Browse Topic: Cams
Technologies transition from dominance to nearly dead at different speeds and for various reasons. That's particularly true for motive power. Pistons, cams and valves are giving way to anodes, cathodes and inverters. Governments and OEMs are pledging hard deadlines (2035!) to end sales of combustion-engine light vehicles. Amid the radical changes, what becomes of the V8 - the engine type that has defined American cars and trucks and has spurred their sales for the past 70 years? It took more than two decades for the automobile to end the horse's reign as the mainstream prime mover. Well into the heyday of Ford's Model T, streets in many U.S. towns remained clogged with horse-drawn vehicles, period photos show.
In the current situation and upcoming government regulations, hybrid vehicles are very promising in terms of meeting fuel economy and stringent requirements of emission norms. Herein, hybridization will be mostly done with gasoline and CNG vehicles. As a normal practice, engine is switched off at the signal and again restart with engine start-stop technology. So, instances of engine start/stop are increased in hybrid vehicle in comparison with standard IC engine vehicle. In order to achieve smooth engine start, engine starting torque can be optimized by adjusting engine valve timing. As Electric Cam Phaser (ECP) meets valve timing target even before first engine combustion start, this is one of the critical technologies in reducing engine starting torque and time reaching to idle speed. This engine starting strategy also gives benefits in terms of reducing engine start emissions and improving fuel economy. This paper describes selection of electric cam phaser for hybrid vehicle depending on specific engine starting and vehicle requirements. In addition to this, engine starting vibration is very critical, as its frequency increases due to multiple engine start/stop operation in hybrid vehicle either on traffic signal or on smooth highways. This work also shows detail understanding of engine start vibrations and ECP strategy to reduce these vibrations by optimizing engine valve timing.
Dynamic Skip Fire (DSF) is a proven cylinder deactivation strategy developed at Tula Technology that, in production, has proven to deliver significant fuel consumption improvements across engine and vehicle platforms. DSF allows cylinders to operate near optimal efficiency by reducing pumping losses and improving combustion stability. The Atkinson cycle is also a well-known strategy to improve thermodynamic efficiency by reducing pumping losses and over-expanding combustion gases. This strategy is commonly implemented with long duration intake cams and late intake valve closing. The Atkinson cycle sacrifices power density in a naturally aspirated engine so displacement is commonly increased. The upsized Atkinson cycle engine still shows significant reduction in fuel consumption at high load but has a fuel consumption penalty at low loads due to increased friction and throttling losses. This paper introduces a new synergistic engine concept that employs DSF with Atkinson cycle to operate firing cylinders at peak efficiency and minimize the low load penalty of the Atkinson cycle engine. Engine simulations were used to derive all-cylinder firing engine fuel maps for a state-of-the-art baseline (4-cylinder, 2.0 l) and an upsized Atkinson cycle engine (4-cylinder, 2.5 l) with cooled EGR (CEGR). Simulations for a D-segment vehicle with a 6-speed transmission in the WLTC were used to determine four weighted engine speed/load points with high fuel and time share that represent the total fuel consumed on the drive cycle. The DSF and Atkinson DSF engines were optimized at these conditions, considering appropriate noise, vibration, and harshness constraints, and the estimated cycle fuel consumption was calculated. Compared with the baseline, the Atkinson 2.5L CEGR engine showed a fuel consumption improvement of 0.9%, whereas the baseline DSF engine reduced fuel consumption by 6.1%. The Atkinson-CEGR engine with DSF reduced fuel consumption by 8.4%, exhibiting a synergy of 1.4% that would otherwise not be obtained from each individual technology. DSF improvements include simulated steady state fuel consumption reduction and estimated deceleration cylinder cut-out benefit.
