A torque converter is a type of fluid coupling which transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power source to the load, it is located between the engine's flexplate and the transmission. The equivalent location in a manual transmission would be the mechanical clutch; the key characteristic of a torque converter is its ability to multiply torque when the output rotational speed is so low that it allows the fluid coming off the curved vanes of the turbine to be deflected off the stator while it is locked against its one-way clutch, thus providing the equivalent of a reduction gear. This is a feature beyond that of the simple fluid coupling, which can match rotational speed but does not multiply torque, thus reduces power; some of these devices are equipped with a "lockup" mechanism which rigidly binds the engine to the transmission when their speeds are nearly equal, to avoid slippage and a resulting loss of efficiency.
By far the most common form of torque converter in automobile transmissions is the hydrokinetic device described in this article. There are hydrostatic systems which are used in small machines such as compact excavators. There are mechanical designs for continuously variable transmissions and these have the ability to multiply torque, they include the pendulum-based Constantinesco torque converter, the Lambert friction gearing disk drive transmission and the Variomatic with expanding pulleys and a belt drive. Automatic transmissions on automobiles, such as cars, on/off highway trucks. Forwarders and other heavy duty vehicles. Marine propulsion systems. Industrial power transmission such as conveyor drives all modern forklifts, drilling rigs, construction equipment, railway locomotives. Torque converter equations of motion are dominated by Leonhard Euler's eighteenth century turbomachine equation: τ = ∑ The equation expands to include the fifth power of radius. A fluid coupling is a two element drive, incapable of multiplying torque, while a torque converter has at least one extra element—the stator—which alters the drive's characteristics during periods of high slippage, producing an increase in output torque.
In a torque converter there are at least three rotating elements: the impeller, mechanically driven by the prime mover. The classic torque converter design dictates that the stator be prevented from rotating under any condition, hence the term stator. In practice, the stator is mounted on an overrunning clutch, which prevents the stator from counter-rotating with respect to the prime mover but allows forward rotation. Modifications to the basic three element design have been periodically incorporated in applications where higher than normal torque multiplication is required. Most these have taken the form of multiple turbines and stators, each set being designed to produce differing amounts of torque multiplication. For example, the Buick Dynaflow automatic transmission was a non-shifting design and, under normal conditions, relied upon the converter to multiply torque; the Dynaflow used a five element converter to produce the wide range of torque multiplication needed to propel a heavy vehicle.
Although not a part of classic torque converter design, many automotive converters include a lock-up clutch to improve cruising power transmission efficiency and reduce heat. The application of the clutch locks the turbine to the impeller, causing all power transmission to be mechanical, thus eliminating losses associated with fluid drive. A torque converter has three stages of operation: Stall; the prime mover is applying power to the impeller but the turbine cannot rotate. For example, in an automobile, this stage of operation would occur when the driver has placed the transmission in gear but is preventing the vehicle from moving by continuing to apply the brakes. At stall, the torque converter can produce maximum torque multiplication if sufficient input power is applied; the stall phase lasts for a brief period when the load starts to move, as there will be a large difference between pump and turbine speed. Acceleration; the load is accelerating but there still is a large difference between impeller and turbine speed.
Under this condition, the converter will produce torque multiplication, less than what could be achieved under stall conditions. The amount of multiplication will depend upon the actual difference between pump and turbine speed, as well as various other design factors. Coupling; the turbine has reached 90 percent of the speed of the impeller. Torque multiplication has ceased and the torque converter is behaving in a manner similar to a simple fluid coupling. In modern automotive applications, it is at this stage of operation where the lock-up clutch is applied, a procedure that tends to improve fuel efficiency; the key to the torque converter's ability to multiply torque lies in the stator. In the classic fluid coupling design, periods of high slippage cause the
A clutch is a mechanical device which engages and disengages power transmission from driving shaft to driven shaft. In the simplest application, clutches disconnect two rotating shafts. In these devices, one shaft is attached to an engine or other power unit while the other shaft provides output power for work. While the motions involved are rotary, linear clutches are possible. In a torque-controlled drill, for instance, one shaft is driven by a motor and the other drives a drill chuck; the clutch connects the two shafts so they may be locked together and spin at the same speed, locked together but spinning at different speeds, or unlocked and spinning at different speeds. The vast majority of clutches rely on frictional forces for their operation; the purpose of friction clutches is to connect a moving member to another, moving at a different speed or stationary to synchronize the speeds, and/or to transmit power. As little slippage as possible between the two members is desired. Various materials have been used including asbestos in the past.
