Wheel alignment system

Abstract: An automatic wheel alignment system (10) for aligning the wheels of an automotive vehicle includes head units (18L, 18R, 20L, 20R) adapted for coupling to the wheels of the automotive vehicle and a hand held module. The wheel units provide angle information related to the alignment of the wheels of the automotive vehicle. The hand held module (16) is coupled to the wheel alignment units (18L, 18R, 20L, 20R) and provides information to an operator through a liquid crystal display. The hand held module (16) includes a controller and memory means. A keypad input is provided for receiving an input from the operator. The liquid crystal display includes a liquid crystal display matrix for forming an image. A contrast control means is coupled to the liquid crystal display and provides a contrast signal to the liquid crystal display.

Description: The present invention relates to an automatic wheel alignment measurement system. In particular, the invention relates to a hand held wheel alignment system. Proper alignment of the wheels of an automotive vehicle is important for both proper handling of the vehicle, as well as proper tire wear. The wheel alignment parameters which are measured and adjusted in order to achieve proper wheel alignment are camber, caster, steering axis inclination (SAI) and toe angle. Camber is defined as the angle which the wheel makes with respect to a vertical plane when looking at the wheel from either the front or rear of the automobile. Any wheel of an automobile can have camber. Caster is angle which the steering axis of a steerable wheel (typically one of the front wheels) makes with respect to a vertical plane which perpendicular to the longitudinal direction of the automobile. Steering axis inclination (SAI) is the inclination of the steering axis with respect to a vertical plane which is parallel to the longitudinal direction of the automobile. Toe was originally defined as the difference in the distance between the front edges of two opposite wheels and the distance between the rear edges of the same two wheels. Toe can also be defined in terms of a angular relationship of the plane of a wheel (perpendicular to its turning axis) relative to a predetermined longitudinal vehicle axis. When the forwardmost portions of a pair of adjacent wheels are closer together than the rear portions of those wheels, they are commonly referred to as in a "toe-in" condition. When the rear portions of wheels are closer together than the front portions, the condition is commonly referred to as "toe-out." Camber is a tire wearing angle and also affects handling of the automobile. Caster and SAI do not affect tire wear but are important for directional control. Toe is a tire wearing angle and also affects the position of the steering wheel required to maintain travel of the automobile along a straight line. Caster, Camber, and SAI are typically measured using head units coupled to the wheels of an automobile and attached to a hand held module. For example, U.S. Patent No. 4 594 789 by Marino et al describes an automatic wheel alignment system and is incorporated herein by reference. Prior art automatic wheel alignment systems typically require a console which is set apart from the automobile. Often, it is difficult for an operator to view the console while simultaneously adjusting camber, caster, SAI, and toe of the wheel. US-A-4 718 759 describes a wheel alignment system for measuring wheels of a vehicle. There is provided one or more pairs of wheel unit sensor assembly units, each of a pair of which can be mounted via a wheel clamp assembly upon the parallelly disposed wheels of the vehicle to measure the wheel alignment angles of the steerable and non-steerable wheels of the vehicle. In the patent abstracts of Japan volume 14, No. 348 (E-957) of JP-A-02121571 a remote controller is described with a liquid crystal display coupled to the controller. There is a continuing need for an automatic wheel alignment system which is convenient to use and provides an improved user interface. The present invention is an automatic wheel alignment system for aligning the wheels of an automotive vehicle. The wheel alignment system includes four head units adapted for coupling to the wheels of the automotive vehicle. The head units are coupled to a hand held module which provides alignment information to an operator. The hand held module includes a communication means operably coupled to the head units for receiving angle measurements and providing an output. A memory stores computer program instructions and vehicle specification information. An input