Abstract:
A front axle of a motor vehicle with steerable, driven or non-driven wheels on steering knuckles pivotably hinged at a wheel-guiding element with an upper and a lower bearing position, each of which accommodates a radial bearing for mounting a steering knuckle bolt with a pot-shaped sleeve with a sealed lubricant reservoir and forms a bearing bushing. A stop disk is arranged a bottom of the sleeve to absorb axial forces and roll bodies of the radial bearing are supported with the supporting surfaces at the stop disk.

Description:
FIELD OF THE INVENTION 
   The invention relates to a front axle of a motor vehicle with steerable, driven or non-driven wheels on steering knuckles, which have been pivotably hinged at a wheel-guiding element with an upper and a lower bearing position, each of which accommodates a radial bearing for mounting a steering knuckle bolt with a pot-shaped sleeve having a sealed lubricant reservoir and forming a bearing bushing. 
   The invention also relates to a bearing bushing for a steering knuckle mounting with a pot-shaped sleeve with a sealed lubricant reservoir, accommodating a radial bearing. 
   BACKGROUND OF THE INVENTION 
   Front axles of the foregoing type are used in all-terrain vehicles, SUVs (Sport Utility Vehicles), light to heavy commercial vehicles and buses. The joint connection between the steering knuckle and the wheel-guiding element, such as a rigid axle body or a guide of a single wheel suspension, in known constructions may be a king pin with two bearing sites or two separate steering knuckle bolts. Generally, needle bearings and needle bushings are used as a radial mounting. Axial forces are absorbed by a separate axial friction bearing or axial roller bearing. However, this bearing requires a particularly reliable seal and this has turned out to be a weakness in practice. The bearing must be lubricated at regular intervals in order to force dirt, water and wear debris out of the mounting and to supply the bearing parts with fresh lubricating grease. If the seal fails, a danger exists in that the bearing will become unusable after a short time. 
   There have also already been attempts to make steering knuckle bolt mountings which do not require maintenance. For this purpose, relatively long and thin needle bearings are used, which produce high edge compressions under load. All known constructions furthermore have the disadvantage that different components are required for the upper and lower bearing sites. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to avoid the disadvantages mentioned above and to create a front axle with a reliably sealed steering knuckle mounting. 
   Pursuant to the invention, this objective is accomplished by a front axle including a pot-shaped sleeve and a stop disk arranged at the bottom of the pot-shaped sleeve. The stop disk absorbs axial forces and supports roll bodies of the radial bearing along their supporting surfaces. The stop disk is in a position to support the roll bodies of the radial bearing at the front. A disk spring may be placed on the opposite front surface of the roll bodies so that a constant axial force presses the roll bodies against the stop disk and aligns it parallel to the axis. 
   In the front axle in accordance with the invention, a separate axial bearing may be omitted and the axial forces which arise may be transferred instead directly over the stop disk to the steering knuckle bolt. 
   Pursuant to the invention, the roll bodies may be shorter and have a larger diameter than known mountings so that high radial loads can be absorbed more elastically and reliably prevent distortion of the roll bodies. 
   The front axle in accordance with the invention has the advantage that, because of the absence of an axial bearing, the upper and lower bearing sites can be constructed identically. This leads to a corresponding reduction in the diversity of the components and to economic batch sizes. 
   The properties of the friction bearing are particularly advantages if the stop disk has a coating of polyvinylidene fluoride (PVDF) or consists thereof. This material enables relatively high forces to be transferred by the roller supporting surfaces and has excellent long-term behavior. 
   In a further development of the invention, the lubricant reservoir can alternatively be filled with grease or oil. In both cases, it is filled by the manufacturer for the lifetime of the reservoir so that the front axle is practically maintenance free. Preferably, it is filled with oil, from which a longer lifetime can be expected and which is more effective than grease. Nevertheless, the mounting of the front axle is constructed so that the supply lubricant, if necessary, can be controlled and supplemented. 
   Pursuant to the invention, the bushing may have a sealing unit which seals the mounting and preferably comprises a spring-loaded sealing element. The bearing is enclosed by the sealing unit so that dirt particles cannot penetrate into it from outside. It is well known that, in the course of time, seals are subjected to wear caused by relative movements. However, because the sealing element is spring-loaded, a substantially constant contacting force of the sealing element can be achieved so that the sealing unit seals reliably even after a prolonged period of use. Radial shaft sealing rings are suitable especially when the lubricant reservoir is filled with oil. A seal with several lips can also be used, for reasons of costs, when the reservoir is filled with grease. 
   To facilitate the installation of the front axle, the bushing can be preassembled with the radial bearing and the sealing unit. The bearing bushing can also be produced as a compact unit, ready to be installed, so that the installation, the maintenance, the costs as well as the reliability of the mounting of the front axle are improved. 
   The object of the invention is also accomplished by a bearing bushing in which, at the bottom of the pot-shaped bushing, a stop disk is arranged to absorb axial forces and at the front side of which, the roll bodies of the radial bearing are supported. A disk spring, which is preferably spring-loaded, may be placed on the roll bodies. 
   The stop disk may be is coated with a friction bearing material, preferably with polyvinylidene fluoride (PVDF), or consists thereof. When the coating is lubricated slightly, it enables high forces to be transferred and ensures reliable operation in the long run. 
   The bearing bushing in accordance with the invention can be filled during its production or installation with grease or oil for lifetime of the unit. The invention offers the possibility of filling the bushing with grease or oil, depending on the intended use, so that the area of application of the bearing bushing is exceptionally large without requiring any changes in the components. 
   It has proven to be especially advantageous to use a spring-loaded sealing element, especially a radial shaft seal, as sealing unit. If there is abrasive wear, the seal is continuously adjusted automatically so that it does not leak, even after a prolonged period of use. This is the case particularly also for swiveling motions and when centrifugal forces occur. 
