A method of estimating wave speed in a pipe was proposed by the authors. The estimation process is thought to be influenced by the nature of transient phenomenon in a pipe, the optimized finite element model used as a pipeline dynamics model, and the identification algorithms Major factors that may influence the estimation process are investigated, such as valve operating time, pressure noise caused by quick valve operation, the relationship between the number of elements of the pipeline model, a sampling time and regression gain of identification algorithms. The effects of the major factors are illustrated through experimental study.

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In an automotive hydraulic power steering system a variable-displacement vane pump, which is equipped with a control de vice for adjusting the eccentricity of the cam ring appropriately according to the pump rotational speed (ie., vehicle speed), has gradually begun to be used for energy saving in place of a fixed-displacement vane pump. However, fluid-borne noise radiated into the passenger compartment has greatly increased following this replacement, and therefore countermeasures to reduce pump source flow ripple have been required more than anything else to further spread its usage. This paper presents development research of a quieter (low-fluid-borne noise level) variable-displacement vane pump for HPS systems. First, it is indicated based on both the measurements and simulation analysis of pump source flow ripple that the excessive increase of fluid borne noise produced by existing variable-displacement vane pumps is mainly caused by vane bounce occurring in the trapping sections near dead centers, which is difficult to prevent when conventional cylindrical (completely round profile) cam ring is used Next, a new cam ring profile for preventing vane bounce called the “modified profile cam ring” is proposed and its effectiveness is examined by noise tests in the passenger compartment of a real car as well as measurements of pump source flow ripple in the bench test circuit The proposed cam ring is found to be able to reduce fluid-borne noise at least to the level of a fixed pump. The newly developed types of pumps have already been put into practice in several kinds of automobiles.

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A hydraulic silencer called a “resonator hose”, that places flexible metal tubes (called a “tuning cable”) inside a section of reinforced hose coaxially, is commonly used in automotive power steering hydraulic lines to suppress transmission of pump-induced pressure pulsation and thus reduce fluidborne noise radiated into the passenger compartment. However, finding the optimum design configuration for the resonator hose has been a matter of experience-based trial and error because an accurate mathematical model for pulsation attenuation characteristics of a resonator hose had not been established. This paper presents an optimum design method for a resonator hose, taking into consideration every key circuit factors in a real power steering system. First, a method of determining experimentally the viscoelastic properties of the hose wall from measured transmission loss characteristics, which is necessary for establishing a mathematical model for the resonator hose, is proposed and discussed with estimated results. Next, a successful mathematical means (optimum design method) is outlined for sizing the desired variables (lengths of tuning cables and hose) so that the performance function designated in terms of pressure pulsations is minimized under the designated constraint conditions Calculated results of attenuation characteristics of eight kinds of optimally designed resonator hoses all agree well with experimental results.

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