Browse Topic: Brake calipers
The ever-increasing prevalence of electric vehicles in the global market continues to push automakers towards more stringent brake drag requirements. As OEMs seek to differentiate themselves with greater vehicle range to offset consumer anxiety as a barrier for entry to EVs, brake caliper suppliers see requirements for zero or near-zero drag at the component level becoming commonplace. Despite this pressure, many practical concerns exist with torque measurement capabilities in the sub 1.0 N-m range. Additionally, the authors have observed an industry tendency to employ suboptimal engineering methodology for assessing drag concerns, with trial and error attempts continuing to perplex engineers more than it provides solutions. This paper will seek to reintroduce to the reader the basic physics of brake drag from a fundamental free body diagram level, review statistical approaches for characterizing the individual forces acting within the caliper, and propose a simple – yet effective – virtual tool for characterizing potential solutions. The virtual tool will be correlated with physical assessments, and the practical challenges of full brake corner drag evaluations will be discussed. Finally, recommendations will be presented for evolving sliding caliper design to enable zero drag.
As technology evolves, the number of sensors and available data on vehicles grow exponentially. In this context, it is essential to use sensors for monitoring key components, increasing safety and reliability, and gathering data useful for mechanical dimensioning and control systems. This paper presents an application of strain-gauged bolts on brake calipers fixation of two electric vehicles. With this approach it was possible to evaluate the loads applied to the brake pads fixation zone and correlate them with braking behavior, therefore gaining insights on braking conditions and system state for an improved braking function control. The goal of the study is analyzing the strengths and limitations of the method and proposing developments to deploy it in real applications. This is particularly important and novel for electric vehicles, where powertrains can create positive/negative torques and generate complex interactions with braking system. Strain-gauges are a long-known technology applied in many fields, and its usage in bolts and screws is well established. However, within automotive field, it could represent cutting edge technology for load sensing and monitoring. The application shows promising results and proves a valid option for monitoring safety components due to its low cost, small dimensions, and reliability. The presented case study takes place in a straight-line test track, where three braking maneuvers were performed: low-pressure braking, mid-pressure braking, and emergence braking. The effects of ABS intervention and wet disk conditions were investigated from an experimental point of view. The paper describes the method used for the strain-gauge application in the bolts, calibration in a dynamometer traction and compression test, installation in the vehicle, and data analysis and post-processing. Results present consistent readings in the higher-pressure conditions, while for the low-pressure cases, the challenges related to load sensing sensitivity are more evident, with a clear tradeoff between system stiffness and measure sensitivity. Finally, evolutions of the system and further investigations on this promising technology applied to the automotive field are presented.
Recently, there’s a massive flow of change in the automotive industry with the coming era of electric vehicles and self-driving (autonomous) vehicles. The automotive braking system field is not an exception for the change and there are not only lots of new systems being developed but also demands for researches for optimizations of conventional brake systems fitting to the newly appeared systems such as E-Booster and Electric Motor Brake (EMB) Caliper. Taking the Electric Motor Brake Caliper for example, it is considered as a very important and useful system for autonomous vehicles because the motor actuator of the caliper is much easier to control with ECUs compared to the conventional hydraulic pressure system. However, easy of control is not the only thing that excites brake system engineers. Since the whole actuating mechanism of the brake systems has been changed, engineers now can see some new ways to solve chronic problems in conventional brake systems such as brake residual drag, brake fade and so forth. Brake residual drag can be possibly solved by simply connecting the motor actuator of the caliper to the brake piston so that ECUs can actually control the whole life cycle of brake torque creation and extinction. However, there have to be a few more components needed on top of the fact that its structure inside the brake piston could be much more complex than it used to be and this could cause some side effects as well. With the reasons above, this study illuminates the concept for a way of reducing brake residual drag in the new systems by enhancing the capability of piston roll-back of the caliper without any complex structures. Several test results and CAE analysis are presented and discussed to get a better understanding of the concept.
