Patent Publication Number: US-7908916-B2

Title: Flat belt roadway simulator with steer and/or camber adjustment and method for ascertaining rolling loss

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application entitled “FLAT BELT ROADWAY SIMULATOR WITH STEER AND/OR CAMBER ADJUSTMENT” having Ser. No. 61/059,985 filed Jun. 9, 2008, the content of which is also incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
     Various forms of testing machines have been advanced to test characteristics of rolling tire and/or wheel assemblies. One well known form includes a large rotateable drum that is driven by a suitable drive. A carriage assembly having a spindle to rotateably support the tire and wheel assembly is used to engage the tire against the drum. Commonly, the carriage assembly is configured to apply a selected load upon the tire against the drum as well as pivot the spindle to replicate different configurations of camber and steer of the tire and wheel assembly. Force sensors can be included in the spindle to measure selected forces. Drawbacks of this type of system include the complicated design of the spindle and adjustments needed, if even available, in ascertaining tire characteristics such as rolling loss in view of the crown of the drum. 
     Another form of known tire testing machines uses a roadway simulator that comprises an endless belt. Like the drum machine, a carriage assembly is configured to apply a selected load upon the tire against the endless belt roadway as well as pivot a spindle to replicate different configurations of camber and steer of the fire and wheel assembly. Force sensors can be included in the spindle to measure selected forces. Although such a machine provides a flat portion in the endless belt upon which the tire is rolled against, this machine also uses a complicated spindle to move and adjust the tire and wheel assembly. 
     SUMMARY 
     This Summary and the Abstract herein are provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary and the Abstract are not intended to identify key features or essential features of the claimed subject matter, nor are they intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
     A testing machine includes a frame and a roadway assembly. The roadway assembly includes an endless belt and a carriage supporting the endless belt for rotation on the carriage and providing flat portion in the endless belt. The carriage is pivotally coupled to the frame to move relative to the frame about at least one axis. The carriage includes a bearing arranged to support an inner surface of the flat portion of the endless belt. A spindle carriage has a spindle arranged to support a tire and wheel assembly. The spindle carriage is movably mounted on the frame to move the spindle toward and away from the flat portion. A drive is operably coupled to the roadway assembly or the spindle. An actuator controls pivotal movement of the roadway assembly about said at least one axis. Commonly, the pivotal movement of the tire relative to the flat surface relates to changes in steer or camber. A method of operating such a system for testing a tire and/or wheel assembly such as ascertaining rolling loss of a tire mounted to such a machine is also provided. 
     In a further embodiment, the roadway assembly is configured to pivotally move relative to the frame about a second axis that is perpendicular to the first-mentioned axis. The machine further comprises a second actuator to control pivotal movement of the roadway assembly about the second axis. In this embodiment, both steer and camber of the tire can be adjusted. 
     In a further embodiment, the endless belt includes a second flat portion and the carriage includes a second bearing arranged to support an inner surface of the second flat portion of the endless belt. The machine further comprises a second spindle carriage having a second spindle arranged to support a second tire and wheel assembly. The second spindle carriage is movably mounted on the frame to move the second spindle toward and away from the second flat portion. A compact assembly able to test two tires is thereby provided. 
     Various types of bearing assemblies can be used to allow pivotal movement of the roadway relative to the frame. For instance, a U-joint, Cardin joint or spherical bearing can be used. 
     In a further embodiment, a device can be provide to provide an output indicative of torque in the roadway assembly or spindle (for example, inline torque cells, current flowing in a drive), power used by the drive, power generated by the roadway or spindle if a suitable power indicating component such as a generator is present, or forces on the spindle as measured by force sensors in the spindle or on the spindle carriage. Such device(s) are operably coupled to controller, which provides an output indicative of tire and/or wheel characteristics such as rolling loss of a tire mounted to the spindle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a flat belt roadway testing machine. 
         FIG. 2  is a front elevational view of the testing machine. 
         FIG. 3  is a side elevational view of the testing machine. 
         FIG. 4  is a top plan view of the testing machine. 
