Rack for steering system provided with steering pinion insertion region

Abstract

A rack (1) for a steering system, the rack comprising: a functional zone (Zf) provided with a plurality of functional teeth (2), defining a plurality of functional recesses (Ef) between two consecutive functional teeth; and an insertion region (Zi) extending in an extension of the functional region (Zf), the insertion region (Zi) being provided with at least one insertion tooth (2), defining between the at least one insertion tooth (2) and a functional tooth (2) positioned opposite the insertion region (Zi) at least one insertion recess (Ei, Et), characterized in that the height (Ht1, Ht2, Ht3) of the gauge (3) positioned in the insertion recess (Ei, Et) is greater than the height (Ht1, Ht2) of the functional region (Zf). Hi) is less than the height (Hf) of the gauge (3) positioned in the functional recess (Ef) by a certain offset distance.

Description

Technical Field

[0001] The present invention relates to the field of steering systems and more particularly to a rack for a steering system. Background Art

[0002] The purpose of a vehicle's steering system is to allow the driver to control the vehicle's trajectory by modifying the azimuth angle of the vehicle's wheels by means of the steering wheel.

[0003] There are such steering systems in which the rotational change of the vehicle's wheels is achieved by a mechanical assembly consisting of a steering pinion meshing with a rack. The rack is slidably mounted in the longitudinal direction in a steering housing. Outside the housing, the two end portions of the rack are respectively connected to two steering rods, which are themselves respectively associated with the left and right steering wheels of the vehicle.

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

[0005] In addition, the teeth include a first side and a second side and a vertex connecting the first side to the second side. Each tooth is separated from the adjacent tooth by a recess.

[0006] It is known to those skilled in the art to determine the characteristics of the toothing by means of ratings on a gauge. In other words, the characteristics of the toothing are determined relative to a gauge actually positioned between two teeth (that is, positioned in the recess of the toothing).

[0007] A gauge is a calibrated instrument that allows measurements to be made. In this case, the gauge is, for example, a ball with a predetermined diameter.

[0008] The following characteristics of the rack are defined in the remainder of the specification:

[0009] - The longitudinal axis of the rack is the axis extending along the length of the rack;

[0010] - The center of the rack is the center of a virtual circle, a segment of the rack intercepted in a plane transverse to the longitudinal axis of the rack being at least partially inscribed in the virtual circle;

[0011] - The height of the gauge is the dimension included between the center of the rack and the vertex of the gauge, the gauge being located between two consecutive teeth of the rack.

[0012] - The pitch of the toothing is the length between the centers of two gauges positioned in two consecutive recesses. The pitch of the rack can be fixed or variable.

[0013] - The tooth root is the point of the recess closest to the center of the rack.

[0014] - The height of the tooth root is the dimension between the tooth root and the center of the rack.

[0015] - The tooth height is the dimension included between the center of the rack and the apex.

[0016] During vehicle operation, the force is opposite to the contact between the steering pinion and the rack.

[0017] In order to permanently maintain the engagement of the rack with the steering pinion, it is known to use a so-called "push" device that elastically acts on the back of the rack in the area of the pinion to strongly press the teeth of the rack against the teeth of the pinion. Thus, this push limits the clearance between the corresponding teeth of the rack and the steering pinion, and this push also enables the control of the sliding force of the rack in the steering housing.

[0018] A disadvantage of using the so-called "push" device is that it requires adjustment of the push after assembling the steering pinion and the rack.

[0019] In addition, this "push" device may malfunction, and a large number of patent documents are known to relate to improvements to this device.

[0020] Finally, such devices have a volume, cost, and mass that steering system manufacturers seek to reduce.

[0021] Therefore, there is a need for a mechanical assembly consisting of a steering pinion that meshes with a rack and has fast, easy assembly as well as reduced volume and mass. Summary of the Invention

[0022] One embodiment relates to a rack for a steering system, the rack comprising: a functional zone provided with a plurality of functional teeth, a plurality of functional recesses being defined between two consecutive functional teeth, the functional recesses being configured to cooperate with a steering pinion, the functional zone extending along the 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, at least one insertion recess being defined between the at least one insertion tooth and a functional tooth positioned opposite the insertion zone, characterized in that the height of a gauge positioned in the insertion recess is smaller by a certain offset distance than the height of a gauge positioned in the functional recess.

