Abstract:
An alignment measurement system for a vehicle includes an alignment sensing system and a suspension relaxing system. The suspension relaxing system is configured to receive at least one wheel of the vehicle and is operable between a plurality of states. The alignment sensing system is operatively connected to the suspension relaxing system to select a state of the suspension relaxing system. In a first state, the suspension relaxing system maintains the wheel of the vehicle stationary when the wheel is received by the suspension relaxing system, and in a second state, the suspension relaxing system allows the wheel to turn and/or translate. Prior to performing a measurement on the alignment of the vehicle, the alignment sensing system directs the suspension relaxing system to be operated in the second state.

Description:
TECHNICAL FIELD  
       [0001]     The disclosure relates generally to motor vehicle wheel alignment and, more specifically, to a vehicle wheel alignment system that controls the locking and unlocking of turntables and skid plates at certain times during the alignment of the wheels.  
       BACKGROUND ART  
       [0002]     Motor vehicle alignment systems are important for ensuring that the alignments of wheels on a vehicle are within the specifications provided by motor vehicle manufacturers. If the wheels are out of alignment, there may be excessive or uneven wear of the wheels. In addition, the performance of the vehicle, particularly handling and stability, may be adversely affected if the wheels are not properly aligned. As used herein, the term “wheel” or “vehicle wheel” refers to the tire and wheel assembly found on a motor vehicle. Such an assembly generally includes a conventional tire that is mounted on a metal wheel or “rim.” 
         [0003]     The wheels of a motor vehicle may be aligned in a number of ways. For example, an operator or an alignment technician can use a vision imaging system such as a computer-aided, three-dimensional (3D) machine vision alignment system having optical sensing devices, such as cameras, to determine the positions of various objects. Although such machine vision systems are typically used for alignment purposes, these systems can also be used to obtain other positional and angular orientation information about a motor vehicle. Examples of such apparatus and methods are disclosed in U.S. Pat. No. 5,724,743, entitled “Method and Apparatus for Determining the Alignment of Motor Vehicle Wheels,” issued to Jackson, et al. on Mar. 10, 1998 and in U.S. Pat. No. 5,535,522, entitled “Method and Apparatus for Determining the Alignment of Motor Vehicle Wheels,” issued to Jackson, et al. on Jul. 16, 1996, each incorporated herein by reference.  
         [0004]     Prior to measuring the alignment of a vehicle or performing the realignment of the wheels of the vehicle, it is standard practice within the industry to place the suspension of the vehicle in a “relaxed” condition. Devices commonly used for this purpose are low-friction turntables/turnplates and low-friction skid/slip plates. Prior to alignment, one or more wheels of the vehicle are placed on these devices, and the turntable and skid plate allow the vehicle wheel to turn and move both longitudinally and laterally to relax the forces on the wheels. Otherwise, if the wheels were not placed in a relaxed condition, misalignment of the wheels may create forces on the wheels that under or over exaggerate a misalignment problem, and the realignment of the wheels will not be based upon correct alignment data.  
         [0005]     Notwithstanding that turntables and skid plates are used with alignment systems, these devices may be not always be properly used by an operator. Prior to positioning a vehicle onto a rack for measurement and/or realignment, the turntables and skid plates are locked into position. Once the wheels of the vehicle have been positioned on the turntables and skid plates, the turntables and skid plates are unlocked and the wheels allowed to float freely, which places the vehicle&#39;s suspension in a relaxed state. However, after the vehicle has been proper positioned onto the rack, a common error is that the turntables and skid plates are not unlocked prior to measurement of the alignment of the vehicle, and this creates the aforementioned problem of the realignment being based upon incorrect alignment data. There is, therefore, a need for an alignment system that controls the locking and unlocking of turntables and skid plates at certain times during the alignment of the wheels.  
       SUMMARY OF THE DISCLOSURE  
       [0006]     In one aspect, an alignment system is provided for measuring the alignment of a vehicle. The alignment measurement system includes an alignment sensing system and a suspension relaxing system. The suspension relaxing system is configured to receive at least one wheel of the vehicle and is operable between a plurality of states. The alignment sensing system is operatively connected to the suspension relaxing system to select a state of the suspension relaxing system. In a first state, the suspension relaxing system maintains the wheel of the vehicle stationary when the wheel is received by the suspension relaxing system, and in a second state, the suspension relaxing system allows the wheel to turn and/or translate after being received by the suspension relaxing system. Prior to performing a measurement on the alignment of the vehicle, the alignment sensing system directs the suspension relaxing system to be operated in the second state.  
