Rack and Pinion Steering Mechanism and the Mounting Thereof at an Automotive Vehicle

This invention relates to a rack and pinion steering mechanism and the attachment thereof to an automotive vehicle, especially a passenger car, wherein the rack and pinion steering mechanism is elastically mounted to a part integral with the vehicle.

Rack and pinion steering mechanisms are known which are joined to a part fixedly attached to the vehicle by means of a direct threaded connection, as illustrated, for example, in DAS (German Published Application) 1,215,010. This rigid type of mounting has the result that the steering has a "jerky" effect, ensuing in an unharmonious, angular steering force characteristic.

In another, generally conventional type of mounting, the gearbox of the rack and pinion steering mechanism is surrounded clamplike by two brackets with the interposition of rubber strips, wherein the brackets are threaded together with the chassis. This rubber-elastic mounting of the gearbox extensively overcomes the disadvantages inherent in the aforementioned state of the art. However, the most important disadvantage of such rubber elastic mounting is that this type of mounting is not resistant to axially directed thrust forces whereby the gearbox of the rack and pinion steering can be shifted sideways in case of a thrust force effective in the axial direction, so that in certain cases the threaded connection is loosened.

It has also been proposed according to DOS (German Unexamined Laid-Open Application) 1,957,462 to elastically support the gearbox of the rack and pinion steering mechanism by means of two rubber rings inserted in the gearbox. This type of support, however, can disadvantageously absorb only axially directed thrust forces. Furthermore, this elastic bearing is very expensive from a constructional viewpoint. In the alternative type of arrangement of the reference in question, shown in FIG. 2, only an axially directed, elastic thrust absorption is possible, on the one hand, and furthermore, on the other hand, the bolt fixing the arrangement in place against axial shifting has the effect of a solid sound-conducting bridge.

This invention contemplates an arrangement which overcomes the problem of mounting the gearbox of a rack and pinion steering mechanism in a manner resistant to axial thrust on a part affixed to the vehicle (integral with the vehicle) by simple means, and thus to elastically absorb the forces effective on the gearbox in all directions.

To solve this problem, the invention contemplates providing a diagonally rigid holding means surrounding a gearbox of the rack and pinion steering mechanism in frictional engagement therewith by way of an elastic intermediate layer, wherein the holding means, in turn, is attached to a part integrally joined to the vehicle.

In a preferred embodiment of the invention, the provision is made to join the holding means on a broad base to the part integrally joined with the vehicle, by means of two screws wherein the elastic intermediate layer is arranged essentially in the zones near the end faces of the holding means.

A suitable preferred arrangement of the invention is distinguished in that the holding means for the gearbox consists of a carrier casing which is detachably connected with the front-axle support with its long side facing this support, wherein the shanks of the screws are disposed at a right angle to the longitudinal axis of the gearbox.

Further advantageous embodiments and features of the invention are characterized in the dependent claims.

Within the scope of the present invention, it is contemplated to provide that, in a rack and pinion steering mechanism according to the introduction which is equipped with a steering damper or shock absorber, the piston rod of this damper, joined to a holder -- the latter being in turn attached to a part executing the steering motion -- is to be protected against deleterious influences due to water and dirt. Furthermore, the steering damper is to be disposed so that a minimum bending moment is produced in its mounting elements.

In a preferred embodiment of the invention the steering damper is placed in close spatial relationship with the gearbox and the piston rod of the steering damper and the gear rack together are encompassed by a sealing bellows.

In a further development of this last-mentioned embodiment of the invention, the provision is made that the steering damper is arranged either in the immediate vicinity of the outer wall of the gearbox or it is combined with the gearbox into one unit.

The casing of this invention combines, with structurally simple means, an elastic support of the gearbox and the thrust-resistant mounting thereof at the front-axle support. By the encapsulation of the steering damper, optionally to be utilized, into the carrier casing, the damper is protected against deleterious entrance of water and dirt, as well as against mechanical damage. Furthermore, excessive stresses on the screws joining the carrier casing with the front-axle support are avoided. The advantage of certain preferred embodiments of the invention resides in that the rack and the piston rod are entirely surrounded by the sealing bellows providing complete tightness with regard to air and moisture.

These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.

