Patent Application
20110278368
The invention relates to a fuel injector for supplying gasoline to an engine and, more particularly, to a fuel injector having an intermediate pole to increase the speed and force generated within the injector solenoid while adding an anti-bounce mechanism within the injector.
Conventional direct injection solenoid fuel injectors have anti-bounce mechanisms to limit bouncing of the armature and thus inadvertent opening of the injector. However, these conventional mechanisms cause closing of the injector to be generally slow or the magnetic force generated is not high enough for new, higher pressure applications. Another disadvantage of prior techniques is the configuration of the components for manufacturing. These conventional direct injectors are not configured in a modular manner and thus, cannot be built and tested in modular stages. This results in scrap during manufacturing and thus increases cost.
Thus, there is a need to provide a modular, anti-bounce, solenoid direct fuel injector that provides an increased speed of opening and can be calibrated and tested on a sub-assembly basis.
An objective of the present invention is to fulfill the need referred to above. In accordance with the principles of an embodiment, this objective is obtained by a direct fuel injector for an internal combustion engine including a body having a passage extending along a longitudinal axis between inlet and outlet ends. A seat is at the outlet end and a closure member is associated with the seat. A needle member is associated with the closure member and is movable with respect to a pole piece between a first position and a second position such that in the first position, the needle member engages the closure member so that the closure member engages the seat to close the outlet end, and in the second position, the needle member is in a position permitting the closure member to disengage from the seat, opening the outlet end. A spring biases the needle member to the first position. An armature is constructed and arranged to be free-floating with respect to the needle member. An intermediate pole structure is coupled with the needle member and disposed between the pole piece and the armature and decoupled from both the armature and the pole piece. An armature stop is coupled to the needle member and spaced from the intermediate pole structure. An electromagnetic coil is associated with the pole piece, intermediate pole structure and armature. The coil, when energized, is constructed and arranged to provide magnetic flux that accelerates the armature to impact the intermediate pole structure with the intermediate pole structure impacting the pole piece moving the needle member to the second position, with the armature bouncing with respect to the intermediate pole piece instead of the needle assembly bouncing with respect to the seat. When the coil is de-energized, removing the magnetic flux, the intermediate pole structure and the armature are constructed and arranged to move away from the pole piece with the spring biasing the needle member to the first position, with the armature engaging the armature stop causing the armature to bounce with respect to the armature stop instead of the needle member bouncing with respect to the seat.
In accordance with another aspect of and embodiment, a method is provided for controlling bounce in a direct fuel injector having a seat at an outlet end of the injector, a closure member associated with the seat, a pole piece, electromagnetic coil, and a needle member movable with respect to the pole piece between a first position and a second position such that in the first position, the needle member engages the closure member so that the closure member engages the seat to close the outlet end, and in the second position, the needle member is in a position permitting the closure member to disengage from the seat, opening the outlet end. The method provides an armature to be free-floating with respect to the needle member and an intermediate pole structure coupled with the needle member and disposed between the pole piece and the armature and decoupled from both the armature and the pole piece. When the coil is energized and magnetic flux accelerates the armature to impact the intermediate pole structure, with the intermediate pole structure impacting the pole piece moving the needle member to the second position, the method ensures that the armature bounces with respect to the intermediate pole structure instead of the needle member bouncing with respect to the seat. When the coil is de-energized to remove the magnetic flux, causing the intermediate pole structure and the armature to move away from the pole piece and causing the needle member to move to the first position, the method ensures that the armature impacts and bounces off an armature stop instead of the needle member bouncing with respect to the seat.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.
The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:
Referring to
A closure member, e.g., a spherical valve ball 28, within the injector 10 is moveable between a first, seated or closed position and a second, open position. In the closed position, the valve ball 28 is urged against the seating surface 18 to close the outlet opening 20 to prevent fuel flow. In the open position, the ball 28 is spaced from the seating surface 18 to allow fuel flow through the outlet opening 20.
A needle member 30, preferably in the form of a tube, is disposed in the inlet tube 22 on the axis 14. A generally cylindrical armature 32 is moveable along axis 14 in a tube portion 34 of the valve body 12. The armature 32 is free-floating and thus is not connected to the needle member 30. The armature 32 includes a generally planar end surface 33. A pole piece 35 is associated with the armature 32 in the conventional manner. In a first position, an end 36 of the needle member 30 engages with the valve ball 28 so that the valve ball 28 engages the seating surface 18 in the closed position of the valve ball 28. The valve ball 28 can be considered to be part of the needle member 30. An intermediate pole structure 38 and an armature stop 40 are welded to the needle member 30 for movement therewith. The armature stop 40 is spaced from the intermediate pole structure 38. The intermediate pole structure 38 includes a reduced diameter portion 43 that is welded to the needle member 30 and a larger diameter portion 45 extending from the portion 43. The larger diameter portion 45 has opposing planar surfaces 47, 49, defining impact surfaces, the function of which will be explained below. An annular wave spring 41 is provided between the armature 32 and the intermediate pole structure 38 (e.g., surface 47 thereof) to decouple the armature 32 from the intermediate pole structure 38. As best shown in
A spring 42 engages the intermediate pole structure 38 and thus biases the needle member 30 and the valve ball 28 towards the closed position. The fuel injector 10 may be calibrated by preloading spring 42 to a desired biasing force. A filter 44 is provided within the tube 24 to filter fuel.
As best shown in
On closing of the injector 10, the coil 46 is de-energized, removing the magnetic field and allowing the intermediate pole structure 38 and the armature 32 to move away from the pole piece 35. The spring 42 biases the intermediate pole structure 38 and thus the needle member 30 towards first position thereof and an impact occurs between the end 36 of the needle member 30 and the valve ball 28. In conventional direct injectors, the needle member would bounce off the valve ball 28 causing the valve ball 28 to disengage from the seating surface 18, allowing for a secondary, unwanted injection. In the embodiment, advantageously, the travel of the armature 32 with respect to the needle member 30 is limited, via engagement of the armature 32 with the armature stop 40, reducing the amount of energy that can cause a secondary bounce of the needle member 30. Further, the bounce of the armature 32 against the armature stop 40 removes energy so that any bounce of the needle member 30 with respect to the seat 18 is prevented or limited. As noted above, the wave spring 41 decouples the intermediate pole structure 38 (and thus the needle member 30) from the armature 32.
Thus, the provision of the intermediate pole structure 38 associated with the armature 32 increases the speed of opening of the injector 10 due to the impact of the armature 32 and the intermediate pole structure 38. Since there is a large impact area between the armature 32, intermediate pole structure 38 and the pole piece 35, wear and durability of the injector are improved. The coil 46, spring 42, needle member 30, armature 32, pole piece 35, intermediate pole structure 38 and armature stop 40 define a modular sub-assembly of the injector 10 allowing the injector to be calibrated and tested on a sub-assembly basis.
Thus, the injector 10 has a more powerful opening force compared to conventional injectors, has a stronger closing spring for better leakage capability, and eliminates bounce on both opening and closing. The flow performance is improved due to faster opening and closing and by the elimination of secondary injection by reducing or eliminating bounce of the needle member 30.
The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.
