Method of displaying vehicle wheel alignment conditions

Abstract: A method of displaying an alignment condition of a vehicle, comprising prestoring specifications for one or more wheel alignment conditions, prestoring a plurality of wheel graphics, each graphic corresponding to a difference between a measured wheel alignment condition and the specification for the wheel alignment condition, measuring the wheel alignment condition, determining the difference between the measured wheel alignment condition and the specification for the wheel alignment condition, selecting the graphic corresponding to the difference, and visually displaying the graphic.

Description: This application is based on U.S. Provisional Patent Application Serial No. 60/005,608 filed on October 19, 1995 and U.S. Provisional Patent Application Serial No. 60/005,720 filed on October 20, 1995. Background of the Invention The present invention relates to vehicle wheel aligners which may be adapted for use in performing alignments of non-standard or custom vehicles. Existing wheel aligners comprise a number of sensors for generating data indicative of the relative orientations of the wheels of a vehicle, a computer for calculating alignment values from the data generated by the sensors and a video display for displaying the alignment values. Additionally, these aligners typically comprise a database of vehicle alignment specifications for a majority of vehicle makes and models. During operation, the computer calculates the alignment values for a subject vehicle and compares these values with the alignment specifications for that vehicle. The differences between the calculated alignment values and the specifications may then be displayed. In US-A-4 574 490 the specifications are displayed graphically in combination with indications for upper and lower limits; the actual sensed alignment conditions are indicated with markers. In EP-A-0 679 865 which falls under Art. 54(3) EPC, measured conditions are represented in different colours, depending on whether they are within the specifications or not; their presentation is in reel time. Summary of the Invention According to the present invention, the aligner comprises a preprogrammed set of instructions for creating graphical representations of the alignment conditions of the vehicle based on measurements obtained both before and after adjustments have been made to the vehicle. The representations may be displayed to the operator during the alignment procedure to provide him a better understanding of the condition of the vehicle, and the representations may be printed out for presentation to the customer to evidence that the vehicle has been serviced properly. Brief Description of the Drawings Figure 1 is a representation of an exemplary wheel aligner in combination with which the present invention may be used; Figure 2 is a representation of an angle measuring instrument employed in the wheel aligner of Figure 1; Figure 3 is a flow diagram showing the sequence of steps undertaken to generate graphical representations of the conditions of the vehicle according to the present invention; Figure 4A is a table showing the visualization rules which are used to produce the graphical representations; Figure 4B is a table indexing the graphics referred to in Figure 4A with the representations shown in Figures 5A through 5G; Figures 5A through 5G are exemplary displays of the graphical representations of a vehicle; and Figures 6A through 6C are exemplary printouts of the graphical representations of a vehicle. Detailed Description of the Preferred Embodiments The present invention is primarily implemented through computer software, which can be readily recreated by the person of ordinary skill in the art by following this description. In addition, the invention may be incorporated into a variety of vehicle wheel aligners, but it is particularly useful with wheel aligners designed for use with trucks because of the existence of a great number of components requiring alignment in a truck. Therefore, for purposes of brevity the present invention will be described with reference to an exemplary truck aligner. Referring to Figure 1, an exemplary truck aligner, indicated generally by reference number 10, is shown in association with a truck which is represented by a frame F having a longitudinal axis L and a set of front wheels FW and rear wheels RW. Truck aligner 10 comprises one or more angle measuring heads 12, which are mountable to the wheels of the truck using appropriate wheel clamps 14. In Figure 1, a head 12 is shown mounted to each front wheel FW of the truck. Each wheel clamp 14 comprises a shaft 16 and suitable means for aligning shaft 16 with the axis of rotation 18 of the wheel to which it is connected, and the corresponding head 12 is pivotably mounted on shaft 16. Truck aligner 10 also comprises a console 20 to which heads 12 are connected through cables 22 or, alternatively, cordless data transceiver means. Truck aligner 10 further comprises two frame gauges 24, which each include two scales 26 connected to the opposite ends of frame gauge 24. Each scale 26 in turn comprises a pair of reference marks 28 spaced a known distance from each