[0023] In the remainder of the specification, if two elements differ from each other only by manufacturing tolerances generally accepted in the art, they are said to be "identical".

[0024] According to the rack functional zone of the present invention, the functional zone includes the teeth forming the rack and extends in the longitudinal direction of the rack.

[0025] Each tooth of the rack includes a first side surface, a second side surface, and a vertex connecting the first side surface to the second side surface. Each tooth is separated from adjacent teeth by a recess.

[0026] The features of the toothing are determined relative to a gauge that is actually positioned between two teeth (i.e., positioned in the recess of the toothing).

[0027] The gauge is, for example, a sphere having a center and a predetermined diameter.

[0028] The following features of the rack are defined in the remainder of the description:

[0029] - The longitudinal axis of the rack is the axis that extends along the length of the rack;

[0030] - The center of the rack is the center of a virtual circle in which at least a portion of a segment of the rack intercepted in a plane transverse to the longitudinal axis of the rack is at least partially inscribed;

[0031] - The height of the gauge is the dimension between the center of the rack and the vertex of the gauge, the gauge being located between two consecutive teeth of the rack.

[0032] - The pitch of the toothing is the length between the centers of two gauges positioned in two consecutive recesses. The pitch of the rack can be fixed or variable.

[0033] - The tooth according to the profile of the longitudinal section of the rack includes at least the vertex of the tooth, a first side surface and a second side surface connected to the vertex.

[0034] - The tooth root is the point of the recess closest to the center of the rack.

[0035] - The height of the tooth root is the dimension between the tooth root and the center of the rack.

[0036] - The tooth height is the dimension included between the center of the rack and the vertex.

[0037] The functional zone extends along the longitudinal axis of the rack. All the heights of the gauges positioned in the functional recesses are the same.

[0038] 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.

[0039] The insertion zone allows the assembly of an innovative steering pinion-rack assembly. In fact, according to the invention, the rack is first positioned in the steering housing such that the clearance between the rack and the steering housing is substantially the final desired clearance during the operation of the assembly in the vehicle. Then, the steering pinion is inserted into the steering housing at the insertion zone.

[0040] At least one insertion tooth has a specific function to allow the pinion to be inserted onto the rack when the rack is positioned in the steering housing. Thus, it is obvious that at least one insertion tooth has a defined profile upstream of its manufacture, such that the height of the gauge positioned in the insertion recess is smaller by a certain offset distance than the height of the gauge positioned in the functional recess.

[0041] The lower height of the gauge positioned in the insertion recess than the height of the gauge positioned in the functional recess allows the stress applied to the pinion-rack assembly to be reduced, and thus the pinion can be inserted onto the rack while the rack is already positioned in the steering housing.

[0042] According to the present invention, it is no longer necessary to press the rack against the pinion after insertion, for example via a "pushing" device. In fact, when the pinion engages with the teeth of the functional zone, the final stress can be applied to the pinion-rack assembly.

[0043] During the operation of the assembly in the vehicle, the pinion only travels through the functional zone. The pinion can be prohibited from reaching the insertion zone, for example by means of a travel limiter.

[0044] Therefore, the present invention enables the final adjustment of the rack in the steering housing before inserting the pinion into the steering housing.

[0045] Different from a toothless or flat insertion zone, the insertion zone according to the present invention allows the cross-section of the rack intercepted in a plane transverse to the longitudinal axis of the rack to be maintained with little change in the length of the rack by the presence of at least one tooth. This allows a certain constancy in the deformation of the rack during the heat treatment operation. A toothless or flat insertion zone results in a significant change in the cross-section and will thus undergo significant deformation during heat treatment, weakening the mechanical characteristics of the rack.