This paper provides a summary of a Liquefied Petroleum Gas (LPG) concept engine developed for medium duty applications (class 6-7 trucks) targeting high efficiency with a power density that matches turbocharged diesel engines. The turbocharged in-line 6 cylinder engine incorporates an advanced spark ignition combustion system design, a purpose built medium-duty class engine structure optimized for operation with a direct propane injection system, dual overhead cams with individual cam phasers and twin-entry turbocharger. The high tumble charge motion combustion system targeted for operation with direct injected (DI) LPG has resulted in an engine capable of producing up to 22 bar brake mean effective pressure (BMEP) at high brake thermal efficiency (BTE) throughout the operating map. The high BTE combined with low carbon to hydrogen ratio of LPG results in 12% lower Brake Specific CO2 (BSCO2) emissions on the heavy-duty FTP cycle when compared to a diesel engine of same displacement and power and 15-30% lower BSCO2 when compared to other commercially available medium-duty LPG engines. The present work demonstrates total cost savings between 1 and 40% (depending on the cost differential between LPG and diesel) over 10 years on a drive cycle represented by the FTP cycle when compared to a diesel engine with similar displacement and torque curve. The ability to run at or close to Maximum Brake Torque (MBT) spark timing along with low pumping losses have ensured high BTE over the entire operating region of the engine.
In an accident reconstruction, vehicle speeds and positions are always of interest. When provided with scene photographs or fixed-location video surveillance footage of the crash itself, close-range photogrammetry methods can be useful in locating physical evidence and determining vehicle speeds and locations. Available 3D modeling software can be used to virtually match photographs or fixed-location video surveillance footage. Dash- or vehicle-mounted camera systems are increasingly being used in light vehicles, commercial vehicles and locomotives. Suppose video footage from a dash camera mounted to one of the vehicles involved in the accident is provided for an accident reconstruction but EDR data is unavailable for either of the vehicles involved. The literature to date describes using still photos to locate fixed objects, using video taken from stationary camera locations to determine the speed of moving objects or using video taken from a moving vehicle to locate fixed objects. However, techniques to evaluate the position, speed and acceleration of moving objects seen in video taken from moving locations have not been evaluated. To address the increasing prevalence of dash cams and other in-vehicle video and the value in using such video in vehicle crash reconstruction, this paper describes techniques for determining the position and speed of a moving object from digital video taken from a moving vehicle. Evaluations of the accuracy of those techniques were done when provided three different levels of information about the environment: 1 Aerial Photography (USGS) 2 Survey Data (Total Station) 3 3D Scan Data (of both the environment and vehicles)
Direct drive servo motor and drive technology has many advantages. It reduces an axis’ parts count, mechanical losses, and often its objectionable noise. What’s more, it also increases the machine’s efficiency, lowering operation cost for the user due to its inertia ratio as compared to the more common mechanically advantaged multi-body axis designs. Reducing the mechanical transmission components (gearboxes, timing belts, pulleys, cams, lead screws, etc.) between the motor and its load is only part of the savings.
Advanced SI engines for passenger cars often use the cylinder deactivation technology for dethrottling and thus achieving a reduction of fuel consumption. The gas exchange valves of the deactivated cylinders are closed permanently by a zero lift of the cams. The solutions for cylinder deactivation can vary in the kind of gas composition included in the deactivated cylinders: charge air, exhaust gas or vacuum. All these strategies have in common the frequent loss of captured charge mass from cycle to cycle. Their two-stroke compression-expansion cycle additionally intensifies this phenomenon. Thus, a significant decrease of the minimum cylinder pressure can cause an undesired entry of lubricant into the combustion chamber. The idea was to ventilate the generally deactivated cylinders frequently to compensate the loss of captured cylinder charge mass. The task was to keep the minimum cylinder pressure above a certain limit to prevent the piston rings from a failure. However, a compromise has to be found about the value of IMEP the deactivated cylinders perform in dependence of the included charge mass. The experimental design for this investigation contains a large variety of parameters: type of inclusion, choice of ventilation valves, phase, intensity and frequency of ventilation. Some parametric combinations can be an interesting compromise. They use a ventilation phase at BDC_HP 180°CA before firing TDC in contact to the intake manifold or at BDC_GE 180°CA after firing TDC in contact to the exhaust manifold. Both advantageous strategies use small valve lift curves and low ventilation frequencies.
