Patent Grant
6874703
The present invention relates to fuel injectors used for internal combustion engines, and more particularly to the needle valve thereof. Still more particularly, the present invention relates to a needle valve of the aforesaid type having an anti-bounce feature.
Internal combustion engines, particularly diesel engines, utilize fuel injection systems for providing precise metering of fuel to each cylinder, thereby enhancing performance and fuel economy, as well as reduction of undesirable emissions.
A typical conventional application of a fuel injector 10 with respect to a diesel internal combustion engine 12 is shown at
Engine performance, fuel economy and emissions all depend upon precise timing of the start and end of the fuel injection event. In this regard, it is desirable for the beginning and end of the fuel injection event to be as rapid as possible.
The closure percussion involves a tendency of the needle 22 to bounce at the valve seat 24, with the undesirable consequences of undue seat wear and a second fuel injection occurring during the bounce. The bounce induced fuel injection involves an unwanted low pressure fuel injection late in the combustion cycle which can adversely affect fuel economy and performance and increase undesirable emissions.
The origin of closure percussion bounce relates to the metallic components of the needle and the valve seat colliding in an essentially elastic manner. As such, there is a substantial conservation of kinetic energy which translates into bounce of the needle.
Conventionally, fuel injector manufacturers have struggled with needle bounce, and have attempted to solve this problem by incorporating hydraulic assist systems which serve to assuage needle bounce. Problematically, these hydraulic systems are complex and costly.
Accordingly, what is needed is a fuel injector needle valve in which the needle valve inherently has an absence of bounce.
The present invention is an anti-bounce needle for use in a needle valve of a fuel injector, wherein the anti-bounce needle inherently incorporates the anti-bounce feature.
The anti-bounce needle according to the present invention has a conventionally configured exterior for interfacing with a valve seat of the needle valve with the tip body of a conventional fuel injector. The anti-bounce needle is characterized by a needle body having an interior cavity which is filled with small diameter shot, preferably generally spherical tungsten carbide shot.
In operation, when the anti-bounce needle impacts upon the valve seat at the conclusion of a fuel injection process, the shot causes the needle collision with the valve seat to be inelastic, thereby rendering the kinetic energy of the impact to be non-conserved (transformed to heat) such that no bouncing of the needle with respect to the valve seat can occur.
Accordingly, it is an object of the present invention to provide an anti-bounce needle of a needle valve for a fuel injector.
This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.
Referring now to the drawings,
As shown at
As shown at
As shown at
As shown at
In operation, when the anti-bounce needle impacts upon the valve seat at the conclusion of a fuel injection process, the shot 118 causes the needle collision with the valve seat to be inelastic such that there is no bounce of the anti-bounce needle.
It is believed that the underlying principle of operation is as follows. Although momentum is conserved in any collision, the kinetic energy need not be conserved. Consider a moving object and a target object which is immovable. In a perfectly elastic collision, kinetic energy is conserved so that upon collision, the moving object bounces off the target object. On the other hand, if the collision is perfectly inelastic, upon collision, the moving object will stop at the target object and not bounce. Generally, for any collision, the energy terms may be represented by:
KE1=KE2+Q
wherein KE1 is the kinetic energy (½m(v1)2) of a moving object (the anti-bounce needle) before collision with an immovable target object (the valve seat), KE2 is the kinetic energy (½m(v2)2) of the moving object (the anti-bounce needle) after collision with the immovable target object (the valve seat), and Q is an amount of heat (and sound energy) generated by the collision.
In a conventional fuel injector needle collision with its valve seat, the collision is generally elastic such that Q is small, and since the valve seat is immovable, V2 is large and must be damped by bounce into the spring and/or a conventional hydraulic assist system. However, in the anti-bounce needle according to the present invention, the change of momentum of the shot is spread out over time such that the collision is substantially inelastic, wherein Q is large and V2 is vanishing such that there is no bounce of the needle. This principle of operation is similar to that employed by dead blow hammers.
To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.
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| Number | Date | Country | |
|---|---|---|---|
| 20030226911 A1 | Dec 2003 | US |