[0046] Furthermore, in the case of a steering system having a mechanical connection between the steering wheel and the pinion-rack assembly, the insertion zone according to the present invention allows the angular indexing of the pinion on the rack, thus ensuring the correct alignment of the midpoints of the steering wheel and the pinion-rack assembly.

[0047] The subject matter of the present disclosure may also have one or more of the following features individually or in combination.

[0048] According to one embodiment, the height of the bottom of at least one insertion recess is the same as the height of the bottom of the plurality of functional recesses.

[0049] Thus, the insertion recess and the functional recess are aligned.

[0050] According to one embodiment, the height of the insertion tooth is smaller than the height of the functional tooth.

[0051] Therefore, the insertion teeth are smaller than the functional teeth.

[0052] According to one embodiment, at least one insertion tooth has, along the longitudinal section of the rack, the same upper profile as the upper profile of the functional tooth facing the insertion area.

[0053] The upper profile of the tooth is the profile of the tooth along the longitudinal section of the rack, and it includes at least the apex of the tooth, a part of the first side connected to the apex, and a part of the second side.

[0054] The upper profile of the tooth is determined by a tooth profile calculation known to those skilled in the art.

[0055] The rack according to the invention is remarkable in that the functional tooth facing the insertion area and at least one insertion tooth have the same upper profile.

[0056] Furthermore, since the height of the gauge positioned in the insertion recess is less than the height of the gauge positioned in the functional recess, the apex of at least one insertion tooth is offset towards the center of the rack by a distance relative to the functional tooth positioned opposite the insertion area, and this distance is close to but not necessarily equal to the offset distance.

[0057] In some embodiments, the offset distance is between 20% and 70% of the height of the gauge positioned in the functional recess, preferably between 30% and 50%, and particularly between 35% and 45%.

[0058] In some embodiments, the insertion area includes a plurality of insertion recesses, and preferably includes at least three insertion recesses.

[0059] Therefore, during insertion, the steering pinion can engage with at least three insertion recesses.

[0060] In some embodiments, the insertion area includes an introduction part provided with at least two introduction recesses, and the height of the gauges positioned in the at least two introduction recesses is the same.

[0061] The introduction recesses are also insertion recesses.

[0062] The introduction recesses allow the steering pinion to be inserted more easily.

[0063] In some embodiments, the insertion area includes a transition part provided with at least one transition recess, and 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.

[0064] In some embodiments, the transition part is positioned between the functional area and the introduction part.

[0065] Thus, the transition portion is in contact with the functional zone on one hand and with the introduction portion on the other hand.

[0066] By gradually bringing the pinion into the operating position, that is to say, by gradually increasing the stress exerted on the pinion-rack assembly, the transition portion contributes to the engagement of the pinion on the functional zone.

[0067] In some embodiments, the transition portion is provided with at least two transition recesses.

[0068] In some embodiments, the height of the gauge positioned in at least two transition recesses decreases linearly between the height of the gauge positioned in the functional recess and the height of the gauge positioned in the introduction recess.

[0069] Another aspect of the invention relates to a steering system comprising a rack according to the invention. Description of the Drawings

[0070] The invention will be better understood from the following description, which relates to several embodiments of the invention, given by way of non-limiting example and explained with reference to the accompanying schematic drawings, in which:

[0071] Figure 1 is a longitudinal cross-section of a rack according to the invention;

[0072] Figure 2 is Figure 1 an enlarged view of

[0073] Figure 3a and Figure 3b is a longitudinal cross-section of a pinion-rack assembly according to a first embodiment;

[0074] Figure 4a and Figure 4b is a longitudinal cross-section of a pinion-rack assembly according to a second embodiment;

[0075] Figure 5a and Figure 5b is a longitudinal cross-section of a pinion-rack assembly according to a third embodiment. Detailed Description

[0076] Only the elements necessary for understanding the invention are shown. For ease of reading the drawings, the same elements have the same reference numerals from one figure to the next.

[0077] As Figure 1 shown, the invention relates to a rack 1 for a steering system.

[0078] The rack 1 comprises a toothing formed by a plurality of teeth 2, which toothing extends along the longitudinal axis A (also called the elongation axis) of the rack 1.

