The automobile shock-absorbing test bench is mainly used to test the working performance of the automobile shock-absorbing device. Its detection methods include the empirical method, the pressing car body method and the shock-absorbing test bench detection method.
1. The empirical method is a method of manual visual inspection. It mainly checks from the outside whether there are cracks in the spring of the shock absorber, whether the connecting bolts between the spring and the guide device are loose, and whether the shock absorber is leaking or missing. Items such as oil and damage.
2. The car body pressing method can either manually press the car body or use the power of the test bench to press the car body. Press to make the car body move up and down, observe the working conditions of the shock absorbers and various components of the shock absorbing device, and judge based on experience whether the shock absorbers and other components need to be replaced or repaired.
3. The automobile shock-absorbing test bench can quickly detect and diagnose the working performance of the shock-absorbing device, and can conduct quantitative analysis. According to different vibration excitation methods, the shock absorption device detection platform can be divided into two types: drop type and maximum vibration type. Among them, the anti-vibration damping device detection platform can be divided into two types: force measurement type and displacement measurement type according to different detection parameters. (1) Structure and detection method of shock-absorbing testing platform 1. Working principle of the shock absorber test bench (1) Drop shock absorber test bench During the test, the car is first raised to a certain height through the lifting device, and then the support mechanism is suddenly released, causing free vibration when the vehicle falls. Use a measuring device to measure the amplitude of the vehicle body or use a pressure sensor to measure the impact pressure of the wheel on the table. After analyzing and processing the amplitude or pressure, evaluate the working performance of the automobile shock absorber. (2) The maximum vibration damping device testing platform is shown in Figure 1 (see the picture below, click to enlarge the display). Through the vibration exciter composed of the motor, eccentric wheel, energy storage flywheel and spring of the test bench, the vibration is forced to The test bench top and the shock-absorbing device of the vehicle under inspection on it produce vibrations. Cut off the power supply to the motor a few seconds after starting up, so that the energy-storing flywheel generates frequency sweep vibration. Since the frequency of the motor is higher than the natural frequency of the wheel, the frequency sweep excitation process of the energy storage flywheel gradually reducing its speed can always sweep to the natural vibration frequency of the wheel, thereby causing maximum vibration in the table-car system. By detecting the vibration curve of force or displacement during the vibration attenuation after excitation, and obtaining the frequency and attenuation characteristics, the working performance of the shock absorber of the shock absorber can be judged.
Figure-1? (See the picture below, click to enlarge the display) ***Vibration damping test bench
1-Energy storage flywheel; 2-Electric motor; 3-Eccentric wheel ; 4-excitation spring; 5-table; 6-measuring device. The force-measuring damping device detection platform and the displacement-measuring damping device detection platform. One is to measure the force during the vibration attenuation process, and the other is to measure the vibration attenuation process. The displacement amount in , their structure is shown in Figure 4-15. Due to the stable performance and reliable data of the anti-vibration damping device detection platform, it is widely used.
Figure-2 (See the picture below, click to enlarge the display)? Structure of force-measuring and displacement-measuring shock-absorbing testing platforms
a) Displacement-measuring type; b) Force-measuring type
1. 6-wheel; 2-displacement sensor; 3-eccentric wheel; 4-force sensor; 5-eccentric shaft 2. The structure of the anti-vibration damping device detection platform The anti-vibration damping device detection platform generally consists of a mechanical part and an electronic and electrical control part. (1) Mechanical part The mechanical part of the vibration damping device detection platform consists of a box and two identical vibration systems on the left and right. The structure is shown in Figure 4-16. Each vibration system consists of an upper swing arm, a middle swing arm, a lower swing arm, a support table, an excitation spring, a drive motor, an energy storage flywheel and a sensor. One end of the sensor is fixed on the box, and the other end is fixed on the table.
Figure-3? (See the picture below, click to enlarge the display) Simple diagram of the single-wheel support structure of the ***vibration-type shock-absorbing testing platform
1-Support table; 2-Upper Swing arm; 3-middle swing arm; 4-lower arm; 5-excitation spring; 6-drive motor; 7-eccentric inertia structure. The upper swing arm, middle swing arm and lower swing arm pass through three swing arm shafts and six bearings. Installed on the box.
The upper swing arm and the middle swing arm are connected to the supporting table and form a parallelogram-shaped four-bar linkage mechanism to ensure that they can move parallelly when moving up and down, and that the table top always remains level when loaded. There is a spring between the ends of the center swing arm and the lower swing arm.