         [0007]     In another aspect, the suspension relaxing system is positioned on a rack and includes a turntable, a skid plate, and one or more release and securement devices attached to the turntable and the skid plate. Depending upon the state, the release and securement device either prevents the turntable from rotating and the skid plate from translating or allows the turntable to rotate and the skid plate to translate.  
         [0008]     In one aspect of the suspension relaxing system, the release and securement device has a first portion and a second portion movable relative to one another into first and second positions. In one state, the first portion and/or the second portion are moved relative to one another into the first position, which prevents rotation and/or translation of the first portion relative to the second portion, and in another state, the first portion and/or the second portion are moved relative to one another into the second position, which allows rotation and/or translation of the first portion relative to the second portion. The alignment sensing system is connected to the release and securement device to control movement of the first portion and/or the second portion relative to one another.  
         [0009]     In another aspect of the suspension relaxing system, the suspension relaxing system includes a first portion, a second portion, and a release and securement device. In one state, the first portion contacts the second portion, which prevents rotation and/or translation of the first portion relative to the second portion, and in the second state, the first portion is separated from the second portion by a film of a fluid from the release and securement device, which allows rotation and/or translation of the first portion relative to the second portion. The alignment sensing system controls a pressure of the fluid entering the release and securement device.  
         [0010]     Other aspects and advantages of the present disclosure will become apparent to those skilled in this art from the following description of preferred aspects taken in conjunction with the accompanying drawings. As will be realized, the disclosed concepts are capable of other and different embodiments, and its details are capable of modifications in various obvious respects, all without departing from the spirit thereof. Accordingly, the drawings, disclosed aspects, and description are to be regarded as illustrative in nature, and not as restrictive.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The foregoing and other features, aspects and advantages of the present concepts are described in the following detailed description which examples are supplemented by the accompanying drawings, in which:  
         [0012]      FIG. 1  shows an exemplary alignment system, according to the disclosure;  
         [0013]      FIG. 2A  is a perspective of a combined turntable and skid plate;  
         [0014]      FIG. 2B  is a perspective of turntable separate from a skid plate;  
         [0015]      FIGS. 3A and 3B  are diagrams of a release and securement device respectively in a disengaged position and an engaged position;  
         [0016]      FIGS. 4A and 4B  are diagrams of another release and securement device respectively in a disengaged position and an engaged position; and  
         [0017]      FIG. 5  is a diagrams of yet another release and securement device; and  
         [0018]      FIG. 6  is a diagram of the alignment system. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     In accord with the disclosed concepts, there is provided, as shown in  FIG. 1 , an alignment system  100  used to determine the position of wheels  126 ,  128 ,  130 ,  132  on a vehicle and to aid in the alignment of the vehicle. The alignment system  100  includes an alignment sensing system  102 , and the alignment sensing system  102  has a controller  300  and a pair of fixed, spaced-apart cameras  110 ,  112  mounted on a beam  114 . The beam  114  has a length sufficient to position the cameras  110 ,  112  respectively outboard of the sides of the vehicle to be imaged by the position determination system  100 . Also, the beam  114  positions the cameras  110 ,  112  high enough above the shop floor  116  to ensure that the two targets  118 ,  120  on the left side of the vehicle are both within the field of view of the left side camera  110 , and two targets  122 ,  124  on the right side of the vehicle are both within the field of view of the right side camera  112 .  
         [0020]     A vehicle under test is driven onto the lift  140 . Targets  118 ,  120 ,  122 ,  124  are mounted on each of the wheels  126 ,  128 ,  130 ,  132  of the vehicle, with each target  118 ,  120 ,  120 ,  124  including a target body  134 , target elements  136 , and an attachment apparatus  138 . The attachment apparatus  138  attaches the target  118 ,  120 ,  120 ,  124  to wheel  126 ,  128 ,  130 ,  132 . An example of an attachment apparatus is described in U.S. Pat. No. 5,024,001, entitled “Wheel Alignment Rim Clamp Claw” issued to Borner et al. on Jun. 18, 1991, incorporated herein by reference. Other types of attachment apparatus may also be used. The target elements  136  are positioned on the target body  134 , and examples of target bodies  134  and target elements  112  are described in U.S. Pat. No. 5,724,743.  
         [0021]     The targets  118 ,  120 ,  122 ,  124 , once attached to the wheel rims, are then oriented so that the target elements  136  on the target body  134  face the respective camera  110 ,  112 . The vehicle and model year can then entered into the alignment sensing system  102  along with other identifying parameters, such as vehicle VIN number, license number, owner name, etc.  