   Further advantages and details of the invention arise out of the description of a particularly suitable example and from the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an inventive bearing bushing in a sectional view, 
       FIG. 2  shows an inventive bearing bushing with an inserted steering knuckle bolt in a sectional view, and 
       FIG. 3  shows the steering knuckle bolt mounting of an inventive front axle in a partially sectional side view. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The bearing bushing  1 , shown in section in  FIG. 1 , consists of a one-part pot-shaped sleeve  2  which is produced preferably by deep drawing. A stop disk  3  is inserted into the sleeve  2  and has a steel back  4  which lies against an inner bottom  5  of the sleeve  2 . At its side opposite to the bottom  5  of the sleeve  2 , the stop disk  3  has a coating  6  of a friction bearing material. In the example shown, a coating  6  of polyvinylidene fluoride (PVDF) is applied. 
   The steering knuckle mounting has a plurality of roll-shaped bodies  7 , which are produced from roller-bearing steel and are supported with their lateral roll bearing surfaces  8  on the PVDF coating  6  of the stop disk  3 . The bearing bushing  1  contains a total of 23 roller bodies  7 , which are inserted between the inside  9  of the sleeve  2  and the outside of a steering knuckle bolt which is inserted in the bearing bushing  1  and not shown in FIG.  1 . 
   A lubricant  10  is applied at several places in the region of the stop disk  3  and the roll bodies  7 . 
   A disk spring  12  is fixed by a holding ring  13  having an inwardly 90° offset collar  14  so that the disk spring  12  is subjected at least to a small prestressing force and the roll body  7  presses with approximately constant force against the coating  6  even if wear occurs. The disk spring  12  acts on the roll supporting surface  11  which is opposite the roll supporting surface  8 . A clamping section of a sealing ring  17  is clamped between the collar  14  of the holding ring  13 , which is offset 90° to the inside, and a locking ring  15 , which is produced from a spring steel. The sealing ring  17  is produced from an elastomer which may be an acrylonitrile/butadiene elastomer. The sealing ring  17  is constructed as a radial shaft sealing ring and has a peripheral steel reinforcing ring  18 . This reinforcing ring  18  exerts a radial pretension on this section of the sealing ring  17  so that, in the installed state, an inner, protruding sealing edge  19  of the sealing ring  17  lies radially entirely against the inserted steering knuckle bolt and the interior of the bearing bushing  1  is sealed completely. 
   The sleeve  2  is also sealed by a sealing ring  20  which has an approximately U-shaped cross section and which is offset twice by 90°. In the interior of the sealing ring  20 , there is a corrosion-protected, sheet steel reinforcement  21  which is coated by an elastomer  22  in the region of the sleeve opening. An outer section  23  of the steel reinforcement  21 , which extends parallel to the longitudinal side of the sleeve  2 , is bent towards the inside at its end and engages a peripheral groove  24  of the sleeve  2 . In the installed state, the steering knuckle bolt is in contact with the surface of the sealing ring  20  having the coating  22  of elastomer, as well as with the sealing edge  19  of the sealing ring  17 . 
     FIG. 2  shows the bearing bushing  1  of  FIG. 1  with an inserted steering knuckle bolt  25  in a sectional view. The steering knuckle bolt  25  has a peripheral collar  26  which protrudes on the outside and lies axially against the sealing ring  20 . The sealing edge  19 , which lies laterally against the steering knuckle bolt  25 , is also sealed radially. As can be seen in  FIG. 2 , the steering knuckle bolt  25  has a radially symmetrical cavity  27 , a threaded borehole  28  adjoining on one side of the cavity  27  and a radial recess  29  which forms a contacting surface for a plug  30  sealing the cavity  27 . The cavity  27  serves as a lubricant reservoir which can be filled with oil as well as grease. The side of the cavity  27  opposite the plug  30  tapers conically. Adjoining this conically tapering side, there is an opening  31  so that the lubricant, accommodated in the cavity  27 , can reach the region of the bearing bushing  1  between the stop disk  3  and the roller bodies  7 . 
   The steering knuckle mounting, shown in  FIG. 2 , is enclosed completely so that a single filling with grease or oil suffices for its entire service life. Due to the relative motions between the steering knuckle bolt  25 , the roll bodies  7  and the sleeve  2  with the stop disk  3 , the lubricating medium is distributed automatically without requiring any control or refilling within the scope of maintenance. During the installation, the sealing lips and the sealing ring interstices of the sealing ring  17 ,  20  are greased in order to avoid penetration of dust, dirt or moisture into this region. 
   Aside from the radial forces which are absorbed by the mounting, there are also axial forces. These axial forces are passed over the sleeve bottom  5 , the stop disk  3  and the steering knuckle bolt  25 . An additional, separate axial bearing is therefore not required. 
     FIG. 3  shows the steering knuckle bolt mounting of a front axle in a partially sectional side view. The steerable wheels, which are not shown, are supported in each case at a steering knuckle  33  which is divided fork-like in the region of the bearing. The steering knuckle  33  is pivotally mounted at an upper bearing site  34  and a lower bearing site  35  at a rigid axle housing  36  which is divided fork-like in the bearing area. 
   The upper bearing site  34  and the lower bearing site  35  each have a bushing  1  with an inserted steering knuckle bolt  25 . The two bearing sites  34 ,  35 , are symmetrical. The steering knuckle bolts  25  are pressed in each case into appropriate, mirror-image bearing seats  37  of the axle housing  36 . Similarly, the bearing bushing  1  is pushed into a bearing seat  38  of a holding device  39  fastened to the steering knuckle  33 .