Abstract:
A roller bearing assembly ( 100 ), such as for use in supporting a vehicle wheel assembly, incorporates a set of rollers ( 104 ) disposed between an outer supporting race ( 102 ) and an inner supporting race ( 106 ). The set of rollers ( 104 ) is maintained between the outer and inner supporting races ( 102, 106 ) by an annular rib ring ( 108 ), which is configured to transfer forces and loads received from the rollers ( 104 ) to one or more sensors ( 110 A) disposed between the annular rib ring ( 108 ) and an annular outer shell ( 114 ) encapsulating the roller bearing assembly ( 100 ). Responsive output signals from the sensors ( 110 A), which are representative of the forces and loads exerted by the rollers ( 104 ), are communicated to an external system to provide a representation of the roller bearing assembly ( 100 ) operating condition.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is related to, and claims priority from, U.S. Provisional Patent Application No. 60/676,414 filed on Apr. 29, 2005, and which is herein incorporated by reference. 
     
    
     BACKGROUND ART 
       [0002]    The present invention relates generally to sensors for measuring bearing load forces, and in particular, to a bearing load sensor configuration which is suitable for use in vehicle wheel bearing applications. 
         [0003]    The ability to measure live vehicle wheel forces and loads enhances the ability to manage vehicle brake and drive systems, particularly to counteract undesirable vehicle responses in a wide range of driving situations. For example, a yaw sensor associated with vehicle may be used to compare the actual rate of turn experienced by a vehicle with the driver&#39;s steering input. If the measured rate of turn does not correspond to the driver&#39;s steering input, a vehicle stability or control system may be activated to selectively redirect torque to different vehicle wheels, or to selectively apply a braking force to individual vehicle wheel in an attempt to achieve the desired vehicle turn. 
         [0004]    Measurements of forces and loads specific to individual vehicle wheels, such as instantaneous frictional coefficients and sliding velocities may provide use useful information to vehicle control systems. However, systems which are capable of providing measurements of instantaneous frictional coefficients and sliding velocities at the individual wheels of a vehicle are generally prohibitively expensive for inclusion in most vehicle applications. 
         [0005]    Accordingly, it would be advantageous to provide an integrated component in a vehicle wheel assembly, such as a bearing, with suitable sensors capable of measuring forces and loads on the vehicle wheel assembly, such as measurements of instantaneous frictional coefficients and sliding velocities. It would be further advantageous if the integrated component, configured with the sensors, was suitable for cost effective mass production to enable the integrated component to be readily incorporated into a wide range of vehicle applications. 
       SUMMARY OF THE INVENTION 
       [0006]    Briefly stated, the present invention provides a roller bearing assembly, such as for use in supporting a vehicle wheel assembly, which incorporates a set of rollers disposed between inner and outer supporting races. The set of rollers are maintained between the inner and outer supporting races by an annular rib ring, which is configured to transfer forces and loads received from the rollers to one or more sensors disposed between the annular rib ring and an annular outer shell encapsulating the roller bearing assembly. Responsive output signals from the sensors are representative of the forces and loads exerted by the rollers, and may be communicated to an external system to provide a representation of the roller bearing assembly operating condition. 
         [0007]    In an alternate embodiment of the present invention, the sensors are compressive load sensors, and are equidistantly disposed in an annular arrangement. Each compressive load sensor is positioned in contact with an associated protrusion on the rib ring, such that loads and forces exerted on the rib ring by the set of rollers are directly transferred to the compressive load sensors. 
         [0008]    In an alternate embodiment of the present invention, the sensors are strain gauges, and are equidistantly disposed in an annular arrangement about a flexible support element retained between the rib ring and outer shell. The flexible element is supported against axial movement at a plurality of raised points on the outer shell, which are offset from a second plurality of raised points on the rib ring which contact the opposite surface of the flexible element. Loads and forces transmitted from the set of rolling elements to the rib ring are in turn, transmitted through the plurality of raised contact points into the flexible element, and eventually to the outer shell. Loads and forces exerted on the flexible element by the raised points generate responsive strain forces in the flexible element which are registered by the strain gauges. Responsive output signals from the strain gauges are representative of the forces and loads exerted by the rollers, and may be communicated to an external system to provide a representation of the roller bearing assembly operating condition. 
         [0009]    In a variation of the present invention, the sensors are pressure sensors, and are equidistantly disposed in an annular arrangement within an annular region between the rib ring and outer shell which is filled with a relatively incompressible material. Loads and forces transmitted from the set of rolling elements to the rib ring are in turn, transmitted through the relatively incompressible material, and eventually to the outer shell. Loads and forces exerted on the relatively incompressible are registered by the pressure sensors. Responsive output signals from the pressure sensors are representative of the forces and loads exerted by the rollers, and may be communicated to an external system to provide a representation of the roller bearing assembly operating condition. 
