Measuring valve for dosing liquids or gases
AssigneeRobert Bosch GmbH
InventorDietrich Trachte
Life of this patent
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Abstract
A metering valve includes a piezoelectric cylinder connected via a spring biased needle to a valving element for closing a metering opening. To compensate for slow changes in the length of the piezoelectric control member, there is provided a damping piston connected axially to the piezoelectric member and being movable in a well formed in the valve housing and defining with the end face of the piston a damping chamber. A tubular membrane surrounds a portion of the damping piston and is attached to the piezoelectric member and to an inner wall of the housing around the opening of the well to define with the piston an annular equalizing space. The damping and equalizing spaces are filled with liquid and communicate with one another via a narrow throttling gap formed between facing walls of the well and of the piston.
Claims7
A metering valve for dosing liquids or gases, particularly an injection valve for a fuel injection system of an internal combustion engine, comprising a valve housing having an end part provided with an outlet passage terminating with a metering opening;
- a valve seat surrounding said metering opening;
- a valving element for closing the valve seat;
- a valve needle connected at one end thereof to said valving element and passing through said outlet passage;
- spring means arranged between said housing and the opposite end of the needle to urge said valving element into a closing position against said valve seat;
- a piezoelectric control member resiliently supported in said housing in axial alignment with said needle;
- means for transmitting axial extensions of the piezoelectric control member to said needle to displace said valving element from its closing position when activated;
- damping means arranged between an opposite end part of the housing and said piezolectric control member to fix relative position of the same during fast changes of its length;
- and throttling means cooperating with said damping means to compensate for slow changes in length of the piezoelectric control member so as to maintain a constant position of the latter relative to said housing, said piezolectric control member being arranged in an intermediate part of the housing, said damping means including a well formed in said opposite end part of the housing and opening into said intermediate housing part, a damping piston attached to said opposite end face of the piezoelectric control member and partially projecting into said well, a tubular membrane arranged in said intermediate housing part around said damping piston to delimit therewith an annular equalizing space;
- said throttling means including an annular throttling gap between the facing walls of said damping piston and said well;
- and said damping and equalizing spaces being filled with a damping liquid and communicating with each other through said throttling gap.
Dependencies are inferred from the claim text.