|Publication number||USRE39838 E1|
|Application number||US 11/299,240|
|Publication date||Sep 18, 2007|
|Filing date||Dec 9, 2005|
|Priority date||Apr 10, 2000|
|Publication number||11299240, 299240, US RE39838 E1, US RE39838E1, US-E1-RE39838, USRE39838 E1, USRE39838E1|
|Inventors||Graham F. McDearmon|
|Original Assignee||The Timken Company|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (24), Non-Patent Citations (10), Referenced by (4), Classifications (4), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is a Continuation-In-Part of application Ser. No. 09/547,129 filed Apr. 10, 2000 now abandoned.
This invention relates in general to bearings and, more particularly, to a bearing assembly which monitors forces and torques transmitted through it to provide electrical signals for use by devices which monitor and control vehicular dynamics based upon calculated tire patch loading or to determine the general stresses, strains, and loads placed upon a bearing.
There are a number of applications where the loads and types of loads placed on a bearing in operation can provide significant information about the bearing and the objects attached to the bearing. One such application is in the automotive industry where such loading information, in electrical signal form, is vital for the proper application of Vehicular Dynamic Control (“VDC”) systems. Another application is in the steel rolling mill industry where electronic processing and control is used to manipulate the speed and torque of rollers during the rolling process. Yet another application is the machine tool industry where programmable controllers and processors monitor and control the speed of spindles in milling, cutting, and drilling machines.
In the automotive industry, many vehicles of current manufacture come equipped with antilock braking systems. A system of this type monitors the rotation of the wheels on a vehicle and, when the brakes of the vehicle are applied, relaxes the breaking force at any wheel which locks up and skids. This reduces the tendency of the vehicle to veer off course when the traction at the wheels differs and makes the vehicle easier to steer under such circumstances. A few vehicles have traction control systems. This type of system monitors the rotation of driven wheels and distributes the tractive effort between those wheels, so that one does not break loose and spin. While both systems enable the driver of a vehicle to maintain better control over the vehicle, other factors influence the operation of the vehicle and, notwithstanding the successful operation of an antilock braking system and a traction control system, those other factors may still cause a vehicle to go out of control.
Significant among those other factors are the centrifugal forces encountered by a vehicle when it negotiates a turn—forces which act laterally on the vehicle. The friction between the vehicle tires and the road surface, that is at the so-called “tire contact patches”, resists these forces, but sometimes the friction may not be enough and the vehicle will slide, and perhaps go out of control, particularly if operated by one having poor driving skills. Then again, the frictional forces at the tire contact patches may prevent sliding, but the centrifugal force generated by the turn, inasmuch as it acts at the center of gravity, which is above the tire contact patches, may be sufficient to topple the vehicle.
Automobile manufactures have turned to VDC systems to prevent automobiles from going out of control in turns. The typical VDC system relies on a yaw sensor which measures the rate of change in yaw (rotation of the vehicle about its vertical axis) and a lateral acceleration sensor to, in effect, measure the centrifugal force imposed on the vehicle as a consequence of negotiating the turn. A VDC system also takes into account the angular velocity of the road wheels, the position of the steering wheel, and the power delivered by the engine. The typical VDC system analyzes the information and modulates the operation of the engine, as well as the brakes, to better maintain control of the vehicle in the turn.
The more sophisticated VDC systems also factor into the real time analysis estimated loads at the individual wheels and thus seek to evaluate conditions at the tire contact patches. But when negotiating a turn, each tire contact patch experiences forces and torques that do not comport with simle analytical procedures. Thus, measuring the displacement of a shock absorber piston, for example, does not give a very reliable indication of conditions that exist at the tire contact patch below that shock absorber. Certainly, it provides no indication of the torque at the tire contact patch, much less of the location at which the resultant of the force at the tire contact patch is acting.
Bearing assemblies exist which incorporate the use of strain gages to provide certain information regarding various bearing loads. For example, an antifriction rolling bearing disclosed in U.S. Pat. No. 5,140,849 issued Aug. 25, 1992, uses two strain gages to monitor the general loads applied to a bearing. This bearing, however, is unable to provided the multi-faceted data needed by high level VDC electronic systems or by the processor controlled systems in the rolling mills industry or the machine tool industry.
U.S. Pat. No. 4,748,844 discloses a load detection device more related to the automotive industry. That device consists of a multi-component load cell structure fixed to a hub on which a road wheel is mounted, the load cell structure being attached so as to rotate with the tire of the wheel. While that device provides some signal benefits, this device cannot provide signals indicating all loads and all torques required to enable a high level VDC electronic device to function properly. In particular, that device mounts all of its strain gages in only one plane which is perpendicular to the axis about which the wheel rotates. As a result, the signals from the strain gages on that device are unable to detect the forces tending to cause a vehicle to skid sideways or to roll the vehicle over.
