Workers and peasants, a 5-type tractor handlebar vibration analysis and evaluation of the test

 

    At present, China's holdings tractor than 800 million units, the use of a wide range, not only for agricultural operations, and is used extensively for short-distance transport. Since tractor handle a cantilever structure, single-cylinder diesel engine power, causing severe vibration handle tractor work through research found that when the hand being longer severe vibrations, light work efficiency, road feeling sluggish, and even lead to accidents, weight will lead to limb vascular spasm, joint deformity, nerve endings disorders, dizziness and memory loss and other symptoms, handlebar vibration seriously endanger the driver's health and safety, therefore, the opponent Rotary handle vibration characteristics of tractors has important theoretical significance and practical value.

 

A vibration source analysis

 

    Tractor hand vibration from the engine and road two main excitation sources.

 

1.1 Engine incentive

 

    Tractor engine is single cylinder, the balance of performance is poor, the piston and connecting rod, etc. generated by the movement of the inertia force and the gas pressure within the cylinder holding hands of the main vibration excitation source.

 

    '11 Kinetic theory shows that the internal combustion engine, four-stroke single cylinder engine torque Y 'by the cylinder gas pressure inside the torque generated? '. And the inertial force torque generated l ', composed of 11. And F are cyclical fluctuations, harmonic analysis on them can be obtained ceremony. Called for the engine angular velocity, we can see not only the torque of an engine speed should contain the same frequency corresponding to an integer multiple of the harmonic components, but also contains a 1/2 frequency harmonic components.

 

1.2 road excitation

 

    Tractor is driving on country roads, rough terrain will produce road excitation, causing vibration handle, but because of tractor tire pressure is low, when you encounter road bump at large deformation tires, road long contact time with the tire, and the tire rubber layer is very thick, to have a greater impact damping effect, the vibration caused by the impact decreases rapidly. Results of previous studies show that road excitation induced vibration handlebar handlebar vibration acceleration accelerated approach of taking only about 20% of the mouth]. Visible hand of the main vibration excitation source is the engine, which can be used instead of the static test road test, the test work greatly simplified.

 

2 handle vibration testing

 

2.1 Test methods and test equipment

 

2.1.1 Test Method the tractor parked on a flat concrete floor, hold the handle driver simulates working condition, the engine speed is 3 000 r / min, respectively, to take each measuring point measured three-acceleration signal, according to IS0 5349 -1986 (E) [31 requirements, test point (H point) should be in place between the handle and hand contact or near the origin of coordinates to be placed in the hands of the third metacarpal. (In this experiment, the H-point of the handle part of the rubber cap from the end portion 2/3 '41), the direction shown in Figure 1. In order to study the vibration transmitted across the handlebar to ensure compliance with three-axis orthogonal with each other intersect, the one sensor made law, on the other hand we take four test points (Figure 2). Bracket mounted on the handlebars. Test, the acceleration sensor test 2.1.2 Test Equipment handlebar three to measure the acceleration signal from the YE5938 dynamic data acquisition acquisition and remember with three light weight, frequency response characteristics of a good CA-YD127 record, use of the collection can be display signal directly in the field instead of the overall acceleration sensor acceleration sensor, time domain waveforms, power spectrum and the maximum and rms acceleration in order to monitor the testing process.

 

2.2 Test results and analysis

 

    Test, YE 5938 the dynamic data collection recorded data via RS 232-C serial interface AST486 transmitted to computer processing systems, the use of vibration monitoring MFD2 software for data processing and analysis, frequency analysis of 0-2000 Hz.

 

    Engines 3 000 r / min when H-point alum, yh, ‰ three directions and time-domain waveform amplitude spectrum shown in Figure 3, Figure 3 can be clearly seen in the engine excitation frequency characteristics. Xh, Philip, Z three directions of the maximum peak point of the vibration occurred at 50 Hz (ie, the engine speed is 3 000 rlmin the operating frequency) at, the other major peak point in 25,75,100,125,150, 175 and 200 Hz, etc.. The handle including the operating frequency of the frequency of vibration and the speed of 1/2, 3/2, 2,5 / 2,3,7 / 2 and 4 times the frequency of the harmonic components such as this and theoretical analysis in Section 1.1 The result is an exact match. In addition, also found that the vibration energy is concentrated in the range of 0 ~ 200 Hz, 3 direction, z direction, the most serious vibration.

 

    A, B, C, D and so the law of vibration at the point and H point is very similar to the limited space, the time-domain waveform and amplitude spectrum is omitted here. For each point of the vibration acceleration spectrum major peaks (Table 1) seen by comparing the vibration transmission in hand armrest frame is enlarged gradually, indicating that not only armrest frame structure without attenuation of the vibration effect, opposite from the engine while filling a certain degree of vibration amplification.

 

3 Evaluation of vibration at the handles

 

    This article IS05349 standards to evaluate the relative evaluation method. Standard recommended by the weighted three-axis accelerometer to evaluate the biggest one axis, Figure 4 shows the evaluation of IS05349 standard curve, which represents the four hours frequency-weighted energy equivalent acceleration of vibration disease before the onset of age 7'r by vibration and morbidity C the relationship between which four hours can be frequency-weighted energy equivalent acceleration