Automotive NVH (Noise, Vibration, Harshness) has been widely used in the industry, and occupies 1/3 of the proportion of research and development and testing in vehicle research and development and testing. In the cost of the entire vehicle, the interior parts also account for 1/3 of the entire vehicle. The application of NVH in automotive interior parts is focused on power seats, power sunroofs, and power windows. The degree of attention is accelerating with the increase in car prices, that is to say, the more high-end cars, the higher the requirements for noise, vibration and sensory comfort. The research focus of this thesis is the application of interior noise and vibration test in the industry.
For the evaluation test of car occupants’ sensory comfort, the commonly used method in the industry is the tester’s ear monitoring test, that is, the subjective test. Although it is direct, it is because of the differences between individuals and the instability of individual states. The test method has very inconsistent judgment standards, and it is difficult to control the quality stability of the overall product, resulting in a high proportion of complaints, but it is impossible to provide objective after-sales service, which is an urgent problem in the industry. How to find a method that can use objective data as the main means of judgment and at the same time guarantee the comprehensiveness of the test has become the focus of industry research. Through long-term research and development and repeated design, we finally found a suitable application method, which not only met the requirements of comprehensive testing, but also achieved the effect of using objective data as the evaluation standard. It has been recognized and praised by the industry. At present, the four major international automotive interior parts groups: American Johnson, Lear, French Virginia and Toyota, have all adopted our products.
Design purpose and main indicators
Noise floor: less than 33dB(A), we generally use A-weighted sound pressure level as the unit
Vibration cut-off frequency: less than 10Hz
Sound field environment: Approximately half free field, five sides are designed with equal sound absorption principle
Material and people entry and exit channels: including the tested products can enter and exit in an assembly line, and maintenance and operators can enter and exit
Safety environment: three-proof alarm, observation window, ventilation
Environmental control: control of temperature and humidity field
Structure description:
The silent room is lined with sound-absorbing cotton with a density of more than 40㎏/m3, and the wallboard is composed of a composite sound-absorbing material combination, that is, double-layer sound insulation board + sound-absorbing cotton + perforated sound-absorbing board. All wall materials need to be made of flame-retardant materials; in order to prevent low-frequency vibration and noise from being transmitted to the test room through the ground, the ground uses steel spring vibration isolators to hold up the floor dragon frame, and the dragon frame is covered with 6mm thick steel plate to make a floating floor . The floor can not only effectively prevent the introduction of low-frequency vibration and noise, but also the ground strength is reliable and can be demolished and reused. In order to better prevent the impact of low-frequency noise on the test, a layer of steel platform is added to the original steel platform foundation , Laying damping spring cushions. The silent room on the right is divided into two parts, with sound insulation boards in the middle, and a set of double-layer hollow glass windows, the size: 1000mm*800mm, 800mm from the ground. The outer wall structure and the ground have shock damping, and the inner sound-proof room is equipped with damping shock isolator underground, so the force is even. The shock isolator is placed in a specific location for easy positioning when relocation in the future.
Online skeleton assembly test system
Function realization:
1. Non-stop line test
2. Full inspection at the factory
3. Improve the detection rate of abnormal sound parts
4. Automatic detection to reduce the interference of human subjective factors
5. Objective judgment, data can be traced back.
6. Various forms of analysis such as sound pressure level, frequency spectrum, Song value, etc.
7. The frame is pre-lubricated before leaving the factory to reduce the abnormal noise rate of the whole chair.
Scope of application:
1. Require 100% inspection products
2. The production line is an automatic assembly line method
3. An assembly line with insufficient distance between production lines and low utilization of length space
Project example:
Online skeleton assembly test system
Function realization:
1. Non-stop line test
2. One hundred inspections at the factory
3. Improve the detection rate of abnormal sound parts
4. Automatic detection to reduce the interference of human subjective factors
5. Objective judgment, data can be traced back.
6. Various forms of analysis such as sound pressure level, frequency spectrum, Song value, etc.
7. The frame is pre-lubricated before leaving the factory to reduce the abnormal noise rate of the whole chair.
Scope of application:
1. Require 100% inspection products
2. The production line is an automatic assembly line method
3. An assembly line with insufficient distance between production lines and low utilization of length space
Project example:
Line-side whole chair assembly test system
Function realization:
1. Offline sampling, individual data analysis
2. Sample detection
3. New model and new function test data analysis.
Project example