Modern clutches use a compound organic resin with copper wire facing or a ceramic material. Ceramic materials are used in heavy applications such as racing or heavy-duty hauling, though the harder ceramic materials increase flywheel and pressure plate wear. In the case of "wet" clutches, composite paper materials are common. Since these "wet" clutches use an oil bath or flow-through cooling method for keeping the disc pack lubricated and cooled little wear is seen when using composite paper materials. Friction-disc clutches are classified as push type or pull type depending on the location of the pressure plate fulcrum points. In a pull-type clutch, the action of pressing the pedal pulls the release bearing, pulling on the diaphragm spring and disengaging the vehicle drive; the opposite is true with a push type, the release bearing is pushed into the clutch disengaging the vehicle drive. In this instance, the release bearing can be known as a thrust bearing. A clutch damper is a device. In automotive applications, this is provided by a mechanism in the clutch disc centres.
In addition to the damped disc centres, which reduce driveline vibration, pre-dampers may be used to reduce gear rattle at idle by changing the natural frequency of the disc. These weaker springs are compressed by the radial vibrations of an idling engine, they are compressed and no longer in use once the main damper springs take up drive. Mercedes truck examples: A clamp load of 33 kN is normal for a single plate 430; the 400 Twin application offers a clamp load of a mere 23 kN. Bursts speeds are around 5,000 rpm with the weakest point being the facing rivet. Modern clutch development focuses its attention on the simplification of the overall assembly and/or manufacturing method. For example, drive straps are now employed to transfer torque as well as lift the pressure plate upon disengagement of vehicle drive. With regard to the manufacture of diaphragm springs, heat treatment is crucial. Laser welding is becoming more common as a method of attaching the drive plate to the disc ring with the laser being between 2-3KW and a feed rate 1m/minute.
This type of clutch has several driving members interleaved or "stacked" with several driven members. It is used in racing cars including Formula 1, IndyCar, World Rally and most club racing. Multiplate clutches see much use in drag racing, which requires the best acceleration possible, is notorious for the abuse the clutch is subjected to. Thus, they can be found in motorcycles, in automatic transmissions and in some diesel locomotives with mechanical transmissions, it is used in some electronically controlled all-wheel drive systems as well as in some transfer cases. They can be found in some heavy machinery such as tanks and AFV's and earthmoving equipment, as well as components in certain types of limited slip differentials; the benefit in the case of motorsports is that you can achieve the same total friction force with a much smaller overall diameter. In motorsports vehicles that run at high engine/drivetrain speeds, the smaller diameter reduces rotational inertia, making the drivetrain components accelerate more as well as reducing the velocity of the outer areas of the clutch unit, which could become stressed and fail at the high drivetrain rotational rates achieved in sports such as Formula 1 or drag racing.
In the case of heavy equipment, which deal with high torque forces and drivetrain loads, a single plate clutch of the necessary strength would be too large to package as a component of the driveline. Another, different theme on the multiplate clutch is the clutches used in the fastest classes of drag racing specialized, purpose-built cars such as Top Fuel dragsters or Funny Cars; these cars are so powerful that to attempt a start with a simple clutch would result in complete loss of traction. To avoid this problem, Top Fuel cars use a single, fixed gear ratio, a series of clutches that are engaged one at a time, rather than in unison, progressively allowing more power to the wheels. A single one of these clutch plates can not hold more than a fr
The Hotchkiss drive is a shaft drive form of power transmission. It was the dominant means for rear-wheel drive layout cars in the 20th century; the name comes from the French automobile manufacturer Hotchkiss, although other makers, such as Peerless, used similar systems before Hotchkiss. During the early part of the 20th century chain-drive power transmission was the main direct drive competitor of the Hotchkiss system, with the torque tube popular until the 1950s. Most shaft-drive systems consist of a drive shaft extending from the transmission in front to the differential in the rear; the differentiating characteristic of the Hotchkiss drive is the fact that the axle housing is attached to the leaf springs to transfer the axle torque through them to the car body. It uses universal joints at both ends of the driveshaft, not enclosed; the use of two universal joints, properly phased and with parallel alignment of the drive and driven shafts, allows the use of simple cross-type universals. In contrast, a torque tube arrangement uses only a single universal at the end of the transmission tailshaft a constant velocity joint.