         FIG. 5A  is a schematic side elevational view of a portion of a first embodiment of the testing machine. 
         FIG. 5B  is a schematic sectional view of the portion of the first embodiment of  FIG. 5A . 
         FIG. 6A  is a schematic side elevational view of a portion of a first embodiment of the testing machine. 
         FIG. 6B  is a schematic sectional view of the portion of the first embodiment of  FIG. 6A . 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Referring to the Figures, a testing machine  10  allows testing of vehicle tires  12 ,  14  using a flat belt roadway drive system which has camber adjustment and/or steer adjustment via a roadway assembly  22  movably mounted to a frame  20 . The roadway assembly  22  includes an endless belt  24  that is supported by two rollers  28 ,  30 . In one embodiment, one of the rollers, herein roller  28 , is a drive roller while the other, herein roller  30 , is in an idler roller. A drive motor  36  is coupled to the drive roller  28  by a drive mechanism  34  comprising suitable, belts, chains, gears, pumps, etc. Flat surfaces  24 A and  24 B of the roadway assembly belt  24  are oriented vertically such that a first tire and wheel assembly  40  engages one side of the roadway assembly belt  24 , while a second tire and wheel assembly  42  engages the other side of the roadway assembly belt  24 . Two tire and wheel assembly support spindle carriages  50 ,  52  respectively, are provided on the frame  20 , one being on each side of the roadway assembly  22 . Typically, each of the spindle carriages  50 ,  52  include linear guides and suitable actuators so that each of the tire and wheel assemblies  40 ,  42 , mounted thereto on a rotatable spindle, can individually be brought into contact with the corresponding sides (flat portions  24 A,  24 B) of the roadway assembly  22 . In this manner, radial loading on each of the tire and wheel assemblies  40 ,  42  due to simulating the weight of a corresponding vehicle is oriented horizontally on the frame  20 . This allows the test machine  10  to conveniently test two tire and wheel assemblies  40 ,  42  at the same time. Although the vertical orientation of the roadway assembly  22  herein illustrated is convenient, it should not be considered limiting. Rather, it should be understood other orientations of the roadway assembly  22  and different configurations of frames  20  used to moveably support the roadway assembly  22  can be used with one or more aspects of the invention herein described, if desired. For example, the roadway assembly  22  can be movably mounted to the frame  20  such that one or two tire and wheel assemblies contact surfaces of the assembly  22  from above and/or below, or at any inclination relative to a base floor. 
     At this point should be noted that all actuators herein described can be hydraulic, pneumatic and/or electric as desired. As appreciated by those skilled in the art, the actuators can include single or double acting piston/cylinder assemblies, screw-driven rods, cams, bell cranks, levers, gears, etc. 
     The roadway assembly  22  is pivotally connected to the frame  20  so as to pivot about at least one or two axes that are perpendicular to an axis parallel to an axis of rotation of the roller  28  or  30 . Any of the rotatable degrees of freedom may be restrained or controlled to provide the desired rotation degrees of freedom necessary for the testing application. Referring by way of example to tire and wheel assembly  40 , the roadway assembly  22  can be pivotally connected to the frame  20  such that the roadway assembly  22  can pivot about a first axis  60  (perpendicular to the flat portion  24 A or  24 B) that simulates steering of a tire and wheel assembly  40  so as to introduce tire slip angle represented by double arrow  61 . In addition, or in the alternative, the roadway assembly  22  can be pivotally connected to the frame  20  such that the roadway assembly  22  can pivot about a second axis  62  (typically perpendicular to the steer axis  60  or parallel to flat portion  24 A or  24 B) and parallel to the direction of belt travel (in the flat portions  24 A,  24 B) that simulates a camber change of the tire and wheel assembly  40  as represented by double arrow  63 . 
