This application generally relates to a fuel injector for a combustion engine. More particularly, this invention relates to a fuel injector that heats fuel to aid the combustion process.
Combustion engine suppliers continually strive to improve emissions and combustion performance. Once method of improving both emissions and combustion performance includes heating or vaporizing fuel prior to entering the combustion chamber. Starting a combustion engine often results in undesirably high emissions since the engine has not yet attained an optimal operating temperature. Heating the fuel replicates operation of a hot engine, and therefore improves performance. Further, alternative fuels such as ethanol can perform poorly in cold conditions, and therefore also may benefit from pre-heating of fuel.
Various methods of heating fuel at a fuel injector have been employed. Such methods include the use of a ceramic heater, or resistively heated capillary tube within which the fuel passes. In another example, positive temperature coefficient (PTC) heating elements have been used. One disadvantage of these devices is that that they do not heat the fuel quickly or hot enough to have the desired effect at start-up. Another disadvantage of prior art fuel injector heaters is that the wires to the heater are often in the fuel flow path, which is undesirable if the insulation about the wires fails. These wires also create an additional potential fuel leakage path.
What is needed is a fuel injector having a heater that does not create additional fuel leak paths while still providing rapid heating and vaporization of fuel.
A fuel injector includes a common member that provides both an actuator and a heater. The member generates a first magnetic field in response to a DC signal, for example, to move a pole-piece between open and closed positions for providing fuel to a combustion chamber. The same member generates a second magnetic field in response to an AC signal, for example, to inductively heat a structure within the fuel injector. In one example, a fuel flow path is arranged between the pole-piece and the structure.
A driver is in communication with the member and provides the AC signal superimposed over the DC signal, for example, to heat the fuel and move the pole-piece, respectively.
An example fuel injector 10 is shown in
The fuel injector 10 includes a pole-piece 19 that is actuated between open and closed positions. The pole-piece 19 includes an armature tube 22 that supports a ball 23 received by a seat 22 when the pole-piece 19 is in a closed position, which is shown in the figures. A return spring 17 biases the ball 23 to the closed position. The ball 23 is spaced from the seat 21 in the open position to provide fuel to the combustion chamber 13.
A coil 16 is arranged near the outlet 36 in the example shown. The coil 16 heats the fuel within an annular flow path 24 arranged between a valve body 20 and the armature tube 22. In one example, the coil 16 inductively heats the valve body 20 and/or the armature tube 22. In the example, a barrier 33 seals the coil 16 relative to the internal passages of the fuel injector 10. Electrical wires (shown in
In one example, a driver 12 provides a DC signal 30 to the coil 16, which is shown schematically in
The driver 12 also provides an AC signal 32, for example 70 volts at 40 kHz, to the coil 16. The AC signal 32 produces a time varying and reversing second magnetic field that heats up the components within the field. Heat is generated within the valve body 20 and/or armature tube 22 by hysteretic and eddy-current losses by the magnetic field. The amount of heat generated is responsive to the specific resistivity of the material being acted upon and the generation of an alternating flux. The time varying magnetic field produces a flux flow in the surface of the material that alternates direction to generate heat. The higher resistivity of the material, the better the generation of heat responsive to the magnetic field. The heated valve body 20 and/or armature tube 22 rapidly transfers heat to the fuel within the annular flow path 24 to provide a well vaporized fuel exiting the outlet 36 when the pole-piece 19 is opened.
In the example fuel injector, a single coil is used to provide the actuator and heater. In this manner, the number of components may be reduced, and the number of wires required for each injector can be reduced to two in the example. In one example, the driver 12 sends a DC signal with an AC signal superimposed on the DC signal, as shown in
The driver 12 and the controller 50 are exterior to the fuel injector 10 in the example shown. The driver 12 can be separate structures and/or software, as shown, or integrated with one another and/or the controller 50.
Although a preferred embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.
The application claims priority to U.S. Provisional Application No. 60/786,576 which was filed on Mar. 28, 2006.
Number | Date | Country | |
---|---|---|---|
60786576 | Mar 2006 | US |