Rack for a steering system provided with an insertion area for a steering pinion

Abstract

Rack (1) for a steering system comprising a functional zone (Zf) provided with a plurality of functional teeth (2) defining a plurality of functional recesses (Ef) between two successive functional teeth, and an insertion zone (Zi) extending in an extension of the functional zone (Zf), the insertion zone (Zi) being provided with at least one insertion tooth (2) defining at least one insertion recess (Ei, Et) between the at least one insertion tooth (2) and the functional tooth (2) positioned opposite the insertion zone (Zi), characterized in that a height (Ht1, Ht2, Hi) of a gauge (3) positioned in the insertion recess (Ei, Et) is less by an offset distance than the height (Hf) of the gauge (3) positioned in a functional recess (Ef). Figure 2

Description

Title of the invention: Rack for a steering system provided with an insertion zone for a steering pinion Technical field

[0001] The invention relates to the field of steering systems and more particularly to a rack for a steering system. State of the prior art

[0002] A vehicle steering system is intended to enable a driver to control a trajectory of the vehicle by changing an orientation angle of the vehicle's wheels by means of a steering wheel.

[0003] There are steering systems in which a variation in rotation of the vehicle wheels is effected by a mechanical assembly composed of a steering pinion which meshes with a rack. The rack is mounted to slide in a longitudinal direction in a steering casing. The two ends of the rack, external to the casing, are coupled respectively to two steering rods, which are themselves associated respectively with the left and right steering wheels of the vehicle.

[0004] The rack comprises on the one hand a toothing formed of teeth and, on the other hand, a toothing back opposite the toothing. The toothing extends in a longitudinal direction of the rack.

[0005] Further, a tooth comprises a first flank and a second flank and a crest connecting the first flank to the second flank. Each tooth is spaced from the successive tooth by a recess.

[0006] It is known to those skilled in the art to determine characteristics of the teeth by a gauge rating. In other words, the characteristics of the teeth are determined relative to a gauge which is virtually positioned between two teeth, i.e. in the recesses of the teeth.

[0007] The gauge is a calibrated instrument for carrying out measurements. In this case, the gauge is, for example, a ball having a predefined diameter.

[0008] The following characteristics of the rack are defined in the remainder of the description: - A longitudinal axis of the rack is an axis which extends along a length of the rack; - A rack center is the center of the virtual circle in which a section of the rack taken in a plane transverse to the longitudinal axis of the rack is at least partly inscribed; - A gauge height is the dimension between the center of the rack and a top of the gauge, the gauge resting between two successive teeth of the rack. - A tooth pitch is the length between two centers of two gauges positioned in two successive recesses. The pitch of the rack can be fixed or variable. - A tooth bottom is the point of the recess closest to the center of the rack. - A tooth bottom height is the dimension between the tooth bottom and the center of the rack. - A tooth height is the dimension between the top and the center of the rack.

[0009] During operation of the vehicle, forces oppose contact between the steering pinion and the rack.

[0010] In order to permanently maintain a meshing of the rack against the steering pinion, it is known to use a so-called "pushbutton" device, acting elastically on the back of the rack in the region of the pinion to strongly press the teeth of the rack against a tooth of the pinion. Thus the pushbutton limits the play between the respective teeth of the steering pinion and the rack, and this pushbutton also makes it possible to control a sliding force of the rack in the steering housing.

[0011] The disadvantage of using a so-called "pushbutton" device is that it requires adjustment of the pushbutton after assembly of the steering pinion and the rack.

[0012] Furthermore, the "push" device can have failures and a large number of patent documents are known relating to improvements to this device.

[0013] Finally, such a device has a volume, a cost and a mass that manufacturers of steering systems seek to reduce.

