Search Results

This research aims presents the method classifying the noise source and evaluating the sound quality of the noise caused by operating of electric power steering wheel in an electric vehicle. The steering wheel has been operated by the motor drive by electric power and it called motor-driven electric power (MDPS) system. If the motor is attached to the steering column of the steering device, it is called C-MDPS system. The steering device of the C-MDPS system comprises of motor, bearings, steering column, steering wheel and worm shaft. Among these components the motor and bearings are main noise sources of C-MDPS system. When the steering wheel is operated in an electric vehicle, the operating noise of the steering device inside the vehicle is more annoying than that in a gasoline engine vehicle since the operating noise is not masked by engine noise. Defects in the C-MDPS system worsen the operating noise of the steering system.

It is widely believed or speculated that higher pad compressibility leads to reduced brake squeal and that caliper design can affect brake squeal. After encountering anecdotal contradictory cases, this investigation was undertaken to systematically generate basic data and clarify the beliefs or speculations. In order to adjust pad compressibility, it is common to modify pad molding temperatures, pressures and times, which in addition to changing the compressibility, changes friction coefficient and physical properties of the pad at the same time. In order to separate these two effects, NAO disc pads were prepared under the same molding conditions while using different thicknesses of the underlayer to achieve different compressibilities, thus changing the compressibility only without changing the friction coefficient and physical properties of the pad.

When two identical brakes are simultaneously tested on a vehicle chassis dynamometer, very often the left hand brake is found to squeal more or less than the right hand brake, all at different frequencies. This study was performed to develop some understanding of this puzzling phenomenon. It is found that as the wear rate difference between the inner pad and the outer pad increases, low frequency (caliper and knuckle) squeals occur more and more, and as the differential wear becomes larger and larger, high frequency (disc) squeals occur less and less, finally disappearing all together. Discs and calipers are found to affect the differential pad wear, in turn affecting brake squeal generation.

Electric vehicles are considered not only eco-friendly but also quieter than vehicles with conventional internal combustion engines. However, less noisy environments in cabins make passengers feel uncomfortable to moderate noise. This paper discusses noise reduction for electric vehicles radiated from traction motors. In the analysis of the noise generation mechanisms it is demonstrated that frequency ranges of the highest level in the noise spectrum of electromagnetic harmonic orders of the induction motor coincide with structural resonances of the motor housing. Interfacial friction between the inner and outer housings of the motor is employed in reducing structural vibration of the motor. Measured noise in the cabin and vibration at the motor housing indicates that slip damping presented from interfacial friction between the inner and outer housing is effective in reducing noise from the traction motor and in the cabin.

The effects of pad properties and thermal coning of discs on high speed judder were investigated using dynamometer and vehicle tests. The friction materials of different thermal conductivities were manufactured and the discs were design-modified to control the thermal coning during braking under high speed conditions. Brake Torque Variation(BTV) was measured to evaluate the judder propensity in the dynamometer tests and the vibration on steering wheel and brake pedal was measured in the vehicle tests. The results showed that the increase of thermal conductivity of pad could not affect the judder propensity during high speed braking below 350°C of disc temperature, however better disc design reduced judder propensity due to the lower thermal deformation. Moreover, the increase of pad compressibility can reduce judder propensity due to the increase of damping capacity.

ABS assembly is supported by the mounting bracket which is installed at the body inside engine room. Such feature of the mounting bracket requires consideration of durability performance under the dynamic random loads imposed by engine excitation. So, modal parameters, such as natural frequencies and mode shapes, of ABS assembly and its bracket should be considered when evaluating the fatigue life. Therefore, fatigue analyses and experiments of ABS assembly and its bracket were performed in the frequency domain rather than the time domain. After that, analysis results were compared and correlated with experimental results, and the analysis method was updated to improve analysis accuracy.

As well as performance and safety, sensibility factor such as brake squeal noise has become an important factor to consider in today’s automotive industry. However, regardless of its importance, reduction of brake squeal noise has remained as one of the biggest challenges that have not yet been solved. Recently, many studies are being conducted to reduce squeal noise with the development of numerical analysis using FEM(Finite Element Method). This paper deals with complex eigenvalue analysis with commercial software program ABAQUS to resolve the squeal noise related to disc in-plane mode which is reported to occur frequently in the squeal noise frequency band 1~20kHz. As the reliability of the FE model is the most critical factor in numerical analysis, the FE model is first correlated with FRF modal test of each brake part and measurement of material property of pad with the anisotropic character through ultrasonic methods.

Not only for the carmakers but also for the automotive parts suppliers, cost reduction and short development cycle are strongly required to survive in highly competitive market. The simulation models predicting acoustic performance of cockpit module at early design stage could be a part of time-saving and cost-effective solution for those demands. Via experimental, analytical, and virtual statistical energy analysis (SEA) approach, the simulation models of cockpit module predicting acoustic performance are developed and validated. Recently proposed virtual SEA using FE models from crash analysis are useful to reduce the ambiguity of SEA modeling which could make a big difference in the result. The SEA models simulate the transmission loss tests of a cockpit module attached with several kinds of acoustical treatments between two connected reverberation chambers.

In spite of many squeal noise studies, it is still hard to predict squeal noise these days. Squeal analysis is a useful technique in reducing or removing squeal noise. As a result, several papers that contain reasonable finite element model with correlation, squeal mode analysis, and design proposals that can reduce the squeal noise have been released. In this paper, Generalized Frictional Stiffness Matrix was extracted using Generalized Coordinate in ABAQUS. GFSM(Generalized Frictional Stiffness Matrix) is an unsymmetrical matrix which creates a real-eigen-value (unstable mode) in complex eigenvalue problem. Then, sensitivity of each term in GFSM is calculated. The least modification was proposed from the sensitivities to reduce the squeal noise. To verify this proposal, a reasonable finite element model was generated by correlating component and assembly modal tests.

Nowadays, brake squeal noise is one of the most difficult problems and is a big issue in the automobile industry. Finite element analysis is a useful tool in predicting the noise occurrence of a conventional brake system during the design stage. This paper explains the technical procedure and method to resolve the squeal noise with commercial software programs. Friction coefficient under the operating conditions of the brake system was considered as a variable with respect to disc velocity and there was a dynamic behavior within the pad assembly during brake action. First of all, our Finite Element (FE) model was verified using the results of the parts and assembly's FRF measurements and an inertia noise dynamometer, followed by complex eingen value analysis to detect unstable frequencies. Subsequently, mode analysis was conducted for each part of the brake system through the MAC values.