In the Hotchkiss drive, slip-splines or a plunge-type eliminate thrust transmitted back up the driveshaft from the axle, allowing simple rear-axle positioning using parallel leaf springs. In the torque-tube type this thrust is taken by the torque tube to the transmission and thence to the transmission and motor mounts to the frame. While the torque-tube type, when combined with rear coil springs, requires additional locating elements, such as a Panhard rod, this is not needed with a torque tube/leaf spring combination; some Hotchkiss driveshafts are made in two pieces with another universal joint in the center for greater flexibility in trucks and specialty vehicles built on firetruck frames. Some installations use rubber mounts to isolate vibration; the 1984–1987 RWD Toyota Corolla coupe is another example of a car that uses a 2-part Hotchkiss driveshaft with a rubber-mounted center bearing. This design was the main form of power transmission for most cars from the 1920s through the 1970s; as of 2016 it remains common in pick-up trucks, sport utility vehicles.
There is no connection between The Hotchkiss drive and the modern suspension-modification company Hotchkis. Automobile Engineering: A General Reference Work
Fuel cell vehicle
A fuel cell vehicle or fuel cell electric vehicle is a type of electric vehicle which uses a fuel cell, instead of a battery, or in combination with a battery or supercapacitor, to power its on-board electric motor. Fuel cells in vehicles generate electricity to power the motor using oxygen from the air and compressed hydrogen. Most fuel cell vehicles are classified as zero-emissions vehicles that emit only heat; as compared with internal combustion vehicles, hydrogen vehicles centralize pollutants at the site of the hydrogen production, where hydrogen is derived from reformed natural gas. Transporting and storing hydrogen may create pollutants. Fuel cells have been used in various kinds of vehicles including forklifts in indoor applications where their clean emissions are important to air quality, in space applications; the first commercially produced hydrogen fuel cell automobile, the Hyundai Tucson FCEV, was introduced in 2013, Toyota Mirai followed in 2015 and Honda entered the market. Fuel cells are being developed and tested in trucks, boats and bicycles, among other kinds of vehicles.
As of 2017, there was limited hydrogen infrastructure, with 36 hydrogen fueling stations for automobiles publicly available in the U. S. but more hydrogen stations are planned in California. Some public hydrogen fueling stations exist, new stations are being planned, in Japan and elsewhere. Critics doubt whether hydrogen will be efficient or cost-effective for automobiles, as compared with other zero emission technologies. All fuel cells are made up of three parts: an anode and a cathode. In principle, a hydrogen fuel cell functions like a battery, producing electricity, which can run an electric motor. Instead of requiring recharging, the fuel cell can be refilled with hydrogen. Different types of fuel cells include polymer electrolyte membrane Fuel Cells, direct methanol fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, reformed methanol fuel cell and Regenerative Fuel Cells; the concept of the fuel cell was first demonstrated by Humphry Davy in 1801, but the invention of the first working fuel cell is credited to William Grove, a chemist and physicist.
Grove's experiments with what he called a "gas voltaic battery" proved in 1842 that an electric current could be produced by an electrochemical reaction between hydrogen and oxygen over a platinum catalyst. English engineer Francis Thomas Bacon expanded on Grove's work and demonstrating various Alkaline fuel cells from 1939 to 1959.. The first modern fuel cell vehicle was a modified Allis-Chalmers farm tractor, fitted with a 15 kilowatt fuel cell, around 1959; the Cold War Space Race drove further development of fuel cell technology. Project Gemini tested fuel cells to provide electrical power during manned space missions. Fuel cell development continued with the Apollo Program; the electrical power systems in the Apollo capsules and lunar modules used alkali fuel cells. In 1966, General Motors developed the Chevrolet Electrovan, it had a range of 120 miles and a top speed of 70 mph. There were only two seats, as the fuel cell stack and large tanks of hydrogen and oxygen took up the rear portion of the van.
Only one was built. General Electric and others continued working on PEM fuel cells in the 1970s. Fuel cell stacks were still limited principally to space applications in the 1980s, including the Space Shuttle. However, the closure of the Apollo Program sent many industry experts to private companies. By the 1990s, automobile manufacturers were interested in fuel cell applications, demonstration vehicles were readied. In 2001, the first 700 Bar hydrogen tanks were demonstrated, reducing the size of the fuel tanks that could be used in vehicles and extending the range. There are fuel cell vehicles for all modes of transport; the most prevalent fuel cell vehicles are cars, buses and material handling vehicles. The Honda FCX Clarity concept car was introduced in 2008 for leasing by customers in Japan and Southern California and discontinued by 2015. From 2008 to 2014, Honda leased a total of 45 FCX units in the US. Over 20 other FCEVs prototypes and demonstration cars were released in that time period, including the GM HydroGen4, Mercedes-Benz F-Cell.