[0014] There is therefore a need for a mechanical assembly composed of a steering pinion which meshes with a rack having a quick, easy assembly, as well as a reduced volume and mass. Statement of the invention

[0015] One embodiment relates to a rack for a steering system comprising a functional area provided with a plurality of functional teeth defining a plurality of functional recesses between two successive functional teeth, the functional recesses being configured to cooperate with a pinion of direction, the functional zone extending along a longitudinal axis of the rack, and an insertion zone extending in an extension of the functional zone, the insertion zone being provided with at least one insertion tooth defining at least one insertion recess between the at least one insertion tooth and the functional tooth positioned opposite the insertion zone, characterized in that a height of a gauge positioned in the insertion recess is less by an offset distance than the height of the gauge positioned in a functional recess.

[0016] In the remainder of the description, two elements are said to be “identical” if they differ from each other only by the manufacturing tolerances commonly accepted in the field.

[0017] The rack according to the invention comprises the functional zone forming a toothing of the rack and extending in a longitudinal direction of the rack.

[0018] Each tooth of the rack comprises a first flank, a second flank and a vertex connecting the first flank to the second flank. Each tooth is spaced from the successive tooth by a recess.

[0019] Characteristics of the teeth are determined with respect to a gauge which is virtually positioned between two teeth, i.e. in the recesses of the teeth.

[0020] The gauge is for example a ball having a center and a predefined diameter.

[0021] The characteristics of the rack are defined in the following description. following: - A longitudinal axis of the rack is an axis which extends along a length of the rack; - A rack center is the center of the virtual circle in which a section of the rack taken in a plane transverse to the longitudinal axis of the rack is at least partly inscribed; - A gauge height is the dimension between the center of the rack and a top of the gauge, the gauge resting between two successive teeth of the rack. - A tooth pitch is the length between two centers of two gauges positioned in two successive recesses. The pitch of the rack can be fixed or variable. - A profile of a tooth according to a longitudinal section of the rack comprises at least the top, the first flank and the second flank of the tooth, connected to the top. - A tooth bottom is the point of the recess closest to the center of the rack. - A tooth bottom height is the dimension between the tooth bottom and the center of the rack. - A tooth height is the dimension between the top and the center of the rack.

[0022] The functional area extends along the longitudinal axis of the rack. All the heights of the gauges positioned in the functional recesses are identical.

[0023] The insertion zone is positioned at one end of the functional zone along the longitudinal axis of the rack. The insertion zone is in contact with the functional zone.

[0024] The insertion zone allows for an assembly of an innovative steering rack and pinion assembly. Indeed, according to the invention, the rack is first positioned in a steering housing such that a clearance between the rack and the steering housing is substantially the final clearance desired during operation of the assembly in a vehicle. Then the steering pinion is inserted into the steering housing at the insertion zone.

[0025] The at least one insertion tooth has a specific function, to allow the insertion of the steering pinion on the rack when the rack is positioned in the steering housing. Thus, it is obvious that the at least one insertion tooth has a profile determined upstream of its manufacture so as to guarantee that the height of the gauge positioned in the insertion recess is less than the height of the gauge positioned in a functional recess by the offset distance.

[0026] The height of the gauge positioned in the insertion recess being lower than the height of the gauge positioned at a functional recess allows a reduction in the stresses exerted on the steering pinion - rack assembly and thus it is possible to insert the steering pinion on the rack, while the rack is already positioned in the steering housing.

[0027] According to the invention, it may no longer be necessary to push the rack against the steering pinion after insertion, for example via a "push" type device. Indeed, the final stressing of the steering pinion - rack assembly can be carried out when the steering pinion meshes with the teeth of the functional zone.

[0028] During operation of the assembly in the vehicle, the steering pinion travels only within the functional area. The insertion area may be prevented from the steering pinion, for example, by means of a travel limiter.

[0029] The invention can therefore make it possible to carry out a definitive adjustment of the rack in the steering housing before inserting the steering pinion into said steering housing.

[0030] Unlike a toothless or flat insertion zone, the insertion zone according to the invention makes it possible, by the presence of at least one tooth, to maintain the section of the rack, taken in the plane transverse to the longitudinal axis of the rack, with little variation over the length of the rack. This allows a certain constancy of a deformation of the rack during a heat treatment operation. An insertion zone without a tooth or flat causes a significant variation in section and will therefore undergo significant deformations during a heat treatment, thus weakening the mechanical characteristics of the rack.

