Thrust piece arrangement for a motor vehicle steering system

Description

[0001] The invention relates to a pressure piece arrangement for a motor vehicle steering system with the features of the preamble of patent claim 1.

[0002] A thrust piece assembly for a motor vehicle steering system with the features of the preamble of patent claim 1 is known from US 2008 / 034903 A1. Its radially inner first common stop region and radially outer second common stop region are formed by mutually parallel stop surfaces. The first stop region is axially soft, so that after a certain force level is exceeded, the second stop signal also comes into effect.

[0003] Pressure piece arrangements comprising a pressure piece for bearing against a handlebar, which can be arranged in a bushing so as to be slidably movable in an axial direction, an adjusting element which can be screwed into the bushing and limits the axial displacement path of the pressure piece in one direction, wherein the pressure piece has a first end wall facing the adjusting element and the adjusting element has a second end wall facing the pressure piece, and a spring device which is arranged between the pressure piece and the adjusting element so as to press their end walls apart, are equally known from DE 10 2012 019 934 A1 and DE 10 2013 201 916 A1.

[0004] Pressure piece assemblies are used to force a steering rod, in particular a rack, into close contact with a gear member engaging therewith, such as a steering pinion, in a motor vehicle steering system, in order to ensure that the engagement is free of play.

[0005] However, rattling noises can occur on the known pressure piece arrangements, especially when driving on rough roads.

[0006] The sole use of an O-ring between the end walls of the pressure piece and the adjustment element, as shown in DE 10 2013 201 916 A1, has not proven to be sufficient.

[0007] Increasing the preload force of the spring device could reduce acoustic abnormalities, but has the disadvantage of reducing the service life of the spring and, with an identical design, generally leads to an undesirable increase in friction in the vehicle steering system.

[0008] The invention is therefore based on the object of demonstrating alternatives for reducing acoustic abnormalities in the area of a pressure piece arrangement of a motor vehicle steering system.

[0009] This object is achieved by a pressure piece arrangement for a motor vehicle steering system according to patent claim 1.

[0010] By dividing the stop area between the pressure piece and the adjustment element according to the invention, acoustic abnormalities can be reduced without endangering the support of the pressure piece against the adjustment element.

[0011] The second common stop area primarily serves to support very high forces, but is generally ineffective during normal operation. However, when driving on rough roads, tilting loads can occur on the pressure piece due to the slight radial play between the pressure piece and the bushing that guides it, which is necessary for its function. By offsetting the second common stop area compared to the first common stop area, a certain amount of clearance is created for this case, so that if the pressure piece tilts in its guide, the furthest protruding edge areas of the pressure piece's end wall do not strike the adjusting element, thus preventing the corresponding noise generation.

[0012] An annular groove is formed in the end wall of the adjustment element, which separates the first common stop area and the second common stop area from each other and divides them into an inner ring and an outer ring. An elastomer element is arranged in the annular groove, which projects beyond the annular groove in the direction of the pressure piece and, in an elastically compressed state, can be completely accommodated in the annular groove. This dampens impact, particularly when the pressure piece is not tilted or is only slightly tilted.

[0013] The outer ring forms a conical annular surface, which reduces the weakening of the adjusting element. Alternatively or additionally, as with the adjusting element, the radially outer stop area, i.e., the second section of the end wall of the thrust piece, is designed as a conical annular surface.

[0014] The above-mentioned clearance may be provided on the side of the adjusting element, on the side of the pressure piece, or on both sides.

[0015] Particular embodiments of the invention are the subject of further patent claims.

[0016] In a special embodiment of the invention, the outer ring on the adjusting element is recessed relative to the inner ring. The inner ring thus protrudes toward the thrust piece. Such a design can be implemented on the adjusting element with little effort, especially if its end wall requires precise machining to create the annular groove.

[0017] In one design variant, the outer ring and the inner ring are flat and parallel ring surfaces, which are easy to manufacture.

[0018] The corresponding end wall of the pressure piece can be a flat surface over the two common stop areas, which keeps the machining effort on the pressure piece to a minimum.

[0019] According to a further particular embodiment of the invention, a second section of the end wall of the pressure piece opposite the outer ring of the adjusting element can be set back from a first section of the end wall of the pressure piece opposite the inner ring of the adjusting element in order to create the free space explained above.

[0020] In one embodiment, the first and second sections can also be formed by mutually parallel flat annular surfaces.

