Rack and pinion for a steering system 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 a continuation 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 equipped 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. Prior art

[0002] A vehicle steering system is designed to allow a driver to control the vehicle's trajectory by changing the orientation angle of the vehicle's wheels using a steering wheel.

[0003] Steering systems exist in which the rotation of the vehicle's wheels is varied by a mechanical assembly consisting of a steering pinion that meshes with a rack. The rack is mounted to slide along its longitudinal axis within a steering housing. The two ends of the rack, outside the housing, are coupled respectively to two tie 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 toothed section formed of teeth and, on the other hand, a toothed back opposite the toothed section. The toothed section extends along a longitudinal direction of the rack.

[0005] Furthermore, a tooth comprises a first flank and a second flank and a vertex connecting the first flank to the second flank. Each tooth is separated from the successive tooth by a recess.

[0006] It is known to a person skilled in the art to determine the characteristics of the gear teeth by a gauge measurement. In other words, the characteristics of the gear teeth are determined with respect to a gauge which is virtually positioned between two teeth, that is to say in the recesses of the gear teeth.

[0007] A gauge is a calibrated instrument used to perform 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 that extends along a length of the rack; - A center of the rack 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 inscribed at least in part; - A gauge height is the dimension between the center of the rack and a peak of the gauge, the gauge resting between two successive teeth of the rack. - A tooth pitch is the length between the centers of two gauges positioned in two successive recesses. The rack pitch can be fixed or variable. - A tooth root is the point of the recess closest to the center of the rack. - The tooth root height is the dimension between the tooth root and the center of the rack. - A tooth height is the dimension between the apex and the center of the rack.

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

[0010] In order to maintain permanent meshing of the rack against the steering pinion, it is known to use a device called a "pusher," which acts elastically on the back of the rack in the pinion region to press the rack teeth firmly against a pinion tooth. Thus, the pusher limits the backlash between the respective teeth of the steering pinion and the rack, and this pusher also allows for control of the rack's sliding force within the steering housing.

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

[0012] In addition, the "pusher" device may have failures and a large number of patent documents relating to improvements of this device are known.

[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 consisting of a steering pinion that meshes with a rack that has a quick and easy assembly, as well as a reduced volume and mass. Description of the invention

[0015] One embodiment relates to a rack for a steering system comprising a functional zone 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 following 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 includes the functional area forming a tooth of the rack and extending along 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 separated 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 that extends along a length of the rack; - A center of the rack 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 inscribed at least in part; - A gauge height is the dimension between the center of the rack and a peak of the gauge, the gauge resting between two successive teeth of the rack. - A tooth pitch is the length between the centers of two gauges positioned in two successive recesses. The rack pitch can be fixed or variable. - A profile of a tooth according to a longitudinal section of the rack includes at least the apex, the first flank and the second flank of the tooth, connected to the apex. - A tooth root is the point of the recess closest to the center of the rack. - The tooth root height is the dimension between the tooth root and the center of the rack. - A tooth height is the dimension between the apex 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 area allows for the assembly of an innovative steering rack and pinion assembly. According to the invention, the rack is first positioned in a steering housing such that the clearance between the rack and the steering housing is substantially the final clearance required during operation of the assembly in a vehicle. Then, the steering pinion is inserted into the steering housing at the insertion area.

[0025] At least one insertion tooth has a specific function: to allow the steering pinion to be inserted onto the rack when the rack is positioned in the steering housing. Thus, it is evident that at least one insertion tooth has a profile determined prior to 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 less than the height of the gauge positioned at the level of a functional recess allows a reduction of the stresses exerted on the steering pinion - rack assembly and thus it is possible to insert the steering pinion onto 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 "pusher" type device. Indeed, the final tensioning of the steering pinion-rack assembly can be achieved when the steering pinion engages with the teeth of the functional zone.

[0028] During operation of the assembly in the vehicle, the steering pinion travels only within the functional zone. The insertion zone can be restricted to the steering pinion, for example, by means of a travel limiter.

[0029] The invention can therefore allow a final adjustment of the rack in the steering housing before the insertion of the steering pinion into said steering housing.

[0030] Unlike a toothless or flat insertion zone, the insertion zone according The invention, through the presence of at least one tooth, allows the cross-section of the rack, measured in the plane transverse to the longitudinal axis of the rack, to be maintained with minimal variation in the rack's length. This ensures a degree of consistency in rack deformation during heat treatment. A toothless or flat insertion area results in a significant change in cross-section and will therefore undergo substantial deformation during heat treatment, thus weakening the rack's mechanical properties.

[0031] Furthermore, in the case of a steering system with a mechanical link between a steering wheel and the steering pinion-rack assembly, the insertion area 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 object of this presentation 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 root of at least one insertion recess is identical to the height of the tooth root of the plurality of functional recesses.

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

[0035] According to one embodiment, the 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, at least one insertion tooth has a top profile in a longitudinal section of the rack identical to the top profile of the functional tooth opposite the insertion area.

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

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

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

[0041] In addition, 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 at least one insertion tooth is offset towards 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 some 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 zone 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 includes an inlet part provided with at least two inlet recesses, the heights of the gauges positioned in the at least two inlet recesses being identical.

[0046] The introduction recesses are also insertion recesses.

[0047] The inlet recesses allow insertion of the steering pinion facilitated.