According to the European Environment Agency, air pollution is the biggest environmental health risk in Europe. Since traffic is one of the main contributors of fine dust, technical solutions are necessary to reduce the particulate emission footprint of vehicles. Also, the Health Effects Institute hosted recently an international workshop on non-tailpipe emissions. Brake dust filtration concepts have proven to be a promising solution to significantly reduce fine dust emissions from brakes directly at the source. While CFD simulations for inner-ventilated brakes have become state-of-the-art, a holistic model from particle generation and emission to particle dynamics in the vicinity of the brake is not yet available. However, a good modeling approach of particle tracks is essential to predict filtration efficiencies of brake dust particle filters. Based on current literature data and models, and independent of the turbulence model, filtration efficiencies cannot be predicted with required accuracy of <10%. Therefore, a new, reliable and quantifiable simulation model is developed. The simulation model has been implemented in ANSYS Fluent using the Discrete Particle Model. The rotation of the inner-ventilated brake disc is modeled via a Multiple Reference Frame combined with moving wall boundary conditions. Several emission locations are defined, and a subsequent parameter optimization was used to determine the parameters not accessible so far by experimental means. For validation, experiments were conducted based on an enclosure-in-chamber setup on an inertia brake dynamometer (LINK 3900) with low background concentration (<10 #/cm^3 measured with a TSI CPC 3756). Based on the WLTC Class 3 driving cycle, four floating caliper brakes in combination with 10 different filter designs are tested to validate the model. A maximum deviation between simulation and experiments of <10% in terms of filtration efficiency was achieved.
Constant innovation in machine design, compatible materials and design software is leading additive manufacturing from the prototype shop to the production floor. While the 3D-printed vehicle remains a dream, the technology also known as additive manufacturing (AM) already has proven its ability to create impressively complex part geometries in concepts such as EDAG's ‘Light Cocoon’ (https://www.edag.com/en/innovation/concept-cars). AM enabled the exquisite 8-piston brake calipers used by Bugatti, among other boutique components, and AM machines are becoming as ubiquitous as Bridgeport mills once were for advanced-prototype builds. Low-volume series production use has arrived - see VW news below. Greater scale is on the horizon, driven by constant innovation in machine design, compatible materials and design software. 3D printing technology and applications are exploding in the mobility space, high-lighted by the following recent examples.
This SAE Recommended Practice (RP) applies to the validation process for test systems used to measure deflection (compressibility, creep, or swell and growth) of friction materials and friction material assemblies. The materials or assemblies can fit passenger cars, light trucks, and commercial vehicles equipped with hydraulic or air brake systems, using disc or drum brakes.
The particulate emissions of two brake systems were characterized in a dilution tunnel optimized for PM10 measurements. The larger of them employed a fixed caliper (FXC) and the smaller one a floating caliper (FLC). Both used ECE brake pads of the same lining formulation. Measured properties included gravimetric PM2.5 and PM10, Particle Number (PN) concentrations of both untreated and thermally treated (according to exhaust PN regulation) particles using Condensation Particle Counters (CPCs) having 23 and 10 nm cut-off sizes, and an Optical Particle Sizer (OPS). The brakes were tested over a section (trip-10) novel test cycle developed from the database of the Worldwide harmonized Light-Duty vehicles Test Procedure (WLTP). A series of trip-10 tests were performed starting from unconditioned pads, to characterize the evolution of emissions until their stabilization. Selected tests were also performed over a short version of the Los Angeles City Cycle. PM2.5 emissions of burnished pads averaged at 2.6 mg/km/brake and 4.1 mg/km/brake for the FLC and the FXC system, respectively. A large fraction of the airborne PM was found to be larger than 2.5 μm, leading to 2.7 times higher PM10 emissions. Therefore, proper PM10 measurements will require careful considerations on the operating tunnel parameters to minimize particle losses. The FXC system yielded ~50% higher PM and two times higher PN emissions despite the 22% lower disc temperatures measured with an embedded thermocouple. No indication of volatile particle formation was observed, with more than 80% of total PN having an optical diameter larger than 300 nm. The results illustrate the challenges associated with the use of disc temperature measurements for the control of a representative braking procedure.
The objective of the research is to develop a lightweight yet stiff, 2 piston fixed brake caliper which can be used in formula student race car. To make a race car, its components need to be lighter. To stop a car with minimum stopping distance, it needs to have a sophisticated braking system with well-designed components. The designing of the caliper is carried out on the Altair Inspire software. The topology optimisation algorithm is used to minimise the weight of the caliper without compromising the stiffness. The structural analysis is also carried out on the Altair Inspire. The caliper is also tested for fatigue failure using Ansys.