The Hyundai ix35 FCEV Fuel Cell vehicle has been available for lease since 2014, when 54 units were leased. Sales of the Toyota Mirai to government and corporate customers began in Japan in December 2014. Pricing started at ¥6,700,000 before taxes and a government incentive of ¥2,000,000. Former European Parliament President Pat Cox estimated that Toyota would lose about $100,000 on each Mirai sold; as of December 2017, global sales totaled 5,300 Mirais. The top selling markets were the U. S. with 2,900 units, Japan with 2,100 and Europe with 200. Retail deliveries of the 2017 Honda Clarity Fuel Cell began in California in December 2016; the Clarity Fuel Cell, with range of 366 mi, has the highest EPA driving range rating of any zero-emissions vehicle in the U. S. including fuel cell and battery electric vehicles. The 2017 Clarity has the highest combined and city fuel economy ratings among all hydrogen fuel cell cars rated by the EPA, with a combined city/highway rating of 67 miles per gallon gasoline equivalent, 68 MPGe in city driving.
In 2017 Daimler phased out of its FCEV development, citing declining battery costs and increasing range of EVs, most of the automobile companies developing hydrogen cars had switched their focus to battery electric vehicles. The following table compares EPA's fuel
An epicyclic gear train consists of two gears mounted so that the centre of one gear revolves around the centre of the other. A carrier connects the centres of the two gears and rotates to carry one gear, called the planet gear, around the other, called the sun gear; the planet and sun gears mesh. A point on the pitch circle of the planet gear traces an epicycloid curve. In this simplified case, the sun gear is the planetary gear roll around the sun gear. An epicyclic gear train can be assembled so the planet gear rolls on the inside of the pitch circle of a fixed, outer gear ring, or ring gear, sometimes called an annular gear. In this case, the curve traced by a point on the pitch circle of the planet is a hypocycloid; the combination of epicycle gear trains with a planet engaging both a sun gear and a ring gear is called a planetary gear train. In this case, the ring gear is fixed and the sun gear is driven. Epicyclic gears get their name from their earliest application, the modelling of the movements of the planets in the heavens.
Believing the planets, as everything in the heavens, to be perfect, they could only travel in perfect circles, but their motions as viewed from Earth could not be reconciled with circular motion. At around 500 BC, the Greeks invented the idea of epicycles, of circles travelling on the circular orbits. With this theory Claudius Ptolemy in the Almagest in 148 AD was able to predict planetary orbital paths; the Antikythera Mechanism, circa 80 BC, had gearing, able to approximate the moon's elliptical path through the heavens, to correct for the nine-year precession of that path. Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer gears, or planet gears, revolving about a central, or sun gear; the planet gears are mounted on a movable arm or carrier, which itself may rotate relative to the sun gear. Epicyclic gearing systems incorporate the use of an outer ring gear or annulus, which meshes with the planet gears. Planetary gears are classified as simple or compound planetary gears.
Simple planetary gears have one sun, one ring, one carrier, one planet set. Compound planetary gears involve one or more of the following three types of structures: meshed-planet, stepped-planet, multi-stage structures. Compared to simple planetary gears, compound planetary gears have the advantages of larger reduction ratio, higher torque-to-weight ratio, more flexible configurations; the axes of all gears are parallel, but for special cases like pencil sharpeners and differentials, they can be placed at an angle, introducing elements of bevel gear. Further, the sun, planet carrier and ring axes are coaxial. Epicyclic gearing is available which consists of a sun, a carrier, two planets which mesh with each other. One planet meshes with the sun gear. For this case, when the carrier is fixed, the ring gear rotates in the same direction as the sun gear, thus providing a reversal in direction compared to standard epicyclic gearing. In the 2nd-century AD treatise Almagest, Ptolemy used rotating deferent and epicycles that form epicyclic gear trains to predict the motions of the planets.
Accurate predictions of the movement of the Sun and the five planets, Venus, Mars and Saturn, across the sky assumed that each followed a trajectory traced by a point on the planet gear of an epicyclic gear train. This curve is called an epitrochoid. Epicyclic gearing was used in the Antikythera Mechanism, circa 80 BCE, to adjust the displayed position of the moon for the ellipticity of its orbit, for the apsidal precession of its orbit. Two facing gears were rotated around different centers, one drove the other not with meshed teeth but with a pin inserted into a slot on the second; as the slot drove the second gear, the radius of driving would change, thus invoking a speeding up and slowing down of the driven gear in each revolution. Richard of Wallingford, an English abbot of St Albans monastery is credited for reinventing epicyclic gearing for an astronomical clock in the 14th century. In 1588, Italian military engineer Agostino Ramelli invented the bookwheel, a vertically-revolving bookstand containing epicyclic gearing with two levels of planetary gears to maintain proper orientation of the books.