[0031] Furthermore, in the case of a steering system with a mechanical connection between a steering wheel and the steering pinion-rack assembly, the insertion zone according to the invention allows angular indexing of the steering pinion on the rack so as to guarantee correct alignment of the steering wheel and a midpoint of the steering pinion-rack assembly.

[0032] The subject matter of the present disclosure may also have one or more of the following characteristics taken alone or in combination.

[0033] According to one embodiment, a height of a tooth bottom of the at least one insertion recess is identical to the height of the tooth bottom of the plurality of functional recesses.

[0034] Thus, the insertion recesses and the functional recesses are aligned.

[0035] According to one embodiment, a height of an insertion tooth is less than the height of a functional tooth.

[0036] The insertion teeth are therefore smaller than the functional teeth.

[0037] According to one embodiment, the at least one insertion tooth has an upper profile along a longitudinal section of the rack identical to the upper profile of the functional tooth opposite the insertion zone.

[0038] The upper profile of the teeth is called the profile of a tooth according to a longitudinal section of the rack and which comprises at least the top, a part of the first flank and a part of the second flank of the tooth, connected to the top.

[0039] The upper profile of the teeth is determined by a tooth calculation known to those skilled in the art.

[0040] The rack according to the invention is remarkable in that the functional tooth facing the insertion zone and the at least one insertion tooth have an identical upper profile.

[0041] Furthermore, since the height of the gauge positioned in the insertion recess is less than the height of the gauge positioned in a functional recess, the top of the at least one insertion tooth is offset toward the center of the rack by a distance, which is close to but not necessarily equal to the offset distance, relative to the functional tooth positioned opposite the insertion area.

[0042] In certain embodiments, the offset distance is between 20% and 70%, preferably between 30% and 50% and in particular between 35% and 45% of the height of the gauge positioned in the functional recess.

[0043] In some embodiments, the insertion area comprises a plurality of insertion recesses, and preferably at least three insertion recesses.

[0044] Thus the steering pinion can mesh with the at least three insertion recesses during insertion.

[0045] In some embodiments, the insertion zone comprises an insertion portion provided with at least two insertion recesses, the heights of the gauges positioned in the at least two insertion recesses being identical.

[0046] The introduction recesses are also insertion recesses.

[0047] The insertion recesses allow insertion of the steering pinion made easier.

[0048] In some embodiments, the insertion zone comprises a transition portion provided with at least one transition recess, the height of the gauge positioned in the at least one transition recess is between the height of the gauge positioned in the functional recess and the height of the gauge positioned in the insertion recess.

[0049] In some embodiments, the transition portion is positioned between the functional area and the introduction portion.

[0050] The transition part is therefore in contact on the one hand with the functional zone and on the other hand with the introduction part.

[0051] The transition portion facilitates the meshing of the steering pinion with the functional area by gradually bringing the steering pinion into an operating position, i.e. by gradually increasing the stresses exerted on the steering pinion-rack assembly.

[0052] In some embodiments, the transition portion is provided with at least two transition recesses.

[0053] In some embodiments, the heights of the gauges positioned in the at least two transition recesses are linearly decreasing between the height of the gauge positioned in the functional recess and the height of the gauge positioned in the introduction recess.

[0054] Another aspect of the invention relates to a steering system comprising a rack according to the invention. Brief description of the drawings

[0055] The invention will be better understood, thanks to the following description, which relates to several embodiments according to the present invention, given as examples. non-limiting and explained with reference to the attached schematic drawings, in which:

[0056] [Fig. 1] is a longitudinal sectional representation of a rack according to the invention;

[0057] [Fig.2] is an enlargement of [Fig.l];

[0058] [Fig.3] is a longitudinal sectional view of a steering pinion-rack assembly according to a first embodiment;

[0059] [Fig.4] is a longitudinal sectional view of the steering pinion-rack assembly according to a second embodiment;

[0060] [Fig.5] is a longitudinal sectional view of the steering pinion-rack assembly according to a third embodiment. Description of the embodiments

[0061] Only the elements necessary for understanding the invention have been shown. To facilitate reading of the drawings, the same elements bear the same references from one figure to another.