other. Frame gauges 24 are mounted to opposite ends of frame F using suitable attachment devices 30 having appropriate biasing means for maintaining the same distance between longitudinal axis L and each pair of reference marks 28. Each angle measuring head 12 operates to measure the angles between the axis of rotation 18 of the wheel on which it is mounted and the lines 32 extending to reference marks 28 on the same side of the truck. Referring to Figure 2, each head 12 is shown to comprise a light source 34, a collimating lens 36 for focusing the light into a thin beam 38 and a mirror 40 for reflecting beam 38 ninety degrees into an approximately horizontal plane. Mirror 40 is mounted on the shaft 42 of a motor 44, and rotation of mirror 40 by motor 44 causes beam 38 to rotate in the horizontal plane. A rotary encoder 46 mounted relative to shaft 16 continuously tracks the instantaneous angular position of shaft 42, and thus beam 38, with respect to shaft 16. Since shaft 16 is effectively aligned with the axis of rotation 18 of the wheel, encoder 46 measures the angle of beam 38 with respect to the axis of rotation 18. Reference marks 28 on targets 26 are comprised of a retroreflective material, and as rotating beam 38 impinges on a reference mark 28, it will be reflected back to head 12 and received by a detector 48. The signals from encoder 46 and detector 48 are input into an appropriate logic circuit 50, which outputs data indicative of the angle of reference mark 28 relative to shaft 16. As beam 38 rotates through 360 degrees, data relating to the angles of the other three reference marks 28 on the same side of the truck is similarly produced. The data from each head 12 is transmitted over cables 22, or via cordless data transceiver means, to console 20. Although not shown in the drawings, heads 12 may also include conventional inclinometers for measuring the orientations of the wheels with respect to known vertical reference planes to yield such information as the camber and caster angles of the wheels. The data generated by the inclinometers is transmitted to console 20 in a manner similar to that described above. Referring again to Figure 1, console 20 is shown to comprise a programmable computer 52 for controlling the operation of truck aligner 10. In one mode of operation, computer 52 processes the data generated by heads 12 according to preprogrammed instructions and displays the alignment values for the truck on a monitor 54. A keyboard 56 is provided for entering instructions and vehicle information into computer 52. Computer 52 may also access programs and vehicle information through a floppy disk or CD ROM drive (not shown). According to the present invention, computer 52 comprises a preprogrammed set of instructions for creating graphical representations of the alignment conditions of the vehicle based on measurements obtained both before and after adjustments have been made to the vehicle. Although for purposes of brevity and clarity the invention will be described with respect to the alignment of a truck, it should be understood that the principles of the invention apply to the alignment of many types of vehicles. The person of ordinary skill in the art will readily understand how the invention may be adapted for use with other types of vehicles. According to the present invention, computer 52 is provided with a set of preprogrammed instructions which will generate video and print representations of the initial conditions of the axles of the vehicle both before and after adjustments are effected. Referring to Figure 3, the video and print representations are generated by first obtaining measurements of the initial vehicle alignment values and applying the measurements thus obtained to a set of predetermined visualization rules, which are shown in Figure 4A. Based on these rules, computer 52 generates the graphic and digital representations of the conditions of the axles. These representations are then displayed on monitor 54 and, at the operator's discretion, may be printed out on a standard printer. The vehicle is then adjusted and measurements of the alignment values are again obtained. Computer 52 applies these measurements to the set of visualization rules to generate graphic and digital representations of the final conditions of the axles, which may then be displayed on monitor 54 and/or printed by the printer. As stated above, Figure 4A lists the visualization rules that computer 52 employs to generate the graphical representations of the vehicle. The rules select predetermined graphics based on the amount the measured alignment condition differs from the preferred specifications for the alignment condition. Thus, computer 52 will compare the measured alignment condition with the specifications and select one of the predetermined graphics depending on the difference. For example, if the absolute value of the measured toe, or ABS [Toe], for a subject wheel is different from the specification by less than 1.5 millimeters per meter, computer 52 will display the Straight Graphics Position graphic for the wheel. Similarly, if the measured Toe Out for a subject wheel is greater than 1.5 mm/m and less than 3.0 mm/m, the computer