FIG. 1 is a top plan view which shows a rack and pinion steering mechanism with steering damper and a mounting arrangement for same according to a first preferred embodiment of the present invention;

FIG. 2 is a partial front view of a portion of FIG. 1 on an enlarged scale;

FIG. 3 is a top plan view similar to FIG. 1 which shows a rack and pinion steering mechanism without a steering damper and a mounting arrangement for same according to a further preferred embodiment of the present invention;

FIG. 4 shows a section, rotated by 90.degree., along line IV--IV of FIG. 1 on an enlarged scale;

FIG. 5 shows a section along line V--V of FIG. 4;

FIG. 6 shows a section, rotated by 90.degree., along line VI--VI of FIG. 3 on an enlarged scale;

FIG. 7 is a sectional view similar to FIGS. 4 and 6 which shows another preferred embodiment of the invention, wherein the casing parts are of an asymmetrical configuration and include a cover surrounding the steering damper;

FIG. 8 is a partial sectional top plan view of a rack and pinion steering mechanism with a steering damper and mounting arrangement according to another preferred embodiment of the invention wherein the piston rod is connected to a holder joined to the rack; and

FIG. 9 is a front view of FIG. 8.

Throughout the various views, like reference numerals designate like structures.

The rack and pinion steering mechanisms schematically illustrated in FIGS. 1 and 3, denoted by reference numeral 1, each comprises essentially a gearbox 2, 2' with a rack 3, respectively one tie rod 4 being articulated to the rack at both of its ends. The rack and pinion steering mechanism 1 shown in FIG. 1 has a steering damper 5 arranged axially in parallel with the rack 3. This damper 5 is mounted to a holder 6 and its piston rod 7 cooperates with an arm 8 projecting from the gearbox 2. The gearboxes 2, 2' exhibit at each of their respective ends a collar 2 " extending away from their outer periphery.

As shown in FIGS. 4 and 6, the housings 2, 2' are largely surrounded along their outer periphery by an elastic intermediate layer 15. On the long side of the gearboxes 2, 2' facing the front axle support 25, an insert part 18 is embedded in this intermediate layer, the cross-sectional profile of this insert part 18 corresponding approximately to the outer configuration of the respective gearbox 2, 2'.

It can be seen from FIGS. 1-3 that the intermediate layer 15 contacts laterally each collar 2" of the gearboxes 2,2' and consists of two parts arranged near the respective two ends of the gearboxes 2,2'. The intermediate layer 15 and thus the gearboxes 2, 2' are encompassed with a clamping action by a carrier casing 9 consisting of two housing parts 10. The housing parts 10 are connected with each other by means of two screws 16 with the interposition of respectively one spacer sleeve 17 (see FIGS. 1-4 and 6). The free ends of the housing parts 10 are attached to mounting tongues 12 projecting from a front-axle support 25 by means of two screws 13 inserted at a right angle to the longitudinal axis of the respective gearboxes 2,2' with the interposition of respectively one spacer sleeve 14.

The housing parts 10 have respectively one offset portion forming a shoulder 11, 11' in the zone encompassing the gearbox 2, 2', this shoulder extending toward the plane of symmetry of the gearbox. The shoulders 11, 11' effect advantageously a flush abutment of the elastic intermediate layer 15 in this region against the outer shell of the gearboxes, 2, 2' when the screws 13 and 16 are tightened. By the inclined legs of the insert part 18 disposed adjacent to the shoulder 11', the elastic intermediate layer 15 is, when the screws 13 are tightened, pressed by means of the insert part 18 against the outer shell of the gearbox 2, 2' also in the zone between the free ends of the housing parts 10.

The required elastic axial fixation of the gearboxes 2, 2' is accomplished, as shown especially in FIG. 2, by the feature that the two collars 2" contact with pretensioning the axial end faces of the carrier casing 9, 90 by way of the elastic intermediate layer 15 present at this location. For this purpose, the housing parts 10 or 100, 101 are provided on their two outer ends advantageously with respectively one radially projecting flange.

Inasmuch as the gearboxes 2, 2' are embedded in this way in a compact manner and under a certain pretensioning, i.e. with elastic frictional engagement and without metallic contact, in the carrier casing 9, the shocks caused especially by an uneven roadway and introduced into the rack 3 are dampingly absorbed in all directions by the intermediate layer 15 within the scope of its elasticity. Besides, due to the elastic intermediate layer 15, a less direct response of the steering is obtained and a resultant harmonious steering power characteristic is thus achieved.

The extension 8 (FIG. 1 and FIG. 4) projecting from the gearbox 2, 2' and optionally connected with the piston rod 7 is surrounded on its free end on all sides by an elastic cap 19 (FIG. 4 and FIG. 5). If the steering damper 5 is used, the extension 8 has a continuous bore 20 penetrated by the piston rod 7, the latter being provided with a spacer sleeve 21. In place of the piston rod 7, it is also contemplated to use for this purpose another mounting element attached to the steering damper 5. On the end faces of the spacer sleeve 21, respectively one thrust washer 22 is provided in contact therewith, this washer being in connection with the outside of the elastic cap 19. When the threaded nut 23 engaging at the end of the piston rod 7 is tightened, a clamping connection is established between the piston rod 7 and the extension 8. To prevent metallic contact between the spacer sleeve 21 and the extension 8, the continuous bore 20 has a radial play with respect to the spacer sleeve 21 (FIG. 5).

