汽车空调嘶声测试

汽车空调嘶声测试

Christopher Lietz

【摘 要】介绍了适合于车辆空调热膨胀阀(TXV)的嘶嘶声和流动声的测试方法.嘶嘶声测试系统包括人工头、麦克风和加速度传感器,它可以采集噪声和振动信号,并通过观察窗来评估流过位于TXV前部的液体管里的冷凝剂的质量.测试表明,嘶嘶声的根本原因是制冷剂没有完全冷凝成液态,致使气体和液体的混合物进入TXV,混合物的膨胀产生嘶嘶声.若制冷剂是以液体形式进入热膨胀阀,嘶嘶卢基本就听小到了.TXV的设计(文章中没有涉及)和蒸发器的隔离均对嘶嘶卢有影响.此外还采用本文所提出的测试方法进行了实际测试和原因分析.

【期刊名称】《汽车工程学报》

【年(卷),期】2011(001)004

【总页数】9页(P263-271)

【关键词】空调;风扇;热膨胀阀;测试方法;高通滤波器

【作 者】Christopher Lietz

【作者单位】美国贝洱公司 密歇根 特洛伊48083 美国

【正文语种】中 文

【中图分类】TB5353

Automotive occupant noise comfort is very important during vehicle

HVAC(Heating, Ventilation and Air Conditioning) operation.This paper reviews vehicle and HVAC noise test methods relating to thermal

expansion valve (TXV) “hiss noise”；the current test methods associated

with testing TXVs；enhancements to the procedures to improve

repeatability；post processing and filtering techniques to quantify

transient hiss noise；possible causes of the noise.Figure 1 shows a typical

TXV based system and the location of the TXV related to the other

components in the system. Figure 2 shows an exampleof a typical

automotive thermal expansion valve.1

1 Noise Measurements

1.1 Vehicle Noise Testing

In-vehicle climate control noise is typically measured in a semi-anechoic

room using a binaural head. To assess noise from the front HVAC

module,the binaural head is typically located in the driver seat. For an

HVAC module located in the rear of the vehicle, the binaural head should

be located in the rear-most seating position closest to the module. Here

are a set of typical in-vehicle test set-up parameters:

(1)Place a binaural head in the driver seat and in the rear seat for rear

HVAC modules. Adjust the seat travel to the relevant customer, internal, or

industry standard. A typical position for the binaural head for front HVAC

measurements would be with the seat adjusted so that the facial reference

point of the binaural head being 450 mm from the top front of the

steering wheel [1]. Position all panel registers in a neutral position；verify

that there is no direct air flow from the panel registers impinging on either

ear of the binaural head. Adjust panel registers slightly if needed to prevent flow-induced noise at the ears of the binaural head while keeping

the registers as close to neutral as possible.

Fig.1 Typical TXV Refrigeration System

Fig.2 Typical Automotive TXV

(2) Mount a speed sensor to measure the compressor speed. An optical

speed sensor can be used. It is preferred to measure the compressor speed

from the clutch of the compressor rather than the pulley so that the clutch

engagement can be seen in the data. Place the re flective strip for the

optical RPM sensor on the front face of the compressor clutch.

(3)Measure the voltage to the compressor clutch either at the clutch relay

or at the clutch connector.

(4)Measure the voltage of each of the condenser fans if they are

electrically driven, or measure the revolutions per minute of the condenser

fan with an optical sensor if it is engine driven.

(5)Set up data acquisition to record the compressor speed, noise levels,

compressor voltage,condenser fan voltage and ambient air temperature.If

the data acquisition system is not capable of measuring all of the signals

on the same system, then two systems can be used as long as a

synchronization signal is able to be measured on both systems.

1.2 Vehicle Expansion Valve Hiss Root Cause Testing

Once it has been established that there is an issue with hissing noise from

the refrigerant system, a well thought out test plan should be developed. A

thorough understanding of what causes a system to “hiss”can help

avoid unnecessary testing and reduce costs associated with the testing. What causes hiss? Hiss is typically caused by refrigerant that is not

completely in liquid form passing through an expansion valve, and once

understood looking at the most logical things first can help root cause the

problem.

1.2.1 Refrigerant Charge

Does the vehicle have a proper charge of refrigerant? Check if the system

is leaking. The suspect vehicle should have the refrigerant charge amount

verified. The quickest but least accurate way to check if a vehicle is low on

refrigerant is to simply monitor low side system pressures. If the system

pressure is abnormally low, this could be a possible cause of hiss. Another

method and the most accurate way to measure charge is performing a dry

ice extraction (this will be explained later). The third way is to simply

evacuate the system and recharge the system with a proper charge

amount and retest the vehicle for hiss. Figure 3 demonstrates the effect of

refrigerant charge amount and noise.

Fig. 3 Acoustic Plot Showing Effects of Refrigerant Charge