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Viewing 1 to 30 of 423
2016-10-17
Technical Paper
2016-01-2353
Kazunori Harima, Shinji Tsuchiya, Takuro morino, Yuji Nagasawa
CVT belts are constructed with multiple elements and layered rings, and friction loss occurs between each parts. Due to belt geometry, a large belt friction loss occurs between the elements and the inner most ring. Therefore, to improve efficiency, it is effective to decrease the slip between the elements and the inner most ring. So, the torque transmitted is influenced by the slip between the elements and the inner most ring. When the slip is decreased, it is thought that the amount of torque transmitted by the ring change. For efficiency improvement, it is necessary to analyze the change of the torque transmitted by the ring due to the decrease of slip between the elements and the inner most ring, but to verify of the internal thrust force in the real load state is difficult because it is a phenomenon inside the belt.
2016-10-17
Technical Paper
2016-01-2204
Takafumi Mori, Masanori Suemitsu, Nobuharu Umamori, Takehisa Sato, Satoshi Ogano, Kenji Ueno, Oji Kuno, Kotaro Hiraga, Kazuhiko Yuasa, Shinichiro Shibata, Shinichiro Ishikawa
One effective and easy way to improve fuel economy for automobiles is to decrease viscosity of lubricants, as it brings less churning loss. However, this option creates a higher potential for thinner oil film, which could damage the mechanical parts. This paper describes a new low-viscosity gear oil technology which was successfully developed to improve wear at tapered-roller bearings in differential gear units, whereas achieving higher fuel economy performance. As for tapered-roller bearings in differential gear units protected by gear oils, one major damage is supposed to cause wear at large end face of rollers and the counterpart, so-called bearing bottom wear. In order to understand the wear mechanism, wear at rolling contact surface of rollers and the counterparts, so-called bearing side wear was additionally observed to confirm the wear impact on tapered-roller bearing.
2016-10-17
Technical Paper
2016-01-2276
Toyoharu Kaneko, Kazuo Yamamori, Hiroyuki Suzuki, Ko Onodera, Satoshi Ogano
This paper describes our newly developed friction reduction technology for low viscosity engine oils formulated with molybdenum dithio-carbamate (MoDTC) and magnesium detergents. The surface chemistry of additive interactions will also be discussed. Low viscosity grade engine oils are being utilized in modern engines to achieve improved fuel economy. As a result, engine conditions increase in severity through a tendency to operate in a higher degree of boundary lubrication conditions. Therefore, MoDTC, a friction modifier known to reduce friction under these conditions, is becoming a key component. In addition to fuel economy, formulation chemistry to prevent Low Speed Pre-Ignition (LSPI) is also required. These chemistry advances are a necessity for downsized, turbocharged engines to maximize fuel economy improvement. To ensure sufficient engine oil performance, magnesium detergents are a key additive to prevent damaging LSPI events in the engine.
2016-10-17
Technical Paper
2016-01-2198
Chikara Dodate, Sachio Mori, Masato Kawauchi, Rio Shimizu
In recent years, a lot of direct-injection gasoline engines are developed due to the high rated power, low end torque and fuel efficiency because of increased volumetric efficiency and reduced knocking. On the other hand, the measure for particular matters (PM) and the oil dilution become important. Therefore it is necessary to identify a spray behavior in cylinder with the combination of flow to design a direct injector. To identify the spray behavior, a CFD analysis has been utilized. However, before it was necessary to fit spray model constants and parameters based on measurement results including a penetration and SMD. Especially, in the case of the nozzle whose sectional area of exit is larger than that of inlet like a fan-shape spray nozzle, the fitting process is complicated, because of an inhomogeneity internal flow. In this study, new simulation method of spray is developed.
2016-04-05
Technical Paper
2016-01-0973
Takafumi Yamauchi, Yoshiki Takatori, Koichiro Fukuda, Masatoshi Maruyama
Abstract Urea-SCR (Selective Catalytic Reduction) systems are getting a lot of attention as the most promising NOx reduction technology for heavy-duty diesel engine exhaust. In order to promote an effective development for an optimal urea-SCR after-treatment system, it is important to clarify the decomposition behavior of the injected urea and a detailed reaction chemistry of the reactants on the catalyst surface in exhaust gases. In this paper we discuss experimental and numerical studies for the development of a numerical simulation model for the urea-SCR catalyst converter. As a first step, in order to clarify the behavior of reductants in an urea-SCR converter, two types of diagnostic technique were developed; one is for measuring the amount of NH3, and the other is for measuring the amount of total reductants including unreacted urea and iso-cyanic acid. These techniques were applied to examine the behavior of reductants at the inlet and inside the SCR converter.