         [0010]    The foregoing features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    In the accompanying drawings which form part of the specification: 
           [0012]      FIG. 1  is a partial sectional view of a roller bearing assembly of the present invention configured with compression sensors; 
           [0013]      FIG. 2  is a perspective view of an annular circuit board of the present invention, having equidistantly spaced gaps over which load sensors are secured; 
           [0014]      FIG. 3  is a partial sectional view of an alternate roller bearing assembly of the present invention configured with strain sensors; 
           [0015]      FIG. 4  is a simplified exploded perspective view of the rib ring, flexible element, and outer shell of the embodiment shown in  FIG. 3 , illustrating load and force transfers there between; 
           [0016]      FIG. 5  is a perspective illustration of a flexible element of  FIG. 3 , illustrating placement of the strain sensors and flexible circuit; and 
           [0017]      FIG. 6  is a partial sectional view of an alternate roller bearing assembly of the present invention configured with pressure sensors. 
       
    
    
       [0018]    Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. It is to be understood that the drawings are for illustrating the concepts of the invention and are not to scale. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. 
         [0020]    Referring to  FIG. 1 , a roller bearing assembly  100  for supporting a vehicle wheel assembly  10  comprises at least one non-rotating outer race  102 , with at least one set of rollers  104 , acting against a corresponding inner race  106  that rotates with the wheel assembly  10 . A rib ring  108  is provided at each end of the outer race  102  to resist the tendency of the rollers  104  to move axially outwardly from their normal position between the outer race  102  and the inner race  106 . The rib ring  108  is axially restrained by at least three equidistantly spaced compressive load sensors  110  which are mounted to an annular circuit board  112  abutted to an outer shell  114 , which in turn, is fixed to the outer race  102 . The outer shell  114  additionally supports a lip-type seal  116  to prevent a loss of lubrication and any intrusion of contaminants to the bearing surfaces. Preferably, the outer shell  114  is rolled over a groove  115  in the outer race  102  to facilitate low cost manufacturing and assembly. 
         [0021]    Each of the three compressive load sensors  110  is preferably a surface mounted integrated circuit (IC), which extends through a hole or gap G in the annular circuit board  112 , as shown in  FIGS. 1 and 2 . The rib ring  108  applies a compressive force to a raised portion  110 A of each load sensor  110 , which is axially unsupported by the circuit board  112  due to the presence of the hole or gap G, causing a localized stress within the load sensor  110 , and a corresponding change in resistance of the load sensor  110 . The circuit board  112  itself is not stressed by the applied loads, which are applied only to the load sensor  110  and to associated the integrated circuit (IC). The output of the load sensor  110  is proportional to the stress on the load sensor  110 , providing a measurement which is representative of the applied load from the rib ring  108 . Output signals from each load sensor  110  are communicated via a connecting cable  120  to a vehicle control system (not shown), where they are processed and utilized to determine a force or load acting on the vehicle wheel assembly  10  supported by the bearing assembly  100 . Those of ordinary skill in the art will recognize that the load sensors  110  may be secured within the bearing assembly  100  to receive tension loads as well as compressive loads, and to provide corresponding output signals. 
         [0022]    Turning to  FIG. 3  through  FIG. 5 , an alternate embodiment of the roller bearing assembly of the present invention is shown generally at  200  for supporting a vehicle wheel assembly  10 . The roller bearing assembly  200  comprises a non-rotating outer race  202 , with at least one set of rollers  204 , such as tapered rollers, acting against a corresponding inner race  206  that rotates with the wheel assembly  10 . A rib ring  208  is provided at each end of the outer race  202  to resist the tendency of the rollers  204  to move axially outwardly from their normal position between the outer race  202  and the inner race  206 . The rib ring  208  is axially restrained by an annular flexing element  210 , such as a spring disc, which receives a load or force from the rib ring  208  at three equidistantly spaced protrusions  208 A disposed on the rib ring  208 . The loads or forces received at the flexing element  210  are in turn, transferred to another element of the bearing assembly  200 , such as the outer shell  214 , at three equidistantly spaced protrusions  214 A, which are circumferentially offset from the three equidistantly spaced protrusions  208 A on the rib ring  208 . The outer shell  214  fixed to the outer race  202  and supports a lip-type seal  216  to prevent a loss of lubrication and any intrusion of contaminants to the bearing surfaces. The outer shell  214  may be rolled over a groove  215  in the outer race  202  to facilitate low cost manufacturing and assembly. 