means receives an input from an operator. A microprocessor coupled to the communication means, the memory and the input means provides a display data output related to an angular relationship of the wheels of the vehicle. A liquid crystal display is coupled to the microprocessor and includes a liquid crystal display matrix for forming an image based upon the display data output. A contrast control means coupled to the liquid crystal display provides a contrast signal. A liquid crystal display back light control controls back lighting to the liquid crystal display. The hand held module provides audible feedback to an operator so that the wheels can be aligned without visually monitoring the display. The invention is described in detail in connection with the drawings in which: Figure 1 shows a wheel alignment system in accordance with the present invention coupled to the wheels of an automotive vehicle. Figure 2 is a front view of a hand held module for the wheel alignment system of Figure 1. Figure 3 is a perspective view of the hand held module. Figure 4 is a block diagram of the wheel alignment system of the present invention. Figure 5 is a diagram which shows the relationship of Figures 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5I, 5J, and 5K. Figures 5A through 5K show a schematic diagram for a hand held module in accordance with the present invention. Figure 6 shows a block diagram of a liquid crystal display module. Figure 7 shows a flow chart of a method for generating audible signals in accordance with the present invention. In Figure 1, wheel alignment system 10 of the present invention is used to measure the alignment of left front wheel 12L, right front wheel 12R (shown in phantom), left rear wheel 14L, and right rear wheel 14R (shown in phantom) of an automotive vehicle. For clarity, the remaining portions of the vehicle are not shown. System 10 includes a hand held module 16, left and right front head units 18L and 18R, and left and right rear head units 20L and 20R. Head units 18L, 18R, 20L, and 20R are connected to hand held module 16 through power source 17. Head units 18L, 18R, 20L and 20R are supported on wheels 12L, 12R, 14L and 14R by rim clamps 22L, 22R, 24L and 24R, respectively. Rim clamps 22L, 22R, 24L and 24R are self-centering, four-leg rim clamps which fit a wide range of different wheel sizes without the need for special adapters. Each head unit (18L, 18R, 20L, 20R) includes a housing 25, a sleeve 26 and an arm 27. Sleeve 26 mounts over a spindle of the corresponding rim clamp. Each head unit (18L, 18R, 20L, 20R) is locked into position on the spindle of the corresponding rim clamp (22L, 22R, 24L, 24R) by spindle clamp 28. A bubble level 29 mounted on arm 27 provides a visual indication to the mechanic that the head unit (18L, 18R, 20L, 20R) is level horizontally before spindle clamp 28 is clamped. A set of switches 30 on housing 25 allows an operator to signal hand held module 16 that a measurement should be made and to respond to messages displayed by hand held module 16. In wheel alignment system 10 shown in Figure 1, there are a total of six angle sensor units which are used to measure toe angles and a total of four sensors which are used to measure camber and pitch values. (New wheel units will have six sensors for camber and pitch.) Front left head unit 18L carries left-to-right sensor 32L and front-to-rear sensor 34L. Left rear head unit 20L carries rear-to-front angle sensor 36L. Right front head unit 18R includes right-to-left sensor 32R and front-to-rear sensor 34R. Right rear head unit 20R carries rear-to-front angle sensor 36R. The angle sensor units are arranged to operate as pairs. Sensors 32L and 32R are mounted at the front ends of arms 27 of front head units 18L and 18R and face one another. Sensor 34L is mounted at the rear of housing 25 of head unit 18L and faces sensor 36L which is mounted at the front end of head unit 20L. Similarly, sensor 34R of head unit 18R faces sensor 36R of head unit 20R. Figure 2 shows a front view of hand held module 16. Hand held module 16 includes liquid crystal display 100 and operator buttons 102L and 102R. Buttons 102L are positioned for operation by the left hand of an operator. Similarly, operator buttons 102R are positioned for right hand operation. Figure 3 is a perspective view of hand held module 16 and shows left hand grip region 104L and right hand grip region 104R. Cable 106 connects hand held module 16 to power supply 17. Figure 4 is a block diagram of a wheel alignment system 10 of the present invention. Wheel alignment system 10 is centered around controller 122. Controller 