2016-04-05
Technical Paper
2016-01-0960
Arifumi Matsumoto, Kenji Furui, Makoto Ogiso, Toru Kidokoro
Abstract Urea selective catalytic reduction (SCR) systems are a promising technology for helping to lower NOx emissions from diesel engines. These systems also require on-board diagnostic (OBD) systems to detect malfunctioning catalysts. Conventional OBD methodology for a SCR catalyst involves the measurement of NOx concentration downstream of the catalyst. However, considering future OBD regulations, erroneous diagnostics may occur due to variations in the actual environment. Therefore, to enhance OBD accuracy, a new methodology was examined that utilizes NH3 slip as a new diagnostic parameter in addition to NOx. NH3 slip increases as the NOx reduction performance degrades, because both phenomena are based on deterioration in the capability of the SCR catalyst to adsorb NH3. Furthermore, NH3 can be measured by existing NOx sensors because NH3 is oxidized to NO internally. To make use of NH3 slip, an estimation model was developed.
2016-04-05
Technical Paper
2016-01-1363
Nobuhiro Ide, Jun Hioki, Hiroki Okada
Abstract Because of its convenience, electronic key systems are adopted by many automakers. Ensuring the performance of low frequency (LF) and ultra-high frequency (UHF) electromagnetic waves is a critical part of system development. One of the most important performance aspects of this system is ensuring communication in the required area, and the tuning process is a key factor in the development phase. Conventionally, a large amount of work hours and cost is required for this tuning process, which usually adopts a cut-and-try approach based on technical experience to satisfy the required specifications in the LF band. The development process was successfully shortened by applying the newly developed LF electromagnetic simulation technique described in this paper.
2016-04-05
Technical Paper
2016-01-1609
Yusuke Nakae, Jun Yamamura, Hiroshi Tanaka, Tsuyoshi Yasuki
Abstract The unsteady aerodynamic loads produced due to vehicle dynamic motions affect vehicle dynamic performance attributes such as straight-line stability or handling characteristics. To improve these dynamic performances, understanding the detailed mechanisms by which unsteady aerodynamic loads are caused during dynamic motions and the effects of unsteady aerodynamic loads on vehicle dynamic performance are needed. This paper describes the numerical study of unsteady aerodynamics of a 1/4 scale car model in dynamic pitching motion to clarify the detailed mechanisms by which unsteady aerodynamic loads are caused during the motion. Vortical structures around front wheelhouse and front under side of the body are analyzed by introducing schematic views to understand the mechanisms of unsteady flow fields. Furthermore, effects of aerodynamic devices devised based on the analyses on unsteady aerodynamics are discussed.
2016-04-05
Technical Paper
2016-01-1674
Takao Kobayashi, Etsuo Katsuyama, Hideki Sugiura, Eiichi Ono, Masaki Yamamoto
Abstract The research described in this paper aimed to study the cornering resistance and dissipation power on the tire contact patch, and to develop an efficient direct yaw moment control (DYC) during acceleration and deceleration while turning. A previously reported method [1], which formulates the cornering resistance in steady-state cornering, was extended to so-called quasi steady-state cornering that includes acceleration and deceleration while turning. Simulations revealed that the direct yaw moment reduces the dissipation power due to the load shift between the front and rear wheels. In addition, the optimum direct yaw moment cancels out the understeer augmented by acceleration. In contrast, anti-direct yaw moment optimizes the dissipation power during decelerating to maximize kinetic energy recovery. The optimization method proved that the optimum direct yaw moment can be achieved by equalizing the slip vectors of all the wheels.
2016-04-05
Technical Paper
2016-01-1677
Hiroshi Himeno, Etsuo Katsuyama, Takao Kobayashi
Abstract Electric vehicles (EVs) are attracting attention due to growing awareness of environmental issues such as fossil fuel depletion and global warming. In particular, a wide range of research has examined how direct yaw moment controls (DYCs) can enhance the handling performance of EVs equipped with multiple in-wheel motors (IWMs) or the like. Recently, this research has focused on reducing energy consumption through driving force distribution control. The first report proposed a method to minimize energy consumption through an efficient DYC for extending the cruising range of a vehicle installed with four IWMs, and described the vehicle behavior with this control. Since motors allow high design flexibility, EVs can be developed with a variety of drive systems. For this reason, various driving force distribution control methods can be considered based on the adopted system.