will select the Toe Out Graphics Position 1 graphic for the wheel. It should be understood that visualization rules for other components of a vehicle may be created in a similar fashion, and that any number of predetermined graphics may be employed in the visualization rules. Based on the graphic which the computer selects for each component of the vehicle, the computer will generate a graphical representation of the vehicle. This graphical representation will then be shown on monitor 54 to help the operator understand the alignment condition of the vehicle. In the exemplary truck aligner embodiment, the computer will apply the visualization rules to select a graphic for each axle, which usually includes two wheel sets and a connecting axle. The graphics referred to in Figure 4A are illustrated in Figures 5A through 5G, which are exemplary displays that may appear on monitor 54, depending on the measured alignment condition of a vehicle. For purposes of this description, Figure 4B references the graphics presented in Figures 5A through 5G to the graphics positions designated in Figure 4A. Thus, to view an exemplary Toe Out Graphics Position 1 graphic, reference may be made to the left wheel of the axle shown in Figure 2. Finally, Figures 6A through 6C illustrate exemplary printouts obtainable from the present invention. Thus, the operator is provided with a visual representation of the conditions of the axles before he performs the alignment adjustments. This illustration of the initial condition of the vehicle may be presented to the customer as evidence that the vehicle does indeed require service. Furthermore, the operator is provided with a visual representation of the conditions of the axles after the operator performs the alignment adjustments. This enables the operator to determine whether the alignment has been performed properly. In addition, the illustration for the final condition of the vehicle may be presented to the customer as evidence that an alignment has been performed. It should be recognized that, while the present invention has been described in relation to the preferred embodiments thereof, those skilled in the art may develop a wide variation of structural details without departing from the principles of the invention, as defined in the appended claims.

Claims: A method of displaying an alignment condition of a vehicle, comprising: prestoring specifications for one or more wheel alignment conditions; prestoring a plurality of wheel graphics, each graphic corresponding to a difference between a measured wheel alignment condition and the specification for the wheel alignment condition; measuring the wheel alignment condition; determining the difference between the measured wheel alignment condition and the specification for the wheel alignment condition; selecting the graphic corresponding to the difference; and visually displaying the graphic. The method according to claim 1, wherein the plurality of wheel graphics represents an alignment condition for an axle of the vehicle and each wheel on the axle. The method according to claim 2, wherein the plurality of wheel graphics provides a visual representation that the vehicle requires service. The method according to claim 2, wherein the plurality of wheel graphics provides a visual representation that an alignment has been properly performed. The method according to claim 2, wherein the plurality of wheel graphics provides a visual representation after an alignment operation is performed. The method according to claim 2, wherein the plurality of wheel graphics is represented in video and print form. The method according to claim 1, wherein said method further comprises the step of displaying a corresponding digital representation of a wheel alignment condition with the graphic. The method according to claim 1, wherein the step of measuring a wheel alignment condition is performed by an apparatus that includes at least one angle measuring head (12) mountable to a wheel of the vehicle for alignment with an axis of rotation of the wheel, the at least one angle measuring head (12) adapted to produce a light beam (38) projecting along an approximately horizontal plane, and a rotation device (44) adapted to rotate the beam (38) in said horizontal plane. The method according to claim 8, wherein the wheel alignment condition measuring apparatus further includes a pair of gauges (24) each mounted to opposite ends of the vehicle, said pair of gauges (24) each having a pair of reference marks (28) spaced a preset distance from each other, the pair of reference marks (28) each comprised of a retroreflective material to reflect the beam (38). The method according to claim 9, wherein the wheel alignment condition measuring apparatus further includes an encoder (46) configured to measure an angle of the beam (38) relative to the axis of rotation (18) of the wheel, and a detector (48) that receives a light beam (38) reflected from the reference marks (28).

Inventors: JOHNSON NORMAN H, O'MAHONY PATRICK, JOHNSON, NORMAN H., O'MAHONY, PATRICK
Applicants: SNAP ON TECH INC, SNAP-ON TECHNOLOGIES, INC.
Application year: 1996
Main classification: G01B11
IPC codes: B62D65, G01B11, G01C15, G09G5, B62D17