122 is connected to memory modules 124 and 126 and memory cartridge 128. Controller 122 is also connected to keypad 130 and audio output 132. Controller 122 is connected to liquid crystal display 134 through driver 136. Controller 122 is also connected to left front head unit 18L, right front head unit 18R, left rear head unit 20L, and right rear head unit 20R through power supply/interface 17. As shown in Figure 4, controller 122 is connected to head units 18L, 18R, 20L, and 20R through power supply/interface 17 and a communication/power bus 140. Bus 140 consists of cables 90L, 90R, 92L, 92R, and 106 shown in Figure 1. Figure 5 shows the relationship between Figures 5A through 5K. Figures 5A through 5K show the schematic diagram for controller 122, memory 124 and 126 and audio output 132 shown in Figure 4. An optional printer 141 connects to communication/power bus 140. Figure 5A shows integrated circuit 314 which includes address lines A0 through A12 and data lines DO through D7. Integrated circuit 314 comprises an 8K EEPROM such as µPD28C64. Integrated circuit 314 is connected to a +5 volt power supply and ground. Integrated circuit 314 includes a CE input. Figure 5B shows controller 316. In a preferred embodiment, controller 316 comprises an 80C188 microprocessor. Controller 316 includes VCC connections to a +5 volt supply and VSS connections to electrical ground. Crystal 318 is connected to ground by capacitors 320 and 322 and is connected to X1 and X2 inputs to controller 316. Inputs T10, T11 and TEST are connected a +5 volt power supply. RES input to integrated circuit 316 connects to a +5 volt power supply through diode 323 and resistor 324. Capacitor 325 connects RES input to electrical ground. DRQO, DRQ1, INT1, INT2, and NMI inputs to controller 316 are connected to electrical ground. Interrupts inputs INTO, and INT3 are connected to an INT bus. ARDY and SARDY inputs are connected to the +5 volt supply. A HOLD input to controller 316 is connected to electrical ground. PCSO through PCS5 (Peripherial Chip Select) lines are connected to a PCS bus. Controller 316 includes address outputs AD0 through AD7 and A8 through A19. WR, RD, CLK, and RST lines are connected to a control bus. Figure 5C shows integrated circuit 330 having data inputs D0 through D7 and outputs Q0 through Q7. Integrated circuit 330 is a buffer such as an HC373. Integrated circuit 330 includes a +5 volt power supply connection and a ground connection. Integrated circuit 330 includes an enable input. Data inputs DO through D7 of integrated circuit 330 are coupled to address outputs AD0 through AD7 of controller 316. Integrated circuit 332 shown in Figure 5C includes DO through D7 inputs and Q0 through Q3 outputs. Integrated circuit 332 comprises a buffer such as an HC373. Integrated circuit 332 includes a +5 volt power supply connection and a ground connection. Integrated circuit 332 also includes an enable input which is coupled to integrated circuit 316 shown in Figure 5B. Integrated circuit 334 includes address inputs A0 through A14, data lines D0 through D7, a VCC power supply connection, and a ground connection. Integrated circuit 334 comprises a 32K RAM such as a 62256. Integrated circuit 334 includes output enable and write enable inputs connected to control data bus CONTL. Integrated circuit 334 is also connected to OR gate 336. OR gate 336 is connected to address bus ADDR and integrated circuit 316 shown in Figure 5B. Figure 5D shows integrated circuit 338 having address inputs A0 through A14 connected to address bus ADDR and data connection DO through D7 connected to data bus DATA. Integrated circuit 338 comprises a 32K RAM such as a 62256. Integrated circuit 338 includes a VCC power supply connection and a ground GND connection. Integrated circuit 338 also includes CE , OE , and WE connections. The CE connection to integrated circuit 338 is connected to OR gate 340 which has one input connected to invertor 342 shown in Figure 5C. OR gates 336 and 340 and invertor 342 form a RAM chip select circuit 344. Figure 5D also shows liquid crystal display contrast control circuitry 350. Liquid crystal display contrast control circuitry 350 includes integrated circuit 352 and OPAMP 354. Integrated circuit 352 comprises an AD558 and is connected to a +5 volt power supply and electrical ground. Integrated circuit 352 includes DB0 through DB7 inputs which are connected to a data bus. Integrated circuit 352 also includes a voltage output V out which is connected to the non-inverting input of OPAMP 354 through a resistor 356. Non-inverting input is also connected to ground through resistor 358. The inverting