NOTCHED NEEDLE BOUNCE ELIMINATOR

Abstract: A device (10) comprises an armature movable in a first direction and a second direction for causing a needle (34) to contact and separate from a seat assembly (24). Stop means (28) provide a motion stop in at least the first direction. Damping means (42) are applied to the needle (36) for reducing bounce of the needle when the needle contacts the stops means (28), by altering spring rates and vibration modes of the needle.

Description: NOTCHED NEEDLE BOUNCE ELIMINATOR Field of the Invention The present invention relates to a solenoid actuated valve assembly and, more particularly, to means for controlling the bounce of a needle in a solenoid valve. Background of the Invention Typically, a solenoid valve comprises an armature movable between a first and second position for causing a needle valve to contact and separate from a valve seat. The extremes of these first and second positions are often defined by mechanical stops. Armatures can be moved in one direction by an electro-magnetic force generated by a coil of wire and moved in the opposite direction by a return spring. When the armature needle impacts a stop, the fuel injector bounces. In high speed fluid metering solenoids, needle bounce is a problem because each bounce of the needle meters a small uncontrolled amount of fuel into the engine, to the detriment of emissions. As can be appreciated, the leakage of fuel into the engine will result in very unfavorable fuel economy. At either end of its motion, the armature has kinetic energy as a result of its mass and velocity. With no means for dissipating that energy, it is returned to the armature by the elastic collision with the stop. Eventually, the energy is dissipated after a series of collisions and bounces. The bounce of the armature and needle affects the operation of a fuel injector by prolonging or shortening the duration of injection, causing excessive wear in the valve seat area. This bounce causes increased injection time and quantity, reduced precision of fuel quantity delivery, and poor atomization. It is seen then that there exists a need for a means of controlling the bounce of an armature needle, thereby diminishing the amount of fuel into the engine and the wear in the valve seat area. Summary of the Invention This need is met by the present invention, wherein the moving needle of a pulse width modulated solenoid valve is notched, grooved, or otherwise indented in order to reduce or eliminate bounce when it strikes rigid stops. The present invention alters the axial or bending spring rates and vibration modes of the needle in order to accomplish controlled bounce. In accordance with one aspect of the present invention, a device comprises an armature movable in a first and a second direction for causing a needle valve to contact and separate from a valve seat. Stop means provide a motion stop in at least the first direction. Damping means are applied to the needle for reducing bounce of the needle when the needle contacts the stop means, by altering spring rates and vibration modes of the needle. For a full understanding of the nature and objects of the present invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawings and the appended claims. Brief Description of the Drawings In the Drawings: FIG. 1 is a partially cutaway cross section view of a high pressure fuel injector incorporating a preferred embodiment of the notched needle bounce eliminator in accordance with the present invention; FIGS. 2-5 are views of alternative embodiments of the notched needle bounce eliminator of the present invention. Description of the Preferred Embodiment Referring to FIG. 1 there is illustrated in cross section, a typical spherical needle and cone fuel injector solenoid 10 designed to operate at fuel pressures over 1000 psi. The injector 10 includes a tubular housing 1 2 made from nonmagnetic stainless steel. The inside of the -3- tubular housing 12 contains an inlet tube 14 and a plurality of different diameters to form typical various shoulders for a variety of different functions. Positioned along the outside of the housing 12 are sealing means 16 to seal the injector 10 in a bore of an engine or manifold where it is located. The housing 12 has an open end 18, and an outlet end 20. The outlet end 20 is counterbored to form a shoulder 22 for locating a seat assembly 24 and a spray generator 26. The seat assembly 24 is comprised of a needle stop means such as valve seat 28, and a swirl guide 30. Adjacent to the valve seat 28 is the spray generator 26 having an axially aligned bore 32 through which reciprocates a needle valve 34. The needle valve 34 has an essentially spherical radius for mating with the valve seat 28 to close the injector 10. At an end of the needle valve 34, opposite the spherical radius, there is a needle- armature means (not shown) comprising an armature member and a damping member. The armature member is located on