Therefore, while the automotive industry is continuing to develop electronic devices which assist the driver to maintain control of his vehicle through various combinations of brake application and continuous suspension adjustment, the more sophisticated of these systems require reliable input signals indicating the full spectrum of loading which are indicative of the loads exerted at the tire contact patch.
Similarly, the rolling mill and machine tool industry utilize various forms of process controls which require monitoring of the loads placed on bearings. Specifically, rolling mills need bearing feedback regarding indications of belt slipping on rollers or indications that a particular set of rollers is experiencing higher loads and torques. Computer controlled machine tools need to monitor the amount of torque being experienced by a bearing supporting a spindle in order to assess whether cutting and drilling tools have becomes dull or whether the cutting or drilling speeds exceed the limits established for proper machining operations.
The present invention resides in a bearing assembly that couples a road wheel to a suspension system component on an automotive vehicle. The bearing assembly includes a hub to which the road wheel is attached and a housing which is attached to the suspension system component. The hub rotates in the housing on rolling elements which are arranged in two rows, with each row being between opposed raceways on the but and housing. The rolling elements impart minute flexures to the housing, and the flexures are detected by strain sensors attached to the housing. In one embodiment the sensors are located at 90° intervals around each raceway of the housing. In another they are on a flange at which the housing is attached to the suspension system component. In still another they are located along an intervening surface that lies between the two raceways of the housing. The invention also resides in the bearing assemblies of the several embodiments apart from a wheel and suspension system component. Additionally, the present invention resides in a bearing assembly equipped with strain sensors used to generate electrical signals of a type and mode which are usable by various types of electronic processing and controlling devices which require such electrical signals to calculate loads within the mechanical system in which the bearing is incorporated.
The invention also resides in the method of using strain sensors to generate electrical signals of a type and mode which are usable by other automotive devices which function to provide dynamic control of a vehicle under various loading conditions, or by other electronic devices in the rolling mill industry or the machine tool industry.
Referring now to the drawings, a road wheel W (FIG. 1), which supports an automotive vehicle on a road surface, experiences several forces F and torques T when the wheel W rolls along the road surface. First there is the vertical force Fv which generally represents the weight of the vehicle and any inertial forces generated by irregularities in the road surface and by braking. The wheel W also experiences horizontal forces Fh which act generally in the direction the wheel is headed. Also, there are thrust loads Ft, which are forces directed axially, that is in the direction on the axis X of rotation. Then there is the vertical torque Tv, that is to say, torque about an axis passing vertically through the wheel W and sometimes referred to as the steering torque. Finally, horizontal torque Th, sometimes referred to as the overturning moment, which acts about an axis passing horizontally through the wheel W in the direction of advance for the wheel W. Altogether the current invention measures the loads for five degrees of freedom which include three forces, Fv, Fh, and Ft, and two moments, Tv and Th.
The wheel W has a rim 2 and a tire 4 mounted on the rim 2. The tire 4 contacts the road surface along a tire contact patch 6, where the tire 4 experiences the forces F and torques T. The magnitude of the forces and torques indicate conditions at the tire contact patch 6 and, when evaluated with other conditions in real time, provide a good representation of the capacity of the vehicle to remain under control, or, on the other hand, go out of control.
The wheel W is coupled to a component C (
More specifically, the hub 12 includes a flange 26 and a hollow spindle 28 which projects from the flange 26 at a shoulder 30 located on the back face of the flange 26. Outwardly from the shoulder 30, the flange 26 is fitted with lug bolts 32 which project axially from its other face and pass through the rim 2 of the road wheel W. Beyond the wheel W, lug nuts 34 are threaded over the bolts 32 to secure the wheel W to the hub 12.
At its end remote from the flange 26, the spindle 28 is upset, that is, deformed outwardly in the provision of a formed end 36 having an abutment face 38 that lies perpendicular to the axis X and is presented toward the shoulder 30. The bearing 16 is captured between the shoulder 30 on the flange 26 and the face 38 of the formed end 36.
