Device for pressing a rack

Abstract

Device for pressing a rack against a pinion meshing with the rack, for a steering system of a motor vehicle, comprising a pressure piece (13) which can be loaded in the direction of the rack by a compression spring (16) and is slidably guided in a housing (12), and an adjusting device (14) for compensating for play occurring in the steering system, wherein a spring washer (22) is arranged between the adjusting device (14) and the pressure piece (13), wherein the adjusting device (14) has a shoulder (24) and the pressure piece (13) has a recess (23), or the pressure piece (13) has a shoulder and the adjusting device (14) has a recess (23) in the area of ​​the spring washer (22), and the adjusting device (14) further comprises two adjusting discs (20, 21) which are rotatable relative to each other and bear against each other at contact surfaces, and the contact surfaces have at least two inclined surfaces (18, 19), characterized in thatthat the complete adjusting device (14) is pre-assembled as an assembly unit with pressure piece (13), spring washer (22), compression spring (16) using a tension pin (27), wherein the tension pin (27) extends axially in the central axis of the assembly unit.

Description

[0001] The invention relates to a device for pressing a rack onto a pinion according to the type defined in the preamble of claim 1.

[0002] EP 0 680 430 B1 discloses a device for pressing a rack against a pinion meshing with the rack, particularly for a motor vehicle steering system. To eliminate or adjust the pressure piece play, component tolerances of the pinion, rack, housing, and pressure piece are eliminated and a predetermined pressure piece play is set by selectively assembling various retaining rings of varying thickness. Gradations of 0.05 mm are generally used, meaning that, for possible tolerance ranges of approximately 0.5 to 1 mm, a large number of different retaining rings with correspondingly graduated thicknesses are necessary. A further disadvantage is that adjustments during operation are not readily possible due to wear and settling of individual parts.

[0003] In the earlier patent application DE 10 2008 054 782 A1, a device for pressing a toothed rack has therefore been proposed, in which existing tolerances can be eliminated in a simple manner and a predetermined pressure piece play can be set.

[0004] To compensate for tolerances, an adjustment device is provided with two adjusting discs that can be rotated relative to each other and that rest against each other at contact surfaces, with the contact surfaces featuring at least two inclined surfaces. The two adjusting discs can be clamped against each other by a torsion spring placed between them, thus compensating for tolerances in the individual components.

[0005] The adjustment device further comprises a spring washer arranged between the pressure piece and the first of the two adjusting discs facing the pressure piece. For this purpose, a shoulder is provided, whereby this shoulder is provided in the pressure piece or on the adjusting disc and the other part in each case has a recess. The shoulder of the adjustment device or the pressure piece forms a play that is at least large enough to compensate for, for example, unevenness in the toothing between a pinion and a rack, out-of-roundness of the pinion, or other errors. The recess in the pressure piece or in the adjustment device allows the spring washer the spring travel it needs to compensate for the aforementioned play.

[0006] In the older application, the adjustment device with the two adjusting discs and the torsion spring is designed as an assembly unit. The two adjusting discs are fastened together by a screw and prevented from rotating. After the compression spring is subsequently installed, the adjusting screw is tightened to a specific torque so that the play created by the shoulder is bridged. The adjusting disc is then opened again by a specific angle, whereby the opening angle should correspond to the play created by the shoulder. Finally, the adjusting screw must be secured against rotating, for example, by caulking or gluing.

[0007] DE 10 2008 049 489 A1 discloses a wear compensation device for a pressure piece, wherein the adjustment unit is secured for assembly with three pins.

[0008] The present invention is based on a further improvement of the earlier application, in particular a simpler assembly, wherein the advantages with regard to a predetermined pressure piece play and tolerance compensation are to be retained.

[0009] According to the invention, this object is achieved by the features mentioned in the characterizing part of claim 1.

[0010] As can be seen, the complete adjustment device, including the thrust piece, spring washer, and compression spring, is now designed as a pre-assembled unit. Instead of a clamping screw, a dowel pin is used, which rests under preload on one side against a shoulder of the thrust piece and on the other side against the rear side of the adjusting disc, facing away from the beveled surfaces.