the needle 34 abutting the damping member and is free to move, very slightly, axially along the needle 34 against the damping member. The end of the needle valve 34 is received in a spring retainer 36 which is slidably received in a bore 38 in an inner pole 40 of the solenoid core. The relative organization and arrangement of these various parts are essentially the same as in the fuel injector of commonly assigned US Patent 4,610,080. The injector is of the type which is commonly referred to as a top-feed type, wherein fuel is introduced through inlet connector 14 and emitted as injections from the axially opposite nozzle, or tip, end. The differences essentially relate to the inventive features of the present disclosure. The mechanism of the invention is to reduce the spring rate of the needle 36 either in bending or in compression. The kinetic energy of the moving needle can then be more readily stored as strain energy in the deflected needle. The larger this deflection on impact the more of this energy can be dissipated in the internal damping of the material. In this way, the strain energy returned to kinetic energy is reduced. FIG. 1 illustrates a preferred embodiment of the present invention wherein a "stairstep" arrangement of notches 42 are provided from opposite sides of the needle 36, as a damping means, in order to reduce the axial spring rate of the needle by the addition of any number of double cantilevered beams. Needle spring rate is thereby adjusted to a precise level for closing bounce elimination. It will be obvious to those skilled in the art that there are a multitude of various embodiments which fall within the scope of the invention. FIGS. 2-5 illustrate only some of the numerous alternative embodiments of the present invention. The embodiment illustrated in FIG. 2 functions by adjusting the bending mode shape in order to eliminate closing bounce, incorporating a notch 44. FIG. 3 illustrates a plurality of notches 46. As will be obvious to those skilled in the art, any number of notches, grooves or other indentations can be used as necessary located anywhere along the needle length. FIG. 4 illustrates a circumferential groove 48, rather than the flat-bottomed notches 42, 44 and 46 of FIGS. 1-3. FIG. 5 illustrates an embodiment wherein a rippled tube 50 replaces the needle. The ripples, or crimps, 52 in the tube 50 are designed to reduce the spring rate in a similar manner to the other constructions. The tube 50 could also be deformed in other ways, such as with scalloped dents instead of circumferential dents, in order to adjust the axial and bending spring rates, or any combination of the two. Those skilled in the art will recognize that the concept of the present invention can be applied to other portions of the fuel injector 10. For example, similar features can be added to the stator or armature in order to reduce opening bounce. Also, the needle can be modified at the stator end which will be especially useful for reducing opening bounce if the needle instead of the armature is used as the opening stop. Having described the invention in detail and by reference to the preferred embodiment thereof, it will be apparent that other modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims: CLAIMS What is claimed is: 1 . A device comprising: an armature movable in a first direction and a second direction for causing a needle to contact and separate from a seat assembly; stop means for providing a motion stop in at least said first direction; damping means applied to said needle fo r reducing bounce of said needle when said needle contacts said stop means, by altering spring rates and vibration modes of said needle. 2. A device as claimed in claim 1 wherein said first direction is a closing direction for causing said needle to contact said seat assembly and said second direction is an opening direction for causing said needle to separate from said seat assembly. 3. A device as claimed in claim 2 wherein said damping means provides damping for said first direction. 4. A device as claimed in claim 1 wherein said damping means comprises at least one indentation on said needle. 5. A device as claimed in claim 4 wherein said at least one indentation comprises multiple notches formed on opposite sides of said needle in a stairstep arrangement. 6. A device as claimed in claim 4 wherein said at least one indentation comprises multiple notches formed on opposite sides of said needle in a stairstep arrangement. 7. A device as claimed in claim 4 wherein said at least one indentation comprises at least one groove formed on said needle. 8. A device as claimed in claim 1 wherein said needle comprises a rippled tube.

Inventors: BRIGHT JOHN S, KILGORE DAVID C, WAKEMAN RUSSELL J, BRIGHT, JOHN, S., KILGORE, DAVID, C., WAKEMAN, RUSSELL, J.
Applicants: SIEMENS AUTOMOTIVE CORP LP, SIEMENS AUTOMOTIVE CORPORATION
Application year: 1995
Main classification: F02M51
IPC codes: F02M51, F02M61, F02M63