FR2530508A1 - METAL RACK BAR, METHOD OF MANUFACTURING THE RACK BAR, AND STEERING GEAR - Google Patents

Abstract

METAL RACK BAR, METHOD FOR MANUFACTURING THIS BAR AND RACK GEAR USING THE SAME. RACK BAR CHARACTERIZED IN THAT IT IS SHAPED FROM A RAW METAL BAR SHORTER THAN THE RACK BAR 2 TO BE OBTAINED, THIS BAR 2 HAS A PARTIAL LENGTH 3 CARRYING A SET OF RACK TEETH, AND A LENGTH PARTIAL 5 OF REDUCED DIAMETER CONNECTING TO THE PRECEDING BY A SHOULDER 6, THE PARTIAL LENGTH 5 BEING SHAPED BY STAMPING SO AS TO REDUCE ITS DIAMETER BY STRETCHING IT TO THE DESIRED LENGTH. THE INVENTION APPLIES TO STEERING RACK GEARS.

Description

Metal rack bar, manufacturing method

  of this rack bar, and steering gear

  This invention relates to a metal rack bar, a method of manufacturing this rack bar from a raw metal bar, and a

  steering gear using this cremail bar-

  leer. Rack and pinion-type steering gears are well known in the automotive and ancillary industries. Conventionally, these gears comprise a pinion rotatably mounted in a housing, and whose teeth engage with a set of rack-and-pinion teeth. formed on a rack bar mounted longitudinally in the housing so that

  when the pinion is spinning in response to an order from

  direction, the rack bar moves longitudinally relative to the housing to provide a

direction output control.

  In its current form, the rack bar has, at one end, a certain length of bar on which the rack teeth are formed by

  machining (eg by machining in the forest or by stamping

  weaving or any other pressure molding technique

  the other end of the rack bar being

  generally smooth to form an extension

  suitable for coupling the rack bar to an appropriate steering linkage, as is

well known from the prior art.

  Classically, the rack bars are

  from raw metal parts and their manufacture

  This requires very large machining operations where the metal is to be removed from the bar, particularly in finishing the bar length from the rack portion. The workpiece is cut to a length corresponding at least to the length of the rack bar completed, and the weight, size and cost of a rack bar as well

  obtained by conventional means represent a proportion

  significant weight, size and cost of

  the steering gear using this bar.

  There is an ever increasing demand in the steering gear industry to achieve the gear elements more economically by reducing the overall size and weight of the gear without reducing its expected characteristics.

  efficiency, reliability and security.

  The invention therefore aims to create a bar of

  advanced rack and a method of manufacturing

  this bar meets the needs above.

  For this purpose, the invention relates to a rack bar comprising a first partial length carrying a set of rack teeth and a second

  completely smooth partial length lying long

  dinalement in the extension of the first partial length, the second partial length having a constant cross-section of surface less than that of the cross section of the first partial length and a peripheral shoulder being formed between these two partial lengths, rack bar characterized in that the surface thereof, on its second partial length between the end or a position adjacent the end opposite the first

  partial length, and on the transition part cor-

  corresponding to the length of the shoulder between the first and second partial lengths, does not exhibit any breakage so as to form a metallic grain

continuous on all this surface.

  The invention also relates to a manufacturing process

  cation of the rack bar above from a raw metal bar along a partial length of which

  is or must be formed a set of teeth cre-

  said method being characterized in that

  is machining a second partial length of the bar

  to reduce the cross-section of the latter by

  port to that of the first partial length and form a peripheral shoulder between these partial lengths

  while simultaneously increasing the longitudinal dimension

  of the second partial length, this machining

  providing a non-breaking surface over at least most of the second partial length from the shoulder and over the partial transition length of the bar corresponding to that shoulder between the first and second partial lengths, so as to obtain a continuous metallic grain on any

this surface.

  The invention finally relates to a steering gear

  using a rack bar as described

  above, manufactured by the method also described above.

above.