[0079] Each tooth 2 includes a vertex, a first side surface, and a second side surface, and the first side surface and the second side surface are each connected to the vertex at a determined angle.

[0080] As Figure 2 shown, the tooth 2 includes at least the vertex of the tooth 2, a part of the first side surface, and a part of the second side surface according to the top contour of the longitudinal section of the rack 1, and the part of the first side surface and the part of the second side surface are connected to the vertex. The top contour of the tooth 2 is determined by a tooth profile calculation known to those skilled in the art.

[0081] The tooth profile is characterized relative to a gauge 3 that is actually positioned between two teeth 2, that is, positioned in the recess E of the tooth profile, as Figure 2 shown.

[0082] The gauge 3 is, for example, a sphere having a center and a predetermined diameter.

[0083] The center C of the rack 1 is the center of a virtual circle, and a segment of the rack 1 intercepted in a plane transverse to the longitudinal axis A of the rack 1 is at least partially inscribed in the virtual circle.

[0084] The height H of the gauge 3 is the dimension included between the center C of the rack 1 and the vertex of the gauge 3, and the gauge 3 is located between two consecutive teeth 2 of the rack 1.

[0085] The tooth profile includes a functional zone Z f and an insertion zone Z i , and the insertion zone Z i includes a transition portion P t and an introduction portion P i .

[0086] Two consecutive teeth 2 are separated by a recess E

[0087] On the functional zone Z f , the tooth 2 is called a functional tooth, and the recess is called a functional recess E f . The functional recess E f is configured to cooperate with the steering pinion 10 during the normal operation of the steering system. The functional zone Z f extends along the longitudinal axis A of the rack 1.

[0088] All the heights H of the gauge 3 positioned in the functional recess E f are the same. f

[0089] On the insertion zone Z i , the tooth 2 is called an insertion tooth, and the recess E is called an insertion recess E i , E t .

[0090] Insertion zone Z i extends in an extension of the functional zone Z f The insertion zone Z i is positioned along the longitudinal axis A of the rack 1 at one end of the functional zone Z f The insertion zone Z i is in contact with the functional zone Z f .

[0091] The insertion zone Z i includes a plurality of insertion recesses E i 、E t and preferably includes at least three insertion recesses E i 、E t .

[0092] The height H i 、E t of the gauge 3 positioned in the insertion recesses E i 、H t1 、H t2 is smaller by a certain offset distance than the height H f of the gauge 3 positioned in the functional recess E f .

[0093] More precisely, the offset distance is included between 20% and 70% of the height H f of the gauge 3 positioned in the functional recess E f , preferably between 30% and 50%, and particularly between 35% and 45%.

[0094] According to one embodiment, the height of the bottom of the teeth of at least one insertion recess E i 、E t is the same as the height of the bottom of the teeth of the plurality of functional recesses E f .

[0095] Thus, the insertion recesses E i 、E t and the functional recess E f are aligned.

[0096] According to one embodiment, the height of the insertion teeth 2 is less than the height of the functional teeth 2.

[0097] Thus, the insertion teeth are smaller than the functional teeth.

[0098] According to one embodiment, at least one insertion tooth 2 has the same upper profile as the upper profile of the functional tooth 2 opposite to the insertion zone Z i in accordance with the longitudinal section of the rack 1.

[0099] The upper profile of tooth 2 is the profile of tooth 2 according to the longitudinal section of the rack 1, and it at least includes the apex of the tooth, a part of the first side connected to the apex, and a part of the second side.

[0100] According to an embodiment, the rack 1 according to the present invention is characterized in that the functional tooth 2 facing the insertion area Z i and at least one insertion tooth 2 have the same upper profile. In addition, since the height H i 、E t of the gauge 3 located in the insertion recess E i 、H t1 、H t2 is less than the height H f of the gauge 3 located in the functional recess E f , so the apex of at least one insertion tooth 2 is offset by a certain distance in the direction of the center C of the rack 1 relative to the functional tooth 2 positioned to face the insertion area Z i . This distance is close to but not necessarily equal to the offset distance.