input of operational amplifier 354 is connected to a +5 volt supply through resistor 360. Feedback is provided from the output of operational amplifier 354 through resistor 366. Operational amplifier 354 is also connected to the +5 volt power supply and a -20 volt power supply. Figure 5E shows an EPROM chip select circuit 370. EPROM chip select circuit 370 comprises OR gates 372 and 374, NOR gate 376 and invertor 378. OR gate 372 and NOR gate 376 are coupled the address bus ADDR and invertor 378 is connected to the control bus CONTL. Figure 5E also shows liquid crystal display control circuit 380. Liquid crystal display control circuit 380 includes buffer 382, NOR gate 384, invertor 386 and integrated circuit 388. Integrated circuit 388 comprises an HC175 and includes a +5 volt power supply connection and a ground connection. Integrated circuit 388 include clear, clock, and D0 through D3 inputs and Q0 through Q3 outputs. Figure 5E also shows liquid crystal display back lighting control circuitry 390. Liquid crystal display back lighting control circuitry 390 includes integrated circuit 392 and transistor 394. Integrated circuit 392 comprises an AD558 having data inputs DB0 through DB7 connected to the data bus. Integrated circuit 392 also includes power supply VCC and ground connections. An output VOUT from integrated circuit 392 is connected to the base of transistor 394. The emitter of transistor 394 is connected to ground through a resistor 396. Resistor 396 comprises a 7.5Ω resistor. Figure 5F shows liquid crystal display connector 398 and memory cartridge connector 400. Liquid crystal display connector 398 is connected to the data bus. In a preferred embodiment, liquid crystal display connector 398 connects an LMH4129BG5212 available from Densitron Corporation of Torrance, California. Memory cartridge connector 400 is coupled to the data bus and address bus and is designed to connect to EPROM modules. Figure 5G shows +5 volt regulator circuit 402, -20 volt regulator circuit 404. +5 volt regulator circuit 402 comprises integrated circuit 408, capacitor 410, and capacitor 412. Integrated circuit 408 comprises a 78SR105 IC with an input connected to a +12 volt source. Integrated circuit 408 provides a +5 volt output. Filter capacitor 414 is connected between the +5 volt output and ground. Filter capacitor 414 comprises a 22 µFarad capacitor. -20 volt regulator 404 includes an integrated circuit 416. Integrated circuit 416 is an MAX637 and has a power supply input connected to the +5 volt power supply through diode 418. The power supply input to integrated circuit 416 is also connected to electrical ground through capacitor 420. A voltage output from integrated circuit 416 is connected to electrical ground. A VREF input is connected to electrical ground through capacitor 422. A VFB connection to integrated circuit 416 is connected to the VREF connection through resistor 424. Resistor 424 comprises a 10K Ω. An LB1 connection to integrated circuit 416 is connected to GND. The -20 volt output is connected to the LX connection of integrated circuit 416 through diode 434 and to electrical ground and a VOUT connection to integrated circuit 416 through inductor 436. Inductor 436 comprises a 330 µH inductor. The -20 volt output connects to electrical ground through capacitor 438 and 440. Capacitor 438 comprises a 0.1 µFarad and capacitor 440 comprises a 100 µFarad capacitor. The -20 volt output also connects to the VFB connection to integrated circuit 416 through 140K Ω resistor 442. Figure 5H shows Darlington pair driver circuit 446. Darlington pair driver circuit 446 includes transistors 448 and 450, speaker 452, and resistors 454 and 456. Transistor 448 comprises a PNP transistor. Transistor 450 comprises an NPN transistor. The base of transistor 448 is connected to integrated circuit 316 through resistor 456 and capacitor 458. The base of transistor 448 is also connected to a +12 volt power supply through resistor 454. Resistor 454 comprises a 4.7K Ω resistor and resistor 456 comprises a 1.24K Ω resistor. Figure 5I shows integrated circuit 460 having a VDD connection to the +5 volt power supply and a ground connection connected to electrical ground. Integrated circuit 460 comprises a UART such as a 71-05171051. Integrated circuit 460 includes data inputs D0 through D7 connected to the data bus. Figure 5J shows integrated circuit 462. Preferably, integrated circuit 462 comprises an HC175 latch. Integrated circuit 462 include data inputs DO, D1, D2, and D3. Integrated circuit 462 include CLK input connected NOR gate 464. Integrated circuit 462 includes a CLR input connected to a +5 