Automobile Inspection Technology

Chapter 15 Automobile Chassis Inspection Technology (4)
1. Wheel Aligner

The four-wheel aligner is a device specially used to measure wheel alignment parameters.It is very suitable for the detection of four-wheel alignment parameters of vehicles with not only front wheel alignment, but also rear wheel alignment.The items that can be detected by the four-wheel aligner include: wheel toe-in and front tension angle, wheel camber angle, kingpin caster angle, thrust angle and wheelbase difference between left and right.The structure and measurement method of Cheboshi A-850/G computer four-wheel aligner are taken as an example below.

(1) The structure of the four-wheel aligner
Cheboshi A-850/G computerized four-wheel aligner is composed of four-wheel aligner host, sensor head, fixture, corner wheel, steering wheel fixing frame, charging cable, etc., as shown in Figure 3-16.

① Host: It is an operation control platform for users, mainly composed of computer, interface circuit and power supply.

②Clamp: When assembling, first clamp it tightly on the rim of the car by adjusting the knob.

③Sensor head: left front sensor head, right front sensor head, left rear sensor head, right rear sensor head, the four sensor heads cannot be interchanged.When installing, the sensor is plugged into the fixture, and the sensor is kept horizontal through the indicator light on the machine head.

④ Corner plate: Place it at the front wheel of the car on the lift. During the test, try to make the front wheel of the car face the center of the corner plate as much as possible.

⑤Steering wheel fixing frame: During the test, it is necessary to follow the prompts to ensure that the direction of the car wheels will not change by fixing the steering wheel during the test.

⑥ Brake plate fixing plate: During the test, fix the brake pedal of the car so that the car will not move back and forth during the test.

⑵ Detection method and steps
In order to facilitate detection and adjustment, the inspected vehicle should be placed on the ditch or the lifting platform, the ditch or the lifting platform should be in a horizontal state, and the four-wheel aligner should be installed on both sides of the ditch or on the lifting platform, as shown in Figure 3-17. The situation where the four-wheel aligner is installed on the lifting platform.

Preparation before testing:
① Drive the car onto the lift so that the front wheels are exactly in the center of the corner disc, and lock the corner disc with the locking pin before driving, and tighten the parking brake after driving.Hold the wheels and lift the car 0.5m (the first lift).

②Hold the body and lift the car until the wheels can rotate freely (the second lift).

③Remove each wheel, and check whether the tire pressure and tire specification, as well as the pattern type and depth of the two front wheels are consistent.

④ Do the dynamic balance test of the wheel. After the dynamic balance is completed, put the wheel back on the vehicle.

⑤ Check the height of the vehicle body, check the height of the four corners of the vehicle body and the technical condition of the shock absorber. If the vehicle body is uneven, level it first, and check whether the steering system and suspension are loose. If they are loose, fasten or replace parts first.

⑥Use the steering wheel fixing bracket to lock the steering wheel, and use the brake plate to support the brake pedal to make the vehicle immobile.Loosen the corner plate locking pin.

①Cabinet; ②Computer; ③Fixture hanger; ④Right front sensor head piece;

⑦The whole head of the right rear sensor; ⑧Clamp; ⑨Brake plate fixing frame; ⑩Steering wheel fixing frame; Corner plate; Four charging cables (short); ⑏ Two charging cables (long)
Detection steps:
①Install the fixture and sensor head correctly and keep it level.

② Turn on the host computer to enter the test program, and input the model and production year of the car under test.

③Rim deformation compensation is carried out, the steering wheel is in the straight driving position, and each wheel rotates once, and the rim deformation error can be input into the computer.

④ Lower the second lift to make the wheels fall on the platform, and press the front and rear of the car down 4-5 times to make each
Parts are down to earth.

⑤ Press down the brake pedal with the brake lock to put the car in the braking state.

⑥Turn the steering wheel to the left until the computer displays "STOP", and input the angle of left turn; then turn the steering wheel to the right until the computer displays "STOP", and input the angle of right turn.

⑦Correct the steering wheel, and the computer will display the toe-in and camber values ​​of the rear wheels.

Figure 3-17 The four-wheel aligner is installed on the lifting platform ⑧Turn down the steering wheel, and lock the steering wheel with the steering wheel lock so that it cannot be rotated.

⑨ Adjust the level of the positioning correction head installed on the four wheels to the horizontal line. At this time, the computer displays the values ​​of caster angle, kingpin inclination angle, steering wheel camber angle and toe-in angle of the steering wheel.The computer will compare the measured values, and if it does not meet the requirements (the red arrow indicates that it is out of the standard range), it will be adjusted to the standard range indicated on the computer screen (the green arrow indicates that it is within the qualified range).

⑩If "beyond the allowable range", make targeted adjustments according to the adjustment method prompted by the computer.If the problem cannot be solved after adjustment, the relevant parts should be replaced.

Pressure test the car again, turn the steering wheel left and right, observe whether the value on the screen changes, if there is any change, it should be readjusted.

Remove the alignment correction head and bracket, conduct a road test, and check the effect of the four-wheel alignment adjustment.

