Search Results

Automatic engine start/stop systems are becoming more prevalent and increasing market share of these systems is predicted due to demands on improving fuel efficiency of vehicles. Integration of an engine start/stop system into a “conventional” drivetrain with internal combustion engine and 12V board system is a relatively cost effective measure to reduce fuel consumption. Comfort and NVH aspects will continue to play an important role for customer acceptance of these systems. Possible delay during vehicle launch due to the engine re-start is not only a safety relevant issue but a hesitating launch feel characteristic will result in reduced customer acceptance of these systems. The engine stop and re-start behavior should be imperceptible to the driver from both a tactile and acoustic standpoint. The lack of masking effects of the engine during the engine stop phases can cause other “unwanted” noise to become noticeable or more prominent.

The automotive industry continues to develop new powertrain and vehicle technologies aimed at reducing overall vehicle-level fuel consumption. Specifically, the use of electrified propulsion systems, including electrified and electric drive units (EDU), is expected to play a significant role in helping OEMs meet fleet CO2 reduction targets for 2025 and beyond. The change to vehicles propelled by electrified powertrains leads to a reduction in vehicle noise levels. Despite the overall noise levels being low, the NVH behavior of such vehicles can be objectionable due to the presence of tonal noise coming from electric machines and geartrain components. In order to ensure customer acceptance of electrically propelled vehicles, it is imperative that these NVH challenges are understood and solved. Specifically, this paper discusses the EDU NVH development process. This includes considerations for CAE/test-based development and validation processes to ensure optimal NVH development.

Integration of automatic engine Stop/Start systems in “conventional” drivetrains with 12V starters is a relatively cost-effective measure to reduce fuel consumption. Therefore, automatic engine Stop/Start systems are becoming more prevalent and increasing market share of such systems is predicted. A quick, reliable and consistent engine start behavior is essential for customer acceptance of these systems. The launch of the vehicle should not be compromised by the Stop/Start system, which implies that the engine start time and transmission readiness for transmitting torque should occur within the time the driver releases the brake pedal and de-presses the accelerator pedal. Comfort and NVH aspects will continue to play an important role for customer acceptance of these systems. Hence, the engine stop and re-start behavior should be imperceptible to the driver from both a tactile and acoustic standpoint.

Automotive companies are studying to add extra value in their vehicles by enhancing powertrain sound quality. The objective is to create a brand sound that is unique and preferred by their customers since quietness is not always the most desired characteristic, especially for high-performance products. This paper describes the process of developing a brand powertrain sound for a high-performance vehicle using the DFSS methodology. Initially the customer's preferred sound was identified and analyzed. This was achieved by subjective evaluations through voice-of-customer clinics using vehicles of similar specifications. Objective data were acquired during several driving conditions. In order for the design process to be effective, it is very important to understand the relationship between subjective results and physical quantities of sound. Several sound quality metrics were calculated during the data analysis process.

The automotive industry continues to develop new technologies aimed at reducing overall vehicle level fuel consumption. Powertrain and driveline related technologies will play a key role in helping OEM’s meet fleet CO2 reduction targets for 2025 and beyond. Specifically, use of technologies such as downsized engines, idle start-stop systems, aggressive torque converter lock-up schedules, wide-ratio spread transmissions, and electrified propulsion systems are vital towards meeting aggressive fuel economy targets. Judicious combinations of such powertrain and driveline technology packages in conjunction with measures such as the use of low rolling resistance tires and vehicle lightweighting will be required to meet future OEM fleet CO2 targets. Many of the technologies needed for meeting the fuel economy and CO2 targets come with unique NVH challenges. In order to ensure customer acceptance of new vehicles, it is imperative that these NVH challenges be understood and solved.

The automotive industry continues to develop new powertrain technologies aimed at reducing overall vehicle level fuel consumption. The ongoing trends of “downsizing” and “down speeding” have led to the development of turbocharged engines with low displacement and high torque density. In order to meet the launch response requirements with these engines as well as fuel economy needs, transmissions with large ratio spreads will need to be developed. Due to the lack of torque amplification from the torque converter, the next generation of dual clutch transmissions (DCT) will need to have larger launch ratios and ratio spreads than currently available in production today. This paper discusses the development of a new family of DCT (called “xDCT”) for use in front wheel drive vehicles, aimed at meeting some of these challenges. The xDCT family features two innovative concepts, the idea of “gear generation” and “supported shifts”.