Gasoline engine downsizing has become a popular and effective approach to reduce CO2 emissions from passenger cars. This is typically achieved in the form of a boosted direct injection gasoline engine, which are typically equipped with variable valve timing (VVT) devices on the intake and/or exhaust valves. This paper describes the synergies between valve timings and boost based on experimental investigations in a single cylinder gasoline direct injection spark ignited (DISI) engine with variable cam phasing on both the intake and exhaust cams. Two cam profiles have been tested to realize Miller cycle and compared with the standard camshaft. One cam features a long opening duration and standard valve lift for Late Intake Valve Closing (LIVC) and the other cam has a short opening duration and low valve lift for Early Intake Valve Closing (EIVC). An external boost rig was used to provide adjustable pressurized air charge, allowing conditions of up to 4000rpm and 25.6 bar NIMEP to be studied. Results have shown that the EIVC cam produced the best net Indicated Specific Fuel Consumption (ISFC) among the three cam profiles, with up to 11% improvement in net ISFC relative to the standard cam profile. The benefits of late split injections have also been studied to overcome the issue of low combustion speed when using low valve lift.
Suppliers and engine designers are attacking every potential source of internal friction-no longer a “low-hanging fruit”-as the battle to squeeze more mechanical work from less fuel intensifies. Reducing internal friction has always been a priority of powertrain designers, but recently the subject has taken on greater urgency in the crunch to meet tough new global CO2 regulations. In piston engines, friction loss rises with the square of rpm, which is one reason OEMs are “downspeeding” their new engine families. And with their key suppliers, they're digging deeper to find cost-effective solutions to this century-old challenge-from “rollerizing” camshafts to optimizing lubrication schemes, to new gas-cushion shaft seals, to decoupling front-end drive systems. New materials and surface coatings are also enablers. “We looked across the entire propulsion system to find places we could reduce spin and drag losses and minimize internal friction,” said Tim Grewe, GM's General Director of Vehicle Electrification, speaking to Automotive Engineering about the 2016 Chevrolet Volt. “This is a major area of focus in vehicle development at GM and the industry going forward.”
Over the years, internal combustion engines have been researched and improved in the search for more power and for lower fuel consumption. An automotive subsystem that directly affects the performance of the engine is the valve train system. This system allows for the control of the admittance and release of gases from the combustion chamber. This system operates in all phases, ensuring that the valves open and close properly and ensuring the sealing of the cylinder. Several researchers have studied the kinematics and dynamics of the valve actuation system to improve engine performance. As the actuation of the valves occurs usually by cams, every movement and timing of the system is dictated by the design characteristics of the profile of the cams: it has a predominant action on the dynamics of the system. Many phenomena, such as the vibration of the drive system, impacts on the valve seat, and loss of physical contact between cam and follower can be understood and optimized by manipulation of the profile. One can minimize unwanted effects with concise understanding of the computational manipulation of the curve representing the cam profile. In industry, there are few institutions holders of such structured knowledge, which makes it difficult and costly to develop and optimize projects. Thus, the objective of this work is to present an efficient computational way to manipulate the curve representing the profile of cams, aiming their application in computer simulations and optimization routines.
Mechanisms are used widely in engineering applications due to their ability to translate force and movement. They are found in kinematic pairs, gears, cams, linkages, and in flexure mechanisms (also known as compliant mechanisms). Mechanisms and flexures are used widely in spacecraft design, especially in the area of optics, where precise positioning of telescope mirrors requires elastic flexing of elements. A compliant mechanism is generally defined as a flexible mechanism that uses an elastic body deformation to cause a displacement (such as positing a mirror). The mechanisms are usually constructed as a single monolithic piece of material, and contain thin struts to allow for large elastic bending with low input force. This creates the largest problem with developing precise mechanisms; they must be fabricated from a single piece of metal, but are required to have strict accuracy on their dimensions. They are generally required to have high strength, elasticity, and low coefficient of thermal expansion.