One end of the drive motor is equipped with an energy storage flywheel, the other end is equipped with a flange, and there is an eccentric shaft on the flange. One end of the connecting rod is connected to the eccentric shaft through a bearing, and the other end is connected to the end of the lower swing arm.
During the test, drive the car onto the supporting platform, start the test program, and drive the motor to drive the eccentric mechanism to vibrate the entire car-table system. After the vibration reaches a stable forced vibration with an angular frequency of ω0 for several seconds, the power supply of the drive motor is cut off, and then the energy storage flywheel performs frequency sweep excitation at an angular frequency of ω0. Since the natural frequency of the wheel parked on the table is between ω0 and 0, the frequency sweep excitation of the energy storage flywheel can always cause the car-table system to vibrate. While disconnecting the power supply of the drive motor, start the sampling test device, record the data and waveforms, and then analyze, process and evaluate them. (2) Electronic and electrical control part The electronic and electrical control part of the vibration damping device detection station is mainly composed of microcomputer, sensor, A/D converter, electromagnetic relay and control software. The control software is the bridge between the electronic and electrical control part and the mechanical part of the shock-absorbing device test bench. The software not only controls the test process of the shock absorber test bench, but also analyzes and processes the data collected by the shock absorber test bench, and finally displays and prints the test results. 3． Methods for testing shock-absorbing characteristics using a testing bench (1) Car tire specifications and air pressure should meet the specified values, and the vehicle should be unloaded and not occupied. (2) Drive the wheels of each axle of the vehicle onto the shock absorption testing platform so that the tires are located in the center of the platform, and the driver leaves the vehicle. (3) Start the testing platform so that the exciter forces the car suspension to vibrate, increasing the vibration frequency to exceed the maximum vibration frequency of the oscillation. (4) After the maximum oscillation point is passed, the excitation source is turned off, the vibration frequency is reduced, and it will pass the maximum oscillation point. (5) Record the attenuation vibration curve. The ordinate is the dynamic wheel load and the abscissa is time. Measure the dynamic wheel load during maximum vibration. Calculate and display the difference between the percentage of dynamic wheel load and static wheel load and the percentage of coaxial left and right wheels. (2) The diagnostic standard for the working performance of the shock absorber device GB18565-2001 "Comprehensive Performance Requirements and Inspection Methods for Commercial Vehicles" stipulates that for passenger vehicles with a maximum design speed ≥100km/h and an axle load mass ≤1500kg, shock absorption testing should be applied The station detects the shock absorption characteristics according to the prescribed method. The absorption rate of the wheels of the vehicle under test is measured under external excitation vibration, that is, the percentage of the minimum dynamic wheel vertical load and the static wheel vertical load when the vehicle under test is vibrating. The value (also known as the wheel grounding index) should not be less than 40, and the difference in the absorption rate of the coaxial left and right wheels should not be greater than 15. The wheel contact index can characterize the working performance of the shock absorber. The wheel contact index indicates the minimum ability of the shock absorber to ensure that the wheels are in contact with the road while the car is driving. When the car is driving, the grounding index of all wheels is different. This is due to the different working performance of the shock absorbing device of each wheel, the different loads on each wheel, and the different air pressure of each wheel. If the load on each wheel is artificially made consistent with the tire pressure on the test bench, then the wheel grounding index mainly depends on the working performance of the shock absorber. Therefore, the wheel grounding index can be used to evaluate the performance of the shock absorber. In some European and American countries, shock absorber testing benches have been widely used to test the working performance of automobile shock absorbers. The main manufacturers of shock absorber testing benches used in Europe include Germany's HOFMANN and Italy's CEMB. During the inspection of the shock-absorbing testing platform they produced, the platform of the shock-absorbing testing platform and the inspected car on it vibrated vertically according to the sinusoidal law. The excitation amplitude was fixed and the frequency changed. The force sensor senses the vertical force exerted by the wheel on the platen and stores the force signal in the memory. After all the wheel shock absorbers of the entire vehicle have been tested, the microcomputer will analyze and process the force signals to obtain the grounding index of the wheels.
The reference standards recommended by the European Shock Absorber Manufacturing Association (EUSAMA) for evaluating wheel grounding index are listed in Table 4-6, which can be used as a reference when testing the working performance of shock absorbing devices in my country.
The following table: Wheel grounding index reference standard
Wheel grounding index ()? Wheel grounding status? Wheel grounding index ()? Wheel grounding status
60～100 Excellent 20～30 Poor
45～60? Good 1～20? Very poor
30～45? Fair? 0 The wheels are off the road