2016-04-05
Technical Paper
2016-01-1664
Yoshio Masuda, Yosuke Yamasoe, Yosuke Kuki, Takahiro Okano, Kiyoyuki Uchida
Abstract To solve various environmental problems, fuel-efficient vehicles that reduce CO2 emissions as well as exhaust gas emissions have been developed. In such vehicles, a regenerative brake is used to further reduce fuel consumption. Because the market size for such vehicles is expanding, a brake system is required that can be used in a wide range of vehicles extending from internal combustion engine vehicles (ICEVs) to electric vehicles (EVs). In addition, issues such as deceleration fluctuation and brake pedal fluctuation arise because the regenerative brake force is dependent on the vehicle speed. This paper presents a brake system configuration and its element technologies that can replace existing brake systems in different vehicles ranging from ICEVs to EVs. The proposed system can realize a regenerative cooperative brake not only by replacing the brake booster unit but also without replacing the modulator.
2016-04-05
Technical Paper
2016-01-1668
Hideki Fukudome
Abstract This study analyzed the longitudinal vibration of a vehicle body and unsprung mass. Calculations and tests verified that longitudinal vibration can be reduced using in-wheel motors, which generate torque very quickly. Despite increasing demand for measures to enhance ride comfort considering longitudinal vibration, this type of vibration cannot be absorbed or controlled using a conventional suspension. This paper describes the reduction of vehicle longitudinal vibration that cannot be controlled by conventional actuators.
2016-04-05
Technical Paper
2016-01-0034
Shunsuke Kobuna, Tomoyuki Kaga, Tomoya Yamaguchi
Abstract As vehicle control software becomes larger and more complex, it is increasingly important to improve the efficiency of the software development process. This study developed search-based testing technology to increase the efficiency of the validation process. Search-based testing can generate dynamic test data automatically, but it tends to overlook the generation of correct test data to detect problems when the software has many branches and paths. To resolve this problem, a method was devised that combines search-based testing [1] and formal methods such as model checking. This paper describes this method and shows application examples of engine control.
2016-04-05
Technical Paper
2016-01-0124
Andrew Scott Alden, Brian Mayer, Patrick Mcgowen, Rini Sherony, Hiroyuki Takahashi
Abstract Animal-vehicle collision (AVC) is a significant safety issue on American roads. Each year approximately 1.5 million AVCs occur in the U.S., the majority of them involving deer. The increasing use of cameras and radar on vehicles provides opportunities for prevention or mitigation of AVCs, particularly those involving deer or other large animals. Developers of such AVC avoidance/mitigation systems require information on the behavior of encountered animals, setting characteristics, and driver response in order to design effective countermeasures. As part of a larger study, naturalistic driving data were collected in high AVC incidence areas using 48 participant-owned vehicles equipped with data acquisition systems (DAS). Continuous driving data including forward video, location information, and vehicle kinematics were recorded. The respective 11TB dataset contains 35k trips covering 360K driving miles.
2016-04-05
Technical Paper
2016-01-1458
Ryuta Ono, Wataru Ike, Yuki Fukaya
Abstract Toyota Safety Sense is a safety system package developed to help drivers avoid accident types with a high frequency of occurrence. This paper deals with pre-collision system which forms the core of Toyota Safety Sense, especially Toyota Safety Sense P which uses a combined sensor configuration consisting of a monocular camera paired with millimeter wave radar, in order to achieve both high recognition performance and reliability. The use of a wide-angle monocular camera, millimeter wave radar integrated in the front grill emblem, and a collision determination algorithm for pedestrian targets enabled the development of a pre-collision system comprising detection capability of crossing pedestrians. Toyota has developed warning and pre-collision brake assist for driver to assist in avoiding a collision effectively; In addition, Pre-collision brake has achieved high level of performance for the drivers who cannot avoid a collision.
