- Injection pump
An Injection Pump is the device that pumps fuel into the cylinders of a diesel engine or less typically, a gasoline engine. Traditionally, the pump is driven indirectly from the crankshaft by gears, chains or a toothed belt (often the timing belt) that also drives the camshaft on overhead-cam engines ( OHC ). It rotates at half crankshaft speed in a conventional four-stroke engine. Its timing is such that the fuel is injected only very slightly before top dead centre of that cylinder's compression stroke. It is also common for the pump belt on gasoline engines to be driven directly from the camshaft. In some systems injection pressures can be as high as 200Mpa.
Because of the need for positive injection into a very high-pressure environment, the pump develops great pressure—typically 15,000 psi (100 MPa) or more on newer systems. This is a good reason to take great care when working on diesel systems; escaping fuel at this sort of pressure can easily penetrate skin and clothes, and be injected into body tissues with medical consequences serious enough to warrant amputation.
Earlier diesel pumps used an in-line layout with a series of cam-operated injection cylinders in a line, rather like a miniature inline engine. The pistons have a constant stroke volume, and injection volume (ie, throttling) is controlled by rotating the cylinders against a cut-off port that aligns with a helical slot in the cylinder. When all the cylinders are rotated at once, they simultaneously vary their injection volume to produce more or less power from the engine. Inline pumps still find favour on large multi-cylinder engines such as those on trucks, construction plant, static engines and agricultural vehicles.
For use on cars and light trucks, the rotary pump or distributor pump was developed. It uses a single injection cylinder driven from an axial cam plate, which injects into the individual fuel lines via a rotary distribution valve. Later incarnations such as the Bosch VE pump vary the injection timing with crank speed to allow greater power at high crank speeds, and smoother, more economical running at slower revs. Some VE variants have a pressure-based system that allows the injection volume to increase over normal to allow a turbocharger or supercharger equipped engine to develop more power under boost conditions.
All injection pumps incorporate a governor to cut fuel supply if the crank speed endangers the engine - the heavy moving parts of diesel engines do not tolerate overspeeding well, and catastrophic damage can occur if they are over-revved.
Mechanical pumps are gradually being phased out in order to comply with international emissions directives, and to increase performance and economy. Alternatives include common rail diesel systems and electronic unit direct injection systems. These allow for higher pressures to be developed, and for much finer control of injection volumes compared to mechanical systems.
Wikimedia Foundation. 2010.
См. также в других словарях:
injection pump — A pump which receives fuel from the fuel tank (often through the fuel feed pump in the case of diesel engines) and delivers it under pressure to the injectors. Also see fuel injection pump … Dictionary of automotive terms
injection pump — inžekcinis siurblys statusas T sritis Energetika apibrėžtis Čiurkšlinis siurblys, skirtas dujoms arba skysčiui suslėgti ir tiekti aplinkai didesniu slėgiu. atitikmenys: angl. injection pump vok. Einspritzpumpe, f rus. инжектор, m pranc. pompe à… … Aiškinamasis šiluminės ir branduolinės technikos terminų žodynas
injection pump — An engine driven pump supplying fuel at high pressure to the injector of a reciprocating engine, where it is atomized and ignites as it leaves the injection nozzle. The pump is in lieu of the conventional carburetor. The supply of fuel is… … Aviation dictionary
injection pump — впрыскивающий насос … Pipeline dictionary
injection pump governor — Device which controls fuel deliver to limit the minimum and maximum engine speeds, as well as intermediate throttle positions … Dictionary of automotive terms
distributor injection pump — A fuel injection pump using pistons which pressurizes fuel for injection in the proper cylinder based on the relative port position of the rotating shaft in the hydraulic head … Dictionary of automotive terms
water injection pump — čiurkšlinis vandens siurblys statusas T sritis fizika atitikmenys: angl. water injection pump; water jet injector vok. Wasserstrahlinjektor, m; Wasserstrahlpumpe, f rus. водоструйный инжектор, m; водоструйный насос, m pranc. injecteur à jet d’eau … Fizikos terminų žodynas
fuel injection pump — A pump which receives fuel from the fuel tank (often through the fuel feed pump in the case of diesel engines) and delivers it under pressure to the injectors … Dictionary of automotive terms
pump —  A device for moving liquid or gas by decreasing or increasing the pressure on it. See accelerator pump air pump canned motor pump cell pump centrifugal pump charging pump circulating pump coolant pump diaphragm pump … Dictionary of automotive terms
injection — See air injection direct injection electronic fuel injection fuel injection engine fuel injection pump fuel injection high speed direct injection indirect injection engine indirect … Dictionary of automotive terms