[0101] In the transition part P t , the recess E is called the transition recess E t , while in the introduction part P i , the recess is called the introduction recess E i .

[0102] The introduction recess E i and the transition recess E t are also the insertion recesses E i 、E t .

[0103] The introduction part P i is provided with at least two introduction recesses E i , and the height H i of the gauge located in at least two introduction recesses E i is the same.

[0104] The introduction recess E i allows the steering pinion 10 to be inserted more easily.

[0105] The height H t of the gauge 3 located in at least one transition recess E t1 、H t2 is included between the height H f of the gauge 3 located in the functional recess E f and the height H i of the gauge 3 located in the introduction recess E i .

[0106] The transition part P tIs positioned in the functional zone Z f And the introduction part P i Between.

[0107] Therefore, the transition part P t On the one hand, it is in contact with the functional zone Z f On the other hand, it is in contact with the introduction part P i In contact.

[0108] By gradually placing the pinion gear 10 in the operating position, that is, by gradually increasing the stress applied to the pinion gear 10 - rack 1 assembly, the transition part P t Contributes to the meshing of the pinion gear 10 on the functional zone Z f On.

[0109] The transition part P t Is provided with at least two transition recesses E t .

[0110] The height H of the gauge 3 positioned in at least two transition recesses E t 、H t1 、H t2 Linearly decreases between the height H of the gauge 3 positioned in the functional recess E f And the height H of the gauge 3 positioned in the introduction recess E f And the height H of the gauge 3 positioned in the introduction recess E i In. i Linearly decreases.

[0111] Figure 3a 、 Figure 3b 、 Figure 4a 、 Figure 4b And Figure 5a 、 Figure 5b Show embodiments of assembling the pinion gear 10 on the rack 1 in different steering housings 20, 20', 20”. More specifically, Figure 3a 、 Figure 4a And Figure 5a Show the position of the pinion gear relative to the rack 1 when the pinion gear 10 is inserted into the steering housings 20, 20', 20”. Figure 3b 、 Figure 4b And Figure 5b Show the position of the pinion gear 10 relative to the rack 1 during normal operation of the steering system.

[0112] When assembling the pinion gear 10 - rack 1 assembly according to the present invention, first position the rack in the steering housings 20, 20', 20”.

[0113] According to Figure 3a 、 Figure 3bIn a first embodiment, the steering housing 20 includes a "pushing" device 30 which is pre-adjusted such that the "pushing" device exerts a force equal to the force that must be exerted during normal operation towards the rack.

[0114] According to Figure 4a 、 Figure 4b In the second embodiment shown, the steering housing 20' includes a spring 30' which exerts a predetermined force towards the rack 1. The spring 30' cannot be adjusted.

[0115] According to Figure 5a 、 Figure 5b In the third embodiment, the steering housing 20'' does not include any specific device for exerting a thrust force towards the rack 1.

[0116] In each of the said embodiments, the rack 1 is slidably mounted in the steering housings 20, 20', 20''.

[0117] In each of the said embodiments, the insertion zone Z i allows the assembly of the innovative pinion 10 - rack 1 assembly. In fact, according to the invention, the rack 1 is first positioned in the steering housings 20, 20', 20'' as Figure 3a 、 Figure 4a 、 Figure 5a shown, such that the clearance between the rack 1 and the steering housings 20, 20', 20'' is substantially the final desired clearance during the operation of the assembly in the vehicle.

[0118] Then, as Figure 3a 、 Figure 4a and Figure 5a shown, the pinion 10 is inserted into the steering housings 20, 20', 20'' at the insertion zone Z i (more precisely at the introduction part P i ). In fact, the height H i of the gauge 3 positioned in the introduction recess E i is lower than the height H f of the gauge 3 positioned in the functional recess E f which allows the stress exerted on the rack 1 to be reduced and thus the pinion 10 can be inserted into the steering housings 20, 20', 20''.