The new 2.0L gasoline engine for ACCORD Plug-in Hybrid was developed as a next-generation Honda engine series. This engine's features are low fuel consumption and good emission performance. Variable valve Timing and Electric Control (VTEC) system is applied to this engine, so we can have two characteristic cams, output cam and fuel economy (FE) cam. Output cam is narrow duration, used for power and engine starting. FE cam is wide duration, so it can get Atkinson cycle effect by late intake valve close timing (IVC). Cooled exhaust gas recirculation (Cooled-EGR) is applied to this engine. Low fuel consumption is achieved by combining VTEC and cooled EGR. We made the improvement of control systems. First is the new control which can secure the pressure difference before and behind the EGR valve. As a result, EGR flow control performance is improved. Second is improvement of torque control. It can predict an engine torque decrease when ignition retard is carried out. We keep drivability and fuel consumption in severe condition. Last is the control which changes an operating point according to atmospheric pressure. It can keep low fuel consumption, if environmental change occurs. New quick warm-up system for hybrid vehicle catalyst is developed. At engine starting, engine load was controlled by changing operation of the motor. It became possible to warm catalyst effectively. As a result, tail pipe emissions could be reduced and SULEV20 regulation was suited.
The objective of this investigation was to evaluate the effects of a variable intake and exhaust valve timing in terms of opening, closing, opening duration, lift curve and number of active valves per pair on a four cylinder direct-injecting SI engine for the catalyst heating idling phase at the beginning of an NEDC emission test procedure. The first step evaluated the engine behavior at a reference point of operation. Its parameters in valve timing were adjusted to match the valve timing of the base production engine. The second step investigated the effects of an earlier exhaust valve opening while the exhaust valve closing time was kept and the exhaust valve opening duration was extended. The third step was to answer the question for the optimum number of exhaust valves in order to minimize the wall heat losses inside the cylinder head. The optimum 3V exhaust valve timing has been defined as the basis for exhaust valve timing for steps four and five. The fourth step contained the variation of intake valve opening and closing. The group of selected optimum valve timing / ignition timing combinations mainly consists of late intake valve opening and decreased intake valve opening durations. The fifth and final step was to evaluate the optimum number of intake valves in order to find out whether it makes sense to add another source of charge motion. It can be stated that a combination of both a late intake valve opening and intake valve deactivation must be excluded for this evaluated catalyst heating point of operation. From this point of view, two alternative VVT strategies with comparable potential can be seen: either late intake valve opening with decreased intake valve opening duration, or intake valve deactivation with standard intake valve opening duration and a slight valve overlap. Both of these intake valve strategies have at least one thing in common: a valve train with the digital ability to change the cams is necessary for their realization. Their general potential can be numbered in a 3-13 % increase of exhaust gas and catalyst temperature, a 5-30 % decrease of gaseous emissions output, and a 80-95% decrease of FSN. It also has the potential of a 5-25 % decrease in related standard deviation of imep.
Setting the correct valve timing and lift based on the operating speed will be the key to achieving good volumetric efficiency and torque. Continuously variable valve timing systems are the best choice but are too expensive. In this work a novel two stage variable valve actuation system was conceived and developed for a small single cylinder three wheeler spark ignition engine. The constraints were space, cost and complexity. The developed system uses one cam for low speeds and another cam that has a higher lift and duration for high speeds. The shift between the cams occurs through the mechanism even as the engine runs by the operation of a stepper motor which can be connected to the engine controller. A one dimensional simulation model validated with experimental data was used to predict the suitable valve timings and lifts in low and high speed ranges. Two profiles were then selected. The mechanism to achieve shifting between cams was conceived and modeled in standard software for verifying the kinematics. A prototype of the mechanism was made and tested on the engine under motored conditions. A stepper motor with a controller was employed to operate the mechanism. The developed system resulted in improved volumetric efficiency and smooth shifting between the cams at specified speeds without difficulty. This system can be easily integrated into the existing vehicle.
Miniaturization of medical devices offers tangible advantages to clinicians and patients alike. Smaller pill cams, for example, are more easily ingested. Likewise, smaller hearing aids are less invasive and therefore more comfortable for the wearer. But before either of these devices — and many others like them — can be reduced in size, their components must be made smaller. Magnetic reed switches are increasingly being used to enable manufacturers to reduce their footprint while maintaining tight sensitivities and performance characteristics.
