Abstract:
An ABS encoder arrangement for a driven wheel bearing unit, with a multi-pole ring, a sensor device with a sensor head, and an annular cap element that has an annular wall portion which shields a cap interior against the exterior. The annular wall section extends through an intermediate region lying between the multi-pole ring and an end face of the sensor head. An extension concentric with the axis of rotation of the multi-pole ring and extending axially over a circumferential area of an articulated shaft head is connected to the annular wall section on a side facing away from the multi-pole ring. In the end portion of the extension facing away from the multi-pole ring and extending over the articulated shaft head, the extension forms a circumferential profile that radially stiffens the extension and forms an annular edge which extends into a circumferential groove of the articulated shaft head and forms a channel cross-section open to the outside.

Description:
[0001]    The present invention relates to an ABS encoder system, which as such is used to generate signals indicating wheel rotation in the area of a wheel bearing, the ABS encoder system including a wheel-side revolving multi-pole ring and a sensor device for detecting the magnetic field generated on the part of the multi-pole ring. 
       BACKGROUND 
       [0002]    Such a wheel bearing unit with an ABS encoder system is known from DE 10 2004 048 A1. A seal arrangement is provided in this wheel bearing unit, which includes a hub-side fixed sealing ring having a sealing lip. The sealing ring has an extension that axially overlaps an end section of a drive shaft head. Affixed to the end section of the extension is an elastomer sealing lip, which is in rubbing connection against an outer circumferential surface of the drive shaft head. 
         [0003]    An ABS encoder system is known from U.S. Pat. No. 5,967,669 A1, which includes a wheel-side revolving multi-pole ring and a sensor device. The sensor device is affixed to the inside of a cover cap. The cover cap is provided with a socket section, into which a sensor cable is pluggable. Plug contacts, which are connected to the sensor device, are situated in the interior of the socket section. The multi-pole ring itself includes a cylinder jacket section on the inner wall on which the multi-pole structure is situated, which has zones with varying degrees of field emission. The sensor device radially engages from within, in an interior area of the multi-pole ring and in this way detects the magnetic field generated by the multi-pole ring. 
         [0004]    An ABS encoder system is known from U.S. Pat. No. 7,147,379, which includes a multi-pole ring integrated into a cartridge seal, which as such is covered by a cover ring which is made of a non-magnetic material. A sensor head is situated on one side of the cover ring facing away from the multi-pole ring. This detects the field emitted by the multi-pole ring. 
         [0005]    A wheel bearing unit is likewise known from JP 2006 038 160 A1, which is provided with an encoder system in the area of a bearing ring gap. This encoder system includes a multi-pole ring which is covered from its outside via a ring element fixed in a stationary manner to the hub carrier. Also in this case, similar to the prior art according to DE 10 2004 048 A1, the required sealing effect is achieved through the use of a sealing ring element which is made of an elastomer material and is in rubbing contact with a circumferential component of the wheel bearing unit. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the invention to provide an ABS encoder system which is characterized by a long operating life through high functional reliability. 
         [0007]    The present invention advantageously provides an ABS encoder system in which the sensor head is accessible from the outside, the multi-pole ring is advantageously protected and moreover any particles adhering to the multi-pole structure are effectively shielded from the sensor head. 
         [0008]    According to a particularly preferred specific embodiment of the present invention, the circumferential profile formed on the axial end area of the extension is designed in such a way that it forms at least one radially, outwardly open circumferential channel. This circumferential channel may be designed in such a way that it dips at least partially into a circumferential groove formed on the drive shaft head, while leaving a clearance gap, and thus forms a labyrinth structure with this circumferential groove. The channel depth measured in the radial direction in this case preferably corresponds to approximately two to six times the wall thickness of the extension. The axial length measured on the channel bottom of the circumferential channel preferably corresponds to approximately two to seven times the wall thickness of the extension. The channel cross-section of the circumferential channel is preferably designed in such a way that it appears as a trapezoid in an intersecting plane containing the circumferential axis of the multi-pole ring. The width of the channel cross-section measured in the direction of the circumferential axis widens as the distance from the circumferential axis increases. 
         [0009]    The extension may be designed as an essentially cylindrical annular body. It may also be designed as a cone-shaped jacket. The extension may furthermore form one or multiple steps and in this way taper toward the drive shaft head during operation. The axial length of the extension is larger than the width of the multi-pole structure. 
         [0010]    According to a particularly preferred specific embodiment of the present invention, the annular cap element is made of a non-ferromagnetic material. In this case, the annular cap element may be made as a deep-drawn part from a sheet material, in particular a corrosion-resistant chromium-nickel steel, or even from a non-ferrous metal sheet. 