The bearing 16 includes an inner race in the form of two cones 40 which fit around the spindle 28, there being an interference fit between each cone 40 and the spindle 28. Each cone 40 has a tapered raceway 42 that is presented outwardly away from the axis X, a thrust rib 44 at the large end of its raceway 42, and a back face 46, which is squared off with respect to the axis X on the end of the thrust rib 44. The inboard cone 40 is somewhat longer than the outboard cone 40 by reason of a cylindrical cone extension 48 which projects beyond the small end of its raceway 42. The cone extension 48 may serve as a seat for a target wheel that is monitored by a speed sensor in the housing 14. The inboard cone 40 at its cone extension 48 abuts the small end of the outboard cone 40 along the spindle 28, that is to say, the two cones 40 abut at their front faces. The back face 46 of the outboard cone 40 abuts the shoulder 30 that lies along the flange 16, whereas the back face 46 of the inboard cone 40 abuts the end face 38 on the formed end 36.
In addition to the cones 40, the bearing 16 includes tapered rollers 54 arranged in two rows, there being a separate row around each cone 40. Actually, the rollers 54 extend around the raceways 42 for the cones 40, there being essentially line contact between the tapered side faces of the rollers 54 and the raceways 42. The large end faces of the rollers 54 bear against the thrust ribs 46. The rollers 54 of each row are essentially on apex, which means that the envelopes in which their tapered side faces lie have their apices located at a common point along the axis X. Each row of rollers 54 has a cage 56 to maintain the proper spacing between the rollers 54 in that row.
The housing 14 surrounds the spindle 28 as well as the two cones 40 and the two rows of rollers 54. It forms part of the bearing 16 in that is has tapered raceways 58 which are presented inwardly toward the axis X. In that sense, the housing 14 constitutes the outer race of the bearing 16. The raceways 58 on the housing 14 tape downwardly toward a cylindrical intervening surface 59 which separates them. The rollers 54 likewise lie along the raceways 58 of the housing 14, there being essentially line contact between the raceways 58 and the tapered side faces of the rollers 54. At their large ends, the raceways 58 open into short end bores 60 in which the thrust ribs 44 of the two cones 40 are located. Thus, each end of the bearing 16 has an annular space, with that space being between the thrust rib 44 at that end and the surrounding surface of the end bore 60.
The housing 14 has an exterior surface 62 that is generally cylindrical and also a triangular or rectangular flange 64 that projects from the surface 62 generally midway between its ends. In the region behind the flanged 64, the diameter of the surface 62 is slightly less than the diameter of the through bore 18 in the suspension system component C. This portion of the housing 14 fits into the bore 18 with some clearance, while the back face of the flange 64 bears against the end face 20 on the component C. The housing 14 is secured firmly to the component C with bolts 66 that pass through the latter and tread into the flange 64 on the former.
The annular spaces at the ends of the bearing 16 are closed with seals 68 which fit into the end bores 60 of the housing 14 and around the thrust ribs 44 of the cones 40. U.S. Pat. No. 5,022,659 discloses suitable seals for both locations.
The formed end 36 unitizes the assembly A. But the hub 12 does not always have the formed end 36. Initially, the spindle 28 of the hub 12 extends from the shoulder 30 all the way to its free end as a cylindrical surface. The two cones 40, with their complements of rollers 54 and with the housing 14 captured between the rollers 54 of the two rows, are installed over the cylindrical surface of the spindle 28 and advanced until the back face 46 of the outboard cone 40 comes against the shoulder 30 at the other end of the spindle 28. When the cones 40 are so positioned, a portion of the spindle 28 projects beyond the back face 46 of the inboard cone 40. This portion is deformed into the formed end 36. PCT application GB 98/01823 (International Publication No. WO98/58762) discloses a rotary forming process for upsetting the initially extended end of the spindle 28 and converting that end into the integral formed end 36 which in effect unitizes the entire assembly A.
Other means may secure the two cones 40 on the spindle 28 as well. For example, the end of the spindle 28 may have threads and a nut engaged with those threads and turned down against the back face 46 of the inboard cone 40.
When the assembly A is so unitized, its bearing 16 exists in a condition of slight preload. Actually the spacing between the inner raceways 42 on the cones 40 determines the setting of the bearing 16, and that spacing depends on the length of the cone extension 48 for the inboard cone 40, inasmuch as the rotary forming procedure which produces the formed end 46 drives the inboard cone 40 toward the outboard cone 40 with enough force to cause the cone extension 48 on the former to abut the small end of the latter. A nut threaded over the spindle 28 and turned down snugly against the back face 46 of the inboard cone 40 will have the same effect.