Intelligent networking of cars and infrastructure promises a future of enhanced active safety and traffic efficiency, though as an open and decentralized system, car-to-X is exposed to various attacks against security and driver’s privacy. Field operational tests (FOTs) are under way that examine car-to-car and car-to-infrastructure communication (car-to-X) applications with regard to effects on traffic safety and efficiency. With a vehicle fleet up to 400 vehicles and 100 roadside units (RSUs), a German project, sim (Safe and Intelligent Mobility), is said to be the first FOT large enough to test and validate applications, technologies, and systems for car-to-X communication in a real-life environment that exceeds the demonstrator status. Sim includes various kinds of applications from different categories. With respect to road safety, Electronic Brake Light, Collision Avoidance on Intersections, or Weather Hazard Warning are applications that may enable drivers to avoid some of the most frequent causes of accidents. Also, traffic-management systems may react on related events more dynamically because mobility data of all vehicles are constantly monitored by RSUs.
This work presents the results of a simulation using the Finite Elements Method (FEM) to study the contact pressure between cams and followers in assembled camshafts. The geometry was chosen based on an iron casting camshaft from a commercial car in order to have a base to ensure that the assembled camshaft is a great solution to increase the performance and to reduce weight. Surfaces that are in contact with high levels of contact pressure can increase the wear and reduce the lifetime of the components. In contact stress analysis, the most critical modeling consideration is to choose the ideal meshing, so, as a preparatory step we summarized with some simulations, defined an acceptable model to run 3D finite elements analysis and calculated the contact pressure.
Advanced valvetrain coupled with Direct Injection (DI) provides an opportunity to simultaneous reduction of fuel consumption and emissions. Because of their robustness and cost performance, multi-hole injectors are being adopted as gasoline DI fuel injectors. Ethanol and ethanol-gasoline blends synergistically improve the performance of a turbo-charged DI gasoline engine, especially in down-sized, down-sped and variable-valvetrain engine architecture. This paper presents Mie-scattering spray imaging results taken with an Optical Accessible Engine (OAE). OAE offers dynamic and realistic in-cylinder charge motion with direct imaging capability, and the interaction with the ethanol spray with the intake air is studied. Two types of cams which are designed for Early Intake Valve Close (EIVC) and Later Intake Valve Close (LIVC) are tested, and the effect of variable valve profile and deactivation of one of the intake valves are discussed. Multi-dimensional Computation Fluid Dynamics (CFD) results for predicting DI multi-hole ethanol spray behaviors are presented as well. The effects of injection timing on the bulk flow motion and fuel-air mixing, in terms of tumble and swirl ratios, turbulence, and fuel wall film behaviors are discussed. Combined with metal engine test results which run with gasoline, the important mechanisms for reducing fuel consumption and emissions in a SIDI, variable-valve actuated engine are demonstrated.
The small B-Max MAV uses familiar Ford “kinetic” design cues. DRAWING HEAVILY ON FORD'S IOSIS MAX CONCEPT from the 2009 Geneva Motor Show, the Ford B-Max unveiled at the 2011 Geneva Motor Show is a near production-ready model, which features the sliding rear doors and lack of B-pillar from the Iosis-Max. Ford says the door arrangement has already been engineered for production. B-Max will extend the Ford MAV (Multi Activity Vehicle) range downwards from the C-Max and will effectively serve as a replacement for the European-market Fusion based on an earlier Fiesta B-segment platform. The new MAV is based on Ford's global B-car platform first used with the latest-generation Fiesta three years ago. The new car measures 4060 mm (159.8 in) long, 110 mm (4.3 in) longer than a Fiesta five-door and 320 mm (12.6 in) shorter than the latest C-Max. It stands 110 mm taller than a Fiesta. With the front and rear passenger seats folded, it can accommodate items up to 2350 mm (92.5 in) long.
Sprag handle wrenches have been proposed for general applications in which conventional pawl-and-ratchet wrenches and sprag and cam “clickless” wrenches are now used. Sprag handle wrenches are so named because they would include components that would function both as parts of handles and as sprags (roller locking/unlocking components). In comparison with all of the aforementioned conventional wrenches, properly designed sprag handle wrenches could operate with much less backlash; in comparison with the conventional clickless wrenches, sprag handle wrenches could be stronger and less expensive (because the sprags would be larger and more easily controllable than are conventional sprags and cams).