[0062] The invention relates to a rack 1, as shown in [Fig.l], for a steering system.

[0063] The rack 1 comprises a toothing formed from a plurality of teeth 2, the toothing extending along a longitudinal axis A, also called the elongation axis, of the rack 2.

[0064] Each tooth 2 comprises a top, a first flank and a second flank, the first flank and the second flank each being connected to the top at a determined angle.

[0065] An upper profile of a tooth 2 according to a longitudinal section of the rack 1, as shown in [Fig.2], comprises at least the top, a part of the first flank and a part of the second flank of the tooth 2, the part of the first flank and the part of the second flank being connected to the top. The upper profile of the teeth 2 is determined by a toothing calculation known to those skilled in the art.

[0066] Characteristics of the teeth are determined with respect to a gauge 3 which is virtually positioned between two teeth 2, i.e. in recesses E of the teeth as shown in [Fig.2].

[0067] Gauge 3 is for example a ball having a predefined center and diameter.

[0068] A center C of the rack 1 is the center of the virtual circle in which a section of the rack 1 taken in a plane transverse to the longitudinal axis A of the rack 1 is at least partly inscribed.

[0069] A height H of the gauge 3 is the dimension between the center C of the rack 1 and a top of the gauge 3, the gauge 3 resting between two successive teeth 2 of the rack 1.

[0070] The toothing comprises a functional zone Zf, and an insertion zone Zi5, said insertion zone Z; comprising a transition part Pt and an introduction part P i*

[0071] Two successive teeth 2 are spaced apart by a recess E

[0072] In the functional zone Zf, the teeth 2 are called functional teeth, and the recesses are called functional recesses Ef. The functional recesses Ef are configured to cooperate with a steering pinion 10 during normal operation of the steering system. The functional zone Zf extends along the longitudinal axis A of the rack 1. All the heights Hf of the gauges 3 positioned in the functional recesses Ef are identical.

[0073] On the insertion zone Zi5 the teeth 2 are called insertion teeth and the recesses E are called insertion recess Ei5 Et.

[0074] The insertion zone Z; extends in an extension of the functional zone Zf. The insertion zone Zi is positioned at one end of the functional zone Zf along the longitudinal axis A of the rack 2. The insertion zone Z; is in contact with the functional zone Zf.

[0075] The insertion zone Z; comprises a plurality of insertion recesses E;, Et, and preferably at least three insertion recesses E;, Et.

[0076] The height H;, Htb Ht2 of the gauge 3 positioned in the insertion recess E;, Et is lower by an offset distance than the height Hf of the gauge 3 positioned in the functional recess Ef.

[0077] More precisely, the offset distance is between 20% and 70%, preferably between 30% and 50% and in particular between 35% and 45% of the height Hf of the gauge 3 positioned in the functional recess Ef.

[0078] According to one embodiment, a height of a tooth bottom of the at least one insertion recess E;, Et is identical to the height of the tooth bottom of the plurality of functional recesses Ef.

[0079] Thus, the insertion recesses E;, Et and the functional recesses Ef are aligned.

[0080] According to one embodiment, a height of an insertion tooth 2 is less than the height of a functional tooth 2.

[0081] The insertion teeth are therefore smaller than the functional teeth.

[0082] According to one embodiment, the at least one insertion tooth 2 has an upper profile according to a longitudinal section of the rack 1 identical to the upper profile of the functional tooth 2 opposite the insertion zone Zi.

[0083] The upper profile of the teeth 2 is called the profile of a tooth 2 according to a longitudinal section of the rack 1 and which comprises at least the top, a part of the first flank and a part of the second flank of the tooth, connected to the top.

