SUMMARY OF THE INVENTIONĪccordingly, the primary object of the present invention is to provide a fuel injector which will improve the engine performance by creating a sufficiently high fuel injection pressure and will minimize the engine running noise by enabling a pilot injection which will obviate the abrupt movement of the needle.Īnother object of the present invention is to provide a fuel injector which eliminates the need for a mechanism to distribute fuel to the above-mentioned fuel injector provided at each of the cylinders of a multi-cylinder internal combustion engine, permitting the construction of the fuel injection pump to be simplified.Īccording to the present invention, a fuel injector is provided which comprises a housing, a piezo-actuator, a needle valve, a check valve, and an electric circuit controlling the voltage applied to the piezo-actuator. This fuel injection rate control must be such that the injection rate is low in the low-speed, low-load domain of the engine and is high in the high-speed, high-load domain. To minimize this noise, the fuel injection rate of the internal combustion engine should be controlled in accordance with the running conditions of the engine. Also, the conventional fuel injector is so constructed that the needle valve is opened when the fuel supply is stopped, and is closed as the fuel pressure within the accumulator decreases therefore, the operating noise is loud, since the fuel injection time is extremely short and thus the needle is opened and closed rapidly and abruptly. In other words, fuel atomization is limited and it is difficult to further improve the engine performance. Accordingly, since the needle valve can be opened under a relatively low pressure, a sufficient fuel injection pressure cannot be obtained. In the conventional fuel injector having the above construction, the valve-closing pressure depends upon the force (i.e., size) of the spring, and thus the size of the fuel injector is necessarily limited. In addition, the needle valve is so arranged that when the supply of fuel is stopped, the valve opens to allow fuel to be injected from the nozzle hole so that the fuel pressure within the accumulator is reduced, and thus the needle valve can close, terminating the fuel injection. In the conventional accumulator nozzle type fuel injector, the pressure of fuel supplied from a fuel source does not act on the needle valve in the valve-closing direction but acts only in the valve-opening direction, with the force of a spring acting in the valve-closing direction. More particularly, it relates to an accumulator nozzle type fuel injector and a fuel injection system provided with the same. **Price stated does not include shipping cost and is negotiable if per order is greater than 50 units.The present invention relates to a fuel injector intended for use in an internal combustion engine, especially in a Diesel engine. *The number is based on our calculations. MechaTrans® was originally named only for the displacement enlargement mechanism, however we currently use this name on the actuator with a piezoelectric device. As the mechanism is similar to a transformer which is used in electric circuits, we call it mechanical transformer and abbreviate it to MechaTrans® later on as a registered trademark in Japan. The displacement enlargement mechanism is a kind of a passive structure and no additional energy is required. The enlarged displacement achieves one hundred times of the piezoelectric device itself. In order to overcome the disadvantage, Mechano Transformer Corporation developed the displacement enlargement mechanism by using an unique lever principle. However, as the displacement to be generated ranges from a few μm up to 40μm, the application is limited due to the very small displacement. For example, a piezoelectric device of 10mm × 10mm cross section size produces 3,500N(357kgf). The electrical energy can be converted to mechanical energy at 60% of the conversion efficiency rate. Piezoelectric device generates a required displacement with low voltage.
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