How to control car noises
Table of Contents
Part.1 What is the abnormal noise of the sealing strip
The abnormal sound of the sealing strip is simply described as the abnormal sound caused by the friction between the sealing strip and the parts in direct contact with it.
Part.2 Intuitively feel the abnormal sound of the sealing strip
Intuitively feel the abnormal sound of the sealing strip through the audio files of several typical abnormal sound of the sealing strip
a、 Abnormal sound of the sunroof seal under the twisted road
The high frequency component of sound is obvious and sharp, which is easy to be identified by drivers and passengers in the car, and has a greater impact on the subjective feelings of drivers and passengers
b、Abnormal sound of door seal strip under bumpy road
The sound has more middle and low frequency components, and the sharpness is not high. For inexperienced drivers and passengers, it is easy to think that it is an abnormal impact noise.
c、Abnormal sound of the sealing strip when the door is opened and closed
The sound is similar to that on twisting roads, but static operations occur much more frequently during vehicle use than on twisting roads.
Part.3 Abnormal sound characteristics of sealing strip
There are many abnormal noise points: abnormal noise may occur on the sealing strips in the car doors, rear tailgate, sunroof, water tank, etc.
There are many abnormal noise conditions: torsional conditions, bumpy conditions, and static operating conditions (opening and closing operations of doors and sunroofs) may cause abnormal noise from the sealing strip.
Part.4 Mechanism of abnormal sound of sealing strip
From a microscopic point of view, the contact surface is uneven. When the sealing strip and the contacting parts produce a relative speed, the sealing strip will not directly produce relative sliding, but will first produce elastic deformation until the maximum static friction force is reached. Finally, the sealing strip will slide relative to the contact parts. During the period from the maximum static friction to the stable sliding friction, stick-slip will occur, causing abnormal noise of the sealing strip.
In the above process, the displacement corresponding to the maximum static friction point is very important for controlling the abnormal noise of the sealing strip. We define the displacement corresponding to the maximum static friction point as the minimum abnormal noise displacement .
In the process of controlling the abnormal noise of the sealing strip, in addition to the minimum abnormal noise displacement of the sealing strip, there is another quantity that is also very important. This quantity is the single noise of the sealing strip.
Only when the actual displacement of the sealing strip is greater than the minimum abnormal sound displacement of the sealing strip, and at the same time, the single noise of the sealing strip is greater than a certain threshold, can it be clearly perceived by people.
Part.5 During the occurrence of abnormal noise of the sealing strip
During the occurrence of abnormal noise of the sealing strip, the key parameters are the actual displacement, the minimum abnormal noise displacement and the single noise. From these three parameters, two directions for controlling the abnormal sound of the sealing strip can be obtained. One direction is to control the actual displacement of the sealing strip from the perspective of the entire vehicle and the system level, and the other direction is to control the minimum from the perspective of the single sealing strip. Abnormal displacement and monomer noise.
Part.6 Control process of abnormal sound of sealing strip
A complete sealing strip abnormal noise control process should first include three stages: preliminary design, component verification and vehicle verification.
Part.7 Case analysis of abnormal sound of sealing strip
The abnormal sound of the four-door sealing strip on a bumpy road. After analysis, it was found that after the model was equipped with a sunroof, the overall rigidity of the car body decreased, resulting in an increase in the relative displacement between the door and the door frame, which in turn caused the abnormal sound of the sealing strip. This kind of abnormal sound of the sealing strip caused by the insufficient design of the overall quantity such as stiffness and mode, whether it is to increase the rigidity of the body or re-match the coating of the sealing strip, will lead to a sharp increase in cost. Therefore, in the early stage of design, it is extremely necessary to control the vehicle-level parameters such as stiffness and mode through CAE means.
The abnormal noise caused by the friction between the water tank sealing strip and the front windshield under a low temperature condition. During the analysis, it was found that the surface of the water tank sealing strip is smooth. Another form of water tank on the market is sandblasted. For processing, such a sandblasting structure will increase the minimum abnormal sound displacement of the sealing strip, which is beneficial to the abnormal sound. After the rectification, replace it with a sandblasted sealing strip, and the abnormal sound will be eliminated. This case illustrates the effect of surface treatment on the abnormal sound of the sealing strip. A good surface treatment is beneficial to the abnormal sound performance of the sealing strip.
An example of abnormal friction between the left and right front windshields and the body under bumpy conditions. Its initial design, the sealing strip and the sheet metal are in the form of point contact. After rectification, it is modified to the form of surface contact. The single noise of the sealing strip is greatly improved, so that the abnormal noise is eliminated. This case illustrates the influence of the surface contact form on the abnormal sound of the sealing strip, and a good surface contact form is beneficial to the abnormal sound performance of the sealing strip.
In the component verification stage, the surface characteristics and contact forms of the sealing strip can be matched, and the problem of unreasonable surface matching of the sealing strip can be found and solved in time to reduce the probability of problems in the later stage.
The abnormal sound of the sealing strip of the right front door on a bumpy road. It is caused by the improper control of the sealing gap of the right front door. Due to the problem of production control, the actual state of the sealing strip is inconsistent with the design state, which leads to This is a typical manufacturing problem. Such problems need to be discovered and controlled in the later stage of vehicle verification.
Summarize the role of each stage of the management and control process through the case: in the early design stage, it is mainly a control of the stiffness and modal of the vehicle level and a preliminary verification of the feasibility of the design scheme; in the component verification stage, it is mainly timely Find the gap between the stiffness, modal and other parameters of the actual parts and the relevant parameters in the CAE analysis, and timely feedback and rectify some problematic positions. At the same time, you can compare different design details of the parts through testing, and carry out the design plan And the selection of some parts. The final vehicle verification stage is to carry out the vehicle-level verification work through road evaluation, high and low temperature evaluation, etc., and complete the last pass before the car enters the market.