[0084] According to one embodiment, the rack 1 according to the invention is remarkable in that that the functional tooth 2 facing the insertion zone Z; and the at least one insertion tooth 2 have an identical upper profile. Furthermore, since the height H;, Hü, Ht2 of the gauge 3 positioned in the insertion recess E;, Et is less than the height Hf of the gauge 3 positioned in the functional recess Ef, the top of the at least one insertion tooth 2 is offset in the direction of the center C of the rack 1 by a distance, which is close but not necessarily equal to the offset distance, relative to the functional tooth 2 positioned facing the insertion zone Zj.

[0085] On the transition part Pt, the recesses E are called transition recesses Et, while on the introduction part P, the recesses are called introduction recesses E;.

[0086] The introduction recesses E; and the transition recesses Et are also insertion recesses E;, Et.

[0087] The introduction part P; is provided with at least two introduction recesses E;, the heights H; of the gauges positioned in the at least two introduction recesses E; being identical.

[0088] The insertion recesses E; allow for easier insertion of the steering pinion 10.

[0089] The height Hü, Ht2 of the gauge 3 positioned in the at least one transition recess Et is between the height Hf of the gauge 3 positioned in the functional recess Ef and the height H; of the gauge 3 positioned in the introduction recess E;.

[0090] The transition part Pt is positioned between the functional zone Zf and the introduction part P;.

[0091] The transition part Pt is therefore in contact on the one hand with the functional zone Zf and on the other hand with the introduction part P;.

[0092] The transition part Pt facilitates the meshing of the steering pinion 10 on the functional zone Zf by gradually putting the steering pinion 10 into an operating position, that is to say by gradually increasing the stresses exerted on the steering pinion 10 - rack 1 assembly.

[0093] The transition part Pt is provided with at least two transition recesses Et.

[0094] The heights Hü, Ht2 of the gauges 3 positioned in the at least two transition recesses Et are linearly decreasing between the height Hf of the gauge 3 positioned in the functional recess Ef and the height H; of the gauge 3 positioned in the introduction recess E;.

[0095] Figures 3, 4 and 5 illustrate embodiments of an assembly of the steering pinion 10 on the rack 1 in different steering housings 20, 20', 20”. More particularly, Figures 3a, 4a and 5a illustrate the position of the steering pinion 10 relative to the rack 1 when it is inserted into the steering housing. 20, 20', 20”. Figures 3b, 4b, and 5b illustrate the position of the steering pinion 10 relative to the rack 1 during normal operation of the steering system.

[0096] When assembling the steering pinion 10 - rack 1 assembly according to the invention, the rack is first positioned in the steering housing 20, 20', 20”.

[0097] According to the first embodiment, [Fig. 3], the steering casing 20 comprises a “push” device 30 previously adjusted so that the “push” device exerts a force towards the rack equal to the force which must be exerted in normal operation.

[0098] According to the second embodiment, [Fig.4], the steering casing 20' comprises a spring 30' exerting a predetermined force towards the rack 1. Said spring 30' cannot be adjusted.

[0099] According to the third embodiment, [Fig.5], the steering casing 20” does not include any specific device exerting a thrust towards the rack 1.

[0100] In each of the embodiments, the rack 1 is slidably mounted in the steering casing 20, 20', 20”.

[0101] In each of the embodiments, the insertion zone Zi allows an assembly of the innovative steering pinion 10 - rack 1 assembly. Indeed, according to the invention, the rack 1 is first positioned in the steering casing 20, 20', 20” as illustrated in figures 3a, 4a, 5a so that a clearance between the rack 1 and the steering casing 20, 20', 20” is substantially the final clearance desired during operation of the assembly in a vehicle.

[0102] Then the steering pinion 10 is inserted into the steering casing 20, 20', 20” at the insertion zone Z, as illustrated in figures 3a, 4a and 5a, and more precisely at the insertion part P;. Indeed, the height H; of the gauge 3 positioned in an insertion recess E; lower than the height Hf of the gauge 3 positioned in a functional recess Ef allows a reduction of the stresses exerted on the rack 1 and thus it is possible to insert the steering pinion 10 into the steering casing 20, 20', 20”.