(Section [-]) Automobile chassis training

[Training project [-]] Detection of wheel balance

Due to the unbalanced mass of the wheel rotation, when the car is running at high speed, it will cause the wheel to jump up and down and swing laterally, which not only affects the ride comfort and handling stability of the car, but also brings great harm to the safe driving of the car. Will increase tire wear.Therefore, it is very necessary to regularly check the balance of the wheel.

1. Training purpose and requirements

①Master the method and principle of off-vehicle wheel balancer to detect wheel dynamic balance.

②According to the test results, the wheel balance can be corrected.

2. Training equipment and equipment

① 1 set of common tools.

②One off-vehicle wheel balancer.

③ 1 wheel.

3. Training content and steps

①Remove dirt, stones and old balance weights from the wheel under test.

② Check the tire pressure and charge it to the specified value if necessary.

③ Select the cone according to the size of the center hole of the rim, carefully install the wheel, and tighten it with a large pitch nut.

④ Turn on the power switch of the wheel balancer, and check whether the indication on the panel of the indication and control device is correct.

⑤ Use a caliper to measure the rim width 6 and rim diameter (can also be read from the sidewall), measure the distance a from the rim edge to the chassis with the ruler on the balancing machine, and then align the measured value with the key or the selector knob to a. , b, d value key people indicate and go in the control device.

⑥ Put down the wheel guard, press the start button, the wheel rotates, the balance test starts, and the data is collected automatically.

⑦ After the wheels stop automatically or after hearing the "beep" sound, press the stop button and operate the brake device to stop the wheels, then read the inner and outer unbalanced quantities and unbalanced positions of the wheels from the indicating device.

⑧ Lift the wheel guard and turn the wheel slowly by hand.Stop rotating when the pointing device gives an instruction (sound, light on the indicator light, brake, display dot matrix or display detection data, etc.).An indicator device is installed on the inside or outside of the rim (at the 12 o'clock position of the clock) to display the quality of the balance weight on this side.The inner and outer sides should be carried out separately, and the balance block should be firmly installed.

⑨After the balance weight is installed, new unbalance may occur, and the balance test should be carried out again until the unbalanced amount is <5g (0.3oz), and the indicating device shows "00" or "OK".When the difference in unbalance is about 10g, if the balance weight can be moved back and forth along the edge of the rim for a certain angle, satisfactory results will be obtained.The more practical experience you have, the faster you can balance.

⑩After the test, turn off the power switch.

4. Precautions for training
① Operate the wheel dynamic balancing machine in strict accordance with the operating procedures.

②Pay attention to personal safety.

[Training project [-]] Four-wheel alignment detection

The technical status of the wheel alignment parameters has a direct impact on the vehicle's handling stability, steering ability, straight-line driving performance, tire wear and fuel consumption, so it is very necessary to regularly check and adjust the wheel alignment parameters.

1. Training purpose and requirements

①Learn the installation, wiring and computer operation methods of the four-wheel aligner.

②Use the four-wheel aligner to test the wheel alignment parameters of the car.

2. Training equipment and equipment

①A set of Shenzhen Cheboshi A-850/G four-wheel aligner.

②A set of adjustment tools.

③ A car with wheels.

④One lift (including secondary lift).

3. Training content and steps

(1) Detection content

① Wheel toe (toe angle or toe value).

② Wheel camber.

③ Kingpin caster angle.

④ kingpin inclination.

⑤ Propelling angle of the rear wheel.

⑥ Retraction angle.

(2) Detection steps

Different types of four-wheel aligners have different usage methods. Here, Shenzhen Cheboshi A-850/G four-wheel aligner is used as an introduction.

① Drive the car on the lift, make the front wheel to the center of the corner disc, brake with the hand brake and lift it up.

②Use the brake lock to lock the brake pedal to the braking position.

③Install the sensor bracket (fixture), install the sensor and keep it level.

④Start the computer and make the sensor connect with the computer.

⑤ Make preparations according to the instructions of the computer.

⑥ Make eccentricity compensation for the vehicle to be tested according to the prompts, and perform detection according to the computer.

⑦Print the test results and adjust according to the results.

⑧ After the test is completed, pack the instrument.

4. Precautions for training
① Minimize unplugging and plugging sensor signal lines to avoid poor contact.

② After the car drives on the lift platform, pay attention to keep the steering wheel in the middle position.

③ After the test is completed, the computer should be turned off according to the normal procedure, and the power cannot be turned off immediately.

thinking and practice
1. What instrument is used to detect the swimming angle of the drive train, and how to detect it?
2. What are the car wheel alignment parameters?What is the role of each?
3. Briefly describe the use method of the microcomputer four-wheel aligner.

4. What are the main reasons for wheel imbalance?What are the effects of wheel imbalance?
5. How to detect clutch slippage?
6. How to use off-vehicle wheel balancer for wheel balance inspection?
7. Why do you need to test the car suspension?
8. Describe the detection method of the amount of free rotation of the steering wheel.

9. What are the requirements of the national standard for the drive train?

(End of this chapter)