     In the embodiments illustrated in the schematic figures of  FIGS. 5A ,  5 B,  6 A, and  6 B a first actuator  70  is coupled to the frame  20  and the roadway assembly  22  to control pivoting of the roadway assembly  22  about the first or steer axis  60 . (An alternative location for the steer actuator is illustrated in  FIG. 2 ) In addition, or in the alternative, a second actuator  72  is coupled to the frame  20  and the roadway assembly  22  to control pivoting of the roadway assembly  22  about the second or camber axis  62 . Pivot mechanisms or bearings that allow pivotal movement of the roadway assembly  22  relative to the frame  20  can be configured so the camber axis  62  can intersect with the steer axis  60  between the rollers  28 ,  30  and under or between tire support bearings  28 A,  28 B of the roadway assembly  22 . Tire support bearings  28 A,  28 B are mounted to a carriage assembly  81  of the roadway assembly  22 . The tire support bearings  28 A,  28 B provide reaction structure for each corresponding tire and wheel assembly  40 ,  42  by supporting an inner surface of the belt  24 . The tire support bearings  28 A,  28 B can use a fluid (e.g. air or liquid) between the flat portions of the belt and the opposed surfaces of the tire support bearings  28 A,  28 B to minimize friction. Such bearings are well known in the art. Carriage assembly  81  also supports rollers  28  and  30 . If desired, actuators can be used to support one or both of the rollers  28  or  30 . By way of example, actuators  53  support the idler roller  30  on the carriage  81 , which with actuation allow selective tensioning of the belt  24 . 
     Depending on the type of drive mechanism  36  employed, the drive motor/pump components may or may not move with pivoting movement of the road assembly  22 . For instance, if the drive mechanism  34  comprises belts and pulleys, a drive motor  36  may have to be structurally connected to move with the road assembly  22 . However, if the drive mechanism  34  is hydraulic or pneumatic having hoses connecting the drive motor  36  to a drive pump (not shown), the drive pump can be stationary. In a further embodiment, the drive motor  36  can be mounted to the frame  20  where the drive shaft coupling the drive motor to the drive roller  28  (and/or torque cell or sensor  79  discussed below) has angular motion and plunge (axial sliding) flexibility. 
     In one embodiment illustrated in  FIGS. 5A and 5B , rotation bearing assembly  76  comprises bearing portions  76 A and  76 B that that allow pivotal steer and camber movement, respectively. In the embodiment illustrated, one of the bearing portions  76 A,  76 B, herein bearing portion  76 A, is within the roadway assembly  22  (i.e., between the rollers  28 ,  30  and under or between tire load support bearings  28 A,  28 B), thereby providing a steer axis that intersects with the belt  24  of the roadway assembly  22 . By placing the steer rotation bearing portion  76 A within the roadway assembly  20 , two tires  12 ,  14  can be tested on the same roadway assembly  22  as illustrated. The bearing portion  76 B for the second (camber) rotation axis  62  can also be disposed in the roadway assembly  22  so as to cause the axis  62  to intersect with the belt  24 , or the bearing portion  76 B can be arranged so that the axis  62  is slightly outboard of the roadway assembly  22  (i.e., does not intersect with the belt  24 ). Arranging the bearing portion  76 B so that the camber rotation axis  62  is outboard of the roadway assembly  22  provides favorable pitch restraint on the roadway assembly  22 . Herein, “pitch” is movement of the roadway assembly  22  about an axis that is perpendicular to both axes  60  and  62 , in other words, an axis that is parallel to an axis of rotation of roller  28  or  30 . This movement is generally undesired and spacing the bearing portions  76 A and  76 B as illustrated in  FIGS. 5A and 5B  inhibits such movement, and thereby, provides restraint. 
     In the embodiment illustrated in  FIGS. 5A and 5B , rollers  28 ,  30  are supported on suitable bearings by the carriage assembly  81 , which in turn, is supported by a first support  83  of bearing portion  76 A. A second support  85  of bearing portion  76 A is also a support of bearing portion  76 B, while a second support  87  of bearing portion  76 B is coupled to frame  20 . Bearing portions  76 A and  76 B with support  83 ,  85  and  87  essentially form a U-joint or Cardin joint where a distance “D” between axes  60  and  62  can be zero or a non-zero value. Placement of the camber pivot axis  62  in the plane of the tire and wheel assembly reduces the amount of radial travel in the tire carriage. 