The carrier casing 9 encompasses the narrow-sided outer wall surface 19' of the elastic cap 19 under a certain pretensioning action, whereby the extension 8 and thus the gearbox 2 are held in the carrier casing 9 so that they are completely secured against rotation.

To maintain security against rotation, the gearbox 2' illustrated in FIG. 6 is provided with an outer configuration made up of planar surfaces, for example in the shape of an octagon and can be provided, if necessary, additionally with the extension 8 as shown in FIG. 3. In this connection -- since the rack and pinion steering mechanism 1 shown herein does not include a steering damper -- the elastic cap 19 is attached to the extension8 by means of a connecting element 24 (FIG. 3).

The rack and pinion mounting arrangement with carrier casing 90 shown in FIG. 7 is extensively similar to the mounting arrangement with carrier casing 9. Therefore, identical parts have in each case the same reference numerals. The carrier casing 90 consists of a first housing part 100 provided with a shoulder 110, contacting predominantly in a straight plane the outer periphery of the gearbox 2 with the elastic intermediate layer 15 associated therewith, whereas a second housing part 101, which is also provided with a shoulder 110, extends around a partial distance of the outer periphery of the gearbox 2 up to the first housing portion 100 and is joined to the latter; a screw connection 102 serving for establishing this connection. The elastic intermediate layer 15 is likewise (as described above for the other embodiments) arranged at the outer periphery of the gearbox 2, this intermediate layer consisting of two parts and being equipped with the insert part 18. If the rack and pinion steering mechanism 1 supported by the carrier casing 90 is provided with a steering damper 5, a cover 103 is mounted to the carrier casing 90 to shield this damper. The elastic clamping of the gearbox 2 in the carrier casing 90 and its mounting to the front-axle support 25 is effected in complete analogy to that of the carrier casing 9, so that no detailed remarks in this connection are required. The necessary security against rotation of the gearbox 2 held by the carrier casing 90 is likewise effected by the extension 8 projecting from the gearbox (not illustrated in FIG. 7), or by means of a noncircular outer configuration of the housing and, if necessary, additionally by the extension 8.

Due to the mounting of the carrier casing 9, 90 according to this invention to the front-axle support 25 by means of the screws 13 arranged at a right angle to the longitudinal axis of the gearbox 2, 2', these screws are subjected to a "double-shearj" stress, namely a stress effective at the upper and lower mounting straps 12, whereby advantageously the required screw strength can be dimensioned to be weaker than in the type of prior-art mounting mentioned in the foregoing.

In the rack and pinion steering mechanism 1 shown in portions in FIGS. 8 and 9, the steering damper 5 is inserted in a turned-around position as compared to the rack and pinion steeri;ng mechanism 1 illustrated in FIGS. 1-3. The holder 6 is preferably firmly joined to the rack 3; it would likewise be possible according to the invention to connect this holder with another part executing the steering motions, for example with a spherical joint 29. At its free end, the holder 6, which has a rectangular cross-sectional profile, is braced with the interposition of a rubber element 30 against the piston rod 7 of the steering damper 5 by means of a threaded nut 31 engaging the end of the piston rod 7.

In order to minimize the bending moment produced, when the steering damper 5 becomes effective, in its mounting elements, especially in the holder 6, and thus be able to make the mounting elements with minimum dimensions, the steering damper 5 is directly attached to the outer shell of the gearbox 2, 2', as shown in FIG. 8. Embodiments of the invention are also contemplated which combine the steering damper 5 with the gearbox 2, 2' into one structural unit (module), preferably by means of a single cast housing.

As illustrated in FIG. 8, a wall 27 extends radially away from one end of the gearbox 2, 2'; a bellows collar 26 is mounted to this wall, for example by means of a clamp strap 32, this bellows collar being attached on its other end to the tie rod 4. Thereby, the space within the bellows collar 26 -- i.e. the piston rod 7 and the rack 3 -- is advantageously sealed off entirely from air and moisture.

An elastic sealing ring 28 is inserted in the wall 27, this ring receiving the steering damper 5 and sealing same off from the outside, so that thus the space encompassed by the bellows collar 26 is also sealed off at this location.

Embodiments of the invention are also contemplated wherein the carrier casing is constructed of a single piece. The longitudinal division of this casing is provided according to the illustrated preferred embodiments for the reason that the manufacture thereof is made more advantageous from a technical viewpoint by this feature.

While we have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and we therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.