[0119] Then, the pinion 10 is rotationally moved along the rack 1 so as to travel through the transition part P t . The transition part P t gradually subjects the pinion 10 - rack 1 assembly to stress. Finally, the pinion 10 is positioned on the functional zone Z f as Figure 3b 、 Figure 4b, Figure 5b as shown. Then, the pinion 10 is prohibited from reaching the insertion zone Z i , for example by means of a travel limiter.

[0120] According to the invention, it is no longer necessary to press the rack 1 against the pinion 10 via a "pushing" device 30 which is adjusted, for example, after positioning the pinion 10. In fact, when the pinion 10 meshes with the teeth 2 of the functional zone Z f , the final stress is applied. During the operation of the components in the vehicle, the pinion 10 only travels through the functional zone Z f . Thus, the invention enables the rack 1 in the steering housings 20, 20', 20'' to be adjusted before inserting the pinion 10.

[0121] Although the invention has been described with reference to specific embodiments, it is obvious that these examples can be modified and changed without departing from the general scope of the invention defined by the claims. Specifically, the various features of the various illustrated / mentioned embodiments can be combined in additional embodiments. Therefore, the description and drawings should be regarded as illustrative rather than restrictive.

[0122] It is also obvious that all features described with reference to the method can be applied to the device, either individually or in combination, and conversely, all features described with reference to the device can be applied to the method, either individually or in combination.

Claims

1. A rack (1) for a steering system, the rack comprising A functional area (Z) is provided with a plurality of functional teeth (2) f ), and the functional area defines a plurality of functional recesses (E f ) between two consecutive functional teeth, and the functional recesses (E f ) are configured to cooperate with a pinion (10), and the functional area (Z f ) extends along a longitudinal axis (A) of the rack (1). and an insertion area (Z f ) extending in an extension of the functional area (Z i ), the insertion area (Z i ) being provided with at least one insertion tooth (2), and at least one insertion recess (E i , E i ) being defined between the at least one insertion tooth (2) and a functional tooth (2) positioned opposite the insertion area (Z t ). It is characterized in that The height (H i , H t ) of the gauge (3) positioned in the insertion recess (E t1 , E t2 , H i ) is smaller than the height (H f ) of the gauge (3) positioned in the functional recess (E f ) by a certain offset distance.

2. The rack (1) according to claim 1, wherein, Said at least one insertion tooth (2) has, according to the longitudinal section of the rack (1), an upper profile that is the same as the upper profile of the functional tooth (2) positioned opposite the insertion zone (Z i ).

3. The rack (1) according to any one of the preceding claims, wherein, The offset distance is included between 20% and 70%, preferably between 30% and 50%, and particularly between 35% and 45% of the height (H f ) of the gauge (3) positioned in the functional recess (E f ).

4. The rack (1) according to any one of the preceding claims, wherein, The insertion area (Z i ) includes a plurality of insertion recesses (E i , E t ), and preferably includes at least three insertion recesses (E i , E t ).

5. The rack (1) according to claim 4, wherein, The insertion zone (Z i ) includes an introduction part (P i ) provided with at least two introduction recesses (E i ), and the height (H i ) of the gauge (3) positioned in the at least two introduction recesses (E i ) is the same.

6. The rack (1) according to claim 5, wherein, Said insertion zone (Z i ) comprises a transition portion (P t ) provided with at least one transition recess (E t ), the height (H t , H t1 ) of the gauge (3) positioned in said at least one transition recess (E t2 ) being comprised between the height (H f ) of the gauge (3) positioned in said functional recess (E f ) and the height (H i ) of the gauge (3) positioned in said introduction recess (E i ).

7. The rack (1) according to claim 6, wherein, The transition part (P t ) is positioned between the functional area (Z f ) and the introduction part (P i ).

8. The rack (1) according to any one of claims 6 or 7, wherein, The transition portion (P t ) is provided with at least two transition recesses (E t ).

9. The rack (1) according to claim 8, wherein, The height (H t ), H t1 ), of the gauge (3) positioned in the at least two transition recesses (E t2 ) decreases linearly between the height (H f ) of the gauge (3) positioned in the functional recess (E f ) and the height (H i ) of the gauge (3) positioned in the introduction recess (E i ).

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

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