2016-04-05
Technical Paper
2016-01-1516
Takahiro Suzaki, Noritaka Takagi, Kosho Kawahara, Tsuyoshi Yasuki
Abstract Approximately 20% of traffic fatalities in United States 2012 were caused by rollover accidents. Mostly injured parts were head, chest, backbone and arms. In order to clarify the injury mechanism of rollover accidents, kinematics of six kinds of Anthropomorphic Test Devices (ATD) and Post Mortem Human Subjects (PMHS) in the rolling compartment, whose body size is 50th percentile male (AM50), were researched by Zhang et al.(2014) using rollover buck testing system. It was clarified from the research that flexibility of the backbone and thoracic vertebra affected to occupant’s kinematics. On the other hand, the kinematics research of body size except AM50 will be needed in order to decrease traffic fatalities. There were few reports about the researches of occupant kinematics using FE models of body sizes except AM50.
2016-04-05
Technical Paper
2016-01-1420
Shinichi Kojima, Shigeyoshi Hiratsuka, Nobuyuki Shiraki, Kazunori Higuchi, Toshihiko Tsukada, Keiichi Shimaoka, Kazuya Asaoka, Sho Masuda, Kazuhiko Nakashima
Abstract This study aims at the development of a projection pattern that is capable of shortening the time required by a driver to perceive a pedestrian at night when a vehicle’s high beams are utilized. Our approach is based on the spatio-temporal frequency characteristics of human vision. Visual contrast sensitivity is dependent on spatiotemporal frequency, and maximum contrast sensitivity frequency varies depending on environmental luminance. Conventionally, there are several applications that utilize the spatio-temporal frequency characteristics of human vision. For example, the National Television System Committee (NTSC) television format takes into consideration low-sensitivity visual characteristics. In contrast, our approach utilizes high-sensitivity visual characteristics based on the assumption that the higher contrast sensitivity of spatio-temporal frequencies will correlate more effectively with shorter perception times.
2016-04-05
Technical Paper
2016-01-1412
Takeshi Hamaguchi, Satoshi Inoue, Shigeyuki Kimura, Terumasa Endo
Abstract In driver-focused vehicle development, driver workload is generally evaluated subjectively, with physiological, psychological, and behavioral indexes used to quantify and substantiate the subjective rating. In contrast, a model of driver behavior expresses the driver’s behavioral characteristics which make it possible to estimate how the driver will incorporate information into vehicle operation. Therefore, it is presumed to be capable of estimating the internal state of a driver. Conventionally, a model of driver behavior related to pedal operation has been used for evaluating the driver’s habits and the acceptability of various types of support devices. However, it has not been used for estimating driver workload related to pedal operation. To examine driver workload, this study divided pedal operation magnitude into two components: a learning/judgment component and a correcting component for prediction errors. A method was devised of separating these two components.
2016-04-05
Technical Paper
2016-01-1452
Eiichiro Murata, Tasuku Usui, Kazunori Nogi, Hiroyuki Takahashi
Abstract In order to help avoid or mitigate rear-end collisions a Pre-Collision System (PCS) was developed. The purpose of this study is to clarify the Time-to-Collision (TTC) distribution when approaching a lead vehicle under normal driving condition. To enhance the effectiveness of PCS, warnings and/or automatic brake activation should happen as early as possible, however, if too early there is a high possibility of false warnings or activations, which is not desirable. If the distribution of distance to a lead vehicle under normal driving conditions is quantified, an approach limit can be estimated. In this study, we try to clarify a TTC distribution that is approximated by a log-normal distribution. Then, we investigate the Enhanced Time-to-Collision (ETTC) that is the secondary predictive value of TTC. And, we clarify the log-normal distribution of ETTC is a more stable approximator of normal driving than a log-normal distribution of TTC.
2016-04-05
Technical Paper
2016-01-1454
Libo Dong, Stanley Chien, Jiang-Yu Zheng, Yaobin Chen, Rini Sherony, Hiroyuki Takahashi
Abstract Pedestrian Automatic Emergency Braking (PAEB) for helping avoiding/mitigating pedestrian crashes has been equipped on some passenger vehicles. Since approximately 70% pedestrian crashes occur in dark conditions, one of the important components in the PAEB evaluation is the development of standard testing at night. The test facility should include representative low-illuminance environment to enable the examination of the sensing and control functions of different PAEB systems. The goal of this research is to characterize and model light source distributions and variations in the low-illuminance environment and determine possible ways to reconstruct such an environment for PAEB evaluation. This paper describes a general method to collect light sources and illuminance information by processing large amount of potential collision locations at night from naturalistic driving video data.