[0021] Preferably, the axial setback is a maximum of 0.1 to 0.3 mm. This has been shown to be generally sufficient to reduce acoustic disturbances caused by tilting movements of the pressure piece. On the other hand, the second common stop area also comes into play under high axial loads.

[0022] The thrust piece assembly described above is used in a motor vehicle steering system comprising a steering housing, a steering rod, and said thrust piece assembly. The bushing is attached or formed on the steering housing, the thrust piece is inserted into the bushing while bearing against the steering rod, the adjusting element is fixed to the steering housing, and the spring device, which bears against the adjusting element, urges the thrust piece into bearing against the steering rod. This motor vehicle steering system is characterized by improved acoustic properties.

[0023] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawing. The drawing shows: Fig. 1 is a schematic view of a motor vehicle steering system according to an embodiment of the invention, Fig. 2 is a sectional view of a pressure piece arrangement according to an embodiment of the invention, Fig. 3 is a detailed view of the pressure piece arrangement from Fig. 3 , and in Fig. 4a-e different embodiments for the design of the common stop areas between the pressure piece and the adjusting element, wherein the variants 4a and 4c are not the subject of the invention.

[0024] The embodiment in Fig. 1 shows a motor vehicle steering system 1 using the example of an electromechanical steering system 1 for a passenger vehicle.

[0025] The motor vehicle steering system 1 has a steering housing 2 through which a steering rod 3 extends. A transmission element 4, for example a steering pinion, engages the steering rod 3 in order to transmit a steering command applied by the driver to a steering handle 5 to the vehicle wheels 6.

[0026] Furthermore, the motor vehicle steering system 1 can have an electric drive unit for generating a steering torque, which comprises at least one electric motor 7 and optionally also a transmission. The electric motor 7 can, as shown, be arranged axially parallel to the handlebar 3. However, it is also possible to arrange the electric motor 7 coaxially to the handlebar 3 or at another location.

[0027] In the illustrated embodiment, the drive torque of the electric motor 7 is applied as an axial force to the steering rod 3 via a gear stage 8 and a ball screw drive 9 supported in the steering gear housing 2. The gear stage 8 is embodied here, for example, as a belt drive, with a first pulley arranged on an output shaft of the electric motor 7 and a second pulley arranged on a ball screw nut of the ball screw drive 9. However, other transmissions, such as gear transmissions or the like, are also possible.

[0028] Furthermore, a pressure piece arrangement 10 is provided on the motor vehicle steering system 1, which serves to ensure a play-free engagement between the steering rod 3 and the transmission element 4. This pressure piece arrangement 10 is described below with reference to the Fig. 2 bis 4 explained in more detail.

[0029] The pressure piece arrangement 10 comprises a pressure piece 11, an adjusting element 12, a spring device 13 and an elastomer element 14.

[0030] The pressure piece 11 serves to press the handlebar 3 against the transmission element 4. For this purpose, in the installed state, the pressure piece 11 bears against the handlebar 3, as described, for example, in DE 10 2012 019 934 A1. The relevant content of DE 10 2012 019 934 A1 is expressly incorporated into the present disclosure.

[0031] The pressure piece 11 is arranged in a bushing 15, which is formed or fastened to the steering housing 2, for sliding movement in an axial direction A. A sealing ring 16 can be provided between the inner wall of the bushing 15 and the outer circumference of the pressure piece 11.

[0032] The adjusting element 12 is screwed into the bushing 15 when installed and, in this case, has an external thread 17 for this purpose. It serves to limit the axial displacement of the pressure piece 11 in one direction. Furthermore, the adjusting element 12 can be used to adjust the preload force with which the pressure piece 11 is pressed against the handlebar 3 during assembly.

[0033] This preload force is generated by compressing the spring device 13, which is arranged between the pressure piece 11 and the adjusting element 12.

[0034] The spring device 13 is supported in recesses 18 and 19 formed in opposing end walls 21 and 22 of the pressure piece 11 and the adjustment element 12. In the installed state, the end walls 21 and 22 of the pressure piece 11 and the adjustment element 12 are thus pushed apart by the spring device 13. The spring device 13 can be a helical spring. However, it can also be designed, for example, as a disc spring or disc spring assembly.

[0035] As particularly in the Fig. 3 and 4 As shown in more detail, the mutually facing end walls 21 and 22 of the pressure piece 11 and the adjusting element 12 are specially matched to one another.