  The continuous metal grain obtained on the surface of the rack bar extending over the shoulder between the first and second partial lengths of the bar and from there on the second partial length is preferably obtained by subjecting the raw metal bar to a striping operation to progressively reduce the cross-section of the bar.

  machining is cylindrical in shape, its corresponding diameter

  to the required diameter to obtain the first partial length on which the row of

housewarming.

  The diameter of the longitudinal portion corresponding to the second partial length of the bar can then be reduced by stamping, this operation preferably being carried out by a rotary stamping technique in which the bar is subjected to radial action percussion rollers. the reduction in diameter (and therefore cross-section) of the machined part as indicated above, it occurs

  necessarily an increase in the long-term

  The length of the second partial length can be taken into account in such a way that after the stamping operation, the length of the second partial length obtained is compatible with the total length of the rack rod that one wants. get. The tin technology has the advantages

  following: The decrease in diameter of the crest bar

  for much of its length can

  to reduce its weight (compared to

  a cylindrical bar of the same size presenting a di-

  constant meter); the bar can be machined with precision

  to its required final length; falls of material

  riau used to manufacture the rack bar

  deleted and, as a result of the transaction.

  page, the finishing machining of the surface of the bar on its transition length and on its second partial length, is deleted It thus appears clearly

  that the above benefits reduce manufacturing costs

  cation of the rack bar.

  In addition, the cross-sectional reduction of the second partial length of the rack bar with respect to its first partial length is very interesting because it makes it possible to use a housing smaller than the usual housings housing the rack bar in steering gears This section reduction also allows the use of pads smaller than the usual pads in which the second partial length of the bar of

  rack is housed to move longitudinally-

  in the housing (or in a tubular extension

of this case).

  It is also possible, by reducing the dimensions

  side of the second partial length, for example by stamping as described above, so that the metal grain of the specified surface of the rack bar is not broken, to obtain a greater rigidity than that of a rack bar of the same size in which we simply reduced the

  diameter of the second partial length (comparative

  to the diameter of the partial length carrying the rack teeth) by removing metal by machining

at f 3 ret.

  The raw metal bar from which the rack bar is made can be solid or tubular. It is frequently desirable for the rack bar to have an axial passage through which a fluid such as air or a fluid can be passed.

  between axially separated chambers in the

  what can penetrate the rack bar of an engg-

  steering swim Making the rack bar

  from a tubular blank, we can

  to obtain the axial passage above from the central hole of the blank (even if it is assumed that the cross section of this central hole is reduced in

  diameter when reducing the section of the second lon-

  part of the rack bar).

  Preferably, the second partial length of the rack bar forms an extension from its

  part of rack, so as to allow the coupling

  from the rack bar to a steering linkage

  tion, for example through a universal joint-

  salt, to connect it to a drawbar or a servo

  engine such as a cylinder and steering piston device

  Although the invention eliminates the machining of the blank in the sense that no metal is removed during the formation of the second partial length, it is obvious that the end of this second the partial length farthest from the rack teeth must then be machined, as required, by a

  If, for example, the end of the second

  part of the rack bar, this end may be provided with a

  no internal or external screw allowing the accou-

  to another element of the steering linkage.

  However, it is considered that the second length

  should not necessarily extend from the

  until the end of the rack bar.

  This rack bar can for example be of the type "central catch" in which it is expected, at a point

  the length of this bar far from its two extremes

  mated, the connection of a coupling allowing ob-

  hold an exit movement to activate the trin-

  This result can be obtained in

  subjecting the bar to a machining or com-

  pressure after formation of the second partial length.

  The set of gear teeth may be formed on the bar before or after the formation of the second partial length of reduced diameter of this bar. The gear teeth may be formed in any suitable manner, such as for example by machining with the drill or by any other cutting technique, or by stamping or by any other forging technique. Although the steering gear using the

  rack bar according to the invention, generally

  Of the rack and pinion type, it is obvious that the rack bar according to the invention can also be fitted in other types of steering gears where the toothed element which engages with the rack teeth is present in a form other than that of a pinion and may be constituted for example by a

toothed sector.