     In this embodiment, camber actuator  72  ( FIG. 5B ) is operably coupled between frame  20  and support  85 , while steer actuator  70  ( FIG. 5A ) is operably coupled between support  85  and carriage  81 . As appreciated by those skilled in the art, in an alternative configuration the steer actuator  70  could be operably coupled to the support  85  and the frame  20 , while the camber actuator  72  is operably coupled to the support  85  and the carriage  81 . In such a configuration, bearing portions  76 A and  76 B would be interchanged. It should also be noted the actuators  70  and  72  and components they are connected to can be lengthened or otherwise changed to increase or decrease associated lever arms as desired. 
     In another embodiment illustrated schematically in  FIGS. 6A and 6B , a spherical bearing  90  is used to support the roadway assembly  22  on the frame  20 . It should be noted the same reference numbers have been used to identify components performing the same or similar functions as described above. The spherical bearing  90  can be positioned within the roadway assembly  22  (i.e., between the rollers  28 ,  30 , for example, centered and under or between tire load support bearings  28 A,  28 B). In the embodiment illustrated, the spherical bearing  90  includes a ball  91  that is rigidly mounted to the frame  20 , while a ball receiver or socket  93  is mounted to the carriage  81 . Using such a bearing, places both the steer axis  60  and the camber axis  62  within the center of the roadway assembly  22  so that each intersects with the belt  24 . 
     It should be noted, the spherical bearing  90  provides a third degree of freedom of pivotal motion, which is perpendicular to both the steer axis  60  and the camber axis  62 , where movement about this axis was referred to as “pitch” above. Various link assemblies can be employed to provide pitch restraint. In one embodiment, pitch restraint is implemented with the camber actuator mechanism  72 . Camber actuator mechanism includes an actuator joined to the frame and a bell crank assembly  92  pivotally joined to the frame  20  with bearings  105 . The bell crank assembly  92  includes a torque tube  94  and link(s)  95  connected to the roadway assembly  22 . 
     The testing machine  10  herein described provides a compact assembly for steering and cambering the roadway to provide slip angle and camber rotation. Pivotal movement of the roadway assembly  22  provides slip angle and camber angle rotation for one or two tire and wheel assemblies  40 ,  42  mounted on corresponding carriages. Pivotal movement of the roadway assembly  22  avoids the cost and complexity of replicating the motions of each tire carriage so as to provide the required steer and camber adjustments. The test machine  10  is particularly advantageous when pivotal movements of the roadway assembly  22  are approximately ±5 degrees, on in another embodiment, approximately ±2 degrees. Small rotation angles are useful on flat belt roadways for a variety of tests including but not limited to rolling resistance, residual alignment moment, residual lateral force, or cornering power tests. 
     It should be noted, use of the flat surfaces provided by the roadway assembly  22  does not require the camber and steer rotation to be at the surface of the roadway for steady state testing. Only the angular relation of the tire wheel plane relative to the road surface plane and direction of rotation is important. It is desirable to have the steer rotation axis to be near the center of the fire contact patch to prevent the steer rotation from causing tire fore-aft motion on the fire load support bearing  28 A,  28 B so that the size of the tire load support bearing  28 A,  28 B can be minimized. 
     The testing machine  10  allows use of a flat belt testing surface for each tire  12 ,  14  at small slip and camber angles. The roadway assembly  22  has lower rotation inertia than a comparable drum commonly used in the prior art. Lower inertia is favorable for measurement of roadway drive torque or power as a measure of tire rolling loss. Commonly, the roadway assembly  22  employs an air bearing as the tire load support bearings  28 A,  28 B which contributes low friction errors to the measurement. For ease of use, it is desirable to use carriage assemblies  50  and  52  having cantilevered spindles that make tire installation faster and simpler. If desired, force and moment load cells or sensors can be provided in the carriage assemblies  50  and  52 . 