[0036] Thus, the end walls 21 and 22 of the pressure piece 11 and the adjusting element 12 define a radially inner first common stop region A1 and a radially outer second common stop region A2, which surrounds the first common stop region A1.

[0037] The second common stop area A2 is offset from the first common stop area A1 in such a way that when the end walls 21 and 22 abut against each other, abutment against the first common stop area A1, i.e., the radially further inner stop area A1, takes effect before abutment against the second common stop area A2. This prevents the sections of the end wall 21 of the pressure piece 11 that then project furthest axially in the direction of the adjusting element 12 from striking the end wall 22 of the adjusting element 12 without being damped and generating a corresponding noise when the pressure piece 11 tilts in its guide by the bushing 15.

[0038] However, if the end wall 21 of the pressure piece 11 moves essentially in parallel alignment against the end wall 22 of the adjusting element 12, a hard stop by the elastomer element 14 can be avoided.

[0039] For such an elastomer element 14, an annular groove 20 can be formed in the end wall 22 of the adjusting element 12, and optionally also in the end wall 21 of the pressure piece 11.

[0040] The elastomer element 14 in the form of an O-ring is arranged such that it projects beyond the annular groove 20 in the direction of the pressure piece 11 and can be completely received in the annular groove 20 in an elastically compressed state.

[0041] In the present case, the annular groove 20 separates the first common stop area A1 and the second common stop area A2 from one another on the end wall 22 of the adjusting element 12.

[0042] As a result, the end wall 22 of the adjusting element 12 is divided into an inner ring 23 and an outer ring 24.

[0043] At the Fig. 3 In the exemplary embodiment shown, the outer ring 24 of the end wall 22 of the adjusting element 12 is set back from the inner ring 23 of the end wall 22 of the adjusting element 12. In Fig. 3 This is indicated by the axial recess z, which is preferably a maximum of 0.1 to 0.3 mm.

[0044] In this embodiment, the inner ring 23 and the outer ring 24 are designed as flat and mutually parallel ring surfaces.

[0045] The end wall 21 of the pressure piece 11 is in Fig. 3 a flat surface over the two common stop areas A1 and A2.

[0046] When the two end walls 21 and 22 approach each other in parallel, they only come into contact with each other in the area of the first common stop area A1 at low impact forces, after the damping effect of the elastomer element 14 has been overcome. In this case, the elastomer element 14 prevents any noticeable noise generation.

[0047] At higher axial loads, a certain elastic deformation occurs, so that the end walls 21 and 22 also come into contact with each other in the second common stop area A2 and overloading of the adjusting element 12 is avoided.

[0048] If increased tilting moments occur at the pressure piece 11, the effect of the elastomer element 14 may no longer be sufficient. However, the clearance created in the area of the second common stop area A2 by the recess z nevertheless prevents an acoustically relevant contact. Rather, even in such a case, initial contact occurs in the area of the first common stop area A1. This can also cause a parallelization of the end faces 21 and 22, counteracting the tilting movement.

[0049] Naturally, the extent of the retraction z is adjusted to a maximum tilting of the thrust piece 11. The range specified above is generally sufficient for a motor vehicle steering system for passenger cars.

[0050] The above-mentioned Fig. 3 The free space described can also be obtained in other ways, as shown below using Fig. 4 To illustrate the presentation, Fig. 4 only the end faces 21 and 22 are shown without taking into account the recesses 18 and 19.

[0051] Fig. 4a represents the Fig. 3 explained variant.

[0052] Fig. 4b shows as a variation of this the possibility, in contrast to Fig. 4a to form the outer ring 24 of the end wall 21 of the adjusting element 12 as a conical annular surface 25, whereby the adjusting element 12 is weakened somewhat less.

[0053] Furthermore, according to the variants of the Fig. 4c und 4d a second section 27 of the end wall 21 of the pressure piece 11 opposite the outer ring 24 is set back from a first section 26 of the end wall 21 of the pressure piece 11 opposite the inner ring 23.

[0054] In Fig. 4c The first and second sections 26 and 27 are formed by mutually parallel, flat annular surfaces. A small step then forms between the two sections 26 and 27.

[0055] However, a stepless connection is also possible, as shown in Fig. 4d Here, the second section 27 forms a conical annular surface 28, which preferably adjoins the first section 26 in a stepless manner and slopes radially outwards.