         [0022]     The location of the targets  118 ,  120 ,  122 ,  124  relative to the rim of the wheels  126 ,  128 ,  130 ,  132  to which the targets are attached are typically known to an accuracy of about 0.01″ and about 0.01°. It should be understood that the position determination system  100  is not limited to these accuracies. Once the targets  118 ,  120 ,  122 ,  124  have been imaged in one position, the wheels  126 ,  128 ,  130 ,  132  are rolled to another position and a new image can be taken. Using the imaged location of the targets  118 ,  120 ,  122 ,  124  in the two positions, the actual position and orientation of the wheels  126 ,  128 ,  130 ,  132  and wheel axis can be calculated by the alignment sensing system  102 . Although the distance between the two positions varies, the distance is often approximately 8 inches.  
         [0023]     As illustrated in  FIGS. 2A and 2B , the rack  140  includes one or more suspension relaxation systems  160  (i.e., turntables/skid plates) configured to allow a vehicle wheel to turn and translate (i.e., move both longitudinally and/or laterally) to relax forces on the wheel and suspension of the vehicle. As used herein, when the vehicle wheel is described as turning, this turning/rotation is about an axis different than the normal axis of rotation of the wheel, typically perpendicular to a contact plane between the vehicle wheel and the turntable. Many types of turntable/skid plate combinations  160  are known to exist and the alignment system  100  is not limited as to a particular type or configuration. For example, as illustrated in  FIG. 2A , the turntable  162  and the skid plate  164  can be integrated to provide both angular and lateral relaxation at a single position on the rack  140 . In another example, as illustrated in  FIG. 2B , the turntable  162  and the skid plate  164  can be detached from one another so that lateral relaxation and angular relaxation are provided to the wheel at separate locations on the rack  140 .  
         [0024]     In the illustrated example, a top portion of the turntable  162  rotates relative to a base portion  166  via a shaft  165  to allow angular relaxation of the suspension. With regard to the skid plate  164 , a top portion of the skid plate  164  is located on rails  168  that allow lateral relaxation of the suspension. Other types of devices capable of providing angular rotation and lateral movement are also acceptable.  
         [0025]     According to the present alignment system  100 , each turntable/skid plate combination  160  may include at least one actuated release and securement device  174  (shown in  FIGS. 3A, 3B ,  4 A,  4 B, and  5 ). During operation, the release and securement device  174  selectively allows the turntable  162  to rotate or prevent rotation, and selectively allows the skid plate  164  to longitudinally and/or laterally move or remain fixed. A single release and securement device  174  can be used for both the turntable  162  and the skid plate  164 , or alternatively release and securement devices  174  may be provided for the turntable  162  and the skid plate  164  individually. Although not limited to the particular examples illustrated therein,  FIGS. 3A, 3B ,  FIGS. 4A, 4B , and  FIG. 5  disclose different types of actuated release and securement devices  174  capable of being used with the alignment system.  
         [0026]     Referring to  FIGS. 3A, 3B  in more detail, an example of an actuated release and securement device  174  is shown that may be used with either the turntable  162  or the skid plate  164 . The securement device  174  is connected to a first portion  170  and a second portion  172  of either the turntable  162  or the skid plate  164 . For example, the first portion  170  may be a portion of the turntable  162  that rotates, and the second portion  172  may be a portion, such as the base portion  166  of the turntable  162  or the rack  140 , that is angularly fixed. Alternatively, the second portion  172  may be a portion of the turntable  162  that rotates, and the first portion  170  may be a portion that is angularly fixed. Similarly, with regard to the skid plate  164 , the first portion  170  may be a portion of the skid plate  164  that translates, and the second portion  172  may be a portion, such as the rails  168  or the rack  140 , that is stationary. Alternatively, the second portion  172  may be a portion of the skid plate  164  that translates, and the first portion  170  may be a portion that is stationary.  
         [0027]     In a disengaged position, as illustrated in  FIG. 3A , the release and securement device  174  allows the first portion  170  to rotate or translate relative to the second portion  172 . In  FIG. 3A , fingers  178  of the release and securement device  174  engage teeth  176  of release and securement mechanism  174  and prevents the first portion  170  from rotating or translating relative to the second portion  172 . The fingers  178  and teeth  176  of the release and securement mechanism  174  are only one of many possible combinations capable of preventing the rotation or translation of the first portion  170  relative to the second portion  172 , and the alignment system  100  is not limited to as a particular combination so capable.  