         [0011]    As an alternative to the aforementioned specific embodiment of the annular cap element as a sheet metal deep-drawn part, it is also possible to make the annular cap element out of a plastic material, for example as an injection-molded part or as a blown part. 
         [0012]    The annular cap element may be designed with respect to its external geometry in such a way that each annular wall section is formed as an annular disk section which is essentially radially oriented to the bearing shaft. This variant is particularly suitable for the implementation of encoder systems in which the multi-pole ring forms an annular disk which is scanned from the front side, i.e., “from in front.” The annular wall section preferably extends over an angular range of 360° essentially equidistant from the multi-pole ring. 
         [0013]    As an alternative to the aforementioned specific embodiment, it is also possible to design the annular cap element in such a way that the annular wall section is formed as an essentially cylindrical ring bushing section essentially coaxially oriented to the bearing shaft. This configuration makes it possible to design the multi-pole ring as a cylinder bush, the field of which is scanned radially from the outside. It is also possible to design the multi-pole ring as a cone-shaped jacket structure. 
         [0014]    The annular cap element is preferably designed in such a way that it forms a passage opening for an axle journal. This passage opening is preferably formed by an extension concentrical to the bearing shaft, which adjoins the annular wall section. The passage opening skirting the annular border may be provided with a profiling which stiffens the wall section skirting the passage opening, and furthermore forms a retaining structure which wards any particles or splash water off the annular gap formed from the interaction with the axle journal. That extension may constitute a tapering structure and, for example, be formed for this purpose as a relatively flat and essentially radially oriented annular disk section, as a cone-shaped jacket section or even as a cylinder jacket section. 
         [0015]    According to one particular aspect of the invention, a support structure may be formed on the annular cap element, which makes it possible to fix the sensor head to the annular cap element. This support structure may be formed as a socket section, into which the sensor head is pluggable. Otherwise, the support structure may also form other types of anchoring geometries in which the sensor head may be secured via corresponding complementary structures. 
         [0016]    The anchoring of the annular cap element to a bearing carrier is preferably carried out in combination with a seat ring section which is integrally formed with the annular cap element and, for example, may be pressed onto a cylindrical collar section of the bearing carrier using a strong press fit. 
         [0017]    A discharge opening is preferably provided on the annular cap element, in particular a bore hole. This is situated on a place underneath the mounting position of the annular cap element. A cap or cover structure is formed in the area of the discharge opening, which prevents direct entry of splash water or thrown particles. The sensor head may rest against the annular cap element, or approach it, leaving a gap. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]    Further details and features of the present invention are derived from the following description in connection with the drawings. 
           [0019]      FIG. 1  shows an axial sectional view of a first specific embodiment of an ABS encoder system according to the present invention; and 
           [0020]      FIG. 2  shows an axial sectional view of a second specific embodiment of an ABS encoder system according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    An ABS encoder system according to the present invention is illustrated in  FIG. 1  in the form of a detailed representation of its structure. The ABS encoder unit according to the present invention is incorporated into a wheel bearing. The wheel bearing itself includes a hub carrier  1  having a rolling element track la formed directly thereon, a bearing inner ring  2  which likewise forms a rolling element track  2   a,  as well as rolling elements  3  which are accommodated in a rolling element circumferential space formed between both rolling element tracks  1   a  and  2   a . The rolling bearing formed in hub carrier  1  is only partially represented in this case, and is designed, for example, as an angular ball bearing. Bearing inner ring  2  rests on a hub pin  4 . Although not shown in detail here, hub pin  4  is designed as a hollow pin with internal gear teeth. Within this hollow pin sits an externally toothed section of a drive shaft head  5 . 
         [0022]    The bearing unit accommodated in hub carrier  1  is sealed by a sealing device  6 . This sealing device  6  is designed as a cartridge seal and includes a sealing ring  7  which has a ring core  7   a  and a molded-on elastomer structure  7   b.  Elastomer structure  7   b  forms multiple sealing lips  7   c,    7   d  and  7   e.  These sealing lips  7   c,    7   d  and  7   e  form a sealing system on angular ring  8 . A so-called multi-pole structure  9  is attached to a side of angular ring  8  facing away from sealing lips  7   c,    7   d  and  7   e.  This multi-pole structure  9  contains magnetized particles. Overall, the magnetization of these particles is coordinated in such a way that the multi-pole structure in the circumferential direction is made up of + and − zones. Angular ring  8  and multi-pole structure  9  resting thereon form a so-called multi-pole ring  10 . The multi-pole ring rests on a cylindrical section of bearing inner ring  2 . Sealing ring  7  rests in a cylindrical inner circumferential surface lb of hub carrier  1 . 