     Tire testing applications like a rolling resistance are customarily in the prior art done using large drums and with the tire and wheel assembly supported by tire carriages that only load the tire against a drum while tire steer (slip angle) and camber (inclination angle) are fixed at zero. Typically, when slip angle and/or camber angle are desired the carriage is configured to move the tire and wheel assembly with three degrees of motion. Accordingly, these carriages are typically relatively large and complex. In addition, single drum roadway simulators of the prior art use a drum that is larger than the tires under test as a means of reducing curvature effects on the tires. These large drums and the associated support structure and drive motors are not convenient to move in order to provide steer or camber rotation. Such movement would cause the tire contact to move off the crown of the drum and induce measurement errors so it is necessary to have centerline camber and steer with a curved surface. For drum type test systems it is thus move convenient to move the tire to achieve this. 
     Furthermore, it is difficult to place the steer and camber rotation axes so they intersect at the tire contact patch, which is necessary if testing on the rotatable drum of the prior art. However, testing on a flat surface eliminates this constraint particularly for steady state testing. Testing against a flat surface also eliminates measurement errors due to curvature of the large drum of the prior art, especially when slip angle and camber angle cause the tire to deflect out of plane. 
     Stated another way, use of flat surface portions  24 A,  24 B of the roadway assembly  20  can eliminate uncertainty due to curvature found in prior art drum type of tire test systems. There are a number of benefits of testing on a flat surface. When testing at zero slip angle, the inclination angle of the simulated roadway curvature from a drum causes the tire under test to deflect differently than on a flat surface. This can result in more tire hysteresis and energy consumption. The rolling resistance on a flat surface is believed to be about 10 to 23% lower than on a curved surface. The tire testing community thus uses a formula to convert curved surface data to flat surface data when tests are run at zero slip and camber angle. Although this formula is an accepted practice the SAE rolling resistance recommended practice cautions that the validity is not proven for universal use. 
     When a tire is steered or cambered, the tire deflects out of plane and generates lateral forces related to vehicle handling. However, this also causes the tire contact patch to shift on the roadway surface. This shift changes where the forces and moments are generated on the road surface. The effects of simulated roadway surface curvature on a tire that is deflected due to slip angle or inclination angle are complex. It is believed, there is no accepted flat surface approximation formula for converting curved surface data to corresponding flat surface data under such testing conditions. 
     Although the testing machine described above can be used for testing various aspects of a tire and/or wheel, another aspect herein described is that the system allows for rolling resistance and rolling loss measurement of vehicle tire(s) using a flat surface roadway simulation. Rolling resistance measurement can be done using a force or a torque method. Furthermore, the rolling loss measurement can be done at small camber (e.g. ±2 degrees) and/or steer (e.g. ±1 degree) angles. Tire load in the vertical (z) direction (i.e. simulated vehicle weight along axis  60 ) is reacted using bearing(s)  28 A,  28 B. The combination of a flat belt roadway assembly  22  that can be moved in motions reflecting changes in steer and camber of a wheel and a torque sensor  79  to measure torque (herein being connected in series with drive mechanism  34  and driver roller  28 ). The torque sensor  79  provides an output indicative of torque applied to the drive roller  28 . The measured torque can be used to provide and indication of rolling resistance. The force vector in the direction of roadway velocity is the tire rolling loss that is measured by the torque sensor  79 . The bearing(s)  28 A,  28 B contribute to the feasibility of making this measurement via a torque measurement because the bearing(s)  28 A,  28 B support tire load with very low friction. The bearing(s)  28 A,  28 B also allow the roadway orientation to be in any direction. 
     The torque method measures tire rolling loss by measuring the torque to drive the roadway assembly  22  with the tire loaded and then unloaded with the difference in power, for example, as measured directly, or as torque, or as forces, to name just a few, at the two load states representing or used as a basis for calculating a value related to tire rolling loss. Such calculations are known in the art. Referring back to  FIG. 1 , a controller  100  (analog and/or digital) receives as input(s) an indication of torque applied to the drive roller  28  and/or other forces for example measured at spindles of the carriages  50 , 52  and provides as outputs control signals to one or more of the afore-mentioned actuators and an output indicative of rolling loss of tire(s) operably mounted to spindle(s). In one aspect of the invention, a measurement of rolling loss is obtained using a measurement of torque such as a relatively simple rotating torque cell  79  on the roadway drive shaft ( FIGS. 5A ,  6 A). This allows the rolling loss to be calculated based on the measurement of one sensor on the roadway assembly  22  rather than adding sensors (load cells) to each spindle of the carriages  50  and  52 . In a further aspect, a measurement related to torque is also convenient for it automatically accounts for the orientation of the roadway assembly  22 , being pivotable relative to the tire and wheel assembly. In an alternative embodiment, a measurement of torque can be obtained as sensed or known current flowing in the drive motor  36 . In yet another embodiment, a difference in power used by the drive mechanism  34  can be used as an indication of rolling loss. 