         [0028]     Furthermore, the manner in which the release and securement mechanism  174  is actuated is also not limited. For example, an electrical servo (not shown) can be used to raise and lower the fingers  178  to respectively engage and disengage the teeth  176 . Alternatively, a hydraulic or pneumatic system (not shown) can be used to raise and lower the fingers  178  to respectively engage and disengage the teeth  176 .  
         [0029]      FIGS. 4A, 4B  disclose another example of an actuated release and securement device  174  that may be used with either the turntable  162  or the skid plate  164 . The release and securement device  174  of this particular example includes an air bearing, also referred to as a “fluid film” bearing. Although many types of air bearings may be used as the release and securement device  174 , in this particular example, a passage  184  in the first portion  170  opens to a gap  186  between the first portion  170  and the second portion  172 . A fluid (e.g., air) passes from a fitting  182  passes into the passage  184  and creates the gap  186  between the first portion  170  and the second portion  172 . When the pressure of the air passing through the passage  184  decreases to a certain point, forces (e.g., gravity, a spring) push the first and second portions  170 ,  172  together.  
         [0030]     When the first and second portions  170 ,  172  are apart, as illustrated in  FIG. 4A , the first portion  170  can rotate or translate relative to the second portion  172 . Alternatively, when the first and second portions  170 ,  172  are together, as illustrated in  FIG. 4B , friction between the first portion  170  and the second portion  172  prevents the first portion  170  from rotating or translating relative to the second portion  172 .  
         [0031]      FIG. 5  discloses yet another example of an actuated release and securement device  174  that may be used with either the turntable  162  or the skid plate  164 . The release and securement device  174  of this particular example includes a magnetic clutch. Magnetic clutches are well known, and the securement device  174  is not limited as to a particular type of magnetic clutch. In the present example, the magnetic clutch includes at least one electromagnet  190  attached to the first portion  170  or the second portion  172  and a magnetized material  192  attached to the other of the first portion  170  or the second portion  172 .  
         [0032]     When the electromagnet  190  pulls against the magnetized material  192 , the electromagnet  190 , the first and second portions  170 ,  172  are forced together. This force creates friction between the first portion  170  and the second portion  172  that prevents the first portion  170  from rotating or translating relative to the second portion  172 . When the electromagnet  190  does not pull against the magnetized material  192 , the first portion  170  can rotate or translate relative to the second portion  172 .  
         [0033]      FIG. 6  schematically illustrates the alignment system  100  with both the alignment sensing system  102  and at least one turntable/skid plate combination  160 . The controller  300  of the alignment sensing system  102  is also connected to an actuator  190  to control operation of the release and securement device  174  (not shown) attached to the turntable  162  and/or skid plate  164  of the turntable/skid plate combination  160 . Depending upon the type of release and securement device  174  used, the actuator  190  may be, for example, a relay switch to operate an electro servo or a valve to control pressure of air being supplied to an air bearing. The connections to and from the controller  300  to the actuator  190  and to and from the actuator  190  to the release and securement system  174  are not limited in any manner, and may be electrical (wireless and non-wireless) and/or mechanical.  
         [0034]     Once the vehicle  180  has been positioned on the lift  140 , and the wheels  126 ,  128 ,  130 ,  132  of the vehicle  180  are on one or more of the turntable/skid plate combination  160 , the controller  300  of the alignment sensing system  102  directs the actuator  190  to disengage the release and securement device  174  attached to the turntable  162  and/or skid plate  164 . This allows the turntable  162  to rotate and the skid plate  164  to translate. In so doing, the suspension of the vehicle  180  is placed in a “relaxed” condition. The actuator  190  may release the turntable/skid plate combinations  160  all at once. Alternatively, one or more turntable/skid plate combinations  160  may be released prior to others.  
         [0035]     Prior to the alignment sensing system  102  measuring the positions of the wheels  126 ,  128 ,  130 ,  132  of the vehicle  180  and after a position of the wheels  126 ,  128 ,  130 ,  132  on the rack  140  has stabilized, the controller  300  may direct the actuator  190  to engage the release and securement device  174  to prevent the turntable  162  from rotating and the skid plate  164  from translating. In so doing, accurate measurement of the positions of the wheels  126 ,  128 ,  130 ,  132  by the alignment sensing system  102  can be ensured.  
         [0036]     The embodiments described herein may be used with any desired alignment sensing system, including but not limited to alignment sensing systems relying upon visual information. Various aspects of the present concepts have been discussed in the present disclosure for illustrative purposes. It is to be understood that the concepts disclosed herein is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the concepts expressed herein. Moreover, although examples of the system and method were discussed, the present concepts are not limited by the examples provided herein and additional variants are embraced by the claims appended hereto.