         [0023]    The wheel bearing represented is provided with an ABS encoder system. This ABS encoder system includes the previously mentioned multi-pole ring  10 , which carries that multi-pole structure  9 . Furthermore, the ABS encoder system also includes a sensor device  11  having a sensor head l la for detecting the magnetic field generated on the part of multi-pole structure  9 . The ABS encoder system according to the present invention is characterized in that an annular cap element  12  is provided, which has an annular wall section  12   a,  which seals off a cap interior, housing the multi-pole ring, toward the outside. That annular wall section  12   a  is designed in such a way that it extends through an intermediate area  13  situated between multi-pole ring  10  and a front surface of sensor head l la. In addition, an essentially cylindrical extension  12   b  is connected to annular wall section  12   a  on a side facing away from multi-pole ring  10 , concentrical to the circumferential axis of the multi-pole ring, and which axially overlaps in the mounting position a circumferential area of a drive shaft head  5 , extension  12   b,  in its end area facing away from the multi-pole ring and surrounding the drive shaft head, forming a circumferential profile which radially stiffens extension  12   b.    
         [0024]    The annular cap element in this case is made of a non-ferromagnetic sheet material as a deep-drawn part. The annular wall section  12   a  extending through intermediate area  13  is designed in this exemplary embodiment as an extending annular disc section aligned essentially radially to the bearing shaft, equidistant over 360° to the multi-pole ring. 
         [0025]    An extension  12   b  concentrical to the bearing shaft is connected to annular wall section  12   a  on its radially internal inner border area. This extension  12   b  extends into the area of drive shaft head  5  and there forms an annular border  12   c  which skirts a passage opening. This annular border  12   c  extends into a circumferential groove  5   a  of drive shaft head  5 . The clearances are dimensioned in such a way that component contact is reliably avoided, and that a preferably effective shielding of the inner area of that extension  12   b  is achieved. 
         [0026]    By the cross-sectional configuration shown here of annular cap element  12  in the area of the passage opening, there is a sufficiently effective particle protection and also an advantageous stiffening of annular border  12   c.    
         [0027]    Here, multi-pole ring  10  forms an “axial coding” structure, i.e., a structure that generates a rising magnetic field across the front face of the multi-pole ring. The sensor head is axially moved towards multi-pole ring  10 , but is shielded from it by annular wall section  12   a , and is therefore situated outside of the cap interior. The magnetic field generated by multi-pole ring  10  penetrates annular wall section  12   a  and may therefore be detected by sensor head  11   a . Sensor head  11   a  is protected from any metallic particles revolving with the multi-pole ring by annular wall section  12   a.    
         [0028]    Annular cap element  12  has a seat ring section  12   d  and is anchored via this seat ring section  12   d  to a collar section  1   c  of hub carrier  1  under a strong press fit. Collar section  1   c  forms that inner circumferential wall  1   b , on which sealing ring  7  rests. 
         [0029]    An ABS encoder system according to the present invention is likewise illustrated in  FIG. 2  in the form of a detailed representation of its structure according to a second specific embodiment of the present invention. This is similar to the aforementioned encoder system in many features. The ABS encoder unit according to the present invention is again incorporated into a wheel bearing. The wheel bearing itself includes a hub carrier  1  having a rolling element track la formed directly thereon, a bearing inner ring  2  which likewise forms a rolling element track  2   a,  as well as rolling elements  3  which are accommodated in a rolling element circumferential space formed between both rolling element tracks  1   a  and  2   a.    
         [0030]    Also in this exemplary embodiment, the rolling bearing formed in hub carrier  1  is only partially represented, and overall is designed as an angular ball bearing. Bearing inner ring  2  rests on a hub pin  4 . Hub pin  4  is designed as a hollow pin having interior and front-facing gear teeth. A drive shaft head  5  engages in the hub pin with axial or radial gear teeth. 
         [0031]    The bearing unit accommodated in hub carrier  1  is sealed by a sealing device  6 . This sealing device  6  is designed as a cartridge seal and includes a sealing ring  7  which has a ring core  7   a  and a molded-on elastomer structure  7   b.  Elastomer structure  7   b  forms multiple sealing lips  7   c,    7   d  and  7   e  in a manner similar to that in the exemplary embodiment according to  FIG. 1 . These sealing lips  7   c,    7   d  and  7   e  form a sealing system toward angular ring  8 . 
