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Technical Paper

Booming noise analysis of passenger car using integrated approach of CAT/CAE

The need of lightweight vehicle design is motivated by the recent global trend of less fuel consumption and lower emission in vehicle. However in NVH development of vehicle, it becomes more difficult for the lightweight vehicle to reach low vibro-acoustic sensitivity than, for the heavy weight one to do so. Inthis environment, this paper describes about the practical finite element (FE) modeling of vehicle structure and acoustics, in order to predict "boom" response to powertrain excitation. The FE modeling process through validation and updating with experimental mode makes, the accumulation of considerable expertise for improving prediction accuracy, possible. FE analysis based on this modeling process is so useful for predicting "boom" levels up to 200 Hz. Using the result of FE analysis, structural optimization is executed in order to improve "boom" level of 80 Hz.
Technical Paper

Analysis of Vehicle Wind Throb Using CFD and Flow Visualization

Passenger cars with sunroofs sometimes experience a low frequency pulsation noise called “wind throb” when traveling with the roof open. This “wind throb” should be suppressed because it is an unpleasant noise which can adversely affect the acoustic environment inside a car. In this paper, 3-dimensional numerical flow analysis is applied around a car body to investigate the wind throb phenomenon. The computational scheme and the modeling method of the car body is first described. A flow visualization test in a water tunnel was completed for the simple car body shape to compare against the numerical procedure. The numerical and the visualized results compared well and the numerical simulation method employed was considered to be a reliable tool to analyze the wind throb phenomenon. Calculated results of pressure and vorticity distribution in the sunroof opening were analyzed with the spectrum of pressure fluctuation at the sunroof opening with and without a deflector.
Technical Paper

Development of Damping SMC and Its Application as Material for a Rockercover

When replacing a metal engine part with plastic, it is necessary to regard vibration damping as one of the important factors in terms of noise reduction as well as strength and heat resistance as being characteristics of the material. Plastics are far better for vibration damping than steel or aluminum, but this property is reduced by the addition of glassfiber-reinforced or high heat-resisting resins. We have taken notice of SMC (Sheet Molding Compound) which has the excellent strength and heat resistance properties and studied it in order to increase its vibration damping property. Since organic polymers show the peak value for vibration damping performance in the vicinity of the glass transition temperature (Tg), we studied a method to shift the Tg near the operating temperature region in order to improve the vibration damping property.
Technical Paper

Application of Common Rail Fuel Injection System to a Heavy Duty Diesel Engine

In the diesel engine industry, the growing trends are toward wider use of electronically controlled high pressure fuel injection equipment to provide better engine performance, while conforming to the stringent exhaust emission standards. Although there have been some recent announcements of a diesel engine that applies an electronically controlled common rail type fuel injection system, there is little literature published about any attempt to reduce both exhaust emissions and noise and to improve engine performance by varying injection pressure and injection timing independently and introducing pilot injection in combination. This paper describes the details of a study made on the parameters associated with injection timing, injection pressure and pilot injection and the procedures for their optimization, with an electronically controlled common rail type fuel injection system installed in an in-line 6-cylinder 6.9 liter turbocharged and intercooled DI diesel engine.
Technical Paper

New Mitsubishi L4 5-Liter DI Diesel Engine

The 4M5 series of four-cylinder, in-line, direct-injection diesel engines has been released by Mitsubishi Motors Corporation for light and medium-duty trucks and buses. Featuring an updated structure and reflecting the employment of state-of-the-art technology in the design of every component, the new engine series offers high reliability and compact dimensions. Moreover, the new series well meets contemporary demands for high performance, low noise, and clean combustion.
Technical Paper

Measurement of Structural Attenuation of a Diesel Engine and its Applications for Reduction of Noise and Vibration

Structural attenuation of a running diesel engine measured by a new technique showed a constant value regardless of engine speeds. It was verified by this result that structural attenuation is a physical quantity unique to the structure of each engine and, therefore, a good indicator for evaluation of low noise engine structure. In addition, a hydraulic excitation test rig was devised to measure structural attenuation directly and to make effective use of it for noise reduction. Based on the accurate measurements by the excitation test rig, modal analysis and system simulation were conducted for implementation of countermeasures against noise.
Technical Paper

Reduction of Idling Rattle Noise in Trucks

Optimization of the clutch torsional characteristics is one of the effective methods to reduce the idling rattle noise. Many researches on th.s problem have been reported, but only few of them give sufficient consideration to the drag torque applied to the clutch disc during engine idling. This paper pays attention to the drag torque and discusses the mechanism of idling rattle noise by using vehicle testing, bench test with rotating torsional exciter and computer simulation. Reauction of Idling
Technical Paper

Acoustic Analysis of Truck Cab

This paper presents the results of acoustic analyses of light duty truck cabs by actual vehicle testing and by numerical analysis utilizing the boundary element method (BEM). In the resonance mode analysis using BEM, by taking into account the vibration characteristics of cab panels, the presence of the modes other than the purely acoustic cavity resonance modes were confirmed. The contribution of the panel vibrations to booming noise that occurs in actual light duty trucks was analyzed. BEM analysis showed that some of the panel vibration had a negative contribution to booming noise. In other words, decreasing vibration in such a section was shown to increase sound pressure. The results of the BEM analysis match well with actual test results. It has thus been demonstrated that BEM is an effective method for analyzing truck interior noise reduction.
Technical Paper

