated in a matrix, the loop opposite this end being subjected to a restraint so that the tension on said ribbon resulting from said winding operation creates a radial pressure of said ribbon on each of said zones of said bar thus ensuring said embedding 2. Method according to claim I characterized in that the winding is pushed practically until the contact of said loop with the outer surface of the last turn of the winding.   3. Method according to claims 1 and 2, characterized   in that said winding is made over a strip of elastic fall around the bar.   4. Method according to any one of claims 1 to   3, characterized in that said loop is itself wound   around a spindle sheathed with elastomeric material.   5. Procedure5 according to any one of claims I to   4, characterized in that more windings are combined   identical ribbons distributed preferably equiangSlaire-   lie around the bar, overlapping successively equal lengths.   6. Method according to any one of claims X to   , characterized in that, with the aim of creating a bi-directional system, usable in particular with the drive shaft,   two series of ribbons are wound side by side in opposite directions.   7. Method according to any one of claims 1 to   6, characterized in that the torsion bar is made of steel, the   ends of the ribbons attached to it by gluing or vulcanizing tion.   8. Method according to any one of claims 1 to   7, characterized in that the reinforcing elements are wholly or partly glass fibers, tenitle, carbon fibers,   rira t R ^ i ^ te ou.anel; g esD a3] des ru ans c5étZXlUquos t_ë.-   r-2.e DcTi i {Ota or es. a U O a 1i ie s r aZy-   -._ 3 q., 53 e O a rLou d 7ra 5 - el r e t a Zmi En ium o71   magnesium to form a composite material.   9. Method according to claim 8, characterized in that the bar is itself also made of composite material, of   so that each installation zone constitutes a single head to hush up.   10. Method according to claims I to 5, characterized   in that all of the loops play the role of the male grooves cooperating with the female grooves made in the hollow   in a fixed frame to form a grooved recess.   11. Installation head for torsion bar, suspension   drive shaft or other metallic member subjected to torques, characterized in that it results from   the implementation of the method according to any one of the claims 1 to 10.