[0011] For final assembly, the assembly unit, pre-assembled outside the steering gear, is pushed into a housing bore. The assembly unit is then secured in the housing bore. This can advantageously be achieved using a retaining ring, which can be arranged in a housing groove.

[0012] The rotation of the two adjusting discs relative to each other in order to achieve tolerance compensation can be achieved by a torsion spring arranged between the two adjusting discs.

[0013] For pre-assembly, the dowel pin is guided through axially extending slots in the adjusting discs and rests against the shoulder of the pressure piece with an extension at its front end, facing the pressure piece. On the other side, on the rear side of the adjusting disc, facing away from the beveled surfaces, it also rests with a shoulder under preload.

[0014] In order to obtain a preload for the pre-assembled assembly unit, the elongated holes of the adjusting discs can advantageously be rotated by a few degrees in the circumferential direction.

[0015] To ensure a play-free connection of the assembly unit, the shoulder on the pressure piece can be provided with rising bevels.

[0016] The dowel pin that holds the individual parts of the assembly unit together is removed after final assembly.

[0017] Advantageous further developments and refinements emerge from the subclaims and from the exemplary embodiment described in principle below with reference to the drawing.

[0018] It shows: Fig. 1: a sectional view through the device according to the invention with the pressure piece and the adjusting device; Fig. 2: a perspective view in an exploded view of the device according to the invention according to the Fig. 1 without housing.

[0019] The Fig. 1 shows a device 10 for pressing a rack (not shown here) onto a pinion (also not shown) for a steering system of a motor vehicle. An insert film 11 is arranged between the pressure piece 13 and the rack (not shown), adjacent to or behind the side of the pressure piece facing away from the rack. A compression spring 16 is arranged between a retaining ring 15 and the pressure piece 13, which presses the pressure piece 13 against the rack (not shown). The adjustment device 14 has two adjusting discs 20 and 21. A spring washer 22 is arranged between the adjusting disc 20 facing the pressure piece 13 and the pressure piece. A recess 23 is located in the pressure piece 13. The two adjusting discs 20, 21 rest against one another on contact surfaces provided with inclined surfaces 18, 19 (see Fig. 2).

[0020] In order to use a simple retaining ring 15 instead of the adjusting screw of the older application, the component tolerances must be compensated. This is achieved by the adjusting device 14, which initially compensates for the tolerance range and subsequently for wear and settling during operation. The thrust piece clearance itself is adjusted using the spring washer 22 and a recess 24 in the adjusting disc 20.

[0021] The complete adjustment device 14 is pre-assembled as an assembly unit with the pressure piece 13, the spring washer 22, the compression spring 16, and the two adjusting discs 20, 21, together with a torsion spring 26 located between the two adjusting discs 20, 21, by means of a roll pin 27 outside the steering gear. For this purpose, the roll pin 27 rests under preload on one side against a shoulder 17 of the pressure piece 13 and on the other side against the rear of the adjusting disc 21, which is located on the side facing away from the contact surfaces with the inclined surfaces 18, 19 of the two adjusting discs 20, 21.

[0022] The torsion spring 26 is preloaded by the two adjusting discs 20, 21 and held in the pre-assembled position. This pre-assembled position of the two adjusting discs is maintained by a two-flat section 28 of the clamping pin 27.

[0023] The front end of the two-flat portion 28 is provided with a diameter reduction and two adjacent, opposing extensions 29, which bear against the shoulder 17 of the pressure piece 13. The clamping pin rests against an annular recess 25 via a further annular shoulder 30 on the end face of the adjusting discs 21 facing away from the pressure piece 13.

[0024] The two-flat surface 28 of the clamping pin 27 is pushed through slots 31 running in the axial direction in the adjusting discs 20, 21 (see Fig. 2). The elongated holes 31 of the two adjusting discs 20, 21 are rotated by a few degrees in the circumferential direction to achieve a preload.