         [0023]    As best seen in  FIG. 4 , loads or forces Fin transferred from the protrusions  208 A into the flexing element  210  are supported by counteracting loads or forces Fout at the offset protrusions  214 A, such that the flexing element  210  is axially deflected at multiple points in response to the applied loads or forces. Preferably, the flexing element  210  is mounted with a limited clearance for movement, so that the flexing element  210  is not damaged by overload forces. To measure the axial deflection, the flexing element  210  is fitted with a set of circumferentially oriented strain gauges  220 , as shown in  FIG. 5 , to measure the bending strains in the flexing element  210 . A flexible circuit  222  is laid over the strain gauges  220  and operatively coupled thereto, such as by soldering to contact pads of the strain gauges  220 . The flexible circuit  222  contains suitable integrated circuits to provide electrical power the individual strain gauges  220 , to adjust the strain gauge output signals for temperature, and to translate the strain gauge output signals to a noise-immune analog current or digital signal, which is subsequently routed to the vehicle control system (not shown) via the interconnecting wiring  222 . Those of ordinary skill in the art will recognize that the flexing element  210  may be secured within the bearing assembly  200  to receive tension loads as well as compressive loads, and to provide corresponding output signals. 
         [0024]    Prior to use it is necessary to calibrate the sensors  110  and  220 . The sensors  110  and  220  may be calibrated by discretely placing a known axial load or force directly at the locations of the individual sensors  110 ,  220 . Each sensor will generate a response signal to the applied loads or forces. For example, for a known applied load at a first sensor  110 ,  220 , designated sensor A, a direct sensitivity factor is defined as the known load divided by the sensor A response, while the cross sensitivity factors of the second and third sensors (designated sensor B and sensor C) will be the known load divided by the corresponding sensor response. During a calibration procedure, a response is observed at each sensor. The actual load at each sensor is defined as the corresponding sensor response multiplied by the direct sensitivity factor, minus the sensor response at each of the other sensors multiplied by the associated cross sensitivity factors. The actual loads of the three sensors are then summed and ranked for magnitude. The ratio (MX RATIO ) of the maximum sensor load to the sum of the sensor loads is calculated, as is the ratio (SIDE RATIO ) of the second highest sensor load to that of the lowest sensor load. The parameters MX RATIO  and SIDE RATIO  identify: (1) the ratio of the sensor force sum to the radial load; (2) the ratio of the sensor force sum to the axial load; and (3) the rotational angle from the sensor with the maximum load to the radial load vector. These relationships can be empirically determined by applying combinations of axial and radial loads and saving the observed ratios in a look-up table, or they can be analytically determined such as by using known relationships. 
         [0025]    Sensors other than compressive load sensors  110  and strain gauges  220  may be utilized to acquire measurements of the forces and loads at a vehicle wheel assembly  10 . For example in  FIG. 6 , a third alternate embodiment of the of the roller bearing assembly of the present invention is shown generally at  300  for supporting a vehicle wheel assembly  10 . The roller bearing assembly  300  comprises a non-rotating outer race  302 , with at least one set of rollers  304 , such as tapered rollers, acting against a corresponding inner race  306  that rotates with the wheel assembly  10 . A rib ring  308  is provided at each end of the outer race  302  to resist the tendency of the rollers  304  to move axially outwardly from their normal position between the outer race  302  and the inner race  306 . The rib ring  308  includes both a disk section  308 A, and a cylindrical section  308 B. The rib ring forms a first seal to the outer shell  310  at the outer periphery of the disk section  308 A, and a second seal to the outer shell  310  at the outer circumference of the cylindrical section  308 B, while providing clearance for a small amount of axial movement of the rib ring  308 . 
         [0026]    Measurements of the loads or forces exerted on the roller bearing assembly  300  by the wheel assembly  10  are acquired by at least three pressure sensors  312  secured to an annular circuit board  314  disposed in the annular cavity  316  between the rib ring  308  and the outer shell  310 . The cavity  316  is filled with an essentially incompressible material  316 A which resists circumferential flow, such as a room temperature vulcanizing (RTV) type of material. Loads or forces from the rolling elements  304  are transferred to the rib ring  308 , and through the material  316 A to the pressure sensors  312 , which provide proportional output signals representative of a load distribution on the rib ring  308 . While a minimum of three pressure sensors  312  may be utilized with the roller bearing assembly  300 , when load zones within the cavity  316  have an arcuate range of less than approximately 270 degrees, it will be necessary to dispose a pressure sensor  312  near the point of maximum load to avoid negative loads at some of the remaining pressure sensors, due to a tendency of the rib ring  308  to tilt in response to the non-uniform load. 
         [0027]    Integrated circuits (not shown) disposed on the annular circuit board  314  provide electrical power the individual pressure sensors  312  and translate the pressure sensor output signals to noise-immune analog currents or digital signals, which are subsequently routed to the vehicle control system (not shown) via the interconnecting wiring  320 . 
         [0028]    As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.