     However, it should be noted in an alternative method of measuring rolling loss, force measurements Fx and Fy (both of which are perpendicular to each other and perpendicular to the vertical direction z, or radial loading along the axis  60 , which is the simulated vehicle weight) at the spindle of the carriage  50 ,  52 . In  FIG. 4 , the force sensors are schematically illustrated at  97  as being part of the spindle. Nevertheless, it should be understood suitable force sensors can be operably coupled to various components of the carriage  50 ,  52  as appreciated by those skilled in the art. The addition of a sensor(s) to measure Fx and Fy forces on the spindle/carriage may be less favorable for it complicates the carriage design. Additionally, increasing the number of load cells or sensors on the spindle increases compliance and introduces camber and slip angle errors. Nevertheless, such measurements can be used to calculate rolling loss when using the pivotable roadway assembly  22  as provided herein. 
     In yet another embodiment, the carriage  50 ,  52  can include a drive (hydraulic, pneumatic or electric), schematically indicated at  99  in  FIG. 3  on carriage  50 , operably coupled to the spindle to drive the spindle and thus the tire and wheel assembly  40 ,  42  on the roadway assembly  22  to move the belt  24 . Again, with the tire loaded and then unloaded a difference in power used by drive  99  between these states can be used to provide an indication of rolling loss. If desired motor  36  can operate as a generator to provide an indication of power transferred to the roadway assembly  22 , wherein the difference between power generated in the loaded and unloaded states, or the difference in power used by drive  99  and the power generated can be used to provide an indication of rolling loss. Likewise, component  99  can represent a generator, wherein the difference between power generated in the loaded and unloaded states at the spindle (the roadway  22  being driven by drive  34 ), or the difference in power used by drive  34  and the power generated by generator  99  can be used to provide an indication of rolling loss. Furthermore, as in the embodiment described above, torque measured directly via a torque cell on drive  99  or current flowing in drive  99 , or spindle force sensors  97  as described above can also be used to provide an indication of rolling loss. 
     Measurement of simulated vertical forces of the vehicle (along axis  60 ) can be measured with one or more sensors or load cells  98  supporting bearings  28 A,  28 B ( FIGS. 5B ,  6 B), incorporated in sensor  97  on the spindle of the carriage  50 ,  52 , and/or as suitable sensors operably coupled to components of the carriage  50 ,  52 . 
     The inertia of the roadway assembly  22  is much smaller than any drum system that meets the curvature recommendation of ISO and SAE. A conventional aluminum drum of the prior art has an estimated inertia of 300 kg m 2  based on Goodyear Luxembourg&#39;s specification. It is believed, a flat-belt system having features herein described and for the same application would have an estimated roadway inertia that is 10 to 20 times less than the best possible curved surface machine. In one exemplary embodiment it is estimated the roadway inertia for a system herein described will be between 15 and 30 kg m 2 . This lower inertia is favorable for sensor such as torque cell sizing, drive motor sizing and acceleration capabilities of the system. 
     The flat surface test system  10  herein described is also a much smaller machine that a drum type of tire test system for the same application. Drum type systems commonly have a drum diameter of between 1.7 to 2 m. The flat belt roadway is typically less then 0.5 m between tire load surfaces resulting in a machine that is 1.2 to 1.5 m smaller, where overall material costs are thus less. There are also benefits to the end user by conserving laboratory space and reducing costs associated with building and operating the laboratory facility. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above as has been determined by the courts. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.