Measurement And Analysis Of The Noise Of Hydraulic Power Steering Pump

The purpose of hydraulic power steering system which equipped on passenger vehicles is reducing drivers’ steering force under an appropriate steering ratio. As a core component of this system, the vibration and noise of power steering pump is one of the most important factors influence vehicle NVH level.Shortly after a new model passenger car launched, manufacturer received a lar ge number of consumer complaints. They claimed that they could hear a buzzing which differed from the normal engine noise at low speed, the problem is more e vident when steering. Clients’ complaints were so strongly that it has make an imp act to the manufacturer’s brand and sales, also, led to a high after-sales maintenan ce cost. Therefore, to reduce noise level of power steering pump, nose tests and a nalysis must be carried out.(1) Investigation and statistical analysis : Complaints about power steering pu mp’s noise began only two month after research car launched. With the increasing of sales volume and market holding volume, complaints increased to more than 200 cases per month. There is a degradation trend with the accumulation of driving mileage. On the geographical distribution, there is no significant concentration. In the entire 3 years or 100,000 km assurance period, Complains and claims are sust ained happened.(2) Interior noise caused by power steering pump are tested and analyzed in a semi-anechoic room. According to interior noise dimensional order waterfall ma p which selected from 20 mass production cars and 10 customers complains car, when the engine rotation speed is about 1500 rpm, the interior overall noise increas e suddenly, and pump’s second order noise RO2 is the main source of interior nois e. Taking the consideration of engine rotation speed, the frequency of pump’s seco nd order noise RO2 is about 533 Hz.(3) Depended on experimental analysis, the cause of diving, response and tran smit path, this dissertation has gained the following three effective noise abatement measures. 1) Excitation source improvement. By reducing load of the Power Steer ing Pump(flow) and amount of unbalance(CAM eccentricity), the pump’s second order noiseRO2’s peak are reduced 1d B(A) and 2d B(A) at the key speed 2) Redes ign belt pulley of the pump to cut down pump’s inherent frequency. This measure can effectively lessen the pump second order noiseRO2’s peak 5d B(A) at the key speed. 3) Control the vibration amplification effect of transmit path: equipped amo unts of damping material on specific area to inhibit resonance of body parts, incre ase the density of pad to absorb and insulate noise and vibration, add a rubber m at between pump oil tank blanket and body. These two measures decrease the pu mp second order noiseRO2’s peak 1d B(A) and the pump first order noiseRO1’s peak 6.4d B(A).Above mentioned measures have been completed applied on research vehicle a nd derived model. By tracking the monitoring results, those improvement can solve the noise problem of power steering pump.