         [0032]    Angular ring  8  carries an annular cylinder section  8   a.  A multi-pole structure  9  is attached to an outer circumferential surface of annular cylinder section  8   a.  This multi-pole structure  9  again contains magnetized particles. The magnetization of these particles is coordinated in such a way that the multi-pole structure in the circumferential direction is made up of + and − zones. Angular ring  8  and multi-pole structure  9  resting thereon form a multi-pole ring  10 . Multi-pole ring  10  rests via an inner ring section  8   b  with moderate press fit on a cylindrical section of bearing inner ring  2 . Sealing ring  7  rests on a cylindrical inner circumferential surface lb of hub carrier  1 . 
         [0033]    The wheel bearing represented is again provided with an ABS encoder system. This ABS encoder system includes the previously mentioned multi-pole ring  10 , which carries that multi-pole structure  9 . Furthermore, the ABS encoder system also includes a sensor device  11  having a sensor head  11   a  for detecting the magnetic field generated on the part of multi-pole structure  9 . The ABS encoder system according to the present invention is again characterized in that an annular cap element  12  is provided, which has an annular wall section  12   a,  which seals off a cap interior, housing the multi-pole ring, toward the outside. That annular wall section  12   a  is designed in such a way that it extends through an intermediate area  13  situated between multi-pole ring  10  and a front surface of sensor head  11   a . In addition, here an essentially truncated, conically tapering extension  12   b  is connected to the annular wall section  12   a  on a side facing away from multi-pole ring  10 , concentrical to the circumferential axis of the multi-pole ring  10 , and which axially overlaps in the mounting position a circumferential area of a drive shaft head  5 , extension  12   b,  in its end area facing away from the multi-pole ring and surrounding the drive shaft head, forming a circumferential profile which radially stiffens extension  12   b.    
         [0034]    Annular cap element  12  is made of a non-ferromagnetic sheet material, as a deep-drawn part, in a manner similar to the exemplary embodiment according to  FIG. 1 . The annular wall section  12   a  extending through intermediate area  13  is designed in this exemplary embodiment as a cylinder jacket section aligned essentially coaxially to the bearing shaft. 
         [0035]    An extension  12   b  concentrical to the bearing shaft is connected to annular wall section  12   a  on its side facing away from hub carrier  1 . This extension  12   b  extends into the area of drive shaft head  5  and there forms an annular border  12   c  that skirts a passage opening. The extent of the gap remaining between the inner wall of annular border  12   c  and the outer wall of drive shaft head  5  is dimensioned in such a way that component contact is reliably avoided, and a preferably effective shielding of the inner area of that extension  12   b  is achieved. 
         [0036]    Here, multi-pole ring  10  forms a “radial coding” structure, i.e., a structure which generates a radially rising magnetic field across the outer circumferential surface of the multi-pole ring  10 . The sensor head is radially moved toward multi-pole ring  10 , but is shielded from it by annular wall section  12   a.  The radially emitted magnetic field generated by multi-pole ring  10  penetrates annular wall section  12   a  and may therefore be detected by sensor head  11   a . Annular wall section  12   a  extends over the entire circumferential area of the multi-pole ring. 
         [0037]    Annular cap element  12  has a seat ring section  12   d  and is anchored via this seat ring section  12   d  to a collar section  1   c  of hub carrier  1  under a strong press fit. Collar section  1   c  forms that inner circumferential wall  1   b , in which sealing ring  7  rests as in the exemplary embodiment according to  FIG. 1 . 
         [0038]    Although not shown here, it is possible to form a support structure on annular cap element  12 , e.g., in the form of a socket section, to secure sensor head  11   a  directly to annular cap element  12 . 
       LIST OF REFERENCE NUMERALS 
       [0039]      1  hub carrier 
         [0040]      1   a  rolling element track 
         [0041]      1   b  inner circumferential surface 
         [0042]      1   c  collar section 
         [0043]      2  bearing inner ring 
         [0044]      2   a  rolling element track 
         [0045]      3  rolling element 
         [0046]      4  hub pin 
         [0047]      5  drive shaft head 
         [0048]      5   a  circumferential groove 
         [0049]      6  sealing device 
         [0050]      7  sealing ring 
         [0051]      7   a  ring core 
         [0052]      7   b  elastomer structure 
         [0053]      7   c  sealing lip 
         [0054]      7   d  sealing lip 
         [0055]      7   e  sealing lip 
         [0056]      8  angular ring 
         [0057]      8   a  annular cylinder section 
         [0058]      8   b  inner ring section 
         [0059]      9  multi-pole structure 
         [0060]      10  multi-pole ring 
         [0061]      11  sensor device 
         [0062]      11   a  sensor head 
         [0063]      12  annular cap element 
         [0064]      12   a  annular wall section 
         [0065]      12   b  extension 
         [0066]      12   c  annular border 
         [0067]      12   d  seat ring section 
         [0068]      13  intermediate area