2016-04-05
Technical Paper
2016-01-1447
Qiang Yi, Stanley Chien, Jason Brink, Wensen Niu, Lingxi Li, Yaobin Chen, Chi-Chen Chen, Rini Sherony, Hiroyuki Takahashi
Abstract As part of active safety systems for reducing bicyclist fatalities and injuries, Bicyclist Pre-Collision System (BPCS), also known as Bicyclist Autonomous Emergency Braking System, is being studied currently by several vehicles manufactures. This paper describes the development of a surrogate bicyclist which includes a surrogate bicycle and a surrogate bicycle rider to support the development and evaluation of BPCS. The surrogate bicycle is designed to represent the visual and radar characteristics of real bicyclists in the United States. The size of bicycle surrogate mimics the 26 inch adult bicycle, which is the most popular adult bicycle sold in the US. The radar cross section (RCS) of the surrogate bicycle is designed based on RCS measurement of the real adult sized bicycles.
2016-04-05
Technical Paper
2016-01-1446
Rini Sherony, Qiang Yi, Stanley Chien, Jason Brink, Mohammad Almutairi, Keyu Ruan, Wensen Niu, Lingxi Li, Yaobin Chen, Hiroyuki Takahashi
Abstract According to the U.S. National Highway Traffic Safety Administration, 743 pedal cyclists were killed and 48,000 were injured in motor vehicle crashes in 2013. As a novel active safety equipment to mitigate bicyclist crashes, bicyclist Pre-Collision Systems (PCSs) are being developed by many vehicle manufacturers. Therefore, developing equipment for evaluating bicyclist PCS is essential. This paper describes the development of a bicycle carrier for carrying the surrogate bicyclist in bicyclist PCS testing. An analysis on the United States national crash databases and videos from TASI 110 car naturalistic driving database was conducted to determine a set of most common crash scenarios, the motion speed and profile of bicycles. The bicycle carrier was designed to carry or pull the surrogate bicyclist for bicycle PCS evaluation. The carrier is a platform with a 4 wheel differential driving system.
2016-04-05
Technical Paper
2016-01-1319
Kimitoshi Tsuji, Katsuhiko Yamamoto
Abstract It is important for vehicle concept planning to estimate fuel economy and the influence of vehicle vibration using virtual engine specifications and a virtual vehicle frame. In our former study, we showed the 1D physical power plant model with electrical starter, battery that can predict combustion transient torque, combustion heat energy and fuel efficiency. The simulation result agreed with measured data. For idling stop system, the noise and vibration during start up is important factor for salability of the vehicle. In this paper, as an application of the 1D physical power plant model (engine model), we will show the result of analysis that is starter shaft resonance and the effect on the engine mount vibration of restarting from idle stop. First, an engine model for 3.5L 6cyl NA engine was developed by energy-based model using VHDL-AMS. Here, VHDL-AMS is modeling language registered in IEC international standard (IEC61691-6) to realize multi physics on 1D simulation.
2016-04-05
Technical Paper
2016-01-0740
Kazuhisa Inagaki, Jyunichi Mizuta, Kiyomi Kawamura, Yoshinori Idota, Takeshi Hashizume
Abstract 1 Recently, demand for small-bore compact vehicle engines has been increasing from the standpoint of further reducing CO2 emissions. The generalization and formulation of combustion processes, including those related to emissions formation, based on a certain similarity of physical phenomena regardless of engine size, would be extremely beneficial for the unification of development processes for various sizes of engines. The objective of this study is to clarify what constraints are necessary for engine/nozzle specifications and injection conditions to achieve the same combustion characteristics (such as heat release rate and emissions) in diesel engines with different bore sizes.
2016-04-05
Technical Paper
2016-01-0891
Teri D. Kowalski, Satoshi Hirano, William A. Buscher, Eric Liu, Jerry C. Wang, James L. Linden
Abstract The study described in this paper covers the development of the Sequence IVB low-temperature valvetrain wear test as a replacement test platform for the existing ASTM D6891 Sequence IVA for the new engine oil category, ILSAC GF-6. The Sequence IVB Test uses a Toyota engine with dual overhead camshafts, direct-acting mechanical lifter valvetrain system. The original intent for the new test was to be a direct replacement for the Sequence IVA. Due to inherent differences in valvetrain system design between the Sequence IVA and IVB engines, it was necessary to alter existing test conditions to ensure adequate wear was produced on the valvetrain components to allow discrimination among the different lubricant formulations. A variety of test conditions and wear parameters were evaluated in the test development. Radioactive tracer technique (RATT) was used to determine the wear response of the test platform to various test conditions.