volt power supply. Integrated circuit 462 is also connected to keyboard connector 466 through diode 468, 470, 472, and 474. Integrated circuit 462 is also connected to the +5 volt power supply and electrical ground. Keyboard connector 466 includes ROW connections ROW1, ROW2, ROW3, AND ROW4 and column connections COL1, COL2, and COL3. Keyboard connector 476 includes ROW connection, ROW1, ROW2, ROW3, and ROW4 and column connections COL4, COL5, and COL6. Keyboard connectors 466 and 476 are connected to electrical ground through resistors 478. Resistors 478 comprise 1K Ω resistors. Keyboard connectors 466 and 476 are coupled to the DATA bus through tri-state buffers 479, 480, 482, 484, and 486. Keyboard connectors 466 and 476 are also connected to the system interrupt through multi-input NOR gate 488. Keyboard connectors 466 and 476 are also connected to DATA bus through gate 490 which is also connected to NOR gate 464 through invertor 492. Figure 5K shows connector 496 for connected to wheel units. Connector 496 include +12 volt, ground, data, and command connections. Connector 496 is connected to the +12 volt power supply through capacitor 498 and 500. Connector 496 is connected to integrated circuit 460 through driver transistors 502 and 504, resistors 506, 508, 510, and 512 and invertors 514 and 516. Connector 496 is also connected to integrated circuit 460 through invertor 518 and 520, and resistor 522. In the circuit diagram of Figures 5A through 5J, liquid crystal display connector 398 connects to liquid crystal display 134 shown in Figure 4. Driver circuitry 136 of Figure 4 includes liquid crystal display control circuit 380, liquid crystal display back lighting control 390, and liquid crystal display contrast control 350. Audio output block 132 shown in Figure 4 include speaker driver 446. Keypad 130 shown in Figure 4 connects to keypad connectors 466 and 476. Connector 496 provides a serial data connector for coupling to head units 18L, 18R, 20L, and 20R through power supply/interface 17. Figure 6 shows a liquid crystal display module 134 in accordance with the present invention. Liquid crystal display module is coupled to connector 398 and is in communication with controller 316. Liquid crystal display module 134 includes liquid crystal display matrix 612, interface 614, back light 616, contrast circuitry 618, and driver 136. Driver 136 is connected to liquid crystal display matrix 612 to drive the liquid crystal element in matrix 612. Contrast control circuitry 618 is connected to control the contrast of liquid crystal display matrix 612. Back light 616 is positioned to provide a lighting source for liquid crystal display matrix 612. In operation, an operator connects head units 18L, 18R, 20L, and 20R to wheels 12L, 12R, 14L, and 14R of an automotive vehicle. Head units 18L and 18R are connected to power supply 17 through multiconductor cables 90L and 90R, respectively. Head units 20L and 20R are connected to power supply 17 through multiconductor cables 92L and 92R, respectively. Cables 90L, 90R, 92L, and 92R carry power to head units 18L, 18R, 20L, and 20R. Cables 90L, 90R, 92L, and 92R also are used by alignment system 10 to communicate with head units 18L, 18R, 20L, and 20R. Hand held module 16 is connected to power supply 17 and receives power through cable 106. Cable 106 is also used for communication with head units 18L, 18R, 20L, and 20R. During operation, an operator can move hand held module 16 around the vehicle while wheels 12L, 12R, 14L, and 14R are aligned. Power supply/interface 17 is mounted on a wall or table (not shown) or may be contained in a rack (not shown) which is used to lift the vehicle. The operator receives instructions through display 100 and enters commands and information through buttons 102L and 102R on hand held module 16 or through buttons 30 on head units 18L, 18R, 20L, and 20R. Alignment system 120 is controlled by microprocessor 316 shown in Figure 5B. Controller 316 stores information in RAMs 334 and 338. Controller 316 receives input from the operator through keypad 130 which is connected to keyboard connectors 466 and 476. Each time a key on keypad 130 is pressed, an interrupt is triggered in controller 316. Hand held module 16 is capable of audio output using speaker 452 driven by transistors 448 and 450 under the control of controller 316. Hand held module 16 includes circuitry to generate various power supply values. The +5 volt power supply is created using integrated circuit 408. The power source for integrated circuit 408 is a +12 volt power supply provided from power supply/interface 17 shown in Figure 4. A -20 volt power