Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2000-04-26
2001-07-17
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
Reexamination Certificate
active
06260541
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a hydraulic lash adjuster and, more particularly, to a hydraulic lash adjuster for use in a piezoelectric actuated fuel injector.
BACKGROUND OF THE INVENTION
Piezoelectric devices are attractive candidates as control valve actuators in common rail fuel injectors for diesel engines. The precise longitudinal deflection characteristic of piezoelectric devices in conjunction with their rapid dynamic response provides the potential of achieving meaningful control over the rate of fuel injection. Additionally, the relative high load capability of piezoelectric devices is consistent with the extremely high pressure environment of common rail fuel injectors.
Unfortunately, piezoelectric devices suffer from an extremely small deflection capability. Furthermore, piezoelectric devices are made from materials that exhibit a coefficient of thermal expansion that is much lower than the iron-based materials commonly used to house the piezoelectric devices within the fuel injectors. Accordingly, piezoelectric devices exhibit thermally induced lash that is significantly greater than their deflection capability. As a result, piezoelectric devices are rendered unusable as an actuator for fuel injectors without a means for thermal expansion compensation.
A hydraulic lash adjuster has been considered as a means for achieving thermal expansion compensation in a piezoelectric actuated fuel injector. A conventional hydraulic lash adjuster typically uses a relatively large volume liquid filled working chamber to compensate between the actuated and the actuating members. However, due to the extremely high pressures encountered in common rail fuel injectors, these conventional hydraulic lash adjusters will experience a loss in length caused by compression of the liquid. Since the piezoelectric actuator has a very short stroke, this length loss makes the conventional hydraulic lash adjuster unusable as a means for thermal expansion compensation in a piezoelectric actuated fuel injector.
Therefore, it is desirable to provide a hydraulic lash adjuster having a sufficiently small internal working volume to properly compensate for the length differences of the piezoelectric actuated fuel injector.
SUMMARY OF THE INVENTION
In accordance with the present invention, a hydraulic lash adjuster is provided for interfacing between a piezoelectric element and a control valve in a piezoelectric actuated fuel injector. The hydraulic lash adjuster includes an inner plunger having an axial passage for storing a working fluid therein, and an outer body having a socket dimensioned to receive the inner plunger. The inner plunger is movably coupled into the socket of the outer body so as to form a working chamber between a bottom outer surface of the inner plunger and a bottom surface of the socket in the outer body. The hydraulic lash adjuster further includes a feed valve assembly disposed in the passage of the inner plunger for providing the working fluid from the passage to the working chamber, thereby minimizing the volume of the working chamber.
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Bosch Russell Harmon
Ricci-Ottati Giulio Angel
Delphi Technologies Inc.
Moulis Thomas N.
VanOphem John A.
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