2016-04-05
Technical Paper
2016-01-0351
Yuki Kudo, Akinori Sato, Kazutaka Kimura, Shoichi Iwamoto, Hiroyuki Ohba, Motoya Sakabe, Yasuhiro Shirai
Abstract Replacing the metal car roof with conventional solar modules results in the increase of total car weight and change of center of mass, which is not preferable for car designing. Therefore, weight reduction is required for solar modules to be equipped on vehicles. Exchanging glass to plastic for the cover plate of solar module is one of the major approaches to reduce weight; however, load bearing property, impact resistance, thermal deformation, and weatherability become new challenges. In this paper a new solar module structure that weighs as light as conventional steel car roofs, resolving these challenges is proposed.
2016-04-05
Technical Paper
2016-01-0181
Yasuki Hirota, Ryuichi Iwata, Takafumi Yamauchi, Manabu Orihashi, Masaki Morita
Abstract In order to reduce the energy consumption of the automotive air conditioning system, adsorption heat pump (AHP) system is one of the key technologies. We have been developing compact AHP system utilizing the exhaust heat from the engine coolant system (80-100 °C), which can meet the requirements in the automotive application. However, AHP systems have not been practically used in automotive applications because of its low volumetric power density of the adsorber. The volumetric power density of the adsorber is proportional to sorption rate, packing density and latent heat. In general, the sorption rate is determined by mass transfer resistance in primary particle of an adsorbent and heat and mass transfer resistance in packed bed. In order to improve the volumetric power density of the adsorber, it is necessary to increase the production of the sorption rate and the packing density.
2016-04-05
Technical Paper
2016-01-0184
Toshio Murata, Tadashi Nakagawa, Hisashi Nishino, Kazunari Matsuura
In order to speed up engine coolant warm-up, the exhaust heat recirculation system collects and reuses the heat from exhaust gases by utilizing the heat exchanger. The conventional system improves actual fuel economy at the scene of the engine restart in winter season only. The heat recirculation system becomes more effective at the low outside temperature because it takes longer time to warm up engine coolant. However, the heat recirculation system becomes less effective at the high outside temperature because it takes shorter time to warm up engine coolant. Therefore, the new exhaust heat recirculation system is developed, which adopted as follows: 1) a fin-type heat exchanger in order to enhance exhaust recirculation efficiency 2) a thinner heat exchanger component and smaller amount of engine coolant capacity in the heat exchanger in order to reduce the heat mass As a result, the actual fuel economy is more improved in winter season.
2016-04-05
Technical Paper
2016-01-0621
James Kapinski, Xiaoqing Jin, Jyotirmoy Deshmukh, Alexandre Donze, Tomoya Yamaguchi, Hisahiro Ito, Tomoyuki Kaga, Shunsuke Kobuna, Sanjit Seshia
Abstract Test and verification procedures are a vital aspect of the development process for embedded control systems in the automotive domain. Formal requirements can be used in automated procedures to check whether simulation or experimental results adhere to design specifications and even to perform automatic test and formal verification of design models; however, developing formal requirements typically requires significant investment of time and effort for control software designers. We propose Signal Template Library (ST-Lib), a uniform modeling language to encapsulate a number of useful signal patterns in a formal requirement language with the goal of facilitating requirement formulation for automotive control applications. ST-Lib consists of basic modules known as signal templates. Informally, these specify a characteristic signal shape and provide numerical parameters to tune the shape.
2016-04-05
Technical Paper
2016-01-0411
Yosuke Akita, Kenji Abe, Yoshihiro Osawa, Yoshitsugu Goto, Yuji Nagasawa, Noboru Sugiura, Satoshi Wakamatsu, Kyoko Kosaka
Abstract If a vehicle is left in a humid environment, the coefficient of friction between the brake pads and discs increases, generating a discomforting noise during braking called brake squeal. It is assumed that this increase in the coefficient of friction in a humid environment is the effect of moisture penetrating between the brake friction surfaces. Therefore, this paper analyzes the factors causing coefficient of friction variation with moisture between the friction surfaces by dynamic observation of these surfaces. The observation was achieved by changing the disc materials from cast iron to borosilicate glass. One side of the glass brake disc was pushed onto the brake pad and the sliding surface was observed from the opposite side by a charge coupled device (CCD) camera. First, a preliminary test was carried out in a dry state using two pad materials with different wear properties to select the appropriate pad for observing the friction surfaces.
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