[0056] Fig. 4e shows an example of a possibility to gain the clearance by measures on both the pressure piece 11 and the adjusting element 12, whereby it should be expressly pointed out at this point that any combination of the measures of the Fig. 4a bis 4d is possible. The maximum axial offset z is preferably in the range of 0.1 to 0.3 mm.

[0057] The invention has been explained in more detail above using exemplary embodiments and further modifications. The exemplary embodiments and modifications serve to demonstrate the feasibility of the invention. Individual technical features explained above in the context of further individual features can also be implemented independently of these and in combination with other individual features, even if this is not expressly described, as long as this is technically possible. The invention is therefore expressly not limited to the specifically described exemplary embodiment, but encompasses all configurations defined by the patent claims. Bezugszeichenliste

[0058] 1Motor vehicle steering system 2Steering housing 3Steering rod 4Gear link (steering pinion) 5Steering handle 6Vehicle wheel 7Electric motor 8Gear stage 9Ball screw 10Thrust piece arrangement 11Thrust piece 12Adjusting element 13Spring device 14Elastomer element 15Bushing 16Sealing ring 17External thread 18Recess 19Recess 20Anal groove 21End wall on the thrust piece 22End wall on the adjusting element 23Inner ring 24Outer ring 25Conical ring surface 26First section 27Second section 28Conical ring surface AAxial direction A1First common stop area A2Second common stop area zReset

Claims

1. Pressure piece arrangement (10) for a motor vehicle steering system (1), comprising: ∘ a pressure piece (11) for bearing against a steering rod (3), which can be arranged to slide in an axial direction (A) in a bushing (15), ∘ an adjustment element (12) that can be screwed into the bushing (15) and limits the axial displacement path of the pressure piece (11) in one direction, ∘ wherein the pressure piece (11) has a first end wall (21) facing the adjustment element (12) and the adjustment element (12) has a second end wall (22) facing the pressure piece (11), ∘ and a spring device (13) arranged between the pressure piece (11) and the adjustment element (12) to push their end walls (21, 22) apart, ∘ wherein the end walls (21, 22) of the pressure piece (11) and the adjustment element (12) have a radially inner first common stop area (A1) and a radially outer second common stop area (A2) surrounding the first common stop area (A1), wherein the second common stop area (A2) is offset relative to the first common stop area (A1) such that when the end walls (21, 22) strike against each other, a strike against the first common stop area (A1) becomes effective before a strike against the second common stop area (A2), ∘ characterized in that ∘ a ring groove (20) is formed in the end wall (22) of the adjustment element (12), which separates the first common stop area (A1) and the second common stop area (A2) from each other and divides them into an inner ring (23) and an outer ring (24), ∘ and that an elastomer element (14) in the form of an O-ring is arranged in the ring groove (20), which protrudes from the ring groove (20) in the direction of the pressure piece (11) and can be completely accommodated in the ring groove (20) in an elastically compressed state, ∘ and the outer ring (24) is a conical ring surface (25) and / or a second section (27) of the end wall (21) of the pressure piece (11) opposite the outer ring (24) is a conical ring surface (28).

2. Pressure piece arrangement (10) according to claim 1, characterized in that the outer ring (24) is recessed relative to the inner ring (23).

3. Pressure piece arrangement (10) according to claim 1 or 2, characterized in that the outer ring (24) and the inner ring (23) are flat and parallel ring surfaces.

4. Pressure piece arrangement (10) according to one of claims 1 to 3, characterized in that the end wall (21) of the pressure piece (11) is a flat surface over the two common stop areas (A1, A2).

5. Pressure piece arrangement (10) according to one of claims 1 to 3, characterized in that the second section (27) of the end wall (21) of the pressure piece (11) opposite the outer ring (24) is recessed relative to a first section (26) of the end wall (21) of the pressure piece (11) opposite the inner ring (23).

6. Pressure piece arrangement according to claim 5, characterized in that the first and second sections (26, 27) are formed by flat and parallel ring surfaces.

7. Pressure piece arrangement according to one of claims 1 to 7, characterized in that the axial recess is a maximum of 0.1 to 0.3 mm.

8. Motor vehicle steering system (1) with a steering housing (2), a steering rod (3), and a pressure piece arrangement (10) according to one of the preceding claims, wherein the bushing (15) is attached or formed on the steering housing (2), the pressure piece (11) is inserted into the bushing (15) bearing against the steering rod (3), the adjustment element (12) is fixed to the steering housing (2), and the spring device (13), which is supported against the adjustment element (12), pushes the pressure piece (11) against the steering rod (3).