  The invention will be described in detail by means of the accompanying drawings in which Fig. 1 shows a crude cylindrical bar-length from which the rack bar is made. Fig. 2 shows an embodiment of a rack bar having "end socket" made from the blank of Figure 1 to which it

  should be compared to appreciate the increase in

  obtained during this manufacture; -

  Fig. 3 shows a second embodiment of a "center plug" rack bar made from the blank of Fig. 1; and FIG. 4 is a sectional view along the

line IV-IV of Figure 3.

  A solid cylindrical steel bar 1 is cut,

  in a piece of raw material, with a length of

  determined shorter than the rack bar 2 to be made therefrom The rack bar 2 has a first partial length 3

  in which is formed a set of cremation teeth

  lere 4 The partial length 3 has a diameter

  corresponding exactly to that of the blank 1.

  A smooth cylindrical partial length of relative diameter

  5 partially extends longitudinally, in the embodiment of FIG. 2, in the extension of the partial length 3. The partial lengths 3 and 5 are concentric and are connected by a partial transition length 6 forming a shoulder between the

parts 3 and 5.

  The partial length of reduced diameter 5 is obtained by subjecting the blank 1 (except in its partial length corresponding to the partial length 3 of the

  cogwheel bar to be obtained) to a state operation

  page to gradually reduce its diameter

  The transformation of the blank 1 to form the shoulder 6 and the second stretched partial length 5 can be done by using a fast stamping machine using a radial action roll percussion system. wherein the blank is placed in a jaw plate and subjected to radial pressure allowing

  to obtain the cylindrical reduction during this operation.

  The stamping surface of the blank on which the shoulder 6 and the second partial length 5 are formed does not undergo any break, so that the continuous metal grain which existed at the

  surface of the raw part 1, is preserved in the shoulder-

  6 and in the partial length 5 of the rack bar.

  Before or after the formation of the length

  5, the set of rack teeth 4 can be suitably formed using conventional means such as drill machining or any other means such as

  itching or any other cold forming process.

  In a gabled and cremated steering gear-

  Typical example using the rack bar 2, one may need an "end plug" in which the ends of the rack bar must then be coupled to the drawbar (not shown) to form the linkage rod. direction For this coupling, the ends of the rack bar 2 must be machined, for example by a cutting tool, to form threaded holes 7 in these ends,

  or the end of the partial length 5 the furthest

  4 of the rack 4 can be machined or compressed to form a flat (not shown) on which can be

do the mating.

  If necessary, the blank 1 can be

  tubular so that its axial hole 8 can be

  serve as a fluid passage within the

rack bar 2.

  In the embodiment of Figures 3 and 4, the rack bar 2 is still manufactured from the blank 1, but this example provides a "central grip" according to which the rack bar

  can be mounted in a steering linkage of ma-

  to provide an outlet at a distance from its ex-

  The rack bar of FIG. 3 comprises two coaxial parts of reduced diameter 5 a and 5 b between which a coupling part 9 is placed axially. The parts 5 a and 5 b are formed by subjecting the

  piece 1 (except in the corresponding parts)

  to the partial length 3 and part 9 of the rack bar to be obtained), to stamping operations similar to those of the embodiment

of Figure 2.

  After this stamping, the coupling part 9 can be machined in the form of a flat, as shown in FIG. 4, and pierced by lateral holes 10 through which the coupling can be effected. During the stamping process f the surface of the raw part, on any

  its length serving to form the shoulder 6 and the extension

  5a of the second partial length, undergoes no rupture, which keeps a continuous metal grain on the shoulder 6 and along the portion 5a.

  Comparing Figures 1 and 2 or 3, we can

  tater that the rack bar 2 is significantly more

  longer than the blank 1, which constitutes an economic

  a significant amount of raw material compared to a rack bar manufacturing technique in which the 5 or 5a partial length is formed by removing metal from a similarly sized blank

  that the cogwheel bar to get In addition, getting

  continuous grain on the shoulder 6 and on the partial length 5 or 5a of the rack bar eliminates the risk of inadvertent weakening of the rack bar in the region of its shoulder 6 (which would be not occur in the case of cutting machining according to the prior art for the

  partial length 5 or 5 a).