The research on coasting resistance is vital to electric vehicles, since the smaller the coasting resistance, the longer the coast-down distance. Vehicle coast resistance consists of rolling resistance, vehicle inner resistance and the aerodynamic drag. The vehicle inner resistance is mainly caused by driveline’s friction loss and oil splash loss. The rolling resistance is decided by tire resistance coefficient, which is influenced by tires and road conditions. And the aerodynamic drag is affected by vehicle’s shape and air. In this paper, four factors including tire pressure, road surface condition, atmosphere temperature, and recirculation on or off are examined. Experimental tests have been conducted on three different vehicles: one subcompact sedan, one compact sedan and one subcompact SUV. Then experimental results have been imported to simulation model to investigate the corresponding influence on NEDC range. The outcome shows that, when the tire pressure is 20% less, the average coasting resistance is increased by 1% to 3% depending on vehicle types, which indicates a decrease in NEDC range by around 2%. And with atmosphere temperature in 6 to 32°C range, the resistance is decreased by 0.48% for every 1°C increased. On wet road surface, the average coasting resistance is increased by 10% - 20%, which could decrease the NEDC range by 6% to 12%. As for the recirculation on or off, one vehicle with inside air recirculation on experiences an average 6% coasting resistance reduction. Other two vehicles have similar coasting resistances whether the recirculation is on or off. The overall results give a better understanding on how the coasting resistance is influenced by various factors and can instruct future vehicle’s low coasting resistance development. More factors such as brake calipers, tire size, and other corresponding influences will be studied in future tests.
The strong focus on reducing brake drag, driven by a historic ramp-up in global fuel economy and carbon emissions standards, has led to renewed research on brake caliper drag behaviors and how to measure them. However, with the increased knowledge of the range of drag behaviors that a caliper can exhibit comes a particularly vexing problem - how should this complex range of behaviors be represented in the overall road load of the vehicle? What conditions are encountered during coastdown and fuel economy testing, and how should brake drag be measured and represented in these conditions? With the Environmental Protection Agency (amongst other regulating agencies around the world) conducting audit testing, and the requirement that published road load values be repeatable within a specified range during these audits, the importance of answering these questions accurately is elevated. This paper studies these questions, and even offers methodology for addressing them. It includes a review of how variation in brake drag can affect fuel economy and carbon emissions certification, a review of the many transient and driver-dependent behaviors and operating conditions that can affect drag at a vehicle level (and means of measuring them) and then offers a methodology (based on probabilistic modeling) for predicting the range of drag that can be encountered in fuel economy testing. In the course of developing the methodology, a significant database of vehicle level brake drag measurements is analyzed, and a case study vehicle is used to show correlation in a “walk” from component level to vehicle level caliper drag behavior.
Caused by a number of beneficial properties inherently from the zinc-nickel material, this electrodeposited alloy is used more and more for cathodically protecting layers on ferrous components like cast iron brake calipers. Direct plating from acidic solutions is the state-of-the-art solution for zinc-nickel surface finishing of these components. To contribute to the continuous improvement of the final component and reduce the finishing cost, areas for improvement have been scrutinized in a current finishing system. Areas for improvement have been identified in the uniformity of the nickel distribution within different current densities and in the handling and economy of the metallic zinc anodes used for zinc metal replenishment. While today’s acidic zinc-nickel electrolytes suit and usually exceed the requirements for an alloy containing 10-15% nickel, nickel incorporation may drop just below 12% incorporation rate in areas which are plated at high current densities. Formation of white corrosion products is observed in those areas earlier than in areas bearing higher (>12%) nickel. Development on the zinc-nickel plating electrolyte’s additive system has resulted in a significantly more uniform plated deposit with improved resistance against white corrosion. Previous disadvantages in the plating system including rising metal concentrations, anode passivation and insufficient zinc metal utilization will be overcome using the new membrane anode system. This separates the zinc metal anode from the plating bath. The electrolyte can then be operated at constant metal concentrations, constant anode voltages, with no need to remove anodes in idle periods, without any anode reactivation and significantly better anode metal utilization. These developments provide important contributions for improved operating efficiencies through higher productivity and improved material economy. The significant effect of these developments on higher and more consistent quality of the plated layers finally also contributes to the overall reliability of cast iron brake systems.
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