[0103] Then the steering pinion 10 is rotated along the rack 1 so as to travel through the transition portion Pt. The transition portion Pt gradually places the steering pinion 10 - rack 1 assembly under stress. Finally, the steering pinion 10 is positioned on the functional zone Zf, as illustrated in FIGS. 3b, 4b, 5b. The insertion zone Z is then prohibited for the steering pinion 10, for example by means of a travel limiter.

[0104] According to the invention, it is no longer necessary to push the rack 1 against the steering pinion 10 via, for example, a “push” type device 30 adjusted after the positioning of the steering pinion 10. In fact, the final stressing is carried out when the steering pinion 10 meshes with the teeth 2 of the functional zone Zf. During operation of the assembly in the vehicle, the steering pinion 10 travels only through the functional zone Zf. The invention can therefore make it possible to carry out an adjustment of the rack 1 in the steering housing 20, 20', 20” before inserting the steering pinion 10.

[0105] Although the present invention has been described with reference to specific embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0106] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims

Claims

1. Rack (1) for a steering system comprising a functional zone (Zf) provided with a plurality of functional teeth (2) defining a plurality of functional recesses (Ef) between two successive functional teeth, the functional recesses (Ef) being configured to cooperate with a steering pinion (10), the functional zone (Zf) extending along a longitudinal axis (A) of the rack (1), and an insertion zone (Z) extending in an extension of the functional zone (Zf), the insertion zone (Z) being provided with at least one insertion tooth (2) defining at least one insertion recess (E;, Et ) between the at least one insertion tooth (2) and the functional tooth (2) positioned opposite the insertion zone (Z), characterized in that a height (Htb Ht2, H;) of a gauge (3) positioned in the insertion recess (E;, Et) is less than an offset distance from the height (Hf) of the gauge (3) positioned in a functional recess (Ef).;

2. Rack (1) according to claim 1, in which the at least one insertion tooth (2) has an upper profile according to a longitudinal section of the rack (1) identical to the upper profile of the functional tooth (2) positioned opposite the insertion zone (Z).

3. Rack (1) according to any one of the preceding claims in which the offset distance is between 20% and 70%, preferably between 30% and 50% and in particular between 35% and 45% of the height (Hf) of the gauge (3) positioned in the functional recess (Ef

4. h Rack (1) according to any one of the preceding claims, wherein the insertion zone (Z) comprises a plurality of insertion recesses (E;, Et), and preferably at least three insertion recesses (E;, Et).

5. Rack (1) according to claim 4, wherein the insertion zone (Z) comprises an insertion part (P;) provided with at least two insertion recesses (E;), the heights (H;) of the gauges (3) positioned in the at least two insertion recesses (E;) being identical.

6. Rack (1) according to claim 5, wherein the insertion zone (Z) comprises a transition portion (Pt) provided with at least a transition recess (Et), the height (Htb Ht2) of the gauge (3) positioned in the at least one transition recess (Et) is between the height (Hf) of the gauge (3) positioned in the functional recess (Ef) and the height (H;) of the gauge (3) positioned in the introduction recess (E;).

7. Rack (1) according to claim 6, wherein the transition portion (Pt) is positioned between the functional zone (Zf) and the introduction portion (P;).

8. Rack (1) according to any one of claims 6 or 7, wherein the transition portion (Pt) is provided with at least two transition recesses (Et).

9. Rack (1) according to claim 8, wherein the heights (Htb Ht2) of the gauges (3) positioned in the at least two transition recesses (Et) are linearly decreasing between the height (Hf) of the gauge (3) positioned in the functional recess (Ef) and the height (H;) of the gauge (3) positioned in the introduction recess (E;).

10. A steering system comprising a rack (1) according to any one of the preceding claims.

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