supply is derived from the +5 volt power supply using integrated circuit 416. Controller 316 is coupled to memory cartridge 128 through connector 400. Memory cartridge 128 provides information related to wheel alignment for various make and model year automobiles. Memory cartridge 128 also carries program instructions used by controller 316. Memory cartridge 128 is replaceable and may be updated for subsequent model years. Memory cartridge 128 includes a read only memory for storing the information. Hand held module 16 is connected to head units 18L, 18R, 20L, and 20R by a serial data bus through connector 496. UART 460 is used for serial communication so that data and instructions may be exchanged between controller 316 and head units 18L, 18R, 20L, and 20R. Head units 18L, 18R, 20L, and 20R include microprocessors (not shown) for controlling head unit operation. The microprocessors in head units 18L, 18R, 20L, and 20R communicate with controller 316 through UART 460. Liquid crystal display 134 is connected to the circuitry shown in Figures 5A through 5K through connector 398. Liquid crystal display contrast control circuitry 350 is used to control the contrast of liquid crystal display matrix 612 through contrast circuitry 618. Liquid crystal display contrast control circuitry 350 includes a digital-to-analog conversion integrated circuit 352 which converts an 8 bit word received on inputs DB0 through DB7 into a voltage level which is applied to OPAMP 354. The output of OPAMP 354 is applied to contrast circuitry 618. Back light 616 in liquid crystal display module 134 is controlled by liquid crystal display back lighting control circuitry 390. Integrated circuit 392 receives a digital value on inputs DBO through DB7 from the DATA bus. This input is converted into an analog value and applied to the base of transistor 394. In a preferred embodiment, back light 616 comprises a light emitting diode. Liquid crystal display control 380 provides input for liquid crystal display driver 136. Three databits are used to control driver 136 using integrated circuit 388. Integrated circuit 388 is clocked using NOR gate 384. Clock signals are provided to driver 136 through invertor 382. A reset signal can be sent to interface 614 using invertor 382. EPROM chip select circuit 370 is used to select memory chips in memory cartridge 128 which is connected to memory cartridge connector 400. During operation, the present invention allows an operator to align the wheels of the vehicle without viewing display 134. Speaker 452 is used to audibly indicate the alignment of a wheel. For example, a first tone indicates that an adjustment has been made too far in a first direction, a second tone indicates that an adjustment has been made too far in a second direction while a third tone indicates that the adjustment is within a predetermined tolerance of the desired value. These tones may be of different frequencies or comprise a series of frequency pulses. In another embodiment, a short low-to-high tone will sound when an adjustment meter goes into specification range and a short high-to-low tone will sound when an adjustment meter goes out of specification range. Figure 7 shows a flow chart 522 of the steps used to generate an audible tone in accordance with the present invention. The steps of flow chart 522 are performed by controller 316. At block 524, controller 316 obtain angle measurements for the wheels of the automotive vehicle and control is passed to block 526. At block 526, the measurement is compared with specified limits for the automotive vehicle under test and control is passed to block 528. At block 528, if the measured value is within specification, control is passed to block 530. If the measured value is not within specification, control is passed to block 532. At block 530, a first audible signal is provided which indicates that the measured value is within specification. At block 532, a second audible signal is provided which indicates that the measured value is not within specification. Both block 530 and block 532 return control to block 524 where subsequent measurements are obtained. To further simplify operation, display 100 of hand held module 16 provides information in the form of icons to a system operator. These icons direct the operator through the steps of wheel alignment in an easy to read format. The icons are generated by controller 316. The present invention may be powered using a car battery. Therefore, the alignment system is easily moved to remote locations. Furthermore, the present invention is suitable for aligning the wheels of a truck on-site, outside of a garage.