[0025] For assembly, the adjustment device is inserted with the roll pin 27 into the pressure piece 13 with the mounted spring washer 22 and compression spring 16 and twisted. The annular shoulder 29 of the roll pin 27 acts like a key. Since the shoulder 17 in the pressure piece 13 is provided with rising bevels, a play-free connection of the pre-assembly can be achieved.

[0026] The assembly unit is then inserted into a bore in the housing 12, where it is then positioned by the retaining ring 15 inserted into a groove 32 of the housing 12. The clamping pin 27 is then removed by turning and pulling it outward. This activates the pressure piece 13, and the two adjusting discs 20, 21 are rotated relative to each other via the torsion spring 26. Due to the two inclined surfaces 18, 19 in the adjusting discs 20, 21, an axial displacement occurs, thus compensating for tolerances in the individual components.

[0027] The two inclined surfaces 18, 19 in the front contact surfaces of the adjusting discs 20, 21 are designed for 2 x 180° so that even high component tolerances and wear can be compensated, especially since the locking ring 15 no longer allows any adjustment in comparison to the adjusting screw in the older application.

[0028] The device is closed off to the outside in the bore of the housing 12 on the side facing away from the rack by a simple closure cover 33. List of reference symbols 10 Device 11 Insert film 12 housings 13 Pressure piece 14 Adjustment device 15 Retaining ring 16 compression spring 17 paragraph 18 Inclined surface 19 Inclined surface 20 adjusting disc 21 Adjusting disc 22 spring washer 23 Recess 24 paragraph 25 recess 26 torsion spring 27 dowel pin 28 Two-flat 29 Extension of the dihedral 30 ring heel 31 elongated holes 32 Housing groove 33 Cover cap

Claims

[1] A device for pressing a rack against a pinion engaging with the rack, for a steering system of a motor vehicle, comprising a pressure piece (13) which is loadable in the direction of the rack by a compression spring (16) and displaceably guided in a housing (12), and an adjusting device (14) for compensating for play occurring in the steering system, wherein a spring washer (22) is arranged between the adjusting device (14) and the pressure piece (13), wherein the adjusting device (14) has a shoulder (24) and the pressure piece (13) has a recess (23) or the pressure piece (13) has a shoulder and the adjusting device (14) has a recess (23) in the region of the spring washer (22), and the adjusting device (14) further comprises two adjusting discs (20, 21) which are rotatable relative to one another and which bear against one another at contact surfaces, and the contact surfaces have at least two inclined surfaces (18, 19), characterized bythat the complete adjusting device (14) is pre-assembled as an assembly unit with pressure piece (13), spring washer (22), compression spring (16) using a clamping pin (27), wherein the clamping pin (27) extends axially in the central axis of the assembly unit. [2] Device according to claim 1, characterized by that the clamping pin (27) rests under prestress on one side on the pressure piece (13) and on the other side on the back of the adjusting disc (21) facing away from the inclined surfaces (18, 19). [3] Device according to claim 2, characterized by that the clamping pin (27) rests against a shoulder (17) of the pressure piece (13). [4] Device according to claim 1, 2 or 3, characterized by that a torsion spring (26) is arranged between the two adjusting discs (20,21). [5] Device according to one of claims 1 to 4, characterized by that the clamping pin (27) is guided through axially extending slots (31) in the adjusting discs (20,21). [6] Device according to claim 5, characterized by that the elongated holes (31) in the adjusting discs (20,21) are rotated by a few degrees in the circumferential direction. [7] Device according to one of claims 1 to 6, characterized by that the assembly unit inserted into a housing bore of the housing (12) is held on the side facing away from the rack by a retaining ring (15). [8] Device according to claim 7, characterized by that the retaining ring (15) is arranged in a housing groove (32). [9] Device according to one of claims 1 to 8, characterized by that the inclined surfaces (18,19) each extend over 180°. [10] Device according to one of claims 1 to 9, characterized by that the shoulder (17) on the pressure piece (13) is provided with rising slopes to ensure a play-free connection of the assembly unit.

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