Influence of Powertrain Torsional Rigidity on NVH of 6x4 Trucks

Torsional vibration of a truck's powertrain system is due to the exciting force generated by the angular velocity fluctuation originating from the setting angle of the universal joint of the propeller shaft, which can cause such problems as rattling noise, booming noise, etc.. This paper will clarify the difference between a 6x4 truck and a 6x2 truck in the torsional vibration characteristics from the experimental results. This is accomplished by computation with a simple torsional vibration model of the powertrain system and investigating the contribution of torsional rigidities of the powertrain system's various components by a parameter study. As a result it has been clarified that the torsional rigidity of the through shaft for transmitting power to the two rear axles has a great influence on Noise, Vibration and Harshness of 6x4 trucks.
Technical Paper

Development of a New Torsional Rubber Damper for Diesel Engines

It is well-known that double-mass torsional rubber dampers which have two masses and springs in parallel are effective for controlling torsional vibration characteristics over a wide range of engine speed. On the occasion of reliability estimation of the rubber dampers, it is important to consider generation of heat in the rubber due to torsional vibration. By predicting generation of heat at the designing stage, optimum design of the torsional rubber dampers can be achieved. By development and application of this prediction method, a new type double-mass damper was developed. It provided higher vibration control characteristics and reliability than conventional viscous dampers, and also it provided advantages in terms of noise, productivity and weight.
Technical Paper

Reduction of Cooling Fan Noise Caused by Crankshaft Torsional Vibration

Improvements of interior and exterior noise are important targets in vehicle engineering. There are many reports concerning the reduction of radiator cooling fan noise. But, most of those reports are associated with studies of air flow noise. A radiator cooling fan connected to a crankshaft occasionally radiates structure-borne noise in addition to air flow noise. This structure-borne noise is caused by fan blade vibration excited by torsional vibration of a crankshaft. In this paper, we surveyed the mechanism of the structure-borne noise and discussed some methods for the noise reduction. And, as a result, we developed one of the noise reduction technique aiming at isolation of crankshaft vibration by modifying viscosity of the oil in a fan clutch.
Technical Paper

Sound Quality Evaluation of Passenger Vehicle Interior Noise

Objective measures to evaluate sound quality are important for proper sound design and noise improvement. In this paper, the objective measures of interior noise of passenger vehicle, which is operated at constant engine revolution speed, are discussed. Subjective evaluation test of the interior noise was done using the semantic differential method. By applying factor analysts to the subjective evaluation scores, three important factors of the sound quality were extracted, i.e. comfortable, powerful and booming factors. Each factor was correlated with various physical values, for example octave band levels. Furthermore, the data is analyzed by multiple linear regression analysis with stepwise variable selection, of the each factor scores against the various physical values. Finally, an objective measure to evaluate each of these factors was conducted using the combination of simple physical values. Each of these measures was good correlation with each of the subjective evaluations.
Technical Paper

The Influence of Tire Deformation on Ride Comfort of a Truck

When truck tires have a deformation such as radial runout, flat spot, and abnormal wear as a result of panic braking, they affect vehicle vibration in the form of displacement input whose spectrum involves higher order terms of tire revolution. While a truck has vibration modes of frame bending as well as pitching and unsprung-mass viberation in the input frequency range, the tire displacement input induces vehicle vibration as a combination of these modes. Results of calculations and experiments of a 4x2 medium-duty truck are analyzed and an example of means for improving ride comfort is described in this paper.
Technical Paper

Active Control for Body Vibration of F.W.D. Car

A Vehicle Vibration Control System by Active Control has been developed. The experimental results using a 4-cylinder gasoline engine installed in a car showed that at the position of the driver's seat, the acceleration of the vibration was reduced by 16 dB. This system operates stably and at low cost because of having a feedforward system, so many applications can be expected in the near future as methods for vehicle vibration reduction.
Technical Paper

Powertrain Model Selection and Reduction for Real Time Control Algorithm Design and Verification in Rapid Controller Prototyping Environment

New systems or functionalities have been rapidly introduced for fuel economy improvement. Active vibration suppression has also been introduced. Control algorithm is required to be verified in real time environment to develop controller functionality in a short term. Required frequency domain property concept is proposed for representation of target phenomena with reduced models. It is shown how to select or reduce engine, transmission and vehicle model based on the concept. Engine torque profile which has harmonics of engine rotation is required for engine start, take-off from stand still, noise & vibration suppression and misfire detection for OBD simulation. An engine model which generates torque profile synchronous to crank angle was introduced and modified for real time simulation environment where load changes dynamically. Selected models and control algorithms were modified for real time environment and implemented into two linked universal controllers.
Technical Paper

Interior Noise evaluation of Electric Vehicle: Noise source contribution analysis

Global environment protection, Co2 emission reduction and so on, is an important problem in automotive industry. An Electric Vehicle (EV) production is one of policies. Co2 emission of EV is lower than Internal Combustion Engine (ICE), petrol and diesel engine. On the other hand, customer's needs for the comfort on driving increase year after year. So it's an important factor for new car performance. Generally speaking, it's thought that the noise and vibration performance of EV have the better of ICE performance. However the aerodynamic noise and road noise contribution for interior noise in EV rise in comparison with ICE, and moreover the sound quality change by new noise component of the motor noise. Therefore new sound evaluation method is needed for EV. So this paper demonstrates each noise component contribution in EV by new noise separation technology, and show the comparison result with EV and ICE.