Concern for engine particle emission led to EC regulations of the number of solid particles emitted by LDV and HDV. However, all conventional piston-driven combustion engines emit metal oxide particles of which only little is known. The main sources are abrasion between piston ring and cylinder, abrasion of bearing, cams and valves, catalyst coatings, metal-organic lubrication oil additives, and fuel additives. While abrasion usually generates particles in the μm range, high concentrations of nanosize metal oxide particles are also observed, probably resulting from nucleation processes during combustion. In general, metal oxides, especially from transition metals, have high surface reactivity and can therefore be very toxic, especially nanosize particles, which evidently provide a high specific bioactive surface and are suspected to penetrate into the organism. Hence, these particles must be scrutinized for quantity, size distribution and composition. Published data are summarized and data from investigations of various engines with respect to metal oxide particle emission are reported. These investigations were performed without and with VERT-approved particle filters, where VERT is an international verification standard for emission reduction technologies, which, besides of filtration effectiveness, durability and limited pollutants also includes the analysis of secondary emissions, potentially formed by these technologies and of size specific metal emissions. In good agreement with literature, the overall metal mass in the exhaust of IC engines without particle filter is in the range of 0.1-1 mg/km metal. This combines wear metals and metals from lubrication oil additives. Size-specific chemical analysis has shown that a large part of metal oxide particles are to be found in the size classes below 60 nm. However there are more metal oxide particles in the exhaust attached to soot particles of larger size, as chemical analysis also revealed. If there are less soot particles prevalent, like at idle conditions some of them do appear unattached in a separate fraction of much smaller size. SMPS particle size distribution at idle shows peaks of up to 108 particles per cc in the size range of 10-30 nm. It must be assumed that these are all metal oxide particles since PMP sampling was applied which means that these particles survived 300°C and thus cannot be volatiles. This high number of solid metal oxide particles implies a potential health risk. Hence, there is a need to further focus on small metal oxide particle emissions. For diesel engines, industry has demonstrated that particle filters are available which can very efficiently filter those nanoparticles. There is little known about metal oxide emissions of other engines but it must be anticipated that all IC piston engines do emit such particles. Elimination of such metal oxide particles by highly efficient filtration therefore might become an urgent future requirement for all engine categories.
The High Efficiency Hybrid Cycle (HEHC) is a thermodynamic cycle which borrows elements of Diesel, Otto and Atkinson cycles, including: Air compression to a high ratio, followed by fuel injection and compression ignition (Diesel). Constant volume combustion (Otto) Over-expansion (Atkinson) Optionally, internal cooling heat recovery via steam generation (Rankine). Simple air standard analysis predicts this cycle to be 17% more efficient than diesel and 19% more efficient than Otto. The construction of a prototype rotary engine implementing this cycle is also described in detail. The main engine components consist of a rotor in pure rotation and two reciprocating gates directly driven by overhead cams. This combination separates the working mixture into three separate volumes. At a given rotor position each volume operates at a different part of the cycle. For instance, intake/compression, combustion, expansion/exhaust are occurring simultaneously in separate chambers. As the rotor moves, the cavity formed by the side of the rotor, the retracting compressor gate, and the stationary housing is decreasing in volume, producing compression. The gate fully retracts, as the rotor passes beneath. The air is fully compressed into a combustion chamber within the housing and held at constant volume. Fuel is injected, and combustion occurs at relatively constant volume. As the rotor continues its motion, the volume defined by the housing, expander-gate, and the rotor is increasing through the completion of the expansion stroke. Due to the geometry, a higher expansion ratio is achieved relative to the compression ratio. The result is a high power density, high speed engine. A 20 HP prototype is currently being tested. Predicted output is 143 Hp/L and 30% thermal efficiency.
As modern machines have become more advanced, the complexity involved in motion control has escalated. Today, servos have replaced cams and gears on machines and multiple axis of synchronized motion control have become commonplace. Distributed motion control requires busses able to handle rigid jitter and timing demands including:
Mechanical CAD (computer-aided design) programs have become very sophisticated during the past few years. Unfortunately, there is still a portion of the engineering spectrum that cannot be handled well in a traditional CAD program: optical modeling. If you are creating a complicated optical system (think of a camera zoom lens), then it is best to perform almost all of the design in a specialized optical design software program and then transfer the optical design to a CAD program for the later stages of the design process where items like housings, threads, cams, and motors are designed and integrated into the model.
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