Demanding CO2 and fuel economy regulations are continuing to pressure the automotive industry into considering innovative powertrain and vehicle-level solutions. Powertrain engineers continue to minimize engine internal friction and transmission parasitic losses with the aim of reducing overall vehicle fuel consumption. In Part 1 of the study (2017-01-0893) described aspects of the test stand design that provides flexibility for adaptation to various test scenarios. The results from measurements for a number of front-end accessory drive (FEAD) components were shown in the context of scatterbands derived from multiple component tests. Key results from direct drive and belt-driven component tests were compared to illustrate the influence of the belt layout on mechanical efficiency of the FEAD system. The second part of the series will focus exclusively on the operation of the alternator. Two main elements of the study are discussed.

NVH refinement is an important aspect of the powertrain development process. Powertrain NVH refinement is influenced by overall sound levels as well as sound quality. The sound quality and hence the level of powertrain NVH refinement can be negatively affected by the presence of excessive impulsive noise. This paper describes a process used to develop an understanding of impulsive powertrain noise. The paper begins with an introductory discussion of various sources of impulsive noise in an automotive powertrain. Following this, the paper outlines a process for identifying the source of the impulsive powertrain noise using examples from case studies. The remainder of the paper focuses on certain examples of impulsive noise such as Diesel knocking noise, injector ticking, impulsive cranktrain noise, and gear rattle. For these examples, the development of key objective metrics, optimization measures, and improvement potential are examined.

NVH refinement of passenger vehicles is crucial to customer acceptance of contemporary vehicles. This paper describes the vehicle NVH development process, with specific examples from a Diesel sedan application that was derived from gasoline engine-based vehicle architecture. Using an early prototype Diesel vehicle as a starting point, this paper examines the application of a Vehicle Interior Noise Simulation (VINS) technique in the development process. Accordingly, structureborne and airborne noise shares are analyzed in the time-domain under both steady-state and transient test conditions. The results are used to drive countermeasure development to address structureborne and airborne noise refinement. Examples are provided to highlight the refinement process for “Diesel knocking” under idle as well as transient test conditions. Specifically, the application of VINS to understanding the influence of high frequency dynamic stiffness of hydro-mounts on Diesel clatter noise is examined.

Combustion noise plays a considerable role in the acoustic tuning of gasoline and diesel engines. Even though noise levels of modern diesel engines reach extremely low values, they are still higher than those of conventional gasoline engines. On the other hand, new combustion procedures designed to improve fuel consumption lead to elevated combustion noise excitations as in case of today's direct injecting gasoline engines whose vibration excitation and airborne noise emissions are slightly increased during stratified operation. The partly conflicting development goals resulting from this can only be realized by integrating the NVH specialists' expertise into every development step from concept to SOP.

The sound quality and performance of an automotive engine are both significantly influenced by the “air-to-air” system, i.e., the intake system, the exhaust system, and the engine gas dynamics. Only a full systems approach can result in an optimized air-to-air system, which fulfills engine performance requirements, overall sound pressure level targets for airborne vehicle noise, as well as sound quality demands. This paper describes an approach, which considers the intake system, engine, and exhaust system within one CAE model that can be utilized for engine performance calculations as well as acoustic simulations. Examples comparing simulated and measured sound are discussed. Finally, the simulated sound (e.g., at the tailpipe of the exhaust system) is combined with an interior noise simulation technique to evaluate its influence inside the vehicle's interior.

The automotive industry continues to develop new powertrain and vehicle technologies aimed at reducing overall vehicle-level fuel consumption. Specifically, the use of electrified propulsion systems is expected to play an increasingly important role in helping OEM’s meet fleet CO2 reduction targets for 2025 and beyond. Electric and hybrid electric vehicles do not typically utilize IC engines for low-speed operation. Under these low-speed operating conditions, the vehicles are much quieter than conventional IC engine-powered vehicles, making their approach difficult to detect by pedestrians. To mitigate this safety concern, many manufacturers have synthesized noise (using exterior speakers) to increase detection distance. Further, the US National Highway Traffic Safety Administration (NHTSA) has provided recommendations pursuant to the Pedestrian Safety Enhancement Act (PSEA) of 2010 for such exterior noise signatures to ensure detectability.

Demanding CO2 and fuel economy regulations are continuing to pressure the automotive industry into considering innovative powertrain and vehicle-level solutions. Powertrain engineers continue to minimize engine internal friction and transmission parasitic losses with the aim of reducing overall vehicle fuel consumption. Strip friction methods are used to determine and isolate components in engines and transmissions with the highest contribution to friction losses. However, there is relatively little focus on friction optimization of Front-End-Accessory-Drive (FEAD) components such as alternators and Air Conditioning (AC) compressors. This paper expands on the work performed by other researchers’ specifically targeting in-depth understanding of system design and operating strategy.