The forces Fv, Fh and Ft and the torques Tv and Th which act upon the wheel W reflect conditions at the tire contact patch 6. For example, a balanced thrust load Ft will reflect travel in a straight line and will represent somewhat more than the preload in the bearing 16. On the other hand, a larger unbalanced thrust Ft, that is more in one direction than the other, will indicate a turn or perhaps a significant inclination of the vehicle to one side or the other. An increase in the vertical force Fv will reflect a turn or the application of brakes if the wheel W is at the front of the vehicle.
The forces Fv, Fh, Ft and the torques Tv and Th which the wheel W experiences are transferred to the suspension system component C through the bearing assembly A, so the bearing assembly A experiences those forces F and torques T as well. The forces F and torque T manifest themselves in minute expansions and contractions of the housing 14, and these minute expansions and contractions are detected at sensor modules M (
In one embodiment, each sensor module M includes (
In addition to its sensor 70, each sensor module M includes a temperature compensator 84 and a terminal block 86. The temperature compensator 84 should operate at the same temperature as the sensor 70, and to this end, should be located on the housing 14 adjacent to the sensor 70, even on the carrier matrix 72 of the sensor 70. In this regard, the resistances of the resistance elements 74 and 76 not only vary will expansions and contractions of the matrix 72, but also with temperature. The temperature compensator 84 is connected to the resistance elements 74 and 76, either through a bridge circuit or through a processor, such that it compensates or offsets changes in the resistances of the elements 74 and 76 attributable to temperature variations. Thus, the signals derived from the resistance elements 74 and 76 reflect only variations in strain. The terminal block 86 contains terminals 88 to which the tabs 82 on the resistance elements 74 and 76 are connected and to which the temperature compensator 84 is likewise connected, all through leads. The terminals 88 are in turn connected to a processor for evaluating and processing the signals produced by the resistance elements 74 and 76 and the temperature compensator 84.
Four sensor modules M are attached to the exterior surface 62 of the housing 14 radially outwardly from the outboard raceway 58 and they are arranged at 90° intervals, (
When the road wheel W rolls over a road surface and carries the suspension system component C with it—as well as the entire vehicle of which the component C is a part—the spindle 28 of the hub 12 rotates in the housing 14. The cones 40 of the bearing 16, being fitted to the spindle 28 with an interference fit, likewise rotate. The tapered rollers 54 of the outboard row roll along the raceway 42 of the outboard cone 40 and the outboard raceway 58 of the housing 14. The tapered rollers 54 of the inboard row roll along the raceway 42 of the inboard cone 40 and the inboard raceway 58 of the housing 16. As the rollers 54 roll between their respective raceways 42 and 58 they transfer radial loads between the cones 40 and the housing 14. The radial load exerted by any roller 54 against the outer raceway 58 along which it rolls causes the housing 14 to flex minutely, and this flexure, while existing at the raceway 58, transfers through the housing 14 to the exterior surface 62 and manifests itself as a slight circumferential, and somewhat smaller, axial elongation of the surface 62 radially outwardly from the line of contact between the roller 54 and the raceway 58. Thus, each time a loaded roller 58 passes between a sensor 70 and the axis X, the flexure that occurs along its raceway 58 is transmitted to the exterior surface 62 at the sensor 70 where it elongates the parallel legs 78 of the resistance element 74 for sensor 70 and increases the resistance of the resistance element 76. The magnitude of the change in resistance depends on the load, for a roller which bears against its raceway 58 with a heavy force will impart a greater flexure than one which bears with a lesser force. By comparing the flexure—and thus the roller loads—reflected in the signals from the sensors 70, one can ascertain conditions at the tire patch 6 in real time.
A modified bearing assembly B (
Another modified bearing assembly D (
Another embodiment resembles the bearing assembly A in every respect except there is not road wheel W, rim 2, or hub 12. Instead, the bearing assembly A is mounted to any rotating shaft installation and the bearing sensors are thereafter used to provide electrical signals indicative of the circumferential, circumferential-axial, axial torque, and shear strains on the bearing generally. Examples of applications which would need such information are process controls for rolling mills and process controls for machine tools. It will be obvious to one skilled in the art of bearing design and bearing use that there are many other applications wherein the loading sustained by a bearing would require the use of a bearing capable of providing electrical signals for monitoring those bearing loads.
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|US7444888 *||Jul 16, 2004||Nov 4, 2008||Ab Skf||Method and sensor arrangement for load measurement on rolling element bearing|
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|U.S. Classification||73/795, 73/862.55|
|Sep 8, 2009||CC||Certificate of correction|
|Jun 3, 2011||FPAY||Fee payment|
Year of fee payment: 8
|Jun 5, 2015||FPAY||Fee payment|
Year of fee payment: 12