[0048] In some embodiments, the insertion zone includes a transition part 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 introduction recess.

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

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

[0051] The transition part facilitates the engagement of the steering pinion on the functional area by progressively putting the steering pinion into an operating position, that is to say by progressively increasing the stresses exerted on the steering pinion - rack assembly.

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

[0053] In certain 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 from the following description, which relates to several embodiments of the present invention, given by way of example. non-exhaustive and explained with reference to the attached schematic drawings, in which:

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

[0057] [Fig.2] is an enlargement of [Fig.1];

[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 cross-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 implementation methods

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

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

[0063] The rack 1 comprises a toothing formed of 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 vertex, a first flank and a second flank, the first flank and the second flank each being connected to the vertex at a determined angle.

[0065] A top profile of a tooth 2 in a longitudinal section of the rack 1, as shown in [Fig. 2], comprises at least the apex, a portion of the first flank, and a portion of the second flank of the tooth 2, the portion of the first flank and the portion of the second flank being connected to the apex. The top 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 center and a predefined diameter.

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

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

[0070] The gear teeth comprise a functional zone Zf, and an insertion zone Zi5, said insertion zone Z; comprising a transition portion Pt and an introduction portion P i*

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

[0072] On the functional zone Zf, the teeth 2 are called functional teeth, and the These 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 area Zf extends along the longitudinal axis A of the rack 1. All heights Hf of the gauges 3 positioned in the functional recesses Ef are identical.

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

[0074] The insertion zone Z; extends as a continuation 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 less than by an offset distance the height Hf of the gauge 3 positioned in the functional recess Ef.

[0077] More specifically, 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 root of at least one insertion recess E;, Et is identical to the height of the tooth root 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, the 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, at least one insertion tooth 2 has an upper profile in 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 teeth 2 is called the profile of a tooth 2 according to a longitudinal section of the rack 1 and which includes at least the apex, a part of the first flank and a part of the second flank of the tooth, connected to the apex.

[0084] According to one embodiment, the rack 1 according to the invention is remarkable in that that the functional tooth 2 opposite 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 towards the center C of the rack 1 by a distance, which is close to but not necessarily equal to the offset distance, relative to the functional tooth 2 positioned opposite 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 introductory 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 introduction 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 engagement of the steering pinion 10 on the functional area Zf by progressively putting the steering pinion 10 into an operating position, that is to say by progressively 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 the latter is inserted into the steering housing. 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] During assembly of 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 housing 20 includes a "pusher" device 30 pre-set so that the "pusher" device exerts a force towards the rack equal to the force that must be exerted in normal operation.

[0098] According to the second embodiment, [Fig.4], the steering housing 20' includes 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 housing 20” does not include any specific device exerting a thrust towards the rack 1.

[0100] In each embodiment, the rack 1 is mounted to slide within the steering housing 20, 20', 20”.

[0101] In each embodiment, the insertion zone Zi allows for an innovative assembly of the steering pinion 10 - rack 1 assembly. Indeed, according to the invention, the rack 1 is first positioned in the steering housing 20, 20', 20" as illustrated in Figures 3a, 4a, 5a such that a clearance between the rack 1 and the steering housing 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 housing 20, 20', 20" at the insertion zone Z, as illustrated in Figures 3a, 4a and 5a, and more precisely at the insertion portion P;. Indeed, the height H; of the gauge 3 positioned in an insertion recess E; being less than the height Hf of the gauge 3 positioned in a functional recess Ef, it allows a reduction in the stresses exerted on the rack 1 and thus it is possible to insert the steering pinion 10 into the steering housing 20, 20', 20”.

[0103] Then the steering pinion 10 is rotated along the rack 1 so as to traverse the transition section Pt. The transition section Pt gradually puts the steering pinion 10 - rack 1 assembly under stress. Finally, the steering pinion 10 is positioned in the functional zone Zf, as illustrated in Figures 3b, 4b, 5b. The insertion zone Z is then blocked 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 "pusher" type device 30 adjusted after the positioning of the steering pinion 10. Indeed, the final stress is This operation is performed when the steering pinion 10 engages with the teeth 2 of the functional zone Zf. During the operation of the assembly in the vehicle, the steering pinion 10 travels only within the functional zone Zf. The invention therefore allows for adjustment of the rack 1 in the steering housing 20, 20', 20" before the insertion of the steering pinion 10.

[0105] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can 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 embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

[0106] It is also evident that all the characteristics described with reference to a process 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 process.

Claims

Demands

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 a continuation of the functional zone (Zf), the insertion zone (Z) being provided with at least one insertion tooth (2) defining at least one insertion recess (E1, E2) 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, H1) of a gauge (3) positioned in the insertion recess (E;, Et) is less than by an offset distance to the height (Hf) of the gauge (3) positioned in a functional recess (Ef).;

2. Rack (1) according to claim 1, wherein at least one insertion tooth (2) has an upper profile along 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 wherein 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 infeed part (P;) provided with at least two infeed recesses (E;), the heights (H;) of the gauges (3) positioned in the at least two infeed 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 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 part (Pt) is positioned between the functional zone (Zf) and the inlet part (P;).

8. Rack (1) according to any one of claims 6 or 7, wherein the transition part (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. Steering system comprising a rack (1) according to any one of the preceding claims.

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