The automotive industry continues to develop technologies for reducing vehicle fuel consumption. Specifically, vehicle lightweighting is expected to be a key enabler for achieving fleet CO2 reduction targets for 2025 and beyond. Hybrid glass laminates that incorporate fusion draw and ion exchange innovations are thinner and thereby, offer more than 30% weight reduction compared to conventional automotive laminates. These lightweight hybrid laminates provide additional benefits, including improved toughness and superior optics. However, glazing weight reduction leads to an increase in transmission of sound through the laminates for certain frequencies. This paper documents a study that uses a systematic test-based approach to understand the sensitivity of interior vehicle noise behavior to changes in acoustic attenuation driven by installation of lightweight glass.

It is important to develop powertrain NVH characteristics with the goal of ultimately influencing/improving the in-vehicle NVH behavior since this is what matters to the end customer. One development tool called dB(VINS) based on a process called Vehicle Interior Noise Simulation (VINS) is used for determining interior vehicle noise based on powertrain level measurements (mount vibration and radiated noise) in combination with standardized vehicle transfer functions. Although this method is not intended to replace a complete transfer path analysis and does not take any vehicle specific sensitivity into account, it allows for powertrain-induced interior vehicle noise assessments without having an actual test vehicle available. Such a technique allows for vehicle centric powertrain NVH development right from an early vehicle development stage.

It is commonly accepted that refined “powertrain sound quality” is essential to the development of a vehicle which will be well received by today's discriminating automotive customer. However, though there are several metrics which correlate well with a subjective impression of powertrain level inputs, what is ultimately important is the sound quality at driver's ear. Vehicle level powertrain sound quality is influenced by the powertrain noise and vibration (source) as well as the vehicle airborne and structureborne transfer functions (path). In development as well as benchmarking activities, it can be difficult to separate the influence of source and path on overall vehicle sound quality.

Increased customer expectation for NVH refinement creates a significant challenge for the integration of Diesel powertrains into passenger vehicles that might have been initially developed for gasoline engine applications. A significant factor in the refinement of Diesel powertrain sound quality is calibration optimization for NVH, which is often constrained by performance, emissions and fuel economy requirements. Vehicle level enablers add cost and weight to the vehicle and are generally bounded by vehicle architecture, particularly when dealing with a carry-over vehicle platform, as is often the case for many vehicle programs. These constraints are compounded by the need to make program critical sound package content decisions well before the availability of prototype vehicles with the right powertrain. In this paper, a case study on NVH development for integration of a light duty Diesel powertrain is presented.

The definition of vehicle and powertrain level targets is one of the first tasks toward establishing where a vehicle will reside with respect to the current or future state of industry. Though development of sound quality metrics is ongoing to better correlate objective data with subjective assessments, target setting at the vehicle level is relatively straightforward. However, realization of these targets depends on effective cascading to system and component levels. Often, component level targets are derived based on experience from earlier development programs, or based on selected characteristics observed during component level benchmarking. An approach is presented here to complement current strategies for component level target definition. This approach involves a systematic concept for definition of component NVH targets based on desired vehicle level performance and a consequent target break down.

The automotive industry continues to develop new powertrain and vehicle technologies aimed at reducing overall vehicle-level fuel consumption. Specifically, the use of innovative drivetrain technologies including conventional and electrified propulsion systems is expected to play an increasingly important role in helping OEMs meet fleet CO2 reduction targets for 2025 and beyond. NVH development for vehicles with electrified powertrains introduces new challenges, which need to be understood and solved. The electrified vehicle space spans variants from micro and mild hybrids all the way through plug-in hybrids and fully electric vehicles. In addition to conventional NVH development methodologies, active sound design (ASD) can play a crucial role to enhance the interior sound perception of such vehicles and hence, improve customer acceptance of new technologies. This paper will begin with an introduction to the NVH challenges posed by electrified vehicles.

The European as well as U.S. market share of modern Diesel engines has increased significantly in recent years, due to their excellent torque and performance behavior combined with low fuel consumption. The overall improved noise and vibration behavior of modern Diesel engines has also contributed to this trend. Despite overall improvements in Diesel engine noise and vibration, certain aspects of Diesel engines continue to present significant challenges. One such issue is the presence of Diesel knocking that is prevalent during cold start and warm-up conditions. This paper discusses a technique used to optimize the cold start noise behavior of modern Diesel engines. The methods used in this study are based on optimizing the engine calibration to improve the vehicle interior and exterior (engine) noise, even at low ambient temperatures.