Claims: An automotive vehicle wheel alignment system for aligning the four wheels of an automotive vehicle, comprising: a left front head unit for coupling to a left front wheel of the automotive vehicle and providing an angle measurement output; a right front head unit for coupling to a right front wheel of the automotive vehicle and providing an angle measurement output; a left rear head unit for coupling to a left rear wheel of the automotive vehicle and providing an angle measurement output; a right rear head unit for coupling to a right rear wheel of the automotive vehicle and providing an angle measurement output; The wheel allignment system characterized by a hand held module operable coupled to the left front head unit, the right front head unit, the left rear head unit, and the right rear head unit for obtaining wheel alignment measurements and providing alignment information to an operator, the hand held module comprising: communications means operably coupled to the head units for receiving angle measurements and providing an output; memory means for storing computer program instructions; input means for receiving an input from the operator; a controller coupled to the communications means, the nonvolatile memory means and the input means for processing the output from the communications means based upon the input from the operator and computer program instructions in the memory means and providing a display data output related to an angular relationship of the wheels of the automotive vehicle; a liquid crystal display coupled to the controller wherein the liquid crystal display includes a liquid crystal display matrix for forming an image based upon the display data output from the controller; and contrast control means coupled to the liquid crystal display for providing a contrast signal to the liquid crystal display whereby contrast of the image formed by the liquid crystal display matrix is controlled by the contrast signal. The automotive vehicle wheel alignment system of claim 1 including a liquid crystal display back light control means for controlling back lighting of the liquid crystal display. The automotive vehicle wheel alignment system of claim 1 or 2 wherein the hand held module includes a housing having a plurality of buttons, the housing adapted for being held by an operator such that the buttons are operable. The automotive vehicle wheel alignment system of any of claims 1 to 3 including a power supply/interface connected to the left front head unit, the right front head unit, the right rear head unit, the left rear head unit, and the hand held module for providing power to the left front head unit, the right front head unit, the left rear head unit, the right rear head unit, and the hand held module and providing a communications path between the hand held module.and the left front head unit, right front head unit, left rear head unit, and right rear head unit. The automotive vehicle wheel alignment system of any of claims 1 to 4 including means for providing a first audible signal in response to a first relationship between a measured alignment angle of the automotive vehicle and a predetermined alignment angle specified for the automotive vehicle and for providing a second audible signal which is different from the first audible signal in response to a second relationship between the measured alignment angle of the automotive vehicle and the predetermined alignment angle specified for the automotive vehicle. The automotive vehicle wheel alignment system of any of claims 1 to 5 wherein the hand held module includes a removable non-volatile memory cartridge for storing automotive vehicle wheel alignment specifications. The automotive vehicle wheel alignment system of any of claims 1 to 6 including power down interrupt means for providing an interrupt to the controller upon detection of loss of power to the hand held module whereby information related to wheel alignment is stored in the memory means by the controller.

Inventors: ALUSICK MICHAEL P, KERCHEK GARY R, KLING MICHAEL J, KRUEGER JEFF C, SCHMITZ DUANE M, VISSER JAMES LEONARD, ALUSICK, MICHAEL P., KERCHEK, GARY R., KLING, MICHAEL J., KRUEGER, JEFF C., SCHMITZ, DUANE M., VISSER, JAMES LEONARD
Applicants: SPX CORP, SPX CORPORATION
Application year: 1992
Main classification: G01B11
IPC codes: B62D17, G01B11