Collision Velocity of a Needle with Its Seat in a Fuel Injection Valve

概要

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To ensure durability of an injector on a diesel engine, the lift of a needle itself and oil pressure around the needle, etc. are measured. As the result, it is found that the change in injection characteristics is not substantial in the range of the maximum needle height (h=0.25〜0.85 mm) ; the collision velocity of a needle with its seat increases, as the pressure-drop time rate on the pump side, the cam shaft speed, the height of needle stopper increase and the spring constant and the weight of movable parts decrease ; this collision velocity is almost independent of the fore-opening pressure ; and the oil pressure change rate dp/dt on the nozzle side may be proportional only to the cam shaft speed squared. Assuming the rate of pressure change dp/dt, a theoretical equation of collision velocity of a needle with its seat is introduced. The theoretical velocity generally agrees with the experimental one.
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