The gear ratio of an epicyclic gearing system is somewhat non-intuitive because there are several ways in which an input rotation can be converted into an output rotation. The three basic components of the epicyclic gear are: Sun: The central gear Carrier: Holds one or more peripheral Planet gears, all of the same size, meshed with the sun gear Ring or Annulus: An outer ring with inward-facing teeth that mesh with the planet gear or gearsThe overall gear ratio of a simple planetary gearset can be calculated using the following two equations, representing the sun-planet and planet-ring interactions respectively: N s ω s + N p ω p − ω c = 0
The Diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel, injected into the combustion chamber, is caused by the elevated temperature of the air in the cylinder due to the mechanical compression. Diesel engines work by compressing only the air; this increases the air temperature inside the cylinder to such a high degree that atomised Diesel fuel injected into the combustion chamber ignites spontaneously. With the fuel being injected into the air just before combustion, the dispersion of the fuel is uneven; the process of mixing air and fuel happens entirely during combustion, the oxygen diffuses into the flame, which means that the Diesel engine operates with a diffusion flame. The torque a Diesel engine produces is controlled by manipulating the air ratio; the Diesel engine has the highest thermal efficiency of any practical internal or external combustion engine due to its high expansion ratio and inherent lean burn which enables heat dissipation by the excess air.
A small efficiency loss is avoided compared with two-stroke non-direct-injection gasoline engines since unburned fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed Diesel engines can reach effective efficiencies of up to 55%. Diesel engines may be designed as either four-stroke cycles, they were used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in ships. Use in locomotives, heavy equipment and electricity generation plants followed later. In the 1930s, they began to be used in a few automobiles. Since the 1970s, the use of Diesel engines in larger on-road and off-road vehicles in the US has increased. According to Konrad Reif, the EU average for Diesel cars accounts for 50% of the total newly registered; the world's largest Diesel engines put in service are 14-cylinder, two-stroke watercraft Diesel engines. In 1878, Rudolf Diesel, a student at the "Polytechnikum" in Munich, attended the lectures of Carl von Linde.
Linde explained that steam engines are capable of converting just 6-10 % of the heat energy into work, but that the Carnot cycle allows conversion of all the heat energy into work by means of isothermal change in condition. According to Diesel, this ignited the idea of creating a machine that could work on the Carnot cycle. After several years of working on his ideas, Diesel published them in 1893 in the essay Theory and Construction of a Rational Heat Motor. Diesel was criticised for his essay, but only few found the mistake that he made. Diesel's idea was to compress the air so that the temperature of the air would exceed that of combustion. However, such an engine could never perform any usable work. In his 1892 US patent #542846 Diesel describes the compression required for his cycle: "pure atmospheric air is compressed, according to curve 1 2, to such a degree that, before ignition or combustion takes place, the highest pressure of the diagram and the highest temperature are obtained-that is to say, the temperature at which the subsequent combustion has to take place, not the burning or igniting point.
To make this more clear, let it be assumed that the subsequent combustion shall take place at a temperature of 700°. In that case the initial pressure must be sixty-four atmospheres, or for 800° centigrade the pressure must be ninety atmospheres, so on. Into the air thus compressed is gradually introduced from the exterior finely divided fuel, which ignites on introduction, since the air is at a temperature far above the igniting-point of the fuel; the characteristic features of the cycle according to my present invention are therefore, increase of pressure and temperature up to the maximum, not by combustion, but prior to combustion by mechanical compression of air, there upon the subsequent performance of work without increase of pressure and temperature by gradual combustion during a prescribed part of the stroke determined by the cut-oil". By June 1893, Diesel had realised his original cycle would not work and he adopted the constant pressure cycle. Diesel describes the cycle in his 1895 patent application.
Notice that there is no longer a mention of compression temperatures exceeding the temperature of combustion. Now it is stated that the compression must be sufficient to trigger ignition. "1. In an internal-combustion engine, the combination of a cylinder and piston constructed and arranged to compress air to a degree producing a temperature above the igniting-point of the fuel, a supply for compressed air or gas. See US patent # 608845 filed 1895 / granted 1898In 1892, Diesel received patents in Germany, the United Kingdom and the United States for "Method of and Apparatus for Converting Heat into Work". In 1894 and 1895, he filed patents and addenda in various