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The Roots type supercharger or Roots blower is a positive displacement lobe pump which operates by pumping a fluid with a pair of meshing lobes not unlike a set of stretched gears. Fluid is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust. It is frequently used as a supercharger in engines, where it is driven directly from the engine's crankshaft via a belt, chain, or gears. It is named after the American inventors and brothers Philander and Francis Marion Roots, founders of the Roots Blower Company, Connersville, Indiana, who first patented the basic design in 1860 as an air pump for use in blast furnaces and other industrial applications. In 1900, Gottlieb Daimler included a Roots-style supercharger in a patented engine design, making the Roots-type supercharger the oldest of the various designs now available. Roots blowers are commonly referred to as air blowers or PD (positive displacement) blowers,〔(), Air Blower Services〕 and can be commonly called "huffers" when used with the gasoline-burning engines in hot rod customized cars.〔''Hot Rod'' Magazine's ''Street Machines and Bracket Racing'' #3 (Los Angeles: Petersen Publishing, 1979), p.65.〕 == Applications == The Roots-type supercharger is simple and widely used. It can be more effective than alternative superchargers at developing positive intake manifold pressure (i.e., above atmospheric pressure) at low engine speeds, making it a popular choice for passenger automobile applications. Peak torque can be achieved by about 2000 rpm. Unlike the basic illustration, most modern Roots-type superchargers incorporate three-lobe or four-lobe rotors; this allows the lobes to have a slight spiral along the rotor axes, which in turn reduces pulsing in the input and output (this is impractical with two lobes, as even a slight spiral could open up a free path through the supercharger at certain angles). Accumulated heat is an important consideration in the operation of a compressor in an internal combustion engine. Of the three basic supercharger types, the Roots design historically possessed the worst thermal efficiency, especially at high pressure ratios.〔Bell, Corky. ''Supercharged!''. Bentley Publishers, 2001, p. 48.〕 In accordance with the ideal gas law, a compression operation will raise the temperature of the compressed output. Additionally, the operation of the compressor itself requires energy input, which is converted to heat and can be transferred to the gas through the compressor housing, heating it more. Although intercoolers are more commonly known for their use on turbochargers, superchargers may also benefit from the use of an intercooler. Internal combustion is based upon a thermodynamic cycle, and a cooler temperature of the intake charge results in a greater thermodynamic expansion and vice versa. A hot intake charge robs the engine of efficiency and produces diminishing returns from the compression process, while an intercooling stage adds complexity but can improve the efficiency by releasing some of the unneeded heat. Above about the intercooling improvement can become dramatic. With a Roots-type supercharger, one method successfully employed is the addition of a thin heat exchanger placed between the blower and the engine. Water is circulated through it to a second unit placed near the front of the vehicle where a fan and the ambient air-stream can dissipate the collected heat. The Roots design was commonly used on two-stroke diesel engines (popularized by the Detroit Diesel (and bus ) and Electro-Motive () divisions of General Motors), which require some form of forced induction, as there is no separate intake stroke. The ''Rootes'' Co. two-stroke diesel engine, used in ''Commer'' and ''Karrier'' vehicles, had a Roots-type blower but the two names are not connected. The superchargers used on top fuel engines, funny cars, and other dragsters, as well as hot rods, are in fact derivatives of ''General Motors Coach Division'' blowers for their industrial diesel engines, which were adapted for automotive use in the early days of the sport of drag racing. The model name of these units delineates their size; i.e. the once commonly used "4–71" and "6–71" blowers were designed for ''General Motors'' diesels having four or six cylinders of 71 cubic inches each. Current competition dragsters use aftermarket GMC variants similar in design to the −71 series, but with the rotor and case length increased for added pumping capacity, identified as the 8–71, 12–71, 16–71, etc. Roots blowers are typically used in applications where a large volume of air must be moved across a relatively small pressure differential. This includes low vacuum applications, with the Roots blower acting alone, or use as part of a high vacuum system, in combination with other pumps. Some civil defense sirens used Roots blowers to pump air to the rotor (chopper). The most well known are the Federal Signal Thunderbolt Series, and ACA (now American Signal Corporation) Hurricane. These sirens are known as "supercharged sirens". Roots blowers are also used in reverse to measure the flow of gases or liquids, for example, in gas meters. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Roots-type supercharger」の詳細全文を読む スポンサード リンク
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