  As will be seen from the description of

  above, the length of the blank 1 may

  to determine without difficulty when you know the length of

  of the rack bar (in particular the length required for partial lengths 5, 5 a

  and 5 b, and the diameter that one wants to obtain for these lon-

partial healers).

Claims (2)

CLAIM 5) Rack bar (2) comprising a first partial length (3) carrying a set of rack teeth (4) and a second completely smooth partial length (5) lying longitudinally in the extension of the first partial length (3), the second partial length (5) having a constant cross-section of area less than that of the cross section of the first partial length (3) and a peripheral shoulder (6) being formed between these two partial lengths; rack (2) characterized in that the surface thereof, on its second partial length (5) between the end or a position adjacent the end opposite the first partial length (3), and on the transition portion corresponding to the length of the shoulder (6) between the first and second partial lengths does not show any break in to form a continuous metallic grain on all this surface -   20) rack bar according to claim 1, characterized in that the first and second lengths   parts (3, 5) consist of tubular parts   together defining a longitudinal passage (8) inside the bar.   30) Rack bar according to any one of   claims 1 and 2, characterized in that the second   partial length (5) is perfectly cylindrical.   ) Rack bar according to any one of   claims 1 to 3, characterized in that the second   partial length (5) lies longitudinally between   the peripheral shoulder (6) and coupling means   (7) for mounting the rack bar   (2) in a steering gear.   ) Rack bar according to any one of   Claims 1 to 4, characterized in that the means   of coupling (7) are constituted by a machined part of the bar (2).   ) Rack bar according to any one of   Claims 1 to 5, characterized in that the second   partial length (5) is in fact a part   end of the rack bar (2).   ) A method of manufacturing a cremation bar   ler according to any one of claims 1 to 6,   from a raw metal bar (1) having a first partial length (3) on which is formed or to be formed a set of rack teeth (4), characterized in that it consists in machining a   second partial length (5) of the bar (2) to re-   the cross-section of the latter from that of the first partial length (3) and form a   peripheral shoulder (6) between these partial lengths   while simultaneously increasing the long-term   tudinal of the second partial length (5), this   swimming maintaining a surface without breaking on at least the   most of the second partial length (5)   both of the shoulder (6) and the partial transition length of the bar corresponding to this shoulder (6)   between the first and second partial lengths   ls, so as to obtain a metal grain con- tinu on all this surface.   Method according to claim 7, characterized in that the first partial length (3) essentially constitutes a first end portion of the bar (2) and in that the second partial length (5) essentially constitutes the other part of the bar (2). end of the bar (2).   Process according to any one of the claims   7 and 8, characterized in that it consists in machining the second partial length (5) of the bar (2) by stamping to reduce the cross section of this   part and form the peripheral shoulder (6).   Process according to any one of the claims   7 to 9, characterized in that it consists in machining the rack bar (2) from a tubular raw metal bar (1).   Process according to any one of the claims   7 to 10, characterized in that it consists in machining the tubular bar (1) by keeping it tubular on   at least part of its length, this length   thereby having a longitudinal passage (8) to inside the bar.   Process according to any one of the claims   7 to 11, characterized in that it consists in forming   on the bar, at the end of the second length par-   opposed to the first partial length (3), coupling means (7) making it possible to connect the   rack bar to a steering linkage -   Process according to any one of the claims   7 to 12, characterized in that it consists in machining   the bar (2) to form the coupling means (7).   Process according to any one of the claims   7 to 13, characterized in that it consists in forming   the coupling means (7) essentially at the end   of the second partial length (5) of the bar   opposed to the first partial length (3).   Process according to any one of the claims   7 to 14, characterized in that it consists in forming the set of rack teeth (4) in the first partial length (3) of the bar after having reduced to the desired surface the cross section of the second   partial length (5) of this bar.   ) Steering gear characterized in that   uses the rack bar (2) according to any one   Claims 1 to 6 obtained by the process   according to any one of claims 7 to 15.